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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 1,117 records · Page 62
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Unravelling donor–acceptor film morphology formation for environmentally-friendly OPV ink formulations

The challenge of coating organic photovoltaics (OPV) from green solvents is to achieve the required nanostructured interpenetrating network of donor and acceptor domains based on a rational choice of solvent approach as opposed to the usual trial-and-error methods. We demonstrate here that we can achieve a bicontinuous interpenetrating network with nanoscale phase separation for the chosen donor–acceptor material system poly[2,3-bis-(3-octyloxyphenyl)quinoxaline-5,8-diyl-alt-thiophene-2,5-diyl]:phenyl-C 61 butyric acid methyl ester (TQ1:PC 61 BM) when processing from green solvent ink formulations. This structure is achieved by first calculating the Hansen solubility parameters (HSP) of the donor and acceptor materials, followed by careful choice of solvents with selective relative solubilities for the two materials based on the desired order of precipitation necessary for forming a nanostructured interdigitated network morphology. We found that the relative distances in Hansen space (R a ) between TQ1 and the primary solvent, on the one hand, and PC 61 BM and the primary solvent, on the other hand, could be correlated to the donor–acceptor morphology for the formulations based on the solvents d-limonene, anisole, and 2-methyl anisole, as well as the halogenated reference solvent o-dichlorobenzene. This nanostructured blend film morphology was characterised with scanning transmission X-ray microscopy (STXM) and transmission electron microscopy (TEM), and the film surface composition was analysed by near edge X-ray absorption fine structure (NEXAFS) spectroscopy. Hansen solubility theory, based on solution thermodynamics, has been used and we propose an HSP-based method that is a general platform for the rational design of ink formulations for solution-based organic electronics, in particular facilitating the green solvent transition of organic photovoltaics. Our results show that the bulk heterojunction morphology for a donor–acceptor system processed from customised solvent mixtures can be predicted by the HSP-based method with good reliability.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1974

Effect of trailing-edge flap deflection on the lateral and longitudinal-stability characteristics of a supersonic transport model having a highly-swept arrow wing

A low-speed investigation has been made on a highly-swept wing model having a thickened leading edge to determine the effect of inboard trailing-edge flaps on the characteristics of the model in pitch and sideslip. The tests were made at a Mach number of 0.227 which corresponds to a Reynolds number of about 5.53 million based on the reference chord. The results showed that deflection of the trailing-edge flaps decreased the roll due to sideslip by about 20 percent at a landing lift coefficient of 0.5. The directional-stability parameter, was increased by deflection of the flaps and the range of lift coefficients over which it was positive was also increased. The longitudinal stability characteristics of the model without leading-edge devices were improved by increased flap deflection, that is, the pitch-up tendency was delayed to higher lift coefficients. The lift coefficient increment resulting from the 15 deg flap deflection compared favorably with that predicted.

Lockwood, V. E.↗
DOE OSTI2016

Toroidal silicon polarization analyzer for resonant inelastic x-ray scattering

Resonant Inelastic X-ray Scattering (RIXS) is a powerful probe for studying electronic excitations in materials. Standard high energy RIXS measurements do not measure the polarization of the scattered x-rays, which is unfortunate since it carries information about the nature and symmetry of the excitations involved in the scattering process. Here we report the fabrication of thin Si-based polarization analyzers with a double-concave toroidal surface, useful for L-edge RIXS studies in heavier atoms such as the 5-d transition metals.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1998

