检索结果-南通市图书馆

Chinese Journal of Electronics 2016年第1期25卷 100-105页

作者： GAO Fei ZHANG Ye WANG Jun SUN Jinping School of Electronic and Information Engineering Beihang University

S transform is a time-frequency representation which has been applied in various fields, yet suffers the problem of time and resource consumption. In order to overcome this problem and facilitate its application in image analysis, we introduce a fast algorithm for inverse twodimensional S transform. A two-dimensional S transform time-frequency filter for Synthetic aperture radar(SAR)image despeckling is proposed on the basis of this fast algorithm. Synthetic and actual SAR images are both used to quantitatively evaluate its performance. The proposed algorithm is compared with several classical algorithms with better results both in speckle noise reduction and detail preservation.

关键词： time-frequency representation Fast al gorithm Two-dimensional S transform time-frequency filter Synthetic aperture radar(SAR) image Speckle noise reduction

Scattering center modeling for low-detectable targets

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Systems Engineering and Electronics 2022年第3期33卷 511-521页

作者： CHEN Yanxi GUO Kunyi XIAO Guangliang SHENG Xinqing Institute of Radio frequency Technology and Software School of Integrated Circuits and ElectronicsBeijing Institute of TechnologyBeijing 100081China

The scattering centers(SCs)of low-detectable targets(LDTs)have a low scattering *** is difficult to build the SC model of an LDT using the existing methods because these methods mainly concern dominant SCs with strong scattering *** paper presents an SC modeling approach to acquire the weak SCs of *** employ the induced currents at the LDT to search SCs,and the joint time-frequency transform together with the Hough transform to separate the scattering contributions of different *** swarm optimization(PSO)is applied to improve the estimation results of *** accuracy of the SC model built by this approach is verified by a full-wave numerical *** validation results show that the SC model of the LDT can precisely simulate the signatures of high-resolution images,such as high-resolution range profile and inverse synthetic aperture radar(ISAR)images.

关键词： low-detectable target(LDT) stealth target scattering center(SC)model time-frequency representation full-wave method

Scattering Center Modeling Using Adaptive Segmental Compressive Sampling

在线全文

学校读者我要写书评

暂无评论

Journal of Beijing Institute of Technology 2017年第4期26卷 484-493页

作者： Qifeng Li Kunyi Guo Jiaxin Wang Xinqing Sheng Tianshu Liu Center for Electromagnetic Simulation School of Information and ElectronicsBeijing Institute of Technology Science and Technology on Special System Simulation Laboratory Beijing Simulation Center

In order to deal with aliasing distortions of Doppler frequencies shown in time-frequency representation（ TFR） with aspect undersampling,an approach using adaptive segmental compressive sampling according to the aspect dependencies of the scattering centers is proposed. The random noise problem induced by compressive sampling is solved by employing a series of signal processing techniques of filtering,image transformation and Hough Transform. Three examples are presented to verify the effectiveness of this approach. The comparisons between the built models and the precise scattered fields computed by a well-validated full-wave numerical method are investigated,and the results showgood agreements between each other.

关键词： scattering center undersampling compressive sensing time-frequency representation parameter estimation

Complex matrix interpolation model of the S-transform for electric load movement forecast

在线全文

学校读者我要写书评

暂无评论

International Journal of Modeling, Simulation, and Scientific Computing 2014年第3期5卷 153-170页

作者： Yang Zong-Chang School of Information and Electrical Engineering Hunan University of Science and Technology Xiangtan P.R.China 411201

Electric load movement forecast is increasingly importance for the *** study addresses the load movement forecast modeling based on complex matrix interpolation of the S-transform(ST).In complex matrix of time-frequency representation of the ST,each row follows conjugate symmetric property and each column appears a certain degree of *** on these characteristics,a complex matrix interpolation method for the time-frequency representation of the ST is proposed to interpolate each row of the complex matrix based on the conjugate symmetric property,and then to perform nearestneighbor interpolation on each *** with periodic extension for daily and yearly electric load movement,a forecast model employing the complex matrix interpolation of the ST is *** forecast approach is applied to predict daily load movement of the European Network on Intelligent Technologies(EUNITE)load dataset and annual electric load movement of State Gird Corporation of China and its branches in 2005 and *** analysis indicates workability and effectiveness of the proposed method.

