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1
COLOMBO, ANNALISA. « Synthesis and characterization of TiO2 polymeric nanocomposites with tailorable optical properties ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2012. http://hdl.handle.net/10281/28632.
Texte intégralRésumé :
Main aim of this work was the fabrication and characterization of polymeric TiO2 hybrid nanocomposites. When dispersed at the nanoscale level, TiO2 can tune the optical properties of the polymeric matrix, such as the UV absorption and the increase of refractive index, preserving the transparency in the visible and the flexibility of the polymer.
TiO2 nanopaticles were modified on the surface with different molecules; they were then dispersed in MMA and polymerized in bulk, in order to obtain optically transparent TiO2/Poly-methylmethacrylate (PMMA) sheets. The application of these objects was in the solid-state lighting field, where the nanoparticles play the role of light diffusers according to Rayleigh Scattering.
Films based on poly 2-ethyl-2-oxazoline (PEOX) and TiO2 nanoparticles with concentrations up to 44 % in weight were also prepared by casting from water solutions. Nanocomposites films remained highly transparent in the visible, and absorbed UV radiation up to the proximity of the visible range. The refractive indices of the films raised from about 1.52 to 1.65 with increasing of TiO2 concentration. The good optical properties and the solubility in water of these materials could allow their application in the paint and coating industry, and in the field of conservation of cultural heritage as consolidants or varnishes of paintings.
2
Vandadi, Aref. « Optimization of Superhydrophobic Surfaces to Maintain Continuous Dropwise Condensation ». Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc500016/.
Texte intégralRésumé :
In the past decade, the condensation on superhydrophobic surfaces has been investigated abundantly to achieve dropwise condensation. There is not a specific approach in choosing the size of the roughness of the superhydrophobic surfaces and it was mostly selected arbitrarily to investigate the behavior of condensates on these surfaces. In this research, we are optimizing the size of the roughness of the superhydrophobic surface in order to achieve dropwise condensation. By minimizing the resistances toward the transition of the tails of droplets from the cavities of the roughness to the top of the roughness, the size of the roughness is optimized. It is shown that by decreasing the size of the roughness of the superhydrophobic surface, the resistances toward the transition of the tails of droplets from Wenzel state to Cassie state decrease and consequently dropwise condensation becomes more likely.
3
Thoreson, Erik J. « From nanoscale to macroscale using the atomic force microscope to quantify the role of few-asperity contacts in adhesion ». Link to electronic dissertation, 2006. http://www.wpi.edu/Pubs/ETD/Available/etd-010906-204218/.
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Ștefan, Gheorghiu. « Standard and nonstandard roughness - consequences for the physics of self-affine surfaces / ». free to MU campus, to others for purchase, 2000. http://wwwlib.umi.com/cr/mo/fullcit?p9988664.
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Berry, Elizabeth. « Fabrication of multiscale random rough surfaces with prescribed surface statistics ». Thesis, Imperial College London, 1986. http://hdl.handle.net/10044/1/37944.
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Yang, Hongta. « Fundamentals, preparation, and characterization of superhydrophobic wood fiber products ». Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24796.
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Thesis (M. S.)--Chemical Engineering, Georgia Institute of Technology, 2008.Committee Chair: Yulin Deng; Committee Member: Jeffery S. Hsieh; Committee Member: Sujit Banerjee; Committee Member: Zhong Lin Wang.
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Zhang, Yilei. « The effect of surface roughness parameters on contact and wettability of solid surfaces ». [Ames, Iowa : Iowa State University], 2007.
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8
Mamo, Andrew Benedict 1982. « Surface roughness of Mars ». Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/32744.
Texte intégralRésumé :
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2004.Includes bibliographical references (p. 35-36).
In this thesis, I created an algorithm to compensate for the saturation of data collected by the Mars Orbiter Laser Altimeter (MOLA). Saturation of the energy measurements had made it impossible to measure surface roughness at 100 m length scales. By calculating the returned energy, the problem of saturation can be avoided. This algorithm was applied to MOLA data across the Martian surface to create an estimate of surface roughness across the planet. The method calculates pulse spreading from returned pulse energy using the link equation. The accuracy of the method is limited by the accuracy of albedo measurements. This analysis improved the estimation of surface roughness on Mars. Further improvements could be gained by correcting for the opacity of atmospheric dust as a cause of pulse spreading.
by Andrew Benedict Mamo.
S.B.
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Li, Hongchun. « A study on wear and surface roughness of work roll in cold rolling ». School of Mechanical, Materials and Mechatronic Engineering - Faculty of Engineering, 2008. http://ro.uow.edu.au/theses/125.
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The objective of this study is to improve our understanding of the evolution and tribological behaviour of work roll surfaces in cold rolling because surface deterioration affects the quality of products and the efficiency of production. The cost of rolls is almost 25% of the cost of cold steel production. An experimental Lateral Set-testing (LST) mini-mill was developed to make use of the Gleeble 3500 thermo-mechanical simulator functions to evaluate, for the first time, the roll material surface features, surface roughness, fast Fourier transform (FFT) and Power Spectral Density (PSD) of frequency distribution, after single and multi-pass rolling. A low carbon-steel was prepared for the paired disc and then experiments on disc-to-disc wear were carried out to test surface deterioration and friction. In the laboratory, material imitating an industrial roll was manufactured. One batch contained 4%Cr and another contained 4%Cr plus approximately 0.1% Ti. These materials were compared against each other in the LST and disc-to-disc experiments. Experiments considered a series of parameters, including strip reduction, speed, and lubrication, while the disc-to-disc experiments considered duration of wear, forward and backward slip and load amplitude. The surfaces of the LST roller and disc were evaluated by surface technologies such as Atomic Force Microscope (AFM), Scanning Electron Microscope (SEM), and surface profile-meters. Transmission Electron Microscope (TEM) and X-ray diffraction wear properties. Test results from the mini-mill reveal that dominant waviness of the surface roughness still exists on the surface after a single pass of rolling and a 30.5% reduction is a critical reduction level that has a significant influence on the density of power spectrum. A rougher work piece results in a larger power spectrum of the surface profile. It has found that the PSD altitude of the roller surface is significantly affected axially but is more sensitive to its original surface roughness circumferentially. It is distributed in an inverse order to the surface roughness in a high frequency domain. The addition of Ti alters surface deterioration. Lubrication has a significant effect on surfaces containing either 4Cr% or 4%Cr+Ti, affecting surface roughness of rollers containing 4%Cr more significantly. In the disc-to-disc tests, more material was removed in the first 60 minutes from the disc containing Ti than the disc containing only 4%Cr. In general, roll material with 4%Cr+Ti reveals to have better anti-abrasive properties than the roll with only 4%Cr, while lubrication significantly reduced the wear rate and amount of material removed from both materials. The speed of the disc influences the weight loss, ie, the higher the speed the greater the amount of material removed. The slip rate also affects roll wear and weight loss because as the speed increases, so do the slip and loss of weight. The coefficients of friction are between 0.35~0.75 when the contact was dry and 0.06~0.11 when lubrication was applied. Adhesive friction dominated the dry contact while a mixed lubrication regime features friction behaviour when emulsion lubrication was applied. A backward slip of 2% and a forward slip of 1.5% resulted in a different coefficient of friction in dry contact mode although the corresponding torques were similar. The torque and coefficient of friction are found to increase with disc speed in dry contact condition. Lubrication alters the friction of both materials. The coefficient of friction decreases with speed on the disc with added Ti but the effect of load is in the opposite trend, while the disc with 4%Cr was less influenced by speed. The coefficient of friction is more sensitive to load at higher speeds on the disc with 4%Cr than at slower speeds on the disc with Ti added. This indicates that the addition of Ti enhances the tribological behaviour of rollers because the disc with Ti additive is characterised by carbonitrades precipitated in a refined tempered martensitic matrix. Coarse carbides characterise the 4%Cr disc materials. Surface defects of the work rolls, including banding, spalling, marking and welding in a cold strip plant, were investigated. It was found that early failures principally resulted from operational factors and roll material off-specification micro-structure defects rather than wear. It is recommended that different grades materials of the roll and strip with different roughness and hardness to be tested and studied on the evolution and tribological behaviour of roll surfaces in the future.
