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Standard Atmosphere (unit)
The standard atmosphere (symbol: atm) is a unit of pressure defined as Pa. It is sometimes used as a ''reference pressure'' or ''standard pressure''. It is approximately equal to Earth's average atmospheric pressure at sea level. History The standard atmosphere was originally defined as the pressure exerted by a 760 mm column of mercury at and standard gravity (''g''n = ). It was used as a reference condition for physical and chemical properties, and the definition of the centigrade temperature scale set 100 °C as the boiling point of water at this pressure. In 1954, the 10th General Conference on Weights and Measures (CGPM) adopted ''standard atmosphere'' for general use and affirmed its definition of being precisely equal to dynes per square centimetre (). This defined pressure in a way that is independent of the properties of any particular substance. In addition, the CGPM noted that there had been some misapprehension that the previous definition (from the 9th CGPM ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pressure
Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and even by industry. Further, both spellings are often used ''within'' a particular industry or country. Industries in British English-speaking countries typically use the "gauge" spelling. is the pressure relative to the ambient pressure. Various #Units, units are used to express pressure. Some of these derive from a unit of force divided by a unit of area; the International System of Units, SI unit of pressure, the Pascal (unit), pascal (Pa), for example, is one newton (unit), newton per square metre (N/m2); similarly, the Pound (force), pound-force per square inch (Pound per square inch, psi, symbol lbf/in2) is the traditional unit of pressure in the imperial units, imperial and United States customary units, US customary systems. Pressure ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemistry
Chemistry is the scientific study of the properties and behavior of matter. It is a physical science within the natural sciences that studies the chemical elements that make up matter and chemical compound, compounds made of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they undergo during chemical reaction, reactions with other chemical substance, substances. Chemistry also addresses the nature of chemical bonds in chemical compounds. In the scope of its subject, chemistry occupies an intermediate position between physics and biology. It is sometimes called the central science because it provides a foundation for understanding both Basic research, basic and Applied science, applied scientific disciplines at a fundamental level. For example, chemistry explains aspects of plant growth (botany), the formation of igneous rocks (geology), how atmospheric ozone is formed and how environmental pollutants are degraded (ecology), the prop ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
International Standard Atmosphere
The International Standard Atmosphere (ISA) is a static atmospheric model of how the pressure, temperature, density, and viscosity of the Earth's atmosphere change over a wide range of altitudes or elevations. It has been established to provide a common reference for temperature and pressure and consists of tables of values at various altitudes, plus some formulas by which those values were derived. The International Organization for Standardization (ISO) publishes the ISA as an international standard, ISO 2533:1975.International Organization for Standardization, Standard Atmosphere', ISO 2533:1975, 1975. Other standards organizations, such as the International Civil Aviation Organization (ICAO) and the United States Government, publish extensions or subsets of the same atmospheric model under their own standards-making authority. Description The ISA mathematical model divides the atmosphere into layers with an assumed linear distribution of absolute temperature ''T'' against ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Technical Atmosphere
Technical may refer to: * Technical (vehicle), an improvised fighting vehicle * Technical area, an area which a manager, other coaching personnel, and substitutes are allowed to occupy during a football match * Technical advisor, a person who advises the director on the convincing portrayal of a subject in a film production * Technical analysis, a discipline for forecasting the future direction of prices through the study of past market data * Technical drawing, showing how something is constructed or functions (also known as drafting) ** Technical file, a set of technical drawings * Technical death metal, a subgenre of death metal that focuses on complex rhythms, riffs, and song structures * Technical foul, an infraction of the rules in basketball usually concerning unsportsmanlike non-contact behavior * Technical geography, one of the main branches of geography * Technical rehearsal for a performance, often simply referred to as a technical * Technical support, a range of ser ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Absolute Pressure
Pressure measurement is the measurement of an applied force by a fluid (liquid or gas) on a surface. Pressure is typically measured in unit of measurement, units of force per unit of surface area. Many techniques have been developed for the measurement of pressure and vacuum. Instruments used to measure and display pressure mechanically are called pressure gauges, vacuum gauges or compound gauges (vacuum & pressure). The widely used Bourdon gauge is a mechanical device, which both measures and indicates and is probably the best known type of gauge. A vacuum gauge is used to measure pressures lower than the ambient atmospheric pressure, which is set as the zero point, in negative values (for instance, −1 bar or −760 mmHg equals total vacuum). Most gauges measure pressure relative to atmospheric pressure as the zero point, so this form of reading is simply referred to as "gauge pressure". However, anything greater than total vacuum is technically a form of pressure. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pounds Per Square Foot
