Study of interfacial stiffness ratio of a rough surface in contact using a spring model

This study proposes the use of a simple spring model that relates the interfacial stiffness with the complex reflection coefficient of ultrasound in a rough contact. The spring model cannot be directly related to the real area of contact as this depends on the amount, shape and distribution of contacting asperities. However, it is clear that the model provides a non-destructive tool to easily evaluate both longitudinal and shear interfacial stiffnesses and their ratio. Experimental findings indicate that the interfacial stiffness ratio K-tau/K-sigma determined during loading/unloading cycles is sensitive to the roughness level and load hysteresis. The results deviate from the theoretical available micromechanical models, indicating that actual contacting phenomenon is more complex and other variables needed are not accounted for by the models. (C) 2009 Elsevier B.V. All rights reserved

Escala do comportamento do treinador: versão treinador (ECT-T) e versão atleta (ECT-A): o que o treinador diz é confirmado pelos seus atletas?

Objetivou-se verificar o nível de associação entre as percepções de atletas e treinadores de esportes coletivos e individuais nas seis dimensões do comportamento do treinador - Treinamento Físico (TF), Treinamento Técnico (TT), Preparação Mental (PM), Estabelecimento de Objetivos (EO), Reforço Pessoal Positivo (RPP), Reforço Pessoal Negativo (RPN) - acessado pela Escala do Comportamento do Treinador - Versão Treinador (ECT-T) e Versão Atleta (ECT-A). Participaram 181 atletas (114 homens e 67 mulheres) de nove modalidades esportivas com idade média de 17,15 anos (± 1,48) e seus respectivos treinadores (N = 32), todos do sexo masculino, com idade média de 32,88 (± 8,91). Treinadores e atletas responderam aos 38 itens de mesmo conteúdo dos questionários mencionados. A correlação não-paramétrica de Spearman mostrou a inexistência de associação significativa, ao nível a = 0,05, entre as percepções treinadores e atletas de modalidades coletivas nas dimensões TT, PM, EO e RPP. Entre treinadores e atletas de modalidades individuais também não foram verificadas associações significativas em cinco dimensões: TF, TT, PM, EO e RPP. Dentre outras razões, a baixa compatibilidade entre as percepções de atletas treinadores, pode estar relacionada a falhas no processo de organização do treinamento. Além disso, o relacionamento de cada treinador com os atletas sob o seu comando parece informar mais do que a simples categorização: modalidades coletivas versus individuaisThe purpose of this study was to verify the level of association between athletes and their coaches' perceptions, according to the kind of sport (individual or group), in the six dimensions of coaching behavior - Physical Training (PT); Technical Training (TT); Mental Preparation (MP); Goal Setting (GS); Personal Positive Rapport (PPR) Personal Negative Rapport (PNR) - accessed by the two Brazilian versions of Coaching Behavior Scale for Sport: Coaches (ECT-T) and Athletes Versions (ECT-A). Participated 181 athletes (114 male and 67 female) of nine different sports with mean age of 17.15 years (± 1.48) and their respective coaches (N = 32), all male, with mean age of 32.88 years (± 8.91). Coaches and athletes answered the 38 items, which have the same content, in the mentioned questionnaires. The non-parametric Spearman correlation showed the inexistence of significant association, at a level = 0.05, between the coaches and athletes perception of group sports in the dimensions TT, MP, GS and PPR. In addition, there were no significant correlations between coaches and athletes perceptions of individual sports in the following dimensions: PT, TT, MP, GS and PPR. Among others reasons, the low compatibility involving the coaches and athletes perceptions can be associated with failures in the training organization process. Besides, the relationship of each coach with their athletes appears to add more information than the simple categorization: group modalities versus individual modalitie