Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Performance Rating Method”

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 1,765 records · Page 98
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Identification of multiple eigenmode growth rates towards real time detection in DIII-D and KSTAR tokamak plasmas

Abstract The successful application of three-dimensional (3D) magnetohydrodynamic (MHD) spectroscopy enables us to identify the multi-mode eigenvalues in DIII-D and KSTAR tokamak experiments with stable plasmas. The temporal evolution of the multi-modes’ stabilities have been detected. The new method is numerically efficient allowing the real time detection of MHD modes’ stabilities during the discharge. The method performs active detection of the plasma stability by utilizing the upper and lower rows of internal non-axisymmetric coils to apply a wide variety of 3D fields. Multi-mode eigenvalues are extracted using subspace system identification of the plasma response measured by 3D-field magnetic sensors distributed at different poloidal locations. The equivalence of this new method with the one introduced by Wang (2019 Nucl. Fusion 59 024001) has been numerically corroborated. The more robust and efficient calculation developed here will enable real time monitoring of the plasma stability based on the extracted eigenvalues of stable modes.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

The feasibility study and characterization of a two-dimensional diode array in “magic phantom” for high dose rate brachytherapy quality assurance

Purpose: High dose rate (HDR) brachytherapy is a radiation treatment technique capable of delivering large dose rates to the tumor. Radiation is delivered using remote afterloaders to drive highly active sources (commonly {sup 192}Ir with an air KERMA strength range between 20 000 and 40 000 U, where 1 U = 1 μGy m{sup 2}/h in air) through applicators directly into the patient's prescribed region of treatment. Due to the obvious ramifications of incorrect treatment while using such an active source, it is essential that there are methods for quality assurance (QA) that can directly and accurately verify the treatment plan and the functionality of the remote afterloader. This paper describes the feasibility study of a QA system for HDR brachytherapy using a phantom based two-dimensional 11 × 11 epitaxial diode array, named “magic phantom.”Methods: The HDR brachytherapy treatment plan is translated to the phantom with two rows of 10 (20 in total) HDR source flexible catheters, arranged above and below the diode array “magic plate” (MP). Four-dimensional source tracking in each catheter is based upon a developed fast iterative algorithm, utilizing the response of the diodes in close proximity to the {sup 192}Ir source, sampled at 100 ms intervals by a fast data acquisition (DAQ) system. Using a {sup 192}Ir source in a solid water phantom, the angular response of the developed epitaxial diodes utilized in the MP and also the variation of the MP response as a function of the source-to-detector distance (SDD) were investigated. These response data are then used by an iterative algorithm for source dwelling position determination. A measurement of the average transit speed between dwell positions was performed using the diodes and a fast DAQ.Results: The angular response of the epitaxial diode showed a variation of 15% within 360°, with two flat regions above and below the detector face with less than 5% variation. For SDD distances of between 5 and 30 mm the relative response of the epitaxial diodes used in the MP is in good agreement (within 8%) with radial dose function measurements found within the TG-43 protocol, with SDD of up to 70 mm showing a 40% over response. A method for four-dimensional localization of the HDR source was developed, allowing the source dwell position to be derived within 0.50 mm of the expected position. An estimation of the average transit speed for varying step sizes was determined and was found to increase from (12.8 ± 0.3) up to (38.6 ± 0.4) cm/s for a step size of 2.5 and 50 mm, respectively.Conclusions: Our characterization of the designed QA “magic phantom” with MP in realistic HDR photon fields demonstrates the promising performance for real-time source position tracking in four dimensions and measurements of transit times. Further development of this system will allow a full suite for QA in HDR brachytherapy and analysis, and for future in vivo tracking.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2012

Study of the secondary neutral radiation in proton therapy: Toward an indirect in vivo dosimetry

