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Nondestructive evaluation of civil structures is of increasing interest to utility owners. Several methods exist to evaluate different properties of concrete, pavement, cemented sands and others. UPVM is the most commonly used ultrasonic technique in civil structures due to its simplicity and ease of use. UPVM is fast and requires minimal skill from operators. It has been used for flaw detection, study of material contents, deduction of general deterioration, determination of elastic properties , measurement of strength, and others. In such applications, accurate measurements of velocity are essential for proper parameter evaluation and thus to increase the validity of conclusions obtained from measurements. Previous research in ultrasonic pulse velocity have found that UPVM are susceptible to specimen size, attenuation and frequency but no clear conclusions have yet to be made on the fundamental reason for the differences. This work seeks to identify the main factors responsible for velocity differences due to specimen size and measuring frequency in civil engineering materials. The effects are investigated by first performing numerical simulations of concrete specimens of varying sizes, and properties, excited by both a low (55 kHz) and high (850 kHz) frequency input source. Simulations are used to model wave propagation in cylindrical concrete specimen. Transducer sound fields are also numerically studied using known analytical solutions. An experimental program is conducted to study variations in UPVM in 12 mortar and 11 concrete cylindrical specimens of varying widths and heights caused by different measuring frequencies. Simulations are completed for 12 specimen of different dimensions having heights of 5,10,20 and 30 cm as well as diameters of 10, 20 and 30 cm. Both a low (f = 55 kHz) and high (f = 850 MHz) frequency input source are used on each specimen. Numerical simulations using low frequencies are made for both a damped and undamped series of specimen. Results from low frequency simulations of damped models indicate that wave attenuation can lead to significant errors in first arrivals when complex wave interference is present. Conditions for wave interference at the receiver location are studied and minimum size conditions for both height and width are derived. These conditions guarantee proper pulse separation for UPVM and are dependent on source size, and source pulse width. It is argued that with proper use these conditions will lead to accuracy of measurement better than one quarter of a period of the main excitation frequency when using a full waveform and a skilled operator. Finally, experiments are performed to assess differences in first arrivals between high and low frequency measurements. Readings are made on 11 mortar and 12 concrete specimen of different heights and widths. Experimentally significant time differences are observed between high and low frequency readings. It is found that differences in first arrivals will increase with specimen length but differences in velocity will decrease with length. Specimens 4 wavelengths in height are deemed sufficient to diminish surface effects to a minimum provided the specimens are healthy (e.g. no internal flaws). Any increase past 4 wavelengths is found to have negligible effects on measured velocity in healthy specimens.

The aim of this master's thesis is to develop a method that fully automates a trimming step in the production of a fiber-optical power spectrometer, based on a unique Acusto-Optical Scanning Filter. The filter is created by letting an ultrasonic mechanical pulse pass through a chirped Fiber Bragg Grating. The pulse introduces a disturbance in the grating, creating a thin optical transmission window in the otherwise reflective bandwidth. The high demands on the window requires a precise, unit dependent pulse form with unknown properties. Thus each unit needs to be trimmed to reach required performance. The manual trimming is largely a trial and error process, that contains two performance tests. We redefine one, eliminating the need to reroute the optical path and reducing the number of fiber weldings. The tests are then quantified, allowing a figure of merit to be based on weighted performance values. A brute force method, testing a large set of pulses, is implemented. The set is defined by the parameter space spanned by previously produced units. Due to the large space, the method is too time consuming. Instead it is used to measure the performance spaces of three units. An attempt to largely reduce the parameter space using PCA failed. An alternating variables method that finds local performance optima in the parameter space is developed. By using a set of several starting points, the method tends to find several qualified pulses. The method is implemented and successfully verified by trimming new units. Finally we propose where to focus improvements of the method in a production ramp up.

