机车空调逆变电源设计

本文讨论的是机车空调逆变电源系统的设计与研究。该电源系统主要是由DC/DC的BOOST升压部分和DC/AC三相逆变部分两部分组成。DC/DC部分所得直流电压通过DC/AC部分逆变成三相交流电,供给空调机组工作。同时,为使电源系统能更可靠的运行,也设计了相应的故障检测、保护等辅助电路。     

传输线信号完整性的反射分析

针对高速电路系统的传输线信号完整性问题,通过对高速电路PCB上传输线等效电路的分析,给出了信号传输时产生反射现象的原因;介绍了常用的消除反射的方法,即选择均匀传输线、采用合适的拓扑结构布线和阻抗匹配法,指出阻抗匹配法可解决信号传输的反射现象;阐述了源端阻抗匹配法和负载端阻抗匹配法消除反射的原理和适用条件。针对时钟电路中的反射问题,采用PADS/Hyperlynx软件对阻抗匹配法进行仿真,结果表明,阻抗匹配法能够改善信号传输的反射现象。     

Abstraction of levels of abstraction

The notion of level of abstraction (LoA) is one of the foundations of the Floridi's Philosophy of Information. It also serves for many practical purposes as in information ethics. But the notion of abstraction is not new; it has been given many different meanings in various fields, especially in scientific disciplines and, in particular, in computer science. Our purpose here is to examine the use of abstraction in Floridi's works in conjunction with some of the meanings of abstraction in computer science. The article is divided into five sections. After a general introduction to the Floridi's method of abstraction (MoA) in Section 1, Section 2 revisits Floridi's definition of abstraction and Section 3 gives the different senses of abstraction in computer science. The Section 4 compares them with the Floridi's LoAs and proposes to generalise the Floridi's approach to abstraction using an abstraction of the LoAs, while Section 5 concludes on what we think to be some new arguments in favour of MoA and LoA.     

Synthesis of subminimum-time bounded control of system of rigid bodies

An algorithm of control of a system of rigid bodies in a form of feedback in special coordinates is discussed. The control is bounded, and it is also subminimum-time in the sense that it coincides with the optimal in linear approximation and in the case of a system with one degree of freedom. It is shown that the controller endows the unperturbed motion of the system with the property of asymptotic stability in large and is also robust. The results of numerical experiments, demonstrating the closeness of the trajectories to the time-optimal ones, are presented.     

支持向量机多类目标分类器的结构简化研究

由于支持向量机(SVM)在模式识别和回归分析中有着独特优势，因此成为近来研究的热点，其优势主要体现在处理非线性和高维数据问题方面。最初的SVM特别适合解决两类目标分类问题，而对于多类目标分类，则需将其转化为多个两类目标分类问题，相应地即可构造多个两类目标子分类器，但由于这种情况导致了分类器结构的过于复杂，从而导致判决速度的降低。为了快速地进行分类．提出了一种简化结构的多类目标分类器，其不仅使得子分类器数目大大减少，而且使分类速度明显提高；同时对其分类精度和复杂度进行了对比分析。实验结果证明。该分类器是有效的。     

生育观念的变迁与年画儿童形象造型衍变研究

年画中儿童形象是民众理想与国家理想的物化,形成于中国特定的社会心理文化土壤中。年画中儿童形象作为反映我国民间对＂求生＂一类祈福形式和社会心理,从内容到形式都随着时代的变迁而不断演化。年画中儿童形象造型的衍变,既与历史的传承性和制度的阶级性有着深刻的内在关联,又因为年画中的儿童形象造型是一种社会存在,因而具有发展的动态性和主题的时代性。在当下,重新审视生育观念的变迁并诠释其对年画中儿童形象造型衍变和重构的意义,是一种文化自觉。     

手腕骨X线片兴趣区域图像分割的研究

提出了一种准确分割骨骺兴趣区域边缘位置的方法。针对手腕骨X线片图像的特征,采用Gibbs 随机场对兴趣区域进行初始分割,将骨从图像中分割出来;针对骨与软组织的灰度值相差不大,Gibbs 随机场正确分割困难的问题,再进一步利用主动轮廓法对初始轮廓进行改善,将软骨与软组织准确分割开,从而得到了正确的骨的边缘位置。实验验证了该方法对分割出的底部区域骨的轮廓线有较大的改善,同时这种联合的方法具有较强的抗噪声能力。     

The computation of zones of influence of linear geological structures

The concept of a zone of influence of a linear geological structure provides a method of quantifying the effect of the structure on the properties of its neighborhood. For example, a fault may exert some influence on the local roof conditions in a mine opening, or on the location of mineral deposits, where the influence at any given distance (up to the specified half-width of the zone of influence) from the fault is estimated by some postulated influence function. Any area of interest may be partitioned into a large number of cells, and the sum of the influences due to the nearby faults calculated for the midpoint of each cell. The program groups the cells, by midpoints, into sets comprising those cells affected by precisely 0,1,2,... faults, calculates the proportion each set constitutes of the area of interest, and the total of the midpoint sums of the cells in each set. Although the program was developed for a specific problem in a New South Wales colliery, the method is not specific to this problem and has application to many situations in rock mechanics, metallogenesis, seismicity, and in other fields in which the concept of a zone of influence may be relevant.     

