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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Extraction de métabolites du lichen "Pseudevernia furfuracea" via la technologie des liquides ioniques sous irradiation micro-onde / Extraction of metabolites of lichen "Pseudevernia furfuracea" via ionic liquids technology under microwave irradiation

Komaty, Sarah 02 July 2014 (has links)
Les lichens sont des organismes symbiotiques constitués d'un champignon (mycobionte) associé à une algue et/ou une cyanobactérie (photobionte). Leurs métabolites secondaires sont des molécules originales appartenant au groupe des depsides, depsidones, dibenzofuranes et présentent un intérêt pour la cosmétique et/ou la pharmaceutique en raison de leur propriété antibiotique, anti-inflammatoire, antioxydant, filtre UV. Nous avons choisi d'étudier le lichen Pseudevenia furfuracea qui est l'un des lichens utilisés en tant que matière première pour la parfumerie et la cosmétique (1900 tonnes / an), car il est d'une part abondant dans la nature et d'autre part, il possède des métabolites secondaires très variés. Classiquement, les extraits utilisés sont obtenus par extraction au reflux de solvants organiques; cette méthode à l'inconvénient d'induire des durées d'extractions relativement longues et est consommatrice en solvants. L'objectif de notre travail est d'extraire les métabolites secondaires d'une manière sélective et innovante tout en diminuant la durée d'extraction. Pour cela, nos travaux reposent sur l'extraction assistée sous micro-onde (EAM) combinée ou non aux liquides ioniques. Dans ce dessein, deux familles de liquides ioniques (LIs) "hydrophiles" et "hydrophobes" ayant un cation imidazolium et pyridinium ont été synthétisés. Trois différentes préparations de lichen (mixé, broyé au mortier et broyé planétaire) ont été effectuées en faisant varier la granulométrie et chaque préparation a été étudiée par microscopie électronique à balayage. L'optimisation de l'EAM a été effectuée à une température d'extraction optimale de 75 °C et a permis de générer un énorme gain de temps (24 h sous conditions classiques contre 15 min sous irradiation micro-onde). Une étude comparative des taux d'extraction entre l'EAM et l'extraction en condition classique a été éffectuée par analyse au spectrodensitomètre CAMAG®, celle-ci a montré que la première est plus performante dans la plupart des cas. L'utilisation des liquides ioniques a mis en évidence l'existence d'une sélectivité d'extraction en fonction de la structure des LIs qui résulte d'interactions intermoléculaires entre les LIs et les substances extraites. L'effet de chaque liquide ionique sur la dégradation d'un des métabolites, en particulier l'atranorine, a également été étudié. Également, les interactions entre un liquide ionique et la surface du lichen ont été étudiées par mesure d'angle de contact et par les mesures de Brunauer Emett et Teller. Une extraction à plus grande échelle a été réalisée pour étudier la reproductibilité de la méthode et la possibilité de recycler le liquide ionique. / Lichens are symbiotic organisms constituted of fungus (mycobiont) associated to algae and/or cyanobacteria (photobiont). Their secondary metabolites are original molecules belonging to the group of depsides, depsidones, dibenzofurans. Lichens presented special interest for cosmetic and pharmaceutical industry due to their antibiotic, anti-inflammatory, antioxidant and UV filter properties. In this work we focused our study on Pseudevenia furfuracea lichen, which is intensively used as a raw material in perfumery and cosmetics (1900 tons/year), due to its large availability in nature as well as possessing various secondary metabolites. In this work we presented extraction of the secondary metabolites using a selective and innovative solventfree method in shorter extraction time in comparison to the conventional extraction methods requiring under reflux of large quantities of solvents with longer times for extraction. The proposed method is based on the use of microwave irradiation for extraction (MIE) associated to (or not) appropriate ionic liquids. Two kinds of hydrophilic or hydrophobic imidazolium- and pyridinium-based ionic liquids (ILs) were synthesized. Three different methods of grinding for lichen were used, leading to different particle size and the crushed products were observed by scanning electron microscopy (SEM). Heating optimization of MIE was performed during 15 min at optimal temperature (75 °C) (instead of 24 h under conventional heating). A comparative study of extraction rates between MIE and extraction with conventional heating was realized with a CAMAG® spectrodensitometer and results of analysis showed that MIE is efficient in most of the studied cases. The use of ionic liquids showed selectivity for extraction and it depended on the structure of ILs and also intermolecular interactions between ILs and extracted substances.Effect of each ionic liquid on the degradation of one of the secondary metabolites, atranorin, was also been studied. In addition, interactions between IL and the surface of the lichen surface were studied by measurements of the angle of contact and by Brunauer Emett and Teller measurements. Scale-up for extraction was carried out to investigate the reproducibility of the method and the possibility of reuse of the ionic liquid.
2

