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Study of the correlations between main shocks and aftershocks and aftershock synthesis method

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Earthquake Engineering and Engineering Vibration 2019年第4期18卷 759-775页

作者： Zhang Yingnan Zhi Xudong fan feng Key Laboratory of Structural Engineering Disaster Control of Education Ministry (Harbin Institute of Technology) Harbin 150090 China Key Laboratory of Civil Engineering Intelligent Disaster Prevention and Mitigation Control of Ministry of Industry and Information (Harbin Institute of Technology) Harbin 150090 China School of Civil Engineering Harbin Institute of Technology Harbin 150090 China

To consider the infl uence of aftershocks in engineering design, the correlations between main shocks and aftershocks should be examined, and an aftershock simulation method with main shock ground motions needs to be developed. In this study, the data on the sequences of main shock–aftershock ground motions and other related parameters were collected. Using these data, correlations between the magnitude, frequency, duration and energy of the main shock–aftershock ground motions were investigated. The results showed that the magnitude of the aftershock can be larger than that of the main shock. The shapes of the Fourier amplitude spectra of main shocks and aftershocks were similar;however, the predominant frequency and high-frequency components of the aftershock tended to be larger. Considering the magnitude diff erence between the main shock and the aftershock, the correlation of durations was explored. Additionally, a new concept, the duration ratio, was defi ned to describe the concentration of seismic energy release, and main shock energy was strongly positively correlated with the energy attenuated during the main shock–aftershock sequence. Finally, based on these results regarding correlation, an aftershock synthesis using recorded main shock ground motions was constructed with the trigonometric series method for seismic design, and some examples are given to analyze the rationality of this synthetic method.

关键词： main shock-aftershock sequence correlation aftershock synthesis seismic design

Simplified design method and seismic performance of space trusses with consideration of the influence of the stiffness of their lower supporting columns

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Earthquake Engineering and Engineering Vibration 2016年第2期15卷 401-409页

作者： fan feng Sun Menghan Zhi Xudong Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education Harbin Institute of Technology School of Civil Engineering Harbin Institute of Technology

Static and dynamic force performance of two types of space truss structures i.e. square pyramid space truss（SPST） and diagonal on square pyramid space truss（DSPST）, are studied to determine the effect of stiffness of their lower supporting members. A simplified model for the supporting columns and the equivalent spring mass system are presented. Furthermore, the feasibility of the simplified model is demonstrated through theoretical analysis and examples of comparative analysis of the simplified model with the entire model. Meanwhile, from the elastic analysis under frequently occurring earthquakes and elasto-plastic analysis under seldom occurring earthquakes subjected to TAFT and EL-Centro seismic oscillation it is shown that the simplified method can be encompassed in the results from the normal model. It also showed good agreement between the two methods, as well as greatly improved the computational efficiency. This study verified that the dynamic effect of the supporting structures was under considered in space truss design in the past. The method proposed in the paper has important significance for other space truss structures.

关键词： simplified supporting pyramid stiffness truss verified diagonal elasto columns seldom

A Simulation-Extrapolation Approach to the Analysis of Interval-Censored Failure Time Data with Mis-Measured Covariates

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Journal of Systems Science & Complexity 2024年第6期37卷 2721-2737页

作者： feng fan ZHAO Shishun LI Shuwei SUN Jianguo School of Economics and Statistics Guangzhou University School of Mathematics Jilin University School of Mathematics Jilin University Department of Statistics University of Missouri

Interval-censored failure time data arise frequently in periodical follow-up studies including clinical trials and epidemiological surveys. In addition, some covariates may be subject to measurement errors due to the instrumental contamination, biological variation or other reasons. For the analysis of interval-censored data with mis-measured covariates, the existing methods either assume a parametric model or rely on the availability of replicated surrogate measurements for the error-prone covariate, which both have obvious limitations. To overcome these shortcomings, the authors propose a simulation-extrapolation estimation procedure under a general class of transformation models. The resulting estimators are shown to be consistent and asymptotically normal. The numerical results obtained from a simulation study indicate that the proposed method performs reasonably well in *** particular, the proposed method can reduce the estimation bias given by the naive method that does not take measurement errors into account. Finally, the proposed method is applied to a real data set on hypobaric decompression sickness.

