Dissertations / Theses: 'Amplitude'

1

Tew, David Peter. "Large amplitude vibration." Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.619693.

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2

Ullmo, Emmanuel. "Hauteurs et amplitude arithmétique." Paris 11, 1993. http://www.theses.fr/1993PA112022.

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On etudie la notion d'amplitude arithmetique. On en deduit l'existence de points entiers de hauteur controlee. On montre ensuite que sur une courbe elliptique semi-stable ayant au moins une place de mauvaise reduction, il n'existe qu'un nombre fini de points de torsion qui passent partout par la composante neutre du modele de neron

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3

Hill, Simon John. "Large amplitude fish swimming." Thesis, University of Leeds, 1998. http://etheses.whiterose.ac.uk/12760/.

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A fish swims by stimulating its muscles and causing its body to "wiggle", which in turn generates the thrust required for propulsion. The relationship between the forces generated by the fish muscles and the observed pattern of movement is governed by the mechanics of the internal structure ofthe fish, and the fluid mechanics of the surrounding water. The mathematical modell ing of how fish swim involves coupling the external "biofluiddynamics" to the body's internal solid mechanics. The best-known theory for the hydrodynamics of fish swimming is Lighthill's elongated body theory (Lighthill, 1975). In Lighthill's theory the curvature of the fish is assumed small and the effect on the fish of the vortex wake is neglected. Cheng et al. (1991) did not make these simplifications in developing their vortex lattice panel method, but the fish was assumed to be infinitely thin and its undulations of small amplitude. Lighthill's "recoil correction" is the addition of a solid-body motion to ensure that an imposed "swimming description" satisfies the conservation of momentum and angular momentum. A real fish is expected to minimize such sideways translation and rotation to avoid wasteful vortex shedding. Cheng and Blickhan (1994) found that the panel method model required a smaller recoil than did Lighthill's model. Our approach is to extend Cheng's model to large amplitude. Thus we include the effect of the wake on the fish, and the self-induced deformation of the wake itself. In studying the internal mechanics of the body we model the fish as an active bending beam. Using the equations of motion of cross-sectional slices of the body we can form a set of coupled differential equations for the bending moment distribution. At large amplitude the bending moment equations involve the tangential forces acting on the body (which may be neglected in the small amplitude version). Consequently we include the boundary layer along the fish in order to estimate the viscous drag directly. The panel method has been used successfully for the fluid mechanical calculations associated with large-amplitude fish swimming. We are able to use its results as input to calculate the bending moment distribution. The boundary layer calculations are based on a crude model; solutions to the large amplitude bending moment equations should also be considered in this light.

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4

Jena, Trividesh. "Precise measurement of the matter power spectrum amplitude and the background radiation amplitude /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC IP addresses, 2004. http://wwwlib.umi.com/cr/ucsd/fullcit?p3127637.

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5

Vanelle, Claudia. "Traveltime based true amplitude migration." [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=964567148.

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6

Grech, Michael. "True amplitude processing in VSPs." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0007/MQ34368.pdf.

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7

P, Moghaddam Peyman. "Curvelet-based migration amplitude recovery." Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/24421.

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Migration can accurately locate reflectors in the earth but in most cases fails to correctly resolve their amplitude. This might lead to mis-interpretation of the nature of reflector. In this thesis, I introduced a method to accurately recover the amplitude of the seismic reflector. This method relies on a new transform-based recovery that exploits the expression of seismic images by the recently developed curvelet transform. The elements of this transform, called curvelets, are multi-dimensional, multi-scale, and multi-directional. They also remain approximately invariant under the imaging operator. I exploit these properties of the curvelets to introduce a method called Curvelet Match Filtering (CMF) for recovering the seismic amplitude in presence of noise in both migrated image and data. I detail the method and illustrate its performance on synthetic dataset. I also extend CMF formulation to other geophysical applications and present results on multiple removal. In addition of that, I investigate preconditioning of the migration which results to rapid convergence rate of the iterative method using migration.

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8

Martínez, Nuevo Pablo. "Amplitude sampling for signal representation." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/107285.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2016.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 153-159).
The theoretical basis for conventional acquisition of bandlimited signals typically relies on uniform time sampling and assumes infinite-precision amplitude values. This thesis explores signal representation and recovery based on uniform amplitude sampling with either assuming infinite-precision timing information or time restricted to a uniform grid. If time is allowed to lie on the continuum, the approach is based on a structure that is equivalent to reversibly transforming the input signal into a monotonic function which is then uniformly sampled in amplitude. In effect, the source signal is then implicitly represented by the times at which the monotonic function crosses a predefined set of amplitude values. We refer to this technique as amplitude sampling. This approach can be viewed alternatively as nonuniform time sampling of the original source signal whereas the resulting monotonic signal produces an associated amplitude-time function which is uniformly sampled in amplitude. The duality and frequency-domain properties for the functions involved in the transformation are derived. Reconstruction from amplitude samples is shown to be possible through iterative algorithms. If both time and amplitude are restricted to equally-spaced values, then the sampling strategy, referred to as lattice sampling, simultaneously uses both uniform amplitude and uniform time sampling. A class of bandlimited signals is characterized that can be sampled and reconstructed in this manner in order to derive spectral characteristics of quantized discrete-time signals.
by Pablo Martínez Nuev.
Ph. D.

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9

Moghaddam, Peyman P., Felix J. Herrmann, and Christiaan C. Stolk. "Seismic Amplitude Recovery with Curvelets." European Association of Geoscientists & Engineers, 2007. http://hdl.handle.net/2429/543.

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A non-linear singularity-preserving solution to the least-squares seismic imaging problem with sparseness and continuity constraints is proposed. The applied formalism explores curvelets as a directional frame that, by their sparsity on the image, and their invariance under the imaging operators, allows for a stable recovery of the amplitudes. Our method is based on the estimation of the normal operator in the form of an ’eigenvalue’ decomposition with curvelets as the ’eigenvectors’. Subsequently, we propose an inversion method that derives from estimation of the normal operator and is formulated as a convex optimization problem. Sparsity in the curvelet domain as well as continuity along the reflectors in the image domain are promoted as part of this optimization. Our method is tested with a reverse-time ’wave-equation’ migration code simulating the acoustic wave equation.

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Cheah, Victoria Vik Ee. "Prosodic rhythm in the speech amplitude envelope : amplitude modulation phase hierarchies (AMPHs) and AMPH models." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.607862.

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11

Reese, Lorie. "Laryngeal-level amplitude modulation in vibrato /." Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd1535.pdf.

