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At least 289 records · Page 16

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NASA NTRS1975

Clusius-Dickel Separations (CDS): A new look at an old technique

The history, applications, and theoretical basis of the CDS technique are reviewed. The advantage to be realized by conduction of CDSs in low-g, space environments are deduced. The results are reported of investigations aimed at further improving CDS efficiencies by altering convective flow patterns. The question of whether multicellular flow or turbulence can introduce a new separation mechanism which would boost separation efficiencies at least an order of magnitude is considered. Results are presented and discussed.

Grodzka, P. G.↗

NASA NTRS1986

Transonic Navier-Stokes wing solutions using a zonal approach. Part 2: High angle-of-attack simulation

A computer code is under development whereby the thin-layer Reynolds-averaged Navier-Stokes equations are to be applied to realistic fighter-aircraft configurations. This transonic Navier-Stokes code (TNS) utilizes a zonal approach in order to treat complex geometries and satisfy in-core computer memory constraints. The zonal approach has been applied to isolated wing geometries in order to facilitate code development. Part 1 of this paper addresses the TNS finite-difference algorithm, zonal methodology, and code validation with experimental data. Part 2 of this paper addresses some numerical issues such as code robustness, efficiency, and accuracy at high angles of attack. Special free-stream-preserving metrics proved an effective way to treat H-mesh singularities over a large range of severe flow conditions, including strong leading-edge flow gradients, massive shock-induced separation, and stall. Furthermore, lift and drag coefficients have been computed for a wing up through CLmax. Numerical oil flow patterns and particle trajectories are presented both for subcritical and transonic flow. These flow simulations are rich with complex separated flow physics and demonstrate the efficiency and robustness of the zonal approach.

Chaderjian, N. M.↗

DOE OSTI2017

Direct Writing of X-ray Gratings Using Zone-Plate-Array Lithography (ZPAL)

With the objective of providing the synchrotron and free-electron-laser communities with rapid turnaround and low prices for the highest quality and most advanced gratings and diffractive-focusing optics, LumArray has made specific improvements to its ZP-150 maskless photolithography system, which is based on Zone-Plate-Array Lithography (ZPAL), a technology unique to Lumarray. ZPAL’s advantages include an ability to correct in software for systematic patterning errors. Emphasis was placed on interferometric measurements of various contributors to patterning errors using Fizeau interferometry and a Mireau technique that was developed specifically for measuring errors within a micron-scale area. Average line-placement error was reduced below 20 nm using both pattern-file distortion and address-grid modification. The preferred implementation, address-grid modification, is hardware-based and requires no user intervention while also correcting more types of error. With continued iteration and refinement of the error measurements, we anticipate achieving global line-placement error below10nm. In order to investigate line-edge smoothness and high-frequency line-placement errors, a scheme for inspecting micron-sized areas was invented and implemented based on Mireau interferometry. This enabled the various contributions to be separately evaluated and measured. These included: exposure-dose variation, pattern-writing strategy and errors in the positioning of the microlenses. Deleterious crosstalk between microlenses was minimized via a pattern-dependent software modification. The impact of exposure threshold was revealed and adjustment made. The impact of address-grid fineness on line-edge roughness was likewise shown. Lastly, techniques were developed to measure and correct errors in the positioning of microlenses within the array. We expect final calibration of microlens positions to within 5nm.

