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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 883 records · Page 49
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

SU-E-J-214: Comparative Assessment On IGRT On Partial Bladder Cancer Treatment Between CT-On-Rails (CTOR) and KV Cone Beam CT (CBCT)

Purpose: Image-Guided radiation therapy(IGRT) depends on reliable online patient-specific anatomy information to address random and progressive anatomy changes. Large margins have been suggested to bladder cancer treatment due to large daily bladder anatomy variation. KV Cone beam CT(CBCT) has been used in IGRT localization prevalently; however, its lack of soft tissue contrast makes clinicians hesitate to perform daily soft tissue alignment with CBCT for partial bladder cancer treatment. This study compares the localization uncertainties of bladder cancer IGRT using CTon- Rails(CTOR) and CBCT. Methods: Three T2N0M0 bladder cancer patients (total of 66 Gy to partial bladder alone) were localized daily with either CTOR or CBCT for their entire treatment course. A total of 71 sets of CTOR and 22 sets of CBCT images were acquired and registered with original planning CT scans by radiation therapists and approved by radiation oncologists for the daily treatment. CTOR scanning entailed 2mm slice thickness, 0.98mm axial voxel size, 120kVp and 240mAs. CBCT used a half fan pelvis protocol from Varian OBI system with 2mm slice thickness, 0.98axial voxel size, 125kVp, and 680mAs. Daily localization distribution was compared. Accuracy of CTOR and CBCT on partial bladder alignment was also evaluated by comparing bladder PTV coverage. Results: 1cm all around PTV margins were used in every patient except target superior limit margin to 0mm due to bowel constraint. Daily shifts on CTOR averaged to 0.48, 0.24, 0.19 mms(SI,Lat,AP directions); CBCT averaged to 0.43, 0.09, 0.19 mms(SI,Lat,AP directions). The CTOR daily localization showed superior results of V100% of PTV(102% CTOR vs. 89% CBCT) and bowel(Dmax 69.5Gy vs. 78Gy CBCT). CTOR images showed much higher contrast on bladder PTV alignment. Conclusion: CTOR daily localization for IGRT is more dosimetrically beneficial for partial bladder cancer treatment than kV CBCT localization and provided better soft tissue PTV identification.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Creation And Ordering Of Oxygen Vacancies At WO3-d And Perovskite Interfaces

Changes in structure and composition resulting from oxygen deficiency can strongly impact the physical and chemical properties of transition metal oxides. However, it is extremely difficult to accurately characterize the oxygen deficiency levels and pinpoint how these materials properties change in response. In this paper, the effects of substrate strain and oxidizing power on the creation and distribution of oxygen defects in WO3 thin films are investigated in detail. An 18O2 isotope labeled time-of-flight secondary ion mass spectrometry (ToF-SIMS) study reveals that WO3-films grown on STO display a significantly larger oxygen vacancy gradient along the growth direction. This result is corroborated by scanning transmission electron microscopy (STEM) images which reveal a large number of defects present close to the interface to accommodate interfacial strain, leading to ordering of oxygen vacancies and formation of semi-aligned Magnéli phases. The strain is gradually released and tetragonal phase with much better crystallinity is observed at the film/vacuum interface. The changes in structure resulting from oxygen defect creation are shown to have a direct impact on the electronic and optical properties of the films.

Zhang, Kelvin H.↗
DOE OSTI2016

FORCED FIELD EXTRAPOLATION OF THE MAGNETIC STRUCTURE OF THE H α FIBRILS IN THE SOLAR CHROMOSPHERE

We present a careful assessment of forced field extrapolation using the Solar Dynamics Observatory /Helioseismic and Magnetic Imager magnetogram. We use several metrics to check the convergence property. The extrapolated field lines below 3600 km appear to be aligned with most of the H α fibrils observed by the New Vacuum Solar Telescope. In the region where magnetic energy is far larger than potential energy, the field lines computed by forced field extrapolation are still consistent with the patterns of H α fibrils while the nonlinear force-free field results show a large misalignment. The horizontal average of the lorentz force ratio shows that the forced region where the force-free assumption fails can reach heights of 1400–1800 km. The non-force-free state of the chromosphere is also confirmed based on recent radiation magnetohydrodynamics simulations.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Nondestructive millimeter wave imaging and spectroscopy using dielectric focusing probes

