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51-584: A small grommet may also be called an eyelet , used for example on shoes, tarps and sails for lacing purposes. Grommets in electrical applications are referred to as "insulating bushings". Most common are molded rubber bushings that are inserted into hole diameters up to 2″ (51 mm). There are many hole configurations from standard round to assorted U-shapes. Larger penetrations that are irregular in shape as well as long straight edges are often fitted with extruded or stamped strips of continuous length, referred to as "grommet edging". This type of protective bushing

102-694: A digital circuit , or a mixed-signal circuit (a combination of analog circuits and digital circuits). The most widely used semiconductor device in electronic circuits is the MOSFET (metal–oxide–semiconductor field-effect transistor ). Analog electronic circuits are those in which current or voltage may vary continuously with time to correspond to the information being represented. The basic components of analog circuits are wires, resistors, capacitors, inductors, diodes , and transistors . Analog circuits are very commonly represented in schematic diagrams , in which wires are shown as lines, and each component has

153-411: A field-effect transistor can be modeled as a current source from the source to the drain, with the current controlled by the gate-source voltage. When the circuit size is comparable to a wavelength of the relevant signal frequency, a more sophisticated approach must be used, the distributed-element model . Wires are treated as transmission lines, with nominally constant characteristic impedance , and

204-543: A consequence, extremely complex digital circuits, with billions of logic elements integrated on a single silicon chip, can be fabricated at low cost. Such digital integrated circuits are ubiquitous in modern electronic devices, such as calculators, mobile phone handsets, and computers. As digital circuits become more complex, issues of time delay, logic races , power dissipation, non-ideal switching, on-chip and inter-chip loading, and leakage currents, become limitations to circuit density, speed and performance. Digital circuitry

255-420: A drying and softening operation, and may include splitting, shaving, dyeing , whitening or other methods. For some leathers, tanners apply a surface coating, called "finishing". Finishing operations can include oiling, brushing, buffing, coating, polishing, embossing, glazing , or tumbling , among others. Leather can be oiled to improve its water resistance. This currying process after tanning supplements

306-432: A flexible form that does not become putrid when rewetted. Many tanning methods and materials exist. The typical process sees tanners load the hides into a drum and immerse them in a tank that contains the tanning "liquor". The hides soak while the drum slowly rotates about its axis, and the tanning liquor slowly penetrates through the full thickness of the hide. Once the process achieves even penetration, workers slowly raise

357-642: A properly managed facility. A review of the total pollution load decrease achievable according to the United Nations Industrial Development Organization posts precise data on the abatement achievable through industrially proven low-waste advanced methods, while noting, "even though the chrome pollution load can be decreased by 94% on introducing advanced technologies, the minimum residual load 0.15 kg/t raw hide can still cause difficulties when using landfills and composting sludge from wastewater treatment on account of

408-429: A receiver, analog circuitry is used to amplify and frequency-convert signals so that they reach a suitable state to be converted into digital values, after which further signal processing can be performed in the digital domain. In electronics , prototyping means building an actual circuit to a theoretical design to verify that it works, and to provide a physical platform for debugging it if it does not. The prototype

459-483: A unique symbol. Analog circuit analysis employs Kirchhoff's circuit laws : all the currents at a node (a place where wires meet), and the voltage around a closed loop of wires is 0. Wires are usually treated as ideal zero-voltage interconnections; any resistance or reactance is captured by explicitly adding a parasitic element, such as a discrete resistor or inductor. Active components such as transistors are often treated as controlled current or voltage sources: for example,

510-430: A variety of items, including clothing, footwear, handbags, furniture, tools and sports equipment, and lasts for decades. Leather making has been practiced for more than 7,000 years and the leading producers of leather today are China and India. Critics of tanneries claim that they engage in unsustainable practices that pose health hazards to the people and the environment near them. The leather manufacturing process

561-480: A variety of ways. They have been utilized as chest handles or on row boats as a soft oar lock. They are a rope ring that is made by first disassembling the rope then re-weaving the strands to the desired size. Holes in metal or another hard material will often have sharp edges. Electrical wires , cord , rope , lacings, or other soft vulnerable material passing through the hole can become abraded or cut, or electrical insulation may break due to repeated flexing at

