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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Theoretical analysis of key factors achieving reversed magnetic shear q -profiles sustained with lower hybrid waves on EAST

The phase space analysis technique is applied to provide new insights into the fully non-inductive lower hybrid current driven (LHCD) discharges on EAST. The analysis shows that there are bounded and unbounded topologies of lower hybrid (LH) waves in phase space. For typical parameters on EAST, the propagation domain for 4.6 GHz LH waves is bounded, while unbounded for 2.45 GHz LH waves and one of the conditions is recognized to be good for achieving an off-axis current profile driven by 4.6 GHz LH waves on EAST. The parametric analysis on the potential power deposition (PPD) region for those experiments demonstrates that the reversed magnetic shear dominates the wave behavior, and confines the LH power absorption to the far off-axis region as long as it occurs in the 4.6 GHz dominated LHCD discharge. GENRAY/CQL3D simulations also confirm this effect of reversed shear on the power absorption of 4.6 GHz waves. A bounded propagation domain and a positive feedback loop between magnetic shear reversal and off-axis LHCD profile could explain the LH-only-sustained strong reversed magnetic shear observed in experiments on multiple machines. In contrast, there is no such effect for 2.45 GHz waves on EAST since the PPD region is less sensitive to the change of reversed shear due to the unbounded propagation domain.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Theoretical analysis of key factors achieving reversed magnetic shear q-profiles sustained with lower hybrid waves on EAST

The phase space analysis technique is applied to provide new insights into the fully non-inductive lower hybrid current driven (LHCD) discharges on EAST (Garofalo et al 2017 Nucl. Fusion 57 076037). The analysis shows that there are bounded and unbounded topologies of lower hybrid (LH) waves in phase space. For typical parameters on EAST, the propagation domain for 4.6 GHz LH waves is bounded, while unbounded for 2.45 GHz LH waves and one of the conditions is recognized to be good for achieving an off-axis current profile driven by 4.6 GHz LH waves on EAST. The parametric analysis on the potential power deposition (PPD) region for those experiments demonstrates that the reversed magnetic shear dominates the wave behavior, and confines the LH power absorption to the far off-axis region as long as it occurs in the 4.6 GHz dominated LHCD discharge. GENRAY/CQL3D simulations also confirm this effect of reversed shear on the power absorption of 4.6 GHz waves. A bounded propagation domain and a positive feedback loop between magnetic shear reversal and off-axis LHCD profile could explain the LH-only-sustained strong reversed magnetic shear observed in experiments on multiple machines. In contrast, there is no such effect for 2.45 GHz waves on EAST since the PPD region is less sensitive to the change of reversed shear due to the unbounded propagation domain.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2017

Factors influencing moisture analysis in the 3013 destructive examination surveillance program

Thermogravimetric analysis of a solid sample with mass spectrometry (TGA-MS) of the evolved gas is used in the destructive examination (DE) portion of the Integrated Surveillance Program to quantify the moisture content of the material stored in a 3013 container. As with any measurement determined from a small sample, the collection, storage, transportation, and handling of the sample can affect its ability to represent the properties of the bulk material. During the course of the DE program, questions have periodically arisen concerning the ability of the moisture sample to reflect reliably the actual moisture content of the entire material stored in the 3013 container. Most concerns are related to the ability to collect a representative sample and to preserve the moisture content of the sample between collection and analysis. Recent delays in analysis caused by maintenance issues with the TGA-MS instrument presented a unique opportunity to document and quantify the effects various factors have on the TGA-MS moisture measurement. This report will use recent data to document the effects that current sample collection and handling practices have on the TGA-MS moisture measurement. Some suggestions will be made which could improve the current sample collection and handling practices for the TGA-MS moisture measurement so that the analytical results more accurately reflect the moisture content of the material stored in the 3013 container.

