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Rehabilitation will increase the 'capacity' of your.... -insert musculoskeletal tissue here..... Defining 'tissue capacity': A core concept for clinicians

- Cook, Jill, Docking, Sean

  • Authors: Cook, Jill , Docking, Sean
  • Date: 2015
  • Type: Text , Journal article , Editorial
  • Relation: British Journal of Sports Medicine Vol. 49, no. 23 (2015), p. 1484-1485
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  • Description: Capacity is a helpful term in clinical practice to indicate to clients that they (and more importantly their musculoskeletal tissues) are either able or unable to complete a task or participate in physical activity. In the context of injury—having exceeded the capacity of the tissue—the term has immediacy for muscle and ligament: a musculotendinous or ligament strain is an acute injury due to a loading event beyond the tissue's capacity. The tissue response in tendon is usually more gradual—acute traumatic injury of normal tendon is rare, whereas the pathological tendon can fail catastrophically (rupture).

Remediation of monoethanolamine after exposure to brown coal flue gases

- Lim, Jinah, Aguiar, Alita, Reynolds, Alicia, Pearson, Pauline, Kentish, Sandra, Meuleman, Erik

  • Authors: Lim, Jinah , Aguiar, Alita , Reynolds, Alicia , Pearson, Pauline , Kentish, Sandra , Meuleman, Erik
  • Date: 2015
  • Type: Text , Journal article
  • Relation: International Journal of Greenhouse Gas Control Vol. 42, no. (2015), p. 545-553
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  • Description: Monoethanolamine (MEA) is the solvent most commonly considered for post-combustion capture. However, the solvent will accumulate a range of contaminants during use, notably heat stable salts, that reduce its performance. This work considers the removal of these contaminants from MEA solutions that had been exposed to over 50 and 1800h of post combustion capture of flue gases from a brown coal-fired power station. Analysis indicated that these MEA solutions contained significant quantities of heat stable salts including iron, potassium, sulphate, nitrate and organic anions, particularly in the older sample. Both solutions were initially neutralised to free the protonated amine, which led to precipitation of some impurities within the older solvent. Nanofiltration was considered as an approach to further concentrate impurities, but was ineffective due to low permeation rates and low rejection of monovalent salts, at less than 20%. It was effective in concentrating metal contaminants and may be useful into the future for this reason. Conversely, electrodialysis was effective in removing up to 91% of the ionic content of the solutions, although the current efficiency fell at low feed conductivities. Monovalent salts such as sodium, potassium and nitrate were removed more readily than multivalent salts such as iron and sulphate. MEA loss was consistent with our prior work at around 0.15g/m2s and was predominantly as the free amine rather than the carbamate salt.

Research trends in selected blanching pretreatments and quick freezing technologies as applied in fruits and vegetables : A review

- Xin, Ying, Zhang, Min, Xu, Baoguo, Adhikari, Benu, Sun, Jincai

  • Authors: Xin, Ying , Zhang, Min , Xu, Baoguo , Adhikari, Benu , Sun, Jincai
  • Date: 2015
  • Type: Text , Journal article
  • Relation: International Journal of Refrigeration Vol. 57, no. (2015), p. 11-25
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  • Description: Abstract This paper presents a comprehensive review of recent developments in thermal (radio frequency, microwave and ohmic), non-thermal (high pressure, ultrasound and infrared) methods in blanching pretreatment. Recent developments in quick freezing technology (high pressure, dehydrofreezing and ultrasound-assisted) as applied to freezing of fruits and vegetables are also reviewed. The thermal and non-thermal blanching methods provide rapid and uniform heating; reduce the loss of soluble nutrients and minimize thermal damage compared to conventional hot water blanching. High pressure freezing seems to promote instantaneous and homogeneous ice nucleation in fruits and vegetables. Dehydrofreezing is capable of reducing the damage to plant texture by removal partial of water before freezing. Ultrasound-assisted freezing is found to be effective in the initiation of nuclei and subsequent growth of crystals. More fundamental researches are needed for better design and scale up, so that these technologies can be transferred from laboratory to industry. © 2015 Elsevier Ltd and IIR.

