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Incipient Motion of Sediment Under Currents

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China Ocean Engineering 2000年第4期15卷 391-406页

作者：窦国仁 Chinese Academy of Sciences Nanjing 210029 China Chinese Society of Ocean Engineering Nanjing 210029 China Nanjing Hydraulic Research Institute Nanjing 210029 China

Summarized in the paper are the author's studies on incipient motion of sediment in recent 40 years. In addition to the forces of gravity, drag and lift, the cohesive force and the additional static pressure are important for fine particles. The relations between three stages of incipient motion are defined by use of instantaneous velocity. Formulas for initial velocity and critical shear stress are given and overall verified by the author's and others' experimental data.

关键词： sediment incipient motion initial velocity critical shear stress

Experimental Investigation into Low-velocity Water Entry of Cylinder Structure

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Journal of Shanghai Jiaotong university(Science) 2015年第6期20卷 703-712页

作者：初文华封峰张健 College of Marine Sciences Shanghai Ocean University Collaborative Innovation Center for Distant-Water Fisheries Shanghai Waigaoqiao Shipbuilding & Offshore Co. Ltd.

The process of low-velocity water entry is utilized on a large scale for the military and engineering purposes. However, there are rarely systematic experimental investigations into the low-velocity water entry of cylinder structure for reference. In order to obtain typical phenomena and relevant laws, we design a set of experimental facilities with adjustable parameters and better repeatability to study this process with a high-speed photography system. The influences of cylinder radius, initial velocity and entry angle on the process of lowvelocity water entry are tested. Results show that six typical phases exist in this process: structure submersion,necking, cavity formation, cavity abscission, spray at the free surface and jet formation. Three factors mentioned above are key parameters and influence the process in different degrees, and some laws obtained in this paper have a reasonable agreement with the theoretical results. Our results provide references for the relevant numerical researches and engineering applications.

关键词： low-velocity water entry cylinder structure cylinder radius initial velocity entry angle

Baseline correction for digital strong-motion records by using the pre-event portion

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Geodesy and Geodynamics 2011年第1期2卷 43-46页

作者： Li Heng Yao Yunsheng Zheng Shuiming Cai Yongjian Lei Dongning Institute of Seismology China Earthquake Administration Wuhan 430071 China Wuhan Institute of Earthquake Engineering Wuhan 430071 China

Baseline offset in digital strong-motion acceleration record and initial velocity can produce unrealistic results for ground velocity and displacement derived from the acceleration by integration. A new method is proposed for the baseline correction and initial velocity calculation. It is based on linear least-squares fitting of the pre-event portion of velocity derived from the uncorrected acceleration data. Compared with the conventional method,which is based on removing the mean values of the pre-event portions of the acceleration and velocity traces,this method has clearer physical meaning and better stability.

关键词： baseline offset correction acceleration records initial velocity least-square fitting

Development of High-Resolution Time-of-Flight Mass Spectrometry–Theoretical and Experimental Study

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Development of High-Resolution Time-of-Flight Mass Spectrome...