Inhomogeneities in heteroassociative memories with linear learning rules

We investigate how various inhomogeneities present in synapses and neurons affect the performance of feedforward associative memories with linear learning, a high-level network model of hippocampal circuitry and plasticity. The inhomogeneities incorporated into the model are differential input attenuation, stochastic synaptic transmission, and memories learned with varying intensity. For a class of local learning rules, we determine the memory capacity of the model by extending previous analysis. We find that the signal-to-noise ratio (SNR), a measure of fidelity of recall, depends on the coefficients of variation (CVs) of the attenuation factors, the transmission variables, and the intensity of the memories, as well as the parameters of the learning rule, pattern sparsity and the number of memories stored. To predict the effects of attenuation due to extended dendritic trees, we use distributions of attenuations appropriate to unbranched and branched dendritic trees. Biological parameters for stochastic transmission are used to determine the CV of the transmission factors. The reduction in SNR due to differential attenuation is surprisingly low compared to the reduction due to stochastic transmission. Training a network by storing memories at different intensities is equivalent to using a learning rule incorporating weight decay. In this type of network, new memories can be stored continuously at the expense of older ones being forgotten (a palimpsest). We show that there is an optimal rate of weight decay that maximizes the capacity of the network, which is a factor of e lower than its nonpalimpsest equivalent.     

A software for simulating steady-state properties of passive dendrites based on the cable theory

In this study, a computer software, CableTeo, is introduced for simulating the steady-state electrical properties of passive dendrite based on the cable theory. The cable theory for dendritic neurons addresses to current-voltage relations in a continuous passive dendritic tree. It is briefly summarized that the cable theory related to passive cables and dendrites, which is a useful approximation and an important reference for excitable cases. The proposed software can be used to construct user-defined dendritic tree model. The user can define the model in detail, display the constructed dendritic tree, and examine the basic electrical properties of the dendritic tree using transfer impedance approach. The software addresses to ones who want to run simple simulations of the cable theory without need to any programming language skills or expensive software. It can also be used for educational purposes.     

联盟结构图的代数性质及应用

将联盟结构的空间抽象为联盟结构图,并在该图上定义2种运算并和交,从而联盟结构图中所有顶点关于并和交构成代数结构--联盟结构格.为了简化该格性质的研究,又引入整数拆分图,并在联盟结构图和整数拆分图之间建立映射关系F,且由映射关系,诱导一个等价关系E_F.这样在联盟结构图中搜索最优联盟结构时,可以利用某个联盟结构对E_F产生的等价类的上界和平均值作为剪枝函数,当某个等价类的上界低于剪枝函数时,该等价类中的大量联盟结构就被剪枝掉.最后设计一种动态规划算法.实验表明它的有效性.在20个Agent时,它比原动态规划算法减少43%的搜索次数.     

Computerized enumeration of staggered alkane conformers

An alkanoid is defined as a tree (in the graph-theoretical sense) which can be embedded in the diamond lattice. It corresponds to a staggered conformer of an alkane. A computer program for enumerating non-overlapping alkanoids is described. In these systems there is no pair of coalescing vertices. Results for the unbranched and branched alkanoids are given separately, and the symmetry groups of the systems are determined.     

单层平面索网玻璃幕墙数值风洞风载荷分析

针对现行幕墙设计规范没有明确规定单层平面索网幕墙体系的风载荷计算的问题,以某大厦裙房幕墙为研究对象,用ADINA分析考虑流固耦合作用的玻璃 索网体系风振响应分析,并与通常采用的等效静风载荷方法得到的结构风效应比较.分析表明,对于非线性的索网玻璃幕墙结构,现行载荷规范采用的等效静风载荷方法会导致偏于不安全的设计计算结果.     

