Experimental measurement of the electrical conductivity of pyroxenite at high temperature and high pressure under different oxygen fugacities

Electrical conductivities of pyroxenite were measured between frequencies of 10^?1 and 10⁶ Hz in a multi-anvil pressure apparatus using different solid buffers (Ni+NiO, Fe+Fe₃O₄, Fe+FeO and Mo+MoO₂) to stabilize the partial pressure of oxygen. The temperature ranged from 1073 to 1423 K (800 to 1200 °C) and the pressure from 1.0 to 4.0 GPa. We observe that: (1) the electrical conductivity (σ) of pyroxenite depends on frequency; (2) σ tends to increase with rising temperature (T), and Log σ and 1/T obey a linear Arrhenius relationship; (3) under control of the buffer Fe+Fe₃O₄, σ tends to decrease with rising pressure, nevertheless the activation enthalpy tends to increase. For the first time we have obtained values for the activation energy and activation bulk volume of the main charge carriers, which are (1.60±0.07) eV and (0.05±0.03) cm³/mol, respectively; (4) for a given pressure and temperature, σ tends to rise with increased oxygen fugacity, whereas the activation enthalpy and preexponential factor tend to decrease; and (5) the behaviour of the electrical conductivity at high temperature and high pressure can be reasonably interpreted by assuming that small polarons provide the dominant conduction mechanism in the pyroxenite samples.     

Addition of multiwalled carbon nanotube and graphene nanosheet in cobalt oxide film for enhancement of capacitance in electrochemical capacitors

In order to enhance the capacitance of electrochemical capacitors, multiwalled carbon nanotubes (MWCNTs) and graphene nanosheets (GNS) were added to cobalt oxide (Co₃O₄) paste. The composite film based on Co₃O₄/MWCNT/GNS (95:4:1 wt%) exhibited a capacitance of 294 F/g while the capacitance of Co₃O₄/MWCNT (95:5 wt%) and pure Co₃O₄ film is 205 and 163 F/g, respectively. The enhanced capacitance of Co₃O₄/MWCNT/GNS composite film was attributed to the electrochemical contributions of the Co₃O₄ nanoparticle attached to the GNS as well as their significantly increased specific surface areas by MWCNTs. Furthermore, the composite films showed faradaic redox capacitive behavior to double-layer capacitive behavior due to the different nanostructures of the composites.     

Size effects on tensile and fatigue behaviour of polycrystalline metal foils at the micrometer scale

Tensile and fatigue properties of as-rolled and annealed polycrystalline Cu foils with different thicknesses at the micrometer scale were investigated. Uniaxial tensile testing results showed that with decreasing foil thickness the uniform elongation decreases for both as-rolled and annealed foils, whereas the yield strength and ultimate tensile strength increase for as-rolled foils, but decrease for the annealed foils. For both the as-rolled or annealed foils, bending fatigue resistance decreases with decreasing the foil thickness. Deformation and fatigue damage behaviour of the free-standing foils were characterised as a function of foil thickness. In addition, the fatigue strength of various small-scale Cu foils was compared to understand the physical mechanisms of size effects on mechanical properties of the metallic material at micrometer scales.     

激光产生温稠密物质的微观动力学过程及状态诊断

随着大型激光装置的建立和精密测量技术的发展,强激光与固体相互作用成为实验室产生温稠密物质的一个重要手段。温稠密物质的结构复杂性、瞬态性和非平衡性给理论建模和实验测量带来了巨大挑战。本文系统介绍了激光产生温稠密物质的实验手段和理论模拟方法方面的重要进展,分析了其中的电子激发动力学、电子-离子能量弛豫过程、离子动力学等物理过程,总结了温稠密物质状态诊断的实验技术和理论方法,并论述了激光产生温稠密物质的发展趋势。     

HgCdTe薄膜的输运特性及其应力调控

窄禁带直接带隙半导体材料碲镉汞(Hg1–xCdxTe)是一种在红外探测与自旋轨道耦合效应基础研究方面都具有重要应用意义的材料.本文对单晶生长的体材料Hg0.851Cd0.149Te进行阳极氧化以形成表面反型层,将样品粘贴在压电陶瓷上减薄后进行磁输运测试,在压电陶瓷未加电压时观察到了明显的SdH振荡效应.对填充因子与磁场倒数进行线性拟合,获得样品反型层二维电子气的载流子浓度为ns=1.25×10^16m^-2.在不同磁场下,利用压电陶瓷对样品进行应力调控,观测到具有不同特征的现象,分析应是样品中存在二维电子气与体材料两个导电通道.零磁场下体材料主导的电阻的变化应来源于应力导致的带隙的改变;而高场下产生类振荡现象的原因应为应力导致的二维电子气能级的分裂.     

Applications of Markov spectra for the weighted partition network by the substitution rule

The weighted self-similar network is introduced in an iterative way. In order to understand the topological properties of the self-similar network, we have done a lot of research in this field.Firstly, according to the symmetry feature of the self-similar network, we deduce the recursive relationship of its eigenvalues at two successive generations of the transition-weighted matrix.Then, we obtain eigenvalues of the Laplacian matrix from these two successive generations.Finally, we calculate an accurate expression for the eigentime identity and Kirchhoff index from the spectrum of the Laplacian matrix.     

无绝缘高温超导双饼线圈的瞬态电热特性分析

无绝缘高温超导线圈具有良好的电热稳定性和机械紧凑性,但其充电过程中却有明显的磁场延迟现象。为详细了解无绝缘高温超导线圈励磁过程的瞬态特性,建立了无绝缘高温超导线圈的同轴圆环等效电路模型。通过绕制一个670匝的无绝缘高温超导双饼线圈,在液氮温度下进行不同充电速率的励磁实验,初步验证了等效电路模型的正确性。基于该模型,针对线圈励磁过程的充电和恒流阶段,仿真得到了线圈各匝的径向电流分布规律和电热损耗特性。     

XGS—12型高速电影摄影机

XGS-12型摄影机是西安光机所新近推出的又一种16mm棱镜补偿式高速电影摄影机,其画幅尺寸为7.5×10.4mm~2时的最高拍摄频率为11000fps。该机性能优异,附件齐全,本文对该机将从光学系统摄影机和电控制系统三个部分加以介绍。