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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Pressure loss modulus correlation for Delta p across uniformly distributed-loss devices

A dimensionless group, called a pressure loss modulus (N(sub PL)), is introduced that, in conjunction with an appropriately defined Reynolds number, is of considerable engineering utility in correlating steady-state Delta p vs flow calibration data and subsequently as a predictor, using the same or a different fluid, in uniformly distributed pressure loss devices. It is particularly useful under operation in the transition regime. Applications of this simple bivariate correlation to three diverse devices of particular interest for small liquid rocket engine fluid systems are discussed: large L/D capillary tube restrictors, packed granular catalyst beds, and stacked vortex-loss disk restrictors.

Nunz, Gregory J.↗
DOE OSTI2017

Unravelling the origin of irreversible capacity loss in NaNiO 2 for high voltage sodium ion batteries

Layered transition metal compounds have attracted much attention due to their high theoretical capacity and energy density for sodium ion batteries. However, this kind of material suffers from serious irreversible capacity decay during the charge and discharge process. Here, using synchrotron-based operando transmission X-ray microscopy and high-energy X-ray diffraction combined with electrochemical measurements, the visualization of the dissymmetric phase transformation and structure evolution mechanism of layered NaNiO2 material during initial charge and discharge cycles are clarified. Phase transformation and deformation of NaNiO2 during the voltage range of below 3.0 V and over 4.0 V are responsible for the irreversible capacity loss during the first cycling, which is also confirmed by the evolution of reaction kinetics behavior obtained by the galvanostatic intermittent titration technique. These findings reveal the origin of the irreversibility of NaNiO2 and offer valuable insight into the phase transformation mechanism, which will provide underlying guidance for further development of high-performance sodium ion batteries.

high voltage↗
DOE OSTI2022

Overall Performance Losses and Activated Mechanisms in Double Glass and Glass-backsheet Photovoltaic Modules with Monofacial and Bifacial PERC Cells, under Accelerated Exposures

Commercial PV modules have various packaging choices nowadays, which influence their long-term reliability. This study compared the degradation behaviors of sixteen module variants from two brands with varying encapsulant materials (EVA or POE), encapsulant types, module architectures (GB or DG), and cell types (monofacial or bifacial) using null hypothesis testing to determine statistical significant findings. The modules were exposed for 2,520 hours under two accelerated exposures: modified damp heat (mDH) and modified damp heat with full-spectrum light (mDH+FSL). For both brands, two DG module variants with UV-Cutoff rear encapsulant are found to have significantly lower average power loss than the module variants of EVA+GB with opaque rear encapsulant after each accelerated exposure. Metallization interconnect corrosion is identified as the primary degradation mechanism. Furthermore, unsupervised hierarchical clustering finds that the degradation behaviors of modules from one brand with a more strict manufacturing quality control depends on module architectures only.

14 SOLAR ENERGY↗
DOE OSTI2023

Differentiating the bonding states in calcium carbonate polymorphs by low-loss electron-energy-loss spectroscopy

Calcium carbonate is one of the important building components in organisms, especially the two most common polymorphs, calcite and aragonite. Here, to understand the difference in bonding state, the two polymorphs are characterized by valence (low-loss) electron energy loss spectroscopy. It is found that the difference in Ca M 23 edge originating from 3p to 3d states is consistent with the change of Ca-O bonds in the two studied polymorphs. Surprisingly, the measured Ca M 23 edge is in qualitative agreement with the calculated partial density of states (PDOS) of Ca-d states in contrast to their L edges (from 2p to 3d states) which are strongly influenced by atomic multiplet effect (spin-orbit coupling). This is because the atomic multiplet effect is much reduced for the Ca 3p orbital, which permits the corresponding Ca M 23 edge to be compared with the PDOS results. Our findings show insights that PDOS can potentially be used to interpret the M 23 edge of lighter 3d transition metals such as scandium, titanium, vanadium and chromium when such interpretation may not be achieved for their L edges.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Impacts of coastal reclamation on wetlands: Loss, resilience, and sustainable management