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612-628: A wet cloth or soaking the leather in water. Various treatments are available such as conditioners . Saddle soap is used for cleaning, conditioning, and softening leather. Leather shoes are widely conditioned with shoe polish . Due to its high resistance to abrasion and wind, leather found a use in rugged occupations. The enduring image of a cowboy in leather chaps gave way to the leather-jacketed and leather-helmeted aviator . When motorcycles were invented, some riders took to wearing heavy leather jackets to protect from road rash and wind blast; some also wear chaps or full leather pants to protect

663-401: A wide variety of sizes and lengths expressly for this purpose; they are usually a single piece which can be inserted by hand. Two-piece hard plastic devices are available which also grip the wire that passes through. These are called strain relief bushings and are often used to insulate, anchor, and protect power cords where they enter panels. Preventing a tug or twist on the wire from stressing

714-416: Is a process that stabilizes the proteins , particularly collagen , of the raw hide to increase the thermal, chemical and microbiological stability of the hides and skins, making it suitable for a wide variety of end applications. The principal difference between raw and tanned hides is that raw hides dry out to form a hard, inflexible material that, when rewetted, will putrefy , while tanned material dries to

765-534: Is also used for falconry jesses, soccer footwear, (e.g. Adidas Copa Mundial ) and boxing speed bags. Although originally raised for their feathers in the 19th century, ostriches are now more popular for both meat and leather. Ostrich leather has a characteristic "goose bump" look because of the large follicles where the feathers grew. Different processes produce different finishes for many applications, including upholstery, footwear, automotive products, accessories, and clothing. In Thailand , stingray leather

816-411: Is called bating. Lipases are used in the degreasing operation to hydrolyze fat particles embedded in the skin. Amylases are used to soften skin, to bring out the grain, and to impart strength and flexibility to the skin. These enzymes are rarely used. The natural fibers of leather break down with the passage of time. Acidic leathers are particularly vulnerable to red rot , which causes powdering of

867-698: Is composed of individual electronic components , such as resistors , transistors , capacitors , inductors and diodes , connected by conductive wires or traces through which electric current can flow. It is a type of electrical circuit. For a circuit to be referred to as electronic , rather than electrical , generally at least one active component must be present. The combination of components and wires allows various simple and complex operations to be performed: signals can be amplified, computations can be performed, and data can be moved from one place to another. Circuits can be constructed of discrete components connected by individual pieces of wire, but today it

918-405: Is divided into three fundamental subprocesses: preparatory stages, tanning, and crusting. A further subprocess, finishing, can be added into the leather process sequence, but not all leathers receive finishing. The preparatory stages are when the hide is prepared for tanning. Preparatory stages may include soaking, hair removal, liming , deliming , bating , bleaching , and pickling . Tanning

969-449: Is known as static random-access memory (SRAM). Memory based on the storage of charge in a capacitor, dynamic random-access memory (DRAM), is also widely used.) The design process for digital circuits is fundamentally different from the process for analog circuits. Each logic gate regenerates the binary signal, so the designer need not account for distortion, gain control, offset voltages, and other concerns faced in an analog design. As

1020-495: Is much more common to create interconnections by photolithographic techniques on a laminated substrate (a printed circuit board or PCB) and solder the components to these interconnections to create a finished circuit. In an integrated circuit or IC, the components and interconnections are formed on the same substrate, typically a semiconductor such as doped silicon or (less commonly) gallium arsenide . An electronic circuit can usually be categorized as an analog circuit ,

1071-450: Is often constructed using techniques such as wire wrapping or using a breadboard , stripboard or perfboard , with the result being a circuit that is electrically identical to the design but not physically identical to the final product. Open-source tools like Fritzing exist to document electronic prototypes (especially the breadboard-based ones) and move toward physical production. Prototyping platforms such as Arduino also simplify

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1122-452: Is one of the most exploited reptile species in the world in the leather trade. However, it is not endangered and while monitored, trade is legal in most South American countries. Kangaroo leather is used to make items that must be strong and flexible. It is the material most commonly used in bullwhips . Some motorcyclists favor kangaroo leather for motorcycle leathers because of its light weight and abrasion resistance. Kangaroo leather

