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Hierarchical Feature-Based Detection Method for SAR Targets Under Complex Environment

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Chinese Journal of Electronics 2017年第3期26卷 647-653页

作者： GAO Fei MA Fei LUO Xiling WANG Jun SUN Jinping school of Electronic and {1. engineering Beihang University

A reliable target detection method for Synthetic aperture radar(SAR)images is needed urgently with the wide application of SAR *** performance of conventional detection algorithms,such as Constant false alarm rate(CFAR),degrade significantly in low SCR or complex regions while the Human visual system(HVS)can identify targets of interest without knowing characteristics of the background even in complicated *** combination of HVS with the SAR-ATR system may effectively achieve real-time multi-target detection in complex occlusion scenes.A new effective target detection algorithm is put forward using hierarchical characteristics of *** by different roles of the retina and visual cortex in the HVS,this detection algorithm is divided into coarse detection and fine detection *** kinds of features based on the correlation between target features and suspicious targets,namely overall feature and refined feature,are used in these two stages respectively to extract real *** results verify its correctness and effectiveness in complex environment.

关键词： Synthetic aperture radar(SAR) Targets detection Human visual system(HVS) Complex background Hierarchical model and X(HMAX)

Efficient schedulability analysis for mixed-criticality systems under deadline-based scheduling

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Chinese Journal of Aeronautics 2014年第4期27卷 856-866页

作者： Chen Yao Li Qiao Li Zheng Xiong Huagang school of Electronic and {1. engineering Beihang University

Safety-critical avionics systems which become more complex and tend to integrate multiple functionalities with different levels of criticality for better cost and power efficiency are subject to certifications at various levels of rigorousness. In order to simultaneously guarantee temporal constraints at all different levels of assurance mandated by different criticalities, novel scheduling techniques are in need. In this paper, a mixed-criticality sporadic task model with multiple virtual deadlines is built and a certification-cognizant dynamic scheduling approach referred as earliest virtual-deadline first with mixed-criticality（EVDF-MC） is considered, which exploits different relative deadlines of tasks in different criticality modes. As for the corresponding schedulability analysis problem, a sufficient and efficient schedulability test is proposed on the basis of demand-bound functions derived in the mixed-criticality scenario. In addition, a modified simulated annealing（MSA）-based heuristic approach is established for virtual deadlines assignment. Experiments performing simulations with randomly generated tasks indicate that the proposed approach is computationally efficient and competes well against the existing approaches.

关键词： Avionics systems Mixed-criticality Real-time scheduling Schedulability analysis Simulated annealing

ISAR imaging based on improved phase retrieval algorithm

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Journal of Systems engineering and Electronics 2018年第2期29卷 278-285页

作者： SHI Hongyin XIA Saixue TIAN Ye school of {1. Science and engineering Yanshan University

Traditional inverse synthetic aperture radar(ISAR)imaging methods for maneuvering targets have low resolution and poor capability of noise suppression. An ISAR imaging method of maneuvering targets based on phase retrieval is proposed,which can provide a high-resolution and focused map of the spatial distribution of scatterers on the target. According to theoretical derivation, the modulus of raw data from the maneuvering target is not affected by radial motion components for ISAR imaging system, so the phase retrieval algorithm can be used for ISAR imaging problems. However, the traditional phase retrieval algorithm will be not applicable to ISAR imaging under the condition of random noise. To solve this problem, an algorithm is put forward based on the range Doppler(RD) algorithm and oversampling smoothness(OSS) phase retrieval algorithm. The algorithm captures the target information in order to reduce the influence of the random phase on ISAR echoes, and then applies OSS for focusing imaging based on prior information of the RD algorithm. The simulated results demonstrate the validity of this algorithm, which cannot only obtain high resolution imaging for high speed maneuvering targets under the condition of random noise, but also substantially improve the success rate of the phase retrieval algorithm.

