三轴试验离散元模拟是探究砂土等岩土材料变形破坏机制的一种重要手段,合理地模拟侧向边界是三轴试验离散元模拟的一个重要环节。基于有限差分法(finite difference method,简称FDM)-离散元法(discrete element method,简称DEM)FDM-DEM...三轴试验离散元模拟是探究砂土等岩土材料变形破坏机制的一种重要手段,合理地模拟侧向边界是三轴试验离散元模拟的一个重要环节。基于有限差分法(finite difference method,简称FDM)-离散元法(discrete element method,简称DEM)FDM-DEM耦合开展了柔性侧向边界条件下砂土三轴固结排水和不排水试验的数值模拟,并与相应的刚性侧向边界三轴数值试验进行了对比分析。结果表明:相比刚性侧向边界,基于FDM-DEM耦合的柔性侧向边界三轴试验能更好地再现室内砂土三轴试样的宏观力学响应和微观颗粒运动学特征;对于所模拟的砂土三轴固结排水试验,柔性侧向边界试样峰值强度后的应变软化和剪胀性明显弱于刚性侧向边界试样;对于所模拟的砂土三轴固结不排水试验,当轴向应变较大时,柔性侧向边界试样的偏应力小于刚性侧向边界试样,且产生绝对值较小的负孔压;三轴固结不排水试验中,当轴向应变较大时,柔性侧向边界对试样的约束和支撑作用弱于刚性侧向边界,其力链的稳定性较低,力链屈曲数较多,剪切带形成较早,故其各向异性和偏应力均较低。展开更多
面向能耗优化的面积(核数)-功率(频率)分配问题是当前众核处理器研究热点之一.通过性能-功耗模型了解其在核数-频率空间的分布规律,然后在核数和频率级别这2个维度上通过实测执行逐步搜索,可以获取"核数-频率"配置的最优解,...面向能耗优化的面积(核数)-功率(频率)分配问题是当前众核处理器研究热点之一.通过性能-功耗模型了解其在核数-频率空间的分布规律,然后在核数和频率级别这2个维度上通过实测执行逐步搜索,可以获取"核数-频率"配置的最优解,从而达到能耗优化的目的;然而本领域现有方法在核数-频率空间内实测搜索最低能耗时收敛速度慢、搜索开销大、可扩展性差.针对此问题,提出了一种基于求解最优化问题的经典数学方法——可行方向法的最低能耗搜索方法(energy-efficient optimization based on feasible direction method,EOFDM),每次执行都能从核数和频率2个维度上同时减小搜索空间,在迭代执行中快速收敛至最低能耗点.该方法与现有研究中最优的启发式爬山法(hill-climbing heuristic,HCH)进行了对比实验,平均执行次数、执行时间和能耗分别降低39.5%,46.8%,48.3%,提高了收敛速度,降低了搜索开销;当核数增加一倍时,平均执行次数、执行时间和能耗分别降低48.8%,51.6%,50.9%;当频率级数增加一倍时,平均执行次数、执行时间和能耗分别降低45.5%,49.8%,54.4%,在收敛速度、搜索开销和可扩展性方面均有提高.展开更多
A modeling tool for simulating three-dimensional land frequency-domain controlled-source electromagnetic surveys,based on a finite-element discretization of the Helmholtz equation for the electric fields,has been deve...A modeling tool for simulating three-dimensional land frequency-domain controlled-source electromagnetic surveys,based on a finite-element discretization of the Helmholtz equation for the electric fields,has been developed.The main difference between our modeling method and those previous works is edge finite-element approach applied to solving the three-dimensional land frequency-domain electromagnetic responses generated by horizontal electric dipole source.Firstly,the edge finite-element equation is formulated through the Galerkin method based on Helmholtz equation of the electric fields.Secondly,in order to check the validity of the modeling code,the numerical results are compared with the analytical solutions for a homogeneous half-space model.Finally,other three models are simulated with three-dimensional electromagnetic responses.The results indicate that the method can be applied for solving three-dimensional electromagnetic responses.The algorithm has been demonstrated,which can be effective to modeling the complex geo-electrical structures.This efficient algorithm will help to study the distribution laws of3-D land frequency-domain controlled-source electromagnetic responses and to setup basis for research of three-dimensional inversion.展开更多
