In a stopping rule problem, a real-time player decides to stop or continue at stage n based on the observations up to that stage, but in a k-step look-ahead stopping rule problem, we suppose the player knows k steps ahead. The aim of this Ph.D. dissertation is to study this type of prophet problems for simple random walk, determine the optimal stopping rule and calculate the expected return for them. The optimal one-step look-ahead stopping rule for a finite simple random walk is determined in this work. We also study two infinite horizon stopping rule problems, sum with negative drift problems and discounted sum problems. The optimal one, two and three-step look-ahead stopping rules are introduced for the sum with negative drift problem for simple random walk. We also compare the maximum expected returns and calculate the upper bound for the advantage of the prophet over the decision maker. The last chapter of this dissertation concentrates on the discounted sum problem for simple random walk. Optimal one-step look-ahead stopping rule is defined and lastly we compare the optimal expected return for one-step look-ahead prophet with a real-time decision maker.

Electromagnetic induction (EMI) has been used in archaeology for decades, but still lags in use and development when compared to magnetometry and ground-penetrating radar. While it has become more popular than electrical resistivity area survey, it is now less commonly used than electrical resistivity tomography. The EMI method is likely underutilized due to drift problems and a lack of multi-sensor, vehicle-towed systems capable of rapid, high-density data collection. In this article we demonstrate not only the effectiveness of EMI survey, but a case where entire villages would have remained undetected without it. At the Singer-Hieronymus Site in central Kentucky, USA, a vehicle-towed frequency domain EMI survey detected the location of plazas, residential areas, and trash disposal areas across multiple Fort Ancient villages that contained both intact and heavily disturbed deposits. Additionally, three new villages were revealed. Through this process, we discovered how Fort Ancient village dynamics may be studied through a geophysical investigation of village shape, size, and spatial organization.

Estimations of the intensity of short-period perturbations of the horizontal drift velocity at 80 - 110 km altitude are made using data from the regular low-frequency D1 ionospheric reflection observations at Collm, Germany (52° N, 15° E) for the period 1983 - 1999. A simple half-hourly-difference numerical filter is used to extract perturbations with time scales between 0.7 and 3 hours. The results are compared with the mean drift analyses in order to study the interaction between short-period perturbations and the mean circulation. The average monthly variances of short-period perturbations of the zonal velocity near 80 km altitude show a main maximum in summer, a smaller maximum in winter, and minimum values at the equinoxes. At higher altitudes the summer maximum is shifted towards spring, and another maximum of perturbation variances in autumn appears at altitudes near and above 100 km. The seasonal changes of variances of the meridional velocity show maximum values in spring and summer, also some indications for an increase of the summer maximum at altitudes larger than 100 km are found. The observed altitude changes of the seasonal variations of drift perturbation variances are consistent with some numerical calculations of the height structure of a spectrum of internal gravity waves in the middle and upper atmosphere. / Die Intensität kurzperiodischer Störungen der horizontalen Driftgeschwindigkeit im Höhenbereich zwischen 80 und 110 km wurde anhand der regulären D1 Langwellenreflexionsmessungen in Collm (52° N, 15° E), bestimmt. Verwendet wurden Daten der Jahre 1983 - 1999. Ein einfache numerische Filter basierend auf den Unterschieden aufeinanderfolgender halbstündiger Windmittelwerte wurde verwendet, um Störungen im Zeitbereich von 0.7 - 3 Stunden zu ermitteln. Die Ergebnisse wurden mit Analysen der mittleren Drift verglichen, um die Wechselwirkungen zwischen kurzperiodischen Störungen und der mittleren Zirkulation zu untersuchen. Die mittlere monatliche Varianz der kurzperiodischen Störungen der Zonalgeschwindigkeit bei etwa 80 km zeigt ein Hauptmaximum im Sommer und ein schwächeres Maximum im Winter, wobei die Minima während der Aquinoktien auftreten. In grösseren Höhen verschiebt sich das Sommermaximum zum Frühjahr hin, und in Höhen über 100 km erscheint im Herbst ein weiteres Maximum. Der Jahresgang der meridionalen Windstörungen zeigt maximale Werte in Frühjahr/Sommer, und es sind auch Hinweise auf eine Verstärkung des Sommermaximums oberhalb von 100 km zu finden. Die gemessenen Höhenänderungen im Jahresgang der kurzperiodischen Driftschwankungen entsprechen numerischen Ergebnissen der Höhenabhängigkeit interner Schwerewellen in der mittleren und oberen Atmosphäre.

