816 résultats pour "number"

• Complex Numbers I INTRODUCTION Complex Numbers, in mathematics, the sum of a real number and an imaginary number.

  sometimes referred to as an Argand diagram. If a complex number in the plane is thought of as a vector joining the origin to that point, then addition of complexnumbers corresponds to standard vector addition. Figure 1 shows the complex number 3 + 2 i obtained by adding the vectors 1 + 4 i and 2 - 2 i. Figure 1: Complex Plane in Cartesian CoordinatesThis graph illustrates the addition of two complex numbers by using vectors in the complex plane with cartesiancoordinates. The parallelogram shows...

• Number Theory I INTRODUCTION Number Theory, branch of mathematics that deals with the properties and relationships of numbers (see Number).

• Number (mathematics) I INTRODUCTION Number (mathematics), word or symbol used to designate quantities or entities that behave like quantities.

• Number Systems I INTRODUCTION Number Systems, in mathematics, various notational systems that have been or are being used to represent the abstract quantities called numbers.

• Complementary Number.

• Alphabet I INTRODUCTION Bengali Script India developed a number of different writing systems over the course of its history.

  A Pictographic and Ideographic Systems Early systems of writing used pictures to represent things and then to represent the sounds of those things. Pictographic writing, in which a simplified picture of the sunstood for the word sun, was probably the first step toward a written language. Chinese began as a pictographic language. To represent abstract ideas, the Chinese writing system combined pictographs. For example, the pictographs for sun and tree were combined to represent the concept of...

• One. Number 31 1950 Jackson Pollock (1912-1956)

  One. Number 31 1 199 Sans chevalet La femme de Pollock, Lee Krasner, raconte que, dans ses toiles abstraites, Pollock commençait par un dessin figuratif que petit à petit il recouvrait de coulées de peinture jusqu'à ce qu'il soit complètement voilé. Jackson Pollock ne travaillait pas sur_ un che­ valet. Non, il posait sa toile à même le sol et, trempant ses pin­ ceaux dans les pots d'émail, avec l'assurance d'un danseur, tout en tournant autour d...

• Zero. Zero, term applied to the number representing naught, denoted by

• International Standard Book Number [ISBN] - informatique.

• Number eight - dissertation

  can see that it is omniscient. It is also part of the driver's voice. When he employed “I”, the reader identifies with the characters but when he employed “He”, the readers is distanced from the characters. The narrator sees the story through the eyes of the main character. To conclude, I would like to say that personally, I loved this short story. There was a lot of suspense, and the fact that the killer discovers just at the end of the story leaves the mystery and doubt during all hist...

• Arithmetic I INTRODUCTION Arithmetic, branch of mathematics that arises from counting, the most basic mathematical operation.

  Subtract the units: 6 - 3 = 3. Then subtract the tens column: 6 – 2 = 4. The results of these two single-digit subtractions, written side by side, provide the answer: Subtraction is a bit more complicated if we need to subtract a larger digit from a smaller one. For example, when subtracting 47 from 92, the units value (7) of 47 isgreater than the units value (2) of 92. We can handle this situation using a procedure called borrowing, which is like carrying in reverse. Ten units can be borrowe...

• Japanese Art and Architecture I INTRODUCTION Otani Oniji as Eitoku Otani Oniji as Eitoku is one of a number of woodblock prints created by the artist T? sh ?sai Sharaku between 1794 and 1795 during the Edo period in Japan.

  Jō mon PotteryJapan’s J ōmon people, who thrived from 10,000 to 300 bc, made distinctive pottery for boiling, steaming, and storing food.The pots were made with coils of clay and then decorated by rolling carved sticks, plant fibers, or braided cords over theouter surface. This cord-marked (j ōmon) pottery gave the culture its name.Scala/Art Resource, NY The first settlers of Japan, the J ōmon people (10,000?-300? BC), named for the cord markings that decorated the surfaces of their clay vessel...

• Atom I INTRODUCTION Water Molecule A water molecule consists of an oxygen atom and two hydrogen atoms, which are attached at an angle of 105°.

  spontaneously break apart and change, or decay, into other atoms. Unlike electrons, which are fundamental particles, protons and neutrons are made up of other, smaller particles called quarks. Physicists know of six different quarks.Neutrons and protons are made up of up quarks and down quarks —two of the six different kinds of quarks. The fanciful names of quarks have nothing to do with their properties; the names are simply labels to distinguish one quark from another. Quarks are unique amo...

