Dissertations / Theses: 'Acoustical engineering'

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Ozgenel, Caglar Firat. "Developing A Tool For Acoustical Performance Evaluation Throughout The Design." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614066/index.pdf.

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Performance of the buildings has always been a concern for the architects. With the enhancements in the technology, it is possible to measure, analyze and evaluate the performance of an architectural design before it is built via simulation tools developed. With the evaluation of the analysis performance of the concerned space can be upgraded if simulation tools are employed throughout the design process. However, even though the simulation tools are developed for the acoustical simulation and performance analysis, it is not always simple to integrate the simulation tools to whole design process because of both specific knowledge required for the usage of the tools and the nature of the acoustical simulation tools. Within the scope of the thesis, a simulation tool, which does not require advanced knowledge on acoustics and which provides rapid feedbacks about the performance of the design for the enhancement of the performance is developed using method of image sources.

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Terry, Jonathan. "Acoustic modeling of an enclosed reverberant environment." Diss., Online access via UMI:, 2007.

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Thesis (M.S.)--State University of New York at Binghamton, Thomas J. Watson School of Engineering and Applied Science, Department of Mechanical Engineering, 2007.
Includes bibliographical references.

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Onur, Cagla. "Acoustic Tracking Of Ship Wakes." Phd thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615656/index.pdf.

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Theories about ship wake structure, bubble dynamics, acoustic propagation through bubble clouds, backscattering and target strength of bubble clouds have been investigated and related Matlab simulations have been carried on. Research has been carried on algorithms for ship wake acoustic detection and tracking. Particle filter method has been simulated with Matlab for target tracking using wake echo measurements. Simulation results are promising.

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Lévesque, Sylvain. "Acoustical imaging using wave propagation tomography." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/106041.

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Lin, Yiqiang Farouk Bakhtier. "Acoustic wave induced convection and transport in gases under normal and micro-gravity conditions /." Philadelphia, Pa. : Drexel University, 2007. http://hdl.handle.net/1860/1795.

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Rinker, Brett A. "A single-sided access simultaneous solution of acoustic wave speed and sample thickness for isotropic materials of plate-type geometry." Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/4585.

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Thesis (M.S.)--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 April 17, 2009) Vita. Includes bibliographical references.

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Tan, Lin. "Development of micro-acoustic devices with applications of viscous effects." Diss., Online access via UMI:, 2006.

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Abouchakra, Rabih. "Delay estimation for transform domain acoustical echo cancellation." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ37254.pdf.

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9

Zlobec, S. "Linear predictive spectral shaping for acoustical echo cancellation." Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=23763.

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The purpose of this Thesis is to study adaptive acoustical echo cancellation for signals with variable-rank covariance matrices. Solutions based on the least-mean-square (LMS) algorithm are presented, with the focus being on discrete-cosine-transform-(DCT) domain finite-impulse-response (FIR) filters.
In speech-related applications, the covariance matrix of the reference signal is ten nearly singular, i.e., rank-deficient, which has the effect that some of the transform-domain tap coefficients stop adapting and effectively "freeze". During is low-rank phase, this frozen taps can retain any value without effect on the mean-square error (MSE), while the remaining taps track the evolution of the system and keep the MSE at a minimum.
When the covariance matrix becomes nonsingular, however, there are no longer any frozen coefficients, and a unique tap coefficient vector yields minimum MSE. The MSE abruptly "jumps", and convergence of the taps to the unique vector will take additional time due to the (obsolete) values of the previously frozen coefficients. To remedy the situation, one applies a method dubbed "spectral shaping".
The objective of spectral shaping is to replace, during the low-rank phase, each frozen coefficient by an estimate of the corresponding coefficient of the unique full-rank solution. This is achieved in the transform domain by a combination of forward and backward linear predictors. By using spectral shaping, the frozen coefficients are thus "prepared" to be unfrozen when the covariance matrix gains full rank, resulting in a reduced jump in the MSE.

