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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.
201

Design and Evaluation of a logging system in a power-constrained environment / Design och Utvärdering av ett loggsystem i en strömbegränsad miljö

Adamsson, Morgan January 2023 (has links)
Logging plays a crucial role in debugging endeavors, assisting technicians in identifying errors and improving the overall sustainability of electrical systems. This thesis focuses on integrating local logging capabilities into the Balise Transmission Module (BTM), a legacy control system that lacks such features. The project also aims to incorporate real-time remote logging functionalities. It should be noted that the BTM does not have power output, necessitating the logging system to derive energy from existing signals while ensuring the safe operation of the control system. The thesis starts by introducing the project’s context, then explains the system architecture and relevant background information. Subsequently, it delves into the design aspects of a power supply that efficiently extracts energy from the control system. Additionally, the thesis explores wireless data transfer solutions and local data storage alternatives, addressing other pertinent details related to the logging system. Finally, it presents an evaluation of the design and an analysis of the results. The power supply design was developed to incorporate in-rush current limiting, a buck converter, and current limiting mechanisms to ensure the safe operation of the BTM. Through simulations, this thesis demonstrates that the power supply can operate within the safe boundaries of the BTM while efficiently harnessing sufficient current to power the system. The wireless transmission protocols investigated in this study were Bluetooth Low Energy (BLE) and WiFi. The thesis evaluates BLE as sufficiently power-efficient but identifies throughput limitations due to the raw data generated by the BTM exceeding the available throughput. On the other hand, WiFi exhibits no throughput issues but consumes excessive power, making it unsuitable for legacy versions of the BTM. Flash memory was designed and implemented as a feasible solution for local storage. / Loggning spelar en avgörande roll i felsökning, vilket underlättar felidentifiering och förbättrar den övergripande hållbarheten för elektiska system. Detta arbete belyser processen att integrera lokala loggningsfunktioner i ett specifikt äldre kontrollsystem, Balise Transmission Module, som helt saknar sådana funktioner. Dessutom strävar projektet efter att integrera realtidsfunktioner för fjärrloggning. I detta särskilda fall saknar det äldre kontrollsystemet utgångseffekt, vilket kräver att loggningssystemet utnyttjar energi från befintliga signaler, utan att påverka kontrollsystemets drift. Arbetet inleds med att introducera projektets sammanhang, följt av en exposition av systemarkitekturen och relevant bakgrundsinformation som är associerad med denna arkitektur. Därefter går arbetet in på designaspekterna av strömförsöjningen som effektivt utvinner energi från kontrollsystemets befintliga signaler. Dessutom utforskas den trådlösa dataöverföringen och alternativ för lokal datalagring, och tar upp andra relevanta detaljer för loggingsystemet. Slutligen presenterar arbetet en utvärdering av designen och en analys av resultaten. Strömförsörjningsdesignen utvecklades för att inkludera begränsning av startström, en buck-omvandlare och strömbegränsningsmekanismer för att säkerställa säker drift av BTM. Genom simuleringar visar detta arbete att strömförsörjningen kan fungera inom de säkra gränserna för BTM samtidigt som den effektivt utvinner tillräcklig ström för att driva systemet. De trådlösa överföringsprotokoll som undersöktes i denna studie var Bluetooth Low Energy (BLE) och WiFi. Arbetet utvärderar BLE som tillräckligt energieffektivt, men identifierar genomströmningsbegränsningar på grund av att den råa data som genereras av BTM överstiger den tillgängliga genomströmningskapaciteten. Å andra sidan uppvisar WiFi inga genomströmningsproblem men förbrukar överdriven ström, vilket gör det olämpligt för äldre versioner av BTM. Flash-minne designades och implementerades som en genomförbar lösning för lokal lagring.
202

Kan Anderssons hus bli ett passivhus?

