Magnesium alloys are the lightweight structural materials with high strength to weigh ratio that permits their application in fuel economy sensitive automobile industries. Among the several flavors of of Mg-alloys, precipitation hardenable Mg-rare earth (RE) based alloys have shown good potential due to their favorable creep resistance within a wide window of operating temperatures ranging from 150°C to 300°C. A key aspect of Mg-RE alloys is the presence of precipitate phases that leads to strengthening of such alloys. Several notable works, in literature, have been done to examine the formation of such precipitate phases. However, there are very few studies that evaluated the effect stress induced deformation on the precipitation in Mg-RE alloys. Therefore, the objective of this work is to examine influence of deformation on the precipitation of Mg-Nd based alloys. To address this problem, precipitation in two Mg-Nd based alloys, subjected to two different deformation conditions, and was examined via transmission electron microscopy (TEM) and atom probe tomography (APT). In first deformation condition, Md-2.6wt%Nd alloy was subjected to creep deformation (90MPa / 177ºC) to failure. Effect of stress-induced deformation was examined by comparing and contrasting with precipitation in non-creep tested specimens subjected to isothermal annealing (at 177ºC). In second condition, Mg-4.0Y-3.0Nd-0.5Zr (wt %) or WE43 alloy (with comparable Nd content as model Mg-Nd system) was subjected to hot rolling deformation at a sub-solvus temperature.

The effects of octadecylamine-functionalized reduced graphene oxide (FRGO) on the frictional and wear properties of diglycidylether of bisphenol-A (DGEBA) epoxy are studied using a pin-on-disk tribometer. It was observed that the addition of FRGO significantly improves the tribological, mechanical, and thermal properties of epoxy matrix. Graphene oxide (GO) was functionalized with octadecylamine (ODA), and then reduction of oxygen-containing functional groups was carried out using hydrazine monohydrate. The Raman and x-ray photoelectron spectroscopy studies confirm significant reduction in oxygen-containing functional groups and formation of ODA functionalized reduced GO. The nanocomposites are prepared by adding 0.1, 0.2, 0.5 and 1.0 wt % of FRGO to the epoxy. The addition of FRGO increases by more than an order of magnitude the sliding distance during which the dynamic friction is ≤ 0.1. After this distance, the friction sharply increases to the range of 0.4 - 0.5. We explain the increase in sliding distance during which the friction is low by formation of a transfer film from the nanocomposite to the counterface. The wear rates in the low and high friction regimes are approximately 1.5 x 10-4 mm3/N·m and 5.5 x 10-4 mm3/N·m, respectively. The nanocomposites exhibit a 74 % increase in Young’s modulus with 0.5 wt. % of FRGO, and an increase in glass transition and thermal degradation temperatures.

Joining two dissimilar metals, specifically Mg and Al alloys, using conventional welding techniques is extraordinarily challenging. Even when these alloys are able to be joined, the weld is littered with defects such as cracks, cavities, and wormholes. The focus of this project was to use friction stir welding to create a defect-free joint between Al 2139 and Mg WE43. The stir tool used in this project, made of H13 tool steel, is of fixed design. The design included an 11 mm scrolled and concave shoulder in addition to a 6 mm length pin comprised of two tapering, threaded re-entrant flutes that promoted and amplified material flow. Upon completion of this project an improved experimental setup process was created as well as successful welds between the two alloys. These successful joints, albeit containing defects, lead to the conclusion that the tool used in project was ill fit to join the Al and Mg alloy plates. This was primarily due to its conical shaped pin instead of the more traditional cylindrical shaped pins. As a result of this aggressive pin design, there was a lack of heat generation towards the bottom of the pin even at higher (800-1000 rpm) rotation speeds. This lack of heat generation prohibited the material from reaching plastic deformation thus preventing the needed material flow to form the defect free joint.

