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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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All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Scalar Field Comparison with Topological Descriptors: Properties and Applications for Scientific Visualization

In topological data analysis and visualization, topological descriptors such as persistence diagrams, merge trees, contour trees, Reeb graphs, and Morse–Smale complexes play an essential role in capturing the shape of scalar field data. Herein we present a state–of–the–art report on scalar field comparison using topological descriptors. We provide a taxonomy of existing approaches based on visualization tasks associated with three categories of data: single fields, time–varying fields, and ensembles. These tasks include symmetry detection, periodicity detection, key event/feature detection, feature tracking, clustering, and structure statistics. Our main contributions include the formulation of a set of desirable mathematical and computational properties of comparative measures, and the classification of visualization tasks and applications that are enabled by these measures.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2022

Combining Particle Tracking with Electromagnetic Radiation Showers: Merging GPT and Geant4 with Visualization

Field emitted electrons can seriously affect the operation of high-field, high-duty factor electron accelerators. Accelerated field emission can result in high average power beams which can radiation damage beamline components. In addition, localized losses generate thermal hot spots whose outgassing degrades the ultra-high vacuum required in photoinjectors and cryomodules. However, despite their importance, the effects of field emission are rarely included in the design and engineering of electron injectors. This work attempts to remedy this situation by combining two well-known and well-documented programs, GPT and Geant4, to track electrons and their losses in an injector beamline. This paper describes a system of programs which simulates electron paths and losses along the beamline. In addition, the tracking results can be zoomed and panned along and about the beampipe envelope using an open-source 3D CAD program. The scattering albedo calculations of the combined program, GPT-Geant4, are shown to be in good agreement with the literature albedos. The paper concludes with a dark current simulation for the LCLS-II injector from the cathode to the collimator at 1.5 m from the cathode.

Dowell, David H.↗
DOE OSTI2016

Topological Methods for Visualization

This slide presentation describes basic topological concepts, including topological spaces, homeomorphisms, homotopy, betti numbers. Scalar field topology explores finding topological features and scalar field visualization, and vector field topology explores finding topological features and vector field visualization.

58 GEOSCIENCES↗
DOE OSTI2020

Hidden fluid mechanics: Learning velocity and pressure fields from flow visualizations

For centuries, flow visualization has been the art of making fluid motion visible in physical and biological systems. Although such flow patterns can be, in principle, described by the Navier-Stokes equations, extracting the velocity and pressure fields directly from the images is challenging. We addressed this problem by developing hidden fluid mechanics (HFM), a physics-informed deep-learning framework capable of encoding the Navier-Stokes equations into the neural networks while being agnostic to the geometry or the initial and boundary conditions. We demonstrate HFM for several physical and biomedical problems by extracting quantitative information for which direct measurements may not be possible.

Raissi, Maziar↗
DOE OSTI2014

Silent Corticotroph Adenomas After Stereotactic Radiosurgery: A Case–Control Study

Purpose: To investigate the safety and effectiveness of stereotactic radiosurgery (SRS) in patients with a silent corticotroph adenoma (SCA) compared with patients with other subtypes of non–adrenocorticotropic hormone staining nonfunctioning pituitary adenoma (NFA). Methods and Materials: The clinical features and outcomes of 104 NFA patients treated with SRS in our center between September 1994 and August 2012 were evaluated. Among them, 34 consecutive patients with a confirmatory SCA were identified. A control group of 70 patients with other subtypes of NFA were selected for review based on comparable baseline features, including sex, age at the time of SRS, tumor size, margin radiation dose to the tumor, and duration of follow-up. Results: The median follow-up after SRS was 56 months (range, 6-200 months). No patients with an SCA developed Cushing disease during the follow-up. Tumor control was achieved in 21 of 34 patients (62%) in the SCA group, compared with 65 of 70 patients (93%) in the NFA group. The median progression-free survival (PFS) was 58 months in the SCA group. The actuarial PFS was 73%, 46%, and 31% in the SCA group and was 94%, 87%, and 87% in the NFA group at 3, 5, and 8 years, respectively. Silent corticotroph adenomas treated with a dose of ≥17 Gy exhibited improved PFS. New-onset loss of pituitary function developed in 10 patients (29%) in the SCA group, whereas it occurred in 18 patients (26%) in the NFA group. Eight patients (24%) in the SCA group experienced worsening of a visual field deficit or visual acuity attributed to the tumor progression, as did 6 patients (9%) in the NFA group. Conclusion: Silent corticotroph adenomas exhibited a more aggressive course with a higher progression rate than other subtypes of NFAs. Stereotactic radiosurgery is an important adjuvant treatment for control of tumor growth. Increased radiation dose may lead to improved tumor control in SCA patients.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2024

