title: Supercapacitor-assisted refrigerator for DC powered households

authors: Sirimanne, Don Charles Themiya

abstract: Energy efficiency is a prime concern in power generation as well as in usage. Product developers and end users are encouraged to reduce their carbon footprint for help in the fight against climate change. In this effect designing power electronic systems with high end to end efficiency is paramount. Direct DC application with tactical circuit topologies show promising results for improved efficiency gains resulting in increased attention for the DC microgrid concept. DC powered households are developed, where solar photovoltaics on rooftops generate purely DC electricity to power the immediate community. Recent developments have made solar generation quite economical for this to be realized. Unfortunately, solar power is not consistent due to environmental factors, thus needing an alternate DC source or energy storage for uninterrupted supply of power. To meet this demand research into energy storage has ramped up. As a result, supercapacitor technology has advanced considerably with superior characteristics compared to rechargeable batteries. Almost all modern white goods run on DC internally. The inverter-based refrigerator operates using a variable frequency inverter for efficient and smooth operation. The refrigerator has shown to function efficiently within a range around the nominal operating voltage. This has allowed the application of the well matured supercapacitor assisted loss management (SCALoM) technique to develop a power converter to operate the refrigerator with the characteristic DC power supply of a solar photovoltaic (PV) array. The system benefits from the replacement of the battery and Maximum Power Point Tracking (MPPT) Charge controller with supercapacitors for a solar power system with long operation time in between of service intervals. While MPPT charge controller is based on a high frequency switch mode DC-DC converter, the proposed power converter allows for switching frequencies in the mHz region, allowing lower switching losses and reduction in potential electromagnetic interference and radio frequency interference. The concept was proven by using a 24V DC camping fridge and obtaining an efficiency of up to 94%. This work will lead to the development of the converter for a consumer grade 240Vac inverter driven refrigerator where the AC-DC converter is bypassed to achieve improved efficiency. This thesis covers the broader design and technical aspects of the power converter.

text: Supercapacitor-assisted refrigerator for DC powered households Energy efficiency is a prime concern in power generation as well as in usage. Product developers and end users are encouraged to reduce their carbon footprint for help in the fight against climate change. In this effect designing power electronic systems with high end to end efficiency is paramount. Direct DC application with tactical circuit topologies show promising results for improved efficiency gains resulting in increased attention for the DC microgrid concept. DC powered households are developed, where solar photovoltaics on rooftops generate purely DC electricity to power the immediate community. Recent developments have made solar generation quite economical for this to be realized. Unfortunately, solar power is not consistent due to environmental factors, thus needing an alternate DC source or energy storage for uninterrupted supply of power. To meet this demand research into energy storage has ramped up. As a result, supercapacitor technology has advanced considerably with superior characteristics compared to rechargeable batteries. Almost all modern white goods run on DC internally. The inverter-based refrigerator operates using a variable frequency inverter for efficient and smooth operation. The refrigerator has shown to function efficiently within a range around the nominal operating voltage. This has allowed the application of the well matured supercapacitor assisted loss management (SCALoM) technique to develop a power converter to operate the refrigerator with the characteristic DC power supply of a solar photovoltaic (PV) array. The system benefits from the replacement of the battery and Maximum Power Point Tracking (MPPT) Charge controller with supercapacitors for a solar power system with long operation time in between of service intervals. While MPPT charge controller is based on a high frequency switch mode DC-DC converter, the proposed power converter allows for switching frequencies in the mHz region, allowing lower switching losses and reduction in potential electromagnetic interference and radio frequency interference. The concept was proven by using a 24V DC camping fridge and obtaining an efficiency of up to 94%. This work will lead to the development of the converter for a consumer grade 240Vac inverter driven refrigerator where the AC-DC converter is bypassed to achieve improved efficiency. This thesis covers the broader design and technical aspects of the power converter.

year: 2023

title: Lake-floor sediment texture and composition of a hydrothermally-active, volcanic lake, Lake Rotomahana

authors: Pittari, Adrian

subjects: Lake Rotomahana

abstract: Young volcanic lakes undergo a transition from rapid, post-eruptive accumulation of volcaniclastic sediment to slower pelagic settling under stable lake conditions, and may also be influenced by sublacustrine hydrothermal systems. Lake Rotomahana is a young (129 year-old), hydrothermally-active, volcanic lake formed after the 1886 Tarawera eruption, and provides a unique insight into the early evolution of volcanic lake systems. Lake-bottom sediment cores, 20–46 cm in length, were taken along a transect across the lake and characterised with respect to stratigraphy, facies characteristics (i.e., grain size, componentry) and pore water silica concentrations. The sediments generally comprise two widespread facies: (i) a lower facies of light grey to grey, very fine lacustrine silt derived from the unconsolidated pyroclastic deposits that mantled the catchment area immediately after the eruption, which were rapidly reworked and redeposited into the lake basin; and (ii) an upper facies of dark, fine-sandy diatomaceous silt, that settled from the pelagic zone of the physically stable lake. Adjacent to sublacustrine hydrothermal vents, the upper dark facies is absent, and the upper part of the light grey to grey silt is replaced by a third localised facies comprised of hydrothermally altered pale yellow to yellowish brown, laminated silt with surface iron-rich encrustations. Microspheres, which are thought to be composed of amorphous silica, although some may be halloysite, have precipitated from pore water onto sediment grains, and are associated with a decrease in pore water silicon concentration. Lake Rotomahana is an example of a recently-stabilised volcanic lake, with respect to sedimentation, that shows signs of early sediment silicification in the presence of hydrothermal activity.

