Mn掺杂LiFePO4的第一性原理研究

采用基于密度泛函理论的第一性原理方法, 计算了不同Mn掺杂浓度LiFe_1-xMn_xPO₄ (x=0,0.25,0.50,0.75) 的电子结构. 同时采用流变相辅助高温固相碳热还原法制备了LiFe_1-xMn_xPO₄ (x= 0,0.25,0.50,0.75) 材料. 理论计算表明: LiFePO₄具有E_g = 0.725 eV的带隙宽度, 为半导体材料. 通过Fe位掺杂25%的Mn离子可最大程度地 减小材料带隙宽度、降低Fe---O键及Li---O键键能, 进而提高材料的电子电导率及锂离子扩散速率. 实验结果亦表明, 当Mn掺杂量x=0.25时, 材料具有最优的电化学性能, 其具有约为158 mAh· g^-1的放电比容量以及551 Wh· kg^-1的能量密度. 理论计算与实验结果非常符合.     

硫和银共掺杂介孔TiO2的制备、表征及其对染料的光催化降解活性

以P123为模板,以钛酸四正丁酯、硝酸银和硫脲为原料采用模板法制备了一系列硫和银共掺杂介孔TiO₂光催化材料．利用SEM、XRD、BET和紫外-可见光谱等技术对其形貌、晶体结构及表面结构、光吸收特性等进行了表征．以甲基橙溶液的光催化降解为模型反应,考察了不同掺杂量的样品在紫外和可见光下的光催化性能．结果表明,用模板法制备的共掺杂介孔TiO₂光催化材料在紫外和可见光条件下较纯介孔TiO₂和单掺杂介孔TiO₂对甲基橙溶液具有更好的光催化降解效果, 且硫和银的掺杂量及样品焙烧温度显著影响该材料的催化性能．当硫掺杂量为2mol%和银掺杂量为1mol%,在500 oC 焙烧2 h所得光催化材料的催化性能最佳,4 h即可使甲基橙的降解率达98.8%,重复使用4次仍可使甲基橙的降解率保持在87.5%以上     

Al2O3钝化及其在晶硅太阳电池中的应用

介绍了Al₂O₃的材料性质及其原子层沉积制备方法, 详细阐述了该材料的钝化机制(化学钝化和场效应钝化), 并从薄膜厚度、热稳定性及叠层钝化等角度阐释其优化方案. 概述了Al₂O₃钝化在晶体硅太阳电池中的应用, 主要包括钝化发射极及背面局部扩散电池和钝化发射极及背表面电池. 最后, 对Al₂O₃钝化工艺的未来研究方向和大规模的工业应用进行了展望.     

铁和镧共掺杂纳米二氧化钛光催化剂的制备、表征及其光催化活性

以葡聚糖为模板,钛酸四正丁酯、硝酸铁和硝酸镧为前驱体采用模板法制备了一系列铁、镧单掺杂及共掺杂纳米TiO₂光催化剂. 利用SEM、XRD、BET比表面积测定和UV-Vis等技术对其形貌、晶体结构及表面结构、光吸收特性等进行了表征. 以甲基橙溶液的光催化降解为模型反应,考察了不同掺杂的样品在紫外和可见光下的光催化性能. TiO₂材料具有较大的比表面积(约150 m²/g),铁和镧共掺杂纳米TiO₂在可见光区域有较强的吸收,在紫外和可见光条件下较纯TiO₂和单掺杂TiO₂对甲基橙溶液具有更好的光催化降解效果,且铁和镧的掺杂量显著影响该材料的催化性能. 当铁掺杂量为0.5mol%、镧掺杂量为0.3mol%,在500 ℃焙烧2 h所得光催化材料的催化性能最佳,焙烧4 h即可使甲基橙的降解率达98.8%,且该复合材料有较高的循环回收利用率,重复使用4次仍可使甲基橙的降解率保持在88%以上.     

