凝固超声处理对Al/Zn-3Al/Cu钎焊接头显微形貌及性能的影响

主要研究了Al/Zn-3Al/Cu钎焊接头在凝固过程中实施超声处理时其钎缝层显微结构和性能的演变。研究结果表明,在未经凝固超声处理的钎焊接头中,钎缝层呈现出一种各向异性的显微结构;然而,在经过凝固超声处理的钎焊接头中,钎缝层有着均匀的显微结构,其由一种等轴的花瓣状Cu Zn5/Al复合物以及弥散其间的细小α-Al晶粒和Zn-Al共晶组织组成。性能测试结果表明,与未经凝固超声处理的钎焊接头相比,经过凝固超声处理的接头钎缝层的硬度增加了26.2%,热膨胀系数降低了38%。     

传统手工会计与用友软件对项目管理处理方法比较

企业在实际业务处理中,需要对多种类型的项目进行核算和管理。传统手工会计对项目管理采用明细科目方式处理存在的问题,相对而言,用友软件对项目管理采用辅助项目目录处理方式具有一些优点,实用性与灵活性大大提高,更能提高管理的效率,提高单位获取项目管理信息的质量。     

一种改进的层次型移动组播协议

论文介绍了现有层次性移动组播协议——Mobi Cast协议,分析了该协议的优缺点。在Mobi Cast协议的基础上通过加入隧道技术,并减轻基站开销等方面进行了改进。仿真与分析表明,改进后的Mobi Cast协议具有组播数据丢包率低、网络维护开销小、切换延迟短等特点。     

基于快速8-连通域标记的视频字幕提取新算法

提出了一种基于彩色Roberts边缘算子、形态学和快速8-连通区域标记的视频字幕提取新方法.首先用彩色边缘算子提取出字幕的边缘信息,再通过形态学处理得到字幕连通区域,最后采用快速8-连通区域标记新方法进行连通区域分析得到最终字幕区域.实验证明,该算法能够快速定位字幕区域,定位精度较高,具有较好的稳健性.     

WDM光网络中的组播路由算法研究

组播是一种应用广泛的点到多点或多点到多点的通信方式.本文剖析了光层组播的特点,在综合分类的基础上,对光网络组播路由算法的最新研究进展进行了归纳和总结,指出了其面临的问题与挑战,并对今后需重点研究的方向进行了展望.     

基于WinCE的AX88796 NDIS网络驱动程序

在WinCE5．0提供的NE2000驱动程序基础上,讨论了NDIS网络驱动程序结构,在S3C2410开发平台上实现了基于WinCE5．0的AX88796网卡小端口驱动程序,讨论了其在视频监控系统中的应用。     

Short-Term Schedulability Analysis of Multiple Distiller Crude Oil Operations in Refinery With Oil Residency Time Constraint

Because of the complexity of a short-term scheduling problem for crude oil operations, some constraints are ignored in modeling the system by the existing approaches, leading to an infeasible solution. To avoid this, the short-term scheduling problem can be studied in control theory perspective by viewing an operation decision in the schedule as a control. With this idea, this paper conducts the schedulability analysis for systems with two and more than two distillers, and the schedulability conditions are presented with the help of Petri net theory. It shows that the number of charging tanks and their capacity, the amount of crude oil of different types in the charging tanks, the oil transportation rate of the pipeline, and the production rate of the system affect the safeness of the system. It also presents the conditions under which the system can reach its maximal production rate. With the safeness conditions and proved results presented in this paper, if a refining schedule is realizable, a feasible detailed schedule for the refining schedule can be easily obtained by creating the operation decisions for the schedule one by one. In the schedule obtained, the starting time of each operation decision can be at any continuous time point, and the schedule is certainly feasible, which overcomes the difficulty faced by techniques that are based on mathematical programming methods.     

Si微陀螺结构与接口电路的混合仿真

为了快速有效地验证接口电路的可行性,对Si微陀螺建模方法及陀螺结构与接口电路的混合仿真方法进行了研究。在Si微陀螺动力学特性分析的基础上,利用硬件描述语言建立一种以低阶微分方程描述的Si微陀螺解析模型,该模型利用Si微陀螺运动特性来描述陀螺模态之间的耦合行为。利用该模型实现了陀螺结构与接口电路的快速混合仿真。对Si微陀螺自激控制环路进行分析制作了实验电路板,并对电路仿真结果进行了实验验证,测试结果与仿真结果趋势一致。实验表明,该方法能够快速有效地验证接口电路的可行性,为设计Si微陀螺接口电路提供了依据。     

Study on BMT Millimeter Wave Dielectric Resonators

The microwave dielectric properties and microstructures of Ba(Mg_1/3Ta_2/3)O₃ (BMT) ceramics were investigated. In order to reduce the evaporation of MgO at high temperature, burying in MgO powders sintered BMT ceramics. The relationship between the composition and Q value of BMT ceramics was discussed. Dielectric resonators using in millimeter wave band have been designed and fabricated. Their attenuations at central resonation frequency (τ_f) are less than 35dB. Temperature coefficients of resonant frequency are adjustable and less than 2 ppm/°C.     

低缺陷密度和平整表面的硅基砷化镓外延

Device-quality GaAs thin films have been grown on miscut Ge-on-Si substrates by metal-organic chemical vapor deposition. A method of two-step epitaxy of GaAs is performed to achieve a high-quality top-layer. The initial thin buffer layer at 360 ℃ is critical for the suppression of anti-phase boundaries and threading dislocations. The etch pit density ofGaAs epilayers by KOH etching could reach 2.25 × 10^5 cm^-2 and high-quality GaAs top epilayers are observed by transmission electron microscopy. The band-to-band photoluminescence property of GaAs epilayers on different substrates is also investigated and negative band shifts of several to tens of meVs are found because of tensile strains in the GaAs epilayers. To achieve a smooth surface, a polishing process is performed, followed by a second epitaxy of GaAs. The root-mean-square roughness of the GaAs surface could be less than 1 nm, which is comparable with that of homo-epitaxial GaAs. These low-defect and smooth GaAs epilayers on Si are desirable for GaAs-based devices on silicon substrates.