Thesis (M.S. in Applied Science (Operations Research))--Naval Postgraduate School, June 2004. / Thesis advisor(s): Susan M. Sanchez. Includes bibliographical references (p. 79-80). Also available online.

Thesis--Ph. D., University of Hong Kong. / Contents: v.1. Text.- v.2. Appendices. Typewritten.

Thesis--M. Sc.(Eng.)--University of Hong Kong. / Mimeographed.

Thesis (Ph.D.)--University of Central Florida, 2009. / Adviser: Michael Proctor. Includes bibliographical references (p. 187-191).

Interference is fundamental to wireless networks. It is hard to achieve good performance when design routing metrics or algorithms without taking it into account. We study interference in wireless networks through empirical experiments and simulations. We find out that current routing protocols face difficulties in effectively managing it, which can lead to severe problems. For instance, a simple network of two links with one flow is vulnerable to severe performance degradation if interference is not properly accounted for. Motivated by these observations, we develop a simple and effective model to capture effects of interference in a wireless network. Different from the existing interference models, our model captures IEEE 802.11 DCF under both homogeneous and heterogeneous traffic and link characteristics, and is simple enough to be directly used as a basic building block for wireless performance optimization. Based on thismodel, we develop optimization algorithms for several objectives, such as network throughput and fairness. Given traffic demands as input, these algorithms compute rates at which individual flows must send to achieve these objectives. We implement these algorithms in Qualnet simulations and 19-node testbed. Our experiment and simulation results show that our methods can systematically account for and control interference to achieve good performance. More specifically, when optimizing fairness, our methods can achieve almost perfect fairness; when optimizing network throughput, they can lead to 100-200% improvement for UDP traffic and 10-50% for TCP traffic. / text

Crisis management in law enforcement context is considered to be a kind of Naturalistic Decision-making (NDM), which is hard to acquire due to the ill-structured, non-determined nature of crisis is also a challenge. Crisis either natural or man-made comes in all forms and degree of intensity. In a NDM situation, the crisis management personnel are usually anticipated in a dynamic environment of high level stress and uncertainty. Therefore, each critical incident is different; it can neither be treated identically nor pre-determined. In addition, crisis management is a small group activity that involves a number of parties or roles at different geographic locations. Groupthink is a term coined by psychologist (Janis, 1972), Groupthink victims ignore alternatives and tend to make irrational decisions in facing crises. The literature review finds that group think tendency is high for crisis management, especially in law enforcement agencies. In fact, the danger of groupthink is the most serious threat to good decision-making for effective crisis management. There are two sets of research questions for this study. The first set comprises three research questions on how the design features of an online role play simulation affect the effectiveness of crisis management training in a law enforcement context. The research focuses on three aspects: storytelling, use of multimedia and recording facilities. The second set comprises two research questions on whether and how the use of an online role play simulation affects trainees’ learning and understanding of groupthink tendency. Many researchers suggest that role play simulation (RPS) is a suitable tool for crisis management training for the realisation of collaboration and authentic situation awareness. In this paper, a case study of crisis management training in the context of law enforcement using online RPS is illustrated. By using Bales' Interaction Process Analysis (IPA) method, the interactions of participants in training are observed and categorised. The results show that using online role play simulation in crisis management training has positive effect on the reduction of Groupthink tendency. The existing groupthink research is mainly based on content analysis of retrospective data, and information or empirical observations gathered in laboratory settings. Very often, only a partial model is examined. Therefore, online role play simulations can be a new method to groupthink research. Since online role play simulations can provide a holistic scenario for the crisis management exercise. As such, the whole crisis process can be visualised by researchers and facilitators. Finally, the groupthink tendency can be observed, recorded and analysed. In fact, due to the complexity of the groupthink model, many researchers can only focus on partial or several variables of the whole process in their studies. This study provides a ground work on online role play simulation research with an application on crisis management training. Design-based Research (DBR) is adopted in this study and this methodology is new to this kind of research. DBR is proved to be a suitable methodology as researcher can improve and generate evidence-based claims about learning through iterations of refinement. In addition, this study also shows that online role play simulation can be a research tool for the holistic study of groupthink. / published_or_final_version / Education / Doctoral / Doctor of Education

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Current research on thermal effects on guideways has addressed many aspects of the behavior of guideways using two-dimensional models. The two-dimensional models are acceptable for existing guideway designs, in which cross sectional shapes are uniform along the length of the guideway. However, three-dimensional models are necessary for a modular design, in which the track structures that interact with Maglev vehicles are made separately and are assembled into the support structure, and in which the cross sectional shapes are not uniform. A three-dimensional numerical model of the thermal environment, in which the effect of partial shading is taken into account, is implemented for the study of guideway behavior under various thermal environments. The numerical model of the thermal environment is calibrated to the experimental results under the thermal environment at Austin, Texas, and is extrapolated to predict the behaviors of guideways under the thermal environment in Las Vegas, Nevada, which is one of the candidate sites for the implementation and deployment of the high speed Maglev transportation system. This study addresses the suitability of a modular steel guideway design under such a thermal environment. Characteristics of the behavior of guideways under various thermal environments are identified, and the behavior of guideways under the effect of partial shading is summarized. / text