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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.
61

Paper Spray - Mass Spectrometry: Investigation of Sampling Devices for Illicit Drug Detection and Quantification

Chau Bao Nguyen (11178123) 06 August 2021 (has links)
Different sampling devices for paper spray - mass spectrometry (PS - MS) were investigated to improve the assay’s simplicity and sensitivity over traditional approaches. In the first one, pressure-sensitive adhesive paper was used as both sampling tool to collect drug residues on surfaces and paper substrate in PS - MS analysis. This method showed a significant improvement in drug collection on surfaces leading to low nano-gram level detection limits. Other sampling device being investigated was snap-in solid-phase extraction column, which demonstrated the ability to detect trace amounts of drugs in plasma while allowed easy transportation and the use of PS - MS automated system.
62

Neue Methoden und Konzepte für hochintegrierte Gas- und Drucksensoren

Komenko, Vladislav 20 January 2022 (has links)
Im Rahmen der vorliegenden Arbeit wurden die technologischen Ansätze zur Erzeugung von Mikro-Kavitäten als Grundlage zur Entwicklung und Erprobung neuer Konzepte der MEMS-basierten Aktoren und Sensoren erfolgreich eingesetzt. Im Verlauf der Integration eines IR-Emitters wurde der SON-Prozess weiterentwickelt, um eine hohe und homogene Verteilung der Dotierstoffe innerhalb der SON-Membran zu erreichen. Dabei wurde ein technologischer Ablauf entwickelt, welcher die genannten Randbedingungen erfüllt und darüber hinaus eine optimierte Herstellung anbietet, indem die zeitaufwändige Formierung der Kavität in einem Batch- anstatt eines RTP-Ofens erfolgt. Die Opferschichttechnik wurde bei der Integration von beiden vorgestellten Bauelementen eingesetzt und mit Rücksicht auf die einzelnen Randbedingungen angepasst. So konnte z. B. eine Kavität mit einer Höhe von 700 nm zur Abdeckung von IR-Emitter hergestellt werden, wodurch die thermische Isolation verbessert wurde. Im Konzept des druckempfindlichen Feldeffekttransistors wurde eine Opferschicht mit einer Dicke von 70 nm verwendet, um die Größe der Gate-Kapazität so anzupassen, dass der hergestellte Transistor steuerbar und druckempfindlich ist. Somit konnten die Flexibilität und das Potenzial der beiden Prozessknotenpunkte verdeutlicht werden.:Symbolverzeichnis Abkürzungsverzeichnis 1 Einleitung 1.1 Einführung zum Thema 1.2 Technologien zur Herstellung von Mikro-Kavitäten für MEMS 1.2.1 Silicon-On-Nothing Technologie 1.2.2 Opferschichttechnik 2 Das neue Konzept einer breitbandigen Infrarotquelle 2.1 Grundlegende Ideen der Infrarot-Sensorik 2.1.1 Wechselwirkung von Infrarotstrahlung mit CO2-Gas 2.1.2 Prinzipielle Funktionsweise eines IR-Emitters 2.1.3 CMOS-kompatible Materialien und Integrationsmöglichkeiten eines IR-Emitters 2.1.4 Das neue Konzept eines Infrarot-Emitter-Systems basierend auf monokristallinem Silizium 2.2 Finite-Elemente-Methode-Simulation des IR-Emitter-Systems 2.2.1 Geometrievarianten 2.2.2 Temperaturabhängige elektrische Eigenschaften des Bauelements 2.2.3 Betrachtung der thermischen Verluste 2.2.4 Simulation der Wärmeentwicklung 3 Herstellung und Charakterisierung eines IR-Emitters 3.1 Module der CMOS-basierten 3D-Integration 3.1.1 FEOL - Front End of Line 3.1.2 BEOL - Back End of Line 3.2 Elektrische Charakterisierung des IR-Emitters 3.2.1 I(V)-Spektren 3.2.2 Optische Eigenschaften 3.2.3 Zeitabhängiges Verhalten 4 Das neue Konzept eines druckempfindlichen Feldeffekttransistors 4.1 Einleitung zum Konzept des Bauelements 4.1.1 Konzepte zur Herstellung von MOSFET - basierten Sensoren 4.1.2 Prinzipieller Aufbau und Funktionsweise des neuen Konzepts 4.1.3 Geometrievarianten 5 Herstellung und Charakterisierung eines druckempfindlichen Feldeffekttransistors 5.1 CMOS-basierte 3D-Integration 5.1.1 Herstellung des MEMS-Elements: FEOL - Module 5.1.2 Herstellung des MEMS-Elements: BEOL - Module 5.2 Elektrische Charakterisierung des Feldeffekttransistors 5.2.1 Ausgangskennlinienfeld unter Normaldruck 5.2.2 Eingangskennlinien und deren Besonderheiten unter Normaldruck 5.3 Verhalten des Transistors bei veränderbarem Gasdruck 5.3.1 Designvariante I 5.3.2 Designvariante II 5.3.3 Designvariante III 5.3.4 Druckmessung mit Konstantstromquelle 5.4 Optimierung der Transistoreigenschaften 5.4.1 Anpassung des Gate-Dielektrikums und der Dotierung des Kanals 5.4.2 Ausgangskennlinien unter Normaldruck nach der Optimierung 5.4.3 Eingangskennlinien unter Normaldruck nach der Optimierung 5.4.4 Druckmessung nach der Optimierung 5.4.5 Bewertung der Prozessoptimierung anhand der Referenz-Strukturen 6 Zusammenfassung und Ausblick 6.1 Zusammenfassung zum IR-Emitter 6.2 Zusammenfassung zum Drucksensor Literatur Abbildungsverzeichnis Tabellenverzeichnis
63