SBFEM for fracture analysis of piezoelectric composites under thermal load

- Li, Chao, Ooi, Ean Tat, Song, Chongmin, Natarajan, Sundararajan

  • Authors: Li, Chao , Ooi, Ean Tat , Song, Chongmin , Natarajan, Sundararajan
  • Date: 2015
  • Type: Text , Journal article
  • Relation: International Journal of Solids and Structures Vol. 52, no. 1 (2015), p. 114-129
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  • Description: This paper extends a semi-analytical technique, the so-called scaled boundary finite element method (SBFEM), to analyze fracture behaviors of piezoelectric materials and piezoelectric composites under thermal loading. In this method, only the boundary is discretized leading to a reduction of the spatial dimension by one. The temperature field in the domain is obtained using the SBFEM and expressed as a series of power functions of the radial coordinate. The resulting stress and electric displacement distribution along the radial direction is represented analytically. This permits the generalized stress and electric displacement intensity factors to be directly evaluated from the solution by following standard stress recovery procedures in the finite element method (FEM). Numerical examples are presented to verify the proposed technique with the analytical solutions and the results from the literature. The present results highlight the accuracy, simplicity and efficiency of the proposed technique. © 2014 Elsevier Ltd.

Stable isotopes as indicators of water and salinity sources in a southeast Australian coastal wetland: Identifying relict marine water, and implications for future change

- Currell, Matthew, Dahlhaus, Peter, Ii, Hiroyuki

The impact performance of headguards for combat sports

- McIntosh, Andrew, Patton, Declan

  • Authors: McIntosh, Andrew , Patton, Declan
  • Date: 2015
  • Type: Text , Journal article
  • Relation: British Journal of Sports Medicine Vol. 49, no. 17 (2015), p. 1113-1117
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  • Description: Background/aim: To assess the impact energy attenuation performance of a range of headguards for combat sports. Methods: Seven headguards worn during combat sport training or competition, including two Association Internationale de Boxe Amateur (AIBA)-approved boxing models, were tested using drop tests. An International Organization for Standardization (ISO) rigid headform was used with a 5.6 kg drop assembly mass. Tests were conducted against a flat rigid anvil both with and without a boxing glove section. The centre forehead and lateral headguard areas were tested. Peak headform acceleration was measured. Tests from a selection of drop heights and repeated tests on the same headguard were conducted. Results: Headguard performance varied by test condition. For the 0.4 m rigid anvil tests, the best model headguard was the thickest producing an average peak headform acceleration over 5 tests of 48 g compared with 456 g for the worst model. The mean peak acceleration for the 0.4, 0.5 and 0.6 frontal and lateral rigid anvil impact tests was between 32% and 40% lower for the Top Ten boxing model compared with the Adidas boxing model. The headguard performance deterioration observed with repeat impact against the flat anvil was reduced for impacts against the glove section. The overall reduction in acceleration for the combination of glove and headguard in comparison to the headguard condition was in the range of 72-93% for 0.6 and 0.8 m drop tests. Conclusions: The impact tests show the benefits of performance testing in identifying differences between headguard models.

Vibration spectrum imaging : A novel bearing fault classification approach

- Amar, Muhammad, Gondal, Iqbal, Wilson, Campbell

  • Authors: Amar, Muhammad , Gondal, Iqbal , Wilson, Campbell
  • Date: 2015
  • Type: Text , Journal article
  • Relation: IEEE Transactions on Industrial Electronics Vol. 62, no. 1 (2015), p. 494-502
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  • Description: Incipient fault detection in low signal-to-noise ratio (SNR) conditions requires robust features for accurate condition-based machine health monitoring. Accurate fault classification is positively linked to the quality of features of the faults. Therefore, there is a need to enhance the quality of the features before classification. This paper presents a novel vibration spectrum imaging (VSI) feature enhancement procedure for low SNR conditions. An artificial neural network (ANN) has been used as a fault classifier using these enhanced features of the faults. The normalized amplitudes of spectral contents of the quasi-stationary time vibration signals are transformed into spectral images. A 2-D averaging filter and binary image conversion, with appropriate threshold selection, are used to filter and enhance the images for the training and testing of the ANN classifier. The proposed novel VSI augments and provides the visual representation of the characteristic vibration spectral features in an image form. This provides enhanced spectral images for ANN training and thus leads to a highly robust fault classifier.

