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In this thesis, some fundamentals and possible applications of high-pressure microfluidics have been explored. Furthermore, handling fluids at high pressures has been addressed, specifically by creating and characterizing strong microvalves and pumps. A variety of microstructuring techniques was used to realize these microfluidic devices, e.g., etching, lithography, and bonding. To be able to handle high pressures, the valves and pumps need to be strong. This necessitates a strong actuator material. In this thesis, the material of choice is paraffin wax. A new way of latching paraffin-actuated microvalves into either closed or open position has been developed, using the low thermal conductivity of paraffin to create large thermal gradients within a microactuator. This allows for long open and closed times without power consumption. In addition, three types of paraffin-actuated pumps are presented: A peristaltic high-pressure pump with integrated temperature control, a microdispensing pump with high repeatability, and a pump system with two pumps working with an offset to reduce flow irregularities. Furthermore, the fundamental behavior of paraffin as a microactuator material has been explored by finite element modeling. One possibility that arises with high-pressure microfluidics, is the utilization of supercritical fluids for different applications. The unique combination of material properties found in supercritical fluids yields them interesting applications in, e.g., extraction and cleaning. In an attempt to understand the microfluidic behavior of supercritical carbon dioxide, the two-phase flow, with liquid water as the second phase, in a microchannel has been studied and mapped with respect to both flow regime and droplet behavior at a bi-furcating outlet.

Mud pumps used on offshore installations for drilling operations have been known to experience unpredictable breakdowns, including during critical stages of drilling. The fluid end has been identified as requiring more maintenance work due to component failure, compared to the power end. The most common maintenance strategies in use include breakdown maintenance, time-based maintenance and condition monitoring. Time-based maintenance, based on running hours, is the most commonly preferred method by most, if not all, mud pump operators. However, the nature of drilling operations require pump performance with variable loads (pressures), variable speed characteristics and time-based maintenance would not be able to account for the different operating conditions within any identical time frames. To address this shortcoming, this research looked at the postulation that material wear loss is related to the energy expended and developed a dedicated reciprocating wear test system to identify and investigate the effect of operating variables on the wear loss of piston rubbers, which was considered to be the most problematic of the fluid end components.

Thesis advisor: Torsten Fiebig / This dissertation introduces a new field of DNA photonics centering on the electronic properties of DNA, which emerges after the initial controversies regarding the long-range conductivity and wire-type behavior of DNA have been widely settled. DNA photonics study is not solely focused on charge transfer phenomena but encompasses all possible photophysical processes and their potentially complex interplays. For instance, ultrafast electronic energy migration, dissipation, and (de)localization on the femtosecond time scale are shown to be crucial for the description of light-induced dynamics in DNA and have been thoroughly investigated in this dissertation. In addition to measurements on natural single and double-stranded DNA, this dissertation also presents experimental data on a series of functionalized DNA systems (derivatized by stilbene, ethidium, 2-aminopurine, etc.), obtained by state-of-the-art femtosecond broadband pump–probe spectroscopy. The results illustrate the distance dependence of charge transfer, emphasize the role of the initial electronic excitation on energy transfer dynamics, and highlight the influence of structural factors on both processes in DNA. Finally, as one initial step towards DNA electronics application, a DNA mimicking system of tertiary arylureas were employed to demonstrate molecular wire behavior, implying its potential use in molecular electronics. Thus, both the experimental and theoretical research accumulated for DNA π–π coupling can be translated into designing and testing various molecular systems with similar π-stacked structures. / Thesis (PhD) — Boston College, 2008. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Este trabalho apresenta a analise do efeito da concentração da mistura etilenoglicol / água, pressão do sistema, rotação da bomba e temperatura, sobre o fenômeno cavitação em sistemas de arrefecimento, tendo dois principais objetivos: 1 Explorar as principais características do fenômeno cavitação, através da analise crítica e citação de publicações existentes; 2 Mapear as condições de trabalho de um sistema de arrefecimento, para então simular em bancada as interações da variação dos fatores citados acima, comparando os resultados com publicações já existentes, contribuindo então com um banco de dados que possibilite a otimização do dimensionamento de novos sistemas de arrefecimento. / This work presents the effect analysis of the water / ethyleneglycol mixture, system pressure, pump speed and temperature upon the cavitation phenomenon in cooling systems. Moreover, it has two main targets which are: 1 To explore the main features of the cavitation phenomenon through a critical analysis and citation of available publications; 2 To monitor the cooling system work conditions in order to simulate in a test rig the variation of the parameters described above, understanding its interaction, for than to provide a database that make possible the design optimization of new cooling systems.

