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  • General Chemistry  (7,564)
  • Organic Chemistry  (4,475)
  • STRUCTURAL MECHANICS  (1,510)
  • COMMUNICATIONS  (1,377)
  • Cell & Developmental Biology
  • 1970-1974  (12,002)
  • 1910-1914
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Years
Year
  • 1
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    Radio communications with extra-terrestrial civilizations (1974)
    In:  CASI
    Details
    Publication Date: 2006-01-11
    Description: Communications between civilizations within our galaxy at the present level of radio engineering is possible, although civilizations must begin to search for each other to achieve this. If an extra-terrestrial civilization possessing a technology at our level wishes to make itself known and will transmit special radio signals to do this, then it can be picked up by us at a distance of several hundreds of light years using already existing radio telescopes and specially built radio receivers. If it wishes, this civilization can also send us information without awaiting our answer.
    Keywords: COMMUNICATIONS
    Type: Inhabited Space, Pt. 2 (NASA-TT-F-820); p 79-82
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  • 2
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    Noise and vibration level reduction by covering metal structures with layers of damping materials (1974)
    In:  CASI
    Details
    Publication Date: 2006-01-11
    Description: One of the most important methods of reducing the noise and vibration level is the damping of the secondary sources, such as metal plates, often used in vehicle structures, by means of covering materials with high internal viscosity. Damping layers are chosen at an optimum thickness corresponding to the frequency and temperature range in which a certain structure works. The structure's response corresponding to various real situations is analyzed by means of a measuring chain including electroacoustical or electromechanical transducers. The experimental results provide the dependence of the loss factor and damping transmission coefficient as a function of the damping layer thickness or of the frequency for various viscoelastic covering materials.
    Keywords: STRUCTURAL MECHANICS
    Type: The 4th Natl. Conf. on Acoustics, Vol. 1A (NASA-TT-F-15375); p 246-253
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  • 3
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    Vibration and recoil control of pneumatic hammers (1974)
    In:  CASI
    Details
    Publication Date: 2006-01-11
    Description: Vibration sources are described for pneumatic hammers used in the mining industry (pick hammers), in boiler shops (riveting hammers), etc., bringing to light the fact that the principal vibration source is the variation in air pressure inside the cylinder. The present state of the art of vibration control of pneumatic hammers as it is practiced abroad, and the solutions adopted for this purpose, are discussed. A new type of pneumatic hammer with a low noise and vibration level is presented.
    Keywords: STRUCTURAL MECHANICS
    Type: The 4th Natl. Conf. on Acoustics, Vol. 1A (NASA-TT-F-15375); p 79-84
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  • 4
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    Vibration control in forge hammers (1974)
    In:  CASI
    Details
    Publication Date: 2006-01-11
    Description: Special measures are discussed for calculating, designing and executing a forge hammer foundation, so that the vibrations that occur during its working will not be transmitted to neighboring machinery, workrooms and offices. These vibrations are harmful to the workers near the forge hammer.
    Keywords: STRUCTURAL MECHANICS
    Type: The 4th Natl. Conf. on Acoustics, Vol. 1A (NASA-TT-F-15375); p 73-78
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  • 5
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    Experimental determination of the vibration level in 5,100 kW electric locomotive assemblies (1974)
    In:  CASI
    Details
    Publication Date: 2006-01-11
    Description: Because of the high vibration level occurring during the running of electric locomotives, mechanical defects occur in the control mechanisms of auxiliary services. This fact has given rise to the necessity of determining the values of these vibrations in electric locomotives during their running. Measurements were conducted on the Craiova-Drobeta-Turnu Severin line, and measures to reduce the vibration level in electric locomotives were instituted.
    Keywords: STRUCTURAL MECHANICS
    Type: The 4th Natl. Conf. on Acoustics, Vol. 1A (NASA-TT-F-15375); p 50-54
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  • 6
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    Random vibrations of linear viscoelastic beams with lumped masses (1974)
    In:  CASI
    Details
    Publication Date: 2006-01-11
    Description: A method is presented of determining the mean square transversal deflection of an isotropic and homogeneous linear viscoelastic beam having a certain number of lengthwise distributed lumped masses. It is assumed that the beam is acted upon by a stationary random process uniformly distributed along the beam. The method is useful in vibration level control by means of additional lumped masses.
    Keywords: STRUCTURAL MECHANICS
    Type: The 4th Natl. Conf. on Acoustics, Vol. 1A (NASA-TT-F-15375); p 36-42
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  • 7
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    Random vibrations of quadratic damping systems (1974)
    In:  CASI
    Details
    Publication Date: 2006-01-11
    Description: An oscillating system with quadratic damping subjected to white noise excitation is replaced by a nonlinear, statistically equivalent system for which the associated Fokker-Planck equation can be exactly solved. The mean square responses are calculated and the optimum damping coefficient is determined with respect to the minimum mean square acceleration criteria. An application of these results to the optimization of automobile suspension damping is given.
    Keywords: STRUCTURAL MECHANICS
    Type: The 4th Natl. Conf. on Acoustics, Vol. 1A (NASA-TT-F-15375); p 29-35
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  • 8
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    The response of many-storied structures under seismic actions (1974)
    In:  CASI
    Details
    Publication Date: 2006-01-11
    Description: A seismic action which is characterized by the acceleration function of the seismic motion is analyzed. The equations of motion in the direction of the seismic action are determined for a completely rigid ground and for a ground with linear deformability characteristics (rotation deformability). The equation for the rotation motion is derived by considering elastic and viscoelastic properties of the foundation ground. The differential equations are written by treating the mechanical model of a many-storied structure as a fixed vertical beam with a uniformly distributed mass as well as with concentrated masses on each floor.
    Keywords: STRUCTURAL MECHANICS
    Type: The 4th Natl. Conf. on Acoustics, Vol. 1A (NASA-TT-F-15375); p 43-49
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  • 9
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    Insulation of nonlinear and random vibrations in the mining industry (1974)
    In:  CASI
    Details
    Publication Date: 2006-01-11
    Description: The insulation of nonlinear and random vibrations is considered for some ore preparing and sorting implements: rotary crushers, resonance screens, hammer mills, etc. The appearance of subharmonic vibrations is analyzed, and the conditions for their appearance are determined. A method is given for calculating the insulation of these vibrations by means of elastic elements made of rubber. The insulation of the random vibrations produced by Symons crushers is calculated by determining the transmissability and deformation of the insulation system for a narrow band random response.
    Keywords: STRUCTURAL MECHANICS
    Type: The 4th Natl. Conf. on Acoustics, Vol. 1A (NASA-TT-F-15375); p 22-28
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  • 10
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    A mathematical model for storied buildings subjected to automatic loom stresses (1974)
    In:  CASI
    Details
    Publication Date: 2006-01-11
    Description: Expressions are derived for the displacements of a many storied building subjected to the action of classical weaving looms located at different levels of the building. The building is regarded as a vertical fixed beam with a uniformly distributed mass as well as concentrated masses at each level. The calculation relations are obtained on the assumption of harmonic variation of the forces acting at each level as well as the assumption of narrow band stationary random excitatory forces.
    Keywords: STRUCTURAL MECHANICS
    Type: The 4th Natl. Conf. on Acoustics, Vol. 1A (NASA-TT-F-15375); p 15-21
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  • 11
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    Study of vibrations produced by a vibrating beam used for vibrating concretes (1974)
    In:  CASI
    Details
    Publication Date: 2006-01-11
    Description: For compacting concretes in building, vibrating beams are used. The vibrations are generated by inertial vibrators, and the beam is normally displaced by the operator by means of a handle that is elastically fastened to the beam by means of rubber pads. Considered are vibrations transmitted to the operator, taking into account the beam's shock vibration motions. The steady state motion of a dynamic beam pattern is studied, and results of experimental tests with existing equipment are presented.
    Keywords: STRUCTURAL MECHANICS
    Type: The 4th Natl. Conf. on Acoustics, Vol. 1A (NASA-TT-F-15375); p 9-14
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  • 12
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    Intermediate memory devices (1974)
    In:  CASI
    Details
    Publication Date: 2006-01-11
    Description: Several methods of transfer and processing of data whose practical implementation requires operational memory devices are described. Devices incorporating multistable elements are proposed and their main parameters are given. The possibility of using the proposed devices for storing information for transmission in space radio communications channels is examined.
