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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 1,729 records · Page 96
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Microstructural, mechanical and electrochemical behaviour of a 7017 Al–Zn–Mg alloy of different tempers

The aim of the investigation is to assess the microstructural features and associated physical, mechanical and electrochemical properties of a 7017 Al–Zn–Mg alloy of various tempers. A 7017 Al–Zn–Mg alloy was subjected to different ageing schedules to produce under-(T4), peak-(T6), over-(T7) and highly over-aged tempers. Optical microscopy, hardness measurement, electrical conductivity measurement, tensile testing and SEM fractographs, differential scanning calorimetry (DSC), transmission electron microscopy (TEM), and electrochemical polarization studies have been used to characterize the alloy tempers. Hardness measurement and tensile testing showed the characteristic age hardening phenomenon of aluminium alloys. Optical and TEM micrographs have revealed the variation in size of matrix strengthening η′ (MgZn{sub 2}) and also the size and distribution of grain boundary η (MgZn{sub 2}) precipitate with ageing time. DSC thermograms exhibiting exothermic and endothermic peaks indicated the characteristic solid state reaction sequence of the 7017 alloy. Potentiodynamic polarization study of the 7017 alloy of various tempers in 3.5 wt.% NaCl solution at near neutral pH showed typical active metal dissolution behaviour, but at pH 12 an active–passive–transpassive transition behaviour has been observed. - Graphical abstract: TEM micrograph of the 7017 aluminium alloy of various tempers (a, b) under aged (T4), (c, d) peak aged (T6), (e, f) over aged (T7) and (g, h) highly over-aged. Display Omitted - Highlights: • 7017 Al-Zn-Mg alloy was subjected to different artificial ageing treatments. • Characterization of 7017 alloy tempers by hardness, tensile, DSC, TEM and electrochemical behaviour. • Structure-properties relationship of the 7017 Al-Zn-Mg alloy of various tempers.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

An ALMA Survey of Submillimeter Galaxies in the Extended Chandra Deep Field South: Spectroscopic Redshifts

We present spectroscopic redshifts of S{sub 870μm} ≳2 mJy submillimeter galaxies (SMGs), which have been identified from the ALMA follow-up observations of 870 μm detected sources in the Extended Chandra Deep Field South (the ALMA-LESS survey). We derive spectroscopic redshifts for 52 SMGs, with a median of z = 2.4 ± 0.1. However, the distribution features a high-redshift tail, with ∼23% of the SMGs at z⩾3. Spectral diagnostics suggest that the SMGs are young starbursts, and the velocity offsets between the nebular emission and UV ISM absorption lines suggest that many are driving winds, with velocity offsets of up to 2000 km s{sup −1}. Using the spectroscopic redshifts and the extensive UV-to-radio photometry in this field, we produce optimized spectral energy distributions (SEDs) using Magphys, and use the SEDs to infer a median stellar mass of M{sub ⋆} = (6 ± 1)× 10{sup 10} M {sub ⊙} for our SMGs with spectroscopic redshift. By combining these stellar masses with the star formation rates (measured from the far-infrared SEDs), we show that SMGs (on average) lie a factor of ∼5 above the so-called “main sequence” at z∼2. We provide this library of 52 template fits with robust and uniquely well-sampled SEDs as a resource for future studies of SMGs, and also release the spectroscopic catalog of ∼2000 (mostly infrared-selected) galaxies targeted as part of the spectroscopic campaign.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRSDate not supplied