Full-field quantitative visualization of shock-driven pore collapse and failure modes in PMMA

The dynamic collapse of pores under shock loading is thought to be directly related to hot spot generation and material failure, which is critical to the performance of porous energetic and structural materials. However, the shock compression response of porous materials at the local, individual pore scale is not well understood. This study examines, quantitatively, the collapse phenomenon of a single spherical void in PMMA at shock stresses ranging from 0.4 to 1.0 GPa. Using a newly developed internal digital image correlation technique in conjunction with plate impact experiments, full-field quantitative deformation measurements are conducted in the material surrounding the collapsing pore for the first time. The experimental results reveal two failure mode transitions as shock stress is increased: (i) the first in situ evidence of shear localization via adiabatic shear banding and (ii) dynamic fracture initiation at the pore surface. Numerical simulations using thermo-viscoplastic dynamic finite element analysis provide insights into the formation of adiabatic shear bands (ASBs) and stresses at which failure mode transitions occur. Further numerical and theoretical modeling indicates the dynamic fracture to occur along the weakened material inside an adiabatic shear band. Finally, analysis of the evolution of pore asymmetry and models for ASB spacing elucidate the mechanisms for the shear band initiation sites, and elastostatic theory explains the experimentally observed ASB and fracture paths based on the directions of maximum shear.

42 ENGINEERING↗
DOE OSTI2017

Visualizing Electric Fields at Au(111) Step Edges via Tip-Enhanced Raman Scattering

Tip-enhanced Raman scattering (TERS) can be used to image plasmon-enhanced local electric fields on the nanoscale. This is illustrated through ambient TERS measurements recorded using silver atomic force microscope tips coated with 4-mercaptobenzonitrile molecules and used to image step edges on an Au(111) surface. The observed 2D TERS images uniquely map electric fields localized at Au(111) step edges following 671-nm excitation. We establish that our measurements are not only sensitive to spatial variations in the enhanced electric fields but also to their vector components. We also experimentally demonstrate that (i) few nanometer precision is attainable in TERS nanoscopy using corrugated tips with nominally radii on the order of 100-200 nm, and (ii) TERS signals do not necessarily exhibit the expected E4 dependence. Overall, we illustrate the concept of electric field imaging via TERS and establish the connections between our observations and conventional TERS chemical imaging measurements.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2020

Towards Feature-Preserving 2D and 3D Vector Field Compression

The objective of this work is to develop error-bounded lossy compression methods to preserve topological features in 2D and 3D vector fields. Specifically, we explore the preservation of critical points in piecewise linear vector fields. We define the preservation of critical points as, without any false positive, false negative, or false type change in the decompressed data, (1) keeping each critical point in its original cell and (2) retaining the type of each critical point (e.g., saddle and attracting node). The key to our method is to adapt a vertex-wise error bound for each grid point and to compress input data together with the error bound field using a modified lossy compressor. Our compression algorithm can be also embarrassingly parallelized for large data handling and in situ processing. We benchmark our method by comparing it with existing lossy compressors in terms of false positive/negative/type rates, compression ratio, and various vector field visualizations with several scientific applications.

critical points↗
DOE OSTI2025

Advanced Model Development for Large Eddy Simulation of Oxy-Combustion and Supercritical Carbon Dioxide Power Cycles

