A study of predator–prey models with the Beddington–DeAnglis functional response and impulsive effect

In this paper, the predator–prey system with the Beddington–DeAngelis functional response is developed, by introducing a proportional periodic impulsive catching or poisoning for the prey populations and a constant periodic releasing for the predator. The Beddington–DeAngelis functional response is similar to the Holling type II functional response but contains an extra term describing mutual interference by predators. This model has the potential to protect predator from extinction, but under some conditions may also lead to extinction of the prey. That is, the system exists a locally stable prey-eradication periodic solution when the impulsive period satisfies an inequality. The condition for permanence is established via the method of comparison involving multiple Liapunov̀ functions. Further, by numerical simulation method the influences of the impulsive perturbations and mutual interference by predators on the inherent oscillation are investigated. With the increasing of releasing for the predator, the system appears a series of complex phenomenon, which include (1) period-doubling, (2) chaos attractor, (3) period-halfing. (4) non-unique dynamics (meaning that several attractors coexist).     

Synchronization of complex dynamical networks with time delays

In the present paper, two kinds of dynamical complex networks are considered. The first is that elements of every node have different time delays but all nodes in such networks have the same time-delay vector. The second is that different nodes have different time-delay vectors, and the elements of each node also have different time delays. Corresponding synchronization theorems are established. Numerical examples show the efficiency of the derived theorems.     

使用超声估计肌肉疲劳的初步研究

表面肌电信号把神经肌肉活动和肌肉收缩联系起来，已被视为一种估计肌肉疲劳比较客观的方法，但也存在一些不足。另一方面，超声已广泛应用于医学诊断和研究，在骨骼肌方面也有不少研究报道，但还未见文献报道超声用于肌肉疲劳的估计。本文介绍一套自行开发的新的同步连续采集B超图像、力矩和肌电信号的采集系统，并利用它对肱二头肌的肌肉疲劳进行了估计。试验表明在30秒的肌肉疲劳过程中，肌肉厚度会以非线性的方式增加。     

The monomial ideal of a finite meet-semilattice

Squarefree monomial ideals arising from finite meet-semilattices and their free resolutions are studied. For the squarefree monomial ideals corresponding to poset ideals in a distributive lattice, the Alexander dual is computed.

     

Comparison between smoothed dissipative particle dynamics and Voronoi fluid particle model in a shear stationary flow

We present a numerical comparison between two Lagrangian techniques for the simulation of fluids, smoothed dissipative particle dynamics (SDPD) and Voronoi fluid particle model. These methods reproduce the movement of the fluid with extensive particles. The main differences between these techniques are the volume definition and the implementation of the second derivatives. The Voronoi model is computationally more efficient than SDPD. For quasi-regular meshes, the Voronoi method is more accurate than SDPD but for arbitrary configurations its precision degrades. This means that the SDPD discrete versions of the second derivative operators are better than the ones used in the Voronoi method.     

椭圆强非局域空间光孤子

对傍轴椭圆高斯光束在具有椭圆对称响应特性的强非局域非线性介质中的演化规律进行研究，得到了光束各参量演化的精确解析解，分析了单向空间光孤子和强非局域椭圆空间光孤子的形成条件，发现了椭圆光孤子的相移与介质响应函数的椭圆率有关. 关键词： 椭圆对称强非局域响应介质 椭圆强非局域空间光孤子 相移     

Regular and singular components of periodic flows in the fluid interior

The structure of infinitesimal periodic motions in the interior of a rotating compressible fluid which has been stratified using salt is analyzed taking account of dissipation effects. In the general case, the system of fundamental equations of motion belongs to the class of singularly perturbed equations, the solutions of that consist of functions which are regular and singular with respect to the dissipative coefficients that describe both propagating hybrid waves as well as several types of accompanying singular components including boundary layers. The thicknesses of the singular components are determined by the kinematic viscosity, the diffusion coefficient of the salt and the characteristic frequencies of the problem. In the model of a barotropic or homogeneous fluid, the singular components of spatial periodic flows combine together, which is indicative of degeneracy of the system of equations. Taking account of the full set of components, which are regular and singular with respect to the dissipative characteristics, enables one to construct exact solutions of problems of the generation and non-linear interaction of waves.     

A multi-layer demand-responsive logistics control methodology for alleviating the bullwhip effect of supply chains

This paper presents a multi-layer demand-responsive logistics control strategy for alleviating, effectively and efficiently, the bullwhip effect of a supply chain. Utilizing stochastic optimal control methodology, the proposed method estimates the time-varying demand-oriented logistics system states, which originate directly and indirectly downstream to the targeted member of a supply chain, and associate these estimated demands with estimates of different time-varying weights under the goal of systematically optimizing the logistical performance of chain members. In addition, an experimental design is conducted where the proposed method is evaluated with the two specified criteria. Numerical results indicate that the proposed method permits alleviating, to a great extent, the bullwhip effect in comparison with the existing logistics management strategies. Furthermore, the methodology presented in this study is expected to help address issues regarding the uncertainty and complexity of the distortion of demand-related information existing broadly among supply chain members for an efficient supply chain coordination.     

Ishihara's proof technique in constructive analysis

Two surprising constructive lemmas of Ishihara, with extremely useful proof techniques, are placed in a general setting. This both clarifies the ideas underlying those lemmas and raises the possibility that some other applications of their proof techniques in constructive analysis are, in fact, corollaries of our general results.