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Kondis, Antonios 1980. "Acoustical wave propagation in buried water filled pipes." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/30199.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2005.
Includes bibliographical references (p. 145-151).
This thesis presents a comprehensive way of dealing with the problem of acoustical wave propagation in cylindrically layered media with a specific application in water-filled underground pipes. The problem is studied in two stages: First the pipe is considered to be very stiff in relation to the contained fluid and then the stiffness of the pipe and the soil are taken into account. In both cases the solution process can take into account signals of any form, generated in any point inside the pipe. The simplified method provides the basic understanding on wave propagation and noise generation in the pipe in relation to pipe radius and frequency of excitation. Following the simplified analysis, the beam forming method is discussed and applied in order to reduce the noise in the pipe. Moving on to the complete analysis of the pipe, the stiffness matrix method is used to take into account the properties of the system. The solution time is proven to be much higher in this case, but the results vary from the simplified case in many real value problems. The results of the two methods are compared in more detail and then a decision making process for the choice of method is developed. This decision process is based on the frequency of the excitation, the properties of the materials and the dimensions of the system.
by Antonios Kondis.
S.M.

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11

Boerner, James R. "CaO sorption of HCl gas in an acoustic field." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/7012.

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12

Weiland, Nathan T. "Feasibility Analysis of an Open Cycle Thermoacoustic Engine with Internal Pulse Combustion." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4789.

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Thermoacoustic engines convert thermal energy into acoustic energy with few or no moving parts, thus they require little maintenance, are highly reliable, and are inexpensive to produce. These traits make them attractive for applications in remote or portable power generation, where a linear alternator converts the acoustic power into electric power. Their primary application, however, is in driving thermoacoustic refrigerators, which use acoustic power to provide cooling at potentially cryogenic temperatures, also without moving parts. This dissertation examines the feasibility of a new type of thermoacoustic engine, where mean flow and an internal pulse combustion process replace the hot heat exchanger in a traditional closed cycle thermoacoustic engine, thereby eliminating the heat exchangers cost, inefficiency, and thermal expansion stresses. The theory developed in this work reveals that a large temperature difference must exist between the hot face of the regenerator and the hot combustion products flowing into it, and that much of the convective thermal energy input from the combustion process is converted into conductive and thermoacoustic losses in the regenerator. The development of the Thermoacoustic Pulse Combustion Engine, as described in this study, is designed to recover most of this lost thermal energy by routing the inlet pipes through the regenerator to preheat the combustion reactants. Further, the developed theory shows that the pulse combustion process has the potential to add up to 7% to the engines acoustic power output for an acoustic pressure ratio of 10%, with linearly increasing contributions for increasing acoustic pressure ratios. Computational modeling and optimization of the Thermoacoustic Pulse Combustion Engine yield thermal efficiencies of about 20% for atmospheric mean operating pressures, though higher mean engine pressures increase this efficiency considerably by increasing the acoustic power density relative to the thermal losses. However, permissible mean engine pressures are limited by the need to avoid fouling the regenerator with condensation of water vapor out of the cold combustion products. Despite lower acoustic power densities, the Thermoacoustic Pulse Combustion Engine is shown to be well suited to portable refrigeration and power generation applications, due to its reasonable efficiency and inherent simplicity and compactness.

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Farhat, Ali Farag. "Basic problems of fibre-reinforced structural components when fibres resist bending." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/31095/.

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This thesis generates certain sets of analytical and approximate solutions to a new class of partial differential equations stemming from a version of asymmetricstress elasticity theory appropriate for the study and prediction of the behaviour of fibre-reinforced materials containing fibres that resist bending. These new solutions are of theoretical and practical interest in the static and dynamic analysis of thinwalled, linearly elastic fibre-reinforced structures influenced by couple-stress and unsymmetric stress due to fibre bending stiffness. The static and free vibration solutions are constructed considering bending resistance fibres in a small deformation of beams and plates. Numerical results for displacements, stresses, couple-stress and natural frequencies of vibration are provided to investigate the influence of the fibres resistance in bending on the deformed beams and plates.

