局域支持向量回归与误差区间估计的概率预报方法及其应用研究

 针对工程应用对预报技术要求的不断提高以及现有预报方法存在的问题,本文提出了一种局域支持向量回归(Local Support Vector Regression,LSVR)和误差区间估计相结合的概率预报方法,该方法利用局域支持向量回归降低噪声对点预报的干扰,提高预报的可靠性和准确性,利用非参数核估计获取误差区间,避免误差概率分布特性假设,再将点预报和误差区间结合获得预报置信区间,并进一步给出了联合预报置信区间.最后,给出了电网负荷预报和供热负荷预报算例,验证了所提出方法的有效性和实用性.     

基于EMD和误差匹配的动态测试系统误差溯源

为掌握动态测试系统的误差特性及传输特性,在全系统动态精度理论的基础上,提出了一种基于EMD和误差匹配相结合的方法。该方法首先采用EMD对动态测试系统的输出误差进行分解,然后根据分解结果进行误差匹配溯源。仿真结果表明,该方法能够有效地追溯到误差产生的源头,速度快,效率高,具有较强可行性和应用性。     

偏振正交误差对偏振光导航定位系统测量精度的影响

偏振正交误差是影响四通道时分复用大气偏振检测系统精度的主要因素。通过建立检偏器阵列偏振正交误差对偏振光导航系统定位精度的影响模型,分析了该误差对大气偏振测量精度与导航定位精度的影响,并进行了实验验证。理论与实验结果表明,降低检偏器阵列偏振正交误差,可以显著提高系统大气偏振测量精度与导航定位精度。当检偏器阵列偏振正交误差无法消除时,调整定位初始角可以明显提高系统测量精度与导航定位精度。     

应变测量系统误差分析

电阻应变式传感器在实际工程中应用较广。介绍影响电阻应变式传感器精度的一些因素,并对其在实际应用中可能出现的问题进行全面细致的分析。分析电测试验中应变片粘贴质量、非线性及导线长度、温度、不同组桥方式对测试结果所产生的影响,修正了导线电阻引起的误差,大大提高了测量精度,得出了应变电测试试验中减小误差的方法。     

Content Analysis—A Probabilistic Approach

A probabilistic model is presented which may be applied to perform content analysis on the computer. The procedure employs word stems as category entries and probabilities rather than units for allocating and enumerating content among categories. An application of the model was made to compare content coverage in monopoly and competitive newspapers. There was no appreciable difference due to interaction among monopoly and competitive paper types and content categories. Comparisons among categories showed an appreciably greater probability of news of more‘everyday’than of a violent classification, a finding which challenges a common criticism that the press presents disproportionate content of an inflammatory or violent nature.     

电磁定位系统测量误差校正技术研究

在电磁定位系统中, 若没有考虑环境磁场、制造工艺等误差因素的影响, 会导致系统定位精度下降。介绍了一种提高电磁定位系统定位精度的方法, 该方法为了克服经典磁偶极子模型过于理想化的缺点, 提出了误差修正模型, 介绍了天线参数标定原理, 同时给出了修正因子的标定方法、标定流程以及装置。通过对比试验可以看出, 经过模型修正的系统定位精度可达到未修正模型的5倍。     

应答着陆系统测角误差分析

应答着陆系统(Transponder Landing System,TLS)是一种基于应答机的精密进近着陆引导系统,采用相位干涉仪测角原理获得飞机的方位和仰角信息。从应答着陆系统的基本测角原理入手,分析了该系统的测角精度和误差来源。重点分析了因接收通道不平衡和多基线干涉仪测角的相位模糊引起的相位误差,并针对各自的特点提出了消除接收通道失衡和噪扰条件下解相位模糊的办法。通过计算机仿真验证了理论分析的正确性。     

计算OFDM系统误码率的新方法

介绍一种计算分组均衡的OFDM系统的误码率的新方法。该方法可利用付立叶级数展开写出误码率的近似表达式。用该方法分析了采用最小均方根(MMSE)分组均衡器的OFDM系统误码率,实例计算表明,此方法计算量小,精度高。     

基于HP3048A系统的晶体振荡器相位噪声的快速测量方法

介绍了一种基于HP3048A相位噪声测量系统的相位噪声的拓展测量方法(即用USB接口卡取代HPIB接口卡,用与待测信号源具有相同中心频率的VCO取代HP8662),讨论了该拓展方法在射频信号源相位噪声测量中的应用,并给出了测量系统噪声本底的方法以及射频晶振的典型测量结果。     

小机芯离焦检测系统特性的新型测量方法

利用聚焦预搜索原理,测量出小机芯离焦检测系统特性的关键参数：离焦偏置、离焦灵敏度和线性区范围。首先将周期电压输入小机芯的聚焦力矩器使小机芯进行聚焦预搜索,同时得到聚焦误差曲线;然后根据聚焦误差曲线计算出小机芯离焦检测系统的特性,利用聚焦误差曲线S状脉冲的出现时刻计算出离焦偏置,利用S状脉冲的斜率和峰峰值得到离焦灵敏度和线性区范围;最后给出测量实例。该方法采用电信号测量小机芯的离焦检测系统特性,无需进一步的聚焦闭环控制以及互维精密工作台,具有设备简单、易于实现等特点。     

基于OFDM的LDPC误码测试系统设计

通过比较国内外几种LDPC误码平台测试系统,设计了一种基于OFDM的用于测试LDPC解码误码性能的窄带系统,采用了时域同步正交频分复用调制方式,具有抵抗多径干扰和多普勒频移的能力.该系统用FPGA予以实现,不仅可用于实验室测试,也可用于测试真实多径环境下的误码性能,还能作为通用系统用于其他信道纠错码的解码误码测试.     