A tool for interrogating objects over a wide band of frequencies with subwavelength resolution at small standoff distances (near field region) in the transmission mode using a single source and detector measurement setup in the millimeter wave band is presented. The design utilizes optics like principles for guiding electromagnetic millimeter waves from large cross-sectional areas to considerably smaller sub-wavelength areas. While plano-convex lenses can be used to focus waves to a fine resolution, they usually require a large stand-off distance thus resulting in alignment and spacing issues. The design procedure and simulation analysis of the focusing probes are presented in this study along with experimental verification of performance and imaging and spectroscopy examples. Nondestructive evaluation will find benefit from such an apparatus including biological tissue imaging, electronic package integrity testing, composite dielectric structure evaluation for defects and microfluidic sensing.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

SU-F-J-188: Clinical Implementation of in Room Mobile CT for Image Guided Proton Therapy

Purpose: To implement soft-tissue image-guided proton therapy using inroom mobile CT. Methods: Anthropomorphic phantom was first used to determine the setup accuracy using in- room mobile CT. Laser and bbs were used for the initial setup (marked isocenter). CT data was then acquired with in-room mobile CT (daily CT). The shift between the marked isocenter and the planned isocenter (final isocenter) was determined from the daily CT using in-house Computer Assisted Targeting (CAT) software. Orthogonal DRRs of the day was also generated from the daily CT. The phantom was then transferred on the treatment couch top to the treatment machine using a transportation system, and again aligned to the marked isocenter. Couch shifts were made to align the phantom to the final isocenter using the shifts as determined using the CAT software, and verified using orthogonal X-ray images with the daily DRRs. Results: Phantom data suggests that following the setup procedure as described above, targeting accuracy could be within 1 mm. Patient data are being acquired and analyzed. Conclusion: In-room mobile CT is capable of providing soft-tissue image-guided proton therapy.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2024

3D Reconstruction of a High-Energy Diffraction Microscopy Sample Using Multi-modal Serial Sectioning with High-Precision EBSD and Surface Profilometry

High-energy diffraction microscopy (HEDM) combined with in situ mechanical testing is a powerful nondestructive technique for tracking the evolving microstructure within polycrystalline materials during deformation. This technique relies on a sophisticated analysis of X-ray diffraction patterns to produce a three-dimensional reconstruction of grains and other microstructural features within the interrogated volume. However, it is known that HEDM can fail to identify certain microstructural features, particularly smaller grains or twinned regions. Characterization of the identical sample volume using high-resolution surface-specific techniques, particularly electron backscatter diffraction (EBSD), can not only provide additional microstructure information about the interrogated volume but also highlight opportunities for improvement of the HEDM reconstruction algorithms. In this study, a sample fabricated from undeformed “low solvus, high refractory” nickel-based superalloy was scanned using HEDM. The volume interrogated by HEDM was then carefully characterized using a combination of surface-specific techniques, including epi-illumination optical microscopy, zero-tilt secondary and backscattered electron imaging, scanning white light interferometry, and high-precision EBSD. Custom data fusion protocols were developed to integrate and align the microstructure maps captured by these surface-specific techniques and HEDM. The raw and processed data from HEDM and serial sectioning have been made available via the Materials Data Facility (MDF) at https://doi.org/10.18126/4y0p-v604 for further investigation.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Analyzing shear band formation with high resolution X-ray diffraction

