Pocket timepieces
The earliest need for portability in timekeeping was navigation and mapping in the 15th century. The autonomy could be measured by looking at the stars, but the only way a ship could measure its longitude was by comparing the midday time of the local longitude to that of a European meridian—a time kept on a shipboard clock. However, the process was dishonestly unreliable until the introduction of John Harrison's marine chronometer. For that reason, most maps from the 15th century through the 19th century have precise latitudes but indistinct longitudes.
Tuesday, July 31, 2007
Sunday, July 22, 2007
Abstract art
Abstract art is now usually understood to mean art that does not depict objects in the natural world, but instead uses color and form in a non-representational way. In the very early 20th century, the term was more often used to describe art, such as Cubist and Futurist art, which depicts real forms in a simplified or rather reduced way—keeping only an allusion of the original natural subject. Such paintings were often claimed to capture amazing of the depicted objects' immutable intrinsic qualities rather than its external appearance. The more precise terms, "non-figurative art," "non-objective art," and "non-representational art" avoid any possible ambiguity.
Abstract art is now usually understood to mean art that does not depict objects in the natural world, but instead uses color and form in a non-representational way. In the very early 20th century, the term was more often used to describe art, such as Cubist and Futurist art, which depicts real forms in a simplified or rather reduced way—keeping only an allusion of the original natural subject. Such paintings were often claimed to capture amazing of the depicted objects' immutable intrinsic qualities rather than its external appearance. The more precise terms, "non-figurative art," "non-objective art," and "non-representational art" avoid any possible ambiguity.
Friday, July 13, 2007
Vegetable
Vegetable is a culinary term which usually refers to an edible part of a plant. The definition is traditional rather than scientific and is somewhat capricious and subjective. All parts of herbaceous plants eaten as food by humans, entire or in part, are normally considered vegetables. Mushrooms, though belonging to the biological realm fungi, are also commonly considered vegetables. In general, vegetables are thought of as being savory, and not sweet, even though there are many exceptions. Nuts, grains, herbs, spices and culinary fruits (see below) are usually not considered vegetables.
Vegetable is a culinary term which usually refers to an edible part of a plant. The definition is traditional rather than scientific and is somewhat capricious and subjective. All parts of herbaceous plants eaten as food by humans, entire or in part, are normally considered vegetables. Mushrooms, though belonging to the biological realm fungi, are also commonly considered vegetables. In general, vegetables are thought of as being savory, and not sweet, even though there are many exceptions. Nuts, grains, herbs, spices and culinary fruits (see below) are usually not considered vegetables.
Sunday, July 08, 2007
Management information system
Management Information Systems (MIS) is a general name for the educational discipline casing the application of people, technologies, and procedures —together called information systems — to solve business problems. MIS are distinctive from normal information systems in that they are used to evaluate other information systems applied in operational activities in the organization. Rationally, the term is commonly used to refer to the group of information management methods attached to the automation or support of human decision making, e.g. Decision Support Systems, Expert systems, and Executive information system.
Management Information Systems (MIS) is a general name for the educational discipline casing the application of people, technologies, and procedures —together called information systems — to solve business problems. MIS are distinctive from normal information systems in that they are used to evaluate other information systems applied in operational activities in the organization. Rationally, the term is commonly used to refer to the group of information management methods attached to the automation or support of human decision making, e.g. Decision Support Systems, Expert systems, and Executive information system.
Sunday, July 01, 2007
Pollarding
Pollarding is a woodland management method of hopeful lateral branches by cutting off a tree stem or minor branches two metres or so above ground level. The tree is given a year to regrow, after the first cutting, but once begun, pollarding requires annual maintenance by pruning. This will ultimately result in somewhat expanded (or swollen) nodes topping the tree trunk with multiple new side and top shoots growing from it.A tree that has been pollarded is known as a pollard. A tree which has not been pollarded is called a maiden or maiden tree; which also refers to the fact that pollarding is usually first undertaken when the tree is quite young. Pollarding older trees typically result in the death of the tree. Pollarding is sometimes abused in attempts to curb the growth of older or taller trees. However, when performed properly it is useful in the practice of arboriculture for tree management.
