Medium-range order in cesium borate glasses probed by double-resonance NMR

Rotational-echo double-resonance NMR is used to probe the proximity of Cs+ network modifiers to network-forming boron in binary cesium borate glasses. Low- and high-alkali glasses show distinctly different dephasing curves, which indicate preferential association of Cs+ with four-co-ordinate boron ([4]degrees )B) at low-alkali contents only. Different [4]B sites within a given glass appear to be subject to the same 133Cs dipolar field, thus placing constraints on the possible assignments of multiple tetrahedral boron peaks to different types of medium-range order and guiding future structural modeling studies.     

Charge state of ions in liquid metal field ion sources

The post-ionization model of field evaporation is shown to be consistent with observations of singly and doubly charged ions in liquid metal field ion sources. The model can be used to estimate the field strength at the apex of the Taylor cone which is found to be 1.9–2.0 V/Å for a Ga source. Experiments to test the post-ionization model and to determine the apex field strength more accurately are suggested. A possible method of obtaining ～μA currents of highly charged ions, e.g. Zr⁴⁺, Ta⁴⁺, Ga³⁺, As³⁺, is proposed.     

Medium-range structural order in liquid Ni20Al80 alloy: Experimental and molecular dynamics studies

In this Letter, structural properties of liquid Ni₂₀Al₈₀ have been studied through molecular dynamics (MD) simulations, and results agree well with X-ray experiments. The prepeak in the structure factor manifests the existence of medium-range structural order (MRSO) in liquid Ni₂₀Al₈₀. Analyses in MRSO reveal the dominance of ideal icosahedra and defective icosahedra which, furthermore, form clusters and share common atoms.     

On the structure of quenched condensed germanium-noble metal films

Electron diffraction patterns of quenched condensed pure Ge and Ge-noble metal films with concentrations of Cu of Au between 23 at-% and 60 at-% are taken directly after the condensation at 4.2 K and during annealing up to 330 K. The changes of the radii of the first and second diffraction rings, the annealing behaviour and the change in residual resistance point to the fact that a changed short range order more or less similar to that of liquid Ge is responsible for the metallic behaviour and superconductivity.     

Solar-assisted liquid metal MHD power generation: A state of the art study

The research and development of LMMHD energy conversion (EC) systems which started in the 1960s has already come a long way and is heading towards commercialization. Design and development of such systems has to deal with a number of questions relating to single- and two-phase flows of molten metals, including different patterns of two-phase flow, interphase, phenomena, heat transfer, performance of LMMHD components and compatibility of liquid metals with other fluids and with confinement materials. Liquid metal MHD (LMMHD) power conversion systems proposed many years ago are gaining increasing attention in their various proposed modes, consisting of single-phase or two-phase fluid flow for a wide range of heat sources, e.g. solar energy, waste heat, nuclear energy, etc.Liquid metal MHD (LMMHD) power systems have been recently proposed for direct electrical energy conversion of low grade thermal sources of energy, like solar energy. Solar-powered LMMHD power generation systems are very attractive regarding efficiency and cost per unit of installed power. Theoretical and experimental investigations carried out in the various aspects of these systems are presented. A state of the art review of activities in the solar-powered LMMHD power systems field which have taken place so far is described here.     

Short-range order in metal alloys

Research on Short-range order presently develops along many lines [1].Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 40–52, August, 1976.     

Anisotropic vortex plasticity in the liquid state of YBa2Cu3O7: evidence for quenched c-axis vortex correlation length

A generalized methodology, based on anisotropic angular dependent magnetoresistance measurements, is presented to deconvolute the contributions to the vortex activation energy (i.e., plastic and pinning energies) in the vortex liquid state of high temperature superconductors. Experimental evidence is given for the appearance of a partially entangled liquid vortex state in YBa 2Cu 3O (7) when random quenched and correlated disorders compete, as in twinned melt textured YBa 2Cu 3O (7) quasisingle crystals with Y 2BaCuO (5) precipitates. The hallmark of this new phase is a quench of the c-axis vortex correla-tion length.     

Glassy liquid crystals Observation of a quenched twisted nematic

A twisted nematic liquid crystalline layer has been rapidly solidified by exposure to liquid nitrogen. The resultant glass retained the macroscopic and microscopic liquid crystalline order.     

��ʪ�Լ��ų���Һ̬�������ɱ���Ĥ������״̬��Ӱ��

通过数值模拟及实验研究了润湿性及磁场对液态金属膜流流动状态的影响.首先,通过数值模拟研究了润湿性对膜流流动状态的影响.结果表明,当润湿性不好时,液态金属膜流容易发展为溪状流而不能完全覆盖底壁,入口膜厚较薄时更易发展为溪状流;在入口膜厚及其它情况相同时,密度越小越易发展为溪状流.其次,研究了磁场对膜流流动状态的影响.结果表明,槽道与流体润湿性不好时,有磁场情况下液态金属膜流覆盖底壁的区域较无磁场时增加,强磁场对膜流的湍流有抑制作用.最后,液态金属膜流实验结果表明,润湿性不好时,镓铟锡合金膜流容易收缩发展为溪状流,这与数值模拟的结果是一致的.上述研究结果对磁约束聚变堆液态第一壁的设计具有指导意义.     

润湿性及磁场对液态金属自由表面膜流流动状态的影响

通过数值模拟及实验研究了润湿性及磁场对液态金属膜流流动状态的影响。首先,通过数值模拟研究了润湿性对膜流流动状态的影响。结果表明,当润湿性不好时,液态金属膜流容易发展为溪状流而不能完全覆盖底壁,入口膜厚较薄时更易发展为溪状流;在入口膜厚及其它情况相同时,密度越小越易发展为溪状流。其次,研究了磁场对膜流流动状态的影响。结果表明,槽道与流体润湿性不好时,有磁场情况下液态金属膜流覆盖底壁的区域较无磁场时增加,强磁场对膜流的湍流有抑制作用。最后,液态金属膜流实验结果表明,润湿性不好时,镓铟锡合金膜流容易收缩发展为溪状流,这与数值模拟的结果是一致的。上述研究结果对磁约束聚变堆液态第一壁的设计具有指导意义。     

Incompressible paired hall state, stripe order, and the composite fermion liquid phase in half-filled landau levels

We consider the two lowest Landau levels at half filling. In the higher Landau level (nu = 5/2), we find a first-order phase transition separating a compressible striped phase from a paired quantum Hall state, which is identified as the Moore-Read state. The critical point is very near the Coulomb potential and the transition can be driven by increasing the width of the electron layer. We find a much weaker transition (either second-order or a crossover) from pairing to the composite fermion Fermi-liquid behavior. A very similar picture is obtained for the lowest Landau level, but the transition point is not near the Coulomb potential.     

Long-range order in smectic liquid crystals

The instability of the long-range positional order in smectic A and C liquid crystals under thermal fluctuations is discussed, along with the nematic-smectic A phase transition. The correlation function of the density fluctuations is calculated. It is shown that the long-range orientational order of a layered structure is stable.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 32–36, August, 1978.     

Microstructure of rapidly quenched nickel-enriched TiNi binary alloys in the initial state and after annealing

The microstructure of shape-memory melt-spun TiNi binary alloys of nonstoichiometric composition in the initial state and after annealing has been studied for the first time by transmission electron microscopy and X-ray diffraction in a wide temperature range.