Dissertations / Theses on the topic 'Evaporation mechanism'

Non statistical effects in the emission of light charged particles from fusion-evaporation nuclear reactions are known for light and medium mass nuclei. Cases previously reported by the NUCL-EX collaboration show discrepancies between experimental data and statistical calculations in decay channels with even residues, possibly due to alpha clusterization. This thesis is focused on the analysis of an experimental campaign carried out at the Legnaro National Laboratories with the GARFIELD+RCo setup to further investigate these topics. The studied systems are: 18O+13C at 112.5 MeV and 18O+12C at 122 and 300 MeV. This thesis work covers the various steps of a typical nuclear experiment conducted with the GARFIELD array. After data taking, preliminary experimental data have been reconstructed through data cleaning, calibration and particle identification. Being the experimental data reconstruction still ongoing, no final experimental reconstructed data have been reported. Nonetheless, simulated data by Monte Carlo statistical decay code have been analysed to investigate the evolution of fusion-evaporation processes from a statistical point of view. The analysis has been focused on the study of global observables like total charge and multiplicity and on single-particle observables like energy spectra and angular distributions. GEMINI++ statistical decay code simulating the fragment emission from a hot source has been considered in the study of the 122 MeV reaction and for a direct comparison of the three reactions. Finally, the HFl statistical code conceived by the collaboration for the light nuclei decay and containing the details of the known excited levels has been compared with GEMINI++. This thesis work paves the way for further studies on the reconstructed data to highlight possible agreements with theoretical models.

Il est bien connu que l'évaporation d'eau joue un rôle essentiel dans l'interaction entre le sol et l'atmosphère. Pendant le processus d'évaporation, le comportement thermo-hydro-mécanique des sols change, engendrant ainsi des problèmes préoccupants. Ceci peut concerner différents domaines comme l'agronomie, l'hydrologie, la science des sols, la géotechnique, etc. Par conséquent, il est essentiel d'étudier les mécanismes d'évaporation de façon approfondie. Cette étude porte sur les mécanismes d'évaporation dans des conditions atmosphériques contrôlées. Le sable de Fontainebleau et l'argile d'Hércourt utilisée pour la construction du remblai expérimental dans le cadre du projet ANR TerDOUEST (Terrassements Durables - Ouvrages en Sols Traités, 2008-2012) ont été étudiés à cet effet. Une chambre environnementale (900 mm de haut, 800 mm de large et 1000 mm de long) équipée de différents capteurs a d'abord été développée, permettant un suivi complet des paramètres concernant l'atmosphère et le sol au cours d'évaporation. Quatre essais expérimentaux ont été réalisés sur le sable de Fontainebleau compacté à une densité sèche de 1,70 Mg/m3, avec une nappe phréatique constante au fond de l'échantillon, et sous différentes conditions atmosphériques (différentes valeurs de l'humidité relative de l'air, de la température et du débit d'air). La pertinence du système a été mise en évidence par la bonne qualité des résultats. La température de l'air à l'intérieur de la chambre a été trouvée affectée par la température du tube de chauffage, le débit d'air et l'évaporation d'eau; la température du sol est fortement affectée par les conditions atmosphériques et l'état d'avancement de l'évaporation ; l'humidité relative dans la chambre diminue au cours du temps et son évolution peut être considérée comme un indicateur du processus d' évaporation ; la teneur en eau volumique dans la zone proche de la surface est fortement influencée par le processus d'évaporation et présente une relation linéaire avec la profondeur ; la succion du sol diminue avec la profondeur et augmente au fil du temps ; le taux d'évaporation est fortement affecté par les conditions de l'air en particulier dans la phase initiale de vitesse d'évaporation constante. Après les essais sur le sable de Fontainebleau, l'échantillon de l'argile d'Hércourt compactée à une densité sèche de 1,40 Mg/m3 a été soumis à une infiltration d'eau afin d'étudier ses propriétés hydrauliques. Pour obtenir un meilleur aperçu du mécanisme d'évaporation pour l'argile, deux essais d'évaporation sur l'argile d'Hércourt compactée avec une nappe phréatique constante au fond de l'échantillon ont été effectuées sous des conditions atmosphériques contrôlées. Les résultats permettent de comprendre les mécanismes d'évaporation en cas de fissuration due à la dessiccation. En outre, afin d'étudier les mécanismes d'évaporation potentiels, des essais avec une couche d'eau libre ont été également réalisés en faisant varier la vitesse du vent et la température de l'air. L'initiation et la propagation de fissures de dessiccation pendant le processus d'évaporation et son effet sur l'évaporation ont également été étudiés par la technique de traitement d'image. En termes de modélisation, le taux d'évaporation potentiel a été modélisé à travers l'évaluation des modèles existants et des modèles combinés. Il apparait que le modèle développé par Ta (2009) est le plus approprié. Le taux d'évaporation réelle depuis le sable a été ensuite analysé. Il semble important de considérer l'avancement du front sec pendant le processus d'évaporation pour les sols sableux. Pour l'argile d'Héricourt, une bonne prévision a été également obtenue en utilisant un modèle qui tient compte de l'effet des fissures de dessiccation
As a well-known phenomenon, soil water evaporation plays an important role in the interaction between soil and atmosphere. Water evaporates during this process resulting in changes of soil thermo-hydro-mechanical behavior and in turn causing problems in different domains such as agronomy, hydrology, soil science, geotechnical engineering, etc. Therefore, it is essential to investigate the soil water evaporation mechanisms in depth.This study deals with the soil water evaporation mechanisms under controlled atmospheric conditions. The Fontainebleau sand and the Hércourt clay used for the construction of the experimental embankment with the ANR project TerDOUEST (Terrassements Durables - Ouvrages en Sols Traités, 2008 - 2012) were used in this investigation. A large-scale environmental chamber system (900 mm high, 800 mm large and 1000 mm long) equipped with various sensors was firstly developed, allowing a full monitoring of both atmospheric and soil parameters during the evaporation process. Four experimental tests were carried out on the Fontainebleau sand compacted at 1.70 Mg/m3 dry density with a steady water table at soil bottom under different atmospheric conditions (different values of air relative humidity, temperature and air flow rate). The performance of the environmental chamber system in investigating soil water evaporation was evidenced by the quality and the relevance of results. The air temperature inside the chamber was found to be affected by the heating tube temperature, the air flow rate and the soil water evaporation process; the soil temperature was strongly affected by the air conditions and the evaporation progress; the relative humidity in the chamber was decreasing during the evaporation progress and its evolution could be considered as an indicator of the evaporation progress; the volumetric water content in the near-surface zone was strongly affected by the evaporation process and exhibited a linear relationship with depth; the soil suction was decreasing over depth and increasing over time; the evaporation rate was strongly affected by the air conditions especially at the initial constant evaporation rate stage. After the tests on the Fontainebleau sand, the Hércourt clay sample compacted at 1.40 Mg/m3 dry density was subjected to an infiltration experiment for investigating its hydraulic properties. To get a better insight into the water evaporation mechanism for clay, two compacted Hércourt clay evaporation tests with a steady water table at bottom were carried out under controlled atmospheric conditions. The results allow understanding the evaporation mechanisms in case of desiccation cracks. Furthermore, in order to investigate the potential evaporation mechanisms, tests with a free water layer was also conducted with varying wind speed and air temperature. The initiation and propagation of desiccation cracking during the evaporation process and its effect on water evaporation were also investigated by the digital image processing technique. In terms of modeling, the potential evaporation rate was first modeled through evaluation of the existing models and the combined models. It reveals that the model developed by Ta (2009) is the most appropriate one. The actual evaporation rate for sand was then analyzed. It appears important to consider the progress of the dry front during the evaporation process for sandy soils. For the Héricourt clay, good simulation was also obtained using a model that accounts for the effect of desiccations cracks

