An anti-lock braking system, or ABS (from the German, Antiblockiersystem) is a safety system which prevents the wheels on a motor vehicle from locking while braking.A rotating road wheel allows the driver to maintain steering control under heavy braking by preventing a skid and allowing the wheel to continue interacting tractively with the road surface as directed by driver steering inputs. While ABS offers improved vehicle control in some circumstances, it can also present disadvantages including increased braking distance on slippery surfaces such as ice, packed snow, gravel, steel plates and bridges, or anything other than dry pavement.
ABS has also been demonstrated to create a false sense of security in drivers, who may drive more aggressively as a result.Since initial widespread use in production cars, anti-lock braking systems have evolved considerably. Recent versions not only prevent wheel lock under braking, but also electronically control the front-to-rear brake bias. This function, depending on its specific capabilities and implementation, is known as electronic brakeforce distribution (EBD), traction control system (TCS or ASR), emergency brake assist (BA, EBA or HBA), or electronic stability control (ESP, ESC or DSC).
Anti-lock braking systems were first developed for aircraft in 1929, by the French automobile and aircraft pioneer, Gabriel Voisin, as threshold braking an airplane is nearly impossible. An early system was Dunlop's Maxaret system, introduced in the 1950s and still in use on some aircraft models.A fully mechanical system saw limited automobile use in the 1960s in the Ferguson P99 racing car, the Jensen FF and the experimental all wheel drive Ford Zodiac, but saw no further use; the system proved expensive and, in automobile use, somewhat unreliable.
However, a limited form of anti-lock braking, utilizing a valve which could adjust front to rear brake force distribution when a wheel locked, was fitted to the 1964 Austin 1800.Chrysler, together with the Bendix Corporation, introduced a true computerized three-channel all-wheel antilock brake system called "Sure Brake" on the 1971 Imperial. It was available for several years thereafter, functioned as intended, and proved reliable.
Tuesday, January 27, 2009
WI-FI
Wi-Fi (IPA: /ˈwaɪfaɪ/) is a trademark of the Wi-Fi Alliance, founded in 1999 as WECA (Wireless Ethernet Compatibility Alliance). The organization comprises more than 300 companies, whose products are certified by the Wi-Fi Alliance, based on the IEEE 802.11 standards (also called WLAN (Wireless LAN) and Wi-Fi). This certification warrants interoperability between different wireless devices.
The alliance was founded because many products did not correctly implement IEEE 802.11, and some included proprietary extensions. This led to incompatibilities between products from different manufacturers.The Wi-Fi Alliance tests the wireless components to their own terms of reference. Products that pass become Wi-Fi certified and may carry the Wi-Fi logo. Only products of Wi-Fi Members are tested, as they pay membership and per-item-fees. A missing Wi-Fi logo does not necessarily mean non-compliance with the standard.
In some countries (USA, France, Poland...) the term "Wi-Fi" is often used by the public as a synonym for wireless Internet (W-LAN), although not every wireless Internet product has a Wi-Fi certification. This may be due to certification costs that must be paid for each certified device type.Wi-Fi certification is provided for technology used in home networks, mobile phones, video games and other devices that require wireless networking. It covers IEEE 802.11 standards including 802.11a, 802.11b, 802.11g, and 802.11n.
Wi-Fi is supported by most personal computer operating systems, many game consoles, laptops, smartphones, printers and other peripherals. The purpose of Wi-Fi is to provide inter-operable wireless access between devices. Wi-Fi generally makes access to information between devices from many different manufacturers easier, as it can eliminate some of the physical restraints of wiring which can be especially true for mobile devices.
The alliance was founded because many products did not correctly implement IEEE 802.11, and some included proprietary extensions. This led to incompatibilities between products from different manufacturers.The Wi-Fi Alliance tests the wireless components to their own terms of reference. Products that pass become Wi-Fi certified and may carry the Wi-Fi logo. Only products of Wi-Fi Members are tested, as they pay membership and per-item-fees. A missing Wi-Fi logo does not necessarily mean non-compliance with the standard.