Effects of Nose Radius and Aerodynamic Loading on Leading Edge Receptivity

An analysis is presented of the effects of airfoil thickness and mean aerodynamic loading on boundary-layer receptivity in the leading-edge region. The case of acoustic free-stream disturbances, incident on a thin cambered airfoil with a parabolic leading edge in a low Mach number flow, is considered. An asymptotic analysis based on large Reynolds number is developed, supplemented by numerical results. The airfoil thickness distribution enters the theory through a Strouhal number based on the nose radius of the airfoil, S = (omega)tau(sub n)/U, where omega is the frequency of the acoustic wave and U is the mean flow speed. The influence of mean aerodynamic loading enters through an effective angle-of-attack parameter ti, related to flow around the leading edge from the lower surface to the upper. The variation of the receptivity level is analyzed as a function of S, mu, and characteristics of the free-stream acoustic wave. For an unloaded leading edge, a finite nose radius dramatically reduces the receptivity level compared to that for a flat plate, the amplitude of the instability waves in the boundary layer being decreased by an order of magnitude when S = 0.3. Modest levels of aerodynamic loading are found to further decrease the receptivity level for the upper surface of the airfoil, while an increase in receptivity level occurs for the lower surface. For larger angles of attack close to the critical angle for boundary layer separation, a local rise in the receptivity level occurs for the upper surface, while for the lower surface the receptivity decreases. The effects of aerodynamic loading are more pronounced at larger values of S. Oblique acoustic waves produce much higher receptivity levels than acoustic waves propagating downstream parallel to the airfoil chord.

Hammerton, P. W.↗
NASA NTRS2004

Modifying Ship Air-Wake Vortices for Aircraft Operations

Columnar-vortex generators (CVG) have been proposed as means to increase the safety of takeoffs and landings of aircraft on aircraft or helicopter carriers and other ships at sea. According to the proposal, CVGs would be installed at critical edge locations on ships to modify the vortices in the air wakes of the ships. The desired effects of modifications are to smooth airflows over takeoff and landing deck areas and divert vortices from takeoff and landing flight paths. With respect to aircraft operations, the wake flows of primary interest are those associated with the bow and side edges of aircraft-carrier decks and with superstructures of ships in general (see Figure 1). The bow and deck-edge vortices can adversely affect airplane and helicopter operations on carriers, while the superstructure wakes can primarily affect operations of helicopters. The concept of the CVG is not new; what is new is the proposed addition of CVGs to ship structures to effect favorable modifications of air wakes. Figure 2 depicts a basic CVG, vertical and horizontal CVGs installed on a simple superstructure, and horizontal CVGs installed on the bow and deck edges. The vertical CVGs would be closed at the deck but open at the top. Each horizontal CVG would be open at both ends. The dimensions of the CVGs installed on the aft edges of the superstructure would be chosen so that the portion of the flow modified by the vertical CVGs would interact synergistically with the portion of the flow modified by the horizontal CVG to move the air wake away from the takeoff-and-landing zone behind the superstructure. The deck-edge CVGs would be mounted flush with, and would extend slightly ahead of the bow of, the flight deck. The overall length of each tube would exceed that of the flight deck. Each deck-edge CVG would capture that portion of the airflow that generates a deck-edge vortex and would generate a columnar vortex of opposite sense to that of the unmodified vortex. The vortex generated by the CVG could be dispersed at its base, thereby removing unwanted turbulence in the path of an approaching airplane. The deck-edge CVGs would promote smooth flow over the entire flight deck. In the case of a Nimitz-class aircraft carrier like that of Figure 1, there would be a CVG on each of the outer edges of the two left portions of the flight deck and a single CVG on the right side of the flight deck. The forward-most CVG on the left side would take the generated vortex underneath the angled flight deck. A CVG could also be installed on the bow of the flight deck to smooth the flow of air onto the flight deck. In the case of wind incident on the deck from an azimuth other than straight ahead, the vortex generated by the bow CVG could, perhaps, be used to feed the CVG(s) of the leeward side edge of the flight deck.

Lamar, John E.↗
DOE OSTI2013

The use of computed radiography plates to determine light and radiation field coincidence

Purpose: Photo-stimulable phosphor computed radiography (CR) has characteristics that allow the output to be manipulated by both radiation and optical light. The authors have developed a method that uses these characteristics to carry out radiation field and light field coincidence quality assurance on linear accelerators.Methods: CR detectors from Kodak were used outside their cassettes to measure both radiation and light field edges from a Varian linear accelerator. The CR detector was first exposed to a radiation field and then to a slightly smaller light field. The light impinged on the detector's latent image, removing to an extent the portion exposed to the light field. The detector was then digitally scanned. A MATLAB-based algorithm was developed to automatically analyze the images and determine the edges of the light and radiation fields, the vector between the field centers, and the crosshair center. Radiographic film was also used as a control to confirm the radiation field size.Results: Analysis showed a high degree of repeatability with the proposed method. Results between the proposed method and radiographic film showed excellent agreement of the radiation field. The effect of varying monitor units and light exposure time was tested and found to be very small. Radiation and light field sizes were determined with an uncertainty of less than 1 mm, and light and crosshair centers were determined within 0.1 mm.Conclusions: A new method was developed to digitally determine the radiation and light field size using CR photo-stimulable phosphor plates. The method is quick and reproducible, allowing for the streamlined and robust assessment of light and radiation field coincidence, with no observer interpretation needed.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2015