Parameter extraction in lithium ion batteries using optimal experiments / Parameterbestämning av litium-jonbatterier med hjälp av optimala experiment

Prathimala, Venu Gopal January 2021 (has links)
Lithium-ion (Li-Ion) batteries are widely used in various applications and are viable for automotive applications. The effective management of Li-Ion batteries in battery electric vehicles (BEV) plays a crucial role in performance and range. One can achieve good performance and range by using efficient battery models in battery management systems (BMS). Hence, these battery models play an essential part in the development process of battery electric vehicles. Physics-based battery models are used for design purposes, control, or to predict battery behaviour, and these require much information about materials and reaction and mass transport properties. Model parameterization, i.e., obtaining model parameters from different experimental sets (by fitting the model to experimental data sets), can be challenging depending on model complexity and the type and quality of experimental data. Based on the idea of parameter sensitivity, certain current/voltage data sets could be chosen that theoretically has a more considerable sensitivity for a given model parameter that is of interest to extract. In this thesis work, different methods for extracting model parameters for a Nickel-Manganese-Cobalt (NMC) battery composite electrode are experimentally tested and compared. Specifically, model parameterization using \emph{optimal experiments} based on performed parameter sensitivity analysis has been benchmarked against a 1C discharge test and low rate pulse tests. The different parameter sets obtained have then been validated on a drive cycle and 2C pulse tests. Comparing the methods show some promising results for the optimal experiment design (OED) method, but consideration regarding the state of charge (SOC) dependencies, the number of parameters has to be further evaluated. / Litiumjonbatterier (Li-jon) används i olika applikationer och är ett bra alternativ förfordonsapplikationer. Den effektiva hanteringen av litiumjonbatterier i elbilar har en viktigroll för fordonens prestanda och räckvidd. Man kan nå bra prestanda och räckviddgenom att använda bra batterimodeller i batteriets övervakningssystem (BMS). Därförspelar dessa batterimodeller en viktig roll i utvecklingen av elbilar. Fysikbaseradebatterimodeller används för design, reglering eller för att prediktera beteendet hos batteriet,vilket kräver mycket information om material samt dess reaktion och andra beskaffenheter.Modellparametrisering, dvs. att införskaffa modellparametrar från olika experiment (genom attanpassa modell till experimentella data) kan vara utmanande beroende på modellkomplexitetoch typen samt kvalitén på experimentell data. Baserat på idén om parametersensitivitet kan data om ström och spänning väljas så att de teoretiskt har mer sensitivitet för engiven modellparameter som är av intresse att extrahera. I detta examensarbete testas ochjämförs olika metoder för att extrahera modellparametrar för en Nickelmangankobolt (NMC)batterielektrod. Mer specifikt, modellparametrisering genom optimala experiment baseradepå genomförd parametersesitivitetsanalys jämförts med 1C urladdningstest och låg nivåpulstest. Jämförande av metoderna visar goda resultat för OED metoden men flera parametrarmåste fortsatt utvärderas gällande laddningstatusberoenden (SOC).
3

