Showing papers by "Ames Research Center published in 1974"
01 Dec 1974
TL;DR: In this article, the Hamilton's principle and the Newtonian method are used to derive the equations of motion for long, straight, slender, homogeneous, isotropic beams undergoing moderate displacements.
Abstract: The equations of motion are developed by two complementary methods, Hamilton's principle and the Newtonian method. The resulting equations are valid to second order for long, straight, slender, homogeneous, isotropic beams undergoing moderate displacements. The ordering scheme is based on the restriction that squares of the bending slopes, the torsion deformation, and the chord/radius and thickness/radius ratios are negligible with respect to unity. All remaining nonlinear terms are retained. The equations are valid for beams with mass centroid axis and area centroid (tension) axis offsets from the elastic axis, nonuniform mass and stiffness section properties, variable pretwist, and a small precone angle. The strain-displacement relations are developed from an exact transformation between the deformed and undeformed coordinate systems. These nonlinear relations form an important contribution to the final equations. Several nonlinear structural and inertial terms in the final equations are identified that can substantially influence the aeroelastic stability and response of hingeless helicopter rotor blades.
576 citations
TL;DR: In this paper, the stability and accuracy of finite-difference approximations to simple linear PDEs are analyzed by studying the modified partial differential equation, which is derived by first expanding each term of a difference scheme in a Taylor series and then eliminating time derivatives higher than first order by certain algebraic manipulations.
563 citations
TL;DR: In this paper, Stokes' infinitesimal-wave expansion for steady progressive free-surface waves has been extended to high order using a computer to perform the coefficient arithmetic, which is valid for any finite value of the wavelength and solutions of high accuracy can be obtained for most values of the wave height and water depth.
Abstract: Stokes' infinitesimal-wave expansion for steady progressive free-surface waves has been extended to high order using a computer to perform the coefficient arithmetic. Stokes' expansion has been found to be incapable of yielding the highest wave for any value of the water depth since convergence is limited by a square-root branch-point some distance short of the maximum. By reformulating the problem using a different independent parameter, the highest waves are obtained correctly. Series summation and analytic continuation are facilitated by the use of Pade approximants. The method is valid in principle for any finite value of the wavelength and solutions of high accuracy can be obtained for most values of the wave height and water depth.
362 citations
TL;DR: A general theory of subsonic potential aerodynamic flow around a lifting body having arbitrary shape and motion is presented in this article, where an integral representation for the velocity potential is obtained by using the Green function method.
Abstract: A general theory of subsonic potential aerodynamic flow around a lifting body having arbitrary shape and motion is presented. By using the Green function method, an integral representation for the velocity potential is obtained for both supersonic and subsonic flow. Under the small perturbation assumption, the potential at any point in the field depends only upon the values of the potential and its normal derivative on the surface of the body. On the surface of the body, this representation reduces to an integro-differential equation relating the potential and its normal derivative (which is known from the boundary conditions) on the surface. The theory is applied to finite-thickness wings in subsonic steady and oscillatory flows.
329 citations
TL;DR: In this article, the Pioneer 10 vector helium magnetometer was used along with models of the intrinsic magnetic field of Jupiter and its magnetosphere, and a model of the Jovian magnetosphere was presented in which the essential feature is an eastward current sheet that forms an annulus with Jupiter at the center.
Abstract: Data obtained by the Pioneer 10 vector helium magnetometer are presented along with models of the intrinsic magnetic field of Jupiter and its magnetosphere. Data acquired between 2.84 and 6.0 Jupiter radii, where the intensity of the planetary field ranged between 1900 and 18,400 gamma, were used to develop a six-parameter eccentric dipole model of the field. The dipole so derived has a moment of 4.0 G (R sub J) cubed and a tilt angle with respect to Jupiter's rotation axis of 11 deg. A model of the Jovian magnetosphere is presented in which the essential feature is an eastward current sheet that forms an annulus with Jupiter at the center. At large distances from the planet the current sheet is nearly parallel to Jupiter's equator but, in general, does not lie in it. The current sheet is warped, so that it is above the equator on one side and below it on the other. The current sheet rotates with the planet, more or less like a rigid body, this behavior causes an apparent up and down motion and periodic crossings of the current sheet by Pioneer.
279 citations
TL;DR: In this article, the theory of large-amplitude hydromagnetic waves and their behavior in the interplanetary medium are examined, and it is shown that the transverse Alfven wave is the predominant propagating fluctuation at 1 AU.
