DR-NTU (Digital Repository of NTU)
Not a member yet
116018 research outputs found
Sort by
Offshore embeddedness beyond the wall: Chinese cloud providers in Southeast Asia’s data governance landscape
No full textWhy do middle power states permit companies from institutionally controversial jurisdictions to build and run critical cloud infrastructure on their soil, despite pronounced data governance concerns? How do such firms convert deep suspicion into durable market legitimacy amid intensifying geopolitical competition? Drawing on case studies of Alibaba Cloud and Tencent Cloud across five ASEAN countries (2015–2024), this article proposes the concept of offshore embeddedness: a legitimacy strategy that combines demonstrable separation from home-state control with deep integration into host-state governance structures. Three mechanisms underpin this strategy: regulatory-infrastructure convergence through exhaustive certification and sovereign cloud builds, network integration via stakeholder coalitions that fuse firm survival to domestic political interests, and organizational decoupling accomplished through verifiable legal separation from home-country governance. ASEAN governments shape these outcomes by acting as gatekeeper-regulators (imposing localization and audit preconditions), infrastructure brokers (exchanging market access for domestic data center investment and skills transfer), and coalition orchestrators (embedding foreign clouds within host-led political-economic networks). Through these roles, domestic data governance frameworks shift from exclusionary shields to leverage tools, recalibrating digital governance and binary US–China narratives.Published versio
Topological optical skyrmion transfer to matter
No full textThe ability of structured light to mimic exotic topological skyrmion textures encountered in high-energy physics, cosmology, magnetic materials, and superfluids has recently received considerable attention. Despite their promise as mechanisms for data encoding and storage, there has been a lack of studies addressing the transfer and storage of the topology of optical skyrmions to matter. Here, we demonstrate a high-fidelity mapping of skyrmion topology from a laser beam onto a gas of cold atoms, where it is detected in its new non-propagating form. Within the spatial overlap of the beam and atom cloud, the skyrmion topological charge is preserved, with a reduction from Q ≃ 0.91 to Q ≃ 0.84, mainly due to the beam width exceeding the sample size. Our work potentially opens novel avenues for topological photonic state storage and the analysis of more complex structured light topologies.Ministry of Education (MOE)Published versionThis work was supported by the CQT/MoE (Grant No. R-710-002-016-271), the Singapore Ministry of Education Academic Research Fund Tier 2 (Grant No. MOE-T2EP50220-0008), and EPSRC UK (Grant No. EP/S002952/1)
Effective presentations, reductions, and degrees
No full textThe primary focus of this thesis is in computability theory, investigating the broad question "How much of mathematics can be done algorithmically?" More specifically, we focus on studying this question in the context of mathematical structures.
In Part I, we study the different notions of effectively presented topological spaces and groups. Within the literature, the most common notions of presentations for Polish spaces are computably, left-c.e., and right-c.e. presented spaces. While these notions have been around for quite some time, only recently has there been an interest in attempting to compare and separate these notions. In this thesis, we study the various notions mentioned above for both Polish groups and Polish spaces, separating them up to homeomorphism. In particular, we prove that there exists Polish spaces and groups that are left-c.e. and right-c.e. presentable but not homeomorphic to any computably presented Polish space and group respectively.
In Part II, we present some results regarding a relatively recent research program in the study of primitive recursion. Under this program, one of the areas of interest is in the degree structure induced by the reduction "being primitively recursively isomorphic", referred to as the punctual degrees (of an algebraic structure). We mainly study density and non-density of the punctual degrees of various structures, like the dense linear order, equivalence relations, and the class of discrete linear orders. Additionally, following the pattern of computable structure theory, we also present results regarding an analogue of relativised categoricity for punctual structures (to be defined).
