Improved high pressure turbine shroud

A new high pressure turbine shroud material has been developed from the consolidation of prealloyed powders of Ni, Cr, Al and Y. The new material, a filler for cast turbine shroud body segments, is called Genaseal. The development followed the identification of oxidation resistance as the primary cause of prior shroud deterioration, since conversion to oxides reduces erosion resistance and increases spalling under thermal cycled engine conditions. The NICrAlY composition was selected in preference to NIAL and FeCRALY alloys, and was formulated to a prescribed density range that offers suitable erosion resistance, thermal conductivity and elastic modulus for improved behavior as a shroud

Quasiclassical approach to the spin-Hall effect in the two-dimensional electron gas

We study the spin-charge coupled transport in a two-dimensional electron system using the method of quasiclassical ($\xi$-integrated) Green's functions. In particular we derive the Eilenberger equation in the presence of a generic spin-orbit field. The method allows us to study spin and charge transport from ballistic to diffusive regimes and continuity equations for spin and charge are automatically incorporated. In the clean limit we establish the connection between the spin-Hall conductivity and the Berry phase in momentum space. For finite systems we solve the Eilenberger equation numerically for the special case of the Rashba spin-orbit coupling and a two-terminal geometry. In particular, we calculate explicitly the spin-Hall induced spin polarization in the corners, predicted by Mishchenko et al. [13]. Furthermore we find universal spin currents in the short-time dynamics after switching on the voltage across the sample, and calculate the corresponding spin-Hall polarization at the edges. Where available, we find perfect agreement with analytical results.Comment: 9 pages, 6 figure

Sum rules for spin-Hall conductivity cancelation

It has been shown recently that the universal dc spin conductivity of two-dimensional electrons with a Rashba spin-orbit interaction is canceled by vertex corrections in a weak scattering regime. We prove that the zero bulk spin conductivity is an intrinsic property of the free-electron Hamiltonian and scattering is merely a tool to reveal this property in terms of the diagrammatic technique. When Zeeman energy is neglected, the zero dc conductivity persists in a magnetic field. Spin conductivity increases resonantly at the cyclotron frequency and then decays towards the universal value.Comment: 4 pages, 1 figur

Electronic Aharonov-Bohm Effect Induced by Quantum Vibrations

Mechanical displacements of a nanoelectromechanical system (NEMS) shift the electron trajectories and hence perturb phase coherent charge transport through the device. We show theoretically that in the presence of a magnetic feld such quantum-coherent displacements may give rise to an Aharonov-Bohm-type of effect. In particular, we demonstrate that quantum vibrations of a suspended carbon nanotube result in a positive nanotube magnetoresistance, which decreases slowly with the increase of temperature. This effect may enable one to detect quantum displacement fluctuations of a nanomechanical device.Comment: 4 pages, 3 figure

Measurement of energy eigenstates by a slow detector

We propose a method for a weak continuous measurement of the energy eigenstates of a fast quantum system by means of a "slow" detector. Such a detector is only sensitive to slowly-changing variables, e. g. energy, while its back-action can be limited solely to decoherence of the eigenstate superpositions. We apply this scheme to the problem of detection of quantum jumps between energy eigenstates in a harmonic oscillator.Comment: 4 page

Crossover from diffusive to non-diffusive dynamics in the two-dimensional electron gas with Rashba spin-orbit coupling

We present the calculation of the density matrix response function of the two-dimensional electron gas with Rashba spin-orbit interaction, which is applicable in a wide range of parameters covering the diffusive and non-diffusive, the dirty and the clean limits. A description of the crossover between the different regimes is thus provided as well. On the basis of the derived microscopic expressions we study the propagating charge and spin-polarization modes in the clean, non-diffusive regime, which is accessible in the modern experiments.Comment: 8 pages, 6 figures, a considerable extension of the first versio

Wheat Loads and Vertical Pressure Distribution in a Full-scale Bin Part II—Detention

The vertical loads imposed on a full-scale bin floor by wheat were measured during a storage time of 6 h. The floor loads were determined to be dependent on the length of storage time. A linear regression model was developed to predict this change in loads in relation to detention time. The linear regression equation had coefficient of determination values ranging from 0.230 to 0.817. Analysis of the model slopes also indicated that fill height and radial location affect the vertical floor loads with a statistical significance level of 0.05. The radial distribution of vertical pressure during detention was measured. The vertical pressure distribution is dependent on radial location and is not uniformly distributed. Radial location significantly influenced the vertical pressure at the 0.05 significance level. The distribution pattern is similar to the filling condition

Wheat Loads and Vertical Pressure Distribution in a Full-scale Bin Part I — Filling

Flat-bottom cylindrical grain bins are subjected to unique loads and pressures during the filling process. The vertical and lateral loads imposed on a bin wall and the vertical load on a bin floor by wheat during filling were measured. The radial distribution of vertical pressure during filling was also measured. The vertical pressure was determined to be dependent on the radial location and was not uniformly distributed. The load distribution in a bin with an H/D ratio of 3 was 83% on the floor and 17% on the walls. Three widely used prediction equations of Janssen, Reimbert, and Walker were compared to the measured loads and pressures and were determined to have similar shapes but different parameters for a best fit to observed data

Temperature Cable Load Comparison Between Model And Full-Scale Grain Bins

The vertical frictional loads imposed by wheat on five different temperature cables in a model and full-scale bin were measured. tests were conducted to determine the influence of radical positioning of the cable, grain discharge rate, and surface characteristics on the vertical frictional loads. qualitative and quantitative comparisons were made between the model and full-scale temperature cable loads. a scale factor was developed by a similitude analysis and was statistically verified by data