Dissertations / Theses on the topic 'Beams'
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ROSSETTI, CONTI MARCELLO. "BEAM DYNAMICS FOR EXTREME ELECTRON BEAMS." Doctoral thesis, Università degli Studi di Milano, 2019. http://hdl.handle.net/2434/622706.
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The extreme electron beams are characterized by parameters that are comparable or superior to the state of the art. The beams parameters proposed in the more advanced machines under development or in operation demonstrate that extreme beam qualities are necessary to conceive experiments meeting the demands of cutting-edge research.
The optimization of parameters such as brightness, beam current or energy spread plays a major role in the design choices of new and competitive machines.
A large amount of simulations of beam dynamics is required, accompanied later by a specific R&D of machine components and demonstration experiments.
In the field of beam dynamics, the development and improvement of tracking simulators and optimization tools is a main topic. For this reason, in the beam physics group of INFN & University of Milan the code GIOTTO, based on a genetic algorithm, is being developed for years specifically for this purpose.
During the work of PhD, I developed new features in the GIOTTO code that allowed me to apply it to new type of problems: simulation of a beam based method for the increase of the brightness of linac beams, design from scratch of matching lines for plasma driven FELs (Free Electron Lasers), the study of new linear acceleration and compression techniques and a preliminary study on how to produce an ultra-cold beam for a quantum-FEL.
All these works are united by being applied to linear machines dedicated to the production of high-brightness electron beams for various purposes.
During the last year of PhD, I had the opportunity to participate in the design of an FEL source, named MariX. MariX is based on a compact acceleration scheme where the electron beam propagates twice through a superconducting standing wave linac thanks to an arc compressor that reverses the direction of the beam and compresses it.
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Sosa, Alejandro. "Development of beam instrumentation for exotic particle beams." Thesis, University of Liverpool, 2015. http://livrepository.liverpool.ac.uk/2038259/.
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Modern nuclear physics makes extensive use of exotic particle beams created using accelerators, such as unstable ion isotopes and antiprotons. These give access to a wide range of fundamental studies that are at the cutting edge of science. The commissioning and operation of these accelerators require powerful beam diagnostic devices that are specially adapted to these unusual, and often very faint, beams. The work leading to this thesis, focuses on the development of the beam diagnostic system of the future superconducting linear accelerator at the High Intensity and Energy Isotope Separator On-Line Device (HIE-ISOLDE), which shall deliver stable and unstable isotope beams ranging from Helium to Radium at beam energies between 0.3 and 10 MeV/u and intensities from few particles per second up to 1 nA. The main elements of the diagnostics system are a Faraday cup for the measurement of the absolute beam current, a scanning blade with a V-shaped slit, which together with the Faraday cup allows one to measure the transverse beam profile and the beam position, a silicon detector for energy spectroscopy and time of flight measurements, plus a set of collimators and attenuating or stripping foils. The performance of the beam instrumentation will impact directly on the operation of the facility, therefore a lot of care has been put to identify the performance requirements and ensure that the design fulfills the needs. The techniques used by the systems studied during this work are widely used, but had to be adapted to the special design of the superconducting HIE-ISOLDE Radioactive EXperiment (REX) linac. In particular the compactness of the accelerator, and as a consequence of the diagnostic devices, required pushing the understanding of the physics behind the techniques in order to overcome limitations in the design parameters usually considered unbreakable. For this realistic models of all devices had to be developed that allowed detailed numerical studies. This new set of diagnostics for the HIE-ISOLDE REX linac is the most compact in the facility, and has been tested extensively in a wide range of ion beams. In addition to the HIE-ISOLDE work, a Secondary Emission Monitor (SEM) was tested at the Antiproton Decelerator (AD) facility using a 300 keV antiproton beam, together with other detector groups in the AEgIS collaboration such as nuclear emulsions, the MIMOTERA and the 3D pixel detector. In the frame of this thesis, a performance comparison among these detector technologies is done with the aim to identify an ideal set of diagnostics for the AD and for other similar antiproton facilities. This thesis first presents the models developed as well as the results of the numerical simulations, then the design of the prototypes and the experimental results obtained with beams in antiproton and ion accelerator facilities. All devices and techniques part of this R&D are characterized in detail, their performance and limitations described and options for further improvements indicated.
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Kimstrand, Peter. "Beam Modelling for Treatment Planning of Scanned Proton Beams." Doctoral thesis, Uppsala University, Oncology, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8640.
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Scanned proton beams offer the possibility to take full advantage of the dose deposition properties of proton beams, i.e. the limited range and sharp peak at the end of the range, the Bragg peak. By actively scanning the proton beam, laterally by scanning magnets and longitudinally by shifting the energy, the position of the Bragg peak can be controlled in all three dimensions, thereby enabling high dose delivery to the target volume only. A typical scanned proton beam line consists of a pair of scanning magnets to perform the lateral beam scanning and possibly a range shifter and a multi-leaf collimator (MLC). Part of this thesis deals with the development of control, supervision and verification methods for the scanned proton beam line at the The Svedberg laboratory in Uppsala, Sweden.
Radiotherapy is preceded by treatment planning, where one of the main objectives is predicting the dose to the patient. The dose is calculated by a dose calculation engine and the accuracy of the results is of course dependent on the accuracy and sophistication of the transport and interaction models of the dose engine itself. But, for the dose distribution calculation to have any bearing on the reality, it needs to be started with relevant input in accordance with the beam that is emitted from the treatment machine. This input is provided by the beam model. As such, the beam model is the link between the reality (the treatment machine) and the treatment planning system. The beam model contains methods to characterise the treatment machine and provides the dose calculation with the reconstructed beam phase space, in some convenient representation. In order for a beam model to be applicable in a treatment planning system, its methods have to be general.
In this thesis, a beam model for a scanned proton beam is developed. The beam model contains models and descriptions of the beam modifying elements of a scanned proton beam line. Based on a well-defined set of generally applicable characterisation measurements, ten beam model parameters are extracted, describing the basic properties of the beam, i.e. the energy spectrum, the radial and the angular distributions and the nominal direction. Optional beam modifying elements such as a range shifter and an MLC are modelled by dedicated Monte Carlo calculation algorithms. The algorithm that describes the MLC contains a parameterisation of collimator scatter, in which the rather complex phase space of collimator scattered protons has been parameterised by a set of analytical functions.
Dose calculations based on the phase space reconstructed by the beam model are in good agreement with experimental data. This holds both for the dose distribution of the elementary pencil beam, reflecting the modelling of the basic properties of the scanned beam, as well as for complete calculations of collimated scanned fields.