42 ENGINEERING↗

NASA NTRS2007

Aperture-Coupled Thin-Membrane L-Band Antenna

The upper part of the figure depicts an aperture-coupled L-band antenna comprising patterned metal conductor films supported on two thin polyimide membranes separated by an air gap. In this antenna, power is coupled from a microstrip line on the lower surface of the lower membrane, through a slot in a metal ground plane on the upper surface of the lower membrane, to a radiating metal patch on the upper surface of the upper membrane. The two-membrane configuration of this antenna stands in contrast to a three-membrane configuration heretofore considered as the basis for developing arrays of dual-polarization, wideband microwave antennas that could be thin and could be, variously, incorporated into, or supported on, thin structures, including inflatable structures. By reducing the number of membranes from three to two, the present design simplifies the problems of designing and fabricating such antennas or arrays of such antennas, including the problems of integrating such antennas or arrays with thin-membrane-mounted transmit/ receive modules. In addition, the use of aperture (slot) coupling eliminates the need for rigid coaxial feed pins and associated solder connections on thin membranes, making this antenna more mechanically reliable, relative to antennas that include coaxial feed pins. This antenna is designed for a nominal frequency of 1.26 GHz. The polyimide membranes are 0.05 mm thick and have a relative permittivity of 3.4. The radiating patch is square, 8.89 cm on each side. This radiating patch lies 1.27 cm above the ground plane. The feeding microstrip line is 0.12 mm wide and has a characteristic impedance of 50 . The aperture-coupling slot, etched in the ground plane, is 0.48 mm wide and 79.5 mm long. In order to maximize coupling, the microstrip line is extended beyond the middle of the slot by a length of 36 mm, which corresponds to a transmission- line electrical length of about a quarter wavelength. The other end of the microstrip line is transformed to a 50-Ohm coplanar waveguide line, which is used for connection to a transmit/receive module. Some plated-through vias are added to the outer conductors of the coplanar waveguide to suppress parallel-plate modes. The measured and calculated 10-dB-return-loss bandwidth of the antenna is 100 MHz. By eliminating the radiating patch and the upper membrane that supports it, and performing two other simple modifications, one can convert the two-membrane antenna described above to a paper-thin single-membrane antenna, shown in the lower part of the figure. One modification is to increase the slot length to 104.95 mm; the other is to extend the microstrip to 36.68 mm past the middle of the slot. With these modifications, the slot now becomes a half-wavelength radiator with a nearly omnidirectional radiation pattern. In one potential use, such a paper-thin antenna could be pasted on an automobile window to enable omnidirectional communication.

Huang, John↗

NASA NTRS1987

The production of braids in Saturn's F ring

The braided structure noted in Voyager images of the Saturn F ring is presently addressed by two models. In the first, the pattern is generated by a narrow and initially uniform ring's passing of a nearby satellite, followed by an embedded moonlet gravitational acceleration-induced doubling back so that trajectories of the ring particles traverse one end of the classic horseshoe orbit. In the second model, the F ring is composed of two separated strands before the Moon's passage, so that a long braided pattern can be generated by the subsequent drift in relative phase; the embedded moonlet is thereby obviated.

Lissauer, Jack J.↗

NASA NTRS1986

The production of 'braids' in Saturn's F ring

The 'braided' structure noted in Voyager images of the Saturn F ring is presently addressed by two models. In the first, the pattern is generated by a narrow and initially uniform ring's passing of a nearby satellite, followed by an embedded moonlet gravitational acceleration-induced doubling back so that trajectories of the ring particles traverse one end of the classic 'horseshoe' orbit. In the second model, the F ring is composed of two separated strands before the moon's passage, so that a long braided pattern can be generated by the subsequent drift in relative phase; the embedded moonlet is thereby obviated.

Lissauer, J. J.↗

NASA NTRS1973

Pattern Recognition and the Potential Function

An algorithm is presented for construction of a separation function in the case of two non-intersecting sets in a Hilbert space. An example illustrating the algorithm usage is given and the results are discussed.

Roberts, M. R.↗

NASA NTRS1986

A numerical study of separation on a spheroid at incidence

The three-dimensional incompressible, steady and laminar flow field around a prolate spheroid at incidence is considered. The parabolized Navier-Stokes equations are solved numerically. The method can handle vortex types as well as bubble type flow separation because the pressure is one of the dependent variables. Here, the distribution of the skin friction is reported for two test cases. The first test case is a prolate spheroid of aspect ratio of 4:1 at 6 degrees incidence and Reynolds number of 1 million (based on half the major axis). The second case is a spheroid with a 6:1 aspect ratio at 10 degrees incidence and Reynolds number of 0.8 x 1 million. The properties of the flow field near the body are discussed on the basis of the pattern of the skin friction lines, and the shape of the separation lines. Favorable agreement with experimental results is obtained.