The pound per square inch (abbreviation: psi) or, more accurately, pound-force per square inch (symbol: lbf/in2), is a unit of measurement of pressure or of stress based on avoirdupois units and used primarily in the United States. It is the pressure resulting from a force with magnitude of one pound-force applied to an area of one square inch. In SI units, 1 psi is approximately . The pound per square inch absolute (psia) is used to make it clear that the pressure is relative to a vacuum rather than the ambient atmospheric pressure. Since atmospheric pressure at sea level is around , this will be added to any pressure reading made in air at sea level. The converse is pound per square inch gauge (psig), indicating that the pressure is relative to atmospheric pressure. For example, a bicycle tire pumped up to 65 psig in a local atmospheric pressure at sea level (14.7 psi) will have a pressure of 79.7 psia (14.7 psi + 65 psi). When gauge pressure is referenced to so ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Inch Of Water
Inches of water is a non- SI unit for pressure. It is also given as inches of water gauge (iwg or in.w.g.), inches water column (inch wc, in. WC, " wc, etc. or just wc or WC), inAq, Aq, or inHO. The units are conventionally used for measurement of certain pressure differentials such as small pressure differences across an orifice, or in a pipeline or shaft, or before and after a coil in an HVAC unit. It is defined as the pressure exerted by a column of water of 1 inch in height at defined conditions. At a temperature of 4 °C (39.2 °F) pure water has its highest density (1000 kg/m3). At that temperature and assuming the standard acceleration of gravity, 1 inAq is approximately . Alternative standard in uncommon usage are 60 °F (15,6 °C), or 68 °F (20 °C), and depends on industry standards rather than on international standards. Feet of water is an alternative way to specify pressure as height of a water column; it is conventionally ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Inch Of Mercury
Inch of mercury (inHg, ″Hg, or in) is a non- SI unit of measurement for pressure. It is used for barometric pressure in weather reports, refrigeration and aviation in the United States. It is the pressure exerted by a column of mercury in height at the standard acceleration of gravity. Conversion to metric units depends on the density of mercury, and hence its temperature; typical conversion factors are: In older literature, an "inch of mercury" is based on the height of a column of mercury at .Barry N. Taylor, ''Guide for the Use of the International System of Units (SI),'' 1995, NIST Special Publication 811, Appendix /ref> :1 inHg60 °F = In Imperial units: 1 inHg60 °F = 0.489 771 Pounds per square inch, psi, or 2.041 771 inHg60 °F = 1 psi. Applications Aircraft and automobiles Aircraft altimeters measure the relative pressure difference between the lower ambient pressure at altitude and a calibrated reading on the grou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Millimetre Of Mercury
A millimetre of mercury is a manometric unit of pressure, formerly defined as the extra pressure generated by a column of mercury one millimetre high. Currently, it is defined as exactly , or approximately 1 torr = atmosphere = pascals.Council Directive 80/181/EEC of 20 December 1979 on the approximation of the laws of the Member States relating to units of measurement and on the repeal of Directive 71/354/EEC of the It is denoted mmHg or mm Hg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Centimetre Of Water
A centimetre or millimetre of water (US spelling ''centimeter'' or ''millimeter of water'') are less commonly used measures of pressure based on the pressure head of water. Centimetre of water A ''centimetre of water''NOTE: A centimetre of water is abbreviated as ''cm'' or ''cm H2O''. is a unit of pressure. It may be defined as the pressure exerted by a column of water of 1 cm in height at 4 °C (temperature of maximum density) at the standard acceleration of gravity, so that = × × 1 cm = ≈ , but conventionally a nominal maximum water density of is used, giving . The centimetre of water unit is frequently used to measure the central venous pressure, the intracranial pressure while sampling cerebrospinal fluid, as well as determining pressures during mechanical ventilation or in water supply networks (then usually in metres water column). It is also a common unit of pressure in the speech sciences. This unit is commonly used to specify the pressure to which a CP ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kilogram-force
The kilogram-force (kgf or kgF), or kilopond (kp, from ), is a non-standard Gravitational metric system, gravitational metric unit of force. It is not accepted for use with the International System of Units (SI) and is deprecated for most uses. The kilogram-force is equal to the magnitude of the force exerted on one kilogram of mass in a gravitational field (standard gravity, a conventional value approximating the average magnitude of gravity on Earth). That is, it is the weight of a kilogram under standard gravity. One kilogram-force is defined as .NIST]''Guide for the Use of the International System of Units (SI)''Special Publication 811, (1995) page 51 Similarly, a gram-force is , and a milligram-force is . History The gram-force and kilogram-force were never well-defined units until the CGPM adopted a ''standard acceleration of gravity'' of 9.80665 m/s2 for this purpose in 1901, though they had been used in low-precision measurements of force before that time. Even then, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
International Union Of Pure And Applied Chemistry
The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations working for the advancement of the chemical sciences, especially by developing nomenclature and terminology. It is a member of the International Science Council (ISC). IUPAC is registered in Zürich, Switzerland, and the administrative office, known as the "IUPAC Secretariat", is in Research Triangle Park, North Carolina, United States. IUPAC's executive director heads this administrative office, currently Greta Heydenrych. IUPAC was established in 1919 as the successor of the International Congress of Applied Chemistry for the advancement of chemistry. Its members, the National Adhering Organizations, can be national chemistry societies, national academies of sciences, or other bodies representing chemists. There are fifty-four National Adhering Organizations and three Associate National Adhering Organizations. IUPAC's Inter-divisional Committee ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
