Measurement units, energy

Several additional terms related to the absorption of x-radiation require definition energy of a x-ray photon is properly represented in joules but more conveniently reported in eV fluence is the sum of the energy in a unit area intensity or flux is the fluence per unit time and the exposure is a measure of the number of ions produced in a mass of gas. The unit of exposure in medicine is the Rn ntgen, R, defined as the quantity of radiation required to produce 2.58 x C/kg of air. The absorbed dose for a tissue is a measure of energy dissipated per unit mass. The measure of absorbed dose most... 

Measurements and Audits. The enabling element of continuous improvement is measurement. An old rule of thumb says that increased accuracy in measuring an energy use ultimately yields a reduction in use equal to 10% of the increased closure of the balance. A basic principle of economics is that any thing that is free is used in excess, ie, an unmetered electrical use is bigger than expected by at least 10%. Metering of the cost elements at each unit in a chemical plant provides effective accountabhity. Measurements should be linked via computer software to production as weh as to weather to result in maximum feedback. 

Measurements of energy are made in terms of absolute joules, but engineering practice has persistently retained the thermochemical calorie as the unit of energy. The two are related by the definition ... 

Sound intensity is a measure of energy, and its units are watts per meter. Intensity is proportional to the square of pressure ... 

FIGURE 26.51 Brasion loss per unit energy (abradability) (—) as function of temperature for four different compounds on a silicon carbide track at a speed of 1 cm/s together with energy density measurements (—) at an extension rate of 10 /s. (From Grosch, K.A. and Schallamach, A., Trans IRI, 40, T80, 1961 Rubber Chem. Technol, 39, 267, 1966. 

The number of rotor revolutions per mix cycle relates directly to unit work input and to temperature rise. This variable can be employed when checking between mixed batches for changes in feeding operations, materials and mixer conditions. Power/work input measures the energy consumed by the mixer. A greater compensation for variations in feed stocks and mixer temperatures is provided by power control. 

Calorimetry is the measurement of energy changes accompanying chemical or physical changes. We usually want to know how much energy is liberated or consumed per unit mass or mole of... 

The Po value will be called a spatial-energy parameter, and the PE value - effective P-parameter. Effective PE-parameter has a physical sense of some averaged energy of valence electrons in atom and is measured in energy units, e.g. in electron-volts (eV). 

A summary of the electrochemical formulae developed above is provided in Table 7.3. AG, pe, E, and K contain virtually the same thermodynamic information. While is the quantity that is analytically measured, pe is preferred by marine chemists as it is temperature independent and numerically easier to work with. AG is often used to compare the relative stability of species because it provides a measure of energy yields in units of calories or joules. A comparison of the three electrochemical scales at 25°C is given in Figure 7.3. The merits of each thermodynamic parameter will become evident in the next section of the chapter where the energetics of some marine redox processes are considered. 

ICRU (1970). International Commission on Radiation Units and Measurements. Linear Energy Thinfer, ICRU Report No. 16 (International Commission on Radiation Units and Measurements, Bethesda, Maryland). 

The expression declares that the transition in energy which corresponds to the emission of resonance is 16960 cm-1. This unit is employed to measure the energies (E = h.c/X) with A = 1 jv and A = 589.62 nm. It is the first component of the doublet called the resonance line (E = 2.102eV). The second is not a resonance emission. 

Bjarnholt and coworkers (Refs 13 and 21) used a semi-empirical approach to estimate the useful energy of HE via underwater expln energy measurements. In essence, their approach involves computation of a shock toss factor, ft > 1, to estimate the shock energy at the HE/water boundary from measured shock energies at some distance from the HE. This is coupled with the assumption that the measured bubble energy at some distance from the HE equals the bubble energy at the HE/water boundary. Then the total underwater expansion work per unit mass of HE, A0, is given by ... 

The area of contact between two phases is called the interface, or (especially if one of the phases is gaseous) the surface. The properties of interfaces and surfaces are determined by the number, kind, and orientation of the molecules located in them. A widely used measure is energy per unit area. It is the work required to extend the surface by unit area or force required per unit length, is expressed as ergs cm-2 or dynes cm-1, and is often symbolized by the Greek letter gamma (7). 

In standard abrasion tests, it is usually weight loss which is the parameter measured, although in certain cases the change in test piece thickness is more convenient. Because it is the amount of material lost which matters, it is usual to convert the weight loss to volume loss by dividing by the density. The volume loss can be expressed as the loss per unit distance travelled over the abradant, per 1000 revolutions of the apparatus, or whatever. A less usual practice is to express the result as loss per unit energy consumed in... 

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