Purpose: Secondary particles produced in the collision of protons with beam modifiers are of concern in proton therapy. Nevertheless, secondary radiation can provide information on the dosimetric parameters through its dependency on the modulating accessories (range shifter and range modulating wheel). Relatively little data have been reported in the literature for low-energy proton beams. The present study aims at characterizing the neutron and photon secondary radiation at the low-energy proton therapy facility of the Centre Antoine Lacassagne (CAL), and studying their correlation to the dosimetric parameters to explore possible practical uses of secondary radiation in the treatment quality for proton therapy. Methods: The Monte Carlo code MCNPX was used to simulate the proton therapy facility at CAL. Neutron and photon fluence, {Phi}, and ambient dose equivalent per proton dose, H*(10)/D, were determined across the horizontal main plane spanning the whole treatment room. H*(10)/D was also calculated at two positions of the treatment room where dosimetric measurements were performed for validation of the Monte Carlo calculations. Calculations and measurements were extended to 100 clinical spread-out Bragg Peaks (SOBPs) covering the whole range of therapeutic dose rates (D/MU) employed at CAL. In addition, the values of D and MU were also calculated for each SOBP and the results analyzed to study the relationship between secondary radiation and dosimetric parameters. Results: The largest production of the secondary particles takes place at the modulating devices and the brass collimators located along the optical bench. Along the beam line and off the beam axis to 2.5 m away, H*(10)/D values ranged from 5.4 {mu}Sv/Gy to 5.3 mSv/Gy for neutrons, and were 1 order of magnitude lower for photons. H*(10)/D varied greatly with the distance and angle to the beam axis. A variation of a factor of 5 was found for the different range of modulations (SOBPs). The ratios between calculations and measurements were 2.3 and 0.5 for neutrons and photons, respectively, and remained constant for all the range of SOBPs studied, which provided validation for the Monte Carlo calculations. H*(10)/D values were found to correlate to the proton dose rate D/MU with a power fit, both for neutrons and photons. This result was exploited to implement a system to obtain D/MU values from the measurement of the integrated photon ambient dose equivalent H*(10) during treatment, which provides a method to control the dosimetric parameters D/MU and D. Conclusions: The treatment room at CAL is moderately polluted by secondary particles. The constant ratio between measurements and calculations for all SOBPs showed that simulations correctly predict the dosimetric parameters and the dependence of the production of secondary particles on the modulation. The correlation between H*(10)/D and D/MU is a useful tool for quality control and is currently used at CAL. This system works as an indirect in vivo dosimetry method, which is so far not feasible in proton therapy. This tool requires very simple instrumentation and can be implemented from the measurement of either photons or neutrons.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

TiO 2 Microboxes with Controlled Internal Porosity for High‐Performance Lithium Storage

Abstract Titanium dioxide (TiO 2 ) is considered a promising anode material for high‐power lithium ion batteries (LIBs) because of its low cost, high thermal/chemical stability, and good safety performance without solid electrolyte interface formation. However, the poor electronic conductivity and low lithium ion diffusivity of TiO 2 result in poor cyclability and lithium ion depletion at high current rates, which hinder them from practical applications. Herein we demonstrate that hierarchically structured TiO 2 microboxes with controlled internal porosity can address the aforementioned problems for high‐power, long‐life LIB anodes. A self‐templating method for the synthesis of mesoporous microboxes was developed through Na 2 EDTA‐assisted ion exchange of CaTiO 3 microcubes. The resulting TiO 2 nanorods were organized into microboxes that resemble the microcube precursors. This nanostructured TiO 2 material has superior lithium storage properties with a capacity of 187 mAh g −1 after 300 cycles at 1 C and good rate capabilities up to 20 C.

Gao, Xuehui↗
DOE OSTI2012

Lung Radiofrequency Ablation for the Treatment of Unresectable Recurrent Non-Small-Cell Lung Cancer After Surgical Intervention

