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598 records · Page 34
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Preparation and testing of corrosion and spallation-resistant coatings

The goal of this project was to take a recently developed method of bonding oxide dispersion-strengthened (ODS) FeCrAl plating to nickel superalloys closer to commercial use in syngas-fired turbines. The project was designed to better understand and develop the bonding process and to determine if plating APMT®, a specific highly oxidation-resistant ODS FeCrAl alloy made by Kanthal, onto nickel-based superalloy turbine parts is a viable method for substantially improving the lifetimes and maximum use temperatures of the parts. The superalloys investigated for protection were CM247LC and Rene® 80, both alumina scale-forming alloys. The method for bonding the APMT plate to the superalloys is called evaporative metal bonding, which involves placing a thin foil of zinc between the plate and the superalloy, clamping them together, and heating in an atmosphere-controlled furnace. Upon heating, the zinc melts and dissolves the oxide skins of the alloys at the bond line, allowing the two alloys to diffuse into each other. The zinc then diffuses through the alloys and evaporates from their surfaces, creating a bond between the APMT and the superalloy that is stronger than the APMT itself. Testing showed that the diffusivity of zinc in both APMT and CM247LC is quite similar at 700°C but 15 times higher in the APMT at 1214°C. Coefficients of thermal expansion were determined for each of the alloys as a function of temperature. This information was entered into a finite-element model using ANSYS, which was used to design a clamping jig for pressing the APMT to the superalloys at the bonding temperature. Scanning electron microscopy analyses of representative joints showed that no zinc remained in the alloys after bonding Unfortunately, the analyses also showed some small pieces of broken aluminum oxide scale near the bond lines, indicating that its scale was not sufficiently removed during prebonding cleaning. Samples from each of the bonded blocks were sent to Siemens for its standard oxidation, spallation, and corrosion testing, which was scheduled for completion in the spring of 2016. However, because of commercial demands, the tests were not completed by the time of this report except some initial spallation tests at 1150°C. In those tests, several of the APMT plates separated from the CM247LC, likely because of the remaining aluminum oxide scale on the surface of the CM247LC. This implies that surface preparation may need to include machining to remove the oxide scale before bonding rather than just sandblasting. In previous tensile testing at 950°C, the breaks in the tensile samples always occurred in the APMT and not at the joints. Gasifier sampling was completed to determine what types of trace contaminants may occur in cleaned and combusted syngas and that could lead to corrosion or deposition in turbines firing coal syngas. The sampling was done from a pressurized fluidized-bed gasifier and a pressurized entrained-flow gasifier. The particles captured on a filter from syngas were typically 0.2 to 0.5 μm in diameter, whereas those captured from the combusted syngas were slightly larger and more spherical. X-ray photoelectron spectroscopy done at Oak Ridge National Laboratory showed that the particles do not contain any metals and have an atomic composition almost identical to that of the polycarbonate filter. This indicates that the particles are primarily soot-based and not formed from volatilization of metals in the gasifiers.