The analysis of nonlinear cable net systems and their supporting structures

The analysis of large cable net systems is feasible only with the aid of high speed digital computers. However, even computerized design of cable nets requires careful formulation and the selection of efficient solution techniques. This paper describes the solution of a general integrated structural system which includes three-dimensional beam members and cable elements that is useful to the design engineer. This solution is used to analyze an example prestressed cable structure, and results are presented to demonstrate the efficiency and accuracy of different solution techniques and to illustrate the effect of variation of important parameters.NET 3 is the general solution program. Input includes: (1) cable sizes, weights, and stress-strain characteristics; (2) initial coordinate points and cable forces due to prestressing; (3) support conditions for the cable net; (4) applied loads; and (5) data for supporting structure. The initial shape and cable forces are computed with the aid of an auxilliary program, SHAPE, given the coordinates of the cable end points, the initial prestressing forces, and an initial interior coordinate. The cable stress-strain characteristics may be linear or nonlinear. The supporting structure may be replaced with equivalent spring stiffnesses or actual three-dimensional elements.The assumptions used in the solution are: (1) cable elements are straight between nodal points and have no flexural stiffnesses; (2) the roofing and decking provide no stiffness; (3) all loads are applied at the nodal points; and (4) all supporting structural elements are elastic. It should be noted that no displacements of the cable nodal points are neglected. Even at boundaries, the elastic stiffness can be considered. Temperature changes can be analyzed to determine their effect upon the structure.Cable net structures usually have many elements and require relatively large amounts of computer time. In addition many loading and geometric conditions must be considered. To be useful as a practical design tool, it was essential that the program be as efficient as possible and require a minimum of storage. The solution utilizes a variation of the Newton-Raphson method. Initially the tangent-modulus stiffness is used. At each iteration the change in the element force is compared with the change in element force for the previous iteration to determine if the convergence rate is within a prescribed value. If it is acceptable, the stiffness for the previous iteration is used; if unacceptable for any element, tangent stiffnesses for all elements are recalculated. This technique attempts to combine the best features of the Newton-Raphson and the modified Newton-Raphson methods by increasing convergence probability and decreasing solution time.To minimize storage requirements, NET 3 has the capability of utilizing tapes in the problem solution. The storage requirements are determined internally before the solution is initiated. If the required storage exceeds that alloted for the system of equations, the solution is effected through the use of tapes.Output for the cables includes nodal point displacements, nodal point forces, and element forces; for beam elements, forces and moments are given. The solution has been verified by comparison with results by other investigators.An elliptical shaped structure, 220 by 240 ft, has been analyzed with the program to investigate the influence of several parameters. The short direction cables were prestressed, and a uniform load of 40 psf was assumed. The variables investigated include: (1) initial prestress force; (2) degree of stiffness of supporting structure; (3) cable sizes; (4) sag-span ratio; and (5) temperature change.     

Dendritic stylization

Dendritic or branching structures are commonly seen in natural phenomena such as lightning, cracks, and vegetal growth. They are also often used for artistic or decorative purposes. We present a new procedural method for modeling dendritic structures based on a path planning approach. Our method includes the use of a partial non-scalar distance metric that gives us powerful and responsive control over the evolving dendritic structure. We demonstrate the effectiveness of our approach by creating dendritic stylizations of input images. We also show how our approach can be used to model more complex dendritic structures, such as trees; our algorithm allows us to create pareidolia effects, where an image is embedded within the branches of the tree.     

Analysis and design of cable structure S

As a class, suspension structures are generally more flexible than framed or trussed structures. A consequency of this flexibility is that factors often need be considered when engineering cable structures which may be neglected when designing more conventional structural systems. Among these factors are: difficulties associated with mathematically defining the suspension structure's initial shape and the member forces corresponding to that state, the nonlinear relationship between changes of loading and displacement, and the susceptibility of some types of cable structures to wind-induced oscillations.

In the paper, cable structures are classified and examples of some types are illustrated together with a discussion of their advantages and disadvantages. The problem of establishing the initial shape of the structure is discussed. Some techniques for computing the displacements of suspension structures resulting from changes in static loading, considering the geometrical nonlinearity, are described. A procedure for determining the displacements of stiffened and unstiffened cable three-dimensional structures is outlined that is suitable for computer solution. Results of numerical studies made utilizing this technique are presented.     

多索-单梁耦合结构的动力学建模及非线性特性研究

大跨度斜拉桥通常采用密索体系,拉索的振动频率非常接近,同时拉索之间也可能存在倍频关系.因此,可能存在索与索之间的相互耦合振动.索是斜拉桥的重要承重构件,对多索-单梁的动力学特性进行研究至关重要.本文考虑到索梁、索塔及塔梁的边界条件和连接点处的连接条件,基于Hamilton变分原理,建立了多索-单梁结构的运动微分方程.经过无量纲化处理,根据分离变量法,得到了其降维约化后的运动微分方程.本文取相邻的两根索考虑两种工况模型,对不同工况下的双索-单梁耦合结构的动力学行为进行了参数分析.研究发现,不同于以往资料中的“频率转向”现象,在本文中,两条频率曲线在频率值接近处,并未迅速分离,而是在相对一小段参数范围内继续保持平行且相互靠近,随后再迅速分离.最后,研究了双索-单梁耦合结构的非线性特性,分别对结构进行了两自由度和单自由度离散,研究发现,结构单模态假设在非共振区域能反映结构的非线性特性,但是在共振区域,结构的非线性特性会发生跳跃变化,应用2自由度模态理论进行研究更为准确.     

