任楼煤矿电容电流危害分析与治理研究

针对中性点不接地系统单向接地电容电流易造成配电网络次生灾害和设备损害、易产生单向电弧接地过电压和铁磁谐振过电压的问题,分析评估了任楼煤矿电网电容电流的测试数据,根据评估结果制定了电容电流治理方案,即将中性点不接地系统改为中性点经消弧线圈接地运行方式,并给出了具体实施方案。运行结果表明,该方案大大减少了高幅值电弧接地过电压发生的几率,抑制了铁磁谐振过电压,有利于提高电缆寿命。     

伪码调相雷达高度表中多径信号抑制算法研究

多径误差是伪码调相雷达高度表中重要的误差源之一,为了提高系统的测距精度,建立了采用strobe相关器的伪码跟踪环数学模型,给出了其实现的结构框图;在考虑单路多径信号的基础上分析了多径信号的参数对伪码跟踪环的跟踪误差的影响,并在Matlab环境下对伪码跟踪环的跟踪性能进行了仿真;仿真结果表明在相同的多径参数条件下,strobe相关器可以有效地减小多径引起的跟踪误差,性能优于窄相关器,运算量较多径估计延迟锁定环要小,易于在硬件上实时实现,具有实际应用价值。     

基于确定性测试图形的BIST构建方法

为降低内建自测试(Build-in Self Test,BIST)的测试功耗,提出了一种基于确定性测试图形的内建自测试构建方法:首先采用D算法生成测试所需的测试图形,然后使用粒子群算法对其进行优化,使内建自测试的功耗大幅度降低;文中最后以ISCAS'85Benchmark中的部分电路作为实验对象,并给出了测试图形优化前后的功耗数;实验结果证明该方法能够有效降低内建自测试的测试功耗,并且具有方法简单、无需额外硬件开销的特点.     

Construction and basic performance tests of an underwater monitoring network

With the rapid development of the economy, environmental pollution has become one of the major problems in coastal areas and in cities along rivers. Real-time observations of the water quality along rivers have been considered to be an efficient way to control wastewater emission and manage environmental water quality. Traditional ways to observe the ocean environment, including satellite telemetry, radar, investigation ships, ocean observation stations, etc., are not applicable for water-quality observations along rivers because of their high cost, poor real-time information, low accuracy, and so on. Based on wireless sensor networks (WSN), the study reported here proposes a new observation system using underwater multisensory information. After processing the multisensory data from each sensor, the system transmits it to a hub node through WSN, and then transmits it to a land data center through a general packet radio service (GPRS) wireless network. In order to check the basic performance of this system, we completed a node positioning experiment based on a GPS module, and a communication experiment based on ZigBee. This article reports the design of the hardware and the experimental results.     

Traceable content protection based on chaos and neural networks

In this paper, a media content encryption/decryption algorithm is designed based on a chaos system and neural networks, which generates random sequences with chaos, and encrypts or decrypts media contents with neural networks in a parallel way. In this scheme, different decryption keys can be used to recover the media content into different copies. That is, the decryption operation gets the content containing certain random sequence that can be used as the identification. With respect to this property, the scheme is used for secure content distribution. Taking the audio content for example, it is encrypted by a key at the sender side and decrypted by different keys at the receiver side. The differences between decryption keys lead to different decrypted audio copies. If one customer distributes his copy to other unauthorized customers, the chaotic sequence contained in the copy can tell the illegal customer. The performances, including security, imperceptibility and robustness, are analyzed, and some experimental results are given to show the scheme's practicability.     

Implementation of a transient adaptive sub-cell module for the parallel-DSMC code using unstructured grids

A method of transient adaptive sub-cells (TAS) suitable for unstructured grids that is modified from the existing one for the structured grids of DSMC is introduced. The TAS algorithm is implemented within the framework of a parallelized DSMC code (PDSC). Benchmarking tests are conducted for steady driven cavity flow, steady hypersonic flow over a two-dimensional cylinder, steady hypersonic flow over a cylinder/flare and the unsteady vortex shedding behind a two-dimensional cylinder. The use of TAS enables a reduction in the computational expense of the simulation since larger sampling cells and less simulation particles can be employed. Furthermore, the collision quality of the simulation is maintained or improved and the preservation of property gradients and vorticity at the scale of the sub-cells enables correct unsteady vortex shedding frequencies to be predicted. The use of TAS in a parallel-DSMC code allows simulations of unsteady processes at a level to be carried out efficiently, accurately and with acceptable computational time.     

Web服务图及其在服务发现中的应用研究

Web服务是一种崭新的Web应用.随着Web 环境下服务数量的快速增长,要在海量的服务中发现所需的服务是非常耗时的.UDDI V2 增加了一个新特性publisherAssersion来描述UDDI注册中心里的商业实体间的关系,类似于网页之间的超链接,这样就产生了Web服务图.首先研究Web服务的新特征,然后提出并分析构建Web服务图的原理和算法,最后利用Web服务图进行服务发现.从仿真实验可看出提出的Web服务图对组合的Web服务发现是有效的.     

应用于LTE上行链路的MMSE-TEDF均衡器

提出了一种适用于LTE上行SC-FDMA中的判决反馈均衡架构TEDF.依照最小均方误差准则,组成MMSE-TEDF均衡器.在3GPP LTE协议中常用的EVA信道下将这种均衡器进行计算机仿真,结果表明该均衡器在EVA信道下系统性能明显提高.     

基于Micro2440视觉处理平台的构建

采用Micro2440开发板和OV9650摄像头,成功获取了视频图像,并且能够对视频中的每一帧图像同步进行自定义的图像处理,其处理的结果同时能够在LCD上予以显示.实验结果证明该视觉处理平台具有良好的视觉处理特性,适合作为数字图像处理平台,为进一步的图像处理、功能扩展以及嵌入式应用创造了条件.     

Ranked Query Processing in Uncertain Databases

Recently, many new applications, such as sensor data monitoring and mobile device tracking, raise up the issue of uncertain data management. Compared to "certain” data, the data in the uncertain database are not exact points, which, instead, often reside within a region. In this paper, we study the ranked queries over uncertain data. In fact, ranked queries have been studied extensively in traditional database literature due to their popularity in many applications, such as decision making, recommendation raising, and data mining tasks. Many proposals have been made in order to improve the efficiency in answering ranked queries. However, the existing approaches are all based on the assumption that the underlying data are exact (or certain). Due to the intrinsic differences between uncertain and certain data, these methods are designed only for ranked queries in certain databases and cannot be applied to uncertain case directly. Motivated by this, we propose novel solutions to speed up the probabilistic ranked query (PRank) with monotonic preference functions over the uncertain database. Specifically, we introduce two effective pruning methods, spatial and probabilistic pruning, to help reduce the PRank search space. A special case of PRank with linear preference functions is also studied. Then, we seamlessly integrate these pruning heuristics into the PRank query procedure. Furthermore, we propose and tackle the PRank query processing over the join of two distinct uncertain databases. Extensive experiments have demonstrated the efficiency and effectiveness of our proposed approaches in answering PRank queries, in terms of both wall clock time and the number of candidates to be refined.