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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Relation of Observable Stellar Parameters to Mass-loss Rate of AGB Stars in the LMC

Using the data set of Riebel et al. for 6889 pulsating AGB stars in the LMC, we have derived formulae for mass-loss rate as a function of luminosity and pulsation period, or luminosity and mass, in three ways, for each of five subsets of data: fundamental-mode oxygen-rich stars, first-overtone-mode oxygen-rich stars, fundamental-mode carbon stars, first-overtone-mode carbon stars, and extreme carbon stars. Using the distribution of the stars in period versus luminosity and mass versus luminosity, we are able to derive a power-law fit to the dependence of mass-loss rate on those quantities. This results in formulae that reproduce observed mass-loss rates and are in general agreement with the expectation from mass-loss models that the mass-loss rate is highly sensitive to luminosity, mass, and pulsation period. In the process of carrying out this analysis we have found radius–mass–luminosity relations and examined pulsation–mass–radius relations using published evolutionary and pulsation models. These allow us to derive mass and radius from the observed quantities luminosity and pulsation period. We also derived new mass-loss rate versus color relations.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2015

Understanding and Mitigating Tip Leakage and Endwall Losses in High Pressure Ratio Cores

Reducing endwall and tip secondary flow losses will be a key enabler for the next generation of commercial and military air transport and will be an improvement on the state-of-the-art in turbine loss reduction strategies. The objective of this research is three-fold: 1) To improve understanding of endwall secondary flow and tip clearance losses 2) To develop novel technologies to mitigate these losses and test them in low-speed cascade and rig environments 3) To validate predictive tools To accomplish these objectives, Pratt & Whitney (P&W) has teamed with Pennsylvania State University (PSU) to experimentally test new features designed by P&W. P&W will create new rim-cavity features to reduce secondary flow loss and improve purge flow cooling effectiveness and new blade tip features to manage leakage flows and reduce tip leakage secondary flow loss. P&W is currently developing technologies in these two areas that expect to be assimilated in the N+2/N+3 generation of commercial engines.

Turbomachinery↗
NASA NTRS2014

Role of Oxidative Damage in Radiation-Induced Bone Loss

During prolonged spaceflight, astronauts are exposed to both microgravity and space radiation, and are at risk for increased skeletal fragility due to bone loss. Evidence from rodent experiments demonstrates that both microgravity and ionizing radiation can cause bone loss due to increased bone-resorbing osteoclasts and decreased bone-forming osteoblasts, although the underlying molecular mechanisms for these changes are not fully understood. We hypothesized that excess reactive oxidative species (ROS), produced by conditions that simulate spaceflight, alter the tight balance between osteoclast and osteoblast activities, leading to accelerated skeletal remodeling and culminating in bone loss. To test this, we used the MCAT mouse model; these transgenic mice over-express the human catalase gene targeted to mitochondria, the major organelle contributing free radicals. Catalase is an anti-oxidant that converts reactive species, hydrogen peroxide into water and oxygen. This animal model was selected as it displays extended lifespan, reduced cardiovascular disease and reduced central nervous system radio-sensitivity, consistent with elevated anti-oxidant activity conferred by the transgene. We reasoned that mice overexpressing catalase in mitochondria of osteoblast and osteoclast lineage cells would be protected from the bone loss caused by simulated spaceflight. Over-expression of human catalase localized to mitochondria caused various skeletal phenotypic changes compared to WT mice; this includes greater bone length, decreased cortical bone area and moment of inertia, and indications of altered microarchitecture. These findings indicate mitochondrial ROS are important for normal bone-remodeling and skeletal integrity. Catalase over-expression did not fully protect skeletal tissue from structural decrements caused by simulated spaceflight; however there was significant protection in terms of cellular oxidative damage (MDA levels) to the skeletal tissue. Furthermore, we used an array of countermeasures (Antioxidant diets and injections) to prevent the radiation-induced bone loss, although these did not prevent bone loss, analysis is ongoing to determine if these countermeasure protected radiation-induced damage to other tissues.

oxidative damage↗
NASA NTRS2017

The Effectiveness of Shrouding on Reducing Meshed Spur Gear Power Loss - Test Results

