Weld microfissuring in Inconel 718 minimized by minor elements

Manganese, silicon, and magnesium markedly reduce the tendency of Inconel 718 to weld microfissuring. By combining a manganese, 0.20 percent by content, with silicon, greater than 0.25 percent content, or by adding 20 ppm of magnesium, the weld microfissuring decreased in the standard alloy

Development of small bore, high speed tapered roller bearing

The performance of four rolling bearing configurations for use on the input pinion shaft of a proposed commercial helicopter transmission was evaluated. The performance characteristics of a high speed tapered roller bearing operating under conditions comparable to those existing at this input pinion shaft were defined. The tapered roller bearing shaft support configuration was developed for the gearbox using commercially available bearing designings. The configuration was optimized and interactive thermomechanically system analyzed. Automotive pinion quality tapered roller bearings were found to be reliable under load and speed conditions in excess of those anticipated in the helicopter transmission. However, it is indicated that the elastohydrodynamic lubricant films are inadequate

Design improvement of a pump wear ring labyrinth seal

The investigation was successful in obtaining two improved designs for the impeller wear ring seal of the liquid hydrogen turbopump of interest. A finite difference computer code was extensively used in a parametric computational study in determining a cavity configuration with high flow resistance due to turbulence dissipation. These two designs, along with that currently used, were fabricated and tested. The improved designs were denoted Type O and Type S. The measurements showed that Type O and Type S given 67 and 30 percent reduction in leakage over the current design, respectively. It was found that the number of cavities, the step height and the presence of a small stator groove are quite important design features. Also, the tooth thickness is of some significance. Finally, the tooth height and an additional large cavity cut out from the stator (upstream of the step) are of negligible importance

Effective transport barriers in nontwist systems

In fluids and plasmas with zonal flow reversed shear, a peculiar kind of transport barrier appears in the shearless region, one that is associated with a proper route of transition to chaos. These barriers have been identified in symplectic nontwist maps that model such zonal flows. We use the so-called standard nontwist map, a paradigmatic example of nontwist systems, to analyze the parameter dependence of the transport through a broken shearless barrier. On varying a proper control parameter, we identify the onset of structures with high stickiness that give rise to an effective barrier near the broken shearless curve. Moreover, we show how these stickiness structures, and the concomitant transport reduction in the shearless region, are determined by a homoclinic tangle of the remaining dominant twin island chains. We use the finite-time rotation number, a recently proposed diagnostic, to identify transport barriers that separate different regions of stickiness. The identified barriers are comparable to those obtained by using finite-time Lyapunov exponents.FAPESPCNPqCAPESMCT/CNEN (Rede Nacional de Fusao)Fundacao AraucariaUS Department of Energy DE-FG05-80ET-53088Physic

The Moment of Inertia of the Binary Pulsar J0737-3039A: Constraining the Nuclear Equation of State

We construct numerical models of the newly discovered binary pulsar J0737-3039A, both with a fully relativistic, uniformly rotating, equilibrium code that handles arbitrary spins and in the relativistic, slow-rotation approximation. We compare results for a representative sample of viable nuclear equations of state (EOS) that span three, qualitatively different, classes of models for the description of nuclear matter. A future dynamical measurement of the neutron star's moment of inertia from pulsar timing data will impose significant constraints on the nuclear EOS. Even a moderately accurate measurement (<~ 10 %) may be able to rule out some of these competing classes. Using the measured mass, spin and moment of inertia to identify the optimal model computed from different EOSs, one can determine the pulsar's radius.Comment: 4 pages, ApJL in pres

Appropriate Selection Processes Are Available For Choosing Hospitality texts

First Student: I know what you mean; I fall asleep every time I try to read this stuff. (Meanwhile, in the faculty lounge) First Professor: I do not understand what\u27s wrong with my students; they expect me to teach textbook information from the podium. Second Professor: I\u27ve noticed the same thing. They do not want to be responsible for their readings