Thesis (PH. D.)--Johns Hopkins university, 1913. / Life. Reprinted from Astrophysical journal, v. 39, 1914. eContent provider-neutral record in process. Description based on print version record.

Thesis (PH. D.)--Johns Hopkins university, 1913. / Life. Reprinted from Astrophysical journal, v. 39, 1914. eContent provider-neutral record in process. Description based on print version record.

Inaug.-diss.--Jena.

Th.--Math. appliquées--Bordeaux I, 1991. / Bibliogr. p. 242-244.

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擴散光學對生物醫學應用的近期發展有著一個很大的影響。光在生物組織中散播時，會發生很多的散射和吸收事件。當光束進入散射介質，在介質表面的光強度稱為擴散反射，而它包含了介質中吸收體和散射體的信息。這些信息可以幫助我們確定介質中發色團的濃度。 / 對於有特定光學特性的介質，利用蒙特卡羅模擬和擴散理論可以成功地模擬和計算出在三維空間和時間軸上的擴散反射。在實際應用上，我們更感興趣的是從擴散反射的信息中找出介質的光學性質。目前，大多數的解決方法只適用於光學特性均勻的介質。由於生物組織的光學特性並非均勻，所以我們很難去衡量其光學特性。為了獲取光學參數的二維空間分佈，傳統的方法會使用有多個點的光源和探測器陣列，得到多點的數值後再做圖像重建，因此空間分辨率非常有限。相比之下，提供高分辨率的解決方案，都具有較高的計算複雜性。 / 在這篇論文中，我們提出了一個快速和簡單的算法，以從二維空間的擴散反射得到光學特性非均勻的介質的光學性質（有效衰減率）。 這算法不只是給出單一組吸收和簡化散射系數，而是從擴散反射中得到一個有效衰減率分佈。這種算法會應用在重建有效衰減率的二維分佈。我們通過從數位相機取得的擴散反射圖像，並使用該算法，實現了能快速成像和具有高空間分辨率的有效衰減率二維分佈的影像重建。 / Diffusion optics has a great impact on recent development of biomedical applications. Scattering and absorption take place when light is propagating in biological tissue. Diffuse reflectance, which is the light intensity on the medium surface when a light beam enters a scattering medium, contains information on the absorbers and scatterers in the medium. This information can help us identify the concentration of chromophores in the tissue. / Monte Carlo simulation and diffusion theory, for given optical properties, can successfully simulate and calculate the spatial and temporal diffuse reflectance. In practice, we are more interested to find out the optical properties from the diffuse reflectance. At present, most methods that spatially resolve the optical properties are only applicable to homogenous medium. Biological tissue is non-homogeneous in nature. It is difficult to measure its optical properties, due to non-uniformity throughout the tissue being tested. To obtain the spatial distribution of optical parameters, conventional approaches use an array of light sources and detectors to reconstruct the image, thus spatial resolution is very limited. In contrast, solutions that provide high resolution have a high computational complexity. / In this thesis, we propose a fast, simple scheme to resolve the effective attenuation profile from the spatial diffuse reflectance. Rather than giving one single value for the absorption and reduced scattering coefficients, a novel algorithm is proposed for the reconstruction of an effective attenuation profile from a diffuse reflectance curve. This technique is applied to the reconstruction of a 2-D effective attenuation profile. By obtaining the diffuse reflectance image from a camera and using the algorithm developed here, fast imaging of the effective attenuation profile with relatively high spatial resolution can be achieved. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Tse, Jorden Yeong Tswen. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 91-99). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Acknowledges --- p.i / Abstract --- p.iii / 摘要 --- p.v / Table of Content --- p.vi / List of Figures --- p.xi / Introduction --- p.1 / Chapter 1.1 --- Optical imaging in Biomedical Sciences --- p.1 / Chapter 1.2 --- Light Diffusion in Biological Tissue --- p.3 / Chapter 1.2.1 --- Optical Parameters --- p.4 / Chapter 1.2.2 --- Diffusion Theory --- p.5 / Chapter 1.2.3 --- Monte Carlo Simulation --- p.8 / Chapter 1.2.4 --- Optical Absorption and Near Infra-red Spectroscopy --- p.10 / Chapter 1.3 --- Inverse Problem --- p.11 / Chapter 1.3.1 --- Time and frequency resolved system --- p.12 / Chapter 1.3.2 --- Spatial resolved system --- p.14 / Chapter 1.4 --- Major Contribution of this thesis --- p.14 / Chapter 1.5 --- Outline of the Thesis --- p.15 / Chapter Chapter 2 --- Experiment on Tissue Oximeter --- p.17 / Chapter 2.1 --- Principle of Tissue Oximeter --- p.17 / Chapter 2.2 --- Tissue Oximeter Design --- p.21 / Chapter 2.3 --- Estimating absorption coefficient from Diffuse Reflectance --- p.23 / Chapter 2.4 --- NIRS Tests on Farm Pigs --- p.24 / Chapter 2.4.1 --- Experiment Protocol --- p.25 / Chapter 2.4.2 --- Venous Occlusion --- p.27 / Chapter 2.4.3 --- Arterial Occlusion --- p.29 / Chapter 2.4.4 --- Total Occlusion --- p.31 / Chapter 2.5 --- Discussions --- p.33 / Chapter 2.6 --- Summary --- p.34 / Chapter Chapter 3 --- Monte Carlo Simulation and Diffusion Theory --- p.35 / Chapter 3.1 --- Monte Carlo Simulation for Light Diffusion in Biological Tissue --- p.35 / Chapter 3.1.1 --- Initialization --- p.37 / Chapter 3.1.2 --- Movement --- p.37 / Chapter 3.1.3 --- Interactions --- p.38 / Chapter 3.1.4 --- Termination --- p.40 / Chapter 3.1.5 --- Physical Quantities --- p.41 / Chapter 3.2 --- Comparison with Diffusion Theory --- p.42 / Chapter 3.2.1 --- Isotropic source --- p.44 / Chapter 3.3 --- Effects of optical parameters on diffuse reflectance --- p.45 / Chapter 3.3.1 --- Absorption Coefficient --- p.45 / Chapter 3.3.2 --- Scattering Coefficient --- p.46 / Chapter 3.3.3 --- Anisotropy and Reduced Scattering Coefficient --- p.47 / Chapter 3.3.4 --- Effective Attenuation Coefficient --- p.49 / Chapter 3.4 --- Summary --- p.51 / Chapter Chapter 4 --- Spatially Resolved Algorithm --- p.52 / Chapter 4.1 --- Previous works on spatially resolved diffuse optics --- p.52 / Chapter 4.2 --- Simplified Diffusion Approximation Model --- p.55 / Chapter 4.2.1 --- Homogeneous Medium --- p.57 / Chapter 4.2.2 --- Non-homogeneous Medium --- p.59 / Chapter 4.3 --- Discussions --- p.63 / Chapter 4.4 --- Summary --- p.64 / Chapter Chapter 5 --- 2-Dimensional Effective Attenuation Imaging System --- p.65 / Chapter 5.1 --- Overview --- p.65 / Chapter 5.1.1 --- Previous works on 2D oxygenation imaging --- p.65 / Chapter 5.2 --- Algorithm and Simulation --- p.69 / Chapter 5.2.1 --- Resolving Algorithm on PC --- p.70 / Chapter 5.2.2 --- 2-D Monte Carlo Simulation and Effective Attenuation Profile Resolving --- p.71 / Chapter 5.3 --- 2-D Effective Attenuation Imaging Instrument --- p.74 / Chapter 5.3.1 --- CCD Linearity --- p.75 / Chapter 5.3.2 --- Image Capturing --- p.78 / Chapter 5.3.3 --- System Calibration using Phantom --- p.80 / Chapter 5.3.4 --- Preliminary Study on Biological Tissue --- p.82 / Chapter 5.4 --- Discussions --- p.83 / Chapter 5.5 --- Summary --- p.87 / Chapter Chapter 6 --- Conclusions and Future Works --- p.88 / Chapter 6.1 --- Summary of the thesis --- p.88 / Chapter 6.2 --- Future Works --- p.89 / Bibliography --- p.91 / List of Publications --- p.100