Nonlinear Buckling Analysis of Tow-Steered Composite Cylinders with Cutouts

The buckling and postbuckling behavior of two composite tow-steered shells with cutouts of different sizes is assessed using nonlinear finite element (FE) analysis and compared to experimental measurements. The cylindrical shells are manufactured using an automated fiber placement system, where the shells’ fiber orientation angles vary continuously around the shell circumference from ±10 degrees on the crown and keel to ±45 degrees on the sides. One shell features thickness variations due to tow overlaps that result from application of all 24 tows during each pass of the fiber placement system. The second shell uses the system’s tow drop/add capability to achieve a more uniform wall thickness without overlaps. Unreinforced cutouts of two different sizes—the first smaller cutout representing a passenger door on a commercial aircraft and the second larger cutout a cargo door—were machined into each of the two cylinders resulting in a total of four test cases. These cylinders were tested in axial compression and buckled elastically in previous work and are now analyzed using nonlinear FE models to compare bifurcation buckling loads as well as the load-displacement response in the prebuckling and postbuckling regimes. For all four shells analyzed, the prebuckling stiffness, buckling load, and deformation mode sequence throughout the loading-unloading cycle is accurately reproduced by the models. In particular, the shells first buckle locally around the cutouts in a stable (super-critical) manner with only a slight decrease in axial stiffness, which occurs due to the favorable load redistribution facilitated by tow steering. The shells then buckle globally in an unstable (sub-critical) manner with diamond-shaped buckles forming to the left and right of the cutouts. The buckling load of all shells with cutouts is at least 82% of the buckling load of the pristine shells without cutouts. Overall, the ability to sustain local buckling phenomena, and the relatively small reductions in global buckling load compared to pristine shells without cutouts, demonstrates the great potential of using tow steering to mitigate the adverse effects of cutouts in axially-compressed shell structures.

composites↗
NASA NTRSDate not supplied

Nonlinear Buckling Analysis of Tow-Steered Composite Cylinders with Cutouts

The buckling and postbuckling behavior of two composite tow-steered shells with cutouts of different sizes is assessed using nonlinear finite element (FE) analysis and compared to experimental measurements. The cylindrical shells are manufactured using an automated fiber placement system, where the shells’ fiber orientation angles vary continuously around the shell circumference from 10 degrees on the crown and keel to 45 degrees on the sides. One shell features thickness variations due to tow overlaps that result from application of all 24 tows during each pass of the fiber placement system. The second shell uses the system’s tow drop/add capability to achieve a more uniform wall thickness without overlaps. Unreinforced cutouts of two different sizes—the first smaller cutout representing a passenger door on a commercial aircraft and the second larger cutout a cargo door—were machined into each of the two cylinders resulting in a total of four test cases. These cylinders were tested in axial compression and buckled elastically in previous work and are now analyzed using nonlinear FE models to compare bifurcation buckling loads as well as the load-displacement response in the prebuckling and postbuckling regimes. For all four shells analyzed, the prebuckling stiffness, buckling load, and deformation mode sequence throughout the loading-unloading cycle is accurately reproduced by the models. In particular, the shells first buckle locally around the cutouts in a stable (super-critical) manner with only a slight decrease in axial stiffness, which occurs due to the favorable load redistribution facilitated by tow steering. The shells then buckle globally in an unstable (sub-critical) manner with diamond-shaped buckles forming to the left and right of the cutouts. The buckling load of all shells with cutouts is at least 82% of the buckling load of the pristine shells without cutouts. Overall, the ability to sustain local buckling phenomena, and the relatively small reductions in global buckling load compared to pristine shells without cutouts, demonstrates the great potential of using tow steering to mitigate the adverse effects of cutouts in axially-compressed shell structures.