Questo lavoro di tesi è inserito in uno studio, nell'ambito della collaborazione NUCL-EX, delle collisioni tra ioni pesanti per indagare le proprieta statistiche e la struttura della materia nucleare per sistemi con massa A<40. In particolare è stata studiata la reazione 16O+12C, ad energie di fascio di 90.5 MeV, 110 MeV e 130 MeV. Lo scopo della misura è quello di studiare il meccanismo di fusione-evaporazione e le possibili deviazioni da un decadimento puramente statistico del nucleo composto (28Si) che si viene a formare. Il confronto tra i dati sperimentali e quelli ottenuti da una previsione basata sul modello statistico Hauser-Feschbach, ottimizzato per lo studio di nuclei leggeri (HFl), è in grado di fornire indicazioni su effetti di struttura come già evidenziato in passato dalla collaborazione in reazioni analoghe. Questi sono principalmente legati nel nostro caso alla possibile struttura a cluster di particelle alfa che persistono oltre le soglie di emissione di particella. La misura è stata effettuata presso i Laboratori Nazionali di Legnaro sfruttando il fascio fornito da un acceleratore Tandem XTU e l'apparato sperimentale formato dai rivelatori GARFIELD e Ring Counter (RCo). L'analisi si è concentrata sia sullo studio di osservabili inclusivi come le distribuzioni energetiche e angolari delle particelle emesse che di osservabili esclusivi come la probabilità di decadimento in canali specifici. Questi risultati preliminari ottenuti per la reazione 16O+12C hanno in effetti evidenziato la presenza di effetti di struttura legate all'emissione di cluster-alfa, in particolare quando il residuo e un nucleo di carica pari. Si discute anche della dipendenza dall'energia incidente, e quindi dall'energia di eccitazione del 28Si, di questi effetti. In conclusione si indicano gli aspetti da investigare con maggior dettaglio per ottenere risultati piu consolidati e cercare di definire le cause di queste deviazioni dal modello statistico.

In this thesis we propose a model for laminar natural convection within a mixture of two cryogenic fluids with preferential evaporation. This full model was developed after a number of smaller models of the behaviour of the surface of the fluid had been examined. Throughout we make careful comparison between our analytical and computational work and existing experimental and theoretical results. The coupled differential equations for the main model were solved using an explicit upwind scheme for the vorticity-transport, temperature and concentration equations and the multigrid method for the Poisson equation. From plots of the evolution of the system, it is found that convection becomes stronger when preferential evaporation is included. This new model demonstrates how to include preferential evaporation, and can be applied to other fluid systems.

Cette thèse étudie théoriquement les processus de transport au voisinage de la ligne triple de contact liquide-gaz-solide et leur impact sur l'évaporation macroscopique. Dans la première partie de la thèse, l'hydrodynamique au voisinage de la ligne de contact est étudiée sous les conditions de mouillage partiel. L'évaporation induite par le chauffage du substrat dans l'atmosphère de vapeur du même fluide est considérée. La relaxation de la singularité hydrodynamique de la ligne triple est considérée. La principale conclusion de la thèse est que l'effet Kelvin (dépendance de la température de saturation de la pression) est suffisant en soi, pour faire disparaitre la singularité des variables hydrodynamiques. La microrégion (le voisinage de la ligne de contact) est résolue numériquement et analytiquement pour de faibles pentes de l'interface liquide-vapeur. Les échelles de longueur caractéristiques du problème sont identifiées et la nature multi-échelle du phénomène est prise en compte. Les études paramétriques effectuées révèlent le rôle de la résistance thermique de l'interface vapeur-liquide, de la longueur de glissement, du terme thermocapillaire, du recul de vapeur et ainsi que des forces de surface. Une extension de l'approximation de lubrification pour de pentes élevées de l'interface gaz-liquide à l'évaporation est discutée. Dans la seconde partie de la thèse, le modèle précédemment établi pour la microrégion est couplé à des simulations numériques de la croissance d'une bulle de vapeur. Le départ de la bulle de vapeur de la paroi chauffante pendant l'ébullition a également été étudiée. Il a été proposé dans la thèse, que sous des charges thermiques élevées, l'augmentation de l'angle de contact apparent provoque l'étalement de la bulle de vapeur sur la paroi chauffante. Ce phénomène peut conduire, au séchage de la paroi observé pendant la crise d'ébullition.

Droplet evaporation (and condensation) is one of the most common instancesof multiphase flow with phase change, encountered in nature as well as intechnical and industrial applications. Examples include falling rain drops, fogsand mists, aerosol applications like electronic cigarettes and inhalation drugdelivery, engineering applications like spray combustion, spray wet scrubbing orgas absorption, spray drying, flame spray pyrolysis.Multiphase flow with phase change is a challenging topic due to the inter-twined physical phenomena that govern its dynamics. Numerical simulation isan outstanding tool that enables us to gain insight in the details of the physics,often in cases when experimental studies would be too expensive, impracticalor limited.In the present work we focus on simulation of the evaporation of smalldroplets. We perform simulation of evaporation of a pure and two−componentdroplet, that includes detailed thermodynamics and variable physical andtransport properties. Some of the conclusions drawn include the importance ofenthalpy transport by species diffusion in the thermal budget of the system, andthe identification and characterization of evaporating regimes for an azeotropicdroplet.In the second part we develop a method based on the immersed boundaryconcept for interface resolved numerical simulation of laminar and turbulentflows with a large number of spherical droplets that undergo evaporation orcondensation.
Droppförångning (och kondensation) är en av de vanligaste fallen av flerfasflöde med fasförändring, både i naturen och i tekniska och industriella tillämpningar. Exempel är fallande regndroppar, dimma, aerosol-tillämpningar som elektroniskacigaretter och läkemedelsleverans via inandning, tekniska tillämpningar som sprayförbränning, våtskrubbning med sprayning, gasabsorption, spraytorkning samt flammsprayspyrolys. Flerfasflöde med fasförändring är ett utmanande ämne på grund av de sammanflätade fysikaliska fenomen som styr dess dynamik. Numerisk simulering är ett utmärkt verktyg som gör det möjligt för oss att få insikt i detaljerna i fysiken, ofta i fall då experimentella studier skulle vara för dyra, opraktiska eller begränsade. I det nuvarande arbetet fokuserar vi på simulering av förångning av små droppar. Vi utför simulering av förångning av en ren och två−komponentdroppe, som inkluderar detaljerad termodynamik samt varierande fysikaliska och transportegenskaper. Några av de slutsatser som dras inbegriper betydelsen av entalpitransport genom diffusion av olika ämnen i systemets termiska budget samt identifieringen och karakterisering av förångningsregimer för en azeotropiskdroppe. I den andra delen utvecklar vi en metod baserad på det nedsänkta rand konceptet för gränssnittskompletterad numerisk simulering av laminära och turbulenta flöden med ett stort antal sfäriska droppar som genomgår förångning eller kondensering.