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Al-Maaitah, Ayman Adnan. « Effect of roughness element on the stability of boundary layers ». Thesis, Virginia Tech, 1986. http://hdl.handle.net/10919/45741.
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The instability of flows around hump and dip imperfections is investigated. The mean flow is calculated using interacting boundary layers, thereby accounting for viscous/inviscid interaction and separation bubbles. Then, the two-dimensional linear instability of this flow is analyzed, and the amplification factors are computed. Results are obtained for several height/width ratios and locations. The theoretical results have been used to correlate the experimental results of Greening and Walker. The observed transition locations are found to correspond to amplification factors varying between 7.4 and 10, consistent with previous results for flat plates. The method accounts for Tollmien-Schlichting waves, the shear layer instability, and their interaction. Separation is found to increase significantly the amplification factor.Master of Science
11
Beyer, Ross A. « Martian surface roughness and stratigraphy ». Diss., The University of Arizona, 2004. http://hdl.handle.net/10150/290105.
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Orbital datasets can be combined and manipulated to learn about the three-dimensional structure of planetary surfaces, and the processes that have acted on them. The Mars Orbital Camera (MOC) is providing high-resolution images. These images allow qualitative inspection of features, and contain quantitative information about the shape of the surface. Using a photoclinometry technique derived from a lunar-Lambert photometric function, I am able to obtain estimates of the down-sun slope of each pixel in an image. This technique was calibrated against synthetic topography, compared to an area photoclinometry technique, and applied to the Viking and Pathfinder landing sites. It is a robust technique for obtaining the roughness and slope characteristics of large areas. It was applied to the potential landing sites for the Mars Exploration Rovers to evaluate site safety. The slopes from this point photoclinometry technique can be used to obtain a rough estimate of topography, which I used in a number of studies where topographic information was crucial. MOC images have shown that layering is pervasive on the martian surface. Mars Orbital Laser Altimeter (MOLA) data can be registered to MOC images to provide elevation constraints on layer outcrops. Such layers are observed in eastern Coprates Chasma both in the chasma rim and in a flat-topped massif. Observations indicate that the chasma stratigraphy consists of thin sequences of resistant layers and intervening thicker sequences of relatively less resistant layers. More resistant units cap the massif against erosion and result in steeper slopes than the weaker units would otherwise allow. These resistant layers can be used as stratigraphic markers which have allowed me to measure the subsidence and tilting of the massif relative to the chasma walls, providing evidence for tectonic motion in this portion of the Valles Marineris. These outcrops indicate that some of these layers may be analogus to terristrial flood basalts in both composition and extent. I have constrained the dip angle of finely layered sequences in Ganges and Hebes Mensae. These layers are either flat lying or dip shallowly, but do not dip steeply, which places some constraints on the origin of these mensae.
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Alexander, William Nathan. « Normalization of Roughness Noise on the Near-Field Wall Pressure Spectrum ». Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/33643.
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Roughness noise can be a significant contributor of sound in low Mach number, high Reynolds number flows. Only a small amount of experimental research has been conducted to analyze roughness noise because of its often low energy levels that are hard to isolate even in a laboratory setting. This study details efforts to scale the roughness noise while independently varying roughness size and edge velocity. Measurements were taken in the Virginia Tech Anechoic Wall Jet Facility for stochastic rough surfaces varying from hydrodynamically smooth to fully rough as well as deterministic rough surfaces including 1mm and 3mm hemispheres and a 2D wavy wall. Inner and outer variable normalizations were applied to recorded far field data in an attempt to find specific driving variables of the roughness noise. Also, a newly formulated derivation that attempts to scale the far field sound from a single point wall pressure measurement was used to collapse the far field noise. From the results, the inner and outer variable scalings were unable to collapse the noise generated by all velocities and roughness sizes. The changing spectral shapes of noise generated by rough surfaces with significantly varying wavenumber spectra make it impossible to scale the produced noise using the proposed inner and outer variable scalings. They use only one a single scaling value for the entire frequency range of each spectrum. The analyzed wall pressure normalization, which is inherently frequency dependent, produces a tight collapse within the uncertainty of the measurements for all rough surfaces studied except the larger hemispherical roughness which had individual elements that dominated the surrounding region of the wall pressure microphone. This indicates that the roughness generated noise is directly proportional to the wall pressure spectrum. The collapsed data displayed a slope of Ï ^2, the expected dipole efficiency factor. This is the clearest confirmation to date that the roughness noise source is of a dipole nature.Master of Science
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Lee, Hyunjin. « Radiative properties of silicon wafers with microroughness and thin-film coatings ». Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-07092006-181152/.
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Thesis (Ph. D.)--Mechanical Engineering, Georgia Institute of Technology, 2006.Zhang, Zhuomin, Committee Chair ; Joshi, Yogendra, Committee Member ; Lee, Kok-Meng, Committee Member ; Gallivan, Martha, Committee Member ; Zhao, Yiping, Committee Member.
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Wallqvist, Viveca. « Interactions between non-polar surfaces in water : Fokus on talc, pitch and surface roughness effects ». Doctoral thesis, KTH, Ytkemi, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10283.
