The Experts below are selected from a list of 14682 Experts worldwide ranked by ideXlab platform
Rodrigues, Renata Mendonça - One of the best experts on this subject based on the ideXlab platform.
-
Controle on-line para o número de não-conformidades em um ítem inspecionado
Universidade Federal do Rio Grande do Norte, 2009Co-Authors: Rodrigues, Renata MendonçaAbstract:O procedimento usual de Controle on-line de processo por atributos consiste em inspecionar um item a cada m itens produzidos. Se o item examinado for conforme, a produção continua; caso contrário pára-se o processo. No entanto, em muitas situações práticas, nem sempre existe interesse em classificar o item como defeituoso ou não defeituoso, mas sim monitorar o número de não-conformidades no item inspecionado. Neste caso, se o número de não-conformidades for superior a um Limite de Controle, pára-se o processo para o ajuste. A contribuição deste trabalho está em propor um sistema de Controle on-line baseado no número de não-conformidades do item inspecionado. Através das propriedades de uma cadeia de Markov ergódica, obteve-se uma expressão analítica do custo médio por item produzido do sistema de Controle on-line que pode ser minimizada por dois parâmetros: o intervalo entre inspeções e o Limite superior de Controle para o número de não-conformidades no item inspecionado. Um exemplo numérico ilustra o procedimento propostoThe on-line processes Control for attributes consists of inspecting a single item at every m produced ones. If the examined item is conforming, the production continues; otherwise, the process stops for adjustment. However, in many practical situations, the interest consist of monitoring the number of non-conformities among the examined items. In this case, if the number of non-conformities is higher than an Upper Control Limit, the process needs to be stopped and some adjustment is required. The contribution of this paper is to propose a Control system for the number of nonconforming of the inspected item. Employing properties of an ergodic Markov chain, an expression for the expected cost per item of the Control system was obtained and it will be minimized by two parameters: the sampling interval and the Upper Limit Control of the non-conformities of the examined item. Numerical examples illustrate the proposed procedur
-
Controle on-line para o número de não-conformidades em um ítem inspecionado
Probabilidade e Estatística; Modelagem Matemática, 2009Co-Authors: Rodrigues, Renata MendonçaAbstract:The on-line processes Control for attributes consists of inspecting a single item at every m produced ones. If the examined item is conforming, the production continues; otherwise, the process stops for adjustment. However, in many practical situations, the interest consist of monitoring the number of non-conformities among the examined items. In this case, if the number of non-conformities is higher than an Upper Control Limit, the process needs to be stopped and some adjustment is required. The contribution of this paper is to propose a Control system for the number of nonconforming of the inspected item. Employing properties of an ergodic Markov chain, an expression for the expected cost per item of the Control system was obtained and it will be minimized by two parameters: the sampling interval and the Upper Limit Control of the non-conformities of the examined item. Numerical examples illustrate the proposed procedureCoordenação de Aperfeiçoamento de Pessoal de Nível SuperiorO procedimento usual de Controle on-line de processo por atributos consiste em inspecionar um item a cada m itens produzidos. Se o item examinado for conforme, a produção continua; caso contrário pára-se o processo. No entanto, em muitas situações práticas, nem sempre existe interesse em classificar o item como defeituoso ou não defeituoso, mas sim monitorar o número de não-conformidades no item inspecionado. Neste caso, se o número de não-conformidades for superior a um Limite de Controle, pára-se o processo para o ajuste. A contribuição deste trabalho está em propor um sistema de Controle on-line baseado no número de não-conformidades do item inspecionado. Através das propriedades de uma cadeia de Markov ergódica, obteve-se uma expressão analítica do custo médio por item produzido do sistema de Controle on-line que pode ser minimizada por dois parâmetros: o intervalo entre inspeções e o Limite superior de Controle para o número de não-conformidades no item inspecionado. Um exemplo numérico ilustra o procedimento propost
Koel Chaudhury - One of the best experts on this subject based on the ideXlab platform.
-
Upper Control Limit of reactive oxygen species in follicular fluid beyond which viable embryo formation is not favorable
Reproductive Toxicology, 2010Co-Authors: Saikat Jana, Narendra Babu K, R Chattopadhyay, Baidyanath Chakravarty, Koel ChaudhuryAbstract:Though the role of reactive oxygen species (ROS) in female infertility has been a subject of rigorous research worldwide, there is inadequate information on the cut-off value of ROS in the oocyte microenvironment beyond which ART outcome may be adversely affected. An Upper ROS level in follicular fluid (FF) samples of women undergoing IVF beyond which good quality embryo formation is unlikely, is established. ROS, lipid peroxidation and total antioxidant capacity were estimated. The Upper cut-off ROS level beyond which viable embryo formation is not favorable was found to be ∼107 cps/400 μl FF. This level, determined in women with tubal factor infertility, was further validated in women with endometriosis and PCOS and correlated with fertilization and pregnancy rate and embryo quality. Summarizing, a threshold level in FF has been established for the first time beyond which ROS may be considered toxic for viable embryo formation and pregnancy outcome.
