矿井供电系统弧光接地过电压影响因素研究

为了全面研究接地电阻、线路电阻、故障位置、对地电容、相间电容、燃弧时刻这6种因素对矿井供电系统弧光接地过电压的影响,采用实时数字仿真仪搭建典型矿井供电系统模型和间歇性电弧接地模型,结合工频熄弧理论和高频熄弧理论对弧光接地过电压的形成过程及影响因素进行理论分析和仿真研究。结果表明,电弧重燃时刻对弧光接地过电压的影响最为显著,线路电阻、接地电阻及相间电容的影响较大,故障位置、对地电容的影响较小;弧光接地过电压是系统参数的综合反映,不同的矿井供电系统过电压值会有很大差异。     

煤矿供电系统电容电流自动补偿装置的设计

根据煤矿安全供电的要求,文章设计了一种煤矿供电系统电容电流自动补偿装置,介绍了该装置的硬件组成、工作原理、软件设计及装置的抗干扰设计。该装置实现了供电系统电容电流的自动补偿,提高了供电系统运行的可靠性。     

超级电容在地铁牵引供电系统中的节能应用

近年来随着超级电容的应用和发展,车载式和地面式电容型储能系统已经成功地应用于地铁牵引供电系统,对电网的节能和稳压起到了良好的作用。本文对电容型储能系统在地铁牵引供电系统断电时需要把车辆紧急召回的极端条件下的应用做了进一步的探索。     

单相三绕组永磁同步电动机的稳态性能

在使用电容的单相电源供电系统的电路中,异步电机的运行是众所周知的。异步电机在单相电源供电系统中的详细研究已有文献记载[1],但是在永磁同步电动机中却较少进行这样的研究。为提高电能的利用率,解决电力不足而导致电能消耗急剧上升时,电能的高效利用率问题,对单相电源供电系统下的永磁同步电动机的稳态运行性能进行了详细研究。利用对称分量理论结合坐标变换理论进行分析,推导出在单相电源供电系统下,永磁电动机运行时所需电容值大小的几种计算方法,并对其进行比较,通过Matlab进行仿真实验。结果表明:利用最小不平衡因数和最大效率法所求得电容值为最佳电容值,可使永磁同步电机达到良好的运行性能,有效的提高了电机的效率。     

推进装置面向对象实时仿真研究

为设计、论证和优化舰船推进装置，采用面向对象技术和实时仿真软件对其进行仿真计算，动态、实时地模拟舰船推进装置的工作过程。利用该仿真系统，对某型舰船推进装置进行实时仿真，计算出该推进装置的动态性能参数，与实际符合较好。因此对舰船推进装置进行仿真计算，可以为设计、论证和优化提供重要的依据。     

南海舰船数据可视化分析系统设计与实现

为了更好地对南海舰船数据进行展现和分析,基于百度地图API,以南海舰船数据为基础数据,采用B/S架构,结合数据可视化图表库Echarts、百度地图大数据可视化库、百度地图热力图库,采用数据库等技术对舰船数据进行管理,在时间和空间上对舰船数据进行可视化和分析。设计并实现具有舰船位置和轨迹可视化、舰船统计分析、舰船轨迹查询、舰船热力图为核心功能的Web应用。该系统能够更加直观高效地对舰船数据进行管理分析,对航道安全的提升具有分析参考作用。     

基于极小误差阈值分割的舰船自动检测方法

针对中、高分辨率(0.6m ~5m)可见光卫星遥感图像，提出了一种基于极小误差分割的海上舰船自动检测算法，该方法利用自适应定向正交投影的高斯分解法，拟合海洋区域直方图，采用改进的信息熵极小误差分割算法，确定分割阈值。对于候选舰船目标采用基于多判据的目标检测思想检测舰船，对100多幅可见光图像进行了试验。结果表明，该方法能够自动、快速、准确地检测图像中的舰船，具有较高的检测能力。     

SAR图像中海上舰船目标自动检测新方法

针对中分辨率近岸海域SAR图像,结合已有的舰船检测算法,提出了一种新的海上舰船目标自动检测方法。该方法先根据相应的抽取算法和图像数据映射准则,分离图像中的海洋和陆地区域,并结合最大熵分割法提取海洋背景中包含候选目标的感兴趣区域,最后利用特征匹配方法检测出真正的舰船目标。对50多幅SAR图像进行了试验,其结果表明该方法能自动、快速、准确地检测出图像中舰船目标。     

