基于 SOLT 校准技术的S参数测量不确定度评定磁

目前,常用的 S 参数测量不确定度评定方法中均未考虑 S 参数相关性的问题,论文给出了一种2GHz ～18GHz 频率范围内 S 参数测量不确定度的评定方法,该方法从校准件的定义出发,基于 SOLT 校准技术对矢量网络分析仪进行自校准,将校准件引入的不确定度通过矢量网络分析仪传递给被测件（DUT ）,通过使用蒙特卡洛仿真的方法（MCM ）得到矢量网络分析仪测量 DUT S 参数的测量不确定度,评定过程中考虑了相关性问题,提高了 S 参数测量不确定度的可靠性和合理性。     

基于SOLT校准技术的S参数测量不确定度评定

目前,常用的S参数测量不确定度评定方法中均未考虑S参数相关性的问题,论文给出了一种2GHz~18GHz频率范围内S参数测量不确定度的评定方法,该方法从校准件的定义出发,基于SOLT校准技术对矢量网络分析仪进行自校准,将校准件引入的不确定度通过矢量网络分析仪传递给被测件(DUT),通过使用蒙特卡洛仿真的方法(MCM)得到矢量网络分析仪测量DUT S参数的测量不确定度,评定过程中考虑了相关性问题,提高了S参数测量不确定度的可靠性和合理性。     

被动微波土壤水分反演中消除植被影响的方法研究

针对被动微波反演土壤水分中,ω-τ模型忽略植被内部多次散射的局限,将光线跟踪原理的双矩阵(Matrix Doubling)算法应用到植被覆盖地区的地表辐射以及植被与地表之间多次散射问题.这种方法可以有效地弥补ω-τ模型的缺陷,但需要的参数较多且形式复杂,很难被直接应用到模拟计算和土壤水分反演中.针对这些问题,本文将基于双矩阵(Matrix Doubling)的算法进行简化,分别考虑植被内仅存在一次散射、两次散射、三次散射以及多次散射的情况.将散射矩阵和传输矩阵表达式简化,利用野外楸树林实验得到的植被参数进行模拟.结果显示当仅考虑两次散射时模拟结果与原始模型的差别已经很小.     

一种低复杂度的鲁棒自适应波束形成算法

传统基于干扰噪声协方差矩阵（interference-plus-noise covariance matrix,INCM）重构的鲁棒自适应波束形成（robust adaptive beamformer,RAB）算法在多种样本数据协方差矩阵误差和信号导向向量误差的失配环境中具有较强的鲁棒性,但目前主流的INCM重构法都是对信号和干扰的导向向量通过建立凸优化模型来估计,这带来了很高的计算复杂度。为了解决这个问题,提出了一种低复杂度的基于INCM重构的RAB算法。该算法首先将干扰信号的导向向量分解为对应标称项和误差项的和,然后通过一种子空间方法估计得到误差项的单位向量。接下来对一个Capon空间谱功率最大问题进行求解,得到误差项的模值,以此得到重构的INCM。同时利用Capon空间谱中残差噪声的存在,使用交替投影法估计得到期望信号的导向向量,最后得到所提算法的权重向量。仿真实验表明所提算法在多种误差环境下具有较强鲁棒性的同时,还具有较低的计算复杂度。     

一种用于高频S参数的去嵌算法

在S参数的测量过程中，需通过去嵌方法去除测试夹具带来的结果误差。该算法通过时域的方法对夹具进行分解。接着将分解得到的夹具S参数采用ABCD矩阵运算进行去除，从而得到待测器件的S参数。通过设计测试板来进行实验，将该算法与传统的AFR和Delta L方法进行了比较，验证了该去嵌算法对高频信号的有效性以及准确性。同时由于该算法先分解再去嵌的特性，使其可应用于左右夹具不一致的情况。     

