Showing papers by "Ames Research Center published in 1973"

CONMIN: A FORTRAN program for constrained function minimization: User's manual

Abstract: CONMIN is a FORTRAN program, in subroutine form, for the solution of linear or nonlinear constrained optimization problems. The basic optimization algorithm is the Method of Feasible Directions. The user must provide a main calling program and an external routine to evaluate the objective and constraint functions and to provide gradient information. If analytic gradients of the objective or constraint functions are not available, this information is calculated by finite difference. While the program is intended primarily for efficient solution of constrained problems, unconstrained function minimization problems may also be solved, and the conjugate direction method of Fletcher and Reeves is used for this purpose. This manual describes the use of CONMIN and defines all necessary parameters. Sufficient information is provided so that the program can be used without special knowledge of optimization techniques. Sample problems are included to help the user become familiar with CONMIN and to make the program operational.

A simple method for studying slow crack growth.

Abstract: A simple, inexpensive method for studying slow crack growth is described. The method entails measurements of load relaxation at constant displacement using a double torsion specimen. It is demonstrated that the data generated using this technique are in excellent agreement with data obtained using the more complex conventional techniques, for a range of materials - steel, titanium, glass, aluminum oxide, PMMA. These encouraging initial results suggest that additional and more detailed studies using this test procedure are merited.

Analysis of Embedded Shock Waves Calculated by Relaxation Methods

Abstract: The requirements for uniqueness of the calculated jump conditions across embedded shock waves are investigated for type-dependent difference systems used in transonic flow studies. A mathematical analysis shows that sufficient conditions are (1) the equations should be differenced in conservative form and (2) a special difference operator should be used when switching from a hyperbolic to an elliptic operator. The latter results in a consistency condition on the integral equations, rather than the differential, at these points. Calculated jump conditions for several embedded and detached shock waves are analyzed in the physical and hodograph planes. Comparisons are made with previous results, a time-dependent calculation, and data.

Abstracts of Contributed Papers

Abstract: The strength of the K line of singly ionized calcium has been measured for several hundred A-type stars within a few hundred parsecs of the Sun and for the A stars in several galactic star clusters. The derived abundance of calcium varies from star to star by up to a factor of 2, and there is no correlation of abundance with the space motion of the stars.

The ascending fiber projections from the principal sensory trigeminal nucleus in the rat.

Abstract: Persisting reports of uncrossed secondary trigeminothalamic pathways originating from the principal sensory trigeminal nucleus (PrV) are based mainly on data obtained from surgically induced lesions analyzed by methods other than reduced silver impregnation techniques. After complete stereotaxic or direct surgical lesions of PrV, degenerating fibers proceed ventrally and rostrally from the nucleus and cross the midline in the rostral pons, completing their decussation caudal to nucleus interpeduncularis. These fibers form a large trigeminal lemniscus that ascends through the midbrain dorsomedial to the smaller medial lemniscus. PrV fibers terminate in the posterior thalamic nucleus and throughout the medial two-thirds of the ventrobasal thalamic complex (VBm) contralateral to the side of the lesion. Connections with the ventral part of zona incerta were also found similar to those reported for the medial lemniscus. Another fiber system proceeds dorsad from the parvicellular reticular formation in the PrV region and terminates on cells of the ipsi-and contralateral motor trigeminal nuclei and the adjacent contralateral parvicellular reticular formation. Differential lesions indicate that these “intertrigeminal” commissural connections arise chiefly from the parvicellular reticular formation that lies between PrV and the motor trigeminal nucleus. These experiments, which also included selective lesions of dorsal and rostral portions of PrV, failed to produce any evidence supporting the existence of an uncrossed principal sensory trigeminothalamic pathway in the rat. While selective, ventral zona incerta PrV connections can be demonstrated, no PrV intralaminar projections appear to exist. Initial findings show that comparable fully decussated PrV–VBm connections also exist in the guinea pig but that some ipsilaterally ascending fibers occur in monkeys (Smith, '72). These and other recent data demonstrate that phyletic neural variations exist in the PrV-thalamic projections in various mammalian species.

Rapid Scanning, Three-Dimensional Hot-Wire AnemometerSurveys of Wing-Tip Vortices

Abstract: The use of CADD has effected many changes in traditional work methods of the various interfacing disciplines at MCAIR. We have streamlined our tasks by utilizing the cost/time saving techniques presently afforded by this system, and plan to continue additional development efforts which will further improve it. As we discover more and more practical applications for CADD, new or modified software routines will be formulated to make the system as responsive and reliable as possible. Since the potential for substantial dollar savings exists, particularly in the area of manufacturing, we are consciously attempting to align our techniques to make engineering data as usable as possible by manufacturing personnel in its existing form, thus eliminating as many intermediate manual processes as possible. Our final objectives, however, cannot now be defined. CADD's utility will increase as we continue to conceive new ideas for its application. Its ultimate benefits can only be determined by the limits of our creative imagination.