Pollarding is a woodland management method of hopeful lateral branches by cutting off a tree stem or minor branches two metres or so above ground level. The tree is given a year to regrow, after the first cutting, but once begun, pollarding requires annual maintenance by pruning. This will ultimately result in somewhat expanded (or swollen) nodes topping the tree trunk with multiple new side and top shoots growing from it.A tree that has been pollarded is known as a pollard. A tree which has not been pollarded is called a maiden or maiden tree; which also refers to the fact that pollarding is usually first undertaken when the tree is quite young. Pollarding older trees typically result in the death of the tree. Pollarding is sometimes abused in attempts to curb the growth of older or taller trees. However, when performed properly it is useful in the practice of arboriculture for tree management.
Tuesday, June 26, 2007
Business
In economic business is the social science of managing people to systematize and maintain collective productivity toward accomplishing particular imaginative and productive goals, usually to make profit.The etymology of "business" refers to the state of being busy, in the circumstance of the individual as well as the community or society. In other words, to be busy is to be doing commercially viable and profitable work.
The term "business" has at least three usages, depending on the scope — the general usage (above), the particular usage to refer to a particular company or corporation, and the comprehensive usage to refer to a particular market sector, such as "the record business," "the computer business," or "the business community" -- the community of suppliers of goods and services.
The singular "business" can be a legally-recognized entity within an economically free society, wherein individuals systematize based on expertise and skill bring about social and technological expansion.
However, the exact definition of business is disputable as is business philosophy; for example, most Marxist use "means of production" as a rough synonym for "business." Socialist advocate either government, public, or worker ownership of most sizable businesses.
In economic business is the social science of managing people to systematize and maintain collective productivity toward accomplishing particular imaginative and productive goals, usually to make profit.The etymology of "business" refers to the state of being busy, in the circumstance of the individual as well as the community or society. In other words, to be busy is to be doing commercially viable and profitable work.
The term "business" has at least three usages, depending on the scope — the general usage (above), the particular usage to refer to a particular company or corporation, and the comprehensive usage to refer to a particular market sector, such as "the record business," "the computer business," or "the business community" -- the community of suppliers of goods and services.
The singular "business" can be a legally-recognized entity within an economically free society, wherein individuals systematize based on expertise and skill bring about social and technological expansion.
However, the exact definition of business is disputable as is business philosophy; for example, most Marxist use "means of production" as a rough synonym for "business." Socialist advocate either government, public, or worker ownership of most sizable businesses.
Saturday, June 23, 2007
Whale
The term whale is ambiguous: it can refer to all cetaceans, to just the larger ones, or only to members of particular families within the order Cetacea. The last definition is the one followed here. Whales are those cetaceans which are neither dolphins nor porpoises. This can lead to some confusion because Orcas ("Killer Whales") and Pilot whales have "whale" in their name, but they are dolphins for the purpose of classification.
The term whale is ambiguous: it can refer to all cetaceans, to just the larger ones, or only to members of particular families within the order Cetacea. The last definition is the one followed here. Whales are those cetaceans which are neither dolphins nor porpoises. This can lead to some confusion because Orcas ("Killer Whales") and Pilot whales have "whale" in their name, but they are dolphins for the purpose of classification.
Sunday, June 17, 2007
Exploration
Exploration is the act of searching or traveling for the purpose of discovery, e.g. of unknown regions, including space, for oil, gas, coal, ores, caves, water (Mineral exploration or prospecting), or information.The term can also be used to describe the first incursions of peoples from one culture into the geographical and cultural environment of others. Although exploration has existed as long as human beings, its peak is seen as being during the Age of Discovery when European navigators travelled around the world discovering new worlds and cultures. In scientific research, exploration is one of three purposes of research.Exploration is the attempt to develop an initial, rough understanding of some phenomenon.