基于矩阵的数据流Top-k频繁项集挖掘算法

传统的数据挖掘算法在挖掘频繁项集时会产生大量的冗余项集,影响挖掘效率。为此,提出一种基于矩阵的数据流Top-k频繁项集挖掘算法。引入2个0-1矩阵,即事务矩阵和二项集矩阵。采用事务矩阵表示滑动窗口模型中的事务列表,通过计算每行的支持度得到二项集矩阵。利用二项集矩阵得到候选项集,将事务矩阵中对应的行做逻辑与运算,计算出候选项集的支持度,从而得到Top-k频繁项集。把挖掘的结果存入数据字典中,当用户查询时,能够按支持度降序输出Top-k频繁项集。实验结果表明,该算法在挖掘过程中能避免冗余项集的产生,在保证正确率的前提下具有较高的时间效率。     

基于TDOA的室内超声波定位方法的改进

基于超声波和射频信号的TDOA（Time Difference Of Arrival,TDOA）室内无线传感网定位系统得到了越来越普遍的研究。其以距离测量为基础计算待测节点坐标。测距的误差影响定位结果的准确性。因此,文中主要目的是介绍基于超声波技术和射频技术定位系统的工作原理,通过采用总体最小二乘法（Total Least Square,TLS）的直线拟合方法对距离测量误差进行补偿,修正距离值,然后采用极小极大算法（Min-Max algorithm）进行定位的位置坐标计算,得到系统测距误差较小和定位准确性高的结果。实验数据仿真表明,该方法提高了距离测量精度和系统的定位准确性。     

融合2DPCA和模糊2DLDA的人脸识别

结合模糊集理论、双向二维主成分-线性鉴别分析((2D)2PCALDA)的特点,提出一种新的人脸图像特征提取方法。算法首先对人脸图像进行二维主成分分析(2DPCA)处理,再用模糊K近邻算法计算图像的隶属度矩阵,并将其融入到2DLDA过程中,从而得到模糊类间散射矩阵和模糊类内散射矩阵。与(2D2PCALDA相比,该算法充分利用了(2D)2PCALDA的优点,有效地提取了行和列的识别信息,并充分考虑了样本的分布信息。在Yale和FERET人脸数据库上的实验结果表明,该方法识别效果优于(2D)2PCALDA、双向二维主成分分析((2D)2PCA)等方法。     

结合极大似然距离估计的MDS-MAP节点定位算法

基于多维定标的定位算法通常利用节点间的最短路径长度代替欧式距离构建距离矩阵,当网络拓扑结构不规则时,会导致较大的定位误差。针对这一问题,提出了一种结合极大似然距离估计和多维定标的节点定位算法MDS-MAP（MLE）。算法将待测节点的一跳邻居节点信息作为极大似然方法的输入,利用与邻居节点的距离信息计算待测节点的相对坐标,然后根据已知锚节点的坐标,将所有节点的相对坐标映射为绝对坐标。实验结果表明,针对规则网络和不规则网络,MDS-MAP （MLE）算法均可取得较好的定位精度,且当网络连通度在一定范围内变化时,定位误差可保持在较低的稳定区间内。     

基于正则代数重建算法的二维温度场重建

在使用代数重建算法(Algebraic Reconstruction Technique,ART)对二维非均匀温度场进行重建时,离散误差和投影噪声会随着迭代修正被引入,为了平衡离散误差,减小算法对噪声的敏感度,在ART中引入了正则化项,并使用留一交叉验证法对单位正则化参数进行了选取,根据投影穿过待测区域路径的长度和单位正则化参数动态调整每条投影的正则化权重,实现了对每条投影离散误差和噪声水平的衡量。在不同的投影分布情况下,使用该算法对高斯单峰对称和高斯单峰偏置温度场进行了仿真重建,重建结果表明相比于传统迭代算法,该算法可有效提高温度场的重建精度,并且具有较好的稳定性。     

馈电网络子结构三端口散射参数测量方法研究

从多模馈电网络子结构的特性出发,对可能获取子结构三端口散射参数的方法进行了分析、比较,在现有二端口矢量网络分析仪的基础上,考虑了端口的阻抗匹配,对馈电网络子结构的三端口散射参数测量进行了实验研究,并应用混合模式散射参数验证了测量方法的准确性,为整个多模馈电网络的设计和优化提供有力的支持。     

