Analysis of design of pure ethanol engines
- Authors: Boretti, Alberto
- Date: 2010
- Type: Text , Conference paper
- Relation: Paper presented at International Powertrains, Fuels & Lubricants Meeting 2010, Rio De Janeiro, Brazil : 5th-7th May 2010 p. 1-13
- Full Text:
- Description: Ethanol, unlike petroleum, is a renewable resource that can be produced from agricultural feed stocks. Ethanol fuel is widely used by flex-fuel light vehicles in Brazil and as oxygenate to gasoline in the United States. Ethanol can be blended with gasoline in varying quantities up to pure ethanol (E100), and most modern gasoline engines well operate with mixtures of 10% ethanol (E10). E100 consumption in an engine is higher than for gasoline since the energy per unit volume of ethanol is lower than for gasoline. The higher octane number of ethanol may possibly allow increased power output and better fuel economy of pure ethanol engines vs. flexi-fuel engines. High compression ratio ethanol only vehicles possibly will have fuel efficiency equal to or greater than current gasoline engines. The paper explores the impact some advanced technologies, namely downsizing, turbo charging, liquid charge cooling, high pressure direct injection, variable valve actuation may have on performance and emission of a pure ethanol engine. Results of simulations are described in details providing guidelines for development of new dedicated engines.
- Authors: Boretti, Alberto
- Date: 2010
- Type: Text , Conference paper
- Relation: Paper presented at International Powertrains, Fuels & Lubricants Meeting 2010, Rio De Janeiro, Brazil : 5th-7th May 2010 p. 1-13
- Full Text:
- Description: Ethanol, unlike petroleum, is a renewable resource that can be produced from agricultural feed stocks. Ethanol fuel is widely used by flex-fuel light vehicles in Brazil and as oxygenate to gasoline in the United States. Ethanol can be blended with gasoline in varying quantities up to pure ethanol (E100), and most modern gasoline engines well operate with mixtures of 10% ethanol (E10). E100 consumption in an engine is higher than for gasoline since the energy per unit volume of ethanol is lower than for gasoline. The higher octane number of ethanol may possibly allow increased power output and better fuel economy of pure ethanol engines vs. flexi-fuel engines. High compression ratio ethanol only vehicles possibly will have fuel efficiency equal to or greater than current gasoline engines. The paper explores the impact some advanced technologies, namely downsizing, turbo charging, liquid charge cooling, high pressure direct injection, variable valve actuation may have on performance and emission of a pure ethanol engine. Results of simulations are described in details providing guidelines for development of new dedicated engines.
Coupling of a KERS powertrain and a 4 Litre gasoline engine for improved fuel economy in a full size car
- Authors: Boretti, Alberto
- Date: 2010
- Type: Text , Conference paper
- Relation: Paper presented at SAE 2010 Powertrains Fuels & Lubricants Meeting, San Diego, USA : 25th-27th October 2010
- Full Text:
- Description: Improvements of vehicle fuel economy are being considered using a mechanically driven flywheel to reduce the amount of mechanical energy produced by the thermal engine recovering the vehicle kinetic energy during braking. A mechanical system having an overall efficiency over a full regenerative cycle of about 70%, about twice the efficiency of battery-based hybrids, is coupled to a naturally aspirated gasoline engine powering a full size sedan. Results of chassis dynamometer experiments and engine and vehicle simulations are used to evaluate the fuel benefits introducing a kinetic energy recovery system and downsizing of the engine. Preliminary results running the new European driving cycle (NEDC) show KERS may reduce fuel consumption by 25% without downsizing, and 33% with downsizing of the 4 litre engine to 3.3 litres.
- Authors: Boretti, Alberto
- Date: 2010
- Type: Text , Conference paper
- Relation: Paper presented at SAE 2010 Powertrains Fuels & Lubricants Meeting, San Diego, USA : 25th-27th October 2010
- Full Text:
- Description: Improvements of vehicle fuel economy are being considered using a mechanically driven flywheel to reduce the amount of mechanical energy produced by the thermal engine recovering the vehicle kinetic energy during braking. A mechanical system having an overall efficiency over a full regenerative cycle of about 70%, about twice the efficiency of battery-based hybrids, is coupled to a naturally aspirated gasoline engine powering a full size sedan. Results of chassis dynamometer experiments and engine and vehicle simulations are used to evaluate the fuel benefits introducing a kinetic energy recovery system and downsizing of the engine. Preliminary results running the new European driving cycle (NEDC) show KERS may reduce fuel consumption by 25% without downsizing, and 33% with downsizing of the 4 litre engine to 3.3 litres.
Coupling of a KERS power train and a downsized 1.2TDI diesel or a 1.6TDI-JI H2 engine for improved fuel economies in a compact car
- Authors: Boretti, Alberto
- Date: 2010
- Type: Text , Conference paper
- Relation: Paper presented at SAE 2010 Powertrains Fuels & Lubricants Meeting, San Diego, USA : 25th-27th October 2010
- Full Text:
- Description: Recovery of braking energy during driving cycles is the most effective option to improve fuel economy and reduce green house gas (GHG) emissions. Hybrid electric vehicles suffer the disadvantages of the four efficiency reducing transformations in each regenerative braking cycle. Flywheel kinetic energy recovery systems (KERS) may boost this efficiency up to almost double values of about 70% avoiding all four of the efficiency reducing transformations from one form of energy to another and keeping the vehicle's energy in the same form as when the vehicle starts braking when the vehicle is back up to speed. With reference to the baseline configuration with a 1.6 liters engine and no recovery of kinetic energy, introduction of KERS reduces the fuel usage to 3.16 liters per 100 km, corresponding to 82.4 g of CO2 per km. The 1.6 liters Turbo Direct Injection (TDI) Diesel engine without KERS uses 1.37 MJ per km of fuel energy, reducing with KERS to 1.13 MJ per km. Downsizing the engine to 1.2 liters as permitted by the torque assistance by KERS, the fuel consumption is further reduced to 3.04 liters per 100 km, corresponding to 79.2 g of CO2 per km and 1.09 MJ per km of fuel energy. These CO2 and fuel usage values are 11% and 13% better than those of today’s highest fuel economy hybrid electric vehicle. The car equipped with a 1.6 liter Turbo Direct Injection Jet Ignition (TDI-JI) H2ICE engine finally consumes 8.3 g per km of fuel, corresponding to only 0.99 MJ per km of fuel energy.
