京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第19168号 / 理博第4108号 / 新制||理||1591(附属図書館) / 32160 / 京都大学大学院理学研究科地球惑星科学専攻 / (主査)准教授 重 尚一, 准教授 林 泰一, 教授 余田 成男 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

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In this paper¡Awe use both beam propagation method and BPM_CAD to analysis the characteristics of nonlinear optical waveguide structures. The refractive index of optical waveguide medium changes with field intensity called nonlinear optical waveguide. We use Mode Theory to solve three layers optical waveguide. There are nonlinear cladding, substrate layers and linear film. Not only find the disperson relation curve, but also observe the affections of the input power to field distribution. With the help of this, we propose a general math method to analysis symmetric muti-layer optical waveguide with periodic index that both cladding and substrate are nonlinear. According to the nonlinear dispersion relation we consider both the affections of the input power to refractive index in the film and space soliton at nonlinear interface. We propose a optical coupler and feed-back optical switch. And also, we analysis 2¡Ñ3 branches optical waveguides by changing their media to nonlinear media. According to the result, we find that they have both logic function and optical switch.

In several practical applications, hot-finished steel pipe that exhibits Lüders bands is bent to strains of 2-3%. Lüders banding is a material instability that leads to inhomogeneous plastic deformation in the range of 1-4%. This work investigates the influence of Lüders banding on the inelastic response and stability of tubes under rotation controlled pure bending. It starts with the results of an experimental study involving tubes of several diameter-to-thickness ratios in the range of 33.2 to 14.7 and Lüders strains of 1.8% to 2.7%. In all cases, the initial elastic regime terminates at a local moment maximum and the local nucleation of narrow angled Lüders bands of higher strain on the tension and compression sides of the tube. As the rotation continues, the bands multiply and spread axially causing the affected zone to bend to a higher curvature while the rest of the tube is still at the curvature corresponding to the initial moment maximum. With further rotation of the ends, the higher curvature zone(s) gradually spreads while the moment remains essentially unchanged. For relatively low D/t tubes and/or short Lüders strains, the whole tube eventually is deformed to the higher curvature entering the usual hardening regime. Subsequently it continues to deform uniformly until the usual limit moment instability is reached. For high D/t tubes and/or materials with longer Lüders strains, the propagation of the larger curvature is interrupted by collapse when a critical length is Lüders deformed leaving behind part of the structure essentially undeformed. The higher the D/t and/or the longer the Lüders strain is, the shorter the critical length. This class of problems is analyzed using 3D finite elements while the material is modeled as an elastic-plastic solid with an “up-down-up” response over the extent of the Lüders strain, followed by hardening. The analysis reproduces the main features of the mechanical behavior provided the unstable part of the response is suitably calibrated. The uniform curvature elastic regime terminates with the nucleation of localized banded deformation. The bands appear in pockets on the most deformed sites of the tube and propagate into the hitherto intact part of the structure while the moment remains essentially unchanged. The Lüders-deformed section has a higher curvature, ovalizes more than the rest of the tube, and develops wrinkles with a characteristic wavelength. For every tube D/t there exists a threshold of Lüders strain separating the two types of behavior. This bounding value of Lüders strain was studied parametrically. / text

Zur numerischen Simulation piezoelektrischer Probleme mit linearem Materialgesetz wird die adaptive Finite-Element-Methode genutzt. Bei der Lösung der entstehenden Gleichungssysteme vom Sattelpunktstyp wird auf eine Variante des Bramble-Pasciak-CG zurückgegriffen. Die Einbettung von Projektionstechniken in den Löser erlaubt eine Behandlung von verschiedenen Problembesonderheiten, speziell wird hier auf die Fälle konstanten Potentials auf Teilrändern sowie Kontaktprobleme an wachsenden Rissen eingegangen. Erste numerische Ergebnisse werden an einigen Beispielen demonstriert.

Previous experimental observations have shown that the pseudoelastic response of NiTi shape memory alloys (SMA) is localized in nature and proceeds through nucleation and propagation of localized deformation bands. It has also been observed that the mechanical response of SMAs is strongly affected by loading rate and cyclic degradation. These behaviors significantly limit the accurate modeling of SMA elements used in various devices and applications. The aim of this work is to provide engineers with a constitutive model that can accurately describe the dynamic, unstable pseudoelastic response of SMAs, including their cyclic response, and facilitate the reliable design of SMA elements. A 1-D phenomenological model is developed to simulate the localized phase transformations in NiTi wires during both loading and unloading. In this model, it is assumed that the untransformed particles located close to the transformed regions are less stable than those further away from the transformed regions. By consideration of the thermomechanical coupling among the stress, temperature, and latent heat of transformation, the analysis can account for strain-rate effects. Inspired by the deformation theory of plasticity, the 1-D model is extended to a 3-D macromechanical model of localized unstable pseudoelasticity. An important feature of this model is the reorientation of the transformation strain tensor with changes in stress tensor. Unlike previous modeling efforts, the present model can also capture the propagation of localized deformation during unloading. The constitutive model is implemented within a 2-D finite element framework to allow numerical investigation of the effect of strain rate and boundary conditions on the overall mechanical response and evolution of localized transformation bands in NiTi strips. The model successfully captures the features of the transformation front morphology, and pseudoelastic response of NiTi strip samples observed in previous experiments. The 1-D and 3-D constitutive models are further extended to include the plastic deformation and degradation of material properties as a result of cyclic loading.