Buckling↗
DOE OSTI2016

Structural Features Essential to the Antimicrobial Functions of Human SPLUNC1

SPLUNC1 is an abundantly secreted innate immune protein in the mammalian respiratory tract that exerts bacteriostatic and antibiofilm effects, binds to lipopolysaccharide (LPS), and acts as a fluid-spreading surfactant. Here, we unravel the structural elements essential for the surfactant and antimicrobial functions of human SPLUNC1 (short palate lung nasal epithelial clone 1). A unique α-helix (α4) that extends from the body of SPLUNC1 is required for the bacteriostatic, surfactant, and LPS binding activities of this protein. Indeed, we find that mutation of just four leucine residues within this helical motif to alanine is sufficient to significantly inhibit the fluid spreading abilities of SPLUNC1, as well as its bacteriostatic actions against Gram-negative pathogens Burkholderia cenocepacia and Pseudomonas aeruginosa. Conformational flexibility in the body of SPLUNC1 is also involved in the bacteriostatic, surfactant, and LPS binding functions of the protein as revealed by disulfide mutants introduced into SPLUNC1. In addition, SPLUNC1 exerts antibiofilm effects against Gram-negative bacteria, although α4 is not involved in this activity. Interestingly, though, the introduction of surface electrostatic mutations away from α4 based on the unique dolphin SPLUNC1 sequence, and confirmed by crystal structure, is shown to impart antibiofilm activity against Staphylococcus aureus, the first SPLUNC1-dependent effect against a Gram-positive bacterium reported to date. Altogether, these data pinpoint SPLUNC1 structural motifs required for the antimicrobial and surfactant actions of this protective human protein.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

S2M: A Stochastic Simulation Model of Poliovirus Genetic State Transition

Modeling the molecular mechanisms that govern genetic variation can be useful in understanding the dynamics that drive genetic state transition in quasispecies viruses. For example, there is considerable interest in understanding how the relatively benign vaccine strains of poliovirus eventually revert to forms that confer neurovirulence and cause disease (ie, vaccine-derived poliovirus). This report describes a stochastic simulation model, S2M, which can be used to generate hypothetical outcomes based on known mechanisms of genetic diversity. S2M begins with predefined genotypes based on the Sabin-1 and Mahoney wild-type sequences, constructs a set of independent cell-based populations, and performs in-cell replication and cell-to-cell infection cycles while quantifying genetic changes that track the transition from Sabin-1 toward Mahoney. Realism is incorporated into the model by assigning defaults for variables that constrain mechanisms of genetic variability based roughly on metrics reported in the literature, yet these values can be modified at the command line in order to generate hypothetical outcomes driven by these parameters. To demonstrate the utility of S2M, simulations were performed to examine the effects of the rates of replication error and recombination and the presence or absence of defective interfering particles, upon reaching the end states of Mahoney resemblance (semblance of a vaccine-derived state), neurovirulence, genome fitness, and cloud diversity. Simulations provide insight into how modeled biological features may drive hypothetical outcomes, independently or in combination, in ways that are not always intuitively obvious.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Frequent Fulcrum Functions: The Basics of SCALE’s Graphical User Interface [Slides]

This tutorial introduces the Fulcrum graphical user interface and the basic functions that enhance the common activities of creating, editing, navigating, executing, and visualizing SCALE input files. This tutorial will help you become familiar with the Fulcrum input file text editor and the integrated input development environment features of autocompletion, automatic checking, cursor context, and input navigation. In addition, the Fulcrum and SCALE runtime environment will be reviewed to improve the understanding of job execution workflow. This tutorial does not cover data and geometry plotting. Please see the Advanced User Interface Capabilities tutorial for details regarding plotting data and geometry. No prior experience with SCALE is required. You can follow along using SCALE 6.2 or 6.3-beta.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

INTERFEROMETRY OF ϵ AURIGAE: CHARACTERIZATION OF THE ASYMMETRIC ECLIPSING DISK

We report on a total of 106 nights of optical interferometric observations of the ϵ Aurigae system taken during the last 14 years by four beam combiners at three different interferometric facilities. This long sequence of data provides an ideal assessment of the system prior to, during, and after the recent 2009–2011 eclipse. We have reconstructed model-independent images from the 10 in-eclipse epochs which show that a disk-like object is indeed responsible for the eclipse. Using new three-dimensional, time-dependent modeling software, we derive the properties of the F-star (diameter, limb darkening), determine previously unknown orbital elements (Ω, i), and access the global structures of the optically thick portion of the eclipsing disk using both geometric models and approximations of astrophysically relevant density distributions. These models may be useful in future hydrodynamical modeling of the system. Finally, we address several outstanding research questions including mid-eclipse brightening, possible shrinking of the F-type primary, and any warps or sub-features within the disk.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Genetics and Genomics of Pathogen Resistance in Switchgrass (Final Report)

