Now showing items 1883-1902 of 3446

• #### Modeling and exploring battery management strategies for use of LiCoO₂ lithium polymer cells in cold climates

As the use of batteries to power vehicles becomes more common, a robust battery management system becomes necessary to monitor and maintain the batteries. Cold weather places a further burden on this system especially in small electric vehicles such as snowmobiles where it is desirable to use every bit of available energy from the battery cells. The problem with current battery management technology is that use of batteries in cold temperatures is often not addressed. The objective of this research was to develop an appropriate model of a lithium polymer cell with a cathode comprised of LiCoO₂ and develop an optimized charge/discharge method taking into account the effects of extreme cold weather and cell state of charge imbalance. A cell model was adapted and tuned that accurately captures the dynamics of a lithium polymer cell when discharged at temperatures below freezing. The model results were verified against cells discharged in an environmental chamber, which allowed accurate control of ambient temperature. Multiple scenarios were explored, looking at the effects of ambient temperature, cell initial temperature, internal heating, battery pack insulation, and how rapidly the cells were discharged. The results of the optimized battery management strategies showed improvements in the energy delivery capability of lithium polymer battery packs for small vehicles operating in extreme cold environments. In addition, this research extended the LiCoO₂ model down to -20 °C using validated data, showed that perceived cell capacity loss at low temperatures is primarily due to increased internal resistance, demonstrated that measured cell terminal voltage can rise under load at low temperatures, and showed that increasing the capacity of a battery pack has a better than linear gain in usable energy versus increased battery capacity. I.e., doubling battery pack capacity will more than double the useable range of the vehicle.
• #### Modeling and optimization of hybrid electric power systems for remote locations in extreme northern climates

This thesis presents a long-term performance model of a hybrid electrical power system for remote locations in various parts of the world. The model incorporates the performance of different components of the hybrid power system in extreme northern climates. The hybrid model presented uses the graphical user interface available in MATLAB Simulink. Two variations of the hybrid model were developed. One model consists of a photo voltaic (PV) array with a diesel-battery system and the other model consists of a wind turbine with a diesel-battery system. The main performance criterion by which the system was evaluated is the percentage of fuel savings relative to the diesel only case. The results show the significant savings in fuel consumption due to the penetration of the battery bank, the photovoltaic module and the wind turbines in the diesel-only system, while increasing the overall efficiency of the system. This simulation tool will help designers to determine the best hybrid mix of diesel generation, battery storage, photovoltaics, and wind generation for optimal performance of the system in remote villages like those found in Alaska and other developing countries. Examples are presented based on actual systems in the remote Alaskan communities of Lime Village (PV with a diesel-battery) and Wales Village (wind with a diesel-battery).
• #### Modeling Biosorption Of Cadmium, Zinc And Lead Onto Native And Immobilized Citrus Peels In Batch And Fixed Bed Reactors

Biosorption, i.e., the passive uptake of pollutants (heavy metals, dyes) from aqueous phase by biosorbents, obtained cheaply from natural sources or industrial/agricultural waste, can be a cost-effective alternative to conventional metal removal methods. Conventional methods such as chemical precipitation, membrane filtration or ion exchange are not suitable to treat large volumes of dilute discharge, such as mining effluent. This study is a continuation of previous research utilizing citrus peels for metal removal in batch reactors. Since fixed bed reactors feature better mass transfer and are typically used in water or waste water treatment using ion-exchange resins, this thesis focuses on packed bed columns. A number of fixed bed experiments were conducted by varying Cd inlet concentration (5-15 mg/L), bed height (24-75 cm) and flow rate (2-15.5 ml/min). Breakthrough and saturation uptake ranged between 14-29 mg/g and 42-45 mg/g respectively. An empty bed contact time of 10 minutes was required for optimum column operation. Breakthrough curves were described by mathematical models, whereby three popular models were shown to be mathematically identical. Citrus peels were immobilized within an alginate matrix to produce uniform granules with higher uptake capacity than raw peels. All breakthrough curves of native and immobilized peels were predicted using external and intra-particle mass transfer resistances from correlations and batch experiments, respectively. Several analogous mathematical models were identified; other frequently used models were shown to be the approximate derivatives of a single parent model. To determine the influence of competing metals, batch and fixed bed experiments were conducted in different binary combinations of Pb, Cd, Zn and Ca. Equilibrium data were analyzed by applying competitive, uncompetitive and partially competitive models. In column applications, high affinity Pb replaced previously bound Zn and Cd in Pb-Zn and Pb-Cd systems, respectively. However, the Cd-Zn system did not show any overshoot. Calcium, which is weakly bound, did not affect target metal binding as much as other metals. Saturated columns were desorbed with 0.1 N nitric acid to recover the metal, achieving concentration factors of 34-129. Finally, 5 g of citrus peels purified 5.40 L mining wastewater.
• #### Modeling changes in the length of the agricultural growing season in Interior Alaska