Enhanced adhesives for the encapsulation of flexible organic photovoltaic modules / Adhésifs améliorés pour l'encapsulation des modules organiques photovoltaïques flexibles

Boldrighini, Patrick Mark 30 June 2015 (has links)
La limitation de perméation des gaz aux bordes de l’encapsulation des photovoltaïques organiques flexibles a été adressée par l’identification des chemins de perméation du vapeur d’eau et par la formulation des nanocomposites adhésives. Une version modifiée du test de calcium optique a été développée pour identifier l’importance des chemins de perméation différents présent dans l’encapsulation des modules photovoltaïques organiques flexibles. Les nanoparticules des phyllosilicates et les nanoparticules des zéolithes ont été dispersées dedans les formulations des adhésifs différents incluant les adhésifs acryliques sensibles à pression et les adhésifs UV réticulables. Les propriétés mécaniques, optiques, et barrières de vapeur d’eau des nanocomposites ont été caractérisés en plus de leur photo-stabilité sous irradiation UV. Les nanocomposites ont été également utilisés pour encapsuler les cellules photovoltaïques organiques et la stabilité des dispositifs a été évaluer sous les conditions de vieillissement accélérés d’humidité et température. / In order to address the issue of lateral water and oxygen permeation through the sides of the encapsulation and into flexible organic photovoltaic (OPV) devices, the water vapor permeation pathways were identified and several adhesive nanocomposites formulated and tested to limit these pathways. To identify the relative importance of the various water vapor permeation pathways present in the encapsulation of flexible OPV devices, a modified version of the optical calcium test was developed. Passive nanoparticles (phyllosilicates) and active nanoparticles (zeolites) were both evaluated dispersed in UV curing acrylate adhesives and acrylic block copolymer pressure sensitive adhesives. The nanocomposites were characterized for their mechanical and optical properties as well as their water vapor permeation and UV photostability. The adhesives were also used to encapsulate OPV devices and tested in accelerated humidity aging.
64

[en] INTEGRO-DIFFERENTIAL SOLUTIONS FOR FORMATION MECHANICAL DAMAGE CONTROL DURING OIL FLOW IN PERMEABILITY-PRESSURE-SENSITIVE RESERVOIRS / [pt] SOLUÇÕES ÍNTEGRODIFERENCIAIS PARA CONTROLE DE DANO MECÂNICO À FORMAÇÃO DURANTE ESCOAMENTO DE ÓLEO EM RESERVATÓRIOS COM PERMEABILIDADE DEPENDENTE DA PRESSÃO DE POROS