In some countries (USA, France, Poland...) the term "Wi-Fi" is often used by the public as a synonym for wireless Internet (W-LAN), although not every wireless Internet product has a Wi-Fi certification. This may be due to certification costs that must be paid for each certified device type.Wi-Fi certification is provided for technology used in home networks, mobile phones, video games and other devices that require wireless networking. It covers IEEE 802.11 standards including 802.11a, 802.11b, 802.11g, and 802.11n.
Wi-Fi is supported by most personal computer operating systems, many game consoles, laptops, smartphones, printers and other peripherals. The purpose of Wi-Fi is to provide inter-operable wireless access between devices. Wi-Fi generally makes access to information between devices from many different manufacturers easier, as it can eliminate some of the physical restraints of wiring which can be especially true for mobile devices.
BLU-RAY DISC
Blu-ray Disc (also known as Blu-ray or BD) is an optical disc storage medium. Its main uses are high-definition video and data storage. The disc has the same physical dimensions as standard DVDs and CDs.The name Blu-ray Disc is derived from the blue laser (violet-colored) used to read and write this type of disc. Because of the wavelength (405 nanometres), substantially more data can be stored on a Blu-ray Disc than on the DVD format, which uses a red (650 nm) laser. A two-layer Blu-ray Disc can store 50 gigabytes, almost six times the capacity of a two-layer DVD, or ten and a half times that of a single-layer DVD.
During the format war over high-definition optical discs, Blu-ray Disc competed with the HD DVD format. On February 19, 2008, Toshiba—the main company supporting HD DVD—announced that it would no longer develop, manufacture, or market HD DVD players and recorders, leading almost all other HD DVD companies to follow suit, effectively ending the format war.
Blu-ray Disc was developed by the Blu-ray Disc Association, a group representing makers of consumer electronics, computer hardware, and motion pictures. As of December 21, 2008, more than 890 Blu-ray disc titles are available in Australia, more than 720 Blu-ray Disc titles are available in Japan, more than 1,140 Blu-ray Disc titles are available in the United Kingdom, and more than 1,220 Blu-ray Disc titles are available in the United States.
Commercial HDTV sets began to appear in the consumer market around 1998, but there was no commonly-accepted, inexpensive way to record or play HD content. In fact, there was no medium with the storage required to accommodate HD codecs, except JVC's Digital VHS and Sony's HDCAM.[6] Nevertheless, it was well known that using lasers with shorter wavelengths would enable optical storage with higher density. When Shuji Nakamura invented practical blue laser diodes, it was a sensation, although a lengthy patent lawsuit delayed commercial introduction.[7] Dr. Dave Irvine-Halliday was given the proceeds from the patent lawsuit to continue his ongoing work for the Light Up the World Foundation.
During the format war over high-definition optical discs, Blu-ray Disc competed with the HD DVD format. On February 19, 2008, Toshiba—the main company supporting HD DVD—announced that it would no longer develop, manufacture, or market HD DVD players and recorders, leading almost all other HD DVD companies to follow suit, effectively ending the format war.
Blu-ray Disc was developed by the Blu-ray Disc Association, a group representing makers of consumer electronics, computer hardware, and motion pictures. As of December 21, 2008, more than 890 Blu-ray disc titles are available in Australia, more than 720 Blu-ray Disc titles are available in Japan, more than 1,140 Blu-ray Disc titles are available in the United Kingdom, and more than 1,220 Blu-ray Disc titles are available in the United States.
Commercial HDTV sets began to appear in the consumer market around 1998, but there was no commonly-accepted, inexpensive way to record or play HD content. In fact, there was no medium with the storage required to accommodate HD codecs, except JVC's Digital VHS and Sony's HDCAM.[6] Nevertheless, it was well known that using lasers with shorter wavelengths would enable optical storage with higher density. When Shuji Nakamura invented practical blue laser diodes, it was a sensation, although a lengthy patent lawsuit delayed commercial introduction.[7] Dr. Dave Irvine-Halliday was given the proceeds from the patent lawsuit to continue his ongoing work for the Light Up the World Foundation.
