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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 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Pore and grain boundary migration under a temperature gradient: A phase-field model study

In this study, the collective migration behavior of pores and grain boundaries under a temperature gradient is studied for simple single crystal, bi-crystal and polycrystal configurations with a phase-field model formulism. For simulation of the microstructure of solids, composed of pores and grain boundaries, the results indicate that not only the volume fraction of pores, but also its spatial partitioning between the grain boundary junctions and the grain boundary segments appears to be important. In addition to various physical properties, the evolution kinetics, under given temperature gradients, will be strongly influenced with the initial morphology of a poly-crystalline microstructure.

36 MATERIALS SCIENCE↗
DOE OSTI2023

CT_Data_of_Gas_Migration_in_Setting_Cement

Computed tomography experimental data associated with the submitted manuscript "Migration of air bubbles in a column of cement slurry" by N’dri Arthur Konan, Eilis Rosenbaum, Dustin Crandall, Mehrdad Massoudi. Full description with citation to be updated when manuscript is accepted.

Computed Tomography↗
DOE OSTI2016

Report on Evaluation, Verification, and Assessment of Porosity Migration Model in Fast Reactor MOX Fuel

Abstract This report documents the progress of simulating pore migration in ceramic (UO 2 and mixed oxide or MOX) fuel using BISON. The porosity field is treated as a function of space and time whose evolution is governed by a custom convection-diffusion-reaction equation (described here) which is coupled to the heat transfer equation via the temperature field. The porosity is initialized to a constant value at every point in the domain, and as the temperature (and its gradient) are increased by application of a heat source, the pores move up the thermal gradient and accumulate at the center of the fuel in a time-frame that is consistent with observations from experiments. There is an inverse dependence of the fuel’s thermal conductivity on porosity (increasing porosity decreases thermal conductivity, and vice-versa) which is also accounted for, allowing the porosity equation to couple back into the heat transfer equation. Results from an example simulation are shown to demonstrate the new capability.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

Mitigating cerium migration for perfluorosulfonic acid membranes using organic ligands

Improving the electrochemical stability of proton exchange membranes is a pressing priority for heavy-duty fuel cell vehicles. The lifetime of the most widely used perfluorosulfonic acid membranes is limited by reactive free radicals generated inside the system. Cerium has been found to reduce the chemical degradation of the membranes. However, cerium migration during fuel cell operation limits the chemical durability enhancement effect expected from the radical scavenging activity of cerium. Here we investigate a wide range of organic immobilizers for cerium, measuring their suitability concerning cerium retention, radical scavenging activity, and fuel cell performance. We report that partially fluorinated phosphonic acids enhance cerium retention up to 45 times and reduce fluoride emission rate by 38% compared to the commercial Nafion™ XL membrane pre-impregnated with cerium. The energetics of cerium-phosphonic acid complex systems by density functional theory calculations rationalizes effective cerium immobilization.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2016

Migration and growth of protoplanetary embryos. III. Mass and metallicity dependence for FGKM main-sequence stars

Radial velocity and transit surveys have found that the fraction of FGKM stars with close-in super-Earth(s) (η {sub ⊕}) is around 30%–50%, independent of the stellar mass M {sub *} and metallicity Z {sub *}. In contrast, the fraction of solar-type stars harboring one or more gas giants (η {sub J}) with masses M {sub p} > 100 M {sub ⊕} is nearly 10%–15%, and it appears to increase with both M {sub *} and Z {sub *}. Regardless of the properties of their host stars, the total mass of some multiple super-Earths systems exceeds the core mass of Jupiter and Saturn. We suggest that both super-Earths and supercritical cores of gas giants were assembled from a population of embryos that underwent convergent type I migration from their birthplaces to a transition location between viscously heated and irradiation-heated disk regions. We attribute the cause for the η {sub ⊕}–η {sub J} dichotomy to conditions required for embryos to merge and to acquire supercritical core mass (M{sub c}∼10 M{sub ⊕}) for the onset of efficient gaseous envelope accretion. We translate this condition into a critical disk accretion rate, and our analysis and simulation results show that it weakly depends on M {sub *} and decreases with metallicity of disk gas Z {sub d}. We find that embryos are more likely to merge into supercritical cores around relatively massive and metal-rich stars. This dependence accounts for the observed η {sub J}–M {sub *}. We also consider the Z{sub d}--Z{sub ∗} dispersed relationship and reproduce the observed η {sub J}–Z {sub *} correlation.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2020