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The aim of this thesis work was to gain understanding of the interactions between talc mineral and surfaces, liquids and chemicals relevant for industrial applications, such as pulp and paper. Talc is used in the pulp and paper industry as a filler pigment, in control of pitch (lipophilic extractives) deposits and as a coating pigment. A deeper understanding of talc interactions will be beneficial in optimizing its use. Long-range attractive interactions between talc and hydrophobic model probes, as well as pitch probes, have been measured using the atomic force microscope (AFM) colloidal probe method. Two procedures for preparation of pitch colloidal probes were developed to allow these studies. Model hydrophobic, nanorough surfaces with surface energy characteristics similar to talc have also been prepared and their interactions with hydrophobic model probes compared to interactions between hydrophobic model probes and talc. It is demonstrated that talc mineral interacts with model hydrophobic particles, as well as with pitch, by long-range attractive forces, considerably stronger than the expected van der Waals force. The possible origin of the measured interaction forces is discussed, and the conclusion is that the main cause is an attractive capillary force due to formation of a gas/vapor capillary between the surfaces. Force measurements using model hydrophobic, nanorough surfaces show that a large-scale waviness does not significantly influence the range and magnitude of the capillary attraction, but large local variations in these quantities are found. It is demonstrated that a large variation in adhesion force corresponds to a small variation in local contact angle of the capillaries at the surfaces. The nature of the surface topographical features influences the capillary attraction by affecting the local contact angle and by pinning of the three-phase contact line. The effect is clearly dependent on the size of the surface features and whether they exist in the form of crevices or as extending ridges. Entrapment of air also affects the imbibition of water in pressed talc tablets. The effects of wetting and dispersion agents on the interactions between talc and hydrophobic probes have also been investigated. It is demonstrated that a common dispersing agent used for talc, poly(acrylic acid), does not affect the capillary attraction between talc and non-polar probes. In fact, the results strongly suggest that poly(acrylic acid) does not adsorb on the basal plane of talc. From this finding it is inferred that the stabilizing effect of this additive most likely is due to adsorption to the edges of talc. In contrast, a wetting agent (the non-ionic triblock copolymer Pluronic PE6400) removes the long-range capillary attraction. It is suggested that such an ability to replace air at the talc surface is of great importance for an efficient wetting agent. The Hamaker constant for talc has also been estimated by using optical data obtained from spectroscopic ellipsometry. It is demonstrated that a nanocrystalline talc mineral, cut in different directions displays very small differences in Hamaker constant between the different crystallographic orientations, whereas a microcrystalline sample displays a significantly higher value. The estimated Hamaker constants are discussed for different material combinations of relevance for the pulp- and paper industry, such as cellulose and calcium carbonate.Målet med detta avhandlingsarbete var att öka förståelsen för interaktioner mellan talkmineral och ytor, vätskor och kemikalier relevanta för industriella applikationer, såsom papper och massa. Talk används i pappers- och massaindustrin som fyllmedel, för kontroll av hartsrika (lipofila extraktivämnen) avsättningar och som bestrykningspigment. En djupare förståelse för talkinteraktioner kommer att vara användbart för att optimera dess användning. Långväga attraktiva interaktioner mellan talk och hydrofoba modellpartiklar, såväl som mellan talk och hartspartiklar, har uppmätts med hjälp av atomkraftsmikroskopi (AFM) genom att fästa kolloidala partiklar på kraftsensorn. Två metoder för att framställa partiklar gjorda av harts har utvecklats för att möjliggöra dessa studier. Hydrofoba, nanostrukturerade modellytor med ytenergier liknande de för talk har också tillverkats och deras växelverkan med hydrofoba modellpartiklar har jämförts med dem mellan talk och hydrofoba modellpartiklar. Studierna visar att talkmineral växelverkar med hydrofoba modellpartiklar, såväl som med harts, genom långväga attraktiva krafter som är betydligt starkare än den förväntade van der Waals kraften. Möjliga orsaker till de uppmätta växelverkanskrafterna diskuteras och slutsatsen blir att huvudorsaken är en attraktiv kapillärkraft som uppkommer genom att en gas-/ångkapillär bildas mellan ytorna. Kraftmätningar gjorda med hydrofoba nanostrukturerade modellytor visar att en storskalig vågighet inte nämnvärt påverkar storleken av kapillärattraktionen, men stora lokala variationer existerar. Det demonstreras att en stor variation i adhesionskraft motsvaras av en liten variation i lokal kontaktvinkel för kapillärerna på ytorna. Ytornas topografi påverkar kapillärattraktionen genom att påverka den lokala kontaktvinkeln samt genom att trefaskontaktlinjen inte kan röra sig fritt över ytan. Effekten är tydligt beroende av huruvida ytojämnheterna existerar i form av nedsänkningar eller upphöjningar. Instängd luft påverkar också pressade talktabletters uppsugningsförmåga av vatten. Vätnings- och dispergeringsmedels inverkan på växelverkan mellan talk och hydrofoba partiklar har undersökts. Resultaten visar att ett vanligt dispergeringsmedel för talk, polyakrylsyra, inte påverkar kapillärattraktionen. I själva verket tyder data på att polyakrylsyra inte adsorberas på talks basalplan. Utifrån dessa resultat dras slutsatsen att polyakrylsyra stabiliserar talkdispersioner genom att adsorbera på talkkanterna. Ett vanligt vätmedel (nonjonisk triblock sampolymer Pluronic PE6400) tar å andra sidan bort långväga kapillärattraktion. Detta antyder att egenskapen att ersätta luft på talkytan är av stor betydelse för effektiva vätmedel. Hamakerkonstanten för talk har uppskattats genom att utnyttja optiska data från ellipsometrimätningar. Det demonstreras att ett nanokristallint talkmineral kapat i olika riktningar uppvisar mycket små skillnader i Hamakerkonstant mellan de olika kristallografiska orienteringarna, medan ett mikrokristallint prov uppvisar ett betydligt högre värde. De beräknade Hamakerkonstanterna diskuteras för olika materialkombinationer relevanta för pappersindustrin, såsom cellulosa och kalciumkarbonat.
QC 20100813
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Fujiwara, Yuko. « Evaluation of wood surface roughness as related to tactile roughness ». Kyoto University, 2004. http://hdl.handle.net/2433/145425.
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Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第11112号
農博第1442号
新制||農||898(附属図書館)
学位論文||H16||N3962(農学部図書室)
22662
UT51-2004-L909
京都大学大学院農学研究科森林科学専攻
(主査)教授 奥村 正悟, 教授 増田 稔, 教授 池田 善郎
学位規則第4条第1項該当
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Liu, Yu. « Surface roughness generated boundary layer noise ». Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612403.
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Konidaris, Spyridon G. « Electromagnetic scattering from rough surfaces using the On-Surface Radiation Boundary Condition (OSRC) method ». Thesis, Monterey, California. Naval Postgraduate School, 1990. http://hdl.handle.net/10945/30624.
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Approved for public release, distribution unlimitedElectromagnetic scattering from rough surfaces is of prime importance in the engineering field since it affects communications, radar, remote sensing, acoustics, etc. The actual problem of scattering from rough surfaces is complicated and involves three dimensional scattering from either lossy or dielectric, electrically large surface. Integral equations are widely utilized to solve this kind of problem but this solution to the problem is generally computationally intensive. In the On-Surface Radiation Boundary Condition (OSRC) method, a higher order radiation condition is imposed directly on the surface of the scatterer. This reduces the integral equation for the scattered field to a line integral which can be easily evaluated numerically. In this thesis, the OSRC method is used to formulate the problem of scattering from periodic rough, two dimensional surfaces illuminated by a transverse magnetic, plane electromagnetic wave. Three geometric surfaces are considered. A comparison is made between the present formulation, the exact solution, and the physical optics approximation.
