542,232 research outputs found

    The velocities of intranetwork and network magnetic fields

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    We analyzed two sequences of quiet-Sun magnetograms obtained on June 4, 1992 and July 28, 1994. Both were observed during excellent seeing conditions such that the weak intranetwork (IN) fields are observed clearly during the entire periods. Using the local correlation tracking technique, we derived the horizontal velocity fields of IN and network magnetic fields. They consist of two components: (1) radial divergence flows which move IN fields from the network interior to the boundaries, and (2) lateral flows which move along the network boundaries and converge toward stronger magnetic elements. Furthermore, we constructed divergence maps based on horizonal velocities, which are a good representation of the vertical velocities of supergranules. For the June 4, 1992 data, the enhanced network area in the field of view has twice the flux density, 10% higher supergranular velocity and 20% larger cell sizes than the quiet, unenhanced network area. Based on the number densities and flow velocities of IN fields derived in this paper and a previous paper (Wang et al., 1995), we estimate that the lower limit of total energy released from the recycling of IN fields is 1.2 × 10²⁸ erg s⁻¹, which is comparable to the energy required for coronal heating

    On the convergence of autonomous agent communities

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    This is the post-print version of the final published paper that is available from the link below. Copyright @ 2010 IOS Press and the authors.Community is a common phenomenon in natural ecosystems, human societies as well as artificial multi-agent systems such as those in web and Internet based applications. In many self-organizing systems, communities are formed evolutionarily in a decentralized way through agents' autonomous behavior. This paper systematically investigates the properties of a variety of the self-organizing agent community systems by a formal qualitative approach and a quantitative experimental approach. The qualitative formal study by applying formal specification in SLABS and Scenario Calculus has proven that mature and optimal communities always form and become stable when agents behave based on the collective knowledge of the communities, whereas community formation does not always reach maturity and optimality if agents behave solely based on individual knowledge, and the communities are not always stable even if such a formation is achieved. The quantitative experimental study by simulation has shown that the convergence time of agent communities depends on several parameters of the system in certain complicated patterns, including the number of agents, the number of community organizers, the number of knowledge categories, and the size of the knowledge in each category

    Analytical Results For The Steady State Of Traffic Flow Models With Stochastic Delay

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    Exact mean field equations are derived analytically to give the fundamental diagrams, i.e., the average speed - car density relations, for the Fukui-Ishibashi one-dimensional traffic flow cellular automaton model of high speed vehicles (vmax=M>1)(v_{max}=M>1) with stochastic delay. Starting with the basic equation describing the time evolution of the number of empty sites in front of each car, the concepts of inter-car spacings longer and shorter than MM are introduced. The probabilities of having long and short spacings on the road are calculated. For high car densities (ρ1/M)(\rho \geq 1/M), it is shown that inter-car spacings longer than MM will be shortened as the traffic flow evolves in time, and any initial configurations approach a steady state in which all the inter-car spacings are of the short type. Similarly for low car densities (ρ1/M)(\rho \leq 1/M), it can be shown that traffic flow approaches an asymptotic steady state in which all the inter-car spacings are longer than M2M-2. The average traffic speed is then obtained analytically as a function of car density in the asymptotic steady state. The fundamental diagram so obtained is in excellent agreement with simulation data.Comment: 12 pages, latex, 2 figure

    Macroporous materials: microfluidic fabrication, functionalization and applications

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    This article provides an up-to-date highly comprehensive overview (594 references) on the state of the art of the synthesis and design of macroporous materials using microfluidics and their applications in different fields

    Intimate Partner Violence in Immigrant/Refugee Populations

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    Intimate partner violence (IPV) is the most common type of violence affecting women. Globally, Central Africa and South Asia have some of the highest rates of IPV. In Vermont, the majority of refugees are from these regions. Individual, interpersonal, and especially cultural values play critical roles in the definition/appraisal and decision to seek help in these women. This study examines ways to mitigate challenges that healthcare professionals have in identifying women who need help and barriers preventing these women from seeking help.https://scholarworks.uvm.edu/fmclerk/1276/thumbnail.jp

    H∞ fuzzy control for systems with repeated scalar nonlinearities and random packet losses

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    Copyright [2009] IEEE. This material is posted here with permission of the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of Brunel University's products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to [email protected]. By choosing to view this document, you agree to all provisions of the copyright laws protecting it.This paper is concerned with the H∞ fuzzy control problem for a class of systems with repeated scalar nonlinearities and random packet losses. A modified Takagi-Sugeno (T-S) fuzzy model is proposed in which the consequent parts are composed of a set of discrete-time state equations containing a repeated scalar nonlinearity. Such a model can describe some well-known nonlinear systems such as recurrent neural networks. The measurement transmission between the plant and controller is assumed to be imperfect and a stochastic variable satisfying the Bernoulli random binary distribution is utilized to represent the phenomenon of random packet losses. Attention is focused on the analysis and design of H∞ fuzzy controllers with the same repeated scalar nonlinearities such that the closed-loop T-S fuzzy control system is stochastically stable and preserves a guaranteed H∞ performance. Sufficient conditions are obtained for the existence of admissible controllers, and the cone complementarity linearization procedure is employed to cast the controller design problem into a sequential minimization one subject to linear matrix inequalities, which can be readily solved by using standard numerical software. Two examples are given to illustrate the effectiveness of the proposed design method