This project was funded by DOE under Grant no. DE-SC0016108. Originally approved for the 2016-2019 period, two no-cost extensions were solicited and approved, which prolonged the lifespan through July 2021. This final report informs on the results obtained so far from the research implemented. The research hinged on integrating genomics (genomic selection, RNAseq, virus-plant interactions) with classical genetics (conventional breeding) to incorporate durable resistance to fungal (rust) and viral (mosaic) diseases in switchgrass (Panicum virgatum) populations being bred for bioenergy. Higher biomass yield, higher quality (low lignin content), and durable disease resistance are key features to make lignocellulosic switchgrass feedstocks economically competitive and sustainable. Genomic selection is being applied on three generations of a switchgrass population derived from crossing two ecotypes (Kanlow as lowland female and Summer as upland male) with differential performance in terms of biomass yield and quality, disease resistance, and winter survivability. Target populations were screened for rust and mosaic in field and/or lab and phenotyped for biomass yield and quality traits. Genetic analyses were applied across generations to capture the joint inheritance of the targeted traits and predict breeding values for parents and progeny with greater accuracy. Parental and a panel of different switchgrass populations were genotyped with the DArTseq technology to develop SNP (0, 1, 2) and in-silico (presence/absence) DArT markers. Rust inoculations techniques were developed and applied successfully on switchgrass. The original populations (Kanlow and Summer) were sequenced with RNAseq to capture the gene expression profiles across sequential time-points and appraise the basis of greater resistance in the Kanlow vs the Summer ecotype. Constructs of PMV and sPMV mosaic virus were assembled and tested first on proso millet to find the best protocol to use later on switchgrass. Results from the preliminary analyses indicate that 1) ample additive genetic variation is available for selection and improving this inter-ecotypic population for yield, quality, and disease traits, 2) significant gains are to be expected with the genetic correlations being favorable between yield and lignin content and between yield and disease ratings, 3) substantial differences exist in the genetic regions controlling rust resistance in the two ecotypes, 4) co-infection with PMV isolates from Nebraska and its satellite from Kansas elicit severe mosaic symptoms, and 5) two different genetic systems are responsible for imparting resistance to rust and virus in switchgrass.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1974

Apollo 17 Index: 70 mm, 35 mm, and 16 mm Photographs

This index lists and provides supplemental data for all Apollo 17 70 mm, 35 mm, and 16 mm photographs. The 70 mm and 35 mm photographs are indexed in three ways: (1) all photographs are listed in numerical sequence according to NASA photograph number, (2) photographs exposed in lunar orbit are listed according to longitude in 10deg increments, and (3) all photographs exposed on the lunar surface are listed in chronological order. In indexing the 70 mm and 35 mm orbital photographs, individual frames were matched to imagery on the 1:2,750,000 scale Lunar Planning Charts (LOC). Each frame was outlined on the LOC base map, and the principal point determined. The latitude and longitude of each principal point, to the nearest 0.1 degree, is recorded in this index, If the principal point of a photograph is in space or its location obscured by shadow, an approximate longitude was recorded so that the photograph would not be excluded from the computer-generated listing by longitude. Each frame is described in terms of a named lunar surface feature within the boundaries of the frame or, if no named features are within the frame boundaries, a major nearby feature.

Wells, Ronald A.↗
DOE OSTI2026

Dissipation Enables Strongly Detuning-Dependent Interference in Pulsed Dynamical Decoupling

One of the defining features of pulsed dynamical decoupling is its suppression of a driven qubit's sensitivity to static detuning errors between the drive field and qubit resonance. In this paper, we show that dissipation, in the form of excited-state decay, can change this behavior entirely, producing an interference signal with a strong detuning dependence. This signal arises from decay during driven evolution and relies on coherence retained by the qubit after such a decay event. We develop analytical and numerical models that capture the underlying mechanism and observe this same dissipation-induced detuning dependence experimentally in both a free-space strontium atom interferometer and a superconducting transmon qubit system. We also use this dissipation-induced detuning dependence as the basis for a new spectroscopic technique called Dissipative Carr-Purcell Spectroscopy (DCPS) and compare it with a traditional Ramsey sequence. Our results establish a regime of pulsed dynamical decoupling in which dissipation reshapes, rather than merely degrades, coherent control, and we expect these dynamics to be relevant to a wide range of quantum systems.