QC 20171117

Diesel engines produce large amounts of nitrogen oxides (NOX) while running. Nitrogen oxides are highly toxic and also contribute towards the formation of tropospheric ozone. Increasingly stringent legislation regarding the amount of nitrogen oxides that are allowed to be emitted from diesel-powered vehicles has forced manufacturers of diesel-engines to develop after-treatment systems that reduce the amount of nitrogen oxides in the exhaust. One of the main components in such a system is selective catalytic reduction (SCR), where nitrogen oxides are reduced to diatomic nitrogen and water with the help of ammonia. A vital part of this process is the spraying of a urea-water-solution (UWS), which is needed in order to produce the reducing agent ammonia. UWS spraying introduces the risk of solid deposits (such as biuret, ammelide and ammeline) forming in the after-treatment system, should the flow conditions be unfavourable. Risk factors include high temperatures, but also low dynamics and high thickness of the resulting liquid film that forms as the UWS spray hits the surfaces of the after-treatment system. It is thus essential that manufacturers of SCR after-treatment systems have correct data on how much UWS that should be sprayed into the exhaust for any given flow condition. Experimental tests are thoroughly used to assess this but are very expensive and are thus limited to prototype testing during product development. When assessing a wider range of concepts and geometries early on in the product development stage, simulation tools such as computational fluid dynamics (CFD) are used instead. One of the most computationally heavy processes to simulate within a SCR after-treatment system is the UWS spray and its interaction with surfaces inside the after-treatment system, where correct prediction of the formation of solid deposits are of great importance. Most CFD models used for this purpose hold a relatively good level of accuracy and are utilized throughout the whole industry where SCR aftertreatment is applied. Despite this, these models are limited in the fact that they are only able to cover timescales in the scope of seconds to minutes while using a tolerable amount of computational power. However, the time spectrum for solid deposit formation is minutes to hours. Scania is one of Sweden’s biggest developers of SCR after-treatment, with the technology being incorporated directly into its silencers. AVL Fire is the main UWS spray simulation tool for engineers at Scania at the moment. One major drawback of using AVL Fire for UWS spray simulations is that it is deemed too time-consuming to set up new cases and too unstable during simulation, which makes it too costly in terms of expensive engineering hours. This project has investigated the potential of using STAR-CCM+ for UWS spray simulations at Scania instead. A standard method has been evaluated, as well as parameters that will prove useful in further investigations of a potential speedup method. The studied method in STAR-CCM+ is easy to setup and the simulation process is robust and stable. Various other perks come from using STAR-CCM+ as well, such as: a user-friendly interface, easy and powerful mesh-generation and great post-process capabilities. Several different parameters have been investigated for their impact on the studied method, such as mesh refinement of the spray injector area and the number of parcels injected every time-step through the spray injector (simply put the resolution of the spray). A possible speedup by freezing the momentum equations when allowed and lowering the amount of inner iterations has also been investigated. A handful of operating conditions have been studied for two different geometries. The attained simulation results display correlations with physical measurements, but further assessment for identifying the risk of solid deposit needs to be performed on the studied cases to assess the full accuracy of solid deposit prediction of the studied method. Recommendations for future work includes fully implementing and evaluating the speedup method available for spray simulations in STAR-CCM+ as well as directly comparing how the accuracy and performance of the method relates to that of the method used in AVL Fire for spray simulations.
Dieselmotorer producerar under körning stora mängder kväveoxider (NOx). Kväve-oxider är starkt giftiga föreningar som även bidrar till att öka mängden marknära ozon. Allt strängare lagstiftning gällande mängden kväveoxider som får släppas ut från fordon med dieselmotorer har lett till att tillverkare av dieselmotorer blivit tvingade att utveckla efterbehandlingssystem som renar avgasen från motorn. En av huvudkomponenterna i ett sådant system idag är selective catalytic reduction (SCR; på svenska selektiv katalytisk reduktion), där kväveoxider omvandlas till kvävgas och vatten med hjälp av ammoniak. För att producera ammoniak används en lösning av urea och vatten (t.ex. AdBlue®), som introduceras till efterbehandlingssystemet via spray. Denna process har dock en stor nackdel, då det under omvandlingsprocessen kan finnas risk för klumpbildning av ämnen som biuret, ammelid och ammelin ifall flödesförhållandena är ogynnsamma. Riskfaktorer för klumpbildning inkluderar höga temperaturer samt låg dynamik och hög tjocklek för den vätskefilm som bildas när sprayen med urea-lösning kommer i kontakt med ytor i efterbehandlingssystemet. Det är därför av stor vikt för tillverkare av efterbehandlingssystem som använder SCR att känna till hur mycket urealösning som kan sprayas in för varje givet flöde. Experimentella tester används till stor del för att utvärdera detta, men är väldigt dyra och kan endast göras för ett fåtal prototyper under en produkts utveckling. För att kunna utvärdera ett större antal koncept och geometrier tidigare i utvecklingsstadiet av en ny produkt används därför ofta datorkraft med simuleringsverktyg som CFD (Computational Fluid Dynamics). En av de mest beräkningstunga processerna att simulera i ett efterbehandlingssystem med SCR är sprayandet av urea-lösning och dess interaktion med ytor, där korrekta förutbestämmelser av huruvida det finns risk för klumpbildning eller inte är av stor betydelse. De flesta CFD modeller som används i detta syfte har förhållandevis god noggrannhet och används i stor utsträckning i den bransch där efterbehandling med SCR tillämpas. Däremot är dessa modeller begränsade i att de endast kan åstadkomma simuleringar (med en acceptabel mängd datorkraft) som sträcker sig i tidsintervallet sekunder till minuter. Bildningen av klump är dock en process som kan ta upp till flera timmar. Scania är en av Sveriges största tillämpare av SCR, då tekniken används i de efterbehandlingssystem som finns inbyggda i tillverkarens ljuddämpare. Scania använder främst AVL Fire för simulering av spray med urea. AVL Fire anses dock vara för tidskrävande vid skapelsen av nya simuleringsfall och för instabilt under simulering. Detta projekt har därför undersökt möjligheten att använda STAR-CCM+ för simulering av spray med urea hos Scania. Den metod i STAR-CCM+ som utvärderats är enkel att använda då nya simuleringsfall ska skapas, samtidigt som den är robust och stabil under simulering. Relevanta parametrar för en potentiell uppsnabbningsmetod har också undersökts. STAR-CCM+ i sin helhet är användarvänligt, där verktyget för att skapa och generera mesh är enkelt att använda såväl som kraftfullt när mer avancerade operationer krävs. Möjligheterna för postprocessing är väldigt smidiga för transienta förlopp, vilket är ett stort plus för simuleringar med urea-spray, vars injektion och resulterande processer är väldigt transienta skeenden i sig. Flera olika parametrar har undersökts, för att granska hur stor påverkan de har på prestandan och noggrannheten hos den studerade metoden. Två av dessa är tätheten av beräkningsnoder i den region där spray-munstycket är placerat samt antalet paket med urea-vatten lösning som injiceras varje tidssteg via spray-munstycket. En möjlig uppsnabbning av metoden, som går ut på att frysa ekvationerna för bevarelse av rörelsemängd (eng - momentum equations) när det är tillåtet och samtidigt minska antalet inre iterationer för varje tidssteg, har också undersökts. Ett flertal olika flödesförhållanden har också undersökts för två olika geometrier. De erhållna resultaten tyder på korrelation med data från fysiska experiment. Dock bör ytterligare hydrodynamiska utvärderingar tillämpas för att ordentligt kunna redogöra för hur väl STAR-CCM+ kan användas för att förutse risken för klump- bildning i en spray-process med urea-vatten lösning. Framtida arbete borde fokusera på att utvärdera den uppsnabbningsmetod som finns för spray-simuleringar i STAR-CCM+, samt direkt jämföra hur väl metodens noggrannhet och prestanda står sig gentemot den metod som används i AVL Fire för spray-simuleringar.