Dactylography - History, Present and Future This thesis introduces one of the most important identification methods - dactylography (or dactyloscopy), e.g. the method based on analysis and classification of patterns of friction ridges (especially fingerprints). This thesis consists of three main chapters considering its name. The first chapter describes interesting history of this method from first discoveries, through various breakthroughs, to reaching the status of forensic evidence. This chapter mainly focuses on individual pioneers on the field of dactylography, but tells as well the story of Czechoslovak dactylography and reminds cases, that were very close to prove this method wrong at its fragile beginning. The second chapter focuses on the present of dactylography. This chapter starts with three basic laws of dactylography, but the essence of it lies in the term "dactyloscopic evidence". The methods of revelation, analysis and preservation of dactyloscopic evidence are described here as well as their comparison. If it comes to analysis, I am trying to compare two approaches used today (holistic and numerical) and offer my opinion which one is better. Also, I am trying to answer the question, if it is possible to tell how old the dactyloscopic evidence is. The third and the last chapter...

FINGERPRINTING - PAST, PRESENT AND FUTURE The objective of this thesis is to present the forensic fingerprinting as a scientific method which, although in comparison with other forensic sciences being one of the oldest, is not out-dated at all, quite to the contrary - it presents an ever-changing and continuously developing field of science. The objective is approached through three distinctive and yet intertwined chapters corresponding with the title of the thesis - past, present and future of the fingerprinting. They are also designed, at least in part, to capture this constant forward motion. Accordingly, the first chapter aims to describe briefly scientific roots of the method, the way it drew in its beginnings from various scientific discoveries, inspired by the rise of Darwinism. Particular emphasis is put on the description of the formulation and empirical confirmation of three physiological laws of fingerprinting that even today serve as its grounds. The second chapter deals with and tries to describe the current state of knowledge and particular methods used in detection, development and preservation of fingerprints, especially latent ones. To do this it seems to be necessary to describe briefly the anatomy and physiology of friction ridge skin, as it enables to fully comprehend the way in...

The objective of the report is to investigate the feasibility and reliability of additive friction stir manufacturing of 7055 aluminum alloy. This is a technique in which multiple lap welds are performed to create a three-dimensional part out of relatively thin plate aluminum. To accomplish this, a four inch stack of 7055 aluminum alloy lap welds must be created. The solid weld nugget is then machined out of the center of the welded stack to create ASTM approved subsize tensile coupons. Rockwell hardness, yield strength, ultimate tensile strength, and percent elongation information is gathered from the tensile coupons to investigate the effectiveness of the additive friction stir manufacturing process. The data shows that the additive manufactured material experiences a significant reduction in strength and percent elongation while not showing any significant response to heat treatment. Suggestions are made regarding possible changes to the weld schedule that could improve the material properties of the additive manufactured aluminum.

A thesis submitted to the Faculty of engineering. University of Witwatersrand. Johannesburg, in fulfilment of the requirements for the Degree of Doctor of Philosophy Pretoria, 1995 / This thesis describes a study of the friction and wear characteristics of a range of oxide and silicon-based ceramics sliding against AlSI 440C stainless steel, as well as various sliding combinations of two types of De Beers polycrystalline diamond (PCD), namely Syndite and Syndax, To facilitate the former work, a high-speed reciprocating sliding test machine with computerized data acquisition and control was developed. It was confirmed that under water-lubricated sliding, the oxide ceramics (alumina, PSZ, 3YTZP, and Ce-TZP) showed higher friction coefficients and Weal' rates than the silicon-based ceramics (Sialon and silicon nitride). This was related to different levels of adhesion and the formation of metallic transfer films. For the zirconia ceramics, increased transformation toughening was associated with increased surface fracture damage and metallic film formation. In general, the metallic transfer films were beneficial, protecting the underlying ceramic and dominating the friction and wear behaviour. The superior performance of the silicon-based ceramics was related to the formation of lubricious tribofilms containing silicon oxides and hydroxides. Experiments with synthetic mine water as lubricant demonstrated that the presence of significant amounts of chloride and sulphate in the water generally reduced friction and wear. This was tentatively explained in terms of reduced adhesion and the promotion of iron oxide and hydroxide formation. It is suggested that the influence of sulphate may be more important in thi'3 regard than that of chloride. The tribological behaviour of self-mated Syndite PCD sliding couples is dominated by the formation of Co-rich trlbofilms, which nrc associated with increased friction coefficients and reduced load carrying capacity (LCC). Syndax, which employs silicon as the binder phase, shows lower friction coefficients anti higher LCe under both dry and water-lubricated sliding conditions. Mixed Syndax/Syndite couples show superior performance to self-mated Synditc tinder dry sliding conditions, but 110 improvements in the presence of water. The former effect is related to the preferential removal of Co 11'0111 the Syndite surface to the Syndax / GR 2017

