The Random Waypoint Mobility Model with Uniform Node Spatial Distribution

In this paper, we solve a long standing open problem by presenting two versions of the well-known random waypoint mobility model in bounded regions generating a uniform steadystate node spatial distribution. In the first version, named temporal-RWP, we exploit the temporal dimension of node mobility and achieve uniformity by continuously changing the speed of a mobile node as a function of its location and of the density function of trajectories in the movement region R. In the second version, named spatial-RWP, we instead exploit the spatial dimension and achieve uniformity by selecting waypoints according to a suitably defined mix of probability density functions. Both proposed models can be easily incorporated in wireless network simulators, and are thus of practical use. The RWP models presented in this paper allow for the first time completely removing the well-known border effect causing possible inaccuracies in mobile network simulation, thus completing the picture of a "perfect" simulation methodology drawn in existing literature

eStorys: A visual storyboard system supporting back-channel communication for emergencies

This is the post-print version of the final paper published in Journal of Visual Languages & Computing. The published article is available from the link below. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. Copyright @ 2010 Elsevier B.V.In this paper we present a new web mashup system for helping people and professionals to retrieve information about emergencies and disasters. Today, the use of the web during emergencies, is confirmed by the employment of systems like Flickr, Twitter or Facebook as demonstrated in the cases of Hurricane Katrina, the July 7, 2005 London bombings, and the April 16, 2007 shootings at Virginia Polytechnic University. Many pieces of information are currently available on the web that can be useful for emergency purposes and range from messages on forums and blogs to georeferenced photos. We present here a system that, by mixing information available on the web, is able to help both people and emergency professionals in rapidly obtaining data on emergency situations by using multiple web channels. In this paper we introduce a visual system, providing a combination of tools that demonstrated to be effective in such emergency situations, such as spatio/temporal search features, recommendation and filtering tools, and storyboards. We demonstrated the efficacy of our system by means of an analytic evaluation (comparing it with others available on the web), an usability evaluation made by expert users (students adequately trained) and an experimental evaluation with 34 participants.Spanish Ministry of Science and Innovation and Universidad Carlos III de Madrid and Banco Santander

From deep dyslexia to agrammatic comprehension on silent reading

We report on a case of a French-speaking patient whose performance on reading aloud single words was characteristically deep dyslexic (in spite of preserved ability to identify letters), and whose comprehension on silent sentence reading was agrammatic and strikingly poorer than on oral reading. The first part of the study is mainly informative as regards (i) the relationship between letter identification, semantic paralexias and the ability to read nonwords, (ii) the differential character of silent and oral reading tasks, and (iii) the potential modality-dependent character of the deficits in comprehension encountered. In the second part of the study we examine the patient's sensitivity to verb-noun ambiguity and probe her skills in the comprehension of indexical structures by exploring her ability to cope with number agreement and temporal and prepositional relations. The results indicate the patient's sensitivity to certain dimensions of these linguistic categories, reveal a partly correct basis for certain incorrect responses, and, on the whole, favor a definition of the patient's disorders in terms of a deficit in integrating indexical information in language comprehension. More generally, the present study substantiates a microgenetic approach to neuropsychology, where the pathological behavior due to brain damage is described as an arrest of microgenesis at an early stage of development, so that patient's responses take the form of unfinished "products" which would normally undergo further development

Diamonds are Forever

We defend the thesis that every necessarily true proposition is always true. Since not every proposition that is always true is necessarily true, our thesis is at odds with theories of modality and time, such as those of Kit Fine and David Kaplan, which posit a fundamental symmetry between modal and tense operators. According to such theories, just as it is a contingent matter what is true at a given time, it is likewise a temporary matter what is true at a given possible world; so a proposition that is now true at all worlds, and thus necessarily true, may yet at some past or future time be false in the actual world, and thus not always true. We reconstruct and criticize several lines of argument in favor of this picture, and then argue against the picture on the grounds that it is inconsistent with certain sorts of contingency in the structure of time

