MOTION PATTERN CONSISTENCY OF THE RIDER-HORSE SYSTEM

INTRODUCTION: Dressage riding is difficult to judge, because the aesthetics of the performance cannot be measured simply. The aim of this study was to show a method of visualizing and quantifying the harmony of the motion of a rider and a horse by evaluating their coordination. Rider and horse have a natural frequency when trotting; they can therefore be considered a system of coupled biological oscillators. The characteristics of such a system are determined by the innate and learned motion patterns, anatomy and physical condition of both participants. Any periodic motion can be described as a limit-cycleattractor in the phase space. The characteristics of an oscillator or a system of oscillators can be depicted as a phase plane diagram (PPD), which is a suitable method to visualize the characteristics (e.g., longterm behavior and limit-cycle) of a complex system, such as the ridden horse. METHODS: Twenty horses aged 4 to 22 years on different training levels were measured being ridden at trot by a professional rider and a hobby rider. The measurements were carried out from the right side, with six cameras (sample rate 120 Hz, resolution 240 x 833 points) tracing 20 reflecting spherical markers placed on the horse’s and rider’s right side. At least eight recordings of five seconds each were taken with the ExpertVision System of the Motion Analysis Corporation with the horse trotting on a 12 m long pressed sand track in an indoor riding arena. At least eight motion cycles of each rider-horse combination were analyzed. The 3-dimensional movements of the markers were used to deduce the angle between the linkages of rider’s head to rider’s back and of rider’s back to the horse’s head. Then the data were normalized to 100% of the length of the motion cycle. Angle velocity and angle acceleration were computed and from all three data-sets, scaled to 100% of the professional rider’s angle, angle velocity and angle acceleration; the trajectories in the phase-space were plotted and the lengths of the resulting vectors (LV) in the phase-space were computed. The mean and average deviation (variation of LV) of LV of every horse and rider were determined and grouped for each rider. The normal distribution of each group was tested with the Kolmogorov-Smirnov test. The Student test of paired samples and one-way analysis of variance were used to check the differences between the mean of the groups of LV and average deviation. RESULTS AND DISCUSSION: There was no significant difference in the mean of LV between the 2 riders, but there was a significant () difference in the average deviation of the LV, showing that the motion of the horse-professional rider system is more consistent than of the horse-hobby rider system. With this method the rhythm and the natural balance of the rider-horse system can be evaluated, and this information might prove a useful feedback for the education of riders

THE INFLUENCE OF THE RIDER ON THE TROTTING MOTION OF A HORSE

Introduction: The characteristics of trot, such as collection, impulsion, action of the hind quarter, the position of the head and the balance of the horse are described in the Rules of Dressage Events of the Federation Equestre International. Up to now, these characteristics were judged subjectively by dressage judges, but no objective measures have been developed to substantiate these judgments. The aim of our study was to establish measurable criteria that make possible the quantification of dressage characteristics, by comparing the motion pattern of trotting horses ridden by two riders of different skill and being led on hand. Materials and Methods: Twenty horses aged 4 to 22 years at different training levels were measured being ridden at trot by a professional rider and a hobby rider, as well as being trotted on hand. The measurements were carried out from the right side, with six cameras (sample rate 120 Hz, resolution 240 x 833 points) tracing 20 reflecting spherical markers placed on the horse’s and rider’s right side. At least eight recordings of five seconds each were taken with the ExpertVision System of Motion Analysis Corporation with the horse trotting on a 12 m long pressed sand track in an indoor riding arena. At least eight motion cycles of each rider-horse combination and of the horses being trotted on hand were analyzed. The 3-dimensional movement of the markers was calculated, and the stridelength, speed, and vertical movement of the fetlock joints were compared. The data were normalized to the trotting speed. The normal distribution of each group was tested using the Kolmogorov- Smirnov test, and the Student test of paired samples was used to check the differences between the means of the groups of the above described parameters. Results and Discussion: With the hobby rider the horses had the significantly lowest trotting speeds, the smallest stride length, the highest head position, the smallest vertical movement of the fetlock joint and the longest duration of stancephase when compared to when the horse is ridden by the professional rider and trotted on hand. Between the horse’s motion when ridden by the professional rider and trotted on hand no significant differences could be detected in the trotting speed and the duration of stance-phase, whereas significant differences were established for head position and stride length. The vertical movement of the fetlock joint did not differ significantly when ridden by the hobby rider and trotted on the hand, but both did differ significantly from the vertical movement of the fetlock joint when ridden by the professional rider. The results of this study show that some terms used by the Federation Equestre International can be translated into measurable quantities, and thus a more objective judgment of dressage may evolve

Medienkompetenz: Anmerkungen anlässlich einer Untersuchung der Medienkompetenz von und durch SchülerInnen an Neuen Mittelschulen in Wien.

