• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 7645
  • 4355
  • 2026
  • 1278
  • 838
  • 759
  • 290
  • 206
  • 197
  • 172
  • 143
  • 142
  • 103
  • 96
  • 89
  • Tagged with
  • 21252
  • 4981
  • 4818
  • 3088
  • 2647
  • 1888
  • 1877
  • 1408
  • 1364
  • 1362
  • 1245
  • 1239
  • 1144
  • 1106
  • 1095
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
61

Applications of source signature deconvolution to airgun seismic profiling and the measurement of attenuation from reflection seismograms

Wrolstad, Keith H. 04 August 1978 (has links)
Deterministic source signature deconvolution is applied to the processing of marine wide angle and vertical profiler data with air-gun sources. Optimum results are obtained with a source signature measured by stacking the signal reflected from a relatively homogeneous abyssal plain sedimentary environment. This eliminates the need for the unstable inverse source-receiver ghost filter. Improved resolution of reflection event timing allows the computation of more reliable interval velocities by the T² - X² method, provided the layer thickness limitation of the method is not exceeded. Accurate timing of primary reflection events in the deconvolved vertical profiler data permits computation of frequency dependent attenuation by univariate least-squares regression in the Fourier transform domain. The technique successfully extracts input amplitude attenuation functions from model reflection coefficient sequences with additive random noise. This success is attributed to the stability of singular value analysis in solving the least-squares regression model. Statistical tests on the solution vectors for model and field data give criteria for evaluating their reliability. The model data studies suggest that multiple and primary events not included in the regression may be considered part of the noise term without seriously affecting the accuracy of the computed spectral ratios. The method is tested on field data from the following sedimentary environments off the coast of Oregon and northern California: a continental shelf basin, an abyssal plain environment, the base of the continental slope and two locations on the Astoria sea fan, one near the Cascadia sea channel and one north of DSDP site 174. Velocity versus depth and frequency dependent spectral ratio plots are determined for each environment. The computed surface layer interval velocity of 1.77 km/sec over a thickness of 455 m for the station north of DSDP site 174 is in good agreement with the average material type found in the drill core (sandy-silt with greater than 60% sand). Maximum attenuation coefficients are estimated from the spectral ratios for the upper sediment intervals of the study areas using typical acoustic impedance values of surface sediment types determined from nearby piston cores. Some maximum attenuation coefficients are too high suggesting the possibility of a stratigraphic component. The maximum attenuation in the upper interval for SB 46 over the Tufts abyssal plain where fine-grained material (silts and clays) is expected is 0.025 dB/m at 127 Hz compared with 0.004 dB/m at 80 Hz for the upper interval of the turbidite environment north of DSDP site 174. / Graduation date: 1979 / Best scan available for figures.
62

Marine seismic studies near Newport, Oregon

Erickson, Barrett H. 08 August 1966 (has links)
In July 1964 three seismic refraction profiles were recorded over Stonewall Bank (44°32'N, 124°24'W) to determine gross sub-bottom geological structure to depths of thousands of feet. In August 1964 a continuous seismic reflection profiler was used to document shallow geological structure within the rocks forming the Bank. Stonewall Bank is composed of eastward dipping Pliocene siltstones which emerge westward from beneath unconsolidated Quaternary sediments. These siltstones form gentle dip slopes on the Bank's ea-stern flank but rougher topography is found on the top and western flank where the bedding planes intersect the sea floor at greater angles. Refraction data from this study indicate the siltstones thicken southward by 5000 feet over a six mile distance which accounts for almost all of the thickness change in the measured section. A deeper layer, 5000 feet thick, which appears to be Miocene may be exposed west of the Bank beneath the sediments. The base of this deeper layer has a southerly dip component of about six degrees and lies 12, 000 feet below the southern end of the Bank. Although this was the deepest interface encountered, the underlying material is not believed to be basement. / Graduation date: 1967
63

Finite volume methods and adaptive refinement for tsunami propagation and inundation /

George, David L., January 2006 (has links)
Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (p. 181-188).
64

