title: A brief review of recent cyanobacteria monitoring results in the Waikato River

authors: Hamilton, David P.

subjects: New Zealand

abstract: Herewith is a report on possible reasons for low concentrations of cyanobacteria (blue-green algae) cells in the Waikato River in summer 2007-08 compared with previous records from 2003 to 2007. Because of time constraints, this report is a cursory consideration and does not provide the level of detail and analysis required to more fully evaluate phytoplankton succession as it relates to the complex interplay amongst physical, chemical and biological variables.
This report was requested by Mighty River Power following a summer when, as a result of drought conditions, the hydro system was operated in a manner similar to 2003, when cyanobacteria blooms(>15,000 cells mL⁻¹) occurred in the upper river and water temperatures were elevated. These operating conditions were characterised by maintenance of high water levels in the hydro dams and low inflows into the system, resulting in relatively long water residence times.

text: A brief review of recent cyanobacteria monitoring results in the Waikato River Herewith is a report on possible reasons for low concentrations of cyanobacteria (blue-green algae) cells in the Waikato River in summer 2007-08 compared with previous records from 2003 to 2007. Because of time constraints, this report is a cursory consideration and does not provide the level of detail and analysis required to more fully evaluate phytoplankton succession as it relates to the complex interplay amongst physical, chemical and biological variables.
This report was requested by Mighty River Power following a summer when, as a result of drought conditions, the hydro system was operated in a manner similar to 2003, when cyanobacteria blooms(>15,000 cells mL⁻¹) occurred in the upper river and water temperatures were elevated. These operating conditions were characterised by maintenance of high water levels in the hydro dams and low inflows into the system, resulting in relatively long water residence times.

year: 2008

title: Prior Robustness for Bayesian Implementation of the Fault Tree Analysis

authors: Joshi, Chaitanya

subjects: Science & Technology

abstract: We propose a prior robustness approach for the Bayesian implementation of the fault tree analysis (FTA). FTA is often used to evaluate risk in large, safety critical systems but has limitations due to its static structure. Bayesian approaches have been proposed as a superior alternative to it, however, this involves prior elicitation, which is not straightforward. We show that minor misspecification of priors for elementary events can result in a significant prior misspecification for the top event. A large amount of data is required to correctly update a misspecified prior and such data may not be available for many complex, safety critical systems. In such cases, prior misspecification equals posterior misspecification. Therefore, there is a need to develop a robustness approach for FTA, which can quantify the effects of prior misspecification on the posterior analysis. Here, we propose the first prior robustness approach specifically developed for FTA. We not only prove a few important mathematical properties of this approach, but also develop easy to use Monte Carlo sampling algorithms to implement this approach on any given fault tree with and and/or or gates. We then implement this Bayesian robustness approach on two real-life examples: a spacecraft re-entry example and a feeding control system example. We also provide a step-by-step illustration of how this approach can be applied to a real-life problem.

text: Prior Robustness for Bayesian Implementation of the Fault Tree Analysis We propose a prior robustness approach for the Bayesian implementation of the fault tree analysis (FTA). FTA is often used to evaluate risk in large, safety critical systems but has limitations due to its static structure. Bayesian approaches have been proposed as a superior alternative to it, however, this involves prior elicitation, which is not straightforward. We show that minor misspecification of priors for elementary events can result in a significant prior misspecification for the top event. A large amount of data is required to correctly update a misspecified prior and such data may not be available for many complex, safety critical systems. In such cases, prior misspecification equals posterior misspecification. Therefore, there is a need to develop a robustness approach for FTA, which can quantify the effects of prior misspecification on the posterior analysis. Here, we propose the first prior robustness approach specifically developed for FTA. We not only prove a few important mathematical properties of this approach, but also develop easy to use Monte Carlo sampling algorithms to implement this approach on any given fault tree with and and/or or gates. We then implement this Bayesian robustness approach on two real-life examples: a spacecraft re-entry example and a feeding control system example. We also provide a step-by-step illustration of how this approach can be applied to a real-life problem.

year: 2018

title: Moko – A Research Project

authors: Te Awekotuku, Ngahuia

subjects: Maori

abstract: Moko colours the lives, and the skins, of all the people involved in the making of this book “Mau Moko”, which began as the Marsden project, “Ta Moko – Culture, Body Modification, and the Psychology of Identity”, 2001-2005. We proposed to study the origins, significance, technology and practice of Ta Moko from the pre-contact period to contemporary times, and to explore how this important art form has become a dynamic and positive assertion of being Maori in our changing world.

text: Moko – A Research Project Moko colours the lives, and the skins, of all the people involved in the making of this book “Mau Moko”, which began as the Marsden project, “Ta Moko – Culture, Body Modification, and the Psychology of Identity”, 2001-2005. We proposed to study the origins, significance, technology and practice of Ta Moko from the pre-contact period to contemporary times, and to explore how this important art form has become a dynamic and positive assertion of being Maori in our changing world.

year: 2008