Wave impedance of W-Mo system composite

W-Mo composites with different mass fractions of W and Mo were prepared at 1473 K by Spark Plasma Sintering technique. The transverse and longitudinal wave velocities of the samples were accurately measured using the ultrasonic pulse echo overlap method, and the wave impedance values of the samples were then calculated. The results show that W-Mo system composites are of nearly full dense and can be regarded as a mechanical mixture system. The ideal mixture model was adopted to estimate the wave impedance of W-Mo composites. Comparisons with the experimental data demonstrate that the suggested model is sufficiently accurate to predict the wave impedance of W-Mo composites.     

Morphological segmenting and neighborhood pixel-based locality preserving projection on brain fMRI dataset for semantic feature extraction: an affective computing study

Two specific chemical receptive fields of brain, namely the amygdala and the orbital-frontal cortex, are related to valence and arousal in medical experiments. Functional magnetic resonance imaging (fMRI), which is a noninvasive, repeatable, and atomical tool for medical imaging in clinic system, was widely used in affective computing; however, it faces its dataset processing difficulty for dimensional reduction as well as for decreasing the computational complexity. In addition, features extraction from those de-dimensionality datasets is a challenging issue. The current work solved the de-dimensionality issue by using some preprocessing algorithms including clustering, morphological segmenting, and locality preserving projection. In order to keep useful information in fMRI dataset for reduction process, improved neighborhood pixel-based locality preserving projection (NP-LPP) algorithm was addressed and continuously for feature extraction operating using Otsu weighted sum of histogram. Furthermore, a modified covariance power spectral density (MC-PSD) separately in an fMRI Valence–Arousal experiments was measured. The results were analyzed and compared with affective norms English words system. The experiments established that the proposed methods of NP-LPP effectively simplified high complexity of fMRI, and Otsu weighted sum of histogram exhibited superior performance for features extraction compared to the MC-PSD through the calculation root mean standard error. The current proposed method provided a potential application and promising research direction on human semantic retrieval through medical imaging dataset.

     

W热力学性质和弹性性质的第一性原理研究

使用第一性原理方法结合准谐近似理论研究了立方结构钨的热力学性质,包括平衡体积V、体弹模量B0、线膨胀系数α、熵S、振动自由能F、等压热容CP和等容热容CV随温度的变化关系。在计算体系的线膨胀系数、熵、振动自由能、等压热容和等容热容时考虑了热电子和热振动对自由能的贡献。计算结果表明：考虑热电子对自由能贡献后得到的线膨胀系数、熵、振动自由能和等压热容在0~2000 K范围内均与实验值符合较好。在得到平衡体积随温度变化的基础上,计算了钨立方结构的弹性性质,得到了弹性常数、体积模量、剪切模量和杨氏模量随温度的变化关系,所得结果与实验测量值符合较好     

Whisker formation on a thin film tin lithium-ion battery anode

Tin (Sn) is a candidate material for anodes (negative electrodes) of lithium-ion batteries because of its high theoretical energy capacity. In this paper, we report an observation of Sn-whisker growth on Sn-thin films after lithiation and delithiation. The compressive stress generated by electrochemical lithiation of the Sn-thin films is likely the driving force for the growth of the Sn whiskers. Attention should therefore be paid to the issue of Sn-whisker growth for Sn-based electrodes since Sn whiskers may penetrate through the separator, and short-circuit the electrochemical cell.     

冲击波压力和脉冲持续时间对铁和镍微结构的影响

用一级轻气炮对铁和镍两种材料动态加载。用透射电镜观察两种材料的位错结构。结果发现：受动加载作用后铁和镍的位错结构分别是类似于网状的和网状的结构。冲击波压力与位错密度有直接关系，而在本试验的条件下脉冲持续时间对位错密度没有影响。     

Dissolution of bioactive glasses: The effects of crystallinity coupled with stress

Fixing the chemical composition of bioactive ceramic glass does not dictate biological response. Processing history can alter the microstructure, phase composition, degree of crystallinity, and residual stress—all of which can contribute to mechanical performance and bioactive response. This paper discusses effects of thermal and mechanical processing performed on bioactive glass 45S5 with regard to the micro-structural changes that occur during in vitro immersion, and how such changes can be related to bioactivity with respect to implant materials. The underlying theme is the relationship between mechanical properties, stress, microstructure, and bioactivity, and how to achieve optimization.     

Effect of DC Current on the Creep Deformation of Tin

Impression creep testing of tin was performed in the temperature range of 343 K to 398 K and under a punching stress of 12 MPa to 55 MPa. During the impression test at constant load, a direct electric current in the range of 0 A to 6 A flowed through the punch into the sample, introducing an electromechanical interaction. Steady-state creep was observed under the simultaneous action of the electric current and mechanical stress. The steady-state impression velocity increased with increasing temperature, punching stress, and electric current. A hyperbolic sine relation was used to describe the stress dependence of the steady-state impression velocity for impression creep of tin. The apparent activation energy decreased with increasing electric current.     

钨在铁中动态扩散的研究

用Ｘ－射线能谱仪测量了７．１～１３．１６ＧＰａ不同压力冲击作用下钨铁耦合体的钨在铁中的扩散浓度。通过研究钨浓度的对数值与扩散深度幂指数的关系，得到了钨动态扩散动力学的类型。找到了一种不用扩散深度计算扩散系数的方法