This thesis is primarily about the mapping and analyze of the phenomenon of an impinging jet by experimental measurements and numerical simulations by CFD. The mapping shows the characteristics of velocity in and around the impinging jet with different conditions. Additional studies were made by analyzing the pressure along the vertical jet axis, but also weight measurements were part of the investigation. The measurements covered the range from 10 m/s, 20 m/s and 30 m/s, which corresponds to a Reynolds number of 17 000, 34 000 and 50 000. The impinging jet is therefore considered to be highly turbulent. The main difference from previous studies is the use of the ultrasonic anemometer to measure the velocities. These create the ability of measuring the velocities on three coordinates. The jet’s contour was crucial to determine the penetration of ambient air flowing into the jet with an angle of around 88° and the entrainment of the ambient air multiple the jet volume flow. In comparison with CFD, the number of cells in the mesh design and the type of model plays a substantial role. The model k-ε Realized came closest to the experimentally measurements, while the SST k-ω and RNG k-ε EWF had far more entrainment of the ambient air into the impinging jet. / Detta examensarbete handlar om att kartlägga och analysera fenomenet av en ”impinging jet” genom experimentella mätningar samt numeriska simuleringar som CFD. Undersökningen visar karakteristiken av hastigheten i och kring strålen med olika förutsättningar. Kompletterande undersökningar gjordes för trycket i luftstrålens centrum längs den vertikala axeln, men även viktmätningar var del av undersökningen. Mätningarna omfattade hastigheter från 10 m/s, 20 m/s och 30 m/s som motsvarar ett Reynoldstal med 17 000, 34 000 och 50 000. Luftstrålen betraktas därför som turbulent. Det som skiljer sig från tidigare experiment är att hastigheten mättes med en ultrasonic anemometer som egentligen används inom metrologin för att mäta vindhastigheter. Därmed skapades en tredimensionell bild av hastigheten i och kring luftstrålen. Mätområdet sträckte sig från strålens utgångspunkt ner till strax ovanför plattan. Luftstrålens fastställda kontur var avgörande för att bestämma den inträngande omgivningsluften som strömmar in i strålen med en genomsnittlig vinkel av 88°. Denna inströmmande omgivningsluft flerfaldigade strålens volym. I jämförelse med CFD simuleringen visades att antal celler i meshen är avgörande för att skapa liknande och reala förutsättningar. Vid undersökningen av den inträngande omgivningsluften visades även att själva modellen spelar en avgörande roll. Det var modellen k-ε Realized som kom närmast mätningarna. Däremot uppvisade SST k-ω och RNG k-ε EWF modellerna mycket mer inträngande omgivningsluft i jämförelse med mätningarnas resultat.

I detta examensarbete har ett system för navigering och styrning av ett autonomt fordon implementerats. Syftet med detta arbete är att vidareutveckla fordonet som ska användas vid utvärdering av banplaneringsalgoritmer och studier av andra autonomifunktioner. Med hjälp av olika sensormodeller och sensorkonfigurationer går det även att utvärdera olika strategier för navigering. Arbetet har utförts utgående från en given plattform där fordonet endast använder sig av enkla ultraljudssensorer samt pulsgivare på hjulen för att mäta förflyttningar. Fordonet kan även autonomt navigera samt följa en enklare given bana i en känd omgivning. Systemet använder ett partikelfilter för att skatta fordonets tillstånd med hjälp av modeller för fordon och sensorer. Arbetet är en fortsättning på projektet Collision Avoidance för autonomt fordon som genomfördes vid Linköpings universitet våren 2005. / In this thesis a system for navigation and control of an autonomous ground vehicle has been implemented. The purpose of this thesis is to further develop the vehicle that is to be used in studies and evaluations of path planning algorithms as well as studies of other autonomy functions. With different sensor configurations and sensor models it is also possible to evaluate different strategies for navigation. The work has been performed using a given platform which measures the vehicle’s movement using only simple ultrasonic sensors and pulse encoders. The vehicle is able to navigate autonomously and follow a simple path in a known environment. The state estimation is performed using a particle filter. The work is a continuation of a previous project, Collision Avoidance för autonomt fordon, at Linköpings University in the spring of 2005.

