The chance of an Interplanetary Coronal Mass Ejection (ICME) observed by widely-separated spacecraft is rare. However, such an event provides us a good opportunity to study the propagation and evolution of ICMEs in th...The chance of an Interplanetary Coronal Mass Ejection (ICME) observed by widely-separated spacecraft is rare. However, such an event provides us a good opportunity to study the propagation and evolution of ICMEs in the heliosphere. On day 72 of 1975, an ICME was observed by Helios 1 at 0.3 AU, while a similar solar wind structure was observed by IMP 8 at Earth on day 70 of 1975. On the basis of comparison of the plasma signatures and the transit time from Helios 1 to IMP 8, we hypothesize the observed ICMEs by both spacecraft are resulted from the same active region on the solar surface. A one-dimensional MHD model was used to track the ICME from Helios 1 (0.3 AU) to Earth. The observed plasma profiles and timing are close to those predicted by our MHD model and thus, give the supports to the model.展开更多
评介隋允康和彭细荣教授的专著《结构拓扑优化ICM方法新进展——概念深化及理论拓展》,其中ICM(independent continuous and mapping)意思是独立、连续和映射,该方法是结构拓扑优化的主流研究方法之一。该书借助于鉴史(力学史)和驭法(...评介隋允康和彭细荣教授的专著《结构拓扑优化ICM方法新进展——概念深化及理论拓展》,其中ICM(independent continuous and mapping)意思是独立、连续和映射,该方法是结构拓扑优化的主流研究方法之一。该书借助于鉴史(力学史)和驭法(方法论),总结了自2014年以来ICM方法的发展成果:深入阐述了ICM方法的阶跃函数的离散本质及对其光滑逼近的近似连续本质、逼近的快慢特性和多种映射策略;介绍了ICM方法的数学基础、求解算法和本体理论等方面的拓展性研究成果,包括可分离凸规划转换为求解对偶规划显式模型(dual programming-explicit model,DP-EM)解法、互逆规划理论及其优化应用等;探讨了该领域忽视的结构拓扑优化合理化建模问题;发展了包含疲劳寿命性能的局部性能约束的结构拓扑优化解法;归纳了破损-安全设计理论的演化,给出了位移、应力及频率约束的破损-安全拓扑优化问题的建模及求解;移植ICM方法至国际上广泛应用的变密度方法中。该书可供结构优化领域从事科研的师生和技术人员借鉴和参考。展开更多
The traditional topology optimization method of continuum structure generally uses quadrilateral elements as the basic mesh.This approach often leads to jagged boundary issues,which are traditionally addressed through...The traditional topology optimization method of continuum structure generally uses quadrilateral elements as the basic mesh.This approach often leads to jagged boundary issues,which are traditionally addressed through post-processing,potentially altering the mechanical properties of the optimized structure.A topology optimization method of Movable Morphable Smooth Boundary(MMSB)is proposed based on the idea of mesh adaptation to solve the problem of jagged boundaries and the influence of post-processing.Based on the ICM method,the rational fraction function is introduced as the filtering function,and a topology optimization model with the minimum weight as the objective and the displacement as the constraint is established.A triangular mesh is utilized as the base mesh in this method.The mesh is re-divided in the optimization process based on the contour line,and a smooth boundary parallel to the contour line is obtained.Numerical examples demonstrate that the MMSB method effectively resolves the jagged boundary issues,leading to enhanced structural performance.展开更多
基金Supported by the National Natural Science Foundation of China(40325010)
文摘The chance of an Interplanetary Coronal Mass Ejection (ICME) observed by widely-separated spacecraft is rare. However, such an event provides us a good opportunity to study the propagation and evolution of ICMEs in the heliosphere. On day 72 of 1975, an ICME was observed by Helios 1 at 0.3 AU, while a similar solar wind structure was observed by IMP 8 at Earth on day 70 of 1975. On the basis of comparison of the plasma signatures and the transit time from Helios 1 to IMP 8, we hypothesize the observed ICMEs by both spacecraft are resulted from the same active region on the solar surface. A one-dimensional MHD model was used to track the ICME from Helios 1 (0.3 AU) to Earth. The observed plasma profiles and timing are close to those predicted by our MHD model and thus, give the supports to the model.
基金supported by the National Natural Science Foundation of China(Grant 12472113).
文摘The traditional topology optimization method of continuum structure generally uses quadrilateral elements as the basic mesh.This approach often leads to jagged boundary issues,which are traditionally addressed through post-processing,potentially altering the mechanical properties of the optimized structure.A topology optimization method of Movable Morphable Smooth Boundary(MMSB)is proposed based on the idea of mesh adaptation to solve the problem of jagged boundaries and the influence of post-processing.Based on the ICM method,the rational fraction function is introduced as the filtering function,and a topology optimization model with the minimum weight as the objective and the displacement as the constraint is established.A triangular mesh is utilized as the base mesh in this method.The mesh is re-divided in the optimization process based on the contour line,and a smooth boundary parallel to the contour line is obtained.Numerical examples demonstrate that the MMSB method effectively resolves the jagged boundary issues,leading to enhanced structural performance.