Unéus, Viktor January 2016 (has links)
I detta arbete studeras vilka möjligheter det finns för en av 3D hus kunders hus att klara kraven för passiv- eller minienergihus. Baserat på ett projekterat hus studeras hur olika konstruktioner och produktval påverkar husets möjlighet att uppfylla kraven. Trots att samtliga konstruktionsalternativ påstods vara anpassade för energisnåla hus visar vår undersökning att transmissionsförlusterna varierade mycket mellan de olika lösningarna. Även vilka garantier de olika företagen kunde ge gällande lufttäta konstruktioner varierade stort.De områdena som särskilt studeras i detta arbete är energiförluster genom en bostads klimatskal beroende av olika konstruktioner av väggarna, samt vilka fönster och dörrar som är lämpliga.Vår studie visar att utformningen av huset som studerats kommer kräva mycket höga krav på konstruktionen för att huset ska kunna nå kraven för ett passiv- eller minienergihus. Utformningen gör däremot att förlusterna varierar stort mellan de olika valen och det kan därför vara en god idé att se över vilka produkter som ska väljas inom de olika områdena. / This report considers the possibilities to build a passive house or mini-energy house within reasonable demands on manufacturers and construction firms for one of 3D House’s customers. The client has already been in contact with different manufacturers and construction firms with different demands, but with the same warranty of energy efficient materials. In this study there’s a comparison of these demands and warrants show that, even with the same stated terms of low efficient material, the transmission loss vary considerably. Especially the warrants for airtight constructions vary much.Because of the buildings shape it becomes clear that it would need very high requirement on the products and the work to meet the requirements for passive house. The shape of the house does on the other hand make sure that it's a big difference between the different products which would make it a good idea to look over the different chose.The areas there this report is in first hand how the different companies for walls because of that is an area there it's a big different between different choice and it's a big part of the climate shield. It will also have a look over what kind of windows and doors that exist that meet both the requirements for passive house and the costumer.
203

Développement de méthodologies de synthèse d’hydroxyméthyl furfural (HMF) à partir de biomasse lignocellulosique. / Development of methodologies for the synthesis of hydroxy methyl furfural (HMF) from lignocellulosic biomass.

Despax, Solenne 05 December 2013 (has links)
L'acide furan-2,5-dicarboxylique (FDCA) a été répertorié en 2010 comme l'une des 10 principales molécules bio sourcées, pouvant servir de blocs de construction moléculaire pour remplacer l'acide téréphtalique d'origine pétrochimique, dans la production des polyesters à base de végétal. Ce composé fait partie de la famille des furanes et est obtenu après déshydratation et oxydation de sucres. Une des voies de synthèse utilise un intermédiaire clé, le 5-hydroxyméthylfurfural (HMF). Cependant, il n'existe aujourd'hui aucune production industrielle du HMF, en raison de sa réactivité intrinsèque. La formation de ce composé représente ainsi une des étapes limitantes dans la production de FDCA. Dans ce contexte, nous avons envisagé de nouvelles stratégies de synthèse du HMF économiquement favorables et respectueuses de l'environnement. L'étude de la déshydratation des monosaccharides présents en abondance dans la biomasse lignocellulosique a tout d'abord été effectuée. Les voies de synthèse ont été choisies dans la perspective d'un possible dimensionnement industriel et les coûts de production ont été minimisés afin d'obtenir le HMF à un prix compétitif. Des cristaux de HMF d'une pureté suffisante, pour une application industrielle, ont