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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Frequency-resolved Raman for transient thermal probing and thermal diffusivity measurement

Steady state Raman has been widely used for temperature probing and thermal conductivity/conductance measurement in combination with temperature coefficient calibration. In this work, a new transient Raman thermal probing technique: frequency-resolved Raman (FR-Raman) is developed for probing the transient thermal response of materials and measuring their thermal diffusivity. The FR-Raman uses an amplitude modulated square-wave laser for simultaneous material heating and Raman excitation. The evolution profile of Raman properties: intensity, Raman wavenumber, and emission, against frequency are measured experimentally and reconstructed theoretically. They are used for fitting to determine the thermal diffusivity of the material under test. A Si cantilever is used to investigate the capacity of this new technique. The cantilever’s thermal diffusivity is determined as 9.57 × 10 -5 m 2 /s, 11.00 × 10 -5 m 2 /s and 9.02 × 10 -5 m 2 /s by fitting the Raman intensity, wavenumber and emission. The deviation from the reference value is largely attributed to thermal stress-induced material deflection and Raman drift, which could be significantly suppressed by using a higher sensitivity Raman spectrometer with lower laser energy. As a result, the FR-Raman provides a novel way for transient thermal characterization of materials with a ?m spatial resolution.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Search for supersymmetry at s =8 TeV in final states with jets and two same-sign leptons or three leptons with the ATLAS detector

CERN-LHC. A search for strongly produced supersymmetric particles is conducted using signatures involving multiple energetic jets and either two isolated leptons (e or mu) with the same electric charge, or at least three isolated leptons. The search also utilises jets originating from b-quarks, missing transverse momentum and other observables to extend its sensitivity. The analysis uses a data sample corresponding to a total integrated luminosity of 20.3 fb^-1 of sqrt(s) = 8 TeV proton-proton collisions recorded with the ATLAS detector at the Large Hadron Collider in 2012. No deviation from the Standard Model expectation is observed. New or significantly improved exclusion limits are set on a wide variety of supersymmetric models in which the lightest squark can be of the first, second or third generations, and in which R-parity can be conserved or violated.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2026

NMF-Based Anomaly Detection in CMS 2D Tracking Occupancy Histograms

The CMS experiment relies on Data Quality Monitoring (DQM) to ensure that recorded collision data are suitable for physics analysis. During LHC Run 3, each run contains many lumisections and tracking monitoring elements, making offline inspection challenging, especially for localized detector effects that may appear only for short periods of time. This poster presents an unsupervised machine-learning approach to identify anomalous lumisections in CMS tracking occupancy histograms using Non-Negative Matrix Factorization (NMF). The workflow uses offline CMS DQMIO tracking histograms retrieved with the CMS DIALS API and organized as two-dimensional occupancy maps for each lumisection. After selecting stable lumisections, the occupancy maps are normalized and arranged into a non-negative data matrix. The NMF model learns a compact set of basis patterns describing normal tracking occupancy. Each lumisection is then reconstructed from these learned components, and the reconstruction error is used as an anomaly score. Large residuals indicate occupancy patterns that deviate from normal detector behavior and are flagged for further inspection. This NMF-based approach provides a fast and interpretable way to flag lumisections whose tracking occupancy patterns differ from normal detector behavior. Preliminary studies show sensitivity to known tracking anomalies, and ongoing work is focused on validating the method across additional Run 3 Pixel and Strip detector issues.

Rodríguez Ramos, Iliomar [Puerto Rico U., Mayaguez↗
DOE OSTI2025

Evaluating the feasibility of using downwind methods to quantify point source oil and gas emissions using continuously monitoring fence-line sensors

The dependable reporting of methane (CH 4 ) emissions from point sources, such as fugitive leaks from oil and gas infrastructure, is important for profit maximization (retaining more hydrocarbons), evaluating climate impacts, assessing CH 4 fees for regulatory programs, and validating CH 4 intensity in differentiated gas programs. Currently, there are disagreements between emissions reported by different quantification techniques for the same sources. It has been suggested that downwind CH 4 quantification methods using CH 4 measurements on the fence line of production facilities could be used to generate emission estimates from oil and gas operations at the site level, but it is currently unclear how accurate the quantified emissions are. To investigate the accuracy of downwind methods, this study uses fence-line simulated data collected during controlled-release experiments as input for a non-standard closed-path eddy covariance (EC), the Gaussian plume inverse model (GPIM), and the backward Lagrangian stochastic (bLs) model in a range of atmospheric conditions. This study's EC attempt was unsuccessful due to data collection and instrumentation issues, resulting in invalid results characterized by underestimated emissions, large negative fluxes, and cospectra/ogives that deviated from their ideal shapes. Consequently, the EC results could not be compared with the GPIM and bLS model. The bLs model demonstrated the highest accuracy for single-release single-point emissions, though it exhibited greater uncertainty than GPIM under multi-release conditions. Across the GPIM and bLs model, the most reliable quantification was achieved with 15 min averaging and a narrow 5° wind sector range. Although EC was limited in this context, future studies should consider employing a standard EC system and further optimizing GPIM and bLs approaches – particularly for complex multi-source scenarios – to enhance quantification accuracy and reduce uncertainty.

