基于卡尔曼滤波理论的脑电逆问题反演

由头皮上的电压推断出大脑内神经活动源的过程称之为脑电逆问题,这一问题的解决具有重要的研究意义和应用价值。为了有效地进行脑电逆问题的反演计算,提出了一种基于状态空间的新的脑电逆问题求解算法。该方法首先根据神经系统的动力学方程得到状态方程,并由脑电系统的观测方程构成测量方程;然后应用卡尔曼滤波方法来反演大脑内活动源的信息。这种新的求逆算法不仅可以处理脑电系统中的不确定因素,而且还可以将静态和动态脑电逆问题的求解统一到同一框架下,因此具有一定的新颖性;最后分别给出了模拟数据和实际脑电数据的实验结果。实验结果证明,卡尔曼滤波法更具优越性。     

脑电逆问题方法研究

本文阐述了脑电逆问题的模型和求解方法,并介绍了求解脑电逆问题的发展方向。     

LQ最优控制之逆问题的研究

本文通过适当地选取LQ性能指标函数中的加权矩阵R,给出了该二次型性能指标函数中的另一个加权矩阵Q与系统的开环特征多项式、闭环特征多项式的系数以及系数的系数矩阵A、B之间的对应关系。如果给定一个系统以及该系统的一组最优闭环极点,就可以求得矩阵Q。同时,用本文的研究结果,还可以直接确定系统的最优状态反馈系数矩阵。     

基于OPNET的BGP4重分布的仿真

边界网关协议BGP4是用于自治系统之间交换路由信息的动态分布式路由协议。作为BGP4路由策略之一的路由重分布是自治系统之间信息交互时控制流量的重要环节。文中首先简单介绍了BGP4路由协议及相关内容,然后以BGP4路由重分布为主要讨论对象,利用OPNET仿真软件建立网络仿真模型,通过具体实例详细探讨了BGP4路由重分布在网络设计过程中存在的问题及相应的解决方法,深入理解BGP4路由重分布的机理,从而为网络规划设计更好地提供客观、可靠的定量依据。     

用边界元法研究冻土的温度分布状况

冻土,即具有负温和含冰的土体岩石.本文主要以数值方法数值模拟研究二维水热耦合问题,从宏观尺度上研究冻土在外界温度一定时,系统本身的温度分布状况.     

自适应遗传算法在脑电逆问题中的应用

脑电逆问题是指利用脑电图 (EEG)数据去反演可以反映脑电活动等效偶极子源的参数信息。优化方法是解决这一问题的有力工具。自适应遗传算法根据算法的不同情况自动改变遗传算子 ,将这一算法应用于脑电逆问题 ,其运算速度和防止局部最优的性能较基本遗传算法有较大提高     

用边界元法研究冻土的温度分布状况

冻土,即具有负温和含冰的土体岩石。本文主要以数值方法数值模拟研究二维水热耦合问题,从宏观尺度上研究冻土在外界温度一定时,系统本身的温度分布状况。     

LQ逆问题研究

本文研究了线性定常系统LQ逆问题解的存在性问题,给出了逆问题解的参数化公式,得到了加权矩阵Q与开环、闭环特征多项式系数之间的解析关系.只要给定一组稳定的闭环极点,即可确定与之对应的Q阵.     

关于文\"LQ逆问题研究\"的问题讨论

关于文“ＬＱ逆问题研究”的问题讨论傅诒辉（华中理工大学自控系武汉４３００７４）关键词ＬＱ逆问题,加权矩阵,极点配置．文［门定理２给出了连续系统ＬＱ逆问题有解的充分条件以及确定加权矩阵Ｑ和Ｒ的参数化方法．本文构造性地给出了满足文［１］定理２全部条件的参...     

基于TGAM的无线脑电监测系统

针对飞行人员日常模拟训练时监测装置便携式、无线化的特殊要求,设计并实现了一种基于脑波模块TGAM的无线脑电监测系统。采用Nordic 2.4G超低功耗无线平台,实现了采集设备与监测电脑之间的无线传输。系统具有低功耗、小型化、易使用的特点,可实时监控飞行员模拟训练期间的脑电图并反馈专注度和冥想度指标。     

Reconstruction of the corrosion boundary for the Laplace equation by using a boundary collocation method

In this paper, we consider the identification of a corrosion boundary for the two-dimensional Laplace equation. A boundary collocation method is proposed for determining the unknown portion of the boundary from the Cauchy data on a part of the boundary. Since the resulting matrix equation is badly ill-conditioned, a regularized solution is obtained by employing the Tikhonov regularization technique, while the regularization parameter is provided by the generalized cross-validation criterion. Numerical examples show that the proposed method is reasonable and feasible.     

Reconstruction of heat transfer coefficients using the boundary element method

This paper describes the reconstruction of the heat transfer coefficient (space, Problem I, or time dependent, Problem II) in one-dimensional transient inverse heat conduction problems from surface temperature or average temperature measurements. Since the inverse problem posed does not involve internal temperature measurements, this means that non-destructive testing of materials can be performed. In the formulation, convective boundary conditions relate the boundary temperature to the heat flux. Numerical results obtained using the boundary element method are presented and discussed.     

