Effects of Crossover Operators on Genetic Algorithms for the Extraction of Solar Cell Parameters from Noisy Data

This study analyzed the accuracy of solar cell modeling parameters extracted from noisy data using Genetic Algorithms (GAs). Three crossover operators (XOs) were examined, namely the Uniform (UXO), Arithmetic (AXO), and Blend (BXO) operators. The data used were an experimental benchmark cell and a simulated curve where noise levels (p) from 0 to 10% were added. For each XO, the analysis was carried out by running GAs 100 times and varying p and population size (Npop). Simulation results showed that UXO and AXO suffered from premature convergence and failed to provide parameters with good precision even with very high Npop, although they provided good fitting. In all analyzed cases, BXO outperformed UXO and AXO and the results showed that it can compete with the most efficient methods. For the benchmark curve, BXO reproduced the best RMSE found in the literature (0.7730062 mA) while providing the exact values of the parameters and a very low RMSE (1E-13) for the clean curve (p=0). For noisy curves, the errors of the extracted parameters were smaller than 10% for p lower than or equal to 6%. For higher values of p, the errors were smaller than 30%

Investigations of reactive transport processes using geological labs on chip with applications to geological subsurface exploitation : (CO2 geological storage)

L'exploitation du sous-sol géologique, soit pour extraire des ressources naturelles (eau, chaleur, gaz, substances minérales utiles, etc.), soit pour injecter/stocker des ressources (eau, chaleur, hydrocarbures) ou des composés indésirables (eaux et saumures industrielles, déchets radioactifs, gaz acides, CO2, etc.) nécessite la maîtrise des processus de transport réactif dans les milieux géologiques poreux et fracturés à différentes échelles de temps et d'espace. Cependant, à ce jour, peu de choses sont connues et maîtrisées concernant la compréhension des mécanismes physico-chimiques et cinétiques aux interfaces à l'origine des transferts de masse entre phases (minéraux - eau - gaz). En effet, plusieurs questions clés et verrous scientifiques limitent l'exploitation des connaissances actuelles, relativement incohérentes et plutôt éparses, et empêchent toute généralisation des approches théoriques disponibles pour pouvoir modéliser le devenir de ces systèmes sous influence des intrusions humaines.Ainsi, dans le cadre de ce travail de thèse, nous avons étudié, à l'échelle du pore, les processus de précipitation et de dissolution de minéraux modèles représentatifs d’environnements géologiques profonds : les carbonates et les sulfates. L’objectif est ici de comprendre les mécanismes physiques et chimiques à l'interface des différentes phases (minéraux / phase aqueuse).Pour ce faire, nous avons utilisé des réacteurs microfluidiques couplés à différentes techniques de caractérisation in-situ (i.e. imagerie optique, microscopie confocal, etc.) pour étudier les mécanismes de précipitation et de carbonatation du gypse. Nous avons contrôlé expérimentalement certains paramètres susceptibles d'affecter les vitesses de réaction, comme la concentration en éléments alcalino-terreux (Ca, Mg) et les mécanismes de transport (convectifs / diffusifs). Des cristaux de gypse (CaSO4.2H2O) ont d'abord été précipités dans des microcavités sur puce en mélangeant des solutions aqueuses réactives de CaCl2 et de Na2SO4. L'état de saturation du fluide réactif (0-0.86) par rapport aux phases de sulfate de calcium a été calculé à l'aide du logiciel PHREEQC. Par la suite, l’injection contrôlée de carbonates au sein du système entraîne un mécanisme de carbonatation du gypse, qui a été suivi en temps réel. Dans les expériences réalisées, le transport a volontairement été limité à de la diffusion en contrôlant l’hydrodynamique du système (réalisation de designs microfluidique adaptés). Il a été mis en évidence un