Induced Ramsey-type theorems

We present a unified approach to proving Ramsey-type theorems for graphs with a forbidden induced subgraph which can be used to extend and improve the earlier results of Rödl, Erd?s-Hajnal, Prömel-Rödl, Nikiforov, Chung-Graham, and ?uczak-Rödl. The proofs are based on a simple lemma (generalizing one by Graham, Rödl, and Ruciński) that can be used as a replacement for Szemerédi's regularity lemma, thereby giving much better bounds. The same approach can be also used to show that pseudo-random graphs have strong induced Ramsey properties. This leads to explicit constructions for upper bounds on various induced Ramsey numbers.     

L-Fuzzy模的层次结构

本文基于Ｌ－不分明集上的诱导映射理论，较深入地研究Ｌ－Ｆｕｚｚｙ模的层次结构及应用，得到一系列重要的结果     

Induced effects and technological innovation with strategic environmental policy

This paper investigates an environmental policy designed to reduce the emission of pollutants under uncertainty, where the agents’ problem is formulated as an optimal stopping problem. We first analyze the single-agent’s case according to Pindyck [Pindyck, R.S., 2002. Optimal timing problems in environmental economics. Journal of Economic Dynamics and Control 26, 1677–1697]. We then extend the model to the case in which there are two competing agents. Therefore, we consider the external economic effects that are peculiar to an agent’s environmental policy decision. Finally, we consider the effect of technological innovation. The results of the analysis suggest that if there are two competing agents, they implement environmental policy simultaneously. Furthermore, the threshold for implementing environmental policy is higher when there are two agents, and how long these two agents take to implement environmental policy depends on the magnitude of the external economic effect. Furthermore, when we consider the effect of technological innovation, we show that the incentive to be the leader occurs if an additional condition is satisfied.     

Claw-free graphs. III. Circular interval graphs

Construct a graph as follows. Take a circle, and a collection of intervals from it, no three of which have union the entire circle; take a finite set of points V from the circle; and make a graph with vertex set V in which two vertices are adjacent if they both belong to one of the intervals. Such graphs are “long circular interval graphs,” and they form an important subclass of the class of all claw-free graphs. In this paper we characterize them by excluded induced subgraphs. This is a step towards the main goal of this series, to find a structural characterization of all claw-free graphs.This paper also gives an analysis of the connected claw-free graphs G with a clique the deletion of which disconnects G into two parts both with at least two vertices.     

On the approximability of the maximum induced matching problem

In this paper we consider the approximability of the maximum induced matching problem (MIM). We give an approximation algorithm with asymptotic performance ratio d−1 for MIM in d-regular graphs, for each d3. We also prove that MIM is APX-complete in d-regular graphs, for each d3.     

Evidence of Cooperative Rearranging Region size anisotropy for drawn PET

In this work, we determined the Cooperative Rearranging Region (CRR) average sizes at the glass transition temperature according to Donth’s approach. From Temperature Modulated Differential Scanning Calorimetry (TMDSC) and Dynamical Mechanical Analysis (DMA) investigations, the CRR average size has been estimated for drawn poly(ethylene terephthalate) (PET) with various draw ratios ranging from λ = 1 to λ = 4. We show that the CRR size becomes anisotropic as a function of a specific molecular orientation induced by drawing effect.     

Effect of induced magnetic field on natural convection in vertical concentric annuli

In the present paper,we have considered the steady fully developed laminar natural convective flow in open ended vertical concentric annuli in the presence of a radial magnetic field.The induced magnetic field produced by the motion of an electrically conducting fluid is taken into account.The transport equations concerned with the considered model are first recast in the non-dimensional form and then unified analytical solutions for the velocity,induced magnetic field and temperature field are obtained for the cases of isothermal and constant heat flux on the inner cylinder of concentric annuli.The effects of the various physical parameters appearing into the model are demonstrated through graphs and tables.It is found that the magnitude of maximum value of the fluid velocity as well as induced magnetic field is greater in the case of isothermal condition compared with the constant heat flux case when the gap between the cylinders is less or equal to 1.70 times the radius of inner cylinder,while reverse trend occurs when the gap between the cylinders is greater than 1.71 times the radius of inner cylinder.These fields are almost the same when the gap between the cylinders is equal to 1.71 times the radius of inner cylinder for both the cases.It is also found that as the Hartmann number increases,there is a flattening tendency for both the velocity and the induced magnetic field.The influence of the induced magnetic field is to increase the velocity profiles.     

