El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / The washing of Panca chili seeds requires innovative solutions that allow controlling this process. It is necessary to handle variables (conductivity, pH, colorimetry) in the face of the challenge of working with small seeds. At present, there are no machines that are dedicated to the washing of this type of seeds, since in many companies this work is done manually, which is not the one indicated because this technique cannot guarantee homogeneity in the seed washing. In addition, direct handling of this type of seeds can cause irritation to the eyes and skin of the person who maintains contact with the seeds. That is why, it is proposed to make a machine to scale by means of a motorized rotary agitator inside a tank, in order to guarantee the homogeneity of the mixture when washing seeds. The present work will allow to determine, among two different types of agitators (axial and radial), which type of agitator is the most efficient in the washing of seeds of Panca chili, to achieve this objective the measurement of pH and electrical conductivity to the water will be carried after the mixture, after stirring. Finally, the analysis of the tests performed on the mixture obtained and washed by each type of agitator allowed to identify the turbine-type radial agitator, like the one that obtained greater efficiency in the washing of seeds, with respect to the helical agitator and pallets, designed for development of this work, in turn, could also confirm that this type of palette with the conductivity control allows to guarantee the homogeneity of the mixture during washing. © 2021, The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG. / Revisión por pares

Esta tese apresenta os resultados de estudo de eletrólitos poliméricos obtidos a partir de agar com o propósito de serem aplicados em dispositivos eletrocrômicos (ECDs). Modificações físico-químicas foram efetuadas no agar através da adição do plastificante glicerol, bem como de formaldeído, além da adição de uma fonte de prótons, a partir de ácido acético, ou uma fonte de íons, utilizando-se LiClO4, para promover a condutividade iônica dos filmes. Foram também preparadas blendas a partir de agar com gelatina, com quitosana e com poli(etileno dióxido de tiofeno):poli(estireno) (PEDOT:PSS) com o objetivo de se obter novos materiais alternativos, para serem utilizados como eletrólitos poliméricos. O estudo revelou que todas as membranas apresentaram-se homogêneas, com estabilidade térmica até 200°C e com a estrutura predominantemente amorfa, com valores de temperatura vítrea em torno de -70 °C e transparência no visível de 90%. O manuseio das amostras obtidas revelou boa maleabilidade e aderência ao vidro. Os valores de condutividade iônica das membranas variaram entre 1x10-6 S/cm e 1,1x10-4 S/cm dependendo da composição e quantidade de ácido ou sal de lítio adicionado. No caso das amostras onde foi adicionado PEDOT:PSS, os resultados de condutividade obtidos foram na ordem de 10-4 S/cm, no entanto as amostras apresentaram a transparência somente de 17%. Foi feito um estudo preliminar, de aplicação dos melhores eletrólitos em ECDs revelando mudança de coloração entre o estado colorido e transparente de 25%, reversível inserção de carga entre 11 e 5,0 mC/cm2 e tempo de coloração de 15 segundos e de descoloração de 2 s. / With the aim to develop new electrochromic devices (ECDs), we present a study on polymer electrolytes obtained from agar. Agar was submitted to physicochemical modifications by adding glycerol as plasticizer and formaldehyde; besides, to promote ionic conductivity of the films, a proton source such as acetic acid, or an ion source, LiClO4, were also added. Moreover new alternative materials to be used as polymer electrolytes composed by blends of agar with gelatin, chitosan and poly (ethylene dioxide thiophene):poly(styrene sulfonate) (PEDOT:PSS) were also prepared and characterized. The study revealed that the membranes were homogeneous, with thermal stability up to 200°C and predominantly amorphous. The glass transition values were found to be around -70 °C and the transparency in the visible region of 90%. The ionic conductivity values were in the range of 1x10-6 S/cm to 1.1x10-4 S/cm, depending on composition and amount of added acid or salt. The ionic conductivity of the samples containing PEDOT:PSS were of the order of 10-4 S/cm, however, the corresponding transparencies were found to be about 17%, only. A preliminary study to qualify the performance of our best electrolytes in ECDs have shown a color change of 25%, reversible inserted charge of 5 to 11 mC/cm2 and coloring/bleaching times of 15 and 2 seconds, respectively.

