Resistivity: defined, 464 units

The difference between the two ordinate origins represents the log of the coefficient in the equation between abrasion resistance, defined by the energy required to remove unit volume of mbber (J/mm ) and the energy density at break in the same units. 

The lumped material resistance properties of intestinal membranes as defined by permeability can be described macroscopically by the ratio of mass flux (J) through the membrane to the solute concentration difference across the membrane. Permeability (reciprocal resistance) has units of length per unit time. 

C Can wc define the convection resistance per unit surface area as the inverse of the convection heal transfer... 

The impedance response of electrochemical systems is often normalized to the effective area of the electrode. Such a normalization applies only if the effective area can be well defined, and is not used in this chapter on the impedance response of electrical circuits. The capacitance used in this chapter, therefore, has units of F rather than F/cm, the resistance has units of O rather than fl cm, and the inductance has units of H rather than H cm. ... 

In Ohm s law, the coefficient of proportionality indicated by the symbol cr, and which is usually determined experimentally, is defined as the conductivity of the medium. The units of conductivity are siemens per meter, or mho per meter. In logging practice, the reciprocal of conductivity, p = 1/cr, is often used and is called resistivity. The units for resistivity are ohm-meters. 

The sediment resistivity, defined in Equation 4.27 as electrical resistance per unit length of a unit cross-sectional area of the sediment, is calculated from the voltage drop/potential difference of an electric current passing through the soil between two electrodes that are in line and placed at a known distance apart (a). 

The electrical conductivity of coal is generally discussed in terms of specific resistance, p (units of p are ohm-centimeters), and is defined as the resistance of a block of coal 1 cm long and having a 1 cm cross section. Substances having a specific resistance greater than approximately 1 x 10 ohm-cm are classified as insulators while those with a specific resistance of less than 1 ohm-cm are conductors materials between these limits are semiconductors. 

A unit of resistivity, defined in terms of the resistance of a cube, one meter of length on each side. A similar term is ohm-centimeter, measured on a smaller cube. 

The raw plasma etch rate in dif t plasmas is a useful number to conq>are, but even more useful is die plasma etch selectivity toward the substrate of interest Both of these criteria are inqxntant, however there may even be more value in determining the time to strip the resist in a given plasma as a n asure of plaana etch resistance for die t resists that are required for 157-nm lithognqihy. The allowable resist thickness is dependent on the absorbance of the resist defined as some value of optical density per unit thickness. The time to strip the resist is therefore a function of bodi the resist thickness allowed at a defined optical density and the resist etch rate. 

In these equations, k is the heat conductivity, is the diffusion coefficient of compound k and Uk is the concentration of compound k. Ohm s law is usually stated as (16.1.5a) in which / is the electrical current, R is the resistance and V is the voltage. It can also be stated in terms of the electric current density I, the electric field E and the resistivity p (resistance per unit length per unit area of cross section). Other quantities in the above equations are as defined in Table 15.1... 

Flow resistance is also known as static flow resistance and is the ratio of the pressure drop across a porous element to the volume velocity flowing through it under conditions of steady low speed flow. The flow resistance is almost independent of the volume velocity at low speeds. However, flow resistance is dependent on the acoustic frequency. Dynamic specific flow resistance of a thin (compared to acoustic wavelengths) porous textile layer is the real part of the complex specific flow impedance at a specified frequency, which is defined as the complex ratio of the pressure drop across the layer to the relative face velocity through the layer. When the frequency tends to zero, the dynamic specific flow resistance varies little with frequency, so it is almost equal to the static flow resistance. In the international standard, flow resistance is defined as the real part of the ratio between the pressure drop and the flow velocity through a layer of material of unit thickness (ISO 9053,1991). Flow resistance characterizes a layer of specified thickness, whereas flow resistivity characterizes a bulk material in terms of resistance per unit thickness. 

The thickness of the skin barrier and the diffusion coefficient are combined and defined as a resistance, = h /D. The resistance has units of time per length. Equation 7.33 can be simplified to ... 

Conductivity. The standard unit of conductance is electrolytic conductivity (formerly called specific conductance) k, which is defined as the reciprocal of the resistance of a 1-m cube of liquid at a specified temperature m— ]. See Table 8.33 and the definition of the cell constant. 

Olefin fibers, also called polyolefin fibers, are defined as manufactured fibers in which the fiber-forming substance is a synthetic polymer of at least 85 wt % ethylene, propjiene, or other olefin units (1). Several olefin polymers are capable of forming fibers, but only polypropylene [9003-07-0] (PP) and, to a much lesser extent, polyethylene [9002-88-4] (PE) are of practical importance. Olefin polymers are hydrophobic and resistant to most solvents. These properties impart resistance to staining, but cause the polymers to be essentially undyeable in an unmodified form. 

A guarded hot-plate method, ASTM D1518, is used to measure the rate of heat transfer over time from a warm metal plate. The fabric is placed on the constant temperature plate and covered by a second metal plate. After the temperature of the second plate has been allowed to equiUbrate, the thermal transmittance is calculated based on the temperature difference between the two plates and the energy required to maintain the temperature of the bottom plate. The units for thermal transmittance are W/m -K. Thermal resistance is the reciprocal of thermal conductivity (or transmittance). Thermal resistance is often reported as a do value, defined as the insulation required to keep a resting person comfortable at 21°C with air movement of 0.1 m/s. Thermal resistance in m -K/W can be converted to do by multiplying by 0.1548 (121). 

A crystal yields when the force xh (per unit length) exceeds /, the resistance (a force per unit length) opposing the motion of a dislocation. This defines the dislocation yield strength... 

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