Penetration of long strikers under hydrodynamic conditions with allowance for the material compressibility

The influence of compressibility on the fast penetration of long metallic strikers into different barriers at interaction speeds of up to 10 km/s is investigated. The investigation is based on the hydrodynamic theory of penetration. Compressibility-related corrections to Lavrent’ev’s rate and depth of penetration, which were obtained in terms of the concept representing the penetration process as collisions of ideal incompressible liquid jets, are estimated. The variation of these corrections with the interaction speed under subsonic and supersonic conditions is analyzed. If the compressibilities of the striker and barrier materials differ radically, the penetration depth disagrees with that predicted by the hydrodynamic theory (assuming the incompressibility of the materials) by 10–15%.     

Synthesis of ZnO films with a special texture and enhanced field emission properties

ZnO films with special textures are fabricated on Mo-coated Al₂O₃ ceramic substrates by the catalyst-free electron beam evaporation method, and the as-deposited films are treated by hydrogen plasma. It is found that the surface morphologies of the films are changed significantly after hydrogen plasma treatment and that the films consist of vertically standing and intersecting nanosheets. A lower turn-on field of 1.2 V/μm and an enhanced current density ～0.11 mA/cm² at 2.47 V/μm are achieved. The low threshold field and the high emission current density are attributed primarily to the unique shape and smaller resistivity of the ZnO nanosheet films.     

硼氢协同掺杂Ib型金刚石大单晶的高温高压合成与电学性能研究

在压力6.0 GPa和温度1600 K条件下, 利用温度梯度法研究了(111)晶面硼氢协同掺杂Ib型金刚石的合成. 傅里叶红外光谱测试表明: 氢以sp³杂化的形式存在于所合成的金刚石中, 其对应的红外特征吸收峰位分别位于2850 cm^-1和2920 cm^-1处. 此外, 霍尔效应测试结果表明: 所合成的硼氢协同掺杂金刚石具有p型半导体材料特性. 相对于硼掺杂金刚石而言, 由于氢的引入导致硼氢协同掺杂金刚石电导率显著提高. 为了揭示硼氢协同掺杂金刚石电导率提高的原因, 对不同体系进行了第一性原理理论计算, 计算结果表明其与实验结果符合. 该研究对金刚石在半导体领域的应用有重要的现实意义.     

A new nanocluster carbyne-based material synthesized under high pressure

The DC and AC conductivities and the magnetoresistance and thermopower of carbyne samples were studied over the temperature range 1.8–300 K at frequencies 10 MHz–1 GHz. It was established that a variation in the fraction of sp ² bonds in carbynes induces a transition from one-to two-and then to three-dimensional conduction. The physical properties of the new carbyne-based solids may be understood within the model treating carbyne as a nanocluster material based on linear carbon chains and having a characteristic cluster size of 1 to 10 nm.     

A study of the properties of erythrocytes with polarized light under hypotonic conditions

We consider the application of polarized radiation to the study of the properties of blood and erythrocyte suspensions, including the case of disturbance of the osmotic balance in the erythrocyte-surrounding-medium system. We study experimentally erythrocyte suspensions prepared by diluting whole donor blood with autoplasma, serum, and NaCl aqueous solutions of different concentrations. The Stokes parameters of scattered radiation have been measured with a Stokes polarimeter using a He-Ne laser as a source of linearly or elliptically polarized radiation (λ = 0.63 μm). We show that, upon illumination of erythrocyte suspensions with linearly or circularly polarized radiation, the Stokes parameters of the scattered radiation are highly sensitive to changes in the shape and size of erythrocytes upon hypotonic swelling.     

Correlation of superconductivity with material properties

A simple model is used to study the trends of the electron-phonon interaction parameter γ.     

Wave properties of a methyl group under ambient conditions

Liquid-phase NMR studies on hindered rotation of methyl group in a 9-methyltriptycene derivative are reported where the standard, classical jump model of the methyl dynamics proves inadequate. On the other hand, accurate reproduction of the observed NMR line shape effects is afforded by the use of a recent quantum mechanical model in which the relevant methyl dynamics are described in terms of two quantum rate (coherence-damping) processes, characterized by two different rate constants. For ambient temperatures, such a direct evidence of the quantum nature of a rate process generally believed to be classical seems to have no precedence in the literature.     

Development of a new amblyopia-training device with polarizing films used under binocular conditions

Optical Review - We developed an amblyopia-training device, which can be used easily and inexpensively under binocular conditions with polarizing films. The device uses two polarizing films: one is...     

Mechanical properties of flame-retardant polypropylene compositions

The application of pentabromobenzyl acrylate monomer (PBB-MA) extrusion polymerized in ethylene-propylene-diene monomer (EPDM) terpolymer allows the production of flame-retardant polypropylene (PP) with very high impact and elongation at break and good resistance to thermal aging.

The explanation of the high level of mechanical properties and of thermal aging resistance of PP/(EPDM/PBB-MA) is based on the hypothesis of EPDM/PBB-MA graft polymerization on EPDM double bonds, resulting in PP amor-phization and in specific morphology: better dispersion of flame retardant (FR) in PP and in EPDM and the formation of a honeycomb structure of EPDM/PBB-MA particles.

Addition of either EPDM/PBB-MA or EPDM + PBB-PA to glass-fiber-reinforced polypropylene (GFR PP) makes feasible the combining of two modes of PP toughening: via glass fiber reinforcement and via EPDM-based particle dispersion in PP matrix.     