Neste trabalho, a relação entre a adesão e o grau de desordem de superfícies em contato é estudada por meio de simulações por dinâmica molecular. O sistema em estudo é composto por um indentador cilíndrico rígido e um bloco deformável. Um reservatório térmico é colocado logo abaixo do bloco, de forma a manter o sistema a temperatura ambiente. Os sólidos são feitos do mesmo material e são modelados por intermédio do potencial genérico de Lennard-Jones. A adesão entre as superfícies é variada gradualmente por meio da variação do raio de corte do potencial que descreve a interação entre as superfícies indentador-bloco. Cada simulação se inicia com um recozimento, após o qual são realizadas as simulações de contato propriamente ditas, até que ocorra penetração de 1,7 raios atômicos. A força normal, a energia potencial, a temperatura e a energia cinética são acompanhadas ao longo do processo. Os resultados reforçam a importância da adesão no jump-to-contact, estando este fenômeno relacionado à geração de defeitos cristalinos. Há indícios de que a distribuição da carga, bem como a dissipação de energia, seja influenciada pela adesão na interface. Mostra-se que a desordem apresentada pelos átomos do bloco é proporcional à contribuição da adesão. / In this work, the relationship between adhesion and the degree of disorder of surfaces in contact is studied by means of molecular dynamics simulations. The system consists of a rigid cylindrical indenter and a deformable block. A heat reservoir is placed just below the block, in order to maintain the system at room temperature. Both solids are made of the same material and are modeled through the generic Lennard-Jones potential. Adhesion between the surfaces is gradually varied by varying the cut-off radius of the potential describing the interaction between the indenter surface and the block. Each contact simulation is preceeded by an annealing step, and is conducted until the penetration reaches 1.7 atomic radii. The normal force, the potential energy, kinetic energy and temperature are monitored throughout the process. The results reinforce the importance of adhesion in the phenomenon of jump-to-contact, which is also related to the generation of crystalline defects. The results indicate that the load distribution and power dissipation is influenced by the adhesion at the interface. It is shown that the disorder presented by the atoms of the block is proportional to the contribution of adhesion.