<p>The valve plate/cylinder block interface in an axial piston pump is often subject to extreme pressures, which can cause wear of the valve plate and ultimately, failure of the pump. The purposes of this study were to: a) experimentally investigate the film thickness generated between a floating valve plate and cylinder block in situ using proximity probes, b) develop a model which can predict the motion, film thickness and pressures of the floating valve plate and corroborate with experimental results, c) investigate surface pockets to provide additional lubricant at the valve plate interface by measuring the flow velocities and cavitation areas in a thrust washer bearing, d) numerically investigate surface modifications of the floating valve plate to observe any changes in lubricant pressure, temperature, cavitation, or valve plate deformation. Two different test rigs were designed, developed and used to investigate the performance of axial piston pumps and surface pockets. The axial piston pump test rig (APTR) was designed to operate and measure the steady state conditions of an axial piston pump. The APTR utilizes three non-contact proximity probes to measure the valve plate motion and film thickness between the cylinder block at various speeds and pressures. A thrust washer test rig (TWTR) was developed to measure the cavitation areas and flow velocities of lubricant in a pocketed thrust washer using μPIV. Through a novel interpolation approach, the depths of the micro-particles in the bearing pocket were determined using an analytical model. Using this approach, the μPIV measured 2D velocity field was employed to develop a 3D velocity field, which illustrates the fluid motion inside a pocketed thrust bearing at various speeds and viscosities. A dynamic lubrication model was developed using the thermal Reynolds equation augmented with the JFO boundary condition and the energy equation to determine the pressure, cavitation regions and temperature of the lubricant at the valve plate cylinder block interface. The lubricating pressures were then coupled with the equations of motion of the floating valve plate to develop a dynamic lubrication model. The stiffness and damping coefficients of the floating valve plate system used in the dynamic lubrication model were determined using a parametric study. The elastic deformation of the valve plate was also considered using the influence coefficient matrix approach. The experimental and analytical motion of the valve plate were then corroborated and found to be in good agreement. 4 and 8 pocket designs were then added as surface modifications to the floating valve plate in the dynamic lubrication model. The addition of surface modifications improved the lubricating conditions at the valve plate/cylinder block interface and resulted in increased minimum film thicknesses and lowered lubricant temperatures at the same operating conditions.</p>

The current generation of Airbus long-range civil transport aircraft actively control the centre of gravity of the aircraft by adjusting the fuel distribution between the horizontal tail surface and the forward tanks in order to minimise cruise drag. Here, it is proposed that the current on-off control method could be replaced by a variable flow rate, provided by a variable speed centrifugal pump. The impacts of this at the aircraftlevelintermsof cruisefuelburnreduction,valveoperationcycle reductionand power consumption are investigated here using an extension to an existing fuel system simulationpackage and ageneric aircraftfuel systemdefinition. Itis shownthat using such a control system reduces fuel burn and the number of valve cycles, which could translate into a reduction in operating costs. The benefit of changing the controller to use tailplane trim angle directly rather than inferred centre of gravity position is assessed, and is shown to further reduce the fuel burn. It is suggested that such centre of gravity could provide significant benefits over the existing method. Steady-state anddynamic models ofcentrifugalpumps,ACinductiondrives andtypical aircraft fuel system pipework components are developed. These are validated against experimentaldatafrom a test rig of a representative system. Test rig simulation results areshowntoagreewell with thosefromexperimentation. Anewsecondary noisesource is developed for the dynamic analysis of the centrifugal pump, and a new acoustic experimental method is developed for the prediction of fluid inductance in pipework components. The results are compared against an existing CFD based method and showgood agreement. Thenewmethod representsamuch simplerexperimental means of determining the effects of fluid inertia than the existing secondary source method. Itisdemonstrated thatthedynamicbehaviourof thecentrifugalpumpis, asexpected, insignificant when considering systems containing long pipes, and that steady-state pump models are sufficient for analysing their behaviour. Thepumpmodels aregeneralisedby non-dimensionalisation,in order to maximise their applicability to analysis of aircraftfuel systems. They are applied to ageneric aircraft fuel system simulation, in order to model the behaviour of the system during a trim transfer. Thisisused todemonstratethe application of theproposed variable flowrate trim control system. The results of these simulations agree well with those used to demonstratethebenefitsof thecontrol systemattheaircraftlevel. Conceptsof system health monitoring tools are discussed with reference to the system simulations.