- Authors: Boretti, Alberto
- Date: 2010
- Type: Text , Conference paper
- Relation: Paper presented at SAE 2010 Powertrains Fuels & Lubricants Meeting, San Diego, USA : 25th-27th October 2010
- Full Text:
- Description: Recovery of braking energy during driving cycles is the most effective option to improve fuel economy and reduce green house gas (GHG) emissions. Hybrid electric vehicles suffer the disadvantages of the four efficiency reducing transformations in each regenerative braking cycle. Flywheel kinetic energy recovery systems (KERS) may boost this efficiency up to almost double values of about 70% avoiding all four of the efficiency reducing transformations from one form of energy to another and keeping the vehicle's energy in the same form as when the vehicle starts braking when the vehicle is back up to speed. With reference to the baseline configuration with a 1.6 liters engine and no recovery of kinetic energy, introduction of KERS reduces the fuel usage to 3.16 liters per 100 km, corresponding to 82.4 g of CO2 per km. The 1.6 liters Turbo Direct Injection (TDI) Diesel engine without KERS uses 1.37 MJ per km of fuel energy, reducing with KERS to 1.13 MJ per km. Downsizing the engine to 1.2 liters as permitted by the torque assistance by KERS, the fuel consumption is further reduced to 3.04 liters per 100 km, corresponding to 79.2 g of CO2 per km and 1.09 MJ per km of fuel energy. These CO2 and fuel usage values are 11% and 13% better than those of today’s highest fuel economy hybrid electric vehicle. The car equipped with a 1.6 liter Turbo Direct Injection Jet Ignition (TDI-JI) H2ICE engine finally consumes 8.3 g per km of fuel, corresponding to only 0.99 MJ per km of fuel energy.
Combining epidemiology and biomechanics in sports injury prevention research : A new approach for selecting suitable controls
- Finch, Caroline, Ullah, Shahid, McIntosh, Andrew
- Authors: Finch, Caroline , Ullah, Shahid , McIntosh, Andrew
- Date: 2011
- Type: Text , Journal article
- Relation: Sports Medicine Vol. 41, no. 1 (2011), p. 59-72
- Relation: http://purl.org/au-research/grants/nhmrc/565900
- Full Text:
- Reviewed:
- Description: Several important methodological issues need to be considered when designing sports injury case-control studies. Major design goals for case-control studies include the accounting for prior injury risk exposure, and optimal definitions of both cases and suitable controls are needed to ensure this. This article reviews methodological aspects of published sports injury case-control studies, particularly with regard to the selection of controls. It argues for a new approach towards selecting controls for case-control studies that draws on an interface between epidemiological and biomechanical concepts. A review was conducted to identify sport injury case-control studies published in the peer-review literature during 1985-2008. Overall, 32 articles were identified, of which the majority related to upper or lower extremity injuries. Matching considerations were used for control selection in 16 studies. Specific mention of application of biomechanical principles in the selection of appropriate controls was absent from all studies, including those purporting to evaluate the benefits of personal protective equipment to protect against impact injury. This is a problem because it could lead to biased conclusions, as cases and controls are not fully comparable in terms of similar biomechanical impact profiles relating to the injury incident, such as site of the impact on the body. The strength of the conclusions drawn from case-control studies, and the extent to which results can be generalized, is directly influenced by the definition and recruitment of cases and appropriate controls. Future studies should consider the interface between epidemiological and biomechanical concepts when choosing appropriate controls to ensure that proper adjustment of prior exposure to injury risk is made. To provide necessary guidance for the optimal selection of controls in case-control studies of interventions to prevent sports-related impact injury, this review outlines a new case-control selection strategy that reflects the importance of biomechanical considerations, which ensures that controls are selected based on the presence of the same global injury mechanism as the cases. To summarize, the general biomechanical principles that should apply to the selection of controls in future case-control studies are as follows: (i) each control must have been exposed to the same global injury mechanism as the case, (e.g. head impact, fall onto outstretched arm); and (ii) intrinsic (individual) factors (e.g. age, sex, skill level) that might modify the person's response to the relevant biomechanical loads are adjusted when either selecting the controls or are in the analysis phase. The same considerations for control selection apply to other study designs such as matched cohort studies or case-crossover studies. © 2011 Adis Data Information BV. All rights reserved.
- Authors: Finch, Caroline , Ullah, Shahid , McIntosh, Andrew
- Date: 2011
- Type: Text , Journal article
- Relation: Sports Medicine Vol. 41, no. 1 (2011), p. 59-72
- Relation: http://purl.org/au-research/grants/nhmrc/565900
- Full Text:
- Reviewed:
- Description: Several important methodological issues need to be considered when designing sports injury case-control studies. Major design goals for case-control studies include the accounting for prior injury risk exposure, and optimal definitions of both cases and suitable controls are needed to ensure this. This article reviews methodological aspects of published sports injury case-control studies, particularly with regard to the selection of controls. It argues for a new approach towards selecting controls for case-control studies that draws on an interface between epidemiological and biomechanical concepts. A review was conducted to identify sport injury case-control studies published in the peer-review literature during 1985-2008. Overall, 32 articles were identified, of which the majority related to upper or lower extremity injuries. Matching considerations were used for control selection in 16 studies. Specific mention of application of biomechanical principles in the selection of appropriate controls was absent from all studies, including those purporting to evaluate the benefits of personal protective equipment to protect against impact injury. This is a problem because it could lead to biased conclusions, as cases and controls are not fully comparable in terms of similar biomechanical impact profiles relating to the injury incident, such as site of the impact on the body. The strength of the conclusions drawn from case-control studies, and the extent to which results can be generalized, is directly influenced by the definition and recruitment of cases and appropriate controls. Future studies should consider the interface between epidemiological and biomechanical concepts when choosing appropriate controls to ensure that proper adjustment of prior exposure to injury risk is made. To provide necessary guidance for the optimal selection of controls in case-control studies of interventions to prevent sports-related impact injury, this review outlines a new case-control selection strategy that reflects the importance of biomechanical considerations, which ensures that controls are selected based on the presence of the same global injury mechanism as the cases. To summarize, the general biomechanical principles that should apply to the selection of controls in future case-control studies are as follows: (i) each control must have been exposed to the same global injury mechanism as the case, (e.g. head impact, fall onto outstretched arm); and (ii) intrinsic (individual) factors (e.g. age, sex, skill level) that might modify the person's response to the relevant biomechanical loads are adjusted when either selecting the controls or are in the analysis phase. The same considerations for control selection apply to other study designs such as matched cohort studies or case-crossover studies. © 2011 Adis Data Information BV. All rights reserved.