A Logical and Comprehensive Sequence of Skills for Teaching Children the Cello

Bebe, David Martin 09 May 2009 (has links)
The main purpose of this essay is to develop the most effective and logical sequence of skills for teaching children how to play the cello. This essay deals with the questions "When does one introduce specific skills for playing the cello?" and "Is there a sequence of skills that is universally the most beneficial for learning how to play the cello?" The chapters include a detailed examination of the existing cello methods currently available to cello teachers, and explore whether the ideal comprehensive cello sequence exists. It is important for teachers to have a complete plan for the young cellist and to have the proper repertoire that will make this thorough education a possibility. Many teachers use multiple scale and method books that do not fit into a sequence. These books are not designed to be used with each other, and it can be inconvenient to have numerous books in every lesson. I have created a method that contains a logical sequence of skills, spans from the very beginning stages of learning to the most advanced stages of learning, has corresponding scales and exercises for each piece, and avoids confusion and clutter of multiple books by placing scales, exercises, and pieces side by side. This study is meant to assist young teachers by providing a clearly progressive and comprehensive cello method with a corresponding instructional website.
65

A guide for implementation of the Montessori theory of education in the lower elementary curriculum

Wolfe, Sheila G. January 2006 (has links) (PDF)
Thesis (M.Ed.)--Regis University, Denver, Colo., 2006. / Title from PDF title page (viewed on Feb. 14, 2006). Includes bibliographical references.
66

Art experiences in Waldorf education graduates' meaning making reflections /

Nordlund, Carrie Y., January 2006 (has links)
Thesis (Ph.D.)--University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (February 28, 2007). Vita. Includes bibliographical references.
67

Adaptive finite element analysis for 2D elastostatic problems

Lee, Chi-king. January 1992 (has links)
Thesis (M.Phil.)--University of Hong Kong, 1993. / Also available in print.
68

Asymptotics and computations for approximation of method of regularization estimators

Lee, Sang-Joon 29 August 2005 (has links)
Inverse problems arise in many branches of natural science, medicine and engineering involving the recovery of a whole function given only a finite number of noisy measurements on functionals. Such problems are usually ill-posed, which causes severe difficulties for standard least-squares or maximum likelihood estimation techniques. These problems can be solved by a method of regularization. In this dissertation, we study various problems in the method of regularization. We develop asymptotic properties of the optimal smoothing parameters concerning levels of smoothing for estimating the mean function and an associated inverse function based on Fourier analysis. We present numerical algorithms for an approximated method of regularization estimator computation with linear inequality constraints. New data-driven smoothing parameter selection criteria are proposed in this setting. In addition, we derive a Bayesian credible interval for the approximated method of regularization estimators.
69

Continuum- based computational models of biological living cell

Cheng, Feifei 15 May 2009 (has links)
All living creatures, despite their profound diversity, share a common architectural building block: the cell. Cells are the basic functional units of life, yet are themselves comprised of numerous components with distinct mechanical characteristics. It is well established that cells have the ability to sense and respond to externally applied forces. However, the detailed mechanism of mechanosensation is still not clearly understood, and is an active area of research involving experimental and theoretical works. Mathematical modeling of the mechanical stimulus correlating to different experimental stimulation procedures forms the first step to understanding the mechanosensation in cellular system. In this thesis, a continuum -based computational model of living cells that explicitly incorporate the material properties of various cellular components are developed. In the constitutive modeling of cell, the continuum standard linear solid viscoelastic model (SLS), its natural extension for large scale deformation standard Neo-Hookean solid viscoelastic model (SnHS) as well as polymer mechanics- based dynamic shear modulus model was introduced. Finite element simulations of three widely used experiments- atomic force microscopy (AFM), magnetic twisting cytometry (MTC) and micropipette aspiration in the quantification of cell properties were carried out to verify the developed constitutive model. From the results of AFM finite element simulation, it was observed that the force-deformation and strain-relaxation curves obtained fit the experimental results very well. The influences of cytoplasm shear modulus which varies due to the formation of stress fiber, and cortex shear modulus which alters with the actin filament concentration factors and load frequency were systematically studied. Similarly, in magnetic twisting cytometry (MTC) simulation, the role of cytoplasm material properties, constant/sinusoidal forcing rates and various frequencies on the overall mechanical response of a cell was obtained. Numerical results are validated against experiments results. Micropipette aspiration simulation was also carried out in which the typical creep deformation test was carried out to study the viscoelastic behavior of the cell. Based on the results from finite element simulation, the effect of pipette radius, effect of cortex shear modulus and effect of pressure rate have been derived for the interpretation of the mechanical parameters from the micropipette aspiration.
70

On the use of Quasi-Maximum Likelihood Estimation and Indirect Method for Stochastic Volatility models

Ishakova, Gulmira January 2008 (has links)
Stochastic volatility models have been focus for research in recent years. One interesting and important topic has been the estimation procedure. For a given stochastic volatility model this project aims to compare two methods of parameter estimation.

Page generated in 0.0527 seconds