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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Comparative study on the overall energy performance between photovoltaic and Low-E insulated glass units

In this report a novel semi-transparent building integrated photovoltaic (BIPV) laminate was developed and introduced in this paper. It was produced by cutting standard mono-crystalline silicon solar cells into small strips and then making electrical connections between each strip before laminating the cells between two layers of glass. The overall energy performance and energy saving potential of the BIPV insulated glass unit (IGU) under real world conditions were identified through a side by side comparative study. Compared to the reference IGU, the BIPV IGU had lower solar heat gain coefficient (SHGC) but much higher U-factor. The average HVAC electricity saving of the BIPV IGU was about 10% relative to the reference IGU. Daylighting measurement and analysis were carried out to evaluate the trade-offs associated with the BIPV IGU between daylight, glare, and lighting energy use. The results indicated that the BIPV IGU is better than the reference IGU in reducing discomfort glare. However, if the most conservative viewpoint near the window is used for the assessment, a lower transmittance BIPV IGU is required to bring the overall discomfort levels below the perceptible level. Lastly, the net energy saving potential associated with the novel BIPV IGU was identified based on the power, thermal and daylighting performance. On average, the BIPV IGU saved 16.8% of the total electricity use of the room. Further studies and improvement on the energy conversion efficiency of solar cells, the optimal transmittance as well as the thermal properties would make this technology more energy-efficient and affordable.

14 SOLAR ENERGY↗
DOE OSTI2025

Deep Learning for Subsurface Flow: A Comparative Study of U‐Net, Fourier Neural Operators, and Transformers in Underground Hydrogen Storage

Subsurface flow research is essential for the sustainable management of natural resources and the environment. Deep learning (DL) has significantly advanced this field by developing efficient and accurate surrogate models to replace computationally expensive physics‐based simulations. These surrogate models are commonly used to predict the spatiotemporal evolution of state variables, such as gas saturation and reservoir pressure, in heterogeneous geological formations. Despite the various DL models applied to this task, there is a lack of studies systematically comparing their performance. This absence of comparative analysis leads to somewhat arbitrary DL model selection in subsurface flow research, resulting in suboptimal performance and potentially inaccurate predictions. To bridge this gap, we conduct a systematic comparison study of three popular DL architectures—U‐Net, Fourier Neural Operators (FNO), and Segmentation Transformer (SETR)—in surrogate modeling of underground hydrogen storage (UHS). We focus on UHS due to its promise of enhancing clean energy resilience and its cyclic operational conditions that represent common scenarios in various subsurface applications. We evaluate the models based on accuracy, training cost, and inference speed. The comparison shows that U‐Net achieves the highest accuracy, followed by SETR and FNO. Despite its lower accuracy, FNO has the highest inference speed. SETR offers competitive accuracy with the least training memory usage, demonstrating the potential of transformers in learning subsurface flow. Our results provide guidance for selecting DL models for surrogate modeling in a wide range of subsurface flow problems.

42 ENGINEERING↗
DOE OSTI2023

A Comparative Study of Deep Learning Models for Fracture and Pore Space Segmentation in Synthetic Fractured Digital Rocks

This study focuses on the comparative study of deep learning (DL) models for pore space and discrete fracture networks (DFNs) segmentation in synthetic fractured digital rocks, specifically targeting low-permeability rock formations, such as shale and tight sandstones. Accurate characterization of pore space and DFNs is critical for subsequent property analysis and fluid flow modeling. Four DL models, SegNet, U-Net, U-Net-wide, and nested U-Net (i.e., U-Net++), were trained, validated, and tested using synthetic datasets, including input and label image pairs with varying properties. The model performance was assessed regarding pixel-wise metrics, including the F1 score and pixel-wise difference maps. In addition, the physics-based metrics were considered for further analysis, including sample porosity and absolute permeability. Particularly, We first simulated the permeability of porous media containing only pore space and then simulated the permeability of porous media with DFNs added. The difference between these two values is used to quantify the connectivity of segmented DFNs, which is an important parameter for low-permeability rocks. The pixel-wise metrics showed that the nested U-Net model outperformed the rest of the DL models in pore space and DFNs segmentation, with the SegNet model exhibiting the second-best performance. Particularly, nested U-Net enhanced segmentation accuracy for challenging boundary pixels affected by partial volume effects. The U-Net-wide model achieved improved accuracy compared to the U-Net model, which indicated the influence of parameter numbers. Similarly, nested U-Net has the closest match to the ground truth of physics-based metrics, including the porosity of pore space and DFNs, and the permeability difference quantifying the connectivity of DFNs. The findings highlight the effectiveness of DL models, especially the U-Net++ model with nested architecture and redesigned skip connections, in accurately segmenting pore spaces and DFNs, which are crucial for pore-scale fluid flow and transport simulation in low-permeability rocks.

