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At least 883 records · Page 49

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DOE OSTI2016

πScope: Python based scientific workbench with MDSplus data visualization tool

In this work, a newly developed python based scientific data analysis and visualization tool, πScope (http://piscope.psfc.mit.edu), is reported. The primary motivation is 1) to provide an updated tool to browse the MDSplus data beyond existing dwscope/jScope and 2) to realize a universal foundation to construct interface tools to perform computer modeling from experimental data. To visualize MDSplus data, πScope has many features including overplotting different signals and discharges, generating various plot types (line, contour, image, etc.), performing in-panel data analysis using python scripts, and producing publication quality graphics. The logic to generate multi-panel plots is designed to be backward compatible with dwscope, enabling smooth migration for users. πScope uses multi-threading in data loading, and is easy to modify and expand due to its object-oriented design. Furthermore, A user can access the data structure both from a GUI and a script, enabling relatively complex data analysis workflow built quickly on πScope.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2019

Photoinduced Carrier Generation and Distribution in Solution-Deposited Titanyl Phthalocyanine Monolayers

We prepared titanyl phthalocyanine (TiOPc) monolayers on sapphire-prism supported Au{111} substrates through solution deposition and characterized their photoresponses using a custom-built laser-assisted scanning tunneling microscope under ambient conditions. Two types of lattice structures (hexagonal and rectangular) were observed, and the distributions of photoinduced charges were measured under evanescently introduced 633 and 780 nm laser illumination. The distributions of photoexcited electrons in molecules in hexagonal lattices match theoretically calculated charge density changes in TiOPc molecules upon excitation. However, the photoresponses of TiOPc molecules in rectangular lattices are different than those predicted and TiOPc molecules in these arrangements may have lower excitation probabilities at 633 and 780 nm. Our results suggest that the photocarrier generation efficiency of TiOPc molecules is related to their packing arrangements in monolayers and local environments. The growth mechanisms of the monolayers and their connections to different polymorphs of TiOPc are worth to be further explored so that the photogenerated electronic property changes that we observed at the molecular level can provide more accurate guidance to the application of TiOPc crystals and assemblies.

36 MATERIALS SCIENCE↗

DOE OSTI2025

Integrating Ultra-Coarse-Grained Protein Models into Accessible Workflows for Multiscale Molecular Dynamics

To capture protein conformational transitions using molecular dynamics (MD), several simulation resolutions covering different spatial and temporal scales are typically needed. All-atom (AA) simulations provide fine resolution, but are computationally infeasible for large systems over longer durations. Coarse-grained (CG) and ultra-coarse-grained (UCG) models have a lower resolution and computational cost while still being able to conserve essential protein features. Prior work on a Multiscale Machinelearned Modeling Infrastructure (MuMMI) combined both AA and CG simulations to study RAS-RAF protein interactions, leveraging CG models for longer time scales and using AA to investigate unusual conformations in greater detail. However, MuMMI is still resource-intensive, and this study aims to maximize exploration of the protein conformational space while reducing computational cost. In this paper, we build on prior work that integrates UCG models based on heterogeneous elastic network modeling (hENM) into the MuMMI workflow. We demonstrate that UCG models enable accurate sampling of protein conformations, focusing on simulating RAS-RAF protein interactions. Using higher-resolution CG Martini simulation data, we can automatically refine intramolecular interactions in UCG models. We present a scalable Python package that uses fluctuations observed in higher-resolution CG Martini simulations to estimate bond coefficients of the UCG model. We built novel machine learning-based backmapping methods to recover more detailed CG Martini structures from UCG structures, using diffusion models to learn the mapping between scales. Finally, we present UCG-mini-MuMMI, an accessible and less compute-intensive version of MuMMI as a resource for the scientific community. Incorporating UCG models into MD studies is applicable to a broad range of systems and proteins, and our study offers insights into the advantages and limitations of these methods.

Chemical structure↗

DOE OSTI2016

MgZnO High Voltage Thin Film Transistors on Glass for Inverters in Building Integrated Photovoltaics

Building integrated photovoltaics (BIPV) have attracted considerable interests because of its aesthetically attractive appearance and overall low cost. In BIPV, system integration on a glass substrate like windows is essential to cover a large area of a building with low cost. But, the conventional high voltage devices in inverters have to be built on the specially selected single crystal substrates, limiting its application for large area electronic systems, such as the BIPV. We demonstrate a Magnesium Zinc Oxide (MZO) based high voltage thin film transistor (HVTFT) built on a transparent glass substrate. We designed devices with unique ring-type structures and use modulated Mg doping in the channel - gate dielectric interface, resulting in a blocking voltage of over 600 V. In addition to BIPV, the MZO HVTFT based inverter technology also creates new opportunities for emerging self-powered smart glass.

