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51.
将动态焦散线法与高速摄影技术相结合,本文记录了高分子材料悬臂梁内裂纹扩展加速、减速过程。一方面,利用动态焦散线可确定扩展裂尖的瞬态应力强度因子;另一方面,利用最小二乘法将裂纹扩展的水平、垂直位移分量拟合成时间(t)的四次多项式,描述了裂纹扩展方向、裂纹扩展加速度以及裂纹扩展加速度与动态应力强度因子的关系。结果表明:裂纹扩展加速度与动态应力强度因子之间存在一定的依赖关系;利用最小二乘法将裂纹扩展的水平、垂直分量拟合成时间(t)的四次多项式,可以对裂纹的扩展方向、加速度进行定量分析。 相似文献
52.
The effect of lanthanide ions (Ln3+) and their coordination compounds of diethylenetriamine pentaacetic acid (DTPA) on the phase behavior of dipalmitoylphosphatidylcholine (DPPC) multi-lamellar liposomes has been studied by differential scanning calorimetry (DSC), Raman spectroscopy, and freeze-fracture electron microscopic techniques. The displacement of Ca2+ binding on DPPC liposomes by lanthanide ions was also studied. The results show that the binding degree of four kinds of chloride salts with DPPC liposomes is: YbCl3 > GdCl3 > LaCl3 > CaCl2. Lanthanide ions increase the phase transition temperature of DPPC liposomes and decrease the membrane fluidity. Freeze-fracture electron microscopic results show that La3+ enhances the order of DPPC membrane. The effect of coordination compounds of lanthanides with DTPA on the phase behavior of DPPC liposomes is smaller than that of their chlorides. La3+, Gd3+, and Yb3+, can displace Ca2+ binding on DPPC liposomes, but there coordination compounds of DTPA can hardly displace Ca2+. Raman spectroscopic results show that a very slight effect in lateral packing order of DPPC liposomes was observed at various concentrations of lanthanides. 相似文献
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55.
双辊式薄带连铸工艺研究 总被引:6,自引:0,他引:6
进行了双辊法薄带连铸的试验研究。阐述了双辊连铸机浇注系统的研究结果、工艺参数对连铸的影响,以及18—8不锈钢薄带坯的凝固组织和冷轧特性,该工作为薄带连铸的中间生产机组的研究奠定了基础。 相似文献
56.
The IEEE 802.11e medium access control (MAC) layer protocol is an emerging standard to support quality of service (QoS) in
802.11 wireless networks. Some recent work shows that the 802.11e hybrid coordination function (HCF) can improve significantly
the QoS support in 802.11 networks. A simple HCF referenced scheduler has been proposed in the 802.11e which takes into account
the QoS requirements of flows and allocates time to stations on the basis of the mean sending rate. As we show in this paper,
this HCF referenced scheduling algorithm is only efficient and works well for flows with strict constant bit rate (CBR) characteristics.
However, a lot of real-time applications, such as videoconferencing, have some variations in their packet sizes, sending rates
or even have variable bit rate (VBR) characteristics. In this paper we propose FHCF, a simple and efficient scheduling algorithm
for 802.11e that aims to be fair for both CBR and VBR flows. FHCF uses queue length estimations to tune its time allocation
to mobile stations. We present analytical model evaluations and a set of simulations results, and provide performance comparisons
with the 802.11e HCF referenced scheduler. Our performance study indicates that FHCF provides good fairness while supporting
bandwidth and delay requirements for a large range of network loads.
Pierre Ansel received a multidisciplinary in-depth scientific training in different fields such as Pure and Applied Mathematics, Physics,
Mechanics, Computer Science and Economics from the Ecole Polytechnique, Palaiseau, France. Then, he joined the Ecole Nationale
Superieure des Telecommunications, Paris, France in 2005 where he went further into electronics, databases, computer network
security and high speed networks. He received a multidisciplinary master of sciences degree and an additional master of sciences
degree in telecommunications in 2005. He did a summer internship in 2003 in INRIA, Sophia Antipolis, France where he worked
on the Quality of Service in 802.11 networks at Planete Group, France. Then in 2004, he joined France Telecom R&D, Issy-les-Moulineaux,
France to work on Intranet Security issues. He designed a WiFi security supervision architecture based on WiFi Intrusion Detection
Sensors. He is currently a French civil servant and belongs to the French Telecommunications Corps.