• Algebra I INTRODUCTION Algebra, branch of mathematics in which symbols (usually letters) represent unknown numbers in mathematical equations.

  B Order of Operations and Grouping Algebra relies on an established sequence for performing arithmetic operations. This ensures that everyone who executes a string of operations arrives at the sameanswer. Multiplication is performed first, then division, followed by addition, then subtraction. For example: 1 + 2 · 3 equals 7 because 2 and 3 are multiplied first and then added to 1. Exponents and roots have even higher priority than multiplication: 3 · 2 2 = 3 · 4 = 12 Grouping symbols override...

• Atom - chemistry.

  Atoms have several properties that help distinguish one type of atom from another and determine how atoms change under certain conditions. A Atomic Number Each element has a unique number of protons in its atoms. This number is called the atomic number (abbreviated Z). Because atoms are normally electrically neutral,the atomic number also specifies how many electrons an atom will have. The number of electrons, in turn, determines many of the chemical and physical properties ofthe atom. The ligh...

• Statistics I INTRODUCTION Statistics, branch of mathematics that deals with the collection, organization, and analysis of numerical data and with such problems as experiment design and decision making.

  Professional pollsters typically conduct their surveys among sample populations of 1,000 people. Statistical measurementsshow that reductions in the margin of error flatten out considerably after the sample size reaches 1,000.© Microsoft Corporation. All Rights Reserved. The raw materials of statistics are sets of numbers obtained from enumerations or measurements. In collecting statistical data, adequate precautions must be taken tosecure complete and accurate information. The first problem of...

• Chemistry - chemistry.

  parts of oxygen by weight, which is a ratio of about 1 to 8, regardless of whether the water came from the Mississippi River or the ice of Antarctica. In other words, acompound has a definite, invariable composition, always containing the same elements in the same proportions by weight; this is the law of definite proportions. Many elements combine in more than one ratio, giving different compounds. In addition to forming water, hydrogen and oxygen also form hydrogen peroxide.Hydrogen peroxide h...

• Radioactivity I INTRODUCTION Marie Curie Working with her husband, Pierre Curie, French physicist Marie Curie discovered the radioactive elements polonium and radium in 1898.

  Rutherford when he allowed an alpha-emitting substance to decay near an evacuated thin-glass vessel. The alpha particles were able to penetrate the glass and werethen trapped in the vessel, and within a few days the presence of elemental helium was demonstrated by use of a spectroscope. Beta particles were subsequentlyshown to be electrons, and gamma rays to consist of electromagnetic radiation of the same nature as X rays but of considerably greater energy. A The Nuclear Hypothesis Rutherford...

• Telephone.

  digits is dialed. The development of inexpensive and reliable amplification provided by the introduction of the transistor in the 1960s made practical the design of adialing system based on the transmission of relatively low power tones instead of the higher-power dial pulses. Today most telephones have push buttons instead of a rotary dial. Touch-Tone is an optional service, and telephone companies still maintain the ability to receive pulsedialing. Push-button telephones usually have a switch...

• Statistics I INTRODUCTION Statistics, branch of mathematics that deals with the collection, organization, and analysis of numerical data and with such problems as experiment design and decision making.

  frequency, column (d), is the ratio of the frequency of an interval to the total count; the relative frequency is multiplied by 100 to obtain the percent relative frequency.The cumulative frequency, column (e), represents the number of students receiving grades equal to or less than the range in each succeeding interval; thus, thenumber of students with grades of 30 or less is obtained by adding the frequencies in column (c) for the first three intervals, which total 53. The cumulative relativef...

• Inorganic Chemistry - chemistry.

  two electrically charged plates (positively charged top plate and negatively charged bottom plate). By measuring the difference in how fast these electron-laden oildrops fell when the metal plates were charged and uncharged, Millikan was able to calculate the total charge on each oil drop. Because each measurement was a wholenumber multiple of -1.60 × 10 -19 coulombs, Millikan concluded this was the charge carried by a single electron. Using Thomson’s electron charge-to-mass ratio, Millikan then...

