This thesis presents techniques to implement analog-to-digital converters (ADCs) under an ultra-low-supply-voltage of 0.2 V to reduce the power consumption. The thesis proposes a dynamic bulk biasing circuit to adjust the PMOS bulk voltage to balance the NMOS and PMOS drain currents to guarantee functionality in the presence of process, voltage, and temperature variations. The dynamic bulk bias circuit is analyzed rigorously to show its functionality. This thesis also describes a new comparator suitable for a 0.2-V supply using ac-coupling, stacked input pairs, and voltage-boosted load capacitor. A 10-bit 5-kS/s successive-approximation-register (SAR) ADC in a 180-nm CMOS process with a supply voltage of 0.2 V demonstrates these ideas. The ADC exhibits a differential nonlinearity (DNL) and integral nonlinearity (INL) within +0.42/-0.45 and +0.62/-0.67 LSB, respectively. The measured SFDR and SNDR at 5 kS/s with a Nyquist-frequency input are 65.9 dB and 52.1 dB, respectively. The entire ADC and dynamic bulk biasing circuitry consume 22 nW including leakage power to yield a figure-of-meirt (FoM) of 8.8 fJ/conv.-step. Measurements of multiple chips show the proposed dynamic bulk biasing fully recovers the ADC performance when the supply voltage is varied. The nW power consumption makes the design well suited for wireless sensor node and energy harvester applications.

Bakgrund: Värmepåverkan vid magnetkameraundersökningar är ett känt fenomen som påverkar patienterna och temperaturmätningar kan vara missvisande. Antalet undersökningar ökar, fler patienter med och utan implantat kommer för diagnostisering, detta kräver att personalen har bra rutiner och kunskap för att förhindra brännskador. Syftet: Syftet med studien var att beskriva faktorer som påverkar uppvärmning av patienten vid magnetkameraundersökningar. Metod: Studien har genomförts som en allmän litteraturöversikt där elva artiklar inkluderats. Resultat: Tre kategorier har identifierats: tekniska aspekter, riskgrupper och bristande rutiner. Resultatet visar att det totala SAR-värdet inte är tillförlitligt vilket kan öka risken för lokala brännskador, i synnerhet för riskgrupper som har ökad risk för uppvärmning. I händelse av att röntgensjuksköterskan inte väljer rätt anpassat protokoll vid en undersökning finns det risk för ökad uppvärmning samt att positioneringar av patient, spole och kablar är viktigt för att förhindra brännskador. Ett bra teamarbete, kommunikation och kunskap om uppvärmning vid magnetkameraundersökningar leder till ökad patientsäkerhet. Slutsats: Studiens resultat visar att uppvärmningen har en stor betydelse på magnetkameraundersökningar och att adekvat mätutrustning ska användas. Uppvärmningen kan minskas genom olika omvårdnadsåtgärder som kan vara att inte bädda in patienten samt öka styrkan på fläktar i magnetkameran.

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Multiple SAR interferograms with judiciously selected height sensitivities can be iteratively combined to create a high accuracy digital elevation map. An initial height estimate is refined by iteratively using larger baselines to obtain a height estimation accuracy limited by the spatial decorrelation of the antenna baseline. Spatial filtering is used to reduce the propagation of errors for accurate height estimation. Images containing regions isolated by phase discontinuities, as often found in urban environments, can be resolved by this iterative multi-baseline technique. Computationally demanding and potentially unreliable phase unwrapping is not required to determine scene elevation using SAR inMultiple SAR interferograms with judiciously selected height sensitivities can be iteratively combined to create a high accuracy digital elevation map. An initial height estimate is refined by iteratively using larger baselines to obtain a height estimation accuracy limited by the spatial decorrelation of the antenna baseline. Spatial filtering is used to reduce the propagation of errors for accurate height estimation. Images containing regions isolated by phase discontinuities, as often found in urban environments, can be resolved by this iterative multi-baseline technique. Computationally demanding and potentially unreliable phase unwrapping is not required to determine scene elevation using SAR interferometry.

