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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.
41

Detecting Inclusions in a Silicone Rubber Phantom Using Standing Lamb Waves and Multiple Frequency Footprints

Jonsson, Ulf G January 2014 (has links)
The thesis deals with one major question: is it possible, using one piezoelectric sensor/vibrator, to detect a hard inclusion in a silicone rubber phantom? The question was approached with an open mind and the task was subdivided into three clearly identifiable parts: characterization of the piezoelectric sensor/vibrator (paper I), creating a model of the visco-elastic properties of a tissue-like material (phantom) in contact with the sensor/vibrator (paper II), and to detect the presence of a hard inclusion in the phantom (paper III). All vibrations of the sensor/vibrator and phantom was modeled using a finite element method (FEM). To minimize the computational time and to maximize the FEM model's ability to correctly reproduce the vibrations, a two-dimensional model system consisting of a cylindrical piezoelectric sensor/vibrator, emitting radial elastic waves in to a cylindrical disk-shaped phantom, was chosen. The piezoelectric sensor/vibrator was characterized using a parameter tuning procedure using harmonic overtones. The procedure enables tuning of the electro-elastic parameters of the sensor/vibrator so that the measured and calculated impedance frequency responses match. Silicone rubber was chosen as a phantom to mimic soft tissue. The properties of the phantom was modeled using a fractional derivative visco-elastic model. The hyperelastic effect at the first radial resonance of the sensor vibrator was corrected for by a compensating function. The high frequency complex visco-elastic modulus of the silicone rubber was determined using the transitions of standing Lamb waves in the phantom. The presence of a ring-shaped inclusion in the phantom, of polyamide, was detected using the change of the transitional Lamb wave patterns in the phantom. The tuning of the PZT5A1 sensor/vibrator parameters yielded a match between the calculated and the measured impedance spectra better than 0.54%. The average, complex, elastic modulus of three silicone rubber, Silgel 612, samples were: (0.97 + 0.009i) GPa  at 100 kHz and (0.97 + 0.005i) GPa at 250 kHz. The presence of a polyamide inclusion, PA6GPE, was detected in the phantom using multiple frequency footprints. / Denna avhandling berör frågan: är det möjligt, med en piezoelektrisk sensor/vibrator, att detektera ett hårt objekt inneslutet i en fantom av silikongummi? Frågan närmades utan begränsningar och uppgiften delades upp i tre tydliga delar: karaktäriseringen av den piezoelektriska sensorn/vibratorn (paper I), skapa en modell av det viskoelastiska uppförandet hos ett vävnadsliknande material (fantom) som står i kontakt med sensorn-/vibratorn (paper II) och att detektera förekomsten av ett hårt objekt inneslutet i fantomen (paper III). En finit element modell (FEM) skapades för att beräkna vibrationerna hos sensorn/vibratorn och fantomen. För att minimera beräkningstiden och maximera modellens förmåga att återge vibrationer på ett korrekt sätt, så skapades ett tvådimensionellt modellsystem bestående av en cylindrisk piezoelektrisk sensor/vibrator i kontakt med en cylindrisk fantom av silikongummi. Sensorn/vibratorn skickar radiella elastiska vågor in i fantomen. Den piezoelektriska sensorn/vibratorn karakteriserades med hjälp av en procedur som anpassar parametervärden med hjälp av övertoner. Proceduren möjliggör en justering av parametervärdena så att uppmätta och beräknade impedansspektra överensstämmer. En 'fractional derivative' modell av de viskoelastiska egenskaperna hos silikongummit skapades. De hyperelastiska egenskaperna vid första radiella resonansen blev kompenserade med hjälp av en sigmoidformad funktion. Den komplexa viskoelastiska modulen bestämdes för höga frekvenser med hjälp av transitioner hos stående Lambvågor i fantomen. Närvaron av ett hårt ringformat objekt i fantomen detekterades med hjälp av förändringar i mönstret hos de stående Lambvågorna. Justeringen av de piezoelektriska parametrarna hos elementet PZT5A1 gav som mest en skillnad på 0.54% mellan uppmätta och beräknade impedansspektra. Medelvärdet hos tre prov av silikongummit Silgel 612 av den komplexa elastiska modulen uppmättes till (0.97 + 0.009i) GPa  vid 100 kHz och (0.97 + 0.005i) GPa vid 250 kHz. Närvaron av ett hårt objekt, gjort av polyaramid (PA6GPE), detekterades i fantomen med hjälp av multifrekvensiella fotavtryck.
42

