title: 3D-printed polylactide composites reinforced with short lyocell fibres – Enhanced mechanical properties based on bio-inspired fibre fibrillation and post-print annealing

authors: Gauss, Christian

abstract: In this study, 3D printable polylactide (PLA) composites reinforced with 10, 20 and 30 mass% of short lyocell fibres were produced by melt compounding PLA modified with maleic anhydride. Based on bio-inspired anchoring systems, fibrillated fibres were also employed in 30 mass% fibre composites. The resulting 3D printed samples displayed outstanding mechanical performance, particularly with high fibre content. Compared to neat PLA, unmodified formulations showed reduced tensile strength and strain at break with the addition of fibres, but they had a moderate improvement in Young's modulus. However, by combining fibre fibrillation, matrix modification, and post-printing annealing, we achieved an excellent balance of tensile strength (85 MPa), Young's modulus (7.2 GPa), and strain at break (3.2%) - the highest reported values for such composites. Incorporating fibres and increasing PLA crystallinity via heat treatment significantly enhanced the thermo-mechanical stability of the composites, raising the storage modulus up to 38 times at 60 °C and 200 times at 80 °C compared to neat PLA. This combined strategy paves the way for the 3D printing of high-performance structures using 100% bio-derived materials.

text: 3D-printed polylactide composites reinforced with short lyocell fibres – Enhanced mechanical properties based on bio-inspired fibre fibrillation and post-print annealing In this study, 3D printable polylactide (PLA) composites reinforced with 10, 20 and 30 mass% of short lyocell fibres were produced by melt compounding PLA modified with maleic anhydride. Based on bio-inspired anchoring systems, fibrillated fibres were also employed in 30 mass% fibre composites. The resulting 3D printed samples displayed outstanding mechanical performance, particularly with high fibre content. Compared to neat PLA, unmodified formulations showed reduced tensile strength and strain at break with the addition of fibres, but they had a moderate improvement in Young's modulus. However, by combining fibre fibrillation, matrix modification, and post-printing annealing, we achieved an excellent balance of tensile strength (85 MPa), Young's modulus (7.2 GPa), and strain at break (3.2%) - the highest reported values for such composites. Incorporating fibres and increasing PLA crystallinity via heat treatment significantly enhanced the thermo-mechanical stability of the composites, raising the storage modulus up to 38 times at 60 °C and 200 times at 80 °C compared to neat PLA. This combined strategy paves the way for the 3D printing of high-performance structures using 100% bio-derived materials.

year: 2023-09-05

title: Closed-form inverses for the mixed pixel/multipath interference problem in AMCW lidar

authors: Godbaz, John Peter

subjects: mixed pixels

abstract: We present two new closed-form methods for mixed pixel/multipath interference separation in AMCW lidar systems. The mixed pixel/multipath interference problem arises from the violation of a standard range-imaging assumption that each pixel integrates over only a single, discrete backscattering source. While a numerical inversion method has previously been proposed, no close-form inverses have previously been posited. The first new method models reflectivity as a Cauchy distribution over range and uses four measurements at different modulation frequencies to determine the amplitude, phase and reflectivity distribution of up to two component returns within each pixel. The second new method uses attenuation ratios to determine the amplitude and phase of up to two component returns within each pixel. The methods are tested on both simulated and real data and shown to produce a significant improvement in overall error. While this paper focusses on the AMCW mixed pixel/multipath interference problem, the algorithms contained herein have applicability to the reconstruction of a sparse one dimensional signal from an extremely limited number of discrete samples of its Fourier transform.

text: Closed-form inverses for the mixed pixel/multipath interference problem in AMCW lidar We present two new closed-form methods for mixed pixel/multipath interference separation in AMCW lidar systems. The mixed pixel/multipath interference problem arises from the violation of a standard range-imaging assumption that each pixel integrates over only a single, discrete backscattering source. While a numerical inversion method has previously been proposed, no close-form inverses have previously been posited. The first new method models reflectivity as a Cauchy distribution over range and uses four measurements at different modulation frequencies to determine the amplitude, phase and reflectivity distribution of up to two component returns within each pixel. The second new method uses attenuation ratios to determine the amplitude and phase of up to two component returns within each pixel. The methods are tested on both simulated and real data and shown to produce a significant improvement in overall error. While this paper focusses on the AMCW mixed pixel/multipath interference problem, the algorithms contained herein have applicability to the reconstruction of a sparse one dimensional signal from an extremely limited number of discrete samples of its Fourier transform.

