Learning to build correctly,from a good set of plans is not rocket science. However there are some basic factors that make the whole system work well. Reading plans, is to some people, scary. As soon as they here the words plans, or blueprints they get the heebie- jeebies. Actually reading plans and blueprints is easy. The best way is to just jump in with both feet.
It is really interesting, more than anything else. These do it yourself shed plans should be classified as documents more than anything else. Usually created by draftsmen, architects, and engineers. These plans and blueprints are progressively laying out each aspect of the building process step by step.
First what scale are the plans in? More often than not I've found that the scale is in 1/8 th scale. I'm sure you under stand the concept of having to use scale. It would be awful hard to draw plans at full scale.
The first page would be the Index. This index will tell you which pages are in the set.The symbols, references and abbreviations are also explained here. Give them a good look. Go over the whole thing,then come back as need be go over the floor plans and get a general feel for the whole picture, don't worry you can come back and go over it several times.
Understanding the column lines is easy, just think of the column lines like the earths latitude and longitude. With that analogy it really starts to make sense. After a few times then it just becomes simple shed plans, or blueprints.
It wont take but a short time before you are an expert.This is something you can get a handle on, very quickly. This is one of those subjects, the more you use it the better you will become. It really Is easy. In only a few short minutes you too will become very comfortable with it.
So to sum it all up
1.Scale=
All building plans or construction plans and blueprints are drawn to scale. Knowing the scale can tell the contractor what dimensions to build any peticular item. At 1/4 scale every 1/4'' on the plan equals 1' in actual length,
2.Elevations=
Elevations are for exterior architectural styling. Elevation show roof pitches, exterior finishes, final grade of the lot or lots.and of course other details, depending on the complexity of the proposed project.
3.Electrical Layout=
There is a legend on the page explaining all the symbols and what they represent
4.Floor plan=
Floor plans are easy to understand. they will explain things such as,walls, fixtures,sinks,central air,water heaters, etc.
5.Mechanical and plumbing=
These blueprints and drawings and designs are for the plumbing or engineer specialist
6.Changing field
The design of blueprints and plans in these modern times is an ever changing scenario although basically things stay the same, with new technology comes new designs and regulations
About the Author
Tony Brazier has been involved in the construction business almost his whole life. I hope This was of interest to you,I know I enjoy helping anytime I can. Enjoys building all types of projects. Has a zest for life and loves all types of animals and wildlife. I have personally used "storage shed plans and blueprints". When I build animal, dog food, equipment housing and storage I use plans and blueprints from
The mobile elbow results from using the mobile for long hours. Called the 'cubital tunnel syndrome', it is also called cell phone elbow'. The problem occurs when the ulnar nerve, which runs across the elbow, down to the ring and little fingers, gets over-stretched and blood supply is restricted, sparked by holding a phone to the ear for long periods.
WHY DOES STEEL GLOW WHEN IT'S HOT?
Hot steel glows red when hot because its atoms vibrate with a lot of energy. The amount of energy varies in atoms re- sulting in a range of colours.
WHAT DOES JANUARY MEAN?
The original Roman calendar had 10 named months from March to December and two unnamed months during winter. These two months were named January and February by Numa Pompilius, the second king of Rome circa 700 BC. January is named after Janus, the Roman 'god of gates, doors and the beginnings'.
WHAT'S THE AAFBAU PRINCIPLE?
The physical and chemical properties of elements are determined by the atomic structure. This, in turn, is determined by electrons and the shells, sub-shells and orbitals they reside in. The rules of placing electrons within shells is known as the Aafbau principle, which originally means 'building up'.
WHAT IS CHAPTER 11 BANKRUPTCIES IN THE US?
A case filed under Chapter 11 bankruptcy protection is commonly referred to as a 'reorganization or restructuring bankruptcy'. Chapter 11 is a part of the US Bankruptcy Code under which an insolvent company is allowed to reorganize and is not liquidated. It is not shut down and sold off.
WHY DOES THE JASMINE BLOOM ONLY AT NIGHT?
Like all other flowering plants, jasmine also produces a flower inducing hormone in its leaves when exposed to bright sunlight. This hormone is called florigen (flower-generating hormone) and it migrates from the leaves to flowering shoots during the day. It accumulates in the flowering shoots of the jasmine plant and induces flowering during the night.
WHAT IS A ROMAN CIRCUS?
It was an open air stadium used for public events in the Roman empire, empire. The events usually held in such a circus were chariot and horse races and performances commemorating historical events. The performance space would be rectangular or oval surrounded by several tiers of seats for spectators. The circus would be decorated with ornate columns, obelisks and statues. The first circus built in Rome was the Circus Maximus which also happened to be its largest.
WHAT DOES THE PHRASE 'CHICKEN OUT' MEAN?
To chicken out is to stop doing something because of fear or lose courage while doing something. Sometimes, it is also used to ask a person, "Are you chicken?" or even as "Jack chickened out..." The chicken is a timid bird, which also gave rise to 'chicken-hearted'.
WHAT IS CONTACT SCRAPING?
Social networking has brought about a new trend called contact scraping, where an online company with access to a person's mail account goes through the contact list and sends out an invitation to all to join the site. Once a person enters his/her credentials, like user name or password, the company sweeps through the contact list. The company gets free publicity and widens its user base, but could put the person concerned in an embarrassing and annoying situation, especially when there are friendly mails from strangers in return.
HOW ARE DEEMED UNIVERSITIES DIFFERENT FROM OTHERS?
Ordinary universities are officially approved by the University Grants Commission (UGC) of India as per the latter's guidelines for the universities' overall supervision and administration. 'Deemed university' is a term indicative of status of autonomy granted to high performing institutes and departments of various universities. Such status enables deemed universities not only full autonomy in setting course work, syllabus and research centres, but also allows it to set it's own guidelines for admission, fee and instructions to students. Parent universities have no control over deemed universities in matters of overall administration.
WHY IS SEA WATER VERY HIGH IN SALT CONTENT?
The average salinity of sea water is about 3.5%. One cubic mile of sea water contains 166 million tonne of salt. The salts of the sea come from the breaking up of rocks and gradual wearing away of mountains releasing salts that are washed down by rainwater. It is estimated that more than 400 million tonne of dissolved salts are brought to the sea every year by 27,000 cubic km of water. The second source of salt is rocks beneath the ocean bed. There has been a constant slow addition of sea salinity due to evaporation from the ocean surface, combined by discharge from land.
WHAT IS A CHEMICAL BOND? HOW IS IT FORMED?
A chemical bond is one in which atoms of different or same elements combine to become stable. There are two types of chemical bonds —electro-valent bond and covalent bond. In an electrovalent bond, a metal donates an electron to a non-metal and forms the bond. Such bonds are very strong. A covalent bond is formed between non-metals only. These are easy to break.
IS RAIN WATER COMPLETELY PURE?
Rain water is considered the purest form of water. Impurities and salts present in water on earth are left behind during vaporisation by the sun. However, the rain water we receive on earth is not necessarily pure, as it brings down impurities and particles present in the atmosphere along with it.
WHAT IS 'THE MAGIC OF SCHEHERAZADE'?
The Magic of Scheherazade is a game for the Nintendo Entertainment System released by Culture Brain in 1989. It is the translation of the 1987 Famicom game Arabian Dream Scheherazade. The game was innovative for its time, incorporating elements of adventure and RPG styles.
WHAT IS FUNEMPLOYMENT?
'Funemployment' came into being with the recession, when people began losing jobs. It means unemployed individuals making use of the break to enjoy their free time — travel, take up physical activity and have a good time but at little cost. They may not have been able to do this earlier. The funemployed are young people who have few responsibilities and commitments and can afford a break. They also use the time to find another job, but don't spend time worrying about it.
WHAT IS MEDIAWIKI?
A wiki is a web application that allows users to create and edit web page content using a web browser. The term wiki also refers to the collaborative software used to create such a website. Mediawiki is a wiki software package licensed under the GNU General Public License, making it free and open source software. This Mediawiki software is used to run the popular web encyclopaedia Wikipedia, besides all projects of Wikimedia, wikis hosted by Wikia, and many other wikis.
WHY DON'T THE TEETH OF ANIMALS DECAY THOUGH THEY NEVER BRUSH THEIR TEETH?
According to WHO, decaying of teeth is a localized, post-eruptive pathologic external process, involving hard tooth tissue and formation of cavities. There is demineralization of teeth by acids produced in the oral environment, due to action of oral acidogenic bacteria on carbohydrates found in cooked food and drinks. Animals are either herbivorous or carnivorous or both, and survive on uncooked, raw food, rich in fibre, which needs a lot of chewing to digest, thereby cleansing the teeth naturally It is like brushing teeth and massaging gums the natural way But tooth decay is common in pets like dogs, which eat cooked food and junk food like biscuits etc.
WHICH IS THE BIGGEST STAR?
The biggest star found till date is Vy Canis Majoris, in the constellation of Canis Major. It is a red supergiant and one of the most luminous stars, 5,000 light years away from the earth with a radius of 1,800-2,100 times that of the sun. It is so large that its surface extends beyond the orbit of Saturn, were it placed in our solar system. Even light would take eight hours to complete its circumference. Though it is great, it is relatively cool, with a surface temperature of 3500 Kelvin.
WHICH IS THE WORLD'S SLEEPIEST ANIMAL?
The sleepiest animal, considered by the average number of hours of sleep a day is the koala, an arboreal animal with the scientific name Phascclarctos Cinerus, found only in Australia. Though it resembles a teddy bear, scientifically it is close to kangaroos, because it carries its young in a pouch. It lives mostly on eucalyptus trees, sleeping in the fork for 19-22 hours a day
WHAT IS THE GOLDEN ANGLE?
The golden angle separates the florets of a sunflower. Ills an approximation, since three golden arcs add up to slightly more than enough to make a circle. One of the old leaves overlaps and is pushed out in a radial line. This makes space in the inner system for a new leaf to form. New leaves move into the spaces opened as old leaves diverge.
WHO IS CALLED A DIGITAL NOMAD?
A person who works on the move is called a digital nomad. Such a worker may or may not be on the rolls of a company, and could he a consultant/freelancer/a writer on the move. They are persons with a free spirit who like a remote lifestyle and earn as they move, and believe that with discipline and the correct technology, they can be as productive as a person sitting in office. This is new tribe of people and for them, the economic downturn has brought little distress as companies turn to part-timers to save on costs.
WHAT IS A BLACK BLIZZARD?
During the drought of the 1930s in America, with no natural anchors in place, the soil dried, turned to dust and blew eastward and southward in large dark clouds. They blackened the sky and reached all the way to East Coast cities such as New York and Washington DC. Much of the soil ended up as deposits in the Atlantic Ocean, and were called 'Black Blizzards' and 'Black Rollers', and reduced visibility to a few feet. The Dust Bowl or Dirty Thirties —1930-36 and even up till 1940 — were caused by drought and decades of extensive farming without crop rotation.
WHY DO NEWSPAPERS PRINT A COMBINATION OF FOUR DOTS —BLUE, PINK, YELLOW, BLACK— AT THE BOTTOM OF EACH PAGE
The four dots — blue (cyan), pink (magenta), yellow and black are registration marks used during printing to help ensure the print is aligned properly In offset printing technology which newspapers use, the inked image is transferred from a plate to a rubber blanket, then to the printing surface. These primary colours go into printing a multi-coloured image and have separate plates. Each plate has its individual mark, like the colour dot.
ON WHAT BASIS ARE PINCODES DISTRIBUTED?
A Postal Index Number or PIN or Pincode is the post office numbering or postal code system used by India Post. It's sixdigits long, and was introduced on August 15,1972. There are nine PIN zones in India. The first digit of the PIN code indicates the region in which a given post office falls, the second digit the sub-region, the third the sorting district. The final three digits are assigned to individual post offices.
WHO FOUNDED YOUTUBE?
Chad Hurley, Steve Chen and Jawed Karim, all early employees of PayPal, founded YouTube. Hurley studied design at Indiana University of Pennsylvania, while Chen and Karim studied computer science together at the University of Illinois at UrbanaChampaign. It was founded on February 15,2005. In Sfovember 2006, YouTube, LLC, was bought by Google me. for $1.65 billion, and is now operated as a subsidiary of Google.
