Now showing items 849-868 of 918

• #### Thermophysical properties measurements and numerical modeling of nanofluids

This thesis covers measurements of the thermo physical properties of various nanofluids containing copper oxide (CuO), silicon dioxide (SiO₂) and aluminum oxide (Al₂O₃) nanoparticles and numerical investigation on the fluid dynamic and heat transfer characteristics of nanofluids. Nanofluids are dispersions of nanometer-sized particles (<100 nm) in heat transfer liquids such as water, ethylene glycol or propylene glycol. An ethylene glycol and water (60:40 by mass) mixture was used as a base fluid in which various volume concentrations of nanofluids were dispersed. These nanofluids will be useful in the sub-arctic and arctic environments. Experiments were performed to investigate the rheological properties of CuO, SiO₂ and Al₂O₃ nanofluids. New viscosity correlations for different nanofluids as a function of volume concentration and temperature were developed. Using these correlations heat transfer performance of nanofluids as compared to the base fluid was numerically analyzed for laminar as well as for turbulent flows. Developing laminar flows in a parallel plate duct were computed for Reynolds number ranging from 100 to 2000 for various concentrations of CuO nanofluids. Turbulent convective heat transfer in circular tube geometry under a prescribed heat flux was numerically analyzed for Reynolds numbers ranging from 10⁴ to 10⁵. Heat transfer enhancement of various nanofluids over the base fluid was evaluated. The numerical results show enhanced heat transfer with increase in the volume concentration of nanoparticles.
• #### Thermosyphon Devices and Slab-on-Grade Foundation Design

Subgrade cooling methods to prevent thermal degradation of permafrost in cold regions include the use of thermosyphons with inclined evaporator sections. This laboratory study was conducted to determine the thermal performance characteristics of two commercially available thermosyphons. Evaporator inclination angles ranged from 0(degrees) to 12(degrees) from the horizontal, and air speeds ranged from 0 to 13.4 miles per hour over the finned condenser sections. Two standard full size thermosyphons, one charged with CO2, carbon dioxide and the other with NH3, anhydrous ammonia, were tested in CRREL's atmospheric wind tunnel. Empirical expressions are presented for heat removal rates as a function of air speed, ambient air temperature and evaporator inclination angle. An analytical method is also presented to approximate thermal design of foundations using thermosyphons under buildings with a slab-on-grade. We present heat gains from the slab and pad to the thermosyphon as well as the evaporator temperature as functions of time.
• #### Third annual conference on Alaskan placer mining

This Conference has been designed to present pertinent information on the foregoing facets of Placer Mining for the benefit of the industry; to allow discussion with fellow miners, and to permit sharing experience so that each may benefit i n conducting his own operation.

• #### Three dimensional computational fluid dynamics models of fugitive dust dispersion in high-latitude open-pit mines

The Arctic region contains vast mineral resources and mining of these resources is a major activity in several countries, including the United States. With the advancement of open-pit mining technology, the depth to which minerals can be profitably mined has increased, resulting in deeper pits than ever before. This increase in depth has several inherent challenges for mining operations. The ventilation of an open-pit mine is mostly dependent on natural airflow patterns. The dispersion behavior of the pollutants generated in a mine is also dependent on the atmospheric conditions. The control of fugitive dust in high-latitude open-pit mines is challenging due to unique atmospheric phenomena resulting in complicated flow regimes as well as atmospheric inversion due to the lack of adequate insolation during prolonged winter seasons. The development of a computational fluid dynamics (CFD) model of an open-pit mine is challenging due to the presence of several sharp and irregular features at the pit surface. A good quality mesh of the model domain is a prerequisite for convergence in solution. Besides good quality meshing, choices of various simulation setup parameters have significant impact in convergence or divergence of the simulation. Appropriate choices of simulation type, boundary and initial conditions, time stepping and various convergence criteria are important for realistic simulation of a model domain. Environmental conditions in the mine vary from season to season; hence, fugitive dust dispersion simulations using a commercial CFD software are conducted for various seasonal conditions along with several cloud conditions. Clear sky and cloudy sky conditions result in different radiative and turbulent energy fluxes. In each scenario, fugitive dust particles varying in size (PM₀.₁ to PM₁₀) and concentrations are generated at various locations of the selected mine. The simulation results predict a speedy removal of fugitive dust in summer. However, during winter, the presence of an inversion layer in the open-pit results in extensive retention of fugitive dust. For removal of the atmospheric inversion during winter, it is observed that the presence of cloud cover and convective wind are the most important factors.
• #### Three dimensional computational fluid dynamics models of pollutant transport in a deep open pit mine under Arctic air inversion and mitigation measures

