title: Feasibility study of green hydrogen to decarbonise New Zealand’s industries

authors: Walmsley, Michael R.W.

subjects: green hydrogen

abstract: Adopting renewable feedstocks is a transformative approach to diminish the reliance on fossil feedstocks such as natural gas and coal in the chemical industry. This research evaluates the potential for Aotearoa-New Zealand, particularly in the North Island, to harness green hydrogen production as a substitute for fossil fuels across industries. The study's scope encompasses examining renewable energy technologies, their capacity factors based on location, types of electrolysers, the conversion process, and the sizing of hydrogen storage reservoirs. An analysis of the levelized cost of hydrogen (LCOH) throughout the value chain in various scenarios has been conducted for the years 2020 to 2040 while considering the country’s resource constraints. The issue is addressed through an optimization-based framework characterized by a multi-period, mixed-integer linear programming (MILP) model. The outcomes demonstrate the capability of integrating all these components within the mathematical framework to yield optimal solutions for transitioning towards a sustainable hydrogen economy.

text: Feasibility study of green hydrogen to decarbonise New Zealand’s industries Adopting renewable feedstocks is a transformative approach to diminish the reliance on fossil feedstocks such as natural gas and coal in the chemical industry. This research evaluates the potential for Aotearoa-New Zealand, particularly in the North Island, to harness green hydrogen production as a substitute for fossil fuels across industries. The study's scope encompasses examining renewable energy technologies, their capacity factors based on location, types of electrolysers, the conversion process, and the sizing of hydrogen storage reservoirs. An analysis of the levelized cost of hydrogen (LCOH) throughout the value chain in various scenarios has been conducted for the years 2020 to 2040 while considering the country’s resource constraints. The issue is addressed through an optimization-based framework characterized by a multi-period, mixed-integer linear programming (MILP) model. The outcomes demonstrate the capability of integrating all these components within the mathematical framework to yield optimal solutions for transitioning towards a sustainable hydrogen economy.

year: 2024

title: Proposed mechanism for learning and memory erasure in a white-noise-driven sleeping cortex

authors: Steyn-Ross, Moira L.

subjects: REM

abstract: Understanding the structure and purpose of sleep remains one of the grand challenges of neurobiology. Here we use a mean-field linearized theory of the sleeping cortex to derive statistics for synaptic learning and memory erasure. The growth in correlated low-frequency high-amplitude voltage fluctuations during slow-wave sleep (SWS) is characterized by a probability density function that becomes broader and shallower as the transition into rapid-eye-movement (REM) sleep is approached. At transition, the Shannon information entropy of the fluctuations is maximized. If we assume Hebbian-learning rules apply to the cortex, then its correlated response to white-noise stimulation during SWS provides a natural mechanism for a synaptic weight change that will tend to shut down reverberant neural activity. In contrast, during REM sleep the weights will evolve in a direction that encourages excitatory activity. These entropy and weight-change predictions lead us to identify the final portion of deep SWS that occurs immediately prior to transition into REM sleep as a time of enhanced erasure of labile memory. We draw a link between the sleeping cortex and Landauer's dissipation theorem for irreversible computing [R. Landauer, IBM J. Res. Devel. 5, 183 (1961)], arguing that because information erasure is an irreversible computation, there is an inherent entropy cost as the cortex transits from SWS into REM sleep.

text: Proposed mechanism for learning and memory erasure in a white-noise-driven sleeping cortex Understanding the structure and purpose of sleep remains one of the grand challenges of neurobiology. Here we use a mean-field linearized theory of the sleeping cortex to derive statistics for synaptic learning and memory erasure. The growth in correlated low-frequency high-amplitude voltage fluctuations during slow-wave sleep (SWS) is characterized by a probability density function that becomes broader and shallower as the transition into rapid-eye-movement (REM) sleep is approached. At transition, the Shannon information entropy of the fluctuations is maximized. If we assume Hebbian-learning rules apply to the cortex, then its correlated response to white-noise stimulation during SWS provides a natural mechanism for a synaptic weight change that will tend to shut down reverberant neural activity. In contrast, during REM sleep the weights will evolve in a direction that encourages excitatory activity. These entropy and weight-change predictions lead us to identify the final portion of deep SWS that occurs immediately prior to transition into REM sleep as a time of enhanced erasure of labile memory. We draw a link between the sleeping cortex and Landauer's dissipation theorem for irreversible computing [R. Landauer, IBM J. Res. Devel. 5, 183 (1961)], arguing that because information erasure is an irreversible computation, there is an inherent entropy cost as the cortex transits from SWS into REM sleep.

year: 2005

title: Huikau

authors: Maxwell, Te Kahautu

abstract: Huikau is dedicated to my life long mentor and educator Mrs Ema Rogers who imparted her knowledge of Te Haahi Ringatū and things Māori to me. She housed me for months while I reseearched my MA Thesis Te Kōpura. Mrs Rogers passed away in December 2012. This new composition was performed by Ōpōtiki Mai Tawhiti Kapa Haka at the Mātaatua Regional Kapa Haka Competition. This composition placed first in the Waiata Tira category.

text: Huikau Huikau is dedicated to my life long mentor and educator Mrs Ema Rogers who imparted her knowledge of Te Haahi Ringatū and things Māori to me. She housed me for months while I reseearched my MA Thesis Te Kōpura. Mrs Rogers passed away in December 2012. This new composition was performed by Ōpōtiki Mai Tawhiti Kapa Haka at the Mātaatua Regional Kapa Haka Competition. This composition placed first in the Waiata Tira category.

year: 2012