With advancements in space technology, remote sensing applications, and computer vision, significant improvements in the data describing our planet are seen today. Researchers want to gather different kinds of data and perform data fusion techniques between them to increase our understanding of the world. Two such data types are Electro-Optical images and Synthetic Aperture Radar images. For data fusion, the images need to be accurately aligned. Researchers have investigated methods for robustly and accurately registering these images for many years. However, recent advancements in imaging systems have made the problem more complex than ever. Currently, the imaging satellites that capture information around the globe have achieved a resolution of less than a meter per pixel. There is an increase in signal complexity for high-resolution SAR images due to how the imaging system operates. Interference between waves gives rise to speckled noise and geometric distortions, making the images very difficult to interpret. This directly affects the image registration accuracy. In this thesis, the complexity of the problem regarding registration between SAR and EO data was described, and methods for registering the images were investigated. The methods were feature- and area-based. The feature-based method used a KAZE filter and SURF descriptor. The method found many key points but few correct correspondences. The area-based methods used FFT and MI, respectively. FFT was deemed best for higher quality images, whereas MI better dealt with the non-linear intensity difference. More complex techniques, such as dense neural networks, were excluded. No method achieved satisfying results on the entire data set, but the area-based methods accomplished complementary results. A conclusion was drawn that the distortions in the SAR images are too significant to register accurately using only CV algorithms. Since the area-based methods achieved good results on images excluding significant distortions, future work should focus on solving the geometrical errors and increasing the registration accuracy

Titan is an important planetary body for aeolian research because of the vast equatorial sand seas that span 20% of its surface. Previous studies have determined the general margins of sand and sand seas on Titan, and have speculated about the source of Titan's sand. Little research has been done concerning where sand collects in the sand seas. Additionally, the relationships be-tween material distributions as observed by the Cassini Visual and Infrared Mapping Spectrometer (VIMS) and the history of erosion and transportation of sediments across equatorial latitudes is not fully understood. This work focuses on an in depth evaluation of sand distribution and abundance across the sand seas, and presents evidence for an alternative sand source. This work also addresses a potential stratigraphy for the equatorial regions based on the excavation of materials from impact craters. We mapped the extent of relative sand abundances by comparing different Cassini image datasets, largely by mapping where the Imaging Science Subsystems (ISS) regions were darkest, in-dicating the presence of more sand. Our results revealed that greater abundances of sand accumu-late near the eastern margins of sand seas. This is in agreement with previous studies that demon-strated general W to E transport, and fits a general model of sand transport across the sand seas to collect at the downwind margins, perhaps ahead of topographic obstacles that mark the eastern ends of the sand seas. Additionally, we found that the largest continuous expanse of abundant sand de-posits lie across Belet, a large sand sea that occupies a broad equatorial lowland. Another sand sea of interest is Shangri-La, which has a recessed SE margin adjacent to the broad, albedo-bright de-pression Xanadu. We also found abundant sand deposits within Shangri-La across a corridor be-tween highlands and along the SE boundary of the sand sea. Dune crest orientations across eastern Shangri-La indicate WNW to ESE transport in the region. We propose that the low topography of Xanadu, coupled with the strong gradient in albedo between Shangri-La and Xanadu would gener-ate atmospheric disturbances similar to those responsible for transporting sand across positive changes in elevation on Mars, and may be responsible for the distinct boundary. VIMS-blue materials are generally associated with water ice mixed with organic com-pounds. We found that VIMS-blue surfaces across equatorial latitudes tend to be directly adjacent to and upwind of sand seas. This, coupled with geomorphological observations of erosional charac-teristics and examination of material properties, suggests that sand could at least in part be derived from VIMS-blue materials. We propose 3 environments (alluvial fans, dry lakebeds, and ejecta from impact craters) for sand production using this interpretation and making comparisons with SAR, ISS, and VIMS imagery. Modeling suggests that Titan's lithosphere significantly thickened 500 m.y. ago. We inter-pret an elongate exposure of VIMS-blue materials adjacent to Aztlan to be a rift caused by a thick-ening of the lithosphere, similar to many of the other icy bodies of the solar system. Our interpreta-tion is further supported by the distribution of cryovolcanic features alongside the proposed rift. Anomalous VIMS-blue and bright regions within eastern Xanadu are distributed in a pattern that resembles a multi-ringed impact basin. Additionally, when a value threshold was applied to ISS imagery, a bright circular feature was revealed within western Xanadu. These observations suggest two large impacts may have been significantly responsible for creating Xanadu. Comparisons of impact crater models with VIMS imagery of Paxsi, Menrva, Sinlap, Selk, and other craters suggest alternating layers of VIMS-bright and VIMS-blue cover much of the equatorial latitudes of Titan. We completed ground penetrating radar (GPR) and global positioning system (GPS) surveys across margins of the Kelso Dunes to evaluate the effects of fluvial interaction on sand depth. Our terres-trial model was compared to sand seas on Titan that appear to also have interactions with fluvial channels. Distributions of sand suggest that in both the Kelso Dunes and on Titan, fluvial obstruc-tion is temporary and on Titan isolated across small regions. This work leads to a better understanding of sand production, accumulation and transport on Titan and in sand seas in general, and reveals a basic stratigraphy of the equatorial regions of Titan. This region is of particular interest because it is the landing site of the Dragonfly mission, now in design.

