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Recent Extensions (recent + extension)

Distribution by Scientific Domains

Business, Economics, Finance and Accounting	50%

Selected Abstracts

OPTIMAL AND ADAPTIVE SEMI-PARAMETRIC NARROWBAND AND BROADBAND AND MAXIMUM LIKELIHOOD ESTIMATION OF THE LONG-MEMORY PARAMETER FOR REAL EXCHANGE RATES,

THE MANCHESTER SCHOOL, Issue 2 2005
SAEED HERAVI
The nature of the time series properties of real exchange rates remains a contentious issue primarily because of the implications for purchasing power parity. In particular are real exchange rates best characterized as stationary and non-persistent; nonstationary but non-persistent; or nonstationary and persistent? Most assessments of this issue use the I(0)/I(1) paradigm, which only allows the first and last of these options. In contrast, in the I(d) paradigm, d fractional, all three are possible, with the crucial parameter d determining the long-run properties of the process. This study includes estimation of d by three methods of semi-parametric estimation in the frequency domain, using both local and global (Fourier) frequency estimation, and maximum likelihood estimation of ARFIMA models in the time domain. We give a transparent assessment of the key selection parameters in each method, particularly estimation of the truncation parameters for the semi-parametric methods. Two other important developments are also included. We implement Tanaka's locally best invariant parametric tests based on maximum likelihood estimation of the long-memory parameter and include a recent extension of the Dickey,Fuller approach, referred to as fractional Dickey,Fuller (FD-F), to fractionally integrated series, which allows a much wider range of generating processes under the alternative hypothesis. With this more general approach, we find very little evidence of stationarity for 10 real exchange rates for developed countries and some very limited evidence of nonstationarity but non-persistence, and none of the FD-F tests leads to rejection of the null of a unit root. [source]

A Primer on Topological Persistence

COMPUTER GRAPHICS FORUM, Issue 3 2006
Herbert Edelsbrunner
The idea of topological persistence is to look at homological features that persist along a nested sequence of topo-logical spaces. As a typical example, we may take the sequence of sublevel sets of a function. The combinatorial characterization of persistence in terms of pairs of critical values and fast algorithms computing these pairs make this idea practical and useful in dealing with the pervasive phenomenon of noise in geometric and visual data. This talk will 1. recall the relatively short history of persistence and some of its older roots; 2. introduce the concept intuitively while pointing out where algebra is needed to solidify the more difficult steps; 3. discuss a few applications to give a feeling of the potential of the method in dealing with noise and scale. Besides the initial concept, the talk will touch upon recent extensions and their motivation. [source]

Adaptive control using multiple models, switching and tuning

INTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 2 2003
Kumpati S. Narendra
Abstract The past decade has witnessed a great deal of interest in both the theory and practice of adaptive control using multiple models, switching, and tuning. The general approach was introduced in the early 1990s to cope with large and rapidly varying parameters in control systems. During the following years, detailed mathematical analyses of special classes of systems were carried out. Considerable empirical evidence was also collected to demonstrate the practical viability of the methods proposed. This paper attempts to review critically the stability questions that arise in the study of such systems, describes recent extensions of the approach to non-linear adaptive control, and discuss briefly promising new areas of research, particularly related to the location of models. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Analysing disruptive potential: the case of wireless local area network and mobile communications network companies

R & D MANAGEMENT, Issue 1 2005
Stefan Hüsig
In this article, we analyse the prediction that wireless local area network (W-LAN) technologies will be disruptive for incumbent mobile communications network operators. For this purpose, we develop a methodology of guided interviews to assess technologies for their disruptive characteristics based on theory of disruptive technology developed by Christensen (1997) and recent extensions. The application of our comprehensive step-by-step method improves the precision of the disruptive technology concept and its usability for practitioners to make ex ante distinctions between disruptive technologies and other phenomena caused by emerging technologies. Our method predicts that contrary to common assumptions, W-LAN is not likely to represent a disruptive technology for the established mobile communications network firms in terms of Christensen's concept. This research was conducted in close collaboration with Vodafone Pilotentwicklung, an R&D and technology monitoring unit of the Vodafone Group. Vodafone provided part of the empirical data through expert interviews and market reports. [source]