Food security is a growing global concern as population growth continues in a period of rapid climatic change. The amplification of climate change and dependence upon imported foods at high latitudes makes Alaskans especially vulnerable to both global and local changes. Although many climate impacts present challenges, rising air temperatures could provide economic opportunities for Alaskan agriculturalists by extending growing seasons. Future growing season length has previously been estimated, however these estimates did not explicitly account for the constraints of agricultural systems. This research explores the relationship between air temperature, soil temperature and growing season length in agricultural management systems in Interior Alaska to better understand how climate scenarios can be used to identify future opportunities. Air and soil temperature data were collected under four different crop systems and used in combination with historical observations to inform a model that projects usable growing degree-days in Interior Alaska to the end of the century. Increases of usable degree-days were projected to increase from 33-70% by 2100. The projected increases could increase success of currently marginally successful crops (e.g., canola, corn, and sunflowers). Such opportunities could lead to increased food security, but future planning will require culturally appropriate planning and institutional support.
• #### Modeling fish movement in sonar beam

Enumerating salmon in the Yukon River drainage allows for assessment of annual harvest management guidelines and prediction of long-term salmon population trends in Alaska. Sonar is currently used to enumerate migrating salmon and determine salmon location in the river. To understand these results, a model of fish movement is required. This thesis analyzes the existing sonar data on fish movement to construct a model that predicts typical spatial and temporal distribution of fish. A model of the sonar measurement system, which includes target strength, transmission loss, transducer beam pattern, time delay, and noise is developed. This system will simulate a sonar signature for an arbitrary distribution of fish by making several simplifying assumptions. This thesis compares the simulated system sonar signature with assumed fish distribution to predict the accuracy of the sonar fish counting system.
• #### Modeling Future Sea Level Rise From Melting Glaciers

Melting mountain glaciers and ice caps (MG&IC) are the second largest contributor to rising sea level after thermal expansion of the oceans and are likely to remain the dominant glaciological contributor to rising sea level in the 21st century. The aim of this work is to project 21st century volume changes of all MG&IC and to provide systematic analysis of uncertainties originating from different sources in the calculation. I provide an ensemble of 21st century volume projections for all MG&IC from the World Glacier Inventory by modeling the surface mass balance coupled with volume-area-length scaling and forced with temperature and precipitation scenarios from four Global Climate Models (GCMs). By upscaling the volume projections through a regionally differentiated approach to all MG&IC outside Greenland and Antarctica (514,380 km 2) I estimated total volume loss for the time period 2001-2100 to range from 0.039 to 0.150 m sea level equivalent. While three GCMs agree that Alaskan glaciers are the main contributors to the projected sea level rise, one GCM projected the largest total volume loss mainly due to Arctic MG&IC. The uncertainties in the projections are addressed by a series of sensitivity tests applied in the methodology for assessment of global volume changes and on individual case studies for particular glaciers. Special emphasis is put on the uncertainties in volume-area scaling. For both, individual and global assessments of volume changes, the choice of GCM forcing glacier models is shown to be the largest source of quantified uncertainties in the projections. Another major source of uncertainty is the temperature forcing in the mass balance model depending on the quality of climate reanalysis products (ERA-40) in order to simulate the local temperatures on a mountain glacier or ice cap. Other uncertainties in the methods are associated with volume-area-length scaling as a tool for deriving glacier initial volumes and glacier geometry changes in the volume projections. Nevertheless, the lack of more detailed knowledge of global ice volume constrains the estimates of the potential and projected sea level rise from melting MG&IC. Any progress in this field is limited without a more complete glacier inventory database.
• #### Modeling investigation of northern hemisphere extratropical storm variability and changes in a warming climate

