Kliknij ten link, aby zobaczyć inne rodzaje publikacji na ten temat: ULTRASONIC APPLICATIONS.
Rozprawy doktorskie na temat „ULTRASONIC APPLICATIONS”
Utwórz poprawne odniesienie w stylach APA, MLA, Chicago, Harvard i wielu innych
Sprawdź 50 najlepszych rozpraw doktorskich naukowych na temat „ULTRASONIC APPLICATIONS”.
Przycisk „Dodaj do bibliografii” jest dostępny obok każdej pracy w bibliografii. Użyj go – a my automatycznie utworzymy odniesienie bibliograficzne do wybranej pracy w stylu cytowania, którego potrzebujesz: APA, MLA, Harvard, Chicago, Vancouver itp.
Możesz również pobrać pełny tekst publikacji naukowej w formacie „.pdf” i przeczytać adnotację do pracy online, jeśli odpowiednie parametry są dostępne w metadanych.
Przeglądaj rozprawy doktorskie z różnych dziedzin i twórz odpowiednie bibliografie.
1
Guldiken, Rasim Oytun. "Dual-electrode capacitive micromachined ultrasonic transducers for medical ultrasound applications". Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/31806.
Pełny tekst źródłaStreszczenie:
Thesis (Ph.D)--Mechanical Engineering, Georgia Institute of Technology, 2009.Committee Chair: Degertekin, F. Levent; Committee Member: Benkeser, Paul; Committee Member: Berhelot, Yves; Committee Member: Brand, Oliver; Committee Member: Hesketh, Peter. Part of the SMARTech Electronic Thesis and Dissertation Collection.
2
Ciulla, M. M. "Ultrasonic myocardial tissue characterization: clinical applications". Doctoral thesis, Università degli Studi di Milano, 2001. http://hdl.handle.net/2434/49004.
Pełny tekst źródła
3
Hopko, Sandra N. "Laser ultrasonic probe for industrial or high temperature applications". Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/16433.
Pełny tekst źródła
4
Ashraf, Muhammad. "A 3D ultrasonic camera for subsea applications". Thesis, University of Liverpool, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318304.
Pełny tekst źródła
5
Johansson, Patrick. "Capacitive Micromachined Ultrasonic Transducers for Underwater Applications". Thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-447067.
Pełny tekst źródłaStreszczenie:
Capacitive micromachined ultrasonic transducers (CMUT:s) are often used in medical imaging and they show some promise as underwater transducers. This thesis collates the available information about how CMUT:s operate, their strengths and weaknesses and investigates their efficiency as an underwater transducer. The accumulated knowledge was channelled into a simulation of a CMUT as a dampened spring system done in MATLAB and Simulink. The simulation investigated the resonance frequency and bandwidth through simulation and compared the results to experimental results from literature. CMUT:s have good acoustic matching with water making them sensitive, broadband transducers when used under water. Special care must be taken when choosing the CMUT so that materials and designs can fulfil the task for which it is intended, such as the radius of the membrane, the material of the membrane, the insulating layers in or around the CMUT and the height of the air gap inside. CMUT:s are, for the transmission of sound, less capable than existing lead zirconate-titanate-transducers (PZT-transducers). This problem can be somewhat alleviated through operating the CMUT in collapse-mode but care must be taken so that the CMUT is not damaged during this operation. Simulation results and results from literature show that it is possible to simulate CMUT:s with accuracy. By simulating 10 different CMUT:s, using the geometries and material properties of experimentally tested devices and testing for resonance frequency and bandwidth the results were as follows:The average relative error of resonance frequency was found to be -14 %, if outlier results are excluded and the average relative error of bandwidth proved inaccurate at -54 %
6
McLean, Jeffrey John. "Interdigital Capacitive Micromachined Ultrasonic Transducers for Microfluidic Applications". Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/7625.
Pełny tekst źródłaStreszczenie:
The goal of this research was to develop acoustic sensors and actuators for microfluidic applications. To this end, capacitive micromachined ultrasonic transducers (cMUTs) were developed which generate guided acoustic waves in fluid half-spaces and microchannels. An interdigital transducer structure and a phased excitation scheme were used to selectively excite guided acoustic modes which propagate in a single lateral direction. Analytical models were developed to predict the geometric dispersion of the acoustic modes and to determine the sensitivity of the modes to changes in material and geometric parameters. Coupled field finite element models were also developed to predict the effect of membrane spacing and phasing on mode generation and directionality.
After designing the transducers, a surface micromachining process was developed which has a low processing temperature of 250C and has the potential for monolithically integrating cMUTs with CMOS electronics. The fabrication process makes extensive use of PECVD silicon nitride depositions for membrane formation and sealing. The fabricated interdigital cMUTs were placed in microfluidic channels and demonstrated to sense changes in fluid sound speed and flow rate using Scholte waves and other guided acoustic modes. The minimum detectable change in sound speed was 0.25m/s, and the minimum detectable change in flow rate was 1mL/min. The unique nature of the Scholte wave allowed for the measurement of fluid properties of a semi-infinite fluid using two transducers on a single substrate. Changes in water temperature, and thus sound speed, were measured and the minimum detectable change in temperature was found to be 0.1C. For fluid pumping, interdigital cMUTs were integrated into microchannels and excited with phase-shifted, continuous wave signals. Highly directional guided waves were generated which in turn generated acoustic streaming forces in the fluid. The acoustic streaming forces caused the fluid to be pumped in a single, electronically-controlled direction. For a power consumption of 43mW, a flow rate of 410nL/min was generated against a pressure of 3.4Pa; the thermodynamic efficiency was approximately 5x10-8%. Although the efficiency and pressure head are low, these transducers can be useful for precisely manipulating small amounts of fluid around microfluidic networks.
7
Kalem, Volkan. "Development Of Piezoelectric Ceramics For Ultrasonic Motor Applications". Phd thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12612935/index.pdf.
Pełny tekst źródłaStreszczenie:
This study has been carried out to develop and manufacture piezoelectric ceramic materials which are utilized for ultrasonic motor (USM) applications. For this purpose, the effect of compositional modifications on the dielectric and piezoelectric properties of lead zirconate titanate (PZT) based ceramics was investigated.
PZT based powders were produced using the mixed oxide method. The base composition was selected as Pb(Zr0.54Ti0.46)O3. The samples in the proximity of morphotrophic phase boundary were doped with strontium, lanthanum, lead manganese niobate (PMnN) and lead manganese antimonate (PMS) in order to improve the structural characteristics and electromechanical properties which are very important for USM applications. The dielectric constant, planar coupling coefficient, mechanical quality factor, piezoelectric strain constant and tangent loss values were evaluated in accordance with standard IRE (Institute of Radio Engineers) test procedures.
The results on dielectric and piezoelectric properties showed that piezoelectric ceramics with high mechanical quality factor, high piezoelectric strain constant and low tangent loss could be produced by using the aforementioned dopants. As a result, a new piezoelectric ceramic named as 0.97[PSLZT]-0.024[PMnN]-0.006[PMS] was produced with KT= 1913, Qm= 1240, d33= 540 pC/N, tan delta= 0.89%, kp= 0.57 and Tc= 235 °C. This composition is a good candidate for high power applications. The ceramic samples with the developed compositions were used to produce an ultrasonic-wave type motor and the performance of the USM was evaluated in terms of speed, torque and efficiency.
8
Wang, Kevin John 1981. "An ultrasonic compass for context-aware mobile applications". Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/16689.
Pełny tekst źródłaStreszczenie:
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2004.Includes bibliographical references (p. 95-96).
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
If we are to realize the everyday benefits promised by pervasive computing and context-aware applications, we must first develop the infrastructure to provide contextual location and orientation information through pervasive computing elements. I lay the foundations for leveraging the Cricket indoor location system to supply orientation information. I first characterize the use of ultrasound in Cricket for distance and orientation measurements. I then propose a set of methods to calculate 3-DOF orientation from an array of well placed ultrasonic sensors operating in the Cricket system. I design and implement a prototype of this Cricket Compass using a combination of hardware and software and demonstrate end-to-end functionality of the system.
by Kevin John Wang.