Abstract: Several aspects of the theory of large-amplitude hydromagnetic waves and their behavior in the interplanetary medium are examined. The characteristic modes of the full (i.e., nonlinearized) MHD equations and their modification by collisionless and finite-frequency effects are considered. Special attention is paid to the transverse Alfven mode, which is undamped and characterized by strictly constant pressure, density, and B; this seems to be the predominant propagating fluctuation at 1 AU. It is shown that its propagation in the small-wavelength (WKB) approximation is essentially identical to that of the small-amplitude Alfven wave of linearized theory. It is also suggested that its presence at 1 AU may provide a natural explanation of the observed power anisotropy of the fluctuations. A second-order analysis is used to study fluctuations that are not characteristic modes. It is found that for a small range of propagation directions, and subject to third-order effects, a finite-amplitude wave can exist that is linearly polarized with delta B perpendicular to both B sub zero and k; such a wave can damp nonlinearly.
229 citations
TL;DR: In this paper, the adsorption and condensation of Cu up to several monolayers in thickness on tungsten 110 and 100 single-crystal surfaces were studied by combining low-energy electron diffraction, Auger electron spectroscopy, thermal desorption, work function measurements, and quartz microbalance thickness measurements in one experimental system.
Abstract: The adsorption and condensation of Cu up to several monolayers in thickness on tungsten 110 and 100 single-crystal surfaces are studied by combining low-energy electron diffraction, Auger electron spectroscopy, thermal desorption spectroscopy, work-function measurements, and quartz microbalance thickness measurements in one experimental system. The results show drastic differences in the evolution of the structure, work function, and desorption behavior between 110 and 100 surfaces. These differences are understandable in terms of the atomic roughness of the surfaces.
218 citations
TL;DR: In this paper, the application of magnetic field measurements to the study of properties of the lunar crust and deep interior is reviewed, and electrical conductivity and temperature calculations from analyses of poloidal induction for data taken in both the solar wind and in the geomagnetic tail are reviewed.
Abstract: The application of lunar magnetic field measurements to the study of properties of the lunar crust and deep interior is reviewed. Following a brief description of lunar magnetometers and the lunar magnetic environment, measurements of lunar remanent fields and their interaction with the solar plasma are discussed. The magnetization induction mode is considered with reference to lunar magnetic permeability and iron abundance calculations. Finally, electrical conductivity and temperature calculations from analyses of poloidal induction, for data taken in both the solar wind and in the geomagnetic tail, are reviewed.
169 citations
01 Jul 1974
TL;DR: A practical procedure for optimum design of aerodynamic shapes using an optimization program based on the method of feasible directions coupled with an analysis program that uses a relaxation solution of the inviscid, transonic, small-disturbance equations.
Abstract: A practical procedure for optimum design of aerodynamic shapes is demonstrated. The proposed procedure uses an optimization program based on the method of feasible directions coupled with an analysis program that uses a relaxation solution of the inviscid, transonic, small-disturbance equations. Results are presented for low-drag, nonlifting transonic airfoils. Extension of the method to lifting airfoils, other speed regimes, and to three dimensions if feasible.
161 citations
TL;DR: Pyrolysis of several structurally different amino acids in a column at 500 C showed differences in the mechanisms and final products, and alpha amino acids with alpha alkyl substituents appear to stabilize the developing negative charge formed by partial heterolytic cleavage of the alpha carbon - NH3 bond.
Abstract: Pyrolysis of several structurally different amino acids in a column at 500 C showed differences in the mechanisms and final products. The aliphatic protein amino acids decompose mainly by simple decarboxylation and condensation reactions, while the beta amino acids undergo deamination to unsaturated acids. Alpha amino acids with alpha alkyl substituents undergo an unusual intramolecular SN1 reaction with the formation of an intermediate alpha lactone which decomposes to yield a ketone. The alpha alkyl substituents appear to stabilize the developing negative charge formed by partial heterolytic cleavage of the alpha carbon - NH3 bond. The gamma and delta amino acids give 2-pyrrolidinone and 2-piperidone respectively, while the epsilon acids yield mixed products.
155 citations
01 Jan 1974
TL;DR: In this article, a probabilistic model for mixing and turnover rates for the lunar regolith due to meteoritic impact is presented and evaluated using results from laboratory impact experiments and estimated meteoritic fluxes.
Abstract: A probabilistic model for mixing and turnover rates for the lunar regolith due to meteoritic impact is presented and evaluated using results from laboratory impact experiments and estimated meteoritic fluxes. The upper millimeter of the lunar surface is shown to be the primary mixing zone in the regolith and an important source for impact melts and vapors. Below this 'mixing layer' the rate of mixing and turnover decreases very rapidly with increasing depth, consistent with well-preserved stratigraphy and resident times deduced from deep drill core tube samples.
