• Application of wicking fabric to reduce damage in Alaskan pavements

      Presler, Wendy A.; Zhang, Xiong; Liu, Juanyu; Shur, Yuri; Connor, Billy (2016-05)
      Beaver Slide is located near kilometer 177.8 (mile 110.5) on the Dalton Highway. The road is sloped downhill when heading north. The road gradient is approximately 11%, and the road prism is on a side hill. Each year, soft spots usually appear in the pavement structure in late April and remain all summer. These soft spots have been called “frost boils”. The “frost boils” have resulted in extremely unsafe driving conditions and frequent accident occurrences. Conventional repair methods have not worked. A newly developed geosynthetic wicking fabric was installed in the road structure in August 2010. The fabric has a high specific surface area (consequently high wettability and high capillary action) and high directional permittivity. Test results over the initial two year period proved the effectiveness of the wicking fabric to mitigate “frost boils” and the subsequent road softening issue. Data collected during the past four years were analyzed to evaluate the long-term performance of the wicking fabric. A scanning electron microscope (SEM) was used to explore the interaction between the wicking fabric and in situ soils, and to determine the condition of the fabric five years after installation.
    • Approximate bayesian computation for probabilistic decline curve analysis in unconventional reservoirs

      Paryani, Mohit; Ahmadi, Mohabbat; Hanks, Catherine; Awoleke, Obadare (2015-12)
      Predicting the production rate and ultimate production of shale resource plays is critical in order to determine if development is economical. In the absence of production from the Shublik Shale, Alaska, Arps' decline model and other newly proposed decline models were used to analyze production data from oil producing wells in the Eagle Ford Shale, Texas. It was found that shales violated assumptions used in Arps' model for conventional hydrocarbon accumulations. Newly proposed models fit the past production data to varying degrees, with the Logistic Growth Analysis (LGA) and Power Law Exponential (PLE) models making the most conservative predictions and those of Duong's model falling in between LGA and PLE. Using a regression coefficient cutoff of 95%, we see that the LGA model fits the production data (both rate and cumulative) from 81 of the 100 wells analyzed. Arps' hyperbolic and the LGA equation provided the most optimistic and pessimistic reserve estimates, respectively. The second part of this study investigates how the choice of residual function affects the estimation of model parameters and consequent remaining well life and reserves. Results suggest that using logarithmic rate residuals maximized the likelihood of Arps' equation having bounded estimates of reserves. We saw that approximately 75% of the well histories that were fitted using the logarithmic rate residual had hyperbolic b-values < 1, as opposed to 40% using the least squares error function--an 87.5% increase. This is because they allow the most recent production data to be weighted more heavily, thereby ensuring that the fitted parameters reflect the current flow regime in the drainage area of the wells. In the third part of this work, in order to quantify the uncertainty associated with Decline Curve Analysis (DCA) models, a methodology was developed that integrated DCA models with an approximate Bayesian probabilistic method based on rejection sampling. The proposed Bayesian model was tested by history matching the simulation results with the observed production data of 100 gas wells from the Barnett Shale and 21 oil wells from the Eagle Ford Shale. For example, in Karnes County, the ABC P90-P50-P10 average interval per well was 170-184-204 MSTB, while the true average cumulative production per well was 183 MSTB. The ABC methodology coupled with any deterministic DCA model will help in long-term planning of operations necessary for optimal/effective field development.
    • Assessing the fate of crude oil in Arctic coastline sediments: effect of exposure time and sediment structure