高功率离子束的应用研究

 给出用“闪光二号”加速器高功率离子束轰击19F靶产生6~7MeV准单能脉冲γ射线的实验结果；提出采用离子束传输法分离和降低轫致辐射干扰的方法，利用闪烁体探测器和半导体探测器，测出质子传输不同距离后轰击C₂F₄靶产生的6~7MeV准单能脉冲γ射线信号以及相比轫致辐射的延迟时间；介绍了模拟材料的软X射线的热 力学效应等方面的高功率离子束的应用，给出一些实验和理论计算结果。     

钙钛矿晶体的电荷复合动力学研究

本文利用紫外吸收光谱和稳态荧光光谱技术结合理论模型,研究了钙钛矿材料CH₃NH₃PbI₃晶体在光激发过程中的电荷复合动力学行为,进而获得晶体的扩散长度. 电荷载体的扩散长度是判断光电材料的重要参数. 研究通过合成两种不同缺陷态浓度的CH₃NH₃PbI₃晶体,测量这两种晶体在0.019∽4.268 μJ/cm²的激光激发下的时间分辨荧光光谱,利用动力学模型对光谱进行拟合,可以获得每个晶体的掺杂浓度,空穴浓度以及电荷复合参数. 将这些参数结合已有公式,最终可获得每个晶体的电荷载体的扩散长度.     

Gd3Ga5O12:Ag薄膜电致发光材料的制备及其发光性质

研究了Gd₃Ga₅O₁₂:Ag材料的制备及其发光性质.Gd₃Ga₅O₁₂:Ag材料通过固相反应法制得,采用X射线衍射法分 析了材料的结晶度及成分.用电子束蒸发将该材料制备成交流的薄膜电致发光器件,得到了 较好的蓝紫色发光,发光峰分别位于397和467nm.通过对材料的光致发光和激发光谱的研究 和比较,得出397和467nm分别来自于氧空位和Ag⁺的发光.     

酸碱分步催化对溶胶-凝胶ZrO2膜光学性能的影响

 以丙醇锆作为前驱体,利用酸碱分步催化法制备了ZrO₂溶胶,用粒度仪检测胶体粒度;用N₂吸脱附表征凝胶的结构;采用旋转镀膜法在K9基片上镀制单层ZrO₂薄膜;用分光光度计和椭偏仪检测膜层的透过率、折射率及膜层厚度;用红外光谱仪检测胶体内部粒子间化学键状态。实验结果发现,在脉宽1 nm,波长1 064 nm时,采用此种胶体镀制的单层ZrO2膜层折射率达到1.74,单层膜损伤阈值为9.0 J/cm²,表明该方法集中了酸与碱两种催化方式的优点,一定程度上提高了膜层的光学性能。     

高功率激光宽光谱减反膜的溶胶-凝胶旋转法制备工艺

 采用溶胶-凝胶法用旋转镀膜工艺在K9玻璃基片上制备出了SiO₂和有机硅单层减反膜以及有机硅-SiO₂双层减反膜。考察了旋转速度对SiO₂和有机硅单层膜的中心透射波长、膜层折射率等基本光学性质的影响，实验确定了双层膜的涂敷工艺。透射光谱测量表明，采用本文工艺条件制备的有机硅 SiO₂双层膜在430～800nm范围内透射率达99％以上。     

铈和磷钨酸共掺杂纳米二氧化钛中空纤维的制备及其光催化活性

以棉花纤维为模板,以钛酸四正丁酯、硝酸铈铵和磷钨酸为原料采用模板法制备了一系列铈和磷钨酸共掺杂的、具有中空纤维结构的TiO₂光催化材料, 利用扫描电子显微镜、X射线衍射、BET和紫外-可见光谱等技术对其形貌、晶体结构及表面结构、光吸收特性等进行了表征. 以苯酚溶液的光催化降解为模型反应,考察了不同掺杂量的样品在紫外和可见光下的光催化性能. 结果表明,用模板法制备的TiO₂纤维材料具有中空结构,共掺杂的TiO₂纤维在紫外和可见光条件下较纯TiO₂纤维和单掺杂TiO₂纤维对苯酚溶液具有更好的光催化降解效果, 且铈和磷钨酸的掺杂量显著影响该纤维材料的催化性能;当铈掺杂量为0.3mol%和磷钨酸掺杂量为2mol%,在500 oC焙烧2 h所得中空纤维材料的催化性能最佳,4 h即可使苯酚溶液的降解率达98.5%;重复使用4次仍可使苯酚溶液的降解率保持在87%以上,且该催化剂材料易于离心分离去除.     