In der vorliegenden Arbeit wird die großflächige Abscheidung von organischen Leuchtdioden (OLED) für Beleuchtungsanwendungen in einer neuartigen Beschichtungsanlage vorgestellt. Ausgehend von den speziellen Anforderungen an gleichförmige Schichtdickenverteilung und hohe Abscheideraten für die organischen Schichten, sind die Verfahren der thermischen Vakuumverdampfung (VTE) und der organischen Dampfphasenabscheidung (OVPD) auf Substraten der Größe 370 x 470 mm² unter Fertigungsbedingungen kombiniert. Die Quellensysteme der Anlage wurden hinsichtlich der Verteilung des Materialauftrages und der Oberflächenrauigkeit qualifiziert. Die Kontrolle der Schichteigenschaften ist bei der organischen Dampfphasenabscheidung durch Variation der Parameter Substrattemperatur und Abscheiderate in einem weiten Bereich möglich. Die in situ Kontrolle der Schichtdicke mittels spektroskopischer Reflektometrie wird vorgestellt. Ein Messsystem ist in die Beschichtungsanlage integriert und abgeschiedene Schichten charakterisiert worden. Die Arbeit zeigt, dass die genaue Bestimmung der Dicke einzelner Schichten oder ganzer Schichtstapel mit diesem Verfahren möglich ist und zur ex situ Ellipsometrie vergleichbare Ergebnisse liefert. Um robuste OLED-Bauelemente herzustellen, wird eine organische Kurzschlussunterdrückungsschicht eingeführt, die konform mittels der OVPD-Technologie abgeschieden wird. Die strombegrenzenden Eigenschaften dieser Schicht wirken Defektströmen innerhalb der OLED entgegen. Die reproduzierbare Herstellung von 100 x 100 mm² großen, weißes Licht emittierenden OLED-Modulen mit mittleren Leistungseffizienzen von über 13 lm/W zeigt das Potential dieser Technologie
The thesis deals with the large area deposition of organic light-emitting diodes (OLED) for lighting applications with a novel deposition tool. The special needs of film thicknesses homogeneity and high deposition rates for organic layers request the combination of thermal vacuum deposition (VTE) and organic vapour phase deposition (OVPD) processes to fabricate OLEDs on 370 x 470 mm² substrates. The deposition sources are qualified regarding layer homogeneity and morphology of the deposition processes. The layer properties are controlled in a wide range by the variation of the organic vapour phase deposition parameters: substrate temperature and deposition rate. The in situ determination of the substrate thickness is shown by the application of spectroscopic reflectometry. The thesis demonstrates the thickness analysis of single and multi-layer stacks by reflectometry. The data fit well to ex situ ellipsometry. Robust OLED devices with an additional short-circuit protection layer deposited by OVPD technology are introduced. The current limiting properties of this layer reduce the leakage currents in the OLED device. The fabrication of 100 x 100 mm² white emitting OLED modules with power efficiencies about 13 lm/W shows the great potential of the manufacturing technology

L'OBJECTIF DE CE TRAVAIL DE THESE EST DE METTRE EN EVIDENCE LE ROLE DU TRANSFERT THERMIQUE DANS LA PAROI CHAUFFANTE LORS DE L'EBULLITION D'UN LIQUIDE STAGNANT A LA SATURATION. CET EFFET, HABITUELLEMENT NEGLIGE DANS LES MODELES D'EBULLITION, PEUT EXPLIQUER CERTAINES CARACTERISTIQUES DU CYCLE D'EBULLITION ET DE L'ACTIVITE DES SITES DE NUCLEATION. IL A ETE MONTRE QUE LE CYCLE D'EBULLITION PEUT ETRE DECRIT PAR DEUX PHASES: (1) LORS DE LA CROISSANCE DE LA BULLE, LA TEMPERATURE DE LA PAROI DIMINUE GLOBALEMENT PAR EVAPORATION DE LA MICROCOUCHE A LA BASE DE LA BULLE; (2) LA SURCHAUFFE INITIALE EST RETABLIE PRINCIPALEMENT PAR CONDUCTION RADIALE DE LA CHALEUR DANS LA PAROI. ON PEUT ALORS DONNER UNE EXPLICATION DE L'EVOLUTION DE LA TEMPERATURE DE LA PAROI MIS EN EVIDENCE EXPERIMENTALEMENT A L'AIDE DE CRISTAUX LIQUIDES THERMOCHROMIQUES ET DE L'INFLUENCE DE L'ANGLE DE CONTACT SUR LES ECHANGES THERMIQUES.

This thesis investigates the performance of compact brazed plate heat exchangers (CBE) operating as evaporator in heat pump applications. The thesis, and the performances investigated, has been divided into three main sections; One zone evaporator performance; Two zone evaporator performance; and finally Local performance. The 'One zone evaporator performance' section considers the evaporator as one "black box". It was found that "approaching terminal temperatures" were obtained as low overall heat flux is employed. It was also found that the total area averaged film heat transfer coefficient was affected by changes of the brine mass flow rate. This indicates that the widespread Wilson plot method may not be used to determine flow boiling heat transfer coefficients. Further, it seems that co- and counter-current flow configuration performs equally well if the superheat is kept low. A numerical simulation of the above investigations indicates that a nucleate boiling model better predicts the performance compared to a convective evaporation model. Finally, the significant impact of the refrigerant inlet distributor design was illustrated using several CBEs with different inlet geometries but with identical heat transfer surfaces. The 'Two zone evaporator performance section' considers the evaporator as two "black boxes", i.e. the boiling and superheating boxes. Thermochromic liquid crystals (TLC) was used to determine the boiling heat transfer area. The resulting flow boiling heat transfer coefficient was found to correlate with heat flux. The superheated heat transfer area was then estimated using single phase correlations. It was observed that the TLC measurements and the predicted superheating area did not agree. Possible causes for this deviation were discussed. The most likely explanation found was the presence of mist flow at the higher vapor quality range in the boiling section of the evaporator. The 'Local Performance' section considers local pressure drop and flow boiling heat transfer. The Chisholm parameter was found not to be a constant and was found to correlate well with the kinetic energy per volume. The resulting predictions of the pressure drop were better than ± 10%. The resulting local flow boiling heat transfer coefficient, at different vapor quality, mass flux and heat flux, was compared to flow boiling correlations available in the literature. It was found that the saturated nucleate pool boiling correlation by Cooper (1984) and narrow channel flow boiling correlations (Tran 1999, Lazarek and Black 1982) predicted the experimental data better than several traditional flow boiling correlations, developed for larger tubes.
QC 20100524

De nos jours, la combustion représente encore un 90% de la production totale d'énergie au monde. La plupart des brûleurs de type industriel utilisent comme carburant des hydrocarbures en forme liquide. Cependant, un grand nombre d'études ont été dédiés aux flammes gazeuses et l'impact du spray liquide est encore loin d'être totalement compris. Le but de cette étude est l'amélioration de la modélisation des deux phénomènes principaux qui ont lieu entre l'atomisation du spray et la combustion, i.e. la dispersion des gouttes par la turbulence gazeuse et le procès d'évaporation dans le contexte de la Simulation Aux Grandes Echelles (SGE) des configurations complexes. Premièrement, l'approche Euler-Euler mésoscopique (Février et al. (2005)), basée sur une moyenne d'ensemble conditionnée et implémentée dans AVBP est améliorée. Le modèle de fermeture (Simonin et al. (2001); Kaufmann (2004)) pour les moments de deuxième ordre qui apparait dans les équations de transport résolues échoue quand appliqué à des configurations cisaillées (Riber (2007)). Plusieurs modèles proposés récemment par Masi (2010) et qui ont été valides a priori dans une configuration de nappe chargée de particules sont validés a posteriori dans la même configuration. Une analyse quantitative sur plusieurs cas avec diffèrent nombres de Stokes, nombres de Reynolds de la phase gazeuse et résolutions du maillage ont permit de retenir un modèle non-linéaire nommé 2EASM3, qui utilise le tenseur de déformations de la phase dispersée comme échelle de temps caractéristique. La deuxième partie a pour but l'amélioration du modèle d'évaporation implémenté dans AVBP. Ce modèle suppose une conduction infinie dans la phase liquide et symétrie sphérique dans la phase gazeuse ainsi que des lois simplifiées pour les propriétés thermodynamiques et de transport. Un nouveau modèle prenant en compte la dépendance de la viscosité du mélange gazeux avec la composition locale, et des nombres de Prandtl et Schmidt fixés par les valeurs à l'équilibre obtenus par moyen d'une simulation prenant en compte des lois complexes pour les propriétés thermodynamiques et de transport est proposé. Cette nouvelle méthode produit des résultats en bon accord avec les mesures expérimentales pour l'évaporation d'une goutte isolée en une atmosphère d'azote au calme sans pourtant augmenter le cout du calcul. Finalement, l'impact des nouveaux modèles est analysé dans une SGE de la configuration semi-industrielle MERCATO (García-Rosa (2008)). Bien que les données expérimentales ne soient pas suffisantes pour confirmer les résultats, les distributions de gouttes et de carburant gazeux sont significativement affectés par les modèles, ce qui pourrait avoir un impact direct sur le procès d'allumage.

