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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Water and Nitrogen in Designed Ecosystems: Biogeochemical and Economic Consequences

January 2010 (has links)
abstract: More than half of all accessible freshwater has been appropriated for human use, and a substantial portion of terrestrial ecosystems have been transformed by human action. These impacts are heaviest in urban ecosystems, where impervious surfaces increase runoff, water delivery and stormflows are managed heavily, and there are substantial anthropogenic sources of nitrogen (N). Urbanization also frequently results in creation of intentional novel ecosystems. These "designed" ecosystems are fashioned to fulfill particular needs of the residents, or ecosystem services. In the Phoenix, Arizona area, the augmentation and redistribution of water has resulted in numerous component ecosystems that are atypical for a desert environment. Because these systems combine N loading with the presence of water, they may be hot spots of biogeochemical activity. The research presented here illustrates the types of hydrological modifications typical of desert cities and documents the extent and distribution of common designed aquatic ecosystems in the Phoenix metropolitan area: artificial lakes and stormwater retention basins. While both ecosystems were designed for other purposes (recreation/aesthetics and flood abatement, respectively), they have the potential to provide the added ecosystem service of N removal via denitrification. However, denitrification in urban lakes is likely to be limited by the rate of diffusion of nitrate into the sediment. Retention basins export some nitrate to groundwater, but grassy basins have higher denitrification rates than xeriscaped ones, due to higher soil moisture and organic matter content. An economic valuation of environmental amenities demonstrates the importance of abundant vegetation, proximity to water, and lower summer temperatures throughout the region. These amenities all may be provided by designed, water-intensive ecosystems. Some ecosystems are specifically designed for multiple uses, but maximizing one ecosystem service often entails trade-offs with other services. Further investigation into the distribution, bundling, and tradeoffs among water-related ecosystem services shows that some types of services are constrained by the hydrogeomorphology of the area, while for others human engineering and the creation of designed ecosystems has enabled the delivery of hydrologic ecosystem services independent of natural constraints. / Dissertation/Thesis / Ph.D. Biology 2010
42

Projection Properties and Analysis Methods for Six to Fourteen Factor No Confounding Designs in 16 Runs

January 2012 (has links)
abstract: During the initial stages of experimentation, there are usually a large number of factors to be investigated. Fractional factorial (2^(k-p)) designs are particularly useful during this initial phase of experimental work. These experiments often referred to as screening experiments help reduce the large number of factors to a smaller set. The 16 run regular fractional factorial designs for six, seven and eight factors are in common usage. These designs allow clear estimation of all main effects when the three-factor and higher order interactions are negligible, but all two-factor interactions are aliased with each other making estimation of these effects problematic without additional runs. Alternatively, certain nonregular designs called no-confounding (NC) designs by Jones and Montgomery (Jones & Montgomery, Alternatives to resolution IV screening designs in 16 runs, 2010) partially confound the main effects with the two-factor interactions but do not completely confound any two-factor interactions with each other. The NC designs are useful for independently estimating main effects and two-factor interactions without additional runs. While several methods have been suggested for the analysis of data from nonregular designs, stepwise regression is familiar to practitioners, available in commercial software, and is widely used in practice. Given that an NC design has been run, the performance of stepwise regression for model selection is unknown. In this dissertation I present a comprehensive simulation study evaluating stepwise regression for analyzing both regular fractional factorial and NC designs. Next, the projection properties of the six, seven and eight factor NC designs are studied. Studying the projection properties of these designs allows the development of analysis methods to analyze these designs. Lastly the designs and projection properties of 9 to 14 factor NC designs onto three and four factors are presented. Certain recommendations are made on analysis methods for these designs as well. / Dissertation/Thesis / Ph.D. Industrial Engineering 2012
43

