Warm deformation was investigated for steels containing carbon of 0. 45%,0. 79%, and 1. 26% respeetively with martensite starting structure, using Gleeble 3500 thermomechanical simulator at the temperature ranging fro...Warm deformation was investigated for steels containing carbon of 0. 45%,0. 79%, and 1. 26% respeetively with martensite starting structure, using Gleeble 3500 thermomechanical simulator at the temperature ranging from 873 K to 973 K and the strain rate ranging from 0.1 s^-1 to 0. 001 s^-1. The effect of carbon content on the deformation activation energy, Z value and the deformation resistance was analyzed, The results showed that the deformation resistance decreased with increasing carbon content. The peak stress of the steel containing earbon of 1.26% was decreased by 16.2% compared to the steel containing carbon of 0.45% under the same condition. This may be attributed to the weakening effect of solid solution strengthening which outweighs the precipitation strengthening of cementite.展开更多
大规模安全约束机组组合(security constrained unit commitment,SCUC)问题的混合整数线性规划(mixed integer linear programming,MILP)模型因其高维、非凸的特点导致求解困难,尤其在考虑故障态安全约束后模型规模骤增,MILP算法常遇到...大规模安全约束机组组合(security constrained unit commitment,SCUC)问题的混合整数线性规划(mixed integer linear programming,MILP)模型因其高维、非凸的特点导致求解困难,尤其在考虑故障态安全约束后模型规模骤增,MILP算法常遇到收敛间隙下降瓶颈问题。为满足现货市场出清对SCUC问题求解时间的要求,提出了基于热启动的快速求解方法,从待求模型的一个可行解出发,根据节点边际电价和机组收益分析进行整数变量固定,同时削减无约束力的安全约束,以缩减模型规模,加快收敛进程。仿真结果表明:所提方法能够大幅缩减SCUC模型规模,尤其对于考虑故障态安全约束的大规模SCUC问题,能有效克服收敛间隙下降瓶颈问题,求解效率提高特别显著。展开更多
基金Item Sponsored by National Natural Science Foundation of China (50821001 ,50371074,50271060)Natural Science Foundation of Hebei Province of China (E2008000784)
文摘Warm deformation was investigated for steels containing carbon of 0. 45%,0. 79%, and 1. 26% respeetively with martensite starting structure, using Gleeble 3500 thermomechanical simulator at the temperature ranging from 873 K to 973 K and the strain rate ranging from 0.1 s^-1 to 0. 001 s^-1. The effect of carbon content on the deformation activation energy, Z value and the deformation resistance was analyzed, The results showed that the deformation resistance decreased with increasing carbon content. The peak stress of the steel containing earbon of 1.26% was decreased by 16.2% compared to the steel containing carbon of 0.45% under the same condition. This may be attributed to the weakening effect of solid solution strengthening which outweighs the precipitation strengthening of cementite.
文摘大规模安全约束机组组合(security constrained unit commitment,SCUC)问题的混合整数线性规划(mixed integer linear programming,MILP)模型因其高维、非凸的特点导致求解困难,尤其在考虑故障态安全约束后模型规模骤增,MILP算法常遇到收敛间隙下降瓶颈问题。为满足现货市场出清对SCUC问题求解时间的要求,提出了基于热启动的快速求解方法,从待求模型的一个可行解出发,根据节点边际电价和机组收益分析进行整数变量固定,同时削减无约束力的安全约束,以缩减模型规模,加快收敛进程。仿真结果表明:所提方法能够大幅缩减SCUC模型规模,尤其对于考虑故障态安全约束的大规模SCUC问题,能有效克服收敛间隙下降瓶颈问题,求解效率提高特别显著。