SU-E-J-140: Simulation Study Using Thermoacoustics to Image Proton Dose and Range in Water and Skull Phantom

Purpose: In this study, thermoacoustic pressure signals generated from a proton beam were simulated in water and currently within a skull phantom to investigate the sensitivity of radioacoustic CT imaging in the brain. Methods: Thermoacoustically generated pressure signals from a pulse pencil proton beam (12, 15, 20, and 27cm range) were simulated in water. These simulated pressure signal are detected using a (71) transducer array placed along the surface of a cylinder (30cm × 40cm) and rotated over 2π (in 2 degree increments), where the normal vector to the surface of each transducer intersects the isocenter of the scanner. Currently, a software skull phantom is positioned at isocenter, where the scattering, absorption and speed of dispersion of the thermoacoustic signal through a three layer cortical-trabecular-cortical structure is being simulated. Based on data obtained from the literature, the effects of acoustic attenuation and speed-of-sound (dispersion) will be applied within the 3D FBP algorithm to obtain dosimetric images. Results: Based on hydrophone detector specifications, a 0.5MHz bandwidth and 50dB re 1μPa per Hz^1/2, a 1.6cGy sensitivity at the Bragg peak was demonstrated while maintaining a 1.0 mm (FWHM) range resolution along the central axis of the beam. Utilizing this same information, the integral dose within the Bragg peak and distal edge compared to MC had a 2% (statistical) and 5% voxel-based RMS at this same dose sensitivity. We plan to present preliminary data determining the range sensitivity for a head phantom for this scanner design and the feasibility of imaging the proton dose in patients with a brain tumor undergoing therapy. Conclusion: RACT scanner provides 3D dosimetric images with 1.6cGy (Bragg peak) sensitivity with 1mm range sensitivity. Simulations will be performed to determine feasibility to treat brain cancer patients.

60 APPLIED LIFE SCIENCES↗
NASA NTRS1978

A study of axial compressor blade optimization for operation in the low Reynolds number regime

Original and previously published experimental data is presented in this study of axial compressor blade optimization for use in the subcritical Reynolds number region. Three methods of increasing cascade performance at these low Rc are presented, discussed, and compared: (1) use of sharp-leading-edge profiles, (2) trip wires or roughness elements, and (3) high free-stream turbulence. The original data was collected in the VKI C-1 cascade wind tunnel; during these tests blade chord Reynolds number was varied from 250,000 down to about 17,000. Each technique demonstrated an increase in low Reynolds number (based on chord) performance for certain profiles, with the sharp-leading-edge profile as the potential optimum. Axial compressors or pumps that must operate for a significant amount of their design life under low Reynolds number conditions might benefit substantially from these methods.

Roberts, W. B.↗
DOE OSTI2016

Enabling the democratization of the genomics revolution with a fully integrated web-based bioinformatics platform

Continued advancements in sequencing technologies have fueled the development of new sequencing applications and promise to flood current databases with raw data. A number of factors prevent the seamless and easy use of these data, including the breadth of project goals, the wide array of tools that individually perform fractions of any given analysis, the large number of associated software/hardware dependencies, and the detailed expertise required to perform these analyses. To address these issues, we have developed an intuitive web-based environment with a wide assortment of integrated and cutting-edge bioinformatics tools in pre-configured workflows. These workflows, coupled with the ease of use of the environment, provide even novice next-generation sequencing users with the ability to perform many complex analyses with only a few mouse clicks and, within the context of the same environment, to visualize and further interrogate their results. As a result, this bioinformatics platform is an initial attempt at Empowering the Development of Genomics Expertise (EDGE) in a wide range of applications for microbial research.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1985