    Keywords: COMMUNICATIONS
    Type: Space Res. in the Ukraine, No. 3 (NASA-TT-F-15537); p 155-162
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  • 13
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    Electromagnetic processes in the atmosphere of pulsars (1974)
    In:  CASI
    Details
    Publication Date: 2006-01-11
    Description: The work consists of two parts. The first deals with the fine structure of radio pulses. Based on kinetic theory, processes occurring in the plasma shell of a pulsar when external electromagnetic radiation is present are investigated. It is shown that electromagnetic waves cause electrons to drift relative to ions, and initiate longitudinal oscillations. A dispersion equation describing the longitudinal oscillations in magnetized plasma is derived. Conditions for excitation of oscillations are found. Correlation functions of electron density are calculated, along with the coefficients of electromagnetic wave scattering. It is shown that variations in the amplitude of pulsar pulses are associated with scintillations caused by fluctuations in the plasma electron density. The second part of the study presents a mechanism for the radio emission of pulsars. The model of a rotating and a pulsating star, a neutron star with dipolar or more complex magnetic field, is examined.
    Keywords: COMMUNICATIONS
    Type: Space Res. in the Ukraine, No. 3, (NASA-TT-F-15537); p 44-53
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  • 14
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    The tropospheric calibration model for Mariner Mars 1971 (1974)
    In:  CASI
    Details
    Publication Date: 2006-01-11
    Description: The effects of the troposphere on arrival time, range, and range rate measurement of radio signals propagating from spacecraft are examined. A tropospheric calibration model which takes into account seasonal variations, various elevations, and apparent location changes was developed. A comparison was made of the effects before and after calibration. Without calibration, a 16-m change in the distance off the spin axis, is induced for a 10-deg minimum elevation symmetrical pass. Even after calibration with the old model, the error in spin axis is still greater than 1 m. Calibration results and estimated uncertainties of the model are given in tabular form. Test results also show that the model met the required accuracy for the Mariner Mars 1971 mission.
    Keywords: COMMUNICATIONS
    Type: Tracking System Analytic Calibration Activities for the Mariner Mars 1971 Mission; p 61-76
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  • 15
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    Stresses in dome-shaped shells of revolution with discontinuities at the apex (1974)
    In:  CASI
    Details
    Publication Date: 2006-04-02
    Description: Asymptotic solutions of Novozhilov's equations of shells of revolution are derived for axisymmetric and first harmonic loadings. The solutions obtained are valid throughout the shallow and nonshallow regions. Stresses in dome shaped shells of revolution with a discontinuity in the form of a circular hole, a circular rigid insert, or a nozzle at the apex have been investigated. Numerical results are obtained for spheres, ellipsoids, and paraboloids, containing a discontinuity under a internal pressure and moment. Curves depicting stress distributions are given. The influence of three types of discontinuity on the stresses of the shells is also given.
    Keywords: STRUCTURAL MECHANICS
    Type: Multivariant Function Model Generation; 118 p
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  • 16
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    Current structural vibration problems associated with noise (1974)
    In:  CASI
    Details
    Publication Date: 2011-10-14
    Description: As the performance of aerospace vehicles has increased, the noise generated by the propulsion system and by the passage of the vehicle through the air has also increased. Further increases in performance are now underway for space vehicles such as the space shuttle vehicle and for short distance takeoff and landing (STOL) aircraft, and are being planned for supersonic aircraft. The flight profiles and design features of these high-performance vehicles are reviewed and an estimate made of selected noise-induced structural vibration problems. Considerations for the prevention of acoustic fatigue, noise transmission, and electronic instrument malfunction are discussed.
    Keywords: STRUCTURAL MECHANICS
    Type: AGARD Noise Mech.; 16 p
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  • 17
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    Inclusion of transverse shear deformation in finite element displacement formulations (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: A stiffness matrix is derived for a beam element with transverse shear deformation. It is shown that straightforward energy minimization yields the correct stiffness matrix in displacement formulations when transverse shear effects are considered. Since the TIM4 beam element does not represent the geometric boundary conditions for a cantilever beam the rotation of the normal must be retained as a grid point degree of freedom.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal; 12; Nov. 197
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  • 18
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    Optical antenna gain. II - Receiving antennas (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Expressions are developed for the gain of a centrally obscured, circular optical antenna used as the collecting and focusing optics in a laser receiver, involving losses due to (1) incoming light blockage by central obscuration, (2) energy spillover at the detector, and (3) the effect of local oscillator distribution in the case of heterodyne or homodyne detection. Numerical results are presented for direct detection and for three types of local oscillator distribution (uniform, Gaussian, and matched).
    Keywords: COMMUNICATIONS
    Type: Applied Optics; 13; Oct. 197
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  • 19
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    Optical antenna gain. I - Transmitting antennas (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The gain of centrally obscured optical transmitting antennas is analyzed in detail. The calculations, resulting in near- and far-field antenna gain patterns, assume a circular antenna illuminated by a laser operating in the TEM-00 mode. A simple polynomial equation is derived for matching the incident source distribution to a general antenna configuration for maximum on-axis gain. An interpretation of the resultant gain curves allows a number of auxiliary design curves to be drawn that display the losses in antenna gain due to pointing errors and the cone angle of the beam in the far field as a function of antenna aperture size and its central obscuration. The results are presented in a series of graphs that allow the rapid and accurate evaluation of the antenna gain which may then be substituted into the conventional range equation.
    Keywords: COMMUNICATIONS
    Type: Applied Optics; 13; Sept
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  • 20
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    Microcraters formed in glass by projectiles of various densities (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: An experiment was conducted investigating the effect of projectile density on the structure and size of craters in soda lime glass and fused quartz. The projectiles were spheres of polystyrene-divinylbenzene (PS-DVB), aluminum, and iron with velocities between 0.5 and 15 km/sec and diameters between 0.4 and 5 microns. The projectile densities spanned the range expected for primary and secondary particles of micrometer size at the lunar surface, and the velocities spanned the lower range of micrometeoroid velocities and the upper range of secondary projectile velocities. There are changes in crater morphology as the impact velocity increases, and the transitions occur at lower velocities for the projectiles of higher density. The sequence of morphological features of the craters found for PS-DVB impacting soda lime glass for increasing impact velocity, described in a previous work (Mandeville and Vedder, 1971), also occurs in fused quartz and in both targets with the more dense aluminum and iron projectiles. Each transition in morphology occurs at impact velocities generating a certain pressure in the target. High density projectiles require a lower velocity than low-density projectiles to generate a given shock pressure.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Geophysical Research; 79; Aug. 10
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  • 21
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    Approximate techniques of structural reanalysis (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: A study is made of two approximate techniques for structural reanalysis. These include Taylor series expansions for response variables in terms of design variables and the reduced-basis method. In addition, modifications to these techniques are proposed to overcome some of their major drawbacks. The modifications include a rational approach to the selection of the reduced-basis vectors and the use of Taylor series approximation in an iterative process. For the reduced basis a normalized set of vectors is chosen which consists of the original analyzed design and the first-order sensitivity analysis vectors. The use of the Taylor series approximation as a first (initial) estimate in an iterative process, can lead to significant improvements in accuracy, even with one iteration cycle. Therefore, the range of applicability of the reanalysis technique can be extended. Numerical examples are presented which demonstrate the gain in accuracy obtained by using the proposed modification techniques, for a wide range of variations in the design variables.