How do healthy individuals adapt to reversed vision generated when using mirror specs? : an investigation into mirror devices, adaptation to body schema and imagery ability in healthy participants

Walker, Joanna Louise January 2010 (has links)
Introduction: This study investigates a new form of Mirror Therapy (MT), the Mirror Specs. Evidence suggests that MT is a non-invasive, cost effective method of reducing pain and increasing functioning in some chronic pain conditions. There is no clear explanation for the underlying mechanisms of MT, however, a plausible hypothesis suggests that adaptation to the Body Schema is an integral component. Aims and Hypotheses: The current study examined Body Schema adaptation in healthy participants when performing a Finger Tapping Task with both Mirror Specs and a Mirror Box. It was hypothesised that adaptation would be indicated by increases in Reaction Times (RTs) and Error Rates when comparing unimanual phases of a Finger Tapping Task, following a bimanual „adaptation‟ phase. It was hypothesised that there would be no difference between participants‟ ability to adapt to each device. Finally, the study proposed that there would be a relationship between the adaptation observed on the Finger Tapping Task and participants individual imagery abilities. Method: Participants performed 4 phases of a Finger Tapping Task with alternate bimanual and unimanual phases when using both the Mirror Specs and Mirror Box. Imagery abilities were measured using self-report questionnaires and a Motor Imagery computer task. Results and Discussion: Repeated Measures ANOVAs revealed reductions in RTs and Error Rates in Phase 3 compared to Phase 1 on the Finger Tapping Task. There were no differences between RTs and Error Rates when using the Mirror Specs and Mirror Box. These findings suggest that healthy participants were able to use each Mirror Device effectively and this provide impetus for the proposal that Mirror Specs could provide a practical, cost effective addition to rehabilitation services. Finally, there were no clinically significant relationships between use of the Mirror Devices and imagery abilities, thereby indicating imagery abilities did not influence how participants adapted to using the Mirror Devices.
43

The Phantom Menace: the F-4 in Air Combat in Vietnam

Hankins, Michael W. 08 1900 (has links)
The F-4 Phantom II was the United States' primary air superiority fighter aircraft during the Vietnam War. This airplane epitomized American airpower doctrine during the early Cold War, which diminished the role of air-to-air combat and the air superiority mission. As a result, the F-4 struggled against the Soviet MiG fighters used by the North Vietnamese Air Force. By the end of the Rolling Thunder bombing campaign in 1968, the Phantom traded kills with MiGs at a nearly one-to-one ratio, the worst air combat performance in American history. The aircraft also regularly failed to protect American bombing formations from MiG attacks. A bombing halt from 1968 to 1972 provided a chance for American planners to evaluate their performance and make changes. The Navy began training pilots specifically for air combat, creating the Navy Fighter Weapons School known as "Top Gun" for this purpose. The Air Force instead focused on technological innovation and upgrades to their equipment. The resumption of bombing and air combat in the 1972 Linebacker campaigns proved that the Navy's training practices were effective, while the Air Force's technology changes were not, with kill ratios becoming worse. However, the last three months of the campaign introduced an American ground radar system that proved more effective than Top Gun in improving air-to-air combat performance. By the end of the Vietnam War, the Air Force and Navy overcame the inherent problems with the Phantom, which were mostly of their own making.
44

