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Dual-Energy Technique at Low Tube Voltages for Small Animal Imaging

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Tsinghua Science and Technology 2010年第1期15卷 79-86页

作者： CHO Seungryong SIDKY Emil Y Department of Radiology University of ChicagoChicagoIL 60637USA

We investigate the feasibility of dual-energy method for image contrast enhancement in small animal studies using a low kV X-ray radiographic system. A robust method for X-ray spectrum estimation from transmission measurements, based on expectation-maximization （EM） method, is applied to an X-ray specimen radiographic system for dual energy imaging of a mouse. From transmission measurements of two known attenuators at two different X-ray tube voltages, the X-ray energy spectra are reconstructed using the EM-based method. From the spectra information thus obtained, the transmission data for bone and soft tissue in terms of vadous thicknesses are generated. Two polynomial functions of transmission data are then sought for to fit the inverted thicknesses of bone and soft-tissue. Scatters in cone-beam projection data acquired at two X-ray energies were corrected. From the scatter-corrected data, a bone thickness map is separated from a soft-tissue thickness map by use of the polynomial functions.

关键词： dual-energy specimen radiography spectrum estimation

Improvement of Attributed Scattering Center Extraction by Using SAR Super-Resolution Preprocessing

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Journal of Beijing Institute of Technology 2023年第6期32卷 685-695页

作者： Guozhen Cheng Jiacheng Chen Fengming Hu Feng Xu Key Laboratory for Information Science of Electromagnetic Waves(MoE) Fudan UniversityShanghai 200433China

Synthetic aperture radar(SAR)is able to acquire high-resolution method using the active microwave imaging *** images are widely used in target recognition,classification,and surface analysis,with extracted *** scattering center(ASC)is able to describe the image features for these ***,sidelobe effects reduce the accuracy and reliability of the estimated ASC model *** paper incorporates the SAR super-resolution into the ASC extraction to improve its *** filter bank and subspace methods are demonstrated for preprocessing to supress the *** on the preprocessed data,a reinforcement based ASC method is used to get the *** experimental results show that the super-resolution method can reduce noise and suppress sidelobe effect,which improve accuracy of the estimated ASC model parameters.

关键词： synthetic aperture radar(SAR) spectrum estimation attributed scattering center(ASC) reinforcement learning

Studies on MB-SAR 3D imaging algorithm using Yule-Walker method

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Science China(Information Sciences) 2010年第9期53卷 1848-1859页

作者： WANG Bin1,2*,WANG YanPing1,HONG Wen1,TAN WeiXian1,2 & WU YiRong1 1National Key Laboratory of Microwave Imaging Technology,Institute of Electronics,Chinese Academy of Sciences,Beijing 100190,China 2Graduate University of Chinese Academy of Sciences,Beijing 100049,China National Key Laboratory of Microwave Imaging Technology Institute of Electronics Chinese Academy of Sciences Beijing China Graduate University of Chinese Academy of Sciences Beijing China

Multibaseline synthetic aperture radar(MB-SAR) can form a synthetic aperture in the height direction with multiple parallel observations,so it has the resolving capability in the height direction and can realize three-dimensional(3D) imaging for the *** analytic model of MB-SAR based on spectrum estimation is analyzed in this *** on the more general geometric model,we derive the signal model for MB-SAR 3D *** then Yule-Walker algorithm is proposed to realize MB-SAR 3D imaging meanwhile the principle is analyzed and the steps of Yule-Walker algorithm are *** algorithm can get the 3D image of the target with high resolution using fewer ***,the experimental results of MB-SAR 3D imaging using Yule-Walker algorithm are presented,which are generated with the simulated data and the data collected in anechoic chamber.

关键词： MB-SAR 3D SAR imaging algorithm SAR spectrum estimation Yule-Walker method

Coherent Doppler lidar wind retrieval for a typhoon based on the genetic simulated annealing algorithm

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Chinese Optics Letters 2024年第4期22卷 1-7页

作者：刘珍原禄城汤杰张云鹏刘继桥竹孝鹏杨巨鑫时伟陈卫标 Aerospace Laser Technology and Systems Department Shanghai Institute of Optics and Fine MechanicsChinese Academy of SciencesShanghai 201800China Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of SciencesBejing 100049China Shanghai Typhoon Institute China Meteorological AdministrationShanghai 200030China

A method of spectrum estimation based on the genetic simulated annealing(GSA)algorithm is proposed,which is applied to retrieve the three-dimensional wind field of typhoon Nangka observed by our research *** to the genetic algorithm(GA),the GSA algorithm not only extends the detection range and guarantees the accuracy of retrieval results but also demonstrates a faster retrieval *** results indicate that both the GA and GSA algorithms can enhance the detection range by 35%more than the least squares ***,the convergence speed of the GSA algorithm is 17 times faster than that of the GA,which is more beneficial for real-time data processing.

关键词： coherent Doppler lidar three-dimensional wind field retrieval genetic simulated annealing algorithm spectrum estimation typhoon

Two modified discrete chirp Fourier transform schemes

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Science in China(Series F) 2001年第5期44卷 329-341页

作者：樊平毅夏香根 TheStateKeyLaboratoryonMicrowaveandDigitalCommunications DepartmentofElectronic~gineeringTsinghuaUniversityBeijing100084China DepartmentofElectricalandComputerEngineering UniversityofDelawareNewarkDE19711USA

This paper presents two modified discrete chirp Fourier transform (MDCFT) schemes. Some matched filter properties such as the optimal selection of the transform length, and its relation-ship to analog chirp-Fourier transform are studied. Compared to the DCFT proposed previously, theo-retical and simulation results have shown that the two MDCFTs can further improve the chirp rate reso-lution of the detected signals.

关键词： discrete chirp Fourier transform signal detection spectrum estimation synthetic aperture radar.

A method for improving the performance of MVDR beamforming

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Chinese Journal of Acoustics 1995年第1期14卷 19-26页

作者： ZHU Shimeng SONG Mingkai and GONG Xianyi (Hangzhou Applied Acoustics Research Institute. Hangzhou 311400) Hangzhou Applied Acoustics Research Institute Hangzhou 311400 SU.EDU

Minimum Variance Distortionless signal Response (MVDR) beamforming can be used as a wavenumber spectrum (bearing) estimation, whose precision or resolution is deter mined primarily by signal-to-noise ratio. This paper presents a method for improving MVDR beamforming bearing resolution by using an enhancement factor in its weight vector design for emulating a high signal-to-noise ratio condition which is known to be a principal factor in res olution improvement. This method can providc improved rcsolution not at the expense of sig nal-to noise plus interference ratio gain. Some of computer simulation results are also given.

关键词： MVDR beamforming spectrum estimation Bearing resolution