Дисертації з теми "Parameter of the type of stress state"

Дисертаційна робота присвячена розробці критерія граничного стану конструкційних матеріалів, які працюють в умовах складного напруженого стану у випадку статичного навантаження з урахуванням пошкоджуваності. Для визначення величини параметра пошкоджуваності використовувалися різні енергетичні підходи, які базуються на зміні фізико-механічних характеристик матеріалів при простих навантаженнях (розтяг та кручення). На основі отриманих експериментальних результатів на різних конструкційних матеріалах, вдосконалено модель опису кінетики накопичення пошкодження, запропонований Бонора, в залежності від рівня пластичної деформації. Отримано залежність параметрів моделі та критерія граничного стану від пружно-пластичних характеристик матеріала. Проведено порівняння отриманих теоретичних значень з експериментальними. Розроблена методика визначення кінетики накопичення пошкодження у випадку кручення циліндричних зразків з врахуванням неоднорідності розподілу деформації в перерізі зразка. На основі підходу Давіденкова-Фрідмана розроблено критерій граничного стану конструкційних матеріалів з врахуванням виду напруженого стану та пошкоджуваності. Представлено порівняння результатів граничного стану, отриманих за розробленим критерієм, експериментальними даними, та іншими методами.

[Formulae and special characters can not be reproduced here. Please see the pdf version of the Abstract for an accurate reproduction.] The thesis provides a comprehensive study on the behaviour of sand with a small amount of fines [i.e.1/3 plastic fines and 2/3 non-plastic fines]. The work is carried out experimentally under axi-symmetric conditions using the triaxial apparatus. Conventional drained triaxial tests are conducted on isotropic consolidated specimens and all the tests indicate that sand with fines does not manifest any unusual behaviour under drained conditions. However in undrained shearing the so-called ???reverse behaviour??? is noted. The study demonstrates that the reverse behaviour conforms to the critical state framework because significant changes in the position and geometry of the critical state [CS] and isotropic consolidation [IL] lines are caused by the presence of fines. These changes cannot be adequately modelled by the intergranular void ratio as proposed by Thevanayagam and Mohan (2000). This study also demonstrates that the original state parameter [special character] as proposed by Been and Jefferies (1985) is not an adequate parameter to predict the undrained behaviour trend. A new parameter termed ???modified state parameter??? [special character] is proposed to account for the combined effects of density and confining pressure. The suitability of the modified state parameter to characterise the response of parent sand and sand with fines is assessed for a range of void ratios and confining pressures. The effect of drained stress history is an important factor affecting the subsequent undrained response. Drained pre-shearing to failure is found to improve considerably the subsequent undrained response to the extent that liquefaction may not occur. Different drained pre-shearing histories have different effects on the undrained response. However in these tests [special character] has limitations in quantifying the subsequent undrained stress-strain response. Hence, a new framework of ???yielding parameter??? [special character] extends the capability of [special character] and additional data is presented to demonstrate the suitability of this concept. The implementation of [special character] depends on whether the previous stress state reached during the stress history is below or at failure. The effects of drained pre-shearing on the position and movement of failure surface are investigated. It is found that drained pre-shearing to failure at larger confining pressures has the effect of shifting upwards part of the drained failure surface. The shift at larger stress ratios [special character] may be described in terms of dilatancy and modified state parameter at failure. The so-called strain path tests are conducted to study the influence of strain increment ratio on the deformation behaviour of sand with fines. It is found that the value of [special character] has significant effects on the stress-strain behaviour. Along negative [special character] paths the soil strain softens in the form of decreasing the shear resistance before reaching the failure state. In contrast, along positive [special character] paths the soil strain hardens to an asymptotic stress ratio. The asymptotic stress ratio decreases with increasing [special character] along a linear relationship. The framework of [special character] cannot quantify the stress-strain response along positive and negative strain paths. Consequently an ???instability parameter??? [special character] is proposed to extend the capabilities of [special character] and the reliability of this parameter is further assessed. The behaviour along a range of positive and negative [special character] paths is investigated on pre-sheared specimens. In negative [special character] the effective stress paths reach a surface located higher than the monotonic failure surface on which they trace downward towards the origin of stress space. The results indicate this surface may be the same as the drained failure envelope which has been shifted as a result of drained pre-shearing. In positive [special character] paths a large improvement is noted in both the strength and stiffness of the soil. Note The parameters [special character] and [special character] are all generalisations of [special character] so that the behaviour under complex conditions can be characterised.

