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Publications

2014

Distributed Prime Sieve in Heterogeneous Computer Clusters

Authors
Costa, CM; Sampaio, AM; Barbosa, JG;

Publication
COMPUTATIONAL SCIENCE AND ITS APPLICATIONS - ICCSA 2014, PT IV

Abstract
Prime numbers play a pivotal role in current encryption algorithms and given the rise of cloud computing, the need for larger primes has never been so high. This increase in available computation power can be used to either try to break the encryption or to strength it by finding larger prime numbers. With this in mind, this paper provides an analysis of different sieve implementations that can be used to generate primes to near 2(64). It starts by analyzing cache friendly sequential sieves with wheel factorization, then expands to multi-core architectures and ends with a cache friendly segmented hybrid implementation of a distributed prime sieve, designed to efficiently use all the available computation resources of heterogeneous computer clusters with variable workload and to scale very well in both the shared and distributed memory versions.

2014

Evaporation of fluids in suspended-core fibres

Authors
Moura, JP; Baierl, H; Auguste, JL; Jamier, R; Roy, P; Santos, JL; Frazao, O;

Publication
2014 THIRD MEDITERRANEAN PHOTONICS CONFERENCE

Abstract
A segment of a suspended-core microstructured fibre was dipped in a droplet of acetone and the evaporation dynamics of remaining acetone inside the cavity were simultaneously analysed with an optical microscope and an optical spectrum analyser. When the fibre is immersed it suffers a 14 dB signal drop. Different menisci form in each cladding cavity, with different evaporation times and rates. The signal restores its initial state not when the evaporation process is complete but after the collapse of a dominant meniscus.

2014

Modeling lotsizing and scheduling problems with sequence dependent setups

Authors
Guimaraes, L; Klabjan, D; Almada Lobo, B;

Publication
EUROPEAN JOURNAL OF OPERATIONAL RESEARCH

Abstract
Several production environments require simultaneous planing of sizing and scheduling of sequences of production lots. Integration of sequencing decisions in lotsizing and scheduling problems has received an increased attention from the research community due to its inherent applicability to real world problems. A two-dimensional classification framework is proposed to survey and classify the main modeling approaches to integrate sequencing decisions in discrete time lotsizing and scheduling models. The Asymmetric Traveling Salesman Problem can be an important source of ideas to develop more efficient models and methods to this problem. Following this research line, we also present a new formulation for the problem using commodity flow based subtour elimination constraints. Computational experiments are conducted to assess the performance of the various models, in terms of running times and upper bounds, when solving real-word size instances.

2014

Inferring User Interface Patterns from Execution Traces of Web Applications

Authors
Nabuco, M; Paiva, ACR; Faria, JP;

Publication
COMPUTATIONAL SCIENCE AND ITS APPLICATIONS - ICCSA 2014, PT V

Abstract
This paper presents a dynamic reverse engineering approach to extract User Interface (UI) Patterns from existent Web Applications. Firstly, information related to user interaction is saved, in particular: user actions and parameters; the HTML source pages; and the URLs. Secondly, the collected information is analysed in order to calculate several metrics (e.g., the differences between subsequent HTML pages). Thirdly, the existent UI Patterns are inferred from the overall information calculated based on a set of heuristic rules. The overall reverse engineering approach is evaluated with some experiments over several public Web Applications.

2014

A new electric conductance conversion method suitable for very low power applications

Authors
Miranda, N; Serodio, C; Morais, R;

Publication
MEASUREMENT

Abstract
This article describes a new electrical conductance converter method suitable for low power applications and an implementation in standard CMOS technology. Despite being designed to meet specific measurements requirements, this converter is intended for applications where device power requirements are determinative such self powered sensors networks and implantable devices. The topology is described and an implementation is presented. Results show the possibility of being powered by a single 1.2 V accumulator cell with a consumption of 8 nJ per conversion.

2014

Integrated Management of IaaS Resources

Authors
Meireles, F; Malheiro, B;

Publication
EURO-PAR 2014: PARALLEL PROCESSING WORKSHOPS, PT II

Abstract
This paper proposes and reports the development of an open source solution for the integrated management of Infrastructure as a Service (IaaS) cloud computing resources, through the use of a common API taxonomy, to incorporate open source and proprietary platforms. This research included two surveys on open source IaaS platforms (OpenNebula, OpenStack and CloudStack) and a proprietary platform (Parallels Automation for Cloud Infrastructure - PACI) as well as on IaaS abstraction solutions (jClouds, Libcloud and Deltacloud), followed by a thorough comparison to determine the best approach. The adopted implementation reuses the Apache Deltacloud open source abstraction framework, which relies on the development of software driver modules to interface with different IaaS platforms, and involved the development of a new Deltacloud driver for PACI. The resulting interoperable solution successfully incorporates OpenNebula, OpenStack (reuses pre-existing drivers) and PACI (includes the developed Deltacloud PACI driver) nodes and provides a Web dashboard and a Representational State Transfer (REST) interface library. The results of the exchanged data payload and time response tests performed are presented and discussed. The conclusions show that open source abstraction tools like Deltacloud allow the modular and integrated management of IaaS platforms (open source and proprietary), introduce relevant time and negligible data overheads and, as a result, can be adopted by Small and Medium-sized Enterprise (SME) cloud providers to circumvent the vendor lock-in problem whenever service response time is not critical.

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