Graphical summaries are becoming important tools for evaluating designs. The need to compare designs in term of their prediction variance properties advanced this development. A recent graphical tool, the Fraction of Design Space plot, is useful to calculate the fraction of the design space where the scaled prediction variance (SPV) is less than or equal to a given value. In this dissertation we adapt FDS plots, to study three specific design problems: robustness to model assumptions, robustness to measurement error and design properties for generalized linear models (GLM). This dissertation presents a graphical method for examining design robustness related to the SPV values using FDS plots by comparing designs across a number of potential models in a pre-specified model space. Scaling the FDS curves by the G-optimal bounds of each model helps compare designs on the same model scale. FDS plots are also adapted for comparing designs under the GLM framework. Since parameter estimates need to be specified, robustness to parameter misspecification is incorporated into the plots. Binomial and Poisson examples are used to study several scenarios. The third section involves a special type of response surface designs, mixture experiments, and deals with adapting FDS plots for two types of measurement error which can appear due to inaccurate measurements of the individual mixture component amounts. The last part of the dissertation covers mixture experiments for the GLM case and examines prediction properties of mixture designs using the adapted FDS plots. / Ph. D.

Exotic invasive plants have become a significant issue in the Southeastern United States for private landowners. These plants possess characteristics that allow for rapid growth and easy adaptation to many growing conditions, often outcompeting native vegetation and altering wildlife habitat, especially in disturbed areas. Disturbance, including access roads, trails, harvest sites, powerline corridors, and fence rows, is common on private land. Private landowners are often left to combat these problems without many monetary or expertise resources that are available to federal lands. Three field sites, each in a different physiographic province in Virginia, were surveyed for exotic invasive populations and sampled with nested overstory, understory, and regeneration plots and wildlife point intercept transects using paired plots during the summers of 2006 and 2007. Species richness of the overstory and understory did differ, but native percent understory cover and sapling density remained unchanged. Tree density and forest basal area were reduced with presence of exotic invasive plants. Regeneration diversity and density decreased in areas of exotic plant invasion. Eastern cottontail habitat suitability increased with the presence of exotic invasive plants. Suitability of habitat for the gray squirrel, downy woodpecker food, black-capped chickadee reproduction, and eastern wild turkey cover declined with the occurrence of exotic invasive plants. Twenty three of thirty seven total invasive plots were within twenty feet of a disturbance area. Continual assessment of impacts will help provide a better understanding of the nature of exotic invasive plants to landowners and may help them to manage and prevent plant invasions. / Master of Science

No description available.

No description available.

Magistro darbe tiriama sumedėjusios augalijos kaita Vištytgirio botaninio-zoologinio draustinio miško aikštėse. Darbo objektas – miško aikštelės Vištytgirio botaniniame-zoologiniame draustinyje. Darbo tikslas – nustatyti susidariusiose aikštėse sumedėjusios ir žolinės augalijos kaitą ir įvertinti mikroklimato įtaką Vištytgirio botaniniame-zoologiniame draustinyje. Darbo metodai – sumedėjusiai augalijai įvertinti naudojama juostinė transekta. Sumedėjusios augalijos žėlinių tankis vertintas iki 50 cm ir virš 50 cm. Žolinės augalijos projekcinis padengimas įvertinamas vizualiai, įvertinama, kokią paviršiaus dalį (procentais) dengia kiekviena žolinių augalų rūšis. Dirvožemio temperatūra ir drėgnumas nustatytas prietaisu „Wet“, o dirvožemio rūgštingumas prietaisu „PMT 3000“. Apšvietimas įvertintas aikštelėse ir po medžių lajomis prietaisu „Hemi View Canopy System“. Taikant sumedėjusios ir žolinės augalijos bei dirvožemio temperatūros, drėgnumo ir rūgštingumo taip pat apšvietimo vertinimo metodus, nustatyta ir įvertinta miško aikščių sumedėjusios augalijos kaita, bei ją įtakojantys mikroklimatiniai veiksniai skirtingo dydžio miško aikštėse. Darbo rezultatai. Tyrimo metu buvo įvertinta Vištytgirio botaninio-zoologinio draustinio miško aikščių sumedėjusios ir žolinės augalijos rūšinė sudėtis ir gausa. Mažose miško aikštėse nustatytos šešios savaiminukų rūšys, vidutinio dydžio – septynios, didelėse – penkios rūšys. Mažose aikštelėse vyravo šviesos trūkumą pakeliančios, vidutinio... [toliau žr. visą tekstą] / Changes in the woody vegetation of clearances in Vištytgitis botanical-zoological reserve are analysed in the work of master science. Object of the work – forest observation plots in Vištytgiris botanical-zoological rezerve. Aim of the research – to determine the changes of woody and herbaceous vegetation in stand clearings and to assess the impact of microclimate. Method of the work – to determine woody vegetation, strip transect was used. The density of woody vegetation was measured up to 50 cm and above 50 cm. Projection coveraged was determined visually. It was determined what surface (in percentage points) is covered by each species of herbaceous plants. Soil temperature and moisture content were determined using device “Wet“ and soil acidity with device “PMT 3000“. Lighting was measured in each plot and under the trees crown using the device “Hemi View Canopy System“. Using woody and herbaceous vegetation and soil temperature, moisture content and acidity as well as lighting assessments methods to identified and evaluated vegetation changes and influencing factors in formed forest clearances. The results of the work. After the research in Vištytgiris botanical-zoological reserve was evaluated woody and herbaceous vegetation species composition and abundance in forest plots. In small forest plots were determined 6 species of natural regeneration, in medium-sized forest plots – 7 and in large – 5 species. In small plots dominated tree species, which is not demanding to... [to full text]