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Famighetti, Tina Marie. "Investigations into the performance of the reverberation chamber of the integrated acoustics laboratory." Thesis, Available online, Georgia Institute of Technology, 2005, 2005. http://etd.gatech.edu/theses/available/etd-04022005-223652/unrestricted/famighetti%5Ftina%5Fm%5F200505%5Fmast.pdf.

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Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2005.
Berthelot, Yves, Committee Member ; Cunefare, Kenneth A, Committee Chair ; Lynch, Christopher, Committee Member. Includes bibliographical references.

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Turek, Gabriella. "Multiple scattering from submerged bodies dissimilar acoustical properties." Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/17056.

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Sujith, R. I. "Behavior of droplets in axial acoustic fields." Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/12487.

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Fane, de Salis Max Henry. "Acoustic sizing and location of blockages in ducts." Thesis, University of Liverpool, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250484.

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18

Findlay, David A. "Three multi-track recording projects : an analysis of aesthetic and technical engineering considerations." Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63956.

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19

Wurman, Peter Richard. "Anechoic chamber design and acoustical analysis of room 1-051." Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/14621.

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20

Epcacan, Erdal. "Underwater Channel Modeling For Sonar Applications." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12612991/index.pdf.

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Underwater acoustic channel models have been studied in the context of communication and sonar applications. Acoustic propagation channel in an underwater environment exhibits multipath, time-variability and Doppler eects. In this thesis, multipath fading channel models, underwater physical properties and sound propagation characteristics are studied. An underwater channel model for sonar applications is proposed. In the proposed model, the physical characteristics of underwater environment are considered in a comprehensive manner. Experiments /simulations were carried out using real-life data. Model parameters are estimated for a specific location, scenario and physical conditions. The channel response is approximated by fitting the model output to the recorded data. The optimization and estimation are conducted in frequency domain using Mean Square Error criterion.

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21

Pendergraft, Karen Anne. "Frequency dependent acoustic transmission in nonuniform materials." Thesis, Virginia Tech, 1988. http://hdl.handle.net/10919/43265.

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A one dimensional normalized model for the frequency response of the acoustic power transmitted through nonuniform materials is developed. Using the ideal mixture model to relate acoustic velocity and impedance, this normalized model demonstrates that the power transmission characteristics are completely determined using only a composition profile and the parameters defining percent variation in acoustic velocity and impedance. For purposes of comparison, an analytically exact solution for exponential tapers is obtained.
Master of Science

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22

Barber, Matthew James. "Experimental investigation of normal, sonic injection through a wedge-shaped nozzle into supersonic flow." Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-08222009-040226/.

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23

Smith, Jerome P. "Active control of broadband acoustic radiation from structures." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-01242009-063336/.

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24

Cazzolato, Ben S. "Sensing systems for active control of sound transmission into cavities." Title page, contents and abstract only, 1999. http://web4.library.adelaide.edu.au/theses/09PH/09phc386.pdf.

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Thesis (Ph.D.)--University of Adelaide, Dept. of Mechanical Engineering, 1999.
Copies of author's previously published articles inserted. One computer disc (CD-ROM) in plastic jacket pasted onto back cover. Bibliography: leaves 319-339. Also available electronically.

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Frimpong, George Kwabena. "Acoustic detection and location of partial discharges in power transformer tanks." Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/15708.

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26

Martin, James Stephen. "An experimental study of the scattered near field of submerged objects with surface impedance discontinuities." Thesis, Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/16095.

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27

McKinnie, Douglas J. "Objective selection of critical material for subjective testing of low bit-rate audio coding systems." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=29771.

