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

PRESENCE SIGNALLING IN UNIFIED COMMUNICATION SYSTEMS – A FRAMEWORK FOR CUSTOMISATION IN CONTEXT

In this paper we present Unified Communications (UC) as a new class of communication systems, marketed by vendors as a means for integrating communication media and creating presence awareness. Designed as complex infrastructures, UC systems enfold their full potential when being customised to a particular social context. In doing so, the technology allows creating contextspecific presence signalling solutions. The main contribution of this paper is a conceptualisation of the various design questions relevant in the customisation of UC presence signalling aspects. To this end, we present a seven-step process framework as guidance for implementers of UC infrastructures

(My) Data for (my) Health – Privacy Calculi of Terminally-ill Patients with Rare Diseases

Digital healthcare information systems promise to improve care efficiency, to reduce complexity for patients, and to increase access to information and advance research efforts. A prominent example are multi-sided-platforms (MSP), which are essentially an information business, linking key healthcare stakeholders for individualized as well as aggregated information services. However, platform-based health innovation relies on the extensive collection, storage, and use of sensitive health information, raising issues of information privacy. This study uses the privacy calculus perspective to shed light on patients’ trade-off considerations. We use the case of a MSP, which connects patients, care providers and researchers, in order to model a multi-level calculus for health information of terminally ill patients. These insights inform stepwise consent options, which highlight the trade-offs between information value and patient privacy. By reflecting on the implications for patient empowerment this conceptual paper develops a research agenda on how to study and design responsible health information systems

Twenty years of electronic markets research: looking backwards towards the future

Over the past 20 years the field of electronic markets has seen a considerable proliferation and differentiation. This position paper takes the opportunity of the 21st volume of “Electronic Markets” to look back at important developments and insights, suggesting a framework that captures the multiple facets and indeed empirical breadth and depths of this concept. It comprises three perspectives which include the market environment, governance choices by economic actors as well as the entrepreneurial dynamics of firms who initiate and operate market platforms as their business. In addition, we propose to study the interplay of technological, market, and institutional drivers in order to understand the phenomenon of electronic markets, which is also a precondition for designing electronic markets. Both activities involve more than an economically motivated choice between the discrete alternatives of markets and hierarchies. Rather, electronic markets are configurations across multiple, interdependent dimensions: Technology is an important force in shaping the field, but needs to be complemented by considerations of the competitive environment and the setting of rules in order to ensure efficient and effective plays of the game. Based on this framework, this position paper develops six propositions for the future of electronic markets. Overall, the advantages of intermediated structures, an ongoing technological sophistication, as well as further innovation in market mechanisms and services make electronic markets an ena-bler for many interorganizational value chains. While we are confident that the ingenuity of inventors will yield a flow of innovations, recent economic crises have shed a dark shadow over the sustainability of electronic markets. They call for suitable rules and regulation amenable to economic prosperity and stability to be agreed upon on a broad level