Gleam: the GLAST Large Area Telescope Simulation Framework

This paper presents the simulation of the GLAST high energy gamma-ray telescope. The simulation package, written in C++, is based on the Geant4 toolkit, and it is integrated into a general framework used to process events. A detailed simulation of the electronic signals inside Silicon detectors has been provided and it is used for the particle tracking, which is handled by a dedicated software. A unique repository for the geometrical description of the detector has been realized using the XML language and a C++ library to access this information has been designed and implemented.Comment: 10 pages, Late

The Araucaria Project. OGLE-LMC-CEP-1718: An exotic eclipsing binary system composed of two classical overtone Cepheids in a 413-day orbit

We have obtained extensive high-quality spectroscopic observations of the OGLE-LMC-CEP-1718 eclipsing binary system in the Large Magellanic Cloud which Soszynski et al. (2008) had identified as a candidate system for containing two classical Cepheids in orbit. Our spectroscopic data clearly demonstrate binary motion of the Cepheids in a 413-day eccentric orbit, rendering this eclipsing binary system the first ever known to consist of two classical Cepheid variables. After disentangling the four different radial velocity variations in the system we present the orbital solution and the individual pulsational radial velocity curves of the Cepheids. We show that both Cepheids are extremely likely to be first overtone pulsators and determine their respective dynamical masses, which turn out to be equal to within 1.5 %. Since the secondary eclipse is not observed in the orbital light curve we cannot derive the individual radii of the Cepheids, but the sum of their radii derived from the photometry is consistent with overtone pulsation for both variables. The existence of two equal-mass Cepheids in a binary system having different pulsation periods (1.96 and 2.48 days, respectively) may pose an interesting challenge to stellar evolution and pulsation theories, and a more detailed study of this system using additional datasets should yield deeper insight about the physics of stellar evolution of Cepheid variables. Future analysis of the system using additional near-infrared photometry might also lead to a better understanding of the systematic uncertainties in current Baade-Wesselink techniques of distance determinations to Cepheid variables.Comment: accepted to be published in Ap

EXPLAINING THE TERRITORIAL ADOPTION OF NEW TECHNOLOGIES - A SPATIAL ECONOMETRIC APPROACH

The notion that Information and Communication Technology would have reduced the economic importance of geographic distance has been proposed with energy in the post-Internet literature (Cairncross, 2001). According to this view, the New Economy would work in a space rather than a place, cost of transport would be drastically reduced, distance would be less important, and peripheral regions would benefit from opportunities that were not available in the economy based on manufacturing industry (Negroponte, 1995; Cairncross, 1997; Kelly, 1998; Compaine, 2001). Since ICT are mostly based on immaterial and human capital investment, regions or areas that have historically suffered from isolation, large cost of transportation, or lack of physical private and public infrastructure might find new paths for growth. Consequently, according to this view, the concentration of income opportunities and wealth should decrease over time. Although other predictions were also present in the debate over the impact of the digital economy (e.g. Norris, 2001; UNDP; 2001), this view was largely dominant. The reality is not so rosy. Not only there are huge disparities in the intensity with which ICT are adopted and used across countries, but also there are still large differences within industrialized countries. Indeed, differences in economic development still shape the rate of the adoption of these technologies, at the firm, regional and country level. The reasons behind these stylized facts have been investigated at length in recent times. This paper contributes to the literature in several ways. First, it focuses on intra-national or regional differences, which is a much less explored dimension of the digital divide. Second, it uses a new metric for the adoption of ICT, namely the number of second level Internet domain names, registered under the ccTLD “.it.”. Finally, it explicitly combines the analysis of determinants with a spatial econometric approach. Thanks to the availability of panel data for both the dependent and the explanatory variables (time period: 1990-2001), spatial and temporal effect are simultaneously taken into account. Panel data techniques that account for temporal correlations are in widespread use while there have been a variety of studies accounting for spatial autocorrelation (see for instance Coughlin et al. 2003; Dubin, 1992; McMillan, 2004). However one of the major drawbacks to many analyses is that they fail to integrate the spatial and temporal correlations that are present in geographical systems (Elhorst, 2003).

3D virtual reconstructions at the service of computer assisted archaeological measurements

Technological advances have enabled photogrammetric and surveying methods to produce recording materials surpassing the traditional line drawings in accuracy and completeness. These methodologies may offer products not possible in the past. This paper relates the difficult experience of collecting, archiving, processing, combining, visualizing and exploiting data from a multitude of sources to make accurate geometric records of monuments, implementing the most contemporary, innovative and technologically advanced methods. Issues analysed include collecting and processing field data from a variety of sources and their respective properties, but also the production of different end products, vector and raster, with the main emphasis on complex 3D visualizations. Different approaches are assessed for their usefulness and potential accuracy. Examples covering a variety of Greek and Cypriot monuments are presented, which are acquired from the rich experience of the archaeological surveys of the Laboratory of Photogrammetry of NTUA

A novel tactile display for softness and texture rendering in tele-operation tasks

Softness and texture high-frequency information represent fundamental haptic properties for every day life activities and environment tactual exploration. While several displays have been produced to convey either softness or high-frequency information, there is no or little evidence of systems that are able to reproduce both these properties in an integrated fashion. This aspect is especially crucial in medical tele-operated procedures, where roughness and stiffness of human tissues are both important to correctly identify given pathologies through palpation (e.g. in tele-dermatology). This work presents a fabric yielding display (FYD-pad), a fabric-based tactile display for softness and texture rendering. The system exploits the control of two motors to modify both the stretching state of the elastic fabric for softness rendering and to convey texture information on the basis of accelerometer-based data. At the same time, the measurement of the contact area can be used to control remote or virtual robots. In this paper, we discuss the architecture of FYD-pad and the techniques used for softness and texture reproduction as well as for synthesizing probe-surface interactions from real data. Tele-operation examples and preliminary experiments with humans are reported, which show the effectiveness of the device in delivering both softness and texture information

Proxy chain method and its application to scientific visualization

Journal ArticleWe present a method for combining multiple point-based constraints in haptic programming environments. Instead of using a single proxy point for haptic feedback, the method maintains a separate proxy for each constraint. The reaction force is computed by linking the proxies in a chain. Constraints are applied in sequential order, such that the proxy found in the current step becomes the probe for the next step in the chain. The advantage of the method over previous approaches is that the constraints are maintained precisely and the output is well-defined. We illustrate the method with examples from the domain of 3D scientific data visualization. Finally, we present the results of an experiment conducted to quantify the contribution of haptic guidance in two representative vector field exploration tasks

Analytical and mathematical methods for revealing hidden details in ancient manuscripts and paintings: A review

In this work, a critical review of the current nondestructive probing and image analysis approaches is presented, to revealing otherwise invisible or hardly discernible details in manuscripts and paintings relevant to cultural heritage and archaeology. Multispectral imaging, X-ray fluorescence, Laser-Induced Breakdown Spectroscopy, Raman spectroscopy and Thermography are considered, as techniques for acquiring images and spectral image sets; statistical methods for the analysis of these images are then discussed, including blind separation and false colour techniques. Several case studies are presented, with particular attention dedicated to the approaches that appear most promising for future applications. Some of the techniques described herein are likely to replace, in the near future, classical digital photography in the study of ancient manuscripts and paintings