      Iverson, Anna Christine; Schiewer, Silke; Perkins, Robert; Barnes, David (2015-08)
      The research presented in this thesis will allow for a better understanding of how crude oil interacts with the shoreline. Offshore oil production along Alaska's arctic coast is expected to increase in coming years. While this is likely to create large economic benefits for the state, crude oil spills may occur. An oil spill may reach the shoreline, where it could create adverse short and long-term ecological effects. Mass transfer processes, affected by sediment characteristics, play an important role in determining the fate of crude oil along shorelines. Crude oil viscosity and diffusion are strongly temperature dependent. Nutrients, commonly added to stimulate bioremediation, may be washed out with waves and tides. It is therefore necessary to study how factors such as the beach matrix, nutrient addition and temperature affect hydrocarbon distribution. Laboratory experiments were implemented to help better understand how the soil composition and tidal action will affect the oil's movement through the shoreline sediments. Experiments were conducted for two different sediment types (sandy-gravel versus pebble) obtained from Barrow, AK and two different temperatures (20° and 3° Celsius). A microcosm study using a PVC pipe set-up was used to simulate the transport of oil through the sediment profile. Data obtained from this study show that the amount of pooling and its location was dependent on sediment structure. In sandy gravel sediment, Total petroleum hydrocarbons (TPH) persisted 6 inches below the surface, indicating pooling does occur. In pebble sediment, TPH persisted at the top and bottom of the column, but only for the first few days, indicating the pooling would not be a long term problem. Both sediments had higher CO₂ production at higher temperatures, with the highest respiration, i.e. more biodegradation, found in sandy-gravel. While CO₂ releases were slightly higher in sediments with the addition of fertilizer, overall the application of fertilizer did not have a significant impact on the fate of crude oil in shoreline sediments.
    • Assessing the potential of Salix alaxensis for the rhizoremediation of diesel contaminated soil

      Starsman, Jessica; Leigh, Mary Beth; Schiewer, Silke; Schnabel, William (2016-08)
      Alaska has over 280 remote communities that rely on diesel as their main source of heat; as a result, there have been multiple diesel spills across the state. Research has shown that plants are able to assist in the degradation of diesel through rhizoremediation, relying on the interaction between microorganisms, plant roots, and other components of the soil environment. Greater attention is now being given to the potential role of secondary plant compounds released during fine root turnover and the stimulatory effects they may have on the rhizoremediation process. For this study the native plant species, Salix alaxensis (felt leaf willow) was chosen. Fine root turnover in the sub-Arctic was mimicked through a microcosm study performed with sub-Arctic soil contaminated with weathered and fresh diesel, incubated at 4 °C and 20 °C. The effect of adding crushed willow roots was compared against addition of pure salicylic acid, a secondary plant compound found in the salicaceae family, and/or addition of fertilizer. Results showed that the addition of crushed fine willow roots with or without fertilizer increased diesel loss. Overall, greater loss and higher respiration occurred at 20 °C. The addition of salicylic acid with or without fertilizer increased soil toxicity. Toxicity may have been the result of observed phenol production and/or fungal growth. Findings show promise for the use of Salix alaxensis for the rhizoremediation of diesel contaminated soils in the sub-Arctic.
    • Assessment of contaminant concentrations and transport pathways in rural Alaska communities' solid waste and wastewater sites

