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Analysis of relative error in detection caused by signal-induced noise in Na lidar system

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Science China Earth Sciences 2018年第1期61卷 109-118页

作者： ZHANG YunPeng YI Fan kong wei School of Electronic Information Wuhan University

Signal-induced noise(SIN) in a photomultiplier tube(PMT) introduces bias into the Na density results that are retrieved from the backscattered signals of Na resonance fluorescence lidar systems. The response characteristics of a PMT when stimulated by a series of light pulses with a fixed width of 1 μs are therefore used to develop a precise SIN model to estimate the relative error caused by SIN. Unless the strong signals that are returned from the lower atmosphere are excluded, the measured density results are always smaller than the actual values, and the resulting relative error may be 50% or more. Three potential solutions to reduce the SIN were quantified for comparison, including use of a chopper system, use of a gated circuit, and separation of the laser beam and the telescope receiver. When optimized parameters are used for these technologies, the relative error can then be reduced to less than 2%.

关键词： Lidar Signal-induced noise Photomultiplier tube

Blind source separation of ship-radiated noise based on generalized Gaussian model

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Journal of Systems Engineering and Electronics 2006年第2期17卷 321-325页

作者： kong wei Yang Bin Information Engineering Coll. of Shanghai Maritime Univ. Shanghai 200135 China

When the distribution of the sources cannot be estimated accurately, the ICA algorithms failed to separate the mixtures blindly. The generalized Gaussian model （GGM） is presented in ICA algorithm since it can model non- Ganssian statistical structure of different source signals easily. By inferring only one parameter, a wide class of statistical distributions can be characterized. By using maximum likelihood （ML） approach and natural gradient descent, the learning rules of blind source separation （BSS） based on GGM are presented. The experiment of the ship-radiated noise demonstrates that the GGM can model the distributions of the ship-radiated noise and sea noise efficiently, and the learning rules based on GGM gives more successful separation results after comparing it with several conventional methods such as high order cumnlants and Gaussian mixture density function.

关键词： blind source separation (BSS) independent component analysis (ICA) generalized Gaussian model(GGM) maximum likelihood (ML).

Measuring the beaming angle of GRB 030329 by fitting the rebrightenings in its multiband afterglow

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Research in Astronomy and Astrophysics 2010年第11期10卷 1119-1126页

作者： wei Deng Yong-Feng Huang Si-wei kong Department of Astronomy Nanjing University Nanjing 210093 China Key Laboratory of Modern Astronomy and Astrophysics （Nanjing Univ.） Ministry of EducationNanjing 210093 China

Multiple rebrightenings have been observed in the multiband afterglow of GRB 030329. In particular, a marked and quick rebrightening occurred at about t 1.2 × 10^5 s. Energy injection from late and slow shells seems to be the best interpretation for these rebrightenings. Usually it is assumed that the energy is injected into the whole external shock. However, in the case of GRB 030329, the rebrightenings are so quick that the usual consideration fails to give a satisfactory fit to the observed light curves. Actually, since these late/slow shells freely coast in the wake of the external shock, they should be cold and may not expand laterally. The energy injection then should only occur at the central region of the external shock. Considering this effect, we numerically re-fit the quick rebrightenings observed in GRB 030329. By doing this, we were able to derive the beaming angle of the energy injection process. Our result, with a relative residual of only 5% - 10% during the major rebrightening, is bet- ter than any previous modeling. The derived energy injection angle is about 0.035. We assume that these late shells are ejected by the central engine via the same mechanism as those early shells that produce the prompt gamma-ray burst. The main difference is that their velocities are much slower, so that they catch up with the external shock relatively late and are manifested as the observed quick rebrightenings. If this were true, then the derived energy injection angle can give a good measure of the beaming angle of the prompt γ-ray emission. Our study may hopefully provide a novel method to measure the beaming angle of gamma-ray bursts.