Increasing cut surface quality with various cutting nozzle head oscillations for abrasive aquajet machining
- Patel, Keyurkumar, Chen, Frank
- Authors: Patel, Keyurkumar , Chen, Frank
- Date: 2003
- Type: Text , Journal article
- Relation: Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture Vol. 217, no. 7 (2003), p. 1037-1041
- Full Text:
- Reviewed:
- Description: The short paper introduces different nozzle oscillation cutting methods, which are developed using theoretical formulae as well as experimental resources. A comparison study was conducted using different surface texture parameters between a straight cut and different oscillation cutting methods with the same cutting parameters. An optimum oscillation cutting method is suggested. A significant amount of increase in surface quality was obtained.
- Description: C1
- Description: 2003000346
- Authors: Patel, Keyurkumar , Chen, Frank
- Date: 2003
- Type: Text , Journal article
- Relation: Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture Vol. 217, no. 7 (2003), p. 1037-1041
- Full Text:
- Reviewed:
- Description: The short paper introduces different nozzle oscillation cutting methods, which are developed using theoretical formulae as well as experimental resources. A comparison study was conducted using different surface texture parameters between a straight cut and different oscillation cutting methods with the same cutting parameters. An optimum oscillation cutting method is suggested. A significant amount of increase in surface quality was obtained.
- Description: C1
- Description: 2003000346
The limacon of Pascal : mechanical generation and utilization for fluid processing
- Authors: Sultan, Ibrahim
- Date: 2005
- Type: Text , Journal article
- Relation: Proceedings of the Institution of Mechanical Engineers Part C-Journal of Mechanical Engineering Science Vol. 219, no. 8 (Aug 2005), p. 813-822
- Full Text:
- Reviewed:
- Description: The limaçon of Pascal is a plane curve that possesses some characteristics which qualify it for fluid processing applications. However, the curve has not yet attracted enough attention, neither from industry nor from the mechanical engineering research community, despite the few attempts that have been conducted over the past century. The work presented here is intended to explore various mechanical linkages that can be employed to produce the limaçon and the aspects of these linkages. Mathematical analysis will show that machines based on the limaçon curve possess sinusoidal volumetric relationships and hence, simplified pressure and torque equations can be obtained in closed forms. The concepts discussed here will be demonstrated by using a compressor as a sample application
- Description: C1
- Description: 2003001087
Performances of a turbocharged E100 engine with direct injection and variable valve actuation
- Authors: Boretti, Alberto
- Date: 2010
- Type: Text , Conference paper
- Relation: Paper presented at SAE 2010 Powertrains Fuels & Lubricants Meeting, San Diego, USA : 25th-27th October 2010
- Full Text:
- Description: Current flexi fuel gasoline and ethanol engines have brake efficiencies generally lower than a dedicated gasoline engines because of the constraints to accommodate a variable mixture of the two fuels. Considering ethanol has a few advantages with reference to gasoline, namely the higher octane number and the larger heat of vaporization, the paper explores the potentials of dedicated pure ethanol engines using the most advanced techniques available for gasoline engines, specifically direct injection, turbo charging and variable valve actuation. Computations are performed with state-of-the-art, well validated, engine and vehicle performance simulations packages, generally accepted to produce accurate results targeting major trends in engine developments. The higher compression ratio and the higher boost permitted by ethanol allows larger top brake efficiencies than gasoline, while variable valve actuation produces small penalties in efficiency changing the load. Finally, small, high power density, turbo charged, direct injection, variable valve actuation load controlled engines are proved to operate very efficiently over driving cycles.
- Authors: Boretti, Alberto
- Date: 2010
- Type: Text , Conference paper
- Relation: Paper presented at SAE 2010 Powertrains Fuels & Lubricants Meeting, San Diego, USA : 25th-27th October 2010
- Full Text:
- Description: Current flexi fuel gasoline and ethanol engines have brake efficiencies generally lower than a dedicated gasoline engines because of the constraints to accommodate a variable mixture of the two fuels. Considering ethanol has a few advantages with reference to gasoline, namely the higher octane number and the larger heat of vaporization, the paper explores the potentials of dedicated pure ethanol engines using the most advanced techniques available for gasoline engines, specifically direct injection, turbo charging and variable valve actuation. Computations are performed with state-of-the-art, well validated, engine and vehicle performance simulations packages, generally accepted to produce accurate results targeting major trends in engine developments. The higher compression ratio and the higher boost permitted by ethanol allows larger top brake efficiencies than gasoline, while variable valve actuation produces small penalties in efficiency changing the load. Finally, small, high power density, turbo charged, direct injection, variable valve actuation load controlled engines are proved to operate very efficiently over driving cycles.
A numerical control algorithm for navigation of an operator-driven snake-like robot with 4WD-4WS segments
- Authors: Percy, Andrew , Spark, Ian
- Date: 2010
- Type: Text , Journal article
- Relation: Robotica Vol. 29, no. 3 (2010), p. 471-482
- Full Text:
- Reviewed:
- Description: This paper presents a new algorithm for the control of a snake-like robot with passive joints and active wheels. Each segment has four autonomously driven and steered wheels. The algorithm approximates the ideal solution in which all wheels on a segment have the same centre of curvature with wheel speeds, providing cooperative redundancy. Each hitch point joining segments traverses the same path, which is determined by an operator, prescribing the path curvature and front hitch speed. The numerical algorithm developed in this paper is simulation tested against a previously derived analytical solution for a predetermined path. Further simulations are carried out to show the effects of changing curvature and front hitch speed on hitch path, wheel angles and wheel speeds for a one, two and three segment robot.
- Authors: Percy, Andrew , Spark, Ian
- Date: 2010
- Type: Text , Journal article
- Relation: Robotica Vol. 29, no. 3 (2010), p. 471-482
- Full Text:
- Reviewed:
- Description: This paper presents a new algorithm for the control of a snake-like robot with passive joints and active wheels. Each segment has four autonomously driven and steered wheels. The algorithm approximates the ideal solution in which all wheels on a segment have the same centre of curvature with wheel speeds, providing cooperative redundancy. Each hitch point joining segments traverses the same path, which is determined by an operator, prescribing the path curvature and front hitch speed. The numerical algorithm developed in this paper is simulation tested against a previously derived analytical solution for a predetermined path. Further simulations are carried out to show the effects of changing curvature and front hitch speed on hitch path, wheel angles and wheel speeds for a one, two and three segment robot.
