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Long/continuous bio-derived fibre reinforced PLA composites for FDM 3D printing
No full textHigh mechanical performance applications often rely on fibre-reinforced composites using continuous synthetic fibres and petrochemical-based polymers. A shift towards bio-derived fibres and bio-derived polymers can reduce the reliance on non-sustainable materials. Long/continuous high-strength bio-derived fibres, such as flax and viscose, offer the potential to achieve mechanical properties similar to synthetic fibre composites. Polylactic acid (PLA), a sustainable bio-derived thermoplastic polymer known for its relatively high strength and stiffness compared to other polymers, is a promising alternative to petrochemical-derived counterparts. This study used long flax fibres and continuous viscose fibres in yarn form to reinforce PLA matrices, resulting in high-performance composite filaments. These filaments are designed for a recently developed and evolving manufacturing method, Fused Deposition Modelling (FDM) 3D printing, for which product performance has been limited by the commercially available filaments. Achieving high-performance FDM filaments requires addressing challenges related to fibre wetting and uniform fibre/polymer distribution, which this study addresses through impregnation and consolidation techniques. The research covers comprehensive experimental investigations into the physical, mechanical, and thermal properties of viscose, flax fibres, and PLA matrices. Successful outcomes include the development of long/continuous bio-derived fibre-reinforced composite filaments by employing two impregnation methods: solution and emulsion impregnation. Analysis covers the morphology, porosity, fibre weight fraction, and mechanical and thermal properties of the composite filaments and 3D printed composites.
Composite filaments were produced using three reinforcement yarns in their as-received form: viscose, two types of flax – standard flax and bleached flax. Viscose fibres were purchased in the form of fully continuous bio-derived fibres, while flax fibres were long and discontinuous, twisted into continuous yarns. Two PLA grades, PLA 2003D (in the form of granules) and PL 1005 (in the form of a PLA/water emulsion), were employed for solution and emulsion impregnation, respectively. Tensile testing of single fibres and matrices yielded results consistent with literature values. Bleached flax fibres exhibited the highest tensile strength (921.6 MPa), standard flax fibres displayed the highest Young’s modulus (31.8 GPa), and viscose fibres demonstrated the highest elongation at break (13.2%). PLA 2003D exhibited the highest tensile properties of the two PLA grades. Thermal stability, as assessed by TGA, demonstrated stability of both bio-derived reinforcements and matrices up to 250 oC. DSC analysis confirmed the semi-crystalline nature of PLA 2003D and the amorphous nature of PL 1005.
An impregnation and consolidation methodology was developed to produce composite filaments using both PLA solution and emulsion. Initially employing a single impregnation bath, it was later upgraded to dual baths in tandem for enhanced efficiency. A yarn spooler directed the fibre into the impregnation bath with squeezing rollers, followed by excess resin removal through a nozzle. The impregnated filament was collected on a winding mandrel and passed through a heated consolidation die. Various formulations with different impregnation cycles were tested for solution and emulsion impregnation methods. Polymer uptake depended on the affinity between the fibre and impregnating liquid, while yarn twist influenced polymer distribution. Emulsion impregnated composites exhibited higher polymer uptake due to better affinity between water and bio-derived fibres. However, solution impregnated composites showed better polymer distribution, particularly for twisted flax-reinforced filaments, relating to the efficient impregnation of PLA/DCM solution. For both impregnation methods, standard flax and bleached flax reinforced composites exhibited improved interfacial adhesion compared to viscose, attributed to mechanical interlocking between the rough surface of flax fibres and PLA in contrast to smooth viscose fibres. For PLA/viscose composites, emulsion impregnation resulted in higher tensile strength (254.7 MPa) and Young’s modulus (9.1 GPa), surpassing reported values in the literature. On the other hand, for PLA/standard flax and PLA/bleached flax, solution impregnation yielded superior tensile properties. Solution impregnated PLA/bleached flax, for the 7wt% x 3 formulation, had the highest tensile strength (356.1 MPa), while the 7wt% x2 tandem formulation showed the highest Young’s modulus (17.6 GPa) of all composites. The achieved tensile strength for PLA/bleached flax in this study also exceeded values reported in existing literature for PLA/flax composites.
