Using the envelope theory, the mathematical model of the end face profile and the working tool path of a special optical fiber polishing machine is deve- loped in this study. During the polishing process, the polisher is controlled by three parameters including the fiber rotational angle, the height H and the angle between the fiber and polisher. The contact points between the optical fiber and the polishing plate will determine the profile of the fiber end face. The 3-D end face with double-variable curvatures can be fabricated by properly controlling these three parameters. Since the grinding (polishing) material removal rate is related to machining time and normal contact force, the grinding (polishing) tool path and parameters are needed some modification in order to get the precise end profiles. Example of fiber end faces of 2-D elliptical face and 3-D ellipsoid are given to check the developed mathematical model in this study by computer solid modeling.

Oak savannas are among the most imperiled ecosystems in the United States as a result of habitat degradation and consequently, associated vegetation and wildlife communities have also declined. I evaluated savanna restoration strategies on twelve case studies in Tennessee and Kentucky. These case studies represented a broad range of disturbances and the most advanced savanna restoration sites within the region. I evaluated vegetation and breeding bird responses to landscape and overstory conditions across sites through a meta-analysis. Total grass and forb cover were influenced by overstory metrics but not by topography (P >0.05). Oak regeneration density was influenced by canopy cover, while oak competitor regeneration density was influenced by percent slope and sapling density (P <0.05). With respect to breeding birds, I found forest species persisted within case studies despite substantial disturbance; shrub/scrub birds were common on disturbed sites. Only three obligate grassland bird species, Tyrannus tyrannus, Aimophila aestivalis, Spiza americana, were observed on my sites. Relative abundance of Passerina cyanea was positively related to the groundlayer development; whereas that of Melanerpes erythrocephalus was positively related to basal area of dead trees (P <0.05). Based on my results, canopy reduction and growing-season burns may both be critical for the restoration of savannas within the region. Drum-chopping is a tool that may expedite oak savanna restoration through improved woody competition control, however, its effectiveness has not been investigated. Therefore, I evaluated drum-chopping effects on vegetative structure at Catoosa Wildlife Management Area, Tennessee, during 2008 and 2009 using two adjacent sites with similar fire and overstory removal histories. One site was subjected to drum-chopping in September of 2007, while an adjacent site (control) was not chopped. Drum-chopping reduced grass and forb cover, and oak seedling density, but increased bare ground and density of vines and shrubs versus the control (P <0.05). Except for bare ground, differences were no longer apparent in the second year. Based on my results, drum chopping may reduce midstory vegetation too thick to be effectively controlled by fire, but otherwise has limited utility as a restoration tool. Although wildlife managers have tried to restore savannas using prescribed fire and overstory canopy removal, use of other tools may be warranted. One such method is drum-chopping, which has been used elsewhere to reduce woody competition. However, the effectiveness of this method in restoring oak savannas has not been evaluated. Therefore, I evaluated drum-chopping effects on plant composition at Catoosa Wildlife Management Area on the Cumberland Plateau in Tennessee. Two adjacent sites with similar fire and overstory removal histories were selected for this study. One of these sites was subjected to drum-chopping (CHOP) in September of 2007, the adjacent site was not chopped (NOCHOP). Grass cover differed by treatment (P <0.01) and year*treatment (P = 0.03). Forb cover differed by treatment (P <0.01) and legume cover differed by year (P <0.01), treatment (P <0.01), and year*treatment (P = 0.01). Exposed bare ground differed by year (P <0.01) and treatment (P <0.01). Exposed leaf litter differed by year (P <0.01). Vines and shrubs (<1.37m tall) differed by treatment (P <0.01). Oak seedling (0-30.48 cm tall) densities differed by treatment (P = 0.05). Based on my results, drum chopping may be a valuable tool where woody encroachment has become too thick for fire to be effective or herbicides are not a viable option, but otherwise has limited utility as a tool for oak savanna restoration.

Thesis (M.A.)--University of North Texas, Aug., 2009. / Title from title page display. Includes bibliographical references.

Diss. (sammanfattning) Linköping : Linköpings universitet, 2008. / Härtill 5 uppsatser. Includes bibliographical references.

Thesis (M.S.)--Marshall University, 2002. / Title from document title page. Document formatted into pages; contains vi, 81 p. including illustrations. Includes bibliographical references (p. 41-44).

