分段线性强化问题的全量无迭代解

本文应用[1]提出的塑性全量理论中的控制变量(也称参变量)变分原理,对各级分段线性强化规律建立了相应的本构状态方程以及有限元求解公式,可使分段线性强化全量问题的数值解不需迭代.对于一般的(?)—(?)曲线,适当选择分段数目可达到足够的精度。本文给出了有一定代表性的手工及数值算例。     

Second-order sufficient conditions for control problems with mixed control-state constraints

References 1–4 develop second-order sufficient conditions for local minima of optimal control problems with state and control constraints. These second-order conditions tighten the gap between necessary and sufficient conditions by evaluating a positive-definiteness criterion on the tangent space of the active constraints. The purpose of this paper is twofold. First, we extend the methods in Refs. 3, 4 and include general boundary conditions. Then, we relate the approach to the two-norm approach developed in Ref. 5. A direct sufficiency criterion is based on a quadratic function that satisfies a Hamilton-Jacobi inequality. A specific form of such a function is obtained by applying the second-order sufficient conditions to a parametric optimization problem. The resulting second-order positive-definiteness conditions can be verified by solving Riccati equations.The authors wish to thank K. Malanowski for helpful discussions.     

Modelling and resonance of a flexible rod using a floating reference frame

A direct variational approach with a floating frame is presented to derive the ordinary differential equations of motion of a flexible rod, constant crank speed slider-crank mechanism. Potential energy terms contained in the derivation include beam-bending energy and energy in foreshortening of the rod tip (which were selected because of the importance of these terms in a pinned-pinned rod parametric resonance). A symbolic manipulator code is used to reduce the constrained equations of motion to unconstrained nonlinear equations. A linearized version of these equations is used to explore parametric resonance stability-instability zones by a monodromy matrix technique.     

线性交叉规划的等价形式

本文利用参数规划的逆问题考虑交叉规划与多目标规划的关系,把交叉规划转变为部分同变量规划组,再把部分同变量规划组转化为一个多目标规划,并说明了交叉规划的均衡解与多目标规划的最优解的关系．     

拱型结构在参、强激励下的非线性振动分析

利用数值解析法研究了拱型结构在参数激励与强迫激励联合作用下的非线性振动特性。得到了轴向力与固有频率的关系及轴向力对发生主共振,１／２亚谱共振的影响,由于１／２亚谐共振是高频激振低频响应,是最危险区域,应得到足够的重视,为工程设计提供了可靠的理论依据。     

Stability of Thermal Vibrational Flow in an Inclined Liquid Layer Against Finite‐Frequency Vibrations

Stability of the flow that arises under the action of a gravity force and streamwise finitefrequency vibrations in a nonuniformly heated inclined liquid layer is studied. By the Floquet method, linearized convection equations in the Boussinesq approximation are analyzed. Stability of the flow against planar, spiral, and threedimensional perturbations is examined. It is shown that, at finite frequencies, there are parametricinstability regions induced by planar perturbations. Depending on their amplitude and frequency, vibrations may either stabilize the unstable ground state or destabilize the liquid flow. The stability boundary for spiral perturbations is independent of vibration amplitude and frequency.     

参数激励下非线性受控系统的动力学和稳定性

研究两自由度参数激励系统的非线性动力学与控制问题．利用Lagrange方程建立含反馈控制的参激捅及其驱动机构组成的系统动力学方程，以多尺度方法获得一阶近似控制方程．然后，对系统受一阶摸态参激主共振与一、二阶模态间3：1内共振联合作用下的幅额响应及其稳定性，以及反馈参数对系统稳态行为的影响作了详细分析．结果表明，响应的稳定域位置和大小取决于位移反馈，位移立方反馈改变了系统的非线性程度，速度反馈类似于阻尼，可使系统呈现自激振动特性．     

基于参量放大器的光通信系统中QC-LDPC码的研究

由于光在光纤中传输受到色散的作用以及光纤参量 放大器(FOPA)的不理想均会导致光信号在传输过程中的畸 变,从而影响光传输系统的误码率(BER)性能。为了减小高 非线性光纤(HNLF)和泵浦的影响,本文通过采用由最小环长 最大化算法构造的QC-LDPC码作为基于FOPA的40Gbit/s非归零差分 移相键控(NRZ-DPSK)调制光通信系统的前 向纠错码来降低系统的BER,从而达到提高整个通信系统性能 的目的。仿真结果表明,在10km传输光 纤条件下,相同码长不同码率的QC-LDPC码可以使BER达到10－11数量级;在相同码型和不同传输光纤 长度的条件下,BER也可以达到10－11数量级。利用最小环长最大化算法构造的QC-LDPC码可以纠正通 信光在传输中受到光纤色散以及FOPA中HNLF和泵浦抖动引起的相位失配 而导致的误码,从而达到了提高通信质量的目的。     

基于参数化的防空武器平台系统仿真建模技术

针对防空武器平台仿真系统快速、高效建模需求,从多学科领域功能模型划分角度出发研究其仿真系统建模技术,建立了合理的领域功能模型划分框架及自底向上的系统多层建模结构;在此基础上结合多粒度参数化建模技术研究了通用领域功能模型建立方法。最后通过对某典型防空武器平台仿真系统的建模验证了该建模技术的有效性和可行性。     

基于GEESE算法的GTD模型参数估计

基于信号子空间特征向量的广义特征值（GEESE）算法具有比MUSIC和ESPRIT估计速度快的特点。将GEESE算法应用到能够精确描述高频电磁散射的几何绕射（GTD）模型中,利用特征子空间分解方法中信号子空间与噪声子空间的正交特性分离出信号子空间,使GEESE算法既能够精确估计目标散射中心的位置,又能估计散射中心的类型。仿真表明,这种算法有较好的效果,无需搜索,且估计的速度快,精度高。