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#851 2020-11-16 00:29:12

ganesh
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Re: Miscellany

829) Rattlesnake

Rattlesnake, any of 33 species of venomous New World vipers characterized by a segmented rattle at the tip of the tail that produces a buzzing sound when vibrated. Rattlesnakes are found from southern Canada to central Argentina but are most abundant and diverse in the deserts of the southwestern United States and northern Mexico. Adults usually vary in length from 0.5 to 2 metres (1.6 to 6.6 feet), but some can grow to 2.5 metres (8.2 feet). A few species are marked with transverse bands, but most rattlesnakes are blotched with dark diamonds, hexagons, or rhombuses on a lighter background, usually gray or light brown; some are various shades of orange, pink, red, or green.

The most common species in North America are the timber rattlesnake (Crotalus horridus) of the eastern United States, the prairie rattlesnake (C. viridis) of the western United States, and the eastern and western diamondbacks (C. adamanteus and C. atrox). These are also the largest rattlers. Twenty-six other species also belong to the genus Crotalus, including the small North American sidewinder (C. cerastes). The other three species belong to a more primitive genus, Sistrurus, which includes the North American massasauga (S. catenatus) and pygmy rattler (S. miliarius). These rattlesnakes have nine large scales on the upper surface of their heads.

Rattlesnakes are not aggressive and will not attack humans if unprovoked; in fact, they are quite shy and timid. However, they are venomous and can be dangerous if molested or handled. With improved methods of treatment and the abandonment of folk cures (many of which presented more danger than benefit to the victim), a rattlesnake bite is no longer the threat to life that it once was, but medical assessment should always be sought after any bite. A rattlesnake bite is very painful, and that of a snake more than 1 metre (3.3 feet) long can be fatal. The snake should be killed and brought in for identification, even for “dry” bites, in which venom is not injected. A person with a “dry” bite should not be treated with antivenin because many people are allergic to the horse serum used in its production. The allergic reaction can result in shock and death. The most dangerous species are the Mexican west coast rattlesnake (C. basiliscus), the Mojave rattlesnake (C. scutulatus), and the South American rattlesnake, or cascabel (C. durissus). Their venom attacks the nervous system more strongly than that of other rattlesnakes. The South American rattlesnake has the largest distribution of any rattlesnake; it ranges from Mexico to Argentina and is the only rattlesnake found throughout Central and South America.

Rattlesnakes are pit vipers (subfamily Crotalinae of the family Viperidae), a group named for the small heat-sensing pit between each eye and nostril that aids in hunting. The pits provide the snake with stereoscopic heat “vision,” enabling them to detect and accurately strike a living target in complete darkness. Most rattlesnakes live in arid habitats and are nocturnal, hiding during the day but emerging in the evening or at twilight to hunt for prey, which consists primarily of small mammals, especially rodents. Young and small rattlesnakes feed largely on lizards.

A rattlesnake fang is similar to a curved hypodermic needle. At the top it meets with the end of the venom duct. Soft tissue surrounds the end of the venom duct and the base of the fang, providing a seal against leakage. Large venom glands at the base of the jaws are responsible for the distinctly triangular shape of the head. Fangs are periodically lost owing to wear and breakage. Each fang has a series of seven developing fangs behind the functional fang, each smaller and less developed than the one preceding it. Fang length depends on the species and size of the snake, but large rattlers can have fangs 10–15 cm (4–6 inches) long. When the snake’s mouth is closed, the fangs are folded back and lie parallel to the roof of the mouth. Linkages of bones in the upper jaw allow the fangs to be deployed into a vertical position for stabbing and biting.

Like other reptiles, rattlesnakes cannot tolerate extreme heat or cold. During the heat of the day, rattlesnakes hide themselves underground in burrows or under rocks. In the fall they congregate in rock slides or crevices for their winter hibernation in dens that may shelter hundreds of individuals of several different species. Upon emerging in the spring, the males mate with females and then disperse from the den site to spend the summer in surrounding countryside. In the fall they all return to the same den.

