title: Combining Hydromorphic and Shape-Shifting Effects for Programmable Passive Actuation in 4D-Printed Biocomposites

authors: Bachmann, Phil Aron

abstract: 4D printing involves the fabrication of structures that respond dynamically to external stimuli. While various actuation mechanisms have been extensively studied, the integration of multiple actuation effects remains relatively unexplored. This study examines the combined influence of hydromorphic and shape-shifting effects in a biocomposite containing 40 wt% cellulose fibres. The biocomposite was combined with polylactide (PLA) and processed via 3D printing to produce bi-material strips, which were then comprehensively analysed for their material properties and shape-changing behaviour. Upon immersion in water, the biocomposite expanded by 3.2 % perpendicular to the printing direction and exhibited a marked decrease in Young’s modulus with increasing water content. Bi-material strips 1 mm thick displayed pronounced hydromorphic behaviour, achieving maximum curvatures of 0.036 - 0.052 mm-1 depending on the passive-to-active layer thickness ratio. Thicker strips (4 mm) reached 0.012 mm-1 under the same conditions. When both heat and water were applied as external stimuli, the biocomposite and neat PLA layers became simultaneously active, and curvatures of up to 0.057 mm⁻¹ were obtained for 4 mm strips. This curvature surpassed the hydromorphic-only and shape-shifting-only responses by factors of 4.77 and 1.82, respectively. The results demonstrate that integrating water- and heat-induced stimuli increases achievable curvature and accelerates the response, enabling high-curvature deformations even in relatively thick structures. The approach therefore holds promise for applications that demand significant shape transformations without compromising structural integrity.

text: Combining Hydromorphic and Shape-Shifting Effects for Programmable Passive Actuation in 4D-Printed Biocomposites 4D printing involves the fabrication of structures that respond dynamically to external stimuli. While various actuation mechanisms have been extensively studied, the integration of multiple actuation effects remains relatively unexplored. This study examines the combined influence of hydromorphic and shape-shifting effects in a biocomposite containing 40 wt% cellulose fibres. The biocomposite was combined with polylactide (PLA) and processed via 3D printing to produce bi-material strips, which were then comprehensively analysed for their material properties and shape-changing behaviour. Upon immersion in water, the biocomposite expanded by 3.2 % perpendicular to the printing direction and exhibited a marked decrease in Young’s modulus with increasing water content. Bi-material strips 1 mm thick displayed pronounced hydromorphic behaviour, achieving maximum curvatures of 0.036 - 0.052 mm-1 depending on the passive-to-active layer thickness ratio. Thicker strips (4 mm) reached 0.012 mm-1 under the same conditions. When both heat and water were applied as external stimuli, the biocomposite and neat PLA layers became simultaneously active, and curvatures of up to 0.057 mm⁻¹ were obtained for 4 mm strips. This curvature surpassed the hydromorphic-only and shape-shifting-only responses by factors of 4.77 and 1.82, respectively. The results demonstrate that integrating water- and heat-induced stimuli increases achievable curvature and accelerates the response, enabling high-curvature deformations even in relatively thick structures. The approach therefore holds promise for applications that demand significant shape transformations without compromising structural integrity.

year: 2025

title: Insider threat modeling: An adversarial risk analysis approach

authors: Joshi, Chaitanya

abstract: Insider threats entail major security issues in geopolitics, cyber security and business organizations. Most earlier work in the field has focused on standard game theoretic approaches. We provide here two alternative, more realistic models based on adversarial risk analysis (ARA). ARA does not assume common knowledge and solves the problem from the point of view of just one of the players, the defender (typically), taking into account their knowledge and uncertainties regarding the choices available to them, to their adversaries, the possible outcomes, their payoffs/utilities and their opponents payoffs/utilities. The first model depicts the problem as a standard Defend-AttackDefend model. The second model segments the set of involved agents in three classes of users and considers both sequential as well as simultaneous actions. A data security example illustrates the discussion.

text: Insider threat modeling: An adversarial risk analysis approach Insider threats entail major security issues in geopolitics, cyber security and business organizations. Most earlier work in the field has focused on standard game theoretic approaches. We provide here two alternative, more realistic models based on adversarial risk analysis (ARA). ARA does not assume common knowledge and solves the problem from the point of view of just one of the players, the defender (typically), taking into account their knowledge and uncertainties regarding the choices available to them, to their adversaries, the possible outcomes, their payoffs/utilities and their opponents payoffs/utilities. The first model depicts the problem as a standard Defend-AttackDefend model. The second model segments the set of involved agents in three classes of users and considers both sequential as well as simultaneous actions. A data security example illustrates the discussion.

year: 2019

title: Mā ngā huruhuru ka rere te manu: Understanding leadership for critical educational reform in Aotearoa New Zealand

authors: Anderson, Zac Kylie Elizabeth

subjects: educational leadership

abstract: The research project presented in this thesis explores the leadership journeys of four first-time principals engaging in Kia Eke Panuku, a professional development initiative in English-medium secondary schools in Aotearoa New Zealand.  It seeks to understand the role these first-time principals play in insitutionalising to depth, educational reform to enable Māori students to pursue their potential as Māori under the Ka Hikitia imperative.  This thesis investigates the type of leadership required to achieve educational reform for Māori learners in Aotearoa, embedded in the inherent promise of the Treaty of Waitangi.
  
This thesis contends these principals contribute to educational reform by bringing criticality to their leadership and embracing an ongoing and iterative process of conscientisation and resistance, leading to transformative praxis.  These principals recognised their role as educators leading pedagogical change in their schools, as well as leading others within their sphere of influence to ultimately change the fabric of society in Aotearoa.  They both learned and led alongside each other, displaying an openness to embracing multiple worldviews with a deeply held moral imperative to eradicate oppression of Māori students.  Such a stance actively creates bicultural spaces within schools, where both Treaty partners can benefit from the principles of the Treaty promises.

text: Mā ngā huruhuru ka rere te manu: Understanding leadership for critical educational reform in Aotearoa New Zealand The research project presented in this thesis explores the leadership journeys of four first-time principals engaging in Kia Eke Panuku, a professional development initiative in English-medium secondary schools in Aotearoa New Zealand.  It seeks to understand the role these first-time principals play in insitutionalising to depth, educational reform to enable Māori students to pursue their potential as Māori under the Ka Hikitia imperative.  This thesis investigates the type of leadership required to achieve educational reform for Māori learners in Aotearoa, embedded in the inherent promise of the Treaty of Waitangi.
  
This thesis contends these principals contribute to educational reform by bringing criticality to their leadership and embracing an ongoing and iterative process of conscientisation and resistance, leading to transformative praxis.  These principals recognised their role as educators leading pedagogical change in their schools, as well as leading others within their sphere of influence to ultimately change the fabric of society in Aotearoa.  They both learned and led alongside each other, displaying an openness to embracing multiple worldviews with a deeply held moral imperative to eradicate oppression of Māori students.  Such a stance actively creates bicultural spaces within schools, where both Treaty partners can benefit from the principles of the Treaty promises.

year: 2018