Tensile Properties and Failure Mechanism of a New 3D Nonorthogonal Woven Composite Material

Tensile properties and failure mechanism of a newly developed three-dimensional (3D) woven composite material named 3D nonorthogonal woven composite are investigated in this paper. The microstructure of the composite is studied and the tensile properties are obtained by quasi-static tensile tests. The failure mechanism of specimen is discussed based on observation of the fracture surfaces via electron microscope. It is found that the specimens always split along the oblique yarns and produce typical v-shaped fracture surfaces. The representative volume cell (RVC) is established based on the microstructure. A finite element analysis is conducted with periodical boundary conditions. The finite element simulation results agree well with the experimental data. By analyzing deformation and stress distribution under different loading conditions, it is demonstrated that finite element model based on RVC is valid in predicting tensile properties of 3D nonorthogonal woven composites. Stress distribution shows that the oblique yarns and warp yarns oriented along the x direction carry primary load under x tension and that warp yarns bear primary load under y tension.     

Reliability analysis on systems with self-healing and self-repairing under different environments and shock models

Inspired by the process of self-healing of biological damage, high technology materials with self-healing and self-repairing mechanisms have been developed for high reliability and long lifetime. Therefore, the reliability modeling on intelligent systems with healing performance has become a research hotspot. Based on the diversity of healing mechanisms, this paper proposes a two-phase reliability model method on self-healing and self-repairing systems. Impacts of environments, shock loads, self-healing, and self-repairing mechanisms are taken into account in this novel model. Besides, system lifetime and some reliability indexes under two shock models are derived, respectively. Moreover, Monte Carlo simulations are conducted to verify the accuracy of reliability under two models. Finally, an engineering case of metallized film capacitor is provided to illustrate the effectiveness and applicability of the proposed models by comparing numerical results and simulation results.     

Comparison of approaches based on optimization and algebraic iteration for binary tomography

Binary tomography represents a special category of tomographic problems, in which only two values are possible for the sought image pixels. The binary nature of the problems can potentially lead to a significant reduction in the number of view angles required for a satisfactory reconstruction, thusly enabling many interesting applications. However, the limited view angles result in a severely underdetermined system of equations, which is challenging to solve. Various approaches have been proposed to address such a challenge, and two categories of approaches include those based on optimization and those based on algebraic iteration. However, the relative strengths, limitations, and applicable ranges of these approaches have not been clearly defined in the past. Therefore, it is the main objective of this work to conduct a systematic comparison of approaches from each category. This comparison suggested that the approaches based on algebraic iteration offered both superior reconstruction fidelity and computation efficiency at low (two or three) view angles, and these advantages diminished at high view angles. Meanwhile, this work also investigated the application of regularization techniques, the selection of optimal regularization parameter, and the use of a local search technique for binary problems. We expect the results and conclusions reported in this work to provide valuable guidance for the design and development of algorithms for binary tomography problems.     

基于激光超声表面波检测的瓦斯检测研究

利用SnO2/Pt气敏薄膜对瓦斯气体的选择性吸附作用将引起声表面波在其表面的传播速度发生相应改变的性质,并结合激光超声检测技术,提出了一种新的瓦斯检测方法.采用激光在覆有选择性气体吸附薄膜的抛光铝材表面激发出声表面波,用单芯光纤耦合的反射式光束偏转法对所激发声表面波信息进行采集,进而通过合理的算法可以准确检测出环境中瓦斯气体的体积分数.为瓦斯监测方法提供了一种新途径.     

一种安全有效的基于身份的门限签密方案

签密是一种将加密和数字签名技术结合在一起的思想,它比采用先签名后加密的方法具有更高的效率.基于双线性对技术,提出了一种新的基于身份的门限签密方案.它利用决策双线性Diffie-Hellman(DBDH)问题的困难性在随机预言模型下给出了方案的语义安全性证明,并利用计算Diffie-Hellman(CDH)问题的困难性证明了方案的不可伪造性,同时指出方案具有较高的效率.     

炼油化工MES功能与架构研究

MES经过多年的研究和发展,逐步实现了功能和接口的标准化.在炼油化工行业,结合行业特点和生产运行管理的需求,形成了模块化、可配置的行业解决方案.在功能架构方面,形成了覆盖生产计划、生产执行、生产运行管理和生产统计等业务的软件产品.在应用架构方面,可以根据企业规模、管理模式和地域分布,建立集中式或分布式的架构.由于炼化企业生产自动化水平较高,大部分数据实现了自动采集,建立实时数据库和关系数据库.由于信息技术的进步,促进MES系统架构和性能不断完善,向集成化、标准化、实时性、可视化和可维护性发展.     

偏最小二乘方法在中药指纹图谱相似度研究中的应用

本文介绍了偏最小二乘作为1种新的方法应用于指纹图谱的相似度比较计算中.偏最小二乘方法通过从中药色谱或光谱数据中提取大量信息来预测出1个响应值.本文中利用偏最小二乘方法为基础来计算中药色谱指纹图谱的相似度.相比较于传统的相似度计算方法,上述方法得到的结果更加明确可靠,并且计算量少于其他算法.