03 NATURAL GAS↗
DOE OSTI2013

Long-Term Results for Trigeminal Schwannomas Treated With Gamma Knife Surgery

Purpose: Surgical resection is considered the desirable curative treatment for trigeminal schwannomas. However, complete resection without any complications remains challenging. During the last several decades, stereotactic radiosurgery (SRS) has emerged as a minimally invasive treatment modality. Information regarding long-term outcomes of SRS for patients harboring trigeminal schwannomas is limited because of the rarity of this tumor. The aim of this study was to evaluate long-term tumor control and functional outcomes in patients harboring trigeminal schwannomas treated with SRS, specifically with gamma knife surgery (GKS). Methods and Materials: Fifty-three patients harboring trigeminal schwannomas treated with GKS were evaluated. Of these, 2 patients (4%) had partial irradiation of the tumor, and 34 patients (64%) underwent GKS as the initial treatment. The median tumor volume was 6.0 cm{sup 3}. The median maximum and marginal doses were 28 Gy and 14 Gy, respectively. Results: The median follow-up period was 98 months. On the last follow-up image, 7 patients (13%) had tumor enlargement, including the 2 patients who had partial treatment. Excluding the 2 patients who had partial treatment, the actuarial 5- and 10-year progression-free survival (PFS) rates were 90% and 82%, respectively. Patients with tumors compressing the brainstem with deviation of the fourth ventricle had significantly lower PFS rates. If those patients with tumors compressing the brainstem with deviation of the fourth ventricle are excluded, the actuarial 5- and 10-year PFS rates increased to 95% and 90%, respectively. Ten percent of patients had worsened facial numbness or pain in spite of no tumor progression, indicating adverse radiation effect. Conclusions: GKS can be an acceptable alternative to surgical resection in patients with trigeminal schwannomas. However, large tumors that compress the brainstem with deviation of the fourth ventricle should be surgically removed first and then treated with GKS when necessary.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2016

High‐frequency daily temperature variability in China and its relationship to large‐scale circulation

ABSTRACT Two measures of intra‐seasonal variability, indicated respectively by standard deviations ( SD ) and day‐to‐day ( DTD ) fluctuations denoted by absolute differences between adjacent 2‐day periods, as well as their relationships with large‐scale circulation patterns were investigated in China during 1962–2008 on the basis of homogenized daily temperature records from 549 local stations and reanalysis data. Our results show that both the SD and DTD of daily minimum temperatures ( T min ) in summer as well as the minimum and maximum temperatures in winter have been decreasing, while the daily maximum temperature ( T max ) variability in summer is fluctuating more, especially over southern China. In summer, an attribution analysis indicates that the intensity of the Western Pacific Subtropical High ( WPSH ) and high‐level East Asian Subtropical Jet stream ( EASJ ) are positively correlated with both SD and DTD , but the correlation coefficients are generally greater with the SD than with the DTD of the daily maximum temperature, T max . In contrast, the location of the EASJ shows the opposite correlation pattern, with intensity regarding the correlation with both SD and DTD . In winter, the Arctic Oscillation ( AO ) is negatively correlated with both the SD and DTD of the daily minimum temperature, but its intra‐seasonal variability exhibits good agreement with the SD of the T min . The Siberian High acts differently with respect to the SD and DTD of the T min , demonstrating a regionally consistent positive correlation with the SD . Overall, the large‐scale circulation can well explain the intra‐seasonal SD, but DTD fluctuations may be more local and impacted by local conditions, such as changes in the temperature itself, the land surface, and so on.

