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Simutaneous radar imaging and velocity measuring with step frequency waveforms

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Journal of Systems Engineering and Electronics 2009年第4期20卷 741-747页

作者： Yuan Haotian Wen Shuliang cheng zhen Beijing Inst. of Radio Measurement Beijing 100854 P. R. China

The principle and method of both radar target imaging and velocity measurement simultaneously based on step frequency waveforms is presented. Velocity compensation is necessary in order to obtain the good High resolution range profile since this waveform is greatly sensitive to the Doppler shift. The velocity measurement performance of the four styles is analyzed with two pulse trains consisted of positive and negative step frequency waveforms. The velocity of targets can be estimated first coarsely by using the pulse trains with positive-positive step frequency combination, and then fine by positive-negative combination. Simulation results indicate that the method can accomplish the accurate estimation of the velocity with efficient computation and good anti-noise performance and obtain the good HRRP simultaneously.

关键词： high resolution radar step frequency waveform velocity measuring high resolution range profile.

Unified Classification and Rejection:A One-versus-all Framework

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Machine Intelligence Research 2024年第5期21卷 870-887页

作者： zhen cheng Xu-Yao Zhang cheng-Lin Liu State Key Laboratory of Multimodal Artificial Intelligence Systems Institute of AutomationChinese Academy of SciencesBeijing100190China School of Artificial Intelligence University of Chinese Academy of SciencesBeijing100049China

Classifying patterns of known classes and rejecting ambiguous and novel(also called as out-of-distribution(OOD))inputs are involved in open world pattern *** neural network models usually excel in closed-set classification while perform poorly in rejecting OOD *** tackle this problem,numerous methods have been designed to perform open set recognition(OSR)or OOD rejection/detection *** methods mostly take post-training score transformation or hybrid models to ensure low scores on OOD inputs while separating known *** this paper,we attempt to build a unified framework for building open set classifiers for both classification and OOD *** formulate the open set recognition of K-known-class as a(K+1)-class classification problem with model trained on known-class samples *** decomposing the K-class problem into K one-versus-all(OVA)binary classification tasks and binding some parameters,we show that combining the scores of OVA classifiers can give(K+1)-class posterior probabilities,which enables classification and OOD rejection in a unified *** maintain the closed-set classification accuracy of the OVA trained classifier,we propose a hybrid training strategy combining OVA loss and multi-class cross-entropy *** implement the OVA framework and hybrid training strategy on the recently proposed convolutional prototype network and prototype classifier on vision transformer(ViT)*** on popular OSR and OOD detection datasets demonstrate that the proposed framework,using a single multi-class classifier,yields competitive performance in closed-set classification,OOD detection,and misclassification *** code is available at https://***/zhen-cheng121/CPN_OVA_unified.

关键词： Open set recognition out-of-distribution detection misclassification detection convolutional prototype network oneversus-all Dempster-Shafer theory of evidence

New Age Indicators for Stellar Populations

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Chinese Physics Letters 2000年第9期17卷 700-702页

作者： Kong Xu cheng Fu-zhen Center for Astrophysics University of Science and Technology of ChinaHefei 230026 National Astronomical Observatories Chinese Academy of SciencesBeijing 100012 CAS-Peking University Joint Beijing Astrophysics Center Beijing 100871

We apply the method of principal component analysis to a sample of simple stellar populations to select some age sensitive spectral indices. Besides the well-known age sensitive index Hβ, we also find some new age sensitive indices, G4300 and Fe4383, C_(2)4668, and Mgb. In addition, we find that these spectral indices sensitive to age depend on the metallicity of stellar population, Hβ and G4300 are more suitable to determine the age of loy metallicity stellar population, while C_(2)4668 and Mgb are more suitable to the high metallicity stellar population.