Aerodynamic characteristics of a distinct wing-body configuration at Mach 6: Experiment, theory, and the hypersonic isolation principle

An experimental investigation has been conducted to determine the effect of wing leading edge sweep and wing translation on the aerodynamic characteristics of a wing body configuration at a free stream Mach number of about 6 and Reynolds number (based on body length) of 17.9 x 10 to the 6th power. Seven wings with leading edge sweep angles from -20 deg to 60 deg were tested on a common body over an angle of attack range from -12 deg to 10 deg. All wings had a common span, aspect ratio, taper ratio, planform area, and thickness ratio. Wings were translated longitudinally on the body to make tests possible with the total and exposed mean aerodynamic chords located at a fixed body station. Aerodynamic forces were found to be independent of wing sweep and translation, and pitching moments were constant when the exposed wing mean aerodynamic chord was located at a fixed body station. Thus, the Hypersonic Isolation Principle was verified. Theory applied with tangent wedge pressures on the wing and tangent cone pressures on the body provided excellent predictions of aerodynamic force coefficients but poor estimates of moment coefficients.

Penland, J. A.↗
NASA NTRS2003

An Automated Cloud-edge Detection Algorithm Using Cloud Physics and Radar Data

An automated cloud edge detection algorithm was developed and extensively tested. The algorithm uses in-situ cloud physics data measured by a research aircraft coupled with ground-based weather radar measurements to determine whether the aircraft is in or out of cloud. Cloud edges are determined when the in/out state changes, subject to a hysteresis constraint. The hysteresis constraint prevents isolated transient cloud puffs or data dropouts from being identified as cloud boundaries. The algorithm was verified by detailed manual examination of the data set in comparison to the results from application of the automated algorithm.

Ward, Jennifer G.↗
NASA NTRS1987

Solid modelling for the manipulative robot arm (power) and adaptive vision control for space station missions

The structure of a flexible arm derived from concatenation of the Stewart-Table-based links were studied. Solid modeling provides not only a realistic simulation, but is also essential for studying vision algorithms. These algorithms could be used for the adaptive control of the arm, using the well-known algorithms such as shape from shading, edge detection, orientation, etc. Details of solid modeling and its relation to vision based adaptive control are discussed.

Harrand, V.↗
DOE OSTI2023

Classifying metal‐binding sites with neural networks

Abstract To advance our ability to predict impacts of the protein scaffold on catalysis, robust classification schemes to define features of proteins that will influence reactivity are needed. One of these features is a protein's metal‐binding ability, as metals are critical to catalytic conversion by metalloenzymes. As a step toward realizing this goal, we used convolutional neural networks (CNNs) to enable the classification of a metal cofactor binding pocket within a protein scaffold. CNNs enable images to be classified based on multiple levels of detail in the image, from edges and corners to entire objects, and can provide rapid classification. First, six CNN models were fine‐tuned to classify the 20 standard amino acids to choose a performant model for amino acid classification. This model was then trained in two parallel efforts: to classify a 2D image of the environment within a given radius of the central metal binding site, either an Fe ion or a [2Fe‐2S] cofactor, with the metal visible (effort 1) or the metal hidden (effort 2). We further used two sub‐classifications of the [2Fe‐2S] cofactor: (1) a standard [2Fe‐2S] cofactor and (2) a Rieske [2Fe‐2S] cofactor. The accuracy for the model correctly identifying all three defined features was >95%, despite our perception of the increased challenge of the metalloenzyme identification. This demonstrates that machine learning methodology to classify and distinguish similar metal‐binding sites, even in the absence of a visible cofactor, is indeed possible and offers an additional tool for metal‐binding site identification in proteins.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2017

Temperature and radiation effects at the fluorine K-edge in LiF

Here, the fluorine K-edge of LiF is studied both experimentally and theoretically as a function of temperature. Instantaneous thermal fluctuations in atomic positions are shown in molecular dynamics simulations to increase in amplitude from 0.029 to 0.064 nm in the temperature range from 40 to 298 K. This is sufficient to cause instantaneous deviations from local octahedral atomic symmetry in this rock-salt crystal, resulting in altered electronic structure. The lowered symmetry of the lowest core-excited states of fluorine atoms is evident in X-ray absorption spectra at the F K-edge. In addition, sufficient radiation exposure produces a new X-ray absorption peak, below the F K-edge of LiF, which is assigned to defects in LiF based on both calculations and comparison to previous experiments.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

