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Untersuchungen zur spätrömischen Keramik aus Syene/Assuan in Oberägypten (4.-7. Jahrhundert AD). Haus 9 und seine Umgebung in Areal 1. Grabungskampagnen 1 bis 4
Full text linkSeit dem Jahr 2000 werden in der südlichsten Stadt des römischen Reiches Syene/Assuan vom Schweizer Institut für Ägyptische Bauforschung und Altertumskunde in Zusammenarbeit mit dem ägyptischen Antikendienst systematische Rettungsgrabungen durchgeführt. Die von der Autorin untersuchte Keramik stammt aus stratigraphischen Einheiten aus Areal 1 der Ausgrabungen der 1. bis 4. Grabungskampagnen (2000-2004). Die keramischen Untersuchungen fanden im Rahmen eines Projektes des Instituts für Archäologische Wissenschaften der Universität Bern unter der Leitung von Frau Prof.em. Stefanie Martin-Kilcher statt. Die Verfasserin war in der Zeit von 2003 bis 2007 mehrfach vor Ort, um die Keramik zu dokumentieren.
In Teil A wird auf Befund und Kontext der untersuchten Häuser 9 und 10 sowie der umliegenden Gassenschichten eingegangen, wobei der Schwerpunkt auf Haus 9 liegt. Die Baugeschichte des Hauses 9 konnte – soweit durch Analyse der Stratigraphie und anhand der Auswertung der Keramik möglich – vom ausgehenden 4. bis zur Mitte des 7. Jahrhunderts aufgezeigt werden. Besonders interessant ist der geschlossene Befund in einem verstürzten Raum im Erdgeschoss. Hier wurden bei Einsturz des Hauses rund 60 zum Teil ganz erhaltene Gefässe verschüttet. Durch die Analyse von Fundlage und Erhaltung der Gefässe konnte gezeigt werden, dass diese – z.T. leer und ineinander gestapelt - direkt auf dem Fussboden abgestellt worden waren. Es handelte sich bei dem Raum um ein Geschirrlager. Des Weiteren zeigte die Korrelation von Schichten, die durch die sorgfältige Analyse der Keramik möglich war, die Zusammenhänge zwischen den Häusern 9 und 10 auf.
Die Analyse der Schichten und der darin enthaltenen Keramik führte zur Bildung von Keramik-Horizonten. Aus rund 16‘000 Scherben und 3'040 Mindestindividuen aus Haus 9, Haus 10 und den Gassenschichten konnten 34 Horizonte gebildet werden.
Wichtig ist die Erfassung der Keramik in ihrem Kontext sowie in gesamten Fundkomplexen, daher werden alle Gefässe stets in ihren Fundensembles abgebildet und beschrieben (Katalog und Tafeln im Anhang).
Teil B enthält die Resultate aus den Untersuchungen zur relativen und absoluten Chronologie. Zur Erarbeitung eines für das spätrömische Oberägypten bisher nicht vorhandenen chronologischen Rasters wurde die Methode der Seriation / Kombinationstabelle angewendet. Diese lieferte die Grundlage für die weiteren Untersuchungen an der Keramik. Die Verfasserin bildete 6 Zeitstufen (E-K), die durch stufenbildende Elemente (Keramiktypen, Varianten, Dekorationen/Stempel) voneinander abgegrenzt werden können.
Die erarbeitete relative Abfolge sowie die definierten Zeitstufen E bis K konnte mit absoluten Daten versehen werden. Dazu wurde in erster Linie auf Importe zurückgegriffen sowie Münzen und deren terminus post quem geprüft. Da sowohl Importe als auch brauchbare Münzen selten vorhanden sind, musste ausserdem mit der lokalen Keramik und mit Quervergleichen zu African Red Slip Ware gearbeitet werden. Wo sinnvoll, wird auf andere Fundstellen und deren Zeitansätze hingewiesen und verglichen.
Häufig vorkommende und charakteristische Gefässtypen und deren formale Entwicklung werden einzeln besprochen. Aufgrund der erarbeiteten Zeitstufen können ausserdem typische Vergesellschaftungen von Gefässen und formalen Elementen aufgezeigt werden.
Die vorgelegte Analyse der Keramik aus sehr gut stratifizierten Befunden aus Syene/Assuan sowie das erarbeitete chronologische Raster liefert einen ersten wichtigen Grundstein, um die spätrömische Keramik aus Oberägypten besser einordnen zu können. Die Ergebnisse schliessen eine Lücke und sollen dazu ermuntern, durch weiterführende Studien die erzielten Resultate zu festigen und zu verfeinern.