关键词： inverse synthetic aperture radar(ISAR) maneuvering target autofocus imaging phase retrieval oversampling smoothness(OSS)

Multi-scale UDCT dictionary learning based highly undersampled MR image reconstruction using patch-based constraint splitting augmented Lagrangian shrinkage algorithm

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Frontiers of information Technology & Electronic {1. 2015年第12期16卷 1069-1087页

作者： Min YUAN Bing-xin YANG Yi-de MA Jiu-wen ZHANG Fu-xiang LU Tong-feng ZHANG school of {1. Science & engineering Lanzhou University

Recently, dictionary learning(DL) based methods have been introduced to compressed sensing magnetic resonance imaging(CS-MRI), which outperforms pre-defined analytic sparse priors. However, single-scale trained dictionary directly from image patches is incapable of representing image features from multi-scale, multi-directional perspective, which influences the reconstruction performance. In this paper, incorporating the superior multi-scale properties of uniform discrete curvelet transform(UDCT) with the data matching adaptability of trained dictionaries, we propose a flexible sparsity framework to allow sparser representation and prominent hierarchical essential features capture for magnetic resonance(MR) images. Multi-scale decomposition is implemented by using UDCT due to its prominent properties of lower redundancy ratio, hierarchical data structure, and ease of implementation. Each sub-dictionary of different sub-bands is trained independently to form the multi-scale dictionaries. Corresponding to this brand-new sparsity model, we modify the constraint splitting augmented Lagrangian shrinkage algorithm(C-SALSA) as patch-based C-SALSA(PB C-SALSA) to solve the constraint optimization problem of regularized image reconstruction. Experimental results demonstrate that the trained sub-dictionaries at different scales, enforcing sparsity at multiple scales, can then be efficiently used for MRI reconstruction to obtain satisfactory results with further reduced undersampling rate. Multi-scale UDCT dictionaries potentially outperform both single-scale trained dictionaries and multi-scale analytic transforms. Our proposed sparsity model achieves sparser representation for reconstructed data, which results in fast convergence of reconstruction exploiting PB C-SALSA. Simulation results demonstrate that the proposed method outperforms conventional CS-MRI methods in maintaining intrinsic properties, eliminating aliasing, reducing unexpected artifacts, and removing noise. It

关键词： Compressed sensing(CS) Magnetic resonance imaging(MRI) Uniform discrete curvelet transform(UDCT) Multi-scale dictionary learning(MSDL) Patch-based constraint splitting augmented Lagrangian shrinkage algorithm(PB C-SALSA)

When the gain of predictive resource allocation for content delivery is large?

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Science China(information Sciences) 2023年第12期66卷 179-193页

作者： Chenzuo ZHANG Jia GUO Chenyang YANG school of Electronic and {1. engineering Beihang University

By predicting future information such as data rate with sensory wireless data, radio resources can be pre-allocated for content delivery. Such an integrated sensing and communications technique can help improve network performance and user experience. To justify the cost paid for predicting future information,it is important to understand in which scenarios predictive resource allocation yields a large gain over the non-predictive counterpart. In this paper, we strive to identify the key factors that affect the gain of predictive resource allocation by deriving the closed-form expression of the gain. We are concerned with minimizing the transmission time required for content delivery such as file downloading to users with an expected deadline,where the resources of base stations are shared with real-time services. Then, the performance gain is measured by the difference of the average time required by predictive and non-predictive resource *** by the solution of the optimization problem, we resort to the theory of order statistics for deriving the performance gain. We find that the gain depends on the statistics(i.e., mean value and standard deviation)of the user’s average data rates in the prediction window. Then, we separately analyze how the statistics of the bandwidth available for content delivery and user mobility affect the gain. We use simulation with a real dataset of traffic load to validate the analysis and quantify the impact of the key factors. Our results show that predictive resource allocation can reduce the transmission time even for non-moving users. The performance gain is high when the network is busy or the cell radius is large.

关键词： predictive resource allocation performance analysis average data rates residual bandwidth user mobility

Fuzzy working state evaluating function and its algorithm for analogue circuits

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The Journal of China Universities of Posts and Telecommunications 2015年第1期22卷 83-88页

作者： Huang Liang Song Wei school of Electronic and {1. engineering Beijing Jiaotong University school of {1. engineering Minzu University of China

The working state （WS） evaluation is a valuable task in the process of failure diagnosis in the analogue circuits. A fuzzy evaluating algorithm was proposed to quantify the working condition of analogue circuit regarded as fuzzy system. Several familiar WS evaluating functions based on fuzzy membership functions were also proposed to calculate the local working state indexes （WSI） of each node in an analogue circuit. The decision function combined with the WS evaluating functions is used to synthesize all the local WSI to the global WSI of the whole circuit. An example was presented to verify that the working status of the analogue circuits can be described by the new WS evaluating algorithm and the global WSI objectively and accurately.

