title: Dynamic Nonlinear Resistance Model for a Power MOSFET in an Oscillatory RLC Circuit

authors: Raju, S

abstract: This paper presents the development of a new Matlab mosfet model specifically designed for RLC circuits. The key contribution is the formulation of a novel equation that accurately captures the device behavior across subthreshold, above-threshold regions and at threshold point, addressing limitations in existing models. The developed model treats the mosfet as a variable resistance element, with the resistance changing dynamically at each instant, enabling the solution of differential equations governing the RLC circuit. Curve fitting and refinement were conducted based on experimental results, leading to a close match between the simulations and experimental data. The model was tested with triangle, sinusoidal and quadrilateral gate voltages, and the simulation results show good match with the experimental data, demonstrating the model's accuracy. It provides a straightforward way to predict performance, making it easier to refine and optimize the design gate voltage before physical implementation. This work provides a solid foundation for mosfet modeling in oscillatory RLC circuits, which can be applied to a wide range of power electronics applications.

text: Dynamic Nonlinear Resistance Model for a Power MOSFET in an Oscillatory RLC Circuit This paper presents the development of a new Matlab mosfet model specifically designed for RLC circuits. The key contribution is the formulation of a novel equation that accurately captures the device behavior across subthreshold, above-threshold regions and at threshold point, addressing limitations in existing models. The developed model treats the mosfet as a variable resistance element, with the resistance changing dynamically at each instant, enabling the solution of differential equations governing the RLC circuit. Curve fitting and refinement were conducted based on experimental results, leading to a close match between the simulations and experimental data. The model was tested with triangle, sinusoidal and quadrilateral gate voltages, and the simulation results show good match with the experimental data, demonstrating the model's accuracy. It provides a straightforward way to predict performance, making it easier to refine and optimize the design gate voltage before physical implementation. This work provides a solid foundation for mosfet modeling in oscillatory RLC circuits, which can be applied to a wide range of power electronics applications.

year: 2025

title: Evaluating the potential of constructed groundwater systems to improve the water supply operations of Auckland City, New Zealand

authors: Brown, Edmund

abstract: A range of constructed groundwater systems are evaluated for augmenting the potable water supply of Auckland City, New Zealand. The term ‘constructed groundwater systems’ encompasses any constructed means of recharging or extracting water from an aquifer. This may for example include infiltration wells and basins, injection wells, aquifer storage and recovery wells, and horizontal wells. The study motivation is to increase the sustainable yield from Auckland’s existing groundwater resources to help meet Auckland’s increasing water demand. Presently, 97% of the water supply comes from 10 storage reservoirs in the Hunua and Waitakere Ranges, and up to three percent from the Onehunga - Mt Wellington aquifer.

The Onehunga - Mt Wellington aquifer is a highly fractured basalt aquifer and has the potential to store water in its unsaturated zone. Various methods of artificially increasing the recharge of the Onehunga - Mt Wellington aquifer to increase its sustainable summer yield were investigated using a FEMWATER numerical model. Three sources of recharge water were identified in the Auckland Region: winter spillage from Watercare’s 10 reservoirs, groundwater from the dewatering of the Three Kings quarry, and wastewater from the Mangere Wastewater Treatment Plant. Artificial storage and recovery (ASR) wells, and soakage wells were simulated as a means of increasing the aquifer’s yield. The greatest simulated increase in yield was from winter injection of reservoir water via ASR wells, in conjunction with the summer extraction of the stored reservoir water. This simulation resulted in the average summer aquifer yield increasing from 9,100 to 44,100 cubic metres per day.

A hydrogeological review of the both the Hunua and Waitakere Ranges showed that there is little opportunity for utilising constructed groundwater systems below the regolith zone in those two locations. However, the storage capacity of the unconfined aquifers in the regolith layer of the Waitakere and Hunua Ranges could potentially be used to increase the efficiency of the existing water supply reservoirs presently losing water to seasonal spillage.

To increase the efficiency of the existing water supply reservoirs it is proposed that horizontal wells can be used to control the water table elevation in the reservoir catchments, permitting a degree of control over the discharge of the streams flowing to the reservoirs. The use of horizontal wells provides a range of control options, including increasing stream discharge during summer and reducing and delaying peak discharges from rainfall events during winter. The use of horizontal wells in this manner is most suited to catchments where the magnitude of stream quickflow discharge is dependent on the depth of the surrounding water table. That is, for similar-sized rainfall events, a water table near the ground surface results in more quickflow stream discharge compared to a deeper water table.