Purpose: A retrospective evaluation was done of clinical utility of lung radiofrequency (RF) ablation in recurrent non-small-cell lung cancer (NSCLC) after surgical intervention. Methods: During May 2003 to October 2010, 44 consecutive patients (26 male and 18 female) received curative lung RF ablation for 51 recurrent NSCLC (mean diameter 1.7 {+-} 0.9 cm, range 0.6 to 4.0) after surgical intervention. Safety, tumor progression rate, overall survival, and recurrence-free survival were evaluated. Prognostic factors were evaluated in multivariate analysis. Results: A total of 55 lung RF sessions were performed. Pneumothorax requiring pluerosclerosis (n = 2) and surgical suture (n = 1) were the only grade 3 or 4 adverse events (5.5%, 3 of 55). During mean follow-up of 28.6 {+-} 20.3 months (range 1 to 98), local tumor progression was found in 5 patients (11.4%, 5 of 44). The 1-, 3-, and 5-year overall survival rates were 97.7, 72.9, and 55.7%, respectively. The 1- and 3-year recurrence-free survival rates were 76.7 and 41.1%, respectively. Tumor size and sex were independent significant prognostic factors in multivariate analysis. The 5-year survival rates were 73.3% in 18 women and 60.5% in 38 patients who had small tumors measuring {<=}3 cm. Conclusion: Our results suggest that lung RF ablation is a safe and useful therapeutic option for obtaining long-term survival in treated patients.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

Yb-doped fiber laser mode-locked with Au nanocages/SiO{sub 2} saturable absorber

Au nanocages/SiO{sub 2} (Au-NCs/SiO{sub 2}) are prepared through a seed-mediated growth method, and the performance is investigated in an all-fiber passively mode-locked ytterbium-doped fiber laser, for the first time. Its saturating intensity and modulation depth are measured to be about 0.461 MW/cm{sup 2} and 5.3%, respectively. With the Au-NCs/SiO{sub 2} saturable absorbers (SA) film, the pulse with the pulse duration of 1.116 ns and repetition rate of 32.02 MHz was generated at 1063.14 nm, under the pump power of 342 mW. And the corresponding average output power of 4.82 mW was obtained. These results indicate that Au-NCs/SiO{sub 2} has excellent saturable absorption properties with the potential for important applications in the field of ultra-short pulse lasers.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Repeatable and reproducible measurements of myocardial oxidative metabolism, blood flow and external efficiency using {sup 11}C-acetate PET

