The dynamic analysis of a Tension Leg Platform （TLP） in random wave is investigated by considering the set-down of a floating body. The nonlinear restoring stiffness is derived with the set-down motion of a floating...The dynamic analysis of a Tension Leg Platform （TLP） in random wave is investigated by considering the set-down of a floating body. The nonlinear restoring stiffness is derived with the set-down motion of a floating body and the coupled motion of the tension leg and platform and the differential equations of the motion are established. The study focuses on the influence of the set-down motion on the nonlinear response of the platform. By considering different significant wave heights and currents, motion responses of the platform are calculated and compared. The analysis shows that the set-down motion significantly increases the heave motion with low frequency and the equilibrium position of the heave motion with the set-down motion is much lower than that without set-down motion. The results in this paper indicate that the set-down motion has a major impact on the safety of the platform inproduction operation, and it is also a threat to the strength of tension legs and risers.展开更多
In this paper we study a continuous time random walk in the line with two boundaries [a,b], a < b. The particle can move in any of two directions with different velocities v1 and v2. We consider a special type of b...In this paper we study a continuous time random walk in the line with two boundaries [a,b], a < b. The particle can move in any of two directions with different velocities v1 and v2. We consider a special type of boundary which can trap the particle for a random time. We found closed-form expressions for the stationary distribution of the position of the particle not only for the alternating Markov process but also for a broad class of semi-Markov processes.展开更多
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
Apparent motion stimulus induces visual perception of smooth motion even though there is no speed information. We examined whether human brain response as measured by magnetoencephalography carries direction informati...Apparent motion stimulus induces visual perception of smooth motion even though there is no speed information. We examined whether human brain response as measured by magnetoencephalography carries direction information in the visually presented apparent motion of a randomdot pattern in a similar manner as continuous motions that have speed and direction information. Although there was no significant effect of motion direction on the peak response latency and amplitude, mutual information entropy (IE) significantly increased after the motion onset at approximately 36 ms after the response latency in 41% of the evaluations. Detailed analysis of the data from five subjects who participated in both the present apparent motion and our previous coherent motion studies revealed that the maximum IE latency (delay) for apparent motion was significantly longer than that for coherent motion, although the mean maximum IE was the same. The results indicate that direction is represented in the response waveform evoked by apparent motion but the manner is different from that for coherent motion probably due to the distinct neural processes engaged only for the apparent motion perception. We consider that direction and speed can be processed separately in the human brain because direction information was generated without speed information for the perception of apparent motion.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51239008 and 51279130)
文摘The dynamic analysis of a Tension Leg Platform （TLP） in random wave is investigated by considering the set-down of a floating body. The nonlinear restoring stiffness is derived with the set-down motion of a floating body and the coupled motion of the tension leg and platform and the differential equations of the motion are established. The study focuses on the influence of the set-down motion on the nonlinear response of the platform. By considering different significant wave heights and currents, motion responses of the platform are calculated and compared. The analysis shows that the set-down motion significantly increases the heave motion with low frequency and the equilibrium position of the heave motion with the set-down motion is much lower than that without set-down motion. The results in this paper indicate that the set-down motion has a major impact on the safety of the platform inproduction operation, and it is also a threat to the strength of tension legs and risers.
文摘In this paper we study a continuous time random walk in the line with two boundaries [a,b], a < b. The particle can move in any of two directions with different velocities v1 and v2. We consider a special type of boundary which can trap the particle for a random time. We found closed-form expressions for the stationary distribution of the position of the particle not only for the alternating Markov process but also for a broad class of semi-Markov processes.
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.
文摘Apparent motion stimulus induces visual perception of smooth motion even though there is no speed information. We examined whether human brain response as measured by magnetoencephalography carries direction information in the visually presented apparent motion of a randomdot pattern in a similar manner as continuous motions that have speed and direction information. Although there was no significant effect of motion direction on the peak response latency and amplitude, mutual information entropy (IE) significantly increased after the motion onset at approximately 36 ms after the response latency in 41% of the evaluations. Detailed analysis of the data from five subjects who participated in both the present apparent motion and our previous coherent motion studies revealed that the maximum IE latency (delay) for apparent motion was significantly longer than that for coherent motion, although the mean maximum IE was the same. The results indicate that direction is represented in the response waveform evoked by apparent motion but the manner is different from that for coherent motion probably due to the distinct neural processes engaged only for the apparent motion perception. We consider that direction and speed can be processed separately in the human brain because direction information was generated without speed information for the perception of apparent motion.
