This paper presents a modeling method by stochastic Petri net for reliability analysis of phased mission system( PMS) with phase backup. The model consisting of petri nets,depicts the system behaviors of unit level,sy...This paper presents a modeling method by stochastic Petri net for reliability analysis of phased mission system( PMS) with phase backup. The model consisting of petri nets,depicts the system behaviors of unit level,system logic level and phase level. Guard functions of petri nets are used to avoid modeling complexity and make the model flexible to different reliability logical structures. It was shown that the time redundancy within phase and from phase backup for PMS can both be described by use of the proposed model.展开更多
The safety of astronauts would be severely threatened if the lunar-landing spacecraft were under an emergency during the near moon phase of flight, which was far from the Earth. For the problem of mission abort caused...The safety of astronauts would be severely threatened if the lunar-landing spacecraft were under an emergency during the near moon phase of flight, which was far from the Earth. For the problem of mission abort caused by the main engine (service propulsion system, SPS) failure during lunar orbit insertion, firstly, the family of trajectories resulted from SPS premature shutdown and corresponding abort trajectories were analyzed; then an algorithm that can be applied to the near moon abort trajectories was proposed using patched-conic technique. The characteristics of the abort trajectory, such as energy consumption and return time of flight, were analyzed and presented. Finally, simulation examples were given to demonstrate various cases of near moon SPS failure. The results of the simulation have validated the approach proposed.展开更多
A simulated study of mechanism for variations and distributions of ozone and its precursors was made by using the three-dimensional regional Eulerian model.The results showed that the ozone production was controlled b...A simulated study of mechanism for variations and distributions of ozone and its precursors was made by using the three-dimensional regional Eulerian model.The results showed that the ozone production was controlled by NO,but there is a complicated nonlinear relation between them.The photochemical reactions controlled by solar radiation are the determinative factors affecting the variations of the surface ozone and its precursors.The relations of ozone and CO, PAN were studied.We compared the simulated and observed results during the PEM-WEST A in order to better under- stand the photochemical processes of ozone and its precursors.展开更多
基金Nationd Natural Science Foundation of China(No.71671185)
文摘This paper presents a modeling method by stochastic Petri net for reliability analysis of phased mission system( PMS) with phase backup. The model consisting of petri nets,depicts the system behaviors of unit level,system logic level and phase level. Guard functions of petri nets are used to avoid modeling complexity and make the model flexible to different reliability logical structures. It was shown that the time redundancy within phase and from phase backup for PMS can both be described by use of the proposed model.
文摘The safety of astronauts would be severely threatened if the lunar-landing spacecraft were under an emergency during the near moon phase of flight, which was far from the Earth. For the problem of mission abort caused by the main engine (service propulsion system, SPS) failure during lunar orbit insertion, firstly, the family of trajectories resulted from SPS premature shutdown and corresponding abort trajectories were analyzed; then an algorithm that can be applied to the near moon abort trajectories was proposed using patched-conic technique. The characteristics of the abort trajectory, such as energy consumption and return time of flight, were analyzed and presented. Finally, simulation examples were given to demonstrate various cases of near moon SPS failure. The results of the simulation have validated the approach proposed.
基金This work is partly supported by the National Natural Science Foundation of China.
文摘A simulated study of mechanism for variations and distributions of ozone and its precursors was made by using the three-dimensional regional Eulerian model.The results showed that the ozone production was controlled by NO,but there is a complicated nonlinear relation between them.The photochemical reactions controlled by solar radiation are the determinative factors affecting the variations of the surface ozone and its precursors.The relations of ozone and CO, PAN were studied.We compared the simulated and observed results during the PEM-WEST A in order to better under- stand the photochemical processes of ozone and its precursors.