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Steeves, Adam H. 1980. "Electronic signatures of large amplitude motions." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/49555.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2009.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Vita.
Includes bibliographical references (p. 259-271).
In this thesis, I demonstrate that measurements of electronic-structure-induced splittings in the rotational spectrum of a vibrationally excited state can identify the nature and extent of the distortion of the equilibrium electronic wavefunction and thereby provide a measure of progress along a reaction coordinate. One-dimensional models of the large amplitude bending reaction coordinates and their associated electronic signatures are constructed for two prototypical unimolecular isomerizations: acetylene<-->vinylidene (HCCH<-->CCH2), and hydrogen cyanide$hydrogen isocyanide (HCN<-->HNC). The nuclear quadrupole hyperne structures of HCN and HNC are distinct at their equilibrium geometries due to the dissimilar natures of bonding in the vicinity of the 14N nucleus. High resolution rotational spectroscopy has been used to determine the hyperne coupling parameters for the ground and excited vibrational levels of HCN and HNC, with up to ten quanta of bending excitation in HCN and up to four quanta in HNC. These spectra reveal the evolution of electronic structure along the isomerization path. Large amplitude local-bending vibrational eigenstates of the ... state of acetylene are shown to be unique in that they possess significant electric dipole moments as a result of the dynamical symmetry breaking in the local-mode limit. Stimulated emission pumping (SEP), through Franck{Condonforbidden vibrational levels of the A~ 1Au state, has been employed to populate the lowest few eigenstates that manifest large amplitude local-bending behavior.
(cont.) Locating appropriate SEP intermediate states has required thorough analysis of the A~-state level structure, particularly the overtones and combination levels involving the nearly degenerate low frequency bending modes, 04 and 06, that are directly related to two possible paths for trans{cis isomerization on the excited state surface. Recent developments in chirped-pulse rotational spectroscopy will enable identification of the higher energy local-bending eigenstates, which approach the acetylene<-->vinylidene transition state, based on their predicted Stark coefficients.
by Adam H. Steeves.
Ph.D.

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13

Poole, Travis L. "Geoacoustic inversion by mode amplitude perturbation." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/38932.

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Thesis (Ph. D.)--Joint Program in Applied Ocean Physics and Engineering (Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and the Woods Hole Oceanographic Institution), 2007.
Includes bibliographical references (p. 124-126).
This thesis introduces an algorithm for inverting for the geoacoustic properties of the seafloor in shallow water. The input data required by the algorithm are estimates of the amplitudes of the normal modes excited by a low-frequency pure-tone sound source, and estimates of the water column sound speed profiles at the source and receiver positions. The algorithm makes use of perturbation results, and computes the small correction to an estimated background profile that is necessary to reproduce the measured mode amplitudes. Range-dependent waveguide properties can be inverted for so long as they vary slowly enough in range that the adiabatic approximation is valid. The thesis also presents an estimator which can be used to obtain the input data for the inversion algorithm from pressure measurements made on a vertical line array (VLA). The estimator is an Extended Kalman Filter (EKF), which treats the mode amplitudes and eigenvalues as state variables. Numerous synthetic and real-data examples of both the inversion algorithm and the EKF estimator are provided. The inversion algorithm is similar to eigenvalue perturbation methods, and the thesis also presents a combination mode amplitude/eigenvalue inversion algorithm, which combines the advantages of the two techniques.
by Travis L. Poole.
Ph.D.

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14

Hooper, J. "Fretting fatigue under variable amplitude loading." Thesis, Cranfield University, 2003. http://dspace.lib.cranfield.ac.uk/handle/1826/11046.

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Fretting fatigue is a major concern in the design of engineering components that will be subjected to clamping pressures whilst operating in a vibrational environment. The type of loading environment generated in these applications is generally of a variable amplitude nature. Therefore it is important for engineers to understand how such loading affects the severity of fretting fatigue. In the absence of this understanding, engineering designers are left to apply simplistic plain fatigue life prediction rules, such as Miners linear damage law, to try to estimate the damage generated from a particular loading history. In order to try to establish a baseline for the understanding of fretting fatigue under variable amplitude loading, a structured series of CAL and V AL tests were designed and carried out. The aim of the CAL tests was to characterise the fretting fatigue test rig (designed by the author) so that an experimental foundation could be developed, upon which the fretting fatigue study was based. A structured investigation into the effects on fretting fatigue of applying various specifically designed loading histories was carried out and some very distinct relationships between the applied loading spectra and fretting fatigue life were found. For the application of overloads it was observed that overload size, overload application interval and the number of overloads in each application all had a sizeable effect on the severity of fretting. Two-level, three-level and five-level block loading tests were also investigated and numerous loading history dependent results were obtained. The applicability of Miners law to fretting fatigue was assessed. Combining Miners law with well-defined CAL stress-life results gave reasonable predictions for all of the V AL fretting fatigue tests carried out, with damage summations at failure ranging from 0.64 (non-conservative) to 3.19 (conservative). However, a more detailed investigation into the relationship between fretting fatigue lives and damage summations due to the individual loading levels highlighted that the assumption of linear damage may not be applicable to fretting fatigue, especially during crack initiation and early crack growth. A hypothesis was proposed to explain the fretting fatigue life and Miner damage results observed for the different loading spectra, and reasonable success was obtained for tests where the Miners law proved conservative (in 27 of 36 tests), although the hypothesis was not able to explain the non-conservative results obtained in the other nine tests.

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15

Hooper, Jeremy. "Fretting fatigue under variable amplitude loading." Thesis, Cranfield University, 2003. http://dspace.lib.cranfield.ac.uk/handle/1826/11046.

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Fretting fatigue is a major concern in the design of engineering components that will be subjected to clamping pressures whilst operating in a vibrational environment. The type of loading environment generated in these applications is generally of a variable amplitude nature. Therefore it is important for engineers to understand how such loading affects the severity of fretting fatigue. In the absence of this understanding, engineering designers are left to apply simplistic plain fatigue life prediction rules, such as Miners linear damage law, to try to estimate the damage generated from a particular loading history. In order to try to establish a baseline for the understanding of fretting fatigue under variable amplitude loading, a structured series of CAL and V AL tests were designed and carried out. The aim of the CAL tests was to characterise the fretting fatigue test rig (designed by the author) so that an experimental foundation could be developed, upon which the fretting fatigue study was based. A structured investigation into the effects on fretting fatigue of applying various specifically designed loading histories was carried out and some very distinct relationships between the applied loading spectra and fretting fatigue life were found. For the application of overloads it was observed that overload size, overload application interval and the number of overloads in each application all had a sizeable effect on the severity of fretting. Two-level, three-level and five-level block loading tests were also investigated and numerous loading history dependent results were obtained. The applicability of Miners law to fretting fatigue was assessed. Combining Miners law with well-defined CAL stress-life results gave reasonable predictions for all of the V AL fretting fatigue tests carried out, with damage summations at failure ranging from 0.64 (non-conservative) to 3.19 (conservative). However, a more detailed investigation into the relationship between fretting fatigue lives and damage summations due to the individual loading levels highlighted that the assumption of linear damage may not be applicable to fretting fatigue, especially during crack initiation and early crack growth. A hypothesis was proposed to explain the fretting fatigue life and Miner damage results observed for the different loading spectra, and reasonable success was obtained for tests where the Miners law proved conservative (in 27 of 36 tests), although the hypothesis was not able to explain the non-conservative results obtained in the other nine tests.