关键词： Interval censoring measurement error regression analysis semiparametric model SIMEX

Visuals to Text:A Comprehensive Review on Automatic Image Captioning

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IEEE/CAA Journal of Automatica Sinica 2022年第8期9卷 1339-1365页

作者： Yue Ming Nannan Hu Chunxiao fan fan feng Jiangwan Zhou Hui Yu Beijing University of Posts and Telecommunications Beijing 100876China School of Creative Technologies University of PortsmouthPortsmouth PO12DJUK

Image captioning refers to automatic generation of descriptive texts according to the visual content of *** is a technique integrating multiple disciplines including the computer vision(CV),natural language processing(NLP)and artificial *** recent years,substantial research efforts have been devoted to generate image caption with impressive *** summarize the recent advances in image captioning,we present a comprehensive review on image captioning,covering both traditional methods and recent deep learning-based ***,we first briefly review the early traditional works based on the retrieval and *** deep learning-based image captioning researches are focused,which is categorized into the encoder-decoder framework,attention mechanism and training strategies on the basis of model structures and training manners for a detailed *** that,we summarize the publicly available datasets,evaluation metrics and those proposed for specific requirements,and then compare the state of the art methods on the MS COCO ***,we provide some discussions on open challenges and future research directions.

关键词： Artificial intelligence attention mechanism encoder-decoder framework image captioning multi-modal understanding training strategies

Numerical Calculations of Aerodynamic and Acoustic Characteristics for Scissor Tail-Rotor in Forward Flight

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Transactions of Nanjing University of Aeronautics and Astronautics 2016年第3期33卷 285-293页

作者： fan feng Huang Shuilin Lin Yongfeng China Helicopter Research and Development Institute Aviation Industry Corporation of China

The aerodynamic and aeroacoustic characteristics of a scissor tail-rotor in a forward flight are numerically calculated.A novel computational fluid dynamics(CFD)model based on Navier-Stokes(N-S)equations is presented to simulate the unsteady flowfield and the aerodynamic characteristics of a scissor tail-rotor in the forward *** the Farassat Formulation 1 Aderived from the FW-H equation is coupled into the CFD model in order to compute the aeroacoustic characteristics of the scissor *** addition,two different scissor tail-rotor configurations,i.e.,the L-and U-configuration,are analyzed in details and compared with a conventional *** influence of scissor angles on the aerodynamic and aeroacoustic characteristics of the scissor tail-rotor is also *** simulation results demonstrate that the flowfield,aerodynamic force and aeroacoustic characteristics of a scissor tail-rotor are significantly different from the conventional one,and the aerodynamic interaction decreases with the increase of scissor angle,which leads to a reduction of amplitude variation of the tail-rotor thrust in the forward *** scissor angle has an important effect on the aerodynamics and aeroacoustics of the scissor tail-rotor.

关键词： computational fluid dynamics(CFD) scissor tail-rotors aerodynamic characteristics aeroacoustic characteristics Navier-Stokes(N-S)equations

Self-organizing fuzzy clustering neural network and application to electronic countermeasures effectiveness evaluation

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Journal of Systems Engineering and Electronics 2008年第1期19卷 119-124页

作者： Li Zhisheng Li Junshan feng fan Zhao Xin The Second Artillery Engineering Coll. Xi'an 710025 P. R. China PLA 92941 Huludao 125000 P. R. China School of Information Science and Technology Beijing Inst. of Technology Beijing 100081 P. R. China

A self-organizing fuzzy clustering neural network by combining the self-organizing Kohonen clustering network with the fuzzy theory is proposed. This network model is designed for the effectiveness evaluation of electronic countermeasures, which not only exerts the advantages of the fuzzy theory, but also has a good ability in machine learning and data analysis. The subjective value of sample versus class is computed by the fuzzy computing theory, and the classified results obtained by self-organizing learning of Kohonen neural network are represented on output layer. Meanwhile, the fuzzy competition learning algorithm keeps the similar information between samples and overcomes the disadvantages of neural network which has fewer samples. The simulation result indicates that the proposed algorithm is feasible and effective.

关键词： fuzzy clusteringself-organizing neural network effectiveness evaluation

A New Single-blade Based Hybrid CFD Method for Hovering and Forward-flight Rotor Computation

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Chinese Journal of Aeronautics 2011年第2期24卷 127-135页

作者： SHI Yongjie ZHAO Qijun fan feng XU Guohua National Key Laboratory of Rotorcraft Aeromechanics Nanjing University of Aeronautics and Astronautics Nanjing 210016 China

A hybrid Euler/full potential/Lagrangian wake method,based on single-blade simulation,for predicting unsteady aerodynamic flow around helicopter rotors in hover and forward flight has been *** this method,an Euler solver is used to model the near wake evolution and transonic flow phenomena in the vicinity of the blade,and a full potential equation（FPE） is used to model the isentropic potential flow region far away from the rotor,while the wake effects of other blades and the far wake are incorporated into the flow solution as an induced inflow distribution using a Lagrangian based wake *** further reduce the execution time,the computational fluid dynamics（CFD） solution and rotor wake analysis（including induced velocity up-date） are conducted parallelly,and a load balancing strategy is employed to account for the information exchange between two *** the developed method,several hover and forward-flight cases on Caradonna-Tung and Helishape 7A rotors are *** agreements of the loadings on blade surface with available measured data demonstrate the validation of the ***,the CPU time required for different computation runs is compared in the paper,and the results show that the pre-sent hybrid method is superior to conventional CFD method in time cost,and will be more efficient with the number of blades increasing.

