TRANSPORTATION

Transportation in India

NAMES OF TRANSPORTATION USED IN INDIA

Cycle rickshaws 

Bullock carts/Horse carriages

Bicycles

Rickshaws

Bus

Ambulance

Boat

Train

Air plane

Metro

 Transports from one location to another. Modes of transport include air, land (rail and road), water, cable, pipeline and space. The field can be divided into infrastructure, vehicles and operation .or or transportation is the movement of humans, animals and goo

WHAT DO YOU MEAN  BY TRANSPORTATION SYSTEM

A Transportation System or mode is a system for moving persons or goods consisting of three components: (a) The vehicle (equipment) is what moves objects or traffic (people, goods

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DOGS

DOGS

There are more than 150 dog breeds, divided into 8 classes: sporting, hound, working, terrier, toy, non-sporting, herding, and miscellaneous.

– According to a recent survey, the most popular name for a dog is Max. Other popular names include Molly, Sam, Zach, and Maggie.

– Dogs can vary in size from a 36 inch (150+ lb.) Great Dane to a 2 lb. Chihuahua.

– Puppies and kittens can be adopted as early as 8 weeks of age. Until then, they should stay with their moms and littermates.

– About 1/3 of the dogs that are surrendered to animal shelters are purebred dogs.

– Contrary to popular belief, dogs do not sweat by salivating. They sweat through the pads of their feet.

– Dogs may not have as many taste buds as we do (they have about 1,700 on their tongues, while we humans have about 9,000), but that doesn’t mean they’re not discriminating eaters. They have over 200 million scent receptors in their noses (we have only 5 million) so it’s important that their food smells good and tastes good.

– The term “dog days” has nothing to do with dogs. It dates back to Roman times, when it was believed that Sirius, the Dog Star, added its heat to that of the sun from July 3 to August 11, creating exceptionally high temperatures.

– Did you know they were female? Toto’s role in The Wizard of Oz was played by a female Cairn Terrier named Terry, and the Taco Bell dog is actually a female Chihuahua named Gidget.

– Former US President Teddy Roosevelt had a Pit Bull named Pete.

– An adult dog has 42 teeth.

– If a dog isn’t spayed or neutered, a female dog, her mate and their offspring can product 67,000 dogs in 6 years.

– The most successful mountain rescue dog ever was a St Bernard named Barry, who lived during the early 1800’s and saved 40 lives.

– It was recently discovered that dogs do see in color, just not as vivid as we see.

– Nearly all but two breeds of dogs have pink tongues: the Chow Chow and the Shar-pei both have black tongues.

– The Poodle haircut was originally meant to improve the dog’s swimming abilities as a retriever, with the pom-poms left in place to warm their joints.

– The top five favorite breeds of dogs in the US are: Labrador Retriever, Golden Retriever, German Shepherd, Beagle, and Dachshund.

– The Basenji is the only barkless dog in the world.

– Greyhounds can reach a speed of up to 45 miles per hour.

– When a puppy is born, he is blind, deaf, and toothless.

– All dogs, regardless of breed, are direct descendants of wolves and technically of the same species.

– A dog’s whiskers — found on the muzzle, above the eyes and below the jaws — are technically known as vibrissae. They are touch-sensitive hairs than actually sense minute changes in airflow.

– Dogs are capable of locating the source of a sound in 6/100ths of a second by using their swiveling ears like radar dishes.

CATS

CATS

To their owners, cats will always be fascinating creatures. So here are a few facts about cats you may find interesting.

The cat

  • Cats have been domesticated for around 4,000 years. While they were once valued for their hunting abilities, they are now valued for their companionship and loving behaviour.
  • While not well known, the collective nouns used for cats and kittens are a clowder of cats and a kindle of kittens.
  • Our domestic cats are known as little cats. They differ from large cats such as lions and tigers because they are naturally active at night and can purr.
  • Cats are now the most popular pet in the UK and in the US.

The feline body & behaviour

With 48 recognised cat breeds and pedigrees in Australia plus an endless combination of cross breeds it’s amazing just how different each cat can look and behave. But there are many amazing physical characteristics that all cats possess, read on for more fascinating facts about your feline friend.

  • Cats have 30 teeth (dogs have 42) and most of us know how sharp they are!
  • Cats have a reflective layer in their eyes, known as the tapetum lucidum, which magnifies incoming light allowing them to see up to 6 times better than humans can in low light. Cats (as well as dogs) also have a ‘third eyelid’ called the nictitating membrane which is found on the inside corner of the eye which is an extra protective function of the eye.
  • Cats have 32 muscles in their ears (humans have only 12). This gives the ear mobility, enabling it to precisely locate prey such as mice or the opening of their cat food! Cats can also hear frequencies that are both below and above those that can be heard by humans. The ear also has the job of helping to maintain balance and the ability to right themselves when falling – which is where the phrase “Cats always land on their feet” came from.
  • More cats are left-pawed than right.
  • The texture of cat food is more important to cats than taste and cats can often be quite fussy about the smells of food. If your cat have ever licked you, you might compare the feel of their tongue to that of coarse sandpaper – that’s because a cats’ tongue is covered in tiny backwards facing thorn like barbs that guide food to the back of the mouth. These rough tongues are also perfectly designed for grooming and lapping up water.
  • Cats can retract their front claws. This keeps them sharp so they can be used for climbing and of course, as effective weapons!
  • Cats rub against us and scratch as a form of communication. They have scent glands on their cheeks and paws, so rubbing against us or scratching on vertical surfaces transfers their scent.
  • Around 75% of cats respond to catnip. This herb stimulates those cats that are genetically programmed to respond.
  • Those long whiskers around your cats’ mouth and face which form a vital part of their sense of touch. These whiskers are attached to nerve cells and are used to judge the size of openings as well as providing your cat information about everything he/she touches, as well as shifts in air pressure.
  • Cats can travel at speeds of up to 30km per hour.
  • The largest breed of cat in Australia is the Maine . Males can regularly weigh up to 12kgs!

Feline- human relationship

  • Cats are good for our health. People who own cats have a lower risk of cardio-vascular disease than non-cat owners. Elderly cat owners suffer less from depression and loneliness than non-cat owners.
  • Cats can be trained. Teach your cat to share a “high five” with you by rewarding her with a special treat every time she lifts her paw.
  • Cats need to interact with people from two weeks of age to enable them to be social towards humans. After 16 weeks of age it is very difficult to tame a cat.
  • Psychological studies have shown that cat owners are more logical and practical than dog owners. They tend to be more introverted than dog owners. Cat owners, however, tell more stories about their cats than dog owners.
  • The record number of cats kept by any one person was by an owner named Jack Wright, from Ontario, Canada who kept 689 cats!

Can’t get enough cat facts? Check out our other cat care topics.

 

About Dr Joanne Righetti

Dr Joanne RighettiDr Joanne Righetti is an animal behaviourist, educating the public and professionals in all aspects of the human–animal relationship. Her background is in zoology, with a PhD in animal behaviour and a counselling diploma – qualifications which enable her to work with all sorts of animals – including the human variety! Joanne likes to help pet owners understand their pet’s behaviour and solve any pet behaviour problems. She also consults to a variety of organisations including non-profit organisations, commercial companies and councils and is involved in a variety of media including regular spots on radio. Joanne is an honorary associate of the Faculty of Veterinary Sciences, University of Sydney. Find out more about Joanne at www.petproblemsolved.com.au

MATHEMATICS

MATHEMATICS

Mathematics is the science that deals with the logic of shape, quantity and arrangement. Math is all around us, in everything we do. It is the building block for everything in our daily lives, including mobile devices, architecture (ancient and modern), art, money, engineering, and even sports.

Since the beginning of recorded history, mathematic discovery has been at the forefront of every civilized society, and in use in even the most primitive of cultures. The needs of math arose based on the wants of society. The more complex a society, the more complex the mathematical needs. Primitive tribes needed little more than the ability to count, but also relied on math to calculate the position of the sun and the physics of hunting.

Several civilizations — in China, India, Egypt, Central America and Mesopotamia — contributed to mathematics as we know it today. The Sumerians were the first people to develop a counting system. Mathematicians developed arithmetic, which includes basic operations, multiplication, fractions and square roots. The Sumerians’ system passed through the Akkadian Empire to the Babylonians around 300 B.C. Six hundred years later, in America, the Mayans developed elaborate calendar systems and were skilled astronomers. About this time, the concept of zero was developed.

As civilizations developed, mathematicians began to work with geometry, which computes areas and volumes to make angular measurements and has many practical applications. Geometry is used in everything from home construction to fashion and interior design.

Geometry went hand in hand with algebra, invented in the ninth century by a Persian mathematician, Mohammed ibn-Musa al-Khowarizmi. He also developed quick methods for multiplying and diving numbers, which are known as algorithms — a corruption of his name.

Algebra offered civilizations a way to divide inheritances and allocate resources. The study of algebra meant mathematicians were solving linear equations and systems, as well as quadratics, and delving into positive and negative solutions. Mathematicians in ancient times also began to look at number theory. With origins in the construction of shape, number theory looks at figurate numbers, the characterization of numbers, and theorems.

Math and the Greeks

The study of math within early civilizations was the building blocks for the math of the Greeks, who developed the model of abstract mathematics through geometry. Greece, with its incredible architecture and complex system of government, was the model of mathematic achievement until modern times. Greek mathematicians were divided into several schools:

  • The Ionian School, founded by Thales, who is often credited for having given the first deductive proofs and developing five basic theorems in plane geometry.
  • The Pythagorean School, founded by Pythagoras, who studied proportion, plane and solid geometry, and number theory.
  • The Eleatic School, which included Zeno of Elea, famous for his four paradoxes.
  • The Sophist School, which is credited for offering higher education in the advanced Greek cities. Sophists provided instruction on public debate using abstract reasoning.
  • The Platonic School, founded by Plato, who encouraged research in mathematics in a setting much like a modern university.
  • The School of Eudoxus, founded by Eudoxus, who developed the theory of proportion and magnitude and produced many theorems in plane geometry
  • The School of Aristotle, also known as the Lyceum, was founded by Aristotle and followed the Platonic school.

In addition to the Greek mathematicians listed above, a number of Greeks made an indelible mark on the history of mathematics. Archimedes, Apollonius, Diophantus, Pappus, and Euclid all came from this era. To better understand the sequence and how these mathematicians influenced each other, visit this timeline.

During this time, mathematicians began working with trigonometry. Computational in nature, trigonometry requires the measurement of angles and the computation of trigonometric functions, which include sine, cosine, tangent, and their reciprocals. Trigonometry relies on the synthetic geometry developed by Greek mathematicians like Euclid. For example, Ptolemy’s theorem gives rules for the chords of the sum and difference of angles, which correspond to the sum and difference formulas for sines and cosines. In past cultures, trigonometry was applied to astronomy and the computation of angles in the celestial sphere.

After the fall of Rome, the development of mathematics was taken on by the Arabs, then the Europeans. Fibonacci was one of the first European mathematicians, and was famous for his theories on arithmetic, algebra, and geometry. The Renaissance led to advances that included decimal fractions, logarithms, and projective geometry. Number theory was greatly expanded upon, and theories like probability and analytic geometry ushered in a new age of mathematics, with calculus at the forefront.

Development of calculus

In the 17th century, Isaac Newton and Gottfried Leibniz independently developed the foundations for calculus. Calculus development went through three periods: anticipation, development and rigorization. In the anticipation stage, mathematicians were attempting to use techniques that involved infinite processes to find areas under curves or maximize certain qualities. In the development stage, Newton and Leibniz brought these techniques together through the derivative and integral. Though their methods were not always logically sound, mathematicians in the 18th century took on the rigorization stage, and were able to justify them and create the final stage of calculus. Today, we define the derivative and integral in terms of limits.

In contrast to calculus, which is a type of continuous mathematics, other mathematicians have taken a more theoretical approach. Discrete mathematics is the branch of math that deals with objects that can assume only distinct, separated value. Discrete objects can be characterized by integers, whereas continuous objects require real numbers. Discrete mathematics is the mathematical language of computer science, as it includes the study of algorithms. Fields of discrete mathematics include combinatorics, graph theory, and the theory of computation.

People often wonder what relevance mathematicians serve today. In a modern world, math such as applied mathematics is not only relevant, it’s crucial. Applied mathematics is the branches of mathematics that are involved in the study of the physical, biological, or sociological world. The idea of applied math is to create a group of methods that solve problems in science. Modern areas of applied math include mathematical physics, mathematical biology, control theory, aerospace engineering, and math finance. Not only does applied math solve problems, but it also discovers new problems or develops new engineering disciplines. Applied mathematicians require expertise in many areas of math and science, physical intuition, common sense, and collaboration. The common approach in applied math is to build a mathematical model of a phenomenon, solve the model, and develop recommendations for performance improvement.

While not necessarily an opposite to applied mathematics, pure mathematics is driven by abstract problems, rather than real world problems. Much of what’s pursued by pure mathematicians can have their roots in concrete physical problems, but a deeper understanding of these phenomena brings about problems and technicalities. These abstract problems and technicalities are what pure mathematics attempts to solve, and these attempts have led to major discoveries for mankind, including the Universal Turing Machine, theorized by Alan Turing in 1937. The Universal Turing Machine, which began as an abstract idea, later laid the groundwork for the development of the modern computer. Pure mathematics is abstract and based in theory, and is thus not constrained by the limitations of the physical world.

According to one pure mathematician, pure mathematicians prove theorems, and applied mathematicians construct theories. Pure and applied are not mutually exclusive, but they are rooted in different areas of math and problem solving. Though the complex math involved in pure and applied mathematics is beyond the understanding of most average Americans, the solutions developed from the processes have affected and improved the lives of all.

 

PAINT

PAINT

Related image

In 2003 and 2004, South African archeologists reported finds in Blombos Cave of a 100,000-year-old human-made ochre-based mixture that could have been used like paint.[1][2] Further excavation in the same cave resulted in the 2011 report of a complete toolkit for grinding pigments and making a primitive paint-like substance.[2][3] Cave paintings drawn with red or yellow ochre, hematite, manganese oxide, and charcoal may have been made by early sapiens as long as 40,000 years ago.

Ancient colored walls at Dendera, Egypt, which were exposed for years to the elements, still possess their brilliant color, as vivid as when they were painted about 2,000 years ago. The Egyptians mixed their colors with a gummy substance, and applied them separately from each other without any blending or mixture. They appear to have used six colors: white, black, blue, red, yellow, and green. They first covered the area entirely with white, then traced the design in black, leaving out the lights of the ground color. They used minium for red, and generally of a dark tinge.

Pliny mentions some painted ceilings in his day in the town of Ardea, which had been done prior to the foundation of Rome. He expresses great surprise and admiration at their freshness, after the lapse of so many centuries.

Paint was made with the yolk of eggs and therefore, the substance would harden and adhere to the surface it was applied to. Pigment was made from plants, sand, and different soils. Most paints used either oil or water as a base (the diluent, solvent or vehicle for the pigment).

A still extant example of 17th-century house oil painting is Ham House in Surrey, England, where a primer was used along with several undercoats and an elaborate decorative overcoat; the pigment and oil mixture would have been ground into a paste with a mortar and pestle. The process was done by hand by the painters and exposed them to lead poisoning due to the white-lead powder.

In 1718, Marshall Smith invented a “Machine or Engine for the Grinding of Colours” in England. It is not known precisely how it operated, but it was a device that increased the efficiency of pigment grinding dramatically. Soon, a company called Emerton and Manby was advertising exceptionally low-priced paints that had been ground with labour-saving technology:

One Pound of Colour ground in a Horse-Mill will paint twelve Yards of Work, whereas Colour ground any other Way, will not do half that Quantity.

