In-Au复合焊料研究

大功率半导体激光器封装过程中,为降低封装引入的应力,踊般用In焊料进行焊接。In焊料具有易氧化、易"攀爬"的特性,因而导致封装成品率很低。提出了一种新型焊料——In-Au复合焊料,使用此焊料进行封装,很好地解决了上述问题。通过理论分析及实验摸索,确定了In-Au复合焊料蒸发条件,分别利用纯In焊料和In-Au复合焊料封装了一批激光器样品,通过对比这两组样品的焊料浸润性、电光参数、剪切强度等,发现利用In-Au复合焊料封装的样品优于纯In焊料封装的样品。     

采用接收与协作双重分集的系统性能分析

研究了一种同时采用两种分集技术的通信方式。在给定的工作环境中,分析了双重分集系统的工作原理,以及信号的传输与接收的过程。并把本文研究的双重分集技术与单纯的空间分集、单纯的协作分集两种技术作了比较。最后通过理论分析与数值计算的结果表明,与单纯的协作分集和单纯的空间分集相比,本文研究的双重分集系统性能更为优越。     

基于铂电阻的数字温度测量系统设计

设计的数字温度测量系统采用铂电阻PT100、XTR105、MSP430及LCD等组成,德州仪器公司的MSP430系列是一种低功耗的混合信号微处理器,微处理器可设计成电池供电并能长时间工作的单片机系统,此温度测量系统具有低功耗、结构简单、测量准确度高、稳定性好等优点。     

CO2激光弯曲玻璃薄片微观结构变化分析

利用红外(IR)光谱、X射线衍射(XRD)、扫描电镜(SEM)等手段研究了CO2激光扫描弯曲对硼硅酸盐玻璃微观结构的影响.结果表明激光扫描产生的熔化冷却过程使玻璃存在轻微的分相倾向,导致玻璃中原先存在的[BO3]三角体结构单元与Na2O结合向[BO4]四面体结构转化,同时si聚集程度提高,si-O键强增加.未经激光加工样品存在SiO2晶相引起的微弱衍射峰,且晶粒呈大小不一的近似球状,激光扫描过的样品不存在明显晶相,呈较为均匀的玻璃态.     

Porous alumina nano-membranes: Soft replica molding for large area UV-nanoimprint lithography

High-density ordered arrays of h-PDMS nanopillars were fabricated using an anodic aluminium oxide (AAO) template. The pore diameter and the interpore distance of the replica h-PDMS molding are well consistent with that of AAO template. The inverse h-PDMS has the surface characteristic of hydrophobic and surface energy of 130°. Hexagonally arranged array can be obtained by UV-nanoimprint lithography using our proposed h-PDMS mold, and their morphologies can be transferred truly. Besides, the h-PDMS mold has been used to fabricate photonic crystal structure on GaN by nanoimprint process, which could be found an application in the light output of GaN LED.     

移动城域传送网建设模式浅析

本文针对业务IP化及无线网络的不断扩大对现有城域网的影响,提出业务转型期内移动城域网的建设模式。     

济南市现代测绘基准体系建设

概述了济南市现代测绘基准体系建设背景和基本情况,详细介绍高精度GPS网、精密水准网、济南似大地水准面精化、JNCORS系统的建立、数据处理及测试等有关情况,分析了济南市现代测绘基准体系的创新点和应用前景。     

纳米材料改性PVC技术的研究

本文主要综述了纳米CaCO3改性PVC、蒙脱土纳米复合材料改性PVC以及其他纳米复合材料改性PVC的方法,研究结果表明：纳米复合技术在聚氯乙烯增韧改性中具有同时提高材料韧性和强度的特点,纳米复合技术将成为聚氯乙烯增韧改性的一种重要方法。     

A Robust, Digital-Audio Watermarking Method

Most of the previous audio-watermarking schemes are robust to common signal-processing attacks, but show severe problems when faced with desynchronization attacks. To solve the problems associated with these approaches, we propose an audio-watermarking scheme based on support-vector-machine (SVM) theory to protect against desynchronization attacks by using audio statistics characteristics and a synchronization code technique. Experimental results with SVM show that our proposed scheme is inaudible, robust against common signal processing, and robust against desynchronization attacks.     

Leveraging Multi-AP Diversity for Transmission Resilience in Wireless Networks: Architecture and Performance Analysis

With the increasing development of IEEE 802.11 based wireless local area network (WLAN) devices, large-scale multi-cell WLANs with a high density of users and access points (APs) have emerged widely in various hotspots. Providing resilient data transmission has been a primary challenge for scaling the WLANs because the high density of users and APs results in too many collisions. In this paper, we analyze and point out the defect of the single association mechanism defined in IEEE 802.11 on transmission reliability from a network perspective. Then, we propose a "multi-AP" architecture with which a MAC layer device called an AP controller (AC) is employed to enable each user to associate and cooperate with multiple APs. In this way, the users can benefit from the diversity effect of multipaths with independent collisions and transmission errors. This paper concentrates on the theoretical analysis of performance comparison between the proposed ldquoMulti-APrdquo architecture and that in IEEE 802.11. Extensive simulation results show that the proposed ldquomulti-APrdquo architecture can obtain much better performance in terms of the throughput per user and the total throughput, and the performance gain is position dependent. Moreover, the unfairness issue in traditional WLANs due to capture effect can be alleviated properly in the ldquomulti-APrdquo framework.