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Publications

2016

Simulation and Experimental Evaluation of a Resonant Magnetic Wireless Power Transfer System for Seawater Operation

Authors
Pereira, MR; Santos, HM; Pessoa, LM; Salgado, HM;

Publication
OCEANS 2016 - SHANGHAI

Abstract
The use of high efficiency resonant coupling wireless power systems for subsea operations is here considered for the charging of autonomous underwater vehicles. In this paper, two architectures based on two different inductors are analysed for their potential as resonant wireless power couplers. Both systems were designed and optimised through electromagnetic 3D simulations, upon which two prototypes were constructed and measured. Efficiencies as high as 75% for distances up to 5 cm were achieved on experimental testing.

2016

Economic Evaluation of Combined Generation and Storage Solutions in Low Voltage Portuguese Consumers

Authors
Soares, RA; Saraiva, JT;

Publication
2016 13TH INTERNATIONAL CONFERENCE ON THE EUROPEAN ENERGY MARKET (EEM)

Abstract
This paper presents the results that were obtained in the scope of a consultancy study developed by INESC TEC for a Portuguese distribution network company to evaluate the interest of installing storage devices and PV panels in LV installations. We conducted simulations for consumers with annual demands of 5000 kWh (Type C consumers) and 7500 kWh (Type B consumers). In general, we concluded that the installation of storage devices is still of little economic interest given the current investment level and the tariffs paid to inject electricity in the networks. The largest NPV values were obtained when only installing PV panels in Type B consumers, the larger ones, and selling the surplus energy to the network.

2016

Impacts of Stochastic Wind Power and Storage Participation on Economic Dispatch in Distribution Systems

Authors
Bizuayehu, AW; Sanchez de la Nieta, AAS; Contreras, J; Catalao, JPS;

Publication
IEEE TRANSACTIONS ON SUSTAINABLE ENERGY

Abstract
Evaluating the impact related to stochastic wind generation and generic storage on economic dispatch in distribution system operation is an important issue in power systems. This paper presents the analysis of the impacts of high wind power and storage participation on a distribution system over a period of 24 h using grid reconfiguration for electrical distribution system (EDS) radial operation. In order to meet this objective, a stochastic mixed integer linear programming (SMILP) is proposed, where the balance between load and generation has to be satisfied minimizing the expected cost during the operation period. The model also considers distributed generation (DG) represented by wind scenarios and conventional generation, bus loads represented through a typical demand profile, and generic storage. A case study provides results for a weakly meshed distribution network with 70 buses, describing in a comprehensive manner the effects of stochastic wind scenarios and storage location on distribution network parameters, voltage, substation behavior as well as power losses, and the expected cost of the system.

2016

A physical packing sequence algorithm for the container loading problem with static mechanical equilibrium conditions

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

Publication
INTERNATIONAL TRANSACTIONS IN OPERATIONAL RESEARCH

Abstract
The container loading problem (CLP) is a combinatorial optimization problem for the spatial arrangement of cargo inside containers so as to maximize the usage of space. The algorithms for this problem are of limited practical applicability if real-world constraints are not considered, one of the most important of which is deemed to be stability. This paper addresses static stability, as opposed to dynamic stability, looking at the stability of the cargo during container loading. This paper proposes two algorithms. The first is a static stability algorithm based on static mechanical equilibrium conditions that can be used as a stability evaluation function embedded in CLP algorithms (e.g. constructive heuristics, metaheuristics). The second proposed algorithm is a physical packing sequence algorithm that, given a container loading arrangement, generates the actual sequence by which each box is placed inside the container, considering static stability and loading operation efficiency constraints.

2016

Knowledge Sharing in Industrial Associations and Science and Technology Parks

Authors
Inomata, DO; Costa, E; Mazzaroto, S; Santos, C; Barros, AC; Soares, AL; Varvakis, G;

Publication
COLLABORATION IN A HYPERCONNECTED WORLD

Abstract
Knowledge management practices are used in collaborative networks promoting innovation in order to share critical knowledge among network members towards improving organizational results. This paper proposes to explore the channels and practices for knowledge sharing in collaborative networks, by means of an exploratory multiple case study carried out in two types of collaborative networks: (i) industrial associations; and (ii) science and technology parks. Empirical evidence has been collected from interviews with managers of the collaborative networks and of organizations participating in the collaborative networks. The contribution of this paper to the knowledge management literature is twofold: (i) it provides a characterization of the channels and technology used for knowledge sharing in collaborative networks based on empirical evidence and (ii) it describes knowledge sharing practices used among organizations to foster new forms of connectivity between groups and individuals.

2016

Resource Usage Prediction in Distributed Key-Value Datastores

Authors
Cruz, F; Maia, F; Matos, M; Oliveira, R; Paulo, J; Pereira, J; Vilaca, R;

Publication
DISTRIBUTED APPLICATIONS AND INTEROPERABLE SYSTEMS, DAIS 2016

Abstract
In order to attain the promises of the Cloud Computing paradigm, systems need to be able to transparently adapt to environment changes. Such behavior benefits from the ability to predict those changes in order to handle them seamlessly. In this paper, we present a mechanism to accurately predict the resource usage of distributed key-value datastores. Our mechanism requires offline training but, in contrast with other approaches, it is sufficient to run it only once per hardware configuration and subsequently use it for online prediction of database performance under any circumstance. The mechanism accurately estimates the database resource usage for any request distribution with an average accuracy of 94 %, only by knowing two parameters: (i) cache hit ratio; and (ii) incoming throughput. Both input values can be observed in real time or synthesized for request allocation decisions. This novel approach is sufficiently simple and generic, while simultaneously being suitable for other practical applications.

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