802 research outputs found
On solving wave equations on fixed bounded intervals involving Robin boundary conditions with time-dependent coefficients
No full textIn this paper, it is shown how characteristic coordinates, or equivalently how the well-known formula of d'Alembert, can be used to solve initial-boundary value problems for wave equations on fixed, bounded intervals involving Robin type of boundary conditions with time-dependent coefficients. A Robin boundary condition is a condition that specifies a linear combination of the dependent variable and its first order space-derivative on a boundary of the interval. Analytical methods, such as the method of separation of variables (SOV) or the Laplace transform method, are not applicable to those types of problems. The obtained analytical results by applying the proposed method, are in complete agreement with those obtained by using the numerical, finite difference method. For problems with time-independent coefficients in the Robin boundary condition(s), the results of the proposed method also completely agree with those as for instance obtained by the method of separation of variables, or by the finite difference method.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Mathematical Physic
Enigmas
No full textArising from the 2020 Darwin College Lectures, this book presents eight essays from prominent public intellectuals on the theme of Enigmas. Each author examines this theme through the lens of their own particular area of expertise, together constituting an illuminating and diverse interdisciplinary volume. Enigmas features contributions by professor of physics Sean M. Carroll, author Jo Marchant, writer and broadcaster Adam Rutherford, professor of earth sciences Tamsin A. Mather, professor of the history of the book Erik Kwakkel, reader in cultural history Tiffany Watt Smith, mathematician and public speaker James Grime, assistant professor of positive AI J. Derek Lomas, and explorer Albert Y.- M. Lin. This volume will appeal to anyone fascinated by puzzles and mysteries, solved and unsolved
The Difficult Reception of Rigorous Descriptive Social Science in the Law
No full textMutual disdain is an effective border patrol at the demarcation lines between disciplines. Social scientists tend to react with disdain when they observe how their findings are routinely stripped of all the caveats, assumptions and careful limitations once they travel into law. Likewise, lawyers tend to react with disdain when they read all the laborious proofs and checks for what looks to them like a minuscule detail in a much larger picture. But mutual disdain comes at a high price. All cross-border intellectual trade is stifled. This paper explores the social science/law border from the legal side. The natural barriers turn out to be significant, but not insurmountable. Specifically the paper looks at the challenges of integrating rigorous descriptive social science into the application of the law in force by courts and administrative authorities. This is where the gap is most difficult to bridge. The main impediments are implicit value judgments inherent in models, conceptual languages and strictly controlled ways of generating empirical evidence; the difference between explanation, hypothesis testing and prediction, on the one hand, and decision-making, on the other; the ensuing difference between theoretical and practical reasoning, and the judicial tradition of engaging in holistic thinking; last but not least, the strife of the legal system for autonomy, in order to maintain its viability. If a legal academic assumes the position of an outside observer, she may entirely ignore all these concerns and simply follow the methodological standards of descriptive social science. This is, for instance, what most of law and economics does. The legal academic may, instead, choose to contribute to the making of new law. She will then find it advisable to partly ignore the strictures of rigorous methodology in order to be open to more aspects of the regulatory issue. But it is not difficult, at least, to follow the standards of the social sciences for analysing the core problem. The integration is most difficult if an academic does doctrinal work. But it is precisely here where the division of intellectual labour between legal practice and legal academia is most important. Academics who themselves are versatile in the respective social science translate the decisive insights into suggestions for a better reading of statutory provisions or case law.law and economics, law and statistics, explanation vs. decision-making, practical reasoning, psychology of judicial decision-making
A Residential Energy Demand System for Spain
No full textSharp price fluctuations and increasing environmental and distributional concerns, among other issues, have led to a renewed academic interest in energy demand. In this paper we estimate, for the first time in Spain, an energy demand system with household microdata. In doing so, we tackle several econometric and data problems that are generally recognized to bias parameter estimates. This is obviously relevant, as obtaining correct price and income responses is essential if they may be used for assessing the economic consequences of hypothetical or real changes. With this objective, we combine data sources for a long time period and choose a demand system with flexible income and price responses. We also estimate the model in different sub-samples to capture varying responses to energy price changes by households living in rural, intermediate and urban areas. This constitutes a first attempt in the literature and it proved to be a very successful choice.households, energy, demand, spain, location
Income Elasticity of Environmental Amenities
No full textIn this paper we are concerned with the estimation of income elasticities of environmental amenities. The novelty is the application of econometric methods that take into account the problem of measurement errors when estimating these elasticities, which are common in microeconomic data and are not usually considered in the applied literature related with this issue. Our aim is to discuss whether the measurement error has signi…cant e¤ects on the elasticities. Data from the Expenditure Budget Survey of Uruguay (1996) are used.
