Design optimization for the two-stage bivariate pattern recognition scheme

In manufacturing operations, unnatural process variation has become a major contributor to a poor quality product. Therefore, monitoring and diagnosis of variation is critical in quality control. Monitoring refers to the identification of process condition either it is running within in statistically in-control or out-of-control, whereas diagnosis refers to the identification of the source of out-of-control process. Selection of SPC scheme becomes more challenging when involving two correlated variables, which are known as bivariate quality control (BQC). Generally, the traditional SPC charting schemes were known to be effective in monitoring aspects, but there were unable to provide information towards diagnosis. In order to overcome this issue, many researches proposed an artificial neural network (ANN) - based pattern recognition schemes. Such schemes were mainly utilize raw data as input representation into an ANN recognizer, which resulted in limited performance. In this research, an integrated MEWMA-ANN scheme was investigated. The optimal design parameters for the MEWMA control chart have been studied. The study focused on BQC with variation in mean shifts (μ = ±0.75 ~ 3.00) standard deviations and cross correlation function (ρ = 0.1 ~ 0.9). The monitoring and diagnosis performances were evaluated based on the average run length (ARL0, ARL1) and recognition accuracy (RA) respectively. The selected optimal design parameters with λ=0.10, H=8.64 gave better performance among the other designs, namely, average run length, ARL1=3.24 ~ 16.93 (for out-of-control process) and recognition accuracy, RA=89.05 ~ 97.73%. For in-control process, design parameters with λ=0.40, H=10.31 parameter gave superior performance with ARL0 = 676.81 ~ 921.71, which is more effective in avoiding false alarm with any correlation

Method of lines and runge-kutta method in solving partial differential equation for heat equation

Solving the differential equation for Newton’s cooling law mostly consists of several fragments formed during a long time to solve the equation. However, the stiff type problems seem cannot be solved efficiently via some of these methods. This research will try to overcome such problems and compare results from two classes of numerical methods for heat equation problems. The heat or diffusion equation, an example of parabolic equations, is classified into Partial Differential Equations. Two classes of numerical methods which are Method of Lines and Runge-Kutta will be performed and discussed. The development, analysis and implementation have been made using the Matlab language, which the graphs exhibited to highlight the accuracy and efficiency of the numerical methods. From the solution of the equations, it showed that better accuracy is achieved through the new combined method by Method of Lines and Runge-Kutta method

Contributo para a melhoria da qualidade de processos de extrusão na indústria de cabos elétricos

Dissertação de mestrado integrado em Engenharia e Gestão IndustrialA aposta em programas de melhoria da qualidade dos processos é cada vez mais um caminho adotado pelas empresas para fazer face ao mercado competitivo em que estão inseridas. Através da implementação deste tipo de programas, é possível conferir robustez aos processos e, consequentemente, reduzir os custos com desperdícios internos relacionados com a qualidade. As ferramentas da qualidade representam um vetor importante no sucesso de qualquer programa de melhoria contínua da qualidade do processo. Estas ferramentas constituem meios úteis no controlo, análise e organização de dados relevantes para as tomadas de decisão nas organizações. A presente dissertação tem como principal objetivo a implementação de um programa da melhoria da qualidade dos processos de extrusão de uma indústria de cabos elétricos, tendo por base a aplicação de algumas ferramentas da qualidade, nomeadamente: o diagrama de Pareto, diagrama de Ishikawa e gráficos de controlo. Assim, a metodologia empregue inicia com a identificação e priorização dos defeitos registados nos processos em estudo, cujas causas e potenciais medidas corretivas devem ser alvo de estudo. A participação ativa dos operadores e das chefias no estudo dos defeitos críticos foi conseguida com recurso a sessões de brainstorming, em que se introduziu e aplicou o diagrama de Ishikawa para o levantamento das principais causas dos defeitos críticos, assim como o estudo de eventuais medidas corretivas. Paralelamente, estimaram-se os custos envolvidos nas falhas da qualidade dos dois processos, nomeadamente os custos com sucata e retrabalho. Os resultados obtidos indicaram que os defeitos relacionados com características dimensionais dos produtos representavam uma parte significativa dos defeitos registados nos dois processos, o que revelou a pertinência da monitorização destes parâmetros através da aplicação de gráficos de controlo. Através da aplicação dos procedimentos introduzidos foi possível identificar algumas causas de variabilidade de processos, tais como a variação da velocidade da linha de extrusão e (in)consistência entre turnos de trabalho. O projeto culmina com a sugestão de algumas propostas de melhoria que visam aumentar a eficácia dos procedimentos introduzidos, bem como incentivar a adoção da filosofia de melhoria contínua.Nowadays, the quality improvement programs have been adopted by the companies to develop their several processes. Due to this program, the companies can reduce quality related wastes, such as, scrap and rework costs. The quality tools are keys to the continuous quality improvement and are very important to the companies' success. These tools can be useful in control, analysis and data organization, that are relevant to the decision making process. This thesis' main goal is to create a quality improvement program in the extrusion process of a wire cable industry, applying some quality tools such as: Pareto analysis, cause and effect diagram and control charts. Therefore, this research begins with the identification of the registered defects in the processes, which causes should be case of study. The workers and supervisors involvement in this study were achieved with brainstorming sessions, where it was applied the Ishikawa diagram to find the main causes of the critic defects and corrective measures as well. Simultaneously, the costs involved in the processes' quality defects, such as scrap and rework costs, were calculated. The results have shown that the defects related with the product's dimensions were a significant part of the flaws registered, which reveals that these parameters should be monitored through control charts. Through the application of these procedures, it was possible to identify some causes of the process variability, such as the changes of the extrusion line speed and the (in)consistency between shifts. The project is finished with some advices to improve the effectiveness of the procedures and how to incentive the adoption of the continuous improvement philosophy