基于LS-PSO的北斗伪距单点定位算法

北斗伪距单点定位具有易于实现、不存在整周模糊度、速度快等特点,具有很大的研究和应用价值;传统最小二乘法由于引入了线性误差、对初始值依赖性强而导致定位精度低;为了提高北斗伪距单点定位的精度,通过分析最小二乘法和粒子群算法的优缺点,提出了一种LS-PSO组合算法;首先利用最小二乘法定位计算接收机的大约位置,作为粒子群算法解的基准值并建立解的搜索空间,然后利用粒子群算法得到全局最优值,解算出精度更高的结果;经过实验验证,LS-PSO组合算法可以稳定的解算出m级精度的定位结果,并且三维方向偏差都在大约5 m以内;最后通过与遗传算法的收敛情况和最小二乘法的定位精度进行对比,证明LS-PSO组合算法可以快速的收敛到最优解并且有效的提高了北斗伪距单点定位精度。     

无线传感中的WPSO-DVHOP算法在节点定位中的研究

节点的定位一直都是无线传感网中的重要研究对象,针对使用传统算法定位节点容易出现估算不准确,定位精度低,算法自身局部收敛速度快等缺点,提出一种基于权值粒子群优化(WPSO)算法,首先分析了采用锚节点估算未知节点的距离与真实距离误差,采用最小二乘法的距离修正值策略,其次针对粒子群算法的收敛速度不足,提出了采用权值来调节粒子的速度,改进后的算法对节点定位误差进行修正。在仿真平台Matlab上的实验说明WPSO算法相对于基本的定位算法,粒子群定位算法相比提高了传感器节点定位精度,从算法的收敛性,节点定位的精度以及能量消耗等方面说明该算法具有一定的有效性,如何能够更好进行权值的设置使之能够更加有效提高算法的效率是下一步研究的重点。     

基于角度信息的递推最小二乘无源定位算法

针对机载单站无源定位的定位精度和实时性等问题,提出了一种基于角度信息的递推最小二乘(RLS)无源定位算法;首先建立了机载单站三维无源定位模型,求出最小二乘(LS)解;然后依据机载单站无源定位的实时性要求将最小二乘估计转化为递推最小二乘估计的形式;最后通过不同的仿真实验研究了影响定位精度和收敛速度的因素;仿真结果表明:RLS算法与LS算法在定位精度和收敛速度方面性能相似,但RLS算法运算复杂度低,所需存储空间小,能够实时的对目标进行定位,满足机载单站无源定位的需求。     

基于群波时差信息的地下震动目标定位方法

针对现代战争技术中地下炸点三维定位难,精度低的问题,本文提出了一种改进粒子群算法,并利用其解决群波时差地下震动目标定位的问题。该算法克服了粒子群算法本身种群数量和和质量的选择、后期容易陷入局部最优的问题。通过结合直达P波优势频率的相位差特点,利用群波时差测量信息进行定位计算,以提高定位结果的精确度。目标定位的测试结果表明,新算法在20m*20m的区域内,该方法能有效地提高目标定位精度,加入的随机噪声干扰方差的条件下,定位误差不超过10cm,且收敛速度增快,性能稳定。     

无人机侦察多目标实时定位技术研究

目标定位是无人机侦察系统中至关重要一步。为增强无人机侦察目标定位的实时性、提高定位精度及侦察效率,提出一种多目标实时定位的方法,建立主次目标定位几何关系及坐标转换模型,结合已知数据信息求取各目标大地坐标,并用蒙特卡洛法分析目标定位误差。最后,基于即将组网成功"北斗二代"卫星导航系统对无人机空中定位,同时采用递归最小二乘算法滤波处理,提高了目标定位精度。研究及实验结果表明,北斗导航定位能够有效提高无人机空中定位精度,且有望达到厘米级精度,同时采用RLS滤波处理能使目标定位精度提高10 m左右。该方法能够有效增强无人机定位实时性,提高定位精度及侦察效率。     

