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Publications

2015

Development of a Robotic Prototype System for the Preparation and Partition of Radioactive Products

Authors
Guevara, G; Lima, J; Leitao, P; Baptista, MD;

Publication
2015 IEEE INTERNATIONAL CONFERENCE ON INDUSTRIAL TECHNOLOGY (ICIT)

Abstract
The ionizing radiation is used in the nuclear medicine field during the execution of diagnosis exams. The continuous exposure of humans to the radiation may cause organs and tissues damage, being its severity dependent of the quantity of the radiation and the exposure time. The main objective of this work is to design a virtual environment to carry out the simulation of the several stages for the preparation of radioactive products based on the use of a robotic arm. In this work, the V-REP robotic simulation tool was used for the specification and development of the manipulation processes, without the need to consider the real manipulator, being timely and costly efficient. During this study, the preparation process of the dosages in the diagnostic exams was analyzed, being posteriorly translated into mechanical processes for a better perception. The materials and equipment needed were designed as virtual 3D models and posteriorly imported into the V-REP simulation platform in order to be distributed and programmed to achieve a closer approximation to reality.

2015

Control of Modular Multilevel Converters for Integration of Distributed Generation Sources into the Power Grid

Authors
Pouresmaeil, E; Mehrasa, M; Amin Shokridehaki, MA; Rodrigues, EMG; Catalao, JPS;

Publication
2015 IEEE INTERNATIONAL CONFERENCE ON SMART ENERGY GRID ENGINEERING (SEGE 2015)

Abstract
This paper presents a control technique for control of a Modular Multilevel Converter (MMC) based DG system in the grid-connected mode. Circulating currents of MMC are considered as a state variable, besides the AC currents and dc-link voltage of interfaced converter, which is the main novelty and contribution of the proposed control technique over the other potential control techniques in DG technology. By this assumption, the proposed control technique is included by three outer, central and inner control loops for regulating the operation of interfaced MMC under steady state operating conditions, and during load and parameter variations. Passivity based controller, sliding mode method and reference currents calculator are employed as outer loop controller (OLC), central loop controller (CLC) and inner loop controller (ILC), respectively, in the proposed control technique. Simulation results confirm the effectiveness of the proposed control technique in the proposed DG model during dynamic and steady-state operating conditions.

2015

Assessment of the effectiveness of fuel and toll pricing policies in motorway emissions: An ex-post analysis

Authors
Fontes, T; Pereira, SR; Bandeira, JM; Coelho, MC;

Publication
RESEARCH IN TRANSPORTATION ECONOMICS

Abstract
In this paper the environmental impacts of fuel and toll pricing policies were evaluated for eight Portuguese motorways for the period between 2008 and 2011. To perform such study, firstly the analysis of the elasticity was done to assess the sensitive of traffic demand. Then emission costs were estimated considering an integrated approach of environmental and human health impacts. Two motorway groups were analyzed: one originally built with both conventional and electronic toll systems (G1); and another recently equipped with non-stop electronic tolls (G2). The results show that the elasticity of the system changes with the fluctuation prices, particularly influenced by toll prices variation. During the analysis period, traffic volumes decreased (8-11% in G1, and 15-41% in G2). About 75% of traffic flow shows a high statistical significance correlation (p < 0.05) with toll prices, which highlight the impact of toll prices. Differences between emission costs can be close to 50% in those motorway groups. Nevertheless, due the absence of data in alternative routes, the obtained results show only the potential maximum environmental gains of these policies in motorways. This limitation is very important in the quantification of the environmental global impacts. Non-toll roads are usually characterized by slower speeds and higher emissions. Therefore the above mentioned gains can be converted, in these cases, in losses. (C) 2015 Published by Elsevier Ltd.

2015

Dynamic stability metrics for the container loading problem

Authors
Galrao Ramos, AG; Oliveira, JF; Goncalves, JF; Lopes, MP;

Publication
TRANSPORTATION RESEARCH PART C-EMERGING TECHNOLOGIES

Abstract
The Container Loading Problem (CLP) literature has traditionally evaluated the dynamic stability of cargo by applying two metrics to box arrangements: the mean number of boxes supporting the items excluding those placed directly on the floor (M1) and the percentage of boxes with insufficient lateral support (M2). However, these metrics, that aim to be proxies for cargo stability during transportation, fail to translate real-world cargo conditions of dynamic stability. In this paper two new performance indicators are proposed to evaluate the dynamic stability of cargo arrangements: the number of fallen boxes (NFB) and the number of boxes within the Damage Boundary Curve fragility test (NB_DBC). Using 1500 solutions for well-known problem instances found in the literature, these new performance indicators are evaluated using a physics simulation tool (StableCargo), replacing the real-world transportation by a truck with a simulation of the dynamic behaviour of container loading arrangements. Two new dynamic stability metrics that can be integrated within any container loading algorithm are also proposed. The metrics are analytical models of the proposed stability performance indicators, computed by multiple linear regression. Pearson's r correlation coefficient was used as an evaluation parameter for the performance of the models. The extensive computational results show that the proposed metrics are better proxies for dynamic stability in the CLP than the previous widely used metrics.

2015

Ontologies for Research Data Description: A Design Process Applied to Vehicle Simulation

Authors
Castro, JA; Perrotta, D; Amorim, RC; da Silva, JR; Ribeiro, C;

Publication
METADATA AND SEMANTICS RESEARCH, MTSR 2015

Abstract
Data description is an essential part of research data management, and it is easy to argue for the importance of describing data early in the research workflow. Specific metadata schemas are often proposed to support description. Given the diversity of research domains, such schemas are often missing, and when available they may be too generic, too complex or hard to incorporate in a description platform. In this paper we present a method used to design metadata models for research data description as ontologies. Ontologies are gaining acceptance as knowledge representation structures, and we use them here in the scope of the Dendro platform. The ontology design process is illustrated with a case study from Vehicle Simulation. According to the design process, the resulting model was validated by a domain specialist.

2015

Production Planning of Perishable Food Products by Mixed-Integer Programming

Authors
Pires, MJ; Amorim, P; Martins, S; Almada Lobo, B;

Publication
OPERATIONAL RESEARCH

Abstract
In this paper, the main complexities related to the modeling of production planning problems of food products are addressed. We start with a deterministic base model and build a road-map on how to incorporate key features of food production planning. The different "ingredients" are organized around the model components to be extended: constraints, objective functions and parameters. We cover issues such as expiry dates, customers' behavior, discarding costs, value of freshness and age-dependent demand. To understand the impact of these "ingredients", we solve an illustrative example with each corresponding model and analyze the changes on the solution structure of the production plan. The differences across the solutions show the importance of choosing a model suitable to the particular business setting, in order to accommodate the multiple challenges present in these industries. Moreover, acknowledging the perishable nature of the products and evaluating the amount and quality of information at hands may be crucial in lowering overall costs and achieving higher service levels. Afterwards, the deterministic base model is extended to deal with an uncertain demand parameter and risk management issues are discussed using a similar illustrative example. Results indicate the increased importance of risk-management in the production planning of perishable food goods.

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