Liquid metal batteries are discussed today as an economic grid-scale energy storage, as required for the deployment of fluctuating renewable energies. These batteries consist of three stably stratified liquid layers: two liquid metal electrodes are separated by a thin molten salt electrolyte, this way forming an electrochemical concentration cell. The completely liquid interior, which is on the one hand very beneficial for the energy efficiency, also poses some major challenges on the other hand. Strong cell currents in combination with electromagnetic fields make liquid metal batteries highly susceptible to various kinds of magnetohydrodynamic instabilities. In particular, the so-called metal pad roll instability, which can drive uncontrollable wave motions in both interfaces, was identified as a key limiting factor for the operational safety. The metal pad roll instability is well known from conceptually similar aluminum reduction cells, but still poorly understood in the framework of liquid metal batteries. Mainly by developing analytical wave models, but also by employing numerical simulations and by setting up a newly designed wave experiment, the present thesis pursues the goal of providing a better understanding of interfacial wave dynamics and the manifestation of the metal pad roll instability in liquid metal batteries. As a main result, a three-layer formulation of standing gravity-capillary waves reveals that the pressure coupling between the two interfaces plays a crucial role in the cell stability. Three different coupling regimes, which partially involve novel types of interfacial wave instabilities, are identified and classified by two dimensionless parameters. Building on this theoretical work, the wave experiment is exploited to further investigate different metal pad roll-related wave properties. The crucial importance of the contact line dynamics is emphasized and viscous damping, which is important for the estimation of instability onsets, is discussed as a function of the layer heights. Finally, a hybrid interfacial sloshing model is formulated and equipped with recently derived two-layer damping rates to account for viscous dissipation. The model allows to study and interpret the forced wave mechanics in the wave experiment as a function of eight dimensionless parameters and can, as an additional application, be exploited to optimize mixing in orbitally shaken bioreactors. As a further key result, the sloshing model reveals the formation of novel spiral wave patterns under the effect of strong damping.

This dissertation presents a series of studies relating to optimization of kinematics and consumables during chemical mechanical planarization processes. These are also evaluated with the purpose of minimizing environmental and cost of ownership impacts.In order to study diamond micro-wear and substrate wear during planarization processes, a series of static etch tests and wear tests were performed using different types of diamond discs and subjected to various treatments. Scanning Electron Microscopy (SEM) and Inductively Coupled Plasma Membrane Spectroscopy (ICPMS) were used to estimate the extent of diamond micro-wear and substrate wear.Next, the impact of various factors (type of slurry abrasive, pH, abrasive content and abrasive concentration) on pad wear rate during planarization process was studied. Another study in this dissertation focuses on the development of a novel technique of using coefficient of friction (COF) data to distinguish between good and bad diamond discs. This study made use of the innovative tool diamond disc dragging device (DDD-100) designed and developed for the purpose of this study.It is known that the performance of chemical mechanical planarization depends significantly on the polishing pad grooving type and the kinematics involved in the process. Variations in pad grooving type as well as pressure and sliding velocity can affect polishing performance. One study in this dissertation investigates the effect of pressure and sliding velocity on the polishing performance. The study is conducted on multiple pressure and sliding velocity variations to understand the characteristic of each condition. A subsequent study focuses on the impact of pad grooving type on polishing performance.The greatest contribution of this dissertation involves development of the novel slurry injector to optimize the utilization of slurry during planarization processes. Slurry is a critical component in chemical mechanical planarization processes and accounts for approximately 50 percent of the cost of ownership (CoO). The novel injector apart from reducing the consumption of slurry, also contributed in addressing problems associated with foaming, reduced the number of defects and achieved better within wafer non-uniformity (WIWNU).

2 pp. / In the semi-arid climate of southern AZ, evaporative cooling systems are commonly used and very effective for cooling homes (swamp coolers), outdoor areas (misters), and for greenhouses used for commercial and horticultural plant production (pad-and-fan, high-pressure-fog). The purpose of this brochure is to educate users about strategies they can employ to save water and improve the performance of evaporative cooling systems. Principles of operation, a list of advantages and disadvantages, and a comparison of common systems is also included, to help users decide the best system for them.

