一种改进的PID参数整定方法

当使用先进策略整定PID控制器参数时,往往要依赖于系统所辨识的对象模型。为了降低对系统模型的依赖性,提出了一种基于同时扰动随机逼近的在线、无模型的参数整定方法。算法的核心思想是利用高效的同时扰动技术对PID控制器性能指标函数的梯度进行估计,并利用随机逼近技术对PID的三个参数进行在线调整。仿真结果验证了该方法的有效性。     

基站环评验收关键参数设置标准

环保部门对移动基站的验收标准和要求越来越高,不通过环评验收的基站将不予建设.环评验收中对基站的关键参数设置将至关重要,主要是发射功率及俯角.本文重点就如何设置发射功率及俯角进行了深入研究,得到了适用于工程实际的设置标准.     

ATM网中压缩视频业务模型综述

压缩视频业务建模是ＡＴＭ研究中的重要方向。本文综述了这一领域的最新进展，特别是包含了可描述视频业务的统计特性的模型的情况。另外，对ＭＰＥＧ视频业务建模也作了比较全面的探讨。     

IP over ATM技术及其应用模式

说明了IP技术与ATM技术结合的必要性以及结合的优势,介绍了IP over ATM技术的原理及其应用模式,其中包括经典IP模式、捷径IP模式和集成IP模式,最后简要分析了IP over ATM技术的发展趋势。     

参数设定电源箱设计

为了满足舰船陆地和岸基作业的需要,设计的电源箱系统的三种工作模式,即AC/DC模式、充电模式和电池输出模式。AC/DC模式和充电模式主电路拓扑选用同一双管正激电路。分别做了电池放电实验,电池充电实验和恒压输出实验,其技术指标满足舰船供电系统的需要。     

ATM Network Design: Traffic Models and Optimization-Based Heuristics

We consider the design and capacity expansion of ATM networks as an optimization problem in which flows representing end-to-end variable bit-rate services of different classes are to be multiplexed and routed over ATM trunks and switches so as to minimize the costs of additional switches and transport pipes while meeting service quality and survivability constraints. After an overview of the underlying fractional Brownian motion model for aggregate flows, a nonlinear multicommodity optimization problem is formulated and LP-based heuristics for its approximate solutions are described. Finally, computational results are produced that demonstrate realistic size problems can be solved with the proposed method to shed light on key economic characteristics of ATM traffic, such as safe levels of statistical multiplexing, as well as robust and efficient design alternatives.     

Estimation and setting starting values in ARMA algorithms

For the given observations set of the ARMA (autoregressive moving average) process, the likelihood function depends, not only on model parameters, but on the starting values of the input and output. Therefore, it is called theconditional likelihood function. Theunconditional likelihood function can be obtained in two ways. The first is to set the starting values to zero, as is often done, and the second is to set them to the properly estimated values. The difference between these two types of likelihood functions is significant when the given data sequence is short, and any of the zeros of the moving average part is close to the boundary of the unit circle.In this paper the direct method of starting value estimation and its application to two off-line ARMA estimation algorithms, the maximum likelihood (ML) algorithm and the iterative inverse filtering (ITIF) algorithm, is proposed. Experimental results prove both increased efficiency and stability of these algorithms.The importance of setting the starting values properly is also significant when the recursive algorithm, with previously estimated parameters, has to be restarted. The advantage of the proposed reinitialization method is shown on the recursive lattice algorithm working in the block mode.     

Determination of power semiconductor model parameter values from structure data

The paper presents equations for an scr model suitable for cad implementation. The model components are specified in terms of the device doping profile and junction areas and data is presented for medium power inverter and converter scr's. Built-in but inherent temperature scaling is included. Certain electrical ratings can be determined from structure information. The approach developed is applicable to high voltage transistors, rct's and triacs and can be extended to include the modelling of hi-lo junctions.     

ATM Interface Technologies for an ATM Switching System

Realization of the economical, reliable, and efficient ATM interface block becomes an important key to development of the ATM switching system when we consider new issues raised recently. In this paper, we summarize requirements for the ATM interface block and present the UNI (User Network Interface)/NNI (Network Node Interface) architecture to meet these requirements. We also evaluate the performance of the multiplexer adopting the various multiplexing schemes and service disciplines. For ATM UNI/NNI interface technologies, we have developed a new policing device using the priority encoding scheme. It can reduce the decision time for policing significantly. We have also designed a new spacer that can space out the clumped cell stream almost perfectly. This algorithm guarantees more than 99 % conformance to the negotiated peak cell rate. Finally, we propose the interface architecture for accommodation of the ABR (Available Bit Rate) transfer capability. The proposed structure that performs virtual source and virtual destination functions as well as a switch algorithm can efficiently accommodate the ABR service.     

