Cryogenic fluid flow instabilities in heat exchangers

Analytical and experimental investigation determines the nature of oscillations and instabilities that occur in the flow of two-phase cryogenic fluids at both subcritical and supercritical pressures in heat exchangers. Test results with varying system parameters suggest certain design approaches with regard to heat exchanger geometry

Very Low Mass Stellar and Substellar Companions to Solar-like Stars from MARVELS. II. A Short-period Companion Orbiting an F Star with Evidence of a Stellar Tertiary and Significant Mutual Inclination

We report the discovery via radial velocity (RV) measurements of a short-period (P = 2.430420 ± 0.000006 days) companion to the F-type main-sequence star TYC 2930-00872-1. A long-term trend in the RV data also suggests the presence of a tertiary stellar companion with P > 2000 days. High-resolution spectroscopy of the host star yields T_(eff) = 6427 ± 33 K, log g = 4.52 ± 0.14, and [Fe/H] = –0.04 ± 0.05. These parameters, combined with the broadband spectral energy distribution (SED) and a parallax, allow us to infer a mass and radius of the host star of M_1 = 1.21 ± 0.08 M_☉ and R_1 = 1.09^(+0.15)_(–0.13) R_☉. The minimum mass of the inner companion is below the hydrogen-burning limit; however, the true mass is likely to be substantially higher. We are able to exclude transits of the inner companion with high confidence. Further, the host star spectrum exhibits a clear signature of Ca H and K core emission, indicating stellar activity, but a lack of photometric variability and small v sin I suggest that the primary's spin axis is oriented in a pole-on configuration. The rotational period of the primary estimated through an activity-rotation relation matches the orbital period of the inner companion to within 1.5 σ, suggesting that the primary and inner companion are tidally locked. If the inner companion's orbital angular momentum vector is aligned with the stellar spin axis as expected through tidal evolution, then it has a stellar mass of ~0.3-0.4 M_☉. Direct imaging limits the existence of stellar companions to projected separations <30 AU. No set of spectral lines and no significant flux contribution to the SED from either companion are detected, which places individual upper mass limits of M_([2,3]) ≾ 1.0 M_☉, provided they are not stellar remnants. If the tertiary is not a stellar remnant, then it likely has a mass of ~0.5-0.6 M_☉, and its orbit is likely significantly inclined from that of the secondary, suggesting that the Kozai-Lidov mechanism may have driven the dynamical evolution of this system

Shallow grooves in journal improve air bearing performance

Bearing designs, which shape the surface to create artificial fluid-film wedges in the absence of any applied radial load, generate radial restoring forces to keep journals from whirling. Helical- or herringbone-grooved journals or rotors show most promise of stable operation, with no sacrifice in load capacity

The Labor Court Idea

When the War Labor Board first began to exert pressure on companies and unions to adopt grievance arbitration clauses during World War II, there was a considerable hesitance on both sides. Both groups worried that while third party decision making might momentarily improve productive efficiency, it would do so at the price of a long-run loss in institutional integrity and autonomy, and peace at any price held little fascination for either side. Nevertheless, grievance arbitration was accepted and gradually became the normal mechanism for resolving contractual disputes in the United States

Some Problems of Evidence Before the Labor Arbitrator

Legal rules of evidence do not, of course, apply before the labor arbitrator. This is not surprising since such rules were developed in connection with jury trials, and do not apply strictly in any tribunal but a jury-court. The whole theory of the arbitration tribunal is that it is composed of experts who repeatedly inquire into a relatively homogeneous kind of cases. Exclusionary rules are hardly required as a precautionary measure. Indeed, as the late Harry Shulman said in his classic Oliver Wendell Holmes lecture at Harvard in 1955, The more serious danger is not that the arbitrator will hear too much irrelevancy, but rather that he will not hear enough of the relevant.\u27\u2

Discovery of a Low-mass Companion to a Metal-rich F Star with the MARVELS Pilot Project

We report the discovery of a low-mass companion orbiting the metal-rich, main sequence F star TYC 2949-00557-1 during the Multi-object APO Radial Velocity Exoplanet Large-area Survey (MARVELS) pilot project. The host star has an effective temperature T_(eff) = 6135 ± 40 K, logg = 4.4 ± 0.1, and [Fe/H] = 0.32 ± 0.01, indicating a mass of M_⊙ = 1.25 ± 0.09 M_⊙ and R = 1.15 ± 0.15 R_⊙. The companion has an orbital period of 5.69449 ± 0.00023 days and straddles the hydrogen burning limit with a minimum mass of 64 M_J , and thus may be an example of the rare class of brown dwarfs orbiting at distances comparable to those of "Hot Jupiters." We present relative photometry that demonstrates that the host star is photometrically stable at the few millimagnitude level on time scales of hours to years, and rules out transits for a companion of radius ≳ 0.8 R_J at the 95% confidence level. Tidal analysis of the system suggests that the star and companion are likely in a double synchronous state where both rotational and orbital synchronization have been achieved. This is the first low-mass companion detected with a multi-object, dispersed, fixed-delay interferometer

Experimental dynamic stiffness and damping of externally pressurized gas-lubricated journal bearings

A rigid vertical shaft was operated with known amounts of unbalance at speeds to 30,000 rpm and gas supply pressure ratios to 4.8. From measured amplitude and phase angle data, dynamic stiffness and damping coefficients of the bearings were determined. The measured stiffness was proportional to the supply pressure, while damping was little affected by supply pressure. Damping dropped rapidly as the fractional frequency whirl threshold was approached. A small-eccentricity analysis overpredicted the stiffness by 20 to 70 percent. Predicted damping was lower than measured at low speeds but higher at high speeds

Experiments on rotating externally pressurized air journal bearings. Part 2 - Attitude angle and air flow

Air flow and attitude angle compared with theory for rotating externally pressurized air journal bearing

Series-hybrid bearing - An approach to extending bearing fatigue life at high speeds

Fluid film bearing of hybrid device consists of orifice compensated annular thrust bearing and self-acting journal bearing. In series hybrid bearing, both ball bearing and annular thrust bearing carry full system thrust load, but two bearings share speed. Operation of system is stable and automatically fail-safe