To see the other types of publications on this topic, follow the link: Physical-mechanical properties of AAM.
Dissertations / Theses on the topic 'Physical-mechanical properties of AAM'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Physical-mechanical properties of AAM.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Ghorai, Suman. "Chemical, physical and mechanical properties of nanomaterials and its applications." Diss., University of Iowa, 2013. https://ir.uiowa.edu/etd/2501.
Full textAbstract:
The contribution of atmospheric aerosols towards radiative forcing has a very high uncertainty due to their short atmospheric lifetime. The aerosol effects are largely controlled by the density, elemental composition, and hygroscopic properties of the aerosol particles. Therefore, we have performed designed new methodology using Scanning Transmission X-ray Microscopy (STXM), Atomic force spectroscopy (AFM), micro-FTIR spectroscopy and Scanning Electron Microscopy (SEM) to quantify these important aerosol properties. Hygroscopic properties are quantified by plotting the mass of water on a single particle basis, calculated from STXM, as a function of relative humidity. Alternatively, micro-FTIR spectra have been used to study the effect of composition of aerosol particles on the hygroscopic properties of NaCl. Moreover, a unique combination of STXM and AFM has been utilized to quantify density and elemental composition of micrometer dimensional particles. This method has also been extended towards exploring mixing state of particles, consisting of heterogeneously mixed inorganic and organic compounds. In addition to these above mentioned properties, the fate of an atmospheric particle is often altered by chemical transformation and that in turn is influenced by the atmospheric RH. Therefore, we have studied an unusual keto-enol tautomerism in malonic acid particles at high RH, which is not observed in bulk. This observation could potentially be utilized to significantly improve the models to estimate Secondary Organic Aerosols (SOA). Using STXM and micro-FTIR technique, RH dependent equilibrium constant of the tautomerism reaction has been quantified as well.
Organic nanocrystals capable of undergoing solid state photochemical changes in a single-crystal-to-single-crystal (SCSC) manner have been particularly important in fabricating molecular switches, data storage devices etc. Mechanical properties of these nanomaterials may control its SCSC reactivity. In addition, investigation of mechanical stiffness is important to define allowable limit of stiffness towards device application. Therefore, we studied mechanical properties of series organic nano cocrystals primarily consisting of trans-1,2-bis(4-pyridyl)ethylene and substituted resorcinol using AFM nanoindentation technique. Dependence of mechanical properties and SCSC reactivity on the resorcinol structure is also investigated as well. Moreover, photolithography on the thin film of these organic cocrystals has been performed to demonstrate its applicability as a photoresist.
2
Tucker, Chauncey Lewis. "Mechanical and Physical Properties of Spider Silk Films Made from Organic and Water-Based Dopes." DigitalCommons@USU, 2014. https://digitalcommons.usu.edu/etd/2326.
Full textAbstract:
In this project, we focus on developing a method to produce synthetic spider silk thin films. Using these films we optimized mechanical properties, lowered cost, and improved the environmental impact using different processing methods. Applications for spider silk films are broad, ranging from physical protection to biocompatible materials. This project was designed to improve mechanical properties and production methods of films made from synthetic forms of MaSp1 and MaSp2 from the dragline silk of Nephila clavipes. We have increased the mechanical stress (200 MPa) to more than 4 times that of similar products with elongations as high as 35%. The films have also been analyzed using NMR, XRD, and AFM or SEM showing that the secondary structure in as-poured films is mainly alpha-helical and after processing this structure turns to an aligned betasheet formation similar to that in spider silk fibers.
3
Ševčík, Marek. "Vývoj kompozitů na bázi alkalicky aktivovaných matric odolných vůči působení extrémních teplot." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2021. http://www.nusl.cz/ntk/nusl-444262.
Full textAbstract:
The diploma thesis is focused on the development of composites from alkali activated materials (AAM) and their resistance to extreme temperatures. The theoretical part describes alkaline activation and precursors for the production of AAM. Furthermore, the problem of the effect of extreme temperatures on these materials is described. In the experimental part, the optimal silicate modulus with respect to the properties of AAM was gradually determined, and the effect of extreme temperatures on the AAM matrix was verified. In the next stage, the effect of the filler with respect to the behavior at extreme temperatures was tested and then the final formulation was optimized.
4
Zhang, Shu. "Mechanical and physical properties of electrospun nanofibers." NCSU, 2009. http://www.lib.ncsu.edu/theses/available/etd-07102009-165411/.
Full textAbstract:
The process of electrospinning was utilized to fabricate randomly aigned nylon6 nanofibers and aligned nylon6 nanofibers. Polymer concentration affecting electrospinning was investigated. This parameter was evaluated using degree of crystallinity by differential scanning calorimetry (DSC) as well as visual images produced by scanning electron microscopy (SEM). DSC data demonstrated that more crystals were formed with lower polymer concentrations; SEM images revealed that slimmer fibers were produced by lower concentrations. The mechanical properties of unoriented fibers and aligned fibers were tested on Instron 5544. The result of tensile tests indicated higher Youngâs modulus and tensile strength of aligned nanofibers than that of unaligned fibers. The SEM images at broken edges of fibers illustrated different broken mechanisms of these two forms of nanofibers. The broken mechanism of aligned nanofibers was further confirmed by crystallinity parameters obtained from DSC and fiber diameter shown from SEM images.
5
Alcock, Joseph Patrick. "Mechanical and physical properties of orthodontic archwires." Thesis, University of Bristol, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.492645.
Full textAbstract:
The aim of this study was to investigate the nanomechanical properties of as received, autoclaved and clinically exposed orthodontic archwires. This study was prospective. The clinical component took place in the Orthodontic department of a district general hospital in Bath. Laboratory tests were performed at Bristol Dental School.
6
Zanganeh, Mehdi. "Mechanical properties of fiber reinforced concrete with ACM applications." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0013/MQ52021.pdf.
Full text
7
Kock, Jeffrey Wayne. "Physical and Mechanical Properties of Chicken Feather Materials." Thesis, Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/10555.
Full textAbstract:
Materials derived from chicken feathers could be used advantageously in composite building material applications. Such applications could potentially consume the five billion pounds of feathers produced annually as a by-product of the U.S. poultry industry. To aid the development of successful applications for chicken feather materials (CFM), the physical and mechanical properties of processed CFM have been characterized in this research. Results describing the moisture content, aspect ratio, apparent specific gravity, chemical durability, Youngs modulus, and tensile strength for processed CFM and specifically their fiber and quill components are presented herein. Processed chicken feather fiber and quill samples were found to have similar moisture contents in the range of 16 - 20%. The aspect ratio (i.e., length/diameter) of samples were found to be in the range of 30 - 50, and the fiber material was found to have a larger aspect ratio than the quill material. A comparison with values in the literature suggests that different processing regimes produce CFM with higher aspect ratios. Samples were found to have apparent specific gravities in the range of 0.7 - 1.2, with the fiber material having a higher apparent specific gravity than the quill material. A comparison with values in the literature suggests that apparent specific gravity results vary with fiber length and approach the value for keratin as fiber length decreases and internal voids become increasingly accessible. Chemical durability results showed that CFM rapidly degrade in highly alkaline (pH=12.4) environments and are, thus, likely incompatible with cement-based materials without special treatment. The Youngs modulus of processed chicken feather materials was found to be in the range of 3 - greater than 50 GPa and, thus, comparable to the Youngs moduli of other natural fibers. The tensile strength of oven-dried samples was found to be in the range of 10 - greater than 70 MPa. In agreement with results in the literature, the fiber material was found to have a greater tensile strength than the quill material. Finally, a simplified approach for comparing the effective Youngs moduli and effective tensile strengths of various processed CFM samples was introduced.
8
Kirkpatrick, John Warren. "Mechanical and physical properties of preservative-treated strandboard." Master's thesis, Mississippi State : Mississippi State University, 2005. http://sun.library.msstate.edu/ETD-db/ETD-browse/browse.
Full text
9
Butsch, Susan Laurel. "Mechanical and physical properties of particulate reinforced composites." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-10312009-020333/.
Full text
10
Traitler, Nikolaus. "Physical and mechanical properties of biopolymer cellular solids." Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612327.
Full text
11
Neugirg, Benedikt R., Sean R. Koebley, Hannes C. Schniepp, and Andreas Fery. "AFM-based mechanical characterization of single nanofibres." Royal Society of Chemistry, 2016. https://tud.qucosa.de/id/qucosa%3A36361.
Full textAbstract:
Nanofibres are found in a broad variety of hierarchical biological systems as fundamental structural units, and nanofibrillar components are playing an increasing role in the development of advanced functional materials. Accurate determination of the mechanical properties of single nanofibres is thus of great interest, yet measurement of these properties is challenging due to the intricate specimen handling and the exceptional force and deformation resolution that is required. The atomic force microscope (AFM) has emerged as an effective, reliable tool in the investigation of nanofibrillar mechanics, with the three most popular approaches—AFM-based tensile testing, three-point deformation testing, and nanoindentation—proving preferable to conventional tensile testing in many (but not all) cases. Here, we review the capabilities and limitations of each of these methods and give a comprehensive overview of the recent advances in this field.
