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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.
451

Effects of high pressure water jet on aluminum surfaces prior to thermal spray coating

Accardo, Mario G. 22 October 2009 (has links)
<p>Most thermal spray coating processes can be divided into three sub-processes; substrate surface preparation, the thermal spray operation and a post-coating surface finishing operation such as honing or grinding. Reliable and robust surface preparation is needed to guarantee maximum coating adhesion to substrates. Traditionally, the grit blasting process is used for surface preparation of materials receiving a thermal spray coating. However, in high volume production, the reproducibility of surface topography decays with time as grit particles are recycled through surface preparation operation. The focus of this project is to enhance the coating's ability to adhere to an aluminum substrate by incorporating high pressure water jet as a surface preparation operation. </p> <p>Water pressure, standoff distance, number of orifices, orifice size and rotation speed are process parameters identified as having an effect on surface roughness and coating adhesion strength. Through classical statistical analysis, main effects as well as 2 and 3 factor interactions are revealed and studied.</p> <p>A direct and significant relationship exists between water pressure, standoff distance and number of orifices. Correlation exists among adhesion strength and surface roughness parameters Ra, Rq and Rtm, respectively. Recommendations are made for further investigation into reducing water pressure and rotation speed requirements while sustaining the same level of surface modification.</p> / Master of Science
452

Hur substrat och avstånd från vatten påverkar strandvegetation vid Ölmans avrinningsområde / Effects of substrate and distance from the stream on riparian vegetation in the Ölman watershed

Johansson, Julia January 2020 (has links)
Avrinningsområden är landområden där det ofta finns förutsättningar för stor biologisk mångfald. År 2017 var ett område som undersöktes Ölmans avrinningsområde, där man dokumenterade och räknade antal individer av de olika växtarter som fanns på olika avstånd från vattnet, samt de olika vegetationstypernas procentuella täckning av marken. Det här är en undersökning som, i hopp om att ge en bättre förståelse för vegetationszonering vid vattendrag, försöker upptäcka huruvida det finns en skillnad i artmångfald och artfördelning på två olika substrat och på tre olika avstånd från vattnet vid Ölmans avrinningsområde i Värmland, Sverige. Alla data som användes i undersökningen hade redan samlats in i juli 2017. Analysen skedde under hösten 2018. Resultaten påvisade inget samband mellan substrat och artmångfald och artfördelning. Avståndet från vattnet hade inte heller någon inverkan på artmångfald och artfördelning. Ölmans avrinningsområde är påfallande litet, vilket med sannolikhet påverkar förekomst av naturlig zonering – eller en brist därav. Det finns också flera andra biotiska och abiotiska faktorer som kan påverka växtlivet, såsom pH-värden i vattnet och jorden, mänsklig påverkan, påverkan från djur, och så vidare. Att enbart känna till grovleken på det underliggande substratet ger inte tillräckligt med information för att tillåta dragande av några definitiva slutsatser gällande vegetationsstrukturen. / Watersheds are areas of land that often have the prerequisites for great biological diversity. In 2017 one area being examined was the Ölman watershed, where different plant species were accounted for, both by species and amount of individuals, on different distances from the water, as well as the percentage of ground coverage of different types' of vegetation. This is a study that, in an attempt to better understand vegetation zones along rivers and streams, tries to discover whether there is a statistically significant difference between the species diversity and species distribution on two different substrates and three different distances from the water of the Ölman watershed in Värmland, Sweden. All data used for the study were collected in July 2017 and analysed in autumn 2018. The results showed no relationship between substrate and species diversity or species distribution. The distance from the water did not have any effect on the species diversity or species distribution either. The Ölman watershed is quite small, which is likely to affect the presence of natural zoning – and the lack thereof. There are also several other biotic and abiotic factors that can influence plant life, such as pH of the water and soil, human and animal interference, etc. Only knowing the coarseness of the substrate does not provide enough information to be able to draw any definite conclusions on the vegetation structure.
453

Substrato com composto de lixo e poda de árvore para produção de mudas de Pterogyne nitens /

