88 resultados para Computer Simulation
Resumo:
Brain-computer interfaces (BCIs) are becoming more and more popular as an input device for virtual worlds and computer games. Depending on their function, a major drawback is the mental workload associated with their use and there is significant effort and training required to effectively control them. In this paper, we present two studies assessing how mental workload of a P300-based BCI affects participants" reported sense of presence in a virtual environment (VE). In the first study, we employ a BCI exploiting the P300 event-related potential (ERP) that allows control of over 200 items in a virtual apartment. In the second study, the BCI is replaced by a gaze-based selection method coupled with wand navigation. In both studies, overall performance is measured and individual presence scores are assessed by means of a short questionnaire. The results suggest that there is no immediate benefit for visualizing events in the VE triggered by the BCI and that no learning about the layout of the virtual space takes place. In order to alleviate this, we propose that future P300-based BCIs in VR are set up so as require users to make some inference about the virtual space so that they become aware of it,which is likely to lead to higher reported presence.
Resumo:
By means of computer simulations and solution of the equations of the mode coupling theory (MCT),we investigate the role of the intramolecular barriers on several dynamic aspects of nonentangled polymers. The investigated dynamic range extends from the caging regime characteristic of glass-formers to the relaxation of the chain Rouse modes. We review our recent work on this question,provide new results, and critically discuss the limitations of the theory. Solutions of the MCT for the structural relaxation reproduce qualitative trends of simulations for weak and moderate barriers. However, a progressive discrepancy is revealed as the limit of stiff chains is approached. This dis-agreement does not seem related with dynamic heterogeneities, which indeed are not enhanced by increasing barrier strength. It is not connected either with the breakdown of the convolution approximation for three-point static correlations, which retains its validity for stiff chains. These findings suggest the need of an improvement of the MCT equations for polymer melts. Concerning the relaxation of the chain degrees of freedom, MCT provides a microscopic basis for time scales from chain reorientation down to the caging regime. It rationalizes, from first principles, the observed deviations from the Rouse model on increasing the barrier strength. These include anomalous scaling of relaxation times, long-time plateaux, and nonmonotonous wavelength dependence of the mode correlators.
Resumo:
The computer simulation of reaction dynamics has nowadays reached a remarkable degree of accuracy. Triatomic elementary reactions are rigorously studied with great detail on a straightforward basis using a considerable variety of Quantum Dynamics computational tools available to the scientific community. In our contribution we compare the performance of two quantum scattering codes in the computation of reaction cross sections of a triatomic benchmark reaction such as the gas phase reaction Ne + H2+ %12. NeH++ H. The computational codes are selected as representative of time-dependent (Real Wave Packet [ ]) and time-independent (ABC [ ]) methodologies. The main conclusion to be drawn from our study is that both strategies are, to a great extent, not competing but rather complementary. While time-dependent calculations advantages with respect to the energy range that can be covered in a single simulation, time-independent approaches offer much more detailed information from each single energy calculation. Further details such as the calculation of reactivity at very low collision energies or the computational effort related to account for the Coriolis couplings are analyzed in this paper.
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We present molecular dynamics (MD) simulations results for dense fluids of ultrasoft, fully penetrable particles. These are a binary mixture and a polydisperse system of particles interacting via the generalized exponential model, which is known to yield cluster crystal phases for the corresponding monodisperse systems. Because of the dispersity in the particle size, the systems investigated in this work do not crystallize and form disordered cluster phases. The clusteringtransition appears as a smooth crossover to a regime in which particles are mostly located in clusters, isolated particles being infrequent. The analysis of the internal cluster structure reveals microsegregation of the big and small particles, with a strong homo-coordination in the binary mixture. Upon further lowering the temperature below the clusteringtransition, the motion of the clusters" centers-of-mass slows down dramatically, giving way to a cluster glass transition. In the cluster glass, the diffusivities remain finite and display an activated temperature dependence, indicating that relaxation in the cluster glass occurs via particle hopping in a nearly arrested matrix of clusters. Finally we discuss the influence of the microscopic dynamics on the transport properties by comparing the MD results with Monte Carlo simulations.
