Autonomous vehicles are increasingly being used in mission-critical applications, and robust methods are needed for controlling these inherently unreliable and complex systems. This thesis advocates the use of model-based programming, which allows mission designers to program autonomous missions at the level of a coach or wing commander. To support such a system, this thesis presents the Spock generative planner. To generate plans, Spock must be able to piece together vehicle commands and team tactics that have a complex behavior represented by concurrent processes. This is in contrast to traditional planners, whose operators represent simple atomic or durative actions. Spock represents operators using the RMPL language, which describes behaviors using parallel and sequential compositions of state and activity episodes. RMPL is useful for controlling mobile autonomous missions because it allows mission designers to quickly encode expressive activity models using object-oriented design methods and an intuitive set of activity combinators. Spock also is significant in that it uniformly represents operators and plan-space processes in terms of Temporal Plan Networks, which support temporal flexibility for robust plan execution. Finally, Spock is implemented as a forward progression optimal planner that walks monotonically forward through plan processes, closing any open conditions and resolving any conflicts. This thesis describes the Spock algorithm in detail, along with example problems and test results.

Model checking is an automated technique for deciding whether a computer program satisfies a temporal property. Abstraction is the key to scaling model checking to industrial-sized problems, which approximates a large (or infinite) program by a smaller abstract model and lifts the model checking result over the abstract model back to the original program. In this thesis, we study abstraction in model checking based on \emph{exact-approximation}, which allows for verification and refutation of temporal properties within the same abstraction framework. Our work in this thesis is driven by problems from both practical and theoretical aspects of exact-approximation. We first address challenges of effectively applying symmetry reduction to \emph{virtually} symmetric programs. Symmetry reduction can be seen as a \emph{strong} exact-approximation technique, where a property holds on the original program if and only if it holds on the abstract model. In this thesis, we develop an efficient procedure for identifying virtual symmetry in programs. We also explore techniques for combining virtual symmetry with symbolic model checking. Our second study investigates model checking of \emph{recursive} programs. Previously, we have developed a software model checker for non-recursive programs based on exact-approximating predicate abstraction. In this thesis, we extend it to reachability and non-termination analysis of recursive programs. We propose a new program semantics that effectively removes call stacks while preserving reachability and non-termination. By doing this, we reduce recursive analysis to non-recursive one, which allows us to reuse existing abstract analysis in our software model checker to handle recursive programs. A variety of \emph{partial} transition systems have been proposed for construction of abstract models in exact-approximation. Our third study conducts a systematic analysis of them from both semantic and logical points of view. We analyze the connection between semantic and logical consistency of partial transition systems, compare the expressive power of different families of these formalisms, and discuss the precision of model checking over them. Abstraction based on exact-approximation uses a uniform framework to prove correctness and detect errors of computer programs. Our results in this thesis provide better understanding of this approach and extend its applicability in practice.

Temporal lobe epilepsy (TLE) is a common form of intractable epilepsy that can be treated with surgical resection of the epileptogenic medial temporal lobe tissue, specifically the hippocampus. This resection can lead to a variable degree of memory deficit and considerable research has been directed at identifying predictors of these deficits. This thesis explores the relationship between structural predictors and functional predictors in TLE. I looked at fMRI activation asymmetry produced by a scene encoding task as well as volume asymmetry ratios within the hippocampus and the relationship of these predictors to memory performance in patients with TLE. Mediation analysis was performed according to Baron and Kenny (1986) and showed that fMRI activation asymmetry mediated the relationship between volume asymmetry and memory asymmetry in patients with TLE. This suggests that activation asymmetry may be a preferred variable for assessing functional adequacy in the medial temporal region.

Temporal lobe epilepsy (TLE) is a common form of intractable epilepsy that can be treated with surgical resection of the epileptogenic medial temporal lobe tissue, specifically the hippocampus. This resection can lead to a variable degree of memory deficit and considerable research has been directed at identifying predictors of these deficits. This thesis explores the relationship between structural predictors and functional predictors in TLE. I looked at fMRI activation asymmetry produced by a scene encoding task as well as volume asymmetry ratios within the hippocampus and the relationship of these predictors to memory performance in patients with TLE. Mediation analysis was performed according to Baron and Kenny (1986) and showed that fMRI activation asymmetry mediated the relationship between volume asymmetry and memory asymmetry in patients with TLE. This suggests that activation asymmetry may be a preferred variable for assessing functional adequacy in the medial temporal region.