The Upper Nihotupu water supply reservoir catchment in the Waitakere Ranges was selected as a study site to gather hydrological data to simulate use of horizontal wells. In the Upper Nihotupu catchment, there is a fourfold increase in quickflow discharge for similar sized rainfall events for a water table 0.5 m below the ground surface, compared to a water table 2.7 m below the surface. Based on this, a MODFLOW numerical groundwater model was utilised to simulate the operation of hypothetical horizontal wells within the Upper Nihotupu catchment, and to evaluate if the manipulation of stream discharge will increase the reservoir’s storage capacity. Simulation results suggest there is potential for a significant increase in summer stream flow by draining the surrounding aquifer with the horizontal wells. During the 30 day period that the wells are draining the aquifer, the corresponding average reservoir delivery increased from 10,000 to 25,000 cubic metres per day. During the winter, the draining of the aquifer using horizontal wells results in reduced and delayed quickflow stream discharge. This in turn resulted in less spillage from the Upper Nihotupu reservoir. The increased control of the stream hydrograph by the simulated horizontal wells increased the average annual delivery of water from the Upper Nihotupu reservoir by seven percent.

text: Evaluating the potential of constructed groundwater systems to improve the water supply operations of Auckland City, New Zealand A range of constructed groundwater systems are evaluated for augmenting the potable water supply of Auckland City, New Zealand. The term ‘constructed groundwater systems’ encompasses any constructed means of recharging or extracting water from an aquifer. This may for example include infiltration wells and basins, injection wells, aquifer storage and recovery wells, and horizontal wells. The study motivation is to increase the sustainable yield from Auckland’s existing groundwater resources to help meet Auckland’s increasing water demand. Presently, 97% of the water supply comes from 10 storage reservoirs in the Hunua and Waitakere Ranges, and up to three percent from the Onehunga - Mt Wellington aquifer.

The Onehunga - Mt Wellington aquifer is a highly fractured basalt aquifer and has the potential to store water in its unsaturated zone. Various methods of artificially increasing the recharge of the Onehunga - Mt Wellington aquifer to increase its sustainable summer yield were investigated using a FEMWATER numerical model. Three sources of recharge water were identified in the Auckland Region: winter spillage from Watercare’s 10 reservoirs, groundwater from the dewatering of the Three Kings quarry, and wastewater from the Mangere Wastewater Treatment Plant. Artificial storage and recovery (ASR) wells, and soakage wells were simulated as a means of increasing the aquifer’s yield. The greatest simulated increase in yield was from winter injection of reservoir water via ASR wells, in conjunction with the summer extraction of the stored reservoir water. This simulation resulted in the average summer aquifer yield increasing from 9,100 to 44,100 cubic metres per day.

A hydrogeological review of the both the Hunua and Waitakere Ranges showed that there is little opportunity for utilising constructed groundwater systems below the regolith zone in those two locations. However, the storage capacity of the unconfined aquifers in the regolith layer of the Waitakere and Hunua Ranges could potentially be used to increase the efficiency of the existing water supply reservoirs presently losing water to seasonal spillage.

To increase the efficiency of the existing water supply reservoirs it is proposed that horizontal wells can be used to control the water table elevation in the reservoir catchments, permitting a degree of control over the discharge of the streams flowing to the reservoirs. The use of horizontal wells provides a range of control options, including increasing stream discharge during summer and reducing and delaying peak discharges from rainfall events during winter. The use of horizontal wells in this manner is most suited to catchments where the magnitude of stream quickflow discharge is dependent on the depth of the surrounding water table. That is, for similar-sized rainfall events, a water table near the ground surface results in more quickflow stream discharge compared to a deeper water table.

The Upper Nihotupu water supply reservoir catchment in the Waitakere Ranges was selected as a study site to gather hydrological data to simulate use of horizontal wells. In the Upper Nihotupu catchment, there is a fourfold increase in quickflow discharge for similar sized rainfall events for a water table 0.5 m below the ground surface, compared to a water table 2.7 m below the surface. Based on this, a MODFLOW numerical groundwater model was utilised to simulate the operation of hypothetical horizontal wells within the Upper Nihotupu catchment, and to evaluate if the manipulation of stream discharge will increase the reservoir’s storage capacity. Simulation results suggest there is potential for a significant increase in summer stream flow by draining the surrounding aquifer with the horizontal wells. During the 30 day period that the wells are draining the aquifer, the corresponding average reservoir delivery increased from 10,000 to 25,000 cubic metres per day. During the winter, the draining of the aquifer using horizontal wells results in reduced and delayed quickflow stream discharge. This in turn resulted in less spillage from the Upper Nihotupu reservoir. The increased control of the stream hydrograph by the simulated horizontal wells increased the average annual delivery of water from the Upper Nihotupu reservoir by seven percent.

