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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Tailoring nanopore formation in atomic layer deposited ultrathin films [Nanopore formation in atomic layer deposited ultrathin films]

Selectivity is a critical attribute of catalysts used in manufacturing of essential and fine chemicals. An excellent way to induce selectivity in catalysts is by using ultrathin films with tailored nanoporosity. For instance, nanopores can be created in atomic layer deposition (ALD) ultrathin over-coatings on supported metal nanoparticles by subjecting the coatings to high temperature annealing. These nanopores expose the active surface of the underlying metal nanoparticles. The dimensions of these nanopores can be tuned to impart shape selectivity: only reactants or products with a specific size or shape can fit inside the pore. In this work, the authors explore the underlying mechanism driving nanopore formation in ALD films. Ultrathin films of ALD TiO 2 (similar to 2.5 nm thick) and ALD Al 2 O 3 (similar to 4.9 nm thick) were deposited on nonporous gamma-Al 2 O 3 nanoparticles. The pore formation and evolution were monitored in situ during thermal annealing using small-angle x-ray scattering (SAXS), and the crystallinity was monitored by in situ x-ray diffraction. A correlation between the nanopore formation and amorphous to crystalline phase transitions in the ALD layers was observed. The authors hypothesize that the pores form through the relaxation of stress induced by densification of the ALD films during the phase transitions. In conclusion, the authors developed a mathematical model to evaluate this hypothesis and found remarkable agreement between the model and the SAXS measurements.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Benchmark of numerical modeling approaches on the systematic performance evaluation of wave energy converters

Different numerical modeling methods have been developed and applied to evaluate a variety of performance indicators of wave energy converters (WECs), including the power performance, structural loads, levelized cost of energy, etc. Based on the modeling fidelity, the commonly used numerical modeling approaches can be classified as linear modeling, weakly nonlinear modeling and fully nonlinear modeling approaches. Each method differs in accuracy and computational efficiency, making them suitable for different stages of WEC design. However, the selection of modeling approach could significantly impact evaluation outcomes. For instance, simplified linear models may underestimate structural loads or overestimate energy production in some operational conditions, potentially leading to less cost-effective designs. Given the widespread utilization of these models, it is essential to understand the uncertainties brought by them in performance evaluations. This work is dedicated to benchmarking different linear-potential-flow-based numerical models for evaluating the systematic performance of WECs. Three representative numerical modeling approaches are considered in this work, including linear frequency-domain modeling, statistically linearized spectral-domain modeling and Cummins equation-based nonlinear time-domain modeling. A generic point absorber WEC is considered as the research reference in this work, and different sea sites are taken into account. The numerical models are utilized to predict critical performance indicators, including power performance, the annual energy production, the capacity factor, the levelized cost of energy and the PTO fatigue loads. By comparing the results, this work identifies the uncertainties associated with different modeling approaches in evaluating WEC performance.

Fatigue↗
DOE OSTI2019

A Split DNA Scaffold for a Green Fluorescent Silver Cluster

Silver molecules are chromophores with diverse spectra and rich photophysics, and DNA strands act as ligands that develop specific molecular silver species. For instance, C 4 AC 4 T*C 3 GT 4 selectively yields a Ag 10 6+ fluorophore with λ ex /λ em = 490/550 nm. This single-stranded DNA coordinates and protects the cluster, and its integrity was challenged by breaking the phosphodiester backbone at the innocuous T*. The resulting C 4 AC 4 T and C 3 GT 4 fragments also develop the same Ag 10 6+ fluorophore but only when all three components (two fragments + Ag) are present. This C 4 AC 4 T/C 3 GT 4 /Ag 10 6+ complex is favored by higher DNA concentrations and preferentially forms when hybridization forces C 4 AC 4 T and C 3 GT 4 onto a shared DNA duplex. The C 4 AC 4 T/C 3 GT 4 assembly reverses when the cluster photodegrades, which suggests that the cluster is labile. C 4 AC 4 T forms an alternate cluster at low temperatures, but C 3 GT 4 recovers the λ = 490 nm fluorophore at higher temperatures. Thus, the reciprocal interactions between the host DNA strands and the cluster adduct combine to create a highly specific, split-DNA fluorescent Ag cluster capable of sensing target DNA sequences with high specificity and on–off contrast.

