Convergence of linear barycentric rational interpolation for analytic functions

Polynomial interpolation to analytic functions can be very accurate, depending on the distribution of the interpolation nodes. However, in equispaced nodes and the like, besides being badly conditioned, these interpolants fail to converge even in exact arithmetic in some cases. Linear barycentric rational interpolation with the weights presented by Floater and Hormann can be viewed as blended polynomial interpolation and often yields better approximation in such cases. This has been proven for differentiable functions and indicated in several experiments for analytic functions. So far, these rational interpolants have been used mainly with a constant parameter usually denoted by d, the degree of the blended polynomials, which leads to small condition numbers but to merely algebraic convergence. With the help of logarithmic potential theory we derive asymptotic convergence results for analytic functions when this parameter varies with the number of nodes. Moreover, we present suggestions on how to choose d in order to observe fast and stable convergence, even in equispaced nodes where stable geometric convergence is provably impossible. We demonstrate our results with several numerical examples

Estimating the expected cost of equity capital using consensus forecasts

In this study, we develop a technique for estimating a firm’s expected cost of equity capital derived from analyst consensus forecasts and stock prices. Building on the work of Gebhardt/Lee/-Swaminathan (2001) and Easton/Taylor/Shroff/Sougiannis (2002), our approach allows daily estimation, using only publicly available information at that date. We then estimate the expected cost of equity capital at the market, industry and individual firm level using historical German data from 1989-2002 and examine firm characteristics which are systematically related to these estimates. Finally, we demonstrate the applicability of the concept in a contemporary case study for DaimlerChrysler and the European automobile industry

Electronic Commerce: The Flip Side of a Buzzword

Electronic Commerce has suffered the typical fate of a buzzword and fashion: after the hype, the downturn has been particularly painful. However, the sobering effect of the downturn has opened a unique opportunity to ask more fundamental questions. This paper addresses limitations in our understanding of Electronic Commerce as a phenomenon which is inextricably linked to the new economy and discusses implications for Electronic Commerce research within IS as well as in an interdisciplinary context

Fast Bayesian Optimization of Machine Learning Hyperparameters on Large Datasets

Bayesian optimization has become a successful tool for hyperparameter optimization of machine learning algorithms, such as support vector machines or deep neural networks. Despite its success, for large datasets, training and validating a single configuration often takes hours, days, or even weeks, which limits the achievable performance. To accelerate hyperparameter optimization, we propose a generative model for the validation error as a function of training set size, which is learned during the optimization process and allows exploration of preliminary configurations on small subsets, by extrapolating to the full dataset. We construct a Bayesian optimization procedure, dubbed Fabolas, which models loss and training time as a function of dataset size and automatically trades off high information gain about the global optimum against computational cost. Experiments optimizing support vector machines and deep neural networks show that Fabolas often finds high-quality solutions 10 to 100 times faster than other state-of-the-art Bayesian optimization methods or the recently proposed bandit strategy Hyperband

The struggle for \u27appropriateness\u27 - new sources of (techno-)stress

Information and communication technologies are employed in every aspect of contemporary life. Facilitated by ICT, many innovations in the organization of work have taken hold. The effects of these developments on the quality of life are disputed. By referring to the phenomenon of ‘technostress,’ scholars’ caution against potentially harmful effects of ICT on workers’ health. This relatively new line of research roots the sources of stress for the individual in features of ICT. The present paper is motivated by the observation that ICT is also rooted in social relations. The way it is used is heavily influenced by social norms and sensemaking. Based on this, the paper theorizes about new sources of stress originating from the social sphere that are enabled and facilitated by ICT. In particular, the paper investigates the notion of ‘appropriateness’ as a theoretical building block for a more complex understanding of stress in today’s workplaces. In doing so, the paper seeks to establish a new theoretical framework capable of investigating new sources of stress on a theoretical as well as empirical level

Prosuming in der Telekommunikationsbranche: Konzeptionelle Grundlagen und Ergebnisse einer Delphi-Studie

Der vorliegende Bericht systematisiert verschiedene Formen des Prosuming und erarbeitet einen Klassifikationsrahmen speziell für die computergestützte Konfiguration digitaler Produkte. Innovative Telekommunikationsdienstleistungen wie unified messaging oder locationbased services sind gleichsam der Prototyp computergestützter Konfiguration, da sie kundenindividuelle, situativ differenzierte Einstellungen erfordern, um ihre Leistungen entfalten zu können. Obwohl die verstärkte Einbindung von Kunden in den Konfigurationsprozess die Voraussetzung für die Weiterentwicklung und Verbreitung innovativer Telekommunikationsdienstleistungen ist, sind am Markt erst rudimentäre Ansätze, zumeist in Form von Selbstbedienungs-Portalen, erkennbar. Um diesen wirklichen oder scheinbaren Widerspruch aufzulösen und eine Abschätzung der gegenwärtigen Bedeutung wie der künftigen Potenziale von Konfiguration und Selbstbedienungselementen in der Telekommunikationsbranche zu erhalten, haben wir mit einem Expertenpanel eine Delphi-Studie durchgeführt, deren Ergebnisse im zweiten Teil des Arbeitsberichts vorgestellt werden