A fragility calculation scheme is estabtished in this paper for porcelain-type equipments subjected to random earthquake ground motions. All steps of the method are illustrated by the seismic damage analysis of GW4-11...A fragility calculation scheme is estabtished in this paper for porcelain-type equipments subjected to random earthquake ground motions. All steps of the method are illustrated by the seismic damage analysis of GW4-110 disconnect switch. The model of the equipment is built applying the finite element method with flexible joints, and the seismic response of the equipment is analyzed using elastic time history method. On the base, according to the strength damage index and Monte-Carlo Method, the seismic damage ratios are counted and the seismic fragility curves are presented. Then the seismic damage of GW4-110 disconnect switch can be predicted.展开更多
Using the path-integral method, the corrections to the Casimir energy due to the combined effect of surface roughness and the finite temperature are calculated. For the specific case of two sinusoidally corrugated pla...Using the path-integral method, the corrections to the Casimir energy due to the combined effect of surface roughness and the finite temperature are calculated. For the specific case of two sinusoidally corrugated plates, the lateral Casimir force at finite temperature is obtained. The amplitude of the lateral Casimir force has a maximum at an optimal wavelength of λ≈ 2H with the mean plate distance H. This optimal parameter relation is almost independent of temperature.展开更多
We calculate the contributions of the vacuum fluctuations and radiation reaction to the rate of change of the mean atomic energy for a multi-level hydrogen atom in the multipolar coupling scheme in a spacetime with a ...We calculate the contributions of the vacuum fluctuations and radiation reaction to the rate of change of the mean atomic energy for a multi-level hydrogen atom in the multipolar coupling scheme in a spacetime with a reflecting boundary. Our results show that, due to the presence of the boundary, the polarizations of the atom in the parallel direction and in the normal direction are weighted differently in terms of their contributions to the spontaneous emission rate, which is an oscillating function of the atom distance from the boundary. The possible experimental implications of our result are briefly discussed.展开更多
Basic fluid mechanics and stochastic theories are applied to show that the concentration distribution of suspended solid particles in a direction normal to the mean streamlines of a two-dimensional turbulent flow is g...Basic fluid mechanics and stochastic theories are applied to show that the concentration distribution of suspended solid particles in a direction normal to the mean streamlines of a two-dimensional turbulent flow is greatly influenced by the lift force exerted on them in the vicinity of the wall.Analytic solution shows that,when the direction of the mean flow is horizontal,the probability density function p(y,t)for random displacements of the particles will have a maximum value at a point from the wall where the perpendicular component of the lift force precisely balances particle gravity.Interpretation of experimental observations is presented using this theory.展开更多
To solve the path following problem in navigation tasks for under-actuated autonomous surface vehicles(ASVs),this paper proposed a path following control method which combines trajectory dataset of random ship motion ...To solve the path following problem in navigation tasks for under-actuated autonomous surface vehicles(ASVs),this paper proposed a path following control method which combines trajectory dataset of random ship motion and offline reinforcement learning(RM-ORL).The method does not require the reinforcement learning(RL)agent to interact with the environment while training the policy,and it can obtain training datasets with a lower cost.In RM-ORL,the irregular motion data of the ASV in open water is first collected.Then the desired path is reconstructed using the B-spline function and the path points along the motion trajectories.Thus the offline dataset will be enhanced with the motion data and the new path.Finally,the conservative Q-learning algorithm is utilized to train the path following controller.The path deviation in simulation maps,rudder data and ship motion parameters of RM-ORL,online RL and other offline RL policies trained on different datasets are compared.The simulation results illustrate that the RM-ORL achieves comparable path following accuracy to that of online RL agent and offline RL agent trained on expert data,while surpassing the one trained on online agent replay buffer data.The rudder steering amplitude of RM-ORL is also smaller than that of other policies,which verifies the effectiveness of our method applied to the path following control of under-actuated ASV.展开更多
We establish a central limit theorem for a branching Brownian motion with random immigration under the annealed law,where the immigration is determined by another branching Brownian motion.The limit is a Gaussian rand...We establish a central limit theorem for a branching Brownian motion with random immigration under the annealed law,where the immigration is determined by another branching Brownian motion.The limit is a Gaussian random measure and the normalization is t3/4for d=3 and t1/2for d≥4,where in the critical dimension d=4 both the immigration and the branching Brownian motion itself make contributions to the covariance of the limit.展开更多
基金supported by the Science and Technology Commission of Shanghai Municipality (Grant No.04JC14035)
文摘A fragility calculation scheme is estabtished in this paper for porcelain-type equipments subjected to random earthquake ground motions. All steps of the method are illustrated by the seismic damage analysis of GW4-110 disconnect switch. The model of the equipment is built applying the finite element method with flexible joints, and the seismic response of the equipment is analyzed using elastic time history method. On the base, according to the strength damage index and Monte-Carlo Method, the seismic damage ratios are counted and the seismic fragility curves are presented. Then the seismic damage of GW4-110 disconnect switch can be predicted.
