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#26 2017-11-03 00:41:06

ganesh
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Re: Miscellany

26) Great Wall Of China

The Great Wall of China is a series of fortifications made of stone, brick, tamped earth, wood, and other materials, generally built along an east-to-west line across the historical northern borders of China to protect the Chinese states and empires against the raids and invasions of the various nomadic groups of the Eurasian Steppe. Several walls were being built as early as the 7th century BC; these, later joined together and made bigger and stronger, are now collectively referred to as the Great Wall. Especially famous is the wall built 220–206 BC by Qin Shi Huang, the first Emperor of China. Little of that wall remains. Since then, the Great Wall has on and off been rebuilt, maintained, and enhanced; the majority of the existing wall is from the Ming Dynasty.

Other purposes of the Great Wall have included border controls, allowing the imposition of duties on goods transported along the Silk Road, regulation or encouragement of trade and the control of immigration and emigration. Furthermore, the defensive characteristics of the Great Wall were enhanced by the construction of watch towers, troop barracks, garrison stations, signaling capabilities through the means of smoke or fire, and the fact that the path of the Great Wall also served as a transportation corridor.

The Great Wall stretches from Dandong in the east, to Lop Lake in the west, along an arc that roughly delineates the southern edge of Inner Mongolia. A comprehensive archaeological survey, using advanced technologies, has concluded that the Ming walls measure 8,850 km (5,500 mi). This is made up of 6,259 km (3,889 mi) sections of actual wall, 359 km (223 mi) of trenches and 2,232 km (1,387 mi) of natural defensive barriers such as hills and rivers. Another archaeological survey found that the entire wall with all of its branches measure out to be 21,196 km (13,171 mi).

e269212a41dd4f999d9a4d26_298x199.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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#27 2017-11-05 01:10:53

ganesh
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Registered: 2005-06-28
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Re: Miscellany

27) The Four Largest Islands of Japan

The Japanese archipelago consists of nearly 7,000 islands. However, roughly 97% of Japan's landmass (377,835 sq km / 234,776 sq. miles) is comprised of the four main islands: Hokkaido, Honshu, Kyushu, and Shikoku.

The Japanese archipelago consists of thousands of islands, but the Japan of world maps -- the bow-shaped country in the Pacific curling around the east coast of continental Asia -- is made up of four main islands: Hokkaido, Honshu, Kyushu and Shikoku. Honshu is the largest, roughly the size of Minnesota, followed by Hokkaido, Kyushu and Shikoku. Each island offers something a little different for the tourist, but the four are unified by Japan's technology and hospitality.

Honshu

When you look at a map of Japan, you can see the divides between its four main land masses. Honshu is central, with Tokyo in the central part of the island. The main island is also home Osaka, Kobe, Kyoto and Nagoya, and the majority of Japan's population lives here. Most international flights to Japan arrive through Tokyo or Osaka, so Honshu is the most frequently visited island, partly by default. Its large cities take some getting used to for the traveler, but with great reward. Starting a Honshu trip in Osaka makes sense, as Kobe, Kyoto and the spectacular Nara are only an hour away by train, some high-speed, some commuter. All major cities in Honshu are connected by rail, though flying on the longer trips -- Hiroshima to Tokyo, for example -- might be more economical.

Hokkaido

Hokkaido is the dot on the Japanese "j," the second-largest and northernmost island. Hokkaido's largest city is Sapporo, where the well known Japanese beer of the same name comes from, and most Hokkaido vacations begin here. The island is known for its natural landscape, with an abundance of national parks and festivals celebrating its earthly beauty. Hokkaido's Winter Festival brings visitors from around the world and around Japan to the region each year, and the Hokkaido's mountains draw skiers and snowboarders to their deep, pristine powder.

Kyushu

Kyushu is Japan's third-largest island and the southernmost of the main four. Despite being separated by a small gulf from Honshu, Kyushu is well-connected by rail and bus service to Honshu. Kyushu's largest city is Fukuoka, the fourth-largest city in Japan, an industrial metropolis on the northern edge of Kyushu. While Fukuoka is the central hub of the island, it's by no means the most interesting city. Nagasaki is smaller, but quaint, with old stone streets, trolleys, shopping and museums. Kumamoto, two hours south of Fukuoka, is an old fortress city, with one of Japan's oldest and best-maintained feudal castles and walls evoking the Japan of the nation's nightly historical dramas.

Shikoku

The smallest of Japan's four main islands, Shikoku has a bit of a little-sibling complex. It doesn't boast mountains as big as those in northern Honshu or Hokkaido, and it doesn't have the same near-tropical climate as southern Kyushu. So Shikoku is modest, offering tourists a tamer version of the busier tourist regions of Japan. Its natural scenery is its key draw, with smallish mountains under 6,000 feet that appeal to outdoors enthusiasts in moderate physical shape. Each year, Shikoku is home to a Buddhist pilgrimage, as pilgrims, mostly from around Japan, come to circumnavigate the island. In the past, pilgrims walked clockwise around the island and some disappeared forever in the mountainside forests; now, motorways and cell phones make disappearing almost impossible, but the festival remains strongly rooted in the Shikoku consciousness.

japan.gif


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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#28 2017-11-07 23:01:17

ganesh
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Re: Miscellany

28) Laser

A laser is a coherent and focused beam of photons; coherent, in this context, means that it is all one wavelength, unlike ordinary light which showers on us in many wavelengths.

The acronym laser stands for "light amplification by stimulated emission of radiation." Lasers work as a result of resonant effects. The output of a laser is a coherent electromagnetic field. In a coherent beam of electromagnetic energy, all the waves have the same frequency and phase.

In a basic laser, a chamber called a cavity is designed to internally reflect infrared (IR), visible-light, or ultraviolet (UV) waves so they reinforce each other. The cavity can contain gases, liquids, or solids. The choice of cavity material determines the wavelength of the output. At each end of the cavity, there is a mirror. One mirror is totally reflective, allowing none of the energy to pass through; the other mirror is partially reflective, allowing approximately 5 percent of the energy to pass through. Energy is introduced into the cavity from an external source; this is called pumping.

As a result of pumping, an electromagnetic field appears inside the laser cavity at the natural (resonant) frequency of the atoms of the material that fills the cavity. The waves reflect back and forth between the mirrors. The length of the cavity is such that the reflected and re-reflected wave fronts reinforce each other in phase at the natural frequency of the cavity substance. Electromagnetic waves at this resonant frequency emerge from the end of the cavity having the partially-reflective mirror. The output may appear as a continuous beam, or as a series of brief, intense pulses.

The ruby laser, a simple and common type, has a rod-shaped cavity made of a mixture of solid aluminum oxide and chromium. The output is in pulses that last approximately 500 microseconds each. Pumping is done by means of a helical flash tube wrapped around the rod. The output is in the red visible range.

A blue laser has a shorter wavelength than the red laser, and the ability to store and read two to four times the amount of data.

The helium-neon laser is another popular type, favored by electronics hobbyists because of its moderate cost. As its name implies, it has a cavity filled with helium and neon gases. The output of the device is bright crimson. Other gases can be used instead of helium and neon, producing beams of different wavelengths. Argon produces a laser with blue visible output. A mixture of nitrogen, carbon dioxide, and helium produces IR output.

Lasers are one of the most significant inventions developed during the 20th century. They have found a tremendous variety of uses in electronics, computer hardware, medicine, and experimental science.

laser-experiment.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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#29 2017-11-10 07:49:33

ganesh
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Re: Miscellany

29) United Nations

Overview

The United Nations is an international organization founded in 1945.  It is currently made up of 193 Member States.  The mission and work of the United Nations are guided by the purposes and principles contained in its founding Charter.

Member States

Each of the 193 Member States of the United Nations is a member of the General Assembly.  States are admitted to membership in the UN by a decision of the General Assembly upon the recommendation of the Security Council.

Main Organs

The main organs of the UN are the General Assembly, the Security Council, the Economic and Social Council, the Trusteeship Council, the International Court of Justice, and the UN Secretariat.  All were established in 1945 when the UN was founded.

