基于小波域的两阶段多描述图像编码

为加强图像在不可靠网络上传输的鲁棒性,提出基于小波域的两阶段图像多描述编码方案.第1阶段对原始图像经小波变换后的系数进行SPIHT编码,形成第1部分描述;第2阶段对SPIHT编码后的系数进行解码,与原始小波系数作差分,实现差值信号的四叉树抽样,通过SPIHT编码形成第2部分描述.将2部分描述复制并同步传送到两信道中.实验结果表明,该方案冗余调节方便,编码后的数据流能适应各种网络传输状况.     

南京长江第四大桥航行条件数值模拟研究

结合二维水流数学模型和船舶运动数学模型,研究了拟建南京长江第四大桥对通航水流条件的影响,分析了桥墩周围的水流条件变化,模拟了船队在建桥前后通过桥区河段的航迹线,得到了航行过程中的航行参数,综合分析认为南京四桥修建对通航水流条件影响很小,对船舶航行也无明显影响。     

三相有源电力滤波器的灰色变结构控制器设计

结合灰色系统理论和变结构控制理论,设计一种新型三相有源电力滤波器的灰色变结构控制器。此控制器是在传统VSC的滑模面附近增设边界层,同时将饱和函数代替传统变结构中符号函数,再通过灰色预测下一状态值来调整滑模控制增益大小,有效地减弱了传统变结构控制的“抖动”现象。仿真结果表明:在GVSC控制下的APF具有更好的补偿效果,且直流电容电压更稳定。     

一种原子性和公平匿名性的电子支付协议

在分析电子交易的原子性和公平匿名性的基础上，提出了一种可同时实现原子性的公平匿名的电子支付协议，而且在整个支付过程中，可信第三方可以离线，只有发生争议时才参与仲裁解决。给出了协议的6个子协议，详细描述了各子协议的执行过程，并且非形式化地分析了协议的原子性和公平匿名性，保证了公平的电子交易和私密性。     

软件项目需求波动原因及风险分析方法评述

从需求波动风险的定义出发，总结了需求波动形成的原因和对软件项目影响，列举了一些代表性风险分析和评估方法，指出当前研究的不足，提出了更进一步研究思路。     

复Gaussian小波核函数及多参数同步优化策略

对复Gauss ian小波满足Mercy条件及其在Hilbert空间具有再生性的命题作了证明．用复Gaussian小波构建出一种核函数，与主成分分析方法相结合，对非线性非平稳信号进行参数辨识和预测．针对多参数模型优化时间过长，不利于工程应用的问题，提出了一种多参数同步优化策略．仿真实验验证了该方法的可行性和有效性，表明该方法具有较好的实用价值．     

悬置线交指型带通滤波器设计

介绍了悬置线交指型带通滤波器的设计原理和方法,利用计算机辅助设计工具进行数值计算,给出了悬置线的电路板尺寸参数,并应用仿真软件对该悬置线交指型带通滤波器进行仿真和优化设计,通过仿真得到了该滤波器的响应曲线,与实验结果吻合的较好。     

汽车性能强化试验台测控系统的研究

介绍了基于滚筒、液压控制系统与相关机构等构成的模拟强化试验路面的汽车试验台，并配置了一套性能优良的测控系统。该系统包括模拟扭曲路面的支撑平台升降系统、液压驱动马达系统、抗车轮侧移装置、抗车轮前后窜动装置、三轴车辆后桥车轮支撑平台升降系统、前台架前后移动系统、前台架与机座之间相互紧固装置及滚筒对之间支撑车轮的平台升降系统等子系统。对试验台的测控系统进行了详细的分析与研究，阐述了测控系统的控制流程。该测控系统功能强、操作方便、自动化程度高，能够满足试验台实时测控的要求。     

Numerical analysis of different ventilation schemes during the construction process of inclined tunnel groups at the Changheba Hydropower Station,China

During the excavation process of underground caverns, the rational selection of the ventilation scheme is very important for the safety and health of construction workers. The flood discharge tunnel groups at the Changheba Hydropower Station are selected as a case to study the design of ventilation schemes in inclined tunnel groups; these groups are characterized by a gradient of approximately 10% and a complex intersecting relationship among the tunnels. The Computational Fluid Dynamics (CFD) method is used to simulate the fluid dynamics in tunnel groups when different ventilation schemes are employed. Four ventilation schemes with the same duct at different positions along the transverse section are formulated, and the scheme approaching the right side with most of the construction adits is adopted in engineering after a comparative analysis, as it offers a well-distributed velocity field and sufficient security distance. The study reveals that flow vortices appear in the tunnels with a long axis length ranging from 5 m to 20 m; the observation that the flow velocity on the transverse sections is away from the heading face indicates that a low-velocity area is always present in the vicinity of an air duct, and the security distance on the upstream side is 60% shorter than on the downstream side with the same air-blower when the tunnels have a 10% gradient. In addition, when the excavation distance rises 200 m, the ventilation condition in the tunnels, especially in the areas around tunnel intersections, is greatly improved by the completion of pilot tunnels and shafts in advance.     

Optimization of the polymer concrete used for manufacturing bases for precision tool machines

Due to its superior damping ratio, high adhesion and fast curing, polymer concrete is used in manufacturing bases for a wide range of precision machines. The coefficient of thermal expansion for polymer concrete is one of the main parameters that can affect the level of accuracy in precision tool machines. Flexural strength is a fundamental strength of the base. In this study six aggregates (basalt, spodumene, fly ash, river gravel, sand and chalk) were investigated. Polymer concrete samples were prepared with different compositions of aggregates containing the same resin volume fraction (aggregates 83% and risen 17%). A four points flexural test was employed to measure the flexural strength of the polymer concrete samples. The coefficient of thermal expansion for polymer concrete was measured using a custom built device. The preliminary optimum composition, with the highest flexural strength and lowest thermal expansion coefficient, was found to be basalt, spodumene and fly ash. Basalt, sand and fly ash composition was the second in the rank. The second composition was nominated for further optimization in terms of resin volume fraction in consideration of its ability to adapt a smaller amount of resin. Different samples of polymer concrete were prepared with a variety of resin volume fractions as follows; 17%, 15% and 13%. The resin volume fraction has been demonstrated to have a significant effect on the coefficient of thermal expansion and flexural strength for polymer concrete. The final optimized composition was basalt, sand and fly ash (filler 87% and resin 13%). ANSYS 13 software was employed in visualizing the influence of polymer concrete compositions on the thermal expansion of the base and how it affected the level of precision of the tool machine.