12
Graham, John Stephen. "Mechanical properties of complex biological systems using AFM-based force spectroscopy." Diss., Columbia, Mo. : University of Missouri-Columbia, 2005. http://hdl.handle.net/10355/4191.
Full textAbstract:
Thesis (Ph. D.)--University of Missouri-Columbia, 2005.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on October 18, 2007) Vita. Includes bibliographical references.
13
Yang, Lanti. "Mechanical properties of collagen fibrils and elastic fibers explored by AFM." Enschede : University of Twente [Host], 2008. http://doc.utwente.nl/58870.
Full text
14
Hekimi, Benjamin. "The physical and mechanical properties of an argillaceous limestone." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=116910.
Full textAbstract:
This thesis presents the work undertaken to characterize the mechanical, physical and fabric characteristics of the argillaceous Lindsay-Cobourg Limestone (LCL), which is a candidate host rock for the construction of a Deep Ground Repository (DGR) for storing low and intermediate level radioactive waste. The work includes a range of tests that were conducted to determine the fabric of the rock, the physical properties of the discrete species of rock and the bulk hydraulic and mechanical properties of representative volume elements of the rock. Emphasis is placed on the application of the "Plug Test" developed at McGill for estimating the tensile strength of the rock as a convenient alternative to the conventional tests such as the Brazilian splitting test. The influence of stratification on the estimation of tensile strength of the LL is discussed.Cette thèse décrit le travail entrepris pour caractériser la roche calcaire argileuse Lindsay-Cobourg (LCL), une strate géologique candidate pour la construction du Deep Ground Repository (DGR), un site pour disposer de déchets radioactifs de niveau d'intensité basse ou moyenne. La recherche inclut des expériences pour déterminer la résistance à la compression et la traction, les propriétés physiques, la perméabilité et la composition du matériau. La recherche porte principalement sur des expériences sur la résistance à la traction, ce qui inclut une méthode alternative pour tester la résistance d'un matériau cassant, le test d'expansion de la cavité centrale, ainsi que la plus traditionnelle méthode indirect dite « Brésilienne ». L'effet de l'anisotropie du LCL est discuté dans le cas des expériences sur la résistance à la traction.
15
Alrahlah, Ali Awad. "Physical, mechanical and surface properties of dental resin-composites." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/physical-mechanical-and-surface-properties-of-dental-resincomposites(213a08bf-5791-4e1c-bce9-a45ca268d1d3).html.
Full textAbstract:
Since resin composites were first presented to dentistry more than half a century ago, the composition of resin composites has developed significantly. One major change was that the reinforcing filler particles were reduced in size to generate materials of a given filler content that display better physical and mechanical properties. Resin composites may absorb water and chemicals from the surrounding environment but at the same time, composites may release constituents to their surroundings. The physical/mechanical properties of a restorative material provide an indication of how the material will function under stress in the oral environment. The aims of this research were to examine the effects of water at 37°C on the physical and mechanical properties, and the effect of food-simulating solvents of a variety of experimental and contemporary resin composites, on the surface properties. Eight representative resin composites were selected (Exp. VT, BL, NCB, TEC, GSO, XB, VDF and CXD). Due to the recent development of bulk fill materials on the market during the course of this research, the post-cure depth of cure of new bulk fill materials was also investigated. Five representative resin composites were selected: TBF, XB, FBF, VBF and SF. Water sorption and solubility were investigated at 37°C for 150 days. Sorption and solubility are affected by the degree of hydrophilicity of the resin matrix. The bulk fill materials examined showed the lowest water sorption and solubility. Laser scan micrometer (LSM) was used to investigate hygroscopic expansion. The extent of the hygroscopic expansion positively correlated with the amount of water sorption. The effect of water on fracture toughness was also examined. A self-adhesive hydrophilic resin matrix decreased in fracture toughness after 7 days of storage at 37°C. By contrast, the least water absorbed bulk fill material increased in fracture toughness over time. The effect of food-simulating solvents (distilled water, 75% ethanol/water and MEK) on surface micro-hardness, colour stability and gloss retention were investigated. The MEK solvent resulted in the lowest micro-hardness and the greatest colour change (ΔE) for most of the examined composites, while the 75% ethanol/water solution caused the greatest loss in gloss for most of the examined composites. A highly filled nano-composite showed the best result over time, regardless of the condition of storage. Surface micro-hardness profiles were used as an indirect method to assess the depth of cure of bulk fill resin composites. The examined bulk fill resin composites can be cured to an acceptable depth (4 mm).
16
Krishnamurthy, Harish. "Physical and mechanical properties of paper mulches in assessing degradation." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=20229.
Full textAbstract:
A series of tests was performed in winter 1996 to measure degradation of paper mulches with the help of physical and mechanical properties. Four types of paper used for mulching, kraft paper gauge 40, 60 and 80 and waxed paper were laid over soil in two growth chambers. They were kept under observation for 27 days under controlled temperature, humidity and light. Mulches were sprayed with water to simulate rain. Tensile and puncture tests were performed on each type of paper every day. Four mechanical properties; stress, strain, energy and tensile energy absorption were calculated from the force-deformation curve obtained by tensile test. Two mechanical properties; displacement and force to break were calculated from the force-deformation curve obtained by puncture test. A special die had to be designed to perform puncture tests. This design eliminated shear loading which otherwise would have been present in normal puncture tests.Results showed that paper - 3 (kraft paper gauge - 80) was best suited for mulching as the mechanical properties were stable through 27 days with negligible fluctuations. Waxed paper required less force to break but was stable through 27 days of experimentation.
A three-way factorial model was developed to analyze the results statistically. A SAS program was written to model the results. The fitted model was in very good agreement with the actual values.
17
Richman, Jacinda. "Soil physical properties under the influence of different mechanical weeders." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0003/MQ44259.pdf.
Full text
18
Krishnamurthy, Harish. "Physical and mechanical properties of paper mulches in assessing degradation." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0001/MQ44091.pdf.
Full text
19
Rizzante, Fabio Antonio Piola. "Mechanical and physical properties assessment of Bulk Fill resin composites." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/25/25148/tde-31082018-181145/.
