2008年12月1日星期一

Ermine


The Ermine (Mustela erminea) is a small mammal of the family Mustelidae. It is also known as the stoat and the short-tailed weasel

Natural history
The Ermine can be found almost everywhere throughout the northern temperate, subarctic and Arctic regions, of Europe, Asia, and North America. In an unsuccessful attempt to control the rabbit population, it was introduced into New Zealand. Ermine are largely nocturnal or crepuscular but will sometimes come out during the day.

Physical description
The Ermine is a member of the family Mustelidae, which also includes other weasels, mink, otters, ferret, badgers, polecats, the wolverine, martens, the tayra, the fisher and in some taxonomical classifications skunks.
This is one of the most species-rich families in order Carnivora. The Ermine moves in a sinuous manner when pursuing its prey extremely quick over the ground considering its small size, and is also a strong swimmer that is able to colonize offshore islands. Although it inhabits northern latitudes, the Ermine is built long and thin, leading to an increased surface area-to-volume ratio and increased dissipation of heat from its body. The advantage of this shape is that it is one of the few species able to follow burrowing animals into their own homes. It partly compensates for this shape by having short legs, small ears, a fast metabolism and, in winter, thick fur. Ermines may grow up to 30 cm long, with males much larger than the females. In most areas it coexists with the weasel (Mustela nivalis, also known as the Least Weasel), the smallest member of order Carnivora. Where the weasel is absent the Ermine is smaller (~70 g).
The Ermine's coat is a rich medium brown with an off-white belly. In winter, the coat is thicker and in regions that experience an inch or more of snow for at least forty days of the year (such as in Armenia), the color changes to clean white. This white fur is known as "ermine", a term originating either from the Latin phrase "Armenius mūs" ("Armenian rat")or from a word common to the Germanic and Baltic languages, hence the scientific name. At this stage, where the animal is known as a "stoat", it may be referred to as ermine, or as being "in ermine". The winter Ermine has been used in art as a symbol of purity or virginity. The white fur was highly prized, and used in the robes of the Lord Chief Justice of England. Both the animal and the heraldic tincture are symbols of Brittany. The furs would be sewn together making a pattern of black dots. A version of this pattern is used in heraldry as ermine tincture.
In all seasons the Ermine has a black tip to its tail. The black tip probably serves as a decoy to predators, which would include almost any carnivore large enough to eat a Ermine (e.g. wolves, foxes, wolverines, and some birds of prey). This kind of coat is very similar to the coat of the long-tailed weasel (Mustela frenata), a related animal of about the same size which also moults into white in the northern part of its range, and it is easy to confuse these kinds of weasels. The North American name for the Ermine, the "Short-tailed weasel" arose because its tail length distinguishes it from the long-tailed weasel. In general it is found farther north. Both species can be distinguished from the weasel because the weasel lacks a black tip on its tail.

Geographical range
The Ermine is native to the area between the 40th parallel (north) and the beginning of the Arctic Circle, which encompasses most of northern Eurasia and North America.
They have been introduced to New Zealand and Australia to control a rabbit overpopulation but found an alternative source of food easier to catch thus leaving the rabbit problem unsolved. They were also brought to Terschelling Island to control water voles (Arvicola terrestris). Ermines can swim up to 1.5 kilometers across seawater and have already reached several New Zealand offshore islands unaided. Maud Island which is 900 meters offshore has been colonised multiple times in the past 20 years.[citation needed]

Diet
The Ermine is a carnivore. It eats insects, rabbits; rodents such as the mouse, vole and rat; other small mammals; birds and their eggs and young; and sometimes fish, reptiles, amphibians, and invertebrates. It is a very skillful tree climber and can descend a trunk headfirst, like a squirrel. The Ermine is capable of killing animals much larger than itself. When it is able to obtain more meat than it can eat it will engage in "surplus killing" and often stores the extra food for later. When this is the case, it will often kill by breaking the prey's neck without marking the body, presumably so its cache does not spoil easily.
There are several recorded instances of Ermines 'transfixing' rabbits by exhibiting a tumbling routine akin to a dance. Rabbits appear hypnotised by this activity and fail to notice the Ermine approach within striking distance. Once close enough, the rabbit falls easy prey to the Ermine.
Like other mustelids it typically dispatches its prey by biting into the base of the skull to get at the centers of the brain responsible for such important biological functions as breathing. Sometimes it will also make preliminary bites to other areas of the body. In most areas in which Ermines and least weasels co-exist, the weasel generally takes smaller prey and the Ermine slightly larger prey. The larger male Ermines generally take larger prey than females. Commonly, the Ermine falls prey to animals such as the wolf, fox, cat or badger.