By the proper onset of the Industrial Revolution, paint was being ground in steam-powered mills and an alternative to lead-based pigments was found in a white derivative of zinc oxide. Interior house painting increasingly became the norm as the 19th century progressed, both for decorative reasons and because the paint was effective in preventing the walls rotting from damp. Linseed oil was also increasingly used as an inexpensive binder.

In 1866, Sherwin-Williams in the United States opened as a large paint-maker and invented a paint that could be used from the tin without preparation.

It was not until the stimulus of World War II created a shortage of linseed oil in the supply market that artificial resins, or alkyds, were invented. Cheap and easy to make, they also held the color well and lasted for a long time.[4][not in citation given][citation needed]

Components

Vehicle

The vehicle is composed of the binder; or, if it is necessary to thin the binder with a diluent like solvent or water, it is the combination of binder and diluent.[5][6] In this case, once the paint has dried or cured very nearly all of the diluent has evaporated and only the binder is left on the coated surface. Thus, an important quantity in coatings formulation is the “vehicle solids”, sometimes called the “resin solids” of the formula. This is the proportion of the wet coating weight that is binder, i.e. the polymer backbone of the film that will remain after drying or curing is complete.

Binder or film former

The binder is the film-forming component of paint.[7] It is the only component that is always present among all the various types of formulations. Many binders are too thick to be applied and must be thinned. The type of thinner, if present, varies with the binder.

The binder imparts properties such as gloss, durability, flexibility, and toughness.[8]

Binders include synthetic or natural resins such as alkyds, acrylics, vinyl-acrylics, vinyl acetate/ethylene (VAE), polyurethanes, polyesters, melamine resins, epoxy, silanes or siloxanes or oils.

Binders can be categorized according to the mechanisms for film formation. Thermoplastic mechanisms include drying and coalescence. Drying refers to simple evaporation of the solvent or thinner to leave a coherent film behind. Coalescence refers to a mechanism that involves drying followed by actual interpenetration and fusion of formerly discrete particles. Thermoplastic film-forming mechanisms are sometimes described as “thermoplastic cure” but that is a misnomer because no chemical curing reactions are required to knit the film. Thermosetting mechanisms, on the other hand, are true curing mechanism that involve chemical reaction(s) among the polymers that make up the binder.[9]

Thermoplastic mechanisms: Some films are formed by simple cooling of the binder. For example, encaustic or wax paints are liquid when warm, and harden upon cooling. In many cases, they resoften or liquify if reheated.

Paints that dry by solvent evaporation and contain the solid binder dissolved in a solvent are known as lacquers. A solid film forms when the solvent evaporates. Because no chemical crosslinking is involved, the film can re-dissolve in solvent; as such, lacquers are unsuitable for applications where chemical resistance is important. Classic nitrocellulose lacquers fall into this category, as do non-grain raising stains composed of dyes dissolved in solvent. Performance varies by formulation, but lacquers generally tend to have better UV resistance and lower corrosion resistance than comparable systems that cure by polymerization or coalescence.

The paint type known as Emulsion in the UK and Latex in the United States is a water-borne dispersion of sub-micrometer polymer particles. These terms in their respective countries cover all paints that use synthetic polymers such as acrylic, vinyl acrylic (PVA), styrene acrylic, etc. as binders.[10] The term “latex” in the context of paint in the United States simply means an aqueous dispersion; latex rubber from the rubber tree is not an ingredient. These dispersions are prepared by emulsion polymerization. Such paints cure by a process called coalescence where first the water, and then the trace, or coalescing, solvent, evaporate and draw together and soften the binder particles and fuse them together into irreversibly bound networked structures, so that the paint cannot redissolve in the solvent/water that originally carried it. The residual surfactants in paint, as well as hydrolytic effects with some polymers cause the paint to remain susceptible to softening and, over time, degradation by water. The general term of latex paint is usually used in the United States, while the term emulsion paint is used for the same products in the UK and the term latex paint is not used at all.

Thermosetting mechanisms: Paints that cure by polymerization are generally one- or two-package coatings that polymerize by way of a chemical reaction, and cure into a crosslinked film. Depending on composition they may need to dry first, by evaporation of solvent. Classic two-package epoxies or polyurethanes would fall into this category.[11]

The “drying oils”, counter-intuitively, actually cure by a crosslinking reaction even if they are not put through an oven cycle and seem to simply dry in air. The film formation mechanism of the simplest examples involve first evaporation of solvents followed by reaction with oxygen from the environment over a period of days, weeks and even months to create a crosslinked network.[5] Classic alkyd enamels would fall into this category. Oxidative cure coatings are catalyzed by metal complex driers such as cobalt naphthenate.

Recent environmental requirements restrict the use of volatile organic compounds (VOCs), and alternative means of curing have been developed, generally for industrial purposes. UV curing paints, for example, enable formulation with very low amounts of solvent, or even none at all. This can be achieved because of the monomers and oligomers used in the coating have relatively very low molecular weight, and are therefore low enough in viscosity to enable good fluid flow without the need for additional thinner. If solvent is present in significant amounts, generally it is mostly evaporated first and then crosslinking is initiated by ultraviolet light. Similarly, powder coatings contain little or no solvent. Flow and cure are produced by heating of the substrate after electrostatic application of the dry powder.[12]

Combination mechanisms: So-called “catalyzed” lacquers” or “crosslinking latex” coatings are designed to form films by a combination of methods: classic drying plus a curing reaction that benefits from the catalyst. There are paints called plastisols/organosols, which are made by blending PVC granules with a plasticiser. These are stoved and the mix coalesces.

Diluent or solvent or thinner

The main purposes of the diluent are to dissolve the polymer and adjust the viscosity of the paint. It is volatile and does not become part of the paint film. It also controls flow and application properties, and in some cases can affect the stability of the paint while in liquid state. Its main function is as the carrier for the non volatile components. To spread heavier oils (for example, linseed) as in oil-based interior house paint, a thinner oil is required. These volatile substances impart their properties temporarily—once the solvent has evaporated, the remaining paint is fixed to the surface.

This component is optional: some paints have no diluent.

Water is the main diluent for water-borne paints, even the co-solvent types.

Solvent-borne, also called oil-based, paints can have various combinations of organic solvents as the diluent, including aliphatics, aromatics, alcohols, ketones and white spirit. Specific examples are organic solvents such as petroleum distillate, esters, glycol ethers, and the like. Sometimes volatile low-molecular weight synthetic resins also serve as diluents.

Pigment and filler

Pigments are granular solids incorporated in the paint to contribute color. Fillers are granular solids incorporate to impart toughness, texture, give the paint special properties,[13] or to reduce the cost of the paint. Alternatively, some paints contain dyes instead of or in combination with pigments.

Pigments can be classified as either natural or synthetic. Natural pigments include various clays, calcium carbonate, mica, silicas, and talcs. Synthetics would include engineered molecules, calcined clays, blanc fixe, precipitated calcium carbonate, and synthetic pyrogenic silicas.

Hiding pigments, in making paint opaque, also protect the substrate from the harmful effects of ultraviolet light. Hiding pigments include titanium dioxide, phthalo blue, red iron oxide, and many others.

Fillers are a special type of pigment that serve to thicken the film, support its structure and increase the volume of the paint. Fillers are usually cheap and inert materials, such as diatomaceous earth, talc, lime, barytes, clay, etc. Floor paints that must resist abrasion may contain fine quartz sand as a filler. Not all paints include fillers. On the other hand, some paints contain large proportions of pigment/filler and binder.

Some pigments are toxic, such as the lead pigments that are used in lead paint. Paint manufacturers began replacing white lead pigments with titanium white (titanium dioxide), before lead was banned in paint for residential use in 1978 by the US Consumer Product Safety Commission. The titanium dioxide used in most paints today is often coated with silica/alumina/zirconium for various reasons, such as better exterior durability, or better hiding performance (opacity) promoted by more optimal spacing within the paint film.[14]

Micaceous iron oxide (MIO) is another alternative to lead for protection of steel, giving more protection against water and light damage than most paints. When MIO pigments are ground into fine particles, most cleave into shiny layers, which reflect light, thus minimising UV degradation and protecting the resin binder. Most pigments used in paint tend to be spherical, but lamellar pigments, such as glass flake and MIO have overlapping plates, which impede the path of water molecules.[15] For optimum performance MIO should have a high content of thin flake-like particles resembling mica. ISO 10601 sets two levels of MIO content.[16] MIO is often derived from a form of hematite.

Additives

Besides the three main categories of ingredients, paint can have a wide variety of miscellaneous additives, which are usually added in small amounts, yet provide a significant effect on the product. Some examples include additives to modify surface tension, improve flow properties, improve the finished appearance, increase wet edge, improve pigment stability, impart antifreeze properties, control foaming, control skinning, etc. Other types of additives include catalysts, thickeners, stabilizers, emulsifiers, texturizers, adhesion promoters, UV stabilizers, flatteners (de-glossing agents), biocides to fight bacterial growth, and the like.

Additives normally do not significantly alter the percentages of individual components in a formulation.[17]

Color-changing paint

Various technologies exist for making paints that change color. Thermochromic paints and coatings contain materials that change conformation when heat is applied or removed, and so they change color. Liquid crystals have been used in such paints, such as in the thermometer strips and tapes used in aquaria and novelty/promotional thermal cups and straws. These materials are used to make eyeglasses.

Color-changing paints can also be made by adding halochrome compounds or other organic pigments. One patent[18] cites use of these indicators for wall coating applications for light colored paints. When the paint is wet it is pink in color but upon drying it regains its original white color. As cited in patent, this property of the paint enabled two or more coats to be applied on a wall properly and evenly. The previous coats having dried would be white whereas the new wet coat would be distinctly pink. Ashland Inc. introduced foundry refractory coatings with similar principle in 2005[19][20] for use in foundries.

Electrochromic paints change color in response to an applied electric current. Car manufacturer Nissan has been reportedly working on an electrochromic paint, based on particles of paramagnetic iron oxide. When subjected to an electromagnetic field the paramagnetic particles change spacing, modifying their color and reflective properties. The electromagnetic field would be formed using the conductive metal of the car body.[21] Electrochromic paints can be applied to plastic substrates as well, using a different coating chemistry. The technology involves using special dyes that change conformation when an electric current is applied across the film itself. This new technology has been used to achieve glare protection at the touch of a button in passenger airplane windows.

Art

Watercolors as applied with a brush

Since the time of the Renaissance, siccative (drying) oil paints, primarily linseed oil, have been the most commonly used kind of paints in fine art applications; oil paint is still common today. However, in the 20th century, water-based paints, including watercolors and acrylic paints, became very popular with the development of acrylic and other latex paints. Milk paints (also called casein), where the medium is derived from the natural emulsion that is milk, were popular in the 19th century and are still available today. Egg tempera (where the medium is an emulsion of raw egg yolk mixed with oil) is still in use as well, as are encaustic wax-based paints. Gouache is a variety of opaque watercolor that was also used in the Middle Ages and Renaissance for manuscript illuminations. The pigment was often made from ground semiprecious stones such as lapis lazuli and the binder made from either gum arabic or egg white. Gouache, also known as ‘designer color’ or ‘body color’ is commercially available today.

Poster paint has been used primarily in the creation of student works, or by children.

The “painter’s mussel“, a European freshwater mussel. Individual shell valves were used by artists as a small dish for paint.

Application

Paint can be applied as a solid, a gaseous suspension (aerosol) or a liquid. Techniques vary depending on the practical or artistic results desired.

As a solid (usually used in industrial and automotive applications), the paint is applied as a very fine powder, then baked at high temperature. This melts the powder and causes it to adhere to the surface. The reasons for doing this involve the chemistries of the paint, the surface itself, and perhaps even the chemistry of the substrate (the object being painted). This is called “powder coating” an object.

As a gas or as a gaseous suspension, the paint is suspended in solid or liquid form in a gas that is sprayed on an object. The paint sticks to the object. This is called “spray painting” an object. The reasons for doing this include:

  • The application mechanism is air and thus no solid object touches the object being painted;
  • The distribution of the paint is uniform, so there are no sharp lines;
  • It is possible to deliver very small amounts of paint;
  • A chemical (typically a solvent) can be sprayed along with the paint to dissolve together both the delivered paint and the chemicals on the surface of the object being painted;
  • Some chemical reactions in paint involve the orientation of the paint molecules.

In the liquid application, paint can be applied by direct application using brushes, paint rollers, blades, scrapers, other instruments, or body parts such as fingers and thumbs.

Rollers generally have a handle that allows for different lengths of poles to be attached, allowing painting at different heights. Generally, roller application requires two coats for even color. A roller with a thicker nap is used to apply paint on uneven surfaces. Edges are often finished with an angled brush.

  • Using the finish flat one would most likely use a 1/2″ nap roller
  • Using the finish eggshell one would most likely use a 3/8″ nap roller
  • Using the finish satin or pearl one would most likely use a 3/8″ nap roller
  • Using the finish semi-gloss or gloss one would most likely use a 3/16″ nap roller

[22]

After liquid paint is applied, there is an interval during which it can be blended with additional painted regions (at the “wet edge”) called “open time”. The open time of an oil or alkyd-based emulsion paint can be extended by adding white spirit, similar glycols such as Dowanol (propylene glycol ether) or open time prolongers. This can also facilitate the mixing of different wet paint layers for aesthetic effect. Latex and acrylic emulsions require the use of drying retardants suitable for water-based coatings.

Paint application by spray is the most popular method in industry. In this, paint is aerosolized by the force of compressed air or by the action of high pressure compression of the paint itself, and the paint is turned into small droplets that travel to the article to be painted. Alternate methods are airless spray, hot spray, hot airless spray, and any of these with an electrostatic spray included. There are numerous electrostatic methods available.

Dipping used to be the norm for objects such as filing cabinets, but this has been replaced by high speed air turbine driven bells with electrostatic spray. Car bodies are primed using cathodic elephoretic primer, which is applied by charging the body depositing a layer of primer. The unchanged residue is rinsed off and the primer stoved.

Many paints tend to separate when stored, the heavier components settling to the bottom, and require mixing before use. Some paint outlets have machines for mixing the paint by shaking the can vigorously for a few minutes.

The opacity and the film thickness of paint may be measured using a drawdown card.

Water-based paints tend to be the easiest to clean up after use; the brushes and rollers can be cleaned with soap and water.

Proper disposal of left over paint is a challenge. Sometimes it can be recycled: Old paint may be usable for a primer coat or an intermediate coat, and paints of similar chemistry can be mixed to make a larger amount of a uniform color.

