4,416 research outputs found

    Modelamiento y simulación de algoritmos adaptivos de alocación de bits para sistemas multiuser

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    Este proyecto se enfoca en el análisis y desarrollo de un algoritmo que nos permitirá entender con mayor facilidad lo que es la alocación adaptiva de bit en un sistema multiuser OFDM.La solución que hemos planteado para el desarrollo de este proyecto es de tipo “Multi-userdiscrete bit-loading”, la cual podremos ver desarrollada más adelante {3.3}, pero que con una sencilla explicación podemos decir que esta solución trata de encontrar la forma más optima de transmitir una cierta cantidad de bits, con el único propósito de minimizar la potencia total de transmisión.la solución planteada será desarrollada en un escenario específico con valores determinados con la finalidad de que cumpla con las condiciones necesarias para trabajar en un medio VDSL2. Gracias a análisis realizado se pudo verificar la eficiencia del algoritmo y la gran utilidad al momento de realizar la alocación ya que permite minimizar al máximo la potencia total de transmición. El algoritmo planteado en este proyecto fue desarrollado en el software MATLAB, ya que consideramos que es un software nos permite recopilar datos de una manera más real, con el propósito de brindar la explicación más clara a lector

    Landau parameters for isospin asymmetric nuclear matter based on a relativistic model of composite and finite extension nucleons

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    We study the properties of cold asymmetric nuclear matter at high density, applying the quark meson coupling model with excluded volume corrections in the framework of the Landau theory of relativistic Fermi liquids. We discuss the role of the finite spatial extension of composite baryons on dynamical and statistical properties such as the Landau parameters, the compressibility, and the symmetry energy. We have also calculated the low lying collective eigenfrequencies arising from the collisionless quasiparticle transport equation, considering both unstable and stable modes. An overall analysis of the excluded volume correlations on the collective properties is performed.Comment: 24 pages, 6 figure

    Modelos mentales de comunicación y consumo. Una comparación intercultural de publicidad televisiva

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    Este estudio prospectivo plantea la interrogante si la publicidad televisiva difiere entre distintas culturas y si es así, cómo y en qué medida. En contraste a la mayoría de los estudios respectivos, nos hemos concentrado en un protocolo detallado basado en un análisis formal que está estadísticamente orientado. En una perspectiva más amplia, la relación entre la comunicación cara-a-cara y la comunicación mediatizada por la tecnología está escrutada. Asumiendo que hay varias diferencias, una hipótesis sería que éstas se originan en hábitos de comunicación antiguos a aquellos encontrados en la comunicación por medios tecnológicos. En parte, eso supondría una transferencia entre diferentes medios, relacionando la organización del habla con la de las imágenes. Como solamente por medio de estudios comparativos se puede responder dichas interrogantes, se compararon dos muestras de publicidad alemana y ecuatoriana. Para evitar una sobreestimación de las diferencias culturales es inevitable el investigar también el nivel intercultural para evaluar las fluctuaciones relacionadas con los contenidos

    The Bolocam 1.1 mm Lockman Hole Galaxy Survey: SHARC II 350 micron Photometry and Implications for Spectral Models, Dust Temperatures, and Redshift Estimation

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    We present 350 micron photometry of all 17 galaxy candidates in the Lockman Hole detected in a 1.1 mm Bolocam survey. Several of the galaxies were previously detected at 850 microns, at 1.2 mm, in the infrared by Spitzer, and in the radio. Nine of the Bolocam galaxy candidates were detected at 350 microns and two new candidates were serendipitously detected at 350 microns (bringing the total in the literature detected in this way to three). Five of the galaxies have published spectroscopic redshifts, enabling investigation of the implied temperature ranges and a comparison of photometric redshift techniques. Lambda = 350 microns lies near the spectral energy distribution peak for z = 2.5 thermally emitting galaxies. Thus, luminosities can be measured without extrapolating to the peak from detection wavelengths of lambda > 850 microns. Characteristically, the galaxy luminosities lie in the range 1.0 - 1.2 x 10^13 L_solar, with dust temperatures in the range of 40 K to 70 K, depending on the choice of spectral index and wavelength of unit optical depth. The implied dust masses are 3 - 5 x 10^8 M_solar. We find that the far-infrared to radio relation for star-forming ULIRGs systematically overpredicts the radio luminosities and overestimates redshifts on the order of Delta z ~ 1, whereas redshifts based on either on submillimeter data alone or the 1.6 micron stellar bump and PAH features are more accurate.Comment: In Press (to appear in Astrophysical Journal, ApJ 20 May 2006 v643 1) 47 pages, 10 figures, 4 table