TWO-WAY SATELLITE-ONLY COMMUNICATION
Two-way satellite Internet service involves both sending and receiving data from the remote VSAT site via satellite to a hub teleport, which then sends relays data via the terrestrial Internet. The satellite dish at each location must be precisely pointed to avoid interference with other satellites. Some providers oblige the customer to pay for a member of the provider's staff to install the system and correctly align the dish — although the European ASTRA2Connect system encourages user-installation and provides detailed instructions for this.
Many customers in the Middle East and Africa are also encouraged to do self installs. At each VSAT site the uplink frequency, bit rate and power must be accurately set, under control of the service provider hub.There are several types of two way satellite Internet services, including time division multiple access (TDMA) and single channel per carrier (SCPC). Two-way systems can be simple VSAT terminals with a 60–100cm dish and output power of only a few watts intended for consumers and small business or larger systems which provide more bandwidth.
Such systems are frequently marketed as "satellite broadband" and can cost two to three times as much per month as land-based systems such as ADSL. The modems required for this service are often proprietary, but some are compatible with several different providers. They are also expensive, costing in the range of US$600 to $2000.the two-way "iLNB" used on the ASTRA2Connect terminal dish has a 500mW transmitter and single-polarity receive LNB, both operating in the Ku band.
Pricing for Astra2Connect modems range from 299 to 350€. These types of system are generally unsuitable for use on moving vehicles, although some dishes may be fitted to an automatic pan and tilt mechanism to continuously re-align the dish—but these are cumbersome and very expensive. The technology for ASTRA2Connect was delivered by a Belgian company called Newtec.Satellite internet customers range from individual home users with one PC to large remote business sites with several hundred PCs.
Many customers in the Middle East and Africa are also encouraged to do self installs. At each VSAT site the uplink frequency, bit rate and power must be accurately set, under control of the service provider hub.There are several types of two way satellite Internet services, including time division multiple access (TDMA) and single channel per carrier (SCPC). Two-way systems can be simple VSAT terminals with a 60–100cm dish and output power of only a few watts intended for consumers and small business or larger systems which provide more bandwidth.
Such systems are frequently marketed as "satellite broadband" and can cost two to three times as much per month as land-based systems such as ADSL. The modems required for this service are often proprietary, but some are compatible with several different providers. They are also expensive, costing in the range of US$600 to $2000.the two-way "iLNB" used on the ASTRA2Connect terminal dish has a 500mW transmitter and single-polarity receive LNB, both operating in the Ku band.
Pricing for Astra2Connect modems range from 299 to 350€. These types of system are generally unsuitable for use on moving vehicles, although some dishes may be fitted to an automatic pan and tilt mechanism to continuously re-align the dish—but these are cumbersome and very expensive. The technology for ASTRA2Connect was delivered by a Belgian company called Newtec.Satellite internet customers range from individual home users with one PC to large remote business sites with several hundred PCs.
TEXTILE MANUFACTURE DURING THE INDUSTRIAL REVOLUTION
The key British industry at the beginning of the 18th century was the production of textiles made with wool from the large sheep-farming areas in the Midlands and across the country (created as a result of land-clearance and enclosure). Handlooms and spinning wheels were the tools of the trade of the weavers in their cottages, and this was a labor-intensive activity providing employment throughout Britain, with major centers being the West Country; Norwich and environs; and the West Riding of Yorkshire.
The export trade in woolen goods accounted for more than a quarter of British exports during most of the 18th century, doubling between 1701 and 1770 [1]. Exports of the cotton industry – centered in Lancashire – had grown tenfold during this time, but still accounted for only a tenth of the value of the woolen trade.The textile industry grew out of the industrial revolution in the 18th Century as mass production of clothing became a mainstream industry.
