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Full-Text Articles in Physical Sciences and Mathematics
Dynamic Characteristics Research Of Torsional Vibration Generator, Jialin Tian, Du Fan, Yonghao Zhu, Chuanhong Fu
Dynamic Characteristics Research Of Torsional Vibration Generator, Jialin Tian, Du Fan, Yonghao Zhu, Chuanhong Fu
Journal of System Simulation
Abstract: Aiming at poor drill ability and low rate of penetration during the drilling process, a torsional vibration generator is presented. The structure and the operational principle of the torsional vibration generator are analyzed according to the torsional theory. The relationships among the collision frequency,the amount of hydraulic hammer compression, the torque, the inlet pressure, and inlet flow are obtained on the basis of its dynamic model, which is established in light of the actual working condition. Compared with the example calculation, the experimental test verifies the accuracy and reliability of calculation method. The research results show that when the …
Recent Trends In The Frequency And Duration Of Global Floods, Nasser Najibi, Naresh Devineni
Recent Trends In The Frequency And Duration Of Global Floods, Nasser Najibi, Naresh Devineni
Publications and Research
Frequency and duration of floods are analyzed using the global flood database of the Dartmouth Flood Observatory (DFO) to explore evidence of trends during 1985–2015 at global and latitudinal scales. Three classes of flood duration (i.e., short: 1–7, moderate: 8–20, and long: 21 days and above) are also considered for this analysis. The nonparametric Mann–Kendall trend analysis is used to evaluate three hypotheses addressing potential monotonic trends in the frequency of flood, moments of duration, and frequency of specific flood duration types. We also evaluated if trends could be related to large-scale atmospheric teleconnections using a generalized linear model framework. …