text: Lake-floor sediment texture and composition of a hydrothermally-active, volcanic lake, Lake Rotomahana Young volcanic lakes undergo a transition from rapid, post-eruptive accumulation of volcaniclastic sediment to slower pelagic settling under stable lake conditions, and may also be influenced by sublacustrine hydrothermal systems. Lake Rotomahana is a young (129 year-old), hydrothermally-active, volcanic lake formed after the 1886 Tarawera eruption, and provides a unique insight into the early evolution of volcanic lake systems. Lake-bottom sediment cores, 20–46 cm in length, were taken along a transect across the lake and characterised with respect to stratigraphy, facies characteristics (i.e., grain size, componentry) and pore water silica concentrations. The sediments generally comprise two widespread facies: (i) a lower facies of light grey to grey, very fine lacustrine silt derived from the unconsolidated pyroclastic deposits that mantled the catchment area immediately after the eruption, which were rapidly reworked and redeposited into the lake basin; and (ii) an upper facies of dark, fine-sandy diatomaceous silt, that settled from the pelagic zone of the physically stable lake. Adjacent to sublacustrine hydrothermal vents, the upper dark facies is absent, and the upper part of the light grey to grey silt is replaced by a third localised facies comprised of hydrothermally altered pale yellow to yellowish brown, laminated silt with surface iron-rich encrustations. Microspheres, which are thought to be composed of amorphous silica, although some may be halloysite, have precipitated from pore water onto sediment grains, and are associated with a decrease in pore water silicon concentration. Lake Rotomahana is an example of a recently-stabilised volcanic lake, with respect to sedimentation, that shows signs of early sediment silicification in the presence of hydrothermal activity.

year: 2016

title: Management of patients with early stage lung cancer - why do some patients not receive treatment with curative intent?

authors: Lawrenson, Ross

subjects: Lung cancer

abstract: BACKGROUNDS: This study aims to understand the factors that influence whether patients receive potentially curative treatment for early stage lung cancer. A key question was whether indigenous Māori patients were less likely to receive treatment. 
METHODS: Patients included those diagnosed with early stage lung cancer in 2011-2018 and resident in the New Zealand Midland Cancer Network region. Logistic regression model was used to estimate the odds ratios of having curative surgery/ treatment. The Kaplan Meier method was used to examine the all-cause survival and Cox proportional hazard model was used to estimate the hazard ratio of death. 
RESULTS: In total 419/583 (71.9%) of patients with Stage I and II disease were treated with curative intent - 272 (46.7%) patients had curative surgery. Patients not receiving potentially curative treatment were older, were less likely to have non-small cell lung cancer (NSCLC), had poorer lung function and were more likely to have an ECOG performance status of 2+. Current smokers were less likely to be treated with surgery and more likely to receive treatment with radiotherapy and chemotherapy. Those who were treated with surgery had a 2-year survival of 87.8% (95% CI: 83.8-91.8%) and 5-year survival of 69.6% (95% CI: 63.2-76.0%). Stereotactic ablative body radiotherapy (SABR) has equivalent effect on survival compared to curative surgery (hazard ratio: 0.77, 95% CI: 0.37-1.61). After adjustment we could find no difference in treatment and survival between Māori and non-Māori. 
CONCLUSIONS: The majority of patients with stage I and II lung cancer are managed with potentially curative treatment - mainly surgery and increasingly with SABR. The outcomes of those being diagnosed with stage I and II disease and receiving treatment is positive with 70% surviving 5 years.

text: Management of patients with early stage lung cancer - why do some patients not receive treatment with curative intent? BACKGROUNDS: This study aims to understand the factors that influence whether patients receive potentially curative treatment for early stage lung cancer. A key question was whether indigenous Māori patients were less likely to receive treatment. 
METHODS: Patients included those diagnosed with early stage lung cancer in 2011-2018 and resident in the New Zealand Midland Cancer Network region. Logistic regression model was used to estimate the odds ratios of having curative surgery/ treatment. The Kaplan Meier method was used to examine the all-cause survival and Cox proportional hazard model was used to estimate the hazard ratio of death. 
RESULTS: In total 419/583 (71.9%) of patients with Stage I and II disease were treated with curative intent - 272 (46.7%) patients had curative surgery. Patients not receiving potentially curative treatment were older, were less likely to have non-small cell lung cancer (NSCLC), had poorer lung function and were more likely to have an ECOG performance status of 2+. Current smokers were less likely to be treated with surgery and more likely to receive treatment with radiotherapy and chemotherapy. Those who were treated with surgery had a 2-year survival of 87.8% (95% CI: 83.8-91.8%) and 5-year survival of 69.6% (95% CI: 63.2-76.0%). Stereotactic ablative body radiotherapy (SABR) has equivalent effect on survival compared to curative surgery (hazard ratio: 0.77, 95% CI: 0.37-1.61). After adjustment we could find no difference in treatment and survival between Māori and non-Māori. 
CONCLUSIONS: The majority of patients with stage I and II lung cancer are managed with potentially curative treatment - mainly surgery and increasingly with SABR. The outcomes of those being diagnosed with stage I and II disease and receiving treatment is positive with 70% surviving 5 years.

year: 2020