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A procedure to enhance the faded colours of museums artefacts is presented. The method is based on adjusting the spectral profile of the light while maintaining a given white colour of the illumination. The procedure is tested using colour LED clusters and a series of damaged samples and their good condition counterparts. The intensity of the three components of four feasible LED clusters is computed in order to produce white illumination metameric to a white LED light source taken as a reference. Colorimetric calculations are performed to model the colour changes undergone by target colour samples using illumination based on colour LED association with respect to the white LED reference. The model is based on CIELAB specification and allows to optimize the choice of three-colour LED associations that modify the hue and the saturation of a few target colour areas of illuminated samples while other areas are left moderately desaturated. Modelling and experimental visual validation were practically obtained by adjusting the intensity of five calibrated colour LEDs, blue, cyan, green, amber and red, accommodated in a light booth. A visual validation was conducted asking 20 observers to rate the colourfulness appearance of aged inkjet prints under every LED cluster with respect to the colourfulness of their original counterparts under the reference white LED source. The visual assessments agreed with the colorimetric predictions. Finally, a demonstration is shown of the feasibility of the method by simulating the rejuvenated appearance of a natural history specimen of which the museum possesses two differently aged items. 相似文献
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The aims of this study were to (1) investigate the influence of general anthropometric variables, handball-specific anthropometric variables, and upper-limb power and strength on ball-throwing velocity in a standing position (ν(ball)), and (2) predict this velocity using multiple regression methods. Forty-two skilled male handball players (age 21.0?±?3.0 years; height?=?1.81?±?0.07?m; body mass?=?78.3?±?11.3?kg) participated in the study. We measured general anthropometric variables (height, body mass, lean mass, body mass index) and handball-specific anthropometric parameters (hand size, arm span). Upper-limb dynamic strength was assessed using a medicine ball (2?kg) throwing test, and power using a one-repetition maximum bench-press test. All the variables studied were correlated with ball velocity. Medicine ball throwing performance was the best predictor (r?=?0.80). General anthropometric variables were better predictors (r?=?0.55-0.70) than handball-specific anthropometric variables (r?=?0.35-0.51). The best multiple regression model accounted for 74% of the total variance and included body mass, medicine ball throwing performance, and power output in the 20-kg bench press. The equation formulated could help trainers, athletes, and professionals detect future talent and test athletes' current fitness. 相似文献
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Execution time, kinetics, and kinematics of the mae-geri kick: comparison of national and international standard karate athletes 总被引：1，自引：1，他引：0
Little is known of the performance characteristics of the shotokan karate mae-geri kick. The aim of this study was to compare the execution time, the lower limb kinetics and kinematics, and their respective repeatability in the mae-geri kick of karate athletes of two different standards. Seventeen adult black belt karate competitors (9 national and 8 international athletes) performed six kicks with their dominant lower limb on a striking surface, combining maximum force impact and velocity. Execution time of movement and lower limb kinematics were recorded with a high-speed camera. Maximum force at impact and the forces exerted on the ground were measured using three force plates. The duration of the kick was significantly shorter for international than for national standard athletes. However, no significant difference in the maximum impact force of the kick was observed between the two groups. In addition, significant kinematic differences were observed between the groups, with two angles of motion and one velocity peak occurring sooner in the kick movement for the international athletes, specifically for the knee joint. International athletes also performed the kick with a significantly higher repeatability for duration and kinematics, specifically during the pre-loading phase that precedes the attack phase. We conclude that the duration of the kick and repeatability of lower limb kinematics could be useful in selecting top-level karate athletes and monitoring their training status. 相似文献
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Martinus Buekers Jorge Ibáñez-Gijón Antoine H.P. Morice Guillaume Rao Nicolas Mascret Jerome Laurin 《Quest (Human Kinetics)》2017,69(1):65-79
While the call for interdisciplinary studies has been loud and clear over the last decade or so, the number of interdisciplinary publications in sport sciences is rather limited. One of the reasons for this scarcity is the complexity of the research process itself. Still, the combination and integration of information from different scientific disciplines seems to be important to better explain how elite performance comes about. In this article, we focus on this issue and discuss the advantages of interdisciplinary research for understanding how elite athletes are able to achieve such high-proficiency levels. The first section provides an overview of the studies that investigated elite performance in sports. In the second section, we focus on the issue of interdisciplinarity and illustrate how the ecological–dynamical approach and the concept of dimensional reduction can be used to explain how elite performers cope with the complex nature of sport skills. In the last section, we present a research outline and some practical considerations that can be helpful for researchers who aim to study sport skills from an interdisciplinary perspective. 相似文献
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Classroom and School Predictors of Civic Engagement Among Black and Latino Middle School Youth 
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下载免费PDF全文 Robert J. Jagers Fantasy T. Lozada Deborah Rivas‐Drake Casta Guillaume 《Child development》2017,88(4):1125-1138
This study used short‐term longitudinal data to examine the contributions of democratic teaching practices (e.g., the Developmental Designs approach) and equitable school climate to civic engagement attitudes, beliefs, and behaviors among 515 Black and Latino middle school students (47.9% male). Concurrent experiences of democratic homeroom and classroom practices, and equitable school climate were associated with higher scores on each civic engagement component. The relation between classroom practices and civic attitudes was more robust when school climate was seen as more equitable. Longitudinally, homeroom practices and equitable school climate predicted higher civic attitudes 1 year later. Discussion focuses on civic attitudes and future research on school experiences that support civic engagement among youth of color. 相似文献