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Perceptual low bit-rate audio coding schemes cannot be evaluated with the traditional method of measuring the difference between input signal and output signal. A valid measure is the severity of differences between input and output that are audible to human listeners, measurement of which requires well-conducted subjective testing. Test sensitivity is improved through the use of "critical" audio program. Selection of such audio material has in the past been done by subjective listening. An objective method of selecting critical material could offer many advantages, including faster and simpler selection of new materials, the ability to evaluate a much larger number of potential materials, and the potential of much better critical materials as a larger portion of available music is explored. The use of perceptual models for selection of critical materials has been investigated. Prediction of criticality was found to be inadequate with the models used.

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Petrina, Denys E. "Performance measurement of a mini thermoacoustic refrigerator and associated drivers." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2002. http://library.nps.navy.mil/uhtbin/hyperion-image/02Jun%5FPetrina.pdf.

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29

Jung, Sungmin. "Advancement of small-scale thermoacoustic engine." Pullman, Wash. : Washington State University, 2009. http://www.dissertations.wsu.edu/Thesis/Spring2009/s_jung_042109.pdf.

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Thesis (M. in mechanical engineering )--Washington State University, May 2009.
Title from PDF title page (viewed on Apr. 12, 2010). "School of Mechanical and Material Engineering." Includes bibliographical references (p. 48-49).

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Shi, Yinghui. "Acoustical Performance of Lined Induction Furnace in Electric Field Configuration." University of Dayton / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1627658524197215.

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31

Bekoz, Alican. "Modeling Of Plosive To Vowel Transitions." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608804/index.pdf.

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This thesis presents a study concerning stop consonant to vowel transitions which are modeled making use of acoustic tube model. Characteristics of the stop consonant to vowel transitions are tried to be obtained first. Therefore several transitions including fricative to vowel transitions are examined based on spectral and time related properties. In addition to these studies, x-ray snapshots, lip videos and also experiments including subjects are used to intensify the characterization, from the production and the perception side of views. As results of these studies the plosive to vowel transitions are observed to be uttered by exponential vocal tract movements and the perception mechanism is observed to be highly related with exponential spectral changes. A model, based on the acoustic tube model, is tried to be established using the knowledge and the experience gained during characterization therefore proposed model involves the vocal tract parameters observed in characterization part. Finally, plosive to vowel transitions including three types of plosives (alveolar, labial and velar) are synthesized by the proposed model. The formants of the synthesized sounds are compared with the formants of the natural sounds. Also the intelligibility tests of these sounds are done. Performance evaluation tests show the proposed model&rsquo
s performance to be satisfactory.

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Cameron, Peter J. K. "An acoustic countermeasure to supercavitating torpedoes." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29666.

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Thesis (Ph.D)--Mechanical Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Rogers, P. H.; Committee Member: Ferri, A. A.; Committee Member: Ruzzene, M.; Committee Member: Smith, M. K.; Committee Member: Trivett, D.; Committee Member: Zinn, B. T. Part of the SMARTech Electronic Thesis and Dissertation Collection.

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Aktas, Murat K. Farouk Bakhtier. "Thermoacoustically induced and acoustically driven flows and heat transfer in enclosures /." Philadelphia, Pa. : Drexel University, 2004. http://dspace.library.drexel.edu/handle/1860/313.

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Unal, Ayhun. "Acoustical Analysis And Design Of Horn Type Loudspeakers." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/3/12607890/index.pdf.

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Computer aided auto-construction of various types of folded horns and acoustic analysis of coupled horn and driver systems are presented in this thesis. A new procedure is developed for auto construction of folded horn shapes. Linear graph modeling technique is employed for specification of horn driver output in terms of diaphragm velocity or throat pressure. In the final phase of the design procedure, acoustic analysis of folded horns is carried by means of finite element analysis. A commercial software package MSC.ACTRAN is used to calculate directivity patterns and resulting acoustic pressure in the free field. Horn geometry consisting of linear, exponential, hyperbolic and tractrix shapes is automatically constructed by parallel working of Delphi and finite element analysis program. The enclosure bordering the horn contours are considered rigid in the analyses. Maximum number of folding is limited to two. This study is made possible to evaluate the performance of these four types of horn contours for a specified range of frequencies.