TL;DR: The surface morphology and optical properties of Mercury resemble those of the moon in remarkable detail and record a very similar sequence of events, suggesting Mercury is probably a differentiated planet with a large iron-rich core.
Abstract: The surface morphology and optical properties of Mercury resemble those of the moon in remarkable detail and record a very similar sequence of events. Chemical and mineralogical similarity of the outer layers of Mercury and the moon is implied; Mercury is probably a differentiated planet with a large iron-rich core. Differentiation is inferred to have occurred very early. No evidence of atmospheric modification of landforms has been found. Large-scale scarps and ridges unlike lunar or martian features may reflect a unique period of planetary compression near the end of heavy bombardment by small planetesimals.
TL;DR: Jupiter's magnetic field and its interaction with the magnetized solar wind were observed with the Pioneer 10 vector helium magnetometer, suggesting substantial plasma effects inside the magnetosphere, such as thermal pressure, centrifugal forces, and differential rotation.
Abstract: Jupiter's magnetic field and its interaction with the magnetized solar wind were observed with the Pioneer 10 vector helium magnetometer. The magnetic dipole is directed opposite to that of the earth with a moment of 4.0 gauss R_J^3 (R_J, Jupiter radius), and an inclination of 15° lying in a system III meridian of 230°. The dipole is offset about 0.1 R_J north of the equatorial plane and about 0.2 R_J toward longitude 170°. There is severe stretching of the planetary field parallel to the equator throughout the outer magnetosphere, accompanied by a systematic departure from meridian planes. The field configuration implies substantial plasma effects inside the magnetosphere, such as thermal pressure, centrifugal forces, and differential rotation. As at the earth, the outer boundary is thin, nor diffuse, and there is a detached bow shock.
TL;DR: Radioactive D- and L-alanine hydrochloride in 10-5 molar dimethylformamide solution was adsorbed by d- and 1-quartz to the extent of 20 to 30 percent, as shown by radioactivity loss.
Abstract: Radioactive D- and L-alanine hydrochloride in 10(-5) molar dimethylformamide solution was adsorbed by d- and 1-quartz to the extent of 20 to 30 percent, as shown by radioactivity loss. d-Quartz preferentially adsorbs D-alanine and 1-quartz adsorbs L-alanine. The extent of asymmetric preferential adsorption is about 1.0 to 1.8 percent, at the 99.9 percent confidence level.
TL;DR: Halobacterium halobium carries out photophosphorylation, the first step in energy transduction, the conversion of light energy into a chemiosmotic gradient which can drive phosphorylation of ADP to ATP.
Abstract: Halobacterium halobium carries out photophosphorylation. A rhodopsin-like protein, bacteriorhodopsin, located in the cell membrane mediates the first step in energy transduction, the conversion of light energy into a chemiosmotic gradient. After absorption of a photon, bacteriorhodopsin undergoes a series of fast reactions, returning to its original state in a few milliseconds. In continuous light it cycles continuously at 100 to 200 cps. During a cycle protons are taken up on the cytoplasmic side of the membrane and released on the outer surface, thus generating a chemiosmotic gradient which can drive phosphorylation of ADP to ATP.
01 Aug 1974
TL;DR: In this paper, the authors presented results from extensive wind-tunnel tests that include variations in axial and cross-sectional shape, fineness ratio, bluntness, strakes, and boundary-layer trips over a wide range of conditions (angles of attack to 90 degrees, angles of sideslip to 30 degrees, Reynolds numbers from subcritical to supercritical, and Mach numbers from 0.1 to 0.7).
Abstract: Selected results are presented from extensive wind-tunnel tests that include variations in axial and cross-sectional shape, fineness ratio, bluntness, strakes, and boundary-layer trips over a wide range of conditions (angles of attack to 90 deg, angles of sideslip to 30 deg, Reynolds numbers from subcritical to supercritical, and Mach numbers from 0.1 to 0.7). Pointed forebodies at zero sideslip can experience side forces as large as maximum normal forces. The angle of attack at the onset of side force can be correlated with nose angle and afterbody length. Furthermore, these side forces can be reduced or eliminated by bluntness or nose strakes.
TL;DR: In this paper, wind tunnel simulations were conducted to determine the flow field over raised rim craters and associated zones of deposition and erosion, which indicated that some dark zones around Martian craters are erosional and some light zones are depositional.