20 FOSSIL-FUELED POWER PLANTS↗
DOE OSTI2018

Layered Atlantic Smoke Interactions with Clouds (LASIC) Field Campaign Report

Southern Africa is the world’s largest emitter of biomass burning aerosols. Their westward transport over the remote southeast Atlantic Ocean co-locates some of the largest atmospheric loadings of absorbing aerosol with the least examined of the Earth’s major subtropical stratocumulus decks. Global aerosol model results highlight that the largest positive top-of-atmosphere (TOA) forcing in the world occurs in the southeast Atlantic, but this region exhibits large differences in magnitude and sign between reputable models, in part because of high variability in the underlying model cloud distributions. Many uncertainties contribute to the highly variable model radiation fields: the aging of the shortwave-absorbing aerosol during transport, how much of the aerosol mixes into the cloudy boundary layer, and how the low clouds adjust to smoke-radiation and smoke-cloud interactions. In addition, the ability of the biomass burning aerosol to absorb shortwave radiation is known to vary seasonally as the fuel type on land changes. LASIC (Layered Atlantic Smoke Interactions with Clouds) is a strategy to improve our understanding of aged carbonaceous aerosol, its seasonal evolution, and the mechanisms by which clouds adjust to the presence of the aerosol. The observational strategy centers on deploying the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility first ARM Mobile Facility (AMF1) cloud, aerosol, and atmospheric profiling instrumentation to Ascension Island, located within the trade-wind shallow cumulus regime (14.50W, 80S) 3000 km offshore of continental Africa. The location is within the latitude zone of the maximum outflow of aerosol, with the deepening boundary layer known to entrain free-tropospheric smoke. The primary activities for LASIC are: 1) to improve current knowledge on aged biomass burning aerosol and its radiative properties as a function of the seasonal cycle; 2) to use surface-based remote sensing to sensitively interrogate the atmosphere for the relative vertical location of aerosol and clouds; 3) to improve our understanding of the cloud adjustments to the presence of shortwave-absorbing aerosol within the vertical column, both through aerosol-radiation and through aerosol-cloud interactions; 4) to aid low cloud parameterization efforts for climate models. The measurements span June 1, 2016-October 31, 2017, encompassing two July-October biomass burning seasons. The August-September, 2016, months include an intensive operational period (IOP) with 8x/daily radiosondes. In 2017, from 16 August through 7 September, the United Kingdom Facility for Airborne Atmospheric Measurements (FAAM) BAe-146 plane was deployed from Ascension, providing complementary data on the atmosphere’s vertical structure as part of the Cloud-Aerosol-Radiation Interactions and Forcing (CLARIFY) project, with similar scientific goals. The National Aeronautics and Space Administration (NASA) Observations of Clouds above Aerosols and their Interactions (ORACLES) aircraft campaign, sharing similar objectives to LASIC, deployed from Namibia in September, 2016, and Sao Tome in August, 2017. The latter included a suitcase flight to Ascension spanning August 18-21. In 2017 a cavity-attenuated phase shift single-scattering albedo (CAPS-SSA) instrument belonging to Aerodyne was brought to Ascension, gathering data primarily for August, towards providing a second, independent measurement of aerosol absorption. Ascension Island is also an Aerosol Robotic Network (AERONET) site.

biomass burning, aerosols, black carbon, boundary-↗
NASA NTRS2017

Computational Modeling to Limit the Impact Displays and Indicator Lights Have on Habitable Volume Operational Lighting Constraints