捷联惯导/北斗高精度组合导航方法研究

提出采用紧组合方式进行捷联惯导/北斗组合导航设计,首先对捷联惯导与北斗系统进行误差分析与建模,将捷联惯导系统误差、北斗等效时钟误差相应的距离(伪距误差)以及等效时钟频率误差相应的距离率(伪距率误差)作为组合导航系统状态;利用捷联惯导位置输出与北斗接收机星历输出构造获得等效伪距,将其与北斗接收机测量的伪距对应相减作为量测,推导建立对应的量测方程,采用卡尔曼滤波设计捷联惯导/北斗组合导航滤波算法。仿真结果表明,该组合导航方法的速度精度达到±0.05m/s,位置精度达到±3.2m,水平姿态精度达到±0.4′,航向精度达到±1.6′。     

基于相似日的支持向量机短期负荷预测

摘要：为提高电网短期负荷预测的精度,对以往学者基于相似日和最小二乘支持向量机(LS-SVM)短期负荷预测方法进行改进,形成一种改进的基于相似日和细菌趋化改进粒子群算法优化最小二乘支持向量机(least squares support vector machine based on improved particle swarm optimization for bacterial chemotaxis, PSOBC-LSSVM)的预测模型。克服了标准粒子群算法容易早熟收敛和陷入局部最优的问题,并充分考虑短期负荷的连续性与周期性对选取相似日造成的影响,将二者结合到一起综合考虑,利用改进的粒子群得到二者的最佳匹配值,并将其融合到时间距离这一因子当中。算例表明该方法预测精度较更高,可行且有效。     

基于蝙蝠优化算法的无线传感器网络节点定位研究

节点定位是无线传感器网络应用中的关键技术,Dv-Hop算法的定位精度不尽人意,因此将三方面改进的蝙蝠算法应用于Dv-Hop平均跳距的计算过程中,在Dv-Hop的第三阶段引入改进后的蝙蝠算法代替最小二乘法来计算未知节点的坐标,大大降低平均跳距导致的定位误差,提高定位精度;仿真结果表明,改进的BA算法优化的DV-hop定位算法在不同锚节点密度、不同通信半径、不同节点数量以及定位精确度等方面表现出良好的性能。     

基于粒子群优化的最小二乘支持向量机在混合气体定量分析中的应用

针对混合气体建模过程中最小二乘支持向量机参数难以确定及红外光谱数据计算量过大的问题,提出一种粒子群优化的最小二乘支持向量机方法,用于建立基于主成分分析特征提取的红外光谱多组分气体定量分析模型。首先对主吸收峰区域的550个红外光谱数据利用主成分分析技术进行了特征提取,将降维得到的7个特征值作为模型的输入变量从而有效地降低了计算量。混合气体主要由浓度范围分别是0.1%～1%的甲烷、乙烷及0.1%～1.5%的丙烷三种组分气体组成。采用最小二乘支持向量机技术分别建立了各组分气体的定量分析模型,利用粒子群优化算法对最小二乘支持向量机算法中的参数进行了优化选取,取代了传统的遍历优化方法,然后利用取得的最优参数重建定量分析模型。实验结果表明,采用此方法离线建模所用时间比采用遍历优化方法节省40倍以上,预测结果误差水平相当,满足实测要求。粒子群优化算法在全局优化及收敛速度方面具有较大优势。粒子群优化算法与最小二乘支持向量机技术相结合用于混合气体定量分析是切实可行的,具有一定的实际意义和应用价值。     

基于惯性信息辅助的北斗动动定位方法的研究

针对北斗动动定位中接收机信号易受遮挡导致无法实时准确定位的问题,对复杂信号条件下的动动定位测试进行了研究,提出了一种利用惯性信息辅助解算动态模糊度的方法,即一种将运动载体的惯导信息与北斗测量信息相结合,实现两运动载体之间精确动态相对定位的算法。通立基于载波相位双差的观测模型,采取融合滤波算法,讨论在在不同卫星数目下的模糊度求解方法。在此基础上,利用实地车载试验完成了对上述组合定位方法的试验验证以及精度测试,事后着重对各历元数据进行解算,对定位精度、可用性进行了研究。结果表明,基于惯性信息辅助的北斗动动定位可用性指标变好,定位精度有一定的提高。     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Characterization of PolyA and PolyC mismatches by Raman spectroscopy

A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands.     