Reproduction

Young Mustela erminea
The Ermine is territorial and intolerant of others in its range, especially others of the same sex. Within its range, it typically uses several dens, often taken from prey species. It usually travels alone, except when it is mating or is a mother with older offspring. It breeds once a year, producing several young kits (or kittens) per litter, and its mating system is promiscuous. Copulation occurs during the mating season with multiple partners and is often forced by the male, who does not help raise the offspring. Sometimes it occurs when the female is so young she has not even left the den. In spite of being such a small animal, the Ermine's gestation is among the longest reported for mammals (11 months) because of the adaptation of delayed implantation, or embryonic diapause, in which a fertilized egg is not implanted in the uterus until months later. The animal's "real" gestation is much shorter. This is presumably an adaptation to the highly seasonal environment in which the Ermine lives.

Lapis lazuli


Lapis lazuli (pronounced ) (sometimes abbreviated to lapis) is a semi-precious stone prized since antiquity for its intense blue color.
Lapis lazuli has been mined in the Badakhshan province of Afghanistan for 6,500 years, and trade in the stone is ancient enough for lapis jewelry to have been found at Predynastic Egyptian sites, and lapis beads at neolithic burials in Mehrgarh, the Caucasus, and even as far from Afghanistan as Mauritania.

Lapis lazuli is a rock, not a mineral: whereas a mineral has only one constituent, lapis lazuli is formed from more than one mineral.
The main component of lapis lazuli is lazurite (25% to 40%), a feldspathoid silicate mineral composed of sodium, aluminium, silicon, oxygen, sulfur, and chloride. Its formula is (Na,Ca)8(AlSiO4)6(S,SO4,Cl)1-2.Most lapis lazuli also contains calcite (white), sodalite (blue) and pyrite (metallic yellow). Other possible constituents are augite, diopside, enstatite, mica, hauynite, hornblende and nosean. Some contain trace amounts of the sulfur rich lollingite variety geyerite.
Lapis lazuli usually occurs in crystalline marble as a result of contact metamorphism.
The finest color is intense blue, lightly dusted with small flecks of golden pyrite. There should be no white calcite veins and the pyrite inclusions should be small. Stones that contain much calcite at all or too much pyrite are not as valuable. Patches of pyrite are an important help in identifying the stone as genuine and do not detract from its value. Often, inferior lapis is dyed to improve its color, but this is often a very dark blue with a noticeable grey cast, may also appear as a milky shade.

Lapis takes an excellent polish and can be made into jewelry, carvings, boxes, mosaics, ornaments and vases. In architecture it has been used for cladding the walls and columns of palaces and churches.
It was also ground and processed to make the pigment ultramarine for tempera paint and, more rarely, oil paint. Its usage as a pigment in oil paint ended in the early 19th century as a chemically identical synthetic variety, often called French Ultramarine, became available.

The best lapis lazuli is found in limestone in the Kokcha river valley of Badakhshan province in northeastern Afghanistan, and these deposits in the mines of Sar-e-Sang have been worked for more than 6,000 years. Badakhshan was the source of lapis for the ancient Egyptian and Mesopotamian civilizations, as well as the later Greek and Roman; during the height of the Indus valley civilization about 2000 B.C., the Harappan colony now known as Shortugai was established near the lapis mines.
More recently, during the 1980s conflict with the USSR, Afghanistan resistance fighters disassembled unexploded Soviet landmines and ordnance and used the scavenged explosive to help mine lapis to further fund their resistance efforts.[citation needed]
In addition to the Afghan deposits, lapis has been extracted for years in the Andes near Ovalle, Chile, where the deep blue stones compete in quality with those from Afghanistan. Other less important sources include the Lake Baikal region of Russia, Siberia, Angola, Burma, Pakistan, USA (California and Colorado), Canada and India.

