Tech Briefs

X-Ray Flaw Size Parameter for POD Studies

Lyndon B. Johnson Space Center, Houston, Texas Nondestructive evaluation (NDE) method capability is determined by a statistical flaw detection study called probability of detection (POD) study. In many instances, the NDE flaw detectability is given as a flaw size such as crack length. The flaw is either a crack or behaving like a crack in terms of affecting the structural integrity of the material. Although the crack size relates to structural integrity of the part, it may not be the only factor that affects the flaw detectability for most NDE methods. Crack length, depth, and opening may relate differently to the flaw detectability. Part surface roughness and cleanliness may affect the flaw detectability. The proposed flaw size parameter and the computer application described here give an alternative approach to conduct the POD studies and apply results of the POD study to reliably detect small flaws through better assessment of effect of interaction between various geometric parameters.

Posted in: Information Sciences, Electronics & Computers, Briefs, TSP

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Large Eddy Simulation Composition Equations for Two-Phase Fully Multicomponent Turbulent Flows

The composition probability density function moment variables are based on a new type of filter. NASA’s Jet Propulsion Laboratory, Pasadena, California Liquid sprays are commonly used to inject fuels into combustion devices, making it important to study multicomponent (MC) two-phase flows in order to reveal their physics. “Multicomponent” is the terminology describing all fuels that are combinations of a myriad of species. Single-component simulations lack a detailed representation of the complex composition and reaction mechanisms of realistic fuels, which can contain hundreds to thousands of species. Some species may be responsible for fuel ignition, other species may be the initiators of soot formation, and yet others may be involved in surface corrosion, all of which demonstrates the importance of being able to track the multitude of species.

Posted in: Information Sciences, Electronics & Computers, Briefs

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Scheduling Targeted and Mapping Observations with State, Resource, and Timing Constraints

NASA’s Jet Propulsion Laboratory, Pasadena, California This innovation creates observations of both targeted geographical regions of interest and general mapping observations, while respecting spacecraft constraints such as data volume, observation timing, visibility, lighting, season, and science priorities. This tool, therefore, addresses both geometric and state/timing/resource constraints by using a grid-based approach. These set covering constraints are then incorporated into a greedy optimization scheduling algorithm that incorporates operations constraints to generate feasible schedules. The resultant tool generates schedules of hundreds of observations per week out of potentially thousands of observations.

Posted in: Information Sciences, Electronics & Computers, Briefs, TSP

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Processing COSMIC/FORMOSAT-3 Data for Slant Total Electron Content Measurements

New leveling algorithm uses GPS multipath signals to provide an improved leveling of ionospheric measurements. NASA’s Jet Propulsion Laboratory, Pasadena, California The COSMIC (Constellation Observing System for Meteorology, Ionosphere, and Climate) mission has GPS (Global Positioning System) radio occultation dual-band receivers onboard. The received signals slice through the ionosphere, layer by layer, in much the same way as peeling off the layers of an onion. In order to use GPS signals for ionospheric measurements, they must be edited, phase leveled, and the hardware biases removed. The leveling algorithm used for ground-based GPS receivers is inadequate for space-based receivers due to substantially different multipath characteristics.

Posted in: Test & Measurement, Briefs

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Gridded Atmosphere Products from GPS Radio Occultation Measurements with Bayesian Interpolation Technique

NASA’s Jet Propulsion Laboratory, Pasadena, California GPS radio occultation measurements are vital for climate monitoring and atmospheric temperature change detection. However, the data are irregularly distributed in space and time, which makes it inconvenient for many applications.

Posted in: Test & Measurement, Software, Briefs, TSP

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Optical Phased Array with Digitally Enhanced Interferometry

NASA’s Jet Propulsion Laboratory, Pasadena, California A proof-of-concept technique has been developed for measuring and controlling the individual phases of array elements. Electro-optic steering and beam-forming of laser beams is an emerging field with devices such as optical phased arrays that are capable of steering with significantly reduced noise floors and that are faster by orders of magnitude.

Posted in: Physical Sciences, Test & Measurement, Briefs, TSP

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Durability Analysis of a Vehicle by Virtual Test Model (VTM)

For accurate prediction of fatigue failure in structural components, accurate prediction of dynamic force histories is required. Ashok Leyland Ltd., Chennai, India The criterion for structural failure must be based on failure modes of the component being designed. If the component is to withstand millions of cycles of load application, criterion for fatigue failure must be used. Fatigue damage caused by repeated dynamic loads depends on the number of cycles and the frequency of significant stresses. Therefore, for accurate prediction of fatigue failure in structural components, accurate prediction of dynamic force histories is required.

Posted in: Test & Measurement, Briefs

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