Virtual and smoothed finite elements : A connection and its application to polygonal/polyhedral finite element methods

- Natarajan, Sundararajan, Bordas, Stéphane, Ooi, Ean Tat

  • Authors: Natarajan, Sundararajan , Bordas, Stéphane , Ooi, Ean Tat
  • Date: 2015
  • Type: Text , Journal article
  • Relation: International Journal for Numerical Methods in Engineering Vol. 104, no. 13 (2015), p. 1173-1199
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  • Description: We show both theoretically and numerically a connection between the smoothed finite element method (SFEM) and the virtual element method and use this approach to derive stable, cheap and optimally convergent polyhedral FEM. We show that the stiffness matrix computed with one subcell SFEM is identical to the consistency term of the virtual element method, irrespective of the topology of the element, as long as the shape functions vary linearly on the boundary. Using this connection, we propose a new stable approach to strain smoothing for polygonal/polyhedral elements where, instead of using sub-triangulations, we are able to use one single polygonal/polyhedral subcell for each element while maintaining stability. For a similar number of degrees of freedom, the proposed approach is more accurate than the conventional SFEM with triangular subcells. The time to compute the stiffness matrix scales with the O(dofs)1.1 in case of the conventional polygonal FEM, while it scales as O(dofs)0.7 in the proposed approach. The accuracy and the convergence properties of the SFEM are studied with a few benchmark problems in 2D and 3D linear elasticity. © 2015 John Wiley & Sons, Ltd.

2D dynamic analysis of cracks and interface cracks in piezoelectric composites using the SBFEM

- Li, Chao, Song, Chongmin, Man, Hou, Ooi, Ean Tat, Gao, Wei

  • Authors: Li, Chao , Song, Chongmin , Man, Hou , Ooi, Ean Tat , Gao, Wei
  • Date: 2014
  • Type: Text , Journal article
  • Relation: International Journal of Solids and Structures Vol. 51, no. 11-12 (June 2014), p. 2096-2108
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  • Description: The dynamic stress and electric displacement intensity factors of impermeable cracks in homogeneous piezoelectric materials and interface cracks in piezoelectric bimaterials are evaluated by extending the scaled boundary finite element method (SBFEM). In this method, a piezoelectric plate is divided into polygons. Each polygon is treated as a scaled boundary finite element subdomain. Only the boundaries of the subdomains need to be discretized with line elements. The dynamic properties of a subdomain are represented by the high order stiffness and mass matrices obtained from a continued fraction solution, which is able to represent the high frequency response with only 3-4 terms per wavelength. The semi-analytical solutions model singular stress and electric displacement fields in the vicinity of crack tips accurately and efficiently. The dynamic stress and electric displacement intensity factors are evaluated directly from the scaled boundary finite element solutions. No asymptotic solution, local mesh refinement or other special treatments around a crack tip are required. Numerical examples are presented to verify the proposed technique with the analytical solutions and the results from the literature. The present results highlight the accuracy, simplicity and efficiency of the proposed technique.

A fast scalable implementation of the two-dimensional triangular discrete element Method on a GPU platform

- Zhang, Ling, Quigley, Steven, Chan, Andrew

  • Authors: Zhang, Ling , Quigley, Steven , Chan, Andrew
  • Date: 2014
  • Type: Text , Journal article
  • Relation: Advances in Engineering Software Vol. 60-61, no. June-July (2014), p. 70-80
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  • Description: Real-time solution of the Discrete Element Method is a computational challenge that is hardly achievable on standard PCs, especially when a large number of triangular shaped particles are involved. This paper presents a scalable architecture, including a domain decomposition technique, of a GPU accelerator for the two-dimensional Discrete Element Method for triangular shaped particles. This approach achieved a speed up of about 140 times as a single core and about 80 after domain decomposition on a consumer level GPU compared to a similar algorithm run on a fast desktop PC.

An analytical approach for voice capacity estimation over WiFi network using ITU-T E-model

- Siddique, Md, Kamruzzaman, Joarder, Hossain, Md Jahangir

  • Authors: Siddique, Md , Kamruzzaman, Joarder , Hossain, Md Jahangir
  • Date: 2014
  • Type: Text , Journal article
  • Relation: IEEE Transactions on Multimedia Vol. 16, no. 2 (2014), p. 360-372
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  • Description: To ensure customer satisfaction and greater market acceptance, voice over Wi-Fi networks must ensure voice quality under various network parameters, configurations and traffic conditions, and other practical effects, e.g., channel noise, and capturing effects. An accurate voice capacity estimation model considering these factors can greatly assist network designers. In the current work, we propose an analytical model to estimate voice over Internet Protocol (VoIP) capacity over Wi-Fi networks addressing these issues. We employ widely used ITU-T E-model to assess voice quality and VoIP call capacity is presented in the form of an optimization problem with voice quality requirement as a constraint. In particular, we analyze delay and loss in channel access and queue, and their impacts on voice quality. The proposed capacity model is first developed for a single hop wireless local area network (WLAN) and then extended for multihop scenarios. To model real network scenario closely, we also consider channel noise and capture effect, and analyze the impacts of transmission range, interference range, and WLAN radius. In absence of any existing call capacity model that considers all the above factors concomitantly, our proposed model will be extremely useful to network designers and voice capacity planners.

