The advances in hardware, software, and networks have enabled applications from business enterprises, scientific and engineering disciplines, to social networks, to generate data at unprecedented volume, variety, velocity, and varsity not possible before. Innovation in these domains is thus now hindered by their ability to analyze and discover knowledge from the collected data in a timely and scalable fashion. To facilitate such large-scale big data analytics, the MapReduce computing paradigm and its open-source implementation Hadoop is one of the most popular and widely used technologies. Hadoop's success as a competitor to traditional parallel database systems lies in its simplicity, ease-of-use, flexibility, automatic fault tolerance, superior scalability, and cost effectiveness due to its use of inexpensive commodity hardware that can scale petabytes of data over thousands of machines. Recurring queries, repeatedly being executed for long periods of time on rapidly evolving high-volume data, have become a bedrock component in most of these analytic applications. Efficient execution and optimization techniques must be designed to assure the responsiveness and scalability of these recurring queries. In this dissertation, we thoroughly investigate topics in the area of recurring query processing on big data. In this dissertation, we first propose a novel scalable infrastructure called Redoop that treats recurring query over big evolving data as first class citizens during query processing. This is in contrast to state-of-the-art MapReduce/Hadoop system experiencing significant challenges when faced with recurring queries including redundant computations, significant latencies, and huge application development efforts. Redoop offers innovative window-aware optimization techniques for recurring query execution including adaptive window-aware data partitioning, window-aware task scheduling, and inter-window caching mechanisms. Redoop retains the fault-tolerance of MapReduce via automatic cache recovery and task re-execution support as well. Second, we address the crucial need to accommodate hundreds or even thousands of recurring analytics queries that periodically execute over frequently updated data sets, e.g., latest stock transactions, new log files, or recent news feeds. For many applications, such recurring queries come with user-specified service-level agreements (SLAs), commonly expressed as the maximum allowed latency for producing results before their merits decay. On top of Redoop, we built a scalable multi-query sharing engine tailored for recurring workloads in the MapReduce infrastructure, called Helix. Helix deploys new sliced window-alignment techniques to create sharing opportunities among recurring queries without introducing additional I/O overheads or unnecessary data scans. Furthermore, Helix introduces a cost/benefit model for creating a sharing plan among the recurring queries, and a scheduling strategy for executing them to maximize the SLA satisfaction. Third, recurring analytics queries tend to be expensive, especially when query processing consumes data sets in the hundreds of terabytes or more. Time sensitive recurring queries, such as fraud detection, often come with tight response time constraints as query deadlines. Data sampling is a popular technique for computing approximate results with an acceptable error bound while reducing high-demand resource consumption and thus improving query turnaround times. In this dissertation, we propose the first fast approximate query engine for recurring workloads in the MapReduce infrastructure, called Faro. Faro introduces two key innovations: (1) a deadline-aware sampling strategy that builds samples from the original data with reduced sample sizes compared to uniform sampling, and (2) adaptive resource allocation strategies that maximally improve the approximate results while assuring to still meet the response time requirements specified in recurring queries. In our comprehensive experimental study of each part of this dissertation, we demonstrate the superiority of the proposed strategies over state-of-the-art techniques in scalability, effectiveness, as well as robustness.

In this dissertation, I discuss bounds for the set of possible number of zeros of a homogeneous linear recurring sequence over a finite field of q elements, based on an irreducible minimal polynomials of degree d and order m as the characteristic polynomial. I prove upper and lower bounds on the cardinality of the set of number of zeros. The set is determined when t= (qd-1)/m has the form qa+1 or q2a-qa+1 where a is a positive integer. The connection with coding theory is a key ingredient. Also it is proved that the upper bound defined here is the best bound for the cardinality of the set of zeros, in the sense that it is reached infinitely often.

