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Improved RIP-based performance guarantees for multipath matching pursuit

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Science China(Information Sciences) 2018年第10期61卷 173-186页

作者： Juan ZHAO xia bai Ran TAO School of Information and Electronics Beijing Institute of Technology Beijing Key Laboratory of Fractional Signals and Systems Beijing Institute of Technology

The multipath matching pursuit(MMP) is a generalization of the orthogonal matching pursuit(OMP), which generates multiple child paths for every candidate in each iteration and selects the candidate having the minimal residual as the final support set when iteration ends. In this paper we analyze its performance in both noiseless and noisy cases. The restricted isometry property(RIP)-based condition of MMP that ensures accurate recovery of sparse signals in the noiseless case is derived by using a simple technique. The performance guarantees of the MMP for support recovery in noisy cases are also *** is shown that under certain conditions on the RIP and minimum magnitude of nonzero components of the sparse signal, the MMP will exactly recover the true support of the sparse signal in cases of bounded noises and recover the true support with a high probability in the case of Gaussian noise. Our bounds on the RIP improve the existing results.

关键词： compressed sensing(CS) sparse signal reconstruction multipath matching pursuit(MMP) support recovery restricted isometry property(RIP)

Voltage control of magnetization switching and dynamics

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Chinese Physics B 2018年第6期27卷 443-447页

作者： Hong-Yu Wen Jian-bai xia The State Key Laboratory of Superlattices and Microstructures Institute of Semiconductors Chinese Academy of Sciences Beijing 100083 China

The voltage controlled magnetic switching effect is verified experimentally. The Landau–Lifshitz–Gilbert（LLG）equation is used to study the voltage controlled magnetic switching. It is found that the initial values of magnetic moment components are critical for the switching effect, which should satisfy a definite condition. The external magnetic field which affects only the oscillation period should be comparable to the internal magnetic field. If the external magnetic field is too small, the switching effect will disappear. The precessions of mx and my are the best for the tilt angle of the external magnetic field θt = 0？, i.e., the field is perpendicular to the sample plane.

关键词： magnetic switching voltage control spin transfer torque Landau-Lifshitz-Gilbert (LLG) equa- tion

Spin flip in single quantum ring with Rashba spin–orbit interation

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Chinese Physics B 2018年第3期27卷 397-400页

作者： Duan-Yang Liu Jian-bai xia College of Science Beijing University of Chemical Technology Beijing 100029 China State Key Laboratory for Superlattice and Microstructures Institute of Semiconductors Chinese Academy of Sciences Beijing 100083 China

We theoretically investigate spin transport in the elliptical ring and the circular ring with Rashba spin-orbit interaction. It is shown that when Rashba spin-orbit interaction is relatively weak, a single circular ring can not realize spin flip, however an elliptical ring may work as a spin-inverter at this time, and the influence of the defect of the geometry is not obvious. Howerver if a giant Rashba spin-orbit interaction strength has been obtained, a circular ring can work as a spin-inverter with a high stability.

关键词： Rashba spin-orbit interaction quantum waveguide Aharonov-Bohm ring spin flip spin device

Electronic Structures of T-Shaped Quantum Wires

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Chinese Physics Letters 1997年第5期14卷 371-374页

作者： LI Shu-shen xia Jian-bai National Laboratory for Superlattices and Microstructures Institute of SemiconductorsChinese Academy of SciencesBeijing 100083

In this paper,we propose the periodic boundary condition which can be applied to a variety of semiconductor nanostructures to overcome the difficulty of solving Schrödinger equation under the natural boundary *** the barrier width is large enough,the average of the maximum and minimum of energy band under the periodic boundary condition is very close to the energy level obtained under the natural boundary *** an example,we take the GaAs/Ga_(1-x)Al_(x)As *** the width of the Ga_(1-x)Al_(x)As barrier is 200Å,the average of the maximum and minimum of energy band of the GaAs/Ga_(1-x)Al_(x)As superlattices is very close to the energy level of the GaAs/Ga_(1-x)Al_(x)As quantum wells(QWs).We give the electronic structure effective mass calculation of T-shaped quantum wires(T-QWRs)under the periodic boundary *** lateral confinement energies E1D-2D of electrons and holes,the energy difference between T-QWRs and QWs,are precisely determined.

关键词： boundary quantum periodic

Block Compressed Sensing Image Reconstruction Based on SL0 Algorithm

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Journal of Beijing Institute of Technology 2017年第3期26卷 357-366页

作者： Juan Zhao xia bai Jieqiong xiao School of Information and Electronics Beijing Institute of TechnologyBeijing 100081China Beijing Key Laboratory of Fractional Signals and Systems Beijing 100081China)

By applying smoothed l0norm（SL0）algorithm,a block compressive sensing（BCS）algorithm called BCS-SL0 is proposed,which deploys SL0 and smoothing filter for image ***,BCS-ReSL0 algorithm is developed to use regularized SL0（ReSL0）in a reconstruction process to deal with noisy *** study shows that the proposed BCS-SL0 takes less execution time than the classical BCS with smoothed projected Landweber（BCS-SPL）algorithm in low measurement ratio,while achieving comparable reconstruction quality,and improving the blocking artifacts *** experiment results also verify that the reconstruction performance of BCS-ReSL0 is better than that of the BCSSPL in terms of noise tolerance at low measurement ratio.