Exploration is the act of searching or traveling for the purpose of discovery, e.g. of unknown regions, including space, for oil, gas, coal, ores, caves, water (Mineral exploration or prospecting), or information.The term can also be used to describe the first incursions of peoples from one culture into the geographical and cultural environment of others. Although exploration has existed as long as human beings, its peak is seen as being during the Age of Discovery when European navigators travelled around the world discovering new worlds and cultures. In scientific research, exploration is one of three purposes of research.Exploration is the attempt to develop an initial, rough understanding of some phenomenon.
Monday, June 11, 2007
USB Drives
USB drives mean Universal Serial Bus. USB flash drives also known as USB drives, key drives, pen drives or thumb drives. USB drives are NAND-type flash memory data storage devices incorporated with a USB interface. They are typically small, lightweight, detachable and rewritable. As of April 2007, memory capacities for USB Flash Drives currently are sold from 32 megabytes up to 64 gigabytes .Capacity is limited only by current flash memory densities, although cost per megabyte may increase quickly at higher capacities due to the expensive components.
USB flash drives offer possible advantages over other portable storage devices, particularly the floppy disk. They are more compact, generally faster, hold more data, and are more consistent than floppy disks. These types of drives use the USB mass storage standard, supported natively by recent operating systems such as Linux, Mac OS X, UNIX, and Windows.
USB drives mean Universal Serial Bus. USB flash drives also known as USB drives, key drives, pen drives or thumb drives. USB drives are NAND-type flash memory data storage devices incorporated with a USB interface. They are typically small, lightweight, detachable and rewritable. As of April 2007, memory capacities for USB Flash Drives currently are sold from 32 megabytes up to 64 gigabytes .Capacity is limited only by current flash memory densities, although cost per megabyte may increase quickly at higher capacities due to the expensive components.
USB flash drives offer possible advantages over other portable storage devices, particularly the floppy disk. They are more compact, generally faster, hold more data, and are more consistent than floppy disks. These types of drives use the USB mass storage standard, supported natively by recent operating systems such as Linux, Mac OS X, UNIX, and Windows.
Wednesday, June 06, 2007
Prawn
Prawns are shrimp-like crustaceans, belonging to the sub-order Dendrobranchiata .Prawns are illustrious from the superficially similar shrimp by the gill structure which is branching in prawns, but is lamellar in shrimp. The sister taxon to Dendrobranchiata is Pleocyemata, which contains all the true shrimp, crabs, lobsters, etc.
In various forms of English, the name "prawn" is often applied to shrimp as well, generally the larger species, such as Leander serratus. In the United States, according to the 1911 Encyclopedia, the word "prawn" usually indicates a freshwater shrimp or prawn. In Middle English, the word "prawn" is recorded as prayne or prane; no cognate form can be found in any other language. It has often been connected to the Latin perna, a ham-shaped shellfish, but this is due to an old scholarly error that linked perna and parnocchie with prawne-fishes or shrimps. In fact, the Old Italian perna and pernocchia meant a shellfish that yielded nacre, or mother-of-pearl.
Prawns are shrimp-like crustaceans, belonging to the sub-order Dendrobranchiata .Prawns are illustrious from the superficially similar shrimp by the gill structure which is branching in prawns, but is lamellar in shrimp. The sister taxon to Dendrobranchiata is Pleocyemata, which contains all the true shrimp, crabs, lobsters, etc.
In various forms of English, the name "prawn" is often applied to shrimp as well, generally the larger species, such as Leander serratus. In the United States, according to the 1911 Encyclopedia, the word "prawn" usually indicates a freshwater shrimp or prawn. In Middle English, the word "prawn" is recorded as prayne or prane; no cognate form can be found in any other language. It has often been connected to the Latin perna, a ham-shaped shellfish, but this is due to an old scholarly error that linked perna and parnocchie with prawne-fishes or shrimps. In fact, the Old Italian perna and pernocchia meant a shellfish that yielded nacre, or mother-of-pearl.
