Advanced measurement for sports surface system behaviour under mechanical and player loading

This research project has investigated the mechanical behaviour of artificial turf surface systems used for sports under a range of real player movements, and the contribution of component layers to the overall system response by developing advanced measurement systems and methods. Artificial turf surface systems are comprised of a number of different materials and commonly with several layers, all of which contribute to their composite behaviour. During sports movements a player loads the surface, resulting in deformation that can change the surface behaviour, which in turn modifies the player biomechanical response. Improving the understanding of surface response to actual player loading is important for developing enhanced products for improving play performance. Likewise, by improving knowledge of surface effects on players, the understanding of injury risk can be improved. However, there is currently no published research to measure and analyse the behaviour of artificial turf system during real player locomotion. This research was undertaken to address this current lack of knowledge within the interaction between player and sports surface regarding the effects of player loading on the mechanical behaviour of artificial turf systems. In addition to support player loading regime, mechanical behaviour of hockey and third generation artificial turf surface systems and their component shockpad layers (a rubber shreds bonded shockpad and a polyurethane foam shockpad) was examined through dynamic cyclic compressive loading using an advanced material testing machine in laboratory environment. Each layer and carpet-shockpad system was subjected to controlled loading designed with previous biomechanical data at various loading frequencies (0.9 Hz, 3.3 Hz and 10 Hz) and under two different contact areas (50 mm and 125 mm diameter) to simulate aspects of player walking, running and sprinting. All layers and surface systems tested showed nonlinear stress-strain behaviour with hysteresis. Increasing the contact area resulted in reduced surface vertical deflection and more linear response. Increasing the loading frequency led to stiffer response in the lower stress range ( 600 kPa) and a decrease in maximum strain as the loading frequency increased. Hysteresis loops obtained at different loading frequencies indicated that the amount of energy lost at the same peak load of 1900 N in each surface system decreased with an increase in loading rate. Player loading regime was performed to quantify the load/stress and the resulting surface deformation/strain under subject loading. Measurement systems including motion capture system, force plate and high speed were developed to characterise the response behaviour in a novel way. The mechanical behaviour of artificial turf surface systems under three player movement patterns (heel-toe walking, forefoot running and forefoot single leg landing) was measured. Boot-surface contact area of each movement varied during the stance. The heel-toe walking results indicated that the maximum applied stress and surface strain occurred in very early stance (first 10%) when the boot-surface contact area was small. For forefoot running and landing, the peak surface strain occurred around mid-stance concurrent with the time of peak applied stress. The maximum strain measured under running was smaller than under landing. A thin-film pressure sensing mat was used in both mechanical and player loading regimes and proved to be a useful tool for evaluating the pressure distributions and contact areas at different interfaces of the surface system. The applied stress on surface was observed to greatly reduce with depth over increasing contact area through the surface systems. Although the average pressure was reduced, pressure distribution contour showed directly under the surface load area the pressure at depth was still relatively large and that outside of this area the pressure was much lower. A comparison of the mechanical behaviour of artificial turf systems in terms of compressive strain, modulus of elasticity, stress distribution and energy loss under mechanical and player loading was evaluated. Key loading parameters in different loading regimes and their influence on surface system response were determined. The structure and material intrinsic properties of shockpad were considered to further explain the observed surface system behaviour. Two mathematical models were used to fit through the experimental data and found to be able to describe the loading behaviour. A breakthrough in understanding of the effects of real player loading on the mechanical behaviour response of artificial turf systems, and the contribution of the components to the whole system response has been achieved through the development of advanced measurement techniques

Advanced measurement of sports surface system behaviour under player loading

Artificial turf sport surface systems are comprised of a number of different materials. Improving the understanding of the sports surface system's response to actual player loading is important for developing enhanced products and system designs for improving play performance and durability. Previous research has tested and compared the mechanical properties of artificial turf systems with relatively simple mechanical tests intended to simulate loading from the player or ball. However, these test methods have known shortcomings in representing real in-service loading and it is often assumed a peak value of force or peak deformation is sufficient to describe the surface behaviour. Little literature exists that describes the force-deflection or stress- strain behaviour of artificial turf system under mechanical or player loading. This paper outlines methodologies developed for surface response measurement under real-time player movements including: the advanced measurement systems and data analysis methods for determining surface deflection/strain under player foot strike during a ground contact, and further evaluating the force-deflection and stress-strain relationships of the synthetic carpet-shockpad composite surface systems. The results show the ability of the surface system to accommodate the player applied loads by deforming to large strains with strong non-linearity and rate-dependent energy loss (hysteresis) in the load-unload phases. The contrast between the surface systems’ response to player loading using different shockpads is also presented and discussed. By combining these findings from the development of measurement techniques and the data analysis methods a new surface system evaluation regime is proposed for future studies into mechanical behaviour and cushioning response of artificial turf systems under player loading