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Shi, Kun. "Nonlinear acoustic echo cancellation." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26704.

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Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009.
Committee Chair: G. Tong Zhou; Committee Co-Chair: Xiaoli Ma; Committee Member: David V. Anderson; Committee Member: James Stevenson Kenney; Committee Member: Liang Peng; Committee Member: William D. Hunt. Part of the SMARTech Electronic Thesis and Dissertation Collection.

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Chen, Helen (Haiying Helen) 1975. "An acoustical study of fricatives in the speech of dysarthric speakers." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/49801.

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Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1998.
Includes bibliographical references (leaves 55-57).
The goal of the present study is to better understand dysarthric speakers' speech production through quantitative acoustical analysis of the speech signals. In the past, two acoustical measurements proven to correlate with speech intelligibility in dysarthric speakers are speech rate and slope of the F2 frequency change for certain consonant vowel syllables. In this thesis, several new spectral parameters from acoustical analysis that reflect neuro motor dysfunctions in production of the fricative /s/ have been devised and are presented. These parameters specify the spectrum shape and relative amplitude of the fricative noise, the presence or absence of voicing, and the time variation of the spectrum preceding, during, and following the fricative. Analysis shows that these parameters are highly correlated with the speakers' overall intelligibility as well as intelligibility of the fricative /s/. The top three parameters that differentiate the intelligibility of speakers are related to the spectral shape (spectral tilt), the amount of variation in spectral energy (time variation within the fricative), and the amount of inadvertent spectral energy present prior to frication (precursor). The long-term aim of the study is to develop methods for quantifying disordered speech and for determining the deviation from normal speech. In the long run, these methods can be used to objectively measure the effectiveness of speech therapy as well as the amount of speech degeneration in dysarthric speakers.
by Helen Chen.
M.Eng.

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37

Peng, Shuzhi. "Acoustical wave propagator technique for structural dynamics." University of Western Australia. School of Mechanical Engineering, 2005. http://theses.library.uwa.edu.au/adt-WU2005.0069.

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[Truncated abstract] This thesis presents three different methods to investigate flexural wave propagation and scattering, power flow and transmission efficiencies, and dynamic stress concentration and fatigue failures in structural dynamics. The first method is based on the acoustical wave propagator (AWP) technique, which is the main part described in this thesis. Through the numerical implementation of the AWP, the complete information of the vibrating structure can be obtained including displacement, velocity, acceleration, bending moments, strain and stresses. The AWP technique has been applied to systems consisting of a one-dimensional stepped beam, a two-dimensional thin plate, a thin plate with a sharp change of section, a heterogeneous plate with multiple cylindrical patches, and a Mindlin?s plate with a reinforced rib. For this Mindlin?s plate structure, through the comparison of the results obtained by Mindlin?s thick plate theory and Kirchhoff?s classical thin plate theory, the difference of theoretical predicted results is investigated. As part of these investigations, reflection and transmission coefficients, power flow and transmission efficiencies in a onedimensional stepped beam, and power flow in a two-dimensional circular plate structure, are studied. In particular, this technique has been successfully extended to investigate wave propagation and scattering, and dynamic stress concentration at discontinuities. Potential applications are fatigue failure prediction and damage detection in complex structures. The second method is based on experimental techniques to investigate the structural response under impact loads, which consist of the waveform measuring technique in the time domain by using the WAVEVIEW software, and steady-state measurements by using the Polytec Laser Scanning Vibrometer (PLSV) in the frequency domain. The waveform measuring technique is introduced to obtain the waveform at different locations in the time domain. These experimental results can be used to verify the validity of predicted results obtained by the AWP technique. Furthermore, distributions of dynamic strain and stress in both near-field (close to discontinuities) and far-field regions are investigated for the study of the effects of the discontinuities on reflection and transmission coefficients in a one-dimensional stepped beam structure. Experimental results in the time domain can be easily transferred into those in the frequency domain by the fast Fourier transformation, and compared with those obtained by other researchers. This PLSV technique provides an accurate and efficient tool to investigate mode shape and power flow in some coupled structures, such as a ribbed plate. Through the finite differencing technique, autospectral and spatial of dynamic strain can be obtained. The third method considered uses the travelling wave solution method to solve reflection and transmission coefficients in a one-dimensional stepped beam structure in the time domain. In particular, analytical exact solutions of reflection and transmission coefficients under the given initial-value problem are derived. These analytical solutions together with experimental results can be used to compare with those obtained by the AWP technique.

