Nous considérons le problème d’un électron sur des pavages quasipériodiques en une et deux dimensions. Nous introduisons tout d’abord les pavages quasipériodiques d’un point de vue géométrique, et défendons en particulier l’idée que ces pavages sont les pavages apériodiques les plus proches de la périodicité. Nous concentrant plus particulièrement sur l’un des pavages quasipériodiques les plus simples, la chaîne de Fibonacci, nous montrons à l’aide d’un groupe de renormalisation que la multifractalité des états électroniques découle directement de l’invariance d’échelle de la chaîne. Élargissant ensuite notre champ d’étude à un ensemble de chaînes quasipériodiques, nous nous intéressons au théorème de label des gaps, qui décrit comment la géométrie d’une chaîne donnée contraint les valeurs que peut prendre la densité d’états intégrée dans les gaps du spectre électronique. Plus précisément, nous nous intéressons à la façon dont l’énoncé de ce théorème est modifié lorsque l’on considère une séquence d’approximants périodiques approchant une chaîne quasipériodique. Enfin, nous montrons comment des champs de hauteurs géométriques peuvent être utilisés pour construire des états électroniques exacts sur des pavages en une et deux dimensions. Ces états sont robustes aux perturbations du hamiltonien, sous réserve que ces dernières respectent les symétries du pavage sous-jacent. Nous relions les dimensions fractales de ces états à la distribution de probabilités des hauteurs, que nous calculons de façon exacte. Dans le cas des chaînes quasipériodiques, nous montrons que la conductivité suit une loi d’échelle de la taille de l’échantillon, dont l’exposant est relié à cette même distribution de probabilités. / We consider the problem of a single electron on one and two-dimensional quasiperiodic tilings. We first introduce quasiperiodic tilings from a geometrical point of view, and point out that among aperiodic tilings, they are the closest to being periodic. Focusing on one of the simplest one-dimensional quasiperiodic tilings, the Fibonacci chain, we show, with the help of a renormalization group analysis, that the multifractality of the electronic states is a direct consequence of the scale invariance of the chain. Considering now a broader class of quasiperiodic chains, we study the gap labeling theorem, which relates the geometry of a given chain to the set of values the integrated density of states can take in the gaps of the electronic spectrum. More precisely, we study how this theorem is modified when considering a sequence of approximant chains approaching a quasiperiodic one. Finally, we show how geometrical height fields can be used to construct exact eigenstates on one and two-dimensional quasiperiodic tilings. These states are robust to perturbations of the Hamiltonian, provided that they respect the symmetries of the underlying tiling. These states are critical, and we relate their fractal dimensions to the probability distribution of the height field, which we compute exactly. In the case of quasiperiodic chains, we show that the conductivity follows a scaling law, with an exponent given by the same probability distribution.

Although band theory is about a century old, it remains relevant today as a tool for the treatment of electrons in solids. The confluence of mathematical ideas like geometry and topology with band theory has proven to be a ripe avenue for research in the past few decades. The importance of Fermi surface geometry, especially in conjunction with electronic correlation, has been well recognized. One particular thread in this direction is probing the occurrence of non-trivial Fermi surface geometry, and its influence on macroscopic properties of materials. A notable example of exotic Fermi surface geometry arises from singular points of the dispersion, and these have been known since 1953. The investigation into these was reignited recently, culminating in the work presented in this thesis. In this dissertation, I investigate two broad categories of singular points in bands. At a singular point, either the dispersion or the Fermi surface fail to be smooth. This may cause distinct signatures in transport and spectroscopic properties when the singular point occurs close to the Fermi level. In the two dimensional setting, I classify using catastrophe theory, the point singularities arising from higher order saddles of the dispersion. These are the more exclusive cousins of the regular van Hove saddle that cause, among other things, a power law divergence in the density of states. The role of lattice symmetries in aiding or preventing the occurrence of these singularities is also carefully explored. In the case of three dimensional bands, I investigate the spectroscopic properties of the nodal point singularity, arising from a linear band crossing. In particular, I determine the distinct signature of nodal points in the analytic, momentum resolved, joint density of states (JDOS) and the numerically calculated resonant inelastic x-ray scattering (RIXS) spectrum, within the fast collision approximation that ignores core hole effects. The results presented here will be the stepping stone towards a careful future calculation, incorporating the potential edge singularity effects through core hole potential. Such a calculation may be directly comparable with ongoing experiments.