The interaction of active molybdenum field emission microcathode arrays with oxygen, water, carbon dioxide, methane, hydrogen and helium gases was studied. Experiments were setup to measure the emission characteristics as a function of gas exposures. The resulting changes in the surface work function of the tips were determined from the Fowler-Nordheim plots. The kinetics of the FEA-gas interaction were studied by observing the ion species originating from the array during and after gas exposures with a high resolution quadrupole mass spectrometer. With the work function data and the mass spectrometry information, the mechanisms responsible for emission degradation and subsequent device recovery after exposures have been determined. The data obtained was used in estimating the device lifetimes under various vacuum environments. Also it was found that the gas exposure effects are similar in dc and pulsed modes of operation of the arrays, thus permitting the use of dc mode testing as an effective acceleration method in establishing the device lifetimes under various vacuum conditions. The vacuum conditions required for the long term emission current stability and reliability of vacuum microelectronic devices employing FEAs are established. Exposure of Mo field emitter arrays to oxygen bearing species like oxygen, water and carbon dioxide resulted in serious emission current degradation. Whereas, exposure to methane and hydrogen caused a significant increase in emission current. The control of residual gases like 02, C02 and H20 in the vacuum envelope is essential for the emission current stability and long term reliability of vacuum microelectronic devices employing field emission microcathode technology.

Student Number : 9904953T - PhD thesis - School of Animal, Plant and Environmental Science - Faculty of Science / This study seeks to combine the knowledge of science and society to elicit the relationship between the harvesting of woody plant species and the local availability of woody species in South African savannas. Ten villages located in the former communal areas and homelands within three broad vegetation types (i.e., Mixed lowveld bushveld, Eastern thorn bushveld, and Natal lowveld bushveld) were studied. The study, conducted in the framework of the coupled human-environment system poses challenges to both scientists and managers (e.g., setting common goals). Data were collected using modified Whittaker plots (MWP) and focus group discussions (FGD), denoting ecology and society, respectively. There were nine 1000m² MWP plots sampled per village, each having nested 1m², 10m² and 100m² subplots. The FGD involved six groups of local people based on gender and age. The study revealed that the harvesting of woody plant species is a source of local disturbance to woody vegetation. Generally, there were more woody species in locations farther from settlements, having a mean of 41.97 ± 3.9, than for the intermediate (38.27 ± 5.6) and near locations (19.9 ± 4.2) within the 1000m² plots, the result of the reduction in species closer to settlements from higher harvesting levels. The larger sampling plot size of 1000m² of the MWP had the highest diversity, decreasing sequentially to the smallest scale (1m²). The density of the woody species was highest in the intermediate locations (517 ± 80 plants/ha), followed by the far and near, relative to the settlements. The Natal lowveld bushveld broad vegetation type had the highest mean density of trees (573 ± 71 trees/ha) compared to the Mixed lowveld bushveld (366 ± 64 trees/ha) and the Eastern thorn bushveld (312 ± 40 trees/ha). The stem diameters of trees were generally higher in the villages of the Mixed lowveld bushveld than the other two vegetation types. The study reaffirmed that anthropogenic disturbances within savannas impact vegetation and need to be studied concurrently with other disturbance factors (e.g., biotic and abiotic or environmental). The mean total coppice shoots of stumps within the 1000m² plots was relatively higher in the near locations (38.4%), than the far (33.0%) and intermediate (28.7%). This difference in coppicing shows that although near locations were less species rich, which is a result of disturbance, the growth of shoots may nevertheless be greater. Harvesting disturbance will possibly favour the regeneration of some species, as well as the maintenance of biodiversity. Whilst 135 woody species (from a total 191 from 42 plant families) sampled in the field were used by the local people, the community knowledge yielded almost twice as many (267 species, from 69 plant families). The ratio of mean useful woody species to total woody species remained relatively constant at about 1.0:1.1 from the near to far locations around the villages and accompanied by increased woody species diversity with distance from village. The MWP sampling yielded eight broad use categories (i.e., medicinal, wild edible fruits, fuelwood, housing and fencing poles, craft (e.g., carving), cultural, local beverages (e.g., alcohol)), and nine for the FGD (the eight for the MWP plus indigenous furniture). According to the local people, the highest number of species was used for medicine (27.8% of species), followed by fuelwood (19.2%) and wild edible fruits/seeds (19.1%). Over half of the species had multiple uses (i.e., three to eight uses), raising questions of possible threats to their persistence. Useful woody species were not restricted to any particular location or vegetation type. Large sized trees were subjected to even more uses than smaller trees, another source of conservation concern. Fifteen of the woody plant species are presently protected by law in South Africa (e.g., Adansonia digitata, Podocarpus latifolius, Mimusops caffra, Philenoptera violacea), while others are facing various forms of regional threats (e.g., Alberta magna, Catha edulis, Ocotea bullata). There is the need to popularise and make people (both local and outsiders) aware of the state of NTFP species, using local and village level information as an additional criterion for describing conservation threat (e.g., proposed “Locally Brown List” – Chapter 4). The older generation of local people were highly knowledgeable in terms of the woody species used for medicine, craft, fencing and housing poles, the middle aged in beverage making species, and the younger generation in fuelwood species. Overall, older males were highly knowledgeable of the useful species. The generally strong correlation (r = 0.99, p <0.0001) between the cumulative woody species diversity from field and community knowledge suggests the need to integrate data using multi-disciplinary approach and also to manage NTFP species. Although threat reduction assessments (TRA) and monitoring have previously been suggested, the participation of local people, harvesters and users will be crucial in making TRAs effective. In conclusion, the harvesting of NTFPs, and the impacts of the changes in the NTFP species on total diversity in savannas need to be understood in order to move towards a more holistic approach to conserving the woody species that may be at risk of extinction through harvesting. Disturbance criteria that describe harvesting levels should be set to guide research and management protocols. Finally, when discussing NTFPs and the species from which they are harvested, management should aim at incorporating all the factors that affect sustainability, such as land and resource tenure and local participation, the political economy, appropriate production and development cycles.

