Wideband spectrum sensing using step-sampling based on the multipath nyquist folding receiver

Wideband spectrum sensing with a high-speed analog-digital converter(ADC) presents a challenge for practical systems.The Nyquist folding receiver(NYFR) is a promising scheme for achieving cost-effective real-time spectrum sensing,which is subject to the complexity of processing the modulated outputs.In this case,a multipath NYFR architecture with a step-sampling rate for the different paths is proposed.The different numbers of digital channels for each path are designed based on the Chinese remainder theorem(CRT).Then,the detectable frequency range is divided into multiple frequency grids,and the Nyquist zone(NZ) of the input can be obtained by sensing these grids.Thus,high-precision parameter estimation is performed by utilizing the NYFR characteristics.Compared with the existing methods,the scheme proposed in this paper overcomes the challenge of NZ estimation,information damage,many computations,low accuracy,and high false alarm probability.Comparative simulation experiments verify the effectiveness of the proposed architecture in this paper.

Electrolytic Sampling from Pure Copper and Common Brasses Ⅰ: Calculation of the Mass Dissolved from the Samples according to Faraday's Law

In a procedure for electrolytic dissolving pure copper and common brasses, the approximate electrochemical mole mass(k) of the sample was determined in accordance with the brand of the sample, a stitable electrolyte was selected to make the current efficiency equal to 100%, and then the dissolved mass of samples was calculated according to Faraday's law(m=klt).Three representative samples were sampled by the electrolytic dissolution method and the calculated dissolved amounts were equal to the values by weighing the anode.The cxperimental results of zinc and copper in the anode liquor are in agreement with certified values.

S/N Ratio of 4-Channel A/D Geological Radar Non-uniform Sampling Signals

Using the quantitative error probability density method we studied the S/N ratio of alternately sampled signals digitized by a 4-channel A/D. A complete expression for the S/N ratio of a 4-channel A/D non-uniform sampling signal was deduced. First we obtained an expression for the S/N ratio of a 1-channel A/D uniform sampling signal when the sampling frequency was equal to or greater than 2 times the frequency of the sampled signal. Based on the S/N ratio of a 2-channel A/D,alternating,non-uniform sampling signal,we analyzed the distribution of quantitative error using the quantitative error probability density method and the distribution convolution formula. From this the S/N ratio expression of a 4-channel A/D sampling signal was deduced. The simulation result shows that the deduced expression is correct.

Acceptance Sampling Plans with Truncated Life Tests for the Length-Biased Weighted Lomax Distribution

In this paper,we considered the Length-biased weighted Lomax distribution and constructed new acceptance sampling plans(ASPs)where the life test is assumed to be truncated at a pre-assigned time.For the new suggested ASPs,the tables of the minimum samples sizes needed to assert a specific mean life of the test units are obtained.In addition,the values of the corresponding operating characteristic function and the associated producer’s risks are calculated.Analyses of two real data sets are presented to investigate the applicability of the proposed acceptance sampling plans;one data set contains the first failure of 20 small electric carts,and the other data set contains the failure times of the air conditioning system of an airplane.Comparisons are made between the proposed acceptance sampling plans and some existing acceptance sampling plans considered in this study based on the minimum sample sizes.It is observed that the samples sizes based on the proposed acceptance sampling plans are less than their competitors considered in this study.The suggested acceptance sampling plans are recommended for practitioners in the field.

Improved Attribute Chain Sampling Plan for Darna Distribution

Recently,the Darna distribution has been introduced as a new lifetime distribution.The two-parameter Darna distribution represents is a mixture of two well-known gamma and exponential distributions.A manufacturer or an engineer of products conducts life testing to examine whether the quality level of products meets the customer’s requirements,such as reliability or the minimum lifetime.In this article,an attribute modified chain sampling inspection plan based on the time truncated life test is proposed for items whose lifetime follows the Darna distribution.The plan parameters,including the sample size,the acceptance number,and the past lot result of the proposed sampling plan,are determined with the help of the two-point approach considering the acceptable quality level(AQL)and the limiting quality level(LQL).The plan parameters and the corresponding operating characteristic functions of a new plan are provided in tabular form for various Darna distribution parameters.Also,a few illustrated examples are presented for various distribution parameters.The usefulness of the proposed attribute modified chain sampling plan is investigated using two real failure time datasets.The results indicate that the proposed sampling plan can reduce the sample size when the termination ratio increases for fixed values of the producer’s risk and acceptance number.Hence,the proposed attribute modified chain sampling inspection plan is recommended to practitioners in the field.