Resumo:
From 6 to 8 November 1982 one of the most catastrophic flash-flood events was recorded in the Eastern Pyrenees affecting Andorra and also France and Spain with rainfall accumulations exceeding 400 mm in 24 h, 44 fatalities and widespread damage. This paper aims to exhaustively document this heavy precipitation event and examines mesoscale simulations performed by the French Meso-NH non-hydrostatic atmospheric model. Large-scale simulations show the slow-evolving synoptic environment favourable for the development of a deep Atlantic cyclone which induced a strong southerly flow over the Eastern Pyrenees. From the evolution of the synoptic pattern four distinct phases have been identified during the event. The mesoscale analysis presents the second and the third phase as the most intense in terms of rainfall accumulations and highlights the interaction of the moist and conditionally unstable flows with the mountains. The presence of a SW low level jet (30 m s-1) around 1500 m also had a crucial role on focusing the precipitation over the exposed south slopes of the Eastern Pyrenees. Backward trajectories based on Eulerian on-line passive tracers indicate that the orographic uplift was the main forcing mechanism which triggered and maintained the precipitating systems more than 30 h over the Pyrenees. The moisture of the feeding flow mainly came from the Atlantic Ocean (7-9 g kg-1) and the role of the Mediterranean as a local moisture source was very limited (2-3 g kg-1) due to the high initial water vapour content of the parcels and the rapid passage over the basin along the Spanish Mediterranean coast (less than 12 h).
Resumo:
A la UdGhi ha 2 aerogeneradors minielics: el del terrat del P2 i un de ms petit allaboratori denergies. Aquest segon aerogenerador minielic s el que sha utilitzat en aquestprojecte. Es tracta dun Air-X de la casa Technosun amb les segents caracterstiques:- T un pes de 6Kg, un radi de 0,582 metres, un TSR de 8,8 i unapotncia de 545W.- Perfil de la pala tipus SD2030.- Velocitat dengegada de 3m/s.-Amb vents forts (ms de 15m/s) un dispositiu electrnic redueix lavelocitat fins a 600rpm, reduint les crregues sobre la turbina i lestructuramentre encara segueix produint energia.- Baix manteniment. Noms consta de dues parts mbils.Lobjecte que sha plantejat per aquest projecte ha estat trobar la corbade potncia del minigenerador Air-X mitjanant simulaci amb CFD, iutilitzant noms les dades geomtriques de laparell
Resumo:
Una empresa familiar dembotits ecolgics especialitzada en lelaboraci de xori, volampliar la seva producci. T com apart clau el procs destufatge i lassecament. Aquests processos, que tenen lloc alsassecadors, consisteixen en fer re-circular aire a unes temperatures determinades durant unscerts temps, refredant aquest aire quan surt de la sala per extreuren part del vapor daiguaque cont, i tornant-lo a escalfar per poder absorbir ms aigua en tornar entrar a la sala.Labast daquest projecte consisteix en la descripci del funcionament dels assecadors,i la realitzaci de simulacions de flux daire i temperatura per tal de poder optimitzar unassecador concret. Dins aquest assecador es faran modificacions com pot ser lalada lliure quequeda entre la filera ms elevada de xori i el sostre o el radi inferior que tenen aquestsaparells per tal dobtenir una geometria ptima duna sala dassecatge. Lestudi que es duu a terme consta del comportament del flux daire i del flux detemperatura per tal de poder observar els punts crtics i poder determinar els parmetres queinflueixen en el seu bon funcionament
Resumo:
Previous studies have examined the experience of owning a virtual surrogate body or body part through specific combinations of cross-modal multisensory stimulation. Both visuomotor (VM) and visuotactile (VT) synchronous stimulation have been shown to be important for inducing a body ownership illusion, each tested separately or both in combination. In this study we compared the relative importance of these two cross-modal correlations, when both are provided in the same immersive virtual reality setup and the same experiment. We systematically manipulated VT and VM contingencies in order to assess their relative role and mutual interaction. Moreover, we present a new method for measuring the induced body ownership illusion through time, by recording reports of breaks in the illusion of ownership ("breaks") throughout the experimental phase. The balance of the evidence, from both questionnaires and analysis of the breaks, suggests that while VM synchronous stimulation contributes the greatest to the attainment of the illusion, a disruption of either (through asynchronous stimulation) contributes equally to the probability of a break in the illusion.
Resumo:
El artculo describe la simulacin por ordenador digital de los efectos visuales en el organismo humano sometido a aceleraciones prositivas en sentido craneocaudal. Los resultados obtenidos posibilitan la utilizacin de un mtodo complementario para la evaluacin de la tolerancia a las aceleraciones positivas.