Modelling of engine and vehicle for a compact car with a flywheel based kinetic energy recovery systems and a high efficiency small diesel engine
- Authors: Boretti, Alberto
- Date: 2010
- Type: Text , Conference paper
- Relation: Paper presented at SAE 2010 Powertrains Fuels & Lubricants Meeting, San Diego, USA : 25th-27th October 2010
- Full Text:
- Description: Recovery of kinetic energy during driving cycles is the most effective option to improve fuel economy and reduce green house gas (GHG) emissions. Flywheel kinetic energy recovery systems (KERS) may boost this efficiency up to values of about 70%. An engine and vehicle model is developed to simulate the fuel economy of a compact car equipped with a TDI Diesel engine and a KERS. Introduction of KERS reduces the fuel used by the 1.6L TDI engine to 3.16 liters per 100 km, corresponding to 82.4 g of CO2 per km. Downsizing the engine to 1.2 liters as permitted by the torque assistance by KERS, further reduces the fuel consumption to 3.04 liters per 100 km, corresponding to 79.2 g of CO2 per km. These CO2 values are 11% better than those of today’s most fuel efficient hybrid electric vehicle.
- Authors: Boretti, Alberto
- Date: 2010
- Type: Text , Conference paper
- Relation: Paper presented at SAE 2010 Powertrains Fuels & Lubricants Meeting, San Diego, USA : 25th-27th October 2010
- Full Text:
- Description: Recovery of kinetic energy during driving cycles is the most effective option to improve fuel economy and reduce green house gas (GHG) emissions. Flywheel kinetic energy recovery systems (KERS) may boost this efficiency up to values of about 70%. An engine and vehicle model is developed to simulate the fuel economy of a compact car equipped with a TDI Diesel engine and a KERS. Introduction of KERS reduces the fuel used by the 1.6L TDI engine to 3.16 liters per 100 km, corresponding to 82.4 g of CO2 per km. Downsizing the engine to 1.2 liters as permitted by the torque assistance by KERS, further reduces the fuel consumption to 3.04 liters per 100 km, corresponding to 79.2 g of CO2 per km. These CO2 values are 11% better than those of today’s most fuel efficient hybrid electric vehicle.
On the kinematics and synthesis of a geared five-bar slider-crank mechanism
- Sultan, Ibrahim, Kalim, Azfar
- Authors: Sultan, Ibrahim , Kalim, Azfar
- Date: 2011
- Type: Text , Journal article
- Relation: Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science Vol. 225, no. 5 (2011), p. 1253-1261
- Full Text:
- Reviewed:
- Description: The geared five-bar mechanism possesses kinematic abilities that qualify its utility in various industrial applications. Small changes to the mechanism topology or dimensions create new designs with different motion characteristics. This article presents design-orientated kinematical insights and mathematical treatments for the embodiment of the mechanism in which the end gear is eccentrically pivoted to a sliding element. For its synthesis, a kinematic classification is introduced and approximate curves are used to guide the motion of the slider. A gradient-based Levenberg-Marquardt formulation is employed for the optimization procedure. Geometric, mobility, and dimensional constraints are utilized together with numerical position equations for the analysis. Two case studies are presented at the end of this article to highlight the versatility of the mechanism and prove the validity of the presented mathematical model.
- Authors: Sultan, Ibrahim , Kalim, Azfar
- Date: 2011
- Type: Text , Journal article
- Relation: Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science Vol. 225, no. 5 (2011), p. 1253-1261
- Full Text:
- Reviewed:
- Description: The geared five-bar mechanism possesses kinematic abilities that qualify its utility in various industrial applications. Small changes to the mechanism topology or dimensions create new designs with different motion characteristics. This article presents design-orientated kinematical insights and mathematical treatments for the embodiment of the mechanism in which the end gear is eccentrically pivoted to a sliding element. For its synthesis, a kinematic classification is introduced and approximate curves are used to guide the motion of the slider. A gradient-based Levenberg-Marquardt formulation is employed for the optimization procedure. Geometric, mobility, and dimensional constraints are utilized together with numerical position equations for the analysis. Two case studies are presented at the end of this article to highlight the versatility of the mechanism and prove the validity of the presented mathematical model.
Vehicles with cooperative redundant multiple steering systems: Alternative driver interfaces
- Authors: Spark, Ian , Percy, Andrew
- Date: 2015
- Type: Text , Journal article
- Relation: Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering Vol. 229, no. 3 (2015), p. 311-329
- Full Text:
- Reviewed:
- Description: This paper presents the results of calculations of the wheel angles and the drive wheel speeds to ensure that the steering effect of the wheel angles and the steering effect of the speeds of the drive wheels are identical. These calculations are general insofar as the centre of curvature of the path of the centre of the vehicle can lie anywhere in the 'horizontal' plane, including within the plan view of the vehicle. These minimal turning circles at times require large wheel angles and large differences in the drive wheel speeds. When the driver selects a centre of curvature inside the rectangle defined by the wheelbase and the track, problems arise owing to the multiple solutions of the arctan function. This problem is solved so that flipping of the wheels through 180° is avoided. Similar problems can arise in the calculation of the correct wheel speed because of the ambiguity of the square root function, which has both positive and negative roots. This problem is also solved. Alternative driver interfaces are described in detail. Vehicles with cooperative redundant multiple steering systems promise safety benefits relative to vehicles with a single non-redundant steering system and environmental benefits relative to vehicles with conflicting redundant multiple steering systems. The safety benefits result from increased traction, stability and manoeuvrability (especially on hills). The environmental benefits include reduced ground damage, tyre wear and fuel wastage on turning. These vehicles would be used to best advantage as extreme off-road vehicles. The general case of vehicles described is capable of both pure rotation and pure translation in any direction, and all motion in between. This maximized manoeuvrability also makes the system ideal for vehicles operating in confined spaces, such as forklift trucks.
- Authors: Spark, Ian , Percy, Andrew
- Date: 2015
- Type: Text , Journal article
- Relation: Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering Vol. 229, no. 3 (2015), p. 311-329
- Full Text:
- Reviewed:
- Description: This paper presents the results of calculations of the wheel angles and the drive wheel speeds to ensure that the steering effect of the wheel angles and the steering effect of the speeds of the drive wheels are identical. These calculations are general insofar as the centre of curvature of the path of the centre of the vehicle can lie anywhere in the 'horizontal' plane, including within the plan view of the vehicle. These minimal turning circles at times require large wheel angles and large differences in the drive wheel speeds. When the driver selects a centre of curvature inside the rectangle defined by the wheelbase and the track, problems arise owing to the multiple solutions of the arctan function. This problem is solved so that flipping of the wheels through 180° is avoided. Similar problems can arise in the calculation of the correct wheel speed because of the ambiguity of the square root function, which has both positive and negative roots. This problem is also solved. Alternative driver interfaces are described in detail. Vehicles with cooperative redundant multiple steering systems promise safety benefits relative to vehicles with a single non-redundant steering system and environmental benefits relative to vehicles with conflicting redundant multiple steering systems. The safety benefits result from increased traction, stability and manoeuvrability (especially on hills). The environmental benefits include reduced ground damage, tyre wear and fuel wastage on turning. These vehicles would be used to best advantage as extreme off-road vehicles. The general case of vehicles described is capable of both pure rotation and pure translation in any direction, and all motion in between. This maximized manoeuvrability also makes the system ideal for vehicles operating in confined spaces, such as forklift trucks.
