title: Reliability-based design optimisation of structural systems using high-order analytical moments

authors: Rajan, Arvind

subjects: Science & Technology

abstract: Reliability-based design optimisation paradigm has become increasingly popular to achieve economical yet safer structural designs. However, within the iterative optimisation procedure, it is a challenging problem to simultaneously satisfy both, accuracy and computational efficiency of reliability analysis, particularly for nonlinear or large design problems. Addressing the shortcomings of the mainstream reliability estimation methods, this paper presents a new reliability-based design optimisation method that combines an analytical high-order moment-based uncertainty evaluation with an efficient response surface modelling. The proposed framework allows for the precise calculation of reliability through accurate high-order moments. The fast and accurate reliability estimation in combination with efficient sampling, in turn, reduces the total number of finite element analysis in achieving the final design. The proposed moment-based design optimisation methodology was tested on problems ranging from the design of a simple cantilever to a three-dimensional multistorey steel structure. It outperforms the mainstream methods with higher accuracy and lower computational burden especially when applied to a highly nonlinear numerical problem.

text: Reliability-based design optimisation of structural systems using high-order analytical moments Reliability-based design optimisation paradigm has become increasingly popular to achieve economical yet safer structural designs. However, within the iterative optimisation procedure, it is a challenging problem to simultaneously satisfy both, accuracy and computational efficiency of reliability analysis, particularly for nonlinear or large design problems. Addressing the shortcomings of the mainstream reliability estimation methods, this paper presents a new reliability-based design optimisation method that combines an analytical high-order moment-based uncertainty evaluation with an efficient response surface modelling. The proposed framework allows for the precise calculation of reliability through accurate high-order moments. The fast and accurate reliability estimation in combination with efficient sampling, in turn, reduces the total number of finite element analysis in achieving the final design. The proposed moment-based design optimisation methodology was tested on problems ranging from the design of a simple cantilever to a three-dimensional multistorey steel structure. It outperforms the mainstream methods with higher accuracy and lower computational burden especially when applied to a highly nonlinear numerical problem.

year: 2020

title: Modelling general anaesthesia as a first-order phase transition in the cortex

authors: Steyn-Ross, Moira L.

subjects: anaesthesia

abstract: Since 1997 we have been developing a theoretical foundation for general anaesthesia. We have been able to demonstrate that the abrupt change in brain state broughton by anaesthetic drugs can be characterized as a first-order phase transition in the population-average membrane voltage of the cortical neurons. The theory predicts that, as the critical point of phase-change into unconsciousness is approached, the electrical fluctuations in cortical activity will grow strongly in amplitude while slowing in frequency, becoming more correlated both in time and in space. Thus the bio-electrical change of brain-state has deep similarities with thermodynamic phase changes of classical physics. The theory further predicts the existence of a second critical point, hysteretically separated from the first, corresponding to the return path from comatose unconsciousness back to normal responsiveness. There is a steadily accumulating body of clinical evidence in support of all of the phasetransition predictions: low-frequency power surge in EEG activity; increased correlation time and correlation length in EEG fluctuations; hysteresis separation, with respect to drug concentration, between the point of induction and the point of emergence.

text: Modelling general anaesthesia as a first-order phase transition in the cortex Since 1997 we have been developing a theoretical foundation for general anaesthesia. We have been able to demonstrate that the abrupt change in brain state broughton by anaesthetic drugs can be characterized as a first-order phase transition in the population-average membrane voltage of the cortical neurons. The theory predicts that, as the critical point of phase-change into unconsciousness is approached, the electrical fluctuations in cortical activity will grow strongly in amplitude while slowing in frequency, becoming more correlated both in time and in space. Thus the bio-electrical change of brain-state has deep similarities with thermodynamic phase changes of classical physics. The theory further predicts the existence of a second critical point, hysteretically separated from the first, corresponding to the return path from comatose unconsciousness back to normal responsiveness. There is a steadily accumulating body of clinical evidence in support of all of the phasetransition predictions: low-frequency power surge in EEG activity; increased correlation time and correlation length in EEG fluctuations; hysteresis separation, with respect to drug concentration, between the point of induction and the point of emergence.

year: 2004-01

title: Different coloured tears: Dual cultural identity and Tangihanga – A directed study

authors: Edge, Kiri

subjects: bereavement

abstract: Although whānau/family that are configured by both Pākehā and Māori identities number significantly within New Zealand, there has been little or no attention paid to the ways in which these identities influence the bereavement processes that will inevitably impact upon the lives of these whānau/family. The present study explored the experiences of an individual, whose whānau/family included two life ways; Māori and Pākehā. Of specific focus was the ways in which these identities influenced his bereavement subsequent to the death of his beloved wife, who was of Māori descent. One elderly male Pākehā participant was interviewed, using an open-ended narrative approach. The interview was semi structured around five broad themes, but the focus was upon the participant’s experiences and his preference in expressing these. The data analysis utilised a thematic process, which allowed the participant’s experiences to determine the emergent themes. The results depicted the diversity of issues that may be raised for dual cultural whānau/family within bereavement processes. Two central themes are discussed in relation to intercultural conflict and the eventual resolution that was created. Decision making processes, cultural and language differences played significant roles within the conflict and exclusion experienced by the participant. Communication and compromise provided resolution to the prior conflicts experienced. This created positive and unexpected outcomes which resulted in increased understandings and the strengthening of links between the participant, his whānau/family and his wife’s marae.

text: Different coloured tears: Dual cultural identity and Tangihanga – A directed study Although whānau/family that are configured by both Pākehā and Māori identities number significantly within New Zealand, there has been little or no attention paid to the ways in which these identities influence the bereavement processes that will inevitably impact upon the lives of these whānau/family. The present study explored the experiences of an individual, whose whānau/family included two life ways; Māori and Pākehā. Of specific focus was the ways in which these identities influenced his bereavement subsequent to the death of his beloved wife, who was of Māori descent. One elderly male Pākehā participant was interviewed, using an open-ended narrative approach. The interview was semi structured around five broad themes, but the focus was upon the participant’s experiences and his preference in expressing these. The data analysis utilised a thematic process, which allowed the participant’s experiences to determine the emergent themes. The results depicted the diversity of issues that may be raised for dual cultural whānau/family within bereavement processes. Two central themes are discussed in relation to intercultural conflict and the eventual resolution that was created. Decision making processes, cultural and language differences played significant roles within the conflict and exclusion experienced by the participant. Communication and compromise provided resolution to the prior conflicts experienced. This created positive and unexpected outcomes which resulted in increased understandings and the strengthening of links between the participant, his whānau/family and his wife’s marae.

year: 2010-01