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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 1,351 records · Page 75
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Comparison of Oncentra® Brachy IPSA and graphical optimisation techniques: a case study of HDR brachytherapy head and neck and prostate plans

There are a number of different dwell positions and time optimisation options available in the Oncentra® Brachy (Elekta Brachytherapy Solutions, Veenendaal, The Netherlands) brachytherapy treatment planning system. The purpose of this case study was to compare graphical (GRO) and inverse planning by simulated annealing (IPSA) optimisation techniques for interstitial head and neck (HN) and prostate plans considering dosimetry, modelled radiobiology outcome and planning time. Four retrospective brachytherapy patients were chosen for this study, two recurrent HN and two prostatic boosts. Manual GRO and IPSA plans were generated for each patient. Plans were compared using dose–volume histograms (DVH) and dose coverage metrics including; conformity index (CI), homogeneity index (HI) and conformity number (CN). Logit and relative seriality models were used to calculate tumour control probability (TCP) and normal tissue complication probability (NTCP). Approximate planning time was also recorded. There was no significant difference between GRO and IPSA in terms of dose metrics with mean CI of 1.30 and 1.57 (P > 0.05) respectively. IPSA achieved an average HN TCP of 0.32 versus 0.12 for GRO while for prostate there was no significant difference. Mean GRO planning times were greater than 75 min while average IPSA planning times were less than 10 min. Planning times for IPSA were greatly reduced compared to GRO and plans were dosimetrically similar. For this reason, IPSA makes for a useful planning tool in HN and prostate brachytherapy.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2020

Measurement of the cross section for $\text{t}\bar{\text{t}}$ production with additional jets and b jets in pp collisions at $\sqrt{s}=$ 13 TeV

Measurements of the cross section for the production of top quark pairs in association with a pair of jets from bottom quarks $ \left({\sigma}_{\mathrm{t}\overline{\mathrm{t}}\mathrm{b}\overline{\mathrm{b}}}\right) $ and in association with a pair of jets from quarks of any flavor or gluons $ \left({\sigma}_{\mathrm{t}\overline{\mathrm{t}}\mathrm{jj}}\right) $ and their ratio are presented. The data were collected in proton-proton collisions at a center-of-mass energy of 13 TeV by the CMS experiment at the LHC in 2016 and correspond to an integrated luminosity of 35.9 fb$^{−1}$. The measurements are performed in a fiducial phase space and extrapolated to the full phase space, separately for the dilepton and lepton+jets channels, where lepton corresponds to either an electron or a muon. The results of the measurements in the fiducial phase space for the dilepton and lepton+jets channels, respectively, are $ {\sigma}_{\mathrm{t}\overline{\mathrm{t}}\mathrm{jj}} $ = 2.36±0.02 (stat)±0.20 (syst) pb and 31.0±0.2 (stat)±2.9 (syst) pb, and for the cross section ratio 0.017 ± 0.001 (stat) ± 0.001 (syst) and 0.020 ± 0.001 (stat) ± 0.001 (syst). The values of $ {\sigma}_{\mathrm{t}\overline{\mathrm{t}}\mathrm{b}\overline{\mathrm{b}}} $ are determined from the product of the $ {\sigma}_{\mathrm{t}\overline{\mathrm{t}}\mathrm{jj}} $ and the cross section ratio, obtaining, respectively, 0.040±0.002 (stat)±0.005 (syst) pb and 0.62±0.03 (stat)±0.07 (syst) pb. These measurements are the most precise to date and are consistent, within the uncertainties, with the standard model expectations obtained using a matrix element calculation at next-to-leading order in quantum chromodynamics matched to a parton shower.[graphic not available: see fulltext]

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Syntheses, structures and properties of three metal–organic complexes containing 2,2′-dipyridyl-5,5′-dicarboxylate ligands

