Engineering topics

Davis, Philip A.

Publications and source records attributed to Davis, Philip A..

9 records

NASA NTRS2007

ShareSync: A Solution for Deterministic Data Sharing over Ethernet

As part of upgrading the Contact Dynamics Simulation Laboratory (CDSL) at the NASA Marshall Space Flight Center (MSFC), a simple, cost effective method was needed to communicate data among the networked simulation machines and I/O controllers used to run the facility. To fill this need and similar applicable situations, a generic protocol was developed, called ShareSync. ShareSync is a lightweight, real-time, publish-subscribe Ethernet protocol for simple and deterministic data sharing across diverse machines and operating systems. ShareSync provides a simple Application Programming Interface (API) for simulation programmers to incorporate into their code. The protocol is compatible with virtually all Ethernet-capable machines, is flexible enough to support a variety of applications, is fast enough to provide soft real-time determinism, and is a low-cost resource for distributed simulation development, deployment, and maintenance. The first design cycle iteration of ShareSync has been completed, and the protocol has undergone several testing procedures including endurance and benchmarking tests and approaches the 2001ts data synchronization design goal for the CDSL.

Dunn, Daniel J., II↗

NASA NTRS1990

Discontinuities in the shallow Martian crust at Lunae, Syria, and Sinai Plana

Detailed photoclinometric data are presented for a variety of surface features (pits, troughs, wall valleys, and grabens) within three study areas in the western equatorial regions of Mars (Lunae, Syria, and Sinai Plana) that provide evidence for mechanical discontinuities within the shallow Martian crust in these regions. The data's relation to some of the previously proposed mechanical discontinuities within the Martian crust is discussed, and the geologic significance of these features is speculated upon.

Davis, Philip A.↗

NASA NTRS1988

Tectonic history of the Syria Planum province of Mars

Several new, as well as existing, techniques are employed here to unravel the complex structural history of the Syria Planum province of Mars. Individual faults are first recognized as members of local or extensive fault sets related to distinct tectonic episodes. The relative ages of these fault sets are determined using superposition and intersection relations and crater counts. Correlations are also made with local geology and topography. Morphological characteristics of the fault scarps are measured photoclinometrically from Viking orbiter images and the way that variations in fault morphology are related to tectonic style, thickness of the faulted layer, and amount of extension is interpreted. The overall results present a more complete and coherent, as well as a different, tectonic history for this province than previously attained. The results show that geophysical interpretations of the Tharsis tectonic region require reevaluation.

Tanaka, Kenneth L.↗

NASA NTRS1987

Global petrologic variations of the Moon: A ternary-diagram approach

A ternary-diagram approach is used to show on a single map as much detailed geochemical information concerning petrologic variations within the lunar crust as is possible. The classification map shows the global spatial distributions of end-member compositions, the transitional spatial relations between end-member compositions, and quantitative estimates of relative proportions of each end member at each pixel location within the orbital groundtracks. The use of elemental ratios in this analysis, instead of the commonly used elemental bivariate diagrams, shows geologic information that is otherwise hidden in individual elemental databases.

Davis, Philip A.↗

NASA NTRS1987

A chemical and petrological model of the lunar crust

Information is given on the composition and structure of the lunar crust. A lunar model is illustrated, indicating that it has essentially two layers, anorthositic mixed rocks overlaying a generally noritic crystalline basement. Implications relative to lunar evolution are discussed.

Spudis, Paul D.↗

NASA NTRS1987

History and morphology of faulting in the Noctis Labyrinthus-Claritas Fossae Region of Mars

The topographically high areas cut by Noctis Labyrinthus, Noctis Fossae, and Claritas Fossae were subjected to only minor resurfacing during and following local tectonic activity. Principal resurfacing materials consist of lava flows from Syria Planum and Tharsis Montes. Thus, these areas preserve much of the fault record produced by tectonism in this region. Although recent geologic maps of the area have been produced from Viking images, the only detailed fault histories available until now were described from Mariner 9 images. Much of the faulting in the Tharsis tectonic province was centered in Syria Planum; therefore, understanding the fault history in this region is critical to understanding the stress history and tectonism of Tharsis as a whole.

Tanaka, Kenneth L.↗

NASA NTRS1987

Global petrologic variations on the moon - A ternary-diagram approach

An improved method for global petrologic mapping of the moon is presented, which uses a color-coded ternary diagram whose apexes are assigned the average Fe and Th/Ti ratio (normalized to chondrites) compositions of KREEP/Mg-suite rocks, mare basalts, and ferroan anorthosites. The composition of each pixel within these Apollo orbital gamma ray data bases is used to determine its position within the ternary diagram. The color corresponding to this ternary position is then placed on a classification map at that pixel's position within the orbital data bases. The resultant classification map shows spatial transitions among petrologic units, allows direct determination of the relative proportions of each end-member composition in a pixel, and provides more geologic information than can be obtained by using only the elemental data. The map units correspond remarkably well to previously delineated geologic provinces.

Davis, Philip A.↗

NASA NTRS1987

Small Martian valcanoes

Various types of volcanoes were identified on Mars, mainly on the basis of qualitative morphologic criteria such as relief, circularity, summit craters, and alignment with structural trends. A survey of Viking Orbiter images is being conducted to identify possible candidates for Martian volcanoes. The topographic profiles of the selected Martian volcanoes that are currently being acquired will be compared with tabulated data for terrestrial and lunar volcanoes. Variation in volcanic style with age will also be examined.

Davis, Philip A.↗

NASA NTRS1987

Ablation of Martian glaciers

Glacier like landforms are observed in the fretted terrain of Mars in the latitude belts near + or - 42 deg. It was suggested that sublimation or accumulation-ablation rates could be estimated for these glaciers if their shapes were known. To this end, photoclinometric profiles were obtained of a number of these landforms. On the basis of analyses of these profiles, it was concluded that ice is chiefly ablating from these landforms that either are inactive rock-glaciers or have materials within them that are moving exceedingly slowly at this time. These conclusions are consistent with other geologic information. The analyses were performed using a two-dimensional model of an isothermal glacier.

Moore, Henry J.↗