Gearbox efficiency is reduced at high rotational speeds due to windage drag and viscous effects on rotating, meshed gear components. A goal of NASA aeronautics rotorcraft research is aimed at propulsion technologies that improve efficiency while minimizing vehicle weight. Specifically, reducing power losses to rotorcraft gearboxes would allow gains in areas such as vehicle payload, range, mission type, and fuel consumption. To that end, a gear windage rig has been commissioned at NASA Glenn Research Center to measure windage drag on gears and to test methodologies to mitigate windage power losses. One method used in rotorcraft gearbox design attempts to reduce gear windage power loss by utilizing close clearance walls to enclose the gears in both the axial and radial directions. The close clearance shrouds result in reduced drag on the gear teeth, and reduced power loss. For meshed spur gears, the shrouding takes the form of metal side plates and circumferential metal sectors. Variably positioned axial and radial shrouds are incorporated in the NASA rig to study the effect of shroud clearance on gearbox power loss. A number of researchers have given experimental and analytical results for single spur gears, with and without shrouding. Shrouded meshed spur gear test results are sparse in the literature. Windage tests were run at NASA Glenn using meshed spur gears at four shroud configurations: unshrouded, shrouded (max. axial, max radial), and two intermediate shrouding conditions. Results are compared to available meshed spur gear power loss data analyses as well as single spur gear data/analyses. Recommendations are made for future work.

power loss↗
NASA NTRS2017

The Effectiveness of Shrouding on Reducing Meshed Spur Gear Power Loss Test Results

Gearbox efficiency is reduced at high rotational speeds due to windage drag and viscous effects on rotating, meshed gear components. A goal of NASA aeronautics rotorcraft research is aimed at propulsion technologies that improve efficiency while minimizing vehicle weight. Specifically, reducing power losses to rotorcraft gearboxes would allow gains in areas such as vehicle payload, range, mission type, and fuel consumption. To that end, a gear windage rig has been commissioned at NASA Glenn Research Center to measure windage drag on gears and to test methodologies to mitigate windage power losses. One method used in rotorcraft gearbox design attempts to reduce gear windage power loss by utilizing close clearance walls to enclose the gears in both the axial and radial directions. The close clearance shrouds result in reduced drag on the gear teeth and reduced power loss. For meshed spur gears, the shrouding takes the form of metal side plates and circumferential metal sectors. Variably positioned axial and radial shrouds are incorporated in the NASA rig to study the effect of shroud clearance on gearbox power loss. A number of researchers have given experimental and analytical results for single spur gears, with and without shrouding. Shrouded meshed spur gear test results are sparse in the literature. Windage tests were run at NASA Glenn using meshed spur gears at four shroud configurations: unshrouded, shrouded (max. axial, max. radial), and two intermediate shrouding conditions. Results are compared to available meshed spur gear power loss data analyses as well as single spur gear data analyses.

windage↗
NASA NTRS2022

Turbulent Heat Flux, Downward Longwave Radiation and Large-Scale Atmospheric Circulation Associated with the Wintertime Barents-Kara Sea Extreme Sea Ice Loss Events

We investigate wintertime extreme sea ice loss events on synoptic to subseasonal time scales over the Barents-Kara Sea, where the largest sea ice variability is located. Consistent with previous studies, extreme sea ice loss events are associated with moisture intrusions over the Barents-Kara Sea, which are driven by the large-scale atmospheric circulation. In addition to the role of downward longwave radiation associated with moisture intrusions, which is emphasized by previous studies, our analysis shows strong turbulent heat fluxes are associated with extreme sea ice melting events, with both turbulent sensible and latent heat fluxes contributing, though turbulent sensible heat fluxes dominate. Our analysis also shows that these events are connected to tropical convective anomalies. A dipole pattern of convective anomalies with enhanced convection over the Maritime Continent and suppressed convection over the central to eastern Pacific is consistently detected about 6 to 10 days prior to extreme sea ice loss events. This pattern is associated with either the Madden-Julian Oscillation (MJO) or El Niño–Southern Oscillation (ENSO). Composites show that extreme sea ice loss events are connected to tropical convection via Rossby wave propagation in the midlatitudes. However, tropical convective anomalies alone are not sufficient to trigger extreme sea ice loss events, suggesting that extratropical variability likely modulates the connection between tropical convection and extreme sea ice loss events.

