Prediction of the energy dissipation rate in ductile crack propagation

In this paper, energy dissipation rate D vs. Δa curves in ductile fracture are predicted using a ‘conversion’ between loads, load‐point displacements and crack lengths predicted by NLEFM and those found in real ELPL propagation. The NLEFM/ELPL link was recently discovered for the DCB testpiece, and we believe it applies to other cracked geometries. The predictions for D agree with experimental results. The model permits a crack tip toughness R(Δa) which rises from J_c and saturates out when (if) steady state propagation is reached after a transient stage in which all tunnelling, crack tip necking and shear lip formation is established. J_R is always greater than the crack tip R(Δa) and continues to rise even after R(Δa) levels off. The analysis is capable of predicting the usual D vs. Δa curves in the literature which have high initial values and fall monotonically to a plateau at large Δa. It also predicts that D curves for CCT testpieces should be higher than those for SENB/CT, as found in practice. The possibility that D curves at some intermediate Δa may dip to a minimum below the levelled‐off value at large Δa is predicted and confirmed by experiment. Recently reported D curves that have smaller initial D than the D‐values after extensive propagation can also be predicted. The testpiece geometry and crack tip R(Δa) conditions required to produce these different‐shaped D vs. Δa curves are established and confirmed by comparison with experiment. The energy dissipation rate D vs. Δa is not a transferable property as it depends on geometry. The material characteristic R(Δa) may be the ‘transferable property’ for scaling problems in ELPL fracture. How it can be deduced from D vs. Δa curves (and by implication, J_R vs. Δa curves) is established.     

网络技术在中州分公司计量管理工作中的应用探讨

本文通过对中州分公司正在考虑建设的信息网建设实际情况，结合山东分公司、广西分公司取得的经验，对计量管理信息网的应用进行了探讨。     

圆盘给料机在韶钢烧结厂的应用

介绍了PDX系列圆盘给料机的结构、性能及其特点，以及该设备在韶钢烧结厂的使用情况，并与老式圆盘给料机进行了比较。     

电力设计的节电途径

简要介绍了电能作为一种重要的能源在国民经济建设中的重要性和电力设计的几种节电途径。     

水工隧洞内消能工的研究及应用进展

对于高水头、大流量的水电工程,以往的消能工具有一定的局限性,研究表明,把大面积遭受高速水流作用改为局部承受的消能方式,是高坝泄洪消能的一条有效途径。内消能工主要有孔板(洞塞)式消能工、旋流式消能工、消力井等3种形式。实践表明,内消能工对改善大坝下游水流流态,保护下游环境,保障下游边坡稳定等有积极作用,综合考虑,旋流式消能工具有较大优越性。对水工隧洞内部消能技术尚需开展进一步的研究与实践。     