    Functional Foods Baseline and Requirements Analysis

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    Current spaceflight foods were evaluated to determine if their nutrient profile supports positioning as a functional food and if the stability of the bioactive compound within the food matrix over an extended shelf-life correlated with the expected storage duration during the mission. Specifically, the research aims were: Aim A. To determine the amount of each nutrient in representative spaceflight foods immediately after processing and at predetermined storage time to establish the current nutritional state. Aim B. To identify the requirements to develop foods that stabilize these nutrients such that required concentrations are maintained in the space food system throughout long duration missions (up to five years). Aim C. To coordinate collaborations with health and performance groups that may require functional foods as a countermeasure

    Energy Dissipation and Trapping of Particles Moving on a Rough Surface

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    We report an experimental, numerical and theoretical study of the motion of a ball on a rough inclined surface. The control parameters are DD, the diameter of the ball, θ\theta, the inclination angle of the rough surface and EkiE_{ki}, the initial kinetic energy. When the angle of inclination is larger than some critical value, θ>θT\theta>\theta_{T}, the ball moves at a constant average velocity which is independent of the initial conditions. For an angle θ<θT\theta < \theta_{T}, the balls are trapped after moving a certain distance. The dependence of the travelled distances on EkiE_{ki}, DD and θ\theta. is analysed. The existence of two kinds of mechanisms of dissipation is thus brought to light. We find that for high initial velocities the friction force is constant. As the velocity decreases below a certain threshold the friction becomes viscous.Comment: 8 pages RevTeX, 12 Postscript figure

    Control of quantum interference in the quantum eraser

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    We have implemented an optical quantum eraser with the aim of studying this phenomenon in the context of state discrimination. An interfering single photon is entangled with another one serving as a which-path marker. As a consequence, the visibility of the interference as well as the which-path information are constrained by the overlap (measured by the inner product) between the which-path marker states, which in a more general situation are non-orthogonal. In order to perform which-path or quantum eraser measurements while analyzing non-orthogonal states, we resort to a probabilistic method for the unambiguous modification of the inner product between the two states of the which-path marker in a discrimination-like process.Comment: Submitted to New Journal of Physics, March 200

    Ingested insecticide to control Aedes aegypti: developing a novel dried attractive toxic sugar bait device for intra-domiciliary control

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    © 2020 The Author(s). Background: Illnesses transmitted by Aedes aegypti (Linnaeus, 1762) such as dengue, chikungunya and Zika comprise a considerable global burden; mosquito control is the primary public health tool to reduce disease transmission. Current interventions are inadequate and insecticide resistance threatens the effectiveness of these options. Dried attractive bait stations (DABS) are a novel mechanism to deliver insecticide to Ae. aegypti. The DABS are a high-contrast 28 inch2 surface coated with dried sugar-boric acid solution. Aedes aegypti are attracted to DABS by visual cues only, and the dried sugar solution elicits an ingestion response from Ae. aegypti landing on the surface. The study presents the development of the DABS and tests of their impact on Ae. aegypti mortality in the laboratory and a series of semi-field trials. Methods: We conducted multiple series of laboratory and semi-field trials to assess the survivability of Ae. aegypti mosquitoes exposed to the DABS. In the laboratory experiments, we assessed the lethality, the killing mechanism, and the shelf life of the device through controlled experiments. In the semi-field trials, we released laboratory-reared female Ae. aegypti into experimental houses typical of peri-urban tropical communities in South America in three trial series with six replicates each. Laboratory experiments were conducted in Quito, Ecuador, and semi-field experiments were conducted in Machala, Ecuador, an area with abundant wild populations of Ae. aegypti and endemic arboviral transmission. Results: In the laboratory, complete lethality was observed after 48 hours regardless of physiological status of the mosquito. The killing mechanism was determined to be through ingestion, as the boric acid disrupted the gut of the mosquito. In experimental houses, total mosquito mortality was greater in the treatment house for all series of experiments (P \u3c 0.0001). Conclusions: The DABS devices were effective at killing female Ae. aegypti under a variety of laboratory and semi-field conditions. DABS are a promising intervention for interdomiciliary control of Ae. aegypti and arboviral disease prevention.[Figure not available: see fulltext.
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