Dissolutional voids in the subsurface were examined from three different viewpoints. First, analysis of pseudokarst features on San Salvador Island, Bahamas, uncovered the involvement of organics in the cementation and porosity generation process. This organic material was analyzed using SEM, TEM, and in thin section. While the actual role of organics in the cementation process could not be determined using these tools, the abundance of the material was documented. Holocene samples appear to have more organics than Pleistocene samples. The abundance of this material should have an effect on isotope analyses and needs to be considered in future work on meteoric cements and the environments where they form. Second, work on Mallorca Island, Spain, demonstrated how the placement and abundance of exposed caves could predict subsurface cave distributions. This work measured caves along exposed coastlines and in protected areas known as calas. Results found that caves within the calas have larger volumes and aerial footprints than caves on the exposed cliffs. The cave distributions showed that calas had to form prior to cave formation. Several paleo-slump features were observed and are believed to be the result of collapsed Tortonian flank margin caves, which were later inilled with Messinian sediments, using the caves as limited accommodation space, resulting in these sediment layers unaffected by the collapse further up section. Third, the current method of cave data manipulation to produce cave areal footprints and volume was found to be incorrect and in need of a calibration mechanism. This calibration was determined by reviewing how Compass cave mapping software generates volume estimates, using shapes of known volumes. Cave surveying techniques were also reviewed to determine if survey protocol affected volume outputs. Surveying in straight lines, down the center of a passage, avoiding splay shots, and taking left, right, up and down measurements (LRUDs) were found to generate the most accurate volumes estimates using Compass. These protocols were used to remap caves from paper maps to generate correction factors. Propriety software was used that could “shrink wrap” a 3D cave map rendering to produced values for cave volume and porosity and rock porosity.

A numerical study of axisymmetric synthetic jet flow was conducted. The synthetic jet cavity was modeled as a rigid chamber with a piston-like moving diaphragm at its bottom. The Shear-Stress-Transportation (SST) k-omega and #61559; turbulence model was employed to simulate turbulence. Based on time-mean analysis, three flow regimes were identified for typical synthetic jet flows. Typical vortex dynamics and flow patterns were analyzed. The effects of changes of working frequency, cavity geometry (aspect ratio), and nozzle geometry were investigated. A control-volume model of synthetic jet cavity was proposed based on the numerical study, which consists of two first-order ODEs. With appropriately selected parameters, the model was able to predict the cavity pressure and average velocity through the nozzle within 10% errors compared with full simulations. The cavity model can be used to generate the boundary conditions for synthetic jet simulations and the agreement to the full simulation results was good. The saving of computational cost is significant. It was found that synthetic jet impingement heat transfer outperforms conventional jet impingement heat transfer with equivalent average jet velocity. Normal jet impingement heat transfer using synthetic jet was investigated numerically too. The effects of changes of design and working parameters on local heat transfer on the impingement plate were investigated. Key flow structures and heat transfer characteristics were identified. At last, a parametric study of an active heat sink employing synthetic jet technology was conducted using Large Eddy Simulation (LES). Optimal design parameters were recommended base on the parametric study.

