Dissertations / Theses on the topic 'Confinement loss'

Les centrales nucléaires jouent un rôle important au niveau mondial dans la production d'électricité aujourd'hui. Dans l'histoire humaine, deux accidents tragiques ont déjà eu lieu, à Tchernobyl et Fukushima, provoquant des fuites des matières radioactives. Pour éviter ce genre d'accident dans la future, la construction en béton prend un rôle important en tant que matériau de construction de confinement qui est la dernière barrière pour isoler la matière radioactive de l'environnement. La compréhension des transferts dans le béton dans des circonstances graves, en particulier à étudier le comportement du béton sous haute température jusqu'à 200°C. Dans la première partie, un modèle de déshydratation a été appliqué dans le modèle thermo-hygro. Le modèle thermo-hygro a ensuite été mis en oeuvre pour simuler une maquette dont les résultats expérimentaux sont disponibles dans la littérature, sans tenir compte des comportements mécaniques. Enfin, des études paramétrique ont été réalisées pour étudier l'influence de certains paramètres. Le modèle à ensuite été appliqué à des structures sous vitesse de chauffage différente, et le modèle à ensuite été appliqué à des structure sous rythme de chauffage différents et celles avec des épaisseurs différentes pour comparer les profiles de température et de pression de gaz à travers de la mur<br>Nuclear power plant now takes an important part in the world's electricity generation. In human history, there have already been two tragic accidents in Chernobyl and Fukushima causing severe radioactive matter leakage. To pre- vent this kind of accident from happening again, concrete structure plays an important role as material of containment building, which is the last barrier to isolate the radioactive matter from the environment. Hence, the transfer properties of concrete under severe circumstances, especially high tempera- ture, are important for this usage. This PhD thesis aims to investigate the behavior of the concrete under high temperature up to 200°C. In the first part, a dehydration model was proposed. The model consists of different dehydration sub-models for main hydrates in the cement paste. In the second part, the dehydration model was implemented in a thermo-hygral model. The thermo- hygral model was then used to simulate a mock-up for which experimental results are available in the literature, without considering the mechanical behaviors. At last, parametric studies were performed to investigate the influ- ence of some parameters, and the model was then applied to structures under different heating rates, and structures with different thicknesses to compare the temperature and gas pressure profiles across a wall

Microstructured optical fibres (MOFs), also commonly called photonic crystal fibres or holey fibres, describe a type of optical fibre in which continuous channels of (typically) air run their entire length. These `holes' serve to both confine electromagnetic waves within the core of the fibre and to tailor its transmission properties. In order to understand and quantify both of these functions, a new computational algorithm was developed and implemented. It solves for the eigenvalues of Maxwell's wave equations in the two-dimensional waveguide cross-section, with radiating boundary conditions imposed outside the microstructure. This yields the leaky modes supported by the fibre. The boundary conditions are achieved exactly using a novel refinement scheme called the Adjustable Boundary Condition (ABC) method. Two implementations are programmed and their computational efficiencies are compared. Both use an azimuthal Fourier decomposition, but radially, a finite difference scheme is shown to be more efficient than a basis function expansion. The properties of the ABC method are then predicted theoretically using an original approach. It shows that the method is highly efficient, robust, automated and generally applicable to any implementation or to other radiating problems. A theoretical framework for the properties of modes in MOFs is also presented. It includes the use of the Bloch-Floquet theorem to provide a simpler and more efficient way to exploit microstructure symmetry. A new, but brief study of the modal birefringence properties in straight and spun fibres is also included. The theoretical and numerical tools are then applied to the study of polymer MOFs. Three types of fibres are numerically studied, fabricated and characterised. Each is of contemporary interest. Firstly, fabrication of the first MOFs with uniformly oriented elliptical holes is presented. A high degree of hole ellipticity is achieved using a simple technique relying on hole deformation during fibre draw. Both form and stress-optic birefringence are characterized over a broad scaled-wavelength range, which shows excellent agreement with numerical modelling. Secondly, an analysis of leaky modes in real air core MOFs, fabricated specifically for photonic band gap guidance, is then used to identify alternative guiding mechanisms. The supported leaky modes exhibit properties closely matching a simple hollow waveguide, weakly influenced by the surrounding microstructure. The analysis gives a quantitative determination of the wavelength dependent confinement loss of these modes and illustrates a mechanism not photonic band gap in origin by which colouration can be observed in such fibres. Finally, highly multimode MOFs (also called `air-clad' fibres) that have much wider light acceptance angles than conventional fibres are studied. An original and accurate method is presented for determining the numerical aperture of such fibres using leaky modes. The dependence on length, wavelength and various microstructure dimensions are evaluated for the first time for a class of fibres. These results show excellent agreement with published measurements on similar fibres and verify that bridge thicknesses much smaller than the wavelength are required for exceptionally high numerical apertures. The influence of multiple layers of holes on the numerical aperture and capture efficiency are then presented. It shows that a substantial increase in both these parameters can be achieved for some bridge thicknesses. Simple heuristic expressions for these quantities are given, which are based on the physical insight provided by the full numerical models. The work is then supported by the first fabrication attempts of large-core polymer MOFs with thin supporting bridges. These fibres exhibit relatively high numerical apertures and show good agreement with theoretical expectations over a very wide scaled-wavelength range.

