Search NASA⌕ Search

SEARCH · Search NASA

Results for “EXTRAPOLATION”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,387 records · Page 77
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Reflected entropy in random tensor networks. Part III. Triway cuts

For general random tensor network states at large bond dimension, we prove that the integer Rényi reflected entropies (away from phase transitions) are determined by minimal triway cuts through the network. This generalizes the minimal cut description of bipartite entanglement for these states. A natural extrapolation away from integer Rényi parameters, suggested by the triway cut problem, implies the holographic conjecture S R = 2EW, where S R is the reflected entropy and EW is the entanglement wedge cross-section. Minimal triway cuts can be formulated as integer programs which cannot be relaxed to find a dual maximal flow/bit-thread description. This sheds light on the gap between the existence of tripartite entanglement in holographic states and the bipartite entanglement structure motivated by bit-threads. In particular, we prove that the Markov gap that measures tripartite entanglement is lower bounded by the integrality gap of the integer program that computes the triway cut.

AdS-CFT correspondence↗
DOE OSTI2013

Accurate ab initio potential energy curves and spectroscopic properties of the four lowest singlet states of C 2

The diatomic carbon molecule has a complex electronic structure with a large number of low-lying electronic excited states. In this work, the potential energy curves (PECs) of the four lowest lying singlet states (X-1 Sigma(+)(g), A(1)Pi(u), B-1 Delta(g), and B'(1)Sigma(+)(g)) were obtained by high-level ab initio calculations. Valence electron correlation was accounted for by the correlation energy extrapolation by intrinsic scaling (CEEIS) method. Additional corrections to the PECs included core-valence correlation and relativistic effects. Spin-orbit corrections were found to be insignificant. The impact of using dynamically weighted reference wave functions in conjunction with CEEIS was examined and found to give indistinguishable results from the even weighted method. The PECs showed multiple curve crossings due to the B-1 Delta(g) state as well as an avoided crossing between the two (1)Sigma(+)(g) states. Vibrational energy levels were computed for each of the four electronic states, as well as rotational constants and spectroscopic parameters. Comparison between the theoretical and experimental results showed excellent agreement overall. Equilibrium bond distances are reproduced to within 0.05 %. The dissociation energies of the states agree with experiment to within similar to 0.5 kcal/mol, achieving "chemical accuracy." Vibrational energy levels show average deviations of similar to 20 cm(-1) or less. The B-1 Delta(g) state shows the best agreement with a mean absolute deviation of 2.41 cm(-1). Calculated rotational constants exhibit very good agreement with experiment, as do the spectroscopic constants.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Coupled cluster spectroscopic properties of the coinage metal nitrosyls, M–NO (M = Cu, Ag, Au)

Ab initio near-equilibrium potential energy and dipole moment surfaces for the bent CuNO, AgNO, and AuNO molecules have been calculated under the Feller-Peterson-Dixon (FPD) composite framework at the coupled cluster level of theory including complete basis set extrapolation, outer-core correlation, scalar relativistic effects, and spin-orbit coupling. The Brueckner coupled cluster doubles with perturbative triples method, BCCD(T), was used to greatly improve upon CCSD(T), which was particularly problematic for CuNO. In the latter case the BCCD(T) vibrational frequencies showed significant differences compared to CCSD(T), e.g., nearly 65 cm -1 for the NO stretching frequency, and BCCD(T) also resulted in much better agreement with the available experimental frequencies. A full range of ro-vibrational spectroscopic constants are given for all three molecules of this study using the accurate composite potential energy functions and employing 2nd-order vibrational perturbation theory.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Combined Therapies for the Treatment of Technically Unresectable Liver Malignancies: Bland Embolization and Radiofrequency Thermal Ablation within the Same Session