Y. Ding - One of the best experts on this subject based on the ideXlab platform.
-
Model-based condition monitoring of PEM fuel cell using Hotelling T2 Control Limit
Journal of Power Sources, 2006Co-Authors: Jiong Tang, Nigel M. Sammes, Y. DingAbstract:Although a variety of design and Control strategies have been proposed to improve the performance of polymer electrolyte membrane (PEM) fuel cell systems, temporary faults in such systems still might occur during operations due to the complexity of the physical process and the functional Limitations of some components. The development of an effective condition monitoring system that can detect these faults in a timely manner is complicated by the operating condition variation, the significant variability/uncertainty of the fuel cell system, and the measurement noise. In this research, we propose a model-based condition monitoring scheme that employs the Hotelling T2 statistical analysis for fault detection of PEM fuel cells. Under a given operating condition, the instantaneous load current, the temperature and fuel/gas source pressures of the fuel cell are measured. These measurements are then fed into a lumped parameter dynamic fuel cell model for the establishment of the baseline under the same operating condition for comparison. The fuel cell operation is simulated under statistical sampling of parametric uncertainties with specified statistics (mean and variance) that account for the system variability/uncertainty and measurement noise. This yields a group of output voltages (under the same operating condition but with uncertainties) as the baseline. Fault detection is facilitated by comparing the real-time measurement of the fuel cell output voltage with the baseline voltages by employing the Hotelling T2 statistical analysis. The baseline voltages are used to evaluate the output T2 statistics under normal operating condition. Then, with a given confidence level the Upper Control Limit can be specified. Fault condition will be declared if the T2 statistics of real-time voltage measurement exceeds the Upper Control Limit. This model-based robust condition monitoring scheme can deal with the operating condition variation, various uncertainties in a fuel cell system, and measurement noise. Our analysis indicates that this scheme has very high detection sensitivity and can detect the fault conditions at the early stage.
Saikat Jana - One of the best experts on this subject based on the ideXlab platform.
-
Upper Control Limit of reactive oxygen species in follicular fluid beyond which viable embryo formation is not favorable
Reproductive Toxicology, 2010Co-Authors: Saikat Jana, Narendra Babu K, R Chattopadhyay, Baidyanath Chakravarty, Koel ChaudhuryAbstract:Though the role of reactive oxygen species (ROS) in female infertility has been a subject of rigorous research worldwide, there is inadequate information on the cut-off value of ROS in the oocyte microenvironment beyond which ART outcome may be adversely affected. An Upper ROS level in follicular fluid (FF) samples of women undergoing IVF beyond which good quality embryo formation is unlikely, is established. ROS, lipid peroxidation and total antioxidant capacity were estimated. The Upper cut-off ROS level beyond which viable embryo formation is not favorable was found to be ∼107 cps/400 μl FF. This level, determined in women with tubal factor infertility, was further validated in women with endometriosis and PCOS and correlated with fertilization and pregnancy rate and embryo quality. Summarizing, a threshold level in FF has been established for the first time beyond which ROS may be considered toxic for viable embryo formation and pregnancy outcome.
Marina Karakaltsas - One of the best experts on this subject based on the ideXlab platform.
-
determination of quality Control Limits for serological infectious disease testing using historical data
Clinical Chemistry and Laboratory Medicine, 2015Co-Authors: Wayne Dimech, Giuseppe A Vincini, Marina KarakaltsasAbstract:Background An effective quality Control (QC) program requires the establishment of Control Limits within which the results of the QC sample is expected to fall. Traditionally, the mean plus/minus two standard deviations calculated for a set of QC sample results is used to establish Control Limits. Allowable total error (TEa) and Westgard rules aid in interpreting QC sample results. Westgard rules assume QC sample results are normally distributed and TEa assumes commutability between the QC sample and patient results. None of these paradigms apply to infectious disease testing. Methods RESULTS from the NRL's QC program were extracted and sorted into assay/QC lot number-specific data. Control Limits for selected QC samples used to monitor 64 commonly used serological assays were calculated and validated using the within- and between-QC lot variance of data from each of the assay/QC combinations. Results No assay/QC combination had more than 10% of results less than the lower Control Limit or greater than the Upper Control Limit. Of the 423 assay/QC lot combinations, 14 (3.3%) had more than 5% of results less than the lower Limit and 48 (11.3%) had more than 5% of results greater than the Upper Limit calculated for that assay/QC combination. Conclusions The Control Limits, established by this novel method, are based on more than a decade of QC test results from >300 laboratories from 30 countries and provides users of the NRL QC program evidence-based Control Limits that can be applied in isolation or in conjunction with more traditional methods for establishing Control Limits.
