10,922 research outputs found
Disorder in Extra-Large Pore Zeolite ITQ-33 Revealed by Single Crystal XRD
No full textThe single crystal of the extra-large pore zeolite, ITQ-33, was obtained and used to explore its crystal structure details. The ITQ-33 structure was found to be disordered with the columnar periodic building unit, explaining the morphology changes upon the different Si/Ge ratio, and the formation of the hierarchical structure from assembling of ITQ-33 nanofibers.Chemistry, MultidisciplinaryCrystallographyMaterials Science, MultidisciplinarySCI(E)EI0ARTICLE104168-41711
Electrically injected photonic-crystal nanocavities
No full textNano-emitters are the new generation of laser devices. A photonic-crystal cavity, which highly confines light in small volumes, in combination with quantum-dots can enhance the efficiency and lower the threshold of this device. The practical realisation of a reliable, electrically pumped photonic-crystal laser at room-temperature is, however, challenging.
In this project, a design for such a laser was established. Its properties are split up into electrical, optical and thermal tasks that are individually investigated via various device simulations. The resulting device performance showed that with our design the quantum-dots can be pumped in order to provide gain and to overcome the loss of the system. Threshold currents can be as low as 10’s of μA and Q-factors in the range of 1000’s. Gallium arsenide wafers were grown according to our specifications and their diode behaviour confirmed. Photonic-crystal cavities were fabricated through a newly developed process based on a TiOₓ hard-mask. Beside membraned cavities, also cavities on oxidised AlGaAs were fabricated with help to a unique hard-mask removal method. The cavities were measured with a self-made micro-photoluminescence setup with the highest Q-factor of 4000 for the membrane cavity and a remarkable 2200 for the oxide cavity. The fabrication steps, regarding the electrically pumped photonic-crystal laser, were developed and it was shown that this device can be fabricated.
During this project, a novel type of gentle confinement cavity was developed, based on the adaption of the dispersion curve (DA cavity) of a photonic-crystal waveguide. Q-factors of as high as 600.000 were measured for these cavities made in Silicon
Hanging the harp on the willow tree: music and national identity in postcolonial Ireland
No full textAn inquiry into how music served as a nation building tool in the early decades of the Irish Free State.M.A.Includes bibliographical referencesby Crystal N. Galyea
SUPPLEMENTAL – Supplemental material for Relationship between Parenting Style, Alexithymia and Aggression in Emerging Adults
No full textSupplemental material, SUPPLEMENTAL for Relationship between Parenting Style, Alexithymia and Aggression in Emerging Adults by Agnieszka B. Janik McErlean and Li Xian Crystal Lim in Journal of Family Issues</p
Anonymous_data – Supplemental material for Relationship between Parenting Style, Alexithymia and Aggression in Emerging Adults
No full textSupplemental material, Anonymous_data for Relationship between Parenting Style, Alexithymia and Aggression in Emerging Adults by Agnieszka B. Janik McErlean and Li Xian Crystal Lim in Journal of Family Issues</p
Anonymous_data – Supplemental material for Relationship between Parenting Style, Alexithymia and Aggression in Emerging Adults
No full textSupplemental material, Anonymous_data for Relationship between Parenting Style, Alexithymia and Aggression in Emerging Adults by Agnieszka B. Janik McErlean and Li Xian Crystal Lim in Journal of Family Issues</p
Investigation of nucleation and crystal growth kinetics of nickel manganese oxalates
No full textThe nucleation and the crystal growth rates of mixed nickel manganese oxalates have been determined from the changes of the ionic concentration of the solution and the crystal size distribution during the precipitation process within a supersaturation range 0–0.1 M. Thermodynamic solubility calculations have been used to identify the different species contributing the precipitation reaction and for estimation of the thermodynamic constant. Experimental data show that the nucleation rate of mixed nickel manganese oxalate in this supersaturation range is consistent with a primary heterogeneous mechanism and was found to obey to an exponential law. The crystal growth rates indicate a surface-integration-controlled mechanism with a first-order law with respect to the supersaturation
Thermal Modelling of the Ventilation and Cooling inside Axial Flux Permanent Magnet Generators
No full textAxial flux permanent magnet generators are of particular interest for power generation in harsh and confined conditions. Due to their compactness and high power density, the ventilation and cooling inside axial flux permanent magnet generators have becoming increasingly important for further performance improvement. This thesis describes the developments of a lumped parameter, thermal modelling technique for axial flux permanent magnet generators. The main aim of this research is to develop a fast and accurate thermal modelling tool which can be used for rapid machine design and ultimately, to replace complex and time consuming CFD analyses in the machine design process.
