The architecture of cislunar multi-hop communication networks, which focuses on the requirements of lunar full-coverage and continuous cislunar communications, is presented on the basis of Geosynchronous Orbit (GEO) s...The architecture of cislunar multi-hop communication networks, which focuses on the requirements of lunar full-coverage and continuous cislunar communications, is presented on the basis of Geosynchronous Orbit (GEO) satellite network relays. According to the geographical distribution of the forthcoming Chinese Deep Space Measuring and Controlling Network (DSMCN), two networking schemes are proposed and two elevation angle optimization models are established for locating GEO relay satellites. To analyze the dynamic connectivity, a dynamic network model is constructed with respect to the time-varying characteristics of cislunar trunk links. The advantages of the two proposed schemes, in terms of the Connectivity Rate (CR), Interruption Frequency (IF), and Average Length of Connecting Duration (ALCD), are corroborated by several simulations. In the case of the lunar polar orbit constellation case, the gains in the performance of scheme I are observed to be 134.55%, 117.03%, and 217.47% compared with DSMCN for three evaluation indicators, and the gains in the performance of scheme II are observed to be 238. 22%, 240.40%, and 572.71%. The results validate that the connectivity of GEO satellites outperforms that of earth facilities significantly and schemes based on GEO satellite relays are promising options for cislunar multi-hop communication networking.展开更多
Surface nano-crystallization techniques have been recently developed as one of the most effient ways to optimize materials'structure,and therefore develop the local and global mechanical behavior as to increase st...Surface nano-crystallization techniques have been recently developed as one of the most effient ways to optimize materials'structure,and therefore develop the local and global mechanical behavior as to increase strength without compromising ductility.In this work,we present a constitutive model incorporating grain refinement hardening to simulate the nano-crystallization technique,specifically,surface mechanical attrition treatment.The computation is implemented using user-defined VUMAT subroutines.As an example of its application,a geometry model with full coverage of random impacts are employed.The results show that the model has rather precise predictability of grain size evolution during plastic deformation.The readily embedded with a computational code of material dynamics enables this novel model to be a promising tool to study the dynamic evolution of microstructures under plastic deformation.展开更多
基金supported by the National High Technology Research and Development Program of P.R.China under Grant No.2012 AA121604 the National Natural Science Foundation of China under Grants No.60902042,No.61170014,No.61202079+1 种基金 the National Research Foundation for the Doctoral Program of Higher Education of China under Grant No.20090006110014 the Foundation for Key Program of Ministry of Education of China under Grant No.311007
文摘The architecture of cislunar multi-hop communication networks, which focuses on the requirements of lunar full-coverage and continuous cislunar communications, is presented on the basis of Geosynchronous Orbit (GEO) satellite network relays. According to the geographical distribution of the forthcoming Chinese Deep Space Measuring and Controlling Network (DSMCN), two networking schemes are proposed and two elevation angle optimization models are established for locating GEO relay satellites. To analyze the dynamic connectivity, a dynamic network model is constructed with respect to the time-varying characteristics of cislunar trunk links. The advantages of the two proposed schemes, in terms of the Connectivity Rate (CR), Interruption Frequency (IF), and Average Length of Connecting Duration (ALCD), are corroborated by several simulations. In the case of the lunar polar orbit constellation case, the gains in the performance of scheme I are observed to be 134.55%, 117.03%, and 217.47% compared with DSMCN for three evaluation indicators, and the gains in the performance of scheme II are observed to be 238. 22%, 240.40%, and 572.71%. The results validate that the connectivity of GEO satellites outperforms that of earth facilities significantly and schemes based on GEO satellite relays are promising options for cislunar multi-hop communication networking.
基金the Shanghai UniversityUniversity of West Florida+5 种基金City University of Hong KongShanghai Institute of Applied Physicsthe Research Center of AREVA NPGE Research for the financial supportShenzhen-Hong Kong Science and Technology Innovation Cooperation Zone Shenzhen Park Project:HZQB-KCZYB-2020030RGC&GRF:Hong Kong General Research Fund(GRF)Scheme(CityU 11247516)。
文摘Surface nano-crystallization techniques have been recently developed as one of the most effient ways to optimize materials'structure,and therefore develop the local and global mechanical behavior as to increase strength without compromising ductility.In this work,we present a constitutive model incorporating grain refinement hardening to simulate the nano-crystallization technique,specifically,surface mechanical attrition treatment.The computation is implemented using user-defined VUMAT subroutines.As an example of its application,a geometry model with full coverage of random impacts are employed.The results show that the model has rather precise predictability of grain size evolution during plastic deformation.The readily embedded with a computational code of material dynamics enables this novel model to be a promising tool to study the dynamic evolution of microstructures under plastic deformation.
