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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
401

Comparison of Selected Differential Producing, Ultrasonic, and Magnetic Flow Meters

Prettyman, Johnny B. 01 May 2014 (has links)
Flow meters are used to measure flow accurately. There are many different flow meters and it is necessary to know which will function best for specific situations. A wide variety of flow meters were selected for the study to assist in showing that each flow meter has its tradeoffs. The selected meters include: three types of Venturi meters, a wedge meter, a V-cone meter, an electromagnetic flow meter, and an ultrasonic flow meter. The characteristics researched in this study are discharge coefficient (Cd) over a range of Reynolds numbers (Re), head loss across each flow meter, life, and cost of meter. Each meter was tested over a wide range of Re to find the corresponding Cd and head loss. The life and cost of each meter were researched and estimated based on the flow meter companies and local distributor’s findings. With the findings, the tradeoffs are illustrated and will assist buyers in selecting a flow meter that will best fit their needs. While there are more flow meters available than was tested, the current study can direct buyers in a correct process of selecting meters for all situations.
402

Integration of Ultrasonic Consolidation and Direct-Write to Fabricate an Embedded Electrical System Within a Metallic Enclosure

Hernandez, Ludwing A. 01 December 2010 (has links)
A research project was undertaken to integrate Ultrasonic Consolitation (UC) and Direct-Write (DW) technologies into a single apparatus to fabricate embedded electrical systems within an ultrasonically consolidated metallic enclosure. Process and design guidelines were developed after performing fundamental research on the operational capabilities of the implemented system. In order to develop such guidelines, numerous tests were performed on both UC and DW. The results from those tests, as well as the design and process guidelines for the fabrication of an embedded touch switch, can be used as a base for future research and experimentation on the UC-DW apparatus. The successful fabrication of an embedded touch switch proves the validity of the described design and process parameters and demonstrates the usefulness of this integration.
403

Evaluation of adhesively bonded steel sheets using ultrasonic techniques

Tavrou, Chrysostomos Kyriacou, stavrou@swin.edu.au January 2005 (has links)
Adhesives have presently reached a stage where they have become part of everyday life both in a professional sense as well as for household applications. They offer advantages that in many respects surpass other joining processes such as bonding of large areas, joining a wide range and dissimilar materials; and without the need for special tooling or operator training, that is often required by many other joining processes. They are of course not a panacea to all fastening applications, but they can easily be described as the most versatile and most widely used joining method at present. Engineering applications have also benefited from the advantages offered by adhesives, but they are not as liberally used due to the severe consequences that may result from bond failure. Although adhesives can demonstrate their ability to fulfil the joining strength requirements under laboratory conditions, their application in industry proved to be not as reliable as expected. A number of parameters that can easily be controlled under laboratory conditions such as temperature, humidity, surface preparation and uniform adhesive application are not as easily observed in industry. Quality assurance during manufacturing can achieve excellent results; however even in these cases the probability of having adhesive bond defects is still present. Therefore, there is a need for post process inspection of adhesive bonds where risk levels require higher reliability than what is offered though process quality control. Adhesive bond inspection is a well researched area with respectable outcomes. Non destructive inspection techniques such as x-ray, thermal, and ultrasonic are well utilised in the inspection of adhesive bonds. However, despite all the effort in this area for more than forty years, there is still no singular technique that can achieve the confidence level required in some engineering applications. Therefore, the need for continuing research in the area of non-destructive evaluation of adhesive bonds is as necessary today as it�s ever been. The research presented in this thesis, continues in the same endeavour as many other researchers; that of achieving the ultimate technique in adhesive bond inspection, capable of reaching the confidence level required for all engineering applications. The research in the thesis commenced with coverage of adhesives used for engineering applications and a study of the adhesion science that was considered necessary to enable an informed approach to the problem. Adhesive bond failure is also analysed through a literature survey as well as experimental tests on standard specimens. At the completion of the literature survey and preliminary tests, a decision was taken to follow the ultrasonic path of non-destructive testing of adhesive bonds. The reasons for this, are clearly outlined in the main body of this thesis but in summary, the literature has shown that ultrasonic evaluation is the most widely used technique by industry. Therefore, improvements on data analysis using existing techniques that exploit ultrasonic inspection have the potential to reach the widest spectrum of industrial applications. Ultrasonic inspection equipment was sourced that was capable of achieving experimental results to the accuracy level required in this research. A precision test rig was designed and constructed that was subsequently calibrated using computer based statistical techniques to ensure the validity of all results. Other ancillary equipment, such as a portable tensile testing device were also designed and constructed during the research as it became necessary. Research concentrated on techniques found to be inadequately researched in this domain. The first technique evaluated was to measure bond quality through the stress distribution in adherent and adhesive. Computer based Finite Element Analysis showed that the ability to detect variation in stress distribution at the adhesion interface is capable of revealing the local bond strength. Having found that there is no technique available at present that can measure the stress distribution at the interface, a different direction was taken that showed potential in achieving excellent quantitative results in the analysis of ultrasonic signals from adhesive bonds. This technique was rigorously evaluated and the results are systematically reported in this work.
404

Statistical design and analysis of sonic wave pressure treatment of wood

Nair, Hari U. 22 June 1994 (has links)
Literature reports have indicated that application of sonic pressure waves enhances the rate of impregnation of preservatives in wood. However, these studies have been limited and inconclusive. The technique or process is not in commercial use. In this study a laboratory scale treating cylinder connected to a mechanical sonic wave generator was used to measure the rate of impregnation of water in ponderosa pine at pressures of 0.28, 0.55 and 0.69 MPa and Douglas-fir at pressures of 0.55 and 0.69 MPa at a frequency of 30 Hz. Results were compared with those obtained at the same conditions of static hydraulic pressure. Statistical analysis showed that sonic treatments were at least as effective as, but not consistently superior to, hydraulic pressure treatments in the case of ponderosa pine. Statistical analysis of the results from Douglas-fir treatment showed that sonic treatment was superior than hydraulic treatment. / Graduation date: 1995
405