The use of lexical semantics in interlingual machine translation

This paper describes the lexical-semantic basis for UNITRAN, an implemented scheme for translating Spanish, English, and German bidirectionally. Two claims made here are that the current representation handles many distinctions (or divergences) across languages without recourse to language-specific rules and that the lexical-semantic framework provides the basis for a systematic mapping between the interlingua and the syntactic structure. The representation adopted is an extended version of lexical conceptual structure which is suitable to the task of translating between divergent structures for two reasons: (1) it provides an abstraction of language-independent properties from structural idiosyncrasies; and (2) it is compositional in nature. The lexical-semantic approach addresses the divergence problem by using a linguistically grounded mapping that has access to parameter settings in the lexicon. We will examine a number of relevant issues including the problem of defining primitives, the issue of interlinguality, the cross-linguistic coverage of the system, and the mapping between the syntactic structure and the interlingua. A detailed example of lexical-semantic composition will be presented.     

考虑迟滞及变形影响的主被动混合驱动绳驱空间机械臂运动学建模及求解

在绳驱空间机械臂的非结构化环境灵巧作业中,驱动绳索拉伸和臂段形变给机械臂的精确控制带来了困难。为此,本文提出一种改进运动学模型。首先,建立机械臂“驱动绳索长度－关节角度－末端位姿”的多重映射运动学模型;进一步考虑绳索迟滞、运动方向切换和臂段变形3种因素耦合影响,改进“驱动绳索长度－关节角”的映射模型。其次,设计试验平台,开展不同负载下的绳索迟滞量测定试验。最后,对比改进运动学模型仿真结果和绳驱空间机械臂样机试验数据。与理想几何模型的比较结果表明,长1110 mm的两段绳驱空间机械臂的末端绝对位置误差可减小15.2 mm;末端绝对位置误差减小61.4%,证明了改进运动学模型的有效性。     

连通度问题的三维DNA结构进化算法

针对求连通度这一难解问题,提出了三维DNA图结构进化算法。并提出了一种由k-臂DNA分子构建的图结构。在所述方法中3、4臂DNA分子的顶点构造块被选择性地用来构建一些不同的图结构。然后通过凝胶电泳分离,图的连通度便可确定。并且通过引入进化算法的思想,避免了解空间的穷举。     

Developing intelligent tensegrity structures with stochastic search

Since structural control of civil structures was first proposed in 1972, most research and applications have focused on enhancing the safety of structures under extreme conditions. This paper introduces a new direction in structural control: the use of computational methods and explicitly defined knowledge to improve serviceability and maintenance of civil structures. The objectives of such structures, called intelligent structures, are to maintain and improve structural performance by recognizing changes in behaviors and loads, adapting the structural geometry to meet defined goals, and using past events to improve future performance. A computational framework based on intelligent control methodology is presented that combines reasoning from explicit knowledge, search, learning and planning to illustrate a vision for intelligently controlled civil structures. This is applied to enable global shape control of an adjustable tensegrity structure using a combination of simulated annealing search, dynamic relaxation analysis and structural measurements. Active tensegrity structures are modular, reusable cable structures that do not require expensive anchorages or steep slopes. This provides an innovative solution for temporary structures. Particularly, when used for exhibitions, they could become part of an exhibition, rather than just house one. As part of a multi-stage project, results presented in this paper demonstrate the feasibility of building an intelligent tensegrity structure.     

