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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
331

Server pro automatickou konfiguraci IPv6 tunelu / Server for Automatic IPv6 Tunnel Connectivity

Drahoš, Vojtěch January 2011 (has links)
One of the major problems of modern Internet is the upcoming depletion of addressing space in IPv4 protocol. This master thesis focuses on the study of network protocol IPv6, the possibilities of expanding this protocol in the Internet using the appropriate tunelling method and ways of tunnel management, especially the TIC protocol. Major goal of this work is using knowledge of protocols in a design and implementation of the server part of tunnel broker system, which uses mentioned tunneling method and is compatible with the open source client AICCU. Second part of this work deals with testing and pilot deployment of this system. Main benefit consists in creation an open source tunel broker system. Real deployment of this system is particularly advantage for Czech users as a low latency tunnel IPv6 Internet.
332

Spintronique dans les matériaux 2D : du graphène au h-BN / Spintronics with 2D materials : from graphene to h-BN

Piquemal, Maëlis 26 March 2018 (has links)
Aujourd'hui se pose une question fondamentale sur le futur de l'électronique actuelle. De plus en plus, des circuits hybrides intégrant de nouvelles fonctionnalités sont fabriqués. On envisage même, à plus long terme, des circuits basés sur une technologie différente de l'approche CMOS utilisée actuellement. Une de ces technologies est la spintronique qui tire profit du spin, degré de liberté supplémentaire de l'électron. Elle a rapidement fait ses preuves par le passé dans le stockage non volatile binaire (disques durs) et s'oriente aujourd'hui vers de nouvelles mémoires magnétiques ultra-performantes et basse consommation les MRAMs (Magnetic Random Access Memories). En parallèle, une nouvelle catégorie de matériaux à fort potentiel a émergé : les matériaux bidimensionnels (2D). Ces matériaux, dont le fer de lance est le graphène (une couche d'un atome d'épaisseur de graphite), offrent de nouvelles propriétés inégalées. Leur combinaison via la fabrication d'hétérostructures et la capacité d'avoir un contrôle de leur épaisseur à l'échelle atomique pourrait devenir un atout majeur en électronique et plus particulièrement en spintronique. L'objectif de cette thèse a été l'étude de l'intégration et la démonstration du potentiel en termes de fonctionnalités et de performances de ces nouveaux matériaux 2D au sein de jonctions tunnel magnétiques (MTJs), le dispositif prototype de la spintronique. Au cours de cette thèse, nous avons poursuivi les travaux initiés au laboratoire sur l'intégration dans des MTJs du graphène obtenu via une méthode de dépôt CVD (dépôt chimique en phase vapeur) directe sur l’électrode ferromagnétique inférieure. Nous avons démontré que les propriétés de filtrage en spin et de membrane protectrice contre l'oxydation de l'électrode ferromagnétique (FM) sous-jacente s'étendaient à une unique couche de graphène. Par ailleurs, nous avons aussi pu étudier et améliorer significativement l'amplitude du filtrage en spin et du signal de magnétorésistance observé via l'optimisation des procédés de croissance et d'intégration et le choix de différentes configurations de matériaux ferromagnétiques (Ni(111), Co...). De forts effets de filtrage de spin ont ainsi pu être observés avec des magnétorésistances allant de -15% à plus de +80%, soit presque trois fois l'état de l'art. En parallèle, nous nous sommes aussi intéressés à un autre matériau 2D, le nitrure de bore hexagonal (h-BN), isolant isomorphe du graphène qui s'apparenterait à une barrière tunnel d'un seul atome d'épaisseur. Afin d’étudier le h-BN dans une MTJ, nous avons décidé d’exploiter à nouveau le principe d’une croissance directe par CVD du matériau 2D sur le matériau FM. Des mesures CT-AFM (Conductive Tip Atomic Force Microscopy) nous ont permis de démontrer les propriétés de barrière tunnel homogène du h-BN ainsi que le contrôle possible de la hauteur de barrière avec le nombre de couches de h-BN. De plus, des mesures électriques et de magnétotransport nous ont permis de confirmer l’intégration réussie de la barrière tunnel h-BN dans notre MTJ. Nous avons pu obtenir les premiers résultats de forte magnétorésistance pour du h-BN avec une amplitude de la magnétorésistance de +50%, plus d'un ordre de grandeur au-dessus de l'état de l'art, révélant le potentiel du h-BN. Nous avons enfin aussi pu démontrer