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Reconfigurable computing has the potential for providing significant performance increases to a number of computing applications. However, realizing these benefits requires digital design experience and knowledge of hardware description languages (HDLs). While a number of tools have focused on translation of high-level languages (HLLs) to HDLs, the tools do not always create optimized digital designs that are competitive with hand-coded solutions. This work describes an automatic optimization in the C-to-HDL transformation that reorganizes operations between pipeline stages in order to reduce critical path lengths. The effects of this optimization are examined on the MD5, SHA-1, and Smith-Waterman algorithms. Results show that the optimization results in performance gains of 13%-37% and that the automatically-generated implementations perform comparably to hand-coded implementations.

<p> This research investigates human perception of brief auditory events presented sequentially. Following an analysis of current, relevant theories, two experiments arc described. The results of the first experiment show that two trains consisting of n and n+l pulses become more difficult to discriminate from each other as (i) the time between the pulses decreases (ii) the number of pulses in the trains increase and (iii) the size of the set of stimulus trains increases. The results of Experiment 2 indicate that discrimination between a pair of "empty" intervals differing only by a constant duration depends on the time between the pulses marking the beginning and end of the intervals and not on the duration of the markers. Discrimination decreases as the durations of the pair of intervals increases. This research investigates human perception of brief auditory events presented sequentially. Following an analysis of current, relevant theories, two experiments arc described. The results of the first experiment show that two trains consisting of n and n+l pulses become more difficult to discriminate from each other as (i) the time between the pulses decreases (ii) the number of pulses in the trains increase and (iii) the size of the set of stimulus trains increases. </p> / Thesis / Doctor of Philosophy (PhD)

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Scientists and land managers often focus on the Southeastern Plains and Coastal Plain of the southeastern United States when considering the ecology, restoration, and management of longleaf pine (Pinus palustris P. Mill.) communities and ecosystems. However, the range of this foundation tree species and its associated communities and ecosystems also extend into the Piedmont and Montane Uplands: the Piedmont of Alabama, Georgia, North and South Carolina and Virginia; the Ridge and Valley of Alabama and Georgia; and the Southwestern Appalachians of Alabama. The composition, structure, and dynamics of Piedmont and Montane Uplands longleaf pine communities have been understudied compared to their Southeastern Plains and Coastal Plain counterparts, and knowledge is based on historical accounts and a handful of studies at site-specific scales. The biogeography and ecology of Piedmont and Montane Uplands longleaf pine communities differ significantly from those in the Southeastern Plains and Coastal Plain. My research combines geospatial and ecological approaches to provide insights on current composition, structure, and dynamics of longleaf pine communities in the Southeastern Plains, Piedmont, and Ridge and Valley at multiple scales and highlights differences and similarities with communities in the Coastal Plain. The Piedmont and Montane Uplands longleaf pine communities showed high variation in canopy tree diversity compared to those in the Coastal Plain. Longleaf pine was sometimes the only canopy tree, while in other communities longleaf pine was one constituent in a mixed oak-pine canopy. My study showed that longleaf pine communities were not just restricted to south-facing slopes as previously thought, but were found on northwestern-facing slopes as well. Analysis of tree rings across my study sites showed that as longleaf pine approaches its northern range margin in the Piedmont and Montane Uplands, its radial growth is restricted by minimum temperature especially at longleaf pine's elevational, latitudinal, and longitudinal extremes; at all sties radial growth was influenced by drought and precipitation. At the local scale, I found that an Alabama Piedmont longleaf pine community showed a diameter-class distribution typical of an old-growth site but contrary to current knowledge, diameter was not a good indicator of age. / Ph. D.

Time perception is a universal experience that can be studied from a philosophical, physical, and neuroscientific point of view. Many models and theories of timing, such as the pacemaker-switch-accumulator model and striatal beat frequency model are used to understand such an abstract, yet ubiquitous concept. This paper will discuss brain regions that are crucial to time perception, notably the cerebellum, basal ganglia, prefrontal cortex, supplementary motor cortex, and hippocampus. In addition, this paper investigates several research studies involving distortions in time perception. In these instances of substance use, aging, and cognitive disorders, the neural correlates of time perception are elucidated. In providing a better understanding of these cognitive states and disorders, we can utilize altered time perception as a potential clinical marker or diagnostic tool.

Temporal context memory is a type of episodic memory that refers to memory for the timing of events. Temporal context includes environmental cues that provide information about the time point at which an event happened. The purpose of the present studies is to investigate the brain mechanisms underlying temporal context processing by using both fMRI and ERP techniques. The fMRI study investigated whether hippocampal representations in CA1 and DG/CA3 subfields were sensitive to the flow of physical time, and if so, whether the number of events that occur during a time period influences the temporal representation of a target event. Results showed that both CA1 and DG/CA3 were sensitive to the flow of physical time, which was indicated by higher representational similarity between two pictures that occurred closer in time than those that occurred more distant in time. However, the variety of preceding events did not influence temporal representation, which was demonstrated by the lack of a significant representational similarity difference between two pictures that were interleaved with variable events as opposed to similar events. The ERP study compared the ERP correlates of temporal to spatial context. Results showed that temporal and spatial contexts had overlapping ERP effects except that the ERP effects of temporal context were more frontally distributed than spatial context. Both the fMRI and ERP studies indicate that temporal context is associated with similar neural correlates to other types of context in episodic memory. / Ph. D. / Episodic memory is memory for where and when an event happened. The ability to memorize the timing of events relies on one type of episodic memory: temporal context memory. Temporal context includes environmental cues that provide information about the time point at which an event happened. The purpose of the present studies was to investigate the brain mechanisms underlying temporal context processing by using both functional magnetic resonance imaging (fMRI) and event and event-related potential (ERP) techniques. The fMRI study focused on hippocampus, one of the key brain regions process non-temporal contexts (i.e. spatial context, which refers to where an event happened), and investigated which subfields (CA1 and DG/CA3) in the hippocampus were sensitive to the flow of physical time. And the second purpose of the fMRI study was to examine whether the variety of events that occur during a time period influences the temporal representation. Results showed that both CA1 and DG/CA3 were sensitive to the flow of physical time. However, the variety of events did not influence temporal representation. Since CA1 and DG/CA3 are also critical for non-temporal context processing, these results indicate that temporal context has same neural mechanisms as non-temporal contexts. The ERP study investigated the brain activity as a whole and directly compared the ERP correlates of temporal to non-temporal context. Results showed that temporal and nontemporal contexts had overlapping ERP correlates except that the ERP effects of temporal context were more frontally brain region distributed than spatial context. Therefore, both the fMRI and ERP studies indicate that temporal context is associated with similar neural correlates to other types of context in episodic memory.