D.Econ.

Thesis (Ed.D.)--Boston University

Congestion threshold is embedded in the congestion definition. Two basic approaches exist in current practice for setting the congestion threshold. One common approach uses the “free-flow” or unimpeded conditions as the congestion threshold. Another approach uses target or “acceptable” conditions. The limited research that has been conducted on the congestion threshold issue focuses on operational problems or policy debates, but relatively little investigation of the effect on decision-making for transportation investment and resource allocation. This research investigated the differences inherent in the threshold choices using detailed freeway data from seven metropolitan areas. Congestion performance measures of delay per mile, Travel Time Index and Planning Time Index were evaluated. This research specifically examined: 1) the ranking values of congestion measure for different congestion thresholds under a variety of real-world travel time distributions, 2) the relationship between change of congestion threshold and change of performance measure, and 3) the appropriateness of using speed limit as a congestion threshold choice by evaluating the peak and off-peak average speed changes in relation to a speed limit change in Houston, Texas. The rankings of congestion measures for freeway segments hold steady across the congestion thresholds ranging from 60 mph to 30 mph and across the congestion measures. From an investment point of view, the congestion threshold speed used is not a concern for funding allocation. The relationship between the delay values for an alternative threshold and the 60 mph threshold has a quadratic form. As the alternative threshold decreases further away from 60 mph, the increment is larger. The more congested a section is, the less the threshold affects measured congestion. For very congested sections, most of the delay is associated with speeds below 30 mph. The posted speed limit affects travel time distribution in the free flow driving condition but does not affect travel time distribution during congested driving conditions. However, if the speed limit or a percentage of speed limit is used to estimate the congestion, the amount of congestion may be underestimated because the free flow speed is higher than the speed limit.

Due to numerous definitions for attention and inhibition, it is very difficult to operationalize and measure these constructs (Barkley, 1996). The primary purpose of this study was to determine whether there is evidence for independence between attention and inhibition constructs using measures from the TEA-ch, Gordon CPT, Stroop Task, WISC- Digit Span and Go-No-Go Tasks and tasks of inhibition. Each of 140 students were evaluated on all measures and scores were correlated. In addition, Teacher Ratings and scores from the OLSAT were also correlated with attention and inhibition scores. Gender differences between all scores were also examined. Overall, measures did not correlate as expected. Results showed that there were significant but weak correlations among the sustained and selective attention variables. Similarly, when all inhibition variables were correlated only four significant but weak correlations were found. The lack of convergent validity and low correlations among these measures suggest that attention and inhibition constructs may be multi-dimensional. Intercorrelations between attention and inhibition variables were also weak. Relationships between OLSAT scores, Teachers Ratings and attention and inhibition variables showed that as scores that reflect reasoning skills and Teacher Ratings increased, the ability to attend and inhibit also increased. Gender differences in attention and inhibition scores were also examined and showed that girls were better at paying attention to stimuli and inhibiting impulsive responses than boys.

No description available.

Aviation and the internet are two conveniences without which the modern world would almost grind to a halt given our current dependence levels (on them). If both were to suddenly vanish, mankind would be thrown back to the late 19th century reminiscent of a world which was once a smaller place. / Aviation plays a critical role in our daily life transporting man and material over vast distances in a relatively short period of time. A vital cog in this wheel is the airport that 'facilitates' the safe loading, unloading, take-off and landing of aircraft. / For some time now, aircraft have been the target of various terrorist groups and militant factions seeking to make a point to the world in the most dramatic fashion possible. To maintain the security of civil aviation, laws have been promulgated (both nationally and internationally) to ensure that the perpetrators (of the crime) when caught, will be adequately punished and in a manner that will deter others from committing crimes against civil aviation. However this law-making process (in large part initiated by the International Civil Aviation Organization) has not sufficiently addressed airports and the security therein. / This paper seeks to examine---and in some cases suggest improvements to---aviation security laws at large, with a specific emphasis on airports. It is believed that a more comprehensive set of laws governing aviation security would result in greater efficacy of airport security procedures thus reducing the need for prospective judicial intervention and concomitant lengthy court proceedings.

Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaves 60-61). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaves 60-61). Also available on the Internet.