关键词： S-transform time-frequency representation complex matrix interpolation electric load movement forecast

Testing for Nonlinearity in Dynamic Characteristics of Vertical Upward Oil-Gas-Water Three-phase Bubble and Slug Flows

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Chemical Engineering 2012年第5期20卷 870-882页

作者：朱雷金宁德高忠科杜萌王振亚 School of Electrical Engineering&Automation Tianjin University

Based on the conductance fluctuation signals measured from vertical upward oil-gas-water three-phase flow experiment, time frequency representation and surrogate data method were used to investigate dynamical characteristics of oil-in-water type bubble and slug flows. The results indicate that oil-in-water type bubble flow will turn to deterministic motion with the increase of oil phase fraction f o and superficial gas velocity U sg under fixed flowrate of oil-water mixture Q mix . The dynamics of oil-in-water type slug flow becomes more complex with the increase of U sg under fixed flowrate of oil-water mixture. The change of f o leads to irregular influence on the dynamics of slug flow. These interesting findings suggest that the surrogate data method can be a faithful tool for characterizing dynamic characteristics of oil-in-water type bubble and slug flows.

关键词： oil-gas-water three-phase flow conductaJace fluctuating signals time-frequency representation surrogate data method

A fast time-frequency response based differential spectral energy protection of AC microgrids including fault location

在线全文

学校读者我要写书评

暂无评论

Protection and Control of Modern Power Systems 2017年第1期2卷 331-358页

作者： O.Dharmapandit R.K.Patnaik P.K.Dash Electrical Engineering Department Institute of Technical Education and ResearchInstitute of Technical Education and ResearchSiksha O Anusandhan UniversityBhubaneswar-751030India. Electrical and Electronics Engineering Department GMR Instittute of TechnologyRajamAndhra Pradesh-532127India.

This paper proposes a pattern recognition based differential spectral energy protection scheme for ac microgrids using a Fourier kernel based fast sparse time-frequency representation(SST or simply the sparse S-Transform).The average and differential current components are passed through a change detection filter,which senses the instant of fault inception and registers a change detection point(CDP).Subsequently,if CDP is registered for one or more phases,then half cycle data samples of the average and differential currents on either side of the CDP are passed through the proposed SST technique,which generates their respective spectral energies and a simple comparison between them detects the occurrence and type of the *** SST technique is also used to provide voltage and current phasors and the frequency during faults which is further utilized to estimate the fault *** proposed technique as compared to conventional differential current protection scheme is quicker in fault detection and classification,which is least effected from bias setting,has a faster relay trip response(less than one cycle from fault incipient)and a better accuracy in fault *** significance and accuracy of the proposed scheme have been verified extensively for faults in a standard microgrid system,subjected to a large number of operating conditions and the outputs vindicate it to be a potential candidate for real time applications.

关键词： Microgrid Differential spectral energy protection time-frequency representation Fault classification Fault location

Application of Local Wave time-frequency Spectrum and Neural Networks to Fault Classification in Rotating Machine

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

International Journal of Plant Engineering and Management 2005年第1期10卷 36-41页

作者： HAOZhi-hua MAXiao-jiang InstituteofVibrationEngineering DalianUniversityofTechnologyDalian116024P.R.China／／TangshanCollegeTangshan063000P.R.China InstituteofVibrationEngineering DalianUniversityofTechnologyDalian116024P.R.China

A new method of fault analysis and detection by signal classification inrotating machines is presented. The Local Wave time-frequency spectrum which is a new method forprocessing a non-stationary signal is used to produce the representation of the signal. This methodallows the decomposition of one-dimensional signals into intrinsic mode functions (IMFs) usingempirical mode decomposition and the calculation of a meaningful multi-component instantaneousfrequency. Applied to fault signals , it provides new time-frequency attributes. Then the momentsand margins of the time-frequency spectrum are calculated as the feature vectors. The probabilisticneural network is used to classify different fault modes. The accuracy and robustness of theproposed methods is investigated on signals obtained during the different fault modes (early rub,loose, misalignment of the rotor).

关键词： signal classification neural network local wave empirical modedecomposition time-frequency representation