Damage mechanisms and failure modes in cross-ply laminates under monotonic tensile loading: The influence of fiber sizing

In this study, the effect of fiber-matrix interphase on the damage modes and failure mechanisms in (0, 90₃), cross-ply graphite-toughened epoxy laminates is investigated. Two material systems (designated as 810 A and 810 O) with the same fiber and same matrix, but with different fiber sizings, were used to study the effect of the interphase. The system designated as 810 A contained an unreacted Bisphenol-A (epoxy) sizing, while a thermoplastic polyvinylpyrrolidone (PVP) sizing was used in the 810 O system. Damage accumulation in the cross-ply laminates under monotonic tensile loading was monitored using edge replication, x-ray radiography, acoustic emission, optical and scanning electron microscopy. Results indicate that the fiber-matrix bond strength is lower in the 810 O system compared to the 810 A system. Transverse matrix cracking initiates at a significantly lower stress level in the 810 O laminate. The 810 O laminates also exhibit longitudinal splitting, while the stronger bonding suppress this damage mode in the 810 A laminates. Numerous local delamination occur on the 0/90 interface at the intersection of 0 and 90 degree ply cracks, in the 810 O laminates. These are absent in the 810 A laminates. The failure modes are also different in the two material systems used in this study. The 810 A laminate exhibits a brittle failure, controlled by the local stress concentration effects near broken fibers. In the 810 O laminates, the presence of longitudinal splits result in the reduction of stress concentration effects near fibe fractures. This results in a global strain controlled failure in the 810 O system. It is concluded that the presence of different fiber sizings result in different damage modes and failure mechanisms in the cross-ply laminates used in this study.Research Associate, Research Assistant, Alexander Giacco Professor and Professor respectively.     

LS SIMD微处理器中的三组指令并发执行的设计

文章介绍了LS SIMD微处理器中实现三组指令并发执行的可能性和必要性，分析了三组指令并发执行给流水线带来的影响，并讨论了控制逻辑对三级指令并发执行的控制及其实现形式。     

数字式液压逻辑流量阀的设计

数字工流量阀采用数字控制方式，调节系统流量以达到液压系统调整目的，它本身具有控制响应快、精度高、稳定性好、适应范围大等优点，在行走机械上将会得到广泛地应用。     

南水北调石家庄受水区地下水压采方案探讨

南水北调中线石家庄受水区水资源匮乏严重，由于连年超采地下水已引发了严重的环境地质问题。现对南水北调中线石家庄受水区地下水压采方案进行探讨，通过工程措施、管理措施和相关法规、办法的制定，开源与节流并举，使该区域水资源能够支撑区域社会、经济、环境的可持续发展。     

Characterizing Performance Variation of Product Designs

Quality and reliability design practitioners have utilized Taguchi's methodology of matrix experimentation to generate computer simulation data for characterizing performance variation of product designs. However, the sampling strategy employed renders computer implementation of matrix experimentation cumbersome and statistically invalid. Weaknesses of this approach also include sample size limitation and overestimation of performance variation. An alternative approach that combines Monte Carlo simulation with the strategies of independent sampling across runs and correlated sampling between runs is presented. An application case study shows that the proposed approach constitutes an improvement on the matrix approach with respect to statistical validity and estimation accuracy.     

INCORPORATING PRACTICAL AND SYNTHESIS CONTENTS IN UNDERGRADUATE CONTROL EDUCATION

This paper revisits the effort over the last decade in making undergraduate control education more useful and attractive to both the control engineers and the engineers at large. With the help of further coverage in new textbooks, more practical and synthesis contents in the control courses have been incorporated. Gaps still exist, particularly in the areas of PID control and auto‐tuning, fuzzy control, overall control strategy, control structure and systems thinking, and these will be elaborated. A major challenge is in the coverage of more practical and synthesis contents in the introductory common control course for all engineers. How this may be resolved is discussed. Finally, the need for new teaching approaches such as the use of interesting case studies and the use of problem‐based learning will be outlined.     

CONSTRUCTION OF ADMISSIBLE OPERATION CONDITION DOMAIN FOR WELL-STIRRED REACTORS DURING THEIR DESIGN AND CONTROL STAGES

The work examines the problem of constructing an admissible operation condition domain for a well-stirred reactor which would satisfy restrictions in conversion, selectivity, heat removal and stability. The domain is very important and must be known during the reactor design and control stages because it yields visual information for analyzing the reactor operations and makes it possible to find the variation intervals of decision variables, necessary to calculate and optimize the reactor. Being known, the admissible operation condition domain makes it possible to estimate the limiting restrictions and to choose the necessary reserves. The domain has completely been studied analytically for chemical processes with arbitrary kinetics.     

2~#加压站煤气热值检测及控制

本文叙述了马钢引进美国ＦＬＵＩＤ　ＤＡＴＡ公司的热值仪与计算机控制系统，有效地解决了煤气混合加压生产中热值的检测与控制问题。     

电荷耦合图像传感器在细线直径测控系统中的应用

文中给出了一个以氟化氪固体激光器做光源，以电荷耦合图像传感器为光屏，应用夫朗禾费衍射原理，实现对细丝直径在线检测自动控制。该方案对相关企业质量控制的自动化是有意义的。     

中国油田堵水技术综述

本文论述了我国油田堵水技术的发展及其在油田开发中的作用,总结和阐述了油井化学堵水技术和注水井吸水剖面调整技术的原理和效益,指明了实践证实的有成效的工艺方法和堵水技术发展方向。