To dispose of paint it can be dried and disposed of in the domestic waste stream, provided that it contains no prohibited substances (see container). Disposal of liquid paint usually requires special handling and should be treated as hazardous waste, and disposed of according to local regulations.[23][24]

Product variants

A collection of cans of paint and variants

A huge collection of different kinds of spray cans, markers, paints and inks in the underground graffiti shop. Russia, Tver City, 2011.
  • Primer is a preparatory coating put on materials before applying the paint itself. The primed surface ensures better adhesion of the paint, thereby increasing the durability of the paint and providing improved protection for the painted surface. Suitable primers also may block and seal stains, or hide a color that is to be painted over.
  • Emulsion paints are water-based paints in which the paint material is dispersed in a liquid that consists mainly of water. For suitable purposes this has advantages in fast drying, low toxicity, low cost, easier application, and easier cleaning of equipment, among other factors.
  • Flat Finish paint is generally used on ceilings or walls that are in bad shape. This finish is useful for hiding imperfections in walls and it is economical in effectively covering relatively great areas. However this finish is not easily washable and is subject to staining.
  • Matte Finish is generally similar to flat finish, but such paints commonly offer superior washability and coverage. (See Gloss and matte paint.)
  • Eggshell Finish has some sheen, supposedly like that of the shell on an egg. This finish provides great washability, but is not very effective at hiding imperfections on walls and similar surfaces. Eggshell finish is valued for bathrooms because it is washable and water repellent, so that it tends not to peel in a wet environment.
  • Pearl (Satin) Finish is very durable in terms of washability and resistance to moisture, even in comparison to eggshell finish. It protects walls from dirt, moisture and stains. Accordingly, it is exceptionally valuable for bathrooms, furniture, and kitchens, but it is shinier than eggshell, so it is even more prone to show imperfections.
  • Semi-Gloss Finish typically is used on trim to emphasise detail and elegance, and to show off woodwork, such as on doors and furniture. It provides a shiny surface and provides good protection from moisture and stains on walls. Its gloss does however emphasise imperfections on the walls and similar surfaces. It is popular in schools and factories where washability and durability are the main considerations.[25]
  • Varnish and shellac are in effect paints without pigment; they provide a protective coating without substantially changing the color of the surface, though they can emphasise the colour of the material.
  • Wood stain is a type of paint that is formulated to be very “thin”, meaning low in viscosity, so that the pigment soaks into a material such as wood rather than remaining in a film on the surface. Stain is mainly dissolved pigment or dye plus binder material in solvent. It is designed to add color without providing a surface coating.
  • Lacquer is a solvent-based paint or varnish that produces an especially hard, durable finish. Usually it is a rapidly drying formulation.
  • Enamel paint is formulated to give an especially hard, usually glossy, finish. Some enamel paints contain fine glass powder or metal flake instead of the color pigments in standard oil-based paints. Enamel paint sometimes is mixed with varnish or urethane to improve its shine and hardness.
  • A glaze is an additive used with paint to slow drying time and increase translucency, as in faux painting and for some artistic effects.
  • A roof coating is a fluid that sets as an elastic membrane that can stretch without harm. It provides UV protection to polyurethane foam and is widely used in roof restoration.
  • Fingerpaints are formulations suitable for application with the fingers; they are popular for use by children in primary school activities.
  • Inks are similar to paints, except that they are typically made using finely ground pigments or dyes, and are not designed to leave a thick film of binder. They are used largely for writing or calligraphy.
  • Anti-graffiti coatings are used to defeat the marking of surfaces by graffiti artists or vandals. There are two categories of anti-graffiti coatings: sacrificial and non-bonding:
  • Sacrificial coatings are clear coatings that allow the removal of graffiti, usually by washing the surface with high-pressure water that removes the graffiti together with the coating (hence the term “sacrificial”). After removal of the graffiti, the sacrificial coating must be re-applied for continued protection. Such sacrificial protective coatings are most commonly used on natural-looking masonry surfaces, such as statuary and marble walls, and on rougher surfaces that are difficult to clean.
  • Non-bonding coatings are clear, high-performance coatings, usually catalyzed polyurethanes, that do not bond strongly to paints used for graffiti. Graffiti on such a surface can be removed with a solvent wash, without damaging either the underlying surface or the protective non-bonding coating. These coatings work best on smooth surfaces, and are especially useful on decorative surfaces such as mosaics or painted murals, which might be expected to suffer harm from high pressure sprays.
  • Anti-climb paint is a non-drying paint that appears normal but is extremely slippery. It is useful on drainpipes and ledges to deter burglars and vandals from climbing them, and is found in many public places. When a person attempts to climb objects coated with the paint, it rubs off onto the climber, as well as making it hard for them to climb.
  • Anti-fouling paint, or bottom paint, prevents barnacles and other marine organisms from adhering to the hulls of ships.
  • Insulative paint or insulating paint, reduces the rate of thermal transfer through a surface it’s applied to. One type of formulation is based on the addition of hollow microspheres to any suitable type of paint.
  • Anti-slip paint contains chemicals or grit to increase the friction of a surface so as to decrease the risk of slipping, particularly in wet conditions.
  • Road marking paint[26] is specially used to marking and painting road traffic signs and lines, to form a durable coating film on the road surface. It must be fast drying, provide a thick coating, and resist wear and slipping, especially in wet conditions.
  • Luminous paint or luminescent paint is paint that exhibits luminescence. In other words, it gives off visible light through fluorescence, phosphorescence, or radioluminescence.

Failure

The main reasons of paint failure after application on surface are the applicator and improper treatment of surface.

Defects or degradation can be attributed to:

Dilution
This usually occurs when the dilution of the paint is not done as per manufacturers recommendation. There can be a case of over dilution and under dilution, as well as dilution with the incorrect diluent.
Contamination
Foreign contaminants added without the manufacturers consent can cause various film defects.
Peeling/Blistering
Most commonly due to improper surface treatment before application and inherent moisture/dampness being present in the substrate. The degree of blistering can be assessed according to ISO 4628 Part 2 or ASTM Method D714 (Standard Test Method for Evaluating Degree of Blistering of Paints).
Chalking
Chalking is the progressive powdering of the paint film on the painted surface. The primary reason for the problem is polymer degradation of the paint matrix due to exposure of UV radiation in sunshine and condensation from dew. The degree of chalking varies as epoxies react quickly while acrylics and polyurethanes can remain unchanged for long periods.[27] The degree of chalking can be assessed according to International Standard ISO 4628 Part 6 or 7 or American Society of Testing and Materials(ASTM) Method D4214 (Standard Test Methods for Evaluating the Degree of Chalking of Exterior Paint Films).
Cracking
Cracking of paint film is due to the unequal expansion or contraction of paint coats. It usually happens when the coats of the paint are not allowed to cure/dry completely before the next coat is applied. The degree of cracking can be assessed according to International Standard ISO 4628 Part 4 or ASTM Method D661 (Standard Test Method for Evaluating Degree of Cracking of Exterior Paints).
Erosion
Erosion is very quick chalking. It occurs due to external agents like air, water etc. It can be evaluated using ASTM Method ASTM D662 (Standard Test Method for Evaluating Degree of Erosion of Exterior Paints). The generation of acid by fungal species can be a significant component of erosion of painted surfaces.[28] The fungus Aureobasidium pullulans is known for damaging wall paints.[29]

Dangers

Volatile organic compounds (VOCs) in paint are considered harmful to the environment and especially for people who work with them on a regular basis. Exposure to VOCs has been related to organic solvent syndrome, although this relation has been somewhat controversial.[30] The controversial solvent 2-butoxyethanol is also used in paint production.[31]

In the US, environmental regulations, consumer demand, and advances in technology led to the development of low-VOC and zero-VOC paints and finishes. These new paints are widely available and meet or exceed the old high-VOC products in performance and cost-effectiveness while having significantly less impact on human and environmental health.[citation needed]

A polychlorinated biphenyl (PCB) was reported ( published in 2009 ) in air samples collected in Chicago, Philadelphia, the Arctic, and several sites around the Great Lakes. PCB is a global pollutant and was measured in the wastewater effluent from paint production. The widespread distribution of PCB suggests volatilization of this compound from surfaces, roofs etc. PCB is present in consumer goods including newspapers, magazines, and cardboard boxes, which usually contain color pigments. Therefore, exist hypothesis that PCB congeners are present as byproduct in some current commercial pigments.[32]

See also

References

 

 

Further reading

FASHION

FASHION

Every person nurtures an innate desire of looking good and feel ‘accepted’ in the sociol-economic circle. The word fashion instantaneously brings to mind a flash of colour with a dash of glamour.

Women are taking to fashion in a big way, and are experimenting with different looks, styles, and textures.

Fashion plays an increasingly important role in an indivi­dual’s life because it is considered as a means of self-expression. The garments and accessories that man or women wear, help them to identify with a group of others-whether it is a lifestyle, profession, a religion, or an attitude. Thus, the term ‘fashion’ has become synonymous with the overall growth of the country as well.

Several factors contribute to the evolution of fashion as a whole. It is a widely accepted fact that the rich and the famous, and the political figures and royalty have always moved the seasonal trends of fashion. The advertising media also contributes equally to update us about the daily style checks.

Fashion in India, a land rich in culture and tradition, has evolved through the centuries. This country, rich in culture represents a kaleidoscope of changing trends and traditions. Here, clothes perform different functions depending on the occasion. Be it festivals, parties, profession, or just a matter of reflecting attitude … fashion is simply ‘in’.

Right from women who sport a dash of vermilion in the parting of their hair, to professionals on the go who wield the ladle and the laptop with equal ease, fashion forms an integral 92 Top School Essays

part of their lives. Today, fashion does not necessarily mean glamour, or the urge to follow the current trends. It is more a way of life, a reflection of inner beauty, where the intellect shines through, complete with comfort quotient.

Fashion not only highlights the social history and the needs of person but also the overall cultural aesthetic of the various periods. The evolution of fashion dates back to several hundred years and as our attitude and culture change, fashion comes along with it.

In India, the fashion scenario was different in different political periods. During the British rule in India, the fashion trend within high society was strongly influenced by the British fashion style and western clothes became a status symbol in India.

Again during 1930s, emergence of different ideologies like communism, socialism and fascism imparted a more feminine and conservative touch to the women’s fashion.

However, the period also witnessed the predominance of body hugging dresses with dark shades. The foundation of the Indian cinema also proved to be the strongest influence on revolutionising the fashion scene in those days.

1940s was a decade marked by the second World War and the ensuing independence of India. Hence, the period portrayed relatively simple yet functional women’s clothing.

During 1950s, the advent of art colleges and schools led to popularity of narrow waist and balloon skirts with bouncing patterns. Also, the adoption of khadi by Mahatma Gandhi made khadi garments a rage among women.

In the 1960s, the sweeping changes in fashion and lifestyle resulted in highly versatile fashion trends. In 1970s, the traditional materials were exported in bulk to other nations.

Thus, excess of export materials were sold within the country itself, which resulted in popularity of international fashion in India.

During 1980s and 90s, the advent of television and other advertising means gave a new edge to the Indian fashion scene. Influenced by ideas of several foreign designers, new design and pattern were introduced into garments.

During these periods, power dressing and corporate look were the style statement. The revival of ethnicity was also witnessed in these decades.

Fashion trends keep changing and most fashion divas and models are the one to make them. The youth is a major follower of fashion trends. Fashion trends also get influenced from Bollywood as well as Hollywood. Metros like Mumbai and Delhi witness the quick changes in fashion especially in college going crowds.

India has a rich and varied textile heritage, where each region of India has its own unique native costume and traditional attire. While traditional clothes are still worn in most of rural India, urban India is changing rapidly, with international fashion trends reflected by the young and glamorous, in the cosmopolitan metros of India.

Fashion in India is a vibrant scene, a nascent industry and a colourful and glamorous world where designers and models start new trends every day.

While previously a master weaver was recognised for his skill, today a fashion designer is celebrated for his or her creativity. Young urban Indians can choose from the best of East and West as Indian fashion designers are inspired by both Indian and western styles. This fusion of fashion can be seen

Fashion in India is also beginning to make its mark on the international scene, as accessories such as bindis (red dots worn on the forehead), mehendi (designs made by applying henna to the palms of the hands and other parts of the body) and bangles, have gained international popularity, after being worn by fashion icons, like the pop singers Madonna and Gwen Stefani.

In India, fashion has become a growing industry with international events such as the India Fashion Week and annual shows by fashion designers in the major cities of India.

The victories of a number of Indian beauty queens in International events such as the Miss World and Miss Universe contests have also made Indian models recognised worldwide.

Fashion designers such as Ritu Kumar, Ritu Beri, Rohit Bal, Rina Dhaka, Muzaffar Ah, Satya Paul, Abraham and Thakore, Tarun Tahiliani, JJ Valaya and Manish Malhotra are some of the well- known fashion designers in India.

In India, fashion covers a whole range of clothing from ornate clothes designed for wedding ceremonies to pret lines, sports wear and casual wear.

Traditional Indian techniques of embroidery such as chikhan, crewel and zardosi, and traditional weaves and fabrics have been used by Indian designers to create Indo-western clothing in a fusion of the best of East and West.

Traditional costumes in India vary widely depending on the climate and natural fibres grown in a region. In the cold northern state of Jammu and Kashmir, people wear a thick loose shirt called a phiran to keep them warm.

In the tropical warmth of south India, men wear a sarong like garment called the mundu, while women drape 5 metres of cloth around their bodies in the graceful folds of the saree. Sarees are woven in silk, cotton and artificial fibres. Kanjivaram, Mysore, Paithani, Pochampalli, Jamdani, Balucheri, Benarasi, Sambalpuri,

Bandhini are some varieties of beautiful sarees from different regions of India. In the dry regions of Rajasthan and Gujarat men wrap and twist a length of cloth in the form of a dhoti around their lower limbs and a shirt-like kurta above.

Colourful turbans complete the picture. In the northeastern regions the tribal communities such as Khasis, Nagas, Mizos, Manipuris and Arunachalis wear colourful woven sarong-like clothing and woven shawls that represent the identity of each tribal group.

In urban India the salwar kameez and the churidar kameez, are commonly work by women and the saree is worn on formal occasions. Men wear kurtas and pajamas, or a sherwani for formal wear. Men commonly wear western wear such as shirts and trousers across India.

The young and the young at heart wear Jeans, T-shirts, capris, Bermudas and various kinds of casual clothing, which are the trendsetters of fashion in India.

Comparing the past and the present, fashion for people in India has changed over the decades. Not only India, but also the whole world has witnessed changes in fashion statements for both men and women.

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STORY

STORY

Your business is in deep mud. Not just metaphorically speaking, but for real. The building’s very foundations have started sinking in slime. Best case scenario: your contractor actually takes responsibility for the mess and doesn’t evaporate into thin air, but he is still at a loss. Yes, he has heard about such cases, but has no idea what to do about it. He knows how to construct buildings, but has no idea how to pull them out of the mud. He tries to joke about it, but you are hardly in the mood.

You start sustaining losses. One thing’s for sure: you haven’t much time. You must decide quickly. You wake up each morning and go through the few options you have left. Actually, the option of letting the entire building sink into the mud sounds rather attractive this morning. What the , the entire area seems to lie on one big bog. In fact, you have seen endless neighboring buildings come down, so what on earth made you think it couldn’t happen to you? But that inner voice of yours doesn’t let you give up. Not just yet, anyway.

The second option is to let that huge contractor company help you. After all they are a brand name. They sell. They have spacious offices. Their sales rep has already met with you once. He parked his shiny car far away, careful not to soil it with mud. Throughout your conversation – if his sales pitch could be termed as such – you couldn’t but notice the effort you were making to believe him. To really and truly believe, that is. “The best workers in the business,” he said. “Committed to the highest standards in a variety of technologies,” he added. At some point he even emitted, “a company based on values, in which the client is part of the family.”

it. If only you were one of those people who let sales people sweep them off their feet, you might actually be happy. But unfortunately for you, you are not one of those people. You are one of those miserables who need only take one look at a person and know straight away that “this person hasn’t the faintest idea what he is talking about.”

This morning the situation is somewhat different. “Sustaining losses” no longer describes the problem sufficiently and when the bank manager calls she no longer sounds accommodating. So it’s safe to say you have understood the situation, right? Not a good one. Actually, pretty bad, is more like it.

You heard about that little company quite some time ago. In fact, you heard about it from a number of sources, but you have never really spoken to them. Why? Mainly because you prefer working with big companies. On any other day you would be the first to explain to anyone willing to listen why working with a boutique company isn’t suitable for a company of your scale. However, at this very moment, one of your load-bearing walls appears to be on the verge of collapse.

When you dial the number, sweat pours down your back, and you try to convince yourself that this cannot be the last resort, but your fingers are crossed when you hear the dial tone, and inside you are praying: Let it work! Let it work!