Le développement de la plongée profonde d'assistance à l'industrie pétrolière offshore a considérablement modifié les conditions de travail des scaphandriers. Dans ce type de plongée, les scaphandriers vivent dans des conditions de longue durée sous des pressions élevées correspondant à la profondeur du chantier sous-marin (tous les 10 mètres de profondeur la pression augmente d'une valeur égale à la pression atmosphérique). Au cours de cette étude, nous avons cherché à connaître, en termes de réactions anxieuses, les conséquences de telles conditions de vie et de travail. Pour cela, nous avons utilisé l'échelle d'anxiété de Cattell (ou anxiety scale questionnaire, ASQ). Nos résultats ne montrent l'existence de réactions anxieuses que chez certains sujets, présentant soit une difficulté à gérer et à exprimer de façon appropriée les tensions, soit une prédisposition constitutionnelle à l'anxiété. Par ailleurs, le développement des réponses anxieuses apparaît également en relation avec d'autres facteurs, environnementaux, physiques, ou sociaux. Ainsi, suivant les sujets, on note une relation entre la réaction anxieuse et (1) le niveau de profondeur ; (2) la durée de confinement ; (3) le contexte opérationnel (pression du ca) ; ou (4) des difficultés relationnelles<br>Life conditions during deep diving include long term confinement at pressure environment (pressure increases of 1 bar; i. E the value of atmospheric pressure, every 10 meters depth). During the present study, we used the Cattell anxiety scale questionnaire to determine whether such conditions of occupational diving could induce anxious reactions related to confinement or pressure. Our results show that only few subjects, with psychological characteritics such as an anxious guilt or an incapacity to cope with frustration, developed anxious reactions else where, anxious reactions appear in relations ship with other factors such as time of confinement, pressure, psychosocial events or diving operations

Le verre de conditionnement des déchets issus des solutions radioactives de haute activité est le produit des réactions chimiques entre un précurseur vitreux (fritte de verre) et le déchet. Par une succession d'étape, le déchet est séché, dénitré (calcination) puis mélangé à la fritte de verre (vitrification) pour être vitrifié à haute température. Afin d'obtenir un verre monophasé à l'état liquide puis un verre de qualité optimale après refroidissement, les réactions doivent être complètes pour permettre l'incorporation totale du déchet au sein du réseau vitreux. Dans cet objectif, les paramètres physico-chimiques mis en jeu lors de l'étape de calcination et de vitrification sont fixés grâce à des règles empiriques (température, taux d'adjuvant, taux de charge en déchet). Complémentaire à cette approche, ce travail apporte de nouveaux éléments de compréhension de la chimie et des mécanismes réactionnels mis en jeu dans le processus de vitrification, et permet de développer un modèle mathématique simulant les réactions chimiques dans la zone réactive lors de l'élaboration du verre de déchet. Les résultats expérimentaux obtenus permettent de décrire précisément les différentes réactions chimiques en température à l'état solide, liquide et gazeux (thermique, morphologique, microstructurale et structurale), de calcinats simplifiés (NaNO3-Al2O3 ± MoO3/Nd2O3) en l'absence et en présence de fritte de verre (SiO2-Na2O-B2O3-Al2O3). Ils démontrent en particulier que la cristallisation du calcinat en elle-même n'est pas néfaste à la réactivité chimique mais que la nature et la stœchiométrie des phases cristallines formées ainsi que les cinétiques de transformation des calcinats (dénitration, cristallisation) peuvent modifier la réactivité chimique avec le verre et l'avancement des réactions. Ces résultats mettent alors en évidence comment le mode de dispersion des précurseurs, les propriétés physiques de la fritte de verre (viscosité, transition vitreuse) et la composition du calcinat (rapport Al2O3/Na2O) mais aussi sa cristallisation, peuvent modifier le processus de vitrification et l'homogénéité du verre final<br>The glass used to store high-level radioactive waste is produced by reaction of a solid waste residue and a glassy precursor (glass frit). The waste residue is first dried and calcined (to lose water and