Electron population dynamics in resonant non-linear x-ray absorption in nickel at a free-electron laser
No full textFree-electron lasers provide bright, ultrashort, and monochromatic x-ray pulses, enabling novel spectroscopic measurements not only with femtosecond temporal resolution: The high fluence of their x-ray pulses can also easily enter the regime of the non-linear x-ray–matter interaction. Entering this regime necessitates a rigorous analysis and reliable prediction of the relevant non-linear processes for future experiment designs. Here, we show non-linear changes in the L3-edge absorption of metallic nickel thin films, measured with fluences up to 60 J/cm2. We present a simple but predictive rate model that quantitatively describes spectral changes based on the evolution of electronic populations within the pulse duration. Despite its simplicity, the model reaches good agreement with experimental results over more than three orders of magnitude in fluence, while providing a straightforward understanding of the interplay of physical processes driving the non-linear changes. Our findings provide important insights for the design and evaluation of future high-fluence free-electron laser experiments and contribute to the understanding of non-linear electron dynamics in x-ray absorption processes in solids at the femtosecond timescale.Deutsche Forschungsgemeinschaft 10.13039/501100001659Helmholtz Association 10.13039/501100009318Swiss National Science Foundation 50110000171
Optical control of 4 f orbital state in rare-earth metals
No full textA change of orbital state alters the coupling between ions and their surroundings drastically. Orbital excitations are hence key to understand and control interaction of ions. Rare-earth elements with strong magneto-crystalline anisotropy (MCA) are important ingredients for magnetic devices. Thus, control of their localized 4 f magnetic moments and anisotropy is one major challenge in ultrafast spin physics. With time-resolved x-ray absorption and resonant inelastic scattering experiments, we show for Tb metal that 4 f -electronic excitations out of the ground-state multiplet occur after optical pumping. These excitations are driven by inelastic 5 d -4 f -electron scattering, altering the 4 f -orbital state and consequently the MCA with important implications for magnetization dynamics in 4 f -metals and more general for the excitation of localized electronic states in correlated materials.Optical excitation of 4 f metals can change the 4 f orbital state and alters the 4 f -spin-lattice coupling on femtosecond timescales
Optimality of the Round Robin Routing Policy
No full textIn this paper we consider the problem of routing customers to identical servers, each with its own infinite capacity queue. Under the assumptions that i) the service times form a sequence of independent and identically distributed random variables with increasing failure rate distribution and ii) state information is not available, we establish that the round robin policy minimizes, in the sense of a separable increasing convex ordering, the customer response times and the numbers of customers in the queues. Mathematics Subject Classification: primary: 60K25. secondary: 49K30, 49N30, 68M20, 90B22, 90B80. Keywords: Optimal Routing, Scheduling, Sample Path Analysis, Stochastic Ordering. This work was supported in part by the National Science Foundation under grant ASC 88-8802764 and NCR-9116183. y The work of this author was also partially supported by CEC DG-XIII under the ESPRIT-BRA grant QMIPS. 1 Introduction Consider a stream of customers arriving to a controller which immedi..
Local and global rank tests for multivariate varying-coefficient models
No full textIn a multivariate varying-coefficient model, the response vectors Y are regressed on known functions u(X) of some explanatory variables X and the coefficients in an unknown regression matrix q(Z) depend on another set of explanatory variables Z. We provide statistical tests, called local and global rank tests, which allow to estimate the rank of an unknown regression coefficient matrix q(Z) locally at a fixed level of the variable Z or globally as the maximum rank over all levels of Z, respectively. In the case of local rank tests, we do so by applying already available rank tests to a kernel-based estimator of the coefficient matrix q(z). Global rank tests are obtained by integrating test statistics used in estimation of local rank tests. We present a simulation study where, focusing on global ranks, we examine small sample properties of the considered statistical tests. We also apply our results to estimate the so-called local and global ranks in a demand system where budget shares are regressed on known functions of total expenditures and the coefficients in a regression matrix depend on prices faced by a consumer.varying-coefficient model, kernel smoothing, matrix rank estimation, demand systems, local and global ranks
La epistemología no ideal y el silencio sobre la opresión: sobre non-ideal Epistemology de Robin McKenna
No full textThe aim of this paper is to assess Robin McKenna’s proposal of non-ideal epistemology, which he presents as the epistemological equivalent of Charles Mills’ non-ideal theory. To this end, I begin by reconstructing McKenna’s proposal. The reconstruction unfolds in three steps. First, I provide a general characterization, followed by an exploration of what the author considers to be the key aspects of his proposal, and finally, an instance of application. From there, I systematize a set of criticisms that question whether this proposal maintains a meaningful continuity with Mills’ non-ideal theory. Finally, I introduce the work of Heidi Grasswick, which provides a relevant point of contrast for the discussion on non-ideal epistemology.El objetivo de este trabajo consiste en evaluar la propuesta de epistemología no ideal de Robin McKenna, quien la presenta como el equivalente epistemológico de la teoría no ideal de Charles Mills. A tal efecto, comienzo por reconstruir la propuesta de McKenna. La reconstrucción se desarrolla en tres pasos. Primero ofrezco una caracterización general, a continuación un desarrollo de los que para el autor son los aspectos clave de su propuesta y, por último, una instancia de aplicación. A partir de ello, sistematizo un conjunto de críticas que cuestionan si esta propuesta guarda una continuidad significativa con la teoría no ideal de Mills. Finalmente, introduzco el trabajo de Heidi Grasswick, que ofrece un punto de contraste relevante para la discusión sobre epistemología no ideal
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