Learning to write software requires much practice and frequent assessment. Consequently, the use of computers to assist in the assessment of computer programs has been important in supporting large classes at universities. The main approaches to the problem are dynamic analysis (testing student programs for expected output) and static analysis (direct analysis of the program code). The former is very sensitive to all kinds of errors in student programs, while the latter has traditionally only been used to assess quality, and not correctness. This research focusses on the application of static analysis, particularly structural similarity, to marking student programs. Existing traditional measures of similarity are limiting in that they are usually only effective on tree structures. In this regard they do not easily support dependencies in program code. Contemporary measures of structural similarity, such as similarity flooding, usually rely on an internal normalisation of scores. The effect is that the scores only have relative meaning, and cannot be interpreted in isolation, ie. they are not meaningful for assessment. The SimRank measure is shown to have the same problem, but not because of normalisation. The problem with the SimRank measure arises from the fact that its scores depend on all possible mappings between the children of vertices being compared. The main contribution of this research is a novel graph similarity measure, the Weighted Assignment Similarity measure. It is related to SimRank, but derives propagation scores from only the locally optimal mapping between child vertices. The resulting similarity scores may be regarded as the percentage of mutual coverage between graphs. The measure is proven to converge for all directed acyclic graphs, and an efficient implementation is outlined for this case. Attributes on graph vertices and edges are often used to capture domain specific information which is not structural in nature. It has been suggested that these should influence the similarity propagation, but no clear method for doing this has been reported. The second important contribution of this research is a general method for incorporating these local attribute similarities into the larger similarity propagation method. An example of attributes in program graphs are identifier names. The choice of identifiers in programs is arbitrary as they are purely symbolic. A problem facing any comparison between programs is that they are unlikely to use the same set of identifiers. This problem indicates that a mapping between the identifier sets is required. The third contribution of this research is a method for applying the structural similarity measure in a two step process to find an optimal identifier mapping. This approach is both novel and valuable as it cleverly reuses the similarity measure as an existing resource. In general, programming assignments allow a large variety of solutions. Assessing student programs through structural similarity is only feasible if the diversity in the solution space can be addressed. This study narrows program diversity through a set of semantic preserving program transformations that convert programs into a normal form. The application of the Weighted Assignment Similarity measure to marking student programs is investigated, and strong correlations are found with the human marker. It is shown that the most accurate assessment requires that programs not only be compared with a set of good solutions, but rather a mixed set of programs of varying levels of correctness. This research represents the first documented successful application of structural similarity to the marking of student programs.

In recent years, forestry programmes in British Columbia have increasingly used helicopters to expedite operations, particularly in the areas of fire suppression and prescribed burning. Between 1970 and 1977 the population of Canadian helicopters doubled, reflecting the increased usage resulting from new, more efficient designs. The number of accidents per year decreased in the 8 years, but the percentage of fatal accidents increased In British Columbia, the accident rate per 10,000 hours in the years 1975 and 1976, was 3.6, the third highest in Canada. After an extensive period of field work in this province, by the author, it is clear that the people working in and around helicopters do not generally receive enough training in the safety precautions necessary. This lack of training was evident at both the worker level and the supervisory level. In fire suppression operations, the inadequate training is aggravated by haste, which greatly increases the chances of unnecessary accidents. This report identifies areas of training that need greater-attention, and it offers some guidelines for future training programmes. The report discusses the fundamentals of helicopter flight, in order that the layman may gain some appreciation of what problems the pilot has to tolerate. Several types of operations are then detailed with safety prescriptions for each one. Some causative factors in each operation are also discussed. The report then analyses the use of helicopters in aerial ignition systems. Of the several systems currently in use, it is clear that the helicopter drip torch is potentially the most hazardous, but to date there have been no serious helicopter drip torch accidents. Finally the report looks at crew deployment techniques, in particular, helicopter rappelling and helitack. The level of training and hazard awareness in these two operations is higher than was generally seen elsewhere, and provides a good example of how helicopters can be used safely and efficiently. Throughout the report, reference is made to past accidents. These accidents show a fundamental lack of safe practice; a situation that would be improved with better training programmes. They also illustrate some of the diverse and disastrous results of poor training. The report recommends that the Workers' Compensation Board of British Columbia should seriously consider setting up a series of training films, which, along with posters and leaflets, could be distributed to the various companies and organisations who use helicopters in the course of their operations. Transport Canada is now preparing a series of general training aids, and these will be made available to interested parties. / Forestry, Faculty of / Graduate