关键词： analogue circuit working state fuzzy theory membership function

The initial stages of Li_(2)O_(2) formation during oxygen reduction reaction in Li-O_(2) batteries:The significance of Li_(2)O_(2) in charge-transfer reactions within devices

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Journal of Energy Chemistry 2024年第1期88卷 223-231,I0006页

作者： Daniela M.Josepetti Bianca P.Sousa Simone A.J.Rodrigues Renato G.Freitas Gustavo Doubek Advanced Energy Storage Division LABCenter for Innovation on New EnergiesSchool of Chemical EngineeringUniversity of CampinasAv Albert Einstein 50013083-852CampinasSPBrazil Institute of Physics&Department of Chemistry Laboratory of Computational MaterialsFederal University of Mato Grosso78060-900CuiabáMTBrazil

Lithium-oxygen batteries are a promising technology because they can greatly surpass the energy density of lithium-ion ***,this theoretical characteristic has not yet been converted into a real device with high *** with air contamination,metallic lithium reactivity,and complex discharge and charge reactions are the main issues for this technology.A fast and reversible oxygen reduction reaction(ORR)is crucial for good performance of secondary batteries',but the partial knowledge of its mechanisms,especially when devices are concerned,hinders further *** this perspective,the present work uses operando Raman experiments and electrochemical impedance spectroscopy(EIS)to assess the first stages of the discharge processes in porous carbon electrodes,following their changes cycle by cycle at initial operation.A growth kinetic formation of the discharge product signal(Li_(2)O_(2))was observed with operando Raman,indicating a first-order reaction and enabling an analysis by a microkinetic *** solution mechanism in the evaluated system was ascribed for an equivalent circuit with three time *** the time constant for the anode interface reveals to remain relatively constant after the first discharge,its surface seemed to be more *** model indicated that the reaction occurs at the Li_(2)O_(2) surface,decreasing the associated resistance during the initial discharge ***,the growth of Li_(2)O_(2) forms a hetero-phase between Li_(2)O_(2)/electrolyte,while creating a more compact and homogeneous on the Li_(2)O_(2)/cathode *** methodology here described thus offers a way of directly probing changes in surface chemistry evolution during cycling from a device through EIS analysis.

关键词： Li-O_(2)battery Operando Raman analysis Equivalent circuit modeling Time-constant distribution

An Approximate Maximum Likelihood Algorithm for Target Localization in Multistatic Passive Radar

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Chinese Journal of Electronics 2019年第1期28卷 195-201页

作者： WANG Jun QIN Zhaotao GAO Fei WEI Shaoming school of Electronics and {1. engineering Beihang University

This paper addresses the problem of target localization using Bistatic range(BR) measurements in a distributed multistatic passive radar system. The rangebased positioning technique employs multiple transmitterreceiver pairs, which provide separate BR *** on the Maximum likelihood(ML) function,an efficient algebraic Approximate maximum likelihood(AML) algorithm for single target localization is *** closed-form AML solution has neither initial condition requirements nor convergence difficulty. Simulations are included to compare its performance to that of the CramerRao lower bound(CRLB) and the Two-step Weighted least squares(TS-WLS) algorithm. The proposed method is shown to be able to achieve the CRLB accuracy under Gaussian measurement noise. It is more robust to noise than the TS-WLS method, and presents relative insensitivity to target-sensor geometry.

关键词： Bistatic range(BR) measurement Multistatic passive radar Target localization Approximate maximum likelihood(AML) algorithm Maximum likelihood(ML) function

Stochastic resonance in a time-delayed mono-stable system with correlated multiplicative and additive white noise

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Chinese Physics B 2011年第1期20卷 169-174页

作者：周玉荣 school of {1. and Electric engineering Panzhihua University

This paper considers the stochastic resonance for a time-delayed mono-stable system, driven by correlated multiplicative and additive white noise. It finds that the output signal-to-noise ratio （SNR） varies non-monotonically with the delayed times. The SNR varies non-monotonically with the increase of the intensities of the multiplicative and additive noise, with the increase of the correlation strength between the two noises, as well as with the system parameter.

关键词： stochastic resonance time-delayed mono-stable system signal-to-noise ratio