高斯光束通过空间滤波器的传输特性

采用矩阵分解和用有限个复高斯函数之和逼近硬边光阑窗口函数相结合的方法,从柯林斯衍射积分公式出发,对高斯光束通过空间滤波器的传输特性进行了分析,得到了相应的解析式。通过对解析式的数值模拟,得出了直观的结果,并进行了误差分析。数值计算结果表明,最佳滤波小孔尺寸的选择和计算误差均与光束的截断参数有关。在此基础上,进一步研究了空间滤波器具有像传递功能时,高斯光束和平顶高斯光束(N=12)通过空间滤波器的传输特性,得出了截断参数与滤波后光强分布的关系,并证实了此方法也可用于计算其他类型光束通过空间滤波器的传输。     

臭氧在循环冷却水中分解的数学模型

臭氧可以用于工业循环冷却水的处理.为了更好地指导生产应用实际,建立了臭氧在冷却水中分解的数学模型.研究首先从理论上推导出其分解的数学模型,再通过配制不同浓缩倍数的试验用水,用N aHCO3调节碱度,通入不同浓度的臭氧,测定臭氧的分解速率,得到不同pH和CODC r时的相关数据,进而推出臭氧在实验条件下分解的动力学方程.数学模型的分析表明,影响臭氧分解的因素除了与水中的[OH-]有关外,还与其中的CODC r有关,即与系统中所含微生物、有机物、还原性无机物等有关.在实际应用中,应对运行过程中水质实行连续或间歇监测,根据pH和CODC r的变化调整臭氧的投加量,同时控制系统的CODC r以保证处理效果.     

一种用于篡改证明的小波域图像水印算法

数字技术的发展，以数字方式存储的多媒体信息越来越容易被篡改，传统手段应用在数字多媒体的保护中缺点显现．提出一种新的用于数字图像篡改证明的小波域脆弱水印算法．算法中引入了人眼视觉模型，使得算法有好的视觉隐蔽性．同时，谊算法很好的克服了之前数字水印算法对篡改的综合分析能力弱的缺陷．此外，该算法能够用于多灰度级图像水印的嵌入．以嵌入多灰度级水印的数字图像为对象，对频域改动分析和局部空间篡改检测的试验结果都表明该方案是行之有效的．     

Thermal Instability and Microstructure of Strontium M-type Hexaferrite Nanoparticles Synthesized by Citrate Approach

The dried gel of SrFe12O19, prepared by citrate approach, was investigated by means of infrared spectroscopy （ IR ）, thermogravimetric analysis （ TG ）, differential scanning calorimetry （ DSC ）, X- ray diffraction（ XRD ） techniques, energy dispersive spectroscopy（ EDS ）, and transmission electron microscopy（ TEM ）. The thermal instability and the thermal decomposition of low-temperature strontium M-type hexaferrite crystallized at about 600℃ were confirmed for the first time by XRD method. The decomposition of the low-temperature strontium M-type hexaferrite took place at about 688.6℃ determined by DSC investigation. The low-temperature strontium M-type hexaferrite nanopartieles were decomposed into SrFeO2.5 with an orthorthombic cell and Fe2O3 with a tetragonal cell as well as possibl α-Fe2O3 . The agglomerated particles with sizes less than 200 nm obtained at 800℃ were plesiomorphous to strontium M-type hexaferrite. The thermally stable strontium M-type hexaferrite nanopartieles with sizes less than 100um cotdd take place at 900 ℃ . Up to 1000 ℃ , the phose transformotion to form strontium M-type hexaferrite was ended, the calcinations with the sizes more than 1μm were composed of α-Fe2O3 and strontium M-type hexaferrite. The method of distinguishing γ-Fe2O3 with a spinel structure from Fe2O3 with tetragonal cells by using powder XRD method was proposed. Fe2O3 with tetragonal cells to be crystallized before the crystallization of thermally stable strontium M-type hexaferrite was confirmed for the first time. The reason why α- Fe2O3 as an additional phase appears in the calcinations is the cationic vacancy of stroutium M-type hexaferrite , SrFe12-x□O19 （0≤x ≤0.5）.     