The Desmoinesian Marmaton Group, along the southern portion of the Anadarko Basin in the Granite Wash, comprises over 2,000 feet of stacked tight sandstones and conglomerates, containing unconventional reservoirs. Uncertainty around facies variability and lateral continuity of these reservoirs represents challenges to accurate reservoir characterization due to laterally restricted submarine fan systems, and mountainront faulting. This study examines 206 wire-line well-log suites and nine ice-house flooding surfaces across an 810-square mile study area to frame fine-scale sequences, track facies changes, and estimate fault timing and duration. This high-resolution stratigraphic framework comprises a hierarchy of cycles: one third-order, three fourth-order, and eight fifth-order cycles; these were mapped across fault blocks. Mapping at the fifth-order scale documented previously un-published faults, and showed that movement occurred during two separate fifth-order cycles. Within the stratigraphic framework, well log trends, calibrated to core descriptions, enabled prediction of depositional environments in uncored wells.

No description available.

No description available.

No description available.

Försöksdjursverksamhet är en viktig del inom läkemedelsutveckling och annan forskning, men svårigheterna i att övervaka djurens hälsa och aktivitet utan att stressa dem gör att en hel del studier får opålitliga resultat. Idag sker mycket av övervakningen antingen manuellt av personal som tittar till djuren, eller med automatiska metoder som innefattar något stressande moment. TrackPaw är ett svenskt startup-företag som vill ändra på detta. De utvecklar en sensorplattform som ska ligga på burens botten och mäta djurens aktivitet utan att störa dem. Detta arbete har som mål att med produktutvecklingsmetoder, materialval, beräkningar och CAD-modellering utveckla ett koncept för ett hölje till TrackPaws plattform med syfte att möjliggöra vidare utveckling av deras produkt. Kund- samt myndighetskrav sammanställdes och översattes till mätbara egenskaper i form av en målspecifikation. Konceptprocessen utfördes genom att en problemformulering utarbetades för att sedan brytas ner till delproblem. Lösningar till dessa delproblem söktes sedan internt och externt. Lösningarna sattes ihop i en konceptkombinationstabell ur vilken genererades ett antal koncept. Kriterier för ett lyckat koncept arbetades fram med problembeskrivningen och kravspecen som utgångspunkt. Valet av koncept gjordes sedan med hjälp av en matris, i vilken koncepten poängsattes mot varandra efter hur väl de levde upp till kriterierna. Det valda konceptet detaljutveklades sedan genom materialval, beräkningar och CAD-modellering. Resultatet blev ett hölje bestående av fyra delar; en toppskiva med en tunnare sektion i mitten som ska leda rörelseinformation till plattformens sensorer, en botten som rymmer plattformens komponenter, en monteringsplatta som separerar komponenterna från ytterväggarna och en packning som tätar konstruktionen. Nästa steg som bör tas är att producera höljet för att utföra ytterligare tester och säkerställa dess funktion. Av resultatet dras slutsatsen att höljet bör fylla sitt syfte och tillåta TrackPaw att gå vidare med utvecklandet av plattformen. / Animal testing plays an important part in the development of new medication and in other research, but the dificulties in monitoring the health and activity of the animals without stressing them leads quite a few studies to have unreliable results. Today, a lot of the monitoring is being done manually by personnel looking in on the animals or through automated methods that still induce some stress. TrackPaw is a Swedish start-up who are developing a platform which will change all that by being placed in the bottom of the homing cages and monitoring the animals without causing stress. The goal of this project is to, through product development methods, materials selection, calculations and CAD-modeling, develop a concept for a housing for TrackPaw's sensor platform. The purpose being to allow TrackPaw to continue the development of their product. Client and regulatory requirements were compiled and translated to measurable qualities in the form of goal specifications. The concept development process began by the development of a problem definition which was then broken down into a problem list. Solutions to these problems were sought internally and externally. The solutions were entered into a concept combination table out of which a number of complete concepts were generated. Criteria for a successful concept were created using the goal specifications and problem definition as a starting point. The concept choice was made using a decision matrix where the generated concepts were given points, relative to each other, on how well they met the criteria. The chosen concept was developed in further detail using material choice, calculations and CAD-modeling. The resulting concept is a casing consisting of four parts; a platform with a thinner section in the middle to transfer movement information to the platform's sensors, a bottom which houses the platform's components, a middle platform for mounting components on, separating them from the walls and a gasket to seal the casing. The next step in the development of the platform is to manufacture the casing and perform further testing and evaluation of its function. From the results a conclusion can be drawn that the housing should fill its purpose of allowing TrackPaw to continue the development of their platform.

