Search NASA⌕ Search

SEARCH · Search NASA

Results for “geometric programming”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Planning robot actions under position and shape uncertainty

Geometric uncertainty may cause various failures during the execution of a robot control program. Avoiding such failures makes it necessary to reason about the effects of uncertainty in order to implement robust strategies. Researchers first point out that a manipulation program has to be faced with two types of uncertainty: those that might be locally processed using appropriate sensor based motions, and those that require a more global processing leading to insert new sensing operations. Then, they briefly describe how they solved the two related problems in the SHARP system: how to automatically synthesize a fine motion strategy allowing the robot to progressively achieve a given assembly relation despite position uncertainty, and how to represent uncertainty and to determine the points where a given manipulation program might fail.

Laugier, Christian↗
NASA NTRS1991

Feasibility study of a synthesis procedure for array feeds to improve radiation performance of large distorted reflector antennas

The following subject areas are covered: General Reflector Antenna Systems Program version 7(GRASP7); Multiple Reflector Analysis Program for Cylindrical Antennas (MRAPCA); Tri-Reflector 2D Synthesis Code (TRTDS); a geometrical optics and a physical optics synthesis techniques; beam scanning reflector, the type 2 and 6 reflectors, spherical reflector, and multiple reflector imaging systems; and radiometric array design.

Stutzman, W. L.↗
NASA NTRS1991

Enhancement of surface definition and gridding in the EAGLE code

Algorithms for smoothing of curves and surfaces for the EAGLE grid generation program are presented. The method uses an existing automated technique which detects undesirable geometric characteristics by using a local fairness criterion. The geometry entity is then smoothed by repeated removal and insertion of spline knots in the vicinity of the geometric irregularity. The smoothing algorithm is formulated for use with curves in Beta spline form and tensor product B-spline surfaces.

Thompson, Joe F.↗
NASA NTRS2018

WebGeocalc and Cosmographia: Modern Tools to Access OPS SPICE Data

For more than two decades navigation and other ancillary data from most US and international planetary science missions have been packaged using "SPICE" (Spacecraft, Planet, Instrument, Camera-matrix, Events) system data files (a.k.a. SPICE kernels) and, in conjunction with SPICE Toolkit software used by scientists and engineers to compute observation geometry in various ground system tools ranging from mission planning and analysis applications to data production pipelines to science analysis tools. The traditional way for accessing SPICE data is by downloading necessary SPICE kernels to a user’s workstation, installing the SPICE Toolkit software available from NAIF, and writing an application calling APIs from the SPICE Toolkit library to compute numeric geometric parameters of interest. While this approach did and still does provide the greatest flexibility in implementing geometric computations of interest, it proved to be complicated for users with little programming abilities, required data to be always copied to the users’ workstations, and lacked any out-of-the-box visualization capabilities. To address these shortcomings NAIF developed the WebGeocalc (WGC) tool and extended the publicly available Cosmographia program to use SPICE. Employing these two new tools in mission operations enables easier access to SPICE computations and SPICE-based visualizations for a wider variety of mission personnel.

Semenov, Boris V.↗
NASA NTRS1984

Using a commercial CAD system for simultaneous input to theoretical aerodynamic programs and wind-tunnel model construction

The Computer Aided Design (CAD) system's common geometry database was used to generate input for theoretical programs and numerically controlled (NC) tool paths for wind tunnel part fabrication. This eliminates the duplication of work in generating separate geometry databases for each type of analysis. Another advantage is that it reduces the uncertainty due to geometric differences when comparing theoretical aerodynamic data with wind tunnel data. The system was adapted to aerodynamic research by developing programs written in Design Analysis Language (DAL). These programs reduced the amount of time required to construct complex geometries and to generate input for theoretical programs. Certain shortcomings of the Design, Drafting, and Manufacturing (DDM) software limited the effectiveness of these programs and some of the Calma NC software. The complexity of aircraft configurations suggests that more types of surface and curve geometry should be added to the system. Some of these shortcomings may be eliminated as improved versions of DDM are made available.