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Ratsibi, Humbelani Edzani. "Laser drilling of metals and glass using zero-order bessel beams." University of the Western Cape, 2013. http://hdl.handle.net/11394/5428.
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>Magister Scientiae - MScThis dissertation consists of two main sections. The first section focuses on generating zero order Bessel beams using axicons. An axicon with an opening angle y = 5⁰ was illuminated with a Gaussian beam of width ω₀ = 1.67 mm from a cw fiber laser with central wavelength λ = 1064 nm to generate zero order Bessel beams with a central spot radius r₀ = 8.3 ± 0.3 μm and propagation distance ½zmax = 20.1 ± 0.5 mm. The central spot size of a Bessel beam changes slightly along the propagation distance. The central spot radius r₀ can be varied by changing the opening angle of the axicon, y, and the wavelength of the beam. The second section focuses on applications of the generated Bessel beams in laser microdrilling. A Ti:Sapphire pulsed femtosecond laser (λ = 775 nm, ω₀ = 2.5 mm, repetition rate kHz, pulse energy mJ, and pulse duration fs) was used to generate the Bessel beams for drilling stainless steel thin sheets of thickness 50 μm and 100 μm and microscopic glass slides 1 mm thick. The central spot radius was r₀ = 15.9 ± 0.3 μm and ½zmax = 65.0 ± 0.5 mm. The effect of the Bessel beam shape on the quality of the holes was analysed and the results were discussed. It was observed that Bessel beams drill holes of better quality on transparent microscopic glass slides than on stainless steel sheet. The holes drilled on stainless steel sheets deviated from being circular on both the top and bottom surface for both thicknesses. However the holes maintained the same shape on both sides of each sample, indicating that the walls are close to being parallel. The holes drilled on the glass slides were circular and their diameters could be measured. The measured diameter (15.4±0.3 μm) of the hole is smaller than the diameter of the central spot (28.2 ± 0.1 μm) of the Bessel beam. Increasing the pulse energy increased the diameter of the drilled hole to a value close to the measured diameter of the central spot.
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Linfield, Edmund Harold. "The uses of ion beams with molecular beam epitaxial growth." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386165.
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Chang, Daqing. "Freely vibrating beams." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq23587.pdf.
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Hulland, Meg. "Pultruded GFRP beams : an evaluation of the Expanded Web Beam concept." Thesis, Lancaster University, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.551628.
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This thesis presents the work completed on the evaluation of the expanded web beam concept. The research focussed on investigating methods for expanding the web of a standard pultruded GFRP I-beam to achieve improved mechanical performance whilst achieving an overall saving on mass. The 14 (102 x 102 x 6.4mm) beam was chosen as the standard beam from which the beams were constructed and the mechanical performance of the larger 18 (203 x 203 x 9.5mm) beam as the target for the modified beams. Three designs were proposed and two full-scale beams were built and tested. Of the three designs proposed, one used Quickstep manufactured sandwich panels and another metal connectors fabricated by a Selective Laser Melting facility. All the designs were analysed using theoretical closed form solutions and ANSYS FE software. A tension coupon testing programme was carried out in support of these analyses. The two full-scale beams were tested, together with an 18 beam, in three-point bending and lateral-torsional buckling. The slender nature of the expanded web beams meant that lateral bracing was required for the lateral buckling testing. Of the two modified beams the one that performed the best achieved, 85% of the deflection limit load and 71% of the lateral- torsional buckling load of the 18 beam for an overall mass saving of 38%.
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Lokhande, Ajinkya M. "Evaluation of steel I-section beam and beam-column bracing requirements by test simulation." Thesis, Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53114.
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The ANSI/AISC 360-10 Appendix-6 provisions provide limited guidance on the bracing requirements for beam-columns. In cases involving point (nodal) or shear panel (relative) lateral bracing only, these provisions simply sum the corresponding strength and stiffness requirements for column and beam bracing. Based on prior research evidence, it is expected that this approach is accurate to conservative when the requirements can be logically added. However, in many practical beam-column bracing situations, the requirements cannot be logically added. This is because of the importance of the brace and transverse load position through the cross-section depth, as well as the fact that both torsional and lateral restraint can be important attributes of the general bracing problem. These attributes of the bracing problem can cause the current beam-column bracing requirement predictions to be unconservative.
In addition, limited guidance is available in the broader literature at the current time regarding the appropriate consideration of combined lateral and torsional bracing of I-section beams and beam-columns. Nevertheless, this situation is quite common, particularly for beam-columns, since it is rare that separate and independent lateral bracing systems would be provided for both flanges. More complete guidance is needed for the proper consideration of combined bracing of I-section beams and beam-columns in structural design.
This research focuses on a reasonably comprehensive evaluation of the bracing strength and stiffness requirements for doubly-symmetric I-section beams and beam-columns using refined Finite Element Analysis (FEA) test simulation. The research builds on recent simulation studies of the basic bracing behavior of beams subjected to uniform bending. Various cases of beam members subjected to moment gradient are considered first. This is followed by a wide range of studies of beam-column members subjected to constant axial load and uniform bending as well as axial load combined with moment gradient loading. A range of unbraced lengths are considered resulting in different levels of plasticity at the member strength limit states. In addition, various bracing configurations are addressed including point (nodal) lateral, shear panel (relative) lateral, point torsional, combined point lateral and point torsional, and combined shear panel lateral and point torsional bracing.
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Cheng, Wen. "Optical Vortex Beams: Generation, Propagation and Applications." University of Dayton / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1375370902.
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Batihan, Ali Cagri. "Vibration Analysis Of Cracked Beams On Elastic Foundation Using Timoshenko Beam Theory." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613602/index.pdf.
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In this thesis, transverse vibration of a cracked beam on an elastic foundation and
the effect of crack and foundation parameters on transverse vibration natural
frequencies are studied. Analytical formulations are derived for a beam with
rectangular cross section. The crack is an open type edge crack placed in the
medium of the beam and it is uniform along the width of the beam. The cracked
beam rests on an elastic foundation. The beam is modeled by two different beam
theories, which are Euler-Bernoulli beam theory and Timoshenko beam theory.
The effect of the crack is considered by representing the crack by rotational
springs. The compliance of the spring that represents the crack is obtained by
using fracture mechanics theories. Different foundation models are discussedthese models are Winkler Foundation, Pasternak Foundation, and generalized foundation. The equations of motion are derived by applying Newton'
s 2nd law on an infinitesimal beam element. Non-dimensional parameters are introduced into equations of motion. The beam is separated into pieces at the crack location. By applying the compatibility conditions at the crack location and boundary conditions, characteristic equation whose roots give the non-dimensional natural frequencies is obtained. Numerical solutions are done for a beam with square cross sectional area. The effects of crack ratio, crack location and foundation parameters on transverse vibration natural frequencies are presented. It is observed that existence of crack reduces the natural frequencies. Also the elastic foundation increases the stiffness of the system thus the natural frequencies. The natural frequencies are also affected by the location of the crack.
