基于ADS的LFM脉压雷达系统建模与仿真

指出雷达系统基于传统仿真软件建模与仿真时的缺点;阐述了ADS(Advanced Design System)软件在雷达系统仿真中的优势;然后建立一个基于ADS软件平台的雷达系统仿真模型库.当对某种雷达系统仿真时,只需根据要求修改各个模块的参数或更换子模块即可准确迅速地搭建起系统仿真模型,大大缩减了建模所花费的时间和人力物力.以一个线形调频脉冲压缩雷达系统建模的过程为例,对ADS软件在雷达系统仿真中的应用加以介绍,并给出最终仿真结果.     

基于双环控制的航空静止变流器的建模与仿真

针对航空静止变流器在非线性负载条件下输出电压谐波含量大以及逆变器动态响应过程十分缓慢的问题,采用电容电流内环电压外环的双环控制技术,给出了控制器参数基于极点配置的方法,建立了单相航空静止变流器的数学模型。通过Matlab/Simulink软件平台对模型仿真。结果表明:设计方法能真实反映系统的动、静态性能,同时也验证了采用双环控制技术解决航空静止变流器带非线性负载时输出波形畸变以及动态响应缓慢的问题是行之有效的。     

Integrating scientific modeling and supporting dynamic hazard management with a GeoAgent-based representation of human–environment interactions: A drought example in Central Pennsylvania, USA

Recent natural disasters indicate that modern technologies for environmental monitoring, modeling, and forecasting are not well integrated with cross-level social responses in many hazard-management systems. This research addresses this problem through a Java-based multi-agent prototype system, GeoAgent-based Knowledge System (GeoAgentKS). This system allows: (1) computer representation of institutional regulations and behavioral rules used by multiple social institutions and individuals in cross-level human–environment interactions, (2) integration of this representation with scientific modeling of dynamic hazard development, and (3) application of automated reasoning that suggests to users the appropriate actions for supporting cooperative social responses. This paper demonstrates the software architecture of GeoAgentKS and presents such an integrated approach by modeling the drought management processes in Central Pennsylvania, USA. The results show that it is possible to use GeoAgentKS to represent multilevel human–environment interactions and to use those interactions as input to decision making in hazard management.     

一种基于PSIM的脉宽调制芯片SG3525的建模与仿真

SG3525是一种应用非常广泛的脉宽调制芯片,在开关电源设计中得到了非常广泛的应用。本文以其为研究对象,对其功能详细研究,并根据资料手册在PSIM中对其各个模块进行建模。最后,将所搭建的各个模块相结合并利用PSIM现有的模块封装功能将其封装起来,用于控制一个全桥DC—DC变换,并通过仿真来验证其功能。     

使用NetBeans IDE实现UML建模

NetBeans IDE是当前市场上最流行的、开源且免费的集成开发工具。使用NetBeans不仅可以开发Java程序,还提供了对UML的全面支持。利用NetBeans UML建模模块,可以创建八种类型的UML图,极大地方便了开发人员编写程序。本文首先介绍了NetBeans和UML的基本知识;其次着重介绍了如何在NetBeans IDE中实现UML建模;最后,通过创建一个酒店系统的用例图实例加深理解。     

异构电子商务集成平台的本体模型构建

针对电子商务数据异构的特点,研究用本体技术实现异构电子商务的集成平台.通过不同电子商务本体特征的挖掘和抽取,提出异构电子商务集成平台的本体模型构建方法.实现电子商务本体协同的"即插即用"互操作集成模型.     

Measuring Project Management Performance: Case of Construction Industry

This study develops construction-specific determinants and indicators of project management performance based on the 14 knowledge areas of the project management body of knowledge guide. Interrelations among the knowledge areas and influence of these factors on performance are investigated. Data collected from 121 construction projects are analyzed using structural equation modeling. Research findings suggest that project integration, communications, safety, risk, human resources, financial, and cost management have a direct impact, whereas scope and time management have an indirect effect on performance. The findings reported in this study are expected to help construction project managers devise and implement strategies and develop actions to improve project success. An engineering manager can use the framework developed in this research to define the underlying factors of efficient project management practices.     

The role of topology in engineering design research

Aspects of the mathematical specialty of topology appear within several seemingly distinct areas of engineering design and engineering design theory. Indeed, the expression topology of a design is often used informally. In this article a primary intent is to demonstrate the diversity of applications of topology within engineering design. A complementary goal is to introduce the engineering design community to topology as a rich, formal, well-established mathematical discipline that may be of value for wider study. Upon reviewing some of these topological applications, it appears that topology holds promise as a basis for formalizing engineering design theory. This article considers topology as a basis for unifying design abstractions. The potential benefit may be the realization of commonalities between design aspects previously considered separately, where each now has its own attendant specialized, expensive analyses.     

Orthogonal variant moments features in image analysis

Moments are statistical measures used to obtain relevant information about a certain object under study (e.g., signals, images or waveforms), e.g., to describe the shape of an object to be recognized by a pattern recognition system. Invariant moments (e.g., the Hu invariant set) are a special kind of these statistical measures designed to remain constant after some transformations, such as object rotation, scaling, translation, or image illumination changes, in order to, e.g., improve the reliability of a pattern recognition system. The classical moment invariants methodology is based on the determination of a set of transformations (or perturbations) for which the system must remain unaltered. Although very well established, the classical moment invariants theory has been mainly used for processing single static images (i.e. snapshots) and the use of image moments to analyze images sequences or video, from a dynamic point of view, has not been sufficiently explored and is a subject of much interest nowadays. In this paper, we propose the use of variant moments as an alternative to the classical approach. This approach presents clear differences compared to the classical moment invariants approach, that in specific domains have important advantages. The difference between the classical invariant and the proposed variant approach is mainly (but not solely) conceptual: invariants are sensitive to any image change or perturbation for which they are not invariant, so any unexpected perturbation will affect the measurements (i.e. is subject to uncertainty); on the contrary, a variant moment is designed to be sensitive to a specific perturbation, i.e., to measure a transformation, not to be invariant to it, and thus if the specific perturbation occurs it will be measured; hence any unexpected disturbance will not affect the objective of the measurement confronting thus uncertainty. Furthermore, given the fact that the proposed variant moments are orthogonal (i.e. uncorrelated) it is possible to considerably reduce the total inherent uncertainty. The presented approach has been applied to interesting open problems in computer vision such as shape analysis, image segmentation, tracking object deformations and object motion tracking, obtaining encouraging results and proving the effectiveness of the proposed approach.     

A review of vision-based systems for soccer video analysis

This paper presents a survey of soccer video analysis systems for different applications: video summarization, provision of augmented information, high-level analysis. Computer vision techniques have been adapted to be applicable in the challenging soccer context. Different semantic levels of interpretation are required according to the complexity of the corresponding applications. For each application area we analyze the computer vision methodologies, their strengths and weaknesses and we investigate whether these approaches can be applied to extensive and real time soccer video analysis.