mécanisme de carbonatation en deux étapes comprenant une phase de dissolution du gypse suivi d’une phase de précipitation du carbonate de calcium (calcite et vatérite).Les résultats expérimentaux ont été analysés numériquement pour extrapoler l'évolution réelle de la surface spécifique des minéraux par traitement d'image. Cette évolution a ensuite été utilisée pour la modélisation thermocinétique à l'aide du logiciel PHREEQC V3. Cette modélisation géochimique a permis de calculer la constante cinétique de dissolution du gypse, soit 8 × 10-12 mol.cm-2.s-1. Il a été montré une bonne adéquation entre les tendances observées expérimentalement et celles obtenues par modélisation, ouvrant la possibilité d'études futures utilisant la méthodologie proposée au cours de cette thèse (transport multiphasique, prise en compte des phénomènes de transport convectif, travail sous pression...).The exploitation of the geological subsurface, either to extract natural resources (water, heat, gas, useful mineral substances, etc.), or to inject/store resources (water, heat, hydrocarbons) or undesirable compounds (industrial water and brine, radioactive waste, acid gases, CO2, etc.) requires the control of reactive transport processes in porous and fractured geological media at different time and space scales. However, to date, little is known and mastered concerning the understanding of physicochemical and kinetic mechanisms at the interfaces at the origin of mass transfers between phases (minerals - water - gas). Indeed, several key questions and scientific barriers limit the exploitation of current knowledge, relatively inconsistent and rather scattered, and prevent any generalization of theoretical approaches available to model the fate of these systems under the influence of human intrusions.Thus, in the framework of this thesis, we have studied, at the pore scale, the precipitation and dissolution processes of model minerals representative of deep geological environments: carbonates and sulfates. The objective here is to understand the physical and chemical mechanisms at the interface of the different phases (mineral / aqueous phase).To do so, we used microfluidic reactors coupled to different in-situ characterization techniques (i.e. optical imaging, confocal microscopy, etc.) to study the precipitation and carbonation mechanisms of gypsum. We have experimentally controlled some parameters that may affect the reaction rates, such as the concentration of alkaline earth minerals (Ca, Mg) and the transport mechanisms (convective / diffusive). Gypsum crystals (CaSO4.2H2O) were first precipitated in on-chip microcavities by mixing reactive aqueous solutions of CaCl2 and Na2SO4. The saturation state of the reactive fluid with respect to the calcium sulfate phases was calculated using PHREEQC software. Subsequently, the controlled injection of carbonates within the system results in a gypsum carbonation mechanism, which was monitored in real time. In the experiments, the transport was voluntarily limited to diffusion by controlling the hydrodynamics of the system (realization of adapted microfluidic designs). A two-step carbonation mechanism was demonstrated, including a gypsum dissolution phase followed by a calcium carbonate precipitation phase (calcite and vaterite).The experimental results were numerically analysed to extrapolate the real evolution of the specific surface of the minerals by image processing. This evolution was then used for thermokinetic modelling using the PHREEQC V3 software. This modelling was used to calculate the dissolution kinetic constant for gypsum, i.e. 8 × 10-12 mol.cm-2.s-1. It was shown that there was a good match between the trends observed experimentally and those obtained by modelling, opening up the possibility of future studies using the methodology proposed during this thesis (multiphase transport, consideration of convective transport phenomena, work under pressure, etc.)