Leadership

The Secretary-General of the United Nations is a symbol of the Organization's ideals and a spokesman for the interests of the world's peoples, in particular the poor and vulnerable. The current Secretary-General of the UN, and the ninth occupant of the post, is Mr. António Guterres of Portugal, who took office on 1 January 2017. The UN Charter describes the Secretary-General as "chief administrative officer" of the Organization.

Secretariat

The Secretariat, one of the main organs of the UN, is organized along departmental lines, with each department or office having a distinct area of action and responsibility. Offices and departments coordinate with each other to ensure cohesion as they carry out the day to day work of the Organization in offices and duty stations around the world.  At the head of the United Nations Secretariat is the Secretary-General.

Funds, Programmes, Specialized Agencies and Others

The UN system, also known unofficially as the "UN family", is made up of the UN itself and many affiliated programmes, funds, and specialized agencies, all with their own membership, leadership, and budget.  The programmes and funds are financed through voluntary rather than assessed contributions. The Specialized Agencies are independent international organizations funded by both voluntary and assessed contributions.

united_nations_logo_295.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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#30 2017-11-14 02:01:59

ganesh
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Re: Miscellany

30) Angstrom (Angstrom unit)

The angstrom, also known as the angstrom unit, is a measure of displacement equal to 0.0000000001 meter

. It is sometimes used to express wavelength s of visible light, ultraviolet (UV) light, X rays, and gamma rays.


The visible-light spectrum extends from approximately 7700 angstroms (red light) to 3900 angstroms (violet light). This corresponds to frequencies of 390 to 770 terahertz (THz), where 1 THz = 10 12 Hz. Ultraviolet radiation, X rays, and gamma rays have progressively shorter wavelengths and higher frequencies. Some gamma rays have wavelengths less than
0.0001

angstrom.

The angstrom is not often used nowadays. It has been largely superseded by the nanometer (nm), which is 10 times larger; 1 nm = 10 angstroms =

m.

wavelength-color.PNG


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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#31 2017-11-18 14:43:32

ganesh
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Re: Miscellany

31) Bathyscaphe

Bathyscaphe, navigable diving vessel, developed by the Swiss educator and scientist Auguste Piccard (with assistance in later years from his son Jacques), designed to reach great depths in the ocean.

The first bathyscaphe, the FNRS 2, built in Belgium between 1946 and 1948, was damaged during 1948 trials in the Cape Verde Islands. Substantially rebuilt and greatly improved, the vessel was renamed FNRS 3 and carried out a series of descents under excellent conditions, including one of 4,000 metres (13,000 feet) into the Atlantic off Dakar, Senegal, on February 15, 1954. A second improved bathyscaphe, the Trieste, was launched on August 1, 1953, and dived to 3,150 metres (10,300 feet) in the same year. In 1958 the Trieste was acquired by the United States Navy, taken to California, and equipped with a new cabin designed to enable it to reach the seabed of the great oceanic trenches. Several successive descents were made into the Pacific by Jacques Piccard, and on January 23, 1960, Piccard, accompanied by Lieutenant Don Walsh of the U.S. Navy, dived to a record 10,916 metres (35,814 feet) in the Pacific’s Mariana Trench.

The bathyscaphe consists of two main components: a steel cabin, heavier than water and resistant to sea pressure, to accommodate the observers; and a light container called a float, filled with gasoline, which, being lighter than water, provides the necessary lifting power. The cabin and float are closely linked. On the surface, one or more ballast tanks filled with air provide enough lift to keep the bathyscaphe afloat. When the ballast tank valves are opened, air escapes and is replaced by water, making the whole device heavy enough to start its descent. The gasoline is in direct contact with the sea water and so is compressed at a rate almost exactly in proportion to the prevailing depth. Thus, the bathyscaphe gradually loses buoyancy as it descends, and the speed of its descent tends to increase rapidly. To slow down or to begin the reascent, the pilot releases ballast that consists essentially of iron shot stored in silos and held in place by electromagnets.

bathyscaphe_Trieste.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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#32 2017-11-22 19:43:39

ganesh
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Re: Miscellany

32) Gulf of Mexico

Gulf of Mexico, Spanish Golfo de México, partially landlocked body of water on the southeastern periphery of the North American continent. It is connected to the Atlantic Ocean by the Straits of Florida, running between the peninsula of Florida and the island of Cuba, and to the Caribbean Sea by the Yucatán Channel, which runs between the Yucatán Peninsula and Cuba. Both of these channels are about 100 miles (160 km) wide. The gulf’s greatest east-west and north-south extents are approximately 1,100 and 800 miles (1,800 and 1,300 km), respectively, and it covers an area of some 600,000 square miles (1,550,000 square km). To the northwest, north, and northeast it is bounded by the southern coast of the United States, while to the west, south, and southeast it is bounded by the east coast of Mexico.

Physical Features

Physiography and geology

The Gulf of Mexico consists of several ecological and geologic provinces, chief of which are the coastal zone, the continental shelf, the continental slope, and the abyssal plain. The coastal zone consists of tidal marshes, sandy beaches, mangrove-covered areas, and many bays, estuaries, and lagoons. The continental shelf forms an almost continuous terrace around the margin of the gulf; its width varies from a maximum of more than 200 miles (320 km) to a minimum of about 25 miles (40 km). Off the west coast of Florida as well as off the Yucatán Peninsula, the continental shelf consists of a broad area composed primarily of carbonate material. The remainder of the shelf consists of sand, silt, and clay sediments. On the shelf and on the slope that dips downward to the abyssal plain, buried salt domes occur at various depths; economically important deposits of oil and natural gas are associated with them. The abyssal plain, which forms the floor of the gulf, consists of a large triangular area near the centre, bounded by abrupt fault scarps toward Florida and the Yucatán Peninsula and by more gentle slopes to the north and west. The basin is unusually flat, having a gradient of only about 1 foot (0.3 metre) in every 8,000 feet (2,440 metres). The deepest point is in the Mexico Basin (Sigsbee Deep), which is 17,070 feet (5,203 metres) below sea level. From the floor of the basin rise the Sigsbee Knolls, some of which attain heights of 1,300 feet (400 metres); these are surface expressions of the buried salt domes.

Hydrology

The southeastern portion of the gulf is traversed by a riverlike current that becomes the main source of the North Atlantic Gulf Stream; this is the principal current moving oceanic waters through the gulf. Water from the Caribbean enters through the Yucatán Channel, the floor of which forms a sill (submarine ridge between basins) at about 1 mile (1.6 km) beneath the surface, and flows out in a clockwise direction via the Straits of Florida. Meandering masses of water, called loop currents, break off from the main stream and also move clockwise into the northeastern part of the gulf. Both seasonal and annual variations occur in these loop currents. A less well-defined pattern exists in the western gulf. There the currents are relatively weak, varying appreciably in intensity with season and location. There is extreme variability in both current direction and speed on the continental shelf and in the coastal waters of the gulf, where currents are subjected to seasonal and annual variations caused not only by major circulation patterns but also by changes in the prevailing wind direction.

The various rivers flowing into the Gulf of Mexico drain a land area roughly double that of the gulf, and the salinity of the gulf is subject to wide variations. In the open gulf the salinity is comparable to that of the North Atlantic, about 36 parts per thousand. This proportion, however, varies markedly during the year in coastal waters, particularly near the outflow of the broad delta region of the Mississippi River. During periods when the volume of the Mississippi’s flow is greatest, salinities as low as 14 to 20 parts per thousand occur as far as some 20 to 30 miles (30 to 50 km) offshore.

Sea surface temperatures in February vary between 64 °F (18 °C) in the northern gulf and 76 °F (24 °C) off the Yucatán coast. In the summer, surface temperatures of about 90 °F (32 °C) have been measured, but the usual variation is nearly the same as that experienced in February. Bottom-water temperatures of about 43 °F (6 °C) have been recorded near the northern part of the Yucatán Channel. The thickness of the isothermal layer (a surface layer of water of constant temperature) varies from about 3 to more than 500 feet (1 to more than 150 metres), depending on seasonal and local conditions as well as on location. The tidal range is small, averaging less than two feet in most places; in general, only diurnal tides occur—i.e., one period of high water and one of low water during each tidal day (24 hours and 50 minutes).