Silva, Flávia Gomes da. January 2011 (has links)
Orientador: João Antonio Galbiatti / Banca: Carlos Eduardo Angeli Furlani / Banca: Fábio Olivieri de Nobile / Resumo: A riqueza de nutrientes presentes nos resíduos orgânicos é fonte alternativa para uso de adubo na agricultura e para a recomposição de matas nativas. Com o objetivo de avaliar o comportamento de mudas de Pterogyne nitens (amendoim bravo), espécie florestal nativa da mata atlântica, em substratos contendo composto orgânico de lixo e poda de árvore, conduziu-se experimento em ambiente protegido, no Departamento de Engenharia Rural da Faculdade de Ciências Agrárias e Veterinárias, Unesp, Campus de Jaboticabal-SP. As plantas foram dispostas em tubetes distribuídos ao acaso com 8 tratamentos em esquema fatorial 4x2 (4 substratos e 2 níveis de irrigação) com 3 repetições. Os substratos utilizados foram: 80% composto de poda de árvore e 20% composto de lixo; 100% substrato comercial; 100% composto de poda; 80% poda e 20% substrato comercial. A irrigação foi realizada manualmente calculada em níveis de 50% e 100% da evapotranspiração. Foi avaliado o desenvolvimento da planta por meio da altura, diâmetro do caule, número de folíolos e massa seca. Os parâmetros de desenvolvimento das plantas de amendoim bravo foram significativos, no substrato 80% poda de árvore e 20% composto de lixo. Não houve diferença em relação aos níveis de irrigação. Os resíduos orgânicos da poda de árvore e do lixo domiciliar na proporção 80% poda de árvore e 20% composto de lixo apresentaram melhor desempenho que os demais substratos, incluindo o substrato comercial / Abstract: The richness of nutrients in organic waste is an alternative source of fertilizer for use in agriculture and for restoration of native forests. The use of alternative substrates for the production of seedlings of native species should be studied to achieve higher efficiency and availability of substrate for the farmer, encouraging recovery and environmental sustainability of their property. Aiming to evaluate the performance of seedlings Pterogyne nitens (amendoim bravo), a forest species native to the rainforest, on substrates containing organic compost and pruning the tree, we conducted the experiment in a greenhouse at the Department of Rural Engineering Faculty of Agriculture and Veterinary Sciences, UNESP, Jaboticabal - SP. The plants were placed in tubes randomly allocated to four treatments, two irrigation levels in a 4x2 factorial arrangement and three replications. The substrates used were composed of 80% and tree pruning waste compost 20%, 100% commercial substrate, 100% composed of pruning, pruning 80% and 20% commercial substrate. Irrigation was performed manually at 50% and 100% evapotranspiration. Was evaluated through the development of plant height, stem diameter, number of leaves and dry weight. The development of peanut plants was significantly brave, substrate 80% and 20% of pruning waste compost. No difference in relation to levels of irrigation. We conclude that the conditions under which the experiment was conducted organic waste from tree trimming and garbage at home 4:1 ratio performed better than the other substrates, including the commercial substrate / Mestre
454

The biogas potential from municipal waste and agricultural residues in Hazaribagh, Dhaka city, Bangladesh : - a possible strategy to improve the energy system

Hasan, A S M Monjurul January 2016 (has links)
Energy is considered as the foremost significant factor towards socio-economic growth. Due to the rapid growth of industrialization in Bangladesh, the need of energy is increasing day by day. Considering the environmental issues, sustainable solutions are needed to address the energy crisis. Energy generation from waste through biogas can be a good solution that can address both the energy demand as well as the waste management issue.    The overall aim of this master thesis is to analyze Hazaribagh’s biogas potential from municipal waste and agricultural residues and estimate how much electricity that can be generated from the produced biogas. The feasible sources of Hazaribagh were considered in order to get the information that would be later on analyzed to estimate possible biogas production. The potential sources include wastes from two markets, six slaughterhouses, domestic wastes, three large-scale tanneries and two small scale tanneries, one poultry farm and three crop lands. The calculations made in this thesis to roughly estimate the amount of biogas and electricity from the described sources are done in a simple way, just to illustrate the potential. The result shows that the tannery waste has the highest potential followed by slaughterhouse waste. Furthermore, the calculations show that the tannery waste contributes most for electricity generation also followed by slaughterhouse waste. In order to implement biogas solutions, several actors should be involved like government, future owners, local people etc. Different tools like legislation, financial support etc. are also important for implementing the biogas solutions.   In summary, there is a good potentiality of biogas production and electricity generation from municipal wastes and agricultural residues of Hazaribagh. Biogas solutions from waste and agricultural residues can be beneficial from both the energy and the waste management perspective.
455

Experimental and CFD Study of Flow Phenomenon in Flowrate-amplified Flotation Element

