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At least 991 records · Page 55
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Quantifying the Sensitivity of Condition Incidence Parameters in the Evidence Library

One approach to quantifying spaceflight risk at NASA makes use event driven probabilistic techniques. The Medical Extensible Dynamic Probabilistic Risk Assessment Tool (MEDPRAT) is such a tool that estimates medical risk metrics via simulation and enables optimization of medical resources subject to mission constraints [1]. Previous analyses have informed medical set composition, exercise countermeasures, and water intake, where each analysis quantifies the risk associated with proposed variations in system design. As future mission profiles extend beyond Low-Earth Orbit (LEO) and lengthen in duration, understanding these risks and contributing factors is critical. MEDPRAT employs Monte Carlo sampling techniques to simulate missions and track the occurrence of medical events. These events follow fault-tree-like progressions through levels of severity and mitigation via medical treatment to many possible outcomes and these are reported throughout the mission. Making this possible, are the medical databases that contain evidence gathered by the Human Research Program (HRP). Quantifying the impact of uncertainty or variability in the input data is an important step in evaluating the credibility of modeling and simulation results. In this work, we investigate the sensitivity of medical risk metrics with respect to the condition incidence parameters within the Evidence Library (EL) [2] as the medical database input for MEDPRAT. The medical conditions, contained in the EL, are equipped with incidence rates that describe the likelihood that the condition will occur. These incidence rates reflect historical spaceflight data or when appropriate, terrestrial data. In this presentation, we will explore how uncertainty in these rates propagate to the medical risk described by MEDPRAT. These results identify the conditions and parameters with the largest contribution to medical risks.

Ian Lim↗
NASA NTRS1999

Swept-Wing Receptivity Studies Using Distributed Roughness

Transition to turbulence in swept-wing flows has resisted correlation with linear theory because of its sensitivity to freestream conditions and 3-D roughness and because one of the principal instability modes quickly 'becomes nonlinear. In the face of such a formidable problem, two rather long-term fundamental efforts have been underway at DLR Gottinberg and Arizona State University that address swept-wing transition. These efforts have been recently reviewed by Bippes (1997) and Reibert and Saric (1997). Thus, the present work is a continuation of a series of studies on swept-wing boundary layers which have led to a better understanding of the transition process. In particular, we have taken advantage of the sensitivity to 3-D roughness and the modal nature of the instability in order to propose a particular control strategy. Complementing the two aforementioned reviews, general reviews of the swept-wing transition problem are found in Arnal (1997) and Kachanov (1996). Other recent reviews include Reshotko (t997), Crouch (1997), and Herbert (1997a,b). The failure of linear theory is discussed in Reed et al. (1996). The historical work is found in Reed and Sar-ic (1989). The basic idea is that the combination of sweep and chordwise pressure gradient within the boundary layer creates a velocity component perpendicular to the inviscid streamline. This crossflow profile is inflectional and exhibits both traveling and stationary unstable waves called crossflow vortices that are (approximately) aligned along the inviscid streamlines. Under conditions of low freestream turbulence levels, the dominant crossflow wave is stationary (Reibert and Saric t997) while moderate to high turbulence levels initiate dominant traveling waves (Dehle and Bippes 1996; Bippes 1997). 'Me mechanism is relatively insensitive to sound and 2-D surface roughness (Radeztsky et al. 1993) but very sensitive to 3-D roughness near the attachment line. We concentrate our work on low-turbulence freestream flows and stationary crossflow waves. Although the v' and w' components of the disturbances are very small, by convecting streamwise momentum in the wall-normal direction, they produce 0(l) changes inu'.Thus the mean flow is highly distorted with localized inflection points. Transition is then triggered by a high-frequency secondary instability of the distorted mean profile.