ainsi été fournis à partir de D-fructose, après une synthèse dans le diméthylsulfoxide sans catalyseur et une extraction liquide-liquide du composé. Le recyclage des solvants organiques utilisés pour la synthèse et pour l'extraction représente un réel avantage du procédé. A partir de D-glucose, la synthèse en milieu organique en deux étapes, sans purification intermédiaire, mais avec seulement une filtration, fournit un sirop de HMF concentré. Le catalyseur utilisé pour l'étape d'isomérisation du D-glucose en D-fructose a été recyclé avec succès. La conversion directe de la cellulose en HMF, dans un milieu contenant un solvant organique, a ensuite été abordée. La stratégie mise en place s'inscrit dans une démarche d'éco-conception visant à obtenir le HMF à partir de biomasse lignocellulosique, sans traitement préalable. L'accessibilité de la cellulose par sa solubilisation dans le milieu réactionnel est le premier défi à relever pour sa conversion ultérieure. La combinaison d'un catalyseur chloré et d'un système composé d'un sel d'ammonium et d'un solvant organique a été efficace pour produire le HMF. Du point de vue de la chimie durable, ce procédé présente de réels avantages tels que l'utilisation de réactifs (sel d'ammonium et catalyseur) peu onéreux et une production de HMF à partir de matières premières renouvelables. L'adaptation de cette méthode à la biomasse lignocellulosique a fourni des rendements modestes mais encourageants pour la suite des travaux. / 2,5-Furan dicarboxylique acid (FDCA) was listed in 2010 as one of the top 10 bio sourced molecules which can serve as building blocks to replace the petrochemical terephthalic acid in the production of polyesters based-plant. This compound belongs to the family of furans and can be obtained after dehydration and oxidation of sugars. One way of synthesis uses a key intermediate, 5-hydroxymethylfurfural (HMF). However, there is currently no commercial production of HMF because of its intrinsic reactivity. The formation of this compound thus represents one of the limiting steps in the production of FDCA. In this context, we have explored new strategies for the synthesis of HMF which could be economically and environmentally favorable. The study of the dehydration of monosaccharides which are abundant in lignocellulosic biomass was first carried out. Synthetic routes have been selected in view of a possible industrial development and in order to reduce as possible as we can the cost of production to obtain the HMF at a competitive price. Crystals of HMF with sufficient purity for industrial applications has been supplied from D-fructose after a synthesis in dimethylsulfoxide without catalyst and after a liquid-liquid extraction. Recycling of organic solvents used for the synthesis and the extraction represents a real benefit for this process. From D-glucose, a synthesis in organic medium in two steps without purification but only filtration afforded a syrup of concentrated HMF. The catalyst used for the isomerization step of the D-glucose into D-fructose was successfully recycled. The direct conversion of cellulose into HMF in a medium composed of an organic solvent was then approached. The implemented strategy is part of an eco-design approach to get the HMF from lignocellulosic biomass, without pretreatment. Accessibility of cellulose by its dissolution in the reaction medium was the first challenge for subsequent conversion. The combination of a chloride catalyst and a system composed of an ammonium salt and an organic solvent was effective to produce HMF. From the view point of sustainable chemistry, this method gathers noticeable advantages such as use of cheap ammonium additive, cheap and naturally abundant metal and allows production of HMF from renewable raw materials. The adjustment method to the lignocellulosic biomass has provided modest but encouraging yields for further work.
204

