Martin Marietta Materials, Inc.

About: Martin Marietta Materials, Inc. is a based out in . It is known for research contribution in the topics: Signal & Spacecraft. The organization has 4629 authors who have published 4188 publications receiving 70513 citations.

Indices of landscape pattern

Abstract: Landscape ecology deals with the patterning of ecosystems in space. Methods are needed to quantify aspects of spatial pattern that can be correlated with ecological processes. The present paper develops three indices of pattern derived from information theory and fractal geometry. Using digitized maps, the indices are calculated for 94 quadrangles covering most of the eastern United States. The indices are shown to be reasonably independent of each other and to capture major features of landscape pattern. One of the indices, the fractal dimension, is shown to be correlated with the degree of human manipulation of the landscape.

A first order approximation to the optimum checkpoint interval

Abstract: To avoid having to restart a job from the beginning in case of random failure, it is standard practice to save periodically sufficient information to enable the job to be restarted at the previous point at which information was saved. Such points are referred to as checkpoints, and the saving of such information at these points is called checkpointing [1].

Local Stress Concentrations in Imperfect Filamentary Composite Materials

Abstract: Solutions are presented for two stress distribution problems which result from breaking of the filaments in a composite material composed of high modulus elements embedded in a low modulus matrix. ...

VITS-a vision system for autonomous land vehicle navigation

Abstract: A description is given of VITS (for vision task sequencer), the vision system for the autonomous land vehicle (ALV) Alvin, addressing in particular the task of road-following. The ALV vision system builds symbolic descriptions of road and obstacle boundaries using both video and range sensors. The authors discuss various road segmentation methods for video-based road-following, along with approaches to boundary extraction and transformation of boundaries in the image plane into a vehicle-centered three-dimensional scene model. >

Composition of comet Halley dust particles from Giotto observations

Abstract: Mass spectra of cometary dust particles measured by the PIA dust particle analyzer aboard the Giotto spacecraft show some unexpected and striking features. First, small particles below 10 to the -14th g are much more abundant than anticipated by models. Second, most of the particles are rich in light elements such as H, C, N, and O, suggesting the validity of models that describe the cometary dust as including organic material. Third, the light elements specifically seem to have a low ratio of mass to volume. Three examples of original mass spectra showing typical compositions are given; these have been measured, and are compared with a computer-simulated mass spectrum.