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

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 $0.0125. If the total cost of hauling liquid manure is charged against its nutrients value, the producer cannot afford to haul much more than 2 to 3 miles; therefore, there is a restriction on the distance that manure can economically be moved and the availability of suitable land for manure application becomes a concern. Because of this restriction, manure treatment and the technologies for manure management such as solid/liquid separation or composting become attractive technologies to consider both economically and environmentally. Liquid/solid separation is a step in a complete manure treatment system and it has been utilized to reduce odour and manage phosphorus. There are different technologies available for solid/liquid separation which cost anywhere from$1.22 to $5.38 per pig marketed. Composting could also be utilized in swine manure management but because of high moisture contents, a high carbon source or bulking agent is required. Composting itself could costs anywhere from$4.85 to $13.49 per tonne of raw manure composted depending on type of composting technologies used. Manure storage is also part of integrated manure management system which comes in three main forms: earthen, concrete, and steel. Earthen manure storage systems are the most prominent manure storage systems in Western Canada. The capital cost for earthen manure range from$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

Properties of planetary fluids at high pressure and temperature

In order to derive models of the interiors of Uranus, Neptune, Jupiter and Saturn, researchers studied equations of state and electrical conductivities of molecules at high dynamic pressures and temperatures. Results are given for shock temperature measurements of N2 and CH4. Temperature data allowed demonstration of shock induced cooling in the the transition region and the existence of crossing isotherms in P-V space