NASA has demonstrated an interest in improving astronaut health and performance through the installment of a new lighting countermeasure on the International Space Station. The Solid State Lighting Assembly (SSLA) system is designed to positively influence astronaut health by providing a daily change to light spectrum to improve circadian entrainment. Unfortunately, existing NASA standards and requirements define ambient light level requirements for crew sleep and other tasks, yet the number of light-emitting diode (LED) indicators and displays within a habitable volume is currently uncontrolled. Because each of these light sources has its own unique spectral properties, the additive lighting environment ends up becoming something different from what was planned or researched. Restricting the use of displays and indicators is not a solution because these systems provide beneficial feedback to the crew. The research team for this grant used computer-based computational modeling and real-world lighting mockups to document the impact that light sources other than the ambient lighting system contribute to the ambient spectral lighting environment. In particular, the team was focused on understanding the impacts of long-term tasks located in front of avionics or computer displays. The team also wanted to understand options for mitigating the changes to the ambient light spectrum in the interest of maintaining the performance of a lighting countermeasure. The project utilized a variety of physical and computer-based simulations to determine direct relationships between system implementation and light spectrum. Using real-world data, computer models were built in the commercially available optics analysis software Zemax Optics Studio(c). The team also built a mockup test facility that had the same volume and configuration as one of the Zemax models. The team collected over 1200 spectral irradiance measurements, each representing a different configuration of the mockup. Analysis of the data showed a measurable impact on ambient light spectrum. This data showed that obvious design techniques exist that can be used to bind the ambient light spectrum closer to the planned spectral operating environment for the observer's eye point. The following observations should be considered when designing an operational environment that is dominated by computer displays. When more light is directed into the field of view of the observer, the greater the impact it will make on various human factors issues that depend on spectral shape and intensity. Because viewing angle has a large part to play in the amount of light flux on the crewmember's retina, beam shape, combined with light source location is an important factor for determining percent probable incident flux on the observer from any combination of light sources. Computer graphics design and display lumen output are major factors influencing the amount of spectrally intense light projected into the environment and in the viewer's direction. Use of adjustable white point display software was useful only if the predominant background color was white and if it matched the ambient light system's color. Display graphics that used a predominantly black background had the least influence on unplanned spectral energy projected into the environment. Percent reflectance makes a difference in total energy reflected back into an environment, and within certain architectural geometries, reflectance can be used to control the amount of a light spectrum that is allowed to perpetuate in the environment. Data showed that room volume and distance from significant light sources influence the total spectrum in a room. Smaller environments had a homogenizing effect on total light spectrum, whereas light from multiple sources in larger environments was less mixed. The findings indicated above should be considered when making recommendations for practice or standards for architectural systems. The ambient lighting system, surface reflectance, and display and indicator implementation all factor into the users' spectral environment. A variety of low-cost solutions exist to mitigate the impact of light from non-architectural lighting systems, and much potential for system automation and integration of display systems with the ambient environment. This team believes that proper planning can be used to avoid integration problems and also believes that human-in-the-loop evaluations, real-world test and measurement, and computer modeling can be used to determine how changes to a process, display graphics, and architecture will help maintain the planned spectral operating lighting environment.