The very next day the manager himself shows up on a bike and parks it really close by. Right in the middle of all the mud.

You say hello and start relating the building’s history.

“Okay, gotcha,” he cuts you off after a minute. “Let’s just go inside and see what things are like,” he says calmly. He is the first one to ask to come in.

You try leading him, but he soon overtakes you and disappears into the innermost rooms. Never before in your life have you seen somebody who seems to know his way around your dilapidated building and in no time. After a while he comes back.

“So what do you think?” you venture. You would usually also add, “And don’t make it prettier than it is,” but with this guy you feel there is no need. He is not going to beat around the bush with you.

“Listen, things are pretty up here,” he says without a trace of humor while looking at the load-bearing wall. He knocks on it and half the coating peels off. “I’ve seen worse,” he adds, and by his look you know he is not lying. After a few seconds he says, “Okay, we will take on the job.”

He is so crazily self-confident – a trait belonging either to charlatans or to the very best professionals, you wonder to yourself – that you realize it is up to you to decide whether the guy standing before you is the former or latter.

“Just a moment,” you suddenly take fright, “how much will it cost?”

While he is busy jotting down numbers, you pray that it won’t be expensive. They are a small company after all, so please let it be cheap. He shows you the figure and your stomach does summersaults. He doesn’t wait for you to react, but continues: “We are really good,” and smiles for the first time. Suddenly you realize that the son-of-a- really loves his job. “We will begin tomorrow,” he says, “There is no time to lose. I am going to prepare the work plans. Be by us at 8:00 sharp. Don’t be late.“

You are in a complete daze but somehow manage to say something like, “Oh, okay, yeah sure, I won’t be late. See you in the morning” and he turns around and leaves.

After a few minutes, when you come out of your trance, you feel like shouting after him that you don’t really need him and who the does he think he is and that it’s better working with the big companies. Because they have a standard of values, that is – their values are a standard, that is the best workers in the market are their family, in other words – never mind – they have spacious offices!

True, you must admit to yourself, their clientele list is far more impressive than that of any other company you have heard of, and yet… And yet…

At the end you take a deep breath. And another one. And then you feel something strange. And you ask yourself whether it’s that headache again, caused by the pressure you have been feeling for the past months, but it’s not that. Or perhaps it’s those stomach cramps caused by the fear that everything might soon come to an end? But it isn’t that either.

You haven’t felt like this in a long time, but by now you know exactly what it is you are feeling, although you are still too embarrassed to admit it to yourself. So your inner voice says it out loud for you: You are simply – calm.

Your business is in deep mud. The entire building has started sinking. Not really, only metaphorically speaking.

 

THE GREAT GARBAGE PATCH

 

The Great Pacific garbage patch, also described as the Pacific trash vortex, is a gyre of marine debris particles in the central North Pacific Ocean discovered between 1985 and 1988. It is located roughly between 135°W to 155°W and 35°N to 42°N.[1] The collection of plastic, floating trash halfway between Hawaii and California[2] extends over an indeterminate area of widely varying range depending on the degree of plastic concentration used to define the affected area.

The patch is characterized by exceptionally high relative pelagic concentrations of plastic, chemical sludge, and other debris that have been trapped by the currents of the North Pacific Gyre.[3] Despite the common public image of islands of floating rubbish, its low density (4 particles per cubic meter) prevents detection by satellite imagery, or even by casual boaters or divers in the area. It consists primarily of an increase in suspended, often microscopic, particles in the upper water column.

The Great Pacific garbage patch was described in a 1988 paper published by the National Oceanic and Atmospheric Administration (NOAA) of the United States. The description was based on results obtained by several Alaska-based researchers in 1988 that measured neustonic plastic in the North Pacific Ocean.[4] Researchers found relatively high concentrations of marine debris accumulating in regions governed by ocean currents. Extrapolating from findings in the Sea of Japan, the researchers hypothesized that similar conditions would occur in other parts of the Pacific where prevailing currents were favorable to the creation of relatively stable waters. They specifically indicated the North Pacific Gyre.[5]

Charles J. Moore, returning home through the North Pacific Gyre after competing in the Transpacific Yacht Race in 1997, claimed to have come upon an enormous stretch of floating debris. Moore alerted the oceanographer Curtis Ebbesmeyer, who subsequently dubbed the region the “Eastern Garbage Patch” (EGP).[6] The area is frequently featured in media reports as an exceptional example of marine pollution.[7]

The Pacific garbage patch is not easily seen from the sky, because the plastic is dispersed over a large area. Researchers from The Ocean Cleanup have found the patch to cover an area of 1.6 million square kilometers. The plastic concentration is estimated to be up to 100 kilograms per square kilometer in the center of the patch, going down to 10 kilograms per square kilometer in the outer parts of the patch. There is an estimate of 80,000 metric tons of plastic in the patch, totalling 1.8 trillion pieces. When accounting for the total mass, 92% of the debris found in the patch consists of objects larger than 0.5 centimeters. [8]

A similar patch of floating plastic debris is found in the Atlantic Ocean, called the North Atlantic garbage patch.

Image result for about the great pacific garbage patch

CLOCK

CLOCK

Related image

A clock is an instrument to measure, keep, and indicate time. The clock is one of the oldest human inventions, meeting the need to measure intervals of time shorter than the natural units: the day, the lunar month, and the year. Devices operating on several physical processes have been used over the millennia.

Some predecessors to the modern clock may be considered as “clocks” that are based on movement in nature: A sundial shows the time by displaying the position of a shadow on a flat surface. There is a range of duration timers, a well-known example being the hourglass. Water clocks, along with the sundials, are possibly the oldest time-measuring instruments. A major advance occurred with the invention of the verge escapement, which made possible the first mechanical clocks around 1300 in Europe, which kept time with oscillating timekeepers like balance wheels.[1][2][3][4]

A silent instrument missing such a striking mechanism has traditionally been known as a timepiece.[5] In general usage today, a “clock” refers to any device for measuring and displaying the time. Watches and other timepieces that can be carried on one’s person are often distinguished from clocks.[6] Spring-driven clocks appeared during the 15th century. During the 15th and 16th centuries, clockmaking flourished. The next development in accuracy occurred after 1656 with the invention of the pendulum clock. A major stimulus to improving the accuracy and reliability of clocks was the importance of precise time-keeping for navigation. The electric clock was patented in 1840. The development of electronics in the 20th century led to clocks with no clockwork parts at all.

The timekeeping element in every modern clock is a harmonic oscillator, a physical object (resonator) that vibrates or oscillates at a particular frequency.[2] This object can be a pendulum, a tuning fork, a quartz crystal, or the vibration of electrons in atoms as they emit microwaves.

Clocks have different ways of displaying time, connected to its internal clockwork type: Analog clocks usually indicate time using angles. Digital clocks display a numeric representation of time. Two numeric display formats are commonly used on digital clocks: 24-hour notation and 12-hour notation. Most digital clocks use electronic mechanisms and LCD, LED, or VFD displays. For convenience, distance, telephony or blindness, auditory clocks present the time as sounds. There are also clocks for the blind that have displays that can be read by using the sense of touch. Some of these are similar to normal analog displays, but are constructed so the hands can be felt without damaging them. The evolution of the technology of clocks continues today. The study of timekeeping is known as horology.

History

Etymology

The word clock is derived (via Dutch, Northern French, and Medieval Latin) from the Celtic words clagan and clocca meaning “bell“.

Time-measuring devices

Sundials

Simple horizontal sundial

The apparent position of the Sun in the sky moves over the course of each day, reflecting the rotation of the Earth. Shadows cast by stationary objects move correspondingly, so their positions can be used to indicate the time of day. A sundial shows the time by displaying the position of a shadow on a (usually) flat surface, which has markings that correspond to the hours.[7] Sundials can be horizontal, vertical, or in other orientations. Sundials were widely used in ancient times.[8] With the knowledge of latitude, a well-constructed sundial can measure local solar time with reasonable accuracy, within a minute or two. Sundials continued to be used to monitor the performance of clocks until the modern era.[citation needed] However, practical limitations, such as that sundials only work well on relatively clear days, and never during the night, encouraged the development of other techniques for measuring and displaying time. The Jantar Mantar At Delhi and Jaipur are examples of sundials. They were built by Maharaja Jai Singh II.

Devices that measure duration, elapsed time and intervals

The flow of sand in an hourglass can be used to keep track of elapsed time.

Many devices can be used to mark passage of time without respect to reference time (time of day, minutes, etc.) and can be useful for measuring duration or intervals. Examples of such duration timers are candle clocks, incense clocks and the hourglass. Both the candle clock and the incense clock work on the same principle wherein the consumption of resources is more or less constant allowing reasonably precise and repeatable estimates of time passages. In the hourglass, fine sand pouring through a tiny hole at a constant rate indicates an arbitrary, predetermined, passage of time. The resource is not consumed but re-used.

Water

A scale model of Su Song‘s Astronomical Clock Tower, built in 11th century Kaifeng, China. It was driven by a large waterwheel, chain drive, and escapement mechanism.

Water clocks, also known as clepsydrae (sg: clepsydra), along with the sundials, are possibly the oldest time-measuring instruments, with the only exceptions being the vertical gnomon and the day counting tally stick.[9] Given their great antiquity, where and when they first existed is not known and perhaps unknowable. The bowl-shaped outflow is the simplest form of a water clock and is known to have existed in Babylon and in Egypt around the 16th century BC. Other regions of the world, including India and China, also have early evidence of water clocks, but the earliest dates are less certain. Some authors, however, write about water clocks appearing as early as 4000 BC in these regions of the world.[10]

Greek astronomer Andronicus of Cyrrhus supervised the construction of the Tower of the Winds in Athens in the 1st century B.C.[11] The Greek and Roman civilizations are credited for initially advancing water clock design to include complex gearing, which was connected to fanciful automata and also resulted in improved accuracy. These advances were passed on through Byzantium and Islamic times, eventually making their way back to Europe. Independently, the Chinese developed their own advanced water clocks(水鐘)in 725 A.D., passing their ideas on to Korea and Japan.

Some water clock designs were developed independently and some knowledge was transferred through the spread of trade. Pre-modern societies do not have the same precise timekeeping requirements that exist in modern industrial societies, where every hour of work or rest is monitored, and work may start or finish at any time regardless of external conditions. Instead, water clocks in ancient societies were used mainly for astrological reasons. These early water clocks were calibrated with a sundial. While never reaching the level of accuracy of a modern timepiece, the water clock was the most accurate and commonly used timekeeping device for millennia, until it was replaced by the more accurate pendulum clock in 17th-century Europe.

Islamic civilization is credited with further advancing the accuracy of clocks with elaborate engineering. In 797 (or possibly 801), the Abbasid caliph of Baghdad, Harun al-Rashid, presented Charlemagne with an Asian Elephant named Abul-Abbas together with a “particularly elaborate example” of a water[12] clock. Pope Sylvester II introduced clocks to northern and western Europe around 1000AD[13]

An elephant clock in a manuscript by Al-Jazari (1206 AD) from The Book of Knowledge of Ingenious Mechanical Devices.[14]

In the 13th century, Al-Jazari, an engineer from Mesopotamia (lived 1136–1206) who worked for Artuqid king of Diyar-Bakr, Nasir al-Din, made numerous clocks of all shapes and sizes. A book on his work described 50 mechanical devices in 6 categories, including water clocks. The most reputed clocks included the Elephant, Scribe and Castle clocks, all of which have been successfully reconstructed. As well as telling the time, these grand clocks were symbols of status, grandeur and wealth of the Urtuq State.[citation needed]

Early mechanical

The word horologia (from the Greek ὥρα, hour, and λέγειν, to tell) was used to describe early mechanical clocks,[15] but the use of this word (still used in several Romance languages) [16] for all timekeepers conceals the true nature of the mechanisms. For example, there is a record that in 1176 Sens Cathedral installed a ‘horologe[17] but the mechanism used is unknown. According to Jocelin of Brakelond, in 1198 during a fire at the abbey of St Edmundsbury (now Bury St Edmunds), the monks ‘ran to the clock’ to fetch water, indicating that their water clock had a reservoir large enough to help extinguish the occasional fire.[18] The word clock (from the Celtic words clocca and clogan, both meaning “bell”), which gradually supersedes “horologe”, suggests that it was the sound of bells which also characterized the prototype mechanical clocks that appeared during the 13th century in Europe.

A water-powered cogwheel clock was created in China in AD 725 by Yi Xing and Liang Lingzan. This is not considered an escapement mechanism clock as it was unidirectional, the Song dynasty polymath and genius Su Song (1020–1101) incorporated it into his monumental innovation of the astronomical clock-tower of Kaifeng in 1088.[19][page needed] His astronomical clock and rotating armillary sphere still relied on the use of either flowing water during the spring, summer, autumn seasons and liquid mercury during the freezing temperature of winter (i.e. hydraulics). A mercury clock, described in the Libros del saber, a Spanish work from 1277 consisting of translations and paraphrases of Arabic works, is sometimes quoted as evidence for Muslim knowledge of a mechanical clock. A mercury-powered cogwheel clock was created by Ibn Khalaf al-Muradi[20][21]

In Europe, between 1280 and 1320, there is an increase in the number of references to clocks and horologes in church records, and this probably indicates that a new type of clock mechanism had been devised. Existing clock mechanisms that used water power were being adapted to take their driving power from falling weights. This power was controlled by some form of oscillating mechanism, probably derived from existing bell-ringing or alarm devices. This controlled release of power—the escapement—marks the beginning of the true mechanical clock, which differed from the previously mentioned cogwheel clocks. Verge escapement mechanism derived in the surge of true mechanical clocks, which didn’t need any kind of fluid power, like water or mercury, to work.

These mechanical clocks were intended for two main purposes: for signalling and notification (e.g. the timing of services and public events), and for modeling the solar system. The former purpose is administrative, the latter arises naturally given the scholarly interests in astronomy, science, astrology, and how these subjects integrated with the religious philosophy of the time. The astrolabe was used both by astronomers and astrologers, and it was natural to apply a clockwork drive to the rotating plate to produce a working model of the solar system.

Simple clocks intended mainly for notification were installed in towers, and did not always require faces or hands. They would have announced the canonical hours or intervals between set times of prayer. Canonical hours varied in length as the times of sunrise and sunset shifted. The more sophisticated astronomical clocks would have had moving dials or hands, and would have shown the time in various time systems, including Italian hours, canonical hours, and time as measured by astronomers at the time. Both styles of clock started acquiring extravagant features such as automata.

In 1283, a large clock was installed at Dunstable Priory; its location above the rood screen suggests that it was not a water clock.[citation needed] In 1292, Canterbury Cathedral installed a ‘great horloge’. Over the next 30 years there are mentions of clocks at a number of ecclesiastical institutions in England, Italy, and France. In 1322, a new clock was installed in Norwich, an expensive replacement for an earlier clock installed in 1273. This had a large (2 metre) astronomical dial with automata and bells. The costs of the installation included the full-time employment of two clockkeepers for two years.[citation needed]

Astronomical

Richard of Wallingford pointing to a clock, his gift to St Albans Abbey.

16th-century clock machine Convent of Christ, Tomar, Portugal

Besides the Chinese astronomical clock of Su Song in 1088 mentioned above, in Europe there were the clocks constructed by Richard of Wallingford in St Albans by 1336, and by Giovanni de Dondi in Padua from 1348 to 1364. They no longer exist, but detailed descriptions of their design and construction survive,[22][23] and modern reproductions have been made.[23] They illustrate how quickly the theory of the mechanical clock had been translated into practical constructions, and also that one of the many impulses to their development had been the desire of astronomers to investigate celestial phenomena.