The prediction of settlements in infrastructural design puts high demands on the numerical analysis of the subsoil and the associated constitutive model: complex installation processes and the repetitive character of live loads pose considerable challenges. Although in this context the main focus is on the analytical requirements of a geotechnical problem in order to realistically capture soil behaviour, the needs of engineering practice should not be neglected in constitutive modelling. Along these lines, a new soil model for non-cohesive soils has been developed in the theoretical framework of elastoplasticity. Based on the concept of bounding surface plasticity according to Manzari and Dafalias (1997), soil properties such as strength, stiffness and dilatancy depend on the distance between the current stress state and a corresponding model surface in stress space. This way the multi surface model correctly reproduces elementary behavioural patterns of soil, including for example shear related phenomena such as hardening/softening, contraction/dilation and attainment of critical state (constant volume shear strength). Moreover, the model captures the state dependence of soil behaviour (barotropy and pycnotropy). Thus, with only one set of material parameters, the mechanical behaviour of a wide range of initial soil states with respect to stress and void ratio can be simulated (unified modelling). The kinematic hardening mechanism of the conical yield surface contributes to a realistic stiffness evolution in un- and reloading and is hence essential for stress or strain accumulation due to load reversals. Since the chosen modelling framework is suitable for further development, the original formulation has been extended to adapt the model to the defined needs. In order to adequately simulate geotechnically relevant stress paths of low and higher complexity, first of all, a cap shaped yield surface was added to allow for plastic straining not only in shear, but also in constant stress ratio loading (e. g. isotropic or oedometric compression). When it comes to stress paths of unconventional orientation, to load reversals or composed stress paths with changes in loading direction, a supplementary stiffness increase at small strains and its subsequent strain dependent degradation have proven valuable. Furthermore, an additional mechanism accounts for a regressive accumulation of stresses or strains with increasing number of load cycles (in terms of dissipated energy). In view of its suitability for practical use, all model extensions are structured in a modular fashion, so that the complexity of the model (and hence the amount of parameters) can be adapted to the complexity of the geotechnical problem by activating or deactivating certain features. Most model parameters can be determined by conventional laboratory testing. An internal routine optionally facilitates the parameter choice by calibrating certain bounding surface related parameters from an alternative user input, which is more oriented towards experimental outcome. Since a good understanding of a material model is crucial for its reasonable and responsible use, the present thesis aims at offering a sound documentation. Thus, the first part gives an outline of the underlying bounding surface concept and describes the innovations on the constitutive level with reference to theoretical considerations. It is followed by a detailed analysis of capabilities and limitations of the extended model. The next part is dedicated to the numerical implementation of the soil model and its calibration procedure on the basis of laboratory test results. Moreover, the embedded calibration routine including the applied optimisation algorithm is presented. The subsequent section serves model validation: by means of element test simulations, generation of response envelopes as well as the reproduction of more general (e. g. composed) stress paths the performance of the extended bounding surface model is demonstrated. Finally, the last chapter draws conclusions and discloses potential future perspectives.:1 Introduction 1.1 General aspects on constitutive modelling 1.2 Motivation and outline of the thesis 1.3 Basic assumptions and terminology 2 Literature review 2.1 From elastoplasticity to bounding surface plasticity 2.1.1 Bounding surface model according to Manzari and Dafalias (1997) 2.2 Further development of the original model 2.2.1 Papadimitriou and Bouckovalas (2002) 2.2.2 Taiebat and Dafalias (2008) 2.3 Small strain stiffness 2.3.1 Observations 2.3.2 Micromechanical considerations 2.3.3 Very small strain shear modulus G0 2.3.4 Constitutive modelling approaches 2.4 Dilatancy 3 The extended bounding surface model 3.1 Fundamental capabilities of the bounding surface concept 3.1.1 Elastic region 3.1.2 Critical state 3.1.3 Shear strength 3.1.4 Shear stiffness (monotonic) 3.1.5 Contractancy and dilatancy 3.1.6 Barotropy and pycnotropy 3.1.7 Compressive stiffness 3.1.8 Shear stiffness in reversed loading 3.1.9 Additional features 3.2 New features of the extended bounding surface model 3.2.1 Minor modifications 3.2.2 Dilatancy formulation 3.2.3 Cap yield surface 3.2.4 Small strain stiffness mechanism 3.2.5 Cyclic loading mechanism 3.2.6 Summary 3.3 Limitations of the bounding surface model 3.3.1 Intrinsic insuffciencies of the bounding surface concept 3.3.2 Remaining shortcomings of the advanced model version 3.3.3 Newly introduced deficiencies 4 The numerical model and its calibration procedure 4.1 Octave implementation of an element test programme 4.2 Calibration procedure 4.2.1 Sands for calibration 4.2.2 Calibration of basic parameters 4.2.3 Calibration of extended model parameters 4.3 User friendly calibration routine 4.3.1 Conceptual background 4.3.2 Optimisation algorithm 5 Performance of the extended bounding surface model 5.1 Model performance in element tests 5.1.1 Monotonic drained triaxial compression test 5.1.2 Monotonic undrained triaxial compression test 5.1.3 Monotonic eta-constant tests 5.2 Model performance in non-standard triaxial testing 5.2.1 Concept of response envelopes 5.2.2 Simulation of response envelopes 5.3 Model performance on general stress paths 5.3.1 Triaxial compression at small strains 5.3.2 Cyclic triaxial loading 6 Conclusions and perspectives 6.1 Conclusions 6.2 Future perspectives Bibliography Appendices A Mathematical background A.1 Fundamental equations of elastoplasticity A.2 Compilation of major constitutive equations (multiaxial formulation) A.3 Elastoplastic stiffness matrix for singular yield surfaces A.4 Coefficient matrices S and E for loading constraints A.5 Derivation of Mcap and Hcap A.6 Intergranular strain adjustment A.7 Intergranular strain correlation B Details on particle swarm optimisation C Compilation of simulation results C.1 Monotonic triaxial loading C.1.1 Toyoura sand C.1.2 Sacramento River sand C.1.3 Hostun sand C.2 Monotonic eta-constant loading C.2.1 Sacramento River sand C.2.2 Hostun sand C.3 Cyclic triaxial loading
Die Prognose von Setzungen für die Bemessung von Infrastrukturbauwerken stellt hohe Anforderungen an die numerische Untersuchung des Baugrunds und das damit verbundene Stoffgesetz: komplexe Herstellungsprozesse und zyklisch wiederkehrende Verkehrslasten stellen beachtliche Herausforderungen dar. Während das Hauptaugenmerk zumeist auf der realitätsnahen Abbildung des Bodenverhaltens liegt und damit die analytischen Anforderungen des geotechnischen Problems im Fokus stehen, sollten die Bedürfnisse der Ingenieurspraxis in der Stoffgesetzmodellierung nicht außer Acht gelassen werden. In diesem Sinne wurde im Rahmen der Elastoplastizität ein neues Materialmodell für nichtbindige Böden entwickelt. Auf dem Konzept der Bounding Surface Plastizität nach Manzari und Dafalias (1997) beruhend, sind Eigenschaften wie Festigkeit, Steifigkeit und Dilatanz Funktion des Abstands zwischen aktuellem Spannungszustand und einer zugeordneten Modellfläche im Spannungsraum. Auf diese Weise bildet das Mehrflächenmodell fundamentale Verhaltensmuster von Boden korrekt ab, einschließlich beispielsweise scherbezogener Phänomene wie Ver- und Entfestigung, Kontraktanz und Dilatanz oder das Erreichen des kritischen Zustands (Scherfestigkeit bei konstantem Volumen). Des Weiteren erfasst das Modell die Zustandsabhängigkeit des Bodenverhaltens (Barotropie und Pyknotropie). So kann mit nur einem Parametersatz das mechanische Verhalten einer großen Spannweite unterschiedlicher Anfangszustände hinsichtlich Spannung und Lagerungsdichte simuliert werden. Der kinematische Verfestigungsmechanismus der konusförmigen Fließfläche trägt bei Ent- und Wiederbelastungen zu einer realistischeren Steifigkeitsentwicklung bei und ist damit von essenzieller Bedeutung für die Akkumulation von Spannungen oder Verformungen infolge von Lastwechseln. Da sich der gewählte konstitutive Rahmen für Weiterentwicklungen eignet, wurde die ursprüngliche Formulierung des Stoffgesetzes erweitert, um das Modell an die definierten Anforderungen anzupassen. Um geotechnisch relevante Spannungspfade niedriger und höherer Komplexität adäquat reproduzieren zu können, wurde zunächst eine kappenförmige Fließfläche ergänzt. So können irreversible Verformungen nicht nur bei Scherung, sondern auch bei Belastungen ohne Änderung des Spannungsverhältnisses, wie z. B. bei isotroper oder ödometrischer Kompression, auftreten. Bei Spannungspfaden ungewöhnlicher Orientierung, bei Lastwechseln oder zusammengesetzten Spannungspfaden mit Änderung der Belastungsrichtung hat sich eine erhöhte Steifigkeit bei kleinen Dehnungen mit anschließendem dehnungsabhängigen Abfall als nützlich erwiesen. Darüber hinaus berücksichtigt ein zusätzlicher Mechanismus die rückläufige Akkumulation von Spannung oder Verformung mit zunehmender Zyklenanzahl (mittels dissipierter Energie). Im Hinblick auf die Eignung des Stoffgesetzes für die Praxis ist das Modell modular aufgebaut. So kann die Komplexität des Modells (und damit die Anzahl der Parameter) durch Ein- und Ausschalten bestimmter Erweiterungen an die Komplexität des geotechnischen Problems angepasst werden. Die Mehrzahl der Modellparameter wird mit Hilfe konventioneller Laborversuche bestimmt. Eine interne Routine erleichtert durch die Kalibrierung bestimmter Bounding Surface bezogener Größen anhand eines alternativen, stärker an Versuchsergebnissen orientierten User-Inputs bei Bedarf die Parameterwahl. Da die Kenntnis eines Stoffgesetzes entscheidend ist für dessen vernünftigen und verantwortungsvollen Einsatz, soll die vorliegende Arbeit eine fundierte und umfassende Dokumentation bieten. Der erste Teil vermittelt daher zunächst einen Überblick über das zugrunde liegende Bounding Surface Konzept und beschreibt die Neuerungen auf konstitutiver Ebene mit Bezug auf theoretische Hintergründe. Er wird gefolgt von einer detaillierten Darlegung von Potenzialen und Einschränkungen für die Nutzung des erweiterten Modells. Der nächste Abschnitt widmet sich der numerischen Implementierung des Stoffgesetzes und seiner Kalibrierung auf Basis von Versuchsergebnissen. Des Weiteren wird die Kalibrierungsroutine einschließlich des verwendeten Optimierungsalgorithmus präsentiert. Der nachfolgende Teil dient der Modellvalidierung: durch die Simulation von Elementversuchen, die Erzeugung von Antwortellipsen sowie die Abbildung allgemeinerer (beispielsweise zusammengesetzter) Spannungspfade wird die Leistungsfähigkeit des erweiterten Bounding Surface Modells demonstriert. Abschließend werden Schlussfolgerungen gezogen und potenzielle Perspektiven aufgezeigt.:1 Introduction 1.1 General aspects on constitutive modelling 1.2 Motivation and outline of the thesis 1.3 Basic assumptions and terminology 2 Literature review 2.1 From elastoplasticity to bounding surface plasticity 2.1.1 Bounding surface model according to Manzari and Dafalias (1997) 2.2 Further development of the original model 2.2.1 Papadimitriou and Bouckovalas (2002) 2.2.2 Taiebat and Dafalias (2008) 2.3 Small strain stiffness 2.3.1 Observations 2.3.2 Micromechanical considerations 2.3.3 Very small strain shear modulus G0 2.3.4 Constitutive modelling approaches 2.4 Dilatancy 3 The extended bounding surface model 3.1 Fundamental capabilities of the bounding surface concept 3.1.1 Elastic region 3.1.2 Critical state 3.1.3 Shear strength 3.1.4 Shear stiffness (monotonic) 3.1.5 Contractancy and dilatancy 3.1.6 Barotropy and pycnotropy 3.1.7 Compressive stiffness 3.1.8 Shear stiffness in reversed loading 3.1.9 Additional features 3.2 New features of the extended bounding surface model 3.2.1 Minor modifications 3.2.2 Dilatancy formulation 3.2.3 Cap yield surface 3.2.4 Small strain stiffness mechanism 3.2.5 Cyclic loading mechanism 3.2.6 Summary 3.3 Limitations of the bounding surface model 3.3.1 Intrinsic insuffciencies of the bounding surface concept 3.3.2 Remaining shortcomings of the advanced model version 3.3.3 Newly introduced deficiencies 4 The numerical model and its calibration procedure 4.1 Octave implementation of an element test programme 4.2 Calibration procedure 4.2.1 Sands for calibration 4.2.2 Calibration of basic parameters 4.2.3 Calibration of extended model parameters 4.3 User friendly calibration routine 4.3.1 Conceptual background 4.3.2 Optimisation algorithm 5 Performance of the extended bounding surface model 5.1 Model performance in element tests 5.1.1 Monotonic drained triaxial compression test 5.1.2 Monotonic undrained triaxial compression test 5.1.3 Monotonic eta-constant tests 5.2 Model performance in non-standard triaxial testing 5.2.1 Concept of response envelopes 5.2.2 Simulation of response envelopes 5.3 Model performance on general stress paths 5.3.1 Triaxial compression at small strains 5.3.2 Cyclic triaxial loading 6 Conclusions and perspectives 6.1 Conclusions 6.2 Future perspectives Bibliography Appendices A Mathematical background A.1 Fundamental equations of elastoplasticity A.2 Compilation of major constitutive equations (multiaxial formulation) A.3 Elastoplastic stiffness matrix for singular yield surfaces A.4 Coefficient matrices S and E for loading constraints A.5 Derivation of Mcap and Hcap A.6 Intergranular strain adjustment A.7 Intergranular strain correlation B Details on particle swarm optimisation C Compilation of simulation results C.1 Monotonic triaxial loading C.1.1 Toyoura sand C.1.2 Sacramento River sand C.1.3 Hostun sand C.2 Monotonic eta-constant loading C.2.1 Sacramento River sand C.2.2 Hostun sand C.3 Cyclic triaxial loading

