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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

An evaluation of methodology to determine algal genome completeness

The advancement of sequencing technologies has resulted in a rapid expansion of genome sequencing. One challenge in processing and analyzing this abundance of genomics data is development and application of tools to accurately assess the quality of novel genomes. The quality of a given genome assembly is commonly assessed using the presence of conserved orthologs. However, the applicability and accuracy of identifying conserved orthologs applied to algal genome assemblies, which are uniquely diverse, is unclear. Here, in this study, we analyze the utility of a genome content assessment tool, Benchmarking Universal Single-Copy Orthologs (BUSCO), to evaluate algal genome assembly completeness. We find that Chlorophyta and Stramenopile BUSCO databases are effective tools to analyze genome completeness of these lineages. For other lineages, the Eukaryota database should be utilized until additional lineage-specific databases are developed. Based on these results, suggested best practices for current usage and necessary future improvements are provided.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

Kinetic model development and Bayesian uncertainty quantification for the complete reduction of Fe-based oxygen carriers with CH 4 , CO, and H 2 for chemical looping combustion

In this work, three kinetic models are developed and calibrated for the complete multi-step reduction of an Fe-based oxygen carrier (OC) particle with CH 4 , CO, and H 2 , using data from thermogravimetric analysis. The complete reduction rate profiles exhibit complex dynamics whose trajectory is significantly different depending on the reducing gas. A Bayesian model building and parameter estimation framework is applied for simultaneous parameter and model structure uncertainty quantification. The final models show excellent agreement between model predictions and calibration data, as well as new data not used for calibration (for the reduction of the OC with CH 4 ). Parameter uncertainty is quantified by determining joint posterior distribution, and model structure uncertainty is addressed by incorporating Gaussian process stochastic functions (represented by Bayesian smoothing splines) into the kinetic models. The final kinetic models with discrepancy functions are readily employable in equation-oriented simulation and optimization platforms.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Structural impact of complete CpG methylation within target DNA on specific complex formation of the inducible transcription factor Egr-1

The inducible transcription factor Egr–1 binds specifically to 9–bp target sequences containing two CpG sites that can potentially be methylated at four cytosine bases. Although it appears that complete CpG methylation would make an unfavorable steric clash in the previous crystal structures of the complexes with unmethylated or partially methylated DNA, our affinity data suggest that DNA recognition by Egr–1 is insensitive to CpG methylation. We have determined, at a 1.4–Å resolution, the crystal structure of the Egr–1 zinc–finger complex with completely methylated target DNA. In conclusion, structural comparison of the three different methylation states reveals why Egr–1 can recognize the target sequences regardless of CpG methylation.

5-methylcytosine↗
DOE OSTI2023

Robust Adaptive Control for Large-scale Inverter-based Resources with Partial and Complete Loss of Inverters

This article proposes an approach to address the current and the aggregated active power control challenge for large-scale inverter-based resources subjected to partially or completely loss of inverters and grid voltage variations. To address this problem, a distributed active power mechanism is proposed which generates desired inverters current. Then an adaptive mechanism distributes the voltage control input automatically between inverters in response to the partial or complete loss of inverters. An L2-gain-based controller is designed for each inverter to track the desired current and rejects the grid voltage disturbance. Here, simulation results show a significant robust tracking for collective active power and current.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2019

Scaling the impacts of pore-scale characteristics on unstable supercritical CO 2 -water drainage using a complete capillary number