nitrogen respectively), then mixed with the glass frit to enable vitrification at high temperature. In order to obtain a good quality glass of constant composition upon cooling, the chemical reactions between the solid precursors must be complete while in the liquid state, to enable incorporation of the radioactive elements into the glassy matrix. The physical and chemical conditions during glass synthesis (e. G. Temperature, relative proportions of frit and calcine, amount of radioactive charge) are typically empirically adjusted to obtain a satisfactory final product. The aim of this work is to provide new insights into the chemical and physical interactions that take place during vitrification and to provide data for a mathematical model that has been developed to simulate the chemical reactions. The consequences of the different chemical reactions that involve solid, liquid and gaseous phases are described (thermal effects, changes in crystal morphology and composition, variations in melt properties and structure). In a first series of experiments, a simplified analogue of the calcine (NaNO3-Al2O3 ± MoO3/Nd2O3) has been studied. In a second series of experiments, the simplified calcines have been reacted with a simplified glass frit (SiO2-Na2O-B2O3-Al2O3) at high temperature. The results show that crystallization of the calcine may take place before interaction with the glass frit, but that the reactivity with the glass at high temperature is a function of the nature and stoichiometry of the crystalline phases which form at low temperature. The results also highlight how the mixing of the starting materials, the physical properties of the frit (viscosity, glass transition temperature) and the Na2O/Al2O3 of the calcine but also its crystallization all contribute to the success of the vitrification process and the homogeneity of the final glass

L’énergie électrique est devenue très importante dans la vie quotidienne. Pour atteindre les zones de grande consommation, l’électricité parcourt souvent de très grandes distances. Par exemple, pour acheminer l’énergie électrique de la Baie-James, centre de production important, jusqu’à Montréal, il y a près de 1 000 kilomètres de distance. Les bris de conducteurs causent des efforts dynamiques importants pouvant causer de lourdes pertes sur la ligne de transport. Réduire ces dommages et garder une distribution continue de l’énergie aux consommateurs est une préoccupation majeure pour les gestionnaires de réseaux électriques. Cette recherche porte sur l’étude de l’ajout d’un mécanisme ductile à la console des pylônes d’un canton de ligne soumis à un bris de conducteur. L’objectif principal de cette étude est de présenter une méthode pour évaluer la capacité optimale des consoles ductiles pour confiner la ruine causée par un bris de conducteurs. La clé est de trouver un équilibre entre la réduction du moment à la base des pylônes et le nombre de consoles plastifiées. L’étude comporte deux parties complémentaires. La première consiste à valider le modèle numérique avec les résultats d’un essai à échelle réduite disponible dans la littérature. La deuxième partie consiste à effectuer une étude paramétrique sur un canton composé de pylônes tubulaires en acier avec l’ajout du mécanisme ductile. L’étude paramétrique est effectuée sur le modèle pour étudier l’effet sur la réponse du système de la capacité de la console, la tension dans les câbles, la longueur de portée, la longueur de la chaîne d’isolateur et le choix de la loi de comportement du modèle. L’objectif de la console ductile est de réduire le moment à la base afin de réduire le nombre de pylônes subissant une ruine complète, tout en limitant le nombre de consoles affectées. Les modélisations réalisées avec le logiciel par éléments finis Code-Aster ont permis de reproduire la réponse dynamique du canton étudié après bris de conducteur. Les essais numériques ont permis d’observer une importante réduction du moment à la base au premier pylône. Pour des consoles ductiles dimensionnées pour des valeurs variant entre 40 % à 60 % de la capacité élastique de la console, la réduction du moment à la base du premier pylône peut atteindre de 30 % à 60 % du moment élastique selon le cas de chargement considéré, tandis que le nombre de consoles plastifiées varie entre 1 et 7 consoles.