Effects of rare earth substitution on the optical properties of Bi{sub 2}MoO{sub 6} for coloring applications

Highlights: • New class of colored compounds BiREMoO{sub 6} (RE = Pr, Nd, Sm, Tb, Yb) was synthesized. • The substitution of RE gently red shifts the absorption edge to low energy side. • The differences in band gap depend on the position of the RE f bands. • The yellow colored compounds demonstrated good coloration to plastics. - Abstract: A new class of colored inorganic compounds, BiREMoO{sub 6} (RE = Pr, Nd, Sm, Tb and Yb) has been synthesized by a solid state route. The substitution of different rare earths for Bi{sup 3+} in Bi{sub 2}MoO{sub 6} produces visible light responsive compounds by gently red shifting the absorption edge to low energy side. The visible light absorption is based on the charge transfer transitions from O{sub 2p} valence band to conduction band made of primary Mo{sub 4d} and secondary Bi{sub 6p}. The substitution of RE{sup 3+} introduces partially occupied 4f electronic levels in between the band gap and the position of 4f level depend on the number of f electrons which allows tuning the band gap. Thus the rare earth substitution provides an opportunity to tailor the band gap of Bi{sub 2}MoO{sub 6} from 2.99 eV to 2.19 eV. The developed compounds exhibited different shades of yellow hue and demonstrated good coloration to plastics.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Resonant inelastic X-ray scattering tools to count 5 $f$ electrons of actinides and probe bond covalency

The actinides possess a complex electronic structure, making their chemical and physical properties among the least understood in the periodic table. Advanced spectroscopic tools, able to obtain deep insights into the electronic structure and binding properties of the actinides, are highly desirable. Here, we introduce two sensitive spectroscopic tools: one determines the number of localized 5f electrons on an actinide atom, and another assesses the covalent character of actinide-ligand bonding. Both tools are based on the multiplet structure present in actinide M 4 edge core-to-core resonant inelastic X-ray scattering (CC-RIXS) maps. The spectral intensity of different many-body final-state multiplets directly depends on the local many-electron ground-state symmetry including the local 5 f spin configuration. By comparing U M 4 edge CC-RIXS data for 21 U, Np, Pu and Am compounds, we demonstrate the ability to compare the number of localized 5 f electrons and bond covalency across the actinide series.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2025

A Compact Topological Microwave Isolator

A central goal of topological photonics has been to develop compact isolators using protected, non-reciprocal edge states. Furthermore, a recent demonstration of a ferrite-based microwave isolator leverages the magnon-induced topological photonic bandgap to achieve over 100 dB of isolation in a device smaller than a single free-space wavelength.

Magneto-optics↗
DOE OSTI2024

Observation of magnetic islands in tokamak plasmas during the suppression of edge-localized modes

In tokamaks, a leading platform for fusion energy, periodic filamentary plasma eruptions known as edge-localized modes occur in plasmas with high-energy confinement and steep pressure profiles at the plasma edge. These edge-localized modes could damage the tokamak wall but can be suppressed using small three-dimensional magnetic perturbations. Here we demonstrate that these magnetic perturbations can change the magnetic topology just inside the steep gradient region of the plasma edge. We identify signatures of a magnetic island, and their observation is linked to the suppression of edge-localized modes. We compare high-resolution measurements of perturbed magnetic surfaces with predictions from ideal magnetohydrodynamic theory where the magnetic topology is preserved. Although ideal magnetohydrodynamics adequately describes the measurements in plasmas exhibiting edge-localized modes, it proves insufficient for plasmas where these modes are suppressed. Nonlinear resistive magnetohydrodynamic modelling supports this observation. Our study experimentally confirms the predicted role of magnetic islands in inhibiting the occurrence of edge-localized modes. This will be beneficial for physics-based predictions in future fusion devices to control these modes.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