Purpose: This retrospective study evaluated the feasibility, efficacy, and safety of combining transcatheter arterial embolization (TAE) with radiofrequency thermal ablation (RFA) in a single session for the treatment of technically unresectable liver-only malignancies. Methods: From May 2006 to January 2011, a total of 30 patients affected by liver metastases with single or multiple unresectable liver-only lesions underwent a combined treatment with TAE followed by RFA in the same session, for a total of 36 treated lesions. Patients were extrapolated from a cohort of patients discussed within the weekly institutional tumor board. TAE was performed by using 100 {mu}m microspheres; RFA was performed immediately after TAE by positioning the electrode needle via ultrasound and/or computed tomographic guidance. Local tumor responses and procedure-related complications were evaluated. Results: Completion of both procedures was obtained in all patients for all 36 lesions. Liver lesions had a maximum axial diameter ranging 16-59 mm. Postintervention unenhanced ablated areas ranged 28-104 mm in maximum axial diameter. Safety margins ranged 1-30.5 mm. Complete response, defined as complete devascularization at computed tomography, was obtained in all treated lesions for a maximum period of 12 months. Tumor relapse was observed in one patient at 12 months. Sixteen patients developed new liver lesions or progressive systemic disease during follow-up. Nine patients were still disease-free. Seven patients died as a result of systemic progressive disease. One major treatment-related complication was observed. Conclusions: In patients with technically unresectable liver-only malignancies, single-session combined TAE-RFA is an effective and safe treatment.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2013

Determination of the Nonlethal Margin Inside the Visible 'Ice-Ball' During Percutaneous Cryoablation of Renal Tissue

Objective. The study was designed to determine the distance between the visible 'ice-ball' and the lethal temperature isotherm for normal renal tissue during cryoablation. Methods. The Animal Care Committee approved the study. Nine adult swine were used: three to determine the optimum tissue stain and six to test the hypotheses. They were anesthetized and the left renal artery was catheterized under fluoroscopy. Under MR guidance, the kidney was ablated and (at end of a complete ablation) the nonfrozen renal tissue (surrounding the 'ice-ball') was stained via renal artery catheter. Kidneys were explanted and sent for slide preparation and examination. From each slide, we measured the maximum, minimum, and an in-between distance from the stained to the lethal tissue boundaries (margin). We examined each slide for evidence of 'heat pump' effect. Results. A total of 126 measurements of the margin (visible 'ice-ball'-lethal margin) were made. These measurements were obtained from 29 slides prepared from the 6 test animals. Mean width was 0.75 {+-} 0.44 mm (maximum 1.15 {+-} 0.51 mm). It was found to increase adjacent to large blood vessels. No 'heat pump' effect was noted within the lethal zone. Data are limited to normal swine renal tissue. Conclusions. Considering the effects of the 'heat pump' phenomenon for normal renal tissue, the margin was measured to be 1.15 {+-} 0.51 mm. To approximate the efficacy of the 'gold standard' (partial nephrectomy, {approx}98 %), a minimum margin of 3 mm is recommended (3 Multiplication-Sign SD). Given these assumptions and extrapolating for renal cancer, which reportedly is more cryoresistant with a lethal temperature of -40 Degree-Sign C, the recommended margin is 6 mm.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2013

A Budget Impact Model for Paclitaxel-eluting Stent in Femoropopliteal Disease in France

