RESUMEN

This paper presents an efficient and reliable approach to study the low-velocity impact response of woven composite shells using 3D finite element models that account for the physical intralaminar and interlaminar progressive damage. The authors' previous work on the experimental assessment of the effect of thickness on the impact response of semicylindrical composite laminated shells served as the basis for this paper. Therefore, the finite element models were put to the test in comparison to the experimental findings. A good agreement was obtained between the numerical predictions and experimental data for the load and energy histories as well as for the maximum impact load, maximum displacement, and contact time. The use of the mass-scaling technique was successfully implemented, reducing considerably the computing cost of the solutions. The maximum load, maximum displacement, and contact time are negligibly affected by the choice of finite element mesh discretization. However, it has an impact on the initiation and progression of interlaminar damage. Therefore, to accurately compute delamination, its correct definition is of upmost importance. The validation of these finite element models opens the possibility for further numerical studies on of woven composite shells and enables shortening the time and expenses associated with the experimental testing.

RESUMEN

In this article, we address the problem of simultaneous testing hypothesis about mean and covariance matrix for repeated measures data when both the mean vector and covariance matrix are patterned. In particular, tests about the mean vector under block circular and doubly exchangeable covariance structures have been considered. The null distributions are established for the corresponding likelihood ratio test statistics, and expressions for the exact or near-exact probability density and cumulative distribution functions are obtained. The application of the results is illustrated by both a simulation study and a real-life data example.

Asunto(s)

RESUMEN

Often in food safety and bio-surveillance it is desirable to estimate the probability that a contaminant or a function thereof exceeds an unsafe high threshold. The probability or chance in question is very small. To estimate such a probability, we need information about large values. In many cases, the data do not contain information about exceedingly large contamination levels, which ostensibly renders the problem insolvable. A solution is suggested whereby more information about small tail probabilities are obtained by combining the real data with computer-generated data repeatedly. This method provides short yet reliable interval estimates based on moderately large samples. An illustration is provided in terms of lead exposure data. Copyright © 2016 John Wiley & Sons, Ltd.

Asunto(s)

RESUMEN

No período de janeiro de 1996 a feveiro de 2001, foram operados 38 pacientes com patologias colorretais pelo método laparoscópico, sendo 15 (39,5 por cento) pacientes do sexo masculino e 23 (60,5 por cento) do sexo feminino, com idade variando de 15 a 79 anos (média de 51). Destes pacientes, 10 apresentavam megacólon; 10, doença diverticular; 7, adenocarcinoma de reto; 3, adenocarcinoma intra-mucoso de sigmóide; 2, doença diverticular e adenocarcinoma intra-mucoso de cólon esquerdo; 1, adenoma viloso plano de ceco; 2, colostomia Hartmann; 1, carcinoma espinecelular de canal anal; 1, prolapso retal; e 1, carcinoma de ceco. As cirurgias realizadas foram: 16 retossigmoidectomias, 9 sigmoidectomias, 5 amputaçöes abdominoperineal de reto (cirurgia de Miles), 2 hemicolectomias esquerda, 3 colectomias direita, 1 sacropromontofixaçäo e 2 reconstruçäo de trânsito de colostomia Hartmann. O tempo de cirurgia variou de 110 a 210 minutos com média de 177,2 minutos. O tempo médio de internamento foi de 5,2 dias. Houve 1 (2,6 por cento) conversäo por dificuldade técnica, näo ocorreu complicaçäo intra-operatória. Houve 5 (13 por cento) complicaçöes pós-operatórias, sendo 2 (5,2 por cento) deiscências de anastomose no 4§ dia de pós-operatório, 1 (2,6 por cento) obstruçäo precoce de íleo terminal por bridas, 1 (2,6 por cento) estenose de anastomose mecânica colorretal no 6§ mês de pós-operatório e 1 (2,6 por cento) abscesso de parede.

Asunto(s)