Rattlesnakes give birth to young that develop from eggs retained inside the mother (ovoviviparous). In the late summer, broods of 1–60 are produced; average broods number 4–10 young. Newborn rattlesnakes have functioning fangs and venom glands. Their venom is more potent but of lesser quantity than that of their mother, a condition that helps ensure that the young can secure food. The newborn babies are also equipped with a single button on the end of the tail. After the first shedding of their skin (within a week of birth), they will have two rattle segments. Once the third rattle segment has been obtained, the young snake can buzz like an adult. The rattle, presumably a warning device, is composed of horny, loosely connected hollow segments, one of which is added every time the snake sheds its skin. The age of a rattlesnake cannot be determined from the number of its rattle segments, as rattlesnakes usually shed three or four times a year. In captivity, 10 species have lived from 20 to 30 years.

Every year in the United States, an estimated 5,000 rattlesnakes are collected and destroyed in about 30 highly commercialized “rattlesnake roundups.” Supposedly conducted to save the lives of people and cattle, these spectacles may only reduce rattlesnakes’ valuable service in the control of rodent pests and in maintaining the natural balance of desert ecosystems.

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It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi. 

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#852 2020-11-17 00:54:23

ganesh
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Re: Miscellany

830) Black mamba

Black mamba, (Dendroaspis polylepis), species of mamba snake known for its large size, quickness, and extremely potent venom. It lives in sub-Saharan Africa and is one of the continent’s most dangerous snakes.

The average black mamba is 2–2.5 metres (6.6–8.2 feet) long, with a maximum length of 4.3 metres (14 feet). Despite its name, the snake is not black. Instead, it ranges in colour from gray to dark brown, with a lighter underside. The black actually refers to the colour of the inside of its mouth; green mambas and other snakes have white mouths. The black mamba is found in rocky savannas and lowland forests. Unlike the other mamba species, the black mamba is not primarily arboreal, preferring the ground, where it often sleeps in termite mounds or tree hollows. One of the fastest snakes, it is capable of speeds of more than 12 miles (19 km) per hour. The black mamba typically lays 6 to 20 eggs. Prey consists primarily of small mammals and birds.

Although it has an aggressive reputation, the black mamba is generally shy and nervous, and it will use its incredible speed to escape threats. However, if disturbed or cornered, the snake may rear up and threaten with an open mouth and a slightly expanded or flattened neck (or hood) before striking; once a black mamba attacks, it will bite its victim repeatedly. Its extremely toxic venom—two drops of which will reportedly kill most humans—attacks both the nervous system and the heart. Even though most bites are fatal, it is responsible for only a small number of deaths annually, and unprovoked attacks on humans have not been proved. In the wild, black mambas will typically live at least 11 years, while those in captivity have life spans of more than 20 years.

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It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi. 

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#853 2020-11-18 00:47:15

ganesh
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Re: Miscellany

831) Reindeer

Reindeer, (Rangifer tarandus), in North America called caribou, species of deer (family Cervidae) found in the Arctic tundra and adjacent boreal forests of Greenland, Scandinavia, Russia, Alaska, and Canada. Reindeer have been domesticated in Europe. There are two varieties, or ecotypes: tundra reindeer and forest (or woodland) reindeer. Tundra reindeer migrate between tundra and forest in huge herds numbering up to half a million in an annual cycle covering as much as 5,000 km (3,000 miles). Forest reindeer are much less numerous.

Large males can stand more than 1.2 metres (3.9 feet) tall at the shoulder and exceed 250 kg (550 pounds) in weight; females are slightly smaller. Reindeer have deeply cloven hoofs so the feet can spread on snow or soft ground; they are also good swimmers. Colour varies from whitish in winter to brown in summer. Heavy guard hairs are hollow, which increases the coat’s insulating properties. Antlers with up to 44 points can grow to 1.4 metres long in males; this is the only deer species in which females also have antlers.

Reindeer mature as yearlings if their nutrition is good, though males cannot compete for females until their fourth autumn, when their antlers and body mass (which are correlated) have grown sufficiently large. The rut occurs in October and lasts only 11 days. Tundra males, aggregated with thousands of females for the fall migration, assess other males’ antler size visually and thus generally avoid serious fights. Forest reindeer, on the other hand, defend discrete harems and fight harder. In both varieties a single calf is born in May or June after a gestation of seven and a half months. The calf grows rapidly on its mother’s milk, which is richer than that of any other ungulate. After one month it can eat fresh plant growth, and by three months it can survive if the mother dies, but normally weaning takes place at five to six months. Half of all calves born may be killed by wolves, bears, and lynx. Longevity is about 15 years in the wild, 20 in captivity.