Wu, Fu‐Ting↗
DOE OSTI2016

Transitions From Stochastic to Point Kinetics Models In Fissile Solutions

Fissile solutions form an integral part of the fuel cycle, being used to store and process both fresh fuel and waste. Fissile solutions are also found within Aqueous Homogeneous Reactors (AHRs) including research reactors such as CRAC and SILENE and also potential future systems which could be used for the production of medical isotopes. In the case of fissile solutions in the fuel cycle, avoiding criticality is a priority but accidents have occurred in which a significant number of fissions occurred. In the case of AHRs, a sustained neutron population and fission rate is desired. In both cases the ability to simulate transients where changes in reactivity cause the neutron population to increase are important. A popular method for the simulation of such transients is the point kinetic method which allows the capture of the major features of a transient at a fraction of the computational runtime and code complexity of more comprehensive modelling technologies. A limitation of the point kinetics method and other mainstream methods of predicting neutron behaviour is that they assume the neutron population is large enough that the mean behaviour will be observed. When the neutron population is low, however, the deviation around the mean behaviour is expected to be relatively large as there is an aleatoric uncertainty arising from the uncertain fate of individual neutrons. Such limitations are of particular importance when the reactivity of a system is rapidly increasing while the neutron population is low, which is often true in accident scenarios involving fissile solutions. This provides the motivation for the coupling of point kinetics and a probabilistic models of fissile solutions. This summary aims to explore some of the behaviours resulting from a low neutron population and rising reactivity using a coupled probabilistic and point kinetics model of a fissile solution. As the effects of a low neutron population are the primary concern of this summary, the point kinetics and thermal hydraulic models used will be relatively simple but these models should be sufficient to capture the most important behaviours of the system in the first minute or so of a transient. This work is an extension of the work found in [1]. In that work the methodology was applied to fast pulses produced by systems such as Godiva and its results were found to compare favourably to experimental and analytical results, such as the burst wait time, in [2]. This work focuses on the application of this methodology to a fissile solution but the method could be applied to a number of criticality safety or reactor operation scenarios through suitable modification of the point kinetics model and would produce a more accurate prediction of the peak power obtained when a system first becomes critical compared to the use of a standard point kinetics model. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2014

Simultaneous effect of modified gravity and primordial non-Gaussianity in large scale structure observations

In this work we study the simultaneous effect of primordial non-Gaussianity and the modification of the gravity in f(R) framework on large scale structure observations. We show that non-Gaussianity and modified gravity introduce a scale dependent bias and growth rate functions. The deviation from ΛCDM in the case of primordial non-Gaussian models is in large scales, while the growth rate deviates from ΛCDM in small scales for modified gravity theories. We show that the redshift space distortion can be used to distinguish positive and negative f{sub NL} in standard background, while in f(R) theories they are not easily distinguishable. The galaxy power spectrum is generally enhanced in presence of non-Gaussianity and modified gravity. We also obtain the scale dependence of this enhancement. Finally we define galaxy growth rate and galaxy growth rate bias as new observational parameters to constrain cosmology.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Massive gravity wrapped in the cosmic web

We study how the filamentary pattern of the cosmic web changes if the true gravity deviates from general relativity (GR) on a large scale. The f(R) gravity, whose strength is controlled to satisfy the current observational constraints on the cluster scale, is adopted as our fiducial model and a large, high-resolution N-body simulation is utilized for this study. By applying the minimal spanning tree algorithm to the halo catalogs from the simulation at various epochs, we identify the main stems of the rich superclusters located in the most prominent filamentary section of the cosmic web and determine their spatial extents per member cluster to be the degree of their straightness. It is found that the f(R) gravity has the effect of significantly bending the superclusters and that the effect becomes stronger as the universe evolves. Even in the case where the deviation from GR is too small to be detectable by any other observables, the degree of the supercluster straightness exhibits a conspicuous difference between the f(R) and the GR models. Our results also imply that the supercluster straightness could be a useful discriminator of f(R) gravity from the coupled dark energy since it is shown to evolve differently between the two models. As a final conclusion, the degree of the straightness of the rich superclusters should provide a powerful cosmological test of large scale gravity.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Interannual variability in global mean sea level estimated from the CESM Large and Last Millennium Ensembles

To better understand global mean sea level (GMSL) as an indicator of climate variability and change, contributions to its interannual variation are quantified in the Community Earth System Model (CESM) Large Ensemble and Last Millennium Ensemble. Consistent with expectations, the El Niño/Southern Oscillation (ENSO) is found to exert a strong influence due to variability in rainfall over land (PL) and terrestrial water storage (TWS). Other important contributors include changes in ocean heat content (OHC) and precipitable water (PW). The temporal evolution of individual contributing terms is documented. The magnitude of peak GMSL anomalies associated with ENSO generally are of the order of 0.5 mm·K -1 with significant inter-event variability, with a standard deviation (σ) that is about half as large The results underscore the exceptional rarity of the 2010/2011 La Niña-related GMSL drop and estimate the frequency of such an event to be about only once in every 75 years. In addition to ENSO, major volcanic eruptions are found to be a key driver of interannual variability. Associated GMSL variability contrasts with that of ENSO as TWS and PW anomalies initially offset the drop due to OHC reductions but short-lived relative to them. Furthermore, responses up to 25 mm are estimated for the largest eruptions of the Last Millennium.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2015

