Discovery of graphite deposit
Some time before 1565 (some sources say as early as 1500), an enormous deposit of graphite was discovered on the approach to Grey Knotts from the hamlet of Seathwaite near Borrowdale parish, Cumbria, England.[1][2][3] The locals found that it was very useful for marking sheep. This particular deposit of graphite was extremely pure and solid, and it could easily be sawn into sticks. This remains the only large scale deposit of graphite ever found in this solid form.[4] Chemistry was in its infancy and the substance was thought to be a form of lead. Consequently, it was called plumbago (Latin for "lead ore").[5][6] The black core of pencils is still referred to as "lead," even though it never contained the element lead.
The value of graphite was soon realized to be enormous, mainly because it could be used to line the moulds for cannon balls, and the mines were taken over by the Crown and guarded. When sufficient stocks of graphite had been accumulated the mines were flooded to prevent theft until more was required. Graphite had to be smuggled out for use in pencils. Because graphite is soft, it requires some form of case. Graphite sticks were at first wrapped in string or in sheepskin for stability. The news of the usefulness of these early pencils spread far and wide, attracting the attention of artists all over the "known world".
Although deposits of graphite had been found in other parts of the world, they were not of the same purity and quality as the Borrowdale find, and had to be crushed to remove the impurities, leaving only graphite powder.[citation needed] England continued to enjoy a monopoly on the production of pencils until a method of reconstituting the graphite powder was found. The distinctively square English pencils continued to be made with sticks cut from natural graphite into the 1860s. Today, the town of Keswick, near the original findings of block graphite, has a pencil museum.[7] The first attempt to manufacture graphite sticks from powdered graphite was in Nuremberg, Germany, in 1662. It used a mixture of graphite, sulphur, and antimony.
Pencil "lead" is graphite (carbon) and not the chemical element lead. Residual graphite from a pencil stick is not poisonous, and graphite is harmless if consumed.[8]
Rabu, 11 Februari 2009
Telephone
A traditional landline telephone system, also known as "plain old telephone service" (POTS), commonly handles both signaling and audio information on the same twisted pair of insulated wires: the telephone line. Although originally designed for voice communication, the system has been adapted for data communication such as Telex, Fax and Internet communication. The signaling equipment consists of a bell, beeper, light or other device to alert the user to incoming calls, and number buttons or a rotary dial to enter a telephone number for outgoing calls. A twisted pair line is preferred as it is more effective at rejecting electromagnetic interference (EMI) and crosstalk than an untwisted pair.
A calling party wishing to speak to another party will pick up the telephone's handset, thus operating a button switch or "switchhook", which puts the telephone into an active state or "off hook" by connecting the transmitter (microphone), receiver (speaker) and related audio components to the line. This circuitry has a low resistance (less than 300 Ohms) which causes DC current (48 volts, nominal) from the telephone exchange to flow through the line. The exchange detects this DC current, attaches a digit receiver circuit to the line, and sends a dial tone to indicate readiness. On a modern telephone, the calling party then presses the number buttons in a sequence corresponding to the telephone number of the called party. The buttons are connected to a tone generator that produces DTMF tones which are sent to the exchange. A rotary dial telephone employs pulse dialing, sending electrical pulses corresponding to the telephone number to the exchange. (Most exchanges are still equipped to handle pulse dialing.) Provided the called party's line is not already active or "busy", the exchange sends an intermittent ringing signal (generally over 100 volts AC) to alert the called party to an incoming call. If the called party's line is active, the exchange sends a busy signal to the calling party. However, if the called party's line is active but has call waiting installed, the exchange sends an intermittent audible tone to the called party to indicate an incoming call.
When a landline phone is inactive or "on hook", its alerting device is connected across the line through a capacitor, which prevents DC current from flowing through the line. The circuitry at the telephone exchange detects the absence of DC current flow and thus that the phone is on hook with only the alerting device electrically connected to the line. When a party initiates a call to this line, the ringing signal transmitted by the telephone exchange activates the alerting device on the line. When the called party picks up the handset, the switchhook disconnects the alerting device and connects the audio circuitry to the line. The resulting low resistance now causes DC current to flow through this line, confirming that the called phone is now active. Both phones being active and connected through the exchange, the parties may now converse as long as both phones remain off hook. When a party "hangs up", placing the handset back on the cradle or hook, DC current ceases to flow in that line, signaling the exchange to disconnect the call.
