具时滞效应的多商品蛛网模型及其稳定性分析

构建一类具有时滞效应的多商品非均衡蛛网模型.然后建立一个广义时滞差分不等式,在此基础上讨论该蛛网模型的平衡点存在性,并着重对其稳定性进行分析.     

Impulsive synchronization of time delay bursting neuron systems with unidirectional coupling

In the article, impulsive synchronization of chaotic bursting in Hindmarsh–Rose neuron systems with time delay via partial state signal is investigated. Based on impulsive control theory of dynamical systems, the sufficient conditions on feedback strength and impulsive interval are established to guarantee the synchronization. Numerical simulations show the effectiveness of the proposed scheme. The obtained results may be helpful to understand dynamical mechanism of signal transduction in real neuronal activity. © 2014 Wiley Periodicals, Inc. Complexity 21: 38–46, 2015     

Global exponential stability for interval general bidirectional associative memory (BAM) neural networks with proportional delays

This paper is concerned with interval general bidirectional associative memory (BAM) neural networks with proportional delays. Using appropriate nonlinear variable transformations, the interval general BAM neural networks with proportional delays can be equivalently transformed into the interval general BAM neural networks with constant delays. The sufficient condition for the existence and uniqueness of equilibrium point of the model is established by applying Brouwer's fixed point theorem. By constructing suitable delay differential inequalities, some sufficient conditions for the global exponential stability of the model are obtained. Two examples are given to illustrate the effectiveness of the obtained results. This paper ends with a brief conclusion. Copyright © 2016 John Wiley & Sons, Ltd.     

一类随机延迟微分代数系统的Euler-Maruyama方法

我们主要构造了数值求解一类1指标随机延迟微分代数系统的Euler-Maruyama方法,并且证明用该方法求解此类问题可达到1/2阶均方收敛.最后的效值试验验证了方法的有效性及所获结论的正确性.     

Persistence and global stability in a delayed Leslie-Gower type three species food chain

Our investigation concerns the three-dimensional delayed continuous time dynamical system which models a predator-prey food chain. This model is based on the Holling-type II and a Leslie-Gower modified functional response. This model can be considered as a first step towards a tritrophic model (of Leslie-Gower and Holling-Tanner type) with inverse trophic relation and time delay. That is when a certain species that is usually eaten can consume immature predators. It is proved that the system is uniformly persistent under some appropriate conditions. By constructing a proper Lyapunov function, we obtain a sufficient condition for global stability of the positive equilibrium.     

参变过程中的群速延迟对晶体匹配长度的影响

基于能量守恒和三波耦合波方程,建立了超短脉冲在参变过程中二次谐波产生时的I类和II类相位匹配条件、基波与谐波之间的群速延迟时间、以及群速失配对晶体长度限制的理论基础。以负单轴非线性光学晶体CsLiB6O10为例,分析和数值计算了超短脉冲宽度为100fs时,谐波的群速匹配长度随基波波长变化的规律。研究结果表明在I类相位匹配条件下,基波波长为642nm时,群速延迟最小,相应的群速匹配晶体长度最长为19.1mm;在II类相位匹配条件下,基波波长为767nm,群速延迟最小,群速匹配长度最长为0.89mm。     

光纤中高斯型伪随机序列码偏振度的理论分析和实验研究

推导了准单色光波情况下高斯脉冲伪随机序列偏振度的简洁数学表达式.理论分析结果表明,偏振度与差分群延迟之间的关系与线路啁啾和光纤色散无关,并且此关系可以由光信号频谱半宽度Δω和分光比γ唯一确定.用10 Gbit/s 7级m序列归零码进行的实验表明:实验结果与理论推导基本一致,从而验证了推导公式的正确性.     

An Edge Server Placement Method Based on Reinforcement Learning

In mobile edge computing systems, the edge server placement problem is mainly tackled as a multi-objective optimization problem and solved with mixed integer programming, heuristic or meta-heuristic algorithms, etc. These methods, however, have profound defect implications such as poor scalability, local optimal solutions, and parameter tuning difficulties. To overcome these defects, we propose a novel edge server placement algorithm based on deep q-network and reinforcement learning, dubbed DQN-ESPA, which can achieve optimal placements without relying on previous placement experience. In DQN-ESPA, the edge server placement problem is modeled as a Markov decision process, which is formalized with the state space, action space and reward function, and it is subsequently solved using a reinforcement learning algorithm. Experimental results using real datasets from Shanghai Telecom show that DQN-ESPA outperforms state-of-the-art algorithms such as simulated annealing placement algorithm (SAPA), Top-K placement algorithm (TKPA), K-Means placement algorithm (KMPA), and random placement algorithm (RPA). In particular, with a comprehensive consideration of access delay and workload balance, DQN-ESPA achieves up to 13.40% and 15.54% better placement performance for 100 and 300 edge servers respectively.     

应力对M-Z型InP/InGaAsP-EAM偏振

采用Agilent 81910A光子全参量测试仪,首次实验研究了InP/In1－xGaxAs1－yPy-MQW（Multiple-Quantum-Well,MQW）材料与衬底间因应力而产生的M-Z型光调制器的PDL影响以及由此引起的由差分群时延(Differential Group Delay,DGD)表征的偏振模色散(Polarization Mode Dispersion,PMD).研究结果表明,半导体MQW光调制器的PDL与DGD是一致的.因此在半导体光器件的制作过程中,应尽可能地减小衬底与波导芯层之间的因残存应力的存在造成对光器件的高速性能的不利影响.     

Cooling overall spin temperature: protein NMR experiments optimized for longitudinal relaxation effects

In experiments performed on protonated proteins at high fields, 80% of the NMR spectrometer time is spent waiting for the ¹H atoms to recover their polarization after recording the free induction decay. Selective excitation of a fraction of the protons in a large molecule has previously been shown to lead to faster longitudinal relaxation for the selected protons [K. Pervushin, B. Vögeli, A. Eletsky, Longitudinal ¹H relaxation optimization in TROSY NMR spectroscopy, J. Am. Chem. Soc. 124 (2002) 12898–12902; P. Schanda, B. Brutscher, Very fast two-dimensional NMR spectroscopy for real-time investigation of dynamic events in proteins on the time scale of seconds, J. Am. Chem. Soc. 127 (2005) 8014–8015; H.S. Attreya, T. Szyperski, G-matrix Fourier transform NMR spectroscopy for complete protein resonance assignment, Proc. Natl. Acad. Sci. USA 101 (2004) 9642–9647]. The pool of non-selected protons acts as a “thermal bath” and spin-diffusion processes (“flip-flop” transitions) channel the excess energy from the excited pool to the non-selected protons in regions of the molecule where other relaxation processes can dissipate the excess energy. We present here a sensitivity enhanced HSQC sequence (COST-HSQC), based on one selective E-BURP pulse, which can be used on protonated ¹⁵N enriched proteins (with or without ¹³C isotopic enrichment). This experiment is compared to a gradient sensitivity enhanced HSQC with a water flip-back pulse (the water flip-back pulse quenches the spin diffusion between ¹H^N and ¹H^α spins). This experiment is shown to have significant advantages in some circumstances. Some observed limitations, namely sample overheating with short recovery delays and complex longitudinal relaxation behaviour are discussed and analysed.