3013↗
DOE OSTI2025

Insights from Optimizing HPL Performance on Exascale Systems: A Comparative Analysis of Panel Factorization

High performance LINPACK (HPL) remains the primary benchmark for evaluating supercomputing performance. It includes many parts with substantial internal complexity, and its performance is affected by a large number of parameters that interact in ways that are difficult to predict on large-scale heterogeneous supercomputer systems. We present a comprehensive performance analysis of HPL on Frontier, the world’s first exascale supercomputer, which achieved HPL performance of 1.35 exaflops. Through empirical parameter tuning, detailed modeling, and comparative evaluation, we uncover critical performance insights, share lessons learned, and outline best practices for effective parameter tuning on exascale systems. We introduce and evaluate two novel PDFACT strategies: a dedicated-thread (DT) variant and a GPU-based variant (GPUPDFACT) implementation using HIP cooperative groups, demonstrating that GPU-based factorization outperforms conventional CPU-based PDFACT on Frontier’s architecture. Our findings establish key performance factors for HPL on exascale systems and offer valuable guidance for future high-performance computing and benchmarking efforts.

Lu, Hao [ORNL] (ORCID:000000018941870X)↗
DOE OSTI2020

Novel AC Distribution Factor for Efficient Outage Analysis

We propose novel line outage distribution factors under AC power flow (AC-LODF) for providing very efficient approximate post-outage power flow solution. The AC-LODF is derived by using holomorphic embedding (HE) approach, and the approximate post-outage power flow solution is obtained with Pad approximation (PA). In this work, tests on IEEE 14-bus system, and Polish 2383-bus system verify that the proposed AC-LODF is effective on most outages, and can significantly speed up outage analysis.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2019

Longitudinal analysis of risk factors for dementia based on Mild Cognitive Impairment Screen results and questionnaire responses from healthy Japanese individuals registered in an online database

Abstract Introduction Despite an urgent need for developing remedial measures against dementia, no disease‐modifying drugs have been developed. Efficient protocols for participant recruitment need to be established for conducting clinical trials. To meet this need, a large‐scale online registry system, the Integrated Registry of Orange Plan (IROOP ® ), was created for healthy individuals. Although the risk factors for dementia have been discussed in our previous studies for a short interval of 6 months, some factors remain controversial. The present study aimed to explore factors affecting longitudinal changes in cognitive function for a longer interval of 18 months using the IROOP ® data. Methods This study assessed the longitudinal changes in the collated data for predicting the risk of dementia and included 473 individuals (175 men and 298 women; mean age 59.6 ± 10.1 years) registered in the IROOP ® between July 5, 2016 and January 15, 2018 who completed the initial questionnaire and brief assessment of cognitive function (Mild Cognitive Impairment Screen) at baseline and the regular questionnaire and the Mild Cognitive Impairment Screen at least once after baseline. Statistical analyses were performed using IBM SPSS, version 23.0, for Windows for demographic data and the MIXED procedure in SAS, version 9.4, for the linear mixed‐effect model. In each analysis, the statistical significance level was set at P < .05. Results Mood, sleep, quality of life, and medical histories including cognition were found to influence longitudinal changes in cognitive function. Discussion Given the multifactorial etiology of dementia, preventive measures targeting multiple domains are required for maintaining cognitive function, instead of focusing on one lifestyle factor.

Ogawa, Masayo↗
DOE OSTI2017

Identification and positional distribution analysis of transcription factor binding sites for genes from the wheat fl-cDNA sequences

