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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 973 records · Page 54
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Viscous regularization of the full set of nonequilibrium-diffusion Grey Radiation-Hydrodynamic equations

A viscous regularization technique, based on the local entropy residual, was proposed by Delchini et al. (2015) to stabilize the nonequilibrium-diffusion Grey Radiation-Hydrodynamic equations using an artificial viscosity technique. This viscous regularization is modulated by the local entropy production and is consistent with the entropy minimum principle. However, Delchini et al. (2015) only based their work on the hyperbolic parts of the Grey Radiation-Hydrodynamic equations and thus omitted the relaxation and diffusion terms present in the material energy and radiation energy equations. Here in this paper, we extend the theoretical grounds for the method and derive an entropy minimum principle for the full set of nonequilibrium-diffusion Grey Radiation-Hydrodynamic equations. This further strengthens the applicability of the entropy viscosity method as a stabilization technique for radiation-hydrodynamic shock simulations. Radiative shock calculations using constant and temperature-dependent opacities are compared against semi-analytical reference solutions, and we present a procedure to perform spatial convergence studies of such simulations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Level set topology optimization of structural problems with interface cohesion

Summary This paper presents a finite element topology optimization framework for the design of two‐phase structural systems considering contact and cohesion phenomena along the interface. The geometry of the material interface is described by an explicit level set method, and the structural response is predicted by the extended finite element method. In this work, the interface condition is described by a bilinear cohesive zone model on the basis of the traction‐separation constitutive relation. The non‐penetration condition in the presence of compressive interface forces is enforced by a stabilized Lagrange multiplier method. The mechanical model assumes a linear elastic isotropic material, infinitesimal strain theory, and a quasi‐static response. The optimization problem is solved by a nonlinear programming method, and the design sensitivities are computed by the adjoint method. The performance of the presented method is evaluated by 2D and 3D numerical examples. The results obtained from topology optimization reveal distinct design characteristics for the various interface phenomena considered. In addition, 3D examples demonstrate optimal geometries that cannot be fully captured by reduced dimensionality. The optimization framework presented is limited to two‐phase structural systems where the material interface is coincident in the undeformed configuration, and to structural responses that remain valid considering small strain kinematics. Copyright © 2017 John Wiley & Sons, Ltd.

Behrou, Reza↗
DOE OSTI2023

Quantum Annealing with Inequality Constraints: The Set Cover Problem

Abstract Quantum annealing is a promising method for solving hard optimization problems by transforming them into quadratic unconstrained binary optimization (QUBO) problems. However, when constraints are involved, particularly multiple inequality constraints, incorporating them into the objective function poses challenges. In this paper, the authors present two novel approaches for solving problems with multiple inequality constraints on a quantum annealer and apply them to the set cover problem (SCP). The first approach uses the augmented Lagrangian method to represent the constraints, while the second approach employs a higher‐order binary optimization (HUBO) formulation. The experiments show that both approaches outperform the standard approach for solving the SCP on the D‐Wave Advantage quantum annealer. The HUBO formulation performs slightly better than the augmented Lagrangian method in solving the SCP, but its scalability in terms of embeddability in the quantum chip is worse. The results demonstrate that the proposed augmented Lagrangian and HUBO methods can successfully implement a large number of inequality constraints, making them applicable to a broad range of constrained problems beyond the SCP.

Djidjev, Hristo N.↗
DOE OSTI2020

Soil properties and biochemical composition of ground-dwelling bee nests in agricultural settings

Soils deliver underrecognized ecosystem services by supplying habitat for ground-dwelling pollinators, such as wild bees and other organisms, that pollinate 80% of insect-pollinated plants and play a critical role in securing resilient pollination provisions. Our objective is to identify soil properties of ground nesting bee nests in agricultural settings of western Oregon, USA. We confirmed ground nesting bee and sand wasp activity in 7 agricultural sites and 1 recreational park. Soils from 17 bee and sand wasp nests were analyzed for pH, particle size distribution, and carbon and nitrogen content. We visually confirmed that 8 of the nesting bees were sweat bees from the Halictidae family and identified a captured bee specimen as Lasioglossum (Dialictus) (Hymenoptera: Halictidae). We located 2 sites with sand wasps where specimens were identified as Cerceris and Bembix (Hymenoptera: Crabronidae). The organic matter composition of three soil samples scraped from the linings of active nests were assessed using Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). The FTICR-MS results identified unknown lipid compounds in the nest soil samples, which we hypothesize are waterproofing lipids secreted to line cell walls. Bee nests occurred in slightly acidic, bare-ground soils with low rock/vegetation coverage, low organic carbon content (<1%), and exhibited significantly higher silt-plus-clay fractions (>75%) versus data published for bee nests in prior work. Our findings present important implications for textural controls on nest site selection in wet, cool environments and demonstrate the importance of integrating soil properties to improve our understanding of ground-dwelling organisms and associated soil habitats.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2012