Articular cartilage damage and degeneration is a siginficant clinical problem which no technique has been able to adequately and reliably repair or regenerate. Recent research has investigated the use of cell-based therapies to treat focal cartilage lesions. In clinical practice proliferated autologous chondrocytes are used and clinical trials are investigating the use of mesenchymal stem cells. The aim of this thesis was to assess aspects of current cell-based therapy and to investigate the potential of perivascular stem cells for articular cartilage repair. The phenotype of expanded matrix-applied autologous chondrocytes utilised in current cell therapies was confirmed using immunocytochemistry and polymerase chain reaction (PCR) expression of hyaluronan and proteoglycan link protein 1 (HAPLN1), transcription factor sox-9 (SOX9) and aggrecan (ACAN). Quantitative real-time PCR demonstrated that they were down-regulated for expression of COL2A1, SOX9 and ACAN but up-regulated for COL1A1 compared to unproliferated chondrocytes. Confocal laser-scanning microscopy (CLSM) demonstrated a significant decrease in cell viability and density when the membranes were subjected to levels of trauma similar to those that could be experienced during surgery. Hyperosmolar solutions did not confer a chondroprotective effect. Pericytes and adventitial cells, collectively termed perivascular stem cells (PSCs), from the infra-patellar fat pad were identified using immunohistochemistry and isolated using enzymatic digestion and fluorescence-activated cell sorting (FACS). Cell identity was ascertained using PCR, FACS and mesenchymal differentiation (osteogenesis, adipogenesis and chondrogenesis). Quantitative real-time PCR analysis of micromass cultures indicated that PSCs displayed increased chondrogenic potential compared to mesenchymal stem cells. An ovine model of perivascular stem cells was developed and a pilot study using three sheep was undertaken to confirm the viability of the model. Autologous ovine PSCs were isolated and re-implanted into articular cartilage defects. Green fluorescent protein transfected cells were identified in the cartilage defect four weeks following re-implantation using CLSM. This thesis has examined aspects of matrix-applied autologous chondrocyte implantation for cell based cartilage repair and has identified a new source of prospectively identified and purified stem cells that have demonstrated increased chondrogenic potential compared to mesenchymal stem cells, which are commonly used in clinical research. The methods to identify and purify ovine perivascular stem cells were developed to investigate the use of autologous PSCs and to track the cells following implantation.

La cryptographie ADN est un domaine nouveau et prometteur pour la sécurité de l'information. C'est une combinaison des solutions classiques de cryptographie avec les avantages du matériel génétique. En effet, il est possible de bénéficier des avantages des systèmes cryptographiques classiques et de les rendre plus efficaces sur certaines méthodes grâce à l’utilisation de l'ADN. Il y a différentes façons d'utiliser l'ADN pour sécuriser le contenu de l'information. Cette thèse propose deux solutions différentes pour utiliser l'ADN dans la cryptographie : sous sa forme biologique ou alors sous forme numérique. D ‘une part, l'ADN biologique peut être utilisé pour le stockage et pour cacher des données à l'intérieur de celui-ci. L'information secrète est placée dans une molécule de l'ADN et caché parmi d'autres molécules d'ADN. D’autre part, les nombres aléatoires peuvent être générés à partir de séquences numériques d'ADN. Ils représentent une solution pour la génération et la transmission des clés OTP (One-Time-Pad) symétriques. La transmission d'une très longue clé de cryptage n'est pas nécessaire, car chaque séquence possède un numéro d'identification unique dans la base de données. Ce numéro, ou une combinaison de ces numéros, peut alors être transmis. Enfin, la sécurité et la compression sont très importantes lors de la transmission et du stockage des données informatiques. Cependant, la plupart des systèmes de cryptage peuvent augmenter la taille des données, ou encore augmenter la complexité calcul. Ces inconvénients peuvent être résolus en combinant la compression de données avec le cryptage dans un seul processus ou en effectuant le cryptage sélectif des données. / DNA cryptography is a new and promising field in information security. It combines classical solutions in cryptography with the strength of the genetic material. By introducing DNA into the common symmetric key cryptography, it is possible to benefit from the advantages of the classical cryptosystems and solve some of its limitations. There are different ways how DNA can be used to secure information content. It is about using the biological medium of DNA for storing and hiding data. Secret information can be placed in microscopic size of DNA and hidden among a great amount of other DNA structures. Biomolecular computation is possible with specially designed DNA structures. Random numbers can be generated from DNA sequences which can be found in genetic databases in digital form. Genetic databases represent a feasible solution to the One-Time-Pad (OTP) symmetric key generation and transmission problem. The one-time use is ensured due to the great variety of the publicly available, very long (thousands of bases) sequences. Transmission of a very long key is not required because each sequence has a unique identification number in the database and this number can be sent instead. Compression along with information security have always been topics of interest because, as technology advances, the amount of data that is desired to be transmitted, stored, or used in real time applications is becoming greater. Some of the encryption schemes can increase the size of the data, or bring unwanted additional computations. These drawbacks can be solved by several techniques to combine compression with encryption in one process or by performing a selective encryption of the data.