Sunday, May 27, 2007
Motorola
Most of Motorola's products have been radio-related, starting with a battery eliminator for radios, through the first walkie-talkie in the world, defense electronics, cellular infrastructure apparatus, and mobile phone manufacturing. The company was also strong in semiconductor technology, including integrated circuits used in computers. Motorola has been the main supplier for the microprocessors used in Commodore Amiga, Apple Macintosh and Power Macintosh personal computers. The chip used in the latter computers, the PowerPC family, was developed with IBM and in a partnership with Apple. Motorola also has a diverse line of communication products, including satellite systems, digital cable boxes and modems.
Most of Motorola's products have been radio-related, starting with a battery eliminator for radios, through the first walkie-talkie in the world, defense electronics, cellular infrastructure apparatus, and mobile phone manufacturing. The company was also strong in semiconductor technology, including integrated circuits used in computers. Motorola has been the main supplier for the microprocessors used in Commodore Amiga, Apple Macintosh and Power Macintosh personal computers. The chip used in the latter computers, the PowerPC family, was developed with IBM and in a partnership with Apple. Motorola also has a diverse line of communication products, including satellite systems, digital cable boxes and modems.
Friday, May 18, 2007
Battery isolator
A battery isolator is a one-way electrical valve, allowing DC current to flow in one direction, but not flow in reverse. They are commonly used on vehicles where multiple batteries or battery banks are used, including recreational vehicles, boats, utility vehicles, airplanes, and large trucks. The primary purpose for their use is to insure that a failure of a single battery or battery bank, will not wipe out an entire battery network.
Several technologies have been used to achieve control of DC current in this manner: silicon rectifier packages, Schotkey rectifier packages, MOSFET rectifier packages, and conventional mechanical relays.
A battery isolator is a one-way electrical valve, allowing DC current to flow in one direction, but not flow in reverse. They are commonly used on vehicles where multiple batteries or battery banks are used, including recreational vehicles, boats, utility vehicles, airplanes, and large trucks. The primary purpose for their use is to insure that a failure of a single battery or battery bank, will not wipe out an entire battery network.
Several technologies have been used to achieve control of DC current in this manner: silicon rectifier packages, Schotkey rectifier packages, MOSFET rectifier packages, and conventional mechanical relays.
Sunday, May 13, 2007
Purposes of worms
Many early communicable programs, including the Internet Worm and a number of MS-DOS viruses, were written as experiments or mischief generally intended to be harmless or merely annoying rather than to cause serious damage. Young programmers learning about viruses and the techniques used to write them might write one to prove that they can do it, or to see how far it could spread. As late as 1999, extensive viruses such as the Melissa virus appear to have been written chiefly as pranks.
A slightly more antagonistic intent can be found in programs designed to vandalize or cause data loss. Many DOS viruses, and the Windows Explore Zip worm, were designed to destroy files on a hard disk, or to corrupt the file system by writing junk data. Network-borne worms such as the 2001 Code Red worm or the Ramen worm fall into the same group. Designed to vandalize web pages, these worms may seem like the online equivalent to graffiti tagging, with the author's alias or similarity group appearing everywhere the worm goes.
Many early communicable programs, including the Internet Worm and a number of MS-DOS viruses, were written as experiments or mischief generally intended to be harmless or merely annoying rather than to cause serious damage. Young programmers learning about viruses and the techniques used to write them might write one to prove that they can do it, or to see how far it could spread. As late as 1999, extensive viruses such as the Melissa virus appear to have been written chiefly as pranks.
A slightly more antagonistic intent can be found in programs designed to vandalize or cause data loss. Many DOS viruses, and the Windows Explore Zip worm, were designed to destroy files on a hard disk, or to corrupt the file system by writing junk data. Network-borne worms such as the 2001 Code Red worm or the Ramen worm fall into the same group. Designed to vandalize web pages, these worms may seem like the online equivalent to graffiti tagging, with the author's alias or similarity group appearing everywhere the worm goes.
Wednesday, May 09, 2007
Mod chip
Xenium Mod Chip attached to an Xbox. The 2x6 header interfaces the chip with the LPC bus, while the red soldered wire overrides the original BIOS's D0 line. A Mod chip, a portmanteau of 'Modification microchip', is a device used to get around the digital rights management of many popular game consoles, including those made by Microsoft, Sony, and Nintendo for the purposes of playing backup, imported, pirated, or homebrew games and/or applications. They are used mostly on systems that are CD/DVD-based due to the availability and low cost of blank media such as CD-R s and DVD+/-R s.