Climate

The climate of the gulf region varies from tropical to subtropical. Of particular note are the often-devastating hurricanes (tropical cyclones) that strike the region nearly every year. The hurricane season officially runs from June 1 to November 30, during which time meteorologic and oceanographic conditions are conducive for hurricanes to develop anywhere in the gulf. Particularly damaging hurricanes included one in Galveston, Texas, in 1900 and another in and around New Orleans in 2005. Hurricanes spawned in the North Atlantic may also move through the gulf at that time, often picking up strength.

Economic Aspects

Biological resources

The shores of the Gulf of Mexico are a major habitat for waterfowl and shorebirds. Substantial colonies of noddies, boobies, pelicans, and other seabirds winter along the coasts of Mexico and Cuba, as well as on offshore islands. There is a marked absence of marine mammals; the only one of significance, the Caribbean manatee, is diminishing in number.

The gulf waters contain huge populations of fish, particularly along the continental shelf. Commercial fishing is of major economic importance and supplies roughly one-fifth of the total catch in the United States. Shrimps, flounder, red snappers, mullet, oysters, and crabs are the most important commercial species for human consumption. In addition, a large quantity of the fish caught is used to provide fish protein concentrate for animal feeds; menhaden provide the bulk of this catch.

Mineral resources

The shallow continental shelf regions of the Gulf of Mexico contain large deposits of petroleum and natural gas. These deposits have been developed extensively since the 1940s and provide a substantial proportion of domestic needs in the United States. Offshore wells have been drilled primarily in the waters off the coasts of Texas and Louisiana and off Mexico in the Bay of Campeche. Sulfur is also extracted from wells drilled on the continental shelf off Louisiana. Oyster shells are obtained from the shallow waters of the Texas Gulf Coastal Plain and from bays and estuaries. These are used in the chemical industry as a source of calcium carbonate and also provide material for building roads.

Recreation

The coastal waters of the Gulf of Mexico are used extensively for sport fishing, especially for red snappers, flounder, and tarpon. Boating, swimming, and scuba diving also are popular recreations. The Gulf Coast has become a popular tourist destination, especially during winter. Tourism has developed primarily since World War II and has become one of the major components of the regional economy. In addition, the coastal areas, particularly in Florida, have developed into large retirement communities.

The impact of human activity

Shifting demographic patterns in the United States since 1950 have brought millions of new residents to the gulf region. This growing population has increased the demand for fresh water and generated large quantities of sewage and industrial waste (including heavy metals and polychlorinated biphenyls), much of which have been discharged directly into gulf waters or indirectly by rivers draining into the gulf. Offshore drilling has brought oil spills that, on occasion, have fouled beaches and destroyed marine life. More damaging, however, have been modern agricultural practices in much of the United States and Mexico, resulting in runoff contaminated with tremendous amounts of chemical pesticides, herbicides, and fertilizers. Blooms of red algae (Rhodophyta) and regions of oxygen depletion (hypoxia) have increased in frequency, size, and duration; these occurrences have been tied to the introduction into the gulf of large amounts of phosphates and nitrogen, particularly from the outflow of the Mississippi River. Off Louisiana, erosion and changes in relative sea level have caused the submergence of large areas of coastal wetlands; and pollution, siltation, and filling have resulted in the destruction of large areas of the gulf’s mangroves and many of its coral reefs.

Study And Exploration

After Christopher Columbus first made contact with the region in 1492, waves of Spanish explorers entered the gulf and penetrated into the North American interior. By 1600 the major physical features had been discovered, and a system of towns, silver mines, and missions had been established around the gulf shore. Little scientific study of the gulf was carried out until the 20th century, but since then the gulf has come to resemble something of a vast natural laboratory. Major marine research centres are located throughout the region, notably in Texas, Louisiana, and Florida. The gulf has become renowned for the diversity of its marine biota and the dynamics of its numerous barrier beaches; and, because of its vast oil reserves, the stratigraphy of its continental shelf has been studied by geophysicists and seismologists to a greater degree than perhaps that of any other oceanic basin. The frequent occurrence of hurricanes and other tropical storms in the gulf also has made it the focus of much research in climatology.

289389-Intl-countryimg-mexico-542-312.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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#33 2017-11-26 16:35:44

ganesh
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Re: Miscellany

33) Carburetors

Fuel plus air equals motion—that's the basic science behind most of the vehicles that travel on land, over sea, or through the sky. Cars, trucks, and buses turn fuel into power by mixing it with air and burning it in metal cylinders inside their engines. Exactly how much fuel and air an engine needs varies from moment to moment, depending on how long it's been running, how fast you're going, and a variety of other factors. Modern engines use an electronically controlled system called fuel injection to regulate the fuel-air mixture so it's exactly right from the minute you turn the key to the time you switch the engine off again when you reach your destination. But until these clever gadgets were invented, virtually all engines relied on ingenious air-fuel mixing devices called carburetors (spelled "carburettor" in some countries and often shortened to just "carb"). What are they and how do they work? Let's take a closer look!

How engines burn fuel

Engines are mechanical things, but they're chemical things too: they're designed around a chemical reaction called combustion: when you burn fuel in air, you release heat energy and produce carbon dioxide and water as waste products. To burn fuel efficiently, you have to use plenty of air. That applies just as much to a car engine as to a candle, an outdoor campfire, or a coal or wood fire in someone's home.

With a campfire, you never really have to worry about having too much or too little air. With fires burning indoors, air is in shorter supply and far more important. Having too little oxygen will cause an indoor fire (or even a fuel-burning device like a gas central-heating furnace (boiler)) to produce dangerous air pollution, including toxic carbon monoxide gas. With a car engine, having too much air is just as bad as having too little. Too much air and not enough fuel means an engine burns "lean," while having too much fuel and not enough air is called burning "rich"; both are bad for the engine in different ways.

What is a carburetor?

"The carburetor is called the 'Heart' of the automobile, and it cannot be expected that the engine will act right, give the proper horse-power, or run smoothly if its 'heart' is not performing its functions properly."

That's why gasoline engines are designed to take in exactly the right amount of air so the fuel burns properly, whether the engine is starting from cold or running hot at top speed. Getting the fuel-air mixture just right is the job of a clever mechanical gadget called a carburetor: a tube that allows air and fuel into the engine through valves, mixing them together in different amounts to suit a wide range of different driving conditions.

Who invented the carburetor?

Carburetors have been around since the late 19th century when they were first developed by automobile pioneer (and Mercedes founder) Karl Benz (1844–1929).

Carburetors vary quite a bit in design and complexity. The simplest possible one is essentially a large vertical air pipe above the engine cylinders with a horizontal fuel pipe joined onto one side. As the air flows down the pipe, it has to pass through a narrow kink in the middle, which makes it speed up and causes its pressure to fall. This kinked section is called a venturi. The falling pressure of the air creates a sucking effect that draws air in through the fuel pipe at the side.

The air flow pulls in fuel to join it, which is just what we need, but how can we adjust the air-fuel mixture? The carburetor has two swiveling valves above and below the venturi. At the top, there's a valve called the choke that regulates how much air can flow in. If the choke is closed, less air flows down through the pipe and the venturi drags in more fuel, so the engine gets a fuel-rich mixture. That's handy when the engine is cold, first starting up, and running quite slowly. Beneath the venturi, there's a second valve called the throttle. The more the throttle is open, the more air flows through the carburetor and the more fuel it drags in from the pipe to the side. With more fuel and air flowing in, the engine releases more energy and makes more power and the car goes faster. That's why opening the throttle makes a car accelerate: it's the equivalent of blowing on a campfire to supply more oxygen and make it burn more quickly. The throttle is connected to the accelerator pedal in a car or the throttle on the handlebar of a motorcycle.

The fuel inlet to a carburetor is slightly more complex than we've described it so far. Attached to the fuel pipe there's a kind of mini fuel tank called a float-feed chamber (a little tank with a float and valve inside it). As the chamber feeds fuel to the carburetor, the fuel level sinks, and the float falls with it. When the float drops below a certain level, it opens a valve allowing fuel into the chamber to refill it from the main gas tank. Once the chamber is full, the float rises, closes the valve, and the fuel feed switches off again. (The float-feed chamber works a bit like a toilet, with the float effectively doing the same job as the ballcock—the valve that helps a toilet refill with just the right amount of water after you flush. What do car engines and toilets have in common? More than you might have thought!)