文摘三轴试验离散元模拟是探究砂土等岩土材料变形破坏机制的一种重要手段,合理地模拟侧向边界是三轴试验离散元模拟的一个重要环节。基于有限差分法(finite difference method,简称FDM)-离散元法(discrete element method,简称DEM)FDM-DEM耦合开展了柔性侧向边界条件下砂土三轴固结排水和不排水试验的数值模拟,并与相应的刚性侧向边界三轴数值试验进行了对比分析。结果表明:相比刚性侧向边界,基于FDM-DEM耦合的柔性侧向边界三轴试验能更好地再现室内砂土三轴试样的宏观力学响应和微观颗粒运动学特征;对于所模拟的砂土三轴固结排水试验,柔性侧向边界试样峰值强度后的应变软化和剪胀性明显弱于刚性侧向边界试样;对于所模拟的砂土三轴固结不排水试验,当轴向应变较大时,柔性侧向边界试样的偏应力小于刚性侧向边界试样,且产生绝对值较小的负孔压;三轴固结不排水试验中,当轴向应变较大时,柔性侧向边界对试样的约束和支撑作用弱于刚性侧向边界,其力链的稳定性较低,力链屈曲数较多,剪切带形成较早,故其各向异性和偏应力均较低。
文摘面向能耗优化的面积(核数)-功率(频率)分配问题是当前众核处理器研究热点之一.通过性能-功耗模型了解其在核数-频率空间的分布规律,然后在核数和频率级别这2个维度上通过实测执行逐步搜索,可以获取"核数-频率"配置的最优解,从而达到能耗优化的目的;然而本领域现有方法在核数-频率空间内实测搜索最低能耗时收敛速度慢、搜索开销大、可扩展性差.针对此问题,提出了一种基于求解最优化问题的经典数学方法——可行方向法的最低能耗搜索方法(energy-efficient optimization based on feasible direction method,EOFDM),每次执行都能从核数和频率2个维度上同时减小搜索空间,在迭代执行中快速收敛至最低能耗点.该方法与现有研究中最优的启发式爬山法(hill-climbing heuristic,HCH)进行了对比实验,平均执行次数、执行时间和能耗分别降低39.5%,46.8%,48.3%,提高了收敛速度,降低了搜索开销;当核数增加一倍时,平均执行次数、执行时间和能耗分别降低48.8%,51.6%,50.9%;当频率级数增加一倍时,平均执行次数、执行时间和能耗分别降低45.5%,49.8%,54.4%,在收敛速度、搜索开销和可扩展性方面均有提高.
基金Projects(41674080,41674079)supported by the National Natural Science Foundation of China
文摘A modeling tool for simulating three-dimensional land frequency-domain controlled-source electromagnetic surveys,based on a finite-element discretization of the Helmholtz equation for the electric fields,has been developed.The main difference between our modeling method and those previous works is edge finite-element approach applied to solving the three-dimensional land frequency-domain electromagnetic responses generated by horizontal electric dipole source.Firstly,the edge finite-element equation is formulated through the Galerkin method based on Helmholtz equation of the electric fields.Secondly,in order to check the validity of the modeling code,the numerical results are compared with the analytical solutions for a homogeneous half-space model.Finally,other three models are simulated with three-dimensional electromagnetic responses.The results indicate that the method can be applied for solving three-dimensional electromagnetic responses.The algorithm has been demonstrated,which can be effective to modeling the complex geo-electrical structures.This efficient algorithm will help to study the distribution laws of3-D land frequency-domain controlled-source electromagnetic responses and to setup basis for research of three-dimensional inversion.