FERNANDO BASTOS FERNANDES 03 February 2022 (has links)
[pt] A Equação da Difusividade Hidráulica Não-Linear (EDHN) modela o escoamento monofásico de fluidos em meios porosos levando em conta a variação das propriedades da rocha e do fluido presente no interior de seus poros. Normalmente, a solução adimensional da linha-fonte pD(rD, tD) para escoamento de líquidos é encontrada por meio do uso da transformada de Laplace ou transformação de Boltzmann, o qual, o perfil transiente de pressões em coordenadas cartesianas é descrito pela função erro complementar erfc(xD, yD, tD) e, em coordenadas cilíndricas pela função integral exponencial Ei(rD, tD). Este trabalho propõe a solução analítica pelo método de expansão assíntotica de primeira ordem em séries, para solução de alguns problemas de escoamento de petróleo em meios porosos com permeabilidade dependente da pressão de poros e termo fonte. A solução geral será implementada no software Matlab (marca registrada) e a calibração do modelo matemático será realizada comparandose a solução obtida neste trabalho com a solução calculada por meio de um simulador de fluxo óleo em meios porosos denominado IMEX (marca registrada) , amplamente usado na indústria de petróleo e em pesquisas científicas e que usa o método de diferenças finitas. A solução geral da equação diferencial é dada pela soma da solução para escoamento de líquidos com permeabilidade constante e o termo de primeira ordem da expansão assintótica, composto pela não linearidade devido à variação de permeabilidade. O efeito da variação instantânea de permeabilidade em função da pressão de poros é claramente demonstrado nos gráficos diagnósticos e especializados apresentados. / [en] The Nonlinear Hydraulic Diffusivity Equation (NHDE) models the singlephase flow of fluids in porous media considering the variation in the properties of the rock and the fluid present inside its pores. Normally, the dimensionless linear solution for the flow of oil is performed using the Laplace and Fourier transform or Boltzmann transformation and provides the unsteady pressure profile in Cartesian coordinates given by complementary error function erfc(xD, yD, tD) and in cylindrical coordinates described by the exponential integral function Ei(rD, tD). This work develops a new analytical model based on an integro-differential solution to predict the formation mechanical damage caused by the permeability loss during the well-reservoir life-cycle for several oil flow problems. The appropriate Green s function (GF) to solve NHDE for each well-reservoir setting approached in this thesis is used. The general solution is implemented in the Matlab (trademark) and the mathematical model calibration will be carried out by comparing the solution obtained in this work to the porous media finite difference oil flow simulator named IMEX (trademark). The general solution of the NHDE is computed by the sum of the linear solution (constant permeability) and the first order term of the asymptotic series expansion, composed of the nonlinear effect of the permeability loss. The instantaneous permeability loss effect is clearly noticed in the diagnostic and specialized plots.
65

Σχέσεις δομής και ιξωδοελαστικών, μηχανικών και συγκολλητικών ιδιοτήτων πολυακρυλικών σε στερεά υποστρώματα μέσω ατομιστικών προσομοιώσεων / Structure-property (viscoelastic, mechanical, and adhesive) relationships in polyacrylic adhesives through atomistic simulations

