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All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Structural optimization by generalized, multilevel decomposition

The developments toward a general multilevel optimization capability and results for a three-level structural optimization are described. The method partitions a structure into a number of substructuring levels where each substructure corresponds to a subsystem in the general case of an engineering system. The method is illustrated by a portal framework that decomposes into individual beams. Each beam is a box that can be further decomposed into stiffened plates. Substructuring for this example spans three different levels: (1) the bottom level of finite elements representing the plates; (2) an intermediate level of beams treated as substructures; and (3) the top level for the assembled structure. The three-level case is now considered to be qualitatively complete.

Sobieszczanski-Sobieski, J.↗
NASA NTRS1989

The PARTY parallel runtime system

In the present automated system for the organization of the data and computational operations entailed by parallel problems, in ways that optimize multiprocessor performance, general heuristics for partitioning program data and control are implemented by capturing and manipulating representations of a computation at run time. These heuristics are directed toward the dynamic identification and allocation of concurrent work in computations with irregular computational patterns. An optimized static-workload partitioning is computed for such repetitive-computation pattern problems as the iterative ones employed in scientific computation.

Saltz, J. H.↗
NASA NTRS1990

H-infinity based integrated flight/propulsion control design for a STOVL aircraft in transition flight

This paper presents results from an application of H(infinity) control design methodology to a centralized integrated flight/propulsion control (IFPC) system design for a supersonic STOVL fighter aircraft in transition flight. The overall design methodology consists of a centralized IFPC design with controller partitioning. Design and evaluation vehicle models are summarized, and insight is provided into formulating the H(infinity) control problem such that it reflects the IFPC design objective. The H(infinity) controller is shown to provide decoupled command tracking for the design model. The controller order could be significantly reduced by modal residualization of the fast controller modes without any deterioration in performance.

Garg, Sanjay↗
NASA NTRS1995

Visualization and Tracking of Parallel CFD Simulations

We describe a system for interactive visualization and tracking of a 3-D unsteady computational fluid dynamics (CFD) simulation on a parallel computer. CM/AVS, a distributed, parallel implementation of a visualization environment (AVS) runs on the CM-5 parallel supercomputer. A CFD solver is run as a CM/AVS module on the CM-5. Data communication between the solver, other parallel visualization modules, and a graphics workstation, which is running AVS, are handled by CM/AVS. Partitioning of the visualization task, between CM-5 and the workstation, can be done interactively in the visual programming environment provided by AVS. Flow solver parameters can also be altered by programmable interactive widgets. This system partially removes the requirement of storing large solution files at frequent time steps, a characteristic of the traditional 'simulate (yields) store (yields) visualize' post-processing approach.