M.Eng.
9
Deroo, Frederik. "Damage detection in concrete using diffuse ultrasound measurements and an effective medium theory for wave propagation in multi-phase materials". Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31801.
Pełny tekst źródłaStreszczenie:
Thesis (M. S.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2010.Committee Chair: Laurence J. Jacobs; Committee Member: Jianmin Qu; Committee Member: Jin-Yeon Kim. Part of the SMARTech Electronic Thesis and Dissertation Collection.
10
Swacek, Christian Bernhard. "Optical generation of tone-burst Rayleigh surface waves for nonlinear ultrasonic measurements". Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45812.
Pełny tekst źródłaStreszczenie:
Conventional contact ultrasonic methods suffer from large variability, which
is known to originate from a number of sources such as coupling variability, and the
surface roughness at the transducer/specimen interface. The inherently small higherharmonic
signals can be significantly influenced by the changes in contact conditions,
especially in nonlinear ultrasonic measurements. For this reason, the noncontact
generation and detection techniques are very attractive. This research first focuses
on the optical generation of tone-burst surface acoustic waves in a metallic specimen.
Two methods that use laser light as an optical source are compared for generating
surface acoustics waves in the 5 MHz range. Both the shadow mask and diffraction
grating are used to convert a laser pulse to a tone-burst signal pattern on the specimen.
The generated signals are detected by a wedge transducer at a fixed location and then
the harmonic contents in the generated signals and the repeatability of the methods
are evaluated. Finally, the developed method is used to characterize the material
nonlinearity of aluminum (Al 6061) and steel (A36). The results showed repeatable
measurements for ablative signal excitation on aluminum.
11
Curra, Francesco Pasquale. "Medical ultrasound algorithm for noninvasive high intensity ultrasound applications /". Thesis, Connect to this title online; UW restricted, 2001. http://hdl.handle.net/1773/8006.
Pełny tekst źródła
12
Kiernan, Michael T. "A physical model for the acousto-ultrasonic method". Diss., Virginia Polytechnic Institute and State University, 1989. http://hdl.handle.net/10919/54214.
Pełny tekst źródłaStreszczenie:
A basic physical explanation, a model, and comments on NDE application of the acoustoultrasonic method for composite materials are presented. The basis of this work is a set of experiments where a sending and a receiving piezoelectric transducer were both oriented normal to the surface, at different points, on aluminum plates, various composite plates, and a tapered aluminum plate.
Chapter one introduces the purpose and basic idea of the dissertation, while supporting its need. Also, general comments on the AU method are offered. The second chapter offers a literature review of areas pertinent to the dissertation, such as composite materials, wave propagation, ultrasonics, and the AU method. Special emphasis is given to theory which is used later on and past experimental results that are important to the physical understanding of the AU method. The third chapter describes the experimental set-up, procedure, and the ensuing analysis. In the fourth chapter, the experimental results are presented in both a quantitative and qualitative manner. Chapter five furnishes a physical understanding of experimental results based on elasticity solutions, Lamb wave theory, and through-the-thickness-transverse·resonance (TTTR). Computer results are presented for sake of comparison. The sixth chapter discusses modeling and applications of the AU method for composite materials and the seventh chapter states general conclusions. The unique offering of this work is the physical model of the AU method for composite materials, something which has been much needed and sorely lacking. This physical understanding is possible due to the extensive set of experimental measurements, also reported in this dissertation.Ph. D.
13
Kobayashi, Makiko. "Development and applications of high temperature piezoelectric ultrasonic transducers". Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=85079.
Pełny tekst źródłaStreszczenie:
High temperature ultrasonic transducers (HTUTs) have been developed for non-destructive evaluation (NDE) of metals and on-line monitoring of industrial polymer processes at elevated temperatures. Developed HTUTs are two types; one is sol gel sprayed HTUTs and the other is a crystal of high Curie temperature permanently bonded onto a steel substrate by brazing or diffusion bonding. In sol gel method, piezoelectric powders were dispersed into sol gel precursor. Sol gel precursor of Al2O3, PZT or BIT, serves as adhesion material between powders, LT, PZT or BIT and a substrate to be coated. Spray technique was used so that thick films could be fabricated even onto curved or large surfaces. The composite material, BIT/PZT, derived from bismuth titanate (BIT) powders and lead zirconate titanate (PZT) sol gel precursor had presented excellent characteristics, such as high signal-to-noise ratio, broadband frequency, and acceptable signal strength up to more than 450°C. The film properties such as dielectric constant, piezoelectric constant, density and electromechanical coupling coefficient were characterized. Nondestructive testing of extent of sub-surface defect using BIT/PZT film HTUT was given at 440°C.High temperature immersion type HT ultrasonic probes using BIT/PZT film were also fabricated. They were immersed in molten zinc at 450°C, and able to measure the thickness of the steel sample. Surface and sub-surface imaging with fine resolution were obtained using this HT ultrasonic probe with a focused lens in silicone oil at 200°C.
On-line monitoring of industrial polymer processes had been performed. Sol gel HTUTs had been fabricated on a steel extruder adaptor of a polymer extruder machine, mold inserts of an injection machine and a micro-molding machine, and a barrel of the micro-molding machine. Ultrasonic signals were obtained at the elevated temperatures. The capability for monitoring the barrel wear and screw status during polymer extrusion at 190°C and the filling completion conditions for injection molding at 120°C and micromolding processes up to 200°C have been shown.
Brazing and diffusion bonding had been tried to establish permanent acoustic bonding between a lithium niobate crystal and a steel substrate. The HTUT fabricated by brazing technique had demonstrated broadband characteristics up to 460°C. The HTUT made by diffusion bonding technique had also demonstrated broadband characteristics up to 350°C. This latter HTUT had 20 dB higher signal strength than that of the sol gel BIT/PZT thick film HTUTs.
14
Bashford, Andrew Graham. "Characteristics and applications of air-coupled micromachined ultrasonic transducers". Thesis, University of Warwick, 1998. http://wrap.warwick.ac.uk/91887/.
Pełny tekst źródłaStreszczenie:
This thesis describes the characteristics of a micromachined air-coupled ultrasonic capacitance transducer, using backplates made from chemical etching, ion-beam and laser machining in copper, steel, aluminium and silicon. A series of backplates were produced with micro machined holes on the surface of different depths, diameters and pitch. The resultant characteristics were found to be consistent with previous work. Peak pressure field variations of the capacitance transducers were measured by scanning a detector throughout the radiated field in both air and water. The resulting field compared favourably to a theoretically-generated peak pressure field variation for a plane piston (a FORTRAN program was written which convolved the simulated motion of the membrane with an impulse response for the transducer). Experimental and theoretical peak pressure field variations were measured for an annulus and zoneplate apertures with single and toneburst driving signals. In all cases the experimental field agreed well with the computed theoretical field in air and water. Additionally, with the increase in bandwidth when operated in water, the transducers were used for a pulse-echo C-scan of an artificial defect. Furthermore, the transducers were used to determine the elastic constants in air for glass-epoxy, ceramic and paper card, where the results for glass-epoxy were in good agreement for the values obtained using immersion technique. The transducers were modified by use of a Mica membrane for high temperature use, and were successfully used to monitor the burnout rate of the polymer binder from an injection moulded ceramic.
15
Arya, Ishan, i Viswanaath Sundaram. "A System Study Of Ultrasonic Transceivers For Haptic Applications". Thesis, Linköpings universitet, Elektroniska Kretsar och System, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-152346.
Pełny tekst źródłaStreszczenie:
We are investigating the use of ultrasound in Haptic applications. Initially abrief background of ultrasonic transducers and its characteristics were presented.Then a theoretical research was documented to understand the concepts that govern haptics. This section also discusses the algorithm adopted by various researches to implement haptics in the professional world. Then investigations were made to understand the behavior of ultrasonic transducers and conduct soft-ware simulations to obtain various results. At first simulations were conducted on Field II software. This simulations involved the creation of elements in trans-ducers, transducer’s spatial impulse responses, transducer’s impulse responsein time and frequency domain, effect of adding apodization to the transducers,pulse echo response of the transducers, beam profile variation along the focallength of the transducers. Then a Matlab based GUI was used to study the relationship between number of elements in transducers, the frequency of the input signal and duty cycle variation of the input wave. A concept of phase shift, which explains the time delay generation was also coded in Matlab.