The thesis illustrates the construction of a generic thermal equivalent circuit, which comprises of conductive and convective sub-circuits, to model the conduction and convection heat transfers and temperature distributions in the radial and axial directions, within these machines. The conduction heat transfer between the solid components of these electrical machines is modelled by an annulus conductive thermal circuit derived from previous researchers; whereas, for convection heat transfer between the working fluid (air) and solids, the author has developed two convective thermal circuits, which are demonstrated as the Temperature Passing Method (TPM) and Heat Pick-up method in (HPM) in the thesis. Several case studies were designed to investigate the validity and accuracy of these thermal sub-circuits with both steady and transient boundary conditions. Since all the thermal impedances and capacitances used in the thermal circuits are in dimensionless form, the developed generic thermal equivalent circuit is capable of performing thermal simulations for axial flux generators of different sizes and topologies. Furthermore, special correction factors were introduced into the developed generic thermal equivalent circuit, to take into account the heat transfer in the circumferential direction in axial flux machines.
The thesis also demonstrates how the heat transfer in the stator windings is modelled in the generic thermal equivalent circuit. Two analytical models, which are the Simple Concentric Model (SCM) and Concentric-annulus Layer Model (CLM) were developed, for the evaluation of the thermal resistances of the stator windings. The results evaluated from these analytical models were validated by several numerical models and experimental results of two-phase materials published by previous researchers.
Lastly, experimental validation of the lumped parameter thermal equivalent circuit model and CFD simulations was conducted. Heat transfer coefficient measurements were carried out on two separate test rigs, which were a simplified single-sided axial flux machine test rig and a large-scale low speed axial flux machine. The experimental results were compared with the numerical results obtained from both the lumped parameter and CFD models. Good agreement between the experimental, lumped parameter model and CFD results were found. These indicate that the developed generic thermal circuit is potentially capable of replacing CFD analyses in the axial flux machines design process
Finite element method for 3D optical modeling of liquid crystal on silicon spatial light modulator
No full textAccurate optical modeling for design and optimization of liquid crystal on silicon spatial light modulators (LCoS SLMs) is important for phase-related applications. Traditional matrix method cannot accurately predict the optical performance when the LC distribution is complex, therefore the rigorous finite element method (FEM) is preferred. However, the optical modeling of LCoS is a multidimensional problem, which is difficult to simulate with FEM. Here, we present the development of an improved FEM by combining the scattering matrix method with the domain decomposition method to reduce the computational burden for optical simulation of LCoS. Furthermore, a 2D simulation example with phase grating displayed on LCoS is presented and compared with experiment.Grant ID: ColoOpt- EU H2020 ITN 721465ImPhys/Optic
Gel-mediated chemo-mechanical control of calcium carbonate crystal formation
No full textThe production of synthetic crystals with controlled shapes and properties is an enticing prospect, yet, the production of such materials is an ongoing challenge. Here, we present a strategy for chemo-mechanically directing the growth of crystals with non-equilibrium structures using a custom-designed double-diffusion cell. We combine chemical additives (e.g., Mg2+ ions) and mechanical confinement (e.g., hydrogel networks) to modulate the growth of calcium carbonate crystals. Specifically, the combination of Mg2+ ions with a strong agarose gel results in calcitic structures, at the gel-glass slide interface, with distinct fried egg-like morphologies and radial or Maltese-cross extinction patterns. In contrast, precipitation with only Mg2+ or agarose results in aragonite spherulites or squished calcite rhombohedra, respectively. Raman spectroscopy and energy dispersive spectroscopy of the “fried eggs” reveals that they are composed of Mg-calcite, which becomes less disordered over time, and the “egg whites” make this transition before the “yolks”. We propose that the “fried eggs” form due to a spherulitic growth process molded by the crystallization-induced delamination of the gel away from the glass slide at the gel-glass interface. In support of the importance of the gel-glass interface, the “fried eggs” do not form when the glass slide is treated with a hydrophobic silane, suppressing heterogeneous nucleation and weakening the interfacial adhesion between the gel and glass, making it easier for the gel to delaminate, thus reducing the confinement effect. As such, this work highlights the important chemo-mechanical role that gel environments can play in crystal formation.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Materials and Environmen
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