Industrial flaring can have negative impacts on regional air quality and recent studies have shown that flares are often operated at low combustion efficiency, which exacerbates these air quality impacts. This thesis examines industrial flaring with the objectives of (1) assessing the air quality impacts of flares operating at a variety of conditions, (2) examining the extent to which improvements in flare operations could reduce emissions, (3) identifying opportunities for recycling flared gases in fuel gas networks, and (4) identifying opportunities for reducing the generation of flared gases, using the improved control of catalytic cracking operations as a case study. The work presented in this thesis demonstrates that flares operating at low combustion efficiency can increase localized ambient ozone concentrations by more than 15 ppb under some conditions. The impact of flares on air quality depends most strongly on combustion efficiency, the flow rates to the flares and the chemical composition (photochemical reactivity) of the emissions. Products of incomplete combustion and nitrogen oxides emissions from flaring generally had a smaller impact on air quality than unburned flare gases. The combustion efficiency at which a flare can operate can be constrained by the flare’s design. In a case study of an air-assisted flare, it was demonstrated that choices in blower configurations could lead to emissions that were orders of magnitude greater or less than those predicted using an assumed combustion efficiency of 98%. Designing flares with air-assist rates that can be finely tuned can significantly reduce emissions. Similarly, flaring can be reduced by integrating sources of waste gases into fuel gas networks. Analyses for a petroleum refinery indicated that this integration can often be accomplished with little net cost by expanding boiler capacities. Finally, flared gases can be reduced at their source. A case study of a fluid catalytic cracking indicated that using better temperature control could significantly minimize flared gases. / text

Drawing from the lessons of plant transpiration, this dissertation explores a biomimiced system for fluid transport and thermal regulation. This system utilizes evaporation and benefits from the associated passive pumping with an application of a rooftop solar radiation barrier in mind. By directing the incoming energy towards the phase change of water, lower surface temperatures can be maintained thus reducing heat transfer into the structure by conduction. In order to design and construct such a bio-inspired system, several parameters, i.e., the evaporation surface, the delivery path and the working fluid, must be understood as to how they affect and limit operations. Performance factors such as evaporation rate and suction pressure were monitored for the various design constraints of feeding tube length and diameter, membrane area, and working fluid. Additionally, as a heat flux was imposed on the membrane from above and below, the substrate temperature became important. Over the range of parameters tested, hydrodynamic resistances of the delivery path were shown to affect pumping height but not the evaporation rate. Instead, the evaporation rate was controlled by the substrate temperature. Furthermore, the normalized evaporation rate was found to be inversely related to the evaporation surface area. Under contaminated working fluid conditions, particles deposited in the membrane caused decreases in evaporation rates. When applied to a simulated roof situation, the evaporation system was successful at maintaining considerably lower surface temperatures than other conventional and unconventional roof albedos, which, in turn, would reduce heat flux into the interior by conduction. Lastly, in estimating the water consumption, on a typical August day in Austin, TX, the system could use up to 2 gallons/m² while providing enhanced cooling. When the system's resources were compared to being purposed in other ways, they were arguably better utilized in providing evaporative cooling. / text

Programmers make systematic edits—similar, but not identical changes to multiple places during software development and maintenance in order to add features and fix bugs. Finding all the correct locations and making the ed- its correctly is a tedious and error-prone process. Existing tools for automating systematic edits are limited because they do not create general purpose edit scripts or suggest edit locations, except for specialized or trivial edits. Since many similar changes occur in similar contexts (in code with similar surrounding dependent relations and syntactic structures), there is an opportunity to automate program transformations based on examples of systematic edits. By inferring systematic edits and relevant context from one or more exemplar changes, automated approaches can (1) apply similar changes to other loca- tions, (2) locate code that requires similar changes, and (3) refactor code which undergoes systematic edits. This thesis seeks to improve programmer produc- tivity and software correctness by automating parts of systematic editing and refactoring. Applying similar, but not identical code changes, to multiple locations with similar contexts requires (1) understanding and relating common program context—a program’s syntactic structure, control, and data flow—relevant to the edits in order to propagate code changes from one location to oth- ers, and (2) recognizing differences between locations in order to customize code changes for each location. Prior approaches for propagating nontrivial, general-purpose code changes from one location to another either do not ob- serve the program context when placing edits, or do not handle the differences between locations when customizing edits, producing syntactic invalid or in- correctly modified programs. We design a novel technique and implement it in a tool called Sydit. Our approach first creates an abstract, context-aware edit script which contains a syntax subtree enclosing the exemplar edit with all concrete identifiers abstracted and a sequence of edit operations. It then applies the edit script to user-selected locations by establishing both context matching and identifier matching to correctly place and customize the edit. Although SYDIT is effective in helping developers correctly apply edits to multiple locations, programmers are still on their own to identify all the appropriate locations. When developers omit some of the locations, the edit script inferred from a single code location is not always well suited to help them find the locations. One approach to infer the edit script is encoding the concrete context. However, the resulting edit script is too specific to the source location, and therefore can only identify locations which contain syntax trees identical to the source location (false negatives). Another approach is to encode context with all identifiers abstracted, but the resulting edit script may match too many locations (false positives). To suggest edit locations, we use multiple examples to create a partially abstract, context-aware edit script, and use this edit script to both find edit locations and transform the code. Our experiments show that edit scripts from multiple examples have high precision and recall in finding edit locations and high accuracy when applying systematic edits because the extracted common context together with identified common concrete identifiers from multiple examples improves the location search without sacrificing edit application accuracy. For systematic edits which insert or update duplicated code, our systematic editing approaches may encourage developers in the bad practice of creating or evolving duplicated code. We investigate and evaluate an approach that automatically refactors cloned code based on the extent of systematic edits by factoring out common code and parameterizing any differences between them. Our investigation finds that refactoring systematically edited code is not always feasible or desirable. When refactoring is desirable, systematic ed- its offer a better way to scope the refactoring as compared to whole method refactoring. Automatic clone removal refactoring cannot obviate the need for systematic editing. Developers need tool support for both automatic refactoring and systematic editing. Based on the systematic changes already made by developers for a subset of change locations, our automated approaches facilitate propagating general purpose systematic changes across large programs, identifying locations requiring systematic changes missed by developers, and refactoring code undergoing systematic edits to reduce code duplication and future repetitive code changes. The combination of these techniques opens a new way of helping developers automate tedious and error-prone tasks, when they add features, fix bugs, and maintain software. These techniques also have the potential to guide automated software development and maintenance activities based on existing code changes mined from version histories for bug fixes, feature additions, refactoring, and software migration. / text