基于AR模型和神经网络的舰船水压信号检测方法

为了有效地从风浪背景中检测舰船水压场信号，根据舰船水压场信号和波浪噪声信号的差异，以时间序列的AR模型理论为依据，采用基于AR模型和神经网络的舰船水压信号检测方法。该检测算法的核心是将检测问题转化为模式识别问题，首先对接收信号建立AR模型并提取AR模型系数作为特征向量，然后利用人工神经网络对信号进行检测。在此基础上，通过不同浪级情况下海浪水压力场的仿真信号数据，对某型目标舰船的水压力信号进行了检测计算，验证了该方法的有效性，尤其是达到了在高海况、低信噪比条件下，对目标信号检测率比较高、虚警率比较低的效果。     

仅售399元 黑潮770主板新装上阵

AMD Spider平台除了高人气的780G外。独立芯片组AMD770同样受到不少用户的欢迎，斯巴达克推出黑潮系列新主板BA-120目前已经在全国上市，市场售价为399元。BA-120主板继承黑潮系列一贯扎实严谨的工艺风格，仍采用豪华的高品质固态电容搭配全封闭电感组成五项供电系统，并采用独立的内存、显卡供电设计，     

Using dynamic user models in the recognition of the plans of the user

This paper is concerned with information-seeking dialogues in a restricted domain (we consider a consultation system for a Computer Science Department, delivering information about the various tasks that the users may want to perform: for example, how to access the library, get information about the courses of the Department, etc.) and presents a framework where a plan recognition and a user modeling component are integrated to cooperate in the task of identifying the user's plans and goals. The focus of the paper is centered on the techniques used for building the user model and exploiting it in the determination of the user's intentions. For this task, we use stereotypes and we propose some inference rules for expanding the user model by inferring the user's beliefs from both the sentences s/he utters and the information stored in the plan library of the system, that describes the actions in the domain. Moreover, we introduce some disambiguation rules that are applied to the information in the user model for restricting the set of ambiguous hypotheses on the user's plans and goals to the most plausible ones. This also simplifies a further clarification dialogue if it is necessary for a precise identification of the user's intentions.     

A survey of the state of the art in learning the kernels

In recent years, the machine learning community has witnessed a tremendous growth in the development of kernel-based learning algorithms. However, the performance of this class of algorithms greatly depends on the choice of the kernel function. Kernel function implicitly represents the inner product between a pair of points of a dataset in a higher dimensional space. This inner product amounts to the similarity between points and provides a solid foundation for nonlinear analysis in kernel-based learning algorithms. The most important challenge in kernel-based learning is the selection of an appropriate kernel for a given dataset. To remedy this problem, algorithms to learn the kernel have recently been proposed. These methods formulate a learning algorithm that finds an optimal kernel for a given dataset. In this paper, we present an overview of these algorithms and provide a comparison of various approaches to find an optimal kernel. Furthermore, a list of pivotal issues that lead to efficient design of such algorithms will be presented.     

Computing the volume of the union of spheres

OnO(n ²) exact algorithm is given for computing the volume of a set ofn spheres in space. The algorithm employs the Laguerre Voronoi (power) diagram and a method for computing the volume of the intersection of a simplex and a sphere exactly. We give a new proof of a special case of a conjecture, popularized by Klee, concerning the change in volume as the centres of the spheres become further apart.     

On the boundedness of the Hessian of the potential energy of robot manipulators

Several results on robot manipulator motion control require a uniform bound for the Hessian of the potential energy or equivalently the Jacobian of the gravity vector. Not all robot manipulators, however, ensure the existence of such a uniform bound. The first contribution of this article is the complete characterization of this class which is referred to as class ℬ︁𝒢𝒥 manipulators. The uniform bound of the Hessian is typically part of the control law expression and hence it plays an important role in controller gain synthesis. The second contribution of this article consists of deriving, for class ℬ︁𝒢𝒥 robot manipulators, an easy to compute explicit expression of the uniform bound in terms of kinematic and inertial link parameters. If for a particular robot manipulator the Hessian of potential energy is not uniformly bounded, a bound exists that is valid within the physical workspace of the manipulator. The third contribution of this article is the derivation of an explicit expression for the latter bound which is useful in the design and controller gain synthesis of control laws that are valid locally. ©1999 John Wiley & Sons, Inc.     