Abstract: Preliminary results are reported of an investigation which involves wind tunnel simulations, geologic field studies, theoretical model studies, and analyses of Mariner 9 imagery. Threshold speed experiments were conducted for particles ranging in specific gravity from 1.3 to 11.35 and diameter from 10.2 micron to 1290 micron to verify and better define Bagnold's (1941) expressions for grain movement, particularly for low particle Reynolds numbers and to study the effects of aerodynamic lift and surface roughness. Wind tunnel simulations were conducted to determine the flow field over raised rim craters and associated zones of deposition and erosion. A horseshoe vortex forms around the crater, resulting in two axial velocity maxima in the lee of the crater which cause a zone of preferential erosion in the wake of the crater. Reverse flow direction occurs on the floor of the crater. The result is a distinct pattern of erosion and deposition which is similar to some martian craters and which indicates that some dark zones around Martian craters are erosional and some light zones are depositional.
TL;DR: The Mariner 10 television camieras imaged the planet Venus in the visible and near ultraviolet for a period of 8 days at resolutions ranging from 100 meters to 130 kilometers as discussed by the authors.
Abstract: The Mariner 10 television camieras imaged the planet Venus in the visible and near ultraviolet for a period of 8 days at resolutions ranging from 100 meters to 130 kilometers. Tle general pattern of the atmospheric circulation in the upper tropospheric/lower stratospheric region is displayed in the pictures. Atmospheric flow is symmetrical between north and south hemispheres. The equatorial motions are zonal (east-west) at approxiimnately 100 meters per second, consistent with the previously inferred 4-day retrograde rotation. Angular velocity increases with latitude. The subsolar region, and the region downwind from it, show evidence of large-scale convection that persists in spite of the main zonal motion. Dynamical interaction between the zonal motion and the relatively stationary region of convection is evidenced by bowlike waves.
TL;DR: In this article, the authors studied the effect of elasticity on the breakup altitude of both impacting and orbiting linear elastic solid bodies based on Kelvin's theory of earth tides and showed that there can be more than one mutually exclusive modes of fracture depending on its size and strength.
Abstract: Tidal fission of both impacting and orbiting linear elastic solid bodies based on Kelvin's theory of earth tides is considered. It is shown that there can be more than one mutually exclusive modes of fracture - the particular mode in which a body fractures depending on its size and strength. The analysis gives a vivid picture of the propagation of the fracture with a decreasing distance from the planet. Expressions for the initiation and completion of fracture are obtained which are displayed graphically for a rigid body. The effect of elasticity on the breakup altitude is discussed. For orbiting solid bodies, the study gives the upper limit of the breakup altitude as 0.38R (where R is the radius of planet), which is much less than the value 1.44R used for such bodies in the past. The results presented include a previously given theory by Sekiguchi as a part. For the special case of a liquid body, comparison is made with Roche's calculation and the difference explained.
TL;DR: In this article, it was shown that during Jupiter's earliest contraction history, ices would have preferentially been prevented from condensing within the region containing the orbits of the inner satellites and water should be the only ice present in significant proportions in any of the Galilean satellites.
TL;DR: In this article, exact numerical solutions of the MHD equations for a perfect dissipationless gas with aligned magnetic field were given for conditions representative of steady supersonic solar wind flow past an axisymmetric model of the earth's magnetosphere.
TL;DR: A large suite of aliphatic dicarboxylic acids was found in extracts from the carbonaceous chondrite as discussed by the authors, including many of the branched and straight chained isomers with up to nine carbon atoms.
Abstract: A large suite of aliphatic dicarboxylic acids was found in extracts from the carbonaceous chondrite. This suite includes many of the branched and straight chained isomers with up to nine carbon atoms. The large number of compounds and the isomeric distribution suggest that the acids are the product of an abiotic synthesis. The dicarboxylic acids found have been identified by their gas chromatography retention values and by comparison of their mass spectra with those of authentic standards.
TL;DR: Pioneer 10 plasma analyzer data during the Jupiter flyby are presented in this paper, which show that the interaction of Jupiter's magnetic field with the solar wind is similar in many ways to that at earth, but the scale size is over 100 times larger.
Abstract: Pioneer 10 Plasma Analyzer experiment flight data during the Jupiter flyby are presented. The observations show that the interaction of Jupiter's magnetic field with the solar wind is similar in many ways to that at earth, but the scale size is over 100 times larger. Jupiter is found to have a detached standing bow shock wave of high Alfven Mach number. Jupiter has a prominent magnetopause which deflects the magnetosheath plasma and excludes its direct entry into the Jovian magnetosphere. The sunward hemisphere of Jupiter's outer magnetosphere is found to be highly inflated with thermal plasma and a high beta region which is highly responsive to changes in solar wind dynamic pressure. Observational arguments are presented which tend to discount a thin disklike magnetosphere but, rather, favor a Jovian magnetosphere, albeit probabily considerably flattened as compared to the earth's magnetosphere, yet still with reasonable thickness. Results concerning the shock jump conditions, the magnetosheath flow field and inferred internal magnetospheric plasma are presented.