Canonical dual solutions to nonconvex radial basis neural network optimization problem

- Latorre, Vittorio, Gao, David

  • Authors: Latorre, Vittorio , Gao, David
  • Date: 2014
  • Type: Text , Journal article
  • Relation: Neurocomputing Vol. 134, no. Special issue (2014), p. 189-197
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  • Description: Radial Basis Functions Neural Networks (RBFNNs) are tools widely used in regression problems. One of their principal drawbacks is that the formulation corresponding to the training with the supervision of both the centers and the weights is a highly non-convex optimization problem, which leads to some fundamental difficulties for the traditional optimization theory and methods. This paper presents a generalized canonical duality theory for solving this challenging problem. We demonstrate that by using sequential canonical dual transformations, the nonconvex optimization problem of the RBFNN can be reformulated as a canonical dual problem (without duality gap). Both global optimal solution and local extrema can be classified. Several applications to one of the most used Radial Basis Functions, the Gaussian function, are illustrated. Our results show that even for a one-dimensional case, the global minimizer of the nonconvex problem may not be the best solution to the RBFNNs, and the canonical dual theory is a promising tool for solving general neural networks training problems. © 2014 Elsevier B.V.

Composite cathode based on doped vanadate enhanced with loaded metal nanoparticles for steam electrolysis

- Li, Yuanxin, Wu, Guojian, Ruan, Cong, Zhou, Qi, Wang, Yan, Doherty, Winston, Xie, Kui, Wu, Yucheng

  • Authors: Li, Yuanxin , Wu, Guojian , Ruan, Cong , Zhou, Qi , Wang, Yan , Doherty, Winston , Xie, Kui , Wu, Yucheng
  • Date: 2014
  • Type: Text , Journal article
  • Relation: Journal of Power Sources Vol. 253, no. (2014), p. 349-359
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  • Description: The use of composite electrodes based on La0.7Sr 0.3VO3 (LSV) for steam electrolysis has uncovered the tremendous potential and capacity inherent in this material. Unfortunately, this material has a major setback of inefficient electrolysis triggered by limited electrocatalytic activity. In this work, an infiltration method is employed to load catalytic-active metal nanoparticles onto the composite electrodes in order to achieve an activity-enhanced electrode performance. The electrical properties of LSV are methodically explored and correlated to electrode performance. At 800 C in either pure H2 or low hydrogen partial pressure (pH2) of 5%H2/N2, the polarization resistance of symmetrical cells with Ni-loaded LSV (LSV-Ni) cathode is largely enhanced, in contrast to bare LSV cathode. Similar improvement is also achieved for the Fe-loaded LSV (LSV-Fe) cathode in a wide range of hydrogen partial pressures of 5%-100%. The Faraday efficiencies of LSV-Ni and LSV-Fe composite cathodes were remarkably improved for electrolysis in either 3%H 2O/4.7H2/Ar or 3%H2O/Ar at 800 C. © 2013 Elsevier B.V. All rights reserved.

Convergence and accuracy of displacement based finite element formulations over arbitrary polygons: Laplace interpolants, strain smoothing and scaled boundary polygon formulation

- Natarajan, Sundararajan, Ooi, Ean Tat, Chiong, Irene, Song, Chongmin

  • Authors: Natarajan, Sundararajan , Ooi, Ean Tat , Chiong, Irene , Song, Chongmin
  • Date: 2014
  • Type: Text , Journal article
  • Relation: Finite Elements in Analysis and Design Vol. 85, no. (August 2014 2014), p. 101-122
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  • Description: Three different displacement based finite element formulations over arbitrary polygons are studied in this paper. The formulations considered are the conventional polygonal finite element method (FEM) with Laplace interpolants, the cell-based smoothed polygonal FEM with simple averaging technique and the scaled boundary polygon formulation. For the purpose of numerical integration, we employ the sub-triangulation for polygonal FEM and classical Gaussian quadrature for the smoothed FEM and the scaled boundary polygon formulation. The accuracy and the convergence properties of these formulations are studied with a few benchmark problems in the context of linear elasticity and the linear elastic fracture mechanics. The extension of scaled boundary polygon to higher order polygons is also discussed.