Rosenfeld, M.↗

NASA NTRS1990

A computational study of incipient leading-edge separation on a 65-deg delta wing at M = 1.60

A computational study on a 65-deg delta wing at a freestream Mach number of 1.60 has been conducted by obtaining conical Reynolds-averaged Navier-Stokes solutions on a parametric series of geometries which varied in leading-edge radius and/or circular-arc camber. The computational results showed that increasing leading-edge radius or camber can delay the onset of leading-edge separation on the leeside of a delta wing at a specific angle of attack. Reynolds number was varied from 1 x 10 to the 6th to 5 x 10 to the 6th for a turbulent boundary-layer and was shown to have a minor effect on the effectiveness of leading-edge radius and/or camber in delaying the onset of leading-edge separation. Both laminar and turbulent boundary-layer models were investigated at a Reynolds number of 1 x 10 to the 6th, and the predicted flow pattern was found to change from attached flow for the turbulent boundary-layer model to separated flow for the laminar boundary-layer model. Based upon these results, three wind-tunnel models have been designed to be tested in the Langley Unitary Plan Wind Tunnel.

Mcmillin, S. Naomi↗

NASA NTRS1984

Teleconnection patterns in the Southern Hemisphere

Contemporaneous correlations between geopotential heights on a given pressure surface at widely separated points on Earth, commonly referred to as teleconnections, are calculated from monthly mean sea level pressure and 500 mb geopotential height analyses for the Southern Hemisphere for five-month winter and summer seasons. During summer (November-March), anomalies over the three continents occur out of phase with anomalies over the subtropical oceans and in a wavenumber 3 pattern over the Southern Ocean near 55 deg S. The subtropical part of the pattern appears largely associated with the interannual variation of the seasonal cycle and annual mean. In winter (May-September) 500 mb geopotential heights over Africa exhibit positive correlations with heights over South America and the central South Pacific near New Zealand and negative correlations with height over the Southern Ocean. A striking wavenumber three pattern is apparent which shows the correlation of 500 mb geopotential height anomalies with 500 mb anomalies at 50 deg S, 95 deg E during winter. The strong positive correlations between 50 deg S, 95 E and 58 deg S, 150 deg W and 38 deg S, 15 deg W contrast with negative correlations over Antarctica and in low latitudes. Time variations in a similar pattern in sea level pressure are in phase with variations in the 500 mb pattern, suggesting an equivalent barotropic structure.

Mo, K. C.↗

DOE OSTI2021

3D Printed, Low Tortuosity Garnet Framework For Beyond 500 Wh/kg Batteries

In this project, we developed LLZO garnet ink recipes and processes for 3D-printing highly ordered ionically conductive garnet porous structures on dense garnet separators. Using this technique, we are able to fabricate controlled architecture LLZO garnet solid-state electrolyte (SSE) trilayers for application in solid-state lithium batteries. The trilayer comprises a thin dense center layer sandwiched between a 3D-printed patterned porous layer and a random porous layer. The dense layer functions as the ionic separator between the anode and cathode. The random porous layer hosts the lithium-metal anode and provides the structural support. The 3D-printed SSE patterned porous layer hosts the cathode, providing continuous, low tortuosity pathways for fast 3D Li+ transport through the cell while increasing the electrode/electrolyte interface area to decrease the interfacial resistance. Compared to the random porous structure, this ordered patterned structure possesses more vacant space for higher cathode loading without sacrificing ionically conducting capability, thus potentially greatly increasing the cell energy density. For demonstration purposes, we developed two patterns for the 3D-printed porous layer: grids and columns, for hosting sulfur and NMC cathode, respectively. The corresponding two types of cells were fabricated and tested, and have demonstrated achievement of theoretical discharge capacity without cathode calendaring. In addition, we developed a fundamental solid-state ionic and electronic transport model to optimize the 3D-printed structures for maximum energy and power density. The model was validated by experiment and provides the critical design criteria for achieving the >500 Wh/kg energy goal as function of C-rate.