Depuis la loi du 9 septembre 1986 relative au terrorisme, l’autorité publique fran1taise s'est dotée d'une loi tout a fait singulière pour lutter contre un phénomène qu'on qualifiera de récurent dans l'histoire fran1taise. II s'agissait, a travers une telle loi au moment de son vote en tout cas de faire échec au phénomène terroriste et ce a un moment de tension politique qu'il faisait peser sur l’État a l'origine de cette création législative. On soulignera que la loi indiquée se situait dans une perspective purement judiciaire offrant a la foi un dispositif tout a fait rigoureux dans la répression avec en outre une forme de bienveillance si l'on juge par l'existence de son dispositif visant les repentis. La phase policière comme juridictionnelle s' est dotée avec cette loi d'un appareil juridique désormais robuste apte à endiguer la menace terroriste. L’intérêt d’étudier !'aspect de la lutte antiterroriste depuis la création de cette loi matrice à la base de l’étude permet de lister à la suite de celle-ci l'affirmation d'un grand nombre de loi antiterroriste qui ont remodelé sans aucun doute la vision sur la matière. Ainsi, à un système à la base de sa création purement judiciaire et surtout éminemment rétrospectif, !'évolution du phénomène terroriste et surtout la culture du martyr particulièrement dans l'évolution du terrorisme d'origine moyen-oriental, a orienter le législateur sous le poids d'évènements dramatiques à se focaliser de plus en plus sur l'aspect préventif de la menace. C'est ainsi que subrepticement la phase pré-judiciaire a pris de l'ampleur pour anticiper le phénomène et ou le renseignement a dès lors prospéré. En effet, de multiples lois ont évolué vers l'aspect pré-infractionnel pour pouvoir endiguer les évènements avant même leurs survenances. Une telle évolution n'est pas neutre dans la garantie du respect des libertés publiques dues aux citoyens et ce alors même qu'un activisme législatif sur le sujet ne semble souffrir d'aucune critique de césarisme puisqu'il s'agit de garantir ici la protection du peuple face à la violence aveugle. Une telle évolution connaitra sa consécration avec la réactivation de la loi du 3 avril 1955 relative à l’État d'urgence qui au moment du terrorisme sunnite faisant vaciller la nation française récemment aboutira à de multiple prolongation d'un tel régime dérogatoire de gestion des libertés publiques avec tous ses corollaires de restrictions. La loi du 30 octobre 2017 viendra ensuite couronner ce retour du droit administratif dans la lutte puisqu'elle consacrera des éléments techniques de l’État d'urgence dans le droit commun. La survenance peu de temps après de la crise sanitaire perturbera dans la foulée grandement dans un état de stress permanent la vie démocratique française sur un sujet cette fois sanitaire de restrictions des libertés publiques une nouvelle fois, on constatera des prises de décisions à ce sujet en dehors du parlement avec le conseil de défense. Ainsi, la lutte antiterroriste aujourd'hui emprunte deux voies, d'une part le volet judiciaire quand l'acte eu lieu comme à l'époque de la loi matrice mais d'autre part surtout la voie administrative quand il s'agit de rechercher les risques de passage à l'acte terroriste. L'une comme l'autre de ces législations subissent un contrôle du droit conventionnel comme européen, situation garantissant une forme de protection des citoyens. Cette protection assurée par ce que l'on désigne par l’État de droit subi actuellement des critiques à l'heure ou les gouvernements sont dans des phases de précarités et ont pris goût à des législations sui generis<br>Since the law of September 9, 1986 on terrorism, the French public authority has adopted a very unique law to fight against a phenomenon that will be described as recurrent in French history. It was, through such a law at the time of its vote in any case to defeat the terrorist phenomenon and this at a time of political tension that it weighed on the State at the origin of this legislative creation. Tt should be noted that the law indicated was situated in a purely judicial perspective offering both a completely rigorous device in repression