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Results for “Harmonization”

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.

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At least 1,063 records · Page 59
All sourcesNASA NTRSDOE OSTI
NASA NTRS2001

The use of harmonic drives on NASA's Mars Exploration Rover

The Mars Exploration Rover (MER) mission will send two 185 kg rovers to Mars in 2003 to continue the scientific community's search for evidence of past water on Mars. These twin robotic vehicles will carry harmonic drives and their performance will be characterized at various temperatures, speeds and loads.

harmonic drive↗
NASA NTRS2012

Design of an Ultra-Efficient GaN High Power Amplifier for Radar Front-Ends Using Active Harmonic Load-Pull

This work presents a new measurement technique, mixed-signal active harmonic load-pull (MSALP) developed by Anterverta-mw in partnership with Maury Microwave, that allows for wide-band ultra-high efficiency amplifiers to be designed using GaN technology. An overview of the theory behind active load-pull is presented and why load-pull is important for high-power device characterization. In addition, an example procedure is presented that outlines a methodology for amplifier design using this measurement system. Lastly, measured results of a 10W GaN amplifier are presented. This work aims to highlight the benefit of using this sophisticated measurement systems for to optimize amplifier design for real radar waveforms that in turn will simplify implementation of space-based radar systems

Active Load-pull↗
NASA NTRS2018

The Harmonized Landsat and Sentinel-2 Surface Reflectance Data Set

The Harmonized Landsat and Sentinel-2 (HLS) project is a NASA initiative aiming to produce a VirtualConstellation (VC) of surface reflectance (SR) data acquired by the Operational Land Imager (OLI) and MultiSpectral Instrument (MSI) aboard Landsat 8 and Sentinel-2 remote sensing satellites, respectively. The HLS products are based on a set of algorithms to obtain seamless products from both sensors (OLI and MSI): atmospheric correction, cloud and cloud-shadow masking, spatial co-registration and common gridding, bidirectional reflectance distribution function normalization and spectral bandpass adjustment. Three products are derivedfrom the HLS processing chain: (i) S10: full resolution MSI SR at 10 m, 20 m and 60 m spatial resolutions; (ii)S30: a 30 m MSI Nadir BRDF (Bidirectional Reflectance Distribution Function)-Adjusted Reflectance (NBAR);(iii) L30: a 30 m OLI NBAR. All three products are processed for every Level-1 input products from Landsat 8/OLI (L1T) and Sentinel-2/MSI (L1C). As of version 1.3, the HLS data set covers 10.35 million km2 and spans from first Landsat 8 data (2013); Sentinel-2 data spans from October 2015. The L30 and S30 show a good consistency with coarse spatial resolution products, in particular MODIS Collection 6 MCD09CMG products (overall deviations do not exceed 11%) that are used as a reference for quality assurance. The spatial co-registration of the HLS is improved compared to original Landsat 8 L1T and Sentinel 2A L1C products, for which misregistration issues between multi-temporal data are known. In particular, the resulting computed circular errors at 90% for the HLS product are 6.2 m and 18.8 m, for S10 and L30 products, respectively. The main known issue of the current data set remains the Sentinel-2 cloud mask with many cloud detection omissions. The cross-comparison with MODIS was used to flag products with most evident non-detected clouds. A time series outlier filtering approach is suggested to detect remaining clouds. Finally, several time series are presented to highlight the high potential of the HLS data set for crop monitoring.

