Headwater catchments play a large role in the storage and release of water and chemical constituents, thereby influencing downstream flows and water quality. Recent advances in water quality monitoring technologies have created an opportunity to better assess water chemistry variation by using high temporal resolution, in situ sensors. However, despite these new technologies, there have been limited studies on installation approaches and their effects on sensor measurements. Accurate in situ monitoring is particularly important to capture catchment disturbance effects that may be highly dynamic over time (e.g., following storms) or limited in duration. For example, prescribed fire is a commonly applied forest management tool, but there remain questions regarding how this disturbance affects catchment soils and resultant stream water chemistry. Effective assessment of prescribed fire thus requires coupled monitoring of both soil properties and water chemistry. In this thesis, I addressed two linked objectives: i) assess the effects of commonly used protective housings on in situ sensor measurements (Chapter 2) and ii) evaluate prescribed burn effects in a southwestern Virginia, USA headwater catchment (Chapter 3). In Chapter 2, I compared four different housing types (mesh, screen, holes, and open) using in situ specific conductance measurements over time and from salt tracer injections for discharge estimates. This study demonstrated substantial effects from some of the housing types evaluated, where flow resistance reduced water exchange between stream water and water in contact with the sensor. From these findings, I suggest that in situ water quality sensors should be deployed in housing types with large openings perpendicular to flow. In Chapter 3, I assessed prescribed fire effects on soil properties (particle size, aggregate stability, and chemistry), stream discharge, and fine-scale water chemistry dynamics. Findings demonstrated some significant differences following fire in soil properties (e.g., overall decrease in aggregate stability, general decreases in total carbon and nitrogen of mineral soils), water quality (e.g., increased levels of DOC, turbidity, and nitrate) and discharge (increases in stage and flow). While these changes were statistically significant, differences in parameters before and after fire were generally small. Future work should examine if these effects persist through time, and whether the minor level of disturbance observed in this study results in any negative environmental impacts. / Master of Science / Headwater catchments (where precipitation first becomes streamflow) provide important aquatic habitat and regulate downstream water flows and chemistry. Recent advances in water quality monitoring technologies have created an opportunity to better assess water chemistry variability by using high frequency, submerged water quality sensors. However, these new technologies present new, unique challenges, such as measurement errors that may be induced by different installation methodologies. Accurate measurements are particularly important to evaluate how changes in catchment conditions (e.g., soils, vegetation) impact local and downstream water quality. For example, prescribed fire is a commonly used forest management tool, but questions remain about how it affects catchment soils and headwater stream chemistry. Consequently, understanding the effects of this and other catchment disturbances requires coupled monitoring of both soil properties and water quality. In this thesis, I addressed two objectives: i) assess the effects of commonly used protective housings on water quality sensor measurements (Chapter 2) and ii) evaluate prescribed burn effects in a southwestern Virginia, USA headwater catchment (Chapter 3). In Chapter 2, I demonstrated substantial effects from some of the housings evaluated and suggest that water quality sensors should be deployed in housing types with large openings perpendicular to flow. In Chapter 3, I demonstrated some significant effects of prescribed fire on soil properties (e.g. overall decrease in soil stability, general decreases in total carbon and nitrogen of mineral soils), water quality (e.g., increased levels of dissolved organic matter, turbidity, and nitrate) and flow (increases in stream water levels and flow). While these changes were statistically significant, differences in parameters before and after fire were generally small. Future work should examine if these effects persist through time, and whether this minor level of disturbance causes any negative environmental impacts.