Geological carbon storage in deep aquifers involves displacement of resident brine by supercritical CO 2 (scCO 2 ), which is an unstable drainage process caused by the invasion of less viscous scCO 2 . The unstable drainage is greatly complicated by aquifer heterogeneity and anisotropy and regarded as one of the key factors accounting for the uncertainty in storage capacity estimates. The impacts of pore-scale characteristics on the unstable drainage remain poorly understood. In this study, scCO 2 drainage experiments were conducted at 40 °C and 9 MPa using a homogeneous elliptical micromodel with low or high anisotropy, a homogeneous/isotropic hexagonal micromodel, and a heterogeneous sandstone-analog micromodel. Each initially water-saturated micromodel was invaded by scCO 2 at different rates with logC a (the capillary number) ranging from -7.6 to -4.4, and scCO 2 /water images were obtained. The measured CO 2 saturations in these centimeter-scale micromodels vary considerably from 0.08 to 0.93 depending on the pore-scale characteristics and capillary number. It was also observed that scCO 2 drainage follows the classic flow-regime transition from capillary fingering through crossover to viscous fingering for either of the low-anisotropy elliptical and heterogeneous micromodels, but with disparate crossover zones. The crossover zones of scCO 2 saturation were then unified with the minimum scCO 2 saturation occurring at logC$_a^*$ = -4.0 using the complete capillary number (C$_a^*$)that considers pore characteristics. For the hexagonal and the high-anisotropy elliptical micromodels, a monotonic increase in scCO 2 saturation with increasing C$_a^*$ (without crossover) was observed. It appears that the complete capillary number is more appropriate than the classic capillary number when characterizing flow regimes and CO 2 saturation in different pore networks.

58 GEOSCIENCES↗
DOE OSTI2016

Prognostic Value of p16 Status on the Development of a Complete Response in Involved Oropharynx Cancer Neck Nodes After Cisplatin-Based Chemoradiation: A Secondary Analysis of NRG Oncology RTOG 0129

Purpose: To determine the relationship between p16 status and the regional response of patients with node-positive oropharynx cancer treated on NRG Oncology RTOG 0129. Methods and Materials: Patients with N1-N3 oropharynx cancer and known p16 status who underwent treatment on RTOG 0129 were analyzed. Pathologic complete response (pCR) rates in patients treated with a postchemoradiation neck dissection (with p16-positive or p16-negative cancer) were compared by Fisher exact test. Patients managed expectantly were compared with those treated with a neck dissection. Results: Ninety-nine (34%) of 292 patients with node-positive oropharynx cancer and known p16 status underwent a posttreatment neck dissection (p16-positive: n=69; p16-negative: n=30). The remaining 193 patients with malignant lymphadenopathy at diagnosis were observed. Neck dissection was performed a median of 70 (range, 17-169) days after completion of chemoradiation. Neither the pretreatment nodal stage (P=.71) nor the postradiation, pre-neck dissection clinical/radiographic neck assessment (P=.42) differed by p16 status. A pCR was more common among p16-positive patients (78%) than p16-negative patients (53%, P=.02) and was associated with a reduced incidence of local–regional failure (hazard ratio 0.33, P=.003). On multivariate analysis of local–regional failure, a test for interaction between pCR and p16 status was not significant (P=.37). One-hundred ninety-three (66%) of 292 of initially node-positive patients were managed without a posttreatment neck dissection. Development of a clinical (cCR) was not significantly influenced by p16-status (P=.42). Observed patients with a clinical nodal CR had disease control outcomes similar to those in patients with a pCR neck dissection. Conclusions: Patients with p16-positive tumors had significantly higher pCR and locoregional control rates than those with p16-negative tumors.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2014

Application of stochastic Galerkin FEM to the complete electrode model of electrical impedance tomography

The aim of electrical impedance tomography is to determine the internal conductivity distribution of some physical body from boundary measurements of current and voltage. The most accurate forward model for impedance tomography is the complete electrode model, which consists of the conductivity equation coupled with boundary conditions that take into account the electrode shapes and the contact resistances at the corresponding interfaces. If the reconstruction task of impedance tomography is recast as a Bayesian inference problem, it is essential to be able to solve the complete electrode model forward problem with the conductivity and the contact resistances treated as a random field and random variables, respectively. In this work, we apply a stochastic Galerkin finite element method to the ensuing elliptic stochastic boundary value problem and compare the results with Monte Carlo simulations.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2024

Permutation-adapted complete and independent basis for atomic cluster expansion descriptors

