Dissertations / Theses on the topic 'Elastic layer'
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1
Atay, Mehmet Tarik. "Fracture Of A Three Layer Elastic Panel." Phd thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/3/12606360/index.pdf.
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The panel is symmetrical about both x- and y- axes. The central strip (strip1) of width 2h1 contains a central transverse crack of width 2a on x-axis. The two strips (strip2) contain transverse cracks of width c-b also on x-axis. The panel is subjected to axial loads with uniform intensities p1 and p2 in strip1 and strip2 , respectively at . Materials of all strips are assumed to be linearly elastic and isotropic. Due to double symmetry, only one quarter of the problem and will be considered.
The solutions are obtained by using Fourier transforms both in x and y-directions. Summing several solutions is due to the necessity for sufficient number of unknowns in general expressions in order to be able to satisfy all boundary conditions of the problem. The conditions at the edges of the strips and at the interfaces are satisfied and the general expressions for a three layer panel become expressions for the panel with free edges. Use of remaining boundary conditions leads the formulation to a system of two singular integral equations. These equations are converted to a system of linear algebraic equations which is solved numerically
2
Kushnir, D. V. "Harmonic perturbation of elastic layer with cavity." Thesis, Вид-во СумДУ, 2005. http://essuir.sumdu.edu.ua/handle/123456789/19804.
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3
Sandin, Joakim. "Analysis Methods for Structures with Visco-Elastic Damping Treatment." Thesis, Blekinge Tekniska Högskola, Institutionen för maskinteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-13250.
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During aircraft development, the impact of vibrations is examined and how this affects the aircraft structure under different conditions. Those vibrations can damage electronic equipment that are installed within the fuselage and can even lead to material fatigue within the structure. To reduce vibrations there are two approaches that are preferred to use, installing vibration insulators attached between the structure and the electrical component or change the design of the structure to a stiffer one. Those methods are easiest to implement in an early stage of the development but in later stages, when vibration problems usually are detected, it is too difficult and expensive to do major changes of the structure and there is lack of space to implement vibration insulators. A third method is then to apply passive damping in form of damper mats to surfaces on structures where critical vibrations occurs. The effects on the structural behavior when damper mats are applied to a certain structure are studied in this thesis work. The purpose is to get deeper knowledge about how damper mats can be used to reduce vibrations in aircraft structures. The type of damper mat that is studied is known as Constrained Layer Damping, CLD, which is a sandwich of a visco-elastic material layer and a stiffer constraining material layer. Modelling and simulation methods that are based on commercial FE-software have been developed. The analysis method is based on doing a modal analysis with structural damping taken into account. This makes it possible to predict the overall global damping at each structural mode. The models for damper mats have in this project been verified with experimental testing using typical damper mats. The methodology can be used to predict the behavior of damped structures in order to obtain an effective and lightweight passive damping solution.Under utvecklingen av flygplan undersöks hur vibrationer påverkar flygplansstrukturen under olika förutsättningar. Dessa vibrationer kan skada elektronisk utrustning som är monterad i flygplanskroppen och kan även göra så att materialutmattning uppstår i flygplansstrukturen. För att motverka vibrationer finns det två metoder som är att föredra, antingen att montera vibrationsisolatorer mellan de elektroniska utrustningarna och strukturen eller att ändra designen på strukturer till en styvare. Dessa metoder är enkla att implementera i ett tidigt steg i utvecklingsprocessen men i senare steg, då vibrationsproblem ofta upptäcks, så är det för komplicerat och för dyrt att göra större ändringar på strukturen och så är det ont om plats för att kunna installera vibrations isolatorer. En tredje metod är istället att implementera passiv dämpning i form av dämpningsmattor på ytor av strukturen där kritiska vibrationer uppstår. Effekterna av det strukturella uppförandet när dämpningsmattor är applicerade på en viss struktur har studerats i det här examensarbetet. Syftet är att få en fördjupad kunskap om hur dämpningsmattor kan användas för att reducera vibrationer i flygplan strukturer. Den typ av dämpningsmatta som har studerats är känd som Constrained Layer Damping, CLD, vilken är en sandwich av ett visko-elastiskt lager samt ett styvare lager. Modellerings och simuleringsmetoder som är baserade på kommersiella FE-mjukvaror har utvecklats. Analysmetoderna är baserade på att utföra modalanalys tillsammans med strukturell dämpning. Detta möjliggör att förutse den övergripande dämpningen vid varje strukturell mod. Modellerna för dämpningsmattorna har i det här projektet verifierats med experimental testning av typiska dämpningsmattor. Metodiken kan användas till att prediktera beteendet av dämpade strukturer för att uppnå en effektiv och lättviktig passiv dämpningslösning.
4
Mert, Oya. "Frictionless Double Contact Problem For An Axisymmetric Elastic Layer Between An Elastic Stamp And A Flat Support With A Circular Hole." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613164/index.pdf.
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This study considers the elastostatic contact problem of a semi-infinite cylinder. The cylinder is compressed against a layer lying on a rigid foundation. There is a sharp-edged circular hole in the middle of the foundation. It is assumed that all the contacting surfaces are frictionless and only compressive normal tractions can be transmitted through the interfaces. The contact along interfaces of the elastic layer and the rigid foundation forms a circular area of which outer diameter is unknown. The problem is converted into the singular integral equations of the second kind by means of Hankel and Fourier integral transform techniques. The singular integral equations are then reduced to a system of linear algebraic equations by using Gauss-Lobatto and Gauss-Jacobi integration formulas. This system is then solved numerically. In this study, firstly, the extent of the contact area between the layer and foundation are evaluated. Secondly, contact pressure between the cylinder and layer and contact pressure between the layer and foundation are calculated for various material pairs. Finally, stress intensity factor on the edge of the cylinder and in the end of the sharp-edged hole are calculated.
5
Zhao, Xujun. "Surface loading and rigid indentation of an elastic layer with surface energy effects." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/12598.
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With the growing interest in nanotechnology, it is becoming important to understand the nanoscale mechanics to achieve successful design and fabrication of nanoscale devices. However, the classical continuum theory is not directly applicable to the analysis of nanoscale domains due to size-dependent behavior of nanostructures. Since the surface-to-volume ratio of a nanoscale domain is relatively high compared to that of a macro-scale domain, the energy associated with atoms at or near a free surface is different from that of atoms in the bulk. The effect of surface free energy therefore needs to be considered. Ultra-thin film/substrate systems, which are encountered in applications involving nanocoatings, nanotribology and material characterization based on nano-indentation, may be analyzed using modified continuum elasticity theory incorporating surface energy effects.
This thesis presents a set of analytical solutions for elastic field of a layer of nanoscale thickness bonded to a rigid base under surface loading and indentation by a rigid body. Surface energy effects are accounted for by using Gurtin-Murdoch elasticity theory. Fourier and Hankel integral transforms are used to solve the two- and three- dimensional boundary-value problems involving non-classical boundary conditions associated with the generalized Young-Laplace equation. In the case of a two-dimensional semi-infinite medium, the solutions can be expressed in closed form. The elastic field is found to depend on the layer thickness and surface elastic constants, and the influence of surface energy is shown to be more significant under a horizontal load than under a vertical load. A characteristic length scale related to the surface material properties can be identified for the present class of problems. The solution for the indentation problem is considered for flat, conical and spherical rigid indenters. The mixed boundary-value problem corresponding to a rigid indenter is formulated in terms of a dual integral equation system that is solved by using numerical quadrature. Selected numerical results are presented to show the influence of the indenter shape, surface properties and size-dependency of response.
6
Baudendistel, Craig M. "Effect of a Graded Layer on the Plastic Dissipation During Mixed-Mode Fatigue Crack Growth on Ductile Bimaterial Interfaces." Wright State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=wright1368797452.
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7
Pahlow, Markus. "Atmospheric boundary layer dynamics and inversion technologies to obtain extinction coefficient profiles in the atmosphere from elastic lidar." Available to US Hopkins community, 2002. http://wwwlib.umi.com/dissertations/dlnow/3080740.
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8
Amirova, Svetlana R. "The influence of a simple shear deformation on a long wave motion in a pre-stressed incompressible elastic layer." Thesis, Keele University, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.491831.
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9
Gupta, Shakti Singh. "Elastic constants from molecular mechanics simulations of frequencies of free-free single-walled carbon nanotubes and clamped single-layer graphene sheets." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/27576.
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Elastic constants of single-walled carbon nanotubes (SWCNTs) and single-layer graphene sheets (SLGSs) are determined by studying their free vibration characteristics using molecular mechanics (MM) simulations with the MM3 potential and finding their equivalent continuum structures (ECSs). The computational framework has been validated by comparing the presently computed basal plane stiffness and frequencies of radial breathing modes (RBMs) with those available in the literature.
We have considered armchair, zigzag and chiral SWCNTs of aspect ratios (length/ diameter in the unloaded relaxed configuration) ranging from 2 to 15. The wall thickness of ECSs of SWCNTs is determined by applying continuum theories, viz., beam, shell and 3D-linear elasticity to ECSs and equating their frequencies with those of SWCNTs obtained from the MM simulations. An expression for the wall thickness of an ECS of a SWCNT in terms of its chiral indices is deduced. The wall thickness of an ECS of a SWCNT is found to increase with an increase in its radius and to saturate at 1.37 Ã for the radius exceeding 15 Ã . Poissonâ s ratio for zigzag SWCNTs decreses with an increase in the tube radius, but that for armchair SWCNTs exhibits the opposite trend. For the same radius, Poissonâ s ratio of a chiral SWCNT is slightly more than that for an armchair tube but a little less than that for a zigzag tube. For zigzag SWCNTs, frequencies of inextensional modes of vibration saturate with an increase in the circumferential wave number but those of their ECSs do not.
The MM simulations of uniaxial tensile deformations of SLGSs of aspect ratios (length/width) ~ 10 give the basal plane stiffness of ~ 340 N/m. The MM simulations of free vibrations of clamped SLGSs and the analysis of vibrations of their ECSs with a continuum theory gives a wall thickness of ~ 1 Ã for a SLGS.Ph. D.
10
RADAMPOLA, Senanie Sujeewa, and senanie s. radampola@mainroads qld gov au. "EVALUATION AND MODELLING PERFORMANCE OF CAPPING LAYER IN RAIL TRACK SUBSTRUCTURE." Central Queensland University. Centre for Railway Engineering, 2006. http://library-resources.cqu.edu.au./thesis/adt-QCQU/public/adt-QCQU20060817.115415.