Full textAbstract:
The achievement of predictable and long lasting adhesive restorations in posterior teeth have always been a major objective of studies in the context of materials and techniques development. The use of bulk fill composites could provide better outcomes, but it is important to assess their physico-mechanical properties, responsible for their clinical behavior. The purpose of the present study was to assess the mechanical and physical properties of bulk fill composites. The composites were divided into 2 groups according to their viscosity. For low viscosity composites, the present study assessed: Surefill SDR flow (SDR), X-tra Base (XB), Filtek Bulk Fill Flowable (FBF), and Filtek Z350XT Flow (Z3F- control); and for high viscosity composites: Tetric Evo Ceram Bulk Fill (TBF), X-tra Fil (XF), Filtek Bulk Fill (FBP), Admira Fusion x-tra (ADM) and Filtek Z350 XT (Z3XT- control). Composites were assessed through shrinkage stress test (using 12 and 24mm3 of composite in a custom device adapted in an Universal Testing Machine); volumetric shrinkage (using 64mm3 of composite placed on a Teflon mold and scanned in a micro computed tomography/CT); Youngs modulus (through a 3-point bending test device adapted in an Universal Testing Machine); microhardness and depth of cure tests (using longitudinal Knoop microhardness). All data was evaluated regarding their homogeneity using Shapiro-Wilk test. For polymerization stress, 3-way Variance Analysis (ANOVA) was used. Considering Volumetric Shrinkage, Youngs Modulus, Microhardness and Depth of Cure, one-way ANOVA was used. All ANOVA tests were followed by Tukeys test and 5% was adopted as significance level. Shrinkage stress test with 12mm3 showed SDR, TBF and XF generating the lowest stress after 300s, followed by other high viscosity composites (ADM, FBF, XB and FBP/Z3XT). The regular low viscosity composite (Z3F) generated the highest stress for all assessed times. Considering the same test, with 24mm3, after 300s, SDR, FBP and ADM generated similar stress, followed by TBF and XF. Low viscosity bulk fill composites generated lower stress than Z3F. Considering Youngs modulus, low viscosity composites (SDR, FBF, XB and Z3F) showed the lowest values, followed by ADM and TBF. The other high viscosity composites (Z3XT, FBP and XF) showed the highest values. For microhardness test, all low viscosity composites showed lower values (FBF being the lowest). For high viscosity composites, Z3XT showed the highest values, followed by XF, FBP/TBF and ADM. Assessing depth of cure, regular composites showed lower values when compared with bulk fill composites. All bulk fill composites showed adequate depth of cure over 4.5mm (microhardness 80% of initial reading). SDR and XB showed the highest depth of cure. All high viscosity bulk fill composites generated lower volumetric shrinkage than regular composites. All low viscosity bulk fill composites showed similar volumetric shrinkage when compared to the regular composites (Z3F and Z3XT). Bulk fill composites show characteristics that allow their use in larger increments (i.e. volumetric shrinkage and polymerization stress similar or lower when compared with regular composites). Nonetheless, the mechanical properties of bulk fill composites were widely variable, being important to individually assess each material previously to its clinical application.A obtenção de restaurações adesivas previsíveis e duradouras em dentes posteriores sempre foi objetivo de estudos na área de desenvolvimento de materiais e técnicas. O uso de resinas compostas do tipo bulk fill pode possibilitar melhores resultados, porém é importante o estudo de suas propriedades físico-mecânicas, responsáveis por seus comportamentos clínicos. O objetivo do presente estudo foi o de avaliar as propriedades físicas e mecânicas das resinas bulk fill. As resinas foram divididas em 2 grupos de acordo com sua viscosidade. Para resinas de baixa viscosidade, o presente estudo avaliou: Surefill SDR flow (SDR), X-tra Base (XB), Filtek Bulk Fill Flowable (FBF) e Filtek Z350XT Flow (Z3F-controle); e, para alta viscosidade: Tetric Evo Ceram Bulk Fill (TBF), X-tra Fil (XF), Filtek Bulk Fill (FBP), Admira Fusion x-tra (ADM) e Filtek Z350 XT (Z3XT-controle). As resinas foram avaliadas em relação à tensão de polimerização (utilizando 12 e 24mm3 de resina adaptadas em um dispositivo adaptado a uma máquina de testes universal); contração volumétrica (utilizando 64mm3 de resina composta inserida em um molde de Teflon e escaneada em um micro-tomógrafo/CT), modulo de Young (através de um dispositivo de flexão em 3 pontos adaptado a uma máquina de testes universal), microdureza e profundidade de polimerização (utilizando microdureza Knoop). Todos os resultados foram avaliados em relação à homogeneidade utilizando o teste de Shapiro-Wilk. Para avaliação da tensão de polimerização, foi empregada a Análise de Variância (ANOVA) a 3 critérios. Para as analyses de contração volumétrica, Módulo de Young, microdureza e profundidade de polimerizaçao, ANOVA a um critério foi empregada. Todas as Análises de Variância foram seguidas pelo teste de Tukey e 5% foi adotado como nível de significância. A tensão de polimerização com 12mm3 demonstrou que SDR, TBF e XF geraram valores significantemente mais baixos após 300s, seguidas por outras resinas de alta viscosidade (ADM, FBF, XB e FBP/Z3XT). A resina convencional de baixa viscosidade (Z3F) gerou valores de tensão significantemente mais elevados para todos os tempos avaliados. Considerando o mesmo teste, com 24mm3, após 300s, SDR, FBP e ADM geraram valores estatisticamente inferiores, seguidas por TBF e XF. As resinas bulk fill de baixa visocidade geraram menor tensão de polimerização que a Z3F. Considerando o modulo de Young, resinas de baixa viscosidade (SDR, FBF, XB e Z3F) apresentaram valores significantemente inferiores, seguidas por ADM e TBF. As outras resinas de alta viscosidade (Z3XT, FBP e XF) apresentaram valores significantemente mais elevados. Para o teste de microdureza, todas as resinas de baixa viscosidade apresentaram valores inferiores (FBF apresentou o menor). Para as resinas de alta viscosidade, Z3XT apresentou os valores mais elevados, seguida por XF, FBP/TBF e ADM. Para profundidade de polimerização, resinas compostas convencionais apresentaram valores signifixantemente mais baixos quando comparadas com resinas bulk fill. Todas as resinas bulk fill apresentaram profundidade de polimerização adequada até pelo menos 4,5mm (microdureza 80% da leitura inicial/superfície). SDR e XB apresentaram os valores mais altos de profundidade de polimerização. Todas as resinas bulk fill de alta viscosidade geraram menor contração volumétrica que resinas compostas convencionais. Todas as resinas bulk fill de baixa viscosidade apresentaram contração volumétrica similar às resinas convencionais (Z3F e Z3XT). Resinas compostas bulk fill apresentaram características que possibilitam sua indicação para serem empregadas em grandes incrementos (contração volumétrica e tensão de polimerização similar ou inferiores às resinas convencionais, além de maior profundidade de polimerização). No entanto, as propriedades mecânicas variaram grandemente entre as resinas estudadas sendo importante uma avaliação individual de cada material previamente ao seu uso clínico.
20
Chang, Geng-Wen. "Physical aging in the mechanical properties of miscible polymer blends." Case Western Reserve University School of Graduate Studies / OhioLINK, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=case1056644954.
Full text
21
Köcher, Paul Tilman. "Nanoscale measurements of the mechanical properties of lipid bilayers." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:0b478b9f-70fc-436f-9803-5d3a203f0d7e.
Full textAbstract:
Lipid bilayers form the basis of the membranes that serve as a barrier between a cell and its physiological environment. Their physical properties make them ideally suited for this role: they are extremely soft with respect to bending but essentially incompressible under lateral tension, and they are quite permeable to water but essentially impermeable to ions which allows the rapid establishment of the osmotic gradients. The function of membrane proteins, which are vital for tasks ranging from signal transduction to energy conversion, depends on their interactions with the lipid environment. Because of the complexity of natural membranes, model systems consisting of simpler lipid mixtures have become indispensable tools in the study of membrane biophysics. The objective of the work reported here is to develop a deeper understanding of the underlying physics of lipid bilayers through nanoscale measurements of the mechanical properties of mixed lipid systems including cholesterol, a key ingredient of cell membranes. Atomic force microscopy (AFM) has been used extensively to measure the topographical and elastic properties of supported lipid bilayers displaying complex phase behaviour and containing mixtures of important PC, PE lipids and cholesterol. Phase transformations have been investigated varying the membrane temperature, and the effects of cholesterol in controlling membrane fluidity, phase, and energetics have been studied. Elastic modulus measurements were correlated with phase behaviour observations. To aid in the nanoscale probing of lipid bilayers, AFM probes with a high aspect ratio and tip radii of $sim$4~nm were fabricated and characterised. These probes were used to investigate the phase boundary in binary and ternary lipid systems, leading to the discovery of a raised region at the boundary which has implications for the localisation of reconstituted proteins as well as the role of natural domains or lipid rafts. The electrical properties of the probes were examined to assess their potential application for combined structural and electrical measurements in liquid. A novel technique was developed to aid in the study of the physical properties of lipid bilayers. Membrane budding was induced above microfabricated substrates through osmotic pressure. Modification of the adhesion energy of the bilayer through biotin-avidin linking was successful in modulating budding behaviour of liquid disordered bilayers. The free energy of the system was modelled to allow quantitative information to be extracted from the data.
22
Khammang, Alex. "Investigating Mechanical Properties of Metallic Nanowires using Molecular Dynamics." VCU Scholars Compass, 2014. http://scholarscompass.vcu.edu/etd/3409.
Full textAbstract:
Metallic nanowires have useful applications in scanning tunneling microscopes and atomic force microscopes due to their unique sensitivity to force and electricity. These unique properties arise because of the large surface area to volume ratio. One of these properties is that introducing twinning planes the mechanical properties of metallic nanowires can be altered. The effects of twinning planes on metallic nanowires were studied using molecular dynamics simulations. Silver, copper, and nickel nanowires with and without twinning planes were simulated with engineering strain until the first yielding stress was obtained. The radial simulations showed that as the radius of twinned nanowires increased, the strength gained by introducing the twinning planes increased. The temperature simulations showed that nanowires with twinning planes were stronger than their un-twinned counterparts as temperature increased. The purpose of this investigation was to better understand the effect twinning planes had on metallic nanowires, so that future technological advances would benefit from the results.
23
Lyons, Teresa Elizabeth. "Mechanical properties of nanometre scale protein fibres measured by Atomic Force Microscopy (AFM)." Thesis, University of Liverpool, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.539486.
Full text
24
AZADEH, ARASH. "HEAT INFLUENCE ON PHYSICAL AND MECHANICAL PROPERTIES OF DENDROCALAMUS GIGANTEUS BAMBOO." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2018. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=35612@1.