16
Guo, Jun Feng. "Use of the ultrasonic technique in measuring inclusions in Al-Si alloy melts". Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2007. http://theses.uqac.ca.
Pełny tekst źródłaStreszczenie:
Thèse (M.Eng.) -- Université du Québec à Chicoutimi, 2007.La p. de t. porte en outre: Mémoire présenté à l'Université du Québec à Chicoutimi comme exigence partielle de la maîtrise en ingénierie. CaQQUQ Bibliogr.: f. 101-106. Document électronique également accessible en format PDF. CaQQUQ
17
Yoon, Young Joong. "Ultrasonic phased arrays with variable geometric focusing for hyperthermia applications". Diss., Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/16969.
Pełny tekst źródła
18
Wu, Kuo-Ting. "Development of integrated and flexible ultrasonic transducers for aerospace applications". Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=97060.
Pełny tekst źródłaStreszczenie:
High temperature (HT) integrated (IUTs) and flexible ultrasonic transducers (FUTs) for potential aerospace applications in the area of nondestructive testing (NDT) and structural health monitoring (SHM) are developed. The main merits are that IUTs can be fabricated on-site and FUTs are feasible and attractive for on-site installation. The piezoelectric composite films of these HT ultrasonic transducers (HTUTs) are made by sol-gel spray fabrication. Lead-zirconate titanate composite (PZT-c), bismuth titanate composite (BIT-c), or lithium niobate composite (LiNbO3-c) films were coated onto metallic substrates with planar and curved surfaces and investigated as IUTs. Their maximum operating temperatures were demonstrated at up to 150°C, 400°C, and 800°C, respectively. PZT-c or BIT-c films were coated onto 75 µm or 38 µm thick metallic membranes and were investigated as FUTs. They can be bonded onto flat or curved surfaces for NDT and SHM. An FUT made of BIT-c film coated onto a stainless steel membrane glued onto a steel plate was performed at up to 300°C. Besides being coated onto metallic materials, sol-gel sprayed composite films were also coated onto graphite/epoxy (Gr/Ep) plates as IUTs and 50 µm thick polyimide films as FUTs for the thickness and delamination evaluation.Using acoustic mode conversion techniques, HTUTs for shear (S) wave, surface acoustic wave (SAW), and plate acoustic wave (PAW), have been developed. HT ultrasonic probes simultaneously producing one longitudinal (L) and two orthogonally polarized S waves were demonstrated in metallic and Plexiglas probes. The potential applications of these probes were discussed. Also applying mode conversion approaches, HT symmetrical, anti-symmetrical, and shear horizontal (SH) PAWs UTs for NDT and SHM were developed. The results showed that the SH PAWs may be the best candidate for NDT and SHM purposes for plate structures. Generation and detection of guided acoustic waves for NDT were demonstrated by using IUTs or FUTs with metallic wedges, mechanical gratings or interdigital transducers as well. The experiments with these three approaches were performed at up to 300°C.Furthermore, two non-contact ultrasonic measurement techniques by sol-gel sprayed composite films were presented in this thesis. One is using lasers to generate ultrasound and IUTs as receivers, and the other is using induction-based non-contact ultrasonic measurement technique with IUTs. NDT of bonded composite patches on aluminum plates was performed using laser generated ultrasound and IUT receivers. The induction-based ultrasonic measurement of a Gr/Ep composite plate rotated at 1000 rpm was demonstrated.The IUTs and FUTs developed in this thesis are able to provide signals with good signal-to-noise ratios at elevated temperature on structures and parts having a curved surface. They are light weight and miniature in size. They may be used for real-time, in situ, nondestructive local and global (large area) damage detection and assessment in aerospace NDT and SHM applications.Des capteurs intégrés (CIU) et flexibles (CFU) ultrasonores à haute température (HT) on été développés pour des applications potentielles en aérospatiale dans le domaine des évaluations non destructives (END) et la surveillance de la santé structurelle (SSS). Le principal avantage des CIUs et des CFUs est leur capacité à être fabriqués sur site. Ces capteurs ultrasoniques à haute température (CUHT) sont fabriqués à partir de la technique sol-gel qui consiste à déposer une mince couche d'un composé piézo-électrique. Ces couches peuvent être constituées de zirconate titanate de plomb (PZT-c), ou de titanate de bismuth (BIT-c), ou encore, de niobate de lithium (LiNbO3-c), déposées sur des substrats métalliques plats ou courbes et évaluées comme CFUs. Les températures maximales d'opérations de ces capteurs furent évaluées et sont respectivement de 150°C, 400°C et 800°C. Les couches de PZT-c ou de BIT-c furent déposées sur des membranes métalliques d'épaisseurs de 75 m ou de 38 m et furent évaluées comme CFUs. Ils peuvent être collés sur des surfaces plates ou courbes pour de l'END et de la SSS. Un CFU fait à partir de BIT-c déposé sur des membranes d'acier inoxydable et collé sur une plaque d'acier fut démontré jusqu'à une température de 300°C. De plus, ces composés piézo-électriques peuvent être déposés sur des plaques de graphite/époxy (Gr/Ep) et être traités comme des CIUs, ou encore, sur des films de polyimide comme CFUs pour mesurer des épaisseurs et évaluer le délaminage.En utilisant la technique de conversion de mode acoustique les ondes de cisaillement (C) des CUHTs, les ondes acoustiques de surface (OAS) et les ondes acoustiques de plans (OAP) ont été développées. Les capteurs ultrasonores à HT produisent une onde longitudinale (L) et deux ondes perpendiculaires polarisées (S). Ces deux types d'ondes furent démontrés pour des palpeurs métalliques et en « Plexiglass ». De plus, en utilisant cette technique acoustique pour des CUHTs des OAS symétrique, antisymétrique et cisaillement horizontal (CH) pour l'END et la SSS furent développés. Les résultats démontrent que les CH d'OAS sont probablement les meilleurs candidats pour l'END et la SSS de structures plates. La génération et la détection d'ondes acoustiques guidées pour l'END furent démontrées en utilisant des CUIs et des CFUs avec des coins métalliques, des grilles mécaniques ou bien des capteurs interdigitaux. Les expériences avec ces trois approches furent faites jusqu'à une température de 300°C.En plus, deux méthodes de mesures ultrasoniques sans contact pour des capteurs ultrasoniques faits à partir de la méthode sol-gel sont présentées dans cette thèse. L'une est l'utilisation de LASER pour la génération d'ultrasons et des CIU comme receveurs. L'autre est l'utilisation sans contact d'une technique de mesure ultrasonore basée sur l'induction qui utilise des CIUs comme receveurs. L'END de plaques de composites déposées sur des plaques d'aluminium fut effectué en utilisant le LASER comme générateur et des CFUs comme receveurs. La mesure ultrasonique basée sur l'induction d'une plaque composite de Gr/Ep tournant à 1000 RPM fut démontrée.Les CFU et les CIU développés dans cette thèse ont de très bons ratios signal sur bruit à température élevée sur des structures et des surfaces courbes. Ils sont légés et miniatures. Ils peuvent être utilisés en temps réels, in situ et pour la détection de dommages sur de petite ou large surfaces en END pour les domaines de l'aérospatial et pour des applications en SSS.
19
Liang, Yuan. "Ultrasonic Nanocrystal Surface Modification Produced Surface Texture and Its Applications". University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1510277965591045.
Pełny tekst źródła
20
Hu, Rui, i 胡瑞. "Applications of non-invasive vascular imaging techniques in cardiovascular risk assessment and management". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B36923242.
Pełny tekst źródła
21
Kiernan, Michael T. "An acousto-ultrasonic system for the evaluation of composite materials". Thesis, Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/76441.