Three new metal–organic complexes Cu[Hbpdc]{sub 2} (1), [Ni(bpdc)(H{sub 2}O)]·H{sub 2}O (2) and [Ni(H{sub 2}bpdc)(H{sub 2}O){sub 2}]SO{sub 4} (3) (H{sub 2}bpdc=2,2′-bipyridyl-5,5′-dicarboxylic acid) have been hydrothermally prepared and structurally characterized by elemental analyses, IR spectra, powder X-ray diffraction (PXRD) and single-crystal X-ray diffraction. 1 is a 3-D supramolecular architecture formed by hydrogen bonding interactions between carboxyl O atoms and strong face-to-face π⋯π stacking interactions between bipyridyl rings of Hbpdc{sup −} ligands, 2 exhibits an intriguing 2-D sheet constructed from [Ni(bpdc)(H{sub 2}O)] units and 3 displays an infinite 1-D chain built by ([Ni(H{sub 2}bpdc)(H{sub 2}O){sub 2}]{sup 2+}) fragments through SO{sub 4}{sup 2−}. Moreover, thermogravimetric (TG) and derivative thermogravimetric (DTG) analyses of 3 have been conducted and the TG curve shows two-stage weight loss between 300 and 950 K and the corresponding apparent activation energies are calculated by Ozawa–Flynn–Wall (OFW) method and Friedman method. The most probable kinetic model function of the dehydration reaction of 3 has been estimated by Coats–Redfern integral method and Achar–Bridly–Sharp differential method. - Graphical abstract: Three metal–organic complexes containing 2,2′-dipyridyl-5,5′-dicarboxylate ligands were synthesized and the thermal decomposition kinetics were investigated. - Highlights: • Metal–organic complexes containing 2,2′-dipyridyl-5,5′-dicarboxylate ligands. • 3-D supramolecular architecture. • Thermal decomposition kinetics.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Classification of Cloud Particle Imagery from Aircraft Platforms Using Convolutional Neural Networks

Abstract A vast amount of ice crystal imagery exists from a variety of field campaign initiatives that can be utilized for cloud microphysical research. Here, nine convolutional neural networks are used to classify particles into nine regimes on over 10 million images from the Cloud Particle Imager probe, including liquid and frozen states and particles with evidence of riming. A transfer learning approach proves that the Visual Geometry Group (VGG-16) network best classifies imagery with respect to multiple performance metrics. Classification accuracies on a validation dataset reach 97% and surpass traditional automated classification. Furthermore, after initial model training and preprocessing, 10 000 images can be classified in approximately 35 s using 20 central processing unit cores and two graphics processing units, which reaches real-time classification capabilities. Statistical analysis of the classified images indicates that a large portion (57%) of the dataset is unusable, meaning the images are too blurry or represent indistinguishable small fragments. In addition, 19% of the dataset is classified as liquid drops. After removal of fragments, blurry images, and cloud drops, 38% of the remaining ice particles are largely intersecting the image border (≥10% cutoff) and therefore are considered unusable because of the inability to properly classify and dimensionalize. After this filtering, an unprecedented database of 1 560 364 images across all campaigns is available for parameter extraction and bulk statistics on specific particle types in a wide variety of storm systems, which can act to improve the current state of microphysical parameterizations.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

NATCARB

The National Carbon Sequestration Database (NATCARB) is a geographic information system (GIS)-based tool for viewing carbon capture, use and storage (CCUS) potential across the United States. Through a graphical user interface, NATCARB displays locations and associated metadata about stationary CO2 sources and potential geologic sinks. Users can access, query and model, analyze, display, and download CO2 storage resource data.

Atlas↗
DOE OSTI2014

Tools and Apps to Enhance Situational Awareness for Global Disease Surveillance</strong

Situational awareness is important for both early warning and early detection of a disease outbreak. We will describe a suite of tools developed at Los Alamos National Laboratory that provide actionable information and knowledge for enhanced situational awareness during an unfolding event. The BRD is a searchable database, a one stop shop for disease surveillance resources and can be used for validating information received about disease outbreaks. Furthermore, the BaRD is a searchable database that catalogs and classifies epidemiological model-specific information to allow facile selection. The SWAP is an app to provide a context for a rapidly unfolding event through graphical visualization.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1973

Study of information transfer optimization for communication satellites

The results are presented of a study of source coding, modulation/channel coding, and systems techniques for application to teleconferencing over high data rate digital communication satellite links. Simultaneous transmission of video, voice, data, and/or graphics is possible in various teleconferencing modes and one-way, two-way, and broadcast modes are considered. A satellite channel model including filters, limiter, a TWT, detectors, and an optimized equalizer is treated in detail. A complete analysis is presented for one set of system assumptions which exclude nonlinear gain and phase distortion in the TWT. Modulation, demodulation, and channel coding are considered, based on an additive white Gaussian noise channel model which is an idealization of an equalized channel. Source coding with emphasis on video data compression is reviewed, and the experimental facility utilized to test promising techniques is fully described.