    Keywords: STRUCTURAL MECHANICS
    Type: Computers and Structures; 4; Aug. 197
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  • 22
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    The subsequence weight distribution of summed maximum length digital sequences (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: An attempt is made to develop mathematical formulas to provide the basis for the design of pseudorandom signals intended for applications requiring accurate knowledge of the statistics of the signals. The analysis approach involves calculating the first five central moments of the weight distribution of subsequences of hybrid-sum sequences. The hybrid-sum sequence is formed from the modulo-two sum of k maximum length sequences and is an extension of the sum sequences formed from two maximum length sequences that Gilson (1966) evaluated. The weight distribution of the subsequences serves as an approximation to the filtering process. The basic reason for the analysis of hybrid-sum sequences is to establish a large group of sequences with good statistical properties. It is shown that this can be accomplished much more efficiently using the hybrid-sum approach rather than forming the group strictly from maximum length sequences.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Communications; COM-22; Aug. 197
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  • 23
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    Static, stability, and dynamic analysis of shells of revolution by numerical integration - A comparison (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Recent innovations in digital computer technology have enabled engineers to analyze shell structures of complex configurations without unduly restrictive approximations. An attempt is made to compare the various programs now generally available from the point of view of the advantages of the relative technique utilized, as well as the programmed state of the art. Many of the comparisons are based on the sample problems solved by the STARS-2 system of programs. These examples indicate both the structural detail which can be analyzed by, and the analytical capabilities available in, the numerical shell-of-revolution programs. All advantages and differences are demonstrated by use of solutions for realistic shell problems in the areas of statics, stability, vibrations, and dynamic response of shells subjected to time-dependent loadings.
    Keywords: STRUCTURAL MECHANICS
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  • 24
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    Computer simulation of the Pioneer 10 microwave occultation experiment (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: As Pioneer 10 approaches the planet Jupiter, its trajectory will carry it behind the planet, as seen from the earth. The microwave telemetry signal from the spacecraft will then pass through the Jovian atmosphere on its way to the earth, and analysis of the effects of the atmosphere on the signal should yield information on the atmospheric structure. To help define the capabilities of this experiment and to aid the analysis of the real data, we have simulated the occultation experiment on a computer by using model Jovian atmospheres and a predicted trajectory. The results indicate that the useful depth of penetration of the microwave signal will be governed by ammonia absorption rather than superrefractivity. The experiment is apparently far more sensitive to variations in cloud-top temperature than to variations in the hydrogen-helium ratio. Characteristic 'flashes' in the attenuation record of the signal may yield information on the location of the top of the Jovian convective zone.
    Keywords: COMMUNICATIONS
    Type: Journal of Geophysical Research; 79; May 1
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  • 25
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    Mutual coupling in a finite planar array of circular apertures (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Equations are presented for the calculation of the interelement mutual coupling in a finite-size planar array of waveguide-fed apertures in an infinite flat conductor. The general mutual admittance expression is evaluated for circular apertures, and the mutual coupling calculations are verified experimentally for two Te-(11) mode excited apertures. Qualitative agreement between calculations for a 183-element array and an infinite array establishes the validity of the finite-array theoretical model.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Antennas and Propagation; AP-22; Mar. 197
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  • 26
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    Channel simulation for optical communication systems (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: A technique is reported for simulating the signal fading that will be experienced by typical optical communication systems. The desired irradiance or amplitude fading statistics can be simulated by incorporating a linearized optical modulator subsystem between the transmitter and receiver. This technique has been implemented in the design and construction of a laboratory channel simulator. The design of the processing electronics is discussed along with the results of tests performed for each mode of operation.
    Keywords: COMMUNICATIONS
    Type: Applied Optics; 13; June 197
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  • 27
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    Forced vibrations of multi-component compliant tanks and feedlines (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: An analytical and experimental research program was performed to investigate the effects of flexible tanks and lines and the total system dynamic response of a simple physical system which had some of the essential features of a liquid-fueled launch vehicle. Several vessel-wall materials were used to obtain a range of elastic moduli. Water was used to simulate the fuel and an electromagnetic shaker provided external excitation such as might originate from a rocket-propulsion system. Experimental data were compared to values obtained from mathematical models for the many degree-of-freedom lumped-mass representation.
    Keywords: STRUCTURAL MECHANICS
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  • 28
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    On first cycle slip time of phase-locked loops in cascade (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Precise measurement and spacecraft tracking are obtained by using phase-locked loops in cascade in two-way communications links. Statistics on cycle slip time are of vital importance in system planning and design. This paper presents: (1) results of a computer simulation study of the mean time to first cycle slip of cascade phase-locked loops preceded by bandpass limiters, and (2) the determination of probability distributions of cycle slip. Numerical results are obtained for a typical coherent communication system.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Aerospace and Electronic Systems; AES-10; May 1974
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  • 29
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    Nonproportional loading limit for structures (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The design of most structures involves ensuring integrity for several independent loading conditions. Often, it is rational to design these, exploiting the ductility of the materials to reduce structural costs. Then, ensuring integrity evokes the need for nonmonotonic limit analyses. A groundwork is laid for implementing these analyses. An alternate limit load characterization to that of Greenberg is provided, a mathematical statement of the problem leading to both monotonic (proportional) and nonmonotonic limit loads values is formulated, a direct limit load analysis procedure for analysis within a finite-element framework is described, and limit loads for sets of simple structures are evaluated. A direct limit analysis process is described, and monotonic limit loads are characterized. The process furnishes 'exact' values of limit loads with increasing efficiency as the number of structural elements and force redundancy decreases. Tests show that the accuracy of predicting nonmonotonic limit loads is very sensitive to the number of degrees of freedom in the analysis compared with the total number in the model.
    Keywords: STRUCTURAL MECHANICS
    Type: Computers and Structures; 4; Mar. 197
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  • 30
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    Bistatic scatter from rain (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: An experimental investigation of bistatic scatter from rain was conducted, using a 143-km scatter path at frequencies of 4.5 and 7.7 GHz. The ratio of transmitted to received power (transmission loss) was measured for scattering angles ranging from 6 to 130 deg. Simultaneous weather radar observations were made at a frequency of 1.3 GHz. Transmission loss estimates for the bistatic scatter path were computed, using the weather radar data, the bistatic radar equation, and a model for the scattering cross section per unit volume of rain based upon Rayleigh scattering by an ensemble of water spheres. The measured and estimated transmission loss values were compared to test the use of the scattering model for the estimation of interference. The averaged ratio of measured-to-calculated transmission loss for the 4.5 GHz data is 1.2 plus or minus 0.4 dB. The averaged ratio for the 7.7 GHz data is -1.6 plus or minus 0.5 dB.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Antennas and Propagation; AP-22; Mar. 197
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  • 31
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    Adhesive fracture mechanics (1974)
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    Publication Date: 2011-08-16
    Description: In studies of fracture mechanics the adhesive fracture energy is regarded as a fundamental property of the adhesive system. It is pointed out that the value of the adhesive fracture energy depends on surface preparation, curing conditions, and absorbed monolayers. A test method reported makes use of a disk whose peripheral part is bonded to a substrate material. Pressure is injected into the unbonded central part of the disk. At a certain critical pressure value adhesive failure can be observed. A numerical stress analysis involving arbitrary geometries is conducted.
    Keywords: STRUCTURAL MECHANICS
    Type: International Journal of Fracture; 10; Mar. 197
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  • 32
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    New triangular plate-bending finite element with transverse shear flexibility (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal; 12; Dec. 197
    Format: text
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  • 33
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    Integrated laser/radar satellite ranging and tracking system (1974)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: A laser satellite ranging system that is mounted upon and integrated with a microwave tracking radar is reported. The 1-pulse/sec ruby laser transmitter is attached directly to the radar's elevation axis and radiates through a new opening in the radar's parabolic dish. The laser photomultiplier tube receiver utilizes the radar's existing 20-cm diam f/11 boresight telescope and observes through a similar symmetrically located opening in the dish. The laser system possesses separate ranging system electronics but shares the radar's timing, computer, and data handling/recording systems. The basic concept of the laser/radar is outlined together with a listing of the numerous advantages over present singular laser range-finding systems. The developmental laser hardware is described along with preliminary range-finding results and expectations.