关键词： compressed sensing (CS) block smoothed l0 norm (SLO)

A Novel Long-Time Coherent Integration Method for Moving Target Detection

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Journal of Beijing Institute of Technology 2021年第4期30卷 340-351页

作者： xia bai Yan Wang Juan Zhao Ran Tao School of Information and Electronics Beijing Institute of TechnologyBeijing 100081China

Long-time coherent integration(LTCI)can remarkably improve the detection ability of radar for moving *** increase the processing efficiency,this paper proposes a novel LTCI method based on segment time reversing transform(STRT)and chirp z-transform(CZT).In this method,STRT operation is first presented to estimate the Doppler ambiguity factor,and keystone transform(KT)is used to correct the whole range migration(RM).Then,CZT and non-uniform fast Fourier transform(NUFFT)are used to estimate the parameters as well as correct the second and third order Doppler frequency migration(DFM).Compared with the existing methods,the proposed method can achieve RM correction and DFM correction without repetitive *** effectiveness of the proposed method is validated by both simulated and real data.

关键词： long-time coherent integration range migration Doppler frequency migration

Frequency-,radiation pattern-and polarization-reconfigurable antenna for wireless applications

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The Journal of China Universities of Posts and Telecommunications 2023年第1期30卷 87-92页

作者： bai xia Su Ming Wang Qingmin Liu Yang Gao Zhiwei School of Information Science and Technology Shijiazhuang Tiedao UniversityShijiazhuang 050043China School of Electronic Engineering Beijing University of Posts and TelecommunicationsBeijing 100876China

In this communication,a frequency-,radiation pattern-and polarization-reconfigurable antenna employing liquid metal is *** crossed dipole antennas are surrounded by four independent reflectors and directors to realize multi-beam *** length of dipole arms can be adjusted by extracting the liquid metal from the needle tube to achieve frequency *** polarization can be switched by injecting liquid metal into different dipole microfluidic *** is simple in design and has multiple reconfigurable *** antenna with a relative frequency tuning range of 35.8%extending from 2.43 GHz to 3.49 GHz is *** also can perform 6 kinds of beam steering over a 360°coverage and switch between two different *** antenna has potential to employ cognitive radio(CR)and base station in wireless systems.

关键词： reconfigurable antenna liquid metal crossed dipoles reflectors compound reconfiguration

Experimental investigation of wall-bounded turbulence drag reduction by active control of double piezoelectric vibrator

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Journal of Hydrodynamics 2020年第4期32卷 747-757页

作者： Jian-xia bai Yong-xiang Huang Nan Jiang Xing-yu Ma Zhan-qi Tang Department of Mechanics School of Mechanical EngineeringTianjin UniversityTianjin 300354China Department of Mathematics Tianjin University Renai CollegeTianjin 301636China State Key Laboratory of Marine Environmental Science College of Ocean and Earth SciencesXiamen UniversityXiamen 361102China Tianjin Key Laboratory of Modern Engineering Mechanics Tianjin 300354China

In order to manipulate the large-scale coherent structures in the wall-bounded turbulence and reduce the skin-friction,an active-control experimental investigation is performed by using the synchronous and asynchronous vibrations of double piezoelectric vibrators embedded spanwisely on a smooth flat plate surface.A TSI-IFA300 hot-wire anemometer and a TSI-1621 A-Tl.5 hot-wire probe are used to measure the time series of the instantaneous velocity at different *** influences of the vibrations on the wall-bounded turbulence are compared in a multi-scale point of view.A disturbance Reynolds Number Red=pd2 f/μis introduced to represent the disturbance.A probability density functions(PDFs)of the multi-scale components of the turbulence velocity and the multi-scale conditional phase-averaged waveform are studied in detail using the wavelet *** results show that the maximum drag reduction rate 18.54%is obtained at 100 V/160 Hz and Red=0.54 in the asynchronous vibration *** disturbances generated by the vibrators have a significant influence on the sweep events of the *** asynchronous vibration model is more effective than the synchronous vibration one.A possible physical mechanism is suggested to explain why the disturbance frequency of 160 Hz leads to an optimal parameter set for the drag reduction.

关键词： Wall-bounded turbulence active control drag reduction piezoelectric vibrator multi-scale analysis conditional phase-averaged wavefonns coherent structure

Simulation study and function analysis of the dynamic aortic valve

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Progress in Natural Science:Materials International 2006年第5期16卷 512-517页

作者： xia Dongdong and bai Jing (Department of Biomedical Engineering, Tsinghua University, Beijing 100084, China) Department of Biomedical Engineering Tsinghua University Beijing 100084 China

The dynamic aortic valve (DAV) is a new left ventricular assist device, a micro-axial blood pump implemented at the position of the aortic valve, pumping blood from the left ventricle into the aortic artery. The present dynamic aortic valve operates at 7 different rotation speeds, ranging from 3000 r/min (speed 1) to 9000 r/min (speed 7). Because in vivo experiments need a lot of live animals and take a long period of time, modeling and simulation have been widely used to simulate and analyze hydra-dynamic property of the DAV and its assisting effects. With the measurements from the mock circulatory loop, a mathematic model of the DAV is established and embedded into the previously developed canine circulatory system. Using this model, the effect of the DAV on the failing heart at each rotation speed level is investigated. The vital cardiac variables are computed and compared with in vivo experimental results, which are in good agreement with an acceptable difference mostly 15%. The establishment of the DAV model and its simulation are useful for further improvement of the DAV device.

关键词： dynamic aortic valve mathematic model computer simulation.