Odenwalder, J. P.↗
NASA NTRS1984

The 3SPACE digitizer: A new input device for solid geometry modeling

The 3SPACE Digitizer is a derivation of SPASYN, which is a patented magnetic transducing system offering an accurate method of calculating the location of one object relative to another. SPASYN uses low-frequency magnetic fields to measure both the position and orientation of its sensor relative to its transmitter. The 3SPACE Digitizer unit consists of a system's electronics unit, a model table, a stylus, and a keypad. In operation, the 3SPACE Digitizer determines the X, Y, Z coordinates of any point located on a low-conductive, three-dimensional model. This data, along with the orientation of the Digitizer's stylus, is immediately available for transmission to a host computer or graphics terminal. Digitization is effected by touching the point to be measured with the tip of a handheld stylus. The 3SPACE Digitizer presents new opportunities for interacting with computers in a large number of engineering and scientific applications. Developed from proven military technology, the 3SPACE Digitizer significantly simplifies three-dimensional digitization and overcomes many of the problems that once plagued such procedures. Its ability to digitize solid objects makes it a valuable new tool for computer-aided design and manufacturing.

Scully, J.↗
NASA NTRS1984

STABCAR: A program for finding characteristic root systems having transcendental stability matrices

STABCAR can be used to determine the characteristic roots of flexible, actively controlled aircraft, including the effects of unsteady aerodynamics. A modal formulation and a transfer-matrix representation of the control system are employed. Operable in either a batch or an interactive mode, STABCAR can provide graphical or tabular output of the variation of the roots with velocity, density, altitude, dynamic pressure or feedback gains. Herein the mathematical model, program structure, input requirements, output capabilities, and a series of sample cases are detailed. STABCAR was written for use on CDC CYBER 175 equipment; modification would be required for operation on other machines.

Adams, W. M., Jr.↗
NASA NTRS1993

Automating a human factors evaluation of graphical user interfaces for NASA applications: An update on CHIMES

Capturing human factors knowledge about the design of graphical user interfaces (GUI's) and applying this knowledge on-line are the primary objectives of the Computer-Human Interaction Models (CHIMES) project. The current CHIMES prototype is designed to check a GUI's compliance with industry-standard guidelines, general human factors guidelines, and human factors recommendations on color usage. Following the evaluation, CHIMES presents human factors feedback and advice to the GUI designer. The paper describes the approach to modeling human factors guidelines, the system architecture, a new method developed to convert quantitative RGB primaries into qualitative color representations, and the potential for integrating CHIMES with user interface management systems (UIMS). Both the conceptual approach and its implementation are discussed. This paper updates the presentation on CHIMES at the first International Symposium on Ground Data Systems for Spacecraft Control.

Jiang, Jian-Ping↗
NASA NTRS2004

B-737 Linear Autoland Simulink Model

The Linear Autoland Simulink model was created to be a modular test environment for testing of control system components in commercial aircraft. The input variables, physical laws, and referenced frames used are summarized. The state space theory underlying the model is surveyed and the location of the control actuators described. The equations used to realize the Dryden gust model to simulate winds and gusts are derived. A description of the pseudo-random number generation method used in the wind gust model is included. The longitudinal autopilot, lateral autopilot, automatic throttle autopilot, engine model and automatic trim devices are considered as subsystems. The experience in converting the Airlabs FORTRAN aircraft control system simulation to a graphical simulation tool (Matlab/Simulink) is described.