    Keywords: COMMUNICATIONS
    Type: Applied Optics; 13; Oct. 197
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  • 34
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    Interactive design of large end rings on stiffened conical shells using composites (1974)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: Design study methods and results for a composite reinforced base ring for the conical aeroshell structure of the planetary lander vehicle for Project Viking, an unmanned mission to Mars, are presented. The aeroshell is a ring and stringer-stiffened conical shell structure having a half angle of 70 degrees with a large base ring mounted at the outer edge of the cone and a large pay-load ring in the interior with many smaller rings spaced along the inside shell surface. The purpose of the structure is to develop the aerodynamic drag required to decelerate the lander in the Mars atmosphere to facilitiate a soft landing. The design of a shell structure of this complexity requires the use of the latest technology available in a large general-purpose shell buckling program. The large general-purpose non-linear shell buckling program (BOSOR 2) which was used for this purpose is described.
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  • 35
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    Shortwave telemetric system (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The application of frequency modulation when constructing a telemetric system in the shortwave band. The operating principles, the construction of the system and the decision making device are described and experimental data are presented. The equipment can be used on sounding balloons.
    Keywords: COMMUNICATIONS
    Type: Technol. for the Production of Space Equipment (NASA-TT-F-15766); p 59-65
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  • 36
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    Boundary value problems with incremental plasticity in granular media (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Discussion of the critical state concept in terms of an incremental theory of plasticity in granular (soil) media, and formulation of the governing equations which are convenient for a computational scheme using the finite element method. It is shown that the critical state concept with its representation by the classical incremental theory of plasticity can provide a powerful means for solving a wide variety of boundary value problems in soil media.
    Keywords: STRUCTURAL MECHANICS
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  • 37
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    A solution to the contact of two rough spherical surfaces (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The influence of roughness on the interfacial pressure distribution in the contact of two spherical surfaces is considered. An approximate general solution is presented and it is shown that the pressure for all radii can be determined solely from a reference pressure which is, in turn, a function of two parameters - a dimensionless roughness and a dimensionless hardness. Values for the radius of contact are also presented.
    Keywords: STRUCTURAL MECHANICS
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  • 38
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    Diffraction theory techniques applied to aperture antennas on finite circular and square ground planes (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Expressions which represent the elevation-plane patterns of a large TEM mode coax aperture and a TM-01 mode circular aperture on finite circular and square ground planes have been derived using geometrical theory of diffraction; design curves for the coax case are presented. The expressions for the field pattern were obtained by superposing the infinite ground plane solutions, the first-order diffracted field solutions, and the axial caustic solutions in their respective regions of validity. The pattern analyses for the coax and circular apertures are verified experimentally.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Antennas and Propagation; AP-22; May 1974
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  • 39
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    Mixed mode stress field effect in adhesive fracture (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Numerical or analytical analyses were performed on seven different test specimens including blister test, 90-degree peel test, torsion test, and various cone tests. These specimens are in general subjected to complex stress fields having various amounts of Mode I, Mode II, and Mode III loads. The specimens were then constructed using polymethyl methacrylate for the adherends and a transparent polyurethane elastomer (Solithane 113) for the adhesive. This combination permitted direct observation of the bondline as load was applied. Although initial debonds as well as bond end termination singularities were present in all specimens, in some cases the debond did not initiate at the singularity points as would normally have been expected. An explanation for this behavior is presented, as well as a comparison of loading mode effect on those specimens for which the debond did propagate from a bond terminus singular point.
    Keywords: STRUCTURAL MECHANICS
    Type: International Journal of Fracture; 10; Dec. 197
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  • 40
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    Dependence of plate-bending finite element deflections and eigenvalues on Poisson's ratio (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal; 12; Oct. 197
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  • 41
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    Diffused optical waveguides (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Diffused optical waveguides are studied using the modal and the ray tracing approach, with an emphasis on the case of a hollow waveguide with diffuse cladding. The properties of the guided modes are investigated in detail. The applications of these structures to optical circuits, integrated optics lasers and capillary gas lasers are discussed.
    Keywords: COMMUNICATIONS
    Type: vol. 43; July 197
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  • 42
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    The Apollo Lunar Sounder radar system (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The objectives of the Apollo 17 Lunar Sounder Experiment (ALSE) were to detect subsurface geologic structures, to generate a continuous lunar profile, and to image the moon at radar wavelengths. A three-wavelength synthetic-aperture radar (SAR) operating at 60, 20, and 2 m wavelengths was designed to attain these objectives. The design choices reflected a balance of scientific requirements versus Apollo mission and hardware constraints. The radar data from the lunar mission were recorded on photographic film in a conventional SAR format, and were returned to earth for processing. A combination of optical and digital processing and exploitation techniques was applied to the scientific interpretation of the data. Some preliminary results from the lunar mission have been obtained.
    Keywords: COMMUNICATIONS
    Type: IEEE; vol. 62
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  • 43
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    Mutual coupling in a finite planar array of circular apertures (1974)
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    Publication Date: 2011-08-16
    Description: Equations are presented for the calculation of the interelement mutual coupling in a finite size planar array of wave-guide-fed apertures in an infinite flat conductor. The general mutual admittance expression is evaluated for circular apertures and the mutual coupling calculations are verified experimentally for two TE11 mode excited apertures. Qualitative agreement between calculations for a 183 element array and an infinite array establishes the validity of the finite array theoretical model.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Antennas and Propagation; AP-22; Mar. 197
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  • 44
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    Fracture initiation and propagation in a cylindrical shell containing an initial surface flaw (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: An attempt is made to provide the necessary analytical tools for the application of two different types of fracture criteria to shell structures. Of particular interest is the problem of fracture propagation and arrest in a cylindrical pressure vessel containing an initial surface flaw. It is assumed that the flaw has the most unfavorable geometry and orientation, namely, it is a crack lying on a meridional plane. Stress intensity factor for a part-through crack, and a surface or internal crack with a fully yielded net ligament are considered. Attention is given to constant delta curves for depressurization studies and to depressurization and crack arrest in pressure vessels.
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  • 45
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    An overview of high temperature metal fatigue: Aspects covered by the 1973 International Conference on Creep and Fatigue (1974)
    In:  CASI
    Details
    Publication Date: 2012-05-22
    Description: A summary of papers is presented which covers the following broad aspects of high temperature metal fatigue: (1) materials development and characterization; (2) environmental factors, including air, vacuum, helium, iodine, sodium, and radiation environments; (3) general fatigue life relationships; (4) crack growth laws; (5) design code activities; and (6) design and service experience. Illustrative tables accompany the summary.