14 SOLAR ENERGY↗

DOE OSTI2018

Band alignment and electrocatalytic activity at the p-n La 0.88 Sr 0.12 FeO 3 /SrTiO 3 (001) heterojunction

Ferrites perovskites have exhibited promising p-type conductivity and oxygen evolution reaction (OER) activity. In this work, we investigate heteroepitaxial p-n junctions formed with La 0.88 Sr 0.12 FeO 3 and n-SrTiO 3 (001). Sr substitution for La in LaFeO 3 is shown to be effective for introducing p-type conductivity, lowering the optical bandgap, and enhancing electrocatalytic OER. A staggered, type-II band alignment with a large built-in potential within the LSFO forms due to the polar interface. This electronic structure facilitates charge transfer across the p-n junction and accounts for the strongly thickness-dependent extent of OER we observe.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2023

Regional Economic Impacts of the Los Angeles 100% Renewable Energy Transition

To help mitigate greenhouse gas (GHGs) generation from burning fossil fuels, many state and local governments are requiring utilities to dramatically increase the share of electricity generated from renewable sources. The City of Los Angeles has set a target of 100% renewable energy by 2045 and has formulated a plan that considers nine potential alternative scenarios that differ by technology, location, and timing. Each scenario has a unique set of local investments, operating and maintenance (O&M) costs, and concomitant rate structures. In this study we develop and apply a computable general equilibrium (CGE) model built specifically for LA to estimate and compare the economic impacts for each of the scenarios over time relative to a reference case. We find differences in economic impacts across scenarios, depending on the level and timing of investment and O&M expenditures, as well as differences in the relative rate changes across scenarios. Results show that employment and economic output are positively correlated with greater capital and O&M spending, while higher electricity rates can dampen economic activity. Several scenarios generate positive economic impacts relative to the reference case, showing that the transition need not have harmful economic impacts, and all scenarios generate a number of other positive co-benefits, such as reduced damage to health from the reduction of ordinary air pollutants. The net employment impacts from 2026 to 2045 across the scenarios range from a low of 3,600 job-year losses annually to 4,700 job-year gains, both around only 0.1% of the baseline average annual employment in the city over that period. The analysis also indicates that lower-income households are relatively more affected than others by the scenarios. Overall, even in the most negatively impactful case, the economic output and employment effects are quite small when taken in the context of the overall size of the regional economy and the large reduction in GHGs.

economic impact modeling↗

DOE OSTI2024

Solid-to-plasma transition of polystyrene induced by a nanosecond laser pulse within the context of inertial confinement fusion

Laser Direct Drive (LDD) Inertial Confinement Fusion (ICF) involves irradiating a spherical target of thermonuclear fuel coated with an ablator, usually made of polystyrene. Laser energy absorption near the target surface leads to matter ablation, hydrodynamic shocks, and ultimately capsule implosion. The conservation of spherical symmetry is crucial for implosion efficiency, yet spatial modulations in laser intensity can induce nonuniformities, causing the laser imprint phenomenon. Understanding laser imprint, especially considering the initial solid state, is essential for advancing LDD ICF. A first microscopic model of solid-to-plasma transition was built in 2019, accounting for laser absorption in the solid state with a band structure based ionization model. This model has been improved to include chemical fragmentation and a more accurate description of electron collision frequency in various matter states. The latest development involves assessing the model reliability by comparing theoretical predictions with experimental observations. Despite the success of this approach, questions remain, leading to further investigations and observations under different irradiation conditions. This work presents an experiment with a nanosecond pulse, taking into account hydrodynamic effects, and measures transmission dynamics over the entire laser beam area to observe two-dimensional effects. As a result, the objective is to adapt the theoretical model, couple it with a hydrodynamic code, and observe additional effects related to the initial solid state.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2017

