Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “OPACITY”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,153 records · Page 64
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Viscous regularization of the full set of nonequilibrium-diffusion Grey Radiation-Hydrodynamic equations

A viscous regularization technique, based on the local entropy residual, was proposed by Delchini et al. (2015) to stabilize the nonequilibrium-diffusion Grey Radiation-Hydrodynamic equations using an artificial viscosity technique. This viscous regularization is modulated by the local entropy production and is consistent with the entropy minimum principle. However, Delchini et al. (2015) only based their work on the hyperbolic parts of the Grey Radiation-Hydrodynamic equations and thus omitted the relaxation and diffusion terms present in the material energy and radiation energy equations. Here in this paper, we extend the theoretical grounds for the method and derive an entropy minimum principle for the full set of nonequilibrium-diffusion Grey Radiation-Hydrodynamic equations. This further strengthens the applicability of the entropy viscosity method as a stabilization technique for radiation-hydrodynamic shock simulations. Radiative shock calculations using constant and temperature-dependent opacities are compared against semi-analytical reference solutions, and we present a procedure to perform spatial convergence studies of such simulations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2026

Open quantum system approach to inclusive jet production in heavy-ion collisions

We derive a factorization formula for inclusive jet production in heavy-ion collisions using the tools of Effective Field Theory (EFT). We show how physics at widely separated scales in this process can be systematically separated by matching to EFTs at successively lower virtualities. Owing to a strong scale separation, we recover a vacuum-like DGLAP evolution above the jet scale, while the additional low-energy scales induced by the medium effectively probe the internal structure of the jet. As a result, the cross section can be written as a series with an increasing number of subjets characterized by perturbative matching coefficients each of which is convolved with a distinct function. These functions encode broadening, medium-induced radiations as well as quantum interference such as the Landau-Pomeranchuk-Migdal effect and color coherence dynamics to all orders in perturbation theory. As a first application of this EFT framework, we investigate the case of an unresolved jet and show how the cross section can be factorized and fully separate the jet dynamics from the universal physics of the medium. To compare to the existing literature, we explicitly compute the medium jet function at next-to-leading order in the coupling and leading order in medium opacity.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

Inclusive heavy flavor jet production with semi-inclusive jet functions: from proton to heavy-ion collisions

The past several years have witnessed important developments in the QCD theory of jet production and jet substructure in hadronic collisions. In the framework of soft-collinear effective theory, semi-inclusive jet functions and semi-inclusive fragmenting jet functions have allowed us to combine higher order calculations with resummation of potentially large logarithms of the jet radius, ln R. Very recently, the semi-inclusive jet functions for partons fragmenting into heavy flavor jets were computed by Dai, Kim and Leibovich. In this paper we show how the formalism can be extended to c-jet and b-jet production in heavy ion collisions. The semi-inclusive jet functions for heavy flavor jets in a QCD medium are evaluated up to the next-to-leading order in αs and first order in opacity. For phenomenological applications, we also consider the inclusion of the cold nuclear matter effects and the jet energy dissipation due to collisional interactions in matter. We present the numerical predictions for the cross sections and the corresponding nuclear modification factors in proton-nucleus and nucleus-nucleus collisions and compare our results to data from the Large Hadron Collider.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Treatment of Liver Tumors with Lipiodol TACE: Technical Recommendations from Experts Opinion

Transarterial chemoembolization with Lipiodol (Lipiodol TACE), also called conventional TACE, was developed in the early 1980s and widely adopted worldwide after randomized control trials and meta-analysis demonstrated superiority of Lipiodol TACE to best supportive care. Presently, there is no level one evidence that other TACE techniques are superior to Lipiodol TACE for intermediate stage hepatocellular carcinoma (HCC), which includes patients with preserved liver function and nonsurgical large or multinodular HCC without distant metastases. In addition, TACE is part of the treatment for progressive or symptomatic liver metastases from gastroenteropancreatic neuroendocrine tumors. When injected into the hepatic artery, Lipiodol has the unique property of selective uptake and retention in hyperarterialyzed liver tumors. Lipiodol/drug emulsion followed by particle embolization has been demonstrated to improve the pharmacokinetic of the drug and tumor response. Radio opacity of Lipiodol helps to monitor treatment delivery, with retention of Lipiodol serving as an imaging biomarker for tumor response. For 30 years, Lipiodol TACE has been inconsistently referenced in many publications with various levels of details for the method of preparation and administration, with reported progressive outcomes following improvements in the technique and the devices used to deliver the treatment and better patient selection. Consequently, there is no consensus on the standard method of TACE regarding the use of anticancer agents, embolic material, technical details, and the treatment schedule. In order to develop an internationally validated technical recommendation to standardize the Lipiodol TACE procedure, a worldwide panel of experts participated in a consensus meeting held on May 10, 2014.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2017