A calling party wishing to speak to another party will pick up the telephone's handset, thus operating a button switch or "switchhook", which puts the telephone into an active state or "off hook" by connecting the transmitter (microphone), receiver (speaker) and related audio components to the line. This circuitry has a low resistance (less than 300 Ohms) which causes DC current (48 volts, nominal) from the telephone exchange to flow through the line. The exchange detects this DC current, attaches a digit receiver circuit to the line, and sends a dial tone to indicate readiness. On a modern telephone, the calling party then presses the number buttons in a sequence corresponding to the telephone number of the called party. The buttons are connected to a tone generator that produces DTMF tones which are sent to the exchange. A rotary dial telephone employs pulse dialing, sending electrical pulses corresponding to the telephone number to the exchange. (Most exchanges are still equipped to handle pulse dialing.) Provided the called party's line is not already active or "busy", the exchange sends an intermittent ringing signal (generally over 100 volts AC) to alert the called party to an incoming call. If the called party's line is active, the exchange sends a busy signal to the calling party. However, if the called party's line is active but has call waiting installed, the exchange sends an intermittent audible tone to the called party to indicate an incoming call.
When a landline phone is inactive or "on hook", its alerting device is connected across the line through a capacitor, which prevents DC current from flowing through the line. The circuitry at the telephone exchange detects the absence of DC current flow and thus that the phone is on hook with only the alerting device electrically connected to the line. When a party initiates a call to this line, the ringing signal transmitted by the telephone exchange activates the alerting device on the line. When the called party picks up the handset, the switchhook disconnects the alerting device and connects the audio circuitry to the line. The resulting low resistance now causes DC current to flow through this line, confirming that the called phone is now active. Both phones being active and connected through the exchange, the parties may now converse as long as both phones remain off hook. When a party "hangs up", placing the handset back on the cradle or hook, DC current ceases to flow in that line, signaling the exchange to disconnect the call.
Wire
In antiquity, jewellery often contains, in the form of chains and applied decoration, large amounts of wire that is accurately made and which must have been produced by some efficient, if not technically advanced, means. In some cases, strips cut from metal sheet were made by pulling them through perforations in stone beads. This causes the strips to fold round on themselves to form thin tubes. This strip drawing technique was in use in Egypt by the 2nd Dynasty. From the middle of the 2nd millennium BC most of the gold wires in jewellery are characterized by seam lines that follow a spiral path along the wire. Such twisted strips can be converted into solid round wires by rolling them between flat surfaces or the strip wire drawing method. Strip and block twist wire manufacturing methods were still in use in Europe in the 7th century AD, but by this time there seems to be some evidence of wires produced by true drawing.
Square and hexagonal wires were possibly made using a swaging technique. In this method a metal rod was struck between grooved metal blocks, or between a grooved punch and a grooved metal anvil. Swaging is of great antiquity, possibly dating to the beginning of the 2nd millennium BC in Egypt and in the Bronze and Iron Ages in Europe for torches and fibulae.
Twisted square section wires are a very common filigree decoration in early Etruscan jewellery.
In about the middle of the 2nd millennium BC a new category of decorative wires was introduced which imitated a line of granules. Perhaps the earliest such wire is the notched wire which first occurs from the late 3rd, early 2nd millennium BC in Anatolia and occasionally later.
Wire was drawn in England from the medieval period. The wire was used to make wool cards and pins, manufactured goods whose import was prohibited by Edward IV in 1463.[1] The first wire mill in Great Britain was established at Tintern in about 1568 by the founders of the Company of Mineral and Battery Works, who had a monopoly on this.[2] Apart from their second wire mill at nearby Whitebrook,[3] there were no other wire mills before the second half of the 17th century. Despite the existence of mills, the drawing of wire down to fine sizes continued to be done manually.
Square and hexagonal wires were possibly made using a swaging technique. In this method a metal rod was struck between grooved metal blocks, or between a grooved punch and a grooved metal anvil. Swaging is of great antiquity, possibly dating to the beginning of the 2nd millennium BC in Egypt and in the Bronze and Iron Ages in Europe for torches and fibulae.
Twisted square section wires are a very common filigree decoration in early Etruscan jewellery.
In about the middle of the 2nd millennium BC a new category of decorative wires was introduced which imitated a line of granules. Perhaps the earliest such wire is the notched wire which first occurs from the late 3rd, early 2nd millennium BC in Anatolia and occasionally later.