A numerical control algorithm for a B-double truck-trailer with steerable trailer wheels and active hitch angles
- Authors: Percy, Andrew , Spark, Ian
- Date: 2012
- Type: Text , Journal article
- Relation: Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering Vol. 226, no. 3 (2012), p. 289-300
- Full Text:
- Reviewed:
- Description: This paper presents a new algorithm for the control of a B-double truck–trailer with steerable trailer wheels and active hitch angles, designed to minimize both off-tracking and scuffing. Each trailer has six autonomously steered double wheels, although each double wheel is modelled by a centrally placed single wheel. Each hitch point, joining truck to first trailer and first trailer to second trailer, as well as a nominated point central to the axles of the second trailer, traverses the same path which is determined by an operator controlling the path curvature and truck speed. The algorithm approximates the ideal solution in which all wheels on each trailer have the same centre of curvature. The actively controlled hitch angles, satisfying the path-following constraints, provide a further level of cooperative redundancy of steering systems. Simulations are carried out to show the effects of changing curvature and front hitch speed on hitch path, wheel angles, and hitch angles as well as the accuracy of the algorithm. Further simulation is carried out to show the improvement in off-tracking of the new control system over current B-double fixed-wheel systems.
- Authors: Percy, Andrew , Spark, Ian
- Date: 2012
- Type: Text , Journal article
- Relation: Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering Vol. 226, no. 3 (2012), p. 289-300
- Full Text:
- Reviewed:
- Description: This paper presents a new algorithm for the control of a B-double truck–trailer with steerable trailer wheels and active hitch angles, designed to minimize both off-tracking and scuffing. Each trailer has six autonomously steered double wheels, although each double wheel is modelled by a centrally placed single wheel. Each hitch point, joining truck to first trailer and first trailer to second trailer, as well as a nominated point central to the axles of the second trailer, traverses the same path which is determined by an operator controlling the path curvature and truck speed. The algorithm approximates the ideal solution in which all wheels on each trailer have the same centre of curvature. The actively controlled hitch angles, satisfying the path-following constraints, provide a further level of cooperative redundancy of steering systems. Simulations are carried out to show the effects of changing curvature and front hitch speed on hitch path, wheel angles, and hitch angles as well as the accuracy of the algorithm. Further simulation is carried out to show the improvement in off-tracking of the new control system over current B-double fixed-wheel systems.
A numerical control algorithm for a B-double truck-trailer with steerable trailer wheels and active hitch angles. Part 2: reversing
- Authors: Percy, Andrew , Spark, Ian
- Date: 2013
- Type: Text , Journal article
- Relation: Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering Vol. 227, no. 6 (2013), p. 899-904
- Full Text:
- Reviewed:
- Description: The authors have previously proposed a solution to the twin problems of wheel scuffing and off-tracking of B-double truck–trailer vehicles thereby reducing tyre wear and environmental damage as well as improving maneuverability. The solution to the scuffing problem requires that trailer axles in excess of one per trailer must have steerable wheels. However, if all trailer wheels are steerable, then the off-tracking problem can also be solved. The previous work devised an algorithm for a B-double in forward motion, whereby an on-board computer would be used to calculate the correct wheel and hitch angles and a control system would implement these angles. The purpose of the present technical note is to complete the study of a numerical algorithm for navigating a B-double truck–trailer vehicle by considering travel in the reverse direction. In this case the angle of the front wheels of the truck must also be controlled by the on-board computer. The algorithm for determining the effective angle of the truck’s steerable wheels is derived using an innovative combination of vector geometry and calculus and completes the total control system for these B-double vehicles. The paper concludes with a simulation study of the control algorithm demonstrating its versatility for reversing along twisting paths and effectiveness in reducing off-tracking.
- Authors: Percy, Andrew , Spark, Ian
- Date: 2013
- Type: Text , Journal article
- Relation: Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering Vol. 227, no. 6 (2013), p. 899-904
- Full Text:
- Reviewed:
- Description: The authors have previously proposed a solution to the twin problems of wheel scuffing and off-tracking of B-double truck–trailer vehicles thereby reducing tyre wear and environmental damage as well as improving maneuverability. The solution to the scuffing problem requires that trailer axles in excess of one per trailer must have steerable wheels. However, if all trailer wheels are steerable, then the off-tracking problem can also be solved. The previous work devised an algorithm for a B-double in forward motion, whereby an on-board computer would be used to calculate the correct wheel and hitch angles and a control system would implement these angles. The purpose of the present technical note is to complete the study of a numerical algorithm for navigating a B-double truck–trailer vehicle by considering travel in the reverse direction. In this case the angle of the front wheels of the truck must also be controlled by the on-board computer. The algorithm for determining the effective angle of the truck’s steerable wheels is derived using an innovative combination of vector geometry and calculus and completes the total control system for these B-double vehicles. The paper concludes with a simulation study of the control algorithm demonstrating its versatility for reversing along twisting paths and effectiveness in reducing off-tracking.
Turnpike theorem for an infinite horizon optimal control problem with time delay
- Authors: Mammadov, Musa
- Date: 2014
- Type: Text , Journal article
- Relation: SIAM Journal on Control and Optimization Vol. 52, no. 1 (2014), p. 420-438
- Full Text:
- Reviewed:
- Description: An optimal control problem for systems described by a special class of nonlinear differential equations with time delay is considered. The cost functional adopted could be considered as an analogue of the terminal functional defined over an infinite time horizon. The existence of optimal solutions as well as the asymptotic stability of optimal trajectories (that is, the turnpike property) are established under some quite mild restrictions on the nonlinearities of the functions involved in the description of the problem. Such mild restrictions on the nonlinearities allowed us to apply these results to a blood cell production model. © 2014 Society for Industrial and Applied Mathematics.
- Authors: Mammadov, Musa
- Date: 2014
- Type: Text , Journal article
- Relation: SIAM Journal on Control and Optimization Vol. 52, no. 1 (2014), p. 420-438
- Full Text:
- Reviewed:
- Description: An optimal control problem for systems described by a special class of nonlinear differential equations with time delay is considered. The cost functional adopted could be considered as an analogue of the terminal functional defined over an infinite time horizon. The existence of optimal solutions as well as the asymptotic stability of optimal trajectories (that is, the turnpike property) are established under some quite mild restrictions on the nonlinearities of the functions involved in the description of the problem. Such mild restrictions on the nonlinearities allowed us to apply these results to a blood cell production model. © 2014 Society for Industrial and Applied Mathematics.