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In the design of rail track structures where the subgrade cannot achieve the desired
capacity, enabling the required standard of track geometry to be maintained for the speed,
axle load and tonnage to be hauled, a capping layer of granular material is placed
between the natural ground or the embankment fill material and the ballast to protect the
underlying weaker layers.
In spite of the important role played by the capping layer, very little research has been
carried out on its performance. The current practice of design of the capping layer,
therefore, is based on working stress philosophy where reduced levels of stresses are
assumed not to degrade the subgrade. Even on tracks containing a thick ballast layer that
ensures allowable levels of working stress the subgrade has been found to have
permanently deformed. Design of capping layers based on plastic deformation,
therefore, appears appropriate. This thesis aims at determining the load levels that cause
detrimental plastic deformation in the capping layer.
The suite of material properties that characterise plastic deformations of capping layer is
neither readily available nor easily determined. This thesis proposes a cheaper method of
evaluating a range of capping layer material properties using penetration tests on
specimens contained in California Bearing Ratio (CBR) test moulds coupled with a finite
element modelling based back calculation technique. The suite of material properties
thus determined are used for the simulation of the behaviour of capping layers under the
boundary and loading conditions similar to those in practice. The predicted results are
validated using laboratory experiments on large size capping layer specimens.
11
Макуха, Зінаїда Миколаївна, Зинаида Николаевна Макуха, Zinaida Mykolaivna Makukha, Юрій Михайлович Шабельник, Юрий Михайлович Шабельник, Yurii Mykhailovych Shabelnyk, Ірина Михайлівна Пазуха, et al. "Strain Properties of Nanodimentional Thin Film Systems Based on Ag and Co." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/34874.
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The results of research strain deformation properties of thin films Ag, Co and two-layer film systems
Ag/Co in the range of deformation l 0 – 1% were presented. The plastic deformation in Co layer caused
a similar deformation in the entire film system, even if the strain range of Ag layer is not reached the limits
of the transition elastic/plastic deformation.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/34874
12
Badger, C. "A Study of the Efficacy of Multi-Layer Bandaging and Elastic Hosiery in the Treatment of Lymphoedema, and their Effects on the Swollen Limb." Thesis, Institute of Cancer Research (University Of London), 1997. http://publications.icr.ac.uk/9721/.
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Three factors were identified as having a potentially adverse effect on the outcome of treatment when elastic hosiery was used as the main means of containing lymphoedema: 1. the size of the swollen limb; 2. the effective distribution of interface pressures - determined by the shape of the swollen limb. 3. the composition of the subcutaneous tissues; Clinical experience suggested that the negative impact of these three factors could be overcome by introducing a course of multi-layer bandaging before fitting elastic hosiery. A series of studies was carried out to determine methods of measurement. A non-invasive method of measuring the impact of treatment on the subcutaneous tissues of swollen limbs was investigated using Computed Tomography. Various methods of measuring the volume of limbs were studied and compared and a suitable method selected for the purposes of this study. An objective method of measuring differences in the shapes of normal and contralateral swollen limbs was established and the impact of changes in shape on the profile of interface pressures under bandages and hosiery was also assessed. A randomised, controlled treatment trial was then conducted to investigate the relative impact of two different regimes of treatment on the size and shape of unilaterally swollen limbs over a period of six months. The two treatment regimes were: a course of multi-layer bandaging followed by the application of elastic hosiery elastic hosiery used on its own. Two main outcomes were assessed at prescribed intervals over the six months: limb volume and limb shape. The results revealed that the reduction in limb volume in the bandage plus hosiery group was significantly greater at each assessment than that achieved in the hosiery alone group. By the end of the trial, significantly greater numbers of patients had their distorted limbs returned to a more normal shape by bandaging plus hosiery than by hosiery alone.
13
Wood, Joseph D. "Brittle mixed-mode cracks between linear elastic layers." Thesis, Loughborough University, 2017. https://dspace.lboro.ac.uk/2134/24177.
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Original analytical theories are developed for partitioning mixed-mode fractures on rigid interfaces in laminated orthotropic double cantilever beams (DCBs) based on 2D elasticity by using some novel methods. Note that although the DCB represents a simplified case, it provides a deep understanding and predictive capability for real applications and does not restrict the analysis to a simple class of fracture problems. The developed theories are generally applicable to so-called 1D fracture consisting of opening (mode I) and shearing (mode II) action only with no tearing (mode III) action, for example, straight edge cracks, circular blisters in plates and shells, etc. A salient point of the methods is to first derive one loading condition that causes one pure fracture mode. It is conveniently called the first pure mode. Then, all other pure fracture modes can be determined by using this pure mode and the property of orthogonality between pure mode I modes and pure mode II modes. Finally, these 2D-elasticity-based pure modes are used to partition mixed-mode fractures into contributions from the mode I and mode II fracture modes by considering a mixed-mode fracture as the superposition of pure mode I and mode II fractures. The partition is made in terms of the energy release rate (ERR) or the stress intensity factor (SIF). An analytical partition theory is developed first for a DCB composed of two identical linear elastic layers. The first pure mode is obtained by introducing correction factors into the beam-theory-based mechanical conditions. The property of orthogonality is then used to determine all other pure modes in the absence of through-thickness-shear forces. To accommodate through-thickness shear forces, first two pure through-thickness-shear-force pure modes (one pure mode I and one pure mode II) are discovered by extending a Timoshenko beam partition theory. Partition of mixed-mode fractures under pure through-thickness shear forces is then achieved by using these two pure modes in conjunction with two thickness-ratio-dependent correction factors: (1) a shear correction factor, and (2) a pure-mode-II ERR correction factor. Both correction factors closely follow a normal distribution around a symmetric DCB geometry. The property of orthogonality between all pure mode I and all pure mode II fracture modes is then used to complete the mixed-mode fracture partition theory for a DCB with bending moments, axial forces and through-thickness shear forces. Fracture on bimaterial interfaces is an important consideration in the design and application of composite materials and structures. It has, however, proved an extremely challenging problem for many decades to obtain an analytical solution for the complex SIFs and the crack extension size-dependent ERRs, based on 2D elasticity. Such an analytical solution for a brittle interfacial crack between two dissimilar elastic layers is obtained in two stages. In the first stage the bimaterial DCB is under tip bending moments and axial forces and has a mismatch in Young s modulus; however, the Poisson s ratios of the top and bottom layers are the same. The solution is achieved by developing two types of pure fracture modes and two powerful mathematical techniques. The two types of pure fracture modes are a SIF-type and a load-type. The two mathematical techniques are a shifting technique and an orthogonal pure mode technique. In the second stage, the theory is extended to accommodate a Poisson s ratio mismatch. Equivalent material properties are derived for each layer, namely, an equivalent elastic modulus and an equivalent Poisson s ratio, such that both the total ERR and the bimaterial mismatch coefficient are maintained in an alternative equivalent case. Cases for which no analytical solution for the SIFs and ERRs currently exist can therefore be transformed into cases for which the analytical solution does exist. It is now possible to use a completely analytical 2D-elasticity-based theory to calculate the complex SIFs and crack extension size-dependent ERRs. The original partition theories presented have been validated by comparison with numerical simulations. Excellent agreement has been observed. Moreover, one partition theory is further extended to consider the blister test and the adhesion energy of mono- and multi-layered graphene membranes on a silicon oxide substrate. Use of the partition theory presented in this work allows the correct critical mode I and mode II adhesion energy to be obtained and all the experimentally observed behaviour is explained.
14
Andrews, Gordon Todd. "Elastic and structural properties of supported porous silicon layers." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0004/NQ42470.pdf.
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15
Chow, Leung Choi. "Damping of plates with attached fluid or elastic layers." Thesis, University of Southampton, 1987. https://eprints.soton.ac.uk/52269/.
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The thesis is in three parts. The first is a theoretical and experimental investigation of squeeze-film damping on plates separated by gas, for example. air. For this study a thick excited plate was attached to an auxiliary plate parallel to the surface, thereby trapping a thin layer of air. Relative vibration of these two plates pumps this air at high velocities, resulting in energy loss due to air viscosity. The theory employs an impedance approach to predict the loss factor of the coupled plates. Below the excited plate critical frequency the damping is controlled by gas pumping, while above the critical frequency the plate couplings are the controlling factor. Theoretical predictions were compared with experimental measurements. A brief examination of the bolting effect on the loss factor was also conducted. The second part is a theoretical and experimental investigation of squeeze-film damping on plates separated by heavy fluid, for example, oil. The attached plate can be either perforated or unperforated. The ratio of fluid dynamic viscosity to density controls the losses. Viscosity was artificially increased by inserting porous materials into the oil layer. The properties of the porous materials were obtained from macroscopic flow resistance measurements. Theoretical modelling of the loss factor of these layered configurations with oil alone and with oil impregnated porous material were conducted using the impedance approach and compared with experimental measurements. The third part is a theoretical and experimental investigation of granular infill damping treatments on plates. Sand was used in the experiments and the bulk and shear elastic constants were measured when the sand was subjected to varying hydrostatic pressures. Both the dilatational and rotational motions in the granular layer were considered and the loss factor predictions were compared with measured results.
16
Knight-Percival, Alexander Stephen. "Low energy super-elastic scattering from laser excited calcium." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/low-energy-superelastic-scattering-from-laser-excited-calcium(e37927e1-97d6-41eb-9a88-06109757c1a0).html.
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Super-elastic scattering measurements were taken from calcium using the spectrometer described in this thesis. Calcium atoms were excited from the 41S0 ground state to the 41P1 excited state using a high resolution continuous wave laser set to a wavelength of 423 nm. A beam of electrons with a well defined energy was directed at the laser excited calcium atoms. The excited state was then described by a set of atomic collision parameters P_lin, gamma and L_perp, found from measuring scattered electrons as a function of scattering angle and energy. The scattering chamber was held at a pressure of 3x10 -7 mbar. A resistively heated oven operating at 800 degrees celsius produced a well collimated calcium atomic beam containing the calcium atoms. The electron gun generated a beam of electrons of well defined momentum, whose energy could be changed from ~5 eV to over 100 eV. At energies less than 20 eV the rate of super-elastic electrons was very low, and so modifications were made to the spectrometer to automate data collection for long operating times without the need for user intervention. A new digitally controlled DC voltage supply was constructed to deliver the correct potentials to the electron-optical elements in the spectrometer. An internal microcontroller enabled supply voltages to be programmed either using the front panel or via an attached computer for automatic optimisation of spectrometer voltages using a simplex algorithm. New data was collected for the collision parameters over the full accessible angular range from 25--140 degrees, at energies of 8, 10 and 65 eV. The data at 8 and 10 eV was taken so as to resolve differences between theoretical models at low energies. Comparisons were made with a relativistic distorted wave calculation, an R-matrix calculation, an R-matrix calculation using B-splines and a convergent close coupling theory. A 2 eV discrepancy was identified in the measured electron energy which was thought to be due to stray fields in the chamber. With this considered, convergent close coupling predictions were found to be in excellent agreement with the experimental data.