Belcastro, Celeste↗
NASA NTRS2017

Filter Tuning Using the Chi-Squared Statistic

The Goddard Space Flight Center (GSFC) Flight Dynamics Facility (FDF) performs orbit determination (OD) for the Aqua and Aura satellites. Both satellites are located in low Earth orbit (LEO), and are part of what is considered the A-Train satellite constellation. Both spacecraft are currently in the science phase of their respective missions. The FDF has recently been tasked with delivering definitive covariance for each satellite.The main source of orbit determination used for these missions is the Orbit Determination Toolkit developed by Analytical Graphics Inc. (AGI). This software uses an Extended Kalman Filter (EKF) to estimate the states of both spacecraft. The filter incorporates force modelling, ground station and space network measurements to determine spacecraft states. It also generates a covariance at each measurement. This covariance can be useful for evaluating the overall performance of the tracking data measurements and the filter itself. An accurate covariance is also useful for covariance propagation which is utilized in collision avoidance operations. It is also valuable when attempting to determine if the current orbital solution will meet mission requirements in the future.This paper examines the use of the Chi-square statistic as a means of evaluating filter performance. The Chi-square statistic is calculated to determine the realism of a covariance based on the prediction accuracy and the covariance values at a given point in time. Once calculated, it is the distribution of this statistic that provides insight on the accuracy of the covariance.For the EKF to correctly calculate the covariance, error models associated with tracking data measurements must be accurately tuned. Over estimating or under estimating these error values can have detrimental effects on the overall filter performance. The filter incorporates ground station measurements, which can be tuned based on the accuracy of the individual ground stations. It also includes measurements from the NASA space network (SN), which can be affected by the assumed accuracy of the TDRS satellite state at the time of the measurement.The force modelling in the EKF is also an important factor that affects the propagation accuracy and covariance sizing. The dominant force in the LEO orbit regime is the drag force caused by atmospheric drag. Accurate accounting of the drag force is especially important for the accuracy of the propagated state. The implementation of a box and wing model to improve drag estimation accuracy, and its overall effect on the covariance state is explored.The process of tuning the EKF for Aqua and Aura support is described, including examination of the measurement errors of available observation types (Doppler and range), and methods of dealing with potentially volatile atmospheric drag modeling. Predictive accuracy and the distribution of the Chi-square statistic, calculated based of the ODTK EKF solutions, are assessed versus accepted norms for the orbit regime.

Covariance Analysis↗
DOE OSTI2015

Totarol prevents neuronal injury in vitro and ameliorates brain ischemic stroke: Potential roles of Akt activation and HO-1 induction

The natural product totarol, a phenolic diterpenoid and a major constituent isolated from the sap of Podocarpus totara, has been reported to have a potent antimicrobial activity. In this study, we determined whether totarol possessed an additional neuroprotective activity in vitro and in vivo. We found that totarol prevented glutamate- and oxygen and glucose deprivation-induced neuronal death in primary rat cerebellar granule neuronal cells and cerebral cortical neurons. Totarol increased Akt and GSK-3β phosphorylation, Nrf2 and heme oxygenase-1 (HO-1) protein expressions and suppressed oxidative stress by increasing GSH and SOD activities. The PI3K/Akt inhibitor LY294002 prevented totarol neuroprotective effect by suppressing the totarol-induced changes in HO-1 expression and the activities of GSH and SOD. The HO-1 inhibitor ZnPPIX also prevented totarol-increased GSH and SOD activities. In a model of acute cerebral ischemic injury in Sprague–Dawley rats, produced by occlusion of the middle cerebral artery for 2 h followed by 22 h or 46 h of reperfusion, totarol significantly reduced infarct volume and improved the neurological deficit. In this model, totarol increased HO-1 expression and the activities of GSH and SOD. These observations suggest that totarol may be a novel activator of the Akt/HO-1 pathway protecting against ischemic stroke through reduction of oxidative stress. - Graphical abstract: It is unknown whether the natural product totarol has neuroprotective effects in vitro and in vivo. This study underscores that totarol prevents neuronal injury in vitro, not only by activating PI3K/Akt pathway, but also via induction of Nrf2, HO-1, GSH and SOD expressions. Totarol also ameliorated acute cerebral ischemic injury in a rat ischemic stroke model. The findings highlight that totarol may be exploited for protecting against ischemic stroke through Akt/HO-1 pathway. - Highlights: • Totarol protects glutamate- and OGD-induced neuronal injury in vitro. • Totarol activates PI3K/Akt pathway in neurons. • Totarol induces HO-1, GSH and SOD expression in vitro and in vivo. • Totarol exhibits neuroprotective effects in rat brain ischemic stroke model.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