How a carburetor works.

In summary, then, here's how it all works:

Carburetors vary quite a bit in design and complexity. The simplest possible one is essentially a large vertical air pipe above the engine cylinders with a horizontal fuel pipe joined onto one side. As the air flows down the pipe, it has to pass through a narrow kink in the middle, which makes it speed up and causes its pressure to fall. This kinked section is called a venturi. The falling pressure of the air creates a sucking effect that draws air in through the fuel pipe at the side.

The air flow pulls in fuel to join it, which is just what we need, but how can we adjust the air-fuel mixture? The carburetor has two swiveling valves above and below the venturi. At the top, there's a valve called the choke that regulates how much air can flow in. If the choke is closed, less air flows down through the pipe and the venturi drags in more fuel, so the engine gets a fuel-rich mixture. That's handy when the engine is cold, first starting up, and running quite slowly. Beneath the venturi, there's a second valve called the throttle. The more the throttle is open, the more air flows through the carburetor and the more fuel it drags in from the pipe to the side. With more fuel and air flowing in, the engine releases more energy and makes more power and the car goes faster. That's why opening the throttle makes a car accelerate: it's the equivalent of blowing on a campfire to supply more oxygen and make it burn more quickly. The throttle is connected to the accelerator pedal in a car or the throttle on the handlebar of a motorcycle.

The fuel inlet to a carburetor is slightly more complex than we've described it so far. Attached to the fuel pipe there's a kind of mini fuel tank called a float-feed chamber (a little tank with a float and valve inside it). As the chamber feeds fuel to the carburetor, the fuel level sinks, and the float falls with it. When the float drops below a certain level, it opens a valve allowing fuel into the chamber to refill it from the main gas tank. Once the chamber is full, the float rises, closes the valve, and the fuel feed switches off again. (The float-feed chamber works a bit like a toilet, with the float effectively doing the same job as the ballcock—the valve that helps a toilet refill with just the right amount of water after you flush. What do car engines and toilets have in common? More than you might have thought!)

In summary, then, here's how it all works:

Air flows into the top of the carburetor from the car's air intake, passing through a filter that cleans it of debris.

When the engine is first started, the choke (blue) can be set so it almost blocks the top of the pipe to reduce the amount of air coming in (increasing the fuel content of the mixture entering the cylinders).

In the center of the tube, the air is forced through a narrow kink called a venturi. This makes it speed up and causes its pressure to drop.

The drop in air pressure creates suction on the fuel pipe, drawing in fuel.

The throttle is a valve that swivels to open or close the pipe. When the throttle is open, more air and fuel flows to the cylinders so the engine produces more power and the car goes faster.

The mixture of air and fuel flows down into the cylinders.

Fuel is supplied from a mini-fuel tank called the float-feed chamber.

As the fuel level falls, a float in the chamber falls and opens a valve at the top.

When the valve opens, more fuel flows in to replenish the chamber from the main gas tank. This makes the float rise and close the valve again.

gx390_carburettor.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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#34 2017-11-28 15:14:32

ganesh
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Registered: 2005-06-28
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Re: Miscellany

34) Redshift

Astronomers often use the term redshift when describing how far away a distant object is. To understand what a redshift is, think of how the sound of a siren changes as it moves toward and then away from you. As the sound waves from the siren move toward you, they are compressed into higher frequency sound waves. As the siren moves away from you, its sound waves are stretched into lower frequencies. This shifting of frequencies is called the Doppler effect.

A similar thing happens to light waves. When an object in space moves toward us it light waves are compressed into higher frequencies or shorter wavelengths, and we say that the light is blueshifted. When an object moves away from us, its light waves are stretched into lower frequencies or longer wavelengths, and we say that the light is redshifted.

In the visible portion of the electromagnetic spectrum, blue light has the highest frequency and red light has the lowest. The term blueshift is used when visible light is shifted toward higher frequencies or toward the blue end of the spectrum, and the term redshift is used when light is shifted toward lower frequencies or toward the red end of the spectrum. Today, we can observe light in many other parts of the electromagnetic spectrum such as radio, infrared, ultraviolet, X-rays and gamma rays. However, the terms redshift and blueshift are still used to describe a Doppler shift in any part of the spectrum. For example, if radio waves are shifted into the ultraviolet part of the spectrum, we still say that the light is redshifted - shifted toward lower frequencies.

The light from most objects in the Universe is redshifted as seen from the Earth. Only a few objects, mainly local objects like planets and some nearby stars, are blueshifted. This is because our Universe is expanding. The redshift of an object can be measured by examining the absorption or emission lines in its spectrum. These sets of lines are unique for each atomic element and always have the same spacing. When an object in space moves toward or away from us, the absorption or emission lines will be found at different wavelengths than where they would be if the object was not moving (relative to us).

The change in wavelength of these lines is used to calculate the objects redshift. Redshift is defined as the change in the wavelength of the light divided by the wavelength that the light would have if its source was not moving (called the rest wavelength).

Redshift = (Observed wavelength - Rest wavelength)/(Rest wavelength)

Cosmological Redshift

The cosmological redshift is a redshift caused by the expansion of space. As a result of the Big Bang (the tremendous explosion which marked the beginning of our Universe), the Universe is expanding and most of the galaxies within it are moving away from each other. Astronomers have discovered that all distant galaxies are moving away from us and that the farther away they are, the faster they are moving. This recession of galaxies away from us causes the light from these galaxies to be redshifted. As a result of this, at very large redshifts, much of the ultraviolet and visible light from distant sources is shifted into the infrared part of the spectrum. This means that infrared studies can give us much information about the ultraviolet and visible spectra of very young, distant galaxies.

dopplerwaves.jpg


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

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#35 2017-11-30 07:52:02

ganesh
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Re: Miscellany

35) Trans-Siberian Railroad

Trans-Siberian Railroad, Russian Transsibirskaya Zheleznodorozhnaya Magistral, (“Trans-Siberian Main Railroad”), the longest single rail system in Russia, stretching from Moscow 5,778 miles (9,198 km) east to Vladivostok or (beyond Vladivostok) 5,867 miles (9,441 km) to the port station of Nakhodka. It had great importance in the economic, military, and imperial history of the Russian Empire and the Soviet Union.

Conceived by Tsar Alexander III, the construction of the railroad began in 1891 and proceeded simultaneously in several sections—from the west (Moscow) and from the east (Vladivostok) and across intermediate reaches by way of the Mid-Siberian Railway, the Transbaikal Railway, and other lines. Originally, in the east, the Russians secured Chinese permission to build a line directly across Manchuria (the Chinese Eastern Railway) from the Transbaikal region to Vladivostok; this trans-Manchurian line was completed in 1901. After the Russo-Japanese War of 1904–05, however, Russia feared Japan’s possible takeover of Manchuria and proceeded to build a longer and more difficult alternative route, the Amur Railway, through to Vladivostok; this line was completed in 1916. The Trans-Siberian Railroad thus had two completion dates: in 1904 all the sections from Moscow to Vladivostok were linked and completed running through Manchuria; in 1916 there was finally a Trans-Siberian Railroad wholly within Russian territory. The completion of the railroad marked the turning point in the history of Siberia, opening up vast areas to exploitation, settlement, and industrialization.

The trans-Manchurian line came under full Chinese control only after World War II; it was renamed the Chinese Ch’ang-ch’un Railway. In the Soviet Union, over the years, a number of spur lines have been built radiating from the main trans-Siberian line. From 1974 to 1989 construction was completed on a large alternative route, the Baikal-Amur Mainline; its route across areas of taiga, permafrost, and swamps, however, has made upkeep difficult.

The full rail trip on the passenger train Rossiya from Moscow to Nakhodka (including a compulsory overnight stay in Khabarovsk) now takes about eight days.

transsib.jpeg


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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#36 2017-12-03 15:41:48

ganesh
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Re: Miscellany

36) 49th parallel north

The 49th parallel north is a circle of latitude that is 49 degrees north of the Earth's equatorial plane. It crosses Europe, Asia, the Pacific Ocean, North America, and the Atlantic Ocean.