The Zilver PTX drug-eluting stent (Cook Ireland Ltd., Limerick, Ireland) represents an advance in endovascular treatments for atherosclerotic superficial femoral artery (SFA) disease. Clinical data demonstrate improved clinical outcomes compared to bare-metal stents (BMS). This analysis assessed the likely impact on the French public health care budget of introducing reimbursement for the Zilver PTX stent. A model was developed in Microsoft Excel to estimate the impact of a progressive transition from BMS to Zilver PTX over a 5-year horizon. The number of patients undergoing SFA stenting was estimated on the basis of hospital episode data. The analysis from the payer perspective used French reimbursement tariffs. Target lesion revascularization (TLR) after primary stent placement was the primary outcome. TLR rates were based on 2-year data from the Zilver PTX single-arm study (6 and 9 %) and BMS rates reported in the literature (average 16 and 22 %) and extrapolated to 5 years. Net budget impact was expressed as the difference in total costs (primary stenting and reinterventions) for a scenario where BMS is progressively replaced by Zilver PTX compared to a scenario of BMS only. The model estimated a net cumulative 5-year budget reduction of Euro-Sign 6,807,202 for a projected population of 82,316 patients (21,361 receiving Zilver PTX). Base case results were confirmed in sensitivity analyses. Adoption of Zilver PTX could lead to important savings for the French public health care payer. Despite higher initial reimbursement for the Zilver PTX stent, fewer expected SFA reinterventions after the primary stenting procedure result in net savings.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2026

Input specific neural networks

Neural networks have emerged as powerful tools for mapping between inputs and outputs. However, their black-box nature limits the ability to encode or impose specific structural relationships between inputs and outputs. Many scientific and engineering problems, such as constitutive modeling in solid mechanics, require networks that can enforce convexity, monotonicity, or other structural constraints to ensure physical consistency. Here, we introduce the Input Specific Neural Network (ISNN), a new architecture that enables multiple, distinct constraints to be imposed on different input subsets for scalar-valued outputs. This framework unifies convex, monotone–convex, monotone, and arbitrary mappings within a single network for the first time. Two ISNN architectures with analytical first- and second-order derivatives are developed. We demonstrate the performance on synthetic toy problems, inverse problems in isotropic hyperelasticity, and finite element simulations. ISNNs achieve improved extrapolation behavior, require fewer invariant inputs than standard input convex networks for polyconvex potentials, and enable significant computational savings via manual differentiation. We also show how ISNNs can be used to learn structural relationships between inputs and outputs via a binary gating mechanism. Particularly, ISNNs are employed to model a homogenized anisotropic free energy potential in a decoupled multiscale setting. The network learns whether or not the potential should be modeled as polyconvex and retains only the relevant layers while using the minimum number of inputs. ISNNs provide a flexible foundation for embedding structural priors into neural networks, enhancing both interpretability and stability. They are broadly applicable across computational mechanics and other scientific domains requiring constrained functional relationships.

Jadoon, Asghar A. [Univ. of Texas, Austin, TX (Uni↗
DOE OSTI2013

Benchmark of the No-Core Monte Carlo Shell Model in Light Nuclei

We report the benchmark comparison of the properties in light nuclei among the Monte Carlo Shell Model, Full Configuration Interaction and No Core Full Configuration approaches. For this benchmark process, we compare results for the energies of 9 states from helium-4 to carbon-12 that includes 7 ground states and 2 excited states. The JISP16 NN interaction is adopted. The Coulomb and all other interactions are neglected. The contributions of spurious center-of-mass excitation are not discussed here. The basis space is truncated by the cutoff of the single-particle basis space, N shell . We select the optimal $\hbar$ω that minimizes the energy for that state and basis space cutoff. The MCSM results are obtained by exploiting the recent development in the computation of two-body matrix elements between non-orthogonal Slater determinants and technique of the energy-variance extrapolation. All results are found to be consistent with each other to within quoted uncertainties when they could be quantified. As an exploratory attempt, we also demonstrate how to draw the intrinsic density from no-core MCSM wave functions by taking the 8 Be ground state as an example.