Full textAbstract:
PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
O principal objetivo da presente tese é investigar o efeito do calor nas propriedades físicas e mecânicas do bambu Dendrocalamus giganteus. A análise química foi realizada para estudar e comparar componentes químicos de diferentes espécies e partes internas e externas do bambu Dendrocalamus giganteus. Para estabelecer a faixa de aquecimento e seus intervalos, foi realizado o teste de análise termogravimétrica (TGA) para estudar a degradação de diferentes gêneros e espécies de bambu nos níveis macro, meso, micro e nano. Baseado em ensaios preliminares de exposição ao calor e nos resultados da TGA, ensaios executados a temperaturas iniciais de 25 graus Celsius (considerado como temperatura ambiente), 100 graus Celsius, 125 graus Celsius, 150 graus Celsius, 175 graus Celsius, 200 graus Celsius e 225 graus Celsius foram expostos por um período de 3 horas, considerado como curto prazo, e 24 horas, considerado como um longo prazo de exposição ao calor. Processamento de imagem foi realizado para investigar a meso estrutura do bambu, como functionally graded material (FGM), e a distribuição das fibras da parte interna à parte externa da parede de espessura do bambu, ao longo da direção radial. A fração volumétrica das fibras e da matriz para a parte interna e externa da seção do bambu foi estabelecida e utilizada na investigação da absorção de água por cada componente do bambu. O microscópio eletrônico de varredura (MEV) e a microtomografia de raios X foram usados para estudar os efeitos de diferentes exposições ao calor na microestrutura da fibra e da matriz. As microfissuras iniciam e propagam após 175 graus Celsius. Também foram investigados a influência do calor na higroscopicidade, a absorção de água, o encolhimento e o inchamento das amostras do bambu nas direções longitudinal, radial e tangencial sob diferentes temperaturas e exposições de tempo. O encolhimento não uniforme e a absorção da água de amostras do teste com o bambu, medido na direcção tangencial nos lados internos e externos, permitiram estabelecer a propriedade higroscópica de cada componente. Os resultados mostram que, com a exposição ao calor superior a 175 graus Celsius, a capacidade de absorção de água reduz significativamente. Resistência à tração, compressão e cisalhamento estabelecida ao longo das fibras e somente experimento de tração transversal realizado transversalmente às fibras. Além disso, o módulo dinâmico de elasticidade em flexão, usando a técnica de excitação por impulso aplicada a espécimes considerados. A variação tangível nas propriedades mecânicas ocorreu após a exposição do calor a 175 graus Celsius durante 3h ou a 150 graus Celsius por 24h. Os módulos de elasticidade e resistência à compressão não são reduzidos significativamente e, quase, permanecem os mesmos para amostras tratadas a 225 graus Celsius durante 3h e 200 graus Celsius por 24h mas para as amostras de tração, cisalhamento e tração transversal, a resistência mecânica diminui cerca de 70 por cento - 90 por cento a esta temperatura-tempo.
The principal objective of the present thesis is to investigate the effect of heat on physical and mechanical properties of Dendrocalamus giganteus bamboo. The chemical analysis carried out to study and compare chemical components among different species and the internal and external parts of Dendrocalamus giganteus bamboo. To establish the heating range and its intervals the thermogravimetric analysis test (TGA) carried out to study the degradation of different bamboo genera and species at macro, meso, and micro and nano level. Based on preliminary heat exposure tests and the results of TGA, the tests executed at initial temperatures 25 degrees Celsius considered as ambient temperature, 100 degrees Celsius, 125 degrees Celsius, 150 degrees Celsius, 175 degrees Celsius, 200 degrees Celsius and 225 degrees Celsius for 3 hours duration as short term, and 24 hours duration as long term heat exposure. Image processing carried out to investigate the meso structure of bamboo as a functionally graded material (FGM) and the fiber distribution alongside the radial direction from internal to external bamboo wall thickness. The volume fraction of fibers, matrix and voids for internal and external part of bamboo section established and used in the investigation of water absorption of each component of the bamboo. The scanning electronic microscope (SEM) and X-ray microtomography used to study the effects of different heat exposures on micro structure of fiber and matrix. The micro cracks initiate and propagate after 175 degrees Celsius. The influence of heat on hygroscopicity, water absorption, shrinkage and swelling of bamboo specimens in longitudinal, radial and tangential directions at different temperatures and time exposures investigated. The non-uniform shrinkage and water absorption of bamboo test specimens, measured in tangential direction at internal and external sides which permitted to establish the hygroscopic property of each component. The results show by heat exposure higher than 175 degrees Celsius the water absorption capacity reduces significantly. The tensile, compression, and shear resistance established along the fibers and only tensile experiments realized transversal to the fibers. In addition, the dynamic bending modulus of elasticity using impulse excitation technique applied to considered specimens. The result of mechanical tests shows a close relation between transversal tensile and shear strength with matrix strength. The tangible variation in mechanical properties occurred after heat exposure-time at 175 degrees Celsius-3h or 150 degrees Celsius-24h. The modulus of elasticity and compression strength are not reduced significantly and nearly remain the same for samples treated at 225 degrees Celsius-3h or 200 degrees Celsius-24h while for the tensile, shear and transversal tensile samples, the mechanical strength decreases about 70 percent to 90 percent at these temperature-time.
25
Bajaj, Srikanth. "Effect of Corrosion on Physical and Mechanical Properties of Reinforced Concrete." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1353961865.
Full text
26
Shahin, Mohammad S. M. Massachusetts Institute of Technology. "Irradiation effects on mechanical and physical properties of SS304L-nanotube composites." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/129112.
Full textAbstract:
Thesis: S.M., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, September, 2020Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 44-47).
For decades nuclear power has been a reliable and affordable source of base-load power[1] with relatively small amounts of CO2 emissions.[2] The levelized cost of electricity generated by nuclear power plants is dominated by the capital cost of the structural components,[3] therefore extending the operating lifetime of these plants is of high economic and environmental interests. However, degradation of mechanical behavior of structural materials due to radiation damage is a key limiting factor to service lifetime. The development of advanced materials can potentially improve material performance under irradiation and increase their design lifetime. Traditional alloy design always sacrifices one property for another, such as strength for ductility, or creep strength for radiation resistance.
However, a new approach promises to break this property dependency, allowing for obtaining the best properties potentially without sacrificing others.[3-5] This work aims to study the effects of introducing a variety of NanoTubes (NTs) within the metal matrix of austenitic Stainless SS (SS) type 304L on the radiation resistance of the composites. Rapid non- and semi- destructive methods are used to quantify these effects and study the correlation between them. SS and SS Metal Matrix Composites (MMCs) were synthesized by powder metallurgy and Spark Plasma Sintering (SPS) to densify bulk samples approaching the theoretical density. The synthesized materials were then irradiated by accelerated heavy charged particles to mimic the damage caused by neutron irradiation in a nuclear reactor over a longer period of time.
Finally, the mechanical and physical properties of the irradiated SS as well as the MMCs were characterized and compared to the non-irradiated samples to study the effects of incorporating the NTs, and to test the hypothesis that the metal-nanotube interfaces serve as recombination sites for defects. The experimental examination of the new materials is necessary to assess their potential for future developments in reactor designs, which would allow improvements to overcome current limitations in service lifetime and hence improve the economy of nuclear power. The results show that the dispersion of NTs within the SS304L mostly caused a slight decrease in thermal diffusivity and an increase in hardness. The results also indicate that incorporating NTs did not break the correlation of property changes after irradiation that was observed in the control (NT-free) sample.
In addition, all the SS matrices showed a potential inherent recovery in at least one of the measured properties when irradiated beyond 1 dpa (up to 10 dpa), which suggest the occurrence of onset of defect clustering between 1 and 10 dpa when the SS matrix is irradiated with Ni ions at room temperature.
by Mohammad Shahin.
S.M.
S.M. Massachusetts Institute of Technology, Department of Nuclear Science and Engineering
27
Rupasinghe, R.-A. Thilini Perera. "Probing electrical and mechanical properties of nanoscale materials using atomic force microscopy." Diss., University of Iowa, 2015. https://ir.uiowa.edu/etd/2268.
Full textAbstract:
Studying physical properties of nanoscale materials has gained a significant attention owing to their applications in the fields such as electronics, medicine, pharmaceutical industry, and materials science. However, owing to size constraints, number of techniques that measures physical properties of materials at nanoscale with a high accuracy and sensitivity is limited. In this context, development of atomic force microscopy (AFM) based techniques to measure physical properties of nanomaterials has led to significant advancements across the disciplines including chemistry, engineering, biology, material science and physics. AFM has recently been utilized in the quantification of physical-chemical properties such as electrical, mechanical, magnetic, electrochemical, binding interaction and morphology, which are enormously important in establishing structure-property relationship.