Out of sight : using animation to document perceptual brain states

Moore, Samantha January 2015 (has links)
It is acknowledged that the genre of animated documentary is particularly suited to depicting the subjective point of view (Wells, 1997, Honess Roe, 2013). It has also been suggested that animated documentary may have a tendency toward collaborative working methods (Ward, 2005: 94). This PhD work explores and expands these suggestions and presents the development of a methodology adapted from what has been termed collaborative ethnography (Lassiter, 2005) when using animation to document perceptual brain states. The claim to originality in this thesis lies in the methodological approach taken through the documenting of idiopathic perceptual brain states, previously unrepresented in animation. It involves a shifting of the roles of subject and director to collaborative consultant and facilitator respectively, and differentiates between the recording of an animated document and the creation of an animated documentary . It rejects the sound reliant template of the 'animated interview' (Strøm, 2005: 15) as the dominant model of creating animated documents, which assumes both that the indexical is crucial to documenting, and that this can only be achieved in animation through the use of indexical sound. It agrees with Tom Gunning s argument that Charles Sanders Pierce's original idea of the index as part of an interconnected triad of signs (index, symbol and icon) has been abstracted from its richer signifying context and extracted a simplified version of what Pierce intended it to mean (a trace or impression left by an object) to become a 'diminished concept' (2007:30-1), essentially a short hand coda in this instance for document . The practice in this work challenges this by presenting an alternative; using a collaborative cycle methodology.
45

Development of Assessment Tasks to Measure the Driving Capabilities of Persons with Disabilities

Upadhyay, Ashwin 01 November 2004 (has links)
The need to lead an independent and fuller life is as much a right of a person with physical disability as any other human being. Driving capabilities of a person with a disability have been assessed and evaluated using qualitative techniques. However, certain inadequacies that arise using qualitative measures can be avoided if the assessment is based on quantitative techniques. The above requirement necessitates the need to devise a method and a system which is focused on the right development of the techniques used in assessing and measuring different capabilities (such as range of motion and force input) of the person with a disability in a detailed manner. This thesis focuses on developing an experimental method which can be adopted as an assessment tool to evaluate different capabilities of a person with a disability. The test bed used for this purpose consists of two independent systems combined together by an interface. They are the six-degree of freedom force reflecting hand controller known as the PHANTOM haptic device [12] and a commercially available adaptive driving control system known as the AEVIT system [15]. The test bed provides compatibility between the PHANTOM and AEVIT which makes it feasible for the PHANTOM to model and control the driving input devices (steering and gas/brake) of the AEVIT system.
46

Design and Verification of an Optical System to Interrogate Dermally-implanted Microparticle Sensors

Long, Ruiqi 2012 May 1900 (has links)
Diabetes mellitus affects 25.8 million Americans (8.3%) and over 300 million people worldwide. Clinical trials indicate that proper management of blood glucose levels is critical in preventing or delaying complications associated with diabetes. Thus, there is a common need to monitor and manage blood glucose properly for people with diabetes. However, the patients’ compliance for recommended monitoring frequency is low due to the pain and inconvenience of current standard finger-pricking tests. To promote patient adherence to the recommended self-monitoring frequency, non-invasive/ minimally invasive glucose testing approaches are needed. Luminescent microparticle sensor is an attractive solution. For these sensors to be deployed in vivo, a matched optical system is needed to interrogate dermally-implanted sensors. This research project investigated the light propagation in skin and the interaction with implants using Monte Carlo modeling. The results of the modeling were used to design an optical system with high interrogation and collection efficiency (40~300 times improvement). The optical system was then constructed and evaluated experimentally. A stable skin phantom mimicking the optical properties of human skin was developed as a permanent evaluation medium to minimize the use of animals. The optical properties of the skin phantom matched the maximum published values of human skin in scattering and absorption over the spectral range of 540~700nm in order to avoid overestimation of the capability of the system. The significant photon loss observed at the connection between the designed system and a commercial spectrometer was overcome using two optimized designs: a two-detector system and a customized low-resolution spectrometer system. Both optimization approaches effectively address the photon loss problem and each showed good SNR (>100) while maintaining a sufficient system resolution for use with fluorescent materials. Both systems are suitable for luminescence measurement, because broad bands of the luminescent spectrum are of interest. In the future, either system can be easily modified into a more compact system (e.g. handheld), and it can be directly coupled to an analog-to-digital converter and integrated circuits offering potential for a single compact and portable device for field use with luminescent diagnostic systems as well as implanted sensors.
47