Enomoto, F.↗
DOE OSTI2024

Probabilistic Programming for Transportable Source Characterization and Uncertainty Quantification of the North Korean Nuclear Tests 2006–2017

Here, we introduce a transportable technique to determine the yield and depth of burial (DOB) from seismic source spectra of underground nuclear explosions. We demonstrate this technique on the six declared North Korean nuclear tests. This approach derives source spectra in absolute units from regional phase (Pg) amplitudes by correcting the observations for geometric spreading, attenuation, and site amplification. We couple the source spectra and explosion source models with a probabilistic programming framework that integrates deep learning techniques and Bayesian modeling. This approach permits the exchange of information across various data categories to quantify both the data and model uncertainty. This technique stands out as an innovative use of broad‐area propagation models, making it transportable across various geologic settings. This method proves to be effective in scenarios with diverse and/or limited observational data, even when the source depth is unknown. We present new independent estimates of absolute yield and DOB that are consistent with the prior assessments, underscoring the potential of this method in enhancing transportable nuclear explosion monitoring capabilities.

58 GEOSCIENCES↗
NASA NTRS1981

NASA remote sensing programs: Overview

In the Earth remote sensing area, NASA's three functions are to understand the basic mechanics and behavior of the Earth, evaluate what resources are available (in the way of minerals, and hydrocarbons on a general scale), and to arrange a scheme for managing our national assets. The capabilities offered by LANDSAT D and technology improvements needed are discussed. The French SPOT system, its orbits, possibilities for stereo imagery, and levels of preprocessing and processing with several degrees of radiometric and geometric corrections are examined. Progress in the AgRISTARS project is mentioned as well as future R & D programs in the use of fluorescence, microwave measurements, and synthetic aperture radar. Other areas of endeaver include studying man environment interactions and Earth radiation budgets, and the establishment of data systems programs.

Raney, W. P.↗
NASA NTRS1975

Basic research and data analysis for the earth and ocean physics applications program and for the National Geodetic Satellite program

Data acquisition using single image and seven image data processing is used to provide a precise and accurate geometric description of the earth's surface. Transformation parameters and network distortions are determined, Sea slope along the continental boundaries of the U.S. and earth rotation are examined, along with close grid geodynamic satellite system. Data are derived for a mathematical description of the earth's gravitational field; time variations are determined for geometry of the ocean surface, the solid earth, gravity field, and other geophysical parameters.

Source record↗
NASA NTRS1977

National Geodetic Satellite Program, Part II: National Geodetic Society

Satellite geodesy and the creation of worldwide geodetic reference systems is discussed. The geometric description of the surface and the analytical description of the gravity field of the earth by means of worldwide reference systems, with the aid of satellite geodesy, are presented. A triangulation method based on photogrammetric principles is described in detail. Results are derived in the form of three dimensional models. These mathematical models represent the frame of reference into which one can fit the existing geodetic results from the various local datums, as well as future measurements.

Schmid, H.↗
NASA NTRS1992

Advanced composites structural concepts and materials technologies for primary aircraft structures. Structural response and failure analysis: ISPAN modules users manual

The ISPAN Program (Interactive Stiffened Panel Analysis) is an interactive design tool that is intended to provide a means of performing simple and self contained preliminary analysis of aircraft primary structures made of composite materials. The program combines a series of modules with the finite element code DIAL as its backbone. Four ISPAN Modules were developed and are documented. These include: (1) flat stiffened panel; (2) curved stiffened panel; (3) flat tubular panel; and (4) curved geodesic panel. Users are instructed to input geometric and material properties, load information and types of analysis (linear, bifurcation buckling, or post-buckling) interactively. The program utilizing this information will generate finite element mesh and perform analysis. The output in the form of summary tables of stress or margins of safety, contour plots of loads or stress, and deflected shape plots may be generalized and used to evaluate specific design.

Hairr, John W.↗
DOE OSTI2024

T RI M E ++: Multi-threaded triangular meshing in two dimensions

We present T RI M E ++, a multi-threaded software library designed for generating two-dimensional meshes for intricate geometric shapes using the Delaunay triangulation. Multi-threaded parallel computing is implemented throughout the meshing procedure, making it suitable for fast generation of large-scale meshes. Three iterative meshing algorithms are implemented: the DistMesh algorithm, the centroidal Voronoi diagram meshing, and a hybrid of the two. We compare the performance of the three meshing methods in T RI M E ++, and show that the hybrid method retains the advantages of the other two. The software library achieves significant parallel speedup when generating large-scale meshes containing between 10 4 to 10 7 points. T RI M E ++ can handle complicated geometries and generates adaptive meshes of high quality.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2025

Geometry Mesher

This program implements tetrahedral meshing for implicitly-defined geometries, focusing on meshing unions of geometric primitives like spheres and cylinders. This enables users to quickly generate quality meshes of truss lattice and filament structures.