Im Anhang finden sich nebst Abbildungen auch Typologische Reihen, Farbabbildungen wichtiger Gefässtypen/-gruppen sowie Katalog und Tafeln
Advanced Techniques in Gradient-Domain Rendering
Full text linkRendering realistic images requires solving the notoriously hard physically-based light transport problem. Almost all of the state-of-the-art physically-based rendering methods use Monte-Carlo sampling of the light paths contributing to the image. These methods suffer from variance until convergence. Depending on the scene, an impracticable amount of time might be required to get a clean image. A recently developed method called gradient-domain Metropolis light transport mitigates this problem. It first samples the image-space finite differences of paths alongside the paths themselves and then reconstructs a clean image from the sampled data by applying a screened Poisson reconstruction. The method exploits two properties: first, the gradients of natural images are usually much sparser than the image itself, thus sampling efforts can be concentrated in fewer regions of the path space. Second, sampling finite differences allows using correlated sampling in rendering, which can strongly reduce noise in the finite differences. Both properties combined lead to dramatical speed-ups compared to classical (Markov-chain) Monte-Carlo rendering methods.
This dissertation builds up on the aforementioned gradient-domain Metropolis light transport and proposes a number of improvements and generalizations. We improve the sampling by replacing finite differences by arbitrary differences and by combining different sampling strategies in an unbiased way. We also generalize the method to non-MLT rendering methods like bidirectional path tracing. Further, we develop an algorithm that regularizes the screened Poisson reconstruction by using auxiliary scene information in order to increase image quality. This leads to the first method that combines gradient-domain rendering with classical image-space denoising. And finally, we incorporate temporal finite differences in gradient-domain rendering in order to create stable animations, thus making gradient-domain rendering an even more appealing option for production rendering
Uncertain Reasoning in Justification Logic
Full text linkThis thesis studies the combination of two well known formal systems for knowledge representation: probabilistic logic and justification logic. Our aim is to design a formal framework that allows the analysis of epistemic situations with incomplete information. In order to achieve this we introduce two probabilistic justification logics, which are defined by adding probability operators to the minimal justification logic J. We prove soundness and completeness theorems for our logics and establish decidability procedures. Both our logics rely on an infinitary rule so that strong completeness can be achieved. One of the most interesting mathematical results for our logics is the fact that adding only one iteration of the probability operator to the justification logic J does not increase the computational complexity of the logic
Three Essays on Innovation and Precautionary Cash Holdings
Full text linkThis thesis consists of three papers that investigate firms’ management of innovation and precautionary cash holdings.
The first paper examines innovation efforts and abilities of firms at different stages in the lifecycle. The study exploits unique firm data on investments and sales related to innovation from six waves of the Swiss Innovation Survey between 1996 and 2011. Using firm age to identify established firms, I find that established firms, compared to young firms, invest less in innovation and are less efficient in producing innovation output within the firm. By contrast, established firms are more efficient in using knowledge from outside the firm (e.g., from suppliers, competitors, universities) to produce innovation output. These results largely do not depend on whether the innovation output is incremental or radical in nature. These findings suggest that young and established firms differ in the allocation and productivity of innovation resources.
The second paper examines the importance of the precautionary motive relative to other motives as a determinant of corporate cash holdings. According to the precautionary motive, firms facing future financing constraints hold cash to ensure that they can make investments or meet obligations. I develop an index that includes the precautionary information of six popular firm-level measures: cash flows, cash flow volatility, R&D intensity, market-to-book, net working capital and product market competition. The index explains 32% of the variation in corporate cash holdings and increases to 41% when using the debt and equity constraint indices of Hoberg and Maksimovic (2015) as additional precautionary measures. As the predominant cash determinant, the precautionary motive is particularly strong for firms that face greater opportunity costs of disclosing proprietary information. This finding is consistent with the notion that these firms are more reliant on precautionary cash to protect proprietary information that they otherwise have to disclose to investors to reduce equity constraints.
