包含k-树图的毁裂度条件

连通图G的一个k-树是指图G的一个最大度至多是k的生成树.对于连通图G来说,其毁裂度定义为r(G)=max{ω(G-X)-|X|-m(G-X)|X■V(G),ω(G-X)1}其中ω(G-X)和m(G-X)分别表示G-X中的分支数目和最大分支的阶数.本文结合毁裂度给出连通图G包含一个k-树的充分条件;利用图的结构性质和毁裂度的关系逐步刻画并给出图G包含一个k-树的毁裂度条件.     

Pole placement controllers for linear time-delay systems with commensurate point delays

This paper investigates the exact and approximate spectrum assignment properties associated with realizable output-feedback pole-placement type controllers for single-input single-output linear time-invariant time-delay systems with commensurate point delays. The controller synthesis problem is discussed through the solvability of a set of coupled diophantine equations of polynomials. An extra complexity is incorporated to the above design to cancel extra unsuitable dynamics being generated when solving the above diophantine equations. Thus, the complete controller tracks any arbitrary prefixed (either finite or delaydependent) closed-loop spectrum. However, if the controller is simplified by deleting the above mentioned extra complexity, then the robust stability and approximated spectrum assignment are still achievable for a certain sufficiently small amount of delayed dynamics. Finally, the approximate spectrum assignment and robust stability problems are revisited under plant disturbances if the nominal controller is maintained. In the current approach, the finite spectrum assignment is only considered as a particular case to the designer‘s choice of a (delay-dependent) arbitrary spectrum assignment objective.     

相依序列密度函数的经验似然推断

本文利用了强平稳$m-$相依序列的特殊性质,讨论了$m-$相依序列密度函数的经验似然推断, 给出了似然比统计量的极限分布,可构造参数的经验似然置信区间. 并且通过模拟计算来说明有限样本下应用经验似然方法的合理性.     

Current Reversal Due to Coupling Between Asymmetrical Driving Force and Ratchet Potential

Transport of a Brownian particle moving in a periodic potential is investigated in the presence of an asymmetric unbiased external force. The asymmetry of the external force and the asymmetry of the potential are the two ways of inducing a net current. It is found that the competition of the spatial asymmetry of potential with the temporal asymmetry of the external force leads to the phenomena like current reversal. The competition between the two opposite driving factors is a necessary but not a sufficient condition for current reversals.     

Propagation of Light in an Ensemble of Tripod Level Atoms

We study the propagation of a quantum probe light in an ensemble of tripod level atoms when the atoms are coupled to two other classical control fields. First we calculate the dispersion properties, such as susceptibility and group velocity, of the probe light within such an atomic medium under the case of three-photon resonance via the dynamical algebra method of collective atomic excitations. Then we calculate the dispersion of the probe light in the case that two classical control fields have the different detunings to the relative atomic transitions. Our results show that in both cases the phenomenon of electromagnetically induced transparency can occur. Especially under the second case, we can find two transparency windows for the probe light.     

Secure Direct Communication Using Ensembles with the Same Compressed Density Matrix

In this paper, a quantum secure direct communication protocol using ensembles with the same density matrix is proposed. The two communication parties can realize the message transmission using this method through a quantum channel, each bit of information can be transmitted using an ensemble and read out through global measurement.The eavesdropping behavior can be detected through the channel diagnoses.     

ComBn(m+n≤6)团簇的结构，电子特性和磁性研究

基于密度泛函理论和卡里普索结构预测方法,系统研究了ComBn(m+n≤6)团簇的结构,电子特性和磁性。首先,通过卡里普索结构预测方法获得了体系的基态和亚稳态结构。基于基态结构,利用HOMO-LUMO能隙,垂直电离势,垂直电子亲和势和化学硬度分析了掺杂体系的稳定性。最后,研究了基态结构对应的自然布局分布,自然电子组态等电子特性和磁性。     

P schl-Teller势阱中线性与非线性光学折射率变化

利用量子力学中的密度矩阵算符理论导出了P schl-Teller势阱中的线性与三阶非线性光学折射率的解析表达式。P schl-Teller势阱中有两个可调参数κ和λ,势阱的形状及其非对称性会随势阱参数的取值不同而明显不同,从而其线性与非线性光学折射率变化的大小也会随势阱参数和入射光强的变化而呈规律性的变化。文章以典型的GaAs/AlGaAs势阱为例作了数值计算,数值计算结果表明,势阱的形状和入射光强对光学折射率有着重要的影响。     

恒流应力下E2PROM隧道氧化层的退化特性研究

在电容测量的基础上研究了薄隧道氧化层在恒定Fowler-Nordheim(F-N)隧穿电流下的退化情况. 这种退化是恒流应力和时间的函数，对恒流应力大小的依赖性更加强烈，隧道氧化层在F-N电流下的退化是注入电荷密度(Q_inj)的函数. 在较低Q_inj下氧化层中发生正电荷俘获，在较高Q_inj下发生负电荷俘获，导致栅压变化的反复. 关键词： 2PROM')" href="#">E²PROM 隧道氧化层 退化 恒流应力     

周期性磁谐振材料本构参数的理论分析

将薄的磁谐振介质板等效为面磁流, 利用周期性边界条件, 给出了面磁流的指数形式. 通过计算无穷个面磁流在不同空间位置上产生的总电场和总磁场, 推导出了周期性磁谐振人工材料的色散关系和布洛赫阻抗, 进而获取了布洛赫本构参数的理论计算公式. 由于考虑了磁谐振人工材料中的电反谐振对布洛赫介电常数和磁导率的影响, 所以基于仿真实验的布洛赫本构参数的提取值和布洛赫本构参数理论预测值之间的误差很小, 这说明本文推导的布洛赫本构参数的理论计算公式在描述周期性磁谐振材料的电磁特性方面是十分有效的. 这些理论公式将在解释磁谐振现象、设计和优化周期性磁谐振材料等方面提供重要的理论依据. 关键词： 周期性结构 磁谐振 布洛赫本构参数 面磁流