The overarching objective of the investigations discussed here is to gain quantitative insights into the factors that control electrical and mechanical properties of nano-dimensional organic materials and thereby, potentially, establishing reliable structure-property relationships particularly for organic molecular solids which has not been explored enough. Such understanding is important in developing novel materials with controllable properties for molecular level device fabrication, material science applications and pharmaceutical materials with desirable mechanical stability. First, we have studied electrical properties of novel silver based organic complex in which, the directionality of coordination bonding in the context of crystal engineering has been used to achieve materials with structurally and electrically favorable arrangement of molecules for an enhanced electrical conductivity. This system have exhibited an exceptionally high conductivity compared to other silver based organic complexes available in literature. Further, an enhancement in conductivity was also observed herein, upon photodimerization and the development of such materials are important in nanoelecrtonics.
Next, mechanical properties of a wide variety of nanocrystals is discussed here. In particular, an inverse correlation between the Young’s modulus and atomic/molecular polarizability has been demonstrated for members of a series of macro- and nano-dimensional organic cocrystals composed of either resorcinol (res) or 4,6-di-X-res (X = Cl, Br, I) (as the template) and trans-1,2-bis(4-pyridyl)ethylene (4,4’-bpe) where cocrystals with highly-polarizable atoms result in softer solids. Moreover, similar correlation has been observed with a series of salicylic acid based cocrystals wherein, the cocrystal former was systematically modified. In order to understand the effect of preparation method towards the mechanical properties of nanocrystalline materials, herein we have studied mechanical properties of single component and two component nanocrystals. Similar mechanical properties have been observed with crystals despite their preparation methods. Furthermore, size dependent mechanical properties of active pharmaceutical ingredient, aspirin, has also been studied here. According to results reduction in size (from millimetre to nanometer) results in crystals that are approximately four fold softer.
Overall, work discussed here highlights the versatility of AFM as a reliable technique in the electrical, mechanical, and dimensional characterization of nanoscale materials with a high precision and thereby, gaining further understanding on factors that controls these processes at nanoscale.
28
Zhang, Liqun. "Physical and mechanical properties of model asphalt systems calculated using molecular simulation /." View online ; access limited to URI, 2007. http://0-digitalcommons.uri.edu.helin.uri.edu/dissertations/AAI3301932.
Full text
29
Gauthier, Sylvie 1955. "Synthesis and physical properties of styrene-vinylpyridinium ionomers of various architectures." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=72029.
Full textAbstract:
Styrene-4-vinylpyridinium ionomers of different architectures, random and ABA blocks, were synthesized and their thermal and dynamic mechanical properties investigated.The Tg's of the random ionomers were found to increase regularly with increasing ion content, at a rate of about 3.5(DEGREES)C per mole % of ions. In contrast with other ionomeric systems studied before, however, these materials showed only one peak in their tan delta curves, associated with the Tg of the matrix. The absence of a second, high temperature peak suggests the absence of clusters in these vinylpyridinium ionomers, at least at temperatures above their Tg. The storage modulus curves were in agreement with this conclusion.
An elaborate polymerization line was constructed for the production of the block copolymers by living anionic polymerization; a basic design was modified considerably and two new units were completely designed in this laboratory. Only one Tg, associated with the Tg of the polystyrene phase, was observed in DSC measurements for the resulting ionomers. The glass transition of the ionic domains was detected in dynamic mechanical measurements as a shoulder on the low temperature side of the polystyrene transition. This unexpected low value for the Tg of the ionic domains was attributed to plasticization by water.
30
Parlak, Zehra. "Quantitative imaging of subsurface structures and mechanical properties at nanoscale using atomic force microscope." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37181.
Full textAbstract:
This dissertation focuses on quantitative subsurface and mechanical properties imaging potential of AFM probes. Extensive modeling of AFM probes are presented for thorough understanding of capabilities and limitations of current techniques, these models are verified by various experiments, and different methods are developed by utilizing force-sensing integrated read-out active tip (FIRAT), which is an active AFM probe with broad bandwidth. For quantitative subsurface imaging, a 3-D FEA model of AFM tip-sample contact is developed and this model can simulate AFM tip scan on nanoscale-sized buried structures. FIRAT probe, which is active and broadband, is utilized for interaction forces imaging during intermittent contact mode and mechanical characterization capability of this probe is investigated. It is shown that probe dynamics, stiffness, stiffness ambiguity, assumed contact mechanics, and noise are important parameters for the accuracy of mechanical properties imaging. An active tip control mechanism is introduced to limit contact forces during intermittent contact mode. In addition to these, a combined ultrasonic AFM and interaction forces imaging method is developed and modeled to solve the reduced elasticity measurement sensitivity on composite materials. This method is capable of imaging a broader range of elasticity on combination samples such as metal nanoparticles in polymers at nanoscale.
31
In, Hyun Jin. "Origami-inspired nanofabrication utilizing physical and magnetic properties of in situ grown carbon nanotubes." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/58190.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 123-133).
Carbon nanotubes (CNTs), in particular the vertically-aligned variety grown through a plasma enhanced chemical vapor deposition (PECVD)-based process, are highly versatile nanostructures that can be used in a variety of nanomanufacturing applications. However, process and material compatibility issues have prevented the nanotubes from becoming more fully integrated into various micro- and nanomanufacturing applications. In this thesis, the integration of in situ CNT growth with a 3-D nanomanufacturing platform, namely the Nanostructured Origami TM process, will be shown. Due to the high temperatures involved in CNT growth, a new origami membrane material, titanium nitride (TiN), is introduced. This new origami membrane serves as an excellent diffusion barrier layer throughout the CNT growth process while promoting consistent nanotube growth and maintaining electrical conductivity to the CNTs. Various further modifications are made to the origami process, for example in metallization techniques, to accommodate the addition of CNTs to origami devices. Based on the presented CNT-origami process, a functioning microscale supercapacitor is also fabricated and tested. The integration of high surface area CNT electrodes with a unique 3-D device geometry results in a fabfriendly, high-performance supercapacitor that can easily be integrated as an onboard power source in self-powered microsystem applications. Finally, the magnetic properties of our in situ grown CNTs, derived from their naturally occurring, tip-encapsulated catalyst particles, will be characterized. Furthermore, these properties will be used to magnetically actuate, align, and latch individual as well as large arrays of CNTs and the entire membranes on which they are grown. The magnetic behaviors of CNTs and their underlying membranes will be investigated through computer simulation and experimental verification.
by Hyun Jin In.
Ph.D.
32
Forsén, Rikard. "Mechanical properties and thermal stability of reactive arc evaporated Ti-Cr-Al-N coatings." Licentiate thesis, Linköpings universitet, Nanostrukturerade material, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-79579.
Full textAbstract:
This licentiate thesis reports experimental and theoretical work on the high temperature mechanical properties and the thermal stability of cubic (c)-(Ti-Cr-Al)1-N1 coatings. It is demonstrated that it is possible to tailor and improve the properties of hard nitride coatings by different degrees of multicomponent alloying. When Cr is added to Ti-Al-N the coatings exhibit age hardening up to 1000 ºC which is higher compared to what is observed for Ti-Al-N. In addition, the coatings show a less pronounced hardness decrease when hexagonal (h)-Al-N is formed compared to Ti-Al-N. The improved thermal stability is discussed in terms of a lowered coherency stress and a lowered enthalpy of mixing due to the addition of Cr. When Ti is added to Cr-Al-N the formation and growth of the detrimental h-Al-N phase is suppressed and delayed improving the mechanical properties. This is discussed in terms of kinetic effects where the Ti atoms obstruct the Al diffusion and consequently the growth of h-Al-N precipitates. The microstructure evolution investigated at different stages of spinodal decomposition, coarsening and phase transformations are correlated to the thermal responses and the mechanical hardness of the coatings. Upon annealing up to 1400 ºC the coatings decompose into c-TiN, bcc-Cr and h-AlN. The decomposition takes place via several intermediate phases, c-CrAlN, c-TiCrN and hexagonal (β)-Cr2N. The oxidation resistance of (Tix-Cry-Al60)1-N1 is also investigated and presented for different x/y ratios. The results show that it is possible to generate coatings with both excellent mechanical properties and oxidation resistance improving the functionality in the working temperature range of 850-1100 ºC of for example cutting tools.
33
Naderi, Nader. "Influence of the planing on the physical, mechanical and gluing properties of wood." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ39378.pdf.
Full text
34
Paredes, Heller Juan Jacobo. "The Influence of Hot Water Extraction on Physical and Mechanical Properties of OSB." Fogler Library, University of Maine, 2009. http://www.library.umaine.edu/theses/pdf/ParedesJJ2009.pdf.
Full text
35
Errajhi, Osama Ali Zorgani. "Mechanical and physical properties of aluminised E-glass fibre reinforced unsaturated polyester composites." Thesis, University of Portsmouth, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.419044.
Full text
36
Repka, Michael Andrew. "Physical-mechanical and chemical properties of topical films produced by hot-melt extrusion /." Digital version accessible at:, 2000. http://wwwlib.umi.com/cr/utexas/main.