The city of Paris is about 15 km (9 mi) south of the 49th parallel and is the largest city between the 48th and 49th parallels. Its main airport, Charles de Gaulle Airport, lies on the parallel.

Roughly 3,500 kilometres (2,175 mi) of the Canada–United States border was designated to follow the 49th parallel from British Columbia to Manitoba on the Canadian side, and from Washington to Minnesota on the U.S. side, more specifically from the Strait of Georgia to the Lake of the Woods. This international border was specified in the Anglo-American Convention of 1818 and the Oregon Treaty of 1846, however the border as indicated by survey markers placed in the 19th century deviates from the 49th parallel by tens of meters.

From a point on the ground at this latitude, the sun is above the horizon for 16 hours, 12 minutes during the summer solstice and 8 hours, 14 minutes during the winter solstice. This latitude also roughly corresponds to the minimum latitude in which astronomical twilight can last all night near the summer solstice. Slightly less than 1/8 of the Earth's surface is north of the 49th parallel.

borderlines_49parallel-blog427-v2.jpg


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

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#37 2017-12-05 01:14:04

ganesh
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Re: Miscellany

37) Golden Ratio

The Golden ratio is a special number found by dividing a line into two parts so that the longer part divided by the smaller part is also equal to the whole length divided by the longer part. It is often symbolized using phi, after the 21st letter of the Greek alphabet. In an equation form, it looks like this:

a/b = (a+b)/a = 1.6180339887498948420 …

As with pi (the ratio of the circumference of a circle to its diameter), the digits go on and on, theoretically into infinity. Phi is usually rounded off to 1.618. This number has been discovered and rediscovered many times, which is why it has so many names — the Golden mean, the Golden section, divine proportion, etc. Historically, the number can be seen in the architecture of many ancient creations, like the Great Pyramids and the Parthenon. In the Great Pyramid of Giza, the length of each side of the base is 756 feet with a height of 481 feet. The ratio of the base to the height is roughly 1.5717, which is close to the Golden ratio.

Phidias (500 B.C. - 432 B.C.) was a Greek sculptor and mathematician who is thought to have applied phi to the design of sculptures for the Parthenon. Plato (428 B.C. - 347 B.C.) considered the Golden ratio to be the most universally binding of mathematical relationships. Later, Euclid (365 B.C. - 300 B.C.) linked the Golden ratio to the construction of a pentagram.

Around 1200, mathematician Leonardo Fibonacci discovered the unique properties of the Fibonacci sequence. This sequence ties directly into the Golden ratio because if you take any two successive Fibonacci numbers, their ratio is very close to the Golden ratio. As the numbers get higher, the ratio becomes even closer to 1.618. For example, the ratio of 3 to 5 is 1.666. But the ratio of 13 to 21 is 1.625. Getting even higher, the ratio of 144 to 233 is 1.618. These numbers are all successive numbers in the Fibonacci sequence.

These numbers can be applied to the proportions of a rectangle, called the Golden rectangle. This is known as one of the most visually satisfying of all geometric forms – hence, the appearance of the Golden ratio in art. The Golden rectangle is also related to the Golden spiral, which is created by making adjacent squares of Fibonacci dimensions.

In 1509, Luca Pacioli wrote a book that refers to the number as the "Divine Proportion," which was illustrated by Leonardo da Vinci. Da Vinci later called this sectio aurea or the Golden section. The Golden ratio was used to achieve balance and beauty in many Renaissance paintings and sculptures. Da Vinci himself used the Golden ratio to define all of the proportions in his Last Supper, including the dimensions of the table and the proportions of the walls and backgrounds. The Golden ratio also appears in da Vinci's Vitruvian Man and the Mona Lisa. Other artists who employed the Golden ratio include Michelangelo, Raphael, Rembrandt, Seurat, and Salvador Dali.

The term "phi" was coined by American mathematician Mark Barr in the 1900s. Phi has continued to appear in mathematics and physics, including the 1970s Penrose Tiles, which allowed surfaces to be tiled in five-fold symmetry. In the 1980s, phi appeared in quasi crystals, a then-newly discovered form of matter.

Phi is more than an obscure term found in mathematics and physics. It appears around us in our daily lives, even in our aesthetic views. Studies have shown that when test subjects view random faces, the ones they deem most attractive are those with solid parallels to the Golden ratio. Faces judged as the most attractive show Golden ratio proportions between the width of the face and the width of the eyes, nose, and eyebrows. The test subjects weren't mathematicians or physicists familiar with phi — they were just average people, and the Golden ratio elicited an instinctual reaction.

In the golden ratio, a + b is to a as a is to b.

The Golden ratio is a special number found by dividing a line into two parts so that the longer part divided by the smaller part is also equal to the whole length divided by the longer part. It is often symbolized using phi, after the 21st letter of the Greek alphabet. In an equation form, it looks like this:

a/b = (a+b)/a = 1.6180339887498948420 …

As with pi (the ratio of the circumference of a circle to its diameter), the digits go on and on, theoretically into infinity. Phi is usually rounded off to 1.618. This number has been discovered and rediscovered many times, which is why it has so many names — the Golden mean, the Golden section, divine proportion, etc. Historically, the number can be seen in the architecture of many ancient creations, like the Great Pyramids and the Parthenon. In the Great Pyramid of Giza, the length of each side of the base is 756 feet with a height of 481 feet. The ratio of the base to the height is roughly 1.5717, which is close to the Golden ratio.

Phidias (500 B.C. - 432 B.C.) was a Greek sculptor and mathematician who is thought to have applied phi to the design of sculptures for the Parthenon. Plato (428 B.C. - 347 B.C.) considered the Golden ratio to be the most universally binding of mathematical relationships. Later, Euclid (365 B.C. - 300 B.C.) linked the Golden ratio to the construction of a pentagram.

Around 1200, mathematician Leonardo Fibonacci discovered the unique properties of the Fibonacci sequence. This sequence ties directly into the Golden ratio because if you take any two successive Fibonacci numbers, their ratio is very close to the Golden ratio. As the numbers get higher, the ratio becomes even closer to 1.618. For example, the ratio of 3 to 5 is 1.666. But the ratio of 13 to 21 is 1.625. Getting even higher, the ratio of 144 to 233 is 1.618. These numbers are all successive numbers in the Fibonacci sequence.

These numbers can be applied to the proportions of a rectangle, called the Golden rectangle. This is known as one of the most visually satisfying of all geometric forms – hence, the appearance of the Golden ratio in art. The Golden rectangle is also related to the Golden spiral, which is created by making adjacent squares of Fibonacci dimensions.

The term "phi" was coined by American mathematician Mark Barr in the 1900s. Phi has continued to appear in mathematics and physics, including the 1970s Penrose Tiles, which allowed surfaces to be tiled in five-fold symmetry. In the 1980s, phi appeared in quasi crystals, a then-newly discovered form of matter.

The Golden ratio also appears in all forms of nature and science. Some unexpected places include:

Flower petals: The number of petals on some flowers follows the Fibonacci sequence. It is believed that in the Darwinian processes, each petal is placed to allow for the best possible exposure to sunlight and other factors.

Seed heads: The seeds of a flower are often produced at the center and migrate outward to fill the space. For example, sunflowers follow this pattern.

Pinecones: The spiral pattern of the seed pods spiral upward in opposite directions. The number of steps the spirals take tend to match Fibonacci numbers.

Tree branches: The way tree branches form or split is an example of the Fibonacci sequence. Root systems and algae exhibit this formation pattern.

Shells: Many shells, including snail shells and nautilus shells, are perfect examples of the Golden spiral.

Spiral galaxies: The Milky Way has a number of spiral arms, each of which has a logarithmic spiral of roughly 12 degrees. The shape of the spiral is identical to the Golden spiral, and the Golden rectangle can be drawn over any spiral galaxy.

Hurricanes: Much like shells, hurricanes often display the Golden spiral.

Fingers: The length of our fingers, each section from the tip of the base to the wrist is larger than the preceding one by roughly the ratio of phi.

Animal bodies: The measurement of the human navel to the floor and the top of the head to the navel is the Golden ratio. But we are not the only examples of the Golden ratio in the animal kingdom; dolphins, starfish, sand dollars, sea urchins, ants and honeybees also exhibit the proportion.

