Elastic Modulus and Hardness of Cr-Nb Nano-Multilayers

Cr-Nb nano-multilayered films with various modulation wavelengths A are prepared by e-gun evaporation and their mechanical properties are investigated. Cr and Nb both have bcc structures with large differences in lattice constants and Young＇s modulus, which are supposed to favour modulus enhancement. Nevertheless, nano-indention measurements show no enhancement for the modulus and a slight decrease for the hardness with decreasing A down to 5 nm. This is mainly due to counter-contribution to modulus from adjacent layers subjected to reverse strains, in agreement with recent theoretical study, while the decrease of hardness arises from grain boundary sliding. Interestingly, at A = 3 nm, the hardness of the film has an increase of 44% relative to the value of a rule of mixture, owing to the emergence of a new phase for reconciling the structure difference at the interfaces.     

Hydrogen Passivation Effect on Enhanced Luminescence from Nanocrystalline Si/SiO2 Multilayers

Nanocrystalline Si/SiO2 multilayers are prepared by thermally annealing amorphous Si/SiO2 stacked structures. The photoluminescence intensity is obviously enhanced after hydrogen passivation at various temperatures. It is suggested that the hydrogen trapping and detrapping processes at different temperatures strongly influence the passivation effect. Direct experimental evidence is given by electron spin resonance spectra that hydrogen effectively reduces the nonradiative defect states existing in the Si nanocrystas/SiO2 system which enhances the radiative recombination probability. The luminescence characteristic shows its stability after hydrogen passivation even after aging eight months.     

MOSFET辐照诱生界面陷阱形成过程的1/f噪声研究

基于界面陷阱形成的氢离子运动两步模型和反应过程的热力学平衡假设,推导了金属-氧化物-半导体-场效应晶体管(MOSFET)经历电离辐照后氧化层空穴俘获与界面陷阱形成间关系的表达式.利用初始1/f噪声功率谱幅值与氧化层空穴俘获之间的联系,建立了辐照前的1/f噪声幅值与辐照诱生界面陷阱数量之间的半经验公式,并通过实验予以验证.研究结果表明,由于辐照诱生的氧化层内陷阱通过与分子氢作用而直接参与到界面陷阱的建立过程中,从而使界面陷阱生成数量正比于这种陷阱增加的数量,因此辐照前的1/f噪声功率谱幅值正比于辐照诱生的界面陷阱数量.研究结果为1/f噪声用作MOSFET辐照损伤机理研究的新工具,对其抗辐照性能进行无损评估提供了理论依据与数学模型.     

贴片焊层厚度对功率器件热可靠性影响的研究

贴片工艺是用粘接剂将芯片贴装到金属引线框架(一般是由铜制成)上的过程.富铅的Pb/Sn/Ag软焊料在功率器件封装贴片工艺中作为粘接剂应用十分广泛.从功率器件整体来看,贴片焊层毫无疑问是影响器件可靠性最重要的因素之一,其不仅具有良好的导电导热性能,而且该焊层能够吸收由于芯片和引线框架之间的热失配而产生的应力应变,保护芯片免于受到机械应力的损伤.基于Darveaux的热疲劳寿命分析模型,利用功率循环加速实验以及有限元方法具体分析了贴片焊层厚度BLT对于功率器件热可靠性的影响.并通过实验与仿真的结果,提出提高功率器件热可靠性的设计原则.     

移动城域传送网优化原则与策略

分析了移动城域传送网的现状、承载业务需求和发展中的传送网技术,探讨了组网思路及网络优化原则,提出了网络优化的策略建议.     

移动城域网主流传输技术

目前，城域网解决方案主要有四大类：第一类是以SDH为基础的多业务平台；第二类是基于第二层交换和第三层选路的方案，主要指RPR以太网解决方案；第三类是城域网用WDM方案，即以WDM为基础的多业务平台；第四类是以ATM为基础的多业务平台方案。     

强健“骨架”保障运营

通讯基站是电信网络的骨架，是电信运营商开展业务的基础。随着电信业竞争的加剧，各大电信运营商对通讯基站的建设和维护日益重视。云南联通地处西南边陲，其通讯基站有很多位于电力供应相对恶劣的偏远乡镇和农村。为了确保这些通讯基站始终处于稳定的运行状态，解决因电力供应给基站带来的种种故障和隐患，云南联通携手艾默生对全省相关GSM基站的网络能源系统进行了全面改造，[第一段]     

“做一个合格的联通人”——记中国联通长春分公司宋秋梅

宋秋梅在10年时间里面历经8个部门，不同的员工团队，不同的业务单元，不同的岗位职责以及不断变化的市场需求，让她时刻感受到工作的压力和挑战，但因为工作需要，她时刻准备着面对调整和变化，以最快的速度进入最佳的工作状态。[编者按]     

Computer Modeling and Simulation Evaluation of High Power LED Sources for Secondary Optical Design

Proposed and demonstrated is a novel computer modeling method for high power light emitting diodes（LEDs）. It contains geometrical structure and optical property of high power LED as well as LED dies definition with its spatial and angular distribution. Merits and non-merits of traditional modeling methods when applied to high power LEDs based on secondary optical design are discussed. Two commercial high power LEDs are simulated using the proposed computer modeling method. Correlation coefficient is proposed to compare and analyze the simulation results and manufacturing specifications. The source model is precisely demonstrated by obtaining above 99% in correlation coefficient with different surface incident angle intervals.     

光传输网络中的链路保护与业务保护之间的关系

介绍了用悬链线公式代替抛物线公式计算架空通信导线垂度的方法,并以软件的方式实现了复杂条件下的自动计算。