      Mutter, Edda Andrea; Schnabel, William; Barnes, David; Duddleston, Khrys; Duffy, Lawrence; Hagedorn, Birgit (2014-05)
      Waste management practices currently employed in many rural Alaska communities are potentially contributing to human and environmental health impacts, and this problem may be exacerbated with the anticipated warming climate. For rural communities, factors that contribute to insufficient waste management practices include climate and environmental conditions, limitation of federal and state capital funding for construction, and the continuing financial burden associated with providing adequate operations and maintenance. As a response, federal regulatory exemptions are granted for construction and design of solid waste sites and limited state regulations are in place for wastewater discharge criteria. Due to the absence of proper site assessment and monitoring, very little is known about the fate and transport of point source pollutants arising from these wastewater and solid waste sites. Moreover, these fate and transport processes may be susceptible to changes resulting from human activity or a warming climate. Thus, this knowledge gap associated with waste-related pollutants in rural Alaska could obscure potential threats to human and environmental health by concealing impacts to freshwater systems. This research was intended to achieve a better understanding of rural Alaska waste leachate compositions by evaluating contaminant prevalence and diversity, quantifying contaminant concentration levels, and evaluating their potential migration into nearby freshwater systems. Over the course of three years, waste sites at five rural Alaska communities were sampled and tested for heavy metals, organic constituents, and microbial indicator organisms. The purpose of the analysis was to evaluate the impact of waste sites on soil, surface, and subsurface waters in the vicinity of the sites. The resulting findings are assembled into three chapters describing 1) the assessment of heavy metal leachate in rural Alaska solid waste sites, 2) the identification of new emerging organic pollutants in rural Alaska waste sites, and 3) the partitioning and transport behavior of pathogen indicator organisms in cold regions. The research outcome of E.coli and Enterococcus sp. were observed in waste impacted water and soil samples, heavy metal migration into nearby freshwaters, and pharmaceuticals, phthalates, and benzotriazole in waste impacted water samples. The research findings highlight the need to apply state regulations to remove potentially hazardous components from rural Alaska wastewater and municipal solid waste streams. Additionally, there is a need to establish effective solid waste and wastewater leachate monitoring and assessment strategies for active and closed rural Alaska waste sites.
    • Assessment of formation damage from drilling fluids dynamic filtration in gas hydrate reservoirs of the North Slope of Alaska

      Kerkar, Prasad B.; Patil, Shirish L.; Chukwu, Godwin A.; Dandekar, Abhijit Y.; Khataniar, Santanu (2005-08)
      Gas hydrates in the Alaska North Slope, with a potential of 590 TCF gas-in-place near existing infrastructures of Prudhoe Bay, Kuparuk River and Milne Point Units, have sparked interest among unconventional energy experts. Drilling through gas hydrates has always been critical as a source of heat into the formation, leading to dissociation of hydrates. Moreover, the recent drive toward open hole completions and highly deviated or horizontal wells have emphasized the need for evaluation of drilling or completion fluids suitability from a perspective of formation damage. A significant decrease in well productivity near the well-bore can occur due to the invasion of fine solids from drilling fluids, forming external and internal filter cake under dynamic conditions. An experimental setup for the evaluation of formation damage at in-situ conditions was designed. The dynamic filtration experiments were conducted with Berea sandstone cores. The absolute permeability was measured both before and after the drilling fluid circulation. The drilling fluid type, its flow rate, and shear rate, effective particle size, additive concentration, and amount of overbalance were found to influence drilling mud leak-off volume and the post mud circulation permeability.
    • An assessment of suspended sediment transport in Arctic Alaskan rivers

      Lamb, Erica K.; Toniolo, Horacio; Schnabel, William; Kane, Douglas (2013-05)
      Provided here is an initial assessment of suspended sediment transport in several rivers on the North Slope of Alaska. This study was divided into two parts: the Umiat project, which involved the Chandler, Anaktuvuk and Itkillik Rivers, and the NPR-A study, which considered Prince, Seabee and Fish Creeks, as well as a brief look at the lkpikpuk River, Otuk Creek, Judy Creek and the Ublutuoch River. Methods used included depth-integrated suspended sediment samples, grab samples, automatic pump-style samplers, discharge measurements, bed sediment grain size analysis and the inclusion of a variety of meteorological measurements from other projects. With slightly less than two years of data collection from May 2011 to September 2012, an initial analysis was completed. Suspended sediment rating curves developed for the Anaktuvuk and Chandler Rivers over the two-year study period revealed a strong correlation between suspended sediment concentration (SSC) and discharge. The most data was collected for the Anaktuvuk and Chandler Rivers; on these rivers, suspended sediment discharge was also analyzed, showing that over 90% of suspended sediment transport occurred during the spring melt period in 2011. Spring melt was not measured in 2012, so analysis was only completed for 2011.
    • Assessment of tight gas sands in Cook Inlet Basin

