title: Wondering about ... the intimate geographies of Married at First Sight New Zealand #MAFSNZ

authors: Johnston, Lynda

abstract: Why should I, or any geographers, be wondering about Married at First Sight New Zealand (MAFSNZ, TV3 2019), the franchised reality television show where strangers meet each other at the alter? Pitched, as a ‘ground-breaking social experiment’ there is a lot we can learn from this show about people and places. The success of the show - with ratings of over one million viewers in Australia (Dawson 2019) and up to 170,000 in Aotearoa New Zealand (Grieves 2019) – rests on the adventures of couples as they ‘hothouse’ the highs and lows of marital life. The latest season aired 17 episodes over six weeks as ‘10 singles put it all on the line and embark on a new journey to find love’ (TV3 2019).

text: Wondering about ... the intimate geographies of Married at First Sight New Zealand #MAFSNZ Why should I, or any geographers, be wondering about Married at First Sight New Zealand (MAFSNZ, TV3 2019), the franchised reality television show where strangers meet each other at the alter? Pitched, as a ‘ground-breaking social experiment’ there is a lot we can learn from this show about people and places. The success of the show - with ratings of over one million viewers in Australia (Dawson 2019) and up to 170,000 in Aotearoa New Zealand (Grieves 2019) – rests on the adventures of couples as they ‘hothouse’ the highs and lows of marital life. The latest season aired 17 episodes over six weeks as ‘10 singles put it all on the line and embark on a new journey to find love’ (TV3 2019).

year: 2019

title: Measuring and improving Time-of-Flight camera light source electrical-to-optical power conversion efficiency

authors: Corlett, Dale Owen

subjects: electrical to optical power efficiency

abstract: Time of Flight (ToF) cameras capture three-dimensional depth images of a scene. They do this by transmitting a modulated light signal from a light source, which scatters off objects in the scene and returns to the camera’s modulated image sensor. Distance values for each pixel of the image sensor are calculated from the measured difference in phase between the transmitted and received signal.
There are two circuit topologies typically used for ToF camera light sources, shunt switching and series switching. Chronoptics Limited (Hamilton, New Zealand) is a company that develops ToF cameras. The light source of their Kea ToF camera drives four laser diodes using the iC-HG (iC-Haus GmbH, Bodenheim, Germany) Integrated Circuit (IC).  The iC-HG IC, and therefore the Kea light source, has a series switching topology. Texas Instruments (Dallas, Texas) has designed a ToF camera with a light source that has the shunt switching topology. Texas Instruments claim that the shunt switching topology has a better electrical input power to optical output power than the series switching topology.
The aim of this project is to investigate the shunt topology, in particular the Texas Instruments implementation, and to determine if the shunt topology could provide a substantial increase in efficiency for the Kea light source and future Chronoptics’ light source designs.
In this thesis, we measure the electrical input to optical output power efficiency of the Texas Instruments TIDA 01173 light source and compare it to the Kea light source and find the TIDA1173 does indeed have a higher power efficiency than the Kea light source. However, it is not as efficient as we anticipated, so we also investigate options for improving the power efficiency of the TIDA 01173 light source to maximise the benefits of designing a new light source. 
To achieve the aim, an apparatus is designed and constructed to measure the electrical input power and optical output power of the TIDA 01173 and Kea light sources. The input and output power measurements are used to calculate the efficiency of the light sources over a range of modulation frequencies from 10 MHz to 100 MHz. The electrical to optical power efficiency results show that the shunt switching topology TIDA 01173 light source is more power efficient than the series switching topology Kea light source. The TIDA 01173 has a measured power efficiency of 22% at 10 MHz modulation frequency, and Kea has an efficiency of 11% at the same frequency. These hardware measurement results are corroborated by the results of SPICE simulations made for each of the ToF light sources. To make these simulations, the electrical and optical properties of the BOB850T1000 laser diode (Bob Laser Co, Guangdong, China) used in the ToF light sources are extracted to make a laser diode SPICE model.
An account of the power consumption of each component in both light sources is conducted using the light source SPICE simulations. This account shows that the linear current limiter in the TIDA 01173 consumes the most power, so it is swapped for a buck current regulator. This modification increases the power efficiency of the TIDA 01173 light source to 28% at 10 MHz modulation frequency. The power efficiency of the Kea light source is increased to 13% at 10 MHz modulation frequency by decreasing the input voltage from 5 V to 4 V. Improving the efficiency of the ToF camera light sources allows higher optical output power for a given input power. This enables ToF cameras to be powered from low power sources such as, Universal Serial Bus (USB) ports or battery packs, therefore improving the versatility of ToF cameras.