Atomic cluster expansion (ACE) methods provide a systematic way to describe particle local environments of arbitrary body order. For practical applications it is often required that the basis of cluster functions be symmetrized with respect to rotations and permutations. Existing methodologies yield sets of symmetrized functions that are over-complete. These methodologies thus require an additional numerical procedure, such as singular value decomposition (SVD), to eliminate redundant functions. In this work, it is shown that analytical linear relationships for subsets of cluster functions may be derived using recursion and permutation properties of generalized Wigner symbols. From these relationships, subsets (blocks) of cluster functions can be selected such that, within each block, functions are guaranteed to be linearly independent. It is conjectured that this block-wise independent set of permutation-adapted rotation and permutation invariant (PA-RPI) functions forms a complete, independent basis for ACE. Along with the first analytical proofs of block-wise linear dependence of ACE cluster functions and other theoretical arguments, numerical results are offered to demonstrate this. The utility of the method is demonstrated in the development of an ACE interatomic potential for tantalum. Using the new basis functions in combination with Bayesian compressive sensing sparse regression, some high degree descriptors are observed to persist and help achieve high-accuracy models.

Angular momentum↗
DOE OSTI2025

Numerical schemes for 3-wave kinetic equations: A complete treatment of the collision operator

In our previous work Walton and Tran (2023), numerical schemes for a simplified version of 3-wave kinetic equations, in which only the simple forward-cascade terms of the collision operators are kept, have been successfully designed, especially to capture the long time dynamics of the equation given the multiple blow-up time phenomenon. In this second work in the series, we propose numerical treatments for the complete 3-wave kinetic equations, in which the complete, much more complicated collision operators are fully considered based on a novel conservative form of the equation. Here we then derive an implicit finite volume scheme to solve the equation. The new discretization uses an adaptive time-stepping method which allows for the simulations to be carried to very long times. Our computed solutions are compared with previously derived long-time asymptotic estimates for the decay rate of total energy of time-dependent solutions of 3-wave kinetic equations and found to be in excellent agreement.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2025

Complete coverage fouling model for constant flux crossflow ultrafiltration and experimental validation

A complete coverage model is proposed to describe fouling in constant flux crossflow ultrafiltration. Constant flux crossflow fouling experiments were conducted using dilute latex bead suspensions and commercial poly(ether sulfone) flat sheet ultrafiltration membranes to investigate the influence of operating conditions on evolution of transmembrane pressure (ΔP, TMP) with time. Changes in permeate flux or crossflow rate had little influence on the normalized TMP profile at high latex bead concentration (i.e., above 25 ppm) because the membrane surface was covered with latex beads. At low concentration (i.e., below 25 ppm), increases in permeate flux or foulant concentration increased normalized ΔP. However, this increase in normalized ΔP with permeate flux or foulant concentration diminishes when the permeate flux/concentration is high enough to overwhelm particle removal due to crossflow. Furthermore, these results are in good agreement with the new complete coverage model which describes the influence of operating parameters on fouling better than the previous model.

36 MATERIALS SCIENCE↗
DOE OSTI2019

TENDL: Complete Nuclear Data Library for Innovative Nuclear Science and Technology

The TENDL library is now established as one of the major nuclear data libraries in the world, striving for completeness and quality of nuclear data files for all isotopes, evaluation methods, processing and applied performance. To reach this status, some basic principles have been applied which sets it apart from other libraries: reproducible dedicated evaluations when differential data are available, through determination of nuclear models implemented in TALYS and their parameters, completeness (with or without experimental data), format and processing standardization, automation of production and reproducibility. In this paper, we will outline how such an approach has become a reality, and recall some of the past successes since the first TENDL release in 2008. Next, we will demonstrate the performance of the latest TENDL releases for different application fields, as well as new approaches for uncertainty quantification based on Bayesian inference methods and possible differential and integral adjustments. Also, current limitations of the library performances due to modelling and needs for new and more precise experimental data will be outlined.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

Application of predictive data analytics to model daily hydrocarbon production using petrophysical, geomechanical, fiber-optic, completions, and surface data: A case study from the Marcellus Shale, North America