Introdução: Biofilme consiste em um conjunto de microrganismos embutidos em uma matriz extracelular. O biofilme tradicional (TBF) se desenvolve em locais com contínua hidratação, e o biofilme buildup (BBF), em produtos para a saúde expostos a repetidos ciclos de sujidade, limpeza, desinfecção e secagem. Objetivo: avaliar o impacto do uso de detergente e fricção para remover biofilme buildup-5 (BBF-5) e biofilme tradicional-5 (TBF-5) de canais endoscópicos gastrointestinais flexíveis, bem como o impacto do glutaraldeído após a limpeza. Métodos: O BBF-5 foi desenvolvido após a exposição da superfície interna dos canais de endoscópicos gastrointestinais ao Artificial Test Soil (ATS) contendo 108UFC/ml de Pseudomonas aeruginosa (PA) e Enterococcus faecalis (EF), limpeza, desinfecção de alto nível (DAN), enxágue e secagem durante cinco dias. O mesmo processo foi utilizado para desenvolver o TBF-5, porém a fase de DAN foi omitida. Limpeza com detergentes com enzimas de pH neutro e detergentes sem enzimas com pH alcalino, escova com cerdas e dispositivo de limpeza pull thru foram comparados à limpeza com água e sem fricção para remover o BBF-5 e o TBF-5. Testes de proteína e carboidrato, contagem de bactérias viáveis e adenosina trifosfato (ATP) foram realizados. Teste de Kruskal-Wallis e análise de post hoc Dunn-Bonferroni foram realizados. Resultados: Não houve diferença estatisticamente significante (p>0,05) entre a quantidade de EF e PA nos canais com TBF-5 e BBF-5. Não houve diferença da eficácia para a remoção de PA em TBF-5 entre o detergente enzimático e a água, em ambas as situações, a limpeza apenas não foi eficaz (p>0,05) na ausência de fricção (flush). Por outro lado, o detergente alcalino, associado a todos os procedimentos de limpeza (ausência e presença de fricção) e DAN, foi eficaz para remoção de PA. Para a remoção de EF em TBF-5, a eficácia da limpeza foi alcançada em todas situações avaliadas (com e sem fricção) com o uso do detergente enzimático; com a água, na presença de fricção (pull thru e escovas de cerdas); e com detergente alcalino, apenas com o método de limpeza com escovas de cerdas (p<0,05). Para a remoção de bactérias em BBF-5, formados em canais de PTFE, não houve diferença da eficácia para a remoção de PA entre o detergente enzimático e o alcalino, em ambas situações, todos os procedimentos avaliados foram eficazes (p<0,05), enquanto que a água foi ineficaz para remoção de PA apenas na ausência de fricção (p>0,05). Para a remoção de EF em BBF-5, o detergente enzimático e a água foram eficazes em todas situações avaliadas; o detergente alcalino, foi eficaz na presença de fricção com o dispositivo pull thru e escovas de cerdas (p<0,05). Testes de ATP, proteína e carboidrato foram incapazes de detectar biofilme. Conclusão: Água potável de torneira, detergente com enzimas e detergente alcalino sem enzimas foram eficazes para a completa remoção de BBF-5 e TBF-5 na presença de fricção (pull thru ou escova com cerdas) durante a limpeza. Na ausência de fricção, detergente enzimático apresentou maior habilidade para remover E. faecalis de TBF-5 e BBF-5, detergente alcalino para remover P. aeruginosa e a água não foi eficaz para a remoção de ambos microrganismos. Glutaraldeído destruiu bactérias remanescente após a maioria das combinações de limpeza avaliadas. / Background: Biofilm is the accumulation of microorganisms enclosed in an extracellular matrix. Traditional biofilm (TBF) develops under continuous hydration whereas buildup biofilm (BBF) develops on medical devices that are exposed to repeated cycles of soiling, cleaning, disinfection and drying. Objetive: to evaluat the impact of detergent and friction on BBF-5 and and TBF-5 removal from PTFE channels as well as the killing efficacy of glutaraldehyde post cleaning. Methods: BBF-5 was developed by repeated rounds over five days of exposure to bacteria, cleaning, high level disinfection (HLD), rinsing and drying of the inner surface of new polytetrafluorethylene (PTFE) channels. Artificial Test Soil (ATS) containing 108CFU/ml of Pseudomonas aeruginosa (PA), and Enterococcus faecalis (EF) was used for the bacterial exposure. The same process was used to develop TBF-5, however the HLD step was omitted. Cleaning with enzymatic and alkaline detergents, bristle brush and pull thru cleaner were compared to a water-flush only to determine BBF-5 and TBF-5 removal. The residual organic and microbial levels were tested using carbohydrate, and protein assays as well viable count, and adenosine triphosphate (ATP) testing. Kruskal-Wallis test and the post hoc Dunn-Bonferroni analysis were performed. Results: There was not a statistically significant difference (p> 0.05) between the amount of EF and PA in the channels with TBF-5 and BBF-5. There was not a difference in efficacy for the removal of PA in TBF- 5 between the enzymatic detergent and water and in both situations, only cleaning was not effective (p>0.05) in the absence of friction (flush). Furthermore, the alkaline detergent, associated with all cleaning procedures (absence and presence of friction) and DAN, was effective for the removal of PA. For removal of EF in TBF-5, cleaning efficacy was achieved in all procedures evaluated (with and without friction) with the use of enzymatic detergent; with water in the presence of friction (pull thru and bristle brushes); and an alkaline detergent, the only method of cleaning brushes with bristles (p<0.05). For the removal of bacteria in BBF-5 formed on PTFE channels, there was not a difference in efficacy for PA removal of the enzymatic and alkalyne detergent and in both situations, all procedures were evaluated effective (p<0.05 ), while water was ineffective for PA removal only in the absence of friction (p>0.05). For EF removal on BEF-5, the enzymatic detergent and water were evaluated effective in all situations; alkaline detergent, was effective in the presence of friction with the pull thru device and bristle brushes (p<0.05). ATP, protein and carbohydrate testing were unable to detect biofilm. Conclusion: Tap water, enzymatic and alkaline detergent were effective for complete BBF-5 and TBF-5 removal in the presence of friction (pull thru or bristle brush) and a flushing pump during the cleaning. Without friction, enzymatic detergent was more effective for EF removal of TBF-5 and BBF-5, alkalyne detergent was more effective for PA removal and water was not effective for both types of bacterial removal. Glutaraldehyde effectively killed the remaining microorganisms after some cleaning combinations were tested.