Full text
37
Guo, Ruilan. "Dependence of physical and mechanical properties on polymer architecture for model polymer networks." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/22642.
Full textAbstract:
Thesis (Ph. D.)--Polymer, Textile and Fiber Engineering, Georgia Institute of Technology, 2008.Committee Chair: Karl I. Jacob; Committee Member: Anselm C. Griffin; Committee Member: C. P. Wong; Committee Member: Rina Tannenbaum; Committee Member: William J. Koros; Committee Member: Yonathan S. Thio.
38
Li, Junqiu. "Physical and Mechanical Properties of Medite® MDF Exterior from Acetylated Wood Fibers." Thesis, Linnéuniversitetet, Institutionen för maskinteknik (MT), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-76444.
Full textAbstract:
Currently, the demand for wood-based panels has been growing solidly in European countries. Medium density fibreboard (MDF) manifests the potentialities for outstanding physical and mechanical properties. However, MDF from different fiber sources is normally designed for internal applications due to the poor moisture resistant capability. This study was conducted on acetylated MDF (Medite® MDF Exterior) to evaluate how physical (i.e. density, moisture content, dimensional stability, thickness swelling) and mechanical (i.e. modulus of elasticity, internal bonding strength before and after accelerated aging, bending stiffness and bending strength) properties behave at different relative humidity (i.e. 35 %, 65 % and 85 % RH at constant temperature of 20 ℃) levels. Bending stiffness was measured non-destructively by means of resonance method. The material used for control samples was commercial MDF. The size, quantity, conditioning and test method were followed in accordance with respective standards. The results showed that physical and mechanical properties were less influenced by Medite® MDF Exterior compared to commercial MDF. Medite® MDF Exterior were superior to commercial MDF in moisture resistance. Medite® MDF Exterior had more stable mechanical properties than commercial MDF with the changes of relative humidity.
39
Lee, Cynthia R. (Cynthia Renee) 1975. "Physical and biochemical properties of canine knee articular cartilage are affected by selected surgical procedures." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/80509.
Full text
40
Lai, Chee-Hoong. "Physical ageing and dimensional changes of acrylate polymers /." Title page, table of contents and summary only, 1992. http://web4.library.adelaide.edu.au/theses/09PH/09phl185.pdf.
Full text
41
Msuya, Winston Filipo Seth. "The influence of physical ageing and morphology on yield in polypropylene." Thesis, [Hong Kong] : University of Hong Kong, 1988. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12434036.
Full text
42
Mendez, Mendez Juan. "Mechanical properties of single keloid and normal skin fibroblast measured using an atomic force microscope." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/mechanical-properties-of-single-keloid-and-normal-skin-fibroblast-measured-using-an-atomic-force-microscope(92b79f2e-412f-4eaf-bea1-73e8c358d952).html.
Full textAbstract:
The human body consists of a number of very complex, highly specialised organs which perform a variety of functions that are essential to life and health. One of the main functions of the skin, the largest of the human organs, is to maintain the integrity of the body. It does this by acting as a physical barrier, preventing micro-organisms and other potentially harmful substances from entering the body. When the integrity of the skin is damaged through injury, a self-protective mechanism is triggered and the reparative wound healing process begins. Under normal circumstances the wound healing process culminates in the skin recuperating its normal characteristics and functions at the site of the injury, with only a small visible mark being left behind. However, in some cases the wound healing process may become altered leading to the production of abnormal scars, such as keloids. Keloid scars are formed from scar tissue at the site of an injury, as a result of excessive tissue repair that extends beyond the boundaries of the original wound. These scars are characterised by excess collagen deposition produced during the wound healing process. It is estimated that as many as 20% of the black and Hispanic population are affected by keloid scarring. In addition to the aesthetic aspect, keloid scars can also be painful, itchy and prone to become infected. Keloid scar formation can be triggered by skin injuries caused by, for example, acne, wounds, shaving, burns, and surgical incisions. The mechanism by which keloid scars form is currently not well understood and consequently no effective treatments exist to date.This thesis describes an investigation into the mechanical properties of single keloid and normal skin fibroblast cells for the purpose of establishing if there is a quantitative difference between the two types of cells. This information will be of benefit to researchers looking for a better understanding of the keloid formation mechanism and for those seeking improved treatments. An atomic force microscope (AFM) was employed to indent single Keloid and normal skin fibroblast cells taken from five patients. Values for the apparent Young's modulus of the cells were then calculated by fitting the experimental data using Hertz's model. Apparent Young's modulus values were then compared. The findings of the analysis indicate that statistically, there is a significant difference in the Young's modulus values of normal and keloid cells, with keloid cells exhibiting substantially greater stiffness than normal skin fibroblast cells. To enable the keloid and normal skin fibroblast cells to be studied in as close to their natural, physiological environment as is possible the AFM experiments described in this thesis were undertaken in a phosphate buffered saline (PBS) solution. In such cases the use of a fluid medium presents additional complexities, not least of which is the introduction of a hydrodynamic drag force due to viscous friction of the cantilever with the liquid which can affect the experimental data obtained and consequently any material properties calculated as a result of using these data. In order to investigate the effect of dragging force on the experimental data obtained from the AFM a novel integrated finite element based model was developed. The model, described in this thesis, provides quantification of the drag force in AFM measurements of soft specimens in fluids, consequently enabling more accurate interpretation of the data obtained from AFM experimentation. The model is validated using extensive data obtained from AFM experimentation undertaken in a number of fluids of different viscosities, at a variety of tip velocities and platform-tip separations and by comparison with an existing analytical model. The novel model is shown to accurately account for drag forces in AFM in fluid media without the need for extrapolation of experimental data and can be employed over the range of tip geometries and velocities typically utilised in AFM experimentation.The work described in this thesis demonstrates that the AFM is a valuable tool that can be used to successfully investigate the mechanical properties of biological samples in fluids. It was shown that increased accuracy in the interpretation of data obtained from AFM experimentation can be obtained by taking into account the hydrodynamic drag force due to viscous friction of the cantilever with the liquid. The investigation into the mechanical behaviour of keloid cells described in this thesis significantly adds to the yet small body of research undertaken on keloid cells to date. The findings of the investigation will provide valuable information that will be of benefit in the future to researchers looking to develop effective treatments for the prevention, reduction or removal of keloid scars.
43
Hankin, G. L. "Radiation-induced evolution of microstructure and mechanical properties of stainless steels." Thesis, Loughborough University, 1998. https://dspace.lboro.ac.uk/2134/7065.
Full textAbstract:
Radiation-induced changes in microstructures often lead to significant changes in mechanical properties of alloys used in the construction of nuclear reactors. It is desirable to test small specimens to make efficient use of the small volumes available in test and commercial reactor cores and also because small specimens are less affected by the sometimes steep flux gradients experienced in reactor cores and the sometimes large temperature gradients developed in the specimens from gamma heating. (Continues...).
44
Peña, Duarte Miguel Ángel. "Foam as a soil conditioner in tunnelling : physical and mechanical properties of conditioned sands." Thesis, University of Oxford, 2007. http://ora.ox.ac.uk/objects/uuid:b6317eb9-ab3d-48e8-8daa-295e72d7ae59.
Full textAbstract:
Earth pressure balance (EPB) tunnelling machines are commonly used for the construction of tunnels in soft soils. These machines use the excavated soil in a pressurised head chamber to apply a support pressure to the tunnel face during excavation. How well an unstable face is supported in an EPB machine depends on effectively transferring a constant pressure from the support medium to the surface of the face. If the support pressure is not constant, but instead changes, the varying pressure inevitably leads to collapse of the face or heave on the surface ground. A machine may be designed to work in “Ideal ground” conditions. However, natural soils rarely have these properties, and conditioning of the soil is usually necessary to change its properties to suit the machine. Effective soil conditioning significantly improves the machine performance and control of the soil flow through the screw conveyor. However, for soil conditioning as commonly used in practice, the effects of different conditioning treatments on soil properties and the machine performance are not clearly understood, and problems with EPB machine operations related to the soil properties are often encountered. This thesis presents experimental investigations of direct shear box tests on conditioned sands, compressibility tests on conditioned sands and a model EPB screw conveyor operating with sandy soils. Index tests were performed to investigate effects of foam and polymer conditioning treatments on the plastic fluidity of different Leighton Buzzard (L.B.) sands and Thanet sand. The index tests allowed assessment of conditioning treatments for sandy soils, and optimum ranges of treatments for Leighton Buzzard sand and Thanet sand are suggested. In the series of shear box tests, performed on conditioned Thanet sand and conditioned L.B. sands, one of the most important findings was that the pore water pressure controls the strength of the sand foam mixtures. An increase in foam injection ratio (FIR) might produce an increase of pore water pressure and a decrease of shear stress. In the series of compressibility tests, performed on conditioned Thanet sand and conditioned L.B. fine sand, one of the most important findings was that increasing FIR does not increase maximum gas expelled. The FIR and the initial relative density of the specimen have to be related to the capability of the specimen to retain the gas and establish a coexistence between grains of soil, water and gas bubbles. Finally, from the series of model (1:10 scale), screw conveyor tests, performed on conditioned Thanet sand, conditioned L.B. fine sand and conditioned Garside sand, it can be concluded that the Oxford screw conveyor model can be used as a trial machine to study the effects of different operating conditions on conditioned sand specimens similar to those used on site. This can allow choice of conditioning methods to improve the performance of an EPB machine at a given site.
