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<p> Best estimate and analysis of uncertainty methods are used to examine the variability of the H factor, which converts the global flux in a lattice cell to power. The assumption of a constant H factor is tested, by examining the sensitivity of the components of the H factor to perturbations in reactor conditions, such as, moderator temperature, boron content in the moderator, moderator purity, RIH temperature, ROH pressure, and exit burnup. The local flux profile, which is a component of the H factor, is calculated for a typical CANDU reactor lattice cell using WIMS 2.5d. Another component of the H factor, the distribution of fission energy in a lattice cell, is found by exploring the location of each source of energy released from a fission event. To examine the location of the gamma ray energy deposition a two dimensional Monte Carlo code was created and subsequently benchmarked against an analysis done by C.R.Boss. Using the Monte Carlo code, the best estimate of the percentage of gamma ray energy deposited in the heat transport system was found to be 83.7%. The moderator temperature and the exit channel burnup are shown to have the largest influence on the H factor, which was found to vary between 99.6% and 100.4% of the best estimate value.</p> / Thesis / Master of Applied Science (MASc)

An important aspect in the process of architectural design is the testing of solution alternatives in order to evaluate them on their appropriateness within the context of the design problem. Computational Fluid Dynamics (CFD) analysis is one of the approaches that have gained popularity in the testing of architectural design solutions especially for purposes of evaluating the performance of natural ventilation strategies in buildings. Natural ventilation strategies can reduce the energy consumption in buildings while ensuring the good health and wellbeing of the occupants. In order for natural ventilation strategies to perform as intended, a number of factors interact and these factors must be carefully analysed. CFD simulations provide an affordable platform for such analyses to be undertaken. Traditionally, these simulations have largely followed the direction of Best Practice Guidelines (BPGs) for quality control. These guidelines are built around certain simplifications due to the high computational cost of CFD modelling. However, while the computational cost has increasingly fallen and is predicted to continue to drop, the BPGs have largely remained without significant updates. The need to develop a CFD simulation framework that leverages the contemporary and anticipates the future computational cost and capacity can, therefore, not be overemphasised. When conducting CFD simulations during the process of architectural design, the variability of the wind flow field including the wind direction and its velocity constitute an important input parameter. Presently, however, in many simulations, the wind direction is largely used in a steady state manner. It is assumed that the direction of flow downwind of a meteorological station remains constant. This assumption may potentially compromise the integrity of CFD modelling as in reality, the wind flow field is bound to be dynamic from place to place. In order to improve the accuracy of the CFD simulations for architectural design, it is therefore necessary to adequately account for this variability. This study was a two-pronged investigation with the ultimate objective of improving the accuracy of the CFD simulations that are used in the architectural design process, particularly for the design and analysis of natural ventilation strategies. Firstly, a framework for integrated meso-scale and building scale CFD simulations was developed. Secondly, the newly developed framework was then implemented by deploying it to study the variability of the wind flow field between a reference meteorological station, the Virginia Tech Airport, and a selected localized building scale site on the Virginia Tech campus. The findings confirmed that the wind flow field varies from place to place and showed that the newly developed framework was able to capture this variation, ultimately, generating a wind flow field characterization representative of the conditions prevalent at the localized building site. This framework can be particularly useful when undertaking de-coupled CFD simulations to design and analyse natural ventilation strategies in the building design process. / Doctor of Philosophy / The use of natural ventilation strategies in building design has been identified as one viable pathway toward minimizing energy consumption in buildings. Natural ventilation can also reduce the prevalence of the Sick Building Syndrome (SBS) and enhance the productivity of building occupants. This research study sought to develop a framework that can improve the usage of Computational Fluid Dynamics (CFD) analyses in the architectural design process for purposes of enhancing the efficiency of natural ventilation strategies in buildings. CFD is a branch of computational physics that studies the behaviour of fluids as they move from one point to another. The usage of CFD analyses in architectural design requires the input of wind environment data such as direction and velocity. Presently, this data is obtained from a weather station and there is an assumption that this data remains the same even for a building site located at a considerable distance away from the weather station. This potentially compromises the accuracy of the CFD analyses as studies have shown that due to a number of factors such the urban built form, vegetation, terrain and others, the wind environment is bound to vary from one point to another. This study sought to develop a framework that quantifies this variation and provides a way for translating the wind data obtained from a weather station to data that more accurately characterizes a local building site. With this accurate site wind data, the CFD analyses can then provide more meaningful insights into the use of natural ventilation in the process of architectural design. This newly developed framework was deployed on a study site at Virginia Tech. The findings showed that the framework was able to demonstrate that the wind flow field varies from one place to another and it also provided a way to capture this variation, ultimately, generating a wind flow field characterization that was more representative of the local conditions.

