Ronaldo Martins da Costa

Multi-objective Genetic Algorithm for Variable Selection in Multivariate Classification Problems

This paper proposes multi-objective genetic algorithm for the problem of variable selection in multivariate calibration. We consider the problem related to the classification of biodiesel samples to detect adulteration, Linear Discriminant Analysis classifier. The goal of the multi--objective algorithm is to reduce the dimensionality of the original set of variables; thus, the classification model can be less sensitive, providing a better generalization capacity. In particular, in this paper we adopted a version of the Non-dominated Sorting Genetic Algorithm (NSGA-II) and compare it to a mono-objective Genetic Algorithm (GA) in terms of sensitivity in the presence of noise. Results show that the mono-objective selects 20 variables on average and presents an error rate of 14%. One the other hand, the multi-objective selects 7 variables and has an error rate of 11%. Consequently, we show that the multi-objective formulation provides classification models with lower sensitivity to the instrumental noise when compared to the mono-objetive formulation

Braille Text Entry on Smartphones: A Systematic Review of the Literature

Nowadays, due to touchscreen, mobile devices have become much more dynamic than in the past. However, due the same reason, those devices are less accessible for blind people. It is expected that in 2018, over half of mobile phone users will have a smartphone, therefore researches about mobile accessibility are very important. So, the aim of this systematic review is to cooperate with new research about methods for braille text entry on smartphones. The systematic searches in 5 databases, resulted in 11 papers that answered the research questions that grounded this work.

Intraoral radiographs texture analysis for dental implant planning

BACKGROUND AND OBJECTIVES Computer vision extracts features or attributes from images improving diagnosis accuracy and aiding in clinical decisions. This study aims to investigate the feasibility of using texture analysis of periapical radiograph images as a tool for dental implant treatment planning. METHODS Periapical radiograph images of 127 jawbone sites were obtained before and after implant placement. From the superimposition of the pre- and post-implant images, four regions of interest (ROI) were delineated on the pre-implant images for each implant site: mesial, distal and apical peri-implant areas and a central area. Each ROI was analysed using Matlab® software and seven image attributes were extracted: mean grey level (MGL), standard deviation of grey levels (SDGL), coefficient of variation (CV), entropy (En), contrast, correlation (Cor) and angular second moment (ASM). Images were grouped by bone types-Lekholm and Zarb classification (1,2,3,4). Peak insertion torque (PIT) and resonance frequency analysis (RFA) were recorded during implant placement. Differences among groups were tested for each image attribute. Agreement between measurements of the peri-implant ROIs and overall ROI (peri-implant + central area) was tested, as well as the association between primary stability measures (PIT and RFA) and texture attributes. RESULTS Differences among bone type groups were found for MGL (p = 0.035), SDGL (p = 0.024), CV (p < 0.001) and En (p < 0.001). The apical ROI showed a significant difference from the other regions for all attributes, except Cor. Concordance correlation coefficients were all almost perfect (ρ > 0.93), except for ASM (ρ = 0.62). Texture attributes were significantly associated with the implant stability measures. CONCLUSION Texture analysis of periapical radiographs may be a reliable non-invasive quantitative method for the assessment of jawbone and prediction of implant stability, with potential clinical applications.

Cachaça Classification Using Chemical Features and Computer Vision

Abstract Cacha¸ca is a type of distilled drink from sugarcane with great economic importance. Its classification includes three types: aged, premium and extra premium. These three classifications are related to the aging time of the drink in wooden casks. Besides the aging time, it is important to know what the wood used in the barrel storage in order the properties of each drink are properly informed consumer. This paper shows a method for automatic recognition of the type of wood and the aging time using information from a computer vision system and chemical information. Two algorithms for pattern recognition are used: artificial neural networks and k-NN ( k-Nearest Neighbor ). In the case study, 144 cachac¸a samples were used. The results showed 97% accuracy for the problem of the aging time classification and 100% for the problem of woods classification.

Wrist Player: A Smartwatch Gesture Controller for Smart TVs

Emerging technology on mobile and wearable market, smartwatches have embedded movement sensors whose potential is yet to be fully explored. This paper proposes an interaction method with smart TVs via gestures performed by persons wrist using a smartwatch. Detailed architecture and implementation for a complete prototype, named Wrist Player, is presented. A user study is also conducted, in order to evaluate the prototype performance and the users interest on the proposal. Results show that the method works very well, with participants reporting having a good experience with the prototype. We present our insights on the concept, challenges faced in our research and ideas for future studies.

Development of an Effective Method and a Portable Device to Evaluate the Pupillary Reflex

Examination of the pupil offers an objective evaluation of visual function as well as the vegetative pathways to the eye. In spite of technological advances and substantial progress in many areas, the routine pupil examination with a conventional light source has undergone no significant changes in the last 100 years. This work proposes the development of an effective and objective method and a portable device to test the direct and consensual pupillary reflex. The first results demonstrate the success of a new device construction and new methodology to record the reflex with differ stimulus, in a situation of complete seal of light.