Extratropical cyclones are fundamental elements for shaping weather patterns, causing fluctuations of temperatures, bringing rain or snow, and carrying winds to impact daily life. The intensity and number of North Hemisphere extratropical cyclones have demonstrated large interannual variability and long-term changes. To understand the variability and changes, we conducted a modeling investigation using the National Center for Atmospheric Research (NCAR)'s Community Atmosphere Model. Specifically, we examined the effects of two surface forcing factors, including sea surface temperature (SST) associated with El Niño and Arctic sea-ice cover, which represent a major source of natural variability and climate changes. Our modeling investigation indicates that the tropical Pacific SST and Arctic sea ice have significant impacts on Northern Hemisphere mid-latitude and Arctic cyclone activities. The elevated tropical Pacific SST leads to more numerous intense storms over southwestern, southeastern, and northwestern North America, but fewer weaker storms over the northeast. The underlying physical mechanism is enhanced lower tropospheric baroclinicity, which is attributable to a southward shift and an intensification of the subtropical jet. The decreased Arctic sea-ice cover leads to an increased storm activity over the Arctic but a decrease in the mid-latitudes. A corresponding examination of surface climate shows anomalously higher surface air temperature and precipitation when low Arctic sea-ice cover occurs, due to an integrative contribution from an increase in surface sensible and latent heat fluxes and horizontal heat advection. In contrast, reduced Arctic sea ice weakens storm activity and intensifies anticyclones over Eurasia, giving rise to decreased surface air temperature and precipitation. Unlike many other parameters, the Arctic sea ice has shown a dramatic decline in addition to interannual fluctuations. We therefore conducted further modeling experiments to identify the role of this long term sea-ice trend on storm activity. The results show that the long-term decline causes a weakening of overall storm activity but an increase in extreme storm events over the Northern Hemisphere. The atmospheric energetic analysis suggests that the increased conversion rate between transient available potential energy and transient kinetic energy is a leading factor in supporting the increased frequency of extreme storms. Over Eurasia, changes in storm activity are mainly governed by the mean kinetic energy of the atmospheric circulation and its conversion to the transient kinetic energy.
• #### Modeling life stage dynamics of Pseudocalanus spp. (Copepoda: Calanoida) from Prince William Sound, Alaska

A stage at age 1D numerical model (SAGE) was developed to describe reproduction, development, and growth of a group of neritic copepods Pseudocalanus spp., and to predict structure and demography of this group. The model tests the relative importance of female abundance, temperature and food on productivity. During spring and the beginning of the summer, stage-specific abundance data from one location in Prince William Sound (PWS), Alaska were available to evaluate the reproductive timing and provide model validation. Development of Pseudocalanus spp. was modelled as synchronous, without overlapping broods. Molting costs and assimilation efficiency were estimated from literature data on other calanoid copepods. Wood's population surface method was used to produce a stage at age mortality (SAM) model to evaluate per capita instantaneous stage-specific mortality rates from the field data. The model confirmed the assumption that the abundance of these copepods was controlled by temperature and temporal/stage-to-stage variation in mortality rates, rather than by food availability.
• #### Modeling Of A Novel Triple Turbine Solid Oxide Fuel Cell Gas Turbine Hybrid Engine With A 5:1 Turndown Ratio