and also a form of benevolence if we judge by the existence of it device aimed at repentants. Both the police and the jurisdictional phase have been equipped with this law with a now robust legal apparatus capable of stemming the terrorist threat. The interest in studying the aspect of the fight against terrorism since the creation of this matrix law on which the study is based makes it possible to list after it the assertion of large number of anti-terrorist laws which have undoubtedly remodeled the vision on matter. Thus, to a system at tq.e base of its purely judicial creation and above all eminently retrospective, the evolution of the terrorist phenomenon and especially the culture of the martyr particularly in the evolution of terrorism of Middle Eastern origin, to direct the legislator under the weight dramatic events to focus more and more on the preventive aspect of the threat. This is how surreptitiously the pre-judicial phase grew to anticipate the phenomenon and where intelligence therefore flourished.Indeed, many laws have evolved towards the pre-offence aspect in order to be able to stem events even before they occur. Such a development is not neutral in guaranteeing respect for the public freedoms due to citizens, even though legislative activism on the subject does not seem to suffer from any criticism of Caesarism since it is a question of guaranteeing the protection of the people against indiscriminate violence. Such an evolution will know its consecration with the reactivation of the law of April 3, 1955 relating to the state of emergency which, at the time of Sunni terrorism which recently rocked the French nation, will lead to multiple extensions of such a derogatory regime for the management of civil liberties with all its corollaries of restrictions. The law of October 30, 2017 will then crown this return of administrative law to the fight since it will enshrine technical elements of the state of emergency in common law. The occurrence shortly after of the health crisis will greatly disrupt French democratic life in a state of permanent stress on a subject this time health of restrictions of publie freedoms once again, we will see decision-making on this subject in outside Parliament with the Defense Council. Thus, the fight against terrorism today has two paths, on the one hand the judicial aspect when the act took place as at the time of the matrix law but on the other hand above all the administrative path when it is a question of seeking the risk of a terrorist act. Both of these laws are subject to conventional and Europea law control, a situation guaranteeing a form of protection for citizens. This protection provided by what is referred to as the rule of law is currently being criticized at a time when governments are in precarious phases and have taken a liking tc sui generis legislation

Ce travail de thèse porte sur la modélisation et la simulation numérique des plasmas ionosphérique et Tokamak. La première partie de ce travail concerne la modélisation et la simulation numérique des effets de perturbations ionosphériques sur les communications terre-satellite. Le point départ de cette partie est l’analyse asymptotique du modèle de Euler-Maxwell conduisant ainsi au modèle Dynamo, qui se traduit en un couplage en 3D entre une équation elliptique pour le potentiel électrique et une équation de conservation de masse pour la densité du plasma. Du fait de la forte anisotropie de la matrice de diffusion associée a l’équation elliptique, on a developpé un schéma numérique préservant l’asymptotique permettant ainsi le bon conditionnement du systeme linéaire. La simulation de l’équation de conservation de masse est faite à l’aide de schémas de lois de conservation d’ordre elevé. La validation de ce modèle Dynamo s’obtient par une étude comparative avec le modèle Striation en 2D. Dans la deuxième partie, on s’intéresse au plasma Tokamak. On extrait du modele TOKAM3D, une équation de balance d’énergie de type non-linéaire en dimension 2 contenant toutes les difficultés numériques. Les méthodes numériques standard étant très coûteux en temps CPU, on developpe un schéma