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

ganesh
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Registered: 2005-06-28
Posts: 23,359

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).

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

ganesh
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Registered: 2005-06-28
Posts: 23,359

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.

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

ganesh
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Registered: 2005-06-28
Posts: 23,359

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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Registered: 2005-06-28
Posts: 23,359

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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Registered: 2005-06-28
Posts: 23,359

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 Yesterday 14:43:32

ganesh
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Registered: 2005-06-28
Posts: 23,359

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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