Este trabalho apresenta a analise do efeito da concentração da mistura etilenoglicol / água, pressão do sistema, rotação da bomba e temperatura, sobre o fenômeno cavitação em sistemas de arrefecimento, tendo dois principais objetivos: 1 Explorar as principais características do fenômeno cavitação, através da analise crítica e citação de publicações existentes; 2 Mapear as condições de trabalho de um sistema de arrefecimento, para então simular em bancada as interações da variação dos fatores citados acima, comparando os resultados com publicações já existentes, contribuindo então com um banco de dados que possibilite a otimização do dimensionamento de novos sistemas de arrefecimento. / This work presents the effect analysis of the water / ethyleneglycol mixture, system pressure, pump speed and temperature upon the cavitation phenomenon in cooling systems. Moreover, it has two main targets which are: 1 To explore the main features of the cavitation phenomenon through a critical analysis and citation of available publications; 2 To monitor the cooling system work conditions in order to simulate in a test rig the variation of the parameters described above, understanding its interaction, for than to provide a database that make possible the design optimization of new cooling systems.

Energy efficiency of industrial systems is of great concern to many. Modeling and optimization of industrial systems has been an active research area aiming at improvement of energy efficiency of these systems. Traditional analytical and physics-based methods, reported in literature, limit modeling industrial systems, which are complex, nonlinear, and dynamic. Due to progress in data collection techniques, large volume of data has been collected and stored for analysis. Although much valuable information is contained in such data, utilization of the data in modeling industrial systems is lagging. Data mining is a novel science, providing a platform and techniques to model complex systems and processes. Data mining techniques have been widely applied in modeling various systems. In this Thesis, two energy intensive industrial systems are investigated, a pump system in wastewater treatment plants, and an HVAC system in commercial buildings. Data mining is utilized to derive models describing the relationship between target, operational cost of systems, and system control variables. An optimization model is constructed to minimize operational cost of a system, and intelligent algorithms are employed to solve the optimization models. The study demonstrates a considerable energy saving by applying the proposed control strategy. The approach developed in this Thesis can be applied to industrial systems other than the pump and HVAC systems.