25 ENERGY STORAGE↗

DOE OSTI2018

Composite Structures with Emissive Quantum Dots for Light Enhancement

Since their inception, quantum dots have proven to be advantageous for light management applications due to their high brightness and well-controlled absorption, scattering, and emission properties. As quantum dots become commercially available at large scale, the need for robust, stable, and flexible optical components continues to drive the development of robust and flexible quantum dot composite materials. In this review, after a thorough introduction to quantum dots, discussion delves into methods for fabricating quantum dot loaded composite optical elements such as thin films, microfabricated patterns, and microstructures. The importance of surface chemistry and ligand engineering, host matrixes, wet processing, and unique patterning methodologies is presented by considering photostability, aggregation, and phase separation of quantum dots in corresponding composites. With regard to prospective optical applications of quantum dot materials, emphasis is placed on light emitting and guiding composite materials for lasing applications, specifically whispering gallery mode-based photonic microsystems. These developments will enable novel flexible, portable, and miniaturized optoelectronic devices such as light-emitting diodes, flexible pixelated displays, solar cells, large-area microwaveguides, omnidirectional micromirrors, optical metasurfaces, and directional microlasers.

36 MATERIALS SCIENCE↗

DOE OSTI2016

Enhanced Propagating Surface Plasmon Signal Detection

Overcoming the dissipative nature of propagating surface plasmons (PSPs) is pre-requisite to realizing functional plasmonic circuitry, in which large bandwidth signals can be manipulated over length scales far-below the diffraction limit of light. To this end, we report on a novel PSP enhanced signal detection technique achieved in an all-metallic substrate. We take advantage of two strategically spatio-temporally separated phase-locked femtosecond laser pulses, incident onto lithographically patterned PSP coupling structures. We follow PSP propagation with joint femtosecond temporal and nanometer spatial resolution in a time-resolved non-linear photoemission electron microscopy scheme. Initially, a PSP signal wave packet is launched from a hole etched into the silver surface from where it propagates through an open trench structure and is decoded through the use of a timed probe pulse. FDTD calculations demonstrate that PSP signal waves may traverse open trenches in excess of 10 microns in diameter, thereby allowing remote detection even through vacuum regions. This arrangement results in a 10X enhancement in photoemission relative to readout from the bare metal surface. The enhancement is attributed to an all-optical homodyne detection technique that mixes signal and reference PSP waves in a non-linear scheme. Larger readout trenches achieve higher readout levels, however reduced transmission through the trench limits the trench size to 6 microns for maximum readout levels. However, the use of an array of trenches increases the maximum enhancement to near 30X. The attainable enhancement factor may be harnessed to achieve extended coherent PSP propagation in ultrafast plasmonic circuitry.

Environmental Molecular Sciences Laboratory↗

DOE OSTI2017

Light Water Reactor Sustainability Program Potential to Extend the Range of Established Online Monitoring Technologies, Such as Guided Waves in Nuclear Power Plant Systems

The Light Water Reactor Sustainability Program began to evaluate technologies that could be used to perform online monitoring of piping and other secondary system structural components in commercial NPPs. These online monitoring systems have the potential to identify when a more detailed inspection is needed using real-time measurements, rather than at a pre-determined inspection interval. This transition to condition-based, risk informed automated maintenance will contribute to a significant reduction of operations and maintenance costs that account for most nuclear power generation costs. This report describes the current state of research related to ultrasonic guided wave testing and its application to defect detection in commercial nuclear power plants. The report analyses the applicability of the guided wave technology to secondary piping systems and also study the potential for expanding the range of guided wave technology to include bent piping and other piping components. The ultrasonic guided waves can inspect long stretches of straight piping, however more complex geometries such as elbows, welds, and tees are causing spurious reflections and coherent noise which significantly decrease the sensitivity of the technique. The report analyses two approaches to suppression of coherent noise in guided wave systems: advanced signal processing and pattern recognition based on independent component analysis and blind source separation and hardware-based technique of piezoelectric paint which can be used to facilitate the propagation of mechanical stress waves through piping. It is demonstrated on simulated guided wave data that the independent component analysis is capable of separating different coherent noise components and segregating them from useful signal. The piezoelectric paint approach seem to be a viable alternative to the signal processing methods, however it requires significantly more complicated logistics and initial financial outlay. The future efforts will be concentrated on applying the independent component analysis to real-world guided wave data recorded by the guided wave monitoring system installed on the shell of the low-pressure feedwater heater 13A at Exelon Corporation’s Braidwood Nuclear Generating Station. Also, the joint EPRI-INL research efforts will focus on experimental evaluation of piezoelectric paint as a technique to extend the range of guided wave technology.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