In ancient Egypt lapis lazuli was a favorite stone for amulets and ornaments such as scarabs; it was also used by the Assyrians and Babylonians for seals. Lapis jewelry has been found at excavations of the Predynastic Egyptian site Naqada (3300–3100 BC), and powdered lapis was used as eyeshadow by Cleopatra.
As inscribed in the 140th chapter of the Egyptian Book of the Dead, lapis lazuli, in the shape of an eye set in gold, was considered an amulet of great power. On the last day of the month, an offering was made before this symbolic eye, for it was believed that, on that day, the supreme being placed such an image on his head.
The ancient royal Sumerian tombs of Ur, located near the Euphrates River in lower Iraq, contained more than 6000 beautifully executed lapis lazuli statuettes of birds, deer, and rodents as well as dishes, beads, and cylinder seals. These carved artifacts undoubtedly came from material mined in Badakhshan in northern Afghanistan. Much Sumerian and Akkadian poetry makes reference to lapis lazuli as a gem befitting royal splendor.
In ancient times, lapis lazuli was known as sapphire,which is the name that is used today for the blue corundum variety sapphire. It appears to have been the sapphire of ancient writers because Pliny refers to sapphirus as a stone sprinkled with specks of gold. A similar reference can be found in the Hebrew Bible in Job 28:6.
The Romans believed that lapis was a powerful aphrodisiac. In the Middle Ages, it was thought to keep the limbs healthy, and free the soul from error, envy and fear.
It was once believed that lapis had medicinal properties. It was ground down, mixed with milk and applied as a dressing for boils and ulcers.
Many of the blues in painting from medieval Illuminated manuscripts to Renaissance panels were derived from lapis lazuli. Ground to a powder and processed to remove impurities and isolate the component lazurite, it forms the pigment ultramarine. This clear, bright blue, which was one of the few available to painters before the 19th century, cost a princely sum. As tempera painting was superseded by the advent of oil paint in the Renaissance, painters found that the brilliance of ultramarine was greatly diminished when it was ground in oil and this, along with its cost, led to a steady decline in usage. Since the synthetic version of ultramarine was discovered in the 19th century (along with other 19th century blues, such as cobalt blue), production and use of the natural variety has almost ceased, though several pigment companies still produce it and some painters are still attracted to its brilliance and its romantic history.

[edit] Poetry/literature
Lapis lazuli is repeatedly mentioned in the Sumerian and Akkadian Epic of Gilgamesh. For instance, the Bull of Heaven's horns are composed of lapis lazuli. One version, at least, also suggests that the tale of Gilgamesh was recorded on a lapis lazuli tablet .
Lapis Lazuli is a poem written by William Butler Yeats. Text available at Readprint.com It is also mentioned in Yeats' poem Oil and Blood.
Lapis Lazuli is also mentioned in Robert Browning's The Bishop Orders His Tomb at Saint Praxed's Church as the egotistical Bishop wished to have the rarest stone available to him for his soon to be tomb, ironically contradicting a Bishop's vow of simplicity.
Lapis lazuli also makes an appearance in Marianne Moore's poem, "A Talisman" - which is quoted by T. S. Eliot in his "Introduction to Selected Poems [of Marianne Moore]." The stanza of Moore's poem reads: "Of lapis-lazuli,/A scarab of the sea,/With wings spread-". Eliot, in the next paragraph, raises the question: "I cannot see what a bird carved of lapis-lazuli should be doing with coral feet; but even here the cadence, the use of rhyme, and a certain authoritativeness of manner distinguish the poem."
In Lorna Crozier's poem "The Memorial Wall", "a young man who'd come from Montana to find his brother's name paints the side door lapis lazuli".
In D. H. Lawrence's novel Women in Love, a female character attempts to kill her lover after a quarrel by smashing his head with a lapis lazuli paperweight.
In Robert A. Heinlein's novel Time Enough for Love, the centuries old main character, Lazarus Long, names one of his two twin cloned daughters Lapis Lazuli.
David Foster Wallace's essay "A Supposedly Fun Thing I'll Never Do Again" makes repeated reference to what author Frank Conroy, in a brochure for Caribbean Cruise Lines, dubbed "the lapis lazuli dome of the sky." The more Wallace considers the phrase, the more disingenuous, inexpressive and manufactured it seems to him.
In Katherine Roberts' novel The Babylon Game (the second novel in the series The Seven Fabulous Wonders), the royal seal found by Tiamat in the Princess' Garden is made out of lapis lazuli - the material used for all royal seals.
In Emily Rodda's children's series Deltora Quest, the lapis lazuli, or "Heavenly Stone", is one of the seven lost gems of Deltora.
A lapis lazuli inlaid spittoon forms the central theme of a part of Salman Rushdie's Midnight's Children.
In Clive Cussler's "The Treasure of Khan," lapis lazuli is mentioned as the material for the paths surrounding Shang-tu, the summer home of Kublai Khan near Peking, China. (Page 41)
In The Vampire Diaries by L. J. Smith, vampires wear necklaces or rings that contain lapis lazuli, as protection against the sun.
In Unicorns of Balinor by Mary Stanton, The Scepter, the royal scepter of Balinor, that belongs to Arianna and is capable of speech and providing advice, has a shaft made of lapis lazuli.
In Raymond Chandler's hard boiled detective novels, Philip Marlowe would often describe the blue eyes of beautiful women as having the appearance of lapis lazuli.
In the song Moonshot by Britta Phillips and Dean Wareham, from the album L'Avventura, an angel is described: "his hair was light, his eyes were love, his words were true, his eyes were lapis lazuli."
Throughout the Septimus Heap series by Angie Sage, lapis lazuli is always associated with structures built by wizards.

