Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 21 for “"Ultrasonic Signals"”.
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A Framework for Temperature Imaging using the Change in Backscattered Ultrasonic Signals
… processes resulting from thermal changes in signals. CBE computation was formalized as a ratio between two random variables. Mutual information: MI) was studied as an example of possible parameters for temperature imaging based on the joint distributions. Furthermore, a maximum likelihood …
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Structural health monitoring of bolted joints using thermal contact resistance and ultrasonic signals
… bolted joints. These methods include using ultrasonic signals and thermal contact resistance metrics correlated to contact pressure to assess the joints integrity. Moreover, contact pressure distribution at the joint surface was examined using pressure sensitive films. Experimental …
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An invariance transformation algorithm for defect characterization of ultrasonic signals for the nondestructive evaluation of concrete
… system off-line. However, interpretation of NDE signals in terms of the location, size, and shape of underlying flaws in the material being inspected is fraught with difficulty. Typically, variations in the testing signal due to operational parameters have created a significant challenge for …
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Indoor Positioning Using Synchronized Ultrasonic OFDMA Signals
… phase measurements of synchronized two-tone ultrasonic signals in an Orthogonal Frequency Multiple Access (OFDMA) scheme. This indoor positioning system (IPS) operates at an ultrasonic frequency of approximately 40kHz and synchronizes using an infrared signal. The OFDMA scheme allows for a …
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Fast Chirped Signals for a TDMA Ultrasonic Indoor Positioning System
<p>In this paper, a new concept for ultrasonic indoor positioning based on instantaneous frequency of ultrasonic signals is presented. Nonlinear phase characteristics of ultrasonic transducers introduce a frequency deviation in ultrasonic signals. By sweeping at very fast rates, a large spike in …
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Non-invasive quality evaluation of fruits and vegetables using ultrasound
Ultrasonic techniques were investigated for non-invasive quality evaluation of selected fruits and vegetables. An ultrasonic non-destructive evaluation system was developed and used to investigate physical and acoustical property changes for the selected fruits and vegetables non-invasively. The …
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The observation of phase state and temperature using noninvasive ultrasonic waves.
… investigates the hypothesis that the use of ultrasonic signals and the resulting time of flight and intensity of the high-frequency sound wave may be used to identify a material undergoing a phase change within a confined vessel. A wax melting experiment within a confined chamber has been …
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Location Finding in Natural Environments with Biomimetic Sonar and Deep Learning
… navigate in a dense forest with bat-like FM-CF ultrasonic signals with deep learning. The results presented show that airborne biosonar can classify different areas' plants, in addition to achieving a similar level of navigation granularity compared to GPS, which is about 6 meters of radius …
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A FPGA/DSP design for real-time fracture detection using low transient pulse
… of LTP signal and to demodulate the passband ultrasonic signals sampled at 1MHz which interrupts the DSP at every 1 [Is. This research elaborates on designing a Quadrature Amplitude Modulator - demodulator (QAM) on the FPGA for the received signal from the ultrasound and edge detection on the …
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Signal processing techniques for ultrasonic inspection
… techniques. Special interest has been given to ultrasonic examination techniques and the problems encountered when they are applied to thick welded plates. Some suggestions are given using signal processing methods. Chapter 2 treats the need for nondestructive testing as seen in the light of …
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Design of energy-efficient ultrasonic communication systems on steel pipes
Ultrasonic communication provides an alternative to radio-frequency (RF) by transmitting guided ultrasonic signals along installed or buried metallic pipes. Buried pipe corrosion monitoring and intermittent infrastructure data collection are potential application areas, for which reliable wireless …
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Monitoring Progressive Damage Development in Laminated Fiber Reinforced Composite Materials
… to estimate the arrival of wave modes from ultrasonic signals is presented. Methods are also presented that utilize PLB signals to indicate approaching failure of specimens under monotonic as well as cyclic loading. These processes have been developed prioritizing simplicity and …
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Forming Screen Effect on Ultrasonic Beam Field
… to characterize the interaction between a pulsed ultrasonic wave and a paper forming screen for potential development of a smart paper forming sensor to measure velocity profile of the forming jet as it impinges on the wire. To achieve this goal, a Signal-Processing DOP 2000 pulsed ultrasonic …
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Cure monitoring of composite materials using optical techniques
… technique for the generation and detection of ultrasonics in epoxy materials has been developed at Victoria University. This requires a high power pulsed laser to induce ultrasound in the sample and an optical fibre interferometer for detection. The output of the interferometer can be recorded …
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Low noise techniques applied to a piezoceramic receiver for gas coupled ultrasonic flaw detection
… used for the generation and detection of ultrasonic signals and have applications in, for example, non-destructive testing and medical imaging. A rigorous theoretical investigation of thermal noise in plate transducers has been undertaken with the aim of establishing the absolute limits of …
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Small displacement measurement in ultrasound: quantitative optical noncontacting detection methods
… techniques for the detection and measurement of ultrasonic stress waves and their small displacement amplitudes is presented. The dynamic displacement sensitive interferometers described in the following chapters allow the quantitative point-by-point measurement of both in-plane and out-of-plane …
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An engineering study into the bisonar system of fruitbats in the genus rousettus
… Thesis provides further understanding of the signals and processes involved, and indeed replicates these in the laboratory. The calls of the echolocating fruit-bat Rousettus aegyptiacus are recorded using a novel design of wireless ultrasonic microphone sensor, which uses biomimetic variable …
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An air-coupled ultrasonic array scanning system for rapid through transmission NDT
… Thesis. Existing techniques frequently utilise ultrasonic signals to interrogate the sample under investigation, however, these are cumbersome and scan speed is invariably slow when testing of large samples is considered. This is because large samples are normally tested using a through …
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Synthetic aperture sonar imaging using compressive sensing and an ultrasound transducer array
… (baseline), single-pass configuration with 15 ultrasonic receivers and a single ultrasonic transmitter that operate at about 40 kHz. Signal conditioning circuits for the transmit and receive signals were built on pieces of veroboard. A PC which ran a custom designed LabVIEW virtual instrument …
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Automation of ultrasonic-based product tracking & traceability in supply chains
… interact. This dissertation explores optimizing ultrasonic-based systems as wireless sensors for tracking and traceability in SCM and logistics. While widely used, traditional radio-frequency identification (RFID) tags and barcode systems encounter limitations in environments with interference or …
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