基于测距技术的无线传感器网络定位算法研究

街道、走廊等带状通道具有其环境特殊性,对该环境下无线传感器网络定位算法的研究是研究其他特殊环境下定位工作的基础,其研究成果在工业界具有很高的推广价值;为此,选择基于测距技术的RSSI算法设计了一种带状通道环境下的无线传感器网络定位算法。给出了算法设计思路及硬件条件,并在构建的实验平台下对其进行了实验验证;实验结果证明:算法对带状通道环境下的目标定位可获得较好结果。     

The power of choice in random walks: An empirical study

In recent years random-walk-based algorithms have been proposed for a variety of networking tasks. These proposals include searching, routing, self-stabilization, and query processing in wireless networks, peer-to-peer networks and other distributed systems. This approach is gaining popularity because random walks present locality, simplicity, low-overhead and inherent robustness to structural changes. In this work we propose and investigate an enhanced algorithm that we refer to as random walks with choice. In this algorithm, instead of selecting just one neighbor at each step, the walk moves to the next node after examining a small number of neighbors sampled at random. Our empirical results on random geometric graphs, the model best suited for wireless networks, suggest a significant improvement in important metrics such as energy consumption and the cover time and load-balancing properties of random walks. We also systematically investigate random walks with choice on networks with a square grid topology. For this case, our simulations indicate that there is an unbounded improvement in cover time even with a choice of only two neighbors. We also observe a large reduction in the variance of the cover time, and a significant improvement in visit load balancing.     

VxWorks和RTlinux的性能测试分析

比较并分析了两种操作系统VxWorks和RTlinux的可适用性及可控性;为了使二者之间的差异表现的更加充分,基于统一的硬件平台和相同的测量方法,在两种操作系统稳定运行期间,我们对能反应操作系统性能的四项指标:上下文切换,中断响应能力,同步运行能力和信息传递能力,进行了功能性测试;在优先级反转问题上,对二者的效率进行了检测。测试结果表明,无论VxWorks还是RTlinux都显示出了良好的适用性,但是VxWorks具有更好的可控性和可预知性,因此这使它成为更好发展前景和更严格软硬件的实时操作系统平台。     

基于软核Nios II的SOPC数据采集系统的设计

从自主研发的角度,介绍了一种基于Nios II软核处理器的高速多路数据采集系统的设计和实现过程,并说明了SOPC系统开发的一般流程以及系统软硬件架构的设计;该系统采用AD522芯片实现了信号放大,采用AD976进行数模转换,采用K6T1008C2C-L进行数据存取,采用USB接口芯片ISP1581与工控机进行通讯,FPGA芯片采用ALTERA公司的EP2C5F256C8;该系统是以PFGA为核心,体现了SOPC系统集成度高、灵活性强的特点,并能缩短产品的开发周期。     

两种数据融合算法对扩散硅压力传感器的温度补偿

针对扩散硅压力传感器在实际应用中对温度存在交叉灵敏度的问题,文章采用改进的多维回归分析法和BP神经网络法两种实用的智能化数据融合方法对压力传感器输出进行处理,以消除非目标参量(温度)对传感器的影响;研究结果表明这两种方法均能有效地抑制交叉灵敏度,减小灵敏度温漂和零点温漂;由于这两种融合算法具有各自的特点,因此可应用于不同要求的智能传感器系统中。     

小型飞行器综合测试系统方案设计

针对小型飞行器系统各部件在研制和生产中的测试要求,提出了小型飞行器综合测试系统的方案设计;方案设计中详细介绍了系统组成,并对方案中涉及的航空电子分系统、发动机分系统、无线电数据链分系统的测试内容及测试方法进行了分析说明;根据测试方法和测试内容,给出了综合测试系统的硬件设计原理和软件设计流程;运用该设计方案进行了综合测试设备发动机分系统测试的研制工作,并投入试运行,结果表明该方案设计合理可行,可推广应用于该领域或其它领域的测控系统的研制中。     

