In recent years, social networks have become an important part of our daily lives. Billions of people daily use Facebook and other prominent social media networks. This makes them an effective medium for advertising and marketing. Finding the most influential users in a social network is an interesting problem in this domain, as promoters can reach large audiences by targeting these few influential users. This is the influence maximization problem, where we want to maximize the influence spread using as few users as possible. As these social networks are huge, scalability and runtime of the algorithm to find the most influential users is of high importance. We propose innovative improvements in the implementation of the state-of-the-art sketching algorithm for influence analysis on social networks. The primary goal of this thesis is to make the algorithm fast, efficient, and scalable. We devise new data structures to improve the speed of the sketching algorithm. We introduce the compressed version of the algorithm which reduces the space taken in the memory by the data structures without compromising the runtime. By performing extensive experiments on real-world graphs, we prove that our algorithms are able to compute the most influential users within a reasonable amount of time and space on a consumer grade machine. These modifications can further be enhanced to reflect the constantly updating social media graphs to provide accurate estimations in real-time. / Graduate

The main purpose of this study was to examine some of the effects of normal aging on test performance where: (a) short-term memory was an important component (b) intellectual and psychomotor speed was involved. Six related hypotheses were investigated using a group of tests administered individually to each subject during a one hour testing period. The degree and nature of change in test performance was studied on a sample of 120 volunteers aged eleven to seventy. There were ten males and ten females in each decade group, and subjects were assigned at random to different treatments where this was necessary to avoid practice effects. Hebb's (1949, 1961) theory was used as a frame of reference, augmented by the theories of Welford (1958) and of Broadbent (1958, 1963). An attempt was made to evaluate the Maturation Degeneration Hypothesis on the basis of the experimental results, with reference to Dorken's (1958) contention that the normal effects of aging on intellectual function have often been over-emphasized. The tests were grouped into two general classes: those which measured speed of performance on familiar tasks; and those which examined the relationship between aging and interference on memory with regard to both familiar and unfamiliar tasks. The experimental results showed a tendency to follow the pattern predicted by the Maturation Degeneration Hypothesis, although analysis failed to show a statistically significant relationship between aging and performance on all of the tests. Nevertheless, it is reasonable to conclude, on the basis of these experimental results that: (l) The theoretical formulations of Hebb, Welford and Broadbent may be useful in explaining some changes in mental function which accompany advancing age. (2) Speed of performance decreases from the twenties to the sixties, although this decline is not statistically significant for all tasks involving rote repetition of familiar everyday verbal material. (3) Aging appears to have less effect than commonly supposed, on the amount of verbal and numerical material which can be grasped and retained over a short period of time under the conditions used here. (4) There was no significant relationship between aging and performance on a verbal learning test provided the recognition method was used to test retention. However, there was a significant decrease with aging and performance when tested by recall. (5) There is a relationship between aging and the effects of interference, although this relationship was found not to be statistically significant in the tasks used here. (6) Performance on a test requiring extensive reorganization of pre-existing habits declined significantly with aging which suggests that learning difficulty in older people is partly a function of the amount of interference from old habits. By and large the results were in line with expectation and tended to support Dorken's view that changes in cognitive functions with age, and in the absence of cerebral pathology, are less drastic than is commonly held to be the case. / Arts, Faculty of / Psychology, Department of / Graduate