In this thesis, we study periodic solutions and stability of differential equations with piecewise constant argument of generalized type. These equations can be divided into three main classes: differential equations with retarded, alternately advanced-retarded, and state-dependent piecewise constant argument of generalized type. First, using the method of small parameter due to Poincaré
, the existence and stability of periodic solutions of quasilinear differential equations with retarded piecewise constant argument of generalized type in noncritical case, that is, the unperturbed linear ordinary differential equation has not any nontrivial periodic solution, are investigated. The continuous and differential dependence of the solutions on an initial value and a parameter is considered. A new Gronwall-Bellmann type lemma is proved. Next, quasilinear differential equations with alternately advanced-retarded piecewise constant argument of generalized type is addressed. The critical case, when associated linear homogeneous system admits nontrivial periodic solutions, is considered. Using the technique of Poincaré
-Malkin, criteria of existence of periodic solutions of such equations are obtained. One of the main auxiliary results is an analogue of Gronwall-Bellmann Lemma for functions with alternately advanced-retarded piecewise constant argument. Dependence of solutions on an initial value and a parameter is investigated. Finally, a new class of differential equations with state-dependent piecewise constant argument is introduced. It is an extension of systems with piecewise constant argument. Fundamental theoretical results for the equations: existence and uniqueness of solutions, the existence of the periodic solutions, the stability of the zero solution are obtained. Appropriate examples are constructed.

