具有高能密特性的铝团簇氢化物

通过第一性原理计算得到了稳定的(AlH₃)_n的笼形结构.(AlH₃)_n笼形结构中的铝团簇骨架具有n个顶角,2n条Al-Al边,吸附的氢原子中有n个位于顶位,与Al原子形成共价键,2n个位于桥位,同铝原子一起构成了Al-H-Al 的笼形骨架. 以Al₁₂H₃₆的笼形结构为单元得到了(Al₁₂H₃₆)_n的链状结构,该链状结构与(AlH₃)_n的链状结构具有相同的链接方式. 同时Al₁₂H₃₆的热力学性质研究表明其可能成为一种高能密材料.     

Hybrid natural element method for viscoelasticity problems

A hybrid natural element method(HNEM)for two-dimensional viscoelasticity problems under the creep condition is proposed.The natural neighbor interpolation is used as the test function,and the discrete equation system of the HNEM for viscoelasticity problems is obtained using the Hellinger–Reissner variational principle.In contrast to the natural element method(NEM),the HNEM can directly obtain the nodal stresses,which have higher precisions than those obtained using the moving least-square(MLS)approximation.Some numerical examples are given to demonstrate the validity and superiority of this HNEM.     

Delaunay多边形单元的有理函数插值格式

本文提出了基于Delaunay多边形化的多边形单元有理函数插值格式。给出了Delaunay多边形化的概念和Delaunay多边形单元有理函数插值形函数的计算表达式。与Delaunay三角化网格不同，Delaunay多边形化网格形成对区域的唯一剖分。Delaunay多边形单元有理函数插值是以Delaunay多边形的顶点作为插值点，构造的有理函数形式插值。Delaunay多边形单元有理函数插值克服了有限元方法中难以构造边数大于4单元多项式形式位移插值的困难。有理函数插值形函数在多边形单元的内部是无穷次光滑的，在多边形的边界上是线性的。在三角形单元和矩形单元上，有理函数插值分别等价于有限元的三角形面积坐标插值和四边形双线性插值。给出了Delaunay多边形有理函数插值在圆域温度分布插值近似中的两个算例。     

冷却塔环形基础板的平面应力分析

本文研究了冷却塔的基础环板在水平力作用下的应力分布状况,用弹性反力系数K模拟地基土在水平向的弹性性态,求得了问题的幂级数形式的解。本文探讨了基础环板内的应力分布与地基土的剪切弹性模量及基础板的杨氏弹性模量之间的关系。     

三维数值流形方法及其在复合材料中的应用

数值流形方法在进行接触判断时,传统的直接判断法在三维情况下检索困难,计算量大,对大规模工程问题是不适用的。为此,本文将公共面法引入三维数值流形方法的接触判断,使接触判断的计算量大大减少。目前,数值流形方法主要应用于岩石力学分析,为了拓宽其应用领域,作者比较了复合材料与岩石结构的异同,将其应用于复合材料的数值模拟,数值结果表明,该方法收敛快、精度高,弥补了有限元的不足。     

A New Method to Prepare Boron Nitride Thin Films

We report a new method to prepare boron nitride (BN) thin films on Si (100) substrates in an Ar-N2-BCl3-H2 gas system by magnetron arc enhanced plasma chemical vapour deposition. Fourier transform infrared spectroscopy (FTIR) and x-ray diffraction (XRD) are used to characterize the films. The FTIR spectra show that the deposited boron nitride films experienced a transition from pure h-BN phase to a cubic-containing phase with the variation of arc current ranging from IOA to 18A. The BN film with 42% c-BN was obtained without substrate bias voltage. In the gas system of Ar-N2-BCl3-H2, h-BN can be preferentially etched by chlorine. The chemical etching effect of chlorine allows the formation of c-BN without substrate bias voltage, which may develop a new perspective for the deposition of high quality c-BN film with low stress.     

高阶线性时滞微分方程的广义振动性

该文考虑了一类高阶线性常系数时滞微分方程 y( n) (t) py′(t) qy(t-τ) =0的广义振动性和广义非振动性 ,给出了一些该类方程广义振动和广义非振动的判定定理 .文中的定理 4还给出了一类非振动但广义振动的方程的判别法则     

构造满足特征值要求的杂交元应力子空间

通过引进适当参数给出了杂交元应力空间特征值与参数之间的关系,从而可以通过调节参数来构造满足特征值即模态刚度要求的杂交元应力子空间。本在位移元本征应力模式基础上引进调节参数,同时,利用矩阵H对角化方法计算杂交元应力子空间的本征应力模式,然后由此方便有效地计算特征值,从而大大提高了计算效率。本通过建立Q4杂交应力元特征值与参数之间关系说明了这一方法是确定可行的。     

Cross correlation mediated by distant Majorana zero modes with no overlap

Existing studies via shot noise calculation conclude that the cross correlation between the currents in the two leads connected by a pair of Majorana zero modes(MZMs)vanishes when their coupling energy??∈_M→0.Motivated by the intrinsic nature of nonlocality of the MZMs,we revisit this important problem and propose an experimental scheme to demonstrate the nonvanishing cross correlation even at the limit??∈_M→0.The proposed scheme employs the Andreevprocess-associated branch circuit currents,which are theoretically obtained by applying a decomposition analysis for the total currents while are accessible directly in practical measurement.For different bias voltage setup,we find intriguing results of both negative and positive correlations and carry out simple physical understanding using a quantum jump technique.Importantly,combining together with the evidence of the zero-bias-peak of conductance,the nonlocal cross correlation predicted in this work can help to confirm the existence of the nonlocal MZMs.     

The duality of a single particle with an n-dimensional internal degree of freedom

The wave-particle duality of a single particle with an n-dimensional internal degree of freedom is re-examined theo- retically in a Mach-Zehnder interferometer. The famous duality relation D2 ＋ V2 〈 1 is always valid in this situation, where D is the distinguishability and V is the visibility. However, the sum of the particle information and the wave information, D2 V2, can be smaller than one for the input of a pure state if this initial pure state includes the internal degree of freedom of the particle, while the quantity D2~ V2 is always equal to one when the internal degree of freedom of the particle is excluded.