Localization of crystallographic slip into shear bands during uniaxial compression of a copper single crystal is studied using very far-field high-energy diffraction microscopy (vff-HEDM). Diffracted intensity was collected in-situ as the crystal deformed using a unique mobile detector stage that provided access to multiple diffraction peaks with high-angular resolution. From the diffraction data, single crystal orientation pole figures (SCPFs) were generated and are used to track the evolution of the distribution of lattice orientation that develops as slip localizes. To aid the identification of 'signatures' of shear band formation and analyze the SCPF data, a model of slip-driven lattice reorientation within shear bands is introduced. Confidence is built in conclusions drawn from the SCPF data about the character of internal slip localization through comparisons with strain fields on the sample surface measured simultaneously using digital image correlation. From the diffraction data, we find that the active slip direction and slip plane are not directly aligned with the orientation of the shear bands that formed. In fact, by extracting the underlying slip system activity from the SCPF data, we show that intersecting shear bands measured on the surface of the sample arise from slip primarily on the same underlying single slip system. These new vff-HEDM results raise significant questions on the use of surface measurements for slip system activity estimation. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

36 MATERIALS SCIENCE↗
NASA NTRS1972

The uniform transparent gravitational lens.

An elementary discussion is given of the gravitational deflection of light due to radially and cylindrically symmetric masses. The effect of the deflection on apparent luminosity of distant sources is also considered. All results are limited to weak, static, asymptotically flat gravitational fields. Emphasis here is on observations of sources aligned behind the disc of the deflecting mass so that the possible transparency of this mass is decisive in image formation. Detailed calculations are made for the simple case of the uniformly dense transparent sphere and comparisons are made with the opaque mass sphere. If they have the same mass and radius, the maximum light deflection produced by these lenses is nearly equal. However, their effects on the area of narrow light beams may be quite different. The uniform transparent sphere does not produce multiple images of one source and, to first order, introduces no image distortion.

Clark, E. E.↗
NASA NTRS1976

LANDSAT D position determination and correction study

An assessment of accuracy of the knowledge of LANDSAT D spacecraft ephemeris data, an evaluation of the impact of expected attitude and alignment accuracies and analysis of the various options for the combining of precision ephemeris and attitude data with scene image data are provided. The potential geometric correction system in order to determine overall system costs and impact on other system elements is characterized.

Source record↗
NASA NTRS1986

Theoretical analysis of segmented Wolter/LSM X-ray telescope systems

The Segmented Wolter I/LSM X-ray Telescope, which consists of a Wolter I Telescope with a tilted, off-axis convex spherical Layered Synthetic Microstructure (LSM) optics placed near the primary focus to accommodate multiple off-axis detectors, has been analyzed. The Skylab ATM Experiment S056 Wolter I telescope and the Stanford/MSFC nested Wolter-Schwarzschild x-ray telescope have been considered as the primary optics. A ray trace analysis has been performed to calculate the RMS blur circle radius, point spread function (PSF), the meridional and sagittal line functions (LST), and the full width half maximum (PWHM) of the PSF to study the spatial resolution of the system. The effects on resolution of defocussing the image plane, tilting and decentrating of the multilayer (LSM) optics have also been investigated to give the mounting and alignment tolerances of the LSM optic. Comparison has been made between the performance of the segmented Wolter/LSM optical system and that of the Spectral Slicing X-ray Telescope (SSXRT) systems.

Shealy, D. L.↗
NASA NTRS1991

Collision avoidance sensor skin

The objective was to totally eliminate the possibility of a robot (or any mechanism for that matter) inducing a collision in space operations. We were particularly concerned that human beings were safe under all circumstances. This was apparently accomplished, and it is shown that GSFC has a system that is ready for space qualification and flight. However, it soon became apparent that much more could be accomplished with this technology. Payloads could be made invulnerable to collision avoidance and the blind spots behind them eliminated. This could be accomplished by a simple, non-imaging set of 'Capaciflector' sensors on each payload. It also is evident that this system could be used to align and dock the system with a wide margin of safety. Throughout, lighting problems could be ignored, and unexpected events and modeling errors taken in stride. At the same time, computational requirements would be reduced. This can be done in a simple, rugged, reliable manner that will not disturb the form factor of space systems. It will be practical for space applications. The lab experiments indicate we are well on the way to accomplishing this. Still, the research trail goes deeper. It now appears that the sensors can be extended to end effectors to provide precontact information and make robot docking (or any docking connection) very smooth, with minimal loads impacted back into the mating structures. This type of ability would be a major step forward in basic control techniques in space. There are, however, baseline and restructuring issues to be tackled. The payloads must get power and signals to them from the robot or from the astronaut servicing tool. This requires a standard electromechanical interface. Any of several could be used. The GSFC prototype shown in this presentation is a good one. Sensors with their attendant electronics must be added to the payloads, end effectors, and robot arms and integrated into the system.