基金Supported by the National Basic Research Programme of China under Grant No 2003CB716300, and the National Natural Science Foundation of China under Grant No 10505009.
文摘Using the path-integral method, the corrections to the Casimir energy due to the combined effect of surface roughness and the finite temperature are calculated. For the specific case of two sinusoidally corrugated plates, the lateral Casimir force at finite temperature is obtained. The amplitude of the lateral Casimir force has a maximum at an optimal wavelength of λ≈ 2H with the mean plate distance H. This optimal parameter relation is almost independent of temperature.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10375023 and 10575035, the Programme for NCET （No 04-0784）, and the Key Project of the Ministry of Education of China （No 205110）.
文摘We calculate the contributions of the vacuum fluctuations and radiation reaction to the rate of change of the mean atomic energy for a multi-level hydrogen atom in the multipolar coupling scheme in a spacetime with a reflecting boundary. Our results show that, due to the presence of the boundary, the polarizations of the atom in the parallel direction and in the normal direction are weighted differently in terms of their contributions to the spontaneous emission rate, which is an oscillating function of the atom distance from the boundary. The possible experimental implications of our result are briefly discussed.
文摘Basic fluid mechanics and stochastic theories are applied to show that the concentration distribution of suspended solid particles in a direction normal to the mean streamlines of a two-dimensional turbulent flow is greatly influenced by the lift force exerted on them in the vicinity of the wall.Analytic solution shows that,when the direction of the mean flow is horizontal,the probability density function p(y,t)for random displacements of the particles will have a maximum value at a point from the wall where the perpendicular component of the lift force precisely balances particle gravity.Interpretation of experimental observations is presented using this theory.
基金support of Opening Foundation of State Key Laboratory of Maritime Technology and Safety(Grant No.W24CG000040)the National Natural Science Foundation of China(Grant No.42406205)National Key Research and Development Program of China(Grant No.2023YFC2809801).
文摘To solve the path following problem in navigation tasks for under-actuated autonomous surface vehicles(ASVs),this paper proposed a path following control method which combines trajectory dataset of random ship motion and offline reinforcement learning(RM-ORL).The method does not require the reinforcement learning(RL)agent to interact with the environment while training the policy,and it can obtain training datasets with a lower cost.In RM-ORL,the irregular motion data of the ASV in open water is first collected.Then the desired path is reconstructed using the B-spline function and the path points along the motion trajectories.Thus the offline dataset will be enhanced with the motion data and the new path.Finally,the conservative Q-learning algorithm is utilized to train the path following controller.The path deviation in simulation maps,rudder data and ship motion parameters of RM-ORL,online RL and other offline RL policies trained on different datasets are compared.The simulation results illustrate that the RM-ORL achieves comparable path following accuracy to that of online RL agent and offline RL agent trained on expert data,while surpassing the one trained on online agent replay buffer data.The rudder steering amplitude of RM-ORL is also smaller than that of other policies,which verifies the effectiveness of our method applied to the path following control of under-actuated ASV.
基金Supported by National Natural Science Foundation of China(Grant Nos.11131003 and 11201068)985-Project
文摘We establish a central limit theorem for a branching Brownian motion with random immigration under the annealed law,where the immigration is determined by another branching Brownian motion.The limit is a Gaussian random measure and the normalization is t3/4for d=3 and t1/2for d≥4,where in the critical dimension d=4 both the immigration and the branching Brownian motion itself make contributions to the covariance of the limit.
