title: The effects of delay to reinforcement and inter-trial interval on fixed-ratio schedule performance

authors: Stuart, Stacey Louisa

abstract: A delay to reinforcement has been found in previous studies to influence the effectiveness of a reinforcer. As the delay duration increases, response rates decrease and post reinforcement pause durations increase. The present study tested whether it was the increase in time between the effective response and delivery of reinforcement, or, the increases in intervals between reinforcers that devalue the reinforcer. This study also compared the ability of two demand equations and MPR to predict response rates when effort required was changed. The effects of varying delay to reinforcement and intertrial interval on behaviour was examined while the time available for responding was kept constant. 
	There were four conditions; 4-s ITI, 4-s delay, 16-s ITI and 16-s delay, and 6 hens responded under each of these conditions in an ascending geometric series of fixed ratio (FR) values. It was shown that hens generally responded at a faster rate in the ITI conditions than the equivalent delay conditions and peak response rates were seen highest in the 16-s ITI condition in accordance with the demand data.  The data was described well by both the demand equations and the MPR equation. While there were inconsistencies among the parameters, there was a moderately strong positive relationships between the parameter values of as and α in the 16-s ITI (r = .51, p = 0.29) and delay (r = .44, p = .44) conditions.

text: The effects of delay to reinforcement and inter-trial interval on fixed-ratio schedule performance A delay to reinforcement has been found in previous studies to influence the effectiveness of a reinforcer. As the delay duration increases, response rates decrease and post reinforcement pause durations increase. The present study tested whether it was the increase in time between the effective response and delivery of reinforcement, or, the increases in intervals between reinforcers that devalue the reinforcer. This study also compared the ability of two demand equations and MPR to predict response rates when effort required was changed. The effects of varying delay to reinforcement and intertrial interval on behaviour was examined while the time available for responding was kept constant. 
	There were four conditions; 4-s ITI, 4-s delay, 16-s ITI and 16-s delay, and 6 hens responded under each of these conditions in an ascending geometric series of fixed ratio (FR) values. It was shown that hens generally responded at a faster rate in the ITI conditions than the equivalent delay conditions and peak response rates were seen highest in the 16-s ITI condition in accordance with the demand data.  The data was described well by both the demand equations and the MPR equation. While there were inconsistencies among the parameters, there was a moderately strong positive relationships between the parameter values of as and α in the 16-s ITI (r = .51, p = 0.29) and delay (r = .44, p = .44) conditions.

year: 2013

title: Developing new multiscale models for the numerical simulation of Pultruded GFRP Structural Elements

authors: Abbaszadeh, Hadi

abstract: Pultruded Fibre-Reinforced Polymers (FRP) are innovative structural elements gaining popularity for various structural applications due to their unique properties, such as magnetic transparency and an excellent strength-to-weight ratio. These materials have been extensively studied through experimental and numerical methods to assess their performance as structural components. Accurately describing the micro- and macro-scale mechanical features of FRP elements necessitates complex computational models to predict their strength and investigate design parameters through numerical simulations. 

This research initially reviews the state-of-the-art in numerical modelling of structural fibre-reinforced polymeric elements, particularly pultruded Glass Fibre Reinforced Polymers (GFRP). It highlights their use as load-bearing structural elements and evaluates various numerical methods, including Finite Element Method (FEM), eXtended Finite Element Method (XFEM), Virtual Crack Closure Technique (VCCT), Cohesive Zone Modelling (CZM), Multiscale Reduced Order Modelling (ROM), and Random Lattice Modelling (RLM). Each method's distinctive features, challenges, and capabilities are discussed in detail. The aim is to assess the reliability of these numerical models for simulating FRP structural elements and provide recommendations for future research by discussing 160 references from the literature. 

In the next step, the experimental characterization of Pultruded GFRP materials evaluated. These composites exhibit remarkable strength, comparable or even superior to steel, and resistance to environmental effects. However, their strongly orthotropic behaviour and spatial variability in mechanical properties present challenges. Fibre orientation and distribution significantly affect the ultimate strength and stiffness of these materials. This work includes an experimental campaign on GFRP specimens in uniaxial tension and three-point bending, testing coupon specimens with fibre orientations of 0, 15, 45, and 90 degrees to characterize ultimate strength and failure modes. Detailed statistical measures of the strength values are presented, aiming to understand the variability in mechanical properties of commercially available profiles. 

In addition, the stiffness parameter was considered to investigate by analytical study comparing experimental results. Despite the promising properties of pultruded GFRP, their relatively low stiffness and strength in the direction orthogonal to the fibres limit their widespread adoption in civil engineering applications. This work investigates the mechanical behaviour of pultruded GFRP beams using analytical methods, presenting  experimental results from a small-scale campaign conducted by the researcher. These results validate the analytical model and compare the elastic stiffness concerning fibre orientation, providing insights into the potential and limitations of pultruded GFRP elements in structural applications. 

