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Publications

2014

2DCPackGen: A problem generator for two-dimensional rectangular cutting and packing problems

Authors
Silva, E; Oliveira, JF; Wäscher, G;

Publication
EUROPEAN JOURNAL OF OPERATIONAL RESEARCH

Abstract
Cutting and packing problems have been extensively studied in the literature in recent decades, mainly due to their numerous real-world applications while at the same time exhibiting intrinsic computational complexity. However, a major limitation has been the lack of problem generators that can be widely and commonly used by all researchers in their computational experiments. In this paper, a problem generator for every type of two-dimensional rectangular cutting and packing problems is proposed. The problems are defined according to the recent typology for cutting and packing problems proposed by Wascher, Haussner, and Schumann (2007) and the relevant problem parameters are identified. The proposed problem generator can significantly contribute to the quality of the computational experiments run with cutting and packing problems and therefore will help improve the quality of the papers published in this field.

2014

Integrating Computer Vision Object Recognition with Location Based Services for the Blind

Authors
Fernandes, H; Costa, P; Paredes, H; Filipe, V; Barroso, J;

Publication
HCI (6)

Abstract
The task of moving from one place to another is a difficult challenge that involves obstacle avoidance, staying on street walks, finding doors, knowing the current location and keeping on track through the desired path. Nowadays, navigation systems are widely used to find the correct path, or the quickest, between two places. While assistive technology has contributed to the improvement of the quality of life of people with disabilities, people with visual impairment still face enormous limitations in terms of their mobility. In recent years, several approaches have been made to create systems that allow seamless tracking and navigation both in indoor and outdoor environments. However there is still an enormous lack of availability of information that can be used to assist the navigation of users with visual impairments as well as a lack of sufficient precision in terms of the estimation of the user's location. Blavigator is a navigation system designed to help users with visual impairments. In a known location, the use of object recognition algorithms can provide contextual feedback to the user and even serve as a validator to the positioning module and geographic information system of a navigation system for the visually impaired. This paper proposes a method where the use of computer vision algorithms validate the outputs of the positioning system of the Blavigator prototype. © 2014 Springer International Publishing.

2014

Image Analysis and Modeling in Ophthalmology

Authors
Ng, E; Acharya, U; Suri, J; Campilho, A;

Publication

Abstract

2014

Segmentation of the vascular network of the Retina

Authors
Mendonça A.M.; Dashtbozorg B.; Campilho A.;

Publication
Image Analysis and Modeling in Ophthalmology

Abstract
The retina is a unique region where the vascular condition can be observed in vivo. It is a window to the systemic vasculature, as the retinal blood vessels are exposed to the same stresses and pathologies as the whole vascular system. The retinal vasculature status can be evaluated with high-resolution eye fundus color images, and variations in the retinal microcirculation can be used as an indicator of a lesion in the cerebral microvasculature. The features measured on these images can characterize retinal arteriolar narrowing, which is a marker of hypertension, or diabetic retinopathy (DR).

2014

Improving Branch-and-Price for Parallel Machine Scheduling

Authors
Lopes, M; Alvelos, F; Lopes, H;

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

Abstract
In this paper we present a hybrid exact-heuristic method to improve a branch-and-price algorithm to solve the unrelated parallel machines with sequence-dependent setup times scheduling problem. As most of the computational time in the column generation (CG) process is spent in subproblems, two new heuristics to solve the subproblems are embedded in the branch-and-price (BP) framework with the aim to improve the efficiency of the process in obtaining optimal solutions. Computational results show that the proposed method improves a state-of-the-art BP algorithm from the literature, providing optimal solutions for large instances (e. g. 50 machines and 180 jobs) of the parallel machine scheduling problem with sequence dependent setup times, in significantly less time. One of the proposed approaches reduces, in average, to a half the time spent in the root of the branch-and-price tree and to a quarter the time spent in the full branch-and-price algorithm.

2014

Distributed Adaptive Model Rules for Mining Big Data Streams

Authors
Vu, AT; Morales, GD; Gama, J; Bifet, A;

Publication
2014 IEEE INTERNATIONAL CONFERENCE ON BIG DATA (BIG DATA)

Abstract
Decision rules are among the most expressive data mining models. We propose the first distributed streaming algorithm to learn decision rules for regression tasks. The algorithm is available in SAMOA (SCALABLE ADVANCED MASSIVE ONLINE ANALYSIS), an open-source platform for mining big data streams. It uses a hybrid of vertical and horizontal parallelism to distribute Adaptive Model Rules (AMRules) on a cluster. The decision rules built by AMRules are comprehensible models, where the antecedent of a rule is a conjunction of conditions on the attribute values, and the consequent is a linear combination of the attributes. Our evaluation shows that this implementation is scalable in relation to CPU and memory consumption. On a small commodity Samza cluster of 9 nodes, it can handle a rate of more than 3 0 0 0 0 instances per second, and achieve a speedup of up to 4.7 x over the sequential version.

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