Deadwood, characterized as both downed woody material (DWM) and standing and dead stems, i.e., snags, is a significant component of terrestrial forest ecosystems. Deadwood amount and structure may influence potential wildfire hazard by altering combustible DWM mass and creating fuel structures that increase fire intensity and spread. Deadwood is also critical to carbon storage and nutrient cycling and may vary based upon the size classes of individual deadwood pieces. Lastly, deadwood structural variability has been found to positively affect species richness in bees, salamanders, birds, and small mammals, such as shrews and woodland mice. However, in the Mid-Atlantic Piedmont, there are no accessible tools to rapidly estimate deadwood of long unmanaged second growth forests to help inform future management decisions. Management agencies within this region, such as the National Park Service, may benefit from a greater understanding of the potential factors that influence deadwood accumulation, retention, and decomposition. Therefore, a project was funded by the National Park Service to investigate deadwood dynamics at Prince William Forest Park (PRWI). From May to August 2023, a deadwood inventory was conducted using planar intercepts nested within fixed radius plots along the gradient of forest cover types, aspect, elevation, and soil orders found within PRWI. Forest cover type was significant in the generalized linear model for percent dead basal area, total DWM, fine woody material, litter, and duff mass. The Virginia pine (Pinus virginiana) forest cover type had the highest percent dead basal area and total DWM mass per hectare. Elevation, aspect, and soil order were not significantly related to percent dead basal area, total DWM, 1,000 hr, fine woody material, litter, and duff mass. Data from this study may serve as a baseline for similar second growth forests of the mid-Atlantic Piedmont. / Master of Science / Visitors to Prince William Forest Park (PRWI) in eastern Virginia have voiced concern about forest health within PRWI. The perception of a high number of standing and dead stems, or snags, and a high number of decaying logs, branches, and twigs on the ground has been a focal point for visitors. Some perceive the dead material on the ground as a potential source of fuel for wildfires. Others perceive the potential hazard to humans along trails and vistas if snags were to fall. However, snags and downed woody material, known as deadwood, are critical components of forests because they store carbon and nutrients long-term and may provide habitat and resources for many wildlife species. Many other heavily used recreation locations in the eastern US face similar deadwood and forest health challenges. To respond to this, we assessed deadwood in PRWI to determine how it may be distributed differently across the variety of landscape features that are present within the park. We found the amount of total downed and dead material on the forest floor increased as the percentage of trees that were standing and dead increased. The amount of dead material on the ground was greatest for the Virginia pine (Pinus virginiana) forest community type, whereby PRWI's stands have reached their life expectancy. Prince William Forest Park's managers and those elsewhere at similar locations throughout the eastern US may benefit from this information as they seek to evaluate the status of their resources, manage those resources, and provide thoughtful messaging to the public regarding the significance and maintenance of deadwood as an ecosystem resource.

Harvest-related decreases of downed woody debris (DWD) in forests may have important ecological implications; however, patterns of nutrient release from decaying DWD are poorly understood. The importance of DWD was investigated relative to biomass and nutrient pools in six, second-growth boreal mixedwood forest stands, differing by harvest regime near Kapuskasing, Ontario. Nutrient concentrations and mineralization trends using ion exchange resins at three proximities during the decay of Abies balsamea and Populus tremuloides were also examined. Concentrations of N, P, Ca, and Mg increased with decay, whereas K decreased. DWD was a minor contributor to biomass and nutrient pools. Inorganic N, P, Ca, and Mn were significant between harvest types with decay class interaction for N, Ca, and Mn. Species and proximity effects were found for Al, Fe, and K. These results suggest DWD may be a minor contributor to biomass and nutrient pools, but highlights its dynamic nature.