      Patel, Kanhaiyalal U.; Ogbe, David O.; Zhu, Tao; Patil, Shirish L. (2005-05)
      The Cook Inlet Basin is the source for all of the natural gas used in south-central Alaska. The estimated ultimate recovery from existing Cook Inlet gas fields is approximately 8.5 trillion cubic feet (tcf) and the proven reserves remaining on January 1, 2004 were 1.8 tcf. It will be difficult to meet the peak demand for gas in south-central Alaska after 2009. Cook Inlet Basin contains vast quantities of unconventional gas resources in tight sands. Resources-in-place and producible gas reserves from the tight sands are unknown. It is likely that these tight sands will be developed as additional gas reserves and will be produced along with the high permeability conventional gas reserves in order to meet both local and export demands. The objectives of this study are to quantify the distribution of tight gas sands; to estimate the resources in place and producible gas reserves in the Cook Inlet Basin; and to predict the post-stimulation gas production. Rate transient analysis, well log analysis and reservoir stimulation analysis were therefore conducted on selected key tight sand wells. Results indicate that the tight gas can play an important role in meeting south-central Alaska's gas demand beyond 2009.
    • Attitude determination for small satellites using gps signal-to-noise ratio

      Peters, Daniel; Raskovic, Dejan; Hawkins, Joseph; Thorsen, Denise (2014-05)
      An embedded system for GPS-based attitude determination (AD) using signal-to-noise (SNR) measurements was developed for CubeSat applications. The design serves as an evaluation testbed for conducting ground based experiments using various computational methods and antenna types to determine the optimum AD accuracy. Raw GPS data is also stored to non-volatile memory for downloading and post analysis. Two low-power microcontrollers are used for processing and to display information on a graphic screen for real-time performance evaluations. A new parallel inter-processor communication protocol was developed that is faster and uses less power than existing standard protocols. A shorted annular patch (SAP) antenna was fabricated for the initial ground-based AD experiments with the testbed. Static AD estimations with RMS errors in the range of 2.5° to 4.8° were achieved over a range of off-zenith attitudes.
    • Automated processing system for tidal analysis of MF radar winds

      Vemula, Sreenivas (2005-12)
      The medium frequency (MF) radar at Platteville, Colorado (40.18° N, 104.7° W) is used to estimate the zonal and meridional wind motions in the middle atmosphere. This radar has been in operation since January 2000. We currently have four years of wind estimates sampled every five minutes. An automated processing system has been developed in IDL to process these estimates and obtain the monthly mean winds and tidal parameters. The automated processing currently processes the wind estimates in time domain analysis using a least square fitting technique. The criteria for determining when the estimated tidal parameters are valid have been studied along with the error analysis of the data and processing. The diurnal and semidiurnal parameters are obtained using this least square fitting method and these tidal parameters are assumed to be valid only when the condition number is less than 10. In the spectral domain, the fast Fourier transform and Lomb-Scargle periodogram methods have been studied. A test signal is generated and its performance using both FFT and Lomb-Scargle methods are discussed for three different cases which are equivalent to our actual data. The results of the wind estimates from 2000-2003 collected using the MF radar have been processed using the automated processing system. This automated processing system can be used to generate the wind parameters on a 24 hour, 7 day a week basis for an elaborate study. Our data are compared with MF radar data from Saskatoon, Canada and Urbana, lllinois. Most of the time our data are similar to the behavior of GSWM-02 model.
    • Automatic detection of sensor calibration errors in mining industry