DeRose, Kenneth [Northwestern U.; Fermilab] (ORCID↗
NASA NTRS1990

On domains of convergence in optimization problems

Numerical optimization algorithms require the knowledge of an initial set of design variables. Starting from an initial design x(sup 0), improved solutions are obtained by updating the design iteratively in a way prescribed by the particular algorithm used. If the algorithm is successful, convergence is achieved to a local optimal solution. Let A denote the iterative procedure that characterizes a typical optimization algorithm, applied to the problem: Find x belonging to R(sup n) that maximizes f(x) subject to x belonging to Omega contained in R(sup n). We are interested in problems with several local maxima (x(sub j))(sup *), j=1, ..., m, in the feasible design space Omega. In general, convergence of the algorithm A to a specific solution (x(sub j))(sup *) is determined by the choice of initial design x(sup 0). The domain of convergence D(sub j) of A associated with a local maximum (x(sub j))(sup *) is a subset of initial designs x(sup 0) in Omega such that the sequence (x(sup k)), k=0,1,2,... defined by x(sup k+1) = A(x(sup k)), k=0,1,... converges to (x(sub j))(sup *). The set D(sub j) is also called the basin of attraction of (x(sub j))(sup *). Cayley first proposed the problem of finding the basin of attraction for Newton's method in 1897. It has been shown that the basin of attraction for Newton's method exhibits chaotic behavior in problems with polynomial objective. This implies that there may be regions in the feasible design space where arbitrarily close starting points will converge to different local optimal solutions. Furthermore, the boundaries of the domains of convergence may have a very complex, even fractal structure. In this paper we show that even simple structural optimization problems solved using standard gradient based (first order) algorithms exhibit similar features.

Diaz, Alejandro R.↗
NASA NTRS2013

Advanced Strategic and Tactical Relay Request Management for the Mars Relay Operations Service

This software provides a new set of capabilities for the Mars Relay Operations Service (MaROS) in support of Strategic and Tactical relay, including a highly interactive relay request Web user interface, mission control over relay planning time periods, and mission management of allowed strategic vs. tactical request parameters. Together, these new capabilities expand the scope of the system to include all elements critical for Tactical relay operations. Planning of replay activities spans a time period that is split into two distinct phases. The first phase is called Strategic, which begins at the time that relay opportunities are identified, and concludes at the point that the orbiter generates the flight sequences for on board execution. Any relay request changes from this point on are called Tactical. Tactical requests, otherwise called Orbit - er Relay State Changes (ORSC), are highly restricted in terms of what types of changes can be made, and the types of parameters that can be changed may differ from one orbiter to the next. For example, one orbiter may be able to delay the start of a relay request, while another may not. The legacy approach to ORSC management involves exchanges of e-mail with "requests for change" and "acknowledgement of approval," with no other tracking of changes outside of e-mail folders. MaROS Phases 1 and 2 provided the infrastructure for strategic relay for all supported missions. This new version, 3.0, introduces several capabilities that fully expand the scope of the system to include tactical relay. One new feature allows orbiter users to manage and "lock" Planning Periods, which allows the orbiter team to formalize the changeover from Strategic to Tactical operations. Another major feature allows users to interactively submit tactical request changes via a Web user interface. A third new feature allows orbiter missions to specify allowed tactical updates, which are automatically incorporated into the tactical change process. This software update is significant in that it provides the only centralized service for tactical request management available for relay missions.