Influence of Contrast Agent Dilution on Ballon Deflation Time and Visibility During Tracheal Balloon Dilation: A 3D Printed Phantom Study

PurposeTo determine the effect of contrast medium dilution during tracheal balloon dilation on balloon deflation time and visibility using a 3-dimensional (3D) printed airway phantom.Materials and MethodsA comparison study to investigate balloon deflation times and image quality was performed using two contrast agents with different viscosities, i.e., iohexol and ioxithalamate, and six contrast dilutions with a 3D printed airway phantom.ResultsCompared to 1:0 concentration, 3:1, 2:1, 1:1, 1:2, and 1:3, contrast/saline ratios resulted in a 46% (56.2 s), 59.8% (73.1 s), 74.9% (91.6 s), 81.7% (99.8 s), and 83.5% (102 s) reduction for iohexol, respectively, and a 51.8% (54.7 s), 63.8% (67.6 s), 74.7% (79.2 s), 80.5% (85.3 s), and 82.4% (87.4 s) reduction for ioxithalamate, respectively, in the mean balloon deflation time, although at the expense of decreased balloon opacity (3.5, 6.9, 11.1, 12.4, and 13.9%, for iohexol, respectively, and 3.2, 6, 9.6, 10.8, and 12.4%, for ioxithalamate, respectively).ConclusionsUse of a lower viscosity contrast agent and higher contrast dilution is considered to be able to reduce balloon deflation times and then simultaneously decrease visualization of balloons. The rapid balloon deflation time is likely to improve the safe performance of interventional procedures.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2015

Flash X-Ray measurements on the shock-induced dispersal of a dense particle curtain

The interaction of a Mach 1.67 shock wave with a dense particle curtain is quantified using flash radiography. These new data provide a view of particle transport inside a compressible, dense gas–solid flow of high optical opacity. The curtain, composed of 115-µm glass spheres, initially spans 87 % of the test section width and has a streamwise thickness of about 2 mm. Radiograph intensities are converted to particle volume fraction distributions using the Beer–Lambert law. The mass in the particle curtain, as determined from the X-ray data, is in reasonable agreement with that given from a simpler method using a load cell and particle imaging. Following shock impingement, the curtain propagates downstream and the peak volume fraction decreases from about 23 to about 4 % over a time of 340 µs. The propagation occurs asymmetrically, with the downstream side of the particle curtain experiencing a greater volume fraction gradient than the upstream side, attributable to the dependence of particle drag on volume fraction. Bulk particle transport is quantified from the time-dependent center of mass of the curtain. Furthermore, the bulk acceleration of the curtain is shown to be greater than that predicted for a single 115-µm particle in a Mach 1.67 shock-induced flow.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Poly(n-butyl acrylate)–Casein Nanocomposites as Promising Candidates for Packaging Films

Partially degradable materials, offer an interesting sustainable alternative for short-term use applications where their environmental impact could be importantly reduced. This article investigates the preparation of a series of poly(n-butyl acrylate)–casein nanocomposites with varied bio-component content via emulsifier-free emulsion polymerization. The influence of casein content on the morphological and film properties of the natural/synthetic materials is discussed. Film performance was analyzed in terms of water and vapor resistance, biodegradability in composting conditions, mechanical behavior, opacity, and thermal stability. The obtained results suggest that poly(n-butyl acrylate)–casein nanocomposites, with grafting of acrylic chains onto protein molecules, have great potential as bio-defragmentable packaging materials.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2013

Shock-Induced Optical Changes in AI 2 O 3 at 200 GPa; Implications for Shock Temperature Measurements in Metals [Book Chapter]

A knowledge of the optical property of window materials at shock pressures above 100 GPa is crucial for determining shock temperatures in metals. We have examined the optical properties of Al 2 O 3 at 200-300 GPa pressures using a time-resolved optical method. The strong emission and the partial opacity are observed from the shocked Al 2 O 3 . Wavelength- and time-dependence of the emission will be presented. A new electro-optical technique facilitating time-resolved optical measurements at a 2-stage light gas gun will be described.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Lessons from the light of a neutron star merger

