网络虚拟化互通技术

工业界和学术界提出了许多新的网络虚拟化技术来满足云计算环境对网络服务的需求.网络虚拟化技术的多样化使得云环境面临多种网络虚拟化技术共存的状况.然而,网络虚拟化技术间的差异会导致网络资源被分割成相互间不可通信的“孤岛”.为了解决这个问题,提出了网络虚拟化互通技术,分析了该技术的实现难点,并提出了基于软件定义网络的网络虚拟化互通架构Omni-Bridge,最后给出了Omni-Bridge的原型实现和功能验证.     

高校体育运动场馆管理系统设计

随着科学信息技术的发展,网站管理系统的应用越来越广泛。本文设计了高校体育运动场馆关系系统,以Microsoft Visual Studio2013为开发平台,应用SQL Server 2012数据库和.NET框架体系结构,对系统的整体结构进行设计,阐述了相应的功能模块功能,设计了数据建模,并对系统的功能进行了测试。     

Motor control and torque coordination of an electric vehicle actuated by two in-wheel motors

In this research, an electric vehicle actuated by two in-wheel DC motors is developed. By properly coordinating the motor torques, both drive-by-wire and electrical steering can be achieved. Two critical issues respectively related to the design of motor controllers and the coordination of the two motor torques under control saturation are investigated in this study. Firstly, as for the in-wheel motors that are used for driving and steering simultaneously, their operation covers a wider dynamic range that forward acceleration (deceleration), and reverse acceleration (deceleration) may occur alternately. To perform driving and steering smoothly and efficiently, each motor should be switched to an appropriate mode to generate the torque demanded. Secondly, during the high-speed maneuvering, the high back-emf voltage in the motor coil substantially reduces the motor’s torque generating capability. Since the electrical steering depends on the differential torque of two wheels, when electrical steering is demanded in this case, torque/current saturation may occur in either one of the motors and the electrical steering performance could be seriously degraded. To address these issues, controllers of two levels are proposed. For the low-level controller (the motor controller), it operates the motor automatically in an appropriate mode for performance and efficiency consideration. An input transformation is introduced to cancel the nonlinearity in current dynamics so as to control the motor torque easily and precisely regardless of mode switching. For the high-level controller (the torque coordination controller), besides generating reference commands to the low-level controllers, during control saturation it can also properly re-distributes control signals to maintain consistent steering performance and provides compensation for integrator windup. The control system is implemented and the performance is experimentally and numerically validated.     

An efficient t‐out‐of‐n oblivious transfer for information security and privacy protection

In t‐out‐of‐n oblivious transfer (OT), the receiver can only receive t messages out of n messages sent by the sender, and the sender has no idea about which ones have been received. Majority of the existence of previous efficient OT schemes require t calls of 1‐out‐of‐n OT to construct the t‐out‐of‐n OT. Its computational requirements and bandwidth consumption are quite demanding. On the basis of the elliptic curves cryptography, we propose a new t‐out‐of‐n OT protocol for private information retrieval in this article. It is more suitable for the smart cards or mobile units. Copyright © 2013 John Wiley & Sons, Ltd.     

NON-PARAMETRIC TOPIC MODEL FOR DISCOVERING GEOGRAPHICAL TOPIC VARIATIONS

This paper presents a non-parametric topic model that captures not only the latent topics in text collections, but also how the topics change over space. Unlike other recent work that relies on either Gaussian assumptions or diseretization of locations, here topics are associated with a distance dependent Chinese Restaurant Process （ddCRP）, and for each document, the observed words are influenced by the document＇s GPS-tag. Our model allows both unbound number and flexible distribution of the geographical variations of the topics＇ content. We develop a Gibbs sampler for the proposal, and compare it with existing models on a real data set basis.     

空间谱估计中误差自校正方法研究

阵列误差一直是空间谱估计理论实际应用的一个主要瓶颈。该文提出了一种新的阵列误差自校正方法,结合有源校正与在线自校正理论和方法,通过利用一个空间位置方位不需要精确可知的辅助信号源,利用优化算法完成信号源角度以及阵列复增益误差的联合估计,然后将估计的阵列误差参数应用到其后的空间谱估计中。这种自校正算法具有准确度高的优点,并且属于离线算法,一方面避免了传统的有源校正方法对辅助源位置方位精度的严格要求,同时避免了在线自校正算法的大计算量,可以应用到实际空间谱估计中。      

电子组件温度循环试验研究

为了使温度循环试验在有效提高电子组件的可靠性方面得以广泛应用,基于温度循环试验的机理,对电子组件温度循环试验的关键参数(温度范围、循环次数、保持时间、温变速率、风速)进行了探讨,给出了这些参数的工程经验选取值。在此基础上,借助热分析软件分析了温变速率、保持时间和风速三个参数对试验过程的影响并定性分析了三个参数间的关系。最后,提出了进行温度循环试验时应注意的问题,强调科学、正确地执行温度循环试验的重要性。     

铁镍合金与碳纳米管复合物的制备及吸波性能

以采用溶胶凝胶结合氢气还原法制备出的铁镍合金纳米颗粒为催化剂,原位裂解苯,成功合成铁镍合金与纳米碳管的复合物。场发射扫描电镜和高分辨透射电镜结果显示复合物为一维纳米管状结构。微波电磁参数测量结果表明:随着试样厚度的增加,匹配频率处的理论反射损耗量呈下降趋势;当厚度为1.5mm时,FeNi22@C复合物的微波吸收效果最好,在频率11.35GHz处反射损耗量为-4.74dB;可以通过改变铁镍合金中各成分的比例、复合物吸收厚度,调整复合物的复数介电常数和复数磁导率,优化复合物的微波吸收性能。     

三相共补复合开关的研制

功率因素过低对电网及负载有极大负面影响,在感性负载两端并接电容是常见的无功补偿方法。针对电磁开关和电力电子开关投切电容器在无功补偿装置应用中存在的问题,从分析功率因素补偿意义入手,提出三相共补开关拓扑结构及其电路模型,分析投切过程冲击电流形成机理及其避免对策。研制了一种基于AVR单片机在电压过零时投切并应用于低压无功补偿装置的复合开关。该复合开关的优点是电压过零时投切,冲激电流小;每相过零时触发中断,响应迅速快;采用了atmega16作为主控芯片,样机测试果表明达到设计之要求。