A joint experimental and numerical study is performed to observe the characteristics of a supercritical carbon dioxide turbulent mixing layer in the presence of strong nonlinearities in the thermodynamic and transport properties. A bespoke experimental setup is designed and employed for this purpose and provides insight into macroscopic mixing behavior. The mixing is experimentally observed using two techniques: shadowgraphy and spontaneous Raman scattering. Qualitative and quantitative intensity fields obtained via these techniques yield instantaneous and mean density data. Spanwise temperature data is also collected using analogue resistance temperature detectors. These measurements are used to quantify the level of mixed material within the field. The experimental data are supplemented by a companion high-fidelity numerical study. The numerical results are obtained through fully resolved, three-dimensional direct numerical simulation. The numerical dataset permits observation of the near-field mixing characteristics, which are difficult to measure experimentally due to the rapid dynamics and sharp thermophysical gradients in this area. Qualitative field visualizations are presented, followed by quantitative mixed material results and observations regarding thermodynamic property trends at select locations within the field. One-dimensional spectra of the turbulent kinetic energy and solenoidal dissipation are provided to observe the spectral characteristics of the flow. Reynolds stress anisotropy is analyzed graphically through anisotropy invariance maps (Lumley triangles). The mixing quantification, spectral data and anisotropy analysis of a flow at these thermodynamic conditions represent the main outcomes of the work.

20 FOSSIL-FUELED POWER PLANTS↗
DOE OSTI2017

Apply or Die: On the Role and Assessment of Application Papers in Visualization

Application-oriented papers provide an important way to invigorate and cross-pollinate the visualization field, but the exact criteria for judging an application paper's merit remain an open question. This article builds on a panel at the 2016 IEEE Visualization Conference entitled "Application Papers: What Are They, and How Should They Be Evaluated?" that sought to gain a better understanding of prevalent views in the visualization community. This article surveys current trends that favor application papers, reviews the benefits and contributions of this paper type, and discusses their assessment in the review process. It concludes with recommendations to ensure that the visualization community is more inclusive to application papers.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2022

Local bilinear computation of Jacobi sets

Abstract We propose a novel method for the computation of Jacobi sets in 2D domains. The Jacobi set is a topological descriptor based on Morse theory that captures gradient alignments among multiple scalar fields, which is useful for multi-field visualization. Previous Jacobi set computations use piecewise linear approximations on triangulations that result in discretization artifacts like zig-zag patterns. In this paper, we utilize a local bilinear method to obtain a more precise approximation of Jacobi sets by preserving the topology and improving the geometry. Consequently, zig-zag patterns on edges are avoided, resulting in a smoother Jacobi set representation. Our experiments show a better convergence with increasing resolution compared to the piecewise linear method. We utilize this advantage with an efficient local subdivision scheme. Finally, our approach is evaluated qualitatively and quantitatively in comparison with previous methods for different mesh resolutions and across a number of synthetic and real-world examples.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2014

Magnetic resonance visualization of conductive structures by sequence-triggered direct currents and spin-echo phase imaging

Purpose: Instrument visualization in interventional magnetic resonance imaging (MRI) is commonly performed via susceptibility artifacts. Unfortunately, this approach suffers from limited conspicuity in inhomogeneous tissue and disturbed spatial encoding. Also, susceptibility artifacts are controllable only by sequence parameters. This work presents the basics of a new visualization method overcoming such problems by applying sequence-triggered direct current (DC) pulses in spin-echo (SE) imaging. SE phase images allow for background free current path localization. Methods: Application of a sequence-triggered DC pulse in SE imaging, e.g., during a time period between radiofrequency excitation and refocusing, results in transient field inhomogeneities. Dependent on the additional z-magnetic field from the DC, a phase offset results despite the refocusing pulse. False spatial encoding is avoided by DC application during periods when read-out or slice-encoding gradients are inactive. A water phantom containing a brass conductor (water equivalent susceptibility) and a titanium needle (serving as susceptibility source) was used to demonstrate the feasibility. Artifact dependence on current strength and orientation was examined. Results: Without DC, the brass conductor was only visible due to its water displacement. The titanium needle showed typical susceptibility artifacts. Applying triggered DC pulses, the phase offset of spins near the conductor appeared. Because SE phase images are homogenous also in regions of persistent field inhomogeneities, the position of the conductor could be determined with high reliability. Artifact characteristic could be easily controlled by amperage leaving sequence parameters unchanged. For an angle of 30° between current and static field visualization was still possible. Conclusions: SE phase images display the position of a conductor carrying pulsed DC free from artifacts caused by persistent field inhomogeneities. Magnitude and phase images are acquired simultaneously under the same conditions without the use of extra measurement time. The presented technique offers many advantages for precise instrument localization in interventional MRI.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2014