• Molecule - chemistry.

  attracted to the negatively charged electrons between them. The electrons belong to the molecule as a whole. However, each hydrogen atom now has a complete outershell of two electrons. The formula H 2 describes a hydrogen molecule, a discrete unit. When a molecule contains just two atoms, such as the hydrogen molecule does, it is called a diatomic molecule. Some atoms can form covalent bonds with more than one other atom and thus create a larger molecule. Atoms form molecules with covalent bo...

• Hydrogen - chemistry.

  Hydrogen gas does not usually react with other chemicals at room temperature. That is, it does not split into two hydrogen atoms to combine with other chemicals. Thebond between the hydrogen atoms is very strong and can only be broken with a large amount of energy. However, when heated with a flame or a spark, hydrogen gaswill react violently with oxygen in the air to produce water in the following reaction: 2H2 + O 2 → 2H 2O This chemical equation shows that two hydrogen molecules (H 2) and o...

• Bowling.

  In each of the first nine frames the bowler rolls one or two balls. If the bowler knocks down all ten pins with the first ball, he or she has rolled a strike, the best roll possible. An X is recorded on the scoresheet or screen, and the bowler receives ten points (the number of pins knocked down) plus a bonus of the number of pins thebowler knocks down in his or her next two bowls. The maximum possible score in a strike frame, therefore, is 30: the strike followed by two more strikes on subseq...

• Electoral College.

  III HISTORY OF THE ELECTORAL COLLEGE A Origins One thing is clear about the political theory underpinning the electoral college: The framers of the Constitution could not agree on one. From the outset, the framerswere uncertain about how the president should be chosen. Meeting in the Constitutional Convention in Philadelphia, Pennsylvania, in 1787, the framers originally decidedto have Congress choose the president, and that there should be no popular vote to elect the president. Then the Con...

• Capital Punishment.

  deterrent effect. Capital punishment advocates note that because the death penalty is reserved for the most aggravated murders, the deterrent effect of capitalpunishment on such crimes may not be apparent in data on homicide rates in general. Supporters also urge that the conflicting results of various studies indicate thatthe deterrent effect of the death penalty cannot not be proven or disproven with any certainty. They maintain that in the absence of conclusive proof that the threat ofexecuti...

• Vatican City Facts and Figures.

  Voting qualificationsLimited to cardinals under 80 years old ConstitutionApostolic Constitution of 1967, effective 1 March 1968 Armed forcesTotal number of military personnel Not available Military expenditures as a share of gross domestic product (GDP) Not available ECONOMYGross domestic product (GDP, in U.S.$) Not available GDP per capita (U.S.$) Not available GDP by economic sectorAgriculture, forestry, fishing Not available Industry Not available Services Not available Employ...

• Quantum Theory I INTRODUCTION Quantum Theory, in physics, description of the particles that make up matter and how they interact with each other and with energy.

  electron in the same way a particle with momentum would: It bumps the electron and changes the electron’s path. The light is also affected by the collision as though itwere a particle, in that its energy and momentum changes. Momentum is a quantity that can be defined for all particles. For light particles, or photons, momentum depends on the frequency, or color, of the photon, which in turndepends on the photon’s energy. The energy of a photon is equal to a constant number, called Planck’s cons...

• Geometry I INTRODUCTION Geometry, branch of mathematics that deals with shapes and sizes.

  Conic sections, a commonly studied topic of geometry, are two-dimensional curves created by slicing a plane through a three-dimensional hollow cone. A Euclid’s Postulates Euclid, who lived about 300 BC, realized that only a small number of postulates underlay the various geometric theorems known at the time. He determined that these theorems could be deduced from just five postulates. 1. A straight line may be drawn through any two given points. 2. A straight line may be drawn infinitely or be...

• Genetics - biology.

  construct identical buildings. Just as each contractor would require a full copy of the blueprint to construct a complete building, each new cell needs a complete copy ofan organism’s genetic information to function properly. Organisms use two types of cell division to ensure that DNA is passed down from cell to cell during reproduction. Simple one-celled organisms and other organisms thatreproduce asexually—that is, without the joining of cells from two different organisms—reproduce by a proces...

• Intelligence.

  education. Teachers had no way of knowing which of the “slow” students had true learning problems and which simply had behavioral problems or poor prior education.In 1904 the French Ministry of Public Instruction asked Binet and others to develop a method to objectively identify children who would have difficulty with formaleducation. Objectivity was important so that conclusions about a child’s potential for learning would not be influenced by any biases of the examiner. The governmenthoped tha...

