Derivation of Hillert-type 3D grain growth rate model with topological considerations and discussion on its grain size parameter

A Hillert-type three-dimensional grain growth rate model was derived through the grain topology-size correlation model, combined with a topology-dependent grain growth rate equation in three dimensions. It shows clearly that the Hillert-type 3D grain growth rate model may also be described with topology considerations of microstructure. The size parameter bearing in the model is further discussed both according to the derived model and in another approach with the aid of quantitative relationship between the grain size and the integral mean curvature over grain surface. Both approaches successfully demonstrate that, if the concerned grains can be well approximated by a space-filling convex polyhedra in shape, the grain size parameter bearing in the Hillert-type 3D grain growth model should be a parameter proportional to the mean grain tangent radius.     

一个新的屈服准则及其推广

在现有Ｔｒｅｓｃａ屈服准则、Ｍｉｓｅｓ屈服准则和双剪应力屈服准则的基础上，提出了一个新的屈服准则，并建立了一个统一表达式。分析结果表明，所建立的屈服准则，体育馆了Ｔｒｅｓｃａ准则和Ｍｉｓｅｓ准则，以及介于二之间的一族屈服准则，这些准则不仅满足Ｄｒｕｃｋｅｒ公设的屈服面外凸性条件，而且与材料性质有关。即不同的材料对应不同的屈服准则，Ｔｒｅｓｃａ准则和Ｍｉｓｅｓ准则可作为本的特殊形式。     

密集多径信道中最优S-Rake路径选择与算法

研究了存在径间干扰的准静态密集多径信道中S-Rake (选择式Rake) 路径选择问题. 以系统误比特概率为目标代价函数,经过理论推导,将路径选择问题转化为一个以S-Rake径数为约束条件的最优化问题. 给出了密集多径信道中的路径选择最优化准则和简化的次最优路径选择算法. 数值仿真结果表明,在存在径间干扰的准静态密集多径信道中,所提的次最优路径选择算法优于传统的基于瞬时信噪比排序的路径选择算法.     

基于非线性规划的凸多面体间碰撞检测算法

为了提高碰撞检测算法的速度,提出用顶点的凸包表示凸多面体,将两个凸多面体间距离的问题归结为一个带约束条件的非线性规划问题,利用模拟退火遗传算法对该问题进行求解。利用模拟退火的接收准则进行交叉、变异,降低了时间复杂度。结果表明,模拟退火遗传算法计算效率高、速度快。     

求解凸规划问题的一种新的连续化方法

对于凸规划问题min f(x), s .t .gi(x)≤0(i =1 , 2, … , m), 其中, x ∈ Rn ;f(x), gi(x):R n ※R 为二次连续可微凸函数。利用Fischer 提出的一类新的凸规划问题等价条件, 给出了一个解此问题新的连续化方法。通过路径追踪求解New ton 类同伦方程, 得到凸规划问题的K -K -T 点, 从而得到凸规划问题的解, 并且证明了方法的全局收敛性。最后举例验证了方法的正确性。     

带有非线性扰动时变时滞系统新的稳定性判据

针对一类带有非线性扰动的时变时滞系统的稳定性问题,本文通过构造适合的Lyapunov-Krasovskii泛函,运用交互式凸组合、时滞分解和积分不等式等方法,得到新的基于线性矩阵不等式的时滞相关稳定性新准则,并通过数值实例进行实验验证,实验结果表明,本文结果与文献[11-12]相比有较大改进,所用方法降低了结果的保守性,说明本文结果具有优越性和有效性。     

Nonlinear optimization of load allocation in a manufacturing system

Muchresearchhasbeendoneintheareaofloadal locationinamanufacturingsystem.InRef.[1],loadbalancingistakenastheobjectivefunctionandtheLPmethodasitscomputationaltool.Althoughtheresultisgreatlyimprovedincomputationalcomplexityanddiffi cultycomparedwiththeMulti …     

确定多目标问题有效最小值的新方法

源于支付矩阵的最小值常被认为是多目标线性规划(MOLP)问题中有效集上真实最小值的一个“合理”近似,实际两者之间的差距常常是相当大的,为此,提出了一种确定有效集上真实最小值的精确罚函数法,并给出了相应的数值实例。     

新的区间时变时滞广义系统的稳定性判据

针对一类区间时变时滞广义系统的稳定性问题,本文通过采用新型的增广Lya-punov-Krasovskii泛函,在推导技术上,运用交互式凸组合以及积分不等式等方法处理时滞项,得到基于新的线性矩阵不等式的时滞相关稳定性判据,并通过数值实例进行验证,结果表明,本文方法与文献[9]和[13]相比较具有更低的保守性,能够获得使系统稳定所容许的最大时滞上界值.该方法可以推广到广义系统的H∞控制以及鲁棒控制等问题的研究中.     

Global optimization over linear constraint non-convex programming problem

When solving a general nonlinear problem,the so-lution method used by traditional methods,e.g.,Qua-si-Newton[1,2]and General Reduced Gradient[2],re-quires the computation of derivatives.The finite differ-ence approach often uses the basic scheme to generatederivatives.For highly nonlinear cases,this approachmay have poor numerical precision for computing thematrix of partial derivatives of the constraints[3],theso-called Jacobian.Qualitatively,if a model is non-convex,it means that a solutio…     

一种适用于WiFi Mesh网络的AODV改进路由协议

提出了一种利用wireless fidelity (WiFi) Mesh网络中多传输范围、多速率特性的路由算法. 这种算法引进了跨层设计思想,利用IEEE 802.11的自适应速率切换机制,节点建立路由时以物理层的数据传输速率作为判据,速率相同时则选择跳数少的路径. 提出了通过调整发射功率实现在不同速率下选择路径的方法. 利用这种算法改进了Ad hoc按需距离矢量（AODV）路由协议,提出WiFi－AODV路由算法. 仿真分析表明,该路由算法能建立一条数据速率高、传输时延小、系统吞吐量大的路由.     

