排序方式: 共有95条查询结果,搜索用时 31 毫秒
41.
用光致发光激发(PLE)谱分析吸收谱的亚结构。实验样品是共熔法制备的CdSeS量子点玻璃,量子点的生长时间分别为2h和4h,高分辨透射电子显微镜(HRTEM)分析得到样品中量子点的平均直径分别为3.6nm和3.8nm。在室温下对样品进行了光吸收谱和光致发光激发谱研究。光吸收谱显示了量子尺寸效应,光致发光激发谱中低能端有两个明显的峰。考虑价带简并以及电子与空穴之间的相互作用,通过理论分析和数值计算,得到1S3/2-1Se和2S3/2-1Se的跃迁能量及其随量子点半径的变化,由此确认光致发光激发谱中的两个峰分别为1S3/2-1Se和2S3/2-1Se跃迁。 相似文献
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Two-dimensional discrete gap breathers in a two-dimensional discrete diatomic Klein-Gordon lattice 下载免费PDF全文
We study the existence and stability of two-dimensional discrete breathers in a two-dimensionai discrete diatomic Klein-Gordon lattice consisting of alternating light and heavy atoms, with nearest-neighbor harmonic coupling. Localized solutions to the corresponding nonlinear differential equations with frequencies inside the gap of the linear wave spectrum, i.e. two-dimensional gap breathers, are investigated numerically. The numerical results of the corresponding algebraic equations demonstrate the possibility of the existence of two-dimensional gap breathers with three types of symmetries, i.e., symmetric, twin-antisymmetric and single-antisymmetric. Their stability depends on the nonlinear on-site potential (soft or hard), the interaction potential (attractive or repulsive) and the center of the two-dimensional gap breathers (on a light or a heavy atom). 相似文献
43.
A theoretical description for solitons in polyacetylene 总被引:1,自引:0,他引:1
The bond-alternation domain walls or the solitons in the dimerized polyacetylene are analyzed theoretically. The width of the soliton is many times the period of the chain, so that the soliton can be reasonably well described by a continuum model. Because of the existence of the bond-alternation domain walls, the electron density is different definitely. Thus the electron density can be used to describe the formation of the domain walls, and a self-trapped potential is discussed and introduced in the Hamiltonian. It is shown that the envelope of the wave functions of the chain is governed by the nonlinear Schr?dinger equation which has soliton solutions. Then the shape of the soliton is determined analytically which is in accordance with the numerical calculations by Su, Schrieffer and Heeger. This implies that the bond-alternation domain wall or the soliton is observed as the envelope of the wave function. 相似文献
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交流约瑟夫逊效应与锁频现象 总被引:1,自引:0,他引:1
微波辐照下交流约瑟夫逊效应的夏皮罗台阶是非线性耗散动力学系统的锁频现象.本文在简介锁频现象的基础上,阐明夏皮罗台阶的成因. 相似文献
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电介质的极化机制与介电常量的分析 总被引:6,自引:1,他引:5
在简介电介质极化机制的基础上,通过Lorentz振子模型及其修正,分析电介南的极化机制与介电常量,比较分析了一些电介质介常量有规律的变化,分析了一些电介质介电常量与光频介电常量相等的微观机制。 相似文献
46.
人体肌肉骨骼系统简称肌骨系统, 包括骨骼、骨骼肌与关节连接, 其力学模型是典型的多柔体系统. 从多体动力学角度研究肌骨系统, 主要关注其在运动过程中的肌肉内力、关节力矩及产生的动力学影响, 属于动力学与生物力学的交叉融合. 肌骨系统的多体动力学模型已被广泛地应用于临床医学、竞技体育、军事训练、人机工程等诸多领域, 其仿真结果可为提高人体运动能力、降低关节载荷与能耗、避免运动损伤、加快康复进程等提供重要计算参考数据. 与此同时, 上述研究亦对肌骨动力学研究提出了许多新挑战. 本文综述了人体肌骨多柔体系统动力学相关研究进展, 包括骨骼肌功能解剖与生物力学建模、神经与肌肉控制理论、肌骨系统动力学问题与求解方法, 以及近年来肌骨多体动力学在步态分析、飞行员抗荷动作、口颌手术规划等领域的典型应用. 与工程领域的机械多体系统相比, 人体肌骨多体系统具有肌肉内力主动性与肌肉控制冗余性两大特征. 现有骨骼肌模型难以同时考虑肌肉的解剖结构、三维几何与肌力产生的生物化学机制. 已有大多数肌骨模型采用静态优化假设消除肌肉冗余性, 忽略了肌肉与肌腱内力平衡及兴奋收缩耦联机制. 此外, 目前仍缺乏实现肌骨模型个性化的无创在体测试手段. 未来, 人体肌骨多体动力学研究将会向更精确、智能、个性化的方向发展, 成为动力学与生物力学交叉的热点研究领域. 相似文献
47.
Bin-bin Lü 《Frontiers of Physics》2010,5(2):199
We study a one-dimensional Sine–Gordon lattice of anharmonic oscillators with cubic and quartic nearest-neighbor interactions, in which discrete breathers can be explicitly constructed by an exact separation of their time and space dependence. DBs can stably exist in the one-dimensional Sine–Gordon lattice no matter whether the nonlinear interaction is cubic or quartic. When a parametric driving term is introduced in the factor multiplying the harmonic part of the on-site potential of the system, we can obtain the stable quasiperiodic discrete breathers and chaotic discrete breathers by changing the amplitude of the driver. 相似文献
48.
Localized self-trapping in the two-dimensional discrete molecular lattice with the interaction between Frenkel excitons and phonons 下载免费PDF全文
We investigate the interactions of lattice phonons with Frenkel
exciton, which has a small radius in a two-dimensional discrete
molecular lattice, by the virtue of the quasi-discreteness
approximation and the method of multiple-scale, and obtain that the
self-trapping can also appear in the two-dimensional discrete molecular
lattice with harmonic and nonlinear potential. The excitons' effect
on the molecular lattice does not distort it but only
causes it to localize which enables it to react again through phonon
coupling to trap the energy and prevent its dispersion. 相似文献
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