Within the framework of this thesis, photolysis reactions in the liquid phase were investigated by means of ultrafast optical spectroscopy. Apart from molecular studies dealing with the highly spin-dependent reactivity of diphenylcarbene (DPC) in binary solvent mixtures and ligand dissociation reactions of so-called CO-releasing molecules (CORMs), special emphasis was put on the implementation and characterization of methods improving and extending the signal detection in conventional pump–probe transient absorption setups. The assumption of DPC being an archetypal triplet-ground-state arylcarbene was recently questioned by matrix-isolation studies at low temperatures. DPC embedded in argon matrices revealed a hitherto unknown reactivity when the carbene environment was modified by small amounts of methanol dopant molecules. To complement these findings with liquid-phase experiments at room temperature, femtosecond pump–probe transient absorption spectroscopy with probing in the visible and ultraviolet regime was employed to unravel primary reaction processes of DPC in solvent mixtures. Supported by quantum chemical simulations conducted by our collaborators, it was shown that a competition between the reaction pathways occurs that not only depends on the solvent molecule near-by but also on its interaction with other solvent molecules. In-depth analysis of the solvation dynamics and the amount of nascent intermediates corroborates the importance of a hydrogen-bonded complex with a protic solvent molecule, in striking analogy to complexes found at cryogenic temperatures. Probing the transient absorption of molecules in the mid-infrared spectral range benefits from the high chemical specificity of molecules’ vibrational signatures. The technique of chirped-pulse upconversion (CPU) constitutes a promising alternative to standard direct multichannel MCT detection when accessing this spectral detection window. Hence, one chapter of this thesis is dedicated to a direct comparison between both detection methods. By conducting an exemplary pump–probe transient absorption experiment, it became evident, that the additional nonlinear interaction step is responsible for increased noise levels when using CPU. However, a correction procedure capable of removing these additional noise contributions—stemming from the fundamental laser radiation used for upconversion—was successfully tested. Perhaps most importantly for various spectroscopic applications, CPU scored with a significantly extended detection bandwidth owing to the high pixel numbers of modern CCD cameras. Transition-metal complexes capable of releasing small molecular messengers upon photoactivation are promising sources of gasotransmitters such as carbon monoxide (CO) or nitric oxide (NO) in biological applications. However, only little is known about the characteristic time scales of ligand dissociation in this class of molecules. For this purpose, two complexes were investigated with femtosecond time resolution: [Mn(CO)3(tpm)]Cl with tpm=tris(2-pyrazolyl)methane, a manganese tricarbonyl complex which has proven to be selective and cytotoxic to cancer cells, and [Mo(CO)2(NO)(iPr3tacn)]PF6 with iPr3tacn=1,4,7-triisopropyl-1,4,7-triazacyclononane, a molybdenum complex containing both carbonyl and nitrosyl ligands. By conducting pump–probe transient absorption measurements in different spectral probing windows supported by quantum chemical calculations and linear absorption spectroscopy, it was shown that both complexes are able to release one CO ligand within the first few picoseconds after UV excitation. The results complement existing studies which focused on the molecules’ ligand-releasing properties upon long-term exposure. The additional information gained on an ultrafast time scale provides a comprehensive understanding of individual reaction steps connected with ligand release in this class of molecules. Hence, the studies might create new incentives to develop modified molecules for specific applications. / Im Rahmen dieser Dissertation wurden Methoden der ultraschnellen optischen Spektroskopie angewandt, um Photolysereaktionen in der flüssigen Phase zu untersuchen. Neben molekularen Studien, welche sich mit der stark spin-abhängigen Reaktivität von Diphenylcarben (DPC) in binären Lösungsmittelgemischen und den Ligandendissoziationsreaktionen von sogenannten