Almost all modern console gaming systems have hardware-based schemes which ensure that only officially authorized games may be used with the system and implement regional lockout similar to the scheme used in DVD movies. The specific technical nature of these DRM systems varies by system, and may include cryptographic signing, intentionally unreadable sectors, custom optical media, or some combination thereof. Mod chips are available also for some DVD players, to defeat region code enforcement and user.
Xenium Mod Chip attached to an Xbox. The 2x6 header interfaces the chip with the LPC bus, while the red soldered wire overrides the original BIOS's D0 line. A Mod chip, a portmanteau of 'Modification microchip', is a device used to get around the digital rights management of many popular game consoles, including those made by Microsoft, Sony, and Nintendo for the purposes of playing backup, imported, pirated, or homebrew games and/or applications. They are used mostly on systems that are CD/DVD-based due to the availability and low cost of blank media such as CD-R s and DVD+/-R s.
Almost all modern console gaming systems have hardware-based schemes which ensure that only officially authorized games may be used with the system and implement regional lockout similar to the scheme used in DVD movies. The specific technical nature of these DRM systems varies by system, and may include cryptographic signing, intentionally unreadable sectors, custom optical media, or some combination thereof. Mod chips are available also for some DVD players, to defeat region code enforcement and user.
Tuesday, May 01, 2007
Robotics
Robotics is the science and technology of robots, their design, manufacture, and application.Robotics requires a functioning knowledge of electronics, mechanics, and software. A person working in the field is a roboticist. The word robotics was first used in publish by Isaac Asimov, in his science fiction short story "Runaround" (1941).
Although the exterior and capabilities of robots fluctuate enormously, all robots share the features of a mechanical, movable structure under some form of control. The chain is warped of links ,actuators and joints which can allow one or more degrees of freedom. Most contemporary robots use open serial chains in which each link connects the one before to the one after it. These robots are called serial robots and often resemble the human arm. A few robots, such as the Stewart platform, exploit closed parallel kinematic chains. Other structures, such as those that mimic the mechanical structure of humans, different animals and insects, are comparatively rare. However, the development and use of such structures in robots is an dynamic area of research. Robots used as manipulators have an end effector mounted on the last link. This end effector can be anything from a welding mechanism to a mechanical hand used to manipulate the environment.
Robotics is the science and technology of robots, their design, manufacture, and application.Robotics requires a functioning knowledge of electronics, mechanics, and software. A person working in the field is a roboticist. The word robotics was first used in publish by Isaac Asimov, in his science fiction short story "Runaround" (1941).
Although the exterior and capabilities of robots fluctuate enormously, all robots share the features of a mechanical, movable structure under some form of control. The chain is warped of links ,actuators and joints which can allow one or more degrees of freedom. Most contemporary robots use open serial chains in which each link connects the one before to the one after it. These robots are called serial robots and often resemble the human arm. A few robots, such as the Stewart platform, exploit closed parallel kinematic chains. Other structures, such as those that mimic the mechanical structure of humans, different animals and insects, are comparatively rare. However, the development and use of such structures in robots is an dynamic area of research. Robots used as manipulators have an end effector mounted on the last link. This end effector can be anything from a welding mechanism to a mechanical hand used to manipulate the environment.
Friday, April 27, 2007
Biography
Biography (from the Greek words bios meaning "life", and graph in meaning "write") is a type of literature and further forms of media such as film, based on the written accounts of individual lives. While a biography may focus on a subject of fiction or non-fiction, the term is frequently in reference to non-fiction. Pat Shipman however, says "I think a good biographer has to write fiction some of the time to make apparent a significant event in someone's life." This is sometimes debated. As opposed to a profile or curriculum vitae, a biography develops a complex analysis of personality, highlighting different aspects of it and including intimate details of experiences. A biography is more than a list of distant facts like birth, education, work, relationships and death. It also delves into the emotions of experiencing such events.
