Better Answers to Real Questions

We consider existential problems over the reals. Extended quantifier elimination generalizes the concept of regular quantifier elimination by providing in addition answers, which are descriptions of possible assignments for the quantified variables. Implementations of extended quantifier elimination via virtual substitution have been successfully applied to various problems in science and engineering. So far, the answers produced by these implementations included infinitesimal and infinite numbers, which are hard to interpret in practice. We introduce here a post-processing procedure to convert, for fixed parameters, all answers into standard real numbers. The relevance of our procedure is demonstrated by application of our implementation to various examples from the literature, where it significantly improves the quality of the results

On the formation of coalitions to provide public goods: Experimental evidence from the lab

The provision of public goods often relies on voluntary contributions and cooperation. While most of the experimental literature focuses on individual contributions, many real-world problems involve the formation of institutions among subgroups (coalitions) of players. International agreements serve as one example. This paper experimentally tests theory on the formation of coalitions in different institutions and compares those to a voluntary contribution mechanism. The experiment confirms the rather pessimistic conclusions from the theory: only few players form a coalition when the institution prescribes the full internalization of mutual benefits of members. Contrary to theory, coalitions that try to reduce the freeriding incentives by requiring less provision from their members, do not attract additional members. Substantial efficiency gains occur, however, both along the extensive and intensive margin when coalition members can each suggest a minimum contribution level with the smallest common denominator being binding. The experiment thereby shows that the acceptance of institutions depends on how terms of coalitions are reached. --public goods,institutions,coalition formation,cooperation

Locally Implicit Time Integration for Linear Maxwell\u27s Equations

This thesis is concerned with the full discretization of Maxwell\u27s equations in cases where the spatial discretization has to be carried out with a locally refined grid. In such situations locally implicit time integrators are an appealing choice for the time discretization since they overcome the grid-induced stiffness of these problems. We analyze such a locally implicit time integrator in the case where the space discretization stems from a central fluxes discontinuous Galerkin method. In fact, we prove its stability under a CFL condition which solely depends on the coarse part of the spatial grid and give a rigorous error analysis showing that the integrator is second order convergent. Moreover, we extend this time integrator so that it can be applied to an upwind fluxes discontinuous Galerkin space discretization. We show that this novel integrator preserves the second order temporal convergence and that it inherits the improved properties of an upwind fluxes discretization (better stability, higher spatial convergence rate) compared to the central fluxes case

Theory and Implementation of the Quantum Approximate Optimization Algorithm: A Comprehensible Introduction and Case Study Using Qiskit and IBM Quantum Computers

The present tutorial aims to provide a comprehensible and easily accessible introduction into the theory and implementation of the famous Quantum Approximate Optimization Algorithm (QAOA). We lay our focus on practical aspects and step-by-step guide through the realization of a proof of concept quantum application based on a real-world use case. In every step we first explain the underlying theory and subsequently provide the implementation using IBM's Qiskit. In this way we provide a thorough understanding of the mathematical modelling and the (quantum) algorithms as well as the equally important knowledge how to properly write the code implementing those theoretical concepts. As another central aspect of this tutorial we provide extensive experiments on the 27 qubits state-of-the-art quantum computer ibmq_ehningen. From the discussion of these experiments we gain an overview on the current status of quantum computers and deduce which problem sizes can meaningfully be executed on today's hardware

Auctioning of CO2 Emission Allowances in Phase 3 of the EU Emissions Trading Scheme