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16

Guo, Mu. "Amplitude balancing in [tau]-p domain." Thesis, Virginia Tech, 1994. http://hdl.handle.net/10919/40667.

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An approach to balance the amplitude of seismic data in the Ï -Ï domain is introduced in this study. The idea of amplitude balancing technique is based on the following observation: In the Ï -Ï domain, direct wave, ground-roll, primary reflection, multiple and refraction arrivals are located at different regions. These regions can be viewed as signal region and noise region. By increasing the amplitudes in the signal region and suppressing the amplitudes in the noise region, so called amplitude balancing in T-Ï domain, the signal-to-noise ratio of seismic data can be improved. The Ï -Ï domain amplitude balancing scheme is tested and calibrated on synthetic seismic data using AIMSÂ®' package. The modeled data is also used to illustrate transformation (slant stacking) to and from Ï -Ï domain. The signal-to-noise ratio enhancement using amplitude balancing in Ï -Ï domain is illustrated. This general discussion also includes aliasing effect of slant stack and deconvolution in Ï -Ï domain.

After the calibration with syn1hetic data, the amplitude balancing in Ï -Ï domain is applied to real seismic data recorded on the Atlantic Coastal Plain near Richmond, Virginia and Aiken, South Carolina to explore the possibilities of enhancing the quality of seismic data. Processing of synthetic and real data is carried out on VAX 11/785 and Sun Sparc 10 workstation at the Regional Geophysics Laboratory at Virginia Polytechnic Institute and State University using DISCO@2 seismic data processing package.

The results suggest that Ï -Ï domain amplitude balancing can be combined into conventional seismic data processing sequence to improve the signal-to-noise ratio and thus give a better imaged seismic section. Extensive tests carried out indicate that choice of ray parameter range, the degree of amplitude change, are important aspects of the processing in Ï -Ï domain.

In this study, a complete data processing was carried out to generate a stack section of NRC line 2 in Virginia while the amplitude balancing in Ï -Ï domain was incorporated into a conventional processing scheme. The Ï -Ï domain processing of NRC line 2 improved the data quality. The signal-to-noise ratio enhancement obtained by the amplitude balancing in Ï -Ï domain led to test the method to improve weak reflections from within the Dunbarton Triassic basin on SRP line 2EXP in South Carolina. After the application of amplitude balancing in Ï -Ï domain, CMP gathers showed enhanced signal-to-noise ratio, although the improvement became almost indiscernible after stack.

Master of Science

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17

Moghaddam, Peyman P., Felix J. Herrmann, and Christiaan C. Stolk. "Robust seismic amplitude recovery using curvelets." Society of Exploration Geophysicists, 2007. http://hdl.handle.net/2429/564.

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In this paper, we recover the amplitude of a seismic image by approximating the normal (demigrationmigration)operator. In this approximation, we make use of the property that curvelets remain invariant under the action of the normal operator. We propose a seismic amplitude recovery method that employs an eigenvalue like decomposition for the normal operator using curvelets as eigen-vectors. Subsequently, we propose an approximate non-linear singularity-preserving solution to the least-squares seismic imaging problem with sparseness in the curvelet domain and spatial continuity constraints. Our method is tested with a reverse-time ’wave-equation’ migration code simulating the acoustic wave equation on the SEG-AA salt model.

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18

Bacon, David R. "Finite amplitude propagation in acoustic beams." Thesis, University of Bath, 1986. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.483000.

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19

Reese, Lorie C. "Laryngeal-Level Amplitude Modulation in Vibrato." BYU ScholarsArchive, 2006. https://scholarsarchive.byu.edu/etd/767.

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Research in vocal vibrato has established that vocal tract filtering is primarily responsible for the amplitude modulation (AM) present in Western classical vibrato. Using electroglottography (EGG) and the EGG speed quotient, which is sensitive to fluctuations in the amplitude of vocal fold vibration, AM was detected at the laryngeal (source) level, in addition to the subsequent AM which results from vocal tract filtering. Seventeen classically-trained opera singers sang vowels in three pitch and loudness conditions. EGG and microphone measurements of FM and AM and their rates, extents, and periodicity were made. Airflow was also measured, and the samples were rated by voice professors for vibrato consistency, speed, and width. Physiologic and acoustic data revealed that AM from vocal tract filtering, or the resonance-harmonics interaction (RHI) described by Horii and associates, was present throughout the vibrato samples. Laryngeal-level AM was also present throughout, with soft conditions having the highest mean extents. Singers with lower degrees of laryngeal-level AM were also those rated highest for vibrato consistency. Vibrato rate increased as pitch increased, and, to a lesser extent, as intensity increased. These findings document, in addition to the AM resulting from the RHI, the concurrent presence of laryngeal-level AM in a group of singers representing a range of training and experience.

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20

Deguchi, Kengo. "Finite amplitude solutions in sliding Couette flow." 京都大学 (Kyoto University), 2013. http://hdl.handle.net/2433/174925.

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21

Rodrigues, Ferreira Elizabete. "Finite-amplitude waves in deformed elastic materials." Doctoral thesis, Universite Libre de Bruxelles, 2008. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210464.

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Le contexte de cette thèse est la théorie de l'élasticité non linéaire, appelée également "élasticité finie". On y présente des résultats concernant la propagation d'ondes d'amplitude finie dans des matériaux élastiques non linéaires soumis à une grande déformation statique homogène. Bien que les matériaux considérés soient isotropes, lors de la propagation d'ondes un comportement anisotrope dû à la déformation statique se manifeste.

Après un rappel des équations de base de l'élasticité non linéaire (Chapitre 1), on considère tout d'abord la classe générale des matériaux incompressibles. Pour ces matériaux, on montre que la propagation d'ondes transversales polarisées linéairement est possible pour des choix appropriés des directions de polarisation et de propagation. De plus, on propose des généralisations des modèles classiques de "Mooney-Rivlin" et "néo-Hookéen" qui conduisent à de nouvelles solutions. Bien que le contexte soit tri-dimensionnel, il s'avère que toutes ces ondes sont régies par des équations d'ondes scalaires non linéaires uni-dimensionelles. Dans le cas de solutions du type ondes simples, on met en évidence une propriété remarquable du flux et de la densité d'énergie.

Dans les Chapitres 3 et 4, on se limite à un modèle particulier de matériaux compressibles appelé "modèle restreint de Blatz-Ko", qui est une version compressible du modèle néo-Hookéen.