Eurasian and American forest reindeer live in family groups of 6 to 13, with seasonal ranges of 500 square km (190 square miles) or less. Tundra reindeer spend winter dispersed in forests but aggregate in spring to migrate onto the tundra; in fall they mass again to return to the forest. Summer food is grass, sedges, green leaves of shrubs and new growth of larch, willow, and birch; mushrooms are sought in late summer. In winter, metabolism slows, and reindeer rely on high-carbohydrate lichens called reindeer moss, which they reach by digging craters in the snow. The calf follows its mother and shares this food. The reindeer survive on this low-protein diet by recycling urea (normally a waste product) within the digestive system and making use of its nitrogen.
Females keep their antlers all winter, which enables them to defend feeding craters from each other as well as males, which shed their antlers soon after the rut.

There are about 3.5 million caribou in North America and perhaps 1 million wild reindeer in Eurasia, mostly in Russia. Nearly 3 million domestic reindeer live in northern Europe. They are important to traditional herders such as the Sami (Lapps) of Scandinavia and Russia, who exploit them as pack and draft animals and for meat, milk, and hides; the antlers are carved into tools and totems. The herdsmen use boats to direct herds to offshore islands in summer. In the forests of the Da Hinggan region of northeastern China, the Evenk people use reindeer as pack animals and as mounts, and small numbers of Tsaatan (Dhukha) herders in northern Mongolia utilize the reindeer they keep in a variety of ways.

Of the nine subspecies recognized, two are forest ecotypes, one living in North America and the other in Eurasia. Fossil evidence from Alaska indicates that they evolved during the late Pliocene Epoch (3.6 million to 2.6 million years ago). During the last glaciation  more than 11,700 years ago, they were hunted by the Clovis people of New Mexico and by many early Stone Age tribes in southern Europe.

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It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi. 

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#854 2020-11-19 00:11:23

ganesh
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Re: Miscellany

832) Wrench

Wrench, also called spanner, tool, usually operated by hand, for tightening bolts and nuts. Basically, a wrench consists of a stout lever with a notch at one or both ends for gripping the bolt or nut in such a way that it can be twisted by a pull on the wrench at right angles to the axes of the lever and the bolt or nut. Some wrenches have ends with straight-sided slots that fit over the part being tightened; these tools are known as open-end wrenches and are made in various sizes to fit specific bolt and nut sizes.

Box-end wrenches have ends that enclose the nut and have 6, 8, 12, or 16 points inside the head. A wrench with 12 points is used on either a hexagonal or a square nut; the 8- and 16-point wrenches are used on square members. Because the sides of the box are thin, these wrenches are suitable for turning nuts that are hard to reach with an open-end wrench.

When a nut or a bolt head is in a recess below the surface of a bolted member, a socket wrench must be used; this is essentially a short pipe with a square or hexagonal hole and either an integral or a removable handle. Modern socket wrenches are made in sets, consisting of a number of short sockets with a square hole in one end that fits a removable handle and 8- or 12-point holes in the other end to fit various bolt and nut sizes. There are several types of handles and extensions, such as a T handle, screwdriver-grip handle, and a ratchet handle.

A useful accessory for a socket-wrench set is a handle equipped with a mechanism that measures the amount of torque, or turning effort, exerted by the wrench on the nut or bolt. One type of torque handle has two arms attached to the head, which carries the socket that fits the bolt or nut to be tightened; one arm carries the torque-indicating scale and remains fixed relative to the head, while the other arm carries the handgrip and is bent, relative to the head and the scale, when a bolt is tightened. A pointer on the bent arm indicates the torque on the scale. The purpose of a torque wrench is to make sure that screws and bolts in bolted assemblies are installed with sufficient tightness to prevent loosening during use, without being overtightened.

Wrenches with one fixed and one adjustable parallel jaw can be used on various sizes of bolts and nuts within a limited range. On one type the jaws are at right angles to the handle; this wrench is known as a monkey wrench. On another type, originally called a Crescent wrench, the jaws are almost parallel to the handle. On both types the movable jaw is adjusted by turning a worm that engages a rack of teeth cut into the jaw.

The adjustable pipe, or Stillson, wrench is used to hold or turn pipes or circular bars. This wrench has serrated jaws, one of which is pivoted on the handle to create a strong gripping action on the work.

