Real-Time Simulation of Indoor Air Flow using the Lattice Boltzmann Method on Graphics Processing Unit

This thesis investigates the usability of the lattice Boltzmann method (LBM) for the simulation of indoor air flows in real-time. It describes the work undertaken during the three years of a Ph.D. study in the School of Mechanical Engineering at the University of Leeds, England. Real-time fluid simulation, i.e. the ability to simulate a virtual system as fast as the real system would evolve, can benefit to many engineering application such as the optimisation of the ventilation system design in data centres or the simulation of pollutant transport in hospitals. And although real-time fluid simulation is an active field of research in computer graphics, these are generally focused on creating visually appealing animation rather than aiming for physical accuracy. The approach taken for this thesis is different as it starts from a physics based model, the lattice Boltzmann method, and takes advantage of the computational power of a graphics processing unit (GPU) to achieve real-time compute capability while maintaining good physical accuracy. The lattice Boltzmann method is reviewed and detailed references are given a variety of models. Particular attention is given to turbulence modelling using the Smagorinsky model in LBM for the simulation of high Reynolds number flow and the coupling of two LBM simulations to simulate thermal flows under the Boussinesq approximation. A detailed analysis of the implementation of the LBM on GPU is conducted. A special attention is given to the optimisation of the algorithm, and the program kernel is shown to achieve a performance of up to 1.5 billion lattice node updates per second, which is found to be sufficient for coarse real-time simulations. Additionally, a review of the real-time visualisation integrated within the program is presented and some of the techniques for automated code generation are introduced. The resulting software is validated against benchmark flows, using their analytical solutions whenever possible, or against other simulation results obtained using accepted method from classical computational fluid dynamics (CFD) either as published in the literature or simulated in-house. The LBM is shown to resolve the flow with similar accuracy and in less time

Towards the generation of synchronized and believable non-verbal facial behaviors of a talking virtual agent

This paper introduces a new model to generate rhythmically relevant non-verbal facial behaviors for virtual agents while they speak. The model demonstrates perceived performance comparable to behaviors directly extracted from the data and replayed on a virtual agent, in terms of synchronization with speech and believability. Interestingly, we found that training the model with two different sets of data, instead of one, did not necessarily improve its performance. The expressiveness of the people in the dataset and the shooting conditions are key elements. We also show that employing an adversarial model, in which fabricated fake examples are introduced during the training phase, increases the perception of synchronization with speech. A collection of videos demonstrating the results and code can be accessed at: https://github.com/aldelb/non_verbal_facial_animation

How cyclic chain topology can reduce the crystallization rate of Poly(3- hexylthiophene) and promote the formation of liquid crystalline phases in comparison with linear analogue chains

We have studied how cyclic topology affects the crystallization and morphology of π-conjugated poly(3- hexylthiophene) (P3HT) molecules by comparing linear and cyclic analogues for the first time, with three different chain lengths. We employ a range of experimental techniques including wide-angle X-ray scattering (WAXS), polarized light optical microscopy (PLOM), differential scanning calorimetry (DSC) and a combination of Polarized Light Optical Microscopy (PLOM) and Spectroscopy (S). The crystallization and melting points, melting/crystallization enthalpies, and overall crystallization kinetics of cyclic P3HTs are found to be substantially lower than their linear counterparts. The results are explained by the higher rigidity of cyclic molecules, as predicted by density functional theory (DFT) calculations, in the low molecular weight range explored here, in comparison with linear P3HT chains. Additionally, we have found that cyclic P3HT can form liquid crystalline phases above their crystalline melting points and a new crystal form at lower temperatures. PLOM, WAXS, DSC and PLOM/S results indicate that cyclic P3HTs display bipolar and concentric nematic textures that disappear at a well-defined nematic-isotropic transition temperature. Such liquid crystalline textures are completely absent in the linear P3HTs analogues studied here. We conclude that the cyclic topology induces the formation of liquid crystalline phases as the rigid P3HT oligomers can self-assemble above their crystalline melting temperatures.J.M. acknowledges support from the Provincial Council of Gipuzkoa under the program Fellow Gipuzkoa and “Fomento San Sebastián” in the framework program “Retorno del Talento Local” Donostia up! 2016. We acknowledge the help of Dr. Jaime Martín and Ms. Sara Marina with the combined Microscopy/Spectroscopy measurements. J.M. and A.J.M. acknowledge funding by Mineco MAT2017- 83014-C2-1-P project. N.D. and O.C. are grateful to the Science Policy Office of the Belgian Federal Government (PAI 7/5) and to the Belgian FRFC-FNRS (n°2.4508.12). O.C. is Research Associates of the F.R.S.-FNRS. G.L. is grateful to the Youth Innovation Promotion Association of the Chinese Academy of Sciences (2015026). D.W. and A.J.M acknowledge the support from the National Natural Science Foundation of China (51820105005). All authors gratefully acknowledge the support of the EU through the H2020-MSCA-RISE-2017-778092 BIODEST project. Technical and human support provided by IZO-SGI, SGIker (UPV/EHU, MICINN, GV/EJ, ERDF and ESF) is gratefully acknowledged for assistance and generous allocation of computational resources

