Les ancrages hélicoïdaux, largement utilisés pour résister à des efforts de traction pour une variété d’applications comme les pylônes électriques, les pipelines, les structures offshore, etc., sont soumis à des chargements cycliques qui influent sur la performance d’encrage et peuvent induire une rupture par fatigue. Cependant, l’influence des sollicitations cycliques sur le comportement d’encrage hélicoïdal est mal connue. Une évaluation approfondie de l’effet des charges cycliques sur la réponse effort – déplacement des ancrages avec une seule hélice dans les sols sableux est présentée, incluant un diagramme d’interaction pour aider à évaluer l’impact des différentes conditions de chargement cyclique. La partie expérimentale de cette thèse comprend des essais en centrifugeuse géotechnique et des essais de chargement in situ. Les essais en centrifugeuse ont été effectués sur des modèles réduits d’encrages hélicoïdaux dans du sable à l’IFSTTAR (Nantes, France). Les essais de chargement in situ ont été réalisés sur des ancrages hélicoïdaux installés dans le sol tropical résiduel du site expérimental de l’Université de Sao Paulo (Sao Carlos, Brésil). De plus la modélisation numérique a été utilisée pour prédire les réponses pré et post cycliques des ancrages d’une hélice testée en centrifugeuse. Les principales conclusions de cette recherche sont : (a) le comportement d’un ancrage hélicoïdal est régi par la capacité portante de l’hélice, et aucune perte de capacité portante d’hélice n’a été observée pour la gamme de charges cycliques testée, (b) la dégradation de la résistance par frottement latéral sur le fut a été remarquée principalement pendant les 100 premiers cycles, lorsque l’accumulation des déplacements permanents est plus importante, (c) un diagramme d’interaction montrant les différentes conditions de stabilité cyclique est proposé à partir des résultats des données expérimentales, (d) des valeurs modifiées du facteur de capacité portante (Nq) sont proposées pour l’estimation de la capacité et post-cyclique des ancrages avec une hélice dans du sable, (e) l’effet de l’installation de l’ancrage doit être pris en compte dans le modèle numérique afin d’obtenir des prédictions fiables de la performance de l’ancrage hélicoïdal. / Helical anchors, used widely to resist uplift loading for a variety of applications, including in transmission towers, pipelines, offshore structures, etc., are subjected to environmental cyclic loads that influence the anchor performance and may induce fatigue failure. However, the influence of cyclic loading on helical anchor behaviour is unknown. A comprehensive evaluation of the effect of cyclic loading on the load-displacement response of single-helix anchors in sandy soils is presented here, including an interaction diagram to help designers evaluate the impact of different conditions in cyclic loadings. The experimental work of this thesis includes geotechnical centrifuge modelling and field load tests. The centrifuge model tests were carried out with reduced scale models of helical anchors in sand, at IFSTTAR (Nantes, France). The field load tests were performed on hekical anchors installed in a tropical residual soil of the Experimental Site of the University of Sao Paulo (Sao Carlos, Brazil). In addition, numerical modelling was used to predict the pre- and post-cyclic responses of the single-helix anchors tested in a centrifuge. The main findings of this research are : (a) helical anchor behaviour is governed by helix bearing resistance and no loss of helix bearing capacity was observed in the range of cyclic loadings tested, (b) the degardation of shaft resistance was noticed mainly during the first 100 cycles, when the accumulation of permanent displacements is more significant, (c) an interaction diagramshowing the different conditions of cyclic stability is proposed from the results of the experimental data, (d) modified values of the bearing capacity factor in tension (Nq) are suggested for the estimation of post-cyclic uplift capacity of single-helix anchors in sand, (e) the installation effect of the anchor should be taken into account in the numerical model in order to obtain reliable predictions of the helical anchor performance.