implicite-explicite prouvé efficace et stable pour ce type de problème. Enfin, ce schéma est combiné à une méthode de splitting dimensionnelle pour la discrétisation et des expériences numériques sont alors presentées<br>This thesis focuses on modeling and numerical simulation of ionospheric and Tokamak plasmas.The first part of this work concerns the modeling and simulation of ionospheric perturbations effects for earth-satellite communications. The starting point of this part is an asymptotic analysis of Euler-Maxwell model leading to Dynamo model, which results into a 3D coupling problem between an elliptic equation for the electric potential and a mass conservation equation for the plasma density. Because of the strong anisotropy of the diffusion matrix associated with the elliptic equation, we developed an asymptotic preserving numerical scheme thus allowing the well conditioned linear system. The simulation of the mass conservation equation is made by using high order conservation laws scheme. The validation of this model Dynamo is obtained by a comparison with the 2D Striation model. In the second part, we are interested in tokamak plasma. We extract from TOKAM3D model, a 2D nonlinear energy balance equation containing all the numerical difficulties. Standard numerical methods are very CPU consuming, thus we develop an implicit-explicit scheme shown efficient and stable for this type of problem. Finally, this scheme is combined with dimensional splitting method for the discretization and numerical experiments are then presented

碩士<br>中華大學<br>土木工程學系<br>106<br>In order to explore the applicability of the Convergence Confinement Method to simulate the third-direction forward excavation of the tunnel in two-dimensional analysis mode, the variation of convergence due to advancing excavation at different positions around a circular tunnel is verified with a confinement loss value. This study includes to use the confinement loss in the Convergence Confinement Method, to explore the relevant parameters of tunnel advancing effect function, to propose a method for predicting the confinement loss of tunnel pre-convergence and unsupported spans, and to establish the confinement loss curve of the tunnel. Finally, this analysis method is applied to the actual engineering tunnel cases studies. The numerical simulation of study that uses finite element analysis method (FEM) and explicit analysis method (EAM) is used to simulate the convergence in the tunnel excavation. The conditions of the analysis and simulation include: (1) anisotropic stress field of the lateral stress ratio 0.4 ≤ Ko ≤ 2.0, (2) unsupported/supported tunnel, and (3) Elastic/ elastic-plastic rock mass. The actual case study includes the measured convergence displacement of the Baguashan, New-Yongchun and New-Nanao tunnels. The local conditions include: (1) anisotropic stress field of the lateral stress ratio 0.4 ≤ Ko ≤ 2.0, (2) the different rock mass classifications, (3) the different tunnel excavation non-supported distance, and (4) the tunnel time effect. The convergence of the numerical simulation and the actual case, through the translation calculation and normalized method, that can obtain a confinement loss value that is not affected by the tunnel section locations and the lateral stress ratio. Through the regression analysis of the confinement loss value, we can know that the parameters η of the tunnel advancing effect function are affected by the surrounding rock properties. Regarding the influence of tunnel time effect this study proposes a translational calculation method to correct the convergence caused by the time effect. The results of the regression analysis are the same as those of the same rock mass classification without time effect. According to the above research results, the analysis program can be applied to the actual engineering, and the confinement loss curve which is not affected by the time effect, the tunnel section locations and the lateral stress ratio can be established. Keywords: Tunnel Advancing Effect, Convergence-Confinement Method, Confinement Loss, Finite Element Analysis Method, Explicit Analysis Method.