Numerical estimates of the ability of a green roof to reduce energy consumption in buildings are plagued by a lack of accuracy in thermal properties that are input to the model. An experimental study into the thermal conductivity at different temperatures and moisture contents was performed using four different commercially available substrates for green roofs. In the unfrozen state, as moisture content increased, thermal conductivity increased linearly. In the phase transition zone between +5 ºC and -10ºC, as temperature decreased, thermal conductivity increased sharply during the transition from water to ice. When the substrate was frozen, thermal conductivity varied exponentially with substrate moisture content prior to freezing. Power functions were found between thermal conductivity and temperature (when shifted up by +10.001ºC). Two equally sized, green roof test cells were constructed and tested to compare various roof configurations including a bare roof, varying media thickness for a green roof, and vegetation. The results show that compared with the bare roof, there is a 75% reduction in the interior temperature amplitude for the green roof with 150mm thick substrate. When a sedum mat was added, there’s a 20% reduction in the amplitude of the inner temperature as compared with the cell without sedum mat. / Graduate

La photocatalyse se base sur l’excitation d’un semi-conducteur par des photons d’énergie supérieure ou égale à son gap, générant des paires électron-trous. Celles-ci sont très réactives et susceptibles de réagir à l’interface pour réaliser par exemple l’oxydation totale d’un composé organique. Cette méthode peut être appliquée sur des eaux usées pour éliminer totalement les polluants organiques qui y sont présents. Dans la perspective d’une utilisation du soleil comme source de lumière, cette méthode peut s’avérer très économique et écologique pour le traitement de l’eau.L’interaction lumière-semi-conducteur et la dynamique des porteurs de charge sont des processus physico-chimiques primordiaux pour la photocatalyse, et il est nécessaire de bien les comprendre pour maîtriser le procédé et développer des matériaux plus efficaces. La Time Resolved Microwave Conductivity (TRMC) est une technique qui se base sur la réflexion des micro-ondes sur un semi-conducteur excité qui est directement reliée avec le nombre de porteurs de charge photo-générés. Il s’agit d’un moyen de sonder en temps réel la dynamique des porteurs de charge dans les semi-conducteurs.Ce travail s’inscrit dans le cadre du projet ANR PhotoNorm. Il consiste en une étude par TRMC de dioxyde de titane TiO2 utilisé pour la dépollution de l’eau par photocatalyse. Une partie de cette étude concerne la caractérisation des propriétés opto-électroniques des matériaux, pour lesquels la dynamique des porteurs de charge sera comparée à l’activité photocatalytique. L’effet bénéfique en photocatalyse de la déposition de nanoparticules d'or, d'argent ou bimetallique or-cuivre sur des TiO2 commerciaux sera relié à une capture d’électrons libres observée en TRMC. L’effet bénéfique sur la photocatalyse en lumière visible a été relié à une injection d’électrons dans le TiO2 par des nanoparticules de bismuth. L’autre partie de ce travail consiste en une étude plus fondamentale de la dynamique des porteurs de charge dans des TiO2 commerciaux ou synthétisés dans le cadre du projet PhotoNorm. Il y sera montré l’importance de la longueur d’onde et de l’intensité d’excitation du matériau sur le rendement de génération de porteurs de charge. L’importance des effets de surface et de l’environnement seront aussi mis en évidence de plusieurs façons. La première consiste simplement en un traitement chimique de la surface (lavage), qui peut avoir une grande influence à la fois sur la dynamique des porteurs de charge et sur la photocatalyse, sûrement en lien avec la présence d’impuretés de surface. La seconde consiste à imprégner le TiO2 par des colorants organiques présentant une forte absorption en lumière visible. Les mesures de TRMC sur ces systèmes permettent de mettre en évidence l’interaction entre le semi-conducteur et les molécules extérieures adsorbées à sa surface, notamment l’injection d’électrons du colorant excité vers le semi-conducteur, mais aussi des effets de recombinaison accrus. La troisième méthode consiste à modifier l’atmosphère de travail en TRMC. Il y est observé notamment l’importance de l’oxygène sur la dynamique des porteurs de charge, et notamment les effets de captures d’électrons, phénomènes qui entrent en jeu dans le processus de photocatalyse.Au final, la TRMC s’avère être un bon moyen d’étude de la durée de vie des porteurs de charge dans les semi-conducteurs, qui peut permettre de mieux comprendre les processus fondamentaux associés à la photocatalyse. / The photocatalysis is based on the excitation of semiconductor by photons with an energy superior or equal to the gap, generating electron-hole pairs. These are very reactive and able to react at the interface, involving for exemple the total oxidation of an organic compound. This method can be used on wastewater to eliminate the organic pollutants. With a view to use the sun as a light source this method may become an economical and ecological way for the water treatment. Light interaction between light and semiconductor and the charge-carrier dynamics are fundamental processes for photocatalysis and it is necessary to understand them in order to manage with this process and develop more efficient materials. The Time Resolved Microwave Conductivity (TRMC) is a method based on the reflexion of microwaves on an excited semiconductor which is linked to the number of photo-generated charge-carriers. This method allows us to probe in real time the charge-carrier dynamics in semiconductor. This work is included in the ANR Photonorm project. It consists in a TRMC study on titanium dioxyde TiO2 used for water depollution by photocatalysis. One part of this study consists in the characterization of the opto-electronic properties of materials for which the charge-carrier dynamics will be compared with the photocatalytic activity. The beneficial effect of nanoparticles deposition of gold, silver or gold-copper bimetallics on commercial TiO2 will be linked to the observation of free electrons observed by TRMC . The beneficial effect on photocatalysis in visible light was linked to an electron injection in TiO2 by bismuth nanoparticles. The second part of this work consists in a more fundamental study of charge-carrier dynamics on commercial or synthetized for the Photonorm project. I will be shown the importance of excitation wavelength and intensities on charge carrier generation. The importance of surface effect and environment will be emphasized by several ways. The first one just consist in surface treatment which can have a major importance on charge-carrier dynamics and photocatalysis, probably in connection with the presence or not of impurities on the surface. The second way consists in impregnating TiO2 by organic dyes which show a strong visible light absorption. The TRMC measurements highlight the interaction between the adsorbed molecules and the semiconducteur, including the electron injection from the excited dye to the TiO2 but also an increased recombination effect. The third method consist in modified the working atmosphere in TRMC. The major role of oxygen is so observed on charge-carrier dynamics, with an effect of electron capture, involving in photocatalytic mechanism.Finally TRMC proves to be a convenient method for studying charge-carrier dynamics in semiconductors, which allow a better understanding of fundamental processes bound to photocatalysis.