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Gilliam, David R. « A study of contact between a profile meter stylus and polymer films on roughened substrates ». Thesis, Virginia Tech, 1985. http://hdl.handle.net/10919/45727.
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When a polymer film is deposited onto a roughened substrate, the film masks over the underlying substrate roughness. Then when attempting to measure the roughness of the polymer film surface using a stylus-type profile meter, the pressure between the tip of the stylus and the film is sufficient to plastically deform the polymer surface. The result is a possible erroneous measurement of the surface roughness of the polymer film. This thesis reports on attempts to quantify the actual roughness of the polymer film from the measurement obtained by the profile meter. Extensive surface profile data were collected and analyzed to determine the characteristics of the surface of the substrate and of the coating on the substrate. The tracks made by the stylus in the film were then observed in a scanning electron microscope, from which the depth of the stylus tracks were measured. The effects of the film thickness, stylus traversing speed, and substrate roughness on the stylus penetration depth, the variation in the depth, and the measured film roughness are assessed and discussed. It was found that using the fastest stylus traversing speed minimizes the variation of the stylus penetration depth and thus results in the most accurate measurement of the film surface. To predict this stylus indentation depth, a plane strain plastic deformation model is developed using slip-line field theory. It is found that the slip-line model gives good estimates of the stylus indentation depth when the film thickness is large.Master of Science
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Chen, Quan, et 陳全. « Efficient numerical modeling of random surface roughness for interconnect internal impedance extraction ». Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B3955708X.
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Ward, R. L. « Roughness measurements of machined workpieces ». Thesis, Leeds Beckett University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314787.
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Waigh, David Ross Carleton University Dissertation Engineering Mechanical and Aerospace. « An Improved correlation for representing surface roughness effects on the law of the wall in fully rough conditions ». Ottawa, 1996.
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22
Hakim, Ali. « Characterization of Hard Metal Surfaces after Various Surface Process Treatments ». Thesis, Linköping University, The Department of Physics, Chemistry and Biology, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-12433.
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The aim of this thesis is to investigate how material surfaces are affected by various surface treatments and how this relates to the adhesion of the coating. The materials that were studied were WC-Co and Cermets and the surface treatments used were polishing, grinding with coarser and finer abrasive grains, and finally wet blasting and dry blasting. Focus was on deformations and residual stresses in the surface, surface roughness and cracks. The test methods used for examining the samples included surface roughness measurements, residual stress measurements, adhesion tests using Rockwell indentation and SEM images of the surface and the cross section.
The results concluded that polishing gives very good adhesion. Additionally, the adhesion for ground surfaces was good for WC-Co but very poor for Cermets. Furthermore, it was observed that finer abrasive grains did not result in better adhesion. In fact, the coarser grains gave slightly better results. Finally, it was concluded that wet blasting has a clear advantage over dry blasting and results in much better adhesion, especially for the Cermets. The results for the WC-Co were a bit inconsistent and so further research is required.
23
Park, Jung Hwa. « The role of surface chemistry and wettability of microtextured titanium surfaces in osteoblast differentiation ». Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44732.
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Biomaterial surface energy, chemical composition, charge, wettability and roughness all play an important role in determining the degree of the direct bone-to-implant interface, termed osseointegration. Surface chemistry, which is influenced by surface energy, wettability, and composition, is another factor that determines osteoblast phenotype and regulates osteoblast maturation. Increased surface energy is desirable for bone implants due to enhanced interaction between the implant surface and the biological environment. The extent of bone formation in vivo is also increased with increasing water wettability of implants.
The physiological role of implant surface chemistry is important in determining the success of implant osseointegration because of molecular rearrangements, surface reactions, contamination, and release of toxic or biologically active ions that are determined by the starting chemistry. However, the role of surface chemistry on osteoblast response is not fully studied.
Therefore, the overall goal of this dissertation is to understand how the surface chemistry, including wettability, chemical composition, and charge density, of titanium biomaterials impacts osteoblast maturation (in vitro). This study focuses on the general hypothesis that modifications of surface chemistry of titanium surfaces with sterilization or polyelectrolyte coating on titanium surfaces regulate osteoblast response.
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Lewis, Gareth Dafydd. « Polarimetric signatures of roughened surfaces ». Thesis, Cranfield University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.422187.
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Panth, Mohan. « USING SURFACE TENSION GRADIENTS AND MAGNETIC FIELD TO INFLUENCE FERROFLUID AND WATER DROPLET BEHAVIOR ON METAL SURFACES ». Miami University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=miami1470164188.
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Isleyici, Umut. « Effect Of Surface Roughness On Ultrasonic Testing ». Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606937/index.pdf.
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This study investigates the effect of front surface roughness on ultrasonic echo amplitude. Experiments were carried out on specimens whose front surfaces are machined by milling machine. Machining parameters were changed in milling
process in order to obtain desired roughness values and milling head was tilted to a very small angle to obtain periodic rough surfaces. Experiments were performed with these specimens having roughness value of 0.5, 4.5, 11, 26.5 µm. Ra. The back surface roughness of all specimens was kept constant at 1.5 µ
m Ra by grinding operation. 1.5, 2, 3, 4 mm. holes were drilled at constant depth and to same side of each specimen to represent reference discontinuities. Ultrasonic tests, using pulse echo technique were carried out to monitor echo amplitudes corresponding to different roughness values. The tests were also repeated by using different ultrasonic probes having different frequencies. For additional comparison, different couplants were used through the tests. The results showed that there was a significant increase in the reduction of the sound pressure level with the increase in the surface roughness. Although there was no uncertainty observed about not being able to detect discontinuity because of roughness but correct couplant and frequency selection has a positive effect on correctly sizing the discontinuity and at attenuation measurements. The results obtained with this work can be used as a guide for testing rough surfaces, predicting the effect on ultrasonic examination before testing and discontinuity detecting capability under rough surface conditions.
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Wu, Jiunn-Jong. « Surface roughness and its role in contact ». Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363100.
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Zhang, Cheng. « Influence of surface roughness on thermography measurement ». Thesis, Högskolan Väst, Avd för automationssystem, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-6842.
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This university Bachelor's Thesis was performed to explore the influence of surface roughness on the thermography measurement. Thermography is a non-destructive testing method which can be used to detect cracks. However, it is hard to define how the surface roughness influences the emissivity and the result of a thermography measurement, as well as how the angle of the excitation source influences the result. Therefore, this work aims to define how the heating angle and surface roughness influence the thermography measurement, define the relationship between surface roughness and emissivity for the same crack, and define the influence of the angles which composed of the heating source, the direction of crack and the direction of surface roughness on thermography measurement. In this report, the theories of radiation and Signal-to-noise ratio (SNR) were explained, clearly. Also, two kinds of experiments were set up. One is focus on how the heating angle influence the thermography measurement, the other is focus on how the angle of the heating source, in relation to the crack direction and the direction of surface roughness, influence the SNR value. The conclusions of these experiments are that the heating of a crack increases as the angle decreases (from wide side to narrow side) and the angle ofincreases (from horizontal to vertical). Moreover, the SNR value decreases as the surface roughness increases. For the same surface roughness, the SNR value increases with increased crack angle (0°, 45° or 90°) and with decreased sample position angle (horizontal, 45°or vertical). What is more, the higher surface roughness, the larger the influence of the crack angle and the sample position angle. Finally, when the surface is polish, the crack angle and the sample position angle does not have any influence.