The discovery by Advanced LIGO/Virgo of gravitational waves from the binary neutron star merger GW170817, and subsequently by astronomers of transient emission across the electromagnetic spectrum, has initiated a new era of multi-messenger gravitational wave astronomy. Here I summarize the electromagnetic discoveries in the context of theoretical counterpart models and present personal views on the major take-away lessons and outstanding new questions from this watershed event, focused on the implications for nuclear physics. The luminosity and colors of the early optical emission discovered within a day of the merger agree well with predictions for “kilonova” emission, powered by the radioactive decay of light r-process nuclei (atomic mass number A≲140). The transition of the spectral energy distribution to near-infrared wavelengths on timescales of days indicates that inner portions of the ejecta contain heavy r-process nuclei with high UV/optical opacity due to the presence of at least some lanthanide elements (A≳140). The “blue” and “red” ejecta components likely possess distinct origins (e.g. dynamical ejecta, magnetar-powered wind, or accretion disk outflow), with implications for the merger process (e.g. the lifetime of the remnant prior to black hole formation) and fundamental properties of neutron stars. I outline the predicted diversity in the electromagnetic emission of future mergers−observed with different ingoing binary masses and/or viewing angles−discovered in the years ahead as LIGO/Virgo reach design sensitivity.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

The cataract-associated V41M mutant of human γS-crystallin shows specific structural changes that directly enhance local surface hydrophobicity

Highlights: •We present NMR analysis of V41M, a cataract-causing mutant of human γS-crystallin. •Mutation alters strand–strand interactions throughout the N-terminal domain. •Mutation directly affects Trp46 due to key Met41-S–Trp46-pi interactions. •We identify the basis of the surface hydrophobicity increase and residues involved. -- Abstract: The major crystallins expressed in the human lens are γS-, γC- and γD-crystallins. Several mutations in γS-crystallin are associated with hereditary cataracts, one of which involves the substitution of a highly conserved Valine at position 41 to Methionine. According to a recent report, the mutant protein, V41M, shows lower stability and increased surface hydrophobicity compared to the wild-type, and a propensity for self-aggregation. Here we address the structural differences between the two proteins, with residue-level specificity using NMR spectroscopy. Based on the structural model of the mutant protein, our results clearly show that the mutation creates a major local perturbation almost at the junction of the first and second “Greek-key” motifs in the N-terminal domain. A larger section of the second motif (residues 44–86) appears to be mainly affected. Based on the sizeable chemical shift of the imino proton of the indole side-chain of Trp46 in V41M, we suggest that the sulphur atom of Met41 is involved in an S–π interaction with Trp46. This interaction would bring the last β-strand of the first “Greek-key” motif closer to the first β-strand of the second motif. This appears to lead to a domino effect, towards both the N- and C-terminal ends, even as it decays off substantially beyond the domain interface. During this process discreet hydrophobic surface patches are created, as revealed by ANS-binding. Such changes would not affect the secondary structure or cause a major change in the tertiary structure, but can lead to self-aggregation or aberrant binding interactions of the mutant protein in vivo, and lead to lens opacity or cataract.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Synchrotron-based measurement of aluminum agglomerates at motor conditions

Solid rocket propellant combustion is hindered by agglomeration of aluminum particles on its burning surface and determining the particle size has been a problem for half a century. The actual size of the agglomerates at motor pressures is unknown due to the opacity of the combustion plume, particularly at the elevated pressures seen in operational rocket motors. Sampling techniques can provide data at elevated pressure but may be biased due to the sampling method and do not provide information on the dynamics of agglomerate formation. Here this study uses time-resolved synchrotron x-ray imaging (with both absorption and phase contrast) to view aluminum agglomerate formation in situ at relevant rocket pressures. Finally, we have for the first time observed agglomerate formation at motor-relevant pressures in real time with unprecedented fidelity, providing critical data for understanding the combustion of aluminized solid rocket propellants.

