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Publicações

2014

COMMUNICATIONS UNCERTAINTIES IN ISOLATED MULTI-MICROGRID CONTROL SYSTEMS

Autores
Rua, D; Pecas Lopes, JAP; Ruela, J;

Publicação
2014 POWER SYSTEMS COMPUTATION CONFERENCE (PSCC)

Abstract
Microgrids have been explored as active cells capable of providing enhanced control schemes towards a more secure, reliable and efficient operation of LV distribution networks or MV networks when aggregated in a multi-microgrid. These structures, within the smart grid concept, rely on a communications infrastructure that introduces uncertainty in the data exchange process. In this paper such uncertainty is evaluated considering a multi-microgrid operating in isolated mode.

2014

Optimal life insurance purchase, consumption and investment on a financial market with multi-dimensional diffusive terms

Autores
Duarte, I; Pinheiro, D; Pinto, AA; Pliska, SR;

Publicação
OPTIMIZATION

Abstract
We introduce an extension to Merton's famous continuous time model of optimal consumption and investment, in the spirit of previous works by Pliska and Ye, to allow for a wage earner to have a random lifetime and to use a portion of the income to purchase life insurance in order to provide for his estate, while investing his savings in a financial market comprised of one risk-free security and an arbitrary number of risky securities driven by multi-dimensional Brownian motion. We then provide a detailed analysis of the optimal consumption, investment and insurance purchase strategies for the wage earner whose goal is to maximize the expected utility obtained from his family consumption, from the size of the estate in the event of premature death, and from the size of the estate at the time of retirement. We use dynamic programming methods to obtain explicit solutions for the case of discounted constant relative risk aversion utility functions and describe new analytical results which are presented together with the corresponding economic interpretations.

2014

Procedural Generation of Traversable Buildings Outlined By Arbitrary Convex Shapes

Autores
Adao, T; Magalhaes, L; Peres, E; Pereira, F;

Publicação
CENTERIS 2014 - CONFERENCE ON ENTERPRISE INFORMATION SYSTEMS / PROJMAN 2014 - INTERNATIONAL CONFERENCE ON PROJECT MANAGEMENT / HCIST 2014 - INTERNATIONAL CONFERENCE ON HEALTH AND SOCIAL CARE INFORMATION SYSTEMS AND TECHNOLOGIES

Abstract
Virtual reconstructions are commonly used in archaeology to represent cultural heritage monuments that had been lost or damaged by natural causes. Traditionally, these reconstructions require a huge number of human resources and large ranges of time, resulting in high costs of production. To tackle with this issue, many researchers developed semi-automatic techniques to produce virtual models expeditiously. These procedural techniques provide different ways of represent buildings, including interiors and outer facades, in an archaeological or modern context. However, the existing techniques focusing building interiors only support the production of virtual models composed mainly by regular shapes such as rectangles. In this paper it will be presented the first steps of a novel methodology to provide a solution for the generation of building interiors constrained by arbitrary convex shapes. This methodology uses a specific ontology with a set of rules in order to regulate the generation process. The sequence of steps includes the room placement and area definition, section cuts and area readjustments, room linking and finally the extrusions and roof placement to deliver the final 3D model. (C) 2014 The Authors. Published by Elsevier Ltd.

2014

GTE-Cluster: A Temporal Search Interface for Implicit Temporal Queries

Autores
Campos, R; Dias, G; Jorge, AM; Nunes, C;

Publicação
ECIR

Abstract
In this paper, we present GTE-Cluster an online temporal search interface which consistently allows searching for topics in a temporal perspective by clustering relevant temporal Web search results. GTE-Cluster is designed to improve user experience by augmenting document relevance with temporal relevance. The rationale is that offering the user a comprehensive temporal perspective of a topic is intuitively more informative than retrieving a result that only contains topical information. Our system does not pose any constraint in terms of language or domain, thus users can issue queries in any language ranging from business, cultural, political to musical perspective, to cite just a few. The ability to exploit this information in a temporal manner can be, from a user perspective, potentially useful for several tasks, including user query understanding or temporal clustering. © 2014 Springer International Publishing Switzerland.

2014

An Energy Study on IR-UWB Transmitter Using Integration-and-Fire Modulation

Autores
Kianpour, I; Hussain, B; Tavares, VG; Duarte, C; Mendonca, H; Principe, J;

Publicação
2014 IEEE INTERNATIONAL CONFERENCE ON ULTRA-WIDEBAND (ICUWB)

Abstract
The integrate-and-fire model of a biological neuron is an amplitude to time encoding in the spacing between action potentials (spikes). In principle, this encoding can be used to modulate signals in an Impulse Radio Ultra Wide-Band (IRUWB) transmitter suitable for Wireless Sensor Networks (WSN). This paper presents a system level study on power efficiency using MATLAB/ Simulink to evaluate the required energy for an IR-UWB Transmitter using integrate-and-fire encoding technique. Also, a simple but clear comparison with common systems utilizing Nyquist rate Analog-to-Digital Converters (ADC) is presented. This study has been carried out on a band-limited random Gaussian signal and the results show that IR-IF transmitter consumes roughly seven times less energy than a digital UWB transmitter; moreover, in the proposed architecture the need for power hungry ADC is relaxed.

2014

A Time Synchronization Circuit with an Average 4.6 ns One-Hop Skew for Wired Wearable Networks

Autores
Derogarian, F; Ferreira, JC; Tavares, VMG;

Publicação
2014 17TH EUROMICRO CONFERENCE ON DIGITAL SYSTEM DESIGN (DSD)

Abstract
This paper describes and evaluates a fully digital circuit for one-way master-to-slave highly precise time synchronization in a low-power, wearable system equipped with a set of sensor nodes connected in a mesh network. Sensors are connected to each other with conductive yarns that are used as one-wire bidirectional communication links. The circuit is designed to perform synchronization in the Medium Access Control (MAC) layer. In each sensor node, the synchronization circuit provides a synchronized, programmable clock signal and a real-time counter for time stamping. Experimental results obtained with an implementation in 0.35 mu m CMOS technology for a network of electromyography sensors show that the circuit keeps the one-hop average clock skew below 4.6 ns, a value small enough to satisfy many wearable application requirements.

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