An experimental evaluation of the incidence of fitness-function/search-algorithm combinations on the classification performance of myoelectric control systems with iPCA tuning

BACKGROUND: The information of electromyographic signals can be used by Myoelectric Control Systems (MCSs) to actuate prostheses. These devices allow the performing of movements that cannot be carried out by persons with amputated limbs. The state of the art in the development of MCSs is based on the use of individual principal component analysis (iPCA) as a stage of pre-processing of the classifiers. The iPCA pre-processing implies an optimization stage which has not yet been deeply explored. METHODS: The present study considers two factors in the iPCA stage: namely A (the fitness function), and B (the search algorithm). The A factor comprises two levels, namely A(1) (the classification error) and A(2) (the correlation factor). Otherwise, the B factor has four levels, specifically B(1) (the Sequential Forward Selection, SFS), B(2) (the Sequential Floating Forward Selection, SFFS), B(3) (Artificial Bee Colony, ABC), and B(4) (Particle Swarm Optimization, PSO). This work evaluates the incidence of each one of the eight possible combinations between A and B factors over the classification error of the MCS. RESULTS: A two factor ANOVA was performed on the computed classification errors and determined that: (1) the interactive effects over the classification error are not significative (F(0.01,3,72) = 4.0659 > f( AB ) = 0.09), (2) the levels of factor A have significative effects on the classification error (F(0.02,1,72) = 5.0162 < f( A ) = 6.56), and (3) the levels of factor B over the classification error are not significative (F(0.01,3,72) = 4.0659 > f( B ) = 0.08). CONCLUSIONS: Considering the classification performance we found a superiority of using the factor A(2) in combination with any of the levels of factor B. With respect to the time performance the analysis suggests that the PSO algorithm is at least 14 percent better than its best competitor. The latter behavior has been observed for a particular configuration set of parameters in the search algorithms. Future works will investigate the effect of these parameters in the classification performance, such as length of the reduced size vector, number of particles and bees used during optimal search, the cognitive parameters in the PSO algorithm as well as the limit of cycles to improve a solution in the ABC algorithm

Resection of the liver for colorectal carcinoma metastases - A multi-institutional study of long-term survivors

In this review of a collected series of patients undergoing hepatic resection for colorectal metastases, 100 patients were found to have survived greater than five years from the time of resection. Of these 100 long-term survivors, 71 remain disease-free through the last follow-up, 19 recurred prior to five years, and ten recurred after five years. Patient characteristics that may have contributed to survival were examined. Procedures performed included five trisegmentectomies, 32 lobectomies, 16 left lateral segmentectomies, and 45 wedge resections. The margin of resection was recorded in 27 patients, one of whom had a positive margin, nine of whom had a less than or equal to 1-cm margin, and 17 of whom had a greater than 1-cm margin. Eighty-one patients had a solitary metastasis to the liver, 11 patients had two metastases, one patient had three metastases, and four patients had four metastases. Thirty patients had Stage C primary carcinoma, 40 had Stage B primary carcinoma, and one had Stage A primarycarcinoma. The disease-free interval from the time of colon resection to the time of liver resection was less than one year in 65 patients, and greater than one year in 34 patients. Three patients had bilobar metastases. Four of the patients had extrahepatic disease resected simultaneously with the liver resection. Though several contraindications to hepatic resection have been proposed in the past, five-year survival has been found in patients with extrahepatic disease resected simultaneously, patients with bilobar metastases, patients with multiple metastases, and patients with positive margins. Five-year disease-free survivors are also present in each of these subsets. It is concluded that five-year survival is possible in the presence of reported contraindications to resection, and therefore that the decision to resect the liver must be individualized. © 1988 American Society of Colon and Rectal Surgeons

Intrahepatic Cholangiocarcinoma: Clinical Aspects, Pathology and Treatment

Intrahepatic cholangiocarcinoma (ICC) is the second most common primary tumor of the liver. To further define its clinicopathology and surgical management, we reviewed our experience. Clinical presentations of 32 patients with ICC was similar to that with hepatocellular carcinoma. Jaundice occurred in only 27 percent. ICC was unresectable due to advanced disease stage in 81 percent. Six patients had curative resections with two 5 year disease free survivors. Underlying liver disease was associated with ICC in 34 percent of patients

Algoritmos para Otimização do Desempenho de Geradores a Relutância Variável Aplicados em Geração Eólica

O desempenho do gerador a relutância variável (GRV) está diretamente relacionado às variáveis de ajustes do seu acionamento. Neste trabalho são propostos algoritmos para obter, através de simulações dinâmicas, os parâmetros ótimos de acionamento do GRV quando aplicado em geração eólica. Através de funções de otimização os parâmetros de acionamento do GRV para baixas e altas velocidades de operação são obtidos para manter o balanceamento entre as oscilações de torque, perdas magnéticas e perdas elétricas. Os parâmetros ótimos de acionamento foram verificados experimentalmente e foi confirmada a eficiência da metodologia proposta neste trabalho

Compression of Surface Electromyographic Signals Using Two-Dimensional Techniques

Non

Sistema Automático de Caracterização de Máquinas a Relutância Variável e Modelagem não Linear por Interpolações Utilizando Smoothing Splines

Este trabalho apresenta em detalhes um sistema automa´tico que permite obter as curvas de magnetizac¸a˜o da ma´quina a relutaˆncia varia´vel (MRV). Sa˜o estudadas te´cnicas de interpolac¸o˜es no processamento dos dados dos ensaios para obter o modelo na˜o linear de uma MRV 12/8. E´ proposto o uso da te´cnica smoothing splines que permitiu obter um modelo preciso e condizente com o funcionamento da MRV. Resultados de simulac¸o˜es e ensaios experimentais confirmaram a eficieˆncia do sistema e a importaˆncia da obtenc¸a˜o de curvas reais quando se deseja ter modelos precisos de uma MRV.

Método Analítico Eficiente para o Cálculo das Indutâncias em Máquinas de Relutância Variável com Núcleo do Tipo C

As máquinas de relutâncias variável (MRVs) são consideradas, na literatura científica, as que possuem maior simplicidade de construção e baixo custo de manutenção e reparo quando comparadas com as máquinas elétricas tradicionais. No entanto, a MRV trabalha sob condição de alta saturação, o que dificulta a determinação de um modelo matemático que represente com precisão o seu sistema físico. Este trabalho tem como objetivo apresentar uma proposta de modelo analítico que seja eficiente no cálculo das indutâncias das máquinas de relutância variável de fluxo axial com núcleo do tipo C (MRV-C), proporcionando uma resposta rápida e fidedigna. O método analítico proposto baseia-se no circuito magnético equivalente obtido a partir das dimensões da máquina elétrica. Como principal contribuição desse trabalho destaca-se a utilização de uma metodologia simples e que não utiliza iterações computacionais durante o cálculo das densidades de fluxo magnético. Os resultados experimentais e de simulação indicam que o método proposto foi adequado e satisfatório no cálculo das indutâncias em MRVs-C