Wang, Hongsheng↗
DOE OSTI2019

Comparative Study of the Effect of Magnetic Nanoparticle CoFe{sub 2}O{sub 4} on Fluctuation-Induced Conductivity of Y-123 and Y-358 Superconductors

In this study, a comparative investigation of the electrical conductivity fluctuations in nano-CoFe{sub 2}O{sub 4} added to Y{sub 3}Ba{sub 5}Cu{sub 8}O{sub 18±x} (Y-358) and YBa{sub 2}Cu{sub 3}O{sub 7−d} (Y-123) products is performed. All products were made using the solid-state reaction process. X-ray powder diffraction (XRD) analyses confirmed the formation of different phases. Scanning electron microscope (SEM) analysis shows the reduction of grain size with increasing the quantity of nano-CoFe{sub 2}O{sub 4} particles for both the Y-123 and Y-358 samples. The decrease of grain size is more accentuated in the case of the Y-358 samples compared with the Y-123 ones. The data of conductivity fluctuations are examined in terms of the derivative of the electrical resistivity with respect to temperature and the logarithmic derivative of the conductivity with regard to temperature. The results illustrate the existence of a transition with two stages; intragrain and intergrain. It is demonstrated that the addition of CoFe{sub 2}O{sub 4} nanoparticles affects the electrical conductivity fluctuations, the values of the critical exponents, and the fluctuation dimensionality in YBCO systems.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

A comparative study of calibration techniques for finite strain elastoplasticity: Numerically-exact sensitivities for FEMU and VFM

Accurate identification of material parameters is crucial for predictive modeling in computational mechanics. Here, the two primary approaches in the experimental mechanics community for calibration from full-field digital image correlation data are known as finite element model updating (FEMU) and the virtual fields method (VFM). In VFM, the objective function is a squared mismatch between internal and external virtual work or power. In FEMU, the objective function quantifies the weighted mismatch between model predictions and corresponding experimentally measured quantities of interest. It is minimized by iteratively updating the parameters of an FE model. While FEMU is seen as more flexible, VFM is commonly used instead of FEMU due to its considerably greater computational expense. However, comparisons between the two methods usually involve approximations of gradients or sensitivities with finite difference schemes, thereby making direct assessments difficult. Hence, in this study, we compare VFM and FEMU in the context of numerically-exact sensitivities obtained through local sensitivity analyses and the application of automatic differentiation software. To this end, we conduct a series of test cases to assess both methods under practical challenges using a finite strain elastoplasticity model.

Automatic differentiation↗
DOE OSTI2023

Genomic Features of Antimicrobial Resistance in Staphylococcus pseudintermedius Isolated from Dogs with Pyoderma in Argentina and the United States: A Comparative Study

Staphylococcus pseudintermedius is the most common opportunistic pathogen in dogs and methicillin resistance (MRSP) has been identified as an emerging problem in canine pyoderma. Here, we evaluated the antimicrobial resistance (AMR) features and phylogeny of S. pseudintermedius isolated from canine pyoderma cases in Argentina (n = 29) and the United States (n = 29). 62% of isolates showed multi-drug resistance. The AMR genes found: mecA, blaZ, ermB, dfrG, catA, tetM, aac(6')-aph(2"), in addition to tetK and lnuA (only found in U.S. isolates). Two point mutations were detected: grlA(S80I)-gyrA(S84L), and grlA(D84N)-gyrA(S84L) in one U.S. isolate. A mutation in rpoB (H481N) was found in two isolates from Argentina. SCCmec type III, SCCmec type V, ΨSCCmec 57395 were identified in the Argentinian isolates; and SCCmec type III, SCCmec type IVg, SCCmec type V, and SCCmec type VII variant in the U.S. cohort. Sequence type (ST) ST71 belonging to a dominant clone was found in isolates from both countries, and ST45 only in Argentinian isolates. This is the first study to comparatively analyze the population structure of canine pyoderma-associated S. pseudintermedius isolates in Argentina and in the U.S. It is important to maintain surveillance on S. pseudintermedius populations to monitor AMR and gain further understanding of its evolution and dissemination.

