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.     

Schools and Moral Education: Conformism or Autonomy?

In pluralistic Western societies, schools have a specific task in moral education. This task is to be understood neither as the transmission of specific values, nor as the development of moral reasoning skills or universal values, but as teaching pupils to handle plurality in an autonomous way. The concept of autonomy is interpreted from a Vygotskian and Deweyan position, where learning in school means learning to participate in cultural activities in a reflective and critical way. Participation has both intellectual and moral aspects, and thus moral education can never be separated from cognitive education.     

It doesn’t matter,but: examining the impact of ambient learning displays on energy consumption and conservation at the workplace

This study reports an intervention to initiate environmental learning and facilitate pro-environmental behaviour. The purpose was to examine the impact of ambient learning displays on energy consumption and conservation at the workplace, more specifically the evaluation of learning outcome and behaviour change. Using a quasi-experimental design, the empirical study was conducted among employees working at a university campus. For the experimental treatments, ambient learning display prototypes were varied on two design dimensions, namely representational fidelity and notification level. The results do not provide clear evidence that the design of the displays influences learning outcome or that the displays lead to pro-environmental behaviour change. Nevertheless, the sole deployment of the display prototypes eased the comprehension of the information provided and lowered the need for additional information. Thus, ambient learning displays provide a promising framework in the context of environmental learning and beyond.     

Sources of spillovers for imitation and innovation

We estimate the effect of R&D spillovers on sales realized by products new to the firm (imitation) and new to the market (innovation). It turns out that spillovers from rivals lead to more imitation, while input from customers and research institutions enhance original innovation.     

Knowledge diversity and team creativity: How hobbyists beat professional designers in creating novel board games

This study adds to the literature on household sector (HHS) innovation by investigating how user and professional designer teams differ in their ability to translate knowledge diversity into collective creative output. We test our hypotheses on a unique data set of more than 5,000 board game design projects conducted by either teams of professional game designers or by hobbyist (user) designers. Our study lends support for the notion that knowledge diversity is a double-edged sword that has opposing effects on the two dimensions of team creativity, novelty and usefulness. We argue and find that teams composed of self-rewarded users in the household sector are better able than teams of professionals to translate the informational benefits of knowledge diversity into novel concepts and game designs. Finally, we find that user teams are in general more likely to create truly creative (i.e. novel and useful) game designs. This particular result emphasizes the relevance of research on HHS innovation and shows that user designers from the HHS are able to conduct collective development work more effectively than teams of professional designers.     

Comparing BSEM and EUPD Estimates for Two-Group SB-MTMM Experiments

In 2018, two different approaches have been suggested to solve the estimation problems that have been detected during the analysis of the data of the two-group split ballot multi-trait multi-method (SB-MTMM experiments performed in many countries between 2002 and 2010 in the European Social Survey). One group suggested using the Bayesian estimation. The other group suggested a new estimation procedure (EUPD) that makes use of the pooled data across the different countries. In this note, we present a comparison of the results of the two approaches on the same generated data, which are comparable with the data that created problems in the ESS.     

Stability of three‐wave simplex estimates of reliability

In this article 2 major problems of using the three‐wave quasi simplex model to obtain reliability estimates are illustrated. The 1st problem is that the sampling variance of the reliability estimates can be very large, especially if the stability through time is low. The 2nd problem is that, for the reliability parameter to be identified, the model assumes a particular change process, namely a Markov process. We show that minor violations of this assumption can lead to a large bias in the reliability estimates. The problems are evaluated using both real and Monte Carlo data. A model with repeated measurements in 1 of the waves is also discussed.