Nondestructive evaluation of civil structures is of increasing interest to utility owners. Several methods exist to evaluate different properties of concrete, pavement, cemented sands and others. UPVM is the most commonly used ultrasonic technique in civil structures due to its simplicity and ease of use. UPVM is fast and requires minimal skill from operators. It has been used for flaw detection, study of material contents, deduction of general deterioration, determination of elastic properties , measurement of strength, and others. In such applications, accurate measurements of velocity are essential for proper parameter evaluation and thus to increase the validity of conclusions obtained from measurements. Previous research in ultrasonic pulse velocity have found that UPVM are susceptible to specimen size, attenuation and frequency but no clear conclusions have yet to be made on the fundamental reason for the differences. This work seeks to identify the main factors responsible for velocity differences due to specimen size and measuring frequency in civil engineering materials. The effects are investigated by first performing numerical simulations of concrete specimens of varying sizes, and properties, excited by both a low (55 kHz) and high (850 kHz) frequency input source. Simulations are used to model wave propagation in cylindrical concrete specimen. Transducer sound fields are also numerically studied using known analytical solutions. An experimental program is conducted to study variations in UPVM in 12 mortar and 11 concrete cylindrical specimens of varying widths and heights caused by different measuring frequencies. Simulations are completed for 12 specimen of different dimensions having heights of 5,10,20 and 30 cm as well as diameters of 10, 20 and 30 cm. Both a low (f = 55 kHz) and high (f = 850 MHz) frequency input source are used on each specimen. Numerical simulations using low frequencies are made for both a damped and undamped series of specimen. Results from low frequency simulations of damped models indicate that wave attenuation can lead to significant errors in first arrivals when complex wave interference is present. Conditions for wave interference at the receiver location are studied and minimum size conditions for both height and width are derived. These conditions guarantee proper pulse separation for UPVM and are dependent on source size, and source pulse width. It is argued that with proper use these conditions will lead to accuracy of measurement better than one quarter of a period of the main excitation frequency when using a full waveform and a skilled operator. Finally, experiments are performed to assess differences in first arrivals between high and low frequency measurements. Readings are made on 11 mortar and 12 concrete specimen of different heights and widths. Experimentally significant time differences are observed between high and low frequency readings. It is found that differences in first arrivals will increase with specimen length but differences in velocity will decrease with length. Specimens 4 wavelengths in height are deemed sufficient to diminish surface effects to a minimum provided the specimens are healthy (e.g. no internal flaws). Any increase past 4 wavelengths is found to have negligible effects on measured velocity in healthy specimens.

Nondestructive testing (NDT) uses different wave propagation modes to evaluate the internal structure of materials, revealing internal damage such as corrosion and fracturing that cannot be detected by traditional methods. Civil infrastructures are considered high priority assets in Ontario and Canada because of their value, high consequence of failure, and the continual influence of aging effects. Unexpected failure of infrastructure not only costs more than planned replacements but also results in increased safety risks. The in-situ condition assessment of civil infrastructure is critical for the successful implementation of maintenance and safety programs. Therefore, reliable nondestructive methods of inspection are required for the implementation of economical and efficient maintenance and asset management programs. Continuing technological developments in data collection, acquisition equipment, and data processing techniques have provided useful applications of nondestructive methods in many engineering fields. Among the many applications, this research study examines three applications of nondestructive testing in civil engineering: (1) condition assessment of construction joints in asphalt pavements, (2) average thickness evaluation of steel pipes, and (3) void and debonding detection in grouted steel tanks. The study on asphalt focuses on the improvement of the coupling system between the transducers and the asphalt surface, and the development of a new data processing technique to reduce user input and increase the reliability of the condition assessment of longitudinal joints. The current wavelet transmission coefficient (WTC) method requires user