关键词： stellar indices metallic

LARGE TIME BEHAVIOR OF GLOBAL STRONG SOLUTIONS TO A TWO-PHASE MODEL WITH A MAGNETIC FIELD

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Acta Mathematica Scientia 2022年第5期42卷 1921-1946页

作者： Wenjun WANG zhen cheng College of Science University of Shanghai for Science and TechnologyShanghai 200093China

In this paper,the Cauchy problem for a two-phase model with a magnetic field in three dimensions is *** on a new linearized system with respect to(c−c_(∞),P−P_(∞),u,H)for constants c_(∞)≥0 and P_(∞)>0,the existence theory of global strong solution is established when the initial data is close to its equilibrium in three dimensions for the small H^(2) initial *** improve the existence results obtained by Wen and Zhu in[40]where an additional assumption that the initial perturbations are bounded in L^(1)-norm was *** energy method combined with the low-frequency and high-frequency decomposition is used to derive the decay of the solution and hence the global *** a by-product,the time decay estimates of the solution and its derivatives in the L^(2)-norm are obtained.

关键词： two-phase model magnetic field strong solution global existence decay rates

Design and implementation of a novel enterprise network defense system by maneuvering multi-dimensional network properties

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Frontiers of Information Technology & Electronic Engineering 2019年第2期20卷 238-252页

作者： Yang CHEN Hong-chao HU Guo-zhen cheng National Digital Switching System Engineering & Technological R&D Center

Although the perimeter security model works well enough when all internal hosts are credible, it is becoming increasingly difficult to enforce as companies adopt mobile and cloud technologies, i.e., the rise of bring your own device(BYOD). It is observed that advanced targeted cyber-attacks usually follow a cyber kill chain;for instance, advanced targeted attacks often rely on network scanning techniques to gather information about potential targets. In response to this attack method, we propose a novel approach, i.e., an "isolating and dynamic"cyber defense, which cuts these potential chains to reduce the cumulative availability of the gathered ***, we build a zero-trust network environment through network isolation, and then multiple network properties are maneuvered so that the host characteristics and locations needed to identify vulnerabilities cannot be ***, we propose a software-defined proactive cyber defense solution(SPD) for enterprise networks and design a general framework to strategically maneuver the IP address, network port, domain name, and path, while limiting the performance impact on the benign network user. Third, we implement our SPD proof-of-concept system over a software-defined network controller(OpenDaylight). Finally, we build an experimental platform to verify the system's ability to prevent scanning, eavesdropping, and denial-of-service attacks. The results suggest that our system can significantly reduce the availability of network reconnaissance scan information, block network eavesdropping, and sharply increase the cost of cyber-attacks.

关键词： Intranet defense Software-defined network Multi-dimensional maneuvering

Clustering Property of Wolf-Rayet Galaxies in the SDSS

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Chinese Journal of Astronomy and Astrophysics 2008年第2期8卷 211-218页

作者： Wei Zhang Xu Kong Fu-zhen cheng Center for Astrophysics University of Science and Technology of China Hefei 230026

We have analysed, for the first time, the clustering properties of Wolf-Rayet （W-R） galaxies, using a large sample of 846 W-R galaxies selected from the Data Release 4 （DR4） of the Sloan Digital Sky Survey （SDSS）. We compute the cross-correlation function between W- R galaxies and a reference sample of galaxies drawn from the DR4. We compare the function to the results for control samples of non-W-R star-forming galaxies that are matched closely in redshift, luminosity, concentration, 4000-A break strength and specific star formation rate （SSFR）. On scales larger than a few Mpc, W-R galaxies have almost the same clustering amplitude as the control samples, indicating that W-R galaxies and non-W-R control galaxies populate dark matter haloes of similar masses. On scales between 0.1-1 h^-1 Mpc, W-R galaxies are less clustered than the control samples, and the size of the difference depends on the SSFR. Based on both observational and theoretical considerations, we speculate that this negative bias can be interpreted by W-R galaxies residing preferentially at the centers of their dark matter haloes. We examine the distribution of W-R galaxies more closely using the SDSS galaxy group catalogue of Yang et al., and find that -82% of our W-R galaxies are the central galaxies of groups, compared to -74% for the corresponding control galaxies. We find that W-R galaxies are hosted, on average, by dark matter haloes of masses of 10^12.3M⊙, compared to 10^12.1M⊙ for centrally-located W-R galaxies and 10^12.7M⊙ for satellite ones. We would like to point out that this finding, which provides a direct observational support to our conjecture, is really very crude due to the small number of W-R galaxies and the incompleteness of the group catalogue, and needs more work in future with larger samples.

