Mechanically driven alloying and grain size changes in nanocrystalline Fe-Cu powders

Highly supersaturated nanocrystalline FexCu100-x alloys (10 less-than-or-equal-to x less-than-or-equal-to 95) have been prepared by mechanical alloying of elemental crystalline powders. The development of the microstructure is investigated by x-ray diffraction, differential scanning calorimetry, and transmission electron microscopy. The results are compared with data for ball-milled elemental Fe and Cu powders, samples prepared by inert gas condensation, and sputtered films. The deformation during milling reduces the grain size of the alloys to 6-20 nm. The final grain size of the powders depends on the composition of the material. Single-phase fcc alloys with x less-than-or-equal-to 60 and single-phase bcc alloys with x greater-than-or-equal-to 80 are formed even though the Fe-Cu system exhibits vanishingly small solid solubilities under equilibrium conditions. For 60 less-than-or-equal-to x less-than-or-equal-to 80, fcc and bcc solid solutions coexist. The alloy formation is discussed with respect to the thermodynamic conditions of the material. The role of the large volume fraction of grain boundaries between the nanometer-sized crystals, as well as the influence of internal strains and stored enthalpies introduced by ball milling, is critically assessed

Wind sensitivity studies of a non-return wind tunnel with a 216- by 432-mm (8.5- by 17.0-inches) test section, phase 2

The refinement of inlet and exit treatments were studied which would minimize the effect of external wind on the test-section flow quality of a nonreturn wind tunnel. The investigation was conducted in the Ames Research Center 40- by 80-foot Wind Tunnel which served as the wind source. Several inlets and two exits were tested at wind directions ranging from 0 to 180 degrees and at wind-to-test-section velocity ratios from zero to somewhat greater than one. For the best inlet configuration the flow quality was good, with a velocity deviation in each of the three component directions generally less. The loss in total pressure due to the inlet treatment was low: about 0.035 of the test-section dynamic pressure for the no-wind case

Wind sensitivity studies of a non-return wind tunnel, with a 216- by 432-mm (8.5- by 17.0-inch) test section, phase 1

The study to develop inlet and exit treatments which would minimize the effect of external wind on the test-section flow quality of a nonreturn wind tunnel is reported. The investigation was conducted in the Ames Research Center 40- by 80-Foot Wind Tunnel which served as the wind source. Several inlets and two exits were tested at wind directions ranging from 0 to 180 degrees and at wind-to-test-section velocity ratios between zero and one. For the best inlet configuration the flow quality was good, with a velocity deviation in each of the three directions generally less than 1/2 knot (0.26 m/sec) for wind velocities of 15 knots (7.7 m/sec) or less. The loss in total pressure due to the inlet treatment was low: about 0.03 of the test-section dynamic pressure

A deterministic cavity-QED source of polarization entangled photon pairs

We present two cavity quantum electrodynamics proposals that, sharing the same basic elements, allow for the deterministic generation of entangled photons pairs by means of a three-level atom successively coupled to two single longitudinal mode high-Q optical resonators presenting polarization degeneracy. In the faster proposal, the three-level atom yields a polarization entangled photon pair via two truncated Rabi oscillations, whereas in the adiabatic proposal a counterintuitive Stimulated Raman Adiabatic Passage process is considered. Although slower than the former process, this second method is very efficient and robust under fluctuations of the experimental parameters and, particularly interesting, almost completely insensitive to atomic decay.Comment: 5 pages, 5 figure

Reducing Crop Production Cost

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Pflanzenvergiftungen — psychiatrische Aspekte

Zusammenfassung: Seit der Antike sind Pflanzenvergiftungen dokumentiert, trotzdem werden Intoxikationen mit pflanzlichen Giften im psychiatrischen Schrifttum wenig beachtet, und die Gefahr durch Giftpflanzen wird gemeinhin verkannt. In diesem Artikel wird diese Problematik erörtert. Es werden weiterhin entsprechende Empfehlungen zur Vermeidung von Pflanzenvergiftungen und zum allgemeinen Umgang mit deren Folgen gegebe

Experimental investigation of free-convection heat transfer in vertical tube at large Grashof numbers / E. R. G. Eckert, A. J. Diaguila

Local free-convection heat-transfer coefficients and temperature fields in the turbulent flow range were obtained within a vertical, stationary tube closed at the boom, heated along its walls, and having a length-to-diameter ratio of 5. Convective heat-transfer coefficients were correlated by the general relations for free-convection heat transfer. These coefficients, converted to dimensionless Nusselt numbers were 35 percent below known relations for vertical flat plates. Air temperature measurements within the tube indicated a thin boundary layer along the heated wall surface and unstable conditions in the air flow

Experimental Investigation of Free-Convection Heat Transfer in Vertical Tube at Large Grashof Numbers

Report presents the results of an investigation conducted to study free-convection heat transfer in a stationary vertical tube closed at the bottom. The walls of the tube were heated, and heated air in the tube was continuously replaced by fresh cool air at the top. The tube was designed to provide a gravitational field with Grashof numbers of a magnitude comparable with those generated by the centrifugal field in rotating-blade coolant passages (10(8) to 10(13)). Local heat-transfer coefficients in the turbulent-flow range and the temperature field within the fluid were obtained