Electrical production using solid oxide fuel cell gas turbine (SOFC-GT) hybrid systems has received much attention due to high-predicted efficiencies, low pollution and the availability of natural gas. Solid oxide fuel cell (SOFC) systems and hybrid variants designed to date have had narrow operating ranges due largely to the lack of control variables available to control the thermal requirements within the SOFC. Due to the higher value of peak power, a system able to meet fluctuating power demands while retaining high efficiencies is strongly preferable to only base load operation. This thesis presents results of a novel SOFC-GT hybrid configuration designed to operate over a 5:1 turndown ratio. The proposed system utilizes two control variables that allow the hybrid to maintain the SOFC stack exit temperature at a constant 1000�C throughout the turndown. The first control variable is the setting of a variable-geometry inlet nozzle turbine, which most directly influences the system airflow. The second control variable is an auxiliary combustor, which allows control of the thermal and power needs of the turbomachinery independently from that of the SOFC. At low turndown the proposed hybrid operates similarly to previous hybrids, in that roughly 80% of the power is delivered from the SOFC. However, the newly proposed hybrid uses the unique turbomachinery to drastically increase the delivered power at higher power demands. A unique aspect of the proposed hybrid is the contribution of half the rated power being supplied by the inexpensive turbomachinery with the expensive SOFC contributing the other half. This will significantly lower system capital costs compared to previous hybrid designs. The proposed hybrid has high efficiencies throughout turndown with peak efficiencies occurring at low turndown levels.

• #### Modeling Of Depressurization And Thermal Reservoir Simulation To Predict Gas Production From Methane -Hydrate Formations

Gas hydrates represent a huge potential future resource of natural gas. However, significant technical issues need to be resolved before this enormous resource can be considered to be an economically producible reserve. Developments in numerical reservoir simulations give useful information in predicting the technical and economic analysis of the hydrate-dissociation process. For this reason, a commercial reservoir simulator, CMG (Computer Modeling Group) STARS (Steam, Thermal, and Advanced Processes Reservoir Simulator) has been adapted in this study to model gas hydrate dissociation caused by several production mechanisms (depressurization, hot water injection and steam injection). Even though CMG is a commercially available simulator capable of handling thermal oil recovery processes, the novel approach of this work is the way by which the simulator was modified by formulating a kinetic and thermodynamic model to describe the hydrate decomposition. The simulator can calculate gas and water production rates from a well, and the profiles of pressure, temperature and saturation distributions in the formation for various operating conditions. Results indicate that a significant amount of gas can be produced from a hypothetical hydrate formation overlying a free gas accumulation by several different production scenarios. However, steam injection remarkably improves gas production over depressurization and hot water injection. A revised axisymmetric model for simulating gas production from hydrate decomposition in porous media by a depressurization method is also presented. Self-similar solutions are obtained for constant well pressure and fixed natural gas output. A comparison of these two boundary conditions at the well showed that a higher gas flow rate can be achieved in the long run in the case of constant well pressure over that of fixed gas output in spite of slower movement of the dissociation front. For different reservoir temperatures and various well boundary conditions, distributions of temperature and pressure profiles, as well as the gas flow rate in the hydrate zone and the gas zone, are evaluated.
• #### Modeling of permafrost and gas hydrate stability zone within Alaskan Arctic shelves and continental margins

A mathematical model was used to determine the behavior of the thermal regime and temperature and pressure conditions due to climate and sea level variations of the gas hydrate stability zone formation at four sites within the Alaskan Arctic Shelf. Two soil types, coarse-grained and fine-grained, and three types of programs were used. The programs were distinguished by whether or not they took unfrozen water and latent heat into account. Simulations suggest the presence of subsea permafrost in a vast area of shelf near Prudhoe Bay. Near Barrow and Lonely subsea permafrost extends up to several tens of kilometers offshore, while subsea permafrost near Cape Thompson almost completely disappeared during the last marine transgression. Distribution of subsea permafrost varies with soil type, thermal properties and geothermal heat flow. The possible presence of methane gases in a pore space of the material influences the thermal regime and permafrost distribution. Simulations indicate that a Gas Hydrate Stability Zone can exist at depths from 220 m to 1100 m. Possible formation and presence of gas hydrates in the sediments changes the thermal regime significantly; therefore the shape of subsea permafrost depends on whether or not gases are present in the sediments.
• #### Modeling Of The Fisheries Acoustics Problem