The highest-performing formulations for each reinforcement, employing both solution and emulsion impregnation, were chosen to produce 3D printing filaments. A Makergear® FDM 3D printer, compatible with filament diameters of 1.4 to 2 mm, was utilized. Three filaments were pultruded together into one using a consolidation die to achieve the required filament diameter. PLA/viscose and PLA/bleached flax were selected for 3D printing in both solution and emulsion impregnation formulations, following an analysis of morphology, porosity, fibre weight fraction, and tensile properties of the multiple consolidated filaments. To further optimize diameter and enhance printability, the multiple consolidated filaments underwent melt-impregnation with additional polymer, resulting in 1.45±0.5 mm diameter filaments. Characterization of the 3D printing filaments revealed a reduction in tensile strength and Young's modulus due to increased polymer content.
Optical microscopy and porosity analysis of the 3D printed composites revealed increased porosity in the printed specimens compared to the filaments due to voids between the printed layers and pulling of the fibres onto the surface of the printed part because of the nozzle's drag force exerted during the printing process. Emulsion impregnated PLA/viscose exhibited lower porosity and printing defects compared to other composites relating to better affinity between PLA emulsion and viscose as mentioned earlier. Tensile strength and Young’s modulus values of the 3D printed composites decreased compared to the filaments due to printing induced defects mentioned previously. The highest tensile and flexural properties were obtained for emulsion impregnated PLA/viscose composites, demonstrating the significance of efficient impregnation. The 3D printed emulsion impregnated PLA/viscose composites displayed an impact strength greater than 127KJ/m2, which is higher than what has been reported in the literature for any PLA biocomposite
Intralinguistic motivation for pluralism about truth
No full textCritics of the scope problem that motivates pluralism about truth have argued that it is a pseudo-problem. If the criticism is correct, then truth pluralism is left unmotivated and potentially bankrupt. In this paper, I argue that closely related to the scope problem is another problem, which I call “the scalar problem.” If the property of truth is sensitive to how an agent expresses the truth predicate within a single linguistic discourse and different agents or groups of agents express truth differently within that discourse, then there are different ways of being true within the same linguistic discourse. Given this possibility, even if the scope problem fails, truth pluralism remains fully motivated
Modelling external light transmission through to the human fetus
No full textLittle is known about the visual experience of human fetuses within the womb. For many years, the uterus was assumed to be a dark environment, limited only to illumination under intense radiation. Recent research, however, shows that the human fetus exhibits brain activity when presented with visual stimuli and displays a preference for face-like stimuli presented via laser diode application to the maternal abdominal exterior. Despite growing evidence to support the notion of a visually engaged fetus during gestation, there has been minimal research undertaken to determine the extent to which the human uterus is illuminated by external light sources. Beyond aiding with experimental research in fetal vision, an understanding of uterine illumination begins to reveal the impact of varying environmental conditions on the fetal visual experience, with direct relevance to ongoing research across fields such as fetal vision, photoacoustics, and ectogenesis. This thesis outlines a mathematical model developed for the purposes of simulating the propagation of light sources through maternal tissue to the human fetus, with applications exploring the effect of adipose on transdermal monochromatic stimuli, the degree of uterine illumination imposed by natural light, and an extension to the illumination of a full maternal abdomen via a model that can account for curvature, varying tissue layer thicknesses, and the temporal aspects of pregnancy
Ethical leadership: A multi-study Eastern perspective
No full textLeadership ethics, shaped by diverse cultures, religious beliefs, and philosophical perspectives, exhibit nuanced differences between Western and Eastern perspectives. Despite these differences, ethical leadership scales predominantly adhere to Western conceptualisations, overlooking the unique cultural nuances of the East. The cultural traditions, philosophical views, and religious beliefs in the Eastern world imply culturally specific ethical leadership characteristics that may not align with Western-centric measures. This underscores the need for a comprehensive conceptualisation and scale development for Eastern Ethical Leadership (EEL) that captures the underlying values specific to the East. Drawing on the culturally implicit leadership theory, this thesis aims to address the following research questions, with an overarching focus on conceptualising and developing a scale for EEL:
(1) What is the current state of ethical leadership literature as it pertains to Eastern countries?
(2) What are the dimensions and measures of ethical leadership which are applicable to Eastern
countries?
(3) What is the validity of these measures across Eastern countries?