Ancillary structures are highway support structures such as traffic signals, sign structures, luminaires, and high-mast light towers which are typically fastened to a concrete foundation using embedded anchor rods and anchor nuts. The inventory of ancillary structures across the United States is huge, and these structures vary dramatically in type, age, size, and material. There have been reported cases of anchor nut loosening on ancillary structures in the past few decades, but the cause of loosening is still unknown. Ancillary structures are susceptible to vibrations due to different wind loadings like natural gusts, vortex shedding, galloping, and truck-induced gusts. Wind-induced vibrations are believed to be one of the potential causes of anchor nut loosening. Previous research also suggests that vibrations can lead to loosening of nuts in structural and mechanical connections. There is concern regarding the current tightening procedures specified in the various federal and state specifications. Improper tightening can potentially lead to anchor nut loosening under the effect of wind-induced vibrations. In ancillary structures, the anchor rods and nuts are first snug-tightened using a wrench before fully pretensioning them as per the current specifications. The snug-tight condition is vaguely defined at present and needs revisions to avoid any under-tightening or over-tightening. Galvanization and overtapping of the anchor nuts also pose a potential concern. Anchor nuts are tapped oversize after galvanization to ensure the nuts fit well on the galvanized rod. American Society for Testing and Materials (ASTM) standards provide specific allowable tolerances on the thread parameters of the anchor rod and nut after galvanization and overtapping. Any deviation from the allowable tolerances can lead to gaps between the mating threads, which can contribute to the loosening of nuts under vibrations. This study focuses on investigating the following potential causes of loosening: improper tightening, wind-induced vibrations, snug-tight condition, and thread fabrication tolerance. Current tightening procedures for double-nut and single-nut connections on ancillary structures were verified using a tightening study as part of the investigation. New revisions to the specified nut rotation values for double-nut connections and a draft for proposed new specifications on single-nut connections has been provided as a result of discrepancies and inconsistencies in the current specifications. Vibration testing of a full-scale traffic signal was conducted on the basis of results from a four-month field monitoring program in order to investigate the effects of wind-induced vibrations on anchor nut loosening. It was concluded from testing that improper tightening (pretension < 5ksi) can lead to loosening of anchor nuts under wind-induced vibrations. A small-scale testing was also conducted to verify the results from the large-scale vibration testing. Snug-tight pretension in grade 55, 1-inch and 2-inch anchor rods was found to be highly variable due to different wrench lengths and personnel strength. Thread parameters of galvanized anchor rods and nuts procured from 3 different regional suppliers were found to be within specified tolerances. Various recommendations were then made as a result of the above tightening, vibration, and thread tolerance studies in an effort to reduce the cases related to anchor nut loosening in the future. / Doctor of Philosophy / Ancillary structures like traffic signals, sign structures, and light poles are typically connected to the ground using anchor rods and anchor nuts. There is a very large number of ancillary structures throughout the United States and vary in type, age, size, and material. There have been reported cases of anchor nut loosening on ancillary structures in the past few decades, but the cause of loosening is still unknown. Different types of wind loadings like natural gusts, vortex shedding, galloping, and truck-induced gusts vibrate the ancillary structures. These vibrations due to the wind are believed to be one of the potential causes of anchor nut loosening. Vibrations in the past have been shown to cause loosening of nuts in other structural and mechanical connections. There is also concern that the anchor rods and anchor nuts are not tightened properly as per the specifications, which can lead to loosening of nuts when the ancillary structures vibrate due to wind loadings. In ancillary structures, the anchor nuts are first made tight using a wrench with the full effort of a worker, also known as the snug-tight condition. The snug-tight condition is not properly defined at present and needs to be changed to prevent any under-tightening or over-tightening of the anchor nuts. Also, the anchor rods and nuts are generally coated with a hot zinc layer to prevent their corrosion when exposed to environmental effects like ice, snow, humidity, and rain. This process is called galvanization. The American Society for Testing and Materials (ASTM) provides some guidelines on the amount of coating allowed on the threads of the anchor rods and nuts. Any deviation from the allowable tolerances can lead to gaps between the threads of the anchor rod and nut, which can contribute to the loosening of nuts during vibrations of ancillary structures due to wind. This study focuses on investigating the following potential causes of loosening: improper tightening, vibrations of ancillary structures due to wind, snug-tight condition, and allowable tolerances for the amount of galvanization. Current tightening procedures for anchor rods and nut on ancillary structures were verified using a tightening study as part of the investigation. New revisions to the current tightening procedures have been provided as a result of discrepancies and inconsistencies observed in the current specifications. A traffic signal and a light pole were instrumented with sensors for four months to measure wind-related forces acting on these structures. Further, a full-scale traffic signal was vibrated in the laboratory using an electric motor to simulate the vibrations due to the measured wind forces. It was determined from the testing that if the anchor nuts were not properly tightened, they could become loose during vibrations due to wind. A small-scale testing was also conducted to check the results from the full-scale vibration testing. The snug-tight force in the anchor rods was also found to be dependent on the length of the wrench and the worker tightening it. The amount of galvanization on the rods and nuts procured from 3 different suppliers were found to be within allowable tolerances. Various recommendations were then made as a result of the conclusions in an effort to reduce the cases related to anchor nut loosening in the future.