Source record↗
NASA NTRS1993

Analysis of rocket beacon transmissions for computerized reconstruction of ionospheric densities

Three methods are described to obtain ionospheric electron densities from transionospheric, rocket-beacon TEC data. First, when the line-of-sight from a ground receiver to the rocket beacon is tangent to the flight trajectory, the electron concentration can be obtained by differentiating the TEC with respect to the distance to the rocket. A similar method may be used to obtain the electron-density profile if the layer is horizontally stratified. Second, TEC data obtained during chemical release experiments may be interpreted with the aid of physical models of the disturbed ionosphere to yield spatial maps of the modified regions. Third, computerized tomography (CT) can be used to analyze TEC data obtained along a chain of ground-based receivers aligned along the plane of the rocket trajectory. CT analysis of TEC data is used to reconstruct a 2D image of a simulated equatorial plume. TEC data is computed for a linear chain of nine receivers with adjacent spacings of either 100 or 200 km. The simulation data are analyzed to provide an F region reconstruction on a grid with 15 x 15 km pixels. Ionospheric rocket tomography may also be applied to rocket-assisted measurements of amplitude and phase scintillations and airglow intensities.

Bernhardt, P. A.↗
NASA NTRS1992

Automatic AVHRR image navigation software

This is the final report describing the work done on the project entitled Automatic AVHRR Image Navigation Software funded through NASA-Washington, award NAGW-3224, Account 153-7529. At the onset of this project, we had developed image navigation software capable of producing geo-registered images from AVHRR data. The registrations were highly accurate but required a priori knowledge of the spacecraft's axes alignment deviations, commonly known as attitude. The three angles needed to describe the attitude are called roll, pitch, and yaw, and are the components of the deviations in the along scan, along track and about center directions. The inclusion of the attitude corrections in the navigation software results in highly accurate georegistrations, however, the computation of the angles is very tedious and involves human interpretation for several steps. The technique also requires easily identifiable ground features which may not be available due to cloud cover or for ocean data. The current project was motivated by the need for a navigation system which was automatic and did not require human intervention or ground control points. The first step in creating such a system must be the ability to parameterize the spacecraft's attitude. The immediate goal of this project was to study the attitude fluctuations and determine if they displayed any systematic behavior which could be modeled or parameterized. We chose a period in 1991-1992 to study the attitude of the NOAA 11 spacecraft using data from the Tiros receiving station at the Colorado Center for Astrodynamic Research (CCAR) at the University of Colorado.

Baldwin, Dan↗
NASA NTRS2000

Orbital Verification of the CXO High-Resolution Mirror Assembly Alignment and Vignetting

Prior to launch, the High Resolution Mirror Assembly (HRMA) of the Chandra X-ray Observatory underwent extensive ground testing at the X-ray Calibration Facility (XRCF) at the Marshall Space Flight Center in Huntsville. Observations made during the post-launch Orbital Activation and Calibration period, allow the on-orbit condition of the X-ray optics to be assessed. Based on these ground-based and on-orbit data, we examine the alignment of the x-ray optics based on the PSF, and the boresight and alignment of the optical axis alignment relative to the detectors. We examine the vignetting and the single reflection ghost suppression properties of the telescope. Slight imperfections in alignment lead to a small azimuthal dependence of the off-axis area; the morphology of off-axis images also shows an additional small azimuthal dependence varying as 1/2 the off-axis azimuth angle.