Wallingford’s clock had a large astrolabe-type dial, showing the sun, the moon’s age, phase, and node, a star map, and possibly the planets. In addition, it had a wheel of fortune and an indicator of the state of the tide at London Bridge. Bells rang every hour, the number of strokes indicating the time.[22] Dondi’s clock was a seven-sided construction, 1 metre high, with dials showing the time of day, including minutes, the motions of all the known planets, an automatic calendar of fixed and movable feasts, and an eclipse prediction hand rotating once every 18 years.[23] It is not known how accurate or reliable these clocks would have been. They were probably adjusted manually every day to compensate for errors caused by wear and imprecise manufacture. Water clocks are sometimes still used today, and can be examined in places such as ancient castles and museums. The Salisbury Cathedral clock, built in 1386, is considered to be the world’s oldest surviving mechanical clock that strikes the hours.[24]

Spring-driven

Renaissance Turret Clock, German, circa 1570

Spring driven Matthew Norman carriage clock with winding key

Clockmakers developed their art in various ways. Building smaller clocks was a technical challenge, as was improving accuracy and reliability. Clocks could be impressive showpieces to demonstrate skilled craftsmanship, or less expensive, mass-produced items for domestic use. The escapement in particular was an important factor affecting the clock’s accuracy, so many different mechanisms were tried.

Spring-driven clocks appeared during the 15th century,[25][26][27] although they are often erroneously credited to Nuremberg watchmaker Peter Henlein (or Henle, or Hele) around 1511.[28][29][30] The earliest existing spring driven clock is the chamber clock given to Phillip the Good, Duke of Burgundy, around 1430, now in the Germanisches Nationalmuseum.[4] Spring power presented clockmakers with a new problem: how to keep the clock movement running at a constant rate as the spring ran down. This resulted in the invention of the stackfreed and the fusee in the 15th century, and many other innovations, down to the invention of the modern going barrel in 1760.

Early clock dials did not indicate minutes and seconds. A clock with a dial indicating minutes was illustrated in a 1475 manuscript by Paulus Almanus,[31] and some 15th-century clocks in Germany indicated minutes and seconds.[32] An early record of a seconds hand on a clock dates back to about 1560 on a clock now in the Fremersdorf collection.[33]:417–418[34]

During the 15th and 16th centuries, clockmaking flourished, particularly in the metalworking towns of Nuremberg and Augsburg, and in Blois, France. Some of the more basic table clocks have only one time-keeping hand, with the dial between the hour markers being divided into four equal parts making the clocks readable to the nearest 15 minutes. Other clocks were exhibitions of craftsmanship and skill, incorporating astronomical indicators and musical movements. The cross-beat escapement was invented in 1584 by Jost Bürgi, who also developed the remontoire. Bürgi’s clocks were a great improvement in accuracy as they were correct to within a minute a day.[35][36] These clocks helped the 16th-century astronomer Tycho Brahe to observe astronomical events with much greater precision than before.[citation needed][how?]

Pendulum

From its invention in 1656 by Christiaan Huygens until the 1930s, the pendulum clock was the world’s most precise timekeeper, accounting for its widespread use.

The next development in accuracy occurred after 1656 with the invention of the pendulum clock. Galileo had the idea to use a swinging bob to regulate the motion of a time-telling device earlier in the 17th century. Christiaan Huygens, however, is usually credited as the inventor. He determined the mathematical formula that related pendulum length to time (about 99.4 cm or 39.1 inches for the one second movement) and had the first pendulum-driven clock made. The first model clock was built in 1657 in the Hague, but it was in England that the idea was taken up.[38] The longcase clock (also known as the grandfather clock) was created to house the pendulum and works by the English clockmaker William Clement in 1670 or 1671. It was also at this time that clock cases began to be made of wood and clock faces to utilize enamel as well as hand-painted ceramics.

In 1670, William Clement created the anchor escapement,[39] an improvement over Huygens’ crown escapement. Clement also introduced the pendulum suspension spring in 1671. The concentric minute hand was added to the clock by Daniel Quare, a London clockmaker and others, and the second hand was first introduced.

Hairspring

In 1675, Huygens and Robert Hooke invented the spiral balance spring, or the hairspring, designed to control the oscillating speed of the balance wheel. This crucial advance finally made accurate pocket watches possible. The great English clockmaker, Thomas Tompion, was one of the first to use this mechanism successfully in his pocket watches, and he adopted the minute hand which, after a variety of designs were trialled, eventually stabilised into the modern-day configuration.[40] The rack and snail striking mechanism for striking clocks, was introduced during the 17th century and had distinct advantages over the ‘countwheel’ (or ‘locking plate’) mechanism. During the 20th century there was a common misconception that Edward Barlow invented rack and snail striking. In fact, his invention was connected with a repeating mechanism employing the rack and snail.[41] The repeating clock, that chimes the number of hours (or even minutes) was invented by either Quare or Barlow in 1676. George Graham invented the deadbeat escapement for clocks in 1720.

Marine chronometer

A major stimulus to improving the accuracy and reliability of clocks was the importance of precise time-keeping for navigation. The position of a ship at sea could be determined with reasonable accuracy if a navigator could refer to a clock that lost or gained less than about 10 seconds per day. This clock could not contain a pendulum, which would be virtually useless on a rocking ship. In 1714, the British government offered large financial rewards to the value of 20,000 pounds,[42] for anyone who could determine longitude accurately. John Harrison, who dedicated his life to improving the accuracy of his clocks, later received considerable sums under the Longitude Act.

In 1735, Harrison built his first chronometer, which he steadily improved on over the next thirty years before submitting it for examination. The clock had many innovations, including the use of bearings to reduce friction, weighted balances to compensate for the ship’s pitch and roll in the sea and the use of two different metals to reduce the problem of expansion from heat. The chronometer was tested in 1761 by Harrison’s son and by the end of 10 weeks the clock was in error by less than 5 seconds.[43]

Mass production

The British had predominated in watch manufacture for much of the 17th and 18th centuries, but maintained a system of production that was geared towards high quality products for the elite.[44] Although there was an attempt to modernise clock manufacture with mass production techniques and the application of duplicating tools and machinery by the British Watch Company in 1843, it was in the United States that this system took off. In 1816, Eli Terry and some other Connecticut clockmakers developed a way of mass-producing clocks by using interchangeable parts.[45] Aaron Lufkin Dennison started a factory in 1851 in Massachusetts that also used interchangeable parts, and by 1861 was running a successful enterprise incorporated as the Waltham Watch Company.[46][47]

Early electric

In 1815, Francis Ronalds published the first electric clock powered by dry pile batteries.[48] Alexander Bain, Scottish clockmaker, patented the electric clock in 1840. The electric clock’s mainspring is wound either with an electric motor or with an electromagnet and armature. In 1841, he first patented the electromagnetic pendulum. By the end of the nineteenth century, the advent of the dry cell battery made it feasible to use electric power in clocks. Spring or weight driven clocks that use electricity, either alternating current (AC) or direct current (DC), to rewind the spring or raise the weight of a mechanical clock would be classified as an electromechanical clock. This classification would also apply to clocks that employ an electrical impulse to propel the pendulum. In electromechanical clocks the electricity serves no time keeping function. These types of clocks were made as individual timepieces but more commonly used in synchronized time installations in schools, businesses, factories, railroads and government facilities as a master clock and clocks.

Electric clocks that are powered from the AC supply often use synchronous motors. The supply current alternates with a frequency of 50 hertz in many countries, and 60 hertz in others. The rotor of the motor rotates at a speed that is related to the alternation frequency. Appropriate gearing converts this rotation speed to the correct ones for the hands of the analog clock. The development of electronics in the 20th century led to clocks with no clockwork parts at all. Time in these cases is measured in several ways, such as by the alternation of the AC supply, vibration of a tuning fork, the behaviour of quartz crystals, or the quantum vibrations of atoms. Electronic circuits divide these high-frequency oscillations to slower ones that drive the time display. Even mechanical clocks have since come to be largely powered by batteries, removing the need for winding.

Quartz

The piezoelectric properties of crystalline quartz were discovered by Jacques and Pierre Curie in 1880.[49][50] The first crystal oscillator was invented in 1917 by Alexander M. Nicholson after which, the first quartz crystal oscillator was built by Walter G. Cady in 1921.[2] In 1927 the first quartz clock was built by Warren Marrison and J. W. Horton at Bell Telephone Laboratories in Canada.[51][2] The following decades saw the development of quartz clocks as precision time measurement devices in laboratory settings—the bulky and delicate counting electronics, built with vacuum tubes, limited their practical use elsewhere. The National Bureau of Standards (now NIST) based the time standard of the United States on quartz clocks from late 1929 until the 1960s, when it changed to atomic clocks.[52] In 1969, Seiko produced the world’s first quartz wristwatch, the Astron.[53] Their inherent accuracy and low cost of production resulted in the subsequent proliferation of quartz clocks and watches.[49]

Atomic

As of the 2010s, atomic clocks are the most accurate clocks in existence. They are considerably more accurate than quartz clocks as they can be accurate to within a few seconds over thousands of years.[54] Atomic clocks were first theorized by Lord Kelvin in 1879.[55] In the 1930s the development of Magnetic resonance created practical method for doing this.[56] A prototype ammonia maser device was built in 1949 at the U.S. National Bureau of Standards (NBS, now NIST). Although it was less accurate than existing quartz clocks, it served to demonstrate the concept.[57][58][59] The first accurate atomic clock, a caesium standard based on a certain transition of the caesium-133 atom, was built by Louis Essen in 1955 at the National Physical Laboratory in the UK.[60] Calibration of the caesium standard atomic clock was carried out by the use of the astronomical time scale ephemeris time (ET).[61] As of 2013, the most stable atomic clocks are ytterbium clocks, which are stable to within less than two parts in 1 quintillion (2×10−18).[62]

Operation

A chiming clock’s mechanism.

The invention of the mechanical clock in the 13th century initiated a change in timekeeping methods from continuous processes, such as the motion of the gnomon‘s shadow on a sundial or the flow of liquid in a water clock, to periodic oscillatory processes, such as the swing of a pendulum or the vibration of a quartz crystal,[3][63] which had the potential for more accuracy. All modern clocks use oscillation.

Although the mechanisms they use vary, all oscillating clocks, mechanical, digital and atomic, work similarly and can be divided into analogous parts.[64][65][66] They consist of an object that repeats the same motion over and over again, an oscillator, with a precisely constant time interval between each repetition, or ‘beat’. Attached to the oscillator is a controller device, which sustains the oscillator’s motion by replacing the energy it loses to friction, and converts its oscillations into a series of pulses. The pulses are then counted by some type of counter, and the number of counts is converted into convenient units, usually seconds, minutes, hours, etc. Finally some kind of indicator displays the result in human readable form.

Power source

Keys of various sizes for winding up mainsprings on clocks.
  • In mechanical clocks, the power source is typically either a weight suspended from a cord or chain wrapped around a pulley, sprocket or drum; or a spiral spring called a mainspring. Mechanical clocks must be wound periodically, usually by turning a knob or key or by pulling on the free end of the chain, to store energy in the weight or spring to keep the clock running.
  • In electric clocks, the power source is either a battery or the AC power line. In clocks that use AC power, a small backup battery is often included to keep the clock running if it is unplugged temporarily from the wall or during a power outage. Battery powered analog wall clocks are available that operate over 15 years between battery changes.

Oscillator

The timekeeping element in every modern clock is a harmonic oscillator, a physical object (resonator) that vibrates or oscillates repetitively at a precisely constant frequency.[2]

The advantage of a harmonic oscillator over other forms of oscillator is that it employs resonance to vibrate at a precise natural resonant frequency or ‘beat’ dependent only on its physical characteristics, and resists vibrating at other rates. The possible precision achievable by a harmonic oscillator is measured by a parameter called its Q,[68][69] or quality factor, which increases (other things being equal) with its resonant frequency.[70] This is why there has been a long term trend toward higher frequency oscillators in clocks. Balance wheels and pendulums always include a means of adjusting the rate of the timepiece. Quartz timepieces sometimes include a rate that adjusts a capacitor for that purpose. Atomic clocks are primary standards, and their rate cannot be adjusted.

Synchronized or clocks

Some clocks rely for their accuracy on an external oscillator; that is, they are automatically synchronized to a more accurate clock:

  • clocks, used in large institutions and schools from the 1860s to the 1970s, kept time with a pendulum, but were wired to a master clock in the building, and periodically received a signal to synchronize them with the master, often on the hour.[71] Later versions without pendulums were triggered by a pulse from the master clock and certain sequences used to force rapid synchronization following a power failure.
  • Synchronous electric clocks do not have an internal oscillator, but count cycles of the 50 or 60 Hz oscillation of the AC power line, which is synchronized by the utility to a precision oscillator. The counting may be done electronically, usually in clocks with digital displays, or, in analog clocks, the AC may drive a synchronous motor which rotates an exact fraction of a revolution for every cycle of the line voltage, and drives the gear train. Although changes in the grid line frequency due to load variations may cause the clock to temporarily gain or lose several seconds during the course of a day, the total number of cycles per 24 hours is maintained extremely accurately by the utility company, so that the clock keeps time accurately over long periods.
  • Computer real time clocks keep time with a quartz crystal, but can be periodically (usually weekly) synchronized over the Internet to atomic clocks (UTC), using the Network Time Protocol (NTP). Sometimes computers on a local area network (LAN) get their time from a single local server which is maintained accurately.
  • Radio clocks keep time with a quartz crystal, but are periodically synchronized to time signals transmitted from dedicated standard time radio stations or satellite navigation signals, which are set by atomic clocks.

Controller

This has the dual function of keeping the oscillator running by giving it ‘pushes’ to replace the energy lost to friction, and converting its vibrations into a series of pulses that serve to measure the time.

  • In mechanical clocks, this is the escapement, which gives precise pushes to the swinging pendulum or balance wheel, and releases one gear tooth of the escape wheel at each swing, allowing all the clock’s wheels to move forward a fixed amount with each swing.
  • In electronic clocks this is an electronic oscillator circuit that gives the vibrating quartz crystal or tuning fork tiny ‘pushes’, and generates a series of electrical pulses, one for each vibration of the crystal, which is called the clock signal.
  • In atomic clocks the controller is an evacuated microwave cavity attached to a microwave oscillator controlled by a microprocessor. A thin gas of caesium atoms is released into the cavity where they are exposed to microwaves. A laser measures how many atoms have absorbed the microwaves, and an electronic feedback control system called a phase-locked loop tunes the microwave oscillator until it is at the frequency that causes the atoms to vibrate and absorb the microwaves. Then the microwave signal is divided by digital counters to become the clock signal.[72]

In mechanical clocks, the low Q of the balance wheel or pendulum oscillator made them very sensitive to the disturbing effect of the impulses of the escapement, so the escapement had a great effect on the accuracy of the clock, and many escapement designs were tried. The higher Q of resonators in electronic clocks makes them relatively insensitive to the disturbing effects of the drive power, so the driving oscillator circuit is a much less critical component.[2]

Counter chain

This counts the pulses and adds them up to get traditional time units of seconds, minutes, hours, etc. It usually has a provision for setting the clock by manually entering the correct time into the counter.

  • In mechanical clocks this is done mechanically by a gear train, known as the wheel train. The gear train also has a second function; to transmit mechanical power from the power source to run the oscillator. There is a friction coupling called the ‘cannon pinion’ between the gears driving the hands and the rest of the clock, allowing the hands to be turned to set the time.[73]
  • In digital clocks a series of integrated circuit counters or dividers add the pulses up digitally, using binary logic. Often pushbuttons on the case allow the hour and minute counters to be incremented and decremented to set the time.

Indicator

A Cuckoo clock with mechanical automaton and sound producer striking on the 8th hour on the analog dial.