Finally, in Part III, we study the computably enumerable tt degrees (to be defined), and resolve a question of Cai et al.: there exists a tt minimal pair such that both degrees are wtt complete. Even though the result itself seems like a small improvement to existing results, a substantial change in the strategy of the proof seems to be necessary.Doctor of Philosoph
Advanced modulation for multi-level DC-DC power converters in solar and battery energy storage systems
No full textThis article introduces the application of a novel modulation strategy in photovoltaic systems. The method adopted was implemented in a multi-level converter structure and validated through simulation studies. The results indicate that the referenced modulation scheme significantly reduces overall power loss, which is the main objective of this work. In addition, the system benefits from a reduction in the number of components, which may lower overall costs and complexity. This article validates the application of advanced modulation techniques in photovoltaic systems through simulation and deduction, contributing to improving the efficiency and practicality of photovoltaic power conversion systems.Master's degre
Electoral politics in the East Malaysian state of Sabah and the future of "Sabah for Sabahans"
No full textThe 17th Sabah State Election, due in the next six months, represents a critical juncture for Sabah’s political trajectory, particularly for the “Sabah for Sabahans” ideology, which champions local autonomy and identity within Malaysia’s federal framework. This election will determine whether Sabah can consolidate its push for greater self-governance, as promised under the Malaysia Agreement 1963, amidst a fragmented political landscape, shifting coalitions, and the fallout from a recent corruption scandal. The election is pivotal for advancing the “Sabah for Sabahans” movement, offering Sabahans a chance to strengthen political control and redefine federal-state relations. The outcome, however, hinges on coalition dynamics, the scandal’s impact, and the ability of state-based parties to harness voters’ sentiments beyond the localised context.Published versio
Recent advances of metal-organic frameworks and derivatives for rechargeable aluminum batteries
No full textIn light of cost-effectiveness, high volumetric capacity, and abundant supplies on Earth of aluminum metal, the rechargeable aluminum battery (RAB) represents a cutting-edge alternative for energy storage devices. RABs have achieved significant progress as a result of tireless efforts; however, challenges like as expensive ionic liquid electrolytes, a restricted voltage window of aqueous electrolytes, corroded anode, and rapid capacity degradation limit their practical applications. In terms of increasing RAB mileage, electrode materials can be regarded as the foundation of battery performance. Metal-organic frameworks (MOFs), which have customizable topologies, multiple active sites, and various metal centers and ligands, are promising electrode materials. Herein, for the first time, we deliver in detail the recent advancement of MOFs in RABs. The relationship on structure-properties-performance of MOFs is thoroughly discussed. MOF and MOF-derived electrode materials are first summarized. In Al-S/Se batteries, MOF can serve as a host to capture the sulfides or selenides. Furthermore, the MOF as catalysts for Al-air batteries are provided. Then we focused on the challenges and opportunities that RABs would face in the future, and some prospects are presented. We believe this account will facilitate the exploration of MOFs in RABs and give more inspiration for discovering advanced RABs.Agency for Science, Technology and Research (A*STAR)National Research Foundation (NRF)Published versionFinancial support was provided by the ASTAR MTC programmatic project under Grant No. M23L9b0052, Indonesia-NTU Singapore Institute ofResearch for Sustainability and Innovation (INSPIRASI) under Contract No. 6635/E3/KL.02.02/2023, and Singapore NRF Singapore-China flagship programunder Grant No. 023740-00001
Effect of modulated heat source on diffusive and avalanche-like transport
No full textWe utilize the global full-F gyrokinetic code GYSELA to analyze the nonlocal transport in the presence of modulated heat source, the period of which is in the range of a transport timescale. In submarginal stable case, it is observed that a localized and time-modulated heat source can trigger both diffusive and avalanche-like transport. When heat source-stimulated nonlocal transport occurs, propagation of turbulence is faster than that of heat pulse. In addition, the propagation speed is correlated with both turbulence intensity and period of modulated source. This correlation is also identified from the analytic expression derived from two-field critical gradient model.National Research Foundation (NRF)Published versionThis research is supported by the National Research Foundation, Singapore. The computational work for this article was partially performed on resources of the National Supercomputing Centre, Singapore (www.nscc.sg), provided with computer and storage resources by GENCI at TGCC thanks to the Grant 2024-A0160502224 on the supercomputer Joliot Curie’s the SKL and ROME partition, and granted access to the HPC resources of the EUROfusion High Performance computer (Marconi-Fusion) under the Project GYSHAP
Atomically unveiling the phase evolution in weakly coupled layered transition-metal phosphorus trichalcogenide by chalcogen doping
