Equation of state of fluid nD2 from P-V-T and ultrasonic velocity measurements to 20 kbarSound velocity and the equation of state of N2 to 22 kbarThe molar volume V and ultrasonic velocity u of fluid n-H2 were measured simultaneously in a piston-<:ylinder apparatus over the range 75 < T < 307 K and 2 < P < 20 khar. An equation of state of the Benedict type was formulated to reproduce the approximately 2000 experimental data sets of V and u within an average deviation of 0.7%. Values of the thermal expansion, compressibility, and heat capacity were derived. The equation was extrapolated beyond its experimental limits to make comparisons with existing static measurements at low pressure and with dynamic experiments and calculations at ultrahigh pressure. This is the first comprehensive high pressure study of the properties of fluid hydrogen, a substance that should prove useful in energy related research. the parameters of which are made consistent with those in the thermodynamiC equationCp by minimizing the sum S of n sets of experimental points in the following double-process least-squares fitting routine:The reCiprocal sound velocity l/u is used in Eqs. (2) and (3) because its P and T dependence is similar to that of V. The quantities V and 1/u are measured with
We devised an apparatus and technique for loading diamond-anvil cells with gases at high pressure. Cells were filled quickly and conveniently at room temperature with helium and hydrogen isotopes to initial densities exceeding those of the normal liquids. We report preliminary values of 4He and D2 melting points based on the ruby pressure scale and compare them with extrapolations from our earlier melting curves measured to 20 kbar in a piston-cylinder device. Our filling procedure now makes it possible to use 4He as a pressure medium in diamond cells. The technique is also useful for loading cells with gaseous mixtures.
Passive and active damping in a large space structure (LSS) is important in terms of performance under a dynamic load. Structural damping mostly arises as the result of many energy dissipation mechanisms acting in a system. The purpose of this paper is to present the spectrally formulated finite element analysis for vicsoelastically damped LSS. Using a fractional derivative model, the non-linear damping characteristics of a viscoelastic material have been modelled. The proposed method is then been extended to derive the dynamic response of a large truss structure using a computer program.
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