Vaziri, Arsi↗
NASA NTRS2004

Workshop on Oxygen in the Terrestrial Planets

This volume contains abstracts that have been accepted for presentation at the Workshop on Oxygen in the Terrestrial Planets, July 20-23,2004, Santa Fe, New Mexico. The contents include: 1) Experimental Constraints on Oxygen and Other Light Element Partitioning During Planetary Core Formation; 2) In Situ Determination of Fe(3+)/SigmaFe of Spinels by Electron Microprobe: An Evaluation of the Flank Method; 3) The Effect of Oxygen Fugacity on Large-Strain Deformation and Recrystallization of Olivine; 4) Plagioclase-Liquid Trace Element Oxygen Barometry and Oxygen Behaviour in Closed and Open System Magmatic Processes; 5) Core Formation in the Earth: Constraints from Ni and Co; 6) Oxygen Isotopic Compositions of the Terrestrial Planets; 7) The Effect of Oxygen Fugacity on Electrical Conduction of Olivine and Implications for Earth s Mantle; 8) Redox Chemical Diffusion in Silicate Melts: The Impact of the Semiconductor Condition; 9) Ultra-High Temperature Effects in Earth s Magma Ocean: Pt and W Partitioning; 10) Terrestrial Oxygen and Hydrogen Isotope Variations: Primordial Values, Systematics, Subsolidus Effects, Planetary Comparisons, and the Role of Water; 11) Redox State of the Moon s Interior; 12) How did the Terrestrial Planets Acquire Their Water?; 13) Molecular Oxygen Mixing Ratio and Its Seasonal Variability in the Martian Atmosphere; 14) Exchange Between the Atmosphere and the Regolith of Mars: Discussion of Oxygen and Sulfur Isotope Evidence; 15) Oxygen and Hydrogen Isotope Systematics of Atmospheric Water Vapor and Meteoric Waters: Evidence from North Texas; 16) Implications of Isotopic and Redox Heterogeneities in Silicate Reservoirs on Mars; 17) Oxygen Isotopic Variation of the Terrestrial Planets; 18) Redox Exchanges in Hydrous Magma; 19) Hydrothermal Systems on Terrestrial Planets: Lessons from Earth; 20) Oxygen in Martian Meteorites: A Review of Results from Mineral Equilibria Oxybarometers; 21) Non-Linear Fractionation of Oxygen Isotopes Implanted in Lunar Metal Grains: Solar, Lunar or Terrestrial Origin? 22) Isotopic Zoning in the Inner Solar System; 23) Redox Conditions on Small Bodies; 24) Determining the Oxygen Fugacity of Lunar Pyroclastic Glasses Using Vanadium Valence - An Update; 25) Mantle Redox Evolution and the Rise of Atmospheric O2; 26) Variation of Kd for Fe-Mg Exchange Between Olivine and Melt for Compositions Ranging from Alkaline Basalt to Rhyolite; 27) Determining the Partial Pressure of Oxygen (PO,) in Solutions on Mars; 28) The Influence of Oxygen Environment on Kinetic Properties of Silicate Rocks and Minerals; 29) Redox Evolution of Magmatic Systems; 30) The Constancy of Upper Mantlefo, Through Time Inferred from V/Sc Ratios in Basalts: Implications for the Rise in Atmospheric 0 2; 31) Nitrogen Solubility in Basaltic Melt. Effects of Oxygen Fugacity, Melt Composition and Gas Speciation; 32) Oxygen Isotope Anomalies in the Atmospheres of Earth and Mars; 33) The Effect of Oxygen Fugacity on Interdiffusion of Iron and Magnesium in Magnesiowiistite 34) The Calibration of the Pyroxene Eu-Oxybarometer for the Martian Meteorites; 35) The Europium Oxybarometer: Power and Pitfalls; 36) Oxygen Fugacity of the Martian Mantle from PigeoniteMelt Partitioning of Samarium, Europium and Gadolinium; 37) Oxidation-Reduction Processes on the Moon: Experimental Verification of Graphite Oxidation in the Apollo 17 Orange Glasses; 38) Oxygen and Core Formation in the Earth; 39) Geologic Record of the Atmospheric Sulfur Chemistry Before the Oxygenation of the Early Earth s Atmosphere; 40) Comparative Planetary Mineralogy: V/(CrCAl) Systematics in Chromite as an Indicator of Relative Oxygen Fugacity; 41) How Well do Sulfur Isotopes Constrain Oxygen Abundance in the Ancient Atmospheres? 42) Experimental Constraints on the Oxygen Isotope (O-18/ O-16) Fractionation in the Ice vapor and Adsorbant vapor Systems of CO2 at Conditions Relevant to the Surface of Mars; 43) Micro-XANES Measurements on Experimental Spinels andhe Oxidation State of Vanadium in Spinel-Melt Pairs; 44) Testing the Magma Ocean Hypothesis Using Metal-Silicate Partitioning of Te, Se and S; 45) Solubility of Oxygen in Liquid Iron at High Pressure and Consequences for the Early Differentiation of Earth and Mars Metallic Liquid Segregation in Planetesimals; 46) Oxygen Fugacity of Lunar Basalts and the Lunar Mantle. Range of fo2 and the Effectiveness of Oxybarometers; 47) Thermodynamic Study of Dissociation Processes of Molecular Oxygen in Vapor over Oxide Compounds; 48) Oxygen Profile of a Thermo-Haliophilic Community in the Badwater Salt Flat; 49) Oxygen Barometry Using Synchrotron MicroXANES of Vanadium; 50) Mass-Independent Isotopic Fractionation of Sulfur from Sulfides in the Huronian Supergroup, Canada; 51) Mass Independent Isotopes and Applications to Planetary Atmospheres; 52) Electrical Conductivity, Oxygen Fugacity, and Mantle Materials; 53) Crustal Evolution and Maturation on Earth: Oxygen Isotope Evidence; 54) The Oxygen Isotope Composition of the Moon: Implications for Planet Formation; 55) Oxygen Isotope Composition of Eucrites and Implications for the Formation of Crust on the HED Parent Body; and 56) The Role of Water in Determining the Oxygen Isotopic Composition of Planets.