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Kulkarni, Amit S. « Effects of surface roughness in microchannel flows ». [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0003400.
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Sharma, Priyanka. « Investigations of Titan's Topography and Surface Roughness ». Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/241978.
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Saturn's moon, Titan is a geomorphologically active planetary object, and its surface is influenced by multiple processes like impact cratering, fluvial and aeolian erosion, lacustrine processes, tectonics, cryovolcanism and mantling. Disentangling the processes that compete to shape Titan's landscape is difficult in the absence of global topography data. In this thesis, I utilize techniques in topographic statistics, fractal theory, study of terrestrial analogs and landscape evolution modeling to characterize Titan's topography and surface roughness and investigate the relative roles of surface processes in sculpting its landscape. I mapped the shorelines of 290 North Polar Titanian lakes using the Cassini Synthetic Aperture Radar dataset. The fractal dimensions of the shorelines were calculated via the divider/ruler method and box-counting method, at length scales of (1-10) km and found to average 1.27 and 1.32, respectively. The inferred power-spectral exponent of Titan's topography (β) was found to be ≤ 2, which is lower than the values obtained from the global topography of the Earth or Venus. In order to interpret fractal dimensions of Titan's shorelines in terms of the surficial processes at work, I repeated a similar statistical analysis with 114 terrestrial analogous lakes formed by different processes, using C-band radar backscatter data from the Shuttle Radar Topography Mission (SRTM). I found different lake generation mechanisms on Earth produce 'statistically different' shorelines; however, no specific set of processes could be identified for forming Titanian lake basins. Using the Cassini RADAR altimetry data, I investigated Titan's global surface roughness and calculated median absolute slopes, average relief and Hurst exponent (H) for the surface of Titan. I detected a clear trend with latitude in these roughness parameters. Equatorial regions had the smallest slopes, lowest values of H and smallest intra-footprint relief, compared to the mid-latitudes and polar regions of Titan. I used steady state models of relief generation (tectonic activity) and relief reduction (diffusive mass wasting and advective bedrock channel erosion) to generate synthetic landscapes and simulate Titan's topography. I provided constraints on two environmental variables for Titan that influence surface roughness: diffusivity and erodibility coefficient.
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Wallace, Karen Sue 1957. « SURFACE ROUGHNESS EFFECTS ON SOIL SPECTRAL REFLECTANCE ». Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/275522.
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Shaw, Joseph Alan 1962. « Laser-glint measurements of sea-surface roughness ». Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/290653.
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Optical glint patterns convey information about the roughness of the surface on which they are formed. This dissertation describes two new optical instruments that relate the variations of specular laser reflections (laser glints) from the sea surface in angular, temporal, and wavenumber space to the surface roughness. Measurements from these instruments are interpreted with the objective of improving the capabilities of remote-sensing instruments that view the ocean surface. Particular attention is paid to cm waves, which are resonant structures for microwave sensors and the most significant component of optical roughness. The scanning-laser glint meter counts laser glints in 1° angular bins over a ± 75° nadir-angle range. The video laser-glint imager is a CCD video camera that images glints from an array of diode lasers. Both instruments were deployed on the research platform FLIP in the Pacific Ocean near the Oregon coast for three weeks during September 1995. Normalized histograms of angular glint counts are interpreted as the probability density function (PDF) of sea-surface slope, a Gram-Charlier expansion of which facilitates studying the variation with wind speed and atmospheric stability of moments through order four. The PDF appears approximately Gaussian, but is skewed toward downwind slopes in the along-wind axis due to asymmetric wind waves. No skewness exists in the cross-wind axis. Slope PDFs also have positive peakedness, increasing the probability of very small and large slopes relative to a Gaussian. Surface roughness is shown to depend strongly on atmospheric stability, which is proportional to the air-water temperature difference. Both the mean-square slope and the peakedness increase with negative stability (water warmer than air) relative to the neutral-stability case (water and air temperatures equal). Increased surface roughness, due to increases in wind speed or negative stability, causes glint-count fractal dimensions to increase, glint-image power spectra to flatten, and glint-image autocorrelations to appear more wrinkled. Glint-image spectra are dominated by glint-size effects, which are related to surface curvature. New ways of modeling the interaction of electromagnetic waves with the ocean surface are suggested by the new fractal and spectral characterizations of surface roughness that are introduced here.
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Kozin, Philipp A. « Charge Development at Iron Oxyhydroxide Surfaces : The Interplay between Surface Structure, Particle Morphology and Counterion Identity ». Doctoral thesis, Umeå universitet, Kemiska institutionen, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-85195.
Texte intégralRésumé :
Iron (oxyhydr)oxide (FeOOH) minerals play important roles in various natural, technological and societal settings. The widespread abundance of these minerals has prompted numerous studies on their surface reactivity in aqueous media. Surface charge development, one that namely takes place through the adsorption of potential determining ions (p.d.i.; H+, OH-) and coadsorption of counterions (e.g. Cl-, ClO4-, Na+), is particularly interesting in this regard. Mineral surface charge development is determined by numerous factors related to the interplay of mineral surface structure, particle morphology and counterion identity. In this thesis the interplay between these factors is resolved by monitoring charge development on submicron-sized synthetic iron oxyhydroxide particles of different structures and sizes in aqueous media with counteranions of contrasting charge-to-size ratio (i.e. NaCl, NaClO4). This work, which is summarized in an introductory chapter and detailed in five appendices, is focused on three types of synthetic lepidocrocite (ã- FeOOH) of different shapes and surface roughness, three types of goethite (á-FeOOH) of different levels of surface roughness, and finally akaganéite (â-FeOOH), a mineral representing unique ion exchange properties due to its hollandite-type structure. While charge development was chiefly monitored by high precisition potentiometric titrations, these efforts were supported by a range of techniques including electrolyte ion uptake by cryogenic X-ray photoelectron spectroscopy, particle imaging by (high resolution) transmission electron microscopy, porosity analysis by N2 adsorption/desorption, surface potential development by electrokinetics, as well as thermodynamic adsorption modeling. These efforts showed that lepidocrocite particles of contrasting morphology and surface roughness acquired highly comparable pH and ionic strength p.d.i. loadings. Equilibriation times required to develop these loadings were however altered when particles became aggregated by aging. Goethite particles of contrasting surface roughness also acquired incongruent p.d.i. loadings, which were predominantly explained by the different charge-neutralizing capabilities of these surfaces, some of which were related to pore size distributions controlling the entrance of ions of contrasting sizes. Such size exclusion effects were also noted for the case of akaganéite where its bulk 0.4×0.4 nm wide channels permitted chloride diffusion but blocked perchlorate. Charge development at goethite surfaces in binary mixtures of NaCl and NaClO4 solutions also showed that the larger size-to-charge ratio chloride ion exerted a strong effect on these results even when present as a minor species. Many of these aforementioned effects were also modeled using variable, counterion- and loading-specific, Stern layer capacitance values. The findings summarized in this thesis are providing a better understanding of surface processes occurring at iron oxyhydroxide surfaces. They should impact our ability in designing uses of such particles, for example, effective sorption in aquatic media, as well as to understand how they behave in natural systems.