一种用于篡改证明的小波域图像水印算法

提出了一种新的用于数字图像篡改证明的小波域脆弱水印算法。算法中引入了人眼视觉模型，使得算法有好的视觉隐蔽性。同时，该算法很好的克服了之前数字水印算法对篡改的综合分析能力弱的缺陷。此外，该算法能够用于多灰度级图像水印的嵌入。以嵌入多灰度级水印的数字图像为对象，对频域改动分析和局部空间篡改检测的试验结果都表明该方案是行之有效的。     

一种基于小波分解的无搜索分形图像压缩算法

在不同的小波尺度中，子块基于相应固定位置的父块进行编码，同时利用不同小波尺度之间的相关性进一步缩短编码时间．实验结果表明，与空间域无搜索分形图像压缩方法相比，提出的方法在解码图像质量略有损失的情况下，压缩比提高了近3倍，同时计算量减少了6／7．     

Preparation and Characterization of Porous Yttrium Oxide Powders with High Specific Surface Area

Y2O3isoftenusedinthemanufactureofphos phorsandceramics[1～3].However,itisalsousedas selectivecatalysts[1,4,5],suchasforthedehydrationof2alkanols,thedimerizationofmethane,1butene isomerization,hydrogenationof1,3butadieneandac etonealdoladdition,andsupport[6,7]formetalsthat catalyzetheformationofmethanolfromCO2andH2.It iswidelyacceptedthatthecatalysispropertiesofox idesdependstronglyontheirphysicalcharacteristics,especiallyontheirspecificsurfaceareaandporous structure.Agreatdealofattentionhasb…     

Synthesis and Properties of Ternary Europium Complexes with Aromatic Carboxylic Acid and ,Nitrogen-Containing Heterocyclic Ligand

Synthesis and Properties of Ternary Europium Complexes with Aromatic Carboxylic Acid and Nitrogen-Containing Heterocyclic Ligand     

Si/C负极在实际应用中的失效原因分析

将一种Si/C复合负极材料应用于14500圆柱形电池体系中,对它与碳负极电池的基本性能进行了对比,并对该种Si/C负极材料在实际应用中存在的问题以及失效原因进行了分析.以Si/C为负极的电池,其200次循环后容量维持率仅为69.5%.经分析表明,造成其容量衰减的主要原因为:电极体积膨胀导致电极活性材料脱落,电接触性能变差;由材料体积膨胀导致固体电解质相界面(SEI)膜被破坏而造成的电解液不断的分解,使正、负极界面膜增厚,电阻增加;材料本身结构造成插入的Li无法全部脱出.     

Singular value decomposition based data distortion strategy for privacy protection

Privacy-preserving is a major concern in the application of data mining techniques to datasets containing personal, sensitive, or confidential information. Data distortion is a critical component to preserve privacy in security-related data mining applications, such as in data mining-based terrorist analysis systems. We propose a sparsified Singular Value Decomposition (SVD) method for data distortion. We also put forth a few metrics to measure the difference between the distorted dataset and the original dataset and the degree of the privacy protection. Our experimental results using synthetic and real world datasets show that the sparsified SVD method works well in preserving privacy as well as maintaining utility of the datasets. Shuting Xu received her PhD in Computer Science from the University of Kentucky in 2005. Dr. Xu is presently an Assistant Professor in the Department of Computer Information Systems at the Virginia State University. Her research interests include data mining and information retrieval, database systems, parallel, and distributed computing. Jun Zhang received a PhD from The George Washington University in 1997. He is an Associate Professor of Computer Science and Director of the Laboratory for High Performance Scientific Computing & Computer Simulation and Laboratory for Computational Medical Imaging & Data Analysis at the University of Kentucky. His research interests include computational neuroinformatics, data miningand information retrieval, large scale parallel and scientific computing, numerical simulation, iterative and preconditioning techniques for large scale matrix computation. Dr. Zhang is associate editor and on the editorial boards of four international journals in computer simulation andcomputational mathematics, and is on the program committees of a few international conferences. His research work has been funded by the U.S. National Science Foundation and the Department of Energy. He is recipient of the U.S. National Science Foundation CAREER Award and several other awards. Dianwei Han received an M.E. degree from Beijing Institute of Technology, Beijing, China, in 1995. From 1995to 1998, he worked in a Hitachi company(BHH) in Beijing, China. He received an MS degree from Lamar University, USA, in 2003. He is currently a PhD student in the Department of Computer Science, University of Kentucky, USA. His research interests include data mining and information retrieval, computational medical imaging analysis, and artificial intelligence. Jie Wang received the masters degree in Industrial Automation from Beijing University of Chemical Technology in 1996. She is currently a PhD student and a member of the Laboratory for High Performance Computing and Computer Simulation in the Department of Computer Science at the University of Kentucky, USA. Her research interests include data mining and knowledge discovery, information filtering and retrieval, inter-organizational collaboration mechanism, and intelligent e-Technology.