L’hyperglycémie associée au diabète de type 2 induit des complications vasculaires menant à des désordres cérébrovasculaires, comme l’accident vasculaire cérébral. En effet, l’hyperglycémie altère l’intégrité de la barrière hémato-encéphalique, et les cellules endothéliales cérébrales qui la composent sont particulièrement affectées. Le stress oxydant et l’état pro-inflammatoire engendrés par l’hyperglycémie jouent un rôle causal. Dans ce contexte, un intérêt croissant est accordé aux polyphénols d’origine végétale qui pourraient exercer une action antioxydante et anti-inflammatoire protectrice. L’objectif du travail de thèse était d’évaluer l’impact de l’hyperglycémie sur des marqueurs redox, inflammatoires et vasoactifs des cellules endothéliales cérébrales. L’action protectrice de l’insuline en tant qu’hormone hypoglycémiante clé a été explorée. De plus, nous avons étudié le rôle protecteur de polyphénols antioxydants extraits de la plante médicinale Antirhea borbonica de La Réunion. Pour ce faire, un modèle de cellules endothéliales cérébrales murines ainsi qu’un modèle animal d’ischémie cérébrale en condition d’hyperglycémie ont été utilisés. Nos résultats ont montré que l’hyperglycémie a induit un stress oxydant et une réponse pro-inflammatoire contribuant à une altération de la fonction endothéliale. Plusieurs cibles moléculaires ont été identifiées dont les protéines redox Nox4, Cu/ZnSOD, MnSOD, catalase et HO-1 ainsi que les facteurs vasoactifs ET-1, eNOS et NO. L’implication des médiateurs de signalisation Nrf2, AMPK, PI3K, JNK, ERK, p38 MAPK, NFκB et de la cytokine pro-inflammatoire IL-6 a été mise en évidence. L’insuline et les polyphénols ont exercé des effets antioxydants et anti- inflammatoires protégeant la fonction endothéliale. En situation d’ischémie cérébrale, l’hyperglycémie a exacerbé la dérégulation de l’état redox et pro-inflammatoire cérébral, associée à une altération de la barrière hémato-encéphalique. De plus, l’hyperglycémie a aggravé le déficit neurologique, le volume de l’infarctus cérébral et la transformation hémorragique. Les polyphénols ont exercé un rôle protecteur. L’acide caféique et son métabolite circulant, l’acide férulique, détectés au niveau cérébral, pourraient rendre compte de cette action protectrice. Des travaux complémentaires ont montré que les polyphénols protègent également contre l’altération de la fonction de cellules endothéliales aortiques humaines et la perte de vasorelaxation d’anneaux aortiques isolés de souris exposés à une hyperglycémie associée aux lipopolysaccharides de la bactérie Escherichia coli, qui sont des endotoxines liées de manière causale au contexte diabétique. En conclusion, ce travail de thèse a mis en évidence l’effet délétère de l’hyperglycémie sur la fonction endothéliale et le rôle protecteur de polyphénols antioxydants. L’utilisation des modèles expérimentaux développés permettra d’approfondir l’exploration des voies moléculaires impliquées et d’identifier de possibles cibles thérapeutiques innovantes
Type 2 diabetes promotes vascular complications, leading to cerebrovascular disorders such as stroke. Indeed, hyperglycemia alters the blood-brain barrier integrity by deregulating the cerebral endothelial cell function. Oxidative stress and pro-inflammatory response may play a causal role. Thus, the biological effect of plant polyphenols known to exert antioxidant and anti-inflammatory capacities is of high interest. We evaluated the impact of hyperglycemia on the production of redox, inflammatory and vasoactive markers of cerebral endothelial cells, and the protective effect of polyphenols from the medicinal plant Antirhea borbonica from Reunion island. The murine bEnd.3 cerebral endothelial cells and an ischemia-reperfusion mouse model exposed to hyperglycemia were used. Our results demonstrated that hyperglycemia induced an oxidative stress and a pro-inflammatory state, leading to cerebral endothelial dysfunction through the activation of specific signaling molecules. Importantly, polyphenols extracted from Antirhea borbonica counteracted hyperglycemia deleterious effects and protected cerebral endothelial cells. Moreover, hyperglycemia exacerbated oxidative stress and pro-inflammatory state promoting cerebrovascular damages and loss of endothelial barrier integrity in ischemia-reperfusion mice model. Polyphenols exerted antioxidant and anti-inflammatory activities, attenuating cerebrovascular damages. These findings suggest that polyphenols extracted from Antirhea borbonica exerted protective effects on cerebral endothelial cells and an ischemia-reperfusion mouse model against deleterious effects of hyperglycemia