Finally, the last step of study demonstrates the inherent limitations of traditional lattice models and propose a new model to simulate the orthotropic materials` behaviours in different conditions. This section presents an innovative approach by using irregular lattice networks to simulate the elastic behaviour of orthotropic GFRP structural elements by Voronoi Cell Lattice Modelling (VCLM), focusing on different fibre-to-matrix elasticity ratios and fibre to load orientations. The proposed method first estimates the elastic properties for various fibre orientations and verifies the model against standard deformation cases and experimental data. Additionally, it compares numerical predictions to established theories like the Tsai-Hill criterion. Through sensitivity analysis, it explores how fibre-to-matrix ratios and Young’s modulus affect macroscopic Poisson’s ratio, offering new insights into stiffness effects on anisotropic material simulations.

text: Developing new multiscale models for the numerical simulation of Pultruded GFRP Structural Elements Pultruded Fibre-Reinforced Polymers (FRP) are innovative structural elements gaining popularity for various structural applications due to their unique properties, such as magnetic transparency and an excellent strength-to-weight ratio. These materials have been extensively studied through experimental and numerical methods to assess their performance as structural components. Accurately describing the micro- and macro-scale mechanical features of FRP elements necessitates complex computational models to predict their strength and investigate design parameters through numerical simulations. 

This research initially reviews the state-of-the-art in numerical modelling of structural fibre-reinforced polymeric elements, particularly pultruded Glass Fibre Reinforced Polymers (GFRP). It highlights their use as load-bearing structural elements and evaluates various numerical methods, including Finite Element Method (FEM), eXtended Finite Element Method (XFEM), Virtual Crack Closure Technique (VCCT), Cohesive Zone Modelling (CZM), Multiscale Reduced Order Modelling (ROM), and Random Lattice Modelling (RLM). Each method's distinctive features, challenges, and capabilities are discussed in detail. The aim is to assess the reliability of these numerical models for simulating FRP structural elements and provide recommendations for future research by discussing 160 references from the literature. 

In the next step, the experimental characterization of Pultruded GFRP materials evaluated. These composites exhibit remarkable strength, comparable or even superior to steel, and resistance to environmental effects. However, their strongly orthotropic behaviour and spatial variability in mechanical properties present challenges. Fibre orientation and distribution significantly affect the ultimate strength and stiffness of these materials. This work includes an experimental campaign on GFRP specimens in uniaxial tension and three-point bending, testing coupon specimens with fibre orientations of 0, 15, 45, and 90 degrees to characterize ultimate strength and failure modes. Detailed statistical measures of the strength values are presented, aiming to understand the variability in mechanical properties of commercially available profiles. 

In addition, the stiffness parameter was considered to investigate by analytical study comparing experimental results. Despite the promising properties of pultruded GFRP, their relatively low stiffness and strength in the direction orthogonal to the fibres limit their widespread adoption in civil engineering applications. This work investigates the mechanical behaviour of pultruded GFRP beams using analytical methods, presenting  experimental results from a small-scale campaign conducted by the researcher. These results validate the analytical model and compare the elastic stiffness concerning fibre orientation, providing insights into the potential and limitations of pultruded GFRP elements in structural applications. 

Finally, the last step of study demonstrates the inherent limitations of traditional lattice models and propose a new model to simulate the orthotropic materials` behaviours in different conditions. This section presents an innovative approach by using irregular lattice networks to simulate the elastic behaviour of orthotropic GFRP structural elements by Voronoi Cell Lattice Modelling (VCLM), focusing on different fibre-to-matrix elasticity ratios and fibre to load orientations. The proposed method first estimates the elastic properties for various fibre orientations and verifies the model against standard deformation cases and experimental data. Additionally, it compares numerical predictions to established theories like the Tsai-Hill criterion. Through sensitivity analysis, it explores how fibre-to-matrix ratios and Young’s modulus affect macroscopic Poisson’s ratio, offering new insights into stiffness effects on anisotropic material simulations.

year: 2025

title: Listening and Learning from Rangatahi Māori: the Voices of Māori Youth

authors: Berryman, Mere

subjects: student self-determination

abstract: This paper presents three stories-over-time of the secondary schooling experiences of New Zealand’s rangatahi Māori–or Māori youth. The stories span fifteen years of New Zealand schooling and are told from three perspectives: the experiences of the students as told in their own words; the voices of youth within the prevailing political contexts of government policy; and, the reframing and repositioning of researchers listening to the experiences of rangatahi Māori who believe they have succeeded as Māori. In reality, the stories are interwoven, however, in an effort to make sense of the various methodological dilemmas, risks, and entanglements across the three points of learning, we have endeavored to disentangle these different threads from the whole and follow these independent of each other. We then weave these threads together again, as we sense-make across this complexity to identify implications for other educators, policy makers and researchers.

text: Listening and Learning from Rangatahi Māori: the Voices of Māori Youth This paper presents three stories-over-time of the secondary schooling experiences of New Zealand’s rangatahi Māori–or Māori youth. The stories span fifteen years of New Zealand schooling and are told from three perspectives: the experiences of the students as told in their own words; the voices of youth within the prevailing political contexts of government policy; and, the reframing and repositioning of researchers listening to the experiences of rangatahi Māori who believe they have succeeded as Māori. In reality, the stories are interwoven, however, in an effort to make sense of the various methodological dilemmas, risks, and entanglements across the three points of learning, we have endeavored to disentangle these different threads from the whole and follow these independent of each other. We then weave these threads together again, as we sense-make across this complexity to identify implications for other educators, policy makers and researchers.

year: 2017