This displays the count of seconds, minutes, hours, etc. in a human readable form.

  • The earliest mechanical clocks in the 13th century didn’t have a visual indicator and signalled the time audibly by striking bells. Many clocks to this day are striking clocks which strike the hour.
  • Analog clocks display time with an analog clock face, which consists of a round dial with the numbers 1 through 12, the hours in the day, around the outside. The hours are indicated with an hour hand, which makes two revolutions in a day, while the minutes are indicated by a minute hand, which makes one revolution per hour. In mechanical clocks a gear train drives the hands; in electronic clocks the circuit produces pulses every second which drive a stepper motor and gear train, which move the hands.
  • Digital clocks display the time in periodically changing digits on a digital display. A common misconception is that a digital clock is more accurate than an analog wall clock, but the indicator type is separate and apart from the accuracy of the timing source.
  • Talking clocks and the speaking clock services provided by telephone companies speak the time audibly, using either recorded or digitally synthesized voices.

Types

Clocks can be classified by the type of time display, as well as by the method of timekeeping.

Time display methods

Analog

A linear clock at London‘s Piccadilly Circus tube station. The 24 hour band moves across the static map, keeping pace with the apparent movement of the sun above ground, and a pointer fixed on London points to the current time.

A modern quartz clock with a 24-hour face

Analog clocks usually use a clock face which indicates time using rotating pointers called “hands” on a fixed numbered dial or dials. The standard clock face, known universally throughout the world, has a short “hour hand” which indicates the hour on a circular dial of 12 hours, making two revolutions per day, and a longer “minute hand” which indicates the minutes in the current hour on the same dial, which is also divided into 60 minutes. It may also have a “second hand” which indicates the seconds in the current minute. The only other widely used clock face today is the 24 hour analog dial, because of the use of 24 hour time in military organizations and timetables. Before the modern clock face was standardized during the Industrial Revolution, many other face designs were used throughout the years, including dials divided into 6, 8, 10, and 24 hours. During the French Revolution the French government tried to introduce a 10-hour clock, as part of their decimal-based metric system of measurement, but it didn’t catch on. An Italian 6 hour clock was developed in the 18th century, presumably to save power (a clock or watch striking 24 times uses more power).

A simple 24 hour clock showing the approximate position of the sun.

Another type of analog clock is the sundial, which tracks the sun continuously, registering the time by the shadow position of its gnomon. Because the sun does not adjust to daylight saving time, users must add an hour during that time. Corrections must also be made for the equation of time, and for the difference between the longitudes of the sundial and of the central meridian of the time zone that is being used (i.e. 15 degrees east of the prime meridian for each hour that the time zone is ahead of GMT). Sundials use some or part of the 24 hour analog dial. There also exist clocks which use a digital display despite having an analog mechanism—these are commonly referred to as flip clocks. Alternative systems have been proposed. For example, the “Twelv” clock indicates the current hour using one of twelve colors, and indicates the minute by showing a proportion of a circular disk, similar to a moon phase.[74]

Digital

Digital clocks display a numeric representation of time. Two numeric display formats are commonly used on digital clocks:

  • the 24-hour notation with hours ranging 00–23;
  • the 12-hour notation with AM/PM indicator, with hours indicated as 12AM, followed by 1AM–11AM, followed by 12PM, followed by 1PM–11PM (a notation mostly used in domestic environments).

Most digital clocks use electronic mechanisms and LCD, LED, or VFD displays; many other display technologies are used as well (cathode ray tubes, nixie tubes, etc.). After a reset, battery change or power failure, these clocks without a backup battery or capacitor either start counting from 12:00, or stay at 12:00, often with blinking digits indicating that the time needs to be set. Some newer clocks will reset themselves based on radio or Internet time servers that are tuned to national atomic clocks. Since the advent of digital clocks in the 1960s, the use of analog clocks has declined significantly.

Some clocks, called ‘flip clocks‘, have digital displays that work mechanically. The digits are painted on sheets of material which are mounted like the pages of a book. Once a minute, a page is turned over to reveal the next digit. These displays are usually easier to read in brightly lit conditions than LCDs or LEDs. Also, they do not go back to 12:00 after a power interruption. Flip clocks generally do not have electronic mechanisms. Usually, they are driven by ACsynchronous motors.

Hybrid (analog-digital)

Hybrid real-time animated clock with seconds (12 hours)

Clocks with analog quadrants, with a digital component, usually minutes and hours displayed analogously and seconds displayed in digital mode.

Auditory

For convenience, distance, telephony or blindness, auditory clocks present the time as sounds. The sound is either spoken natural language, (e.g. “The time is twelve thirty-five”), or as auditory codes (e.g. number of sequential bell rings on the hour represents the number of the hour like the bell, Big Ben). Most telecommunication companies also provide a speaking clock service as well.

Word

Software word clock

Word clocks are clocks that display the time visually using sentences. E.g.: “It’s about three o’clock.” These clocks can be implemented in hardware or software.

Projection

Some clocks, usually digital ones, include an optical projector that shines a magnified image of the time display onto a screen or onto a surface such as an indoor ceiling or wall. The digits are large enough to be easily read, without using glasses, by persons with moderately imperfect vision, so the clocks are convenient for use in their bedrooms. Usually, the timekeeping circuitry has a battery as a backup source for an uninterrupted power supply to keep the clock on time, while the projection light only works when the unit is connected to an A.C. supply. Completely battery-powered portable versions resembling flashlights are also available.

Tactile

Auditory and projection clocks can be used by people who are blind or have limited vision. There are also clocks for the blind that have displays that can be read by using the sense of touch. Some of these are similar to normal analog displays, but are constructed so the hands can be felt without damaging them. Another type is essentially digital, and uses devices that use a code such as Braille to show the digits so that they can be felt with the fingertips.

Multi-display

Some clocks have several displays driven by a single mechanism, and some others have several completely separate mechanisms in a single case. Clocks in public places often have several faces visible from different directions, so that the clock can be read from anywhere in the vicinity; all the faces show the same time. Other clocks show the current time in several time-zones. Watches that are intended to be carried by travellers often have two displays, one for the local time and the other for the time at home, which is useful for making pre-arranged phone calls. Some equation clocks have two displays, one showing mean time and the other solar time, as would be shown by a sundial. Some clocks have both analog and digital displays. Clocks with Braille displays usually also have conventional digits so they can be read by sighted people.

Purposes

Many cities and towns traditionally have public clocks in a prominent location, such as a town square or city center. This one is on display at the center of the town of Robbins, North Carolina.

An old clock in a restaurant in Croatia

Clocks are in homes, offices and many other places; smaller ones (watches) are carried on the wrist or in a pocket; larger ones are in public places, e.g. a railway station or church. A small clock is often shown in a corner of computer displays, mobile phones and many MP3 players.

The primary purpose of a clock is to display the time. Clocks may also have the facility to make a loud alert signal at a specified time, typically to waken a sleeper at a preset time; they are referred to as alarm clocks. The alarm may start at a low volume and become louder, or have the facility to be switched off for a few minutes then resume. Alarm clocks with visible indicators are sometimes used to indicate to children too young to read the time that the time for sleep has finished; they are sometimes called training clocks.

A clock mechanism may be used to control a device according to time, e.g. a central heating system, a VCR, or a time bomb (see: digital counter). Such mechanisms are usually called timers. Clock mechanisms are also used to drive devices such as solar trackers and astronomical telescopes, which have to turn at accurately controlled speeds to counteract the rotation of the Earth.

Most digital computers depend on an internal signal at constant frequency to synchronize processing; this is referred to as a clock signal. (A few research projects are developing CPUs based on asynchronous circuits.) Some equipment, including computers, also maintains time and date for use as required; this is referred to as time-of-day clock, and is distinct from the system clock signal, although possibly based on counting its cycles.

In Chinese culture, giving a clock (送鍾/送钟, sòng zhōng) is often taboo, especially to the elderly as the term for this act is a homophone with the term for the act of attending another’s funeral (送終/送终, sòngzhōng).[75][76][77] A UK government official Susan Kramer gave a watch to Taipei mayor Ko Wen-je unaware of such a taboo which resulted in some professional embarrassment and a pursuant apology.[78]

It is undesirable to give someone a clock or (depending on the region) other timepiece as a gift. Traditional superstitions regard this as counting the seconds to the recipient’s death. Another common interpretation of this is that the phrase “to give a clock” (simplified Chinese: 送钟; traditional Chinese: 送鐘) in Chinese is pronounced “sòng zhōng” in Mandarin, which is a homophone of a phrase for “terminating” or “attending a funeral” (both can be written as 送終 (traditional) or 送终 (simplified)). Cantonese people consider such a gift as a curse.[79]

This homonymic pair works in both Mandarin and Cantonese, although in most parts of China only clocks and large bells, and not watches, are called “zhong“, and watches are commonly given as gifts in China.

However, should such a gift be given, the “unluckiness” of the gift can be countered by exacting a small monetary payment so the recipient is buying the clock and thereby counteracting the ‘送’ (“give”) expression of the phrase.

Time standards

For some scientific work timing of the utmost accuracy is essential. It is also necessary to have a standard of the maximum accuracy against which working clocks can be calibrated. An ideal clock would give the time to unlimited accuracy, but this is not realisable. Many physical processes, in particular including some transitions between atomic energy levels, occur at exceedingly stable frequency; counting cycles of such a process can give a very accurate and consistent time—clocks which work this way are usually called atomic clocks. Such clocks are typically large, very expensive, require a controlled environment, and are far more accurate than required for most purposes; they are typically used in a standards laboratory.

Navigation

Until advances in the late twentieth century, navigation depended on the ability to measure latitude and longitude. Latitude can be determined through celestial navigation; the measurement of longitude requires accurate knowledge of time. This need was a major motivation for the development of accurate mechanical clocks. John Harrison created the first highly accurate marine chronometer in the mid-18th century. The Noon gun in Cape Town still fires an accurate signal to allow ships to check their chronometers. Many buildings near major ports used to have (some still do) a large ball mounted on a tower or mast arranged to drop at a pre-determined time, for the same purpose. While satellite navigation systems such as the Global Positioning System (GPS) require unprecedentedly accurate knowledge of time, this is supplied by equipment on the satellites; vehicles no longer need timekeeping equipment.

Specific types

A monumental conical pendulum clock by Eugène Farcot, 1867. Philadelphia, USA.
By mechanism By function By style

See also

Newsgroup

Notes and references

 

 

  1. Susan Kurth Clot deBroissia International Gift Giving Protocol

Bibliography

  • Baillie, G.H., O. Clutton, & C.A. Ilbert. Britten’s Old Clocks and Watches and Their Makers (7th ed.). Bonanza Books (1956).
  • Bolter, David J. Turing’s Man: Western Culture in the Computer Age. The University of North Carolina Press, Chapel Hill, N.C. (1984). ISBN 0-8078-4108-0 pbk. Very good, readable summary of the role of “the clock” in its setting the direction of philosophic movement for the “Western World”. Cf. picture on p. 25 showing the verge and foliot. Bolton derived the picture from Macey, p. 20.
  • Bruton, Eric (1982). The History of Clocks and Watches. New York: Crescent Books Distributed by Crown. ISBN 978-0-517-37744-4.
  • Dohrn-van Rossum, Gerhard (1996). History of the Hour: Clocks and Modern Temporal Orders. Trans. Thomas Dunlap. Chicago: The University of Chicago Press. ISBN 0-226-15510-2.
  • Edey, Winthrop. French Clocks. New York: Walker & Co. (1967).
  • Kak, Subhash, Babylonian and Indian Astronomy: Early Connections. February 17, 2003.
  • Kumar, Narendra “Science in Ancient India” (2004). ISBN 81-261-2056-8.
  • Landes, David S. Revolution in Time: Clocks and the Making of the Modern World. Cambridge: Harvard University Press (1983).
  • Landes, David S. Clocks & the Wealth of Nations, Daedalus Journal, Spring 2003.
  • Lloyd, Alan H. “Mechanical Timekeepers”, A History of Technology, Vol. III. Edited by Charles Joseph Singer et al. Oxford: Clarendon Press (1957), pp. 648–675.
  • Macey, Samuel L., Clocks and the Cosmos: Time in Western Life and Thought, Archon Books, Hamden, Conn. (1980).
  • Needham, Joseph (2000) [1965]. Science & Civilisation in China, Vol. 4, Part 2: Mechanical Engineering. Cambridge: Cambridge University Press. ISBN 0-521-05803-1.
  • North, John. God’s Clockmaker: Richard of Wallingford and the Invention of Time. London: Hambledon and London (2005).
  • Palmer, Brooks. The Book of American Clocks, The Macmillan Co. (1979).
  • Robinson, Tom. The Longcase Clock. Suffolk, England: Antique Collector’s Club (1981).
  • Smith, Alan. The International Dictionary of Clocks. London: Chancellor Press (1996).
  • Tardy. French Clocks the World Over. Part I and II. Translated with the assistance of Alexander Ballantyne. Paris: Tardy (1981).
  • Yoder, Joella Gerstmeyer. Unrolling Time: Christiaan Huygens and the Mathematization of Nature. New York: Cambridge University Press (1988).
  • Zea, Philip, & Robert Cheney. Clock Making in New England: 1725–1825. Old Sturbridge Village (1992).

External links

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FASHION

FASHION

Related image

Fashion is a popular style, especially in clothing, footwear, lifestyle, accessories, makeup, hairstyle and body.[citation needed] Fashion is a distinctive and often constant trend in the style in which people present themselves. A fashion can become the prevailing style in behaviour or manifest the newest creations of designers, technologists, engineers, and design managers.[1][need quotation to verify]

Because the more technical term costume is regularly linked[by whom?] to the term “fashion”, the use of the former has been relegated to special senses like fancy-dress or masquerade wear, while the word “fashion” often refers to clothing, including the study of clothing. Although aspects of fashion can be feminine or masculine, some trends are androgynous.[2][3]

High-flying trendsetters in fashion can aspire to the label haute couture. But if one disapproves of a fashion, one can attempt to dismiss it as a mere fad.

Clothing fashions

Early Western travelers, traveling whether to India, Persia, Turkey or China, would frequently remark on the absence of change in fashion in those countries. The Japanese shōguns secretary bragged (not completely accurately) to a Spanish visitor in 1609 that Japanese clothing had not changed in over a thousand years.[4] However, there is considerable evidence in Ming China of rapidly changing fashions in Chinese clothing.[5] Changes in costume often took place at times of economic or social change, as occurred in ancient Rome and the medieval Caliphate, followed by a long period without major changes. In 8th-century Moorish Spain, the musician Ziryab introduced to Córdoba[6][unreliable source][7] sophisticated clothing-styles based on seasonal and daily fashions from his native Baghdad, modified by his own inspiration. Similar changes in fashion occurred in the 11th century in the Middle East following the arrival of the Turks, who introduced clothing styles from Central Asia and the Far East.[8]

The beginning in Europe of continual and increasingly rapid change in clothing styles can be fairly reliably dated. Historians, including James Laver and Fernand Braudel, date the start of Western fashion in clothing to the middle of the 14th century,[9][10] though they tend to rely heavily on contemporary imagery[11] and illuminated manuscripts were not common before the fourteenth century. The most dramatic early change in fashion was a sudden drastic shortening and tightening of the male over-garment from calf-length to barely covering the buttocks,[12] sometimes accompanied with stuffing in the chest to make it look bigger. This created the distinctive Western outline of a tailored top worn over leggings or trousers.