Striped Mullet Migration Patterns in the Indian River Lagoon: A Network Analysis Approach to Spatial Fisheries Management

Striped mullet (Mugil cephalus) are numerically abundant forage fish, highly valuable as prey and commercially valuable to humans. From September to December, mullet in the Indian River Lagoon (IRL), Florida undergo an annual migration from inshore foraging habitats to oceanic spawning sites. However, their migratory pathways, in particular their intra-estuarine movement pathways, remain unknown. To address this knowledge gap, we utilized passive acoustic telemetry to assess the movement patterns of M. cephalus within the IRL. Thirty-two fish were tagged, generating usable tracks from 18 individuals. The mean (±s.d.) time that fish were detected in the array was ~38 ± 90 days, with the longest at 444 days. We also document the first evidence of skipped spawning in M. cephalus inhabiting waters of the southeastern United States. These data suggest impoundments around the Merritt Island National Wildlife Refuge appear to serve as important refugia for striped mullet while the Banana and Indian Rivers act as corridors during their inshore migratory movements. Through spatial fisheries management, high value habitat and connective elements utilized by mullet and other vital forage fish may be identified, to benefit both natural and human dynamics in estuarine systems.

Acoustic telemetry↗
NASA NTRS2021

An Approach to Reasoning Service Migration in Data and Reasoning Fabric (DRF) Implementation

In this paper we consider service migration problem for Data and Reasoning Fabric (DRF) enabled airspace operations assuming a fixed cloud/edge infrastructure with allocated computing, storage and power resources, where cloud/edge servers, and communication stations are in a wired connected network, while vehicles use a wireless network for communication. The objective is to automatically select the best location for the requested service execution, which achieves minimum cost while satisfying the user quality of service (QoS) and available resources constraints. To this end, estimates of the response time, consumed energy and total cost are defined for each potential compute location. A mixed-integer linear program is then formulated and solved to identify optimal compute locations given QoS constraints, network infrastructure limitations, with worst-case vehicle positioning. The approach is applied to trajectory re-planning use case to avoid a collision with an emergency vehicle in real time.

Air mobility↗
NASA NTRSDate not supplied

Distributed Target Tracking With Optimal Data Migration

The paper presents an Extended Kalman Filter based framework for airborne target tracking using dynamic information fusion from multi-modal sensors with geodiversity. First, the algorithm execution location is determined using an optimal data migration strategy, next the sensors information is dynamically fused at each estimation instance using validity flag for each sensor reading, finally the target estimation is updated based on the fused innovation vector. The approach is applied to synthetic data generated from the radar and camera models located on the ground for the simulated target flight in Reflection simulation environment.

Distributed sensing↗
NASA NTRSDate not supplied

Target Tracking with Distributed Sensing and Optimal Data Migration

The paper presents an Extended Kalman Filter based framework for airborne target tracking using adaptive information fusion from multi-modal multi-rate distributed sensors network. First, the tracking algorithm execution location is determined using an optimal data migration strategy, which also computes the associated delays for each sensor data to arrive at the computing location. Next, the fast (zero-delay) sensors information is dynamically fused in the filter correction procedure at the arrival instance of each valid sensor reading. Finally, the target estimation is updated based on the valid slow (delayed) data, which are grouped according to the delay-time steps before application of the Larsen's method. This approach is applied to the synthetic sensor data generated by means of the ground based radar and camera models for the simulated target flight in Reflection simulation environment.

Distributed sensing↗
NASA NTRSDate not supplied

Target Tracking with Distributed Sensing and Optimal Data Migration

The paper presents an Extended Kalman Filter based framework for airborne target tracking using adaptive information fusion from multi-modal multi-rate distributed sensors network. First, the tracking algorithm execution location is determined using an optimal data migration strategy, which also computes the associated delays for each sensor data to arrive at the computing location. Next, the fast (zero-delay) sensors information is dynamically fused in the filter correction procedure at the arrival instance of each valid sensor reading. Finally, the target estimation is updated based on the valid slow (delayed) data, which are grouped according to the delay-time steps before application of the Larsen's method. This approach is applied to the synthetic sensor data generated by means of the ground based radar and camera models for the simulated target flight in Reflection simulation environment.