Pełny tekst źródłaStreszczenie:
A presentation is given of an acousto-ultrasonic system for the evaluation of composite materials. First, a brief statement will be made on the acousto-ultrasonic technique and its relative worth compared to other nondestructive testing techniques as applied to composite materials. The following two chapters describe the system instrumentation and system software, respectively. Next, comments are given regarding the implementation of the system for research on graphite/epoxy laminates, with additional remarks concerning efforts to evaluate aluminum/graphite tubes with the system. This includes physical descriptions of the composite systems. Subsequently, results are presented comparing parameters and forms of presentation which can be employed to relate results. Finally, conclusions are made on the application of the acousto-ultrasonic system to nondestructive testing of composite materials, with specific results on its application to graphite/epoxy plates. More specifically, comments are made on the variation of SWF factors with azimuthal angle on the graphite/epoxy plates, the identification of specific frequency peaks, and the relationships these may have to certain modes of vibration and material properties. For example, a low frequency mode was found to vary in a manner reminiscent of Ex and to show characteristics of an extensional Lamb wave. In general, results are presented and discussed in order to show how the system can be implemented to gain physical information on composite materials, such as the property of anisotropy.Master of Science
22
Cooper, J. A. "Laser-generated ultrasound with applications to non-destructive evaluation". Thesis, University of Hull, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375636.
Pełny tekst źródła
23
Bruttomesso, Douglas Allen. "Laser ultrasonic techniques to determine the influence of geometric features on Rayleigh waves". Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/21471.
Pełny tekst źródła
24
Law, Masa. "The Development and Modelling of a Novel Clamp-on Ultrasonic-Thermal and Ultrasonic Multiple Reflection Flowmeter for Liquid Applications". Thesis, Cranfield University, 1994. http://dspace.lib.cranfield.ac.uk/handle/1826/4596.
Pełny tekst źródłaStreszczenie:
The development of a novel combined "ultrasonic/thermal" with "ultrasonic multiple
reflections" clamp-on meter for measuring a wide flowrate range of clean liquids in
small diameter pipes is presented. Current existing flowmeters based on ultrasound
cannot measure very low flowrates for single phase liquids. The ultrasonic/thermal
technique can measure single phase flows in the range 0 to 0.6 m s' in pipes with
diameters as small as 15 mm. It can also detect and measure reverse flows. The
minimum flowrate for the ultrasonic multiple reflection technique is about 0.55 m s',
and theoretically, the measurement accuracy increases with increased flow velocity.
The ultrasonic/thermal technique is based on a heating element and transducer pair(s)
which can be clamped to the outside of a pipe. With the heaters switched on, the
changes in the temperature of the pipe and the liquid inside it result in changes in
transit time. The flowrate can be therefore estimated by either the transit time difference
across the pipe at the two symmetric locations with respect to the heater centre, or at
one location with a heater off/on comparison. The latter approach was felt to be the
promising for low flowrate measurements and therefore selected for the numerical and
the experimental investigations. The multiple reflection technique was developed based
on the conventional transit time flowmeter. This technique extended the measuring
range of the flowmeter and provided cross calibration for the ultrasonic/thermal
technique. A computer model was developed for the ultrasonic multiple reflection
technique. However, there was insufficient experimental data to confirm the computer
prediction.
Results from computational fluid dynamics (CFD) analysis of the meter are presented.
For vertical pipes an axisymmetric model was used, but the presence of buoyancy
forces required the use of a 3-D model for horizontal pipes. Temperature and velocity
distributions and ultrasonic transit times have been computed and are presented.
In order to overcome the problem of mode conversion and refraction at the pipe
wall/transducer mounting interface, novel transducers and mounting blocks are
presented. A prototype heater and ultrasonic transducer system together with electronics
for signal generation and transit time measurement have been designed and constructed.
A hydraulic system has also been designed and constructed for testing the developed
clamp-on flowmeter. Experimental results from this apparatus are presented and compared
with the CFD predictions, and a technique for compensating for variations in inlet
temperature is described. The full scale difference between the computed values and
experimental results of the meter for low flowrate measurement was about 3.5%.
25
Voronina, Svetlana. "Modelling of autoresonant control of an ultrasonic transducer for machining applications". Thesis, Loughborough University, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.504068.
Pełny tekst źródłaStreszczenie:
The main purpose of this research is an investigation into the different strategies for the autoresonant control of an ultrasonic transducer. Numerical simulations were considered as the most appropriate method for analysis and a Matlab-Simulink computer model of a non-linear ultrasonic vibrating system with the possibility of autoresonant control was developed. The controlled system consists of two modules, the first of which is an electromechanical model of the ultrasonic transducer comprising a piezoelectric transducer and a step concentrator. The second module simulates influence from the machining process. The coefficients of the electromechanical model were calculated through an identification process based on the real measurement of the ultrasonic transducer's vibrations.
26
Perelli, Alessandro <1985>. "Sparse Signal Representation of Ultrasonic Signals for Structural Health Monitoring Applications". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6321/1/Perelli_Alessandro_tesi.pdf.
Pełny tekst źródłaStreszczenie:
Assessment of the integrity of structural components is of great importance for aerospace systems, land and marine transportation, civil infrastructures and other biological and mechanical applications. Guided waves (GWs) based inspections are an attractive mean for structural health monitoring. In this thesis, the study and development of techniques for GW ultrasound signal analysis and compression in the context of non-destructive testing of structures will be presented. In guided wave inspections, it is necessary to address the problem of the dispersion compensation. A signal processing approach based on frequency warping was adopted. Such operator maps the frequencies axis through a function derived by the group velocity of the test material and it is used to remove the dependence on the travelled distance from the acquired signals. Such processing strategy was fruitfully applied for impact location and damage localization tasks in composite and aluminum panels. It has been shown that, basing on this processing tool, low power embedded system for GW structural monitoring can be implemented. Finally, a new procedure based on Compressive Sensing has been developed and applied for data reduction. Such procedure has also a beneficial effect in enhancing the accuracy of structural defects localization. This algorithm uses the convolutive model of the propagation of ultrasonic guided waves which takes advantage of a sparse signal representation in the warped frequency domain. The recovery from the compressed samples is based on an alternating minimization procedure which achieves both an accurate reconstruction of the ultrasonic signal and a precise estimation of waves time of flight. Such information is used to feed hyperbolic or elliptic localization procedures, for accurate impact or damage localization.
27
Perelli, Alessandro <1985>. "Sparse Signal Representation of Ultrasonic Signals for Structural Health Monitoring Applications". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6321/.
Pełny tekst źródłaStreszczenie:
Assessment of the integrity of structural components is of great importance for aerospace systems, land and marine transportation, civil infrastructures and other biological and mechanical applications. Guided waves (GWs) based inspections are an attractive mean for structural health monitoring. In this thesis, the study and development of techniques for GW ultrasound signal analysis and compression in the context of non-destructive testing of structures will be presented. In guided wave inspections, it is necessary to address the problem of the dispersion compensation. A signal processing approach based on frequency warping was adopted. Such operator maps the frequencies axis through a function derived by the group velocity of the test material and it is used to remove the dependence on the travelled distance from the acquired signals. Such processing strategy was fruitfully applied for impact location and damage localization tasks in composite and aluminum panels. It has been shown that, basing on this processing tool, low power embedded system for GW structural monitoring can be implemented. Finally, a new procedure based on Compressive Sensing has been developed and applied for data reduction. Such procedure has also a beneficial effect in enhancing the accuracy of structural defects localization. This algorithm uses the convolutive model of the propagation of ultrasonic guided waves which takes advantage of a sparse signal representation in the warped frequency domain. The recovery from the compressed samples is based on an alternating minimization procedure which achieves both an accurate reconstruction of the ultrasonic signal and a precise estimation of waves time of flight. Such information is used to feed hyperbolic or elliptic localization procedures, for accurate impact or damage localization.
28
Hall, Ian Damon. "Generation of high resolution tomographic images for NDT applications". Thesis, University of Strathclyde, 2001. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=24263.