1173-426: Is quite common in applications that range from telecom switches and data center cabinets to complex and dense wire/cable and even hydraulic tubing in aircraft, transportation vehicles and medical equipment. Grommets are typically used to reinforce holes in leather , cloth , shoes , canvas and other fabrics . They can be made of metal , rubber , or plastic , and are easily used in common projects, requiring only

1224-545: Is used in wallets and belts. Stingray leather is tough and durable. The leather is often dyed black and covered with tiny round bumps in the natural pattern of the back ridge of an animal. These bumps are then usually dyed white to highlight the decoration. Stingray rawhide is also used as grips on Chinese swords, Scottish basket hilted swords, and Japanese katanas . Stingray leather is also used for high abrasion areas in motorcycle racing leathers (especially in gloves, where its high abrasion resistance helps prevent wear through in

1275-665: Is used to create general purpose computing chips, such as microprocessors , and custom-designed logic circuits, known as application-specific integrated circuit (ASICs). Field-programmable gate arrays (FPGAs), chips with logic circuitry whose configuration can be modified after fabrication, are also widely used in prototyping and development. Mixed-signal or hybrid circuits contain elements of both analog and digital circuits. Examples include comparators , timers , phase-locked loops , analog-to-digital converters , and digital-to-analog converters . Most modern radio and communications circuitry uses mixed signal circuits. For example, in

1326-649: The eardrum to allow air to pass through into the middle ear, and thus release any pressure buildup and help clear excess fluid within. This is also a correcting measure for a patulous Eustachian tube (when air moves to and from the middle ear with each breath making the eardrum flap). Leather Leather is a strong, flexible and durable material obtained from the tanning , or chemical treatment, of animal skins and hides to prevent decay. The most common leathers come from cattle , sheep , goats, equine animals, buffalo, pigs and hogs, and aquatic animals such as seals and alligators. Leather can be used to make

1377-520: The impedances at the start and end determine transmitted and reflected waves on the line. Circuits designed according to this approach are distributed-element circuits . Such considerations typically become important for circuit boards at frequencies above a GHz; integrated circuits are smaller and can be treated as lumped elements for frequencies less than 10GHz or so. In digital electronic circuits , electric signals take on discrete values, to represent logical and numeric values. These values represent

1428-589: The 1970s and 80s) are well known for wearing leather clothing. Extreme metal bands (especially black metal bands) and Goth rock groups have extensive black leather clothing. Leather has become less common in the punk community over the last three decades, as there is opposition to the use of leather from punks who support animal rights . Many cars and trucks come with optional or standard leather or "leather faced" seating. In countries with significant populations of individuals observing religions which place restrictions on material choices, vendors typically clarify

1479-430: The cord from tearing through the hole, thereby providing structural integrity. Small grommets are also called eyelets, especially when used in clothing or crafting. Eyelets may be used purely decoratively for crafting. When used in sailing and various other applications, they are called cringles . Sometimes field workers refer to them as grunyons . Traditionally, rope grommets have been widely used on sailing ships in

1530-421: The drive in place pass through grommets that decouple it acoustically from the chassis. Grommets are used in a similar way to acoustically isolate electronic circuit components that are susceptible to microphonism caused by mechanical vibration or jarring. In chronic cases of otitis media with effusions present for months, surgery is sometimes performed to insert a grommet, called a " tympanostomy tube " into

1581-559: The electrical connections inside the connected equipment. Sleeved grommets have a flexible extension (sleeve), usually tapered or moulded to flex increasingly towards the free end in order to reduce fracturing of electrical insulation. Grommets made of rubber or other elastic material are also used to minimize the transmission of vibration. They were widely used for mounting shock-sensitive computer disk drives , particularly in equipment subject to vibration or jarring, but are not usually used with more robust modern drives. The screws that hold

