Numerical Treatment of the Loss of Hyperbolicity of?the?Two-Layer Shallow-Water System

This article is devoted to the numerical solution of the inviscid two-layer shallow water system. This system may lose the hyperbolic character when the shear between the layer is big enough. This loss of hyperbolicity is related to the appearance of shear instabilities that leads, in real flows, to intense mixing of the two layers that the model is not able to simulate. The strategy here is to add some extra friction terms, which are supposed to parameterize the loss of mechanical energy due to mixing, to get rid of this difficulty. The main goal is to introduce a technique allowing one to add locally and automatically an ??optimal?? amount of shear stress to make the flow to remain in the hyperbolicity region. To do this, first an easy criterium to check the hyperbolicity of the system for a given state is proposed and checked. Next, we introduce a predictor/corrector strategy. In the predictor stage, a numerical scheme is applied to the system without extra friction. In the second stage, a discrete semi-implicit linear friction law is applied at any cell in which the predicted states are not in the hyperbolicity region. The coefficient of this law is calculated so that the predicted states are driven to the boundary of the hyperbolicity region according to the proposed criterium. The numerical scheme to be used at the first stage has to be able to advance in time in presence of complex eigenvalues: we propose here a family of path-conservative numerical scheme having this property. Finally, some numerical tests have been performed to assess the efficiency of the proposed strategy.     

Management Systems: the End of the Beginning?

For many years quality managers have been striving to merge the requirements of management systems into business as usual. Traditional paper-based formats have made this very difficult to achieve. However, the advance of technology and the transfer of information to the electronic medium have provided new opportunities. In the new medium the EFQM Business Excellence Model may be used as a navigational tool to finally solve this problem.     

What can the history of AI learn from the history of science?

There have been few attempts, so far, to document the history of artificial intelligence. It is argued that the historical sociology of scientific knowledge can provide a broad historiographical approach for the history of AI, particularly as it has proved fruitful within the history of science in recent years. The article shows how the sociology of knowledge can inform and enrich four types of project within the history of AI; organizational history; AI viewed as technology; AI viewed as cognitive science and historical biography. In the latter area the historical treatments of Darwin and Turing are compared to warn against the pitfalls of rational reconstructions of the past.     

On the Expression Complexity of Equivalence and?Isomorphism of?Primitive Positive Formulas

We study the complexity of equivalence and isomorphism on primitive positive formulas with respect to a given structure. We study these problems for various fixed structures; we present generic hardness and complexity class containment results, and give classification theorems for the case of two-element (boolean) structures.     

Waht is the ultimate form of communication?

This article addresses the issue of ideal communication and the way to achieve it. First, it is proposed that the technological trend of moving from logical to ideal communication is similar to a journey on the path to find the original self and spiritual enlightenment. Then it is stated that new media, which have interaction capabilities and can realize immersion, may be the means to achieve ideal communication. It is also pointed out, by referring to phenomena in Zen, that there is a danger of developing imperfect communication on the way to achieving ideal communication. This work was presented in part at the Sixth International Symposium on artificial Life and Robotics, Tokyo, January 15–17, 2001.     

What is the academic efficacy of podcasting?

Podcasting may be an answer to some of the challenges to higher education to modernize, to open up, and to develop a competitive edge. However, over the years there have been many high claims for new technology, and not all of them have been redeemed. In terms of academic performance, it may therefore be asked if podcasting really is worth the investment? Looking for at least a tentative answer, the present paper reviews an extensive body of scholarly literature published 2004–2009 on experiences with podcasting in higher education.     

