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ISO 31-2
ISO 31-2 is the part of international standard ISO 31 that defines names and symbols for quantities and units Unit may refer to: Arts and entertainment * UNIT, a fictional military organization in the science fiction television series ''Doctor Who'' * Unit of action, a discrete piece of action (or beat) in a theatrical presentation Music * ''Unit'' (alb ... related to ''periodic and related phenomena''. Its definitions include: Units of time #00031-2 {{standard-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
International Standard
international standard is a technical standard developed by one or more international standards organizations. International standards are available for consideration and use worldwide. The most prominent such organization is the International Organization for Standardization (ISO). Other prominent international standards organizations including the International Telecommunication Union (ITU) and the International Electrotechnical Commission (IEC). Together, these three organizations have formed the World Standards Cooperation alliance. Purpose International standards may be used either by direct application or by a process of modifying an international standard to suit local conditions. Adopting international standards results in creating national standards that are equivalent, or substantially the same as international standards in technical content, but may have (i) editorial differences as to appearance, use of symbols and measurement units, substitution of a point for a com ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ISO 31
ISO 31 (Quantities and units, International Organization for Standardization, 1992) is a superseded international standard concerning physical quantities, units of measurement, their interrrelationships and their presentation. It was revised and replaced by ISO/IEC 80000. Parts The standard comes in 14 parts: *ISO 31-0: General principles (replaced by ISO/IEC 80000-1:2009) *ISO 31-1: Space and time (replaced by ISO/IEC 80000-3:2007) *ISO 31-2: Periodic and related phenomena (replaced by ISO/IEC 80000-3:2007) * ISO 31-3: Mechanics (replaced by ISO/IEC 80000-4:2006) *ISO 31-4: Heat (replaced by ISO/IEC 80000-5) * ISO 31-5: Electricity and magnetism (replaced by ISO/IEC 80000-6) *ISO 31-6: Light and related electromagnetic radiations (replaced by ISO/IEC 80000-7) * ISO 31-7: Acoustics (replaced by ISO/IEC 80000-8:2007) * ISO 31-8: Physical chemistry and molecular physics (replaced by ISO/IEC 80000-9) *ISO 31-9: Atomic and nuclear physics (replaced by ISO/IEC 80000-10) * I ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Physical Quantity
A physical quantity is a physical property of a material or system that can be quantified by measurement. A physical quantity can be expressed as a ''value'', which is the algebraic multiplication of a ' Numerical value ' and a ' Unit '. For example, the physical quantity of mass can be quantified as '32.3 kg ', where '32.3' is the numerical value and 'kg' is the Unit. A physical quantity possesses at least two characteristics in common. # Numerical magnitude. # Units Symbols and nomenclature International recommendations for the use of symbols for quantities are set out in ISO/IEC 80000, the IUPAP red book and the IUPAC green book. For example, the recommended symbol for the physical quantity ''mass'' is ''m'', and the recommended symbol for the quantity ''electric charge'' is ''Q''. Subscripts and indices Subscripts are used for two reasons, to simply attach a name to the quantity or associate it with another quantity, or index a specific component (e.g., row or colum ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Physical Unit
A unit of measurement is a definite magnitude of a quantity, defined and adopted by convention or by law, that is used as a standard for measurement of the same kind of quantity. Any other quantity of that kind can be expressed as a multiple of the unit of measurement. For example, a length is a physical quantity. The metre (symbol m) is a unit of length that represents a definite predetermined length. For instance, when referencing "10 metres" (or 10 m), what is actually meant is 10 times the definite predetermined length called "metre". The definition, agreement, and practical use of units of measurement have played a crucial role in human endeavour from early ages up to the present. A multitude of systems of units used to be very common. Now there is a global standard, the International System of Units (SI), the modern form of the metric system. In trade, weights and measures is often a subject of governmental regulation, to ensure fairness and transparency ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Second
The second (symbol: s) is the unit of time in the International System of Units (SI), historically defined as of a day – this factor derived from the division of the day first into 24 hours, then to 60 minutes and finally to 60 seconds each (24 × 60 × 60 = 86400). The current and formal definition in the International System of Units ( SI) is more precise:The second ..is defined by taking the fixed numerical value of the caesium frequency, Δ''ν''Cs, the unperturbed ground-state hyperfine transition frequency of the caesium 133 atom, to be when expressed in the unit Hz, which is equal to s−1. This current definition was adopted in 1967 when it became feasible to define the second based on fundamental properties of nature with caesium clocks. Because the speed of Earth's rotation varies and is slowing ever so slightly, a leap second is added at irregular intervals to civil time to keep clocks in sync with Earth's rotation. Uses Analog clocks and watches often ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Units Of Time
A unit of time is any particular time interval, used as a standard way of measuring or expressing duration. The base unit of time in the International System of Units (SI) and by extension most of the Western world, is the second, defined as about 9 billion oscillations of the caesium atom. The exact modern SI definition is "he secondis defined by taking the fixed numerical value of the cesium frequency, , the unperturbed ground-state hyperfine transition frequency of the cesium 133 atom, to be 9 192 631 770 when expressed in the unit Hz, which is equal to s−1." Historically, many units of time were defined by the movements of astronomical objects. * Sun-based: the year was the time for the Earth to revolve around the Sun. Historical year-based units include the Olympiad (four years), the lustrum (five years), the indiction (15 years), the decade, the century, and the millennium. * Moon-based: the month was based on the Moon's orbital period around the Earth. * Earth-based: ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