Background: Non-invasive approaches to investigate myocardial efficiency can help track the progression of heart failure (HF). This study evaluates the repeatability and reproducibility of {sup 11}C-acetate positron emission tomography (PET) imaging of oxidative metabolism. Methods and results: Dynamic {sup 11}C-acetate PET scans were performed at baseline and followup (47 ± 22 days apart) in 20 patients with stable HF with reduced ejection fraction. Two observers blinded to patients’ clinical data used FlowQuant{sup ®} to evaluate test–retest repeatability, as well as intra- and inter-observer reproducibility of {sup 11}C-acetate tracer uptake and clearance rates, for the measurement of myocardial oxygen consumption (MVO{sub 2}), myocardial external efficiency (MEE), work metabolic index (WMI), and myocardial blood flow. Reproducibility and repeatability were evaluated using intra-class-correlation (ICC) and Bland–Altman coefficient-of-repeatability (CR). Test–retest correlations and repeatability were better for MEE and WMI compared to MVO{sub 2}. All intra- and inter-observer correlations were excellent (ICC = 0.95-0.99) and the reproducibility values (CR = 3%-6%) were significantly lower than the test–retest repeatability values (22%-54%, P < 0.001). Repeatability was improved for all parameters using a newer PET–computed tomography (CT) scanner compared to older PET-only instrumentation. Conclusion: {sup 11}C-acetate PET measurements of WMI and MEE exhibited excellent test–retest repeatability and operator reproducibility. Newer PET–CT scanners may be preferred for longitudinal tracking of cardiac efficiency. [French] French Abstract: Contexte: Les examens non invasifs de la fonction myocardique aident à suivre la progression de l’insuffisance cardiaque. Dans ce travail, nous avons évalué la répétabilité et la reproductibilité de l’étude du métabolisme oxydatif du myocarde par imagerie tomographique à positrons avec l’acétate marqué au carbone 11. Méthodes et résultats: Une étude de base et un second examen TEP dynamique à l’ acétate marqué au carbone 11 ont été réalisés (47 ± 22 jours) chez 20 patients présentant une insuffisance cardiaque stable avec une fraction d’éjection réduite. Sans aucune connaissance des données cliniques et au moyen du programme FlowQuant®, deux observateurs ont évalué la répétabilité des TEPs de base et de leur suivi, la reproductibilité intra- et inter-observateur, l’absorption et la clearance du traceur, la mesure de la consommation d’oxygène du myocarde (MVO2), l’efficacité contractile du myocarde (MEE), l’index métabolique du travail myocardique (WMI) et le débit sanguin myocardique (MBF). La reproductibilité et la répétabilité ont été évaluées en utilisant la corrélation intra-classe (ICC) et le coefficient de répétabilité Altman (CR). Les corrélations entre les études de base et leur suivi et la répétabilité des données se sont avérées supérieures pour les paramètres MEE et WMI par rapport à MVO2. Toutes les corrélations intra- et inter-observateurs furent excellentes (ICC = 0,95-0,99). Les valeurs de reproductibilité (CR = 3-6%) furent significativement inférieures aux valeurs de répétabilité (22-54%, p <0.001). La répétabilité des paramètres mesurés s’est avérée supérieure avec un scanner TEP-TDM de nouvelle génération par rapport à l’utilisation de la TEP sans TDM Conclusion: Les mesures réalisées dans cette étude TEP 11C-acétate montre une excellent répétabilité et reproductibilité des paramètres WMI et WMI entre les examens de base et leur suivi effectués par des opérateurs différents. Les nouveaux scanners TEP-TDM devraient être préférés pour le suivi longitudinal de la fonction cardiaque. [Spanish] Spanish Abstract: Antecedentes: el abordaje no invasivo para investigar la eficiencia miocárdica puede ayudar en el seguimiento de la progresión de la insuficiencia cardíaca. Este estudio evalúa la repetibilidad y la reproducibilidad del estudio de metabolismo oxidativo con PET 11C-acetato. Métodos y resultados: Se realizaron estudios de PET 11C-acetato dinámicos al inicio y durante el seguimiento (47 ± 22 días de diferencia) en 20 pacientes con insuficiencia cardíaca estable y fracción de eyección reducida. Dos observadores cegados a los datos clínicos de los pacientes utilizaron FlowQuant® para evaluar la repetibilidad de la prueba-reprueba, así como la reproducibilidad intra e interobservador de la captación de radiotrazador 11C-acetato y sus tasas de eliminación, la medición del consumo miocárdico de oxígeno (MVO2), la eficiencia externa miocardica (EEM), el índice trabajo-metabólico (ITM) y flujo sanguíneo miocárdico (FSM). La reproducibilidad y la repetibilidad se evaluaron mediante la correlación intraclase (ICC) y el coeficiente de repetibilidad (CR) de Bland-Altman. Las correlaciones Prueba-Reprueba y la repetibilidad fueron mejores para la EEM y el ITM en comparación con el MVO2. Todas las correlaciones intra e interobservador fueron excelentes (ICC = 0.95-0.99) y los valores de reproducibilidad (CR = 3-6%) fueron significativamente menores que los valores de repetibilidad prueba-reprueba (22-54%, p <0.001). La repetibilidad fue mejor para todos los parámetros utilizando un equipo PET-TC más nuevo en comparación con un equipo PET sin CT. Conclusión: las mediciones del PET con 11C-acetato del ITM y EEM mostraron una excelente repetibilidad prueba-preprueba y reproducibilidad del operador. Los nuevos equipos PET-CT pueden ser elegidos para el seguimiento longitudinal de la eficiencia miocárdica. [Chinese] Chinese Abstract: 背景: 采用非侵入式方法来研究心肌代谢效率可以帮助追踪心力衰竭的过程。本研究评估利用碳-11 醋酸盐为 PET 显影剂行氧化代谢成像的可重复性和可再现性。 方法和结果: 纳入射血分数减低的 20 名稳定性心衰患者,对患者基线和 47±22 天随访都进行碳-11 醋酸盐 PET 扫描。为测量心肌耗氧量(MVO{sub 2}), 心肌外效率(MEE), 工作代谢指标(WMI)和心肌血流量(MBF), 两名观察者按照双盲的方法利用 FlowQuant®对碳-11 醋酸盐的摄取率和清空率进行了重复性测试以及不同观察者之间的可再现性测试。采用组内相关系数(ICC)和 Bland Altman 可重复性系数(CR)分别对可再现性和可重复性进行评估。MEE 和 WMI 的两次试验系数和可重复性优于MVO{sub 2}。所有观察者之间的相关系数都较好(ICC=0.95-0.99),可再现性系数的值(CR=3-6%)明显低于两次试验可重复性的值(22-54%, P<0.001)。相比于旧的只有 PET 的设备, 采用新型 PET-CT 扫描仪能够使所有参数的可再现性都有所提高。 结论: 碳-11醋酸盐 PET 显像测量 WMI 和 MEE 有很好的可重复性和可再现性。新的 PET-CT 扫描仪可能更适合于心脏代谢效率的长期追踪。.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2022