Saric, William S.↗
NASA NTRS2010

Profiling Transboundary Aerosols over Taiwan and Assessing Their Radiative Effects

A synergistic process was developed to study the vertical distributions of aerosol optical properties and their effects on solar heating using data retrieved from ground-based radiation measurements and radiative transfer simulations. Continuous MPLNET and AERONET observations were made at a rural site in northern Taiwan from 2005 to 2007. The aerosol vertical extinction profiles retrieved from ground-based lidar measurements were categorized into near-surface, mixed, and two-layer transport types, representing 76% of all cases. Fine-mode (Angstrom exponent, alpha, approx.1.4) and moderate-absorbing aerosols (columnar single-scattering albedo approx.0.93, asymmetry factor approx.0.73 at 440 nm wavelength) dominated in this region. The column-integrated aerosol optical thickness at 500 nm (tau(sub 500nm)) ranges from 0.1 to 0.6 for the near-surface transport type, but can be doubled in the presence of upper-layer aerosol transport. We utilize aerosol radiative efficiency (ARE; the impact on solar radiation per unit change of tau(sub 500nm)) to quantify the radiative effects due to different vertical distributions of aerosols. Our results show that the ARE at the top-of-atmosphere (-23 W/ sq m) is weakly sensitive to aerosol vertical distributions confined in the lower troposphere. On the other hand, values of the ARE at the surface are -44.3, -40.6 and -39.7 W/sq m 38 for near-surface, mixed, and two-layer transport types, respectively. Further analyses show that the impact of aerosols on the vertical profile of solar heating is larger for the near-surface transport type than that of two-layer transport type. The impacts of aerosol on the surface radiation and the solar heating profiles have implications for the stability and convection in the lower troposphere.

Wang, Sheng-Hsiang↗
DOE OSTI2024

Electrocatalytic Effects of Au Nanoclusters in its Electrochemiluminescence Enhanced by Coreactant Tertiary Amines

Abstract Atomically precise metal nanoclusters are increasingly exploited in electrocatalysis such as water electrolysis and CO 2 reduction. The catalytic effects are generally evaluated by conventional electrochemical methods or end‐product analysis. Herein, near infrared electrochemiluminescence (ECL) of the nanoclusters is introduced as a new signaling mechanism to complement classical voltammetric analysis for elucidating essential electrocatalytic parameters. Coreactant ECL from an aqueous soluble Au 22 nanocluster (NCs) enhanced by a common pH buffer materials 4‐(2‐hydroxyethyl)‐1‐piperazineethanesulfonic acid (HEPES) and by a piperazine drug hydroxyzine (HDZ) is studied under oxidative reduction pathways. Foot of the wave analysis on voltametric features and the kinetics profiles in potential‐step experiments are studied in different nanocluster and coreactant concentrations. Benchmark parameters such as rate constants are determined under EC (Electron‐transfer‐Chemical‐reaction) mechanism as feasibility validations. Because the luminescence properties of AuNCs are sensitive to the surface ligands or adsorbents, ECL is proposed as a new signal readout for operando studies providing insights for governing reaction mechanism and kinetics during catalytic reactions. Retrospectively, mechanistic understanding of the complex multi‐step reactions during ECL generation can provide guidance for the evaluation and optimization of ECL property for better quantitative applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Analysis of RF Sheath-Driven Tungsten Erosion at RF Antenna in the WEST Tokamak

This study applies the newly developed STRIPE (Simulated Transport of RF Impurity Production and Emission) framework to analyze tungsten (W) erosion at RF antenna structures in the WEST tokamak. STRIPE integrates SolEdge3x for edge plasma backgrounds, COMSOL for 3D RF sheath potentials, RustBCA for sputtering yields, and GITR for impurity transport and ion energy–angle distributions. Building on prior work by Kumar et al. (2025) Nuclear Fusion, 65, 076039, which validated STRIPE for WEST ICRH discharge #57877, the present study provides a spatially resolved assessment of gross W erosion at both Q2 antenna limiters under ohmic and ICRH conditions. Simulations using 2D SolEdge3x profiles in COMSOL capture rectified sheath potentials exceeding 300 V, leading to strong upper-limiter localization. Both poloidal and toroidal asymmetries are observed and attributed to RF sheath effects, with modeled erosion patterns deviating from experiment—highlighting sensitivity to sheath geometry and plasma resolution. Erosion is driven primarily by high-charge-state oxygen ions (O6+–O8+), while D+ plays a negligible role. Assuming a plasma composition of 1% oxygen and 98% deuterium, STRIPE predicts a 30-fold increase in gross W erosion from ohmic to ICRH phases, consistent with a >25-fold rise in W-I (400.9 nm) brightness. Quantitative agreement is within 5% in the ohmic phase and 30% under ICRH, demonstrating predictive capability. Importantly, the study shows that the magnitude of ICRH-driven W erosion depends strongly on the concentration of light impurities (O, B, N, C), which drive sputtering through high charge states. Cleaner plasma conditions with reduced impurity content are therefore expected to substantially mitigate antenna W sources in WEST and other toroidal fusion devices. These findings establish STRIPE as a predictive framework for RF-induced plasma–material interactions and support its application to reactor-scale antenna design.