Intensively managed forests of the Southern United States are among the most important sources of wood fiber and timber in this country. There is a great deal of concern that disturbances associated with trafficking by heavy machinery might diminish long-term soil-site productivity. However, determining the effect of harvesting disturbance and silvicultural treatments on the long-term productivity of pine plantations is difficult because, in addition to harvesting effects, growth distributions are affected by changes in climate, silviculture, and genetics. The primary objectives of this study were to determine (1) whether logging disturbances under operationally realistic circumstances affect soil quality, hydrologic function, and loblolly pine (Pinus taeda L.) productivity on wet pine flats, and (2) whether intensive forest management practices mitigate disturbance effects if they exist. Three 20-ha loblolly pine plantations located on wet pine flats in South Carolina were subjected to combinations of wet- and dry-weather harvesting and mechanical site preparations. Changes in soil-site productivity after five years were evaluated using a new rank method. The key advantage of the rank change method is that it is largely independent of the confounding factors (e.g. genetics, silvicultural practices, and climate) that affect comparisons of tree growth and soil quality between growth cycles. After five years, loblolly pine site indexes (base age 25) ranged between 13 and 33 m, and production ranged between 0.5 and 95 Mg ha-1. Soil bulk densities increased from 1.15 to as high as 1.44 g cm-3 after harvesting; by age 7 years it had decreased to approximately 1.25 g cm-3. At the sub-stand scale (0.008 ha), visually assessed soil physical and harvesting residue disturbances had little influence on relative changes in soil-site productivity after five years. Factors that specifically reflect site drainage were the most influential on changes in productivity. At the operational scale (3.3 ha), there were no differences between wet- and dry- harvested sites as long as bedding was applied as a site treatment. These results indicate that when standard site preparation is employed, fertile, wet pine flats such as these are resilient in that they recover from severe, but operationally realistic, harvesting disturbances. / Ph. D.

Forest roads and stream crossings have the potential to be sources of sediment from forest operations. Recent litigation has renewed interest in furthering research related to forest road Best Management Practices (BMPs). Three legacy (100 year old) forest road stream crossings were monitored for suspended sediment for nine months before and six months after upgrading three unimproved ford crossings with one bridge, one culvert, and one improved ford. During construction, rainfall simulation was utilized to estimate the sediment contribution of each crossing with minimal BMPs (BMP-), BMPs equal to state recommendations (BMP), and BMPs beyond state recommendations (BMP+). Construction costs were recorded to quantify the change in cost with a change in BMP level. Three levels of rainfall simulation were used on each BMP treatment for each crossing resulting in 27 rainfall simulations. Water samples collected by an automatic sampler downstream of the crossings were analyzed for suspended sediment. Pre - and post- construction time periods were compared to assess how the improved crossings altered total suspended sediment concentrations downstream of the crossings. The number of stream crossings constructed per year in Virginia was also estimated using satellite imagery on 400 harvest tracts. Site visits were conducted on 240 harvest tracts where data were collected on the presence of crossings, the types of crossings, and the level of BMP implementation. Rainfall simulation experiments showed decreased sediment with increased BMP level and daily total suspended sediment concentrations measured over 15 months showed a decrease in mean daily sediment concentration after construction of the bridge and culvert crossings. There was no decrease in sediment concentration for the ford crossing. Statewide crossing construction and BMP implementation rates were estimated. Approximately 67% of the audited stream crossings were characterized as having BMPs that were equal to or beyond state recommendations. Increased BMPs and upgrading of stream crossings resulted in decreased total suspended sediment. However, increased BMP implementation also increased stream crossing construction costs. Effectiveness of increased levels of BMPs and the pre and post construction analysis suggests the improvement of a legacy stream crossing may reduce total suspended sediment concentrations. / Ph. D.

The advent of industrial, fertilizer-intensive agriculture during the 20th century has promoted export of anthropogenic nutrients, spurring degradation of ecosystem biodiversity and water quality. Exported nitrogen and phosphorus are recognized drivers of this deterioration, and require management. In the mid-1990s, denitrifying bioreactors (DNBRs), a subsurface, edge-of-field best management practice (BMP) that intercepts and treats agricultural drainage by supporting nitrate-attenuating denitrification with a saturated, carbon-filled substrate, were developed. Since then, their utility has expanded, and recent studies have unearthed biochar's capability to stimulate simultaneous nitrate (NO3--N) and phosphate (PO43--P) removal in DNBRs. This study investigated biochar's potential as an amendment to the traditional woodchip media by conducting nine, five-day trials on twelve laboratory-scale, horizontal flow-through DNBR columns. Three media types were tested: woodchips (W), 90% woodchips and 10% biochar (B10), and 70% woodchips and 30% biochar (B30). Simulated agricultural drainage with four unique concentration combinations of 16.1 and 4.5 mg L-1 NO3--N and 1.9 and 0.6 mg L-1 PO43--P was delivered at hydraulic retention times (HRTs) of 3, 6, and 12 h. Mean NO3--N removal efficiencies ranged from 16.9%-93.7%, and media type was insignificant at low influent NO3--N concentrations, but B30 was the most effective at high influent NO3--N concentrations. Mean PO43--P removal efficiencies ranged from -122.0%-74.9%, with B10 and B30 significantly worse than W at removing PO43--P. These findings corroborate previous work indicating boosted NO3--N removal with biochar, but contradict studies upholding PO43--P-removing capabilities. / Master of Science