Distributed sensing↗
DOE OSTI2015

Column testing of the migration and distribution of humate injected into subsurface systems at Savannah River Site's F/H area - 15713

The F-Area seepage basins at Savannah River Site (SRS) have received approximately 1.8 billion gallons of low-level waste solutions, containing nitric acid, radionuclides and dissolved metals due to plutonium separation operations from 1955 to 1988. The waste solutions became a source of contamination for groundwater and soil at the site, with U(VI) and other radionuclides above their maximum contaminant levels (MCLs). For remediation, humic acid (HA) technology has shown to be a potential approach for controlling mobility of radionuclides. Because sorbed HA and uranium develop a strong bond at slightly acidic pH, the mobility of the contaminant molecules should decrease with flushing of SRS groundwater. Column experiments are planned using SRS soil from the F/H Area to examine the sorption and desorption properties of HA in SRS soil. The data from these experiments will then be used to perform modeling of the migration and distribution of HA injected into the subsurface. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2016

Migration and Distribution of Natural Organic Matter Injected into Subsurface Systems - 16523

The Savannah River Site (SRS) was one of the major U.S. Department of Energy facilities that produced large amounts of radioactive and hazardous waste during the Cold War era, a legacy of material production for defense purposes. The unlined F-Area seepage basins received approximately 1.8 billion gallons of acidic waste solutions containing low-level radioactivity from numerous isotopes generated by uranium slug and irradiated fuel processing. Sufficient quantities of uranium isotopes, I-129, Tc-99, and tritium migrated into the groundwater, creating an acidic plume with a pH between 3 and 5.5. Humic substances (HS) are complex heterogeneous mixtures of poly-dispersed materials formed by biochemical and chemical reactions during the decay and transformation of plant and microbial remains. They are known for their excellent binding capacity for metals, making them a strong candidate for remediation efforts to reduce the mobility of uranium (VI) in the subsurface. Studies showed that HS are an important ion exchange and metal-complexing ligand, carrying a large number of functional groups with high complexing capacity that can greatly affect the mobility behavior of actinides in natural systems. Hence, it is a potential in situ amendment for treating groundwater contaminated with these constituents. Column experiments were conducted to address the complexities of HS in flow-through porous media representative of the acidic aquifer at the SRS F-Area Seepage Basins. The humate source used, Huma-K, is high in humic and fulvic compounds. The column studies were done using the soil obtained from SRS's FAW-1 core-hole at a depth interval of 60'-70'. A bromide tracer test was performed to obtain the pore volume (PV), variance and Peclet number. The columns were saturated with an artificial groundwater solution prepared to mimic the groundwater at SRS that was pH adjusted to 3.5 and 5 until the effluent pH reached equilibrium. Approximately one (1) PV of 5000 ppm of Huma-K was injected into the columns at 2 ml/min to study the sorption of Huma-K on the sediment. Desorption of Huma-K was studied by injecting approximately four (4) PVs of the pH adjusted artificial groundwater solution. A faster increase in pH was observed in column 1 (saturated with pH 3.5 AGW) compared to column 2 (saturated with pH 5 AGW). After injection of 2 PV of AGW, the pH of the columns reached 6.5 and 7, respectively, for columns 1 and 2. After injecting an additional PV of AGW, the pH remained relatively stable. With an increase in pH from 3.5 to 5.0, the overall retention of HA increased from 461 mg/kg for the column with pH 3.5 to 642 mg/kg for the column with pH 5. This suggests that retention is not due to adsorption alone, but adsorption coupled with precipitation and re-dissolution of Huma-K as it flows through the columns is a possible explanation for greater retention at pH 5. This negates the use of a simple Langmuir isotherm to explain humate behavior in the acidic environment of column 1. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2018

Numerical Modelling of Radionuclide Migration in the Context of a Near-Surface LILW Disposal Facility - 18618

