32,275 research outputs found
Filler bar heating due to stepped tiles in the shuttle orbiter thermal protection system
An analytical study was performed to investigate the excessive heating in the tile to tile gaps of the Shuttle Orbiter Thermal Protection System due to stepped tiles. The excessive heating was evidence by visible discoloration and charring of the filler bar and strain isolation pad that is used in the attachment of tiles to the aluminum substrate. Two tile locations on the Shuttle orbiter were considered, one on the lower surface of the fuselage and one on the lower surface of the wing. The gap heating analysis involved the calculation of external and internal gas pressures and temperatures, internal mass flow rates, and the transient thermal response of the thermal protection system. The results of the analysis are presented for the fuselage and wing location for several step heights. The results of a study to determine the effectiveness of a half height ceramic fiber gap filler in preventing hot gas flow in the tile gaps are also presented
Interrater and intrarater reliability of arthroscopic measurements of articular cartilage defects in the knee
Superplastic Forming and Diffusion Bonding of Titanium Alloys
New and advanced fabrication methods for titanium components are emerging today to replace age-old fabrication processes and reduce component cost. Superplastic forming and diffusion bonding are two such advanced fabrication technologies which when applied individually or in combination can provide significant cost and weight benefits and a rather broad manufacturing technology base. This paper briefly reviews the state of understanding of the science and technology of super plastic forming of titanium alloys, and their diffusion bonding capability. Emphasis has been placed on the metallurgy of superplastic flow in two phase titanium alloys, the microstructural and external factors which influence this behaviour
Economics and science of hog manure handling and storage technologies
Non-Peer ReviewedHog production has been growing rapidly in Canada and this growth has created concerns over manure handling and the risk of soil and water contamination. There is limited information available to swine producers as to which technologies and manure management systems would best serve them both economically and environmentally. The objective of this study is to assess hog manure handling and storage systems and outline their environmental advantages and disadvantages. Five main technologies are reviewed which include (1) manure handling, (2) solid/liquid separation, (3) composting, (4) land application, and (5) manure storage. The average cost of hauling liquid manure within 2-3 mile distance is about 1.22 to 4.85 to 0.0039 to $0.0953 per gallon depending on availability of equipment and materials and additional costs may also required for adding a liner of clay. Other types of storage system generally cost higher but they might be more environmentally friendly. Operation and maintenance costs of manure storage is mainly limited with seasonal labor for agitation the waste, removal of sludge, and performing pump outs
The social cognition of medical knowledge, with special reference to childhood epilepsy
This paper arose out of an engagement in medical communication courses at a Gulf university. It deploys a theoretical framework derived from a (critical) sociocognitive approach to discourse analysis in order to investigate three aspects of medical discourse relating to childhood epilepsy: the cognitive processes that are entailed in relating different types of medical knowledge to their communicative context; the types of medical knowledge that are constituted in the three different text types analysed; and the relationship between these different types of medical knowledge and the discursive features of each text type. The paper argues that there is a cognitive dimension to the human experience of understanding and talking about one specialized from of medical knowledge. It recommends that texts be studied in medical communication courses not just in terms of their discrete formal features but also critically, in terms of the knowledge which they produce, transmit and reproduce
Acting out our dam future: science-based role-play simulations as mechanisms for learning and natural resource planning
Science often does not make its way into decisions, leading to a problematic gap between scientific and societal progress. To tackle this issue, our research tests a novel science-based negotiation simulation that integrates a role-play simulation (RPS) with a system dynamics model (SDM). In RPSs, stakeholders engage in a mock decision-making process (reflecting real-life institutional arrangements and scientific knowledge) for a set period. System dynamics models (SDMs) are visual tools used to simulate the interactions and feedback within a complex system. We test the integration of the two approaches with stakeholders in New England via a series of two consecutive workshops across two states. The workshops engage stakeholders from diverse groups to foster dialogue, learning, and creativity. Participants discuss a hypothetical (yet realistic) decision scenario to consider scientific information and explore dam management options that meet one another\u27s interests. In the first workshop, participants contributed to the design of the fictionalized dam decision scenario and the SDM. In the second workshop, participants assumed another representative\u27s role and discussed dam management options for the fictionalized scenario. This presentation will briefly report on the practical design of this science-based role-play, and particularly emphasize preliminary results of workshop outcomes, which were evaluated using debriefing sessions, surveys, concept mapping exercises, and interviews. Results will determine the extent to which this new knowledge production process leads to learning, use of science, and more collaborative decision-making about dams in New England and beyond
Coherent electronic transfer in quantum dot systems using adiabatic passage
We describe a scheme for using an all-electrical, rapid, adiabatic population
transfer between two spatially separated dots in a triple-quantum dot system.
The electron spends no time in the middle dot and does not change its energy
during the transfer process. Although a coherent population transfer method,
this scheme may well prove useful in incoherent electronic computation (for
example quantum-dot cellular automata) where it may provide a coherent
advantage to an otherwise incoherent device. It can also be thought of as a
limiting case of type II quantum computing, where sufficient coherence exists
for a single gate operation, but not for the preservation of superpositions
after the operation. We extend our analysis to the case of many intervening
dots and address the issue of transporting quantum information through a
multi-dot system.Comment: Replaced with (approximately) the published versio
Manifolds with 1/4-pinched flag curvature
We say that a nonnegatively curved manifold has quarter pinched flag
curvature if for any two planes which intersect in a line the ratio of their
sectional curvature is bounded above by 4. We show that these manifolds have
nonnegative complex sectional curvature. By combining with a theorem of Brendle
and Schoen it follows that any positively curved manifold with strictly quarter
pinched flag curvature must be a space form. This in turn generalizes a result
of Andrews and Nguyen in dimension 4. For odd dimensional manifolds we obtain
results for the case that the flag curvature is pinched with some constant
below one quarter, one of which generalizes a recent work of Petersen and Tao
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