Principles for use of ball projection machines in elite and developmental sport programmes

Use of ball projection machines in the acquisition of interceptive skill has recently been questioned. The use of projection machines in developmental and elite fast ball sports programmes is not a trivial issue, since they play a crucial role in reducing injury incidence in players and coaches. A compelling challenge for sports science is to provide theoretical principles to guide how and when projection machines might be used for acquisition of ball skills and preparation for competition in developmental and elite sport performance programmes. Here, we propose how principles from an ecological dynamics theoretical framework could be adopted by sports scientists, pedagogues and coaches to underpin the design of interventions, practice and training tasks, including the use of hybrid video-projection technologies. The assessment of representative learning design during practice may provide ways to optimize developmental programmes in fast ball sports and inform the principled use of ball projection machines.

Congo Red adsorption by ball-milled sugarcane bagasse

The adsorption of Congo Red (CR) by ball-milled sugarcane bagasse was evaluated in an aqueous batch system. CR adsorption capacity increased significantly with small changes in bagasse surface area. CR removal decreased with increasing solution pH from 5.0 to 10.0. Maximum adsorption capacity was 38.2 mg/g bagasse at a CR concentration of 500 mg/L. The equilibrium isotherm fitted the Freundlich model and the adsorption kinetics obeyed pseudo-second order equation. CR adsorption obeyed the intra-particle diffusion model very well with bagasse surface area in the range of 0.58–0.66 m2/g, whereas it was controlled by multi-adsorption stages with bagasse surface area in the range of 1.31–1.82 m2/g. Thermodynamic analysis indicated that the adsorption process is an exothermic and spontaneous process. Fourier transform infrared analysis of bagasse containing adsorbed CR indicated interactions between the carboxyl and hydroxyl groups of bagasse and CR function groups.

Centrifuging rotary vacuum filter mud at Tully Mill

Disposal of mud and ash, particularly in wet weather conditions, is a significant expense for mills. This paper reports on one part of a process to pelletise mud and ash, aimed at making mud and ash more attractive to growers across entire mill districts. The full process is described in a separate paper. The part described in this paper involves re-constituting mud cake from the filter station at Tully Mill and processing it in a decanter centrifuge. The material produced by re-constituting and centrifuging is drier and made up of separate particles. The material needs to mix easily with boiler ash, and the mixture needs to be fed easily into a flue gas drier to be dried to low moisture. The results achieved with the particular characteristics of Tully Mill rotary vacuum filter cake are presented. It was found that an internal rotor with a 20º beach was not adequate to process re-constituted rotary vacuum filter mud. A rotor with a 10º beach worked much more successfully. A total of four tonnes of centrifuged mud with a moisture content ranging from 60% to 65% was produced. It was found that the torque, flocculant rate and dose rate had a statistically significant effect on the moisture content. Feed rate did not have a noticeable impact on the moisture content by itself but torque had a much larger impact on the moisture content at the low feed rate than at the high feed rate. These results indicated that the moisture content of the mud can most likely be reduced with low feed rate, low flocculant rate, high dose rate and high torque. One issue that is believed to affect the operation of a decanter centrifuge was the large quantity of long bagasse fibres in the rotary vacuum filter mud. It is likely that the long fibres limited the throughput of the centrifuge and the moisture achieved.

Interacting constraints of defensive pressure and ball displacement trajectories shape locomotor pointing behaviours in association football

Performance of locomotor pointing tasks (goal-directed locomotion) in sport is typically constrained by dynamic factors, such as positioning of opponents and objects for interception. In the team sport of association football, performers have to coordinate their gait with ball displacement when dribbling and when trying to prevent opponent interception when running to kick a ball. This thesis comprises two studies analysing the movement patterns during locomotor pointing of eight experienced youth football players under static and dynamic constraints by manipulating levels of ball displacement (ball stationary or moving) and defensive pressure (defenders absent, or positioned near or far during performance). ANOVA with repeated measures was used to analyse effects of these task constraints on gait parameters during the run-up and cross performance sub-phase. Experiment 1 revealed outcomes consistent with previous research on locomotor pointing. When under defensive pressure, participants performed the run-up more quickly, concurrently modifying footfall placements relative to the ball location over trials. In experiment 2 players coordinated their gait relative to a moving ball significantly differently when under defensive pressure. Despite no specific task instructions being provided beforehand, context dependent constraints interacted to influence footfall placements over trials and running velocity of participants in different conditions. Data suggest that coaches need to manipulate task constraints carefully to facilitate emergent movement behaviours during practice in team games like football.

A genealogy of calculations at an early Queensland sugar mill

This study of a unique historic situation is sociologically framed and politically contextualized. It examines the technical and persuasive rhetorical dimensions of calculations employed at a nineteenth-century Queensland sugar plantation and mill in relation to the employment of indentured labour. Historical archival data is interpreted through the lens of the rhetoric of rationality. Queensland legislation permitted the employment of indentured Pacific islanders to assist in the development of its sugar industry. Accounting practices employed at the Colonial Sugar Refinery (CSR) Company’s Goondi Plantation and Mill focused on recording and controlling labour costs to maximize profits and maintain a healthy dividend to shareholders. The use of this single perspective, while it provides a restricted interpretation of events, nevertheless enables some unique insights about the practice of accounting in this historic context.

