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DOE OSTI2014

A higher‐order unsplit 2D direct Eulerian finite volume method for two‐material compressible flows based on the MOOD paradigms

SUMMARY A higher‐order unsplit multi‐dimensional discretization of the diffuse interface model for two‐material compressible flows proposed by R. Saurel, F. Petitpas and R. A. Berry in 2009 is developed. The proposed higher‐order method is based on the concepts of the Multidimensional Optimal Order Detection (MOOD) method introduced in three recent papers for single‐material flows. The first‐order unsplit multi‐dimensional Finite Volume discretization presented by SPB serves as foundation for the development of the higher‐order unlimited schemes. Specific detection criteria along with a novel decrementing algorithm for the MOOD method are designed in order to deal with the complexity of multi‐material flows. Numerically, we compare errors and computational times on several 1D problems (stringent shock tube and cavitation problems) computed on 2D meshes with the second‐ and fourth‐order MOOD methods using a classical MUSCL method as reference. Several simulations of a 2D shocked R22 bubble in the air are also presented on Cartesian and unstructured meshes with the second‐ and fourth‐order MOOD methods, and qualitative comparisons confirm the conclusions obtained with 1D problems. These numerical results demonstrate the robustness of the MOOD approach and the interest of using more than second‐order methods even for locally singular solutions of complex physics models. Copyright © 2014 John Wiley & Sons, Ltd.

Diot, S.↗

DOE OSTI2016

A parallel adaptive numerical method with generalized curvilinear coordinate transformation for compressible Navier–Stokes equations

A fourth-order finite-volume method for solving the Navier–Stokes equations on a mapped grid with adaptive mesh refinement is proposed, implemented, and demonstrated for the prediction of unsteady compressible viscous flows. The method employs fourth-order quadrature rules for evaluating face-averaged fluxes. Our approach is freestream preserving, guaranteed by the way of computing the averages of the metric terms on the faces of cells. The standard Runge–Kutta marching method is used for time discretization. Solutions of a smooth flow are obtained in order to verify that the method is formally fourth-order accurate when applying the nonlinear viscous operators on mapped grids. Solutions of a shock tube problem are obtained to demonstrate the effectiveness of adaptive mesh refinement in resolving discontinuities. A Mach reflection problem is solved to demonstrate the mapped algorithm on a non-rectangular physical domain. The simulation is compared against experimental results. Future work will consider mapped multiblock grids for practical engineering geometries.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2019

Temperature-dependent structure and compressive mechanical behavior of alginate/polyethylene oxide–poly(propylene oxide)–poly(ethylene oxide) hydrogels

We report here the structural and mechanical behavior of multicomponent hydrogels comprising the commercial poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) block copolymer F127 and alginate. Previous studies on this system have shown thermoreversible behavior in shear rheology. Here we explore the properties of these materials under compression and large deformations, relevant to applications such as wound dressings that require mechanical robustness. For gels with lower F127 concentration, we find that the stiffness of the gels can be ascribed to the alginate network, and that the Young's modulus and fracture stress do not strongly depend on temperatures. Yet, for gels with an F127 concentration of 30 wt %, the Young's modulus is enhanced at higher temperatures. Under large deformations, the fracture stress and fracture strain of the materials can be independently varied using the alginate and F127 concentrations, respectively; without the trade-off in these properties that is often observed in rigid polymer networks. Small-angle X-ray scattering shows a power-law dependence scattering intensity on q arising from the alginate network and scattering peaks consistent with rearranging micelles. For gels with lower F127 concentrations, we find a disordered–body-centered cubic (BCC)-face-centered cubic (FCC) progression of states with temperature, and a BCC/FCC mixture for gels with higher F127 concentrations.