input, making the automatic data processing difficult. In the WTC method, the coupling between the transducers and the asphalt surface requires the use of epoxy and aluminum plates. This procedure is not practical for testing in-service roads. A new coupling mechanism using polyurethane foam to provide a spring action on the transducers and calibrated weights to generate a compression force was developed and showed good results, reducing the testing time by up to 50%. A new and robust data analysis methodology, called instantaneous transmission coefficient (ITC), is proposed based on measured instantaneous frequencies and damping ratios. The main advantage of the ITC procedure is that it can be performed automatically, reducing user input. A laboratory scale asphalt slab is used to evaluate the new methodology. Results show good agreement between the WTC and ITC measurements for both jointed and joint-free areas. The second study investigates the feasibility of the multichannel analysis of surface waves (MASW) technique for the evaluation of the average wall thickness of steel pipes. Electromagnetic NDT methods, such as the eddy current and the remote field testing, are common tools for thickness measurement of conductive materials. However, these methods give only localized results where measurements are made, making the process time consuming and inaccurate for assessing the full cross-sectional area of the pipe. Lamb waves have been used previously in the evaluation of steel pipes; however, the existing techniques require prior calibration to a theoretical wave mode, and their accuracy decreases with the length of the pipe evaluated due to wave attenuation effects. Preliminary results show the capability of the MASW test for providing reliable thickness information. The measured dispersion curves include information of fundamental modes and the higher modes, providing an improved characterization of the medium. Thicknesses between 3.2 mm and 12.7 mm are tested with an error of less than 2%. The third study explores the detection of voids in a steel tank filled with lightweight grout. A joint analysis of surface waves and Lamb waves is used for void detection and the identification of debonding conditions in a laboratory scale model of a steel tank filled with grout. Different configurations of the MASW method are conducted using an instrumented hammer (large wavelengths, 10 cm < λ < 25 cm) and a 50 kHz piezoelectric transmitter (small wavelengths, 5 cm < λ < 9 cm) as sources. The attenuation coefficient computed from the Fourier spectra of the measured signals indicates that the presence of a void has an effect on the propagation of the wave. The comparison between experimental and theoretical dispersion curves show that mainly Lamb waves are generated during the testing of the steel tank; thus, detecting the debonding conditions between the steel plate and the grout. Lamb modes are used successfully for detecting the presence of a void beneath the steel wall. The laboratory measurements are effective in the detection of the void, showing amplitudes up to 50% higher, likely because the deformation of the wall is attenuated by the grout.

Visual interpretation of noisy images is not an easy problem. This is certainly apparent with ultrasound images. Due to the noise inherent in the images, it is often the case that discrepancies as to location of object boundaries and detection of different tissues arise even among highly trained physicians. The relatively low cost and short image acquisition time, however, make ultrasound an attractive imaging modality. Currently, diagnostic evaluation of ultrasound images is performed on two-dimensional (2D) cross-sections of the object of interest. No depth information is available and there is no way of viewing the outer surface of the object. The only way for a physician to visualise the entire object is by mentally reconstructing the object based on a series of a 2D images as well as prior expectations of the morphology of the object. In the case of abnormal or diseased growth, the physician's expectations often do not correspond to the actual morphology of the object. However, the use of three-dimensional (3D) data acquisition and visualisation may be used to overcome these problems. The present work addresses a number of difficulties in processing 3D ultrasound data. This includes special treatment of the volumetric ultrasound data obtained from a 3D probe, determination of 3D features of the different tissue types present in the ultrasound data and identification and localisation of objects (segmentation) in the volumetric ultrasound data. Experimental results obtained from synthesised and real ultrasound data demonstrate that the present work contributes significantly to the use of ultrasound imaging as a diagnostic tool. As well, the present work can be applied to different imaging modalities or different applications areas and is thus beneficial to the area of biomedical image processing, in general.