TL;DR: Wind tunnel experiments have revealed a characteristic flow field pattern over raised-rim craters which causes distinctive zones of aeolian erosion and deposition, and comparisons with Mariner 9 images of Mars show that some crater-associated dark zones result from wind erosion and that some hole-associated light streaks are depositional.
Abstract: Wind tunnel experiments have revealed a characteristic flow field pattern over raised-rim craters which causes distinctive zones of aeolian erosion and deposition. Comparisons of the results with Mariner 9 images of Mars show that some crater-associated dark zones result from wind erosion and that some crater-associated light streaks are depositional.
01 May 1974
TL;DR: In this article, a nine degree-of-freedom theoretical model is developed for investigations of the dynamics of a proprotor operating in high inflow axial flight on a cantilever wing.
Abstract: A nine degree-of-freedom theoretical model is developed for investigations of the dynamics of a proprotor operating in high inflow axial flight on a cantilever wing. The basic characteristics of the rotor high inflow aerodynamics and the resulting rotor aeroelastic behavior are discussed. The problems of classical whirl flutter, the two-bladed rotor, and the influence of the proprotor on the stability derivatives of the aircraft are treated briefly. The influence of various elements of the theoretical model is discussed, including the modeling used for the blade and wing aerodynamics, and the influence of the rotor lag degree of freedom. The results from tests of two full-scale proprotors - a gimballed, stiff-inplane rotor and a hingeless, soft-inplane rotor - are presented; comparisons with the theoretical results show good correlation.
Book•
01 Jan 1974TL;DR: Topics covered include: cardiac ultrastructure and function in the normal and failing heart, myocardial energetics, clinical applications of angiocardiography, use of echocardiographic for evaluating cardiac performance, systolic time intervals in the noninvasive assessment of left ventricular performance in man, and evaluation of passive elastic stiffness for the left ventricle and isolated heart muscle.
Abstract: Recent studies concerning the basic physiological and biochemical principles underlying cardiac muscle contraction, methods for the assessment of cardiac function in the clinical situation, and mathematical approaches to cardiac mechanics are presented. Some of the topics covered include: cardiac ultrastructure and function in the normal and failing heart, myocardial energetics, clinical applications of angiocardiography, use of echocardiography for evaluating cardiac performance, systolic time intervals in the noninvasive assessment of left ventricular performance in man, evaluation of passive elastic stiffness for the left ventricle and isolated heart muscle, a conceptual model of myocardial infarction and cardiogenic shock, application of Huxley's sliding-filament theory to the mechanics of normal and hypertrophied cardiac muscle, and a rheological modeling of the intact left ventricle. Individual items are announced in this issue.
TL;DR: Several numerical integration techniques for solving common aeronomic problems involving species rate equations are compared for speed and accuracy in this article, and a newer technique that defines families of species that are nearly conserved is found to be superior to an iterative technique when both methods are applied to simple test problems.
Abstract: Several numerical integration techniques for solving common aeronomic problems involving species rate equations are compared for speed and accuracy. A newer technique that defines families of species that are nearly conserved is found to be superior to an iterative technique when both methods are applied to simple test problems. The 'conservation' technique is also found to be more economical than the more complex Gear (1969) integration scheme for comparable accuracy.
TL;DR: In the authors' opinion, the lateral vestibular nucleus of the rat is an excellent model to define aging changes in the nerve cells, as opposed to changes linked to vascular degeneration, which is frequently seen in time-associated degeneration of the human brain.
TL;DR: Crude extracts prepared from the extremely halophilic bacterium M6 catalyzed the conversion of glucose to gluconic acid, consistent with the operation of a modified Entner-Doudoroff pathway in this organism.
Abstract: Crude extracts prepared from the extremely halophilic bacterium M6 catalyzed the conversion of glucose to gluconic acid. The latter compound was dehydrated to 2-keto-3-deoxygluconic acid, which in the presence of ATP, was converted to equimolar amounts of pyruvate and 3-phosphoglyceraldehyde, presumably through the intermediate compound 2-keto-3-deoxy-6-phosphogluconic acid. Additional enzymes catalyzing the conversion of 3-phosphoglyceraldehyde to pyruvic acid were also present. These data are consistent with the operation of a modified Entner-Doudoroff pathway in this organism.