Le comportement des systèmes magnétiques submicroniques suscite un vif intérêt, motivé par le progrès continu des techniques de nano-fabrication et entretenu par une multitude d'applications potentielles (mémoires non-volatiles). La compréhension des effets induits par le confinement de la taille latérale des systèmes magnétiques combine le micromagnétisme expérimental et numérique. L'objectif de ce travail est de développer des outils numériques appropriés à l'étude du magnétisme des structures de dimensions réduites, en utilisant la modélisation micromagnétique. L'approximation des différences finies est utilisée pour l'évaluation des énergies et des champs internes qui décrivent l'état du système. L'algorithme de la minimisation de l'énergie libre repose sur l'intégration temporelle de l'équation de Landau-Lifshitz-Gilbert. L'amélioration de l'approche numérique (la précision du calcul, la stabilité du schéma d'intégration) ainsi que sa validation à travers des problèmes test et des résultats expérimentaux représentent les premières étapes de nos travaux. Cette approche numérique flexible nous a permis d'étudier des systèmes bi- et tri-dimensionnels, périodiques et non-périodiques. Ainsi, les détails de la structure interne des parois de domaines dans des couches minces de Co à anisotropie magnétocristalline uniaxiale planaire ou perpendiculaire ont été obtenus et analysés en fonction de l'épaisseur de la couche et du champ externe appliqué. L'étude menée sur les plots cylindriques de Co nous a permis d'établir les limites de stabilité des différents états magnétiques en fonction de la taille latérale et des paramètres de matériau. Notamment l'état de type vortex, favorisé par la symétrie circulaire de l'objet, a été analysé pour un champ appliqué perpendiculairement au plan du plot. Le caractère tridimensionnel des parois de domaines dans des nanofils de Co épitaxiés à anisotropie magnétocristalline parallèle ou perpendiculaire à l'axe du fil a été mis en évidence.

<p>This study examines the relationship between land fragmentation and agricultural productivity in Vietnam, as well as the outcomes of land consolidation programs on productivity. Data from the Vietnam Household Living Standard Survey 2004 and data on the land consolidation process was used for the regression analysis. The results show weak correlations between fragmentation and productivity. Land fragmentation seems to be positively correlated to productivity due to more use of fertilizers and labour input. The communes that have consolidated their land are more productive, but this seems to be explained by initial differences in productivity. Our results suggest that there are no immidiate gains in land consolidation.</p>

This study examines the relationship between land fragmentation and agricultural productivity in Vietnam, as well as the outcomes of land consolidation programs on productivity. Data from the Vietnam Household Living Standard Survey 2004 and data on the land consolidation process was used for the regression analysis. The results show weak correlations between fragmentation and productivity. Land fragmentation seems to be positively correlated to productivity due to more use of fertilizers and labour input. The communes that have consolidated their land are more productive, but this seems to be explained by initial differences in productivity. Our results suggest that there are no immidiate gains in land consolidation.