45
MURAD, JOSE ROBERTO DE LIMA. "THE PHYSICAL, MECHANICAL AND MESO-STRUCTURAL PROPERTIES OF THE BAMBOO GUADUA WEBERBAUERI OF ACRE." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2007. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=10717@1.
Full textAbstract:
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORO bambu apresenta baixo consumo de energia e baixo custo de produção, além de ser um material renovável e ecológico. É um material potencialmente promissor que vem demonstrando grandes qualidades para a construção civil. Estudos mostraram que a relação resistência à tração e peso específico do bambu é 2,77 vezes maior que a do aço. Este trabalho tem como objetivo a caracterização física, mecânica e meso-estrutural do bambu da espécie Guadua weberbaueri para possível aplicação na engenharia civil como material não convencional. Os resultados dos ensaios mecânicos mostraram valores compatíveis a outras espécies pesquisadas. Concluiu-se que o material quando sujeito a carga de tração, cisalhamento ou compressão apresentou comportamento semelhante ao de outras espécies já estudadas, desde 1979, no Departamento de Engenharia Civil da PUC-Rio, sob a orientação do professor Khosrow Ghavami. Onde foram desenvolvidos vários programas de investigação para o emprego do bambu e outras fibras vegetais na construção de edificações de baixo custo, substituindo produtos de asbesto, aço, cimento e outros materiais poluentes e não renováveis. Podendo este ser utilizado como material alternativo na engenharia civil.
The bamboo presents low consumption of energy and low cost of production, beyond being a renewable and ecological material. It is a potentially promising material that comes demonstrating great qualities for the civil construction. Studies had shown that the relation tensile strenght and specific weight of the bamboo is 2,77 times bigger that of the steel. This thesis presents the results of an experimental investigation to establish the physical, mechanics and meso-structural, of the bamboo of the species Guadua weberbaueri for possible application in the civil engineering as a non- conventional material. The results of the mechanical rehearsals showed compatible values to other researched species. It was concluded that the material when subject to traction loads, shear or compression presented similar behavior to the of other studied species already, since 1979, in the Department of Civil Engineering of PUC-Rio, under the orientation of professor Khosrow Ghavami. Where some programs of inquiry for the vegetal job of the bamboo and other staple fibers in the construction of edifications of low cost had been developed, substituting pollutant products of asbestos, steel, cement and other pollutant materials didn´t renew. Being able this being used as non-conventional material in civil engineering.
46
Lafferty, Ian. "The effect of crystallisation variables on the powder characteristics, mechanical properties and compression behaviour of dextrose." Thesis, De Montfort University, 1998. http://hdl.handle.net/2086/4185.
Full text
47
Gillah, Peter Reuben. "The influence of novel forming techniques on the properties of medium density fibreboard." Thesis, Bucks New University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369910.
Full text
48
Ryder, Matthew. "Physical phenomena in metal-organic frameworks : mechanical, vibrational, and dielectric response." Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:c7a51278-19d7-45ae-825a-bac8040775a7.
Full textAbstract:
This thesis entails the utilisation of ab initio density functional theory (DFT) in conjunction with neutron and synchrotron spectroscopy to study the mechanical, vibrational, and dielectric response of metal-organic framework (MOF) materials at the molecular level. MOFs are crystalline materials with nanoscale porosity, which have garnered immense scientific and technological interest for a wide variety of innovative engineering applications. One part of the thesis involves using low-frequency lattice vibrations to characterise the various physical motions that are possible for framework materials. These collective modes detected at terahertz (THz) frequencies have been used to reveal a broad range of exciting possibilities. New evidence has been established to demonstrate that THz modes are intrinsically linked to anomalous elasticity underpinning gate-opening and pore-breathing mechanisms, and to shear-induced phase transitions and the onset of structural instability. The phenomenon of molecular rotor mechanisms and trampoline-like motions are also observed, along with the first experimental confirmation of coordinated shear dynamics. Additionally, a new method to characterise the effects of temperature, and hence thermally-induced structural amorphisation is reported. Finally, for the first time, the frequency-dependent (dynamic) dielectric response of MOF materials, across the extended infrared (IR) spectral region was reported. The results were obtained from experimental synchrotron radiation IR reflectivity and DFT to reveal the low-к dielectric response of MOFs and established structure-property trends that highlight them as promising systems for microelectronic device applications.
49
Baiti, Risa Nurin. "Characterization of nano-mechanical properties of biological lipid membranes with circular mode atomic force microscopy." Thesis, Compiègne, 2017. http://www.theses.fr/2017COMP2403/document.
Full textAbstract:
Les membranes cellulaires sont impliquées dans de nombreux processus cellulaires : la diffusion des médicaments et des ions, la transduction des signaux, la génération d'énergie, le développement cellulaire (fusion et fission). Les bicouches phospholipides sont les principaux composants des membranes cellulaires, elles constituent une barrière dynamique protégeant les réactions biochimiques cellulaires. La détermination des propriétés biochimiques et mécaniques des bicouches lipidiques et leur évolution avec les conditions environnementales est nécessaire pour étudier la nature des processus cellulaires et l'influence des agents externes (résistance mécanique, perméabilité et réponse biologique). Pour mener de telles caractérisations, des modèles simplifiés de membrane biomimétique, tels que des bicouches lipidiques supportées (SLB), ont été développés. Parmi les techniques de caractérisation disponibles, la microscopie à force atomique (AFM) a été largement utilisée pour étudier l'organisation nanométrique des SLB dans des conditions physiologiques. AFM peut produire des images à la haute résolution et peut également être utilisé pour quantifier la résistance mécanique des SLB au moyen d'expériences de perforation. Pendant 30 ans, AFM a traversé de nombreux développements. Très récemment, le Mode circulaire AFM (CM-AFM) a été développé à l'Université de Technologie de Compiègne. CM-AFM est capable de générer un mouvement de glissement de la pointe AFM sur l'échantillon à une vitesse élevée, constante et continue et de mesurer les forces de frottement latéral rapidement et exactement simultanément avec les forces verticales. Pour la première fois, le CM-AFM sert à caractériser les échantillons biologiques dans des conditions physiologiques, ce qui permet de mesurer simultanément les forces de poinçonnage et de frottement en fonction de la vitesse de glissement. Il offre pour la première fois la capacité de décrire le comportement de friction des SLB en complément de la force de perforation. En raison du besoin important de mesure quantitative, l'optimisation du protocole CM-AFM a été effectuée en premier. Le protocole d'étalonnage du scanner a été établi avec succès pour assurer la précision de la vitesse de glissement. En outre, le protocole d'étalonnage des pointes, basé sur la méthode de Wedge et un échantillon rayé, est également conçu pour déterminer la constante d'étalonnage de la force latérale. Nous avons utilisé CM-AFM pour mesurer les propriétés tribologiques des échantillons solides pour améliorer l'équipement sous milieu liquide. Ensuite, les propriétés mécaniques (forces de poinçonnage et de frottement) des SLB ont été mesurées en fonction de la vitesse de glissement. Les SLB purs et mixtes ont été préparés par la méthode de fusion des vésicules. Différents médias ont également été utilisés pour étudier l'effet des cations monovalents sur les propriétés mécaniques des SLB. Dans tous les cas, la force de frottement augmente linéairement avec la vitesse de glissement, ce qui nous permet de déduire le coefficient visqueux de frottement. Comme prévu, la force de poinçonnage et le coefficient visqueux de frottement sont influencés par la composition des mélanges de lipides, par la nature des cations en milieu liquide et par la longueur des chaînes hydrocarbonées mais pas de manière similaire. L'interprétation de l'évolution du coefficient de force de frottement visqueux avec le système étudié est particulièrement délicate car la force de frottement pourrait être influencée par les propriétés d'interface ou de volume. Cette problématique sera le défi pour les prochaines études. Néanmoins, nos résultats illustrent la puissance de la technique CM-AFM et ouvre de nombreuses possibilités pour caractériser d'autres échantillons biologiques (cellules et tissus) afin de mieux comprendre les mécanismes élémentaires de frictionCell membranes are involved in many cellular processes: drugs and ions diffusion, signal transduction, energy generation, cell development (fusion and fission). Phospholipid bilayers are the main components of cell membranes, they act as a dynamic barrier protecting cellular biochemical reactions. The determination of biochemical and mechanical properties of lipid bilayers and their evolution with environmental conditions is necessary to study the nature of cellular processes and the influence of external agents (mechanical resistance, permeability, and biological response). To conduct such characterizations, simplified biomimetic membrane models, such as supported lipid bilayers (SLBs), were developed. Among the available characterization techniques, atomic force microscopy (AFM) has been widely used to study the nanoscale organization of SLBs under physiological conditions. AFM can yield high resolution images and it can also be used to quantify the mechanical resistance of SLBs by means of punch through experiments. For 30 years, AFM has been through many developments. Very recently, the Circular Mode AFM (CM-AFM) has been developed at the Université de Technologie de Compiègne. CM-AFM is able to generate a sliding movement of the AFM tip on the sample at high, constant and continuous velocity and to measure the lateral friction forces fast and accurately simultaneously with the vertical forces. For the first time CM-AFM is used to characterize biological samples under physiological conditions, allowing the simultaneous measurement of both the punch-through and the friction forces as a function of the sliding velocity. It offers for the first time the ability to describe the friction behavior of SLBs in complement of the punch-through force. Due to the important need for quantitative measurement, optimization of the CM-AFM protocol has been done first. Protocol of scanner calibration has been successfully established to ensure the accuracy of sliding velocity. Besides, the protocol for tip calibration, based on wedge method and a scratched sample, is also made to determine the lateral force calibration constant. We have employed CM-AFM to measure the tribological properties of solid samples to improve the equipment under liquid medium. Then, the mechanical properties (punchthrough and friction forces) of SLBs were measured as function of the sliding velocity. Pure and mixed SLBs were prepared by the vesicle fusion method. Various media were also used to study the effect of monovalent cations to the mechanical properties of SLBs. In all cases, the friction force increases linearly with the sliding velocity allowing us to deduce the friction viscous coefficient. As expected both the punchthrough force and the friction viscous coefficient are influenced by the composition of lipid mixtures, by the nature of cations in liquid medium, and by the length of hydrocarbon chains but not in a similar fashion. The interpretation of the evolution of the viscous friction force coefficient with the studied system is particularly tricky as the friction force could be influenced by interface or volume properties. This problematic will be the challenge for the next studies. Nevertheless, our results illustrate how powerful the CM-AFM technique is and it opens wide opportunities to characterize other biological samples (cells and tissues) to gain a better understanding of the elementary mechanisms of friction
50
Nejati, Houshin. "Analysis of physical properties and thermo – mechanical induced fractures of rocks subjected to microwave radiation." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=123156.
