title: Comparison of simulation and experimental results of a tractor seat with nonlinear stiffness and dead-band damping

authors: Duke, Mike

abstract: A low friction tractor seat with nonlinear stiffness and dead-band damping was investigated both by simulation and experimentation. The objective was to determine if a practical, soft suspension system could be developed that offered improved vibration performance compared to a typical mechanical commercial tractor seat suspension. A hard damper was used to prevent end stop impacts that were more likely with the soft suspension. In addition the damper had a dead-band centered at the seat's static equilibrium position. The dead-band damping was achieved with a switchable damper using relative seat displacement as the control signal. The objective of the dead-band was to allow a soft undamped operating region that gave good vibration attenuation. If the relative seat displacement passed the dead-band limits due to sudden harsh inputs, the hard damping would take over and prevent end stop impacts. An experimental rig with nonlinear seat and switchable damping was built and tested with the same parameters and inputs as those used in the simulations. The simulation and experimental results compared well. Both the simulation and experimental results showed that a combination of nonlinear stiffness and dead-band damping used on a tractor seat gives reduced rms acceleration compared to a linear, conventionally damped seat.

text: Comparison of simulation and experimental results of a tractor seat with nonlinear stiffness and dead-band damping A low friction tractor seat with nonlinear stiffness and dead-band damping was investigated both by simulation and experimentation. The objective was to determine if a practical, soft suspension system could be developed that offered improved vibration performance compared to a typical mechanical commercial tractor seat suspension. A hard damper was used to prevent end stop impacts that were more likely with the soft suspension. In addition the damper had a dead-band centered at the seat's static equilibrium position. The dead-band damping was achieved with a switchable damper using relative seat displacement as the control signal. The objective of the dead-band was to allow a soft undamped operating region that gave good vibration attenuation. If the relative seat displacement passed the dead-band limits due to sudden harsh inputs, the hard damping would take over and prevent end stop impacts. An experimental rig with nonlinear seat and switchable damping was built and tested with the same parameters and inputs as those used in the simulations. The simulation and experimental results compared well. Both the simulation and experimental results showed that a combination of nonlinear stiffness and dead-band damping used on a tractor seat gives reduced rms acceleration compared to a linear, conventionally damped seat.

year: 2012

title: Speeding up logistic model tree induction

authors: Sumner, Marc

subjects: computer science

abstract: Logistic Model Trees have been shown to be very accurate and compact classifiers [8]. Their greatest disadvantage is the computational complexity of inducing the logistic regression models in the tree. We address this issue by using the AIC criterion [1] instead of cross-validation to prevent overfitting these models. In addition, a weight trimming heuristic is used which produces a significant speedup. We compare the training time and accuracy of the new induction process with the original one on various datasets and show that the training time often decreases while the classification accuracy diminishes only slightly.

text: Speeding up logistic model tree induction Logistic Model Trees have been shown to be very accurate and compact classifiers [8]. Their greatest disadvantage is the computational complexity of inducing the logistic regression models in the tree. We address this issue by using the AIC criterion [1] instead of cross-validation to prevent overfitting these models. In addition, a weight trimming heuristic is used which produces a significant speedup. We compare the training time and accuracy of the new induction process with the original one on various datasets and show that the training time often decreases while the classification accuracy diminishes only slightly.

year: 2005

title: Genre and authentic written discourse in Maori and their relevance to the education of students in upper secondary and tertiary Maori-medium educational settings

authors: Houia-Roberts, Ngaere

subjects: Māori medium education

abstract: I report here on part of a research project whose primary aim was to investigate a range of authentic Māori texts in terms of the search for commonly occurring organisational and cognitive patterns, and to consider the pedagogic implications of this investigation in terms of the teaching of writing skills in Māori-medium educational settings. An examination of a range of text segments written by educated and highly proficient users of Māori suggests that, in terms of textual relationships, there are characteristic patterns of organisation that characterise the three genres that appear to be most commonly required of student writers in Māori-medium upper secondary and tertiary educational contexts, that is, the genres of arguing, explaining and describing. Another part of the project – an examination of whole texts in terms of overall, structuring – is reported in the next issue of this journal.

text: Genre and authentic written discourse in Maori and their relevance to the education of students in upper secondary and tertiary Maori-medium educational settings I report here on part of a research project whose primary aim was to investigate a range of authentic Māori texts in terms of the search for commonly occurring organisational and cognitive patterns, and to consider the pedagogic implications of this investigation in terms of the teaching of writing skills in Māori-medium educational settings. An examination of a range of text segments written by educated and highly proficient users of Māori suggests that, in terms of textual relationships, there are characteristic patterns of organisation that characterise the three genres that appear to be most commonly required of student writers in Māori-medium upper secondary and tertiary educational contexts, that is, the genres of arguing, explaining and describing. Another part of the project – an examination of whole texts in terms of overall, structuring – is reported in the next issue of this journal.

year: 2003-09