电离层误差对卫星导航系统测距误差影响分析

电离层延迟误差是单频接收机的主要定位误差之一。电离层延迟误差具有多变性,不易准确描述。本文探讨了几种常用单频接收机电离层延迟改正模型,Bent模型IRI模型、Klobuchar模型、NeQuick模型以及IGGSH模型。并利用单频GPS接收机实测数据统计分析各模型对定位误差的修正效果,为单频接收机用户选择合适的电离层改正模型提供参考。     

A Probabilistic Approach to WLAN User Location Estimation

We estimate the location of a WLAN user based on radio signal strength measurements performed by the user's mobile terminal. In our approach the physical properties of the signal propagation are not taken into account directly. Instead the location estimation is regarded as a machine learning problem in which the task is to model how the signal strengths are distributed in different geographical areas based on a sample of measurements collected at several known locations. We present a probabilistic framework for solving the location estimation problem. In the empirical part of the paper we demonstrate the feasibility of this approach by reporting results of field tests in which a probabilistic location estimation method is validated in a real-world indoor environment.     

Probabilistic Bounds on Error Amplification of Randomly Generated Frames

Hilbert space frames have recently attracted attention in the signal processing community. In this paper, we consider the problem of describing the statistical distribution of the error amplification and lower bound of a frame obtained by randomly picking vectors from a larger frame (the frame pool). The key result of this paper is an analytic bound to the probability of having an error amplification larger than a given value. We also consider the possibility of content reconstruction using an approximate, but efficient, algorithm. The theoretical results are completed by means of numerical experiments.      

激光自准直测角系统安装误差分析

分析激光自准直测角系统的安装误差,得出误差主要来源:光学系统和PSD的倾斜安装.针对光学系统的倾斜安装,建立畸变误差模型并仿真分析,得出结论:光学系统光轴平行于转轴时,像点坐标不因平面镜旋转角度的不同而存在误差,变化的仅是折射光线与光轴的夹角;光轴与转轴相交时,像点坐标随光轴与转轴的夹角、焦距和平面镜初始位置法线与转轴夹角的变化而产生较大的畸变误差.建立的误差模型及仿真结果为提高激光自准直测量精度提供了一个有效的理论指导,具有一定的工程实际应用价值.     

纠错编码对OCDMA系统性能的影响

提出了基于RS码(Reed-Solomon Code)的光码分多址(OCDMA)系统的前向纠错编码方案,仿真分析了该方案对一维、二维OCDMA系统的纠错能力.研究结果表明:对于相同码长、相同码重光地址码的OCDMA系统,采用前向纠错(FEC)技术能够有效降低系统误码率,提高系统客量,改善系统性能.对于来自同一码族的OCDMA系统,随码重增加,系统性能改善越好.

Abstract：

A novel forward error-correct (FEC) scheme based on Reed-Solomon code (RS code) is proposed for optical code division multiple access (OCDMA) systems.The error-correcting ability of the presented FEC scheme for one-dimension and two-dimension OCDMA systems are simulated and analyzed.Researched results show that the bit error rate (BER) of OCDMA system using FEC technology is better than that withoutwit using FEC technology at the condition of same code length and code weight.And the capacity is also largely enhanced due to the application of FEC technology.Moreover,for the address code of OCDMA system coming from the same code family,the BER is improved with the increase of the code weight.     

负载牵引测试系统的误差源分析

负载牵引测试系统是一个复杂的微波测试系统,必然存在测试误差。本文从系统的组成、系统的校准、测量仪器自身测试误差和测试环境等角度分析了误差的来源,及其对测试系统的影响。     

四站混合定位系统的平面测量误差

基于最小二乘和误差估计理论,应用数值计算的方法具体分析了一个按形布站、且将时差和径向距离测量信息相融合的四站定位系统,通过与仅基于时差测量技术的定位系统相比较证明,多站混合定位测量系统具有测量误差低、无空间观测盲区等优点。所给出的结果不仅能应用于对非合作目标探测的有源/无源综合定位系统,而且还能应用于对可合作目标定位的多站定位系统的设计。     

A Probabilistic Approach to Diagnose SETs in Sequential Circuits

In recent work, the error latching probability due to an SET is calculated for a single observable point, and this help in hardening the design. This paper utilizes a recently proposed probabilistic framework for SET propagation in order to diagnose the location and time of strike based on errors observed at multiple points. The proposed diagnostic framework requires a new approach to calculate the probability for SET propagation to multiple non-independent variables. It is shown experimentally that error appearances at multiple observable points help in SET diagnosis. The time performance of the proposed diagnostic framework is compared against an alternative implementation. This is particularly important in on-line diagnosis.     

A Competitive Mean-Squared Error Approach to Beamforming

We treat the problem of beamforming for signal estimation where the goal is to estimate a signal amplitude from a set of array observations. Conventional beamforming methods typically aim at maximizing the signal-to-interference-plus-noise ratio (SINR). However, this does not guarantee a small mean-squared error (MSE), so that on average the resulting signal estimate can be far from the true signal. Here, we consider strategies that attempt to minimize the MSE between the estimated and unknown signal waveforms. The methods we suggest all maximize the SINR but at the same time are designed to have good MSE performance. Since the MSE depends on the signal power, which is unknown, we develop competitive beamforming approaches that minimize a robust MSE measure. Two design strategies are proposed: minimax MSE and minimax regret. We demonstrate through numerical examples that the suggested minimax beamformers can outperform several existing standard and robust methods, over a wide range of signal-to-noise ratio (SNR) values. Finally, we apply our techniques to subband beamforming and illustrate their advantage in estimating a wideband signal.