A Laboratory Astrophysical Jet to Study Canonical Flux Tubes

Understanding the interaction between plasma flows and magnetic fields remains a fundamental problem in plasma physics, with important applications to astrophysics, fusion energy, and advanced space propulsion. For example, flows are of primary importance in astrophysical jets even if it is not fully understood how jets become so long without becoming unstable. Theories for the origin of magnetic fields in the cosmos rely on flowing charged fluids that should generate magnetic fields, yet this remains to be demonstrated experimentally. Fusion energy reactors can be made smaller with flows that improve stability and confinement. Advanced space propulsion could be more efficient with collimated and stable plasma flows through magnetic nozzles but must eventually detach from the nozzle. In all these cases, there appears to be a spontaneous emergence of flowing and/or magnetic structures, suggesting a form of self-organization in plasmas. Beyond satisfying simple intellectual curiosity, understanding plasma self-organization could enable the development of methods to control plasma structures for fusion energy, space propulsion, and other applications. The research project has therefore built a theory and an experiment to investigate the interaction between magnetic fields and plasma flows. The theory is called canonical field theory for short, and the experiment is called Mochi after a rice cake filled with surprising, yet delicious fillings.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2018

SNS Resonance Control Cooling Systems and Quadrupole Magnet Cooling Systems DIW Chemistry

This report focuses on control of the water chemistry for the Spallation Neutron Source (SNS) Resonance Control Cooling System (RCCS)/Quadrupole Magnet Cooling System (QMCS) deionized water (DIW) cooling loops. Proper cooling-water chemistry is essential to preserving the DTL and CCL structures during their design lifetime. Appropriate water chemistry will protect cooling-water passages and brazed joints of the structure from erosion, corrosion, and fouling. The RCCS/QMCS DIW chemistry is managed by sidestreams built into the cooling loops; chemicals are not used. Data collected from spring 2013 through spring 2016 are discussed, and an operations regime is recommended. During the evaluation period, the pH, dissolved oxygen, and water resistivity of the cooling water were observed. The data were collected by instruments mounted on mobile chemistry carts, which were moved from one RCCS/QMCS DIW skid to another. During data reading, operational corrections were done on the polishing loops to improve the water chemistry regime. Therefore some trends changed over time. It was found that the RCCS operates with an average pH of 7.24 for all lines (from 7.0 to 7.5, slightly alkaline), the average low dissolved oxygen is in the area of < 36 ppb, and the main loop average resistivity of is > 14 MΩ-cm. The QMCS was found to be operating in a similar regime, with a pH of about 7.5 (slightly alkaline), low dissolved oxygen in the area of < 45 ppb, and main loop resistivity of 10 to 15 MΩ-cm. It is recommended that the cooling loops operate in a regime in which the water has a resistivity that is as high as achievable, a dissolved oxygen concentration that is as low as achievable, and a neutral or slightly alkaline pH. An RCCS/QMCS chemistry guidance document published in May 2017 describes and standardizes the methods and practices for water chemical treatment for the SNS RCCS and QMCS. It is very difficult to accurately measure the pH, dissolved oxygen, and water resistivity in highly pure water. Therefore, a regularly scheduled calibration program will be established for the instruments. Recommendations are given at the end of the report on how to run the RCCS/QMCS cooling water chemistry. Chemical analysis of the material trapped by the polishing loop prefilters is conducted twice a year. The analysis and its benefits are described in Chapter 9.

42 ENGINEERING↗

DOE OSTI2025

Characterization of Build Parameters and Microstructure in Low Heat Input WAAM of Ni-Based Superalloy Haynes 282

Ni-based superalloy Haynes® 282® is being targeted for various applications in advanced power generation systems for its superior fabricability, weldability, and excellent high temperature creep and corrosion performance. This process optimization study aims to use a low heat-input, high deposition rate, controlled Gas Metal Arc Welding (GMAW) process, Cold Metal Transfer (CMT) by Fronius, attempting to achieve fully dense fabrication and possibly avoid the need for HIP. Twenty-one multilayer blocks (~25x100x40 mm3) were deposited to explore a large set of build parameters variations that focused on varying the travel speed from 14 to 42 inches per minute (ipm) and wire feed speed from 150 to 450 ipm. A strong correlation has been observed between arc energy – controlled primarily by travel and wire feed speed. Initial visual inspection, internal microstructural examination, and computed tomography (CT) have been used to determine the effects of built parameters on evolution of internal porosity and defects. Scanning electron microscopy techniques enabled structural and compositional imaging of heterogeneity and changes in microstructural properties.

additive manufacturing↗

DOE OSTI2025

Characterization of Build Parameters and Microstructure in Low Heat Input WAAM of Ni-Based Superalloy Haynes 282

additive manufacturing↗

NASA NTRS1992

Vacuum Plasma Spraying Replaces Electrodeposition

Vacuum plasma spraying used to fabricate large parts with complicated contours and inner structures, without uninspectable welds. Reduces time, and expense of fabrication. Wall of combustion chamber built up inside of outer nickel-alloy jacket by plasma spraying. Particles of metal sprayed partially melted in plasma gun and thrown at supersonic speed toward deposition surface. Vacuum plasma-spray produces stronger bond between the grooves and covering layer completing channels and wall of combustion chamber. In tests, bond withstood pressure of 20 kpsi, three times allowable limit by old method.