基于粗糙集信息等价矩阵的关联规则挖掘

利用粗糙集理论,从矩阵分析的角度来挖掘决策表蕴含的信息,引入粗糙集信息等价关系的同构映射——等价矩阵,等价矩阵可看作是等价关系在信息表内的知识表达。给出了等价矩阵的求取算法以及等价矩阵意义下的属性重要度和核的概念。设计了基于等价矩阵的决策信息表的最小属性约简算法。从等价矩阵本身相关操作运算来挖掘客观知识之间的关联模式,提出了基于信息等价矩阵的关联规则提取的算法。实例证明提出的算法有效,为进一步研究决策信息系统的规则提取和决策算法提供了可行的计算方法。     

基于弱磁探测技术的高压海底电缆精确定位系统设计

高压海底电缆具有耐腐蚀、抗冲击性能好和电气寿命长等优点,是海上输电系统的重要组成部分,为保证海底输电系统正常运行,设计并开发了基于弱磁探测技术的高压海底电缆精确定位系统。装设海底弱磁探测器作为弱磁探测技术的执行元件,改装高压海底电缆精确定位器。根据高压海底电缆的组成结构、电力学工作原理以及磁场分布特征,构建高压海底电缆及其磁场等效模型。采集高压海底电缆的实时状态数据,利用弱磁探测技术获取高压海底电缆周围的磁信号,通过信号特征匹配与坐标计算,得出高压海底电缆精确定位结果。通过系统测试实验得出结论：与传统定位系统相比,优化设计系统定位静态电缆的平均误差降低约10.82m,定位动态电缆的平均误差降低了11.37m,表明了所设计系统在定位精度方面具有明显优势。     

钢丝绳传动机器人运动学的支路分析方法

通过研究分析一类[N+1]条钢丝绳驱动[N]个自由度机器人的运动学,其运动学可通过推导移去钢丝绳后开环链机器人关节空间与笛卡尔空间之间的运动学关系和关节空间与驱动空间之间的运动学关系来完成。在基本回路、共轴条件和传动线运动学分析的基础上,提出了用支路矩阵和等效半径矩阵描述钢丝绳传动机器人运动学的支路分析方法。根据钢丝绳传动原理,通过观察法可直接列写支路矩阵和驱动空间等效半径矩阵,从而得到了驱动空间与关节空间之间的运动学映射关系,解耦了由于钢丝绳传动导致机器人关节间的运动耦合。结合传统机器人运动学,实现了驱动空间、关节空间和笛卡尔空间完整运动学映射关系,加快和简化了钢丝绳传动机器人运动学建模和分析过程。以Stanford/JPL手指为例进行了运动学分析和仿真,验证了用支路矩阵和等效半径矩阵描述钢丝绳传动机器人运动学支路分析方法的正确性,为钢丝绳传动机构的设计、运动学分析与控制奠定了基础。     

Nonlinear elasto-plastic analysis of slack and taut cable structures

This paper presents the geometrically nonlinear analysis of the slack and taut cable structures considering the material inelasticity subjected to self-weight, pretension, and external loads. The finite element procedure is briefly summarized using the Lagrangian formulation associated with isoparametric interpolation polynomials and the Newton–Raphson iterative scheme with incremental load. The simple and efficient method to determine the initial equilibrium state of the slack cable systems under self-weight as well as support motions is presented using the penalty method. The numerical algorithm to evaluate the tangent modulus of elasticity of cable is presented based on the iterative scheme. The accuracy and reliability of the present study are verified by comparing the predictions with those generated by well-reported slack and taut cable structure problems. The effect of the yielding of cable segments on displacements and stresses of cable structures is investigated.     

基于有限元模型修正技术的复杂索拱体系施工稳定性

为准确分析复杂索拱体系结构的施工稳定性,以山东淄博潭溪山桥为例,提出一种基于有限元模型修正技术的分析方法。建立包括细部构造的精细化有限元模型,以节点位移构造目标函数对简化的梁系模型进行静力修正,修正后的梁系模型位移结果得到小幅改进,索力和结构应力得到明显改进。分别计算施工过程各阶段修正模型与未修正模型的线性稳定安全因数与非线性稳性定安全因数,对比分析结果认为：修正模型能够体现实际细部构造的加强作用,可使分析更为精确。将修正模型的稳定性分析结果与规范对比,认为结构施工稳定性满足要求。     

On resource allocation in multistage interconnection network-based systems

A resource allocation problem in a reconfigurable multicomputer architecture based on rectangular banyan multistage interconnection network with arbitrary fanout and arbitrary number of levels is studied. Four commonly used problem structures such as ring, pipeline, broadcast, and macropipeline are introduced and the mapping problem of these structures on the system model, which is equivalent to the resource allocation problem, is discussed. Analytic solutions to several mapping questions are given and generalization of the results to other networks is presented.