<p>Acoustic radiation force impulses (ARFI) have been used to generated transverse-traveling mechanical waves in various biological tissues. The velocity of these waves is related to a medium's stiffness and thus can offer useful diagnostic information. Consequently, shear wave velocimetry has the potential to investigate cardiac disease states that manifest themselves as changes in tissue stiffness (e.g., ischemia).</p><p> The work contained herein focuses on employing ARFI-based shear wave velocimetry techniques, similar to those previously utilized on other organs (e.g., breast, liver), for the investigation of cardiac tissue. To this end, ARFI excitations were used to generate slow-moving (under 3 m/s) mechanical waves in exposed myocardium (with access granted through a thoracotomy); these waves were then tracked with ultrasonic methods. Imaging techniques to increase frame-rate, decrease transducer/tissue heating, and reduce the effects of physiological motion were developed. These techniques, along with two shear wave velocimetry methods (i.e., the Lateral Time-to-Peak and Radon sum transformation algorithms), were utilized to successfully track shear wave propagation through the mid-myocardial layer <italic>in vitro</italic> and <italic>in vivo</italic>. <italic>In vitro</italic> experiments focused on the investigation of a shear wave anisotropy through the myocardium. This experimentation suggests a moderate shear wave velocity anisotropy through regions of the mid-myocardial layer. <italic>In vivo</italic> experiments focused on shear wave anisotropy (which tend to corroborate the aforementioned <italic>in vitro</italic> results), temporal/spatial stability of shear wave velocity estimates, and estimation of wave velocity through the cardiac cycle. Shear wave velocity was found to cyclically vary through the cardiac cycle, with the largest estimates occurring during systole and the smallest occurring during diastole. This result suggests a cyclic stiffness variation of the myocardium through the cardiac cycle. A novel, on-axis technique, the displacement ratio rate (DRR) method, was developed and compared to conventional shear wave velocitmetry and ARFI imaging results; all three techniques suggest a similar cyclic stiffness variation.</p><p> Shear wave velocimetry shows promise in future investigations of myocardial elasticity. The DRR method may offer a means for transthoracic characterization of myocardial stiffness. Additionally, the future use of transesophageal and catheter-based transducers presents a way of generating and tracking shear waves in a clinical setting (i.e., when epicardial imaging is not feasible). Lastly, it is hoped that continued investigations into the physical basis of these ARFI-generated mechanical waves may further clarify the relationship between their velocity in myocardium and material stiffness.</p> / Dissertation

<p>Mice produce many ultrasonic vocalizations (USVs) in the 30 - 100 kHz range including pup isolation calls and adult male songs. These USVs are often used as behavioral readouts of internal states, to measure effects of social and pharmacological manipulations, and for behavioral phenotyping of mouse models for neuropsychiatric and neurodegenerative disorders; however, little is known about the biophysical and neurophysiological mechanisms of USV production in rodents. This lack of knowledge restricts the interpretation of data from vocalization-related experiments on mouse models of communication disorders and vocal medical conditions. Meanwhile, there has been increased interest in the social communication aspect of neural disorders such as autism, in addition to the common disorders involving motor control of the larynx: stroke, Parkinson's disease, laryngeal tremor, and spasmodic dysphonia. Therefore, it is timely and critical to begin assessing the neural substrate of vocal production in order to better understand the neuro-laryngeal deficits underlying communication problems.</p><p>Additionally, mouse models may generate new insight into the molecular basis of vocal learning. Traditionally, songbirds have been used as a model for speech learning in humans; however, the model is strongly limited by a lack of techniques for manipulating avian genetics. Accordingly, there has long been strong interest in finding a mammalian model for vocal learning studies. The characteristic features of accepted vocal learning species include programming of phonation by forebrain motor areas, a direct cortical projection to brainstem vocal motoneurons, and dependence on auditory feedback to develop and maintain vocalizations. Unfortunately, these features have not been observed in non-human primates or in birds that do not learn songs. Thus, in addition to elucidating vocal brain pathways it is also critical to determine the extent of any vocal learning capabilities present in the mouse USV system.</p><p>It is generally assumed that mice lack a forebrain system for vocal modification and that their USVs are innate; however, these basic assumptions have not been experimentally tested. I investigated the mouse song system to determine if male mouse song behavior and the supporting brain circuits resemble those of known vocal learning species. By visualizing activity-dependent immediate early gene expression as a marker of global activity patterns, I discovered that the song system includes motor cortex and striatal regions active during singing. Retrograde and anterograde tracing with pseudorabies virus and biodextran amines, respectively, revealed that the motor cortical region projects directly to the brainstem phonatory motor nucleus ambiguus. Chemical lesions in this region showed that it is not critical for producing innate templates of song syllables, but is required for producing more stereotyped acoustic features of syllables. To test for the basic components of adaptive learning I recorded the songs of mechanically and genetically deaf mice and found that male mice depend on auditory feedback to develop and maintain normal ultrasonic songs. Moreover, male mice that display natural strain specific song features may use auditory experience to copy the pitch of another strain when housed together and stimulated to compete sexually. I conclude that male mice have neuroanatomical and behavioral features thought to be unique to humans and song learning birds, suggesting that mice are capable of adaptive modification of the spectral features of their songs.</p> / Dissertation