博士<br>中華大學<br>土木工程學系<br>105<br>In the tunneling construction, since the cycle tunneling may cause a section of unsupported span on tunnel face, thus supporting structure should be set to maintain the tunnel safety, so as to ensure of keeping wall rock and supporting structure to be in a safety range with stable state during continuously advancing. However, in the analysis and design process of tunnel excavation and supporting, the distance of this cycle tunneling or how to transform the unsupported span into the quantified numbers for the force loss or the increase of displacement becomes a fuzzy and uncertain impact factor. In order to understand the quantified relationship between tunnel surrounding stress or displacement release energy that caused by the unsupported distance during the tunnel advancing; that is, the main purpose of this Study intended to investigate the relationship between the unsupported span and confinement loss during the cycle tunneling process. Methodology of this Study included that adopted the Convergence-Confinement Method theory as the foundation to deduce the relationship between unsupported span and confinement loss during tunneling. In addition, this Study is applied the hyperbolic function, hyperbolic tangent function and exponential function to tend to build the advancing effect function for simulating the convergence tendency on the tunneling measurements, as well as used the statistical Regression Analysis to figure out the relevant parameters for individual function, so as to establish the confinement loss curve to simulate the displacement distribution for the supporting structure during tunneling. Secondly, this Study intended to verify the correctness and feasibility of the confinement loss curve, it adopted the 2D finite element method, within different states of initial stress, to solve the result of measurement calculation of simulating the tunneling in elastic or elastoplastic wall rock with or without supporting. Moreover, this Study used actual cases of measurement convergence for tunneling in highways and railway, and applied the horizontal displacement and normalization to calculate the parameters for the tunnel advancing effect function, and further to obtain the estimation of the distribution tendency and values for the confinement loss curve. By executing theoretic analysis and calculating procedures, this Study achieved these performances: (1) Proposed how to build the analytic equation of the theoretic model for the tunnel advancing effect function and confinement loss curve; (2) Proposed the estimation equation for the initial confinement loss on tunnel face, and the confinement loss of unsupported span during tunneling; (3) Investigated on those relevant parameters of tunnel advancing effect function and their corresponding influence, including the investigation on the changes between initial convergence and convergence slope on tunnel face; (4) The Numerical results showed that the vertical displacement of tunnel wall rock treated by normalization method which can eliminate the impact of the surrounding locations and the lateral stress ratio during tunneling; (5) After comparing the convergence data of actual tunneling cross-section measurements, it showed the hyperbolic function to have more consistent distribution tendency; (6) According to the analytic results of tunneling cases, it can verify the feasibility of the analysis theory and the numerical estimation method for the confinement loss that proposed in this Study, so as to achieve the goal of being the reference to the analysis and design of tunneling construction.

碩士<br>清雲科技大學<br>電子工程所<br>99<br>A high birefringence and low loss of index-guiding photonic crystal fiber (PCF) is proposed and compared to other structures using the finite element method. The proposed structure is composed of a cladding with modifying elliptical air holes and a core of solid silica surrounded with two half-size air holes. Numerical results confirm that the proposed structure at the excitation wavelength of λ= 1550 nm provides extremely high birefringence (~2.085×10-2) and ultralow confinement loss (&amp;lt;1.63×10-5dB/km). The merit of the designed PCFs is that the high birefringence and low confinement loss can be easily achieved by reducing two air holes which are near the fiber core.

In today’s world, the demand of ultra-fast information transfer with ultra-high bandwidths has reached to an extraordinary level. Hence, the transmission in the future internet-backbone will be constrained mostly in the network nodes. Also the power consumption of the network system will increase to indefensible levels. To overcome these constraints power-efficient photonic networks which can provide ultra-fast all-optical switching and routing are necessary. Optical buffering is required for such ultra-fast networks to avoid congestion. Slow-light effect has been investigated as one of the solution of optical buffering. It means slowing down the group velocity of light pulses in a medium. To realize this, many different methods and materials have been developed but due to its significant advantages the nonlinear effect of stimulated Brillouin scattering (SBS) is particularly promising. In this thesis, two different designs of photonic crystal fibers have been proposed for slow-light analysis. The first design is of rectangular core nature with inner air holes having more radius as compared to rest of the air holes. The material used for that design is Tellurite for 100 m long photonic crystal fiber. Another design has been designed with graded index feature i.e. the radius of the air holes keeps on increasing in a regular pattern. The analysis in this fiber has been done for 1 m long photonic crystal fiber with As2Se3 chalcogenide as material of the photonic crystal fiber. Fundamental properties such as confinement loss and effective mode area for both the designs have been simulated. Using those parameters, a maximum time-delay of 154.3 ns has been reported for the first design having tellurite material. The power requirement found to be 26 mW to achieve such high time delay for the length of 100 m long photonic crystal fiber. A Brillouin Gain of 19.07 dB has been reported for that design. For the second design having chalcogenide material, maximum time-delay of 252.8 ns has been reported for 1 m long photonic crystal fiber for a small input pump power of 9.8 mW. The Brillouin Gain achieved for this design was also more as compared to the first design i.e. 99.78 dB. Both the designs were thus compared for slow-light using SBS effect.

