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Tensile tests were carried out on carbon fiber high-entropy alloy, carbon fiber aluminum alloy, carbon fiber titanium alloy, and carbon fiber-reinforced composite laminates. Their mechanical properties were investigated at the tensile strain rates of 3·10–3, 1·10–3, and 1·10–4 s–1. Compression tests on carbon fiber high entropy alloy (HEA) and carbon fiber-reinforced composite laminates were carried out at the strain rates of 3·10–3 and 1·10–3 s–1, respectively. Results showed that the carbon fiber high-entropy alloy composite laminate was more elastic than the carbon fiber-reinforced composite laminate at the strain rates of 3·10–3, 1·10–1, and 1·10–4 s–1. Their strength increased by 27, 16, and 10%, and the breaking strength by 18, 12, and 14%, respectively. Compared with the carbon fiber-reinforced composite laminate, the compressive strength of the carbon fiber HEA composite laminate increased by 44 and 29% at the compressive strain rates of 3·10–3 and 1·10–3s–1, respectively. [ABSTRACT FROM AUTHOR]

In this study, three-dimensional non-uniform strain fields and cracking patterns of a clay-rich rock are investigated. Uniaxial compression creep tests are performed on samples drilled in five different orientations with respect to bedding planes. A digital volume correlation method is applied to X-ray micro-tomographic images taken during the creep tests to calculate both full local strain fields and average global strains. Both instantaneous and time-dependent strains, respectively, induced by applied stress and creep mechanism are analysed. Strain heterogeneity inside samples is quantified by calculating strain concentration zones, which are correlated with the presence of stiff inclusions. Cracking patterns of samples are characterized through reconstructed X-ray micro-tomographic images. Correlations between major cracking patterns and strain concentration zones are investigated. [ABSTRACT FROM AUTHOR]

Data on the distribution of 24 species of carabid beetles in Xinjiang Uygur Autonomous Region of China are presented. Twenty taxa are newly recorded from China: Nebria (Eunebria) psammophila Solsky, 1874, N. (Eunebria) picta Semenov, 1891, Calosoma (Caminara) imbricatum deserticola Semenov, 1897, Carabus (Morphocarabus) henningi henningi Fischer von Waldheim, 1817, Scarites (s. str.) cylindronotus Faldermann, 1836, Apotomus testaceus Dejean, 1825, Pterostichus (Platysma) insignicollis (Tschitschérine, 1893), P. (Platysma) planicollis (Tschitschérine, 1899), P. (Plectes) drescheri (Fischer von Waldheim, 1817), P. (Petrophilus) magus magus (Mannerheim, 1825), Pseudotaphoxenus planicollis (Gebler, 1833), Agonum (Olisares) viduum (Panzer, 1796), Mnuphorus sellatus (Gebler, 1843), Cymindis (Arrhostus) andreae Ménétriés, 1832, C. (Menas) miliaris (Fabricius, 1801), C. (Neomenas) antonowi Semenov, 1891, Lebia (Lamprias) festiva festiva Faldermann, 1836, L. (s. str.) trimaculata (Villers, 1789), Brachinus (s. str.) crepitans (Linnaeus, 1758) and B. (Cnecostolus) cruciatus (Quensel, 1806). Two species are recorded for the first time from Xinjiang: Nebria (Eunebria) przewalskii przewalskii Semenov, 1889 and Lebia (Lamprias) punctata Gebler, 1843. Exact distributional data in China are given for the two species: Scarites (s. str.) salinus Dejean, 1825 and Polistichus connexus (Geoffroy, 1758). [ABSTRACT FROM AUTHOR]

In this work, the electronic structure and magnetic coupling properties of Gd doped AlN have been investigated using first-principles method. We found that in the AlN:Gd system, due to the s-f coupling allowed by the symmetry, the exchange splitting of the conduction band is much larger than that of the valence band, which makes the electron-mediated ferromagnetism possible in this material. This property is also confirmed by the energy differences between anti-ferromagnetic and ferromagnetic phase for AlGdN with different concentrations of electrons (holes), as well as by the calculated exchange constants. The result indicates that Gd-doped AlN is a promising candidate for the applications in future spintronic devices. [ABSTRACT FROM AUTHOR]

The Ca1− xSr xFe2As2 (0≤ x≤1) and Ca0.5Sr0.5 Fe2− yCo yAs2 (0≤ y≤0.6) materials were prepared by a solid state reaction method. X-ray diffraction analysis shows that the lattice parameters of Ca1− xSr xFe2As2 decrease continuously with increasing Ca content. Resistivity measurements reveal that the Ca/Sr ratio has a visible influence on the resistivity anomaly associated with the spin-density-wave (SDW) instability. Experimental measurements on Ca0.5Sr0.5Fe2− yCo yAs2 show clear superconducting transitions for Co in range of 0.26≤ y≤0.43; the highest critical transition temperature is found to be at about 17 K. Transmission electron microscopy (TEM) investigations on the superconducting Ca0.5Sr0.5Fe2− yCo yAs2 samples reveal visible inhomogeneous distribution of Sr and Ca elements, which could result in structural distortions and broaden superconducting transitions as observed in our experiments. [ABSTRACT FROM AUTHOR]

