1,017 research outputs found
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Precision LCVD System Design with Real Time Process Control
A Laser Chemical Vapor Deposition (LCVD) system was designed using a fixed 100
Watt C02 laser focused on a moveable substrate. Temperature and height measurement devices
monitor the reaction at the point of deposition to provide feedback for controlling the process.
The LCVD system will use rapid prototyping technology to directly fabricate fully threedimensional ceramic, metallic, and composite parts of arbitrary shape. Potential applications
include high temperature structures, electronic/photonic devices, and orthopaedic implants.Mechanical Engineerin
Correspondence of perceived vs. objective proximity to parks and their relationship to park-based physical activity
<p>Abstract</p> <p>Background</p> <p>Parks are key environmental resources for encouraging population-level physical activity (PA). In measuring availability of parks, studies have employed both self-reported and objective indicators of proximity, with little correspondence observed between these two types of measures. However, little research has examined how the degree of correspondence between self-reported and objectively-measured distance to parks is influenced by individual, neighborhood, and park-related variables, or which type of measure is more strongly related to physical activity outcomes.</p> <p>Methods</p> <p>We used data from 574 respondents who reported the distance to their closest park and compared this with objective measurements of proximity to the closest park. Both indicators were dichotomized as having or not having a park within 750 m. Audits of all park features within this distance were also conducted and other personal characteristics and neighborhood context variables (safety, connectedness, aesthetics) were gleaned from participants' survey responses. Participants also completed detailed seven-day PA log booklets from which measures of neighborhood-based and park-based PA were derived.</p> <p>Results</p> <p>Agreement was poor in that only 18% of respondents achieved a match between perceived and objective proximity to the closest park (kappa = 0.01). Agreement was higher among certain subgroups, especially those who reported engaging in at least some park-based PA. As well, respondents with a greater number of parks nearby, whose closest park had more features, and whose closest park contained a playground or wooded area were more likely to achieve a match. Having a ball diamond or soccer field in the closest park was negatively related to achieving a match between perceived and objective proximity. Finally, engaging in at least some park-based PA was not related to either perceived or objective proximity to a park, but was more likely when a match between and perceived and objective proximity occurred.</p> <p>Conclusion</p> <p>Poor levels of correspondence were observed between self-reported and objective proximity to parks, but certain individual, neighborhood, and park variables increased the likelihood of a participant being aware of local parks. Future research should examine how people conceptualize parks and what urban and park planners can do to increase awareness and use of these community assets.</p
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Policy Conundrum: Restoring Wild Salmon to the Pacific Northwest
Restoring wild salmon runs to the Pacific Northwest is technically challenging, politically nasty, and socially divisive. Past restoration efforts have been largely unsuccessful. Society’s failure to reverse the continuing decline of wild salmon has the characteristics of a policy conundrum: nearly everyone supports, abstractly at least, restoring salmon runs; considerable public and private resources have been devoted to their restoration; but society collectively remains evidently unwilling to make the painful decisions clearly necessary to arrest their decline. The salmon policy conundrum is characterized by competing societal priorities being adjudicated in a political environment where few are willing to acknowledge publicly the future consequences of prior de facto policy choices. Decisions already made have greatly circumscribed the status of wild salmon in the Pacific Northwest through at least the next several decades. Barring a near wholesale reversal of many of society’s previous decisions (and apparent priorities), and allowing for considerable year-to-year and decade-to-decade variation in run size due in part to oscillations in climate and oceanic conditions, I conclude that through the twenty-first century, many, perhaps most, stocks of wild salmon in the Pacific Northwest likely will remain at their current low levels or continue to decline in spite of current protection and restoration efforts.Keywords: Salmon, Fisheries, Endangered Species, Extinction, Pacific Northwes
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Fabrication of Advanced Thermionic Emitters Using Laser Chemical Vapor Deposition-Rapid Prototyping 498
Laser Chemical Vapor Deposition-Rapid Prototyping (LCVD-RP) is a relatively new manufacturing process. Its capabilities are ideally suited for the manufacturing of a type of electron emitter called an integrated-grid thermionic emitter. The integrated-grid thermionic emitter is composed of wagon wheel-like structures of alternating layers of boron nitride and molybdenum on tungsten. The goal of this paper is to determine the feasibility of using LCVDRP technology to manufacture advanced thermionic emitters.Mechanical Engineerin
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Heat Transfer Analysis of a Gas-Jet Laser Chemical Vapor Deposition (LCVD) Process 461
This paper describes the development of a computer model used to characterize the heat transfer properties of a gas-jet LCVD process. A commercial software package was used to combine heat transfer finite element analysis with the capabilities of computational fluid dynamic software (CFDS). Such a model is able to account for both conduction and forced convection modes of heat transfer. The maximum substrate temperature was studied as a function of laser power and gas-jet velocity.Mechanical Engineerin
Assertion, Uniqueness and Epistemic Hypocrisy
Pascal Engel (2008) has insisted that a number of notable strategies for rejecting the knowledge norm of assertion are put forward on the basis of the wrong kinds of reasons. A central aim of this paper will be to establish the contrast point: I argue that one very familiar strategy for defending the knowledge norm of assertion—viz., that it is claimed to do better in various respects than its competitors (e.g. the justification and the truth norms)— relies on a presupposition that is shown to be ultimately under motivated. That presupposition is the uniqueness thesis—that there is a unique epistemic rule for assertion, and that such a rule
will govern assertions uniformly. In particular, the strategy I shall take here will be to challenge the sufficiency leg of the knowledge norm in a way that at the same time counts against Williamson’s (2000) own rationale for the uniqueness thesis. However, rather than to challenge the sufficiency leg of the knowledge norm via the familiar style of ‘expert opinion’ and, more generally, ‘second-hand knowledge’ cases (e.g. Lackey (2008)), a strategy that has recently been called into question by Benton (2014), I’ll instead advance a very different line of argument against the sufficiency thesis, one which turns on a phenomenon I call epistemic hypocrisy
Identifying lesbian, gay, bisexual, and transgender search terminology: A systematic review of health systematic reviews
Research on the health of lesbian, gay, bisexual, and transgender (LGBT) populations can provide important information to address existing health inequalities. Finding existing research in LGBT health can prove challenging due to the plethora of terminology used. We sought to describe existing search strategies and to identify more comprehensive LGBT search terminology. We iteratively created a search string to identify systematic reviews and meta-analyses about LGBT health and implemented it in Embase, PubMed/MEDLINE, and PsycINFO databases on May 28-29, 2015. We hand-searched the journal LGBT Health. Inclusion criteria were: systematic reviews and meta-analyses that addressed LGBT health, used systematic searching, and used independent coders for inclusion. The published search terminology in each record and search strings provided by authors on request were cross-referenced with our original search to identify additional terminology. Our search process identified 19 systematic reviews meeting inclusion criteria. The number of search terms used to identify LGBT-related records ranged from 1 to 31. From the included studies, we identified 46 new search terms related to LGBT health. We removed five search terms as inappropriate and added five search terms used in the field. The resulting search string included 82 terms. There is room to improve the quality of searching and reporting in LGBT health systematic reviews. Future work should attempt to enhance the positive predictive value of LGBT health searches. Our findings can assist LGBT health reviewers in capturing the diversity of LGBT terminology when searching
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