TU-AB-BRA-04: Quantitative Radiomics: Sensitivity of PET Textural Features to Image Acquisition and Reconstruction Parameters Implies the Need for Standards

Purpose: Despite increased use of heterogeneity metrics for PET imaging, standards for metrics such as textural features have yet to be developed. We evaluated the quantitative variability caused by image acquisition and reconstruction parameters on PET textural features. Methods: PET images of the NEMA IQ phantom were simulated with realistic image acquisition noise. 35 features based on intensity histograms (IH), co-occurrence matrices (COM), neighborhood-difference matrices (NDM), and zone-size matrices (ZSM) were evaluated within lesions (13, 17, 22, 28, 33 mm diameter). Variability in metrics across 50 independent images was evaluated as percent difference from mean for three phantom girths (850, 1030, 1200 mm) and two OSEM reconstructions (2 iterations, 28 subsets, 5 mm FWHM filtration vs 6 iterations, 28 subsets, 8.6 mm FWHM filtration). Also, patient sample size to detect a clinical effect of 30% with Bonferroni-corrected α=0.001 and 95% power was estimated. Results: As a class, NDM features demonstrated greatest sensitivity in means (5–50% difference for medium girth and reconstruction comparisons and 10–100% for large girth comparisons). Some IH features (standard deviation, energy, entropy) had variability below 10% for all sensitivity studies, while others (kurtosis, skewness) had variability above 30%. COM and ZSM features had complex sensitivities; correlation, energy, entropy (COM) and zone percentage, short-zone emphasis, zone-size non-uniformity (ZSM) had variability less than 5% while other metrics had differences up to 30%. Trends were similar for sample size estimation; for example, coarseness, contrast, and strength required 12, 38, and 52 patients to detect a 30% effect for the small girth case but 38, 88, and 128 patients in the large girth case. Conclusion: The sensitivity of PET textural features to image acquisition and reconstruction parameters is large and feature-dependent. Standards are needed to ensure that prospective trials which incorporate textural features are properly designed to detect clinical endpoints. Supported by NIH grants R01 CA169072, U01 CA148131, NCI Contract (SAIC-Frederick) 24XS036-004, and a research contract from GE Healthcare.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Holographic reconstruction of AdS exchanges from crossing symmetry

Motivated by AdS/CFT, we address the following outstanding question in large N conformal field theory: given the appearance of a single-trace operator in the O x O OPE of a scalar primary O, what is its total contribution to the vacuum four-point function (OOOO) as dictated by crossing symmetry? We solve this problem in 4d conformal field theories at leading order in 1/N. Viewed holographically, this provides a field theory reconstruction of crossing-symmetric, four-point exchange amplitudes in AdS 5 . Our solution takes the form of a resummation of the large spin solution to the crossing equations, supplemented by corrections at finite spin, required by crossing. The method can be applied to the exchange of operators of arbitrary twist τ and spin s, although it vastly simplifies for even-integer twist, where we give explicit results. The output is the set of OPE data for the exchange of all double-trace operators [OO] n,ℓ . We find that the double-trace anomalous dimensions γ n,ℓ are negative, monotonic and convex functions of ℓ, for all n and all ℓ > s. This constitutes a holographic signature of bulk causality and classical dynamics of even-spin fields. We also find that the “derivative relation” between double-trace anomalous dimensions and OPE coefficients does not hold in general, and derive the explicit form of the deviation in several cases. Finally, we study large n limits of γ n,ℓ , relevant for the Regge and bulk-point regimes.

1/N expansion↗
DOE OSTI2023

Indirect searches at CMS

In these proceedings, we present several new measurements of Standard Model (SM) processes, in the Higgs sector and beyond, that push the precision frontier forward at CMS. Results are presented in the context of a framework parameterizing deviations in Higgs boson couplings, as well as in the context of SM Effective Field Theory, where new analyses targeting Higgs, top, and multi-boson processes probe an increasingly diverse set of operators. Within these frameworks, CMS is efficiently exploring a large space of new physics models. No significant deviation from SM expectations is found.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Comparing Ocean Surface Boundary Vertical Mixing Schemes Including Langmuir Turbulence

