Performance analysis of a spreading sequence estimator for spread spectrum transmissions

Direct sequence spread spectrum transmissions (DS-SS) are now widely used for secure communications, as well as for multiple access. They have many interesting properties, including low probability of interception. Indeed, DS-SS transmitters use a periodical pseudo-random sequence to modulate the baseband signal before transmission. A receiver which does not know the sequence cannot demodulate the signal.In this paper, we propose a new method which can estimate the spreading sequence in a noncooperative context. The method is based on eigenanalysis techniques. The received signal is divided into windows, from which a covariance matrix is computed. We show that the sequence can be reconstructed from the two first eigenvectors of this matrix, and that useful information, such as desynchronisation time, can be extracted from the eigenvalues.The main achievement of the present paper is a performance analysis of the proposed spreading sequence estimation procedure. An analytical approach is first considered owing to matrix perturbation theory and Wishart matrix properties. Then, complementary Monte Carlo simulations are performed to show the effectiveness of the proposed method.     

山东大磨曲家矿区成矿元素多重分形特征

通过矩方法,以无序数据集中不同品位级次内的频率为测度,研究了胶东大磨曲家金矿矿体及玲珑花岗岩、胶东群等近矿围岩的Au、Ag、As等主要成矿元素分布的广义谱曲线（Dq-q）和多重谱曲线（f（α）-α）特征.在权重-0.2≤q≤1.6时,结果显示矿体与近矿围岩中成矿元素品位分布的广义谱和多重谱特征存在明显的区别.矿体中三种成矿元素的广义谱曲线近似直线,而多重谱曲线的宽度较小,显示成矿元素品位级次密集,较为均匀,接近简单分形;近矿围岩中广义谱曲线弯曲明显,多重谱曲线的宽度较大,显示近矿围岩中元素品位级次范围较宽,相对不均匀.同时,矿体中多重谱曲线f（α）的极值所对应的α比近矿围岩中的小,代表最或然子集的品位增加,指示成矿元素在矿体中富集.多重分形分析显示矿体中的成矿元素较近矿围岩中变得更为富集而均匀.     

2-苯基-5-（6-哒嗪酮-3-基）-1,3,4-噁二唑的分子结构、光谱及热力学性质的理论研究

在B3LYP/6-31＋G＊水平对2-苯基-5-（6-哒嗪酮-3-基）-1,3,4-噁二唑分子进行几何构型优化和频率的计算,得到红外光谱、拉曼光谱和不同温度下的热力学性质.结果显示：该分子的哒嗪环、噁二唑和苯基环在同一个平面上,整个分子不具有对称性;该分子的气态热容、熵、焓等热力学性质与温度之间存在很好的函数关系式.     

Co‐creating a school‐based Facing Your Fears anxiety treatment for children with autism spectrum disorder: A model for school psychology

Across the disciplines of psychology, the research to practice gap is gaining recognition. This study used an integrated knowledge translation (iKT) framework to evaluate the acceptability, feasibility, and sustainability of delivering an anxiety intervention for children with autism spectrum disorders (i.e., FYF), in schools. Five participants (three educators and two parents) offered their perspectives on program strengths, barriers to implementation, and adaptations for the school setting. Qualitative data were collected through focus group discussions and analyzed using thematic analysis techniques. The participants provided valuable information about program structure and considerations for implementation in schools. Results indicated that participants found the proposed modified FYF to be acceptable and feasible and recommended pilot testing the intervention. Specific recommendations for adaptations are discussed. This study offers a model for researchers to collaborate with key stakeholders in adapting interventions for use in schools, thereby, bridging the gap between research and practice.     

闭式高速压力机组合机身的载荷谱分析

基于力学的基本理论对带有平衡机构的曲柄滑块机构进行运动学和动力学分析. 通过近似简化曲轴的力学模型,获得了曲轴与上横梁轴承座之间相互作用的载荷谱理论公式.利用Matlab对空载和打桩2种工况下组合机身的载荷谱数据进行仿真,分析这2种工况下载荷谱曲线的规律.仿真结果表明,在空载情形下,曲轴和上横梁轴承座之间相互作用的理论与仿真载荷谱曲线呈现周期性的正弦波形式;在打桩工况下,曲轴和上横梁轴承座之间相互作用的理论和仿真载荷谱曲线呈现周期性的脉冲波形式.该结果能够为有限元法分析闭式高速压力机组合机身动力学性能过程中载荷的确定提供理论基础.     

氨基酸N-酰化衍生物的合成与表征

用氯乙酰氯作为酰化剂在碱性条件下与氨基酸反应 ,通过改进反应条件 ,控温、调 p H值 ,选择萃取剂、洗涤剂、重结晶溶剂 ,使产品的纯度和产率有较大的提高 .用电喷雾电离质谱等先进手段对产品进行分析、鉴定 .同时对目标物作红外光谱及元素分析 .对化合物红外光谱进行了光谱归属     

拉米夫定与牛血清白蛋白的作用机制

用荧光和紫外光谱法研究Tris-HCl缓冲溶液中拉米夫定与牛血清白蛋白(BSA)作用机制.测定了不同温度下拉米夫定对BSA的荧光猝灭光谱,并对其猝灭机制进行了讨论,认为拉米夫定对BSA的猝灭为静态猝灭;运用位点结合模型,计算得到298K时拉米夫定与BSA结合常数KA为1.79×105L.mol-1和结合位点数n为1.04,说明二者存在一定相互作用,其作用力主要为氢键或范德华力;根据F ster偶极-偶极非辐射能量转移原理,求得拉米夫定在BSA上距色氨酸残基的距离r为2.21nm;最后通过同步荧光光谱发现拉米夫定对BSA构象产生了一定的影响.     

Interactive video usage on autism spectrum disorder training in medical education

This study aimed to compare the effects of interactive and non-interactive videos concerning the autism spectrum disorder on medical students’ achievement. It also evaluated the relation between the interactive videos’ interactivity and the students’ decision-making process. It used multiple methods, including quantitative and qualitative methods. The participants were 60 medical students, divided into two groups. One group watched an interactive video while the other watched a non-interactive video. Pre- and post-tests were used to evaluate the students’ relevant achievements in each group. Moreover, a think-aloud protocol was used to evaluate the decision-making process of the group who watched the interactive video. The pre- and post-test results indicated an increase in the achievements of students in the tested groups. Students who watched the interactive video were found to be more successful. Finally, watching interactive videos was shown to positively affect medical students’ decision-making process.     

基于小波变换的数字图像水印算法

利用小波变换多分辨率特性和人眼视觉特征,提出了一种彩色图像多水印算法.多个有意义的签名水印能提供更可靠的版权识别,而且多水印相互配合使水印图像同时具有很好的鲁棒性.为增强水印的鲁棒性,在添加水印之前对水印进行预处理,在嵌入水印时又应用了扩频技术.实验结果表明,该算法取得了良好的效果.     

一种底片扫描全视场读谱方法

介绍一种适合学生实验和提高学生学习兴趣的光谱底片扫描显示测量方法。通过计算机扫描、显示。或通过打印出纸质实验光谱图，在全视场下测量实验数据，可减少读数误差和差错，提高实验效果和质量。