Development of a Diffused Junction Silicon Solar Cell Pilot Line

January 2014 (has links)
abstract: In the interest of expediting future pilot line start-ups for solar cell research, the development of Arizona State University's student-led pilot line at the Solar Power Laboratory is discussed extensively within this work. Several experiments and characterization techniques used to formulate and optimize a series of processes for fabricating diffused-junction, screen-printed silicon solar cells are expounded upon. An experiment is conducted in which the thickness of a PECVD deposited anti-reflection coating (ARC) is varied across several samples and modeled as a function of deposition time. Using this statistical model in tandem with reflectance measurements for each sample, the ARC thickness is optimized to increase light trapping in the solar cells. A response surface model (RSM) experiment is conducted in which 3 process parameters are varied on the PECVD tool for the deposition of the ARCs on several samples. A contactless photoconductance decay (PCD) tool is used to measure the dark saturation currents of these samples. A statistical analysis is performed using JMP in which optimum deposition parameters are found. A separate experiment shows an increase in the passivation quality of the a-SiNx:H ARCs deposited on the solar cells made on the line using these optimum parameters. A RSM experiment is used to optimize the printing process for a particular silver paste in a similar fashion, the results of which are confirmed by analyzing the series resistance of subsequent cells fabricated on the line. An in-depth explanation of a more advanced analysis using JMP and PCD measurements on the passivation quality of 3 aluminum back-surface fields (BSF) is given. From this experiment, a comparison of the means is conducted in order to choose the most effective BSF paste for cells fabricated on the line. An experiment is conducted in parallel which confirms the results via Voc measurements. It is shown that in a period of 11 months, the pilot line went from producing a top cell efficiency of 11.5% to 17.6%. Many of these methods used for the development of this pilot line are equally applicable to other cell structures, and can easily be applied to other solar cell pilot lines. / Dissertation/Thesis / M.S. Electrical Engineering 2014
44

What affects the tear strength of paperboard? : Consequences of unbalance in a designed experiment

Forsberg, Niklas January 2017 (has links)
This essay covers a designed experiment on paperboard where the quality under study is tear strength alongside and across. The objective is to examine what consequences the loss of balance in a designed experiment has on the explanatory power of the proposed empirical model. As did happen, the trial plan didn’t go as planned when the first run caused a disruption of the paperboard in the machine. Decision from the company was to raise the low level of one of the design factors to prevent this from happening again. The consequence of this is an alteration of the design during ongoing experimentation. This in turn affects what analysis approaches are appropriate for the problem. Three different approaches for analyzing the data are presented, each with different propositions on how to deal with the complication that occurred. The answer to the research question is that the ability of the empirical model to discover significant effects is moderately weakened by the loss of one run (out of eight total). The price payed for retrieving less information from the experiment is that the empirical model, for tear strength across, doesn’t deem the effects significant at the same level as for the candidate model with eight runs. Instead of concluding that the main effect of  and the interaction effect  is significant at the 2%- and 4%-level, respectively, we must now settle with deeming them significant at the 6%- and 7%-level.
45

Development of Manufacturing Systems for Nanocrystalline and Ultraine Grain Materials Employing Indexing Equal Channel Angular Pressing

