HfO2在CHF3,Ar和H2的感应耦合等离子体中的刻蚀行为

通过改变偏压功率和气体气压的宏观条件,利用CHF3,Ar和H2的感应耦合等离子体(ICP)对HfO2和RZJ-306光刻胶进行了刻蚀选择性实验研究.结果表明,HfO2与等离子体化学相互作用的刻蚀产物属于非挥发性的,容易造成边墙的堆积而形成"驼峰"形,因而需要借助于Ar 的辅助轰击来消除边墙堆积,典型的HfO2/光刻胶的刻蚀选择比在0.2～0.5之间.在射频源功率400 W、气压0.5 Pa、射频偏压-400 V、流量比为Ar∶CHF3∶H2=40 sccm∶18 sccm∶2 sccm的优化条件下,利用感应耦合等离子体刻蚀特性,对光刻胶作为掩膜的HfO2/BK7玻璃进行刻蚀,扫描电镜的测试结果表明,光栅的图形转移效果较好.红外激光波长为1064 nm时,所测得的光栅二级衍射效率在71%以上.     

基于程序特征谱整数溢出错误定位技术研究

随着软件业的飞速发展,人们对软件质量的要求也越来越高.整数溢出错误以其高危性和隐蔽性成为影响软件安全性和可靠性的重要因素之一.如何准确定位整数溢出错误是软件安全领域研究的热点.论文改进了现有错误定位模型,构建了整数溢出错误定位模型INTRank.实验结果表明:基于INTRank模型的语句可疑度估计方法可以较为准确地计算语句可疑度,使得程序员能够按照基于语句可疑度的优先级顺序检查源代码,找出导致整数溢出错误的原因,同时本文方法具有较低的漏报率.     

Finite element analysis of contact fatigue and bending fatigue of a theoretical assembling straight bevel gear pair

The aim of this work is to propose a 3D FE model of a theoretical assembling straight bevel gear pair to analyze the contact fatigue on the tooth surface and the bending fatigue in the tooth root. Based on the cumulative fatigue criterion and the stress-life equation, the key meshing states of the gear pair were investigated for the contact fatigue and the bending fatigue. Then, the reliability of the proposed model was proved by comparing the calculation result with the simulation result. Further study was performed to analyze the variation of the contact fatigue stress and the bending fatigue stress under different loads. Furthermore, the roles of the driving pinion and the driven gear pair were evaluated in the fatigue life of the straight bevel gear pair and the main fatigue failure mode was determined for the significant gear. The results show that the fatigue failure of the driving pinion is the main fatigue failure for the straight bevel gear pair and the bending fatigue failure is the main fatigue failure for the driving pinion.     

基于P2P应用的网络流量特征分析

为了解和掌握网络中P2P流量的特征，对网络中的P2P文件共享应用的流量进行了分析。发现在P2P文件共享应用Maze产生的流量中：流量具有突发性特点；流量的局部性比WWW和FTP应用相比更不明显；流长分布明显不同于WWW应用；而在流持续时间上明显比WWW和FTP应用要长；所传输的流量中传输量大的流所占的比例要比WWW和FTP要高。     

大宝山矿区河流表层沉积物重金属污染及潜在生态风险评价

采用Hakanson潜在生态危害指数法对广东大宝山矿区4条河流的水系沉积物重金属污染进行了潜在生态风险评价.多种重金属生态风险指数RI表明:4条河流的重金属污染均达到了强生态危害,导致生态危害的主要重金属元素是Cd、Cu和As,Pb、Hg次之,Zn、Cr影响最小;主要受污染河流为矾洞河与船肚河.分析表明,采矿活动对重金属的含量及分布有很大影响,Pb-Zn、Pb-As、Zn-Cd和Zn-As的同源性很高,Hg则表现出不同于其它元素的累积特征;沉积物的粒度对重金属元素在其中的含量也有较大影响,除Cr、Hg和Pb外,Cd、Cu、As、Zn等元素在沉积物中的含量均受沉积物粒度的影响.     

一个基于矢量量化的数字水印算法

文章提出了一个新的基于矢量量化的数字水印算法,与基于DCT(DiscreteCosineTransform)、DFT(DiscreteFourierTransform)及DWT(DiscreteWaveletTransform)等的传统水印算法不同,该算法利用码书分割方法和矢量量化索引的特点,在矢量量化的不同阶段分别嵌入水印来保护原始图像的版权,水印检测不需要原始图像。实验结果表明,该方法实现的水印具有良好的不可见性,并对JPEG压缩、矢量量化压缩、旋转以及剪切等空域操作也具有较好的稳健性。     

基于应用层组播策略的P2P网络搜索模型研究

介绍了传统P2P网络的搜索模型,并分析了其存在的一些问题.针对这些问题,提出了一种基于应用层组播策略的搜索模型,它可以减少冗余搜索包,提高搜索效率,并且能够适应P2P网络拓扑的动态变化,实现良好的可扩展性和容错性.     

拥塞控制模型在XMSF组播中的研究与性能验证

由于可扩展建模与仿真框架（XMSF）提出的整套方法是建立在与Internet相结合的性能基础之上的,因而底层网络提供的性能在XMSF中起着十分重要的作用。为了满足XMSF网络服务需求,需采用叠加组播技术提供多对多的通信服务,同时应使用拥塞控制机制以保证网络服务质量（Qos）。该文首先介绍了叠加组播的概念,同时和传统的IP组播进行了比较,然后给出了一种组播拥塞控制模型,并在MAX—PLUS代数基础上采用线性循环法,分析了该模型吞吐量的计算方法,最后通过仿真验证了该模型的可行性和灵活性。     

Influence of welding parameters on temperature field characteristics during laser welding of TA15 by infrared thermography

Using an infrared thermographic technique,the temperature field during laser welding of TA15 is quantitatively measured and investigated. The influence of two welding parameters on the weld temperature distribution is analyzed and the mechanism is discussed. New conclusions are drawn that are different from conventional weld temperature distributions. For the face of the weld,changes in welding speed induce changes in the temperature distribution because of different heat inputs and the cooling effect. Similar temperature features in the welds are observed for all speeds,which exhibit a relatively low temperature area below 1 500 ℃ between the high temperature area in the position of laser incidence and the sub-high temperature area at the end of the molten pool. For the influence of laser power on the face of the weld,the temperature on the weld is higher for P = 2. 8 k W compared to P = 2. 0 k W,especially the temperature in the sub-high temperature area. However,for the temperature field of the back of the weld,the influence of welding speeds is quite different compared to the results for the face of the weld. The highest temperature does not locate in the keyhole area,but instead in the middle of the molten pool. And there are different temperature features at different speeds. When v =6 m/min,the temperature field is like a uniform color belt and the temperature along the center of the weld fluctuates between 300 and450 ℃. When v = 4 m/min,the transient temperature distribution is not uniform and is unstable at different times. However,for v =2. 4 m/min and lower speeds,the temperature field becomes stable. The influence of laser power on the back of the weld temperature field is more complex. The measured temperature does not increase with increasing laser power,which seems to conflict with the conventional thermal conduction theory. This may be related with the characteristics of the keyhole area.