semi precious bead


outdoor tv antennas


cooler ice pack


Plastic Hole Plugs


Car Heating Pad


Hand Woven Bag


Outdoor Weather Station


Battery Air Pump


cd manufacturing equipment


High Voltage Resistor


oak kitchen furniture


led display module


blue star sapphire


neon light tubes


grey iron castings


powder spray gun


4x4 mini trucks


boys athletic wear


Graphics LCD Module


cable tv converter


square plastic bottle


Solar Light Pole


handmade beaded necklaces


bulk wine glasses


headset microphone wireless


Powder Filling Machine


cosmetic brush case


fluorescent tube light


Coach Inc.


Coach Inc. is an American luxury leather goods company known for ladies' handbags, as well as items such as luggage, briefcases, wallets and other accessories (belts, shoes, scarves, umbrellas, sunglasses, key chains, etc.). Coach also offers watches and footwear.

History
Coach began as a family-owned business in a loft in Manhattan, New York in 1941 with American designer Bonnie Cashin. In 1960, Miles and Lillian Cahn, owners of a wholesale handbag manufacturing business, asked Cashin to become designer of a proposed retail collection. As Cashin was initially too busy with other design contracts, she did not become their designer until 1962.
In developing accessories for her style of contemporary dress, Cashin dramatically changed handbags with designs akin to modern sculpture, dyed in candy colors of pink, orange, yellow and blue, and lined with linens designed by textile designer Dorothy Liebes. With a greater variety of shapes, colors and textures in her "Cashin-Carry" designs, many featured wide openings or exterior coin purses and pockets. Coach Incorporated is now considered to be a very "fashion-forward" brand and is commonly sold and purchased throughout the country.
Cashin designed matching shoes, pens, key fobs and eyewear and added hardware to her clothes and accessories alike, particularly the silver toggle that became the Coach hallmark, declaring that she had been inspired by a memory of quickly fastening the top on her convertible sports car.and sports cars.

Collections

The company maintains a profit margin several times higher than competitor designer brands. With its longer production runs and lower-cost production facilities in developing countries such as China and the Dominican Republic, Coach is able to take better advantage of economies of scale than its higher-priced and less profitable counterparts.
There are currently 25 stores that carry full Coach collections, including women's footwear, men's bags and briefcases and now the women's ready to wear line and also the new jewelry line. Six are located in New York City and two in Honolulu. Other locations are in Nashville, Atlanta, Chicago, East Hampton, Greenwich, Houston, Boston, Los Angeles, New Orleans, Manhasset, Natick, Palo Alto, Philadelphia, Pittsburgh, San Diego, San Francisco, Scottsdale, Seattle, Troy, Washington, D.C., Edina, Minnesota, Bloomington, Minnesota, and The Westchester shopping mall. There is also an outlet of the popular store in Sandestin's Silver Sands. its awesome
Notably in Canada, there are now eight stores in Ontario with seven of the stores in the Toronto area, one at Yorkdale, Sherway Gardens, Square One, The Promenade Shopping Centre, Toronto Eaton Centre, Shops at Don Mills, and on Bloor Street in the prestigious and upscale Yorkville area, the eighth store is located in Ottawa at the Rideau Centre; two in Alberta, one at West Edmonton Mall in Edmonton, and the other in Southcentre Mall in Calgary; and four in British Columbia, one at Metropolis in Metrotown, Oakridge, Pacific Centre, and on Burrard Street in the heart of Vancouver's downtown and financial district.

