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Publications

2019

An Optimization Model for the Design of Additive Manufacturing Supply Chains

Authors
de Brito, FM; da Cruz Junior, G; Frazzon, EM; Basto, JP; Alcala, SGS;

Publication
2019 IEEE 17TH INTERNATIONAL CONFERENCE ON INDUSTRIAL INFORMATICS (INDIN)

Abstract
The continuous adoption of Additive Manufacturing (AM) can enhance Supply Chain's (SC) effectiveness, adaptability and competitiveness. AM allows for a decentralized SC, bringing production centres nearer to customers, increasing products availability and decreasing inventory level and lead time. However, the integration of SC and AM brings difficulties, leading to the need of a completely new SC design. This paper proposes an optimization model supporting the design of spare parts SCs operating under a Make-To-Order (MTO) strategy. The proposed approach considers the decision of deploying productive resources (3D printers) in locations of a spare parts SC. The problem is represented as a combination of the p-median and location-allocation optimization models, which are solved using a Mixed Integer Linear Programming (MILP). The approach is tested in two scenarios from a real-world use case of an elevator maintenance service provider. Obtained results demonstrated the promising capabilities of the proposed approach for handling the new design challenges arising from the forthcoming widespread use of 3D printers in manufacturing SCs.

2019

A Survey on Computer Programming Learning Environments

Authors
Queirós, RAPd;

Publication
Advances in Computer and Electrical Engineering - Code Generation, Analysis Tools, and Testing for Quality

Abstract
We are assisting the rise of online coding environments as a strategy to promote youth tech employment. With the growing importance of the technology sector, these type of technical training programs give learners emergent tech skills with a big impact and relevance to the current professional market needs. In this realm, MOOCs (massive open online courses) and online coding bootcamps are two increasingly popular options for learners to improve their code development skills and find work within a relatively short amount of time. Among all the features available on these environments, one stands out, which is the code generation. This chapter aims to detail and compare the most popular solutions for both learning contexts based on several criteria such as impact and maturity, user groups, and tools and features. In the features field, the authors highlight the code generation feature as an efficient way to enhance exercise resolution.

2019

Scalable eventually consistent counters over unreliable networks

Authors
Almeida, PS; Baquero, C;

Publication
DISTRIBUTED COMPUTING

Abstract
Counters are an important abstraction in distributed computing, and play a central role in large scale geo-replicated systems, counting events such as web page impressions or social network likes. Classic distributed counters, strongly consistent via linearisability or sequential consistency, cannot be made both available and partition-tolerant, due to the CAP Theorem, being unsuitable to large scale scenarios. This paper defines Eventually Consistent Distributed Counters (ECDCs) and presents an implementation of the concept, Handoff Counters, that is scalable and works over unreliable networks. By giving up the total operation ordering in classic distributed counters, ECDC implementations can be made AP in the CAP design space, while retaining the essence of counting. Handoff Counters are the first Conflict-free Replicated Data Type (CRDT) based mechanism that overcomes the identity explosion problem in naive CRDTs, such as G-Counters (where state size is linear in the number of independent actors that ever incremented the counter), by managing identities towards avoiding global propagation and garbage collecting temporary entries. The approach used in Handoff Counters is not restricted to counters, being more generally applicable to other data types with associative and commutative operations.

2019

Stochastic network-constrained co-optimization of energy and reserve products in renewable energy integrated power and gas networks with energy storage system

Authors
Mirzaei, MA; Yazdankhah, AS; Mohammadi Ivatloo, B; Marzband, M; Shafie khah, M; Catalao, JPS;

Publication
JOURNAL OF CLEANER PRODUCTION

Abstract
Increasing penetration of variable nature wind energy sources (WES) due to environmental issues, impose several technical challenges to power system operation as it is difficult to predict its output power because of wind intermittency. Power generation based on gas turbine with fast starting fitness and high ramping could better deal with inherent uncertainties comparing to other power generation sources. Considering natural gas network constraints impacts flexibility and participation of gas-fueled generation units on reserve and energy markets. Hence, the use of flexible energy storage system can reduce renewable sources alternation and the gas network limitation effects on power system operation cost. This paper proposes a two-stage stochastic network-constrained unit commitment based market clearing model for energy and reserve products in coordinated power and gas networks with the integration of compressed air energy storage (CAES) and WES. A six-bus electric system with a six-node gas system and IEEE reliability test system (RTS) 24-bus electric system with a ten-node gas network are considered to perform numerical tests and demonstrate the performance of the proposed model. The effect of including the constraints of the gas system on the power system operation cost in day-ahead co-optimization of energy and reserve products is evaluated using numerical studies. Also, including CAES reduces the power system operation cost, load shedding and wind spillage. Crown Copyright

2019

Fabry-Perot cavity for curvature measurement in a medical needle

Authors
Novais, S; Silva, SO; Frazao, O;

Publication
SEVENTH EUROPEAN WORKSHOP ON OPTICAL FIBRE SENSORS (EWOFS 2019)

Abstract
A reflective fiber optic sensor based on a Fabry-Perot cavity made by splicing two sections of multimode fiber is demonstrated to measure the needle curvature. The sensing structure was incorporated into a medical needle and characterized for curvature and temperature measurements. The maximum sensitivity of -0.152dB/m(-1) was obtained to the curvature measurements, with a resolution of 0.089m(-1). When subjected to temperature, the sensing head presented a low temperature sensitivity, which resulted in a small cross-sensitivity.

2019

COPADRIVe - A Realistic Simulation Framework for Cooperative Autonomous Driving Applications

Authors
Vieira, B; Severino, R; Vasconcelos, E; Koubaa, A; Tovar, E;

Publication
2019 8TH IEEE INTERNATIONAL CONFERENCE ON CONNECTED VEHICLES AND EXPO (IIEEE CCVE)

Abstract
Safety-critical cooperative vehicle applications such as platooning, require extensive testing, however, the complexity and cost involved in this process, increasingly demands for realistic simulation tools to ease the validation of such technologies, helping to bridge the gap between development and real-word deployment. In this paper we propose a realistic co-simulation framework for cooperative vehicles, that integrates Gazebo, an advanced robotics simulator, with the OMNeT++ network simulator, over the Robot Operating System (ROS) framework, supporting the simulation of advanced cooperative applications such as platooning, in realistic scenarios.

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