17
Sekerak, Edward Michael 1959. "Fluorescence and elastic scattering from laser dye-filled capillaries." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277121.
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We investigated the elastic scattering and fluorescence from laser dye solutions inside 5000, 1100, and 96.5 micron inner-diameter hollow-core capillaries. Incident 4416 A laser illumination of Coumarin 7 dye dissolved in ethanol caused fluorescence from approximately 4600 to 6000 A. This was studied over an angular range from 0° to 360°. A light scattering nephelometer coupled with a spectrometer gave intensity measurements as functions of wavelength (at fixed detection angles) and angle (at fixed wavelengths), while the illumination source, dye-filled capillary, and detector remained stationary. We saw capillary size and detection-angle dependence of the fluorescence and elastic scattering. Results show that angular variations of the elastic scattering and emitted fluorescence can be used to determine an optimum detection angle from the capillary with respect to the incident illumination direction. This work is important in the design and execution of Capillary Zone Electrophoresis (CZE) experiments.
18
Pinarbasi, Seval. "A New Formulation For The Analysis Of Bonded Elastic Layers." Phd thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608310/index.pdf.
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Elastic layers bonded to reinforcing sheets are widely used in many engineering applications, e.g., as elastic foundations to machinery, as seismic isolators to structures, etc. Because of its practical importance, the behavior of bonded elastic layers under some basic deformation modes (e.g., compression, bending and shear modes) has attracted the attention of many researchers. However, the analytical works available in literature involve, with the object of obtaining design formulas, many simplifying assumptions. In this dissertation, a new formulation is developed for the analysis of bonded elastic layers, which removes most of the assumptions used in the earlier formulations. Since the displacement boundary conditions are included in the formulation itself, there is no need to start the formulation with some assumptions on stress and/or displacement distributions or with some limitations on geometrical and/or material properties. For this reason, the solutions derived from this formulation are valid not only for &ldquothin&rdquo
layers of strictly/nearly incompressible materials but also for &ldquo
thick&rdquo
layers and/or compressible materials. The advanced solutions obtained within the framework of the new formulation are used to study the behavior of bonded elastic layers under basic deformation modes. The effects of three key parameters, shape factor, Poisson&rsquo
s ratio and reinforcement flexibility, on effective layer moduli, displacement/stress distributions, and location/magnitude of maximum stresses are investigated. It is shown that the stress assumptions of the &ldquo
pressure&rdquo
method are inconsistent with the results obtained for thick layers and/or compressible materials and/or flexible reinforcements, and that the assumption &ldquo
plane sections remain plane&rdquo
is not valid, in general.
19
Lee, James Jin-Wu. "Fracture of brittle layers joined with high elastic modulus composite." College Park, Md. : University of Maryland, 2007. http://hdl.handle.net/1903/6804.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2007.Thesis research directed by: Material Science and Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
20
Nicely, Clinton R. "Transverse Vibrations of Multi-Walled Nanotubes with Visco-Elastic Layers." University of Akron / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=akron1227460546.
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Jhumka, Sarah. "Super-elastic scattering from laser excited calcium and silver atoms." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/superelastic-scattering-from-laser-excited-calcium-and-silver-atoms(eef2bfaf-5c3d-4044-a751-d0f34073a8c7).html.
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Paeng, Dong-Guk 1966. "Normal mode acoustic scattering considering elastic layers over a half space." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/43546.
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Chebakov, Roman. "Asymptotic models for elastic solids taking into account nonlocal boundary layers." Thesis, Keele University, 2018. http://eprints.keele.ac.uk/5103/.
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The thesis is aimed at asymptotic analysis of the near-surface boundary layers in non-locally elastic solids. The dynamic response of a homogeneous half-space with a traction-free surface is analysed for a nonlocal exponential kernel. A typical wave-length is assumed to be much greater than the length scale associated with internal properties of the elastic medium. The dominant effect of the boundary layer is revealed. The leading order long-wave approximations are shown to coincide with the `local' problem for a half-space having a vertical inhomogeneity localised near the sur-face. An explicit correction to the classical boundary conditions on the surface of a `locally' elastic half-space is obtained by asymptotic analysis of the near-surface behaviour. The order of the derived correction exceeds that of the well-known correction to the governing differential equations of Eringen's model, e.g., see [44]. The obtained refined boundary conditions enable evaluating the interior stress-strain solution outside a narrow boundary layer localised near the surface. As examples, the effect of nonlocal elastic phenomena on the Rayleigh wave speed and also a plane strain problem of a moving load on the surface of a half-space are studied. In addition, a thin layer with a traction-free upper face, subjected to prescribed displacements along its lower face, is investigated. Further, the 3D dynamic equations in nonlocal elasticity for a thin plate are considered, assuming the plate thickness to be much greater than a typical microscale size. The long-wave low-frequency approximations are obtained for both plate bending and extension. Boundary layers characteristic of nonlocal behaviour are revealed near the plate faces. It is established that taking into account the effect of the boundary layers results in first-order corrections to the bending and extensional stiffness in the classical 2D plate theory.
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Гутак, О. І. "Удосконалення технології інтенсифікації видобутку вуглеводнів шляхом різночастотного імпульсно-хвильового впливу на нафтогазонасичені породи." Thesis, Івано-Франківський національний технічний університет нафти і газу, 2013. http://elar.nung.edu.ua/handle/123456789/4449.
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Дисертація присвячена проблемі удосконалення технологій інтенсифікації видобутку вуглеводнів імпульсно-хвильовими методами впливу на нафтогазонасичені породи. У роботі проведено дослідження механізму розповсюдження акустичних хвиль різних частот в насичених середовищах, характерних для родовищ нафти і газу. Отримано рівняння різночастотної суперпозиції циліндричних пружних хвиль, описано явище утворення різнецевої низькочастотної хвилі биття та проведено оцінку їх впливу на продуктивний пласт в залежності від частот та віддалі між випромінювачами. Експериментально підтверджено утворення низькочастотної хвилі внаслідок взаємодії високочастотних хвиль діапазону 50 Гц - 20 кГц з різницею в частоті до 5% в умовах насипної насиченої моделі пласта.
Досліджено характер зміни меніску на межі поділу двох фаз внаслідок дії пружних коливань, проведено теоретичну оцінку їх впливу на динамічну зміну капілярного тиску. Встановлено, що вплив пружними коливаннями інтенсивністю 0,01 Вт/см2 під час фільтрації нафтоводяної суміші в насипній моделі пласта призводить до збільшення фазової проникності для нафти в’язкістю 50 мПа•с на 25 %, а після повного обводнення продукції, дія такими коливаннями призводить до додаткового вилучення залишкової нафти на 5-11%. Теоретичними та експериментальними дослідженнями встановлено, що періодичне збільшення та зменшення тиску в пласті, яке виникає внаслідок впливу пружними коливаннями, призводить до додаткового розгазування нафти, в тому числі за умови повного виділення газу при поточному пластовому тиску. Встановлено, що вплив пружними коливаннями на процес руху рідини в капілярі призводить до збільшення швидкості руху, що дає підстави припускати аналогічний ефект в пористому середовищі. Розроблено технології різночастотного імпульсно-хвильового впливу на нафтогазонасичені породи з використанням пристроїв з декількома випромінювачами, в тому числі різночастотними, які дозволять диференційовано обробляти ближню та віддалену зони пласта, досягаючи при цьому додаткового розгазування та збільшення фазової проникності для нафти в умовах обводнення пласта. Промислові випробування розроблених технологій підтвердили їх ефективність та перспективність широкого впровадження в нафтогазовидобувних свердловинах.Диссертация посвящена проблеме усовершенствования технологии интенсификации добычи углеводородов импульсно-волновыми методами воздействия на нефтегазонасыщенные породы. В работе проведено исследование механизма распространения акустических волн различных частот в насыщенных средах, характерных для месторождений нефти и газа. Получено уравнение разночастотной суперпозиции цилиндрических упругих волн, описано явление образования разностной низкочастотной волны биения и проведена оценка их влияния на продуктивный пласт в зависимости от частот и расстояния между излучателями. Экспериментально подтверждено образование низкочастотной волны вследствие взаимодействия высокочастотных волн диапазона 50 Гц - 20 кГц с разницей в частоте до 5% в условиях насыпной насыщенной модели пласта. Акустические сигналы получали одновременно двумя способами с помощью геофона и сейсмодатчика типа СВ 5 по двухканальной линии и регистрировали на персональном компьютере программой SpectraPLUS. Проведена оценка градиента давления при волновом воздействии, который возникает в призабойной зоне пласта в процессе фильтрации флюида. Нефти многих месторождений характеризуются повышенным содержанием высокомолекулярных парафиновых углеводородов, которые с изменением термобарических условий кристаллизируются в твердую фазу, в результате чего образуются сложные коллоидно-дисперсные системы, которые приобретают вязкопластические свойства. Установлено, что одновременное действие гидродинамического градиента давления и акустического градиента давления, приводит к преодолению предельного напряжения сдвига коллоидно-дисперсных систем, причём, при длительном волновом воздействии частично разрушается их структура и снижается предельное напряжение сдвига. Исследовано характер изменения мениска на границе двух фаз вследствие воздействия упругих колебаний, проведено теоретическую оценку их влияния на динамическое изменение капиллярного давления. Установлено, что влияние упругими колебаниями интенсивностью 0,01 Вт/см2 при фильтрации нефтеводяной смеси в насыпной модели пласта приводит к увеличению фазовой проницаемости для нефти вязкостью 50 мПа•с на 25 %, а после полного обводнения продукции, действие такими колебаниями приводит к дополнительному извлечению остаточной нефти на 5-11%. Теоретическими и экспериментальными исследованиями установлено, что периодическое увеличение и уменьшение давления в пласте, которое возникает вследствие воздействия упругими колебаниями, приводит к дополнительному разгазированию нефти, в том числе при условии полного выделения газа при текущем пластовом давлении. Установлено, что влияние упругими колебаниями на процесс движения жидкости в капилляре приводит к увеличению скорости движения, что даёт основания предполагать аналогичный эффект в пористой среде. Получено зависимости между расходом жидкости через капилляр диаметром 4 мм и частотой упругих колебаний диапазона 22-45 Гц на стенки капилляра для воды и водных растворов КМЦ с вязкостью от 1 до 10 мПа•с. Разработаны технологии разночастотного импульсно-волнового воздействия на нефтегазонасыщенные породы с использованием устройств с несколькими излучателями, в том числе разночастотными, которые позволят дифференцированно обрабатывать ближнюю и отдаленную зоны пласта, достигая при этом дополнительного разгазирования и увеличение фазовой проницаемости для нефти в условиях обводнения пласта. Промышленные испытания разработанных технологий подтвердили их эффективность и перспективность широкого внедрения в нефтегазодобывающих скважинах.
