Heisenberg-Pauli-Weyl uncertainty inequalities and polynomial volume growth

In its simpler form, the Heisenberg-Pauli-Weyl inequality says that

     

Liouville-type results for semilinear elliptic equations in unbounded domains

This paper is devoted to the study of some class of semilinear elliptic equations in the whole space:

基于“雨课堂+对分易”的化工原理混合教学模式探索与实践*

根据新工科建设要求,应积极探索符合时代特征和工程教育规律的培养模式。针对化工原理课程特点,引入“雨课堂”和“对分易”2种现代网络教学平台作为混合式教学工具。雨课堂实现了课前-课中-课后的三环节教学模式;对分易通过提交章节思维导图及“亮考帮”作业,结合课堂讨论,逐一击破学生学习难点,多方位激发学生自主学习的积极性,增加了课堂互动性,提高了教学质量。     

稀土元素La掺杂对AlN性能影响的第一性原理研究

本文通过基于密度泛函理论的第一性原理计算方法研究了稀土元素La掺杂对纤锌矿结构AlN力学性能及压电性能的影响.计算得到的AlN各项力学性能及压电性能与实验值较吻合.掺杂稀土元素La会降低其体模量、剪切模量与杨氏模量,但会使AlN由脆性材料转变为韧性材料.压电性能计算结果表明,掺杂稀土元素La后,可使体系的压电性能提升15%左右.电子结构分析结果表明La的引入会降低体系中化学键的作用强度,从而提升了体系的塑性及压电性能.     

镁离子电池正极材料VS_4掺杂改性的第一性原理研究

阳离子掺杂能够有效提高材料的电化学性能,而对掺杂材料结构和电化学性质的研究能从理论上解释产生这种变化的原因.本文采用基于密度泛函理论的第一性原理方法,研究了过渡族金属掺杂的镁离子电池正极材料TM_(0.125)V_(0.875)S_4(TM=Mo、Fe、Co、Ni)的几何和电子结构变化,计算结果显示:通过采用范德华力修正的GGA+vdw-DF方法,获得了和实验结果相一致的晶格常数.阳离子掺杂后,a轴和b轴晶格常数减小,而c轴晶格常数增大.电子态密度分析表明离子掺杂能够有效降低带隙,提高材料的电子电导率.通过对镁离子扩散进行微动弹性带(NEB)计算,发现Fe掺杂能够有效降低扩散能垒,提高材料的离子迁移率.     

开腔He—Ne激光器谐振腔四步目测调节法

对开腔He-Ne激光器谐振腔的调节进行了分析和整理，总结了一套简便可行的四步目测调节方法，为充分利用该试验平台开展激光原理实验提供一定帮助。     

Structural,electronic and magnetic properties of quaternary half‐metallic Heusler alloy CoFeCrAl

We have investigated the structural, electronic and magnetic properties in quaternary CoFeCrAl Heusler alloy. Rietveld refinement and Mössbauer spectroscopy of samples quenched from 973 K show absence of the A2 phase and presence of a highly ordered B2‐type structure. Full‐potential linearized augmented plane wave calculations using the experimental lattice constant show that there is an energy gap of 0.41 eV around the Fermi level in the bands for minority spin electrons. Partial substitution of Co by Fe in Co₂CrAl thus brings excellent structural ordering while retaining the high Curie temperature, spontaneous magnetization and half‐metallicity necessary for application as spin valves. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Phase stability and mechanical properties of rhenium borides by first‐principles calculations

The phase stability and elastic properties of Re? B system were systematically investigated by use of the density functional theory. The formation enthalpies are negative for Re₃B, Re₇B₃, Re₂B, ReB, Re₂B₃, and ReB₂, indicating that they are thermodynamically stable. Re₇B₃, Re₂B, ReB, Re₂B₃, and ReB₂ are mechanically stable. Combining the study of enthalpy and pressure relationship with the convex hull, it was found that the ground state phases are Re₃B, Re₇B₃, and ReB₂ at zero pressure, in agreement with the experimental observations. At the pressure of 90 GPa, Re₃B, and ReB₂ are the most stable phases. © 2010 Wiley Periodicals, Inc. J Comput Chem 2010     

A phase field model for the formation and evolution of martensitic laminate microstructure at finite strains

The extraordinary properties of shape-memory alloys stem from the formation and evolution of their complex microstructure. At lower temperatures, this microstructure typically consists of martensitic laminates with coherent twin boundaries. We suggest a variational-based phase field model at finite strains for the formation and dissipative evolution of such two-variant martensitic twinned laminate microstructures. The starting point is a geometric discussion of the link between sharp interface topologies and their regularisation, which is connected to the notion of Γ-convergence. To model the energy storage in the two-phase laminates, we propose an interface energy that is coherence-dependent and a bulk energy that vanishes in the interface region, thus allowing for a clear separation of the two contributions. The dissipation related to phase transformation is modelled by use of a dissipation potential that leads to a Ginzburg–Landau type evolution equation for the phase field. We construct distinct rate-type continuous and finite-step-sized incremental variational principles for the proposed dissipative material and demonstrate its modelling capabilities by means of finite element simulations of laminate formation and evolution in martensitic CuAlNi.