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Shafiei-Tehrany, Najmeddin. "Development of small-scale thermoacoustic engine and thermoacoustic cooling demonstrator." Online access for everyone, 2008. http://www.dissertations.wsu.edu/Thesis/Spring2008/N_Shafiei-Tehrany_042308.pdf.

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Aljets, Dirk. "Acoustic emission source location in composite aircraft structures using modal analysis." Thesis, University of South Wales, 2011. https://pure.southwales.ac.uk/en/studentthesis/acoustic-emission-source-location-in-composite-aircraft-structures-using-modal-analysis(6871e94b-6e94-4efd-b563-41b254ee27b4).html.

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The aim of this research work was to develop an Acoustic Emission (AE) source location method suitable for Structural Health Monitoring (SHM) of composite aircraft structures. Therefore useful key signal features and sensor configurations were identified and the proposed method was validated using both artificially generated AE as well as actual AE resulting from damage. Acoustic Emission is a phenomenon where waves are generated in stressed materials. These waves travel through the material and can be detected with suitable sensors on the surface of the structure. These stress waves are attributed to propagating damage inside the material and can be monitored while the structure is in service. This makes AE very suitable for SHM, in particular for aircraft structures. In recent years composite materials such as carbon fibre reinforced epoxy (CFRP) are increasingly being used for primary and secondary structures in aircraft. The anisotropic layup of CFRP can lead to different failure mechanisms such as delamination, matrix cracking or fibre breakage which affects the remaining life time of the structure to different extents. Accurate damage location is important for SHM systems to avoid further inspections and allows for a maintenance scheme which considers the severity of the damage, due to damage type, extent and location. This thesis presents a novel source location method which uses a small triangular AE sensor array. The method determines the origin of an AE wave by a combination of time of arrival and modal analysis. The small footprint of the array allows for a fast and easy installation in hard-to-reach areas. The possibility to locate damage outside and at a relatively far distance from the array could potentially reduce the overall number of sensors needed to monitor a structure. Important wave characteristics and wave propagation in particular in CFRP were investigated using AE simulated by an artificial source and actual damage in composite specimens.

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Coja, Michael. "Effective vibro-acoustical modelling of rubber isolators." Doctoral thesis, Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-266.

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Sangchoom, Wantana. "Fabrication of porous carbons and mesoporous silica materials for energy storage and environmental applications." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/30919/.