      Pothina, Rambabu; Ganguli, Rajive; Ghosh, Tathagata; Lawlor, Orion; Barry, Ronald (2017-12)
      Sensor errors cost the mining industry millions of dollars in losses each year. Unlike gross errors, "calibration errors" are subtle, develop over time, and are difficult to identify. Economic losses start accumulating even when errors are small. Therefore, the aim of this research was to develop methods to identify calibration errors well before they become obvious. The goal in this research was to detect errors at a bias as low as 2% in magnitude. The innovative strategy developed relied on relationships between a variety of sensors to detect when a given sensor started to stray. Sensors in a carbon stripping circuit at a gold processing facility (Pogo Mine) in Alaska were chosen for the study. The results from the initial application of classical statistical methods like correlation, aggregation and principal component analysis (PCA), and the signal processing methods (FFT), to find bias (±10%) in "feed" sensor data from a semi-autogenous (SAG) grinding mill operation (Fort Knox mine, Alaska) were not promising due to the non-linear and non-stationary nature of the process characteristics. Therefore, those techniques were replaced with some innovative data mining techniques when the focus shifted to Pogo Mine, where the task was to detect calibration errors in strip vessel temperature sensors in the carbon stripping circuit. The new techniques used data from two strip vessel temperature sensors (S1 and S2), four heat exchanger related temperature sensors (H1 through H4), barren flow sensor (BARNFL) and a glycol flow sensor (GLYFL). These eight sensors were deemed to be part of the same process. To detect when the calibration of one of the strip vessel temperature sensors, S1, started to stray, tests were designed to detect changes in relationship between the eight temperature sensors. Data was filtered ("threshold") based on process characteristics prior to being used in tests. The tests combined basic concepts such as moving windows of time, ratios (ratio of one sensor data to data from a set of sensors), tracking of maximum values, etc. Error was triggered when certain rules were violated. A 2% error was randomly introduced into one of the two strip vessel temperature data streams to simulate calibration errors. Some tests were less effective than others at detecting the simulated errors. The tests that used GLYFL and BARNFL were not very effective. On the other hand, the tests that used total "Heat" of all the heat exchanger sensors were very effective. When the tests were administered together ("Combined test"), they have a high success rate (95%) in terms of True alarms, i.e., tests detecting bias after it is introduced. In those True alarms, for 75% of the cases, the introduction of the error was detected within 39.5 days. A -2% random error was detected with a similar success rate.
    • Axisymmetric numerical heat transfer analysis of natural gas hydrates reservoir

      Subbaihaannadurai, Vijayagandeeban; Das, Debendra K.; Patil, Shirish L.; Goering, Douglas J. (2004-12)
      Gas hydrates are crystalline substances, occurring in nature under high pressure and low temperature. Numerical studies were conducted on dissociation of gas hydrate to recover natural gas. The model is a cylindrical geometry with a wellbore at the center through which hot water is injected. Through this thermal stimulation technique frozen hydrate reservoir is melted and natural gas is released. The computational fluid dynamics software FLUENT was adopted to generate the model. The initial model was solely comprised of a hydrate layer. This model was refined by adding the overburden and the underburden to the hydrate and exploring the thermal regime of the entire composite medium. Unsteady state results showing the dissociation front propagation with respect to time were calculated. In the first part, the hydrate medium is dissociated by the conduction phenomenon only. In the second part, due to the porous nature of the hydrate medium, both conduction and convection phenomena are considered. This thesis presents the following results obtained from simulations using Fluent. They are: temperature rise within the reservoir with time, temperature profiles in the radial direction, and steady and transient state solutions of the dissociation of gas hydrate with the liquid fraction in the reservoir. Comparison of our results with a finite difference model and a finite element model is also included. Volumes of gas released with respect to time and thermal efficiency ratios are also determined.
    • Behavior Of Granular Materials Under Cyclic And Repeated Loading

      Minassian, George H.; Raad, Lutfi (2003)
      Granular layers are essential contributors to the structural integrity of the pavement system, their premature deformation radically decrease support of the asphalt concrete surface layer, thus leading to the early deterioration of the overall pavement structure. This research was conducted to better understand the behavior of granular materials when subjected to the complex nature of traffic loading. Long-term triaxial tests were conducted on typical Alaskan base course material using both repeated as well as cyclic loading to also account for the shear reversal effects induced by wheel load. Results show that the shear reversal component of the traffic loads, which have been ignored so far, induces considerable damage to the granular layers. Models were presented to predict the different soil moduli while also accounting the effect of strain hardening or densification due to the repetitive nature of the loads applied. Moreover, a simple yet powerful model was presented to predict accumulated permanent strains as function of the stress state, number of load repetitions and the strength level applied. The results obtained in this study also show a clear indication of the existence of given stress level limit beyond which incremental collapse of the system takes place. Furthermore, regions of instability of granular layers subjected to dynamic loading have been defined using a simple response parameter and monotonic shear strength of the soil. An effort was made to explain the instability zones identified in this research by the shakedown theory.* *This dissertation is a compound document (contains both a paper copy and a CD as part of the dissertation). The CD requires the following system requirements: Microsoft Office.
    • Beneficiation of rare earth minerals from Bokan Mountain: Dotson Ridge ore