Wire was drawn in England from the medieval period. The wire was used to make wool cards and pins, manufactured goods whose import was prohibited by Edward IV in 1463.[1] The first wire mill in Great Britain was established at Tintern in about 1568 by the founders of the Company of Mineral and Battery Works, who had a monopoly on this.[2] Apart from their second wire mill at nearby Whitebrook,[3] there were no other wire mills before the second half of the 17th century. Despite the existence of mills, the drawing of wire down to fine sizes continued to be done manually.
Bible
Etymology
An American family Bible dating to 1859 A.D.
According to the Online Etymology Dictionary, the word bible[4] is from Latin biblia, traced from the same word through Medieval Latin and Late Latin, as used in the phrase biblia sacra ("holy book" - "In the Latin of the Middle Ages, the neuter plural for Biblia (gen. bibliorum) gradually came to be regarded as a feminine singular noun (biblia, gen. bibliae, in which singular form the word has passed into the languages of the Western world."[5]). This stemmed from the Greek term τὰ βιβλία τὰ ἅγια (ta biblia ta hagia), "the holy books", which derived from βιβλίον (biblion),[6] "paper" or "scroll," the ordinary word for "book", which was originally a diminutive of βύβλος (byblos, "Egyptian papyrus"), possibly so called from the name of the Phoenician port Byblos from whence Egyptian papyrus was exported to Greece.
Biblical scholar Mark Hamilton states that the Greek phrase Ta biblia ("the books") was "an expression Hellenistic Jews used to describe their sacred books several centuries before the time of Jesus,"[7] and would have referred to the Septuagint.[8] The Online Etymology Dictionary states, "The Christian scripture was referred to in Greek as Ta Biblia as early as c.223."
Tanakh
Main article: Tanakh
The Tanakh (Hebrew: תנ"ך) consists of 24 books. Tanakh is an acronym for the three parts of the Hebrew Bible: the Torah ("Teaching/Law" also known as the Pentateuch), Nevi'im ("Prophets"), and Ketuvim ("Writings," or Hagiographa), and is used commonly by Jews but unfamiliar to many English speakers and others (Alexander 1999, p. 17). (See Table of books of Judeo-Christian Scripture).
Torah
Main article: Torah
The Torah, or "Instruction," is also known as the "Five Books" of Moses, thus Chumash from Hebrew meaning "fivesome," and Pentateuch from Greek meaning "five scroll-cases."
The Torah comprises the following five books:
An American family Bible dating to 1859 A.D.
According to the Online Etymology Dictionary, the word bible[4] is from Latin biblia, traced from the same word through Medieval Latin and Late Latin, as used in the phrase biblia sacra ("holy book" - "In the Latin of the Middle Ages, the neuter plural for Biblia (gen. bibliorum) gradually came to be regarded as a feminine singular noun (biblia, gen. bibliae, in which singular form the word has passed into the languages of the Western world."[5]). This stemmed from the Greek term τὰ βιβλία τὰ ἅγια (ta biblia ta hagia), "the holy books", which derived from βιβλίον (biblion),[6] "paper" or "scroll," the ordinary word for "book", which was originally a diminutive of βύβλος (byblos, "Egyptian papyrus"), possibly so called from the name of the Phoenician port Byblos from whence Egyptian papyrus was exported to Greece.
Biblical scholar Mark Hamilton states that the Greek phrase Ta biblia ("the books") was "an expression Hellenistic Jews used to describe their sacred books several centuries before the time of Jesus,"[7] and would have referred to the Septuagint.[8] The Online Etymology Dictionary states, "The Christian scripture was referred to in Greek as Ta Biblia as early as c.223."
Tanakh
Main article: Tanakh
The Tanakh (Hebrew: תנ"ך) consists of 24 books. Tanakh is an acronym for the three parts of the Hebrew Bible: the Torah ("Teaching/Law" also known as the Pentateuch), Nevi'im ("Prophets"), and Ketuvim ("Writings," or Hagiographa), and is used commonly by Jews but unfamiliar to many English speakers and others (Alexander 1999, p. 17). (See Table of books of Judeo-Christian Scripture).
Torah
Main article: Torah
The Torah, or "Instruction," is also known as the "Five Books" of Moses, thus Chumash from Hebrew meaning "fivesome," and Pentateuch from Greek meaning "five scroll-cases."