关于LLE算法的监督型参数设置方法及应用

采用局部线性嵌入(Locally Linear Embedding,LLE)算法进行数据降维时,不仅能保持数据分布的局部线性特征,同时还能保存数据分布的流形结构,因此该算法常用于高光谱影像的数据降维。其中,关于最近邻像元个数K的设置是执行该算法的关键。然而,关于K值的设置,目前尚无一个行之有效的方案。针对这一问题,文中基于监督型特征提取的思想,从"线性预测误差均值最小化"的角度出发,提出了一个监督型参数设置方法。同时,为了验证该方法的可行性和优越性,结合两个实验区Hyperion影像关于第26至57波段包含的32维光谱数据,进行了降维实验。最后,通过分析对比实验结果,证明了:采用LLE算法进行高光谱影像数据降维时,若依据文中所提方法设置的K值,能获得噪声点少且地物细节信息更加丰富的低维影像数据。     

基于2-D稳定条件的混合流网络参数设置

由于网络容量的限制,任何一个网络都不可能避免拥塞问题。传统的RED算法只考虑了少量TCP用户,没有涉及UDP用户的情况,同时随着网络应用的多样化,如越来越多的UDP用户接入网络,传统的RED机制无法控制它们,保证不了TCP用户的服务质量(QoS)。针对TCP/UDP混合流多用户的情况,本文提出TCP/UDP混合流的区分控制,这里TCP和UDP流使用不同的带宽,及TCP/UDP混合流单瓶颈网络的2-D稳定条件。基于该稳定条件可以选择一个合适的RED控制参数Pmax,获得满意的网络拥塞控制性能。本文建立了一个TCP和UDP流单瓶颈网络的线性时滞系统模型,利用2-D拉普拉斯-Z变换,推导出基于稳定条件的混合流网络参数配置。利用NS2仿真验证所提出的混合流网络参数配置能够有效获得关于路由器队列长度和TCP窗口的稳定性。     

Charging for ATM services

Advances in analog and digital telecommunications technology have provided us with a wide range of telecommunications networks since the invention of the analog telephony network by Bell in 1876, such as wireless and wired CATV networks, local, metropolitan, and wide area networks, and the Internet; and a range of protocols to go with these networks, such as Internet Protocol or ATM. Charging for services delivered across these networks has always been an issue of major concern to providers and users of telecommunications services. The ability to charge accurately and efficiently for a service is directly related to the potential quality, value, flexibility, and customer care available to the customer, and, equally important, provides a means of survival, growth, and profitability to the provider. ATM is becoming a significant carrier of telecommunications services because its technology can accommodate a wide variety of services such as multimedia on demand, voice services, or videoconferencing, demanded by today's rapidly changing market. While there are many schemes in use for the charging of mobile and fixed telephony, the area of Internet charging and, in particular, ATM charging is relatively uncharted to date. In this article we address the challenge of developing methods of charging for ATM services, and show solutions in the form of technical and commercial recommendations and a practical implementation of these recommendations     

ATM测试技术

本文通过对ＡＴＭ网络中可能出现的故障的讨论，指出了对ＡＴＭ网络测试的必要性。并对ＡＴＭＰ比较突出的几个问题提出了解决测试的方法。     

Conceptual issues for ATM

The authors discuss the asynchronous transfer mode (ATM), which has been strongly promoted as the transport structure for future broadband telecommunication networks by CCITT Study Group XVIII (internationally) and TISI (North America). ATM is a transport technique based on fast packet switching, where the information is packed into fixed-size cells of relatively short length. The authors do not question the technical feasibility of ATM at 150 Mb/s rates, but they maintain that the state of system definition is such that ATM cannot be unequivocally supported as a concept. Furthermore, they feel that there is danger in premature standardization of system parameters while the system concept itself is still in flux. They identify four major areas where the system concept needs to be clarified before standardization can proceed: grade of service, accounting, compatibility, and scaling     

X5045 EEPROM在智能过程控制器参数设置中的应用

介绍X5045 EEPROM在智能现场过程控制器中设置参数方面的应用,及其工作原理,设计思想。     

ATM防火墙技术

ATM网络在很多方面与当今的其它通信网络不同.提出一种ATM防火墙结构,研究它对ATM的影响,提出了ATM防火墙的实现方法.为不影响ATM网络的高性能,提出了ATM防火墙中结合入侵检测的思想.     

ATM for narrowband services

ATM is a broadband fast-packet technology, but its modern technological base should make it less expensive than existing circuit switching systems once economies of scale are reached. The article examines the use of ATM to address the growth of emerging narrowband services such as frame relay. ATM's flexibility in supporting variable rates and levels of service make it an ideal network technology to carry multiple services. While B-ISDN services promise many benefits to users, major issues must be addressed before such services can be available on a large scale. Utilizing ATM as a backbone technology to support the growing capacity needs of emerging narrowband services could facilitate more rapid introduction of ATM into the network infrastructure and speed delivery of future BISDN services     

SDMA techniques for wireless ATM

The introduction of space-division multiple access techniques into wireless ATM systems is presented. The concepts are embedded in the framework of the HIPERLAN/2 system, which is currently under standardization by the ETSI Broadband Radio Access Networks (BRAN) project. HIPERLAN/2 aims at the provision of broadband services with guaranteed QoS. Originally started as a WATM standardization initiative, its scope has been broadened and now aims at core network independence. Essential system functions, such as scheduling algorithms and random access, are reviewed in light of the spatial dimension. To give an impression of their performance, some key results are discussed. Although adopted for HIPERLAN/2, the ideas are generally applicable and can be transferred to various systems