Calculation of shock waves in a flow of moist vapor at low pressure

A method is given for calculating oblique shocks in a region of moist vapor, when conditions of phase equilibrium are satisfied in the shock process.     

Thermomolecular pressure difference at low knudsen numbers

The experimental dependence of the thermomolecular pressure difference on the average pressure is found for He, Ne, H₂, and D₂ in the viscous-flow regime (Kn^–1=100–500). The experimental data are compared with analytic expressions in the literature.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 25, No. 3, pp. 456–459, September, 1973.     

Calculation of viscosity of gas mixtures at atmospheric pressure

A method is presented for calculating the viscosity of a multicomponent mixture, based on the use of potential functions with variable parameters (T) and (T). It is shown that the agreement of theory with experiment is good.     

Using split Hopkinson pressure bars to perform large strain compression tests on polyurea at low,intermediate and high strain rates

The strain rate sensitivity of polyurea is characterized using a modified split Hopkinson pressure bar (SHPB) system. The device is composed of a hydraulic piston along with nylon input and output bars. In combination with an advanced wave deconvolution method, the modified SHPB system provides an unlimited measurement time and thus can be used to perform experiments at low, intermediate and high strain rates. A series of compression tests of polyurea is performed using the modified SHPB system. In addition, conventional SHPB systems as well as a universal hydraulic testing machine are employed to confirm the validity of the modified SHBP technique at low and high strain rates. The analysis of the data at intermediate strain rates shows that the strain rate is not constant due to multiple wave reflections within the input and output bars. It is demonstrated that intermediate strain rate SHPB experiments require either very long bars (>20 m) or very short bars (<0.5 m) in order to achieve an approximately constant strain rate throughout the entire experiment.     

The melting pressure of helium-3 at very low temperatures

The melting pressure of³ He at very low temperatures was shown earlier to be determined overwhelmingly by the solid phase. Using an extended solid³He model based on isotropic effective first-neighbor-pair antiferromagnetic and second-neighbor-pair ferromagnetic exchange interactions, the melting process is reinvestigated here. One of its motivating aspects may be said to be tied to its possible use, suggested by us earlier, for the establishment of a thermodynamic temperature scale at very low temperatures. As a consequence of the assumed multineighbor interactions, spin ordering is accelerated and, at the same temperature, the extended-model solid entropy falls below that of the simpler nearest-neighbor-pair interaction model. Equivalently, the spinordering critical transition temperature is raised over that associated with the simpler interaction scheme. The overall result is a decrease in the melting pressure variations at very low temperatures below those arising from the simple solid model. In the absence of a reliable experimental temperature scale at very low temperatures, only a qualified and cursory comparison is justified with recent experimentally estimated melting pressures. Discrepancies arise between theory and preliminary data on the temperature derivatives of the melting pressure or the entropy of the solid at melting. They might be due in part to the tentative experimental temperatures, which appear shifted toward too low temperatures when compared with the theoretical temperature scale implicit in the treatment of the generalized solid model. However, from the viewpoint which accepts the rather preliminary, scarce, very low temperature melting pressure data at face value, failure of the extended exchange model of solid³He at those temperatures must be kept in mind.Work performed under the auspices of the U.S. Atomic Energy Commission.     

A device for high uniaxial compression of single crystal specimens at low temperatures

A design is described with which elastic and sufficiently uniform compression of single-crystal specimens by ～ 0.4 to 0.5% can be achieved at liquid helium temperatures. The provision of a sliding side support for the specimen, which prevents shear deformations arising in the compression process, makes it possible to achieve deformations almost an order of magnitude greater than the limiting elastic deformations possible for free specimens.     

Low pressure polymer precursor for synthesis of diamond at low temperature

Abstracts are not published in this journal     

Low pressure polymer precursor for synthesis of diamond at low temperature

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

Approximate calculation of the ultraviolet radiation of diatomic molecules at low pressure

A method is given of calculating the emission bands of isolated lines for a rigid rotator based on summation of equivalent linewidths. A comparison of this method with the method based on the rotational structure-averaged absorption coefficient is carried out.     

Quantitative analysis of deuterium using laser-induced plasma at low pressure of helium

It was proved that the analysis of deuterium can be conducted using laser-induced plasma spectroscopy. By selecting the appropriate surrounding gas, its pressure, and gating time of the detection system, it was shown that the emission lines of both hydrogen (H(alpha)) and deuterium (D(alpha)), separated by only 0.179 nm, can be fully resolved. A linear calibration curve was also obtained, indicating that this technique has the potential for quantitative analysis of deuterium. The minimum detection limit achieved in this stage of research was estimated to be 50 ppm. We have also shown that this technique can be used as a simple and rapid method for D and H analysis in solid samples.