Dynamics of a Predator-Prey System with Beddington-DeAngelis Functional Response and Delays

We consider a predator-prey system with Beddington-DeAngelis functional response and delays, in which not only the stage structure on prey but also the delay due to digestion is considered. First, we give a sufficient and necessary condition for the existence of a unique positive equilibrium by analyzing the corresponding locations of a hyperbolic curve and a line. Then, by constructing an appropriate Lyapunov function, we prove that the positive equilibrium is locally asymptotically stable under a sufficient condition. Finally, by using comparison theorem and the ω-limit set theory, we study the global asymptotic stability of the boundary equilibrium and the positive equilibrium, respectively. Also, we obtain a sufficient condition to assure the global asymptotic stability

Service Quality Management of Scenic Spot Based on Tourists\u27 Experience--Taking the Three Gorges Dam 5A Scenic Area for Example

Based on the perspective of tourists, the paper takes the empirical analysis of service quality of the three gorges dam scenic spot, tries to put forward some methods to improve service quality, and provide the reference for the tourism sustainable optimization development of the three gorges dam

The peculiar filamentary HI structure of NGC 6145

In this paper, we report the peculiar HI morphology of the cluster spiral galaxy NGC 6145, which has a 150 kpc HI filament on one side that is nearly parallel to its major axis. This filament is made up of several HI clouds and the diffuse HI gas between them, with no optical counterparts. We compare its HI distribution with other one-sided HI distributions in the literature, and find that the overall HI distribution is very different from the typical tidal and ram-pressure stripped HI shape, and its morphology is inconsistent with being a pure accretion event. Only about 30% of the total HI gas is anchored on the stellar disk, while most of HI gas forms the filament in the west. At a projected distance of 122 kpc, we find a massive elliptical companion (NGC 6146) with extended radio emission, whose axis points to an HI gap in NGC 6145. The velocity of the HI filament shows an overall light-of- sight motion of 80 to 180 km/s with respect to NGC 6145. Using the long-slit spectra of NGC 6145 along its major stellar axis, we find that some outer regions show enhanced star formation, while in contrast, almost no star formation activities are found in its center (less than 2 kpc). Pure accretion, tidal or ram-pressure stripping is not likely to produce the observed HI filament. An alternative explanation is the jet-stripping from NGC 6146, although direct evidence for a jet-cold gas interaction has not been found.Comment: 12 pages, 6 figures; Accepted for publication in A

A hybrid analysis of ellipsometry data from patterned structures

Rigorous coupled wave analysis (RCWA) has been used for modeling the polarization dependent reflection from periodic patterns for process monitoring and control. However, the computational load of this vector method is very heavy. In this paper, we will carefully examine a much simpler scalar method for reflection modeling. We also extend the application of the vector analysis to some special non-periodic structures by combining RCWA with the scalar model. We conclude that this hybrid approach is of significant promise for in situ IC production applications. © 2001 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87397/2/373_1.pd

PARTICIPATORY DEVELOPMENT OF POST-SEPARATION DOMESTIC VIOLENCE SERVICES: A COOPERATIVE GROUNDED INQUIRY WITH ABUSED WOMEN AND THEIR TEENAGE SONS/DAUGHTERS IN HONG KONG

This research involves formerly abused women and their teenage children equally with the practitioner-researcher in post-separation domestic violence service design and delivery. It examines how does a co-participative relationship among social work practitioner-researcher, women survivors and their teenage sons/daughters form, and how a co-participative relationship serves post-separation domestic violence service development, delivery and evaluation. Cooperative Grounded Inquiry (CGI) is invented in this research to offer an alternative methodology to Service User and Carer Participation (SUCP), in addition to the current consumerist and emancipatory models. As a result, a theory is generated to explain the formation and displaying of a ‘family-like community of practice’ among inquiry members; meanwhile, the ‘family-like community of practice’ sets the context for the co-construction of local theories and practices that mitigate women and their teenage children’s post-separation problems and enhance their competence in problem solving. This thesis meticulously articulates the experiences of co-constructing local knowledges with formerly abused women and their teenage children, and to contends that practices for facilitating ‘identity (re)construction’ and ‘partnership making’ are of paramount importance in their post-separation lives. Findings of this research pose challenges on the conventional crisis-oriented domestic violence services and the Cartesian model of self that underlies the mainstream understanding of post-separation needs and services. Drawing on the relational approach and Schatzki’s theorization of social practices, the thesis critiques individualization of domestic violence (as acts performed by individuals) and the corresponding services. In the last chapter, building a community of practice is proposed as a possible way of reconciling the women-focused domestic violence services and child protection system

Design of an adaptive dynamic vibration absorber

The aim of this thesis is to investigate the use of a Dynamic Vibration Absorber to control vibration in a beam. Traditional means of vibration control have involved the use of passive and more recently, active methods. This study is different in that it involves an adaptive component in the design of vibration absorber using two novel designs for the adaptive mechanism. The first design incorporates the use of an enclosed air volume to provide the variable stiffness component in the absorber. By adjusting the volume of compressible air within the absorber, the stiffness characteristics of the absorber can be altered, enabling the device to adapt to changing vibration frequencies. Work here includes a theoretical investigation of the device. Following this, two prototypes are constructed and tested, the second of which is the refined model used for further testing. The second design incorporates the use of two concentrated masses cantilevered from two rods. The adaptive solution is achieved by moving the two masses along the length of the rod, producing a changing natural frequency for the absorber device. An analytical model of this device is developed as well as a finite element model. Results from both are compared to those obtained experimentally. Finally, a tuning algorithm is derived for the second absorber, and a control system constructed to make the dynamic vibration absorber "adaptive". Experiments are undertaken to determine the effectiveness of the absorber on the beam subject to changing excitation frequencies. The outcome of this research is that an Adaptive Vibration Absorber has been constructed with a computer interface such that the device can be used "on line".Thesis (M.Eng.Sc.)--Mechanical Engineering, 1999