As open pit mines continue to grow deeper and productivity continues to increase, the management of air pollution can become challenging. One of the challenges, common during winter in deep open pit mines operating in the Arctic, is the occurrence of atmospheric inversion. In itself, inversion is not hazardous. However, due to the emission of gases and particulates during the mining process, the air within the pit can be severely contaminated, rather quickly, leading to serious health and safety consequences. The problem is complex and any solution approach will require a good understanding of the interaction of the aerodynamic movement of air, the air inversion process, the meteorology, the pollutant sources, and the application of mechanical ventilators in open pit mines. Scientific literature related to open pit mine ventilation, particularly with respect to air inversion, is practically non-existent in the English literature. This is perhaps the first account of a three dimensional computational fluid dynamics (CFD) model of pollutant transport in an actual open pit mine under an Arctic air inversion. Advanced technology has made computers faster and more powerful, which allows computational fluid dynamics (CFD) procedures to be applied to many air flow problems. Thus, a CFD approach can be used to understand the transport of contaminant in the pit during inversion by using several turbulence models. An array of data is required to develop CFD models for open pit mine ventilation. The meteorological conditions within deep open pit mines are significantly affected by temperature and roughness conditions, which ultimately generate complex dispersion phenomena including separation of air flow and its recirculation. For the application of CFD, various data such as pollutants concentrations, temperature, velocity, pit contours, equipment locations, and radiation (shortwave and longwave) were collected from the selected open pit mine and the weather stations located nearby. Analysis of the weather data showed that inversions are due to elevated inversions in the selected open pit mine. Because an exact flow situation in open pit mines is not known a-priori, open pit air flow simulation and pollution transport are often highly sensitive to the type of flow model employed. It is therefore necessary to investigate various turbulent models to identify the appropriate model that will simulate the flow phenomena with reasonable accuracy and predict the contaminant distributions within the pit. Dispersion models differ in their assumptions and structures as well as in the algorithm used and as a result, predictions vary from model to model. Furthermore, it is also important to investigate the behavior of a CFD model when simulating complex phenomena, such as the transport and distribution of contaminants in an open pit mine under an Arctic air inversion. The simulation of an enhanced period of turbulence in the stable boundary layer (SBL) is of particular interest because traditional air pollution dispersion models cannot explicitly treat intermittent turbulence events, and yet the SBL is often the worst-case scenario in open pit pollution transport.Realizable κ-ε and Large Eddy Simulation (LES) models were used for understanding flow of gaseous contaminants. The 2010 pit configuration was used to develop models for understanding the gaseous transport under air inversion. During an inversion, turbulence is dominant at the bottom of the pit, while in the middle portion of the pit turbulence is intermittent and flow over the upper portion of the pit is mostly laminar. The realizable κ-ε model tends to over-predict the contaminant concentration, whereas, the LES model under-predicts the level of pollutant concentrations. Validation of the developed model was performed using the 2013 pit configuration. Despite the complex synoptic situations, the different meteorological input data and the fast changing conditions, the simulation results from the validation model were in good agreement regarding the dispersion of pollutants and other turbulent variables. Pollutant concentration values in the selected locations showed differences, but remained within the same order of magnitude in most cases. Removal of the harmful pollutants from the pit is significantly important for the health and safety of the mine workers. The mitigation models were developed for both the 2010 and the 2013 pit configurations. Several remedial measures such as the use of mechanical ventilators in forcing and exhaust mode, push-pull ventilation and a novel approach of using cloud cover were considered. Mitigation efforts employing mechanical means were unsuccessful in removing or diluting the contaminants to a safe level. The novel approach of using cloud cover over an open pit mine showed promise. With this approach, the model showed that the inversion could be lifted and pit could be cleared of all pollutants.

