title: Accounting for stream variability in retrofit problems using Monte Carlo simulation

authors: Lal, Nathan S.

abstract: The aim of this paper is to use Monte Carlo simulation to analyse the effect of stream data variation on the economic performance of retrofit designs. The input stream data is fitted to a distribution which can be sampled from to calculate the outputs of the Heat Exchanger Network model, stochastically. A simple four-stream problem is used to demonstrate the method, comparing two retrofit designs that each reduce the hot utility by 700 kW. Monte Carlo simulation analyses how the similar designs behave differently under the variable conditions and the results show that time-average analysis can not only overestimate the Total Retrofit Profit but can also favour a different design to that favoured by the Monte Carlo results. Of the two compared designs, the Design 2 was selected with an annual Total Retrofit Profit of NZD 215,553, requiring one new exchanger and additional area on an existing one. The Monte Carlo analysis also shed light on controllability and feasibility issues in the Heat Exchanger Network.

text: Accounting for stream variability in retrofit problems using Monte Carlo simulation The aim of this paper is to use Monte Carlo simulation to analyse the effect of stream data variation on the economic performance of retrofit designs. The input stream data is fitted to a distribution which can be sampled from to calculate the outputs of the Heat Exchanger Network model, stochastically. A simple four-stream problem is used to demonstrate the method, comparing two retrofit designs that each reduce the hot utility by 700 kW. Monte Carlo simulation analyses how the similar designs behave differently under the variable conditions and the results show that time-average analysis can not only overestimate the Total Retrofit Profit but can also favour a different design to that favoured by the Monte Carlo results. Of the two compared designs, the Design 2 was selected with an annual Total Retrofit Profit of NZD 215,553, requiring one new exchanger and additional area on an existing one. The Monte Carlo analysis also shed light on controllability and feasibility issues in the Heat Exchanger Network.

year: 2018

title: Fast Algorithms for Nearest Neighbour Search

authors: Kibriya, Ashraf Masood

subjects: Nearest Neighbour

abstract: The nearest neighbour problem is of practical significance in a number of fields. Often we are interested in finding an object near to a given query object. The problem is old, and a large number of solutions have been proposed for it in the literature. However, it remains the case that even the most popular of the techniques proposed for its solution have not been compared against each other. Also, many techniques, including the old and popular ones, can be implemented in a number of ways, and often the different implementations of a technique have not been thoroughly compared either.


  This research presents a detailed investigation of different implementations of two popular nearest neighbour search data structures, KDTrees and Metric Trees, and compares the different implementations of each of the two structures against each other. The best implementations of these structures are then compared against each other and against two other techniques, Annulus Method and Cover Trees. Annulus Method is an old technique that was rediscovered during the research for this thesis. Cover Trees are one of the most novel and promising data structures for nearest neighbour search that have been proposed in the literature.

text: Fast Algorithms for Nearest Neighbour Search The nearest neighbour problem is of practical significance in a number of fields. Often we are interested in finding an object near to a given query object. The problem is old, and a large number of solutions have been proposed for it in the literature. However, it remains the case that even the most popular of the techniques proposed for its solution have not been compared against each other. Also, many techniques, including the old and popular ones, can be implemented in a number of ways, and often the different implementations of a technique have not been thoroughly compared either.


  This research presents a detailed investigation of different implementations of two popular nearest neighbour search data structures, KDTrees and Metric Trees, and compares the different implementations of each of the two structures against each other. The best implementations of these structures are then compared against each other and against two other techniques, Annulus Method and Cover Trees. Annulus Method is an old technique that was rediscovered during the research for this thesis. Cover Trees are one of the most novel and promising data structures for nearest neighbour search that have been proposed in the literature.