On the rubrication of the journal The Physics of Nanoobjects and Nanotechnology from the AJ Physics of the VINITI RAS

The necessity for creating a separate abstract journal on the physics of nanoobjects and nanotechnology, which is a new rapidly developing interdisciplinary knowledge field, is substantiated. The first successes in nanotechnology promise a new scientific-technical revolution. Physics is one of the fundamental bases of nanotechnology and the foundation for this revolution. The publication of a separate journal will permit the data about a greater portion of the research on the physics of nanoobjects and nanotechnology to be gathered in one place.     

Robotics in the factory of the future Role of Robots in the Factory of the Future

Robots represent a flexible source of automation in a variety of manufacturing processes today. As a result of this, robots are being increasingly used as an alternative for automation in a large number of manufacturing concerns. The present trend has been to link these islands of automation together with efficient material handling and computer control to attain to totally automated environment, what is commonly referred to as the “Factory of the Future”. This paper discusses the role of robots in such a factory and draws upon a case study to illustrate the varied aspects that one deals with in robotization in such an environment.     

Thermodynamics of martensitic transformations in the framework of the CALPHAD approach

Martensitic phases occur in a number of metallic materials, and are metastable in many systems. They have been of significant importance in steels for a long time, and have generated a great interest in Shape Memory Alloys (SMA) in recent years. This review describes a thermodynamic and kinetic approach for modelling martensitic phases in the framework of the CALPHAD approach.     

On the evaluation of the eigenvalues of the finite differences laplacian over a hexagon

Fast numerical methods for the evaluation of the eigenvalues of the finite-differences laplacian over a regular hexagon are devised. At first we show how this eigenvalue problem can be splitted into 3 eigenvalue problems, of lower dimension (reduced by a factor of 1/6), for the discrete laplacian over a regular triangle with suitable boundary conditions. Then, expressing explicitely the eigenvalues and the eigenvectors of the discrete laplacian over a triangle in terms of the coefficients of the discrete Fourier transform, we show how to deal efficiently with each subproblem. In particular we show that each step of the shifted inverse power method, for the approximation of the eigenvalues, costs O(n²log n) arithmetic operations in a sequential model of computation, and O(log n) steps with n² processors in a parallel model of computation, where n is the number of the nodes on the edge of the hexagon. Similar estimates hold for the orthogonal iterations (subspaces iterations) method and for Lanczos method. This approach includes the deflation of the eigenvalues of the triangle from those of the hexagon. These results improve the methods given by Bauer and Reiss [1] allowing a higher precision in the approximation of the eigenvalues of the laplacian and reducing the computational cost, either in a sequential or in a parallel model of computation.     

Exploring the Geometry of the Space of Shells

We prove both in the smooth and discrete setting that the Hessian of an elastic deformation energy results in a proper Riemannian metric on the space of shells (modulo rigid body motions). Based on this foundation we develop a time‐ and space‐discrete geodesic calculus. In particular we show how to shoot geodesics with prescribed initial data, and we give a construction for parallel transport in shell space. This enables, for example, natural extrapolation of paths in shell space and transfer of large nonlinear deformations from one shell to another with applications in animation, geometric, and physical modeling. Finally, we examine some aspects of curvature on shell space.     

命题逻辑的子句集中文字的分类

检测和消除命题逻辑公式中的冗余文字,是人工智能领域广泛研究的基本问题。针对命题逻辑的子句集中子句的划分,结合冗余子句和冗余文字的概念,将命题逻辑的子句集中的文字分为必需文字、有用文字和无用文字3类,并分别给出其定义。讨论3种文字与无冗余等价子集的性质,给出其等价子集的等价描述方法。得到题逻辑的子句集中必需文字、有用文字和无用文字的判定方法,借助子句集的可满足性得到3种文字与子句集的可满足性的等价条件。上述结果对命题逻辑中文字属性的判断提供了多种可选择方法,同时为命题逻辑公式的化简奠定了理论基础。