Measurement of active drag during crawl arm stroke swimming

In order to measure active drag during front crawl swimming a system has been designed, built and tested. A tube (23 m long) with grips is fixed under the water surface and the swimmer crawls on this. At one end of the tube, a force transducer is attached to the wall of the swimming pool. It measures the momentary effective propulsive forces of the hands. During the measurements the subjects' legs are fixed together and supported by a buoy. After filtering and digitizing the electrical force signal, the mean propulsive force over one lane at constant speeds (ranging from about 1 to 2 m s-1) was calculated. The regression equation of the force on the speed turned out to be almost quadratic. At a mean speed of 1.55 m s-1 the mean force was 66.3 N. The accuracy of this force measured on one subject at different days was 4.1 N. The observed force, which is equal to the mean drag force, fits remarkably well with passive drag force values as well as with values calculated for propulsive forces during actual swimming reported in the literature. The use of the system does not interfere to any large extent with normal front crawl swimming; this conclusion is based on results of observations of film by skilled swim coaches. It was concluded that the system provides a good method of studying active drag and its relation to anthropometric variables and swimming technique.     

青少年速滑运动员训练及比赛中的心理障碍与消除

运用运动心理学相关知识,采用理论分析的方法,对青少年速滑运动员在训练和比赛中产生心理障碍的原因进行分析。同时提出一些消除心理障碍的训练方法和手段,提高青少年速滑运动员训练与比赛中的心理水平,降低和消除心理障碍对运动成绩的负面影响。     

Adult learners’ social connectedness and online participation: the importance of online interaction quality

ABSTRACT

Online interaction has been associated with positive outcomes, academically and psychologically. Regarding the latter, social connectedness has been recognised as an important outcome on the basis of its link to subjective well-being and course satisfaction. In adult educational settings, how online interaction can foster social connectedness has not been widely examined. The study investigates how (1) adult learners’ online participation operationalised as discussion contribution, collaborative facilitation, and social interaction, and (2) their perceived online interaction quality are related to their feeling of social connectedness. The role of online interaction quality related to the three types of online participation and social connectedness is also examined. A questionnaire was developed to collect data from adult learner participants in Belgium (N?=?170). Multiple regressions and mediation analysis were conducted. The result shows that collaborative facilitation and online interaction quality significantly contribute to adult learners’ perceptions of social connectedness. Furthermore, the finding reveals that online interaction quality fully mediates the relationship between discussion contribution, social interaction, and social connectedness. Thus, the implications for research and instructional design are discussed.     

Understanding floating: A study of children aged between six and eight years

Graphs of real-time experiments are useful tools in science education; their intrinsic features allow innovative didactic approaches. The use of such images is spreading and is likely to become common classroom practice. This paper describes a study in which secondary school students were called upon to read and interpret documents containing images of real-time kinematics graphs specially designed to address common learning problems and to minimize iconic difficulties. Both novice students and those with a little experience of real-time experiments were involved. The overall didactic intentions of the presented documents were fulfilled. Some reading difficulties related to specific features were detected and are discussed. Suggestions are made regarding the acquisition of some specific capabilities that are needed to avoid misinterpreting these images and are of transversal value across several contexts. Finally, some implications for teacher training and class activities are discussed.     

Effects of non-Newtonian power law rheology on mass transport of a neutral solute for electro-osmotic flow in a porous microtube

Mass transport of a neutral solute for a power law fluid in a porous microtube under electro-osmotic flow regime is characterized in this study. Combined electro-osmotic and pressure driven flow is conducted herein. An analytical solution of concentration profile within mass transfer boundary layer is derived from the first principle. The solute transport through the porous wall is also coupled with the electro-osmotic flow to predict the solute concentration in the permeate stream. The effects of non-Newtonian rheology and the operating conditions on the permeation rate and permeate solute concentration are analyzed in detail. Both cases of assisting (electro-osmotic and poiseulle flow are in same direction) and opposing flow (the individual flows are in opposite direction) cases are taken care of. Enhancement of Sherwood due to electro-osmotic flow for a non-porous conduit is also quantified. Effects if non-Newtonian rheology on Sherwood number enhancement are observed.     

Developing capabilities in new ventures: a knowledge management approach

On the basis of a knowledge management perspective, this paper expands the literature on new ventures’ capabilities by considering how these firms fill knowledge gaps and develop the technological, marketing, management, and ICT capabilities they need to compete. In particular, this paper investigates the role of networks in these dynamics. Although new technology-based firms have great potential to introduce innovative products into the market, they might suffer from more critical knowledge gaps and capability weaknesses than established firms. The results of a quantitative investigation of an original data set of more than 400 Italian new ventures specializing in high-tech industries show that these firms acquire knowledge to support their capability growth mainly through the management of intense relations with multiple external sources of knowledge. In addition, capability development is supported by the variety of founders’ industry experience and the presence of young graduates among the founding team.