Synthesis, crystal structure and electrical proprieties of new phosphate KCoP{sub 3}O{sub 9}

Crystals of new tricyclophosphate KCoP{sub 3}O{sub 9} have been grown from solid state reaction and characterized by single crystal X-ray diffraction. KCoP{sub 3}O{sub 9} crystallizes in the hexagonal system, space group P6{sup ¯}c2, with a=6.616 (7) Å; c=9.788 (3) Å; V=371.06 (13) Å{sup 3}, Z=2. The final agreement factors are R=0.014, ωR=0.038, S(F{sup 2})=1.231. The structure of the title compound can be described as a three-dimensional framework built up of corner sharing CoO{sub 6} and PO{sub 4} polyhedra containing wide tunnels oriented along [001] direction and others, less broad, along [100] and [010] directions. The structural model was validated by bond valence sum (BVS) and charge distribution (CD) methods. Ball milling was used to reduce the particles sizes of the synthesized powder. At the optimal sintering temperature of 800 °C, a relative density of 85% was obtained. The microstructure was characterized by scanning electron microscopy. The electrical conductivity was 8.4×10{sup −7} S cm{sup −1} and 1.7×10{sup −4} S cm{sup −1} at 480 °C and 680 °C respectively. The activation energy deduced from the slope is 2.2 eV at low temperature region and 1.2 eV at high temperature region. The BVS model is extended to simulate the ionic migration pathways of alkali cations in the anionic framework. The BVS calculation shows one-dimensional pathways migration along c-axis. - Graphical abstract: 1D pathways link K atoms along c-axis with bond valence mismatch |ΔV(K)|=0.8 v.u. - Highlights: • A new single crystal KCoP{sub 3}O{sub 9} was grown by solid state reaction and its structure determined by single-crystal X-ray diffraction. • The purity polycrystalline of KCoP{sub 3}O{sub 9} sample was verified by Rietveld refinement. • The CIS measurements were optimized and the obtained spectra were fitted by electrical equivalent circuits. • The conduction pathways for the K{sup +} cations are simulated by means of the bond valence sum model.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

SU-D-9A-03: STAMP: Simulator for Texture Analysis in MRI/PET

Purpose: To develop a convenient simulation platform to facilitate PET/MR image analysis with the prospect of gaining a better understanding of the influence of acquisition parameters on PET/MRI textural features. The simulation platform is demonstrated by showing textural variations of a representative case study using different image acquisition parameters. Methods: The simulation platform is composed of MRI simulators JEMRIS and SIMRI to achieve simulations of customized MRI sequences on sample tumor models. The PET simulator GATE is used to get 2D and 3D Monte Carlo acquisitions of voxelized PET sources using a phantom geometry and a customized scanner architecture. The platform incorporates a series of graphical user interfaces written in Matlab. Two GUIs are used to facilitate communication with the simulation executables installed on a computer cluster. A third GUI is used to collect and display the clinical and simulated images, as well as fused PET/MRI images, and perform computation of textural features.To illustrate the capabilities of this platform, one FDG-PET and T1-weighted (T1w) digitized tumor models were generated from clinical images of a soft-tissue sarcoma patient. Numerically simulated MR images were produced using 3 different echo times (TE) and 5 different repetition times (TR). PET 2D images were simulated using an OSEM algorithm with 1 to 32 iterations and a post-reconstruction Gaussian filter of 0, 2, 4 or 6 mm width. Results: STAMP was successfully used to produce numerically simulated FDG-PET and MRI images, and to calculate their corresponding textures. Three typical textures (GLCM-Contrast, GLSZM-ZSV and NGTDM-Coarseness) were found to vary by a range of 45% on average compared to reference scanning conditions in the case of FDG-PET, and by a range of 40% in the case of T1w MRI. Conclusion: We have successfully developed a Matlab-based simulation platform to facilitate PET/MRI texture image analysis for outcome prediction.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

On the application of betweenness centrality in chemical network analysis: Computational diagnostics and model reduction