物联网技术研究进展

目前,物联网因其巨大的应用前景而受到各国政府、学术界和工业界的广泛重视,成为国内外信息通信领域的新研究热点;物联网产业己经成为推动世界经济增长的重要新兴产业,我国已将物联网的发展列为信息产业发展的下一个战略高点;首先总结了物联网的国内外研究进展,其次对物联网的概念、实现原理与体系结构进行了分析,归纳了物联网涉及的关键技术,然后介绍了物联网的一些典型应用,最后指出了物联网进一步研究的方向以及制约国内物联网发展的问题及解决对策。     

《数据库系统概论》教学方法探索

针对<敷据库系统概论>课程的教学性质,结合其理论和实践教学并重的教学特点,对该门课程的本科生教学进行了探索.分析该门课程的体系结构和教学中存在的问题,给出了相应的解决办法,对该门课程的教学方法进行了研究、探索和总结.     

On approximate solution of the problem of formation of the fixed-income portfolio of securities

Consideration was given to optimization of a fixed-income portfolio of securities in terms of the quantile performance index. Solution employed the linearization method based on the expression of the portfolio income linearized in random parameters. Analytical expressions for approximate determination of the optimal portfolio were proposed, and the error of approximation in the value of criterion was estimated.     

液压支架电液控制系统软件在线升级方案设计

针对现有液压支架间架控制器与端头控制器的软件升级需要技术人员在井下对控制器逐一拆装操作,且耗时长、效率低的问题,提出了一种液压支架电液控制系统软件在线升级方案,详细介绍了液压支架电液控制系统组成、代码存储空间变化及在线升级的相关程序流程,并给出了实验数据及分析。该方案实现了对间架控制器和端头控制器的远程在线升级,升级过程简单方便,且升级速度快。     

Computational properties of networks of synchronous groups of spiking neurons

We demonstrate a model in which synchronously firing ensembles of neurons are networked to produce computational results. Each ensemble is a group of biological integrate-and-fire spiking neurons, with probabilistic interconnections between groups. An analogy is drawn in which each individual processing unit of an artificial neural network corresponds to a neuronal group in a biological model. The activation value of a unit in the artificial neural network corresponds to the fraction of active neurons, synchronously firing, in a biological neuronal group. Weights of the artificial neural network correspond to the product of the interconnection density between groups, the group size of the presynaptic group, and the postsynaptic potential heights in the synchronous group model. All three of these parameters can modulate connection strengths between neuronal groups in the synchronous group models. We give an example of nonlinear classification (XOR) and a function approximation example in which the capability of the artificial neural network can be captured by a neural network model with biological integrate-and-fire neurons configured as a network of synchronously firing ensembles of such neurons. We point out that the general function approximation capability proven for feedforward artificial neural networks appears to be approximated by networks of neuronal groups that fire in synchrony, where the groups comprise integrate-and-fire neurons. We discuss the advantages of this type of model for biological systems, its possible learning mechanisms, and the associated timing relationships.     

深圳市景观格局空间梯度分异的研究

选择深圳市作为研究对象,利用2006年的遥感影像,研究了深圳市景观空间格局的梯度变化特征。结果表明：景观多样性指数沿梯度区呈先增大后减少的趋势。在城区内其值较低,在城乡结合区域因类型斑块交错分布其值较高;在城区景观斑块密度与边缘密度较小,景观异质性较低。越靠近城乡结合处景观异质程度越大。从景观平均形状指数和景观平均分维数的变化,可看出人为活动的干扰由市中心向郊区发展是呈增强的趋势。以上分析表明景观格局的空间分布与受人为干扰程度有重要的联系。     

物联网技术在智慧校园建设中的应用

在信息化的时代背景下,信息技术在各行各业中广泛应用,并取得了较好的成效。目前,信息技术在校园生活中广泛渗透,特别是物联网的快速发展为智慧校园的建设提供了重要的技术支持。文章从物联网与智慧校园入手,分析了智慧校园建设中的主要物联网技术,并进一步阐述了物联网技术在智慧校园建设中的应用及发展方向。     

The Grid Methods of the Recognition of the Region of Efficiency of Microwave Devices

Some results for design and optimization of complex microwave devices are considered in this article. The problems are investigated from the standpoint of recognition of region of efficiency in which necessary values of given output characteristics are appeared. The application for optimization of meshes that are uniform in the multidimensional space of parameters is discussed. The solution of the approximate optimization problem using a specially created mathematical model of the device and software packages that implement time-consuming computational procedures is debated.     

Modifications of the method of variation of parameters

In spite of being a classical method for solving differential equations, the method of variation of parameters continues having a great interest in theoretical and practical applications, as in astrodynamics. In this paper we analyse this method providing some modifications and generalised theoretical results. Finally, we present an application to the determination of the ephemeris of an artificial satellite, showing the benefits of the method of variation of parameters for this kind of problems.     

编码器倍频、鉴相电路在FPGA中的实现

VHDL是系统设计领域最佳的硬件描述语言。文章针对用于位置与速度反馈测量的光电编码器信号的特点,介绍了运用VHDL在FPGA中实现编码器倍频、鉴相电路的方法,它对提高编码器分辨率与实现高精度、高稳定性的信号检测及位置伺服控制具有一定的现实意义。