The di raction of a one-dimensional expansion wave over a 90 corner was explored using experiment and simulation methods. Unlike studies in shock di raction, expansion wave di raction was hardly explored in the literature and therefore is considered as novel. Two independent parameters were identi ed for the present study: 1) the initial diaphragm shock tube pressure ratio, and 2) the position of the diaphragm from the apex of the 90 corner. The experimentation only considered variation in the shock tube pressure ratio whereas the simulation varied both independent parameters. A Navier-Stokes solver with Menters SST k-! turbulence model was found to adequately model the ow eld. A number of major ow features were identi ed, that occurred in the vicinity of the 90 corner. The ow features identi ed were: a shear layer which originated by ow separation near the apex of the 90 corner, a separation bubble that remained attached to a wall boundary in absence of rig-dependent e ects, and a re ected compression wave due to perturbation signals generated by di raction of the expansion wave. For a narrow-width expansion wave existing prior to di raction, it was found that after di raction a re ected compression wave developed which would steepen into an outwardly propagating, weak, cylindrical shock wave. Other major ow features identi ed were a strong indication of an oblique shock located near the separation bubble and a large wake region immediately downstream of the separation bubble. The wake region, through schlieren imaging, was found to consist of two distinct layers. The experimental results through shadowgraph and schlieren imaging have indicated large-scale turbulent structures within the separation bubble and the shear layer. Shear layer instability and vortex shedding o the separation bubble were also evident. The Navier-Stokes solver was found not to resolve the experimentally observed turbulence, the wake region and the vortex shedding.