This dissertation presents a mathematical model of the overall fisheries acoustics problem posed by enumeration of fish populations using sonar. Emphasis is placed on three key components: a new geometric model for the target strength (TS) of Pacific salmon, a fish distribution for sockeye salmon, and generation of artificial sonar data. Results of the TS and fish distribution models show TS varies on height and breadth of fish as much as on fish length and TS from the air-filled swimbladder is the major contributor as reported by Foote [1985]. A fish roll factor within 45° leads to TS variations within 7 dB for normal incidence, side aspect and 2 dB for dorsal aspect. Also second order effects of ray propagation through fish flesh on TS from the swimbladder provide TS results up to 20 dB lower at high aspect angles. The geometric model predicts TS values that match extremely well with TS data collected on Pacific salmon and other species in river and ocean environments. By varying fish size and swimbladder parameters and considering the effect of fish flesh, the model covers the range of TS values that occur in the field, thus identifying and quantifying the uncertainty in the experimental data. The overall approach in this work is to construct a direct model providing artificial sonar data, then use an inverse model (echo integration algorithm) with that data or with experimental data to compare results. The echo integration results are not reliable at any fish rate for a fixed river cross-section. Estimated fish counts of 0--7 are obtained from 100 simulations for a known fish distribution of 3 fish (0.1 fish/sec). Similarly, at 0.5 fish/sec with 15 known fish, estimates of 0--30 were obtained; at 1 fish/sec with 30 known fish, estimates of 0--50; and at 5 fish/sec with 150 known fish, estimates of 0--100 fish. Fish counts ranged from 0--19 for 3 known fish when ping rate changed from 1--10 pings/sec and when pulse width varied from 0.1--1.0 ms.
• #### Modeling of the polar ionosphere in the inertial corotating frame

The ionospheric model presented in this thesis is developed from first principles. It is a three-dimensional and time-dependent model that covers the region poleward from 50 degrees of geographic latitude and extends to the height range of 80-500 km. In this model, equations of continuity, motion, and energy balance are self-consistently solved for the densities of 7 ion species $\lbrack O\sp+(\sp4S,\ \sp2D,\ \sp2P),\ NO\sp+,\ O\sb2\sp+,\ N\sb2\sp+,\ N\sp+\rbrack$ and electrons. The model accounts for 40 photochemical processes, the neutral wind drag with its shear, electromagnetic E $\times$ B-drift, and field-aligned ambipolar diffusion. The background thermospheric parameters here are derived from the VSH/MSIS models. Minor species $NO,\ N(\sp4S,\ \sp2D)$ and their molecular and eddy diffusion transfer in the lower ionosphere are considered in this model. Energy balance equations for isotropic electron and ion temperatures are solved. including electron thermal conduction and Joule heating. The model is applicable to a limited polar region (hence the curvature is neglected) and the equations are solved in the corotating Cartesian frame with an azimuthal equidistant projection of all parameters and point-by-point transformation of the inputs specified in the geomagnetic frame. The regular grid has a scaleable resolution; the workstation version of the code presented in this thesis has achieved 100 x 100 km horizontal resolution. The algorithm maintains numerical stability for variable time steps in the range from 10-15 minutes to 1-2 minutes, allowing a flexible time coverage. This effective algorithm and even spatial coverage of the regular grid saves significant computational resources. The model output realistically represents seasonal changes and other large-scale polar ionospheric features such as the abundant day-side ionization, the polar cap tongue of ionization, the auroral oval, the polar hole, and ionospheric troughs of different origins. Ionospheric simulations developed in response to different IMF variations demonstrate destruction of continuous polar cap structures and the creation of "patches" of ionized plasma. Several model simulations have shown good overall agreement with observed ionospheric events.
• #### Modeling of wax precipitation