With the increasing longevity that accompanies advances in medical technology comes a host of other age-related disabilities. Among these are neuro-degenerative diseases such as Alzheimer's disease, Parkinson's disease, and stroke, which significantly reduce the motor and cognitive ability of affected individuals. As these diseases become more prevalent, there is a need for further research and innovation in the field of motor rehabilitation therapy to accommodate these individuals in a cost-effective manner. In recent years, the implementation of social agents has been proposed to alleviate the burden on in-home human caregivers. Socially assistive robotics (SAR) is a new subfield of research derived from human-robot interaction that aims to provide hands-off interventions for patients with an emphasis on social rather than physical interaction. As these SAR systems are very new within the medical field, there is no standardized approach to developing such systems for different populations and therapeutic outcomes. The primary aim of this project is to provide a standardized method for developing such systems by introducing a modular human-robot interaction software framework upon which future implementations can be built. The framework is modular in nature, allowing for a variety of hardware and software additions and modifications, and is designed to provide a task-oriented training structure with augmented feedback given to the user in a closed-loop format. The framework utilizes the ROS (Robot Operating System) middleware suite which supports multiple hardware interfaces and runs primarily on Linux operating systems. These design requirements are validated through testing and analysis of two unique implementations of the framework: a keyboard input reaction task and a reaching-to-grasp task. These implementations serve as example use cases for the framework and provide a template for future designs. This framework will provide a means to streamline the development of future SAR systems for research and rehabilitation therapy.

It is often that images generated from Synthetic Aperture Radar (SAR) are noisy, distorted, or incomplete pictures of a target or target region. As the goal for most SAR research pertains to automatic target recognition (ATR), extensive filtering and image processing is required in order to extract the features necessary to carry out ATR. This thesis investigates the use of Artificial Neural Networks (ANNs) in order to improve upon the feature extraction process by laying the foundation for ANN SAR ATR algorithms and programs. The first technique investigated is that of an ANN edge detector designed to be invariant to multiplicative speckle noise. The algorithm designed uses the Back Propagation (BP) algorithm to teach a multi-layer perceptron network to detect edges. In order to do so, several parameters within a Sliding Window (SW), are calculated as the inputs to the ANN. The ANN then outputs an edge map that includes the outer edge features of the target as well as some internal edge features. The next technique that is examined is a pattern recognition and target reconstruction algorithm based off of the associative memory ANN known as the Hopfield Network (HN). For this version of the HN, the network is trained with a collection of varying geometric shapes. The output of the network is a nearest-fit representation of the incomplete image data input. Because of the versatility of this program, it is also able to reconstruct incomplete 3D models determined from SAR data. The final technique investigated is an automatic rotation procedure to detect the change in perspective relative to the platform. This type of detection can prove useful if used for target tracking or 3D modeling where the direction vector or relative angle of the target is a desired piece of information.

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