The Torah comprises the following five books:
Book
Types of books according to their contents
Novels in a Polish bookstore
A common separation by content are fiction and non-fictional books. By no means are books limited to this classification, but it is a separation that can be found in most collections, libraries, and bookstores.
Fiction
Many of the books published today are fictitious stories. They are in-part or completely untrue or fantasy. Historically, paper production was expensive; too expensive to be used for entertainment. An increase in global literacy and print technology led to the increased publication of books for the purpose of entertainment, and allegorical social commentary. Most fiction is additionally categorized by genre.
The novel is the most common form of fictional book. Novels are stories that typically feature a plot, setting, themes and characters. Stories and narrative are not restricted to any topic; a novel can be whimsical, serious or controversial. The novel has had a tremendous impact on entertainment and publishing markets.[5]
Comic books or graphic novels are books in which the story is told, but not illustrated, with pictures.
A page from a dictionary
Non-fiction
An encyclopedia
In a library, a general type of non-fiction book which provides information as opposed to telling a story, essay, commentary, or otherwise supporting a point of view, is often referred to as a reference book. A very general reference book, usually one-volume, with lists of data and information on many topics is called an almanac. An encyclopedia is a book or set of books designed to have more in-depth articles on many topics. A book listing words, their etymology, meanings, etc. is called a dictionary. A book which is a collection of maps is an atlas. A more specific reference book with tables or lists of data and information about a certain topic, often intended for professional use, is often called a handbook. Books which try to list references and abstracts in a certain broad area may be called an index, such as Engineering Index, or abstracts such as Chemical Abstracts, Biological Abstracts, etc.
An atlas
Books with technical information on how to do something or how to use some equipment are called instruction manuals. Other popular how-to books include cookbooks and home improvement books.
Novels in a Polish bookstore
A common separation by content are fiction and non-fictional books. By no means are books limited to this classification, but it is a separation that can be found in most collections, libraries, and bookstores.
Fiction
Many of the books published today are fictitious stories. They are in-part or completely untrue or fantasy. Historically, paper production was expensive; too expensive to be used for entertainment. An increase in global literacy and print technology led to the increased publication of books for the purpose of entertainment, and allegorical social commentary. Most fiction is additionally categorized by genre.
The novel is the most common form of fictional book. Novels are stories that typically feature a plot, setting, themes and characters. Stories and narrative are not restricted to any topic; a novel can be whimsical, serious or controversial. The novel has had a tremendous impact on entertainment and publishing markets.[5]
Comic books or graphic novels are books in which the story is told, but not illustrated, with pictures.
A page from a dictionary
Non-fiction
An encyclopedia
In a library, a general type of non-fiction book which provides information as opposed to telling a story, essay, commentary, or otherwise supporting a point of view, is often referred to as a reference book. A very general reference book, usually one-volume, with lists of data and information on many topics is called an almanac. An encyclopedia is a book or set of books designed to have more in-depth articles on many topics. A book listing words, their etymology, meanings, etc. is called a dictionary. A book which is a collection of maps is an atlas. A more specific reference book with tables or lists of data and information about a certain topic, often intended for professional use, is often called a handbook. Books which try to list references and abstracts in a certain broad area may be called an index, such as Engineering Index, or abstracts such as Chemical Abstracts, Biological Abstracts, etc.
An atlas
Books with technical information on how to do something or how to use some equipment are called instruction manuals. Other popular how-to books include cookbooks and home improvement books.
Clock
History
Further information: History of timekeeping devices
Replica of an ancient Chinese incense clock
The clock is one of the oldest human inventions, meeting the need to consistently measure intervals of time shorter than the natural units, the day, the lunar month, and the year. Such measurement requires devices. Devices operating on several different physical processes have been used over the millennia, culminating in the clocks of today.
[edit] Sundials and other devices
The sundial, which measures the time of day by the direction of shadows cast by the sun, was widely used in ancient times. A well-designed sundial can measure local solar time with reasonable accuracy, and sundials continued to be used to monitor the performance of clocks until the modern era. However, it has practical limitations - it requires the sun to shine and does not work at all during the night - encouraged the use of other techniques for measuring time. In India, the King of Jaipur the Pink City, Jai Singh II constructed many instruments and sundials in the observatories in cities Jaipur, Varanasi, Ujjain, Mathura between 1724-1730 A.D. He had a good interest in astronomy and town planning.