<p>Denna rapport ger förslag på olika metoder att automatiskt justera flytläget på en statiskt förankrad boj, en överblick över de processer som styr ändringen av vattennivån och en statisktisk analys på vattennivåförändringarna vid Stockholm, Kungsholmsfort och Kungsvik.</p><p>Beroende på vattenivåns variation finns olika metoder för justering. Områden med små variationer av vattennivå lämpar det sig bäst utan någon som helst justering av flytläget. Områden med inte för stora tidvattensförändringar bör justeras med ett system bestående av vinsch, växellåda med en utväxling på 10 000:1, en 12 V DC motor, ett skötselfritt 12 V batteri, en luftlindad linjärgenerator och en trådtöjningsgivare. Områden med stora variationer i tidvatten behöver en avlastning för motorn i form av en fjäder och dämpare. De monteras horizontellt inuti bojen för att skyddas från den yttre miljön.</p><p>Den statistiska analysen påvisade de största vattennivåändringarna vid både Kungsviks och Kungsholmsforts mätstationer, båda uppvisade ett intervall på 1,6 m mellan minimum och maximum. Kungsvik var den station med de största dagliga variationerna, detta på grund av tidvattnets påverkan i området.</p> / <p>This thesis gives examples of different methods of automated adjustment of floatation level for a static moored buoy, an overview of the theories behind water level change and a statistical analysis of the water level changes for Stockholm, Kungsholmsfort and Kungsvik.</p><p>Depending on the range and frequency of the water level change different methods of adjustment are recommended. For areas with small changes in sea level the best choice would be no adjustment of the floatation level. Areas that are influenced by moderate tidal ranges should incorporate a system of regulation consisting of a winch, gearbox with a gear ratio of around 10,000:1, 12 V DC motor, 12 V maintenance free battery, air coiled linear generator and a strain gauge. For areas with large tidal ranges the previous system should be complimented with a horizontally mounted spring, inside the buoy, to lessen the loads on the motor.</p><p>The statistical analysis found the largest extremes in water level of the three sites to be at Kungsvik and Kungsholmsfort, both exhibiting a range of almost 1.6 m. Kungsvik was the station with the largest daily variations, this is because this is the only station influenced by tidal variations.</p>

Single crystal nickel-based superalloys are used in modern gas turbines because of their remarkable resistance to creep deformation at elevated temperatures, which is ensured by the addition of significant amounts of refractory elements. Too high concentrations of refractory elements can lead to the formation of topologically-close packed (TCP) phases during exposure to conditions of high temperature and stress which result in the degradation of the creep properties. The traditional methods for predicting the occurrence of TCP phases in Ni-based superalloys have been based on the PHACOMP and newPHACOMP methodologies which are well-known to fail with respect to new generations of alloys. In this work a novel two-dimensional structure map (Nbar, deltaV/V) for TCP phases where Nbar is the valence-electron count and deltaV/V is a compositional dependent size factor. This map is found to separate the experimental data on the TCP phases of binary, ternary and multi-component TCP phases into well-defined regions corresponding to different structure types such as A15, sigma, chi, delta, P, R, mu, and Laves. In particular, increasing size factor separates the A15, sigma and chi phases from the delta, P, R, mu phases. The structure map is then also used in conjunction with CALPHAD computations of sigma phase stability to show that the predictive power of newPHACOMP for the seven component Ni–Co–Cr–Ta–W–Re–Al system is indeed poor. In order to gain a microscopic understanding of the observed structural trends, namely the differences between the two groups of TCP structures with increasing deltaV/V and the trend from A15 to sigma to chi with increasing Nbar, the electronic structure is coarse-grained from density functional theory (DFT) to tight-binding to bond-order potentials (BOPs). First, DFT is used to calculate the structural energy differences across the elemental 4d and 5d transition metal series and the heats of formation of the binary alloys Mo-Re, Mo-Ru, Nb-Re, and Nb-Ru. These calculations show that the valence electron concentration stabilizes A15, sigma and chi but destablizes mu and Laves phases. The latter are shown to be stabilized instead by relative size difference. Second, a simple canonical TB model and in combination with the structural energy difference theorem is found to qualitatively reproduce the energy differences predicted by the elemental DFT calculations. The structural energy difference theorem rationalizes the importance of the size factor for the stability of the mu and Laves binary phases as observed in the structure map and DFT heats of formation. Finally, analytic BOP theory, is employed to identify the structural origins of the energetic differences between TCP structure-types that lead to the trends found within the two-dimensional structure map.