Geographical Information Systems (GIS) is a worldwide growing technology, however it is not yet completely accepted. Of all of the business processes in an organization, marketing is perhaps one of the natural fitting-processes to apply GIS. Even though there is recent research regarding applications of GIS in the wood products industry, those applications are mostly related to biomass mapping and logistics issues. Little research has been conducted on the utilization of GIS as part of the marketing strategic plan in this industry. Thus, the main goal of this project is to understand GIS uses on marketing application in the wood products industry, specifically in the marketing mix strategic plan. The approach of this project consisted of the collection and analysis of data from secondary wood products industries in the state of Virginia. In addition, a case of study on current users of GIS applications was conducted. Once the data from the survey and the case study were collected, validated, and analyzed; applications and guidelines for the use of GIS in marketing activities were developed. The first application was the creation of a relational database to organize the information and to create an industry directory for secondary wood products industries. Secondly, clustering techniques were used to test if wood products companies cluster around certain geographical regions. Confirmation of the clustering led to the construction of an online map. Finally, guidelines were developed to describe how to use GIS in the marketing process of wood products firms. By increasing the knowledge and developing guidelines on GIS uses on marketing mix applications this study will help the wood products industry, other practitioners and the academic community, by providing insight of the industry, possible uses to simplify the strategic process and gain understanding of the environment among other. / Master of Science

Interest in BMP-related logger education and training has increased dramatically in recent years. Harvest planning is a critical component of forestry water quality BMPs. All states’ BMP manuals recommend written timber harvest plans, and several states require them by law. The objective of this study was to evaluate the impact of harvest planning training and the use of written timber harvest plans on BMP compliance, landowner satisfaction and weather-related downtime in the Virginia Piedmont. Nine randomly chosen loggers (study group) from the Virginia Piedmont participated in two days of intensive harvest planning field training. Nine additional loggers were randomly chosen as a control group. Study loggers prepared and followed written timber harvest plans for the 29 tracts they harvested during the 8-month study period immediately following the training. Study Group loggers outperformed Control Group loggers for mean BMP compliance (90% vs. 86%), mean landowner satisfaction (3.54/4.0 vs. 3.27/4.0), and mean weather-related downtime (10% vs. 13%). Absolute scores for all evaluation criteria for both groups were good, and differences, though statistically significant, were relatively small, leading to conclusions that: • Loggers in the Virginia Piedmont are generally doing a good job. • Loggers in the Virginia Piedmont are planning their operations, whether a written plan is required or not. • Harvest planning training and written harvest plans can marginally improve BMP compliance, landowner satisfaction and weather-related downtime, even for loggers who are already performing well. / Master of Science

Three watersheds located in Westmoreland County, Virginia were monitored to evaluate effectiveness of forestry best management practices (BMPs) for minimizing hydrologic and water quality impacts associated with timber harvesting. One watershed was clear-cut without implementation of BMPs, one watershed was clear-cut with the implementation of BMPs and the third watershed was left undisturbed as a control. The 27 months of pre-harvest monitoring data and 17 months of post-harvest monitoring data were compared using the paired watershed regression analysis and the minimum detectable change (MDC) statistic. Analysis of the hydrologic data showed that peak discharge rates were not impacted by harvesting, regardless of whether BMPs were implemented. Harvesting with or without the implementation of BMPs resulted in no statistically significant change in stormflow volume. BMP implementation was found to be effective in minimizing harvesting impacts on stormflow total suspended solids (TSS), ammonia, total Kjeldahl nitrogen (TKN), total nitrogen (TN), sediment-bound nitrogen and total phosphorous (TP) concentrations and total flow TSS and TP concentrations. BMP implementation was also effective in minimizing harvesting impacts on stormflow TSS, TKN, sediment-bound nitrogen, TP and sediment-bound phosphorous loadings and total ammonia loading. The BMPs were not effective in reducing nitrate concentrations and loadings. The BROOK90 forest hydrology model was used to predict the site hydrology. Model predictions compared favorably with streamflow measurements from watersheds QN3 and QN4 until the time of harvest, but did not predict streamflows as accurately for the control watershed, QN5. / Master of Science