Does the user behavior effect the productivity of hammer drilling? – Analysis of the influences of feed and lateral force

The objective of this study was to investigate the relationship between feed and lateral force with productivity in hammer drilling. Necessary user forces and vibration caused by hammer drilling leads to user fatigue and long-term injuries. Through an increase in productivity, the stress duration and thus injuries caused can be reduced. The user, who influences productivity, applies lateral forces in addition to the feed force during hammer drilling. Their influence and interaction with the feed force on productivity has not yet been investigated. In this study, a total of 1152 boreholes were performed on an automated test bench. Along with the feed and lateral forces, the setup, consisting of hammer drill and drill bit model, was varied in order to investigate interaction effects as well as discuss transferability of the findings. The productivity was evaluated by the rate of penetration (ROP). It was observed that the ROP decreased with increasing lateral forces (p < .001, r = 0.315) and increased with increasing feed force. The detailed courses of these relationships were setup-specific. At low feed forces, the feed and lateral force interacted on the ROP. The investigated relationships indicate an efficient operating range depending on the user forces and setup used, which enables a reduction of the user's stress duration. The findings help engineers develop power tools that provide more efficient and hence less fatiguing work, making them more ergonomic for the user.     

Who are the users? Who are the developers? Webs of users and developers in the development process of a technical standard

The paper presents an empirical study of user involvement in developing a technical standard for a scientific community's information system project. The case illustrates how multiple perspectives are involved when considering the user role in practice. The case presents a situation where both developers and users were pre‐defined in the design and development phases of the standard as homogeneous groups of actors. Groups of actors changed to become more heterogeneous and ‘fluid’ in the deployment and implementation phases, thus forming ‘webs of developers’ and ‘webs of users’. Detailed analysis of the process in its entirety shows the blurredness of boundaries between ‘developer’ and ‘user’ categories and roles, and reveals challenges at social and organizational levels. Three models pertaining to the system development process are presented in order to illuminate differing perspectives on the user and on the development process itself. The paper draws theoretically from information systems, social informatics, and science and technology studies. The research contributes to a deeper, interdisciplinary understanding of ‘the’ user, of multiple roles in systems development, and of dynamic sets of user–developer relations.     

Operation speed limited by the electric properties of?the?photorefractive spatial light modulator

With excellent photo-electric and electro-optical effects, the photorefractive spatial light modulators can work as optically addressed modulators in optical information processing systems and parallel optical computing systems. The photo-induced current pulses of the photorefractive spatial light modulator observed in the experiments are analyzed to conclude the characteristics, and to find the relationship between the properties of the current pulse and the structural parameters. Furthermore, the origin of the photo-induced current pulse is analyzed, and the methods to improve the operation speed of the spatial light modulators are proposed. The research results will be significant for extending the applications of the photorefractive spatial light modulators, and pushing ahead the research of all-optical modulation materials and devices for optical supercomputing.     

Does the level of detail of UML diagrams affect the maintainability of source code?: a family of experiments

Although the UML is considered to be the de facto standard notation with which to model software, there is still resistance to model-based development. UML modeling is perceived to be expensive and not necessarily cost-effective. It is therefore important to collect empirical evidence concerning the conditions under which the use of UML makes a practical difference. The focus of this paper is to investigate whether and how the Level of Detail (LoD) of UML diagrams impacts on the performance of maintenance tasks in a model-centric approach. A family of experiments consisting of one controlled experiment and three replications has therefore been carried out with 81 students with different abilities and levels of experience from 3 countries (The Netherlands, Spain, and Italy). The analysis of the results of the experiments indicates that there is no strong statistical evidence as to the influence of different LoDs. The analysis suggests a slight tendency toward better results when using low LoD UML diagrams, especially if used for the modification of the source code, while a high LoD would appear to be helpful in understanding the system. The participants in our study also favored low LoD diagrams because they were perceived as easier to read. Although the participants expressed a preference for low LoD diagrams, no statistically significant conclusions can be drawn from the set of experiments. One important finding attained from this family of experiments was that the participants minimized or avoided the use of UML diagrams, regardless of their LoD. This effect was probably the result of using small software systems from well-known domains as experimental materials.     

Biomashups: the new world of exploratory bioinformatics?