Indoor air quality investigations often focus on air and settled dust samples to assess chemical and biological contamination. Although the information provided by these techniques is useful, HVAC filters represent a new option for investigating contaminants in the indoor environment. This dissertation explores the potential use of HVAC filters as long-term, passive samplers by investigating the contaminants found in HVAC dust and other indoor locations and by evaluating the likelihood that HVAC filters will capture indoor particles. A field investigation of heavy metal and culturable microbial contaminants found in air, settled dust and HVAC filter dust corroborated the hypothesis that HVAC filters hold promise as a sampling mechanism in residences. However, several factors including filter efficiency, HVAC cycling and particle size seemed to influence the results. Also, it was unclear how the composition of the microbial communities varied with sampling location. Subsequently, the bacterial and fungal communities present in several sampling locations within residences and in an unoccupied test house were investigated. In residences, the microbial communities encountered in HVAC filter dust were not different from those in high surface dust. High efficiency HVAC filters also seem to be a viable alternative to long-term air sampling. Occupants influence the composition of the microbial communities in residences and are viii associated with Actinobacteria and Firmicutes, while Proteobacteria dominate the air samples and might have an outdoor air origin. A fate analysis to assess the magnitude of the different particle removal mechanisms revealed that small and large particles are likely to deposit on surfaces, while intermediate sized particles stay suspended in air longer. HVAC filters can collect particulate matter over a broad size range and may be effective overall samplers of particle-bound contaminants. Nevertheless, filter efficiency and air recirculation rate are important parameters that influence the likelihood that filters will capture particles, while air exchange rate has little effect. The results from this study indicate that HVAC filters can be used as an alternative to traditional indoor sampling mechanisms for contaminants associated with particles.

D. Tech. Chemical Engineering. / This research aims to improve the current state of wastewater treatment technologies by exploiting the characteristics and capabilities of nanomaterials. Also, it aims at protecting the environment and human health by minimizing exposure of toxic contaminants found in waters sources by treatment with cheaply engineered materials. The nanocomposites that will be employed in this study have shown to be effective for removing a number of heavy metals from aqueous solutions during trial experiment. The study is therefore carried out to reduce the water scarcity in South Africa by minimizing the contamination of remaining water resources. With industrial effluents the main targets, the aim is to design systems that will enable industries to recycle their wastewater instead of discharging into the environment. This study will therefore benefit the communities who solely depend on surface and ground water and again it will safe industrial bodies high costs of treating their wastewater with ineffective conventional methods. The research focuses on the application of polypyrrole-clay nanocomposites for removing heavy metals from wastewater streams. The research conducted hereby highlights the application of polymer based nanocomposites as suitable adsorbents for the remediation of the toxic chromium(VI) [Cr(VI)] from water. The work describes the preparation and characterization of the nanocomposites, their application to wastewater laden with Cr(VI) in both batch and continuous adsorption and finally understanding the adsorbent-adsorbate interactions and sorption mechanisms under various physico-chemical conditions.