l'importance du couplage entre le h-BN et l'électrode FM offrant un potentiel de contrôle inédit sur les effets de filtrage en spin et allant jusqu'à rendre le h-BN métallique. Lors de cette thèse, nous avons pu montrer que l’intégration du graphène et du h-BN dans des MTJs via la croissance directe par CVD est un procédé privilégié pour tirer pleinement profit de leurs propriétés. Les résultats obtenus de forte magnétorésistance et de filtrage en spin laissent entrevoir le fort potentiel du graphène, du h-BN mais aussi des autres nouveaux matériaux 2D à venir pour les MTJs. Ces études ouvrent une nouvelle voie d’exploration pour les MTJs : les 2D-MTJs. / Nowadays a critical issue is raised concerning the future of current electronics. Increasingly, hybrid circuits with new functionalities are manufactured. A longer term approach is even contemplated with circuits based on a technology different from the one currently used (CMOS technology). One of these envisioned technologies is spintronics, which benefits from the spin properties, the electron additional degree of freedom. Spintronics has quickly proven its worth in the past in the field of non volatile data storing (hard drives) and is today moving towards new fast and ultra-low-power magnetic random access memories the MRAMs. Meanwhile, these last few years, a new category of materials with high potential has emerged : the bidimensional materials (2D). These materials, with graphene (one atomically thick layer of graphite) as the forerunner, provide new unrivaled properties. Their combination in the form of heterostructures and the ability to obtain a control of their thickness at the atomic scale could be a major asset for electronics and more specifically spintronics. The purpose of this thesis has been the study of the integration and the demonstration of the potential in terms of functionalities and performances of these new 2D materials inside the prototypical spintronic device: the magnetic tunnel junction (MTJ). During this thesis, we have pursued the work initiated by the laboratory on the integration of graphene in MTJs with direct CVD deposition method (chemical vapor deposition) on the underlying ferromagnetic electrode. We demonstrated that the spin filtering and protective membrane properties (preventing the oxidation of the underlying ferromagnetic electrode (FM)) observed earlier expand to a graphene monolayer. Furthermore, we have also studied and improved significantly the amplitude of the spin filtering and the magnetoresistance signal observed. This was done thanks to the optimization of the growth process, integration, and choice of the different configurations of ferromagnetic materials in our structures (Ni(111), Co...). High spin filtering effects have been observed as a function of the configurations with magnetoristances ranging from -15% to beyond +80%, which is almost three times the state of the art. Meanwhile, we looked at another 2D material, the hexagonal boron nitride (h-BN), an insulating isomorph of graphene which could be considered as an atomically thin tunnel barrier. In order to study h-BN into a MTJ, we took again advantage of direct CVD growth of the 2D material on a ferromagnet. CT-AFM (Conductive Tip Atomic Force Microscopy) measurements allowed us to demonstrate the homogeneous tunnel barrier properties of h-BN and the possible control of the barrier height with the number of h-BN layers. Simultaneously, electrical and magnetotransport measurement in the complete junction allowed us to confirm the achieved integration of the h-BN tunnel barrier into our MTJ. We have been able to obtain the first results of high magnetoresistance for h-BN with values one order of magnitude beyond the state of the art. A magnetoresistance of +50% has been reached, thanks to the optimization of the growth process revealing the potential of h-BN. We have also been able to show the important role of the coupling between h-BN and the FM electrode offering an unprecedented potential of control on the spin filtering effects, ranging up to making the h-BN metallic. During this thesis, we have been able to demonstrate that the integration of graphene and h-BN in MTJs through direct CVD growth is a promising process in order to fully exploit their properties. The results obtained of high magnetoresistance and spin filtering point to the high potential for MTJs of graphene and h-BN but also to all the new 2D materials to come. These studies pave the way for exploring a new path for MTJs : the 2D-MTJs.
333