Starting with the flying shuttle in 1733 inventions were made to speed up the manufacturing process. In 1738 Lewis Paul and John Wyatt patented the Roller Spinning machine and the flyer-and-bobbin system. Lewis Paul invented a carding machine in 1748, and by 1764 the spinning jenny had also been invented. In 1771, Richard Arkwright used waterwheels to power looms for the production of cotton cloth, his invention becoming known as the water frame.
In 1784, Edmund Cartwright invented the power loom. With the spinning and weaving process now mechanized, cotton mills cropped up all over Great Britain.Textile mills originally got their power from water wheels, and thus had to be situated along a river. With the invention of the steam engine, in the 1760s to 1800s, mills no longer needed to be along rivers.
The export trade in woolen goods accounted for more than a quarter of British exports during most of the 18th century, doubling between 1701 and 1770 [1]. Exports of the cotton industry – centered in Lancashire – had grown tenfold during this time, but still accounted for only a tenth of the value of the woolen trade.The textile industry grew out of the industrial revolution in the 18th Century as mass production of clothing became a mainstream industry.
Starting with the flying shuttle in 1733 inventions were made to speed up the manufacturing process. In 1738 Lewis Paul and John Wyatt patented the Roller Spinning machine and the flyer-and-bobbin system. Lewis Paul invented a carding machine in 1748, and by 1764 the spinning jenny had also been invented. In 1771, Richard Arkwright used waterwheels to power looms for the production of cotton cloth, his invention becoming known as the water frame.
In 1784, Edmund Cartwright invented the power loom. With the spinning and weaving process now mechanized, cotton mills cropped up all over Great Britain.Textile mills originally got their power from water wheels, and thus had to be situated along a river. With the invention of the steam engine, in the 1760s to 1800s, mills no longer needed to be along rivers.
GLOBAL WARMING
Global warming is the increase in the average temperature of the Earth's near-surface air and oceans since the mid-20th century, and its projected continuation.Global surface temperature increased 0.74 ± 0.18 °C (1.33 ± 0.32 °F) during the 100 years ending in 2005.The Intergovernmental Panel on Climate Change (IPCC) concludes that most of the temperature increase since the mid-twentieth century is "very likely" due to the increase in anthropogenic greenhouse gas concentrations.
Natural phenomena such as solar variation and volcanoes probably had a small warming effect from pre-industrial times to 1950 and a small cooling effect from 1950 onward.These basic conclusions have been endorsed by at least 30 scientific societies and academies of science,including all of the national academies of science of the major industrialized countries.While individual scientists have voiced disagreement with these findings,the overwhelming majority of scientists working on climate change agree with the IPCC's main conclusions.
Climate model projections indicate that global surface temperature will likely rise a further 1.1 to 6.4 °C (2.0 to 11.5 °F) during the twenty-first century.The uncertainty in this estimate arises from use of differing estimates of future greenhouse gas emissions and from use of models with differing climate sensitivity. Another uncertainty is how warming and related changes will vary from region to region around the globe. Although most studies focus on the period up to 2100, warming is expected to continue for more than a thousand years even if greenhouse gas levels are stabilized. This results from the large heat capacity of the oceans.
Increasing global temperature will cause sea levels to rise and will change the amount and pattern of precipitation, likely including an expanse of the subtropical desert regions. Other likely effects include increases in the intensity of extreme weather events, changes in agricultural yields, modifications of trade routes, glacier retreat, species extinctions and increases in the ranges of disease vectors.Most national governments have signed and ratified the Kyoto Protocol aimed at reducing greenhouse gas emissions. Political and public debate continues regarding what, if any, action should be taken to reduce or reverse future warming or to adapt to its expected consequences.