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1632-679: The event of an accident). For a given thickness, fish leather is typically much stronger due to its criss-crossed fibers. Leather produces some environmental impact, most notably due to: Estimates of the carbon footprint of bovine leather range from 65 to 150 kg of CO 2 equivalent per square meter of production. One ton of hide or skin generally produces 20 to 80 m of waste water, including chromium levels of 100–400 mg/L, sulfide levels of 200–800 mg/L, high levels of fat and other solid wastes, and notable pathogen contamination. Producers often add pesticides to protect hides during transport. With solid wastes representing up to 70% of

1683-518: The exit point of the casing of a junction box for example. Rubber, plastic or plastic coated metal grommets are used to avoid this. Tight fitting rubber grommets can also prevent the entry of dirt, air, water, etc. The smooth and sometimes soft inner surface of the grommet shields the wire from damage. Grommets are generally used whenever wires pass through punched or drilled sheet metal or plastic casings for this reason. Molded and continuous strip grommets, also known as edge grommets, are manufactured in

1734-452: The following grades: The term "genuine leather" does not describe a specific grade. The term often indicates split leather that has been extensively processed, and some sources describe it as synonymous with bicast leather, or made from multiple splits glued together and coated. In some countries, when it is the description on a product label the term means nothing more than "contains leather"; depending on jurisdiction, regulations limit

1785-737: The grommet itself and a means of setting it. A simple punch , a metal rod with a convex tip, is often sold with the grommets. It can be struck with a hammer to set the grommet. It can alternatively be set with an electronic, pneumatic, or gas-powered machine. There are also dedicated grommet presses with punch and anvil , as shown in the picture, ranging from inexpensive to better-quality tools, which are somewhat faster to use. Typical applications are footwear for boot and shoe laces, in laced clothing such as corsets , in flags for hoisting, and in curtains and other household items that require hanging from hooks, as when they are used in conjunction with tensioner rods for shower curtains. The grommet prevents

1836-820: The information that is being processed. In the vast majority of cases, binary encoding is used: one voltage (typically the more positive value) represents a binary '1' and another voltage (usually a value near the ground potential, 0 V) represents a binary '0'. Digital circuits make extensive use of transistors , interconnected to create logic gates that provide the functions of Boolean logic : AND, NAND, OR, NOR, XOR and combinations thereof. Transistors interconnected so as to provide positive feedback are used as latches and flip flops, circuits that have two or more metastable states, and remain in one of these states until changed by an external input. Digital circuits therefore can provide logic and memory, enabling them to perform arbitrary computational functions. (Memory based on flip-flops

1887-440: The leather. Chemical damage can also occur from exposure to environmental factors, including ultraviolet light, ozone, acid from sulfurous and nitrous pollutants in the air, or through a chemical action following any treatment with tallow or oil compounds. Both oxidation and chemical damage occur faster at higher temperatures. There are few methods to maintain and clean leather goods properly such as using damp cloth and avoid using

1938-399: The liquor's pH in a process called basification, which fixes the tanning material to the leather. The more tanning material fixed, the higher the leather's hydrothermal stability and shrinkage temperature resistance. Crusting is a process that thins and lubricates leather. It often includes a coloring operation. Chemicals added during crusting must be fixed in place. Crusting culminates with

1989-480: The lower body. Leather's flexibility allows it to be formed and shaped into balls and protective gear. Subsequently, many sports use equipment made with leather, such as baseball gloves and the ball used in cricket and gridiron football . Leather fetishism is the name popularly used to describe a fetishistic attraction to people wearing leather, or in certain cases, to the garments themselves. Many rock groups (particularly heavy metal and punk groups in

2040-400: The natural oils remaining in the leather itself, which can be washed out through repeated exposure to water. Frequent oiling of leather, with mink oil , neatsfoot oil , or a similar material keeps it supple and improves its lifespan dramatically. Tanning processes largely differ in which chemicals are used in the tanning liquor. Some common types include: In general, leather is produced in

2091-538: The regulations currently in force in some countries." In Kanpur , the self-proclaimed "Leather City of World"—with 10,000 tanneries as of 2011 and a city of three million on the banks of the Ganges —pollution levels were so high, that despite an industry crisis, the pollution control board decided to shut down 49 high-polluting tanneries out of 404 in July 2009. In 2003 for instance, the main tanneries' effluent disposal unit