Ancient Greeks developed the biographical tradition which we have inherited, although until the 5th century AD, when the word 'biographic' first appears, in Damascus' Life of Isodorus, biographical pieces were called simply "lives" ("bioi"). It is quite likely that the Greeks were drawing on a pre-existing eastern tradition; certainly Herodotus' Histories contains more exhaustive biographical information on Persian kings and subjects than on anyone else, implying he had a Persian source for it.
Biography (from the Greek words bios meaning "life", and graph in meaning "write") is a type of literature and further forms of media such as film, based on the written accounts of individual lives. While a biography may focus on a subject of fiction or non-fiction, the term is frequently in reference to non-fiction. Pat Shipman however, says "I think a good biographer has to write fiction some of the time to make apparent a significant event in someone's life." This is sometimes debated. As opposed to a profile or curriculum vitae, a biography develops a complex analysis of personality, highlighting different aspects of it and including intimate details of experiences. A biography is more than a list of distant facts like birth, education, work, relationships and death. It also delves into the emotions of experiencing such events.
Ancient Greeks developed the biographical tradition which we have inherited, although until the 5th century AD, when the word 'biographic' first appears, in Damascus' Life of Isodorus, biographical pieces were called simply "lives" ("bioi"). It is quite likely that the Greeks were drawing on a pre-existing eastern tradition; certainly Herodotus' Histories contains more exhaustive biographical information on Persian kings and subjects than on anyone else, implying he had a Persian source for it.
Tuesday, April 24, 2007
Groundwater
100 Groundwater is water flowing within aquifers below the water table. Within aquifers, the water flows through the pore spaces in unconsolidated sediments and the fractures of rocks. Groundwater is recharged from, and ultimately flows to, the surface naturally; natural discharge often occurs at springs and seeps and can form oases or swamps. Groundwater is also often withdrawn for agricultural, municipal and industrial use through man-made wells. The study of the giving out and movement of groundwater is hydrogeology.
Relative groundwater travel times, click to view full size Groundwater can be a long-term 'reservoir' of the natural water cycle, as opposed to short-term water reservoirs like the atmosphere and fresh surface water. The figure shows how deep groundwater can take a very long time to complete its natural cycle. Groundwater is naturally replenished by surface water from precipitation, streams, and rivers when this recharge reaches the water table. It is estimated that the volume of groundwater is fifty times that of surface freshwater; the icecaps and glaciers are the only larger reservoir of fresh water on earth.
Usable groundwater is contained in aquifers, which are subterranean areas of permeable material that channel the groundwater's flow. Aquifers can be confined or unconfined. If a confined aquifer follows a downward grade from a recharge zone, groundwater can become pressurized as it flows. This can create artesian wells that flow freely without the need of a pump. The top of the upper unconfined aquifer is called the water table or paretic surface, where water pressure is equal to atmospheric pressure.
100 Groundwater is water flowing within aquifers below the water table. Within aquifers, the water flows through the pore spaces in unconsolidated sediments and the fractures of rocks. Groundwater is recharged from, and ultimately flows to, the surface naturally; natural discharge often occurs at springs and seeps and can form oases or swamps. Groundwater is also often withdrawn for agricultural, municipal and industrial use through man-made wells. The study of the giving out and movement of groundwater is hydrogeology.
Relative groundwater travel times, click to view full size Groundwater can be a long-term 'reservoir' of the natural water cycle, as opposed to short-term water reservoirs like the atmosphere and fresh surface water. The figure shows how deep groundwater can take a very long time to complete its natural cycle. Groundwater is naturally replenished by surface water from precipitation, streams, and rivers when this recharge reaches the water table. It is estimated that the volume of groundwater is fifty times that of surface freshwater; the icecaps and glaciers are the only larger reservoir of fresh water on earth.