How cyclic chain topology can reduce the crystallization rate of poly(3-hexylthiophene) and promote the formation of liquid crystalline phases in comparison with linear analogue chains

peer reviewe

TAD click chemistry on aliphatic polycarbonates : a first step toward tailor-made materials

peer reviewe

Potential of polymethacrylate pseudo crown ethers as solid state polymer electrolytes

peer reviewe

Real-time flow simulation of indoor environments using lattice Boltzmann method

A novel lattice Boltzmann method (LBM) based 3D computational fluid dynamics (CFD) technique has been implemented on the graphics processing unit (GPU) for the purpose of simulating the indoor environment in real-time. We study the time evolution of the turbulent airflow and temperature inside a test chamber and in a simple model of a four-bed hospital room. The predicted results from LBM are compared with traditional CFD based large eddy simulations (LES). Reasonable agreement between LBM results and LES method is observed with significantly faster computational times

Auto-assemblage par liaisons hydrogène de systèmes p-conjugués (application de la tectonique moléculaire à la réalisation de dispositifs optoélectroniques)

Les concepts de la tectonique moléculaire par liaisons hydrogène de molécules p-conjuguées ont été appliqués à la réalisation de dispositifs optoélectroniques tels que les diodes électroluminescentes et les cellules photovoltaïques organiques. Des couches actives d'OLED's ont été élaborées avec succès (Lm = 1200 Cd.m-2) par auto assemblage de tectons tétraédriques constitués d'un coeur saturé C(CH2-OR)4 porteur de quatre segments pi conjugués fonctionnalisés par des motifs d'association diaminotriazine. Une seconde approche innovante a été proposée pour réaliser des diodes. Elle met en oeuvre l'association par liaisons hydrogène d'un fluorophore phénylènevinylène central fonctionnalisé par des fonctions imides terrminales (motifs de reconnaissance ADA de liaisons hydrogène) et de deux tectons volumineux dotés d'une unité de reconnaissance DAD complémentaires. L'utilisation de la tectonique moléculaire pour la réalisation de couches actives de cellules solaires par auto-assemblage par liaisons hydrogène de chromophores de type donneur et accepteur d'électron à été brièvement abordéeMONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Perception Multimodale des Sons Aériens et des Vibrations Aquatiques chez les Crocodiles

Bien que vivants aussi bien sur terre que dans l’eau, le champ de vision des crocodiles est limité en particulier lorsqu’ils sont sous l’eau. Afin de localiser précisément leurs proies, les crocodiles sont donc amenés à utiliser d’autres modalités sensorielles. Ils sont dotés de nombreux récepteurs mécano-sensoriels affleurant leur peau. Selon les espèces, ces récepteurs sensoriels sont situés soit seulement sur leur tête et leur mâchoire soit sur l’ensemble du corps. Par ailleurs, les crocodiles sont des animaux communicants acoustiquement qui sont connus pour avoir une ouïe très développée aussi bien dans l’eau que sur terre. S’il est donc bien établi que les crocodiles perçoivent les sons ainsi que les vibrations se propageant à la surface de l’eau, nous ne savons pas encore dans quelle mesure ils sont capables d’intégrer ces deux informations. Cette étude a été réalisée avec neuf jeunes crocodiles du Nil au Crocoparc d’Agadir. Le but était de reproduire artificiellement, grâce à des haut-parleurs et à des dispositifs vibratoires, la présence d’un autre jeune crocodile et d’observer les réponses comportementales. Cette expérience a plusieurs objectifs : déterminer dans quelle mesure les crocodiles sont capables d’utiliser simultanément des stimulations auditives et vibratoires, étudier l’éventuelle dominance d’une modalité perceptive sur l’autre et enfin déterminer si ces stimulations peuvent être perceptivement liées entre elles (i.e. perçues comme provenant de la même source)

Mitigation of gender bias in automatic facial non-verbal behaviors generation

Research on non-verbal behavior generation for social interactive agents focuses mainly on the believability and synchronization of non-verbal cues with speech. However, existing models, predominantly based on deep learning architectures, often perpetuate biases inherent in the training data. This raises ethical concerns, depending on the intended application of these agents. This paper addresses these issues by first examining the influence of gender on facial non-verbal behaviors. We concentrate on gaze, head movements, and facial expressions. We introduce a classifier capable of discerning the gender of a speaker from their non-verbal cues. This classifier achieves high accuracy on both real behavior data, extracted using state-of-the-art tools, and synthetic data, generated from a model developed in previous work.Building upon this work, we present a new model, FairGenderGen, which integrates a gender discriminator and a gradient reversal layer into our previous behavior generation model. This new model generates facial non-verbal behaviors from speech features, mitigating gender sensitivity in the generated behaviors. Our experiments demonstrate that the classifier, developed in the initial phase, is no longer effective in distinguishing the gender of the speaker from the generated non-verbal behaviors