Variation with temperature

Although the temperature dependence of the mobihty is crucial for determining the variety of polaron transport that occurs in oligothiophenes, temperature dependent measurements are scarce. 

The field-effect mobility of sexithiophene and dihexyl sexithiophene have then been measured as a function of both the temperature and the gate voltage [59]. This was achieved by estimating /rpE in the linear regime, with the help of Eq. (39), instead of the conventional estimation from the variation of the saturation drain current, Eq. (38a). It appeared that, although the mobility indeed decreases as the 

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Van Velzen s method provides an estimation of hydrocarbon viscosities and their variation with temperature ... 

At the saturation pressure, the viscosity variation with temperature follows a law analogous to that of Clapeyron for the vapor pressure f ) ... 

Although the viscosity index is useful for characterizing petroleum oils, other viscosity—temperature parameters are employed periodically. Viscosity temperature coefficients (VTCs) give the fractional drop in viscosity as temperature increases from 40 to 100°C and is useful in characterizing behavior of siHcones and some other synthetics. With petroleum base stocks, VTC tends to remain constant as increasing amounts of VI improvers are added. Constant B in equation 9, the slope of the line on the ASTM viscosity—temperature chart, also describes viscosity variation with temperature. 

Figure 3.3. The ratio Di, (t)/DHE ( ) and its variation with temperature. (After Frith and Tuckett, reproduced by permission of Longmans, Green and Co. Ltd.)...

Guha [5] pointed out some limitations in the linearised analyses developed by Horlock and Woods to determine the changes in optimum conditions with the three parameters n (and n ),/ and Not only is the accurate determination of (Cpg)i3 (and hence n ) important but also the fuel-air ratio although small, it cannot be assumed to be a constant as r is varied. Guha presented more accurate analyses of how the optimum conditions are changed with the introduction of specific heat variations with temperature and with the fuel-air ratio. 

Figure A The variation with temperature and spin-orbit coupling constant, of the magnetic moments of octahedral, low-spin, d" ions, (The values of at 300 K are marked for individual ions).

Figure 6 Typical plots from dynamic mechanical thermal analysis showing storage modulus and tan6 variation with temperature [27]. SO (---), S2 (--).

Meters are accurate within close limits as legislation demands. However, gas is metered on a volume basis rather than a mass basis and is thus subject to variation with temperature and pressure. The Imperial Standard Conditions are 60°F, 30inHg, saturated (15.56°C, 1913.7405 mbar, saturated). Gas Tariff sales are not normally corrected, but sales on a contract basis are. Correction may be for pressure only on a fixed factor basis based on Boyle s Law or, for larger loads, over 190,000 therms per annum for both temperature and pressure using electronic (formerly mechanical) correctors. For high pressures, the compressibility factor Z may also be relevant. The current generation of correctors corrects for pressure on an absolute basis taking into account barometric pressure. 

Electrical Conductivity This is often a convenient and accurate measurement of salinity or chlorinity. Here, too, there is considerable variation with temperature, so that simultaneous observation of temperature is essential. Figure 2.16 shows the relationship between conductivity and chlorinity at various temperatures. 

Table 4.32 Variation with temperature of mechanical properties of diecast test bars of alloys ...

The satisfactory result shown in Table 12 suggests that one might give a more detailed and quantitative discussion of the variation with temperature. If we are to do this, we need some standard of comparison with which to compare the experimental results. Just as wq compare an imperfect gas with a perfect gas, and compare a non-ideal solution with an ideal solution, so we need a simple standard behavior with which to compare the observed behavior. We obtain this standard behavior if, supposing that. /e is almost entirely electrostatic in origin, we take J,np to vary with temperature as demanded by the macroscopic dielectric constant t of the medium 1 that is to say, we assume that Jen, as a function of temperature is inversely proportional to . For this standard electrostatic term we may use the notation, instead of... 

The 2 -Coefficients. We may pass on now to discuss the JS-coeffi-cients. The experimental values in aqueous solution are given in Tables 21 and 22. The variation with temperature for various pairs of ions is shown in Fig. 52. It will be seen that with rise of temperature the... 

The variation with temperature and pressure of the composition of the equilibrium clathrate is given by the total differential of Eq. 25, ... 

Tables 23-26 show the variation with temperature of some relevant physical properties of liquid sodium.

FIGURE 8.22 The variation with temperature of the solubilities of six substances in water. 

For an incompressible fluid, the density variation with temperature is negligible compared to the viscosity variation. Hence, the viscosity variation is a function of temperature only and can be a cause of radical transformation of flow and transition from stable flow to the oscillatory regime. The critical Reynolds number also depends significantly on the specific heat, Prandtl number and micro-channel radius. For flow of high-viscosity fluids in micro-channels of tq < 10 m the critical Reynolds number is less than 2,300. In this case the oscillatory regime occurs at values of Re < 2,300. 

The equations which describe the variation with temperature of the equilibrium constant, K, for a chemical system and of the rate constant, ki, for a chemical reaction are well known. They are... 

The formation of dew and fog are consequences of this variation in relative humidity. Warm air at high relative humidity may cool below the temperature at which its partial pressure of H2O equals the vapor pressure. When air temperature falls below this temperature, called the dew point, some H2 O must condense from the atmosphere. Example shows how to work with vapor pressure variations with temperature, and our Chemistry and the Environment Box explores how variations in other trace gases affect climate. 

C12-0059. One of the reasons that different aquatic life-forms thrive in water of different temperatures is the variation with temperature in the concentration of dissolved oxygen. Using data in Table 12-2. calculate the percentage change in the equilibrium oxygen concentration when water warms from 0.0 °C to 25.0 °C. 

This accords with both [H" "] and [Fe(II)] dependences and gives values for Ar, and 1 their variations with temperature yield... 

The gas turbine heat rate and its variation with temperature can be defined by9 ... 

The dipole moment of a molecule can be obtained from a measurement of the variation with temperature of the dielectric constant of a pure liquid or gaseous substance. In an electric field, as between the electrostatically charged plates of a capacitor, polar molecules tend to orient themselves, each one pointing its positive end toward the negative plate and its negative end toward the positive plate. This orientation of the molecules partially neutralizes the applied field and thus increases the capacity of the capacitor, an effect described by saying that the substance has a dielectric constant greater than unity (80 for liquid water at 20°C). The dipole moments of some simple molecules can also be determined very accurately by microwave spectroscopy. 

Fig. 2. shows CNO abundance variation with temperature. Abundances are expressed in mass fractions as before and were determined from non-LTE model fits to e.g. Nil 3995 A, CII 4267 A, Oil 4367 A. Nitrogen shows an increase with increasing temperature, whereas oxygen implies a subtle decrease with increasing temperature and carbon does not display a definite trend... 

At the present time, only empirical observations can be made on the FWHP of the H-modes in (X—HY) complexes and on their variation with temperature. In a given material and for a given acceptor, the FWHPs are directly related to the average amplitude of vibration of the H atom, and the smaller the amplitude, the smaller the FWHP. This is derived from the fact that the FWHP of an X—D mode is always smaller than the one for the corresponding X—H mode. 

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