Search results for " Opera"
showing 10 items of 3606 documents
The periodic rural postman problem with irregular services on mixed graphs
2019
Abstract In this paper, we deal with an extension of the rural postman problem in which some links of a mixed graph must be traversed a given number of times over a time horizon. These links represent entities that must be serviced a specified number of times in some subsets of days (or periods) of the time horizon. The aim is to design a set of minimum-cost tours, one for each day/period of the time horizon, that satisfy the service requirements. We refer to this problem as the periodic rural postman problem with irregular services (PRPP–IS). Some practical applications of the problem can be found in road maintenance operations and road network surveillance, for example. In order to solve …
Competition and cooperation for intermodal container transhipment: A network optimization approach
2018
Abstract This study presents an analysis of cross-border competition and cooperation between ports in Bangladesh and India. Nepal and Bhutan are countries without access to seaports — two landlocked countries in South Asia, depending solely on the Indian port of Kolkata for their international seaborne trade. Alternatives do exist in the Bangladeshi ports of Chittagong and Mongla but these are not exploited, in spite of trade agreements that allow access to a third country's port, and/or crossing the land of a third, intermediate, country. We formulate a mixed integer linear programming optimization model to find the optimum economic benefit of port users (serving Bhutan, Nepal and Northeas…
Modéliser le rôle des paysages dans les choix d'itinéraires pédestres
2008
Actuellement, la marche a pied suscite un regain d'interet comme mode de transport complementaire. Dans le cadre de cet article, nous partons de l'hypothese que l'adaptation de l'environnement urbain aux attentes des pietons, notamment d'un point de vue paysager, est une etape essentielle de la revalorisation de ce mode de deplacement. A cette fin, nous proposons une demarche permettant de decrire les comportements pedestres et d'identifier les preferences paysageres des pietons dans les villes de Besancon et de Lille. La methode d'analyse se fonde sur les modeles de choix discret, couramment utilises dans la modelisation des choix individuels. Celle-ci permet de mesurer, de maniere desagre…
History of Data Centre Development
2012
International audience; Computers are used to solve different problems. For solving these problems computer software and hardware are used, but for operations of those computing facilities a Data Centre is necessary. Therefore, development of the data centre is subordinated to solvable tasks and computing resources. We are studying the history of data centres’ development, taking into consideration an understanding of this. In the beginning of the computer era computers were installed in computing centres, because all computing centres have defined requirements according to whom their operation is intended for. Even though the concept of ‘data centre’ itself has been used since the 1990s, t…
Evaluation of the 2-Methoxyethanol as Entrainer in Ethanol–Water and 1-Propanol–Water Mixtures
2013
In this paper, 2-methoxyethanol (commercially known as methyl cellosolve) is proposed as a potential entrainer for extractive distillation processes involving water–alcohol mixtures. The two alcohols studied in this work are ethanol and 1-propanol. Thereby, isobaric vapor–liquid equilibrium (VLE) data at atmospheric pressure have been measured for the ternary systems ethanol + water + 2-methoxyethanol and 1-propanol + water + 2-methoxyethanol. Moreover, data of the binary systems formed by the 2-methoxyethanol and each of the other chemicals used (ethanol, water, 1-propanol) have been obtained. The well-known local composition models Wilson, UNIQUAC, and NRTL have been used to correlate bin…
Building a statistical surveillance dashboard for COVID-19 infection worldwide
2020
When a pandemic like the current novel coronavirus (COVID-19) breaks out, it is important that authorities, healthcare organizations and official decision makers, have in place an effective monitoring system to promptly analyze data, create new insights into problematic areas and generate actionable knowledge for fact-based decision making. The aim of this article is to describe an initial work focused on building a comprehensive statistical surveillance dashboard for the epidemic of COVID-19, which can be exploited also for future needs. We propose novel ways of exploring, analyzing and presenting data, using metrics that have not been used previously. We also show the steps necessary to b…
Lower ST-elevation myocardial infarction incidence during COVID-19 epidemic in Northern Europe
2020
We compared the ST elevation myocardial infarction (STEMI) incidence during COVID-19 pandemic (March 2020) to January-February 2020 and to same time period in earlier years 2017-2019 in five Nordic-Baltic tertiary centers. During 2017-2019, there were no marked differences in STEMI incidence between January, February and March. During 2020, there was an average drop of 32% in STEMI incidence in March. The isolation measures may decrease the risk for respiratory virus infection and contribute to the lower STEMI incidence and that we might benefit from firmer suggestions on hand hygiene and social distancing during flu season at least among high-risk individuals.
Impact of asymptomatic COVID-19 patients in global surgical practice during the COVID-19 pandemic
2020
The rapid spread of COVID-19 has changed the global surgical care. Patients infected with COVID-19 may present without typical symptoms, and such asymptomatic patients may potentially trigger in-hospital outbreaks by transmitting the disease to health care providers and other hospitalized patients. Further, asymptomatic COVID-19 patients have worse postop- erative outcomes with an unexpectedly high morbidity and mortality, reaching 20⋅5 per cent deaths. However, we do not have objective global data on this issue. In an attempt to clarify the current global surgical practice under the COVID-19 pandemic particularly focusing on the preoperative screening of asymptomatic COVID-19 patients, we …
Three solutions for a two-point boundary value problem with the prescribed mean curvature equation
2015
The existence of at least three classical solutions for a parametric ordinary Dirichlet problem involving the mean curvature operator are established. In particular, a variational approach is proposed and the main results are obtained simply requiring the sublinearity at zero of the considered nonlinearity.
Non-convex power allocation games in MIMO cognitive radio networks
2013
Consideramos un escenario de reparto del espectro, basado en la detección, en una red de radio cognitiva MIMO donde el objetivo general es maximizar el rendimiento total de cada usuario de radio cognitiva optimizando conjuntamente la operación de detección y la asignación de potencia en todos los canales, bajo una restricción de interferencia para los usuarios primarios. Los problemas de optimización resultantes conducen a un juego no convexo, que presenta un nuevo desafío a la hora de analizar los equilibrios de este juego. Con el fin de hacer frente a la no convexidad del juego, utilizamos un nuevo concepto relajado de equilibrio, el equilibrio cuasi-Nash (QNE). Se demuestran las condicio…