Pełny tekst źródłaStreszczenie:
Techniques for the generation of quantitative ultrasonic images in non-destructive testing have generally involved a substantial cost in terms of data storage and computational time, and have thus found limited application. Preference has therefore been given to the more straightforward imaging methods, such as main beam projection, which detect the presence of defects and provide a limited flaw sizing capability. The relatively small number of flaws requiring detailed examination, coupled with substantial increases in available data storage and computational power, have made it possible to use a number of straightforward tomographic reconstruction methods to produce high resolution images of flaws contained within the material under examination. A set of these images are then fused together using a novel fuzzy logic image fusion technique into a single image from which more accurate measurements of flaw size, shape and orientation can be made. However, if the quality of the raw A-scan data is not sufficiently high then the data will be filtered using Maximum Likelihood Deconvolution (MLD). The aim of this blind deconvolution method is to improve the time resolution and Signal to Noise Ratio of the A-scan data with only knowledge obtained from the data, this is in contrast to the majority of techniques currently used for this purpose. The three tomographic methods which have been implemented in this work are Reflection tomography, Time-of-flight Diffraction tomography and Transmission tomography. In addition a Single Bounce Image Enhancement method has been developed to improve the images. Selection of images used in the fusion process depends on the nature of the flaw, as each of these methods identifies different characteristics of the flaw shape. The components of the imaging system have been validated experimentally by the generation of high resolution images from a variety of flaws contained within cylindrical aluminium test specimens.
29
Baltazar-Lopez, Martin Eduardo. "Applications of TAP-NDE technique to non-contact ultrasonic inspection in tubulars". Diss., Texas A&M University, 2003. http://hdl.handle.net/1969.1/1614.
Pełny tekst źródłaStreszczenie:
The possibility and feasibility of experimental detection of localized defects in tubes using laser-induced ultrasonic wave approach through Thermo Acousto Photonic Non Destructive Evaluation (TAP-NDE) and Signal processing through wavelet transform is examined in this research. Guided waves in cylindrical surfaces provide solutions for detection of different defects in the material. Several experiments were conducted to this respect. Wave propagation in both axial and circumferential directions was studied. The dispersive wave propagation of ultrasonic waves in hollow cylinders has been investigated experimentally, primarily for use in non-contact and nondestructive inspections of pipes and tubes. The laser ultrasonic waves propagated in cylindrical waveguides are particularly attractive because of their unique characteristics in the applications of nondestructive evaluation (NDE). Contrary to studies making use of only axially symmetric guided waves in hollow cylinders, here are analyzed also nonaxisymmetric waves. The analysis of data is made by using the Gabor wavelet transform. The capability of modeling the guided wave dispersion in hollow cylinders is used in developing guided wave experimental techniques for flaw detection. Good agreement was obtained when comparing the dispersion spectra between theory and experimentation. Measurement of group velocities of guided waves, which are obtained directly from the wavelet transform coefficients, can be used to determine allocation and sizing of flaws.
30
Shackleton, Chris J. "Surface identification with low cost, narrow band ultrasonic sensors for automotive applications". Thesis, University of Reading, 2016. http://centaur.reading.ac.uk/65938/.
Pełny tekst źródłaStreszczenie:
The increasing number of vehicles on the road goes hand in hand with a rising number of traffic related accidents. As such there is a requirement to increase the level of safety provided to both the driver and other road users alike. The ultimate goal would be to realise autonomous vehicles on today’s roads. However few companies are able to provide a fully-fledged autonomous vehicle. That said many manufacturers are able to supply various advanced driver assistance systems in order to increase both the safety level and performance of the vehicle. Currently many different assistance systems are available that utilise a range of sensors, with great variation in cost. Not all vehicles have all sensors fitted, though there has been wide market acceptance of the ultrasonic parking aid. This sensor is low cost and also benefits from an ease of retrofitting, where not fitted as standard. Ultrasonic sensors however can only provide short range distance measurement and as such their uses are limited. This thesis takes ideas from CTFM ultrasound used in mobile robotics and applies them to low costs ultrasonic sensors found in the automotive industry, with the intention to provide additional functionality. In particular the specific challenge of driving surface recognition is considered. The experimental methods for data collection are presented alongside the classification techniques used. This thesis shows that low cost narrowband ultrasonic transducers can be used as an input for the classification of driving surfaces.
31
Venkatesan, Nishant. "AN EVALUATION OF THE TRAVELING WAVE ULTRASONIC MOTOR FOR FORCE FEEDBACK APPLICATIONS". UKnowledge, 2009. http://uknowledge.uky.edu/gradschool_theses/575.
Pełny tekst źródłaStreszczenie:
The traveling wave ultrasonic motor is considered for use in haptic devices where a certain input-output relation is desired between the applied force and the resulting motion. Historically, DC motors have been the standard choice for this purpose. Owing to its unique characteristics, the ultrasonic motors have been considered an attractive alternative. However, there are some limitations when using the ultrasonic motor for force-feedback applications. In particular, direct torque control is difficult, and the motor can only supply torque in the direction of motion. To accommodate these limitations we developed an indirect control approach. The experimental results demonstrate that the model reference control method was able to approximate a second order spring-damper system.
32
Kural, Aleksander. "Ultrasonic lamb wave energy transmission system for aircraft structural health monitoring applications". Thesis, Cardiff University, 2013. http://orca.cf.ac.uk/58395/.
Pełny tekst źródłaStreszczenie:
In this project an investigation of a wireless power transmission method utilising ultrasonic Lamb waves travelling along plates was performed. To the author’s knowledge, this is the first time such a system was investigated. The primary application for this method is the supply of power to wireless structural health monitoring (SHM) sensor nodes located in remote areas of the aircraft structure. A vibration generator is placed in a location where electricity supply is readily available. Ultrasonic waves generated by this device travel through the aircraft structure to a receiver in a remote wireless sensor node. The receiver converts the mechanical vibration of the ultrasonic waves back to electricity, which is used to power the sensor node. An experimental setup comprising a 1000 × 821 × 1.5 mm aluminium plate was designed to model an aircraft skin panel. Pairs of piezoelectric transducers were positioned along the longer edges of the plate. The electric impedance characteristics of three transducer types were measured. A circuit simulation MATLAB code was written. An input and output power measurement system was developed. The MFC M8528-P1 transducer type was identified as providing the best performance. The use of inductors to compensate for the capacitive characteristics of transducers was shown to provide up to 170-fold power throughput increase. The propagation of Lamb waves in the experimental plate was mapped using a scanning laser vibrometer and simulated using LISA finite difference method software. An optimised laboratory system transmitted 17 mW of power across a distance of 54 cm while being driven by a 20 V, 224 kHz signal. This figure can be easily increased by using a higher drive voltage. This shows that the system is capable of supplying sufficient power to wireless SHM sensor nodes, which currently have a maximum power requirement of approximately 200 mW.
33
Altemimi, Ammar Badran. "ULTRASONIC APPLICATIONS- PHYTOCHEMICAL ANALYSES OF SOME MEDICINAL NATURAL PRODUCTS IN FOOD PLANTS". OpenSIUC, 2016. https://opensiuc.lib.siu.edu/dissertations/1149.
