dSH扭曲程序的建立以及在两种基组(NBO, LFMO)下对扭曲分子的能量分解

介绍了d_SH 扭曲法产生的背景, 为d_SH扭曲法研究Mills-Nixon效应提供了一个自动化程序和方法. 通过在程序中引入随机函数模拟并代替了人工调节构型参数的过程, 提高了效率并拓宽了程序的应用范围. 利用此程序算得三元苯并分子C₆B₃H₃ 和C₆O₃的一系列的扭曲结构, 并利用自然键轨道(NBO)和定域片断分子轨道(LFMO)两种基组分别进行了NBO能量分析和Morokuma SCF能量分解, 并以动态的方式分析了扭曲过程中垂直共振能及其各分量的变化趋势, 比较了不同基组和不同分析方法下的扭曲的驱动力和阻力. 由分析知, 由于NBO基组的非绝对定域性和NBO能量分析方法的一次性对角化直接导致NBO基组及其能量分析方法在d_SH扭曲能量分析中的不合理.     

Propagation behavior of SH waves in a piezomagnetic substrate with an orthorhombic piezoelectric layer

The dispersion behavior of the shear horizontal (SH) waves in the coupled structure consisting of a piezomagnetic substrate and an orthorhombic piezoelectric layer is investigated with different cut orientations. The surface of the piezoelectric layer is mechanically free, electrically shorted, or open, while the surface of the piezomagnetic substrate is mechanically free, magnetically open, or shorted. The dispersion relations are derived for four electromagnetic boundary conditions. The dispersion characteristics are graphically illustrated for the layered structure with the PMN-PT layer perfectly bonded on the CoFe₂O₄ substrate. The effects of the PMN-PT cut orientations, the electromagnetic boundary conditions, and the thickness ratio of the layer to the substrate on the dispersion behavior are analyzed and discussed in detail. The results show that, (i) the effect of the cut orientation on the dispersion curves is very obvious, (ii) the electrical boundary conditions of the PMN-PT layer dominate the propagation feature of the SH waves, and (iii) the thickness ratio has a significant effect on the phase velocity when the wave number is small. The results of the present paper can provide valuable theoretical references to the applications of piezoelectric/piezomagnectic structure in acoustic wave devices.     

半空间双相压电介质垂直边界附近圆孔对SH波的散射

利用“Green函数法”和“镜像法”对垂直边界附近含圆孔的半空间双相压电介质对SH波的散射问题进行分析,得到其稳态解。利用镜像法得到满足水平边界应力自由与电位移自由的波函数解析表达式。根据垂直边界连续性条件,利用“契合法”建立第一类Fredholm型积分方程组,得到圆孔周边的动应力集中系数与电场强度集中系数解析表达式。数值算例分析了入射波频率、入射角度、介质参数等对动应力集中系数与电场强度集中系数的影响,并与已有文献进行比较。计算表明,高频SH波垂直入射危害较大。     

径向非均匀压电介质中圆孔对SH波的散射

利用复变函数理论对SH波作用下含圆孔径向非均匀压电介质的反平面动力特性进行了研究。压电介质的密度沿径向按幂函数形式变化,但压电参数、弹性参数、介电参数均为常数。利用变量替换法将非均匀压电介质的变系数波动方程组转化为标准的Helmholtz方程组,得到了满足边界条件的波函数解析表达式。通过数值算例分析了入射角度、入射波频率、幂次等对应力集中系数和电场强度集中系数的影响,并与已有文献进行比较。结果表明,某些参数组合下,动应力集中系数与电场强度集中系数均随幂次增大而增大。     

Improved convergence of binding affinities with free energy perturbation: Application to nonpeptide ligands with pp60src SH2 domain

Free Energy Perturbations (FEP) in the context of Monte Carlo (MC) simulations were conducted to predict the relative free energies of binding for a series of human Src SH2 domain ligands. Two procedures for disappearing atoms during a single-topology FEP are investigated and dramatic differences in free energy convergence behavior are seen. Comparison of these two protocols suggests that the coupling of the removal of angular constraints with the disappearance of an atom may significantly slow free energy convergence. The series of ligands under investigation here cover a range of modifications at the 3-position of 4-({[4-(cyclohexyl methoxy)benzyl]amino}carbonyl) phenyl phosphate. Unlike any other compound in this study, the 3-amide analog can form two hydrogen bonds within the region of the perturbation, one to a backbone amide hydrogen and one to a highly coordinated water molecule. Agreement with experimental trends in binding affinity is seen, although the computed relative free energy of binding of the amido compound is underestimated. These results are reconciled by examination of the hydration energies of model systems, which predict primary amides as too hydrophilic.     