Advanced measurement of sports surface system behaviour under player loading

Artificial turf sport surface systems are comprised of a number of different materials. Improving the understanding of the sports surface system's response to actual player loading is important for developing enhanced products and system designs for improving play performance and durability. Previous research has tested and compared the mechanical properties of artificial turf systems with relatively simple mechanical tests intended to simulate loading from the player or ball. However, these test methods have known shortcomings in representing real in-service loading and it is often assumed a peak value of force or peak deformation is sufficient to describe the surface behaviour. Little literature exists that describes the force-deflection or stress- strain behaviour of artificial turf system under mechanical or player loading. This paper outlines methodologies developed for surface response measurement under real-time player movements including: the advanced measurement systems and data analysis methods for determining surface deflection/strain under player foot strike during a ground contact, and further evaluating the force-deflection and stress-strain relationships of the synthetic carpet-shockpad composite surface systems. The results show the ability of the surface system to accommodate the player applied loads by deforming to large strains with strong non-linearity and rate-dependent energy loss (hysteresis) in the load-unload phases. The contrast between the surface systems’ response to player loading using different shockpads is also presented and discussed. By combining these findings from the development of measurement techniques and the data analysis methods a new surface system evaluation regime is proposed for future studies into mechanical behaviour and cushioning response of artificial turf systems under player loading

Advanced measurement for sports surface system behaviour

Artificial turf surface systems for sport can be comprised of a number of different materials. Measuring the surface system's response to loading from player and ball is important for developing better understanding of its behaviour to enhance product design and optimise performance. Currently, simple mechanical tests are used to test and classify artificial turf systems for compliance to industry standards. However, little literature exists that describes artificial turf system response under player loading or the contribution of the components to the system response. This paper presents data for the stress-strain behaviour of the layer materials (one hockey turf and two types of shockpad) from laboratory controlled loading and data from a dynamic pressure measurement system. The results show strong non linearity, hysteresis and viscoelasticity exhibited by the materials. The pressure measurement results show how the applied loads are dissipated within the system and demonstrate the differing response of two shockpads. The paper provides a contribution in understanding to the response of artificial turf systems to compression loading

Descriptive statistics and zero-order correlations between the study variables.

<p>Descriptive statistics and zero-order correlations between the study variables.</p

Effects of speed-control measures on the safety of unsignalized midblock street crossings in China

<p><b>Objective</b>: The primary objective of this study was to evaluate the effects of different speed-control measures on the safety of unsignalized midblock street crossings.</p> <p><b>Methods</b>: In China, it is quite difficult to obtain traffic crash and conflict data for pedestrians using such crossings, mainly due to the lack of traffic data management and organizational issues. In light of this, the proposed method did not rely on such data, but considered vehicle speed, which is a leading contributing factor of pedestrian safety at mid blocks. To evaluate the speed reduction effects at different locations, the research team utilized the following methods in this study: (1) testing speed differences—on the basis of the collected data, statistical analysis is conducted to test the speed differences between upstream and crosswalk, upstream and downstream, and downstream and crosswalk; and (2) mean distribution deviation—this value is calculated by taking the difference in cumulative speed distributions for the two different samples just mentioned. In order to better understand the variation of speed reduction effects at different distances from speed-control facilities, data were collected from six types of speed-control measures with a visual range of 60 m.</p> <p><b>Results</b>: The results showed that speed humps, transverse rumble strips, and speed bumps were effective in reducing vehicle speeds. Among them speed humps performed the best, with reductions of 21.1% and 20.0% from upstream location (25.01 km/h) and downstream location (24.66 km/h) to pedestrian crosswalk (19.73 km/h), respectively. By contrast, the speed reduction effects were minimal for stop and yield signs, flashing yellow lights, and crossings without treatment.</p> <p><b>Conclusions</b>: Consequently, in order to reduce vehicle speeds and improve pedestrian safety at mid blocks, several speed-control measures such as speed humps, speed bumps, and transverse rumble strips are recommended to be deployed in the vicinity of pedestrian crosswalks.</p

Additional file 2 of Purifying selection leads to low protein diversity of the mitochondrial cyt b gene in avian malaria parasites

Additional file 2

Supplemental Material - Confidence Screening Detector: A New Method for Detecting Test Collusion

Supplementary Material for Confidence Screening Detector: A New Method for Detecting Test Collusion by Yongze Xu, Ying Cui, Xinyi Wang, and Fang Luo in Applied Psychological Measurement.</p