Recessed-head screws or set screws commonly have a hexagonally shaped recess and require a special wrench, usually referred to as an Allen wrench; it consists of a hexagonal bar of tool steel shaped into the form of an L, either end of which fits into the recess.
Power or impact wrenches are used for tightening or loosening nuts quickly. They are essentially small handheld electric or pneumatic motors that can rotate socket wrenches at high speed. They are equipped with a torque-limiting device that will stop the rotation of the socket wrench when a preset torque is reached. Pneumatic wrenches are commonly used in automobile service stations, where compressed air is available and the sparking of electric motors is a fire hazard.

AmPro-Adjustable-Wrench-150mm-WREA-T39805-A.jpg


It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi. 

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#855 2020-11-20 00:18:18

ganesh
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Re: Miscellany

833) Oil extraction

Oil extraction, isolation of oil from animal by-products, fleshy fruits such as the olive and palm, and oilseeds such as cottonseed, sesame seed, soybeans, and peanuts. Oil is extracted by three general methods: rendering, used with animal products and oleaginous fruits; mechanical pressing, for oil-bearing seeds and nuts; and extracting with volatile solvents, employed in large-scale operations for a more complete extraction than is possible with pressing.

Rendering originally implied the application of heat; in its most primitive form, it is practiced by heaping fruits such as olives in piles exposed to the sun and collecting the oil that exudes. A similar, somewhat more advanced process is used to extract oil from palm fruits by boiling in water, then skimming the oil from the surface. Whale blubber is cut into small pieces and heated in vats (tryworks) or cooked in steam digesters; the oil is collected by draining or skimming.

Many oil-bearing seeds and nuts are broken up by grinding, flaking, or rolling, then subjected to mechanical pressing to liberate the oil. The modern continuous screw press exerts pressures as high as 30,000 pounds per square inch. In modern press extraction, oilseeds or nuts are cleaned, and the shells or hulls removed; the kernels or meats are ground to a coarse meal that is pressed with or without preliminary heating. Cold-pressed oil, also called cold-drawn, or virgin, oil, is purer and has a better flavour than oil expressed with the aid of heat. After pressing the meals made from oily seeds or nuts, the remaining cake contains about 5 to 15 percent oil. Most of the oil present in these residues, and in meals made from seeds and nuts that naturally contain little oil, can be removed by extraction with volatile solvents, especially petroleum benzin (also known as petroleum ether, commercial hexane, or heptane). The solvent is percolated through the meal, dissolving the oil, which is finally recovered from the solution by evaporating the solvent. The solvent is also recovered and used over again.

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It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi. 

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#856 2020-11-21 00:19:53

ganesh
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Re: Miscellany

834) Kerosene

Kerosene, also spelled kerosine, also called paraffin or paraffin oil, flammable hydrocarbon liquid commonly used as a fuel. Kerosene is typically pale yellow or colourless and has a not-unpleasant characteristic odour. It is obtained from petroleum and is used for burning in kerosene lamps and domestic heaters or furnaces, as a fuel or fuel component for jet engines, and as a solvent for greases and insecticides.

Discovered by Canadian physician Abraham Gesner in the late 1840s, kerosene was initially manufactured from coal tar and shale oils. However, following the drilling of the first oil well in Pennsylvania by E.L. Drake in 1859, petroleum quickly became the major source of kerosene. Because of its use in lamps, kerosene was the major refinery product for several decades until the advent of the electric lamp reduced its value for lighting. Production further declined as the rise of the automobile established gasoline as an important petroleum product. Nevertheless, in many parts of the world, kerosene is still a common heating and cooking fuel as well as a fuel for lamps. Standard commercial jet fuel is essentially a high-quality straight-run kerosene, and many military jet fuels are blends based on kerosene.

Chemically, kerosene is a mixture of hydrocarbons. The chemical composition depends on its source, but it usually consists of about 10 different hydrocarbons, each containing 10 to 16 carbon atoms per molecule. The main constituents are saturated straight-chain and branched-chain paraffins, as well as ring-shaped cycloparaffins (also known as naphthenes). Kerosene is less volatile than gasoline. Its flash point (the temperature at which it will generate a flammable vapour near its surface) is 38 °C (100 °F) or higher, whereas that of gasoline is as low as −40 °C (−40 °F). This property makes kerosene a relatively safe fuel to store and handle.