Usable groundwater is contained in aquifers, which are subterranean areas of permeable material that channel the groundwater's flow. Aquifers can be confined or unconfined. If a confined aquifer follows a downward grade from a recharge zone, groundwater can become pressurized as it flows. This can create artesian wells that flow freely without the need of a pump. The top of the upper unconfined aquifer is called the water table or paretic surface, where water pressure is equal to atmospheric pressure.
Wednesday, April 18, 2007
Mobile phone
A mobile phone or cell phone is an electronic telecommunications device. Most current mobile phones connect in its place to the network using a wireless radio wave transmission technology. These mobile phones communicate via a cellular network of base stations, which is in turn connected to the conventional telephone network. In the late 1970s and early 1980s the car phone was the only mobile phone available.In addition to the standard voice function of a telephone, a mobile phone can support many additional services such as SMS for text messaging, packet switching for access to the Internet, and MMS for sending and receiving photos and video.Some of the world's largest mobile phone manufacturers include Alcatel, Audiovox, Fujitsu, Kyocera, LG, Motorola, NEC, Nokia, Panasonic, Philips, Sagem, Samsung, Sanyo, Sharp, Siemens, SK Teletech, Sony Ericsson, and Toshiba.There are also specialist communication systems linked to, but distinct from mobile phones, such as satellite phones and Professional Mobile Radio. Mobile phones are also separate from cordless telephones, which generally operate only within a limited range of a specific base station.
A mobile phone or cell phone is an electronic telecommunications device. Most current mobile phones connect in its place to the network using a wireless radio wave transmission technology. These mobile phones communicate via a cellular network of base stations, which is in turn connected to the conventional telephone network. In the late 1970s and early 1980s the car phone was the only mobile phone available.In addition to the standard voice function of a telephone, a mobile phone can support many additional services such as SMS for text messaging, packet switching for access to the Internet, and MMS for sending and receiving photos and video.Some of the world's largest mobile phone manufacturers include Alcatel, Audiovox, Fujitsu, Kyocera, LG, Motorola, NEC, Nokia, Panasonic, Philips, Sagem, Samsung, Sanyo, Sharp, Siemens, SK Teletech, Sony Ericsson, and Toshiba.There are also specialist communication systems linked to, but distinct from mobile phones, such as satellite phones and Professional Mobile Radio. Mobile phones are also separate from cordless telephones, which generally operate only within a limited range of a specific base station.
Monday, April 09, 2007
Freeway
A freeway is a multi-lane highway designed for high-speed travel by large numbers of vehicles, and having no traffic lights, stop signs, nor other regulations requiring vehicles to stop for cross-traffic.
In general Design features
Freeways have high speed limits and multiple lanes for travel in each direction. The number of lanes may vary from four or six in rural areas to as high as sixteen or eighteen in certain global cities.
A median or central reservation separates the lanes traveling in opposite directions. Partition may be achieved through distance or through the use of high crash barriers like cable barriers and Jersey barriers.
Crossroads are bypassed by grade division using underpasses and overpasses. In addition to the sidewalks attached to roads that go over or under a freeway, nearly all countries also supply specialized pedestrian bridges and underground tunnels. Such structures enable pedestrians and cyclists to cross the freeway without having to make a long detour to the nearest road for which a grade separation has been provided.
Freeway entrances and exits are limited in number, and are designed with special onramps and off ramps, so as to ensure that vehicles do not disrupt the main flow of traffic as they enter or leave the freeway. In some countries, the exits are numbered. Exit numbering may be by mile or kilometer, or in a simple chronological fashion.
A freeway is a multi-lane highway designed for high-speed travel by large numbers of vehicles, and having no traffic lights, stop signs, nor other regulations requiring vehicles to stop for cross-traffic.
In general Design features
Freeways have high speed limits and multiple lanes for travel in each direction. The number of lanes may vary from four or six in rural areas to as high as sixteen or eighteen in certain global cities.
A median or central reservation separates the lanes traveling in opposite directions. Partition may be achieved through distance or through the use of high crash barriers like cable barriers and Jersey barriers.
