Distribution and size of elements of Saturn's rings as inferred from 12-cm radar observations

A 64m radar antenna was used to observe Saturn's rings at 12.6 cm wavelength, with reduced Doppler spread. The results show a positive radar return corresponding to about a 60 percent return from an isotropic scatterer with the projected area of the rings, allowing for the Cassini division. A radar spectrogram of the rings is shown with power density plotted against Doppler frequency shift

Ginzburg-landau-type multiphase field model for competing fcc and bcc nucleation

The official published version of the Article can be accesed from the link below - Copyright @ 2011 APSWe address crystal nucleation and fcc-bcc phase selection in alloys using a multiphase field model that relies on Ginzburg-Landau free energies of the liquid-fcc, liquid-bcc, and fcc-bcc subsystems, and determine the properties of the nuclei as a function of composition, temperature, and structure. With a realistic choice for the free energy of the fcc-bcc interface, the model predicts well the fcc-bcc phase-selection boundary in the Fe-Ni system.This work has been supported by the Hungarian Academy of Sciences under contract OTKA-K-62588, and by the ESA under PECS Contract No. 98059. Work by JRM has been sponsored by the Materials Sciences and Engineering Division, Office of Basic Energy Sci- ences, U.S. Department of Energy

Design considerations for remotely piloted, high-altitude airplanes powered by microwave energy

Several types of systems have been considered in a design study of unmanned, microwave-powered, long-endurance, high-altitude airplanes. The study includes vehicles that use power from a continuously transmitted beam and other aircraft that receive intermittent power during cycles of boost-glide flight. Simple design algorithms are presented. Examples of sizing and performance analyses are used to suggest design-procedure guidelines

Theoretical analysis of aerodynamic characteristics of two helicopter rotor airfoils

An analytical study was conducted to predict the aerodynamic characteristics of two helicopter rotor airfoils. Documentation of the predictive process covers the development of empirical factors used in conjunction with computer programs for airfoil analysis. Tables of lift, drag, and pitching-moment coefficient for each airfoil were prepared for two dimensional, steady flow conditions at Mach numbers from 0.3 to 0.9 and Reynolds numbers of 7,700,000 to 23,000,000, respectively

Conceptual study of an advanced supersonic technology transport (AST-107) for transpacific range using low-bypass-ratio turbofan engines

An advanced supersonic technology configuration concept designated the AST-107, using a low bypass ratio turbofan engine, is described and analyzed. The aircraft had provisions for 273 passengers arranged five abreast. The cruise Mach number was 2.62. The mission range for the AST-107 was 8.48 Mm (4576 n.mi.) and an average lift drag ratio of 9.15 during cruise was achieved. The available lateral control was not sufficient for the required 15.4 m/s (30 kt) crosswind landing condition, and a crosswind landing gear or a significant reduction in dihedral effect would be necessary to meet this requirement. The lowest computed noise levels, including a mechanical suppressor noise reduction of 3 EPNdB at the flyover and sideline monitoring stations, were 110.3 EPNdB (sideline noise), 113.1 EPNdB (centerline noise) and 110.5 EPNdB (approach noise)

Unique research challenges for high-speed civil transports

Market growth and technological advances are expected to lead to a generation of long-range transports that cruise at supersonic or even hypersonic speeds. Current NASA/industry studies will define the market windows in terms of time frame, Mach number, and technology requirements for these aircraft. Initial results indicate that, for the years 2000 to 2020, economically attractive vehicles could have a cruise speed up to Mach 6. The resulting research challenges are unique. They must be met with technologies that will produce commercially successful and environmentally compatible vehicles where none have existed. Several important areas of research were identified for the high-speed civil transports. Among these are sonic boom, takeoff noise, thermal management, lightweight structures with long life, unique propulsion concepts, unconventional fuels, and supersonic laminar flow

Intensities of backscatter Mössbauer spectra

The intensities of γ‐ray and x‐ray backscatter Mössbauer spectra of ^(57)Fe nuclei in different matrix materials were studied theoretically and experimentally. A previous analysis by J. J. Bara [Phys. Status Solidi A 58, 349 (1980] showed that negative peak intensities occur in backscatter γ‐ray spectra when the ^(57)Fe nuclei are in a matrix of light elements. We report a confirmation of this work and offer a simple explanation of the phenomenon. The present paper extends Bara’s analysis to the case of conversion x‐ray spectra; expressions for the intensity of conversion x‐ray spectra as a function of absorber thickness and absorber material parameters are presented. We show that negative peak intensities are expected in conversion x‐ray spectra when the ^(57)Fe nuclei are in a matrix of heavy elements

A simplified analysis of propulsion installation losses for computerized aircraft design

A simplified method is presented for computing the installation losses of aircraft gas turbine propulsion systems. The method has been programmed for use in computer aided conceptual aircraft design studies that cover a broad range of Mach numbers and altitudes. The items computed are: inlet size, pressure recovery, additive drag, subsonic spillage drag, bleed and bypass drags, auxiliary air systems drag, boundary-layer diverter drag, nozzle boattail drag, and the interference drag on the region adjacent to multiple nozzle installations. The methods for computing each of these installation effects are described and computer codes for the calculation of these effects are furnished. The results of these methods are compared with selected data for the F-5A and other aircraft. The computer program can be used with uninstalled engine performance information which is currently supplied by a cycle analysis program. The program, including comments, is about 600 FORTRAN statements long, and uses both theoretical and empirical techniques

INTERP3: A computer routine for linear interpolation of trivariate functions defined by nondistinct unequally spaced variables

A report on the computer routine INTERP3 is presented. The routine is designed to linearly interpolate a variable which is a function of three independent variables. The variables within the parameter arrays do not have to be distinct, or equally spaced, and the array variables can be in increasing or decreasing order

Bank lending and monetary policy: evidence on a credit channel

While there is widespread agreement that banks play a key part in the transmission of monetary policy actions to the economy, debate continues on whether bank lending plays a special part in the monetary transmission mechanism. If a special lending or credit channel exists, changes in the willingness and ability of banks to extend credit may have implications for the economy. Moreover, ongoing changes in the role of banks in financial markets may affect the credit channel and so alter the monetary transmission mechanism.> Recent research on a bank credit channel has focused on two questions. Are certain borrowers so dependent on bank lending that any change in banks' willingness to lend has an immediate effect on investment and spending decisions? And, do monetary policy changes directly constrain bank lending? Both conditions are necessary for bank lending to play a special role in the monetary transmission mechanism.> Morris and Sellon provide insight into the second question--whether bank lending is constrained by monetary policy. The authors analyze how banks adjust the amount and terms of business lending when monetary policy is tightened. The analysis differs from previous research by using a more precise measure of monetary policy actions, which allows a more accurate identification of episodes of monetary tightening. The authors suggest that bank business lending is not constrained by restrictive monetary policy. Thus, Morris and Sellon conclude, monetary policy does not operate through a special credit channel.Bank loans ; Monetary policy