Abstract The binding sites of transcription factors (TFs) in upstream DNA regions are called transcription factor binding sites (TFBSs). TFBSs are important elements for regulating gene expression. To date, there have been few studies on the profiles of TFBSs in plants. In total, 4,873 sequences with 5ʹ upstream regions from 8530 wheat fl-cDNA sequences were used to predict TFBSs. We found 4572 TFBSs for the MADS TF family, which was twice as many as for bHLH (1951), B3 (1951), HB superfamily (1914), ERF (1820), and AP2/ERF (1725) TFs, and was approximately four times higher than the remaining TFBS types. The percentage of TFBSs and TF members showed a distinct distribution in different tissues. Overall, the distribution of TFBSs in the upstream regions of wheat fl-cDNA sequences had significant difference. Meanwhile, high frequencies of some types of TFBSs were found in specific regions in the upstream sequences. Both TFs and fl-cDNA with TFBSs predicted in the same tissues exhibited specific distribution preferences for regulating gene expression. The tissue-specific analysis of TFs and fl-cDNA with TFBSs provides useful information for functional research, and can be used to identify relationships between tissue-specific TFs and fl-cDNA with TFBSs. Moreover, the positional distribution of TFBSs indicates that some types of wheat TFBS have different positional distribution preferences in the upstream regions of genes.

Chen, Zhen-Yong↗
DOE OSTI2016

Analysis of governing factors controlling gas transport through fresh and aged triptycene-based polyimide films

In this report the fundamental gas transport properties and physical aging behavior of a series of triptycene-based polyimides with various substitution groups were investigated. Wide-angle x-ray diffraction revealed that the 6FDA-1,4-triptycene polyimides exhibit two chain packing domains with d-spacing values of ~6.7 Å and ~5.3 Å, corresponding to triptycene-induced chain packing disruption and chain segments lacking the triptycene moiety, respectively. Positron annihilation lifetime spectroscopy (PALS) showed a bimodal distribution of microcavity size made up of triptycene cleft cavities that are ~3 Å diameter and larger interchain cavities with an average diameter of ~7 Å. Additionally, PALS confirmed 6FDA-1,4-trip_CH 3 has the lowest fractional free volume, primarily due to smaller contributions from the interchain cavities, and 6FDA-1,4-trip_CF 3 has the largest fractional free volume. It was also found that the addition of substituent groups had a unique and positive effect on the aging properties over nine months, in which the addition of CH 3 and CF 3 groups led to permeability increases of ~20% and ~40%, respectively. This is caused by the combination of the lowered driving force for physical aging, the substituent groups sterically hindering tighter packing with time, and the interconnectivity and/or unblocking of free volume over time through small-scale, local chain motion.

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

Comparative Analysis of Transcription Factors Families across Fungal Tree of Life

Transcription factors (TFs) are proteins that regulate the transcription of genes, by binding to specific DNA sequences. Based on literature (Shelest, 2008; Weirauch and Hughes,2011) collected and manually curated list of DBD Pfam domains (in total 62 DBD domains) We looked for distribution of TFs in 395 fungal genomes plus additionally in plant genomes (Phytozome), prokaryotes(IMG), some animals/metazoans and protists genomes

Salamov, Asaf↗
DOE OSTI2025

A mathematical approach to using the forgetting curve to evaluate experience and training factors in human reliability analysis

Traditional human reliability analysis (HRA) methods have difficulty dealing with the dynamic nature of factors such as time and rely on static and expert-judgment-based assessments of performance-shaping factors (PSFs) across limited levels. In this study, we introduce a mathematical approach for dynamically evaluating the experience and training PSF. Our proposed method integrates the psychological concept of the “forgetting curve” to evaluate how PSFs are impacted by the number of trainings and the time elapsed since training. To confirm the validity of the model, we provide experimental data fitted by identifying the quantitative relationship between training and human performance. This research enables dynamic and objective assessments, thus reducing reliance on subjective expert judgment and improving the accuracy of HRA.

