Coherencia de las políticas públicas y su traducción en esquemas regulatorios consistentes: caso del diesel oil en Chile

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Limitations of trust management schemes in VANET and countermeasures

Vehicular networks ensure that the information received from any vehicle is promptly and correctly propagated to nearby vehicles, to prevent accidents. A crucial point is how to trust the information transmitted, when the neighboring vehicles are rapidly changing and moving in and out of range. Current trust management schemes for vehicular networks establish trust by voting on the decision received by several nodes, which might not be required for practical scenarios. It might just be enough to check the validity of incoming information. Due to the ephemeral nature of vehicular networks, reputation schemes for mobile ad hoc networks (MANETs) cannot be applied to vehicular ad hoc networks (VANET). We point out several limitations of trust management schemes for VANET. In particular, we identify the problem of information cascading and oversampling, which commonly arise in social networks. Oversampling is a situation in which a node observing two or more nodes, takes into consideration both their opinions equally without knowing that they might have influenced each other in decision making. We show that simple voting for decision making, leads to oversampling and gives incorrect results. We propose an algorithm to overcome this problem in VANET. This is the first paper which discusses the concept of cascading effect and oversampling effects to ad hoc networks. © 2011 IEEE.

On data-centric misbehavior detection in VANETs

Detecting misbehavior (such as transmissions of false information) in vehicular ad hoc networks (VANETs) is a very important problem with wide range of implications, including safety related and congestion avoidance applications. We discuss several limitations of existing misbehavior detection schemes (MDS) designed for VANETs. Most MDS are concerned with detection of malicious nodes. In most situations, vehicles would send wrong information because of selfish reasons of their owners, e.g. for gaining access to a particular lane. It is therefore more important to detect false information than to identify misbehaving nodes. We introduce the concept of data-centric misbehavior detection and propose algorithms which detect false alert messages and misbehaving nodes by observing their actions after sending out the alert messages. With the data-centric MDS, each node can decide whether an information received is correct or false. The decision is based on the consistency of recent messages and new alerts with reported and estimated vehicle positions. No voting or majority decisions is needed, making our MDS resilient to Sybil attacks. After misbehavior is detected, we do not revoke all the secret credentials of misbehaving nodes, as done in most schemes. Instead, we impose fines on misbehaving nodes (administered by the certification authority), discouraging them to act selfishly. This reduces the computation and communication costs involved in revoking all the secret credentials of misbehaving nodes. © 2011 IEEE.

A social network approach to trust management in VANETs

In the past few years, vehicular ad hoc networks(VANETs) was studied extensively by researchers. VANETs is a type of P2P network, though it has some distinct characters (fast moving, short lived connection etc.). In this paper, we present several limitations of current trust management schemes in VANETs and propose ways to counter them. We first review several trust management techniques in VANETs and argue that the ephemeral nature of VANETs render them useless in practical situations. We identify that the problem of information cascading and oversampling, which commonly arise in social networks, also adversely affects trust management schemes in VANETs. To the best of our knowledge, we are the first to introduce information cascading and oversampling to VANETs. We show that simple voting for decision making leads to oversampling and gives incorrect results in VANETs. To overcome this problem, we propose a novel voting scheme. In our scheme, each vehicle has different voting weight according to its distance from the event. The vehicle which is more closer to the event possesses higher weight. Simulations show that our proposed algorithm performs better than simple voting, increasing the correctness of voting. © 2012 Springer Science + Business Media, LLC.

Efficiency analysis of an isolated high voltage gain converter operating in resonant and non-resonant mode

This paper presents an efficiency investigation of an isolated high step-up ratio dc-dc converter aimed to be used for energy processing from low-voltage high-current energy sources, like batteries, photovoltaic modules or fuel-cells. The considered converter consists of an interleaved active clamp flyback topology combined with a voltage multiplier at the transformer secondary side capable of two different operating modes, i.e. resonant and non-resonant according to the design of the output capacitors. The main goal of this paper is to compare these two operating modes from the component losses point of view with the aim of maximize the overall converter efficiency. The approach is based on losses prediction using steady-state theoretical models (designed in Mathcad environment), taking into account both conduction and switching losses. The models are compared with steady-state simulations and experimental results considering different operating modes to validate the approach. © 2012 IEEE.

Upconversion luminescence in Er3+ doped Ga10Ge 25S65 glass and glass-ceramic excited in the near-infrared

The infrared-to-visible frequency upconversion was investigated in Er 3+-doped Ga10Ge25S65 glass and in the transparent glass-ceramic obtained by heat-treatment of the glass above its glass-transition temperature. Continuous-wave and pulsed lasers operating at 980 nm and 1480 nm were used as excitation sources. The green (2H 11/2 → 4I15/2; 4S3/2 → 4I15/2) and red (4F9/2 → 4I15/2) photoluminescence (PL) signals due to the Er3+ ions were characterized. The PL decay times were influenced by energy transfer among Er3+ ions, by cross-relaxation processes and by energy transfer from the Er3+ ions to the host material. The PL from the Er3+ ions hosted in the crystalline phase was distinguished only when the glass-ceramic was excited by the 1480 nm pulsed laser. The excitation pathways responsible for the green and red PL bands are discussed to explain the differences between the spectra observed under continuous-wave and pulsed excitation. © 2013 American Institute of Physics.

Tránsito y transporte en la Ciudad de México: el sistema de ejes viales

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Ictiofauna nos trechos médio e baixo rio Pardo, Alto Paraná: inventário

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Carregamento ótimo de veículos elétricos considerando as restrições das redes de distribuição de média tensão

Pós-graduação em Engenharia Elétrica - FEIS

Potencial do eucalipto na fitorremediação de um solo contaminado por chumbo

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo da eficiência do fosfato monoamônico na formação da piromorfita

Pós-graduação em Ciência dos Materiais - FEIS

Desenvolvimento de um perfilômetro laser para determinação da área e volume de contato entre o pneu e o solo: Cristiano Alberto de Paula. -

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Avaliação dos parâmetros hídricos do solo em um plantio adensado de Eucalyptus urograndis

Pós-graduação em Agronomia (Energia na Agricultura) - FCA

Desenvolvimento de um modelo fuzzy para otimização da energia gerada por um sistema híbrido (solar-fotovoltaico e eólico)

Pós-graduação em Agronomia (Energia na Agricultura) - FCA

Ação educativa de prevenção de acidentes domésticos em escolas de ensino fundamental

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)