WHAT IS DERVISH MUSIC?
Dervish word originates from the Turkish word 'darvis', meaning poor or mendicant. Dervish music began among Muslim religious groups, known for their practice of energetic dancing, whirling, chanting or singing.
WHAT IS A BOOMBURB?
Aboomburb is a booming suburb or satellite townships dreamt up by developers. It gives an idea of wealth, a boom. Boomburg is a similar term. These suburbs are usually not complete towns — though they are self-sufficient.
HOW ARE ELECTRIC PYLONS PLACED ACROSS MOUNTAINS TO TRANSMIT ELECTRICITY?
Electric pylons are tall supports— made of galvanized steel lattice, steel tube or wood — used for power line construction. In normal terrain, they are assembled on the site. In mountainous regions, helicopters are used for power line construction, which are efficient but expensive. In the aerial construction method, the entire structure is pre-assembled and shifted in helicopters.
WHAT IS THE ORIGIN OF THE TERM 'CASH COW'?
Management guru Peter F Drucker coined the term in the mid-1960s to describe a business or product line with a large market share in a stagnant or declining market. It can yield profits reliably for some years without further investment and little maintenance. The term also has its origin in a matrix developed by Boston Consulting Group, in which enterprises have po sitions in either a growing or shrinking market, and either a growing or shrinking total market share.
WHAT ARE PERSEIDES?
The word Perseides is found in Greek mythology and refers to the descendants of Perseus — the name of a prolific meteor shower associated with the comet Swift-Tuttie. They are so called because they appear to come from the constellation Perseus. This shower is visible from midJuly each year, with peak activity between August 9 and 14, and is sometimes referred to as the "tears of St Lawrence", as August 10 is the saint's martyrdom.
WHAT ARE JACK-O-LANTERNS?
They are carved pumpkins with lights inside commonly seen on Halloween night. The top of the pumpkin is cut off, the inside flesh scooped out and a face carved on its surface. These are used partly for fun and partly believing that they represent the souls of departed elders who protect houses from evil spirits. Ac cording to an Irish folk tale, the soul of a dishonest farmer called Jack wanders the earth burning amber inside a vegetable. The Jack-o-lantern is supposed to have been named after him.
WHAT IS QUASI-RESONANCE?
A 'quasi-resonant' DC to DC converter with zero-current and zero-voltage switching includes a transformer with primary and secondary windings, and periodic switching means connected in series with the primary winding. The topology of the converter is determined by selecting an input capacitor with a capacitance much lower than the output capacitor.
WHO IS AN EXCEPTOR?
An exceptor is a person who chooses to eat meat on special occasions. A vegetarian by habit, the exceptor makes exceptions for days like weddings, festivals and celebrations. After the vegan,eggetarian and flexitarian, it is the exceptor who is basically vegetarian, but makes changes in diet to suit the occasion.
WHAT IS THIGMOTROPISM?
Thigmotropism is the growth of a plant around a support. Tropism is a phenomena by which a plant, usually climber like money plant and ivy, responds to a stimulus. Stems of the pea plant, for instance, are weak and have coil-like structures called tendrils. When tendrils approach a support (stick), a phytohormone called auxin is released in the side of the tendril away from the support. Auxin, a growth hormone, elongates the cells of that portion and makes it strong. The other portion, devoid of auxin, becomes weak and coils around the support.
WHY DO THE EYES OF SOME ANIMALS GLOW IN THE DARK?
Some animals have a special, reflective surface right behind their retinas, called the tapeturn lucidum, which helps animals see better in the dark. When light enters the eye, it hits a photoreceptor that transmits the information to the brain. But sometimes light doesn't hit the photoreceptor, so the tapetum lucidum acts as a mirror to bounce it back for a second chance.
WHY DON'T WE FEEL THE TONES OF ATMOSPHERIC PRESSURE?
Atmospheric pressure, which is about 1 kg per'sqcm of area, presses down on our body from all sides, but we don't feel it as it is balanced by fluid pressure from inside our body We can feel the difference during rainy season or when we go. to places where atmospheric pressure is less, like hill stations, where due to higher fluid pressure, blood oozes out in blood vessels, making the skin over those pink. The reverse happens under water.
WHY DO FOOD PACKAGES CARRY KCAL WHEN THEY ACTUALLY SPECIFY CALORIES AND NOT KILO-CALORIES?
Kilocalories are commonly known as calories and abbreviated as kcal. One calorie (Kcal) has the same energy value as 4.186 kilojpules-(kJ), while one kilojoule is equivalent to 0.24 calories. One calorie contains the amount of energy that raises the temperature of one litre of water by 1 degree Celsius.
WHAT IS SPIDER SILK?
Spider silk, also known as gossamer, is a protein fibre spun by spiders. Spiders use their silk to make webs. They can also suspend themselves using it. Many small spiders use silk threads for ballooning, the scientific term for the dynamic kiting spiderlings (mostly) used for dispersal. They extrude several threads into the air and let themselves get carried away with upward winds.
WHAT IS A SICK-OUT?
A sick-out is concerted action by a group of employees, who call in sick to protest against the company and its policies. It is meant to hold the company to ransom. In ordinary language, it is a strike to show the power they hold over the company's working. It is a slightly more devious method than taking to the streets openly and raising slogans. Employees hope to put pressure on the company and force it to meet their demands.
WHAT IS UNBREAKABLE GLASS MADE OF, AND IS IT REALLY UNBREAKABLE?
The presence of micro cracks on the glass surface (called Griffith's micro cracks) makes glass breakable under tension or impact. Such micro cracks are unavoidable as the glass surface comes under tension while cooling from a high temperature into various shapes. However, one can increase its impact resistance by various methods, so it can withstand even the impact of a bullet. The idea is to remove the surface micro cracks by chemical etching, or putting the glass surface under compression by physical or chemical toughening. One can even laminate two such toughened glass plates with resin in-between. These glasses are unbreakable, but when the threshold value is very high, it eventually breaks or cracks.
WHAT IS UNIVERSAL TIME COORDINATED?
Universal Time Coordinated (UTC) is a time standard based on International Atomic Time with leap seconds added at irregular intervals to compensate for the Earth's slowing rotation. A leap second is a positive or negative one-second adjustment to the UTC scale that keeps it close to Mean Solar Time at the Royal Observatory, Greenwich. The difference between UTC and Mean Solar Time is not allowed to exceed 0.9 seconds, so if high precision is not required, the general term Universal Time may be used. Time zones are expressed as positive or negative offsets from UTC. While each day contains 24 hours and each hour 60 minutes, the number of seconds in a minute can be 60,61 or 59.
HOW DO SENSOR DOORS WORK?
Sensor doors use motion sensors or presence sensors. The first are used to activate the door when it detects a moving object, such as a pedestrian or shopping cart. Motion sensors can distinguish between objects moving toward the door or away from it. They use microwave technology and utilize the Doppler Effect principle. The sensors emit a high frequency microwave signal — when the wave encounters a moving object, it bounces back and its frequency changes in proportion to the object's speed; Presence sensors detect both moving and non-moving objects in the path of the door. Presence sensors use infrared technology — they emit an invisible pulsed light signal. The receiver looks for the reflected signal and reacts.
WHAT IS WEISURE?
Weisure time is when work is done during leisure time. With the line between work and leisure blurring thanks to online work and smartphones, a new work-life culture has been created. Sociologist Dalton Conley coined this word, having observed that 9-5 jobs are giving way to this new lifestyle.
WHO DISCOVERED COMETS? HOW IS THE TAIL FORMED?
Comets have been known to mankind since eons, hence it cannot be said that comets were discovered by any single individual. A comet, like planets and asteroids, orbits around the sun — with fee orbital period varying from a few years to thousands of years. A comet is formed of rock, ice, dust and a few frozen gases like carbon dioxide, carbon monoxide and methane. When a comet is close to the sun, the radiation from the sun causes the volatile matter in the comet to vaporize and spread out into space in the form of its tail, its dust particles and ions glowing due to sunlight falling on it.
WHAT IS HAY FEVER AND WHY IS IT SO CALLED?
Hay fever is a form of allergy belonging to a group of maladies including hives, asthma and skin problems caused by protein sensitization.During certain seasons, many plants, grasses release their pollens into the air in large quantities. A person is said to have hay fever when he/she is sensitive to these pollens and other substances present in the air. It is called hay fever because the symptoms of the disease appear during spring and fall in England.
HOW IS THE HEIGHT OF WATER TIDES PREDICTED?
As astronomical data is not sufficient to calculate tides, predictions are also based on actual tidal measurements in many areas, over ah extended period. A network of tide stations is equipped to take the following measurements every six minutes: tide levels, wind speed and direction, water current speeds, directions, air and water temperatures and barometric pressure. Stations that provide these daily predictions are called reference stations. Other stations are subordinate stations, which obtain predictions by applying a specific formula to this data. The formula is derived by observing how tides at the two stations related to one another in the past.
HOW DO SOLAR CELLS CONVERT SUNLIGHT INTO ELECTRICITY?
Solar cells use photovoltaic cells to convert sunlight directly into electricity by converting photons (light particles) into electrons (negatively charged particles). Photovoltaic cells are made of semiconductors and silicon, mixed with other material.
WHAT IS THE ORIGIN OF THE WORD COCKTAIL?
The word cocktail was used in 1806 and is of American origin. Bartenders would drain the dregs of all the barrels and mix them together, serving the resultant muddle at a reduced price. Cock was another name for spigot, and tailings is the last bit of alcohol, so this drink was called cock-tailings, quickly shortened to "cocktail".
WHAT IS A CUSHION ACCOUNT?
It is an account a person sets aside which has no demands of monthly expenses on it, and is used as an emergency or luxury fund. A few business people set aside cushion funds to help their business grow, and for stability. The word 'cushion' is used as it gives a certain level of comfort to the person.
WHAT IS MAGIC SAND?
Magic sand is water-repellent sand available in blue, green and red colours. When this sand in powder form is sprinkled on water, it sinks and forms a solid substance. This property is used to separate oil floating in the oceans — it can be sprayed on oil spills to enable it to mix with oil and take solid form. It is also used by utility companies in Arctic areas as it never freezes.
IF LEAVES GET THEIR COLOUR FROM CHLOROPHYLL, WHAT GIVES FLOWERS THEIR COLOUR?
Plant cells have cell organelles known as plastids, which are colouring agents. There are three types of plastids — chloroplasts (contain green pigment chlorophyll), leucoplasts (white or colourless plastids) and chromoplasts (contain other pigments). All cells have varying proportions of these. Flowers have a majority of the third type and get their colours from these.
HOW IS A MOCKTAIL DIFFERENT FROM A COCKTAIL?
Cocktail is a style of mixed drinks, and usually contains one or more types of liquor and mixers, such as bitters, fruit juice or herbs. Mocktail is a non-alcoholic cocktail. Mocktail is also know as 'virgin cocktail'.
WHAT IS A MINSKIAN PONZI DEAL?
The Minskian Ponzi deal was a theory propounded by American economist Minsky, in 1986. Such deals are both unsustainable and hazardous. In Minsky's view, periods of economic and financial stability lead to a lowering of investors' risk aversion and a process of releveraging. Investors borrow excessively and push asset prices excessively high. In this process, there are three types of investors/borrowers. First, sound or hedge borrowers who can afford to pay on their own. Second, speculative borrowers who can only service interest payments out of their cash flows. Finally, there are Ponzi borrowers who can service neither interest nor principal payments, and need to keep on refinancing their debts.
WHAT DOES THE MONTH OF RAMZAN SIGNIFY?
Ramzan is the ninth month of the Islamic lunar calendar. Muslims fast for the entire month. They are obliged to abstain from all food, drink, tobacco and conjugal relations from dawn till sunset. The spiritual aspects include refraining from gossiping, lying, slandering and all such traits of bad character. The month of Ramzan is a time for spiritual reflection, prayer, recitation of the Quran, doing 'Zikr', endurance and selfdiscipline, to train the soul and body to be able to exercise self-restraint.
WHO IS A SEXER?
A sexer is a professional in a hatchery who can tell a male chick from a female. Also known as chick sexers, they are employed to separate the genders as hatcheries have different feeding programmes for them: females are reared to lay eggs and males are bred for their meat. Big hatcheries sex chickens as they have no use for male birds who are killed almost immediately. A sexer is trained to tell the chicks apart by their physical appearance and vents.