The pace of change accelerated considerably in the following century, and women and men’s fashion, especially in the dressing and adorning of the hair, became equally complex. Art historians are therefore able to use fashion with confidence and precision to date images, often to within five years, particularly in the case of images from the 15th century. Initially, changes in fashion led to a fragmentation across the upper classes of Europe of what had previously been a very similar style of dressing and the subsequent development of distinctive national styles. These national styles remained very different until a counter-movement in the 17th to 18th centuries imposed similar styles once again, mostly originating from Ancien Régime France.[13] Though the rich usually led fashion, the increasing affluence of early modern Europe led to the bourgeoisie and even peasants following trends at a distance, but still uncomfortably close for the elites – a factor that Fernand Braudel regards as one of the main motors of changing fashion.[14]

Albrecht Dürer‘s drawing contrasts a well turned out bourgeoise from Nuremberg (left) with her counterpart from Venice. The Venetian lady’s high chopines make her look taller.

In the 16th century, national differences were at their most pronounced. Ten 16th century portraits of German or Italian gentlemen may show ten entirely different hats. Albrecht Dürer illustrated the differences in his actual (or composite) contrast of Nuremberg and Venetian fashions at the close of the 15th century (illustration, right). The “Spanish style” of the late 16th century began the move back to synchronicity among upper-class Europeans, and after a struggle in the mid-17th century, French styles decisively took over leadership, a process completed in the 18th century.[15]

Though different textile colors and patterns changed from year to year,[16] the cut of a gentleman’s coat and the length of his waistcoat, or the pattern to which a lady’s dress was cut, changed more slowly. Men’s fashions were largely derived from military models, and changes in a European male silhouette were galvanized in theaters of European war where gentleman officers had opportunities to make notes of foreign styles such as the “Steinkirk” cravat or necktie.

Marie Antoinette, wife of Louis XVI, was a leader of fashion. Her choices, such as this 1783 white muslin dress called a chemise a la Reine, were highly influential and widely worn.[17]

Though there had been distribution of dressed dolls from France since the 16th century and Abraham Bosse had produced engravings of fashion in the 1620s, the pace of change picked up in the 1780s with increased publication of French engravings illustrating the latest Paris styles. By 1800, all Western Europeans were dressing alike (or thought they were); local variation became first a sign of provincial culture and later a badge of the conservative peasant.[18]

Although tailors and dressmakers were no doubt responsible for many innovations, and the textile industry certainly led many trends, the history of fashion design is normally understood to date from 1858 when the English-born Charles Frederick Worth opened the first true haute couture house in Paris. The Haute house was the name established by government for the fashion houses that met the standards of industry. These fashion houses have to adhere to standards such as keeping at least twenty employees engaged in making the clothes, showing two collections per year at fashion shows, and presenting a certain number of patterns to costumers.[19] Since then, the idea of the fashion designer as a celebrity in his or her own right has become increasingly dominant.[20]

The idea of unisex dressing originated in the 1960s when designers such as Pierre Cardin and Rudi Gernreich created garments, such as stretch jersey tunics or leggings, meant to be worn by both males and females. The impact of unisex expands more broadly to encompass various themes in fashion including androgyny, mass-market retail, and conceptual clothing.[21] The fashion trends of the 1970s, such as sheepskin jackets, flight jackets, duffel coats, and unstructured clothing influenced men to attend social gatherings without a tuxedo jacket and to accessorize in new ways. Some men’s styles blended the sensuality and expressiveness despite the conservative trend, the growing -rights movement and an emphasis on youth allowed for a new freedom to experiment with style, fabrics such as wool crepe, which had previously been associated with women’s attire was used by designers when creating male clothing.[22]

The four major current fashion capitals are acknowledged to be Paris, Milan, New York City, and London, which are all headquarters to the greatest fashion companies and are renowned for their major influence on global fashion. Fashion weeks are held in these cities, where designers exhibit their new clothing collections to audiences. A succession of major designers such as Coco Chanel and Yves Saint-Laurent have kept Paris as the center most watched by the rest of the world, although haute couture is now subsidized by the sale of ready-to-wear collections and perfume using the same branding.

Modern Westerners have a wide number of choices available in the selection of their clothes. What a person chooses to wear can reflect his or her personality or interests. When people who have high cultural status start to wear new or different clothes, a fashion trend may start. People who like or respect these people become influenced by their personal style and begin wearing similarly styled clothes. Fashions may vary considerably within a society according to age, social class, generation, occupation, and geography and may also vary over time. If an older person dresses according to the fashion young people use, he or she may look ridiculous in the eyes of both young and older people. The terms fashionista and fashion victim refer to someone who slavishly follows current fashions.

One can regard the system of sporting various fashions as a fashion language incorporating various fashion statements using a grammar of fashion. (Compare some of the work of Roland Barthes.)

In recent years, Asian fashion has become increasingly significant in local and global markets. Countries such as China, Japan, India, and Pakistan have traditionally had large textile industries, which have often been drawn upon by Western designers, but now Asian clothing styles are also gaining influence based on their own ideas.[23]

Fashion industry

Male and female fashion models on the runaway, Los Angeles Fashion Week, 2008

The notion of global fashion industry is a product of the modern age.[24] Prior to the mid-19th century, most clothing was custom-made. It was handmade for individuals, either as home production or on order from dressmakers and tailors. By the beginning of the 20th century—with the rise of new technologies such as the sewing machine, the rise of global capitalism and the development of the factory system of production, and the proliferation of retail outlets such as department stores—clothing had increasingly come to be mass-produced in standard sizes and sold at fixed prices.

Although the fashion industry developed first in Europe and America, as of 2017, it is an international and highly globalized industry, with clothing often designed in one country, manufactured in another, and sold worldwide. For example, an American fashion company might source fabric in China and have the clothes manufactured in Vietnam, finished in Italy, and shipped to a warehouse in the United States for distribution to retail outlets internationally. The fashion industry has long been one of the largest employers in the United States,[25] and it remains so in the 21st century. However, U.S. employment declined considerably as production increasingly moved overseas, especially to China. Because data on the fashion industry typically are reported for national economies and expressed in terms of the industry’s many separate sectors, aggregate figures for world production of textiles and clothing are difficult to obtain. However, by any measure, the clothing industry accounts for a significant share of world economic output.[26] The fashion industry consists of four levels:

  1. the production of raw materials, principally fibers and textiles but also leather and fur.
  2. the production of fashion goods by designers, manufacturers, contractors, and others.
  3. retail sales
  4. various forms of advertising and promotion

These levels consist of many separate but interdependent sectors. These sectors are Textile Design and Production, Fashion Design and Manufacturing, Fashion Retailing, Marketing and Merchandising, Fashion Shows, and Media and Marketing. Each sector is devoted to the goal of satisfying consumer demand for apparel under conditions that enable participants in the industry to operate at a profit.[27]

Fashion trend

Fashion trends are influenced by several factors including cinema, celebrities, climate, creative explorations, political, economical, social and technological. Examining these factors is called a PEST analysis. Fashion forecasters can use this information to help determine growth or decline of a particular trend. Fashion trends change daily, it can not stay unchanged

Political influences

Advisor to US President and businesswoman Ivanka Trump (right) along with Japanese PM Shinzo Abe wearing Western-style business suits, 2017

Not only did political events make a huge impact on fashion trends but also the political figure played a critical role in forecasting the fashion trend. For example, First Lady Jacqueline Kennedy was a fashionable icon of the early 1960s who led formal dressing trend. By wearing a Chanel suit, a structural Givenchy shift dress or a soft color Cassini coat with huge buttons, it created her elegant look and led a delicate trend.

Furthermore, political revolution also made much impact on the fashion trend. For example, during the 1960s the economy had become wealthier, divorce rate was increasing and government approved the birth control pill. This revolution inspired younger generation to rebellion. In 1964, the leg-baring miniskirt has become a major fashion trend of the 1960s. Given that fashion designers began to experiment with the shapes of garment, loose sleeveless, micro-minis, flared skirts, and trumpet sleeves. In this case, mini-skirt trend became an icon of the 1960s.

Moreover, political movement built an impressive relationship with fashion trend. For instance, during Vietnam war, the youth of America made a movement that affected the whole country. In the 1960s, the fashion trend was full of fluorescent colors, prints patterns, bell-bottom jeans, fringed vests, and skirt became a protest outfit of the 1960s. This trend was called Hippie and it is still affecting current fashion trend.[28]

Technology influences

Technology plays a large role in most aspects of today’s society. Technological influences are growing more apparent in the fashion industry. Advances and new developments are shaping and creating current and future trends.

Developments such as wearable technology have become an important trend in fashion and will continue with advances such as clothing constructed with solar panels that charge devices and smart fabrics that enhance wearer comfort by changing color or texture based on environmental changes.[29]

The fashion industry is seeing how 3D printing technology has influenced designers such as Iris Van Herpen and Kimberly Ovitz. These designers have been heavily experimenting and developing 3D printed couture pieces. As the technology grows, the 3D printers will become more accessible to designers and eventually consumers, which could potentially shape the fashion industry entirely.

Internet technology such as online retailers and social media platforms have given way for trends to be identified, marketed and sold immediately.[30] Styles and trends are easily conveyed online to attract the trendsetters. Posts on Instagram or Facebook can easily increase awareness about new trends in fashion, which subsequently may create high demand for specific items or brands,[31] new “buy now button” technology can link these styles with direct sales.

Machine vision technology has been developed to track how fashions spread through society. The industry can now see the direct correlation on how fashion shows influence street-chic outfits. The effects can now be quantified and provide valuable feedback to fashion houses, designers and consumers regarding trends.[32]

Military technology has played an important role in the fashion industry. The camouflage pattern in clothing was developed to help military personal be less visible to enemy forces. A trend emerged in the 1960s and camouflage fabric was introduced to street wear. The camouflage fabric trend disappeared and resurfaced several times since then. Camouflage started to appear in high fashion by the 1990s.[33] Designers such as Valentino, Dior and Dolce & Gabbana combined camouflage into their runway and ready-to-wear collections.

A company called Hyperstealth is said to have created a technology that can make an object or person invisible. “Quantum Stealth” is a light bending technology that can mask thermal and infrared signs. The company has continued developing this technology, but due to safety and legal concerns minimal information has been released to the public.[34] This technology will not be quickly introduced into the commercial market, but the companies other projects such as non-powered color changing camouflage materials may be. Additional projects such as using interactive or intelligent technology sources that will be embedding into textiles will adjust to surroundings such as weather.[35] As these developments proceed, consumers may see a more modern and technical way of wearing camouflage.

Social influences

Celebrities such as Rihanna have popularised the concept of wearing Latex corset and underwear as outerwear

Red carpet fashion: Italian actors Gabriel Garko and Laura Torrisi wearing designer formal wear at Venice Film Festival, 2009

Fashion trend goes beyond the aesthetic values, it emerges as an expressive tool for designers to deliver their message about the society. With the influence of social media, celebrities and bloggers, their voice are easily being heard and have impact on fashion and trend at any time. Fashion and music are inseparable. Prabal Gurung[36] highlighted the importance of music to his shows, saying “each season we want to tell a story for 10 minutes…. the perfect harmony between cloths and music allows this”. Music is a representation of fashion that expresses the abstract design concept into relatable harmony for viewers.

Fashion relates to social and cultural context of an environment. According to Matika,[37] “Elements of popular culture become fused when a person’s trend is associated with a preference for a genre of music…like music, news or literature, fashion has been fused into everyday lives.” Fashion is not only seen as pure aesthetic values; fashion is also a medium for performers to create an overall atmosphere and express their opinions altogether through music video. The latest music video ‘Formation’ by Beyoncé, according to Carlos,[38] “The pop star pays homage to her Creole root…. tracing the roots of the Louisiana cultural nerve center from the post-abolition era to present day, Beyoncé catalogs the evolution of the city’s vibrant style and its tumultuous history all at once. Atop a New Orleans police car in a red-and-white Gucci high-collar dress and combat boots, she sits among the ruins of Hurricane Katrina, immediately implanting herself in the biggest national debate on police brutality and race relations in modern day.”

Runway show is a reflection of fashion trend and a designer’s thought. For designer like Vivienne Westwood, runway show is a platform for her voice on politics and current events. For her AW15 menswear show, according to Water,[39] “where models with severely bruised faces channeled eco-warriors on a mission to save the planet.” Another recent example is a staged feminist protest march for Chanel’s SS15 show, rioting models chanting words of empowerment with signs like “Feminist but feminine” and “Ladies first.” According to Water,[39] “The show tapped into Chanel’s long history of championing female independence: founder Coco Chanel was a trailblazer for liberating the female body in the post-WWI era, introducing silhouettes that countered the restrictive corsets then in favour.”

Economic influences

Circular economy

As we undergo a global economic downturn[when?], the “Spend now, think later” belief is getting less relevant in our society.[40] Today’s consumer tends to be more mindful about consumption, looking for just enough and better, more durable options. People have also become more conscious of the impact their everyday consumption has on the environment and society. They’re looking for ways to mediate their material desires with an aim to do more good in the world. A linear economy is slowly shifting to a circular one.[citation needed]

In today’s linear economical system, manufacturers extract resources from the earth to make products that will soon be discarded in landfills, on the other hand, under the circular model, the production of goods operates like systems in nature, where the waste and demise of a substance becomes the food and source of growth for something new. Companies such as MUD Jeans, which is based in the Netherlands employs a leasing scheme for jeans. This Dutch company “represents a new consuming philosophy that is about using instead of owning,” according to MUD’s website. The concept also protects the company from volatile cotton prices. Consumers pay €7.50 a month for a pair of jeans; after a year, they can return the jeans to Mud, trade them for a new pair and start another year-long lease, or keep them. MUD is responsible for any repairs during the lease period.[40] Another ethical fashion company, Patagonia set up the first multi-seller branded store on EBay in order to facilitate secondhand sales; consumers who take the Common Threads pledge can sell in this store and have their gear listed on Patagonia.com’s “Used Gear” section.[40]

China’s domestic spending

Consumption as a share of gross domestic product in China has fallen for six decades, from 76 percent in 1952 to 28 percent in 2011. China plans to reduce tariffs on a number of consumer goods and expand its 72-hour transit visa plan to more cities in an effort to stimulate domestic consumption.[41]

The announcement of import tax reductions follows changes in June 2015, when the government cut the tariffs on clothing, cosmetics and various other goods by half. Among the changes — easier tax refunds for overseas shoppers and accelerated openings of more duty-free shops in cities covered by the 72-hour visa scheme. The 72-hour visa was introduced in Beijing and Shanghai in January 2013 and has been extended to 18 Chinese cities.[41]

According to reports at the same time, Chinese consumer spending in other countries such as Japan has slowed even though the yen has dropped.[42] There is clearly a trend in the next 5 years that the domestic fashion market will show an increase.

Consumer’s needs

A tourist couple wearing casual clothes at Cumberland Island, 2015

Consumers all have different needs and demands that have to be suited. A person’s needs change frequently, which is why fashion trends even exist. An important factor to take into consideration when thinking of consumers’ needs is the key demographics of the customer. Gender, age, income, and even profession can help a company better understand the needs of their customers.[43]

For example, a woman who is pregnant could be looking for diapers, baby strollers, and maternity clothes. Her needs would differ greatly from a woman with children that just went off to college or a teen entering high school.

Often consumers need to be told what they want. Fashion companies have to do their research to ensure they know their customers’ needs before developing solutions. Steve Jobs said, “You’ve got to start with the customer experience and work backwards to the technology. You cannot start with the technology and try to figure out where you are going to sell it”.[44]

The best way to understand the consumers’ needs and therefore predict fashion trends is through market research. There are two research methods: primary and secondary.[45] Secondary methods are taking other information that has already been collected, for example using a book or an article for research. Primary research is collecting data through surveys, interviews, observation, and/or focus groups.

