斜弯独塔混合梁斜拉桥参数敏感性分析

为研究斜弯独塔混合梁斜拉桥在成桥状态下受结构设计参数的影响程度,对结构设计、施工监控和关键控制量制定等提供参考,以张家口纬二桥为工程背景,建立有限元模型。基于结构参数敏感性分析的摄动原理,引入敏感度分析指标,选取塔梁固结处弯矩值、桥顶纵向位移值、背索索力、主梁最大挠度为控制目标,对桥梁钢混结合段位置、桥塔局部温度荷载、斜拉索初拉力和背索竖向倾斜角度等结构参数进行敏感性研究。分析结果表明：桥梁钢-混结合段位置、斜拉索初拉力、背索竖向倾斜角度对斜弯独塔混合梁斜拉桥主梁挠度和桥塔线形影响较大。其中,混凝土梁和钢梁的跨度比变化15.73%,塔顶纵向位移、主梁最大挠度将分别变化30.3%和29.4%;桥塔局部温度荷载主要影响此类桥塔的纵向变形,对桥塔受力敏感度较低;背索竖向倾斜角度对斜弯独塔混合梁斜拉桥影响最为显著,背索竖向倾斜角度变化7%,塔顶纵向位移较初始位置最大变化也达到205.8%。     

180°弯道水槽表面流速分布研究

自然界中河流多是弯曲的,弯道水流结构分析是水力学及河流动力学最重要的课题之一,对河道管理和河流开发利用也有着重要意义.基于粒子跟踪测速(particle track velocimetry,PTV)技术对180°弯道水槽不同流量下的水流表面流速进行测量与分析.试验结果表明:除进口断面,凹岸侧表面纵向流速均大于凸岸侧表面纵向流速,中心线上的表面纵向流速沿程变化相对较小;水流进入弯道后,凸岸的水流开始向凹岸方向运动从而产生横向流速,当水流流过弯顶后,由凸岸向凹岸的横向运动逐渐消失.对比两个流量的流速分布结果,较小流量下表面水流的"顶冲点"发生在弯顶前,较大流量下表面水流的"顶冲点"发生在弯顶后,较小流量下的凸岸侧水流更容易向凹岸方向运动.     

双曲拱桥主要失效模式和剩余寿命的研究

通过桥梁检测结论确定以主拱圈破坏导致全桥结构失效作为双曲拱桥结构系统的主要失效模式。确定用动态可靠度方法预测桥梁剩余寿命,以JC法迭代计算出主拱圈主要截面的可靠度,分析双曲拱桥在未来后续服役基准期的可靠度的时间变化规律,以目标可靠度为控制值求出双曲拱桥的剩余寿命。     

曲面对称性研究

研究并给出了曲面关于点、平面及直线对称的三个充要条件。     

Modifications of Electron States,Magnetization, and Persistent Current in a Quantum Dot by Controlled Curvature

The thin‐layer quantization procedure is used to study the physical implications due to curvature effects on a quantum dot in the presence of an external magnetic field. Among the various physical implications due to the curvature of the system, the absence of the $m=0$ state is the most relevant one. This absence affects the Fermi energy and consequently the thermodynamic properties of the system. In the absence of magnetic fields, it is verified that the rotational symmetry in the lateral confinement is preserved in the electronic states of the system and its degeneracy concerning the harmonicity of the confining potential is broken. In the presence of a magnetic field, however, the energies of the electronic states in a quantum dot with curvature are greater than those obtained for a quantum dot in a flat space, and the profile of degeneracy changes when the field is varied. It is shown that the curvature of the surface modifies the number of subbands occupied in the Fermi energy. In the study of both magnetization and persistent currents, it is observed that Aharonov–Bohm‐type oscillations are present, whereas de Haas–van Alphen‐type oscillations are not well defined.     

Effect of curvature on interfacial segregation: Electronic contribution to the point defect/interface binding energy

The electronic contribution to the driving force for segregation to a curved interface between a cylindrical fiber of insulator embedded in a metal matrix is calculated. The solute/curved-interface binding energy is shown to vary as the inverse of the radius of curvature of the interface in the limit of a small radius. This result implies that the propensity for segregation of curved interfaces is larger than that of planar interfaces.     

Radiation from a Charge Supported in a Gravitational Field

We examine whether a charge supported statically in a gravitational field radiates, and find the answer to this question to be positive. Based on our earlier results we find that the important condition for the creation of radiation is the existence of a relative acceleration between the charge and its electric field, where such an acceleration causes the curving of the electric field and the creation of a stress force due to this curvature. This stress force is the reaction force, which creates the radiation. Later we find that this condition do exist for a charge supported statically in a gravitational field, where the electric field of the charge falls in the gravitational field, it curves, and the stress force raised in this curved field, creates electromagnetic radiation.     

有间隙弯叶片近壁面静压分布对叶栅气动性能的影响

对具有叶顶间隙的直叶栅、正弯叶栅和反弯叶棚的近壁画静压和出口流场进行了测量，实验结果发现：叶片正弯减小了叶顶中后部的横向压力梯度，削弱了泄漏流与端壁横流及其相互作用，使下游流动损失明显降低；叶片反弯也削弱了泄漏流动，但下游流动损失比其它两套叶栅大．     

Dirac Equation from the Hamiltonian and the Case With a Gravitational Field

Starting from an interpretation of the classical-quantum correspondence, we derive the Dirac equation by factorizing the algebraic relation satisfied by the classical Hamiltonian, before applying the correspondence. This derivation applies in the same form to a free particle, to one in an electromagnetic field, and to one subjected to geodesic motion in a static metric, and leads to the same, usual form of the Dirac equation—in special coordinates. To use the equation in the static-gravitational case, we need to rewrite it in more general coordinates. This can be done only if the usual, spinor transformation of the wave function is replaced by the 4-vector transformation. We show that the latter also makes the flat-spacetime Dirac equation Lorentz-covariant, although the Dirac matrices are not invariant. Because the equation itself is left unchanged in the flat case, the 4-vector transformation does not alter the main physical consequences of that equation in that case. However, the equation derived in the static-gravitational case is not equivalent to the standard (Fock-Weyl) gravitational extension of the Dirac equation.     

新的圆柱壳剪切屈曲方法及实验分析

提出用两块曲板、简易的夹具及普通万能试验机来进行半径Ｒ≥１０００ｍｍ的圆柱壳剪切屈曲实验．解决了使用单块曲板实验剪流合力不易通过剪力中心的难题．也避免了使用薄壁圆筒或封闭筒体扭转方案的一些缺点．实验结果与有限元计算分析以及国外成熟结果比较，符合良好．