Harvest-related decreases of downed woody debris (DWD) in forests may have important ecological implications; however, patterns of nutrient release from decaying DWD are poorly understood. The importance of DWD was investigated relative to biomass and nutrient pools in six, second-growth boreal mixedwood forest stands, differing by harvest regime near Kapuskasing, Ontario. Nutrient concentrations and mineralization trends using ion exchange resins at three proximities during the decay of Abies balsamea and Populus tremuloides were also examined. Concentrations of N, P, Ca, and Mg increased with decay, whereas K decreased. DWD was a minor contributor to biomass and nutrient pools. Inorganic N, P, Ca, and Mn were significant between harvest types with decay class interaction for N, Ca, and Mn. Species and proximity effects were found for Al, Fe, and K. These results suggest DWD may be a minor contributor to biomass and nutrient pools, but highlights its dynamic nature.

Increasing modernization of the world has brought about a human component to natural disasters, which are exacerbated by the growing threat of climate change. The Western United States and Australia have witnessed some of the deadliest, costliest, and destructive wildfires in the recent past with downed electric power lines being a significant factor amongst the causes. The relationship between wildfires and powerlines is not a newly discovered phenomenon, however, utilities across the globe are struggling to find an optimal solution to this problem. While existing regulations allow utilities to schedule power shutdowns, they are often accompanied by massive financial losses and discomfort to consumers. Utilities also need to factor in the climatic conditions in the region of their service and the flammability of the vegetation surrounding their lines while making decisions pertaining to system planning, load shedding, and protection. This multi-faceted problem can be dealt with in multiple ways – one such technique involves detection of a falling line into sensitive vegetation before it encounters the earth. This approach essentially boils down the problem into detecting a single line open circuit fault. The open circuit is momentary and hence, speed is of the essence in such a protection scheme. In this thesis, detection of an open circuit is carried out in two different ways, viz., with and without communication support between the various elements of the system, with the latter technique being a novel proposal with the aim of achieving a secure protection scheme with minimal additional infrastructural requirements. / Master of Science / The contact of a live wire with the earth is a fault. While most faults can be cleared using traditional protection techniques, there is a higher risk associated with power lines that come in contact with dry surfaces, flammable plants, and bushes, which cannot be detected that easily. These surfaces offer very high resistance to the flow of current and are hence termed high impedance faults. These high impedance faults have the potential to spark and cause a fire, which can snowball into a wildfire depending on the geography and climatic conditions of the area. For years, this has been a major problem in places like Australia and California leading to loss of lives, power, and money, but the optimal solution is evasive. While several techniques to combat this problem exist, the focus of this thesis is essentially what is known as the Open Circuit Fault. The technique revolves around the detection of the fault while the falling conductor is midair. Given the short time frame, high-speed detection is of the essence. This thesis will focus on achieving open circuit detection without the need for any communication support and is a novel contribution to this field.

Downed woody debris (DWD) is a carbon-rich form of forest litter and plays a unique role in carbon and nutrient cycling. I present a novel modeling approach describing DWD decomposition and nutrient storage in a managed northern hardwood forest. The predicted half-life of DWD carbon was 7 years, less than previously observed in similar northern hardwood forests. A stage-based nutrient model indicated that harvest slash DWD was a net nitrogen and phosphorus sink for eight years following harvest and accumulated calcium during decay. Field observations of respiration and leaching supported model results with a respired C half-life of 8 years, while leached carbon export constituted 1.37% of the respired flux. DWD leachate carbon and nitrogen concentrations were 11× and 2× greater than from litter, respectively, and DWD leachate contributed disproportionately to soil C stocks. This work represents an expedient means of forecasting DWD abundance and partitioning carbon flux from DWD.

