A Dynamic Programming Approach to Impulse Control of Brownian Motions

This thesis considers an impulse control problem of a standard Brownian motion under a discounted criterion, in which every intervention incurs a strictly positive cost. The value function and an optimal $(\tau_{*}, Y_{*})$ policy are found using the dynamic programming principle together with the smooth pasting technique. The thesis also performs a sensitivity analysis by analyzing the limiting behaviors of the value function and the $(\tau_{*}, Y_{*})$ policy when the fixed intervention cost converges to zero. It is demonstrated that the limits agree with the classic fuel follower problem. The thesis next formulates and analyzes an $N$-player stochastic game of an impulse control problem under a discounted criterion. In the $N$-player stochastic game, each player controls an object. The objects are molded by an $N$-dimensional Brownian motion. A key aspect of the formulation is that each player aims to minimize her total impulse control cost and the total distance of her object to the moving center of the $N$ objects. The interaction mandates the players to closely follow each other\u27s movements. The Nash equilibrium is characterized and analyzed by a system of Hamilton-Jacobi-Bellman equations. The case when $N=2$ is studied in detail

Vacuum Infusion Process Development for Conformal Ablative Thermal Protection System Materials

Conformal ablators are low density composite materials comprised of a flexible carbon felt based fibrous substrate and a high surface area phenolic matrix. These materials are fabricated to near net shape by molding the substrate, placing in a rigid matched mold and infusing with liquid resin through a vacuum assisted process. The open mold process, originally developed for older rigid substrate ablators, such as PICA, wastes a substantial amount of resin. In this work, a vacuum infusion process a type of liquid composite molding where resin is directly injected into a closed mold under vacuum is advanced for conformal ablators. The process reduces waste over the state-of-the-art technique. Small, flat samples of Conformal Phenolic Impregnated Carbon Ablator are infused using the new approach and subjected to a range of curing configurations and conditions. Resulting materials are inspected for quality and compared to material produced using the standard process. Lessons learned inform subsequent plans for process scale up

Langfristberichterstattung nachhaltiger öffentlicher Finanzen auf subnationaler Ebene : notwendig oder unmöglich?

Nicht erst die jüngste globale Finanzkrise und die daraus resultierenden Schuldenkrisen, von denen vor allem der Euro-Raum stark betroffen war und ist, haben den Fokus auch im öffentlichen Sektor stärker auf eine solide, vergleichbare und transparente Rechnungslegung gelenkt. Neben der traditionell vergangenheitsorientierten Rechnungslegung gewinnt jedoch auch zunehmend eine in die Zukunft gerichtete Prognose der Nachhaltigkeit der öffentlichen Finanzen an Aufmerksamkeit. Während das Thema Langfristperspektiven auf nationaler Ebene an Fahrt gewinnt, ist dessen Relevanz für subnationale Ebenen (Länder, Kantone, Regionen) noch weitgehend unbeleuchtet, aber nicht unkritisch betrachtet. Der Beitrag geht der Fragestellung nach, welchen Nutzen Langfristberichterstattung auf subnationaler Ebene stiften kann und wie sie ausgestaltet sein könnte. The most recent financial crisis and the subsequent debt crisis, which particularly hit the euro zone strongly, has brought the public sector to focus on solid, comparable and transparent financial accounting. In addition to traditional retrospective financial accounting and reporting, future-oriented long term perspectives of sustainable public finances are gaining attention. While longterm projections have become popular at a national level, they have been less relevant at subnational levels (states, cantons, regions). This article addresses the questions, how long-term projections can be beneficial at subnational level and how they could be shaped

Fusionsanalyse Brugg Umiken

Die Stadt Brugg und die Gemeinde Umiken liegen geographisch nahe beieinander. In den letzten Jahren wurde die Zusammenarbeit in verschiedenen Bereichen vertieft. Eine Fusion dieser beiden Aargauer Gemeinden wäre der nächste Schritt. Das Institut für Verwaltungs-Management ermittelte in einer Fusionsanalyse die Ausgangslage und zeigte verschiedene Szenarien auf, welche im Falle einer Fusion beziehungsweise bei weiterer Eigenständigkeit zu beachten sind