SammanfattningInom Kristianstad kommun finns det ett problem gällande driften och driftkostnaden för idrottsföreningar med egna idrottsanläggningar. Det driftbidrag som kommunen har möjlighet att ge ut har en låg kostnadstäckning gällande driftkostnaderna. Syftet med undersökningen var att granska problem som idrottsföreningar i Kristianstad kommun har kopplat till driftkostnader och driftbidrag av driften av sina egna idrottsanläggningar ur ett hållbarhetsperspektiv. Frågeställningarna i undersökningen var:-Vilka driftkostnader har idrottsföreningarna och är driftkostnaderna hållbara?-Vilka driftsförhållanden finns för idrottsföreningar i Kristianstad kommun? -Vilka möjligheter finns det för hållbar utveckling gällande drift och driftförhållanden?Med hjälp av semistrukturerade intervjuer, dokumentanalys och en enkätundersökning samlades empiri in från olika idrottsföreningar i Kristianstad. Det genomfördes två semistrukturerade intervjuer, en med en idrottsförening som har en egen idrottsanläggning och en med en idrottsförening som hyr idrottsanläggning från Kristianstad kommun, för att få olika perspektiv på frågan. En enkätundersökning genomfördes med 11 olika idrottsföreningar i Kristianstad och dokument från Kristianstad kommun och från en av idrottsföreningarna i intervjuerna analyserades. Resultatet från intervjuerna, enkätundersökningen och dokumentanalysen analyserades primärt utifrån de teoretiska begreppen hållbar utveckling samt driftsförhållanden.I resultatet framkom det att de största driftkostnaderna för majoriteten utav idrottsföreningarna som deltog i undersökningen var personalkostnader samt kostnader för el/värme. Dessa kostnader hade för de flesta av idrottsföreningarna ökat under de senaste åren samt att deras totala driftkostnader hade ökat. De primära driftförhållanden som påverkar idrottsföreningarna är arbetskraften, de ökande kostnaderna samt det bristande samarbetet med kommunen. Driftbidragen hade för flera idrottsföreningar en låg kostnadstäckning. Mindre initiativ som en maskinpool och arbetspool samt ett ökat samarbete mellan kommun och idrottsföreningar med problem med drift framkom som förutsättningar för att successivt skapa en hållbar utveckling för driftkostnader och drift av idrottsanläggningar. Detta framstod som den mest realistiska inriktningen framför kortsiktiga och mindre realistiska förslag som att bara öka driftbidragen eller förvänta sig förändring. / AbstractWithin the municipality of Kristianstad there is a problem regarding the operation and operating costs of sports associations with their own sports facilities. The operating contribution that the municipality are able to issue has a low-cost coverage for the operating costs. The purpose of the survey was to investigate problems that sports clubs in Kristianstad municipality have linked to operating costs and operating contributions from the operation of their own sports facilities from a sustainability perspective. The questions in the survey were:- What operating costs do sports clubs have and operating costs are sustainable?- What operating conditions exist for sports clubs in Kristianstad municipality?- What opportunities are there for sustainable development regarding operating and operating conditions?With the help of semi-structured interviews, document analysis and a survey, empirical evidence was gathered from various sports clubs in Kristianstad. Two semi-structured interviews were conducted, one with a sports association that has its own sports facility and one with a sports club that rents a sports facility from Kristianstad municipality, with the purpose of getting different perspectives on the issue. A survey was conducted with 11 different sports clubs in Kristianstad and documents from Kristianstad municipality and from one of the sports clubs in the interviews were analyzed. The results of the interviews, questionnaire and document analysis were analyzed primarily from the theoretical concepts of sustainability and operating conditions.The results showed that the largest operating expenses for most of the sports clubs participating in the survey were personnel costs and electricity/heat costs. These costs had increased for most of the sports clubs in recent years and their total operating costs had also increased. The primary operating conditions that is affecting sports clubs are the labor force, the rising expenses and the lack of cooperation with the municipality. The operating grants had a low-cost coverage for several sports clubs. Minor initiatives such as a machine pool and labor pool as well as increased cooperation between the municipality and the sports clubs with operational problems have emerged as a prerequisite for progressively creating sustainable development regarding operating costs and the operation of sports facilities. This proved to be the most realistic approach instead of short term and less realistic proposals, such as just increasing operating surcharges or just expecting things to change.

