3,979 research outputs found

    Optimal Carbon Taxes for Emissions Targets in the Electricity Sector

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    The most dangerous effects of anthropogenic climate change can be mitigated by using emissions taxes or other regulatory interventions to reduce greenhouse gas (GHG) emissions. This paper takes a regulatory viewpoint and describes the Weighted Sum Bisection method to determine the lowest emission tax rate that can reduce the anticipated emissions of the power sector below a prescribed, regulatorily-defined target. This bi-level method accounts for a variety of operating conditions via stochastic programming and remains computationally tractable for realistically large planning test systems, even when binary commitment decisions and multi-period constraints on conventional generators are considered. Case studies on a modified ISO New England test system demonstrate that this method reliably finds the minimum tax rate that meets emissions targets. In addition, it investigates the relationship between system investments and the tax-setting process. Introducing GHG emissions taxes increases the value proposition for investment in new cleaner generation, transmission, and energy efficiency; conversely, investing in these technologies reduces the tax rate required to reach a given emissions target

    Modelling consumer credit risk via survival analysis

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    Credit risk models are used by financial companies to evaluate in advance the insolvency risk caused by credits that enter into default. Many models for credit risk have been developed over the past few decades. In this paper, we focus on those models that can be formulated in terms of the probability of default by using survival analysis techniques. With this objective three different mechanisms are proposed based on the key idea of writing the default probability in terms of the conditional distribution function of the time to default. The first method is based on a Cox’s regression model, the second approach uses generalized linear models under censoring and the third one is based on nonparametric kernel estimation, using the product-limit conditional distribution function estimator by Beran. The resulting nonparametric estimator of the default probability is proved to be consistent and asymptotically normal. An empirical study, based on modified real data, illustrates the three methods.Peer Reviewe

    Systematic perturbation calculation of integrals with applications to physics

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    In this paper we generalize and improve a method for calculating the period of a classical oscillator and other integrals of physical interest, which was recently developed by some of the authors. We derive analytical expressions that prove to be more accurate than those commonly found in the literature, and test the convergence of the series produced by the approach.Comment: 11 pages, 5 figure

    Control del curculiónido ferruginoso de las palmeras (Rhynchophorus ferrugineus Olivier) mediante inyecciones al tronco y pulverización foliar

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    En 1996 se confirmó la presencia en España, en la costa de la provincia de Granada, de una nueva plaga sobre palmeras conocida como curculiónido ferruginoso de las palmeras, Rhynchophorus ferrugineus Olivier. Dentro de las estrategias de lucha contra este insecto se llevaron a cabo una serie de ensayos de efectividad de distintos productos insecticidas aplicados al suelo, por inyección al tronco, en pulverización foliar o una combinación de estos dos últimos métodos. Los mayores porcentajes de eficacia se obtuvieron mediante la aplicación de insecticidas por inyección al tronco de la palmera, combinada con una pulverización foliar con el mismo insecticida para controlar los estadios del insecto situados en la zona exterior, de pencas y cogollo, donde el insecticida aplicado por inyección no consigue distribuirse. Las materias activas insecticidas que presentaron mayor eficacia fueron Carbaril, Fipronil e Imidacloprid. Asimismo se ha observado la idoneidad de mezclar el insecticida aplicado en pulverización foliar con un aceite mineral parafínico o de verano para mejorar su eficacia

    Extended health visibility in the hospital environment

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    Wireless sensor networks can help healthcare providers enhance patient monitoring and communication capabilities. This paper describes the present state of the development of a vital signal monitoring network applied to the hospital environment. The proposed network is based on non-obstructive sensors able to communicate through a low power wireless sensor network based on the ZigBee protocol. This network enables continuous patient monitoring, creating entirely new mechanisms for providing healthcare under a plethora of cases (e.g. post-op, continuous care, and chronic diseases). The main advantages of this system include increased patient mobility, faster detection of potential problems, real-time feedback to caregivers and patients, and faster response to emergency situations.Fundação para a Ciência e a Tecnologia (FCT)Grupo AMI – Assistência Médica Integral (Casa de Saúde Guimarães, SA

    Towards the design of efficient nonbeacon-enabled ZigBee networks

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    This paper presents experimental results of the communication performance evaluation of a prototype ZigBee-based patient monitoring system commissioned in an in-patient floor of a Portuguese hospital (HPG – Hospital Privado de Guimar~aes). Besides, it revisits relevant problems that affect the performance of nonbeacon-enabled ZigBee networks. Initially, the presence of hidden-nodes and the impact of sensor node mobility are discussed. It was observed, for instance, that the message delivery ratio in a star network consisting of six wireless electrocardiogram sensor devices may decrease from 100% when no hidden-nodes are present to 83.96% when half of the sensor devices are unable to detect the transmissions made by the other half. An additional aspect which affects the communication reliability is a deadlock condition that can occur if routers are unable to process incoming packets during the backoff part of the CSMA-CA mechanism. A simple approach to increase the message delivery ratio in this case is proposed and its effectiveness is verified. The discussion and results presented in this paper aim to contribute to the design of efficient networks, and are valid to other scenarios and environments rather than hospitals.Fundação para a Ciência e a Tecnologia (FCT)Grupo AMI – Assistência Médica Integral (Casa de Saúde Guimarães, SA

    HM4All: A vital signs monitoring system based in spatially distributed ZigBee networks

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    Low power consumption and small footprint make ZigBee based devices well suited for personal healthcare applications, being a promising alternative to general care patient monitoring. However, their use in a healthcare facility to monitor several mobile patients poses several difficulties, mainly because this protocol was primarily designed to operate in low data rate scenarios. This paper introduces HM4All, a remote vital signs monitoring system, and presents a prototype system being deployed in a hospital internment floor. Its architecture, original network topology, software applications and wireless sensors are described.Fundação para a Ciência e a Tecnologia (FCT)Grupo AMI – Assistência Médica Integral (Casa de Saúde Guimarães, SA

    ZigBee-based remote patient monitoring

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    This paper describes a developed continuous patient monitoring system based on the ZigBee protocol. The system was tested in the hospital environment using six sensor devices in two different modes. For electrocardiogram transmission and in the absence of hidden-nodes, the system achieved a mean delivery ratio of 100% and 98.56%, respectively for star and 2-hop tree network topologies. When sensor devices were arranged in a way that three of them were unable to hear the transmissions made by the other three, the mean delivery ratio dropped to 83.96%. However, when sensor devices were reprogrammed to transmit only heart rate values, the mean delivery ratio increased to 99.90%, despite the presence of hidden-nodes.Fundação para a Ciência e a Tecnologia (FCT)Grupo AMI – Assistência Médica Integral (Casa de Saúde Guimarães, SA
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