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

Quadrupolar magnetic excitations in an isotropic spin-1 antiferromagnet

The microscopic origins of emergent behaviours in condensed matter systems are encoded in their excitations. In ordinary magnetic materials, single spin-flips give rise to collective dipolar magnetic excitations called magnons. Likewise, multiple spin-flips can give rise to multipolar magnetic excitations in magnetic materials with spin S ≥ 1. Unfortunately, since most experimental probes are governed by dipolar selection rules, collective multipolar excitations have generally remained elusive. For instance, only dipolar magnetic excitations have been observed in isotropic S = 1 Haldane spin systems. Here, we unveil a hidden quadrupolar constituent of the spin dynamics in antiferromagnetic S = 1 Haldane chain material Y 2 BaNiO 5 using Ni L 3 -edge resonant inelastic x-ray scattering. Our results demonstrate that pure quadrupolar magnetic excitations can be probed without direct interactions with dipolar excitations or anisotropic perturbations. Originating from on-site double spin-flip processes, the quadrupolar magnetic excitations in Y 2 BaNiO 5 show a remarkable dual nature of collective dispersion. While one component propagates as non-interacting entities, the other behaves as a bound quadrupolar magnetic wave. This result highlights the rich and largely unexplored physics of higher-order magnetic excitations.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Harnessing the periplasm of bacterial cells to develop biocatalysts for the biosynthesis of highly pure chemicals

ABSTRACT Although biocatalytic transformation has shown great promise in chemical synthesis, there remain significant challenges in controlling high selectivity without the formation of undesirable by-products. For instance, few attempts to construct biocatalysts for de novo synthesis of pure flavin mononucleotide (FMN) have been successful, due to riboflavin (RF) accumulating in the cytoplasm and being secreted with FMN. To address this problem, we show here a novel biosynthesis strategy, compartmentalizing the final FMN biosynthesis step in the periplasm of an engineered Escherichia coli strain. This construct is able to overproduce FMN with high specificity (92.4% of total excreted flavins). Such a biosynthesis approach allows isolation of the final biosynthesis step from the cytoplasm to eliminate undesirable byproducts, providing a new route to develop biocatalysts for the synthesis of highpurity chemicals. IMPORTANCE The periplasm of Gram-negative bacterial hosts is engineered to compartmentalize the final biosynthesis step from the cytoplasm. This strategy is promising for the overproduction of high-value products with high specificity. We demonstrate the successful implementation of this strategy in microbial production of highly pure FMN.

Yang, Yun↗
DOE OSTI2019

Failure Analysis on Multivariate Time-series Data given Uncertain Labels

Machine failure analysis and detection is critical to today’s industrial society. Given a number of failure events on multivariate temporal data, the ability to identify 1) the discriminative patterns prior to the events and 2) the most relevant features to the failure has practical use for early warning and root cause analysis. However, since these patterns are not necessarily adjacent to the onset of failure in time, faulty labels are often with uncertainty, which makes traditional supervised detection methods inapplicable. To address the label uncertainty and learn the complicated correlation in multivariate time series, we design Failure Analysis on Multivariate Time-series Data (MAMT) that jointly selects the most failure-relevant features and time-instances by a novel dynamic and directional label diffusion process. Extensive experiments demonstrate that MAMT is more effective while more efficient than popular baselines.