En milieu infini (Chapitre 3), on montre que des ondes transversales polarisées linéairement, faisant intervenir deux variables spatiales, peuvent se propager. Bien que la théorie soit non linéaire, le champ de déplacement de ces ondes est régi par une version anisotrope de l'équation d'onde bi-dimensionnelle classique. En particulier, on présente des solutions à symétrie "cylindrique elliptique" analogues aux ondes cylindriques. Comme cas particulier, on obtient aussi des ondes planes inhomogènes atténuées à la fois dans l'espace et dans le temps. De plus, on montre que diverses superpositions appropriées de solutions sont possibles. Dans chaque cas, on étudie les propriétés du flux et de la densité d'énergie. En particulier, dans le cas de superpositions il s'avère que des termes d'interactions interviennent dans les expressions de la densité et du flux d'énergie.

Finalement (Chapitre 4), on présente une solution exacte qui constitue une généralisation non linéaire de l'onde de Love classique. On considère ici un espace semi-infini, appelé "substrat" recouvert par une couche. Le substrat et la couche sont constitués de deux matériaux restreints de Blatz-Ko pré-déformés. L'onde non linéaire de Love est constituée d'un mouvement non atténué dans la couche et d'une onde plane inhomogène dans le substrat, choisies de manière à satisfaire aux conditions aux limites. La relation de dispersion qui en résulte est analysée en détail. On présente de plus des propriétés générales du flux et de la densité d'énergie dans le substrat et dans la couche.

The context of this thesis is the non linear elasticity theory, also called "finite elasticity".

Results are obtained for finite-amplitude waves in non linear elastic materials which are first subjected to a large homogeneous static deformation. Although the materials are assumed to be isotropic, anisotropic behaviour for wave propagation is induced by the static deformation.

After recalling the basic equations of the non linear elasticity theory (Chapter 1), we first consider general incompressible materials. For such materials, linearly polarized transverse plane waves solutions are obtained for adequate choices of the polarization and propagation directions (Chapter 2). Also, extensions of the classical Mooney-Rivlin and neo-Hookean models are introduced, for which more solutions are obtained. Although we use the full three dimensional elasticity theory, it turns out that all these waves are governed by scalar one-dimensional non linear wave equations. In the case of simple wave solutions of these equations, a remarkable property of the energy flux and energy density is exhibited.

In Chapter 3 and 4, a special model of compressible material is considered: the special Blatz-Ko model, which is a compressible counterpart of the incompressible neo-Hookean model.

In unbounded media (Chapter 3), linearly polarized two-dimensional transverse waves are obtained. Although the theory is non linear, the displacement field of these waves is governed by a linear equation which may be seen as an anisotropic version of the classical two-dimensional wave equation. In particular, solutions analogous to cylindrical waves, but with an "elliptic cylindrical symmetry" are presented. Special solutions representing "damped inhomogeneous plane waves" are also derived: such waves are attenuated both in space and time. Moreover, various appropriate superpositions of solutions are shown to be possible. In each case, the properties of the energy density and the energy flux are investigated. In particular, in the case of superpositions, it is seen that interaction terms enter the expressions for the energy density and the energy flux.

Finally (Chapter 4), an exact finite-amplitude Love wave solution is presented. Here, an half-space, called "substrate", is assumed to be covered by a layer, both made of different prestrained special Blatz-Ko materials. The Love surface wave solution consists of an unattenuated wave motion in the layer and an inhomogeneous plane wave in the substrate, which are combined to satisfy the exact boundary conditions. A dispersion relation is obtained and analysed. General properties of the energy flux and the energy density in the substrate and the layer are exhibited.

Doctorat en Sciences
info:eu-repo/semantics/nonPublished

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Umeda, Takayuki. "Vlasov simulation of amplitude-modulated Langmuir waves." American Institute of Physics, 2006. http://hdl.handle.net/2237/8788.

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23

Jakobsson, Anders. "Amplitude path for a polar modulation transmitter." Thesis, Linköpings universitet, Institutionen för teknik och naturvetenskap, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-96252.

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this is master tesis on characterisation and implementation of amplitude path for a polar modulation transmetter, targeted at bluethooth extended data rate ( EDR).bluethooth EDR uses quadrature modulation techniques to obtain higher data rates. these techniques use ampitude an phase modulation of a carrier to increas bitrate without increasing signal bandwidth compared to anly using amplitude or phas modulation. the amplitude path migjt be futher developed by investigating the use of higjer order anti-elaising filters together with group compesation. alternative solutions for the I/V-stage is also an important area of staudy.

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24

Tyurina, Alexandra. "Finite-amplitude undular bores in dispersive hydrodynamics." Thesis, Coventry University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.399522.

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Mayer, Uwe. "Hochfrequenzschaltungen zur Einstellung von Amplitude und Phase." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-88062.

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Die vorliegende Arbeit ist der analytischen Untersuchung und Weiterentwicklung von Methoden und Schaltungen zur Einstellung der Signalphase und -amplitude gewidmet. Hierbei wird zum Ziel gesetzt, die Leistungsfähigkeit dieser Schaltungen als analoge Hochfrequenz-Baugruppen in Empfangs- und Sendeschaltkreisen mit einem vergleichbaren oder geringerem schaltungstechnischen Aufwand und Strombedarf zu verbessern und dies anhand von Implementierungsbeispielen zu bestätigen. Die Dämpfungsglied-Topologien , T, überbrücktes T und X werden modelliert und hinsichtlich der Phasenbeeinflussung analysiert, sodass eine Bewertung ihrer Eignung durchgeführt werden kann. Weiterhin wird ein innovativer Ansatz zur Linearisierung der Steuerkennlinie vorgestellt und mit Hilfe einer Beispielschaltung mit einem Phasenfehler von 3 ° und einem Steuerlinearitätsfehler von 0,35 dB innerhalb der 1 dB Grenzfrequenz und einem Steuerbereich von 20 dB nachgewiesen. Die Arbeit bietet darüber hinaus eine analytische Betrachtung zu aktiven steuerbaren Verstärkern, welche die besondere Eignung der Gilbert-Zelle aufzeigt und eine geeignete Ansteuerschaltung ableitet. Am Beispiel nach diesem Prinzip entworfener Schaltkreise werden Phasenfehler von nur 0,4 ° innerhalb eines besonders hohen Stellbereichs von 36 dB demonstriert, wodurch eine Vergrößerung des Stellbereichs um den Faktor 4 und eine Verbesserung des Phasenfehlers um den Faktor 2 im Vergleich zum Stand der Technik erreicht wurde. Es wird der Zirkulator-Phasenschieber maßgeblich durch eine neuartige geeignete Ansteuerung verbessert. Damit werden die sonst für die Amplitudenbeeinflussung im Wesentlichen verantwortlichen Varaktoren überflüssig, ohne dabei den schaltungstechnischen Aufwand zu erhöhen. Eine Messung der entsprechenden Schaltung bestätigt dies mit einem Amplitudenfehler von nur 0,9 dB für einen Phasenstellbereich von 360 °, was einer Verringerung des Fehlers um den Faktor 3 im Vergleich zu herkömmlichen Zirkulator-Phasenschiebern entspricht. Abschließend wird der Funktionsnachweis mehrerer entworfener Vektor-Modulatoren mit einer effektiven Genauigkeit von bis zu 6 bit in Einzelschaltungen, Hybridaufbauten und schließlich im Rahmen eines vollständig integrierten Empfängerschaltkreises erbracht. Dieser erzielt eine Verdopplung der Reichweite bei einer um nur 35% höheren Leistungsaufnahme gegenüber einem herkömmlichen Kommunikationsverfahren (SISO)
The present work is dedicated to the investigation and enhancement of amplitude and phase control methods and circuits. The aim is to enhance the performance of these circuits in modern radio frequency transceivers with a comparable or even lower effort and power consumption. A prove of concept will be delivered with implementation examples. By means of models of the passive attenuator topologies , T, bridged-T and X, a thorough analysis is performed in order to compare them regarding their impact on the signal phase. Additionally, a novel approach to increase the control linearity of the attenuators is proposed and verified by measurements, showing a phase error of 3 ° and a control linearity error of 0,35 dB at the 1 dB corner frequency, successfully. The work also presents an investigation on variable gain amplifiers and reveals the superior performance of the Gilbert cell with respect to low phase variations. A cascode biasing circuit that supports these properties is proposed. Measurements prove this concept with relative phase errors of 0,4 ° over a wide attenuation control range of 36 dB thus cutting the error by half in a four times wider control range. The circulator based phase shifting approach is chosen and improved significantly by means of tuning the transconductor instead of the varactors thus removing their impact on signal amplitude. The approach is supported by measurements yielding an amplitude error of only 0,9 dB within a phase control range of 360 ° which corresponds to an improvement by a factor of three compared to recent circulator phase shifters. Finally, the design of several vector modulator topologies is shown with hardware examples of single chips, hybrid printed circuit boards and highly integrated system level ICs demonstrating a full receiver. By using improved variable gain amplifiers, an effective vector modulator resolution of 6 bit without calibration is achieved. Furthermore, a multiple-input multiple-output system is demonstrated that doubles the coverage range of common SISO systems with only 35% of additional power consumption

