针对北斗三号系统中轨道Walker导航星座的备份策略问题,提出基于随机时间Petri网(stochastic timed Petri net,STPN)的分析评估方法。通过构建单星、轨道面和导航星座的3层STPN模型,分析不同备份策略下星座运行的逻辑行为特性和操作事...针对北斗三号系统中轨道Walker导航星座的备份策略问题,提出基于随机时间Petri网(stochastic timed Petri net,STPN)的分析评估方法。通过构建单星、轨道面和导航星座的3层STPN模型,分析不同备份策略下星座运行的逻辑行为特性和操作事件的时序关系。建立导航星座的可用性模型和运行成本模型,作为导航星座备份策略的评估指标。最后,利用蒙特卡罗方法对所提出的分析模型的准确性进行评估,并在满足可用性的前提下以成本最小为标准,获得星座在不同条件下的最优备份策略。结果表明,该方法能有效分析不同备份策略对星座运行参数的影响,可为导航星座备份策略设计优化提供量化依据。展开更多
We investigate the Eulerian bond-cubic model on the square lattice by means of Monte Carlo simulations, using an efficient cluster algorithm and a finite-size scaling analysis. The critical points and four critical ex...We investigate the Eulerian bond-cubic model on the square lattice by means of Monte Carlo simulations, using an efficient cluster algorithm and a finite-size scaling analysis. The critical points and four critical exponents of the model are determined for several values of n. Two of the exponents are fractal dimensions, which are obtained numerically for the first time. Our results are consistent with the Coulomb gas predictions for the critical O（n） branch for n 〈 2 and the results obtained by previous transfer matrix calculations. For n = 2, we find that the thermal exponent, the magnetic exponent and the fractal dimension of the largest critical Eulerian bond component are different from those of the critical 0（2） loop model. These results confirm that the cubic anisotropy is marginal at n = 2 but irrelevant for n〈2.展开更多
文摘针对北斗三号系统中轨道Walker导航星座的备份策略问题,提出基于随机时间Petri网(stochastic timed Petri net,STPN)的分析评估方法。通过构建单星、轨道面和导航星座的3层STPN模型,分析不同备份策略下星座运行的逻辑行为特性和操作事件的时序关系。建立导航星座的可用性模型和运行成本模型,作为导航星座备份策略的评估指标。最后,利用蒙特卡罗方法对所提出的分析模型的准确性进行评估,并在满足可用性的前提下以成本最小为标准,获得星座在不同条件下的最优备份策略。结果表明,该方法能有效分析不同备份策略对星座运行参数的影响,可为导航星座备份策略设计优化提供量化依据。
基金Project supported by the National Natural Science Foundation of China (Grant No.10675021)the New Century Excellent Talents in University of China,the Natural Science Foundation of Anhui Province of China (Grant No.090416224)the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No.20103402110053)
文摘We investigate the Eulerian bond-cubic model on the square lattice by means of Monte Carlo simulations, using an efficient cluster algorithm and a finite-size scaling analysis. The critical points and four critical exponents of the model are determined for several values of n. Two of the exponents are fractal dimensions, which are obtained numerically for the first time. Our results are consistent with the Coulomb gas predictions for the critical O（n） branch for n 〈 2 and the results obtained by previous transfer matrix calculations. For n = 2, we find that the thermal exponent, the magnetic exponent and the fractal dimension of the largest critical Eulerian bond component are different from those of the critical 0（2） loop model. These results confirm that the cubic anisotropy is marginal at n = 2 but irrelevant for n〈2.