The third paper investigates whether the debt or equity capital supply shock of the recent financial crisis (2007-2009) caused firms to use precautionary cash holdings to mitigate underinvestment. I find that precautionary cash was used to substitute for the decline in net equity issuance but not net debt issuance. I also find that precautionary cash was used by equity- but not debt-constrained firms to mitigate underinvestment during the crisis. Consistently, precautionary cash was not used in the absence of the equity supply shock, i.e., during placebo crises or during the economy-wide demand shock following the financial crisis. This paper provides new evidence on the importance of corporate liquidity management for equity-constrained firms and identifies the crisis’ equity capital supply shock as a dominant first-order effect on corporate financial policies
Ungleichheit, Umverteilung und der Wohlfahrtsstaat in der Schweiz
Full text linkDie vorliegende Monographie vereint fünf Studien zum Thema Ungleichheit und dem Wohlfahrtsstaat der Schweiz, die aus dem vom Schweizerischen Nationalfonds geförderten Projekt „Ungleichheit der Einkommen und Vermögen in der Schweiz von 1970 bis 2010“ (Projekt Nr.143399) hervorgegangen sind (vgl. auch https://inequalities.ch). Gemeinsamer methodischer Nenner der Arbeiten ist die Datengrundlage. Sie beinhaltet die Verwendung von Steuerdaten und andere Administrativdaten. Damit ergeben sich neuartige Möglichkeiten Fragen rund um ökomische Ungleichheiten zu untersuchen. Der erste Beitrag zeigt die Ungleichheitsentwicklung von Einkommen (1950 bis 2010) und Vermögen (1981 bis 2010) basierend auf archivierte Steuerstatistiken der Eidgenössischen Steuerverwaltung auf. Die Zeitreihen werden vor dem Hintergrund des sich wandelnden ökonomischen, wohlfahrtstaatlichen und demographischen Umfeldes analysiert und besprochen. Der zweite Beitrag stellt Vor‐ und Nachteile von aggregierten, Individualsteuerdaten und Survey‐Erhebungen gegenüber und zeigt den Mehrwert, aber auch Grenzen von Steuerdaten für die Ungleichheitsforschung auf. Dabei werden theoretische Ideale erarbeitet und verglichen und empirische Vergleiche basierend auf Schweizer Steuer‐ und Befragungsdaten durchgeführt. Der dritte Beitrag zeigt Umverteilungseffekte im Steuersystem auf. Mittels sequentieller Gini‐Dekomposition wird dabei der partielle Umverteilungseffekt Schweizerischer Einkommens‐ und Vermögenssteuern ermittelt und ‐ der bisher wenig untersuchte ‐ Effekt von steuerlichen Abzügen quantifiziert. Dier vierte Beitrag untersucht die Dynamik nach einem Sozialleistungsbezug. Wem gelingt eine Reintegration in den Arbeitsmarkt und wer entfernt sich längerfristig davon? Mittels verknüpfter Daten der Sozialen Sicherheit der Schweiz wird die Situation von Personen, die erstmals Sozialleistungen bezogen, über einen Zeitraum von 4 Jahren verfolgt. Unterschiedliche Verläufe werden vor dem Hintergrund sozialstruktureller Theorien analysiert und besprochen. Der fünfte und letzte Beitrag nimmt schliesslich eine Schätzung des Nichtbezugs von Sozialhilfe auf der Basis von Steuerdaten und weiteren Administrativdaten vor und prüft Erklärungsfaktoren für auftretende regionale Unterschiede
Fine-grained indoor positioning and tracking systems
Full text linkIndoor positioning has attracted considerable attention for decades due to the increasing
demands for location based services. In the past years, although numerous
methods have been proposed for indoor positioning, it is still challenging to find a
convincing solution that combines high positioning accuracy and ease of deployment.
Radio-based indoor positioning has emerged as a dominant method due to
its ubiquitousness, especially for WiFi. RSSI (Received Signal Strength Indicator)
has been investigated in the area of indoor positioning for decades. However, it
is prone to multipath propagation and hence fingerprinting has become the most
commonly used method for indoor positioning using RSSI. The drawback of fingerprinting
is that it requires intensive labour efforts to calibrate the radio map
prior to experiments, which makes the deployment of the positioning system very
time consuming. Using time information as another way for radio-based indoor
positioning is challenged by time synchronization among anchor nodes and timestamp
accuracy. Besides radio-based positioning methods, intensive research has
been conducted to make use of inertial sensors for indoor tracking due to the fast
developments of smartphones. However, these methods are normally prone to accumulative
errors and might not be available for some applications, such as passive
positioning.
This thesis focuses on network-based indoor positioning and tracking systems,
mainly for passive positioning, which does not require the participation of targets
in the positioning process. To achieve high positioning accuracy, we work on some
information of radio signals from physical-layer processing, such as timestamps
and channel information. The contributions in this thesis can be divided into two
parts: time-based positioning and channel information based positioning. First,
for time-based indoor positioning (especially for narrow-band signals), we address
challenges for compensating synchronization offsets among anchor nodes, designing
timestamps with high resolution, and developing accurate positioning methods.
Second, we work on range-based positioning methods with channel information to
passively locate and track WiFi targets. Targeting less efforts for deployment, we
work on range-based methods, which require much less calibration efforts than fingerprinting.