Source record↗
NASA NTRS1982

The geochemical coherence of Pu and Nd and the Pu-244/U-238 ratio of the early solar system

Two very different sets of Pu-244/U-238 ratios have been reported for early solar system materials, one high and the other low, and this paper examines how one of these groups may yield an incorrect ratio. Recently measured partition coefficients for Pu and Sm (Jones, 1981) are used to evaluate Pu-Nd fractionation during achondrite genesis, and Pu-244/U-238 ratios of chondrites, achondrites, and Ca-Al-rich inclusions are compared and discussed. A low Pu-244/U-238 ratio is favored, and some implications of this low ratio for galactic nucleosynthesis and meteorite age dating are briefly discussed.

Jones, J. H.↗
NASA NTRS1990

Computational technology for flight vehicles; Proceedings of the Symposium, Washington, DC, Nov. 5-7, 1990

Recent advances in computational fluid mechanics are discussed in reviews and reports. Sections are devoted to (1) the modeling of local phenomena and edge effects in solids, (2) stochastic modeling and simulation of fracture toughness, and (3) partitioning strategy and new finite elements. Particular attention is given to global and local finite-element/spectral-boundary-element techniques for failure analysis, simulations of microfracture in metal-matrix composites, fatigue analysis of cracked anisotropic plates under stochastic loading, mathematical modeling for the analysis of nonlinear aircraft dynamics, physical and mathematical modeling of wave propagation in the Ariane 5 VEB structure, partitioning based on symmetry transformations, an FEM approach to adaptive reliability assurance, and time-domain FEMs for the large rotational dynamics of multibody systems.

Noor, Ahmed K.↗
NASA NTRS2004

Characterization of the Distribution of Siderophile and Highly Siderophile Elements in the Milton and Eagle Station Pallasites

We examine the partitioning characteristics of several siderophile elements and HSE in the Eagle Station and Milton pallasites to determine if the D(sup Metal/Silicate) in natural systems are comparable to the range of values determined for synthetic systems. Eagle Station and Milton are particularly appropriate for this type of study because previous studies have shown that bulk samples of these meteorites have much higher abundances of siderophile elements and HSE than bulk samples of main group pallasites or mesosiderites. Thus, the expectation that initiated this study was that the abundances of at least some elements of interest present in the silicate phases may be at levels sufficiently high to be determined via in situ spot analysis using laser ablation ICP-MS.

Hillebrand, J. T.↗
NASA NTRS2022

Quantifying Spatial Drought Propagation Potential in North America Using Complex Network Theory

Droughts have a dominant three-dimensional (3-D) spatiotemporal structure typically spanning hundreds of kilometers and often lasting for months to years. Here, we introduced a novel framework to explore the 3-D structure of the evolution of droughts based on network theory concepts. The proposed framework is applied to identify critical source regions responsible for large-scale drought onsets during 1901–2014 for the North American continent using the Standardized Precipitation Evaporation Index (SPEI). We built a spatial network connecting the drought onset timings for the North American continent. Using a spatially weighted network partitioning algorithm, the whole continent is then classified into regional spatial drought networks (RSN), where droughts are more likely to propagate within these regional systems. Finally, a customized network metric was applied to identify locations (source regions) where the drought onsets further propagate to other areas within the regional spatial network. Our results indicated that the West coast, Texas coastal region, and Southeastern Arkansas as major source regions through which atmospheric drought propagates to Western, South Central, and Eastern North America. The formation of drought source regions are due to presence of high pressure ridges and anomalous wind patterns. Furthermore, our results indicate that the drought propagation from these source regions may be due to inadequate moisture transport. The proposed framework can help to develop an early warning detection system for droughts and other spatially extensive extreme events such as heatwaves and floods.

