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  • Author: Kerstin Witte x
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Abstract

We conducted a virtual reality (VR) training with ten sessions, performed by fifteen young karate athletes, who responded to attacks of a virtual opponent to improve their response behavior and their decision-making. The control groups continued with their normal training. Results of the Friedman tests with subsequent Dunn-Bonferroni post-hoc-tests and estimation of effect sizes showed that the karate specific response behavior (measured by a movement analysis) improved significantly due to the training. The parameters time for response (as the time for the attack initiation) and response quality improved with large effect sizes for the intervention groups, whereas the control groups demonstrated improvements with only small effect sizes. The unspecific response behavior (analyzed by two forms of the reaction test of the Vienna test system) did not show any significant changes. Paired t-tests revealed an improvement in attack recognition. While in the pretests, the intervention groups responded to late movement stages of the attack (execution of the main phase), they responded to early movement stages (reduction of distance and preparing steps) in the posttests. Furthermore, Friedman-tests and bivariate correlation analysis showed that the intervention groups were highly motivated to perform the VR training because of the new and safe learning conditions.

Abstract

In this work spinel series with the general formula Fe1-xMnxAl2O4 (where x = 0, 0.3, 0.5 and 0.7) were synthesized and characterized with respect to their structure and microstructure. X-ray diffractometry (XRD) was used to identify the phase composition that revealed a single phase spinel material. Rietveld refinements of the XRD patterns were carried out in order to determine the lattice and oxygen positional parameters of the spinel compounds. Mössbauer effect measurements were performed at room temperature to determine the local chemical environment of the Fe ions, their valences, and degrees of spinels inversion. It was shown that an increase in the Mn content led to a decrease in the ratio of Fe2+ to Fe3+. The results obtained from Mössbauer spectroscopy (MS) were used to establish the chemical formulas of the synthesized spinels. Finally, the microstructure that was observed using scanning electron microscopy (SEM) showed a compact microstructure with an octahedral crystal habit.