Allard, Daniel A.↗
DOE OSTI2024

Automating the Analysis of Large Language Models Responses through Zero-Shot Question Answering

Recent advancements in Large Language Models (LLMs) have shown significant potential in various applications, yet their evaluation, particularly in zero-shot question answering scenarios, remains a challenging task. In this study, our objective was to explore precision metrics for Large Language Models (LLM) and design and implement a software pipeline to automatically evaluate LLMs' outputs under zero-shot question answering. Zero-shot question answering involves a model providing answers to questions about topics it hasn't seen during training. It leverages the principles of zero-shot learning by relying on semantic understanding and generalization from related knowledge. The data used was metadata from medical databases on congenital heart disease. We explored eleven LLM metrics and selected three for our evaluation: BLEU, BERTScore, and MoverScore. BLEU calculates a score based on the overlap of n-grams (contiguous sequences of n items, typically words) between the machine-generated translation and the reference translations. Higher BLEU scores indicate better correspondence between the machine-generated and human-generated translations. BERTScore is a metric used to evaluate the quality of machine-generated text by measuring the similarity of token embeddings produced by BERT (Bidirectional Encoder Representations from Transformers) between the generated text and reference text. MoverScore is a metric that quantifies the dissimilarity between the distributions of word embeddings from machine-generated text and reference text, emphasizing semantic similarity over exact token overlap. We also introduced HBKI, a composite metric summarizing these approaches. We tested five models —GPT-3, Llama-2, Gemini 1.5 Pro, Solar 10.7B, and Mixtral-8x7b. Our software pipeline, designed and implemented using Object-Oriented Programming principles, allows users to customize the selection and extraction of features for topics of interest in their own research. Our results show that MoverScore delivered the most precise evaluation of the LLM's outputs, while Mixtral-8x7b achieved the best overall performance in extracting metadata from the databases.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2017

Log-normal Star Formation Histories in Simulated and Observed Galaxies

Gladders et al. have recently suggested that the star formation histories (SFHs) of individual galaxies are characterized by a log-normal function in time, implying a slow decline rather than rapid quenching. We test their conjecture on theoretical SFHs from the cosmological simulation Illustris and on observationally inferred SFHs. While the log-normal form necessarily ignores short-lived features such as starbursts, it fits the overall shape of the majority of SFHs very well. In particular, 85% of the cumulative SFHs are fitted to within a maximum error of 5% of the total stellar mass formed, and 99% to within 10%. The log-normal performs systematically better than the commonly used delayed-τ model, and is superseded only by functions with more than three free parameters. Poor fits are mostly found in galaxies that were rapidly quenched after becoming satellites. We explore the log-normal parameter space of normalization, peak time, and full width at half maximum, and find that the simulated and observed samples occupy similar regions, though Illustris predicts wider, later-forming SFHs on average. The ensemble of log-normal fits correctly reproduces complex metrics such as the evolution of Illustris galaxies across the star formation main sequence, but overpredicts their quenching timescales. SFHs in Illustris are a diverse population not determined by any one physical property of galaxies, but follow a tight relation, where width ∝ (peaktime){sup 3/2}. We show that such a relation can be explained qualitatively (though not quantitatively) by a close connection between the growth of dark matter halos and their galaxies.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Insights into the Ecological Diversification of the Hymenochaetales based on Comparative Genomics and Phylogenomics With an Emphasis on Coltricia

