بازار خرید و فروش انواع پارچه | پارچه بازار قیمت، خرید، فروش انواع پارچه
Although the term metric system is often used as an informal alternative term for the International System of Units,[109] there are other metric systems, some of which have been widely used in the past or are even still used in some areas. There are also individual metric units such as the Sverdrup and darcy that exist outside of a system of units. Most units of other metric systems are not recognized by the IS. [cm] [cp] The current way of defining whether is the result of decades of movement towards an increasingly abstract and idealized formulation in which the achievements of units are conceptually separated from definitions. [2]: 126 In 1890, as a signatory to the Meter Convention, the United States received two copies of the International Prototype Meter, whose construction represented the most advanced standards of the time. Therefore, it seemed that the American measurements would have greater stability and accuracy by accepting the international counter as a basic standard, formalized by the Mendenhall Order in 1893. [36]: 379–۸۱ In March 1791, the Assembly adopted the principles proposed by the Committee for the new decimal measurement system, including the metre defined as 1/10,000,000 of the length of the quadrant of the Earth`s meridian passing through Paris, and approved a study to accurately determine the length of the meridian. In July 1792, the committee proposed the names Meter, Are, Liter, and Grab for the length, area, capacity, and mass of the units. The Committee also suggested that multiples and submultiples of these units be identified by decimal prefixes such as centi for one centi and kilo for thousand. [87]: 82 The old metric system included several groupings of units. The SI was developed in 1960 from one of them, the meter-kilogram-second (MKS) system, and not from the centimeter-gram-second (CGS) system, which in turn had many variants.
When prefixes are used with coherent SI units, the resulting units are no longer consistent because the prefix introduces a numerical factor other than one. [2]: 137 The only exception is the kilogram, the only coherent SI unit whose name and symbol contain a prefix for historical reasons. [ar] (2) requiring each federal agency to apply the metric measurement system to its purchases, subsidies and other business-related activities on a specific date and to the extent economically feasible by the end of fiscal year 1992, unless such use is impractical or could result in significant inefficiencies or market losses for U.S. businesses, . B for example. when foreign competitors manufacture competing products in non-metric units; When scientists studied electricity and magnetism, they realized that other basic units were needed to describe these topics. Until the middle of the 20th century, many different versions of the metric system were used. It was very confusing.
Angström is still used in various fields. Some other unrecognized SI metric units that do not fall into any of the categories already mentioned are, bar, barn, fermi, gradian (gon, degree or grade), metric carat, micrometer, millimeter mercury column, torr, millimeter (or centimeter or meter) of water, millimiron, mho, stere, unit x, γ (unit of mass), γ (unit of magnetic flux density) and λ (unit of volume). [116]: 20–۲۱ In some cases, NON-recognized SI metric units have equivalent SI units formed by combining a metric prefix with a coherent SI unit. For example, 1 γ (unit of magnetic flux density) = 1 nT, 1 gal = 1 cm⋅s−۲, ۱ bary = 1 decipascal, etc. (a related group are the correspondences[cq] such as 1 abampere ≘ ۱ decaampere, 1 abhenry ≘ ۱ nanohenry, etc.[cu]). Sometimes it`s not even a metric prefix: the UNrecognized SI unit can be exactly the same as an SI coherent unit, except that the SI doesn`t recognize the specific name and symbol. For example, the nit is just an unrecognized SI name for the CANDELA SI unit per square meter and the Talbot is an unrecognized SI name for the second lumens SI unit. Often, a non-metric unit SI is related to an SI unit by a factor of ten, but not to a unit that has a metric prefix, e.B. 1 dyn = 10−۵ Newtons, 1 Å = ۱۰−۱۰ m, etc.
(and equivalents [cq] such as 1 Gauss ≘ ۱۰−۴ Tesla). Finally, there are metric units whose conversion factors into SI units are not powers of ten, e.B 1 calorie = 4.184 joules and 1 kilogram of force = 9.806650 Newtons. Some unrecognized metric units are still widely used,. B for example calorie (in nutrition), Rem (in the United States), Jansky (in radio astronomy), Gauss (in industry) and CGS-Gaussian units [ct] in general (in certain subfields of physics), metric power (for engine power in Europe), kilogram force (for engine thrust, in China and sometimes in Europe), etc. Others are rarely used today, such as Sthenes and Rutherford. SI prefixes are used to form decimal multiples and submultiples of SI units. The great advantage of this approach is that with the development of science and technology, new and higher knowledge can be introduced without the need to redefine the units. [ay] Units can now be made with an accuracy that is ultimately limited only by the quantum structure of nature and our technical capabilities, but not by the definitions themselves. [az] Any valid physical equation that connects the definition constants to a unit can be used to achieve unity, creating opportunities for innovation. with increasing accuracy as technology advances.
[۲]: ۱۲۲ In practice, the CIPM Advisory Committees provide “putting into practice”[23], which are descriptions of what is currently considered the best experimental achievements of the units. [30] The International System of Units is a system of measurements based on 7 basic units: meters (length), kilograms (mass), seconds (time), amperes (electric current), Kelvin (temperature), moles (quantity) and candela (luminosity). These base units can be used in combination with each other. This creates derived SI units that can be used to describe other quantities such as volume, energy, pressure, and velocity. Some times, angles and old non-SI units have a long history of use. Most societies used the sunny day and its non-decentralized subdivisions as the basis for time, and unlike the foot or pound, these were the same regardless of where they were measured. .