WHAT IS A SINKING FUND?
It is a fund set aside as a means to repay funds borrowed through a bond issue. The issuer makes periodic payments to a trustee who retires part of the issue by purchasing the bonds in the open market. Rather than the issuer repaying the entire principal of a bond issue on the maturity date, another company buys back a portion of the issue annually, and usually at fixed par value or at the current market value of the bonds, whichever is less. From the investor's point of view, a sinking fund adds safety to a corporate bond issue: with it, the issuing company is less likely to default on repayment.
WHY IS A SWINE FLU MASK CALLED N95?
Respirators or N95 masks can block 95% small particles that contain the H1N1 virus, which causes swine flu. These are expensive and can be used only for a single day. These masks are made of three layers of electrostaticallycharged microfibres, that block 95% particles, thus the name N95.
WHAT IS CLAYTRONICS?
Claytronics is an emerging field of engineering, drawing on nano technology and computer engineering. Claytronics or programmable matter refers to an assemblage of tiny components called claytronic atoms or catoms, which could assume the form of any object, depending on the programmes controlling the claytronics. This term also refers to the art of making clay caricatures of public figures, begun in 1996 by an Indian, Charuvi Agrawal.
WHAT DOES 'TROPICALIZED' ON A RADIO SET SIGNIFY?
Heat and humidity are the greatest enemies of any electrical equipment, so in tropical countries, such equipment is manufactured to withstand those climatic conditions. In a radio set, tropicalized means coating the electrical windings with resin, sealing the speaker hole with acoustically transparent cloth, installing" felt washers on the control knobs, and sealing openings for the antenna and earth connections.
WHAT IS A GRASS SKIRT?
A grass skirt, also called a hula skirt, is a traditional part of the dress worn by hula dancers on tropical islands. It is made of long blades of grass, most popularly seen on the island of Hawaii. Grass skirts are also worn in many cultures and tribes in Africa, like the Zulu tribals.
WHAT IS WHITE NOISE?
Noise that is produced by combining sounds of different frequencies together is called white noise. Since it contains all frequencies, white noise is used to mask other sounds. When two or three people talk, our brain can distinguish the sound of a particular person. But if a crowd cheers in a stadium, no individual voice can be identified. That's white noise and is most effectively used in the emergency siren.
WHAT IS INDUSTRIAL MELANISM?
It is caused when the natural environment of an organism is disturbed due to industrial pollution. As pollutants like soot and smoke darken the landscape, they disturb the environment of many organisms that rely on camouflage to avoid predation. This change makes them vulnerable to predators and creates a strong selective pressure due to which an organism with a darker colour is more likely to survive.
WHAT ARE BATHOLITHS?
Batholiths are enormous masses of igneous rock made up of once-molten material solidified below the earth's surface. These are usually made of granite and extend over thousands of miles. A well known batholith is located in the Sierra Nevada range of California, across 40,000 sqkm.
WHAT IS THE TATE?
The Tate is an art gallery originally titled the National Gallery of British Art. It is situated on Millbank in Pimlico, London. It was founded in 1897 by Henry Tafe with money earned from his sugar refineries. It was initially a collection of British art, concentrating on the works of Victorian painters. It later expanded to include foreign art and in the 20th century became principally a gallery devoted to Modernism. There are several other recently-opened Tate Galleries' in England, but the original gallery is now called Tate Britain.
WHO ARE STAGS IN THE STOCK MARKET?
An investor or speculator who subscribes to a new issue, expecting the price of the stock to rise immediately. upon the start of trading is known as a stag. The sole aim of a stag is to sell the shares soon after allotment to realize a quick profit.
WHAT IS A GREEN COLLAR JOB?
A green collar job involves working to better the environment, and is created by firms and organizations whose mission is to improve environmental quality. Work could include policies related to waste, energy and water conservation, solar energy, whole home performance and strengthening local food systems. These jobs are generated by sectors that produce goods which may need a green angle, like energy retrofits to improve conservation, constructing green buildings, composting, landscaping etc.
WHAT IS RASTAFARIANISM?
The Rastafarian movement originated in Jamaica in 1930s, based on the philosophies of Marcus Mosiah Garvey. Today, it has branched out, including groups that still hold Garvey's beliefs and groups that have disavowed his more controversial stances. His organization's aim was to unite black people (Negroes) with their rightful homeland, Africa. He prophesied about his people being redeemed by a future Black African king. This prediction was fulfilled in November 2, 1930, when Ras Tafari Makonnen was crowned King of Ethiopia.
WHAT ARE WIDGETS?
Widget, literally, is a blend of window and gadget, coined by George S Kaufman in his play 'Beggar on Horseback'. It is a hypothetical manufactured good or product. In computing, the term has become frequently used to refer to objects on a computer screen the user interacts with. A widget is anything that can be embedded within a HTML page. Widgets often take the form of on-screen tools like clocks, event countdowns etc.
WHY DON'T TWO-WHEELERS HAVE A REVERSE GEAR?
A regular motorcycle has a 'sequential' manual transmission, meaning you can only shift up or down one gear at a time. It is also designed to spin one way only. Adding reverse would require the crankshaft to spin backwards, or a much larger, heavier, expensive transmission. So it is easiest to dismount and push the bike backwards.
WHAT IS A DUM DUM BULLET?
It is an expanding bullet designed to grow on impact, increasing in diameter to limit penetration and/or produce a larger diameter wound. There are many expanding bullet designs though the most commonly encountered are hollow-point bullet and the soft-point bullet. Such bullets are Sometimes known as 'dum dum' bullets. After an early British example pro- duced in the Dum Dum arsenal, near Kolkata, India, there were several expanding bullets produced by this arsenal for the .303 British cartridge.
WHO ARE STILT FISHERMEN?
Stilt fishing is an old tradition practised by around 500 fishing families in Galle, in southwestern-most Sri Lanka. These fishermen usually fish at sunset, noon and sunrise, with each one taking an elevated position and balancing about 2 metres above the wa- ter. The stilts are dug into the coral and bed of the sea. Stilt fishing started after the Second World War.
WHAT ARE SIN STOCKS?
They are stocks of companies which manufacture or deal with cigarettes, alcohol, weapons and sex-related products. They could be directly involved in the business or associated with such activities. Such companies are also called sin businesses.
WHY DOES SNOW LOOK WHITE BUT WATER IS COLOURLESS?
Snow is a block of individual ice crystals arranged together. When a light photon enters a layer of snow, it goes through an ice crystal on the top, which changes its direction slightly and sends it on to a new ice crystal, which does the same thing. Basically, all the crystals bounce the light all around, so that it comes right back out of the snow pile. It does the same thing to all the different light frequencies, so all colours of light are bounced back out. The 'colour' of all the frequencies in the visible spectrum combined in equal measure is white, so this is the colour we see in snow.
WHAT IS THE FULL FORM OF AK-47 AND WHAT DOES 47 REFER TO?
AK-47 stands for Russian Avtomat Kalashnikova 1947 (Automatic Kalashnikov 1947). Designed by Russian Mikhail Kalashnikov, it was the assault rifle used by most Eastern Bloc countries during the Cold War. The rifle was adopted and standardized in 1947, thus the name.
HOW IS THE TIME DIFFERENCE BETWEEN TWO COUNTRIES CALCULATED?
The earth has 360 imaginary lines called longitudes or meridians running vertically between the poles. Each of these longitudes is called a degree. The 0 degree longitude passing through Greenwich, near London, is considered as standard and the time of all other time zones are calculated accordingly. The time difference between each longitude (each degree) is 4 minutes. So if it is 12 noon at Greenwich (0 degree), it would be 12:04 pm at 1 degree meridian and so on. In India, the standard meridian is 82-and-half degree. So the time difference between Greenwich and India is 82.5 x 4, which is 330 minutes (5 hours 30 minutes).
WHAT IS LAISSEZ FAIRE?
Laissez faire is a French phrase and means to let things pass. The term is used to describe an economic system where the government intervenes as little as possible and leaves the private sector to organize most economic activity through markets. Classical economists were great advocates of a laissez faire system.
WHAT IS THE FREIMARKT?
Freimarkt means free fair. It was first held on October 16, 1035, in Bremen, Germany. It is the biggest festival in Northern Germany, with more than four million visitors each year. It is celebrated for 17 days in the last two weeks of October. The area covers approximately 100,000 sqm on two areas: the 'Kleiner Freimarkt' (Small Free Fair) on the market square. It is famous for its beer tents and amusement rides. An annual highlight is the 'Freimarktsumzug' (Free Fair Procession).
HOW ARE ULTRA-VIOLET RAYS BLOCKED BY THE OZONE LAYER?
The ozone layer contains ozone molecules — 03 molecules — which are formed by the action of ultra-violet rays on atmospheric oxygen. This oxygen, which is 02, converts into 03 when UV rays fall on it. When these rays fall on the surface of the atmosphere, they are absorbed in the conversion of oxygen into ozone. As a result, ultra-violet rays are blocked by this ozone layer.
HOW IS THE TEMPERATURE OF A STAR MEASURED?
As stars are very far away, their temperatuce cannot be measured directly. Fortunately, the light coming from stars can be analyzed through several scientific instruments. Although all stars appear white, they have different colours when carefully viewed. The variations are a result of their temperature — cold stars appear red, and hot ones blue or white. The colour of a star is measured by an instrument called photoelectric photometer, which involves passing the light through different filters and finding the amount that passes through each filter. The measures from the photometer are converted to temperature, using standard scales.
WHICH IS THE WORLD'S LONGEST STORYBOOK?
Marcel Proust's A La Recherche Du Temps Perdu' (translated as In Search of Past) is the world's longest novel, according to the Guinness World Records. The influential 13-volume work contains 9,609,000 characters, with each letter and space counting as one character.
WHY DOES A FALLING OBJECT HAVE NO WEIGHT?
Every body on this earth is attracted by the gravitational pull of the earth. A freely falling object has weight W=mg, where W-weight, m-mass of the object and g-acceleration produced due to the earth's gravity An object kept in a lift which falls freely, weighs zero on the weighing machine, but its actual weight is still mg. This happens because the normal reaction force exerted on the object in the lift is equal to zero, and normal force equals to mg, which in turn equals the weight of the object.
WHAT IS THE REOG DANCE?
It is a spectacular dance with several dancers wearing bright, colourful costumes, accompanied by merry music. It is always held in open terrain, such as a square, street etc. This dance is a traditional art form combined with a magical show or trance dance. The Reog dates back to the Hindu period in East Java in Indonesia.
WHAT IS CROWD MINING?
Crowd mining is a new business concept where solutions can come from crowds, and marketers are turning to them as a database. The changing economy brought in this concept to tap expensive or even unavailable information and it goes beyond surveys and crowd sourcing.
WHAT IS OCTOBER HEAT?
The weather in the month of October in the Indian sub-continent is called 'October heat'. By the beginning of October, the monsoon withdraws from the northern plains. October and November form the period of transition from the hot rainy season to dry winter conditions.
WHAT IS AWACS?
AWACS stands for Airborne Warning And Control System that helps the Air Force detect incoming missiles and enemy aircraft from across the country's border. AWACS is described as an 'Eye in the Sky' as it can carry out surveillance at about 400-km range under all-weather situations, and to lock on to 60 targets at a time simultaneously.
WHAT IS THE SCHWARZSCHILD RADIUS?
It is a characteristic radius associated with every quantity of mass. This term is used in physics and astronomy, especially in the theory of gravitation and general relativity. m 1916, Karl Schwarzschild obtained an exact solution to Einstein's field equations for gravitational field outside a nonrating, spherically symmetric body. The solution contained a formula, where one of the values came to be known as Schwarzschild Radius.
WHO WERE THE IRON CHANCELLORS?
A hundred years ago, Germany was divided into many small states. In one of these states, Prussia, the chancellor or chief minister to the king, was Otto Von Bismarck. A strong and ruthless man, Bismarck built Prussia into the strongest of all German states. He got his nickname of 'The Iron Chancellor' when he said Germany could become a great power "through blood and iron".
HOW IS THE HEIGHT OF DIFFERENT PLACES ON EARTH MEASURED FROM THE SEA LEVEL?
