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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 145 records · Page 8

2D-to-3D image translation of complex nanoporous volumes using generative networks

Image-based characterization offers a powerful approach to studying geological porous media at the nanoscale and images are critical to understanding reactive transport mechanisms in reservoirs relevant to energy and sustainability technologies such as carbon sequestration, subsurface hydrogen storage, and natural gas recovery. Nanoimaging presents a trade off, however, between higher-contrast sample-destructive and lower-contrast sample-preserving imaging modalities. Furthermore, high-contrast imaging modalities often acquire only 2D images, while 3D volumes are needed to characterize fully a source rock sample. In this work, we present deep learning image translation models to predict high-contrast focused ion beam-scanning electron microscopy (FIB-SEM) image volumes from transmission X-ray microscopy (TXM) images when only 2D paired training data is available. We introduce a regularization method for improving 3D volume generation from 2D-to-2D deep learning image models and apply this approach to translate 3D TXM volumes to FIB-SEM fidelity. We then segment a predicted FIB-SEM volume into a flow simulation domain and calculate the sample apparent permeability using a lattice Boltzmann method (LBM) technique. Results show that our image translation approach produces simulation domains suitable for flow visualization and allows for accurate characterization of petrophysical properties from non-destructive imaging data.

58 GEOSCIENCES↗

Development and characterization of Nb3Sn/Al2O3 superconducting multilayers for particle accelerators

Abstract Superconducting radio-frequency (SRF) resonator cavities provide extremely high quality factors > 10 10 at 1–2 GHz and 2 K in large linear accelerators of high-energy particles. The maximum accelerating field of SRF cavities is limited by penetration of vortices into the superconductor. Present state-of-the-art Nb cavities can withstand up to 50 MV/m accelerating gradients and magnetic fields of 200–240 mT which destroy the low-dissipative Meissner state. Achieving higher accelerating gradients requires superconductors with higher thermodynamic critical fields, of which Nb 3 Sn has emerged as a leading material for the next generation accelerators. To overcome the problem of low vortex penetration field in Nb 3 Sn, it has been proposed to coat Nb cavities with thin film Nb 3 Sn multilayers with dielectric interlayers. Here, we report the growth and multi-technique characterization of stoichiometric Nb 3 Sn/Al 2 O 3 multilayers with good superconducting and RF properties. We developed an adsorption-controlled growth process by co-sputtering Nb and Sn at high temperatures with a high overpressure of Sn. The cross-sectional scanning electron transmission microscope images show no interdiffusion between Al 2 O 3 and Nb 3 Sn. Low-field RF measurements suggest that our multilayers have quality factor comparable with cavity-grade Nb at 4.2 K. These results provide a materials platform for the development and optimization of high-performance SIS multilayers which could overcome the intrinsic limits of the Nb cavity technology.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

High-dynamic-range transmission-mode detection of synchrotron radiation using X-ray excited optical luminescence in diamond

Enhancement of X-ray excited optical luminescence in a 100 µm-thick diamond plate by introduction of defect states via electron beam irradiation and subsequent high-temperature annealing is demonstrated. The resulting X-ray transmission-mode scintillator features a linear response to incident photon flux in the range 7.6 × 10 8 to 1.26 × 10 12 photons s -1 mm -2 for hard X-rays (15.9 keV) using exposure times from 0.01 to 5 s. These characteristics enable a real-time transmission-mode imaging of X-ray photon flux density without disruption of X-ray instrument operation.

Instruments & Instrumentation↗

Soft X-ray measurements of transport and MHD activity in the core and edge NSTX plasma (Final Technical Report)

A comprehensive suite of innovative diagnostic instrumentation and techniques has been developed by the Johns Hopkins collaboration for measurements of transport and MHD activity in the core and edge of the National Spherical Torus Experiment (NSTX) at the Princeton Plasma Physics Laboratory (PPPL). These include ultrafast multi-energy poloidal soft X-ray arrays, high spatial resolution multi-energy tangential soft X-ray arrays, high spectral resolution transmission grating imaging VUV spectrometers and ultrafast bolometric arrays, which measure over a broad range of spatial, spectral, and temporal scales the emission from ohmic, RF, and beam driven NSTX plasmas. The instrumentation was designed to fulfill the specific measurement needs of the Spherical Torus (ST) magnetic fusion concept and is accompanied by a comprehensive set of numerical tools for data analysis and modeling, aimed at determining as many as possible plasma parameters and at extracting as much as possible physics information from NSTX experiments. The Johns Hopkins diagnostics have been and continue to be instrumental for essentially all the NSTX experiments. In addition, our own research and experiments using these diagnostics has led over the years to fundamental conclusions for the ST fusion physics, such as the establishment of near neoclassical impurity transport in the NSTX core and edge plasma, and the critical role of the Global Alfven Eigenmode (GAE) MHD activity for the ST core electron thermal transport. The Johns Hopkins Diagnostics continue to be operational on the upgraded NSTX-U and will provide key plasma information in its upcoming high field, current and power experimental campaigns. The present report summarizes the main technical characteristics and measurement capabilities of the diagnostic instrumentation and methods developed within our research and describes a key physics result achieved during this research. Success in our research was made possible also by the excellent support and cooperation of the NSTX research team and of PPPL researchers, who are warmly acknowledged here.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

Fabrication of a Point-Like Transmission Target for Reducing Computed Tomography Imaging Artifacts

In this study, we address the challenge of enhancing image quality and spatial resolution in computed tomography (CT) imaging by introducing simulation and fabrication of high aspect ratio, point-like transmission targets. Utilizing advanced electroplating techniques, traditionally employed in the fabrication of Through Substrate Via (TSV) interconnects for CMOS circuitry, we successfully embed copper targets within silicon substrates. This method allows us to create high-aspect-ratio features specifically designed for X-ray transmission targets, resulting in micro targets that exhibit a volume increase compared to conventional evaporated surface targets. Furthermore, we present simulation results of the X-ray spectrum generated by these targets, demonstrating their potential to significantly improve both image quality and spatial resolution in CT applications. Our findings suggest that leveraging advanced fabrication techniques can open new avenues for the development of enhanced imaging technologies in medical diagnostics and beyond.