Efficacy of Lower-Extremity Venous Thrombolysis in the Setting of Congenital Absence or Atresia of the Inferior Vena Cava

Purpose: A rare but described risk factor for deep venous thrombosis (DVT), predominately in the young, is congenital agenesis or atresia of the inferior vena cava (IVC). The optimal management for DVT in this subset of patients is unknown. We evaluated the efficacy of pharmacomechanical catheter-directed thrombolysis (PCDT) followed by systemic anticoagulation in the treatment of acute lower-extremity DVT in the setting of congenital IVC agenesis or atresia. Materials and Methods: Between November of 2005 and May of 2010, six patients (three women [average age 21 years]) were referred to our department with acute lower-extremity DVT and subsequently found to have IVC agenesis or atresia on magnetic resonance imaging. A standardized technique for PCDT (the Angiojet Rheolytic Thrombectomy System followed by the EKOS Microsonic Accelerated Thrombolysis System) was used for all subjects. Successful thrombolysis was followed by systemic heparinization with transition to Coumadin or low molecular-weight heparin and compression stockings. Subjects were followed-up at 1, 3, and then every 6 months after the procedure with clinical assessment and bilateral lower-extremity venous ultrasound. Results: All PCDT procedures were technically successful. No venous stenting or angioplasty was performed. The average thrombolysis time was 28.6 h (range 12-72). Two patients experienced heparin-induced thrombocytopenia, and one patient developed a self-limited knee hemarthrosis, No patients were lost to follow-up. The average length of follow-up was 25.8 {+-} 20.2 months (range 3.8-54.8). No incidence of recurrent DVT was identified. There were no manifestations of postthrombotic syndrome. Conclusions: PCDT followed by systemic anticoagulation and the use of compression stockings appears to be safe and effective in relatively long-term follow-up treatment of patients who present with acute DVT and IVC agenesis or atresia.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2016

Radiation Exposure of Interventional Radiologists During Computed Tomography Fluoroscopy-Guided Renal Cryoablation and Lung Radiofrequency Ablation: Direct Measurement in a Clinical Setting

IntroductionComputed tomography (CT) fluoroscopy-guided renal cryoablation and lung radiofrequency ablation (RFA) have received increasing attention as promising cancer therapies. Although radiation exposure of interventional radiologists during these procedures is an important concern, data on operator exposure are lacking.Materials and MethodsRadiation dose to interventional radiologists during CT fluoroscopy-guided renal cryoablation (n = 20) and lung RFA (n = 20) was measured prospectively in a clinical setting. Effective dose to the operator was calculated from the 1-cm dose equivalent measured on the neck outside the lead apron, and on the left chest inside the lead apron, using electronic dosimeters. Equivalent dose to the operator’s finger skin was measured using thermoluminescent dosimeter rings.ResultsThe mean (median) effective dose to the operator per procedure was 6.05 (4.52) μSv during renal cryoablation and 0.74 (0.55) μSv during lung RFA. The mean (median) equivalent dose to the operator’s finger skin per procedure was 2.1 (2.1) mSv during renal cryoablation, and 0.3 (0.3) mSv during lung RFA.ConclusionRadiation dose to interventional radiologists during renal cryoablation and lung RFA were at an acceptable level, and in line with recommended dose limits for occupational radiation exposure.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

An evaluation of the consistency of extremes in gridded precipitation data sets

Noting a strong imperative to understand precipitation extremes, and that considerable uncertainty affects observational data sets, this paper compares the representation of extremes in a number of widely used daily gridded products, derived from rain gauge data, satellite retrieval and reanalysis for the conterminous United States. Analysis is based upon the concept of “tail dependence” arising in multivariate extreme value theory, and we infer the level of temporal dependence in the joint tail of the precipitation probability distribution for pairwise comparisons of products. In this way, we consider the range of products more like an ensemble and examine the relationships between members, and do not attempt to define, or compare products to, some ground truth. Linear correlation between products is also computed. Considerable discrepancy between groups of products, both annually and seasonally, is linked to source data and complex terrain. In particular, products based on rain gauge data showed remarkable similarity, but differed considerably, showing almost total loss of extremal dependence during DJF in mountainous regions, when compared with satellite products. Additionally, simulated re-forecasts revealed reasonable temporal agreement with large scale generated extremes. The diversity and extent of discrepancies identified across all products raises important questions about their use, and we urge caution, particularly for products derived from satellite data.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2013

Orders on Intervals Over Partially Ordered Sets: Extending Allen's Algebra and Interval Graph Results

To make a decision, we need to compare the values of quantities. In many practical situations, we know the values with interval uncertainty. In such situations, we need to compare intervals. Allen’s algebra describes all possible relations between intervals on the real line, and ordering relations between such intervals are well studied. In this paper, we extend this description to intervals in an arbitrary partially ordered set (poset). In particular, we explicitly describe ordering relations between intervals that generalize relation between points. As auxiliary results, we provide a logical interpretation of the relation between intervals, and extend the results about interval graphs to intervals over posets.

