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Publicações

2017

As Secure as Possible Eventual Consistency

Autores
Shoker, A; Yactine, H; Baquero, C;

Publicação
PROCEEDINGS OF THE 3RD INTERNATIONAL WORKSHOP ON PRINCIPLES AND PRACTICE OF CONSISTENCY FOR DISTRIBUTED DATA (PAPOC 17)

Abstract
Eventual consistency (EC) is a relaxed data consistency model that, driven by the CAP theorem, trades prompt consistency for high availability. Although, this model has shown to be promising and greatly adopted by industry, the state of the art only assumes that replicas can crash and recover. However, a Byzantine replica (i.e., arbitrary or malicious) can hamper the eventual convergence of replicas to a global consistent state, thus compromising the entire service. Classical BFT state machine replication protocols cannot solve this problem due to the blocking nature of consensus, something at odd with the availability via replica divergence in the EC model. In this work in progress paper, we introduce a new secure highly available protocol for the EC model that assumes a fraction of replicas and any client can be Byzantine. To respect the essence of EC, the protocol gives priority to high availability, and thus Byzantine detection is performed off the critical path on a consistent data offset. The paper concisely explains the protocol and discusses its feasibility. We aim at presenting a more comprehensive and empirical study in the future.

2017

Spatial Load Forecasting of Electric Vehicle Charging using GIS and Diffusion Theory

Autores
Heyman, F; Pereira, C; Miranda, V; Soares, FJ;

Publicação
2017 IEEE PES INNOVATIVE SMART GRID TECHNOLOGIES CONFERENCE EUROPE (ISGT-EUROPE)

Abstract
The uptake of electric vehicles (EV) will require important modifications in traditional grid planning and load forecasting techniques. Existing literature suggests that the integration of EVs will be more adversarial to elements of the existing electricity infrastructure in terms of power supply (kW) than energy (kWh) delivery. While several studies analyzed the grid impact of electric vehicle fleets, few consider the adoption process itself which may lead to strong spatial variations of the utilization of charging infrastructure. The presented approach extends spatial load forecasting, introducing diffusion theory elements to analyze spatio-temporal clustering of EV charging demand. Using open-access census and grid data, this work develops a deterministic framework to forecast spatial patterns of EV charging applied to a real-world environment. Outcomes suggest substantial spatial clustering of EV adoption patterns, showing substation overrating for EV penetration rates of 25% and above with 7.4kW charging power.

2017

Recent advances in computational science and engineering research

Autores
Veiga, L; El Baz, D; Cardoso, JMP;

Publicação
JOURNAL OF COMPUTATIONAL SCIENCE

Abstract

2017

Preface

Autores
Garrido, P; Soares, F; Moreira, AP;

Publicação
Lecture Notes in Electrical Engineering

Abstract

2017

A bricolage perspective on service innovation

Autores
Witell, L; Gebauer, H; Jaakkola, E; Hammedi, W; Patricio, L; Perks, H;

Publicação
JOURNAL OF BUSINESS RESEARCH

Abstract
Service innovation is often viewed as a process of accessing the necessary resources, (re)combining them, and converting them into new services. The current knowledge on success factors for service innovation, such as formalized new service development (NSD) processes, predominantly comes from studying large firms with a relatively stable resource base. However, this neglect situations in which organizations face severe resource constraints. This paper argues that under such constraints, a formalized new service development process could be counter-productive and a bricolage perspective might better explain service innovation in resource constrained environments. In this conceptual paper, we propose that four critical bricolage capabilities (addressing resource scarcity actively, making do with what is available, improvising when recombining resources, and networking with external partners) influence service innovation outcomes. Empirical illustrations from five organizations substantiate our conceptual development. Our discussion leads to a framework and four testable propositions that can guide further service research.

2017

Simple multimodal optical technique for evaluation of free/bound water and dispersion of human liver tissue

Autores
Carneiro, I; Carvalho, S; Henrique, R; Oliveira, L; Tuchin, VV;

Publicação
JOURNAL OF BIOMEDICAL OPTICS

Abstract
The optical dispersion and water content of human liver were experimentally studied to estimate the optical dispersions of tissue scatterers and dry matter. Using temporal measurements of collimated transmittance [T-c(t)] of liver samples under treatment at different glycerol concentrations, free water and diffusion coefficient (D-gl) of glycerol in liver were found as 60.0% and 8.2 x 10(-7) cm(2)/s, respectively. Bound water was calculated as the difference between the reported total water of 74.5% and found free water. The optical dispersion of liver was calculated from the measurements of refractive index (Rl) of tissue samples made for different wavelengths between 400 and 1000 nm. Using liver and water optical dispersions at 20 degrees C and the free and total water, the dispersions for liver scatterers and dry matter were calculated. The estimated dispersions present a decreasing behavior with wavelength. The dry matter dispersion shows higher Rl values than liver scatterers, as expected. Considering 600 nm, dry matter has an Rl of 1.508, whereas scatterers have an Rl of 1.444. These dispersions are useful to characterize the Rl matching mechanism in optical clearing treatments, provided that [T-c(t)] and thickness measurements are performed during treatment. The knowledge of D-gl is also important for living tissue cryoprotection applications. (C) 2017 Society of Photo-Optical Instrumentation Engineers (SPIE)

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