36 MATERIALS SCIENCE↗
DOE OSTI2022

siRNA high throughput screening identifies regulators of chloropicrin and hydrogen fluoride injury in human corneal epithelial cell models

Corneal injuries induced by various toxicants result in similar clinical presentations such as corneal opacity and neovascularization. Many studies suggest that several weeks post-exposure a convergence of the molecular mechanisms drives these progressive pathologies. However, chemical agents vary in toxicological properties, and early molecular responses are anticipated to be somewhat dissimilar for different toxicants. In this report we chose 3120 targets from the Dharmacon Human Druggable genome to screen for chloropicrin (CP) and hydrogen fluoride (HF) corneal injury as we hypothesized that targets identified in vitro may be effective as therapeutic targets in future studies. Human immortalized corneal epithelial cells (SV40-HCEC) were used for screening. Cell viability and IL-8 were analyzed to down-select hits into validation studies, where multiplex cytokine analysis and high content analysis were performed to understand toxicant effect and target function. Some endpoints were also evaluated in a second human immortalized corneal epithelial cell line, TCEpi. Over 20 targets entered validation studies for CP and HF; of these, only three targets were shared: NR3C1, RELA, and KMT5A. These findings suggest that early molecular responses to different toxicants may be somewhat distinctive and present dissimilar targets for possible early intervention.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Retrieval of water vapor column abundance and aerosol properties from ChemCam passive sky spectroscopy

In this work, we derive water vapor column abundances and aerosol properties from Mars Science Laboratory (MSL) ChemCam passive mode observations of scattered sky light. This paper covers the methodology and initial results for water vapor and also provides preliminary results for aerosols. The data set presented here includes the results of 113 observations spanning from Mars Year 31 L s = 291° (March 30, 2013) to Mars Year 33 L s = 127° (March 24, 2016). Each ChemCam passive sky observation acquires spectra at two different elevation angles. We fit these spectra with a discrete-ordinates multiple scattering radiative transfer model, using the correlated-k approximation for gas absorption bands. The retrieval proceeds by first fitting the continuum of the ratio of the two elevation angles to solve for aerosol properties, and then fitting the continuum-removed ratio to solve for gas abundances. The final step of the retrieval makes use of the observed CO 2 absorptions and the known CO 2 abundance to correct the retrieved water vapor abundance for the effects of the vertical distribution of scattering aerosols and to derive an aerosol scale height parameter. Our water vapor results give water vapor column abundance with a precision of ±0.6 precipitable microns and systematic errors no larger than ±0.3 precipitable microns, assuming uniform vertical mixing. The ChemCam-retrieved water abundances show, with only a few exceptions, the same seasonal behavior and the same timing of seasonal minima and maxima as the TES, CRISM, and REMS-H data sets that we compare them to. However ChemCam-retrieved water abundances are generally lower than zonal and regional scale from-orbit water vapor data, while at the same time being significantly larger than pre-dawn REMS-H abundances. Pending further analysis of REMS-H volume mixing ratio uncertainties, the differences between ChemCam and REMS-H pre-dawn mixing ratios appear to be much too large to be explained by large scale circulations and thus they tend to support the hypothesis of substantial diurnal interactions of water vapor with the surface. Our preliminary aerosol results, meanwhile, show the expected seasonal pattern in dust particle size but also indicate a surprising interannual increase in water–ice cloud opacities.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Simulating the density of organic species in the atmosphere of Titan with a coupled ion-neutral photochemical model

We introduce a one-dimensional coupled ion-neutral photochemical kinetics and diffusion model to study the atmospheric composition of Titan in light of new theoretical kinetics calculations and scientific findings from the Cassini–Huygens mission. The model extends from the surface to the exobase. The atmospheric background, boundary conditions, vertical transport and aerosol opacity are all constrained by the Cassini–Huygens observations. The chemical network includes reactions between hydrocarbons, nitrogen and oxygen bearing species. It takes into account neutrals and both positive and negative ions with masses extending up to 116 and 74 u, respectively. We incorporate high-resolution isotopic photoabsorption and photodissociation cross sections for N 2 as well as new photodissociation branching ratios for CH 4 and C 2 H 2 . Ab initio transition state theory calculations are performed in order to estimate the rate coefficients and products for critical reactions. Critical reactions of production and loss for neutrals and ions are quantitatively assessed and thoroughly discussed. The vertical distributions of neutrals and ions predicted by the model generally reproduce observational data, suggesting that for the small species most chemical processes in Titan’s atmosphere and ionosphere are adequately described and understood; some differences are highlighted. Notable remaining issues include (i) the total positive ion density (essentially HCNH + ) in the upper ionosphere, (ii) the low mass negative ion densities (CN - , C 3 N - /C4H - ) in the upper atmosphere, and (iii) the minor oxygen-bearing species (CO 2 , H 2 O) density in the stratosphere. Pathways towards complex molecules and the impact of aerosols (UV shielding, atomic and molecular hydrogen budget, nitriles heterogeneous chemistry and condensation) are evaluated in the model, along with lifetimes and solar cycle variations.