Zapata, Francisco↗
DOE OSTI2019

Removing Cs within a continuous flow set-up by an ionic exchanger material transformable into a final waste form

Silica monoliths loaded with hexacyanoferrate (HCF) nanoparticles were designed and synthesized to selectively remove Cs + ions from an aqueous saline solution within a continuous flow set-up. The decontamination and hydrodynamic efficiency of this smart material was compared to other granularly supported HCF. Finally, a thermal treatment was applied to transform the HCF functionalized monolith into a final waste form matrix.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2018

Choice of APCS for NPP Based on a Set of Reliability and Risk Criteria

The normative documents for calculating reliability and risk indices when designing and operating APCS are analyzed. The primary groups of standards concerning reliability and risk are examined. It is concluded that the basic criteria for choosing and validating the use of APCS equipment for NPPs need to be reexamined. A set of indices which are expedient for describing automation systems, validating the choice of structure, and using specifi c equipment is formulated on the basis of the analysis.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2025

Automated Fire Detection for Industrial Settings with Pretrained Convolutional Networks

Early fire detection in industrial environments is critical to preventing equipment damage, personal injury, and operational disruptions. Traditional smoke detectors, while effective, often experience delays due to the time required for smoke to reach sensors, allowing fires to spread. Manual fire watch operations and human surveillance of camera feeds are resource-intensive and prone to human error. To address these challenges, this paper explores the application of convolutional neural networks for automated fire detection, specifically in industrial settings. By leveraging 11 different pre-trained machine vision models from TensorFlow and enhancing them with transfer learning on a custom-built industrial fire dataset, we optimized fire detection performance. Here, we analyzed each machine vision model architecture in terms of its depth, width, and input image resolution, considering both resource requirements and detection accuracy. We further explored the option of combining multiple models into an ensemble classifier to evaluate whether the performance improvements could justify the much greater computational complexity and other practical impacts. A cost-benefit analysis is presented to evaluate the trade-offs between performance and computational expense. Our findings identify that EfficientNetV2L, specifically tailored for industrial applications, provides the optimal balance between costs involved in training and using the model versus the overall fire detection performance. Additionally, we present a qualitative analysis of model performance using the technique of gradient-based class activation mapping to provide explainability by visualizing model decisions.

artificial intelligence↗
DOE OSTI2013

Geophysical Constraints on the Hydrogeologic and Structural Settings of the Gulf of Suez Rift-Related Basins: Case Study from the El Qaa Plain, Sinai, Egypt

Groundwater has been identified as one of the major freshwater sources that can potentially meet the growing demands of Egypt’s population. Gravity data (from 381 ground gravity stations) were collected, processed, and analyzed together with the available aeromagnetic (800 line-km) data to investigate the hydrogeologic and structural settings, areal distribution, geometry, and water storage of the aquifers in El Qaa coastal plain in the southwest Sinai Peninsula, and to assess their longevity given projected extraction rates. Findings include (1) complete Bouguer anomaly and total magnetic intensity maps show two connected sub-basins separated by a narrow saddle with an average basin length of 43 km and an average width of 12 km; (2) two-dimensional modeling of both gravity and magnetic data indicates basin fill with a maximum thickness of 3.5 km; (3) using anomalous residual gravity, the volume of water in storage was estimated at 40–56 km3; and (4) progressive increases in extraction rates over time will deplete up to 40 % of the aquifers’ volume in 200–230 years and will cause the water quality to deteriorate due to seawater intrusion in 45 years. Similar geophysical exploration campaigns, if conducted over the entire coastal plains of the Red Sea and the Gulfs of Suez and Aqaba, could assist in the development of sound and sustainable management schemes for the freshwater resources in these areas. The adopted techniques could pave the way toward the establishment of sustainable utilization schemes for a much larger suite of similar aquifers worldwide.

Aeromagnetic↗
DOE OSTI2021

Application of Artificial Neural Network Model for Optimized Control of Condenser Water Temperature Set-Point in a Chilled Water System

Here, in this study, real-time predictive control and optimization model based on an ANN (artificial neural network) was developed to evaluate the cooling energy saving performance of the optimized control of CndWT (condenser water temperature). For this purpose, the difference in TCEC (total cooling energy consumption) between the conventional control strategy when the CndWT produced by the cooling tower is fixed and the optimized control strategy when real-time control of the CndWT through the optimal ANN model is applied was compared and analyzed. For the modeling of the building to be simulated, the co-simulation of EnergyPlus and MATLAB was built through the middleware Building Controls Virtual Test Bed. For the prediction of TCEC, an ANN model was developed through MATLAB's neural network toolbox. The model accuracy of the ANN was examined through Cv(RMSE) index and as a result, Cv(RMSE) of the optimized ANN model turned out to be approximately 25 %. More importantly, the predictive control technique was able to save TCEC by 5.6 % compared to the conventional control method constantly fixing CndWT set-point to 30 °C. These results showed that the CndWT needs to be dynamically controlled using artificial intelligence technique such as ANN model and that significant energy savings were achievable compared to the conventional fixed control.

