This study presents a computer vision application of the structure from motion (SfM) technique in three dimensional high resolution gully monitoring in southern Morocco. Due to impractical use of terrestrial Light Detection and Ranging (LiDAR) in difficult to access gully systems, the inexpensive SfM is a promising tool for analyzing and monitoring soil loss, gully head retreat and plunge pool development following heavy rain events. Objects with known dimensions were placed around the gully scenes for scaling purposes as a workaround for ground control point (GCP) placement. Additionally, the free scaling with objects was compared to terrestrial laser scanner (TLS) data in a field laboratory in Germany. Results of the latter showed discrepancies of 5.6% in volume difference for erosion and 1.7% for accumulation between SfM and TLS. In the Moroccan research area soil loss varied between 0.58 t in an 18.65 m

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Summary We describe implicit and explicit formulations of the hybridizable discontinuous Galerkin method for the acoustic wave equation based on state‐of‐the‐art numerical software and quantify their efficiency for realistic application settings. In the explicit scheme, the trace of the acoustic pressure is computed from the solution on the two elements adjacent to the face at the old time step. Tensor product shape functions for quadrilaterals and hexahedra evaluated with sum factorization are used to ensure low operation counts. For applying the inverse mass matrix of Lagrangian shape functions with full Gaussian quadrature, a new tensorial technique is proposed. As time propagators, diagonally implicit and explicit Runge–Kutta methods are used, respectively. We find that the computing time per time step is 25 to 200 times lower for the explicit scheme, with an increasing gap in three spatial dimensions and for higher element degrees. Our experiments on realistic 3D wave propagation with variable material parameters in a photoacoustic imaging setting show an improvement of two orders of magnitude in terms of time to solution, despite stability restrictions on the time step of the explicit scheme. Operation counts and a performance model to predict performance on other computer systems accompany our results. Copyright © 2015 John Wiley & Sons, Ltd.

The purpose of this study was to evaluate the traction characteristics of four different stud configurations on Fédération Internationale de Football Association (FIFA) 2-Star, third-generation artificial soccer turf. The investigated stud configurations were hard ground design, firm ground design, soft ground design, and an experimental prototype. The concept of this study combines performance, perception, biomechanical, and mechanical testing procedures. Twenty-five soccer players took part in the different testing procedures. Variables of this study were: running times, subjective rankings/ratings, ground reaction forces, and mechanical traction properties. Statistical discrimination between the four stud configurations was shown for performance, perception, and biomechanical testing (p < 0.05). Unsuited stud configurations for playing on artificial turf are characterized by less plain distributed and pronounced studs.

Purpose: Official game play on high quality third-generation artificial soccer turf was approved by the FIFA already in 2004. However, it is still unknown how the 'new' surface affects traction requirements and thus potentially calls for specific footwear, especially with respect to the shoe outsole. This research project aimed to develop an artificial soccer turf outsole that provides very good traction performance to players. Methods: The whole project consisted of three phases that were carried out over three years: (I) status quo evaluation, (II) modified prototype testing, and (III) market comparison. In each phase an identical, comprehensive testing design, incorporating performance, perception and biomechanical testing procedures, was applied on FIFA 2-star artificial soccer turf. Four different shoe models were comparatively examined in each research phase and respective findings guided the selection of shoes for the following phase. Results: Soccer shoes that were traditionally designed for playing on natural grass were not (soft ground) or only limitedly (firm ground) suited for playing on artificial turf. Better traction performance on artificial soccer turf was achieved by usage of multiple and rather low studs being evenly distributed across the rearfoot and the forefoot areas. The final prototype shoe outperformed three commercially available artificial turf soccer shoes on the market at time of testing. Conclusion: This research provides an improved understanding of the mechanisms of artificial soccer shoe traction. Solid recommendations for the requirements of artificial soccer turf outsoles are stated, which generally confirm players' intuitive choice of soccer footwear.