97 MATHEMATICS AND COMPUTING↗
NASA NTRS2020

A 3D Model to Predict Explicit Morphologies and Volume Fraction of Lack-of-Fusion Pores Generated in Selective Laser Melting Processes

The performance of an additively manufactured (AM) component is dependent on the distribution of process-induced defects in addition to the complex microstructure of the material, surface roughness of the component and the process-induced residual stresses. For instance, it has been well demonstrated that lack-of-fusion (LoF) pores produced in the selective laser melting (SLM) AM process can significantly limit the fatigue performance of the material. Although two-dimensional (2D) models exist to predict the 2D profiles of LoF pores, the 2D pore profiles cannot be directly inserted into a three-dimensional (3D) microstructure domain that is output from several prevailing process simulation packages. A few commercial packages that simulate the SLM process can predict LoF pores in a 3D domain, but the morphologies of LoF pores are voxelated and hence do not capture sharp corners of the pores, thereby obviating their use in fatigue crack initiation studies. In order to address the aforementioned gaps, a high-fidelity model that predicts not only the volume fraction, but also the explicit 3D morphologies and spatial distributions of LoF pores has been developed using a computer aided design-based environment. The model has been partially validated for Ti-6Al-4V alloy by comparing the predictions of the volume fraction of LoF pores predicted by the model with experimental data obtained from the literature. Absolute error in predicted volume fraction of LoF pores varied between 5.16% and 1.87% for energy density values between 13 J/mm3 and 45 J/mm3 where a significant amount (over 3% volume fraction) of LoF porosity was measured. The absolute error was within 1.87% for energy density values greater than 45 J/mm3.

Saikumar R. Yeratapally↗
DOE OSTI2018

Defining Modeling and Analysis Complexity Needs for Remediation - 18425

Many subsurface remedy decisions rely on model predictions or other types of data analyses to support site characterization and remedy selection, design, implementation, performance assessment, and closure. Thus, determining the appropriate level of complexity for modeling and data analysis is important to facilitate subsurface remedy decisions. Multiple factors are important in selecting the appropriate level of complexity in modeling and data analysis. For instance, the type and number of inputs required typically increases with increased complexity of analysis, and the ability to obtain or verify those inputs needs to be considered. The approach needs to establish the relationship between parameters or processes and contaminant transport and the detail of the description needed to meet the analysis objectives. Assessing the modeling complexity associated with the appropriate level of detail can be facilitated by considering complexity of the 1) modeling approach, 2) description of process, and 3) description of heterogeneity. As demonstrated by case studies, using a framework to guide determination of modeling and analysis complexity facilitates selection of the appropriate approach for the site situation. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2025

Post-composing ontology terms for efficient phenotyping in plant breeding

Abstract Ontologies are widely used in databases to standardize data, improving data quality, integration, and ease of comparison. Within ontologies tailored to diverse use cases, post-composing user-defined terms reconciles the demands for standardization on the one hand and flexibility on the other. In many instances of Breedbase, a digital ecosystem for plant breeding designed for genomic selection, the goal is to capture phenotypic data using highly curated and rigorous crop ontologies, while adapting to the specific requirements of plant breeders to record data quickly and efficiently. For example, post-composing enables users to tailor ontology terms to suit specific and granular use cases such as repeated measurements on different plant parts and special sample preparation techniques. To achieve this, we have implemented a post-composing tool based on orthogonal ontologies providing users with the ability to introduce additional levels of phenotyping granularity tailored to unique experimental designs. Post-composed terms are designed to be reused by all breeding programs within a Breedbase instance but are not exported to the crop reference ontologies. Breedbase users can post-compose terms across various categories, such as plant anatomy, treatments, temporal events, and breeding cycles, and, as a result, generate highly specific terms for more accurate phenotyping.

