Use of IR spectroscopy for studying the cross-linking of peroxide melamine-formaldehyde oligomer

Translated from Zhurnal Prikladnoi Spektroskoppi, Vol. 48, No. 3, pp. 449–453, March, 1988.     

High-precision measurements of the compressibility of chalcogenide glasses at a hydrostatic pressure up to 9 GPa

The volumes of glassy germanium chalcogenides GeSe₂, GeS₂, Ge₁₇Se₈₃, and Ge₈Se₉₂ are precisely measured at a hydrostatic pressure up to 8.5 GPa. The stoichiometric GeSe₂ and GeS₂ glasses exhibit elastic behavior in the pressure range up to 3 GPa, and their bulk modulus decreases at pressures higher than 2–2.5 GPa. At higher pressures, inelastic relaxation processes begin and their intensity is proportional to the logarithm of time. The relaxation rate for the GeSe₂ glasses has a pronounced maximum at 3.5–4.5 GPa, which indicates the existence of several parallel structural transformation mechanisms. The nonstoichiometric glasses exhibit a diffuse transformation and inelastic behavior at pressures above 1–2 GPa. The maximum relaxation rate in these glasses is significantly lower than that in the stoichiometric GeSe₂ glasses. All glasses are characterized by the “loss of memory” of history: after relaxation at a fixed pressure, the further increase in the pressure returns the volume to the compression curve obtained without a stop for relaxation. After pressure release, the residual densification in the stoichiometric glasses is about 7% and that in the Ge₁₇Se₈₃ glasses is 1.5%. The volume of the Ge₈Se₉₂ glass returns to its initial value within the limits of experimental error. As the pressure decreases, the effective bulk moduli of the Ge₁₇Se₈₃ and Ge₈Se₉₂ glasses coincide with the moduli after isobaric relaxation at the stage of increasing pressure, and the bulk modulus of the stoichiometric GeSe₂ glass upon decreasing pressure noticeably exceeds the bulk modulus after isobaric relaxation at the stage of increasing pressure. Along with the reported data, our results can be used to draw conclusions regarding the diffuse transformations in glassy germanium chalcogenides during compression.     

Numerical analysis of feasibility of the neutral stability conditions for shock waves in the problem of a van der waals gas flow past a wedge

By means of numerical calculations, the question is answered of the feasibility of the conditions of neutral stability for shock waves in the problem of a flow of real gases past a wedge.     

Prediction of higher heating values of plant biomass from ultimate analysis data

For natural plant raw materials and for artificial mixture samples with different lignin content, a comparison between empirical equations for the calculation of higher heating values was carried out relying on the data of ultimate analysis. Selection of tested equations from already known was carried out according to the criteria: equations should be intended for work with plant raw materials; the range of used materials should be rather wide; the data on element content (C, H, N, S) obtained experimentally and in routine mode, as well as ash value of the material, should be variables; ambiguous equations should be excluded. Only 8 from more than 150 published equations were chosen for testing, and 3 of these provide calculation of higher heating values with a less than 5–6% deviation from reference values obtained by means of combustion in an adiabatic calorimeter.     

High-Precision Studies of the Compressibility and Relaxation of g-As2S3 Glasses at High Hydrostatic Pressures up to 8.6 GPa

Journal of Experimental and Theoretical Physics - The high-precision volume measurements of the g-As2S3 glass have been performed at high hydrostatic pressures up to 8.6 GPa, and room temperature....     

Propagation of a Surface Magnetoelastic Wave in a Ferromagnet Near the Orientation Phase Transition

Physics of the Solid State - The frequency dependences of the group velocity and the damping of a magnetoelastic surface wave have been studied at various values of an external magnetic field and...     

Base Drag Reduction and Generation of the Lifting Force Using a Microwave Discharge in a Supersonic Flow

Technical Physics - We report on the results of experimental investigation of forced action of a deeply subcritical microwave discharge initiated in a quasi-optical electromagnetic beam on bodies...     

Special features of electron beam-excited XeCl-laser generation

The results of experimental investigations on generation in Ar(Ne): Xe: CCl₄(HCl) mixtures at excitation by an electron beam are given. It is shown that the use of CCl₄ and HCl with an Ar buffer gas gives equal radiative energies and efficiencies and ā change of Ne for Ar causes a change in generation spectrum. The special features of XeCl-laser generation are discussed.