To address these research questions, three major studies were conducted. Initially, a systematic review of literature on EEL was performed, revealing the distinct characteristics of EEL and the cultural and philosophical perspectives that distinguish it from the West. Following the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) framework, the review identified relevant articles from four academic databases, revealing unique dimensions of EEL. These dimensions include leaders' responsibility and concern for long-term sustainability, aspects often overlooked in existing measures. Notably, while some virtues and values align between Eastern and Western philosophical views, past studies predominantly relied on Western theoretical perspectives to interpret ethical leadership. This underscores the need for measures that authentically capture Eastern cultural distinctions, essential for advancing ethical leadership research amidst the East's growing global influence.
The second study reports a qualitative investigation based on interviews with 21 academics across 15 Asian countries to deepen our understanding of EEL characteristics. Thematic analysis of the interview data unveiled culturally specific elements contributing to the conceptualisation of ethical leadership in the East. The findings highlighted the significance of characteristics identified by interviewees, shaped by the societal context of Asian countries. For example, caring for individuals emerges as a crucial characteristic in collectivist societies, along with demonstrating concern for the welfare of the broader community, particularly in regions facing widespread poverty. Furthermore, the perspectives shared by interviewees offer valuable insights that challenge prevalent Western-dominated views on ethical leadership.
Thirdly, a robust measure for EEL was developed and validated through a rigorous process. This study encompassed item generation based on literature and qualitative interviews, scale purification, cross-cultural validity testing, and an assessment of the psychometric properties of the scale. The developed scale was then applied to examine its impact on employee voice behaviour, serving as a crucial step in testing its nomological validity and providing valuable insights into the practical implications of EEL. The dimensions of EEL identified, including concern for people and concern for wider views, exclusively reflect the cultural nuances of the East and challenge the broad applicability of Western-centric ethical leadership measures, advocating for a more culturally nuanced understanding.
The thesis challenges the prevailing bias in ethical leadership literature towards the West, offering a culturally grounded measure for EEL that enhances conceptual development. The theoretical and practical implications of the scale are discussed, highlighting its potential to bridge the cultural gap in leadership ethics and contribute to the development of a more inclusive and culturally resonant leadership paradigm. Three separate research articles, derived from the systematic review, qualitative study, and scale development, have been submitted to peer-reviewed journals, reflecting the comprehensive approach taken in this endeavour. The outcomes of this research contribute not only to the academic discourse on ethical leadership but also offer practical insights for organisations operating in culturally diverse contexts
The role of Adaptive Energy Digital Twin technology in decarbonising emissions in the New Zealand process heat sector
No full textNew Zealand (NZ) is uniquely placed to meet the goal of net zero emissions in the industry sector by 2050, but only with an 80% expansion of renewable electricity generation (TWh) combined with energy efficiency improvements through advanced process heat integration, improved energy system design and control, future deployment of high temperature heat pumps (HTHP) for process heat up to 200oC and biomass for heat above 200oC, and smart integration of renewable electricity via microgrid connected factories and communities. The development of Adaptive Energy Digital Twin (AEDT) technology applied widely by energy consultants, equipment providers and factory owners, is considered a key development to aid industry decarbonisation. A seven-year research programme is underway in NZ to develop an open source AEDT technology platform and to demonstrate its usefulness for decarbonising a wide variety of industry sectors, such as dairy, meat, food, wood, paper, metals and chemical processing industries of NZ. Electricity supply and demand differences across the regions of NZ for 2020 and predicted for 2050 are also presented
Police education and democratic policing in Taiwan: a longitudinal quasi-experimental study of the effects of selection and police socialisation on human rights, moral reasoning and prejudice
No full textObjectives: To investigate the effects of selection and group socialisation on support of human rights, moral reasoning and prejudice in police officers in Taiwan. Methods: We used a longitudinal quasi-experimental design to track three cohorts of police officers (n = 585) and a comparison group of criminology undergraduates (n = 43). Results: There were no statistically significant differences in measures of human rights, moral reasoning and prejudice between new police recruits and the control group. However, time in police education was associated with a statistically significant reduction in police officer support of human rights, moral reasoning and an increase in prejudice. In the control group, the reverse was true. Conclusions: Exposure to police education in Taiwan resulted in police officers being significantly more prejudiced and significantly less adherent to the principles of human rights and moral reasoning. These results appear to be attributable to police socialisation rather than selection effects