This thesis mainly deals with modeling and static analysis of the ceiling structure in the basic environment of ANSYS. The first part is focused on verifying correctness of the model most stressed parts of the structure with a simple hand-static calculation by the process of stress on a continuous beam. The main part is devoted to modeling composite structure, element types, specifying loads and boundary conditions by ANSYS FEM program. In the end, there are the results of stress and deflection presented, and the structure is evaluated at the ultimate limit state and serviceability limit state.

Дисертація присвячена вирішенню важливої науково-прикладної проблеми забезпечення працездатності обладнання при реалізації технологічних процесів транспортування стиснутого природного газу морськими акваторіями. В роботі встановлено закономірності впливу схем та швидкостей реалізації процесу завантаження ємностей високого тиску, виконаних у вигляді рухомого трубопроводу, на їх напружено-деформований стан. Досліджено умови формування кільцевих тріщин в композитному підсиленні ємностей комбінованого типу, особливості взаємодії підсилення і металевого лейнера в процесі експлуатації та оцінено вплив наявності тріщин на формування напружено-деформованого стану металевих лейнерів з врахуванням можливості їх корозійного пошкодження. Дістали подальший розвиток теоретико-методологічні засади комплектування технологічних морських транспортних засобів обладнанням для підготовки та стиснення газу, запропонований новий підхід до оптимізації процесів розвантаження морських транспортних засобів в існуючу газотранспортну інфраструктуру. Розроблено метод та засоби оцінки працездатності обладнання для транспортування стиснутого природного газу з врахуванням фактичного технічного стану та навантажень, зумовлених особливостями реалізації технологічних процесів. Запропоновано новий критерій досконалості для порівняльної оцінки ємностей різних типів і робочих тисків, який визначається відношенням маси ємності до об’єму газу, що перевозиться в ній, приведеного до нормальних умов.
Диссертация посвящена решению важной научно-прикладной проблемы обеспечения работоспособности оборудования при реализации технологических процессов транспортировки сжатого природного газа путем разработки метода оценки его технического состояния, совершенствования конструкции грузовых емкостей и формирования методологических основ комплектования оборудованием технологических барж и разгрузочных терминалов. Установлены закономерности влияния термодинамических процессов на формирование температурных нагрузок оборудования для транспортировки сжатого природного газа и получены количественные зависимости, учитывая которые можно предотвратить потерю работоспособности емкостей вследствие выхода их рабочих температур за пределы допустимых значений. Для емкостей высокого давления, выполненных в виде подвижного трубопровода, установлены закономерности влияния способов и скоростей реализации процесса загрузки на их напряженно-деформированное состояние, указывающие на необходимость оценки долговечности элементов соединения линейных участков с учетом двухчастотности процесса погрузки. Исследованы условия формирования кольцевых трещин в композитном усилении емкостей комбинированного типа. Доказано, что напряженно-деформированное состояние металлического лейнера возле кольцевых трещин, приближенных к днищам, характеризуется склонностью к росту напряжений и увеличению вероятности разрушения. Предложен метод оценки работоспособности оборудования для транспортировки сжатого природного газа с учетом нагрузок, обусловленных особенностями реализации технологических процессов, и фактического технического состояния. Для его определения на базе высокочастотного индуктивного датчика создана автоматизированная система контроля с возможностью воспроизведения участков потерь металла в трехмерном виде. Разработана технология изготовления многополостного сосуда высокого давления повышенной работоспособности с использованием композитных и стальных труб. Специально введенным для сравнительной оценки емкостей различных типов и рабочих давлений критерием совершенства, который определяется отношением массы емкости до объема газа, приведенного к нормальным условиям, обоснована целесообразность ее использования в виде длинномерной конструкции, ограниченной параметрами морского транспортного средства. Предложен новый подход к оптимизации процессов разгрузки морских транспортных средств в существующую газотранспортную инфраструктуру с использованием двух ветвей соединительного газопровода. Соблюдение рекомендаций по режимам работы разгрузочных терминалов обеспечивает разгрузку из морских транспортных средств до 80% газа без введения в действие компрессорного оборудования, а также минимизирует влияние особенностей технологических процессов на работоспособность магистральных газопроводов. Комплексный учет теоретических и экспериментальных исследований влияния технологических процессов загрузки и разгрузки морских транспортных средств на формирование напряженно-деформированного состояния элементов оборудования позволил разработать меры обеспечения его работоспособности при транспортировке сжатого природного газа.
The dissertation is devoted to solving the important scientific and applied problem of equipment performance assurance in the implementation of compressed natural gas transportation processes across offshore zones. The paper established the influence patterns of charts and speeds for feeding process of the high-pressure reservoirs, constructed in the form of movable pipelines, onto their strain-stress state. The conditions of ring cracks formation in composite reinforcement of combined type reservoirs, peculiarities of reinforcement coupling with metallic liner in operation, were investigated, the impact of cracks presence for metallic liners strain and stress state formation, considering the possibility of corrosion damage, were assessed. The theoretical and methodological principles of processing offshore transport facilities, stocking with equipment for gas treatment and loading, got the further development, the new approach for unloading operations optimization of offshore transport facilities into existing gas transport infrastructure was proposed. The method and operability tools for compressed gas transportation, taking into consideration the existing technical state and loading due to the processes implementation peculiarities were developed. The new criterion of excellence for comparative assessment of various type and operating pressure reservoirs, determined by the ratio of the mass of the reservoir to the volume of gas to be transported in it, reduced to normal conditions, was proposed.

