Kinetics and morphology of electrochemical vapour deposited thin zirconia/yttria layers on porous substrates

By means of electrochemical vapour deposition (EVD), it is possible to grow thin (0.5-5 µm), dense zirconia/yttria layers on porous ceramic substrates. Kinetics of the EVD process, morphology and oxygen permeation properties of the grown layers are investigated. Very thin (~ 0.5 µm) layers are grown at relatively low temperatures (700-800 °C). Water vapour as reactant enhances the surface reaction rate at the solid oxide/oxygen source reactant interface. A transition occurs from pore diffusion (above 1000 °C) to bulk electrochemical diffusion (below 900 °C) as rate-limiting step for layer growth. The zirconia/yttria solid solution is mainly deposited in the cubic phase; the layers grow in a typical columnar way and are polycrystalline. Oxygen permeation measurements show that the oxygen permeation flux through the zirconia/yttria layers is influenced by the layer thickness, morphology, presence of water vapour and the oxygen pressure gradient over the layer

Impact of Farmland Preservation Programs on the Rate of Urban Development

Due to high losses of agricultural land in urbanizing areas over the past several years, state and local governments have adopted zoning regulations, right-to-farm ordinances, preferential property tax programs, and other means to protect agricultural land resources. Critics of the farmland preservation efforts note that these programs may only delay the ultimate conversion of farmland to urban uses and may simply shift urban development to neighboring areas (positive spillover effects). An alternative means of permanently protecting farmland is provided by purchase of development rights (PDR) programs, which enroll acreage from landowners who voluntarily sell the development rights to their farmland. Although ownership and all other property rights are retained by the owner, the option to develop the land for urban uses is removed from the current and all subsequent landowners. The purpose of this paper is to develop an empirical model of the impact of PDR programs on urban land development rates. To estimate the empirical model, we form a dependent variable based on county level rates of urban development from the USDA National Resources Inventory (NRI) data base for nine states in the Northeast US that have adopted farmland protection measures during the sample period (1982-1997). The set of explanatory variables include dummy variables for the existence of an active PDR program in the county and active PDR programs in adjacent counties plus measures of demographics, farm returns, population growth, income, and site-specific factors gathered from several sources (e.g., Census of Agriculture, Census of Population, and USDA). The model is estimated using the ordinary least squares technique. Two key policy-relevant hypotheses: (1) PDR programs did not reduce the rate of urban development and (2) PDR programs did not induce positive spillover effects on neighboring counties. The test results suggest that PDRs may have had important more significant impact in the earlier years and did not cause positive spillover effects.Land Economics/Use,

Generalization of Gutzwiller Approximation

We derive expressions required in generalizing the Gutzwiller approximation to models comprising arbitrarily degenerate localized orbitals.Comment: 6 pages, 1 figure, to appear in J.Phys.Soc.Jpn. vol.6

VPI Processes and Resin Evaluations for CPA Electrical Windings

High energy density requirements for fieldable electric gun applications has led to the air-core compensated pulsed alternator (CPA) or compulsator as the generator of choice to provide pulse power. The air-core nature of the machines combined with ambitious power density requirements has led to the minimizing of metallic supporting structures which places additional structural requirements on the electrical windings within the generators.Center for Electromechanic

Enantiomer fractions instead of enantiomer ratios

The use of enantiomer ratios (ERs) to indicate the relative amounts of a pair of enantiomers in a sample has some disadvantages. Enantiomer fractions (EFs) are proposed as all alternative expression to eliminate the difficulties. (C) 2000 Elsevier Science Ltd

Modelling and analysis of CVD processes for ceramic membrane preparation

A mathematical model is presented that describes the modified chemical vapour deposition (CVD) process (which takes place in advance of the electrochemical vapour deposition (EVD) process) to deposit ZrO2 inside porous media for the preparation and modification of ceramic membranes. The isobaric model takes into account intrapore Knudsen diffusion of ZrCl4 and H2O, which enter the membrane from opposite sides, and Langmuir-Hinshelwood reaction of the solid product ZrO2 on the internal pore wall. The processes occurring in one single pore are investigated, and the change in pore geometry during deposition is taken into account. Based upon this model, the deposition profile is studied. The model fits reasonably well with experimental results

Resilience of a deer hunting system in Southeast Alaska: integrating social, ecological, and genetic dimensions

Thesis (Ph.D.) University of Alaska Fairbanks, 2009I examined the interactions of key components of a hunting system of Sitka black-tailed deer (Odocoileus hemionus sitkensis) on Prince of Wales Island, Alaska to address concerns of subsistence hunters and to provide a new tool to more effectively monitor deer populations. To address hunter concerns, I documented local knowledge and perceptions of changes in harvest opportunities of deer over the last 50 years as a result of landscape change (e.g., logging, roads). To improve deer monitoring, I designed an efficient method to sample and survey deer pellets, tested the feasibility of identifying individual deer from fecal DNA, and used DNA-based mark and recapture techniques to estimate population trends of deer. I determined that intensive logging from 1950 into the 1990s provided better hunter access to deer and habitat that facilitated deer hunting. However, recent declines in logging activity and successional changes in logged forests have reduced access to deer and increased undesirable habitat for deer hunting. My findings suggested that using DNA from fecal pellets is an effective method for monitoring deer in southeast Alaska. My sampling protocol optimized encounter rates with pellet groups allowing feasible and efficient estimates of deer abundance. I estimated deer abundance with precision (±20%) each year in 3 distinct watersheds, and identified a 30% decline in the deer population between 2006-2008. My data suggested that 3 consecutive severe winters caused the decline. Further, I determined that managed forest harvested>30 years ago supported fewer deer relative to young-managed forest and unmanaged forest. I provided empirical data to support both the theory that changes in plant composition because of succession of logged forest may reduce habitat carrying capacity of deer over the long-term (i.e., decades), and that severity of winter weather may be the most significant force behind annual changes in deer population size in southeast Alaska. Adaptation at an individual and institutional level may be needed to build resilience into the hunting system as most (>90%) of logged forest in southeast Alaska transitions over the next couple of decades into a successional stage that sustains fewer deer and deer hunting opportunities.1. General introduction -- 2. Influence of hunter adaptability on resilience of subsistence hunting systems -- 3. Linking hunter knowledge with forest change to understand changing deer harvest opportunities in intensively logged landscapes -- 4. Individual identification of Sitka black-tailed deer using DNA from fecal pellets -- 5. A practical approach for sampling along animal trails -- 6. Estimating abundance of Sitka black-tailed deer using DNA from fecal pellets -- 7. Summary -- 8. Future recommendations -- Appendix

Pore Narrowing and Formation of Ultrathin Yttria-Stabilized Zirconia Layers in Ceramic Membranes by Chemical Vapor Deposition/Electrochemical Vapor Deposition

Chemical vapor deposition (CVD) and electrochemical vapor deposition (EVD) have been applied to deposit yttria-stabilized-zirconia (YSZ) on porous ceramic media. The experimental results indicate that the location of YSZ deposition can be varied from the surface of the substrates to the inside of the substrates by changing the CVD/EVD experimental conditions, i.e., the concentration ratio of the reactant vapors. The deposition width is strongly dependent on the deposition temperature used. The deposition of YSZ inside the pores resulted in pore narrowing and eventually pore closure, which was measured by using permpor-ometry. However, deposition of YSZ on top of porous ceramic substrates (outside the pores) did not result in a reduction of the average pore size. Ultrathin, dense YSZ layers on porous ceramic substrates can be obtained by suppressing the EVD layer growth process after pore closure