Mathematical & Computational Biology↗
DOE OSTI2017

Kinetic characterization of Vibrio cholerae ApbE: Substrate specificity and regulatory mechanisms

ApbE is a member of a novel family of flavin transferases that incorporates flavin mononucleotide (FMN) to subunits of diverse respiratory complexes, which fulfill important homeostatic functions. In this work a detailed characterization of Vibrio cholerae ApbE physiologic activity, substrate specificity and pH dependency was carried out. The data obtained show novel characteristics of the regulation and function of this family. For instance, our experiments indicate that divalent cations are essential for ApbE function, and that the selectivity depends largely on size and the coordination sphere of the cation. Our data also show that ApbE regulation by pH, ADP and potassium is an important mechanism that enhances the adaptation, survival and colonization of V. cholerae in the small intestine. Moreover, studies of the pH-dependency of the activity show that the reaction is favored under alkaline conditions, with a pKa of 8.4. These studies, together with sequence and structure analysis allowed us to identify His257, which is absolutely conserved in the family, as a candidate for the residue whose deprotonation controls the activity. Remarkably, the mutant H257G abolished the flavin transfer activity, strongly indicating that this residue plays an important role in the catalytic mechanism of ApbE.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2016

SU-F-P-30: Clinical Assessment of Auto Beam-Hold Triggered by Fiducial Localization During Prostate RapidArc Delivery

Purpose: To assess the clinical efficacy of auto beam hold during prostate RapidArc delivery, triggered by fiducial localization on kV imaging with a Varian True Beam. Methods: Prostate patients with four gold fiducials were candidates in this study. Daily setup was accomplished by aligning to fiducials using orthogonal kV imaging. During RapidArc delivery, a kV image was automatically acquired with a momentary beam hold every 60 degrees of gantry rotation. The position of each fiducial was identified by a search algorithm and compared to a predetermined 1.4 cm diameter target area. Treatment continued if all the fiducials were within the target area. If any fiducial was outside the target area the beam hold was not released, and the operators determined if the patient needed re-alignment using the daily setup method. Results: Four patients were initially selected. For three patients, the auto beam hold performed seamlessly. In one instance, the system correctly identified misaligned fiducials, stopped treatment, and the patient was re-positioned. The fourth patient had a prosthetic hip which sometimes blocked the fiducials and caused the fiducial search algorithm to fail. The auto beam hold was disabled for this patient and the therapists manually monitored the fiducial positions during treatment. Average delivery time for a 2-arc fraction was increased by 59 seconds. Phantom studies indicated the dose discrepancy related to multiple beam holds is <0.1%. For a plan with 43 fractions, the additional imaging increased dose by an estimated 68 cGy. Conclusion: Automated intrafraction kV imaging can effectively perform auto beam holds due to patient movement, with the exception of prosthetic hip patients. The additional imaging dose and delivery time are clinically acceptable. It may be a cost-effective alternative to Calypso in RapidArc prostate patient delivery. Further study is warranted to explore its feasibility under various clinical conditions.

60 APPLIED LIFE SCIENCES↗
NASA NTRS1992

The European Southern Observatory-MIDAS table file system

The new and substantially upgraded version of the Table File System in MIDAS is presented as a scientific database system. MIDAS applications for performing database operations on tables are discussed, for instance, the exchange of the data to and from the TFS, the selection of objects, the uncertainty joins across tables, and the graphical representation of data. This upgraded version of the TFS is a full implementation of the binary table extension of the FITS format; in addition, it also supports arrays of strings. Different storage strategies for optimal access of very large data sets are implemented and are addressed in detail. As a simple relational database, the TFS may be used for the management of personal data files. This opens the way to intelligent pipeline processing of large amounts of data. One of the key features of the Table File System is to provide also an extensive set of tools for the analysis of the final results of a reduction process. Column operations using standard and special mathematical functions as well as statistical distributions can be carried out; commands for linear regression and model fitting using nonlinear least square methods and user-defined functions are available. Finally, statistical tests of hypothesis and multivariate methods can also operate on tables.

Peron, M.↗
NASA NTRS2014

Dispersion-Engineered Traveling Wave Kinetic Inductance Parametric Amplifier

A traveling wave kinetic inductance parametric amplifier comprises a superconducting transmission line and a dispersion control element. The transmission line can include periodic variations of its dimension along its length. The superconducting material can include a high normal state resistivity material. In some instances the high normal state resistivity material includes nitrogen and a metal selected from the group consisting of titanium, niobium and vanadium. The traveling wave kinetic inductance parametric amplifier is expected to exhibit a noise temperature below 100 mK/GHz.