Could targeted exercise programmes prevent lower limb injury in community Australian football?
- Andrew, Nadine, Gabbe, Belinda, Cook, Jill, Lloyd, David, Donnelly, Cyril, Nash, Clare, Finch, Caroline
- Authors: Andrew, Nadine , Gabbe, Belinda , Cook, Jill , Lloyd, David , Donnelly, Cyril , Nash, Clare , Finch, Caroline
- Date: 2013
- Type: Text , Journal article
- Relation: Sports Medicine Vol. 43, no. 8 (2013), p. 751-763
- Relation: http://purl.org/au-research/grants/nhmrc/565900
- Relation: http://purl.org/au-research/grants/nhmrc/565907
- Full Text:
- Reviewed:
- Description: Background: Australian football is a popular sport in Australia, at both the community and elite levels. It is a high-speed contact sport with a higher incidence of medically treated injuries when compared with most other organized sports. Hamstring injuries, ligament injuries to the knee or ankle, hip/groin injuries and tendinopathies are particularly common and often result in considerable time lost from sport. Consequently, the prevention of lower limb injuries is a priority for both community and elite Australian football organizations. There is considerable literature available on exercise programmes aimed at reducing lower limb injuries in Australian football and other running-related sports. The quality and outcomes of these studies have varied considerably, but indicate that exercise protocols may be an effective means of preventing lower limb injuries. Despite this, there has been limited high-quality and systematic evaluation of these data. Objective: The aim of this literature review is to systematically evaluate the evidence about the benefits of lower limb injury prevention exercise protocols aimed at reducing the most common severe lower limb injuries in Australian football. Methods: The Cochrane Central Register of Controlled Trials, the Cochrane Bone Joint and Muscle Trauma Group Specialized Register, MEDLINE and other electronic databases were searched, from January 1990 to December 2010. Papers reporting the results of randomized controlled trials (RCTs), quasi-RCTs, cohort and case-control studies were extracted. Primary outcomes were injury reduction or risk factor identification and/or modification. Secondary outcomes were adherence to any trialled interventions, injury severity and adverse effects such as secondary injuries and muscle soreness. The methodological quality of extracted manuscripts was assessed and results were collated. Results: Forty-seven papers were identified and reviewed of which 18 related to hamstring injury, eight related to knee or ankle ligament injury, five related to tendon injury and four were hip or groin injury related. Another 12 papers targeted general lower limb injuries. Most (n = 27 [57 %]) were observational studies, investigating injury risk factors. Twenty reported the results of intervention trials. Of these, 15 were efficacy trials reporting the effects of an intervention in reducing injury rates, four were biomechanical interventions in which the impact of the intervention on a known injury risk factor was assessed and one reported changes in injury risk factors as well as injury rates. The strength of the evidence base for exercise programmes for lower limb injury prevention was found to be limited, primarily due to the research methods employed, low adherence to interventions by the study participants and a lack of statistical power. Limited evidence obtained from a small number of RCTs suggests that balance and control exercises might be efficacious in preventing ankle ligament injuries and a programme involving a combination of balance and control exercises, eccentric hamstring, plyometrics and strength exercises could be efficacious in preventing all lower limb injuries. Conclusions: Overall, the evidence for exercise programmes as an efficacious lower limb injury prevention strategy is predominantly restricted to studies addressing injury aetiology and mechanisms. The findings of this review highlight the need to develop and test interventions in well designed population-based trials with an emphasis on promoting intervention uptake and adherence and, hence, intervention effectiveness. The results of this review can inform the development of the components of a future lower limb injury prevention exercise protocol for community-level Australian football. © 2013 Springer International Publishing Switzerland. Funded by the NHMRC.
- Description: 2003011215
- Authors: Andrew, Nadine , Gabbe, Belinda , Cook, Jill , Lloyd, David , Donnelly, Cyril , Nash, Clare , Finch, Caroline
- Date: 2013
- Type: Text , Journal article
- Relation: Sports Medicine Vol. 43, no. 8 (2013), p. 751-763
- Relation: http://purl.org/au-research/grants/nhmrc/565900
- Relation: http://purl.org/au-research/grants/nhmrc/565907
- Full Text:
- Reviewed:
- Description: Background: Australian football is a popular sport in Australia, at both the community and elite levels. It is a high-speed contact sport with a higher incidence of medically treated injuries when compared with most other organized sports. Hamstring injuries, ligament injuries to the knee or ankle, hip/groin injuries and tendinopathies are particularly common and often result in considerable time lost from sport. Consequently, the prevention of lower limb injuries is a priority for both community and elite Australian football organizations. There is considerable literature available on exercise programmes aimed at reducing lower limb injuries in Australian football and other running-related sports. The quality and outcomes of these studies have varied considerably, but indicate that exercise protocols may be an effective means of preventing lower limb injuries. Despite this, there has been limited high-quality and systematic evaluation of these data. Objective: The aim of this literature review is to systematically evaluate the evidence about the benefits of lower limb injury prevention exercise protocols aimed at reducing the most common severe lower limb injuries in Australian football. Methods: The Cochrane Central Register of Controlled Trials, the Cochrane Bone Joint and Muscle Trauma Group Specialized Register, MEDLINE and other electronic databases were searched, from January 1990 to December 2010. Papers reporting the results of randomized controlled trials (RCTs), quasi-RCTs, cohort and case-control studies were extracted. Primary outcomes were injury reduction or risk factor identification and/or modification. Secondary outcomes were adherence to any trialled interventions, injury severity and adverse effects such as secondary injuries and muscle soreness. The methodological quality of extracted manuscripts was assessed and results were collated. Results: Forty-seven papers were identified and reviewed of which 18 related to hamstring injury, eight related to knee or ankle ligament injury, five related to tendon injury and four were hip or groin injury related. Another 12 papers targeted general lower limb injuries. Most (n = 27 [57 %]) were observational studies, investigating injury risk factors. Twenty reported the results of intervention trials. Of these, 15 were efficacy trials reporting the effects of an intervention in reducing injury rates, four were biomechanical interventions in which the impact of the intervention on a known injury risk factor was assessed and one reported changes in injury risk factors as well as injury rates. The strength of the evidence base for exercise programmes for lower limb injury prevention was found to be limited, primarily due to the research methods employed, low adherence to interventions by the study participants and a lack of statistical power. Limited evidence obtained from a small number of RCTs suggests that balance and control exercises might be efficacious in preventing ankle ligament injuries and a programme involving a combination of balance and control exercises, eccentric hamstring, plyometrics and strength exercises could be efficacious in preventing all lower limb injuries. Conclusions: Overall, the evidence for exercise programmes as an efficacious lower limb injury prevention strategy is predominantly restricted to studies addressing injury aetiology and mechanisms. The findings of this review highlight the need to develop and test interventions in well designed population-based trials with an emphasis on promoting intervention uptake and adherence and, hence, intervention effectiveness. The results of this review can inform the development of the components of a future lower limb injury prevention exercise protocol for community-level Australian football. © 2013 Springer International Publishing Switzerland. Funded by the NHMRC.