Pełny tekst źródłaStreszczenie:
There are concerns about using synthetic phenolic antioxidants such as butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA) as food additives because negative effects to human health have been reported. thus, a replacement of these synthetics by antioxidant extractions from various foods has been proposed. By the generation of more than eight thousand different phenolics, fruits and vegetables are the prime sources of natural antioxidants. The consumption of fruits and vegetables has been strongly linked with several health benefits, a result of their medicinal properties and high nutritional value. Antioxidants control and reduce the oxidative damage in foods by delaying or inhibiting oxidation caused by reactive oxygen species (ROHs); ultimately increasing the shelf-life and quality of these foods.Beta-carotene, ascorbic acid, and many phenolics play dynamic roles in delaying aging, reducing inflammations, and preventing certain cancers. Increasing the consumption of fruits and vegetables has been recommended by many agencies and health care systems. In order to extract, measure, and identify bioactive compounds from a wide variety of fruits and vegetables, researchers use many different techniques and methods. Ultrasonic assisted technique (UAE) is known to be one of the easiest extraction techniques because it uses common laboratory equipment such as ultrasonic baths and probes. In this technique, a smashed sample is mixed with the suitable solvent and placed into the ultrasonic bath while temperature and extraction time are controlled. Five experiments were conducted to study the effects of different ultrasonic parameters on the polyphenol and antioxidant content and antimicrobial activity of extracts from plants grown in southern Illinois. In the first experiment, ultrasonic treatments at different frequencies,temperatures, power levels, and exposure times were compared for their effects on the yield of total phenolics, total flavonoids and antioxidant activities of spinach extracts. The best conditions for extraction judged by yields were an ultrasonic frequency of 37 kHz, extraction time of 30 min, reaction temperature of 400C, and ultrasonic power of 50%. The mean yield (mg/100g), total phenolics (mg gallic acid equivalence/ g DW), flavonoids (mg/g DW), % DPPH free radical scavenging activity, and % ferric reducing antioxidant power were all high (64.88±21.84, 33.96±11.30, 27.37±11.85 , 64.18±16.69 and 70.25 ±9.68). In the second experiment, the study was designed to optimize ultrasonic-assisted extraction of lutein and β-carotene from spinach. Further, the identities and purity of the natural products in the TLC spots were assayed using matrix-assisted laser desorption/ionization time-off-light mass spectrometry (MALDI-TOF MS) analysis. The optimal UAE settings for output of lutein and β-carotene simultaneously from spinach extracts were an extraction temperature of 40 °C, extraction power of 40% (28 W/cm3) and extraction time of 16 min. UAE assisted extraction of carotenes from spinach can provide a source of lutein and β-carotene for the dietary supplement industry. In the third study, investigations of the effects of extraction parameters for UAE on antioxidant activity of peach and pumpkin extracts; and studying the chemical structures of samples before and after processing by Fourier transformed infrared spectroscopy were made. The optimal conditions for peach extracts were an extraction temperature of 41.53 ̊C, power of 43.99 % and time of 27.86 min for total phenolics. The optimal conditions for extractions of total phenolics from pumpkins were inferred to be a temperature of 41.45 ̊C, a power of 44.60 % and a time of 25.67 min. In the fourth study, TLC followed by Quantity-OneTM (Biorad) image analysis was used as a simple and rapid method for identification and quantification of compounds in complex mixtures. The results were consistent under optimal conditions among the experimental values and their predicted values. The MALDI-TOF MS technique was also applied for result confirmation. In the last experiments, UAE and Box-Wilson design were applied to optimize the extraction of antimicrobial activities from spinach extracts and to test their antimicrobial activities on both Gram-negative and Gram-positive bacteria. The spinach extracts exhibited antimicrobial activities against both bacterial pathogens with MICs in the 60-100 mg.ml-1 range. SEM showed that cells of the treated bacterial strains were damaged and showed structural defects compared to the controls. RAPD analysis of genomic DNA showed that the number and sizes of amplicons were decreased for the treated pathogens compared with non-treated strains.
34
Sanderson, Terry. "Thermoelastic modeling of laser generated ultrasound for nondestructive materials testing". Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/18978.
Pełny tekst źródła
35
Ibrahim, Rashidi. "Vibration assisted machining : modelling, simulation, optimization, control and applications". Thesis, Brunel University, 2010. http://bura.brunel.ac.uk/handle/2438/4732.
Pełny tekst źródłaStreszczenie:
Increasing demand for precision components made of hard and brittle materials such as glasses, steel alloys and advanced ceramics, is such that conventional grinding and polishing techniques can no longer meet the requirements of today's precision manufacturing engineering. Particularly, in order to undertake micro-milling of optical glasses or other hard-machining materials, vibration assisted machining techniques have been adopted. However, it is essential and much needed to undertake such processes based on a scientific approach, i.e. the process to be quantitatively controlled and optimized rather than carried out with a trial-and-error manner. In this research, theoretical modelling and instrumental implementation issues for vibration assisted micro-milling are presented and explored in depth. The modelling is focused on establishing the scientific relationship between the process variables such as vibration frequency, vibration amplitude, feedrate and spindle speed while taking into account machine dynamics effect and the outcomes such as surface roughness generated, tool wear and material removal rate in the process. The machine dynamics has been investigated including a static analysis, machine tool-loop stiffness, modal analysis, frequency response function, etc, carried out for both the machine structure and the piezo-actuator device. The instrumentation implementation mainly includes the design of the desktop vibration assisted machining system and its control system. The machining system consists of a piezo-driven XY stage, air bearing spindle, jig, workpiece holder, PI slideway, manual slideway and solid metal table to improve the system stability. The control system is developed using LabVIEW 7.1 programming. The control algorithms are developed based on theoretical models developed by the author. The process optimisation of vibration assisted micro-milling has been studied by using design and analysis of experiment (DOE) approach. Regression analysis, analysis of variance (ANOVA), Taguchi method and Response Surface Methodology (RSM) have been chosen to perform this study. The effects of cutting parameters are evaluated and the optimal cutting conditions are determined. The interaction of cutting parameters is established to illustrate the intrinsic relationship between cutting parameters and surface roughness, tool wear and material removal rate. The predicted results are confirmed by validation experimental cutting trials. This research project has led to the following contribution to knowledge: (1) Development of a prototype desktop vibration assisted micro-milling machine. (2) Development of theoretical models that can predict the surface finish, tool wear and material removal rate quantitatively. (3) Establishing in depth knowledge on the use of vibration assisted machining principles. (4) Optimisation of cutting process parameters and conditions through simulations and machining trials for through investigation of vibration assisted machining.
36
Owino, Joseph O. "Study of the propagation of Rayleigh waves in cement-based materials using laser ultrasonic techniques". Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/32800.
Pełny tekst źródła
37
Devaraju, Vadivel Lewin Peter A. "Design, development and characterization of wideband polymer ultrasonic probes for medical ultrasound applications /". Philadelphia : Drexel University, 2003. http://dspace.library.drexel.edu/handle/1721.1/95.
Pełny tekst źródła
38
Luangvilai, Kritsakorn. "Attenuation of Ultrasonic Lamb waves with Applications to Material Characterization and Condition Monitoring". Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16167.
Pełny tekst źródłaStreszczenie:
Engineering industries usually require nondestructive evaluation (NDE) methods to ensure quality control, safety, and optimized use of resources. Among potential NDE techniques, ultrasonic wave methods are widely used because of their versatility and affordability. For applications to layered structures, ultrasonic guided waves are naturally excited and detected, so these guided
waves are the preferred choice when compared to conventional bulk waves. The main advantage of guided waves over bulk waves for layered structures is that these guided waves can propagate a much farther distance, and thus they enable long range inspection. It is important to note that guided waves are multi-mode, so a preferred mode can be selectively used, although it is sometimes more efficient to use multiple wave modes. The characteristics of guided waves, namely dispersive propagation and attenuation, are
directly related to the properties of the system in which they are propagating, so the measurement of these wave characteristics can be used for material characterization and condition monitoring.
Despite a number of successful techniques to experimentally measure propagation characteristics of guided waves, there is a lack of a standard procedure to obtain attenuation characteristics. This research develops such a quantitative and
systematic procedure to extract attenuation characteristics from real guided wave time-domain signals. This research considers multiple wave-modes, and focuses on broadband attenuation
measurements with laser ultrasonic techniques. The analytical model of guided waves with attenuation is studied in general cases, and a numerical simulation is developed to model the point source/receiver laser measurement system. The attenuation extraction technique is developed using synthetic signals generated by the simulation. Finally, this research demonstrates the use of experimentally-measured attenuation data for material characterization and condition monitoring by developing an inversion scheme to back-calculate material properties for a number of practical cases.
39
Berrebi, Jonathan. "Self-diagnosis techniques and their applications to error reduction for ultrasonic flow measurement". Doctoral thesis, Luleå tekniska universitet, EISLAB, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-18555.