Variable features on Mars 2: Mariner 9 global results

Abstract: Systematic Mariner 9 monitoring of the space and time distribution of Martian bright and dark markings, the streaks and splotches, indicates a range of global correlations. The time-variable classical dark markings owe their configurations and variability to their constituent streaks and splotches, produced by windblown dust. Streaks and splotches are consistent wind direction indicators. Correlation of global streak patterns with general circulation models shows that velocities of about 50 to 90 m/sec above the boundary layer are necessary to initiate grain motion on the surface and to produce streaks and splotches. Detailed examples of changes in Syrtis Major, Lunae Palus, and Promethei Sinus are generally consistent with removal of bright sand and dust and uncovering of darker underlying material as the active agent in such changes, although dark mobile material probably also exists on Mars. The generation of streaks and the progressive albedo changes observed require only threshold velocities of about 2 m/sec for about 1 day at the grain surface.

Mechanisms for Mars dust storms.

Abstract: Characteristics of the Mars global dust storm are reviewed. At the Mariner 9 encounter, the dust consisted of highly absorbing particles distributed rather uniformly up to great height (about 50 km). These observations together with temperature distributions inferred from the Mariner 9 IRIS by Hanel et al. (1972) are used to estimate global wind systems during the dust storm. The global distribution and direction of light surface streaks indicate that the axisymmetric circulation was a dominant part of flow during the dust storm. The axisymmetric winds may become strong enough to raise dust over wide areas of Mars' tropics under unusual conditions: the incoming solar radiation must be near its seasonal maximum, the static stability must be low, and the atmosphere must be able to absorb and re-emit a sizeable fraction of the incoming radiation. Strong winds around the periphery of the retreating south polar cap would be driven by the temperature gradient at the cap edge and by the mass outflow due to subliming CO2. These polar winds could generate local dust storms, raising the general level of dustiness, and providing the conditions necessary for onset of a global dust storm.

Debye-Scherrer investigations of experimentally shocked silicates.

Abstract: Small ballistic ranges were used to perform controlled laboratory shock experiments on 12 selected silicates [quartz (30–310 kb), oligoclase (30–340 kb), andesine (40–100 kb), olivine (80–500 kb), forsterite (50–150 kb), enstatite (60–150 kb), biotite (10–90 kb), hornblende (50–150 kb, garnet (40–160 kb), kunzite (60–150 kb), beryl (60–140 kb), topaz (60–150 kb)]. At least 4 pressure points per mineral are available.

Monocarboxylic Acids in Murray and Murchison Carbonaceous Meteorites

Abstract: THAT carbonaceous meteorites contain organic substances has been known for more than a century, and during this time controversies developed concerning whether or not this organic material was a product of extraterrestrial life. Within the past few years studies of carbonaceous meteorites have provided solid evidence that certain organic compounds are indigenous and were most likely produced by non-biological, chemical syntheses1–7. These studies have emphasised the occurrences of amino acids and hydrocarbons in two C2 carbonaceous chondrites, the Murray and the Murchison. We have now found in specimens of both of these meteorites straight and branched-chain mono-carboxylic acids having two to eight carbon atoms. Although many of these acids are of biological significance, the distribution of compounds in these meteorites supports the proposition that they, like the amino acids and hydrocarbons, result from non-biological, chemical syntheses.

Racemization of Amino Acids in Bones

Abstract: IT has been shown that the extent of racemization of amino acids in a fossil can be used with certain limitations to estimate the age of the specimen1–6. For this dating work it is necessary to understand the kinetics and mechanism of the reactions involved. Here we show, by kinetic studies using modern bovine bone fragments heated in sealed ampoules for various time periods at several elevated temperatures, that the order of racemization rates of amino acids in bone is aspartic acid>alanine=glutamic acid>isoleucine≅leucine. Fossil bones not contaminated with modern amino acids are shown to have the same sequence of racemization rates.

Shock Wave/Turbulent Boundary-Layer Interactions in Rectangular Channels

Abstract: Interaction regions created by the impingement of full span, externally generated, shock waves on a nozzle wall boundary layer were investigated. Incident shock strength was varied to produce unseparated, incipient, and fully separated flow fields. Significant departures from two-dimensionality were observed over the entire range of shock strengths tested and were identified with sidewall and corner boundary layer effects. However, comparisons of present centerline results with published two-dimensional data, obtained under similar test conditions and geometrical constraints, showed excellent agreement (e.g., incipient separation pressure levels, wall pressure distributions, free-interaction, and scale of the interaction region). This raises some question concerning the degree of two-dimensionality achieved in these previous investigations.

Time-Split Finite-Volume Method for Three-Dimensional Blunt-Body Flow

Abstract: An efficient numerical method for calculating plane, axisymmetric, and fully three-dimensional blunt-body flow is presented. It is a second-order-accurate, time-dependent finite-volume procedure that solves the Euler equations in integral conservation-law form. These equations are written with respect to a Cartesian coordinate system in which an embedded mesh adjusts in time to the motion of the bow shock that is automatically captured as part of the weak solution. With such an adjusting mesh, oscillations in flow properties near the shock are shown to be virtually eliminated. The scheme uses a time-splitting concept that accelerates the convergence appreciably. Comparisons are made between computed and experimental results.