Application of CT in Diagnosing Carcinoma of the Maxillary Sinuses : PART 2: An Experimental Study of Pitfalls Encountered when Diagnosing Carcinoma of the Maxillary Sinuses with CT

MATSUBARA, KAZUHITO 03 1900 (has links)
No description available.
48

Biophotoacoustic Radar: Study of Tissue Phantoms, Tissues, Contrast Agent and Comparison to Ultrasound Imaging for Deep Subsurface Imaging

Alwi, Rudolf 20 November 2012 (has links)
This study explored the imaging capability of our frequency-domain photoacoustic (FD-PA) system that utilizes correlation processing alias “photoacoustic radar” and ultrasonic phased array for imaging of soft tissues. The probe imaging capabilities were studied using tissue-mimicking phantoms, tissue samples ex vivo, blood vessels in a human wrist and a rat tumour model in vivo. Our experimental results have shown decent image correlation between our FD-PA and a clinical ultrasound modality. In comparison with ultrasound, we have also demonstrated strong potential of the FD-PA for deep (~15 mm) subsurface imaging with excellent contrast and high signal-to-noise ratio. Additionally, we assessed the potential of silica-coated super paramagnetic iron oxide nanoparticles (SPION) as a novel PA contrast agent. Detection of the nanoparticles up to 24 mm inside an optically tissue-like turbid media and about 5-fold PA signal amplification due to their presence in sheep blood (~1.4 mg/ml) are presented.
49

Biophotoacoustic Radar: Study of Tissue Phantoms, Tissues, Contrast Agent and Comparison to Ultrasound Imaging for Deep Subsurface Imaging

Alwi, Rudolf 20 November 2012 (has links)
This study explored the imaging capability of our frequency-domain photoacoustic (FD-PA) system that utilizes correlation processing alias “photoacoustic radar” and ultrasonic phased array for imaging of soft tissues. The probe imaging capabilities were studied using tissue-mimicking phantoms, tissue samples ex vivo, blood vessels in a human wrist and a rat tumour model in vivo. Our experimental results have shown decent image correlation between our FD-PA and a clinical ultrasound modality. In comparison with ultrasound, we have also demonstrated strong potential of the FD-PA for deep (~15 mm) subsurface imaging with excellent contrast and high signal-to-noise ratio. Additionally, we assessed the potential of silica-coated super paramagnetic iron oxide nanoparticles (SPION) as a novel PA contrast agent. Detection of the nanoparticles up to 24 mm inside an optically tissue-like turbid media and about 5-fold PA signal amplification due to their presence in sheep blood (~1.4 mg/ml) are presented.
50

Feasibility of Determining Radioactivity in Lungs Using a Thyroid Uptake Counter

Lorio, Ryan 11 August 2005 (has links)
The feasibility of using a thyroid uptake counter, normally used to measure the uptake of radioactive iodine in thyroid treatments, to assay radioactivity deposited in a persons lungs has been investigated. Variations in radioactive material distributions in the lungs, the response of the detector system to radionuclides of interest to homeland security, and the change in detection efficiency due to the varying thicknesses of intervening tissue of the victims have been simulated using the Monte Carlo N-Particle transport code (MCNP5) developed by Los Alamos National Laboratory. Point source and homogenously distributed models were created for Co-60, I-131, Cs-137, Ir-192, and Am-241 sources to simulate radiation transport between the lungs of multiple phantom models representing children and adults and the radiation detection system. To validate the simulations undertaken, the response of the counter to radiation sources in air and behind layers of Lucite have been modeled and compared to measured results.

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