Candle clocks and sticks of incense that burn down at approximately predictable speeds have also been used to estimate the passing of time. In an hourglass, fine sand pours through a tiny hole at a constant rate and indicates a predetermined passage of an arbitrary period of time.
[edit] Water clocks
Main article: Water clock
A scale model of Su Song's Astronomical Clock Tower, built in 11th century Kaifeng, China. It was driven by a large waterwheel, chain drive, and escapement mechanism.
Water clocks, also known as clepsydrae (sg: clepsydra), along with the sundials, are possibly the oldest time-measuring instruments, with the only exceptions being the vertical gnomon and the day-counting tally stick.[2] Given their great antiquity, where and when they first existed are not known and perhaps unknowable. The bowl-shaped outflow is the simplest form of a water clock and is known to have existed in Babylon and in Egypt around the 16th century BC. Other regions of the world, including India and China, also have early evidence of water clocks, but the earliest dates are less certain. Some authors, however, write about water clocks appearing as early as 4000 BC in these regions of the world.[3]
Further information: History of timekeeping devices
Replica of an ancient Chinese incense clock
The clock is one of the oldest human inventions, meeting the need to consistently measure intervals of time shorter than the natural units, the day, the lunar month, and the year. Such measurement requires devices. Devices operating on several different physical processes have been used over the millennia, culminating in the clocks of today.
[edit] Sundials and other devices
The sundial, which measures the time of day by the direction of shadows cast by the sun, was widely used in ancient times. A well-designed sundial can measure local solar time with reasonable accuracy, and sundials continued to be used to monitor the performance of clocks until the modern era. However, it has practical limitations - it requires the sun to shine and does not work at all during the night - encouraged the use of other techniques for measuring time. In India, the King of Jaipur the Pink City, Jai Singh II constructed many instruments and sundials in the observatories in cities Jaipur, Varanasi, Ujjain, Mathura between 1724-1730 A.D. He had a good interest in astronomy and town planning.
Candle clocks and sticks of incense that burn down at approximately predictable speeds have also been used to estimate the passing of time. In an hourglass, fine sand pours through a tiny hole at a constant rate and indicates a predetermined passage of an arbitrary period of time.
[edit] Water clocks
Main article: Water clock
A scale model of Su Song's Astronomical Clock Tower, built in 11th century Kaifeng, China. It was driven by a large waterwheel, chain drive, and escapement mechanism.
Water clocks, also known as clepsydrae (sg: clepsydra), along with the sundials, are possibly the oldest time-measuring instruments, with the only exceptions being the vertical gnomon and the day-counting tally stick.[2] Given their great antiquity, where and when they first existed are not known and perhaps unknowable. The bowl-shaped outflow is the simplest form of a water clock and is known to have existed in Babylon and in Egypt around the 16th century BC. Other regions of the world, including India and China, also have early evidence of water clocks, but the earliest dates are less certain. Some authors, however, write about water clocks appearing as early as 4000 BC in these regions of the world.[3]
Pants
Function
Undergarments are worn for a variety of reasons. They keep outer garments from being soiled by perspiration. Women's brassieres provide support for their breasts, and men's briefs serve the same function for the male genitalia; a corset is worn to mould the torso into a certain shape. For additional support and protection when playing sports, men often wear more tightly fitting underwear, including jockstraps and trunks. Women may wear sports bras which provide greater support, thus increasing comfort and reducing the chance of damage to the ligaments of the chest during high-impact exercises such as jogging.
In cold climates, undergarments are an additional layer of clothing that help the wearer to keep warm. Undergarments can be used to preserve the wearer's modesty – for instance, some women wear camisoles and slips (petticoats) under clothes that are sheer. Conversely, undergarments can also be worn for erotic effect. It is possible to purchase underwear made specifically for sexual titillation, such as edible underwear and crotchless panties.
Some items of clothing are designed as underwear, while others such as T-shirts and certain types of shorts are suitable both as undergarments and as outer clothing. The suitability of underwear as outer clothing is, apart from the indoor or outdoor climate, largely dependent on societal norms, fashion and the requirements of the law. If made of suitable material, some undergarments can serve as nightwear or swimsuits.
