排序方式: 共有26条查询结果,搜索用时 0 毫秒
21.
In this paper, we discuss the damped unidirectional motions of a coupled lattice in a periodic potential. Each particle in the lattice is subject to a time-periodic ac force. Our studies reveal that a directed transport process can be observed when the ac forces acting on the coupled lattice have a phase shift (mismatch). This directed motion is a collaboration of the coupling, the substrate potential, and the periodic force, which are all symmetric. The absence of any one of these three factors will not give rise to a directed current. We discuss the complex relations between the directed current and parameters in the system. Results in this paper can be accomplished in experiments. Moreover,our results can be generalized to the studies of directed transport processes in more complicated spatially extended systems. 相似文献
22.
23.
电子信息类高校是培养该领域创新人才的重要基地,作为核心基础课程之一的微积分在其中发挥着重要作用.在建设创新型国家的时代背景下,从创新思维、创新能力和创新综合素质等方面讨论了微积分教学改革在电子信息领域创新型人才培养中的积极作用,并从三个不同视角分析了微积分教学改革所面临的诸多机遇和挑战,最后结合教学实践经历对开展微积分教学改革的具体措施浅谈一些思考与尝试. 相似文献
24.
转轴上裂纹开闭模型的研究 总被引:11,自引:0,他引:11
本文提出了一种新的描述转轴裂纹开闭状态的数学模型,此模型描述了裂纹开、闭及过渡状态的持续过程,它将开裂纹、方波和余弦模型统一于同一模型中,它的使用不受动、静挠度关系的限制.用这个模型算得的裂纹轴刚度变化曲线与实验结果吻合程度比余弦和方波模型好.文中还以Jeffcott裂纹转子为例,对各模型进行了理论探讨.结果表明:当研究非同步运动时,本文模型与方波和余弦模型所得的解差别较大,且轴心位移矢量的方向角在静平衡位置处的波动,影响到所得响应的特性.而对同步运动,这种差别及影响都很小. 相似文献
25.
26.