Here, the concept of shortest path and betweenness centrality (BC) is introduced in combustion systems, with its application demonstrated in chemical network analysis and skeletal mechanism generation. After establishing the graphical representation of a chemical network for given pressure, temperature, and species concentrations, a metric BC is defined to rank the shortest paths passed by other nodes between the pair of source and target node, and as such captures the dominant indirect kinetic pathways between any pair of nodes in the network for computational diagnostics. As a result, the controlling pathways are retained by collecting the species with larger BC values. Such a notion then indicates that the index of importance of species could then be assigned based on their BC values to further guide skeletal mechanism generation. Unlike existing methods, the betweenness centrality approach takes into account of both the fluxes between species and their relative positioning within the chemical network. To demonstrate its potential utility to combustion studies, the approach was applied to the GRI-3.0, LLNL and USC-Mech II mechanisms to identify the important pathways in the chemical network at each local reaction state, and develop skeletal mechanisms from all reaction state samples in auto-ignition and perfectly stirred reactor (PSR) simulations. The performance of the BC ranking is compared to the methods of directed relation graph (DRG), DRG with error propagations (DRGEP) and sensitivity analysis (SA), and is shown to possess sufficient utility in producing skeletal mechanisms with good accuracy and flexibility for the cases studied.

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

Steady-State Calibration of a Diesel Engine in Computational Fluid Dynamics Using a Graphical Processing Unit-Based Chemistry Solver

The prospect of analysis-driven precalibration of a modern diesel engine is extremely valuable in order to significantly reduce hardware investments and accelerate engine designs compliant with stricter fuel economy regulations. Advanced modeling tools, such as CFD, are often used with the goal of streamlining significant portions of the calibration process. The success of the methodology largely relies on the accuracy of analytical predictions, especially engine-out emissions. However, the effectiveness of CFD simulation tools for in-cylinder engine combustion is often compromised by the complexity, accuracy, and computational overhead of detailed chemical kinetics necessary for combustion calculations. The standard approach has been to use skeletal kinetic mechanisms (~50 species), which consume acceptable computational time but with degraded accuracy. In this work, a comprehensive demonstration and validation of the analytical precalibration process is presented for a passenger car diesel engine using CFD simulations and a graphical processing unit (GPU)-based chemical kinetics solver (Zero-RK, developed at Lawrence Livermore National Laboratory, Livermore, CA) on high performance computing resources to enable the use of detailed kinetic mechanisms. Diesel engine combustion computations have been conducted over 600 operating points spanning in-vehicle speed-load map, using massively parallel ensemble simulation sets on the Titan supercomputer located at the Oak Ridge Leadership Computing Facility. The results with different mesh resolutions have been analyzed to compare differences in combustion and emissions (NOx, carbon monoxide CO, unburned hydrocarbons (UHC), and smoke) with actual engine measurements. The results show improved agreement in combustion and NOx predictions with a large n-heptane mechanism consisting of 144 species and 900 reactions with refined mesh resolution; however, agreement in CO, UHC, and smoke remains a challenge.

42 ENGINEERING↗
DOE OSTI2018

Double-buffered, heterogeneous CPU + GPU integral digestion algorithm for single-excitation calculations involving a large number of excited states

The most widely used quantum-chemical models for excited states are single-excitation theories, a category that includes configuration interaction with single substitutions, time-dependent density functional theory, and also a recently developed ab initio exciton model. When a large number of excited states are desired, these calculations incur a significant bottleneck in the “digestion” step in which two-electron integrals are contracted with density or density-like matrices. We present an implementation that moves this step onto graphical processing units (GPUs), and introduce a double-buffer scheme that minimizes latency by computing integrals on the central processing units (CPUs) concurrently with their digestion on the GPUs. An automatic code generation scheme simplifies the implementation of high-performance GPU kernels. For the exciton model, which requires separate excited-state calculations on each electronically coupled chromophore, the heterogeneous implementation described here results in speedups of 2–6× versus a CPU-only implementation. For traditional time-dependent density functional theory calculations, we obtain speedups of up to 5× when a large number of excited states is computed.

97 MATHEMATICS AND COMPUTING↗