Incandescent light bulb


The incandescent light bulb, incandescent lamp or incandescent light globe is a source of electric light that works by incandescence, (a general term for heat-driven light emissions which includes the simple case of black body radiation). An electric current passes through a thin filament, heating it until it produces light. The enclosing glass bulb prevents the oxygen in air from reaching the hot filament, which otherwise would be destroyed rapidly by oxidation. Incandescent bulbs are also sometimes called electric lamps, a term also applied to the original arc lamps.
Incandescent bulbs are made in a wide range of sizes and voltages, from 1.5 volts to about 300 volts. They require no external regulating equipment and have a low manufacturing cost, and work well on either alternating current or direct current. As a result the incandescent lamp is widely used in household and commercial lighting, for portable lighting, such as table lamps, some car headlamps and electric flashlights, and for decorative and advertising lighting.
Some applications of the incandescent bulb make use of the heat generated, such as incubators (for hatching eggs), brooding boxes for young poultry, heat lights for reptile tanks, infrared heating for industrial heating and drying processes, and the Easy-Bake Oven toy. In cold weather the heat shed by incandescent lamps contributes to building heating, but in hot climates lamp losses increase the energy used by air conditioning systems.
Incandescent light bulbs are gradually being replaced in many applications by (compact) fluorescent lamps, high-intensity discharge lamps, light-emitting diodes (LEDs), and other devices, which give more visible light for the same amount of electrical energy input. Some jurisdictions are attempting to ban the use of incandescent lightbulbs in favour of more energy-efficient lighting.

History of the light bulb

In addressing the question "Who invented the incandescent lamp?" historians Robert Friedel and Paul Israel list 22 inventors of incandescent lamps prior to Joseph Wilson Swan and Thomas Edison. They conclude that Edison's version was able to outstrip the others because of a combination of these factors: an effective incandescent material, a higher vacuum than others were able to achieve and a high resistance lamp that made power distribution from a centralized source economically viable.
Another historian, Thomas Hughes, has attributed Edison's success to the fact that he invented an entire, integrated system of electric lighting. "The lamp was a small component in his system of electric lighting, and no more critical to its effective functioning than the Edison Jumbo generator, the Edison main and feeder, and the parallel-distribution system. Other inventors with generators and incandescent lamps, and with comparable ingenuity and excellence, have long been forgotten because their creators did not preside over their introduction in a system of lighting."