year: 2012

title: Incidental teacher<->student moments in an Aotearoa New Zealand secondary school: Entangled encounters with key competencies

authors: Graham, Judith Ann

subjects: key competencies

abstract: This study focuses on the performance of Key Competencies of the New Zealand curriculum in incidental teacher<->student moments. It makes visible a significant and often taken-for-granted portion of teachers’ daily work. Situated in one Aotearoa New Zealand secondary school, the research material of this study was generated in two cycles of conversations with teachers. In these conversations the teachers spoke about ordinary, unplanned moments with students. As the school is composed of more than 50% Māori students, I spoke first with individual Māori teachers at the school, inquiring into their knowledge of key competencies, and how that pedagogical knowledge related to knowledge and practice from whakaaro Māori. In the second cycle of generating research material, a collaborative group of Māori and Pākehā teachers engaged in a recursive process of inquiring together into stories participants told of everyday encounters with students. In this inquiry the names of key competency categories were put in the background as the group focused their inquiry on the teacher’s values, knowledges and beliefs that were contributing to action in the moment.
My analysis of the research material is situated in the field of posthuman philosophy and relational<->materialist theorising. Drawing on the work of Deleuze and Guattari, Massumi, Barad and Bennett, I applied Barad’s methodology of diffractive analysis and paid attention to multiple material and discursive forces and intensities at play in each story. In this analysis, diverse forces such as colonised histories, educational discourse, human and more-than-human materialities, whakaaro Māori, hope and belief, were evidenced intra-acting together. I noticed how these forces invited the mobilisation and performance of key competency actions in the service of becoming and relating with the world.
This study shifts thinking with key competencies from the reductionist territory of the individual human and re-territorialises them as dynamic performances of becoming. It contributes to a re-thinking of subjectivity and potentiality in the place of schooling in Aotearoa New Zealand. As the multi-dimensional entangled complexity of day-to-day pedagogical encounters is disclosed, teacher<->student intra-actions become known as ripe opportunities for performances of actions that come under the umbrella of key competencies. The study opens new ways of thinking about how key competency learning is produced in secondary schools, and how the placetimemattering of the school shapes that learning.
I explore diffractive patterns as key competencies entangle with posthumanism and with whakaaro Māori in everyday teacher<->student encounters. I present a way of thinking with key competencies that aligns closely with whakaaro Māori and posthumanism, and offers a creative and ethical orientation to life and learning. I think with the teacher<->student relational moment as a significant site of learning, and how knowledge of affect and relational-practices of knowing and recognition might contribute to teachers’ professional adaptive expertise.

text: Incidental teacher<->student moments in an Aotearoa New Zealand secondary school: Entangled encounters with key competencies This study focuses on the performance of Key Competencies of the New Zealand curriculum in incidental teacher<->student moments. It makes visible a significant and often taken-for-granted portion of teachers’ daily work. Situated in one Aotearoa New Zealand secondary school, the research material of this study was generated in two cycles of conversations with teachers. In these conversations the teachers spoke about ordinary, unplanned moments with students. As the school is composed of more than 50% Māori students, I spoke first with individual Māori teachers at the school, inquiring into their knowledge of key competencies, and how that pedagogical knowledge related to knowledge and practice from whakaaro Māori. In the second cycle of generating research material, a collaborative group of Māori and Pākehā teachers engaged in a recursive process of inquiring together into stories participants told of everyday encounters with students. In this inquiry the names of key competency categories were put in the background as the group focused their inquiry on the teacher’s values, knowledges and beliefs that were contributing to action in the moment.
My analysis of the research material is situated in the field of posthuman philosophy and relational<->materialist theorising. Drawing on the work of Deleuze and Guattari, Massumi, Barad and Bennett, I applied Barad’s methodology of diffractive analysis and paid attention to multiple material and discursive forces and intensities at play in each story. In this analysis, diverse forces such as colonised histories, educational discourse, human and more-than-human materialities, whakaaro Māori, hope and belief, were evidenced intra-acting together. I noticed how these forces invited the mobilisation and performance of key competency actions in the service of becoming and relating with the world.
This study shifts thinking with key competencies from the reductionist territory of the individual human and re-territorialises them as dynamic performances of becoming. It contributes to a re-thinking of subjectivity and potentiality in the place of schooling in Aotearoa New Zealand. As the multi-dimensional entangled complexity of day-to-day pedagogical encounters is disclosed, teacher<->student intra-actions become known as ripe opportunities for performances of actions that come under the umbrella of key competencies. The study opens new ways of thinking about how key competency learning is produced in secondary schools, and how the placetimemattering of the school shapes that learning.
I explore diffractive patterns as key competencies entangle with posthumanism and with whakaaro Māori in everyday teacher<->student encounters. I present a way of thinking with key competencies that aligns closely with whakaaro Māori and posthumanism, and offers a creative and ethical orientation to life and learning. I think with the teacher<->student relational moment as a significant site of learning, and how knowledge of affect and relational-practices of knowing and recognition might contribute to teachers’ professional adaptive expertise.

year: 2019