基于VXI、PXI和LXI的网络化混合测试系统设计

文章介绍了混合测试系统整体结构,重点阐述了系统采用的硬件结构以及两种关键技术。此混合测试系统采用VXI总线、PXI总线和LXI总线共同组建,把三种单一总线系统的优点集于一体,既保护了测试资产中的已有投资而节省资金,又由于能继续使用熟悉的硬件、接口和软件,从而节省了时间。最后通过在项目中的应用得出了系统能缩短延时,并有效工作的结论。     

Buffeting numerical simulation coupled with aerodynamics and structure based on MDDES

Unsteady effect of seriously separated flow is the main factor of modern aircraft buffeting. So accurate simulation of this complex flow becomes the basis associated with the research of aircraft buffeting. This paper constructs an unsteady numerical simulation method for separation flow based on modified delayed detached eddy simulation (MDDES) method by considering both modern computer resources and the credibility of simulating separation flow. The proposed method is also verified through the simulation of the separated flow by a typical fighter at high angle of attack. And then a robust and efficient technology for deforming mesh is established using radial basis function (RBF) and infinite interpolation method. Moreover, the platform for numerical simulation of buffeting is set up in combination with the structural dynamics equations in the modal space, by which the research of vertical tail buffeting caused by edge vortex is carried out on a fighter at large angle of attack. Through spectrum analysis of time-domain response of pressure pulsation on the location of vortex rupture, the results show that the pulsation frequency of vortex structure with different scales covers the inherent modal frequency of vertical tail structure. Compared to the Reynolds-averaged Navier-Stokes equations, the MDDES method can distinguish the more detailed and higher frequency small-scale vortex structure. Unlike flutter, displacement acceleration response of each mode in buffeting is dominated by its own mode. There exists strong coupling between the first bending mode and first torsion mode, and it leads to acceleration and large inertia impact of structure, which is the main factor causing structural fatigue. In sum, the obtained results verify the validity of the numerical means and the corresponding methods in the paper.     

The aeroelastic effects on the scatter phenomenon of wind-tunnel data

The unsteady Reynolds-averaged Navier-Stokes equations coupled with the k SST turbulence model are solved to obtain the steady and unsteady aerodynamic forces for airfoils and wings.The effects of vibration types and amplitudes on aerodynamic forces of airfoils and wings are studied.The deformation characteristics of a swept wing induced by steady aerodynamic load are presented.It is found that for a vibrating elastic wing at small and medium incidences,its mean aerodynamic loads are almost the same as those obtained from the static one.On the contrary,at high incidences especially around the stall incidence,the vibration may change the mean values.In addition,the larger amplitude is,the larger discrepancy will be.For a swept wing,the steady aerodynamic loads usually lead to the "pitching down" effect on the wing tip which delays the stall compared with a rigid one;But this phenomenon dose not occur on a aeroelastic wing which can induce the separation ahead and trigger the stall.The above conclusions are in good agreement with the scatter characteristics of wind-tunnel data.The reason why the data obtained from wind tunnel and CFD are different is also analyzed.Meanwhile,it can be an explanation for scatter phenomenon of wind-tunnel data,especially for high incidence cases,which remains a puzzle so far.     

渗铬P110钢在CO2饱和模拟油田采出液中的耐蚀性

为了提高P110油套管钢的表面性能,以满足其在油田环境下服役的要求,采用包埋法对P110钢进行渗铬处理.借助扫描电镜、能谱仪和x射线衍射仪,对渗铬层的表面形貌、显微组织、成分分布和相结构进行了分析和表征,利用电化学测试技术测定P110钢及其渗铬层在CO₂饱和模拟油田采出液中的开路电位、极化曲线和交流阻抗谱.结果表明：渗铬层由Cr₂₃C₆、Cr₇C₃和（Cr,Fe）₇ C₃等相构成,且均匀、连续,与P110钢相比,具有更高的开路电位和电荷转移电阻及更低的电流密度和腐蚀速率.渗铬处理显著提高了P110钢的耐蚀性.