Efektivnost výstavby nízkoenergetických bytových domů / Construction efficiency of low-energy residential buildings

Zgúthová, Katarína January 2009 (has links)
Construction of low-energy residential buildings (i.e. houses with low energy demand) in the Czech Republic is not as common as in other countries in the region. This thesis examines the reasons for such development and whether or which obstacles potential buyers face. The analysis of the economic choice between "regular" house and a low-energy building will be primarily based on comparison of basic parameters of both types of constructions. Data for this research will be taken from commercial developers. Quality analysis in the form of detailed interviews with developers, architects and potential buyers will follow. The last section of this thesis will deal with the approach of Czech media towards low-energy development. Presentation of this issue to the public will be examined by the frequency and content of reports.
205

Nanoemulsões encapsulando quercetina produzidas pelo método do ponto de inversão da emulsão (EIP): estabilidade físico-química e avaliação da atividade antioxidante in vitro e em produto cárneo / Nanoemulsions encapsulating quercetina produced by the emulsion inversion point method (EIP): physicochemical stability and evaluation of in vitro antioxidant activity and after incorporation in meat product

Carli, Cynthia de 24 March 2017 (has links)
A quercetina é um flavonoide com alta atividade antioxidante reconhecida. Devido a este fato, a indústria alimentícia tem buscado alternativas para a aplicação deste bioativo como antioxidante em matrizes alimentícias. No entanto, incorporar a quercetina em formulações alimentícias pode ser desafiador, pois sua molécula tem relativo grau de hidrofobicidade. Os métodos de encapsulação em nanoemulsões podem tornar viável a proteção do flavonoide, bem como permitir sua dispersibilidade em meios aquosos . O objetivo do presente trabalho foi produzir nanoemulsões (fase oleosa: óleo de girassol) encapsulando quercetina pelo método do ponto de inversão da emulsão (EIP, emulsion inversion point), determinando parâmetros de operação que viabilizem um futuro escalonamento do processo, e a realização de um estudo de caso sobre a incorporação das nanodispersões em patê de frango. Os parâmetros de produção que foram avaliados foram : tipo e concentração de tensoativo (razão SOR, razão tensoativo:óleo), concentração de óleo, concentração de cosolvente e velocidade de agitação. Foram produzidas nanoemulsões utilizando dois tensoativos diferentes, Tween 80 e Brij 30. As porcentagens de quercetina encapsulada foram 0,15 e 0,30% (m/m). Dentre estas, a concentração de 0,30% foi a mais viável para a aplicação no patê de frango, por apresentar melhor distribuição de tamanho de gotícula (diâmetro hidrodinâmico), não apresentar variação significativa de oxidação lipídica e maior conservação da quercetina encapsulada por um período de 90 dias. Os valores de tensão interfacial obtidos mostram que a quercetina provoca abaixamento da tensão interfacial do sistema, o que pode indicar que a quercetina forma um complexo com os tensoativos utilizados, fato que influencia decisivamente na sua localização nas nanogotas. Das formulações testadas para patê de frango contendo quercetina, apenas a formulação usando quercetina livre não apresentou boa avaliação nos itens cor e sabor. Tal resultado justifica a necessidade da incorporação da quercetina em nanoemulsões para não causar alterações sensoriais no produto. / Quercetin is a flavonoid with recognized high antioxidant activity Due to this fact, the food industry has been trying to use it as an alternative as a preservative in food matrices. However, incorporating quercetin into food formulations may be challenging due to its relative degree of hydrophobicity. Encapsulation methods in nanoemulsions may render the protection of the flavonoid viable, as well as enable its dispersibility in aqueous media. The objective of the present study was to produce nanoemulsions (oil phase: sunflower oil) encapsulating quercetin by the emulsion inversion point method (EIP), determining operating parameters that enable a future process scale-up. A case study on the incorporation of nanodispersions into chicken patê was also carried out. The production parameters evaluated were: type and concentration of surfactant (SOR ratio, surfactant:oil ratio), soybean oil concentration, cosolvent concentration and stirring speed. Nanoemulsions were produced using two different surfactants, Tween 80 and Brij 30. The percentages of encapsulated quercetin were 0.15 and 0.30% (m / m). Among these, the concentration of 0.30% was the most feasible for application in chicken pâté, since it presented better droplet size distribution (hydrodynamic diameter), did not present significant variation of lipid oxidation and higher capacity of preserving encapsulated quercetina for a period of 90 days. The interfacial tension values obtained show that quercetin lowered the interfacial tension of the system, which may indicate that quercetin forms a complex with the surfactants used, a fact that decisively influences its location in the nanodroplets. Among the formulations tested in chicken pâté containing quercetin, only the formulation using free quercetin did not show good acceptance evaluation on the color and taste itens. Such an evaluation was important as it justifies the need for the incorporation of quercetin into nanoemulsions in order to not cause significant sensorial changes in the product.
206

Cryptography for Ultra-Low Power Devices

Kaps, Jens-Peter E 04 May 2006 (has links)
Ubiquitous computing describes the notion that computing devices will be everywhere: clothing, walls and floors of buildings, cars, forests, deserts, etc. Ubiquitous computing is becoming a reality: RFIDs are currently being introduced into the supply chain. Wireless distributed sensor networks (WSN) are already being used to monitor wildlife and to track military targets. Many more applications are being envisioned. For most of these applications some level of security is of utmost importance. Common to WSN and RFIDs are their severely limited power resources, which classify them as ultra-low power devices. Early sensor nodes used simple 8-bit microprocessors to implement basic communication, sensing and computing services. Security was an afterthought. The main power consumer is the RF-transceiver, or radio for short. In the past years specialized hardware for low-data rate and low-power radios has been developed. The new bottleneck are security services which employ computationally intensive cryptographic operations. Customized hardware implementations hold the promise of enabling security for severely power constrained devices. Most research groups are concerned with developing secure wireless communication protocols, others with designing efficient software implementations of cryptographic algorithms. There has not been a comprehensive study on hardware implementations of cryptographic algorithms tailored for ultra-low power applications. The goal of this dissertation is to develop a suite of cryptographic functions for authentication, encryption and integrity that is specifically fashioned to the needs of ultra-low power devices. This dissertation gives an introduction to the specific problems that security engineers face when they try to solve the seemingly contradictory challenge of providing lightweight cryptographic services that can perform on ultra-low power devices and shows an overview of our current work and its future direction.
207

Metodologias para a determinação das propriedades de impacto de baixa energia de laminados metal-fibra / Methodologies to determine low-energy impact properties of fiber-metal laminates