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2142-468: The shell. It is prized for its mirror-like finish and anti-creasing properties. Lamb and deerskin are used for soft leather in more expensive apparel. Deerskin is widely used in work gloves and indoor shoes. Reptilian skins, such as alligator , crocodile, and snake , are noted for their distinct patterns that reflect the scales of their species. This has led to hunting and farming of these species in part for their skins. The Argentine black and white tegu

2193-542: The source of leather in their products. Such labeling helps facilitate religious observance, so, for example, a Muslim will not accidentally purchase pigskin or a Hindu can avoid cattleskin. Such taboos increase the demand for religiously neutral leathers such as ostrich and deer . Judaism forbids the comfort of wearing leather shoes on Yom Kippur , Tisha B'Av , and during mourning. Also, see Leather in Judaism , Teffilin and Torah Scroll . Jainism prohibits

2244-400: The surface and a change in consistency. Damage from red rot is aggravated by high temperatures and relative humidities. Although it is chemically irreversible, treatments can add handling strength and prevent disintegration of red rotted leather. Exposure to long periods of low relative humidities (below 40%) can cause leather to become desiccated, irreversibly changing the fibrous structure of

2295-440: The term's use in product labelling. Today, most leather is made of cattle (cow) hides, which constitute about 65% of all leather produced. Other animals that are used include sheep (about 13%), goats (about 11%), and pigs (about 10%). Obtaining accurate figures from around the world is difficult, especially for areas where the skin may be eaten. There are significant regional differences in leather production: i.e. goat leather

2346-674: The use of leather, since it is obtained by killing animals. Many forms of artificial leather have been developed, usually involving polyurethane or vinyl coatings applied to a cloth backing. Many names and brands for such artificial leathers exist, including "pleather", a portmanteau of "plastic leather", and the brand name Naugahyde . Another alternative is cultured leather which is lab-grown using cell-culture methods, mushroom-based materials and gelatin-based textile made by upcycling meat industry waste. Leather made of fungi or mushroom-based materials are completely biodegradable. Electronic circuit An electronic circuit

2397-462: The weekend of 8 April 2017 in the neighborhood. The higher cost associated with the treatment of effluents than to untreated effluent discharging leads to illegal dumping to save on costs. For instance, in Croatia in 2001, proper pollution abatement cost US$ 70–100 per ton of raw hides processed against $ 43/t for irresponsible behavior. In November 2009, one of Uganda's main leather making companies

2448-728: The wet weight of the original hides, the tanning process represents a considerable strain on water treatment installations. Leather biodegrades slowly—taking 25 to 40 years to decompose . However, vinyl and petrochemical-derived materials take 500 or more years to decompose. Tanning is especially polluting in countries where environmental regulations are lax, such as in India, the world's third-largest producer and exporter of leather. To give an example of an efficient pollution prevention system, chromium loads per produced tonne are generally abated from 8 kg to 1.5 kg. VOC emissions are typically reduced from 30 kg/t to 2 kg/t in

2499-544: Was caught directly dumping waste water into a wetland adjacent to Lake Victoria . Enzymes like proteases , lipases , and amylases have an important role in the soaking, dehairing, degreasing, and bating operations of leather manufacturing. Proteases are the most commonly used enzymes in leather production. The enzyme must not damage or dissolve collagen or keratin , but should hydrolyze casein , elastin , albumin , globulin -like proteins, and nonstructural proteins that are not essential for leather making. This process

2550-592: Was dumping 22 tonnes of chromium-laden solid waste per day in the open. In the Hazaribagh neighborhood of Dhaka in Bangladesh , chemicals from tanneries end up in Dhaka's main river. Besides the environmental damage, the health of both local factory workers and the end consumer is also negatively affected. After approximately 15 years of ignoring high court rulings, the government shut down more than 100 tanneries

2601-557: Was historically called "Turkey" or "Morocco" due to its association with the Middle East, while pig skin had historically been used the most in Germany. Other animals mentioned below only constitute a fraction of a percent of total leather production. Horse hides are used to make particularly durable leathers. Shell cordovan is a horse leather made not from the outer skin but from an under layer, found only in equine species, called

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