99 - GENERAL AND MISCELLANEOUS↗
DOE OSTI2016

Pneumothorax Complicating Coaxial and Non-coaxial CT-Guided Lung Biopsy: Comparative Analysis of Determining Risk Factors and Management of Pneumothorax in a Retrospective Review of 650 Patients

PurposeTo assess the scope and determining risk factors related to the development of pneumothorax throughout CT-guided biopsy of pulmonary lesions in coaxial and non-coaxial techniques and the outcome of its management.Materials and MethodsThe study included CT-guided percutaneous lung biopsies in 650 consecutive patients (407 males, 243 females; mean age 54.6 years, SD 5.2) from November 2008 to June 2013 in a retrospective design. Patients were classified according to lung biopsy technique into coaxial group (318 lesions) and non-coaxial group (332 lesions). Exclusion criteria for biopsy were lesions <5 mm in diameter, uncorrectable coagulopathy, positive-pressure ventilation, severe respiratory compromise, pulmonary arterial hypertension, or refusal of the procedure. Risk factors related to the occurrence of pneumothorax were classified into: (a) Technical risk factors, (b) patient-related risk factors, and (c) lesion-associated risk factors. Radiological assessments were performed by two radiologists in consensus. Mann–Whitney U test and Fisher’s exact tests were used for statistical analysis. p values <0.05 were considered statistically significant.ResultsThe incidence of pneumothorax complicating CT-guided lung biopsy was less in the non-coaxial group (23.2 %, 77 out of 332) than the coaxial group (27 %, 86 out of 318). However, the difference in incidence between both groups was statistically insignificant (p = 0.14). Significant risk factors for the development of pneumothorax in both groups were emphysema (p < 0.001 in both groups), traversing a fissure with the biopsy needle (p value 0.005 in non-coaxial group and 0.001 in coaxial group), small lesion, less than 2 cm in diameter (p value of 0.02 in both groups), location of the lesion in the basal or mid sections of the lung (p = 0.003 and <0.001 in non-coaxial and coaxial groups, respectively), and increased needle track path within the lung tissue of more than 2.5 cm (p = 0.01 in both groups). The incidence of pneumothorax in the non-coaxial group was significantly correlated to the number of specimens obtained (p = 0.006). This factor was statistically insignificant in the coaxial group (p = 0.45). The biopsy yield was more diagnostic and conclusive in the coaxial group in comparison to the non-coaxial group (p = 0.008). Simultaneous incidence of pneumothorax and pulmonary hemorrhage was 27.3 % (21/77) in non-coaxial group and in 30.2 % (26/86) in coaxial group. Conservative management was sufficient for treatment of 91 out of 101 patients of pneumothorax in both groups (90.1 %). Manual evacuation of pneumothorax was efficient in 44/51 patients (86.3 %) in both groups and intercostal chest tube was applied after failure of manual evacuation (7 patients: 13.7 %), from which one patient developed a persistent air leakage necessitating pleurodesis.ConclusionPneumothorax complicating CT-guided core biopsy of pulmonary lesions, showed the insignificant difference between coaxial and non-coaxial techniques. However, both techniques have the same significant risk factors including small and basal lesions, increased lesion’s depth from pleural surface, and increased length of aerated lung parenchyma crossed by biopsy needle and passing through pulmonary fissures in the needle tract.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2025

Top-Performing Photovoltaic Cells Compared to the Shockley–Queisser Limit

Top-performing single-junction and two-terminal tandem devices that include at least one polycrystalline cell are compared with each other and their ideal limits. The parameters of open-circuit voltage, short-circuit current, and fill-factor are individually compared to the Shockley–Queisser limit to investigate where different technologies have room to improve. Technologies, such as silicon and cadmium telluride have the most room for improvement in open-circuit voltage currently utilizing 87% and 81% of their maxima, respectively. Detailed diode and fill-factor loss analysis is presented for single-junction devices to give further insight on how they compare and where efficiency is lost. Single-crystal technologies demonstrate a fill-factor closer to the Shockley–Queisser limit than polycrystalline devices. The high diode quality factor of polycrystalline devices is the leading cause of the decreased fill-factor. Similar analysis on tandem cells with at least one thin-film cell shows that although their efficiency exceeds that of the single-junction cells, the fraction of their ideal efficiency is smaller. Here, by comparing parameters to the Shockley–Queisser limit, it becomes clearer where certain technologies have the potential for improvement.

High efficiency↗