The deposition of silica on titanium dioxide surfaces

Furlong, Donald Neil January 1975 (has links)
The deposition of amorphous silica from aqueous solution on to rutile particles has been studied with the aim of elucidating the nature of the silica-titania interactions occurring and of following the progressive build up of the silica coating. The coating process, which involves the addition of an aqueous sodium silicate solution to an aqueous dispersion of titanium dioxide, has been investigated by performing a series of controlled preparations and using the technique of microelectrophoresis. Prepared silica-coated rutile samples ranging from partial to full silica coatings have been characterized using transmission electron microscopy, microelectrophoresis and nitrogen, argon and water sorption. Nitrogen and argon adsorption isotherms have been analysed using the equation of Brunauer, Emmett and Teller (BET). Differential energies of adsorption of nitrogen and argon have been determined calorimetrically. Water sorption isotherms have been analysed using the BET equation and the Frenkel - Halsey - Hill (FHH) equation. It has been shown that uniform silica coatings can be produced if adsorption of monomeric silica is followed by polymerization of silica at the solid/liquid interface. Surface cations on rutile may be hydroxylated or co-ordinately bound to water molecules and it appears that monomeric silica adsorbs preferentially by replacing ligand water molecules. Rutile particles with silica coatings thicker than approximately 2.5nm exhibit characteristics typical of silica and not of the base rutile. Silica coatings deposited at pH 10 contain narrow channels which are accessible to water molecules but not to nitrogen or argon. Neutralization to pH 7 reduces the volume in the coating accessible to water molecules.
4

Surface area determination of porous materials using the Brunauer-Emmett-Teller (BET) method: limitations and improvement

Sinha, Priya 30 July 2018 (has links)
No description available.
5

Evaluation of alternative methods forquality control of Tungsten Carbide : An evaluation of four different particle measuring techniques

Näsman, Markus January 2019 (has links)
The purpose of this study was to evaluate four different measuring methods as potentialquality control tests for Tungsten Carbide (WC) raw material used in the hard metalmanufacturing at Seco Tools Fagersta. This was warranted as the current quality testcalled the HcK test, is very time consuming and the results provided that are used formilling time calculations cannot be relied on. The four measuring methods chosen wasLaser diffraction, X-Ray diffraction, Brunauer Emmett Teller analysis and Fisher Sub-Sieve Sizer measurement. These measuring techniques were chosen by Seco ToolsThe project followed the general structure of the project cycle modified to fit the projectand involving the steps project planning, present state analysis, goals and requirementdetermination, evaluation elimination of options and final of choice of option. Thealternative methods were evaluated using an evaluation matrix containing therequirements determined to be the most relevant for the quality control process. Therequirements were measurement precision, operator influence, ease of use, time requiredand operator time required. The ability of the measurement method to distinguishbetween all of the different WC powders used a Seco Tools was put as a must requirementas the new method is meant to serve as a verification test as well as a quality test.The analysis methods were evaluated practically through experiments and therefore atesting strategy was established. Initial test on two powder types was performed so thatan early evaluation could be done. During this stage both the Laser diffraction and the XRaydiffraction were eliminated due to poor results. The BET analysis and the Fisher Sub-Sieve Sizer performed better and was therefore tested further. Randomized testing wasthe method chosen when testing with all powders to minimize the environmental impacton the testing as this could affect the results of the study.The testing showed that only the Fisher SSS was able to distinguish between all thedifferent powders making it the only viable option as a new quality test. This was onlypossible when measuring on agglomerated material and the values extracted couldtherefore not be used further in the production. The Fisher SSS also performed the bestwhen ranked against the rest of the requirements, showing a high precision whenmeasuring on deagglomerated material and a combination of the two tests was thereforeconsidered.When compared to the HcK test the Fisher SSS showed a significant reduction in lead timebut also a reduction in information gathered and eventual defects controlled. The FisherSSS provides only an average particle size measurement and since no correlation has yetbeen established between the measured particle size and the required milling times it wasrecommended that the HcK test remains.It was recommended that a study is started aimed at establishing a correlation betweenthe measured particle size and the required milling time is started to investigate if this ispossible.

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