No full textThe stacking configuration significantly influences the properties of van der Waals (vdW) layered magnets by dictating crystallographic and magnetic symmetries. Transition-metal phosphorus trichalcogenides (MPX3, X = S, Se) intrinsically exhibit diverse stacking polytypes, being an optimal platform for magnetic phase engineering. Unlike MX2, where chalcogen doping has a minimal impact on stacking, MPX3 allows stacking control via elemental substitution. However, the atomic-scale mechanisms governing stacking variations remain unclear. Using scanning transmission electron microscopy (STEM) and density functional theory (DFT) calculations, we reveal that in 3d transition metal MPX3, tuning the S/Se ratio induces a transition from the C2/m to R3̅ phase due to modified interlayer S–S/Se–Se and P–P interactions. In contrast, stacking control becomes challenging for 4d CdPX3, due to relatively weak interlayer coupling. These insights provide a stacking basis for stacking polytypes in MPX3, paving the way for tuning magnetic couplings via stackingtronics.Ministry of Education (MOE)National Research Foundation (NRF)X.Z. thanks the National Key R&D Program of China (2024YFE0109200, 2024YFA1410000), the Beijing Natural Science Foundation (JQ24010, Z220020), the National Natural Science Foundation of China (52273279, 12374170), the open research fund of Songshan Lake Materials Laboratory (2023SLABFN26), and the Fundamental Research Funds for the Central Universities. We thank Materials Processing and Analysis Center, Peking University, for assistance with STEM (XRD, SEM, Raman) characterization. The authors acknowledge Electron Microscopy Laboratory of Peking University, China, for the use of Cs corrected Nion U-HERMES200 scanning transmission electron microscopy. This work was supported by National Research Foundation−Competitive Research Program NRFCRP22-2019-0007. This work was also supported from the Singapore Ministry of Education Tier 3 Programme “Geometrical Quantum Materials” AcRF Tier 3 (MOE2018-T3-1- 002). This work was also supported from the Singapore Ministry of Education Tier 3 Programme “Geometrical Quantum Materials” AcRF Tier 3 (MOE2018-T3-1-002). This research was also supported by the Ministry of Education, Singapore, under its Research Centre of Excellence award to the Institute for Functional Intelligent Materials (Project No. EDUNC-33-18-279-V12)
Molecular engineering of hybrid perovskites: enhancing versatility, properties, and applications
No full textHybrid halide perovskites (HHPs) have emerged as a prominent class of materials due to their versatile properties, tunable composition, and diverse crystal structures, which make them suitable for various applications, including solar cells, light-emitting diodes (LEDs), and photocatalysts. This thesis explores the molecular engineering of hybrid perovskites to enhance their properties and expand their application potential. The research focuses on the role of organic cations, incorporating transition metal complexes, and integrating viologen-based ligands to introduce new functionalities and improve stability.
The first part of the thesis investigates the influence of organic cations on the optoelectronic properties of hybrid perovskites. While the inorganic framework primarily dictates the electronic band structure, the organic cations indirectly affect dielectric environment, bandgap, and exciton binding energy. Introducing new cations and tailoring their interactions with the inorganic sublattice demonstrates the potential to fine-tune material properties, leading to enhanced performance in photovoltaic and optoelectronic devices.
The second part delves into the incorporation of transition metal complexes, specifically d-elements such as copper and nickel, as metal-organic cations in the perovskite structure. These modifications result in unique optical properties, including wide-range emission and interband transitions. The novel approach of using metal complexes within the organic component of the perovskite structure represents a significant advancement that allows the addition of one more degree of freedom into perovskite tunability, as well as additional levels into electron structure because of d-metals.
In the third part, the thesis explores the incorporation of viologen-based ligands into the perovskite framework, highlighted through two key projects. The first project examines the continuous photo-induced enhancement of photoluminescence in a novel viologen-based complex, benzyl viologen tetrachloroferrate ([BnzV][FeCl4]), rather than a perovskite. The unique behaviour is attributed to photoinduced electron transfer (PIET) and subsequent excitation steps within the viologen-metal framework. For the first time, this project investigates and reports the mechanism of solid-state viologen photoluminescence, which makes it possible to design viologen-based perovskites with targeted excitation, PIET, and structure to get desirable properties.
The second project delves into the study of the one-dimensional (1D) hybrid perovskite, PrVPb₂I₆, which incorporates a propyl viologen ligand. This research highlights the thermochromic behaviour of the material, driven by thermally induced charge transfer processes. The findings demonstrate how the interaction between the viologen cation and the inorganic sublattice can lead to reversible shifts in photoluminescence emission, depending on the temperature. This enhanced thermal stability and unique optical properties make this material a promising candidate for temperature-sensitive applications, including thermal sensors and tunable photonic devices.
The novelty of the Research: This thesis presents a pioneering approach in hybrid halide perovskite design by focusing on the molecular engineering of these materials to introduce novel functionalities and enhanced stability. Unlike previous studies that predominantly explored the role of organic cations in stabilising perovskite structures, this research chose cations which directly can influence band gap and electron transitions in perovskites. This unique tactic modifies the optoelectronic properties and imparts new characteristics such as tunable wide-range emission, photo-induced electron transfer, and thermochromic behaviour. This work represents a significant departure from traditional perovskite research by shifting the focus from merely understanding to actively engineering the organic component, thereby expanding the functional versatility of hybrid perovskites.
The findings of this research contribute to the fundamental understanding of the optical and physical properties of hybrid perovskites and provide a foundation for developing next-generation materials with tailored properties for specific applications. The work also highlights the versatility of viologen ligands and their potential to introduce new functionalities into the perovskite family, paving the way for future innovations in optoelectronic devices.Doctor of Philosoph
The enduring shadow of extremism: tackling radicalisation in the Bangladeshi diaspora
No full textThe recent arrests in Malaysia confirm that radicalisation within the Bangladeshi diaspora is a significant and evolving threat. This problem stems from socioeconomic factors, homeland instability, and online recruitment. A transparent, collaborative, and multi-faceted P/CVE (Preventing and Countering Violent Extremism) approach is essential to mitigate the risk.Published versio