With a boiling point between about 150 and 300 °C (300–575 °F), kerosene is considered to be one of the so-called middle distillates of crude oil, along with diesel fuel. It can be produced as “straight-run kerosene,” separated physically from the other crude oil fractions by distillation, or it can be produced as “cracked kerosene,” by chemically decomposing, or cracking, heavier portions of the oil at elevated temperatures.

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It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi. 

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#857 2020-11-22 00:06:10

ganesh
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Re: Miscellany

835) Cobra

Cobra, any of various species of highly venomous snakes, most of which expand the neck ribs to form a hood. While the hood is characteristic of cobras, not all of them are closely related. Cobras are found from southern Africa through southern Asia to islands of Southeast Asia. Throughout their range, different species are favourites of snake charmers, who frighten them into assuming the upreared defense posture. The snake sways in response to the movement and perhaps also to the music of the charmer, who knows how to avoid the relatively slow strike and who may have removed the snake’s fangs. The short fangs at the front of the mouth have an enclosed groove, which delivers the venom. Cobra venom generally contains neurotoxins active against the nervous system of prey—primarily small vertebrates and other snakes. Bites, particularly from larger species, can be fatal depending on the amount of venom injected. Neurotoxins affect breathing, and although antivenin is effective, it must be administered soon after the bite. Thousands of deaths occur each year in South and Southeast Asia.

The world’s largest venomous snake is the king cobra, or hamadryad (Ophiophagus hannah). Found predominantly in forests from India through Southeast Asia to the Philippines and Indonesia, it preys chiefly on other snakes. Maximum confirmed length is 5.6 metres (18 feet), but most do not exceed 3.6 metres (12 feet). King cobras guard a nest of 20 to 40 eggs, which are laid in a mound of leaves gathered by the female. The guarding parent will strike if a predator or a person approaches too closely. Not all cobras are egg layers.

The Indian cobra (or Indian spectacled cobra, Naja naja) was formerly considered a single species with much the same distribution as the king cobra. Recently, however, biologists have discovered that nearly a dozen species exist in Asia, some being venom spitters and others not. They vary both in size (most ranging between 1.25 and 1.75 metres) and in the toxicity of their venom. Spitters propel venom through the fangs by muscular contraction of the venom ducts and by forcing air out of the single lung.

In Africa there are also spitting and nonspitting cobras, but the African cobras are not related to the Asian cobras, nor are they related to each other. The ringhals, or spitting cobra (Hemachatus haemachatus), of southern Africa and the black-necked cobra (Naja nigricollis), a small form widely distributed in Africa, are spitters. Venom is accurately directed at the victim’s eyes at distances of more than two metres and may cause temporary, or even permanent, blindness unless promptly washed away. The Egyptian cobra (N. haje)—probably the asp of antiquity—is a dark, narrow-hooded species, about two metres long, that ranges over much of Africa and eastward to Arabia. Its usual prey consists of toads and birds. In equatorial Africa there are tree cobras (genus Pseudohaje), which, along with the mambas, are the only arboreal members of the family Elapidae.

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It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi. 

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#858 2020-11-23 00:17:28

ganesh
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Re: Miscellany

836) Gasoline

Gasoline, also spelled gasolene, also called gas or petrol, mixture of volatile, flammable liquid hydrocarbons derived from petroleum and used as fuel for internal-combustion engines. It is also used as a solvent for oils and fats. Originally a by-product of the petroleum industry (kerosene being the principal product), gasoline became the preferred automobile fuel because of its high energy of combustion and capacity to mix readily with air in a carburetor.

Gasoline was at first produced by distillation, simply separating the volatile, more valuable fractions of crude petroleum. Later processes, designed to raise the yield of gasoline from crude oil, split large molecules into smaller ones by processes known as cracking. Thermal cracking, employing heat and high pressures, was introduced in 1913 but was replaced after 1937 by catalytic cracking, the application of catalysts that facilitate chemical reactions producing more gasoline. Other methods used to improve the quality of gasoline and increase its supply include polymerization, converting gaseous olefins, such as propylene and butylene, into larger molecules in the gasoline range; alkylation, a process combining an olefin and a paraffin such as isobutane; isomerization, the conversion of straight-chain hydrocarbons to branched-chain hydrocarbons; and reforming, using either heat or a catalyst to rearrange the molecular structure.

