圆弧拱考虑一般缺陷的面内屈曲

研究了几何缺陷、荷载非均匀分布和支座沉陷对圆弧拱面内屈曲的影响.基于能量的变分原理推导了考虑缺陷的微分方程,得到了外荷载和轴力的关系式以及径向位移的表达式.从微分方程出发用摄动法对屈曲荷载的缺陷敏感性进行了分析,得到了屈曲荷载的近似表达式.结果表明近似解与精确解吻合良好;正对称屈曲荷载对正对称缺陷参数十分敏感;反对称缺陷参数对反对称屈曲荷载影响显著而正对称缺陷参数影响很小.     

Study of the effect of thermal gradient on free vibration of clamped visco-elastic rectangular plates with linearly thickness variation in both directions

The effect of thermal gradient on the free vibration of clamped visco-elastic rectangular plate with linearly thickness variations in both the directions has been studied here. The governing differential equation has been solved using Rayleigh-Ritz technique. The frequency equation is derived for the clamped boundary condition on all the four edges. The effect of linear temperature variation has been considered. Deflection and time period corresponding to the first two modes of vibrations of a clamped plate have been computed for various values of aspect ratio, thermal constants, and taper constants.     

Penultimate Approximations in Extreme Value Theory

Under a general von Mises condition and a second order regular variation condition, we derive exact penultimate approximation rates for maxima w.r.t. the variational distance. The approach is not restricted to the Gumbel domain of attraction. Moreover, it is shown that the improvement by penultimate approximation is of order n ^-1, if the penultimate rate is an algebraic function of the ultimate rate.     

OPTIMAL TRACK SEEKING CONTROL OF DUAL-STAGE ACTUATOR FOR HIGH DENSITY HARD DISK DRIVES

Based on generalized the variation method, by introducing Hamilton function andLagrange multiplier, this paper proposed a linear quadratic optimal control strategy for an in-complete controllable system with fixed terminal state and time. Applying the proposed optimalcontrol to the simple two-input dual-stage actuator magnetic head positioning system with threedegrees-of-freedom, the simulation results show that the system has no residual vibration at theterminal position and time,which can reduce the total access time during head positioning process.To verify the validation of the optimal control strategy of three degrees-of-freedom spring-massmodels in actual magnetic head positioning of hard disk drives, a finite element model of an actualmagnetic head positioning system is presented. Substituting the optimal control force from simplethree degrees-of-freedom spring-mass models into the finite element model, the simulation resultsshow that the magnetic head also has no residual vibration at the end of track-to-track travel.That is to say, the linear quadratic optimal control technique based on simple two-input dual-stage actuator system with three degrees-of-freedom proposed in this paper is of high reliabilityfor the industrial application of an actual magnetic head positioning system.     

向列相液晶盒中的挠曲电体积效应

基于液晶弹性理论研究了电压作用下向列相液晶盒中的挠曲电体积效应.通过变分理论得到了液晶指向矢倾角θ满足的微分方程,利用差分迭代的方法计算了强锚定平行排列液晶盒和混合排列液晶盒中液晶指向矢的分布情况,利用琼斯矩阵的方法计算了两种液晶盒中电光特性曲线.结合计算结果分析了挠曲电体积效应对混合排列液晶盒中液晶指向矢分布及电光特性曲线的影响.     

状态反馈和参数调整控制离散非线性系统的倍周期分岔和混沌

利用系统的状态反馈和参数调节的方法，有效地实现了离散非线性动力系统的倍周期分岔的延迟控制和混沌吸引子中不稳定周期轨道的控制.同时，通过选择合适的调控参数，可以将系统从一个2n周期轨道控制到2m(m关键词： 状态反馈 参量调节 混沌控制 分岔控制     

元件与模式相对重要度对静强度可靠度的影响分析

本文通过研究指出,在运用增量载荷法寻找每级可能破坏元件时,必须考虑每个元件变异系数的影响,以避免漏掉极限承载能力很大但可靠度很低的失效模式;同时指出,结构失效的各个模式对系统可靠性的影响不仅与其本身发生失效的概率有关,而且与这个模式的重要程度有关,并提出了采用加权系数来计及每个失效模式的重要程度对结构系统可靠性影响的方法;最后用算例说明了本文方法的合理性。     

对数梯度材料泊松比不为零时的裂纹尖端场

严格地求出了当泊松比不为零时对数梯度材料的裂纹尖端场. 虽然在本构方程中对数项为\exp(ax), 但严格地证明了在最后应力的表达式中, 它却变为\exp(ax/2+ak_{1}^{1 / 2}y/2-kr/2) 与\exp(ax/2-ak_{1}^{1/2} y/2-kr/2). 对于数值解法, 若考虑了此种严格关系, 将会很容易地解释其结果.     

Theoretical Calculations on the Second-order Nonlinear Optical Property of Chiral Bis-corroles

The second-order nonlinear optical (NLO) properties of 5,10,15-triphenylcorrole (TPC), 5,10,15,20-tetraphenylporphyrin (TPP) and L-amino acid bridged bis-corroles 1, 2, 3 and 4 have been calculated by using TDHF/PM3 method based on the RHF/6-31G (TPC and TPP) or semiempirical PM3 (1, 2, 3, 4) optimized geometries. Calculation results showed TPC and TPP have C1 and D2h symmetry, respectively when N-H protons are localized on the nitrogen atoms. TPC is the second-order NLO active chromophore due to the cancellation of centrosymmetrical structure and its first hyperpolarizability β increases to 11.524×10-30 esu. Under electrical dipole approximation, β values of bis-corroles 1, 2, 3 and 4 vary from 9.831×10-30 to 14.221×10-30 esu, and no much improvement in the first hyperpolarizability was observed as compared to TPC monomer. However, β values of bis-corroles 1, 2, 3 and 4 are improved by about 4 times as compared to their bis-porphyrin counterparts. The analysis of β components indicates that β of this kind of bis-corroles is mainly contributed from its radial component βr. With the variation of amino acid side chains, βHRS, β, βxyz, βr and βa of bis-corroles change remarkably. Chiral L-amino acid bridged bis-corroles 2, 3 and 4 have a right-handed helix structure, and their chiral component βxyz matches βxyz ∝ r2ζ/L4 (helix parameters), showing the second-order chiral NLO response of these bis-corroles could be described by one-electron helical model theory. It was found that the radial component βr of chiral helix bis-corroles also matches β r ∝ r2ζ/L4.     

中国区域全要素能源效率及节能减排潜力分析—基于非期望产出的SBM模型

运用DEA-SBM模型测度了碳排放约束下1999年-2010年中国30省、市、区及四大区域的全要素能源效率,并利用变异系数及K-Means聚类分析考察了区域全要素能源效率的差异,最后对各省份及区域的节能减排潜力进行了测度分析.研究结果表明:不考虑碳排放约束的各省份的全要素能源效率被高估,绿色能源效率总体均值呈现U型趋势;绿色能源效率的区域格局按照由东向西递减.四大区域的变异系数差异较大,均呈现收敛趋势;由聚类分析结果可知处于高效区的省份全部为东部沿海省份;中效区的省份大多是中部省市及东北老工业基地,而西部区域的各省份多数处于低效区;不同省份的节能减排的潜力差异较大,西部区域的节能减排潜力最高,其次为中部和东北部,东部的节能减排潜力最低.