Self mixing oscillators at Q-band using Gunn diode solid state sources

Bibliography: leaves 149-155.This Thesis is a report of research done into the use of a GUNN Diode Millimetre Wave Source as both the Receiver and the Transmitter of a system. The Thesis is divided into three main sections. The first of these sections (Chapter 2) "sets the scene" so to speak. It presents certain preliminary fundamentals that are essential for placing the results obtained later into their proper context. Areas discussed are NOISE FIGURE, TRANSMISSION PATH LOSS and GUNN DIODE operation. The second section (Chapter 3) considers the operation of the device as a mixer. Its operation as a Microwave Power Source is a well-known concept and it will not be discussed here. This section covers such aspects as CONVERSION LOSS, NOISE FIGURE and BIAS CIRCUIT STABILITY. The third section considers those points arising from the second section which seem to be of interest. These include such aspects as Better Correlation of results and theory and ways of applying the device to modern Waveguide structures. The Thesis ends with a Conclusion, Appendix and a Bibliography

Rapid erosion of the Southern African Plateau as it climbs over a mantle superswell

International audienceWe present new sedimentary flux data confirming that a large pulse of erosion affected the Southern African Plateau in the Late Cretaceous and is likely to be related to a major uplift episode of the plateau. This short phase of erosion (i.e., less than 30 Myr in duration) has commonly been difficult to reconcile with a mantle origin for the plateau anomalous uplift: given its size, the rise of the African superplume is likely to have lasted much longer. Here we demonstrate by using a simple model for fluvial erosion that tilting of the continent as it rides over a wide dynamic topography high cannot only cause rapid uplift of the plateau but also trigger continent-wide drainage reorganization, leading to substantial denudation in a relatively short amount of time. The amplitude and short duration of the sedimentary pulse are best reproduced by assuming a strong erodibility contrast between the Karoo sedimentary and volcanic rocks and the underlying basement. We also present a new compilation of paleoclimate indicators that shows a transition from arid to very humid conditions approximately at the onset of the documented erosional pulse, suggesting that climate may have also played a role in triggering the denudation. The diachronism of the sedimentary flux between the eastern and western margins of the plateau and the temporal and geographic coincidence between the uplift and kimberlite eruptions are, however, better explained by our tilt hypothesis driven by the migration of the continent over a fixed source of mantle upwelling

A Product Formula for the Normalized Volume of Free Sums of Lattice Polytopes

The free sum is a basic geometric operation among convex polytopes. This note focuses on the relationship between the normalized volume of the free sum and that of the summands. In particular, we show that the normalized volume of the free sum of full dimensional polytopes is precisely the product of the normalized volumes of the summands.Comment: Published in the proceedings of 2017 Southern Regional Algebra Conferenc

Inverting Passive Margin Stratigraphy for Marine Sediment Transport Dynamics over Geologic Time

Passive margin stratigraphy contains time-integrated records of landscapes that have long since vanished. Quantitatively reading the stratigraphic record using coupled landscape evolution and stratigraphic forward models (SFMs) is a promising approach to extracting information about landscape history. However, there is no consensus about the optimal form of simple SFMs because there has been a lack of direct tests against observed stratigraphy in well-constrained test cases. Specifically, the extent to which SFM behaviour over geologic space and timescales should be governed by local (downslope sediment flux depends only on local slope) versus nonlocal (sediment flux depends on factors other than local slope, such as the history of slopes experienced along a transport pathway) processes is currently unclear. Here, we develop a nonlocal, nonlinear SFM that incorporates slope bypass and long-distance sediment transport, both of which have been previously identified as important model components but not thoroughly tested. Our model collapses to the local, linear model under certain parameterizations such that best-fit parameter values can indicate optimal model structure. Comparing 2-D implementations of both models against seven detailed seismic sections from the Southeast Atlantic Margin, we invert the stratigraphic data for best-fit model parameter values and demonstrate that best-fit parameterizations are not compatible with the local, linear diffusion model. Fitting observed stratigraphy requires parameter values consistent with important contributions from slope bypass and long-distance transport processes. The nonlocal, nonlinear model yields improved fits to the data regardless of whether the model is compared against only the modern bathymetric surface or the full set of seismic reflectors identified in the data. Results suggest that processes of sediment bypass and long-distance transport are required to model realistic passive margin stratigraphy and are therefore important to consider when inverting the stratigraphic record to infer past perturbations to source regions