Gaetz, T. J.↗
NASA NTRS1999

Progress in a Study of Striations in the Dust Tail of Comet Hale-Bopp (C/1995 O1)

We report preliminary results of a massive investigation of the striation patterns observed in the dust tail of comet Hale-Bopp in March and April 1997. Our findings are based on 16 wide-field photographs taken with Schmidt cameras on March 2-20, with six more, from March 31-April 8, still waiting for analysis. Altogether approximately 700 individual striae were examined on the 16 images, which were scanned and computer processed to enhance the morphology. About 5300 stria points, or some 7-8 points per stria per image on the average, were measured and their astrometric positions determined and subsequently converted to a Cartesian coordinate system, aligned with the comet's projected radius vector and centered on the nucleus. The evolution of the striated tail has been studied using the Sekanina-Farrell fragmentation hypothesis (AJ 85, 1538, 1980), previously applied to other comets. This two-step model is characterized by the time of release from the nucleus of a parent object (or objects) whose motion is assumed to have been subjected to a constant repulsive acceleration beta(sub p) (presumably due to solar radiation pressure) until the time of fragmentation.

Sekanina, Z.↗
NASA NTRS2001

Measurement of Separated Flow Structures Using a Multiple-Camera DPIV System

A novel multiple-camera system for the recording of digital particle image velocimetry (DPIV) images acquired in a two-dimensional separating/reattaching flow is described. The measurements were performed in the NASA Langley Subsonic Basic Research Tunnel as part of an overall series of experiments involving the simultaneous acquisition of dynamic surface pressures and off-body velocities. The DPIV system utilized two frequency-doubled Nd:YAG lasers to generate two coplanar, orthogonally polarized light sheets directed upstream along the horizontal centerline of the test model. A recording system containing two pairs of matched high resolution, 8-bit cameras was used to separate and capture images of illuminated tracer particles embedded in the flow field. Background image subtraction was used to reduce undesirable flare light emanating from the surface of the model, and custom pixel alignment algorithms were employed to provide accurate registration among the various cameras. Spatial cross correlation analysis with median filter validation was used to determine the instantaneous velocity structure in the separating/reattaching flow region illuminated by the laser light sheets. In operation the DPIV system exhibited a good ability to resolve large-scale separated flow structures with acceptable accuracy over the extended field of view of the cameras. The recording system design provided enhanced performance versus traditional DPIV systems by allowing a variety of standard and non-standard cameras to be easily incorporated into the system.

Humphreys, William M., Jr.↗
NASA NTRS2013

Development and Calibration of the ART-XC Mirror Modules for the Spectrum Rontgen Gamma Mission

The Spectrum-Röntgen-Gamma (SRG) mission is a Russian-lead X-ray astrophysical observatory that carries two co-aligned X-ray telescope systems. The primary instrument is the German-led extended ROentgen Survey with an Imaging Telescope Array (eROSITA), a 7-module X-ray telescope system that covers the energy range from 0.2-12 keV. The complementary instrument is the Astronomical Roentgen Telescope -- X-ray Concentrator (ART-XC or ART), a 7-module Xray telescope system that provides higher energy coverage, up to 30 keV.

Ramsey, B.↗
NASA NTRS2023

Interrogating Solar Flare Loop Models with IRIS Observations 2: Plasma Properties, Energy Transport, and Future Directions

During solar flares a tremendous amount of magnetic energy is released and transported through the Sun’s atmosphere and out into the heliosphere. Despite over a century of study, many unresolved questions surrounding solar flares are still present. Among those are how does the solar plasma respond to flare energy deposition, and what are the important physical processes that transport that energy from the release site in the corona through the transition region and chromosphere? Attacking these questions requires the concert of advanced numerical simulations and high spatial-, temporal-, and spectral-resolution observations. While flares are 3D phenomenon, simulating the NLTE flaring chromosphere in 3D and performing parameter studies of 3D models is largely outwith our current computational capabilities. We instead rely on state-of-the-art 1D field-aligned simulations to study the physical processes that govern flares. Over the last decade, data from the Interface Region Imaging Spectrograph (IRIS) have provided the crucial observations with which we can critically interrogate the predictions of those flare loop models. Here in Paper 2 of a two-part review of IRIS and flare loop models, I discuss how forward modelling flares can help us understand the observations from IRIS, and how IRIS can reveal where our models do well and where we are likely missing important processes, focussing in particular on the plasma properties, energy transport mechanisms, and future directions of flare modelling.

solar flares↗