Gasoline is a complex mixture of hundreds of different hydrocarbons. Most are saturated and contain 4 to 12 carbon atoms per molecule. Gasoline used in automobiles boils mainly between 30° and 200° C (85° and 390° F), the blend being adjusted to altitude and season. Aviation gasoline contains smaller proportions of both the less-volatile and more-volatile components than automobile gasoline.

The antiknock characteristics of a gasoline—its ability to resist knocking, which indicates that the combustion of fuel vapour in the cylinder is taking place too rapidly for efficiency—is expressed in octane number. The addition of tetraethyllead to retard the combustion was initiated in the 1930s but was discontinued in the 1980s because of the toxicity of the lead compounds discharged in the combustion products. Other additives to gasoline often include detergents to reduce the buildup of engine deposits, anti-icing agents to prevent stalling caused by carburetor icing, and antioxidants (oxidation inhibitors) used to reduce “gum” formation.

In the late 20th century the rising price of petroleum (and hence of gasoline) in many countries led to the increasing use of gasohol, which is a mixture of 90 percent unleaded gasoline and 10 percent ethanol (ethyl alcohol). Gasohol burns well in gasoline engines and is a desirable alternative fuel for certain applications because of the renewability of ethanol, which can be produced from grains, potatoes, and certain other plant matter.

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It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi. 

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#859 2020-11-24 00:22:31

ganesh
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Re: Miscellany

837) Engineering

Engineering, the application of science to the optimum conversion of the resources of nature to the uses of humankind. The field has been defined by the Engineers Council for Professional Development, in the United States, as the creative application of “scientific principles to design or develop structures, machines, apparatus, or manufacturing processes, or works utilizing them singly or in combination; or to construct or operate the same with full cognizance of their design; or to forecast their behaviour under specific operating conditions; all as respects an intended function, economics of operation and safety to life and property.” The term engineering is sometimes more loosely defined, especially in Great Britain, as the manufacture or assembly of engines, machine tools, and machine parts.

The words engine and ingenious are derived from the same Latin root, ingenerare, which means “to create.” The early English verb engine meant “to contrive.” Thus, the engines of war were devices such as catapults, floating bridges, and assault towers; their designer was the “engine-er,” or military engineer. The counterpart of the military engineer was the civil engineer, who applied essentially the same knowledge and skills to designing buildings, streets, water supplies, sewage systems, and other projects.

Associated with engineering is a great body of special knowledge; preparation for professional practice involves extensive training in the application of that knowledge. Standards of engineering practice are maintained through the efforts of professional societies, usually organized on a national or regional basis, with all members acknowledging a responsibility to the public over and above responsibilities to their employers or to other members of their society.

The function of the scientist is to know, while that of the engineer is to do. Scientists add to the store of verified systematized knowledge of the physical world, and engineers bring this knowledge to bear on practical problems. Engineering is based principally on physics, chemistry, and mathematics and their extensions into materials science, solid and fluid mechanics, thermodynamics, transfer and rate processes, and systems analysis.

Unlike scientists, engineers are not free to select the problems that interest them. They must solve problems as they arise, and their solutions must satisfy conflicting requirements. Usually, efficiency costs money, safety adds to complexity, and improved performance increases weight. The engineering solution is the optimum solution, the end result that, taking many factors into account, is most desirable. It may be the most reliable within a given weight limit, the simplest that will satisfy certain safety requirements, or the most efficient for a given cost. In many engineering problems the social costs are significant.

Engineers employ two types of natural resources—materials and energy. Materials are useful because of their properties: their strength, ease of fabrication, lightness, or durability; their ability to insulate or conduct; their chemical, electrical, or acoustical properties. Important sources of energy include fossil fuels (coal, petroleum, gas), wind, sunlight, falling water, and nuclear fission. Since most resources are limited, engineers must concern themselves with the continual development of new resources as well as the efficient utilization of existing ones.