The thesis is devoted to the problem of improvement enhanced hydrocarbons recovery technology using the pulse-wave treatments in the oil and gas saturated rocks. Evaluation study of the different frequencies acoustic waves propagation mechanism in saturated environments typical for oil and gas was presented in the paper. The equation of different frequency interference of cylindrical elastic waves in the reservoir and an assessment of their impact was obtained. The phenomenon of the difference low-frequency waves beating formation and assessed their impact on the productive layer, depending on the frequency and distance between the emitters, was described. The formation of low-frequency waves by the interaction of high-frequency waves in the range of 50 Hz - 20 kHz with a difference in the frequency of 5% in sand packed saturated model was experimentally confirmed. The variation of the meniscus on the two phase border due to the impact of elastic vibrations was investigated. Was determined the effect of elastic vibration treatment with intensity 0.01 W/cm2 at filtering oil-and-water mixture in the sand packed model leads to increasing oil relative permeability at 25% for oil with viscosity of 50 mPa•s, and in case of full watering leads to additional remaining oil recovery at 5-11%. Theoretical and experimental evaluations shows that as a result of elastic vibration treatment the effect of repetitive pressure increasing and decreasing leads to the additional oil degasification, including completely degassing at the current reservoir pressure. Effect of the elastic vibration treatment to the fluid flow process in the capillary leads to the velocity increasing was experimentally founded. It allows suggesting that similar effects take place in porous media. The different frequencies pulse wave treatment technology on oil and gas saturated rocks using devices with several emitters, including different frequencies emitters, that will differentially handle near and remote well bore zone, which allows achieving additional degasification and oii relative permeability increasing in case of watering. Industrial tests of the developed technologies proved their effectiveness and promising wide introduction into the oil and gas wells.
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Charitat, Thierry. "Contributions théorique et expérimentale à l'étude des propriétés élastiques de systèmes physiques "inspirés" de la biologie." Université Joseph Fourier (Grenoble ; 1971-2015), 1997. http://www.theses.fr/1997GRE10179.
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La premiere partie de cette these est consacree a l'etude theorique des proprietes elastiques de reseaux de passages connectant des bicouches phospholipidiques. Elle a ete motivee par des observations experimentales faites par michalet et al. Le calcul que nous proposons prend en compte la conservation du volume du systeme. Il nous a permis de montrer que ces reseaux sont destabilises par les deformations de cisaillement, qui sont energetiquement plus favorables que les deformations de compression. La contrainte de volume permet aussi de determiner la densite de passages dans ces systemes. Enfin, la generalisation aux systemes multilamellaires de la notion de courbure constante introduite par michalet et al, met en evidence un comportement collectif remarquable des passages. La seconde partie concerne l'etude des interactions entre un peptide (la penetratine) et les phospholipides de la membrane cellulaire. Celle-ci est modelisee par une bicouche deposee sur un substrat solide par la methode de langmuir-blodgett. L'essentiel du travail expose dans cette these a consiste a developper un protocole experimental permettant de caracteriser ces bicouches par reflectivite de neutrons. Il a ainsi ete possible d'observer pour la premiere fois des quadricouches controlees de dspc. Enfin, les premiers resultats que nous avons obtenus sur l'etude de l'influence de la penetratine, montrent une influence importante du peptide sur la bicouche. La derniere partie de ce travail s'interesse aux proprietes elastiques d'un fil ferme spontanement courbe. Elle s'inscrit dans le cadre de la theorie classique de l'elasticite, et fait intervenir un couplage local entre la courbure et la torsion qui permet d'expliquer l'existence d'un etat metastable observable sur une rondelle de caoutchouc. Une application a l'adn est envisagee.
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Karásková, Romana. "Funkční zkoušení recyklátů do pozemních komunikací." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2012. http://www.nusl.cz/ntk/nusl-225419.
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The work is divided into two parts. The practical part deals with the testing properties of soils which are using in new road in Nové Město na Moravě and the testing of recycled materials which could replace this soils from road. The aim this part is to obtain values of elastic modulus which are then inserted into the computational model. In the second part of work the track road is modeled in the software which uses the Finite Element Method to calculate and respect physical properties of different materials and a load. The result of work will be studies with comparison of displacement and stress generated to using existing soils and recycled materials.
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Ravish, Masti Sarangapany. "Vibration damping analysis of cylindrical shells partially coated withconstrained visco-elastic layers." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B31242169.
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Bao, Chunyan. "Acoustic scattering by cylindrical scatterers comprising isotropic fluid and orthotropic elastic layers." Diss., Kansas State University, 2016. http://hdl.handle.net/2097/32847.
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Doctor of PhilosophyDepartment of Mechanical and Nuclear Engineering
Liang-Wu Cai
Acoustic scattering by a cylindrical scatterer comprising isotropic acoustic and orthotropic elastic layers is theoretically solved. The orthotropic material is used for the scattering problem because the sound speeds along radial and tangential axes can be different; which is an important property for acoustic cloaking design. A computational system is built for verifying the solutions and conducting simulations. Scattering solutions are obtained based on two theoretical developments. The first one is exact solutions for elastic waves in cylindrically orthotropic elastic media, which are solved using Frobenius method. The second theoretical development is a set of two canonical problems for acoustic-orthotropic-acoustic media. Based on the two theoretical developments, scattering by three specially selected simple multilayer scatterers are analyzed via multiple-scattering approach. Solutions for the three scatterers are then used for solving a “general” multilayer scatterer through a recursive solution procedure. The word “general” means the scatterer can have an arbitrary number of layers and each layer can be either isotropic acoustic or orthotropic elastic. No approximations have been used in the process. The resulting analytically-exact solutions are implemented and verified. As an application example, acoustic scattering by a scatterer with a single orthotropic layer is presented. The effects on the scattering due to changing parameters of the orthotropic layer are studied. Acoustic scattering by a specially designed multilayer scatterer is also numerically simulated. Ratios of the sound speeds of the orthotropic layers along r and θ directions are defined to satisfy the requirement of the Cummer-Schurig cloaking design. The simulations demonstrate that both the formalism and the computational implementation of the scattering solutions are correct.
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Chirita, Mihail Relu. "Brillouin light scattering study of elastic and magnetic excitations in supported layers /." The Ohio State University, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=osu1488199501403201.
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Alrumaih, Wail Saad. "A novel tuned visco-elastic damper for floor vibration abatement." University of Dayton / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1245387294.
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Ravish, Masti Sarangapany. "Vibration damping analysis of cylindrical shells partially coated with constrained visco-elastic layers." Hong Kong : University of Hong Kong, 2001. http://sunzi.lib.hku.hk/hkuto/record.jsp?B23000867.
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Hurlebaus, Stefan. "Laser generation and detection techniques for developing transfer functions to characterize the effect of geometry on elastic wave propagation." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/20742.
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Guo, Shiyan. "Asymptotic Analysis of Wave Propagation through Periodic Arrays and Layers." Thesis, Loughborough University, 2011. https://dspace.lboro.ac.uk/2134/8886.
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In this thesis, we use asymptotic methods to solve problems of wave propagation through infinite and finite (only consider those that are finite in one direction) arrays of scatterers. Both two- and three-dimensional arrays are considered. We always assume the scatterer size is much smaller than both the wavelength and array periodicity. Therefore a small parameter is involved and then the method of matched asymptotic expansions is applicable. When the array is infinite, the elastic wave scattering in doubly-periodic arrays of cavity cylinders and acoustic wave scattering in triply-periodic arrays of arbitrary shape rigid scatterers are considered. In both cases, eigenvalue problems are obtained to give perturbed dispersion approximations explicitly. With the help of the computer-algebra package Mathematica, examples of explicit approximations to the dispersion relation for perturbed waves are given. In the case of finite arrays, we consider the multiple resonant wave scattering problems for both acoustic and elastic waves. We use the methods of multiple scales and matched asymptotic expansions to obtain envelope equations for infinite arrays and then apply them to a strip of doubly or triply periodic arrays of scatterers. Numerical results are given to compare the transmission wave intensity for different shape scatterers for acoustic case. For elastic case, where the strip is an elastic medium with arrays of cavity cylinders bounded by acoustic media on both sides, we first give numerical results when there is one dilatational and one shear wave in the array and then compare the transmission coefficients when one dilatational wave is resonated in the array for normal incidence. Key words: matched asymptotic expansions, multiple scales, acoustic scattering, elastic scattering, periodic structures, dispersion relation.
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Johnson, Anthony N. "Development of a three dimensional perfectly matched layer for transient elasto-dynamic analyses." Monterey, Calif. : Naval Postgraduate School, 2006. http://handle.dtic.mil/100.2/ADA462592.
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Dissertation (Ph.D. in Applied Mathematics)--Naval Postgraduate School, December 2006.Dissertation Supervisor(s): Scandrett, Clyde ; Baker, Steve. "December 2006." Description based on title screen as viewed on Sept. 6, 2007. Includes bibliographical references (p. 131-134). Also available in print.
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Venter, Gerhardus. "Sensitivity analysis with respect to elastic boundary conditions and laser spatial variables within experimental spatial dynamic modeling." Thesis, This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-01102009-063257/.
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Lhotellier, Frederic C. "Matrix-fiber stress transfer in composite materials elasto-plastic model with an interphase layer." Thesis, Virginia Tech, 1987. http://hdl.handle.net/10919/40934.
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The matrix-fiber stress transfer in glass/epoxy composite materials was studied using analytical and experimental methods. The mathematical model that was developed calculates the stress fields in the fiber, interphase, and neighboring matrix near a fiber break. This scheme takes into account the elastic-plastic behavior of both the matrix and the interphase, and it includes the treatment of stress concentration near the discontinuities of the fibers. The radius of the fibers and the mechanical properties of the matrix were varied in order to validate the mathematical model. The computed values for the lengths of debonding, plastic deformation, and elastic deformation in the matrix near the fiber tip were confirmed by measurements taken under polarized light on loaded and unloaded single fiber samples. The fiber-fiber interaction was studied experimentally using dog-bone samples that contained seven fibers forming an hexagonal pattern.