DNA molecules: A DNA molecule measures 34 angstroms by 21 angstroms at each full cycle of the double helix spiral. In the Fibonacci series, 34 and 21 are successive numbers.

golden-rectangle.png


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

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#38 2017-12-07 01:26:20

ganesh
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Re: Miscellany

38) Ape

Ape (superfamily Hominoidea), any tailless primate of the families Hylobatidae (gibbons) and Hominidae (chimpanzees, bonobos, orangutans, gorillas, and human beings). Apes are found in the tropical forests of western and central Africa and Southeast Asia. Apes are distinguished from monkeys by the complete absence of a tail and the presence of an appendix and by their more complex brains. Although human beings are categorized zoologically as members of the broader ape superfamily, they are usually placed within their own subcategories on account of their larger brain size, more advanced cognitive abilities (particularly the ability to speak), and striding two-legged gait.

The gorilla, chimpanzee, bonobo, and orangutan are called great apes in recognition of their comparatively large size and humanlike features; the gibbons are called lesser apes. The great apes are much more intelligent than monkeys and gibbons. Great apes, for example, are able to recognize themselves in mirrors (monkeys and other nonhumans cannot, with the exception of bottlenose dolphins). They can also reason abstractly, learn quasi-linguistic communication, at least when taught by humans, and learn in captivity to make simple tools (though some populations of orangutans and chimpanzees make tools in the wild). The great apes were formerly classified in their own family, Pongidae, but, because of their extremely close relation to humans and the fact that orangutans, gorillas, and chimpanzees are not as closely related to each other as chimpanzees are to humans, all are now grouped with humans in the family Hominidae. Within this family, gorillas, chimpanzees, and humans make up the subfamily Homininae, while orangutans are placed in their own subfamily, Ponginae. Within Homininae, humans are often placed in their own “tribe,” Hominini. Also placed in distinct tribes are gorillas (tribe Gorillini) and chimpanzees (tribe Panini). All nonhuman apes have been classified as endangered species.

Gibbons (family Hylobatidae) typically move about by swinging (brachiation), and it has been theorized that the ancestors of all apes may once have moved in this way. Nonhuman apes can stand or sit erect with great facility, and occasionally they walk upright, especially when carrying an object. Apes have broad chests, scapulae on the back, and full rotation at the shoulder. There is a pad of cartilage (meniscus) between the ulna and the carpal bones in the wrist that gives the wrist great flexibility. The lumbar section of the spine (lower back) has only four to six vertebrae instead of the seven or more of Old World monkeys. There is no external tail; instead, the remnant three to six vertebrae are fused into the tailbone, or coccyx.

The gibbons and the orangutan are arboreal, while the gorilla, chimpanzee, and bonobo spend some or much of their time on the ground. African apes (gorilla, chimpanzee, and bonobo) travel on the ground by quadrupedal knuckle walking, in which the long fingers of the forelimbs are folded under to provide support for the body. Fruits and other plant material are the chief foods, though small invertebrates are eaten occasionally by all apes, and chimpanzees hunt large vertebrates, especially monkeys. Most apes lodge at night in trees, and all except gibbons build nests for sleeping. Group size ranges from the virtually solitary orangutan to the sociable chimpanzees and bonobos, which may live in bands of 100 or more.

Hominidae and Hylobatidae diverged about 18 million years ago, but the evolutionary history of the apes includes numerous extinct forms, many of which are known only from fragmentary remains. The earliest-known hominoids are from Egypt and date from about 36.6 million years ago. Fossil genera include Catopithecus and Aegyptopithecus, possible successive ancestors of both the Old World monkeys and the apes. Later deposits have yielded such fossils as Pliopithecus, once thought to be related to gibbons but now known to be primitive and long separated from them. Closer to the modern apes are Proconsul, Afropithecus, Dryopithecus, and Sivapithecus, the latter being a possible ancestor of the orangutan.

ape-08.jpg


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

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#39 2017-12-09 01:30:03

ganesh
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Re: Miscellany

39) Nickel

Nickel is a strong, lustrous, silvery-white metal that is a staple of our daily lives and can be found in everything from the batteries that power our television remotes to the stainless steel that is used to make our kitchen sinks.

Properties:

Atomic Symbol: Ni
Atomic Number: 28
Element Category: Transition metal
Density: 8.908 g/cubic centimeters
Melting Point: 2651 °F (1455 °C)
Boiling Point: 5275 °F (2913 °C)
Moh’s Hardness: 4.0

Characteristics:

Pure nickel reacts with oxygen and, therefore, is seldom found on the earth's surface, despite being the fifth most abundant element on (and in) our planet. In combination with iron, nickel is extremely stable, which explains both its occurrence in iron-containing ores and its effective use in combination with iron to make stainless steel.

Nickel is very strong and resistant to corrosion, making it excellent for strengthening metal alloys. It is also very ductile and malleable, properties that allow its many alloys to be shaped into wire, rods, tubes, and sheets.

History:

Pure nickel was first extracted by Baron Axel Fredrik Cronstedt in 1751, but it was known to exist much earlier. Chinese documents from around 1500BC make reference to 'white copper' (baitong), which was very likely an alloy of nickel and silver. Fifteenth century German miners, who believed they could extract copper from nickel ores in Saxony, referred to the metal as kupfernickel - 'the devil's copper' - partly due to their futile attempts to extract copper from the ore, but also likely in part due to the health effects caused by the high math content in the ore.

In 1889, James Riley made a presentation to the Iron and Steel Institute of Great Britain on how the introduction of nickel could strengthen traditional steels. Riley's presentation resulted in a growing awareness of nickel's beneficial alloying properties and coincided with the discovery of large nickel deposits in New Caledonia and Canada.

By the early 20th century, the discovery of ore deposits in Russia and South Africa made large-scale production of nickel possible. Not long after, World War I and World War II resulted in a significant increase in steel and, consequently, nickel demand.

Production:

Nickel is primarily extracted from the nickel sulphides pentlandite, pyrrhotite, and millerite, which contain about 1% nickel content, and the iron-containing lateritic ores limonite and garnierite, which contain about 4% nickel content. Nickel ores are mined in 23 countries, while nickel is smelted in 25 different countries.

The separation process for nickel is highly dependent upon the type of ore. Nickel sulphides, such as those found in the Canadian Shield and Siberia, are generally found deep underground, making them labor intensive and expensive to extract. However, the separation process for these ores is much cheaper than for the lateritic variety, such as those found in New Caledonia. Moreover, nickel sulphides often have the benefit of containing impurities of other valuable elements that can be economically separated.

Sulphide ores can be separated using froth flotation and hydrometallurgical or magnetic processes to create nickel matte and nickel oxide.

These intermediate products, which usually contain 40-70% nickel, are then further processed, often using the Sherritt-Gordon Process.

The Mond (or Carbonyl) Process is the most common and efficient method to treat nickel sulphide. In this process, the sulphide is treated with hydrogen and fed into a volatilization kiln. Here it meets carbon monoxide at about 140F° (60C°) to form nickel carbonyl gas. The nickel carbonyl gas decomposes on the surface of pre-heated nickel pellets that flow through a heat chamber until they reach the desired size. At higher temperatures, this process can be used to form nickel powder.

Lateritic ores, by contrast, are usually smelted by pyro-metallic methods because of their high iron content. Lateritic ores also have a high moisture content (35-40%) that requires drying in a rotary kiln furnace.

It produces nickel oxide, which is then reduced using electric furnaces at temperatures between 2480-2930 F° (1360-1610 C°) and volatilized to produce Class I nickel metal and nickel sulfate.

Due to the naturally occurring iron content in lateritic ores, the end product of most smelters working with such ores is ferro-nickel, which can be used by steel producers after silicon, carbon, and phosphorus impurities are removed.

By country, the largest producers of nickel in 2010 were Russia, Canada, Australia and Indonesia. The largest producers of refined nickel are Norilsk Nickel, Vale S.A., and Jinchuan Group Ltd. At present, only a small percentage of nickel is produced from recycled materials.

Applications:

Nickel is one of the most widely used metals on the planet. According to the Nickel Institute, the metal is used in over 300,000 different products. Most often it is found in steels and metal alloys, but it is also used in the production of batteries and permanent magnets.