One of the most concerning trends associated with the ongoing problem of civil wars is that conflicts often flare-up a short period after they appeared to have ended. While significant progress has been made in the study of post-civil war peace building and the causes of civil wars, the tendency for civil wars to recur is one factor which has been largely overlooked. This thesis addresses this shortcoming by analysing the causes of recurring civil war using statistical methods. Relevant civil war research was consulted and hypotheses pertaining to the variables which might influence civil war recurrence were formulated. These factors are organised in a contingency framework which suggests that conflict recurrence is dependent on both pre- and post-conflict environments as well as factors associated with how the original conflict was fought. The Uppsala Conflict Data Program/Centre for the Study of Civil War Armed Conflict Dataset was used to produce a dataset of 238 civil wars which were fought between 1946 and 2004. Additional data pertaining to specific hypotheses was collected from a range of other sources. Statistical analysis was conducted to determine the strength and direction of relationships between different variables and civil war recurrence. Several factors were found to have a significant relationship with civil war recurrence: ethnic diversity, conflicts which were fought over territorial issues and conflicts which were not ended by military victory, particularly those which ended as a result of low or no fatalities. These findings are discussed with reference to improving civil war management and policy recommendations are presented.

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Intelligent Transportation Systems (ITS) play an important role in supporting motorists and first responders to handle major incidents, hazmat spills, security measures and other emergency operations. Increasingly, technology advancements and applications are providing invaluable integration opportunities to interconnect safety, maintenance, ITS, traffic operations, facilities, and transportation equipment programs to maximize available resources and achieve efficiency in transportation operations. This research focuses on one of the prominent ITS devices: Dynamic Message Signs (DMS) operations. Using real time incident management operations data and ITS operations data, an attempt is made to develop ITS Operations Evaluations Models (ITSOEMs) that are capable of quantifying the operations value of DMS and their complementing ITS surveillance and detection systems, such as CCTV, Safety Service Patrol (SSP) and Computer Aided Dispatch (CAD) systems. The I-95 corridor in the state of Virginia is selected as the Study Corridor. Operations data from the Virginia Department of Transportation (VDOT) on DMS and ITS detection systems and incident management is analyzed to accomplish four key research objectives: a) To collect, extract and evaluate real time operations data from VDOT ITS and incident management operations programs and identify the factors contributing to the successful operation of DMS for the duration of incidents and events occurring on the I-95 Study Corridor; b) To develop analytical models to determine measurable influence of incident detections in successfully disseminating messages on DMS; c) To develop ITS Operations evaluation models to determine the effectiveness of DMS messages during incidents by quantifying the influence of DMS messages in the deterrence of secondary incidents on the I-95 Study Corridor; and d) To develop guidelines on the application of these quantitative ITS evaluation models so that transportation engineers can effectively use these models to perform ITS evaluations at other ITS locations. The ITS evaluation framework developed in this research work is expected to assist transportation engineers in the prioritization, selection and implementation of operations and technology integration strategies.