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Peters, Wayne D. « Rough-surface gravity current flows ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0017/NQ46297.pdf.
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Peters, Wayne. « Rough-surface gravity current flows ». Thesis, University of New Brunswick, 1999. http://hdl.handle.net/1882/814.
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Hansson, Petra M. « Hydrophobic surfaces : Effect of surface structure on wetting and interaction forces ». Doctoral thesis, KTH, Yt- och korrosionsvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-103409.
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The use of hydrophobic surfaces is important for many processes both in nature and industry. Interactions between hydrophobic species play a key role in industrial applications such as water-cleaning procedures and pitch control during papermaking but they also give information on how to design surfaces like hydrophobic mineral pigments. In this thesis, the influence of surface properties on wetting and interaction forces has been studied. Surfaces with close-packed particles, pore arrays, randomly deposited nanoparticles as well as reference surfaces were prepared. The atomic force microscope (AFM) was utilized for force and friction measurements while contact angles and confocal Raman microscopy experiments were mainly used for wetting studies. The deposition of silica particles in the size range of nano- to micrometers using the Langmuir-Blodgett (LB) technique resulted in particle coated surfaces exhibiting hexagonal close-packing and close to Wenzel state wetting after hydrophobization. Force measurements displayed long-range interaction forces assigned to be a consequence of air cavitation. Smaller roughness features provided larger forces and interaction distances interpreted as being due to fewer restrictions of capillary growth. Friction measurements proved both the surface structure and chemistry to be important for the observed forces. On hydrophobic pore array surfaces, the three-phase contact line of water droplets avoided the pores which created a jagged interface. The influence of the pores was evident in the force curves, both in terms of the shape, in which the three-phase contact line movements around the pores could be detected, as well as the depth of the pores providing different access and amount of air. When water/ethanol mixtures were used, the interactions were concluded to be due to ethanol condensation. Confocal Raman microscopy experiments with water and water/ethanol mixtures on superhydrophobic surfaces gave evidence for water depletion and ethanol/air accumulation close to the surface. Force measurements using superhydrophobic surfaces showed extremely long-range interaction distances. This work has provided evidence for air cavitation between hydrophobic surfaces in aqueous solution. It was also shown that the range and magnitude of interaction forces could, to some extent, be predicted by looking at certain surface features like structure,roughness and the overall length scales.QC 20121011
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Ellis, Matthew A. « Roughness length variability over heterogeneous surfaces ». Thesis, Monterey, California : Naval Postgraduate School, 2010. http://edocs.nps.edu/npspubs/scholarly/theses/2010/Mar/10Mar%5FEllis.pdf.
Texte intégralRésumé :
Thesis (M.S. in Meteorology)--Naval Postgraduate School, March 2010.Thesis Advisor(s): Wang, Qing. Second Reader: Nuss, Wendell A. "March 2010." Description based on title screen as viewed on April 26, 2010. Author(s) subject terms: Atmospheric Boundary Layer, Turbulence, Roughness Length, Momentum Flux, Heat Flux, Flus-profile Relationships, Monin-Obukhov Similarity Theory, Heterogeneous Surfaces. Includes bibliographical references (p. 73-75). Also available in print.
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Gurau, Lidia. « The roughness of sanded wood surfaces ». Thesis, Brunel University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.399646.
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Manu, Dabankah Emmanuel. « Surface Roughness Characterization of hole walls in fibercomposites ». Thesis, KTH, Industriell produktion, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-140314.
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In the manufacturing of fibrecomposite structures for the aircraft industry many holes are drilled through the composite for the attachment of the composite to a metal frame. These holes have a Ra specification of the cylindrical walls. The measurement of this roughness is tedious work if made by a stylus profiler. In this thesis, a design concept is created and tested by using OSLO raytracing program. This employed raytracing simulation is used to analyze and study variation of the surface features of the hole and evaluate the corresponding resultant image afterwards using image quality indicators. On large scale the aim of the thesis work is to investigate the possibilities of detecting defects of the cylindrical walls and get a quantitative measurement of the roughness of the hole by employing the concept of optical cylindrical imaging. Keywords: Surface roughness, Light scattering, Diffraction , Reflection, Raytracing analysis, Wavefront analysis, Spot diagram, Diffraction limit, PSF, MTF, Energy analysis, Optimization, Entrance pupil, Exit pupil, Carbon Fiber Reinforced Polymers (CFRP), Axicon, He Ne Laser.
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Cullen, Lachlan Michael. « Acoustic receptivity in boundary layers with surface roughness ». Thesis, Queen Mary, University of London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327024.
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Gadsby, Philip. « Surface roughness effects on thermally stressed aviation fuel ». Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/19191/.
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Thermal instability in aviation fuels has been thoroughly explored over the last 50 years. The problem is complex, with coupling of fuel chemistry, heat transfer and fluid dynamics. Most efforts have been applied to the chemical kinetics of deposit formation and studying physical effects such as temperature, flow rate and Reynolds number in a multitude of small to large scale testing devices. However, much less attention has been paid to the effects of wall surface roughness. This is surprising - since for turbulent flow, wall roughness enhances momentum, heat and mass transfer by disrupting the quiescent viscous layer adjacent to the wall and interfering with structures of turbulence further into the boundary layer. Furthermore, a rough surface increases the wall surface area, presenting more active sites for heterogeneous catalytic reactions. Additive Layer Manufacturing (ALM) has been touted as ’game changing’ technology and is now being proposed as a method to create components for gas turbine engines. The technology results in near net shape parts with reduced weight, number of welds and material waste compared to conventional subtractive machining methods. However, the surface roughness of ALM components can be orders of magnitude greater than machined components and can be highly non-uniform. While reducing external surface roughness is trivial, typical methods of internal roughness reduction (ie. abrasive flow machining) may not be possible for small scale passages. This may result in internal fuel passageways with high relative roughness in components which are subject to high thermal loading - for example, injector feed arms which are exposed to compressor discharge air. The effect of wall roughness on deposition of thermally stressed aviation fuel was investigated in both laminar and turbulent flow regimes using small to medium scale test devices. Deposition over ALM components was tested in the laminar regime with a modified Jet Fuel Thermal Oxidation Tester (JFTOT) and in the turbulent regime with the Aviation Fuel Thermal Stability Test Unit (AFTSTU). The High Reynolds Number Thermal Stability Tester (HiReTS) was used to examine deposition in micro-scale tubes with very high relative roughness. As well as microscopy and 3D optical profilometry, momentum and heat transfer experiments were conducted to characterise the roughness as fully as possible. In the laminar regime, the effect of roughness was negligible. For turbulent flow, substantial differences in heat transfer and deposition rate were consistently observed for tubes with the highest relative roughness. The increase in deposition rate is thought to be related to the projection of roughness elements into regions of intense turbulent activity in the boundary layer. The turbulence structures, which are more energetic and have reduced anisotropy over rough walls, increase wall-normal transport - thereby replenishing the near wall region with deposit precursor and providing insoluble particles formed off the wall with inertia with which to deposit.
