Shape optimization of golf clubface using finite element impact models

To model the impact dynamics of a golf drive, finite element (FE) models of the ball and the clubhead are created and combined to simulate the collision of the two bodies. A three-piece golf ball is modelled using only solid elements, while the clubhead is modelled using solid elements for the crucial area of the impact, i.e. the clubface, and using shell elements for the rest of the clubhead to improve the computational efficiency of the simulation. The correct transfer of forces and moments in the transition area between the shell and solid elements is assured by introducing kinematic nodal constraints using rigid elements. The FE model is used to optimize the shape of the clubface in three steps to maximize the launch velocity of the golf ball for central impacts. A final clubface shape is reached and a total improvement of 4.8 m/s over the initial design is obtained. This is a 7% gain in launch velocity, which results in a driving length advantage of approximately 20 m (or 22 yards) until the first contact with the ground. During the optimization process, the mechanical impedances of the two colliding bodies were recorded and compared. It is shown that the optimal clubhead geometry does not agree with the impedance matching theory by comparing the optimization results to those obtained from a simple lumped parameter model.     

Biomechanical validation of a specific upper body training and testing drill in cross-country skiing

The aim of this study was to perform a biomechanical validation of a double poling imitation drill on a rollerboard. Six elite cross-country skiers performed three imitation drill trials at maximal speed at 13 degrees inclination and in double poling on roller skis on a paved road of 3 degrees. Pole and strap forces, elbow and hip angles and EMG activity of eight upper body muscles were measured. Force curves showed similar characteristics, except for impact force occurring only at pole plant in double poling on roller skis. Double poling on a rollerboard includes an eccentric roll-down phase not appearing in double polling on roller skis. Forces on the rollerboard were similar to those on roller skis. Courses of the elbow angles indicated similar shapes, except for the angle at the start of the propulsion phase and, consequently, during flexion (p < 0.01). Propulsion time and cycle duration were longer and frequency lower on the rollerboard (all p < 0.001). Muscle activities were not significantly different, except for stronger biceps brachii (p < 0.01) and weaker erector spinae activation (p < 0.05) on the rollerboard. Muscle coordination patterns showed similar onset and offset points of each muscle and comparable activations in both activities, except for biceps brachii. Two movement strategies on the rollerboard were found, which led to small differences in measured variables. The biomechanical validity of double poling on a rollerboard can be judged as moderately high, being aware of the differences in some variables that might be considered in training sessions on the rollerboard, particularly when using intervals with high number of repetitions.     

Postmodernism: a 'Sceptical' Challenge in Educational Theory

Recently several educational theorists have argued for the incorporation of a scepticism of a postmodern kind into educational theory and into educational research more specifically. Their understanding of postmodernism in terms of scepticism harbours much potential, but to avoid confusion and misunderstanding it is of importance that the 'scepticism' associated with postmodernism is distinguished from traditional philosophical scepticism, be it as part of the very process of theoretical scrutiny or as a challenge towards its results. In this paper it will be argued that the interest of postmodernist 'scepticism' lies not in a quest for ever more certainty but rather in the way it moves beyond both foundationalism and philosophical scepticism. This will be elaborated from the point of view of a Wittgensteinian understanding of theoretical scrutiny (as found in On Certainty). This opens up the possibility of shedding light on postmodernist 'scepticism' in educational theory in terms of an aesthetic distance towards what is reflected upon.     

Das neue Dänische Schulgesetz

Ohne Zusammenfassung     

Enhancing the MeSH thesaurus to retrieve French online health resources in a quality-controlled gateway

The amount of health information available on the Internet is considerable. In this context, several health gateways have been developed. Among them, CISMeF (Catalogue and Index of Health Resources in French) was designed to catalogue and index health resources in French. The goal of this article is to describe the various enhancements to the MeSH thesaurus developed by the CISMeF team to adapt this terminology to the broader field of health Internet resources instead of scientific articles for the medline bibliographic database. CISMeF uses two standard tools for organizing information: the MeSH thesaurus and several metadata element sets, in particular the Dublin Core metadata format. The heterogeneity of Internet health resources led the CISMeF team to enhance the MeSH thesaurus with the introduction of two new concepts, respectively, resource types and metaterms. CISMeF resource types are a generalization of the publication types of medline. A resource type describes the nature of the resource and MeSH keyword/qualifier pairs describe the subject of the resource. A metaterm is generally a medical specialty or a biological science, which has semantic links with one or more MeSH keywords, qualifiers and resource types. The CISMeF terminology is exploited for several tasks: resource indexing performed manually, resource categorization performed automatically, visualization and navigation through the concept hierarchies and information retrieval using the Doc'CISMeF search engine. The CISMeF health gateway uses several MeSH thesaurus enhancements to optimize information retrieval, hierarchy navigation and automatic indexing.     

Gender,Science, and Scientific Organizations in Germany

This article considers the situation of women in science in Germany. We argue that scientific organizations play a crucial role in shaping science careers, often with different consequences for men and women. To sustain the argument, we offer a study of the careers of male and female scientists in the Max Planck Society. Our findings show that external support increases career options and opportunities for men, but not for women scientists.     

Self-fulfilling prophecies in media-based learning: Content relevance moderates quality expectation effects on academic achievement

In the present paper a model of self-fulfilling prophecy effects in media-based learning was developed and tested. The central model assumption was that information about an instructional medium's quality affects students' academic achievement depending on the instructional content's relevance to the student. Experiment 1 (N = 100) demonstrated higher achievement in response to positive compared to negative information, but not the predicted moderating effect of content relevance. Using a revised relevance manipulation, Experiment 2 (N = 199) identified the following moderating function of content relevance: Under moderate relevance positive information led to higher achievement, under high relevance negative information resulted in higher achievement. No differences appeared under low relevance. Path analyses revealed students' cognitive effort as significant mediator for these effects.