直升机载调频连续波旋转式SAR信号分析与成像算法研究

该文研究基于调频连续波(Frequency Modulated Continuous Wave, FMCW)的直升机载旋转式合成孔径雷达(ROtating Synthetic Aperture Radar, ROSAR)成像,提出一种直升机载FMCW-ROSAR成像的新方法。该方法首先利用等效相位中心原理,将收发分置天线系统的回波信号等效为“自发自收”单基系统。在此基础上,给出了其精确的2维频谱同时分析了载机在发射信号和接收信号过程中天线连续运动的影响产生多普勒频移及其补偿方法;然后运用高效的逆Chirp-Z变换校正了距离徙动空变性。整个算法只包含快速傅里叶变换和复乘操作,不涉及插值,易于工程实现。仿真结果验证了分析结论的正确性和算法的有效性。     

Terahertz Transmission Imaging with 2.52 THz Continuous Wave

In this article, two terahertz transmission imaging systems are built with a 2.52 THz continuous wave laser and two types of sensors. One is array scanning system using a 124×124 pyro-electric array camera as the detector; the other is a point-wise scanning system utilizing a Golay cell as the detector. The imaging speed and quality is briefly analyzed. Terahertz （THz） imaging results demonstrate that the array scanning system has higher imaging speed with lower resolution. The point-wise scanning system has higher imaging quality with lower speed.     

一种太阳能供电LED照明系统电路设计

文章以太阳能供电的LED照明系统为研究对象,探讨了其基本构成,重点探讨了太阳能充电控制器的设计及其电路实现。设计了以PWM控制器CS51221为控制核心的充电控制器的电路,探讨了相关元器件参数的计算方法：分析了LED照明驱动系统的组成及其功能,设计了以NCP3066为核心的LED驱动电路、光敏二极管开关电路、PWM波调光电路;完成了简易太阳能供电LED照明系统电路的硬件,并对其功能及工作性能参数进行了测试和分析。结果表明,该LED照明系统满足设计要求,系统运行良好。     

智能开关技术在电力系统无功补偿装置中的应用探究

文章通过无功补偿装置现状与发展情况的总结,简要介绍了无功补偿装置中一些新技术的概况。通过并联电容器投切开关发展的分析,比较了几种投切开关,重点介绍分析了智能复合开关,说明了智能开关技术在电力系统无功补偿装置中广泛应用前景,为智能开关控制装置的研究提供了基础,引导电力工作者继续深如研究。     

光纤激光相干合成中倾斜和锁相同时控制的实验研究

光纤激光的相干合成是获得高能量密度、高光束质量激光输出的有效方法之一。在相干合成中,各个单元光束的倾斜波前畸变和活塞相位误差对合成的效果具有重要影响。搭建了两路光纤激光相干合成系统,利用光纤自适应准直器和相位调制器对相干合成中倾斜波前畸变和活塞相位误差进行校正。实验系统以高速相机采集的光斑数据作为评价依据,通过计算机程序进行控制,控制算法为随机并行梯度下降算法。在倾斜和锁相控制前,合成光斑的条纹对比度为0.03,桶中功率为8.03;在倾斜和锁相控制后,合成光斑的条纹对比度达到了0.59,桶中功率达到了32.89,说明实验中倾斜和锁相控制显著提高了相干合成的效果。     

基于多层多维的环境感知模型研究

在虚拟终端和异构融合网络的复杂环境下,结合多层次适配和多维度信息处理方法,提出了面向业务提供的环境感知模型。该模型能够有效地解决环境信息的处理问题并提供符合特定用户需求且现实可行的智能感知业务。多层次适配引入了多目标决策算法和主观及客观因素综合的权重,而多维度处理提高了信息的智能性。模型在应用场景的部署充分证明了模型的现实可行性,同时仿真结果表明了此模型在满足用户需求和网络资源分配方面的优势以及多层适配算法的良好性能。     

一种全向圆柱共形螺旋阵列天线

基于圆柱共形阵列天线的基本理论,提出了一种螺旋圆柱阵列天线,该阵列由两层沿圆柱外壁交错排列的螺旋单元组成,采用矩量法分析了天线的辐射特性。通过优化螺旋单元的个数及分布,得到最优的单层单元数N=18,层间距H=60 mm,使阵列天线在实现高增益的同时,在θ=90°平面上产生360度全向辐射,最大增益Gmax可达7.5 dBi,不圆度C<1.6 dB。     

High energy‐efficient and privacy‐preserving secure data aggregation for wireless sensor networks

An efficient data process technology is needed for wireless sensor networks composed of many sensors with constrained communication, computational, and memory resources. Data aggregation is presented as an efficient and significant method to reduce transmitted data and prolong lifetime for wireless sensor networks. Meanwhile, many applications require preserving privacy for secure data aggregation. In this paper, we propose a high energy‐efficient and privacy‐preserving scheme for secure data aggregation. Because of the importance of communication overhead and accuracy, our scheme achieves less communication overhead and higher data accuracy besides providing for privacy preservation. For extensive simulations, we evaluate and conclude the performance of our high energy‐efficient and privacy‐preserving scheme. The conclusion shows that the high energy‐efficient and privacy‐preserving scheme provides better privacy preservation and is more efficient than existing schemes. Copyright © 2012 John Wiley & Sons, Ltd.     

Formaldehyde OTFT Sensors Based on Airbrushed Different Ratios of P3HT/ZnO Films

The formaldehyde (HCHO) detecting at room temperature is of great significance. Different ratios of P3HT/ZnO composite films (3:1, 1:1, and 1:3) were deposited on the organic thin film transistor (OTFT) by spray-deposition technology, and the electrical properties and HCHO-sensing properties of all the prepared OTFT devices were measured by Keithley 4200-SCS source measurement unit. The results show that the OTFT sensor based on the P3HT/ZnO films with the ratio of 1:1 exhibited the best output and transfer curves. Different changing tendency were observed with the increase of ZnO proportion when exposed to HCHO at room temperature, and the device with the ratio of 1:1 behaved a good response and recovery characteristics.     

基于ZigBee无线通信的智能家居系统设计

本文提出了一种基于ZigBee无线通信技术的智能家居系统的设计及实现方案,采用了以控制系统为中心、ZigBee无线传感网络为外围通信网络的结构来构建整个智能家居系统,解决了传统总线方案的不足。