Research over the years has established that the Gradient Drift Instability process causes small-scale irregularities, mostly along the edges of the high-latitude polar cap patches. Studying these irregularities will help in the development of a global Scale Ionospheric model, which is a central part of a global space weather forecast system. Much theoretical work has been done with varying degrees of complexity to study this instability in the high latitude patches. In this work we have used the Utah State University Time Dependent Ionospheric Model to model the high-latitude patches, calculate the growth rate of the instability, and perform a macro-scale study of the phenomenon. This is the first time that real ionospheric values have been used to calculate the growth rate and to provide two-dimensional maps identifying Gradient Drift Instability-caused irregularity regions in the polar cap. Our research shows that regions of intense instability occur along the edges of the tongue of ionization and its throat regions with strong rates along the borders of the cusp region.

A mechanistic model is developed to determine the habitat needs of drift-feeding stream salmonids from the direct cause-and- effect relationships of environmental and physiological variables on net energy intake (NEI). The model determines NEI by subtracting energy costs (basal metabolism , swimming cost, digestion cost) and losses (egestion and excretion) from the gross energy intake obtained as a result of simulated prey capture. The prey capture portion of the model utilizes components o f the predation model of C.S. Holling and the prey capture model of N.F. Hughes and L.M. Dill to determine the rate of prey capture (gross energy intake) as a function of fish size, water velocity, water depth, water temperature, and the amount of drift. Physiological input parameters for the model are estimated from the literature. Two separate validation tests of the model's ability to predict stream habitat use of trout, primarily cutthroat trout (Oncorhynchus clarki), in St. Charles Creek, Idaho, are presented. In both cases, the NEI model closely predicts the stream habitat that different size classes of fish utilize. The validation tests provide strong evidence that drift-feeding fish utilize stream habitats that provide high rates of NEI as determined by the model. Sensitivity and simulation analyses of the model are used to identify the most important input parameters and to illustrate in terms of energetics why drift-feeding fish utilize various habitats. Model simulations explain why fish utilize deeper and faster habitats as they get larger and why they utilize slower habitats in the winter. In addition, it is shown that streams with high drift rates should theoretically provide more usable salmonid habitat than similar streams with lower drift rates.

Semiconductors with an additional intermediate band (IB) have the potential to greatly improve solar cell efficiency. Their theoretical efficiency limit is over 50% higher than that of standard semiconductor solar cells at full concentration. In practice however, their efficiencies are low compared to this detailed balance limit. Part of the reason is that it has not been possible to optimize IB device geometry because no device model has existed that could capture all the effects present in IB materials (e.g., charge transport inside the IB and self-consistent optics). In this thesis I introduce my new device model for intermediate band semiconductors called Simudo. The software uses the finite element method to solve the coupled Poisson/drift-diffusion (PDD) system of equations that describe the carrier dynamics inside semiconductor (IB or not) devices, along with optical propagation. I benchmark its accuracy on standard semiconductor problems against Synopsys Sentaurus, and I find that not only does it give valid results but in fact converges to the solution with a smaller number of mesh points by having quartic rather than merely quadratic solution convergence with respect to the number of mesh points. I also demonstrate Simudo's immediate usefulness by answering the question of whether IB mobility can compensate for mismatched optical absorption processes in different regions of the device. The device model work is preceded by three introductory chapters bringing the reader up to speed on semiconductor device physics and providing them with a primer on the finite element method. The coupled PDD equations are numerically challenging to solve, and the road to development of Simudo tried a number of formulations of the problem that were not successful. In the final chapter I discuss some of these formulations and why they did not succeed.