Αναστασίου, Αλέξανδρος 27 August 2014 (has links)
The present Doctoral Thesis focuses on the investigation, characterization and influence of polyacrylic materials in different scientific and technological disciplines via a detailed computer simulation using the Molecular Dynamics (MD) technique, in conjunction with the very accurate, all-atom Dreiding force-field. The main research concepts and objectives are discussed and analyzed in three separate parts. In the first part, atomistic configurations of two model pressure-sensitive acrylic adhesives (PSAs), the atactic homopolymer poly(n-BA) [poly(n-butyl acrylate)] and the atactic copolymer poly(n-BA-co-AA) [poly(n-butyl acrylate-co-acrylic acid)] in the bulk phase or confined between two selected substrates, glassy silica (SiO2) and metallic α-ferrite (α-Fe), were built and simulated by MD in the NPT statistical ensemble. First, an equilibration cycle consisting of temperature annealings and coolings was followed, in order to generate well-equilibrated configurations of the PSA systems. Detailed results from the atomistic simulations are presented concerning their volumetric behavior, glass transition temperature, conformational, structural, viscoelastic and dynamic properties. Particular emphasis was given to the analysis and characterization of the hydrogen bonds that form in the poly(n-BA-co-AA) system. By analyzing the MD trajectories, poly(n-BA-co-AA) was found to exhibit a higher density than poly(n-BA) by about 7% at all temperatures, to be characterized by smaller-size chains for a given molecular weight (MW), to exhibit significantly slower terminal and segmental dynamics properties, and to be characterized by a glass transition temperature that was approximately 40% higher than that of poly(n-BA). We also examined the type and degree of adsorption of the two acrylic systems on the selected substrates by analyzing the MD results for the local mass density as a function of distance from the solid plane and the distribution of adsorbed chain segments in train, loop, and tail conformations, and by computing the work of adhesion at the two substrates. The results revealed a stronger adsorption for both acrylics on the SiO2 surface due to highly attractive interactions between polymer molecules and substrate atoms, and as a consequence a higher value for the work of adhesion compared to that on the α-Fe surface. Furthermore, we have developed a generalized non-equilibrium molecular dynamics (NEMD) algorithm to simulate the mechanical response of the two adhesives under a uniaxial stretching deformation. In the second part of the Thesis, results have been obtained from a hierarchical simulation methodology that led to the prediction of the thermodynamic, conformational, structural, dynamic and mechanical properties of two polymer nanocomposites based on syndiotactic poly(methyl methacrylate) or sPMMA. The first was reinforced with uniformly dispersed graphene sheets and the second with fullerene particles. How graphene functionalization affects the elastic constants of the resulting nanocomposite has also been examined. The phase behavior of the nanocomposite (in particular as we varied the relative size between the sPMMA chains and the diameter of fullerene molecules) has also been studied as a function of fullerene volume fraction. The simulation strategy entailed three steps: 1) Generation of an initial structure, which was then subjected to potential energy minimization and detailed molecular dynamics (MD) simulations at T = 500K and P = 1atm to obtain well relaxed melt configurations of the nanocomposite. 2) Gradual cooling of selected configurations down to room temperature to obtain a good number of structures representative of the glassy phase of the polymer nanocomposite. 3) Molecular mechanics (MM) calculations of its mechanical properties following the method originally proposed by Theodorou and Suter. By analyzing the results under constant temperature and pressure, all nanocomposite systems were found to exhibit slower terminal and segmental relaxation dynamics than the pure polymer matrices. The addition of a small fraction of graphene sheets led in all cases to the enhancement of the elastic constants; this was significantly more pronounced in the case of functionalized graphene sheets. We further mention that, for all polymer/fullerene nanocomposites addressed here, no phase separation or variation of polymer chain dimensions was observed as a function of fullerene size and/or fullerene volume fraction. In the third part of the Thesis, and motivated by the use of acrylic polymers for the design of membranes with aligned carbon nanotubes (CNTs) for several separation technologies (such as water desalination