36 MATERIALS SCIENCE↗

DOE OSTI2022

Enhanced detection of paramagnetic fluorine-19 magnetic resonance imaging agents using zero echo time sequence and compressed sensing

Fluorine-19 ( 19 F) magnetic resonance imaging (MRI) is an emerging technique offering specific detection of labeled cells in vivo. Lengthy acquisition times and modest signal-to-noise ratio (SNR) makes three-dimensional spin-density–weighted 19 F imaging challenging. Recent advances in tracer paramagnetic metallo-perfluorocarbon (MPFC) nanoemulsion probes have shown multifold SNR improvements due to an accelerated 19 F T 1 relaxation rate and a commensurate gain in imaging speed and averages. However, 19 F T 2 -reduction and increased linewidth limit the amount of metal additive in MPFC probes, thus constraining the ultimate SNR. To overcome these barriers, we describe a compressed sampling (CS) scheme, implemented using a “zero” echo time (ZTE) sequence, with data reconstructed via a sparsity-promoting algorithm. Our CS-ZTE scheme acquires k-space data using an undersampled spherical radial pattern and signal averaging. Image reconstruction employs off-the-shelf sparse solvers to solve a joint total variation and -norm regularized least square problem. To evaluate CS-ZTE, we performed simulations and acquired 19 F MRI data at 11.7 T in phantoms and mice receiving MPFC-labeled dendritic cells. For MPFC-labeled cells in vivo, we show SNR gains of ~6.3 × with 8-fold undersampling. We show that this enhancement is due to three mechanisms including undersampling and commensurate increase in signal averaging in a fixed scan time, denoising attributes from the CS algorithm, and paramagnetic reduction of T 1 . Importantly, 19 F image intensity analyses yield accurate estimates of absolute quantification of 19 F spins. Overall, the CS-ZTE method using MPFC probes achieves ultrafast imaging, a substantial boost in detection sensitivity, accurate 19 F spin quantification, and minimal image artifacts.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2022

Self‐gated, dynamic contrast‐enhanced magnetic resonance imaging with compressed‐sensing reconstruction for evaluating endothelial permeability in the aortic root of atherosclerotic mice

High‐risk atherosclerotic plaques are characterized by active inflammation and abundant leaky microvessels. We present a self‐gated, dynamic contrast‐enhanced magnetic resonance imaging (DCE‐MRI) acquisition with compressed sensing reconstruction and apply it to assess longitudinal changes in endothelial permeability in the aortic root of Apoe −/− atherosclerotic mice during natural disease progression. Twenty‐four, 8‐week‐old, female Apoe −/− mice were divided into four groups (n = 6 each) and imaged with self‐gated DCE‐MRI at 4, 8, 12, and 16 weeks after high‐fat diet initiation, and then euthanized for CD68 immunohistochemistry for macrophages. Eight additional mice were kept on a high‐fat diet and imaged longitudinally at the same time points. Aortic‐root pseudo‐concentration curves were analyzed using a validated piecewise linear model. Contrast agent wash‐in and washout slopes ( b 1 and b 2 ) were measured as surrogates of aortic root endothelial permeability and compared with macrophage density by immunohistochemistry. b 2 , indicating contrast agent washout, was significantly higher in mice kept on an high‐fat diet for longer periods of time ( p = 0.03). Group comparison revealed significant differences between mice on a high‐fat diet for 4 versus 16 weeks ( p = 0.03). Macrophage density also significantly increased with diet duration ( p = 0.009). Spearman correlation between b 2 from DCE‐MRI and macrophage density indicated a weak relationship between the two parameters (r = 0.28, p = 0.20). Validated piecewise linear modeling of the DCE‐MRI data showed that the aortic root contrast agent washout rate is significantly different during disease progression. Further development of this technique from a single‐slice to a 3D acquisition may enable better investigation of the relationship between in vivo imaging of endothelial permeability and atherosclerotic plaques' genetic, molecular, and cellular makeup in this important model of disease.