An innovative method for determining hydrological calibration parameters for the WRF-Hydro model in arid regions

The techniques presented herein allow to directly determine certain crucial calibration parameters for the WRF-Hydro flood forecasting model. Typically, calibrations are chosen by an iterative, empirical, trial and error procedure. We suggest a more systematic methodology to arrive at a usable calibration. Our method is based on physical soil properties and does not depend on observed runoff from certain basins during specific storm events. Three specific calibration variables that most strongly affect the runoff predictions are addressed: topographic slope, saturated hydraulic conductivity, and infiltration. We outline a procedure for creating spatially distributed values for each of the three variables. Simulation runs are performed covering several storm events with calculated calibrations, with default values, and with an expert calibration. We show that our calibration, derived solely from soil physical properties, achieves forecast skill better than the default calibration and at least as good as an expert based calibration.     

Calibrating Borg scale ratings of hand force exertion

A study was conducted to assess the efficacy of calibrating subjective worker ratings of hand exertions to reduce error in estimates of applied force. Twenty volunteer subjects applied pinch and power grip forces corresponding to their perceptions of different Borg CR-10 scale levels using both "grip-to-scale" and "guided-grip" procedures. These data were used separately to define relationships between scale ratings and actual force application. Two gripping tasks were performed and corresponding subjective hand force ratings were calibrated using the grip-to-scale calibration data. Results showed that the mean estimation error for a 44.5 N (10 lb) power grip task was significantly reduced from 142.8 (+/-69.0) to 62.3 (+/-58.3) N. The guided-grip calibration method also significantly reduced rating error for the power grip task, however the estimates were biased toward zero. Neither calibration procedure improved rating accuracy of an 8.9 N (2 lb) pinch grip task. The study results indicate that calibration of hand force ratings using the grip-to-scale procedure may improve the accuracy of hand exertion measurements using the Borg CR-10 scale.     

On the thru‐reflect‐line (TRL) numerical calibration and error analysis for parameter extraction of circuit model

In this work, a resistor standard is introduced into our previously proposed numerical thru‐reflect‐line (TRL) calibration procedure in order to determine the characteristic impedance of the line standard of calibration on the basis of a deterministic method of moments (MoM) algorithm. A comprehensive analytical derivation is presented with regards to electrical properties of such a resistor standard in comparison to other standards. In addition, an error analysis is detailed, which reveals correlations of characteristic parameters in connection with equivalent circuit model development from the conversions from field‐based S‐parameters to circuit‐based Y‐ or Z‐parameters. Interesting properties and criteria are derived, allowing accurate parameter extractions. To validate the proposed numerical TRL calibration procedure with this new resistor standard concept and the developed error analysis, the characteristic impedance of a microstrip line is extracted from a commercial software. In addition, a further example with microstrip discontinuity is shown and the effectiveness of the proposed technique is verified. © 2006 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2006.     

温度敏感涂料校准误差实验研究

温度敏感涂料(Temperature Sensitive Paint, TSP)技术是一种极具潜力的光学测温技术,但其测量精度受到多源误差的影响。校准实验是TSP特性研究和风洞实验的关键而独立的阶段,其误差需要单独考虑。分析并明确了校准实验中的主要误差源,建立了各个误差因素不确定度评估方案。重点分析了校准数据拟合中的误差传递规律,提出了基于误差传播方程的TSP校准误差计算方法。误差源不确定度评估结果表明,通过控制校准实验中相机的工作范围和图像帧平均数量可以有效降低校准误差,进而可为TSP校准实验流程的精细化提供指导。TSP特性曲线误差计算结果表明,TSP校准误差在测温范围内呈现凹形分布,其引起的最大测温误差小于0.4 K;结果可直接用作风洞实验中校准误差的给定依据。     

