Test results from a dynamic model dynaflex rotor

A one-fifth scale dynamic model of the Sikorsky Dynaflex rotor was tested in hover and in forward flight conditions in a wind tunnel. The Dynaflex rotor features an advanced composite structure which flexes to provide a constant speed universal joint action. Testing concentrated on confirming that the stability and dynamic response of the rotor were satisfactory. Lift conditions of up to .11 Ct/sigma and advance ratios as high as .46 were reached. Vibratory loads were compared to those of articulated rotors. The Dynaflex rotor concept appears to be a practical concept from the standpoint of dynamic response and stability

Digital filter suppresses effects of nonstatistical noise bursts on multichannel scaler digital averaging systems

Digital filter suppresses the effects of nonstatistical noise bursts on data averaged over multichannel scaler. Interposed between the sampled channels and the digital averaging system, it uses binary logic circuitry to compare the number of counts per channel with the average number of counts per channel

Perspective on Bank Capital Adequacy: Time-Series Analysis

The first part of this paper provides a historical perspective on bank risks. Five-year moving average measures of total risk, market risk, and nonmarket risk are computed for an index of New York banks from 1929-1975 and for an index of outside New York banks from 1950-1976.We use a carefully constructed series of bank balance sheet data to compute correlations among various components of New York banks' port-folios and observe trends over time. The time series relationship between book values and market values is investigated, and classical measures of capital adequacy are calculated using surrogates for market values rather than book values. Finally, data are presented on the movement of interest rates and the term structure over time. Serial correlations and cross-correlations are computed. The second part of the paper uses the technique proposed in Sharpe ("Bank Capital Adequacy, Deposit Insurance and Security Values," June 1978) to gain information about capital adequacy. He has shown that for a bank with deposit liabilities that do not extend beyond the review period a "value preserving spread" in asset risk is likely to increase the value of capital. Moreover, the less adequate the capital, the larger this effect should be. We outline the method used to develop an econometric model to test for this effect. The model is then applied to time series data from 1938 to 1975.

Scintillation Caustics in Planetary Occultation Light Curves

We revisit the GSC5249-01240 light curve obtained during its occultation by Saturn's North polar region. In addition to refractive scintillations, the power spectrum of intensity fluctuations shows an enhancement of power between refractive and diffractive regimes. We identify this excess power as due to high amplitude spikes in the light curve and suggest that these spikes are due to caustics associated with ray crossing situations. The flux variation in individual spikes follows the expected caustic behavior, including diffraction fringes which we have observed for the first time in a planetary occultation light curve. The presence of caustics in scintillation light curves require an inner scale cut off to the power spectrum of underlying density fluctuations associated with turbulence. Another possibility is the presence of gravity waves in the atmosphere. While occultation light curves previously showed the existence of refractive scintillations, a combination of small projected stellar size and a low relative velocity during the event have allowed us to identify caustics in this occultation. This has led us to re-examine previous data sets, in which we have also found likely examples of caustics.Comment: 4 pages, 3 figures; ApJL submitte

Non-linear screening of external charge by doped graphene

We solve a nonlinear integral equation for the electrostatic potential in doped graphene due to an external charge, arising from a Thomas-Fermi (TF) model for screening by graphene's $\pi$ electron bands. In particular, we study the effects of a finite equilibrium charge carrier density in graphene, non-zero temperature, non-zero gap between graphene and a dielectric substrate, as well as the nonlinearity in the band density of states. Effects of the exchange and correlation interactions are also briefly discussed for undoped graphene at zero temperature. Nonlinear results are compared with both the linearized TF model and the dielectric screening model within random phase approximation (RPA). In addition, image potential of the external charge is evaluated from the solution of the nonlinear integral equation and compared to the results of linear models. We have found generally good agreement between the results of the nonlinear TF model and the RPA model in doped graphene, apart from Friedel oscillations in the latter model. However, relatively strong nonlinear effects are found in the TF model to persist even at high doping densities and large distances of the external charge.Comment: 12 pages including 6 figure

Investigation of rock behavior and strength in situ and laboratory techniques adaptability to a lunar exploration program

Rock testing techniques for lunar landing site and for lunar samples returned to earth laborator

Techniques for measuring stresses in rock on the earth - Adaptability to a lunar exploration program

Techniques and instrument developments for stress measurements in rocks on earth and moo

Linear and non-linear theory of a parametric instability of hydrodynamic warps in Keplerian discs

We consider the stability of warping modes in Keplerian discs. We find them to be parametrically unstable using two lines of attack, one based on three-mode couplings and the other on Floquet theory. We confirm the existence of the instability, and investigate its nonlinear development in three dimensions, via numerical experiment. The most rapidly growing non-axisymmetric disturbances are the most nearly axisymmetric (low m) ones. Finally, we offer a simple, somewhat speculative model for the interaction of the parametric instability with the warp. We apply this model to the masing disc in NGC 4258 and show that, provided the warp is not forced too strongly, parametric instability can fix the amplitude of the warp.Comment: 14 pages, 6 figures, revised version with appendix added, to be published in MNRA