• Thailand - country.

  E Natural Resources Thailand possesses a range of mineral resources. Tin is mined in the peninsula. Important gemstones, such as sapphires, are found in the southeast, and coal reserves,particularly lignite, are in the north. Fish are abundant in rivers and coastal waters. In addition to being consumed domestically, fish are also exported. F Climate Thailand experiences a typical monsoon climate. Winds blow from the northeast during the winter months of October to March or April (known as the...

• Boston - geography.

  The neighborhoods of Allston and Brighton occupy the northwest corner of the city to the west of Fenway. The Allston-Brighton area is bordered to the east, north, andwest by the Charles River and to the south by the Massachusetts Turnpike and the town of Brookline. It is an industrial and residential neighborhood that is also thelocation of Boston College and Harvard University Business School. Boston has been unsuccessful in annexing Brookline, the birthplace of U.S. president John F.Kennedy an...

• Sydney (Australia) - geography.

  blocks in the eastern suburbs and around railway stations elsewhere; and homes on large lots in the outer suburbs, especially those to the northwest. For publichousing, the state government built a number of high-rise apartment blocks in run-down inner suburbs after World War II (1939-1945). These housing projects weresoon deemed unsuccessful and were discontinued because they fostered crime and other social problems. More recently, public housing has taken the form of separateor semidetached ho...

• Hungary - country.

  Northern Hungary lacks sufficient water, especially between July and October, when precipitation levels are typically low. Canals irrigate the Great Hungarian Plain,which is subject to drought. Because of the country’s mainly flat terrain, only limited water resources can be harnessed for hydroelectric power. F Environmental Issues Rapid industrialization in Hungary following World War II contributed significantly to a number of major environmental problems, including air, water, and soil pollu...

• Europe .

  D Vegetation Although much of Europe, particularly the west, was originally covered by forest, the vegetation has been transformed by human habitation and the clearing of land.Only in the most northerly mountains and in parts of north central European Russia has the forest cover been relatively unaffected by human activity. On the otherhand, a considerable amount of Europe is covered by woodland that has been planted or has reoccupied cleared lands. The largest vegetation zone in Europe, cuttin...

• Europe - Geography.

  D Vegetation Although much of Europe, particularly the west, was originally covered by forest, the vegetation has been transformed by human habitation and the clearing of land.Only in the most northerly mountains and in parts of north central European Russia has the forest cover been relatively unaffected by human activity. On the otherhand, a considerable amount of Europe is covered by woodland that has been planted or has reoccupied cleared lands. The largest vegetation zone in Europe, cuttin...

• Blacks in Latin America.

  Throughout Latin America and the Caribbean the slave population declined at the astonishing rate of 2 to 4 percent a year; thus, by the time slavery was abolished, theoverall slave population in many places was far less than the total number of slaves imported. The British colony of Jamaica, for example, imported more than 600,000slaves during the 18th century; yet, in 1838, the slave population numbered little more than 300,000. The French colony of Saint-Domingue (present-day Haiti)imported mo...

• Heredity - biology.

  allele from the mother and a mutated allele from the father. In both of these cases, the child will be a carrier. The child develops the disease only if he or she receives amutated allele from each parent. When both parents are carriers, there is a 25 percent chance that a child will be disease-free, a 25 percent chance that it will have thedisease, and a 50 percent chance that it will be a carrier. Examples of genetic diseases that follow the dominant-recessive pattern include sickle-cell anemi...

• Electric Motors and Generators.

  the armature. It is often desirable to generate as high a voltage as possible, and rotating armatures are not practical in such applications because of the possibility of sparkingbetween brushes and slip rings and the danger of mechanical failures that might cause short circuits. Alternators are therefore constructed with a stationary armaturewithin which revolves a rotor composed of a number of field magnets. The principle of operation is exactly the same as that of the AC generator described,...

• Gemstones.

  In the late 1960s a method was developed for “growing” diamonds by heating a diamond particle to a high temperature and subjecting it to methane gas. The gasdecomposes into carbon atoms, which adhere to the diamond crystal. The crystal structure of the enlarged diamond is identical to that of a natural diamond. Diamondsof about 1 carat (200 mg or 0.007 oz) have been produced by this method, but their cost is still considerably higher than that of naturally occurring diamonds. Sapphires are made...