Kumar, Atul [ORNL] (ORCID:0000000277475210)↗
DOE OSTI2022

Effect of Thermal Expansion Coefficient, Viscosity and Melting Range in Simulation of PCM Embedded Heat Exchangers With and Without Fins

Phase change material heat exchangers (PCMHX) have an important role in integrating renewable energy systems. PCMHX can offer high storage density at various temperatures of interest and can be used for grid load shifting purposes. Numerical models enable engineers to estimate PCMHX performance for different design parameters and operating conditions. Modeling phase change phenomena is challenging due to the complex time-dependent nature of the process. The accuracy of models is highly sensitive to PCM thermo-physical properties. Thermal expansion coefficient (β), viscosity (μ) and melting temperature range (MR) of a PCM are important properties, especially when natural convection is not negligible. In PCMHX modeling, using less than accurate values for these properties can have significant impact on the simulation outcomes. These properties and discussions thereof are not readily available in the literature. This paper presents a brief review of the literature and a numerical study investigating the model sensitivity to the above-mentioned properties for PCMHX with and without fins. CFD is used to evaluate the charging (melting) phenomena. The study quantifies the impact of uncertainty in these properties on the melting rate and temperature profile. Constant wall temperature was considered as heat source with no heat loss to ambient. Here, the results show that β and μ has significant effect on the melting rate and evolution of the melting front. For a non-finned domain when comparing results for different published values of β and μ, the deviation in melting time can be up to 12.9% and 57.6% respectively. For high wall temperatures, change in melting range did not impact melting time. But when the wall temperature is reduced, up to 9.8% deviation in melting time is observed.

CFD↗
DOE OSTI2023

Nitrogen thermometry in an inductively coupled plasma torch using broadband nanosecond coherent anti-Stokes Raman scattering

The development of atmospheric hypersonic flight and re-entry capabilities requires the characterization of the thermo-chemical state of representative test environments. This study demonstrates the usage of multiplex nanosecond N 2 coherent anti-Stokes Raman scattering (CARS) to measure temperatures in an atmospheric, high-temperature (>6000K), air plasma plume, generated by an inductively coupled plasma torch. These are some of the highest temperatures ever accessed via gas-phase CARS, to our knowledge. Temperatures of N 2 in the equilibrium plasma plume are determined via theoretical fits to measured CARS spectra. We discuss the practical implementation of CARS at very high temperatures, including the scaling of the N 2 CARS signal strength from 300 to 6700 K, where the expected peak signal from the high-temperature plasma torch gases is two orders of magnitude less than commonly encountered in combustion environments. An intensified CCD camera enables single-laser-shot detection at temperatures as high as 6200 K, by increasing sensitivity and providing a time gate against intense background luminosity. We also discuss the impacts of unwanted two-beam CARS contributions from outside the nominal three-beam measurement volume. We present mean axial and radial temperature profiles, as well as time-series data derived from both single-laser-shot and accumulated CARS spectra. The single-laser-shot precision is 1.7%–2.6% at temperatures of 3500 to 6200 K. The presented results pave the way for the use of CARS at very high temperatures and the measurement of spatially resolved interface processes in high-enthalpy flows.