Holmes, Richard R.↗

NASA NTRS2004

Verification of Java Programs using Symbolic Execution and Invariant Generation

Software verification is recognized as an important and difficult problem. We present a norel framework, based on symbolic execution, for the automated verification of software. The framework uses annotations in the form of method specifications an3 loop invariants. We present a novel iterative technique that uses invariant strengthening and approximation for discovering these loop invariants automatically. The technique handles different types of data (e.g. boolean and numeric constraints, dynamically allocated structures and arrays) and it allows for checking universally quantified formulas. Our framework is built on top of the Java PathFinder model checking toolset and it was used for the verification of several non-trivial Java programs.

Pasareanu, Corina↗

NASA NTRS2014

Performance of a Multifunctional Space Evaporator-Absorber-Radiator (SEAR)

The Space Evaporator-Absorber-Radiator (SEAR) is a nonventing thermal control subsystem that combines a Space Water Membrane Evaporator (SWME) with a Lithium Chloride Absorber Radiator (LCAR). The LCAR is a heat pump radiator that absorbs water vapor produced in the SWME. Because of the very low water vapor pressure at equilibrium with lithium chloride solution, the LCAR can absorb water vapor at a temperature considerably higher than the SWME, enabling heat rejection sufficient for most EVA activities by thermal radiation from a relatively small area radiator. Prior SEAR prototypes used a flexible LCAR that was designed to be installed on the outer surface of a portable life support system (PLSS) backpack. This paper describes a SEAR subsystem that incorporates a very compact LCAR. The compact, multifunctional LCAR is built in the form of thin panels that can also serve as the PLSS structural shell. We designed and assembled a 2 ft² prototype LCAR based on this design and measured its performance in thermal vacuum tests when supplied with water vapor by a SWME. These tests validated our models for SEAR performance and showed that there is enough area available on the PLSS backpack shell to enable rejection of metabolic heat from the LCAR. We used results of these tests to assess future performance potential and suggest approaches for integrating the SEAR system with future space suits.

Izenson, Michael G.↗

NASA NTRS2013

Performance of a Multifunctional Space Evaporator- Absorber-Radiator (SEAR)

The Space Evaporator-Absorber-Radiator (SEAR) is a nonventing thermal control subsystem that combines a Space Water Membrane Evaporator (SWME) with a Lithium Chloride Absorber Radiator (LCAR). The LCAR is a heat pump radiator that absorbs water vapor produced in the SWME. Because of the very low water vapor pressure at equilibrium with lithium chloride solution, the LCAR can absorb water vapor at a temperature considerably higher than the SWME, enabling heat rejection by thermal radiation from a relatively small area radiator. Prior SEAR prototypes used a flexible LCAR that was designed to be installed on the outer surface of a portable life support system (PLSS) backpack. This paper describes a SEAR subsystem that incorporates a very compact LCAR. The compact, multifunctional LCAR is built in the form of thin panels that can also serve as the PLSS structural shell. We designed and assembled a 2 sq ft prototype LCAR based on this design and measured its performance in thermal vacuum tests when supplied with water vapor by a SWME. These tests validated our models for SEAR performance and showed that there is enough area available on the PLSS backpack shell to enable heat rejection from the LCAR.

Izenson, Michael G.↗

NASA NTRSDate not supplied

Arc-jet Testing of Continuously Woven Aeroshells–Spiderweave–for Adaptable Deployable Entry Placement Technology

The Adaptable, Deployable Entry Placement Technology (ADEPT) is an entry system that, when deployed, creates a large, umbrella-like drag surface that can be used to decelerate spacecraft during atmospheric entry, resulting in lower entry loads and heating than a rigid aeroshell of equivalent mass. Until needed for entry, the system can remain stowed, enabling missions to overcome launch vehicle fairing diameter constraints. 12-inch diameter umbrella-like articles, similar to a small reentry probe using ADEPT, were tested in the Ames 20-MWAerodynamic Heating Facility. Performance of the test articles built with a novel, continuously woven aeroshell construction (called Spiderweave) is compared against those built with legacy construction styles. In addition, candidate thermal protective layer treatments applied to structurally sensitive regions of the aeroshell are assessed using data from on-board instrumentation as well as facility optical instruments.