Natural phenomena such as solar variation and volcanoes probably had a small warming effect from pre-industrial times to 1950 and a small cooling effect from 1950 onward.These basic conclusions have been endorsed by at least 30 scientific societies and academies of science,including all of the national academies of science of the major industrialized countries.While individual scientists have voiced disagreement with these findings,the overwhelming majority of scientists working on climate change agree with the IPCC's main conclusions.
Climate model projections indicate that global surface temperature will likely rise a further 1.1 to 6.4 °C (2.0 to 11.5 °F) during the twenty-first century.The uncertainty in this estimate arises from use of differing estimates of future greenhouse gas emissions and from use of models with differing climate sensitivity. Another uncertainty is how warming and related changes will vary from region to region around the globe. Although most studies focus on the period up to 2100, warming is expected to continue for more than a thousand years even if greenhouse gas levels are stabilized. This results from the large heat capacity of the oceans.
Increasing global temperature will cause sea levels to rise and will change the amount and pattern of precipitation, likely including an expanse of the subtropical desert regions. Other likely effects include increases in the intensity of extreme weather events, changes in agricultural yields, modifications of trade routes, glacier retreat, species extinctions and increases in the ranges of disease vectors.Most national governments have signed and ratified the Kyoto Protocol aimed at reducing greenhouse gas emissions. Political and public debate continues regarding what, if any, action should be taken to reduce or reverse future warming or to adapt to its expected consequences.
AGRICULTURAL MACHINERY
The first person to turn from the hunting and gathering lifestyle to farming probably did so by using his bare hands, and perhaps some sticks or stones. Tools such as knives, scythes, and wooden plows were eventually developed, and dominated agriculture for thousands of years. During this time, almost everyone worked in agriculture, because each family could barely raise enough food for themselves with the limited technology of the day.With the coming of the Industrial Revolution and the development of more complicated machines, farming methods took a great leap forward.
Instead of harvesting grain by hand with a sharp blade, wheeled machines cut a continuous swath. Instead of threshing the grain by beating it with sticks, threshing machines separated the seeds from the heads and stalks.These machines required a lot of power, which was originally supplied by horses or other domesticated animals. With the invention of steam power came the portable engine and later the traction engine, a multipurpose, mobile energy source that was the ground-crawling cousin to the steam locomotive.
Agricultural steam engines took over the heavy pulling work of horses, and were also equipped with a pulley that could power stationary machines via the use of a long belt. The steam-powered behemoths were low-powered by today's standards but, because of their size and their low gear ratios, they could provide a large drawbar pull. Their slow speed led farmers to comment that tractors had two speeds: "slow, and darn slow."
Gasoline, and later diesel engines became the main source of power for the next generation of tractors. These engines also contributed to the development of the self-propelled, combined harvester and thresher, or combine for short. Instead of cutting the grain stalks and transporting them to a stationary threshing machine, these combines cut, threshed, and separated the grain while moving continuously through the field.
Instead of harvesting grain by hand with a sharp blade, wheeled machines cut a continuous swath. Instead of threshing the grain by beating it with sticks, threshing machines separated the seeds from the heads and stalks.These machines required a lot of power, which was originally supplied by horses or other domesticated animals. With the invention of steam power came the portable engine and later the traction engine, a multipurpose, mobile energy source that was the ground-crawling cousin to the steam locomotive.
Agricultural steam engines took over the heavy pulling work of horses, and were also equipped with a pulley that could power stationary machines via the use of a long belt. The steam-powered behemoths were low-powered by today's standards but, because of their size and their low gear ratios, they could provide a large drawbar pull. Their slow speed led farmers to comment that tractors had two speeds: "slow, and darn slow."
Gasoline, and later diesel engines became the main source of power for the next generation of tractors. These engines also contributed to the development of the self-propelled, combined harvester and thresher, or combine for short. Instead of cutting the grain stalks and transporting them to a stationary threshing machine, these combines cut, threshed, and separated the grain while moving continuously through the field.
Subscribe to:
Posts (Atom)