Predicting gas production from stimulated unconventional reservoirs has always been a challenge to oil and gas companies because the physics of fluid flow through such reservoirs is not well understood. On the other hand, modeling gas production from shale reservoirs is a complex multi-variate problem that requires proper integration of data from multiple disciplines, such as geology, petrophysics, geomechanics, completions, and surface-based measurements, etc. Here this study demonstrates the application of data-driven machine learning algorithms, integrating geoscientific, distributed acoustic sensing (DAS), distributed temperature sensing (DTS) fiber-optic, completions, flow scanner production log, and surface data to model daily gas production from a 28-stage stimulated horizontal well drilled in the Marcellus Shale of the Appalachian basin in North America. In addition, this study aims to utilize the data from a fiber-optic monitoring system, such as DAS and DTS to evaluate the well performance. We build supervised data-driven machine learning models using Random Forest (RF), Artificial Neural Network (ANN), and Support Vector Machine (SVM) algorithms to understand the well performance and forecast the daily gas production. The study compares the forecasted results, tests the level of accuracy, and addresses different issues with these machine learning algorithms. A spatio-temporal database is constructed and used to perform sensitivity analyses to identify the key drivers for gas production. The results show that RF and ANN algorithms can be used to predict daily gas production with significantly high accuracy; however, RF algorithm is the best predictor in terms of highest accuracy (96%), less computational time and cost. Based on sensitivity analysis, it appears that Poisson's ratio, minimum horizontal stress, DAS, casing pressure, gamma log are the most important parameters to predict gas production.

02 PETROLEUM↗
DOE OSTI2017

Nonadiabatic Ab Initio Molecular Dynamics with the Floating Occupation Molecular Orbital-Complete Active Space Configuration Interaction Method [Non-Adiabatic Ab Initio Molecular Dynamics with Floating Occupation Molecular Orbitals CASCI Method]

Here, we show that the floating occupation molecular orbital complete active space configuration interaction (FOMO-CASCI) method is a promising alternative to the widely used complete active space self-consistent field (CASSCF) method in direct nonadiabatic dynamics simulations. We have simulated photodynamics of three archetypal molecules in photodynamics: ethylene, methaniminium cation, and malonaldehyde. We compared the time evolution of electronic populations and reaction mechanisms as revealed by the FOMO-CASCI and CASSCF approaches. Generally, the two approaches provide similar results. Some dynamical differences are observed, but these can be traced back to energetically minor differences in the potential energy surfaces. We suggest that the FOMO-CASCI method represents, due to its efficiency and stability, a promising approach for direct ab initio dynamics in the excited state.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Determination of the Complete Spin Density Distribution in 13 C-Labeled Protein-Bound Radical Intermediates Using Advanced 2D Electron Paramagnetic Resonance Spectroscopy and Density Functional Theory

Determining the complete electron spin density distribution for protein-bound radicals, even with advanced pulsed electron paramagnetic resonance (EPR) methods, is a formidable task. Here we present a strategy to overcome this problem combining multifrequency HYSCORE and ENDOR measurements on site-specifically 13 C-labeled samples with DFT calculations on model systems. As a demonstration of this approach, pulsed EPR experiments are performed on the primary Q A and secondary Q B ubisemiquinones of the photosynthetic reaction center from Rhodobacter sphaeroides 13C-labeled at the ring and tail positions. Despite the large number of nuclei interacting with the unpaired electron in these samples, two-dimensional X- and Q-band HYSCORE and orientation selective Q-band ENDOR resolve and allow for a characterization of the eight expected 13 C resonances from significantly different hyperfine tensors for both semiquinones. From these results we construct, for the first time, the most complete experimentally determined maps of the s- and p π -orbital spin density distributions for any protein organic cofactor radical to date. This work lays a foundation for understanding the relationship between the electronic structure of semiquinones and their functional properties, and introduces new techniques for mapping out the spin density distribution that are readily applicable to other systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Complete Decomposition of Li 2 CO 3 in Li–O 2 Batteries Using Ir/B 4 C as Noncarbon-Based Oxygen Electrode