Turbulent heat flux↗
NASA NTRS2022

Accelerating Ice Loss From Peripheral Glaciers in North Greenland

In recent decades, Greenland's peripheral glaciers have experienced large-scale mass loss, resulting in a substantial contribution to sea level rise. While their total area of Greenland ice cover is relatively small (4%), their mass loss is disproportionally large compared to the Greenland ice sheet. Satellite altimetry from Ice, Cloud, and land Elevation Satellite (ICESat) and ICESat-2 shows that mass loss from Greenland's peripheral glaciers increased from 27.2 ± 6.2 Gt/yr (February 2003–October 2009) to 42.3 ± 6.2 Gt/yr (October 2018–December 2021). These relatively small glaciers now constitute 11 ± 2% of Greenland's ice loss and contribute to global sea level rise. In the period October 2018–December 2021, mass loss increased by a factor of four for peripheral glaciers in North Greenland. While peripheral glacier mass loss is widespread, we also observe a complex regional pattern where increases in precipitation at high altitudes have partially counteracted increases in melt at low altitude.

Greenland↗
DOE OSTI2022

A Comparison of Preconstruction and Operational Wake Loss Estimates for Land-Based Wind Plants

Recent studies suggest that biases between wind plant pre-construction energy yield estimates and actual energy production are decreasing over time. However, variability in energy yield prediction accuracy across different projects and wind energy consultants remains high. Wake effects are one of the largest categories comprising the pre-construction energy yield assessment process. To assess the accuracy of wake loss predictions, we compare pre-construction wake loss estimates provided by 8 consultants to the estimated operational wake losses for 10 North American wind plants, as part of the Wind Plant Performance Prediction (WP3) Benchmark project. We estimate operational wake losses using supervisory control and data acquisition (SCADA) data by comparing total wind plant energy production to the potential energy production based on the power produced by freestream wind turbines. In the presentation, we will discuss the overall wake loss prediction bias as well as the project-to-project variability in the prediction accuracy. Further, we will highlight challenges encountered when estimating operational wake losses, including the impact of complex terrain and the presence of neighboring wind plants.

benchmark↗
DOE OSTI2016

Sensitivity Tests of Aluminum Precipitate Preparation Methods on Head Loss through Debris Beds on a Sump Screen

During a Loss-of-Coolant Accident (LOCA) in Pressurized Water Reactors (PWRs), buffered borated water as a coolant from the Refueling Water Storage Tank (RWST) will be injected into the primary loop to cool down the core depending on the break size. For long-term cooling, the coolant will be collected in the containment sump. Then, the Emergency Core Cooling System (ECCS) will pump the coolant through the sump strainers into the reactor. During this phase, buffered borated water produces chemical precipitate by reacting with the structural materials in the containment. Chemical effects evaluated as part of Generic Safety Issue 191 (GSI-191) resolution studies are broadly defined as any chemically induced phenomenon that affects ECCS performance. Initial chemical effects studies jointly sponsored by the Nuclear Regulatory Commission (NRC) and Industry collaborators led to a Westinghouse Owners Group (WOG) study that provided bases for deterministic quantification of chemical effects. The WCAP-16530-NP developed protocols to produce Aluminum Oxyhydroxide (AlOOH), Calcium Phosphate, and Sodium Aluminum Silicate (SAS). The surrogate generation protocol used the metal salt (aluminum nitrate and calcium acetate) unlike post-LOCA accident scenarios where metals leach into a buffered borated solution. Bahn et al. demonstrated that the WCAP-16530-NP SAS precipitate did not produce as much head loss as the WCAP-16530-NP AlOOH precipitate, thus, the present study focused on the effect of AlOOH precipitate on head loss through a fibrous debris bed. In the past, most of the tests were conducted in high approach velocity conditions, approximately 0.03 m/s. After modifications of sump strainer size in PWRs, the approach velocity to the sump strainer was reduced by an order of magnitude, approximately 0.001 ∼ 0.003 m/s. Howe et al. and Kim et al. conducted several head loss tests at the approach velocity of 0.003 m/s. In the present study, an approach velocity of 0.0006 m/s was selected for an extremely slow power plant condition. A PCI strainer design was used as previous head loss tests and debris bypass tests conducted by Lee et al. Three different chemical precipitate preparation methods were used in this study. The additional head loss of the debris bed caused by those chemical precipitates was investigated. The debris bed was produced with NUKON{sup R} fiberglass thermal insulator and additional particulates including dirt, Tin powder, acrylic powder, and Calcium silicate (CalSil). (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2019

Quantifying and Understanding Voltage Losses Due to Nonradiative Recombination in Bulk Heterojunction Organic Solar Cells with Low Energetic Offsets