60 APPLIED LIFE SCIENCES↗
NASA NTRS1980

A comparative study of cosmic ray intensity variations during 1972-1977 using spacecraft and ground-based observations

A study of cosmic ray intensity variations using data registered by Detector C on Pioneer 10 and the Sulphur Mountain neutron monitor is presented. The spacecraft data were corrected for temperature, Radioisotope Thermoelectric Generator background, and contamination by energetic solar particle events. A consistent long-term solar cycle variation intensity is observed, but additional contribution is observed in the neighborhood of 5.1 AU which is attributed to energetic electrons of Jovian origin. The spectral variation in long-term changes of the cosmic ray intensity is studied by comparing the low-energy and high-energy data, and an average value of their ratio during 1972-1977 was found to agree with the value for the 1965-1972 interval.

Venkatesan, D.↗
DOE OSTI2024

Crossing The Gap Using Variational Quantum Eigensolver: A Comparative Study

Within the evolving domain of quantum computational chemistry, the Variational Quantum Eigensolver (VQE) has been developed to explore not only the ground state but also the excited states of molecules. In this study, we compare the performance of Variational Quantum Deflation (VQD) and Subspace-Search Variational Quantum Eigensolver (SSVQE) methods in determining the low-lying excited states of $LiH$. Our investigation reveals that while VQD exhibits a slight advantage in accuracy, SSVQE stands out for its efficiency, allowing the determination of all low-lying excited states through a single parameter optimization procedure. We further evaluate the effectiveness of optimizers, including Gradient Descent (GD), Quantum Natural Gradient (QNG), and Adam optimizer, in obtaining $LiH$'s first excited state, with the Adam optimizer demonstrating superior efficiency in requiring the fewest iterations. Moreover, we propose a novel approach combining Folded Spectrum VQE (FS-VQE) with either VQD or SSVQE, enabling the exploration of highly excited states. We test the new approaches for finding all three $H_4$'s excited states. Folded Spectrum SSVQE (FS-SSVQE) can find all three highly excited states near $-1.0$ Ha with only one optimizing procedure, but the procedure converges slowly. In contrast, although Folded spectrum VQD (FS-VQD) gets highly excited states with individual optimizing procedures, the optimizing procedure converges faster.

Chen, I-Chi↗
NASA NTRS1994

Solar system exploration from the Moon: Synoptic and comparative study of bodies in our Planetary system

An observational approach to Planetary Sciences and exploration from Earth applies to a quite limited number of targets, but most of these are spatially complex, and exhibit variability and evolution on a number of temporal scales which lie within the scope of possible observations. Advancing our understanding of the underlying physics requires the study of interactions between the various elements of such systems, and also requires study of the comparative response of both a given object to various conditions and of comparable objects to similar conditions. These studies are best conducted in 'campaigns', i.e. comprehensive programs combining simultaneous coherent observations of every interacting piece of the puzzle. The requirements include both imaging and spectroscopy over a wide spectral range, from UV to IR. While temporal simultaneity of operation in various modes is a key feature, these observations are also conducted over extended periods of time. The moon is a prime site offering long unbroken observation times and high positional stability, observations at small angular separation from the sun, comparative studies of planet Earth, and valuable technical advantages. A lunar observatory should become a central piece of any coherent set of planetary missions, supplying in-situ explorations with the synoptic and comparative data necessary for proper advance planning, correlative observations during the active exploratory phase, and follow-up studies of the target body or of related objects.