Canopy mortality. species abundance. and the species composition and origin of regeneration in mixed oak forests were studied following a 1900 ha man-caused early growing season wildfire in Shenandoah National Park. in the Blue Ridge Physiographic Province. Virginia. Pre-fire stands were dominated by chestnut. scarlet, and northern red oaks growing on medium quality sites (50 year upland oak site index 16-20 m). Permanent vegetation plots were established in four stands for each of high and low levels of fire intensity. and unburned stands. High-intensity fire killed 67% of the basal area and 81% of the trees, whereas low-intensity fire resulted in mortality of 8% of the basal area and 15% of the trees. The mean height of stem-bark char accounted for 91% and 95% of the variation in percent of the basal area and number of trees killed by fire, respectively. Logistic regression models were developed to predict the probability of fire-induced individual tree mortality (top-kill) as a function of DBH and height of stem-bark char for chestnut oak, scarlet and northern red oaks, pignut hickory, blackgum. and red maple. Blackgum and chestnut oak were the most fire resistant species studied. High-intensity fire resulted in the development of a new stand, whereas low-intensity fire resulted in thinning of the overstory and understory. Most species present in pre-fire stand reproduced via basal sprouts, chestnut oak sprouts were the most abundant stems taller than 1 m two growing seasons after high-intensity fire. Tree-of-heaven was the only species to regenerate by seed and able to match the height growth of oak basal sprouts. This research suggests that oaks are capable of replacing themselves on medium quality sites following wildfire-induced canopy removal in 55 to 60 year old stands. / Master of Science

Rosebay rhododendron (Rhododendron maximum L.) is an evergreen ericaceous shrub that plays a dynamic role in the southern Appalachian forests. Commonly located on mesic sites, this understory shrub forms dense thickets that greatly reduce the amount of light available to herbaceous and woody plants found on the forest floor. Past research has shown that silvicultural methods can be used to eradicate R. maximum, however it is unclear which of these methods is most efficient and what effects other than stem mortality may occur. In this study, treatments involving prescribed fire, mechanical cutting, and herbicide applications were applied to R. maximum dominated forests in southwestern Virginia to determine what effect seven different silvicultural treatments had on 1) controlling of R. maximum as a forest weed 2) fuel loading inside of a R. maximum thicket, and 3) canopy tree seedling regeneration. Mechanical cutting treatments were successful in reducing R. maximum basal area per acre; however stump sprouting and increased fuel loading occurred. Herbicide applications were successful in controlling only the smallest diameter class of R. maximum stems. Prescribed fire reduced litter layers and caused delayed mortality on R. maximum stems three years following treatment. Hemispherical photographs taken within each plot showed that silvicultural treatments that successfully increased the amount of light entering each plot were influential in seedling establishment three years following treatments. Results from this study can be used to further perfect silvicultural applications that alleviate R. maximum cover on the forest landscape. / Master of Science

Controlling systems with uncertain dynamics is crucial in systems theory, especially for unmanned vehicles operating in challenging and unknown environments. One key application involves developing control methods to ensure collision-free trajectory tracking for unmanned surface vehicles (USVs) at sea. Modern control methods for such systems often encounter unwanted high-frequency oscillations, known as chattering, in the control signals. To address this, continuous approximations of discontinuous functions in the control law have proven effective in reducing chattering. This approach is integrated into a prescribed-performance control scheme, which has previously achieved asymptotic tracking for systems with uncertain dynamics. We employ Lyapunov stability analysis to determine if theoretical bounds for error performance can be smaller than the prescribed funnel functions when incorporating continuous approximations in a boundary-layer. For both first- and second-order systems, we show that system trajectories reach an arbitrarily small boundary-layer set in finite time. This allows us to derive a priori known error bounds that are smaller than the prescribed funnels. Simulations support the theoretical results, demonstrating a significant reduction in chattering while achieving asymptotic tracking errors two orders of magnitude smaller than the funnel functions.

No description available.

Call number: LD2668 .T4 1985 J36 / Master of Science

Fuel accumulation rate and total soil nitrogen, phosphorus, and sulfur following prescribed fires were studied. Three prescribed fires were conducted in S.E. Arizona ponderosa pine stands during the summers of 1979, 1980, and 1981. Samples of forest floor and larger diameter fuel and soil from the surface 1.5 inches and 1.5 to 3.0 inch layers were collected in the summer of 1981. Forest floor and total fuel accumulation averaged 5.4 to 6.7 and 6.3 to 8.9 tons/acre/year, respectively. Total nitrogen, phosphorus, and sulfur in the surface three inches of mineral soil were not significantly affected by burning. Soil nitrogen, phosphorus, and sulfur content averaged 0.21%, 344 ppm and 150 ppm, respectively, in the surface 1.5 inches and 0.11%, 285 ppm and 74 ppm, respectively, in the 1.5 to 3.0 inch layer.

