9,951 research outputs found
Introduzione
No full textRagione” e “razionalità” sono oggi nozioni problematiche: considerate a lungo, nella storia del pensiero occidentale, come tratti distintivi dell’uomo e della civiltà euro-americana, da un certo punto in poi sono state messe in discussione e lacerate dalla crisi e dal malessere di quest’ultima. Alla luce delle controversie più recenti e delle riflessioni sul tema sviluppate nella prima metà del Novecento, questo libro si propone di riaprire la querelle sulla ratio con l’intento di mettere in luce – attraverso una serie di “casi di studio” – la grana sottile dei molteplici significati e usi della nozione di ragione, ma anche di interrogarsi sulle differenti “epoche” della ragione provando a ricostruirne la “storia”. I saggi contenuti in questo volume, dunque, contestualizzano e analizzano le accezioni e le ambiguità del termine ratio e dei suoi derivati nel quadro delle molteplici discussioni che ne hanno ritmato la storia a partire dalla prima modernità, quando il concetto assunse nuove configurazioni rispetto agli usi attestati nel pensiero antico e medioevale, sino al dibattito contemporaneo
Backward Stochastic Differential Equations driven by càdlàg martingales
No full textBackward stochastic differential equations (BSDEs) arise in many financial problems. Although there exists a growing number of papers considering general financial markets, the theory of BSDEs has been developed just in the Brownian setting. We consider BSDEs driven by an R(d)-valued cadlag martingale and we study the properties of the solutions in the case of a, possibly nonuniform, Lipschitz generator
Trust in Global Computing
No full textWe discuss a formal model for trust in Global Computing scenarios, focusing on the aspects of trust formation, evolution, and propagation. We focus on a particular abstract model, and illustrate its applicability on a simple example. We also discuss a possible operational model for trust based systems
Taxe carbone globale, effet taille de marché et mobilité des firmes
No full textNous analysons l'impact et les déterminants d'une taxe carbone globale dans une économie imparfaitement intégrée composée de pays de différente taille. A l'aide d'un modèle de commerce et de localisation, nous montrons tout d'abord que la concentration de firmes dans le pays disposant d'un avantage de taille de marché accroît les émissions totales de C O2 . L'introduction d'une taxe carbone globale conduit alors à des délocalisations de firmes du grand pays vers le petit pays de sorte que même fixée à un taux unique, une fiscalité carbone ne serait pas neutre du point de vue de la géographie économique. Enfin, parce qu'elles conduisent à une réduction des émissions mondiales de C O2 , ces relocalisations améliorent l'effcacité environnementale de la taxe carbone.fiscalité environnementale; mobilité des firmes; intégration économique
A lab-scale cold flow model reactor to investigate near-wall particle segregation relevant to entrained-flow slagging coal gasifiers
No full textThis paper reports on preliminary results of an experimental investigation aimed at the development of a phenomenological model of the fate of coal/ash particles in entrained-flow slagging coal gasifiers. The study specifically addresses the interaction between the lean-dispersed particle phase and the reactor walls, and the establishment of a particle segregated phase in the near-wall region of the gasifier. Better mechanistic understanding of particle–wall interaction patterns in entrained-flow gasifiers is pursued using the tool of physical modeling. To this end a lab-scale cold flow reactor (0.04 m-ID) has been designed and set up, where molten wax is air-atomized (droplets of 50–100 μm size) into a mainstream of air to simulate the near-wall fate of char/ash particles in a real hot environment. Preliminary characterization of the hydrodynamics of the lean-dispersed phase, of its interaction with the wall, of the build-up of the liquid wall layer has been accomplished with a focus on the “sticky wall–sticky particle” subregime.