Calcagno, Claudia↗

DOE OSTI2022

Dependence of the Elastic Stiffness Tensors of PETN, α‐RDX, γ‐RDX, ϵ‐RDX, ϵ‐CL‐20, DAAF, FOX‐7, and β‐HMX on Hydrostatic Compression

Abstract The dependence of the components of the elastic stiffness tensors (or elastic constants) of the organic explosives PETN, RDX, CL‐20, DAAF, FOX‐7, and HMX on hydrostatic pressure up to 10 GPa have been computed using dispersion‐corrected density functional theory. We report the evolution of lattice parameters and the non‐zero stiffnesses for the tetragonal, orthorhombic, and monoclinic crystal symmetries. Linear and quadratic dependencies of the components of the elastic stiffness tensors on volumetric compression and hydrostatic pressure are tabulated for use in single crystal plasticity models.

36 MATERIALS SCIENCE↗

DOE OSTI2017

Large-Scale Compressible-Flow Direct Numerical Simulations

Direct numerical simulation (DNS) of turbulent flows began in the early 1970s with the study of incompressible isotropic turbulence by Orszag and Patterson (Phys Rev Lett 28(2), 76–79, 1972), and compressible DNS were not conducted until the 1980s.

Mechanics↗

DOE OSTI2026

Search for higgsinos in compressed mass spectra using low-momentum tracks in pp collisions at s=13 TeV with the ATLAS detector

This paper presents two searches for the electroweak production of higgsinos with compressed mass spectra using 140 fb−1 of s=13$$ \sqrt{s}=13 $$ TeV proton-proton collision data collected by the ATLAS experiment at the Large Hadron Collider. Events are required to feature an energetic jet, large missing transverse momentum, and at least one low-momentum charged particle that serves as a candidate higgsino decay product. In the first search, targeting higgsino mass splittings in the range of 0.3–1 GeV, the higgsinos are expected to predominantly decay into pions that are identified as low-momentum charged particles with large transverse impact parameters due to the long higgsino lifetime (cτ ≈ ?(0.1–10 mm)), and neural networks are used to discriminate between signal and background processes. The second search targets larger mass splittings in the range of 1–3 GeV, where the higgsinos are expected to decay promptly into low-momentum leptons, one of which is identified by dedicated low-momentum electron or muon taggers based on neural networks utilising tracking and calorimeter information. No significant excess above the Standard Model prediction is observed in either search and the results are interpreted within simplified models, to set lower limits on the masses of the higgsino-like charginos and neutralinos. Together, these searches exclude chargino masses below 126 GeV at 95% confidence level for mass splittings between the chargino and lightest neutralino in the range of 0.3–2 GeV. This represents the first ATLAS constraints in a portion of this parameter space and surpasses the limits previously set by other experiments.

Aad, G↗

DOE OSTI2019

Search for supersymmetry with a compressed mass spectrum in the vector boson fusion topology with 1-lepton and 0-lepton final states in proton-proton collisions at $ \sqrt{s} $ = 13 TeV

A search for supersymmetric particles produced in the vector boson fusion topology in proton-proton collisions is presented. The search targets final states with one or zero leptons, large missing transverse momentum, and two jets with a large separation in rapidity. The data sample corresponds to an integrated luminosity of 35.9 fb$^{-1}$ of proton-proton collisions at $\sqrt{s}=$ 13 TeV collected in 2016 with the CMS detector at the LHC. The observed dijet invariant mass and lepton-neutrino transverse mass spectra are found to be consistent with the standard model predictions. Upper limits are set on the cross sections for chargino ($\widetilde\chi_1^\pm$) and neutralino ($\widetilde\chi_2^0$) production with two associated jets. For a compressed mass spectrum scenario in which the $\widetilde\chi_1^\pm$ and $\widetilde\chi_2^0$ decays proceed via a light slepton and the mass difference between the lightest neutralino $\widetilde\chi_1^0$ and the mass-degenerate particles $\widetilde\chi_1^\pm$ and $\widetilde\chi_2^0$ is 1 (30) GeV, the most stringent lower limit to date of 112 (215) GeV is set on the mass of these latter two particles.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2016