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26

Otung, Ifiok E. "Amplitude scintillation of Ka-band satellite signals." Thesis, University of Surrey, 1995. http://epubs.surrey.ac.uk/1036/.

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Ingram, C. "The evolutionary basis of the ecological amplitude." Thesis, University of Liverpool, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234831.

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28

Erpolat, Serhat. "Variable amplitude fatigue of adhesively bonded joints." Thesis, Loughborough University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.416966.

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Achelengwa, Edison M. "Emona-based interactive amplitude modulation/demodulation iLab." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/66402.

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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 76-78).
The MIT iLab Project has developed online laboratories (iLabs) which are lab stations that can be accessed and controlled remotely over the Internet. With iLabs, students can conduct real experiments on real equipment over the Internet. With the introduction of the National Instrument's Educational Laboratory Virtual Instrument Suite, NI ELVIS, in the development of iLabs, students to gain a better understanding of engineering concepts by obtaining real data from electronic labs. One of such crucial engineering concepts is telecommunications which plays a key role in transmitting information between people, systems and computers. There are many telecommunication schemes which exist today. The iLab developed in this thesis implements an experiment for studying one of such schemes, Amplitude Modulation. The NI ELVIS is used together with a device called the Emona Digital and Analog Telecommunications Experimenter (DATEx) to achieve the Amplitude Modulation lab setup. This iLab is an Interactive iLab, which gives one student at a time complete, real-time control over the lab set up. The Amplitude Modulation iLab will permit students to tune various controls and observe the behavior and changes of relevant signals, both in time domain and frequency domain. It will also permit students to compare different signals and retrieve data locally for post processing.
by Edison M. Achelengwa.
M.Eng.

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30

Celentano, Carlos Maria. "Finite amplitude resonant acoustic waves without shocks." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/36967.

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Wedgwood, Kyle C. A., Kevin K. Lin, Ruediger Thul, and Stephen Coombes. "Phase-Amplitude Descriptions of Neural Oscillator Models." BioMed Central, 2013. http://hdl.handle.net/10150/610255.

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Phase oscillators are a common starting point for the reduced description of many single neuron models that exhibit a strongly attracting limit cycle. The framework for analysing such models in response to weak perturbations is now particularly well advanced, and has allowed for the development of a theory of weakly connected neural networks. However, the strong-attraction assumption may well not be the natural one for many neural oscillator models. For example, the popular conductance based Morris-Lecar model is known to respond to periodic pulsatile stimulation in a chaotic fashion that cannot be adequately described with a phase reduction. In this paper, we generalise the phase description that allows one to track the evolution of distance from the cycle as well as phase on cycle. We use a classical technique from the theory of ordinary differential equations that makes use of a moving coordinate system to analyse periodic orbits. The subsequent phase-amplitude description is shown to be very well suited to understanding the response of the oscillator to external stimuli (which are not necessarily weak). We consider a number of examples of neural oscillator models, ranging from planar through to high dimensional models, to illustrate the effectiveness of this approach in providing an improvement over the standard phase-reduction technique. As an explicit application of this phase-amplitude framework, we consider in some detail the response of a generic planar model where the strong-attraction assumption does not hold, and examine the response of the system to periodic pulsatile forcing. In addition, we explore how the presence of dynamical shear can lead to a chaotic response.

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32

Lokharu, Evgeniy. "Small-amplitude steady water waves with vorticity." Doctoral thesis, Linköpings universitet, Matematik och tillämpad matematik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-134243.

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The problem of describing two-dimensional traveling water waves is considered. The water region is of finite depth and the interface between the region and the air is given by the graph of a function. We assume the flow to be incompressible and neglect the effects of surface tension. However we assume the flow to be rotational so that the vorticity distribution is a given function depending on the values of the stream function of the flow. The presence of vorticity increases the complexity of the problem and also leads to a wider class of solutions. First we study unidirectional waves with vorticity and verify the Benjamin-Lighthill conjecture for flows whose Bernoulli constant is close to the critical one. For this purpose it is shown that every wave, whose slope is bounded by a fixed constant, is either a Stokes or a solitary wave. It is proved that the whole set of these waves is uniquely parametrised (up to translation) by the flow force which varies between its values for the supercritical and subcritical shear flows of constant depth. We also study large-amplitude unidirectional waves for which we prove bounds for the free-surface profile and for Bernoulli’s constant. Second, we consider small-amplitude waves over flows with counter currents. Such flows admit layers, where the fluid flows in different directions. In this case we prove that the initial nonlinear free-boundary problem can be reduced to a finite-dimensional Hamiltonian system with a stable equilibrium point corresponding to a uniform stream. As an application of this result, we prove the existence of non-symmetric wave profiles. Furthermore, using a different method, we prove the existence of periodic waves with an arbitrary number of crests per period.

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Weerasinghe, Asanka Thushara. "Amplitude-Modulated Electrostatic Nanolithography in Fluourinated Graphene." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1351564667.