text: Measuring and improving Time-of-Flight camera light source electrical-to-optical power conversion efficiency Time of Flight (ToF) cameras capture three-dimensional depth images of a scene. They do this by transmitting a modulated light signal from a light source, which scatters off objects in the scene and returns to the camera’s modulated image sensor. Distance values for each pixel of the image sensor are calculated from the measured difference in phase between the transmitted and received signal.
There are two circuit topologies typically used for ToF camera light sources, shunt switching and series switching. Chronoptics Limited (Hamilton, New Zealand) is a company that develops ToF cameras. The light source of their Kea ToF camera drives four laser diodes using the iC-HG (iC-Haus GmbH, Bodenheim, Germany) Integrated Circuit (IC).  The iC-HG IC, and therefore the Kea light source, has a series switching topology. Texas Instruments (Dallas, Texas) has designed a ToF camera with a light source that has the shunt switching topology. Texas Instruments claim that the shunt switching topology has a better electrical input power to optical output power than the series switching topology.
The aim of this project is to investigate the shunt topology, in particular the Texas Instruments implementation, and to determine if the shunt topology could provide a substantial increase in efficiency for the Kea light source and future Chronoptics’ light source designs.
In this thesis, we measure the electrical input to optical output power efficiency of the Texas Instruments TIDA 01173 light source and compare it to the Kea light source and find the TIDA1173 does indeed have a higher power efficiency than the Kea light source. However, it is not as efficient as we anticipated, so we also investigate options for improving the power efficiency of the TIDA 01173 light source to maximise the benefits of designing a new light source. 
To achieve the aim, an apparatus is designed and constructed to measure the electrical input power and optical output power of the TIDA 01173 and Kea light sources. The input and output power measurements are used to calculate the efficiency of the light sources over a range of modulation frequencies from 10 MHz to 100 MHz. The electrical to optical power efficiency results show that the shunt switching topology TIDA 01173 light source is more power efficient than the series switching topology Kea light source. The TIDA 01173 has a measured power efficiency of 22% at 10 MHz modulation frequency, and Kea has an efficiency of 11% at the same frequency. These hardware measurement results are corroborated by the results of SPICE simulations made for each of the ToF light sources. To make these simulations, the electrical and optical properties of the BOB850T1000 laser diode (Bob Laser Co, Guangdong, China) used in the ToF light sources are extracted to make a laser diode SPICE model.
An account of the power consumption of each component in both light sources is conducted using the light source SPICE simulations. This account shows that the linear current limiter in the TIDA 01173 consumes the most power, so it is swapped for a buck current regulator. This modification increases the power efficiency of the TIDA 01173 light source to 28% at 10 MHz modulation frequency. The power efficiency of the Kea light source is increased to 13% at 10 MHz modulation frequency by decreasing the input voltage from 5 V to 4 V. Improving the efficiency of the ToF camera light sources allows higher optical output power for a given input power. This enables ToF cameras to be powered from low power sources such as, Universal Serial Bus (USB) ports or battery packs, therefore improving the versatility of ToF cameras.

year: 2020

title: Evaluating the effects of invasive brown bullhead catfish (Ameiurus nebulosus) on kōura (freshwater crayfish, Paranephrops planifrons) in Lake Rotoiti

authors: Francis, Laura Beverley

subjects: catfish

abstract: Brown bullhead catfish (Ameiurus nebulosus) are opportunistic carnivores native to North America and were first detected in Te Weta Bay, Lake Rotoiti, in March 2016. A cordon was placed across the bay to try and contain catfish, but they had already established populations elsewhere. Spread of catfish in the lake raised concern for resident populations of freshwater crayfish or kōura (Paranephrops planifrons), which are of ecological and cultural significance to Māori. Given the limited knowledge of the potential impacts of catfish on native biota, this thesis aims to evaluate the effects of catfish on kōura in Lake Rotoiti. To do this, Bay of Plenty Regional Council (BOPRC) routine fyke netting data was used to explore species trends and relationships. A habitat survey was also conducted using whakaweku (bracken fern bundles) and fyke nets, to generate data on species’ habitat preferences and kōura metrics (e.g., sizes and sex ratios). In addition to fishing, kōura and catfish stomachs were dissected to determine diet. Potential food items of catfish were also collected for stable isotope analysis to estimate dietary overlap between catfish and kōura, and long-term resource acquisition. 