Analysis of the Linear Sampling Method for Boundary Reconstruction of Chiral Obstacle in Electromagnetic Scattering Problems

In this paper, we consider the inverse scattering by chiral obstacle in electromagnetic fields, and prove that the linear sampling method is also effective to determine the support of a chiral obstacle from the noisy far field data.

SAMPLING FORMULAE OF HIGHER ORDER

Shannon sampling theorem is the basic theorem in signal reconstruction based ondiscrete sampling values in communication theory. The convergence rate of thisformula, however, is very slow. Professor Pen Rui-reng. after some slight compromiseon sampling rate, has come to the 3rd order, the 4th order and the 5th order samplingformulae. The calculation of the third order formula on the computer proves that itconverges much faster than the Shannon formula. This paper gives a general methodto comstruct a higher order sampling formula.

Assessing the Performance of Some Ranked Set Sampling Designs Using Hybrid Approach

In this paper,a joint analysis consisting of goodness-of-fit tests and Markov chain Monte Carlo simulations are used to assess the performance of some ranked set sampling designs.The Markov chain Monte Carlo simulations are conducted when Bayesian methods with Jeffery’s priors of the unknown parameters of Weibull distribution are used,while the goodness of fit analysis is conducted when the likelihood estimators are used and the corresponding empirical distributions are obtained.The ranked set sampling designs considered in this research are the usual ranked set sampling,extreme ranked set sampling,median ranked set sampling,and neoteric ranked set sampling designs.An intensive Monte Carlo simulation study is conducted using Lindley’s approximation algorithm to compute the different designs’-based estimators.The study showed that the dependent design“neoteric ranked set sampling design”is superior to other ranked set designs and the total relative efficiency is higher than the other designs’total relative efficiency.

Designing Bayesian Two-Sided Group Chain Sampling Plan for Gamma Prior Distribution

Acceptance sampling is used to decide either the whole lot will be accepted or rejected,based on inspection of randomly sampled items from the same lot.As an alternative to traditional sampling plans,it is possible to use Baye-sian approaches using previous knowledge on process variation.This study pre-sents a Bayesian two-sided group chain sampling plan(BTSGChSP)by using various combinations of design parameters.In BTSGChSP,inspection is based on preceding as well as succeeding lots.Poisson function is used to derive the probability of lot acceptance based on defective and non-defective products.Gamma distribution is considered as a suitable prior for Poisson distribution.Four quality regions are found,namely:(i)quality decision region(QDR),(ii)probabil-istic quality region(PQR),(iii)limiting quality region(LQR)and(iv)indifference quality region(IQR).Producer’s risk and consumer’s risk are considered to esti-mate the quality regions,where acceptable quality level(AQL)is associated with producer’s risk and limiting quality level(LQL)is associated with consumer’s risk.Moreover,AQL and LQL are used in the selection of design parameters for BTSGChSP.The values based on all possible combinations of design parameters for BTSGChSP are presented and inflection points’values are found.Thefinding exposes that BTSGChSP is a better substitute for the existing plan for industrial practitioners.

Major Data of China's 1% National Population Sampling Survey,1995

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基于Sub-Nyquist采样的单通道频谱感知技术

宽带频谱感知技术在认知无线电中具有广泛的应用。基于时分的思想,将信号采集时间以固定长度的时间片进行划分,分别与不同的伪随机码信号相乘,经过低通滤波和sub-Nyquist采样,利用采样数据求出信号的频率支集。与已有的多通道频谱感知结构相比,本文用相对简单的单通道结构实现,同样能够利用低速率的采样点完成频谱感知。仿真实验结果表明,在信号的频率支集未知的情况下,该算法能够有效利用sub-Nyquist采样的数据实现频谱感知。