The height of different places on earth is measured with the help of the 'altimeter'. It is basically a barometer without the mercury, and instead of instead of the pressure graduating in a barometer, the corresponding height graduates.
WHAT IS CRAB FOOTBALL?
Crab soccer (American English) or crab football (British English) is an informal sport for two teams. Unlike soccer, players support themselves on their hands and feet and face up, in motions that make them look like crabs, a method known as crab walking. This sport involves kicking, so safety is at the root of many rules. Like soccer, players other than the goalkeeper must not touch the ball with their hands.
HOW DOES A MOBILE VIBRATE?
There is a little motor fitted in a cell phone. This motor is unevenly weighted on its output shaft. When this motor rotates, the rotating uneven weight causes the mobile to vibrate.
WHAT IS TELEPRESENCE?
Telepresence is the next-gen videoconferencing technology, which provides superior images. The demand for telepresence solutions has grown, with companies seeing it as an alternative to send executives for meetings. It also reduces a company's carbon footprint by cutting down frequent flying. Setting up a telepresence suite can be very expensive, though.
HOW IS THE MASS OF HEAVENLY BODIES MEASURED?
The mass of a heavenly body can be measured by knowing the orbital period (time it takes to complete one orbit around the other body), the distance between two bodies and gravitational constant. The orbital time is inversely proportionate to the square root of the sum of the masses of two bodies and directly proportion distance raised to power three by two.
WHAT IS AN ELECTRON GUN?
It is a device in the back of a "cathode ray tube" television or computer monitor (pre-plasma or LCD flat-panel). The electron gun fires a stream of electrons from the back of the TV onto the inside face of the screen, which is coated with a material that glows when hit by electrons. By using powerful magnets to direct the stream across the screen, a series of dots ('pixels') is built over the screen which appears as an image.
WHO INVENTED THE SPEECH BUBBLE AND WHEN WAS IT FIRST USED?
One of the earliest antecedents to the modern speech bubble was the speech scroll — wispy lines that connected first person speech to the mouths of 'speakers in Meso-American art. In Western graphic art, labels that reveal what a figure is saying have appeared even in the 13th century Word balloons began appearing in 18th century printed broadsides and political cartoons from the American Revolution often used them.
WHY ARE CELLPHONES SWITCHED OFF WHILE FLYING?
Mobile phones are radio transmitters and as such, were banned from use in civilian airplanes, for fear they could interfere with airplane avionics. There was also concern that a cellular phone would cause disruption to the cell systems' towers, and distract passengers during take-off and landing.
WHAT IS A DIRTY BOMB?
A dirty bomb is a simple explosive device used not so much to produce extensive damage but to contaminate a designated spot with radioactive material. It's primary role is to spread fear.
WHAT IS THE PEKING OPERA?
The Peking Opera, which originated in the late 18th century, is a synthesis of music, dance, art and acrobatics. It is the most influential of all operas in China, and can be divided into 'civil' pieces characterized by singing, and 'martial' ones featuring acrobatics and stunts. Some operas are a combination of both. The operatic dialogues and monologues are recited in the Beijing dialect.
WHAT IS A PINK ELEPHANT?
The term 'pink elephant' is used to describe something obvious and uncomfortable, but which obody wants to talk about. At the workplace or in business communications, it is something that is buried under the carpet when things go wrong. It refers especially to a situation of unhealthy relationships between women colleagues — one woman may try to bully the other women out of rivalry to stay in control. Broaching such a topic may be embarrassing to all, so it is called a "pink elephant in the room".
WHY IS AN ATOM SPHERICAL IN SHAPE?
The shape of an atom refers to the shape of the imaginary volume in which its electrons orbit. Different electrons orbit at different levels. The shape of the atom depends on several factors, including the angular momentum of electrons. Only the simplest atoms have a spherical shape. Heavy atoms have a more complex shape.
WHAT IS INCOGNITO BROWSING?
It is used for browsing in stealth mode, for a situation when we don't want our history to be tracked. Web pages that are opened and files downloaded while browsing incognito are not logged in the browser.
WHAT IS MICRO-PROPAGATION?
Micro-propagation is the technique of multiple production of plants in-vitro. It is used for plants that do not produce seeds or respond to normal vegetable reproduction. Micro propagation's main advantage is to produce disease-free plants in multiple numbers and cloning of plants.
WHAT IS THE ROLE OF H2O2 IN THE GREY-HAIR PUZZLE?
New research shows that hair turns grey as a result of a chemical reaction that causes it to bleach itself inside out. When there is a dip in levels of an enzyme called catalase, hydrogen peroxide (H202) that naturally occurs in hair can't be broken down. As H202 builds up, the hair becomes grey.
WHO MADE THE FIRST ICE CREAM IN THE WORLD?
The origin of ice cream can be traced to the 4th century BC. Early references include Roman emperor Nero who ordered ice to be brought from the mountains and combined with fruit toppings, and King Tang (AD 618-97) of Shang, China, who had a method of creating ice and milk concoctions. Ice cream was brought from China back to Europe.
WHAT IS 'SMART ANTENNA' TECHNOLOGY?
This is a new technology in the field of wireless and mobile communications in which capacity and performance are usually limited by two major impairments — multipath and co-channel interference. A smart antenna enables a higher capacity by reducing multipath and co-channel interference. This is achieved by focusing the radiation in the desired direction and adjusting to changing traffic conditions.
WHAT IS THE GOLLIWOG ACT?
The golliwog act is a flexible contortion of the body in a dance form to create an impression that the contortionist is a doll. The name is taken from a literary character created by Florence Kate in her novel The Adventures of two Dutch Dolls and a Golliwog'.
WHAT IS A 'CASH AND CARRY STORE' AND WHY IS IT SO CALLED?
A cash and carry store is different from regular retail chains which target professional customers rather than end-consumers. This concept is based around self-service and bulk buying arid serves registered customers only. The core customer groups are hotels, caterers, traders and other business professionals. Such stores aim to prevent any intervention by middlemen and requires buyers to make their own arrangements and assume all risk.
HOW DOES HAIR GEL WORK?
The main ingredient in hair gels is a plastic called PVP, which is a polymer sealer. The polymers in PVP are dissolved in water or alcohol and form a clear film between each hair strand, attaching them to one another. Chemical experts call this "capillary power" because it's similar to how blood capillaries work. When gel is applied to wet hair, the PVP or similar ingredient absorbs water quickly. When the gel dries completely, it forms a fixed connection between hair strands.
WHAT IS A WORMHOLE?
A wormhole is a theoretical entity allowed by Einstein's theory of general relativity in which spacetime curvature connects two distant locations (or times). The term 'wormhole' was coined by American theoretical physicist John A Wheeler in 1957, based on an analogy of how a worm could chew a hole from one end of an apple through the centre to the other, thus creating a shortcut through the intervening space.
WHAT DOES MIRROR IMAGE MEAN IN BIOLOGICAL TERMINOLOGY?
Mirror image is a concept from chemistry applied to organic materials. An example of this is glucose arid fructose. These molecules are mirror images of each other. Although it is possible to flip glucose and superimpose it over a fructose molecule, only in 2D (flat viewing) are they similar.
WHAT IS A 3-D FILM?
A 3-D film is any visual presentation system that attempts to maintain or recreate moving images of the third dimension, the illusion of depth as seen by the viewer. It involves filming two images simultaneously, with two cameras, filming at 90 degree angle via mirrors. When viewed in such a way that each eye sees its photographed counterpart, the viewer's visual cortex will interpret the pair of images as a single three-dimensional image. Modern computer technology also allows for the production of pseudo-SD films using CGI and without the need for dual cameras.
WHAT IS SWEETHEARTING?
Sweet hearting is a method cashiers use to pass on goods to friends by failing to bill one. They do so by passing two items, and obscuring the barcode of one, so it goes unnoticed. Now, there are machines to pick out sweet hearting.
WHAT ARE MANGO SHOWERS?
Mango showers are those experienced prior to the arrival of the monsoon. These showers arrive generally in late April and May and are said to aid in the ripening of mangoes and from dropping prematurely from trees.
WHAT IS TERMINATOR GENE TECHNOLOGY?
The terminator gene is a specific genetic sequence inserted by scientists into a seed's DNA that renders the seed and the crop it produces sterile. Patented by the USDA and Delta and Pine Land Co., now owned by Monsanto, this terminator technology has no agricultural or economic benefits for farmers or consumers.
WHY IS THE FLAME OF A CANDLE POINTED?
The flame of a candle is produced when the wax of the candle melts due to heat and the molten wax rises in the wick. As the heated gas rises above from the base of the flame, it moves faster as the pressure decreases from the base to the top. As the rate at which the gas is released from the base is more or less constant, the flame becomes thinner and thinner from its base to the end, assuming a pointed tip.
HOW DID THE ABBREVIATION DR FOR DOCTORS ORIGINATE, AND WHY DO ENGINEERS NOT USE ER?
The abbreviation originated to separate people qualified to practice medicine from those holding the highest academic degree i.e. doctorate in nonmedical subjects. In USA, only dentists and vets are called doctors. Physicians and surgeons do not put 'Dr' before their names. Engineers, at least in India, put 'Er'.
WHAT IS A FLIPBOOK?
A flipbook is a small book with a series of printed images that create the illusion of motion when its pages are rapidly flipped. Typically, a flipbook is held in one hand while the thumb of the other flicks the pages and the user concentrates on the middle of each page. It relies on a basic optical principle known as persistence of vision. In India, flip books were popular in the seventies, when cola majors brought out flip books of cricketers in action.
WHAT IS THE ORIGIN OF FORMULA I?
Formula One, also known as Formula 1 or Fl, and currently officially referred to as FIA Formula One World Championship, is the highest class of auto racing sanctioned by the Fidiration Internationale de 1'Automobile (FIA). The 'formula' in the name refers to a set of rules that all participants and cars must comply with.
WHAT ARE GTOR-MA CAKES?
Gtor-ma cakes are sacrificial cakes used in Tibetan Buddhist ceremonies as offerings to deities. The unbaked cakes are prepared by kneading parched barley flour and butter into cones. The cakes form part of the phyi-mchod, or eight offerings of external worship.
WHAT IS DIGITAL CLEANSE?
Digital cleanse is a term mooted by John Mayor, musician and avid blogger and tweeter, as a resolution and challenge for the first week of 2010. It means keeping off all digital contraptions — a stop to emailing, texting, social networking, blogging and surfing sites. It is seen as a new health craze, considered good for the body and mind. The basic idea is to unplug and meet people.
HOW DOES THE HYBRID ENGINE WORK?
Hybrid engines use two or more power sources. They consist of a usual fuel engine, complemented by a pollution-free engine, an electric engine for example. The fuel engine and brakes are used to recharge the batteries for the electric engine, eliminating the need to plug in while unused. When brakes are applied, some of the energy being used to stop the vehicle is collected by the regenerative brakes of the electrical engine. Hence, the electrical engine takes control when cruising, stopping or slowly acclerating, reducing the use of fuel.
WHAT IS THE AURORA PHENOMENON?
Charged particles ejected at great speeds from the sun ionise the air molecules resulting in spectacular colour display. These are seen from polar regions and are called aurora or polar lights. It is the luminous phenomenon of earth's upper atmosphere that occurs primarily in high latitudes of both hemispheres; aurorae in the northern hemisphere are called aurora borealis, or northern lights; aurora australis, or southern lights in the southern hemisphere.
WHAT IS THE ORIGIN OF THE TERM 'SLAP-STICK COMEDY'?
The term 'slapstick comedy' is given to comedy characterized by broad humour, absurd situations and vigorous chases, often violent in action. The phrase comes from the term battacchio called the 'slap stick' in English. It is a club-like object composed of two wooden slats, and produces a loud smacking noise when struck, though little force is transferred to the person being struck. Slapstick comedy became popular in 19th-century music halls and Vaudeville theatres.
HOW AND WHEN DID THE TERM 'SIZE ZERO' COME INTO USE?
'Size zero' was first used in 1966 for British supermodel Twiggy, who had a fragile figure. Now, 'size zero' is a women's clothing size in the US system, equivalent to a UK size 4, with a waist measurement of 23 inches, the average girth of an 8-year-old girl. It is a petite size for women with a 32-inch bust, 23-inch waist and 32-inch hips, and is often linked to anorexia nervosa and bulimia.