With the consideration of extending track competition for girls of a middle altitude community to include the sea level valley nearby, the problem for this investigation evolved. The main question to be answered was, "Is the athletic performance of young female athletes, native to middle altitude, impaired when performing at sea level?" Subsidiary problems of the relationship of partial pressure of oxygen to performance, and microhematocrit changes in the subjects were also studied. Eight females between the ages of 12 and 14 participated in this experiment having eight treatments. Four treatments were at sea level and four were at middle altitude. Each treatment included taking a fingertip blood sample for a microhematocrit reading, a 50 yard dash, a 440 yard dash, a softball throw and an 880 yard run. These events were to represent the assortment found at a track meet. Recordings were also made of temperature, humidity, barometric pressure, and air pollution. It was hypothesized that; a) the denser air and increased gravitational pull at sea level cause impairment in throwing and short runs; b) with oxygen uptake reduced at altitude, the 880 yard run is faster at sea level than at middle altitude; c) if hematocrits are in the upper portion of the normal range for sea level, the resultant increase in the oxygen carrying capacity of the blood does not improve sea level performance. The findings indicated that physical training and learning progressed markedly from the start of the experiment to the finish, The only significant altitude effect was found in the 50 yard dash with times being faster at sea level. It is doubtful that this was a result of the change in altitude, more likely, conditions other than barometric pressure were responsible for the differences found at the two testing locations. Wind disadvantage and insufficient warm-up more likely accounted for slower times at altitude. Superior performances occurred in warm weather, and when subjects were psychologically peaked indicating that warm-up and psychological climate may be more important to performance than the change of altitude that was employed. Hematocrits remained within normal ranges for middle altitude dwelling females throughout the experiment. Therefore, a coach of healthy young athletes from middle altitude should have no unusual concerns for competition at a related sea level environment. Concerns should be only those normally attended to at all competitions. / Education, Faculty of / Curriculum and Pedagogy (EDCP), Department of / Graduate

The influence of the major environmental forces on the attitude response of gravity gradient satellites is investigated using analytical and numerical techniques. The study establishes not only the effect of these forces on system performance but also their relative importance. The problem is investigated in the order of increasing difficulty which corresponds to a systematic reduction in altitude. In general, the non-linear, non-autonomous nature of the system renders the determination of a closed form solution virtually impossible. Hence, numerical techniques are employed, in conjunction with invariant surfaces or integral manifolds, to analyse the system. For a given set of parameters, the largest such surface defines the bound of stable motion; on the other hand, the smallest surface that can be found (i.e., a line or set of lines) represents the dominant periodic solution with which these manifolds are associated. The analysis establishes the importance of periodic solutions as they provide the 'frame' about which stability charts are built. Furthermore, a variational stability analysis of these solutions, using Floquet theory, accurately determines the termination of the spikes and establishes the critical eccentricity for stable motion. Phase I investigates the attitude dynamics of satellites at high altitudes where gravity gradient and direct solar radiation constitute the predominant torques. The approximate closed form solution, obtained using the WKBJ and Harmonic Balance methods, was found to predict the librational response of a satellite with considerable accuracy. As the satellites requiring station keeping permit only small amplitude motion, the analytical results are of sufficient accuracy to be useful during preliminary design stages. The response and stability bounds of the system, obtained numerically, are shown through the use of 'system plots' and 'stability charts'. The results indicate a considerable effect due to solar radiation on the attitude dynamics of a satellite. The use of solar radiation in controlling the satellite attitude is explored. The optimized results show this system to be quite effective, being capable of providing a pointing accuracy of 0-5° depending on orbit eccentricity. The extension of the analysis to the intermediate altitude ranges, where direct earth radiation, its albedo and shadow become significant, is undertaken in phase II. A comprehensive investigation was made possible by the determination of closed form expressions for earth radiation forces. This was accomplished through the concept of cutting plane distance ratios. The analysis shows only local variations due to earth radiations without substantially affecting the maximum librational amplitude or mainland stability area. Hence, for all practical purposes, direct earth radiation, its albedo and shadow can be neglected in such studies. Phase III investigates the dynamics of close earth satellites in the presence of aerodynamic and radiation forces, thus covering the remaining altitude range. The results show that a precise dynamic analysis requires the consideration of both aerodynamic and direct solar radiation forces. The investigation helps in establishing an altitude range in which a pure gravity gradient analysis is likely to be most applicable. The application of this analysis to the representative gravity gradient satellite, GEOS-A, over the entire altitude range, exemplifies the findings of the parametric study. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