Religious functions
Two-piece-style Mormon temple garments
Undergarments can also have religious significance:
* Judaism. Male Orthodox Jews wear a four-cornered prayer shawl called a tallit katan, which has tzitzit (fringes) attached to the corners, draped over their shoulders. To conform with societal dress codes, a tallit katan is often worn beneath one's shirt, but above an undershirt as it should not come into contact with the skin.[1]
* Mormonism. Most members of the The Church of Jesus Christ of Latter-day Saints (Mormons) wear special temple garments after they have been endowed in a temple to help them remember the teachings of the temple.[2]
* Sikhism. One of the panj kakaar (five articles of faith) that Sikh men wear is a type of underpants called the kaccha, which are similar to boxer shorts.
Undergarments are worn for a variety of reasons. They keep outer garments from being soiled by perspiration. Women's brassieres provide support for their breasts, and men's briefs serve the same function for the male genitalia; a corset is worn to mould the torso into a certain shape. For additional support and protection when playing sports, men often wear more tightly fitting underwear, including jockstraps and trunks. Women may wear sports bras which provide greater support, thus increasing comfort and reducing the chance of damage to the ligaments of the chest during high-impact exercises such as jogging.
In cold climates, undergarments are an additional layer of clothing that help the wearer to keep warm. Undergarments can be used to preserve the wearer's modesty – for instance, some women wear camisoles and slips (petticoats) under clothes that are sheer. Conversely, undergarments can also be worn for erotic effect. It is possible to purchase underwear made specifically for sexual titillation, such as edible underwear and crotchless panties.
Some items of clothing are designed as underwear, while others such as T-shirts and certain types of shorts are suitable both as undergarments and as outer clothing. The suitability of underwear as outer clothing is, apart from the indoor or outdoor climate, largely dependent on societal norms, fashion and the requirements of the law. If made of suitable material, some undergarments can serve as nightwear or swimsuits.
Religious functions
Two-piece-style Mormon temple garments
Undergarments can also have religious significance:
* Judaism. Male Orthodox Jews wear a four-cornered prayer shawl called a tallit katan, which has tzitzit (fringes) attached to the corners, draped over their shoulders. To conform with societal dress codes, a tallit katan is often worn beneath one's shirt, but above an undershirt as it should not come into contact with the skin.[1]
* Mormonism. Most members of the The Church of Jesus Christ of Latter-day Saints (Mormons) wear special temple garments after they have been endowed in a temple to help them remember the teachings of the temple.[2]
* Sikhism. One of the panj kakaar (five articles of faith) that Sikh men wear is a type of underpants called the kaccha, which are similar to boxer shorts.
Cloth
Incans have been crafting quipus (or khipus) made of fibres either from a protein, such as spun and plied thread like wool or hair from camelids such as alpacas, llamas and camels or from a cellulose like cotton for thousands of years. Khipus are a series of knots along pieces of string. They have been believed to only have acted as a form of accounting, although new evidence conducted by Harvard professor, Gary Urton, indicates there may be more to the khipu than just numbers. Preservation of khipus found in museum and archive collections follow general textile preservation principles and practice.
[edit] Uses
Textiles have an assortment of uses, the most common of which are for clothing and containers such as bags and baskets. In the household, they are used in carpeting, upholstered furnishings, window shades, towels, covering for tables, beds, and other flat surfaces, and in art. In the workplace, they are used in industrial and scientific processes such as filtering. Miscellaneous uses include flags, backpacks, tents, nets, cleaning devices, such as handkerchiefs; transportation devices such as balloons, kites, sails, and parachutes; and strengthening in composite materials such as fibre glass and industrial geotextiles. Textiles can be used for educational purposes. Textiles can be used as a material for children to use and explore in their classrooms as another element of learning. Children can manipulate and come up with creative uses for textiles such as collage materials, art materials and so on.