In this thesis, we investigate the electronic structure and transport properties of topologically trivial and non-trivial cylindrical quantum dots (QDs) defined by further confining InAs1-xBix/AlSb quantum wells (QWs). First we predict that common III-V InAs0.85Bi0.15/AlSb QWs can become 2D topological insulators (TIs) for well thicknesses dc > 6.9 nm with a topologically non-trivial gap of about 30 meV (> kBT), which can enable room temperature TI applications. Furthermore, we investigate the cylindrical QDs defined from these Bi-based wells by additional confinement, both in the topologically trivial (d < dc) and non-trivial (d > dc) regimes. Surprisingly, we find that topologically trivial and non-trivial QDs have similar transport properties in stark contrast with their 2D counterparts (i.e., a strip). More specifically, through detailed calculations, which involve an analytical solution of the quantum-dot eigenvalue problem, we demonstrate that both trivial and non-trivial cylindrical QDs possess edge-like states, i.e., helical spin-angular-momentum-locked quantum states protected against non-magnetic elastic scattering. Interestingly, our trivial QDs exhibit these geometrically robust helical states, similarly to topologically non-trivial QDs, over a wide range of system parameters (e.g., dot radius). We also calculate the circulating currents for the topologically trivial and non-trivial QDs and find no substantial differences. However, we note that ordinary III-V or II-VI cylindrical QDs (i.e., QDs not formed from a BHZ model + confinement) do not feature robust edge-like helical states. We further consider topologically trivial and non-trivial QDs with four edge-like states and calculate their two-terminal conductance G via a standard Green-function approach. For both trivial and non-trivial QDs we find that G shows a double-peak resonance at 2e2/h as a function of the dot radius R and gate voltage Vg controlling the dot energy levels. On the other hand, both trivial and non-trivial QDs can have edge-like and bulk state Kramers pairs coexisting at the same energy within the bulk part of their discrete spectra. In this case, G displays a single-peak resonance at 2e2/h as the four levels (two edge states and two bulk states now) become degenerate at some particular parameter values R = Rc and Vg = Vgc for both topologically trivial and non-trivial QDs. We also extend our investigation to HgTe-based QDs and find similar results. / Nesta tese investigamos a estrutura eletrônica e as propriedades de transporte de pontos quânticos cilíndricos topologicamente triviais e não-triviais, definidos por confinamento de poços quânticos (QWs) InAs1-xBix/AlSb. Primeiramente, nós prevemos que os QWs usuais baseados em InAs1-xBix/AlSb podem se tornar isolantes topológicos 2D para largura de poço dc > 6.9 nm, com um gap topologicamente não-trivial de aproximadamente 30 meV (> kBT), o que pode permitir aplicações em temperatura ambiente. Além disso, investigamos pontos quânticos cilíndricos definidos a partir de confinamento desses poços contendo Bi, em ambos os regimes trivial (d < dc) e não-trivial (d > dc). Surpreendentemente, descobrimos que os pontos quânticos topologicamente triviais e não triviais têm propriedades de transporte semelhantes, um resultado em grande contraste com as suas versões semiinfinitas, como por exemplo uma fita. Mais especificamente, através de cálculos detalhados, que envolvem uma solução analítica do problema de autovalores dos pontos quânticos, demonstramos que pontos quânticos cilíndricos triviais e não-triviais possuem estados de borda semelhantes, isto é, estados quânticos helicoidais protegidos contra espalhamento elástico não magnético. Curiosamente, nossos pontos quânticos triviais exibem estados helicoidais geometricamente robustos, similarmente aos pontos quânticos topologicamente não-triviais, em uma ampla faixa de parâmetros do sistema, como por exemplo, o raio do ponto quântico. Nós também calculamos as correntes circulantes para os pontos quânticos topologicamente triviais e não-triviais e não encontramos diferenças substanciais entre elas. No entanto, notamos que os pontos quânticos cilíndricos feitos de materiais ordinários III-V ou II-VI (isto é, pontos quânticos não descritos pelo Hamiltoniano BHZ com confinamento) não apresentam estados helicoidais robustos. Consideramos ainda pontos quânticos triviais e não-triviais com quatro estados de borda e calculamos sua condutância entre dois terminais G através de uma abordagem padrão das funções de Green. Para os pontos quânticos triviais e não-triviais, encontramos que G mostra uma ressonância de pico duplo em 2e2/h como função do raio do ponto quantico R e da tensão Vg que controla os níveis de energia do ponto quântico. Por outro lado, tanto os pontos quânticos triviais como os não-triviais podem ter pares de Kramers localizados na borda (edge) e em todo seu volume (bulk) coexistindo em uma mesma janela de energia na região dos estados de valência. Nesse caso, G exibe uma ressonância de pico único em 2e2/h, já que os quatro níveis (dois estados de borda e dois estados de volume bulk) se tornam degenerados para alguns valores de parâmetros particulares R = Rc and Vg = Vgc, em pontos quânticos topologicamente triviais e não triviais. Nós também estendemos nossa investigação para os pontos quanticos de HgTe onde encontramos resultados similares.