Estudos recentes mostram que o cobre oriundo do desgaste de materiais de fricção de freio automotivo é a principal fonte do depósito deste metal em rios e lagos, afetando negativamente o meio ambiente. Consequentemente, novas legislações de agências governamentais internacionais têm imposto uma redução drástica da utilização do cobre em materiais de fricção nos próximos anos, sendo esta uma tendência a ser seguida por governos de todo o mundo. Embora o cobre seja largamente utilizado em materiais de fricção, a compreensão dos mecanismos de ação deste metal para esta aplicação ainda é bastante limitada. Este trabalho tem como intuito contribuir para uma melhor compreensão do papel do cobre em pastilhas de freio automotivo no que diz respeito ao coeficiente de atrito e ao desgaste. Ensaios de frenagens foram realizados no tribômetro do Laboratório de Tribologia da UFRGS, onde três tipos de pastilhas de freio (contendo 0%, 10% e 30% de cobre cada) foram testadas em diferentes temperaturas (100 ºC, 200 ºC e 300 ºC). Foram aplicados métodos para avaliar o coeficiente de atrito, desgaste de pastilha, desgaste de disco, parâmetros morfológicos de platôs de contato e depósito de filme no disco O material sem cobre em sua composição apresentou valores de coeficiente de atrito maiores do que os materiais com cobre para os três patamares de temperatura. O material com 10% de cobre apresentou maior sensibilidade do atrito em função da velocidade de deslizamento do que os outros dois materiais. Correlação inversa forte foi observada entre desgaste de pastilha e desgaste de disco. A quantidade de platôs de contato foi o parâmetro morfológico que mais se correlacionou com o coeficiente de atrito em diferentes temperaturas. Em alguns ensaios foi observada uma variação abrupta do coeficiente de atrito em determinadas frenagens dos materiais sem cobre e com 10% de cobre. Juntamente com esta variação, foi constatada uma perturbação do filme depositado sobre o disco, onde este é removido quando ocorre o aumento repentino do atrito. Entretanto, este fenômeno ocorreu apenas para a temperatura de 100 ºC, indicando que esta variação de atrito e perturbação do filme ocorre apenas em baixas temperaturas, e independente do percentual de cobre. / Previous studies have shown that the copper originated from the wear of automotive brake friction materials is the main source of the deposit of this metal in rivers and lakes, leading to environmental impacts. As a result, recent legislations from international governmental agencies have forced a drastic reduction of the copper used in friction materials in next years, which is likely to be followed by other governments in the world. Although the copper is widely used in friction materials, the understanding of the action mechanisms of this metal in friction materials is quite limited. This work aims to contribute to a better understanding of the role of copper in automotive brake pads in terms of friction and wear. Tests were carried out in the tribometer of the Laboratory of Tribology of UFRGS, where three kinds of brake pads (with 0%, 10% and 30% of copper each) were subjected to different temperatures (100 ºC, 200 ºC e 300 ºC). Methodologies to evaluate friction, wear of brake pads, wear of discs, morphological parameters of contact plateaus and deposit of film on disc surface were used. The sample without copper presented higher friction than the samples with copper for the three temperature levels. The material with 10% of copper presented higher friction sensibility due the sliding speed than other samples. Strong inverse correlation between wear of brake pads and wear of discs was observed. Quantity of contact plateaus was the parameter that presented the higher correlation with the friction in different temperatures. An abrupted variation of friction was observed in some experiments for samples without copper and with 10% of copper. At the same time, it was observed a disturbance of the film deposited on the disc surface, where the film was removed when the sudden increase of the friction occurs. However, this phenomenon occurred only at 100 °C, indicating that the variation of friction and the disturbance of film occurs only at low temperatures, and seems to be regardless of percentage of copper.