Textiles used for industrial purposes, and chosen for characteristics other than their appearance, are commonly referred to as technical textiles. Technical textiles include textile structures for automotive applications, medical textiles (e.g. implants), geotextiles (reinforcement of embankments), agrotextiles (textiles for crop protection), protective clothing (e.g. against heat and radiation for fire fighter clothing, against molten metals for welders, stab protection, and bullet proof vests. In all these applications stringent performance requirements must be met. Woven of threads coated with zinc oxide nanowires, laboratory fabric has been shown capable of "self-powering nanosystems" using vibrations created by everyday actions like wind or body movements.[2][3]
[edit] Uses
Textiles have an assortment of uses, the most common of which are for clothing and containers such as bags and baskets. In the household, they are used in carpeting, upholstered furnishings, window shades, towels, covering for tables, beds, and other flat surfaces, and in art. In the workplace, they are used in industrial and scientific processes such as filtering. Miscellaneous uses include flags, backpacks, tents, nets, cleaning devices, such as handkerchiefs; transportation devices such as balloons, kites, sails, and parachutes; and strengthening in composite materials such as fibre glass and industrial geotextiles. Textiles can be used for educational purposes. Textiles can be used as a material for children to use and explore in their classrooms as another element of learning. Children can manipulate and come up with creative uses for textiles such as collage materials, art materials and so on.
Textiles used for industrial purposes, and chosen for characteristics other than their appearance, are commonly referred to as technical textiles. Technical textiles include textile structures for automotive applications, medical textiles (e.g. implants), geotextiles (reinforcement of embankments), agrotextiles (textiles for crop protection), protective clothing (e.g. against heat and radiation for fire fighter clothing, against molten metals for welders, stab protection, and bullet proof vests. In all these applications stringent performance requirements must be met. Woven of threads coated with zinc oxide nanowires, laboratory fabric has been shown capable of "self-powering nanosystems" using vibrations created by everyday actions like wind or body movements.[2][3]
Disc
When the accretion rate is sub-Eddington and the opacity very high, the standard thin accretion disc is formed. It is geometrically thin in the vertical direction (has a disc-like shape), and is made of a relatively cold gas, with a negligible radiation pressure. The gas goes down on very tight spirals, resembling almost circular, almost free (Keplerian) orbits. Thin discs are relatively luminous and they have thermal electromagnetic spectra, i.e. not much different from that of a sum of black bodies. Radiative cooling is very efficient in thin discs. The classic 1974 work by Shakura and Sunyaev on thin accretion discs is one of the most often quoted papers in modern astrophysics. Thin discs have been independently worked out by Lynden-Bell, Pringle and Rees. Pringle contributed in the past thirty years many key results to accretion disc theory, and wrote the classic 1981 review that for many years was the main source of information about accretion discs, and is still very useful today.
When the accretion rate is sub-Eddington and the opacity very low, an adaf is formed. This type of accretion disc was prophesied in 1977 by Ichimaru in a paper that was ignored almost by everybody for twenty years. (Some elements of the adaf model were present in the influential 1982 ion-tori paper by Rees, Phinney, Begelman and Blandford, however.)
Adafs started to be intensely studied by many authors only after their rediscovery in the mid 1990 by Narayan and Yi, and independently by Abramowicz, Chen, Kato, Lasota (who coined the name adaf), and Regev. Most important contributions to astrophysical applications of adafs have been made by Narayan and his collaborators. Adafs are cooled by advection (heat captured in matter) rather than by radiation. They are very radiatively inefficient, geometrically extended, similar in shape to a sphere (or a "corona") rather than a disc, and very hot (close to the virial temperature). Because of their low efficiency, adafs are much less luminous than the Shakura-Sunyaev thin discs. Adafs emit a power-law, non-thermal radiation, often with a strong Compton component.
When the accretion rate is sub-Eddington and the opacity very low, an adaf is formed. This type of accretion disc was prophesied in 1977 by Ichimaru in a paper that was ignored almost by everybody for twenty years. (Some elements of the adaf model were present in the influential 1982 ion-tori paper by Rees, Phinney, Begelman and Blandford, however.)
Adafs started to be intensely studied by many authors only after their rediscovery in the mid 1990 by Narayan and Yi, and independently by Abramowicz, Chen, Kato, Lasota (who coined the name adaf), and Regev. Most important contributions to astrophysical applications of adafs have been made by Narayan and his collaborators. Adafs are cooled by advection (heat captured in matter) rather than by radiation. They are very radiatively inefficient, geometrically extended, similar in shape to a sphere (or a "corona") rather than a disc, and very hot (close to the virial temperature). Because of their low efficiency, adafs are much less luminous than the Shakura-Sunyaev thin discs. Adafs emit a power-law, non-thermal radiation, often with a strong Compton component.
