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Publications

Publications by CTM

2010

Propagation of Airy-related beams

Authors
Carvalho, MI; Facao, M;

Publication
OPTICS EXPRESS

Abstract
New types of finite energy Airy beams are proposed. We consider two different types of beams, namely, beams that are obtained as blocked and exponentially attenuated versions of Airy functions Ai and Bi, and beams of finite width but having the Airy functions typical phase. All of them show very interesting properties, such as parabolic trajectories for longer propagation distances, profile evolution exhibiting less diffraction, or better definiteness of the main peak, when compared with other finite energy Airy beams studied before. (C) 2010 Optical Society of America

2010

An Interactive Documentary Manifesto

Authors
Almeida, A; Alvelos, H;

Publication
INTERACTIVE STORYTELLING

Abstract
In the last few years the word "documentary" has been loosely used to describe multimedia pieces that incorporate video no matter its nature, technique, language or scope, taking advantage of the fuzzy and fragile boundaries of the documentary definition. The present manifesto aims to give a brief insight on the interactive documentary arena and also to sketch some production remarks for future interactive documentary productions.

2010

Three-dimensional reconstruction and characterization of human external shapes from two-dimensional images using volumetric methods

Authors
Azevedo, TCS; Tavares, JMRS; Vaz, MAP;

Publication
COMPUTER METHODS IN BIOMECHANICS AND BIOMEDICAL ENGINEERING

Abstract
This work presents a volumetric approach to reconstruct and characterise 3D models of external anatomical structures from 2D images. Volumetric methods represent the final volume using a finite set of 3D geometric primitives, usually designed as voxels. Thus, from an image sequence acquired around the object to reconstruct, the images are calibrated and the 3D models of the referred object are built using different approaches of volumetric methods. The final goal is to analyse the accuracy of the obtained models when modifying some of the parameters of the considered volumetric methods, such as the type of voxel projection (rectangular or accurate), the way the consistency of the voxels is tested (only silhouettes or silhouettes and photo-consistency) and the initial size of the reconstructed volume.

2010

Style emulation of drum patterns by means of evolutionary methods and statistical analysis

Authors
Bernardes, G; Guedes, C; Pennycook, B;

Publication
Proceedings of the 7th Sound and Music Computing Conference, SMC 2010

Abstract
In this paper we present an application using an evolutionary algorithm for real-time generation of polyphonic drum loops in a particular style. The population of rhythms is derived from analysis of MIDI drum loops, which profile each style for subsequent automatic generation of rhythmic patterns that evolve over time through genetic algorithm operators and user input data. © 2010 Gilberto Bernardes et al.

2010

Using a prioritized MAC protocol to execute the database operation join in networked embedded computer systems

Authors
Andersson, B; Pereira, N; Tovar, E; Pacheco, F;

Publication
8th Workshop on Intelligent Solutions in Embedded Systems, WISES 2010, Heraklion, Crete, Greece, July 8-9, 2010

Abstract
Database query languages on relations (for example SQL) make it possible to join two relations. This operation is very common in desktop/server database systems but unfortunately query processing systems in networked embedded computer systems currently do not support this operation; specifically, the query processing systems TAG, TinyDB, Cougar do not support this. We show how a prioritized medium access control (MAC) protocol can be used to efficiently execute the database operation join for networked embedded computer systems where all computer nodes are in a single broadcast domain. © 2010 IEEE.

2010

Programmable Test Bench for Hemodynamic Studies

Authors
Pereira, HC; Cardoso, JM; Almeida, VG; Pereira, T; Borges, E; Figueiras, E; Ferreira, LR; Simoes, JB; Correia, C;

Publication
WORLD CONGRESS ON MEDICAL PHYSICS AND BIOMEDICAL ENGINEERING, VOL 25, PT 4: IMAGE PROCESSING, BIOSIGNAL PROCESSING, MODELLING AND SIMULATION, BIOMECHANICS

Abstract
The non-invasive assessment of hemodynamic parameters has been a permanent challenge posed to the scientific community. The literature shows many contributions to this quest expressed as algorithms dedicated to revealing some of its characteristics and as new probes or electronics, featuring some enhanced instrumental capability that can improve their insight. A test system capable of replicating some of the basic properties of the cardiovascular system, especially the ones related with the propagation of the arterial pressure wave (APW), is a powerful tool in the development of those probes and in the validation of the various algorithms that extract clinically relevant information from the data that they can collect. This work describes a test bench system, based on the combination of a new programmable pressure wave generator with a flexible tube, capable of emulating some of these properties. It discusses its main characterization issues and demonstrates the system in a relevant case study. Two versions of the system have been set up: one that generates a short duration pulse-like pressure wave from an actuator operated in a switched mode, appropriate to system characterization; a second one, using a long stroke actuator, linearly operated under program control, capable of generating complex, including cardiac-like, pressure waveforms. This configuration finds its main use in algorithm test and validation. Tests with a new piezoelectric probe, designed to collect the APW at the major artery sites are shown, demonstrating the possibility of non-invasive precise recovery of the pressure waveform.

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