Performance evaluation of a wrapped around condenser for heat pump water heater applications

In this report, accurate performance evaluation of a wrapped-around condenser for heat pump water heaters (WHPWH) is critical since the COP of the system depends heavily on thermal stratification and condenser design. An analytical, quasi-steady state heat balance method has been developed to determine the optimal spacing between adjacent channels, tube diameter, tube shape, and total refrigerant charge amount for the condenser. The heat transfer rate is compared among three approaches: the refrigerant thermodynamic model, the condenser-wrap fin model, and the analytical natural convection model on the inside of the tank for the three regions based on the refrigerant phase (e.g., super-heated, saturated, or subcooled). The heat transfer rate was predicted by a combination of slug-plug and annular flow for a D-shaped helical tube. Experimental data were used as boundary conditions for validating the model. The rate of heat transfer based on tube shape and tank wall temperatures was compared by CFD analysis. Parametric analysis indicates a tradeoff between refrigerant mass, pressure drop, tube diameter, and tube length to maximize the heat transfer rate. The model suggests the saturated region length can be extended by 400%, and the condenser pressure drop can be reduced by 23% with an optimal spacing pattern.

42 ENGINEERING↗
DOE OSTI2015

Graphene-containing flowable electrodes for capacitive energy storage

High conductivity and extended particle contacts are required for rapid charge percolation in flowable electrodes. In this study, carbon spheres (CS) were wrapped by highly conductive reduced graphene oxide sheets (rGO) to address these issues. We synthesized various compositions of the conductive, 3D interconnected hybrid materials (rGO@CS) using the hydrothermal method. Synergistic effects of both materials were utilized where CS served to minimize the sheet stacking for better flowability of the suspensions, and wrapped rGO sheets enabled higher conductivity for fast charge transport throughout the suspension network. When we tested as flowable electrodes, the composition with a 1:2 ratio of GO to CS exhibited the highest capacitance of 200 F/g and an improved rate performance. Moreover, the improved performance is attributed to the fast charge transport in the suspension network due to higher conductivity and enhanced connectivity of the active material particles. Optimized electrodes were also examined in a flow mode which yielded a capacitance of 45 F/g.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Percentage of Positive Biopsy Cores: A Better Risk Stratification Model for Prostate Cancer?

