Many different methodologies have been developed for analyzing multithreaded programs. These analyses present a wide variety of approaches and tend to be rather complicated because they work on applications formed by several threads executed in a nondeterministic order. / To address these issues this thesis introduces XThread, a flexible and modular framework for developing different concurrency analyses over multithreaded applications. The main objective of XTHREAD is to reduce the complexity of developing concurrency analyses by providing high level abstractions that close the breach between the language spoken by the researcher and the language the framework provides. Moreover, this framework provides different tools that are often required for solving issues common to many concurrency analyses. XTHREAD's modular organization also delivers a flexible environment for developing and testing different analysis implementations. / In order to demonstrate the usefulness of the framework a client analysis representing known but non-trivial multithreaded analysis is developed which is composed of several other concurrency analysis. A substantial number of benchmarks are used in order to test the implementations, showing that complex programs are accepted and correctly handled by the abstractions provided by the framework. Using the XTHREAD framework we demonstrate implementations that have both comparable accuracy and much better generality than is typically found in existing, research-level implementations of concurrency analyses.

Zugl.: München, Techn. Univ., Diss., 2007

Zugl.: München, Techn. Univ., Diss., 2007

No description available.

Thesis advisor: Frank Gollop / This thesis explores the unanticipated consequences of producing ethanol for use as a transportation fuel in the United States. Statistical analysis is conducted to determine the effect that increased ethanol production has on the prices of two essential American commodities: corn and gasoline. A simultaneous system of the demand and supply of corn is developed to estimate the effect of ethanol on the price of corn. The results of this model suggest that during the period 1986-2001, corn demanded for ethanol production caused the price of corn to be 19% higher than it otherwise would have been. This result is noteworthy because the majority of American foods contain some type of corn product. A second simultaneous system is developed to determine the effect of ethanol on the price of gasoline. Neither a change in the price of ethanol nor a change quantity of ethanol per gallon of gasoline was found to have a significant impact on the price of gasoline. / Thesis (BA) — Boston College, 2009. / Submitted to: Boston College. College of Arts and Sciences. / Discipline: College Honors Program. / Discipline: Economics Honors Program. / Discipline: Economics.

This thesis provides an overview of work conducted to investigate human spatial hearing in situations involving multiple concurrent sound sources. Much is known about spatial hearing with single sound sources, including the acoustic cues to source location and the accuracy of localisation under different conditions. However, more recently interest has grown in the behaviour of listeners in more complex environments. Concurrent sound sources pose a particularly difficult problem for the auditory system, as their identities and locations must be extracted from a common set of sensory receptors and shared computational machinery. It is clear that humans have a rich perception of their auditory world, but just how concurrent sounds are processed, and how accurately, are issues that are poorly understood. This work attempts to fill a gap in our understanding by systematically examining spatial resolution with multiple sound sources. A series of psychophysical experiments was conducted on listeners with normal hearing to measure performance in spatial localisation and discrimination tasks involving more than one source. The general approach was to present sources that overlapped in both frequency and time in order to observe performance in the most challenging of situations. Furthermore, the role of two primary sets of location cues in concurrent source listening was probed by examining performance in different spatial dimensions. The binaural cues arise due to the separation of the two ears, and provide information about the lateral position of sound sources. The spectral cues result from location-dependent filtering by the head and pinnae, and allow vertical and front-rear auditory discrimination. Two sets of experiments are described that employed relatively simple broadband noise stimuli. In the first of these, two-point discrimination thresholds were measured using simultaneous noise bursts. It was found that the pair could be resolved only if a binaural difference was present; spectral cues did not appear to be sufficient. In the second set of experiments, the two stimuli were made distinguishable on the basis of their temporal envelopes, and the localisation of a designated target source was directly examined. Remarkably robust localisation was observed, despite the simultaneous masker, and both binaural and spectral cues appeared to be of use in this case. Small but persistent errors were observed, which in the lateral dimension represented a systematic shift away from the location of the masker. The errors can be explained by interference in the processing of the different location cues. Overall these experiments demonstrated that the spatial perception of concurrent sound sources is highly dependent on stimulus characteristics and configurations. This suggests that the underlying spatial representations are limited by the accuracy with which acoustic spatial cues can be extracted from a mixed signal. Three sets of experiments are then described that examined spatial performance with speech, a complex natural sound. The first measured how well speech is localised in isolation. This work demonstrated that speech contains high-frequency energy that is essential for accurate three-dimensional localisation. In the second set of experiments, spatial resolution for concurrent monosyllabic words was examined using similar approaches to those used for the concurrent noise experiments. It was found that resolution for concurrent speech stimuli was similar to resolution for concurrent noise stimuli. Importantly, listeners were limited in their ability to concurrently process the location-dependent spectral cues associated with two brief speech sources. In the final set of experiments, the role of spatial hearing was examined in a more relevant setting containing concurrent streams of sentence speech. It has long been known that binaural differences can aid segregation and enhance selective attention in such situations. The results presented here confirmed this finding and extended it to show that the spectral cues associated with different locations can also contribute. As a whole, this work provides an in-depth examination of spatial performance in concurrent source situations and delineates some of the limitations of this process. In general, spatial accuracy with concurrent sources is poorer than with single sound sources, as both binaural and spectral cues are subject to interference. Nonetheless, binaural cues are quite robust for representing concurrent source locations, and spectral cues can enhance spatial listening in many situations. The findings also highlight the intricate relationship that exists between spatial hearing, auditory object processing, and the allocation of attention in complex environments.