Improvement of four-wave mixing-based wavelength conversion efficiency in dispersion shifted fiber by 40-GHz clock pumping

40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm.     

Multi-pulse operation of a Kerr-lens mode-locked femtosecond laser

Our experimental results show that the presence of a proper amount of negative group velocity dispersion is essential to multi-pulse operation of a Kerr-lens mode-locked femtosecond laser. We demonstrate that the pulse separations and the number of pulses contained within a cavity round trip are strongly dependent on the initial perturbations. The results allow us to get a better understanding on the influences of the convoluted self-phase modulation and intra-cavity dispersions on the stable multi-pulse oscillation in a Kerr-lens mode-locked femtosecond laser.     

Propagation of Helmholtz-Gauss beams in weak turbulent atmosphere

Based on the Rytov approximation of light propagation in weak turbulent atmosphere,the closed-form expressions of field and average irradiance of each one of the four fundamental families of Helmholtz-Gauss (HzG)beams:cosine-Gauss beams,stationary Mathieu-Gauss beams,stationary parabolic-Gauss beams,and Bessel-Gauss beams,which are propagating in weak turbulent atmosphere,are obtained.The results show that the field and average irradiance can be written as the product of four factors:complex amplitude depending on the z-coordinate only,a Ganssian beam.a factor of complex phase perturbation induced by atmospheric turbulence,and a complex scaled version of the transverse shape of the non-diffracting beam.The effect of weak atmospheric turbulence on irradiance distribution of the HzG beam can be ignored.     

An effective method for reducing speckle noise in digital holography

An effective method for reducing the speckle noise in digital holography is proposed in this paper.Different from the methods based on classical filtering technique,it utilizes the multiple holograms which are generated by rotating the illuminating light continuously.The intensity images reconstructed by a series of holograms generated by rotating the illuminating light possess different speckle patterns.Hence by properly averaging the reconstructed intensity fields,the speckle noises can be reduced greatly.Experimental results show that the proposed method is simple and effective to reduce speckle noise in digital holography.     

Influence of purity of HfO2 on reflectance of ultraviolet multilayer

The impurities in two kinds of HfO2 materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum technology and secondary ion mass spectrometry(SIMS) equipment respectively.It was found that ZrO2 was the main impurity in the two kinds of HfO2 either in the original HfO2 materials or in the electron beam deposited films.In addition,the difference of Zr content in the two kinds of HfO2 single laver films was much laxger than that of the other impurities such as Ti and Fe.which showed that it was just ZrO2 that made the difference between the optical performance of the film products including the two kinds of HfO2.With these two kinds of HfO2 and the same kind of SiO2.we deposited HfO2/SiO2 multilayer reflective coatings at the wavelength of 266 nm.Experimental results showed that the reflectances of these two mirrors were about 99.85% and 99.15% respectively,which agreed well with the designed results what were based on the optical constants obtained from the corresponding single layer thin films.     

Speech enhancement by array crosstalk resistant ANC and spectrum subtraction

Microphone array-based speech enhancement has great importance for speech communications and speech recognition. To reduce the aperture of the microphone array and to increase the effect of the speech enhancement will greatly broaden the application areas of the microphone array. An array crosstalk resistant adaptive noise cancellation method is therefore presented. And then an improved spectral subtraction algorithm is further cascaded to obtain better enhancement results. Theoretic analysis and experiments indicate that the proposed scheme needs only a very small microphone array while it simultaneously achieves a higher SNR improvement. Besides, the proposed scheme can be used in many noisy environments and is easy for real-time implementation.