Nyttan av LCC-analyser vid planering av underhållsarbete i SL:s spårtunnlar

Skoglund, Anna January 2012 (has links)
Detta examensarbete syftar till att belysa hur LCC-analyser i dag används vid planeringen av underhållsarbeten i tunnelbanans bergtunnlar. SL är ett aktiebolag som ägs av Stockholms Läns Landsting och ansvarar för den landburna kollektivtrafiken i Stockholms län, vilken inbegriper tunnelbanan. Stockholms tunnelbana invigdes 1950 och har sedan dess byggts ut i etapper. Drygt hälften av sträckningen går i tunnlar. Ett ständigt pågående underhållsarbete av tunnlarna krävs för att säkerställa en god funktion. Ibland är även större underhållsåtgärder nödvändiga, vilka, genom exempelvis avstängning med ersättningstrafik, till större utsträckning påverkar omgivningen. Hur underhållet organiseras och planeras är av stor ekonomisk betydelse och hänger även direkt ihop med anläggningens standard. LCC-analyser resulterar i ett mått på en investerings sammanlagda ekonomiska konsekvenser under dess livstid, inkluderas gör med andra ord bland annat investerings-, drift-, och underhållskostnader. Då detta mått fås för flera alternativ kan en jämförelse av dessa göras och bilda ett beslutsunderlag där det totalekonomiskt mest lönsamma kan väljas, istället för att basera beslutet på enbart den initiala investeringskostnaden. Givetvis måste även andra randvillkor och krav beaktas. Två fallstudier har gjorts för att belysa hur LCC i dagsläget används av SL vid olika typer av underhållsarbeten. I det första fallet har LCC använts för att ta fram beslutsunderlag och i det andra inte alls. Utgångspunkten för examensarbetet har varit att det överlag kan finnas mycket att vinna på att använda LCC inte bara vid nybyggnation utan även vid underhållsarbeten. I dagsläget används LCC-analyser inte konsekvent vid planeringen av underhålls- och reparationsarbeten av SL:s berganläggningar. Inga krav om detta ställs utifrån och SL har inga egna riktlinjer beträffande LCC. Detta kan vara en av orsakerna till att LCC-analyser inte utförs i större utsträckning. Andra kan vara bristande kunskap om metodiken, tidsbrist och delat budgetansvar mellan avdelningar. För att konsekvent införa LCC-analyser vid bergprojektering skulle krav om detta behöva ställas externt eller internt genom en LCC-policy eller reglerande dokument. För att sedan genomföra detta på ett sätt så att alla inblandade förstår nyttan vore information/utbildning av metodiken nödvändigt. Viktigt är att definiera vilka projekt som ska omfattas och när i projektgången LCC ska användas. Förslagsvis kan LCC användas vid behovsanalys och krav om LCC-analyser/LCC-beräkningar kan ställas i förfrågningsunderlag / This thesis aims to highlight how LCC analyses currently are used in the planning of maintenance work in the rock tunnels of the Stockholm Metro. SL is a company owned by Stockholm County Council and is responsible for land-based public transport in Stockholm County, which includes the metro. The Stockholm Metro opened in 1950 and has since been expanded in stages. More than half of the route goes through tunnels. Maintenance of the tunnels is necessary to ensure a good function. Sometimes bigger maintenance actions are required, which at times also affects the surrounding world. How the maintenance is planned and organized is of great economic importance and is also directly connected with the facility's standard. LCC analyses results in a measure of an investment's total economic impact over its lifetime, including investment, operation, and maintenance costs. As this measure is obtained for a number of options, a comparison of these can be made and form a basis for decisions in which the total economically most profitable solution can be selected, instead of basing the decision solely on the initial investment cost. Two case studies have been done to elucidate how LCC is used by SL at different types of maintenance work today. In the first case, an LCC analysis has been used to create a basis for decision making, and in the other case LCC has not been considered at all. The starting point for this thesis has been that there may be much to gain by using LCC analyses not only for new constructions but also in the planning of maintenance work. Today LCC analysis is not consistently used in the planning of maintenance and repair work of SL's rock tunnels. There are no demands on this externally and SL has no own guidelines regarding LCC. This could be one of the reasons that LCC analyses are not practiced in a greater extent. Others may be lack of knowledge of methodology, lack of time and shared financial responsibility between departments. In order to consistently introduce LCC analyses for rock maintenance work it would have to be required externally or internally by an LCC policy or through regulatory documents. The new procedures would have to be implemented in a way so that everyone involved understands the benefits, thus information / education of the methodology would be necessary. It is important to define which projects should be covered by, and in which stages of the projects LCC should be used. As a suggestion LCC analysis could be used to define needs and requirements of LCC-analyses can be set in tender documents.
334