      Narantsetseg, Purevbaatar; Наранцэцэг, Пүрэвбаатар; Ganguli, Rajive; Ghosh, Tathagata; Akdogan, Guven (2014-12)
      The purpose of this research work was to study the beneficiation of rare earth ore of the Bokan Mountain -- Dotson Ridge deposit, located near Ketchikan, Alaska. Rare earth element (REE) composite ore samples from the Bokan Mountain -- Dotson Ridge deposit were tested using gravity concentration, magnetic separation, flotation, and leaching techniques to separate the REE. The composite ore sample was a product of a preliminary x-ray sorting process. Qualitative electron microprobe analysis of the ore showed that most of the REE minerals in the ore were silicate minerals. Since the electron microprobe analysis samples were coated with carbon during sample preparation, the carbon element was inactivated for analysis. Because of this, carbonate compounds of minerals' particles could not be detected. 95% of the REE mineral particles appear to be smaller than about 10 μm in size (about 100 μm² in area). For the gravity concentration, light rare earth elements (LREE) and heavy rare earth elements' (HREE) individual elemental recovery values were in the ranges of 49.6-52.8% and 46.3-48.8%, respectively, at 25% of mass yield. In order to separate a larger amount of the REE, a wet high intensity magnetic separation (WHIMS) test was carried out on tailings of the gravity concentration tests. The HREE individual elemental recovery values ranged from 56.3-63.1% at 37% mass yield, while LREE individual elemental recovery values were in the 57.9% - 59.1% range. For the combined gravity and magnetic separation processes, the net individual elemental recovery values of the LREE and the HREE were in the range of 79.6-80.5% and 76.5-80.9%, respectively. The combined mass yield of the gravity and magnetic separation processes was 3%. Direct leaching tests conducted on the composite ground ore feed yielded high individual elemental recovery values of 90-92% of the LREE. The HREE individual elemental recovery values ranged from 56.5-87.3%. In the leaching, 20% HCl was used in the 1st and 2nd stages with a duration of 2 hrs in each stage at 90°C. The solid percentage of the leach slurry was 20% w/w. The composite ground ore sample was tested in conventional flotation using a 2.0 L capacity Denver cell. In the flotation, 0.05 kg/tonne of Cytec Aero 6493 collector, 0.05 kg/tonne of Cytec Aero Froth 88, and 0.1 kg/tonne of sodium metasilicate as a depressant were used. Pulp pH was set around 9. Results showed individual elemental recovery values in the range of 44.6-50.4% or the LREE. The HREE individual elemental recovery values ranged from 27.9-44.5%. The mass yield of the flotation was 23%. The flotation recoveries reported here are significantly lower than what was achieved previously. For the Leach after flotation process, leaching was conducted on the first concentrate of flotation. Individual elemental recovery values of the LREE and HREE were 94.7-96.5% and 61.1-90.5%, respectively. The concentrate was leached using 20% HCl in both the 1st and 2nd stages, with a duration of 2 hrs in each stage at 90°C. Flotation/Leach process net recoveries of LREE by individual elemental values ranged from 42.2-48.5%. HREE net recoveries by individual elemental values ranged from 17.1-41.4%.
    • Best practices and metrics for virtual reality user interfaces