A mill design concept for reducing bagasse moisture

This paper describes the development and testing of a novel mill design to reduce the moisture content of bagasse. It takes advantage of gravity to separate juice from bagasse by pushing bagasse upwards while juice drains downwards under gravity. The potential of the design to reduce bagasse moisture content has not been adequately established. The prototype mill had limited power available that prevented typical delivery nip compactions from being achieved. Tests conducted did show a reduction in bagasse moisture but that moisture reduction is less than expected under ideal conditions. Work on the mill design has ceased, at least for the foreseeable future. The design does have potential to reduce bagasse moisture content but presents some engineering challenges to establish a reliable, low maintenance design alternative.

An enhanced mill extraction model

An enhanced mill extraction model has been developed to calculate mill performance parameters and to predict the extraction performance of a milling unit. The model takes into account the fibre suspended in juice streams and calculates filling ratio, reabsorption factor, imbibition coefficient, and separation efficiency using more complete definitions than those used in previous extraction models. A mass balance model is used to determine the fibre, brix and moisture mass flows between milling units so that a complete milling train, including the return stream from the juice screen, is modelled. Model solutions are presented to determine the effect of different levels of fibre in juice and efficiency of fibre separation in the juice screen on brix extraction. The model provides more accurate results than earlier models leading to better understanding and improvement of the milling process.

The effect of mill orientation angle on bagasse moisture content

THIS PAPER DESCRIBES an experimental investigation to explore a concept designed to reduce the moisture content of bagasse. It takes advantage of gravity to separate juice from bagasse by feeding bagasse upwards into the nip of the mill while juice drains downwards under gravity. The investigation found that orienting the feed to a mill upwards does reduce bagasse moisture content and that the benefit is expected to be greater than two units of moisture. While an advantage was found in orienting the feed up to 50° above the horizontal, no extra benefit was found in increasing the angle higher (up to 60° was explored) and so a 50° orientation was identified as the preferred angle for this design concept.

Mixing and drying mud and ash at Tully Mill

Disposal of mud and ash, particularly in wet weather conditions, is a significant expense for mills. This paper reports on part of a process to pelletise mud and ash, aimed at making mud and ash more attractive to growers across entire mill districts. The full process and the re-constituting and centrifuging rotary vacuum filter mud part of the process were described in two papers to the 2011 conference. The component described in this paper involves aspects of mixing mud and ash with subsequent drying using boiler exit gas. The mud material needs to mix easily with boiler ash and the mixture has to feed easily into and be pneumatically conveyed by a flue gas dryer. The performance of a pilot flue gas dryer for drying mud and ash was evaluated. The mud and ash mixture was found to dry much faster than final bagasse, provided the mud and ash material was broken up into individual particles. A previously developed computer model of bagasse drying was updated to take into account the smaller particle size of the mud and ash mixture. This upgraded model predicted the performance of the pilot flue gas dryer well.

Attunement to haptic information helps skilled performers select implements for striking a ball in cricket

This study examined the perceptual attunement of relatively skilled individuals to physical properties of striking implements in the sport of cricket. We also sought to assess whether utilising bats of different physical properties influenced performance of a specific striking action: the front foot straight drive. Eleven, skilled male cricketers (mean age = 16.6 ± 0.3 years) from an elite school cricket development programme consented to participate in the study. Whist blindfolded, participants wielded six bats exhibiting different mass and moment of inertia (MOI) characteristics and were asked to identify their three most preferred bats for hitting a ball to a maximum distance by performing a front foot straight drive (a common shot in cricket). Next, participants actually attempted to hit balls projected from a ball machine using each of the six bat configurations to enable kinematic analysis of front foot straight drive performance with each implement. Results revealed that, on first choice, the two bats with the smallest mass and MOI values (1 and 2) were most preferred by almost two-thirds (63.7%) of the participants. Kinematic analysis of movement patterns revealed that bat velocity, step length and bat-ball contact position measures significantly differed between bats. Data revealed how skilled youth cricketers were attuned to the different bat characteristics and harnessed movement system degeneracy to perform this complex interceptive action.

Effects of rice husk biochar and sugar-mill by-products on methane consumption from two different soils

