基于非线性光纤环形镜的少模脉冲幅度调制再生器

随着网络带宽需求的快速增加,波分复用系统的容量已接近非线性香农极限.为了适应未来网络的发展,空分复用技术引起了越来越多的关注.本文首次提出基于少模非线性光纤环形镜(FM-NOLM)的脉冲幅度调制(PAM)全光再生器,描述了其工作原理和具体设计过程.采用COMSOL软件对组成FM-NOLM的硫化物高非线性光纤进行了模式特性仿真.以LP01,LP11,LP21三个光纤模式为例,确定了再生器的参数,计算出每个模式的功率转移函数曲线.仿真分析了该少模PAM-4全光再生器的噪声抑制(NRR)性能,并与单模情形进行了比较.研究表明,1)对于每个空间模式的PAM信号,所有再生电平具有一致的功率转移性能;2)当输入信噪比(SNR)约大于20 dB时,三种模式的噪声抑制比均可超过3 dB,并随着输入信噪比线性增加,其斜率约为1.2;3)在相同输入SNR条件下,三种模式的噪声抑制比相差不大,不超过1.1 dB.为了说明再生器的再生性能,当输入SNR为25 dB时,我们还给出了再生前后PAM-4信号的功率分布直方图.与现有的再生方案相比,本文方案的均匀多电平再生转移性能,使其更适合高频谱效率的长距空分复用系统和任意电平数的PAM信号再生.此外,该方案也能够扩展到波长域,有效提高光通信系统的传输容量.     

Spherical classes and the Lambda algebra

Let be Singer's invariant-theoretic model of the dual of the lambda algebra with , where denotes the mod 2 Steenrod algebra. We prove that the inclusion of the Dickson algebra, , into is a chain-level representation of the Lannes-Zarati dual homomorphism

The Lannes-Zarati homomorphisms themselves, , correspond to an associated graded of the Hurewicz map

Based on this result, we discuss some algebraic versions of the classical conjecture on spherical classes, which states that Only Hopf invariant one and Kervaire invariant one classes are detected by the Hurewicz homomorphism. One of these algebraic conjectures predicts that every Dickson element, i.e. element in , of positive degree represents the homology class in for 2$">.

We also show that factors through , where denotes the differential of . Therefore, the problem of determining should be of interest.

     

X-pinch负载分流关系研究

研究了X-pinch和回流柱之间的分流关系,以及两个X-pinch之间的分流关系。在X-pinch和回流柱的分流实验中,X-pinch上的电流与回流柱上的电流大体相等,这表明电流分布不只与X-pinch或回流柱的特性有关,而且也与它们所在回路的其他部分有关。在两个X-pinch之间的分流实验中,X-pinch上的电流与X-pinch本身的材料和直径几乎无关,这确认了电流分布与回路中X-pinch之外的部分有关。离绝缘柱远的X-pinch上的电流总是比离绝缘柱近的X-pinch上的电流略大一些,这是并联回路之间的互感造成的。     

k-紧优有向双环网络无限族的构建

本文给出了一种方法用于构造k-紧优双环网络无限族(k≥1),并用此方法构造出了4族3-紧优无限族,3族新的4-紧比无限族,3族5-紧优无限族及2族6-紧优无限族．     

Monte Carlo study of the universal area distribution of clusters in the honeycomb O（n） loop model

We investigate the area distribution of clusters (loops) in the honeycomb O(n) loop model by means of the worm algorithm with n = 0.5, 1, 1.5, and 2. At the critical point, the number of clusters, whose enclosed area is greater than A, is proportional to A-1 with a proportionality constant C. We confirm numerically that C is universal, and its value agrees well with the predictions based on the Coulomb gas method.     

基于市场需求增加的双渠道闭环供应链定价机制研究

针对制造商开辟在线销售渠道现象的普及,考虑混合双渠道销售会增加产品的潜在需求,构建制造商与零售商分散、集中定价两种决策模型,利用博弈理论对模型进行求解分析,研究表明在双方分散、集中两种定价策略模型中,随着双渠道开通导致的市场需求率的增加,制造商的批发价、零售商的销售价格上调,零售商的回收价格下降,闭环供应链系统总利润则呈现先下降后上升的变化。最后,运用数值算例进一步验证和讨论双渠道销售导致的市场需求增加对闭环供应链系统定价策略、双方利润及系统渠道效率的影响。     

Limit cycle bifurcations by perturbing a class of integrable systems with a polycycle

In this paper, we deal with the problem of limit cycle bifurcation near a 2-polycycle or 3-polycycle for a class of integrable systems by using the first order Melnikov function. We first get the formal expansion of the Melnikov function corresponding to the heteroclinic loop and then give some computational formulas for the first coefficients of the expansion. Based on the coefficients, we obtain a lower bound for the maximal number of limit cycles near the polycycle. As an application of our main results, we consider quadratic integrable polynomial systems, obtaining at least two limit cycles.     

Integrable Couplings of the Boiti-Pempinelli-Tu Hierarchy and Their Hamiltonian Structures

Integrable couplings of the Boiti-Pempinelli-Tu hierarchy are constructed by a class of non-semisimple block matrix loop algebras. Further, through using the variational identity theory, the Hamiltonian structures of those integrable couplings are obtained. The method can be applied to obtain other integrable hierarchies.     

基于数字非线性锁相环的相干态相位估计

基于量子理论获取相位参数的导航机制,理论上可以突破经典物理极限对导航精度的限制.利用量子零拍探测对相干态光场相位进行测量时,通常需要相位与之正交的本振光才能使测量精度达到量子标准极限.由于导航信号相位的高非线性特点,想要利用传统的线性锁相环获取完全满足条件的本振光具有一定的难度.为此,本文设计了一种基于容积准则的非线性锁相环,实现了在非正交本振光的条件下对相干态相位进行精确测量的功能.首先,利用相干态的Wigner函数推导了其相位在量子零拍探测的输出结果,设计了量子相位估计的非线性数字锁相环框架.然后基于正交单纯形容积准则设计了非线性滤波算法实现锁相环功能,该锁相环通过对本振相位进行多次状态更新,最终实现非线性迭代估计.实验结果表明,本文方法突破了本振光相位需与相干态相位正交的局限性,避免了传统量子锁相环方法引入的线性化误差,实现了对相干态相位的准确、稳定估计.