Training can enable performers to express music in a personal and emotional way while communicating aesthetic impressions to an audience. Little research has been done on the emotive experiences of performing musicians listening to their own performances. The main goal of this study was to develop a reliable way to investigate emotive content of such experiences through a combination of listening profiles and continuous measurement. This empirical, methodological study used a mixed-method design. Responses from formally and informally trained musicians were tested. The methodology consists of two parts: listening profiles (Part I), and the continuous measurement of self-reported emotional response to music (Part II), supported by interviews. Part I consists of a demographic questionnaire, a listening test and a personality test. Part II consists of a computerised questionnaire with four questions: 1) word sorting, 2) word, colours, and facial expressions checklists, which participants use to indicate their emotional responses while the music plays, 3) free description, and 4) rating scales. Data was obtained during three test periods. Part I results revealed that personality, illness, preferences, and psychological factors influence the emotive content of listening experiences. Participants’ response time and manner of word sorting was also supportive of their profiles. Part II results revealed that listeners pay attention to both structural and performance elements as well as emotive content in both prescribed and personal musical tracks. Only a few participants were able to identify the predetermined emotion of the prescribed musical tracks. Participants’ experiences seemed to be influenced by training and personal preferences. Listening to their own recorded performances, informally trained participants were able to focus progressively less on performance elements and more on emotive content, while formally trained participants seemed to focus progressively more on performance elements, and less on emotive content. / Thesis (MMus)--North-West University, Potchefstroom Campus, 2012

This research was designed to investigate issues of quality in the reading of fiction of 11 – 16 year olds in school; this included the reading of fiction as part of the curriculum and private reading for pleasure. It is research which found its roots in the surveys of children’s reading habits carried out by Jenkinson (1946), Whitehead, Capey, and Maddren, (1977), Hall and Coles (1999) and Clark, Osborne and Akerman (2008). These surveys, over sixty years, show how attitudes to reading for 11 – 16 year olds, their reading habits and their preferred texts have changed. Judgements of quality in children’s chosen reading are implied in those studies but criteria for these judgments of quality are not defined. The National Curriculum (NC) for England (2008) explicitly refers to texts considered to be of high quality and lists prescribed texts and authors, but does not define what is meant by quality. The study was designed to investigate how teachers and students in secondary schools (11 – 16 year olds) in England conceptualised quality in the fiction used in class and for private reading. Individual teachers and groups of 11 – 16 year olds from four schools in the South-West of England were interviewed using semi-structured interviews. The interview data were analysed using a Cultural and Historical Activity Theory (CHAT) framework. The findings indicate that interpretations of quality are complex and often linked to examination syllabus requirements; the iterations of the NC for English in England; and discrete individual school and departmental needs. This can cause professional tension amongst teachers relating to the imposed rules, to external expectations and to the lack of teacher autonomy. The study offers new insights into how fiction for 11 – 16 year olds is used and conceptualised in school. This is represented theoretically through the framework of CHAT and in terms of the confusion at the intersection of boundary objects. The outcomes of the research will also contribute to clarifying how texts written for young adults may be judged and to the conceptualisation of a pedagogy to support the use of fiction with 11 – 16 year olds in school.

Fire may alter both aquatic and terrestrial habitat used by all amphibian life stages, yet, our knowledge of its effects on amphibians is primarily limited to adult responses. I present an integrated approach to test the response of Cope’s Gray Treefrog (Hyla chrysoscelis) to fire by examining responses in tadpole performance and survivorship, adult abundance, and oviposition. Tadpoles raised with burned leaf litter had similar survival, but total mass and total length were 440% and 170% greater, respectively, for tadpoles raised in unburned litter. I assessed terrestrial and aquatic oviposition cues by embedding burned and unburned litter treatments within burned and unburned terrestrial plots. Oviposition was an order of magnitude higher in unburned plots, regardless of the litter treatment. This difference was not statistically significant or driven by adult abundance. My results indicate the need to explore the dynamic effects forest management practices can have on amphibians across life stages.