Deformation of "tunable" clay-polymer composites

- Bishop, Matthew, Kim, Sungho, Palomino, Angelica, Lee, Jong-Sub

  • Authors: Bishop, Matthew , Kim, Sungho , Palomino, Angelica , Lee, Jong-Sub
  • Date: 2014
  • Type: Text , Journal article
  • Relation: Applied Clay Science Vol. 101, no. (2014), p. 265-271
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  • Description: Responsive clay-polymer composites are the next step in the development of polymer-modified clay materials. It has been shown at the micro-scale that these materials respond to the surrounding pore fluid environment, resulting in an alteration in fabric. The purpose of this study is to investigate the impact of the responsive nature of these materials on the consolidation properties. Two composite types were selected to highlight the differences based on modified interparticle and interparticle/interlayer spacings: one made from a kaolinite and one from a montmorillonite. Each composite was made with polyacrylamide as the polymer. The clay-polymer composites were subjected to 1-D consolidation tests during which shear wave velocity was also measured. The pH of the saturating fluid was varied to promote composite response. Results show that the compressibility, compression index, and swelling index of the composite materials are greater than the untreated clay materials. Furthermore, these properties are pH-dependent for both types of composite materials and are consistent with the long-term conformational behavior of PAM. This apparent observation confirms that the behavior of the clay-PAM composites is controlled by the behavior of PAM. On the other hand, the shear wave velocities between the control and composite samples were not significantly different. © 2014 Elsevier B.V.

Distributed proximal-gradient method for convex optimization with inequality constraints

- Li, Jueyou, Wu, Changzhi, Wu, Zhiyou, Long, Qiang, Wang, Xiangyu

  • Authors: Li, Jueyou , Wu, Changzhi , Wu, Zhiyou , Long, Qiang , Wang, Xiangyu
  • Date: 2014
  • Type: Text , Journal article
  • Relation: ANZIAM Journal Vol. 56, no. 2 (2014), p. 160-178
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  • Description: We consider a distributed optimization problem over a multi-agent network, in which the sum of several local convex objective functions is minimized subject to global convex inequality constraints. We first transform the constrained optimization problem to an unconstrained one, using the exact penalty function method. Our transformed problem has a smaller number of variables and a simpler structure than the existing distributed primal-dual subgradient methods for constrained distributed optimization problems. Using the special structure of this problem, we then propose a distributed proximal-gradient algorithm over a time-changing connectivity network, and establish a convergence rate depending on the number of iterations, the network topology and the number of agents. Although the transformed problem is nonsmooth by nature, our method can still achieve a convergence rate, O (1/k), after k iterations, which is faster than the rate, O (1/k), of existing distributed subgradient-based methods. Simulation experiments on a distributed state estimation problem illustrate the excellent performance of our proposed method. Copyright © 2014 Australian Mathematical Society.

Double protection drilling fluid : Optimization for sandstone-like uranium formation

- Hao, Shu-Qing, Kim, Sungho, Qin, Yong, Fu, Xue-Hai

  • Authors: Hao, Shu-Qing , Kim, Sungho , Qin, Yong , Fu, Xue-Hai
  • Date: 2014
  • Type: Text , Journal article
  • Relation: Applied Clay Science Vol. 88-89, no. (2014), p. 233-238
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  • Description: Nuclear energy, an alternative for fossil fuel, is accompanied by the excavation of uranium ores and in turn the use of drilling fluids. Thus, the objective of this study was to optimize the formula of drilling fluid for sandstone-like uranium formation representing the Xinjiang's Yili Basin uranium formation in China. Additives such as Na2CO3, potassium humate (KHM), sodium carboxymethyl cellulose (Na-CMC), and vegetable gum (VG) were introduced to montmorillonite (Mt) slurry to maximize the performance of drilling fluid in terms of rheological behavior and filtration characteristics. Orthogonal testing, soaking test, and pressure-bearing test were conducted to find the optimum formula of drilling fluid. The maximized performance was achieved with a drilling fluid consisting of 4% Mt, 1.6% Na2CO3, 0.1% KHM, 1.5% Na-CMC, and 0.5% VG. The lowest density and water loss, with a sufficiently high viscosity were achieved with this concentration combination of each additive. Soaking and pressure-bearing tests exhibited no visual changes of a specimen treated with the drilling fluid, which confirmed the result of optimization. © 2013 Elsevier B.V.