Dreiaxiale Druckprüfungen können als Einstufenversuche, als Mehrstufenversuche oder als Versuche mit kontinuierlichen Bruchzuständen ausgeführt werden. Bei der Anwendung der Mehrstufentechnik ergeben sich insbesondere Fragestellungen hinsichtlich der richtigen Wahl des Umschaltpunktes und des optimalen Verlaufs des Spannungspfades zwischen den einzelnen Versuchsstufen. Fraglich beim Versuch mit kontinuierlichen Bruchzuständen bleibt, ob im Versuchsverlauf tatsächlich Spannungszustände erfasst werden, welche die Höchstfestigkeit des untersuchten Materials repräsentieren. Die Dissertation greift diese Fragestellungen auf, ermöglicht den Einstieg in die beschriebene Thematik und schafft die Voraussetzungen, die zur Lösung der aufgeführten Problemstellungen notwendig sind. Auf der Grundlage einer umfangreichen Datenbasis gesteinsmechanischer und petrophysikalischer Kennwerte wurde ein numerisches Modell entwickelt, welches das Spannungs-Verformungs-, Festigkeits- und Bruchverhalten eines Sandsteins im direkten Zug- und im einaxialen Druckversuch sowie in dreiaxialen Druckprüfungen zufriedenstellend wiedergibt. Das Festigkeitsverhalten des entwickelten Modells wurde in Mehrstufentests mit unterschiedlichen Spannungspfaden analysiert und mit den entsprechenden Laborbefunden verglichen.

Although the physical characteristics of surfing breaks are well described in the literature, there is little specific research on surfing and coastal management. Such research is required because coastal engineering has had significant impacts to surfing breaks, both positive and negative. Strategic planning and environmental impact assessment methods, a central tenet of integrated coastal zone management (ICZM), are recommended by this thesis to maximise surfing amenities. The research reported here identifies key oceanographic considerations required for ICZM around surfing breaks including: surfing wave parameters; surfing break components; relationship between surfer skill, surfing manoeuvre type and wave parameters; wind effects on waves; currents; geomorphic surfing break categorisation; beach-state and morphology; and offshore wave transformations. Key coastal activities that can have impacts to surfing breaks are identified. Environmental data types to consider during coastal studies around surfing breaks are presented and geographic information systems (GIS) are used to manage and interpret such information. To monitor surfing breaks, a shallow water multibeam echo sounding system was utilised and a RTK GPS water level correction and hydrographic GIS methodology developed. Including surfing in coastal management requires coastal engineering solutions that incorporate surfing. As an example, the efficacy of the artificial surfing reef (ASR) at Mount Maunganui, New Zealand, was evaluated. GIS, multibeam echo soundings, oceanographic measurements, photography, and wave modelling were all applied to monitor sea floor morphology around the reef. Results showed that the beach-state has more cellular circulation since the reef was installed, and a groin effect on the offshore bar was caused by the structure within the monitoring period, trapping sediment updrift and eroding sediment downdrift. No identifiable shoreline salient was observed. Landward of the reef, a scour hole ~3 times the surface area of the reef has formed. The current literature on ASRs has primarily focused on reef shape and its role in creating surfing waves. However, this study suggests that impacts to the offshore bar, beach-state, scour hole and surf zone hydrodynamics should all be included in future surfing reef designs. More real world reef studies, including ongoing monitoring of existing surfing reefs are required to validate theoretical concepts in the published literature.