Investigations of reactive transport processes using geological labs on chip with applications to geological subsurface exploitation : (CO2 geological storage)

L'exploitation du sous-sol géologique, soit pour extraire des ressources naturelles (eau, chaleur, gaz, substances minérales utiles, etc.), soit pour injecter/stocker des ressources (eau, chaleur, hydrocarbures) ou des composés indésirables (eaux et saumures industrielles, déchets radioactifs, gaz acides, CO2, etc.) nécessite la maîtrise des processus de transport réactif dans les milieux géologiques poreux et fracturés à différentes échelles de temps et d'espace. Cependant, à ce jour, peu de choses sont connues et maîtrisées concernant la compréhension des mécanismes physico-chimiques et cinétiques aux interfaces à l'origine des transferts de masse entre phases (minéraux - eau - gaz). En effet, plusieurs questions clés et verrous scientifiques limitent l'exploitation des connaissances actuelles, relativement incohérentes et plutôt éparses, et empêchent toute généralisation des approches théoriques disponibles pour pouvoir modéliser le devenir de ces systèmes sous influence des intrusions humaines.Ainsi, dans le cadre de ce travail de thèse, nous avons étudié, à l'échelle du pore, les processus de précipitation et de dissolution de minéraux modèles représentatifs d’environnements géologiques profonds : les carbonates et les sulfates. L’objectif est ici de comprendre les mécanismes physiques et chimiques à l'interface des différentes phases (minéraux / phase aqueuse).Pour ce faire, nous avons utilisé des réacteurs microfluidiques couplés à différentes techniques de caractérisation in-situ (i.e. imagerie optique, microscopie confocal, etc.) pour étudier les mécanismes de précipitation et de carbonatation du gypse. Nous avons contrôlé expérimentalement certains paramètres susceptibles d'affecter les vitesses de réaction, comme la concentration en éléments alcalino-terreux (Ca, Mg) et les mécanismes de transport (convectifs / diffusifs). Des cristaux de gypse (CaSO4.2H2O) ont d'abord été précipités dans des microcavités sur puce en mélangeant des solutions aqueuses réactives de CaCl2 et de Na2SO4. L'état de saturation du fluide réactif (0-0.86) par rapport aux phases de sulfate de calcium a été calculé à l'aide du logiciel PHREEQC. Par la suite, l’injection contrôlée de carbonates au sein du système entraîne un mécanisme de carbonatation du gypse, qui a été suivi en temps réel. Dans les expériences réalisées, le transport a volontairement été limité à de la diffusion en contrôlant l’hydrodynamique du système (réalisation de designs microfluidique adaptés). Il a été mis en évidence un mécanisme de carbonatation en deux étapes comprenant une phase de dissolution du gypse suivi d’une phase de précipitation du carbonate de calcium (calcite et vatérite).Les résultats expérimentaux ont été analysés numériquement pour extrapoler l'évolution réelle de la surface spécifique des minéraux par traitement d'image. Cette évolution a ensuite été utilisée pour la modélisation thermocinétique à l'aide du logiciel PHREEQC V3. Cette modélisation géochimique a permis de calculer la constante cinétique de dissolution du gypse, soit 8 × 10-12 mol.cm-2.s-1. Il a été montré une bonne adéquation entre les tendances observées expérimentalement et celles obtenues par modélisation, ouvrant la possibilité d'études futures utilisant la méthodologie proposée au cours de cette thèse (transport multiphasique, prise en compte des phénomènes de transport convectif, travail sous pression...).The exploitation of the geological subsurface, either to extract natural resources (water, heat, gas, useful mineral substances, etc.), or to inject/store resources (water, heat, hydrocarbons) or undesirable compounds (industrial water and brine, radioactive waste, acid gases, CO2, etc.) requires the control of reactive transport processes in porous and fractured geological media at different time and space scales. However, to date, little is known and mastered concerning the understanding of physicochemical and kinetic mechanisms at the interfaces at the origin of mass transfers between phases (minerals - water - gas). Indeed, several key questions and scientific barriers limit the exploitation of current knowledge, relatively inconsistent and rather scattered, and prevent any generalization of theoretical approaches available to model the fate of these systems under the influence of human intrusions.Thus, in the framework of this thesis, we have studied, at the pore scale, the precipitation and dissolution processes of model minerals representative of deep geological environments: carbonates and sulfates. The objective here is to understand the physical and chemical mechanisms at the interface of the different phases (mineral / aqueous phase).To do so, we used microfluidic reactors coupled to different in-situ characterization techniques (i.e. optical imaging, confocal microscopy, etc.) to study the precipitation and carbonation mechanisms of gypsum. We have experimentally controlled some parameters that may affect the reaction rates, such as the concentration of alkaline earth minerals (Ca, Mg) and the transport mechanisms (convective / diffusive). Gypsum crystals (CaSO4.2H2O) were first precipitated in on-chip microcavities by mixing reactive aqueous solutions of CaCl2 and Na2SO4. The saturation state of the reactive fluid with respect to the calcium sulfate phases was calculated using PHREEQC software. Subsequently, the controlled injection of carbonates within the system results in a gypsum carbonation mechanism, which was monitored in real time. In the experiments, the transport was voluntarily limited to diffusion by controlling the hydrodynamics of the system (realization of adapted microfluidic designs). A two-step carbonation mechanism was demonstrated, including a gypsum dissolution phase followed by a calcium carbonate precipitation phase (calcite and vaterite).The experimental results were numerically analysed to extrapolate the real evolution of the specific surface of the minerals by image processing. This evolution was then used for thermokinetic modelling using the PHREEQC V3 software. This modelling was used to calculate the dissolution kinetic constant for gypsum, i.e. 8 × 10-12 mol.cm-2.s-1. It was shown that there was a good match between the trends observed experimentally and those obtained by modelling, opening up the possibility of future studies using the methodology proposed during this thesis (multiphase transport, consideration of convective transport phenomena, work under pressure, etc.)