HOW DOES THE 'MADRAS EYE' SPREAD?
Madras eye is the inflammation of the outermost covering of the eyeball and inner layer of eyelid. Medically, it is known as 'conjunctivitis'. It can be caused by various agents like bacteria, virus, wind, smoke, pollen, radiation or chemical agents. If a person comes in close physical contact of the infected person or his infected belongings, the bacteria or virus gets transmitted and thus, causes infection from person to person.
WHY DOES THE ORTHODOX CHURCH CELEBRATE CHRISTINAS ON JANUARY 7?
The Orthodox Church uses the old Julian calender which is 13 days behind the Gregorian calender. In the former Soviet Republic, the Bolsheviks adopted the Gregorian calender at the end of 1917, which put them in line with the rest of the Western world. However, the Orthodox Church, opposed to the Bolsheviks trying to suppress religion, kept the Julian calender.
WHAT IS COSMOPHOBIA?
Cosmophobia is an irrational fear that the world is about to end, and is sparked off by a belief among people that a cosmic end is near. The fear is ancient, and people have been readying for doom on and off — expecting floods, earthquakes, epidemics, drought, or even a collision with another planet. The latest bout was set off by the movie 2012, where the Mayan calendar counts December 21, 2012 as the last day Earlier, the 2000 millennium frenzy had everyone believe that the end was near. For ages now, there have been apocalyptic predictions which have fuelled cosmophobia, but until now, they have all come to nought.
WHAT IS AN ELEPHANT PEARL?
Elephant pearls are not really pearls, however, they are categorised as one of the nine pearls. These are produced in the heads and the sockets of the tusks of some elephants. It was believed that when worn by kings, they proved highly sanctifying and bestowed children, victory and sound health. Even now, they are considered to bring good luck.
WHAT IS A 'BANANA KICK' IN FOOT-BALL?
Banana kick is a checkside punt — a kicking style used in Australian Rules and rugby league football. When kicked, the ball bends away from the body and is usually used when a set shot for goal is lined up on a narrow angle. The banana kick comes off more from the inside of the boot, with the ball spinning in the same direction as the leg swings naturally.
WHAT IS THE ORACLE OF DELPHI?
The Oracle of Delphi was the most important oracle in the classical Greek World, and a major site for the worship of the god Apollo. Built around a sacred spring, Delphi was considered to be the omphalos — the centre of the world. Scholars congregated at Delphi, and it became a focal point for intellectual enquiry Delphi lies on the slopes of Mount Parnassus in Greece.
HOW MANY FLOWERS MUST A BEE TAP TO MAKE A POUND OF HONEY?
A bee taps 2 million flowers and flies 50,000 miles (80,000 kms) to make one pound (454 gm) of honey — traveling more than twice around the world to gather it. The basis of calculation is done after taking many facts for granted and the proof is often lost in the mists of time. C R Ribbands (1949) determined that one bee can visit several hundred of flowers for a load of sweet clover, and up to 1,100-1,446 flowers for a load of limantnes nectar.
WHAT IS THE SPHINX AWARD?
There are several types of Sphinx awards. The most popular one is given by Alpha Phi Alpha Fraternity forcontribution to social service. President Stephen C Ainlay of Union College recently received the Sphinx Award from the brothers of Alpha Phi Alpha Fraternity for his contributions to the Union community. Another Sphinx Award is given in Coventry for outstanding performance in the local soccer league.
WHAT IS A GRAMMY SALUTE?
Grammy awards are presented annually for outstanding achievements in music. There is a week-long function called the Grammy Week, culminating in the Annual Grammy Awards. The rest of the week is marked by several connected events, of which the Salute To series is a part. Each of the Salute To events features a reception, presentation of a special merit certificate and guest performances.
WHEN DID THE PRACTICE OF THE HANDSHAKE BEGIN?
The origin of the handshake goes back to primitive eras: the physical contact of the hand symbolized peace and friendship. Later symbolism of the gesture, apart from a greeting, was the ratification of a contract or pledge. Even today, we clinch a contract or business deal by 'shaking hands on it.' Archaeological ruins and texts show the handshake was in use as a means of greeting as far back as the 2nd century BC.
WHAT IS THE BOXING DAY MATCH AND WHAT IS ITS ORIGIN?
The Boxing Day match is a cricket match hosted in Melbourne, Australia, and Victoria, involving the Australian cricket team and the opposition national team touring Australia at that time. It begins on Boxing Day (Dec 26) and is played at the Melbourne Cricket Ground. Boxing Day is so called as traditionally, it was the day when people would give a present or Christmas 'box' to those who worked for them throughout the year. These days, the 'box' is usually given before Christmas.
WHAT IS BAS-RELIEF?
Bas-relief is a French term meaning 'low-raised work.' A relief is a sculptured artwork where a modelled form is raised. There are three types of reliefs — 'bas-relief or low relief, 'high relief and 'sunken relief.' Bas-relief is suitable for scenes with many figures and other elements such as a landscape or architectural background. Stone carving and metal casting is traditionally done in bas-relief.
Get Reviews On Fashion Drawing And Symbols Drawing
The fashion industry is full of artists and creative individual, who spend their days creating great fashion designs with the help of fashion drawing. To be a designer, you must be comfortable with drawing fashion because all fashion designs start out as sketches before investment in fabrics and the services of other professionals. However, in order to develop skills in fashion drawing, you must first learn the fundamentals of drawing, such as proportion, perspective drawing, shading and how to draw people, textures and movement. There is a lot involved in learning how to draw fashion and proper instruction is key. Changes in technology, leisure, work, cultural and moral values. Homelife and politics also contribute to lifestyle trends, which in turn influence the clothes we wear. These are the changes that make any era of society special in relation to the study of the costume of a period.
The fashion industry is full of artists and creative individual, who spend their days creating great fashion designs with the help of fashion drawings. To be a designer, you must be comfortable with drawing fashion because all fashion designs start out as sketches before investment in fabrics and the services of other professionals. However, in order to develop skills in fashion drawing, you must first learn the fundamentals of drawing, such as proportion, perspective drawing, shading and how to draw people, textures and movement. There is a lot involved in learning how to draw fashion and proper instruction is key. Changes in technology, leisure, work, cultural and moral values. Homelife and politics also contribute to lifestyle trends, which in turn influence the clothes we wear. These are the changes that make any era of society special in relation to the study of the costume of a period.
Symbol level drawing is useful when creating large scale maps with intersecting and overlapping line features. For example, on a large-scale reference map with intersecting highways and streets, it helps you create high-quality representations of street and highway street intersections. It is mostly useful in maps with cased lines as it creates overpass and underpass effects where the line features cross, which is a good way to show connectivity. Symbol level drawing can also be used to achieve other advanced effects. You can alter the draw order of features within feature layers. By using symbol level drawing, you can control the draw order of features on a symbol-by-symbol basis. This means features do not have to be drawn in the same order as feature layers that appear in ArcMap's table of contents (TOC). With symbol level drawing, you can control when a feature draws by controlling when the feature's symbol draws. Furthermore, when multilayer symbols are used, you can control the drawing order of individual symbol layers.
Graphic symbols are used on construction drawings to reference other drawings within the set. It is also used to list drawing notes, identify finishes and revisions. The same graphic is used for one purpose. Standard graphic symbols are used to present complete information concerning construction items and materials. These typical symbols are used so frequently in construction drawings that their meanings must be familiar not only to the preparer, but to the user as well. The main information sources for a particular symbol are the Military (Drawing) Standards (MIL-STD) and the American National Standards Institute (ANSI).
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Types of Structural Drawings – Shop Drawings, Steel Fabrication Drawings
Structural Drawings are mainly considered as a set of drawings of steel, wood, concrete and other materials supposed to be used in construction of building. Structural drawings are heart of any structural project as shapes, symbols and other information evaluated with less complexity. It is used to measure connections, reinforcing, dimensions and material estimation. At present time material estimation must be measured more accurately as wastage of material can make high cost and can waste time.
Structural Drawings includes following:
• Foundation Plan Drawings • Drawings For Shallow and Raft Foundation • Roof Trusses and Joint Details • RCC Joint and Slab Details • Steel Plan and Machine Foundation Details • Cross Sections of Beams and Columns • Bolted Steel Connection Details
It is crucial technique that used for variety of building structures like residential, commercial, institutional, industrial and special structures like sky scrapers. Mainly structural drawings can be described in two types like shop drawings and steel fabrication drawings. Let us get in brief for both phases as described below:
Shop Drawings:
It can be described as a pictorial presentation of building components to be used in construction. Shop drawings include important segments like elevations, dimensions and measurements. The style of shop drawings is different from other drawings. It shows more details than construction documents. Various structural firms assist 2D shop drawings and that include the following:
It is a popular term that used to build accurate buildings. Now a day various structural firms are providing pre fabricated designs so it is easy to use for different steel structures. It includes pre fabricated building components like steel elevators, trusses, window and cabinet. Details like anchor setting plan, structural steel design, connection details and bill of material can be measured using steel fabrication drawings.
Without structural drawings we can't imagine accurate building structures. Structural drawings have own importance in structural industry and it works like a bridge between contactors/builders and structural engineers.
Various offshore structural firms are providing accurate structural drawings. so you can save your time by outsourcing structural drawings.
[simpleaffiliate source="chitika" results="0"][/simpleaffiliate] What does the square symbol mean?
In an engineering drawing, while i was reading a dimension of what seemed to be a shaft. The dimension reading had a square beside. I'd like to know what the square means because the top view shows that it's a cylindrical shaft which means it has a round cross section.It looke like this :- 35x7 So could someone please explain what the cross sign and the square symbol indicates? P.S No printing errors
Without being able to see it, I cannot tell you for sure. But it sounds as though it might be a GD&T symbol, where GD&T = Geometric Dimensioning & Tolerancing.
If you provide a link to an image, I will try to identify it.
MOSFET - Lip Gloss Tubes Manufacturer - China Others
Composition
Photomicrograph of two metal-gate MOSFETs in a test pattern. Probe pads for two gates and three source/drain nodes are labeled.
Usually the semiconductor of choice is silicon, but some chip manufacturers, most notably IBM, recently started using a compound (mixture) of silicon and germanium (SiGe) in MOSFET channels. Unfortunately, many semiconductors with better electrical properties than silicon, such as gallium arsenide, do not form good semiconductor-to-insulator interfaces, thus are not suitable for MOSFETs. Research continues on creating insulators with acceptable electrical characteristics on other semiconductor material.
In order to overcome power consumption increase due to gate current leakage, high- dielectric replaces silicon dioxide for the gate insulator, while metal gates return by replacing polysilicon (see Intel announcement).
The gate is separated from the channel by a thin insulating layer, traditionally of silicon dioxide and later of silicon oxynitride. Some companies have started to introduce a high- dielectric + metal gate combination in the 45 nanometer node.
When a voltage is applied between the gate and body terminals, the electric field generated penetrates through the oxide and creates an alleged "inversion layer" or "channel" at the semiconductor-insulator interface. The inversion channel is of the same type, P-type or N-type, as the source and drain, thus it provides a channel through which current can pass. Varying the voltage between the gate and body modulates the conductivity of this layer and allows to control the current flow between drain and source.
Circuit symbols
A variety of symbols are used for the MOSFET. The basic design is generally a line for the channel with the source and drain leaving it at right angles and then bending back at right angles into the same direction as the channel. Sometimes three line segments are used for enhancement mode and a solid line for depletion mode. Another line is drawn parallel to the channel for the gate.
The bulk connection, if shown, is shown connected to the back of the channel with an arrow indicating PMOS or NMOS. Arrows always point from P to N, so an NMOS (N-channel in P-well or P-substrate) has the arrow pointing in (from the bulk to the channel). If the bulk is connected to the source (as is generally the case with discrete devices) it is sometimes angled to meet up with the source leaving the transistor. If the bulk is not shown (as is often the case in IC design as they are generally common bulk) an inversion symbol is sometimes used to indicate PMOS, alternatively an arrow on the source may be used in the same way as for bipolar transistors (out for NMOS, in for PMOS).