Physics↗
DOE OSTI2017

Sequential Bottomonium Production at High Temperatures

We present that bottomonium production in heavy ion collisions is modified compared with any simple extrapolation from elementary collisions. This modification is most likely caused by the presence of a deconfined system of quarks and gluons for times of several fm/c. In such a medium, bottomonium can be destroyed, but the constituent bottom quarks will likely stay spatially correlated due to small mean free paths in this system. With these facts in mind, we describe bottomonium formation with a coupled set of equations. A rate equation describes the destruction of Υ(1S)Υ(1S) particles, while a Langevin equation describes how the bottom quarks stay correlated for a sufficiently long time so that recombination into bottomonia is possible. Lastly, we show that within this approach it is possible to understand the magnitude of Υ(1S)Υ(1S) suppression in heavy ion collisions and the larger suppression of the Υ(2S)Υ(2S) state, implying that the reduction in the ratio of Υ(1S)/Υ(2S)Υ(1S)/Υ(2S) yield in heavy ion collision does not necessarily correspond to the sequential melting picture.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Multiphysics Lattice Discrete Particle Modeling (M-LDPM) for the Simulation of Shale Fracture Permeability

A three-dimensional multiphysics lattice discrete particle model (M-LDPM) framework is formulated to investigate the fracture permeability behavior of shale. The framework features a dual lattice system mimicking the mesostructure of the material and simulates coupled mechanical and flow behavior. The mechanical lattice model simulates the granular internal structure of shale, and describes heterogeneous deformation by means of discrete compatibility and equilibrium equations. The network of flow lattice elements constitutes a dual graph of the mechanical lattice system. A discrete formulation of mass balance for the flow elements is presented to model fluid flow along cracks and intact materials. The overall computational framework is implemented with a mixed explicit–implicit integration scheme and a staggered coupling method that makes use of the dual lattice topology enabling the seamless two-way coupling of the mechanical and flow behaviors. The proposed model is used for the computational analysis of shale fracture permeability behavior by simulating triaxial direct shear tests on Marcellus shale specimens under various confining pressures. The simulated mechanical response is calibrated against the experimental data, and the predicted permeability values are also compared with the experimental measurements. Moreover, the paper presents the scaling analysis of both the mechanical response and permeability measurements based on simulations performed on geometrically similar specimens with increasing size. The simulated stress strain curves reflect a significant size effect in the post-peak due to the presence of localized fractures. The scaling analysis of permeability measurements enables prediction of permeability for large specimens by extrapolating the numerical results of small ones.

58 GEOSCIENCES↗
DOE OSTI2017

3D Histopathology—a Lung Tissue Segmentation Workflow for Microfocus X-ray-Computed Tomography Scans

Lung histopathology is currently based on the analysis of 2D sections of tissue samples. The use of microfocus X-ray-computed tomography imaging of unstained soft tissue can provide high-resolution 3D image datasets in the range of 2–10 μm without affecting the current diagnostic workflow. Important details of structural features such as the tubular networks of airways and blood vessels are contained in these datasets but are difficult and time-consuming to identify by manual image segmentation. Providing 3D structures permits a better understanding of tissue functions and structural interrelationships. It also provides a more complete picture of heterogeneous samples. In addition, 3D analysis of tissue structure provides the potential for an entirely new level of quantitative measurements of this structure that have previously been based only on extrapolation from 2D sections. In this paper, a workflow for segmenting such 3D images semi-automatically has been created using and extending the ImageJ open-source software and key steps of the workflow have been integrated into a new ImageJ plug-in called LungJ. Results indicate an improved workflow with a modular organization of steps facilitating the optimization for different sample and scan properties with expert input as required. This allows for incremental and independent optimization of algorithms leading to faster segmentation. Representation of the tubular networks in samples of human lung, building on those segmentations, has been demonstrated using this approach.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

A Reconfigurable In Vitro Model for Studying the Blood–Brain Barrier

Much of what is currently known about the role of the blood–brain barrier (BBB) in regulating the passage of chemicals from the blood stream to the central nervous system (CNS) comes from animal in vivo models (requiring extrapolation to human relevance) and 2D static in vitro systems, which fail to capture the rich cell–cell and cell–matrix interactions of the dynamic 3D in vivo tissue microenvironment. In this work we have developed a BBB platform that allows for a high degree of customization in cellular composition, cellular orientation, and physiologically-relevant fluid dynamics. The system characterized and presented in this study reproduces key characteristics of a BBB model (e.g. tight junctions, efflux pumps) allowing for the formation of a selective and functional barrier. We demonstrate that our in vitro BBB is responsive to both biochemical and mechanical cues. This model further allows for culture of a CNS-like space around the BBB. As a result, the design of this platform is a valuable tool for studying BBB function as well as for screening of novel therapeutics.