      Byam, Jay; Chappell, Glenn; Lawlor, Orion; Metzgar, Jonathan (2019-12)
      Virtual Reality (VR) technology has become increasingly effective and accessible within the past decade [15]. With this increase in the technology’s prevalence and cultural significance, certain interaction techniques and design choices have emerged as the most widely used and recommended. This research effort employs a VR experiment in which multiple selection methods, interface placements, and navigation techniques are compared side-by-side, and performance metrics and preference data are collected. Both best practice and to-be-avoided methods are examined, and the performance and preference data is analyzed. Determinations made based on the data gathered are partly in-line with expectations according to best practices, partly inconclusive, and partly contrary to the expected performance and preference results. Results suggest that virtual laser pointers and tapping are equally recommendable selection methods for most VR experiences, hand-mounted menus produce the best results overall, and despite performance advantages, joystick navigation should be avoided in VR due to user comfort concerns.
    • Better understanding of production decline in shale gas wells

      Harongjit, Kananek; Ahmadi, Mohabbat; Patil, Shirish; Dandekar, Abhijit (2014-08)
      Production data from the Eagle Ford shale (an analog to the Alaska Shublik shale) was collected from two neighboring counties and analyzed to correlate well performance with completion parameters including length of horizontal wellbore and number of hydraulic fracturing stages. Thirty-eight dry gas wells with production history range of 18-43 months were analyzed using 6 different decline curve analysis (DCA) models including Arps' exponential, harmonic and hyperbolic, power law exponential (PLE), logistic growth analysis (LGA) and Duong's models. In the matching process, 2/3 of history was used to tune the DCA models and their forecasts were compared to the remaining 1/3 of real history. The matching results were analyzed based on production history length and flow regime to have better understanding of limitations and capabilities of each DCA model. Reservoir simulation models, constructed using range of realistic data and actual completion practices of 4 select wells, were employed to assess reasonable values of remaining reserve and remaining well life that were used as benchmarks for comparison with DCA results. The results showed that there was no strong correlation between well performance (average first year production rate) and the horizontal leg or the number of fracturing stages. This was an indication of extremely heterogeneous medium. In most cases, the accuracy of the DCA models increased when longer production history was used to tune the model parameters. LGA seems to be the most accurate DCA model since it gave the highest matching accuracy 71% of the total wells when using longest history length of 31 months. As the flow regime is concerned, LGA model also performed very well matched in 57% of the wells exhibiting only transient flow and 63% for the wells showing transient flow during early production time followed by boundary-dominated flow during late production. Moreover, the remaining reserve and well life of the select wells predicted by LGA fell into reasonably close range of the estimates from the reservoir simulations.
    • Biodegradation Of Petroleum And Alternative Fuel Hydrocarbons In Moderate To Cold Climate

      Horel, Agota Anna (2009)
      Microbial degradation of hydrocarbon fuels contaminating soil in the Arctic and subarctic environment is a relatively slow process. Nevertheless, due to transportation and logistical limitations in rural Alaska, biodegradation might be the best and cheapest contaminant removal option. The aim of this thesis was to investigate the environmental effects on biodegradation by naturally occurring microorganisms for some innovative hydrocarbon fuels and to determine the overall fate of hydrocarbons in soil, including degradation by fungi and bacteria, volatilization, and transport in the soil. Three major types of fuels were investigated in small scale microcosms and larger soil columns: conventional diesel as a control substance, synthetic diesel (arctic grade Syntroleum) and different types of fish oil based biodiesel. The environmental conditions investigated included different soil types (sand and gravel), different temperatures (constant 6�C, 20�C, and fluctuating between 6 and 20�C), moisture levels (from 2% to 12% GWC), fuel concentrations (from 500 to 20,000 mg fuel/kg soil) and nutrient dosages (0 or 300 mg N/kg soil). Microbial response times and growth phases were also investigated for different inoculum types. Conditions of 20�C, 300 mg N/kg soil, sand, ?4000 mg of fuel/kg soil and ?4% GWC were favorable for bioremediation, with a short lag phase lasting from one day to less than a week, and pronounced peaks of daily CO 2 production between week 2 and 3. At suboptimal conditions, all phases were extended and slow, however at low temperatures steady metabolization continued over a longer time. The relative importance of fungal and bacterial remediation varied between fuel types. Diesel fuel degradation was mainly due to bacterial activities while fish biodiesel degradation occurred largely by mycoremediation. For Syntroleum both bacterial and fungal remediation played key roles. Volatilization contributed up to 13% to overall contaminant removal. In soil columns, degradation was slower than in microcosms, due to an uneven concentration profile of contaminants, nutrients and oxygen with depth. In general, biodegradation showed promising results for soil remediation and the alternate fuel types were more biodegradable compared with conventional diesel fuel.
    • Biosorption of heavy metals by citrus fruit waste materials