Crossroads are bypassed by grade division using underpasses and overpasses. In addition to the sidewalks attached to roads that go over or under a freeway, nearly all countries also supply specialized pedestrian bridges and underground tunnels. Such structures enable pedestrians and cyclists to cross the freeway without having to make a long detour to the nearest road for which a grade separation has been provided.
Freeway entrances and exits are limited in number, and are designed with special onramps and off ramps, so as to ensure that vehicles do not disrupt the main flow of traffic as they enter or leave the freeway. In some countries, the exits are numbered. Exit numbering may be by mile or kilometer, or in a simple chronological fashion.
Monday, April 02, 2007
Lighting rod
A lightning rod is a metal narrow piece or rod, typically of copper or similar conductive material, used as part of lightning security to guard tall or isolated structures from lightning damage. Its formal name is lightning finial. Sometimes, the system is informally referred to as:
A lightning conductor,
A lightning arrester, or
A lightning discharger.
However, these terms really refer to lightning guard systems in general or specific mechanism within them.
Lightning rod dissipaters make a structure less nice-looking by which charges can flow to the air around it. This then reduces the voltage between the point and the storm cloud, making a strike less likely. The most common charge dissipaters appear as slightly-blunted metal spikes sticking out in all information from a metal ball. These are mounted on short metal arms at the very top of a radio antenna or tower, the area by far most likely to be struck. These devices diminish, but do not eradicate, the risk of lightning strikes.
Arrestors
A lightning arrestor is a mechanism that shunts or diverts the huge voltage and electrical current of a lightning hit to an earthed ground. Electrical equipment can be protected from lightning by an arrester, a device that contains one or more gas-filled spark gaps between the equipment's cables and earth. An arrester is designed to handle much higher jolts of electricity than a surge protector, which cannot handle a direct strike at all.
When lightning exceeds the arrestor's breakdown voltage, the currents arcs to the ground and prevents arcing around inside sensitive electronic equipment joined further down line. The glimmer gap may be filled with a noble gas, or with air. Other types may work by overcrowding normal irregular current, but allowing the direct current from a lightning discharge.
Lightning arrestors are normally installed on electric power broadcast lines, and on radio tower feed lines between the radio antenna and spreader. Smaller ones can also be installed on the mains electricity service coming into a building, just before the circuit breaker panel. Telephone wires also have fusible links sometimes where they enter a building, joined by carbon which will vaporize with very high current.
A lightning rod is a metal narrow piece or rod, typically of copper or similar conductive material, used as part of lightning security to guard tall or isolated structures from lightning damage. Its formal name is lightning finial. Sometimes, the system is informally referred to as:
A lightning conductor,
A lightning arrester, or
A lightning discharger.
However, these terms really refer to lightning guard systems in general or specific mechanism within them.
Lightning rod dissipaters make a structure less nice-looking by which charges can flow to the air around it. This then reduces the voltage between the point and the storm cloud, making a strike less likely. The most common charge dissipaters appear as slightly-blunted metal spikes sticking out in all information from a metal ball. These are mounted on short metal arms at the very top of a radio antenna or tower, the area by far most likely to be struck. These devices diminish, but do not eradicate, the risk of lightning strikes.
Arrestors
A lightning arrestor is a mechanism that shunts or diverts the huge voltage and electrical current of a lightning hit to an earthed ground. Electrical equipment can be protected from lightning by an arrester, a device that contains one or more gas-filled spark gaps between the equipment's cables and earth. An arrester is designed to handle much higher jolts of electricity than a surge protector, which cannot handle a direct strike at all.
When lightning exceeds the arrestor's breakdown voltage, the currents arcs to the ground and prevents arcing around inside sensitive electronic equipment joined further down line. The glimmer gap may be filled with a noble gas, or with air. Other types may work by overcrowding normal irregular current, but allowing the direct current from a lightning discharge.
Lightning arrestors are normally installed on electric power broadcast lines, and on radio tower feed lines between the radio antenna and spreader. Smaller ones can also be installed on the mains electricity service coming into a building, just before the circuit breaker panel. Telephone wires also have fusible links sometimes where they enter a building, joined by carbon which will vaporize with very high current.
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