Fries, Dan (ORCID:0000000229513294)↗
DOE OSTI2021

Voltage Control Strategy for Energy Storage System in Sustainable Distribution System Operation

Due to the increasing penetration of distributed energy resources (DERs) required for the sustainable distribution system, new voltage control strategy is needed by utilities. Traditional voltage control strategy can not support the increasing number of DERs in a coordinated and scalable manner to meet the operational voltage regulation requirement. Supported by the power electronics converter, the energy storage system can provide fast, smooth, and flexible voltage control services. In this paper, an effective and easy to implement sensitivity-based voltage control strategy is developed for the energy storage system. The developed control strategy is validated using an industrial feeder data in Northwest Washington. The proposed strategy can mitigate the voltage unbalance issue, improve the voltage profile, and correct power factors while supporting sustainable distribution system operation.

Zhang, Yue (ORCID:0000000241469716)↗
DOE OSTI2025

Ultra-high Information-content Chemical Imaging with Broadband Coherent Anti-Stokes Raman and Two-photon Fluorescence Lifetime Microscopy

Raman fingerprint spectroscopy and fluorescence lifetime imaging are emerging tools for studying metabolic profiles of biological specimens. While Raman fingerprint spectroscopy detects intrinsic molecular vibrations that reflect the molecular composition and chemical environment of a sample, fluorescence lifetime imaging measures changes in the excited-state lifetime of fluorophores that are sensitive to their microenvironments. Here, we present a multimodal imaging platform combining broadband coherent anti-Stokes Raman scattering (BCARS) and two-photon fluorescence lifetime imaging (2p-FLIM) microscopy that can acquire biologically relevant Raman fingerprint spectra and fluorescence lifetime signals in vivo and simultaneously. The tremendous chemical information obtained from spatially co-registered BCARS and 2p-FLIM images allows us to characterize the subtle differences between sub-cellular compartments and verify the potential false-positive results generated by fluorescence imaging alone. This is demonstrated by directly comparing the BCARS, 2p-FLIM, and two-photon excitation fluorescence(TPEF) signals simultaneously obtained from the same dye-stained organelle in the live, intact C. elegans expressing a green fluorescent protein (GFP) marker. In this work, we introduce the BCARS/2p-FLIM/TPEF setup scheme, the image acquisition steps, data processing, and representative results showing that the cross-modality imaging method enables rigorous characterization and in vivo detection at sub-cellular resolution. Furthermore, this protocol provides a framework for simultaneous chemical and fluorescence lifetime imaging to improve the accuracy of biological interpretation in complex living systems.

Xu, Haoyu [Georgia Institute of Technology, Atlant↗
NASA NTRS1986

Airborne Lidar measurements of the atmospheric pressure profile with tunable Alexandrite lasers

The first remote measurements of the atmospheric pressure profile made from an airborne platform are described. The measurements utilize a differential absorption lidar and tunable solid state Alexandrite lasers. The pressure measurement technique uses a high resolution oxygen A band where the absorption is highly pressure sensitive due to collision broadening. Absorption troughs and regions of minimum absorption were used between pairs of stongly absorption lines for these measurements. The trough technique allows the measurement to be greatly desensitized to the effects of laser frequency instabilities. The lidar system was set up to measure pressure with the on-line laser tuned to the absorption trough at 13147.3/cm and with the reference laser tuned to a nonabsorbing frequency near 13170.0/cm. The lidar signal returns were sampled with a 200 range gate (30 vertical resoltion) and averaged over 100 shots.

Korb, C. L.↗
NASA NTRS1987

Pre-main sequence stars

Observations of premain-sequence (PMS) stars obtained with the IUE satellite since its launch in 1978 are reviewed. The major types of PMS stars are listed and briefly characterized: T Tau stars, Herbig Ae stars, FU Ori objects, weak-emission PMS stars, and Herbig-Haro objects. The IUE data for a catalog of PMS objects are then presented in a table, graphs, and sample spectra and described in detail. Topics addressed include general spectral profiles, the Mg II h and k lines, the FUV emission lines, the UV continuum, and the impact of the IUE on astrophysical models of PMS stars. The need for observations with higher spectral resolution and much greater sensitivity is indicated, and the ability of the Hubble Space Telescope High-Resolution Spectrograph and the proposed NASA/ESA Lyman FUV Spectroscopic Explorer to meet these requirements is considered.