Stainless Steel:

About 65% of all nickel produced goes into stainless steel.

Austenitic steels are non-magnetic stainless steels that contain high levels of chromium and nickel, and low levels of carbon.  This group of steels - classified as 300 series stainless - are valued for their formability and resistance to corrosion. Austenitics are the most widely used   grade of stainless steel.

The nickel-containing austenitic range of stainless steels is defined by their face-centered cubic (FCC) crystal structure, which has one atom at each corner of the cube and one in the middle of each face. This grain structure forms when a sufficient quantity of nickel is added to the alloy (eight to ten percent in a standard 304 stainless steel alloy).

nickel-chips-250x250.jpg


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#40 2017-12-11 00:57:17

ganesh
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Re: Miscellany

40) pH Value

pH, quantitative measure of the acidity or basicity of aqueous or other liquid solutions. The term, widely used in chemistry, biology, and agronomy, translates the values of the concentration of the hydrogen ion—which ordinarily ranges between about 1 and

gram-equivalents per litre—into numbers between 0 and 14. In pure water, which is neutral (neither acidic nor alkaline), the concentration of the hydrogen ion is
gram-equivalents per litre, which corresponds to a pH of 7. A solution with a pH less than 7 is considered acidic; a solution with a pH greater than 7 is considered basic, or alkaline.

The measurement was originally used by the Danish biochemist S.P.L. Sørensen to represent the hydrogen ion concentration, expressed in equivalents per litre, of an aqueous solution: pH = −log[H+] (in expressions of this kind, enclosure of a chemical symbol within square brackets denotes that the concentration of the symbolized species is the quantity being considered).

Because of uncertainty about the physical significance of the hydrogen ion concentration, the definition of the pH is an operational one; i.e., it is based on a method of measurement. The U.S. National Bureau of Standards has defined pH values in terms of the electromotive force existing between certain standard electrodes in specified solutions.

The pH is usually measured with a pH meter, which translates into pH readings the difference in electromotive force (electrical potential or voltage) between suitable electrodes placed in the solution to be tested. Fundamentally, a pH meter consists of a voltmeter attached to a pH-responsive electrode and a reference (unvarying) electrode. The pH-responsive electrode is usually glass, and the reference is usually a mercury-mercurous chloride (calomel) electrode, although a silver-silver chloride electrode is sometimes used. When the two electrodes are immersed in a solution, they act as a battery. The glass electrode develops an electric potential (charge) that is directly related to the hydrogen-ion activity in the solution, and the voltmeter measures the potential difference between the glass and reference electrodes. The meter may have either a digital or an analog (scale and deflected needle) readout. Digital readouts have the advantage of exactness, while analog readouts give better indications of rates of change. Battery-powered portable pH meters are widely used for field tests of the pH of soils. Tests of pH may also be performed, less accurately, with litmus paper or by mixing indicator dyes in liquid suspensions and matching the resulting colours against a colour chart calibrated in pH.

In agriculture, the pH is probably the most important single property of the moisture associated with a soil, since that indication reveals what crops will grow readily in the soil and what adjustments must be made to adapt it for growing any other crops. Acidic soils are often considered infertile, and so they are for most conventional agricultural crops, although conifers and many members of the family Ericaceae, such as blueberries, will not thrive in alkaline soil. Acidic soil can be “sweetened,” or neutralized, by treating it with lime. As soil acidity increases so does the solubility of aluminum and manganese in the soil, and many plants (including agricultural crops) will tolerate only slight quantities of those metals. Acid content of soil is heightened by the decomposition of organic material by microbial action, by fertilizer salts that hydrolyze or nitrify, by oxidation of sulfur compounds when salt marshes are drained for use as farmland, and by other causes.

3716766_orig.jpg


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#41 2017-12-13 02:29:06

ganesh
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Re: Miscellany

41) Cathode-ray oscilloscope

Cathode-ray oscilloscope, electronic-display device containing a cathode-ray tube (CRT) that generates an electron beam that is used to produce visible patterns, or graphs, on a phosphorescent screen. The graphs plot the relationships between two or more variables, with the horizontal axis normally being a function of time and the vertical axis usually a function of the voltage generated by the input signal to the oscilloscope. Because almost any physical phenomenon can be converted into a corresponding electric voltage through the use of a transducer, the oscilloscope is a versatile tool in all forms of physical investigation. The German physicist Ferdinand Braun developed the first cathode-ray oscilloscope in 1897.

Speed of response is the cathode-ray oscilloscope’s chief advantage over other plotting devices. General-purpose oscilloscopes have plotting frequencies of up to 100 megahertz (MHz), or 100 million cycles per second. Response times as rapid as 2,000 MHz are achievable with special-purpose high-speed oscilloscopes.

The central component in this device, the cathode-ray tube, consists of an evacuated glass container with a phosphorescent coating at one end (similar to that of a television screen) and an electron gun and a system for focusing and deflecting the beam of electrons at the other. The electron beam emerging from the electron gun passes between pairs of metal plates mounted in such a way that they deflect the beam horizontally and vertically to control the production of a luminous pattern on the screen. The screen image is a visual representation of the voltages applied to the deflection plates. Alternatively, the beam may be deflected magnetically by varying the currents through externally mounted deflection coils. Thus, almost any graph can be plotted on the screen by generating horizontal and vertical deflection voltages or currents proportional to the lengths, velocities, or other quantities being observed.

It is sometimes necessary or desirable to plot more than one waveform at the same time on the screen of an oscilloscope. With the use of a variety of techniques, four or more plots can be simultaneously shown. With a dual-trace amplifier and a single electron gun, two signals may be shown at what appears to be the same time. Actually, the amplifier electronically switches rapidly between the two observed signals. In a split-beam CRT the electron beam from a single gun is split, with the two parts receiving different vertical deflections. A dual-gun CRT uses two separate electron guns, each having its own focus and brightness controls. By combining two dual-trace amplifiers with a dual-gun CRT, four individual plots can be obtained.

The cathode-ray oscilloscope is one of the most widely used test instruments; its commercial, engineering, and scientific applications include acoustic research, television-production engineering, and electronics design.

cathode-ray-oscilloscope-calibration-250x250.jpg


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

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#42 2017-12-14 03:10:16

ganesh
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Re: Miscellany

42) English Channel

English Channel, also called The Channel, French La Manche, narrow arm of the Atlantic Ocean separating the southern coast of England from the northern coast of France and tapering eastward to its junction with the North Sea at the Strait of Dover (French: Pas de Calais). With an area of some 29,000 square miles (75,000 square kilometres), it is the smallest of the shallow seas covering the continental shelf of Europe. From its mouth in the North Atlantic Ocean—an arbitrary limit marked by a line between the Scilly Isles and the Isle of Ushant—its width gradually narrows from 112 miles (180 kilometres) to a minimum of 21 miles, while its average depth decreases from 400 to 150 feet (120 to 45 metres). Although the English Channel is a feature of notable scientific interest, especially in regard to tidal movements, its location has given it immense significance over the centuries, as both a route and a barrier during the peopling of Britain and the emergence of the nation-states of modern Europe. The current English name (in general use since the early 18th century) probably derives from the designation “canal” in Dutch sea atlases of the late 16th century. Earlier names had included Oceanus Britannicus and the British Sea, and the French have regularly used La Manche (in reference to the sleevelike coastal outline) since the early 17th century.

Physical Features

Geology

The contemporary English Channel probably is the result of a complex structural downfolding dating from about 40 million years ago, although signs of a downwarp tendency occur as early as 270 million years ago. The direct ancestor of the channel may well have been a sea occupying the downfold one to two million years ago, with a sea level 600 to 700 feet higher than the present level.

The withdrawal of water by the glaciers of the late Pleistocene Epoch (about 25,000 years ago), produced a sea level at least 300 feet lower than the present. Later the melting of the ice raised the sea level to its present mark, and the ecologically important land bridge across the Strait of Dover finally was submerged about 8,000 years ago.