Gualberto, Alan Rodrigo Marinho 13 June 2008 (has links)
Aplicações dos laminados híbridos metal-fibra incluem, além da indústria aeronáutica, as indústrias naval e automobilística. Diferentemente do setor aeronáutico, pesquisas sobre impactos mecânicos nas duas outras áreas da mobilidade são freqüentemente limitadas pela disponibilidade de equipamentos laboratoriais, de modo que é desejável o desenvolvimento de procedimentos de baixo custo para a determinação da resistência e tolerância a danos por impacto dos materiais de construção. Neste trabalho, a resistência a danos por impacto transversal do laminado híbrido metal-fibra Glare-5® foi determinada via três diferentes metodologias. A primeira utiliza um aparato sofisticado aparato Laser-Doppler para monitorar a aceleração e desaceleração de um impactador esférico de aço com 5 mm de diâmetro durante o evento do choque mecânico. O segundo método se baseia apenas nos valores de carga (força aplicada) vs. o tempo de impacto para a obtenção da energia absorvida pelo material. O terceiro considera somente os dados da velocidade do impactador, ou projétil, imediatamente antes e após o impacto. Concluiu-se que os valores de energia obtidos segundo as duas primeiras metodologias são similares, com o Laser-Doppler gerando resultados levemente não-conservadores, comprovando assim a possibilidade da derivação da resistência ao impacto do laminado através de um experimento simples e rápido, que utiliza apenas uma célula de carga digital para a monitoração da força aplicada em função do tempo. O terceiro método apresentou resultados substancialmente superiores às duas primeiras metodologias, sendo classificado como inadequado aos propósitos do projeto. Determinou-se que o laminado híbrido Glare-5®; absorve entre 60% e 80% da energia disponibilizada em impactos ditos leves, no intervalo de 1 a 6 Joules. Por fim, comprovou-se que a rigidez do material (módulo de elasticidade) é a propriedade residual (numa base de tolerância a danos) mais clara e consistentemente degradada pelo impacto previamente aplicado ao material. / Applications of hybrid fiber-metal laminates include, besides aeronautical industry, the automotive and naval industries. Unlike aeronautical field, impact research activities in the former areas of mobility industry are frequently limited by available laboratory equipment, so that it would be desirable to develop low-cost procedures to determine impact resistance and tolerance properties of construction materials. In this work, the transversal (trans-thickness) impact resistance and tolerance of hybrid fiber-metal laminate Glare-5® have been determined via three different methodologies. The first one utilizes sophisticated apparatus comprising a Laser-Doppler device to monitor deceleration/re-acceleration of 5 mm-diameter steel-ball impactor during the mechanical shock event. The second approach merely relies on the force (applied load) vs. impact time for determining the absorbed energy during the dynamic process. The third methodology requires only impactor velocity data points, immediately before and after the impact. It has been concluded that the energy values obtained from Laser- Doppler and load cell methods are very similar, with the former method producing slightly non-conservative results, allowing one to rapidly derive the impact resistance of hybrid laminate materials through very simple experimental set-ups employing digital load cells only. The third method presented somewhat higher results as compared to the concurrent techniques, so that it has been considered as inadequate for the research purposes. This study has shown that the fibre-metal laminate Glare absorbs between 60% and 80% of the apported impact energy during light impact events (ranging from 1 to Joules). Last, but not the least, materials stiffness was the most clearly and consistently imparted residual mechanical property (in a damage tolerance basis) due to the previous applied impact loading.
208

Uticaj molekularnih svojstava maltodekstrina na tehnološko ponašanje niskoenergetskih prehrambenih emulzija / Influence of molecular characteristics of maltodextrins on technological behaviour of low-energy food emulsions