Coastal wetlands are some of the most valuable ecosystems on Earth because they provide many ecological services for coastal security. However, these wetlands are seriously threatened by accelerated climate change and intensive anthropogenic activities. To understand the impacts of land reclamation on landscape change of coastal wetlands and the long-term effects of disturbances of coastal wetlands on their sustainable management, we used time-series Landsat imagery with an object-oriented classification and Digital Shoreline Analysis System to map wetland changes within a reclaimed area in the Pudong District (PD), in Shanghai, China. Our analysis indicated that from 1989 to 2013, 19,793.4 ha of coastal wetlands have been changed to inland wetlands enclosed by a seawall and dike since 1989, thereby cutting off the exchange of sediment and water flux between the wetlands and the coastal ocean. Subsequently, under the increasing threats of anthropogenic activities, the wetland ecosystem collapsed sharply, in a transformation chain of inland wetland (fresh swamp), artificial wetland (agriculture and aquaculture wetland), and non-wetland (urban land). Under this explosive utilization following coastal reclamation, only 8.9% of natural wetlands remain in the reclaimed area, which has experienced an average annual wetland loss rate of 3.8% over the past 24 years. More than 80% of the wetlands have been developed for agricultural, industrial, and urban land uses, leading to an enormous loss of associated ecological services—benefits arising from the ecological functions provided by wetland ecosystems, thereby undermining the coastal protection these wetlands provided. Nevertheless, considerable regeneration of wetlands occurred because of their inherent resilience. This paper addresses the importance of maintaining a balance between economic growth and coastal ecological protection for sustainable management. It proposes a strategy for how ecosystem-based land planning and ecological engineering should be applied to ensure the effective and sustainable management of living shorelines so that the benefits of healthy ecological functions accrue to coastal ecosystems.

Reclamation, Remote sensing, landscape change, coa↗
DOE OSTI2021

Are 100 Ensemble Members Enough to Capture the Remote Atmospheric Response to +2°C Arctic Sea Ice Loss?

This study presents results from the Polar Amplification Multimodel Intercomparison Project (PAMIP) single-year time-slice experiments that aim to isolate the atmospheric response to Arctic sea ice loss at global warming levels of +2°C. Using two general circulation models (GCMs), the ensemble size is increased up to 300 ensemble members, beyond the recommended 100 members. After partitioning the response in groups of 100 ensemble members, the reproducibility of the results is evaluated, with a focus on the response of the midlatitude jet streams in the North Atlantic and North Pacific. Both atmosphere-only and coupled ocean–atmosphere PAMIP experiments are analyzed. Substantial differences in the midlatitude response are found among the different experiment subsets, suggesting that 100-member ensembles are still significantly influenced by internal variability, which can mislead conclusions. Despite an overall stronger response, the coupled ocean–atmosphere runs exhibit greater spread due to additional ENSO-related internal variability when the ocean is interactive. The lack of consistency in the response is true for anomalies that are statistically significant according to Student’s t and false discovery rate tests. This is problematic for the multimodel assessment of the response, as some of the spread may be attributed to different model sensitivities whereas it is due to internal variability. Here, we propose a method to overcome this consistency issue that allows for more robust conclusions when only 100 ensemble members are used.