CH2SH与NO2双自由基反应机理的理论研究

在B3LYP/6-311＋＋G(2df,p)水平上优化了标题反应驻点物种的几何构型, 并在相同水平上通过频率计算和内禀反应坐标(IRC)分析对过渡态结构及连接性进行了验证. 采用双水平计算方法HL//B3LYP/6-311＋＋G(2df,p)对所有驻点及部分选择点进行了单点能校正, 构建了CH2SH＋NO2反应体系的单重态反应势能剖面. 研究结果表明, CH2SH与NO2反应体系存在4条主要反应通道, 两个自由基中的C与N首先进行单重态耦合, 形成稳定的中间体HSCH2NO2 (a). 中间体a经过C—N键断裂和H(1)—O(2)形成过程生成主要产物P1 (CH2S＋trans-HONO), 此过程需克服124.1 kJ•mol－1的能垒. 中间体a也可以经过C—N键断裂及C—O键形成转化为中间体HSCH2ONO (b), 此过程的能垒高达238.34 kJ•mol－1. b再经过一系列的重排异构转化得到产物P2 (CH2S＋cis-HONO), P3 (CH2S＋HNO2)和P4 (SCH2OH＋NO). 所有通道均为放热反应, 反应能分别为－150.37, －148.53, －114.42和－131.56 kJ•mol－1. 标题反应主通道R→a→TSa/P1→P1的表观活化能为－91.82 kJ•mol－1, 此通道在200～3000 K温度区间内表观反应速率常数三参数表达式为kCVT/SCT＝8.3×10－40T4.4 exp(12789.3/T) cm3•molecule－1•s－1.     

Gradient surface ply model of SH wave propagation in SAW sensors

Investigation of the propagation of the wave in SAW sensors is a basis for the research and design of the sensors. With the advance of the sensor, both the effect of environment on the surface ply and the geometry of waveguide are complicated. To consider the complication, a model with gradient surface ply and multilayer waveguide of SH wave propagation in sensor is proposed. The equation of wave velocity is derived by a transfer matrix method. Through the equation, the function of wave velocity increment via the change of parameters in the surface ply is obtained. The effect of the inhomogeneity on the function is also studied. Finally, some influencing factors of the behavior of the sensor are discussed. This study was supported by the National Natural Science Foundation of China (No. 59635140), the Doctoral Education Foundation of the Ministry of Education of China and Aeronautics Foundation of China.     

麦秸秆的力学性能及加筋滨海盐渍土的抗压强度研究

为开展天然草本纤维材料防腐前后的力学性能及加筋滨海盐渍土的抗压强度增长规律研究,本文探讨了麦秸秆的微结构特征及防腐方法、测试并对比了防腐前后的麦秸秆的质量增加率、吸水率、极限拉力和极限延伸率,证实用SH胶浸泡麦秸秆不仅能起到防腐作用,还可提高麦秸秆的力学性能。完成了不同加筋长度、不同加筋率及浸胶后呈不同状态麦秸秆的加筋滨海盐渍土无侧限抗压强度试验,结果证实：掺加长10mm麦秸秆优于掺加长20 mm麦秸秆;适宜加筋率为0.3%~0.4%;掺加浸泡SH胶后呈潮湿状态的麦秸秆优于掺加浸泡SH胶后呈干燥状态的;麦秸秆加筋盐渍土的抗压强度高于素盐渍土。初步的研究结果表明,麦秸秆适宜作加筋材料使用。     

Local structure distortion and spin Hamiltonian parameters of oxide-diluted magnetic semiconductor Mn-doped ZnO

The local structure distortion, the spin Hamiltonian (SH) parameters, and the electric fine structure of the ground state for Mn²⁺(3d⁵) ion in ZnO crystals are systematically investigated, where spin--spin (SS), spin--other--orbit (SOO) and orbit--orbit (OO) magnetic interactions, besides the well-known spin--orbit (SO) coupling, are taken into account for the first time, by using the complete diagonalization method. The theoretical results of the second-order zero-field splitting (ZFS) parameter D, the fourth-order ZFS parameter (a-F), the Zeeman g-factors: g_// and g_⊥, and the energy differences of the ground state: \delta₁ and \delta₂ for Mn²⁺ in Mn²⁺: ZnO are in good agreement with experimental measurements when the three O^2- ions below the Mn²⁺ ion rotate by 1.085^o away from the [111]-axis. Hence, the local structure distortion effect plays an important role in explaining the spectroscopic properties of Mn²⁺ ions in Mn²⁺: ZnO crystals. It is found for Mn²⁺ ions in Mn²⁺: ZnO crystals that although the SO mechanism is the most important one, the contributions to the SH parameters, made by other four mechanisms, i.e. SS, SOO, OO, and SO～SS～SOO～OO mechanisms, are significant and should not be omitted, especially for calculating ZFS parameter D.     

Propagation,reflection, and transmission of SH-waves in slightly compressible,finitely deformed elastic media

The propagation, reflection, and transmission of SH waves in slightly compressible, finitely deformed elastic media are considered in this paper. The dispersion relation for SH-wave propagation in slightly compressible, finitely deformed layer overlying a slightly compressible, finitely deformed half-space is derived. The present paper also deals with the reflection and refraction (transmission) phenomena due to the SH wave incident at the plane interface between two distinct slightly compressible, finitely deformed elastic media. The closed form expressions for the amplitude ratios of reflection and refraction coefficients of the reflected and refracted SH waves are obtained from suitable boundary conditions. For the numerical discussions, we consider the Neo-Hookean form of a strain energy function. The phase speed curves, the variations of reflection, and transmission coefficients with the angle of incidence, and the plots of the slowness sections are presented by means of graphs.