MIV方法在苹果糖度近红外分析中的应用

针对苹果糖度近红外光谱数据的特点,分析了基于BP神经网络和偏最小二乘PLS的苹果糖度定量预测模型建立方法:,将平均影响值方法:(mean impact value)引入到近红外波长选取的过程中来,并与联合区间偏最小二乘法结合,达到波长优选的目的:。首先,利用联合区间偏最小二乘算法,筛选出与苹果的糖度相关度较大的光谱波长数据,再利用PLS-BP方法:建立预测模型。在此模型基础上,使用平均影响值方法:,对参与建模的每个波长数据进行评价,选取影响值最大的一系列波长点,重新建立模型。模型变量数为124,校正均方根误差(RMSEC)为0.1740,验证均方根误差(RMSEP)为0.4565。结果:表明,校正均方根误差,利用平均影响值与联合区间偏最小二乘方法:结合,对光谱数据进行波长的筛选,可以降低模型复杂度,同时提高模型预测精度。     

Calibration of an smt robot assembly cell

A new calibration method for an assembly robot cell is described. The proposed method is a combination of a model-free, numerical, relative robot calibration procedure and a procedure for the robot periphery calibration. Two important simplifications based on the study of an assembly process are introduced into the calibration strategy. A robot is calibrated in a task (Cartesian) space. The robot workspace and the number of calibrated degrees of freedom (dof) in the task space are reduced in accordance with the difficulty measure of the task. An automatic measurement system for measuring the relative robot accuracy was developed. An original principle of transforming the robot endpoint approach distance into the one-dimensional position displacement error is introduced. The accuracy errors of each particular calibrated dof in the task space is measured separately. The error tables are used in a direct robot calibration procedure that is based on the linear interpolation of the discrete position-error functions. An iterative inverse calibration algorithm used in a particular robot cell is described. An efficient sensor-based system for an additional simultaneous robot periphery calibration is presented. The implementation of the proposed calibration methodology in the pick-and-place robot cell for Surface Mount Technology (SMT) is presented. © 1994 John Wiley & Sons, Inc.     

Improved calibration method for SDINS considering body-frame drift

A calibration method for a strap-down inertial navigation system (SDINS) is presented here. The body-frame drift induced by the variation of the accelerometer sensing axe due to temperature changes is an important source of navigation error not considered in conventional calibration methods. In this paper, we propose an advanced calibration method that can compensate for SDINS error sources including not only bias, scale factor, and misalignment but also the body-frame drift by utilizing a 2-axis turntable. The body-frame drift is estimated using horizontal accelerometer measurements during a calibration procedure. Simulation results show that the body-frame drift behaves like an additional gyro bias error and that the proposed calibration technique can significantly improve pure navigation performance by removing the effect of body-frame drift.     

A robot hand-eye calibration method of line laser sensor based on 3D reconstruction

In the robotic eye-in-hand measurement system, a hand-eye calibration method is essential. From the perspective of 3D reconstruction, this paper first analyzes the influence of the line laser sensor hand-eye calibration error on the 3D reconstructed point clouds error. Based on this, considering the influence of line laser sensor measurement errors and the need for high efficiency and convenience in robotic manufacturing systems, this paper proposes a 3D reconstruction-based robot line laser hand-eye calibration method. In this method, combined with the point cloud registration technique, the newly defined error-index more intuitively reflects the calibration result than traditional methods. To raise the performance of the calibration algorithm, a Particle Swarm Optimization - Gaussian Process (PSO-GP) method is adopted to improve the efficiency of the calibration. The experiments show that the Root Mean Square Error (RMSE) of the reconstructed point cloud can reach 0.1256 mm when using the proposed method, and the reprojection error is superior to those using traditional hand-eye calibration methods.     

一种新型的二元函数分段插值误差校正方法

在对仪器系统误差各种校正方法分析的基础上,从二元函数泰勒级数展开式的模型出发,根据测量仪器输入输出的特定关系,提出了一种适用于交流电参量测量仪器系统误差校正的方法:先根据被测输入电压值进行分段插值校正,再根据被测信号的频率值进行分段插值校正.实验证明了该种方法编程容易实现,校准方便且效果好,具有一定的实用性.