Rapid evaluation of radial basis functions

Over the past decade, the radial basis function method has been shown to produce high quality solutions to the multivariate scattered data interpolation problem. However, this method has been associated with very high computational cost, as compared to alternative methods such as finite element or multivariate spline interpolation. For example. the direct evaluation at M locations of a radial basis function interpolant with N centres requires O(M N) floating-point operations. In this paper we introduce a fast evaluation method based on the Fast Gauss Transform and suitable quadrature rules. This method has been applied to the Hardy multiquadric, the inverse multiquadric and the thin-plate spline to reduce the computational complexity of the interpolant evaluation to O(M + N) floating point operations. By using certain localisation properties of conditionally negative definite functions this method has several performance advantages against traditional hierarchical rapid summation methods which we discuss in detail

Nocturnal depth distribution of western North Atlantic swordfish (Xiphias gladius, Linnaeus, 1758) in relation to lunar illumination

Swordfish are known to undergo large diel vertical movements from surface waters at night to \u3e 300 m depth during the day. Evidence presented over the past several deeades suggests the lunar cycle affects these vertical migrations. This study collected data concurrently from 7 swordfish throughout 3 consecutive lunar cycles using pop-up satellite archival tags. All individuals demonstrated an inverse relationship between recorded nocturnal depths and lunar illumination

An analysis between implied and realised volatility in the Greek Derivatives Market

In this article, we examine the relationship between implied and realised volatility in the Greek derivative market. We examine the differences between realised volatility and implied volatility of call and put options for at-the-money index options with a two-month expiration period. The findings provide evidence that implied volatility is not an efficient estimate of realised volatility. Implied volatility creates overpricing, for both call and put options, in the Greek market. This is an indication of inefficiency for the market. In addition, we find evidence that realised volatility ‘Granger causes’ implied volatility for call options, and implied volatility of call options ‘Granger causes’, the implied volatility of put option

Science Lectures in the Arctic's "Science City": Barrow, Alaska

... Beginning in spring 2002, the Science division of the Utqiagvik Iñupiat Corporation (UIC), Barrow's local village corporation, took over the renovated original powerhouse building at the Northern Arctic Research Laboratory, formerly the Naval Arctic Research Laboratory (NARL). The newly named UIC Science Center, about three miles north of Barrow, has become the venue for a number of programs. One is the Barrow Schoolyard lecture series, funded under the Long-term Ecological Research (LTER) program of the National Science Foundation, which includes a science-education outreach component. Toolik Station, an LTER base on Alaska's North Slope, did not have a community associated with it. Under the urging of Dr. Jerry Brown, Barrow was appointed as the location for the Schoolyard Project. The program teams scientists with local teachers for public presentations of the researchers' projects or areas of interest, and is administered by the Barrow Arctic Science Consortium (BASC). ... A main objective of the Schoolyard Project talks is to make them attractive to students. The Schoolyard funds have also been used to sponsor an ongoing series of tundra experiments involving small greenhouses and fertilizers, similar to those being run at Toolik Lake. ... While it is too soon to measure results, clearly the injection of high-quality science into the community will have a positive effect on science education in the local schools. The hope of NSF and the local scientists is to make science accessible and useful to the community and to stimulate young people to consider a career in science

A Network Topology Approach to Bot Classification

Automated social agents, or bots, are increasingly becoming a problem on social media platforms. There is a growing body of literature and multiple tools to aid in the detection of such agents on online social networking platforms. We propose that the social network topology of a user would be sufficient to determine whether the user is a automated agent or a human. To test this, we use a publicly available dataset containing users on Twitter labelled as either automated social agent or human. Using an unsupervised machine learning approach, we obtain a detection accuracy rate of 70%

A business model design framework for viability:a business ecosystem approach

Purpose: To facilitate the design of viable business models by proposing a novel business model design framework for viability. Design: A design science research method is adopted to develop a business model design framework for viability. The business model design framework for viability is demonstrated by using it to design a business model for an energy enterprise. The aforementioned framework is validated in theory by using expert opinion. Findings: It is difficult to design viable business models because of the changing market conditions, and competing interests of stakeholders in a business ecosystem setting. Although the literature on business models provides guidance on designing viable business models, the languages (business model ontologies) used to design business models largely ignore such guidelines. Therefore, we propose a business model design framework for viability to overcome the identified shortcomings. The theoretical validation of the business model design framework for viability indicates that it is able to successfully bridge the identified shortcomings, and it is able to facilitate the design of viable business models. Moreover, the validation of the framework in practice is currently underway. Originality / value: Several business model ontologies are used to conceptualise and evaluate business models. However, their rote application will not lead to viable business models, because they largely ignore vital design elements, such as design principles, configuration techniques, business rules, design choices, and assumptions. Therefore, we propose and validate a novel business model design framework for viability that overcomes the aforementioned shortcomings

