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CSEE Journal of Power and Energy systems 2024年第5期10卷 1955-1964页

作者： Jingyi Li Jianjun Yang Xiaorong Xie Haozhi Li Ke Wang Zhaohui Shi Key Laboratory of Far-shore Wind Power Technology of Zhejiang Province Huadong Engineering Corporation LimitedPower ChinaHangzhou 310014China. State Key Lab of Control and Simulation of Power systems and Generation Equipment(dept.of electrical engineering Tsinghua University)Beijing 100084China.

Establishing a suitable closed-loop transfer function model for the grid-connected PMSG system is the key basis in performing inter-harmonic characteristics *** closed-loop transfer functions can be constructed when different components of the converter controller are taken into ***,the effect of different components of the converter controller on inter-harmonic stability analysis is not *** this paper,the complete transfer function,considering different loops,is first *** on the complete closed-loop transfer function,the DC-link,PLL and voltage forward-feed are removed step by step to derive different closed-loop transfer *** inter-harmonic related poles of different closed-loop transfer functions are further calculated to analyze the effect of closedloop transfer functions on inter-harmonic characteristics ***,by performing time domain simulation,the correctness of the theoretical analysis results is *** results show that under the conditions of a weak AC system,each loop of the converter control system will reduce the stability of the interharmonic in the sub-synchronous frequency range and influence the inter-harmonic oscillation *** transfer function needs to consider the influence of each loop to accurately calculate the inter-harmonic stability of the system.

关键词： Closed-loop transfer function converter controller inter-harmonic characteristics PMSG

THE GENERALIZED GAMMA DISTRIBUTION OF RAINDROP SIZES AND ITS APPLICATION TO SINGAPORE

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THE GENERALIZED GAMMA DISTRIBUTION OF RAINDROP SIZES AND ITS...

Output only modal identification and structural damage detection using time frequency & wavelet techniques

1993 International Symposium on Radio Propagation(ISRP’93)

作者： L.W.Li P.S.Kooi M.S.Leong T.S.Yeo dept.of elec.& comp.syst.eng. Monash UniversityClaytonVictoriaAustralia 3168 dept.of elec.eng. National Univ.of Singapore10 Kent Ridge CrescentSingapore 0511

The use of a gamma distribution of rain-drop sizes in the calculation of microwave rain attenuation is gaining *** on the CCIR rain attenuation relation aR,a method of calculating the general gamma distribution of raindrop sizes has been developed in this paper using the measured microwave attenuation data varying with the rain *** method,which overcomes the common problems of instability and does not suffer the possibility of multiple solutions,has been tested using a CCIR *** of the calculated results with the data from the CCIR model shows that the method provides the ideal modeling of rain Drop 5ize Distribution(DSD).As an application,the two-year experimental data recorded in Singapore has been used to obtain the parameters of the generalized gamma DSD function.

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Earthquake engineering and engineering Vibration 2009年第4期8卷 583-605页

作者： S.Nagarajaiah B.Basu dept.of Civil & Environmental eng.and dept.of Mechanical eng.& Material Sc. Rice University dept.of Civil Structural& Environmental Eng.Trinity College Dublin

The primary objective of this paper is to develop output only modal identification and structural damage detection. Identification of multi-degree of freedom （MDOF） linear time invariant （LTI） and linear time variant （LTV--due to damage） systems based on Time-frequency （TF） techniques--such as short-time Fourier transform （STFT）, empirical mode decomposition （EMD）, and wavelets--is proposed. STFT, EMD, and wavelet methods developed to date are reviewed in detail. In addition a Hilbert transform （HT） approach to determine frequency and damping is also presented. In this paper, STFT, EMD, HT and wavelet techniques are developed for decomposition of free vibration response of MDOF systems into their modal components. Once the modal components are obtained, each one is processed using Hilbert transform to obtain the modal frequency and damping ratios. In addition, the ratio of modal components at different degrees of freedom facilitate determination of mode shape. In cases with output only modal identification using ambient/random response, the random decrement technique is used to obtain free vibration response. The advantage of TF techniques is that they arc signal based; hence, can be used for output only modal identification. A three degree of freedom 1：10 scale model test structure is used to validate the proposed output only modal identification techniques based on STFT, EMD, HT, wavelets. Both measured free vibration and forced vibration （white noise） response are considered. The secondary objective of this paper is to show the relative ease with which the TF techniques can be used for modal identification and their potential for real world applications where output only identification is essential. Recorded ambient vibration data processed using techniques such as the random decrement technique can be used to obtain the free vibration response, so that further processing using TF based modal identification can be performed.