Due to increasing oil demand, oil companies are moving into deep water and arctic environments for oil production. In these regions, due to lower temperature, wax starts depositing when the temperature in wellbore falls below Wax Appearance Temperature (WAT). This leads to reduced production rates and larger pressure drops. Wax problems in production wells are very costly due to production down time and removal of wax. Therefore, it is necessary to develop the solution to overcome wax deposition. Wax precipitation is one of the most important phenomena in wax deposition, and hence, it needs to be modeled. There are various models present in literature. The purpose of this study is to compare two major classes of wax precipitation models. Won's model which considers the wax phase as a non-ideal solution and Pedersen's model which considers the wax phase as an ideal-solution were compared. Comparison indicated that Pedersen's model gives better results but the assumption of wax phase as an ideal solution is not realistic. Hence, Won's model was modified to consider different precipitation characteristics of the different constituents in the hydrocarbon fraction. The results obtained from the modified Won's model were compared with existing models and it was found that predictions from the modified model are encouraging.
• #### Modeling stand-level canopy maintenance respiration of black spruce ecosystems in Alaska: implications for spatial and temporal scaling

Canopy respiration represents an important part of the carbon budget of black spruce forests. In this study I scaled hourly models of foliar maintenance respiration (Rm) to estimate canopy Rm for individual stands, and investigated issues in scaling the models to estimate canopy Rm using mean monthly temperature data. I used data from several stands to develop hourly stand-specific and stand-independent models of canopy Rm. Analysis of stimulated canopy Rm indicated that stand-level controls over foliar N concentration should be considered in models that estimate canopy Rm of black spruce stands across the landscape. Uncertainty analyses indicated that the parameter that describes maintenance respiration rate at 0C̊ per g N has the greatest influence on annual estimates of canopy maintenance respiration. Finally, comparisons of monthly Rm between the hourly and monthly versions of the models indicated that mean monthly temperature can be used to drive models of canopy Rm with little loss of precision.
• #### Modeling the coseismic and postseismic deformation of the 2002 Mw7.9 Denali, AK earthquake

The 2002 Mw7.9 Denali fault earthquake was among the largest intraplate earthquakes on record, and the ongoing crustal deformation of the event is still observed today. Understanding the deformation patterns in the years following the earthquake can give insight into the viscoelastic properties of the crust and upper mantle. Additionally, an accurate and predictive model of this deformation is essential to developing and increasingly complete tectonic model of Alaska. Using primarily GPS measurements, deformation can be measured to millimeter-level precision. To develop a coseismic and postseismic model of the earthquake, 224 GPS coseismic displacement measurements (along with SAR and geologic measurements from past studies) are inverted for fault slip distribution. Coseismic slip and consequent stress changes drive the forward postseismic deformation model, which is constrained by 119 postseismic GPS time series. Both models use a 1D elastic structure. The preferred 1D coseismic model fits the coseismic data with a weighted residual sum of squares (WRSS) of 4.86e3 m², with more deep slip than a homogeneous model and a geodetic moment of 8.92e20 N m (Mw 7.97). The Maxwell viscoelastic parameters used for the first postseismic model run are 3e19 Pa s for the lower crust; 5e18 Pa s for the viscoelastic shear zone; and 10e19 and 10e20 south and north of the fault, respectively, for the asthenosphere. The respective Kelvin parameters are all an order of magnitude less. The deep coseismic slip (a product of the 1D elastic model) eliminates the need to add deep slip, which was done in past studies. Based on time series analysis, the decade-plus of data will certainly improve the model prediction relative to previous models, but future observations will be needed to verify this. No preferred postseismic model is developed, and more postseismic models will be run to better fit the observations.
• #### Modeling the generation and propagation of dispersive waves in the giant magnetospheres through mass loading and transport using hybrid simulation