    Keywords: STRUCTURAL MECHANICS
    Type: AGARD Low Cycle High Temp. Fatigue; 47 p
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  • 46
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    Identification of structural parameters from helicopter dynamic test data (1974)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A method is presented for obtaining the mass, stiffness, and damping parameters of a linear mathematical model, having fewer degrees of freedom than the structure it represents, directly from dynamic response measurements on the actual helicopter without a priori knowledge of the physical characteristics of the fuselage. The only input information required in the formulation is the approximate natural frequency of each mode and mobility data measured proximate to these frequencies with sinusoidal force excitation applied at only one point on the vehicle. The practicality and numerical soundness of the theoretical development was demonstrated through a computer simulation of an experimental program.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Ames Res. Center Rotorcraft Dyn.; p 239-248
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  • 47
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    Application of antiresonance theory to helicopters (1974)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Antiresonance theory is the principle underlying nonresonant nodes in a structure, and covers both nonresonant nodes occurring naturally and those introduced by devices such as dynamic absorbers and antiresonant isolators. The dynamic antiresonant vibration isolator (DAVI) and the nodale module are examples of the applications of transfer antiresonances. It is shown that antiresonances are eigenvalues, and that they can be determined by matrix iteration. Applications of antiresonance theory to helicopter engineering problems, using the antiresonant eigenvalue equation are suggested.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Ames Res. Center Rotorcraft Dyn.; p 101-106
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  • 48
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    Correlation of finite-element structural dynamic analysis with measured free vibration characteristics for a full-scale helicopter fuselage (1974)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The correlation achieved with each program provides the material for a discussion of modeling techniques developed for general application to finite-element dynamic analyses of helicopter airframes. Included are the selection of static and dynamic degrees of freedom, cockpit structural modeling, and the extent of flexible-frame modeling in the transmission support region and in the vicinity of large cut-outs. The sensitivity of predicted results to these modeling assumptions are discussed. Both the Sikorsky Finite-Element Airframe Vibration analysis Program (FRAN/Vibration Analysis) and the NASA Structural Analysis Program (NASTRAN) have been correlated with data taken in full-scale vibration tests of a modified CH-53A helicopter.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Ames Res. Center Rotorcraft Dyn.; p 67-80
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  • 49
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    Simulation study of communication link for Pioneer Saturn/Uranus atmospheric entry probe (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A digital simulation is presented for a candidate modem in a modeled atmospheric scintillation environment with Doppler, Doppler rate, and signal attenuation typical of the radio link conditions for an outer planets atmospheric entry probe. The results indicate that the signal acquisition characteristics and the channel error rate are acceptable for the system requirements of the radio link. The simulation also outputs data for calculating other error statistics and a quantized symbol stream from which error correction decoding can be analyzed.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-114739
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  • 50
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    Transonic single-mode flutter and buffet of a low aspect ratio wing having a subsonic airfoil shape (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Transonic flutter and buffet results obtained from wind-tunnel tests of a low aspect ratio semispan wing model are presented. The tests were conducted to investigate potential transonic aeroelastic problems of vehicles having subsonic airfoil sections. The model employed NACA 00XX-64 airfoil sections in the streamwise direction and had a 14 deg leading edge sweep angle. Aspect ratio, and average thickness were 4.0, 0.35, and 8 percent, respectively. The model was tested at Mach numbers from 0.6 to 0.95 at angles of attack from 0 deg to 15 deg. Two zero lift flutter conditions were found that involved essentially single normal mode vibrations. With boundary layer trips on the model, flutter occurred in a narrow Mach number range centered at about Mach 0.90. The frequency and motion of this flutter were like that of the first normal mode vibration. With the trips removed flutter occurred at a slightly high Mach number but in a mode strongly resembling that of the second normal mode.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TN-D-7346 , A-4966
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  • 51
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    Transverse vibrations of non-uniform beams (1974)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The free vibrations of elastic beams with nonuniform characteristics are investigated theoretically by a new method. The new method is seen to combine the advantages of a finite element approach and of a Rayleigh-Ritz analysis. Comparison with the known analytical results for uniform beams shows good convergence of the method for natural frequencies and modes. For internal shear forces and bending moments, the rate of convergence is less rapid. Results from experiments conducted with a cantilevered helicopter blade with strong nonuniformities and also from alternative theoretical methods, indicate that the theory adequately predicts natural frequencies and mode shapes. General guidelines for efficient use of the method are presented.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Sound and Vibration; 37; Dec. 22
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  • 52
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    Non-linear behavior of fiber composite laminates (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The non-linear behavior of fiber composite laminates which results from lamina non-linear characteristics was examined. The analysis uses a Ramberg-Osgood representation of the lamina transverse and shear stress strain curves in conjunction with deformation theory to describe the resultant laminate non-linear behavior. A laminate having an arbitrary number of oriented layers and subjected to a general state of membrane stress was treated. Parametric results and comparison with experimental data and prior theoretical results are presented.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-2313 , TFR/7309
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  • 53
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    Failure criteria for viscoelastic materials (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Research projects concerned with developing a theory of fracture of materials are discussed. The effects of the geometry of the structure and the loads acting on the structure as they influence the failure process are analyzed. The effects of the viscoelastic deformation characteristics of the bulk elastomer on failure behavior are examined. Additional material parameters which control the fracture process are identified.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-138125 , GALCIT-120
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  • 54
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    Advance development of a technique for characterizing the thermomechanical properties of thermally stable polymers (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The torsional braid experiment has been interfaced with a centralized hierarchical computing system for data acquisition and data processing. Such a system, when matched by the appropriate upgrading of the monitoring techniques, provides high resolution thermomechanical spectra of rigidity and damping, and their derivatives with respect to temperature.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-138123
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  • 55
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    Low cost ground receiving systems for television signals from high-powered communications satellites. Volume 2: Parts list and engineering drawings (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Parts lists for the 2.25 GHz indoor- and antenna-unit assemblies are followed by drawings that constitute the drafting package for three converter types and the tunnel diode amplifier.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-120933
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  • 56
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    Task 60 test report, evaluation of IRIG-A 21 channel constant bandwith FM multiplexer for shuttle development flight instrumentation (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A frequency modulated (FM) multiplexer, consisting of 21 IRIG-A constant bandwidth (CBW) voltage-controlled oscillators (VCO's) was tested to determine its suitability for use in multiplexing 21 data signals which have frequency ranges of dc to 2 kHz. Tests were preformed with the composite signal, consisting of the mixed outputs of the 21 VCO's connected directly to a set of subcarrier discriminators, with the signal recorded on magnetic tape and played back through the discriminators and with the signal transmitted by a frequency-modulated FM S-band radio frequency RF transmitter to a FM receiver and through the subcarrier discriminators. Tape speed flutter was induced to determine the reduction in flutter noise which can be obtained by the tape speed compensation equipment. The RF transmission test included transmitting the composite signal at a nominal RF received signal of -73 dbm and at RF levels of -83 and -86 dbm.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-134304 , LEC-3558 , JSC-09017
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  • 57
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    Analysis of laminated, composite, circular cylindrical shells with general boundary conditions (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: This report develops: (1) a refined approximate theory for the static and dynamic analyses of finite, laminated, composite, circular cylindrical shells with general boundary conditions; (2) an exact three-dimensional analysis of simply supported, laminated, composite, circular cylindrical shells, and (3) a thin-shell theory for laminated, composite, circular cylindrical shells. In the refined approximate theory the displacements are assumed piecewise linear across the thickness and the effects of transverse shear deformations and transverse normal stress are included. A variational approach is followed to obtain the governing differential equations and boundary conditions. A general solution of the governing differential equations is also presented. The results obtained by using the refined approximate theory and the thin-shell theory are compared with the exact results for the case of free vibrations of simply supported, laminated, composite, circular cylindrical shells. The refined approximate theory is very accurate, even for thick shells with short nodal distances, whereas thin-shell theory is reasonably accurate only for thin shells at moderate nodal distances and wave number less than 2.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TR-R-412 , L-8828
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  • 58
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    Holographic nondestructive tests performed on composite samples of ceramic-epoxy-fiberglass sandwich structure (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: When a hologram storing more than one wave is illuminated with coherent light, the reconstructed wave fronts interfere with each other or with any other phase-related wave front derived from the illuminating source. This multiple wave front comparison is called holographic interferometry, and its application is called holographic nondestructive testing (HNDT). The theoretical aspects of HNDT techniques and the sensitivity of the holographic system to the geometrical placement of the optical components are briefly discussed. A unique HNDT system which is mobile and possesses variable sensitivity to stress amplitude is discribed, the experimental evidence of the application of this system to the testing of the hidden debonds in a ceramic-epoxy-fiberglass structure used for sample testing of the radome of the Pershing missile system is presented.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TR-R-430 , M-461
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  • 59
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    Procedures for experimental measurement and theoretical analysis of large plastic deformations (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Theoretical equations are derived and analytical procedures are presented for the interpretation of experimental measurements of large plastic strains in the surface of a plate. Orthogonal gage lengths established on the metal surface are measured before and after deformation. The change in orthogonality after deformation is also measured. Equations yield the principal strains, deviatoric stresses in the absence of surface friction forces, true stresses if the stress normal to the surface is known, and the orientation angle between the deformed gage line and the principal stress-strain axes. Errors in the measurement of nominal strains greater than 3 percent are within engineering accuracy. Applications suggested for this strain measurement system include the large-strain-stress analysis of impact test models, burst tests of spherical or cylindrical pressure vessels, and to augment small-strain instrumentation tests where large strains are anticipated.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-X-3027 , E-7661
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  • 60
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    Analysis of three-point-bend test for materials with unequal tension and compression properties (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An analysis capability is described for the three-point-bend test applicable to materials of linear but unequal tensile and compressive stress-strain relations. The capability consists of numerous equations of simple form and their graphical representation. Procedures are described to examine the local stress concentrations and failure modes initiation. Examples are given to illustrate the usefulness and ease of application of the capability. Comparisons are made with materials which have equal tensile and compressive properties. The results indicate possible underestimates for flexural modulus or strength ranging from 25 to 50 percent greater than values predicted when accounting for unequal properties. The capability can also be used to reduce test data from three-point-bending tests, extract material properties useful in design from these test data, select test specimen dimensions, and size structural members.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TN-D-7572 , E-7544