Dokić-Baucal Ljubica 10 May 2002 (has links)
<p>Apstrakt je obrađen tehnologijama za optičko prepoznavanje teksta (OCR).</p><p>Maltodekstini, hidrolizati skroba niskog stepena konverzije (dekstrozni ekvivalent manji od 20), imaju &scaron;iroku upotrebu u prehrambenoj, kozmetičkoj i farmaceutskoj industriji. U prehrambenoj industriji koriste se u niskoenergetskim prehrambenim emulzijama (majonez, salatni prelivi, namazi) kao zamena za masne materije da bi obezbedili viskozitet, poželjne senzorne osobine i smanjenje energetske vrednosti proizvoda.<br />Viskozitet razblaženih rastora maltodekstrina različitog dekstroznog ekvivalenta i botaničkog porekla meren je kapilarnim viskozimetrom i izračunate su vrednosti unutra&scaron;njeg viskoziteta za pojedine maltodekstrine. Vrednosti untra&scaron;njeg viskoziteta i molekulske mase pokoravaju se zavisnosti &Scaron;taudingerove jednačine, iako su molekuli maltodekstrina relativno kratki i ne spadaju u grupu polimera. Utvrđena je mogućnost odredivanja DE- vrednosti viskozimetrijskin putem i izvedene su jednačine za dva opsega DE (5-10 / 10-20).<br />Da bi se ispitalo pona&scaron;anje emulzija sa maltodekstrinima (emulgovanje) u procesnim uslovima, kao i osobine fmalnih proizvoda (tečljivost, mazivost) ispitivana je dinamika emulgovanja, veličina kapljica i reolo&scaron;ko pona&scaron;anje, tj. uticaj različitih faktora na disperzione karakteristike emulzija suncokretovog ulja u vodi stabilizovanih prehrambenim emulgatorom, sa dodatkom maltodekstrina u kontinualnoj fazi.<br />Utvrđeno je da osobine maltodekstina kao &scaron;to je stepen konverzije (DE-vrednost) tj. veličina molekula maltodekstrina, utiču na dispezione i reolo&scaron;ke osobine emulzija. Uticaj koncentracije ulja i maltodekstrina, kao i delimična zamena ulja maltodekstrinom, na osobine emulzija su takode ispitivane. Sa povećanjem koncentracije ulja, pri istoj koncentraciji maltodekstrina u kontinualnoj fazi, emulzije menjaju tip proticanja od pseudoplastičnog preko tiksotropnog do antitiksotrpnog. Atitiksotropija izazvana smicanjem rezultat je formiranja unutra&scaron;nje strukture emulzije usled povezivanja kapljica ulja preko molekula maltodekstrina kao i orijentacije i deformacije kapljica ulja i maltodekstrina.<br />Dodatkom maltodekstrina za pri istoj koncentraciju ulja i vremenu emulgovanja dobijene su se emulzije sitnijih kapi.<br />Emulzije sa niskom koncentracijom ulja (30%) sa maltodekstrinom u kontinualnoj fazi bile su nestabilne i pokazivale efekat isplivavanja na povr&scaron;inu (creaming), &scaron;to je posledica interakcija molekula maltodekstrina i molekula emulgatora Tween 80 u kontinualnoj fazi i na povr&scaron;ini kapi.</p> / <p>Abstract was processed by technology for Optical character recognition (OCR).</p><p>Maltodextrins, low converted products of starch hydrolysis (dextrose equivalent less than 20), have been subject of various investigations due to their wide application in food industry, cosmetics and pharmaceuticals. They are used in various low energy food emulsions (mayonnaise, salad dressing, spreads) as fat replacer to provide desirable viscosity, texture and sensory fat-like mouthfeel.<br />Viscosity of diluted maltodextrin solutions of different dextrose equivalent and botanical origin were determined by capillary visometer and intrinsic viscosity [q] of each tested maltodextrin was calculated. The values of [q] together with molecular mass M have shown applicability of Staudinger equation, regardless maltodextrin molecules are rather short. The possibility for the determination of DE-values of maltodextrins by viscometric method has been deduced and the equation was calculated for two ranges of DE (5-10/ 10-20).<br />In order to assess behavior of sunflower oil in water emulsions stabilized with food grade emulsifier with addition of maltodextrins in continuous phase in processing (emulsification), as well as end products in application (pouring, spreading) the emulsification dynamics, globule size changes and rheological behavior, as well as, the influence of different factors on dispersion characteristics of such emulsions were studied.<br />Dispersion and viscous properties of emulsions were influenced by certain specific maltodextrin characteristics such as degree of conversion (DE value) i.e. size of maltodextrin molecules. Influence of oil and maltodextrin concentration and partial substitution of oil with equivalent quantity of maltodextrin were investigated too. With increase of oil concentration at the same concentration of maltodextrin in continuous phase, emulsions undergo changes in flow type from shear-thinning to thixotropic and antithixotropic. Antithxotropy induced by shear, was result of formation of network due to two competing factors; linking of oil droplets through maltodextrin molecules as well as orientation of deformed oil droplets and maltodextrin molecules.<br />Addition of maltodextrin, at the same oil concentration and emulsification time, resulted in formation of emulsions with smaller oil droplets.<br />Emulsions with low oil concentration (30%) with maltodextrin in continuous phase were unstable, showing so called creaming effect. This was mainly due to interactions between maltodextrin and emulsifier Tween 80 molecules which took place in continuous phase and on droplet surfaces.</p>
209