and wastewater treatment), we report results from a detailed computer simulation study for the nano-sorption and mobility of four different small molecules (water, tyrosol, vanillic acid, and p-coumaric acid) inside smooth single-wall CNTs (SWCNTs). Most of the results have been obtained with the molecular dynamics (MD) method, but especially for the most narrow of the CNTs considered, the results for water molecule were further confirmed through an additional Grand Canonical (μVT) Monte Carlo (GCMC) simulation using a value for the water chemical potential μ pre-computed with the particle deletion method. Issues addressed in the Thesis include molecular packing and ordering inside the nanotube for the four molecules, average number of sorbed molecules per unit length of the tube, and mean residence time and effective axial diffusivities, all as a function of tube diameter and tube length. In all cases, a strong dependence of the results on carbon nanotube diameter was observed, especially in the way the different molecules are packed and organized inside the CNT. For water for which predictions of properties such as local structure and packing were computed with both methods (MD and GCMC), the two sets of results were found to be fully self-consistent for all types of SWCNTs considered. Water diffusivity inside the CNT (although, strongly dependent on the CNT diameter) was computed with two different methods, both of which gave identical results. For large enough CNT diameters (larger than about 13 Å), this was found to be higher than the corresponding experimental value in the bulk by about 55%. Surprisingly enough, for the rest of the (phenolic) molecules simulated in this Thesis, the simulations revealed no signs of mobility inside nanotubes with a diameter smaller than the (20, 20) tube. This has been attributed to strong phenyl-phenyl attractive interactions, also to favorable interactions of these molecules with the CNT walls, which cause them to form highly ordered, very stable structures inside the nanotube, especially under strong confinement. The interaction, in particular, of the methyl group (present in tyrosol, vanillic acid, and p-coumaric acid) with the CNT walls seems to play a key role in all these compounds causing them to remain practically immobile inside nanotubes characterized by diameters smaller than about 26 Å. It was only for larger-diameter CNTs that tyrosol, vanillic acid, and p-coumaric acid were observed to demonstrate appreciable mobility. / Η παρούσα Διδακτορική Διατριβή εστιάζει στη μελέτη της σχέσης μεταξύ δομής και μακροσκοπικών φυσικών ιδιοτήτων υλικών από πολυακρυλικά μέσω μίας λεπτομερούς προσομοίωσης στον υπολογιστή με τη μέθοδο της Μοριακής Δυναμικής (ΜΔ), σε συνδυασμό με ένα πολύ επακριβές πεδίο δυνάμεων (το Dreiding) σε ατομιστική λεπτομέρεια. Οι κύριες ερευνητικές έννοιες καθώς και οι στόχοι συζητιούνται και αναλύονται σε τρία ξεχωριστά μέρη. Στο πρώτο μέρος, ατομιστικές απεικονίσεις δύο προτύπων πίεσο-ευαίσθητων συγκολλητικών υλικών (acrylic pressure sensitive adhesives ή PSAs), του ατακτικού πολυ-βουτυλικού-ακρυλικού εστέρα (poly(n-BA)) και του συμπολυμερούς του με ακρυλικό οξύ (poly(n-BA-co-AA)), τόσο μακριά όσο και κοντά σε υποστρώματα σίλικας (SiO2) και α-φερρίτη (α-Fe), μελετήθηκαν στη βάση ενός φάσματος ιδιοτήτων (θερμοδυναμικές, δομικές, ιξωδοελαστικές, δυναμικές, και συγκολλητικές), όπως και η μηχανική τους απόκριση υπό συνθήκες μονοαξονικής εκτατικής παραμόρφωσης. Στο δεύτερο μέρος παρουσιάζονται τα αποτελέσματα που εξήχθησαν από μία ιεραρχική μεθοδολογία προσομοίωσης που οδήγησε στην πρόβλεψη της φασικής συμπεριφοράς και των μηχανικών ιδιοτήτων νανοσύνθετων πολυμερικών υλικών (polymer nanocomposites ή PNCs) βασισμένων στο συνδιοτατκτικό πολυ-μεθακρυλικό μεθυλεστέρα (syndiotactic poly(methyl methacrylate) ή sPMMA), ενισχυμένο με ομοιόμορφα διεσπαρμένα φύλλα γραφενίου (graphene sheets) ή σωματίδια φουλερενίου (fullerene particles). Στο τρίτο μέρος, υποκινούμενοι από τη χρήση των ακρυλικών πολυμερών στο σχεδιασμό μεμβρανών με ενσωματωμένους ευθυγραμμισμένους νανοσωλήνες άνθρακα (ΝΑ, carbon nanotubes ή CNTs) σε διάφορες τεχνολογίες διαχωρισμού μορίων (με έμφαση στον καθαρισμό του νερού), παρουσιάζουμε αποτελέσματα από προσομοιώσεις, για τη νανο-ρόφηση και την κινητικότητα τεσσάρων διαφορετικών μικρών μορίων (water, tyrosol, vanilic acid, και p-coumaric acid) στο εσωτερικό λείων μονο-στρωματικών ΝΑ (single-wall CNTs ή SWCNTs). Τα θέματα που εξετάζονται περιλαμβάνουν τη μοριακή διευθέτηση και τη διάταξη στο εσωτερικό Ν.Α. των τεσσάρων μορίων, το μέσο χρόνο παραμονής τους, καθώς και τους αξονικούς συντελεστές διάχυσής του, συναρτήσει της διαμέτρου και του μήκους των ΝΑ.

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