Data-driven online monitoring of wind turbines

\u3cp\u3eCondition based maintenance is a modern approach to maintenance which has been successfully used in several industrial sectors. A specific problem in wind turbine maintenance is that failures of certain parts may be caused by the malperformance or failure of other parts. This mandates for approaches that can produce timely warnings by combining sensor data from different sources. More concretely, in this paper, we present a hybrid statistical approach to condition based maintenance by combining regression analysis with tools from statistical process control. Our approach improves the wind turbine maintenance practice by using adaptive alarm thresholds for the monitored parameters, whilst correcting for environmental factors or for other relevant parameters. We illustrate our approach with a case study demonstrating that we are able to predict upcoming failures much earlier than the current practice.\u3c/p\u3

A General Measure of Rule Interestingness

The paper presents a new general measure of rule interestingness. Many known measures such as chi² , gini gain or entropy gain can be obtained from this measure by setting some numerical parameters representing the amount of trust we have in the estimates of certain probabilities from the data. Moreover we show that there is a continuum of measures having chi² , Gini gain and entropy gain as boundary cases. Properties and experimental evaluation of the new measure are also presented

The total quasi-steady-state approximation for fully competitive enzyme reactions

none3The validity of the Michaelis-Menten-Briggs-Haldane approximation for single enzyme reactions has recently been improved by the formalism of the total quasi-steady-state approximation. This approach is here extended to fully competitive systems, and a criterion for its validity is provided. We show that it extends the Michaelis-Menten-Briggs-Haldane approximation for such systems for a wide range of parameters very convincingly, and investigate special cases. It is demonstrated that our method is at least roughly valid in the case of identical affinities. The results presented should be useful for numerical simulations of many in vivo reactions.noneM. PEDERSEN; BERSANI AM; BERSANI EPedersen, MORTEN GRAM; Bersani, Am; Bersani, E

Herdabilidades de parâmetros de curvas de crescimento não-lineares em zebuínos, no estado de Pernambuco Heritabilities of nonlinear growth curve parameters in zebu breeds, in Pernambuco State, Northeastern Brazil

Objetivou-se estimar parâmetros genéticos e fenotípicos de curvas de crescimento de modelos não-lineares. Foram analisados dados de pesagem constantes no banco de dados de Controle de Desenvolvimento Ponderal da Associação Brasileira de Criadores de Zebu (ABCZ), referentes a 24.028 animais Zebu, nascidos entre 1960 e 2000, das raças Guzerá, Nelore e Nelore Mocho. As pesagens ocorreram ao nascimento e em intervalos de 90 dias até dois anos de idade. Os seguintes modelos não-lineares foram utilizados na análise dos dados de peso-idade: Brody, Gompertz, Logístico, von Bertalanffy e Richards. Os efeitos fixos estudados no modelo misto foram sexo, rebanho, ano e mês de nascimento e regime de criação. As herdabilidades para os parâmetros foram de baixa a alta magnitude, em geral, para todos os modelos. As correlações genéticas entre peso assintótico e taxa de maturidade e entre peso assintótico e velocidade de crescimento foram negativas, enquanto aquelas entre taxa de maturidade e velocidade de crescimento foram positivas. As correlações fenotípicas foram negativas entre peso assintótico e taxa de crescimento e entre peso assintótico e velocidade de crescimento e positivas entre taxa e velocidade de crescimento. Encontrou-se variabilidade possível de ser explorada em um programa de melhoramento genético, especialmente para a raça Nelore, que apresentou amostra de dados e resultados mais consistentes.<br>Weight records of 24.028 zebu animals from Guzerá, Nelore, and Polled Nelore breeds available from Brazilian Association of Zebu Breeders (ABCZ) database were used to estimate heritabilities of growth curve parameters. Non-linear Brody, Gompertz, Logistic, Mitscherlich, von Bertalanffy, Richards, and Double Logistic models including sex, farm, year of birth, month of birth, raising system, and interaction sex*raising system as fixed effects and sire and dam, as random effects were adjusted using weight-age records of animals which were born between 1960 and 2000, every three months, from birth to 24 months of age. Heritability estimates of growth curve parameters ranged from low to high values for all models and breeds. Genetic correlations between asymptotic weight and mature rate and asymptotic weight and growth rate were negative whereas those between mature rate and growth rate were positive. Phenotypic correlations between asymptotic weight and mature rate and asymptotic weight and growth rate were negative and those between mature rate and growth rate were positive. The variability observed in this study indicates the possibility of changing the growth curve by a breeding program, especially for the Nellore because more consistent records and results obtained for this breed