Determination of a time-dependent heat transfer coefficient from non-standard boundary measurements

In this paper the determination of the time-dependent heat transfer coefficient in one-dimensional transient heat conduction from a non-standard boundary measurement is investigated. For this inverse nonlinear ill-posed problem the uniqueness of the solution holds. Numerical results obtained using the boundary element method are presented and discussed.     

层状地基中桩筏基础的计算机数值模拟

本文选用层状弹性半空间地基模型,将桩和筏板作为整体,进行有限元分析。运用边界元方法建立层状地基的刚度矩阵,通过FEM-BEM耦合,建立了桩筏基础的筏板、桩和层状地基土共同作用的基本方程。编制成计算机程序,可有效地模拟在竖向荷载、横向荷载和弯矩作用下桩筏基础和地基的应力、应变的状态变化。实例计算结果表明文中所提出方法的精确性和有效性,同时说明在工程实际中考虑三者共同作用的可行性与必要性。     

The simulation of 3D elastic scattering produced by thin rigid inclusions using the traction boundary element method

A mixed formulation that uses both the traction boundary element method (TBEM) and the boundary element method (BEM) is proposed to compute the three-dimensional (3D) propagation of elastic waves scattered by two-dimensional (2D) thin rigid inclusions. Although the conventional direct BEM has limitations when dealing with thin-body problems, this model overcomes that difficulty. It is formulated in the frequency domain and, taking into account the 2-1/2D configuration of the problem, can be expressed in terms of waves with varying wavenumbers in the zdirection, k_z. The elastic medium is homogeneous and unbounded and it should be noted that no restrictions are imposed on the geometry and orientation of the internal crack.     

Simulation of ellipsoidal particle-reinforced materials with eigenstrain formulation of 3D BIE

Based on the concepts of eigenstrain and equivalent inclusion of Eshelby for inhomogeneity problems, a computational model and its solution procedure are presented using the proposed three-dimensional (3D) eigenstrain formulation of boundary integral equations (BIE) for simulating ellipsoidal particle-reinforced (and/or void-weakened) inhomogeneous materials. In the model, the eigenstrains characterizing deformation behaviors of each particle embedded in the matrix are determined using an iterative scheme with the aid of the corresponding Eshelby tensors, which can be obtained beforehand either analytically or numerically. With the proposed numerical model, the unknowns of the problem appear only on the boundary of the solution domain, since the interface condition between particles/voids and the matrix is satisfied naturally. The solution scale of the inhomogeneity problem can thus be significantly reduced. Using the algorithm, the stress distribution and the overall elastic properties are identified for ellipsoidal particle-reinforced/void-weakened inhomogeneous materials over a representative volume element (RVE). The effects of a variety of factors on the overall properties of the materials as well as the convergence behavior of the algorithm are studied numerically, showing the validity and efficiency of the proposed algorithm.     

计算机视觉中的三维重构建模

三维重构建模是计算机视觉技术的主要内容之一。相机内外参数的标定、图像特征点的提取以及特征点的立体匹配是三维重构建模的技术核心。本文总结了近来三维重构建模的研究成果和计算方法,并提出了一些观点,对三维重构建模的难点和发展趋势作了说明。     

水下结构声辐射问题之计算机仿真

该文采用混合有限元／边界元法计算水下结构物声辐射问题。为有限元软件包Nastran开发的Fortran代码用于计算外域流体的附加质量和附加阻尼,DMAP实现：Fortran代码与Nastran的结合,成功实现了应用现有有限元软件计算无界流域种结构辐射噪声的问题。采用Patran前后处理软件实现了对水下结构响应及其辐射声场的仿真。     

Reconstruction of the perfusion coefficient from temperature measurements using the conjugate gradient method

We consider the inverse bio-heat transfer problem to determine the space- and time-dependent perfusion coefficient from temperature measurements. In this formulation, the problem is fully determined and the coefficient is identifiable if and only if the temperature has dense support. However, the problem is still ill-posed since small errors in the measured temperature cause large errors in the output perfusion coefficient due to the numerical differentiation of noisy data involved which represents an unstable procedure. In order to overcome this difficulty and restore stability, we employ for the first time the conjugate gradient method (CGM) for solving the inverse problem under investigation. Regularization is achieved by stopping the iteration process at an appropriate threshold dictated by the discrepancy principle. Numerical results show that the CGM is accurate and reasonably stable in retrieving the perfusion coefficient. Moreover, comparison with other methods shows improved efficiency and stability in inverting noisy data.     

多起迄点配送问题的优化调度算法研究与实现

对多起讫点配送问题进行描述,针对不同情况建立了数学模型。通过分析,将供需不平衡模型转化为供需平衡模型,指出用西北角法求解模型的缺点,用最小元素法进行了优化调度。实验结果证明:最小元素法比西北角法优越,是一种有效的优化调度算法,值得推广。