Goutam Konapala↗
NASA NTRS2014

Announced Strategy Types in Multiagent RL for Conflict-Avoidance in the National Airspace

The use of unmanned aerial systems (UAS) in the national airspace is of growing interest to the research community. Safety and scalability of control algorithms are key to the successful integration of autonomous system into a human-populated airspace. In order to ensure safety while still maintaining efficient paths of travel, these algorithms must also accommodate heterogeneity of path strategies of its neighbors. We show that, using multiagent RL, we can improve the speed with which conflicts are resolved in cases with up to 80 aircraft within a section of the airspace. In addition, we show that the introduction of abstract agent strategy types to partition the state space is helpful in resolving conflicts, particularly in high congestion.

National Airspace↗
NASA NTRS2004

Influence of nitrogen nutrition management on biomass partitioning and nitrogen use efficiency indices in hydroponically grown potato

The National Aeronautics and Space Administration (NASA) has been conducting controlled environment research with potatoes (Solanum tuberosum L.) in recirculating nutrient film technique (NFT)-hydroponic systems as a human life support component during long-duration spaceflight. Standard nutrient solution management approaches include constant pH regulation with nitric acid (HNO3) and daily adjustment of electrical conductivity (EC) equivalent to half-strength modified Hoagland's solution, where nitrate (NO3-) is the sole nitrogen (N) source. Although tuber yields have been excellent with such an approach, N use efficiency indices are expected to be low relative to tuber biomass production. Furthermore, the high amount of N used in NFT-hydroponics, typically results in high inedible biomass, which conflicts with the need to minimize system mass, volume, and expenditure of resources for long-duration missions. More effective strategies of N fertilization need to be developed to more closely match N supply with demand of the crop. Hence, the primary objective of this study was to identify the optimal N management regime and plant N requirement to achieve high yields and to avoid inefficient use of N and excess inedible biomass production. In separate 84-day cropping experiments, three N management protocols were tested. Treatments which decreased NO3(-)-N supply indirectly through lowering nutrient solution EC (Expt. I), or disabling pH control, and/or supplying NH4(+)-N (Expt. III) did not significantly benefit tuber yield, but did influence N use efficiency indices. When supplied with an external 7.5 mM NO3(-)-N for the first 42 days after planting (DAP), lowered to 1.0 mM NO3(-)-N during the final 42 days (Expt. II), plants were able to achieve yields on par with plants which received constant 7.5 mM NO3(-)-N (control). By abruptly decreasing N supply at tuber initiation in Expt. II, less N was taken up and accumulated by plants compared to those which received high constant N (control). However, proportionately more plant accumulated N was used (N use efficiency) to produce tuber biomass when N supply was abruptly lowered at tuber initiation in Expt. II. Hence, a hydroponic nutrient solution N management system may be modified to elicit greater plant N-use while maintaining overall high tuber yield as opposed to achieving high tuber yields through excess N supply and shoot growth.

NASA Discipline Life Support Systems↗
NASA NTRS1978

Three-dimensional radiative exchange factors for nongray, nondiffuse surfaces

A computer program using a variation of the Monte Carlo method was developed to predict radiative exchange factors in three-dimensional configurations with curved surfaces. The model allows for arbitrary emission, absorption, and reflection characteristics and for radiation exchange between surfaces as well as external irradiation through openings. It was shown that exchange factors can be determined efficiently by using the normal Monte Carlo method for closed configurations and/or high surface emissivities, while energy partitioning is vastly superior in the case of open configurations and/or low surface emissivities. Comparison with some experiments performed on the Space Shuttle heat rejection system demonstrates the model's accuracy as well as its superiority over a simplified diffuse-surface analysis, which requires similar amounts of computer time.