The particle deposition rate at the wall and the partitioning of wax droplets between the lean-dispersed phase and the wall liquid layer have been assessed under a range of operating conditions. Temperatures of the atomized wax, of the mainstream air and of the reactor wall have been set in a range of values (120–155 °C) at which the wax was fluid. Experiments with wax feeding rate of 0.2 g s−1 and flow rate of atomizing air in the order of 0.30 m3 h−1 demonstrated that the fractional mass of wax in the dispersed phase decreased from 91% to 12% as the reactor length increased from 0.03 m to 0.27 m. The velocity of the descending wall liquid layer, whose thickness was in the order of 0.2 mm, ranged between 3 mm s−1 and 6 mm s−1. The effects of the flow rate of atomization air and of the nozzle temperature were limited
Saccadic eye movements in the dark while performing an automatized sequential high-speed sensorimotor task
No full textFoerster RM, Carbone E, Koesling H, Schneider WX. Saccadic eye movements in the dark while performing an automatized sequential high-speed sensorimotor task. Journal of Vision. 2012;12(2)(8):1-15.Saccades during object-related everyday tasks select visual information to guide hand movements. Nevertheless, humans can perform such a task in the dark provided it was automatized beforehand. It is largely unknown whether and how saccades are executed in this case. Recently, a long-term memory (LTM)-based direct control mode of attention during the execution of well-learned sensorimotor tasks, which predicts task-relevant saccades in the dark, was proposed (R. M. Foerster, E. Carbone, H. Koesling, & W. X. Schneider, 2011). In the present study, participants performed an automatized speed-stacking task in the dark and in the light while their eye movements were recorded. Speed stacking is a sequential high-speed sensorimotor object manipulation task. Results demonstrated that participants indeed made systematic eye movements in the dark. Saccadic scan paths and the number of fixations were highly similar across illumination conditions, while fixation rates were lower and fixation durations were longer in the dark. Importantly, the eye reached a location ahead of the hands even in the dark. Finally, neither eye–hand dynamics nor saccade accuracy correlated with hand movement durations in the dark. Results support the hypothesis of an LTM-based mode of attention selection during the execution of automatized sequential high-speed sensorimotor tasks
Coverage effects on phenol adsorption on Si(100)2 x 1 as: A first principle calculation
No full textWe investigated the adsorption of a 6-dimers Si(100)2 x 1 surface as a function of coverage and adsorption type (molecular/dissociative) by first principle calculations. in particular, we performed calculations on models with 2, 3, 4 and 6 phenol molecules, corresponding to coverage Theta = 0.34, 0.5, 0.67 and 1. We found that total adsorption energy, when at least one phenol is in a molecular state is lower than the sum of the corresponding singly adsorbed molecules. The dissociative adsorption of multiple molecules, both in parallel and switched configuration is most favoured for a coverage Theta = 0.34 (2.6 eV per adsorbed molecule). This values decreases to 2.0 eV and remains constant till the coverage 1 is reached. The energy barrier for the molecular-to-dissociated transition of a phenol molecule, in presence of another dissociatively adsorbed molecule is similar to 0.008 eV and it is similar to the value in case of single adsorption. Possible hydrogen displacements were also considered. (C) 2008 Elsevier B.V. All rights reserved
C 1s core-level photoemission spectra of stilbene on Si(100)2x1 surface from first-principles calculations
No full textAdsorption of the cis and trans stilbene on the Si(100)2 x 1 surface was studied using plane waves density functional theory (DFT). Configurations across a silicon dimer, along the dimers and along the channels between dimers were probed for the two isomers. Trans and cis stilbene both bind preferentially across the dimers. In the former case only the ethylenic carbon atoms are involved and the aromatic character is preserved. In the latter case the adsorption interaction involves also the two phenyl rings with the conversion to two 1,3-cyclohexadiene, yielding a more stable local minimum. The corresponding calculated C 1s core level shifts are distributed in an energy range of about 2.5 eV. The overall shape of the spectra of the two adsorbed isomers shows differences consistent with chemical changes observed upon adsorption. There is a good agreement between the simulated and the experimentally observed spectrum of trans stilbene on the Si surface
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