It is important to calculate the reachable domain(RD)of the manned lunar mission to evaluate whether a lunar landing site could be reached by the spacecraft. In this paper, the RD of free return orbits is quickly eval...It is important to calculate the reachable domain(RD)of the manned lunar mission to evaluate whether a lunar landing site could be reached by the spacecraft. In this paper, the RD of free return orbits is quickly evaluated and calculated via the classification and regression neural networks. An efficient databasegeneration method is developed for obtaining eight types of free return orbits and then the RD is defined by the orbit’s inclination and right ascension of ascending node(RAAN) at the perilune. A classify neural network and a regression network are trained respectively. The former is built for classifying the type of the RD, and the latter is built for calculating the inclination and RAAN of the RD. The simulation results show that two neural networks are well trained. The classification model has an accuracy of more than 99% and the mean square error of the regression model is less than 0.01°on the test set. Moreover, a serial strategy is proposed to combine the two surrogate models and a recognition tool is built to evaluate whether a lunar site could be reached. The proposed deep learning method shows the superiority in computation efficiency compared with the traditional double two-body model.展开更多
在《大学英语》(修订本)精读第三册第一课的完形填空中有这么一个句子: The killer,after paying a 75 fine,walkedout of the court a free man.大部分同学对“afree man”的句子成份存在争论。有的说是主语的同位语,有的说是状语,众...在《大学英语》(修订本)精读第三册第一课的完形填空中有这么一个句子: The killer,after paying a 75 fine,walkedout of the court a free man.大部分同学对“afree man”的句子成份存在争论。有的说是主语的同位语,有的说是状语,众说纭纭。 实际上,“a free man”在此既非同位语。展开更多
Let G be a graph,for any u∈V(G),let N(u) denote the neighborhood of u and d(u)=|N(u)| be the degree of u.For any UV(G),let N(U)=∪_~u∈U N(u), and d(U)=|N(U)|.A graph G is called claw-free if it has no induced subgra...Let G be a graph,for any u∈V(G),let N(u) denote the neighborhood of u and d(u)=|N(u)| be the degree of u.For any UV(G),let N(U)=∪_~u∈U N(u), and d(U)=|N(U)|.A graph G is called claw-free if it has no induced subgraph isomorphic to K_~1,3 .One of the fundamental results concerning cycles in claw-free graphs is due to Tian Feng,et al.: Let G be a 2-connected claw-free graph of order n,and d(u)+d(v)+d(w)≥n-2 for every independent vertex set {u,v,w} of G, then G is Hamiltonian. It is proved that,for any three positive integers s,t and w,such that if G is a (s+t+w-1)-connected claw-free graph of order n,and d(S)+d(T)+d(W)>n-(s+t+w) for every three disjoint independent vertex sets S,T,W with |S|=s,|T|=t,|W|=w,and S∪T∪W is also independent,then G is Hamiltonian.Other related results are obtained too.展开更多
the pursuit of the liberation of all mankind and the comprehensive development of human freedom is the theme of all marxist theories.Marx in the criticism of classical political economics“abstract”,to the whole hist...the pursuit of the liberation of all mankind and the comprehensive development of human freedom is the theme of all marxist theories.Marx in the criticism of classical political economics“abstract”,to the whole history of the definition of“general”,found the abstract“general”of the people behind the objective existence and state of development,so as to clearly indicate the relationship between man and nature of human development has experienced on the basis of the nature of the dependence on one stage,gradually from natural objects depends on the stage and with the natural fusion of freedom comprehensive stage,and the concrete connotation of man’s free overall and implementation path.展开更多
基金supported by the National Natural Science Foundation of China (12072365)the Natural Science Foundation of Hunan Province of China (2020JJ4657)。
文摘It is important to calculate the reachable domain(RD)of the manned lunar mission to evaluate whether a lunar landing site could be reached by the spacecraft. In this paper, the RD of free return orbits is quickly evaluated and calculated via the classification and regression neural networks. An efficient databasegeneration method is developed for obtaining eight types of free return orbits and then the RD is defined by the orbit’s inclination and right ascension of ascending node(RAAN) at the perilune. A classify neural network and a regression network are trained respectively. The former is built for classifying the type of the RD, and the latter is built for calculating the inclination and RAAN of the RD. The simulation results show that two neural networks are well trained. The classification model has an accuracy of more than 99% and the mean square error of the regression model is less than 0.01°on the test set. Moreover, a serial strategy is proposed to combine the two surrogate models and a recognition tool is built to evaluate whether a lunar site could be reached. The proposed deep learning method shows the superiority in computation efficiency compared with the traditional double two-body model.
文摘在《大学英语》(修订本)精读第三册第一课的完形填空中有这么一个句子: The killer,after paying a 75 fine,walkedout of the court a free man.大部分同学对“afree man”的句子成份存在争论。有的说是主语的同位语,有的说是状语,众说纭纭。 实际上,“a free man”在此既非同位语。
文摘Let G be a graph,for any u∈V(G),let N(u) denote the neighborhood of u and d(u)=|N(u)| be the degree of u.For any UV(G),let N(U)=∪_~u∈U N(u), and d(U)=|N(U)|.A graph G is called claw-free if it has no induced subgraph isomorphic to K_~1,3 .One of the fundamental results concerning cycles in claw-free graphs is due to Tian Feng,et al.: Let G be a 2-connected claw-free graph of order n,and d(u)+d(v)+d(w)≥n-2 for every independent vertex set {u,v,w} of G, then G is Hamiltonian. It is proved that,for any three positive integers s,t and w,such that if G is a (s+t+w-1)-connected claw-free graph of order n,and d(S)+d(T)+d(W)>n-(s+t+w) for every three disjoint independent vertex sets S,T,W with |S|=s,|T|=t,|W|=w,and S∪T∪W is also independent,then G is Hamiltonian.Other related results are obtained too.
文摘the pursuit of the liberation of all mankind and the comprehensive development of human freedom is the theme of all marxist theories.Marx in the criticism of classical political economics“abstract”,to the whole history of the definition of“general”,found the abstract“general”of the people behind the objective existence and state of development,so as to clearly indicate the relationship between man and nature of human development has experienced on the basis of the nature of the dependence on one stage,gradually from natural objects depends on the stage and with the natural fusion of freedom comprehensive stage,and the concrete connotation of man’s free overall and implementation path.