关键词： gamma-rays bursts-ISM jets and outflows

Mechanism Analysis of Additional Damping Control Strategies for the High-frequency Resonance of MMC Connected to AC Grid

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CSEE Journal of Power and Energy Systems 2023年第3期9卷 1173-1181页

作者： Yanqi Hou Chongru Liu Yu Wang wei kong State Key Laboratory for Alternate Electrical Power System with Renewable Energy Sources North China Electric Power UniversityBeijing 102206China State Grid Economic and Technological Research Institute Co.Ltd. Beijing 102209China State Grid Corporation of China Beijing 100031China

High-frequency resonance can occur when a modular multilevel converter(MMC)is inserted into an AC *** damping control is a relatively low-cost resonance suppression strategy compared to passive damping *** paper analyzes the influences of a feed-forward voltage filter and feedback current filter for the inner controller for the high-frequency impedance characteristics of the MMC based on a ***,the mechanism,influencing factors,and limitations of the existing strategy including an additional lowpass filter in the voltage feed-forward stage are ***,a resonance suppression strategy for the inclusion of additional cascaded notch filters in the voltage feed-forward stage is proposed,and its parameter design method and applicable scenarios are *** addition,this paper analyzes the effects of the inclusion of an additional control in other stages for the inner controller of the ***,the correctness of the theoretical analysis and the proposed strategy is verified based on the simulation of an actual project on PSCAD/EMTDC.

关键词： Additional damping control strategy additional cascaded notch filters additional low-pass filter modular multilevel converter(MMC) high-frequency resonance

Pretreatment with scutellaria baicalensis stem-leaf total flavonoid prevents cerebral ischemia-reperfusion injury

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Neural Regeneration Research 2013年第34期8卷 3183-3192页

作者： Shumin Zhao wei kong Shufeng Zhang Meng Chen Xiaoying Zheng Xiangyu kong Laboratory of Spinal Cord Injury and Rehabilitation Chengde Medical College

Pretreatment with scutellaria baicalensis stem-leaf total flavonoid has protective effects against ischemia and attenuates myocardial ischemia-reperfusion injury. In this study, rats were given scutellaria baicalensis stem-leaf total flavonoid intragastrically at 50, 100, and 200 mg/kg per day for 7 days before focal cerebral ischemia-reperfusion injury models were established using the suture method. We then determined the protective effects of scutellaria baicalensis stem-leaf total flavon- oid pretreatment on focal cerebral ischemia-reperfusion injury. Results showed that neurological deficit scores increased, infarct volumes enlarged, apoptosis increased and Bcl-2 and Bax protein expression were upregulated at 24 hours after reperfusion. Pretreatment with scutellaria baicalensis stem-leaf total flavonoid at any dose lowered the neurological deficit scores, reduced the infarct volume, prevented apoptosis in hippocampal cells, attenuated neuronal and blood-brain barrier damage and upregulated Bcl-2 protein expression but inhibited Bax protein expression. Doses of 100 and 200 mg/kg were the most efficacious. Our findings indicate that pretreatment with scutel- laria baicalensis stem-leaf total flavonoid at 100 and 200 mg/kg can improve the neurological func- tions and have preventive and protective roles after focal cerebral ischemia-reperfusion injury.

关键词： neural regeneration brainischemia-reperfusion injury neuroregenerationnjury scutellaria baicalensis stem-leaf total flavonoidpretreatment hippocampus apoptosis grants-supported paper

Digital rights management independent of terminals in mobile applications

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The Journal of China Universities of Posts and Telecommunications 2007年第1期14卷 32-38页

作者： ZHANG Li-he kong Xiang-wei YANG Cheng Department of Electronic Engineering Dalian University of Technology Dalian 116023 China School of Information Engineering Communication University of China Beijing 100024 China

At present, most mobile terminals do not have any functions of fights management, and the cryptology-based method cannot resolve all the copyright problems in the mobile digital distribution service. With the urgent demand of digital rights management in digital distribution service, a scheme independent of terminals is proposed in this article. It integrates the watermark and signature techniques. In this article the scheme theory, architecture, service process, and performance are mainly discussed. In the end, the functional relationship between the proposed digital rights management （DRM） and the cryptology-based open mobile alliance digital rights management （OMA-DRM） is given. The analysis shows that the scheme is feasible and secure.