Abstract Open‐circuit voltage ( V OC ) losses in organic photovoltaics (OPVs) inhibit devices from reaching V OC values comparable to the bandgap of the donor–acceptor blend. Specifically, nonradiative recombination losses (∆ V nr ) are much greater in OPVs than in silicon or perovskite solar cells, yet the origins of this are not fully understood. To understand what makes a system have high or low loss, an investigation of the nonradiative recombination losses in a total of nine blend systems is carried out. An apparent relationship is observed between the relative domain purity of six blends and the degree of nonradiative recombination loss, where films exhibiting relatively less pure domains show lower ∆ V nr than films with higher domain purity. Additionally, it is shown that when paired with a fullerene acceptor, polymer donors which have bulky backbone units to inhibit close π–π stacking exhibit lower nonradiative recombination losses than in blends where the polymer can pack more closely. This work reports a strategy that ensures ∆ V nr can be measured accurately and reports key observations on the relationship between ∆ V nr and properties of the donor/acceptor interface.

Rosenthal, Katie D.↗
DOE OSTI2021

Effect of sink strength on coherency loss of precipitates in dilute Cu-base alloys during in situ ion irradiation

In situ irradiations with 1 MeV Kr ions at 50~613 K up to a fluence of 6.25 × 10 14 ions/cm 2 (~1.25 displacements per atom, dpa) have been performed on pre-aged dilute Cu-0.9%Co, Cu-0.9%Fe and Cu-0.8%Cr alloys containing uniform matrix dispersions of coherent precipitates in order to study the effects of initial precipitate sink strength, damage dose and irradiation temperature on radiation-induced coherency loss of precipitates. Coherent precipitates with different point defect sink strengths (2πNd, where N and d are the precipitate density and diameter) were used in this work to examine potential differences in atomic relaxation during absorption of point defects. In all cases, irradiation to low doses (<~1 dpa) was very effective at inducing loss of precipitate coherency. At low sink strengths (~10 13 m -2 ), loss of precipitate coherency could be induced for doses ~0.01 dpa. This suggests there might be an efficient preferential medium-range strain-induced bias for absorption of interstitial defects due to tensile strains emanating from the undersized precipitates, which induces relatively rapid loss of coherency at low precipitate sink strengths. High precipitate sink strength (~10 14 m -2 ) conditions were relatively resistant to the radiation-induced loss of coherency (requiring higher doses approaching ~1 dpa) and this might be due to nearly equal numbers of interstitial and vacancy defects arriving at the precipitate interface for such high sink strength conditions. The precipitate coherency loss was observed to have a weak dependence on irradiation temperature. Molecular dynamics simulations confirm a strong effect of precipitate sink strength on the probability of interstitial absorption at precipitates.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Limited potential of irrigation to prevent potato yield losses in Germany under climate change

Climate models project higher temperatures and a substantial net water deficit during the summer months over Germany until the end of the 21st century. The agricultural sector is particularly vulnerable to changing weather and climate conditions. In this study, we examine the role of irrigation for potato yields as a climate change adaptation measure in Northeast Lower Saxony (Germany). The region represents the largest irrigated area in Germany and is one of the main growing areas of potatoes. We develop a statistical multivariate regression model to investigate whether regional climate and irrigation data at the monthly and county level are suitable to describe potato yield variability from 1978 to 2018. Irrigation is estimated based on the climatic water balance and crop water demand. These estimates are calibrated against irrigation data from local agencies to account for realistic monthly water withdrawals. We analyze future yield changes based on climate model projections for the 21st century and different irrigation scenarios. We find that the potato yield will decrease significantly by 18% on average until 2050 with climate projection uncertainty of ±6.4% under the high emission scenario RCP 8.5 and without irrigation. Irrigation at current levels could compensate for about 54% of these yield losses. Doubling the amount of irrigation minimizes yield losses by as much as 80%. Under the low (middle) emission scenario RCP 2.6 (RCP 4.5), potato yield are projected to decrease moderately by 4.5% ± 3.4% (5.4% ± 2.8%) with irrigation at current levels. We show that the yield losses mainly originate from higher temperatures during the summer. Our analysis indicates that the capacity of irrigation to minimize yield losses is limited. Strengthening climate change mitigation efforts may be more effective in preventing yield losses. However, the effect of elevated CO 2 might buffer the high yield losses, especially in RCP 8.5. The studies supports farmers and decision makers in assessing future risks in potato yields. It can guide policymakers in allocating economic resources to cope with climate change.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