Purpose: To assess the prognostic value of the percentage of positive biopsy cores (PPC) and perineural invasion in predicting the clinical outcomes after radiotherapy (RT) for prostate cancer and to explore the possibilities to improve on existing risk-stratification models. Methods and Materials: Between 1993 and 2004, 1,056 patients with clinical Stage T1c-T3N0M0 prostate cancer, who had four or more biopsy cores sampled and complete biopsy core data available, were treated with external beam RT, with or without a high-dose-rate brachytherapy boost at William Beaumont Hospital. The median follow-up was 7.6 years. Multivariate Cox regression analysis was performed with PPC, Gleason score, pretreatment prostate-specific antigen, T stage, PNI, radiation dose, androgen deprivation, age, prostate-specific antigen frequency, and follow-up duration. A new risk stratification (PPC classification) was empirically devised to incorporate PPC and replace the T stage. Results: On multivariate Cox regression analysis, the PPC was an independent predictor of distant metastasis, cause-specific survival, and overall survival (all p < .05). A PPC >50% was associated with significantly greater distant metastasis (hazard ratio, 4.01; 95% confidence interval, 1.86-8.61), and its independent predictive value remained significant with or without androgen deprivation therapy (all p < .05). In contrast, PNI and T stage were only predictive for locoregional recurrence. Combining the PPC ({<=}50% vs. >50%) with National Comprehensive Cancer Network risk stratification demonstrated added prognostic value of distant metastasis for the intermediate-risk (hazard ratio, 5.44; 95% confidence interval, 1.78-16.6) and high-risk (hazard ratio, 4.39; 95% confidence interval, 1.70-11.3) groups, regardless of the use of androgen deprivation and high-dose RT (all p < .05). The proposed PPC classification appears to provide improved stratification of the clinical outcomes relative to the National Comprehensive Cancer Network classification. Conclusions: The PPC is an independent and powerful predictor of clinical outcomes of prostate cancer after RT. A risk model replacing T stage with the PPC to reduce subjectivity demonstrated potentially improved stratification.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2017

Optical spectroscopy of holmium doped K 2 LaCl 5

Spectroscopic results on the infrared emission properties of trivalent holmium (Ho 3+ ) doped potassium lanthanum chloride (K 2 LaCl 5 ) are presented. Using ~900 nm excitation, Ho 3+ doped K 2 LaCl 5 , which has a maximum phonon energy of 235 cm –1 , exhibited the infrared emissions at ~1660, ~1995, and ~3900 nm at room temperature. The mid-infrared emission at 3900 nm originated from the 5 I 5 → 5 I 6 transition of Ho 3+ ions with an exponential decay time of ~7.8 ms at room temperature. The fluorescence lifetimes were almost independent of temperature, indicating a negligibly small non-radiative decay rate for the 5 I 5 excited state, as predicted by the energy gap law for low phonon energy hosts. The Stark level energies of the lower 5 I J manifolds in Ho:K 2 LaCl 5 were resolved from spectroscopic results performed at cryogenic temperatures. The transition line-strengths, radiative lifetimes, and fluorescence branching ratios were investigated by using the Judd-Ofelt method. In addition, the peak emission cross-section of the 5 I 5 → 5 I 6 transition was calculated to be 1.8 × 10 –20 cm 2 at ~3890 nm.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Nanotubes within transition metal silicate hollow spheres: Facile preparation and superior lithium storage performances

Highlights: • The hollow Co{sub 2}SiO{sub 4}, MnSiO{sub 3} and CuSiO{sub 3} were successfully prepared by a facile hydrothermal method using SiO{sub 2} nanosphere. • The hollow Co{sub 2}SiO{sub 4}, MnSiO{sub 3} and CuSiO{sub 3} were tested as anode materials for lithium batteries. • The hollow Co{sub 2}SiO{sub 4}, MnSiO{sub 3} and CuSiO{sub 3} delivered superior electrochemical performance. • The lithium storage mechanism is probe via cyclic voltammetry and XPS. - Abstract: A series of transition metal silicate hollow spheres, including cobalt silicate (Co{sub 2}SiO{sub 4}), manganese silicate (MnSiO{sub 3}) and copper silicate (CuSiO{sub 3}.2H{sub 2}O, CuSiO{sub 3} as abbreviation in the text) were prepared via a simple and economic hydrothermal method by using silica spheres as chemical template. Time-dependent experiments confirmed that the resultants formed a novel type of hierarchical structure, hollow spheres assembled by numerous one-dimensional (1D) nanotubes building blocks. For the first time, the transition metal silicate hollow spheres were characterized as novel anode materials of Li-ion battery, which presented superior lithium storage capacities, cycle performance and rate performance. The 1D nanotubes assembly and hollow interior endow this kind of material facilitate fast lithium ion and electron transport and accommodate the big volume change during the conversion reactions. Our study shows that low-cost transition metal silicate with rationally designed nanostructures can be promising anode materials for high capacity lithium-ion battery.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2024

