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(2019)ThesisThe main aim of this thesis is to report work done to improve the imaging performance of Atomic Force Microscopes (AFMs). According to this purpose, a data-driven controller is designed using the frequency response data from the capacitive sensors of an AFM. Using an optimization process, the frequency response of the controller is obtained. An input-output error minimization method is considered while forming the optimization norm. The closed-loop stability of the AFM system is guaranteed by using negative-imaginary theory and small-gain theory based constraints. The proposed controller provides significant damping of resonant peaks on both X and Y-axes of the Piezo Tube Scanner (PTS). Conventional raster and spiral tracking performance of the controller are compared to the open-loop tracking. Moreover, the better performance of the designed data-driven controller is obtained compared to the AFM's built-in PI controller. Finally, high speed spiral images are generated by using this proposed controller which shows improved imaging performance of the AFM at high scanning frequencies.
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(2019)ThesisIn Bangladesh, around 30% of the entire population lack the capacity to cope with environmental disasters due to their social and economic disadvantage. This impedes the Nation’s progress towards achieving millennium development goals. The current study, therefore, devises a framework for mapping disaster risk-levels and determining risk management capacity of marginal coastal communities. The novelty of this work is the establishment of a connection between risk management capacity of coastal communities and their living standards. Risk assessments for environmental disasters in the coastal region of Bangladesh have been typically restricted to the analysis of a single hazard or solely to the attributes of vulnerability, which might underestimate the risk level. The current study adopted a heuristic approach to address these incongruities and provide a preliminary insight into risk within a clearly defined coastal sub-district of southwestern Bangladesh. The current method of risk mapping is a parsimonious approach that is inexpensive to conduct and requires limited data input, hence, effective for countries like Bangladesh with a dearth of data sources. The map delineated 21% of the study area as being at very high-risk, 20% at high, 21% at moderate, 20% at low, and 18% at very low risk. This variation is attributable to the variations in the intensity of environmental threats, extent of sensitivity and degree of exposure idiosyncratic to the geographic and socio-demographic features of the corresponding areas. Communities within high-risk areas were then chosen for field study, that comprised of 70 household surveys, 2 focus group discussions and 5 key informant interviews, to gauge their risk management capacity. The surveys revealed a wide range of natural, built and social assets on which people rely for their livelihoods and in the event of disasters. Qualitative analysis identified that the greatest potential for disaster risk reduction comes through the best possible utilization of resources. Quantitative analysis of survey data further established that incrementally improving livelihoodswill correspondingly reduce disaster risk among disadvantaged communities. The outcome is expected to be an invaluable tool for targeting disaster risk reduction and community development concurrently, within the context of integrated coastal zone management.