This thesis deals with the Simultaneous Localisation and Mapping algorithm as it pertains to the deployment of mobile systems in unknown environments. Simultaneous Localisation and Mapping (SLAM) as defined in this thesis is the process of concurrently building up a map of the environment and using this map to obtain improved estimates of the location of the vehicle. In essence, the vehicle relies on its ability to extract useful navigation information from the data returned by its sensors. The vehicle typically starts at an unknown location with no a priori knowledge of landmark locations. From relative observations of landmarks, it simultaneously computes an estimate of vehicle location and an estimate of landmark locations. While continuing in motion, the vehicle builds a complete map of landmarks and uses these to provide continuous estimates of the vehicle location. The potential for this type of navigation system for autonomous systems operating in unknown environments is enormous. One significant obstacle on the road to the implementation and deployment of large scale SLAM algorithms is the computational effort required to maintain the correlation information between features in the map and between the features and the vehicle. Performing the update of the covariance matrix is of O(n�) for a straightforward implementation of the Kalman Filter. In the case of the SLAM algorithm, this complexity can be reduced to O(n�) given the sparse nature of typical observations. Even so, this implies that the computational effort will grow with the square of the number of features maintained in the map. For maps containing more than a few tens of features, this computational burden will quickly make the update intractable - especially if the observation rates are high. An effective map-management technique is therefore required in order to help manage this complexity. The major contributions of this thesis arise from the formulation of a new approach to the mapping of terrain features that provides improved computational efficiency in the SLAM algorithm. Rather than incorporating every observation directly into the global map of the environment, the Constrained Local Submap Filter (CLSF) relies on creating an independent, local submap of the features in the immediate vicinity of the vehicle. This local submap is then periodically fused into the global map of the environment. This representation is shown to reduce the computational complexity of maintaining the global map estimates as well as improving the data association process by allowing the association decisions to be deferred until an improved local picture of the environment is available. This approach also lends itself well to three natural extensions to the representation that are also outlined in the thesis. These include the prospect of deploying multi-vehicle SLAM, the Constrained Relative Submap Filter and a novel feature initialisation technique. Results of this work are presented both in simulation and using real data collected during deployment of a submersible vehicle equipped with scanning sonar.

Thesis (M.S.)--University of Delaware, 2007. / Principal faculty advisor: Guang R. Gao, Dept. of Electrical and Computer Engineering. Includes bibliographical references.

High bandwidth of networks demands high performance communication processors that integrate application processing, network processing, and system support functions into a single, low cost System-On-Chip (SOC) solution. However, conventional processors, when used in network related applications, are beset by the overhead of save/restore of register context, cache misses due to fetching interrupt handler from memory, and the possibility of NIC buffer overflow. Therefore, this paper analyzes the effectiveness of multithreading to service interrupts on an embedded processor from the perspective of a Network processor and a Communication processor. A Simulation environment enhanced with a multithreaded hardware execution model is used and our results reveal that multithreading for interrupts from a single NIC brings a fair improvement in performance of Network processors and little or no effect on Communication processors. However, our analysis also show that multithreading for interrupts has a lot of potential when applied to communication processors with multiple interrupt sources, such as Ethernet, ATM, USB, and HDLC. Index terms: Multithreading, UDP, IP, device driver, interrupt processing, communication processor. / Graduation date: 2003

Simultaneous interpretation is a cognitively demanding task involving concurrent listening and speaking in two languages. Successful performance in this task likely relies on a good working memory, which reflects a person’s ability to process and store information simultaneously. The present study used the theoretical construct of working memory to investigate the task of simultaneous interpretation. Twenty student interpreters at two different levels of training in interpreting and sixteen bilinguals with no training in interpreting, all of whom spoke Chinese as a first language and English as a second language, participated in this study. They were compared on their performance for two measures of working memory – reading span and digit span – and on a simultaneous interpretation task. In addition, a translation judgment task and proficiency self-evaluation measures were administered to explore if language proficiency mediates working memory in participants’ L1 (native language) and L2 (second language). This study also examined the relation between working memory and performance in simultaneous interpretation. Results showed that the student interpreters performed better than bilinguals on simultaneous interpretation. Advanced-level student interpreters also outperformed bilinguals on all language versions of the memory span tasks, though first-year student interpreters did not show higher working memory than the bilinguals. Further, performance in simultaneous interpretation was related to working memory in both L1 and L2. Based on the study’s findings, two years of training in interpreting seemed to have a positive effect on improving working memory, whereas one year of training in interpreting did not help to increase working memory. On the other hand, higher language proficiency did not result in high working memory but contributed to better performance in simultaneous interpretation. Working memory, it is concluded, is important but language proficiency in L1 and L2 assumes a more critical role in simultaneous interpretation performance.