58 GEOSCIENCES↗
NASA NTRS1994

Transitory endolymph leakage induced hearing loss and tinnitus: depolarization, biphasic shortening and loss of electromotility of outer hair cells

There are types of deafness and tinnitus in which ruptures or massive changes in the ionic permeability of the membranes lining the endolymphatic space [e.g., of the reticular lamina (RL)] are believed to allow potassium-rich endolymph to deluge the low [K+] perilymphatic fluid (e.g., in the small spaces of Nuel). This would result in a K+ intoxication of sensory and neural structures. Acute attacks of Meniere's disease have been suggested to be an important example for this event. The present study investigated the effects of transiently elevated [K+] due to the addition of artificial endolymph to the basolateral cell surface of outer hair cells (OHC) in replicating endolymph-induced K+ intoxication of the perilymph in the small spaces of Nuel. The influence of K+ intoxication of the basolateral OHC cell surface on the transduction was then examined. Intoxication resulted in an inhibition of the physiological repolarizing K+ efflux from hair cells. This induced unwanted depolarizations of the hair cells, interfering with mechanoelectrical transduction. A pathological longitudinal OHC shortening was also found, with subsequent compression of the organ of Corti possibly influencing the micromechanics of the mechanically active OHC. Both micromechanical and electrophysiological alterations are proposed to contribute to endolymph leakage induced attacks of deafness and possibly also to tinnitus. Moreover, repeated or long-lasting K+ intoxications of OHC resulted in a chronic and complete loss of OHC motility. This is suggested to be a pathophysiological basis in some patients with chronic hearing loss resulting from Meniere's syndrome.

Non-NASA Center↗
DOE OSTI2019

Direct Nanoscale Characterization of Deep Levels in AgCuInGaSe 2 Using Electron Energy–Loss Spectroscopy in the Scanning Transmission Electron Microscope

A new experimental framework for the characterization of defects in semiconductors is demonstrated. Through the direct, energy-resolved correlation of three analytical techniques spanning six orders of magnitude in spatial resolution, a critical mid-bandgap electronic trap level (E V + 0.56 eV) within Ag 0.2 Cu 0.8 In 1–x Ga x Se 2 is traced to its nanoscale physical location and chemical source. This is achieved through a stepwise, site-specific correlated characterization workflow consisting of device-scale (≈1 mm 2 ) deep level transient spectroscopy (DLTS) to survey the traps present, scanning probe–based DLTS (scanning-DLTS) for mesoscale-resolved (hundreds of nanometers) mapping of the target trap state’s spatial distribution, and scanning transmission electron microscope based electron energy-loss spectroscopy (STEM-EELS) and X-ray energy-dispersive spectroscopy for nanoscale energy-, structure, and chemical-resolved investigation of the defect source. Furthermore, this first demonstration of the direct observation of sub-bandgap defect levels via STEM-EELS, combined with the DLTS methods, provides strong evidence that the longsuspected Cu In/Ga substitutional defects are indeed the most likely source of the E V + 0.56 eV trap state and serves as a key example of this approach for the fundamental identification of defects within semiconductors, in general.

14 SOLAR ENERGY↗
DOE OSTI2018

Structural Characterization of Loblolly Pine Derived Biochar by X-ray Diffraction and Electron Energy Loss Spectroscopy

Biochar from lignocellulosic biomass is emerging as a sustainable material with versatile applications, but its detailed properties are poorly understood because of its structural complexity. We propose a biochar structural development model based on experimental results including composition analysis, surface area and pore analysis, X-ray diffraction analysis, electron microscopy imaging, and electron energy loss spectroscopy. Loblolly pine derived biochars were produced at different carbonization temperatures between 300 to 1000 °C. Fixed carbon, sp 2 content, and number of graphene layers increased with increased carbonization temperature. Alternating average C–C bond length, interlayer spacing distance, and layer coherence length were observed. Bulk plasmon excitation energy was correlated to the average C–C bond length, and it serves as a good indicator of the carbon structure development when compared to the perfect graphitic carbon structure. On the basis of the experimental results, four different structural development phases are identified, which provide a comprehensive understanding of biochar nanocarbon crystallite development. Unlike previous biochar structure models, which proposed radially growing polyaromatic carbon crystallite, we propose a lengthwise growing polyaromatic carbon crystallite model. Furthermore, this experiment-based biochar model should be helpful when determining the structure of unknown biomass-derived carbon materials and disordered pyrolytic carbon materials.

Biomass carbonization↗