The Covid-19 pandemic has generated a serious stress test for welfare states and welfare state institutions. This challenge has been met by unprecedented responses from governments, most notably countrywide shutdowns of substantial sections of economies to facilitate social distancing. Consequently, the health crisis was followed closely by an economic crisis. This situation has created a possibility study a process that predates the pandemic, namely liberalization. The thesis applies the theories of Thelen (2014), who claims that while there is an ongoing liberalization in welfare states, there are varieties of liberalization. She refers to the three trajectories of change deregulatory liberalization, dualizing liberalization and embedded flexibilization. The aim of the thesis is to enhance our understanding of how these varieties of liberalization are affected when countries are faced by massive external change. In pursuing this goal, I construct an analytical framework that illustrates the expected labour market policy responses for two of the three trajectory of change. I then conduct a comparative case study of labour market policy responses in Denmark, the Netherlands, Germany, and Sweden. I compare the expected responses with the actual labour market policy responses to the crisis to detect how their responses relate to the trajectories of change towards liberalization. The findings suggest that while the countries have implemented rather similar responses to the crises, some countries’ path towards liberalization has been strengthened by their labour market policy responses, while other countries have diverted from their path towards liberalization during the Covid-19 crisis. The bigger take-aways from these findings are that the process of liberalization will be affected differently due to countries differing paths towards liberalization, as well as their inherent institutional structures. The findings thus highlight the significance of both path dependence and differing trajectories of change concerning the effects of the Covid-19 crisis on the process of liberalization.

Glacial till from the Mt. Achernar moraine (MAM) records pre- and post- last glacial maximum (LGM) compositional variability of an East Antarctic moraine sequence through time and space. Pebble lithology, detrital zircon geochronology, and till geochemistry were analyzed on samples from a 6.5 km transect. Hummocky topography occurs with the most recently exposed material along the active ice margin (Zone 1), followed by a relatively flat and low region (Zone 2), and then a series of ~2 m high parallel/sub-parallel ridges and troughs accompanied by distinct color changes that are directly related to the dominant lithology of the region (Zones 3–5). Zone 3 is dominated by ~38% more sedimentary rocks than adjacent zones and has an overall shape of a broad arch superimposed with smaller ridges. Zone 4 is composed of distinct colored bands that alternate between dominant sedimentary and mafic igneous lithologies. These dominant sedimentary and intermediate/mafic igneous rocks for all Zones are interpreted to be primarily the Beacon and Ferrar Supergroup rocks respectively. The U/Pb data from the till is consistent with a Beacon Supergroup source as samples consistently show significant populations from the Permian ~250-260 Ma, the Proterozoic ~565–600 Ma, ~950–1270 Ma, and ~2300-2320 Ma, as well as (and) the late Archean ~2700-2770 Ma. The Pagoda, Mackellar, Buckley, and Fremouw Formations are potential sources of the detrital zircons. When paired with surface exposure ages, the U/Pb data indicates that the debris source has been consistent over the past ~555 ka, implying relatively stable ice sheet behavior. However, ice sheet change is indicated by a trim line present on Mt. Achernar that can be traced back to the boundary between Zones 3 and 4, as well as a change in pebble lithology, geochemistry, and morphology of Zone 3. Zone 3 records a time of ice sheet thickening and a change in provenance during the LGM. Zone 4 is pre-LGM, Zone 2 records deglaciation, and Zone 1 is still actively connected to the Law Glacier. This study reveals the broader importance of using multiple provenance techniques when interpreting provenance changes in till over time.

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