A high dynamic range rendering pipeline for interactive applications

Realistic images can be computed at interactive frame rates for Computer Graphics applications. Meanwhile, High Dynamic Range (HDR) rendering has a growing success in video games and virtual reality applications, as it improves the image quality and the player’s immersion feeling. In this paper, we propose a new method, based on a physical lighting model, to compute in real time a HDR illumination in virtual environments. Our method allows to re-use existing virtual environments as input, and computes HDR images in photometric units. Then, from these HDR images, displayable 8-bit images are rendered with a tone mapping operator and displayed on a standard display device. The HDR computation and the tone mapping are implemented in OpenSceneGraph with pixel shaders. The lighting model, together with a perceptual tone mapping, improves the perceptual realism of the rendered images at low cost. The method is illustrated with a practical application where the dynamic range of the virtual environment is a key rendering issue: night-time driving simulation.     

A new classification of datasets for frequent itemsets

The discovery of frequent patterns is a famous problem in data mining. While plenty of algorithms have been proposed during the last decade, only a few contributions have tried to understand the influence of datasets on the algorithms behavior. Being able to explain why certain algorithms are likely to perform very well or very poorly on some datasets is still an open question. In this setting, we describe a thorough experimental study of datasets with respect to frequent itemsets. We study the distribution of frequent itemsets with respect to itemsets size together with the distribution of three concise representations: frequent closed, frequent free and frequent essential itemsets. For each of them, we also study the distribution of their positive and negative borders whenever possible. The main outcome of these experiments is a new classification of datasets invariant w.r.t. minsup variations and robust to explain efficiency of several implementations.     

Three generalizations of the <Emphasis Type="SmallCaps">FOCUS</Emphasis> constraint

The FOCUS constraint expresses the notion that solutions are concentrated. In practice, this constraint suffers from the rigidity of its semantics. To tackle this issue, we propose three generalizations of the FOCUS constraint. We provide for each one a complete filtering algorithm. Moreover, we propose ILP and CSP decompositions.     

Project portfolios in dynamic environments: Organizing for uncertainty

This research investigated the following research question: How is uncertainty affecting project portfolios managed in dynamic environments? While different approaches have been developed in the context of the management of single projects these ideas have not been carried over to the management of project portfolios.     

Thermal and structural characterization of selenium-rich As–Se fibers

Se-rich optical fibers have been drawn from As–Se-based preforms and their corresponding thermal properties have been analyzed. Micro-Raman spectroscopy has been used to characterize and compare the structure of the preform and the resulting fiber. The spectra show that the fibers possessing the same thermal properties as their corresponding preforms, exhibit similar structure while no evidence of crystallization, as assessed via X-ray diffraction analysis, could be detected.     

Resistance A La Corrosion D'ensembles Soudes En Alliages De Titane—Influence De L'etat Structural

An investigation of the potentiodynamic polarization behaviour of some titanium alloys welds has shown that their corrosion resistance is not significantly influenced by variation of micro-structure, even in melted and heat-affected zones. For comparison, some microstructures similar to those observed in welds were also studied. Slight variations concern only the passive behaviour of these alloys which are unaffected in the active state by microstructural changes. Interpretations of peculiar behaviour of Ti–2, 5%Cu alloy are suggested.     

Lipid composition of the liver oil of the ray, Himantura bleekeri

If rays are traditionally fished for their caudal fins, the rest of the body is wasted, except part of the skin that can be transformed into leather. Liver oil of the ray, Himantura bleekeri, was characterized in terms of lipid class composition and fatty acid profile. Liver oil content was high and represented 54% of the liver weight (w/w). Neutral lipids were predominant (92%), major components being triacylglycerols (63%). Other neutral lipids identified were hydrocarbons, sterol esters, mono- and di-acylglycerols, free fatty acids, sterols and glyceryl ethers. Polyunsaturated fatty acids of the n−3 series, namely eicosapentaenoic and docosahexaenoic acids, were high (4% and 16%, respectively). Cholesterol was the major component in the sterol fractions (free or esterified). Hydrocarbons were up to 30 carbons and squalene was present at the level of 22%. Thus, this liver oil proved to be an adequate source of n−3 fatty acids and other valuable lipidic compounds.     

New deep-freezing process using renewable low-grade heat: From the conceptual design to experimental results

An exergy-based analysis applied to ideal thermochemical dipoles allowed to design an original process that could use low-grade energy, produced from a thermal solar collector at around 70 °C, to provide low-temperature cold, below −23 °C, in order to store deep-frozen food. The ideal coefficient of performance (COP) of this system is 0.5 and the exergetic yield is 1. Taking into account the process enthalpies and the sensible heat of the reactants, the COP_thermo is 0.17. The process functioning is described in this paper. It alternates between a regeneration mode during daytime and cold production mode during night-time. An experimental prototype was designed and built. It proved the feasibility of the concept and showed an experimental COP of about 0.06, which is similar to the up-to-date solar cooling systems, but at higher cold temperatures. The mean annual exergetic yield of the process is about 0.06.     

Cathodic behaviour of zirconium and its alloys in concentrated hot sulphuric media

Potentiokinetic investigations show a rapid increase in the rate of corrosion of zirconium and its alloys in H₂SO₄ as its concentration rises above 70%. The rate of dissolution increases with temperature. The apparent activation energy is approximately 83.6 kJ/mol. The cathodic behaviour is modified as a function of the initial cathodic potential value and the length of time that it is applied. These modifications are interpreted through the relative positions of the elementary anodic and cathodic curves. A protective film, principally composed of ZrO₂ and ZrH₂, develops during the prolonged application of the initial cathodic potential.