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  • 61
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    FORTRAN 4 programs for summarization and analysis of fracture trace and lineament patterns (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Systematic and detailed analysis of lineament and fracture trace patterns has long been neglected because of the large number of observations involved in such an analysis. Three FORTRAN 4 programs were written to facilitate this manipulation. TRANSFORM converts the initial fracture map data into a format compatible with AZMAP, whose options allow repetitive manipulation of the data for optimization of the analysis. ROSE creates rose diagrams of the fracture patterns suitable for map overlays and tectonic interpretation. Examples are given and further analysis techniques using output from these programs are discussed.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-X-70596 , X-644-74-3
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  • 62
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    Sensitivity analysis of torsional vibration characteristics of helicopter rotor blades. Part 2: Aerodynamics and sensitivity analysis (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A theoretical investigation of dynamic response characteristics of rotor blades was carried out with special emphasis on torsional degrees-of-freedom. Coupled equations of motion for flapwise bending and torsion were formulated at varying azimuth positions for rotor blades with noncollinear aerodynamic, elastic and mass axes. Both structural and aerodynamic mass, damping and stiffness coefficients were included. The variations of a sample blade at different flight conditions were investigated from these equations. The obtained numerical results were illustrated. The sensitivity of overall blade vibration characteristics to torsional oscillations was also investigated from the equations of motion for the sample blade. The illustrated results show the importance of torsional degrees-of-freedom in rotor blade analysis. Various possibilities of improving the overall response by tuning blade geometric, structural and aerodynamic characteristics are discussed.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-2380
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  • 63
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    Integrated source and channel encoded digital communications system design study (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Studies on the digital communication system for the direct communication links from ground to space shuttle and the links involving the Tracking and Data Relay Satellite (TDRS). Three main tasks were performed:(1) Channel encoding/decoding parameter optimization for forward and reverse TDRS links,(2)integration of command encoding/decoding and channel encoding/decoding; and (3) modulation coding interface study. The general communication environment is presented to provide the necessary background for the tasks and to provide an understanding of the implications of the results of the studies.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-134183 , R7401-2
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    Assembly and analysis of fragmentation data for liquid propellant vessels (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Fragmentation data was assembled and analyzed for exploding liquid propellant vessels. These data were to be retrieved from reports of tests and accidents, including measurements or estimates of blast yield, etc. A significant amount of data was retrieved from a series of tests conducted for measurement of blast and fireball effects of liquid propellant explosions (Project PYRO), a few well-documented accident reports, and a series of tests to determine auto-ignition properties of mixing liquid propellants. The data were reduced and fitted to various statistical functions. Comparisons were made with methods of prediction for blast yield, initial fragment velocities, and fragment range. Reasonably good correlation was achieved. Methods presented in the report allow prediction of fragment patterns, given type and quantity of propellant, type of accident, and time of propellant mixing.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-134538
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    Stress anisotropy and concentration effects in high pressure measurements (1974)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: Sodium chloride is used as an internal pressure standard in high pressure research. Possible corrections are discussed which are needed in the calibration of this standard due to the independent effects of stress anisotropy and stress concentration in pressure vessels. The first is due to the lack of a truly hydrostatic state of stress in solid state pressure vessels. The second is due to the difference in the compressibilities between the pressure transmitting substances (sodium chloride) and a stiffer test specimen. These two corrections are then combined and a total correction, as a function of measured pressure, is discussed for two systems presently in use. The predicted value of the combined effect is about 5-10% of the pressure at 30 GPa.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-142600 , REPT-2345
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    Elastic moduli of precompressed pyrophyllite used in ultrahigh pressure research (1974)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The propagation of ultrasonic pulses in pyrophyllite specimens was studied to determine the effect of specimen precompression on the measured elastic moduli. Measurements were made at room pressure and, for the precompressed specimens, to pressures of 3 kbar. Pyrophyllite was found to be elastically anisotropic, apparently the result of the fabric present in our material. The room pressure adiabatic bulk modulus as measured on specimens made of isostatically compacted powered pyrophyllite was determined to be 96.1 kbar. The wave speeds of ultrasonic pulses in pyrophyllite were found to decrease with increasing specimen precompression. A limiting value of precompression was found, above which no further decrease in wave speed was observed. For the shear wave speeds this occurs at 10 kbar while for the longitudinal wave at 25 kbar. In the limit, the shear waves propagate 20% slower than in the unprecompressed samples; for the longitudinal wave the difference is 30%.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-142598 , REPT-2366
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    Contact and crack problems for an elastic wedge (1974)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The contact and the crack problems for an elastic wedge of arbitrary angle are considered. The problem is reduced to a singular integral equation which, in the general case, may have a generalized Cauchy kernel. The singularities under the stamp as well as at the wedge apex were studied, and the relevant stress intensity factors are defined. The problem was solved for various wedge geometries and loading conditions. The results may be applicable to certain foundation problems and to crack problems in symmetrically loaded wedges in which cracks initiate from the apex.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-132640
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    Effects of turbulence in a planetary atmosphere on radio occultation (1974)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: A formulation is given for the correlation functions for the log-amplitude and phase fluctuations of both spherical and plane waves propagating in a turbulent medium whose correlation function for refractive index fluctuations is described by the product of a function of the average coordinate and a function of the difference coordinate. The results are applied to radio occultation of a flyby space probe by the atmosphere of Venus, assuming that the turbulence in the atmosphere exists as a layer, that it is localized, isotropic, and smoothly varying, and that the localized turbulence is described by the Kolmogorov spectrum. Closed-form solutions for both variances and frequency spectra of the log-amplitude and phase fluctuations are obtained using Rytov's method, and it is seen that the shape of the frequency spectra depends greatly on the characteristics and extent of the turbulence.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Antennas and Propagation; AP-22; July 197
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    The interpretation of ionospheric radio drift measurements. VII - Diffraction methods applied to E-region echo fading: Evidence of a focusing model (1974)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Keywords: COMMUNICATIONS
    Type: Journal of Atmospheric and Terrestrial Physics; 36; May 1974
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  • 70
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    Properties of cutoff corrugated surfaces for corrugated horn design (1974)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Corrugated horns involve a junction between the corrugated surface and a conducting ground plane. Proper horn design requires an understanding of the electromagnetic properties of the corrugated surface and this junction. An integral equation solution has been used to study the influence of corrugation density and tooth thickness on the power loss, surface current, and the scattering from a ground plane/corrugated surface junction.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Antennas and Propagation; AP-22; Mar. 197
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  • 71
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    Derivatives of eigenvalues and eigenvectors for a general matrix (1974)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Expressions are obtained for the derivatives of the eigenvalues and eigenvectors which are expressions of only one left-hand and one right-hand eigenvector. The approach described makes use of a Choleski decomposition or some other decomposition method. The method may be extended to find any order of derivative of the eigenvalue and eigenvector. The expressions obtained for finding the derivatives of eigenvalues and eigenvectors for nonself-adjoint systems may be applied to self-adjoint systems.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal; 12; May 1974
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  • 72
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    An experimental-theoretical study of free vibrations of plates on elastic point supports (1974)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: A theoretical and experimental study is made to investigate the effect on plate vibrations of varying the stiffness of corner elastic point supports. An experiment is conducted in which the bending stiffness of horizontal beams is used to support a square plate at its four corners. The stiffness of these supports can be varied over such a range that the plate fundamental frequency is lowered to 40% of the rigid support frequency. The variation with support stiffness of the frequencies of the first eight plate modes is measured and is compared with results from a theoretical model in which a Rayleigh-Ritz analysis is used which approximates the plate mode shapes as products of free-free beam modes. The elastic point supports are modeled both as massless translational springs and springs with tip masses, which are included to better represent the experimental supports.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Sound and Vibration; 32; Feb. 22
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    Application of an integral equation formulation to the prediction of space shuttle annular slot antenna radiation patterns (1974)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Pitch and roll plane radiation patterns computed by use of an integral equation formulation are presented for a space shuttle annular slot communications antenna. The excellent agreement between computed patterns and experimental patterns obtained from 1/35 scale models supports the use of this method as a design tool for similar spacecraft/aircraft antenna applications.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Antennas and Propagation; AP-22; Jan. 197
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  • 74
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    Design manual: Oxygen Thermal Test Article (OTTA) (1974)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The characteristics of a cryogenic tank for storing liquid hydrogen, nitrogen, oxygen, methane, or helium for an extended period of time with minimum losses are discussed. A description of the tank and control module, assembly drawings and details of major subassemblies, specific requirements controlling development of the system, thermal concept considerations, thermal analysis methods, and a record of test results are provided. The oxygen thermal test article thermal protection system has proven that the insulation system for cryogenic vessels is effective.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-140209 , ER15961
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  • 75
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    Research on the elastic stability of large shells (1974)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: Tests were conducted to determine the elastic stability of large shell structures. The configuration of the shells and the instrumentation used in the measurements are described. The testing procedures are explained. Results of the stress analysis are plotted in polar graph form to show the areas of strain in micro inches at the outer surface of the skin and the inner lip of the stringer.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-139665 , SAPR-6
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  • 76
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    Abating exhaust noises in jet engines (1974)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: A noise abating improvement for jet engines including turbojets, turbofans, turboprops, ramjets, scramjets, and hybrid jets is introduced. A provision is made for an apparatus in the primary and/or secondary flow streams of the engines; the apparatus imparts to the exhaust gases a component rotation or swirl about the engine's longitudinal axis. The rotary component in the exhaust gases causes a substantial suppression of sound energy build up normally produced by an axial flow exhaust system.
