热强度试验中热电偶调理模块的设计与应用

热强度试验现场环境复杂,会对热电偶、热流等微弱电压信号产生较大电磁干扰,影响测量精度甚至控制信号精度。本文描述了热电偶调理模块的设计,对小信号进行隔离放大,有效抑制热强度试验存在的干扰,提高了系统的精度。     

协同过滤技术的改进研究

协同过滤算法应用于个性化推荐系统中取得了巨大成功,它是通过用户项目评分数据,以用户之间或者项目之间相互协作的方式来产生推荐。然而,邻居用户的相似度计算不精确一直是阻碍推荐系统推荐精度进一步提高的主要因素。从提高用户间相似度计算精度出发,提出了一种改进算法,该算法通过考虑不同特征、加强平均值影响、惩罚热门项目的比重,对用户的相似度计算方法进行改进,以期生成更加合理的邻居用户集,最后,根据评分预测公式进行预测,最终产生推荐。在MovieLens数据集上的实验表明,改进算法计算用户间的相似度更加精确,推荐算法的预测精确度有了显著提高。     

样本特征对参数/非参数分类器分类精度的影响分析

为验证理论训练数量(10~30 p)对参数分类器(如最大似然分类)、非参数分类器(如支撑向量机)的适用性以及样本特征(光谱统计、空间分布特征)对分类器分类精度的影响,选择不同规模的训练样本进行最大似然分类和支撑向量机分类,分析分类精度与样本之间的关系。实验结果表明:随着样本量的增加,最大似然、支撑向量机分类精度均随样本量增多而提高并趋于稳定,最大似然分类精度的增长速度要快于支撑向量机。MLC受样本量的影响较大,在小样本的时候(5个),分类精度不稳定,超过30个样本的时候,分类精度稳定下来;对于SVM分类器,在小样本的时候(5个),分类精度较高且稳定,因此SVM分类适合于小样本分类,不受限于理论样本量的影响。当样本量超过最小理论样本量值(30个)的时候,最大似然分类精度要优于支撑向量机,主要是由于当样本量增加后,最大似然更易于获得有效的信息量样本,而对于支撑向量机边缘信息样本的增加数量不大。研究结果为进一步优化样本进行分类打下前期的实验基础。     

轨道平顺性检测方法研究

轨道平顺性是高速铁路安全的重要保障参数,在分析弦测法、光学测量法、惯性基准法及光学摄像法4种常用轨道平顺性检测方法的基础上,研究了惯性连续检测方法.该方法采用中等精度光纤陀螺作为主要传感器,对左、右高低和轨向进行分别测量,设计了专用分组地推算法,能够适应各种速度下的高精度连续检测.最后,对该方法的核心部分进行了实验仿真.结果表明,惯性连续检测方法的惯性器件平顺性检测精度小于0.3 mm,总误差小于1 mm,满足平顺性检测指标要求,为研制新一代轨道检测设备奠定了基础.     

非接触IC卡在铁路巡道系统中的应用

非接触IC卡是世界上最近几年发展起来的一项新技术，它成功地解决了无源和免接触这难题，是电子器件领域的大突破。本文介绍了非接触IC卡的技术原理以及在铁路巡道系统中的应用，文章详细阐述了铁路巡道系统的硬件组成和软件设计。     

A pair of parallel differential magnetic‐field probes with high measurement accuracy and high electric‐field suppression ratio

Magnetic‐field probes can be used for electromagnetic interference measurement of high‐speed circuits. The main magnetic probe performance includes sensitivity, spatial resolution, electric‐field suppression ratio (EFSR), and measurement accuracy. In this article, a pair of differential magnetic‐field probes is proposed to improve measurement accuracy without reducing sensitivity. The proposed differential probes consist of two asymmetric loop probes, which are designed in the same plane and separated by a row of periodic vias. The proposed differential probes are fabricated under PCB process. High accuracy can be achieved by measuring difference between outputs of the two probes. In addition, EFSR can be improved by size optimization of the differential magnetic‐field probes. Simulation and measurement results show the operating bandwidth is from 100 MHz to 12 GHz, the measurement error is 3.4% and the EFSR is about 40 dB. The proposed probes have higher measurement accuracy and higher EFSR than the conventional single probe, and larger operation bandwidth than the stacked differential probes.     

基于启发式的程序轨迹记录优化方法

离线污点分析的轨迹记录过程的时空开销非常巨大,因此研究高效的轨迹记录方式在离线污点分析中具有重要意义。基于此,针对传统指令级轨迹记录存在的时空开销过大的问题,结合程序重放的思想,提出了一种启发式的轨迹记录方法,只在基本块和特殊事件发生时记录寄存器变化状态信息,并对该种记录方法的信息等价性进行了理论证明。实验表明,该方法能够有效降低离线污点分析中轨迹记录的时空开销,提高污点分析效率。     

What do you learn about someone over time? The relationship between length of acquaintance and consensus and self-other agreement in judgments of personality.

Theory and research examining length of acquaintance and consensus among personality judgments have predominantly examined each dimension of personality separately. In L. J. Cronbach's (1955) terminology, this trait-centered approach combines consensus on elevation, differential elevation, and differential accuracy in personality judgments. The current article extends D. A. Kenny's (1991, 1994) weighted average model (WAM)--a theoretical model of the factors that influence agreement among personality judgments--to separate out two of Cronbach's components of consensus: stereotype accuracy and differential accuracy. Consistent with the predictions based on the WAM, as length of acquaintance increased, self-other agreement and consensus differential accuracy increased, stereotype accuracy decreased, and trait-level or raw profile correlations generally remained unchanged. Discussion focuses on the conditions under which a relationship between length of acquaintance and consensus and self-other agreement among personality evaluations emerges and how impressions change over time. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

视频图像变化信息的动态检测算法与实现

研究了一种视频图像变化信息动态检测的方法。该方法采用数字图像处理技术,将中值滤波和自适应阈值分割应用到了检测当中。同时提出了分区域帧间比较的思想,以计算机为工作平台进行移动侦测,较好的解决虚警和漏警问题,有较高的准确性和可靠性。     

电视与红外传感器对机动目标的分布式航迹融合

基于当前统计模型对机动目标进行建模,并用统计的方法对机动目标的多条航迹进行关联和融合,从跟踪性能以及结构的可靠性和可用性上分析了分布式融合结构是目标跟踪最经济和最合理的选择。最后计算机仿真中验证了此结构的实用性和有效性。