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Chen Zhipeng,Luo Feng,Zeng Jingwei,Dai Jiancheng,Zhou Guanghuai,Li Ruijie 한국해양과학기술원 2023 Ocean science journal Vol.58 No.1
Salt marshes are now known to improve coastal safety by attenuating waves and stabilizing the bed. Meanwhile, for salt marsh conservatin and restoration, a great deal of research has been done on the establishment mechanism of vegetation in salt marshes. However, research on the efects of hydrodynamic disturbance on the development of salt marsh vegetation is limited. The purpose of this paper is to investigate how the hydro-morphodynamic process afects the establishment and expansion of plants in salt marshes and to simulate the establishment process. First, we used a 2D fnite-element model to simulate hydro-morphodynamics in the selected tidal fat in Jiangsu, China. We then defned the variables describing the frequency and magnitude of hydrodynamic disturbance and quantifed the efects of disturbance on plant establishment using Spearman correlation coefcients. Finally, the vegetation development process was further analyzed using a logistic regression model, and the vegetation development in the study area was simulated from 2017 to 2021. The results show that salt marsh vegetation colonization has a relatively high correlation with fooding time and bed shear stress (ρ>0.6), and bed shear stress is the main hydrodynamic disturbance parameter limiting further expansion of salt marsh vegetation. The method combining hydrodynamic modeling and logistic regression has the potential to be used to identify hydrodynamic disturbances in future salt marsh restoration and management processes and to help design appropriate restoration measures.
Effects of dynamic transmission errors and vibration stability in helical gears
Jing Wei,Pan Gao,Xinglong Hu,Wei Sun,Jing Zeng 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.6
Transmission error is an important reason for instability in helical gears. A six-degree-of-freedom dynamic model coupled flexional,torsional and axial motion of a helical gear transmission system, which includes time varying mesh stiffness, bearing supporting stiffness,mesh damping and backlash, is developed, after taking into account the dynamic characteristics and vibration responses of helical gear inthree dimensions. Influences of involute contact ratio, bearing supporting stiffness, mesh damping and backlash on the dynamic transmissionerrors and vibration stability of the helical gear system are investigated using numerical simulation technique. The effects on dynamictransmission errors and stabilities by contact ratio, supporting stiffness and mesh damping as well as gear backlash are analyzed. The intrinsic relationship between above parameters and dynamic transmission errors and stabilities for helical gear system are presented. The stable and unstable regions under different parameters are given. The results in this paper can be helpful to the dynamic and stabledesign of a helical gear transmission system.
Dynamic analysis and load-sharing characteristic of multiple pinion drives in tunnel boring machine
Jing Wei,Qinchao Sun,Wei Sun,Jin Cai,Jin Zeng 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.5
A dynamic model of multi-gear drive in a tunnel boring machine is demonstrated in this study in which the effects of inertia on the driving mechanism and cutter head are considered. With the nonlinear coupling factors between the ring gear and multiple pinions considered,a dynamic analysis of multiple pinion drives is conducted, and their load-sharing characteristic is proposed. The load-sharing coefficients at different rotating cutter head speeds and input torques are determined and are found to reach up to 1.2-1.3. A simulated experimental platform of multiple pinion drives is performed, and subsequent torque distributions are measured under step load in the driving shaft of pinions. An imbalance in torque distribution of pinions is verified, and the load-sharing coefficients in each pinion can reach 1.262. Torque load fluctuation is regarded as system noise that can directly be coupled into the control system in the control strategy.