Xinzhe, Wang, Xin, Li January 2016 (has links)
Focusing on reducing the air consumption of an air flotation rail system, a flowrate-amplified flotation element was recently developed. This new flotation element ulitises the rotational flow to intake extra air via an intake hole, and thus, effectively improves the flotation height. Compared to a conventional flotation element, the flowrate-amplified flotation element can reduce air consumption by approximately 50% for the same load and flotation height. To gain an understanding of the flow phenomenon in the flowrate-amplified flotation element, experiments and CFD simulations are conducted in this study. Based on the results, we found that the flowrate-amplified flotation element could take a part of the kinetic energy of the rotating air to suck in extra air. The intake hole greatly affects the pressure field and velocity field of the flotation element. Additionally, the effects of the variant gap height and supplied flow rate were also discussed. The results indicate that the pressure distribution decreases as the gap height increases and increases as the supplied flow rate increases.
456

Aromaticity and Flexibility of Transmembrane Helix 12 Contribute to Substrate Recognition and Transport in Human P-Glycoprotein

Jason A Goebel (9755543) 14 December 2020 (has links)
Human p-glycoprotein (P-gp) is an ATP-binding cassette transporter that actively transports a diverse set of substrates at the plasma membrane. Specifically, P-gp is expressed most highly at important blood tissue barriers on the lumenal side of endothelial cells and secretory tissues asymmetrically where it provides generalized protection against xenobiotics due to its promiscuous substrate binding pocket. Substrates typically interact with P-gp within the inner leaflet of the plasma membrane before being effluxed through large conformation changes driven by ATP binding and hydrolysis. Since many small molecule drugs are substrates of P-gp and P-gp has the ability to transport chemically and structurally diverse molecules, delivery of bioavailable small molecule therapies and treatment of diseases beyond blood-tissue barriers may be difficult. In cancer, expression of P-gp may confer a multidrug resistance phenotype due to upregulation of the MDR1 gene, which encodes P-gp, in response to treatment with chemotherapies. Treatments of diseases beyond blood-tissue barriers and some cancers may be more complex given the protective role of P-gp coupled with it promiscuous substrate binding site.<br>Many studies of P-gp have been centered around understanding the structure function relationship of how P-gp effluxes small molecules across the plasma membrane. Here we have used a transient Vaccinia virus expression system to rapidly express many mutants of P-gp in human cells for analysis. Transient expression using the Vaccinia system was optimized to produce a large amount of protein while avoiding significant cell death. Optimization of the Vaccinia expression system has also helped to show that changes in P-gp surface expression are not correlated to changes in substrate accumulation within cells expressing P-gp, a topic that has yet to be addressed within the field of P-gp study. Reduced surface expression of P-gp to 68% maintained the same level of reduced cellular accumulation of two substrates, calcein-AM and rhodamine 123, relative to a WT P-gp control. Further study of P-gp mutations revealed a Y998A mutation had a 90% reduction of surface expression but the same reduction of cellular accumulation of rhodamine 123 further supporting that changes in surface expression do not correlate to changes in substrate transport.<br>We then sought to demonstrate how flexibility in transmembrane helix (TMH) 12 of P-gp affected overall stability and transport ability in vitro. TMH 12 in inward facing conformations shows a region of decreased hydrogen bonding in the backbone of the helix leading to a “kink” present in many crystal structures of C. elegans and mouse P-gp as well as in an occluded structure of human P-gp. Outward facing crystal structures of C. elegans, mouse, and human P-gp show TMH 12 where the backbone of the helix is fully hydrogen bonded and ordered. The change in hydrogen bonding pattern and the presence of the kink in TMH 12 suggest the importance of flexibility in the function of TMH 12. Clustal Omega was used to align the primary structure of P-gp between 8 species and a conserved sequence of 996-PDYAKA-1001 was identified aligning with the kink observed in crystallographic data. The kinked nature of this region led to our development of a rigid poly-alanine mutation and a flexible poly-glycine mutation based on the propensity of these amnio acids to form helices. The more flexible poly-glycine mutation obtained no significant transport while the poly-alanine mutation maintained some ability to transport fluorescent substrate relative to a WT control. Crosslinking of the nucleotide binding domains (NBDs) revealed a decrease of NBD dimerization likely correlating to decreased transport. Thus, some degree of flexibility within the kink region is critical for substrate transport as rigid and flexible mutations of this region abrogate transport of fluorescent substrates.<br>While the substrate binding pocket it located towards the interior of P-gp within the lipid bilayer, it has been theorized that substrates may interact with P-gp at the lipid-protein interface of the inner leaflet near portals for substrate entry formed by pairs of helices either side of the protein. To test this hypothesis, aromatic residues on TMH 12 and adjacent elbow helix 2 near the interface region of the inner leaflet, that have also been observed to interact with a cyclic peptide in a crystal structure of P-gp, were mutated to alanine. Y998, on TMH 12, was shown to interact with the cyclic peptide and is ideally located at the protein-lipid interface near a surface formed by elbow helix 2 and TMH 9 and was observed to have the largest effect on substrate accumulation. Accumulation of fluorescent substrates, relative to WT P-gp, was increased though not all substrates were affected similarly. No increase of accumulation was observed with rhodamine 123 while accumulation of BD-prazosin increased 65% relative to WT P-gp. It is to be expected that the large diversity of substrates recognized by P-gp would interact preferentially with carrying residues at the protein-lipid interface similar to observations of substrate binding at the substrate binding pocket. Variability in accumulation signifies that substrates do interact with P-gp at the lipid-protein interface and substrates interact differently at this interface similarly to substrate interaction at the substrate biding pocket.<br>
457