Clark, T. A.↗
DOE OSTI2019

Improving perfusion defect detection with respiratory motion correction in cardiac SPECT at standard and reduced doses

Background: In cardiac SPECT perfusion imaging, respiratory motion can cause non-uniform blurring in the reconstructed myocardium. We investigate the potential benefit of respiratory correction with respiratory-binned acquisitions, both at standard dose and at reduced dose, for defect detection and for left ventricular (LV) wall resolution. Methods: We applied two reconstruction methods for respiratory motion correction: post-reconstruction motion correction (PMC) and motion-compensated reconstruction (MCR), and compared with reconstruction without motion correction (Non-MC). We quantified the presence of perfusion defects in reconstructed images by using the total perfusion deficit (TPD) scores and conducted receiver-operating-characteristic (ROC) studies using TPD. We quantified the LV spatial resolution by using the FWHM of its cross-sectional intensity profile. Results: The values in the area-under-the-ROC-curve (AUC) achieved by MCR, PMC, and Non-MC at standard dose were 0.835, 0.830, and 0.798, respectively. Similar AUC improvements were also obtained by MCR and PMC over Non-MC at 50%, 25%, and 12.5% of full dose. Improvements in LV resolution were also observed with motion correction. Conclusions: Respiratory-binned acquisitions can improve perfusion-defect detection accuracy over traditional reconstruction both at standard dose and at reduced dose. Motion correction may contribute to achieving further dose reduction while maintaining the diagnostic accuracy of traditional acquisitions. [French] French Abstract: Contexte: Les mouvements respiratoires peuvent entrainer des artefacts de uniformité lors de la reconstruction des images de perfusion myocardique en SPECT. Dans cet article, nous rapportons nos résultats sur le bénéfice potentiel du « gating » respiratoire avec des doses standards et réduites de radio-pharmaceutiques pour la détection des anomalies de perfusion et les mesures de la paroi ventriculaire gauche. Méthodes: Nous avons appliqué deux méthodes de reconstruction pour la correction du mouvement respiratoire: la première fait appel a une correction après reconstruction des images (PMC) ; la seconde fait appel à la correction des images avant reconstruction (MRC). Les deux approches ont été comparées à la reconstruction sans correction de mouvement (Non-MC). Nous avons quantifié les déficits de perfusion myocardiques sur les images reconstruites avec le système des scores de déficit de perfusion et analysé les résultats en utilisant les courbes ROC. Nous avons quantifié la résolution spatiale du VG en utilisant le FWHM du profil d’intensité de sa section transversale. Résultats: Les valeurs des surfaces en dessous des courbes ROC (AUC) obtenues par MCR, PMC et Non-MC avec doses standard de radio-pharmaceutiques étaient de 0,835, 0,830 et 0,798, respectivement. Des améliorations similaires de l’AUC ont également été obtenues par MCR et PMC sur Non-MC avec 50%, 25% et 12,5% des doses entières. Les mesures de résolution spatiale de la paroi du VG ont également été améliorées avec la correction des mouvements respiratoires. Conclusions: La correction des images de perfusion myocardiques en SPECT par « gating » respiratoire paraît améliorer la quantification des déficits perfusionels à la fois à dose standard et à dose réduite de radio-pharmaceutiques. L’application de cette correction devrait permettre de réduire les doses de radio-pharmaceutiques utilisées tout en maintenant la précision diagnostique des acquisitions traditionnelles. [Spanish] Spanish Abstract: Antecedentes: En los estudios de perfusión cardiaca por SPECT, los movimientos respiratorios pueden causar distorsión no uniforme en el miocardio reconstruido. Investigamos el beneficio potencial de la corrección respiratoria con adquisición de imágenes sincronizadas con la respiración, tanto a dosis estándar como a dosis reducida, para detección de defectos y para resolución de pared de ventrículo izquierdo (VI). Métodos: Aplicamos dos métodos de reconstrucción para corrección de movimientos respiratorios: Corrección de movimiento post reconstrucción (PMC) y reconstrucción compensada a movimiento (MCR), y los comparamos con la reconstrucción sin corrección de movimiento (Non-MC). Cuantificamos la presencia de defectos de perfusión en las imágenes reconstruidas usando los scores de déficit total de perfusión (TPD) y análisis ROC usando el TPD. Cuantificamos la resolución espacial del VI usando la anchura a media altura de su perfil de intensidad transversal. Resultados: Los valores en el área bajo la curva ROC (ABC) obtenidos por MCR, PMC y Non-MC a dosis estándar fueron 0.835, 0.830 y 0.798, respectivamente. Mejorías similares del ABC también se obtuvieron por MCR y PMC, sobre Non-MC a 50%, 25% y 12.5% de la dosis completa. Las mejorías en la resolución del VI fueron observadas también con corrección del movimiento. Conclusiones: Las adquisiciones sincronizadas con la respiración pueden mejorar la precisión de la detección de defectos de perfusión sobre las reconstrucciones tradicionales tanto a dosis estándar como a dosis reducida. La corrección de movimiento puede contribuir a lograr mayor reducción de la dosis manteniendo la precisión diagnóstica de las adquisiciones tradicionales. [Chinese] Chinese Abstract: 背景: 在心脏 SPECT 灌注成像中, 呼吸运动会导致心肌重建的不均匀模糊。我们研究了无论是标准剂量还是减少剂量的情况下, 呼吸跟踪采集的呼吸校正用于图像缺损检测和左心室 (LV) 室壁分辨率的潜在益处。 方法: 我们使用了两种呼吸运动校正的重建方法:重建后运动校正 (PMC) 和运动补偿重建 (MCR), 并与没有运动校正的重建 (Non-MC) 进行比较。 通过总灌注缺损 (TPD) 评分和其接受者操作特性曲线 (ROC) 来量化重建图像中的灌注缺陷。通过LV横截面强度分布的 FWHM来量化 LV 空间分辨率。 结果: MCR, PMC 和 Non-MC 在标准剂量下所获得的 ROC 曲线下面积 (AUC) 的值分别为0.835, 0.830 和 0.798。 在全剂量下, MCR, PMC和 Non-MC也获得类似的 AUC 提高, 分别为 50%, 25% 和 12.5%。 在运动校正下, LV的分辨率也得到了改善。 结论: 在标准剂量和减少剂量的情况下, 呼吸跟踪采集可以改善灌注缺损检测的准确性。 运动校正可能有助于进一步实现减少剂量的目标, 同时保证通过传统检测方法的诊断准确性。.

62 RADIOLOGY AND NUCLEAR MEDICINE↗