• #### Time synchronization and system support for energy efficient wireless sensor networks

This thesis presents a design of a Wireless Sensor Network (WSN) and the implementation of an original time synchronization algorithm. The complete system support for energy efficient WSNs was developed. The new time synchronization algorithm called Sliding Clock Synchronization employs a simple, yet very effective algorithm to compensate for static and dynamic drifts in the frequencies of crystal oscillators used in the WSN nodes. As power is a very scarce and critical resource in most WSN s, a tight synchronization algorithm can reduce power consumption thereby increasing the life of a WSN. An accurate and reliable synchronization algorithm also enables the WSN to be used for applications that require a tight synchronization for data correlation. A hardware and software interface for an embedded web server has been provided so that the WSN can be monitored and controlled over the Internet. An interface for a GPS module enables the network to incorporate GPS time stamps in recording network events. A sensor node emulator has been developed so that a single node can emulate multiple nodes without additional hardware, thus providing a simple and cost, effective means to test the network performance with large number of nodes.
• #### Tire chain damage on bridge deck wearing surfaces

A light weight, durable, and damage-resistant material is needed as a wearing surface replacement for a two-lane bridge deck that is on a 6% grade. The wearing surface to be replaced is 9.2-m wide and is attached to an orthotropic closed cell steel deck that supported by two 155.9-cm wide by 414.0-cm deep steel box girders. This is a 699.5-m long six span bridge over the Yukon River located near the Arctic Circle on the gravel road section of the Dalton Highway. The bridge is located approximately 80 km north of Fairbanks, Alaska. The structure was designed in the early 1970's with a 127-mm two-layer timber deck wearing surface. Since then, the timber deck wearing surface has been replaced in 1981, 1992, 1999, and 2007. Future decking material may be composites. Factors to be considered in the selection of a new decking material include: thermal cracking, abrasion, durability, flexural strain, traction, weight, and fastening methods to the steel deck. Moreover, the material must retain its structural properties in temperatures that range from -50C to 40C. For a majority of the year, the driving surface is covered with ice and snow. Because of the steep grade, trucks typically use tire chains during the winter. These tire chains damage the current timber wearing surface and are a major factor in its deterioration. Further, the more traffic the less traction. Owing to the damage tire chains cause on the current timber wearing surface, other wearing surface materials are being considered. The purpose of this project was to evaluate possible wearing surface in the laboratory for punching shear, structural strain, modulus, traction, and resistance to tire chains. In this paper, preliminary test results for traction, and wear by tire chains are presented. This is an updated version of a paper that was first presented at ISCORD 2007, Proceedings of the 8th International Symposium on Cold Region Development, Tampere, Finland, September 25-27, 2007, with co-author, J. Leroy Hulsey.
• #### Toward computer generated folk music using recurrent neural networks

In this paper, we compare the effectiveness of two different types of Recurrent Neural Networks, fully connected and Long Short Term Memory, for modeling music compositions. We compare both the categorical accuracies of these models as well as the quality of generated compositions, and find that the model based on Long Short Term Memory is more effective in both cases. We find that the fully connected model is not capable of generating non repeating note sequences longer than a few measures, and that the Long Short Term Memory model can do significantly better in some cases.
• #### A Town Meeting on Energy : Prepared for Interior Alaskans

On March 26, 1977, an all-day Town Meeting on Energy was held at the Hutchison Career Development Center on Geist Road in Fairbanks, Alaska. This event was sponsored by the Alaska Humanities Forum in cooperation with the Fairbanks North Star Borough School District; the Institute of Water Resources at the University of Alaska, Fairbanks; and the Fairbanks Town and Village Association. This publication reports the activities during and the information resulting from this town meeting.
• #### Trace element copper distribution and areal geology in a portion of the Clearwater Mountains, Alaska