History Of Engineering

The first engineer known by name and achievement is Imhotep, builder of the Step Pyramid at Ṣaqqārah, Egypt, probably about 2550 BCE. Imhotep’s successors—Egyptian, Persian, Greek, and Roman—carried civil engineering to remarkable heights on the basis of empirical methods aided by arithmetic, geometry, and a smattering of physical science. The Pharos (lighthouse) of Alexandria, Solomon’s Temple in Jerusalem, the Colosseum in Rome, the Persian and Roman road systems, the Pont du Gard aqueduct in France, and many other large structures, some of which endure to this day, testify to their skill, imagination, and daring. Of many treatises written by them, one in particular survives to provide a picture of engineering education and practice in classical times: Vitruvius’s De architectura, published in Rome in the 1st century CE, a 10-volume work covering building materials, construction methods, hydraulics, measurement, and town planning.

In construction, medieval European engineers carried technique, in the form of the Gothic arch and flying buttress, to a height unknown to the Romans. The sketchbook of the 13th-century French engineer Villard de Honnecourt reveals a wide knowledge of mathematics, geometry, natural and physical science, and draftsmanship.

In Asia, engineering had a separate but very similar development, with more and more sophisticated techniques of construction, hydraulics, and metallurgy helping to create advanced civilizations such as the Mongol empire, whose large, beautiful cities impressed Marco Polo in the 13th century.

Civil engineering emerged as a separate discipline in the 18th century, when the first professional societies and schools of engineering were founded. Civil engineers of the 19th century built structures of all kinds, designed water-supply and sanitation systems, laid out railroad and highway networks, and planned cities. England and Scotland were the birthplace of mechanical engineering, as a derivation of the inventions of the Scottish engineer James Watt and the textile machinists of the Industrial Revolution. The development of the British machine-tool industry gave tremendous impetus to the study of mechanical engineering both in Britain and abroad.

The growth of knowledge of electricity—from Alessandro Volta’s original electric cell of 1800 through the experiments of Michael Faraday and others, culminating in 1872 in the Gramme dynamo and electric motor (named after the Belgian Z.T. Gramme)—led to the development of electrical and electronics engineering. The electronics aspect became prominent through the work of such scientists as James Clerk Maxwell of Britain and Heinrich Hertz of Germany in the late 19th century. Major advances came with the development of the vacuum tube by Lee De Forest of the United States in the early 20th century and the invention of the transistor in the mid-20th century. In the late 20th century electrical and electronics engineers outnumbered all others in the world.

Chemical engineering grew out of the 19th-century proliferation of industrial processes involving chemical reactions in metallurgy, food, textiles, and many other areas. By 1880 the use of chemicals in manufacturing had created an industry whose function was the mass production of chemicals. The design and operation of the plants of this industry became a function of the chemical engineer.

Engineering Functions

Problem solving is common to all engineering work. The problem may involve quantitative or qualitative factors; it may be physical or economic; it may require abstract mathematics or common sense. Of great importance is the process of creative synthesis or design, putting ideas together to create a new and optimum solution.
Although engineering problems vary in scope and complexity, the same general approach is applicable. First comes an analysis of the situation and a preliminary decision on a plan of attack. In line with this plan, the problem is reduced to a more categorical question that can be clearly stated. The stated question is then answered by deductive reasoning from known principles or by creative synthesis, as in a new design. The answer or design is always checked for accuracy and adequacy. Finally, the results for the simplified problem are interpreted in terms of the original problem and reported in an appropriate form.

In order of decreasing emphasis on science, the major functions of all engineering branches are the following:

•    Research. Using mathematical and scientific concepts, experimental techniques, and inductive reasoning, the research engineer seeks new principles and processes.
•    Development. Development engineers apply the results of research to useful purposes. Creative application of new knowledge may result in a working model of a new electrical circuit, a chemical process, or an industrial machine.
•    Design. In designing a structure or a product, the engineer selects methods, specifies materials, and determines shapes to satisfy technical requirements and to meet performance specifications.
•    Construction. The construction engineer is responsible for preparing the site, determining procedures that will economically and safely yield the desired quality, directing the placement of materials, and organizing the personnel and equipment.
•    Production. Plant layout and equipment selection are the responsibility of the production engineer, who chooses processes and tools, integrates the flow of materials and components, and provides for testing and inspection.
•    Operation. The operating engineer controls machines, plants, and organizations providing power, transportation, and communication; determines procedures; and supervises personnel to obtain reliable and economic operation of complex equipment.
•    Management and other functions. In some countries and industries, engineers analyze customers’ requirements, recommend units to satisfy needs economically, and resolve related problems.

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It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi. 

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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