CO-freisetzenden Molekülen (CORMs, engl.: CO-releasing molecules) befassten, war ein wesentlicher Bestandteil dieser Arbeit die Implementierung und Charakterisierung von Methoden zur Verbesserung und Erweiterung der Signaldetektion in Aufbauten zur zeitaufgelösten Anrege-Abfrage-Spektroskopie. Die generelle Annahme, dass es sich bei DPC um ein archetypisches Triplett-Grundzustands-Arylcarben handelt, wurde kürzlich durch Matrixisolationsstudien in Frage gestellt. In jenen Untersuchungen offenbarte DPC, eingebettet in Argon-Matrizen, durch die Modifizierung der Carbenumgebung mit geringen Mengen an Methanol-Dotiermolekülen, eine bislang unbekannte Reaktivität. Komplementär dazu wurden im Rahmen dieser Arbeit Messungen in der flüssigen Phase bei Raumtemperatur durchgeführt. Femtosekundenzeitaufgelöste Anrege-Abfrage-Spektroskopie mit Abfragepulsen aus dem sichtbaren und ultravioletten Spektralbereich diente dabei zur Aufkläung der primären Reaktionsprozesse von DPC in Lösungsmittelgemischen. Es zeigte sich, unterstützt durch quantenchemische Simulationen unserer Kollaborateure, dass konkurrierende Reaktionspfade auftreten, welche nicht nur von den Lösungsmittelmolekülen in der unmittelbaren Umgebung abhängen, sondern auch von deren Wechselwirkung mit anderen Lösungsmittelmolekülen. Eine ausführliche Analyse, sowohl der Solvatationsdynamiken als auch der Menge an aufkommenden Intermediaten, bekräftigte die Bedeutung eines Komplexes der durch Wasserstoffbrückenbindung mit einem protischen Lösungmittelmolekül entsteht — in auffallender Ähnlichkeit zu Komplexen die bei kryogenen Temperaturen gefunden wurden. Das Abfragen der transienten Absorption eines Moleküls im mittleren Infrarot wird durch die hohe chemische Spezifität von molekularen Schwingungssignaturen begünstigt. Um dieses spektrale Fenster zu untersuchen, bietet die CPU-Methode (engl.: chirped-pulse upconversion) eine vielversprechende Alternative zur konventionellen direkten Mehrkanal MCT-Detektion. Daher widmet sich ein Kapitel dieser Arbeit einem direkten Vergleich der beiden Detektionsmethoden. Im Rahmen eines exemplarischen Anrege-Abfrage-Experiments zeigte sich, dass die zusätzliche nichtlineare Wechselwirkung zu einem erhöhten Rauschniveau bei der Verwendung der CPU-Technik führt. Dennoch konnte eine Korrekturprozedur erfolgreich getestet werden, die es ermöglicht, jene zusätzlichen Rauschbeiträge, die durch Fluktuationen der fundamentalen Laserstrahlung hervorgerufen werden, zu entfernen. Am wichtigsten für eine Vielzahl spektroskopischer Anwendungen ist jedoch, dass die CPU-Technik auf Grund der hohen Pixel-Anzahl moderner CCD-Kameras mit einer signifikant erhöhten Detektionsbandbreite punkten kann. Für biologische Anwendungen besteht steigendes Interesse an Molekülen zur kontrollierten Verabreichung von Gasotransmittern wie Kohlenstoffmonoxid (CO) oder Stickstoffmonoxid (NO). Vielversprechend sind hierbei Übergangsmetallkomplexe, welche in der Lage sind, jene kleinen Signalmoleküle nach Photoanregung freizusetzen. Dennoch ist nur sehr wenig über die charakteristischen Zeitskalen der Ligandendissoziation in dieser Molekülklasse bekannt. Daher wurden im Rahmen dieser Arbeit zwei Komplexe mit Femtosekundenzeitauflösung untersucht: [Mn(CO)3(tpm)]Cl mit tpm=tris(2-pyrazolyl)methane, ein Mangankomplex mit drei Carbonylliganden, desses selektive und zytotoxische Wirkung gegenüber Krebszellen nachgewiesen ist, und [Mo(CO)2(NO)(iPr3tacn)]PF6 mit iPr3tacn=1,4,7-triisopropyl-1,4,7-triazacyclononane, ein Molybdänkomplex, der sowohl CO- als auch NO-Liganden enthält. Mit Hilfe von Anrege-Abfrage-Spektroskopie in verschiedenen spektralen Bereichen, unterstützt durch quantenchemische Berechnungen und lineare Absorptionsspektroskopie, konnte gezeigt werden, dass beide Komplexe jeweils einen CO-Liganden innerhalb der ersten Pikosekunden nach UV-Anregung abspalten können. Die Ergebnisse ergänzen bestehende Studien, welche die Ligandenfreisetzungseigenschaften der Moleküle unter Langzeitbelichtung untersuchten. Die zusätzliche Information – gewonnen auf der ultraschnellen Zeitskala – ermöglicht ein umfassendes Verständnis der einzelnen Reaktionsschritte, welche mit der Ligandendissoziation in dieser Molekülklasse verbunden sind. Daher könnten die Studien neue Anreize zur Entwicklung modifizierter Moleküle schaffen, welche für spezifische Anwendungen geeignet sind.