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

An algorithm for computing the 2D structure of fast rotating stars

Stars may be understood as self-gravitating masses of a compressible fluid whose radiative cooling is compensated by nuclear reactions or gravitational contraction. The understanding of their time evolution requires the use of detailed models that account for a complex microphysics including that of opacities, equation of state and nuclear reactions. The present stellar models are essentially one-dimensional, namely spherically symmetric. However, the interpretation of recent data like the surface abundances of elements or the distribution of internal rotation have reached the limits of validity of one-dimensional models because of their very simplified representation of large-scale fluid flows. In this article, we describe the ESTER code, which is the first code able to compute in a consistent way a two-dimensional model of a fast rotating star including its large-scale flows. Compared to classical 1D stellar evolution codes, many numerical innovations have been introduced to deal with this complex problem. First, the spectral discretization based on spherical harmonics and Chebyshev polynomials is used to represent the 2D axisymmetric fields. A nonlinear mapping maps the spheroidal star and allows a smooth spectral representation of the fields. The properties of Picard and Newton iterations for solving the nonlinear partial differential equations of the problem are discussed. It turns out that the Picard scheme is efficient on the computation of the simple polytropic stars, but Newton algorithm is unsurpassed when stellar models include complex microphysics. Finally, we discuss the numerical efficiency of our solver of Newton iterations. This linear solver combines the iterative Conjugate Gradient Squared algorithm together with an LU-factorization serving as a preconditioner of the Jacobian matrix.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2024

One-sweep moment-based semi-implicit-explicit integration for gray thermal radiation transport

Thermal radiation transport (TRT) is a time dependent, high dimensional partial integro-differential equation. In practical applications such as inertial confinement fusion, TRT is coupled to other physics such as hydrodynamics, plasmas, etc., and the timescales one is interested in capturing are often much slower than the radiation timescale. As a result, TRT is treated implicitly, and due to its stiffness and high dimensionality, is often a dominant computational cost in multiphysics simulations. Here we develop a new approach for implicit-explicit (IMEX) integration of gray TRT in the deterministic SN setting, which requires only one sweep per stage, with the simplest first-order method requiring only one sweep per time step. The partitioning of equations is done via a moment-based high-order low-order formulation of TRT, where the streaming operator and first two moments are used to capture the asymptotic stiff regimes of the streaming limit and diffusion limit. Absorption-reemission is treated explicitly, and although stiff, is sufficiently damped by the implicit solve that we achieve stable accurate time integration without incorporating the coupling of the high order and low order equations implicitly. Due to nonlinear coupling of the high-order and low-order equations through temperature-dependent opacities, to facilitate IMEX partitioning and higher-order methods, we use a semi-implicit integration approach amenable to nonlinear partitions. In conclusion, results are demonstrated on thick Marshak and crooked pipe benchmark problems, demonstrating orders of magnitude improvement in accuracy and wallclock compared with the standard first-order implicit integration typically used.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2025

Moment-based adaptive time integration for thermal radiation transport

Here, in this paper we develop a framework for moment-based adaptive time integration of deterministic multifrequency thermal radiation transpot (TRT). We generalize our recent semi-implicit-explicit (IMEX) integration framework for gray TRT to multifrequency TRT, and also introduce a semi-implicit variation that facilitates higher-order integration of TRT, where each stage is implicit in all components except opacities. To appeal to the broad literature on adaptivity with Runge–Kutta methods, we derive new embedded methods for four asymptotic preserving IMEX Runge–Kutta schemes we have found to be robust in our previous work on TRT and radiation hydrodynamics. We then use a moment-based high-order-low-order representation of the transport equations. Due to the high dimensionality, memory is always a concern in simulating TRT. We form error estimates and adaptivity in time purely based on temperature and radiation energy, for a trivial overhead in computational cost and memory usage compared with the base second order integrators. We then test the adaptivity in time on the tophat and Larsen problem, demonstrating the ability of the adaptive algorithm to naturally vary the timestep across 4–5 orders of magnitude, ranging from the dynamical timescales of the streaming regime to the thick diffusion limit.

97 MATHEMATICS AND COMPUTING↗