Entropy Increment Research Articles

High vacuum in industry Post-Graduate Study by (Manufacturing course of Professor Georges Doriot at the Harvard Graduate School of Business Administration, 1953). Copyright by Marvin Grossman, et al. Pp. 64

The heat capacity of iron monoarsenide has been determined by adiabatic calorimetry from 5 to 1030 K and by drop calorimetry relative to 298.15 K over the range 875 to 1350 K. A small λ-type transition is observed at TN = (70.95±0.02) K. It is related to the disappearance of a doubly helically ordered magnetic-spin structure on heating. The obviously cooperative entropy increment of transition is only ΔtrsSmoR = 0.021. The higher-temperature heat capacity rises considerably above lattice expectations. Part of the rise is ascribed to low-spin electron redistribution in iron, while the further excess above 800 K presumably arises from a beginning low- to high-spin transition, possibly connected with interstitial defect formation in the MnP-type structure. FeAs melts at about 1325 K with ΔfusHmo = 6180R · K. Thermodynamic functions have been evaluated and the values of Cp, m(T), Smo(T), Hmo(T), and Φmo(T), are 6.057R, 7.513R, 1177R · K, and 3.567R at 298.15 K, and 8.75R, 16.03R · K, and 9.745R at 1000 K.

Theory of the Propagation of Shock Waves from Infinite Cylinders of Explosive

The assumption of energy dissipation at a single shock, formulated in an earlier paper, is employed in the formulation of a pair of ordinary differential equations for peak pressure and shock-wave energy as functions of radial distance from the source for the shock wave produced by an infinite cylinder of explosive along which a stationary detonation wave is traveling with finite velocity. The profile of the wave may be determined by means of an auxiliary integration. The theory takes proper account of the finite entropy increment of the fluid produced by the passage of the shock, and permits the use of the exact Hugoniot curve of the fluid in the numerical integration of the basic equations.

Theory of the Propagation of Shock Waves

A new theory of propagation of one-dimensional shock waves is described. The partial differential equations of hydrodynamics and the Hugoniot relation between pressure and particle velocity are used to provide three relations between the four partial derivatives of pressure and particle velocity, with respect to time and distance from the source, at the shock front. An approximate fourth relation is set up by imposing a similarity restraint on the shape of the energy-time curve of the shock wave and by utilizing the second law of thermodynamics to determine, at an arbitrary distance, the distribution of the initial energy input between dissipated energy residual in the fluid already traversed by the shock wave and energy available for further propagation. The four relations are used to formulate a pair of ordinary differential equations for peak pressure and shock wave energy as functions of distance from the source. The theory takes proper account of the finite entropy increment of the fluid produced by the passage of the shock and permits the use of the exact Hugoniot curve of the fluid in the numerical integration of the basic equations.