Six recent Langmuir turbulence parameterization schemes and five traditional schemes are implemented in a common single-column modeling framework and consistently compared. These schemes are tested in scenarios versus matched large eddy simulations, across the globe with realistic forcing (JRA55-do,WAVEWATCH-III simulated waves) and initial conditions (Argo), and under realistic conditions as observed at ocean moorings. Traditional non-Langmuir schemes systematically underpredict large eddy simulation vertical mixing under weak convective forcing, while Langmuir schemes vary in accuracy. Under global, realistic forcing Langmuir schemes produce 6% (–1% to 14% for 90% confidence) or 5.2 m (–0.2 m to 17.4 m for 90% confidence) deeper monthly mean mixed layer depths than their non-Langmuir counterparts, with the greatest differences in extratropical regions, especially the Southern Ocean in austral summer. Discrepancies among Langmuir schemes are large (15% in mixed layer depth standard deviation over the mean): largest under wave-driven turbulence with stabilizing buoyancy forcing, next largest under strongly wave-driven conditions with weak buoyancy forcing, and agreeing during strong convective forcing. Non-Langmuir schemes disagree with each other to a lesser extent, with a similar ordering. Langmuir discrepancies obscure a cross-scheme estimate of the Langmuir effect magnitude under realistic forcing, highlighting limited understanding and numerical deficiencies. Maps of the regions and seasons where the greatest discrepancies occur are provided to guide further studies and observations.

58 GEOSCIENCES↗
DOE OSTI2014

Detecting differential protein expression in large-scale population proteomics

Mass spectrometry-based high-throughput quantitative proteomics shows great potential in clinical biomarker studies, identifying and quantifying thousands of proteins in biological samples. However, methods are needed to appropriately handle issues/challenges unique to mass spectrometry data in order to detect as many biomarker proteins as possible. One issue is that different mass spectrometry experiments generate quite different total numbers of quantified peptides, which can result in more missing peptide abundances in an experiment with a smaller total number of quantified peptides. Another issue is that the quantification of peptides is sometimes absent, especially for less abundant peptides and such missing values contain the information about the peptide abundance. Here, we propose a Significance Analysis for Large-scale Proteomics Studies (SALPS) that handles missing peptide intensity values caused by the two mechanisms mentioned above. Our model has a robust performance in both simulated data and proteomics data from a large clinical study. Because varying patients’ sample qualities and deviating instrument performances are not avoidable for clinical studies performed over the course of several years, we believe that our approach will be useful to analyze large-scale clinical proteomics data.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2016

Sensitivity of inflationary predictions to pre-inflationary phases

How sensitive are the predictions of inflation to pre-inflationary conditions when the number of efolds of inflation is not too large? In an attempt to address this question, we consider a simple model where the inflationary era is preceded by an era dominated by a radiation fluid, which is coupled to the inflaton only gravitationally and which extends back to the Planck era. We show that there is a natural generalized Bunch-Davies vacuum state for perturbations to the coupled inflaton-gravity-fluid system at early times. With this choice of initial state the model predicts interesting deviations from the standard power spectrum of single field slow-roll inflation at large scales. However, the deviations are too small to be observable in near future CMB observations.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Tempering stochastic density functional theory

Here, we introduce a tempering approach with stochastic density functional theory (sDFT), labeled t-sDFT, which reduces the statistical errors in the estimates of observable expectation values. This is achieved by rewriting the electronic density as a sum of a "warm" component complemented by "colder" correction(s). Since the warm component is larger in magnitude but faster to evaluate, we use many more stochastic orbitals for its evaluation than for the smaller-sized colder correction(s). This results in a significant reduction in the statistical fluctuations and systematic deviation compared to sDFT for the same computational effort. We demonstrate the method's performance on large hydrogen-passivated silicon nanocrystals, finding a reduction in the systematic deviation in the energy by more than an order of magnitude, while the systematic deviation in the forces is also quenched. Similarly, the statistical fluctuations are reduced by factors of ≈4-5 for the total energy and ≈1.5-2 for the forces on the atoms. Since the embedding in t-sDFT is fully stochastic, it is possible to combine t-sDFT with other variants of sDFT such as energy-window sDFT and embedded-fragmented sDFT.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Reproducibility of calculations on Li species with correlation-consistent basis sets

Here we have found that two different basis set series, both labeled cc-pVxZ, are widely available and widely used for calculation on Li compounds such that calculations that should be the same are different, causing a reproducibility problem. Here we study the magnitude of the disagreement of these nominally-the-same basis sets for wave function and density functional calculations of Li clusters. We find deviations among the basis sets of as large as 22 millihartrees. In most cases one obtains lower energies with the noncanonical choices. Therefore, it is important to specify which version of the basis set is used for calculations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