Qiang Ni received the B.Eng., M.Sc. and Ph.D. degrees from Hua Zhong University of Science and Technology (HUST), Wuhan City, China
in 1993, 1996 and 1999 respectively. He is currently a faculty member in the Electronic and Computer Engineering Division,School
of Engineering and Design, Brunel University, West London, U.K. Between 2004 and 2005 he was a Senior Researcher at the Hamilton
Institute, National University of Ireland, Maynooth. From 1999 to 2001, he was a post-doctoral research fellow in the multimedia
and wireless communication laboratory, HUST, China. He visited and conducted research at the wireless and networking group
of Microsoft Research Asia Lab during the year of 2000. From Sept. 2001 until may 2004, he was a research staff member at
the Planète group of INRIA Sophia Antipolis France. Since 2002, he has been active as a voting member at the IEEE 802.11 wireless
LAN standard working group. His current research interests include communication protocol design and performance analysis
for wireless networks, cross-layer optimizations, vertical handover and mobility management in mobile wireless networks, and
adaptive multimedia transmission over hybrid wired/wireless networks. He has authored /co-authored over 40 international journal/conference
papers, book chapters, and standard drafts in this field. He is a member of IEEE. E-mail: Qiang.Ni@ieee.org
Thierry Turletti received the M.S. (1990) and the Ph.D. (1995) degrees in computer science both from the University of Nice – Sophia Antipolis,
France. He has done his PhD studies in the RODEO group at INRIA Sophia Antipolis. During the year 1995–96, he was a postdoctoral
fellow in the Telemedia, Networks and Systems group at LCS, MIT. He is currently a research scientist at the Planete group
at INRIA Sophia Antipolis. His research interests include multimedia applications, congestion control and wireless networking.
Dr. Turletti currently serves on the Editorial Board of Wireless Communications and Mobile Computing. 相似文献
57.
The influence of Zr addition on magnetic properties and temperature coefficient for nanocomposite Nd10Fe78.5-xCO5ZrxB6.5 (x=0~4) bonded magnets was investigated. It was found that the room-temperature magnetic properties were remarkably improved with Zr addition due to the grain refinement and increasing volume fraction of the hard magnetic phase. The optimal magnetic properties of Jr=0.689T, iHc=769.4kA·m-1 and (BH)max=84kJ·m-3 were obtained for 2.5% Zr addition. The temperature coefficient of remanence (α) increases slightly and the temperature coefficient of coercivity (β) decreases obviously with increasing Zr content for nanocomposite Nd10Fe78.5-xCo5ZrxB6.5 (x=0~4) bonded magnets. 相似文献
58.
目前,很多新型调频发射机采用数字激励器,声音质量得到明显改善,技术指标也相应提高,使传统的测量方法和测试仪器受到了一定的限制。本文主要对调频数字激励器几项重要指标的测量进行讨论。 相似文献
59.
无氢类金刚石碳膜的研究进展 总被引:1,自引:0,他引:1
介绍了无氢类金刚石碳膜的制备方法 ,它们的机械、光学、电学性能 ,将无氢与含氢的类金刚石碳膜进行了简单比较 ,总结及探讨了它们的应用 相似文献
60.
NI Jinren LIU Xiaoyong LI Tianhong ZHAO Ye’an & JIN Ling . Department of Environmental Engineering Peking University The Key Laboratory of Water Sedi- ment Sciences Ministry of Education Beijing China . General Institute of Water Resources Hydropower Planning Design Ministry of Water Re- sources Beijing China . The Yellow River Conservancy Commission Zhengzhou China 《中国科学E辑(英文版)》2004,47(Z1)
1IntroductionIntheriversystemwithsediment-ladenflow,WaterUseforSedimentTransport(WUST)isaveryimportantcomponentofecologicalwaterdemands,whichmaintainfundamentalfunctionofallecosystemcomponentsataspecificlevelofcondition[1].EnoughWUSTisthepremisetokeepthestableriver-bedandhealthyriverecosystem;alsoitisthebaseflowofriverfortheexploitationofwaterresources.Comparingwithotherrespectsrelatedwithwaterdemandsofriverecosystemsuchastheminimumflowforfishesorripariantrees,researchesontheWUSTarequite… 相似文献