Some remarks on the TKIP key mixing function of IEEE 802.11i

Temporal key integrity protocol (TKIP) is a sub-protocol of IEEE 802.11i. TKIP remedies some security flaws in wired equivalent privacy (WEP) protocol. TKIP adds four new algorithms to WEP: a message integrity code (MIC) called Michael, an initialization vector (IV) sequencing discipline, a key mixing function and a re-keying mechanism. The key mixing function, also called temporal key hash, de-correlates the IVs from weak keys. Some cryptographic properties of the substitution box (S-box) used in the key mixing function are investigated in this paper, such as regularity, avalanche effect, differ uniform and linear structure. Moen et al pointed out that there existed a temporal key recovery attack in TKIP key mixing function. In this paper a method is proposed to defend against the attack, and the resulting effect on performance is discussed.     

DC gain analysis of scaled CMOS op amp in Sub-100 nm technology nodes: A research based on channel length modulation effect

Metal-oxide-semiconductor field effect transistor (MOSFET) intrinsic gain degradation caused by channel length modulation (CLM) effect is examined. A simplified model based on Berkeley short-channel insulator-gate field effect transistor model version 4 (BSIM4) current expression for sub-100 nm MOSFET intrinsic gain is deduced, which only needs a few technology parameters. With this transistor intrinsic gain model, complementary metal-oxide-semiconductor (CMOS) operational amplifier (op amp) DC gain could be predicted. A two-stage folded cascode op amp is used as an example in this work. Non-minimum length device is used to improve the op amp DC gain. An improvement of 20 dB is proved when using doubled channel length design. Optimizing transistor bias condition and using advanced technology with thinner gate dielectric thickness and shallower source/drain junction depth can also increase the op amp DC gain. After these, a full op amp DC gain scaling roadmap is proposed, from 130 nm technology node to 32 nm technology node. Five scaled op amps are built and their DC gains in simulation roll down from 69.6 to 41.1 dB. Simulation shows transistors biased at higher source-drain voltage will have more impact on the op amp DC gain scaling over technology. The prediction based on our simplified gain model agrees with SPICE simulation results.     

公路风吹雪雪害挡雪墙工程防治技术研究

简述了公路风吹雪雪害对交通的影响,影响挡雪墙作用效果的主要因素、挡雪墙的实用条件、挡雪墙设置原则以及建设技术。     

民族UPS为发展大运量城市轨道交通提供永续动力

随着我国经济的发展趋势,发展大运量的城市轨道交通已成为解决大城市交通矛盾的关键。有数据显示,目前全国轨道交通规划总长度已超过3000千米。计划在2010年前建成的地铁线路长度超过1200千米。2020年。预计中国城市轨道交通线路的总长度将达到2452千米。     

“321”装配式公路钢桥安全性评价

“321”装配式公路钢桥安全性评价的目的是要明确结构的实际安全储备,以避免在使用中发生灾难性后果。基于简单、实用的原则,建立了AHP与目测打分法、分析检算法、荷载试验法相结合的综合评价方法。即首先建立基于设计、制造和使用因素的钢桥安全性评价模型（AHP模型）,进而提出了设计荷载、结构耐久性等九个评价指标的具体评分方法,然后利用关键构件裂纹长度修改系数来评价钢桥的安全等级。实例应用表明,该评价方法是可靠的。研究成果对同类结构的安全性评价工作具有指导意义。     

基于内力包络理论桥梁远程健康监测安全评价

通过安全评价模式、基于桥梁实时监测的抵抗内力图和实时内力图的获取、应用实践等几个方面的阐述,将桥梁设计中使用的内力包络验算方法应用于桥梁远程健康监测系统,提出了一种基于内力包络理论的安全评价方法。与现有方法相比,该方法解决了测点有限、不能反映未测位置及桥梁整体状态的问题,具有更直观、客观的优点,并能较好地克服环境与运营条件的影响,具有良好的应用前景。     

2009年一季度客车行业和三龙一通公交市场总结

1 2009年1～3月与2008年同期对比客车行业销售增长分析 1．1 整体在各长度段的销售增长状况 由表1可以看出：2009年1～3月销售比去年同期下降34．2％,从长度段来分析,全线下降,这是继2009年1月份下降45．9％,2月份下降41．5％后的第三个月的连续下降,     

空心楼盖在工程设计实践中的应用

该文结合工程实例,探讨空心楼盖在工程设计实践中的应用技巧,以及需要考虑的一些因素。     

沥青稳定碎石动态模量主曲线的研究

通过对沥青稳定碎石试件进行不同温度、不同频率下的压缩动态模量试验,根据时间一温度等效原理得出在参考温度下沥青稳定碎石动态模量的主由线及移位因子表达式,从而得出各种频率下沥青稳定碎石的动态模量。     

沥青路面预防性养护时机研究

通过沥青混合料的MTS中点小梁疲劳弯曲试验获得了疲劳寿命方程,分析了裂缝长度与N／Nf的相关关系;结合实际道路情况确定出沥青路面标准轴载作用下的疲劳寿命,并对疲劳破坏进行了定量的预测;针对疲劳破坏对沥青路面性能的影响规律,对沥青路面预防性养护时机进行了研究,提出了基于裂缝长度的沥青路面预防性养护最佳时机的确定方法。