To elucidate the genomic traits of ecological diversification in the Hymenochaetales, we sequenced 15 new genomes, with attention to ectomycorrhizal (EcM) Coltricia species. Together with published data, 32 genomes, including 31 Hymenochaetales and one outgroup, were comparatively analyzed in total. Compared with those of parasitic and saprophytic members, EcM species have significantly reduced number of plant cell wall degrading enzyme genes, and expanded transposable elements, genome sizes, small secreted proteins, and secreted proteases. EcM species still retain some of secreted carbohydrate-active enzymes (CAZymes) and have lost the key secreted CAZymes to degrade lignin and cellulose, while possess a strong capacity to degrade a microbial cell wall containing chitin and peptidoglycan. There were no significant differences in secreted CAZymes between fungi growing on gymnosperms and angiosperms, suggesting that the secreted CAZymes in the Hymenochaetales evolved before differentiation of host trees into gymnosperms and angiosperms. Nevertheless, parasitic and saprophytic species of the Hymenochaetales are very similar in many genome features, which reflect their close phylogenetic relationships both being white rot fungi. Phylogenomic and molecular clock analyses showed that the EcM genus Coltricia formed a clade located at the base of the Hymenochaetaceae and divergence time later than saprophytic species. And Coltricia remains one to two genes of AA2 family. These indicate that the ancestors of Coltricia appear to have originated from saprophytic ancestor with the ability to cause a white rot. This study provides new genomic data for EcM species and insights into the ecological diversification within the Hymenochaetales based on comparative genomics and phylogenomics analyses.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS2008

Object Recognition using Feature- and Color-Based Methods

An improved adaptive method of processing image data in an artificial neural network has been developed to enable automated, real-time recognition of possibly moving objects under changing (including suddenly changing) conditions of illumination and perspective. The method involves a combination of two prior object-recognition methods one based on adaptive detection of shape features and one based on adaptive color segmentation to enable recognition in situations in which either prior method by itself may be inadequate. The chosen prior feature-based method is known as adaptive principal-component analysis (APCA); the chosen prior color-based method is known as adaptive color segmentation (ACOSE). These methods are made to interact with each other in a closed-loop system to obtain an optimal solution of the object-recognition problem in a dynamic environment. One of the results of the interaction is to increase, beyond what would otherwise be possible, the accuracy of the determination of a region of interest (containing an object that one seeks to recognize) within an image. Another result is to provide a minimized adaptive step that can be used to update the results obtained by the two component methods when changes of color and apparent shape occur. The net effect is to enable the neural network to update its recognition output and improve its recognition capability via an adaptive learning sequence. In principle, the improved method could readily be implemented in integrated circuitry to make a compact, low-power, real-time object-recognition system. It has been proposed to demonstrate the feasibility of such a system by integrating a 256-by-256 active-pixel sensor with APCA, ACOSE, and neural processing circuitry on a single chip. It has been estimated that such a system on a chip would have a volume no larger than a few cubic centimeters, could operate at a rate as high as 1,000 frames per second, and would consume in the order of milliwatts of power.

Duong, Tuan↗
DOE OSTI2023

Machine learning-based inversion for acoustic impedance with large synthetic training data: Workflow and data characterization

Where wells are sparse or training data are difficult to label with high-quality wireline-derived impedance logs, machine learning (ML)-based inversion of acoustic impedance typically depends on small training data sets, leading to biased prediction. We have advanced a novel workflow that applies large synthetic seismic training data to reduce facies-related bias. Using a geologically realistic model as the truth model, we randomly select sparse seed wells to perform sequential Gaussian simulation (SGS) for impedance models of the same geometry and simulate facies variability. We implement random forest regression on 30 features extracted from the synthetic volume. We observe that more seed wells tend to reduce facies-induced bias by sampling more types of facies, resulting in a better prediction. We then focus on the responses of SGS models to facies changes, the number of seed wells necessary for a useful synthetic model, and how much a synthetic model can help ML-based inversion. Here, we observe that the SGS synthetic training model outperforms well-direct training in general. For modeled clastic shore-zone systems in Miocene Gulf of Mexico, two or more seed wells are necessary for a significant reduction of root-mean-square error and outliners, and improvement of facies imaging. In a field-data test, we apply a similar workflow to quantitatively predict acoustic impedance, which is then converted to a sand-volume map at a high-frequency sequence (10–100 m), revealing detailed facies and sandstone patterns. Such results are valuable in many geologic and engineering applications, such as hydrocarbon and CO 2 reservoir prospecting, reserve estimation, simulation, etc.

3D seismic↗