Experimental Tests of Lateral Bedload Transport Induced by a Yawed Submerged Vane Array in Open-Channel Flows

This work proposes the use of an array of yawed porous vanes to control the lateral bedload transport by locally steering bedform migration and maximize the amount of sediments redirected toward a potential sediment extraction system or bypass channel. A laboratory experiment was conducted in a quasifield-scale channel with an array of permeable vanes installed on one side, in live-bed conditions under bedload dominant regime, i.e., negligible suspended load. A baseline experiment without vanes was also performed for comparison. The evolution of migrating bedforms of different scales was tracked in space and time using a high-resolution, state-of-the-art laser scanning device. The bedload transport rate in the streamwise direction was first calculated using bedforms’ geometry and migration velocity, and then spatially distributed over the entire monitored area using a new Eulerian-averaged grid-mapping method. This allowed us to introduce a new methodology to estimate the lateral bedload transport using control volume theory and applying mass conservation. Quantitative assessments of lateral bedload transport along the channel yield consistent results, suggesting that the vanes effectively move sediments laterally as intended. Under the investigated setup, the maximum lateral sediment transport rate ranges from 9% to 18% of the whole domain-averaged streamwise transport rate. The developed methodology also allowed to identify the location where sediment capture could be maximized for the given vane spatial distribution.

42 ENGINEERING↗
DOE OSTI2014

First principles studies of proton conduction in KTaO{sub 3}

KTaO{sub 3} (KTO) is a useful prototypical perovskite for examining the mechanisms of proton transport in perovskites. Previously, Gomez et al. [J. Chem. Phys. 126, 194701 (2007)] reported density functional theory (DFT) calculations describing proton hopping in defect-free KTO. We use DFT calculations to extend that work in two directions, namely, understanding isotope effects in low and high temperature proton transport and the role of native point defects in KTO. At cryogenic temperatures, quantum tunneling plays a vital role in the net hopping of protons in KTO. At the elevated temperature characteristic of applications involving proton-conducting perovskites, tunneling is negligible but zero point energy effects still lead to non-negligible isotope effects for H{sup +}, D{sup +}, and T{sup +}. We also use DFT to characterize the populations of relevant point defects in KTO as a function of experimental conditions, and to examine the migration of protons that are close in proximity to these defects. This information gives useful insight into the overall transport rates of protons through KTO under a variety of external environments. We also assess the overall diffusivity of protons in KTO at various ranges of oxygen vacancy concentrations by performing kinetic Monte Carlo simulations.

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

A novel cell weighing method based on the minimum immobilization pressure for biological applications

A novel weighing method for cells with spherical and other regular shapes is proposed in this paper. In this method, the relationship between the cell mass and the minimum aspiration pressure to immobilize the cell (referred to as minimum immobilization pressure) is derived for the first time according to static theory. Based on this relationship, a robotic cell weighing process is established using a traditional micro-injection system. Experimental results on porcine oocytes demonstrate that the proposed method is able to weigh cells at an average speed of 16.3 s/cell and with a success rate of more than 90%. The derived cell mass and density are in accordance with those reported in other published results. The experimental results also demonstrated that this method is able to detect less than 1% variation of the porcine oocyte mass quantitatively. It can be conducted by a pair of traditional micropipettes and a commercial pneumatic micro-injection system, and is expected to perform robotic operation on batch cells. At present, the minimum resolution of the proposed method for measuring the cell mass can be 1.25 × 10{sup −15 }kg. Above advantages make it very appropriate for quantifying the amount of the materials injected into or moved out of the cells in the biological applications, such as nuclear enucleations and embryo microinjections.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Statistical searches for microlensing events in large, non-uniformly sampled time-domain surveys: A test using palomar transient factory data