Societal expectations for functional recovery of primary and secondary school buildings
No full textIn the ongoing investigation of functional recovery requirements, the spectrum of functional requirements for different facility types is necessary to ensure buildings are designed, constructed, and maintained to meet society's expectations. Schools are essential to communities, providing education and shelter to children. Education facilities that remain functional enable the community to recover quickly as parents can return to work or focus on rebuilding. However, functional recovery levels and expectations for schools could be better defined. Using interview responses, this pilot study, focusing on Hamilton, New Zealand, has constructed a five-level functionality continuum for school buildings addressing the societal expectations of community members, including parents, teachers, principals, civil defence, and the ministry of education. The five levels of functionality include life safety, reoccupancy, partial functionality, mostly functional, and fully functional. Each level has been defined in terms of available teaching and community expectations, acceptable damage and infrastructure requirements, and expectations for achievable timelines
Spillover effects of sanctions on airlines
Get PDFTo counter the escalating threat of direct conflict with rogue nations, the use of sanctions packages has become a preferred tactical response. However, although targeted, there are significantly elevated spillover effects that can generate sectoral damage. While the literature on sanctions has focused on analyzing the effectiveness and the impact on the sanctioned and sanctioning country, spillover effects have not been addressed in the tourism and travel industry. Based on behavioral decision theory and modern portfolio theory, this study states hypotheses and confronts two potential results derived from each theory regarding the way negative consequences of sanctions spill over into airlines. Using the aviation sanctions packages derived from the Russia-Ukraine war in 2022 in different regions worldwide, the results indicate greater spillovers flow into airlines than other aviation-related corporations, into big firms than small firms, and with significant differential effects on each analyzed region
Higher wear-resistant surfacing at high temperatures using a hybrid cladding process
Get PDFA novel hybrid cladding process is developed to control the mechanical properties of the inner metallic clad layer by combining direct energy deposition (DED) and ultrasonic nanocrystal surface modification (UNSM). The hybrid process allows the manipulation of the cladding layers' internal and external mechanical properties to the desired surface and bulk properties. To verify the usefulness of this method, the wear resistance test of the Inconel-718 cladding layer at high temperatures of 200 and 400 °C was performed, and it was confirmed that the wear resistance was improved to 25.4 % and 14.4 %, respectively. This work analyzes the wear-resistant characteristics with and without UNSM treatment in the DED process. The proposed method is a promising way to change the internal mechanical properties of the cladding layer with high controllability and repeatability
Repair eXtreme - DNA repair proteins from Antarctic extremophiles
Get PDFThe McMurdo Dry valleys (DV) in Antarctica are one of the harshest environments on Earth, with high levels of UV radiation, freeze-thaw cycles, low moisture, and nutrient content. Bacteria in this extreme environment have adapted to slow growth and low-nutrient conditions. It is proposed that bacteria from Antarctic DV systems may possess unique DNA repair enzymes and pathways that enable their survival in such extreme conditions. Exploring these DNA repair systems may offer valuable insights into microbial survival in extreme environments or even extra-terrestrial settings. To investigate this, DNA repair enzymes were identified from Antarctic DV microbial metagenomes using in silico analysis and in vivo characterisation of recombinantly produced proteins.
Four candidate enzymes were chosen for structural and biological characterisation. Three of these enzymes are characterised as LigB type ATP-dependent DNA ligases, with the typical arrangement of a DNA binding domain, adenylation domain and an OB-fold domain. These ligases can utilise both ATP and ADP nucleotide cofactors for the ligation of nick and mismatch DNA substrates, requiring the addition of magnesium or manganese metal ions. One LigB ligase stands out due to its interesting fusion with an N-terminally located nuclease domain, which resembles an extensively studied MBL-β-CASP domain found in all domains of life. The recombinantly expressed nuclease domain can coordinate several types of metal ions and shows nuclease activity against a diverse range of DNA substrates. Nuclease activity favoured single-stranded DNA substrates, in a 5’ to 3’ direction, and was particularly active on substrates with abasic sites or 5’ flaps. The fourth protein was initially annotated as a hypothetical protein, however in silico analysis revealed that it exhibited homology to NucS nucleases identified in archaea and bacteria. This NucS homolog is a monomeric enzyme, made up of four domains, which is different from other proteins in this family. This enzyme shows a preference for single-stranded DNA and has a broad range of nuclease activity on damaged and mismatched DNA substrates. It can utilise both magnesium and manganese metal ions for activity on DNA substrates. Overall, these findings suggest that the described enzymes will play a role in DNA repair pathways, potentially in high-damage environments like the DVs of Antarctica