CONTROLLING QUASI-2D SEPARATION WITH FLOW INJECTION

Hunter Douglas Nowak (12467895) 27 April 2022 (has links)
<p>Highly loaded aerodynamic devices for propulsion and power generation are emerging to increase power output in a more compact machine are emerging. These devices can experience increased losses due to separation, as in the low-pressure turbine, which arise due to the operation at conditions that increases the adverse pressure gradients ore decrease the Reynolds number of the flow through the device. Therefore, flow control strategies become appealing to reduce losses at these conditions. This work aims to validate flow injection as an effective flow control strategy in the transonic regime.</p> <p>A test facility which was used to study boundary layer separation in a quasi-2d test article was modified to include flow injection and conditions were modified so that the facility was operated in the transonic regime. Valves were chosen which could achieve a wide range of excitation frequencies and the flow control ports were designed to accommodate their nominal flow rate. A preliminary test matrix was built while considering the limitations of the test facility.</p> <p>A numerical study was conducted to identify flow structures of interest and determine a preliminary understanding of the test article. The flow control was then added to the numerical study to guide the experimental set points for injected flow. The response of the flow to continuous slot blowing was characterized, and a 3D simulation with discrete injection ports was done to ensure the set-points determined from the 2D study were viable for discrete injection.</p> <p>Blow-down experiments were then conducted to study the behavior of bulk separation in a transonic regime for a quasi-2D geometry. Once behavior of the separation was understood, steady injection and then pulsated injection were applied in attempts to mitigate the separation. Steady injection was utilized to find the required pressure of injection relative to the total pressure at the inlet of the test article, while the pulsated injection served to identify a frequency at which the time averaged mitigation of separation was greatest.</p> <p>The experiments show that both steady and pulsated flow injection are viable techniques in flow control. It is also shown that pulsation does not allow for a lower pressure injection, but instead allows for the same effect with a lower mass flow requirement. Two-dimensional computational simulations are shown to be effective in determining injection frequencies but not the extent of separation or required injection pressures.</p>
335

Interfacial skew tunneling in group III-V and group IV semiconductors driven by exchange and spin-orbit interactions; Study in the frame of an extended k.p theory / Effet Tunnel Hall Anormal à l’interface de semi-conducteurs contrôlé par les interactions d’échange et spin-orbite. Etude dans le cadre d’une approche k.p étendue