Thermodynamic properties of binary mixtures containing thiaalkanes

Enthalpies of mixing, HE, at 298.15 K were measured for binary RSSR + n-CmH2m + 2 mixtures (R = CH3, C2H5, isO-C3H7 ; m = 6,8, 12, 16) using an isothermal differential microcalorimeter.The experimental data were interpreted quantitatively in terms of surface interchange enthalpies in the zero approximation. Theoretical and experimental HE values compare very well using the same has parameter for R = C2H5 and iSO-C3H7 and a slightly different value for R = CH3 but the same for the whole 77-alkane series C6 through C16. The disordering contributions are relatively small.omparison of the parameters has of RSSR, RSR and (RS)3CR indicates a considerable weakening of the intermolecular forces when the S atoms of a chain are closer or are directly linked

Thermodynamic properties of binary mixtures containing thiaalkanes

Enthalpies of mixing, HE, at 298.15 K were measured for binary R2S + n-CmH2m+2 mixtures (R = CH3, C2H5, n-C3H7, n-C4H9, n-C7H15; m = 6, 8, 12, 16) using a B.C.P. (Anon) isothermal differential microcalorimeter equipped with a special flow mixing unit. The experimental data are interpreted quantitatively in terms of surface interchange enlhalpies in the zero approximation. Theoretical and experimental HE values compare fairly well. However, the deviations show a regular trend which may be explained qualitatively by an endothermic disordering contribution

Investigation of degradation of electrical properties after thermal oxidation of p-type Cz-silicon wafers

In this study we conducted thermal oxidation of Czochralski p-type silicon wafers. The oxidation was carried out at temperatures in the range of 850-1000°C, in a gas mixture of N₂:O₂, in order to deposit a thin layer (10 nm) of thermal silicon dioxide (SiO₂), generally used in the surface passivation of solar cells. The measurements of effective minority carriers lifetime τ_{eff} using the quasi-steady-state photoconductance have shown degradation of different samples after oxidation process. The calculation of surface recombination velocity after the oxidation process at different temperatures, gave the same value of 40 cm s¯¹, showing a low surface recombination velocity and, therefore, a good surface passivation. Finally, a study based on sample illumination technique, allowed us to conclude that our samples are dominated by bulk Shockley-Read-Hall recombination, caused by Fe-related centers, thereby causing the degradation of the lifetime of minority carriers

Structural, elastic, electronic and optical properties of the newly synthesized selenides Tl

Motivated by the growing demand for new performant semiconducting materials, we investigated in detail the structural, elastic, electronic and optical properties of two newly synthesized compounds, namely Tl2CdGeSe4 and Tl2CdSnSe4, using density functional theory calculations. The calculations were performed relativistically, including the spin–orbit coupling (SOC). The computed equilibrium structural parameters are in excellent agreement with available measurements. Note that the calculations of all the considered properties were performed with the theoretically obtained equilibrium lattice parameters. The predicted monocrystalline and polycrystalline elastic constants reveal that the studied compounds are soft, ductile, mechanically stable and substantially structurally and elastically anisotropic materials. Our calculations using the Tran-Blaha modified Becke-Johnson potential with the inclusion of SOC show that Tl2CdGeSe4 and Tl2CdSnSe4 are direct bandgap semiconductors. The inclusion of SOC is found to reduce the fundamental bandgap of Tl2CdGeSe4 from 1.123 to 0.981 eV and that of Tl2CdSnSe4 from 1.097 to 0.953 eV. The l-decomposed atom-projected densities of states were calculated to identify the contribution of each constituent atom to the electronic states in the energy bands. The upper valence subband predominantly comes from the Se-4p states, while the bottom of the conduction band mainly originates from the Se-4p and Ge-4p/Sn-5p states. The frequency-dependent linear optical parameters, viz., the complex dielectric function, absorption coefficient, refractive index, reflectivity and energy-loss function, were calculated for electromagnetic waves polarized parallel and perpendicular to the c-axis in a wide energy window. An attempt was made to identify the microscopic origin of the peaks and structures observed in the calculated optical spectra