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Secan, Stephen R. "Amplitude and frequency modulation in Oboe Vibrato." The Ohio State University, 1997. http://rave.ohiolink.edu/etdc/view?acc_num=osu1407510603.

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35

Gyongy, Istvan. "Phase/amplitude estimation for tuning and monitoring." Thesis, University of Oxford, 2008. http://ora.ox.ac.uk/objects/uuid:f398b986-e8a0-403a-9118-5edae6403e00.

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The benefits of good loop tuning in the process industries have long been recognized. Ensuring that controllers are kept well-configured despite changes in process dynamics can bring energy and material savings, improved product quality as well as reduced downtime. A number of loop tuning packages therefore exist that can, on demand, check the state of a loop and adjust the controller as necessary. These methods generally apply some form of upset to the process to identify the current plant dynamics, against which the controller can then be evaluated. A simple approach to the automatic tuning of PI controllers injects variable frequency sinewaves into the loop under normal plant operation. The method employs a phase-locked loop-based device called a phase-frequency/estimation and uses 'design-point' rules, where the aim is for the Nyquist locus of the loop to pass through a particular point on the complex plane. A number of advantages are offered by the scheme: it can carry out both 'one shot' tuning and continuous adaptation, the latter even with the test signal set to a lower amplitude than that of noise. A published article is included here that extends the approach to PID controllers, with simulations studies and real-life test showing the method to work consistently well for a for a wide range of typical process dynamics, the closed-loop having a response that compares well with that produced by standard tuning rules. The associated signal processing tools are tested by applying them to the transmitter of a Coriolis mass-flow meter. Schemes are devised for the tracking and control of the second mode of measurementtube oscillation alongside the so-called 'driven mode', at which the tubes are usually vibrated, leading to useful information being made available for measurement correction purposes. Once a loop has been tuned, it is important to assess it periodically and to detect any performance losses resulting from events such as changes in process or disturbance dynamics and equipment malfunction such as faulty sensors and actuators. Motivated by the effective behaviour of the controller tuners, a loop monitor developed here, also using probing sinewaves coupled with 'design-point' ideas. In this application, the effect on the process must be minimal, so the device must work with lower still SNRs. Thus it is practical to use a fixed-frequency probing signal, together with a different tool set for tracking it. An extensive mathematical framework is developed describing the statistical properties of the signal parameter estimates, and those of the indices derived from these estimates indicating the state of the loop. The result is specific practical guidelines for the application of the monitor (e.g. for the choices of test signal amplitude and test duration). Loop monitoring itself has traditionally been carried out by passive methods that calculate various performance indicators from routine operating data. Playing a central role amongst these metrics is the Harris Index (HI) and its variants, which compare the output variance to a 'minimum achievable' figure. A key advantage of the active monitor proposed here is that it is able not only to detect suboptimal control but also to suggest how the controller should be adjusted. Moreover, the monitor’s index provides a strong indication of changes in damping factor. Through simple adjustments to the algorithm (by raising the amplitude of the test signal or adding high frequency dither to the control signal), the method can be applied even in the presence of actuator non-linearity, allowing it to identify the cause of performance losses. This is confirmed by real-life trials on a non-linear flow rig.

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Pugh, Jeffrey D. Wiggins Stephen. "Finite amplitude waves in plane Poiseuille flow /." Diss., Pasadena, Calif. : California Institute of Technology, 1988. http://resolver.caltech.edu/CaltechETD:etd-11072007-104253.

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37

Vural, Derya. "The vibrational amplitude of atoms in proteins." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 86 p, 2009. http://proquest.umi.com/pqdweb?did=1885607701&sid=3&Fmt=2&clientId=8331&RQT=309&VName=PQD.

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38

Skinner, Tim. "Effect of Intensity Increment on P300 Amplitude." Scholar Commons, 2004. https://scholarcommons.usf.edu/etd/1251.

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The purpose of this study was to determine the effects of task difficulty on the amplitude and latency of the P300 by altering the intensity of the oddball stimulus. A P300 was obtained on 22 adult subjects ranging in age from 21 to 34 years of age (mean = 24 years) with normal hearing. The "frequent stimulus" was a 1000 Hz or 4000 Hz tone burst, gated with a rise and fall time of 10 msec and 20 msec plateau, presented at 75 dBn HL The "oddball stimulus" was a tone burst of the same frequency (1000 Hz or 4000 Hz)presented at 77, 79, or 81 dBn HL. A four-channel recording was made with linked reference electrodes and the following montages:Cz-A1+A2, Pz-A1+A2, and Fz-A1+A2. The fourth channel was used to monitor "eye blink" activity. The investigation tested the null hypothesis that changing the intensity of the oddball stimuli would not result in a significant change in either the amplitude or latency of the P300. Analyses of Variance (ANOVA) indicate that P300 latency and amplitude did not differ significantly by run, stimulus frequency, intensity of the oddball, or montage. Thus the null hypothesis was supported.

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39

Gao, Jason. "Equalisation for carrierless amplitude and phase modulation." Thesis, Curtin University, 2002. http://hdl.handle.net/20.500.11937/233.

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Carrierless amplitude and phase (CAP) modulation is generally regarded as a bandwidth efficient two-dimensional (2-D) passband line code. It is closely related to the pulse amplitude modulation (PAM) and quadrature amplitude modulation (QAM) schemes. CAP has been proposed for various digital subscriber loop (DSL) systems over unshielded twisted pairs of copper wires. In this thesis, our main focus is on the minimum mean-square error (MMSE) performance of the ideal (i.e., infinite length) linear and non-linear (decision feedback) CAP receivers/equalisers in the presence of additive, coloured Gaussian noise, and/or data-like cross-talks. An in-depth analysis is given on the performance of both receiver structures. In the case of the linear receiver, one possible view of the overall CAP transceiver system which includes both data and cross-talk transmission paths is that it is a linear multiple-input multiple-output (MIMO) system. Accordingly, the existing MMSE results for a general MIMO system are applicable also to CAP systems. However, up to date, this approach was shown to be unsuccessful in the sense that the derived MMSE expressions are too complex and offer little insights. In our analysis, in order to find a more incisive MMSE expression, we reconsider the problem of minimisation of the MSEs at slicers. By exploiting the Hilbert transform pair relationship between the impulse responses of the inphase and quadrature transmit shaping filters, we are able to obtain an elegant and more meaningful MMSE expression, as well as the corresponding transfer functions of the optimum linear receive filters. In the case of the nonlinear, or decision feedback equaliser (DFE), receiver, we start our analysis with the receiver structure of a generic multidimensional (>/= 3) CAP-type system.This receiver consists of a bank of analog receive filters, the number of which equals the dimension of the CAP line code, and a matrix of cross-connected, infinite-length, baud-spaced feedback filters. It is shown that the optimum filters and the corresponding MMSE of the DFE receiver require the factorisation of a discrete-time channel spectral matrix. This mathematically intractable step can be avoided, however, when the DFE results are specialised to a standard 2-D CAP system where we are able to again exploit the Hilbert transform pair relationship to derive a further and more useful MMSE expression. Three sets of numerical studies are given on the MMSE performance of the CAP receivers. In the first set of studies. we model the sum of all crosstalks as an additive, Gaussian noise source and select three test transmission channels over which we compare the MMSE performance of the linear and DFE receiver structures. In the second set of studies, we compare the performance of the two receiver structures, but in a data-like cross-talk environment. The results demonstrate the importance of NEXT equalisation in the design of CAP receivers operating in a NEXT dominant environment. In the final set of studies which follows from the second set of studies, we investigate the relationship between the MMSE performance of the DFE receiver and system parameters which include excess bandwidth, data rate, CAP scheme. and relative phase between the received signal and the NEXT signal. The results show that data-like cross-talks can be effectively suppressed by using a large excess bandwidth (alpha > 1 in the case of a RC transmit shaping filter) alone.The relative phase also affect; the receiver performance. but to a lesser degree. In addition to the MMSE performance analysis. implementation issues of an adaptive linear CAP receiver are also considered. We propose a novel linear receiver by appending two fixed analog filters to the front-end of the existing adaptive linear receiver using fractionally-spaced equalisers (FSE). We show that if the analog filters are matched to the transmit shaping filters, then inphase and quadrature finite-length FSEs in the proposed receiver have the same NINISE solution. We further propose a modified least-mean-square (LMS) algorithm which takes advantage of this feature. The convergence analysis of the proposed LMS algorithm is also given. We show that the modified LMS algorithm converges approximately twice as fast as the standard LMS algorithm, given the same misadjustment, or alternatively, it halves the misadjustment, given the same initial convergence rate.