year: 2002

title: Introduction and dedication to Matiu Dickson

authors: Te Aho, Linda

subjects: Dickson, Matiu

abstract: This edition of the Waikato Law Review is dedicated to our dear friend and colleague, Matiu Dickson, and we thank Judge Craig Coxhead for his wonderful tribute to Matiu. The morning of the 7th of April 2016 will forever be imprinted in our minds and hearts. Matiu passed away that morning having just delivered the final speech in the opening ceremony for our new Law Building here at Waikato University. It was said at his tangi that this was a high price to be paid for such a building. A price that we would never have chosen to pay. That price brings an obligation to honour and respect the legacy that Matiu has left us, his commitment to the Faculty’s founding goals and, in particular, the promotion of a bicultural legal education for Māori and non-Māori alike; that tikanga is recognised as the first law of Aotearoa New Zealand and continues to form a central part of our curriculum. Matiu personified the bicultural mission of Te Piringa Faculty of Law; that, through its curriculum, research activities and its structures, the Faculty would be the forefront of the development of a bicultural legal philosophy. Matiu worked hard to ensure this mission remained a stated goal of the Faculty and to give it meaning over his 20 year tenure. He constantly worked to infuse it into the structures and processes of this Law Faculty. He worked and campaigned for years, and successfully so, to make sure the name gifted to the Faculty by Dame Te Atairangikaahu at its founding, “Te Piringa”, became our Faculty’s officially recognised name. He was passionate about the use of te reo Māori in assessment. He encouraged and facilitated the use of te reo Māori mooting. It was our colleague, Ani Mikaere, who, during her time here as a legal academic, first publicly articulated tikanga Māori as the first law of Aotearoa. Through the years, Matiu and our academic colleagues, including Stephanie Milroy, Craig Coxhead, Caren Fox (all now Māori Land Court judges), Leah Whiu, Harata Paterson, Nan Seuffert, Ruth Bush, Wayne Rumbles, Robert Joseph, Valmaine Toki and ourselves, reaffirmed tikanga as the first law of Aotearoa in our teaching and research. Years later, the article “Lex Aotearoa: An Heroic Attempt to Map the Māori Dimension in Modern New Zealand Law” by Justice Joseph Williams2 developed the idea further and is currently the leading piece on the weaving of tikanga and Anglo-New Zealand law.3 Matiu Dickson was an expert in tikanga, the first law of Aotearoa. He lived it every day. He created and taught courses on it and made sure it was integrated throughout the curriculum. In Matiu’s honour, it is entirely appropriate that there are a number of contributions in this Review that have a Māori or Indigenous theme, and we hope future issues will likewise assure such a balance.

text: Introduction and dedication to Matiu Dickson This edition of the Waikato Law Review is dedicated to our dear friend and colleague, Matiu Dickson, and we thank Judge Craig Coxhead for his wonderful tribute to Matiu. The morning of the 7th of April 2016 will forever be imprinted in our minds and hearts. Matiu passed away that morning having just delivered the final speech in the opening ceremony for our new Law Building here at Waikato University. It was said at his tangi that this was a high price to be paid for such a building. A price that we would never have chosen to pay. That price brings an obligation to honour and respect the legacy that Matiu has left us, his commitment to the Faculty’s founding goals and, in particular, the promotion of a bicultural legal education for Māori and non-Māori alike; that tikanga is recognised as the first law of Aotearoa New Zealand and continues to form a central part of our curriculum. Matiu personified the bicultural mission of Te Piringa Faculty of Law; that, through its curriculum, research activities and its structures, the Faculty would be the forefront of the development of a bicultural legal philosophy. Matiu worked hard to ensure this mission remained a stated goal of the Faculty and to give it meaning over his 20 year tenure. He constantly worked to infuse it into the structures and processes of this Law Faculty. He worked and campaigned for years, and successfully so, to make sure the name gifted to the Faculty by Dame Te Atairangikaahu at its founding, “Te Piringa”, became our Faculty’s officially recognised name. He was passionate about the use of te reo Māori in assessment. He encouraged and facilitated the use of te reo Māori mooting. It was our colleague, Ani Mikaere, who, during her time here as a legal academic, first publicly articulated tikanga Māori as the first law of Aotearoa. Through the years, Matiu and our academic colleagues, including Stephanie Milroy, Craig Coxhead, Caren Fox (all now Māori Land Court judges), Leah Whiu, Harata Paterson, Nan Seuffert, Ruth Bush, Wayne Rumbles, Robert Joseph, Valmaine Toki and ourselves, reaffirmed tikanga as the first law of Aotearoa in our teaching and research. Years later, the article “Lex Aotearoa: An Heroic Attempt to Map the Māori Dimension in Modern New Zealand Law” by Justice Joseph Williams2 developed the idea further and is currently the leading piece on the weaving of tikanga and Anglo-New Zealand law.3 Matiu Dickson was an expert in tikanga, the first law of Aotearoa. He lived it every day. He created and taught courses on it and made sure it was integrated throughout the curriculum. In Matiu’s honour, it is entirely appropriate that there are a number of contributions in this Review that have a Māori or Indigenous theme, and we hope future issues will likewise assure such a balance.

year: 2016