关键词： Time-frequency methods short time Fourier transform Hilbert transform wavelets modal identification:output only structural health monitoring damage detection

The Structural engineering Challenges Following the Wenchuan Earthquake

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四川大学学报（工程科学版） 2009年第3期41卷 223-230页

作者： GRUNDY Paul dept.of Civil eng. Monash Univ.

The "5·12" Wenchuan Earthquake presents two challenges-reconstruction of the devastated areas and building adequate seismic resistance into the rest of *** stages in recovery include structural condition assessment,identification of seismic weaknesses,appreciation of the variable seismicity of PR China,the development of a seismic performance index to aid the decision to relocate,rebuild or retrofit,development and application of the principles of retrofitting which recycles rubble and waste from Wenchuan "5·12",with an emphasis on integrating masonry construction into seismic *** recovery and resilience achieved through structural engineering must be integrated into a broader community involvement in disaster risk reduction.

关键词：建筑工程抗振结构建筑结构建筑物

Slope Stability Analyses of Outang Landslide Based on the Peak and Residual Shear Strength Behavior

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工程科学与技术 2019年第4期51卷 55-68页

作者： YANG Xiuhan VANAPALLI Sai dept.of Civil eng. Univ.of Ottawa

Most of the natural and compacted fine-grained soil slopes that are in saturated or unsaturated condition undergo a large deformation prior to reaching failure *** slopes should be designed taking account of their strain-softening behavior using the residual shear strength (RSS) *** this paper,the slope stability of a recently reactivated Outang landslide near the Three Gorges Dam in China is analyzed based on the RSS parameters of unsaturated *** addition,comparisons are provided in the FOS values of slope using both the peak shear strength (PSS) and RSS ***,a series of site investigations of the hydrologic and geologic conditions,ground surface displacements and cracks were *** PSS and RSS behaviors of the sliding soils derived from a series of direct shear test results performed on saturated and unsaturated soil specimens are ***,a series of slope stability analysis were conducted considering the precipitation and Yangtze River water level variation within a representative period of 7 months,based on the PSS and the RSS *** this study,three different scenarios were considered,which include: i) considering only the precipitation with a constant water level;ii) considering only the decrease in water level without rainfall;iii) considering the combination of precipitation and decrease in water *** each scenario,four steps were included to calculate the values of factor of safety (FOS) at different times.1) A steady-state seepage analysis was conducted with a constant total head at 525 m on the left boundary and 175 m on the slope surface below the Yangtze River water *** initial pore water pressures were simulated in the slope under no precipitation and variation of water level.2) A specific boundary condition was applied on the slope surface to model the precipitation and Yangtze River water level variation.A transient seepage analysis was conducted to calculate pore water pres

关键词： unsaturated soil landslide reactivation residual shear strength slope stability analysis

An air cavity method for increasing the underwater acoustic targets strength of corner reflector

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Defence Technology（防务技术） 2020年第2期16卷 493-501页

作者： Yi Luo Xin Chen Da-wei Xiao Wu-di Wen Tao-tao Xie dept.of Weaponry eng Naval University of EngineeringWuhan 430033China

In order to improve the underwater acoustic target strength of comer reflectors,according to the principle of acoustic impedance mismatch of the boundary layer,the method of using air cavity to increase the underwater acoustic target strength of corner reflectors is *** acoustic reflection coefficients of underwater air layer and single layer metal sheet are calculated and *** results show that the reflection coefficient of single layer metal sheet is greatly affected by frequency and incidence angle,and the reflection coefficient of air layer in water is large and little affected by frequency and incidence *** this basis,a new kind of airfilled cavity corner reflector is *** acoustic scattering characteristics of underwater airfilled cavity comer reflector are calculated cumulatively,and the results are compared with the monolayer metal sheet corner *** simulation results show that the acoustic reflection effect of the airfilled cavity corner reflector is *** order to verify the correctness of the method,the test was carried out in the silencing *** experimental results show that the simulation results are in good agreement with the experimental results,and the airfilled cavity can improve on acoustic reflection performance of the underwater corner reflector.