Zmuidzinas, Jonas↗
NASA NTRS2001

Resource Selection Using Execution and Queue Wait Time Predictions

We developed techniques to predict application execution times for instance-based learning with an average error of 33% of average run time. We developed techniques to predict queue wait times that included a simulation of scheduling algorithms and execution time predictions. We implemented these techniques for the NAS Origin cluster.

Smith, Warren↗
DOE OSTI2017

A spongy nickel-organic CO 2 reduction photocatalyst for nearly 100% selective CO production

Solar-driven photocatalytic conversion of CO 2 into fuels has attracted a lot of interest; however, developing active catalysts that can selectively convert CO 2 to fuels with desirable reaction products remains a grand challenge. For instance, complete suppression of the competing H 2 evolution during photocatalytic CO 2 -to-CO conversion has not been achieved before. We design and synthesize a spongy nickel-organic heterogeneous photocatalyst via a photochemical route. The catalyst has a crystalline network architecture with a high concentration of defects. It is highly active in converting CO 2 to CO, with a production rate of ~1.6 × 10 4 μmol hour –1 g –1 . No measurable H 2 is generated during the reaction, leading to nearly 100% selective CO production over H 2 evolution. When the spongy Ni-organic catalyst is enriched with Rh or Ag nanocrystals, the controlled photocatalytic CO 2 reduction reactions generate formic acid and acetic acid. As a result, achieving such a spongy nickel-organic photocatalyst is a critical step toward practical production of high-value multicarbon fuels using solar energy.

36 MATERIALS SCIENCE↗
NASA NTRSDate not supplied

Use of Assistive Technology to Augment API Capabilities

Application Programming Interfaces (APIs) allow for access to data and capabilities of computer applications by developers or users with experience in computer programming. Recent development with both Thermal Desktop and ESATAN-TMS have provided APIs to allow users to develop their own capabilities that interface with the Graphical User Interfaces (GUI) or manipulate the thermal model data. However, these APIs are only as good as the breadth of features in the native code accessible through the API. If a particular code’s feature is not accessible through the API, then users have very limited options besides waiting for updates to the API that expose the necessary functionality, particularly if model data access or user action, such as a button click, is required. However, Assistive Technology features that allow for users with a disability to more fully experience a software’s capabilities may be creatively utilized to gain further access to data and capabilities not yet exposed by the API. This paper describes the process to augment the features of the OpenTD API via assistive technology and describes how to identify the application instance, navigate GUI elements, updates values on forms, and execute actions such as selecting a listbox item or clicking a button. It concludes with identifying some of the pitfalls to avoid and describes methods to best implement this approach.

Application Programming Interface↗
NASA NTRSDate not supplied

Use of Assistive Technology to Augment API Capabilities

Application Programming Interfaces (APIs) allow for access to data and capabilities of computer applications by developers or users with experience in computer programming. Recent development with both Thermal Desktop and ESATAN-TMS have provided APIs to allow users to develop their own capabilities that interface with the Graphical User Interfaces (GUI) or manipulate the thermal model data. However, these APIs are only as good as the breadth of features in the native code accessible through the API; if a particular code’s feature is not accessible through the API, then users have very limited options besides waiting for updates to the API that expose the necessary functionality, particularly if model data access or user action, such as a button click, is required. However, Assistive Technology features that allow for differently-abled users to more fully experience a software’s capabilities may be creatively utilized to gain further access to data and capabilities not yet exposed by the API. This paper describes the process to augment the features of the OpenTD API via assistive technology and describes how to identify the application instance, navigate GUI elements, updates values on forms, and execute actions such as selecting a listbox item or clicking a button. It concludes with identifying some of the pitfalls to avoid and describes methods to best implement this approach.

Application Programming Interface↗