Bruston, P.↗
DOE OSTI2015

SU-E-T-246: Detector Selection for Small Field Measurements, a Comparative Study

Purpose: To compare commercially available detectors for small field dosimetry. Methods: PTW (Freiburg, Germany) diode E, PTW microDiamond, and SunNuclear (Melbourne, FL) Edge detector were used to measure output factors, PDD, and profiles on a Varian iX linear accelerator (Varian Medical Systems, Palo Alto, CA) using 6MV and 18MV photon beams. The water tank was set to 100cm SSD. Centering profiles at 5cm and 20cm depth confirmed an offset <0.1mm. High resolution PDD (0.1mm) aligned the collecting volume at water surface. For setup and linearity verification, PDD and profiles were matched to annual measurements, which were performed with an A1SL ion chamber.Scans were taken for 6X and 18X, for 10cmx10cm, 10cmx2cm, 10cmx1cm, and 10cmx0.5cm fields. Profiles were measured at Dmax (6X=1.5cm, 18X=3.5cm), 5cm, 10cm, and 20cm depths. All fields used 10cmx10cm jaws with the MLC defining the field in the X-direction. PDDs used 2mm step size and 0.2s discrete collecting time. Profiles used 1mm step size and a 0.4s discrete collecting time. Results: The PTW diode E and Edge detector exhibit centering stability, but all detectors require vertical shifts from Vendor defined vertical alignment. Output factor measurements reveal good agreement between detectors. The Edge detector demonstrates the sharpest penumbra and the closest consistent match to ion chamber measurements in the out of field regions for 6MV (3.2%). Each detector provides comparable curve quality for PDDs, with a maximum difference across detectors giving a standard deviation of 0.6% at 30cm depth, 18X, and 10cmx0.5cm. Profiles match closely across all detectors, depths, energies, and field sizes. The microDiamond detector produces the largest penumbra width, largest deviation from ion chamber dose in the tail region for 6MV, and exhibits centering instability. Conclusion: Based on our findings, the Edge detector was chosen for stereotactic measurements. The PTW diode E is an acceptable alternative.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

SU-F-P-46: Comparative Study Between Two Normalization Prescriptions for Accelerated Partial Breast Irradiation: A Dosimetric Study

Purpose: To compare the Accelerated Partial Breast Irradiation (APBI) plan with the normalized basal dose points and 5mm box prescription. Methods: Five patients of APBI were planned twice in Oncentra Master planning TPS (Version 4.3) using TG-43 algorithm. The number of catheters for all the patients was 10 to 16 and implant plane 2 to 3. For planning all catheters were reconstructed. Source loading was done as per HR-CTV contoured. The HR-CTV volume range was from 75cc to 182cc. Plans were normalized in two methods. First all plans were normalized on Basal dose points (PlanA) and second all the plan were normalized on 5mm box (PlanB). The prescription dose (PD) was 35Gy in 10 fractions. All the plans were completely based on normalization and without optimization. Plan evaluation was based on certain parameters coverage Index (CI), dose homogeneity index (DHI), conformity index (COIN), over dose volume index (OI). Results: The average and median of CI for planA was 0.835 and 0.8154, for planB 0.82 and 0.799 respectively. The median and average of DHI for planA was 0.66 and 0.6062, for planB 0.67 and 0.62 respectively. The range of COIN for planA and planB was from 0.58 to 0.65 respectively. The range of OI was from 0.083 to 0.169 for planA and planB. The treatment time in planA was in average 1.13 times more than planB as V150% of HR-CTV in planA was 4–6% more. The ipsilateral lung was getting 30% of PD which was 0.6% to 3.5%. Conclusion: Treatment Planning should be individualized based on implants characteristics. Planning with prescription to basal dose points should be preferred to 5mm box prescription, in order to achieve better DHI and less treatment time.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Comparative studies of industrial grade carbon black powders

Comparative studies of two dissimilar industrial grade Carbon Black (CB) powders (N375 and N405) were conducted. The structure, surface area and particle size are the three important characteristics of CB powder that determine their processability and application as filler in preparing rubber compounds. The powders were characterized for their structure using dibutyl phthalate absorption (DBPA), particle size via laser particle size analyzer and surface area by nitrogen adsorption method. The structural characterization showed that N405 had lower DBPA in comparison to N375, confirming low structure of N405 grade CB powder. It was observed from the particle size analysis that N375 was coarser than N405 grade CB. The total surface area values were determined by the BET method based on the cross sectional area of the nitrogen molecule. N375, a coarse grade CB powder with high structure, depicted less surface area as compared to N405.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1996