Over the past years, research efforts have focused on adding highly conductive nanoparticles, such as carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs), into polymers to improve their electrical conductivity or to tailor their piezoresistive behavior. Resultant materials are typically described by the weight or volume fractions of their nanoparticles. The weight/volume fraction alone is a very global quantity, making it a poor evaluator of a doping configuration. Knowing which particles actually participate in improving electrical conductivity can optimize the doping strategy. Additionally, conductive particles are only capable of charge transfer over a very short range, thus most of them do not form part of the conduction path. Thus, understanding how these particles are arranged is necessary to increase their efficiency. First, this work focuses on polymers loaded with CNTs. A computational modeling strategy based on a full morphological analysis of the CNT network is presented to systematically analyze conductive networks and show how particles are arranged. A definition of loading efficiency is provided based on the results obtained from this morphology analysis. This study provides useful guidelines for designing these types of materials based on important features, such as representative volume element, nanotube tortuosity and length, tunneling cutoff distance, and efficiency. Second, a computational approach is followed to study the conductive network formed by hybrid particles in polymer nanocomposites. These hybrid particles are synthesized by growing CNTs on the surfaces of GNPs. The objective of this study is to show that the higher electrical conductivity of these composites is due to the hybrids forming a segregated structure. Polymers loaded with hybrid particles have shown a higher electrical conductivity compared with classical carbon fillers: only CNTs, only GNPs or mixed CNTs and GNPs. This is done to understand and compare the doping efficiency of the different types of nanoparticles. Finally, some parameters of the hybrid particle are studied: CNT density on GNPs, and CNT and GNP geometries. Recommendations to further improve the composite’s conductivity based on these parameters are presented. It is noted that this work is the first time the hybrid particle is studied through a computational approach.

京都大学 / 0048 / 新制・課程博士 / 博士(地球環境学) / 甲第21936号 / 地環博第182号 / 新制||地環||36(附属図書館) / 京都大学大学院地球環境学舎地球環境学専攻 / (主査)教授 勝見 武, 教授 高岡 昌輝, 准教授 高井 敦史 / 学位規則第4条第1項該当 / Doctor of Global Environmental Studies / Kyoto University / DFAM

