8,080 research outputs found

    Evaluation of Modification of the Upper Batavia Dam on the Fox River, Illinois

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    Progress Report, Federal Aid Project F-136-R Segment 6Report issued on: August 2004Submitted to Office of Water Resources, Illinois Department of Natural Resource

    A simple operational interpretation of the fidelity

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    This note presents a corollary to Uhlmann's theorem which provides a simple operational interpretation for the fidelity of mixed states.Comment: 1 pag

    Investigation of the factors that contribute to degradation of Songor Ramsar and UNESCO Man and Biosphere Reserve in Ghana

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    This study on the Songor Ramsar and UNESCO Man and Biosphere Reserve in Ghana seeks to investigate the factors that contribute to degradation of Songor Ramsar and UNESCO Man and Biosphere Reserve in Ghana through the administration of structured questionnaires using the drop-and–collect approach, face-to-face interviews and focus group discussions. The study revealed that the ranking of natural resources and occupation of the area are based on the demarcated zones within which the community is situated. Salt, fisheries and arable lands were identified as the most important natural resource in the wetland. The results on environmental degradation of the wetlands in the Songor Ramsar site in Ghana made it clear that the underlying causes of environmental degradation in the Songor Ramsar site are mainly a combination of Institutional and policy failures. It was revealed that the problem of environmental degradation is a consequence of ineffective enforcement of bye-laws. A combination of several factors such as improper waste disposal, poor attitude of residents toward environmental conservation, wildfires and shoreline recession, inadequate public education on the impact of environmental degradation, fishing and farming activities were identified during the administration of structured questionnaire, face-to-face interviews and focus group discussions. The other factors include overgrazing, over exploitation of mangroves, Predation, poaching and over fishing, uncontrolled sand and salt winning. Constraints and weaknesses to the implementation of regulations and laws with respect to conservation and protection of the wetlands identified during the study are lack of public education on the economic importance and the need to conserve the wetland, encroachment by developers, lack of enforcement of bye-laws, over-exploitation of mangroves and waste management

    Stroboscopic Velocities in the Tonoscope

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    The characteristic equation for stroboscopic velocity is v8 = (A-n/m B) D0 (see Proc. Iowa Acad. Sci., Vol. XXIV, 1917, p. 222), where v8 is the stroboscopic velocity, A the frequency of the stroboscopic figures, B the frequency of illumination, n/m a fraction at lowest terms, and D0 the distance of separation of the stroboscopic figures

    Discrete surface solitons in two dimensions

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    We investigate fundamental localized modes in 2D lattices with an edge (surface). Interaction with the edge expands the stability area for ordinary solitons, and induces a difference between perpendicular and parallel dipoles; on the contrary, lattice vortices cannot exist too close to the border. Furthermore, we show analytically and numerically that the edge stabilizes a novel wave species, which is entirely unstable in the uniform lattice, namely, a "horseshoe" soliton, consisting of 3 sites. Unstable horseshoes transform themselves into a pair of ordinary solitons.Comment: 6 pages, 4 composite figure

    Vortices in attractive Bose-Einstein condensates in two dimensions

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    The form and stability of quantum vortices in Bose-Einstein condensates with attractive atomic interactions is elucidated. They appear as ring bright solitons, and are a generalization of the Townes soliton to nonzero winding number mm. An infinite sequence of radially excited stationary states appear for each value of mm, which are characterized by concentric matter-wave rings separated by nodes, in contrast to repulsive condensates, where no such set of states exists. It is shown that robustly stable as well as unstable regimes may be achieved in confined geometries, thereby suggesting that vortices and their radial excited states can be observed in experiments on attractive condensates in two dimensions.Comment: 4 pages, 3 figure

    Mixed perturbative expansion: the validity of a model for the cascading

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    A new type of perturbative expansion is built in order to give a rigorous derivation and to clarify the range of validity of some commonly used model equations. This model describes the evolution of the modulation of two short and localized pulses, fundamental and second harmonic, propagating together in a bulk uniaxial crystal with non-vanishing second order susceptibility χ(2)\chi^(2) and interacting through the nonlinear effect known as ``cascading'' in nonlinear optics. The perturbative method mixes a multi-scale expansion with a power series expansion of the susceptibility, and must be carefully adapted to the physical situation. It allows the determination of the physical conditions under which the model is valid: the order of magnitude of the walk-off, phase-mismatch,and anisotropy must have determined values.Comment: arxiv version is already officia

    Parametrically controlling solitary wave dynamics in modified Kortweg-de Vries equation

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    We demonstrate the control of solitary wave dynamics of modified Kortweg-de Vries (MKdV) equation through the temporal variations of the distributed coefficients. This is explicated through exact cnoidal wave and localized soliton solutions of the MKdV equation with variable coefficients. The solitons can be accelerated and their propagation can be manipulated by suitable variations of the above parameters. In sharp contrast with nonlinear Schr\"{o}dinger equation, the soliton amplitude and widths are time independent.Comment: 4 pages, 5 eps figure

    On the Cauchy problem for a nonlinearly dispersive wave equation

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    We establish the local well-posedness for a new nonlinearly dispersive wave equation and we show that the equation has solutions that exist for indefinite times as well as solutions which blowup in finite times. Furthermore, we derive an explosion criterion for the equation and we give a sharp estimate from below for the existence time of solutions with smooth initial data.Comment: arxiv version is already officia
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