The Climate action and renewable energy package proposed by the European Commission in the beginning of 2008 suggests auctioning as basic principle for allocation for the upcoming third trading phase of the EU Emissions Trading Scheme that runs from 2013 to 2020. Overall, it is estimated that at least two third of the total quantity of allowances will be auctioned in 2013, to be increased to 100 % by 2020. In this paper, we emphasize the importance of a properly chosen auction design as the significantly higher auction share, compared to the past and current trading phase, is expected to yield a thin secondary market for CO2 allowances. We elaborate main criteria that a viable auction design is supposed to fulfil and propose a specific auction design for the third trading phase. The auction we recommend is a simultaneous dynamic uniform double auction. -- Die Europäische Kommission hat in ihrem Klima- und Energiepaket vom Januar 2008 eine Weichenstellung für den europäischen Emissionshandel vorgeschlagen. Bislang wurden die Zertifikate an die betroffenen Unternehmen aus den energieintensiven Sektoren kostenfrei vergeben. Nach den Plänen der Kommission sollen Stromproduzenten ab 2013 alle benötigten Zertifikate ersteigern müssen. Unternehmen aus anderen energieintensiven Branchen sollen zunächst nur 20 % ersteigern, in 2020 dann 100 %. Da insgesamt mindestens zwei Drittel aller Zertifikate versteigert werden, ist zu erwarten, dass der freie Markt für Zertifikate ab 2013 deutlich dünner sein wird als dies bisher der Fall ist. Aus diesem Grund gewinnt das Design der Auktion an Bedeutung, denn vom Auktionspreis, der die Knappheit an Zertifikaten signalisieren soll, werden wichtige Investitionsentscheidungen in CO2-arme Technologien abhängen. Eventuelle Fehler im Auktionsdesign können, wenn die Zertifikate überwiegend versteigert werden, nicht mehr durch einen liquiden freien Markt geheilt werden.climate policy,emissions trading,auction design

Bio-Weidehaltung bei Verwendung von automatischen Melksystemen (AMS) - Ergebnisse von Praxisbetrieben in Österreich

Die Kombination von Weidehaltung mit automatischen Melksystemen (AMS) stellt besondere Herausforderungen an das Betriebs-, Fütterungs- und Weidemanagement. In der vorliegenden Arbeit wurden Ergebnisse und Erfahrungen von 10 österreichischen Bio-AMSWeidebetrieben erfasst. Der Kuhbestand der Betriebe war mit 36 Kühen gering, die AMS-Auslastung lag im Mittel bei nur 44 % (26 bis 60 %). Die Betriebe stockten den Kuhbestand nach Umstellung auf AMS auf und reduzierten das Weideangebot leicht (-12 %), jedoch wurden hier große Streuungen festgestellt (-50 bis + 60 %). Bei der Entscheidung auf das AMS umzustellen waren arbeitswirtschaftliche Überlegungen wichtiger als ökonomische Gesichtspunkte. Die Melkfrequenz lag mit 2,4 Melkungen pro Kuh und Tag während der Weideperiode signifi kant niedriger als während der Stallperiode mit 2,6. Die Milchmenge pro Kuh und Tag war trotz der geringeren Melkfrequenz während der Weideperiode signifi kant höher als während der Stallperiode (20,9 kg Milch zu 19,4 kg Milch), wobei jedoch Wechselwirkungen zwischen Betrieb und Periode bestanden. Die Weidesysteme und Weidestrategien auf den untersuchten Betrieben waren sehr unterschiedlich und wurden auch im Verlauf der Vegetationsperiode gewechselt. Weidezugang wurde den Kühen im Mittel während der Hauptperiode für 11 Stunden (3 bis 24) pro Tag gewährt. Im Frühling und Herbst lag die mögliche Weidezugangszeit im Mittel bei 8 bzw. 6,5 Stunden, die betrieblichen Unterschiede waren jedoch groß. Der Kuhverkehr zwischen Stall und Weide war bei 70 % der Betriebe über die gesamte Vegetation frei. Nur ein Betrieb setzte Selektionstore nach dem AMS bzw. ein Einwegtor beim Rückweg in den Stall ein. Vollweidehaltung wurde auf keinem Betrieb umgesetzt und von den Betriebsleiter/innen auch als nicht realisierbar eingestuft. Der Mehraufwand durch Weidehaltung wurde im Mittel als gering (+3 %) angesehen. Die sehr unterschiedlichen Weide-AMS-Lösungen weisen darauf hin, dass betriebsindividuelle Ansätze bei AMS-Weide-Kombinationen notwendig sind. Aus Ergebnissen vergleichbarer internationaler Studien sowie den vorliegenden Daten wurden Beratungsempfehlungen für biologisch wirtschaftende Betriebe mit AMS abgeleitet (Eilers et al., 2017b)