This thesis was concerned with investigating a visual-illusionary phenomenon that co-occurs with post-traumatic anxiety symptoms. More specifically, individuals who report recurring specific memories of a fearful event (RSM) also tend to report a persistent illusion of movement (PIM) upon prolonged visual fixation (Tym, Dyck & McGrath, 2000). The development of a visual test (i-Test) designed to reliably elicit PIM has enabled research to be conducted on the nature and correlates of this type of visual disturbance. The present research aimed: 1) To develop a standard protocol for assessment of PIM and RSM; 2) to test the reliability of the i-Test in eliciting PIM in a student sample 3) to test the predictive relationship between dissociation and anxiety symptoms with PIM and RSM 4) to formulate and test a hypothesis regarding a mechanism underlying PIM. The first study screened 142 participants for RSM and PIM using self-administered questionnaires designed by Tym (personal communication, 2001). There was an unexpectedly high rate (54.2%) of PIM and RSM (37.3%) in the sample, which appeared to be the product of questionnaire design limitations. Two semi-structured interviews were developed and subsequently tested on a new sample of 50 participants in Study 2. Study 2 documented intra-rater and inter-rater reliability co-efficient of sufficient strength to indicate good reliability for the semi-structured interviews. The results of Study 2 indicate that PIM is a relatively stable symptom over a 30-minute and one-week test-retest time frame. / The onset time for PIM was relatively consistent between participants, with a mean latency of approximately 7 seconds. The oscillation rate of PIM was relatively consistent between individuals, with a mean average oscillation of approximately 0.8Hz. The third study tested a sample of 148 participants using the revised assessment protocols. The base rate for PIM (16.2%) and RSM (18.9%), and the concordance rates (46% to 54%) were slightly stronger than the Tym et al. (2000) community based study (33%). In addition to this, 11 other illusionary phenomena were documented, however none of these visual symptoms significantly correlated with RSM. The average oscillation rate is comparable to the rate documented in Study 2, further establishing the consistency of the reported rate of PIM oscillations between individuals. In Study 3, each participant was assessed for levels of dissociation (Dissociative Experiences Scale), somatic arousal (Mood and Anxiety Symptoms Questionnaire – Anxious Arousal Scale) and anxiety sensitivity (Anxiety Sensitivity Index). The results indicate that gender and dissociation significantly predict RSM status, and self-reported levels of anxious-arousal significantly predict PIM status. A multiway frequency analysis between the sub-components of RSM and PIM revealed that the physiological arousal inducing properties of the recurring memory is the only significant predictor of PIM. / The observed relationship between RSM and PIM may reflect the broader relationship between anxiety and dissociation. A pulsatile hypothesis was proposed as a feasible mechanism underlying PIM, due to the rhythmical nature of the visual disturbance, the range of the documented oscillations, and its specificity to psychological disorders characterised by cardiovascular sensitivities. All participants were administered the i-Test prior to and following aerobic exercise aimed at increasing pulse rate to 80% of maximum load. An increase in physical exertion significantly increased the latency of PIM onset, but did not impact on the rate of PIM. PIM rate appeared relatively consistent between individuals at 0.6Hz to 0.8Hz at the pre-exercise condition. Several participants who reported PIM also displayed obvious nystagmoid-like movements during the i-Test perceptual task. The role of eye-movements in PIM requires further investigation by future ophthalmological research. The final aim of Study 3 was to investigate the relationship between RSM/PIM and flicker sensitivity. Through the use of a Critical Flicker Frequency/Fusion task (CFF), each participant’s sensitivity to flicker was determined. In addition to detecting sensitivity thresholds, CFF is also considered to be a reliable indicator of the level of cortical arousal. / The results of this study suggest that individuals with RSM have a higher sensitivity to flicker than other participants, however there was a non-significant relationship between CFF and PIM. The lack of relationship between PIM and CFF may be due to issues concerning statistical power and effect-size. Future research is required to investigate this link in more detail. The overall results of this thesis suggest that i-Test elicited PIM is a reliable phenomenon that is associated with higher rates of traumatic memories when compared with persons who do not report this visual symptom. The strength of the association between RSM and PIM, however, does not support the use of the i-Test as a marker for the presence of RSM outside a clinical sample. The reliability of PIM as a phenomenon and its association with anxiety symptoms may be of theoretical importance in enabling future research to investigate the relationship between visual symptoms and anxiety-related pathology.

Thesis (Ph.D. (Town and Regional Planning))--North-West University, Potchefstroom Campus, 2008.

Much has been written about the desperate need to seek alternative solutions to the urban traffic congestion problems we face today. To manage these problems, three main streams of intervention have evolved from supply, demand and land-use management paradigms. Whilst their underlying measures all have the ability to reduce traffic congestion one way or another, little has been done to integrate the measures of each stream using a qualitative decision framework or process enabling the selection of site specific measures appropriate to local traffic and transport conditions. To this end the study reports the results of an empirical investigation by which a Multi-Criteria Analysis based Dynamic Adaptive Decision Framework (D.A.D.F.) were developed. This screens selected measures identifying those that have the potential to alleviate site specific road based traffic congestion. The product of the screening process is a set of sustainable measures transposed into an integrated strategy tailored to address local traffic congestion issues. Once the D.A.D.F. was developed, its usefulness and workability was tested by applying it to a case study. The case study results demonstrated that the D.A.D.F. is capable of producing integrated strategies with the ability to manage traffic congestion, encourage sustainable development and alleviate some site specific development challenges within the context of the study areas. Going beyond developing the decision framework, the study recommends positioning the D.A.D.F. within the South African planning system as part of a Traffic Congestion Management Plan (T.C.M.P.), setting out its likely components within the local context. It is concluded that the main innovation of the study is the development of the D.A.D.F., the T.C.M.P., the recommendations to situate both in the planning system and the comprehensive, but still transparent, approach undertaken to create integrated strategies for specific local conditions consisting of elements that work together to produce cumulative short to long term effects that attain a balanced set of environmental, social and economic goals - all imperative for sustainable development. / Thesis (Ph.D. (Town and Regional Planning))--North-West University, Potchefstroom Campus, 2008.