Landsat Sentinel-2↗
DOE OSTI2013

An improved filtered spherical harmonic method for transport calculations

Motivated by the work of R. G. McClarren, C. D. Hauck, and R. B. Lowrie on a filtered spherical harmonic method, we present a new filter for such numerical approximations to the multi-dimensional transport equation. In several test problems, we demonstrate that the new filter produces results with significantly less Gibbs phenomena than the filter used by McClarren, Hauck and Lowrie. This reduction in Gibbs phenomena translates into propagation speeds that more closely match the correct propagation speed and solutions that have fewer regions where the scalar flux is negative. (authors)

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2015

A harmonic pulse testing method for leakage detection in deep subsurface storage formations

Abstract Detection of leakage in deep geologic storage formations (e.g., carbon sequestration sites) is a challenging problem. This study investigates an easy‐to‐implement frequency domain leakage detection technology based on harmonic pulse testing (HPT). Unlike conventional constant‐rate pressure interference tests, HPT stimulates a reservoir using periodic injection rates. The fundamental principle underlying HPT‐based leakage detection is that leakage modifies a storage system's frequency response function, thus providing clues of system malfunction. During operations, routine HPTs can be conducted at multiple pulsing frequencies to obtain experimental frequency response functions, using which the possible time‐lapse changes are examined. In this work, a set of analytical frequency response solutions is derived for predicting system responses with and without leaks for single‐phase flow systems. Sensitivity studies show that HPT can effectively reveal the presence of leaks. A search procedure is then prescribed for locating the actual leaks using amplitude and phase information obtained from HPT, and the resulting optimization problem is solved using the genetic algorithm. For multiphase flows, the applicability of HPT‐based leakage detection procedure is exemplified numerically using a carbon sequestration problem. Results show that the detection procedure is applicable if the average reservoir conditions in the testing zone stay relatively constant during the tests, which is a working assumption under many other interpretation methods for pressure interference tests. HPT is a cost‐effective tool that only requires periodic modification of the nominal injection rate. Thus it can be incorporated into existing monitoring plans with little additional investment.

Sun, Alexander Y.↗
DOE OSTI2019

Quasi-Harmonic Lattice Dynamics of a Prototypical Metal–Organic Framework

Quasi-harmonic lattice-dynamical calculations are performed to investigate the combined effect of temperature and pressure on the structural and mechanical properties of a prototypical metal–organic framework material: MOF-5. The softening upon compression of an A 2 g phonon mode at the Γ point in the high-symmetry F m 3 ¯ m structure is identified, which leads to a symmetry reduction and a group–subgroup phase transition to a low-symmetry F m 3 ¯ phase for compressions larger than 0.8%. The effect of the symmetry reduction on the equation-of-state of MOF-5 is investigated, which provides a static bulk modulus K reducing from 17 to 14 GPa and a corresponding change of K ' (pressure derivative of K ) from positive to negative. The effect of pressure on the negative thermal expansion of the framework and on its mechanical response is analyzed. The evolution of the mechanical anisotropy of MOF-5 as a function of pressure is also determined, which allows identifying the occurrence of a shear-induced mechanical instability at 0.45 GPa.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Effective Labeling of Primary Somatic Stem Cells with BaTiO 3 Nanocrystals for Second Harmonic Generation Imaging

Abstract While nanoparticles are an increasingly popular choice for labeling and tracking stem cells in biomedical applications such as cell therapy, their intracellular fate and subsequent effect on stem cell differentiation remain elusive. To establish an effective stem cell labeling strategy, the intracellular nanocrystal concentration should be minimized to avoid adverse effects, without compromising the intensity and persistence of the signal necessary for long‐term tracking. Here, the use of second‐harmonic generating barium titanate nanocrystals is reported, whose achievable brightness allows for high contrast stem cell labeling with at least one order of magnitude lower intracellular nanocrystals than previously reported. Their long‐term photostability enables to investigate quantitatively at the single cell level their cellular fate in hematopoietic stem cells (HSCs) using both multiphoton and electron microscopy. It is found that the concentration of nanocrystals in proliferative multipotent progenitors is over 2.5‐fold greater compared to quiescent stem cells; this difference vanishes when HSCs enter a nonquiescent, proliferative state, while their potency remains unaffected. Understanding the nanoparticle stem cell interaction allows to establish an effective and safe nanoparticle labeling strategy into somatic stem cells that can critically contribute to an understanding of their in vivo therapeutic potential.

Sugiyama, Nami↗