ENGLISH ABSTRACT: This thesis shows how raytracing can serve as an accurate irradiance mod-elling technique for bifacial PV modules. The electrical behaviour of bifacial modules is also modelled through investigation...
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ENGLISH ABSTRACT: This thesis shows how raytracing can serve as an accurate irradiance mod-elling technique for bifacial PV modules. The electrical behaviour of bifacial modules is also modelled through investigation and development of two electri-cal models. Bifacial PV modules can increase the power output per unit area when compared to monofacial PV modules. This is made possible by exposing the PV cells of a bifacial module to the incident irradiance on the front and the rear side. This potential increase in power output allows bifacial PV to be an important role player in the growth of PV technology in the renewable energy market. In order to advance bifacial PV as the primary technology in the solar market, it is necessary to accurately model and simulate bifacial mod-ules. Existing bifacial PV simulation software mostly implements view factors which proves to be ineffective in accurately modelling the rear side irradiance of modules. There are some uncertainties regarding the electrical performance of bifacial PV, which can be significantly reduced once an accurate model is established for the technology. An irradiance model is developed by implementing raytracing to model the front and rear side irradiance of bifacial modules. The irradiance model is verified by comparing modelled irradiance with irradiance measurements from an experimental bifacial PV installation. Two one-diode electrical models are implemented for bifacial modules. The two models are verified by comparing modelled power with measured power of a single bifacial module in a bifacial installation. The bifacial PV simulation software is developed by integrating the irradiance and electrical models with the python development language. After verification, the simulation software is used to simulate the effects of tilt angles, tracking, module height, albedo and row spacing on energy performance and bifacial gain of bifacial modules. A comparison is also done with existing commercial simulati
An advanced theoretical method to simulate the light delivery in plastic optical fiber is presented. The final objective is to use "light" as a new media for information delivery in wearable computers. A lar...
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An advanced theoretical method to simulate the light delivery in plastic optical fiber is presented. The final objective is to use "light" as a new media for information delivery in wearable computers. A large-time-step-based ray-tracing algorithm, which was improved from our previous research, was used to simulate the light vector movement in a complex weave structure efficiently. NURBS and free-form-deformation-based modeling was used to mimic the arbitrary weave structure. Experimentally, optical fibers were modified to control the direction of light emission. Particularly, half side of a cladding layer in the radial direction was selectively removed to enhance one-sided fabric light scattering. The cladding-removed plastic optical fiber was adopted in a textile weave structure, and its light scattering was measured quantitatively by varying the removal length, fiber curvature, and fabric weave patterns. To show the validity of the proposed simulation technique, twill structures with varying number of cross repeat numbers were used as a testbed. The unit number 2 was found to be the optimal structure for light emission, when a single POF was embedded in the textile. The proposed model showed the similar result with the actual light intensity measurement, with computation time not much than one second.
The acoustic raytracing relations are extended by the inclusion of auxiliary parameters describing variations in the spatial ray coordinates and eikonal vector due to changes in the initial conditions. Computation of...
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The acoustic raytracing relations are extended by the inclusion of auxiliary parameters describing variations in the spatial ray coordinates and eikonal vector due to changes in the initial conditions. Computation of these parameters allows one to define the geometric spreading factor along individual ray paths and assists in identification of caustic surfaces so that phase shifts can be easily identified. A method is developed leveraging the auxiliary parameters to identify propagation paths connecting specific source-receiver geometries, termed eigenrays. The newly introduced method is found to be highly efficient in cases where propagation is non-planar due to horizontal variations in the propagation medium or the presence of cross winds. The eigenray method is utilized in analysis of infrasonic signals produced by a multi-stage sounding rocket launch with promising results for applications of tracking aeroacoustic sources in the atmosphere and specifically to analysis of motor performance during dynamic tests. (C) 2017 Acoustical Society of America.
An approach is proposed to the height and displacement maps normalization from the spectra described by J. Tessendorf. Techniques are considered to avoid some rendering artefacts with projected grids when the viewer i...
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An approach is proposed to the height and displacement maps normalization from the spectra described by J. Tessendorf. Techniques are considered to avoid some rendering artefacts with projected grids when the viewer is (1) far from the origin of a coordinate system and (2) near the waterline. Modeling and lighting of the water surface is described. Techniques based on volumetric models using screen-space raytracing for rendering various atmospheric effects (clouds, fog, rain, snow, etc.) are proposed. Approaches to implementing these techniques applicable to a wide range of real-time applications are described.
A ray-tracing algorithm for interactive visualization of very large and structurally complicated scenes presented in the constructive solid geometry (CSG) form is suggested. The algorithm is capable of visualizing suc...