42 ENGINEERING↗
DOE OSTI2018

Risk Management of NPP Incidents

A diagnostic model for managing the risk of NPP incidents attending different irregularities of equipment operation is examined for the example of the oil delivery system of the main circulation pump. The model includes the construction of a graph of the operation of the oil system and ranking in order to obtain indices of priority for monitoring information flow that reflect the actuation probability of each form of protection. The results of the analysis can used as input data for predicting the duration of a stable state of a technological system in the course of operation on the basis of stochastic extrapolation of the parameters by means of single-channel queuing systems with finite storage – technological protection and blocking.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2020

Linear two-pool models are insufficient to infer soil organic matter decomposition temperature sensitivity from incubations

Abstract Terrestrial carbon (C)-climate feedbacks depend strongly on how soil organic matter (SOM) decomposition responds to temperature. This dependency is often represented in land models by the parameter Q 10 , which quantifies the relative increase of microbial soil respiration per 10 °C temperature increase. Many studies have conducted paired laboratory soil incubations and inferred “active” and “slow” pool Q 10 values by fitting linear two-pool models to measured respiration time series. Using a recently published incubation study (Qin et al. in Sci Adv 5(7):eaau1218, 2019) as an example, here we first show that the very high parametric equifinality of the linear two-pool models may render such incubation-based Q 10 estimates unreliable. In particular, we show that, accompanied by the uncertain initial active pool size, the slow pool Q 10 can span a very wide range, including values as high as 100, although all parameter combinations are producing almost equally good model fit with respect to the observations. This result is robust whether or not interactions between the active and slow pools are considered (typically these interactions are not considered when interpreting incubation data, but are part of the predictive soil carbon models). This very large parametric equifinality in the context of interpreting incubation data is consistent with the poor temporal extrapolation capability of linear multi-pool models identified in recent studies. Next, using a microbe-explicit SOM model (RESOM), we show that the inferred two pools and their associated parameters (e.g., Q 10 ) could be artificial constructs and are therefore unreliable concepts for integration into predictive models. We finally discuss uncertainties in applying linear two-pool (or more generally multiple-pool) models to estimate SOM decomposition parameters such as temperature sensitivities from laboratory incubations. We also propose new observations and model structures that could enable better process understanding and more robust predictive capabilities of soil carbon dynamics.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Fog Formation Related to Gravity Currents Interacting with Coastal Topography

An interesting mixing-fog event was identified during IOP7 of the C-FOG project, where a cold front arriving from the north-east collided with the Downs peninsula in Ferryland, Newfoundland, to produce foggy conditions. A comprehensive set of field observations suggests that this collision caused turbulent mixing of nearly saturated ambient air with an almost saturated cold front, creating conditions for mixing fog. Additionally, laboratory experiments were performed to study the interaction of lock-exchange induced gravity currents with a (rectangular) obstacle to delve into physical processes underlying this phenomenon. Instantaneous velocity and density fields were obtained using particle image velocimetry and planar laser-induced fluorescence. The observations suggest that the obstacle starts affecting the approaching gravity-current propagation at an upstream distance of 2 H and, upon collision, the mixing is taking place over a spatial scale of 0.83 H , where H is the depth of the ambient fluid layer. The time for largerscale turbulent stirring to permeate to the smallest scales of turbulence and activate the condensation nuclei was estimated as 3t * , where t* = √H/g' is the intrinsic time scale of the gravity current and g' the reduced gravity. Extrapolation of results to IOP7 showed a good agreement with observations.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2013