关键词： Underwater corner reflector Acoustic target strength Air cavity Acoustic impedance mismatch

Pattern Recognition of Thermal Analysis Cooling Curves and Quality Evaluation of Melt Cast Alloys

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Journal of Materials Science & Technology 2001年第1期17卷 73-74页

作者： Yanxiang LI Xiao HU Xuerong XU dept.of Mechanical eng. Tsinghua UniversityBeijing 100084China

The development of thermal analysis techniques for evaluation of cast alloy melt quality and its current applications in the foundry were reviewed. The characteristics of the current thermal analysis techniques were analyzed. A new comprehensive method for cooling curve recognition has been proposed. The evaluation of cast alloy melt quality was realized.

关键词： Quality Evaluation Cooling Curves thermal analysis cooling curve recognition comprehensive method alloy melt

An Adaptive Joint Source/Channel Coding Using Error Correcting Arithmetic Codes

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Journal of Shanghai Jiaotong university(Science) 2007年第4期12卷 448-453页

作者：刘军清逄玉叶孙军 dept.of electronic eng. China Three Gorges Univ. dept.of electronic eng. Shanghai Jiaotong Univ.

An approximately optimal adaptive arithmetic coding (AC) system using a forbidden symbol (FS) over noisy channels was proposed which allows one to jointly and adaptively design the source decoding and channel correcting in a single process, with superior performance compared with traditional separated techniques. The concept of adaptiveness is applied not only to the source model but also to the amount of coding redundancy. In addition, an improved branch metric computing algorithm and a faster sequential searching algorithm compared with the system proposed by Grangetto were proposed. The proposed system is tested in the case of image transmission over the AWGN channel, and compared with traditional separated system in terms of packet error rate and complexity. Both hard and soft decoding were taken into account.

关键词： arithmetic coding joint source channel coding maximum a posteriori (MAP) forbidden symbol

EVALUATION OF THE PROBABILITY DISTRIBUTION OF PITTING CORROSION FATIGUE LIFE IN AIRCRAFT MATERIALS

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Acta Mechanica Sinica 2003年第3期19卷 247-252页

作者：王清远 N.KAWAGOISHI Q.Chen R.M.PIDAPARTI dept.of Civil eng.and Mechanics Sichuan UniversityChengdu 610065China

Corrosion and fatigue properties of aircraft materials are known to have a considerable scatter due to the random nature of materials,loading,and environmental conditions.A probabilistic approach for predicting the pitting corrosion fatigue life has been investigated which captures the effect of the interaction of the cyclic load and corrosive environment and all stages of the corrosion fatigue process (*** pit nucleation and growth,pit-crack transition,short- and long-crack propagation).The probabilistic model investigated considers the uncertainties in the initial pit size,corrosion pitting current,and material properties due to the scatter found in the experimental *** Carlo simulations were performed to define the failure probability *** cumulative distribution functions of fatigue life agreed reasonably well with the existing experimental data.

关键词： pitting corrosion fatigue probabilistic modeling fatigue life prediction

A UNIFIED ENERGY APPROACH TO A CLASS OF MICROMECHANICS MODELS FOR compOSITE MATERIALS

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Acta Mechanica Sinica 1995年第1期11卷 59-75页

作者：黄永刚黄克智胡凯雄 A.Chandra dept.of Aerospace and Mech.eng. The University of ArizonaTucsonAZ 85721USA dept.of engineering Mechanics Tsinghua UniversityBeijing 100084China

Several micromechanics models for the determination of composite moduli are investigated in this paper,including the dilute solution,self-consistent method,generalized self-consistent method,and Mori-Tanaka's *** mi- cromechanical models have been developed by following quite different approaches and physical *** is shown that all the micromechanics models share a common ground,the generalized Budiansky's energy-equivalence *** dif- ference among the various models is shown to be the way in which the average strain of the inclusion phase is *** a bonus of this theoretical development,the asymmetry suffered in Mori-Tanaka's method can be circumvented and the applica- bility of the generalized self-consistent method can be extended to materials contain- ing microcracks,multiphase inclusions,non-spherical inclusions,or non-cylindrical *** relevance to the differential method,double-inclusion model,and Hashin-Shtrikman bounds is also *** application of these micromechanics models to particulate-reinforced composites and microcracked solids is reviewed and some new results are presented.

关键词： micromechanics models energy-equivalence framework dilute solution self-consistent method generalized self-consistent method Mori-Tanaka's method