Dang, Thi Huong 09 November 2016 (has links)
Nous avons étudié par des méthodes numériques et en théorie k.p avancée les propriétés tunnel d’électrons et de trous dans des systèmes modèles et hétérostructures composés de semi-conducteurs impliquant des interactions spin-orbite de volume. Nous démontrons que le couplage entre les interactions spin-orbite et d’échange à l’interface de jonctions tunnel résulte en un fort contraste de transmission de porteurs selon le signe de la composante de leur vecteur d’onde dans le plan de la jonction. Cet effet conduit à un effet tunnel anormal d’interface que nous appelons « Effet Hall Tunnel Anormal » (ATHE). De façon similaire, des processus tunnel non-conventionnels se manifestant sur des isolants topologiques ont été prédits par d’autres auteurs. Alors que l’ensemble de ces effets Hall anormaux sont liés aux interactions spin-orbite, les effets tunnel anormaux diffèrent des effets Hall tunnel, des effets Hall et des effets Hall de spin par la forte amplitude prédite ainsi que par des phénomènes de chiralité. Ces propriétés possèdent un lien nontrivial avec la symétrie du système. L’ensemble de ces résultats démontre l’existence d’une nouvelle classe d’effets tunnel qui devaient être étudiés expérimentalement dans un futur proche. En ce qui concerne la bande de valence, nous démontrons, en utilisant un Hamiltonien 14x14 prolongeant un modèle 2x2, que le calcul décrivant l’ATHE repose sur un traitement subtil des états dits « spurious » (états non-physiques) et nous donnons quelques éléments d’amélioration et de compréhension. Dans ce mémoire de thèse, nous développons deux méthodes numériques pour résoudre le problème des états spurious en développant en parallèle des méthodes k.p respectivement à 14 bandes et 30 bandes afin de décrire des matériaux semiconducteurs à gap indirect. Les calculs menés dans la bande de valence d’hétérostructures semiconductrice incluant interfaces et barrières tunnel (approches 6x6 et 14x14) sans centre de symétrie d’inversion mettent en évidence des propriétés d’asymétrie équivalente à celles obtenues dans la bande de conduction. De tels effets sont interprétés, dans le cadre de calculs de perturbation en transport basés sur des techniques de fonctions de Green, par des effets chiraux orbitaux lors du branchement tunnel des fonctions évanescentes dans la barrière. / We report on theoretical, analytical and computational investigations and k.p calculations of electron and hole tunneling, in model systems and heterostructures composed of exchange-split III-V semiconductors involving spin-orbit interaction (SOI). We show that the interplay of SOI and exchange interactions at interfaces and tunnel junctions results in a large difference of transmission for carriers, depending on the sign of their incident in-plane wave vector (k//): this leads to interfacial skew-tunneling effects that we refer to as Anomalous Tunnel Hall Effect (ATHE). In a 2x2 exchange-split band model, the transmission asymmetry (A) between incidence angles related to +k// and -k// wave vector components, is shown to be maximal at peculiar points of the Brillouin zone corresponding to a totally quenched transmission (A = 100%). More generally, we demonstrate the universal character of the transmission asymmetry A vs. in-plane wavevector component, for given reduced kinetic energy and exchange parameter, A being universally scaled by a unique function, independent of the spin-orbit strength and of the material parameters. Similarly, striking tunneling phenomena arising in topological insulators have just been predicted. While they all are related to the spin-orbit directional anisotropy, ATHE differs from the tunneling Hall effect, spontaneous anomalous, and spin Hall effects, or spin-galvanic effect, previously reported for electron transport, by its giant forward asymmetry and chiral nature. These features have non-trivial connection with the symmetry properties of the system. All these results show that a new class of tunneling phenomena can now be investigated and experimentally probed.When valence bands are involved, we show (using 14x14 Hamiltonian and within a 2x2 toy model) that ATHE accurate calculations rely on a subtle treatment of the spurious (unphysical) states and we give an insight into the topology of the complex band structure. We introduce two numerical methods to remove spurious states and successfully, include them in 30-band codes able to describe indirect bandgap group-IV semiconductors. Calculations performed in the valence bands of model heterostructures including tunnel barriers, in both 6x6 and 14x14 k.p Hamiltonians without inversion asymmetry, more astonishingly highlight the same trends in the transmission asymmetry which appears to be related to the difference of orbital chirality and to the related branching (overlap) of the corresponding evanescent wave functions responsible for the tunneling current. Besides, we built an analytical model and developed scattering perturbative techniques based on Green’s function method to analytically deal with electrons and holes and to compare these results with numerical calculations. The agreement between the different approaches is very good. In the case of holes, the asymmetry appears to be robust and persists even when a single electrode is magnetic.
336

