title: Automated aerial seed planting using biodegradable polymers

authors: Cozens, Wade

subjects: Biodegradable

abstract: The purpose of the thesis was to undertake a preliminary product design to assess the feasibility of using drone technology to aid reforestation for automated seed planting. This product would be able to increase productivity and reduce labour costs, especially when applied in difficult to reach terrains around New Zealand. Ultimately, the final product would be a weaponised drone or a swarm of drones that can fire plastic seed capsules into soil to a specific depth to prevent predation and ensure optimal germination conditions. The proof of concept hinges on the success of three objectives: Assessing and controlling the capsule’s biodegradability in soil. A method of mass manufacturing projectile seed capsules that can be delivered at high velocity and the ability of it to be fired into soil to a specific depth to ensure safe germination.  

Novatein was blended with poly(butylene adipate terephthalate) (PBAT) to aid sheet extrusion and improve water resistance. Biodegradability was tested by measuring the ability of bacteria and fungi to metabolise the polymer blends into CO2 by enclosing samples in soil at 25 °C. PBAT showed very little biodegradation under these conditions, where approximately 3 % of the theoretical carbon content of the sample was converted to CO2. Novatein reached 20 %, and the blends were intermediate, based on the amount of PBAT present. It was concluded that PBAT can effectively control the rate and extent of biodegradation in blends with Novatein. 

A method for mass manufacturing seed capsules was evaluated by compression moulding spheres to test mouldability and manufacturing lap welded samples to quantify weld strength. Blends of Novatein and PBAT were successfully moulded and welded above the glass transition temperature of the material; optimal parameters were 105 °C with a three minute hold time. Lap welds were tested by varying the compression force and sheet thickness and thereby reducing the weld times to approximately eight seconds. Welded samples were tested for tensile and peel strength, where 0.68 mm thick sheets, welded at 750 N compression force, yielded the highest tensile strength (88 % that of an un-welded samples). Thicker sheets (1.52 mm) welded at 900 N compression force, resulted in the highest peel force. Producing capsules capable of penetrating soil would benefit from thicker sheets using sufficient pressure to prevent peeling at the seam. 

Finally, seed capsule delivery was assessed using empirical modelling in combination with controlled soil conditions. Models created by Young and Lorenz used a dynamic cone penetrometer (DCP) to measure the soil’s penetration resistance to predict the penetration depth of a known projectile. These models were developed for considerably heavier projectiles (> 2.2 kg) and penetration depths much greater than considered here. Considering the DCP measures the soils resistance to penetration at a depth of one meter, a comparison to a 10th scale model was investigated. Contrary to expected, the standard DCP predicted the penetration depth of high velocity projectiles to a reasonably accuracy (~20 %) using two different types of homogenous sand, tested at three moisture contents. The scaled model failed to account for soil types, which was shown to have significant influence during high velocity testing. The work here highlighted the importance of considering realistic forestry soil, despite the accuracy of the prediction in homogenous sand.

Although an integrated product has not been developed, this project has shown that a strategy exists for controlling the rate of biodegradation of Novatein/PBAT. A plausible method for mass manufacturing seed capsules was demonstrated using compression moulding of Novatein blends. Penetration depth was predicted accurately for homogenous soil, this requires further research into applying the model to realistic top soil conditions. The final stage of the larger project is to integrate a firing mechanism with a drone for automated delivery of seed capsules produced from vacuum forming.

text: Automated aerial seed planting using biodegradable polymers The purpose of the thesis was to undertake a preliminary product design to assess the feasibility of using drone technology to aid reforestation for automated seed planting. This product would be able to increase productivity and reduce labour costs, especially when applied in difficult to reach terrains around New Zealand. Ultimately, the final product would be a weaponised drone or a swarm of drones that can fire plastic seed capsules into soil to a specific depth to prevent predation and ensure optimal germination conditions. The proof of concept hinges on the success of three objectives: Assessing and controlling the capsule’s biodegradability in soil. A method of mass manufacturing projectile seed capsules that can be delivered at high velocity and the ability of it to be fired into soil to a specific depth to ensure safe germination.  

Novatein was blended with poly(butylene adipate terephthalate) (PBAT) to aid sheet extrusion and improve water resistance. Biodegradability was tested by measuring the ability of bacteria and fungi to metabolise the polymer blends into CO2 by enclosing samples in soil at 25 °C. PBAT showed very little biodegradation under these conditions, where approximately 3 % of the theoretical carbon content of the sample was converted to CO2. Novatein reached 20 %, and the blends were intermediate, based on the amount of PBAT present. It was concluded that PBAT can effectively control the rate and extent of biodegradation in blends with Novatein. 

A method for mass manufacturing seed capsules was evaluated by compression moulding spheres to test mouldability and manufacturing lap welded samples to quantify weld strength. Blends of Novatein and PBAT were successfully moulded and welded above the glass transition temperature of the material; optimal parameters were 105 °C with a three minute hold time. Lap welds were tested by varying the compression force and sheet thickness and thereby reducing the weld times to approximately eight seconds. Welded samples were tested for tensile and peel strength, where 0.68 mm thick sheets, welded at 750 N compression force, yielded the highest tensile strength (88 % that of an un-welded samples). Thicker sheets (1.52 mm) welded at 900 N compression force, resulted in the highest peel force. Producing capsules capable of penetrating soil would benefit from thicker sheets using sufficient pressure to prevent peeling at the seam. 