A dynamic policy model to manage temporal performance amongst contracting firms in a competitive situation

Studies have been conducted to measure competitiveness in the construction industry. Such research has focused on all levels from the national picture to individual projects. While useful, the results are limited in that they present a snapshot picture at one point in time. Moreover, they do not suggest how under-performance might be improved. The research reported here is part of a large collaborative study to evaluate sustained competitiveness in the UK construction industry. It enhances previous research in that a system dynamics model of contracting firms operating in competition is used to not only measure each firm’s temporal performance by means of a dynamic competitive index, but it can also suggest high leverage policies which mitigate against under-performance. The model structure is described and simulated scenario runs presented. Besides the contribution to strategic policy making at the level of the contracting firm, the exemplar shows that the system dynamics methodology could have significant utility in the field of construction management

Parental education and family characteristics: educational opportunities across cohorts in Italy and Spain

Drawing on data contained in the 2005 EU-SILC, this paper investigates the disparities in educational opportunities in Italy and Spain. Its main objective is to analyse the predicted probabilities of successfully completing upper-secondary and tertiary education for individuals with different parental backgrounds, and the changes in these probabilities across birth cohorts extending from 1940 to 1980. The results suggest that the disparities in tertiary education opportunities in Italy tend to increase over time. By contrast, the gap in educational opportunity in Spain shows a marked decrease across the cohorts. Moreover, by using an intuitive decomposition strategy, the paper shows that a large part of the educational gap between individuals of different backgrounds is “composed” of the difference in the endowment of family characteristics. Specifically, it seems that more highly educated parents are more able to endow their children with a better composition of family characteristics, which accounts for a significant proportion of the disparities in educational opportunity.Educational Opportunity, Family Background, Birth cohorts, Italy, Spain

Measuring Mimicry in Task-Oriented Conversations: The More the Task is Difficult, The More we Mimick our Interlocutors

The tendency to unconsciously imitate others in conversations is referred to as mimicry, accommodation, interpersonal adap- tation, etc. During the last years, the computing community has made significant efforts towards the automatic detection of the phenomenon, but a widely accepted approach is still miss- ing. Given that mimicry is the unconscious tendency to imitate others, this article proposes the adoption of speaker verification methodologies that were originally conceived to spot people trying to forge the voice of others. Preliminary experiments suggest that mimicry can be detected by measuring how much speakers converge or diverge with respect to one another in terms of acoustic evidence. As a validation of the approach, the experiments show that convergence (the speakers become more similar in terms of acoustic properties) tends to appear more frequently when a task is difficult and, therefore, requires more time to be addressed

How to Ask for a Favor: A Case Study on the Success of Altruistic Requests

Requests are at the core of many social media systems such as question & answer sites and online philanthropy communities. While the success of such requests is critical to the success of the community, the factors that lead community members to satisfy a request are largely unknown. Success of a request depends on factors like who is asking, how they are asking, when are they asking, and most critically what is being requested, ranging from small favors to substantial monetary donations. We present a case study of altruistic requests in an online community where all requests ask for the very same contribution and do not offer anything tangible in return, allowing us to disentangle what is requested from textual and social factors. Drawing from social psychology literature, we extract high-level social features from text that operationalize social relations between recipient and donor and demonstrate that these extracted relations are predictive of success. More specifically, we find that clearly communicating need through the narrative is essential and that that linguistic indications of gratitude, evidentiality, and generalized reciprocity, as well as high status of the asker further increase the likelihood of success. Building on this understanding, we develop a model that can predict the success of unseen requests, significantly improving over several baselines. We link these findings to research in psychology on helping behavior, providing a basis for further analysis of success in social media systems.Comment: To appear at ICWSM 2014. 10pp, 3 fig. Data and other info available at http://www.mpi-sws.org/~cristian/How_to_Ask_for_a_Favor.htm