京都大学 / 新制・課程博士 / 博士(生命科学) / 甲第24304号 / 生博第487号 / 新制||生||65(附属図書館) / 京都大学大学院生命科学研究科高次生命科学専攻 / (主査)教授 渡邊 直樹, 教授 見学 美根子, 教授 今吉 格 / 学位規則第4条第1項該当 / Doctor of Philosophy in Life Sciences / Kyoto University / DFAM

The Sun is of fundamental importance to life on earth and is studied by scientists from many disciplines. It exhibits phenomena on a wide range of observable scales, timescales and wavelengths and due to technological developments there is a continuing increase in the rate at which solar data is becoming available for study which presents both opportunities and challenges. Two satellites recently launched to observe the sun are STEREO (Solar TErrestrial RElations Observatory), providing simultaneous views of the SUN from two different viewpoints and SDO (Solar Dynamics Observatory) which aims to study the solar atmosphere on small scales and times and in many wavelengths. The STEREO and SDO missions are providing huge volumes of data at rates of about 15 GB per day (initially it was 30 GB per day) and 1.5 terabytes per day respectively. Accessing these huge data volumes efficiently at both high spatial and high time resolutions is important to support scientific discovery but requires increasingly efficient tools to browse, locate and process specific data sets. This thesis investigates the development of new technologies for processing information contained in multiple and overlapping images of the same scene to produce images of improved quality. This area in general is titled Super Resolution (SR), and offers a technique for reducing artefacts and increasing the spatial resolution. Another challenge is to generate 3D images such as Anaglyphs from uncalibrated pairs of SR images. An automated method to generate SR images is presented here. The SR technique consists of three stages: image registration, interpolation and filtration. Then a method to produce enhanced, near real-time, 3D solar images from uncalibrated pairs of images is introduced. Image registration is an essential enabling step in SR and Anaglyph processing. An accurate point-to-point mapping between views is estimated, with multiple images registered using only information contained within the images themselves. The performances of the proposed methods are evaluated using benchmark evaluation techniques. A software application called the SOLARSTUDIO has been developed to integrate and run all the methods introduced in this thesis. SOLARSTUDIO offers a number of useful image processing tools associated with activities highly focused on solar images including: Active Region (AR) segmentation, anaglyph creation, solar limb extraction, solar events tracking and video creation.

This work focuses on the high frequency restoration of video sequences captured by a hybrid camera, using key-frames as high frequency samples. The proposed method outlines a hierarchy to the super-resolution process, and is aimed at maximizing both speed and performance. Additionally, an advanced image processing simulator (EngineX) was developed to fine tune the algorithm. / Super-resolution algorithms are designed to enhance the detail level of a particular image or video sequence. However, it is very difficult to achieve in practice due to the problem being ill-posed, and often requires regularization based on assumptions about texture or edges. The process can be aided using high-resolution key-frames such as those generated from a hybrid camera. A hybrid camera is capable of capturing footage in multiple spatial and temporal resolutions. The typical output consists of a high resolution stream captured at low frame rate, and a low resolution stream captured at a high frame rate. Key-frame based super-resolution algorithms exploit the spatial and temporal correlation between the high resolution and low resolution streams to reconstruct a high resolution and high frame rate output stream. The proposed algorithm outlines a hierarchy to the super-resolution process, combining several different classical and novel methods. A residue formulation decides which pixels are required to be further reconstructed if a particular hierarchy stage fails to provide the expected results when compared to the low resolution prior. The hierarchy includes the optical flow based estimation which warps high frequency information from adjacent key-frames to the current frame. Specialized candidate pixel selection reduces the total number of pixels considered in the NLM stage. Occlusion is handled by a final fallback stage in the hierarchy. Additionally, the running time for a CIF sequence of 30 frames has been significantly reduced to within 3 minutes by identifying which pixels require reconstruction with a particular method. A custom simulation environment implements the proposed method as well as many common image processing algorithms. EngineX provides a graphical interface where video sequences and image processing methods can be manipulated and combined. The framework allows for advanced features such as multithreading, parameter sweeping, and block level abstraction which aided the development of the proposed super-resolution algorithm. Both speed and performance were fine tuned using the simulator which is the key to its improved quality over other traditional super-resolution schemes. / Thesis / Master of Applied Science (MASc)