Downed woody debris (DWD) is a carbon-rich form of forest litter and plays a unique role in carbon and nutrient cycling. I present a novel modeling approach describing DWD decomposition and nutrient storage in a managed northern hardwood forest. The predicted half-life of DWD carbon was 7 years, less than previously observed in similar northern hardwood forests. A stage-based nutrient model indicated that harvest slash DWD was a net nitrogen and phosphorus sink for eight years following harvest and accumulated calcium during decay. Field observations of respiration and leaching supported model results with a respired C half-life of 8 years, while leached carbon export constituted 1.37% of the respired flux. DWD leachate carbon and nitrogen concentrations were 11× and 2× greater than from litter, respectively, and DWD leachate contributed disproportionately to soil C stocks. This work represents an expedient means of forecasting DWD abundance and partitioning carbon flux from DWD.

abstract: The safety issue in an electrical power distribution system is of critical importance. In some circumstances, even the continuity of service has to be compromised for a situation that can cause a hazard to the public. A downed conductor that creates an electrical path between a current carrying conductor and ground pose a potential lethal hazard to anyone in the near proximity. Electric utilities have yet to find a fully accepted and reliable method for detecting downed conductors even with decades of research. With the entry of more automation and a smarter grid in the different layers of distribution power system supply, new doors are being opened and new feasible solutions are waiting to be explored. The 'big data' and the infrastructures that are readily accessible through the smart metering system is the base of the work and analysis performed in this thesis. In effect, the new technologies and new solutions are an artifact of the Smart Grid effort which has now reached worldwide dimensions. A solution to problems of overhead distribution conductor failures / faults that use simple methods and that are easy to implement using existing and future distribution management systems is presented. A European type distribution system using three phase supply is utilized as the test bed for the concepts presented. Fault analysis is performed on the primary and the secondary distribution system using the free downloadable software OpenDSS. The outcome is a set of rules that can be implemented either locally or central using a voltage based method. Utilized in the distribution management systems the operators will be given a powerful tool to make the correct action when a situation occurs. The test bed itself is taken from an actual system in Norway. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2014

I examined the effects of potential predators in relation to habitat selection in Peromyscus leucopus. I also examined habitat selection in three other sympatric species (Blarina brevicauda, Blarina carolinensis, Sorex longirostris). I utilized data fiom 49 sampling sites on National Park Service land; Petersburg National Battlefield Eastern Front Unit (15), Five-Forks Unit (17), Appomattox Court House National Historical Park (15) and Booker T. Washington National Monument (12). Sites were categorized by location (park unit) and habitat type (i.e. bottom-land hardwood), and the microhabitat within each sampling site was characterized by four variables (% cover of grasses, herbs, shrubs, and volume of downed wood). Importance values of tree species within each sampling site were also measured. Peromyscus leucopus, B. brevicauda, B. carolinensis, and S. longirostris were captured in all habitat types. Low capture rates for shrew species and high variability in the abundance of shrew species among all sampling sites were likely responsible for the lack of differences in abundance among habitats (p > 0.05). Peromyscus leucopus represented 76% of the captures among prey species and was the only species to demonstrate differences in relative abundance among habitat types. The relative abundance of P. leucopus was higher in bottom-land hardwood habitat when compared to pine forest plantation habitat (ANOVA, p P. leucopus among these habitat types may be explained by differences in understory structural diversity. Furthermore, the corresponding increase in the relative abundance of Procyon lotor (the most abundant predator during the study) in structurally heterogeneous habitat (bottom-land hardwood) suggests the importance of anti-predator behaviors within these habitat types. Ultimately, this may suggest that prey cannot escape the presence or calculate the abundance of predators and instead simply avoid dangerous habitats. Although the relative abundance of the most abundant predator (P. lotor) and prey (P. leucopus) species were positively associated within certain habitat types, a negative association between predator and prey species abundance was evident within parks. In the Eastern Front unit the relative abundance of prey (P. leucopus, S. longirostris) was lower in comparison to the Five-Forks unit while the abundance of P. lotor was higher (ANOVA, p P. lotor, Didelphis virginiana, and Urocyon cinereoargenteus were higher in the Eastern Front unit when compared to the Five-Forks unit. It appeared that the lethal effects of predators are evident at larger scales (within parks) despite the anti-predator behaviors of prey at smaller scales (within microhabitats). My results indicate that at larger scales (within parks) the lethal effects (removal of prey) of abundant predators may overwhelm the non-lethal effects (anti-predator behavior) exhibited by prey at smaller scales, especially in areas where structurally heterogenous habitats are lacking.