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A ray-tracing algorithm for interactive visualization of very large and structurally complicated scenes presented in the constructive solid geometry (CSG) form is suggested. The algorithm is capable of visualizing such scenes in real time by using a graphic processor. As primitives, classical shapes and objects represented in an analytical form (in particular, second-order surfaces and implicit functions) are used. Unlike other similar algorithms, our algorithm produces the final image in a single pass and has no constraints on the maximum number of primitives and on the CSG tree depth. The key feature of the algorithm is a method for optimizing CSG models, which converts the input tree to an equivalent spatially coherent and well-balanced form (a completely balanced equivalent tree may not exist). The performance of visualization after applying the optimization technique is shown to depend on only the computational resource of the GPU (in contrast to multi-pass algorithms whose performance is restricted by memory capacity). It has been shown experimentally that our algorithm is capable of rendering CSG models consisting of more than a million CSG primitives with the tree depth up to 24.
Highly collimated betatron radiation from a laser wakefield accelerator is a promising tool for spectroscopic measurements. Therefore, there is a requirement to create spectrometers suited to the unique properties of ...
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Highly collimated betatron radiation from a laser wakefield accelerator is a promising tool for spectroscopic measurements. Therefore, there is a requirement to create spectrometers suited to the unique properties of such a source. We demonstrate a spectrometer which achieves an energy resolution of < 5 eV at 9 keV (E/Delta E > 1800) and is angularly resolving the x-ray emission allowing the reference and spectrum to be recorded at the same time. The single photon analysis is used to significantly reduce the background noise. Theoretical performance of various configurations of the spectrometer is calculated by a ray-tracing algorithm. The properties and performance of the spectrometer including the angular and spectral resolution are demonstrated experimentally on absorption above the K-edge of a Cu foil backlit by a laser-produced betatron radiation x-ray beam. Published by AIP Publishing.
This paper is devoted to the development of physically correct rendering model of scenes containing volume scattering objects. The solution of the rendering equation is based on the Monte-Carlo bidirectional ray traci...
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This paper is devoted to the development of physically correct rendering model of scenes containing volume scattering objects. The solution of the rendering equation is based on the Monte-Carlo bidirectional raytracing. Two efficient approaches to the solution of the rendering equation for different parameters of the volume scattering medium (typically, concentration of scattering particles) are developed. Examples illustrate how the proposed models can be used for photorealistic visualization of scenes containing volume scattering objects and for the simulation of illuminators based on the volume scattering effect. Possible limitations of the application field of the proposed models are considered.
Lateral penumbra of multileaf collimator plays an important role in radiotherapy treatment planning. Growing evidence has revealed that, for a single-focused multileaf collimator, lateral penumbra width is leaf positi...
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Lateral penumbra of multileaf collimator plays an important role in radiotherapy treatment planning. Growing evidence has revealed that, for a single-focused multileaf collimator, lateral penumbra width is leaf position dependent and largely attributed to the leaf end shape. In our study, an analytical method for leaf end induced lateral penumbra modelling is formulated using Tangent Secant Theory. Compared with Monte Carlo simulation and raytracing algorithm, our model serves well the purpose of cost-efficient penumbra evaluation. Leaf ends represented in parametric forms of circular arc, elliptical arc, Bezier curve, and B-spline are implemented. With biobjective function of penumbra mean and variance introduced, genetic algorithm is carried out for approximating the Pareto frontier. Results show that for circular arc leaf end objective function is convex and convergence to optimal solution is guaranteed using gradient based iterative method. It is found that optimal leaf end in the shape of Bezier curve achieves minimal standard deviation, while using B-spline minimum of penumbra mean is obtained. For treatment modalities in clinical application, optimized leaf ends are in close agreement with actual shapes. Taken together, the method that we propose can provide insight into leaf end shape design of multileaf collimator.
This paper describes a new framework for the synthesis of aircraft flyover noise through a nonstandard atmosphere. Central to the framework is a ray-tracing algorithm that defines multiple curved propagation paths, if...
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This paper describes a new framework for the synthesis of aircraft flyover noise through a nonstandard atmosphere. Central to the framework is a ray-tracing algorithm that defines multiple curved propagation paths, if the atmosphere allows, between the moving source and listener. Because each path has a different emission angle, synthesis of the sound at the source must be performed independently for each path. The time delay, spreading loss, and absorption (ground and atmosphere) are integrated along each path and applied to each synthesized aircraft noise source to simulate a flyover. A final step assigns each resulting signal to its corresponding receiver angle for the simulation of a flyover in a virtual reality environment. Spectrograms of the results from a straight path and a curved path modeling assumption are shown. When the aircraft is at close range, the straight path results are valid. Differences appear especially when the source is relatively far away at shallow elevation angles. These differences, however, are not significant in common sound metrics. Although the framework used in this work performs off-line processing, it is conducive to real-time implementation.
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