高速色散补偿系统中喇曼放大器性能研究

利用喇曼放大器的非线性偏微分耦合方程组,对带喇曼放大器的色散补偿系统进行了仿真,并与传统的仿真方法进行了比较.结果表明:在色散完全补偿系统中,当传输速率较高时,忽略色散后的传统仿真方法的结果,与采用色散补偿技术后使整个系统色散为零的仿真结果有一定偏差,此时不能忽略色散的作用.还对前补偿系统和后补偿系统进行了研究,利用Q值性能判别法,分别得到了信号光脉冲的最佳占空比和最佳脉冲阶数.     

A constructive characterization of the split closure of a mixed integer linear program

Two independent proofs of the polyhedrality of the split closure of mixed integer linear program have been previously presented. Unfortunately neither of these proofs is constructive. In this paper, we present a constructive version of this proof. We also show that split cuts dominate a family of inequalities introduced by Köppe and Weismantel.     

三种群食物链交错扩散模型的整体

本文应用能量估计方法和Gagliardo-Nirenberg型不等式证明了一类强耦合反应扩散系统整体解的存在性和一致有界性，该系统是带自扩散和交错扩散项的三种群Lotka-Volterra食物链模型．通过构造Lyapunov函数给出了该模型正平衡点全局渐近稳定的充分条件．     

Decoherence Induced by Spin Chain Environment

We study the decoherence process of an exact solvable model that consists of a central spin-1/2 coupling to the surrounding anisotropy spin-1/2 chain in transverse fields. The Loschrnidt echo is calculated to study the character of decoherence with different degree of anisotropy. Our results show that the degree of anisotropy γ greatly affects the decoherence process of the central spin-system when the spin chain is in weak transverse fields, but it gives weak effect in the strong transverse field. The decoherence process of the central system changed dramatically along the line of the critical points, and this may be explained as the reflection of quantum phase transitions.     

The Level-split of the Two-level Entangled Atom in an Optical Field

The behavior of a two-level entangled atom in an optical field with circular polarization is studied in this paper. The interaction of an optical field and one of the entangled atoms is analyzed in detail. A general solution of the SchrAo¨Gdinger equation about the motion of the entangled atom is obtained. The properties of the action are dependent on the initial state of the atom. By detecting the entangled atom out of the field, we can obtain the state of the other atom moving in the field. It is shown that the state of the atom out of the field will influence the energies of the split-levels of the atom in the field.     

InxGa1-xAs-GaAs应变层量子阱结构的流体静压光荧光研究

本文报道了对分子束外延(MBE)生长的In_0.25Ga_0.75As-GaAs应变层量子阱结构在77K下的压力光荧光(PL)研究的结果。流体静压力从0到50kbar.,给出了In_0.25Ga_0.75As-GaAs应变层量子阱的Γ谷压力系数,实验观察到了量子阱中能级与势垒GaAs中X谷的能级交叉。通过对其压力行为的分析,给出了In_0.25Ga_0.75As-GaAs异质结的导带与价带跃变比:Q_c=△E_c:△E_v=0.68:0.32。对(InGa)As-GaAs应变量子阱常压下的理论分析与实验符合很好。本文也对Al_0.3Ga_0.70As-GaAs量子阱进行了讨论。 关键词：     

空气比热容比实验的非绝热问题

通过一系列的实验数据分析，发现空气比热容比实验中非绝热现象不可以忽略．     

Hydrodynamical limit for a drift-diffusion system modeling large-population dynamics

In this paper we study the stability of the following nonlinear drift-diffusion system modeling large population dynamics ∂_tρ+div(ρU−ε∇ρ)=0, divU=±ρ, with respect to the viscosity parameter ε. The sign in the second equation depends on the attractive or repulsive character of the field U. A proof of the compactness and convergence properties in the vanishing viscosity regime is given. The lack of compactness in the attractive case is caused by the blow-up of the solution which depends on the mass and on the space dimension. Our stability result is connected, depending of the character of the potentials, with models in semiconductor theory or in biological population.     

Vassiliev invariants for braids on surfaces

We show that Vassiliev invariants separate braids on a closed oriented surface, and we exhibit a universal Vassiliev invariant for these braids in terms of chord diagrams labeled by elements of the fundamental group of the surface.