Different sensing durations‐based cooperative spectrum sensing in cognitive radio systems

In order to provide more accurate detection of the primary user's activity in cognitive radio (CR) systems, cooperative spectrum sensing is proposed. The transmit diversity can also be employed by cooperative spectrum sensing to improve the performance of decision reporting. Hence, in the reporting channels between the cognitive users and the base station (BS), space time block code (STBC) scheme is considered in each cluster with time division multiple access (TMDA) method. In this paper, to improve the time efficiency in the case that one cluster makes sensing report, whereas the others do nothing but wait for their orders, we set each cluster with different sensing durations and the clusters will not stop the spectrum sensing until their results are reported. Furthermore, we also adopt the flexible sensing durations to decrease unnecessary energy consumption based on the clusters’ sensing sensitivities. Simulation results and analysis show the better detection performance and time efficiency of the proposed scheme. Copyright © 2012 John Wiley & Sons, Ltd.     

基于双隐含层BP算法的激光主动成像识别系统

在传统激光主动成像系统的基础上,结合目标识别技术搭建了一个激光主动成像识别系统实验平台,用于研究激光主动成像后的目标识别。介绍了实验平台的工作原理,基于Hu矩特征的双隐含层BP神经网络算法以及实验处理流程和实验结果。特征量由7个不变Hu矩构成,通过240张原始目标样本库对由136个权值系数构成的双隐含层BP神经网络算法进行了训练。利用训练好的双隐含层BP算法对黑夜条件下远处的运动目标--43式冲锋模具枪进行了实验研究,成功获得了清晰的红外激光主动成像效果。实验显示对450 m处2 740帧和550 m处2 420帧激光主动成像图像的统计识别率达到了68.87%和72.11%,其中旋转变换下的统计识别率可达80.05%和84%,好于仿射变换的识别效果。     

基于模糊概率贝叶斯网络的起重机械制动器可靠性分析

针对传统的故障树(FAT)可靠性分析方法,提出了一种基于模糊概率与贝叶斯网络(BN)相结合的分析方法。文中的BN模型通过FAT模型得到,根据专家综合评定BN模型中每一个根节点的语言变量,得出每一个根节点发生故障的精确概率。通过BN模型的正逆互推原理算出每一个叶节点的失效概率和每一个根节点的后验失效概率,进一步进行每个根节点重要度分析。最后通过该方法对桥式起重机用制动器的可靠性分析,发现其具有很高的分析效率。     

A study on the importance of colour in pacharán

 Pacharán is a traditional drink of Navarra (Spain). This liqueur is an alcoholic drink which ranges from intense pink to red in colour and is based on sloe (Prunus spinosa, L.), essential oils of aniseed, and sugar. A sensory analysis was performed using samples from 21 different brands of commercial pacharán. Stepwise regression was employed to identify the physicochemical parameters responsible for the sensory attributes of colour, visual intensity of colour, and overall impression. The physicochemical variables which best predicted the sensorial attribute colour were colour intensity and titratable acidity. For the visual intensity of colour, key indicators were colour intensity, titratable acidity and hue, the last-mentioned variable having a negative effect. With respect to the overall impression, pH, ethanol content and colour intensity correlated to quality. Received: 12 February 1998 / Revised version: 13 May 1998     

基于多层语义融合注意力机制的短期风电功率概率密度预测方法

获得未来风电功率的短期概率性信息将有助于电网的综合能源调度,为此提出一种结合多层语义融合注意力机制的短期风电功率概率密度预测方法。为尽可能获得更多语义层下的编码信息,在编码阶段引入循环高速网络（RHN）并通过深层的RHN网络结构最大程度地提取输入特征的底层关联信息。设计多层语义融合注意力机制以融合不同语义层下的局部注意力向量,进一步加强编码特征向量的表达能力,并将网络的输出与分位数回归和核密度估计方法结合,得到不同分位点下未来短期风电功率的预测结果与连续概率密度分布。实验结果表明：提出的短期风电功率概率密度预测方法不论是在预测的得精度上,还是在具有不确定性的预测结果分布上均优于其他比较模型。     

Microstructural aspects of the flow behaviour in a liquid—solids circulating fluidized bed

The local instantaneous and time‐average suspension densities were determined in a 76 mm diameter by 3 m tall liquid‐solids circulating fluidized bed riser using a fibre‐optic probe. Attempts were made to qualify the microflow structure through statistical analysis of the local bed voidage fluctuations obtained under different operating conditions for the first time. The results show that local microflow structure is uniform in the axial direction but non‐uniform in the radial direction with more flow fluctuation near the wall than in the core of the column for a given axial position. The standard deviation and intermittency index tend to increase with increasing solids circulating rates. Comparing with the gas—solids CFB, the liquid—solids CFB shows much more homogeneous flow structure in both the axial and radial microscopic flow behaviours. The microflow behaviours in the conventional liquid—solids fluidization, liquid—solids circulating fluidization and dilute‐phase liquid transport regimes are also characterized by examining the probability distribution and the intermittency index of the solids holdup.     

多算法融合管道泄漏检测预警系统试验研究

管道泄漏不仅会造成环境污染,还可能引发火灾、人员伤亡等严重后果和巨大的经济损失。传统的管道泄漏在线检测与定位系统均使用单一算法进行信号处理,漏判误判多,应用效果较差。针对目前集输管道泄漏检测准确性和灵敏度较低的现状,研究一种多算法融合的方法,通过采集管道压力、流量等多种特征信号,采用最优加权融合算法,将专家经验分析法、向量机(SVM)模式识别法、序贯概率比检测法等多种信号处理方法进行综合应用,扩展了时间和空间上的检测范围,提高了泄漏检测系统的灵敏度和可靠性。利用正常运行集输管道进行了现场泄漏应用试验,试验结果验证了多算法融合检漏方法比单一检漏方法具有明显的优越性。     

精锐微泡浮选机强化微细粒浮选的机理与实践

微细矿粒质量小、动能低,与气泡的碰撞概率低,难以和气泡发生矿化反应,制约了微细粒矿产资源的回收。精锐微泡浮选机利用矿浆的高速射流生成负压,被负压吸入的空气与射流矿浆剧烈搅拌形成微小气泡,同时水力空化作用产生纳米泡,大大提高了气泡与矿粒碰撞附着几率。工业应用数据表明,精锐微泡浮选机对微小气泡的矿化和细粒矿物的浮选有特殊的功效。     

低压供电可靠性故障模拟算法研究

针对用概率统计方法统计低压用户供电可靠性工作量超大的问题,研究如何进行电力系统设备故障模拟及其算法的实现。根据低压系统可靠性模型可建立其可靠性模拟数据库。电力系统故障服从泊松分布,根据各类设备的运行数据即平均故障率,计算出该类设备故障次数的分布曲线。采用随机取样的方法产生本次故障次数以及故障设备编号。该模拟算法简单清晰、易于实现。     

巡航导弹景象匹配算法适应性研究

文章针对景象匹配制导的需求,研究了去均值归一化、基于直方图拉伸和基于局部平滑相关匹配算法,分析了算法的适应性、计算量和实时性等,比较了每种算法的优缺点.结合巡航导弹的使用,讨论了影响匹配结果的一些基本的、可能的因素,主要是环境因素.用三种分辨率的图像作了大量的实验,针对这些算法的匹配概率及地物适应性等方面进行了编程验证和综合分析,给出了有关结论.