Benefits of primary research is specific information about a fashion brand’s consumer is explored. Surveys are helpful tools; questions can be open-ended or closed-ended. A negative factor surveys and interviews present is that the answers can be biased, due to wording in the survey or on face-to-face interactions. Focus groups, about 8 to 12 people, can be beneficial because several points can be addressed in depth. However, there are drawbacks to this tactic, too. With such a small sample size, it is hard to know if the greater public would react the same way as the focus group.[45] Observation can really help a company gain insight on what a consumer truly wants. There is less of a bias because consumers are just performing their daily tasks, not necessarily realizing they are being observed. For example, observing the public by taking street style photos of people, the consumer did not get dressed in the morning knowing that would have their photo taken necessarily. They just wear what they would normally wear. Through observation patterns can be seen, helping trend forecasters know what their target market needs and wants.

Knowing the needs of the consumers will increase a fashion companies’ sales and profits. Through research and studying the consumers’ lives the needs of the customer can be obtained and help fashion brands know what trends the consumers are ready for.

Media

Fashion breathes on media and medium . The media plays a significant role when it comes to fashion. For instance, an important part of fashion is fashion journalism. Editorial critique, guidelines, and commentary can be found on television and in magazines, newspapers, fashion websites, social networks, and fashion blogs. In recent years, fashion blogging and YouTube videos have become a major outlet for spreading trends and fashion tips, creating an online culture of sharing one’s style on a website or Instagram account. Through these media outlets readers and viewers all over the world can learn about fashion, making it very accessible.[46]

At the beginning of the 20th century, fashion magazines began to include photographs of various fashion designs and became even more influential than in the past. In cities throughout the world these magazines were greatly sought after and had a profound effect on public taste in clothing. Talented illustrators drew exquisite fashion plates for the publications which covered the most recent developments in fashion and beauty. Perhaps the most famous of these magazines was La Gazette du Bon Ton, which was founded in 1912 by Lucien Vogel and regularly published until 1925 (with the exception of the war years).[47]

A see-through top worn along with pasties by a model at a fashion show in USA, 2017. Such fashion trends get popularised through media.

Vogue, founded in the United States in 1892, has been the longest-lasting and most successful of the hundreds of fashion magazines that have come and gone. Increasing affluence after World War II and, most importantly, the advent of cheap color printing in the 1960s, led to a huge boost in its sales and heavy coverage of fashion in mainstream women’s magazines, followed by men’s magazines in the 1990s. One such example of Vogue’s popularity is the younger version, Teen Vogue, which covers clothing and trends that are targeted more toward the “fashionista on a budget”. Haute couture designers followed the trend by starting ready-to-wear and perfume lines which are heavily advertised in the magazines and now dwarf their original couture businesses. A recent development within fashion print media is the rise of text-based and critical magazines which aim to prove that fashion is not superficial, by creating a dialogue between fashion academia and the industry. Examples of this trend are: Fashion Theory (1997) and Vestoj (2009). Television coverage began in the 1950s with small fashion features. In the 1960s and 1970s, fashion segments on various entertainment shows became more frequent, and by the 1980s, dedicated fashion shows such as Fashion Television started to appear. FashionTV was the pioneer in this undertaking and has since grown to become the leader in both Fashion Television and new media channels.

A few days after the 2010 Fall Fashion Week in New York City came to a close, The New Islanders Fashion Editor, Genevieve Tax, criticized the fashion industry for running on a seasonal schedule of its own, largely at the expense of real-world consumers. “Because designers release their fall collections in the spring and their spring collections in the fall, fashion magazines such as Vogue always and only look forward to the upcoming season, promoting parkas come September while issuing reviews on shorts in January”, she writes. “Savvy shoppers, consequently, have been conditioned to be extremely, perhaps impractically, farsighted with their buying.”[48]

The fashion industry has been the subject of numerous films and television shows, including the reality show Project Runway and the drama series Betty. Specific fashion brands have been featured in film, not only as product placement opportunities, but as bespoke items that have subsequently led to trends in fashion.[49]

Videos in general have been very useful in promoting the fashion industry. This is evident not only from television shows directly spotlighting the fashion industry, but also movies, events and music videos which showcase fashion statements as well as promote specific brands through product placements.

Public relations and social media

A Mexican sports reporter wearing little black dress and knee-high boots

Fashion public relations involves being in touch with a company’s audiences and creating strong relationships with them, reaching out to media and initiating messages that project positive images of the company.[50] Social media plays an important role in modern-day fashion public relations; enabling practitioners to reach a wide range of consumers through various platforms.

Building brand awareness and credibility is a key implication of good public relations. In some cases, great hype is built about new designers’ collections before they are released into the market, due to the immense exposure generated by practitioners.[51] Social media, such as blogs, micro blogs, podcasts, photo and video sharing sites have all become increasingly important to fashion public relations.[52] The interactive nature of these platforms allows practitioners to engage and communicate with publics in real time, and tailor their clients’ brand or campaign messages to the target audience. With blogging platforms such as Instagram, Tumblr, WordPress, and other sharing sites, bloggers have emerged as expert fashion commentators, shaping brands and having a great impact on what is ‘on trend’.[53] Women in the fashion public relations industry such as Sweaty Betty PR founder Roxy Jacenko and Oscar de la Renta’s PR girl Erika Bearman, have acquired copious followers on their social media sites, by providing a brand identity and a behind the scenes look into the companies they work for.

Social media is changing the way practitioners deliver messages,[12] as they are concerned with the media, and also customer relationship building.[54] PR practitioners must provide effective communication among all platforms, in order to engage fashion publics in an industry socially connected via online shopping.[55] Consumers have the ability to share their purchases on their personal social media pages (such as Facebook, Twitter, Instagram, etc.), and if practitioners deliver the brand message effectively and meet the needs of its publics, word-of-mouth publicity will be generated and potentially provide a wide reach for the designer and their products.

Anthropological perspective

Anthropology, the study of culture and human societies, studies fashion by asking why certain styles are deemed socially appropriate and others are not. A certain way is chosen and that becomes the fashion as defined by a certain people as a whole, so if a particular style has a meaning in an already occurring set of beliefs that style will become fashion.[56] According to Ted Polhemus and Lynn Procter, fashion can be described as adornment, of which there are two types: fashion and anti-fashion. Through the capitalization and commoditisation of clothing, accessories, and shoes, etc., what once constituted anti-fashion becomes part of fashion as the lines between fashion and anti-fashion are blurred.[57]

The definition of fashion and anti-fashion is as follows: Anti-fashion is fixed and changes little over time. Anti-fashion is different depending on the cultural or social group one is associated with or where one lives, but within that group or locality the style changes little. Fashion is the exact opposite of anti-fashion. Fashion changes very quickly and is not affiliated with one group or area of the world but is spread out throughout the world wherever people can communicate easily with each other. For example, Queen Elizabeth II’s 1953 coronation gown is an example of anti-fashion because it is traditional and does not change over any period whereas a gown from fashion designer Dior’s collection of 1953 is fashion because the style will change every season as Dior comes up with a new gown to replace the old one. In the Dior gown the length, cut, fabric, and embroidery of the gown change from season to season. Anti-fashion is concerned with maintaining the status quo while fashion is concerned with social mobility. Time is expressed in terms of continuity in anti-fashion and as change in fashion. Fashion has changing modes of adornment while anti-fashion has fixed modes of adornment. Indigenous and peasant modes of adornment are an example of anti-fashion. Change in fashion is part of the larger system and is structured to be a deliberate change in style.[58]

Today, people in rich countries are linked to people in poor countries through the commoditization and consumption of what is called fashion. People work long hours in one area of the globe to produce things that people in another part of the globe are anxious to consume. An example of this is the chain of production and consumption of Nike shoes, which are produced in Taiwan and then purchased in North America. At the production end, there is nation-building a hard working ideology that leads people to produce and entices people to consume with a vast amount of goods for the offering[clarification needed]. Commodities are no longer just utilitarian but are fashionable, be they running shoes or sweat suits.[59]

The change from anti-fashion to fashion because of the influence of western consumer-driven civilization can be seen in eastern Indonesia. The ikat textiles of the Ngada area of eastern Indonesia are changing because of modernization and development. Traditionally, in the Ngada area there was no idea similar to that of the Western idea of fashion, but anti-fashion in the form of traditional textiles and ways to adorn oneself were widely popular. Textiles in Indonesia have played many roles for the local people. Textiles defined a person’s rank and status; certain textiles indicated being part of the ruling class. People expressed their ethnic identity and social hierarchy through textiles. Because some Indonesians bartered ikat textiles for food, the textiles constituted economic goods, and as some textile design motifs had spiritual religious meanings, textiles were also a way to communicate religious messages.[60]

In eastern Indonesia, both the production and use of traditional textiles have been transformed as the production, use and value associated with textiles have changed due to modernization. In the past, women produced the textiles either for home consumption or to trade with others. Today, this has changed as most textiles are not being produced at home. Western goods are considered modern and are valued more than traditional goods, including the sarong, which retain a lingering association with colonialism. Now, sarongs are used only for rituals and ceremonial occasions, whereas western clothes are worn to church or government offices. Civil servants working in urban areas are more likely than peasants to make the distinction between western and traditional clothes. Following Indonesia’s independence from the Dutch, people increasingly started buying factory made shirts and sarongs. In textile-producing areas the growing of cotton and production of naturally colored thread became obsolete. Traditional motifs on textiles are no longer considered the property of a certain social class or age group. Wives of government officials are promoting the use of traditional textiles in the form of western garments such as skirts, vests and blouses. This trend is also being followed by the general populace, and whoever can afford to hire a tailor is doing so to stitch traditional ikat textiles into western clothes. Thus, traditional textiles are now fashion goods and are no longer confined to the black, white and brown colour palette but come in array of colours. Traditional textiles are also being used in interior decorations and to make handbags, wallets and other accessories, which are considered fashionable by civil servants and their families. There is also a booming tourist trade in the eastern Indonesian city of Kupang where international as well as domestic tourists are eager to purchase traditionally printed western goods.[61]

The use of traditional textiles for fashion is becoming big business in eastern Indonesia, but these traditional textiles are losing their ethnic identity markers and are being used as an item of fashion.[62]

Intellectual property

In the fashion industry, intellectual property is not enforced as it is within the film industry and music industry. Robert Glariston, an intellectual property expert, mentioned in a fashion seminar held in LA[which?] that “Copyright law regarding clothing is a current hot-button issue in the industry. We often have to draw the line between designers being inspired by a design and those outright stealing it in different places.”[citation needed] To take inspiration from others’ designs contributes to the fashion industry’s ability to establish clothing trends. For the past few years, WGSN has been a dominant source of fashion news and forecasts in encouraging fashion brands worldwide to be inspired by one another. Enticing consumers to buy clothing by establishing new trends is, some have argued, a key component of the industry’s success. Intellectual property rules that interfere with this process of trend-making would, in this view, be counter-productive. On the other hand, it is often argued that the blatant theft of new ideas, unique designs, and design details by larger companies is what often contributes to the failure of many smaller or independent design companies.

Since fakes are distinguishable by their poorer quality, there is still a demand for luxury goods, and as only a trademark or logo can be copyrighted, many fashion brands make this one of the most visible aspects of the garment or accessory. In handbags, especially, the designer’s brand may be woven into the fabric (or the lining fabric) from which the bag is made, making the brand an intrinsic element of the bag.

In 2005, the World Intellectual Property Organization (WIPO) held a conference calling for stricter intellectual property enforcement within the fashion industry to better protect small and medium businesses and promote competitiveness within the textile and clothing industries.[63][64]

Political activism

There has been great debate about politics’ place in Fashion and traditionally, the Fashion Industry has maintained a rather apolitical stance.[65] Considering the U.S.’s political climate in the surrounding months of the 2016 presidential election, during 2017 Fashion weeks in London, Milan, New York, Paris and São Paulo amongst others, many designers took the opportunity to take political stances leveraging their platforms and influence to reach the masses.

Aiming to “amplify a greater message of unity, inclusion, diversity, and feminism in a fashion space”, Mara Hoffman invited the founders of the Women’s March on Washington to open her show which featured modern silhouettes of utilitarian wear, described by critics as “Made for a modern warrior” and “Clothing for those who still have work to do”.[66] Prabal Gurung debuted his collection of T-shirts featuring slogans such as “The Future is Female”, “We Will Not Be Silenced”, and “Nevertheless She Persisted”, with proceeds going to the ACLU, Planned Parenthood, and Gurung’s own charity, “Shikshya Foundation Nepal”.[65] Similarly, The Business of Fashion launched the #TiedTogether movement on Social Media, encouraging member of the industry from editors to models, to wear a white bandana advocating for “unity, solidarity, and inclusiveness during fashion week”.[67]

Fashion may be used to promote a cause, such as to promote healthy behavior,[68] to raise money for a cancer cure,[69] or to raise money for local charities[70] such as the Juvenile Protective Association[71] or a children’s hospice.[72]

One fashion cause is trashion, which is using trash to make clothes, jewelery, and other fashion items in order to promote awareness of pollution. There are a number of modern trashion artists such as Marina DeBris, Ann Wizer,[73] and Nancy Judd.[74]

See also

References

  1. Simon, Stephanie (2009-01-13). “‘Trashion’ Trend: Dumpster Couture Gets a Boost at Green Inaugural Ball”. Wall Street Journal. Retrieved 2013-02-15.

Bibliography

Further reading

  • Breward, Christopher, The culture of fashion: a new history of fashionable dress, Manchester: Manchester University Press, 2003, ISBN 978-0-7190-4125-9
  • Cabrera, Ana, and Lesley Miller. “Genio y Figura. La influencia de la cultura española en la moda.” Fashion Theory: The Journal of Dress, Body & Culture 13.1 (2009): 103–110
  • , Valerie: Understanding Fashion History, Costume & Fashion Press, 2004, ISBN 0-89676-253-X
  • Hollander, Anne, Seeing through clothes, Berkeley: University of California Press, 1993, ISBN 978-0-520-08231-1
  • Hollander, Anne, and suits: the evolution of modern dress, New York: Knopf, 1994, ISBN 978-0-679-43096-4
  • Hollander, Anne, Feeding the eye: essays, New York: Farrar, Straus, and Giroux, 1999, ISBN 978-0-374-28201-1
  • Hollander, Anne, Fabric of vision: dress and drapery in painting, London: National Gallery, 2002, ISBN 978-0-300-09419-0
  • Kawamura, Yuniya, Fashion-ology: an introduction to Fashion Studies, Oxford and New York: Berg, 2005, ISBN 1-85973-814-1
  • Lipovetsky, Gilles (translated by Catherine Porter), The empire of fashion: dressing modern democracy, Woodstock: Princeton University Press, 2002, ISBN 978-0-691-10262-7
  • McDermott, Kathleen, Style for all: why fashion, invented by kings, now belongs to all of us (An illustrated history), 2010, ISBN 978-0-557-51917-0 — Many hand-drawn color illustrations, extensive annotated bibliography and reading guide
  • Perrot, Philippe (translated by Richard Bienvenu), Fashioning the bourgeoisie: a history of clothing in the nineteenth century, Princeton NJ: Princeton University Press, 1994, ISBN 978-0-691-00081-7
  • Steele, Valerie, Paris fashion: a cultural history, (2. ed., rev. and updated), Oxford: Berg, 1998, ISBN 978-1-85973-973-0
  • Steele, Valerie, Fifty years of fashion: new look to now, New Haven: Yale University Press, 2000, ISBN 978-0-300-08738-3
  • Steele, Valerie, Encyclopedia of clothing and fashion, Detroit: Thomson Gale, 2005
  • Davis, F. (1989). Of maids’ uniforms and blue jeans: The drama of status ambivalences in clothing and fashion. Qualitative Sociology, 12(4), 337-355.

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