平行光管主反射镜组件的非线性有限元分析

为了提高对光学仪器中光机结构分析的精度,引入了非线性分析方法,用非线性有限元法研究了某平行光管主镜组件存在的非线性问题。介绍了产生结构非线性的主要来源,并在接触理论的基础上对主反射镜组件进行了合理的有限元建模。采用接触非线性分析方法对螺钉预紧时反射镜的响应及在自重和温度载荷作用下反射镜的变形进行了分析。将线性和非线性分析结果与实际结果进行了对比,结果表明,采用接触非线性分析方法对反射镜组件进行工程分析减小了分析误差。因此,在工程分析中,对某些接触部位采用非线性分析方法可以提高分析精度,得到的结果更加符合实际。     

Application of Information Technologies and Programming Methods of Embedded Systems for Complex Intellectual Analysis

An information model is outlined, which represents an intelligent system of metallographic analysis in the form of a set of subsystems, the interaction of which ensures the performance of metallographic analysis functions. The structure of the information storage subsystem for metallographic analysis is presented. The deployment model of an intelligent metallographic analysis system is proposed and described. The paper outlines the approach to the presentation of an expert subsystem for metallographic quality control of metals based on a neural network. The process of finding a close precedent in metallographic analysis with reference to a multilayer neural network is described. An intelligent metallographic analysis system is described, which based on proposed information model. A specialized software of an intelligent metallographic analysis system is presented. The functioning results of the developed system for processing images of steel microstructures to determine the steel quantitative parameters is presented.     

平行光管主反射镜组件的非线性有限元分析

为了提高对光学仪器中光机结构分析的精度,引入了非线性分析方法,用非线性有限元法研究了某平行光管主镜组件存在的非线性问题。介绍了产生结构非线性的主要来源,并在接触理论的基础上对主反射镜组件进行了合理的有限元建模。采用接触非线性分析方法对螺钉预紧时反射镜的响应及在自重和温度载荷作用下反射镜的变形进行了分析。将线性和非线性分析结果与实际结果进行了对比,结果表明,采用接触非线性分析方法对反射镜组件进行工程分析减小了分析误差。因此,在工程分析中,对某些接触部位采用非线性分析方法可以提高分析精度,得到的结果更加符合实际。     

Deterministic-statistical analysis of a structural-acoustic system

The purpose of this paper is to develop an efficient approach for vibro-acoustic analysis. Being simple and representative, an exited plate-acoustic system is selected as a validation case for the vibro-acoustic analysis as the system presents one two-dimensional statistical component (modal dense structure panel—plate) connected to the other component (deterministic acoustic volume—cavity) through the area junction over a surface domain, rather than at a line boundary. Potential industrial applications of the system vibro-acoustic analysis would be in acoustic modelling of vehicle body panels such as the cabin roof panel, and door panels for the boom noise analysis.A new deterministic-statistical analysis approach is proposed from a combination or hybrid of deterministic analysis and statistical energy analysis (SEA) approaches. General theory of the new deterministic-statistical analysis approach is introduced. The main advantage of the new deterministic-statistical analysis approach is its possibility in place of the time consuming Monte Carlo simulation. In order to illustrate and validate the new deterministic-statistical analysis approach, three approaches of the deterministic analysis, the statistical energy analysis and the new deterministic-statistical analysis are then applied to conduct the plate-acoustic system modelling, and their results will be compared. The vibro-acoustic energy coupling characteristic of the plate-acoustic system will be studied. The most suitable frequency range for the new approach will be identified in consideration of computational accuracy, information and speed.     