Erbin loss promotes cancer cell proliferation through feedback activation of Akt-Skp2-p27 signaling

Erbin localizes at the basolateral membrane to regulate cell junctions and polarity in epithelial cells. Dysregulation of Erbin has been implicated in tumorigenesis, and yet it is still unclear if and how disrupted Erbin regulates the biological behavior of cancer cells. We report here that depletion of Erbin leads to cancer cell excessive proliferation in vitro and in vivo. Erbin deficiency accelerates S-phase entry by down-regulating CDK inhibitors p21 and p27 via two independent mechanisms. Mechanistically, Erbin loss promotes p27 degradation by enhancing E3 ligase Skp2 activity though augmenting Akt signaling. Interestingly, we also show that Erbin is an unstable protein when the Akt-Skp2 signaling is aberrantly activated, which can be specifically destructed by SCF-Skp2 ligase. Erbin loss facilitates cell proliferation and migration in Skp2-dependent manner. Thus, our finding illustrates a novel negative feedback loop between Erbin and Akt-Skp2 signaling. It suggests disrupted Erbin links polarity loss, hyperproliferation and tumorigenesis. - Highlights: • Erbin loss leads to cancer cell excessive proliferation in vitro and in vivo. • Erbin loss accelerates cell cycle though down-regulating p21 and p27 expression. • Erbin is a novel negative modulator of Akt1-Skp2-p27 signaling pathway. • Our study suggests that Erbin loss contributes to Skp2 oncogenic function.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

Responses of estuarine circulation and salinity to the loss of intertidal flats – A modeling study

Intertidal flats in estuaries are coastal wetlands that provide critical marine habitats to support wide ranges of marine species. Over the last century many estuarine systems have experienced significant loss of intertidal flats due to anthropogenic impacts. This paper presents a modeling study conducted to investigate the responses of estuarine hydrodynamics to the loss of intertidal flats caused by anthropogenic actions in Whidbey Basin of Puget Sound on the northwest coast of North America. Changes in salinity intrusion limits in the estuaries, salinity stratification, and circulation in intertidal flats and estuaries were evaluated by comparing model results under the existing baseline condition and the no-flat condition. Model results showed that loss of intertidal flats results in an increase in salinity intrusion, stronger mixing, and a phase shift in salinity and velocity fields in the bay front areas. Model results also indicated that loss of intertidal flats enhances two-layer circulation, especially the bottom water intrusion. Loss of intertidal flats increases the mean salinity but reduces the salinity range in the subtidal flats over a tidal cycle because of increased mixing. Salinity intrusion limits extend upstream in all three major rivers discharging into Whidbey Basin when no intertidal flats are present. Changes in salinity intrusion and estuarine circulation patterns due to loss of intertidal flats affect the nearshore habitat and water quality in estuaries and potentially increase risk of coastal hazards, such as storm surge and coastal flooding. Furthermore, model results suggested the importance of including intertidal flats and the wetting-and-drying process in hydrodynamic simulations when intertidal flats are present in the model domain.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Effects of rows arrangement, soil management, and rainfall characteristics on water and soil losses in Italian sloping vineyards

Highlights: • GC effectiveness varies according to the type of rainfall event and row orientation. • Rows orientation along contour lines prevents runoff also when CT is adopted. • Highest runoff and soil losses depend on “long-lasting” or “intense” events. • Rainfall depth and rainfall maximum intensity count in predicting erosion rate. Erosional processes are highly affected by seasonal climatic fluctuations and soil management practices. Controlled grass cover is one of the most used soil conservation practices adopted in temperate climates, even if the protective effect of grass cover may decrease according to seasonal pattern. This technique is effective and, thus, widely adopted in the inter-rows of orchards such as olives, citrus or vineyards. This study reports the erosive events recorded in two different rain-fed hillslope vineyards with different rows orientation located in the Monferrato region, NW Italy. The study is addressed at compare the effects of different inter-row managements and rainfall characteristics on runoff and soil loss in hillslope vineyards (average slope from 15% to 35%). Rainfall, runoff and erosion variables were monitored in hydraulically bounded vineyard plots, where the inter-rows were managed with tillage and grass cover. Seventy-two erosive events were recorded in the period 1992–1996 in two vineyard plots with rows along the contour lines while 86 erosive events were recorded in two plots with rows up-and-down the slope from 2000 to 2014 (158 erosive events and four plots in total). Events were classified according to rainfall characteristics as “long-lasting”, “intense” and “normal”. In plots with rows along the contour lines, “intense” events were responsible for the highest mean soil loss in tilled plots (0.7 Mg ha{sup −1}) with very high erosion rates (12.3 Mg ha{sup −1}) observed during a single storm. In plots with rows up-and-down the slope the highest erosion rates, 21.2 and 3.4 Mg ha{sup −1}, were recorded during fall “long-lasting” events in the tilled and grass cover plots respectively. The grass cover proved to be effective in decreasing runoff and soil losses during most of the events (at least 68% and 61% of the occurrences, respectively) reducing soil losses especially during summer storms when most of the “intense” events occured. Furthermore, the results show the fundamental role of contour-slope row orientation in reducing runoff and soil losses, disregarding the inter-rows soil management that is adopted.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Low loss polypropylene-silicon composites for millimetre wave applications