Model checking is an automated technique for deciding whether a computer program satisfies a temporal property. Abstraction is the key to scaling model checking to industrial-sized problems, which approximates a large (or infinite) program by a smaller abstract model and lifts the model checking result over the abstract model back to the original program. In this thesis, we study abstraction in model checking based on \emph{exact-approximation}, which allows for verification and refutation of temporal properties within the same abstraction framework. Our work in this thesis is driven by problems from both practical and theoretical aspects of exact-approximation. We first address challenges of effectively applying symmetry reduction to \emph{virtually} symmetric programs. Symmetry reduction can be seen as a \emph{strong} exact-approximation technique, where a property holds on the original program if and only if it holds on the abstract model. In this thesis, we develop an efficient procedure for identifying virtual symmetry in programs. We also explore techniques for combining virtual symmetry with symbolic model checking. Our second study investigates model checking of \emph{recursive} programs. Previously, we have developed a software model checker for non-recursive programs based on exact-approximating predicate abstraction. In this thesis, we extend it to reachability and non-termination analysis of recursive programs. We propose a new program semantics that effectively removes call stacks while preserving reachability and non-termination. By doing this, we reduce recursive analysis to non-recursive one, which allows us to reuse existing abstract analysis in our software model checker to handle recursive programs. A variety of \emph{partial} transition systems have been proposed for construction of abstract models in exact-approximation. Our third study conducts a systematic analysis of them from both semantic and logical points of view. We analyze the connection between semantic and logical consistency of partial transition systems, compare the expressive power of different families of these formalisms, and discuss the precision of model checking over them. Abstraction based on exact-approximation uses a uniform framework to prove correctness and detect errors of computer programs. Our results in this thesis provide better understanding of this approach and extend its applicability in practice.

Bacterial communities are fundamental components of many processes occurring in aquatic ecosystems, since through microbial activities substantial amount of matter and energy is transferred from a pool of DOC to higher trophic levels. Previous studies highlighted the beneficial effects of diversity on ecosystem functioning, however studies on the resistance and resilience in microbial communities are scarce. Similarly, studies focusing on factors that might improve resistance or resilience of communities such as the influence of refuges are equally missing, although an understanding of the underlying mechanisms could be very useful in the field of conservation management. In this study, chemostat cultures were used to investigate the influence of a spatial and a temporal refuge on bacterioplankton communities’ resistance and resilience measured in terms of functioning and community composition after applying a salinity pulse disturbance. Respiration rate and substrate utilization were used to estimate bacterial functioning while community composition was determined by using T-RFLP. The perturbation was found to affect bacterial functioning and community composition. Moreover our findings indicate that the resistance and resilience measured in terms of bacterial functioning and community composition were significantly influenced by the provision of refuges.

A study was conducted using data compiled from two sources to test the hypothesis that killer whales display seasonal variability in their occurrence in the Galapagos Marine Reserve (GMR), Ecuador. Three questions arise from this hypothesis: 1) do killer whale sightings display temporal variability; 2) are sightings spatially associated with resources; and 3) if sightings are spatially associated with resources, does the spatial association change temporally? I combined and evaluated two sets of GMR killer whale sighting data (n=154) spanning a twenty-year time frame collected via opportunistic sightings by an observer network and shipboard line-transect surveys. I tested for a (a) correlation between the total annual sightings and bi-annual seasonality (upwelling versus non-upwelling); (b) correlation between the total annual sightings and the Multivariate El Nino Southern Oscillation Index (MEI); (c) correlation between sightings, the MEI, and seasonality; (d) spatial association between sightings and resources; and (e) spatial change in sightings with seasonality. Sightings were roughly equally distributed between non-upwelling (56%) and upwelling seasons (July-December). No direct correlation was found between sightings and the MEI. Sightings occurred more often than expected by chance during the peak upwelling months of August-November when the MEI was within one standard deviation of the average (binomial z=2.91, p<0.05). Sightings were spatially associated with areas of high chlorophyll a values (binomial z=4.46, p&lt;0.05), pinniped rookeries (binomial z=6.03, p&lt;0.05), and areas with high combined resource value (binomial z=5.36, p&lt;0.05). The spatial distribution of sightings did not shift with seasonality, with the exception that sightings occurred less often than expected in areas of low combined resource value during the upwelling period (binomial z=-3.17, p&lt;0.05). Though variability in observer effort should be considered when evaluating these data, these results do not suggest a strong pattern of seasonal occupancy or that killer whales are responsive to El Nino Southern Oscillation events. Further research is needed to determine if killer whales in the GMR comprise a single resident population, multiple resident and transient populations, or if killer whales observed in the GMR are part of a population inhabiting the eastern tropical Pacific region, which visit the area at various times.

No description available.

In this thesis the concept behind our notion of video sculpture is to imagine an image sequence or movie as a three dimensional volume. We then also imagine that there is a frameset that traverses the image sequence to give us what we commonly think of as a video or movie. In the ordinary sense this frameset moves through an image sequence in a completely timeparallel linear fashion. In video sculpture, we free the frameset from these bounds so that we can sample space and time in completely unorthodox ways. We can view the whenwhere in previously unforeseen perspectives. Slices of the video environment can simultaneously reveal both past and future actions within a single frame. Building on this free representation of video spacetime, we then wrest the frame once more from the present constraints of topography and/or topology. The frame can bend and twist and jump and dive. The view of a fading quadratic surface cutting through two scenes makes for a beautiful curtain transition. We present a framework and an implementation for modeling the frame as it passes through the image sequence volume object.

Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2002. / Includes bibliographical references (leaves 208-215). Also available in electronic version. Access restricted to campus users.