基于高度冗余Gabor框架的欠Nyquist采样系统子空间探测

基于指数再生窗Gabor框架的欠Nyquist采样系统对窄脉冲信号完成采样与重构一般情况下效果较好,但是当框架高度冗余时,使用传统面向系数域的方法对信号进行子空间探测会面临失败或较大误差。该文采用面向信号域的思想,构建了分块的对偶Gabor字典,并对信号分块稀疏表示;根据信号的分块表示推导了采样系统的测量矩阵,提出了测量矩阵受字典相干性约束的分块e-相干性;将信号合成模型引入多观测向量问题,提出基于分块e-闭包的同步正交匹配追踪算法(,B FSOMPe),用于信号子空间探测。此外还证明了算法的收敛约束条件。仿真结果表明,所提子空间探测方法相比传统方法提高了信号重构成功率,降低了采样通道数,并增强了系统鲁棒性。

稀疏信号欠Nyquist采样与重构研究现状分析

传统的信号采样理论要求采样频率需高于Nyquist频率(信号最高频率)的两倍,给射频及超宽带领域的信号采样、存储和传输造成巨大压力。近年来针对可以进行稀疏表示的信号,欠Nyquist采样技术取得了很大的发展,大大降低了精确重构原始信号所需的采样率。综述性地归纳了目前可以进行欠Nyquist采样的信号模型,将出现的各种欠Nyquist采样总结为一个基本模型,并针对频域稀疏和时域稀疏信号分别对采样模型及原理进行了阐述,分析了采样信号的子空间探测和重建方法,讨论了稀疏信号欠Nyquist采样与重构的实现与应用现状,并对研究前景进行了展望。

利用字典优化方法实现sub-Nyquist采样数据的频率估计

在稀疏重构理论中,重构信号需要预先设定稀疏表示字典,针对预设字典与真实字典之间的失配对信号稀疏表示造成的不利影响,提出一种基于字典优化和稀疏贝叶斯学习(Sparse Bayesian Learning,SBL)的频率估计算法。该算法首先构造基于sub-Nyquist采样数据的信号稀疏表达式,然后利用SBL算法估计信号频率,同时根据估计结果优化字典,最后反复迭代上述步骤直至计算出的频率值和对应的幅度值趋于稳定。仿真结果校验了方法的有效性。

基于Nyquist采样的椭圆球面波函数数值解法

为了解决椭圆球面波函数数值解法时积分方程该如何离散化以及采用何种方法求取实对称矩阵的特征值和特征向量问题,提出了基于奈奎斯特采样的椭圆球面波函数数值解法。该数值解法利用奈奎斯特采样定理确定的采样频率对积分方程进行离散化,利用Jacobi方法求取实对称矩阵的全部特征值和相应的特征向量,求得的特征向量就是椭圆球面波函数的近似数值解。对基于奈奎斯特采样的椭圆球面波函数数值解法进行了理论推导、性能分析和仿真。理论分析和仿真结果表明,该数值解法方法简单,实用性强,求得的椭圆球面波函数精度高,椭圆球面波函数之间正交性好。

ADASYN与类别逆比例加权法在阿尔茨海默病不平衡数据中的应用

目的利用自适应合成抽样(adaptive synthetic sampling,ADASYN)与类别逆比例加权法处理类别不平衡数据,结合分类器构建模型对阿尔茨海默病(alzheimer′s disease,AD)患者疾病进程进行分类预测。方法数据源自阿尔茨海默病神经影像学计划(Alzheimer′s disease neuroimaging initiative,ADNI),经随机森林填补缺失值,弹性网络筛选特征子集后,利用ADASYN与类别逆比例加权法处理类别不平衡数据。分别结合随机森林(random forest,RF)、支持向量机(support vector machine,SVM)构建四种模型:ADASYN-RF、ADASYN-SVM、加权随机森林(weighted random forest,WRF)、加权支持向量机(weighted support vector machine,WSVM),与RF、SVM比较分类性能。模型评价指标为宏观平均精确率(macro-average of precision,macro-P)、宏观平均召回率(macro-average of recall,macro-R)、宏观平均F1值(macro-average of F1-score,macro-F1)、准确率(accuracy,ACC)、Kappa值和AUC(area under the ROC curve)。结果ADASYN-RF的分类性能最优(Kappa值为0.938,AUC为0.980),ADASYN-SVM次之。利用ADASYN-RF预测得到的重要分类特征分别为CDRSB、LDELTOTAL、MMSE,在临床上均可得到证实。结论ADASYN与类别逆比例加权法都能辅助提升分类器性能,但ADASYN算法更优。