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Upreti, Manohar Raj. "BEHAVIOR OF FOUNDATION BEAM FOR SHEAR WALL STRUCTURAL SYSTEM WITH COUPLING BEAMS." OpenSIUC, 2019. https://opensiuc.lib.siu.edu/theses/2635.
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The purpose of this study is to analyze the foundation beam linked between two shear walls in the presence of lateral loads. Mat foundation with shear walls is one of the most commonly used reinforced concrete structural systems to resist the lateral load. When two independent walls are connected with a link beam, also known as the coupling beam, the overturning resistance of the building is largely increased. However, the coupling beams are relatively weaker structures and can develop larger stresses. When there is a mat foundation, or pile cap in case of pile foundation, the part of the foundation which is right below the coupling beam where no shear wall is present, will also get large stresses due to the highly rigid nature of adjacent shear walls. Most of the lateral deformations are imposed only on the coupling beams and foundation beam. There is not much literature or design procedure found in books and codes to mitigate the high risks associated with the foundation beam between shear walls on its design vulnerability. This thesis is focused on the risks associated with exceptionally high forces on the foundation beam due to earthquake forces.
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Backström, Daniel. "Vibration of sandwich beams." Doctoral thesis, KTH, Farkost och flyg, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4030.
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Some aspects and properties of the lateral vibration of sandwich beams are investigated, including the concept of apparent bending stiffness and shear modulus, allowing the sandwich beam dynamics to be approximately described by classical beam theory. A sixth order beam model is derived including boundary conditions, and the free and forced response of some beam configurations analyzed. The possibility of computing material parameters from measured eigenfrequencies, i. e. inverse analysis, is considered. The higher order model is also utilized for investigation of the energy propagation through sandwich composite beams and the transmission over different junctions.QC 20100630
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Backström, Daniel. "Vibration of sandwich beams /." Stockholm, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4030.
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Messalti, Mansour. "Viscoelastic damping of beams /." Online version of thesis, 1988. http://hdl.handle.net/1850/10414.
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Gustafsson, Fredrik. "Designing the edge beams." Thesis, Linköpings universitet, Institutionen för teknik och naturvetenskap, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-93601.
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New construction of bridges is the choice of edge beams something that is often discussed. In Sweden currently three different models for the edge beams. When edge beams be elected, all the pros and cons of the different types of edge beams should be considered before deciding on the type of edge beam to be used. Many believe that decisions concerning the selection of edge beams sometimes not correct. This is based in the fact that there are many opinions about what edge beam which should be used. The choice of edge beam controls how advanced dewatering and railing design will be. Edge beam design has a major impact on drainage and bridge railing design. The choice of the edge beam can both simplify the de-watering and provide a better profitability. The purpose of this work is to investigate the problems there are with today's three standard edge beams. The work also aims to provide suggestions for improvement through new designs of edge beam to meet good dewatering properties, and good profitability. Interviews with different people are a great foundation for the work to get a broad perspective over the problem of edge beams. Current bridge snake TK Bro has been a good source in describing the edge beams and the dewatering takes place. Edge Beams in Sweden has been used for a long time without any significant change has occurred. My study shows that there is a demand for the development of the edge beams and find new solutions to achieve profitability. This report describes my suggestion for improvement. The improvements are based on the problems as set forth and the rules that exist in TK Bro.Vid nybyggnation av broar är val av kaltbalkstyp något som ofta diskuteras. I Sverige används idag tre stycken olika standardkantbalkar. När kantbalkstyp ska väljas måste alla för- och nackdelar för de olika kantbalkstyperna övervägas innan beslut tas om vilken typ av kantbalk som ska användas. Många anser att besluten om val av kantbalkstyp ibland inte blir korrekt. Detta grundar sig i att det finns många åsikter om vilken kanbalkstyp som bör användas. Valet av kantbalkstyp styr hur avancerad avvattning och räckeskonstruktion blir. Kantbalksutformningen har stor påverkan på brons avvattning samt räckeskonstruktionen. Valet av kantbalk kan både förenkla avvattningen samt ge en bättre lönsamhet. Syftet med arbetet är att undersöka vilka problem det finns med dagens tre standardkantbalkar. Arbetet syftar också till att ge förslag på förbättringar genom nya utformningar av kantbalken för att uppfylla goda avvattningsegenskaper samt god lönsamhet. Intervjuer av personer insatta i ämnet är till stor grund för arbetet, för att få ett brett perspektiv över problemet med kantbalkar. Aktuella bronormen TK Bro har varit en bra källa vid beskrivningen av kantbalkarna och hur avvattningen sker. Kantbalkarna i Sverige har använts under en lång tid utan att någon större förändring har skett. Min studie visar på att det finns en efterfrågan på att utveckla kantbalken och finna nya lösningar för att uppnå lönsamhet. I rapporten redovisas mina förslag till förbättringar. Förbättringarna bygger på problematiken som frambringats under mina intervjuer.
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Duran, Ezdin. "Design of Edge Beams." Thesis, KTH, Bro- och stålbyggnad, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-147851.
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The purpose of the edge beam is to support the railing and the pavement, function as part of the drainage system and in the case it is integrated into the bridge deck it can serve to distribute concentrated loads. It is located in road environment and therefore exposed to water and salt with chlorides as well as subject to impacts during accidents. It deteriorates in a greater pace than the rest of the bridge and therefore has a shorter lifespan than the bridge in full. A deteriorated edge beam put the safety of the bridge users in jeopardize and increases the need of maintenance, repair and replacement work. These activities affect the surrounding traffic flow due to reduced speed limits as well as closure of traffic lanes. A literature study has been performed to get an understanding of how edge beams are designed and constructed. A great part of this was done by examining codes and regulations. By meeting engineers from different building companies it has been possible to obtain a picture of how it is done in real life and how the path to the final design looks like. Building site visits were carried out to see the process from design to construction i.e. how it is applied in real life. A design study was performed, including a check of crack width in an integrated edge beam over a support, height of bridge deck when a pre-fabricated (brokappa) is used and a comparison in the magnitude of the clamping moment in a steel-concrete bridge with and without an edge beam. All proposals are presented by the Edge Beam Group (EBG, in Swedish, Kantbalksgruppen), which is composed of experienced engineers that works within the frame of the project social optimal edge beam systems governed by the Swedish Transport Administration. The literature research showed that even if the edge bean is prone to deteriorate its lifespan does not have to be governed by its condition. Planned expansion of bridge width and maintenance strategies including the replacement of waterproofing layer could also be a reason for replacement in some cases. A significant increase of reinforcement in the edge beam and top part of the bridge deck over support is needed to obtain an acceptable crack width of 0.15mm. This would however aggravate the casting phase. The use of a pre-fabricated edge beam result in an increase of the bridge deck height. A solution could be to strengthen the anchoring capacity but this could in turn give an over reinforced structure. When it comes to the clamping moment in a steelconcrete composite bridge the integrated edge beam leads to a better distribution of the traffic load. On the other hand, due to the higher dead weight, a bridge deck without an edge beam would result in a lower total moment in the cantilever.