The reference solution for the management of low and intermediate level short-lived waste (LILW) in France consists in their emplacement in concrete vaults built at the near-surface. The corresponding disposal facility under operation by the French waste management organization (Andra), is located in North-eastern France and planned to be closed in 2060. The safety case developed by Andra has to show the evidence that, amongst other aspects, the radionuclide transfer through the confinement barriers will occur in such a way that the human and environmental exposure will be as low as reasonably achievable (ALARA) and in accordance with the dose constraints. For this purpose, modelling is used to integrate uncertainties about the characteristics of concrete components, waste and water table and their evolution in time and space. At last, modelling is finally used to investigate the radiological impact of specific scenarios in which the failure of safety barriers occurs. In the frame of its technical review of the safety assessment, the French Institute for Radiological Protection and Nuclear Safety (IRSN) also performs such kind of numerical modelling of radionuclide fate from the waste to the hydrogeological outlets, in order to check whether the assessment performed by Andra takes into account sufficiently conservative assumptions. The present work aims to evaluate the role of components of the vaults on radionuclide transport during the post-closure period over a few thousand years. For this purpose, IRSN carries out numerical calculations with MELODIE software, which simulates water flow and transport of species, in order to simulate radionuclide migration from waste packages emplaced in a concrete vault to the surrounding groundwater. The developed transport model focuses on 3-H radionuclide and integrates Andra's main assumptions (release model from the waste packages, chemical and hydraulic properties of the vault components, shrinkage and cracks in concrete components). An adaptive mesh method, based on an a posteriori error estimator, was used to model the cracks and the consideration of a strong heterogeneity in the hydraulic and transport parameters values in the different components of the model. This method shows an improvement of results of about 40 times, whereas the mesh size was increased by only 2%. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2014

Robust Spring Drying in the Southwestern U.S. and Seasonal Migration of Wet/Dry Patterns in a Warmer Climate

This study compares climate simulations over the United States produced by a regional climate model with the driving global climate simulations as well as a large multi-model ensemble of global climate simulations to investigate robust changes in water availability (precipitation (P) – evapotranspiration (E)). A robust spring dry signal across multiple models is identified in the Southwest that results from a decrease in P and an increase in E in the future. In the boreal winter and summer, the prominent changes in P – E are associated with a north – south dipole pattern, while in spring, the prominent changes in P – E appear as an east – west dipole pattern. The progression of the north – south and east – west dipole patterns through the seasons manifests clearly as a seasonal “clockwise” migration of wet/dry patterns, which is shown to be a robust feature of water availability changes in the US consistent across regional and global climate simulations.

CMIP5↗
DOE OSTI2023

Imaging Light‐Induced Migration of Dislocations in Halide Perovskites with 3D Nanoscale Strain Mapping

Abstract In recent years, halide perovskite materials have been used to make high‐performance solar cells and light‐emitting devices. However, material defects still limit device performance and stability. Here, synchrotron‐based Bragg coherent diffraction imaging is used to visualize nanoscale strain fields, such as those local to defects, in halide perovskite microcrystals. Significant strain heterogeneity within MAPbBr 3 (MA = CH 3 NH 3 + ) crystals is found in spite of their high optoelectronic quality, and both 〈100〉 and 〈110〉 edge dislocations are identified through analysis of their local strain fields. By imaging these defects and strain fields in situ under continuous illumination, dramatic light‐induced dislocation migration across hundreds of nanometers is uncovered. Further, by selectively studying crystals that are damaged by the X‐ray beam, large dislocation densities and increased nanoscale strains are correlated with material degradation and substantially altered optoelectronic properties assessed using photoluminescence microscopy measurements. These results demonstrate the dynamic nature of extended defects and strain in halide perovskites, which will have important consequences for device performance and operational stability.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Ultrahigh-Rate and Long-Life Zinc–Metal Anodes Enabled by Self-Accelerated Cation Migration

Aqueous zinc ion batteries are receiving unprecedented attention owing to their markedly high safety and sustainability, yet their lifespan particularly at high rates is largely limited by the poor reversibility of zinc (Zn) metal anodes, due to the random ion diffusion and sluggish ion replenishment at reaction interface. In this work, we propose a tunnel-rich and corona-poled ferroelectric thin film coating for Zn metal anode to tackle above conundra. It is demonstrated that the poled ferroelectric coating can better deconcentrate and self-accelerate ion migration at coating/Zn interface upon electroplating process than untreated ferroelectric coating and bare Zn, thus enabling a compact and horizontally-aligned Zn morphology even at ultrahigh rates. Notably, a maximal cumulative plating capacity of over 6500 mAh cm -2 (at 10 mA cm -2 ) is achieved for the surface-modified Zn metal anode, showing extraordinary reversibility of Zn plating/stripping. This work provides new insights in stabilizing Zn metal electrodeposition at the scale of interfacial ion diffusion.

77 NANOSCIENCE AND NANOTECHNOLOGY↗