Incomplete decomposition of Li2CO3 during charge process is a critical barrier for rechargeable Li-O2 batteries. Here we report complete decomposition of Li2CO3 in Li-O2 batteries using ultrafine iridium-decorated boron carbide (Ir/B4C) nanocomposite as oxygen electrode. The systematic investigation on charging the Li2CO3 preloaded Ir/B4C electrode in an ether-based electrolyte demonstrates that Ir/B4C electrode can decompose Li2CO3 with an efficiency close to 100% at below 4.37 V. In contrast, the bare B4C without Ir electrocatalyst can only decompose 4.7% of preloaded Li2CO3. The reaction mechanism of Li2CO3 decomposition in the presence of Ir/B4C electrocatalyst has been further investigated. A Li-O2 battery using Ir/B4C as oxygen electrode material shows highly enhanced cycling stability than that using bare B4C oxygen electrode. These results clearly demonstrate that Ir/B4C is an effecitive oxygen electrode amterial to completely decompose Li2CO3 at relatively low charge voltages and is of significant importance in improving the cycle performanc of aprotic Li-O2 batteries.

boron carbide↗
DOE OSTI2023

Nickel Isonicotinate Framework with Optimal Pore Structure for Complete Discrimination of Hexane Isomers

Efficient separation of physicochemically similar alkanes is of vital importance. Adsorptive separation utilizing porous materials such as metal–organic frameworks with tunable pore structure and surface functionality represents an energy-efficient technology. In this study, we demonstrate successful separation of alkanes with varying degree of branching using a microporous nickel isonicotinate framework, Ni(4-PyC) 2 . Its 2-fold interpenetrated diamondoid structure with well-suited pore size enables selective adsorption of linear and monobranched hexane isomers, while excluding dibranched isomer. Breakthrough experiments validated its capability to completely discriminate all three hexane isomers. Ab initio calculations combined with in situ infrared spectroscopic analysis unveiled the nature of host–guest interactions and differences in the binding energies and diffusion barriers among the isomers. Furthermore, having well-balanced adsorption uptakes (146 and 79 mg g –1 of nHEX and 3MP), high nHEX/DMB uptake ratio (12.2) and fast kinetics, Ni(4-PyC) 2 stands out as a promising adsorbent for complete separation of hexane isomers under ambient conditions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Dielectric metasurfaces for complete control of phase and polarization with subwavelength spatial resolution and high transmission

Metasurfaces are planar structures that locally modify the polarization, phase and amplitude of light in reflection or transmission, thus enabling lithographically patterned flat optical components with functionalities controlled by design1,2. Transmissive metasurfaces are especially important, as most optical systems used in practice operate in transmission. Several types of transmissive metasurface have been realized3,4,5,6, but with either low transmission efficiencies or limited control over polarization and phase. Here, we show a metasurface platform based on high-contrast dielectric elliptical nanoposts that provides complete control of polarization and phase with subwavelength spatial resolution and an experimentally measured efficiency ranging from 72% to 97%, depending on the exact design. Such complete control enables the realization of most free-space transmissive optical elements such as lenses, phase plates, wave plates, polarizers, beamsplitters, as well as polarization-switchable phase holograms and arbitrary vector beam generators using the same metamaterial platform.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Dielectric metasurfaces for complete and independent control of the optical amplitude and phase

Metasurfaces are optically thin metamaterials that promise complete control of the wavefront of light but are primarily used to control only the phase of light. Here, we present an approach, simple in concept and in practice, that uses meta-atoms with a varying degree of form birefringence and rotation angles to create high-efficiency dielectric metasurfaces that control both the optical amplitude and phase at one or two frequencies. This opens up applications in computer-generated holography, allowing faithful reproduction of both the phase and amplitude of a target holographic scene without the iterative algorithms required in phase-only holography. We demonstrate all-dielectric metasurface holograms with independent and complete control of the amplitude and phase at up to two optical frequencies simultaneously to generate two- and three-dimensional holographic objects. We show that phase-amplitude metasurfaces enable a few features not attainable in phase-only holography; these include creating artifact-free two-dimensional holographic images, encoding phase and amplitude profiles separately at the object plane, encoding intensity profiles at the metasurface and object planes separately, and controlling the surface textures of three-dimensional holographic objects.

77 NANOSCIENCE AND NANOTECHNOLOGY↗