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Munoz-Escalona, Patricia. « Surface roughness prediction when milling with square inserts ». Thesis, University of Bath, 2010. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.519033.
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Rellick, Lorraine Mary. « Local packing densities and surface roughness of proteins / ». The Ohio State University, 1991. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487759055158724.
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Almqvist, Andreas. « On the effects of surface roughness in lubrication ». Doctoral thesis, Luleå tekniska universitet, Maskinelement, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-18259.
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Tribology is a multidisciplinary field defined as the science and technology of interacting surfaces in relative motion, and embraces the study of friction, wear and lubrication. A typical tribological application is the rolling element bearing. Tribological contacts may also be found in other types of bearings, cam-mechanisms, gearboxes and hydraulic systems. Examples of bearings inside the human body are the operation of the human hip joint and the contact between teeth during chewing. To fully understand the operation of this type of application one has to understand the couplings between the lubricant fluid dynamics, the structural dynamics of the bearing material, the thermodynamical aspects and the resulting chemical reactions. This makes modeling tribological applications an extremely delicate task. Because of the multidisciplinary nature, such theoretical models lead to mathematical descriptions generally in the form of non-linear integro-differential systems of equations. Some of these systems of equations are sufficiently well posed to allow numerical solutions to be carried out, resulting in accurate predictions on performance. In this work, the influence on performance of a surface microscopical nature, the surface roughness, in contact interfaces between different types of machine element components is the subject of study. An example is the non-conformal lubricated contact between one of the rollers and the inner ring in a rolling element bearing. The tribological contact controlling the operation of the human hip joint is also very similar to this. Another example of a non-conformal contact occurs when driving on rainy roads, where the hydrodynamic action of the water separates the tire. To enable investigations of these types of problems, different theoretical models were studied; for the selected model, a numerical solution technique was developed within this project. This model is based on the Reynolds equation coupled with the film thickness equation. The numerical solution technique involves a multilevel technique to facilitate the solution process. Results presented in this thesis, utilizing this approach, study elementary surface features such as ridges and indentations passing each other inside the lubricated conjunction. The Reynolds equation is derived under the assumptions of thin fluid film and creeping flow, and considers in its most general form shear thinning of the lubricant. This type of equation describes the hydrodynamic action of the lubricant flow and may be used when the interfaces consist of either conformal or non-conformal conjunctions. Examples of applications having conformal interfaces are thrust- and journal- bearings or the contact between the eye and a (optical) contact lens. In such types of applications the load carried by the interface is distributed over a fairly large area that under certain circumstances helps to prevent mechanical deformation of the contacting surfaces. Such applications are said to operate in the hydrodynamic lubrication (HL) regime. Lubricant compressibility and cavitation are important aspects and have received some attention. However, the main objective when modeling HL has been to investigate and develop methods that enable the influence of surface roughness to be to be studied efficiently. Homogenization is a rigorous mathematical concept that when applied to a certain problem may be regarded as an averaging technique as well as it provides information about the induced effects of local surface roughness. Homogenization inflicts no restrictions on the surface roughness representation other than the representative part of the chosen surface roughness being assumed periodically distributed and of course the assumptions of thin film flow made through the Reynolds equation. The homogenization process leads to a two sets of equations one for the local scale describing surface roughness, scale and one for the global scale describing application geometry. The unequivocally determined coefficients of the global problem, which may be regarded as flow factors, are obtained through the solution of local problems. This makes homogenization an eminent approach to be used investigating the influence of surface roughness on hydrodynamic performance. In the present work, homogenization has been used to derive computationally feasible forms of problems originating from incompressible and compressible Reynolds type equations that describe stationary and unstationary flows in both cartezian and cylindrical co-ordinates. This technique enables simulations of surface roughness induced effects when considering surface roughness descriptions originating from measurements. Moreover, the application of homogenization facilitates the interpretation of results. Numerical investigations following the homogenization process have been carried out to verify the applicability of homogenization in hydrodynamic lubrication. Homogenization has also been shown here to enable efficient analysis of rough hydrodynamically lubricated problems. Also of note, in connection to the scientific contribution within tribology, collaboration with a group in applied mathematics has lead to the development of novel techniques in that area. These ideas have also been successfully applied, with some results presented in this thesis. At start-ups, the contact in a rolling element bearing could be both starved and drained from lubricant. In this case the hydrodynamic action becomes negligible in terms of load carrying capacity. The load is carried exclusively by surface asperities, the tribo film, or both. This is hereby modeled as the unlubricated frictionless contact between rough surfaces, i.e. a contact mechanical approach. A variational principle was used in which the real area of contact and the contact pressure distribution minimize the total complementary potential energy. The material model is linear elastic-perfectly plastic and the energy dissipation due to plastic deformation is accounted for. The numerics of this contact mechanical approach involve the fast Fourier transformation (FFT) technique in order to facilitate the solution process. Investigation results of the contact mechanics of realistic surfaces are presented in this thesis. In this investigation the variation in the real area of contact, the plasticity index and some surface roughness parameters due to applied load were studied.Godkänd; 2006; 20061116 (pafi)
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Landais, François. « Lois d’échelles et propriétés statistiques multifractales de la topographie des planètes ». Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS453/document.
