Units Outside the SI

The SI base units and SI derived units, including those with special names, have the important advantage of forming a coherent set, with the effect that unit conversions are not required when one is inserting particular values for quantities into equations involving quantities. 

Nonetheless, it is recognized that some non-SI units still appear widely in the scientific, technical, and commercial literature, and some will probably continue to be used for many years. Other non-SI units, such as the units of time, are so widely used in everyday fife and are so deeply embedded in the history and culture of human beings that they wiU continue to he used for the foreseeable future. For these reasons, some of the more irr5)ortant non-SI units are fisted. 

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In the United States, the National Institute of Standards and Technology (NIST) also has compiled a list of units outside the SI that it has approved for domestic use (see Table 5). It recommends defining them in terms of accepted SI units. The CIPM does not encourage the use of units on the NIST list but accepts all of them, excluding the curie, roentgen, rad,... 

The CGPM recognizes that some units outside the SI continue to be important and useful in particular applications. An example is the hter as the reference volume in clinical analyses. Liter is the name of the submultiple (cubic decimeter) of the SI unit of volume, the cubic meter. Considering that 1 cubic meter represents some 200 times the blood volume of an adult human, the SI unit of volume is neither a convenient nor a reasonable reference volume in a cHnical context. Nevertheless, the CGPM recommends that such exceptional units as the liter should not be combined with SI units and preferably should be replaced with SI units whenever possible. 

Table A.3 Units outside the SI that are accepted for use with the SI.

SI Units International System of Units was established in 1973-74 to develop a uniform method of reporting results worldwide. The basic units are metre (m), kilogram (kg), second (s), ampere (A), Kelvin (K), mole (mol) and candela (cd). Acceptable units outside the SI system are litre (1), grams per litre (g/1), moles per litre (M), day (d), hour (h) and minute (min). 

The International System of Units (SI), Physical Quantities, and Their Dimensions I 2.6 Units Outside the SI 21... 

Units that are outside the SI may be divided into three categories ... 

For practical engineering purposes, relative density at 15°C (288 K), widely used in countries outside the United States, is considered equivalent to specific gravity at 60°F (288.6 K). With the adoption of SI units, the American Petroleum Institute favors absolute density at 288 K instead of degrees API. 

This equation allows the prediction of minimum fluidizing velocity from a knowledge of the mean particle diameter, the particle density, the density of fluidizing medium and fhe viscosity of fluidizing medium (SI units). Couderc (1985) quotes data which show that the inaccuracy of Leva s equation increases significantly outside the range 2 < Re < 30. 

SI is an abbreviation of the French Systeme International d Unites or the International System of Units. It is the most widely used system of units in the world and is the system used in science. The use of many SI units in the United States is increasing outside of science and technology. There are two types of SI units base units and derived units. The base units are ... 

You can find the region in which a particular state lies by referring to one of the two tables for saturation properties. If, at the given T or P, the given specific intensive property lies outside the range of properties that can exist for saturated liquid, saturated vapor, or their mixtures, the state must be in either the superheated or the subcooled region. For example, look at a brief extract from the steam tables in SI units ... 

As illustrated in Figure 7.18, the pore structure, represented as four cylinders called forbidden zones, is first defined in a unit cell, and then atoms are placed outside the forbidden zones on the basis of specified symmetry and distance constraints. Two constraint conditions must be satisfied when placing the atoms (i) no T atom is allowed inside a forbidden zone, and (ii) the distance between any two T atoms should not be less than 3.0 A (Si—Si distance). This method allows a user to specify the pore size, the number and site symmetry of unique atoms, the unit cell, and the space group. 

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