By designing some novel enhanced methods for both ranging and positioning
(including trilateration for stationary targets and particle filter for mobile
targets), we are able to locate WiFi targets with high accuracy solely relying on radio
signals and our proposed enhanced particle filter significantly outperforms the
other commonly used range-based positioning algorithms, e.g., a traditional particle
filter, extended Kalman filter and trilateration algorithms. In addition to using
radio signals for passive positioning, we propose a second enhanced particle filter
for active positioning to fuse inertial sensor and channel information to track indoor
targets, which achieves higher tracking accuracy than tracking methods solely
relying on either radio signals or inertial sensors
The complement of the open orbit for tame quivers
Full text linkLet Q be a tame quiver and d a prehomogeneous dimension vector. We consider the complement of the open orbit of the representation space Rep (Q; d) and generalise the idea of A. Schofield to obtain for each irreducible component of codimension greater than one an ideal in the polynomial ring k [Rep (Q; d)] whose zero set is this component. Moreover, we compare our result with the one of K. Baur and L. Hille, who found for each irreducible component some defining rank conditions in case Q is the equioriented Dynkin quiver of type An
Comparison of treatment strategies for anaemia of prematurity in extremely low birthweight infants between 1997 and 2011
Full text linkMoldable tools
Full text linkDevelopment tools are a prerequisite for crafting software. They offer the lenses through which developers perceive and reason about their software systems. Generic development tools, while having a wide range of applicability, ignore the contextual nature of software systems and do not allow developers to directly reason in terms of domain abstractions. Domain-specific development tools, tailored to particular application domains, can address this problem. While it has clear advantages, incorporating domain abstractions into development tools is a challenging activity. The wide range of domains and contextual tasks that development tools need to support leads to costly or ad hoc mechanisms to incorporate and discover domain abstractions. Inherently, this limits developers from taking advantage of domain-specific information during the development and maintenance of their systems.
To overcome this problem, we propose to embed domain abstractions into development tools through the design of moldable tools that support the inexpensive creation of domain-specific extensions capturing domain abstractions, and that automatically select extensions based on the domain model and the developer’s interaction with the domain model. This solution aims to reduce the cost of creating extensions. Towards this goal, it provides precise extension points together with internal DSLs for configuring common types of extensions. This solution facilitates automatic discovery by enabling extension creators to specify together with an extension an activation predicate that captures the context in which that extension is applicable.
We validate the moldable tools approach by applying it, in the context of objectoriented applications, to improve three development activities, namely: reasoning about run-time objects, searching for domain-specific artifacts, and reasoning about run-time behavior. For each activity we identify limitations of current tools, show how redesigning those tools following the moldable tools approach addresses the identified limitations, and discuss the cost for creating domain-specific extensions. We demonstrate that moldable tools address an existing need by analyzing the increase in domain-specific extensions after we integrated the moldable tools solving the aforementioned tasks with an IDE. We also show what kinds of custom environments developers can create by continuously adapting their development tools
Pension plans: risk and governance
Full text linkPension Risk and Corporate Investment:
This paper studies the relation of systematic pension risk (pension beta) and corporate investment in a large sample of U.S. firms. We present evidence of a negative impact of pension risk on investment, which is consistent with the view that firms forego valuable investment opportunities because they fail to notice that systematic pension risk causes an upward bias in the discount rates they use in capital budgeting decisions. The pension risk bias in investment is economically relevant and not limited to financially constrained firms. The study can be generalized to all firms that base their investment decisions on a firm-wide discount rate without noticing the different sources of systematic risk.
The Duration Gap Matters: How Pension Duration Affects Equity Returns:
This paper empirically studies whether equity returns of U.S. nonfinancial firms reflect the systematic interest rate risk of the sponsored defined benefit pension plans. It is not obvious that they should. Pension accounting rules are complex and pension assets and liabilities are held separately from the firm’s operating assets. We find that the gap between the duration of pension assets and pension liabilities affects the interest rate exposure of the sponsoring firm without bias. This is consistent with the hypothesis of informationally efficient capital markets. Our results are robust to a wide range of assumptions regarding the duration of pension liabilities and pension asset classes and are not driven by firms with negligibly small pension plans or firms in financial distress. Besides, our results are neither caused by the recent financial crisis nor explained by the subsequent years of historically low interest rates.
How the Chairman’s Personal Preferences Affect Public Pension Risk:
Based on the analysis of 343 changes of chairpersons in 110 U.S. state and local government pension boards of trustees, this paper shows that the risk from the mismatch between pension assets and liabilities reflects the personal risk preferences of the chairman of the board (COB). We find that pension risk is negatively affected by an increase in COB age, and that it is lower if the COB is a woman. We also find that pension risk is higher if the COB is an annuitant of the plan, consistent with an incentive of retirees to gamble for higher benefits. Finally, we observe that the risk of public pension plans is higher if the COB is an ex officio trustee, possibly because reporting rules enable politicians to avoid tax increases or spending cuts by boosting the risk of the fund’s assets. The current underfunding problems faced by public pension plans are hence partially a consequence of past decisions of pension COBs. Our results are robust to different definitions of pension risk, economically relevant, and particularly strong for more poorly governed pension plans. We find no evidence of an endogenous selection of COBs to pension plans that match their risk preferences
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