DEVELOPING A CELL-LIKE SUBSTRATE TO INVESTIGATE THE MECHANOSENSITIVITY OF CELL-TO-CELL JUNCTIONS

Kent Douglas Shilts (9182480) 04 August 2020 (has links)
<p>The role of mechanical forces in the fate and function of adherent cells has been revealed to be a pivotal factor in understanding cell biology. Cells require certain physical cues to be present in their microenvironment or the cell will begin apoptosis. Mechanical signals from the environment are interpreted at the cellular level and biochemical responses are made due to the information from outside the cell, this process is known as mechanotransduction. Misinterpretation of physical cues has been indicated in many disease states, including heart disease and asthma. When a cell is bound to the ECM, proteins such as integrins are engaged at static and stable adhesion sites. These tight and static anchoring points found at the ECM exist in stark contrast to the dynamic conditions seen at intercellular junctions. Intercellular junctions, such as gap and adherens junctions, are formed between cells to act as a mechanism to relay information and exchange material. Due to the important role intercellular junctions play in processes of wound healing, epithelial-mesenchymal transition and cancer metastasis developing more sophisticated levels of understanding of these mechanisms would provide valuable insight.</p> <p>Complex biological processes, including immune cell signaling and cellular ECM adhesions, have been effectively replicated in model systems. These model systems have included the use of solid supported lipid bilayers and polymeric hydrogels that display cell adhesion molecules. Studies of cellular mechanotransduction at ECM adhesion sites has also been completed with covalently functionalized polymeric substrates of adjustable elasticity. However, developing model systems that allow the accurate reproduction of properties seen at intercellular junctions, while also allowing the investigation of cellular mechanosensitivity has proven to be a difficult task. Previous work has shown that polymer-tethered lipid bilayers (PTLBs) are a viable material to allow the replication of the dynamics and adhesion seen at intercellular junctions. Although efforts have been made to produce PTLBs with different mechanical properties, there is currently not a material with sufficient tunable elastic properties for the study of cellular mechanotransduction.</p> <p>To establish a system that allows the study of stiffness effects across a biologically relevant range (~0.50 – 40 kPa) while maintaining the dynamic properties seen at cell-to-cell junctions, polymer gel-tethered bilayers (PGTBs) were developed. A fabrication strategy was established to allow the incorporation of a hydrogel support with easily tunable stiffness and a tethered lipid bilayer coating, which produced a powerful platform to study the effects of stiffness at intercellular junctions. Careful attention was given to maintain the beneficial properties of membrane diffusion, and it was shown that on different linking architectures lipid bilayers could be established and diffusion was preserved. Microscopy-based FCS and FRAP methodology were utilized to measure lipid diffusion in these systems, while confocal microscopy was used to analyze cell spreading and adhesion. Three distinct architectures to link the lipid membrane to the underlying polyacrylamide hydrogel were pursued in this work, a non-covalent biotin-streptavidin system, a covalently linked design with fibronectin, and a direct covalent linkage utilizing crosslinker chemistry. In this work, it was shown that cells were able to spread and adhere on these substrates, with cell adhesion zones visualized under plated cells that demonstrate the capability of the cell to rearrange the presented linkers, while maintaining a stable material. Also confirmed is the tunability of the polymer hydrogel across a wide range of stiffness, this was shown by quantitative changes in cell spreading area in response to polymer properties.</p>
458

Fundamentally Based Investigation and Mathematical Modeling of the Delay Observed in the Early Stages of E-coat Deposition

