Compression, adiabatic theory

It is thus evident that the experimental results considered in sect. 4 above are fully consistent with the interpretation based on absolute reaction rate theory. Alternatively, consistency is equally well established with the quantum mechanical treatment of Buhks et al. [117] which will be considered in Sect. 6. This treatment considers the spin-state conversion in terms of a radiationless non-adiabatic multiphonon process. Both approaches imply that the predominant geometric changes associated with the spin-state conversion involve a radial compression of the metal-ligand bonds (for the HS -> LS transformation). 

This theory has also been used to predict mobility for molecular liquids. Neopentane and TMS are liquids that exhibit maxima in the electron mobility at intermediate densities [46]. These maxima occur at the same densities at which Vq minimizes, in accordance with the Basak Cohen theory. The drift mobility in TMS has been measured as a function of pressure to 2500 bar [150]. The observed relative experimental changes of mobility with pressure are predicted quite well by the Basak-Cohen theory however, the predicted value of /i ) is 2.5 times the experimental value at 1 bar and 295 K. In this calculation, the authors used xt to evaluate the mobility. This is reasonable in this case since for liquids, there is little dilference between the adiabatic and isothermal compressibilities. A similar calculation for neopentane showed that the Basak-Cohen theory predicted the Hall mobility of the electron quite well for temperatures between 295 and 400 K [151]. Itoh... 

This theory was tested by Yoffe(Ref 1) by comparing the energies required to initiate NG and PETN with and without entrapped air. Samples prepared without air in the form of a continuous Rim requited much higher energies of initiation than samples with entrapped air. A simple method of including a gas phase in an expl is to spread it as a small annulus on a flat anvil. When this is struck with a flat hammer, the small amt of gas in the center is trapped and compressed. In these experiments the size of the annulus was such that the initial vol of the gas was ca 5 x 10"4 cc. A more detailed description of the theory of adiabatic compression and methods of testing are gi ven in Ref 2... 

CARNOT CYCLE. An ideal cycle or four reversible changes in the physical condition of a substance, useful in thermodynamic theory. Starting with specified values of die variable temperature, specific volume, and pressure, the substance undergoes, in succession, an isothermal (constant temperature) expansion, an adiabatic expansion (see also Adiabatic Process), and an isothermal compression to such a point that a further adiabatic compression will return the substance to its original condition. These changes are represented on the volume-pressure diagram respectively by ub. he. ctl. and da in Fig. I. Or the cycle may he reversed ad c h a. 

Theoretical predictions for the isothermal compressibility can obviously be obtained from any theory of the equation of state. If, in addition, data for the specific heat are supplied, the adiabatic compressibility can be derived in the same way. Thus the compressibility can be derived from the vinual expansion of the equation of stale which expresses the ratio PV/RT in a power series in the density, the coefficients being related to the interactions of groups of two, three, etc., particles. 

In the case of a process in a closed volume, combustion products which appeared earlier also had, at the moment of formation, the same temperature Tc. however, after this, due to adiabatic compression during the pressure increase in combustion, the temperature of the gases grew. Thus, Texpl actually occurs only as an average quantity—cf. Mache s theory of explosion of a gas mixture in a closed volume [12]. 

In the above example of the combustion of carbon monoxide the time found experimentally in which the pressure reaches a maximum is 0.4 sec the combustion time of a single element according to an estimate based on the theory of flame propagation [11, 12], is less than 0.001 sec. The loss of heat in 0.4 sec is considerable the increase in pressure takes place so slowly that the state of the gas does not change adiabatically upon compression, and despite the compression each element cools after combustion. However, in 0.001 sec the loss of heat is negligibly small and each element in burning does attain the temperature Tp. 

It is very interesting that large molecules, such as proteins, behave as particles and can be described by ultrasound scattering theory in the very long wavelength limit. Scattering theory is vindicated by the precise and repeatable nature of the data available for these molecules. In particular, it should be pointed out that the molecular adiabatic compressibility is insensitive to individual bonds and is the sum of the intrinsic compressibility of the primary structure (the amino acid sequence), cavities in the tertiary structure and interaction with the solvent (Kharakoz and Sarvazyan, 1993). Velocity and attenuation spectroscopy relate to different aspects of the molecule... 

The classical theory of detonation is formulated in the ZND model (Zeldovich, Von Neumann, Doring) assuming that the propagation mechanism of a detonation is ignition by shock-induced adiabatic compression. 

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