Observations on Twinning in Zone-refined Tungsten

Observations on twinning in zone-refined tungste

High gas velocity burner tests on silicon carbide and silicon nitride at 1200 C

Specimens of silicon carbide and silicon nitride were exposed to a Mach one gas velocity burner simulating a turbine engine environment. Cyclic tests up to 100 hour duration were conducted at specimen temperatures of 1200 C. A specimen geometry was used that develops thermal stresses during thermal cycling in a manner similar to blades and vanes of a gas turbine engine. Materials were compared on a basis of weight change, dimensional reductions, metallography, fluorescent penetrant inspection, X-ray diffraction analyses, failure mode, and general appearance. One hot pressed SiC, one reaction sintered SiC, and three hot pressed Si3N4 specimens survived the program goal of 100 one-hour cycle exposures. Of the materials that failed to meet the program goal, thermal fatigue was identified as the exclusive failure mode

Powder metallurgy approaches to high temperature components for gas turbine engines

Research is reported for the tensile strength, ductility, and heat performance characterisitics of powder metallurgy (p/m) superalloys. Oxide dispersion strengthened alloys were also evaluated for their strength during thermal processing. The mechanical attributes evident in both p/m supperalloys and dispersion strengthened alloys are discussed in terms of research into their possible combination

Effects of crucible wetting during solidification of immiscible Pb-Zn

Many industrial uses for liquid phase miscibility gap alloys are proposed. However, the commercial production of these alloys into useful ingots with a reasonable amount of homogeneity is arduous because of their immiscibility in the liquid state. In the low-g environment of space gravitational settling forces are abated, thus solidification of an immiscible alloys with a uniform distribution of phases becomes feasible. Elimination of gravitational settling and coalescence processes in low-g also makes possible the study of other separation and coarsening mechanisms. Even with gravitational separation forces reduced, many low-g experiments have resulted in severely segregated structures. The segregation in many cases was due to preferential wetting of the crucible by one of the immiscible liquids. The objective was to analyze the wetting behavior of Pb-Zn alloys on various crucible materials in an effort to identify a crucible in which the fluid flow induced by preferential wetting is minimized. It is proposed that by choosing the crucible for a particular alloy so that the difference in surface energy between the solid and two liqud phases is minimized, the effects of preferential wetting can be diminished and possibly avoided. Qualitative experiments were conducted and have shown the competitive wetting behavior of the immiscible Pb-Zn system and 13 different crucible materials

High temperature mechanical properties of polycrystalline hafnium carbide and hafnium carbide containing 13-volume-percent hafnium diboride

High temperature mechanical properties of polycrystalline hafnium carbide containing 13- volume-percent hafnium diborid

Pressure-Induced Superconductivity in Sc to 74 GPa

Using a diamond anvil cell with nearly hydrostatic helium pressure medium we have significantly extended the superconducting phase diagram Tc(P) of Sc, the lightest of all transition metals. We find that superconductivity is induced in Sc under pressure, Tc increasing monotonically to 8.2 K at 74.2 GPa. The Tc(P) dependences of the trivalent d-electron metals Sc, Y, La, and Lu are compared and discussed within a simple s-d charge transfer framework.Comment: to be published in Phys. Rev. B (Brief Reports

Understanding How Components of Organisations Contribute to Attacks

Attacks on organisations today explore many different layers, including buildings infrastructure, IT infrastructure, and human factor – the physical, virtual, and social layer. Identifying possible attacks, understanding their impact, and attributing their origin and contributing factors is difficult. Recently, system models have been used for automatically identifying possible attacks on the modelled organisation. The generated attacks consider all three layers, making the contribution of building infrastructure, computer infrastructure, and humans (insiders and outsiders) explicit. However, this contribution is only visible in the attack trees as part of the performed steps; it cannot be mapped back to the model directly since the actions usually involve several elements (attacker and targeted actor or asset). Especially for large attack trees, understanding the relations between several model components quickly results in a large quantity of interrelations, which are hard to grasp. In this work we present several approaches for visualising attributes of attacks such as likelihood of success, impact, and required time or skill level. The resulting visualisations provide a link between attacks on an organisations and the contribution of parts of an organisation to the attack and its impact

The Psychosocial Consequences of Sports Participation for Individuals with Severe Mental Illness: A Metasynthesis Review

The purpose of the current metasynthesis review was to explore the psychosocial benefits of sport and psychosocial factors which impact on sports participation for individuals with severe mental illness. AMED, CINAHL Plus, Medline, EMBASE, ProQuest Nursing & Allied Health Source, and Science Citation Index were searched from inception until January 2014. Articles included use qualitative methods to examine the psychosocial effects of sports participation in people with severe mental illness. Methodological quality was assessed using the Consolidated Criteria for Reporting Qualitative Studies and a case study tool. Included studies were analysed within a metasynthesis approach. Eight articles involving 56 patients met the inclusion criteria. The results identified the broader and direct psychosocial benefits of sport. Sport provided a ?normal? environment and interactions that were not associated with an individual?s mental illness. Sport provided individuals with a sense of meaning, purpose, belonging, identity, and achievement. Other findings are discussed. Direct psychosocial benefits are a consequence of sports participation for the vast majority of individuals with severe mental illness. Further to this, sports participation was associated with a reduction in social isolation and an increase in social confidence, autonomy, and independence