O comportamento reológico de suspensões concentradas heterogêneas como concretos e argamassas possui influência direta na energia requerida e na produtividade durante o processamento e aplicação destes materiais, além de ser um fator determinante na obtenção de um produto final qualidade. De um modo geral pode-se dizer que a fluidez destas suspensões está diretamente relacionada à facilidade de movimentação das partículas, logo pode-se inferir que a redução dos fenômenos atrito é um fator determinante para o bom desempenho destas suspensões durante o fluxo. Deste modo, este trabalho buscou por meio de modelos ideais de esferas e silicone líquido avaliar a influência do coeficiente de atrito dos agregados e da viscosidade da matriz no comportamento reológico de suspensões concentradas. O coeficiente de atrito de agregados esféricos com diferentes granulometrias foi determinado experimentalmente através do ensaio de cisalhamento direto, também conhecido como shear box, e o comportamento reológico de suspensões compostas por estes agregados e silicones líquidos de diferentes viscosidades foram avaliadas por meio do ensaio de squeeze flow. Os resultados revelam que a distribuição granulométrica possui um influência no coeficiente de atrito dos agregados e que esta propriedades está relacionada a área e ao tipo de contato entre as partículas. Entretanto, para o tipo de fluxo e para as velocidades as suspensões, não houve uma relação direta entre o coeficiente dos agregados e a viscosidade da suspensão. Além disto, apesar de alterar o comportamento reológico das suspensões a viscosidade da matriz não apresentou uma relação direta com viscosidade da suspensão, o que em partes ser explicados pela provável ocorrência de um fluxo não homogêneo das suspensões nas condições aqui estudadas. / The rheological behavior of concentrated suspensions like concrete and mortars plays an important hole during their processing and application, and also has a great influence on the final product quality. The flowability of these suspensions is directly related to the ease of particle motion in the system, therefore reduction of friction phenomena contributes for a good flow behavior. The aim of this work was to determine the influences of aggregates friction coefficient and the liquid viscosity of the fluid matrix on the rheological behavior of concentrated suspensions. The friction coefficient of glass spheres with different particle size distributions were determined by shear box tests, while the rheological behavior of concentrated suspensions composed by these glass spheres and silicone oils was evaluated by squeeze flow tests. Results revealed that the particle size distribution influences the coefficient of friction, and this property is determined by the type and the area of contact between the particles. However, for the kind of flow and the speed used in the experiments, there was no relation between friction coefficient and the suspension viscosity. Additionally, matrix viscosity has an impact on the rheological behavior of the system, but no clear relation was identified, which may be caused by the occurrence of heterogeneous flow under the applied experimental conditions.