Induced parallel vortex shedding from a circular cylinder at Re of O(10) by using the cylinder end suction technique

In the present work, the objective is to attempt to induce parallel vortex shedding at a moderately high Reynolds number (=1.578 × 10⁴) by using the cylinder end suction method, and measure the associated aerodynamic parameters.We first measured the aerodynamic parameters of a single circular cylinder without end suction, and showed that the quantities measured are in good agreement with equivalent data in the published literature. Next, by using different amount of end suction which resulted in increasing the cylinder end velocity by 1%, 2% and 2.5%, we were able to show that the above corresponded to the situation of under suction, optimal suction and over suction, respectively. With optimal suction, we demonstrated that the end suction method works at Re = 1.578 × 10⁴. The shape of the primary vortex shed became straighter than when there is no end suction, and parameters like cylinder surface pressure distribution, drag force per unit span, as well as vortex shedding frequency all showed negligible spanwise variation. Further careful analyses showed that when compared to the naturally existing curved vortex shedding, with parallel vortex shedding the mid-span drag per unit span became slightly smaller, but the drag averaged over the cylinder span became slightly larger. For cylinder surface pressure, it was found that cylinder end effects mainly influenced the surface pressure in the angular ranges −180°  β < −60° and 60° < β  180°. Without end suction, the cylinder surface pressure in the above ranges was found to increase (become less negative) slightly with |z/d|, but such increase disappeared when optimal end suction was applied, and the cylinder surface pressure distribution became spanwise location independent. As for the vortex shedding frequency (Strouhal number), although the Strouhal number showed spanwise variation when there is no end suction and negligible spanwise variation when optimal suction was applied, the difference between the spanwise averaged Strouhal number was quite negligible. With under suction, the spanwise dependence of various aerodynamic parameters existed, but was found to be not as significant as when no end suction was applied at all. With over suction, the flow situation was found to be practically no change from the optimal suction situation.     

The shock–vortex interaction patterns affected by vortex flow regime and vortex models

We have used a third-order essentially non-oscillatory method to obtain numerical shadowgraphs for investigation of shock–vortex interaction patterns. To search different interaction patterns, we have tested two vortex models (the composite vortex model and the Taylor vortex model) and as many as 47 parametric data sets. By shock–vortex interaction, the impinging shock is deformed to a S-shape with leading and lagging parts of the shock. The vortex flow is locally accelerated by the leading shock and locally decelerated by the lagging shock, having a severely elongated vortex core with two vertices. When the leading shock escapes the vortex, implosion effect creates a high pressure in the vertex area where the flow had been most expanded. This compressed region spreads in time with two frontal waves, an induced expansion wave and an induced compression wave. They are subsonic waves when the shock–vortex interaction is weak but become supersonic waves for strong interactions. Under a intermediate interaction, however, an induced shock wave is first developed where flow speed is supersonic but is dissipated where the incoming flow is subsonic. We have identified three different interaction patterns that depend on the vortex flow regime characterized by the shock–vortex interaction.      

基于GIS与数值模拟的三峡水库库首区诱发地震危险性评价

采用GIS与数值模拟相结合的方法对三峡水库库首区诱发地震危险性进行评价。通过研究水库诱发地震的影响因素,建立模型进行数值模拟。在GIS平台上,综合数值模拟结果与诱发地震监测结果,建立危险性评价数据库。在GIS支持下,采用最大拉应变准则判别拉伸破坏,采用摩尔-库仑准则判别剪切破坏,对单元进行评价。利用诱发地震监测资料,以发生诱发地震单元的第一主应力、第三主应力、位移作为危险单元的标准,对单元进行二次评价。研究结果表明,建立同一GIS平台下的水库区地质环境、监测资料数据库是建立多因素综合评价模型的基础。采用地震评估模型对模拟结果进行评估,结合监测资料对评估成果进行修正,在三峡库首区水库诱发地震危险性评价中具有一定的可信度。