• Pittsburgh - geography.

  College of Allegheny County (1966), with branches in the city and suburbs. Pittsburgh has many outstanding cultural institutions. The Oakland district is where Carnegie Mellon University and the University of Pittsburgh are located. The CarnegieMuseums of Pittsburgh include The Carnegie Museum of Art (including the Scaife Galleries), which holds a distinguished motion-picture and video collection and a uniquestudy of architecture; the Carnegie Museum of Natural History, which displays an extensi...

• Aging - biology.

  Different theories have been proposed to explain how SF works. One theory is based on the assumption that aging, and diseases that occur more frequently withadvancing age, are caused by structural damage to cells. This damage accumulates in tiny amounts each time the cell divides, eventually preventing the cell fromcarrying out normal functions. One cause of this damage may be free radicals, which are chemical compounds found in the environment and also generated by normal chemical reactions in...

• African Theater I INTRODUCTION African Theater, traditional, historical, and contemporary dramatic forms in Africa south of the Sahara.

  The period after World War II ended in 1945 led to the struggle for and achievement of independence in many African countries. The new nation-states were oftenestablished along colonial boundaries and power was handed over to a bourgeois class who had been educated in Europe. The epoch-making era of nationalismproduced a number of African playwrights who merged African theatrical traditions with European forms. These plays are still widely performed and read in many partsof the continent. Nigeri...

• African Theater I INTRODUCTION African Theater, traditional, historical, and contemporary dramatic forms in Africa south of the Sahara.

  The period after World War II ended in 1945 led to the struggle for and achievement of independence in many African countries. The new nation-states were oftenestablished along colonial boundaries and power was handed over to a bourgeois class who had been educated in Europe. The epoch-making era of nationalismproduced a number of African playwrights who merged African theatrical traditions with European forms. These plays are still widely performed and read in many partsof the continent. Nigeri...

• Turbine.

  steam turbine has supplanted the reciprocating engine as a prime mover in large electricity-generating plants and is also used as a means of jet propulsion. Steam turbines are used in the generation of nuclear power and in nuclear ship propulsion. They operate with fuel-fired boilers for power generation. In cogenerationapplications requiring both process heat (heat used in an industrial process) and electricity, steam is raised at high pressure in the boiler and extracted from the turbineat th...

• Ecology.

  an input of nutrients exceeding the capability of the ecosystem to process them. Nutrients eroded and leached from agricultural lands, along with sewage and industrialwastes accumulated from urban areas, all drain into streams, rivers, lakes, and estuaries. These pollutants destroy plants and animals that cannot tolerate theirpresence or the changed environmental conditions caused by them; at the same time they favor a few organisms more tolerant to changed conditions. Thus,precipitation filled...

• Ecology - biology.

  an input of nutrients exceeding the capability of the ecosystem to process them. Nutrients eroded and leached from agricultural lands, along with sewage and industrialwastes accumulated from urban areas, all drain into streams, rivers, lakes, and estuaries. These pollutants destroy plants and animals that cannot tolerate theirpresence or the changed environmental conditions caused by them; at the same time they favor a few organisms more tolerant to changed conditions. Thus,precipitation filled...

• Supernova - astronomy.

  The term hypernova has been proposed for an extremely massive core-collapse supernova—possibly more than 100 times the mass of the Sun. A hypernova is thought to form a black hole. Just before it explodes, a hypernova may release a huge burst of gamma rays in a jet from the rotating black hole at its center. These jets mayexplain the so-called long gamma-ray bursts detected by astronomers. According to some researchers, massive stars with over 40 solar masses may sometimescollapse directly int...

• East Timor Facts and Figures.

  Male 64.6 years (2008 estimate) Infant mortality rate 43 deaths per 1,000 live births (2008 estimate) Population per physician 10,380 people (2004) Population per hospital bed 5 people (2000 estimate) Literacy rateTotal 43 percent (2001 estimate) Female 42.8 percent (2001 estimate) Male 43.1 percent (2001 estimate) Education expenditure as a share of gross national product (GNP) Not available Number of years of compulsory schooling 9 years (2002-2003) Number of students per teache...