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Siviloglou, Georgios. "Accelerating Optical Airy Beams." Doctoral diss., University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2443.
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Over the years, non-spreading or non-diffracting wave configurations have been systematically investigated in optics. Perhaps the best known example of a diffraction-free optical wave is the so-called Bessel beam, first suggested and observed by Durnin et al. This work sparked considerable theoretical and experimental activity and paved the way toward the discovery of other interesting non-diffracting solutions. In 1979 Berry and Balazs made an important observation within the context of quantum mechanics: they theoretically demonstrated that the Schrodinger equation describing a free particle can exhibit a non-spreading Airy wavepacket solution. This work remained largely unnoticed in the literature-partly because such wavepackets cannot be readily synthesized in quantum mechanics. In this dissertation we investigate both theoretically and experimentally the acceleration dynamics of non-spreading optical Airy beams in both one- and two-dimensional configurations. We show that this class of finite energy waves can retain their intensity features over several diffraction lengths. The possibility of other physical realizations involving spatio-temporal Airy wavepackets is also considered. As demonstrated in our experiments, these Airy beams can exhibit unusual features such as the ability to remain quasi-diffraction-free over long distances while their intensity features tend to freely accelerate during propagation. We have demonstrated experimentally that optical Airy beams propagating in free space can perform ballistic dynamics akin to those of projectiles moving under the action of gravity. The parabolic trajectories of these beams as well as the motion of their center of gravity were observed in good agreement with theory. Another remarkable property of optical Airy beams is their resilience in amplitude and phase perturbations. We show that this class of waves tends to reform during propagation in spite of the severity of the imposed perturbations. In all occasions the reconstruction of these beams is interpreted through their internal transverse power flow. The robustness of these optical beams in scattering and turbulent environments was also studied. The experimental observation of self-trapped Airy beams in unbiased nonlinear photorefractive media is also reported. This new class of non-local self-localized beams owes its existence to carrier diffusion effects as opposed to self-focusing. These finite energy Airy states exhibit a highly asymmetric intensity profile that is determined by the inherent properties of the nonlinear crystal. In addition, these wavepackets self-bend during propagation at an acceleration rate that is independent of the thermal energy associated with two-wave mixing diffusion photorefractive nonlinearity.Ph.D.
Optics and Photonics
Optics and Photonics
Optics PhD
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Jaafar, Sidek Mohamed Ariff. "Monte Carlo investigations of radiotherapy beams : studies of conventional, stereotactic and unflattened beams." Thesis, University of Birmingham, 2010. http://etheses.bham.ac.uk//id/eprint/708/.
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Monte Carlo modelling is a useful method of investigating the electron and photon transport in radiotherapy linear accelerators. The probability of interactions of the materials stored in the cross-section library is considered to be theoretically accurate. Calculations made by Monte Carlo techniques have many roles including investigation of unusual situations where measurements are difficult and as a problem solver. The predictions made by a validated model can be used to confirm an assumption or prove a hypothesis. This study is aimed to investigate the performance of the DOSI detector, a prototype detector which is position sensitive with submillimeter resolution. This solid-state detector is made of p-type diode has silicon material as its volume element. Work from other authors has shown that other silicon detectors overestimate the dose as field size and depth increase. To overcome this, a mechanism for correction has to be determined. For this reason, this investigation compares experimental data and calculated results using Monte Carlo method at 6 MV photon energy from a Varian linear accelerator. A small degree of perturbation has been found from this study, and work on improvement of the dose measurements has been carried out. Results have been presented and suggestion for a better dose meter is discussed.
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Maigyte, Lina. "Shaping of light beams with photonic crystals : spatial filtering, beam collimation and focusing." Doctoral thesis, Universitat Politècnica de Catalunya, 2014. http://hdl.handle.net/10803/277571.
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The research developed in the framework of this PhD thesis is a theoretical, numerical and experimental study of light beam shaping (spatial filtering, beam collimation and focusing) in the visible frequency range using photonic crystal structures. Photonic crystals (PhCs) are materials with periodic, spatially modulated refractive index on the wavelength scale. They are primarily known for their chromatic dispersion properties. However, they can also modify the spatial dispersion, which allows managing the spatial properties of the monochromatic light beams.
In the first part of my thesis we experimentally show that particular spatial dispersion modification in PhCs can lead to spatial (angular) filtering of light beams. The study is focused on the spatial filtering efficiency improvement by introducing chirp (the variation of longitudinal period of the structure) in the crystal structure. Additionally, to enhance the effect, we consider different geometries and materials. The work presented in this PhD thesis brings closer to reality the creation of a new generation spatial filters for micro-photonic circuits and micro-devices.
The second part of the study is devoted to the theoretical, numerical and experimental analysis of the formation of negative spatial dispersion in PhCs, which gives rise to collimation and focusing effects behind the PhCs. The ideas developed in my PhD also work in lossy systems, in particular in metallic PhCs. The simulation results for metallic PhCs are presented, in which both effects- spatial filtering and beam focusing, are shown.La recerca desenvolupada en el marc d'aquesta tesi doctoral és un estudi teòric, numèric i experimental de la modificació de la forma de feixos de llum (filtratge espacial, col·limació i focalització) en el rang visible de freqüències utilitzant estructures de cristall fotònic. Els cristalls fotònics (CFs) són materials amb una modulació periòdica de l'índex de refracció en l'escala de la longitud d'ona, i són principalment coneguts per les seves propietats relacionades amb la dispersió temporal. Tot i això, la dispersió espacial també pot ser modificada mitjançant CFs, fet que permet controlar les propietats espacials de feixos monocromàtics de llum. En la primera part de la tesi, mostrem experimentalment el fet que certes modificacions de la dispersió espacial en CFs poden donar lloc a filtratge espacial (angular) de feixos de llum. L'estudi es focalitza en la millora de l'eficiència del filtratge espacial mitjançant la introducció de "chirp" (la variació del període longitudinal de l'estructura) en el CF. A més, per tal d'incrementar l'efecte considerem diferents estructures i materials. El treball presentat en aquesta tesi doctoral acosta a la realitat la creació d'una nova generació de filtres espacials per a circuits micro-fotònics i micro-dispositius. La segona part d'aquest estudi se centra en l'anàlisi teòric, numèric i experimental de la formació de dispersió espacial negativa en CFs, la gual dóna lloc a efectes de col·limació i focalització un cop travessat el CF. Les idees desenvolupades en aquesta tesi doctoral també són aplicables a sistemes amb pèrdues, en particular a CFs metàl·lics. Els resultats de les simulacions mostren l'existència d'ambdós efectes, filtratge espacial i focalització, en CFs metàl·lics.