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The speed of traveling fronts for a two-dimensional model of a delayed reactiondispersal process is derived analytically and from simulations of molecular dynamics. We show that the one-dimensional (1D) and two-dimensional (2D) versions of a given kernel do not yield always the same speed. It is also shown that the speeds of time-delayed fronts may be higher than those predicted by the corresponding non-delayed models. This result is shown for systems with peaked dispersal kernels which lead to ballistic transport
Resumo:
Elmercat de jocs i de pellcules d'entreteniment demana constantment entornsms realistes i efectes que sorprenguin a l'espectador.Els grfics 3D interactius (per exemple, dels jocs) han vist una evolucisorprenent en les dues ltimes dcades. Hem passat de representacions moltesquemtiques i simplificades dels entorns, a una qualitat visual que aviatser indistingible de la realitat. El projecte tracta de desenvolupar un motor 3D des de zero. Es podria haver utilitzatun motor 3D ja disponible com a base, com per exemple el popular Unity,per sha decidit crear-lo ja que aix dna l oportunitat de conixer com funcionen els motoscomercials i provar noves idees. En resum, s un treball difcil, per moltenriquidor, la qual cosa comporta una gran motivacio.Shan utilitzat noves tecnologies. No noms sha volgut desenvoluparun motor 3D des de zero, si no que shan volgut provar noves llibreries grfiques i nous formats de dades 3d. El mercat t fora oferta de les duess, per la qualcosa sha aprofitat l oportunitat per aprendre duess tecnologies noves.El procs de desenvolupar un projecte utilitzant tecnologies desconegudes permetr aprendre els seus punts forts i febles, podent fer-neuna anlisi crtica, que d'altra manera no es tindria.Finalment, sha implementat i comparat quatre algorismes de shading.La selecci dels quatre algorismes ha estat en base a les diferentsnecessitats que intenten cobrir. El primer, el Forward Shading, s l'algorismeclssic, utilitzat des de fa dcades, per que tericament escala malament respecte a la quantitat de llums. El segon, el Deferred Shading, tericament,escala molt b amb moltes llums, per t un cost base elevat, i un consum altde memria. El tercer, el Deferred Lighting, s una variaci de l'anterior queintenta reduir el cost base i l'ss de memria. L'ltim, el Inferred Lighting,intenta explotar la baixa freqncia de la illuminaci dels entorns 3D, persuportar una gran quantitat de llums amb un molt bon rendiment.Un cop implementats aquests quatre algorismes, shan pogut compararrespecte el seu s de la GPU, i el seu comportament en diferents tipusd'escenes, per tal de tenir una visi global de quin algorisme s adequat encada situaci
Resumo:
La simulaci de la realitat s un fenomen que va sorgir fa uns anys per tal de predir esdeveniments sense haver de malbaratar recursos. El problema inicial de la simulaci va ser la necessitat de simplificar la realitat a causa de la manca de capacitat dels ordinadors de lpoca. Amb aquest projecte volem ajudar, per exemple, a estudis cientfics sobre la difusi de la contaminaci en grans nuclis a causa de lefecte del vent, clculs de trajectries amb forces externes degudes al vent, o incorporar en el mn de la multimdia efectes realistes de vent. El principal objectiu daquest projecte s desenvolupar un sistema que permeti realitzar simulacions realistes de vent per un paisatge 2D, i estudiar com el vent s veu afectat per la geometria de lescena. Un punt important, s que tot ha de ser en temps real. Per aconseguir-ho, utilitzarem tcniques basades en el mtode de Lattice-Boltzmann, el qual consisteix en una xarxa regular que representa el fluid en posicions discretes, i estudiar com flueix. Escollint els parmetres correctes de la simulaci, es pot demostrar que aquest mtode convergeix a les equacions continues de Navier-Stokes, les qual sn les ms importants per descriure el comportament macroscpic dun fluid. Per accelerar tots els clculs, utilitzarem la capacitat i la potencia de les targes grfiques, ajustarem lalgorisme per poder-lo utilitzar en parallel, tot tenint en compte les restriccions de les GPUs. Tamb haurem de generar un sistema per poder llegir les escenes 2D sobre les que realitzarem la simulaci. Finalment, haurem de pintar el vent per tal de poder visualitzar el resultat de la simulaci
Resumo:
Un bon sistema dil.luminaci juga un paper molt important per tal que els videojocs siguin realistes i atractius per a lusuari. El projecte intenta optimitzar el sistema dil.luminaci de manera que la crrega que representa per al sistema sigui inferior, sense haver de renunciar a la qualitat que tindrem sense fer servir aquest sistema. Amb dos objectius molt concrets: entendre i implementar lalgoritme de lightcuts i aconseguir una optimitzaci en una escena utilitzant aquest algoritme