Methane (CH4) is an important greenhouse gas with a global warming potential (GWP) 25 times greater than carbon dioxide (CO2) that can be produced or consumed in soils depending on environmental conditions and other factors. Biochar application to soils has been shown to reduce CH4 emissions and to increase CH4 consumption. However, the effects of rice husk biochar (RB) have not been thoroughly investigated. Two 60-day laboratory incubation experiments were conducted to investigate the effects of amending two soil types with RB, raw mill mud (MM) and composted mill mud (CM) on soil CH4 consumption and emissions. Soil cores incubated in 1 L glass jars and gas samples were analysed for CH4 using gas chromatography. Average CH4 consumption rates varied from -0.06 to -0.68 g CH4-C( )/ha/d in sandy loam soil and -0.59 to -1.00 g CH4-C/ha/d in clay soil. Application of RB resulted in CH4 uptake of -0.52 to -0.55 g CH4-C/ha/d in sandy loam and -0.76 to -0.91 g CH4-C/ha/d in clay soil. Addition of MM showed low CH4 emissions or consumption at 60% water-filled pore space (WFPS) in both soils. However, at high water contents (>75% WFPS) the application of MM produced high rates of CH4 emissions which were significantly suppressed when RB was added. Cumulative emissions of the MM treatment produced 108.9 g CH4-C/ha at 75% WFPS and 11 459.3 g CH4-C/ha at 90% WFPS in sandy loam soil over a period of 60 days. RB can increase CH4 uptake under low soil water content (SWC) and decrease CH4 emissions under anaerobic conditions. CM expressed more potential to reduce CH4 emissions than those of MM.

Modelling the flow of juice through a mill

A juice flow model has been developed to estimate the juice expression at the four nips of a sixroller mill. An extended volumetric theory was applied to determine the juice expressed at each nip. The model was applied to a first and final mill, using typical mill settings and an empirical equation to estimate reabsorption. Results of using the model for typical heavy-duty pressure feeder settings show that most of the juice is expressed at the pressure feeder nip. Since the pressure feeders are remote from the mill, a significant portion of the juice is expressed before the bagasse enters the mill.

Effects of a defender on run-up velocity and ball speed when crossing a football

This study evaluated effects of defensive pressure on running velocity in footballers during the approach to kick a stationary football. Approach velocity and ball speed/accuracy data were recorded from eight football youth academy participants (15.25, SD=0.46 yrs). Participants were required to run to a football to cross it to a receiver to score against a goal-keeper. Defensive pressure was manipulated across three counterbalanced conditions: defender-absent (DA); defender-far (DF) and defender-near (DN). Pass accuracy (percentages of a total of 32 trials with 95% confidence limits in parenthesis) did not significantly reduce under changing defensive pressure: DA, 78% (55–100%); DF, 78% (61–96%); DN, 59% (40–79%). Ball speed (m·s−1) significantly reduced as defensive pressure was included and increased: DA, 23.10 (22.38–23.83); DF, 20.40 (19.69–21.11); DN, 19.22 (18.51–19.93). When defensive pressure was introduced, average running velocity of attackers did not change significantly: DA versus DF (m·s−1), 5.40 (5.30–5.51) versus 5.41 (5.34–5.48). Scaling defender starting positions closer to the start position of the attacker (DN) significantly increased average running velocity relative to the DA and DF conditions, 5.60 (5.50–5.71). In the final approach footfalls, all conditions significantly differed: DA, 5.69 (5.35–6.03); DF, 6 .22 (5.93–6.50); DN, 6.52 (6.23–6.80). Data suggested that approach velocity is constrained by both presence and initial distance of the defender during task performance. Implications are that the expression of kicking behaviour is specific to a performance context and some movement regulation features will not emerge unless a defender is present as a task constraint in practice.

Not just another ball game : young adult and adult football fictions are different

Current media attention on the crossover novel highlights the increasing permeability of the boundaries between young adult and adult fiction. This paper will focus upon some of the difficulties around definitions of young adult fiction before considering the fiction of football, or soccer as it is more commonly known in Australia. The football genre exhibits a number of discrete and identifiable differences between young adult and adult readerships including, for example, the role of the protagonist, and the narrative’s distance from the game. This paper will use Franco Moretti’s Mapping as Distant Reading model of abstraction to highlight and unpack these and other characteristic differences in the narratological and stylistic techniques employed across adult and young adult texts. Close reading analysis of the adult football fiction Striker (1992) by Hunter Davies and young adult football fiction Lucy Zeezou’s Goal (2008) by Liz Deep-Jones’ will further illustrate the range of tensions and divergences as they are reflected across those readerships. The texts have been selected because they speak to themes of fear and safety; Joe Swift (Striker) is driven by a need to move away from childhood poverty and insecurity, while Lucy Zeezou shelters a homeless friend. With both protagonists being kidnapped for ransom for example, the texts have also been selected for their striking similarities in form and content.

Engineering the surface of a sugarcane roller mill roll for grip and durability

Roller mills are typically used to crush sugarcane to express the juice from which sugar is manufactured. The mill rolls need to provide sufficient grip to ensure minimal sliding of the sugarcane along the roll surface. The rolls are subject to pressures up to 55 MPa from the sugarcane bagasse (as the sugarcane is called after first being crushed between a pair of rolls). The insoluble component of sugarcane includes typically 10% ash that largely originates from soil that is harvested with the cane. The sugarcane juice is acidic with pH typically between 5.0 and 5.5. As a result of ash and juice, the mill rolls are subjected to a range of abrasive and corrosive wear mechanisms. Solutions to provide grip and resist wear involve the selection of an appropriate roll shell material and compatible hard facing to provide the desired grip and wear characteristics. This paper reviews the various solutions that have been adopted for grip and durability for mill rolls and highlights the advantages and disadvantages of each method.