2,848 research outputs found

    Managerial decisions to recover from Covid-19 disruption: A multi-objective optimization approach applied to public transport operators

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    The resilience of transport systems, facing natural or man-made disruptions, has been widely discussed in literature in terms of recovery capabilities concerning infrastructures, suggesting solutions to provide users an acceptable level of service along the interrupted network. However, in the context of the Covid-19 outbreak, the disruption has stressed the resilience of transport systems not on the supply side but rather at organizational level for transport service providers. Indeed, the sudden and drastic decrease in users due to the restrictions imposed by governments to limit the pandemic spread has implicated severe economic consequences in the running of transport companies. In this paper, attention has been focused on the public transport sector to analyse the effects of different initiatives, which companies could undertake in response to the demand shock caused by the Covid-19 emergency. Notably, an optimization procedure has been developed with the aim of determining feasible Pareto-front solutions, which correspond to trade-off conditions for the concurrent maximization of the company profit and the minimization of outsourcing services. The time span necessary to implement the examined recovery measures has been considered together with the limitation to appropriate threshold values for the main cost and income items influencing the company operations management. The proposed approach has been applied to the case study of an Italian public transport company to appraise different post-Covid-19 resilience strategies

    Experimental Realization of Optimal Noise Estimation for a General Pauli Channel

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    We present the experimental realization of the optimal estimation protocol for a Pauli noisy channel. The method is based on the generation of 2-qubit Bell states and the introduction of quantum noise in a controlled way on one of the state subsystems. The efficiency of the optimal estimation, achieved by a Bell measurement, is shown to outperform quantum process tomography

    Testing a Model of Flow and Heat Transfer for U-shaped Geothermal Exchangers

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    Among renewable resources, geothermal energy is one of the most promising for its independence on weather conditions. However, design and installation of borehole heat exchangers on low enthalpy regions must consider numerous influencing factors. Here, we focus on the efficiency improvement in hot water production and heating and cooling of buildings of a pilot geothermal plant, which was implemented as part of a hybrid system within the frame of a research project at the University of Camerino (Italy). The aims of the geothermal plant were to study the subsoil thermal properties and monitoring the parameters of the system during operation. As an important application for the design and sizing of low enthalpy geothermal systems, we propose a mathematical model to study the heat transfer between the fluid circulating in the pipes and the underground, where the mutual influence between the soil and the exchanger is considered. We present results of these approximated solutions based on experimental measurements acquired in the actual geothermal exchangers. Laboratory and in situ tests were also carried out to investigate the underground thermal properties and thermal regime of the heterogeneous soil sedimentary succession

    Survey of detection techniques, mathematical models and simulation software in pedestrian dynamics

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    The study of pedestrian dynamics has become in the latest years an increasing field of research. A relevant number of technicians have been looking for improving technologies able to detect walking people in various conditions. Several researchers have dedicated their works to model walking dynamics and general laws. Many studiers have developed interesting software to simulate pedestrian behavior in all sorts of situations and environments. Nevertheless, till nowadays, no research has been carried out to analyze all the three over-mentioned aspects. The remarked lack in literature of a complete research, pointing out the fundamental features of pedestrian detection techniques, pedestrian modelling and simulation and their tight relationships, motivates the draft of this paper. Aim of the paper is, first, to provide a schematic summary of each topic. Secondly, a more detailed description of the subjects is displayed, pointing out the advantages and disadvantages of each detection technology, the working logic of each model, outlining the inputs and the provided outputs, and the main features of the simulation software. Finally, the obtained results are summarized and discussed, in order to outline the correlation among the three explained themes

    An analytical approximation scheme to two point boundary value problems of ordinary differential equations

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    A new (algebraic) approximation scheme to find {\sl global} solutions of two point boundary value problems of ordinary differential equations (ODE's) is presented. The method is applicable for both linear and nonlinear (coupled) ODE's whose solutions are analytic near one of the boundary points. It is based on replacing the original ODE's by a sequence of auxiliary first order polynomial ODE's with constant coefficients. The coefficients in the auxiliary ODE's are uniquely determined from the local behaviour of the solution in the neighbourhood of one of the boundary points. To obtain the parameters of the global (connecting) solutions analytic at one of the boundary points, reduces to find the appropriate zeros of algebraic equations. The power of the method is illustrated by computing the approximate values of the ``connecting parameters'' for a number of nonlinear ODE's arising in various problems in field theory. We treat in particular the static and rotationally symmetric global vortex, the skyrmion, the Nielsen-Olesen vortex, as well as the 't Hooft-Polyakov magnetic monopole. The total energy of the skyrmion and of the monopole is also computed by the new method. We also consider some ODE's coming from the exact renormalization group. The ground state energy level of the anharmonic oscillator is also computed for arbitrary coupling strengths with good precision.Comment: 5 pages, 3 tables, Late

    Variational approach to a class of nonlinear oscillators with several limit cycles

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    We study limit cycles of nonlinear oscillators described by the equation x¨+νF(x˙)+x=0\ddot x + \nu F(\dot x) + x =0. Depending on the nonlinearity this equation may exhibit different number of limit cycles. We show that limit cycles correspond to relative extrema of a certain functional. Analytical results in the limits ν−>0\nu ->0 and ν−>∞\nu -> \infty are in agreement with previously known criteria. For intermediate ν\nu numerical determination of the limit cycles can be obtained.Comment: 12 pages, 3 figure

    Dynamics of Saccharomyces cerevisiae strains isolated from vine bark in vineyard: Influence of plant age and strain presence during grape must spontaneous fermentations

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    In this study, two vineyards of different age were chosen. During three years, a sampling campaign was performed for isolating vineyard-associated Saccharomyces cerevisiae (S. cerevisiae) strains. Bark portions and, when present, grape bunches were regularly collected from the same vine plants during the overall sampling period. Each bark portion was added to a synthetic must, while each grape bunch was manually crushed, and fermentations were run to isolate S. cerevisiae strains. All collected yeasts were identified at different species and strain levels to evaluate the genetic variability of S. cerevisiae strains in the two vineyards and strains dynamics. Moreover, bark-associated strains were compared with those isolated from spontaneous fermentations of grapes collected during the two harvests. Regarding the youngest vineyard, no S. cerevisiae was identified on bark and grape surface, highlighting the importance of vine age on yeast colonization. Results reported the isolation of S. cerevisiae from vine bark of the old vineyard at all sampling times, regardless of the presence of the grape bunch. Therefore, this environment can be considered an alternative ecological niche that permanently hosts S. cerevisiae. Bark-associated strains were not found on grape bunches and during pilot-scale vinifications, indicating no significative strain transfer from vine bark to the grape must. Commercial starters were identified as well both in vineyards and during vinifications
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