Mathematical modelling was utilized to evaluate trichloroethylene (TCE) and tetrachloroethylene (PCE) dense non-aqueous phase liquid (DNAPL) source zone remediation in the subsurface environment. Semi-analytical solutions were derived, tested, and employed to evaluate the benefits of source zone concentration reduction and solute degradation mechanisms on the evolution of plumes in porous media and fractured rock domains. Simulations of treatment in complex DNAPL source zones using different remedial technologies were completed with a numerical model that was developed, tested, calibrated, and applied to nine idealized heterogeneous porous media sites. Analytical modelling revealed that, in domains dominated by matrix diffusion, aggressive and moderate source zone concentration reduction may have similar effects on the leading edge of the plume. The tailing (near source) edge of the plume may be more responsive to aggressive concentration reduction, particularly when diffusion processes are negligible. Both the near-field (near-source) and far-field plume responses were strongly influenced by the matrix decay half-life for both transient and steady-state conditions. The degradative capacity of the matrix largely dictated plume extent and life-span for the fractured bedrock site considered here. Numerical simulations of in situ source zone treatment with chemical oxidation (ISCO), enhanced bioremediation (ISEB), and surfactants (SEAR) were compared and contrasted. Treatment efficacy was site specific, with benefits observed at some sites, and detrimental impacts observed at others. Each technology demonstrated some degree of performance enhancement relative to dissolution only (no treatment). The maximum DNAPL mass depletion enhancement factors for ISCO, ISEB and SEAR, were 1.44, 2.91, and 2.70 after 10 years, respectively. Similarly, the maximum boundary mass flux enhancement factors for ISCO, ISEB and SEAR were 9.78, 3.32, and 3.97, respectively. While notable enhancements were observed for many sites during active treatment, the long-term performance of pre-maturely terminated ISCO and ISEB, and to a lesser degree SEAR, was similar to dissolution. Overall, the partial depletion of DNAPL mass from source zones produced on-going persistent boundary mass flux signatures. Only the complete removal of DNAPL mass, which was attained for one site with SEAR, successfully eliminated downgradient boundary mass flux. / Thesis (Ph.D, Civil Engineering) -- Queen's University, 2009-05-21 08:55:04.491

In the last decade, a new wave of socio-technical cyber threats has emerged that is targeting both the technical and social vulnerabilities of organizations and requires fast and efficient threat mitigations. Yet, it is still common that financial organizations rely on yearly reviewed risk management methodologies that are slow and static to mitigate the ever-changing cyber threats. The purpose of this research is to explore the field of Dynamic Risk Management in Information Security from a socio-technical perspective in order to mitigate both types of threats faster and dynamically to better suit the connected world we live in today. In this study, the Design Science Research methodology was utilized to create a Dynamic Information Security Risk Management model based on functionality requirements collected through interviews with professionals in the financial sector and structured literature studies. Finally, the constructed dynamic model was then evaluated in terms of its functionality and usability. The results of the evaluation showed that the finalized dynamic risk management model has great potential to mitigate both social and technical cyber threats in a dynamic fashion. / Under senaste decenniet har en ny våg av sociotekniska cyberhot uppkommit som är riktade både mot de sociala och tekniska sårbarheterna hos organisationer. Dessa hot kräver snabba och effektiva hotreduceringar, dock är det fortfarande vanligt att finansiella organisationer förlitar sig på årligen granskade riskhanteringsmetoder som både är långsamma och statiska för att mildra de ständigt föränderliga cyberhoten. Syftet med denna forskning är att undersöka området för dynamisk riskhantering inom informationssäkerhet ur ett sociotekniskt perspektiv, med målsättningen att snabbare och dynamiskt kunna mildra bägge typerna av hot för att bättre passa dagens uppkopplade värld.  I studien användes Design Science Research för att skapa en dynamisk riskhanteringsmodell med syfte att hantera sociotekniska cyberhot mot informationssäkerheten. Riskhanteringsmodellen är baserad på funktionskrav insamlade genom intervjuer med yrkesverksamma inom finanssektorn, samt strukturerade litteraturstudier.  Avslutningsvis utvärderades den konstruerade dynamiska modellen avseende dess funktionalitet och användbarhet. Resultaten av utvärderingen påvisade att den slutgiltiga dynamiska riskhanteringsmodellen har en stor potential att mitigera både sociala och tekniska cyberhot på ett dynamiskt sätt.