year: 2007

title: Toitu Te Moananui a Toi – The Effects of the MV Rena on the Water Quality, Chemistry and Zooplankton of Otaiti (Astrolabe Reef)

authors: Dempsey, Te Puea Toni

subjects: metal contamination

abstract: Humans have had a profound effect on the world’s oceans, particularly through pollution. Marine pollution incidents are particularly important and increasingly involve both petrochemical and metal contamination. The effects of complex high level, point source pollution events such as ship wrecks on larval recruitment to reef environments is not well understood. Larval settlement is heavily influenced by chemical cues, hence pollution events could have a long term influence on reef ecology, and the likelihood that planktonic zooplankton can entrain contaminants into the reef food web is also of concern.
This thesis aims to address concerns from local Tangata Whenua, government, researchers, stakeholders and the public about the long term recovery of Otaiti following the MV Rena shipwreck and subsequent reef contamination. The incident is a complex one involving metallic container debris contamination along with oil. Research focussed on assessing the effects of water borne contamination surrounding the wreck site in order to examine acute and chronic responses of planktonic invertebrates: (1) the influence of Rena and associated debris to the chemistry and quality of water in the benthic zone around the wreck, (2) the toxicity of contaminants to survivorship of zooplankton, and (3) the influence on contaminant plumes to zooplankton recruitment behaviour of Otaiti.
There is a clear effect from the Rena and its associated debris field on the water quality and chemistry of Otaiti. Aluminium and copper for example, were consistently elevated in dissolved and total metal concentrations around the debris field. Laboratory based exposure of zooplankton to realistic concentration gradients of Rena contaminated sediments resulted in increased mortality with increased contaminant concentrations. Behavioural responses of pelagic and settling invertebrates to Rena pollution influenced sediment highlighted sensitivity to associated contaminant plumes. This could have significant ecological implications to the recruitment behaviour of other planktonic organisms that rely on reef conspecifics and chemical cues to initiate settlement.
Ecological concepts such as ecosystem function and biodiversity dynamics (including recruitment) relate the life force and longevity of a system. Key concerns within the scope of this research were highlighted that may have implications to Tangata Whenua decision making in assessing the Mauri of Otaiti. It can be implied that the Rena continues to impact the Mauri of Otaiti due to the presence of contaminants within the debris field.

text: Toitu Te Moananui a Toi – The Effects of the MV Rena on the Water Quality, Chemistry and Zooplankton of Otaiti (Astrolabe Reef) Humans have had a profound effect on the world’s oceans, particularly through pollution. Marine pollution incidents are particularly important and increasingly involve both petrochemical and metal contamination. The effects of complex high level, point source pollution events such as ship wrecks on larval recruitment to reef environments is not well understood. Larval settlement is heavily influenced by chemical cues, hence pollution events could have a long term influence on reef ecology, and the likelihood that planktonic zooplankton can entrain contaminants into the reef food web is also of concern.
This thesis aims to address concerns from local Tangata Whenua, government, researchers, stakeholders and the public about the long term recovery of Otaiti following the MV Rena shipwreck and subsequent reef contamination. The incident is a complex one involving metallic container debris contamination along with oil. Research focussed on assessing the effects of water borne contamination surrounding the wreck site in order to examine acute and chronic responses of planktonic invertebrates: (1) the influence of Rena and associated debris to the chemistry and quality of water in the benthic zone around the wreck, (2) the toxicity of contaminants to survivorship of zooplankton, and (3) the influence on contaminant plumes to zooplankton recruitment behaviour of Otaiti.
There is a clear effect from the Rena and its associated debris field on the water quality and chemistry of Otaiti. Aluminium and copper for example, were consistently elevated in dissolved and total metal concentrations around the debris field. Laboratory based exposure of zooplankton to realistic concentration gradients of Rena contaminated sediments resulted in increased mortality with increased contaminant concentrations. Behavioural responses of pelagic and settling invertebrates to Rena pollution influenced sediment highlighted sensitivity to associated contaminant plumes. This could have significant ecological implications to the recruitment behaviour of other planktonic organisms that rely on reef conspecifics and chemical cues to initiate settlement.
Ecological concepts such as ecosystem function and biodiversity dynamics (including recruitment) relate the life force and longevity of a system. Key concerns within the scope of this research were highlighted that may have implications to Tangata Whenua decision making in assessing the Mauri of Otaiti. It can be implied that the Rena continues to impact the Mauri of Otaiti due to the presence of contaminants within the debris field.

year: 2015