Two-dimensional van der Waals materials have been a subject of intense research interest in recent years. High thermal conductivity of graphene can be utilized for many thermal management applications. In spite of possessing very high electron mobility, graphene can’t be used as transistors because of the absence of band gap; however transition metal dichalcogenides are another class of two-dimensional van der Waals materials with inherent band gap and show a great promise for future nanoelectronic applications. But in order to tailor these properties for commercial applications, we should develop a better understanding of the effect of extrinsic factors like size, rough edges, grain boundaries, mass-impurities, interaction with substrate etc. on thermal and electrical transport. Most materials exhibit a smooth ballistic-to-diffusive type of thermal transport in which when the sample size is small as compared to mean-free-path of phonons the transport is ballistic, whereas, when the sample size is large as compared to phonon mean-free-path, phonons undergo multiple scattering events and the thermal transport becomes diffusive in nature. However, graphene exhibits an atypical thermal transport behavior where thermal conductivity shows an increasing logarithmic trend even for samples far greater than the mean-free-path of phonons. We show that this anomalous behavior can be attributed to the significant contribution coming from momentum-conserving normal phonon-phonon scattering. Secondly, graphene grain boundaries have been found to significantly reduce thermal conductivity even in the presence of substrates. In spite of numerous studies on the effect of grain boundaries (GBs) on thermal conductivity in graphene, there lacks a complete correlation between GB resistance and misorientation angle across graphene GBs. We show a direct correlation between thermal GB resistance and mismatch angles with low angle mismatch can be captured only by GB roughness, whereas, large mismatch angles will lead to the formation of a disordered patch at the interface and it could significantly deteriorate the overall thermal conductivity even in the presence of substrates. GBs are found to affect electrical transport in two-dimensional systems as well. Owing to the excellent electronic properties and compactness of these two-dimensional materials, high quality 2D heterojunctions are the subject of intense research interest in recent years. Graphene-MoS2 heterojuctions are found to form ohmic contacts and show great potential for future nanoelectronic applications. We show that the interface resistance in Gr-MoS2 heterojuctions can affect the overall resistance of the device if the channel (MoS2) length is small at low carrier densities, whereas, at high carrier densities interface resistance do not play much role in determining the resistance of the entire device. However, if graphene and MoS2 grains are misorientated then interface resistance can play a crucial role in determining the overall resistance of the device. We also show a weak dependence of misorientation angles on GB resistance across MoS2 grain boundaries.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第23172号 / 工博第4816号 / 新制||工||1753(附属図書館) / 京都大学大学院工学研究科都市社会工学専攻 / (主査)教授 角 哲也, 准教授 竹門 康弘, 准教授 Sameh Kantoush / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

京都大学 / 新制・課程博士 / 博士(工学) / 甲第23175号 / 工博第4819号 / 新制||工||1753(附属図書館) / 京都大学大学院工学研究科都市社会工学専攻 / (主査)教授 小池 克明, 教授 林 為人, 准教授 柏谷 公希 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

<div><div>This thesis analyzed three fundamental fluid dynamics problems arising from multiphase flows that may be encountered in hydraulically fractured flow passages. During hydraulic fracturing (``fracking''), complex fluids laden with proppants are pumped into tight rock formations. Flow passages in these formation are naturally heterogeneous with geometric variations, which become even more pronounced due to fracking. Upon increasing the flow area (and, thus, the conductivity of the rock), crude oil, shale gas or other hydrocarbons can then flow out of the formation more easily. In this context, we encounter the following three fluid mechanical phenomena: fluid--fluid interfacial instabilities, flow-wise variation of the hydraulic conductivity, and particle migration in the pumped fluids. </div><div><br></div><div>First, we studied the (in)stability of the interface between two immiscible liquids in angled (tapered) Hele-Shaw cells, as model of a non-uniform flow passage. We derived an expression for the growth rate of perturbations to the flat interface and for the critical capillary number, as functions of the small gap gradient (taper). On this basis, we formulated a three-regime theory to describe the interface's stability. Specifically, we found a new regime in which the growth rate changes from negative to positive (converging cells), or from positive to negative (diverging cells), thus the interface's stability can change type at some location in the cell. We conducted three-dimensional OpenFOAM simulations of the Navier--Stokes equations, using the continuous surface force method, to validate the theory.</div><div><br></div><div>Next, we investigated the flow-wise variation of the hydraulic conductivity inside a non-uniformly shaped fracture with permeable walls. Using lubrication theory for viscous flow, in conjunction with the Beavers--Joseph--Saffman boundary condition at the permeable walls, we obtained an analytical expression for the velocity profile, conductivity, and wall permeation velocity. The new expression highlights the effects of geometric variation, </div><div>the permeability of the walls, </div><div>and the effect of flow inertia.</div><div>The theory was validated against OpenFOAM simulations of the Navier--Stokes equations subject to a tensorial slip boundary condition.</div><div><br></div><div>Finally, we extended the utility of phenomenological models for particle migration in shear flow using the physics-informed neural networks (PINNs) approach. We first verified the approach for solving the inverse problem of radial particle migration in a non-Brownian suspension in an annular Couette flow. Then, we applied this approach to both non-Brownian and Brownian suspensions in Poiseuille slot flow, for which a definitive calibration of the phenomenological migration model has been lacking. Using PINNs, we identified the unknown/empirical parameters in the physical model, showing that (unlike assumptions made in the literature) they depend on the bulk volume fraction and shear P\'eclet number. </div></div>