- Description: 2003011215
Instrumentation and motivations for organised cycling: : The development of the cyclist motivation instrument (CMI)
- Brown, Trent, O'Connor, Justen, Barkatsas, Anastasios
- Authors: Brown, Trent , O'Connor, Justen , Barkatsas, Anastasios
- Date: 2009
- Type: Text , Journal article
- Relation: Journal of Sports Science and Medicine, vol. 8, no. 2, Asist Group, p. 211-218
- Full Text:
- Description: ‘Serious leisure’ cycling has developed as a reinterpretation of the traditional form of the sport. This short term, informal, unstructured and unconventional conceptualisation represents a challenge to participant numbers in the mainstream sport. The purpose of this study was twofold: (i) to ascertain the cultural, subcultural and ecological factors of participation in this new conceptualised form enabling clubs, associations and governments to a deeper understanding about participants practices and (ii) as an ongoing validation to previous qualitative work (see O’Connor and Brown, 2005). This study reports on the development and psychometric properties (principal components analysis, confirmatory factor analysis) of the Cyclists’ Motivation Instrument. Four hundred and twenty two cyclists (371 males, 51 females) who were registered members of the state competitive cycling body completed a fifty-one item instrument. Five factors were identified: social, embodiment, self-presentation, exploring environments and physical health outcomes and these accounted for 47.2% of the variance. Factor alpha coefficients ranged from .63 to .88, overall scale reliability was .92, suggesting moderate to high reliability for each of the factors and the overall scale.
- Authors: Brown, Trent , O'Connor, Justen , Barkatsas, Anastasios
- Date: 2009
- Type: Text , Journal article
- Relation: Journal of Sports Science and Medicine, vol. 8, no. 2, Asist Group, p. 211-218
- Full Text:
- Description: ‘Serious leisure’ cycling has developed as a reinterpretation of the traditional form of the sport. This short term, informal, unstructured and unconventional conceptualisation represents a challenge to participant numbers in the mainstream sport. The purpose of this study was twofold: (i) to ascertain the cultural, subcultural and ecological factors of participation in this new conceptualised form enabling clubs, associations and governments to a deeper understanding about participants practices and (ii) as an ongoing validation to previous qualitative work (see O’Connor and Brown, 2005). This study reports on the development and psychometric properties (principal components analysis, confirmatory factor analysis) of the Cyclists’ Motivation Instrument. Four hundred and twenty two cyclists (371 males, 51 females) who were registered members of the state competitive cycling body completed a fifty-one item instrument. Five factors were identified: social, embodiment, self-presentation, exploring environments and physical health outcomes and these accounted for 47.2% of the variance. Factor alpha coefficients ranged from .63 to .88, overall scale reliability was .92, suggesting moderate to high reliability for each of the factors and the overall scale.
A review of instrumented equipment to investigate head impacts in sport
- Authors: Patton, Declan
- Date: 2016
- Type: Text , Journal article , Review
- Relation: Applied Bionics and Biomechanics Vol. 2016, no. (2016), p. 1-17
- Full Text:
- Reviewed:
- Description: Contact, collision, and combat sports have more head impacts as compared to noncontact sports; therefore, such sports are uniquely suited to the investigation of head impact biomechanics. Recent advances in technology have enabled the development of instrumented equipment, which can estimate the head impact kinematics of human subjects in vivo. Literature pertaining to head impact measurement devices was reviewed and usage, in terms of validation and field studies, of such devices was discussed. Over the past decade, instrumented equipment has recorded millions of impacts in the laboratory, on the field, in the ring, and on the ice. Instrumented equipment is not without limitations; however, in vivo head impact data is crucial to investigate head injury mechanisms and further the understanding of concussion. © 2016 Declan A. Patton.
- Authors: Patton, Declan
- Date: 2016
- Type: Text , Journal article , Review
- Relation: Applied Bionics and Biomechanics Vol. 2016, no. (2016), p. 1-17
- Full Text:
- Reviewed:
- Description: Contact, collision, and combat sports have more head impacts as compared to noncontact sports; therefore, such sports are uniquely suited to the investigation of head impact biomechanics. Recent advances in technology have enabled the development of instrumented equipment, which can estimate the head impact kinematics of human subjects in vivo. Literature pertaining to head impact measurement devices was reviewed and usage, in terms of validation and field studies, of such devices was discussed. Over the past decade, instrumented equipment has recorded millions of impacts in the laboratory, on the field, in the ring, and on the ice. Instrumented equipment is not without limitations; however, in vivo head impact data is crucial to investigate head injury mechanisms and further the understanding of concussion. © 2016 Declan A. Patton.
Extraction and processing of real time strain of embedded FBG sensors using a fixed filter FBG circuit and an artificial neural network
- Kahandawa, Gayan, Epaarachchi, Jayantha, Wang, Hao, Canning, John, Lau, Alan
- Authors: Kahandawa, Gayan , Epaarachchi, Jayantha , Wang, Hao , Canning, John , Lau, Alan
- Date: 2013
- Type: Text , Journal article
- Relation: Measurement: Journal of the International Measurement Confederation Vol. 46, no. 10 (2013), p. 4045-4051
- Full Text:
- Reviewed:
- Description: Fibre Bragg Grating (FBG) sensors have been used in the development of structural health monitoring (SHM) and damage detection systems for advanced composite structures over several decades. Unfortunately, to date only a handful of appropriate configurations and algorithm sare available for using in SHM systems have been developed. This paper reveals a novel configuration of FBG sensors to acquire strain reading and an integrated statistical approach to analyse data in real time. The proposed configuration has proven its capability to overcome practical constraints and the engineering challenges associated with FBG-based SHM systems. A fixed filter decoding system and an integrated artificial neural network algorithm for extracting strain from embedded FBG sensor were proposed and experimentally proved. Furthermore, the laboratory level experimental data was used to verify the accuracy of the system and it was found that the error levels were less than 0.3% in predictions. The developed SMH system using this technology has been submitted to US patent office and will be available for use of aerospace applications in due course. © 2013 Elsevier Ltd. All rights reserved.