"Safety is a value, not just a Priority" Geomechanically stable underground excavations require continuous assessment of rock mass behavior for maximizing safety. Optimizing pillar design is essential for preventing hazardous incidents and improving production in room-and-pillar mines. Maintaining regional and global stability is complicated for underground carbonate or stone deposits, where extensive fracture networks and groundwater flow become leading factors for generating unsteady ground conditions including karsts. A sudden encounter with karst cavities during mine advance may lead to safety issues, including ground collapse and outflow of unconsolidated sediments and groundwater. The presence of these eroded zones in pillars may cause their failure and poses a risk to the lives of miners apart from disrupting the pre-planned mining operations. A pervasive presence of joints and fractures plays a primary role in promoting structurally controlled failures in stone mines, which accelerates upon interaction with the karst cavities. The prevalent empirical and analytical approaches for pillar design ignore the geotechnical complexities such as the spatial density of discontinuities, karst voids, and deviation from the design during short-range mine planning. With the increasing market demand for limestone products, mining organizations, as well as enforcement agencies, are investing in research for increasing the efficiency of extracting valuable resources. While economical productivity is essential, preventing risks and ensuring the safety of miners remains the cardinal objective of mining operations. According to the Mine Safety and Health Administration (MSHA), since 2000, about 31% of occupational fatalities at all underground mines in the United States are caused due to ground collapse, which rises to 39% for underground stone mines. The objective of this study is to provide a reliable and methodological approach for pillar design in underground room-and-pillar hard rock mines for safe and efficient ore recovery. The numerical modeling techniques, implemented for a case study stone mine, could provide a pragmatic framework to assess the effect of karsts on rock mass behavior, and design future pillars detected with voids. The research uses data acquired from using remote sensing techniques, such as LiDAR and Ground-penetrating Radar surveys, to map the excavation characteristics. Discontinuum modeling was valuable for analyzing the pillar strength in the presence of discontinuities and cavities, as well as estimating a safe design standard. Discrete Fracture Networks, created using statistical information from discontinuity mapping, were employed to simulate the joints pervading the rock mass. This proposed research includes the calibration of rock mass properties to translate the effect of discontinuities to continuum models. Continuum modeling proved effective in analyzing regional stability along with characterizing the redistributed stress regime by imitating the excavation sequence. The results from pillar-scale and local-scale analyses are converged to optimize pillar design on a global scale and estimate the feasibility of secondary recovery in stone mines with a dominating discontinuity network and karst terrane. Stochastic analysis using finite volume modeling helped evaluate the performance of modified pillars to assist production while maintaining safety standards. The proposed research is valuable for improving future design parameters, excavation practices, and maintaining a balance between an approach towards increased safety while enhancing production. / Doctor of Philosophy / "The most valuable resource to come back out of a mine is a miner" – Anonymous. The United States accounted for 27% of the global limestone market share which was valued at US$58.5 billion in 2020 [148]. It is projected to reach a target of US$65.3 billion in 2027, growing even in midst of the COVID-19. As surface reserves deplete, much of the mineral demand gap is supplemented by mining underground deposits. Underground mines extract minerals from deep within the earth compared to surface mines. As a result, the miners experience a greater number of accidents in a constricted environment because of roof/tunnel collapse, fewer escape routes, ventilation, explosions, or inundation. According to the Mine Safety and Health Administration (MSHA), about 15% of all underground mine injuries in the US were caused by rockfalls since 1983. The majority of underground stone deposits are mined using the room-and-pillar mining method, which resembles a chessboard design where the light squares are mined, and the dark squares are left as rock pillars to support the tunnels. Limestone, a carbonate rock, contains a lot of fractures and joints (discontinuities). Erosion of rocks due to continuous water flow through the fractures leads to the formation of cavities known as karsts. Interaction of karsts with the prevalent fracture network increases rockfall risk during mining. The collapse of voids along with an inrush of filled rock-clay-water sludge can harm miners' lives, damage machinery, and stop further operations. Literature is scarce on topics that quantify the risk and disruption posed by these cavities in underground mines. Most rock classification systems cannot classify their effect because of the unpredictability and extensive analysis required. The objective of this research is to provide a reliable and methodological approach for designing pillars in underground hard rock mines for ensuring a safe working environment and efficient mineral recovery. This research starts with analyzing the strength of pillars, in which karst cavities were discovered while mining. The safety concerns often lead the miners to not excavate around the cavities and leave valuable resources unmined. Data from ground-penetrating radar and laser scanning surveys were used to characterize the voids and map the discontinuities. Discrete-element numerical modeling was used to simulate the pillars as an assembly of blocks jointed by the discontinuities. The simulation results help us understand the instability issues in the karst-ridden pillars and ways to improve upon the existing design. The findings were used to modulate the parameters for regional-scale models using finite volume modeling for less computationally intensive analyses and simulating rock as a continuum. The continuum models were highly effective in analyzing the instability issues due to the prevalent karstic network. This helps understand any alternative scenario that could have been implemented to optimize ore recovery while preventing risks. The results from the single pillar and regional analyses are combined to optimize pillar design on a global mine scale. This dissertation focuses on improving hazard mitigation in mines with unpredicted anomalies like karsts. Although this research is based on a specific mine site, it empowers the operators to explore the presented techniques to increase safety in all underground mines. The suggested methodology will help devise better strategies for handling instability issues without jeopardizing the mine operations. The primary motivation is to keep the underground miners safe from hazardous situations while fulfilling the secondary objective of maximizing mineral production.

Accurate information about tree volume in tropical vegetation formations is critical for the identification of potential areas for sustainable timber production, carbon estimation and biodiversity conservation. Difficult access and the cost of obtaining a large number of samples needed for accurate wood volume and biomass determination are often barriers for carrying out inventories and studies in natural forests in Brazil. Therefore, the development of more efficient techniques of mensuration in tropical forests is an important mechanism for conservation, management and production advancement. The main purposes of this thesis are: introducing a new method for quantifying vertical and horizontal structures by using principal component analysis (PCA); developing two different approaches of volume modeling, one based on DBH and another based on crown area; proposing a new taper equation for native vegetation in three different formations; and estimating upper section diameters to become the geometric form method useful in natural vegetation in Brazil and reducing dependence on destructive measurements. / Informações corretas sobre o volume de árvores em formações de vegetação natural são fundamentais para a identificação de áreas potenciais para produção madeireira sustentável, estimativa de carbono e conservação da biodiversidade. Dificuldade de acesso e altos custos na obtenção de amostras necessárias para estimativas precisas de volume e biomassa são barreiras frequentes na condução de inventários e estudos florestais no Brasil. Dessa forma, o desenvolvimento de técnicas mais eficientes de mensuração em florestas tropicais é um importante mecanismo para o avanço da conservação, manejo e produção. Os principais objetivos deste trabalho foram: introduzir um novo método de quantificação das estruturas vertical e horizontal por meio do uso de análise de componentes principais (ACP); desenvolver modelos volumétricos baseados em DAP e modelos baseados em área de copa; propor uma nova função de afilamento aplicada a três diferentes formações vegetais; e estimar alturas em que deverão ter diâmetros medidos ao longo da árvore para tornar o método geométrico útil em formações naturais no Brasil, e reduzindo a necessidade de mensurações que requerem o abatimento das árvores.