Watts, SethE [Lawrence Livermore National Laborato↗
NASA NTRS1976

Basic research and data analysis for the earth and ocean physics applications program and for the National Geodetic Satellite Program

Data analysis and supporting research in connection with the following objectives are discussed: (1) provide a precise and accurate geometric description of the earth's surface, (2) provide a precise and accurate mathematical description of the earth's gravitational field, and (3) determine time variations of the geometry of the ocean surface, the solid earth, the gravity field and other geophysical parameters.

Source record↗
NASA NTRS1980

Geometric modeling and analysis of large latticed surfaces

The application of geometrical schemes, similar to geodesic domes, to large spherical antenna reflectors was investigated. The shape and size of flat segmented latticed surfaces which approximate general shells of revolution, and in particular spherical and paraboloidal reflective surfaces, were determined. The extensive mathematical and computational geometric analyses of the reflector resulted in the development of a general purpose computer program capable of generating the complete design parameters of the dish. The program also includes a graphical self contained subroutine for graphic display of the required design.

Nayfeh, A. H.↗
NASA NTRS1991

Algebraic grid generation for complex geometries

An efficient computer program called GRID2D/3D has been developed to generate single and composite grid systems within geometrically complex two- and three-dimensional (2D and 3D) spatial domains that can deform with time. GRID2D/3D generates single grid systems by using algebraic grid generation methods based on transfinite interpolation. The distribution of grid points within the spatial domain is controlled by stretching functions and grid lines can intersect boundaries of the spatial domain orthogonally. GRID2D/3D generates composite grid systems by patching together two or more single grid systems. The patching can be discontinuous or continuous. For 2D spatial domains the boundary curves are constructed by using either cubic or tension spline interpolation. For 3D spatial domains the boundary surfaces are constructed by using a new technique, developed in this study, referred to as 3D bidirectional Hermite interpolation.

Shih, T. I.-P.↗
NASA NTRS2005

SCHIP: Statistics for Chromosome Interphase Positioning Based on Interchange Data

he position of chromosomes in the interphase nucleus is believed to be associated with a number of biological processes. Here, we present a web-based application that helps analyze the relative position of chromosomes during interphase in human cells, based on observed radiogenic chromosome aberrations. The inputs of the program are a table of yields of pairwise chromosome interchanges and a proposed chromosome geometric cluster. Each can either be uploaded or selected from provided datasets. The main outputs are P-values for the proposed chromosome clusters. SCHIP is designed to be used by a number of scientific communities interested in nuclear architecture, including cancer and cell biologists, radiation biologists and mathematical/computational biologists.

Vives, Sergi↗
NASA NTRS1991

Engine Structures Modeling Software System (ESMOSS)

Engine Structures Modeling Software System (ESMOSS) is the development of a specialized software system for the construction of geometric descriptive and discrete analytical models of engine parts, components, and substructures which can be transferred to finite element analysis programs such as NASTRAN. The NASA Lewis Engine Structures Program is concerned with the development of technology for the rational structural design and analysis of advanced gas turbine engines with emphasis on advanced structural analysis, structural dynamics, structural aspects of aeroelasticity, and life prediction. Fundamental and common to all of these developments is the need for geometric and analytical model descriptions at various engine assembly levels which are generated using ESMOSS.

Source record↗
NASA NTRS1972

Shield weight optimization using Monte Carlo transport calculations

Outlines are given of the theory used in FASTER-3 Monte Carlo computer program for the transport of neutrons and gamma rays in complex geometries. The code has the additional capability of calculating the minimum weight layered unit shield configuration which will meet a specified dose rate constraint. It includes the treatment of geometric regions bounded by quadratic and quardric surfaces with multiple radiation sources which have a specified space, angle, and energy dependence. The program calculates, using importance sampling, the resulting number and energy fluxes at specified point, surface, and volume detectors. Results are presented for sample problems involving primary neutron and both primary and secondary photon transport in a spherical reactor shield configuration. These results include the optimization of the shield configuration.

Jordan, T. M.↗