Usta art

Usta art is a generic term used for the media of Naqqashi and Manoti art practiced by Usta artisans from the erstwhile Bikaner State in present-day Rajasthan, India. Naqqashi and Manoti is characterised by painting miniature translucent and opaque watercolour and oil based floral patterns on objects, camel leather, and architectural elements with gold. Naqqashi are items that are unembossed gold layers and Manoti are items that are embossed gold layers. The art of Naqqashi and Manoti flourished between the late-16th to mid-19th century in the Bikaner State. By the mid-20th Century Hisam-ud-din Usta was the only artisan remaining who understood the secrets to this proprietory Usta art. Hisam-ud-din Usta trained one member of his immediate family in the art of Naqqashi and Manoti, his grandson Jamil Usta, and a few other members of the Bikaner Usta community. Jamil Usta and a few other members of the Usta family presently still produce Naqqashi and Manoti art objects in Bikaner city.
Usta is a professional caste of artists, and the word Usta derives from the Persian word of استاد Ustad, meaning master or skilled person.
HISTORICAL BACKGROUND OF USTA ARTIn Bikaner city, the USTA ART has been founded to be in lime light and glorious heights since 16th-17th century. Originally the so called USTA ART, the Art of Golden Painting and embossing on the Camel Hides, was brought to India by Mughal Emperors. They also brought with them a sect of artist in this art from Iran. This art came to the Indian Courts of Emperors at the very initial state that may be called its prime youth. After this rare and historical art reached India, the honour and pride of bringing this art to Bikaner goes to Former Ruler His Highness Rai Singh of Bikaner who was a general in the Court of Emperor Akbar, and was contemporary of Jahangir. After being highly impressed by these arts he request express Akbar to allow some of the experts in this art to work in Bikaner. By accepting this request he fulfill Raja Rai Singh desire, Akbar sent seven Usta artists to work in the Court of Bikaner state. At that time the following were the main expert USTA Artists among those whose feet first touched the land of Bikaner (A group of seven Usta artists paintings can be seen even today in the rooms of the Junagarh fort, Bikaner) :-Ali Raja ji Usta, Shah Mohammad ji Usta, Loofa ji Usta, Nuruddin ji Usta, Ruknuddin ji Usta, Nathu ji Usta, Ahmed ji Usta.WHAT IS THE USTA ART Usta is a professional caste of artists, and the word Usta derives from the Persian word of استاد Ustad, meaning master or skilled person. The art is a generic term used for the media of Naqqashi and Manoti art practiced by Usta artisans from the erstwhile Bikaner State in present-day Rajasthan, India. Naqqashi and Manoti is characterised by painting miniature translucent and opaque watercolour and oil based floral patterns on objects, camel leather, and architectural elements with gold. Naqqashi are items that are unembossed gold layers and Manoti are items that are embossed gold layers. From metal and stone to camel hide, the art of Usta is done by the master craftsmen of Bikaner on walls, ceilings and pillars of forts and castles too.The major manifestations of Usta art in Bikaner can be seen in such places as Phool Mahal, Chandra Palace, Anoop Palace and Karan Palace. Being part of the famous Junagarh fort of Bikaner, all these places have become synonymous to the identity of Usta art. Also, Rampuria Havelis, the Mazaar of Amir Khushro, Nizamudin Oliya and Dargah Ajmer Sharif are some of the prominent locations where one can find the finest imprints of Usta art.Today Bikaner is regarded as one of the exclusive places of Rajasthan where the Usta art has become a part of its heritage due to the extraordinary efforts of people like these:Recipients of NATIONAL AWARD1. Hisamuddin Usta - 19672. Zahiruddin Usta - 19903. Muhammad Hanif Usta - 1991Recipients of STATE AWARD1. Zahiruddin Usta - 19842. Muhammad Asghar Usta - 19853. Muhammad Hanif Usta - 19884. Ajmal Hussain Usta - 1993

floral oil painting


rc gas engine


Counter Marble Top


in-dash lcd monitor


Decorative Glass Bottles


outdoor swing chairs


ir wireless headphone


wall mounted shelf


Fire Alarm Horn


Sodium Light Bulbs


emergency stop switches


Down Coats Winter


ecko long sleeve


cooling fan motor


HYDRAULIC QUICK COUPLING


Nylon Zipper Bag


iron on stud


christmas candle crafts


Stand Up Pouches


silicone rubber mold


gas heater valve


embroidered pillow case


big game lures

Ceramic engineering


Ceramic Engineering is the technology of manufacturing and usage of ceramic materials. Many engineering applications benefit from ceramics characteristics as a material. The characteristics of ceramics have garnered attention from engineers across the world, including those in the fields: Electrical Engineering, Materials Engineering, Chemical Engineering, Mechanical Engineering, and many others. Highly regarded for being resistant to heat, ceramics can be used for many demanding tasks that other materials like Metal and Polymers can not.
Traditional ceramic raw materials include clay minerals such as kaolinite, more recent materials include aluminium oxide, more commonly known as alumina. The modern ceramic materials, which are classified as advanced ceramics, include silicon carbide and tungsten carbide. Both are valued for their abrasion resistance, and hence find use in applications such as the wear plates of crushing equipment in mining operations. Advanced ceramics are also used in the medicine, electrical and electronics industries.
Ceramic Engineers are found in a wide variety of manufacturing, research and educational fields. These include mining, aerospace, medicine, refinery, food industry, chemical industry, packaging science, electronics, industrial electricity, and transmission electricity.