L'évaporation flash est un phénomène qui se caractérise par la vaporisation partielle d'une fraction liquide d'un fluide (chargé ou non en particules solides), provoquant le refroidissement de la matière non vaporisée. Le travail proposé a pour objectif de développer un outil d'aide à la décision pour la conception préliminaire d'un procédé d'évaporation flash bi-étagé. Cet outil est basé sur la mise en oeuvre d'une démarche de formalisation en trois étapes. L'analyse et la structuration du problème (étape 1), visent à déterminer et sélectionner les éléments pertinents du problème de conception préliminaire. Les éléments retenus concernent la modélisation des phénomènes physiques liés au comportement des composants, comme les condenseurs, le dévésiculeur, la pompe à vide, etc. Ils se rapportent également à des critères technico-économiques et à des écocritères. La formulation et la qualification des modèles (étape 2) conduisent à l'expression d'un Problème de Satisfaction de Contraintes (CSP) formulé et adapté à un contexte et à des outils d'aide à la décision. La qualification du modèle lié au comportement physique du procédé d'évaporation flash bi-étagé a été réalisée à partir de résultats expérimentaux obtenus à l'aide d'un pilote instrumenté. Le traitement numérique du problème de conception (étape 3) est ensuite réalisé à l'aide d'un solveur CSP, permettant de résoudre des problèmes hétérogènes (variables définies sur des domaines continus ou énumérés, contraintes égalitaires, inégalitaires ou règles logiques). Les différents problèmes de conception traités dans le cadre de ce travail ont permis la validation de la démarche de formalisation pour la conception préliminaire de procédés d'évaporation flash, en aboutissant à des solutions techniques performantes sur les plans énergétique et environnemental, qui offrent une réduction du volume de l'installation conséquente et permettent une optimisation de l'exploitation de ressources (matériaux, énergie, eau).

The photoactive component of a polymeric organic solar cell can be produced by drying a mixture consisting of a volatile solvent and non-volatile polymers. As the solvent evaporates, the polymers demix and self-assemble into microscale structures, the morphology of which plays a pivotal role in determining the efficiency of the resulting device. Thus, a detailed understanding of the physical mechanisms that drive and influence structure formation in evaporating solvent-polymer mixtures is of high scientific and industrial value. This thesis explores several problems that aim to produce novel insights into the dynamics of evaporating solvent-polymer mixtures. First, the role of compositional Marangoni instabilities in slowly evaporating binary mixtures is studied using the framework of linear stability theory. The analysis is non-trivial because evaporative mass loss naturally leads to a time-dependent base state. In the limit of slow evaporation compared to diffusion, a separation of time scales emerges in the linear stability problem, allowing asymptotic methods to be applied. In particular, an asymptotic solution to linear stability problems that have slowly evolving base states is derived. Using this solution, regions of parameter space where an oscillatory instability occurs are identified and used to formulate appropriate conditions for observing this phenomenon in future experiments. The second topic of this thesis is the use of multiphase fluid models to study the dynamics of evaporating solvent-polymer mixtures. A two-phase model is used to assess the role of compositional buoyancy and to examine the formation of a polymer-rich skin at the free surface. Then, a three-phase model is used to conduct a preliminary investigation of the link between evaporation and phase separation. Finally, this thesis explores the dynamics of a binary mixture that is confined between two horizontal walls using a diffusive phase-field model and its sharp-interface and thin-film approximations. We first determine the conditions under which a homogeneous mixture undergoes phase separation to form a metastable bilayer. We then present a novel mechanism for generating a repeating lateral sequence of alternating A-rich and B-rich domains from this bilayer.

Ce mémoire présente un modèle complexe des transferts de masse et de chaleur entre un sol nu et l'atmosphère. Un code numérique en éléments finis adapté à la présence de stratifications pédologiques est développé. Les résultats des calculs montrent un bon accord avec les observations expérimentales effectuées sur une parcelle agricole de 3600 m². Le modèle est alors utilisé pour analyser les processus physiques intervenant dans la dynamique des transferts s'appuyant sur ces analyses, un modèle simplifié est présenté et une approche vers une paramétrisation des flux d'évaporation est analysée en introduisant le concept de résistance à la surface du sol

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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior
Composites based on PEEK + PTFE + CARBON FIBER + Graphite (G_CFRP) has increased application in the top industries, as Aerospace, Aeronautical, Petroleum, Biomedical, Mechanical and Electronics Engineering challenges. A commercially available G_CFRP was warmed up to three different levels of thermal energy to identify the main damage mechanisms and some evidences for their intrinsic transitions. An experimental test rig for systematize a heat flux was developed in this dissertation, based on the Joule Effect. It was built using an isothermal container, an internal heat source and a real-time measurement system for test a sample by time. A standard conical-cylindrical tip was inserted into a soldering iron, commercially available and identified by three different levels of nominal electrical power, 40W (manufacturer A), 40W (manufacturer B), 100W and 150W, selected after screening tests: these power levels for the heat source, after one hour of heating and one hour of cooling in situ, carried out three different zones of degradation in the composite surface. The bench was instrumented with twelve thermocouples, a wattmeter and a video camera. The twelve specimens tested suffered different degradation mechanisms, analyzed by DSC (Differential Scanning Calorimetry) and TG (Thermogravimetry) techniques, Scanning Electron Microscopy (SEM) and Energy-Dispersive X-Rays (EDX) Analysis. Before and after each testing, it was measured the hardness of the sample by HRM (Hardness Rockwell M). Excellent correlations (R2=1) were obtained in the plots of the evaporated area after one hour of heating and one hour of cooling in situ versus (1) the respective power of heat source and (2) the central temperature of the sample. However, as resulting of the differential degradation of G_CFRP and their anisotropy, confirmed by their variable thermal properties, viscoelastic and plastic properties, there were both linear and non-linear behaviour between the temperature field and Rockwell M hardness measured in the radial and circumferential directions of the samples. Some morphological features of the damaged zones are presented and discussed, as, for example, the crazing and skeletonization mechanism of G_CFRP
Comp?sitos baseados em matrizes polim?ricas de PEEK e PTFE, refor?adas com fibra de carbono e grafite (G_CFRP) apresentam crescente aplica??o e desafios ? Engenharia nas ind?strias Aeroespacial, Aeron?utica, de Petr?leo, Biom?dica, Mec?nica e Eletr?nica. Um comp?sito G_CFRP foi aquecido em tr?s n?veis de energia t?rmica para identificar os principais mecanismos de dano e algumas evid?ncias em suas transi??es de mecanismos. Uma bancada experimental foi desenvolvida para sistematizar o fluxo t?rmico com base no Efeito Joule. Foi constru?da usando-se um recipiente isot?rmico, uma fonte quente interna e um sistema de medidas em tempo real para ensaiar um corpo-de-prova (CP) de cada vez. Uma ponta c?nica-cil?ndrica foi inserida em um ferro de soldar, comercialmente dispon?vel e identificado por tr?s diferentes n?veis de pot?ncia el?trica, 40W (fabricante A), 40W (fabricante B), 100W e 150W, selecionados ap?s ensaios piloto: estes n?veis de pot?ncia para a fonte quente, ap?s uma hora de aquecimento e uma hora de resfriamento in situ, promoveu tr?s zonas diferentes de degrada??o na superf?cie do comp?sito. A bancada foi instrumentada com doze termopares, um watt?metro e uma c?mera de v?deo. Os doze C.P. ensaiados apresentaram diferentes mecanismos de degrada??o, analisados pelas t?cnicas de Calorimetria Diferencial Explorat?ria (DSC) e Termogravimetria (TG), e pelas an?lises de Microscopia Eletr?nica de Varredura (MEV) e Energia Dispersiva de Raios-X (EDS). Antes e ap?s cada ensaio, foram feitos ensaios de dureza Rockwell M (HRM). Excelentes correla??es (R2=1) foram obtidas nas curvas da ?rea evaporada ap?s uma hora de aquecimento e uma hora de resfriamento in situ versus (1) a respectiva pot?ncia da fonte quente e (2) a temperatura central do C.P. entretanto, como resultado da degrada??o diferencial do G_CFRP e da sua anisotropia, confirmadas por suas propriedades t?rmicas vari?veis, propriedades viscoel?sticas e viscopl?sticas, houve comportamentos linear e n?o-linear entre o campo de temperatura e a HRM medidos nas dire??es radial e circunferencial dos C.P. Algumas peculiaridades morfol?gicas das zonas de dano s?o apresentadas e discutidas, como, por exemplo, os mecanismos de dano por crazing e esqueletiza??o do G_CFRP