关键词： hybrid CFD method Euler equations full potential equations wake model rotor helicopters

Study on the effect of ground motion direction on the response of engineering structure

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Earthquake Engineering and Engineering Vibration 2016年第4期15卷 649-656页

作者： Sun Menghan fan feng Sun Baitao Zhi Xudong Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education Harbin Institute of Technology School of Civil Engineering Harbin Institute of Technology Key Laboratory of Earthquake Engineering and Engineering Vibration Institute of Engineering Mechanics China Earthquake Administration

Due to the randomness of earthquake wave magnitude and direction, and the uncertain direction of strong axis and weak axis in the construction of engineering structures, the effect of the direction of ground motion on a structure are studied herein. Ground motion records usually contain three vertical ground motion data, which are obtained by sensors arranged in accordance with the EW （East -West） direction, NS （South- North） direction and perpendicular to the surface （z） direction, referring to the construction standard of seismic stations. The seismic records in the EW and NS directions are converted to Cartesian coordinates in accordance with the rotation of θ = 0°-180°, and consequently, a countless group of new ground motion time histories are obtained. Then, the characteristics of the ground motion time history and response spectrum of each group were studied, resulting in the following observations：（1） the peak and phase of ground motion are changed with the rotation of direction θ, so that the direction θ of the maximum peak ground motion can be determined; （2） response spectrum values of each group of ground motions change along with the direction θ, and their peak, predominant period and declining curve are also different as the changes occur; then, the angle θ in the direction of the maximum peak value or the widest predominant period can be determined; and （3） the seismic response of structures with different directions of ground motion inputs has been analyzed under the same earthquake record, and the results show the difference. For some ground motion records, such as the Taft seismic wave, these differences are significant. Next, the Lushan middle school gymnasium structure was analyzed and the calculation was checked using the proposed method, where the internal force of the upper space truss varied from 25% to 28%. The research results presented herein can be used for reference in choosing the ground motion when checking the actual damage to struct

关键词： direction of grotmd motion structure effect coordinate transformation response spectrum

Boosting carrier dynamics of BiVO_(4) photoanode via heterostructuring with ultrathin BiOI nanosheets for enhanced solar water splitting

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Journal of Materials Science & Technology 2021年第20期79卷 21-28页

作者： Can Li fan feng Jie Jian Youxun Xu fan Li Hongqiang Wang Lichao Jia Key Laboratory of Applied Surface and Colloid Chemistry National Ministry of EducationShaanxi Key Laboratory for Advanced Energy DevicesShaanxi Engineering Lab for Advanced Energy TechnologySchool of Materials Science and EngineeringShaanxi Normal University620 West Chang’an StreetXi’anShaanxi710119China State Key Laboratory of Solidification Processing Center for Nano Energy MaterialsSchool of Materials Science and EngineeringNorthwestern Polytechnical University and Shaanxi Joint Labortary of GrapheneXi’an710072China

Bismuth vanadate(BiVO_(4))has been one of the most promising candidates for solar water splitting while still suffers from poor bulk charge transport that limits its solar to hydrogen conversion *** demonstrate in this work an efficient strategy for boosting bulk charge transport of BiVO_(4) through the facile impregnation of as-prepared BiVO_(4) photoanode in the precursor solution of ultrathin BiOI *** impregnation creates increased oxygen vacancies in the bulk of BiVO_(4) through the reduction of V^(5+)to V^(4+)by I^(-),which greatly improves bulk separation efficiency for BiVO_(4)-BiOI up to 65.9%at 1.23 V_(RHE) from the original 51.9%of pure BiVO_(4).Moreover,the decoration of the BiOI nanosheets on BiVO_(4) photoanode is also beneficial for addressing the carrier dynamics at surface due to the matched energy levels of BiOI nanosheets and BiVO_(4).The introduced plenty of oxygen vacancies in the bulk of BiVO_(4) and the built-in electric field in BiVO_(4)-BiOI synergistically improve the photocurrent density at 1.23 V_(RHE) up to 3.88 mA cm^(-2).We believe that such facile impregnation strategy will pave an alternative way to the development of highly efficient BiVO_(4) photoanode.

关键词： Bismuth vanadate BiOI nanosheets Heterojunction Solution impregnation Oxygen vacancy