An assessment framework of business modelling ontologies to ensure the viability of business models

Organisations operate in an increasingly dynamic environment. Consequently, the business models span several organisations, dealing with multiple stakeholders and their competing interests. As a result, the enterprise information systems supporting this new market setting are highly distributed, and their components are owned and managed by different stakeholders. For successful businesses to exist it is crucial that their enterprise architectures are derived from and aligned with viable business models. Business model ontologies (BMOs) are effective tools for designing and evaluating business models. However, the viability perspective has been largely neglected. In this paper, current BMOs have been assessed on their capabilities to support the design and evaluation of viable business models. As such, a list of criteria is derived from literature to evaluate BMOs from a viability perspective. These criteria are subsequently applied to six well-established BMOs, to identify a BMO best suited for design and evaluation of viable business models. The analysis reveals that, although none of the BMOs satisfy all the criteria, e3-value is the most appropriate BMO for designing and evaluating business models from a viability perspective. Furthermore, the identified deficits provide clear areas for enhancing the assessed BMOs from a viability perspective

Observations on Shorefast Ice Dynamics in Arctic Alaska and the Responses of the Iñupiat Hunting Community

Although shorefast sea ice forms a platform that facilitates travel, camping, and hunting by Iñupiat subsistence hunters and fishers in the western Arctic, the nearshore sea-ice zone remains an unforgiving and dynamic environment. Traditional hunters constantly hone site-specific experiences and skills with which to optimize the reward-to-risk ratio inherent in operating from this coastal ice. Nearshore ice conditions nevertheless can change suddenly, endangering even the most experienced subsistence hunters. This study examines two (of several) 20th-century events, 40 years apart, in which shorefast ice failed, threatening Iñupiat whale hunters with loss of confidence, livelihood, and life. These events differed in character. In one event, the shorefast ice was "crushed" by moving ice floes. In the other, the shorefast ice broke free of land. Our examination focuses on the relationship of subsistence hunters to the ice, the environmental causes of ice failures, the evolving technology for predicting ice behavior, and the longer-term implications of global change for this system. The complexity of geophysical processes underlying coastal ice behavior makes ice failures unpredictable. Thus, hunters must assume and manage risk. The variable and uncertain environment to which whale hunters are accustomed has produced an inherent flexibility that has helped them adapt to new conditions and will continue to do so in the future.Bien que la banquise côtière constitue une plate-forme qui permet aux Iñupiat de l'Arctique de l'Ouest de se déplacer et de camper lorsqu'ils pratiquent la chasse et la pêche de subsistance, la zone de banquise proche du littoral reste un milieu dynamique qui ne pardonne pas. Les chasseurs traditionnels améliorent constamment les habiletés et l'expérience reliées à des sites particuliers, qui leur permettent d'optimiser le rapport récompense-risque inhérent au fait de travailler depuis la glace côtière. Les conditions de cette dernière peuvent toutefois changer brusquement, mettant en danger même les chasseurs de subsistance les plus chevronnés. Cette étude se penche sur deux (parmi plusieurs) épisodes survenus au XXe siècle, à 40 ans d'écart, durant lesquels la banquise côtière s'est rompue, ébranlant la confiance des baleiniers Iñupiat et menaçant leur moyen de subsistance ainsi que leur vie. Ces événements étaient de nature différente. Dans l'un, la glace côtière avait été «écrasée» par des floes en dérive. Dans l'autre, la banquise côtière s'était détachée de la terre ferme. Notre étude se concentre sur le rapport entre les chasseurs de subsistance et la glace, les causes environnementales de la fragilisation de la glace, la technologie mise au point actuellement qui permettrait de prédire le comportement de la glace, et les implications à long terme du changement climatique pour ce système. La complexité des processus géophysiques sous-jacents au comportement de la banquise côtière fait que les ruptures de la banquise sont imprévisibles. Les chasseurs doivent donc assumer le risque et le gérer. L'environnement variable et incertain auquel sont accoutumés les chasseurs de baleine leur a donné une souplesse inhérente qui les a aidés à s'adapter à de nouvelles conditions et continuera de le faire dans l'avenir

Towards the drivers of value creation in the biogas industry:enablers and inhibiters in the Netherlands

The Dutch biogas industry is developing slowly and in many instances still unviable. Insights in the drivers of value creation may help to create viable biogas business networks. This research explores these related drivers and accordingly, proposes a new and comprehensive definition of a driver of value creation. This definition focuses on the enabling and inhibiting factors of value creation in a business network and forms the backbone of three case studies. The results suggest the presence of four specific drivers as necessary for a viable biogas business network: stability and certainty, partner alignment, local opportunities and economies of scale