Distributed Active Sensor Scheduling for Target Tracking in Ultrasonic Sensor Networks

Active ultrasonic sensors for target tracking application may suffer from inter-sensor-interference if these highly dense deployed sensors are not scheduled, which can degrade the tracking performance. In this paper, we propose a dynamic distributed sensor scheduling (DSS) scheme, where the tasking sensor is elected spontaneously from the sensors with pending sensing tasks via random competition based on Carrier Sense Multiple Access (CSMA). The channel will be released immediately when sensing task is completed. Both simulation results and testbed experiment demonstrate the effectiveness of DSS scheme for large scale sensor networks in terms of system scalability and high tracking performance.     

微波信号调制电路设计与实现

在智能微波开关的发射电路中,对高频微波信号采用了低频和中频两级调制的方法。为避免现场多对智能微波开关之间的相互干扰,首先用37～51 Hz分8级可调的低频高占空比方波信号调制21 kHz固定频率的中频信号,再用该信号调制10 GHz的高频微波信号。在信号调制的同时,用低频信号控制MOS管对高频微波模块的DC-DC供电电源反馈回路进行干预,使DC-DC电路工作于最佳状态,输出电压峰值平稳,避免了高频发射模块间歇式工作对电源电路输出的影响,提高了智能微波开关的测量精度和工作的可靠性。设计结果与理论分析结果比较接近,达到了设计要求。     

Quality-of-service provisioning and efficient resource utilization in CDMA cellular communications

One of the major challenges in supporting multimedia services over Internet protocol (IP)-based code-division multiple-access (CDMA) wireless networks is the quality-of-service (QoS) provisioning with efficient resource utilization. Compared with the circuit-switched voice service in the second-generation CDMA systems (i.e., IS-95), heterogeneous multimedia applications in future IP-based CDMA networks require more complex QoS provisioning and more sophisticated management of the scarce radio resources. This paper provides an overview of the CDMA-related QoS provisioning techniques in the avenues of packet scheduling, power allocation, and network coordination, summarizes state-of-the-art research results, and identifies further research issues.     

QoS guarantee and power distribution for soft handoff connections in cellular CDMA downlinks

A two-phase power distribution scheme for supporting quality-of-service (QoS) and best effort traffic is proposed. We first formulate the power distribution for QoS traffic as an optimization problem so that the number of simultaneously transmitting connections is maximized. Optimum power distribution is difficult to implement in practice due to both the computational complexity and the requirement for global information about the mobile station (MS) locations, connection channel conditions, and traffic load in the system. We then propose a heuristic scheme of power distribution for soft handoff (SHO) connections. The full scheme includes an initial power distribution (IPD) and a power distribution adjustment (PDA). IPD allocates BS power resource based on the channel condition of each individual connection, while PDA further coordinates the power distribution between neighboring base stations (BSs) in order to accommodate more connections. The proposed power distribution scheme can achieve a capacity close to that of the optimum power distribution, while providing much higher transmission throughput for best effort data traffic. The proposed power distribution scheme can be applied to existing SHO schemes for efficient BS power resource usage. The scheme does not require global information, and its implementation can be further simplified by performing IPD only with slight performance degradation.     

一种基于用频计划的监测设备部署优化方法

提出了一种基于用频计划的监测设备部署优化方法,根据实际的用频计划提取出包含监测区域、时间和频段的监测要求,结合监测设备的监测能力,运用改进的多目标遗传算法,快速有效地部署监测设备,制定监测计划,提高了对监测要求在时域、空域和频域的监测覆盖率,达到了监测设备部署优化的目的,并通过仿真验证了该算法的可行性和有效性。     

变形协调情况下土钉墙内力和位移的计算方法

 土钉墙的内力主要包括土钉轴力、钉土剪力和面层受力,而土钉墙变形的过程是土钉、面层和土体之间相互协调共同作用的过程,传统的计算模型都是从力矩平衡的力学角度出发,不能合理解释土钉内力和变形的相互关系。通过对土钉墙受力和变形机制的分析,利用Mindlin解计算在虚拟开挖应力和钉土剪力共同作用下土体侧向位移,结合钉土剪力和钉土相对位移的线性关系以及钉土剪力在最危险滑动面位置等于0的特点,计算土钉轴力、钉土剪力和土钉墙在开挖面位置的变形。土钉被动区段钉土剪力超出其极限值的部分转移至面层,假定面层受力增量呈三角形分布,根据静力平衡得到面层受力分布。通过与工程实测资料的对比分析,初步验证土钉墙内力和变形计算方法的合理性和可行性。     

高层框架-剪力墙结构柱轴压比限值讨论

本文从变形能力与破坏机制的角度对框架-剪力墙结构中柱轴压比限值的合理性进行了讨论,指出轴压比限值应根据柱所处位置的不同而加以区别.本文对影响柱延性的主要因素以及改善变形能力的措施进行了阐述,提出两种旨在提高柱承载能力的配筋方式,引入等效轴压比的概念代替传统的轴压比.     

带有双塔楼高层建筑结构动力特性分析

本文通过对带有双塔楼的高层建筑结构动力特性的分析研究，证明在地震作用下这类结构存在五种基本的振动形式，当按现行建筑抗震设计规范理论计算地震作用时，其中有三类振型对结构的内力与位移没有贡献，因而在实际工程中此类结构可以用简单的力学模型进行计算分析。本文算例给出的结果与理论推导完全一致。     

开放式企业信息系统的构架与实践研究

Ｉｎｔｒａｎｅｔ问世为传统的企业信息系统开辟了崭新的思路，利用Ｉｎｔｒａｎｅｔ技术改造传统企业ＭＩＳ，建立开放式企业信息系统必成为新的潮流，本文就基于Ｉｎｔｒａｎｅｔ开放式企业信息系统进行了研究，并地其层次结构、信息处理方式进行了探讨。     

温度继电器温度特性自动检测系统的研究

研究设计了基于空气测定法原理,简单实用、高精度的温度继电器温度特性自动检测系统。该检测系统,是用电阻加热炉模拟温度继电器周围的环境温度,通过控制加热炉内温度的变化,从而测得温度继电器的动作温度。系统按设定的控温曲线对温场温度进行控制,并采用模糊算法,采取最小二乘法误差校准,将电阻加热炉炉丝按功率进行分组,并在试验腔的检测段放置孔板,使测试区域的温度均匀,有效提高了系统检测精度。经测试该系统测试精度满足要求,具有良好的使用效果。