Master of Science
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Rocadenbosch, Burillo Francesc. "Lidar sensing of the atmosphere: receiver design and inversion algorithms for an elastic system." Doctoral thesis, Universitat Politècnica de Catalunya, 1996. http://hdl.handle.net/10803/6909.
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LIDAR es un acrónimo de LIght Detection And Ranging. En la presente tesis, se usan técnicas basadas en lidar elástico para monitorizar la atmósfera remotamente y derivar información cuantitativa acerca de sus parámetros ópticos. Esta tesis doctoral comprende el diseño y operación de una estación lidar elástica basada en un láser pulsado de Nd:YAG operando a las longitudes de onda de 1064 y 532 nm, en lo que se refiere a los sistemas de recepción, control y diseño de algoritmos de inversión. Básicamente, puede dividirse en tres partes bien diferenciadas: La primera (Caps. 1, 2 y 3) comprende el estudio de la dispersión elástica (Rayleigh y Mie) en la atmósfera, orientada al cálculo del balance de enlace, e intenta vislumbrar la interrelación entre variables físicas tales como la temperatura, la presión y la humedad, y el fenómeno de dispersión, dejando de lado su posible extrapolación a modelos meteorologicos. Partiendo de esta base, se estiman valores de extinción y retrodispersión para diferentes condiciones atmosféricas y, como resultado, se presenta un balance de enlace para el sistema. El mismo incluye el estudio del alcance lidar, la estimación de la relación señal a ruido, y la evaluación de fotodiodos para diferentes librerías del usuario. Esta primera parte se cierra con las especificaciones globales del sistema. La segunda parte de este trabajo (Caps. 4, 5 y 6) atiende al diseño e implemen-tación del receptor, sistemas de sincronización y control. El receptor optoelectrónico se basa en amplificadores realimentados en corriente y cuenta con un excelente producto ganancia ancho de banda. Por lo que respecta al subsistema de sincronismo, se presentan dos unidades distintas con vistas a un futuro sistema lidar de escaneo, lo cuál ofrece la posibilidad de realizar scans entrelazados. Para terminar, el sistema de control diseñado se basa en el software de control LabView, que ofrece una filosofía de control distribuido. Con este propósito, se han especificado e implementado protocolos de bus lidar y su señalización para la presente estación lidar. Finalmente, la tercera parte comprende el diseño de algoritmos de inversión con y sin memoria (Caps. 7 y 8). Los algortimos sin memoria para atmósferas homogéneas se basan en procedimientos de ajuste por regresión como son el método de la pendiente y el de mínimos cuadrados y, en el caso de atmósferas inhomogéneas, se basan en el método de Klett y calibraciones adecuadas. Los algortimos con memoria se basan en diferentes modelos estocásticos para la atmósfera y filtrado de Kalman no lineal. Además de los algortimos de inversión, también se calculan y discuten las curvas del error de inversión. El Cap. 9 describe las medidas llevadas a cabo con el sistema que este trabajo ha permitido construir así como el resultado de aplicar los algoritmos de inversión presentados en los capítulos precedentes. La inversión de escenas reales comprende estudios de la estructura de polución, estudios de nubes (ceilometría, básicamente desplazamiento y estructura de las nubes) y señala posibles fuentes de error en el factor de solapamiento.LIDAR is an acronym of LIght Detection And Ranging. In the present case, the elastic lidar techniques are used to remotely sense the atmosphere and to derive quantitative information about its optical parameters.This thesis comprises the design and operation of an elastic lidar station based on a pulsed Nd:YAG laser operating at the 1064- and 532-nm wavelengths, in the parts concerning receiver, control systems, and inversion algorithms.Basically, it can be divided in three different parts: The first one (Chaps. 1, 2, and 3) encompasses the study of the elastic scattering (Rayleigh and Mie) in the atmosphere for link-budget purposes and gives some insight into the interweaving between physical variables such as temperature, pressure and humidity, and the scattering phenomena, letting apart any possible extrapolation to meteorological models. From this basis, extinction and backscatter figures for different atmospheric conditions can readily be assessed and, as result, a system link budget is presented. This includes lidar range study, signal-to-noise ratio assessment, and photodiode evaluation from custom-made libraries. At the end of the first part, the system specification is made. The second part of this work (Chaps. 4, 5, and 6) is concerned with the design and implemen-tation of receiver, synchronization, and control systems. The optoelectronic receiver is based on current-feedback amplifiers and features a very large gain-bandwidth product. As for the synchronization subsystem, two different units are presented with a view to a future scanning lidar system, which makes room for interspersed scans. Eventually, the control system designed is LabView based and features a distributed control philosophy. For that purpose, lidar bus protocols and signals are specified and built for the actual lidar station. Finally, the third part encircles the design of inversion algorithms with and without memory (Chaps. 7 and 8). Non-memory algorithms for homogeneous atmospheres are based on regression curve-fitting procedures, such as the slope-method and the least squares while in instances of inhomogeneous atmospheres they are based on Klett's method and appropriate calibrations. Memory algorithms are based on different stochastic models for the atmosphere and on non-linear Kalman filtering. In addition to these inversion procedures, error assessment plots are also derived and discussed. Chap. 9 describes the measurements carried out with the system this work has contributed to build and the results of applying to them the inversion algorithms discussed in the preceding chapters.The inversion of live-scenes involves pollution structure studies, cloud studies (ceilometry, cloud motion and wave clouds, basically), and hints overlap factor error sources.
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Du, Xinpeng. "Laser-Ultrasonic Measurement of Single-Crystal Elastic Constants from Polycrystalline Samples by Measuring and Modeling Surface Acoustic Wave Velocities." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1524177819455643.
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Duru, Kenneth. "Perfectly Matched Layers and High Order Difference Methods for Wave Equations." Doctoral thesis, Uppsala universitet, Avdelningen för beräkningsvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-173009.
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The perfectly matched layer (PML) is a novel technique to simulate the absorption of waves in unbounded domains. The underlying equations are often a system of second order hyperbolic partial differential equations. In the numerical treatment, second order systems are often rewritten and solved as first order systems. There are several benefits with solving the equations in second order formulation, though. However, while the theory and numerical methods for first order hyperbolic systems are well developed, numerical techniques to solve second order hyperbolic systems are less complete. We construct a strongly well-posed PML for second order systems in two space dimensions, focusing on the equations of linear elasto-dynamics. In the continuous setting, the stability of both first order and second order formulations are linearly equivalent. We have found that if the so-called geometric stability condition is violated, approximating the first order PML with standard central differences leads to a high frequency instability at most resolutions. In the second order setting growth occurs only if growing modes are well resolved. We determine the number of grid points that can be used in the PML to ensure a discretely stable PML, for several anisotropic elastic materials. We study the stability of the PML for problems where physical boundaries are important. First, we consider the PML in a waveguide governed by the scalar wave equation. To ensure the accuracy and the stability of the discrete PML, we derived a set of equivalent boundary conditions. Second, we consider the PML for second order symmetric hyperbolic systems on a half-plane. For a class of stable boundary conditions, we derive transformed boundary conditions and prove the stability of the corresponding half-plane problem. Third, we extend the stability analysis to rectangular elastic waveguides, and demonstrate the stability of the discrete PML. Building on high order summation-by-parts operators, we derive high order accurate and strictly stable finite difference approximations for second order time-dependent hyperbolic systems on bounded domains. Natural and mixed boundary conditions are imposed weakly using the simultaneous approximation term method. Dirichlet boundary conditions are imposed strongly by injection. By constructing continuous strict energy estimates and analogous discrete strict energy estimates, we prove strict stability.
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Zhao, Peng. "A STUDY OF SURFACE ACOUSTIC WAVE AND SPIN PRECESSION USING AN ULTRAFAST LASER FOR LOCALIZED ELASTIC AND MAGNETIC PROPERTY MEASUREMENT." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1367591435.
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La, Joie Elaine Naomi. "Tissue welding : studies of pulsed diode laser interaction with ICG stained porcine aorta and elastin-based biomaterial /." Full text open access at:, 1995. http://content.ohsu.edu/u?/etd,249.
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Martinez, Adam W. "Design and development of an elastin mimetic stent with therapeutic delivery potential." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/45926.
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Stenting remains a common treatment option for atherosclerotic arteries. The main drawback of early stent platforms was restenosis, which has been combated by drug eluting stents; however, these stents have suffered from a higher incidence of late stage thrombosis. To address current stenting limitations, the major research focuses have been the development of the next generation of drug eluting stents and first generation bioabsorbable stents. The main objective of this dissertation was the design and development of a new class of bioabsorbable stent composed of elastin mimetic protein polymers. The first phase explored different stent design schemes and fabrication strategies. Successfully fabricated stents were then mechanically tested to ensure they possessed sufficient mechanical strength. Additionally, described herein is the potential to modulate the properties of the elastin mimetics through different crosslinking strategies. We have demonstrated that chemical crosslinking allows for the tailoring of the physical, mechanical, drug delivery, and endothelialization properties of these materials. The potential for drug delivery from this elastin mimetic stent was benchmarked as was the potential to endothelialize these stents. Furthermore, we developed the necessary delivery systems to allow for deployment in the rat aorta model.
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Paine, Helen. "Laser shaping : a method for controlling the elastic behaviour of stretch fabrics for a targeted and graduated compressive effect on the body." Thesis, Royal College of Art, 2016. http://researchonline.rca.ac.uk/1805/.