A MATLAB-based finite-element visualization of quantum reactive scattering. I. Collinear atom-diatom reactions

We restate the application of the finite element method to collinear triatomic reactive scattering dynamics with a novel treatment of the scattering boundary conditions. The method provides directly the reactive scattering wave function and, subsequently, the probability current density field. Visualizing these quantities provides additional insight into the quantum dynamics of simple chemical reactions beyond simplistic one-dimensional models. Application is made here to a symmetric reaction (H+H{sub 2}), a heavy-light-light reaction (F+H{sub 2}), and a heavy-light-heavy reaction (F+HCl). To accompany this article, we have written a MATLAB code which is fast, simple enough to be accessible to a wide audience, as well as generally applicable to any problem that can be mapped onto a collinear atom-diatom reaction. The code and user's manual are available for download from http://www2.chem.umd.edu/groups/alexander/FEM.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Evaluation of Visualization Heuristics

Heuristics have been used since the early 1990's in the Human Computer Interaction (HCI) domain, for evaluating user interfaces. Most notably, heuristics developed by Nielsen and Molich (1990) have been used by the HCI community. Forsell and Johansson (2010) used the same methodology as Nielsen and Molich and developed a set of 10 heuristics for information visualization. Currently, neither the information visualization or the visual analytics community has adopted these heuristics. However, several studies have been conducted using heuristics. Hearst et al. (2015) found that using the heuristics for visualizations along with asking questions about the data resulted in complementary results as the questions about the data could compensate for heuristics that were difficult to understand and apply. Heli Väätäjä et al. (2016) found that heuristics related to interaction, veracity, and aesthetics needed to be added to the Forsell and Johansson (2010) set. They also noted that a lack of domain knowledge caused the evaluators issues in conducting a heuristic evaluation. We conducted a controlled experiment to determine what factors might impact the expert evaluators' capability to conduct a heuristic evaluation of a static information visualization. In particular, we wanted to understand how their familiarity with the visualizations and their experience in conducting heuristic evaluations impacted their evaluations of visualizations. We recruited 10 participants who were domain experts in the visualization field each having experience with one of more of the following: user experience design or research, user interface development, and human computer interaction research. We used a heuristic set proposed by Forsell and Johansson. Participants were also asked to complete a demographic survey in which they rated their experience with each visualization type generally, their experience conducting heuristic evaluations, their experience using each visualization type to extract information, and their experience developing and creating each visualization type. The participants were shown a series of 5 common visualizations (Scatterplots, Sunbursts, Tree Maps, Parallel Sets, and Area Graphs) all displaying the VAST 2008 Mini Challenge Two- Migrant Boats data . Participants were given a suggested analytical question related to each visualization to keep in mind as they applied the 10 heuristics to each visualization. They were asked if they could find any usability problems in the visualizations and which heuristic(s) helped them to identify these problems. The participants were asked to rate how relevant each heuristic was for evaluating each visualization along with rating how confident they felt in their ability to apply the heuristic to evaluate each visualization. At the conclusion of the study, participants provided qualitative feedback on the usability issues of each visualization. Additionally, we collected eye tracking data on 6 of the 10 participants. We will be using this data to determine how long participants looked at the various visualizations and what parts of the visualizations they focused on. We had two hypotheses for this empirical evaluation: 1.The Forsell and Johansson heuristics of Orientation and help, Data set reduction, and Prompting are less useful for static visualizations because they require some interaction in order to test completely. 2.Participants that do not have experience with heuristic evaluation will provide lower evaluation scores for the heuristics compared to those that have experience. Related to hypothesis 1, as our study used only static visualizations, interaction-related usability challenges should be harder to identify. This should result in lower usefulness ratings for those heuristics. Preliminary results indicate that participants found it more difficult to apply heuristics to unfamiliar visualizations.