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In the context of limited availability of fossil fuel and the impact of fossil-based energy utilization to the environment, novel porous materials have been extensively investigated for applications in environmentally friendly energy generation and storage. This thesis describes work wherein porous carbons and mesoporous silica materials have been systematically studied to include new synthesis strategies, material characterization. Two main themes of this thesis are, firstly, to investigate how porosity affects the utilization of activated carbons in energy storage and gas adsorption, and secondly, explore the stabilization of mesoporous silica materials. Chapter 1 discusses structures and classifications of pores. Porous carbons and mesoporous silica materials are introduced including the fundamental properties, preparation and important applications of the materials. Chapter 2 gives the basics of techniques used for characterization of the porous materials fabricated in this work. Gas sorption techniques applied for hydrogen storage and carbon dioxide uptake are introduced. The chapter also presents the electrochemistry and electrochemical methods used in this work. Chapter 3 briefly describes the preparation of highly porous carbons from lignin via hydrothermal carbonisation followed by chemical activation using KOH as activating agent. The work evidences the influence of activation temperature and KOH/carbon weight ratio on the structure of activated carbon and the performance of the gas storage capacity. Activation at KOH/carbon ratio of 2 generates highly microporous carbons which exhibit excellent CO2 uptake capacity; up to 4.6 mmol/g at 1 bar and 25 oC. Activation at KOH/carbon ratio of 4 can, on the other hand, generate lignin-derived carbons with ultrahigh porosity. These higher surface area lignin-derived carbons exhibit attractive hydrogen uptake capacity of up to 6.2 wt% at -196 oC and 20 bar. Chapter 4 is devoted to the use of lignin-derived activated carbons (LAC) as electrode materials for supercapacitors in aqueous and ionic liquid electrolytes. The study shows several factors affecting the electrochemical performance of carbon electrodes. It is demonstrated that a high surface area carbon (designated as LAC4800) electrode in 2 M H2SO4 exhibits a high capacitance value of 223 F/g or surface capacitance of 11.49 µF/cm2 and good cycling stability over 1000 cycles. The LAC electrodes also showed attractive capacitive performance with 175 F/g (6.92 µF/cm2) and the energy density can be enhanced in ionic electrolytes to reach 97.2 Wh/kg and power density of 2.0 kW/kg at 0.5 A/g for sample LAC4800 in BMImBF4 electrolyte. Chapter 5, regarding non-carbon materials, new forms of MCM-41 type silica mesostructures have been prepared by increasing the applied crystallization temperature to between 150 and 190 oC. The high temperature crystallisation resulted in enlargement of pore size and generated thicker pore walls. The sample prepared at 190 oC shows exceptional hydrothermal and thermal stability, even retaining long-range mesostructural ordering after refluxing in boiling water for 24 h or heating at 1000 oC for 4 h, which is unprecedented for pure silica MCM-41 materials. Finally, the conclusions for the thesis including the suggestion for future work are proposed in Chapter 6.

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42

Ehrlich, Christian. "Experimental characterization of creep damage using the nonlinearity ultrasonic technique." Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/42752.

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Welded steel pipes are an essential structural part of any power plant. Longer lifetimes and higher pressures in the pipes cause an increased probability of failure due to creep damage. To maintain safe operation, nondestructive evaluation techniques to detect creep damage are needed. Nonlinear acoustic techniques employing longitudinal waves have been proven to be sensitive to creep damage. The objective of this research is to develop a robust experimental procedure to reliably measure the acoustic nonlinearity parameter using longitudinal waves, and then to validate the procedure on samples of different materials and sizes. Finally the technique is applied to characterize creep damage levels around the weld of a welded steel pipe. While the experimental technique presented can only measure the relative nonlinearity, it is accurate enough to detect changes in nonlinearity due to creep damage. Measurements show an increase in nonlinearity in the heat affected zone (HAZ). Experiments after annealing the creep damaged specimen show a decrease in nonlinearity in accordance with a decrease in dislocation density. Measurements on an undamaged welded A36 steel component suggest that the heat itself is not responsible for the increase in nonlinearity.

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43

Anders, William S. "Structural acoustic analysis of shape memory alloy hybrid composite panels." Thesis, This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-11012008-063243/.

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44

Cordeiro, Helio de Miranda. "Stochastic dynamical system identification applied to combustor stability margin assessment." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/28167.

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Thesis (M. S.)--Aerospace Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Zinn, Ben; Committee Member: Ferri, Aldo; Committee Member: Lieuwen, Timothy; Committee Member: Prasad, J. V. R.; Committee Member: Ruzzene, Massimo.