      Patil, Santosh Bramhadev (2004-12)
      Conventionally used processes for removing heavy metals from wastewater are usually either expensive, such as ion exchange, or inefficient, such as precipitation. An innovative technique that is both efficient and economical is biosorption, in which living and dead biomass can act as biosorbents through physical-chemical processes like ion exchange and micro-precipitation. Pectin, a structural polysaccharide present in plant cell walls, is similar to alginate, a molecule that is often responsible for the high metal uptake by algae. Based on the structural similarity between alginate and pectin, it was expected that pectin rich bio-wastes may be as good a biosorbent material as brown algae. A comparison between different pectin-rich materials showed high stability and metal binding capacity of citrus peels. Sorption isotherms for citrus peels showed higher metal uptake capacity at pH 5 compared to pH 3. Kinetic studies revealed the time required to reach equilibrium for lemon fruit waste (0.177 mm) was 20 min while for larger particles the time increased to 30 min-60 min. For lemon fruit waste, the content and pKa values of acidic groups were determined by using a pKa spectrum technique. Isotherm modeling was carried out by using Langmuir isotherms and pH sensitive modeling.
    • Biosorption of lead by citrus pectin and peels in aqueous solution

      Balaria, Ankit (2006-05)
      Biosorption of heavy metal ions by different pectin rich materials such as waste citrus peels is emerging as a promising technique for metallic contaminant removal. While binding rate and capacity of citrus peels were previously investigated, there is a lack of mechanistic information about Pb-citrus pectin/peels interaction mechanisms. Present research focused on evaluating this binding mechanism by corroborating macroscopic studies with spectroscopic techniques. Citrus pectins of two different methoxylation degrees and orange peels were characterized using potentiometric titrations and Fourier transform infrared (FTIR) spectroscopy. Binding mechanisms were evaluated using molecular scale FTIR analyses. The effects of particle size, pH, co-ion presence, and background electrolyte concentrations were also investigated for biosorption of Pb by orange peels. Both citrus pectin and orange peels reached their sorption equilibrium within 45 minutes. The maximum uptake capacity for orange peels was found to be 2.32 mmol/g. Citrus peels have very similar FTIR spectra to citrus pectin, suggesting that they have similar functional groups and pectin can be used as a model for citrus peels. Furthermore, carboxylic acid groups were found to be responsible for binding of Pb by citrus pectin and orange peels.
    • Building a toolset for fuel cell turbine hybrid modeling

      Burbank, Winston S. (2006-12)
      Fuel cell/gas turbine hybrids show promise of high efficiency power generation, with electrical efficiencies of 70% or better shown by modeling, although these efficiency levels have not yet been demonstrated in hardware. Modeling of such systems is important to optimize and control these complex systems. This work describes a modeling tool developed to examine steady-state operation of different hybrid configurations. This model focuses on the area of compressor-turbine modeling, which is a key component of properly controlling fuel cell/gas turbine hybrids. Through side-by-side comparisons, this model has been tested and verified by Dr. Wolf of Brayton Energy [1]. This modeling tool will be used in further work to evaluate various configurations of turbines and fuel cells in hybrid configurations, focusing on both the performance and cost of such systems.