Bed
The Ancient World
Tutankhamun's gold-plated bed from the 14th century BC
Early beds were little more than piles of straw or some other natural materials. An important change was raising them off the ground, to avoid draughts, dirt, and pests. The Egyptians had high bedsteads which were ascended by steps, with bolsters or pillows, and curtains to hang round. The elite of Egyptian society such as its pharaohs and queens even had beds made of wood and gilded with gold. Often there was a head-rest as well, semi-cylindrical and made of stone, wood or metal. Assyrians, Medes and Persians had beds of a similar kind, and frequently decorated their furniture with inlays or appliqués of metal, mother-of-pearl and ivory.
The oldest account of a bed is probably that of Odysseus: a charpoy[1] woven of rope, plays a role in the Odyssey. A similar bed can be seen at the St Fagans National History Museum in Wales. Odysseus also gives an account of how he crafted the nuptial bed for himself and Penelope, out of an ancient, huge olive tree trunk that used to grow on the spot before the bridal chamber was built. His detailed description finally persuades the doubting Penelope that the shipwrecked, aged man is indeed her long-lost husband. Homer also mentions the inlaying of the woodwork of beds with gold, silver and ivory.The Greek bed had a wooden frame, with a board at the head and bands of hide laced across, upon which skins were placed. At a later period the bedstead was often veneered with expensive woods; sometimes it was of solid ivory veneered with tortoise-shell and with silver feet; often it was of bronze. The pillows and coverings also became more costly and beautiful; the most celebrated places for their manufacture were Miletus, Corinth and Carthage. Folding beds, too, appear in the vase paintings.
The Roman mattresses were stuffed with reeds, hay, wool or feathers; the last was used towards the end of the Republic, when custom demanded luxury. Small cushions were placed at the head and sometimes at the back. The bedsteads were high and could only be ascended by the help of steps. They were often arranged for two persons, and had a board or railing at the back as well as the raised portion at the head. The counterpanes were sometimes very costly, generally purple embroidered with figures in gold; and rich hangings fell to the ground masking the front. The bedsteads themselves were often of bronze inlaid with silver, and Elagabalus had one of solid silver. In the walls of some of the houses at Pompeii bed niches are found which were probably closed by curtains or sliding partitions. Ancient Romans had various kinds of beds for repose. These included:
Tutankhamun's gold-plated bed from the 14th century BC
Early beds were little more than piles of straw or some other natural materials. An important change was raising them off the ground, to avoid draughts, dirt, and pests. The Egyptians had high bedsteads which were ascended by steps, with bolsters or pillows, and curtains to hang round. The elite of Egyptian society such as its pharaohs and queens even had beds made of wood and gilded with gold. Often there was a head-rest as well, semi-cylindrical and made of stone, wood or metal. Assyrians, Medes and Persians had beds of a similar kind, and frequently decorated their furniture with inlays or appliqués of metal, mother-of-pearl and ivory.
The oldest account of a bed is probably that of Odysseus: a charpoy[1] woven of rope, plays a role in the Odyssey. A similar bed can be seen at the St Fagans National History Museum in Wales. Odysseus also gives an account of how he crafted the nuptial bed for himself and Penelope, out of an ancient, huge olive tree trunk that used to grow on the spot before the bridal chamber was built. His detailed description finally persuades the doubting Penelope that the shipwrecked, aged man is indeed her long-lost husband. Homer also mentions the inlaying of the woodwork of beds with gold, silver and ivory.The Greek bed had a wooden frame, with a board at the head and bands of hide laced across, upon which skins were placed. At a later period the bedstead was often veneered with expensive woods; sometimes it was of solid ivory veneered with tortoise-shell and with silver feet; often it was of bronze. The pillows and coverings also became more costly and beautiful; the most celebrated places for their manufacture were Miletus, Corinth and Carthage. Folding beds, too, appear in the vase paintings.
The Roman mattresses were stuffed with reeds, hay, wool or feathers; the last was used towards the end of the Republic, when custom demanded luxury. Small cushions were placed at the head and sometimes at the back. The bedsteads were high and could only be ascended by the help of steps. They were often arranged for two persons, and had a board or railing at the back as well as the raised portion at the head. The counterpanes were sometimes very costly, generally purple embroidered with figures in gold; and rich hangings fell to the ground masking the front. The bedsteads themselves were often of bronze inlaid with silver, and Elagabalus had one of solid silver. In the walls of some of the houses at Pompeii bed niches are found which were probably closed by curtains or sliding partitions. Ancient Romans had various kinds of beds for repose. These included:
Langganan:
Postingan (Atom)