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    Design of a 12 channel fm microwave receiver (1974)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The design, fabrication, and performance of elements of a low cost FM microwave satellite ground station receiver is described. It is capable of accepting 12 contiguous color television equivalent bandwidth channels in the 11.72 to 12.2 GHz band. Each channel is 40 MHz wide and incorporates a 4 MHz guard band. The modulation format is wideband FM and the channels are frequency division multiplexed. Twelve independent CATV compatible baseband outputs are provided. The overall system specifications are first discussed, then consideration is given to the receiver subsystems and the signal branching network.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-140056 , R(T)-74/2
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    High temperature antenna development for space shuttle, volume 2 (1974)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: An S-band antenna system and a group of off-the-shelf aircraft antenna were exposed to temperatures simulating shuttle orbital cold soak and entry heating. Radiation pattern and impedance measurements before and after exposure to the thermal environments were used to evaluate the electrical performance. The results of the electrical and thermal testing are given. Test data showed minor changes in electrical performance and established the capability of these antenna to withstand both the low temperatures of space flight and the high temperatures of entry.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-140226 , MDC-E0896-VOL-2
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    Method and apparatus for decoding compatible convolutional codes (1974)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: This invention relates to learning decoders for decoding compatible convolutional codes. The decoder decodes signals which have been encoded by a convolutional coder and allows performance near the theoretical limit of performance for coded data systems. The decoder includes a sub-bit shift register wherein the received sub-bits are entered after regeneration and shifted in synchronization with a clock signal recovered from the received sub-bit stream. The received sub-bits are processed by a sub-bit decision circuit, entered into a sub-bit shift register, decoded by a decision circuit, entered into a data shift register, and updated to reduce data errors. The bit decision circuit utilizes stored sub-bits and stored data bits to determine subsequent data-bits. Data errors are reduced by using at least one up-date circuit.
    Keywords: STRUCTURAL MECHANICS
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    Noise suppressor (1974)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: A tuned noise suppressor is described consisting of annular acoustically porous elements for incorporation into the inlet and exhaust ducts of turbofan engines. The apparatus uses sound wave absorption, reflection, and incompatibility for achieving high noise reduction in the short distance. In addition, it has a duct of uniform inner diameter which does not block the duct flow.
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    Dual frequency dichroic feed performance (1974)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The NASA Deep Space Net (DSN) in support of the Viking Mars Project in 1976, and for science and technology demonstrations during the Mariner-Venus-Mercury mission in 1974, has developed and implemented a dual (S- and X-band) feed for large ground microwave antennas. This feed provides for a multiplicity of functions; very low listening capability at each downlink (spacecraft-to-earth) band as well as simultaneous diplexed very high cw power uplink (earth-to-spacecraft) at the S-band frequency. Total 64-m antenna system performance, is considered in terms of gain, operating noise temperature and dual beam pointing or boresight coincidence. Because of the unique ability to fold or stow the dual band feed elements for single band operations, the performance definition between single and dual band operations will be reliable and accurate.
    Keywords: COMMUNICATIONS
    Type: AGARD Antennas for Avionics; 10 p
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  • 82
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    Effects of turbulence in the atmosphere of Venus on Pioneer Venus radio, phase 2 (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Two problems related to the effects of turbulence in the atmosphere of Venus on the Pioneer entry probe radio link were studied. In the first problem, the cross correlation between the log amplitude and phase fluctuations of the Pioneer Venus communications link is examined. Data show that for fluctuation frequencies above approximately 1 Hz there is little or no correlation. For frequencies below this region the correlation is weak and the square root of the coherence has a peak value close to 0.65. The second problem consists of interferring turbulence characteristics of the Venus atmosphere from the Mariner 5 phase fluctuations. Data show that with the data processing techniques developed and currently available, the phase error due to oscillator drift, assumed trajectory delay, and spline curve fit exceed the turbulence induced fluctuations. Results show that it is not possible to interfere with the turbulence characteristics from Mariner 5 phase fluctuations.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-139657 , JPL-TM-33-702
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    The potential for congressional use of emergent telecommunications: An exploratory assessment (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A study of the use of newly emerging communications technology for improving the understanding between members of Congress and their constituents was conducted. The study employed a number of specific methodologies such as interdisciplinary systems model building, technology analysis, a sample survey, and semi-structured interviews using sketches of the emergent channels. The following configurations were identified as representative of emergent channel characteristics: (1) the teleconference, (2) the videoconference, (3) the videophone, (4) cable television, (5) cable television polling, and (6) information retrieval. Analysis of the interview data resulted in an overview of the current congressional-constituent communication system and an assessment of the potential for emergent telecommunications, as perceived by congressmen and senior staff from 40 offices in the stratified judgement sample.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-139669 , GWPS-MON-20
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    Ultrasonic measurement of stress in railroad wheels and in long lengths of welded rail (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The failure of high speed emergency braking is discussed for railroad wheels and track. It is shown that high compressive residual stresses exist in the rims of new wheels which generate excessive heat, reducing the stress levels. Thermal stresses that build up in continuous lengths of welded track are reported and nondestructive methods of measuring stresses in thick steel are presented for identification, replacement, or adjustment before hazardous failures occur.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-X-64863
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    Evaluation of a metal shear web selectively reinforced with filamentary composites for space shuttle application (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A final program summary is reported for test and evaluation activities that were conducted for space shuttle web selection. Large scale advanced composite shear web components were tested and analyzed to evaluate application of advanced composite shear web construction to a space shuttle orbiter thrust structure. The shear web design concept consisted of a titanium-clad + or - 45 deg boron/epoxy web laminate stiffened with vertical boron-epoxy reinforced aluminum stiffeners and logitudinal aluminum stiffening. The design concept was evaluated to be efficient and practical for the application that was studied. Because of the effects of buckling deflections, a requirement is identified for shear buckling resistant design to maximize the efficiency of highly-loaded advanced composite shear webs.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-2409 , D180-17969-1
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    Variably positioned guide vanes for aerodynamic choking (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A choking device to cause a sonic barrier to be formed which reduces the transmission of noise in a direction opposed to the direction of air flow in a compressor that may be part of an aircraft gas turbine engine is described. The noise reduction is accomplished by proper shaping and movement of inlet guide vanes, and an actuator is connected to selected guide vanes to effect movement by programmed amounts as required to choke or partially choke within the design range of the axial-flow-air compressor.