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Reys, De Otiz Iclea. "Strut-and-tie modelling of reinforced concrete : short beams and beam-column joints." Thesis, University of Westminster, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334612.
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Ruggerini, Andrea Walter <1988>. "Geometrically nonlinear analysis of thin-walled beams based on the Generalized Beam Theory." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amsdottorato.unibo.it/8497/7/Geometrically-nonlinear-GBT-beam-AndreaW-Ruggerini.pdf.
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The thesis addresses the geometrically nonlinear analysis of thin-walled beams by the Generalized Beam Theory ( GBT ). Starting from the recent literature, the linear theory is illustrated, along with some issues related to GBT finite element formulation. Potential benefits of using
the GBT in design are exemplified with reference to the design of roofing systems. To assess the deterioration of member capacity due to cross-section distortion phenomena, the formulation of a geometrically nonlinear GBT is then pursued. The generalization of the GBT to the nonlinear context is performed by using the Implicit Corotational Method ( ICM ), devising a strategy to effectively apply the ICM when considering higher order deformation modes. Once, obtained, the nonlinear model has been implemented using a state-of-the-art mixed-stress finite element. The nonlinear finite element is then implemented starting from the linear GBT one. Extensive numerical results show the performance of the proposed approach in buckling and path-following analyses.
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WISSMANN, JORGE AUGUSTO. "STUDY OF STEEL BEAMS WITH WEB OPENINGS INCLUDING CELLULAR, LITZKA AND DEPTH-EXPANDED BEAMS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2009. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=31879@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
PROGRAMA DE EXCELENCIA ACADEMICA
Estruturas cada vez mais esbeltas têm sido usadas para otimizar edifícios de grande porte e reduzir custos, inclui-se nisto o pé-direito das edificações e portanto a altura das vigas. Grandes vãos são cada vez mais comuns, principalmente quando se utiliza aço em edificações, gerando então amplos espaços de serviço em uma direção, mas obstáculos na outra pela continuidade das vigas. A utilização de aberturas na alma das vigas para passagem de tubulações de ar-condicionado, incêndio, etc., evita um acréscimo na altura. Em consequência há uma grande diminuição da capacidade resistente nestes elementos estruturais que dependem diretamente da forma, do tamanho e da posição destas aberturas. A presente dissertação descreve alguns métodos construtivos de aberturas em almas de vigas de aço, cálculos de dimensionamentos e normas relacionadas. Alguns estudos numéricos com aplicações do método dos elementos finitos foram realizados investigando: angulação de aberturas hexagonais, vigas com três aberturas nos terços médios, vigas casteladas (tipo Litzka, com quantidades diferentes de aberturas), vigas expandidas em altura e uma viga Litzka Expandida. Para tal, utilizou-se de seis perfis de uso prático e comparando-os entre estas alternativas descritas. A viga Litzka Expandida se destacou em resistência quando comparada com outros métodos de fabricação, como também pelo menor peso linear, praticidade na fabricação e posicionamento das aberturas.
More slender structures are used in order to reduce costs, floors depht and floor to ceiling clear heights. Steel construction and composite construction for buildings often employs long spans for beams and girders, offering service room between beams in one direction only. The use of web openings for passage of service ducts avoids increasing the depth of construction. Beams with web openings have reductions on flexural and shear resistances depending on the geometry, size and position of such openings on the beam. This dissertation presents some construction methods of beam web openings, analysis and design recommendations, related standards and codes. Some numerical studies by the finite elements method were carried out and results are presented for: type of openings, number and spacing of openings, castelled beams (Litzka type and nonuniform distribution of openings) and expanded in depth beams. For this purpose, six commonly used profiles were used for testing the described web openings solutions. Some comparison results are presented. The Litzka type of web expanded beam presented the best performance in terms of strength, easy of fabrication and reduction of material costs.
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Lam, Wai-yin. "Plate-reinforced composite coupling beams experimental and numerical studies /." Click to view the E-thesis via HKUTO, 2006. http://sunzi.lib.hku.hk/hkuto/record/B37311797.
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Ghneim, Said Nimr 1953. "Laser pulse amplification through a laser-cooled active plasma." Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/276868.
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Recent advances in experimental laser cooling have shown the possibility of stopping an atomic beam using the light pressure force of a counter-propagating laser wave. As an application to laser cooling, it is proposed to build a single frequency cesium laser that has a narrow linewidth. Laser cooling techniques are used to cool an atomic beam of cesium to an average velocity of 5 m/s, corresponding to a temperature of 0.2°K. Expressions of the basic forces that a laser wave exerts on atoms are derived according to a semi-classical approach. The experimental problems and methods of avoiding these problems are treated in detail. A computer Monte-Carlo simulation is used to discuss the feasibility of building the proposed laser. This simulation was done for an ensemble of 10,000 atoms of cesium, and it included the effects of the gravitational force and the related experimental variables. The possibility of building single frequency lasers that use a cooled medium of noble gases, and many other applications of laser cooling are briefly discussed at the end of this work.
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Gaw, Raymond C. "Electron beams at geosynchronous orbit." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1993. http://handle.dtic.mil/100.2/ADA275471.
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Koplow, Michael A. "Dynamic response of discontinuous beams." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0011829.
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Ozdemir, Kerem Murat. "Lateral Buckling Of Overhanging Beams." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606488/index.pdf.
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Lateral torsional buckling should be taken into account during the design of overhanging steel beams. One special type of overhanging beams is the crane trolley monorails. Lateral buckling of overhanging monorails under idealized loading and
boundary conditions has been studied in the past using classical mathematical procedures. This thesis aims to present a detailed investigation of overhanging monorails using finite element analysis. Effects of different loading and boundary
conditions were studied in detail. It was found out that the location of loading and supports on the cross section have significant effects on the buckling capacity. Beams having different warping and torsional properties were analyzed. The effects of cross section distortion on buckling capacity were investigated for beams with single and double overhangs. The reduction in capacity due to cross section distortion has been
quantified. Based on the analysis results simple design recommendations were developed for lateral buckling of overhanging monorails and they are presented herein.