Pełny tekst źródłaStreszczenie:
Flow metering plays a major role in modern life. In the process industry, flow metering is critical in industries ranging from food processing to cosmetics. It is also essential in custody transfer or billing, as flow meters are present in gas pumps and district heating substations. In the district heating industry, the ultrasonic flow meter has become the desired meter in many of its applications because it has a low cost while being accurate. This accuracy is however sensitive to installation effects and other sources of errors. This thesis stems from research that addresses the recognition of these installation effects, informs when they are unacceptable and considers reducing the measurement errors. To present these concepts, the thesis details the estimation of the mean flow velocity, the calibration of the meter and the measurement noise properties. Once installed, any kind of meter provides larger errors than in the facility where it has been calibrated and compensated. It is particularly true for ultrasonic flow meters as they are very sensitive to installation effects. Installation effects can either be static or dynamic. Special attention is paid to errors generated by temperature and velocity profile variations. Velocity profile variations can be due to pipe bends or flow pulsations. Such disturbances often induce a bias error and change the properties of the measurement noise. It is therefore with help of the change in noise that velocity profile disturbances can be detected. The detection of such abnormal behaviour of the measurement process constitutes a diagnosis. A diagnosis of the sensitivity of the meter to installations effects would allow for compensations for the errors. Signal analysis allows detection of specific noise properties, characteristic of installation effects. An example of self-diagnosis showing the detection of real pulsations in a flow is described in details. The detection of the flow pulsations and the estimation of their frequency allow to reduce the error of estimation on the flow rate. This technique is confirmed by the simulations of a pulsating flow. To empower one with the decision whether a flowmeter performance is normal or abnormal, a study of the relative error as a function of flow rate and temperature has been conducted.Godkänd; 2004; 20080708 (evan)
40
Unger, Alexander [Verfasser], Mario [Akademischer Betreuer] Kupnik i Gerhard [Akademischer Betreuer] Sessler. "Air Coupled Ultrasonic Transducers for Industrial Applications / Alexander Unger ; Mario Kupnik, Gerhard Sessler". Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2019. http://d-nb.info/119317791X/34.
Pełny tekst źródła
41
Gachagan, Anthony. "An evaluation of 1-3 connectivity composite transducers for air-coupled ultrasonic applications". Thesis, University of Strathclyde, 1996. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=29597.
Pełny tekst źródłaStreszczenie:
Conventional ultrasonic non-destructive evaluation techniques require some form of liquid coupling between the piezoelectric transducer and the sample under inspection to facilitate mechanical energy transfer. Under automated conditions, maintaining a consistent couplant layer can constitute a problem and is manifest in slower scanning rates. To improve scanning speed the ultrasound should ideally propagate across an intermediate airgap. This possibility has been inhibited by the lack of a suitable transducer technology to overcome the practical difficulties inherent in the air medium. The large acoustic impedance mismatch, between a piezoelectric element and air, and the large air attenuation factor ensures both poor sensitivity and resolution characteristics. This Thesis advances transducer technology, enabling these problems to be challenged effectively. Initially, the Thesis describes the creation of a wideband characterisation methodology for aircoupled ultrasonic transducers op erating in the range 100kHz - 2MHz. The proposed technique utilises piezopolymer transducers in both transmission and reception modes and despite the obvious measurement difficulties, good agreement between theory and experiment is illustrated. Results are presented on the characterisation of both electrostatic and 1-3 connectivity piezocomposite devices, in which the inherent narrowband nature of the piezocomposite transducer demonstrates considerable potential for airborne applications. Subsequently, the performance of air-coupled 1-3 connectivity piezocomposite transducers is investigated using both uni-dimensional and finite element modelling techniques. Experimental verification of these techniques enables the finite element approach to be used as the benchmark for evaluation of practical transducer configurations. Consequently, a series of design guidelines are presented for practical air-coupled composite transducer systems. For many applications, the conventional metho improve system resolution, through attachment of a backing block, produces an unacceptably low system sensitivity. Hence, an alternative approach is proposed, utilising strong coupling between the fundamental thickness mode and the first lateral resonance in a 1-3 piezocomposite. Finite element analysis has been employed in the design of a laterally-coupled composite receiver and a -6dB bandwidth of 150% at a centre frequency of 1 MHz is presented. Finally, the new transducer design techniques were applied to three different airborne non-destructive testing applications. Successful detection of various defects in carbon-fibre reinforced composite plates is demonstrated.
42
Smith, Gregory J. (Gregory John). "Managing process development risk : aluminum ultrasonic wire bonding for chip-on-board applications". Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/12393.
Pełny tekst źródłaStreszczenie:
Thesis (M.S.)--Massachusetts Institute of Technology, Sloan School of Management, 1993, and Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1993.Includes bibliographical references (p. 207-209).
by Gregory J. Smith.
M.S.
43
Chen, Z. "The applications of ultrasonic imaging and signal processing in two-phase flow measurement". Thesis, Cranfield University, 1996. http://dspace.lib.cranfield.ac.uk/handle/1826/10516.
Pełny tekst źródłaStreszczenie:
The
applications of ultrasonic imaging and signal processing in two-phase flow
measurement have been
investigated in this thesis. The scattering by single and many
scatterers was studied
experimentally and numerically. The statistical properties of the
scattered waves from
many scatterers were examined and the corresponding results are
presented. Ultrasonic transmission/reflection mode tomography was introduced. The
theories of reflection mode
computerised tomography were developed, by which
reflectivity functions and scattering amplitude functions can be reconstructed. Image
restoration and
interpretation methods are presented. Computer simulation of ultrasonic
measurements were carried out. A ultrasonic tomographic imaging system was
developed, in which fan-shaped sound beam insonification was employed. Static physical
models were used to simulate
two-phase flows. In order to speed up the data acquisition
of a
tomographic imaging system, the single receiver mode and multiple receiver mode
data
acquisition arrangements were studied by experiments. Experiments on imaging
small and
large objects were carried out. Several signal and image processing methods
were examined. A modified histogram equalisation algorithm was developed for
processing the resultant ultrasonic images. The experiment results show that the
proposed image reconstruction methods are satisfactory. Possible future developments
are
proposed.
44
Chen, Zhenxiang. "The applications of ultrasonic imaging and signal processing in two-phase flow measurement". Thesis, Cranfield University, 1996. http://dspace.lib.cranfield.ac.uk/handle/1826/10516.
Pełny tekst źródłaStreszczenie:
The applications of ultrasonic imaging and signal processing in two-phase flow measurement have been investigated in this thesis. The scattering by single and many scatterers was studied experimentally and numerically. The statistical properties of the scattered waves from many scatterers were examined and the corresponding results are presented. Ultrasonic transmission/reflection mode tomography was introduced. The theories of reflection mode computerised tomography were developed, by which reflectivity functions and scattering amplitude functions can be reconstructed. Image restoration and interpretation methods are presented. Computer simulation of ultrasonic measurements were carried out. A ultrasonic tomographic imaging system was developed, in which fan-shaped sound beam insonification was employed. Static physical models were used to simulate two-phase flows. In order to speed up the data acquisition of a tomographic imaging system, the single receiver mode and multiple receiver mode data acquisition arrangements were studied by experiments. Experiments on imaging small and large objects were carried out. Several signal and image processing methods were examined. A modified histogram equalisation algorithm was developed for processing the resultant ultrasonic images. The experiment results show that the proposed image reconstruction methods are satisfactory. Possible future developments are proposed.
45
Unger, Alexander [Verfasser], Mario [Akademischer Betreuer] Kupnik i Gerhard Martin [Akademischer Betreuer] Sessler. "Air Coupled Ultrasonic Transducers for Industrial Applications / Alexander Unger ; Mario Kupnik, Gerhard Sessler". Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2019. http://nbn-resolving.de/urn:nbn:de:tuda-tuprints-89745.
Pełny tekst źródła
46
Campbell, Eimear. "Applications of ultrasonic technology : an investigation into the impact on fluid saturated rock". Thesis, University of Glasgow, 2018. http://theses.gla.ac.uk/8782/.