Fragestellung: Wie nützlich ist das Mehrschicht-Spiral-CT bei der Diagnostik der Darmischämie? Studiendesign: Retrospektive Studie Patientenkollektiv: 112 Patienten, die in einem Zeitraum von drei Jahren bei Verdacht auf Darmischämie in einem Mehrschicht-Spiral-CT untersucht wurden. Ergebnis: Bei den 112 Verdachtsfällen handelte es sich in 26 Fällen um eine Darmischämie. Das CT erkannte davon 24 (92%), ein Fall wurde falsch negativ (4%) befundet und ein Fall (4%) wurde als unklar eingestuft. Von den 86 Fällen ohne Darmischämie wurden 77 (89%) korrekt erkannt, drei (4%) wurden falsch positiv befundet und 6 (7%) Fälle wurden als unklar eingestuft. Die Ergebnisse der bei manchen Patienten zusätzlich durchgeführten Sonografie – und Röntgenuntersuchungen waren erheblich schlechter (Sono: Sensitivität: , Spezifität: ; Röntgen: Sensitivität: , Spezifität: ). Die erhobenen Laborparameter (Leukozyten, Lactat, D-Dimere) waren zur Beurteilung, ob es sich um eine Darmischämie handelt, nicht spezifisch genug. Schlussfolgerung: Das Mehrschicht-Spiral-CT ist mit einer Sensitivität von 92% und einer Spezifität von 97% gut zur Erkennung einer Darmischämie geeignet. Unklare Fälle sind mit hoher Wahrscheinlichkeit nicht operationswürdig. / Objective: To verify the diagnostic importance of helical CT in the diagnosis of mesenteric ischemia. Design: Retrospective study Subjects: 112 patients, who where examined by helical CT during a 3-year-period, with suspected mesenteric ischemia. Main Outcome: 26 cases proved to be mesenteric ischemia. Helical CT was diagnostic in 24 (92%) cases, wrong in one (4%) case and uncertain in one (4%) case. No ischemia was correctly diagnosed in 77/86 (89%) cases, wrongly in three (4%) and 6 (7%) were uncertain. Sonografie and plain film radiographs were taken on some patients, but the results were unsatisfactory. Sonography: Sensitivity: 0%, specificy: 85,7%. Plain film radiographs sensitivity: 0%, specificy: 100%. Results of laboratory test were of little diagnostic value (white blood cell count, lactate, d-dimere). Conclusions: Helical CT is a valuable tool for detecting mesenteric ischemia with a sensitifity of 92% and a specificy of 97%. Suspected mesenteric ischemia which cannot be proved by helical CT are most probable non surgical cases.

Helical anchors, used widely to resist uplift loading for a variety of applications, including in transmission towers, pipelines, offshore structures, etc., are subjected to environmental cyclic loads that influence the anchor performance and may induce fatigue failure. However, the influence of cyclic loading on helical anchor behaviour is unknown. A comprehensive evaluation of the effect of cyclic loading on the load-displacement response of single-helix anchors in sandy soils is presented here, including an interaction diagram to help designers evaluate the impact of different conditions in cyclic loadings. The experimental work of this thesis includes geotechnical centrifuge modelling and field load tests. The centrifuge model tests were carried out with reduced scale models of helical anchors in sand, at IFSTTAR (Nantes, France). The field load tests were performed on helical anchors installed in a tropical residual soil of the Experimental Site of the University of São Paulo (São Carlos, Brazil). In addition, numerical modelling was used to predict the pre- and postcyclic responses of the single-helix anchors tested in a centrifuge. The main findings of this research are: (a) helical anchor behaviour is governed by helix bearing resistance, and no loss of helix bearing capacity was observed in the range of cyclic loadings tested, (b) the degradation of shaft resistance was noticed mainly during the first 100 cycles, when the accumulation of permanent displacements is more significant, (c) an interaction diagram showing the different conditions of cyclic stability is proposed from the results of the experimental data, (d) modified values of the bearing capacity factor in tension (Nq) are suggested for the estimation of post-cyclic uplift capacity of single-helix anchors in sand, (e) the installation effect of the anchor should be taken into account in the numerical model in order to obtain reliable predictions of the helical anchor performance. / As estacas helicoidais são largamente utilizadas para resistir a carregamentos de tração em uma variedade de aplicações como torres de linhas de transmissão de energia, dutos enterrados, estruturas offshore, etc. Estes tipos de estruturas são normalmente submetidos a carregamentos cíclicos que influenciam o desempenho de fundações por estacas helicoidais submetidas a esforços de tração, e podem induzir ruptura por degradação da capacidade de carga. Contudo, a influência do carregamento cíclico no comportamento das estacas helicoidais (ou ancoragens helicoidais, quando submetidas apenas a esforços de tração) é pouco conhecida. Uma avaliação abrangente do