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40

Gao, Jason. "Equalisation for carrierless amplitude and phase modulation." Curtin University of Technology, Western Australian Telecommunications Research Institute (WATRI), 2002. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=14683.

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Carrierless amplitude and phase (CAP) modulation is generally regarded as a bandwidth efficient two-dimensional (2-D) passband line code. It is closely related to the pulse amplitude modulation (PAM) and quadrature amplitude modulation (QAM) schemes. CAP has been proposed for various digital subscriber loop (DSL) systems over unshielded twisted pairs of copper wires. In this thesis, our main focus is on the minimum mean-square error (MMSE) performance of the ideal (i.e., infinite length) linear and non-linear (decision feedback) CAP receivers/equalisers in the presence of additive, coloured Gaussian noise, and/or data-like cross-talks. An in-depth analysis is given on the performance of both receiver structures. In the case of the linear receiver, one possible view of the overall CAP transceiver system which includes both data and cross-talk transmission paths is that it is a linear multiple-input multiple-output (MIMO) system. Accordingly, the existing MMSE results for a general MIMO system are applicable also to CAP systems. However, up to date, this approach was shown to be unsuccessful in the sense that the derived MMSE expressions are too complex and offer little insights. In our analysis, in order to find a more incisive MMSE expression, we reconsider the problem of minimisation of the MSEs at slicers. By exploiting the Hilbert transform pair relationship between the impulse responses of the inphase and quadrature transmit shaping filters, we are able to obtain an elegant and more meaningful MMSE expression, as well as the corresponding transfer functions of the optimum linear receive filters. In the case of the nonlinear, or decision feedback equaliser (DFE), receiver, we start our analysis with the receiver structure of a generic multidimensional (>/= 3) CAP-type system.
This receiver consists of a bank of analog receive filters, the number of which equals the dimension of the CAP line code, and a matrix of cross-connected, infinite-length, baud-spaced feedback filters. It is shown that the optimum filters and the corresponding MMSE of the DFE receiver require the factorisation of a discrete-time channel spectral matrix. This mathematically intractable step can be avoided, however, when the DFE results are specialised to a standard 2-D CAP system where we are able to again exploit the Hilbert transform pair relationship to derive a further and more useful MMSE expression. Three sets of numerical studies are given on the MMSE performance of the CAP receivers. In the first set of studies. we model the sum of all crosstalks as an additive, Gaussian noise source and select three test transmission channels over which we compare the MMSE performance of the linear and DFE receiver structures. In the second set of studies, we compare the performance of the two receiver structures, but in a data-like cross-talk environment. The results demonstrate the importance of NEXT equalisation in the design of CAP receivers operating in a NEXT dominant environment. In the final set of studies which follows from the second set of studies, we investigate the relationship between the MMSE performance of the DFE receiver and system parameters which include excess bandwidth, data rate, CAP scheme. and relative phase between the received signal and the NEXT signal. The results show that data-like cross-talks can be effectively suppressed by using a large excess bandwidth (alpha > 1 in the case of a RC transmit shaping filter) alone.
The relative phase also affect; the receiver performance. but to a lesser degree. In addition to the MMSE performance analysis. implementation issues of an adaptive linear CAP receiver are also considered. We propose a novel linear receiver by appending two fixed analog filters to the front-end of the existing adaptive linear receiver using fractionally-spaced equalisers (FSE). We show that if the analog filters are matched to the transmit shaping filters, then inphase and quadrature finite-length FSEs in the proposed receiver have the same NINISE solution. We further propose a modified least-mean-square (LMS) algorithm which takes advantage of this feature. The convergence analysis of the proposed LMS algorithm is also given. We show that the modified LMS algorithm converges approximately twice as fast as the standard LMS algorithm, given the same misadjustment, or alternatively, it halves the misadjustment, given the same initial convergence rate.

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41

Lize, Matheus Loss. "Scattering amplitudes using twistor strings." São Paulo, 2017. http://hdl.handle.net/11449/154417.

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Orientador: Nathan Jacob Berkovits
Banca: Andrey Yuryevich Mikhaylov
Banca: Diego Trancanelli
Resumo: Neste trabalho revisamos as amplitudes de MHV no contexto da teoria de super-Yang-Mills. Nós estudamos as simetrias das amplitudes de MHV no espaço de twistors como uma motivação para introduzir a teoria de cordas com twistors . A teoria de cordas com twistors feita por Nathan Berkovits [3] é revisada e uma fórmula geral é dada para calcular amplitudes de espalhamento com n gluons. No final, a partir desta fórmula deduzimos a amplitude de MHV
Abstract In this work we review the maximal helicity violating (MHV) scattering amplitude in the context of super-Yang-Mills theory. We study the symmetries of the MHV amplitude in the twistor space as a motivation to introduce the twistor string theory. The twistor string action introduced by Nathan Berkovits [3] is reviewed and also a general formula is given for the scattering amplitude with n gluons. In the end, the MHV amplitude is derived from this formula
Mestre

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42

Angelo, Clayton Mamedes. "Fadiga de amplitude variável como parâmetro de projeto para eixos traseiros automotivos: uma análise do efeito das sobrecargas e da filtragem matemática na predição de vida em fadiga." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/3/3133/tde-03072007-181251/.