碩士
華梵大學
機電工程研究所
96
The pixel design of the manufacture process in the organic light-emitting diodes (OLED) is more precise in the pass decade. The stability of manufacture process depends on the magnetic force and polarity of magnetic pad regarding the shielding mask during the evaporation process in fabricating the OLED devices. In this thesis, we will discuss the relative properties using the The pixel design of the manufacture process in the organic light-emitting diodes (OLED) is more precise in the pass decade. The stability of manufacture process depends on the magnetic force and polarity of magnetic pad regarding the shielding mask during the evaporation process in fabricating the OLED devices. In this thesis, first of all, we will discuss the relative properties using the mass-production equipments then calculated and monitoring through the SPC chart or the fundamental quality-analysis; secondly, the influence on process yield against the magnetic force and polarity of magnetic pad regarding the shadow mask will also be investigated in the research. Finally, we will build up an appropriate operation process on gap tuning and define the gap range of the assembly-mechanism. In the end, the optimization on the arrangement, distribution and the strength of the magnetic force should be clarified in this work. Key words： Organic Light-Emitting Diodes（OLED），Pixel，Shadow Mask，Magnet Pressing Mechanism，Magnetic Force，Magnetic Polarity，Shadow Effect

碩士
淡江大學
航空太空工程學系碩士班
101
This paper discussed the evaporation of droplets on a high-temperature plate. The study was divided into two parts. First part concerned the dimensional analysis of the parameters of the flow and droplet. Second part included the numerical simulation of the characteristics of the heat and mass transfer induced by evaporation through heating of the moving droplets. Using dimensional analysis, the evaporation of the droplets were function of the temperature of the environment , the air flow rate from the nozzle, the concentration, the droplet size and the droplet velocity. The DPM (Discrete Phase Model) module included in Fluent was used for the computation of the velocity and temperature distributions above a heated plate. From the result of simulation, the upflowing heated air stream was impacted by the nozzle flow. This affected the movement and temperature of the droplet. According to both analytical and numerical results, the larger the diameter , the higher evaporation rate would be. However, the larger the diameter, the smaller diameter reduction rate was observed.

碩士
國立中興大學
材料科學與工程學系所
102
We product CIGS absorb layers by three-stage evaporation process. The CIGS thin films deposited on the Mo/Al2O3 and Mo/SLG, The experimentals are the Cu flux, Cu/(In + Ga) ratio and substrate temperature. In the second stage, CIGS thin film is deposited on a Mo/Al2O3. In、Ga are transported quickly by Cu vacancy of Cu2-xSe, so that it helps the grain size of CIGS grows, and becauce diffusivity of Ga is slower than In, that causes Ga granding.When changing the Cu flux, the distribution of Cu in the thin film is non-uniform and this phenomenon can improve the deffusion rate of In, Ga durning the third stage. CIGS thin films almost form (112) orintaion, but in the high Cu flux and high Cu/(In+Ga) ratios it will change the orintaion to (220/204). CIGS thin film is depositied on Mo/SLG durning the third stage. Na is increasing the mobility of surface atoms to promote Ga diffusion in the thin films and the more Cu vacancy which can generat the more NaInSe2. CIGS thin film is depositied on different substrate temperature durning the third stage.When the substrate temperature rised, the Ga diffuse to the top of thin film of CIGS. Na added to CIGS thin film, when the substrate temperature rised, the grain size is increasing, and Na2SeO3 prohibit the Ga deffusion in the surface.