efeito de carregamentos cíclicos sobre o comportamento das ancoragens helicoidais é apresentada nesta tese, incluindo um diagrama de interação para auxiliar na avaliação do impacto de diferentes condições de carregamento cíclico. O trabalho experimental desta tese inclui modelagem em centrífuga geotécnica e ensaios de carregamento cíclico em estacas na grandeza real em campo. Os ensaios em centrífuga foram realizados com modelos reduzidos de estacas helicoidais em areia, no IFSTTAR (Nantes, França). Os ensaios de campo foram realizados em ancoragens helicoidais instaladas no solo residual tropical do Campo Experimental de Fundações da Universidade de São Paulo (São Carlos, Brasil). Além disso, modelos numéricos foram utilizados para simular os resultados do comportamento das ancoragens helicoidais ensaiadas em centrífuga nas condições pré- e pós-ciclos. Os principais resultados desta pesquisa são: (a) a capacidade de carga à tração da ancoragem helicoidal é controlada pela capacidade de carga da hélice, (b) a degradação da resistência por atrito lateral foi observada principalmente durante os primeiros 100 ciclos, período em que a acumulação dos deslocamentos permanentes é mais significante, (c) um diagrama de interação mostrando as diferentes condições de estabilidade cíclica é proposto a partir dos resultados experimentais em centrífuga, (d) valores modificados do fator de capacidade de carga em tração (Nq) são sugeridos para estimativa da capacidade pós-ciclos de ancoragens helicoidais com uma hélice em areia, (e) o efeito da instalação da ancoragem deve ser levado em consideração no modelo numérico para que se obtenha previsões confiáveis do desempenho de ancoragens helicoidais.

O monitoramento em campo de fundações em estacas metálicas helicoidais é baseado em correlações empíricas entre a capacidade de carga à tração e o torque medido durante a instalação. Nesta pesquisa é proposto um modelo teórico da relação entre o torque de instalação e a capacidade de carga à tração deste tipo de estaca em areias para ser utilizado como procedimento de controle durante a execução deste tipo de fundação. Para validar esta relação teórica e para avaliar o desempenho desta fundação em solos arenosos, foi realizado um programa experimental dividido em dois grupos: ensaios de campo e ensaios de laboratório. Em campo foram realizadas provas de carga à tração na Escola de Engenharia de São Carlos (EESC) e em Contagem (Minas Gerais). Os ensaios de laboratório foram divididos em três grupos. O primeiro corresponde aos ensaios de modelagem física em centrífuga realizados no Laboratoire Central des Ponts et Chaussées (LCPC) em Nantes, França. O segundo engloba ensaios de cisalhamento direto de interface entre o aço da hélice da estaca e diferentes areias, parte executada no LCPC e parte na EESC. O terceiro grupo refere-se a ensaios de torção de tubos de estacas metálicas helicoidais efetuados na EESC. A partir dos resultados dos ensaios, o modelo teórico proposto nesta tese foi verificado e mostrou-se adequado para estacas metálicas helicoidais profundas com diferentes dimensões e número de hélices instaladas em solos arenosos. Os resultados das provas de carga realizadas em centrífuga e em campo foram examinados por meio dos métodos existentes na literatura para estimativa de capacidade de carga à tração desenvolvidos para este tipo de fundação. Por meio dos resultados obtidos nos ensaios em centrífuga, constatou-se que nas estacas multi-hélices a porcentagem de capacidade de carga relativa à hélice da ponta aumenta de acordo com o diâmetro da hélice e com a densidade da areia. Nos ensaios de torção de fustes de estacas helicoidais observou-se que, para tubos de mesmo diâmetro e espessura, a ruptura se inicia a partir do mesmo valor de momento torçor aplicado, independentemente de conter ou não emenda. / Empirical correlations between installation torque and uplift capacity of helical screw piles are routinely used as a procedure for quality control on site of this type of foundation. In this work, a theoretical model of the relationship between uplift capacity and installation torque of deep helical screw piles in sand was presented to be used as a quality control method for this type of foundation. An experimental program of laboratory and field investigations was carried out in order to validate this theoretical relationship. The field study included uplift tests of full-scale piles installed at the Escola de Engenharia de São Carlos (EESC) and in Contagem (Minas Gerais). The laboratory tests were performed in the Laboratoire Central des Ponts et Chaussées (LCPC/ Nantes) and at the EESC. In the LCPC a program of centrifuge and direct shear interface tests was completed. A set of torsion tests on pile shafts and of direct shear interface tests were carried out at the EESC. The results showed that the theoretical model presented is applicable to different pile dimensions, number of helices, and sand relative density. The methods existing in the literature for estimating uplift capacity of helical screw piles were used to verify the results of uplift capacities measured in field and in centrifuge studies. The results of centrifuge modelling tests demonstrated that the fraction of uplift capacity corresponding to the bottom helix increases with helix diameter and sand density. The torsion tests showed that the failure of the pile shaft begins at the same torque magnitude in experiments on shafts with and without connections.