Effective properties of multicomponent simultaneous maskers under conditions of uncertainty

When more than one sinusoid is used as a masker, more masking is observed than would be predicted by a simple combination of their individual effects. This masking is dramatically increased when the masker components vary in frequency and intensity with each presentation. These studies manipulated several masker parameters under conditions of high masker uncertainty, examining the effect of excluding critical-band components, fixing or randomizing component amplitudes and frequencies, and narrowing the frequency range of the components. The signal was always a 200-ms, 1000-Hz sinusoid, presented simultaneously with the 200-ms masker. Removing critical-band components reduced the amount of masking, but considerable masking remained that appears to be nonperipheral in origin. Fixing masker frequencies across the two intervals of a trial greatly reduced the masking observed, whereas fixing masker amplitudes had no effect. Reducing the frequency range from 5000 to 2700 Hz generally increased the masking observed, but appeared to depend on other masker parameters. Summaries across ten listeners show individual differences that are resistant to extensive training. It is difficult to account for most of the masking observed in terms of masker energy falling near the region of the signal.     

Magnetic structural properties in Alnico alloys under equilibrium conditions and under magnetization

Magnetic structure is studied as a function of the orientation of the easy magnetic axis with respect to ac (4 Hz) and dc magnetizing fields in specimens with various coercivities. Alternating boundary polarity was observed, and a system of magnetization distribution in the equilibrium state is given. Domain width in equilibrium states is measured for various angles of the demagnetizing field. Upon magnetization at various angles, various structural change processes were observed, which have been conditionally divided into four distinct types.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 68–73, August, 1975.     

Electrical conduction properties of rare earth orthophosphates under reducing conditions

Electrical conduction properties of Sr-doped PrPO₄, NdPO₄ and SmPO₄ with the monazite structure were investigated at 500–925 °C under H₂/H₂O reducing conditions. From H/D isotope effects and p(H₂)-dependencies of the conductivities, it was found that the materials dominantly conducted protons under the wet reducing conditions although the materials slightly showed n-type electronic conduction at higher temperatures. Based on p(H₂O) and p(H₂)-dependencies of the conductivities, defect structures of the materials under the reducing conditions were discussed. As a result, it was considered that major positive defects were oxygen deficits at higher temperatures and protons at lower temperatures.     

Thermo-physical properties of body-centered cubic iron-magnesium alloys under extreme conditions

Using density functional theory formulated within the framework of the exact muffin-tin orbitals method, we investigate the thermo-physical properties of body-centered cubic (bcc) iron-magnesium alloys, containing 5 and 10 atomic % Mg, under extreme conditions, at high pressure and high temperature. The temperature effect is taken into account via the Fermi-Dirac distribution of the electrons. We find that at high pressures pure bcc iron is dynamically unstable at any temperature, having a negative tetragonal shear modulus (C^′). Magnesium alloying significantly increases C^′ of Fe, and bcc Fe-Mg alloys become dynamically stable at high temperature. The electronic structure origin of the stabilization effect of Mg is discussed in detail. We show that the thermo-physical properties of a bcc Fe-Mg alloy with 5% Mg agree well with those of the Earth’s inner core as provided by seismic observations.     

Ni-Ge共掺杂下对AgSnO2触头材料性能的第一性原理分析

AgSnO₂触头材料是一种环保型低压触头材料,由于具备良好的耐电弧以及抗熔化焊能力,广泛适用于接触器,继电器以及低电压断路器中.采用金属元素Ni与Ge共掺杂的方式对SnO₂的导电性能进行改良.运用CASTEP软件对元素掺杂前后的SnO₂各项性能进行了仿真试验.结果表明：金属元素Ni与Ge单掺杂和共掺杂与本征SnO₂相比,其禁带宽度均会有不同程度的减小,其中Ni-Ge两种元素共掺杂时的禁带宽度值最小,这就表示电子可以更加容易的进行跃迁,其导电性也最好;由弹性常数分析可知,金属元素Ni-Ge共掺杂时材料的弹性最弱,韧性最强.     

The vibration and stability of orthotropic conical shells with non-homogeneous material properties under a hydrostatic pressure

In this paper, the vibration and stability of orthotropic conical shells with non-homogeneous material properties under a hydrostatic pressure are studied. At first, the basic relations have been obtained for orthotropic truncated conical shells, Young's moduli and density of which vary continuously in the thickness direction. By applying the Galerkin method to the foregoing equations, the buckling pressure and frequency parameter of truncated conical shells are obtained from these equations. Finally, carrying out some computations, the effects of the variations of conical shell characteristics, the effects of the non-homogeneity and the orthotropy on the critical dimensionless hydrostatic pressure and lowest dimensionless frequency parameter have been studied, when Young's moduli and density vary together and separately. The results are presented in tables, figures and compared with other works.     

Diagnostics of the acoustic properties of unconsolidated media under natural conditions

Results of experimental studies carried out at the Bezvodnoe test area in 2005 and 2006 are presented. The goal of the studies is to investigate the potentialities of vibration diagnostics of the surface layers of soil under natural conditions. The most attention is given to the problem of measuring the shear modulus of soil and determining the power of seismic acoustic radiation with the help of an impedance method. The results obtained testify to the high sensitivity of the impedance method soil diagnostics and to the possibility of monitoring the variations of soil properties. Sources of nonlinear distortions and the problem of stability of radiation characteristics are also considered. A comparison with theoretical estimates is performed. It confirmed a special role of the contact region as the major source of radiation signal distortions. The results of the study are important for seismoacoustic investigation of the structure of natural media under natural conditions.