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This research was commissioned and funded by The Welding Institute (TWI). The Welding Institute are a global research and development facility specialising in the joining of materials for industrial applications. The purpose of this research was to develop capability in textiles joining, particularly ultrasonic and laser welding technologies, which is relatively new to TWI. The appointed researcher adopted a ‘multi-strategy’ (Cresswell 2009) approach to the research; encompassing methods that were both familiar and unfamiliar to those usually adopted by TWI employees and researchers, whom mostly come from engineering and scientific backgrounds. The research was primarily undertaken with the adoption of a ‘craft-design’ approach that uses material investigation to explore and uncover interesting leads for investigation, which was the familiar approach of the researcher coming from a background in textile design. Material studies were carried out inquisitively without the formation of a particular hypothesis and insights were discussed with industry to identify potential commercial and functional application opportunities. Following the identification of an interest in welding stretchy fabrics Speedo agreed to become the main industry partner for the research, providing materials, access to testing equipment and validation of commercial opportunities for material samples relative to their application. The main hypothesis for the research Laser melted patterns can be used to control the elastic behaviour of stretchy textiles to have a targeted and variable compressive effect on the body developed through discussion with Speedo in response to material samples produced using transmission laser welding equipment. A predominant scientific approach was adopted during the second phase of the research to quantify and control this effect: to demonstrate repeatability and test it both on fabric and the body. Methods that were unfamiliar to the researcher prior to this research such as mechanical testing and microscopic analysis were employed. Selection of either a ‘craft design’ or ‘scientific’ approach was made pragmatically in response to the research as it developed. Through a retrospective analysis of applied methods throughout the research trajectory it has been possible to define this particular ‘multi-strategy’ project as a ‘sequential exploratory’ design (Cresswell 2009), whereby periods of subjective investigation are followed by empirical testing. The main process that has been developed by this research is a decorative method of controlling the elastic behaviour of stretchy fabrics using transmission laser welding equipment for a controlled and variable compressive effect on the body. Compression fabrics are used widely within the medical, lingerie and sportswear fields to apply pressure to the body either for an aesthetic or functional advantage. In swimwear, compression fabrics are applied to streamline the silhouette and minimise drag resistance. The technique developed by this research makes a contribution to knowledge within the field of laser processing of textiles, specifically within the field of transmission laser welding, and within the field of compression apparel. In the field of transmission laser welding a new functional capability for all-over surface patterns has been demonstrated. In the field of compression apparel a new decorative method for achieving an increasingly variable compressive effect for a smoother transition between different zones of stretch has been achieved. N.B. All redacted information throughout this thesis is confidential to Speedo.
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Howell-Smith, S. J. "Tribological optimisation of the internal combustion engine piston to bore conjunction through surface modification." Thesis, Loughborough University, 2011. https://dspace.lboro.ac.uk/2134/8449.
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Internal combustion (IC) engines used in road transport applications employ pistons to convert gas pressure into mechanical work. Frictional losses abound within IC engines, where only 38- 51% of available fuel energy results in useful mechanical work. Piston-bore and ring-bore conjunctions are fairly equally responsible for circa 30% of all engine friction - equivalent to 1.6% of the input fuel each. Therefore, reduction in piston assembly friction would have a direct impact on specific performance and / or fuel consumption. In motorsport, power outputs and duty cycles greatly exceed road applications. Consequently, these engines have a shorter useful life and a high premium is placed on measures which would increase the output power without further reducing engine life. Reduction of friction offers such an opportunity, which may be achieved by improved tribological design in terms of reduced contact area or enhanced lubrication or both. However, the developments in the motorsport sector are typically reactive due to a lack of relative performance or an ad-hoc reliance, based upon a limited number of actual engine tests in order to determine if any improvement can be achieved as the result of some predetermined action. A representative scientific model generally does not exist and as such, investigated parameters are often driven by the supply chain with the promise of improvement. In cylinder investigations are usually limited to bore surface finish, bore and piston geometrical form, piston skirt coatings and the lubricant employed. Of these investigated areas newly emerging surface coatings are arguably seen as predominate. This thesis highlights a scientific approach which has been developed to optimise piston-bore performance. Pre-existing methods of screening and benchmarking alterations have been retained such as engine testing. However, this has been placed in the context of validation of scientifically driven development. A multi-physics numerical model is developed, which combines piston inertial dynamics, as well as thermo-structural strains within a thermoelastohydrodynamic tribological framework. Experimental tests were performed to validate the findings of numerical models. These tests include film thickness measurement and incylinder friction measurement, as well as the numerically-indicated beneficial surface modifications. Experimental testing was performed on an in-house motored engine at Capricorn Automotive, a dynamometer mounted single-cylinder 'fired' engine at Loughborough University, as well as on other engines belonging to third party clients of Capricorn. The diversity of tests was to ascertain the generic nature of any findings. The multi-physics multi-scale combined numerical-experimental investigation is the main contribution of this thesis to knowledge. One major finding of the thesis is the significant role that bulk thermo-structural deformation makes on the contact conformity of piston skirt to cylinder liner contact, thus advising piston skirt design. Another key finding is the beneficial role of textured surfaces in the retention of reservoirs of lubricant, thus reducing friction.
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Ramos, Helena Hotz Arroyo. "Estudo histológico dos efeitos agudos de lesão com laser de diodo 980 nm em pregas vocais de coelhos." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/5/5143/tde-09052018-090014/.
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INTRODUÇÃO: A cicatriz em prega vocal que ocorre após injúria constitui causa importante de disfonia. A fonocirurgia ideal é aquela em que a lesão efetivamente removida com o menor dano possível ao tecido adjacente, a fim de reestabelecer a função da prega vocal ao mesmo tempo em que a sua ultraestrutura sua ultraestrutura é preservada. Tanto o bisturi frio quanto lasers em geral são aceitos como instrumentos para fonocirurgia. O laser de diodo tem sido usado no tratamento de doenças laríngeas. Entretanto, não há consenso quanto os parâmetros ideais desse aparelho para tal finalidade. Inexistem trabalhos que mostrem a forma ou a extensão da lesão provocada com laser de diodo em laringe e tampouco as reações histológicas e cicatriciais provocadas por ele. OBJETIVO: O objetivo desta pesquisa é estudar as alterações morfométricas e histopatológicas observadas nas pregas vocais de coelhos, sete dias após a lesão provocada com o laser de diodo, comparando diferentes configurações do dispositivo. MÉTODO: Vinte e um coelhos machos albinos da raça New Zealand foram distribuídos aleatoriamente em três grupos com sete animais por grupo. Foi realizada uma lesão única durante 20 segundos em cada prega vocal com a ponta da fibra em contato superficial com o tecido. Duas frequências de pulso foram comparadas no Grupo I (10Hz versus 1000Hz), diferentes potências no Grupo II (3W versus 5W) e modos de radiação distintos no Grupo III (pulsado versus contínuo). Após sete dias, as laringes foram excisadas e submetidas à coloração com hematoxilina-eosina, além de coloração histoquímica para colágeno e elastina. Foi realizada análise histológica quantitativa e subjetiva. RESULTADOS: o laser de diodo provocou: exocitose de células inflamatórias; edema de mucosa e submucosa; infiltrado celular extenso em torno da úlcera, composto por polimorfonucleares (especialmente eosinófilos), linfócitos e histiócitos; tecido de granulação com a presença de fibroblastos e vasos neoformados e áreas de necrose do tipo coagulativa. A extensão do processo inflamatório e a extensão linear da úlcera apresentaram diferença significativa entre as duas potências, e foi maior com uso do laser ajustado para 5W. A extensão do processo inflamatório, extensão linear da úlcera, profundidade da úlcera e profundidade do processo inflamatório apresentaram diferença significativa entre os dois modos de emissão do laser, isto é, maior no modo contínuo. A densidade das fibras colágenas apresentaram-se elevadas apenas ao uso do laser no modo contínuo, quando comparado ao modo pulsado. Não houve diferença estatística quanto à densidade de fibras elásticas. CONCLUSÃO: O uso do laser de diodo ajustado em potência de 5W ao invés 3W e o uso do modo contínuo ao invés do pulsado são capazes de aumentar significativamente a injúria térmica nas pregas vocais de coelhosINTRODUCTION. Scarring of the vocal folds is a relevant cause of dysphonia after injury. The ideal phonomicrosurgery would be the one that removes the vocal fold disease in order to restore the biomechanical function, while providing minimal disruption to the surrounding vocal fold layered structure. Steel scalpel and laser systems are widely accepted tools for vocal fold surgical procedures. The diode laser technique has been used in the treatment of laryngeal diseases. However, there is great variability among surgeons with regard to the use of the diode laser for laryngeal surgery and the ideal parameters for this procedure remain unclear. No description of the lesion extent or the vocal fold healing after injury with this device have been reported to date. OBJECTIVE: The aim of this research was to study the morphometric and histopathological changes seen in the vocal fold seven days after injury with the diode laser in a rabbit model, comparing different settings of the device. METHODS: Twenty-one male New Zealand white rabbits were randomized into three groups with seven animals per group. A single spot injury during 20 seconds was performed in each vocal fold with the fiber tip in superficially contact with the tissue. Two pulse frequency were compared in group I (10Hz versus 1000Hz), different powers in group II (3W versus 5W) and distinct wave mode of radiation in group III (pulsed versus continuous). After seven days, the larynges were harvested and subjected to H&E staining, histochemical staining for collagen and elastin, with quantitative and subjective histological analysis. RESULTS: the diode laser provoked exocytosis of inflammatory cells; edema of mucosa and submucosa; extensive cell infiltrate around the ulcer with polymorphonuclear cells (especially eosinophils), lymphocytes and histiocytes; granulation tissue with the presence of fibroblasts and neoformed vessels and areas of coagulative necrosis. The extent of the inflammatory infiltrate and the extent of the ablation crater showed to be greater with the 5W power use. The analyzes of extension of the extent of the inflammatory infiltrate, the extent of the ablation crater, the depth of the ablation crater and depth of the inflammatory process presented greater measurements with the continuous mode. The density of collagen fibers was higher when the laser was used in continuous wave mode. There was no statistically significant difference in elastic fiber density. CONCLUSION: Increasing power from 3W to 5W and using continuous wave rather than pulsed wave mode of the diode laser significantly increased the extent of thermal injury in the rabbit vocal folds
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Beuton, Romain. "Modélisation de la structuration d'un matériau diélectrique irradié par une impulsion laser femtoseconde." Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0231/document.