<div>A leading cause of premature failure and excessive wear and tear in mechanical components that rely on compression springs for their operation is the development of unwanted side forces when the spring is compressed.</div><div>These side forces are usually around 10% - 20% of the magnitude of the axial load and point in different directions in the plane perpendicular to the axis of the spring.</div><div>The magnitude and direction of the resultant of side forces varies very non-linearly and unpredictably even though the axial force behavior of the spring is very consistent and predictable.</div><div>Since these side forces have to be resisted by the housing components that hold the spring in place, it is difficult to design these components for optimal operation.</div><div><br></div><div>The hypothesis of this study is that side forces are highly sensitive to small changes in spring geometry and its placement configuration in the housing. <br></div><div><div>Several experiments are conducted to measure the axial and side forces in barrel springs and two different types of finite element models are developed and calibrated to model the spring behavior. </div><div>Spring geometry and placement are parameterized using several control variables and an approach based on design of experiments is used to identify the critical parameters that control the behavior of side-forces. </div><div>The models resulted in deeper insight into the development of side forces as the spring is progressively loaded and how its contact interactions with the housing lead to changes in the side force.</div><div>It was found that side-forces are indeed sensitive to variations in spring geometry and placement.</div><div>These sensitivities are quantified to enable designers to and manufacturers of such springs to gain more control of side force variations between different spring specimens.</div></div>

Ma thèse est consacrée aux nouveaux phénomènes nano-optiques et aux dispositifs basés sur l'interaction spin-orbite de la lumière (SOI). Tout d'abord, il a été démontré un SOI uniquement piloté par le champ magnétique de la lumière permettant de diriger avec précision les ondes de surface de Bloch, offrant ainsi une nouvelle manifestation du champ magnétique optique. Ensuite, nous avons proposé et démontré le concept de nano-antenne plasmonique hélicoïdale à ondes progressives (TW-HPA), c’est-à-dire un fil hélicoïdal en or étroit alimenté optiquement par une nano-antenne dipolaire dans une configuration « end-firing ». Une telle nano-antenne a été démontrée comme la première optique de polarisation sublongueur d’onde. L’agencement de TW-HPAs à l’échelle de quelques microns a permis de convertir « à la carte » un faisceau polarisé linéairement en une distribution de faisceaux directifs présentant des polarisations différentes définies de façon déterministe par la géométrie et les dimensions des nano-antennes. Par le biais d’un couplage en champ proche de quatre nano-antennes à hélicités opposées, nous avons obtenus une optique sublongueur d’onde permettant un degré de liberté dans le contrôle de la polarisation qui est interdit avec les composants et méthodes classiques basées sur l’exploitation de matériaux biréfringents ou dichroïques, ou de métamatériaux imitant ces propriétés. / My thesis is devoted to novel nano-optical phenomena and devices based on spin-orbit interaction (SOI) of light. First, magnetic spin-locking, i.e., an SOI solely driven by the magnetic field of light, is demonstrated with Bloch surface waves. It provides a new manifestation of the magnetic light field. Then, we propose and demonstrate the concept of traveling-wave plasmonic helical antenna (TW-HPA), consisting of a narrow helical gold-coated wire non-radiatively fed with a dipolar nano-antenna. By swirling surface plasmons, the TW-HPA combines subwavelength illumination and polarization transformation. The TW-HPA is demonstrated to radiate on the subwavelength scale almost perfectly circularly polarized optical waves upon illumination with linearly polarized light. With this subwavelength plasmonic antenna, we developed strongly integrated arrays of point-light emissions of opposite handedness and tunable intensities. Finally, by coupling two couples of TW-HPAs of opposite handedness, we obtained new polarization properties so far unattainable.