The study concerns that portion of the Clearwater Mountains defined by north latitudes 63' 03' and 63' 08' and west longitudes 147' 09' and 147' 30'. Outcrop within the area consists predominantly of a sequence of intercalated andesitic and basaltic flows. Sedimentary rocks are present but comprise a very small percentage of the total section. Dikes and a small pluton are also present. The prevailing attitude of the volcanic and sedimentary rocks is east-northeast with a consistent north dip. A Triassic age is accepted for the volcanic and sedimentary rocks. Areal and local sampling indicates that all rock types are abnormally high in trace copper content, and average background is 1000 ppm. Copper distribution suggests a syngenetic origin. Frequent small copper deposits crop out along the north side of the area. The deposits are epigcnctic and are structurally controlled. The origin of these deposits may have potential exploration significance.
• #### Transport of fecal bacteria in a rural Alaskan community

People living without piped water and sewer can be at increased risk for fecal-oral diseases. One Alaskan village that relies on hauled water and honeybuckets was studied to determine the pathways of fecal contamination of drinking water and the human environment so that barriers can be established to protect health. Samples were tested for the fecal indicators Escherichia coli and Enterococcus. Several samples were also tested for the pathogens Giardia lamblia and Cryptosporidium parvum. All terrain vehicle (ATV) use and foot traffic transported bacteria within the village and into the home. Surface water flow transported bacteria within the community during spring thaw, but flow from the dump did not appear to contribute to contamination in town. Within the home, viable fecal bacteria were found on waterdippers, kitchen counters and floors, and in washbasin water. Giardia was found at the dump, but not in water from the river adjacent the community. Exposure to fecal contamination could be reduced by cleaning up after dogs, careful disposal of honey bucket bags and gray water, and by protecting stored drinking water.
• #### Transportation economics of coal resources of northern slope coal fields, Alaska

This paper describes the Northern coal fields, the environment in which they are situated, and various routes and systems for transporting metallurgical qua1ity coal from these deposits to a potential market in Japan. Each transportation mode is discussed with respect to northern Alaska conditions. Capitol and operating costs were developed for each system. If the coal must support the entire transportation system cost, the transportation of coal from the North Slope of Alaska to Japan appears to be economically feasible only from easily mined areas which are close to an ocean shipping port. In the case of transportation cost sharing by other users, or by government subsidization, the prospects of northern coal exploitation would be enhanced. The final feasibility of developing any of this coal deposit cannot be determined until the mining costs and the factors which influence these costs are known.
• #### Transportation Life Cycle Assessment Synthesis Phase II

Center for Environmentally Sustainable Transportation in Cold Climates, 2018-04-24
The Transportation Life Cycle Assessment (LCA) Synthesis includes an LCA Learning Module Series, case studies, and analytics on the use of the modules. The module series is a set of narrated slideshows on topics related to environmental LCA. Phase I produced 27 modules, and Phase II added 10 more. The modules are available for download on the Lamar CEE website https://www.lamar.edu/engineering/civil/faculty/haselbach/lca-modules.html and on the CESTiCC website http://cem.uaf.edu/cesticc/publications/lca.aspx. The modules are around 20 minutes long and may be used for various purposes such as for class lectures or part thereof, and for background learning in research or application. The modules are organized into four topical areas, each containing overview and detailed modules. The A and α groups cover the international standards that define environmental LCA. The B and β groups summarize some of the typical environmental impact categories in LCA. The G and γ groups include software tools for LCA. The T and τ groups focus on the growing field of transportation with respect to LCA, a complex area of importance. The analytics section provides data on downloads of the modules from the websites and summary survey results from course implementation.
• #### Transportation Life Cycle Assessment Synthesis: Life Cycle Assessment Learning Module Series

The Life Cycle Assessment Learning Module Series is a set of narrated, self-advancing slideshows on various topics related to environmental life cycle assessment (LCA). This research project produced the first 27 of such modules, which are freely available for download on the CESTiCC website http://cem.uaf.edu/cesticc/publications/lca.aspx. Each module is roughly 15- 20 minutes in length and is intended for various uses such as course components, as the main lecture material in a dedicated LCA course, or for independent learning in support of research projects. The series is organized into four overall topical areas, each of which contain a group of overview modules and a group of detailed modules. The A and α groups cover the international standards that define LCA. The B and β groups focus on environmental impact categories. The G and γ groups identify software tools for LCA and provide some tutorials for their use. The T and τ groups introduce topics of interest in the field of transportation LCA. This includes overviews of how LCA is frequently applied in that sector, literature reviews, specific considerations, and software tutorials. Future modules in this category will feature methodological developments and case studies specific to the transportation sector.
• #### Treatment of Low Quality Water by Foam Fractionation

