The WaveGyro

The WaveGyro – A new Concept for Ocean Wave Energy Capture (Master Thesis by Gebhard Waizmann, University of Southampton 22.09.2011) Abstract Climate change, environmental pollution and the proceeding resource depletion give awareness of the necessity towards more sustainable energy economics. Energy from ocean waves may once play a contributing role towards this step but is as yet in its fledgling stages. This is mainly due to the harsh sea environment, which implies the need for simple and robust wave energy converter. The work presented in this thesis picks up this thought when dealing with the so-called WaveGyro. Introductory chapters explain how this novel concept arose, followed by a detailed explanation of the working principle. The WavGyro utilizes gyroscopes to provide an internal reaction moment against the wave excitation. This internal reaction permits designing a completely enclosed and thus environmentally resistant device. The gyroscopic precession is used to convert the wave-induced moment into a moment that accelerates the flywheels. Equations of motion, which describe the gyroscope kinetics, are deduced. The gyroscopic motions and moment is then implemented into the first-order wave hydrodynamics. Two main approaches to describe the wave excitation are presented. The first approach is superposition of radiation and exci-tation and the second approach makes use of the relative motion principle, which relates the excitation to the extent of displacement. Both approaches are employed to deduce the maximum power capture condition in relation to the device’s dimensions and operational parameters. The influence of real sea state, analytically expressed by the Pierson-Moskowitz spec-trum, on the optimum power analysis is considered and implementation methods are de-veloped. Subsequently the spin-up mechanism is explained and examined; this is the mechanism converting the precession moment into torque accelerating the flywheel. It is shown that a simple configuration, composed of an ordinary cogwheel and a sprag-clutch only is not sufficient for this mechanism. Ideas for alternative mechanisms are considered but require further investigation to allow conclusive results. Finally, an approximate plan for the design of model is developed, which includes basic considerations of scaling laws. Recommendations for further theoretical and practical work on the WaveGyro are provided

Scalar Symmetries of the Hubbard Models with Variable Range Hopping

Examples of scalar conserved currents are presented for trigonometric, hyperbolic and elliptic versions of the Hubbard model with non-nearest neighbour variable range hopping. They support for the first time the hypothesis about the integrability of the elliptic version. The two- electron wave functions are constructed in an explicit form.Comment: 9 pages, LaTex2e, no figure

Periodic solutions for the N-vortex problem via a superposition principle

We examine the $N$-vortex problem on general domains $\Omega\subset\mathbb{R}^2$ concerning the existence of nonstationary collision-free periodic solutions. The problem in question is a first order Hamiltonian system of the form $$\Gamma_k\dot{z}_k=J\nabla_{z_k}H(z_1,\ldots,z_N),\quad k=1,\ldots,N,$$ where $\Gamma_k\in\mathbb{R}\setminus\{0\}$ is the strength of the $k$th vortex at position $z_k(t)\in\Omega$, $J\in\mathbb{R}^{2\times 2}$ is the standard symplectic matrix and $$H(z_1,\ldots,z_N)=-\frac{1}{2\pi}\sum_{\underset{k\neq j}{k,j=1}}^N\Gamma_j\Gamma_k\log|z_k-z_j|-\sum_{k,j=1}^N\Gamma_j\Gamma_k g(z_k,z_j)$$ with some regular and symmetric, but in general not explicitely known function $g:\Omega\times\Omega\rightarrow \mathbb{R}$. The investigation relies on the idea to superpose a stationary solution of a system of less than $N$ vortices and several clusters of vortices that are close to rigidly rotating configurations of the whole-plane system. We establish general conditions on both, the stationary solution and the configurations, under which multiple $T$-periodic solutions are shown to exist for every $T>0$ small enough. The crucial condition holds in generic bounded domains and is explicitely verified for an example in the unit disc $\Omega=B_1(0)$. In particular we therefore obtain various examples of periodic solutions in $B_1(0)$ that are not rigidly rotating configurations.Comment: 27 pages, 1 figur

The Lost Popularity Function: Are Unemployment and Inflation no longer Relevant for the Bahaviour of German Voters?

Up to now there was a general conviction that increasing unemployment and inflation have a negative impact on the government’s popularity. This was true for Germany as well, but it does not seem to hold any longer. This paper first reviews the results of earlier periods before presenting new results for the last part of the Kohl government after unification and for the Schröder government. While the results for the former show the known pattern, neither unemployment nor inflation is significant in the equations of the Schröder government, the latter has even the wrong sign. The missing impact of unemployment might be due to statistical reasons: the short observation period and the low variance of the explanatory variables. With respect to inflation, however, the citizens might have recognised that they cannot any longer hold the government responsible as the European Central Bank is performing monetary policy in Europe since 1999 and is, therefore, also responsible for price stability in Germany.government popularity, popularity function, Germany, unemployment, inflation

Tax Morale, Tax Evasion, and the Shadow Economy

Under which conditions is moral justification of taxation possible? This question does not only interest philosophers and economists from a scientific point of view, but can have considerable practical relevance as well because the willingness of citizens to pay taxes may depend upon whether they consider taxation to be morally justified or not. We first consider theoretical arguments on the role of tax morale, and when tax evasion might be considered as justified by citizens or not. Then we ask how tax morale can be measured. Next, we discuss the role of tax morale for the shadow economy, before determinants of tax morale and empirical results for the impact of tax morale on tax compliance are discussed. For a high tax morale, institutional and cultural factors are at least as important as economic incentives.Tax morale, tax evasion, principles of taxation, trust, direct democracy, federalism

(Why) Are Economists Different?

After presenting some casual evidence about the difference between economists and the rest of the population, first the survey and experimental evidence which has been presented on this topic during the last 20 years is discussed. But can these results really be transferred to real world situations? To show this, examples of referenda results in Switzerland are presented where the citizens decided against recommendations of most economists. But what is so particular in economic theory that causes these different convictions? Some explanations are given with respect to positive economic theory and with respect to the normative convictions of economists. The paper concludes with possible consequences which economists might draw. Nachdem an Fallbeispielen Unterschiede in den Auffassungen von Ökonomen einerseits und dem Rest der Bevölkerung andererseits aufgezeigt wurde, wird zunächst die empirische Evidenz zu diesem Faktum aus Umfragen und Experimenten zusammengefasst. Wie weit sind diese Ergebnisse auf Situationen realen Handelns übertragbar? Um dies zu zeigen, wird auf Ergebnisse von Referenden verwiesen, in welchen sich die Bürger entgegen den Empfehlungen fast aller Ökonomen entschieden haben. Dann wird gezeigt, welche Eigenheiten der (positiven) ökonomischen Theorie wie der normativen Überzeugungen der (meisten) Ökonomen zu diesen Unterschieden führen. Die Arbeit schliesst mit Hinweisen zu Konsequenzen, zu denen sich Ökonomen in dieser Situation veranlasst sehen könnten.Cooperative Behaviour, Indoctrination, Self-Selection, Referenda Results, Economic Model of Behaviour, Commitment, Fairness of the Market

Econometric Estimates of Deterrence of the Death Penalty: Facts or Ideology?

In 2007, the Wall Street Journal published an article claiming that each execution saves more than 70 lives. This example is used to show how easy it is, using simple or advanced econometric techniques, to produce results that do or do not support the deterrence hypothesis. Moreover, we also point to some puzzles which have not been satisfactorily solved so far. We then present a critical survey of the papers published in the last ten years. It is shown how simple changes can produce quite different results using the same data. Finally, we draw some conclusions about the usefulness of statistical arguments in policy debates, but also on the moral questions involved in this particular debate.death penalty, deterrence, econometric evidence, ideology