Ambivalenzen in der Umsetzung schulischer Inklusion am Beispiel des Förderschwerpunkts Lernen in Nordrhein-Westfalen

Dieser Aufsatz thematisiert die aktuellen Schulentwicklungsprozesse im Bundesland Nordrhein-Westfalen, in welchem, unterstützt durch rechtliche Sicherung, zunehmend inklusive Strukturen etabliert werden. Die Autorin und der Autor nehmen dabei weiterhin bestehende Ambivalenzen, wie zum Beispiel das Spannungsfeld von Zuschreibungspraxis und Sicherung im Kontext von Unterstützung bzw. Förderung, in den Blick. Bezogen auf den Förderschwerpunkt Lernen werden – nach einem kurzen historischen Einblick – unterschiedliche Szenarien von Ressourcenzuweisungen theoretisch durchdacht und Herausforderungen für an Inklusion orientierte Schulen formuliert. (DIPF/Autor

On leap-frog-Chebyshev schemes

This paper is dedicated to the improvement of the efficiency of the leap-frog method for second order differential equations. In numerous situations the strict CFL condition of the leap-frog method is the main bottleneck that thwarts its performance. Based on Chebyshev polynomials new methods have been constructed that exhibit a much weaker CFL condition than the leap-frog method. However, these methods do not even approximately conserve the energy of the exact solution which can result in a bad approximation quality. In this paper we propose two remedies to this drawback. For linear problems we show by using energy techniques that damping the Chebyshev polynomial leads to approximations which approximately preserve a discrete energy norm over arbitrary long times. Moreover, with a completely different approach based on generating functions, we propose to use special starting values that considerably improve the stability. We show that the new schemes arising from these modifications are of order two and can be modified to be of order four. These convergence results apply to semilinear problems. Finally, we discuss the efficient implementation of the new schemes and give generalizations to fully nonlinear equations

A new model for the infrared emission of IRAS F10214+4724

We present a new model for the infrared emission of the high redshift hyperluminous infrared galaxy IRAS F10214+4724 which takes into account recent photometric data from Spitzer and Herschel that sample the peak of its spectral energy distribution. We first demonstrate that the combination of the AGN tapered disc and starburst models of Efstathiou and coworkers, while able to give an excellent fit to the average spectrum of type 2 AGN measured by Spitzer, fails to match the spectral energy distribution of IRAS F10214+4724. This is mainly due to the fact that the nuSnu distribution of the galaxy falls very steeply with increasing frequency (a characteristic of heavy absorption by dust) but shows a silicate feature in emission. We propose a model that assumes two components of emission: clouds that are associated with the narrow-line region and a highly obscured starburst. The emission from the clouds must suffer significantly stronger gravitational lensing compared to the emission from the torus to explain the observed spectral energy distribution.Comment: 4 pages, 1 figure, to be published in 'The Spectral Energy Distribution of Galaxies' J. Tuffs \& C.C.Popescu, ed

Auctioning of CO2 Emission Allowances in Phase 3 of the EU Emissions Trading Scheme

The “Climate action and renewable energy package” proposed by the European Commission in the beginning of 2008 suggests auctioning as basic principle for allocation for the upcoming third trading phase of the EU Emissions Trading Scheme that runs from 2013 to 2020. Overall, it is estimated that at least two third of the total quantity of allowances will be auctioned in 2013, to be increased to 100 % by 2020. In this paper, we emphasize the importance of a properly chosen auction design as the significantly higher auction share, compared to the past and current trading phase, is expected to yield a thin secondary market for CO2 allowances. We elaborate main criteria that a viable auction design is supposed to fulfil and propose a specific auction design for the third trading phase. The auction we recommend is a simultaneous dynamic uniform double auction