The effect of specific active environment on the fracture strength of glass and polymethyl methacrylate was investigated using an indirect tensile testing technique. The strength of glass was not affected by exposure to dry gaseous N₂ and CO₂. At low water vapour coverages, (<1/3 monolayer), the tensile strength of glass was reduced by approximately 50%. Further increase in water vapour pressure did not weaken the solid to a much greater extent. The existence of surface microcracks governs the absolute tensile fracture strength, and any process which varies the flaw geometry acts to vary the tensile fracture strength. Soaking in the liquid has the same effect as adsorption from the vapour phase near saturation. All vapour adsorbates caused a weakening, the magnitude of the decrease increasing with increasing ability of the adsorbate to screen the surface Si++++ cores. Moisture was the most active environment encountered. Polymethyl methacrylate did not weaken in the vapour phase despite multilayer adsorption, but stressing in wetting liquids did cause drastic failure, with a 57% decrease in tensile strength. Non-wetting liquids do not affect the strength of the acrylic plastics. Fracture experiments on a quartzitic rock in aqueous solutions of surfactant, (quartenary ammonium salts), show that the weakening due to surfactant adsorption is negligible, since water itself causes the maximum strength reduction. The adsorption of surfactant is only a secondary effect. A mechanism has been proposed for the stress-environmental failure of brittle solids. This mechanism recognizes the existence of micro-cracks, regards the stable crack propagation stage of the fracture process to be environment sensitive, and involves the strain-activated adsorption resulting in a decrease in cohesion at the flaw apex. The magnitude of the weakening is critically dependent on the nature of the bonding in the solid surface. A literature review of stress-sorption cracking, with an emphasis on non-metallic systems, is included. / Applied Science, Faculty of / Mining Engineering, Keevil Institute of / Graduate

A main purpose of the thesis is to demonstrate and explain to what extend do media influence foreign policy of a state. Foreign policy is always under internal and external influences and media are considered to be one of those external influences that shape it. Agenda setting theory forms the theoretical frame for this thesis because it takes into consideration not just direct media-government relations but the public as well that inside of this relation serves as some sort of mediator. Besides this theory and the CNN effect as its main 'extension' identifiable victim effect and third person effect as important elements in the process of influence will be introduced as well as influence of visualization. When word 'media' is mentioned in this case it implies to television and newspapers' (both printed and online versions) messages and their influences (not just verbal but the visual ones as well). Examples and case studies in this case focus mostly on the US foreign policy due to its influential role, fact that the US is still the country with the most superlatives inside of international arena and the size, influence and role-model identity of its big media companies (for ex. CNN).

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Digital Citizenship Tools for Cause-Based Campaigns: A Broadened Spectrum of Social Media Engagement and Participation-Scale Methodology develops and applies two new tools for understanding, measuring, and recursively adjusting small to medium-size social media-based philanthropic campaigns to better foster participation and engagement—in other words, democratic digital citizenship. First, a theoretical model is offered broadening current binary conceptions of success and failure or impact of campaigns, situating specific participant actions in social media on a spectrum. Then, from that model, a new methodology is provided to measure participation and engagement generated by campaign posts. Recommendations are also offered for recursively adjusting campaign posts to better foster democratic digital citizenship. These tools were developed from data generated by #TheFaceOffChallenge, a research project representative of a typical small to medium-size cause-based campaign. #TheFaceOffChallenge also serves as a sample for analysis illustrating how to use these tools. While explicating these tools, this dissertation explores a broad range of topics related to better understanding democratic digital citizenship: online philanthropy, awareness, and digital activism; viral and memetic transmission; tensions between consumption and creation of ideas, content, and knowledge; public(s), counterpublics, and counter-efforts; literacies and access for engagement and participation in algorithmic environments; and visual communication and semiotics.

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No description available.