Due to the increasing interest in low-cost, lightweight, and wearable technologies, flexible and printed electronics has become an intensive field of research during the last two decades. This research is mainly focused on the development of solution-processed organic materials, the evolution of diverse appropriate printing technologies and the enhancement of electronic device performance. Compared to conventional electronics, printed technologies allow for cheaper and easier processing but much poorer resolution, which results in comparatively large organic field effect transistor (OFET) channel lengths of a few ten microns. Reducing the channel length requires the use of additional methods such as wetting-based and non-printed approaches. The minimisation of the channel length is crucial in order to obtain higher frequencies and increasing currents. Therefore, overcoming the resolution limitation is one of the challenging topics in the field of printed electronics. In this thesis, a new approach for the realisation of fully inkjet-printed small-channel OFETs is investigated. For this purpose, a piezoelectric Drop-on-Demand (DOD) inkjet printer with 10 pl printheads is employed. This approach involves a self-aligned, dewetting-based technique for the reproducible fabrication of source and drain electrodes with homogeneous and well-controllable channel lengths down to 4 μm. For the realisation of these electrodes, a water-based, hydrophobic nanoparticle (NP) dispersion is initially printed and dried at room temperature in order to spontaneously form a thin hydrophobic twin-line of few microns due to the so-called coffee ring effect (CRE). This mechanism is responsible for the migration of the NPs from the center to the edge of the printed line during evaporation. An alcohol-based silver NP ink is subsequently printed on the hydrophobic lines and self-aligned to split into two separated source and drain electrodes. Dispersions with different materials such as polytetrafluoroethylene (PTFE) and fluoroplastic NPs, different particle sizes and concentrations are evaluated in order to optimize the twin line deposition and the dewetting of the silver ink. Optimum dispersions are printed, then characterised on untreated polyethylene naphthalate (PEN) foils and oxygen plasma treated dielectrics such as cross-linked poly-4-vinylphenol (c-PVP) and cross-linked polymethyl methacrylate (c-PMMA). To evaluate the influencing parameters on the twin-line deposition, a model is developed for the calculation of the printed rivulet width and the electrode gap, which is determined by the width of the hydrophobic ring. These dimensions are investigated as functions of the printing parameters, NP concentration, line geometry, and wetting properties. Multiple simulations are used to determine the influence of each parameter on the twin-line deposition and calculate the critical channel length, below which the dewetting of the conductive ink on the hydrophobic line is no more possible. Based on the simulation results, the optimum parameters are used to control the gap between the printed source and drain electrodes. The underlying mechanism is finally employed for the realisation of fully inkjet-printed OFETs on plastic substrates with small channel lengths and a bottom gate bottom contact configuration (BGBC). For this purpose, a silver NP ink is used for the electrodes, a PTFE NP dispersion is printed on c-PVP and a small-molecule 6,13-Bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene) solution is used for the semiconducting layer. Multiple small-channel OFET arrays are furthermore fabricated with a good reproducibility of the channel length and a high yield, which proves the industrial applicability of the proposed approach.
Die Integration kostengünstiger, leichter und tragbarer Technologien gewinnt zunehmend an Interesse. Dies führt kontinuierlich zu einer rasanten Zunahme der Forschungsaktivitäten im Bereich der flexiblen und gedruckten Elektronik. Der Fokus liegt hierbei überwiegend auf der Entwicklung organischer Materialien, Herstellung von geeigneten Druckverfahren und Verbesserung der Leistungsfähigkeit gedruckter elektronischer Bauteile. Ein ausschlaggebender Vorteil der gedruckten gegenüber der konventionellen Elektronik liegt darin, dass sie eine preiswerte und einfache Prozessierung ermöglicht. Die Beeinträchtigung dieser jungen Technologie ist immer noch die schwächere Auflösung, welche zur Erstellung von organischen Feldeffekttransistoren (OFETs) mit vergleichbar größeren Kanallängen von einigen zehn Mikrometern führt. Die Reduzierung der Kanallänge erfordert die Verwendung zusätzlicher Hilfsmethoden z.B. oberflächenspannungsstrukturiertes Drucken oder “non-printing”-Technologien. Die Minimierung der Kanallänge ist entscheidend, um höhere Frequenzen und Ströme zu erzielen. Daher ist die Optimierung der Auflösung ein wesentlicher Parameter, um die Technologie weiter zu entwickeln. Die vorliegende Arbeit stellt ein neu entwickeltes Verfahren zur Realisierung von All-Inkjet-gedruckten OFETs mit kleinen Kanallängen dar. Hierbei wird ein Drop- on-Demand (DOD) Inkjet-Drucker mit 10pl-Druckköpfen eingesetzt. Dieses Verfahren basiert auf einem oberflächenspannungsabhängigen Ansatz für die reproduzierbare Erstellung von Source- und Drainelektroden mit homogenen und kontrollierbaren Kanallängen bis 4 μm. Beim Erstellen dieser Elektroden wird zuerst eine wasserbasierte Dispersion mit hydrophoben Nanopartikeln gedruckt und bei Raumtemperatur getrocknet. Während der Trocknungsphase wird der sogenannte Kaffeeringeffekt (CRE) zu Nutze gemacht. So führt der CRE zur Migration der Nanopartikeln vom Zentrum bis zum Rand der gedruckten Struktur. Diese gerichtete Migration bewirkt eine spontane Erstellung einer dünnen hydrophoben Doppellinie mit einer Breite von nur wenigen Mikrometern. In einem weiteren Schritt wird eine alkoholbasierte Silbernanopartikeltinte über die hydrophobe Linie gedruckt. Aufgrund der niedrigen Oberflächenenergie der darunter befindlichen hydrophoben Linie, teilt sich die leitfähige Tinte in zwei voneinander getrennte Strukturen, die zunächst als Source- und Drainelektroden eingesetzt werden. Um dieses Verfahren zu optimieren, werden im Rahmen dieser Arbeit Dispersionen mit verschiedenen hydrophoben Materialien wie Teflon- oder fluoroplastische Nanopartikeln unterschiedlicher Partikelgrößen und Konzentrationen untersucht. Die optimale Dispersion wird darauffolgend auf unbehandelten PEN-Folien und sauerstoffplasmabehandelten Dielektrika wie vernetztem Poly-4-Vinylphenol (c- PVP) und vernetztem Polymethylmethacrylat (c-PMMA) gedruckt und anschließend charakterisiert. Um den Einfluss verschiedener Parameter auf dieses Verfahren zu evaluieren, wurde ein Modell für die Berechnung der Breiten der gedruckten Struktur und der getrockneten hydrophoben Doppellinie, die den Elektrodenabstand bestimmt, entwickelt. Diese Dimensionen werden in Abhängigkeit verschiedener Druckparameter, Nanopartikelkonzentrationen, Liniengeometrien und Benetzungseigenchaften untersucht. Zunächst werden Simulationen durchgeführt, um den Einfluss von jedem Parameter auf die Doppellinienentstehung zu bestimmen. Dieses Modell ist ebenfalls erforderlich für die Berechnung der kritischen Kanallänge, unter welcher keine Entnetzung der leitfähigen Tinte auf der hydrophoben Linie mehr möglich ist. Die gewonnenen Simulationsergebnisse bzw. die optimalen Parameter werden für die Kontrolle des Abstands zwischen den Source- und Drainelektroden beim Drucken eingesetzt. Das beschriebene Verfahren wird zur Realisierung von All-Inkjet-gedruckten OFETs mit kleinen Kanallängen auf Plastiksubstraten in einer Bottom-Gate-Bottom-Contact-Konfiguration (BGBC) verwendet. Die benutzten Materialien bestehen aus einer Silbernanopartikeltinte für die Source-, Drain- und Gateelektroden, c-PVP für das Dielektrikum und TIPS-Pentacen für den Halbleiter. Multiple OFET-Arrays werden zum Schluss mit hoher Reproduzierbarkeit der Kanallängen und hoher Ausbeute gedruckt, um die industrielle Anwendbarkeit des vorgestellten Verfahren zu zeigen.

碩士
國立虎尾科技大學
機械與電腦輔助工程系碩士班
105
PVD coatings are today frequently used in order to improve the tribological performance of cutting tools, forming tools and machine components. In this study, optical emission spectroscopy (OES) was employed to identify the species present in the plasma and to correlate them with the properties of the deposited thin films. VN-based coatings are known to show a combination of high hardness and toughness and the possibility to form a low friction Magnéli phase, promoting low friction coefficient in sliding contact, and consequently these coatings are of interest for sliding contact tribosystems. In this study, TiVN coatings were synthesized by cathodic arc evaporation (CAE). Pure Ti and TiV alloy cathodes were used for the deposition of TiVN coatings. By controlling the different bias voltage, the deposited monolayered TiVN coatings possessed different mechanical properties and plasma characteristics of TiVN hard coatings. Plasma characteristics were observed by optical emission spectroscopy (OES). The microstructure of the deposited coatings was investigated by a field emission scanning electron microscope (FE-SEM), equipped with an X-ray energy dispersive spectrometer (EDS). Glancing angle X-ray diffraction was used to characterize the microstructure and phase identification of the films. A field emission transmission electron microscope (FE-TEM) to characterize the microstructure and phase identification of TiVN-200V coating after oxidation at 500˚C. The information of surface element distribution and chemical bonding of wear tracks is measured by X-ray photoelectron spectrometer (XPS). Mechanical properties, such as the hardness, were measured by means of Vickers indentation. The adhesion strength and impact fatigue performance of the coatings were evaluated by Rockwell indentation and dynamic impact fatigue device. Ball-on-disk wear test at room temperature and high temperature was conducted to evaluate the tribological properties of the deposited coatings. Finally, a field end milling test of SUS 304 stainless steel was conducted to investigate the tool performance by employing the TiVN coatings. Flank wear of the coated end mills and the surface roughness of the machined workpieces were measured. The experimental result showed that monolayered TiVN-200V coating possessed the B1-NaCl structure and the fewest microparticles. It possessed the highest hardness (25.8GPa) and the best adhesion (class 0). Besides, the TiVN-200V coating showed good impact resistance (higher than 4×105 impacts). The residual stress of TiVN coatings increased as bias voltage increased. The best tribological performance of TiVN coatings is TiVN-200V. It possessed low friction coefficient (0.38) and low wear rate (7.5×10-7mm3/Nm). A field end milling test also showed TiVN-200V coating possessed the lowest flank wear (40.7µm) and the best surface roughness (Ra：0.5µm) of the machined workpieces. Finally, it can be concluded that vanadium incorporation provided self-lubricous abilities achieving low friction coefficient due to oxide formation at elevated temperatures.

碩士
國立高雄應用科技大學
機械與精密工程研究所
96
In recent years, numerical analysis of finite element method is widely used in metal forming. Simulation analysis was confirmed to be a very useful tool in the design stage. The goal of this research is to design a new evaporator for nitrogen liquid for semiconductor usage which is composed of aluminum tube and stainless pipe. The mechanical tests, such as macro etching, tensile test and hole-expansion test, were used to verify the strength of seam aluminum tube. From experiments, these tubes did not break. It means that they have sufficient strength at welding line. Two engineering analysis software (DEFORM 2D and 3D) were used for simulating the extrusion of aluminum seam tube and rolling process for gap closing of aluminum tube and stainless pipe. Most important issues related to metal forming process, such as stress, strain and gap closing mechanism were studied. Through the locking process simulation of two-part fins, although the assembly process has been completed, gaps happened. These gaps will result in ice phenomenon which become thermal resistance of evaporator. It further reduces the efficiency of thermal conductivity. Modification design becomes a single piece of aluminum fin tube coming from hot hollow extrusion process. Through DEFORM simulation of extrusion process, several issues were studied, such as stress concentration of extrusion die and flow pattern of extrude aluminum part. An aluminum fin tube with more than 6 meter long has been successfully extruded in factory. Further, a roll forming mechanism was designed to make sure the gap will close after stainless pipe inserted into aluminum fin tube to produce an IC-level evaporator of hydrogen liquid.