ADEPT↗

NASA NTRS2020

Data Processing for High-Contrast Imaging with the James Webb Space Telescope

The James Webb Space Telescope (JWST) will probe circumstellar environments at an unprecedented sensitivity.However, the performance of high-contrast imaging instruments is limited by the residual light from the star at close separations (<2-3”), where the incidence of exoplanets increases rapidly. There is currently no solution to get rid of the residual light down to the photon noise level at those separations, which may prevent some crucial discoveries. JWST’s debut is planned for October 2021 for a baseline mission lifetime of only five years. Thus,it is crucial to find a solution to this problem before its launch. We are further developing and implementing an innovative approach of post-processing built on a Bayesian framework that provides a more robust determination of faint astrophysical structures around a bright source. This approach uses a model of high-contrast imaging instrument that takes advantage of prior information, such as data from wavefront sensing (WFS) operations on JWST, to estimate simultaneously instrumental aberrations and the circumstellar environment. With this approach, our goal is to further improve the contrast gain over the contrast that can be achieved with JWST instruments, starting with NIRCam imaging and coronagraphic imaging. This work will pave the way for the future space-based high-contrast imaging instruments such as the Nancy Grace Roman Space Telescope Coronagraph Instrument (Roman CGI). This technique will be crucial to make the best use of the telemetry data that will be collected during the CGI operations.

Jewell, Jeffrey B.↗

DOE OSTI2014

Structure and photoluminescence properties of Na{sub 2}Y{sub 2}B{sub 2}O{sub 7}:Ce{sup 3+},Tb{sup 3+} phosphors for solid-state lighting application

Novel phosphors of Na{sub 2}Y{sub 2}B{sub 2}O{sub 7}:Ce{sup 3+} and Na{sub 2}Y{sub 2}B{sub 2}O{sub 7}:Ce{sup 3+},Tb{sup 3+} were synthesized by a solid-state process and characterized with X-ray diffraction, photoluminescence (PL), PL excitation (PLE), and fluorescence decay time. The relationship between the observed Ce{sup 3+} emission properties and the crystal structure of Na{sub 2}Y{sub 2}B{sub 2}O{sub 7} is built and the result shows that Ce{sup 3+} ions occupy two non-equivalent Y{sup 3+} sites in the host. The codoping of Tb{sup 3+} in Na{sub 2}Y{sub 2}B{sub 2}O{sub 7}:Ce{sup 3+} can tune the emitting colour from blue to green and increase the luminescence quantum efficiency to 75.2% by the energy transfer of Ce{sup 3+}→Tb{sup 3+}. The energy transfer processes of Ce{sup 3+}–Ce{sup 3+} and Ce{sup 3+}–Tb{sup 3+} are analysed and determined to be electric dipole–dipole and dipole–quadrupole, respectively. The broad PLE spectra of Na{sub 2}Y{sub 2}B{sub 2}O{sub 7}:Ce{sup 3+} and Na{sub 2}Y{sub 2}B{sub 2}O{sub 7}:Ce{sup 3+},Tb{sup 3+} are well matched with the emission from near UV LED chips, which indicates that they are promising blue and green phosphors for phosphor-converted white LEDs. - Graphical abstract: Colour-tunable phosphors Na{sub 2}Y{sub 2}B{sub 2}O{sub 7}:Ce{sup 3+},Tb{sup 3+} with optimal quantum yield of 75.2% are synthesized and the phosphors can be served as n-UV pumped materials for LEDs. - Highlights: • Green phosphor Na{sub 2}Y{sub 2}B{sub 2}O{sub 7}:Ce{sup 3+},Tb{sup 3+} with quantum efficiency of 75.2% for n-UV application is synthesized. • The site occupation of Ce{sup 3+} in Na{sub 2}Y{sub 2}B{sub 2}O{sub 7} is investigated with the crystal structure and photoluminescence spectra. • The energy transfer of Ce{sup 3+}–Ce{sup 3+} and Ce{sup 3+}–Tb{sup 3+}, which is responsible to the tunable emitting colour of the phosphor, is demonstrated and the mechanism is studied.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