Pełny tekst źródłaStreszczenie:
With dwindling worldwide petroleum supplies, there is an ever increasing pressure on the oil industry to develop new reservoir recovery mechanisms or maximise the effectiveness of those currently utilised. Fluctuations of reservoir recovery as a result of nearby seismic activity has been observed, initiating a range of studies into what is causing this effect. The generation of ultrasonic wave fields due to the dispersion of seismic wave fields as they travel through saturated porous rock has been shown, both analytically and experimentally. The feasibility of these generated ultrasonic waves being capable of this observed modification to reservoir is investigated. For the initial stage of this research, the feasibility of changing the behaviour of fluid in rock using an ultrasonic field is considered. Research into the interaction between acoustic waves, the porous rock and the pore fluid indicates two key areas of permeability enhancement - increasing rock permeability and modifying the fluid behaviour within the pores. By increasing the permeability of the rock, previously unobtainable sources may be recovered and less energy would be necessary to obtain these reserves. Cavitation erosion or localised rock weakening due regions of high stress resulting from complex internal wave interactions are the two mechanisms proposed to increase permeability. Modification of the relative fluid behaviours within the rock as a result of mechanical agitation of the fluid from peristaltic transport and cavitation bubbles generated due to the acoustic field was explored. Sandstone cores saturated partially with tap water were placed in a degassed fluid and a low or high acoustic field applied. Tensile strength measurements are taken following exposure to the acoustic field and measurements compared to control samples. Samples were weighed prior to and following testing to determine fluid and gas motion between the surrounding fluid and pore volume. Samples exposed to the low amplitude acoustic pressure field showed no change in tensile strength when compared to control samples. The high pressure acoustic field caused samples to have an increase of strength when compared to the control batch of samples. The partial saturation of the samples exposed to the acoustic pressure field showed an increased in mass following exposure. An exchange of gas bubbles trapped within the pores and fluid with the surrounding degassed water explains this mass increase during testing.
47
Belsito, Luca <1982>. "Design and fabrication of MOMS-based ultrasonic probes for minimally invasive endoscopic applications". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3564/1/Belsito_Luca_Tesi.pdf.
Pełny tekst źródłaStreszczenie:
A Micro-opto-mechanical systems (MOMS) based technology for the fabrication of ultrasonic probes on optical fiber is presented. Thanks to the high miniaturization level reached, the realization of an ultrasonic system constituted by ultrasonic generating and detecting elements, suitable for minimally invasive applications or Non Destructive Evaluation (NDE) of materials at high resolution, is demonstrated. The ultrasonic generation is realized by irradiating a highly absorbing carbon film patterned on silicon micromachined structures with a nanosecond pulsed laser source, generating a mechanical shock wave due to the thermal expansion of the film induced by optical energy conversion into heat. The short duration of the pulsed laser, together with an appropriate emitter design, assure high frequency and wide band ultrasonic generation. The acoustic detection is also realized on a MOMS device using an interferometric receiver, fabricated with a Fabry-Perot optical cavity realized by means of a patterned SU-8 and two Al metallization levels. In order to detect the ultrasonic waves, the cavity is interrogated by a laser beam measuring the reflected power with a photodiode. Various issues related to the design and fabrication of these acoustic probes are investigated in this thesis. First, theoretical models are developed to characterize the opto-acoustic behavior of the devices and estimate their expected acoustic performances. Tests structures are realized to derive the relevant physical parameters of the materials constituting the MOMS devices and determine the conditions theoretically assuring the best acoustic emission and detection performances. Moreover, by exploiting the models and the theoretical results, prototypes of acoustic probes are designed and their fabrication process developed by means of an extended experimental activity.
48
Belsito, Luca <1982>. "Design and fabrication of MOMS-based ultrasonic probes for minimally invasive endoscopic applications". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3564/.
Pełny tekst źródłaStreszczenie:
A Micro-opto-mechanical systems (MOMS) based technology for the fabrication of ultrasonic probes on optical fiber is presented. Thanks to the high miniaturization level reached, the realization of an ultrasonic system constituted by ultrasonic generating and detecting elements, suitable for minimally invasive applications or Non Destructive Evaluation (NDE) of materials at high resolution, is demonstrated. The ultrasonic generation is realized by irradiating a highly absorbing carbon film patterned on silicon micromachined structures with a nanosecond pulsed laser source, generating a mechanical shock wave due to the thermal expansion of the film induced by optical energy conversion into heat. The short duration of the pulsed laser, together with an appropriate emitter design, assure high frequency and wide band ultrasonic generation. The acoustic detection is also realized on a MOMS device using an interferometric receiver, fabricated with a Fabry-Perot optical cavity realized by means of a patterned SU-8 and two Al metallization levels. In order to detect the ultrasonic waves, the cavity is interrogated by a laser beam measuring the reflected power with a photodiode. Various issues related to the design and fabrication of these acoustic probes are investigated in this thesis. First, theoretical models are developed to characterize the opto-acoustic behavior of the devices and estimate their expected acoustic performances. Tests structures are realized to derive the relevant physical parameters of the materials constituting the MOMS devices and determine the conditions theoretically assuring the best acoustic emission and detection performances. Moreover, by exploiting the models and the theoretical results, prototypes of acoustic probes are designed and their fabrication process developed by means of an extended experimental activity.
49
Panteli, Alexandra Hannah. "Friction joining of aluminium-to-magnesium for lightweight automotive applications". Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/friction-joining-of-aluminiumtomagnesium-for-lightweight-automotive-applications(00c7f0f5-ae47-412f-8ac8-d9e8c0ef29c5).html.
Pełny tekst źródłaStreszczenie:
Friction joining techniques, such as Friction Stir Spot Welding (FSSW) and high power Ultrasonic Welding (USW), could offer a solution for joining dissimilar materials combinations, such as aluminium (Al) to magnesium (Mg), where high intermetallic reaction rates make the use of conventional joining techniques problematic. Ultrasonic welds have been produced between 1 mm gauge Al 6111-T4 and Mg AZ31-H24 sheets, and the interfacial reaction has been studied as a function of welding time. For this welding system, the mechanical properties of the joints were optimised when a double reed welding system was employed to join materials that had been prepared using 800 grit SiC paper under a clamping force of 1.9 kN, and when the materials were oriented with the rolling direction parallel to the vibration direction. Welds produced between Al and Mg achieved similar peak lap shear strengths to those produced between Mg and Mg at welding times of 0.4 s, but the failure energy of the Al-Mg welds was less than half that of the parent material. In addition, the Al-Mg welds always failed at the interface between the sheets, rather than the desirable, and more energy intensive, pullout mechanism. The inferior mechanical properties were attributed to the rapid formation of a brittle intermetallic layer that initially formed as islands of the γ-Al12Mg17 phase. These islands rapidly spread and became continuous within 0.3 s of welding time, at which point a second sublayer of the β-Al3Mg2 phase began to form on the Al side of the intermetallic reaction layer. The combined layers reached a total thickness of 20 µm within 0.9 s of welding time, with the β-Al3Mg2 sublayer becoming the thicker of the two by this point. At longer welding times, interface liquation was observed at temperatures below the recognised lowest temperature eutectic reaction in the Al-Mg binary phase diagram. This was the result of the alloying elements present in the system and there was no depression in the melting point as a result of the high strain rate associated with this process, as has been proposed elsewhere. The rate of growth of the intermetallic layer during welding was higher than in static heat treatments, which was most likely due to the deformation causing microcracking in the brittle intermetallic layer, allowing short circuit diffusion to occur, and enhancing the growth rate by a factor of approximately 2. Finally, attempts were made to limit the rate of intermetallic compound (IMC) formation by applying coatings to the Mg sheet. The effect of the coatings was to reduce the overall IMC layer thickness by 50 %.
50
Chen, Wei. "Low cost instrumentation for high temporal resolution ultrasonic NDE with applications to solid objects". Thesis, University of Nottingham, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.537625.
Pełny tekst źródła