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Este trabalho tem como objetivo a comparação dos resultados de ensaios de durabilidade em um suporte do eixo traseiro de um veículo leve de passeio, submetido a dois tipos distintos de testes: durabilidade em rodagem real e em simuladores de estradas. Após o término dos ensaios, o componente apresentou resultados diferentes: as trincas podem ser observadas na peça submetida à rodagem real, e os danos não ocorrem no eixo que foi testado em simulador. As discrepâncias citadas podem estar ligadas a possíveis erros, ocorridos durante a transferência dos dados pertinentes ao teste real para o simulador.
The aim of this research is comparing results from durability tests performed at a rear axle bracket of a small passenger car. The part was tested using two different kinds of tests: real (proving ground) durability and simulated (road simulator) durability. After that, the part showed different final results: several cracks can be observed at the part that was tested at the proving ground and no real damage was inflicted at the part that was test at the road simulator. These differences can be related to transferability problems that occurred during data analysis and transfer from real test to a simulated one.

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43

Grennek, David S. "Amplitude modulation using a nonlinear optical loop mirror." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1998. http://handle.dtic.mil/100.2/ADA358980.

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Thesis (M.S. in Applied Physics) Naval Postgraduate School, December 1998.
"December 1998." Thesis advisor(s): Andres Larraza, H. Sarma Lakkaraju. Includes bibliographical references (p. 41). Also available online.

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44

Tsang, Hing-ho. "Probabilistic seismic hazard assessment direct amplitude-based approach /." Click to view the E-thesis via HKUTO, 2006. http://sunzi.lib.hku.hk/hkuto/record/B36783456.

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45

Marquart, Chad A. "Sliding-mode amplitude control techniques for harmonic oscillators." Texas A&M University, 2003. http://hdl.handle.net/1969.1/5767.

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This thesis investigates both theoretical and implementation-level aspects of switching- feedback control strategies for the development of voltage-controlled oscillators. We use a modified sliding-mode compensation scheme based on various norms of the system state to achieve amplitude control for wide-tuning range oscillators. The proposed controller provides amplitude control at minimal cost in area and power consumption. Verification of our theory is achieved with the physical realization of an amplitude controlled negative-Gm LC oscillator. A wide-tuning range RF ring oscillator is developed and simulated, showing the effectiveness of our methods for high speed oscillators. The resulting ring oscillator produces an amplitude controlled sinusoidal signal operating at frequencies ranging from 170 MHz to 2.1 GHz. Total harmonic distortion is maintained below 0:8% for an oscillation amplitude of 2 Vpp over the entire tuning range. Phase noise is measured as -105.6 dBc/Hz at 1.135 GHz with a 1 MHz offset.

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46

Tsang, Hing-ho, and 曾慶豪. "Probabilistic seismic hazard assessment: direct amplitude-based approach." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B36783456.

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The Best PhD Thesis in the Faculties of Dentistry, Engineering, Medicine and Science (University of Hong Kong), Li Ka Shing Prize, 2005-2006.
published_or_final_version
abstract
Civil Engineering
Doctoral
Doctor of Philosophy

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47

Wright, Dean. "Temporal phase and amplitude statistics in coherent radiation." Thesis, University of Nottingham, 2005. http://eprints.nottingham.ac.uk/12126/.

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Interest in coherent remote sensing systems has stimulated investigations in the properties laser propagation through extended atmospheric turbulence. This thesis investigates the statistics of phase, and phase related, observables using analytical and computational techniques, together with experimental results. The phase screen technique is used to simulate perturbations to the refractive index of a medium through which the radiation propagates. Several different turbulence models (Gaussian correlated noise, Kolmogorov turbulence, Tatarski and Von Karman spectral models) are investigated, and their relative merits for describing experimental conditions and descriptive statistical measures are compared and contrasted. The phase power spectrum is crucial to an understanding of the practical operation of a coherent imaging system, and later part of the thesis is devoted to the investigation of a LIDAR system in particular. Several turbulence regimes are investigated, from an analytical treatment of a weakly turbulent, extended atmosphere, to large 3D computations designed to simulate experimental arrangements. The 3D simulation technique presented herein has been developed to allow for the investigation of temporal statistics. New power law behaviours are found to appear in temporal frequency spectra which differ from the -8/3 power law form that has been accepted in much of the literature. Strongly turbulent regimes result in a -2 power law while the use of a Gaussian beam profile in an extended medium gives a -11/3 power law under weak turbulence conditions. Please note: Pagination in electronic reproduction differs from print original. The print version is the version of record.

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Barros, M. de P. "Crystal filters having prescribed amplitude and phase characteristics." Thesis, University of Essex, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374712.

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49

Devoy, Peter. "Amplitude bifurcation in the peeling relaxation ELM model." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/amplitude-bifurcation-in-the-peeling-relaxation-elm-model(6027b2aa-b766-4505-a9a0-015c66d15d13).html.

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In this report we build on existing theories of Edge Localised Modes (ELMs) that incorporate the theory of Magnetic Relaxation, firstly by introducing the effects of the bootstrap current and secondly by applying the relaxation model to the field of ELM mitigation. The bootstrap current is a toroidal plasma current that arises spontaneously as a result of the confinement of the plasma. It is shown that the effect of introducing this current is to split the ELM widths associated with this model into two classes; one group with large ELM widths, the other with small ELM widths. An analytical study is then carried out which provides a theoretical basis for this bifurcation of results. Finally the idea of ELM mitigation using Resonant Magnetic Perturbations will be introduced before the Relaxation Theory of ELMs is used to give new insight into ELM mitigation results.

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Xu, Ruize Ph D. Massachusetts Institute of Technology. "Low-frequency, low-amplitude MEMS vibration energy harvesting." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/115673.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 187-195).
Vibration energy harvesters work effectively only when the operating conditions match with the available vibration source. Typical resonating MEMS structures cannot be used with low-frequency, low-amplitude and unpredictable nature of ambient vibrations. Bi-stable nonlinear oscillator based energy harvesters are developed for lowering the operating frequency while widening the bandwidth, and are realized at MEMS scale for the first time. This design concept does not rely on the resonance of the MEMS structure but operates with the large snapping motion of the beam at very low frequencies when proper conditions are provided to overcome the energy barrier between the two energy wells of the structure. A fully functional piezoelectric MEMS energy harvester is designed, monolithically fabricated and tested. An electromechanical lumped parameter model is developed to analyze the nonlinear dynamics and to guide the design of the multi-layer buckled beam structure. Residual stress induced buckling is achieved through the progressive control of the deposition along the fabrication steps. Static surface profile of the released device shows bi-stable buckling of 200 [mu]m which matches very well with the design. Dynamic testing demonstrates the energy harvester operates with 35% bandwidth under 70Hz at 0.5g, operating conditions that have not been met before by MEMS vibration energy harvesters.
by Ruize Xu.
Ph. D.

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Dissertations / Theses on the topic 'Amplitude'

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