Attenuation and space diversity statistics calculated from radar reflectivity data of rain
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Goldhirsh, J.↗
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Results for “attenuator”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Refractive attenuation formulas for an unstable critical ray in a circularly symmetric medium
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Lipa, B. J.↗
Dynamic load attenuator
Instrument consists of special bolt head that cuts material from splined washer. Required shear and tensile forces absorb kinetic energy. Cut-away material is retained by shearing action, making device useful where production of loose metal particles is not acceptable.
Crum, P. N.↗
Energy-absorbing attenuator
Simple, inexpensive, one-shot load device uses thin-walled soft-metal tube to absorb kinetic energy by controlled buckling.
Galovich, P.↗
Wing-tip vanes as vortex attenuation and induced drag reduction devices
Analytical studies have been conducted to examine the feasibility of utilizing wing tip turbines to remove swirl from the wing trailing vortex, and hence reduce the potential for upset of following aircraft. Energy recovery from the turbines is also analyzed. A computer routine has been developed to permit rapid parametric studies of various tip turbine designs. It is shown that the optimum turbine is a non-rotating set of vanes which reduce swirl and recover energy in the form of reduced overall configuration induced drag. A specific case study indicates a 23% reduction in induced drag for a rectangular wing of aspect ratio 5.33, operated at a lift coefficient at 1.0.
Wentz, W. H., Jr.↗
Pin puller impact shock attenuation
Design of a pin arresting mechanism for a pyrotechnically actuated pin puller is reviewed. The investigative approach is discussed and the impact shock test results for various candidate designs are presented. The selected pin arresting design reduced the peak value of the shock response spectrum by five to one.
Auclair, G. F.↗
Prediction methods for rain attenuation statistics at variable path angles and carrier frequencies between 13 and 100 GHz
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Goldhirsh, J.↗
Equations of state and impact-induced shock-wave attenuation on the moon
Current equation of state formulations, used for finite difference cratering flow calculations, are cast into a framework permitting comparison of peak pressures attained upon impact of a sphere, with a half-space, along the impact symmetry axis, to one dimensional impedance match solutions. On the basis of this formulation and application of thermochemical data, the regimes of melting and vaporization are examined. For the purpose of identifying material which will, upon isentropic release from the impact-induced shock state, result in a solid just brought to its melting point, i.e., incipiently melted (IM); completely melted (CM); just brought to its boiling point, i.e., incipiently vaporized (IV); and completely vaporized (CV) state, the pressures at which the critical isentropes intersect the Hugoniots of iron and gabbroic anorthosite (GA) are examined in detail. The latter rock type is assumed to be representative of the lunar highlands. The Hugoniot pressures, for which IM, CM, IV, and CV will occur upon isentropic expansion, are calculated to be 2.2, 2.6, 4.2, and 16.8 Mbar, respectively.
Ahrens, T. J.↗
Scintillating plastic fibers as light pipes for a cosmic ray hodoscope: Feasibility calculations and measured attenuation characteristics
A candidate hodoscope uses arrays of scintillator fibers, followed by an image intensifier and imaging system such as that proposed for the X-ray shadowgraph. A literature search was performed to ascertain the experience of other workers with hodoscopes using this or similar principles. Calculations were performed to determine the feasibility of candidate systems and some laboratory experiments were performed to attempt to check these numbers.
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Optokinetic motion sickness - Continuous head movements attenuate the visual induction of apparent self-rotation and symptoms of motion sickness
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Lackner, J. R.↗
Pulse-width-modulated attenuator for AGC
Automatic-gain-control (AGC) circuit regulates gain of intermediate-frequency and radio-frequency signals over wide dynamic range with high linearity and very low phase shift. Device has potential uses in radio and television receivers, signal distribution systems, and test and measurement instruments.
Macconnell, J. W.↗
A Depolarization and Attenuation Experiment Using the CTS and COMSTAR Satellites. Mathematical Formulations and Definitions for Dual Polarized Reception of a Wave Passing Through a Depolarizing Medium (A Polarization Primer)
The theoretical fundamentals and mathematical definitions for calculations involved with dual polarized radio links are given. Detailed derivations and results are discussed for several formulations applied to a general dual polarized radio link.
Stutzman, W. L.↗
Methods of attenuating wind turbine ac generator output variations
Wind speed variation, tower blockage and structural and inertial factors produce unsteady torque in wind turbines. Methods for modifying the turbine torque so that steady torque is delivered to the coupled ac generator are discussed. The method that may evolve will be influenced by the power use that develops and the trade-offs of cost, weight and complexity.
Gold, H.↗
High frequency sound attenuation in short flow ducts
A geometrical acoustics approach is proposed as a practical design tool for absorbent liners in such short flow ducts as may be found in turbofan engine nacelles. As an example, a detailed methodology is presented for three different types of sources in a parallel plate duct containing uniform ambient flow. A plane wave whose wavefronts are not normal to the duct walls, an arbitrarily located point source, and a spatially harmonic line source are each considered. Optimal wall admittance distributions are found, and it is shown how to estimate the insertion loss for any admittance distribution. The extension of the methodology to realistic source distributions in variable area cylindrical or annular ducts containing arbitrary flow is shown to be conceptually straightforward and computationally practical on a vector-hardware digital computer.
Posey, J. W.↗
Use of a simple external nonreciprocal attenuator in coupled-cavity TWT's
A technique has been developed for introducing a nonreciprocal sever in a traveling-wave tube design. It employs an output coupler followed by a ferrite isolator, a variable phase shifter, and an input coupler. The input and output couplers are similar to those already needed at the ends of the tube. The isolator and phase shifter are similar to commercially available waveguide components. A computer simulation has suggested the technique may yield a significant improvement in efficiency.
Connolly, D. J.↗
Low-frequency attenuator circuit
Circuit uses only single operational amplifier and few passive components to remove background noise from miniature "wristwatch" pulse detector. It can be applied to other systems where background noise is slowly varying, such as ultrasonics, strain-gage sensors, and accelerometers.
Cash, W. H., Jr.↗
Determination of the time delay in the case of two-path propagation on the basis of the attenuation characteristics for two adjacent frequencies
Pronounced fading occurring in the line of sight radio links at frequencies below 10 GHz can be traced to the effects of multipath propagation. Modulation disturbances depend on travel time differences between the direct wave and the wave which is reflected at atmospheric layers. A method described for the determination of the time delay is based on an indirect approach which utilizes the difference in fading at various frequencies. The method was employed in measurements involving a distance of 181 km. The results obtained in the measurement are discussed.
Gilroi, H. G.↗
An analytical and experimental study of sound propagation and attenuation in variable-area ducts
The performance of sound suppression techniques in ducts that produce refraction effects due to axial velocity gradients was evaluated. A computer code based on the method of multiple scales was used to calculate the influence of axial variations due to slow changes in the cross-sectional area as well as transverse gradients due to the wall boundary layers. An attempt was made to verify the analytical model through direct comparison of experimental and computational results and the analytical determination of the influence of axial gradients on optimum liner properties. However, the analytical studies were unable to examine the influence of non-parallel ducts on the optimum linear conditions. For liner properties not close to optimum, the analytical predictions and the experimental measurements were compared. The circumferential variations of pressure amplitudes and phases at several axial positions were examined in straight and variable-area ducts, hard-wall and lined sections with and without a mean flow. Reasonable agreement between the theoretical and experimental results was obtained.
Nayfeh, A. H.↗