Padash, Fardin 06 January 2022 (has links)
The objective of this work is to enhance the understanding of the delay observed in the early stages of E-coat deposition. E-coat deposition has been widely used by industries such as the automotive industry to form the primary protective coating against corrosion. Currently, models that are used to find the best conditions under which the desired coating coverage for the entire auto body can be achieved do not accurately predict the coating coverage in recessed areas. The accuracy of large-scale models can be improved by enhancing our understanding of the mechanisms responsible for the observed delay. To accomplish this, experiments are performed to define the processes that control deposition initiation and then a model is developed to describe those processes. Simulation results are compared with experimental measurements for a range of conditions to assess the validity of the results. The delay before the onset of deposition is influenced by the type of substrate and properties of the E-coat solution. The impact of the substrate type on the onset of deposition was experimentally investigated. The results of experiments indicated that surface characteristics such as adhesion of bubbles to the surface and the formation of an initial coating increase the local current density on the surface. Investigations of the morphology of the initial coating on different types of substrates indicated that deposition began at areas where the local current density was higher. Increasing the local current density due to the adhesion of bubbles to the surface resulted in a 40% reduction in the time required for the onset of deposition on galvanized steel compared to bare steel. The processes in the solution adjacent to the surface were also investigated to understand the mechanisms responsible for the onset of deposition. Convection was used as a tool to determine the impact of the accumulation of hydroxide ions on the onset of deposition. The results of rotating disk electrode (RDE) experiments showed that the observed delay before deposition was not due to the time required for accumulation of hydroxide ions at the surface. The results of additional experiments showed that the accumulation of micelles was critical to the deposit initiation. The impact of micelle accumulation on the deposit initiation was further explored by developing a mathematical model of the physical processes in the solution adjacent to the surface. The model was evaluated at different conditions and was found to agree with experimental results at different current densities and bulk micelle concentrations. The model and the experimental results from this study help to explain the observed delay in the early stages of E-coat deposition and provide a basis for improving large-scale simulation of E-coat deposition.
459

Study of different methodologies to determine relative dielectric constant of given substrate using fabrication, modelling and measurement strategies

Lundberg, Anders January 2021 (has links)
In this thesis, different methods for measuring the relative dielectric constant is investigated using simulations and experimental approaches. The first method is known as the S-parameter inversion method. In this method formulae is used to calculate the characteristic impedance of the microstrip line from measured S-parameters. To calculate the value of relative dielectric constant, four expressions for the microstrip line that relate the characteristic impedance to the relative dielectric constant were used. Second method uses an implementation of a band-pass filter and is commonly known as the band-pass filter method. In this method, a band-pass microstrip filter was designed using a predicted relative dielectric constant value. Center frequency of the band-pass filter is chosen to be at the frequency of interest, since relative dielectric constant will be determined around this frequency. The designed band-pass filter was manufactured and the frequency response was measured. To determine the true relative dielectric constant one changes the relative dielectric constant parameter used in the simulation until it matches the measured response of the manufactured PCB. Third method is called the quarter wavelength stub method. It uses implementations of a microstrip quarter wavelength stub because it resonance at different frequencies. The relative dielectric constant is determined using the frequencies on which the reflection occurred. In the fourth method, called the two microstrip line method, two lines of different lengths were designed and the phase difference between the propagating waves were measured. The phase difference and difference in length of the two lines is then used to calculate the relative dielectric constant. The thesis shows that a majority of the methods generates a similar result, thus indicates that they are suitable to determine the relative dielectric constant of any given substrate. The two methods that gave the most accurate results are the quarter wavelength stub method and the band-pass filter method. S-parameter inversion method is the method that has high variations in the results. Since the characteristic impedance that is calculated using the S-parameters are sensitive towards any sort of disturbances. The resulting relative dielectric constant aren't within the expected range for FR-4 both higher and lower values were obtained. The band-pass filter method gives the most accurate results of the methods. As the resulting relative dielectric constant are within the expected range for FR-4. Quarter wavelength stub method gives the results of the relative dielectric constant that are within the expected values of FR-4 and the variation is moderate. Two microstrip line method shows deviations in the results and has non-linearity as well. This is probably coming due to resonance of the line that gives rise to a phase change. This method is also acceptable since the results of the relative dielectric constant are within the expected range for FR-4.
460

Untersuchung von Ansätzen zur Optimierung des Beschichtungspfades beim Ionenstrahlsputtern eines Substrats mit räumlichem Tiefenprofil

Ullmann, Florian 06 May 2021 (has links)
Die Arbeit thematisiert die Optimierung von Beschichtungsvorgängen mithilfe der Ionenstrahlsputterdeposition hinsichtlich der Homogenität von Substraten mit Tiefenprofil. Dazu wurde eine Simulationssoftware entwickelt und hinsichtlich der Problemstellung an mehreren Beispielen getestet.

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