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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Online Image Analysis of Jurkat T Cells using in situ Microscopy

Joensuu, Jenny January 2015 (has links)
Cell cultivation in bioreactors would benefit from developed monitoring systems with online real-time imaging to evaluate cell culture conditions and processes. This opportunity can be provided with the newly developed in situ Microscope also called ISM. The ISM probe is mounted into the wall of a bioreactor and consists of a measurement zone with an illuminating light source to obtain real-time images of moving cells in suspension. The instrument is linked to advanced imaging analysis software which can be specifically adapted for the objects in study. The aim of this project is to analyze the T lymphocyte cell line Jurkat T cells using the ISM equipment and identify specific features of the cells that can be obtained. The results show that the equipment and linked software are suitable for monitoring cell density, cell size distribution and cell surface analysis of the Jurkat cells during cultivation. The ISM could also detect induced changes in cell size caused by osmotic shifts and the course of an infection occurring in the cell suspension using a developed software for online real-time monitoring.
2

Reducing Image Artifacts in Motion Blur Prevention

Zixun Yu (15354811) 27 April 2023 (has links)
<p>Motion blur is a form of image quality degradation, showing as content in the image smearing and not looking sharp. It is usually seen in photography due to relative motion between the camera and the scene (either camera moves or objects in the scene move). It is also seen in human vision systems, primarily on digital displays.</p> <p><br></p> <p>It is often desired to remove motion blurriness from images. Numerous works have been put into reducing motion blur <em>after</em> the image has been formed, e.g., for camera-captured ones. Unlike post-processing methods, we take the approach to prevent/minimize motion blur for both human and camera observation by pre-processing the source image. The pre-processed images are supposed to look sharp upon blurring. Note that, only pre-processing methods can deal with human-observed blurriness since the imagery can't be modified after it is formed on the retina.</p> <p><br></p> <p>Pre-processing methods face more fundamental challenges than post-processing ones. A problem inherent to such methods is the appearance of ringing artifacts which are intensity oscillations reducing the quality of the observed image. We found that these ringing artifacts have a fundamental cause rooted in the blur kernel. The blur kernel usually have very low amplitudes in some frequencies, significantly attenuating the signal intensity in these frequencies when it convolves an image. Pre-processing methods can usually reconstruct the targeted image to the observer but inevitably lose energy in those frequencies, appearing as artifacts. To address the artifact issue, we present a few approaches: (a) aligning the image content and the kernel in the frequency domain, and (b) redistributing their intensity variations elsewhere in the image. We demonstrate the effectiveness of our method in a working prototype, in simulation, and with a user study.</p>
3

MODEL-BASED IMAGE CHARACTERIZATION AND EMPIRICAL MODELING OF HIGH BURNUP MONOLITHIC U-MO FUEL

Alejandro Luis Figueroa (15354469) 30 April 2023 (has links)
<p> Monolithic uranium molybdenum alloys (U-Mo) are considered a candidate for converting high-performance research and test reactors from high-enriched uranium to low enrichment alternatives. The metallic fuel is capable of conversion due to the high U loading and favorable radiation performance. During irradiation, the fuel undergoes a three-part swelling behavior, with an initial linear swelling rate followed by an increase in the swelling rate represented by an increase in the nucleation of fission-gas bubbles, and ending with stabilization at the highest fission densities. Understanding the high burnup regime is critical to extending the life of the reactor and creating accurate fuel performance models. To accurately inform swelling models, it is necessary to experimentally characterize the pore evolution as a function of burnup and the influence of diffusion barrier-fuel interaction on the morphology. Therefore, a systematic approach was conducted to experimentally characterize the influence of irradiation and fuel-diffusion barrier interaction on the pore morphology and then empirically model the porosity evolution. Initially, three separate locations in a monolithic U-Mo fuel plate with burnups ranging from 8.9-9.4x1021 fissions/cm3 were investigated using scanning electron micrography (SEM) to characterize the morphological porosity dependence on fission density. To investigate the impact of the Zr-fuel interface on the pore morphology, two specimens were imaged using synchrotron microcomputed tomography (Sr-µCT) from a U-Mo monolithic miniplate irradiated to 9.8x1021 fissions/cm3, one at the diffusion barrier and one in the bulk fuel. Synchrotron microcomputed tomography allows for the characterization of the influence of fuel-Zr diffusion barrier interaction on the pore morphology in three dimensions; however, due to the novelty of this technique applied to nuclear fuels the results were verified with SEM serial sectioning. The multimodal comparison between the Sr-µCT and SEM serial sectioning allows for a direct assessment of the capabilities of each technique for nuclear fuel applications. Due to the complex microstructure and imaging challenges in analyzing these samples, several model-based image processing and characterization tools were developed to aid in the analysis. An empirical model for porosity evolution in high-burnup U-Mo was developed and accurately modeled the porosity behavior. The experimental results from the current work and the empirical model developed can be used to inform mechanistic modeling efforts in the community. </p>

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