11,519 research outputs found
Deformation processes in forging ceramics Progress report, 19 Jun. - 19 Sep. 1969
Deformation processes involved in forging of polycrystalline oxide ceramic
Improving the toughness of refractory compounds
Composition and processing studies were conducted on silicon nitride and silicon carbide materials. Charpy mode impact testing to 2415 F established the effectiveness of higher purity silicon nitride powder sources in reducing the scatter of measurements and in improving short time bend strengths as well as bend stress rupture properties. Stabilized zirconia additions in particular were observed to dramatically enhance low and high temperature bend strengths and stress rupture properties for all grades of silicon nitride powder. Silicon carbide samples showed relatively poor impact resistance, although the maxima in stress rupture behavior was exhibited by this material
Deformation processes in forging ceramics Progress report, 19 Dec. 1969 - 19 Mar. 1970
Deformation processes in forging ceramic
High temperature compounds for turbine vanes
Fabrication and microstructure control studies were conducted on SiC, Si3N and composites based on Si3N. Charpy mode impact testing to 2400 F established that Si3N4/Mo composites have excellent potential. Attempts to fabricate composites of Si3N4 with superalloys, both by hot pressing and infiltration were largely unsuccessful in comparison to using Mo, Re, and Ta which are less reactive. Modest improvements in impact strength were realized for monolithic Si3N4; however, SiC strengths increased by a factor of six and now equal values achieved for Si3N4. Correlations of impact strength with material properties are discussed. Reduced MgO densification aid additions to Si3N4 were found to decrease densification kinetics, increase final porosity, decrease room temperature bend strength, increase high temperature bend strength, and decrease bend stress rupture properties. The decrease in bend strength at high temperature for fine grain size SiC suggested that a slightly larger grain size material with a nearly constant strength-temperature relation may prove desirable in the creep and stress rupture mode
Fixation of virgin lunar surface soil
Two systems are shown to be suitable for fixing loose particulate soils with a polymer film, without visually detectable disturbance of the soil particle spatial relationships. A two-component system is described, which uses a gas monomer condensible at the soil temperature and a gas phase catalyst acting to polymerize the monomer. A one-component system using a monomer which polymerizes spontaneously on and within the top few millimeters of the soil is also considered. The two-component system employs a simpler apparatus, but it operates over a narrower temperature range (approximately -40 to -10 C). Other two-component systems were identified which may operate at soil temperatures as high as +100 C, at relatively narrow temperature ranges of approximately 30 C. The one-component system was demonstrated to operate successfully with initial soil temperatures from -70 C or lower to +150 C
Experience with a Computerized Interactive Protocol System Using HELP
journal articleBiomedical Informatic
Invariant Peano curves of expanding Thurston maps
We consider Thurston maps, i.e., branched covering maps
that are postcritically finite. In addition, we assume that is expanding in
a suitable sense. It is shown that each sufficiently high iterate of
is semi-conjugate to , where is equal to the
degree of . More precisely, for such an we construct a Peano curve
(onto), such that
(for all ).Comment: 63 pages, 12 figure
Media literacy, curriculum and the rights of the child
Engaging with digital media is part of everyday living for the majority of children, yet opportunities to learn about, through and with media are denied many pupils in compulsory schooling. Whilst Media Studies in the UK is internationally reputed to be well established, changes made to the primary and secondary national curriculum in 2014 included removal of existing media study elements. We demonstrate what is lost by these actions in relation to the United Nations Rights of the Child and, in particular, the right of the child to express identity. We demonstrate how media literacy had previously been included in curriculum, enabling opportunities to address children’s rights, and propose that the absence of media education is part of an overall trend of the non-prioritisation of children’s rights in England and Northern Ireland. The paper calls for media literacy to be reintroduced into primary and secondary curriculum
Interoperability in the GENESIS 3.0 Software Federation : the NEURON Simulator as an Example
© 2013 Cornelis et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Poster presented at CNS 2013Non peer reviewe
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