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Wilson, Glen. "Crashworthiness of side impact beams." Thesis, University of Strathclyde, 2002. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=29199.
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This thesis describes the investigations carried out into the crashworthiness of side impact beams. Two specific beams were investigated: a commercially used steel beam and a prospective composite beam made from a glass fibre weave within a polypropylene matrix. The components were simply supported and were subjected to quasi-static and impact loading, the latter experiments being performed using a Drop Weight Test (DWT) rig. Static and dynamic Finite Element Analysis (FEA) was used to model the behaviour observed during testing. Ansys v5.4 was used for the static FEA while LS-Dyna3D v940 was used for the dynamic FEA. The objectives of the project were to assess and then model the behaviour of the steel and composite side impact beams. This behaviour is in terms of both the beams' static and impact response. The beams were tested to determine their elastic behaviour, when and how failure occurs and their post-failure response. Important factors in their performance were identified. The modelling offered insights into the beams' behaviour and could potentially be used as a predictive tool in design activity. It was found that, for the loading conditions and material type used, both the static and dynamic FEA could provide accurate predictions of the behaviour of the beams although both types of FEA had their limitations.
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Megharief, Jihad Dokali. "Behavior of composite castellated beams." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ37273.pdf.
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Jordan, Andrew R. "Wetpreg Reinforcement of Glulam Beams." Fogler Library, University of Maine, 1998. http://www.library.umaine.edu/theses/pdf/JordanA1998.pdf.
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Randall, Robert William. "Infrared spectroscopy of molecular beams." Thesis, University of Oxford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318871.
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Ring, James David. "Incomplete catastrophes and paraxial beams." Thesis, University of Bristol, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.629412.
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Molenstra, Nadia Julia. "Ultimate strength of composite beams." Thesis, University of Warwick, 1990. http://wrap.warwick.ac.uk/34713/.
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The study of composite beams is characterised by the connection between the two components: the concrete slab and the steel girder. In this thesis, two different problems, related to this connection were studied: the problem of partial interaction in composite beams of long spans with low degrees of shear connection, and the problem of transverse flexibility of the stud connection 'joint' between the concrete slab and the steel beam as part of a discrete inverted U-frame. This thesis is therefore divided into two separate parts. The study of beams with partial shear connection and solid slabs or slabs with metal decking is considered in the first part. Such beams, with a uniform stud spacing over each shear span, with spans longer than 10 m - generally propped during construction, and with low degrees of shear connection, could fail prematurely and suddenly in shear rather than gradually in bending, due to the limited slip deformation capacity of the studs in shear. In order to investigate the behaviour of simply supported and continuous composite beams with different degrees of shear connection, different geometry and different shear spans under design ultimate loading conditions, a numerical computer simulation program was written. The program takes account of the relative displacement between the slab and the beam and the non-linear behaviour of steel, concrete and stud connectors. A data bank of maximum slip results for different beams is obtained for ultimate beam loads designed to the interpolation method in Eurocode 4. The computer simulation gives a conservative but safe assessment of the suitability of the degree of interaction for a specific design ultimate load . The results were used to formulate a tentative design method for composite beams with solid slabs and partial shear connection. Discrete inverted U-frame action exists between composite bridge beams with intermittent vertical web stiffeners which provide lateral restraint to the bottom flange in the hogging bending region near the internal supports. The design method in BS 5400:Part 3 for discrete U-frame action gives values for the transverse flexibility of a number of standard structural steel connections which are used in the calculation of the effective buckling length and the lateral deflection of the compression flange. To obtain similar values for steel-concrete joints, tests were done to scale 1:1 on six flange-slab connections with different stud configurations, but constant conservative dimensions for the steel flange and the concrete slab. Their crack patterns can be predicted by using a truss analogy. All test specimens either failed in shear or by puffing out of the studs, and shear cracking and shear failure criteria for concrete beams can be used to predict the cracking and failure loads. The transverse elastic flexibiities of the joints in these tests only represent the behaviour of the same joints in a complete structure up to the point where the shear cracks propagated over the full width of the specimens. Based on these few test results, a limited tentative design equation is proposed for the transverse flexibility of these type of stud connections, although further research is required into the influence of the increased flexibility on the buckling mode and the variation of the flexibility with variables other than the stud configurations.
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Jabboor, Wasseem. "Dynamic structural analysis of beams." Thesis, Heriot-Watt University, 2011. http://hdl.handle.net/10399/2469.
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The research reviews the various methods, accurate and approximate, analytical and numerical, used for the analysis of beams that are subjected to dynamic loads. A review of previous research is presented. A detailed description of one of the methods, the Simplified Elastic Plastic Method (the SEP Method), a well-developed approximate method, is given. A finite element model, built with the aid of the computer software ABAQUS, is described. Results of 20 experiments made by others are provided and used as a benchmark for the finite element analysis. The methodology used for the validation of the ABAQUS Model and the SEP Method is to do, for various study cases, a comparison between the experimental results, those computed using the ABAQUS Model and those predicted using the SEP Method. Having validated the ABAQUS Model, it has been used as a benchmark with which to check the SEP Method. Therefore, additional cases have been analysed using the ABAQUS Model in order to cover a more comprehensive range of variables. A good agreement has been found between the results. The accuracy of the ABAQUS model and the conservatism of the SEP Method are shown. A design procedure using the SEP Method has been developed. Calibration factors are also proposed in order to reduce the conservatism in the SEP Method. The results and recommendations of the research can be employed in the defence industry, civil and structural engineering.
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Fan, Chun Keung Roger. "Buckling in continuous composite beams." Thesis, University of Warwick, 1990. http://wrap.warwick.ac.uk/106724/.