Highlights: • Developed polypropylene-silicon composite. • The composite shows a decrease in loss tangent with increasing frequency. • The composite is useful for high frequency applications such as Internet of Things and 5th Generation wireless communication. - Abstract: Polypropylene-silicon composite laminates were fabricated via hot pressing and their dielectric properties up to 35 GHz were studied. The loss tangent was found to decrease with increasing frequency whereas an increasing trend of loss tangent has previously been reported in the literature for such composites. The decreasing trend of the loss tangent with frequency is due to the decreasing conductor loss of silicon (Si) and indicates the possibility for use in high frequency applications such as the Internet Of Things and 5 t h generation wireless communication. The composite containing 25 vol% of Si had a relative permittivity of 3.5 and a loss tangent of 0.001 at 35 GHz. The coefficient of thermal expansion and the thermal conductivity of 40 vol% Si loaded composites were 51 ppm/{sup o}C and 2.23 W/mK, respectively. The thermal conductivity of the composite increased by 163% and 913% for 25 and 40 vol% Si addition, respectively.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Layered Oxide Cathodes for Li-Ion Batteries: Oxygen Loss and Vacancy Evolution

Loss of oxygen in layered transition metal oxides is a major reason for the structural degradation and thus the fade of electrochemical performance in the cathodes for Li-ion batteries. Via in-situ transmission electron microscopy observations of LiNi 0.80 Co 0.15 Al 0.05 O 2 (NCA), we found that the oxygen loss in the layered cathode is a two-stage process with distinct release rates. The initial rapid oxygen loss generates a high concentration of oxygen vacancies that results in the formation of an amorphized, vacancy-containing rock-salt layer in the surface. In the second stage, the slower rate of oxygen loss allows recrystallization of this defective phase via coalescing of atomic oxygen vacancies, which results in the formation of a cavity-containing surface layer with a crystalline rock-salt structure over the layered phase in the bulk. Comparison of the in-situ results with electrochemically cycled NCA cathodes confirms this two-stage process of oxygen loss. Furthermore, these results provide unprecedented microscopic details regarding the structural degradation of layered oxides arising from oxygen loss and have broader implications in manipulating the oxygen activity in the electrode.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Quantifying the Effect of Magnetic Field Line Curvature Scattering on the Loss of Ring Current Ions

During geomagnetic storms, the ring current ions sometimes exhibit rapid loss as suggested by the fast recovery of the Dst index on a time scale of a few hours. Here, the effects of magnetic field line curvature (FLC) scattering on the loss of ring current ions, which have not been well quantified, are studied here by test particle simulations under the T89c magnetic field model. Our simulation results show that the prediction of ion loss based on a single–value cutoff of the κ parameter or maximum of δμ/μ of a single FLC scattering is not accurate. Instead, the e–folding lifetime (τ) for the loss of ring current ions due to cumulative FLC scattering has been calculated for different initial ion energies, equatorial pitch angles, and L shells under different geomagnetic conditions. The results show that in general the FLC scattering loss is faster for ions of higher energy, higher mass, smaller pitch angle, higher L, and at high Kp level. Specifically, we find that at Kp = 6 the lifetime can be <10 h at L > 5 for 100 s keV protons and at L > 4 for 100 s keV O + , which demonstrates that FLC scattering can be an important mechanism for the observed fast loss (τ < 10 h) of ring current ions during geomagnetic storms. Furthermore, we formulate an empirical formula for τ as a function of ion energy, pitch angle, position, species, and Kp. The empirical formula can be directly included in ring current models to account for the FLC scattering effects.

79 ASTRONOMY AND ASTROPHYSICS↗