Many photometric time-domain surveys are driven by specific goals, such as searches for supernovae or transiting exoplanets, which set the cadence with which fields are re-imaged. In the case of the Palomar Transient Factory (PTF), several sub-surveys are conducted in parallel, leading to non-uniform sampling over its ∼20,000 deg{sup 2} footprint. While the median 7.26 deg{sup 2} PTF field has been imaged ∼40 times in the R band, ∼2300 deg{sup 2} have been observed >100 times. We use PTF data to study the trade off between searching for microlensing events in a survey whose footprint is much larger than that of typical microlensing searches, but with far-from-optimal time sampling. To examine the probability that microlensing events can be recovered in these data, we test statistics used on uniformly sampled data to identify variables and transients. We find that the von Neumann ratio performs best for identifying simulated microlensing events in our data. We develop a selection method using this statistic and apply it to data from fields with >10 R-band observations, 1.1 × 10{sup 9} light curves, uncovering three candidate microlensing events. We lack simultaneous, multi-color photometry to confirm these as microlensing events. However, their number is consistent with predictions for the event rate in the PTF footprint over the survey's three years of operations, as estimated from near-field microlensing models. This work can help constrain all-sky event rate predictions and tests microlensing signal recovery in large data sets, which will be useful to future time-domain surveys, such as that planned with the Large Synoptic Survey Telescope.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Identification of multiple eigenmode growth rates in DIII-D and EAST tokamak plasmas

Here, the successful application of three-dimensional (3D) magnetohydrodynamic (MHD) spectroscopy in the stable DIII-D and EAST plasmas enables to directly extract the multi-mode plasma transfer function in tokamak experiments. The transfer function not only reveals the contribution of each dominant MHD eigenmode in the multi-model plasma response, but also quantifies the corresponding eigenvalue which is the critical stability index of MHD mode. The method performs the active detection of stable plasma by utilizing the upper and lower rows of internal coils to scan the frequency and poloidal spectrum of the applied 3D field, and reconstructing the multi-mode transfer functions model through the least square fitting of the plasma response measured by 3D-field magnetic sensors distributed at different poloidal locations. The results point to the potential development of an advanced strategy for tracking the plasma stability based on the extracted eigenvalues of stable modes. The improved understanding of the dominant eigenmodes' behavior in multi-mode plasma response through transfer function can also help to optimize the applied 3D fields for the purposes, such as the type-I edge localized mode suppression and the core stability control in future fusion reactors.

3D MHD spectroscopy↗
DOE OSTI2024

AstroCLIP: a cross-modal foundation model for galaxies

ABSTRACT We present AstroCLIP, a single, versatile model that can embed both galaxy images and spectra into a shared, physically meaningful latent space. These embeddings can then be used – without any model fine-tuning – for a variety of downstream tasks including (1) accurate in-modality and cross-modality semantic similarity search, (2) photometric redshift estimation, (3) galaxy property estimation from both images and spectra, and (4) morphology classification. Our approach to implementing AstroCLIP consists of two parts. First, we embed galaxy images and spectra separately by pre-training separate transformer-based image and spectrum encoders in self-supervised settings. We then align the encoders using a contrastive loss. We apply our method to spectra from the Dark Energy Spectroscopic Instrument and images from its corresponding Legacy Imaging Survey. Overall, we find remarkable performance on all downstream tasks, even relative to supervised baselines. For example, for a task like photometric redshift prediction, we find similar performance to a specifically trained ResNet18, and for additional tasks like physical property estimation (stellar mass, age, metallicity, and specific-star-formation rate), we beat this supervised baseline by 19 per cent in terms of R2. We also compare our results with a state-of-the-art self-supervised single-modal model for galaxy images, and find that our approach outperforms this benchmark by roughly a factor of two on photometric redshift estimation and physical property prediction in terms of R2, while remaining roughly in-line in terms of morphology classification. Ultimately, our approach represents the first cross-modal self-supervised model for galaxies, and the first self-supervised transformer-based architectures for galaxy images and spectra.

Parker, Liam (ORCID:0009000749521674)↗