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45

Reed, Darrin Kiyoshi. "Virtual audio localization with simulated early-reflections and generalized head-related transfer functions." Thesis, Montana State University, 2009. http://etd.lib.montana.edu/etd/2009/reed/ReedD1209.pdf.

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In a natural sonic environment a listener is accustomed to hearing reflections and reverberation. It is conceived that early reflections could reduce front-back confusion in synthetic 3-D audio. This thesis describes experiments which seek to determine whether or not simulated reflections can reduce front-back confusions for audio presented with non-individualized head-related transfer functions (HRTFs) via headphones. To measure the contribution of the reflections, 13 human subjects participated in localization experiments which compared their localization ability with anechoic HRTF processing versus HRTF processing with a single early-reflection. The results were highly subject dependent; some showed improvement while others seemed to be inhibited by the reflections. Statistical analysis of the overall results concluded that a single reflection does not provide a significant difference in localization ability. Although this data rejects the hypothesis of this investigation, some suspicion regarding the contribution of lateral reflections in an auditory environment remains.

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46

Dater, Brian Scott. "Structural acoustic optimization of an aircraft fuselage using the complex method." Thesis, Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/17689.

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47

Clark, Robert L. "Advanced sensing techniques for active structural acoustic control /." This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-05222007-091351/.

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48

Cepel, Raina. "The spatial cross-correlation coefficient as an ultrasonic detection statistic." Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/5054.

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Thesis (M.S.)--University of Missouri-Columbia, 2007.
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 April 7, 2008) Includes bibliographical references.

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Allen, Nancy J. "Computation of pseudosonic logs in shallow fresh/brackish water wells: a test case in Brunswick, Georgia." Thesis, Virginia Tech, 1989. http://hdl.handle.net/10919/44105.

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Due to the usefulness of sonic logs in formation evaluation, efforts have been made to develop a method for calculating pseudosonic logs for wells in which sonic logs were not originally obtained. These efforts attempt to use electrical resistivity data in the calculation of pseudosonic logs by means of empirical scale functions. The purpose of this study is to examine ways of applying these relationships in relatively shallow wells where the principal formation fluid is fresh or brackish water. Data from four wells situated in Brunswick, Georgia were used in this study.

Conventional focused resistivity logs are sensitive to beds as thin as one foot and can provide detail similar to that seen on sonic logs. Focused resistivity logs should be best for conversion to pseudosonic logs in shallow wells, where invasion is minimal and the water used for drilling fluid has electrical resistivity close to that of formation water. Sonic and resistivity logs from a representative well are needed in the procedure for finding an empirical relationship between sonic transit time and resistivity. Values of transit time plotted versus resistivity are read from corresponding depths on both types of logs. The graphs obtained in this study reveal significantly more scatter than previously published graphs based upon deep well data.

An important feature clearly evident in the graphs is the presence of groups of points which me offset from each other. A separate scale function relating transit time and resistivity can be obtained from each group of points. It is noted that the different groups correspond to differences ir1 the chlorinity of the formation water. The results of this study indicate that it is necessary to consider the salinity of the formation water as well as electrical resistivity for purposes of calculating pseudosonic logs. In previous studies three constant coefficients were deterrnined experimentally in order to obtain an empirical scale function. The present study suggests that it may be possible to replace these constants with chlorinity dependent coefficients. The final results of this study indicate that reasonably reliable pseudosonic logs can be obtained only by using high quality focused resistivity logs from wells where information about the salinity of the formation water is also available.

Master of Science

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Locey, Lance Lester. "Analysis and Comparison of Three Acoustic Energy Density Probes." Diss., CLICK HERE for online access, 2004. http://contentdm.lib.byu.edu/ETD/image/etd561.pdf.

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Dissertations / Theses on the topic 'Acoustical engineering'

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