Much has been written about the desperate need to seek alternative solutions to the urban traffic congestion problems we face today. To manage these problems, three main streams of intervention have evolved from supply, demand and land-use management paradigms. Whilst their underlying measures all have the ability to reduce traffic congestion one way or another, little has been done to integrate the measures of each stream using a qualitative decision framework or process enabling the selection of site specific measures appropriate to local traffic and transport conditions. To this end the study reports the results of an empirical investigation by which a Multi-Criteria Analysis based Dynamic Adaptive Decision Framework (D.A.D.F.) were developed. This screens selected measures identifying those that have the potential to alleviate site specific road based traffic congestion. The product of the screening process is a set of sustainable measures transposed into an integrated strategy tailored to address local traffic congestion issues. Once the D.A.D.F. was developed, its usefulness and workability was tested by applying it to a case study. The case study results demonstrated that the D.A.D.F. is capable of producing integrated strategies with the ability to manage traffic congestion, encourage sustainable development and alleviate some site specific development challenges within the context of the study areas. Going beyond developing the decision framework, the study recommends positioning the D.A.D.F. within the South African planning system as part of a Traffic Congestion Management Plan (T.C.M.P.), setting out its likely components within the local context. It is concluded that the main innovation of the study is the development of the D.A.D.F., the T.C.M.P., the recommendations to situate both in the planning system and the comprehensive, but still transparent, approach undertaken to create integrated strategies for specific local conditions consisting of elements that work together to produce cumulative short to long term effects that attain a balanced set of environmental, social and economic goals - all imperative for sustainable development. / Thesis (Ph.D. (Town and Regional Planning))--North-West University, Potchefstroom Campus, 2008.

Det nutida samhället kännetecknas av en alltmer ökande förändringstakt där organisationer kontinuerligt behöver göra förändringar för att behålla konkurrenskraften på marknaden, vilket resulterat i att återkommande organisationsförändringar blivit ett vanligt inslag. Studiens syfte är att undersöka hur återkommande organisationsförändringar upplevs ur ett medarbetarperspektiv. Genom att besvara följande forskningsfrågor har syftet besvarats: Hur upplever anställda att arbetets krav påverkats av återkommande organisationsförändringar? Hur upplever anställda att deras kontroll över arbetssituationen påverkats av återkommande organisationsförändringar? Vilken betydelse har socialt stöd för den anställde vid återkommande organisationsförändringar? Metoden som använts är kvalitativ, där åtta semistrukturerade intervjuer genomförts med anställda inom ett telekombolag för insamling av empirin. De teorier som använts för analys av empirin är Karasek & Theorells krav-kontroll-stödmodell. Resultatet visar att de anställda upplever att deras arbetskrav har ökat samtidigt som deras kontroll och delaktighet minskat i samband med återkommande organisationsförändringar, och att det sociala stödet fyller en viktig funktion vid denna obalans. Ett förslag till förändring för den studerade organisationen är att avsätta tid och resurser för att skapa delaktighet, så att de anställda erhåller en jämnare balans mellan arbetskrav och kontroll. / The present society is characterized by an ever-increasing rate of change where organizations continually need to make changes to maintain market competitiveness, resulting in recurring organizational changes becoming a common feature. The purpose of this study is to investigate how recurrent organizational changes are perceived from an employee perspective. By answering the following research questions, the purpose has been answered: How do employees experience that the demands of the work have been affected by recurrent organizational changes? How do employees experience that their control over the work situation has been affected by recurrent organizational changes? What is the significance of social support for the employee during regular organizational changes? The method used is qualitative, where eight semi-structured interviews were conducted with employees within a telecom company for collecting the empirical data. The theories used for analyzing the empirical data are Karasek & Theorell's demand-control-support model. The result shows that employees feel that their work demands have increased while their control and participation has decreased in connection with recurrent organizational changes, and that social support fulfills an important function in this imbalance. A proposal for change for the studied organization is to set aside time and resources to create participation, so that employees receive a more even balance between work requirements and control.