Advanced technologies for the automotive industry require improved designed precision in different areas. Research is needed in order to meet customer demand and satisfaction to increase durability, efficiency, and reliability. That is why continuous development in transmission system has been an exciting topic for many years. The gears in the transmission system demand high resistance against repeated loads acting on the teeth and the ability to engage without energy loss. The intention is to support that effort by investigating seven design cases of a parallel helical gear pair. This master thesis aims to study a gear design concept of adding a supporting ring to reduce the root bending- and contact stresses. To implement this study, seven different design cases were modelled to study the effect of changing the design. One or two support ring structures were added, or the thickness was increased of the gear considered exposed to high stresses. The purpose is to gain a comparative advantage in the automotive industry. M1 is a reference standard design, while the other models (M2-M5/P1-P3) are modified designs with additional rings or changed in thickness. Simulation is an effective and an useful tool to understand and visualize how the complex interaction of the transmission component appears to be. A finite element method (FEM) program was used to investigate these models. The gear pairs were imported into the pre-processor ANSA, the FEM program Abaqus 2017 was used as a solver, and the results were extracted from the post-processor META. To support the aim of this thesis, two of the seven FEM models were validated against a specialized gear calculated program, WindowsLDP, in order to determine the robustness of the simulation models. The transmission error (TE) measurements, root bending- and contact stresses were observed for the validation. Introducing the different models M3-M5 and P1-P3, the root and contact stresses were reduced by 1.2-4.4 and 0.07-4.3 %, respectively, compared to M1. The transmission error TE could differ as much as 85% in M2-M3 as compared to M1. Systematic errors were generated in model M2, therefore the low root stresses obtained in M2 should be considered carefully. Implementing the so-called misalignment measurement, tilting parameter, microgeometry, and profile modification related to crowning and tip relief is discussed and believed to reduce TE measurements, root- and contact stresses. These modifications have not been studied in this thesis. The LDP results showed a trend of higher values compared to the FEM results, which was suggested to be further investigated in the future. / Dagens avancerade teknik inom fordonsindustrin kräver förbättrad precision hos konstruktioner inom olika områden. Forskning behövs för att möta kundernas efterfrågan och för att öka hållbarhet, effektivitet och tillförlitlighet. Detta är varför kontinuerlig utvecklingen av växellådssystem har varit ett hett ämne i många år. Kugghjulstransmission skall ha högt motstånd mot upprepande belastning som förekommer på tänderna och skall även ha en minimal energiförlust. Detta examensarbete siktar mot att stödja den fortsatta utvecklingen inom området genom en fallstudie, mer specifikt för att studera sju olika kugghjulsmodeller som behandlar ett parallellt spiralformade kugghjul. Målet med detta examensarbete är att studera ett kugghjulskoncept där en ring appliceras för att reducera rot- och kontaktspänningar. Utförandet sker genom att studera sju olika modeller, för att veta hur stor påverkan designen utgör. En eller två stödringstrukturer appliceras, eller att öka kuggbredden på det kugghjul som anses vara det mest kritiska för höga spänningar. Denna studie görs för att kugghjulstillverkaren ska vara i utvecklingens framkant och kunna konkurrera inom fordonsindustrin. M1 ären referens och standard designmodell, medan de andra modellerna (M2-M5/ P1-P3) är modifierade design där med ytterligare ringar eller ändrad kuggbredd. Simulering är en effektiv metod för att förstå och visualisera komplexiteten av komponenter inom växellådan. Ett finita elementmetodens program användes för att undersöka dessa modeller, genom att importera geometrierna till pre-processorn ANSA, där Abaqus 2017 användes som en lösare, där sedan resultaten extraheras från post-processorn META. För att stödja denna studien användes två av de sju FEM-modellerna till att valideras mot ett annat specialiserat kugghjulsprogram inom kuggberäkning som heter WindowsLDP. Detta med avsikt att fastställa simuleringsmodellernas robusthet. Det så kallade överföringsfelet, rotböjnings- och kontaktspänningarna var ingående parametrar