碩士
國立臺灣科技大學
營建工程技術學系
82
The steady-state of sands has been studied many years, but there still exist some questions. For example, are critical state and steady state the same? or does it depend on initial fabric and stress path of the test? ...etc. Triaxial compression and extension tests, resonant column tests and undrained monotonic torsional shear tests were preformed by using quasi-static torsional simple shear/resonant column apparatus and triaxial test apparatas with enlarged lubricated platens on remolded samples of Taipei silty sand to study the effects of stress path, fine contents, gradation, end restraint effect on steady state line and undrained steady state strength of soils. The critical and steady states are shown to be equal and independent of stress path from triaxial compression and extension test results. But, there are significant difference between the steady state line of triaxial test and that of monotonic torsional simple shear test. The end restraint and fabric behavior have some noticeable effect on test results of monotonic torsional simple shear test. Fine contents, gradation and end restraint have significant influence on the slope and position of steady state line.

碩士
大同大學
機械工程學系(所)
103
The mechanical properties of material are important in the application or design in a product. Therefore the correct assessment of mechanical properties will improve the overall selection process. In the thesis, we utilize finite element method (FEM) to investigate two issues of hardness in mechanical properties: how roughness and internal stress affect the hardness. In roughness, two types of silicon substrate roughness (regular and random) with various magnitude of roughness were deposited with diamond-like carbon films. The hardness was measured via nanoindentation. The results show that the hardness in regular roughness substrate tends to be higher than that in random roughness under same average roughness. This indicates that if the roughness is modeled as regular distribution, the hardness is overestimated. Meanwhile the hardness in large roughness substrate is higher than the small roughness counterpart. Apart from substrate roughness, the effect of internal stress in hardness is also investigated. The effect of internal stress of hardness is investigated by varying different ratio of biaxial stress. To clarify the constitutive effect, three different elastic materials with isotropic, transversely isotropic and orthotropic constitutive laws are proposed coupled with perfect-plasticity and kinematic hardening plastic constitutive behaviors. The results show under general loading conditions, the internal stress has little effect on hardness measurement. However, there exists some discrepancies in hardness measurement in elastic and plastic loading. For hardness variation, elastic deformation seems to exhibit larger impact than that in plastic deformation. In different elastic constitutive laws the order of variation in hardness is transversely isotropic > orthotropic > isotropic. For plastic constitutive laws, hardness in kinematic hardening has bigger variation than that in perfect-plasticity. Even though the internal stress does not play a critical role in hardness, the material anisotropy is critical in hardness measurement.

碩士
國立高雄科技大學
電子工程系
107
Low Temperature Poly Silicon thin film transistors (LTPS TFTs) have a wide range of applications because of their excellent electrical performance. Currently, they are the mainstream of small and medium-sized panels. Academia and industry have invested a lot of resources in research and development. However, when a thin film transistor (TFT) is operated under high voltage, high current, and illumination, it’s easy to cause degradation of the electrical characteristics in the devices. For instance, a hot-carrier effect and a self-heating effect are important reliability issues in TFTs. From the electrical performance point of view in LTPS TFTs, its disadvantage is a large leakage current in the off state. Unlike most of the device in the on-state study, this paper focuses on the reliability analysis of LTPS TFTs in off-state. In the experimental design part, we apply a pulse voltage to the gate to stress the device. Next, operation mode of the TFT array is simulated to switch repeatedly. The degradation behavior of TFTs in the long term off-state operation is investigated. In the first part of the paper, we applied an AC bias to the gate to do 1000s stress, and the device was found degraded. It is seen from the I-V diagram that the threshold voltage (Vth) shifts to the right, the on current (Ion) rises, and the off current (Ioff) has a tendency to decrease. In addition, the C-V diagram indicates the capacitance (C) abnormally rises early. From the experimental results of DC-stress and changing the rising / falling time, the degradation of the device is mainly positive proportion to the rising time (on-state to off-state). During the switching process, the carriers cannot be excluded in time due to the strong electric field on both sides. The impact ionization happens and produces more electron hole pairs. Some electrons are trapped close to the gate insulator near source/drain and lead to electrical characteristics degradation. This research mainly analyzes the reliability issues during switching. Next, based on the experimental method in the first part, the active layer in LTPS TFTs with different excimer laser annealing (ELA) conditions (560, 580, 620mJ/cm2) are used for AC stress. It is found that the higher ELA energies, which possess large grain size, will cause the large number of the grain boundary defects (Ntrap). More captured carriers in the grain boundary defects will be affected by the strong electric field which is from the on state to off state. Therefore, the most serious degradation will occur in the devices with the large Ntrap. However, the protrusions which cause by the crystallization will be proportional to the ELA energy, the electric field from protrusions will be stronger in the higher ELA energy. Therefore, the devices reliability is quite important in the off state AC stress.

This dissertation addresses the role of welfare state/family care regimes, intersecting social locations and stress process factors in influencing the mental health and subjective well-being of informal caregivers of care recipients with age-related needs or disabilities within a European international context. Empirical analyses were conducted with secondary data from the 2012 and 2016 European Quality of Life Surveys. The study sample included informal caregivers (n=6,007) residing in seven different welfare state/family care regimes, including Denmark, Sweden, France, Germany, Italy, Greece and the United Kingdom. Ordinary least squares and ordered logit regression models revealed that welfare state/family care regime, social location (including both additive and interactive associations among gender, age group, marital status, and income), and stress process factors were independently associated with the mental health and life satisfaction of informal caregivers. Furthermore, there was some evidence to suggest that social location and stress process factors mediate some of the relationships between regime type and self-reported health and well-being and that stress process factors mediate relationships between social location factors and mental health and well-being. Overall, the results provide support for integrating welfare state/family care regime type and intersectionality factors into the SPM. Thus, future research on informal caregivers‘ mental health and well-being ought to incorporate such factors into their empirical analyses. The results also have some policy and practice implications. Residence in social democratic formal (Denmark), semi-formal (Sweden) and conservative formal (France) care regimes was the most beneficial to informal caregivers self-reported mental health. This was also the case for life satisfaction, except that residence in the liberal semi-formal (UK) was more beneficial than in the conservative formal (France) care regime. Mediating social location and stress process factors suggest that UK policy makers should address the greater social location disparities, greater role overload, and lack of coping resources that advantage Danish and Swedish informal caregivers compared to those residing in the UK. Lastly, policy makers from all the European countries assessed in the study should address the poorer mental health status of women and rural informal caregivers, those who experience role overload, secondary stressors, and lack coping resources. They should also address the the lower levels of formal education, more secondary stressors, and lack of coping resources associated with poorer subjective well-being.
Graduate

