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The distribution of valence electrons in metals usually follows the symmetry of the underlying ionic lattice. Modulations of this distribution often occur when those electrons are not stable with respect [...]

This paper presents a weathering test apparatus developed for testing the deformation and shear strength behavior of rockfill materials for high dams under coupling actions of drying/wetting cycles, cooling/heating cycles, and vertical loads. The apparatus was integrated with a vertical load unit, a lateral shear unit, a drying/wetting circulation unit, and a cooling/heating circulation unit. A cell was designed to perform direct shear tests under normal pressures up to 5.5 MPa after long-term weathering associated with wide variations in temperature and moisture content. It accommodates specimens 150 mm in diameter and 150 mm in height. The related experimental procedures and calibration of the device are discussed. Results of tests performed on an argillaceous siltstone used as the rockfill material for a 261.5 m high dam are presented in order to highlight the features of the apparatus and the weathering effects on soft rock. [ABSTRACT FROM AUTHOR]

Abstract: With the photovoltaic effect and the converse piezoelectric effect, the lanthanum-modified lead zirconate titanate (PLZT) actuator can transform the narrow-band photonic energy to mechanical strain/stress—the photodeformation effect. This photodeformation process can be further used for non-contact precision actuation and control in various structural, biomedical and electromechanical systems. Although there are a number of design configurations of distributed actuators, e.g., segmentation and shaping, been investigated over the years, this study is to explore a new actuator configuration spatially bonded on the surface of shell structures to enhance the spatial modal controllability. A mathematical model of a new multiple degree-of-freedom (multi-DOF) photostrictive actuator configuration is presented first, followed by the photostrictive/shell coupling equations of a cylindrical shell structure laminated with the newly proposed multi-DOF distributed actuator. Distributed microscopic photostrictive actuation and its contributing components of a one-piece actuator and the multi-DOF actuator are evaluated in the modal domain. Effects of shell''s curvature and actuator''s size are also evaluated. Parametric analyses suggest that the new multi-DOF distributed actuator, indeed, provides better performance and control effect to shell actuation and control. This multi-DOF configuration can be further applied to actuation and control of various shell and non-shell structures. [Copyright &y& Elsevier]

In order to study the effect of densification due to weathering on the strength behavior of soft rocks, this paper presents results of consecutive weathering and direct shear tests performed on an argillaceous siltstone. A specimen prepared with fresh argillaceous siltstone first underwent combined water and temperature variations under various stresses. Densification in weathering-related physical and mechanical conditions was indicated by measured dry densities. Then the weathered specimen was subjected to direct shear without remolding. The effect of densification during weathering on the shear strength behavior obtained from the subsequent direct shear tests was discussed. The study highlights that: (1) Densification during weathering is significant at stress values greater than 200 kPa. (2) Weathering leads to a 44% strength reduction of the fresh material with a stress of 50 kPa. (3) Weathering induced densification with a stress of 1400 kPa enhances the shear strength of the fresh material up to 259%. [ABSTRACT FROM AUTHOR]

Highlights: [•] Incorporation of Cu3SbSe4 in β-Zn4Sb3 can yield reduction of k and enhancement of PF. [•] ZT=1.23 is achieved at 648K for f(Cu3SbSe4)/β-Zn4Sb3 with f =15 vol.%. [•] Second phase of larger S can improve the thermoelectric performance of the host. [ABSTRACT FROM AUTHOR]

Abstract: Here we apply high resolution angle-resolved photoemission spectroscopy (ARPES) using a wide excitation energy range to probe the electronic structure and the Fermi surface topology of the Ba1− x K x Fe2As2 (T c =32K) superconductor. We find significant deviations in the low energy band structure from that predicted in calculations. A set of Fermi surface sheets with unexpected topology is detected at the Brillouin zone boundary. At the X-symmetry point the Fermi surface is formed by a shallow electron-like pocket surrounded by four hole-like pockets elongated in Γ−X and Γ−Y directions. [Copyright &y& Elsevier]

Abstract: YBa2Cu4O8 is a stoichiometric oxide superconductor of T c∼80K. Unlike YBa2Cu3O7− δ , this compound is free from oxygen vacancy or twin formation and does not have any microscopic disorder in the crystal. Doping with Ca raises its T c to 90K. The compound is a promising superconductor for technological application. Up to now, single crystals have not been grown without using specialized apparatus with extremely high oxygen pressure up to 3000bar and at over 1100°C due to the limited range of reaction kinetics of the compound. This fact has delayed the progress in the study of its physical properties and potential applications. We present here a simple growth method using KOH as flux that acts effectively for obtaining high-quality single crystals in air/oxygen at the temperature as low as 550°C. As-grown crystals can readily be separated from the flux and exhibit a perfect orthorhombic morphology with sizes up to 0.7×0.4×0.2mm3. Our results are reproducible and suggest that the crystals can be grown using a conventional flux method under ambient condition. [Copyright &y& Elsevier]

Abstract: We have performed 75As nuclear magnetic resonance measurements on a single crystal of the hole-doped superconductor Ba0.72K0.28Fe2As2 (T c =31.5K). The spin–lattice relaxation rate 1/T 1 decreases below T c with no coherence peak and shows a step-wise variation at low temperatures, which is indicative of multiple superconducting gaps. In the normal state, we find that Fe antiferromagnetic spin fluctuations are anisotropic. [ABSTRACT FROM AUTHOR]