Finally, seed capsule delivery was assessed using empirical modelling in combination with controlled soil conditions. Models created by Young and Lorenz used a dynamic cone penetrometer (DCP) to measure the soil’s penetration resistance to predict the penetration depth of a known projectile. These models were developed for considerably heavier projectiles (> 2.2 kg) and penetration depths much greater than considered here. Considering the DCP measures the soils resistance to penetration at a depth of one meter, a comparison to a 10th scale model was investigated. Contrary to expected, the standard DCP predicted the penetration depth of high velocity projectiles to a reasonably accuracy (~20 %) using two different types of homogenous sand, tested at three moisture contents. The scaled model failed to account for soil types, which was shown to have significant influence during high velocity testing. The work here highlighted the importance of considering realistic forestry soil, despite the accuracy of the prediction in homogenous sand.

Although an integrated product has not been developed, this project has shown that a strategy exists for controlling the rate of biodegradation of Novatein/PBAT. A plausible method for mass manufacturing seed capsules was demonstrated using compression moulding of Novatein blends. Penetration depth was predicted accurately for homogenous soil, this requires further research into applying the model to realistic top soil conditions. The final stage of the larger project is to integrate a firing mechanism with a drone for automated delivery of seed capsules produced from vacuum forming.

year: 2019

title: How children find books for leisure reading: implications for the digital library

authors: Cunningham, Sally Jo

subjects: observational study

abstract: Finding a good book can be difficult, particularly for young readers. This paper adds to our understanding of how children select books for recreational reading by exploring the ‘native’ strategies (both successful and ineffective) that children employ in bookstores and libraries.

text: How children find books for leisure reading: implications for the digital library Finding a good book can be difficult, particularly for young readers. This paper adds to our understanding of how children select books for recreational reading by exploring the ‘native’ strategies (both successful and ineffective) that children employ in bookstores and libraries.

year: 2011

title: Honouring our ancestors: Reclaiming the power of Māori maternities

authors: Simmonds, Naomi Beth

abstract: Māori¹ maternal knowledges are intimately tied to ancestors, to ancestral knowledges, and to whenua (land).² Iwi (tribes), hapū (smaller tribal groupings), and whānau (families)³ have their own maternal knowledges, which are woven into their cosmologies, histories, songs, carvings, place names, chants, and incantations. These knowledges, though spatially and temporally specific, speak to the sanctity of the maternal body, the power and prestige of women’s reproductive capabilities, and the empowering collective approach to raising children. Māori knowledges pertaining to pregnancy, childbirth, and parenting were imparted generation to generation as they were lived, embodied and emplaced by our ancestors, sustaining the sacred and empowering approach to maternities within our communities.
This chapter considers the challenges and possibilities of reclaiming Māori maternal knowledges and their associated practices and ceremonies for Māori women and whānau in contemporary Aotearoa-New Zealand. Three key themes frame this chapter. First, I consider the ways in which colonialism has served to silence Māori maternal knowledges to such an extent that whānau are left trying to find meaning in the voices, knowledges, and advices of others. Indigenous women are largely birthing within Western ideologies and institutions that do not adequately provide for Indigenous ways of being and birthing. The chapter then considers the ways in which women and whānau are reclaiming ancient knowledges and practices in new and contemporary ways. I seek to illustrate the ways in which traditional practices and ritual customs have the potential to transform and empower individual and collective experiences of birth and afterbirth. The chapter ends with arguing that Indigenous maternities, Māori maternities, are an important site of decolonization. Reclaiming the messages and embodied practices left to us by our ancestors can provide an empowering collective approach to pregnancy, birth, and afterbirth, and can facilitate a “decolonized pathway” (Simpson 28) into and through the world for our children and for generations to come.

text: Honouring our ancestors: Reclaiming the power of Māori maternities Māori¹ maternal knowledges are intimately tied to ancestors, to ancestral knowledges, and to whenua (land).² Iwi (tribes), hapū (smaller tribal groupings), and whānau (families)³ have their own maternal knowledges, which are woven into their cosmologies, histories, songs, carvings, place names, chants, and incantations. These knowledges, though spatially and temporally specific, speak to the sanctity of the maternal body, the power and prestige of women’s reproductive capabilities, and the empowering collective approach to raising children. Māori knowledges pertaining to pregnancy, childbirth, and parenting were imparted generation to generation as they were lived, embodied and emplaced by our ancestors, sustaining the sacred and empowering approach to maternities within our communities.
This chapter considers the challenges and possibilities of reclaiming Māori maternal knowledges and their associated practices and ceremonies for Māori women and whānau in contemporary Aotearoa-New Zealand. Three key themes frame this chapter. First, I consider the ways in which colonialism has served to silence Māori maternal knowledges to such an extent that whānau are left trying to find meaning in the voices, knowledges, and advices of others. Indigenous women are largely birthing within Western ideologies and institutions that do not adequately provide for Indigenous ways of being and birthing. The chapter then considers the ways in which women and whānau are reclaiming ancient knowledges and practices in new and contemporary ways. I seek to illustrate the ways in which traditional practices and ritual customs have the potential to transform and empower individual and collective experiences of birth and afterbirth. The chapter ends with arguing that Indigenous maternities, Māori maternities, are an important site of decolonization. Reclaiming the messages and embodied practices left to us by our ancestors can provide an empowering collective approach to pregnancy, birth, and afterbirth, and can facilitate a “decolonized pathway” (Simpson 28) into and through the world for our children and for generations to come.

year: 2017