Pseudo minimum translational distance between convex polyhedra (II)

By using the pseudo minimum translational distance between convex objects, this paper presents two algorithms for robot path planning. First, an analytically tractable potential field is defined in the robot configuration space, and the concept, of virtual obstacles is introduced and incorporated in the path planner to handle the local minima of the potential function. Second, based on the Lipschitz continuity and differentiability of the pseudo minimum translational distance, the flexible-trajectory approach is implemented. Simulation examples are given to show the effectiveness and efficiency of the path planners for both mobile robots and manipulators.     

Pseudo minimum translational distance between convex polyhedra (Ⅱ)——Robot collision-free path planning

By using the pseudo minimum translational distance between convex objects, this paper presents two algorithms for robot path planning. First, an analytically tractable potential field is defined in the robot configuration space, and the concept of virtual obstacles is introduced and incorporated in the path planner to handle the local minima of the potential function. Second, based on the Lipschitz continuity and differentiability of the pseudo minimum translational distance, the flexible-trajectory approach is implemented. Simulation examples are given to show the effectiveness and efficiency of the path planners for both mobile robots and manipulators.     

基于R_N(K)准则的测试用例生成技术

针对完整路径覆盖测试的可行性,提出了R_N(K)测试覆盖准则。首先,将测试问题归纳为多目标函数的优化问题,为了提高生成效率,对遗传模拟退火算法中的编码、适应度函数和退火规则做了相应的改进,并利用其结果和程序插装理论来生成测试用例。试验表明,该方法与随机法和遗传算法相比有较好的效果。     

一个基于CMSP方法的快速隐线消除算法

本文提出了自相关矩阵、轮廓多边形等概念,使得基于CMSP方法的快速隐线消除算法的处理过程简化,执行速度提高.这个算法的执行分多面体自身隐线消除和多面体间遮挡隐线消除两步.该算法已在IBM PC/AT机上使用BASIC语言实现,并从实践的角度验证了它的合理性,可行性.     

Modified Mohr-Coulomb strength criterion considering rock mass intrinsic material strength factorization

With the increase of mining depth of mineral resources,the rock mass stress state is being more and more complex.The rock mass show different features,namely,with the increase of hydrostatic pressure,rock mass failure mode turns from brittle tension failure to structure ductile failure and its limit strength also increases.The restriction of minimal principal stress on the initiation and development of microcrack and the change of micro-unit stress state by the intermediate principal stress play a decisive role in the increase of rock mass limit strength.Based on the rock mass failure behavior law under complex stress state and theσ2-dependence on the rock mass strength,we proposed a Modified Mohr-Coulomb(M-MC)strength criterion which is smooth and convex.Finally,the M-MC criterion is validated by multiaxial test data of eight kinds of rock mass.We also compared the fitting results with Mohr-Coulomb criterion(MC).It shows that the new criterion fits the test data better than the Mohr-Coulomb criterion.So the M-MC strength criterion well reveals the rock mass bearing behavior and can be widely used in the rock mass strength analysis.The results can provide theoretical foundations for stability analysis and reinforcement design of complex underground engineering.     

Power allocation strategy for target tracking in asynchronous multistatic radar systems

A power allocation scheme for target tracking in asynchronous multistatic radar systems (MSRS) is proposed. An optimal centralized method for asynchronous target tracking is first introduced with the derivation of the Bayesian Cramer-Rao lower bound (BCRLB) on the target tracking mean square error (MSE). Then, the BCRLB is utilized as a criterion for the power allocation strategy. The resulting nonconvex optimization problem is solved by the integration of convex relaxation with the gradient projection algorithm. Simulation results demonstrate that equal allocation of the predetermined power budget is not necessarily the best choice and that the tracking accuracy can be greatly improved by the proposed power allocation algorithm.     

路径规划中两个多面体的快速碰撞检测算法

如何进一步提高碰撞检测的速度在智能机器人路径规划中非常关键,为此给出了一种新的碰撞检测算法;它是以空间中的平面方程为基础,将一组平面方程进行几次代数变换得到一组常数不等式,观察这组常数不等式中是否含有矛盾不等可判定机器臂是否与空间中的障碍物相撞。     

带包络约束的优化滤波器设计方法

对信道均衡、雷达或声纳脉冲压缩等应用领域中要求满足波形条件且使输出噪声增益最小化的滤波器设计问题进行了研究。用波形包络约束表达式和极值条件可以准确地描述滤波器的性能要求,从而将该设计问题转化为半无限二次凸规划问题进行分析。利用Lagrangian对偶理论和Carathéodory维度理论把半无限二次凸规划问题转化成等价的易于求解的有限维对偶优化问题,并给出了求解有限维对偶优化问题的迭代算法,设计实例表明了此方法的有效性。     

非理想互连的传输线模型及串扰分析

在理想互连传输矩阵级联模型的基础上,通过引入返回路径不连续的传输矩阵,提出了一种新的模型．把非理想返回路径传输矩阵级联模型分析结果与S参数模型分析结果对比,验证了新模型的准确性,新模型可以准确地得到非理想互连上信号的耦合串扰噪声．最后分析研究了开槽对串扰的影响．仿真结果表明,传输线应紧挨开槽端口布线,并且传输线间距应尽量大．