Imhoff, Catherine L.↗
NASA NTRS1989

Statistical retrieval of precipitation cell-top altitude using passive 118-GHz observations

A nonlinear statistical-retrieval operator for precipitation cell-top altitude using high-spatial-resolution passive 118-GHz O2 brightness spectra is demonstrated. The retrieval operator consists of a Karhunen-Loeve transformation followed by a rank reduction, a linearization, and a linear minimum mean-square-error estimator. Information from the 118-GHz data on the ambient atmospheric-temperature profile and the precipitation cell size is also incorporated into the linear stage of the retrieval operator. The rms retrieval error is 1.5 km for cumulus-stage cells with tops ranging from 1.5 to 16 km. The sensitivity of nadiral 118-GHz spectra to the cell-top altitude is predominantly due to the scattering and absorption of radiation originating from low, warm atmospheric levels by colder liquid and frozen precipitation This effect causes cold perturbations in the brightness spectrum, which typically become stronger with increasing cell-top altitude.

Gasiewski, A. J.↗
NASA NTRS1995

MODTRAN3: An update and recent validations against airborne high resolution interferometer measurements

MODTRAN, the Moderate Resolution Atmospheric Radiance and Transmittance Model, encompasses all the capabilities of LOWTRAN 7, the widely used 20 cm(exp -1) resolution radiance code, but incorporates a much more sensitive molecular band model with 2 cm(exp -1) resolution. MODTRAN contains many important elements that other band model based radiative transfer codes do not incorporate. It shares with FASCODE: spherical geometry, single and multiple scattering default atmospheric profile descriptors (gases, aerosols, clouds, fogs, and rain), and molecular continua (H2O, CO2, O3, O2, N2). In addition, it can calculate the solar/lunar direct and scattered radiation. MODTRAN3 was released to the general public in November 1994. It has several important features that the previous version, MODTRAN2, does not have. Chloro-fluorocarbon (CFC) and related heavy molecules (whose spectroscopic properties first appear on the HITRAN92 data base as temperature-dependent cross sections) have been incorporated into pseudo-band models, with provision for using both default and user supplied profiles. The addition of SO2 and O2 in the UV, along with upgraded ozone Chappuis bands in the visible is also part of MODTRAN3. An improved multiple scattering algorithm, the DIScrete Ordinate Radiative Transfer (DISORT) has also been incorporated into MODTRAN3. MODTRAN is very fast: simple timing runs of MODTRAN3 vs. FASCOD3 show an improvement of more than a factor of 100 for a typical 500 cm(exp -1) spectral interval and comparable vertical layering. Speed is an important consideration in heating/cooling rates calculations, where a large number of radiative transfer calculations are needed. The MODTRAN3 used in this study is based on HITRAN92, but as mentioned, above, it will be upgraded to HITRAN94 upon its release at the end of 1994. MODTRAN has been adopted by: some researchers in the AVIRIS program as one radiative transfer code to derive surface reflectance from AVIRIS measurements. The accuracy of the code is very important because any errors in the radiative transfer calculation will directly translate into errors in the derived surface reflectance. In this paper, the new solar irradiance calculated by Kurucz, which is adopted in MODTRAN3, will be presented. Recent validations of MODTRAN3 with airborne high resolution interferometer measurements over ocean will be discussed. Good agreeement between model calculations and measurements was achieved.

Anderson, Gail P.↗
NASA NTRS2002

Cloud-Resolving Model Simulations of LBA Convective Systems: Easterly and Westerly Regimes

The 3D Goddard Cumulus Ensemble (GCE) model was used to simulate convection that occurred during the TRMM LBA field experiment in Brazil. Convection in this region can be categorized into two different regimes. Low-level easterly flow results in moderate to high CAPE and a drier environment. Convection is more intense like that seen over continents. Low-level westerly flow results in low CAPE and a moist environment. Convection is weaker and more widespread characteristic of oceanic or monsoon-like systems. The GCE model has been used to study both regimes in order to provide cloud data sets that are representative of both environments in support of TRMM rainfall and heating algorithm development. Two different case are presented: Jan 26,1999, an easterly regime case, and Feb 23,1999, a westerly regime case. The Jan 26 case is an organized squall line and is initialized with a standard cold pool. The sensitivity to mid-level sounding moisture and wind shear will also be shown. The Feb 23 case is less-organized with only transient lines and is initialized with either warm bubbles or prescribed surface fluxes. Heating profiles, rainfall statistics and storm characteristics are compared and validated for the two cases against observations collected during the experiment.