Accurate information about tree volume in tropical vegetation formations is critical for the identification of potential areas for sustainable timber production, carbon estimation and biodiversity conservation. Difficult access and the cost of obtaining a large number of samples needed for accurate wood volume and biomass determination are often barriers for carrying out inventories and studies in natural forests in Brazil. Therefore, the development of more efficient techniques of mensuration in tropical forests is an important mechanism for conservation, management and production advancement. The main purposes of this thesis are: introducing a new method for quantifying vertical and horizontal structures by using principal component analysis (PCA); developing two different approaches of volume modeling, one based on DBH and another based on crown area; proposing a new taper equation for native vegetation in three different formations; and estimating upper section diameters to become the geometric form method useful in natural vegetation in Brazil and reducing dependence on destructive measurements. / Informações corretas sobre o volume de árvores em formações de vegetação natural são fundamentais para a identificação de áreas potenciais para produção madeireira sustentável, estimativa de carbono e conservação da biodiversidade. Dificuldade de acesso e altos custos na obtenção de amostras necessárias para estimativas precisas de volume e biomassa são barreiras frequentes na condução de inventários e estudos florestais no Brasil. Dessa forma, o desenvolvimento de técnicas mais eficientes de mensuração em florestas tropicais é um importante mecanismo para o avanço da conservação, manejo e produção. Os principais objetivos deste trabalho foram: introduzir um novo método de quantificação das estruturas vertical e horizontal por meio do uso de análise de componentes principais (ACP); desenvolver modelos volumétricos baseados em DAP e modelos baseados em área de copa; propor uma nova função de afilamento aplicada a três diferentes formações vegetais; e estimar alturas em que deverão ter diâmetros medidos ao longo da árvore para tornar o método geométrico útil em formações naturais no Brasil, e reduzindo a necessidade de mensurações que requerem o abatimento das árvores.

The objective of this report is to carry out a pre-study and develop a framework for how the liquidity and interest rate risk of a bank's demand deposits can be modeled. This is done by first calibrating a Vasicek short rate model and then deriving models for the bank's deposit volume and deposit rate using multiple regression. The volume model and the deposit rate model are used to determine the liquidity and interest rate risk, which is done separately. The liquidity risk is determined by a liquidity quantile which estimates the minimum deposit volume that is expected to remain in the bank over a given time period. The interest rate risk is quantified by an arbitrage-free valuation of the demand deposit which can be used to determine the sensitivity of the net present value of the demand deposit caused by a parallel shift in the market rates. Furthermore, an immunization and a replicating portfolio are constructed and the performances of these are tested when introducing the same parallel shifts in the market rates as in the valuation of the demand deposit. The conclusion of this thesis is that the framework for the liquidity risk management that is developed gave satisfactory results and could be used by the bank if the deposit volume is estimated on representative data and a more accurate model for the short rate is used. The interest rate risk framework did however not yield as reliable results and would be more challenging to implement as a more advanced model for the deposit rate is required. / Målet med denna rapport är att utveckla ett ramverk för att bestämma likviditets-och ränterisken som är relaterad till en banks inlåningsvolym. Detta görs genom att först ta fram en modell för korträntan via kalibrering av en Vasicek modell. Därefter utvecklas, genom multipelregression, modeller för att beskriva bankens inlåningsvolym och inlåningsränta. Dessa modeller används för att kvantifiera likviditets- och ränterisken för inlånings-volymen, vilka beräknas och presenteras separat. Likviditetsrisken bestäms genom att en likviditetskvantil tas fram, vilken estimerar den minimala inlånings-volymen som förväntas kvarstå hos banken över en given tidsperiod. Ränterisken kvantifieras med en arbitragefri värdering av inlåningen och resultatet används för att bestämma känsligheten för hur nuvärdet av inlåningsvolymen påverkas av ett parallellskifte. Utöver detta bestäms en immuniseringsportfölj samt en rep-likerande portfölj och resultatet av dessa utvärderas mot hur nuvärdet förändras givet att samma parallellskifte i ränteläget som tidigare introduceras. Slutsatsen av projektet är att det framtagna ramverket för att bestämma likviditetsrisken för inlåningen gav bra resultat och skulle kunna implementeras i dagsläget av banken, förutsatt att volymmodellen estimeras på representativ data samt att en bättre modell för korträntan används. Ramverket för att bestämma ränterisken gav dock inte lika tillförlitliga resultat och är mer utmanande att implementera då en mer avancerad modell för inlåningsräntan krävs.