认知定位系统的自适应精度研究

为了能够实现定位精度的自适应,本文分析了认知无线电定位系统(cognitive positioning systems,CPS)的原理。该系统利用频谱及环境感知等模块中的传感器单元来获取所需的定位参数,并将其与到达时间(time of arrival,TOA)定位估计算法相结合,以克拉美罗下界(Cramer-Rao lower bound,CRLB)为准则分析最大似然(maximum likelihood,ML)定位精度自适应算法。本文还对单径和多径环境条件下定位精度自适应性能进行了比较。仿真结果表明,该算法能够实现定位精度的自适应,并能通过改善系统可用的频带带宽、分散频谱的数目、信号的调制方式等因素来提高定位精度。     

Image quality evaluation for OLED-based smart-phone displays at various lighting conditions

The image quality of three organic light-emitting diode (OLED) based smart-phone displays was assessed at three levels of ambient lighting conditions corresponding to the darkroom, indoor and outdoor environment, respectively. Seven perceptual attributes, i.e., naturalness, colorfulness, brightness, contrast, sharpness, preference, and overall image quality (IQ), were evaluated in both standard dynamic range (SDR) and high dynamic range (HDR) mode via psychophysical experiments by rank order method, while readability was assessed only in SDR mode and gradation was investigated only in HDR mode. The experimental results demonstrate that, besides the color gamut, the tone reproduction curve is also an important factor affecting the colorfulness of mobile display in the two modes. Higher peak luminance would not mean better performance on brightness and contrast for HDR images, which is opposite to SDR mode. Further analysis of variance (ANOVA) indicates that the ranking results of all perceptual attributes are not significantly affected by the ambient lighting levels in both SDR and HDR modes.     

Randomized range-maxima in nearly-constant parallel time

Given an array ofn input numbers, therange-maxima problem is that of preprocessing the data so that queries of the type what is the maximum value in subarray [i..j] can be answered quickly using one processor. We present a randomized preprocessing algorithm that runs inO(log^* n) time with high probability, using an optimal number of processors on a CRCW PRAM; each query can be processed in constant time by one processor. We also present a randomized algorithm for a parallel comparison model. Using an optimal number of processors, the preprocessing algorithm runs inO( (n)) time with high probability; each query can be processed inO ( (n)) time by one processor. (As is standard, (n) is the inverse of Ackermann function.) A constant time query can be achieved by some slowdown in the performance of the preprocessing stage.     

图像中的文本定位技术研究综述

介绍了图像中文本定位技术的研究现状,依据定位所利用的特征进行分类,分析了其中几种典型算法,并对文本定位算法的性能评价标准进行了深入讨论。     

金属及合金中射程参数的研究SCIEI

本文应用金属中Wigner-Sietz(W-S)半径数据和引入等效电荷概念,结合Ziegler的质子注入数据,导出了计算重离子注入各种金属中的电子阻止本领S_c(E)的公式,计算结果与文献中的实测值结果甚为一致。同样,应用合金中的W-S半径,导出了适用于合金硼化物和CsCl型合金的S_c(E)计算公式。计算结果表明,公式对单硼或二硼化合物符合得较好,而对一些复杂结构的合金以及Cr_5B_3和W_2B_5是不适合的。对CsCl型合金,S_c(E)对Bragg定律的偏离系数γ和合金中电荷转移量成正比,后者越大表明金属键越强,则合金对离子的阻止本领越大,这与实验结果是吻合的。合金中两元素在同一周期中位置相差越远,这种趋势越明显。不同周期元素组成的合金更加强了这种趋势。     

基于并查集和边缘检测模板的非理想虹膜定位

非理想虹膜图像往往存在虹膜边缘模糊、灰度变化不均匀、位置偏移及光斑干扰等问题, 这些问题的存在会在一定程度上影响虹膜内、外边界定位的准确率. 针对这个问题, 本文提出采用并查集和边缘检测模板的方法来对非理想虹膜进行内、外边界定位. 内边界定位是首先采用并查集方法完成瞳孔区域粗定位, 然后采用Hough变换对瞳孔进行精确定位; 外边界定位是先利用一系列边缘检测模板大致确定外圆的位置, 然后再依据外边界附近圆环内边缘点的密度来最终完成外边界的精确定位. 实验结果表明, 对于非理想虹膜图像, 本文方法的定位正确率和定位速度均高于其他同类方法.     

铝电解电容器用新型宽温高压工作电解液

采用异癸二酸铵为主溶质,乙二醇和γ-丁内酯为复合溶剂,制备新型宽温(-40~105℃)、高压(400 V)铝电解电容器工作电解液,并检测了该电解液和用该电解液生产的电解电容器的性能。测试结果表明,该工作电解液25℃时电导率达到1.6 mS/cm,闪火电压为480 V,-40℃下未见晶体析出;CD 110/400 V铝电解电容器试样的漏电流≤10μA,损耗0.03,容量变化率只有-3%。经过105℃高温贮存250 h后各项电气性能不仅优于国家标准,而且能达到严格的企业标准。     

基于FPGA的高频全数字低电平系统算法实现

本套加速器高频低电平系统(LLRF)是中国ADS注入器II高频系统的原型机,其工作频率为162.5 MHz,以实现超导加速腔的幅度与相位稳定控制和谐振频率调节。该系统主要由射频前端和数字信号处理FPGA两部分组成。射频前端主要实现高频信号的上下变频和电平匹配;数字信号处理FPGA是系统的核心,主要完成射频信号幅值与相位的数字稳定控制,超导腔谐振频率控制,以及1 000 M以太网通信。在实验室环境下,对该系统进行了幅度和相位稳定度测试,相位稳定度峰峰值为±0.3°,有效值为0.09°,幅值相对稳定度峰峰值为±5×10-3,有效值为3.2×10-3,达到了设计要求。     

成形压力对氧化铝瓷球性能的影响

本文以不同的压力等静压成形瓷球，研究了成形压力对瓷球烧结温度、密度及耐磨性的影响。结果表明：在本研究系统内随着压力的增加瓷球的烧结温度下降，烧成温度范围拓宽。采用150MPa成形的瓷球密度最大且耐磨性最好。     

Chemical properties of femoral gland secretions in the desert iguana,Dipsosaurus dorsalis

This study investigates the chemistry of femoral gland secretions in the desert iguana,Dipsosaurus dorsalis (Lacertilia: Iguanidae), and discusses their possible functional significance. Electrophoretic and proton NMR studies indicated that the secretions are composed of approximately 80 % protein and 20% lipid material. Individual differences in polyacrylamide gel banding patterns of femoral gland proteins were found. Reflectance spectroscopy revealed that the secretions strongly absorb longwave ultraviolet light, a feature that may be important in the localization of secretion deposits in the environment.