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Two aspects of the buckling behaviour of continuous composite beams of steel and concrete are considered. The first part relates to the study of moment redistribution in braced slender beams (Class 3 draft Eurocode 4) due to local buckling in the hogging moment regions. The second part describes the experimental work to investigate the ultimate load behaviour of unbraced compact beams (Classes 1 and 2 draft Eurocode 4) in the hogging moment regions. For a braced continuous slender composite beam, local buckling at an internal support allows a redistribution of bending moment from the hogging regions to the sagging regions, in addition to material nonlinearity. This effect was studied by a computer simulation on two-span beams. The program takes into account not only the effect of local buckling, but also material nonlinearity and residual stresses, on moment redistribution. The ultimate loads designed to the less conservative method for Class 3 beans in the draft Eurocode 4 were used as a datum in the parametric study. The simulation then gave an independent assessment of the appropriateness and safety of these loads at the ultimate limit state. It is shown that the design method is slightly conservative. Residual stresses have very little effect on the ultimate carrying capacity. Furthermore, in design to the draft Eurocode 4, unpropped construction is more restrictive than propped construction, and hence the results are also more conservative. Lateral buckling of continuous unbraced composite beams in the hogging moment regions can only occur in a distortional mode, and is most unlikely to happen in practical building or bridge structures using hot-rolled steel sections of span up to about 30m. Various design methods based on numerical studies now exist to predict the ultimate strength of continuous composite beams affected by distortional lateral buckling, but few experimental results are available to validate their theoretical assumptions and accuracy. Tests at realistic scale on two T-beams and two inverted U-frames at the Class 2-3 Interface, in accordance with the draft Eurocode 4, are reported. Their results are compared with predictions by five design methods, four of which are satisfactory for the beams tested except BS5400:Part 3. Due to premature fracture of reinforcing fabric in one of the U-frame tests, it is recommended not to include their contribution in moment resistance, when the composite cross-section is plastic and a design requires a large amount of rotation capacity in the hogging moment regions. Based on limited test results, a tentative method is proposed to provide a quick check, whether distortional lateral buckling needs to be considered or not, for continuous composite beams with Class 1 or 2 cross-sections.
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Arafat, Haider Nabhan. "Nonlinear Response of Cantilever Beams." Diss., Virginia Tech, 1999. http://hdl.handle.net/10919/27182.
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The nonlinear nonplanar steady-state responses of cantilever beams to direct and parametric harmonic excitations are investigated using perturbation techniques. Modal interactions between the bending-bending and bending-bending-twisting motions are studied. Using a variational formulation, we obtained the governing equations of motion and associated boundary conditions for monoclinic composite and isotropic metallic inextensional beams. The method of multiple scales is applied either to the governing system of equations and associated boundary conditions or to the Lagrangian and virtual-work term to determine the modulation equations that govern the slow dynamics of the responses. These equations are shown to exhibit symmetry properties, reflecting the conservative nature of the beams in the absence of damping.
It is popular to first discretize the partial-differential equations of motion and then apply a perturbation technique to the resulting ordinary-differential equations to determine the modulation equations. Due to the presence of quadratic as well as cubic nonlinearities in the governing system for the bending-bending-twisting oscillations of beams, it is shown that this approach leads to erroneous results. Furthermore, the symmetries are lost in the resulting equations.
Nontrivial fixed points of the modulation equations correspond, generally, to periodic responses of the beams, whereas limit-cycle solutions of the modulation equations correspond to aperiodic responses of the beams. A pseudo-arclength scheme is used to determine the fixed points and their stability. In some cases, they are found to undergo Hopf bifurcations, which result in limit cycles. A combination of a long-time integration, a two-point boundary-value continuation scheme, and Floquet theory is used to determine in detail branches of periodic and chaotic solutions and assess their stability. The limit cycles undergo symmetry-breaking, cyclic-fold, and period-doubling bifurcations. The chaotic attractors undergo attractor-merging and boundary crises as well as explosive bifurcations.
For certain cases, it is determined that the response of a beam to a high-frequency excitation is not necessarily a high-frequency low-amplitude oscillation. In fact, low-frequency high-amplitude components that dominate the responses may be activated by resonant and nonresonant mechanisms. In such cases, the overall oscillations of the beam may be significantly large and cannot be neglected.Ph. D.
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Inokawa, Hiroshi. "SEMICONDUCTOR METALLIZATION BY ION BEAMS." Kyoto University, 1985. http://hdl.handle.net/2433/74652.
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West, Ray A. "Damping of elastic-viscoelastic beams /." Online version of thesis, 1992. http://hdl.handle.net/1850/11111.
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Tanushev, Nicolay M. "Gaussian beams theory and applications /." Diss., Restricted to subscribing institutions, 2007. http://proquest.umi.com/pqdweb?did=1464114031&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Jamal, Dany. "Solution methods of composite beams." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2012. http://www.nusl.cz/ntk/nusl-264913.
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Solutions of composite beams encounter some specific problems, such as shrinkage and creep of concrete, cracking of concrete and plasticity of steel, partial interaction of elements or history of erection and loading process. These factors and others affect the distribution of internal forces along the beam, the distribution of stresses along the cross-section and also stiffness and deflection of beams. The goal is to describe and compare methods for analysis of composite steel and concrete beams by more simplified approaches allowed by Eurocode with more advanced techniques. The studies will be carried out on the simply supported and continuous beams designed with respect to Eurocode 1, 2, 3 and 4.
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Horger, John. "Multiple plane wave analysis of acousto-optic diffraction of Gaussian shaped light beams." Thesis, Virginia Tech, 1987. http://hdl.handle.net/10919/44053.
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A short history of acousto-optics research is presented
along with a general description of how light and sound
interact.
The Multiple Scattering model is derived and used with a Gaussian light beam to observe the distortion in light beam profile within the sound field. Numerical results are presented for comparison to previous studies using thick holograms and two orders of light. The results from using two light orders are compared to four light order results.
A Hamming sound amplitude distribution is introduced as
a possible way to reduce the amount of light beam profile
distortion.
Master of Science
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FORTNEY, PATRICK JOSEPH. "THE NEXT GENERATION OF COUPLING BEAMS." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1115837131.
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Eriksson, Samuel, and Erik Rudqvist. "Double-decker beam of beam of bamboo - An alternative to I-section beams in construction of multistory housing." Thesis, KTH, Skolan för teknikvetenskap (SCI), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-278903.