The magnetodiscs of Jupiter and Saturn are characterized by turbulence in the magnetic field. Broadband spectra of precipitating electrons at Jupiter suggest that a process is underway whereby large scale perturbations undergo a turbulent cascade in the magnetodisc. The cascade couples large perturbations to dispersive scales (kinetic and inertial Alfvén waves). Plasma transport in the rapidly rotating giant magnetospheres is thought to involve a centrifugally-driven flux tube interchange instability, similar to the Rayleigh-Taylor (RT) instability. Mass loading from satellites such as Io and Enceladus also cause dispersive wave formation in the magnetosphere, which is a source for broadband aurora. This dissertation presents a set of hybrid (kinetic ion/fluid electron) plasma simulations of the RT instability and the Io flux tube using conditions appropriate for the magnetospheres of Jupiter and Saturn. Both the Io torus and the planetary magnetodisc act as resonant cavities for counter propagating waves, which creates turbulence. The transmission ratio of wave power from the Io torus is 53%, an improvement from previous models (20% transmission), which is important to the generation of the Io auroral footprint. The onset of the RT instability begins at the ion kinetic scale and cascades to larger wavelengths. Strong guide field reconnection is a mechanism for radial transport of plasma in the magnetodisc. Counter propagating waves within the RT instability is the origin of turbulence within the magnetodisc.
• #### Modeling The Influences Of Climate Change, Permafrost Dynamics, And Fire Disturbance On Carbon Dynamics Of High -Latitude Ecosystems

A Soil Thermal Model (STM) with the capability to operate with a 0.5-day internal time step and to be driven with monthly input data was developed for applications with large-scale ecosystem models. The use of monthly climate inputs to drive the STM resulted in an error of less than 1�C in the upper organic soil layer and in an accurate simulation of seasonal active layer dynamics. Uncertainty analyses identified that soil temperature estimates of the upper organic layer were most sensitive to variability in parameters that described snow thermal conductivity, moss thickness, and moss thermal conductivity. The STM was coupled to the Terrestrial Ecosystem Model (TEM), and the performance of the STM-TEM was verified for the simulation of soil temperatures in applications to black spruce, white spruce, aspen, and tundra sites. A 1�C error in the temperature of the upper organic soil layer had little influence on the carbon dynamics simulated for a black spruce site. Application of the model across the range of black spruce ecosystems in North America demonstrated that the STM-TEM has the capability to operate over temporal and spatial domains that consider substantial variations in surface climate. To consider how fire disturbance interacts with climate change and permafrost dynamics, the STM was updated to more fully evaluate how these factors influence ecosystem dynamics during stand development. The ability of the model to simulate seasonal patterns of soil temperature, gross primary production, and ecosystem respiration, and the age-dependent pattern of above-ground vegetation carbon storage was verified. The model was applied to a post-fire chronosequence in interior Alaska and was validated with estimates of soil temperature, soil respiration, and soil carbon storage that were based on measurements of these variables in 1997. Sensitivity analyses indicate that the growth of moss, changes in the depth of the organic layer, and nitrogen fixation should be represented in models that simulate the effects of fire disturbance in boreal forests. Furthermore, the sensitivity analyses revealed that soil drainage and fire severity should be considered in spatial application of these models to simulate carbon dynamics at landscape to regional scales.
• #### Modeling the injection of CO₂-N₂ in gas hydrates to recover methane using CMG STARS

The objective of this project was to develop a reservoir simulation model using CMG STARS for gas hydrates to simulate the Ignik Sikumi#1 field trial performed by ConocoPhillips at the North Slope, Alaska in 2013. The modeling efforts were focused exclusively on the injection of CO₂-N₂ in gas hydrate deposits to recover methane after an endothermic reaction. The model was history matched with the available production data from the field trial. Sensitivity analysis on hydrate saturation, intrinsic permeability, relative permeability curves, and hydrate zone size was done to determine the impact on the production. This was followed by checking the technical feasibility of the reservoir model for a long-term production of 360 days. This study describes the details of the reservoir simulation modeling concepts for gas hydrate reservoirs using CMG STARS, the impact on the long term production profile, and challenges and development schemes for future work. The results show that appropriate gas mixture can be successfully injected into hydrate bearing reservoir. The reservoir heat exchange was favorable, mitigating concerns for well bore freezing. It can be stated that CO₂-CH₄ exchange can be accomplished in hydrate reservoir although the extent is not yet known since the production declined for long term production period during forecasting study.