Drying and denaturation characteristics of α-LACTALBUMIN, β-lactoglobulin, and bovine serum albumin in a convective drying process

- Haque, M. Amdadul, Aldred, Peter, Chen, Jie, Barrow, Colin, Adhikari, Benu

  • Authors: Haque, M. Amdadul , Aldred, Peter , Chen, Jie , Barrow, Colin , Adhikari, Benu
  • Date: 2014
  • Type: Text , Journal article
  • Relation: Journal of Agricultural and Food Chemistry Vol. 62, no. 20 (2014), p. 4695-4706
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  • Description: Drying and denaturation kinetics of aqueous droplets of α-lactalbumin (α-lac), β-lactoglobulin (β-lg), and bovine serum albumin (BSA) were measured in a convective drying environment. Single droplets having an initial droplet diameter of 2 ± 0.1 mm and containing 10% (w/v) protein concentration were dried using conditioned air (65 and 80 °C, 2-3% RH, 0.5 m/s velocity) for 600 s. The denaturation of these proteins was measured by using reversed-phase HPLC. At the end of 600 s of drying 13.3 and 19.4% α-lac was found to be lost due to denaturation at 65 and 80 °C, respectively. Up to 31.0% of β-lg was found to be denatured, whereas BSA was not found to be significantly (p > 0.05) denatured in these drying conditions. The formation and strength of skin and the associated morphological features were found to be linked with the degree of denaturation of these proteins. The secondary structure of these proteins was significantly (p < 0.05) affected and altered by the drying stresses. The β-sheet and random coil contents were increased in α-lac by 6.5 and 4.0%, respectively, whereas the α-helix and β-turn contents decreased by 5.5 and 5.0%, respectively. The β-sheet and random coil contents in β-lg were increased by 7.5 and 2.0%, respectively, whereas the α-helix and β-turn contents decreased by 3.5 and 6.0%, respectively. In the case of BSA the β-sheet, α-helix, and random coil contents were found to increase, whereas the β-turn content decreased. © 2014 American Chemical Society.

From zero to hero. A case study of industrial injury reduction : New Zealand Aluminium Smelters Limited

- Young, Stephen

  • Authors: Young, Stephen
  • Date: 2014
  • Type: Text , Journal article
  • Relation: Safety Science Vol. 64, no. (2014), p. 99-108
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  • Description: There is a need to pursue more evidence to support the zero accident vision (ZAV). New Zealand Aluminium Smelters Limited (NZAS) has been operating under a ZAV for more than two decades and now consistently has fewer than ten lost-time injuries (LTI) per annum. While the ZAV has not been fully realised, NZAS is now one of the safest heavy industrial worksites in the world. This mixed method case study substantiates the significant reduction in LTIs and describes the interventions used to achieve the improvement. The interventions are rated using a hazard intervention effectiveness matrix and by contextualising their apparent efficacy within the available literature. The NZAS ZAV achievement is further analysed using goal theory. The study concludes by attributing NZAS' relative success to an assiduous application of hierarchy of control methodology with a particularly strong ergonomic focus. © 2013.

One, two, three or four: Does the number of Clegg hammer drops alter ground hardness readings on natural grass?

- Twomey, Dara, Ullah, Shahid, Petrass, Lauren

  • Authors: Twomey, Dara , Ullah, Shahid , Petrass, Lauren
  • Date: 2014
  • Type: Text , Journal article
  • Relation: Proceedings of the Institution of Mechanical Engineers, Part P: Journal of Sports Engineering and Technology Vol. 228, no. 1 (2014), p. 33-39
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  • Description: The Clegg hammer is currently used to measure hardness of natural turf surfaces to inform performance and safety decisions. However, the number of Clegg hammer drops reported in natural grass testing varies from one to four drops, and the impact of the choice of the number of drops is unknown. The aim of this article is to determine whether significant differences exist between the four Clegg hammer drops on natural grass across a variety of conditions. Hardness readings (using a 2.25 kg Clegg hammer), soil moisture and botanical composition were recorded at nine different sites on seven football fields during an 18-week playing season. A total of 1255 hardness readings were collected for each of four consecutive Clegg hammer drops. Overall, there were significant differences between drop 1 and the other three consecutive drops, on all fields and on all sites. Deep soil moisture was the only factor that significantly influenced the hardness readings. The results of this study demonstrate that the decision regarding the number of drops recorded needs careful consideration as conclusions drawn on playability of a ground or the association with injury risk may vary considerably depending on the number of drops. © 2013 IMechE.