关键词： galaxies: distances and redshifts -- galaxies: starburst -- stars: Wolf-Rayet

Reconstruction of cylindrically layered media using an iterative algorithm with a stable solution

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The Journal of China Universities of Posts and Telecommunications 2007年第4期14卷 118-121页

作者： cheng Ji-zhen NIU Zuo-yuan cheng Chong-hu College of Communications and Information Engineering Nanjing Universityof Posts and Telecommunications Nanjing 210003 China

Abstract The reconstruction of cylindrically layered media is investigated in this article. The inverse problem is modeled using a source-type integral equation with a series of cylindrical waves as incidences, and a conventional Born iterative procedure is modified for solving the integral equation. In the modified iterative procedure, a conventional single-point approximation for the calculation of the field inside media is replaced by a multi-points approximation to improve the numerical stability of its solution. Numerical simulations for different permittivity distributions are demonstrated in terms of artificial scattering data with the procedure. The result shows that the procedure enjoys both accuracy and stability in the numerical computation.

关键词： layered media inverse problems integral equations,iterative methods

Improving Throughput of Communication Link in IEEE 802.15.4 Based Energy-Harvesting Wireless Sensor Network

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Chinese Journal of Electronics 2019年第4期28卷 841-849页

作者： BAI Nana GONG Siliang SHI Haiyan cheng zhen ZHU Yihua School of Computer Science and Technology Zhejiang University of Technology School of Mechanical and Electrical Engineering Shaoxing University

It is critical to design a reliable packet transmission scheme to improve throughput in Energy harvesting Wireless sensor network(EH-WSN) or Battery free Wireless sensor network(BF-WSN). We present the Optimal size and rate(OSR) scheme to improve throughput of communication links in the IEEE 802.15.4 based BF-WSN that harvests radio frequency *** on the defined truncated geometrical distribution,we formulate the optimization problem that maximizes the effective throughput of communication link. The solution of the optimization problem yields the optimal triple,namely the optimal packet size, data rate, and Maximum number of transmission trials(MNTT), which is used in the OSR so that throughput is considerably *** results show the OSR scheme can improve throughput.

关键词： Wireless sensor network Energy harvesting Wireless sensor network Data delivery Throughput

Discovery of emerging organic pollutants in the atmosphere through an omics approach

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Frontiers of Environmental Science & Engineering 2023年第4期17卷 71-81页

作者： zhen cheng Xinghua Qiu Xiaodi Shi Xing Jiang Tong Zhu State Key Joint Laboratory for Environmental Simulation and Pollution Control College of Environmental Sciences and EngineeringCenter for Environment and HealthPeking UniversityBeijing 100871China

Ambient air pollution,containing numerous known and hitherto unknown compounds,is a major risk factor for public *** discovery of harmful components is the prerequisite for pollution control;however,this raises a great challenge on recognizing previously unknown *** we systematically review the analytical techniques on air pollution in the framework of an omics approach,with a brief introduction on sample preparation and analysis,and in more detail,compounds prioritization and *** high-resolution mass spectrometry(HRMS,typically coupled with chromatography),the complicated environmental matrix can be digitalized into“fullcomponent”data.A key step to discover emerging compounds is the prioritization of compounds from massive *** fingerprints,suspect lists and biological effects are the most vital untargeted strategies for comprehensively screening critical and hazardous ***,compressed data of compounds can be identified at various confidence levels according to exact mass and the derived molecular formula,MS libraries,and authentic *** an omics approach on full-component data provides a paradigm for discovering emerging air pollutants;nonetheless,new technological advancements of instruments and databases are warranted for further tracking the environmental behaviors,hence to evaluate the health risk of key pollutants.

关键词： Air pollution Emerging pollutants Full-component High-resolution mass spectrometry Omics approach