Іванченко Д. В. Особливості синдрому емоційного вигорання у алекситимічного типу особистості : кваліфікаційна робота магістра спеціальності 053 «Психологія» / наук. керівник В. В. Грандт. Запоріжжя : ЗНУ, 2020. 66 с.
UA : Робота викладена на 66 сторінки, 8 таблиць. Перелік посилань включає 70 джерел. Об'єкт дослідження - синдром «емоційного вигорання» у працівників. Проблема в професійного стресу вже досить довгий час цікавить зарубіжних та вітчизняних дослідників. На роботі людина підлягається в великій кількості стресогених факторів, серед яких такі як соціальна оцінка, невизначеність, повсякденна рутина тощо. Але не слід забувати і про те, що стресові фактори впливають на людину не тільки на роботі, а й вдома, на вулиці, у повсякденному житті. Все це створює досить великий ризик виникнення стресових розладів. Актуальною проблемою на сьогоднішній день є розповсюдження серед працівників організацій синдрому «емоційного вигорання» (СЕВ). Найбільш характерним він є для людей кому Що працюють в системі лапки людина і людина. На нашу думку, дуже важливо дослідити можливі причини виникнення такого роду стресу та виявити можливі шляхи його подолання. Наукова новизна полягає у уточненні й розширенні уявлень про фактори, що впливають на розвиток синдрому «емоційного вигорання» в професійній діяльності.
EN : The work is set out on 66 pages, 8 tables. The list of links includes 70 sources. The object of study - the syndrome of "emotional burnout" in employees. The problem of occupational stress has long been of interest to foreign and domestic researchers. At work, a person is exposed to a large number of stressors, including such as social evaluation, uncertainty, daily routine and so on. But we should not forget that stress factors affect a person not only at work but also at home, on the street, in everyday life. All this creates a fairly high risk of stress disorders. An urgent problem today is the spread of the syndrome of "emotional burnout" (CEM) among employees of organizations. It is most characteristic of people who work in the system of paws man and man. In our opinion, it is very important to investigate the possible causes of this type of stress and identify possible ways to overcome it. The scientific novelty lies in the clarification and expansion of ideas about the factors influencing the development of the syndrome of "emotional burnout" in professional activities.

The project focuses on dietary interventions in type 2 diabetes(T2D). The aim was to investigate how glucose metabolism and other manifestations of insulin resistance should be influenced by a) the composition of macronutrients and b) frequency of meals; and to characterize the possible mechanisms of these dietary interventions in patients with T2D. A. In a randomized crossover study, 50 patients T2D and 50 age-matched healthy subjects underwent in a random order meal tolerance tests with three isocaloric meals (vegan sandwich; V-meal, hamburger; M-meal, or cheese sandwich; S-meal. Blood samples for analysis were taken at time 0 and after 30, 60, 120 and 180 minutes after meal ingestion. Plasma concentrations of plasma glucose, insulin, C-peptide, lipids, oxidative stress markers and gastrointestinal hormones (GIHs) were investigated. Both basal and postprandial plasma concentrations of glucose and insulin were significantly higher in patients with T2D (p<0.001); basal and postprandial concentrations of almost all other GIHs (except for ghrelin) and thiobarbituric acid reactive substances (TBARS) were significantly increased (p<0.001), while ascorbic acid, reduced glutathione and superoxide dismutase activity were decreased in patients with T2D compared to healthy controls (p<0.001). The meal rich...

Dreiaxiale Druckprüfungen können als Einstufenversuche, als Mehrstufenversuche oder als Versuche mit kontinuierlichen Bruchzuständen ausgeführt werden. Bei der Anwendung der Mehrstufentechnik ergeben sich insbesondere Fragestellungen hinsichtlich der richtigen Wahl des Umschaltpunktes und des optimalen Verlaufs des Spannungspfades zwischen den einzelnen Versuchsstufen. Fraglich beim Versuch mit kontinuierlichen Bruchzuständen bleibt, ob im Versuchsverlauf tatsächlich Spannungszustände erfasst werden, welche die Höchstfestigkeit des untersuchten Materials repräsentieren. Die Dissertation greift diese Fragestellungen auf, ermöglicht den Einstieg in die beschriebene Thematik und schafft die Voraussetzungen, die zur Lösung der aufgeführten Problemstellungen notwendig sind. Auf der Grundlage einer umfangreichen Datenbasis gesteinsmechanischer und petrophysikalischer Kennwerte wurde ein numerisches Modell entwickelt, welches das Spannungs-Verformungs-, Festigkeits- und Bruchverhalten eines Sandsteins im direkten Zug- und im einaxialen Druckversuch sowie in dreiaxialen Druckprüfungen zufriedenstellend wiedergibt. Das Festigkeitsverhalten des entwickelten Modells wurde in Mehrstufentests mit unterschiedlichen Spannungspfaden analysiert und mit den entsprechenden Laborbefunden verglichen.