- Authors: Kahandawa, Gayan , Epaarachchi, Jayantha , Wang, Hao , Canning, John , Lau, Alan
- Date: 2013
- Type: Text , Journal article
- Relation: Measurement: Journal of the International Measurement Confederation Vol. 46, no. 10 (2013), p. 4045-4051
- Full Text:
- Reviewed:
- Description: Fibre Bragg Grating (FBG) sensors have been used in the development of structural health monitoring (SHM) and damage detection systems for advanced composite structures over several decades. Unfortunately, to date only a handful of appropriate configurations and algorithm sare available for using in SHM systems have been developed. This paper reveals a novel configuration of FBG sensors to acquire strain reading and an integrated statistical approach to analyse data in real time. The proposed configuration has proven its capability to overcome practical constraints and the engineering challenges associated with FBG-based SHM systems. A fixed filter decoding system and an integrated artificial neural network algorithm for extracting strain from embedded FBG sensor were proposed and experimentally proved. Furthermore, the laboratory level experimental data was used to verify the accuracy of the system and it was found that the error levels were less than 0.3% in predictions. The developed SMH system using this technology has been submitted to US patent office and will be available for use of aerospace applications in due course. © 2013 Elsevier Ltd. All rights reserved.
Compliance with sport injury prevention interventions in randomised controlled trials : A systematic review
- van Reijen, Miriam, Vriend, Ingrid, van Mechelen, Willem, Finch, Caroline, Verhagen, Evert
- Authors: van Reijen, Miriam , Vriend, Ingrid , van Mechelen, Willem , Finch, Caroline , Verhagen, Evert
- Date: 2016
- Type: Text , Journal article , Review
- Relation: Sports Medicine Vol. 46, no. 8 (2016), p. 1125-1139
- Full Text:
- Reviewed:
- Description: Introduction Sport injury prevention studies vary in the way compliance with an intervention is defined, measured and adjusted for. Objective The objective of this systematic review was to assess the extent to which sport injury prevention randomised controlled trials (RCTs) have defined, measured and adjusted results for compliance with an injury prevention intervention. Methods An electronic search was performed in MEDLINE, PubMed, the Cochrane Center of Controlled Trials, CINAHL (Cumulative Index to Nursing and Allied Health Literature), PEDro (Physiotherapy Evidence Database) and SPORTDiscus. English RCTs, quasi-RCTs and cluster-RCTs were considered eligible. Trials that involved physically active individuals or examined the effects of an intervention aimed at the prevention of sport-or physical activity-related injuries were included. Results Of the total of 100 studies included, 71.6 % mentioned compliance or a related term, 68.8 % provided details on compliance measurement and 51.4 % provided compliance data. Only 19.3 % analysed the effect of compliance rates on study outcomes. While studies used heterogeneous methods, pooled effects could not be presented. Conclusions Studies that account for compliance demonstrated that compliance significant affects study outcomes. The way compliance is dealt with in preventions studies is subject to a large degree of heterogeneity. Valid and reliable tools to measure and report compliance are needed and should be matched to a uniform definition of compliance.
- Authors: van Reijen, Miriam , Vriend, Ingrid , van Mechelen, Willem , Finch, Caroline , Verhagen, Evert
- Date: 2016
- Type: Text , Journal article , Review
- Relation: Sports Medicine Vol. 46, no. 8 (2016), p. 1125-1139
- Full Text:
- Reviewed:
- Description: Introduction Sport injury prevention studies vary in the way compliance with an intervention is defined, measured and adjusted for. Objective The objective of this systematic review was to assess the extent to which sport injury prevention randomised controlled trials (RCTs) have defined, measured and adjusted results for compliance with an injury prevention intervention. Methods An electronic search was performed in MEDLINE, PubMed, the Cochrane Center of Controlled Trials, CINAHL (Cumulative Index to Nursing and Allied Health Literature), PEDro (Physiotherapy Evidence Database) and SPORTDiscus. English RCTs, quasi-RCTs and cluster-RCTs were considered eligible. Trials that involved physically active individuals or examined the effects of an intervention aimed at the prevention of sport-or physical activity-related injuries were included. Results Of the total of 100 studies included, 71.6 % mentioned compliance or a related term, 68.8 % provided details on compliance measurement and 51.4 % provided compliance data. Only 19.3 % analysed the effect of compliance rates on study outcomes. While studies used heterogeneous methods, pooled effects could not be presented. Conclusions Studies that account for compliance demonstrated that compliance significant affects study outcomes. The way compliance is dealt with in preventions studies is subject to a large degree of heterogeneity. Valid and reliable tools to measure and report compliance are needed and should be matched to a uniform definition of compliance.
A scaled boundary finite element formulation with bubble functions for elasto-static analyses of functionally graded materials
- Ooi, Ean Tat, Song, Chongmin, Natarajan, Sundararajan
- Authors: Ooi, Ean Tat , Song, Chongmin , Natarajan, Sundararajan
- Date: 2017
- Type: Text , Journal article
- Relation: Computational Mechanics Vol. 60, no. 6 (2017), p. 943-967
- Full Text:
- Reviewed:
- Description: This manuscript presents an extension of the recently-developed high order complete scaled boundary shape functions to model elasto-static problems in functionally graded materials. Both isotropic and orthotropic functionally graded materials are modelled. The high order complete properties of the shape functions are realized through the introduction of bubble-like functions derived from the equilibrium condition of a polygon subjected to body loads. The bubble functions preserve the displacement compatibility between the elements in the mesh. The heterogeneity resulting from the material gradient introduces additional terms in the polygon stiffness matrix that are integrated analytically. Few numerical benchmarks were used to validate the developed formulation. The high order completeness property of the bubble functions result in superior accuracy and convergence rates for generic elasto-static and fracture problems involving functionally graded materials. © 2017, Springer-Verlag GmbH Germany.
- Authors: Ooi, Ean Tat , Song, Chongmin , Natarajan, Sundararajan
- Date: 2017
- Type: Text , Journal article
- Relation: Computational Mechanics Vol. 60, no. 6 (2017), p. 943-967
- Full Text:
- Reviewed:
- Description: This manuscript presents an extension of the recently-developed high order complete scaled boundary shape functions to model elasto-static problems in functionally graded materials. Both isotropic and orthotropic functionally graded materials are modelled. The high order complete properties of the shape functions are realized through the introduction of bubble-like functions derived from the equilibrium condition of a polygon subjected to body loads. The bubble functions preserve the displacement compatibility between the elements in the mesh. The heterogeneity resulting from the material gradient introduces additional terms in the polygon stiffness matrix that are integrated analytically. Few numerical benchmarks were used to validate the developed formulation. The high order completeness property of the bubble functions result in superior accuracy and convergence rates for generic elasto-static and fracture problems involving functionally graded materials. © 2017, Springer-Verlag GmbH Germany.