Previous experimental observations have shown that the pseudoelastic response of NiTi shape memory alloys (SMA) is localized in nature and proceeds through nucleation and propagation of localized deformation bands. It has also been observed that the mechanical response of SMAs is strongly affected by loading rate and cyclic degradation. These behaviors significantly limit the accurate modeling of SMA elements used in various devices and applications. The aim of this work is to provide engineers with a constitutive model that can accurately describe the dynamic, unstable pseudoelastic response of SMAs, including their cyclic response, and facilitate the reliable design of SMA elements. A 1-D phenomenological model is developed to simulate the localized phase transformations in NiTi wires during both loading and unloading. In this model, it is assumed that the untransformed particles located close to the transformed regions are less stable than those further away from the transformed regions. By consideration of the thermomechanical coupling among the stress, temperature, and latent heat of transformation, the analysis can account for strain-rate effects. Inspired by the deformation theory of plasticity, the 1-D model is extended to a 3-D macromechanical model of localized unstable pseudoelasticity. An important feature of this model is the reorientation of the transformation strain tensor with changes in stress tensor. Unlike previous modeling efforts, the present model can also capture the propagation of localized deformation during unloading. The constitutive model is implemented within a 2-D finite element framework to allow numerical investigation of the effect of strain rate and boundary conditions on the overall mechanical response and evolution of localized transformation bands in NiTi strips. The model successfully captures the features of the transformation front morphology, and pseudoelastic response of NiTi strip samples observed in previous experiments. The 1-D and 3-D constitutive models are further extended to include the plastic deformation and degradation of material properties as a result of cyclic loading.

Previous experimental observations have shown that the pseudoelastic response of NiTi shape memory alloys (SMA) is localized in nature and proceeds through nucleation and propagation of localized deformation bands. It has also been observed that the mechanical response of SMAs is strongly affected by loading rate and cyclic degradation. These behaviors significantly limit the accurate modeling of SMA elements used in various devices and applications. The aim of this work is to provide engineers with a constitutive model that can accurately describe the dynamic, unstable pseudoelastic response of SMAs, including their cyclic response, and facilitate the reliable design of SMA elements. A 1-D phenomenological model is developed to simulate the localized phase transformations in NiTi wires during both loading and unloading. In this model, it is assumed that the untransformed particles located close to the transformed regions are less stable than those further away from the transformed regions. By consideration of the thermomechanical coupling among the stress, temperature, and latent heat of transformation, the analysis can account for strain-rate effects. Inspired by the deformation theory of plasticity, the 1-D model is extended to a 3-D macromechanical model of localized unstable pseudoelasticity. An important feature of this model is the reorientation of the transformation strain tensor with changes in stress tensor. Unlike previous modeling efforts, the present model can also capture the propagation of localized deformation during unloading. The constitutive model is implemented within a 2-D finite element framework to allow numerical investigation of the effect of strain rate and boundary conditions on the overall mechanical response and evolution of localized transformation bands in NiTi strips. The model successfully captures the features of the transformation front morphology, and pseudoelastic response of NiTi strip samples observed in previous experiments. The 1-D and 3-D constitutive models are further extended to include the plastic deformation and degradation of material properties as a result of cyclic loading. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

Introduction: Functional motility disorders of the colon are poorly defined. Hence, patients with chronic colonic motor dysfunction are treated or undergo surgery without proper diagnosis. Most colonic motility assessment centers around the largest propagating motor pattern in the colon- the High Amplitude Propagating Pressure Wave (HAPW). However, there is no consensus regarding a definition of this important motor pattern. Additionally, no consideration is given to other aspects of colonic motility such as colo-ano-rectal coordination and control by the autonomic nervous system (ANS). The aim of this thesis was to improve understanding of HAPWs and other features of colonic motility in health and constipation, understand how autonomic dysfunction is related to observations in patients, and evaluate the effect of neuromodulation of the ANS. Methods: Motility was assessed in healthy volunteers and patients using water-perfused High Resolution Colonic Manometry (HRCM). To assess the association between ANS and colonic motor activity Heart Rate Variability (HRV) was measured in patients. Spatiotemporal maps were created using HRCM to analyse and quantify colonic motor activity following baseline, and interventions which included proximal balloon distention, meal, and rectal bisacodyl. Low-Level Light Therapy (LLLT) was also applied during HRCM as a method of neuromodulation, to observe its effect on colonic motility. Results: Normal HAPWs are those which have an amplitude of more than 50 mmHg and belong to one of 3 categories: proximally originating, proximal continuing, and transverse/descending. The best intervention sequence to generate these during HRCM assessment is baseline, proximal balloon distention, meal, rectal bisacodyl. Based on their responses to these interventions and the type of HAPWs present, patients could be classified into strong responder, weak responder and non-responder groups. Overall, patients in the strong responder group were most similar to healthy volunteers both with regard to motility and ANS control. Conversely, the weak and non-responders had showed decreased or no motility with decreased parasympathetic input and occasionally sympathetic inhibition. Additionally, other features of motility such as the sphincter of O'Beirne, and lack of colo-ano-rectal coordination were found to lead to constipation even in presence of normal HAPWs. LLLT shows promise in initiating colonic motor activity through neuromodulation of the sacral defecation center. Conclusions: HAPWs can be defined into one of three categories and used to categorize patients based on their HAPW response to different interventions. However, other aspects of colonic motility such as the colo-ano-rectal coordination and autonomic nervous system control of colonic motility should be taken into consideration in diagnosis of constipation, as they can point towards more non-invasive treatment methods such as neuromodulation using LLLT. / Thesis / Master of Science in Medical Sciences (MSMS)