Chemical Mechanical Planarization (CMP) has emerged as the central technology for polishing wafers in the semiconductor manufacturing industry to make integrated multi-level devices. As the name suggests, both chemical and mechanical processes work simultaneously to achieve local and global planarization. In spite of extensive work done to understand the various components and parameters affecting the performance of this process, many aspects of CMP remain poorly understood. Among these aspects of CMP is the role of abrasives in the processes of conditioning and polishing. These abrasives are present in the chemical slurry between the wafer and the pad for polishing and play an important role during the conditioning to regenerate the clogged polishing pads. This thesis has focused on the study of abrasives, both in conditioning and polishing. The first part of the thesis concentrates on the effect of abrasive size for conditioning purposes. Diamond is being widely used as an abrasive for conditioning the polishing pad. Five different sizes of diamonds ranging from 0.25µm to 100µm were selected to condition the commercially available IC 1000 polishing pad. Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) analysis were carried out on the pad to study the effect of the abrasive size on the pad morphology. In-situ 'coefficient of friction' was also monitored on the CETR bench top Tester. The final impact was seen in the form of surface defects on the polished copper wafers. As pad morphologies resulting from different conditioning affect contact areas, the second part of the thesis focuses on developing a simple method to quantify the area of contact between the wafer and pad using optical microscopy. Optical images that were obtained were analyzed for the change in contact area with the change in operating conditions. Finally, the third part of the thesis details the synthesis and characterization of nano-zirconia for potential slurry applications. Nano-zirconia was synthesized using the plasma route and then characterized using different analytical techniques like TEM and XRD. These nanoparticles were then used to make abrasive slurry for oxide CMP and the polished wafers were analyzed for surface defects.

Abstract Background: Over 100 million people in the United States (U.S.) have diagnosed diabetes or pre-diabetes. People with this condition are at an increased risk of Peripheral Arterial Disease (PAD). There is a high prevalence of people with risk factors of diabetes especially in the rural Central Appalachia region. People with diabetes are at a higher risk of developing atherosclerosis, which is the most common cause of PAD. Although about 20–30% of 12 million people affected with PAD in the U.S. have diabetes, little is known about diabetes in PAD patients in Central Appalachia. Therefore, this study aimed to examine the risk factors of diabetes in patients with PAD within the Central Appalachian region. Methods: The study population consisted of patients with PAD with medical comorbidities of Cardiovascular disease (CVD). All patients were admitted to a large health system in Central Appalachia between 2008 and 2018. 13,455 index cases were extracted from the Electronic Medical Records (EMR) using the ICD-9 and ICD-10 codes. With diabetes as the outcome variable under study, the risk factors included Myocardial Infarction (MI) history, hypertension, smoking status and hypercholesterolemia. Socio-demographic variables considered in the study included gender, age, ethnicity and marital status and the covariates were Body Mass Index (BMI), Low density lipoproteins (LDL), High density lipoproteins (HDL), Total Cholesterol, and Triglycerides (TG). Multivariable logistic regression was performed to examine potential risk factors of diabetes in PAD patients. Results: The results showed that BMI {OR =1.056 (CI: 1.039, 1.073)}, HDL {OR =0.980 (CI: 0.965, 0.995)}, TG {OR=1.003 (CI: 1.001, 1.005)}, MI history {OR= 1.375 (CI: 1.111, 1.703)}, hypertension {OR=2.822 (CI: 1.804, 4.415)} and smoking {OR =0.802(CI: 0.641, 1.003)} were significant for diabetes in known PAD. To control for potential confounders, Stratification was used. Among males and females with PAD, diabetes was associated with last BMI, MI, hypertension and TG. HDL seemed to be negatively associated with hypertension and female diabetics while smoking seemed to be negatively associated in males. Upon stratification with hypertension, diabetes in PAD patients was significant with BMI, TG, MI history and HDL. After stratification with MI, diabetes in PAD female patients was associated with BMI, and previous MI history. On the other hand, patients without MI had an elevated TG level and an increased risk of hypertension. Conclusion: CVD risk factors are strongly associated with PAD comorbidities, which are worsened in the presence of diabetes. We suggest that hospitals and health care systems should strongly control for the risk factors of diabetes and adopt a multi-risk-factor approach for improving health outcomes for PAD patients.

