9,714 research outputs found

    Superfluidity of Dense 4^4He in Vycor

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    We calculate properties of a model of 4^4He in Vycor using the Path Integral Monte Carlo method. We find that 4^4He forms a distinct layered structure with a highly localized first layer, a disordered second layer with some atoms delocalized and able to give rise to the observed superfluid response, and higher layers nearly perfect crystals. The addition of a single 3^3He atom was enough to bring down the total superfluidity by blocking the exchange in the second layer. Our results are consistent with the persistent liquid layer model to explain the observations. Such a model may be relevant to the experiments on bulk solid 4^4He, if there is a fine network of grain boundaries in those systems.Comment: 4 pages, 4 figure

    Dynamics of Learning with Restricted Training Sets I: General Theory

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    We study the dynamics of supervised learning in layered neural networks, in the regime where the size pp of the training set is proportional to the number NN of inputs. Here the local fields are no longer described by Gaussian probability distributions and the learning dynamics is of a spin-glass nature, with the composition of the training set playing the role of quenched disorder. We show how dynamical replica theory can be used to predict the evolution of macroscopic observables, including the two relevant performance measures (training error and generalization error), incorporating the old formalism developed for complete training sets in the limit α=p/N→∞\alpha=p/N\to\infty as a special case. For simplicity we restrict ourselves in this paper to single-layer networks and realizable tasks.Comment: 39 pages, LaTe

    Integration of Renewable Energies in Mobile Employment Promotion Units for Rural Populations

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    The article aims to analyze, evaluate, and improve solutions for the integration of hybrid energy sources (Solar Photovoltaic PV/Batteries/Diesel Generator (DG)) in mobile service units (MSU), designed to provide services to rural populations (drug delivery, vaccination, training, employment promotion, bank, laboratory, etc.). The first objective is to evaluate the performance of two already deployed photovoltaic systems installed on the roofs of trucks, with respective powers of 2.12 and 3.54 kWp. Solar production, consumption, and SOC (State of Charge) of batteries are collected and analyzed. We modelled the energy conversion chain and simulated its behavior on all days of the year. Simulated results are then compared to the on-site measurements. Several association scenarios (PV/batteries) are then studied to propose the optimal combination, taking into account the surface offered for the installation of the PV modules (roof of the truck), the weight, and the lifespan of the batteries. The developed and deployed solution proposes more advantageous association scenarios (PV/Storage), and reduces the time of recourse to the DG. From this perspective, we simulated the operation of the hybrid system for the three battery capacities: 40,000, 31,680, and 19,200 Wh (~1667, 1320, and 800 Ah). The results reveal that the uncaptured energy for a 3540 Wp field is five times greater than that of a 2120 Wp field. On the other hand, the number of battery charge/discharge cycles is divided by ten. Doi: 10.28991/CEJ-2022-08-07-07 Full Text: PD

    Estimation of Kumaraswamy Distribution Parameters Using the Principle of Maximum Entropy

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    This paper proposes using maximum entropy approach to estimate the parameters of the Kumaraswamy distribution subject to moment constraints. Kumaraswamy [7] introduced the double pounded probability density function which was originally used to model hydrological phenomena. It was mentioned that this probability density function is applicable to bounded natural phenomena which have values on two sides. The distribution share several properties with the beta distribution and it has the extra advantages that is possesses a closed form distribution function, but it remained unknown to most statisticians until it was developed by Jones [6] as a beta-type distribution with some tractability advantages in particular as it has fairly simple quantile function and it has explicit formula for L-Moment. Using the principle of maximum entropy to propose new estimators for the Kumaraswamy parameters and compared with maximum likelihood and Bayesian estimation methods. A simulation study is performed to investigate the performance of the estimators in terms of their mean square errors and their efficiency

    Solutions for certain classes of Riccati differential equation

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    We derive some analytic closed-form solutions for a class of Riccati equation y'(x)-\lambda_0(x)y(x)\pm y^2(x)=\pm s_0(x), where \lambda_0(x), s_0(x) are C^{\infty}-functions. We show that if \delta_n=\lambda_n s_{n-1}-\lambda_{n-1}s_n=0, where \lambda_{n}= \lambda_{n-1}^\prime+s_{n-1}+\lambda_0\lambda_{n-1} and s_{n}=s_{n-1}^\prime+s_0\lambda_{k-1}, n=1,2,..., then The Riccati equation has a solution given by y(x)=\mp s_{n-1}(x)/\lambda_{n-1}(x). Extension to the generalized Riccati equation y'(x)+P(x)y(x)+Q(x)y^2(x)=R(x) is also investigated.Comment: 10 page
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