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Les lasers femtosecondes sont un outil efficace pour induire des modifications structurelles localisées en volume dans les matériaux diélectriques. Initialement transparents, les diélectriques ne commencent à absorber efficacement l’énergie laser que lorsque l’intensité excède le seuil de claquage optique du matériau. Cette propriété, couplée à une durée d’impulsion femtoseconde plus courte que les temps caractéristiques de relaxation de la matière, permet d’obtenir un dépôt d’énergie précis et localisé dans le volume irradié. Pour modéliser la formation de telles structures, un modèle thermo-élasto-plastique en géométrie 2D planaire, incluant la transition solide-liquide via un modèle de ramollissement, a été implémenté dans un code hydrodynamique lagrangien. Des études de la formation d’une cavité et de l’interaction de multiple cavités ont tout d’abord été réalisées en supposant un dépôt instantané d’énergie laser dans le volume d’une cible de silice fondue. La relaxation de la matière chauffée, portée à l’état de plasma dense, induit alors la propagation d’ondes de choc dans le solide froid environnant. Des déformations permanentes peuvent apparaître dans le matériau si la contrainte, induite par ces ondes, excède la limite élastique. Ces premières études ont notamment permis de comprendre et de décrire les différentes étapes de la formation de micro-structures, fortement corrélées au comportement élasto-plastique du solide environnante. De plus, en utilisant une loi de Weibull, tenant compte de la densité de défauts dans la matière, des probabilités de fractures dans le matériau ont été calculées. Dans un second temps, la structuration de la silice fondue par un faisceau de Bessel a été considérée. Un solveur de Maxwell 3D, couplé à une description fluide de la dynamique électronique, a été utilisé pour modéliser le dépôt d’énergie laser. Les résultats ont permis de comprendre comment s’établit le dépôt d’énergie et rendent compte des effets des différents processus d’ionisation sur les évolutions des profils de densité et d’énergie électronique. Des simulations thermo-élasto-plastiques ont ensuite étaient réalisées en utilisant le dépôt d’énergie calculé. Différents types de déformations induites dans la silice ont pu être mis en évidence en fonction de l’énergie et de la durée de l’impulsion incidente, en accord avec les observations expérimentalesFemtosecond laser pulses are an efficient tool to induce localized structural modifications in the bulk of dielectrics materials. The dielectrics, initially transparent, start to efficiently absorb the energy when the laser intensity exceeds the optical breakdown threshold of the material. This property, coupled to a femtosecond pulse duration smaller than the caracteristic relaxation times of matter, allows to induce a localized and accurate energy deposition in the irradiated volume. In order to model the formation of such structures, a 2D thermo-elasto-plastic model, including solid-liquid transitions through a softening model, has been implemented in a lagrangian hydrodynamic code. Studies on the formation of a single cavity and several interacting cavities have been firstly performed, assuming an instantaneous energy deposition in the bulk of fused silica. The relaxation of the heated matter, transformed to a warm dense plasma, induces shock waves in the surrounding cold solid. Permanent deformations may appear if the stress, induced by the waves, exceeds the yield strength of the material. This first study allowed to understand and describe the various steps of the micro-structures formation, which are strongly correlated to the elasto-plastic behavior of the surrounding solid. Furthermore, by using a Weibull’s law, accounting for defects density in the material, cracks probabilities have been predicted. Secondly, the structuration of fused silica by a Bessel beam has been considered. For that purpose, a 3D Maxwell solver coupled to a fluid description of the electron dynamics has been used to model the laser energy deposition. Results allow to understand how the energy deposition establishes and show the effects of the different ionization processes on the electron density and energy profiles. Then, thermo-elasto-plastic simulations have been carried out including the calculated energy deposition. Various kinds of induced deformations in fused silica have been obtained depending on the incident pulse energy and duration, which is in agreement with experimental observations
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Chernukha, Yevheniia. "Investigation of phase transitions triggered by laser-induced focusing shock waves." Thesis, Le Mans, 2019. http://www.theses.fr/2019LEMA1038.
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La capacité de certains matériaux à changer d'état fondamental sous excitation laser a ouvert un champ de recherche autour de la manipulation de leurs propriétés par la lumière. Les processus chimiques et physiques mis alors en jeu sont riches et complexes. Dans ce contexte, le rôle prédominant de la coopérativité élastique pour l’amplification et la stabilisation de la transition a été mis en évidence récemment dans un matériau à transitions de spin irradié par laser. Ces observations font apparaître la perspective de commuter de façon permanente certaines propriétés des matériaux par des ultrasons non-linéaires, des ondes de choc excitées par laser.Dans un premier temps, nous introduisons le dispositif expérimental d’imagerie mono-coup résolu en temps, associée à la technique de focalisation des ondes de chocs excitées par laser au niveau de la surface de l’échantillon. La séparation spatiale des régions irradiées par le laser et influencées par les ondes de choc propagatives permet de discerner clairement les changements du matériaux induits uniquement par les ondes de choc. Dans un second temps, nous présentons nos résultats expérimentaux en lien avec cette technique innovante, aux matériaux dont les changements de phases impliquent un changement de volume macroscopique (systèmes spin-crossover, isolants de Mott). Des analyses post-mortem des échantillons ont permis de confirmer, dans certaines conditions expérimentales, une modification permanente de la phase du matériau par action de l'onde de choc. Ces résultats ouvrent des perspectives pour la généralisation à de nombreux matériaux du phénomène de coopérativité élastique donnant lieu à des transition permanentThe ability of certain materials to change its ground state due to laser excitation has arisen a lot of opportunities for light-control of material properties. The field of photo-induced phase transitions counts a rich variety of chemical and physical processes triggered by light-matter interactions involved during the phase transition process. Recently it was reported that elastically driven cooperativity leads to the amplification of spin state in molecular crystals and prolonged the lifetime of the transient state with an ultra-short laser pulse. The cooperative response appears during the propagation of non-linear coherent strain waves, in other words shock waves, coupled with the order parameter field. Shock waves can be seen as a new challenging pathway to achieve a permanently switched state with appropriate excitations.First, we introduce time-resolved single-shot imaging combined with the laser shock focusing technique that makes it possible to generate, acoustically focus, and directly visualize under a microscope shock waves propagating and focusing along the sample surface. The spatial separation of the laser-influenced and strain-influenced regions makes it possible to disentangle the material changes produced solely by the shock waves. Second, we present experimental results involving the shock-focusing technique to materials undergoing phase transitions linked with a macroscopic change of their volume (spin-crossover systems, Mott insulators). Post-mortem analyses of the samples confirm permanent phase transition under specific experimental conditions. These innovative results open doors for a generic elastically driven cooperativity
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Shrestha, Santosh Kumar Physical Environmental & Mathematical Sciences Australian Defence Force Academy UNSW. "Characterisation of indium nitride films with swift ions and radioisotope probes." Awarded by:University of New South Wales - Australian Defence Force Academy. School of Physical, Environmental and Mathematical Sciences, 2005. http://handle.unsw.edu.au/1959.4/38734.
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[Formulae and special characters can not be reproduced here. Please see the pdf version of the Abstract for an accurate reproduction.] Indium nitride is an important III-V nitride semiconductor with many potential applications such as in high frequency transistors, laser diodes and photo voltaic cells. The mobility and peak drift velocity of this material are predicted to be extremely high and superior to that of gallium nitride. However, many material properties such as the origin of the n-type conductivity and the electronic band gap are not well understood. Moreover, there is limited information on the stoichiometry and the level of impurity contaminations in the films from different growth techniques. The n-type conductivity observed for as-grown indium nitride films has long been attributed to nitrogen vacancies, implying that the material is nitrogen deficient. A band gap value around 2 eV, as measured by the optical absorption method, is suggested by some authors to be a result of the formation of an InNIn2O3 alloy. Alternatively, the observation of a lower absorption edge, suggesting a band gap around 0.7 eV, may be caused by Mie scattering at indium clusters that may form during film growth. Secondary ion mass spectroscopy and x-ray techniques provide only qualitative composition information. The quantitative interpretation of the results relies on calibration samples which are not available for indium nitride. In Rutherford backscattering spectroscopy, while quantitative, the carbon, nitrogen and oxygen signals cannot be separated unless the film is very thin ([tilde]150 nm). However, with heavy ion Elastic Recoil Detection (ERD) analysis all the elements in indium nitride films can be fully separated even for a film thickness of [tilde] 800 nm. In this work, indium nitride films from different growth techniques have been analysed with ERD using 200 MeV 197Au projectiles. The observed nitrogen depletion during the ERD analysis was monitored as a function of projectile fluence using a gas ionisation detector with a large solid angle. Different models have been tested and it has been shown that the bulk molecular recombination model accurately describes the nitrogen depletion so that the original nitrogen-to- indium ratio can be measured with an accuracy of [plus or minus]3 [percent]. The correlation of nitrogen depletion rate and stopping power of the projectile ion has been investigated. The study has shown that the rate of depletion is slower for low-Z projectiles. It has been shown that for a film with good structural properties, no loss of nitrogen occurs during the ERD analysis with low-Z projectiles such as 42 MeV 32S. Thus, the original nitrogen-to-indium ratio can be obtained without any theoretical modelling, and with a precision of better than [plus or minus]1 [percent]. All the indium nitride films studied in this work, for which X-ray diffraction shows no metallic indium, are nitrogen-rich which is contradictory to expectation. Therefore, the common assertion that nitrogen vacancies are the cause of n-type conductivity in as-grown films is diffcult to explain. Instead, the existence of In vacancies, N antisites and interstitial N2 may be speculated. The carbon and oxygen contamination is an issue for films grown by all common growth techniques. However, the suggested correlation of oxygen content in the film with the apparent band gap is not supported by the ERD results. Instead, a correlation between nitrogen-to-indium ratio and the measured band gap has been observed for films grown by RF-sputtering. This work reports the implantation of radioisotope probes using negative ions. The 111In/Cd probe was selected for this work as it is a common Perturbed Angular Correlation (PAC) probe and ideally suited for the study of indium nitride. For the synthesis of the probe 111In/Cd, several possibilities, such as the production of 111In/Cd via nuclear fusion evaporation reactions and from commercially available 111InCl3 solutions, were explored. Different materials, including powders of Al2O3 and In2O3, were investigated as a carrier for the probe in the ion source of the radioisotope implanter. It has been established that combining the 111InCl3 solution as the source and In2O3 powder as the carrier material gives optimum implantation efficiency. The radioisotope implanter facility has been developed to a stage that the radioisotope probe 111In/Cd can be routinely implanted into materials as molecular 111InO?? ions. An implantation rate of 3x10 4[th] Becquerel per hour has been demonstrated. Measurements on different materials (Ag, In, Ni, Si, InP) have shown that condensed matter spectroscopies such as Low Temperature Nuclear Orientation, Nuclear Magnetic Resonance on Oriented Nuclei (NMRON) and Perturbed Angular Correlation can be reliably performed. NMRON measurements on silver indicate a new resonance frequency of 75.08 MHz for 111InAg at 8.0 T. The local lattice environment of indium nitride thin films has been investigated with PAC spectroscopy. Several methods of introducing a radioisotope probe into a host material have been investigated for indium nitride. The thermal diffusion of the radioisotope probe 111In/Cd into indium nitride at a temperature below the dissociation temperature (about 550 [degrees] C) was not possible. The probe was, however, successfully introduced into indium nitride films with ion implantation techniques. Recoil implantation at MeV energies following fusion evaporation reactions and ion implantation at keV energies, both have been investigated for indium nitride films. An interaction frequency of v = 28 MHz has been measured for the 111In/Cd probe in indium nitride. This result is consistent with that obtained for indium nitride bulk grains. The PAC results suggest that all types of indium nitride films have a highly disordered lattice which could only be partially improved by annealing. Furnace annealing in nitrogen atmosphere above 400 [degrees] C resulted in the dissociation of the film. However, such dissociation could be avoided with rapid thermal annealing up to 600 [degrees] C. More detailed defect studies with PAC require the availability of better material. This study has also shown that indium nitride is highly sensitive to ion beam irradiation. Severe depletion of nitrogen during exposure to ions with MeV and KeV energies is an issue for the ion beam characterisation and processing of indium nitride.