TUNNEL BEHAVIOR UNDER COMPLEX ANISOTROPIC CONDITIONS

Osvaldo Paiva Maga Vitali (8842580) 15 May 2020 (has links)
Rock masses may present remarked geostatic stress anisotropy and anisotropic material properties; thus, the tunnel alignment with the geostatic principal stress directions and with the axes of material anisotropy is unlikely. Nevertheless, tunnel design often neglects those misalignments and; yet, the misalignment effects were unknown. In this doctoral research, tunnels under complex anisotropic conditions were modelled analytically and numerically with 3D nonlinear Finite Element Method (FEM). When the tunnel misaligns with the geostatic principal stress directions, anti-symmetric axial displacements and shear stresses are induced around the tunnel. Analytical solutions for misaligned shallow and deep tunnels in isotropic elastic ground are provided. The analytical solutions were validated with 3D FEM analyses. Near the face, the anti-symmetric axial displacements are partially constrained by the tunnel face, producing asymmetric radial displacements and stresses. The asymmetric radial displacements at the face can be divided into a rigid body displacement of the tunnel cross-section and anti-symmetric radial displacements. Those asymmetries may affect the rock-support interaction and the plastic zone developed around the tunnel. In anisotropic rock masses, the tunnel misalignment with the axes of material anisotropy also produces anti-symmetric axial displacements and stresses around the tunnel. It occurs because when the tunnel is not aligned with the principal material directions, the in-plane stresses are coupled with the axial displacements (i.e. the compliance matrix is fully populated). Thus, tunnels in anisotropic rock mass not aligned with the geostatic principal stresses and with the axes of material anisotropy are substantially more complex than tunnels not aligned with the principal stress directions in isotropic rock mass. An analytical solution for misaligned tunnels in anisotropic rock mass is provided. It was observed that the relative orientation of the geostatic principal stresses with respect to the axes of material anisotropy plays an important role. The axial displacements produced by far-field axial shear stresses and by the rock mass anisotropy may compensate each other; thus, axial and radial displacements around the tunnel are reduced. On the other hand, those anti-symmetric axial displacements may be amplified; thus, the ground deformations are increased. Asymmetric radial and axial deformations, and asymmetric spalling of the tunnel walls are commonly observed on tunnels in anisotropic rock masses. The tunnel misalignment with the geostatic principal stress directions and with the axes of material anisotropy could be associated with those phenomena that, so far, are not well comprehended
337

Modeling contingency infiltration scenarios in MODFLOW : Stockholm Bypass and tunnel induced groundwater drawdown

Abdo, Aslan January 2019 (has links)
Subsurface constructions, such as tunnels, create hydrogeological challenges in mitigating risk of subsidence due to groundwater drawdown. Presenting readily made precautionary mitigation plans, such as strategically planned artificial recharge applications, can help effectivise the mitigation process. The Bypass Stockholm project comprises of several subsurface constructions which may lower the surrounding groundwater level through tunnel leakage. Risk of land subsidence persists in the nearby urban area of Vinsta, Stockholm, where a groundwater drawdown may cause the clays in the area to experience land subsidence. A hydrogeological modelling approach was used in the area to create strategic artificial infiltration plans that could be employed as a mitigative response to the drop in groundwater head. In order to simulate the potential tunnel drainage, a steady state hydrogeological model was built using MODFLOW. A 220 l/s tunnel leakage was then simulated. Four different artificial groundwater infiltration scenarios were then conceptualized and simulated to observe effects on groundwater heads. The groundwater levels of the baseline model of the area fit the calibration targets with average absolute deviation of 0.18 m. The tunnel drainage scenario lowered the groundwater level in the till aquifer and bedrock by 0 - 1.5 m and 0.5 - 5 m respectively, with higher drawdowns observed closer to the tunnel. The infiltration scenarios mitigate the groundwater drawdown with different efficacies; proximity to the recharge point, and discharge into the till aquifer were observed to have the highest effect on groundwater recharge in the model. The model could have been improved by improving the data quality surrounding the hydraulic conductivity of the bedrock, as it had the highest effect according to the parameter sensitivity analysis. / Konstruktioner under mark kan skapa hydrogeologiska utmaningar, såsom sättningsrisk orsakade av grundvattenavsänkning. Ett sätt att effektivisera åtgärdsprocessen är att förbereda för eventuell artificiell grundvatteninfiltration. Vägprojektet Förbifart Stockholm innefattar konstruktioner under mark och riskerar, genom inläckage, att sänka grundvattennivån i omgivningen. Ett potentiellt problemområde är stadsdelen Vinsta, delar av vars är byggd på sättningskänslig lera som kan påverkas av en grundvattenavsänkning. För att kunna motverka en grundvattensänkning i Vinsta har hydrogeologisk modellering utförts för att strategiskt planera artificiell grundvatteninfiltration. Ett tunnelläckage på 220 l/s har simulerats genom en hydrogeologisk steady state-modell i MODFLOW. Fyra olika scenarier för grundvatteninfiltration har konceptualiserats och simulerats för att observera påverkan på grundvattennivån. Den spatialt variabla grundvattennivån i grundmodellen nådde kalibreringsmålen med en genomsnittlig absolutavvikelse på 0,18 m. Modellen för tunnelläckage resulterade i att grundvattennivån i moränakvifären och berget sjönk med 0 – 1,5 resp. 0,5 – 5 m, med större grundvattensänkning närmare tunneln. Scenarierna för infiltration motverkade grundvattensänkningen i olika grad. Närhet tilltunneln, eller platsen för inläckage, samt den hydrauliska konduktiviteten mellan infiltrationen och akvifären visade störst påverkan på resultatet för att motverka grundvattensänkningen. Känslighetsanalysen för parametrarna i modellen visade att berget och dess hydrauliska konduktivitet hade störst påverkan på resultatet. Tillgång till bättre data för berget möjliggör förbättrat modelleringsresultat.
338