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    Analysis of the proposed utilization of TDRS system by the HEAO-C satellite (1974)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The primary function of the study was to assess the impact upon the HEAO telecommunications system of the proposed relay satellite-to-ground-link configuration. The system is designed to perform the function of most of the NASA ground tracking and communications network at a net cost savings for NASA.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-139393
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    An application of queueing theory to the design of channel requirements for special purpose communications satellites (1974)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: Special purpose satellites are very cost sensitive to the number of broadcast channels, usually will have Poisson arrivals, fairly low utilization (less than 35%), and a very high availability requirement. To solve the problem of determining the effects of limiting C the number of channels, the Poisson arrival, infinite server queueing model will be modified to describe the many server case. The model is predicated on the reproductive property of the Poisson distribution.
    Keywords: COMMUNICATIONS
    Type: NASA-TM-X-71590
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    Digital communication system (1974)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: A digital communication system is reported for parallel operation of 16 or more transceiver units with the use of only four interconnecting wires. A remote synchronization circuit produces unit address control words sequentially in data frames of 16 words. Means are provided in each transceiver unit to decode calling signals and to transmit calling and data signals. The transceivers communicate with each other over one data line. The synchronization unit communicates the address control information to the transceiver units over an address line and further provides the timing information over a clock line. A reference voltage level or ground line completes the interconnecting four wire hookup.
    Keywords: STRUCTURAL MECHANICS
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  • 90
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    Coherent receiver employing nonlinear coherence detection for carrier tracking (1974)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The concept of nonlinear coherence employed in carrier tracking to improve telecommunications efficiency is disclosed. A generic tracking loop for a coherent receiver is shown having seven principle feedback signals which may be selectively added and applied to a voltage controlled oscillator to produce a reference signal that is phase coherent with a received carrier. An eighth feedback signal whose nonrandom components are coherent with the phase detected and filtered carrier may also be added to exploit the sideband power of the received signal. A ninth feedback signal whose nonrandom components are also coherent with the quadrature phase detected and filtered carrier could be additionally or alternatively included in the composite feedback signal to the voltage controlled oscillator.
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  • 91
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    On thermal stress failure of the SNAP-19A RTG heat shield (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Results of a study on thermal stress problems in an amorphous graphite heat shield that is part of the launch-abort protect system for the SNAP-19A radio-isotope thermoelectric generators (RTG) that will be used on the Viking Mars Lander are presended. The first result is from a thermal stress analysis of a full-scale RTG heat source that failed to survive a suborbital entry flight test, possibly due to thermal stress failure. It was calculated that the maximum stress in the heat shield was only 50 percent of the ultimate strength of the material. To provide information on the stress failure criterion used for this calculation, some heat shield specimens were fractured under abort entry conditions in a plasma arc facility. It was found that in regions free of stress concentrations the POCO graphite heat shield material did fracture when the local stress reached the ultimate uniaxial stress of the material.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-X-3097 , A-5516
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  • 92
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    Stress intensity factors for deep cracks emanating from the corner formed by a hole intersecting a plate surface (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A technique consisting of freezing photo-elasticity and a numerical method was used to obtain stress intensity factors for natural cracks emanating from the corner at which a hole intersects a plate surface. Geometries studied were: (1) crack depth to thickness ratios of approximately 0.2, (2) 0.5 and 0.75; (3) crack depth to crack length ratios of approximately 1.0 to 2.0; and (4) crack length to hole radius ratios of about 0.5 to 2.0. All final crack geometries were grown under monotonic loading and growth was not self similar, with most of the growth occuring through the thickness under remote extension. Stress intensity factors were determined at the intersection of the flaw border.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-132484 , VPI-E-74-1-REV
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  • 93
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    Application of a substructuring technique to the problem of crack extension and closure (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A substructuring technique, originally developed for the efficient reanalysis of structures, is incorporated into the methodology associated with the plastic analysis of structures. An existing finite-element computer program that accounts for elastic-plastic material behavior under cyclic loading was modified to account for changing kinematic constraint conditions - crack growth and intermittent contact of crack surfaces in two dimensional regions. Application of the analysis is presented for a problem of a centercrack panel to demonstrate the efficiency and accuracy of the technique.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-132458 , RE-480
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    Deformation characteristics and time-dependent notch sensitivity of Udimet 700 at intermediate temperatures (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Time dependent notch sensitivity was observed in Udimet 700 sheet, bar, and investment castings between 1000 and 1400 F (538 -760 C), but not at 1600 F (871 C). As was the case for modified Waspaloy, Waspaloy and Inconel 718, it occurred in notched specimens loaded below the yield strength when the creep deformation was localized. For each alloy and notched specimen geometry, a stress-average particle size zone can be defined that characterizes the notch sensitive behavior.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-134613 , REPT-043680-20-F
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  • 95
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    Analysis of wing-body interaction flutter for a preliminary space shuttle design (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Subsonic flutter analyses for a preliminary space shuttle design were performed to determine the effect of wing-body aerodynamic interaction on the vehicle flutter speed. It was found that the proximity of the large bodies of the shuttle to the wing reduces critical flutter speed by 11%. Aerodynamic reflection off the bodies is the dominant interaction effect while aerodynamic forces caused by body motion are of secondary importance in most cases. The analyses employed a doublet-lattice representation of the space shuttle, where in the wing and body surfaces were modeled by a lattice of nonplanar lifting surface elements. Axial singularities were introduced to account for body incidence, volume, and camber (slender body) effects. A series of studies on the placement and number of these elements was performed to ensure convergence of the results.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-2429
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  • 96
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    Analysis of complex elastic structures by a Rayleigh-Ritz component modes method using Lagrange multipliers (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The free vibrations of elastic structures of arbitrary complexity were analyzed in terms of their component modes. The method was based upon the use of the normal unconstrained modes of the components in a Rayleigh-Ritz analysis. The continuity conditions were enforced by means of Lagrange Multipliers. Examples of the structures considered are: (1) beams with nonuniform properties; (2) airplane structures with high or low aspect ratio lifting surface components; (3) the oblique wing airplane; and (4) plate structures. The method was also applied to the analysis of modal damping of linear elastic structures. Convergence of the method versus the number of modes per component and/or the number of components is discussed and compared to more conventional approaches, ad-hoc methods, and experimental results.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-138942 , AMS-1159
    Format: application/pdf
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  • 97
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    Tracking and Data Relay Satellite System (TDRSS), users' guide (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The system concept and characteristics are described along with support and orbital coverage capabilities. Information on user acquisition procedures is given. System impact on single and multiple access users is discussed.
    Keywords: COMMUNICATIONS
    Type: NASA-TM-X-70710 , X-805-74-176
    Format: application/pdf
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  • 98
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    An integral equation formulation for predicting radiation patterns of a space shuttle annular slot antenna (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An integral equation formulation is applied to predict pitch- and roll-plane radiation patterns of a thin VHF/UHF (very high frequency/ultra high frequency) annular slot communications antenna operating at several locations in the nose region of the space shuttle orbiter. Digital computer programs used to compute radiation patterns are given and the use of the programs is illustrated. Experimental verification of computed patterns is given from measurements made on 1/35-scale models of the orbiter.
    Keywords: COMMUNICATIONS
    Type: NASA-TN-D-7594 , L-9279
    Format: application/pdf
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  • 99
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    Channel coding and data compression system considerations for efficient communication of planetary imaging data (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: End-to-end system considerations involving channel coding and data compression which could drastically improve the efficiency in communicating pictorial information from future planetary spacecraft are presented.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-139362 , JPL-TM-33-695
    Format: application/pdf
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  • 100
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    Rotation in vibration, optimization, and aeroelastic stability problems (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The effects of rotation in the areas of vibrations, dynamic stability, optimization, and aeroelasticity were studied. The governing equations of motion for the study of vibration and dynamic stability of a rapidly rotating deformable body were developed starting from the nonlinear theory of elasticity. Some common features such as the limitations of the classical theory of elasticity, the choice of axis system, the property of self-adjointness, the phenomenon of frequency splitting, shortcomings of stability methods as applied to gyroscopic systems, and the effect of internal and external damping on stability in gyroscopic systems are identified and discussed, and are then applied to three specific problems.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-138805
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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