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Patriota, Regina Celli Ribeiro. "Estudo do laser Erbium Glass fracionado não ablativo no tratamento do fotoenvelhecimento cutâneo: avaliação clínica, histopatológica, microscopia eletrônica e imuno-histoquímica." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/5/5133/tde-23012014-093858/.
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Introdução: Os lasers fracionados não ablativos são efetivamente utilizados no rejuvenescimento da pele. As novas tecnologias a laser permitem uma remodelação dérmica seletiva, sem ablação da epiderme. Objetivo: Avaliar a eficácia do laser Erbium Glass (Sellas Evo) fracionado não ablativo 1550nm no rejuvenescimento facial através do estudo da quantificação histomorfométrica de fibras colágenas e elásticas, a expressão da molécula de adesão intercelular 1 (ICAM-1) por imuno-histoquímica , a análise das fases do ciclo celular, o potencial elétrico da membrana mitocondrial, a expressão de interleucina-1 (IL-1), o marcador celular endotelial CD34, o receptor do fator transformador de crescimento beta (TGF-beta), atividade da caspase-3 por citometria de fluxo e as alterações ultraestruturais na pele por microscopia eletrônica de varredura, 4 meses após o tratamento com laser. Materiais e Métodos: Quinze indivíduos (média de 56,4 anos, fototipo II-IV), com fotoenvelhecimento cutâneo na face fizeram 3 tratamentos com laser Erbium Glass fracionado não ablativo 1550nm usando uma fluência de 70 mJ e uma densidade de 100 cm2. Foram avaliados biópsias na região pré-auricular em 15 pacientes no início e 4 semanas após o tratamento final. Os níveis de expressão dos receptores e a atividade do potencial elétrico mitocondrial foram analisados na suspensão de células da derme obtida a partir da digestão por colagenase. A avaliação clínica e fotográfica foi analisada quatro semanas após o final do tratamento. Resultados: Após 4 meses do início do tratamento foi observada melhora clínica moderada, com uma média de satisfação de 8,8, as fibras de colágeno aumentaram em 6,68%, as fibras elásticas mostraram uma diminuição de 12,85%, o ICAM-1 aumentou 4,47% significativamente na área dos vasos. Houve aumento significativo dos níveis de expressão do receptor de IL-1 e TGF-beta após o tratamento com laser Erbium Glass. As respostas proliferativas e a ausência de apoptose dependente da caspase-3 foram observadas nas suspensões de células após o tratamento. Conclusão: Rejuvenescimento facial com laser Erbium Glass fracionado não ablativo 1550nm demonstrou melhora visível no fotoenvelhecimento, assim como, aumento significativo da expressão de IL-1 e receptores de TGF-beta, que estão envolvidos na remodelação e indução da proliferação de componentes da matriz extracelular da pele. O grau de satisfação foi alto especialmente em relação à textura, rugas e discromiasBackground: Non-ablative fractional lasers have been effectively used in skin rejuvenation. The new laser technologies allow selective dermal remodeling without ablation of the epidermal surface. Objectives: to evaluate the efficacy of the 1550nm Erbium Glass Laser (Sellas Evo) for facial rejuvenation through study of the histomorphometric quantification of colagen and elastic fibers; the expression of intercellular adhesion molecule 1 (ICAM-1) by immnohistochemistry; and analysis of the cell cycle phases, the electrical potential of the mitochondrial membrane and the expression of interleukin 1 (IL-1), the endothelial cell marker CD34 and transforming growth factor beta (TGF-beta) receptors, caspase-3 activity by flow cytometry and the ultrastructural changes in the skin by scanning electron microscopy 4 months after the laser treatment. Materials and methods: fifteen subjects (mean age 56,4 skin typoes II-IV) with photodamage on the face and wrinkles had 3 treatments with the 1550 nm Erbium Glass Laser using a fluence of 70 mJ and a density of 100 cm2. Pre-auricular biopsies from 15 subjects were evaluated at baseline and 4 weeks after the final treatment. Receptor expression levels and the presence of potentially functional mitochondria were analyzed in a cell suspension obtained from collagenase digestion of the skin. Data from the photo assessments and the subjects\' self-assessed improvements were analyzed 4 weeks after the final treatment.Results: Four months after the last treatmenbt application, clinical improvement was observed, with an average satgisfation score of 8.8, corresponding to moderate improvement. After 4 months of treatment, collagen fibers had increased up to 6.68%, while the average proportion of collagen fibers in the dermis, the elastic fibers, showed a 12.85% decrease of ICAM-1 and a mean increase in vessel area of 4.47%.Significantly enhanced IL-1 and TGF-beta receptor expression levels were identified after Erbium Glass Laser treatment. Proliferative responses and non-apoptosis-dependent caspase-3 activity were both observed in the cell suspensions after dermal treatment. Conclusion: Non-ablative rejuvenation with the 1550 mn Erbium Glass Laser was of the IL-1 and TGF-beta receptors, that are involved in remodeling and induced proliferation components in the extracellular matrix of skin fibers. The subjects were highly satisfied, especially regarding texture, rhytids and dyschromia
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Bremond, Florian. "Lubrification des contacts sous-alimentés : apport de la micro-texturation de surface." Thesis, Ecully, Ecole centrale de Lyon, 2012. http://www.theses.fr/2012ECDL0019/document.
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L’appauvrissement en lubrifiant d’un contact élasto-hydrodynamique peut menacer la pérennité du film interfacial séparant les surfaces, entraîner l’augmentation des forces de frottement et l’endommagement rapide du tribosystème. Industriellement, la volonté de réduire les quantités de lubrifiant embarquées et de limiter les opérations de maintenance favorisent la sous-alimentation. L’objectif de cette thèse est de contrôler l’alimentation d’un contact EHD sous-alimenté par une texturation de surface multi-échelle, afin d’assurer une lubrification minimale à l’interface. Une démarche scientifique s’appuyant sur la dissociation des échelles spatiales, temporelles ainsi que sur l’analyse des contributions des écoulements dans les différentes zones du contact a été mise en oeuvre. La compréhension de l’interaction laser/matière en irradiation ultra-brève a permis de générer des texturations nanométriques (ripples) et micrométriques (ondulations et réseaux de cavités) à l’aide d’un laser femtoseconde. La contribution de chaque échelle topographique sur la lubrification d’un contact a été étudiée. Lorsque les forces hydrodynamiques sont faibles (contact statique), l’alimentation d’un contact résulte d’une compétition entre une contribution capillaire et une contribution visqueuse. La macro géométrie des solides déformés ainsi que la viscosité pilotent au premier ordre la propagation du lubrifiant à l’extérieur de la zone haute pression. L’imbibition de la zone de Hertz n’est possible qu’avec l’introduction d’une surface nanotexturée et sa cinétique dépend de l’orientation et de l’amplitude des ripples. Pour des nombres capillaires élevés (contact dynamique), un critère de prédiction de l’apparition de la sous-alimentation a été établi. En présence de réseaux de cavités et sous l’action d’un cisaillement interfacial, les surfaces texturées possédant une capacité de rétention élevée réalimentent la zone de haute pression. Le volume piégé envahit alors le contact puis crée une surépaisseur de lubrifiant qui protège les solides de l’endommagement tout en limitant l’augmentation du frottement. Les texturations nanométriques (ripples) et micrométriques, anisotropes et périodiques, modifient l’équilibre entre les débits de réalimentation et les débits de fuite. Une orientation adaptée des motifs peut contenir le drainage du lubrifiant dans le contact et ainsi empêcher ou retarder l’apparition d’un régime de sous-alimentation totale. Au final, chaque échelle topographique contribue à la réalimentation d’un contact sousalimenté, soit en favorisant l’expansion des réservoirs latéraux, soit en apportant localement du lubrifiant, ou en maintenant un film fluide résiduel sur les surfacesThe lubricant depletion of an elasto-hydrodynamic contact may threaten the sustainability of the interfacial film separating the surfaces, can result in the increase of frictional forces and a rapid damage of the tribosystem. Industrially, the trend to reduce the amount of initial lubricant and to limit maintenance promotes starvation of the lubricated contact. The aim of this work is to control the lubricant feeding of a starved EHL contact by a multi-scale surface texturing, in order to ensure minimal lubrication at the interface. A scientific approach based on the separation of spatial and temporal scales, as well as the analysis of the flow contributions in different zones of the contact has been implemented.The understanding of the laser/matter interaction in ultra-short irradation has helped us to generate both nanoscale texturing (ripples) and microscale texturing such as microwaves and networks of micrometric cavities, using a femtosecond laser. The contribution of each topographic scale on the contact lubrication has been analysed. When the hydrodynamic forces are low (static contact), the feeding of the contact results from a competition between capillary and viscous contributions. The macro geometry of the deformed solids and the lubricant viscosity mainly control the lubricant spread around the high-pressure zone. The imbibition of the Hertz contact area is only possible with the introduction of a nanotextured surface. The imbibition kinetics depends on the orientation and amplitude of the ripples. For high capillary numbers (dynamic contact), a criterion has been established in order to predict the occurrence of starvation. Using a network of micro cavities and the action of an interfacial shear, the high retention capacity textured surfaces brings lubricant to the high-pressure zone. The trapped volume propagates inside the contact and creates a film thickness that protects the solids from damages while limiting the increase in friction. Anisotropic and periodic nanoscale and microscale texturing, like ripples, influences the balance between re-feeding and leakage flow rates. A suitable orientation of the geometries may prevent the lubricant from drainage and thus delay the onset of a starved lubrication regime. In conclusion, each topographic scale contributes to re-feed a starved contact, by promoting lateral reservoir extension, by providing lubricant locally where it is needed, or maintaining a residual fluid film on surfaces