Hester, Michael Wayne 09 May 2015 (has links)
Nanotechnology offers significant opportunities in providing solutions to existing engineering problems as well as breakthroughs in new fields of science and technology. In order to fully realize benefits from such initiatives, nanomanufacturing methods must be developed to integrate enabling constructs into commercial mainstream. Even though significant advances have been made, widespread industrialization in many areas remains limited. Manufacturing methods, therefore, must continually be developed to bridge gaps between nanoscience discovery and commercialization. A promising technology for integration of top-down nanomanufacturing yet to receive full industrialization is equal channel angular pressing, a process transforming metallic materials into nanostructured or ultraine grained materials with significantly improved performance characteristics. To bridge the gap between process potential and actual manufacturing output, a prototype top-down nanomanufacturing system identified as indexing equal channel angular pressing (IX-ECAP) was developed. The unit was designed to capitalize on opportunities of transforming spent or scrap engineering elements into key engineering commodities. A manufacturing system was constructed to impose severe plastic deformation via simple shear in an equal channel angular pressing die on 1100 and 4043 aluminum welding rods. 1/4 fraction factorial split-plot experiments assessed significance of five predictors on the response, microhardness, for the 4043 alloy. Predictor variables included temperature, number of passes, pressing speed, back pressure, and vibration. Main effects were studied employing a resolution III design. Multiple linear regression was used for model development. Initial studies were performed using continuous processing followed by contingency designs involving discrete variable length work pieces. IX-ECAP offered a viable solution in severe plastic deformation processing. Discrete variable length work piece pressing proved very successful. With three passes through the system, 4043 processed material experienced an 88.88% increase in microhardness, 203.4% increase in converted yield strength, and a 98.5% reduction in theoretical final grain size to 103 nanometers using the Hall-Petch relation. The process factor, number of passes, was statistically significant at the 95% confidence level; whereas, temperature was significant at the 90% confidence level. Limitations of system components precluded completion of studies involving continuous pressing. Proposed system redesigns, however, will ensure mainstream commercialization of continuous length work piece processing.
46

The Building That Learns to Fish: Architecture, Peak Oil, and the Need for Adaptability

Pelland, Justin M 01 January 2012 (has links) (PDF)
Oil is a finite resource; This much has been established as fact and is commonly agreed upon. We will, some day, find our supplies depleted. The question that remains hotly debated, however, is when this will happen and what impacts it will have on our modern lives. Estimates and forecasts abound, but still no one can answer these questions definitively. As fossil fuels, the energy behind virtually every aspect of our lives, become scarce, our patterns of growth will face a reckoning. We will be forced to adapt and adjust; either shifting our energy demand to more renewable sources, or reducing it by significant amounts. Although there are a plethora of what-if scenarios when predicting the effects of an end to oil, it’s easy to recognize that the peak oil crisis will significantly impact our lives. It will change how we live them and, by extension, where and how we construct our buildings. So what does this mean for buildings - one of the country’s largest consumers of energy? This thesis proposes that a theory of adaptability, when applied properly to the design and construction process, can begin to equip our building to handle the range of possible outcomes that an energy-poor future poses. This thesis also aims to address, in the broadest of terms, how our current approach to design could lead to significant issues in a post-oil, energy hungry world. It does so by encouraging a more holistic approach to problem solving and building design, while outlining how the values of cost efficiency and speed have polarized global construction techniques.
47

The Rational Design of Coiled-Coil Peptides towards Understanding Protein-Crystal Interactions and Amorphous-to-Crystalline Transitions

Chang, Eric P. 16 April 2013 (has links)
No description available.
48

Computational Design and Optimization of Bone Tissue Engineering Scaffold Topology

Uth, Nicholas P. 14 January 2016 (has links)
No description available.
49

Att behålla hjärna och kropp igång vid åldrandet - Vårdpersonals syn på aktivitet på särskilda boenden

Erlandsson, Anna, Greitans, Sofie January 2010 (has links)
The purpose of this study is to examine how activities are looked upon, organized and put into practice at homes designed for the elderly. To achieve this we have done a survey study, based upon the caregiver´s point of view regarding the subject activity. The result of this study has been interpreted and analyzed with help from the engagement- and disengagement theories. The result shows us that the caregiver´s find the term activity slightly abstract, and rather difficult to define. All of the caregiver´s did agree on the matter that it’s good to activate elderly people and that the elderly people are activated at a large extent. The result also shows us that it’s not always the elderly people’s own wishes and desires of activity that gets organized and put into practice at homes designed for the elderly. In conclusion we find the engagement theory to be very dominant in the thoughts and actions of caregiver´s in Swedish geriatric care, rather than the disengagement theories.
50

Elements of depth

Kidd, Mairi January 1994 (has links)
Depth is an architectural quality created by progression, delineation, and repetition. This project explores depth through the design of three major elements- floor, wall, and roof. Each element is created using one or more aspect of depth and combined to produce a house which is an integral part of its site. / Master of Architecture

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