Photonic Crystal fibers consisting of defect region at a center surrounded by multiple air holes running along its length have been the topic of most interest of researchers because of unique properties over conventional optical fibers. Here basics of Photonic Crystal Fibers, PCFs modeling methods are discussed. A rectangular core photonic crystal fiber structure has been designed based on higher order mode filtering, in which single polarization is obtained with asymmetric design and introducing different loss for x-polarization and ypolarization of fundamental mode. Single polarization single mode operation of a highly birefringent photonic crystal fiber is investigated in detail by using a full vector finite element method with anisotropic perfectly matched layer. The variations of confinement loss and effective mode area of x-polarization and y-polarization of fundamental mode have been simulated by varying the structural parameters of the proposed photonic crystal fiber. At optimized parameters, the confinement loss and effective mode area is obtained as 0.94 dB/m and 60.67 µm2 for x-polarization as well as 26.67 dB/m and 67.23 µm2 for y-polarization of fundamental mode respectively at 1.55 µm. Therefore, 0.75 m length of fiber will be sufficient to get x-polarized fundamental mode with effective mode area as large as 60.67 µm2.

Photonic Crystal fibers consisting of defect region at a center surrounded by multiple air holes running along its length have been the topic of most interest of researchers because of unique properties over conventional optical fibers. Here basics of Photonic Crystal Fibers, PCFs modeling methods are discussed. A rectangular core photonic crystal fiber structure has been designed based on higher order mode filtering, in which single polarization is obtained with asymmetric design and introducing different loss for x-polarization and ypolarization of fundamental mode. Single polarization single mode operation of a highly birefringent photonic crystal fiber is investigated in detail by using a full vector finite element method with anisotropic perfectly matched layer. The variations of confinement loss and effective mode area of x-polarization and y-polarization of fundamental mode have been simulated by varying the structural parameters of the proposed photonic crystal fiber. At optimized parameters, the confinement loss and effective mode area is obtained as 0.94 dB/m and 60.67 μm2 for x-polarization as well as 26.67 dB/m and 67.23 μm2 for y-polarization of fundamental mode respectively at 1.55 μm. Therefore, 0.75 m length of fiber will be sufficient to get x-polarized fundamental mode with effective mode area as large as 60.67 μm2.

Plasmonic properties and the related novel applications are studied on various types of metallic nano-structures in one, two, or three dimensions. For 1D nanostructure, the motion of free electrons in a metal-film with nanoscale thickness is confined in its normal dimension and free in the other two. Describing the free-electron motion at metal-dielectric surfaces, surface plasmon polariton (SPP) is an elementary excitation of such motions and is well known. When further perforated with periodic array of holes, periodicity will introduce degeneracy, incur energy-level splitting, and facilitate the coupling between free-space photon and SPP. We applied this concept to achieve a plasmonic perfect absorber. The experimentally observed reflection dip splitting is qualitatively explained by a perturbation theory based on the above concept. If confined in 2D, the nanostructures become nanowires that intrigue a broad range of research interests. We performed various studies on the resonance and propagation of metal nanowires with different materials, cross-sectional shapes and form factors, in passive or active medium, in support of corresponding experimental works. Finite- Difference Time-Domain (FDTD) simulations show that simulated results agrees well with experiments and makes fundamental mode analysis possible. Confined in 3D, the electron motions in a single metal nanoparticle (NP) leads to localized surface plasmon resonance (LSPR) that enables another novel and important application: plasmon-heating. By exciting the LSPR of a gold particle embedded in liquid, the excited plasmon will decay into heat in the particle and will heat up the surrounding liquid eventually. With sufficient exciting optical intensity, the heat transfer from NP to liquid will undergo an explosive process and make a vapor envelop: nanobubble. We characterized the size, pressure and temperature of the nanobubble by a simple model relying on Mie calculations and continuous medium assumption. A novel effective medium method is also developed to replace the role of Mie calculations. The characterized temperature is in excellent agreement with that by Raman scattering. If fabricated in an ordered cluster, NPs exhibit double-resonance features and the double Fano-resonant structure is demonstrated to most enhance the four-wave mixing efficiency.