Comparison of enhancement-mode and depletion-mode MOSFET symbols, along with JFET symbols (drawn with source and drain ordered such that higher voltages appear higher on the page than lower voltages):
P-channel
N-channel
JFET
MOSFET enh
MOSFET enh (no bulk)
MOSFET dep
For the symbols in which the bulk, or body, terminal is shown, it is here shown internally connected to the source. This is a typical configuration, but by no means the only important configuration. In general, the MOSFET is a four-terminal device, and in integrated circuits many of the MOSFETs share a body connection, not necessarily connected to the source terminals of all the transistors.
MOSFET operation
Example application of an N-Channel MOSFET. When the switch is pushed the LED lights up.
Metalxideemiconductor structure on P-type silicon
Metalxideemiconductor structure
A traditional metalxideemiconductor (MOS) structure is obtained by growing a layer of silicon dioxide (SiO2) on top of a silicon substrate and depositing a layer of metal or polycrystalline silicon (the latter is commonly used). As the silicon dioxide is a dielectric material, its structure is equivalent to a planar capacitor, with one of the electrodes replaced by a semiconductor.
When a voltage is applied across a MOS structure, it modifies the distribution of charges in the semiconductor. If we consider a P-type semiconductor (with NA the density of acceptors, p the density of holes; p = NA in neutral bulk), a positive voltage, VGB, from gate to body (see figure) creates a depletion layer by forcing the positively charged holes away from the gate-insulator/semiconductor interface, leaving exposed a carrier-free region of immobile, negatively charged acceptor ions (see doping (semiconductor)). If VGB is high enough, a high concentration of negative charge carriers forms in an inversion layer located in a thin layer next to the interface between the semiconductor and the insulator. Unlike the MOSFET, where the inversion layer electrons are supplied rapidly from the source/drain electrodes, in the MOS capacitor they are produced much more slowly by thermal generation through carrier generation and recombination centers in the depletion region. Conventionally, the gate voltage at which the volume density of electrons in the inversion layer is the same as the volume density of holes in the body is called the threshold voltage.
This structure with P-type body is the basis of the N-type MOSFET, which requires the addition of an N-type source and drain regions.
MOSFET structure and channel formation
Cross section of an NMOS without channel formed: OFF state
Cross section of an NMOS with channel formed: ON state
A metalxideemiconductor field-effect transistor (MOSFET) is based on the modulation of charge concentration by a MOS capacitance between a body electrode and a gate electrode located above the body and insulated from all other device regions by a gate dielectric layer which in the case of a MOSFET is an oxide, such as silicon dioxide. If dielectrics other than an oxide such as silicon dioxide (often referred to as oxide) are employed the device may be referred to as a metalnsulatoremiconductor FET (MISFET). Compared to the MOS capacitor, the MOSFET includes two additional terminals (source and drain), each connected to individual highly doped regions that are separated by the body region. These regions can be either p or n type, but they must both be of the same type, and of opposite type to the body region. The source and drain (unlike the body) are highly doped as signified by a '+' sign after the type of doping.
If the MOSFET is an n-channel or nMOS FET, then the source and drain are 'n+' regions and the body is a 'p' region. As described above, with sufficient gate voltage, above a threshold voltage value, electrons from the source (and possibly[citation needed] also the drain) enter the inversion layer or n-channel at the interface between the p region and the oxide. This conducting channel extends between the source and the drain, and current is conducted through it when a voltage is applied between source and drain.
For gate voltages below the threshold value, the channel is lightly populated, and only a very small subthreshold leakage current can flow between the source and the drain.
If the MOSFET is a p-channel or pMOS FET, then the source and drain are 'p+' regions and the body is a 'n' region. When a negative gate-source voltage (positive source-gate) is applied, it creates a p-channel at the surface of the n region, analogous to the n-channel case, but with opposite polarities of charges and voltages. When a voltage less negative than the threshold value (a negative voltage for p-channel) is applied between gate and source, the channel disappears and only a very small subthreshold current can flow between the source and the drain.
The source is so named because it is the source of the charge carriers (electrons for n-channel, holes for p-channel) that flow through the channel; similarly, the drain is where the charge carriers leave the channel.
The device may comprise a Silicon On Insulator (SOI) device in which a Buried OXide (BOX) is formed below a thin semiconductor layer. If the channel region between the gate dielectric and a Buried OXide (BOX) region is very thin, the very thin channel region is referred to as an Ultra Thin Channel (UTC) region with the source and drain regions formed on either side thereof in and/or above the thin semiconductor layer. Alternatively, the device may comprise a SEMiconductor On Insulator (SEMOI) device in which other semiconductors than silicon are employed. Many alternative semicondutor materials may be employed.
When the source and drain regions are formed above the channel in whole or in part, they are referred to as Raised Source/Drain (RSD) regions.
Modes of operation
The operation of a MOSFET can be separated into three different modes, depending on the voltages at the terminals. In the following discussion, a simplified algebraic model is used that is accurate only for old technology. Modern MOSFET characteristics require computer models that have rather more complex behavior.
For an enhancement-mode, n-channel MOSFET, the three operational modes are:
Cutoff, subthreshold, or weak-inversion mode
When VGS < Vth:
where Vth is the threshold voltage of the device.
According to the basic threshold model, the transistor is turned off, and there is no conduction between drain and source. In reality, the Boltzmann distribution of electron energies allows some of the more energetic electrons at the source to enter the channel and flow to the drain, resulting in a subthreshold current that is an exponential function of gateource voltage. While the current between drain and source should ideally be zero when the transistor is being used as a turned-off switch, there is a weak-inversion current, sometimes called subthreshold leakage.
In weak inversion the current varies exponentially with gate-to-source bias VGS as given approximately by:
,
where ID0 = current at VGS = Vth and the slope factor n is given by
n = 1 + CD / COX,
with CD = capacitance of the depletion layer and COX = capacitance of the oxide layer. In a long-channel device, there is no drain voltage dependence of the current once VDS > > VT, but as channel length is reduced drain-induced barrier lowering introduces drain voltage dependence that depends in a complex way upon the device geometry (for example, the channel doping, the junction doping and so on). Frequently, threshold voltage Vth for this mode is defined as the gate voltage at which a selected value of current ID0 occurs, for example, ID0 = 1 A, which may not be the same Vth-value used in the equations for the following modes.
Some micropower analog circuits are designed to take advantage of subthreshold conduction. By working in the weak-inversion region, the MOSFETs in these circuits deliver the highest possible transconductance-to-current ratio, namely: gm / ID = 1 / (nVT), almost that of a bipolar transistor.
The subthreshold I curve depends exponentially upon threshold voltage, introducing a strong dependence on any manufacturing variation that affects threshold voltage; for example: variations in oxide thickness, junction depth, or body doping that change the degree of drain-induced barrier lowering. The resulting sensitivity to fabricational variations complicates optimization for leakage and performance.
MOSFET drain current vs. drain-to-source voltage for several values of VGS Vth; the boundary between linear (Ohmic) and saturation (active) modes is indicated by the upward curving parabola.
Cross section of a MOSFET operating in the linear (Ohmic) region; strong inversion region present even near drain
Cross section of a MOSFET operating in the saturation (active) region; channel exhibits pinch-off near drain
Triode mode or linear region (also known as the ohmic mode)
When VGS > Vth and VDS < ( VGS - Vth )
The transistor is turned on, and a channel has been created which allows current to flow between the drain and the source. The MOSFET operates like a resistor, controlled by the gate voltage relative to both the source and drain voltages. The current from drain to source is modeled as:
where n is the charge-carrier effective mobility, W is the gate width, L is the gate length and Cox is the gate oxide capacitance per unit area. The transition from the exponential subthreshold region to the triode region is not as sharp as the equations suggest.
Saturation or active mode
When VGS > Vth and VDS > ( VGS - Vth )
The switch is turned on, and a channel has been created, which allows current to flow between the drain and source. Since the drain voltage is higher than the gate voltage, the electrons spread out, and conduction is not through a narrow channel but through a broader, two- or three-dimensional current distribution extending away from the interface and deeper in the substrate. The onset of this region is also known as pinch-off to indicate the lack of channel region near the drain. The drain current is now weakly dependent upon drain voltage and controlled primarily by the gateource voltage, and modeled very approximately as:
The additional factor involving , the channel-length modulation parameter, models current dependence on drain voltage due to the Early effect, or channel length modulation. According to this equation, a key design parameter, the MOSFET transconductance is:
,
where the combination Vov = VGS - Vth is called the overdrive voltage. Another key design parameter is the MOSFET output resistance rO given by:
.
If is taken as zero, an infinite output resistance of the device results that leads to unrealistic circuit predictions, particularly in analog circuits.
As the channel length becomes very short, these equations become quite inaccurate. New physical effects arise. For example, carrier transport in the active mode may become limited by velocity saturation. When velocity saturation dominates, the saturation drain current is more nearly linear than quadratic in VGS. At even shorter lengths, carriers transport with near zero scattering, known as quasi-ballistic transport. In addition, the output current is affected by drain-induced barrier lowering of the threshold voltage.
Body effect
Ohmic contact to body to ensure no body bias; top left:subthreshold, top right:Ohmic mode, bottom left:Active mode at onset of pinch-off, bottom right: Active mode well into pinch-off - channel length modulation evident
The body effect describes the changes in the threshold voltage by the change in the source-bulk voltage, approximated by the following equation:
,
where VTN is the threshold voltage with substrate bias present, and VTO is the zero-VSB value of threshold voltage, is the body effect parameter, and 2 is the surface potential parameter.
The body can be operated as a second gate, and is sometimes referred to as the "back gate"; the body effect is sometimes called the "back-gate effect".
The primacy of MOSFETs
In 1959, Ernesto Labate, Dawon Kahng, and Martin M. (John) Atalla at Bell Labs invented the metalxideemiconductor field-effect transistor (MOSFET). Operationally and structurally different from the bipolar junction transistor, the MOSFET was made by putting an insulating layer on the surface of the semiconductor and then placing a metallic gate electrode on that. It used crystalline silicon for the semiconductor and a thermally oxidized layer of silicon dioxide for the insulator. The silicon MOSFET did not generate localized electron traps at the interface between the silicon and its native oxide layer, and thus was inherently free from the trapping and scattering of carriers that had impeded the performance of earlier field-effect transistors. Following the (expensive) development of clean rooms to reduce contamination to levels never before thought necessary, and of photolithography and the planar process to allow circuits to be made in very few steps, the SiiO2 system possessed such technical attractions as low cost of production (on a per circuit basis) and ease of integration. Largely because of these two factors, the MOSFET has become the most widely used type of integrated circuit.
CMOS circuits
The principal reason for the success of the MOSFET was the development of digital CMOS logic, which uses p- and n-channel MOSFETs as building blocks. Overheating is a major concern in integrated circuits since ever more transistors are packed into ever smaller chips. CMOS logic reduces power consumption because no current flows (ideally), and thus no power is consumed, except when the inputs to logic gates are being switched. CMOS accomplishes this current reduction by complementing every nMOSFET with a pMOSFET and connecting both gates and both drains together. A high voltage on the gates will cause the nMOSFET to conduct and the pMOSFET not to conduct and a low voltage on the gates causes the reverse. During the switching time as the voltage goes from one state to another, both MOSFETs will conduct briefly. This arrangement greatly reduces power consumption and heat generation. Digital and analog CMOS applications are described below.
Digital
The growth of digital technologies like the microprocessor has provided the motivation to advance MOSFET technology faster than any other type of silicon-based transistor. A timeline can be found at computerhistory.org. A big advantage of MOSFETs for digital switching is that the oxide layer between the gate and the channel prevents DC current from flowing through the gate, further reducing power consumption and giving a very large input impedance. The insulating oxide between the gate and channel effectively isolates a MOSFET in one logic stage from earlier and later stages, which allows a single MOSFET output to drive a considerable number of MOSFET inputs. Bipolar transistor-based logic (such as TTL) does not have such a high fanout capacity. This isolation also makes it easier for the designers to ignore to some extent loading effects between logic stages independently. That extent is defined by the operating frequency: as frequencies increase, the input impedance of the MOSFETs decreases.