Bioinformatics is dominated by online databases and sophisticated web‐accessible tools. As such, it is ideally placed to benefit from the rapid, purpose specific combination of services achievable via web mashups. The recent introduction of a number of sophisticated frameworks has greatly simplified the mashup creation process, making them accessible to scientists with limited programming expertise. In this paper we investigate the feasibility of mashups as a new approach to bioinformatic experimentation, focusing on an exploratory niche between interactive web usage and robust workflows, and attempting to identify the range of computations for which mashups may be employed. While we treat each of the major frameworks, we illustrate the ideas with a series of examples developed under the Popfly framework ^‡ . Copyright © 2010 John Wiley & Sons, Ltd.     

Are we forgetting the risks of information technology?

The complexity and interconnectedness of information systems is growing. There must be some way to systematically assess the risk to critical infrastructures. Work began two decades ago (1980s) on a comprehensive theoretical framework to model and identify risks to large-scale and complex systems. The framework, hierarchical holographic modeling (HHM) (Y.Y. Haimes, 1981; 1998) is to conventional modeling schemes what holography is to conventional photography. Holography captures images in three dimensions, as compared with conventional photography's two-dimensional, planar representation. Likewise, HHM endorses a gestalt and holistic philosophy, which allows it to capture more dimensions than modeling schemes that yield planar models. HHM promotes a systemic process that identifies most, if not all, important and critical sources of risk.     

What influences the accuracy of decision tree ensembles?

An ensemble in machine learning is defined as a set of models (such as classifiers or predictors) that are induced individually from data by using one or more machine learning algorithms for a given task and then work collectively in the hope of generating improved decisions. In this paper we investigate the factors that influence ensemble performance, which mainly include accuracy of individual classifiers, diversity between classifiers, the number of classifiers in an ensemble and the decision fusion strategy. Among them, diversity is believed to be a key factor but more complex and difficult to be measured quantitatively, and it was thus chosen as the focus of this study, together with the relationships between the other factors. A technique was devised to build ensembles with decision trees that are induced with randomly selected features. Three sets of experiments were performed using 12 benchmark datasets, and the results indicate that (i) a high level of diversity indeed makes an ensemble more accurate and robust compared with individual models; (ii) small ensembles can produce results as good as, or better than, large ensembles provided the appropriate (e.g. more diverse) models are selected for the inclusion. This has implications that for scaling up to larger databases the increased efficiency of smaller ensembles becomes more significant and beneficial. As a test case study, ensembles are built based on these findings for a real world application—osteoporosis classification, and found that, in each case of three datasets used, the ensembles out-performed individual decision trees consistently and reliably.     

The field becomes the laboratory? The impact of the contextual digital footprint on the discipline of E/HF

Abstract

The increasing prevalence of affordable digital sensors, ubiquitous networking and computation puts us at what is only the start of a new era in terms of the volume, coverage and granularity of data that we can access about individuals and workplaces. This paper examines the consequences of harnessing this data deluge for the practice of E/HF. Focusing on what we term the ‘contextual digital footprint’, the trail of data we produce through interactions with many different digital systems over the course of even a single day, we describe three example scenarios (drawn from health care, distributed work and transportation) and examine how access to data directly drawn in considerable volume from the field will potentially change our application of design and evaluation methods. We conclude with a discussion of issues relevant to ethical and professional practice within this new environment including the increased challenges of respecting anonymity, working with n = all data-sets and the central role of ergonomists in promulgating positive uses of data while retaining a systems-based humanistic approach to work design.

Practitioner summary: The paper envisions the impact of new and emerging sources of data about people and workplaces upon future practice in E/HF. We identify practical consequences for ergonomics practice, highlight new areas of professional competence likely to be required and flag both the risks and benefits of adopting a more data-driven approach.     

Study the Works of Peter Eisenman? Why?!

In this paper, some design applications of Fuzzy Control are reviewed and discussed. Design conveys multiplicities, contradictions, differences, into temporary hypotheses. Actual realizations, papers, are the place where reflections consist; the reflections matured in several technological ambits appear in terms of sums of experiences and solutions’shifted’ from their own place of origin to the detailed synthesis that rules the assembling. We ask ourselves how fuzzy logic, that finds its reason for existence in the interpretation of the reality and exalt the ‘shifts’ can point towards the architectural process.