Super duplex stainless steels are applied in highly corrosive environments. To withstand such conditions, they designed with increased content of alloying elements and a duplex microstructure consisting of austenitic and ferritic phases. The result of this combination is the desired improvement in corrosion resistance, but also, the enhancement of mechanical properties. Machining super duplex stainless steels involves strain hardening of the workpiece, intense adhesive wear and elevated temperatures within the cutting zone leading to rapid tool wear and poor machined surface integrity. This research pertains to the application of commercially available PVD coatings to minimize the detrimental effects when turning super duplex stainless steel S32750. The selected coatings for this study were Alcronos (AlCrN), Alnova (AlCrN + AlCrSiN), Formera (CrN + CrAlTiN), Croma Plus (Cr + CrN + OX), Fortiphy (CrN) and Certiphy (TiAlN). The wear behavior and mechanisms in two distinct machining experiments were evaluated, and all tools failed by chipping preceded by intense adhesive wear and BUE formation. The use of AlCrN coatings improved tool life significantly. Data on the cutting force, chip formation, and workpiece surface integrity indicate less workpiece strain hardening effects, improved friction conditions at the tool/chip interface, as well as thinner chips being formed when machining with Alcronos coated carbide inserts. The micro-mechanical properties of the selected coatings were assessed and Alcronos combined high hardness and elastic modulus with a high plasticity index value that allows this coating to better manage the friction in the cutting zone and better dissipate the energy generated during cutting. / Thesis / Master of Applied Science (MASc) / Super duplex stainless steels are designed to be applied in highly corrosive environments. Like any other stainless steels, processing the super duplex grade can be challenging, especially when it comes to machining. The major causes of poor machined surface quality and rapid tool wear are high temperature, the workpiece enhanced mechanical properties, surface hardening and the tendency to stick to the cutting tool causing adhesive wear. This research explores the application of coated cutting tools to improve the machinability of the super duplex stainless steel UNS S32750. Different commercially available coatings were tested and two, Alcronos and Alnova, improved tool life significantly. These two coatings were capable of improving the friction conditions within the cutting zone which, in turn, helps with the formation of the chips and leads to a better machined surface integrity and an approximately 5 to 6 times longer tool life.

This dissertation includes a collection of studies that aim to improve the way we represent and visualize volume data. The advancement of medical imaging has revolutionized healthcare, providing crucial anatomical insights for accurate diagnosis and treatment planning. Our first study introduces an innovative technique to enhance the utility of medical images, transitioning from monochromatic scans to vivid 3D representations. It presents a framework for reference-based automatic color transfer, establishing deep semantic correspondences between a colored reference image and grayscale medical scans. This methodology extends to volumetric rendering, eliminating the need for manual intervention in parameter tuning. Next, it delves into deep learning-based super-resolution for volume data. By leveraging color information and supplementary features, the proposed system efficiently upscales low-resolution renderings to achieve higher fidelity results. Temporal reprojection further strengthens stability in volumetric rendering. The third contribution centers on the compression and representation of volumetric data, leveraging coordinate-based networks and multi-resolution hash encoding. This approach demonstrates superior compression quality and training efficiency compared to other state-of-the-art neural volume representation techniques. Furthermore, we introduce a meta-learning technique for weight initialization to expedite convergence during training. These findings collectively underscore the potential for transformative advancements in large-scale data visualization and related applications.

Optical microscopy is the oldest form of microscopy that has been visually aiding scientific research. In our research, I have reported here two such optical microscopy techniques for two different projects. In the first project, we re-developed an instrumentation of a cost-effective, high-performing, single-molecular localization super-resolution microscopy setup that breaks the diffraction limitation barrier. Then we use a stochastic image capturing technique to capture the best precision image positions of gold nanoparticles. In our second project, we apply confocal microscopy technique to image DNA molecular nanoscale structural alterations of chromatin in cell nuclei of gut tissues caused by total body irradiation (TBI). We then quantify these alterations using a light localization technique called inverse participation ratio (IPR) using the confocal micrographs of the sample. Our results show radiation causes reduction and saturation of DNA spatial mass density fluctuations that were observed for different durations of post-irradiation.

No description available.

No description available.

No description available.

No description available.