Full textAbstract:
This doctoral thesis investigates the microwave heating process, and its influence upon the physical properties and propagation of fractures in Rocks Under Illumination (RUI).In order to best understand microwave-assisted rock fracturing, it is critical to investigate the different aspects of this process. These range from the electromagnetic study (i.e., dielectric heating and heat generation), to the mechanical aspects (i.e., heat transfer, strength reduction material mechanics and fracture mechanics), and finally to the final fracturing behaviour of RUIs (i.e., fractography). In order to understand the various elements of the microwave fracturing of rocks, this research is divided into three investigations: 1) An investigation of the magnitude of heat generation within a rock body, and the extent to which illumination parameters can influence the efficiency of a microwave rock fracturing system. In addition, this research sought to expand the scope of microwave rock fracturing beyond the basaltic rocks utilized, and to apply this technique to other rock samples. This research investigates the possibility of substantially reducing the required energy input for a microwave-assisted rock fracturing system. This is made possible when operating at the optimal illumination parameters, with regard to each material property of the rock. To study the microwave heating process of rocks over a wide frequency range, the dielectric properties of some rocks are measured over frequencies ranging from 200 MHz to 20 GHz; with various water content, from fully dried to fully saturated; and at elevated temperatures ranging from 23ºC to 80oC.2) An investigation of the mechanical aspects of microwaves. This study sought to evaluate the influence of microwave illumination properties (i.e., input microwave power and exposure duration) on the fracture toughness of basalt samples and fracturing. It also attempted to experimentally quantify the fracture strength reduction of Chinese basalt after microwave illumination, at a variety of power levels and durations of exposure. Finally, the investigation sought to evaluate any correlation between the density of micro-cracks caused by microwave heating and any reduction in fracture toughness. This correlation was then modeled with the aid of numerical modeling (i.e., Discrete Element Modeling).3) A quantitative and qualitative investigation of the fracture development of Basalt Specimens Under Microwave Illuminations (BSUI) at macroscopic and microscopic scales. This research describes results of the visual investigations of the Fracture Growth Path (FGP) and the fracturing behaviour of SCBs after being exposed to microwave illuminations. FGPs are classified via their surface temperature level and the required input of microwave power. The Petrography Standard Test aided this approach, and allowed me to best describe fracture behaviour and the interactions between the fractures and mineralogical composition of Chinese basalt. A comprehensive fractographic investigation using Scanning Electron Microscopy (SEM) investigated microwave induced fracturing (i.e., fracture morphologies, fracture behaviours and the interaction of micro-fractures with rock forming minerals) in Chinese basalt fracture surfaces.Microwaves rock fracturing has potential to be employed for space applications: In Situ Resource Utilization (ISRU), sampling and In Situ material analysis sampling, in addition to mining and full face tunnelling applications on earth.Cette thèse de doctorat examine le procédé de chauffage par micro-ondes, et son influence sur les propriétés physiques et la propagation de fractures de roche sous illumination micro-onde (RUI). Pour bien comprendre la fracturation de roche avec assistance d'illumination micro-onde, il est essentiel de se pencher sur différents aspects du procédé. Ceux-ci vont de l'étude électromagnétique (chauffage diélectrique et génération de chaleur), jusqu'aux aspects mécaniques (transfère de chaleur, réduction de la résistance mécanique, mécanique de fracturation), et finalement jusqu'au comportement de fracturation final de la roche sous illumination micro-onde (fractographie). En tout, l'étude est divisée en trois parties :1) Une étude sur la magnitude de la génération de chaleur dans un corps rocheux, et dans quelle mesure les paramètres de l'illumination micro-ondes peut influencer l'efficacité d'un système de fracturation de roche avec chauffage par micro-ondes. Cette recherche tente d'élargir l'utilisation de chauffage par micro-ondes au-delà des roches basaltiques en appliquant cette technique à d'autres spécimens de roche. Cette recherche étudie aussi la possibilité de réduire substantiellement l'énergie d'entrée requise pour un système de fracturation de roche avec chauffage par micro-ondes. Ceci est possible lorsque les paramètres d'illumination micro-ondes sont optimisés par rapport aux propriétés de la roche. Pour étudier le processus de chauffage par micro-ondes à travers une ample gamme de fréquences, les propriétés diélectriques de plusieurs roches sont mesurées entre des fréquences de 200MHz à 20GHz. Le contenu d'eau varie entre parfaitement séché et complètement saturé, et la température varie entre la température de la pièce et 80oC.2) Une étude des aspects mécaniques des micro-ondes. Cette étude tente d'évaluer l'influence des propriétés de l'illumination micro-onde (puissance d'entrée micro-onde, durée d'exposition) sur la résistance de rupture de spécimens de basalte. L'étude tente aussi de quantifier expérimentalement la réduction de la résistance de rupture de spécimens de basalte chinois après l'illumination aux micro-ondes, en variant la puissance d'illumination ainsi que la durée d'exposition. Finalement, l'étude cherche à évaluer la corrélation entre la densité des micro-fractures causées par le chauffage par micro-ondes et la réduction de la résistance de rupture de la roche. La corrélation est ensuite modélisée à l'aide de modélisation numérique.3) Une étude qualitative et quantitative du développent de fractures dans des spécimens de basalte sous illumination micro-onde à l'échelle macroscopique et microscopique. Cette recherche décrit les résultats the l'étude visuelle du chemin de rupture (FGP) et le comportement de fracturation des SCBs après l'illumination par micro-ondes. Les FGP sont classifiés par rapport à la température de surface et la puissance d'entrée de micro-ondes requise. Le test standard de pétrographie aide à cette approche, et permet de mieux décrire le comportement de fracturation, et l'interaction entre les fractures et la composition minéralogique du basalte chinois. Une étude fractographique compréhensive sur la surface des ruptures induites dans le basalte chinois par l'illumination micro-onde (morphologie de rupture, comportement de rupture) est conduite en utilisant un microscope électronique à balayage (MEB). Cette recherche discute la possibilité d'utiliser les micro-ondes pour des applications spatiales : l'utilisation de ressources in-situ, l'échantillonnage et l'analyse d'échantillons in-situ, ainsi que des applications sur terre tel que l'extraction minière et la construction de tunnels.