On ultrasonic propagation through mercury in tubes

January 1948 (has links)
H.B. Huntington. / "July, 1948." "Reprinted from The Journal of the Acoustical Society of America, Vol. 20, No. 4, 424-432, July, 1948." / Army Signal Corps Contract No. W-36-039 sc-32037.
406

Ultrasonic velocity and absorption in liquid helium

January 1947 (has links)
by John R. Pellam and Charles F. Squire. / "August 1, 1947." / Bibliography: p. 16. / Army Signal Corps Contract No. W-36-039 sc-32037
407

Ultrasonic measurements on single crystals

January 1947 (has links)
by H.B Huntington. / "March 21, 1947." / Bibliography: p. 21. / Army Signal Corps Contract No. W-36-039 sc-32037
408

Piezoelectric Micromotors for Microrobots

Flynn, Anita M., Tavrow, Lee S., Bart, Stephen F., Brooks, Rodney A. 01 February 1991 (has links)
By combining new robot control systems with piezoelectric motors and micromechanics, we propose creating micromechanical systems which are small, cheap and completely autonomous. We have fabricated small - a few millimeters in diameter - piezoelectric motors using ferroelectric thin films and consisting of two pieces: a stator and a rotor. The stationary stator includes a piezoelectric film in which we induce bending in the form of a traveling wave. Anything which sits atop the stator is propelled by the wave. A small glass lens placed upon the stator becomes the spinning rotor. Using thin films of PZT on silicon nitride memebranes, various types of actuator structures have been fabricated.
409

Laboratory measurements of static and dynamic elastic properties in carbonate

Bakhorji, Aiman M 06 1900 (has links)
The fact that many of the giant hydrocarbon reservoirs, such as the Ghawar field in Saudi Arabia and the Grosmont formation in Alberta, are formed from carbonates make these rocks important research topics. Compressional and shear wave velocities (at 1 MHz) and the quasi-static strains of thirty seven carbonate rock samples were measured as functions of saturating fluid and confining pressure. Furthermore, P- and S-wave velocities of the saturated samples were measured at constant differential pressure of 15 MPa. The quasi-static strains of the samples under jacketed and unjacketed conditions were also simultaneously acquired. The lithology, mineralogy, porosity and pore type and size distribution of each sample were obtained using a combination of thinsection and scanning electron microscopy, helium porosimetry and mercury intrusion porosimetry. Due to the lack of closing microcracks and compliant pores in low porosity samples, the travel times show slight changes with the confining pressure. Whereas the high porosity samples show remarkable reduction of travel time with the increase of confining pressure in both P- and S-wave. The samples show no changes in travel time with increasing confining pressure under constant differential pressure, and this behavior is taken to be representative of full saturation of the sample and hence used as a measure of quality control. The comparisons of Biot, Gassmann, squirt-Biot and squirt-Gassmann model predictions with the measured water saturated velocities show that the squirt mechanism is not active on all the studied samples. Biot mechanism is likely to be the principle dispersion mechanism in these samples. For S-wave velocities, Gassmanns model consistently over-predict the saturated at low pressure and closely fit the measured velocities at high pressure, whereas, Biot model over-predicts the saturated velocities in most of the studied samples. The strains over the horizontal axis are higher than the vertical axis suggesting that the majority of the compliant pores and crack-like pores are oriented almost in direction parallel to the length of the sample. The static bulk modulus is always lower than dynamic one for all measured samples. The measured grain bulk modulus is reasonably close to the bulk modulus of the constituent mineral. / Geophysics
410

The development and implementation of an ionic-polymer-metal-composite propelled vessel guided by a goal-seeking algorithm

Vickers, Jason Aaron 17 September 2007 (has links)
This thesis describes the use of an ultrasonic goal-seeking algorithm while using ionic polymer metal composite (IPMC), an electroactive polymer, as the actuator to drive a vessel towards a goal. The signal transmitting and receiving circuits as well as the goal seeking algorithm are described in detail. Two test vessels were created; one was a larger vessel that contained all necessary components for autonomy. The second was a smaller vessel that contained only the sensors and IPMC strips, and all power and signals were transmitted via an umbilical cord. To increase the propulsive efforts of the second, smaller vessel, fins were added to the IPMC strips, increasing the surface area over 700%, determined to yield a 22-fold force increase. After extensive testing, it was found that the three IPMC strips, used as oscillating fins, could not generate enough propulsion to move either vessel, with or without fins. With the addition of fins, the oscillating frequency was reduced from 0.86-Hz to 0.25-Hz. However, the goal-seeking algorithm was successful in guiding the vessel towards the target, an ultrasonic transmitter. When moved manually according to the instructions given by the algorithm, the vessel successfully reached the goal. Using assumptions based on prior experiments regarding the speed of an IPMC propelled vessel, the trial in which the goal was to the left of the axis required 18.2% more time to arrive at the goal than the trial in which the goal was to the right. This significant difference is due to the goal-seeking algorithm’s means to acquire the strongest signal. After the research had concluded and the propulsors failed to yield desired results, many factors were considered to rationalize the observations. The operating frequency was reduced, and it was found that, by the impulse-momentum theorem, that the propulsive force was reduced proportionally. The literature surveyed addressed undulatory motion, which produces constant propulsive force, not oscillatory, which yields intermittent propulsive force. These reasons among others were produced to rationalize the results and prove the cause of negative results was inherent to the actuators themselves. All rational options have been considered to yield positive results.

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