Williams, Ryan G.↗
DOE OSTI2021

System-on-chip upgrade of millimeter-wave imaging diagnostics for fusion plasma

Monolithic, millimeter wave “system-on-chip” technology has been employed in chip heterodyne radiometers in a newly developed Electron Cyclotron Emission Imaging (ECEI) system on the DIII-D tokamak for 2D electron temperature and fluctuation diagnostics. The system employs 20 horn-waveguide receiver modules each with customized W-band (75–110 GHz) monolithic microwave integrated circuit chips comprising a W-band low noise amplifier, a balanced mixer, a ×2 local oscillator (LO) frequency doubler, and two intermediate frequency amplifier stages in each module. Compared to previous quasi-optical ECEI arrays with Schottky mixer diodes mounted on planar antennas, the upgraded W-band array exhibits >30 dB additional gain and 20× improvement in noise temperature; an internal eight times multiplier chain is used to provide LO coupling, thereby eliminating the need for quasi-optical coupling. The horn-waveguide shielding housing avoids out-of-band noise interference on each module. The upgraded ECEI system plays an important role for absolute electron temperature and fluctuation measurements for edge and core region transport physics studies. An F-band receiver chip (up to 140 GHz) is under development for additional fusion facilities with a higher toroidal magnetic field. Visualization diagnostics provide multi-scale and multi-dimensional data in plasma profile evolution. Finally, a significant aspect of imaging measurement is focusing on artificial intelligence for science applications.

47 OTHER INSTRUMENTATION↗
DOE OSTI2025

Breaking the barrier of human-annotated training data for machine learning-aided plant research using aerial imagery

Machine learning (ML) can accelerate biological research. However, the adoption of such tools to facilitate phenotyping based on sensor data has been limited by (i) the need for a large amount of human-annotated training data for each context in which the tool is used and (ii) phenotypes varying across contexts defined in terms of genetics and environment. This is a major bottleneck because acquiring training data is generally costly and time-consuming. This study demonstrates how a ML approach can address these challenges by minimizing the amount of human supervision needed for tool building. A case study was performed to compare ML approaches that examine images collected by an uncrewed aerial vehicle to determine the presence/absence of panicles (i.e. “heading”) across thousands of field plots containing genetically diverse breeding populations of 2 Miscanthus species. Automated analysis of aerial imagery enabled the identification of heading approximately 9 times faster than in-field visual inspection by humans. Leveraging an Efficiently Supervised Generative Adversarial Network (ESGAN) learning strategy reduced the requirement for human-annotated data by 1 to 2 orders of magnitude compared to traditional, fully supervised learning approaches. The ESGAN model learned the salient features of the data set by using thousands of unlabeled images to inform the discriminative ability of a classifier so that it required minimal human-labeled training data. This method can accelerate the phenotyping of heading date as a measure of flowering time in Miscanthus across diverse contexts (e.g. in multistate trials) and opens avenues to promote the broad adoption of ML tools.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Event-related brain potentials reveal how multiple aspects of semantic processing unfold across parafoveal and foveal vision during sentence reading

Recent event–related brain potential (ERP) experiments have demonstrated parafoveal N400 expectancy and congruity effects, showing that semantic information can be accessed from words in parafoveal vision (a conclusion also supported by some eye–tracking work). At the same time, it is unclear how higher–order integrative aspects of language comprehension unfold across the visual field during reading. In the current study, we recorded ERPs in a parafoveal flanker paradigm, while readers were instructed to read passively for comprehension or to judge the plausibility of sentences in which target words varied in their semantic expectancy and congruity. We directly replicated prior work showing graded N400 effects for parafoveal viewing, which are then not duplicated when the target words are processed foveally. Critically, although N400 effects were not modulated by task goals, a posteriorly distributed late positive component thought to reflect semantic integration processes was observed to semantic incongruities only in the plausibility judgment task. Furthermore, this effect was observed at a considerable delay, appearing only after words had moved into foveal vision. Our findings thus suggest that semantic access can be initiated in parafoveal vision, whereas central foveal vision may be necessary to enact higher–order (and task–dependent) integrative processing.

60 APPLIED LIFE SCIENCES↗