With the increase of the interest in solar sailing, it is required to provide a basis for future detailed planetary escape mission analysis by drawing together prior work, clarifying and explaining previously anomalie...With the increase of the interest in solar sailing, it is required to provide a basis for future detailed planetary escape mission analysis by drawing together prior work, clarifying and explaining previously anomalies. In this paper, a technique for escaping the Earth by using a solar sail is developed and numerically simulated. The spacecraft is initially in a geosynchronous transfer orbit (GTO). Blended solar sail analytical control law, explicitly independent of time, are then presented, which provide near-optimal escape trajectories and maintain a safe minimum altitude and which are suitable as a potential autonomous onboard controller. This control law is investigated from a range of initial conditions and is shown to maintain the optimality previously demonstrated by the use of a single-energy gain control law but without the risk of planetary collision. Finally, it is shown that the blending solar sail analytical control law is suitable for solar sail on-board autonomously control system.展开更多
In this work,the corrosion behavior of the sintered Nd_(2)Fe_(14)B in which Nd was substituted by Ce to form dual-main-phased magnet with/without annealing process was studied.The mass loss of as-sintered magnets(SM)i...In this work,the corrosion behavior of the sintered Nd_(2)Fe_(14)B in which Nd was substituted by Ce to form dual-main-phased magnet with/without annealing process was studied.The mass loss of as-sintered magnets(SM)is larger than that of as-annealed magnets(AM)in the accelerated corrosion tests.In particular,the mass loss of SM increases sharply when the corrosion time increases to48 h.The free corrosion current of the SM samples is larger than that of AM in 0.1 mo1·L^(-1)HCl;this is due to that the content of RE-rich phase at the intergranular triple junctions(TJs)of the SM samples is larger than that of AM samples and the corrosion rate of the RE-rich phase at the TJs is higher than that at grain boundaries.But the free corrosion current of the SM samples is smaller than that of AM samples in 3.5 wt%NaCl as the electron transfer resistance(R_(ct))of SM is larger than that of AM.Inductive loop in the Nyquist diagrams at low frequency of SM is observed,which originated from the pitting.It shows that pitting of SM occurs more easily than that of AM.Corrosion morphology of samples indicates that the corrosion area of SM is bigger and deeper than that of AM after accelerated corrosion for 60 h.Through the annealing process,the distribution of rare-earth-rich phase becomes more uniform,which changes the free corrosion current and effectively suppresses the occurrence and propagation of pitting.展开更多
基金Sponsored by the National Natural Science Foundation of China ( Grant No. 61005060)
文摘With the increase of the interest in solar sailing, it is required to provide a basis for future detailed planetary escape mission analysis by drawing together prior work, clarifying and explaining previously anomalies. In this paper, a technique for escaping the Earth by using a solar sail is developed and numerically simulated. The spacecraft is initially in a geosynchronous transfer orbit (GTO). Blended solar sail analytical control law, explicitly independent of time, are then presented, which provide near-optimal escape trajectories and maintain a safe minimum altitude and which are suitable as a potential autonomous onboard controller. This control law is investigated from a range of initial conditions and is shown to maintain the optimality previously demonstrated by the use of a single-energy gain control law but without the risk of planetary collision. Finally, it is shown that the blending solar sail analytical control law is suitable for solar sail on-board autonomously control system.
基金financially supported by the National Natural Science Foundation of China(No.51571064)the National Basic Research Program of China(No.2014CB643701)。
文摘In this work,the corrosion behavior of the sintered Nd_(2)Fe_(14)B in which Nd was substituted by Ce to form dual-main-phased magnet with/without annealing process was studied.The mass loss of as-sintered magnets(SM)is larger than that of as-annealed magnets(AM)in the accelerated corrosion tests.In particular,the mass loss of SM increases sharply when the corrosion time increases to48 h.The free corrosion current of the SM samples is larger than that of AM in 0.1 mo1·L^(-1)HCl;this is due to that the content of RE-rich phase at the intergranular triple junctions(TJs)of the SM samples is larger than that of AM samples and the corrosion rate of the RE-rich phase at the TJs is higher than that at grain boundaries.But the free corrosion current of the SM samples is smaller than that of AM samples in 3.5 wt%NaCl as the electron transfer resistance(R_(ct))of SM is larger than that of AM.Inductive loop in the Nyquist diagrams at low frequency of SM is observed,which originated from the pitting.It shows that pitting of SM occurs more easily than that of AM.Corrosion morphology of samples indicates that the corrosion area of SM is bigger and deeper than that of AM after accelerated corrosion for 60 h.Through the annealing process,the distribution of rare-earth-rich phase becomes more uniform,which changes the free corrosion current and effectively suppresses the occurrence and propagation of pitting.