Analog
The MOSFET's advantages in most digital circuits do not translate into supremacy in all analog circuits. The two types of circuit draw upon different features of transistor behavior. Digital circuits switch, spending most of their time outside the switching region, while analog circuits depend on MOSFET behavior held precisely in the switching region of operation. The bipolar junction transistor (BJT) has traditionally been the analog designer's transistor of choice, due largely to its higher transconductance and its higher output impedance (drain-voltage independence) in the switching region.
Nevertheless, MOSFETs are widely used in many types of analog circuits because of certain advantages. The characteristics and performance of many analog circuits can be designed by changing the sizes (length and width) of the MOSFETs used. By comparison, in most bipolar transistors the size of the device does not significantly affect the performance. MOSFETs' ideal characteristics regarding gate current (zero) and drain-source offset voltage (zero) also make them nearly ideal switch elements, and also make switched capacitor analog circuits practical. In their linear region, MOSFETs can be used as precision resistors, which can have a much higher controlled resistance than BJTs. In high power circuits, MOSFETs sometimes have the advantage of not suffering from thermal runaway as BJTs do. Also, they can be formed into capacitors and gyrator circuits which allow op-amps made from them to appear as inductors, thereby allowing all of the normal analog devices, except for diodes (which can be made smaller than a MOSFET anyway), to be built entirely out of MOSFETs. This allows for complete analog circuits to be made on a silicon chip in a much smaller space.
Some ICs combine analog and digital MOSFET circuitry on a single mixed-signal integrated circuit, making the needed board space even smaller. This creates a need to isolate the analog circuits from the digital circuits on a chip level, leading to the use of isolation rings and Silicon-On-Insulator (SOI). The main advantage of BJTs versus MOSFETs in the analog design process is the ability of BJTs to handle a larger current in a smaller space. Fabrication processes exist that incorporate BJTs and MOSFETs into a single device. Mixed-transistor devices are called Bi-FETs (Bipolar-FETs) if they contain just one BJT-FET and BiCMOS (bipolar-CMOS) if they contain complementary BJT-FETs. Such devices have the advantages of both insulated gates and higher current density.
BJTs have some advantages over MOSFETs for at least two digital applications. Firstly, in high speed switching, they do not have the "larger" capacitance from the gate, which when multiplied by the resistance of the channel gives the intrinsic time constant of the process. The intrinsic time constant places a limit on the speed a MOSFET can operate at because higher frequency signals are filtered out. Widening the channel reduces the resistance of the channel, but increases the capacitance by the exact same amount. Reducing the width of the channel increases the resistance, but reduces the capacitance by the same amount. R*C=Tc1, 0.5R*2C=Tc1, 2R*0.5C=Tc1. There is no way to minimize the intrinsic time constant for a certain process. Different processes using different channel lengths, channel heights, gate thicknesses and materials will have different intrinsic time constants. This problem is mostly avoided with a BJT because it does not have a gate.
The second application where BJTs have an advantage over MOSFETs stems from the first. When driving many other gates, called fanout, the resistance of the MOSFET is in series with the gate capacitances of the other FETs, creating a secondary time constant. Delay circuits use this fact to create a fixed signal delay by using a small CMOS device to send a signal to many other, many times larger CMOS devices. The secondary time constant can be minimized by increasing the driving FET's channel width to decrease its resistance and decreasing the channel widths of the FETs being driven, decreasing their capacitance. The drawback is that it increases the capacitance of the driving FET and increases the resistance of the FETs being driven, but usually these drawbacks are a minimal problem when compared to the timing problem. BJTs are better able to drive the other gates because they can output more current than MOSFETs, allowing for the FETs being driven to charge faster. Many chips use MOSFET inputs and BiCMOS outputs (see above).
MOSFET scaling
Over the past decades, the MOSFET has continually been scaled down in size; typical MOSFET channel lengths were once several micrometres, but modern integrated circuits are incorporating MOSFETs with channel lengths of tens of nanometers. Intel began production of a process featuring a 32 nm feature size (with the channel being even shorter) in late 2009. The semiconductor industry maintains a "roadmap", the ITRS , which sets the pace for MOSFET development. Historically, the difficulties with decreasing the size of the MOSFET have been associated with the semiconductor device fabrication process, the need to use very low voltages, and with poorer electrical performance necessitating circuit redesign and innovation (small MOSFETs exhibit higher leakage currents, and lower output resistance, discussed below).
Reasons for MOSFET scaling
Smaller MOSFETs are desirable for several reasons. The main reason to make transistors smaller is to pack more and more devices in a given chip area. This results in a chip with the same functionality in a smaller area, or chips with more functionality in the same area. Since fabrication costs for a semiconductor wafer are relatively fixed, the cost per integrated circuits is mainly related to the number of chips that can be produced per wafer. Hence, smaller ICs allow more chips per wafer, reducing the price per chip. In fact, over the past 30 years the number of transistors per chip has been doubled every 23 years once a new technology node is introduced. For example the number of MOSFETs in a microprocessor fabricated in a 45 nm technology is twice as large as in a 65 nm chip. This doubling of the transistor count was first observed by Gordon Moore in 1965 and is commonly referred to as Moore's law.
Trend of Intel CPU transistor gate length
It is also expected that smaller transistors switch faster. For example, one approach to size reduction is a scaling of the MOSFET that requires all device dimensions to reduce proportionally. The main device dimensions are the transistor length, width, and the oxide thickness, each (used to) scale with a factor of 0.7 per node. This way, the transistor channel resistance does not change with scaling, while gate capacitance is cut by a factor of 0.7. Hence, the RC delay of the transistor scales with a factor of 0.7.
While this has been traditionally the case for the older technologies, for the state-of-the-art MOSFETs reduction of the transistor dimensions does not necessarily translate to higher chip speed because the delay due to interconnections is more significant.
Difficulties arising due to MOSFET size reduction
Producing MOSFETs with channel lengths much smaller than a micrometer is a challenge, and the difficulties of semiconductor device fabrication are always a limiting factor in advancing integrated circuit technology. In recent years, the small size of the MOSFET, below a few tens of nanometers, has created operational problems.
Higher subthreshold conduction
As MOSFET geometries shrink, the voltage that can be applied to the gate must be reduced to maintain reliability. To maintain performance, the threshold voltage of the MOSFET has to be reduced as well. As threshold voltage is reduced, the transistor cannot be switched from complete turn-off to complete turn-on with the limited voltage swing available; the circuit design is a compromise between strong current in the "on" case and low current in the "off" case, and the application determines whether to favor one over the other. Subthreshold leakage (including subthreshold conduction, gate-oxide leakage and reverse-biased junction leakage), which was ignored in the past, now can consume upwards of half of the total power consumption of modern high-performance VLSI chips.
Increased gate-oxide leakage
The gate oxide, which serves as insulator between the gate and channel, should be made as thin as possible to increase the channel conductivity and performance when the transistor is on and to reduce subthreshold leakage when the transistor is off. However, with current gate oxides with a thickness of around 1.2 nm (which in silicon is ~5 atoms thick) the quantum mechanical phenomenon of electron tunneling occurs between the gate and channel, leading to increased power consumption.
Insulators (referred to as high-k dielectrics) that have a larger dielectric constant than silicon dioxide, such as group IVb metal silicates e.g. hafnium and zirconium silicates and oxides are being used to reduce the gate leakage from the 45 nanometer technology node onwards. Increasing the dielectric constant of the gate dielectric allows a thicker layer while maintaining a high capacitance (capacitance is proportional to dielectric constant and inversely proportional to dielectric thickness). All else equal, a higher dielectric thickness reduces the quantum tunneling current through the dielectric between the gate and the channel. On the other hand, the barrier height of the new gate insulator is an important consideration; the difference in conduction band energy between the semiconductor and the dielectric (and the corresponding difference in valence band energy) also affects leakage current level. For the traditional gate oxide, silicon dioxide, the former barrier is approximately 8 eV. For many alternative dielectrics the value is significantly lower, tending to increase the tunneling current, somewhat negating the advantage of higher dielectric constant.
Increased junction leakage
To make devices smaller, junction design has become more complex, leading to higher doping levels, shallower junctions, "halo" doping and so forth, all to decrease drain-induced barrier lowering (see the section on junction design). To keep these complex junctions in place, the annealing steps formerly used to remove damage and electrically active defects must be curtailed increasing junction leakage. Heavier doping is also associated with thinner depletion layers and more recombination centers that result in increased leakage current, even without lattice damage.
MOSFET version of gain-boosted current mirror; M1 and M2 are in active mode, while M3 and M4 are in Ohmic mode, and act like resistors. The operational amplifier provides feedback that maintains a high output resistance
Lower output resistance
For analog operation, good gain requires a high MOSFET output impedance, which is to say, the MOSFET current should vary only slightly with the applied drain-to-source voltage. As devices are made smaller, the influence of the drain competes more successfully with that of the gate due to the growing proximity of these two electrodes, increasing the sensitivity of the MOSFET current to the drain voltage. To counteract the resulting decrease in output resistance, circuits are made more complex, either by requiring more devices, for example the cascode and cascade amplifiers, or by feedback circuitry using operational amplifiers, for example a circuit like that in the adjacent figure.
Lower transconductance
The transconductance of the MOSFET decides its gain and is proportional to hole or electron mobility (depending on device type), at least for low drain voltages. As MOSFET size is reduced, the fields in the channel increase and the dopant impurity levels increase. Both changes reduce the carrier mobility, and hence the transconductance. As channel lengths are reduced without proportional reduction in drain voltage, raising the electric field in the channel, the result is velocity saturation of the carriers, limiting the current and the transconductance.
Interconnect capacitance
Traditionally, switching time was roughly proportional to the gate capacitance of gates. However, with transistors becoming smaller and more transistors being placed on the chip, interconnect capacitance (the capacitance of the wires connecting different parts of the chip) is becoming a large percentage of capacitance. Signals have to travel through the interconnect, which leads to increased delay and lower performance.
Heat production
Large heatsinks to cool power transistors in a TRM-800 audio amplifier
The ever-increasing density of MOSFETs on an integrated circuit is creating problems of substantial localized heat generation that can impair circuit operation. Circuits operate slower at high temperatures, and have reduced reliability and shorter lifetimes. Heat sinks and other cooling methods are now required for many integrated circuits including microprocessors.
Power MOSFETs are at risk of thermal runaway. As their on-state resistance rises with temperature, if the load is approximately a constant-current load then the power loss rises correspondingly, generating further heat. When the heatsink is not able to keep the temperature low enough, the junction temperature may rise quickly and uncontrollably, resulting in destruction of the device.
Process variations
With MOSFETS becoming smaller, the number of atoms in the silicon that produce many of the transistor's properties is becoming fewer, with the result that control of dopant numbers and placement is more erratic. During chip manufacturing, random process variations affect all transistor dimensions: length, width, junction depths, oxide thickness etc., and become a greater percentage of overall transistor size as the transistor shrinks. The transistor characteristics become less certain, more statistical. The random nature of manufacture means we do not know which particular example MOSFETs actually will end up in a particular instance of the circuit. This uncertainty forces a less optimal design because the design must work for a great variety of possible component MOSFETs. See design for manufacturability, reliability engineering, six sigma and statistical process control.
Modeling challenges
Modern ICs are computer-simulated with the goal of obtaining working circuits from the very first manufactured lot. As devices are miniaturized, the complexity of the processing makes it difficult to predict exactly what the final devices look like, and modeling of physical processes becomes more challenging as well. In addition, microscopic variations in structure due simply to the probabilistic nature of atomic processes require statistical (not just deterministic) predictions. These factors combine to make adequate simulation and "right the first time" manufacture difficult.
MOSFET construction
Gate material
The primary criterion for the gate material is that it is a good conductor. Highly-doped polycrystalline silicon is an acceptable but certainly not ideal conductor, and also suffers from some more technical deficiencies in its role as the standard gate material. Nevertheless, there are several reasons favoring use of polysilicon:
The threshold voltage (and consequently the drain to source on-current) is modified by the work function difference between the gate material and channel material. Because polysilicon is a semiconductor, its work function can be modulated by adjusting the type and level of doping. Furthermore, because polysilicon has the same bandgap as the underlying silicon channel, it is quite straightforward to tune the work function to achieve low threshold voltages for both NMOS and PMOS devices. By contrast, the work functions of metals are not easily modulated, so tuning the work function to obtain low threshold voltages becomes a significant challenge. Additionally, obtaining low-threshold devices on both PMOS and NMOS devices would likely require the use of different metals for each device type, introducing additional complexity to the fabrication process.
