140,088 research outputs found

    LOcalized modes on an Ablowitz-Ladik nonlinear impurity

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    We study localized modes on a single Ablowitz-Ladik impurity embedded in the bulk or at the surface of a one-dimensional linear lattice. Exact expressions are obtained for the bound state profile and energy. Dynamical excitation of the localized mode reveals exponentially-high amplitude oscillations of the spatial profile at the impurity location. The presence of a surface increases the minimum nonlinearity to effect a dynamical selftrapping.Comment: 11 pages, 6 figures, accepted in PL

    Evaluaci贸n de la satisfacci贸n del turista y la congesti贸n en la pr谩ctica de observaci贸n de ballenas jorobadas, el caso de Puerto L贸pez 鈥 Ecuador

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    [EN] The effect of crowding on tourist satisfaction is a widely studied aspect. Its knowledge is valuable not only to guide ordering of tourism activity but also to ensure a satisfactory experience that contributes to its economic sustainability. However, studies of this type are scarce in the context of whale watching tourism. Therefore, this research aims to evaluate tourist satisfaction and crowding in the practice of humpback whale - watching in Puerto L贸pez - Ecuador. At the methodological level, a survey was applied to 340 tourists who observed whales in the June-September 2017 season. Data analysis was based on descriptive record, the structuring of an importance-performance analysis matrix, principal components analysis and binary logistic regression model. Unlike others, this research incorporated the calculation of a perceived crowding threshold and the analysis of the relationship between perceived crowding of boats and people on board. Among main results, the study finds that crowding influences tourist satisfaction when four or more boats coincide at a sighting site. In that sense, the activity in Puerto L贸pez is satisfactory in the face of a reported crowding scenario of 3.7 boats and 16.3 people per boat, on average. The limitations of this study are its exploratory nature because it is based on a non-probabilistic sampling and the questionnaire application exclusively in standard capacity boats, without considering those of 35 passengers.[ES] El efecto de la congesti贸n sobre la satisfacci贸n del turista constituye un aspecto ampliamente estudiado. Su conocimiento resulta valioso no solo para orientar el ordenamiento de la actividad tur铆stica sino adem谩s para asegurar una experiencia satisfactoria que contribuya a su sostenibilidad econ贸mica. Sin embargo, son escasos los estudios de este tipo en el contexto del turismo de observaci贸n de ballenas. Por tanto, esta investigaci贸n tiene como objetivo evaluar la satisfacci贸n del turista y la congesti贸n en la pr谩ctica de observaci贸n de ballenas jorobadas en Puerto L贸pez 鈥 Ecuador. A nivel metodol贸gico se aplic贸 una encuesta a 340 turistas que observaron ballenas en la temporada junio-septiembre de 2017. El an谩lisis de datos se apoy贸 en el registro descriptivo, la estructuraci贸n de una matriz de an谩lisis importancia-desempe帽o, el an谩lisis de componentes principales y un modelo de regresi贸n log铆stica binaria. A diferencia de otras, esta investigaci贸n incorpor贸 el c谩lculo de un umbral de congesti贸n percibida y el an谩lisis de la relaci贸n entre congesti贸n percibida de botes y de personas a bordo. Como resultado, el estudio encuentra que la congesti贸n influye en la satisfacci贸n del turista cuando cuatro o m谩s embarcaciones coinciden en un sitio de avistamiento. En ese sentido, la actividad en Puerto L贸pez es satisfactoria frente a un escenario de congesti贸n reportada de 3,7 botes y 16,3 personas por bote, en promedio. Constituyen limitaciones del estudio su car谩cter exploratorio por basarse en un muestreo no probabil铆stico y la aplicaci贸n exclusiva del cuestionario en botes de capacidad est谩ndar, sin considerar aquellos de 35 pasajeros

    Service Learning Project

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    The social issue is the lack of collaborative work from the community, or only provided in dire times.https://digitalscholarship.unlv.edu/educ_sys_202/1014/thumbnail.jp

    Investigation on the Electrical Properties of CdO/ZnO thin films using THz Spectroscopy

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    In this work, we study the electrical properties of transparent conducting oxides using physical and optical techniques. The objective is to characterize the conductivity of a series of cadmium oxide zinc-oxide thin films with varying cadmium concentrations using three methods. The Hall Effect estimates carrier concentration, sheet conductivity, and carrier mobility. Optical methods, such as FTIR spectroscopy, can provide estimates of the plasma frequency, which describes a metal鈥檚 transition from being transparent to opaque to light. THz spectroscopy extracts the complex conductivity of materials in the far infrared spectrum and provides insights on the optical transport properties of conductors. Our findings show that DC/AC measurements of the conductivity of Cd/ZnO thin films exhibit frequency independent conductivity, indicating that the films are homogeneous Drude metals

    Uncertainty under a multivariate nested-error regression model with logarithmic transformation

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    Assuming a multivariate linear regression model with one random factor, we consider the parameters defined as exponentials of mixed effects, i.e., linear combinations of fixed and random effects. Such parameters are of particular interest in prediction problems where the dependent variable is the logarithm of the variable that is the object of inference. We derive bias-corrected empirical predictors of such parameters. A second order approximation for the mean crossed product error of the predictors of two of these parameters is obtained, and an estimator is derived from it. The mean squared error is obtained as a particular case

    Quantum Vibrational Impurity Embedded in a One-dimensional Chain

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    We perform a fully quantum mechanical numerical calculation for the problem of a single electron (or excitation) propagating in a N-site one-dimensional chain in the presence of a single Holstein impurity. We compute the long-time averaged probability for finding the electron on the impurity site as a function of the nonlinearity parameter, defined in terms of the electron-phonon coupling strength and the oscillator frequency. The results, in the intermediate nonlinearity parameter range, differ substantially from the ones obtained through the use of the discrete nonlinear Schroedinger equation, even in the high-frequency regime.Comment: 8 pages, 4 figure