47 OTHER INSTRUMENTATION↗

Acquisition, Search, Track

Video image data transmission using millimeter wave relay satellites - satellite acquisition, searching, and tracking

Source record↗

The Millimeter Wave Link

Video image data transmission using millimeter wave relay satellites - millimeter wave links

Source record↗

Mariner Mars 1971 photogrammetric calibrations.

One of the major objectives of the Mariner Mars 1971 mission was the systematic mapping of Mars. This required a complex and thorough photogrammetric calibration of both the wide-angle and narrow-angle cameras mounted on the spacecraft scan platform. Because of the peculiarities of the TV imaging techniques (transmission quality, low resolution, electronic distortion, etc.), combined with the extremely small vidicon format, many unique difficulties were encountered and many unprecedented problems had to be solved. Their successful solution, based on experience gained during the Surveyor and Mariner Mars 1969 projects, is discussed, and the calibration procedure for the parameters of interior orientation, as well as for opto-mechanical orthogonality, is described in detail.

Benesh, M.↗

An analytical and experimental evaluation of a Fresnel lens solar concentrator

An analytical and experimental evaluation of line focusing Fresnel lenses with application potential in the 200 to 370 C range was studied. Analytical techniques were formulated to assess the solar transmission and imaging properties of a grooves down lens. Experimentation was based on a 56 cm wide, f/1.0 lens. A Sun tracking heliostat provided a nonmoving solar source. Measured data indicated more spreading at the profile base than analytically predicted, resulting in a peak concentration 18 percent lower than the computed peak of 57. The measured and computed transmittances were 85 and 87 percent, respectively. Preliminary testing with a subsequent lens indicated that modified manufacturing techniques corrected the profile spreading problem and should enable improved analytical experimental correlation.

Hastings, L. J.↗

An analytical and experimental evaluation of the plano-cylindrical Fresnel lens solar concentrator

Plastic Fresnel lenses for solar concentration are attractive because of potential for low-cost mass production. An analytical and experimental evaluation of line-focusing Fresnel lenses with application potential in the 200 to 370 C range is reported. Analytical techniques were formulated to assess the solar transmission and imaging properties of a grooves-down lens. Experimentation was based primarily on a 56 cm-wide lens with f-number 1.0. A sun-tracking heliostat provided a non-moving solar source. Measured data indicated more spreading at the profile base than analytically predicted. The measured and computed transmittances were 85 and 87% respectively. Preliminary testing with a second lens (1.85 m) indicated that modified manufacturing techniques corrected the profile spreading problem.

Hastings, L. J.↗

An experimental study of the concatenated Reed-Solomon/Viterbi channel coding system performance and its impact on space communications

The need for efficient space communication at very low bit error probabilities to the specification and implementation of a concatenated coding system using an interleaved Reed-Solomon code as the outer code and a Viterbi-decoded convolutional code as the inner code. Experimental results of this channel coding system are presented under an emulated S-band uplink and X-band downlink two-way space communication channel, where both uplink and downlink have strong carrier power. This work was performed under the NASA End-to-End Data Systems program at JPL. Test results verify that at a bit error probability of 10 to the -6 power or less, this concatenated coding system does provide a coding gain of 2.5 dB or more over the Viterbi-decoded convolutional-only coding system. These tests also show that a desirable interleaving depth for the Reed-Solomon outer code is 8 or more. The impact of this "virtually" error-free space communication link on the transmission of images is discussed and examples of simulation results are given.

Liu, K. Y.↗

Remote-Imaging Parameters

Image resolution, image quality and data transmission rate of remote imaging systems continuously controlled by operator intervention. Set of levers allows operator to control independently frame rate, frame size and image quality in bits per pixel. System used for imaging systems in aircraft or remotely piloted vehicles.

Rice, R. F.↗

The COSPAS/SARSAT demonstration and evaluation. Results of the first year in the United States

The COSPAS/SARSAT location accuracy, coverage, location probability, 406 MHz message transmission, and image rejection were tested using a commercially available beacon (EPIRB) with modulated, coherent, 121.5 and 243.0 MHz distress signals emitted at a minimum of 75 mW, a 406 MHz EPIRB with electronics designed to meet the international specification for experimental beacons, and a beacon with the same electronics as the other 406 MHz EPIRB, incorporating a floating antenna design. The COSPAS/SARSAT system contributed to 15 out of 33 rescue missions, in which 35 of the 85 lives were rescued. In 10% of the cases the COSPAS/SARSAT system provided the only means of notification, and in 18% it was the first means. Tests show that 121.5 MHz accuracy is adequate, but 406 MHz must improve. The 121.5 MHz location probability is 82%, but ambiguity resolution is inferior to 406 MHz. Performance of both 406 MHz beacons at low elevation angles and in high wave heights is good.

Gilbert, M. E.↗

Semiannual status report

The work performed in the previous six months can be divided into three main cases: (1) transmission of images over local area networks (LAN's); (2) coding of color mapped (pseudo-color) images; and (3) low rate video coding. A brief overview of the work done in the first two areas is presented. The third item is reported in somewhat more detail.

Source record↗

An image compression technique for use on token ring networks

A low complexity technique for compression of images for transmission over local area networks is presented. The technique uses the synchronous traffic as a side channel for improving the performance of an adaptive differential pulse code modulation (ADPCM) based coder.

Gorjala, B.↗