基于镜像源方法的室内声场脉冲响应仿真

针对基于室内声场脉冲响应描述声场音质特性时其精确度不高的问题,以经典镜像源方法为核心,讨论了基于变换频域和反射系数的改进算法.以矩形空间为具体实例,给定接收点和声源位置,并利用计算机仿真室内声场脉冲响应.在不同参数条件下,对各个算法进行了分析,估计了能量衰减曲线和房间混响时间.结果表明,基于变换频域和反射系数的改进算法具有更高的准确性和可靠性.     

Cognitive work analysis to comprehend operations and organizations in the mining industry

Complex industrial systems, including mining, have a prominent challenge in understanding the interrelationship among the cognitive processes, working environment and available equipment. The concept of cognitive work analysis(CWA) transcends the traditional analytic methods of evaluating human tasks solely based on perceptual and physical traits, and rather implements the notions of behavioral and cognitive awareness indispensable for the intricacy of modern technology. In the last few decades, academic and industrial settings employ this type of analysis to set a suitable standard for a system's safety feasibility, and as a result reduce human-based errors. This research paper analyzes current CWA methods and proposes a five-level quantification model portraying the overall cognitive quality of a mining operation.     

基于场景元模型的软件产品线追踪方法

针对软件产品线需求追踪方法进行了研究,基于软件产品线领域需求分析、设计、实现三个阶段的信息传播,提出了一种基于场景元模型的多层次软件产品线追踪模型,完整描述了追踪信息变化的整体框架;建立了需求—用例追踪矩阵、用例—动作追踪矩阵、动作—构件追踪矩阵;根据矩阵运算,描述了具体追踪实现过程,通过一个ATM案例验证了该方法对于软件产品线领域需求获取以及需求变更等问题的解决有较好的效果。     

基于Legendre多项式展开的双基SAR二维频域成像算法

针对任意构型双基SAR基于传统Taylor级数展开斜距方法的边缘点散焦问题,提出了一种基于Legendre正交多项式逼近的双基SAR二维频域成像算法。该算法基于对斜距函数的Legendre多项式展开推导了点目标二维频谱,解除了回波信号距离—方位的耦合,使成像处理更高效。在二维频域对场景区域的点目标采用二维频域成像算法进行成像。该算法改善了场景边缘点的聚焦效果,增加了场景边缘点的聚焦深度。理论推导和仿真结果验证了该算法的有效性和可行性。     

直接驱动XY平台位置域轮廓跟踪控制

针对直接驱动XY平台轮廓误差近似模型建立困难的问题,提出一种提高轮廓跟踪性能的位置域轮廓跟踪控制方法.通过将双轴运动系统等效为主-从运动方式,主动轴(X轴)以位置量作为自变量,将从动轴(Y轴)的运动描述为不同轮廓跟踪要求的X的函数.通过从时域到位置域的一一映射,得到双轴运动系统的位置域动态模型.提出了位置域PD控制策略,主动轴运动以自身为参考产生的位置跟踪误差为零,仅有从动轴的运动跟踪误差影响到了最后的轮廓误差.仿真结果表明,位置域轮廓控制相比时域轮廓控制能够获得更好的跟踪精度.     

Low-Field Nuclear Magnetic Resonance Time Domain Characterization of Polyunsaturated Fatty Acid–Rich Linseed and Fish Oil Emulsions during Thermal Air Oxidation

Linseed contains high levels of polyunsaturated fatty acids (PUFA), such as α-linolenic acid (> 50% ALA-18:3), that are naturally protected against thermal oxidation by their encapsulation within linseed oil bodies (OB) by multiple components including antioxidant proteins and mucilage emulsifying agents. Linseed OB emulsions (LSE) can be produced by grinding linseed seeds, adding water, adjusting pH, and sonication. This is a process that can encapsulate externally added PUFA to minimize their thermal oxidation, as it does for the intrinsic ALA PUFA. Fish oil (FO) encapsulation into this LSE platform to form linseed fish oil emulsions (LSFE) offers the possibility of a nutritive delivery system of the biologically essential FO PUFA eicosapentaenoic acid and docosahexaenoic acid. In this study, ¹H low-field nuclear magnetic resonance (LF-NMR) is used to characterize LSE's and LSFE's chemical and structural properties as well as their stability and changes under thermal oxidation (55 °C for 96 hours). ¹H LF-NMR data processing was developed to generate one-dimensional (1D) T₁ (spin–lattice), 1D T₂ (spin–spin), and 2D (T₁ vs. T₂) relaxation time spectra that can characterize OB emulsions and monitor their time domain fingerprints (spectrum peaks) of chemical and structural changes during the oxidation process. The ¹H LF-NMR analysis were further supported and correlated with conventional peroxide value test, self-diffusion, droplet size distribution, zeta potential estimation of surface stability, and gas chromatography–mass spectrometry analysis of fatty acid profile changes under thermal oxidation conditions. The 1D and 2D LF-NMR relaxation spectra showed that the LSE and LSFE did not suffer intense oxidation process, due to PUFA assembly in OB oxidative protection. These results were further confirmed by the supportive analytical methodologies. The results of this study demonstrate the efficacy of ¹H LF-NMR methodology to monitor PUFA's rich oil and emulsion thermal oxidation.     

Al2O3和Sialon陶瓷中LiTaO3第二相的断裂行为

将LiTaO3压电陶瓷颗粒分别添加到Al2O3和Sialon结构陶瓷基体中，通过对复相陶瓷试样断口形貌和裂纹扩展路径的观察，研究了Al2O3和Sialon结构陶瓷基体中LiTaO3第二相的断裂行为。研究结果表明：Al2O3和Sialon陶瓷基体的断裂均为沿晶断裂，LiTaO3压电陶瓷颗粒的断裂为穿晶断裂，在LiTaO3第二相的断口上，观察到了许多断裂台阶，这些断裂台阶是由于试样断裂时，裂纹扩展过程中遇到LiTaO3晶粒内的90°电畴发生裂纹偏转和分支引起的。     

数字化射线检测中缺陷影像的频域处理

研究频域处理在数字化射线检测缺陷影像增强处理过程中的应用.采用Matlab 7实现高通滤波处理流程,对处理结果进行分析,证实频域处理可有效改善数字化射线检测的灵敏度、提高图像分辨率.将其用于各类典型缺陷的数字化射线检测影像处理,可提高缺陷的检出率.     

Study on Magnetic Domains in Sm-Co Based Alloy

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云计算身份认证模型研究

云计算是在继承和融合众多技术基础上的一个突破性创新,已成为当前应用和研究的重点与热点。其中,云用户与云服务之间以及云平台中不同系统之间的身份认证与资源授权是确保云计算安全性的前提。在简要介绍云计算信息基础架构的基础上,针对云计算统一身份认证的特点和要求,综合分析了SAML2.0、OAuth2.0和Open ID2.0等技术规范的功能特点,提出了一种开放标准的云计算身份认证模型,为云计算中逻辑安全域的形成与管理提供了参考。