Comparative Study Of Four Models Of Turbulence

Report presents comparative study of four popular eddy-viscosity models of turbulence. Computations reported for three different adverse pressure-gradient flowfields. Detailed comparison of numerical results and experimental data given. Following models tested: Baldwin-Lomax, Johnson-King, Baldwin-Barth, and Wilcox.

Menter, Florian R.↗
DOE OSTI2022

Surrogate Modeling of Nonlinear Dynamic Systems: A Comparative Study

Surrogate models play a vital role in overcoming the computational challenge in designing and analyzing nonlinear dynamic systems, especially in the presence of uncertainty. This paper presents a comparative study of different surrogate modeling techniques for nonlinear dynamic systems. Four surrogate modeling methods, namely, Gaussian process (GP) regression, a long short-term memory (LSTM) network, a convolutional neural network (CNN) with LSTM (CNN-LSTM), and a CNN with bidirectional LSTM (CNN-BLSTM), are studied and compared. All these model types can predict the future behavior of dynamic systems over long periods based on training data from relatively short periods. The multi-dimensional inputs of surrogate models are organized in a nonlinear autoregressive exogenous model (NARX) scheme to enable recursive prediction over long periods, where current predictions replace inputs from the previous time window. Three numerical examples, including one mathematical example and two nonlinear engineering analysis models, are used to compare the performance of the four surrogate modeling techniques. The results show that the GP-NARX surrogate model tends to have more stable performance than the other three deep learning (DL)-based methods for the three particular examples studied. The tuning effort of GP-NARX is also much lower than its deep learning-based counterparts.

42 ENGINEERING↗
NASA NTRS1993

A comparative study between shielded and open coplanar waveguide discontinuities

A comparative study between open and shielded coplanar waveguide (CPW) discontinuities is presented. The space domain integral equation method is used to characterize several discontinuities such as the open-end CPW and CPW series stubs. Two different geometries of CPW series stubs (straight and bent stubs) are compared with respect to resonant frequency and radiation loss. In addition, the encountered radiation loss due to different CPW shunt stubs is evaluated experimentally. The notion of forced radiation simulation is presented, and the results of such a simulation are compared to the actual radiation loss obtained rigorously. It is shown that such a simulation cannot give reliable results concerning radiation loss from printed circuits.

Dib, Nihad I.↗
DOE OSTI2014

Comparative study of laminar and turbulent flow model with different operating parameters for radio frequency-inductively coupled plasma torch working at 3 MHz frequency at atmospheric pressure

This paper provides 2D comparative study of results obtained using laminar and turbulent flow model for RF (radio frequency) Inductively Coupled Plasma (ICP) torch. The study was done for the RF-ICP torch operating at 50 kW DC power and 3 MHz frequency located at BARC. The numerical modeling for this RF-ICP torch is done using ANSYS software with the developed User Defined Function. A comparative study is done between laminar and turbulent flow model to investigate how temperature and flow fields change when using different operating conditions such as (a) swirl and no swirl velocity for sheath gas flow rate, (b) variation in sheath gas flow rate, and (c) variation in plasma gas flow rate. These studies will be useful for different material processing applications.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2015

Complete synchronization of uncertain chaotic systems via a single proportional adaptive controller: A comparative study

This paper addresses a comparative computational study on the synchronization quality, cost and converging speed for two pairs of identical chaotic and hyperchaotic systems with unknown time-varying parameters. It is assumed that the unknown time-varying parameters are bounded. Based on the Lyapunov stability theory and using the adaptive control method, a single proportional controller is proposed to achieve the goal of complete synchronizations. Accordingly, appropriate adaptive laws are designed to identify the unknown time-varying parameters. The designed control strategy is easy to implement in practice. Numerical simulations results are provided to verify the effectiveness of the proposed synchronization scheme.

42 ENGINEERING↗