基于CD-BSMOTE的D-S证据融合变压器故障诊断

针对变压器油中溶解气体数据集不均衡特性对故障诊断结果的影响,提出一种基于清除临界点改进的边界合成少数类过采样算法均衡数据集和Pearson冲突距离改进D-S证据融合的变压器故障诊断模型。首先,对少数类样本进行均衡化处理,根据K-means聚类结果清除处于临界位置的样本;其次,搭建梯度提升树、随机森林、BP神经网络的故障诊断模型,实现变压器故障初步诊断;接着引入Pearson冲突距离改进D-S证据融合模型,实现诊断结果的融合决策;最后,经实际算例分析,诊断精确率达到92.65%。结果表明,所建模型能有效解决数据不平衡对诊断结果的影响,提高故障诊断精度。

基于傅里叶系数实部的脉冲流信号欠Nyquist采样方法

有限新息率(FRI)采样理论可以远低于信号Nyquist频率的采样速率实现对脉冲流信号的欠采样。经典的FRI重构算法大多基于傅里叶系数进行运算,其中存在大量的对复数矩阵的奇异值分解,降低了算法的执行效率。针对该问题,该文提出基于傅里叶系数实部的脉冲流信号FRI采样及重构方法。首先利用离散余弦变换从脉冲流信号的低速采样值中获取其傅里叶系数实部信息,并在重构算法中使用实部的Toeplitz矩阵以提高奇异值分解(SVD)的效率;其次,为了提升经典的零化滤波器算法的鲁棒性,该文从傅里叶系数实部协方差矩阵的旋转不变特性以及零空间特性出发,提出基于离散余弦变换的协方差矩阵分解算法以及基于离散余弦变换的零空间搜索算法来估计脉冲流信号的特征参数,并针对出现的共轭根问题,提出基于交替方向乘子法的去共轭算法。仿真结果表明:在信号新息率较高的情况下,使用傅里叶系数实部信息会极大提高算法的执行效率,同时保证参数估计的准确性。

Scanning electron microscopy coupled with energydispersive X-ray spectrometry for quick detection of sulfuroxidizing bacteria in environmental water samples

Detection of sulfur-oxidizing bacteria has largely been dependent on targeted gene sequencing technology or traditional cell cultivation, which usually takes from days to months to carry out. This clearly does not meet the requirements of analysis for time-sensitive samples and/or complicated environmental samples. Since energy-dispersive X-ray spectrometry(EDS) can be used to simultaneously detect multiple elements in a sample, including sulfur, with minimal sample treatment, this technology was applied to detect sulfur-oxidizing bacteria using their high sulfur content within the cell. This article describes the application of scanning electron microscopy imaging coupled with EDS mapping for quick detection of sulfur oxidizers in contaminated environmental water samples, with minimal sample handling. Scanning electron microscopy imaging revealed the existence of dense granules within the bacterial cells, while EDS identified large amounts of sulfur within them. EDS mapping localized the sulfur to these granules. Subsequent 16S rRNA gene sequencing showed that the bacteria detected in our samples belonged to the genus Chromatium, which are sulfur oxidizers. Thus, EDS mapping made it possible to identify sulfur oxidizers in environmental samples based on localized sulfur within their cells, within a short time(within 24 h of sampling). This technique has wide ranging applications for detection of sulfur bacteria in environmental water samples.

Fault tolerant synchronization of chaotic systems based on T-S fuzzy model with fuzzy sampled-data controller

In this paper the fault tolerant synchronization of two chaotic systems based on fuzzy model and sample data is investigated. The problem of fault tolerant synchronization is formulated to study the global asymptotical stability of the error system with the fuzzy sampled-data controller which contains a state feedback controller and a fault compensator. The synchronization can be achieved no matter whether the fault occurs or not. To investigate the stability of the error system and facilitate the design of the fuzzy sampled-data controller, a Takagi Sugeno （T-S） fuzzy model is employed to represent the chaotic system dynamics. To acquire good performance and produce a less conservative analysis result, a new parameter-dependent Lyapunov-Krasovksii functional and a relaxed stabilization technique are considered. The stability conditions based on linear matrix inequality are obtained to achieve the fault tolerant synchronization of the chaotic systems. Finally, a numerical simulation is shown to verify the results.