Analysis and Optimization of the Energy Efficiency in the 802.11 DCF

This paper introduces an analytical model to investigate the energy efficiency of the IEEE 802.11 distributed coordinated function (DCF). This model not only accounts for the number of contending nodes, the contention window, but also the packet size, and the channel condition. Based on this model, we identify the tradeoff in choosing optimum parameters to optimize the energy efficiency of DCF in the error-prone environment. The effects of contention window and packet size on the energy efficiency are examined and compared for both DCF basic scheme and DCF with four-way handshaking. The maximum energy efficiency can be obtained by combining both the optimal packet size and optimal contention window. To validate our analysis, we have done extensive simulations in ns-2, and simulation results seem to match well with the presented analytical results. The Ohio Board of Regents Doctoral Enhancements Funds and the National Science Foundation under Grant CCR 0113361 have supported this work. Xiaodong Wang received his B.S. degree in communication engineering from Beijing Information Technical Institute of China in 1995, and his M.S. degree in electric engineering from Beijing University of Aeronautics and Astronautics of China in 1998. He joined China Telecom in 1998 where he worked on communication protocols for telecommunication. From June 2000 to July 2002, he worked on GSM base station software development at Bell-labs China, Beijing, China. Currently he is a Ph.D. student in Computer Engineering at University of Cincinnati. His research activities include wireless MAC protocols, energy saving for wireless sensor networks. He is a student member of the IEEE. Jun Yin received the BS degree in automatic control from Dalian Railway Institute of China in 1997, and the MS degree in flight control from Beijing University of Aeronautics and Astronautics of China in 2001. Since 2001 she has been a Ph.D. student in the OBR Research Center for Distributed and Mobile Computing at the University of Cincinnati. Her research interests include performance evaluation of 802.11 MAC protocol, wireless ad hoc networks and sensor networks. She is a student member of the IEEE. Dharma P.Agrawal IEEE Fellow, 1987; ACM Fellow, 1998; AAAS Fellow, 2003 Dr. Agrawal is the Ohio Board of Regents Distinguished Professor of Computer Science and Computer Engineering in the department of Electrical and Computer Engineering and Computer Science, University of Cincinnati, OH. He has been a faculty member at Wayne State University, (1977–1982) and North Carolina State University (1982–1998). He has been a consultant to the General Dynamics Land Systems Division, Battelle, Inc., and the U. S. Army. He has held visiting appointment at AIRMICS, Atlanta, GA, and the AT&T Advanced Communications Laboratory, Whippany, NJ. He has published a number of papers in the areas of Parallel System Architecture, Multi computer Networks, Routing Techniques, Parallelism Detection and Scheduling Techniques, Reliability of Real-Time Distributed Systems, Modeling of C-MOS Circuits, and Computer Arithmetic. His recent research interest includes energy efficient routing, information retrieval, and secured communication in ad hoc and sensor networks, effective handoff handling and multicasting in integrated wireless networks, interference analysis in piconets and routing in scatternet, use of smart directional antennas (multibeam) for enhanced QoS, Scheduling of periodic real-time applications and automatic load balancing in heterogeneous workstation environment. He has four approved patents and three patent filings in the area of wireless cellular networks.     

Thermally stimulated discharge current (TSDC) and dielectric constant of semiconducting glasses

In this paper the results of thermally stimulated discharge current (TSDC) and dielectric constant for 40PbO-60Bi₂O₃ glass thermoelectrets are presented. Measurements of TSDC and dielectric constant, ǵe, have been carried out in the temperature range 30–300°C. The thermoelectrets were prepared at different polarizing fields. The various observed peaks in the thermograms are discussed on the basis of space charge polarization. The trap energy is evaluated from the Garlick-Gibson plot of initial rise method. Similarly other parameters such as relaxation time, charge release etc are evaluated.     

传感器网络中基于二元簇的节能路由算法

传感器网络中的分簇算法已经被证明能够有效地节约能量。据此提出了一种基于二元簇的路由算法,其基本思想是网络中的每个节点同时属于2个不同簇,利用二元性来减少在路由发现中的资源浪费,并能够更加确定地发现路由以节约资源。理论分析和模拟实验都表明,该算法在能量消耗和网络生命周期延长方面较优。     

量子阱红外探测器能带结构的计算

利用电子波在阱与垒的界面上的反射及干涉效应，计算了量子阱红外探测器(QWIP)的能带结构，并对其适用性进行了分析和讨论。通过与K-P模型比较发现，本方法对计算较宽势阱(阱宽大于4nm)的量子阱结构的电子态适合。在垒宽和阱宽不变条件下，用两种方法计算得到的AlGaAs／GaAs量子阱材料中Al组分x与吸收峰值波长λp的关系曲线基本相同。结果说明，在较宽的范围内，本方法对QWIP能带结构的计算是适用且简便的。     

能量分析法在空气源热泵除霜中的应用

针对空气源热泵冷热水机组冬季制热运行时换热器结霜与除霜的问题，提出了一种能量分析法。从能量转换和能量传递的角度出发，分析一种常见的除霜方法——逆循环除霜。通过对除霜过程的讨论，找出了相应的减少除霜损失的方法。