Modest, M. F.↗
NASA NTRS1986

Optical constants of GaAs-AlGaAs superlattices and multiple quantum wells

The optical properties of GaAs-Al sub x Ga sub 1-xAs superlattices are calculated as a function of the frequency and superlattice structure. The comutations are performed using a partition method which combines the vectors k.p method with the pseudopotential technique. The influence of the super-structure on the electronic properties of the systems is accounted for by appropriate quantization conditions. The anisotropy and structure dependence of the dielectric constant result mainly from the contribution of the gamma region while the contributions of the other regions of the Brillouin zone are rather insensitive to the superlattice structure. The superlattice index of refraction values are shown to attain maxima at the various quantized transition energies, where for certain structures, the difference between the refractive indices of the superlattices and its corresponding Al sub x Ga sub 1-xAs alloy can be as large as 2%. In general results are in good agreement with the experimental data.

Kahen, K. B.↗
NASA NTRS1993

An experimental study of trace element partitioning between olivine, orthopyroxene and melt in chondrules - Equilibrium values and kinetic effects

Mineral/melt partition coefficients were measured using an ion microprobe for 32 elements in orthopyroxene and olivine in equilibrium and dynamic crystallization experiments on compositions corresponding to chondrules. The mineral/melt partition coefficients calculated from the measured concentrations for both olivine and orthopyroxene show very little change between equilibrium experiments and dynamic experiments with cooling rates of up to 100 C/h. The results provide a self-consistent set of partition coefficients that can be used in thermodynamic models of equilibrium and kinetic partitioning between olivine, orthopyroxene, and melt. These data can be used in models of partial melting and crystal fractionation in olivine- and orthopyroxene-rich systems, such as chondrules. The results may also be applicable to mantle peridotites, komatiitic and picritic lavas, and ultramafic intrusions.

Kennedy, A. K.↗
NASA NTRS1994

Redundant Disk Arrays in Transaction Processing Systems

We address various issues dealing with the use of disk arrays in transaction processing environments. We look at the problem of transaction undo recovery and propose a scheme for using the redundancy in disk arrays to support undo recovery. The scheme uses twin page storage for the parity information in the array. It speeds up transaction processing by eliminating the need for undo logging for most transactions. The use of redundant arrays of distributed disks to provide recovery from disasters as well as temporary site failures and disk crashes is also studied. We investigate the problem of assigning the sites of a distributed storage system to redundant arrays in such a way that a cost of maintaining the redundant parity information is minimized. Heuristic algorithms for solving the site partitioning problem are proposed and their performance is evaluated using simulation. We also develop a heuristic for which an upper bound on the deviation from the optimal solution can be established.

Mourad, Antoine Nagib↗
NASA NTRS1994

Automated Instrumentation, Monitoring and Visualization of PVM Programs Using AIMS

We present views and analysis of the execution of several PVM (Parallel Virtual Machine) codes for Computational Fluid Dynamics on a networks of Sparcstations, including: (1) NAS Parallel Benchmarks CG and MG; (2) a multi-partitioning algorithm for NAS Parallel Benchmark SP; and (3) an overset grid flowsolver. These views and analysis were obtained using our Automated Instrumentation and Monitoring System (AIMS) version 3.0, a toolkit for debugging the performance of PVM programs. We will describe the architecture, operation and application of AIMS. The AIMS toolkit contains: (1) Xinstrument, which can automatically instrument various computational and communication constructs in message-passing parallel programs; (2) Monitor, a library of runtime trace-collection routines; (3) VK (Visual Kernel), an execution-animation tool with source-code clickback; and (4) Tally, a tool for statistical analysis of execution profiles. Currently, Xinstrument can handle C and Fortran 77 programs using PVM 3.2.x; Monitor has been implemented and tested on Sun 4 systems running SunOS 4.1.2; and VK uses XIIR5 and Motif 1.2. Data and views obtained using AIMS clearly illustrate several characteristic features of executing parallel programs on networked workstations: (1) the impact of long message latencies; (2) the impact of multiprogramming overheads and associated load imbalance; (3) cache and virtual-memory effects; and (4) significant skews between workstation clocks. Interestingly, AIMS can compensate for constant skew (zero drift) by calibrating the skew between a parent and its spawned children. In addition, AIMS' skew-compensation algorithm can adjust timestamps in a way that eliminates physically impossible communications (e.g., messages going backwards in time). Our current efforts are directed toward creating new views to explain the observed performance of PVM programs. Some of the features planned for the near future include: (1) ConfigView, showing the physical topology of the virtual machine, inferred using specially formatted IP (Internet Protocol) packets: and (2) LoadView, synchronous animation of PVM-program execution and resource-utilization patterns.