Scratch-pad memory (SPM), a fast on-chip SRAM managed by software, is widely used in embedded systems. Compared to hardware-managed cache, SPM can be more efficient in performance, power and area cost, and has the added advantage of better time predictability. In this thesis, SPMs should be seen in a general context. For example, in stream processors, a software-managed stream register file is usually used to stage data to and from off-chip memory. In IBM's Cell architecture, each co-processor has a software-managed local store for keeping data and instructions. SPM management is critical for SPM-based embedded systems. In this thesis, we propose two novel methodologies, the memory colouring methodology and the perfect colouring methodology, to place the static data aggregates such as arrays and structs of a program in SPM. Our methodologies are dynamic in the sense that some data aggregates can be swapped into and out of SPM during program execution. To this end, a live range splitting heuristic is introduced in order to create potential data transfer statements between SPM and off-chip memory. The memory colouring methodology is a general-purpose compiler approach. The novelty of this approach lies in partitioning an SPM into a pseudo register file then generalising existing graph colouring algorithms for register allocation to colour data aggregates. In this thesis, a scheme for partitioning an SPM into a pseudo register file is introduced. This methodology is inter-procedural and therefore operates on the interference graph for the data aggregates in the whole program. Different graph colouring algorithms may give rise to different results due to live range splitting and spilling heuristics used. As a result, two representative graph colouring algorithms, George and Appel's iterative-coalescing and Park and Moon's optimistic-coalescing, are generalised and evaluated for SPM allocation. Like memory colouring, perfect colouring is also inter-procedural. The novelty of this second methodology lies in formulating the SPM allocation problem as an interval colouring problem. The interval colouring problem is an NP problem and no widely-accepted approximation algorithms exist. The key observation is that the interference graphs for data aggregates in many embedded applications form a special class of superperfect graphs. This has led to the development of two additional SPM allocation algorithms. While differing in whether live range splits and spills are done sequentially or together, both algorithms place data aggregates in SPM based on the cliques in an interference graph. In both cases, we guarantee optimally that all data aggregates in an interference graph can be placed in SPM if the given SPM size is no smaller than the chromatic number of the graph. We have developed two memory colouring algorithms and two perfect colouring algorithms for SPM allocation. We have evaluated them using a set of embedded applications. Our results show that both methodologies are efficient and effective in handling large-scale embedded applications. While neither methodology outperforms the other consistently, perfect colouring has yielded better overall results in the set of benchmarks used in our experiments. All these algorithms are expected to be valuable. For example, they can be made available as part of the same compiler framework to assist the embedded designer with exploring a large number of optimisation opportunities for a particular embedded application.

This dissertation deals with three research topics; i) the catcher bearings life prediction method, ii) the Morton effect, and iii) the two dimensional modified Reynolds equation. Firstly, catcher bearings (CB) are an essential component for rotating machine with active magnetic bearings (AMBs) suspensions. The CB's role is to protect the magnetic bearing and other close clearance component in the event of an AMB failure. The contact load, the Hertzian stress, and the sub/surface shear stress between rotor, races, and balls are calculated, using a nonlinear ball bearing model with thermal growth, during the rotor drop event. Fatigue life of the CB in terms of the number of drop occurrences prior to failure is calculated by applying the Rainflow Counting Algorithm to the sub/surface shear stress-time history. Numerical simulations including high fidelity bearing models and a Timoshenko beam finite element rotor model show that CB life is dramatically reduced when high-speed backward whirl occurs. Secondly, the theoretical models and simulation results about the synchronous thermal instability phenomenon known as Morton Effect is presented in this dissertation. A transient analysis of the rotor supported by tilting pad journal bearing is performed to obtain asymmetric temperature distribution of the journal by solving variable viscosity Reynolds equation, energy equation, heat conduction equation, and equations of motion for rotor. The tilting pad bearing is fully nonlinear model. In addition, thermal mode approach and staggered integration scheme are utilized in order to reduce computation time. The simulation results indicate that the temperature of the journal varies sinusoidally along the circumferential direction and linearly across the diameter, and the vibration envelope increased and decreased, which considers as a limit cycle that is stable oscillation of the envelope of the amplitude of synchronous vibration. Thirdly, the Reynolds equation plays an important role to predict pressure distribution in the fluid film for the fluid film bearing analysis. One of the assumptions on the Reynolds equation is that the viscosity is independent of pressure. This assumption is still valid for most fluid film bearing applications, in which the maximum pressure is less than 1 GPa. In elastohydrodynamic lubrication (EHL) which the lubricant is subjected to extremely high pressure, however, the pressure independent viscosity assumption should be reconsidered. With considering pressure-dependent viscosity, the 2D modified Reynolds equation is derived in this study. The solutions of 2D modified Reynolds equation is compared with that of the classical Reynolds equation for the plain journal bearing and ball bearing cases. The pressure distribution obtained from modified equation is slightly higher pressures than the classical Reynolds equations. / PDF file replaced 10-21-2012 at the request of the Thesis Office.