UMD Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/3
New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a given thesis/dissertation in DRUM.
More information is available at Theses and Dissertations at University of Maryland Libraries.
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Item Sound and Documentary in Cardiff and Miller's 'Pandemonium'(2015) Wichmann, Cecilia T.; Shannon, Joshua; Art History and Archaeology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)From 2005 to 2007, Canadian artists Janet Cardiff and George Bures Miller automated a live performance of simple robots striking furniture detritus and pipes in the cells of Eastern State Penitentiary, a Philadelphia prison that once specialized in isolation and silence. Oscillating between referential and abstract sounds, 'Pandemonium' suspended percipients between narrative and noise. So far scholars have investigated only the work's narrative aspects. This projects examines Cardiff and Miller's specific use of percussive sounds to position 'Pandemonium' in dialogue with noise music, sound art, and documentary-related practices in contemporary art. 'Pandemonium''s representational sounds coalesced into a curious kind of concrete documentary that triggered a sense of radical proximity between the percipient's body and the resonant environment of Eastern State Penitentiary. In doing so, it explored the potential for sensory relations and collectivity in a complex, contemporary world.Item Authentication of Fingerprint Scanners(2012) Ivanov, Vladimir Iankov; Baras, John S; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)To counter certain security threats in biometric authentication systems, particularly in portable devices (e.g., phones and laptops), we have developed a technology for automated authentication of fingerprint scanners of exactly the same type, manufacturer, and model. The technology uses unique, persistent, and unalterable characteristics of the fingerprint scanners to detect attacks on the scanners, such as detecting an image containing the fingerprint pattern of the legitimate user and acquired with the authentic fingerprint scanner replaced by another image that still contains the fingerprint pattern of the legitimate user but has been acquired with another, unauthentic fingerprint scanner. The technology uses the conventional authentication steps of enrolment and verification, each of which can be implemented in a portable device, a desktop, or a remote server. The technology is extremely accurate, computationally efficient, robust in a wide range of conditions, does not require any hardware modifications, and can be added (as a software add-on) to systems already manufactured and placed into service. We have also implemented the technology in a demonstration prototype for both area and swipe scanners.Item Information Power Efficiency Tradeoffs in Mixed Signal CMOS Circuits(2010) Mcfarlane, Nicole; Abshire, Pamela; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Increasingly sensors for biological applications are implemented using mixed signal CMOS technologies. As feature sizes in modern technologies decrease with each generation, the power supply voltage also decreases, but the intrinsic noise level increases or remains the same. The performance of any sensor is quantified by the weakest detectable signal, and noise limits the ability of a sensor to detect the signal. In order to explore the trade-offs among incoming signal, the intrinsic physical noise of the circuit, and the available power resources, we apply basic concepts from information theory to CMOS circuits. In this work the circuits are modeled as communication channels with additive colored Gaussian noise and the signal transfer characteristics and noise properties are used to determine the classical Shannon capacity of the system. The waterfilling algorithm is applied to these circuits to obtain the information rate and the bit energy is subsequently calculated. In this dissertation we restricted our attention to operational transconductance amplifiers, a basic building block for many circuits and sensors and oftentimes a major source of noise in a sensor system. It is shown that for typical amplifiers the maximum information rate occurs at bandwidths above the dominant pole of the amplifier where the intrinsic physical circuit noise is diminished, but at the same time the output signal is attenuated. Thus these techniques suggest a methodology for the optimal use of the amplifier, but in many cases it is not practical to use an amplifier in this manner, that is at frequencies above its 3dB cutoff. Further, a direct consequence of applying the classic waterfilling algorithm leads to the idea of using modulation techniques to optimize system performance by shifting signals internally to higher frequencies, providing a practical means to achieve the information rates predicted by waterfilling and at the same time maintaining the real world application of these amplifiers. In addition, the information rates and bit energy for basic CMOS amplifier configurations are studied and compared across configurations and processes. Further the additional design constraints formed by adding the information rate and the bit energy to traditional design characteristics is explored.Item Correlation of Signals, Noise, and Harmonics in Parallel Analog-to-Digital Converter Arrays(2009) Lauritzen, Keir Christian; Peckerar, Martin; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Combining M analog-to-digital converters (ADC) in parallel increases the maximum signal-to-noise ratio (SNR) by a factor of M, assuming the noise is uncorrelated from one channel to the next. This allows for a significant increase in SNR over a single ADC; however, noise and harmonic correlation degrade this improvement. ADCs have three sources of noise: thermal (and other random physical processes), sampling, and quantization noise. There are two system components creating harmonics: the sampler and the quantizer. In this thesis, I determine, analytically and experimentally, the degree of correlation between signals, noise, and harmonics in a parallel ADC array. To test the analysis experimentally, I developed a 16-channel test-bed using 16-bit, state-of-the-art ADCs and 16 direct-digital synthesizers as low-noise signal sources. The test bed provides excellent signal isolation between channels and minimal digital noise to enable the measurement of very low levels of correlation. I investigated the feasibility of measuring the very high levels of signal correlation in the presence of channel nonlinearities with different measurement signals. For a completely linear channel, the channel matching is limited by noise. With nonlinearities, the ability to measure the signal correlation depends on the measurement signal. I verified that the thermal noise is uncorrelated across 16 channels as expected. I also demonstrated that sampling noise is fully correlated from channel-to-channel when a common clock drives the ADCs. Efforts to reduce the correlation using two previously developed de-correlation techniques-phase randomization and frequency offsets-successfully reduced the correlated noise by a factor of two. I then demonstrated analytically and experimentally that harmonics from quantizers are largely uncorrelated; however, harmonics from the sampler are largely correlated confirming the need for decorrelation techniques. I demonstrated the impact of the previously developed decorrelation techniques to reduce harmonic correlation and developed two new decorrelation techniques: phase cancellation and clock offsets, which offer significant advantages over phase randomization and frequency offsets. Each technique offers different levels of dynamic range improvement and complexity, allowing for a range of techniques to target the optimal level of decorrelation.Item Infant Speech-in-Noise Perception and Later Phonological Awareness: A Longitudinal Study(2008-10-20) Stimley, Sarah Elizabeth; Newman, Rochelle; Hearing and Speech Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)While differences have been found in the ability of infants on a variety of speech perception skills including speech perception in the presence of background noise, the implications of these differences on later language skills are currently unknown. This study examines the relationship between a specific measure of infant speech perception in noise and later phonological awareness outcomes. In order to test this relationship, individuals who participated in Newman's (2005) study on infant speech perception in the presence of background noise were administered a battery of language, phonological awareness, and intelligence tests. Scores from these tests were analyzed to see if performance differences existed between those who had performed well as infants in the original study and those who had not. No significant differences between these two groups were found on the phonological awareness measures. Potential reasons for these findings and suggestions for future research are discussed.