Survival of Arthrobacter crystallopoietes During Prolonged Periods of Extreme Desiccation

Abstract: Cells of Arthrobacter crystallopoietes mixed in sand and air-dried have survived for up to 6 months after an initial period in which approximately half the cells lost their viability. Comparative survival curves have been obtained from inoculated sands maintained under CaSO4 or P2O5. Selections for more desiccation-resistant progeny capable of surviving the initial period were unsuccessful. Both the coccoid and rod-shaped forms are equally resistant to several months of desiccation. Desiccated spherical cells converted 0.0005% of their cell carbon to carbon dioxide per hr, which corresponds to a half-life for self-consumption of approximately 12 years.

On the inviscid rolled-up structure of lift-generated vortices

Abstract: A simple form is presented of the relationships for the inviscid, fully developed structure of lift-generated vortices behind aircraft wings. The method is then extended to arbitrary span-load distributions by inferring guidelines for the selection of rollup centers for the vortex sheet, along with rules for calculating the fully developed structure of the resulting multiple vortices. These techniques yield realistic estimates of the rolled-up structure of vortices produced by a wider variety of span-load distributions than possible with the original form of the theory.

Multishocked, Three-Dimensional Supersonic Flowfields with Real Gas Effects

Abstract: This program determines the supersonic flowfield surrounding three-dimensional wing-body configurations of a delta wing. It was designed to provide the numerical computation of three dimensional inviscid, flowfields of either perfect or real gases about supersonic or hypersonic airplanes. The governing equations in conservation law form are solved by a finite difference method using a second order noncentered algorithm between the body and the outermost shock wave, which is treated as a sharp discontinuity. Secondary shocks which form between these boundaries are captured automatically. The flowfield between the body and outermost shock is treated in a shock capturing fashion and therefore allows for the correct formation of secondary internal shocks . The program operates in batch mode, is in CDC update format, has been implemented on the CDC 7600, and requires more than 140K (octal) word locations.

Controllability of discrete bilinear systems with bounded control

Abstract: Controllability of time-invariant discrete-time bilinear systems is discussed. Bilinear systems are classified into two categories: homogeneous and inhomogeneous. Sufficient conditions which ensure the global controllability of discrete-time bilinear systems are obtained by localized analysis in control variables.

Computation of Space Shuttle Flowfields Using Noncentered Finite-Difference Schemes

Abstract: Second- and third-order, noncentered finite-difference schemes are described for the numerical solution of the hyperbolic equations of fluid dynamics. The advantages of noncentered methods over the more conventional centered schemes are: simpler programming logic, nonhomogeneous terms are easily included, and generalization to multidimensional problems is direct. Second- and third-order methods are compared with regard to dissipative and dispersive errors and shock-capturing ability. These schemes are then used in a shock-capturing technique to determine the inviscid, supersonic flow field surrounding space shuttle vehicles (SSV). Resulting flow fields about typical pointed and blunted, delta-winged SSVs at angle of attack are presented and compared with experiment.

Convection in the Earth's Mantle

Abstract: The computer is used to solve for thermal convection within the earth's mantle. A review of the knowledge of surface displacements and of the present understanding of the mantle and its relevant physical and chemical properties is contained in the paper. Applicable equations assume a Newtonian fluid layer heated from below and within, with gravity acting downward. The numerical method employs finite differences and was constructed with a view toward the faithful simulation of coupling mechanisms. It enables surveying the effect of a parameter using a relatively coarse computing mesh. Some of the results obtained are presented.

Two-color dual-beam backscatter laser Doppler velocimeter.

Abstract: A laser Doppler velocimeter has been developed that uses two of the colors emitted from an argon-ion laser for the simultaneous measurement of orthogonal velocities. Designed for use in a 2.13-m by 3.05-m wind tunnel, it is capable of traversing its focal volume across spatially unstable flows at scan speeds of up to 1.5 m/sec. Its optical layout and principles of operation are discussed, and the data from a typical traversal of a trailing wing-tip vortex are presented.

Effect of surface catalytic activity on stagnation heat-transfer rates.

Abstract: An experiment was made to determine the effect heterogeneous catalytic surface reactions have on heat-transfer rates in highly frozen low-density stagnation-point boundary layers. Data were obtained in arc-heated facilities that were capable of producing large percentages of chemical energy frozen in a supersonic freestream. The heat-transfer rate to a silicon-dioxide surface was reduced to a minimum value of only one-third of the value obtained on relatively active nickel and platinum surfaces. This is the result of its low catalytic efficiency. Ionization energy was recovered on both the active and the inactive surfaces, indicating that this energy either was released many times faster than the recombination energy or was not controlled by the surface composition.

Alfvén wave refraction by interplanetary inhomogeneities

Abstract: Pioneer 6 magnetic data reveal that the propagation direction of Alfven waves in the interplanetary medium is strongly oriented along the ambient field. Magnetic fluctuations of frequencies up to 1/30 sec in the spacecraft frame are shown to satisfy a necessary condition for Alfven waves, and a variance matrix analysis is used to determine the Alfven wave normal. It appears from this analysis that geometrical hydromagnetics may satisfactorily describe deviation of the wave normal from the background field. The rotational discontinuity is likely also to propagate along the field lines.