Routine BOPRC fyke netting results indicated that kōura catch per unit effort (CPUE) has declined in Lake Rotoiti, with mean catch rates dropping from 10.6 kōura net-1 night-1 in 2016 to 4.2 kōura net-1 night-1 in 2018. Over the same period, catfish CPUE has increased in the lake, with the highest catch rates in Te Weta Bay, where mean catch rates have increased from 1.1 catfish net-1 night-1 in 2016 to 63.7 catfish net-1 night-1 in 2018. Catfish catch rates were negatively associated with catch rates of kōura (r = −0.180). Mean catfish density also had a significant effect on kōura catch rates, with significantly more kōura being caught at sites without catfish. The negative association between catfish and kōura could be due to catfish eating or competing with kōura, or their differing habitat preferences. Catfish were positively associated with sites that are weedy or muddy and kōura were negatively associated with muddy habitats and were positively associated with rocky habitats. Whakaweku set at shallow depths <1 m in the lake littoral zone were ineffective at catching kōura during the habitat survey. 

Catfish diet consisted largely of chironomid larvae (Chironomidae), detritus, common bullies (Gobiomorphus cotidianus), and to a lesser extent kōura. Kōura were found in 12% of large catfish (>200 mm fork length; FL) stomachs analysed and contributed 5% volumetrically to large catfish diet. Unfortunately, the contribution of kōura to catfish diet could not be established using stable isotopes because isotopic signatures of kōura and bullies were too close to differentiate. Kōura diet consisted primarily of animal remains (common bullies and invertebrates) and detritus. Stable isotopes of carbon and nitrogen revealed that diets of kōura and catfish overlapped, with kōura sharing more of their diet with catfish than vice versa, likely reflecting catfish’s broad diet. This study suggests that catfish are responsible for the recent decline in kōura CPUE in Lake Rotoiti and that catfish are directly and indirectly affecting kōura through predation and competition for shared food resources.

text: Evaluating the effects of invasive brown bullhead catfish (Ameiurus nebulosus) on kōura (freshwater crayfish, Paranephrops planifrons) in Lake Rotoiti Brown bullhead catfish (Ameiurus nebulosus) are opportunistic carnivores native to North America and were first detected in Te Weta Bay, Lake Rotoiti, in March 2016. A cordon was placed across the bay to try and contain catfish, but they had already established populations elsewhere. Spread of catfish in the lake raised concern for resident populations of freshwater crayfish or kōura (Paranephrops planifrons), which are of ecological and cultural significance to Māori. Given the limited knowledge of the potential impacts of catfish on native biota, this thesis aims to evaluate the effects of catfish on kōura in Lake Rotoiti. To do this, Bay of Plenty Regional Council (BOPRC) routine fyke netting data was used to explore species trends and relationships. A habitat survey was also conducted using whakaweku (bracken fern bundles) and fyke nets, to generate data on species’ habitat preferences and kōura metrics (e.g., sizes and sex ratios). In addition to fishing, kōura and catfish stomachs were dissected to determine diet. Potential food items of catfish were also collected for stable isotope analysis to estimate dietary overlap between catfish and kōura, and long-term resource acquisition. 

Routine BOPRC fyke netting results indicated that kōura catch per unit effort (CPUE) has declined in Lake Rotoiti, with mean catch rates dropping from 10.6 kōura net-1 night-1 in 2016 to 4.2 kōura net-1 night-1 in 2018. Over the same period, catfish CPUE has increased in the lake, with the highest catch rates in Te Weta Bay, where mean catch rates have increased from 1.1 catfish net-1 night-1 in 2016 to 63.7 catfish net-1 night-1 in 2018. Catfish catch rates were negatively associated with catch rates of kōura (r = −0.180). Mean catfish density also had a significant effect on kōura catch rates, with significantly more kōura being caught at sites without catfish. The negative association between catfish and kōura could be due to catfish eating or competing with kōura, or their differing habitat preferences. Catfish were positively associated with sites that are weedy or muddy and kōura were negatively associated with muddy habitats and were positively associated with rocky habitats. Whakaweku set at shallow depths <1 m in the lake littoral zone were ineffective at catching kōura during the habitat survey. 

Catfish diet consisted largely of chironomid larvae (Chironomidae), detritus, common bullies (Gobiomorphus cotidianus), and to a lesser extent kōura. Kōura were found in 12% of large catfish (>200 mm fork length; FL) stomachs analysed and contributed 5% volumetrically to large catfish diet. Unfortunately, the contribution of kōura to catfish diet could not be established using stable isotopes because isotopic signatures of kōura and bullies were too close to differentiate. Kōura diet consisted primarily of animal remains (common bullies and invertebrates) and detritus. Stable isotopes of carbon and nitrogen revealed that diets of kōura and catfish overlapped, with kōura sharing more of their diet with catfish than vice versa, likely reflecting catfish’s broad diet. This study suggests that catfish are responsible for the recent decline in kōura CPUE in Lake Rotoiti and that catfish are directly and indirectly affecting kōura through predation and competition for shared food resources.

year: 2019