Lang, Stephen E.↗
NASA NTRS2011

Evaluation of the Combined Effects of Gamma Radiation and High Dietary Iron on Peripheral Leukocyte Distribution and Function

NASA is concerned with the health risks to astronauts, particularly those risks related to radiation exposure. Both radiation and increased iron stores can independently increase oxidative damage, resulting in protein, lipid and DNA oxidation. Oxidative stress increases the risk of many health problems including cancer, cataracts, and heart disease. This study, a subset of a larger interdisciplinary investigation of the combined effect of iron overload on sensitivity to radiation injury, monitored immune parameters in the peripheral blood of rats subjected to gamma radiation, high dietary iron or both. Specific immune measures consisted of (A) peripheral leukocyte distribution; (B) plasma cytokine levels; (C) cytokine production profiles following whole blood stimulation of either T cells or monocytes.

Crucian, Brian E.↗
NASA NTRS2015

Minimum-Cost Aircraft Descent Trajectories with a Constrained Altitude Profile

An analytical formula for solving the speed profile that accrues minimum cost during an aircraft descent with a constrained altitude profile is derived. The optimal speed profile first reaches a certain speed, called the minimum-cost speed, as quickly as possible using an appropriate extreme value of thrust. The speed profile then stays on the minimum-cost speed as long as possible, before switching to an extreme value of thrust for the rest of the descent. The formula is applied to an actual arrival route and its sensitivity to winds and airlines' business objectives is analyzed.

altitude restrictions↗
NASA NTRS2015

Temperature Sensitivity of an Atomic Vapor Cell-Based Dispersion-Enhanced Optical Cavity

Enhancement of the response of an optical cavity to a change in optical path length, through the use of an intracavity fast-light medium, has previously been demonstrated experimentally and described theoretically for an atomic vapor cell as the intracavity resonant absorber. This phenomenon may be used to enhance both the scale factor and sensitivity of an optical cavity mode to the change in path length, e.g. in gyroscopic applications. We study the temperature sensitivity of the on-resonant scale factor enhancement, S(sub o), due to the thermal sensitivity of the lower-level atom density in an atomic vapor cell, specifically for the case of the Rb-87 D(sub 2) transition. A semi-empirical model of the temperature-dependence of the absorption profile, characterized by two parameters, a(sub o)(T) and gamma(sub a)(T) allows the temperature-dependence of the cavity response, S(sub o)(T) and dS(sub o)/dT to be predicted over a range of temperature. We compare the predictions to experiment. Our model will be useful in determining the useful range for S(sub o), given the practical constraints on temperature stability for an atomic vapor cell.

Myneni, K.↗
DOE OSTI2024

Coupling Microdroplet-Based Sample Preparation, Multiplexed Isobaric Labeling, and Nanoflow Peptide Fractionation for Deep Proteome Profiling of the Tissue Microenvironment

There is increasing interest in developing in-depth proteomic approaches for mapping tissue heterogeneity in a cell-type-specific manner to better understand and predict the function of complex biological systems such as human organs. Existing spatially resolved proteomics technologies cannot provide deep proteome coverage due to limited sensitivity and poor sample recovery. Herein, we seamlessly combined laser capture microdissection with a low-volume sample processing technology that includes a microfluidic device named microPOTS (microdroplet processing in one pot for trace samples), multiplexed isobaric labeling, and a nanoflow peptide fractionation approach. The integrated workflow allowed us to maximize proteome coverage of laser-isolated tissue samples containing nanogram levels of proteins. We demonstrated that the deep spatial proteomics platform can quantify more than 5000 unique proteins from a small-sized human pancreatic tissue pixel (∼60,000 μm2) and differentiate unique protein abundance patterns in pancreas. Furthermore, the use of the microPOTS chip eliminated the requirement for advanced microfabrication capabilities and specialized nanoliter liquid handling equipment, making it more accessible to proteomic laboratories.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