som behandlades under valideringen. Modellerna M3-M5/P1-P3 introducerades, där rotböjsspänningen och kontaktspänningen reducerades med 1.2-4.4 och 0.07-4.3% när de jämfördes med M1. Överföringsfelet (TE) kunde skilja upp mot 85% mellan M2-M3 jämfört med M1. Ett systematiskt fel uppstod i modell M2, modellens robusthet kunde därmed ej fastställas, då modellens resultat bör övervägas noggrant. Införande av så kallade växelförskjutning, lutning/vippning parametrar, mikrogeometrier och profilmodifieringen relaterat till kronning och tipavlastning, kommer att genera minskade TE-mätningar samt rot- och kontaktspänningar för de spiralformade kugghjulen. Dessa ämne har ej studerats under detta examensarbete. LDP-resultaten visade högre värden relativt jämfört med de FEM resultat, där en trend kunde observeras. Slutsatsen föreslog att detta bör undersökas ytterligare i framtiden.

ΔPhe an analogue of a coded amino acid phenylalanine (Phe) residue but with double bond between Cα and Cβ atoms, is one of the well studied residue among all the dehydro amino acids, as a conformation constraining amino acid. Due to the presence of double bond Cα=Cβ, and consequent conjugation of ΔPhe ring electrons with Cα=Cβ double bond, ΔPhe gains conformation restricting (constraining) characteristics compared to coded amino acid Phe. ΔPhe which assumes an achiral residue has all its atoms restricted to an approximate plane. Apart from the conformation constraining property, the designer friendly ΔPhe residue has its ability to i) engage in side chain aromatic interactions ii) act as nuclei for C-HLO/N-HLπ weak interactions involving the side chain and/ or backbone atoms, and iii) acquire ambidextrous conformation as observed in many model peptides. It is these properties, which makes ΔPhe, a residue of intense research in the field of de novo protein secondary and super secondary design. Analysis of solid state and solution state structures of containing ΔPhe residues suggests that ΔPhe, in general induces β-bend in short peptides and 310-helical conformation in longer peptides (>4).

This report delves into two of the major truncated data problems in helical cone-beam tomography: Axial truncation and Lateral truncation. The problem of axial truncation, also classically known as the Long Object problem, was a major challenge in the development of helical scan tomography. Generalization of the Feldkamp method (FDK) for circular scan to the helical scan trajectory was known to give reasonable solutions to the problem. The FDK methods are approximate in nature and hence provide only approximate solution to the long object problem. Recently, many methods which provide exact solution to this problem have been developed the major breakthrough being the Katsevich’s algorithm which is exact, efficient and also requires lesser detector area compared to Feldkamp methods. The first part of the report deals with the implementation strategies for methods capable of handling axial truncation. Here, we specifically look at the exact and efficient Katsevich’s solution to long object problem and the class of approximate solutions provided by the generalized FDK formulae. The later half of the report looks at the lateral truncation problem and suggests new methods to handle such truncation in helical scan CT. Simulation results for reconstruction with laterally truncated projection data, assuming it to be complete, gives severe artifacts which even penetrates into the field of view (FOV). A row-by-row data completion approach using Linear Prediction is introduced for helical scan truncated data. An extension/improvement of this technique known as Windowed Linear Prediction approach is introduced. Efficacy of both these techniques are shown using simulation with standard phantoms. Various image quality measures for the resulting reconstructed images are used to evaluate the performance of the proposed methods against an already existing technique. Motivated by a study of the autocorrelation and partial autocorrelation functions of the projection data the use of a non-stationary linear model, the ARIMA model, is proposed for data completion. The new model is first validated in the 2D truncated data situation. Also a method of incorporating the parallel beam data consistency condition into this new method is considered. Performance evaluation of the new method with consistency condition shows that it can outperform the existing techniques. Simulation experiments show the efficacy of the ARIMA model for data completion in 2D as well as 3D truncated data scenario. The model is shown to work well for the laterally truncated helical cone-beam case.