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91.
Wenxia Feng Haiquan Hu Shouxin Cui Guiqing Zhang Zengtao Lv Xiaoguang Xiao Zizheng Gong 《Physica B: Condensed Matter》2012,407(3):547-550
Investigations into crystal structure, electronic and elastic properties of M3AlN (M=Hf, Zr) had been conducted by plane-wave pseudopotential calculations. The absence of band gap at the Fermi level and the finite value of the density of states at the Fermi energy reveal the metallic behavior of these two compounds. The charge density distributions and density of states indicate that there exist relatively soft Al-M and strong N-M covalent bonds, which might be contributed to layered chemical bonding character of M3AlN. By analyzing Cauchy pressure and the bulk modulus to C44 ratio, Hf3AlN was predicted to be more ductile than Zr3AlN. 相似文献
92.
采用可求解可压缩流动与传热的全速度SIMPLE算法,对低功率氩电弧加热发动机内部的传热与流动进行了数值模拟,获得了电弧加热发动机内的温度、速度、马赫数及流线分布。计算结果表明:电弧加热发动机内最高温度出现在阴极下游附近中心轴线处,这是因为电弧在阴极表面收缩形成阴极弧点,从而焦耳热成为该高温区的主要加热机制;沿着发动机中心轴线,气体温度和速度开始时随着距阴极距离的增加而迅速增加,然后在等离子体流向喷管出口的过程中,气体温度和速度逐渐下降。此外还详细考察了弧电流变化对电弧加热发动机内部传热与流动特性的影响,计算获得的发动机流量和比冲与实验结果基本一致。 相似文献
93.
94.
物理化学计算机辅助教学软件的研制 总被引:3,自引:0,他引:3
随着时代的发展和科技的进步 ,传统的教学思想、教学方法、教学手段等都面临着挑战。特别是在当今信息技术和其他现代教育技术迅速发展的时代 ,计算机、多媒体技术、网络技术等应用于教学 ,将会引起教学方法和手段的革命[1] 。目前 ,世界范围的教学手段逐渐由“黑板+粉笔”向计算机多媒体辅助教学演变。在 2 0世纪 90年代初 ,我国 6 0多所高校的 2 0 0多位化学教师在原国家教委高教司和高等学校化学教育研究中心的领导和组织下 ,编写了我国第一套计算机辅助化学教学软件[2 ] 。计算机辅助教学 (CAI)是电子技术、通信技术和计算机技术在教… 相似文献
95.
We consider those subsets of the self‐affine Sierpinski carpets that are the union of an uncountable number of sets each of which consists of the points with their location codes having prescribed group frequencies. It is proved that their Hausdorff dimensions equal to the supremum of the Hausdorff dimensions of the sets in the union. The main advantage is that we treat these subsets in a unified manner and the value of the Hausdorff dimensions do not need to be guessed a priori. 相似文献
96.
Fang J Huang D Zhao W Ge H Luo HB Xu J 《Journal of chemical information and modeling》2011,51(6):1431-1438
Glycogen synthase kinase 3β (GSK-3β) is a potential therapeutic target for cancer, type-2 diabetes, and Alzheimer's disease. This paper proposes a new lead identification protocol that predicts new GSK-3β ATP competitive inhibitors with topologically diverse scaffolds. First, three-dimensional quantitative structure-activity relationship (3D QSAR) models were built and validated. These models are based upon known GSK-3β inhibitors, benzofuran-3-yl-(indol-3-yl) maleimides, by means of comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA). Second, 28?826 maleimide derivatives were selected from the PubChem database. After filtration via Lipinski's rules, 10?429 maleimide derivatives were left. Third, the FlexX-dock program was employed to virtually screen the 10?429 compounds against GSK-3β. This resulted in 617 virtual hits. Fourth, the 3D QSAR models predicted that from the 617 virtual hits, 93 compounds would have GSK-3β inhibition values of less than 15 nM. Finally, from the 93 predicted active hits, 23 compounds were confirmed as GSK-3β inhibitors from literatures; their GSK-3β inhibition ranged from 1.3 to 480 nM. Therefore, the hits rate of our virtual screening protocol is greater than 25%. The protocol combines ligand- and structure-based approaches and therefore validates both approaches and is capable of identifying new hits with topologically diverse scaffolds. 相似文献
97.
Shouxin Cui Wenxia Feng Guiqing Zhang Zizheng Gong 《Journal of solid state chemistry》2011,184(4):786-789
An investigation into the structural stability, electronic and elastic properties of Ti3GeC2 under high hydrostatic pressure was conducted using first-principles calculations based on density functional theory (DFT). From the energy and enthalpy calculations, and the variations of elastic constants with pressure, we conclude that α‐Ti3GeC2 is most stable upon compression to 100 GPa, which is not consistent with the nonhydrostatic in situ synchrotron X-ray diffraction studies. The higher structural stability was analyzed in terms of electronic level. The absence of band gap at the Fermi level and the finite value of the density of states at the Fermi energy reveal the metallic behavior of all polymorphs of Ti3GeC2. 相似文献
98.
Wenxia Feng Shouxin Cui Haiquan Hu Guiqing Zhang Zengtao Lv 《Physica B: Condensed Matter》2011,406(19):3631-3635
The structural, electronic and elastic properties of TiCxN1−x, ZrxNb1−xC and HfCxN1−x alloys have been investigated by using the plane-wave pseudopotential method within the density-functional theory. The calculations indicate that the variations of the equilibrium lattice constants and bulk modulus with the composition are found to be linear. The calculated elastic constants C44 and shear constants as a function of alloy concentration reveal the anisotropic hardness of these compounds. The partial and total density of states (DOS) for the binary and ternary compounds had been obtained, and the metallic behavior of these alloys had been confirmed by the analysis of DOS. 相似文献
99.
采用给水冷管状静电探针施加负偏置电压、并使探针以一定速度垂直于射流轴线扫过层流氩等离子体射流的方法,测量探针所收集到的累积离子饱和电流随侧向位置的变化,利用Abel变换推导出了局部离子饱和电流密度沿射流径向的分布;采用自制的水冷动压探针,以动态扫描法测量了射流动压沿射流径向的分布;根据局部离子饱和电流密度和射流动压的测量数据,由理论关系式推导出了等离子体射流横截面上的温度分布,同时,采用谱线相对强度法测量了等离子体射流的激发温度。结果表明:两种方法得到的等离子体射流中心温度吻合较好,所得到的射流中心温度随弧电流加大而增大的变化趋势也一致。 相似文献
100.
通过耦合迭代求解流体力学方程和电磁场方程,数值模拟了转移式自由燃烧电弧和具有细长中间段及突扩阳极结构的壁稳式非转移直流电弧的流场,分析了洛伦兹力对这两种典型直流电弧流场的影响。结果显示:在自由燃烧电弧情况下,电流自感磁场的洛伦兹力对流场特性有显著影响,自磁压缩是约束电弧的主要机制;而在壁稳式非转移直流电弧情况下,相对于强壁面约束和气动力作用而言,洛伦兹力对流场的影响有限。特别在中间段出口以后,洛伦兹力与气动力的比值小于0.010,因此,当主要考虑壁稳式非转移直流电弧发生器出口参数时,为了提高数值模拟效率,可忽略洛伦兹力的作用。 相似文献