Neutron detection is important in several fields, especially detection of illicit nuclear material. Historically, 3He has been the basis for these technologies. Modern realities have necessitated the development of new technologies and the exploration of new materials to meet this need. One potential solution is known as capture-gating, which is a measurement approach that is good at differentiating between incident neutrons and gamma rays. The key issue is that materials used in current capture-gating devices can suffer from poor optical performance. This is due to the fact that the these detectors, whether composed of a heterogeneous or homogeneous mixture of materials, are made of dissimilar materials. In the homogeneous case, this frequently results in a cloudy material (e.g. lithium-gadolinium-borate crystals), while heterogeneous cases suffer from index mismatch (e.g. glass inside a plastic scintillator). The goal of this thesis is material development and processing toward an index-matched, gadolinium-based glass, heterogeneous capture-gated neutron detector. This involved identifying the refractive index range of known gadolinium glasses and the development of polystyrene (PS) and polyvinyl toluene (PVT) co-polymers with a range of refractive indices. Specifically 1:3, 1:1, and 3:1 PS:PVT ratios were manufactured and their refractive indices were compared to those of pure PS and PVT. Two methods for uniform glass dispersion were explored; the use of a rotisserie oven and the use of centrifugal planetary mixer. Ellipsometry, refractometry, and spectroscopic transmission were all performed to optically evaluate the manufactured polymers and polymer/glass composites. The ability to produce a PS/PVT copolymer with a refractive index in the range of known gadolinium glasses was demonstrated. In addition, the benefit of matching the refractive indices when producing a glass/polymer composite was explored and the effect of index mismatch was observed. The ability to predict the refractive index of a PS/PVT blend was demonstrated but can still be improved upon. While a novel index-matched gadolinium-based heterogeneous capture-gated neutron detector was not developed as part of this work, progress was made on all material aspects to further develop a detector meeting that description. More work still needs to be done in fine tuning the index match of the glass and polymer components, in determining the ideal method of glass dispersion, and in producing larger samples.

The family of semiconducting 2H-phase group-VI transition metal dichalcogenides (TMDs) have been suggested to be promising candidates for hosting optically accessible spin qubits due to their desirable optical and electrical properties, however, experimental progress towards this goal has been impeded by the difficulties associated with the fabrication of clean structures with quality contacts. In this thesis, we present the complex process for obtaining functional contacts to two particular TMDs, molybdenum disulfide (MoS2) and tungsten diselenide (WSe2), from which we use as the foundation for the fabrication of three important gate defined quantum structures: quantum dots, a charge detector, and a long 1D channel. These structures all play an important role in furthering the understanding of these materials and are the building blocks for achieving functional spin qubits. More precisely, we investigate the contact resistances associated with various cleaning procedures and contact architectures and report a recipe that results in an ultra-low contact resistance even at cryogenic temperatures. We then demonstrate electrical control of hole quantum dots, the host of the spin qubit, in gated heterostructure devices based on monolayer WSe2 and study its properties. With a similar structure, we demonstrate that a gate-defined nano-constriction is sensitive to the charge occupation of a nearby quantum dot and is therefore suitable to be used as a charge sensor, a valuable component of elaborate quantum circuits. Finally, we demonstrate the realization of a gate-defined quantum confined 1D channel in a high mobility monolayer WSe2 sample and observe an anomalous conductance quantization in units of e2/h. These results pave the way for the development of quantum devices based on electrostatically confined quantum dots defined in semiconducting TMDs and push forward our understanding of their electronic properties.

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Spillways are hydraulic structures that allow dams to release and convey surplus water or flood from the reservoir to the downstream channel. The spillway is a safety structure that prevents the overtopping of the dam. Many dam failure disasters were due to the inadequate capacity of the spillway, which fully illustrates the prominence of spillway design. According to the control structure, spillways can be divided into gated and ungated type. The gated spillway provides better control of the managed water level and reduces the elevation of the top of the dam. Researchers have mostly used experimental models to investigate these two types of spillways in previous literature. In the past few years, following the rapid development of numerical simulation technology, there have been more studies on the numerical modeling of spillways. However, most of the literature was about ungated spillways and most of it considered the case of low head ratios, while the case with gates, especially the case of vertical plane gates, was less investigated. In this study, the hydraulic characteristics, such as velocity, pressure, and discharge coefficient, of the ungated and gated ogee spillways are investigated by means of physical and numerical models for the case of low and high head ratios. The study covered head ratios varying from 1.4 to 4.6 and the relative gate-openings varying from 0.5 to 2. The second main objective of this study was to evaluate the performance of the numerical model to simulate gated and ungated spillways. It mainly employed 2DV OpenFOAM to simulate three turbulence models (realizable k-ε, RNG k-ε, k-ω SST), and the results were compared and calibrated with the experimental results from the physical model tests performed by the author to verify the performance of the numerical model. This study aims to demonstrate that the numerical model can be used as a complementary tool to the physical model to measure the hydraulic performance of ogee spillways.

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