Improving the Assessment and Valuation of Climate Change Impacts for Policy and Regulatory Analysis

The social cost of carbon (SCC) is a monetized metric for evaluating the benefits associated with marginal reductions in carbon dioxide (CO2) emissions. It represents the expected welfare loss from the future damages caused by the release of one tonne of CO2 in a given year, expressed in consumption equivalent terms. It is intended to be a comprehensive measure, taking into account changes in agricultural productivity, human health risks, loss of ecosystem services and biodiversity, and the frequency and severity of flooding and storms, among other possible impacts. Estimating the SCC requires long-term modeling of global economic activity, the climate system, and the linkages between the two through anthropogenic greenhouse gas (GHG) emissions and the effects of changing climatic conditions on economic activity and human well-being. The United States government currently uses the SCC in regulatory benefit-cost analyses to assess the welfare effects of changes in CO2 emissions. Consistent application of the SCC to federal rulemaking analyses began in 2009-2010 with the development of a set of global SCC estimates that employed three prominent integrated assessment models (IAMs) -- DICE, FUND, and PAGE. The U.S. government report identified a number of limitations associated with SCC estimates in general and its own assumptions in particular: an incomplete treatment of damages, including potential “catastrophic” impacts; uncertainty regarding the extrapolation of damage functions to high temperatures; incomplete treatment of adaptation and technological change; and the evaluation of uncertain outcomes in a risk-neutral fashion. External experts have identified other potential issues, including how best to model long-term socio-economic and emissions pathways, oversimplified physical climate and carbon cycle modeling within the IAMs, and an inconsistency between non-constant economic growth scenarios and constant discount rates. The U.S. government has committed to updating the estimates regularly as modeling capabilities and scientific and economic knowledge improves. To help foster further improvements in estimating the SCC, the U.S. Environmental Protection Agency and the U.S. Department of Energy hosted a pair of workshops on “Improving the Assessment and Valuation of Climate Change Impacts for Policy and Regulatory Analysis.” The first focused on conceptual and methodological issues related to integrated assessment modeling and the second brought together natural and social scientists to explore methods for improving damage assessment for multiple sectors. These two workshops provide the basis for the 13 papers in this special issue.

Climate Change↗
DOE OSTI2013

Implications of weak near-term climate policies on long-term mitigation pathways

While the international community has set a target to limit global warming to no more than 2°C above pre-industrial levels, only a few concrete climate policies and measures to reduce greenhouse gas (GHG) emissions have been implemented. We use a set of three global integrated assessment models to analyze the implications of current climate policies on long-term mitigation targets. We define a weak-policy baseline scenario, which extrapolates the current policy environment by assuming that the global climate regime remains fragmented and that emission reduction efforts remain unambitious in most of the world’s regions. In this scenario, GHG concentrations stabilize at approximately 650 ppm CO2e, which clearly falls short of the international community’s long-term climate target. We investigate the cost and achievability of the stabilization of atmospheric GHG concentrations at 450 ppm CO2e by 2100, if countries follow the weak policy pathway until 2020 or 2030, before global cooperative action is taken to pursue the long-term mitigation target. Despite weak near-term action, a 450 ppm CO2e target is achievable in all the models. However, we find that a deferral of ambitious action exacerbates the challenges of low stabilization. Specifically, weak near-term action leads to (a) higher temporary overshooting of radiative forcing, (b) faster and more aggressive transformations of energy systems after target adoption, (c) more stranded investments in fossil-based capacities, and (d) higher long-term mitigation costs and carbon prices._

Luderer, Gunnar↗
DOE OSTI2017

Algorithms and Experience with Prediction of Technical Operating Failures in Nuclear Power Plant Equipment

The development of algorithms for the prediction of technological operating failure of nuclear power plant equipment based on stochastic extrapolation of the values of technical parameters is discussed. The algorithms are tested on real archived data on the operation of the oil circulation system of the main circulating pumps in a power generating unit at a nuclear power plant.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