Im Beitrag wird vorgeschlagen, Medienkompetenz auch als Ordnungsbegriff zu verstehen. Dazu wird eine präskriptive, eine empirische und eine selektive Ordnung unterschieden. Mit einer induktiv-empirischen Untersuchung wird demonstriert, dass so ein Beitrag zum Verständnis des Medienkompetenzbegriffs geleistet werden kann, mit dem zugleich eine Kritik deduktiv-empirischer Ordnungen erreicht wird. Dabei wird gezeigt, dass ein Bezug auf aktuelle materielle Zeichenträger zugleich problematisch und notwendig ist

The effects of forest cover and disturbance on torrential hazards

Global human population growth, limited space for settlements and a booming tourism industry have led to a strong increase of human infrastructure in mountain regions. As this infrastructure is highly exposed to natural hazards, a main role of mountain forests is to regulate the environment and reduce hazard probability. However, canopy disturbances are increasing in many parts of the world, potentially threatening the protection function of forests. Yet, large-scale quantitative evidence on the influence of forest cover and disturbance on natural hazards remains scarce to date. Here we quantified the effects of forest cover and disturbance on the probability and frequency of torrential hazards for 10 885 watersheds in the Eastern Alps. Torrential hazard occurrences were derived from a comprehensive database documenting 3768 individual debris flow and flood events between 1986 and 2018. Forest disturbances were mapped from Landsat satellite time series analysis. We found evidence that forests reduce the probability of natural hazards, with a 25 percentage point increase in forest cover decreasing the probability of torrential hazards by 8.7%± 1.2%. Canopy disturbances generally increased the probability of torrential hazard events, with the regular occurrence of large disturbance events being the most detrimental disturbance regime for natural hazards. Disturbances had a bigger effect on debris flows than on flood events, and press disturbances were more detrimental than pulse disturbances. We here present the first large scale quantification of forest cover and disturbance effects on torrential hazards. Our findings highlight that forests constitute important green infrastructure in mountain landscapes, efficiently reducing the probability of natural hazards, but that increasing forest disturbances can weaken the protective function of forests.Austrian Climate Research ProgramAustrian Science Fund https://doi.org/10.13039/501100002428Peer Reviewe

Flood Protection by Forests in Alpine Watersheds: Lessons Learned from Austrian Case Studies

This chapter highlights the influence of mountain forests on runoff patterns in alpine catchments. We discuss the forest impact at different spatial scales and bridge to the requirements for an integrated natural hazard risk management, which considers forest as an efficient protection measure against floods and other water-related natural hazards. We present results from a wide range of research studies from Austria, which all reveal the runoff-reducing effect of forest vegetation in small and medium-size catchments ( 100 km2), e.g., by reducing surface runoff and delaying interflow, but above all by stabilising slopes and therefore reducing bedload transport during major runoff events. To avoid that forests become a hazard due to enhanced driftwood release, managing of steep riparian slopes for a permanent forest cover (“Dauerbestockung”) is a basic prerequisite. Often protective effects of forests are impaired by man-made impacts like dense forest road networks, insensitive use (e.g., false design of skid roads, compacting machinery, forest operations during adverse weather on wet and saturated soils), and delayed or omitted reforestation and regeneration. Flood risk management in mountain regions should include Ecosystem-based Disaster Risk Reduction measures, with particular emphasis on sustainable and climate change-adapted management of protective forests. This will require integral and catchment-based approaches such as comprehensive management concepts coordinated with spatial planning, and verifiable, practicable and correspondingly adapted legal guidelines as well as appropriate funding of protective forest research to close the existing knowledge gaps

DebrisInterMixing-2.3: a finite volume solver for three-dimensional debris-flow simulations with two calibration parameters. Part 2: Model validation with experiments

Here, we present validation tests of the fluid dynamic solver presented in von Boetticher et al. (2016), simulating both laboratory-scale and large-scale debris-flow experiments. The new solver combines a Coulomb viscoplastic rheological model with a Herschel-Bulkley model based on material properties and rheological characteristics of the analyzed debris flow. For the selected experiments in this study, all necessary material properties were known - the content of sand, clay (including its mineral composition) and gravel as well as the water content and the angle of repose of the gravel. Given these properties, two model parameters are sufficient for calibration, and a range of experiments with different material compositions can be reproduced by the model without recalibration. One calibration parameter, the Herschel-Bulkley exponent, was kept constant for all simulations. The model validation focuses on different case studies illustrating the sensitivity of debris flows to water and clay content, channel curvature, channel roughness and the angle of repose. We characterize the accuracy of the model using experimental observations of flow head positions, front velocities, run-out patterns and basal pressures.Peer ReviewedPostprint (published version

Radioaktivität im Unterricht.: Ergebnisse einer repräsentativen Erhebung zur Didaktik der auditiven Medien bei LehrerInnen in Österreich.

Die sechs AutorInnen untersuchen die Vielzahl von Audioproduktionsmethoden in pädagogischen Handlungsfeldern Österreichs anhand einer empirischen Studie. Dabei wird deutlich, dass Audioproduktionen mediendidaktisch sehr gut eingesetzt werden können, aber als Methode unterschätzt werden