The Ceramic Process

A general definition of a ceramic material could be: A ceramic is any inorganic crystalline oxide material. It is solid and inert. Ceramic materials are brittle, hard, strong in compression, weak in shearing and tension. They withstand chemical erosion that occur in an acidic or caustic environment. In many cases withstanding erosion from the acid and bases applied to it. Ceramics generally can withstand very high temperatures such as temperatures that range from 1,000°C to 1,600°C (1,800°F to 3,000°F). Exceptions include inorganic materials that do not have oxygen such silicon carbide. Glass by definition is not a ceramic because it is an amorphous solid (non-crystalline). However, glass involves several steps of the ceramic process and its mechanical properties behave similarly to ceramic materials.
The ceramic process generally follows this flow.
Milling→ Batching→ Mixing→ Forming→ Drying→ Firing→ Assembly→
Milling is the process by which materials are reduced from a larger size to a smaller size. Milling may involve breaking up cemented material, thus the individual particle retain their shape or pulverization which involves grinding the particles themselves to a smaller size. Pulverization is actually fracturing the grains and breaking them down.
Generally milling is done through mechanical means. The means include attrition which is particle to particle collision that results in agglomerate break up or particle shearing. Compression which is applying compressive forces that result in break-up or fracturing. Another means is impact which involves a milling media -or the particles themselves- that cause break up or fracturing.
Examples of equipment that achieve attrition milling is a planetary mill or an wet attrition mill, also called wet scrubber. A wet scrubber is a machine that has paddles in water turning in opposite direction causing two vortexes turning into each other. The material in the vortex collide and break up.
Equipment that achieve compression milling include a jaw crusher, roller crusher, and cone crushers.
Finally impact mills may include a ball mill with media that tumble and fracture material. Shaft impactors cause particle to particle attrition and compression which achieve size reduction.
Batching is the process of weighing the oxides according to recipes, and preparing them for mixing and drying.
Mixing occurs after batching and involve a variety of equipment such as dry mixing ribbon mixers (a type of cement mixer), Mueller mixers, and pug mills. Wet mixing generally involve the same equipment.
Forming is making the mixed material into shapes, ranging from toilet bowls to spark plug insulators. Forming can involve: 1) Extrusion, such as extruding "slugs" to make bricks 2) Pressing to make shaped parts. 3) Slip casting, as in making toilet bowls, wash basins and ornamentals like ceramic statues. Forming produces a "green" part, ready for drying. Green parts are soft, pliable, and over time will lose shape. Handling the green product will change its shape. For example, a green brick can be "squeezed", and after squeezing it will stay that way.
Drying is removing the water or binder from the formed material. Spray drying is widely used to prepare powder for pressing operations. Other dryers are tunnel dryers and periodic dryers. Controlled heat is applied in this two-stage process. First, heat removes water. This step needs careful control, as rapid heating causes cracks and surface defects. The dried part is smaller than the green part, and is brittle, necessitating careful handling, since a small impact will cause crumbling and breaking.
Firing is where the dried parts pass through a controlled heating process, and the oxides are chemically changed to cause sintering and bonding. The fired part will be smaller than the dried part.
Assembly This process is for parts that require additional subassembly parts. In the case of a spark plug, the electrode is put into the insulator. This step does not apply to all ceramic products.

2008年11月20日星期四

Chessboard


A chessboard is the type of checkerboard used in the game of chess, and consists of 64 squares (eight rows and eight columns) arranged in two alternating colors (light and dark). The colors are called "black" and "white" (or "light" and "dark"), although the actual colors are usually dark green and buff for boards used in competition, and often natural shades of light and dark woods for home boards. Materials vary widely; while wooden boards are generally used in high-level games, vinyl and cardboard are common for low-level and informal play. Decorative glass and marble boards are available but not usually accepted for sanctioned games.
The board is structurally similar to that used in English draughts (American checkers), although the latter is usually in red and black. Some low-cost sets (especially those sold in toy stores) may use red and black squares and include pieces for both games; though suitable for informal play, such boards are often not accepted for sanctioned play, depending on the local authority's rules on equipment standards.
The board is always placed so that the rightmost square on the row nearest each player is a "white" square. The size of the board is usually chosen to be appropriate for the chess pieces used, and squares should be between 50mm and 65mm in size (2.0 to 2.5 inches). A square size approximately 1.25 to 1.3 times the size of the base of the king is preferred (the base of the king should be about 78 percent as wide as the size of the squares.)
In modern commentary, the columns (called files) are labeled by the letters a to h from left to right from the white player's point of view, and the rows (called ranks) by the numbers 1 to 8, with 1 being closest to the white player, thus providing a standard notation called algebraic chess notation.
In older English commentary, the files are labeled by the piece originally occupying its first rank (i.e. Queen, King's rook, Queen's bishop), and ranks by the numbers 1 to 8 from each player's point of view, depending on the move being described. This is called descriptive chess notation, and is no longer commonly used.