Quality of Service in VoIP Communication

The focus of this paper lies in the practical aspects of voice over IP communication. VoIP configurations in the H.323 standard will be presented briefly. Following that, the fundamental protocol procedure of H.323 communication will be briefly explained. A further part of the paper will address the subject QoS (quality of service), and present the common measurement methods used in QoS. Results gained from experiments conducted in a VoIP environment will then follow. The investigations concentrate primarily on the load behavior of voice packets in relation to important parameters of this service. The results obtained are presented and evaluated in diagrams. The paper concludes with a summary.     

铁路罐车密闭装车计量系统的运行分析

从中国石化股份公司济南分公司新上铁路罐车密闭装车计量系统的背景出发，阐述该系统的设计思想和组成；通过分析实际运行过程中仪表比对数据，讨论影响仪表贸易交接准确性的各种因素，提出相应的解决方法；最后通过铁路罐车密闭装车计量系统投用效果。证实该系统可产生明显的经济效益。     

Joint scheduling and power control supporting multicasting in wireless ad hoc networks

This paper addresses the problem of power control in a multihop wireless network supporting multicast traffic. We face the problem of forwarding packet traffic to multicast group members while meeting constraints on the signal-to-interference-plus-noise ratio (SINR) at the intended receivers. First, we present a distributed algorithm which, given the set of multicast senders and their corresponding receivers, provides an optimal solution when it exists, which minimizes the total transmit power. When no optimal solution can be found for the given set of multicast senders and receivers, we introduce a distributed, joint scheduling and power control algorithm which eliminates the weak connections and tries to maximize the number of successful multicast transmissions. The algorithm allows the other senders to solve the power control problem and minimize the total transmit power. We show that our distributed algorithm converges to the optimal solution when it exists, and performs close to centralized, heuristic algorithms that have been proposed to address the joint scheduling and power control problem.     

自动交换光网络控制平面功能结构的探讨

文章主要讨论了自动交换光网络(ASON)控制平面的两种不同结构：控制平面在网元外部的结构和控制平面部分集成在网元内部的结构，并对这两种结构进行了比较．     

海底输油管道内智能引导装置研究

对海底输油管道内智能引导装置研究的必要性进行了分析;介绍了国内外在该领域的技术发展状况。针对智能引导装置的作业对象和环境,提出了技术要求和指标,对智能引导装置进行了总体设计,分析了其作业机理,建立了力学模型并进行了计算。对智能引导装置的控制系统进行了设计,提出了设计过程中应注意的问题。所研制的管内轮式智能引导装置具有质量轻、输出牵引力大、体积小、结构紧凑等特点,对较小管内空间类似系统的设计有一定参考价值。     

低密度微泡沫压井液的研究与应用

吐哈油田部分区块地层压力系数小于0.9,常规水基压井液对储层伤害大,若使用油基压井液成本高,环境污染严重。通过实验优选出了一种低密度水基微泡沫压井液。该压井液具有密度低、泡沫强度高、稳定性好、携砂能力强等优点。现场应用表明,低密度微泡沫压井液稳定时间大于48 h,密度在0.70~0.99 g/cm3之间可调,抗油污染能力强,抗油大于8%,抗温在100℃以上,岩心污染后渗透率恢复值大于80%;并且施工方便,成本低,具有储层保护能力,使用微泡沫压井液的井表皮系数在0.20~2.34之间。     

Finite element piezothermoelasticity analysis and the active control of FGM plates with integrated piezoelectric sensors and actuators

 An efficient finite element model is presented for the static and dynamic piezothermoelastic analysis and control of FGM plates under temperature gradient environments using integrated piezoelectric sensor/actuator layers. The properties of an FGM plate are functionally graded in the thickness direction according to a volume fraction power law distribution. A constant displacement-cum-velocity feedback control algorithm that couples the direct and inverse piezoelectric effects is applied to provide active feedback control of the integrated FGM plate in a closed loop system. Numerical results for the static and dynamic control are presented for the FGM plate, which consists of zirconia and aluminum. The effects of the constituent volume fractions and the influence of feedback control gain on the static and dynamic responses of the FGM plates are examined. Received: 13 March 2002 / Accepted: 5 March 2003 The work described in this paper was supported by a grant awarded by the Research Grants Council of the Hong Kong Special Administrative Region, China (Project No. CityU 1024/01E).     

可并联逆变器中的同步控制技术及其实现

论述了可并联逆变器中的同步控制技术及其实现方法。在分析了同步的重要性之后，提出了抢占与并发相结合的同步控制策略及其实现方法，实践证明该方法具有很高的控制精度。     

双波长稳频CO_2激光模糊控制系统的建模与优化

报导一种模糊逻辑控制系统的建模与优化方法。以此方法设计的模糊逻辑控制器，用于双波长稳频ＣＯ２激光器的控制得到令人满意的结果。     

微机监控技术 一

本文系统地讲述了以微型计算机为中心的微机监控系统的工作原理、系统组成和应用方面的有关技术。分为监控系统的功能和结构、硬件系统和软件系统三个部分。本文为第一部分。