关键词： DRM copyright protection digital watermarking,mobile distribution service

Amplification assisted difference frequency generation for efficient mid-infrared conversion based on monolithic tandem lithium niobate superlattice

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Photonics Research 2017年第4期5卷 355-361页

作者： TAO CHEN HAO LIU wei kong RONG SHU Key Laboratory of Space Active Opto-Electronics Technology Shanghai Institute of Technical Physics Chinese Academy of Sciences

We report the investigation on the performance of an amplification assisted difference frequency generation(AA-DFG) system driven by pulsed pump and continuous-wave primary signal lasers. A monolithic tandem lithium niobate superlattice was employed as the nonlinear crystal with a uniform grating section for the DFG process, followed by a chirp section for the optical parametric amplification process. The impacts of pump pulse shape, primary signal power, input beam diameter, and crystal structure on the pump-to-idler conversion efficiency of the AA-DFG system were comprehensively studied by numerically solving the coupled wave equations. It is concluded that square pump pulse and high primary signal power are beneficial to high pump-to-idler conversion efficiency. In addition, tighter input beam focus and smaller DFG length proportion could redeem the reduction in conversion efficiency resulting from wider acceptance bandwidths for the input lasers. We believe that such systems combining the merits of high stability inherited from cavity-free configuration and high efficiency attributed from the cascaded nonlinear conversion should be of great interest to a wide community,especially when the pulse shaping technique is incorporated.

关键词： DFG Amplification assisted difference frequency generation for efficient mid-infrared conversion based on monolithic tandem lithium niobate superlattice OPO

Ring-Shaped Jets in Gamma-Ray Bursts

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Chinese Journal of Astronomy and Astrophysics 2008年第4期8卷 411-420页

作者： Ming Xu Yong-Feng Huang Si-wei kong Department of Astronomy Nanjing University Nanjing 210093 China

When the axis of a gamma-ray burst （GRB） does not coincide with the spin axis of its source, there may result a ring-shaped jet. Using some refined jet dynamics, we calculate multi-wavelength afterglow light curves for such ring-shaped jets. In the R-band we find an obvious break in the afterglow light curve due to the beaming effect and the break is affected by many parameters, such as the electron energy fraction ζe, the magnetic energy fraction ζB^2, the width of ring △θ and the medium number density n. The overall light curve can be divided into three power-law stages, i.e., an ultra-relativistic stage, an after-break stage and a deep Newtonian stage. For each stage the power-law index is larger in the ring-shaped jet than in the corresponding conical jet.

关键词： gamma rays bursts - ISM jets and outflows

Increment-Dimensional Scaled Boundary Finite Element Method for Solving Transient Heat Conduction Problem

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Transactions of Nanjing University of Aeronautics and Astronautics 2018年第6期35卷 1073-1079页

作者： Li Fengzhi Li Tiantian kong wei Cai Junfeng College of Aerospace Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016P.R.China College of Aeronautic Science and Engineering Beihang UniversityBeijing 100191P.R.China The 610 Research Institute of Chinese Aeronautical Establishment Xiangyang 441000P.R.China

An increment-dimensional scaled boundary finite element method (ID-SBFEM) is developed to solve the transient temperature *** improve the accuracy of SBFEM,the effect of high frequency factor on dynamic stiffness is considered,and the first-order continued fraction technique is *** the derivation,the SBFE equations are obtained,and the dimensions of thermal conduction,the thermal capacity matrix and the vector of the right side term in the equations are *** example is presented to illustrate the feasibility and good accuracy of the proposed method.

关键词： heat conduction scaled boundary finite element method(SBFEM) temperature field accuracy