Development of an Infrared Thermography System to Measure Boundary Layer Transition in a Low Speed Wind Tunnel Testing Environment

Horton, Damien 01 March 2021 (has links) (PDF)
The use of infrared thermography for boundary layer detection was evaluated for use in the Cal Poly Low Speed Wind Tunnel (LSWT) and recommendations for the successful use of this technique were developed. In cooperation with Joby Aviation, an infinite wing model was designed, manufactured and tested for use in the LSWT. The wing was designed around a custom airfoil profile specific for this project, where the nearly-flat pressure gradient at a zero pitch angle would delay the chordwise onset of boundary layer transition. Steady-state, RANS numerical simulations predicted the onset of transition to occur at 0.75 x/c for the design Reynolds Number condition of 6.25x105. The wing was manufactured from 3D printed aluminum, with a wall thickness of 0.125 inches and a chord length of 13.78 inches. Two central rows of static pressure taps were used, each with 12 functional chordwise locations. The taps were able to generate strong correlation to the numerically predicted pressure coefficient distribution. The use of an infrared camera visualized and confirmed the presence of boundary layer transition at the chordline location anticipated by the early simulations. To do so, the model was pre-heated such that the differential cooling properties of laminar and turbulent flow would generate a clear temperature gradient on the surface correlating to boundary layer transition. Adjustment of the model’s pitch angle demonstrated a change in the onset location of boundary layer transition during the infrared testing. The change of onset location was seen to move forward along the chordline as the aerodynamic angle of attack was increased. Testing with a Preston Tube system allowed for the interpolation of local skin friction coefficient values at each static tap location. Application of both laminar and turbulent empirical assumptions, when compared to numerical expectations, allowed for the qualitative assessment of boundary layer transition onset. Overall, the wing model developed for this research proved capable of producing quality and repetitive results for the experimental goals it was designed to meet. The model will next be used in continued tests which will further explore the use of infrared thermography.
339

Feasibility Study for Testing the Dynamic Stability of Blunt Bodies with a Magnetic Suspension System in a Supersonic Wind Tunnel

Sevier, Abigail 05 June 2017 (has links)
No description available.
340

Abiotic Factors during Spring and Fall in Ohio: Their Measurement and Shaping of Lettuce Tissue Abundance and Composition

Bumgarner, Natalie Ruth 25 June 2012 (has links)
No description available.

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