The structural and physical properties of the layered Yb2Fe3O7 have been extensively investigated. Transmission electron microscopy (TEM) observations at room temperature reveal the presence of diffuse zigzag-type streaks at 1/3(h h l) running along the c* axis direction, suggesting the presence of a charge ordered state with a shorter coherence length in comparison with that in Lu2Fe3O7. The measurements of magnetization demonstrate that the replacement of Lu3+ by the magnetic Yb3+ ion in this layered system could result in visible effects on the low-temperature magnetic properties: the ferrimagnetic phase transition temperature decreases and an additional magnetic anomaly possibly attributed to antiferromagnetic coupling between Yb and Fe layers appears at around 50 K. Analysis of the dielectric properties shows that the Yb2Fe3O7 material in general has a large dielectric constant of about 5000 at room temperature, and a broader relaxation time distribution in comparison with ErFe2O4. [ABSTRACT FROM AUTHOR]

The crystal structure, mechanical properties and electronic structure of ground state BeH2 are calculated employing the first-principles methods based on the density functional theory. Our calculated structural parameters at equilibrium volume are well consistent with experimental results. Elastic constants, which well obey the mechanical stability criteria, are firstly theoretically acquired. The bulk modulus B, Shear modulus G, Young's modulus E, and Poisson's ratio υ are deduced from the elastic constants. The bonding nature in BeH2 is fully interpreted by combining characteristics in band structure, density of states, and charge distribution. The ionicity in the Be-H bond is mainly featured by charge transfer from Be 2s to H 1s atomic orbitals while its covalency is dominated by the hybridization of H 1s and Be 2p states. The Bader analysis of BeH2 and MgH2 are performed to describe the ionic/covalent character quantitatively and we find that about 1.61 (1.6) electrons transfer from each Be (Mg) atom to H atoms. [ABSTRACT FROM AUTHOR]

Using a first-principles band-structure method and a special quasirandom structure (SQS) approach, we systematically calculate the band gap bowing parameters and p-type doping properties of (Zn, Mg, Be)O related random ternary and quaternary alloys. We show that the bowing parameters for ZnBeO and MgBeO alloys are large and dependent on composition. This is due to the size difference and chemical mismatch between Be and Zn(Mg) atoms. We also demonstrate that adding a small amount of Be into MgO reduces the band gap indicating that the bowing parameter is larger than the band-gap difference. We select an ideal N atom with lower p atomic energy level as dopant to perform p-type doping of ZnBeO and ZnMgBeO alloys. For N doped in ZnBeO alloy, we show that the acceptor transition energies become shallower as the number of the nearest neighbor Be atoms increases. This is thought to be because of the reduction of p- d repulsion. The NO acceptor transition energies are deep in the ZnMgBeO quaternary alloy lattice-matched to GaN substrate due to the lower valence band maximum. These decrease slightly as there are more nearest neighbor Mg atoms surrounding the N dopant. The important natural valence band alignment between ZnO, MgO, BeO, ZnBeO, and ZnMgBeO quaternary alloy is also investigated. [ABSTRACT FROM AUTHOR]

The crystal structure, mechanical properties and electronic structure of ground state BeH2 are calculated employing the first-principles methods based on the density functional theory. Our calculated structural parameters at equilibrium volume are well consistent with experimental results. Elastic constants, which well obey the mechanical stability criteria, are firstly theoretically acquired. The bulk modulus B, Shear modulus G, Young's modulus E, and Poisson's ratio υ are deduced from the elastic constants. The bonding nature in BeH2 is fully interpreted by combining characteristics in band structure, density of states, and charge distribution. The ionicity in the Be-H bond is mainly featured by charge transfer from Be 2s to H 1s atomic orbitals while its covalency is dominated by the hybridization of H 1s and Be 2p states. The Bader analysis of BeH2 and MgH2 are performed to describe the ionic/covalent character quantitatively and we find that about 1.61 (1.6) electrons transfer from each Be (Mg) atom to H atoms. [ABSTRACT FROM AUTHOR]

The structural and physical properties of the layered Yb2Fe3O7 have been extensively investigated. Transmission electron microscopy (TEM) observations at room temperature reveal the presence of diffuse zigzag-type streaks at 1/3(h h l) running along the c* axis direction, suggesting the presence of a charge ordered state with a shorter coherence length in comparison with that in Lu2Fe3O7. The measurements of magnetization demonstrate that the replacement of Lu3+ by the magnetic Yb3+ ion in this layered system could result in visible effects on the low-temperature magnetic properties: the ferrimagnetic phase transition temperature decreases and an additional magnetic anomaly possibly attributed to antiferromagnetic coupling between Yb and Fe layers appears at around 50 K. Analysis of the dielectric properties shows that the Yb2Fe3O7 material in general has a large dielectric constant of about 5000 at room temperature, and a broader relaxation time distribution in comparison with ErFe2O4. [ABSTRACT FROM AUTHOR]