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I en värld i ständig utveckling, med en befolkningsökning och en urbanisering större än någonsin, ställs stora krav på nya bostäder. Dessa bör ha ett lågt klimatavtryck och ska kunna vara bostad åt många människor. Även att hålla städerna kompakta är viktigt för att kunna tillhandahålla med allmänna tjänster såsom kollektivtrafik, sophämtning, avlopp, vatten etc. Detta löses ofta genom att bygga de nya husen på höjden. Ett alternativ till att minska klimatavtrycket är att bygga dessa hus i det snabbt växande materialet bambu. Avsikten är att dessa hus byggs i moduler av balkar, pelare etc. Denna rapport behandlar den balk, eller den dubbeldäckarbalk, som skulle användas i en sådan konstruktion. I rapporten finns beskrivet hur dubbeldäckarbalken ska konstrueras för att uppnå optimala egenskaper med avseende på spänning och deformation. Dubbeldäckarbalken är konstruerad med två parallella bambustjälkar som sammanfogas med hjälp av ett antal invändigt armerade stöd gjorda av betong. Dubbeldäckarbalken optimeras utifrån antal stöd, avstånd mellan stöden, vinkel på stöden och avstånd mellan stjälkarna. Dessa valueras med hjälp av beräkningar och förenkligar gjorda i Matlab, och valideras sedan med hjälp av verktyget ANSYS Mechanical. Den slutgiltiga verionen av en 4 meter lång dubbeldäckarbalk har fem stycken stöd, där två av dessa placeras vid ytterkant, två placeras 0.84 meter från ytterkant och det sista placeras i mitten. De fyra yttre stöden är vinklade 45° mot mitten jämfört med bambustjälkarnas riktning. Det slutgiltiga avståndet mellan bambustjälkarnas centrum är 30 centimeter, vilket ger en total höjd av 40 centimeter.In a world in constant development, with an increase in population and an urbanisation greater than ever, huge requirements are put on the housing industry. A need for small impact on the environment, to be able to house multiple families in one building, and also keeping the cities compact to be able to supply basic public services in an efficient manner. This is often solved by building higher and higher. An alternative solution to make these higher buildings more environmentally friendly and cheaper would be to use a material vastly available, bamboo. This report deals with the double-decker beam, the brain child of Saevfors Consulting, that would be used in such a construction. It is described how this double-decker beam would be constructed in order to be optimized in regards to deformation and stresses. The double-decker beam consists of two bamboo culms interconnected by reinforced concrete struts. It is optimized in regards to four main design parameters. Namely, the number of struts, the strut placement, the angle of the struts and the distance between the two bamboo culms. These were evaluated with the help of simplified calculations made in Matlab, which were in turn verified by more complex simulations in ANSYS Mechanical. The final version of the 4 m long double-decker beam had a total of five struts. The outermost strut being placed at the origin of the culm, and the second strut placed at a distance of 0,84 m from the origin, both being reclined 45°. These are then mirrored in the vertical central strut, and so the double-decker beam takes on a symmetrical appearance.
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Levy, Kelly Rebecca. "Bond behavior of prestressed reinforcement in beams constructed with self-consolidating concrete." Auburn, Ala., 2007. http://repo.lib.auburn.edu/2007%20Spring%20Theses/LEVY_KELLY_6.pdf.
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Clemons, John L. "Electron-enhanced etching of SI(100) by atomic and molecular hydrogen." Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/30416.
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Kaluza, Malte Christoph. "Characterisation of laser-accelerated proton beams." [S.l.] : [s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=972318054.
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Näsholm, Sven Peter. "Ultrasound beams for enhanced image quality." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Det medisinske fakultet, 2008. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-2163.
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The contents of this thesis consider new methods for generating ultrasound beams for enhanced image quality in medical imaging. The results presented are produced through computer simulations. The thesis consists of an introductory chapter and four papers, which are all intended to be individually readable. Chapter 1 gives a brief overview of ultrasound and medical ultrasound imaging, as well as different aspects of ultrasound image quality and acoustic noise. A non-linear wave equation is presented and analyzed. This equation describes ultrasound propagation within, and interaction with tissue. In Paper A, a transducer annular array design method is presented. The method involves a geometric pre-focusing, which may vary between the array elements. This is useful for producing narrow receive beams within a large imaging depth window. It is advantageous for avoiding problems that occur when combining high frequencies and large receive apertures when utilizing the conventional equal-area design method. Paper B introduces a method to produce synthetic transmit beams that are useful for suppression of reverberation noise caused by multiple scattering of the forward-propagating imaging pulse. This is done through combination of two transmit pulse complexes denoted Second order UltRasound Field (SURF). Each such complex consists of a conventional high-frequency imaging pulse added to a low-frequency sound-speed manipulation pulse. The SURF transmit beam is generated by forming the difference between the propagated fields, filtered around the imaging frequency. This beam has suppressed amplitude near the transducer, where a reflection-generating body-wall is often present during in vivo imaging. Furthermore, a method to produce a combined second-harmonic pulse inversion (PI) and SURF beam is also presented, here denoted SURF-PI. Two imaging setups are defined for which the feasibility of the method is tested through simulations in case of propagation through homogeneous tissue. SURF beams and combined SURF-PI beams are compared to fundamental imaging and PI imaging beams for the two setups. The SURF-PI beams are the most suppressed in the near-field, followed by the approximately equally suppressed SURF and PI beams. The signal level within the imaging depth region becomes higher for SURF than for PI. In Paper C, two signal processing methods for further adjustment of the SURF beams are introduced. This is achieved through post-processing, either by application of a time-shift, or of a general filter, to one of the propagated fields. The processing is done prior to carrying out the subtraction that is done to form the SURF beam. This provides a flexible way of adjustment to choose the depth position where the scattering sources wished to be suppressed are located. Different adjustments may be realized without need for re-transmission or resumed propagation of the SURF pulse complexes. The post-processing methods are applied to a dataset generated for Paper B. Adjusted transmit beam examples are presented and their reverberation suppression abilities are compared to non-adjusted SURF. In Paper D, the feasibility study of the SURF beam generation as presented in Paper B, and its post-processing adjustment as presented in Paper C, are enlarged to include propagation within an inhomogeneous medium where a body-wall model producing severe aberration delays is present. It is shown that both the generation of the SURF beams and the post-processing adjustment are attainable under the modeled conditions.artikle I: "This work has been submitted to the IEEE for possible publication. Copyright may be transferred without notice, after which this version may no longer be accessible."
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Rivet, Adam. "Distortional analysis of thin walled beams." Thesis, University of Ottawa (Canada), 2010. http://hdl.handle.net/10393/28687.
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A general solution for the stress-deformation analysis of interconnected plates subjected to general loading conditions is developed. The solution is based on the assumptions of thin-walled plate theory and is limited to combinations of straight plates made of linearly elastic isotropic material.
The principle of stationary potential energy is used in conjunction with series expansion for the displacement fields to formulate the equilibrium conditions and boundary conditions. In general, the differential equilibrium equations are coupled. A quasi-closed form solution for the displacement fields is nonetheless provided.
The solution developed is successfully adopted to solve several example problems. Three of the problems involve individual plates, while six involve multiply connected plates. Comparisons with established finite element solutions demonstrate the ability of the model to accurately capture the behaviour with a remarkably small number of degrees of freedoms.
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Liu, Jianhui. "Dynamic behaviour of rigid-plastic beams." Thesis, University of Liverpool, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.480541.
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Behdinan, Kamran. "Dynamics of geometrically nonlinear sliding beams." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ32734.pdf.
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