长距离分布式光纤传感中基于STM32的遗传算法偏振控制

基于STM32微处理器采用偏振控制器反馈技术并结合遗传算法对50km长距离分布式光纤振动传感系统中偏振衰落进行抑制.结合STM32与PCD-M02型偏振控制模块特性,优化遗传算法相关参量,在STM32微处理器上实现了遗传算法对传感系统的偏振控制.实验结果表明,基于STM32微处理器的遗传算法在短时间内能得到全局近似最优解,有效实现偏振控制,该方案适用于对实时性和集成度要求较高的长距离分布式光纤传感系统.     

大气湍流中空间光至单模光纤耦合的跟踪算法

 通过模拟湍流波前的振幅起伏及相位起伏,研究了采用CCD探测器的湍流波前倾斜校正系统的空间光到单模光纤耦合功率的衰落特性,对CCD图像的跟踪算法进行了研究。仿真结果表明,在接收孔径直径与Fried 参数的比值较大时,采用质心跟踪算法的倾斜校正系统的性能很差,耦合光功率会产生严重衰落。提出了一种高斯模板匹配的倾斜校正跟踪算法,在湍流较强时,可以有效地降低耦合光功率的衰落深度,并且可以避免采用质心算法可能出现的大孔径接收性能低于小孔径的不利情况。     

Indoor cognitive radio operation within the broadcast TV protection contour

Although the broadcast television (TV) spectrum is currently open for unlicensed operation in the USA, a considerably large geographic area still remains excluded from the unlicensed operation due to potential interference to the licensed users. However, it might be possible to reuse primary spectrum within the protection contour if the frequency reuse occurs inside a building that shields radio signals and reduces interference to the primary system. Interference to outdoor licensed users from the indoor operations can be minimized if the unlicensed users adjust their transmit power according to their locations in the building. This paper presents an analysis and effectiveness evaluation of a novel cognitive radio (CR) system which enables CRs to access the licensed spectrum inside a building in the area within the protection contour. The system utilizes an indoor sensor network for (i) interference sensing, (ii) CR transmit power control, to limit the interference to the outdoor primary receiving antennas. Power control model of the indoor system has been developed to estimate safe transmit power for the indoor users. Two cases have been considered; single-user single-sensor (single indoor user and single sensor), and multi-user multi-sensor. Based on the power control model, a power control algorithm has been developed and its effectiveness is assessed through simulations. The algorithm is effective in realistic propagation scenarios, e.g. when internal partition walls and multipath fading are present. The outage probabilities in these propagation scenarios are found and the procedure of determining the transmit powers for CRs is presented.     

Modeling the lossy transmission of correlated sources in multiple access fading channels

In this paper, we develop accurate distortion models for the lossy transmission of two correlated sources in a multiple access Rayleigh fading channel. We focus on a class of real-life communication systems, where the source and channel coders have already been designed separately and can only be configured during the system operation. We investigate three different source coding schemes: distributed source coding (DSC), layered source coding, and independent compression through quantization. With the later scheme the sources are jointly decoded with minimum mean square error (MMSE) estimation at the receiver. We also consider two different transmission schemes: Orthogonal transmissions and interfering transmissions decoded with a successive interference cancellation (SIC) decoder. Our final closed-form analytical models are used to determine the optimal combination of source coding and transmission schemes, as well as their optimal configuration. Hence, we exercise joint source and channel coding (JSCC) by optimizing the system configuration. Through simulations, we first validate the analytical model and illustrate the performance of different schemes. Finally, we demonstrate the JSCC gains achieved by our system.     

抗多径的线性合并SFH／MFSK系统在短波信道中的性能

在线性合并接收机的基础上，引入了抗多径干扰的措施，并分析了这类新型接收机在存在部分边带干扰的多径瑞利衰落信道中的性能，着重研究了多径加权因子对系统性能的影响．研究结果表明，最佳加权因子ω＊与多径干扰强度，分集重数，调制阶数和信道热噪声有关。对多径合适地加权可明显地改善系统的性能，在分集和编码相结合时，能使Ｐｂ下降２～３个数量级同时本文还研究了分集重数Ｌ和调制阶数Ｍ对系统性能的影响．     

三相供电线路的漏电流分布规律

面对安全用电的严峻形式 ,经国内外的实践证明 ,安装使用漏电保护开关对于防止触电身亡 ,避免设备接触地故障损坏和漏电引起火灾事故 ,及减少漏电引起的电能损耗 ,具有明显效果。然而对于漏电保护开关的跳闸临界值具有很大歧义 ,因此我们首先对漏电流进行分布拟合 ,将得出的参数值进行随机模拟 ,以此来制定漏电保护开关的跳闸临界值     

短波瑞利衰落信道FH／MFSK编码系统的性能

基于ＳｔｕｂｅｒＧ．Ｌ．的系统模型，研究带反馈链路的选择式频率分集与编码ＦＨ／ＭＦＳＫ系统在具有加性白高斯噪声（ＡＷＧＮ）的瑞利衰落信道中的编码性能，给出了采用ＲＳ码、双－ｋ码、重发码时，编码前与编码后系统的码符差错概率与比特能量噪声比的关系曲线．研究结果表明：无编码时，单纯增加分集重数Ｌ对系统性能的改善并不是十分明显的，只有同时采用分集与编码技术，才能有效地改善系统的性能．     

阳离子染料在真丝绸上的光褪色机理

用电化学循环伏安法研究真丝绸上染料的光褪色，发现真丝绸中的某些氨基酸和染料、氧分子３者间可以形成电荷转移复合物。这些三元电荷转移复合物的还原电位比染料本身的还原电位明显正移。用的光照射，证明是真丝绸中的氨基酸加速了阳离子染料的光褪色。     

抑制褪色光度法测定油炸面制食品中痕量铝

建立抑制褪色光度法快速测定食品中痕量铝的方法。在硫酸介质中,一定量的铝离子对溴酸钾氧化罗丹明B褪色有抑制作用,据此建立了抑制褪色光度法快速测定食品中痕量铝的新体系,最大吸收波长为550 nm。在1 mol/L硫酸介质中,铝含量在0.07~0.4μg/mL范围内与吸光度具有良好的线性关系,相关系数r=0.9995,检出限为0.02μg/mL。用该方法测定油炸面制食品中痕量铝,测定结果的相对标准偏差为1.3%~3.1%(n=11),加标回收率为99.3%~103.5%。该方法测定结果准确可靠,可用于食品中痕量铝的测定。     

盐酸小檗碱-十二烷基苯磺酸钠缔合微粒体系的共振散射光谱研究及其分析应用

在pH 4 .80NaAc HAc缓冲介质中 ,盐酸小檗碱 (BH)与十二烷基苯磺酸钠 (DBS)由于静电引力和疏水作用力形成缔合微粒 ,在 4 70nm处有一共振散射峰。随着DBS浓度增大 ,该峰急剧增强 ,即存在缔合微粒的散射光增强效应 ;345nm处的吸光度减弱 ,即存在缔合微粒的减色效应。研究了共振散射光谱测定BH的影响因素 ,提出了测定 (0 .35～ 4 .4 )× 10 -5mol/L盐酸小檗碱的共振散射光谱新方法 ,用于复方黄连素片剂和针剂样品的测定 ,结果满意