Mehra, Pankaj↗
NASA NTRS1995

Growth and photomorphogenesis of pepper plants under red light-emitting diodes with supplemental blue or far-red lighting

Light-emitting diodes (LEDs) are a potential irradiation source for intensive plant culture systems and photobiological research. They have small size, low mass, a long functional life, and narrow spectral output. In this study, we measured the growth and dry matter partitioning of 'Hungarian Wax' pepper (Capsicum annuum L.) plants grown under red LEDs compared with similar plants grown under red LEDs with supplemental blue or far-red radiation or under broad spectrum metal halide (MH) lamps. Additionally, we describe the thermal and spectral characteristics of these sources. The LEDs used in this study had a narrow bandwidth at half peak height (25 nm) and a focused maximum spectral output at 660 nm for the red and 735 nm for the far-red. Near infrared radiation (800 to 3000 nm) was below detection and thermal infrared radiation (3000 to 50,000 nm) was lower in the LEDs compared to the MH source. Although the red to far-red ratio varied considerably, the calculated phytochrome photostationary state (phi) was only slightly different between the radiation sources. Plant biomass was reduced when peppers were grown under red LEDs in the absence of blue wavelengths compared to plants grown under supplemental blue fluorescent lamps or MH lamps. The addition of far-red radiation resulted in taller plants with greater stem mass than red LEDs alone. There were fewer leaves under red or red plus far-red radiation than with lamps producing blue wavelengths. These results indicate that red LEDs may be suitable, in proper combination with other wavelengths of light, for the culture of plants in tightly controlled environments such as space-based plant culture systems.

NASA Discipline Life Support Systems↗
NASA NTRS2003

Performance of the CELSS Antarctic Analog Project (CAAP) crop production system

Regenerative life support systems potentially offer a level of self-sufficiency and a decrease in logistics and associated costs in support of space exploration and habitation missions. Current state-of-the-art in plant-based, regenerative life support requires resources in excess of allocation proposed for candidate mission scenarios. Feasibility thresholds have been identified for candidate exploration missions. The goal of this paper is to review recent advances in performance achieved in the CELSS Antarctic Analog Project (CAAP) in light of the likely resource constraints. A prototype CAAP crop production chamber has been constructed and operated at the Ames Research Center. The chamber includes a number of unique hardware and software components focused on attempts to increase production efficiency, increase energy efficiency, and control the flow of energy and mass through the system. Both single crop, batch production and continuous cultivation of mixed crops production studies have been completed. The crop productivity as well as engineering performance of the chamber are described. For each scenario, energy required and partitioned for lighting, cooling, pumping, fans, etc. is quantified. Crop production and the resulting lighting efficiency and energy conversion efficiencies are presented. In the mixed-crop scenario, with 27 different crops under cultivation, 17 m2 of crop area provided a mean of 515 g edible biomass per day (85% of the approximate 620 g required for one person). Enhanced engineering and crop production performance achieved with the CAAP chamber, compared with current state-of-the-art, places plant-based life support systems at the threshold of feasibility. c2002 Published by Elsevier Science Ltd on behalf of COSPAR.

Lettuce/growth & development↗