This thesis describes an investigation into the influences of arcing and conductor deflection due to magnetic forces on the accuracy of fault locator algorithms in electrical distribution networks. The work also explores the possibilities of using the properties of an arc to identify two specific types of faults that may occur on an overhead distribution line. A new technique using the convolution operator is introduced for deriving differential equation algorithms. The first algorithm was derived by estimating the voltage as an array of impulse functions while the second algorithm was derived using a piecewise linear voltage signal. These algorithms were tested on a simulated single-phase circuit using a PI-model line. It was shown that the second algorithm gave identical results as the existing dynamic integration operator type algorithm. The first algorithm used a transformation to a three-phase circuit that did not require any matrix calculations as an equivalent sequence component circuit is utilised for a single-phase to ground fault. A simulated arc was used to test the influence of the non-linearity of an arc on the accuracy of this algorithm. The simulations showed that the variation in the resistance due to arcing causes large oscillations of the algorithm output and a 40th order mean filter was used to increase the accuracy and stability of the algorithm. The same tests were performed on a previously developed fault locator algorithm that includes a square-wave power frequency proximation of the fault arc. This algorithm gave more accurate and stable results even with large arc length variations. During phase-to-phase fault conditions, two opposing magnetic fields force the conductors outwards away from each other and this movement causes a change in the total inductance of the line. A three dimensional finite element line model based on standard wave equations but incorporating magnetic forces was used to evaluate this phenomenon. The results show that appreciable errors in the distance estimations can be expected especially on poorly tensioned di stribution lines.New techniques were also explored that are based on identification of the fault arc. Two methods were successfully tested on simulated networks to identify a breakingconductor. The methods are based on the rate of increase in arc length during the breaking of the conductor. The first method uses arc voltage increase as the basis of the detection while the second method make use of the increase in the non-linearity of the network resistance to identify a breaking conductor. An unsuccessful attempt was made to identifying conductor clashing caused by high winds: it was found that too many parameters influence the separation speed of the two conductors. No unique characteristic could be found to identify the conductor clashing using the speed of conductor separation. The existing algorithm was also used to estimate the voltage in a distribution network during a fault for power quality monitoring purposes.

Made available in DSpace on 2016-08-17T14:53:02Z (GMT). No. of bitstreams: 1 Julio Cesar Nascimento Sousa.pdf: 971697 bytes, checksum: b4ee5e79977202a1c5eba4528ed34766 (MD5) Previous issue date: 2006-09-22 / This work focuses on the modeling of single-phase and three-phase distribution with earth return, for high impedance faults analysis. The main motivation is the lack of definitive solutions for such faults. These faults often occur when an overhead conductor breaks and falls on high impedance surface such as asphalt road, cement, trees, among others. That fault is analyzed in a Single wire earth return system - SWER, and in a rural three-phase feeder. The SWER is deduced starting from a generic three-phase system, where simplifications based on practical assumptions are added. Simulations are accomplished in two distribution test systems, with the objective of identifying the behavior pattern of the high impedance faults. It is also included a discussion and analysis of results and suggestions related to future works. / Este trabalho focaliza a modelagem das redes de distribuição monofásicas e trifásicas com retorno por terra, para análise das faltas de alta impedância. A motivação principal está no fato de não existirem soluções definitivas para essas faltas. Este tipo de falta ocorre quando um cabo energizado rompe e cai sobre um tipo de superfície, tal como asfalto, areia, árvores, dentre outros. Essa falta é analisada em uma rede Monofásica com Retorno por Terra MRT em uma rede trifásica rural. A rede MRT é deduzida a partir de uma rede trifásica genérica, onde são adicionadas hipóteses simplificadoras práticas. São realizadas simulações em dois sistemas testes de distribuição, com o objetivo de identificar o padrão de comportamento das faltas de alta impedância. É realizada uma discussão e análise de resultados, sugerindo-se trabalhos futuros.