NASA NTRS1974

ERTS: A multispectral image analysis contribution for the geomorphological evaluation of southern Maracaibo Lake Basin

Multispectral analysis of ERTS-A images at scales of 1:1,000,000 and 1:500,000 has been conducted with conventional photointerpretation methods. Specific methods have been developed for the geomorphological analysis of southern Maracaibo Lake Basin which comprises part of the Venezuelan Andean Range, Perija Range, the Tachira gap and the Southern part of the Maracaibo Lake depression. A steplike analysis was conducted to separate macroforms, landscapes and relief units as well as drainage patterns and tectonic features, which permitted the delineation of tectonic provinces, stratigraphic units, geomorphologic units and geomorphologic positions. The geomorphologic synthesis obtained compares favorably with conventional analysis made on this area for accuracy of 1:100,000 scale, and in some features with details obtained through conventional analysis for accuracy of 1:15,000 and field work. Geomorphological units in the mountains were identified according to changes in tone, texture, forms orientation of interfluves and tectonic characteristics which control interfluvial disimetrics.

Salas, F.↗

NASA NTRS1975

Photointerpretation of Skylab photography

The author has identified the following significant results. In terms of film grain texture and object definition, the S190B color positive film is distinctly superior to the S190A films, when both are compared in the 9 x 9 inch format. Within the six S190A films, the panchromatic black and white films are superior to the infrared black and white, and the color positive film is superior to the color infrared. Minimum relief differences on the order of 500 to 100 feet could be detected by stereoscopic study, however, it is not possible to determine to what extent vegetation and cultural practices assist in such delineations. Water and wind gaps through major ridges were easily seen. Streams of third order and larger were clearly visible and easy to trace; second order streams were not identified with consistency. Differences in color, tone, and textural patterns rarely supplied clues for differentiating soils or bedrock. The separation of naturally forested areas from areas of cultivation and pasture was effective and a valuable clue to the underlying geology. Suburban and industrial developments were clearly differentiated from urban areas and surrounding agricultural fields. Soil associations could be identified on a regional basis, but no sharp boundary could be drawn separating soil associations.

Mcmurtry, G. J.↗

NASA NTRS1981

Comparison of Michigan Basin crude oils

Michigan Basin oils from the Ordovician Trenton, Silurian Niagaran, and Devonian Dundee formations have been geochemically compared by GC, GC-MS, and carbon isotope mass spectrometry. One oil from each formation was selected for detailed analysis which included measurement of individual n-alkane delta 13 C values. The Ordovician and Devonian oils are strikingly similar to one another, yet clearly different from the Silurian oil. This pattern is unexpected because Ordovician and Devonian reservoirs are physically separated by the Silurian strata. From time-temperature considerations, the Devonian oil probably was formed in older strata and has migrated to its present location. Our analyses suggest a common source for the Devonian and Ordovician oils.

Vogler, E. A.↗

NASA NTRS1982

A possible common origin for the rare gases on Venus, earth, and Mars

The rare gas concentrations in the terrestrial planets and the carbonaceous chondrites could have been derived from a single source an early solar wind. The fractionation processes responsible for the varying concentration patterns in this model are differential ionization and the relative separation of neutrals from ions due to interaction with the solar magnetic field. If species dependent effects are small relative to radius dependent effects, this process can explain in detail both the relative and absolute abundances in the terrestrial planets and carbonaceous chondrites. The electron temperatures predicted by the data are consistent with astrophysical constraints previously derived for the solar nebula, and the timeline of events necessary for this model is consistent with accretion in a gas free environment. If species dependent fractionations are small, or approximately cancel each other, the earth is found to be outgassed by an order of magnitude more efficiently than Venus or Mars.

Hostetler, C. J.↗