Mechanism and kinetics of aging in Inconel 718

Age hardening in Inconel 718 is investigated using Brinell hardness measurements. Formation of a precipitate causes an increase in hardness

Generalized Effective Reducibility

We introduce two notions of effective reducibility for set-theoretical statements, based on computability with Ordinal Turing Machines (OTMs), one of which resembles Turing reducibility while the other is modelled after Weihrauch reducibility. We give sample applications by showing that certain (algebraic) constructions are not effective in the OTM-sense and considerung the effective equivalence of various versions of the axiom of choice

Maintaining the Mental Model: An Exploratory Study of Dialogic Processes on Good Teaching Practice

This paper presents some outcomes of an exploratory, mixed-method study that examined mental models of teaching and understanding of learning processes in 26 educators from a small suburb in the Northeastern United States. Participants, in semi-structured written interviews, were asked to rate variables contributing to their mental model of effective teaching. They were then presented with a specific educational problem and asked to provide pedagogic solutions. One finding of this exploration was that some educators did not adhere to their own described mental model of best teaching practices when faced with an educational problem. However, those who responded to the problem in concert with stated mental constructions for teaching were more likely to have engaged in daily dialogue about pedagogic practices with their colleagues. The role of self-reflection, through daily dialogue as a mediator of teacher development is discussed, along with implications for policy and practice in elementary and secondary education

Silicon on Ceramic Process: Silicon Sheet Growth and Device Development for the Large-area Silicon Sheet and Cell Development Tasks of the Low-cost Solar Array Project

The technical and economic feasibility of producing solar cell quality sheet silicon was investigated. It was hoped this could be done by coating one surface of carbonized ceramic substrates with a thin layer of large-grain polycrystalline silicon from the melt. Work was directed towards the solution of unique cell processing/design problems encountered with the silicon-ceramic (SOC) material due to its intimate contact with the ceramic substrate. Significant progress was demonstrated in the following areas; (1) the continuous coater succeeded in producing small-area coatings exhibiting unidirectional solidification and substatial grain size; (2) dip coater succeeded in producing thick (more than 500 micron) dendritic layers at coating speeds of 0.2-0.3 cm/sec; and (3) a standard for producing total area SOC solar cells using slotted ceramic substrates was developed

Project Cerberus: Flyby Mission to Pluto

The goal of the Cerberus Project was to design a feasible and cost-effective unmanned flyby mission to Pluto. The requirements in the request for proposal for an unmanned probe to Pluto are presented and were met. The design stresses proven technology that will avoid show stoppers which could halt mission progress. Cerberus also utilizes the latest advances in the spacecraft industry to meet the stringent demands of the mission. The topics covered include: (1) mission management, planning, and costing; (2) structures; (3) power and propulsion; (4) attitude, articulation, and control; (5) command, control, and communication; and (6) scientific instrumentation

Resonant-to-nonresonant transition in electrostatic ion-cyclotron wave phase velocity

Because of the implications for plasmas in the laboratory and in space, attention has been drawn to inhomogeneous energy-density driven (IEDD) waves that are sustained by velocity-shear-induced inhomogeneity in cross-field plasma flow. These waves have a frequency vr in the lab frame within an order of magnitude of the ion gyrofrequency vci, propagate nearly perpendicular to the magnetic field (kz/k^ \u3c\u3c 1), and can be Landau resonant (0 \u3c v1/kz \u3c nd) with a parallel drifting electron population (drift speed nd), where subscripts 1 and r indicate frequency in the frame of flowing ions and in the lab frame, respectively, and kz is the parallel component of the wavevector. A transition in phase velocity from 0 \u3c v1/kz \u3c nd to 0 \u3e v1/kz \u3e nd for a pair of IEDD eigenmodes is observed as the degree of in-homogeneity in the transverse E × B flow is increased in a magnetized plasma column. For weaker velocity shear, both eigenmodes are dissipative, i.e. in Landau resonance, with kz nd \u3e 0. For stronger shear, both eigenmodes become reactive, with one\u27s wavevector component kz remaining parallel, but with v1/kz \u3e nd , and the other\u27s wavevector component kz becoming anti-parallel, so that 0 \u3e v1/kz . For both eigenmodes, the transition (1) involves a small frequency shift and (2) does not involve a sign change in the wave energy density, which is proportional to vr v1, both of which are previously unrecognized aspects of inhomogeneous energy-density driven waves

Transition jump system for the Fermilab Booster

A transition-jump system recently installed in the Fermilab Booster is described. Early results of the commissioning are presented. 13 refs., 7 figs