The Silicon-SiO2 interface has been well studied and is known to have relatively few defects. By contrast many metalnsulator interfaces contain significant levels of defects which can lead to Fermi-level pinning, charging, or other phenomena that ultimately degrade device performance.
In the MOSFET IC fabrication process, it is preferable to deposit the gate material prior to certain high-temperature steps in order to make better-performing transistors. Such high temperature steps would melt some metals, limiting the types of metal that can be used in a metal-gate-based process.
While polysilicon gates have been the de facto standard for the last twenty years, they do have some disadvantages which have led to their likely future replacement by metal gates. These disadvantages include:
Polysilicon is not a great conductor (approximately 1000 times more resistive than metals) which reduces the signal propagation speed through the material. The resistivity can be lowered by increasing the level of doping, but even highly doped polysilicon is not as conductive as most metals. In order to improve conductivity further, sometimes a high-temperature metal such as tungsten, titanium, cobalt, and more recently nickel is alloyed with the top layers of the polysilicon. Such a blended material is called silicide. The silicide-polysilicon combination has better electrical properties than polysilicon alone and still does not melt in subsequent processing. Also the threshold voltage is not significantly higher than with polysilicon alone, because the silicide material is not near the channel. The process in which silicide is formed on both the gate electrode and the source and drain regions is sometimes called salicide, self-aligned silicide.
When the transistors are extremely scaled down, it is necessary to make the gate dielectric layer very thin, around 1 nm in state-of-the-art technologies. A phenomenon observed here is the so-called poly depletion, where a depletion layer is formed in the gate polysilicon layer next to the gate dielectric when the transistor is in the inversion. To avoid this problem, a metal gate is desired. A variety of metal gates such as tantalum, tungsten, tantalum nitride, and titanium nitride are used, usually in conjunction with high-k dielectrics. An alternative is to use fully-silicided polysilicon gates, a process known as FUSI.
Insulator
As devices are made smaller, insulating layers are made thinner, and at some point tunneling of carriers through the insulator from the channel to the gate electrode takes place. To reduce the resulting leakage current, the insulator can be made thicker by choosing a material with a higher dielectric constant. To see how thickness and dielectric constant are related, note that Gauss' law connects field to charge as:
,
with Q = charge density, = dielectric constant, 0 = permittivity of empty space and E = electric field. From this law it appears the same charge can be maintained in the channel at a lower field provided is increased. The voltage on the gate is given by:
,
with VG = gate voltage, Vch = voltage at channel side of insulator, and tins = insulator thickness. This equation shows the gate voltage will not increase when the insulator thickness increases, provided increases to keep tins / = constant (see the article on high- dielectrics for more detail, and the section in this article on gate-oxide leakage).
The insulator in a MOSFET is a dielectric which can in any event be silicon oxide, but many other dielectric materials are employed. The generic term for the dielectric is gate dielectric since the dielectric lies directly below the gate electrode and above the channel of the MOSFET.
Junction design
The source-to-body and drain-to-body junctions are the object of much attention because of three major factors: their design affects the current-voltage (I-V) characteristics of the device, lowering output resistance, and also the speed of the device through the loading effect of the junction capacitances, and finally, the component of stand-by power dissipation due to junction leakage.
MOSFET showing shallow junction extensions, raised source and drain and halo implant. Raised source and drain separated from gate by oxide spacers.
The drain induced barrier lowering of the threshold voltage and channel length modulation effects upon I-V curves are reduced by using shallow junction extensions. In addition, halo doping can be used, that is, the addition of very thin heavily doped regions of the same doping type as the body tight against the junction walls to limit the extent of depletion regions.
The capacitive effects are limited by using raised source and drain geometries that make most of the contact area border thick dielectric instead of silicon.
These various features of junction design are shown (with artistic license) in the figure.
Junction leakage is discussed further in the section increased junction leakage.
Other MOSFET types
Dual gate MOSFET
The dual gate MOSFET has a tetrode configuration, where both gates control the current in the device. It is commonly used for small signal devices in radio frequency applications where the second gate is normally used for gain control or mixing and frequency conversion.
FinFET
A double-gate FinFET device.
The Finfet, see figure to right, is a double gate device, one of a number of geometries being introduced to mitigate the effects of short channels and reduce drain-induced barrier lowering.
Depletion-mode MOSFETs
There are depletion-mode MOSFET devices, which are less commonly used than the standard enhancement-mode devices already described. These are MOSFET devices that are doped so that a channel exists even with zero voltage from gate to source. In order to control the channel, a negative voltage is applied to the gate (for an n-channel device), depleting the channel, which reduces the current flow through the device. In essence, the depletion-mode device is equivalent to a normally closed (on) switch, while the enhancement-mode device is equivalent to a normally open (off) switch.
Due to their low noise figure in the RF region, and better gain, these devices are often preferred to bipolars in RF front-ends such as in TV sets. Depletion-mode MOSFET families include BF 960 by Siemens and BF 980 by Philips (dated 1980s), whose derivatives are still used in AGC and RF mixer front-ends.
NMOS logic
n-channel MOSFETs are smaller than p-channel MOSFETs and producing only one type of MOSFET on a silicon substrate is cheaper and technically simpler. These were the driving principles in the design of NMOS logic which uses n-channel MOSFETs exclusively. However, unlike CMOS logic, NMOS logic consumes power even when no switching is taking place. With advances in technology, CMOS logic displaced NMOS logic in the 1980s to become the preferred process for digital chips.
Power MOSFET
Cross section of a Power MOSFET, with square cells. A typical transistor is constituted of several thousand cells
Main article: Power MOSFET
Power MOSFETs have a different structure than the one presented above. As with all power devices, the structure is vertical and not planar. Using a vertical structure, it is possible for the transistor to sustain both high blocking voltage and high current. The voltage rating of the transistor is a function of the doping and thickness of the N-epitaxial layer (see cross section), while the current rating is a function of the channel width (the wider the channel, the higher the current). In a planar structure, the current and breakdown voltage ratings are both a function of the channel dimensions (respectively width and length of the channel), resulting in inefficient use of the "silicon estate". With the vertical structure, the component area is roughly proportional to the current it can sustain, and the component thickness (actually the N-epitaxial layer thickness) is proportional to the breakdown voltage.
It is worth noting that power MOSFETs with lateral structure are mainly used in high-end audio amplifiers. Their advantage is a better behaviour in the saturated region (corresponding to the linear region of a bipolar transistor) than the vertical MOSFETs. Vertical MOSFETs are designed for switching applications.
DMOS
DMOS stands for double-diffused metalxideemiconductor. Most of the power MOSFETs are made using this technology.
RHBD MOSFETs
Semiconductor sub-micron and nano-meter electronic circuits are the primary concern for operating within the normal tolerance in harsh radiation environments like space. One of the design approaches for making a radiation-hardened-by-design (RHBD) device is Enclosed-Layout-Transistor (ELT). Normally, the gate of the MOSFET surrounds the drain, which is placed in the center of the ELT. The source of the MOSFET surrounds the gate. Another RHBD MOSFET is called H-Gate. Both of these transistors have very low leakage current with respect to radiation. However, they are large in size and take more space on silicon than a standard MOSFET.
Newer technologies are emerging for smaller devices for cost saving, low power and increased operating speed. The standard MOSFET is also becoming extremely sensitive to radiation for the newer technologies. A lot more research works should be completed before space electronics can safely use RHBD MOSFET circuits of nanotechnology.
When radiation strikes near the silicon oxide region (STI) of the MOSFET, the channel inversion occurs at the corners of the standard MOSFET due to accumulation of radiation induced trapped charges. If the charges are large enough, the accumulated charges affect STI surface edges along the channel near the channel interface (gate) of the standard MOSFET. Thus the device channel inversion occurs along the channel edges and the device creates off-state leakage path, causing device to turn on. So the reliability of circuits degrades severely. The ELT offers many advantages. These advantages include improvement of reliability by reducing unwanted surface inversion at the gate edges that occurs in the standard MOSFET. Since the gate edges are enclosed in ELT, there is no gate oxide edge (STI at gate interface), and thus the transistor off-state leakage is reduced very much.
Low-power microelectronic circuits including computers, communication devices and monitoring systems in space shuttle and satellites are very different than what we use on earth. They are radiation (high-speed atomic particles like proton and neutron, solar flare magnetic energy dissipation in earth's space, energetic cosmic rays like X-ray, Gamma-ray etc.) tolerant circuits. These special electronics are designed by applying very different techniques using RHBD MOSFETs to ensure the safe space journey and also space-walk of astronauts.
MOSFET analog switch
MOSFET analog switches use the MOSFET channel as a lown-resistance switch to pass analog signals when on, and as a high impedance when off. Signals flow in both directions across a MOSFET switch. In this application the drain and source of a MOSFET exchange places depending on the voltages of each electrode compared to that of the gate. For a simple MOSFET without an integrated diode, the source is the more negative side for an N-MOS or the more positive side for a P-MOS. All of these switches are limited on what signals they can pass or stop by their gate-source, gate-drain and source-drain voltages, and source-to-drain currents; exceeding the voltage limits will potentially damage the switch.
Single-type MOSFET switch
This analog switch uses a four-terminal simple MOSFET of either P or N type. In the case of an N-type switch, the body is connected to the most negative supply (usually GND) and the gate is used as the switch control. Whenever the gate voltage exceeds the source voltage by at least a threshold voltage, the MOSFET conducts. The higher the voltage, the more the MOSFET can conduct. An N-MOS switch passes all voltages less than (Vgatetn). When the switch is conducting, it typically operates in the linear (or Ohmic) mode of operation, since the source and drain voltages will typically be nearly equal.
In the case of a P-MOS, the body is connected to the most positive voltage, and the gate is brought to a lower potential to turn the switch on. The P-MOS switch passes all voltages higher than (Vgate+|Vtp|). Threshold voltage (Vtp) is typically negative in the case of P-MOS.
A P-MOS switch will have about three times the resistance of an N-MOS device of equal dimensions because electrons have about three times the mobility of holes in silicon.
Dual-type (CMOS) MOSFET switch
Main article: Transmission gate
This "complementary" or CMOS type of switch uses one P-MOS and one N-MOS FET to counteract the limitations of the single-type switch. The FETs have their drains and sources connected in parallel, the body of the P-MOS is connected to the high potential (VDD) and the body of the N-MOS is connected to the low potential (Gnd). To turn the switch on the gate of the P-MOS is driven to the low potential and the gate of the N-MOS is driven to the high potential. For voltages between (VDDtn) and (Gnd+Vtp) both FETs conduct the signal, for voltages less than (Gnd+Vtp) the N-MOS conducts alone and for voltages greater than (VDDtn) the P-MOS conducts alone.
The only limits for this switch are the gate-source, gate-drain and source-drain voltage limits for both FETs. Also, the P-MOS is typically three times the width of the N-MOS so the switch will be balanced.
Tri-state circuitry sometimes incorporates a CMOS MOSFET switch on its output to provide for a low ohmic, full range output when on and a high ohmic, mid level signal when off.
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^ Body effect
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See also
BSIM
Transistor models
External links
Wikimedia Commons has media related to: MOS(FET)
An introduction to depletion-mode MOSFETs
MOSFET Process Step by Step A Flash slide showing the fabricating process of a MOSFET in detail step
MOSFET Calculator MOSFET Calculator
Advanced MOSFET Issues
MOSFET applet Very nice applet that helps to understand MOSFET.
MIT OpenCourseWare courses:
MIT Open Courseware 6.002 - Spring 2007 -- Link to the intro electrical engineering course at MIT on circuits and electronics.
MIT Open Courseware 6.012 - Fall 2005 -- Link to a more advanced class taught at MIT all about microelectronics and MOSFETs
Georgia Tech BJT and FET Slides Slides from a Microelectronic Circuits class at Georgia Tech
CircuitDesign: MOS Diffusion Parasitics Crude illustrations of MOS diffusion structure and sample circuit layouts to minimize their parasitics
Categories: Transistor typesHidden categories: All articles with unsourced statements | Articles with unsourced statements from January 2010