An efficient numerical approach to electrostatic microelectromechanical system simulation

Computational analysis of electrostatic microelectromechanical systems (MEMS) requires an electrostatic analysis to compute the electrostatic forces acting on micromechanical structures and a mechanical analysis to compute the deformation of micromechanical structures. Typically, the mechanical analysis is performed on an undeformed geometry. However, the electrostatic analysis is performed on the deformed position of microstructures. In this paper, a new efficient approach to self-consistent analysis of electrostatic MEMS in the small deformation case is presented. In this approach, when the microstructures undergo small deformations, the surface charge densities on the deformed geometry can be computed without updating the geometry of the microstructures. This algorithm is based on the linear mode shapes of a microstructure as basis functions. A boundary integral equation for the electrostatic problem is expanded into a Taylor series around the undeformed configuration, and a new coupled-field equation is presented. This approach is validated by comparing its results with the results available in the literature and ANSYS solutions, and shows attractive features comparable to ANSYS.     

基于接触非线性分析方法的反射镜组件工程分析

工程中将实际的非线性系统近似为线性系统,用线性分析方法对所研究的对象进行分析往往会带来较大的求解误差。介绍了产生结构非线性的主要因素,并在接触理论基础上,对某空间相机反射镜组件进行了合理的有限元建模。采用接触非线性分析方法对螺钉预紧时反射镜的响应及在自重和温度载荷作用下反射镜的变形进行了分析。通过比较线性分析与非线性分析的结果表明:采用非线性分析的结果更接近实际;在空间相机的工程分析中,对某些接触部位采用非线性的分析方法可以提高分析精度。     

基于压缩感知理论的非线性γ谱分析方法

γ谱分析是一种重要的放射性核素定量分析方法. 弱峰的检测和重叠峰的分解是γ 谱分析中的难点. 为了解决这两个问题, 基于压缩感知理论, 提出了一种新的γ 谱分析方法. 这一方法从谱仪对γ 谱调制的物理机理出发, 通过数学建模, 将γ 谱分析转化为一个以真实γ 谱为解的求逆问题, 并在压缩感知理论框架下, 运用γ 谱特征峰的稀疏性, 进行逆问题的求解, 直接获得γ 谱的估计结果. 数值模拟结果和蒙特卡洛模拟结果表明: 该方法能在降低统计涨落的同时, 有效减小谱仪调制带来的能谱展宽, 从而提高γ 谱分析精度. 关键词： γ谱分析')" href="#">γ谱分析 压缩感知 非线性 逆问题     

Image encryption based on a delayed fractional-order chaotic logistic system

A new image encryption scheme is proposed based on a delayed fractional-order chaotic logistic system.In the process of generating a key stream,the time-varying delay and fractional derivative are embedded in the proposed scheme to improve the security.Such a scheme is described in detail with security analyses including correlation analysis,information entropy analysis,run statistic analysis,mean-variance gray value analysis,and key sensitivity analysis.Experimental results show that the newly proposed image encryption scheme possesses high security.     

Whole field spatial frequency analysis of double-or multiple-exposed PIV images

Speckle Velocimetry or high-image density PIV gives a velocity vector map of a twodimensional flow field by point-by-point spatial frequency analysis of local pattern at an interrogation spot in a double- or a multiple-exposed image of laser speckle or pseudo-speckle pattern generated by pulsed laser-light-sheet illuminations of a plane in the flow densely seeded with fine particles. The whole field spatial frequency analysis of the double- or multiple-exposed PIV image gives more useful information of the flow field. Optical Fourier transform is a conventional technique not only for the local spatial frequency analysis but for the whole field analysis. Filtering of spatial frequency is one of the typical techniques for the latter which can reconstruct a velocity contour or a component velocity contour map of the flow. Fundamentally this technique is a simple and efficient analogue method to get more information in the velocity field analysis of the flow than a digital image processing, but in practical applications the measurement is restricted to simple flows because of optical noise and low spatial resolution. In order to improve the technique, the fundamental characteristics of the filtering and the noise yielded in the filtering process must be investigated. Meanwhile, wavelet analysis can also be applied to the whole field spatial frequency analysis of PIV image. In this paper the filtering technique is examined by numerical convolution integral, and the results obtained are compared with ones obtained by the wavelet analysis.     

小波分析在遥测信号处理中的应用

综述了小波分析的发展现状,通过对比小波变换与短时傅里叶变换之间的差异,指出小波分析是一种多分辨分析方法,特别适合于非平稳信号的分析与处理,并且应用该方法对遥测速变信号进行处理,取得了较好的效果。