42 ENGINEERING↗
DOE OSTI2018

Indexing and Querying Character Sets in One- and Two-Dimensional Words

We give a detailed review of results obtained for a relatively new problem of finding, indexing, and querying character sets, which are called fingerprints in fragments of one- and two-dimensional words, and explain basic ideas used for obtaining these results.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2016

Interval-Valued Rank in Finite Ordered Sets

We consider the concept of rank as a measure of the vertical levels and positions of elements of partially ordered sets (posets). We are motivated by the need for algorithmic measures on large, real-world hierarchically-structured data objects like the semantic hierarchies of ontolog- ical databases. These rarely satisfy the strong property of gradedness, which is required for traditional rank functions to exist. Representing such semantic hierarchies as finite, bounded posets, we recognize the duality of ordered structures to motivate rank functions which respect verticality both from the bottom and from the top. Our rank functions are thus interval-valued, and always exist, even for non-graded posets, providing order homomorphisms to an interval order on the interval-valued ranks. The concept of rank width arises naturally, allowing us to identify the poset region with point-valued width as its longest graded portion (which we call the “spindle”). A standard interval rank function is naturally motivated both in terms of its extremality and on pragmatic grounds. Its properties are examined, including the relation- ship to traditional grading and rank functions, and methods to assess comparisons of standard interval-valued ranks.

Joslyn, Cliff↗
DOE OSTI2018

An active-set algorithm and a trust-region approach in constrained minimax problem

In this paper, we propose an algorithm to solve a finite minimax problem with side constraints. An active-set strategy is used in the algorithm to transform inequality constraints to equality constraints. This allows the use of the well-developed techniques for solving the equality constrained optimization problems. A trust-region globalization strategy is added to the proposed algorithm to ensure global convergence. A projected Hessian technique is used in the algorithm to overcome the difficulty of having an infeasible trust-region subproblem.A global convergence theory for the proposed algorithm is presented under standard assumptions. Finally, numerical experiments are reported to indicate that the new algorithm performs efficiently in practice.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2022

Complete collision data set for electrons scattering on molecular hydrogen and its isotopologues: III. Vibrational excitation via electronic excitation and radiative decay

We present state-resolved cross sections for vibrational excitation via electronic excitation followed by radiative decay (ERD), for electrons scattering on all bound vibrational levels of the ground electronic state ($X\hspace{1.5 mm} ^1Σ_g^+$) of molecular hydrogen and its isotopologues (H 2 , HD, HT, D 2 , DT and T 2 ). We consider excitation of the singlet $\textit{n}$ = 2–3 states (where n refers to the united-atoms-limit principle quantum number) and account for all possible decay pathways back to the bound vibrational levels of the ground electronic state ($X\hspace{1.5 mm} ^1Σ_g^+$) to produce an estimate for the ERD cross sections. A selection of the results are presented in graphical form and a full data set is provided as both numerical values and analytic fit functions in supplementary data files. The uncertainty in the cross sections is estimated to be 11%, except for scattering on the highest bound vibrational level of HD, HT, D 2 , and DT, where the uncertainty is 21%. The data can be downloaded from the MCCC database at mccc-db.org.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2023

Complete collision data set for electrons scattering on molecular hydrogen and its isotopologues: IV. Vibrationally-resolved ionization of the ground and excited electronic states

Here, we present a comprehensive set of vibrationally-resolved cross sections for electron-impact ionization of molecular hydrogen and its isotopologues (H 2 , D 2 , T 2 , HD, HT, and DT) in both the ground and excited electronic states. We apply the adiabatic-nuclei molecular convergent close-coupling (MCCC) method to calculate cross sections from threshold to 1000 eV for ionization of the ground and excited vibrational levels of the X 1 Σ$^{+}_{g}$, B 1 Σ$^{+}_{u}$, C 1 π u , EF 1 Σ$^{+}_{g}$, a 3 Σ$^{+}_{g}$, and c 3 π u electronic states, representing all states with united-atoms-limit principle quantum number n=1–2. The cross sections are presented in graphical form and provided as both numerical values and analytic fit functions in supplementary data files. The data can also be downloaded from the MCCC database at mccc-db.org.

74 ATOMIC AND MOLECULAR PHYSICS↗