RESUMO
OBJETIVO: Propor um método reprodutível, de fácil utilização e de baixo custo para a digitalização de filmes radiográficos de todos os tamanhos padrões, concentrando nossos esforços em filmes radiográficos de tórax. MATERIAIS E MÉTODOS: O objetivo de baixo custo ditou o uso de um escâner A4 com adaptador de transparência, bem como um software de costura de imagens otimizado, que tira proveito da geometria do escâner e área de captura constante, bem como o conhecimento das dimensões dos filmes radiográficos padrões. RESULTADOS: O resultado final do método proposto é uma imagem de alta resolução com bom contraste e sem artefatos de costura perceptíveis. CONCLUSÃO: O método de digitalização proposto usando um escâner A4 possibilita reprodutibilidade, excelente qualidade de imagem e alto grau de certeza na identificação de lesões.
OBJECTIVE: To propose a reproducible, user friendly and low cost method for digitization of radiographic films of all the standard sizes, focusing efforts on chest X-ray films. MATERIALS AND METHODS: The focus on low cost have dictated the use of an A4 scanner with transparency adapter, as well as an optimized image stitching software that takes advantage of the scanner geometry and constant capture area, besides the knowledge of the standard X-ray film sizes. RESULTS: The end result of the proposed method is a high resolution image with good contrast and no perceptible stitching artifacts. CONCLUSION: The proposed digitization method with an A4 scanner allows reproducibility, excellent image quality and high degree of certainty in the identification of lesions.
Assuntos
Humanos , Intensificação de Imagem Radiográfica , Radiografia Torácica , Sistemas de Informação em Radiologia , Telerradiologia , Filme para Raios XRESUMO
This paper introduces a threshold policy with hysteresis (TPH) for the control of one-predator one-prey models. The models studied are the Lotka-Volterra and Rosenzweig-MacArthur two species density-dependent predator-prey models and the Arditi-Ginzburg nondimensional ratio-dependent model. The proposed policy (TPH) changes the dynamics of the system in such a way that a bounded oscillation is achieved confined to a region that does not allow extinction of either species. The policy can be designed by a suitable choice of so called virtual equilibrium points in a simple and intuitive manner.
Assuntos
Ecossistema , Modelos Biológicos , Comportamento Predatório , Animais , Densidade Demográfica , Dinâmica PopulacionalRESUMO
This paper develops an algorithm that extracts explanatory rules from microarray data, which we treat as time series, using genetic programming (GP) and fuzzy logic. Reverse polish notation is used (RPN) to describe the rules and to facilitate the GP approach. The algorithm also allows for the insertion of prior knowledge, making it possible to find sets of rules that include the relationships between genes already known. The algorithm proposed is applied to problems arising in the construction of gene regulatory networks, using two different sets of real data from biological experiments on the Arabidopsis thaliana cold response and the rat central nervous system, respectively. The results show that the proposed technique can fit data to a pre-defined precision even in situations where the data set has thousands of features but only a limited number of points in time are available, a situation in which traditional statistical alternatives encounter difficulties, due to the scarcity of time points.
Assuntos
Análise em Microsséries/estatística & dados numéricos , Modelos Genéticos , Algoritmos , Animais , Arabidopsis/genética , Análise por Conglomerados , Lógica Fuzzy , Perfilação da Expressão Gênica/estatística & dados numéricos , Mutação , Ratos , Biologia de SistemasRESUMO
Gradient dynamical systems with discontinuous righthand sides are designed using Persidskii-type nonsmooth Lyapunov functions to work as support vector machines (SVMs) for the discrimination of nonseparable classes. The gradient systems are obtained from an exact penalty method applied to the constrained quadratic optimization problems, which are formulations of two well known SVMs. Global convergence of the trajectories of the gradient dynamical systems to the solution of the corresponding constrained problems is shown to be independent of the penalty parameters and of the parameters of the SVMs. The proposed gradient systems can be implemented as simple analog circuits as well as using standard software for integration of ODEs, and in order to use efficient integration methods with adaptive stepsize selection, the discontinuous terms are smoothed around a neighborhood of the discontinuity surface by means of the boundary layer technique. The scalability of the proposed gradient systems is also shown by means of an implementation using parallel computers, resulting in smaller processing times when compared with traditional SVM packages.
Assuntos
Algoritmos , Inteligência Artificial , Análise por Conglomerados , Armazenamento e Recuperação da Informação , Reconhecimento Automatizado de Padrão , Animais , Biologia Computacional/métodos , Humanos , Modelos Estatísticos , Dinâmica não Linear , PlantasRESUMO
The stability of predator-prey models, in the context of exploitation of renewable resources, subject to threshold policies (TP) is studied in this paper using the idea of backstepping and control Liapunov functions (CLF) well known in control theory, as well as the concept of virtual equilibria. TPs are defined and analysed for different types of one and two species predator-prey models. The models studied are the single species Noy-Meir herbivore-vegetation model, in a grazing management context, as well as the Rosenzweig-MacArthur two species predator-prey model, in a fishery management context. TPs are shown to be versatile and useful in managing renewable resources, being simple to design and implement, and also yielding advantages in situations of overexploitation.
Assuntos
Ecossistema , Cadeia Alimentar , Modelos Biológicos , Modelos Estatísticos , Comportamento Predatório , Criação de Animais Domésticos/métodos , Animais , Pesqueiros/métodos , Peixes , Densidade DemográficaRESUMO
It is pointed out that the so called momentum method, much used in the neural network literature as an acceleration of the backpropagation method, is a stationary version of the conjugate gradient method. Connections with the continuous optimization method known as heavy ball with friction are also made. In both cases, adaptive (dynamic) choices of the so called learning rate and momentum parameters are obtained using a control Liapunov function analysis of the system.