Physiography

The seafloor dips fairly steeply near the coasts but is generally flat and remarkably shallow (especially in relation to nearby land elevations); its greatest depth, 565 feet (172 metres) in the Hurd Deep, is one of a group of anomalous deep, enclosed troughs in the bed of the western channel. The channel has been shaped by the effect upon its rock strata (with their varying degrees of hardness) of such forces as weathering and erosion (when much of the area was dry land), sea-level changes, and contemporary erosion and deposition by marine currents.

The floor of the western channel generally is 200 to 400 feet deep and is relatively flat and featureless, reflecting fairly uniform rock types, mostly limestone. Harder igneous rocks cause shoals to emerge—as in the case of the Scilly Isles and Channel Islands—and submerged cliffs and narrow depressions provide some additional variety.

In the central channel (150 to 200 feet deep), depths are fairly uniform over chalk outcrops, but alternations of clays and limestones give rise to an undulating terrain, with deeps reaching almost twice the average. A continuation of the Seine River valley system north of the Cotentin Peninsula of Normandy complicates the relief forms. Farther east again, the seafloor is smoother and the geology simpler. Depths range from 6 to 160 feet, with such elongated banks as the Varne and the Ridge greatly constricting shipping lanes.

Because the English Channel, unlike the Irish or North seas, lay beyond the action of Pleistocene glaciers, superficial deposits are either very thin (three feet or less) or entirely absent. They represent a complex reworking of deposits of various ages, and their distribution reflects tidal streams. Where the streams are strong, the seabed is bare except for pebbles; decreasing velocities give rise to sand and gravel ribbons and waves (the latter up to 40 feet thick) and to thick beds of fine-grained deposits in sheltered areas, notably the Gulf of Saint-Malo.

Hydrology

Tides in the English Channel generally are strong, especially in the Strait of Dover, and may be visualized as an oscillation (modified by the Earth’s rotation and configuration) about a north-south line through the centre of the channel—i.e., with a rise to the west accompanying a fall to the east. The central portion experiences semidiurnal (twice-daily) tides (helpful to shipping movements at Southampton, which has a double, or prolonged, high tide), and the Gulf of Saint-Malo experiences the greatest tidal range, 28 feet or more.

Surface temperatures range from 45° F (7° C) in February to 61° F (16° C) in September, although shallow coastal waters are warmer in summer. There is little temperature change with depth in the well-mixed eastern waters of the channel, but bottom-water temperatures fall to 41° F (5° C) in the west. Surface salinities decline eastward from slightly less than the Atlantic level of 35.5 parts per thousand; coastal salinity readings are further reduced by the influx of river water, especially from the larger French landmass. There is an overall water flow through the English Channel to the North Sea, with complete replacement taking about 500 days.

Climate

The weather over the English Channel is highly variable. Often, but especially from October to April, it is cloudy, chilly, and wet, with strong winds and poor visibility. At other times, it is fair and dry, with light winds and good visibility. During periods of unsettled weather, daytime high temperatures rise to about 54° F (12° C) in winter and 68° F (20° C) in summer. When the weather is clear, temperature extremes can range from a winter morning low of 23° F (−5° C) to more than 86° F (30° C) on a summer afternoon. Precipitation averages 28 to 39 inches (700 to 1,000 millimetres) per year. Gales may blow from any direction but most commonly come from the southwest or west.

Economic Aspects

Resources

Connecting the Atlantic Ocean and the North Sea, the respective waters of which are rich in warm- and cold-water plankton, the English Channel is favoured from the latter with cod, herring, and whiting and from the former with hake, pilchard, and mullet. The traditional fishing industry declined in the 20th century with the development of deep-sea fishing, the exhaustion of resources, and the advent of pollution problems, but coastal fishing remains important in Brittany.

A good climate, sandy beaches, and an attractive coast have encouraged the growth of tourism on both sides of the channel, starting with the fashionable resorts of the late 18th century. The English ports of Portsmouth and Plymouth have declined from their former levels of naval and commercial activity. Cherbourg on the Contentin Peninsula has changed little in character, but Southampton and Le Havre have lost passenger traffic while gaining tremendous container and oil-refining capacity and also experiencing a general commercial growth. Both England and France use channel waters for cooling nuclear-powered generating stations, while the tidal-power generating station on the Rance River (in Brittany), utilizing a tidal range of 35 feet and more, is a unique feature.

Transportation

The English Channel is a major route for passenger and freight traffic. Crossings are provided by ferry and air services. Hundreds of watercraft traverse the Strait of Dover daily; and this frequency, as well as the increase in ship size and speed, has led to the introduction of sophisticated navigational safeguard systems, including radar tracking of all ships in the strait.

The idea of a channel tunnel was first conceived in 1802, and in the late 19th century such a tunnel was actually initiated and then abandoned. In 1957 the idea was revived, and in 1973 Britain and France decided to carry out the project (the “Chunnel”) jointly. Work was begun, only to be canceled early in 1975, but in 1978 the matter of a channel crossing was again raised, this time by the British and French national railways and the European Communities. Construction resumed in 1987 on twin single-track railway tunnels and a central service tunnel for ventilation, maintenance, and emergency evacuation; by 1990 the service tunnel had been completed. The Eurotunnel (as it came to be called) connects the road and rail networks of Britain and the Continent by carrying both rail freight and automobiles. The terminals are located at Folkestone in England and Calais in France.

Study And Exploration

From earliest times, depending on historical factors, the English Channel served as a route for, and a barrier to, invaders of Britain from the Continent. Early Stone Age people crossed the Strait of Dover; later invaders crossed the western end of the channel, trading the copper, tin, and lead they found in Devon and Cornwall, and successive Bronze and Iron Age invaders followed the same route. Julius Caesar’s invasion of 55 bc again favoured the Dover route in the east, while William the Conqueror in 1066 crossed from Normandy to Hastings. With Britain’s later loss of Normandy, the channel again became a defensive line. In the 20th century its strategic role was critical during the two world wars, particularly during the Allied invasion of France in 1944.

Scholars adduced reasons for the English Channel’s existence as early as the 17th century, but detailed scientific study awaited the first official hydrographic surveys (French coast, 1829; English coast, 1847). The geologic map of the seabed based on borings made in 1866 was the world’s first of its kind. Further studies were associated with early plans for a channel tunnel, and modern surveys done since World War II have made the channel seabed one of the most intensively studied seafloors in the world.

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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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#43 2017-12-14 21:29:22

ganesh
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Registered: 2005-06-28
Posts: 23,463

Re: Miscellany

43) Pascal's triangle

Pascal's triangle is an infinite, equilateral triangle composed of numbers. The numbers that make up Pascal's triangle follow a simple rule: each number is the sum of the two numbers above it.

Looking at Pascal's triangle, you'll notice that the top number of the triangle is one. All of the numbers in each of the sides going down from the top are all ones. The numbers in the middle vary, depending upon the numbers above them.

Since Pascal's triangle is infinite, there's no bottom row. It just keeps going and going. Pascal's triangle is named for Blaise Pascal, a French mathematician who used the triangle as part of his studies in probability theory in the 17th century.

Blaise Pascal didn't really "discover" the triangle named after him, though. It has actually been studied all over the world for thousands of years. For example, historians believe ancient mathematicians in India, China, Persia, Germany, and Italy studied Pascal's triangle long before Pascal was born. Pascal did develop new uses of the triangle's patterns, which he described in detail in his mathematical treatise on the triangle.

The basic pattern of Pascal's triangle is quite simple. Despite its simplicity, though, Pascal's triangle has continued to surprise mathematicians throughout history with its interesting connections to so many other areas of mathematics, such as probability, combinatorics, number theory, algebra, and fractals.

So why is Pascal's triangle so fascinating to mathematicians? The more you study Pascal's triangle, the more interesting patterns you find. This is important in mathematics, because mathematics itself has been called the "study of patterns" and even the "science of patterns."

Many of the mathematical uses of Pascal's triangle are hard to understand unless you're an advanced mathematician. Even young students, however, can recognize a couple of the simpler patterns found within Pascal's triangle.

For example, the left side of Pascal's triangle is all ones. The next set of numbers in, known as the first diagonal, is the set of counting numbers: one, two, three, four, five, etc. You'll also notice an interesting pattern if you add up the numbers in each horizontal row, starting at the top. The sums double each time you descend one row, making them the powers of the number two!

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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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