The removal of iron from Alaskan groundwaters by a foam fractionation technique has been shown to very effective. Finished waters with less than 0.2 mg/l iron have been produced from raw waters containing in excess of 25 mg/l. Ethylhexadecyldimethylammonium bromide was used as the principal foaming agent. Low temperature oxidation of the ferrous iron tended to interfere with the removal rates, but high temperature oxidation followed by low temperature fractionation did not exhibit the same adverse influence. All experiments were performed in four-liter laboratory batch columns. For the Alaskan environment batch processing is thought to have advantages over continuous processes because of the need for uncomplicated equipment.
• #### Tunnel lining studies II

In the CRREL tunnel (Fig. B1, B2), sublimation is extremely apparent, but because of the tunnels limited usage it poses no significant problems. However, in an operating mine with forced air ventilation and continuously operating machinery, the problems associated with sublimation may no longer be insignificant. The dust released by the evaporating ice poses not only the obvious respiratory threat, but an additional safety threat, as fine silt suspended in the air reduces visibility, and removal or suppression of the dust will be of importance.
• #### Two dimensional computational fluid dynamics model of pollutant transport in an open pit mine under Arctic inversion

A better understanding of the microscale meteorology of deep, open pit mines is important for mineral exploitation in arctic and subarctic regions. During strong temperature inversions in the atmospheric boundary layer--which are common in arctic regions during the winter--the concentrations of gaseous pollutants in open pit mines can reach dangerous levels. In this research, a two dimensional computational fluid dynamics (CFD) model was used to study the atmosphere of an open pit mine. The natural airflow patterns in an open pit mine are strongly dependent on the geometry of the mine. Generally, mechanical turbulence created by the mine topography results in a recirculatory region at the bottom of the mine that is detached from the freestream. The presence of a temperature inversion further inhibits natural ventilation in open pit mines, and the air can quickly become contaminated if a source of pollution is present. Several different exhaust fan configurations were modeled to see if the pollution problem could be mitigated. The two dimensional model suggests that mitigation is possible, but the large quantity of ventilating air required would most likely beimpractical in an industrial setting.
• #### Two-dimensional analysis of natural convection and radiation in utilidors

Central heating plants are often used on large building complexes such as university campuses or military bases. Utilidors can be used to contain heat distribution lines and other utilities between a utility station and serviced buildings. Traditional thermal analysis of utilidors is one-dimensional, with heat transfer correlations used to estimate the effects of convection, radiation, and two-dimensional geometric effects. The expanding capabilities of computers and numerical methods suggest that more detailed analysis and possibly more energy-efficient designs could be obtained. This work examines current methods of estimating the convection and radiation that occur across an air space in square and rectangular enclosures and compares them with numerical and experimental data. A numerical model was developed that solves the energy, momentum, and continuity equations for the primitive variables in two dimensions; radiation between free surfaces was also included. Physical experiments were conducted with two 10-ft-long apparatuses; one had a 1-ft $\times$ 1-ft cross section, the other was 2 ft $\times$ 4 ft. Several pipe sizes and configurations were studied with the 1-ft $\times$ 1-ft apparatus. The 2-ft $\times$ 4-ft apparatus was limited to containing 4- and 8-inch insulated pipes. Corresponding numerical studies were conducted. Difficulties in modeling large enclosures or those with large temperature differences (Rayleigh numbers above 10$\sp7$) were encountered. Results showed good agreement between numerical and experimental average heat transfer rates, and for insulated pipe cases these results also compared well with rates obtained from one-dimensional analysis. A new effective conductivity correlation for air in a square enclosure was developed, and its use was demonstrated in numerical conduction solutions and compared with full numerical convection and radiation solutions and with experimental data. Reasonably good results were achieved when there was a small temperature difference across the air gap.