Dynamique de collisions moléculaires à très basse énergie : mise en évidence expérimentale de résonances quantiques / Molecular collision dynamics at very low energy

Chefdeville, Simon 12 December 2014 (has links)
Les calculs théoriques prévoient que la dynamique d’excitation rotationnelle desmolécules CO et O2, induite par collision avec H2, est dominée par des résonancesquantiques aux très basses énergies. Leur mise en évidence expérimentale estrendue difficile par la nécessité d’obtenir des énergies de collision très faibles et unegrande résolution en énergie. Les expériences menées grâce à un montage defaisceaux moléculaires croisés à angle d’intersection variable, nous permettent ainsid’observer le seuil des transitions j = 0  1 de CO à 3,85 cm-1 et Nj = 10  11 de O2à 3,96 cm-1. Ces énergies correspondent à l’énergie cinétique moyenne d’un gaz àune température inférieure à 4 K. Les pics dans le tracé des sections efficacesintégrales en fonction de l’énergie de collision, constituent la première observationexpérimentale de résonances pour des processus inélastiques. Le bon accord avecles calculs théoriques permet de valider les potentiels d’interaction et ainsi dedéduire les constantes de vitesse pour la modélisation du milieu interstellaire. Nosrésultats expérimentaux mettent en relief la nature quantique des interactionsmoléculaires aux très basses énergies. / Theoretical calculations predict that the dynamics of rotational excitation of CO or O2molecules, induced by collisions with H2, are dominated by quantum scatteringresonances at very low energies. However, experimental observation of these effectsis challenging: very low collision energies and high energy resolution are bothrequired. Experiments performed with a crossed molecular beam apparatus withvariable intersection angle allow us to observe the thresholds of the CO (j = 0  1)transition at 3.85 cm-1 and the O2 (Nj = 10  11) transition at 3.96 cm-1, whichcorrespond to the average kinetic energy of a gas below 4 K. The peaks in theintegral cross section’s collision energy dependence constitute the first experimentalobservation of resonances in an inelastic process. The good agreement betweentheory and experiment reinforces the confidence in the interaction potentials used todeduce rate coefficients for modeling the interstellar medium in the 1-20 K range. Ourexperimental results highlight the quantum nature of molecular interactions at verylow energies.
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Low Energy (e,2e) Studies of Inner Valence Ionization

Haynes, Matthew, n/a January 2002 (has links)
This thesis presents a series of electron impact ionization measurements on the gas phase targets of argon and krypton. The (e,2e) coincidence technique has been employed to measure the triple differential cross section (TDCS) using a new coincidence spectrometer designed to operate in the low energy regime (2 to 5 times the ionization energy) and in the coplanar geometry. The spectrometer is a conventional device utilizing a non-energy selected electron gun and two 1800 hemispherical electron analysers fitted with channel electron multipliers for detection of the outgoing electrons. A series of TDCS measurements were performed on the 3s inner-valence and 3p valence orbitals of argon employing coplanar asymmetric kinematics. Measurements for both orbitals were performed at an incident energy of 113.5 eV, ejected energies of 10, 7.5, 5 and 2 eV and a scattering angle of -15°. The energy of the scattered electron in each case was chosen to satis~' energy conservation and is dependent on the ionization energies of the different orbitals. The experimental cross sections are compared to theoretical TDCS calculations using the distorted wave Born approximation (DWBA) and variations of the DWBA in an attempt to investigate the role that post collisional interaction (PCI), polarization and electron exchange play in describing the TDCS in the low energy regime. To further extend this analysis, a series of TDCS measurements were performed on the 3s and 4s. orbitals of argon and krypton, respectively, employing coplanar symmetric kinematics. Measurements were performed for the 3s orbital at outgoing energies of 50, 20, 10 and 4eV and for the 4s orbital at outgoing energies of 85, 50, 20 and 10 eV. The kinematics were chosen to coincide with several of the (e,2e) measurements made in the same geometry on the 3p orbital of argon by Rouvellou et al (1998). The experimental results were again compared to a DWBA calculation and similar variations to those employed for the asymmetric measurements.

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