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Au cours des 20 dernières années, le développement des méthodes de télédétection et le succès des missions spatiales ont considérablement enrichi nos connaissances sur les surfaces planétaires révélant une immense diversité de morphologies. Etant le reflet de l'interaction et de la compétition entre des processus géologiques dont les modalités sont variables d'un corps à l'autre, elles sont largement étudiées pour retracer l'histoire géologique des planètes telluriques. En particulier, des informations précieuses sur la nature des processus et sur les lois générales qui contrôlent la formation et l'évolution des paysages sont enregistrées dans le champ topographique qui peut être analysé en tant que champ statistique. Nous rapportons dans cette thèse les résultats d'une étude comparative des propriétés statistiques de la topographie des principaux corps du système solaire en nous appuyant sur le volume croissant de données altimétriques et photogrammétriques. Notre approche est centrée sur la notion de loi d'échelle qui vise à caractériser les symétries du champ en traduisant le caractère auto-similaire des surfaces naturelles : les détails d'une surface ressemblent en général à des versions réduites de l'ensemble. Nous mettons en oeuvre plusieurs méthodes d'analyse de données dites «multifractales» pour dégager le meilleur modèle statistique capable de décrire la topographie dans différents contexte et proposons de nouveaux indicateurs de rugosité à l'échelle globale, régionale et locale. Nous montrons qu'en dépit de leur diversité, les surfaces du système solaire respectent des lois statistiques similaires que nous explicitons. En particulier nous montrons que la distribution globale des pentes d'un corps respecte en général des lois multifractales pour les échelles supérieures à 10-20km et présente une structure statistique différente pour les échelles inférieures. Enfin nous proposons une méthode pour générer des topographies synthétique sphériques dont le propriétés statistiques sont similaires aux topographie planétaire du système solaireOver the past 20 years, the development of remote sensing methods and the success of space missions have considerably enriched our knowledge of planetary surfaces revealing an immense diversity of morphologies. Being the reflection of the interaction and the competition between geological processes whose modalities are variable from one body to the other, they are widely studied to trace the geological history of the telluric planets. In particular, precise information on the nature of processes and general laws controlling the formation and evolution of landscapes is recorded in the topographic field which can be analyzed as a statistical field. We report in this thesis the results of a comparative study of the statistical properties of the topography of the main bodies of the solar system based on the increasing volume of altimetric and photogrammetric data. Our approach focuses on the notion of scaling law which aims to characterize the symmetries of the field by translating the self-similar nature of natural surfaces: the details of a surface generally look like reduced versions of the whole. We use several methods of analyzing so-called "multifractal" to derive the best statistical model capable of describing the topography in different contexts and propose new indicators of roughness at the global, regional and local scale. We show that in spite of their diversity, the surface of the solar system respects similar statistical laws. In particular, we show that the overall distribution of the slopes of a body generally respects multifractal laws for scales greater than 10-20 km and presents a different statistical structure for the lower scales. Finally, we propose a method for generating spherical synthetic topographies whose statistical properties are similar to the topographies in the solar system
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Sen, Mehmet Ali. « Proper Orthogonal Decomposition Methodology to Understand Underlying Physics of Rough-Wall Turbulent Boundary Layer ». Fogler Library, University of Maine, 2007. http://www.library.umaine.edu/theses/pdf/SenMA2007.pdf.
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Valkonen, Aki Ensio. « Plastic deformation and roughness of free metal surfaces / ». The Ohio State University, 1987. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487330761216718.
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Ergin, Fahrettin Gökhan. « Roughness Induced Transition ». Case Western Reserve University School of Graduate Studies / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=case1121435967.
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Lee, Christopher Gee-Yin. « The design of a towed laser slopemeter system for the measurement of short scale sea waves ». Thesis, University of Southampton, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295613.
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Pike-Wilson, Emily Alexandra. « Flow boiling of R245fa in vertical small metallic tubes ». Thesis, Brunel University, 2014. http://bura.brunel.ac.uk/handle/2438/10625.
Texte intégralRésumé :
The research presented is part of a larger study, dedicated to investigating flow boiling in small to microchannels. The test facility, originally designed by Huo (2005) and since used by Chen (2006) and Mahmoud (2011), has been used to investigate flow boiling of R134a across a range of channel diameters and both seamless cold drawn and welded channels. These previous studies concluded that one of the reasons for discrepancies in reported data is the result of surface characteristics. The objective of this current study is to further investigate the effect of channel characteristics and changing the refrigerant to R245fa. Surface characteristics are investigated with stainless steel, copper and brass channels, all seamless cold drawn and 1.1 mm internal diameter. Experiments using R245fa were initially conducted in the same stainless steel channel used with R134a by Mahmoud (2011). This allowed for the surface characteristics to be negated and the comparison to be based purely on the changes in the thermophysical properties between R134a and R245fa. Experiments were conducted at inlet pressures of 1.85 and 2.45 bar, mass fluxes of 100 – 400 kg/m2s, heat fluxes from 1 – 60 kW/m2 and vapour qualities from 0 – 0.95. The test section surfaces were evaluated based on scanning electron microscopy (SEM) and confocal laser microscopy (CFLSM). SEM allowed for a visual inspection of the channel surface, with clear differences in the surface stricter evident. The surfaces were then compared based on two CFLSM profilers. The values of the surface parameters differed between the two profilers but the same trend was seen, brass being the roughest surface and copper the smoothest. Changes in the surface parameter values were found to be a function of the scan area, scan resolution and cut-off value. A borosilicate glass tube, at the test section exit, allowed for flow visualisation. Mahmoud (2011) reported bubbly, slug, churn and annular flow for R134a, with no effect of hysteresis. Churn and annular flow were present for R245fa with an increasing heat flux. This was a result of a higher surface tension for R245fa which facilitates annular flow. Hysteresis was evident for R245fa, with bubbly, slug, churn and annular flow seen with a decreasing heat flux. The hysteresis effect is a result of nucleation sites activating during the increase in heat flux and remaining activated as the heat flux is decreased. The activation of nucleation sites depends on the size, which was constant due to the same channel being used, and the wall superheat. The wall superheat is lower for R245fa which does not allow for the nucleation sites to be initially activated with an increasing heat flux. The same effect of hysteresis was evident for copper and brass. Differences in the exit vapour quality and heat flux at which flow patterns occurred were seen between the three materials. The heat transfer coefficient varied in both magnitude and trend between R134a and R245fa. Mahmoud (2011) reported an almost constant heat transfer coefficient with vapour quality at a higher magnitude than seen for R245fa. R245fa showed an increasing trend with vapour quality. Peaks in the heat transfer coefficient were seen to be a result of surface flaw, evident when plotting as a function of the axial location. The test section was reversed in orientation, moving the location of the peak from near the entry of the test section to near the exit. A similar heat transfer coefficient peak was seen at the same axial location, near the exit of the test section, confirming that the peak was a result of a surface flaw and a result of the flow developing. The heat transfer coefficient changed in magnitude and trend for copper and brass. The magnitude of the recorded heat transfer coefficient did not follow the same trend as the surface parameters. The heat transfer correlations in literature did not predict the increase in the heat transfer with vapour quality, performing poorly compared with R134a. The best correlation for the prediction of both refrigerants was that of Mahmoud and Karayiannis I (2012). The pressure drop for R245fa was over 300 % higher than that of R134a, with a steeper increase with heat flux. This is attributed to a higher liquid viscosity and lower vapour density for R245fa. The pressure drop was highest for the roughest channel, brass, but lowest for stainless steel which had the intermediate roughness. The smoothest channel, copper, showed the largest difference in the effect of inlet pressure on the measured pressure drop and the roughest surface, brass, the smallest difference. The effect of surface characteristics on pressure drop is greater than the effect of changes in the fluid properties with inlet pressure. Pressure drop correlations performed poorly for R245fa in comparison with R134a, with the majority under predicting the pressure drop. Only one pressure drop correlation included a function of the surface parameters, Del Col et al. (2013), but this correlation under predicted the effect of the surface parameters on pressure drop. There was no one correlation which gave satisfactory results for all three materials.