Due to failure of the continuum hypothesis for higher Knudsen numbers, rarefied gases and microflows of gases are particularly difficult to model. Macroscopic transport equations compete with particle methods, such as the direct simulation Monte Carlo method (DSMC) to find accurate solutions in the rarefied gas regime. Due to growing interest in micro flow applications, such as micro fuel cells, it is important to model and understand evaporation in this flow regime. To gain a better understanding of evaporation physics, a non-steady simulation for slow evaporation in a microscopic system, based on the Navier-Stokes-Fourier equations, is conducted. The one-dimensional problem consists of a liquid and vapor layer (both pure water) with respective heights of 0.1mm and a corresponding Knudsen number of Kn=0.01, where vapor is pumped out. The simulation allows for calculation of the evaporation rate within both the transient process and in steady state. The main contribution of this work is the derivation of new evaporation boundary conditions for the R13 equations, which are macroscopic transport equations with proven applicability in the transition regime. The approach for deriving the boundary conditions is based on an entropy balance, which is integrated around the liquid-vapor interface. The new equations utilize Onsager relations, linear relations between thermodynamic fluxes and forces, with constant coefficients that need to be determined. For this, the boundary conditions are fitted to DSMC data and compared to other R13 boundary conditions from kinetic theory and Navier-Stokes-Fourier solutions for two steady-state, one-dimensional problems. Overall, the suggested fittings of the new phenomenological boundary conditions show better agreement to DSMC than the alternative kinetic theory evaporation boundary conditions for R13. Furthermore, the new evaporation boundary conditions for R13 are implemented in a code for the numerical solution of complex, two-dimensional geometries and compared to Navier-Stokes-Fourier (NSF) solutions. Different flow patterns between R13 and NSF for higher Knudsen numbers are observed which suggest continuation of this work.
Graduate

The first part of the thesis investigates the use of theoretical quantum chemical calculations for the study of the reaction pathways of the atmospheric aromatic-OH reaction. The computational model is comprised of a semi-empirical PM3 geometry optimization followed by a single point calculation performed using the Becke3LYP hybrid density functional and a 6-31G(d,p) basis. Zero-point energies were calculated using PM3, and transition states barrier heights estimated by a constrained optimization procedure developed for this study. Full mechanisms for the OH-initiated photooxidation of toluene, m-xylene, p-xylene, 1,2,4-trimethylbenzene and m-ethyltoluene are developed. The lowest energy intermediates have been determined and predicted products from these structures are compared to available experimental product data. These studies serve to refine proposed mechanisms currently available for toluene, mxylene and p-xylene, while providing new information on the 1,2,4-trimethylbenzene and m-ethyltoluene reaction pathways. In the second part of the thesis, an experimental technique is described for probing the mechanism and dynamics of charged droplet breakup in electrospray ionization. At its core is an instrument that can perform simultaneous, in situ measurements of size and charge on individual droplets. Charged droplets are sampled directly from the spray source into a drift cell with a uniform electric field. A simultaneous diameter and charge measurement is made on individual droplets at the center of the cell using phase Doppler anemometry. By reversing the field in the drift chamber once the initial size and charge measurement is made, the droplet can be made to pass again through the measurement region of the phase Doppler anemometer. In this way, repeated measurements of the size and charge can be made on a single droplet. This technique has been applied to a variety of solutions used commonly in electrospray ionization and lead to the following generalizations. (1) The discharge dynamics of droplets with the same initial diameter and charge are highly reproducible for all solvents and analyte/solvent combinations studied to date. (2) Published over a hundred years ago, Lord Rayleigh's analysis of charged droplet instabilities resulting from solvent evaporation is remarkably accurate in predicting observed discharge events for all three solvents. (3) Droplet discharge events are characterized by loss of 15-20% of the charge from methanol and acetonitrile droplets, and 20-40% from water droplets, with little accompanying loss of solvent. (4) Discharge events occur in a reproducible temporal pattern, with decreasing time intervals between successive events, dictated by solvent evaporation and the approach to the Rayleigh limit. The droplet size decrease agrees well with a model of solvent evaporation. (5) The addition of biomolecules or salt (up to 10[superscript -3] M to the solution does not significantly alter discharge dynamics. The size-charge correlation and discharge dynamics of negatively charged droplets formed in electrospray ionization of 10[superscript -4] M NaCl in methanol are similar to those observed for positively charged droplets. (6) The life history of a single electrosprayed droplet can be followed through numerous discharge events (sequences with up to 50 measurements and 6 discharges have been observed) in the absence of radial confinement. This implies that no significant displacement of the droplet arises from discharge events and is inconsistent with any notion of high energy chaotic fission processes. (7) Droplet size-charge correlations show that, in certain instances, droplets from an electrospray fall into discrete groupings that can be attributed to fission events.

In der vorliegenden Arbeit wird die großflächige Abscheidung von organischen Leuchtdioden (OLED) für Beleuchtungsanwendungen in einer neuartigen Beschichtungsanlage vorgestellt. Ausgehend von den speziellen Anforderungen an gleichförmige Schichtdickenverteilung und hohe Abscheideraten für die organischen Schichten, sind die Verfahren der thermischen Vakuumverdampfung (VTE) und der organischen Dampfphasenabscheidung (OVPD) auf Substraten der Größe 370 x 470 mm² unter Fertigungsbedingungen kombiniert. Die Quellensysteme der Anlage wurden hinsichtlich der Verteilung des Materialauftrages und der Oberflächenrauigkeit qualifiziert. Die Kontrolle der Schichteigenschaften ist bei der organischen Dampfphasenabscheidung durch Variation der Parameter Substrattemperatur und Abscheiderate in einem weiten Bereich möglich. Die in situ Kontrolle der Schichtdicke mittels spektroskopischer Reflektometrie wird vorgestellt. Ein Messsystem ist in die Beschichtungsanlage integriert und abgeschiedene Schichten charakterisiert worden. Die Arbeit zeigt, dass die genaue Bestimmung der Dicke einzelner Schichten oder ganzer Schichtstapel mit diesem Verfahren möglich ist und zur ex situ Ellipsometrie vergleichbare Ergebnisse liefert. Um robuste OLED-Bauelemente herzustellen, wird eine organische Kurzschlussunterdrückungsschicht eingeführt, die konform mittels der OVPD-Technologie abgeschieden wird. Die strombegrenzenden Eigenschaften dieser Schicht wirken Defektströmen innerhalb der OLED entgegen. Die reproduzierbare Herstellung von 100 x 100 mm² großen, weißes Licht emittierenden OLED-Modulen mit mittleren Leistungseffizienzen von über 13 lm/W zeigt das Potential dieser Technologie.
The thesis deals with the large area deposition of organic light-emitting diodes (OLED) for lighting applications with a novel deposition tool. The special needs of film thicknesses homogeneity and high deposition rates for organic layers request the combination of thermal vacuum deposition (VTE) and organic vapour phase deposition (OVPD) processes to fabricate OLEDs on 370 x 470 mm² substrates. The deposition sources are qualified regarding layer homogeneity and morphology of the deposition processes. The layer properties are controlled in a wide range by the variation of the organic vapour phase deposition parameters: substrate temperature and deposition rate. The in situ determination of the substrate thickness is shown by the application of spectroscopic reflectometry. The thesis demonstrates the thickness analysis of single and multi-layer stacks by reflectometry. The data fit well to ex situ ellipsometry. Robust OLED devices with an additional short-circuit protection layer deposited by OVPD technology are introduced. The current limiting properties of this layer reduce the leakage currents in the OLED device. The fabrication of 100 x 100 mm² white emitting OLED modules with power efficiencies about 13 lm/W shows the great potential of the manufacturing technology.