Patient Satisfaction After Femoral Arterial Access Site Closure Using the ExoSeal{sup ®} Vascular Closure Device Compared to Manual Compression: A Prospective Intra-individual Comparative Study

PurposeTo intra-individually compare discomfort levels and patient satisfaction after arterial access closure using the ExoSeal{sup ®} vascular closure device (VCD) and manual compression (MC) in a prospective study design.MethodsPatients undergoing two planned interventions from 07/2013 to 09/2014 could participate in the study. Access closure was performed with an ExoSeal{sup ®}-VCD in one and MC in the other intervention. Patients were clinically and sonographically examined and were given questionnaires 1 day after intervention [groin- and back-pain during bedrest (100-point visual analog scale; 0: no pain); comfortability of bedrest (10-point Likert scale, 1: comfortable), satisfaction with closure (10-point Likert scale, 1: very satisfied)]. Results were analyzed in a cross-over design.Results48 patients (29 male, median age 62.5 (32–88) years) were included. An ExoSeal{sup ®}-VCD was used first in 25 cases. As four of these subsequently refused MC as second intervention, data from 44 patients could be analyzed. All closures were technically successful (successful device deployment) without major complications. Groin- and back-pain after VCD-use/MC was 0 (0–15) vs. 10 (0–80) and 0 (0–75) vs. 25 (0–90), respectively (p < 0.0001). Bedrest after VCD-use was more comfortable than after MC [1 (range 1–7) vs. 6 (2–10); p < 0.0001]. Satisfaction with the closure procedure and with the intervention in general was higher after VCD-use compared to MC [1 (1–3) vs. 5 (2–10) and 1 (1–2) vs. 2 (1–4), respectively; p < 0.0001].ConclusionIntra-individual comparison showed pain levels and discomfort to be significantly lower after ExoSeal{sup ®} use compared to MC. VCD closure was associated with higher satisfaction both with the closure itself and with the intervention in general.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

DOE OSTI2019

ISRM Suggested Method: Determining Deformation and Failure Characteristics of Rocks Subjected to True Triaxial Compression

The purpose of this ISRM Suggested Method is to introduce a guideline on determining deformation and failure characteristics of rocks subjected to true triaxial compression on different stress path. Here, the true triaxial testing apparatus was reviewed by means of the function and engineering application. Some key techniques, such as stress and strain measurements, and reduction of end effect between specimen and metal platens, preventing metal platens interference, were stated and suggested in detail. Methodology of specimen processing, specimen shape, and testing procedure are characterized. There is an explanation of the experimental data processing on stress–strain curves, strength, and fracture mode.

42 ENGINEERING↗

DOE OSTI2018

Sensible-Enthalpy-Based Conditional Moment Closure Model for Homogeneous Charge Compression Ignition with Temperature Inhomogeneity

Abstract This paper presents a sensible-enthalpy-based conditional moment closure (CMC) model for homogeneous charge compression ignition (HCCI) with temperature inhomogeneity. The focus of study is placed on the effects of a conditioning variable on the prediction of heat release rates and developing the mixing models for sensible enthalpy, a reacting scalar. The sensible-enthalpy-based CMC model is validated a priori with 2-D direct numerical simulation (DNS) data for HCCI, and compared with the total-enthalpy-based formulation. Sensible enthalpy is shown to be strongly correlated with temperature, which makes sensible enthalpy well suited for a conditioning variable in CMC for HCCI. Results show that sensible-enthalpy-based CMC performs well for the prediction of heat release rates for all temperature stratification levels investigated in this study, while total-enthalpy-based CMC leads to the overprediction of heat release rates when the temperature stratification level is high. While conditional fluctuations of species mass fractions are substantial, sensible-enthalpy-based CMC is found to accurately estimate heat release rates during ignition, as well as reaction rates of key species, due to substantially suppressed conditional temperature fluctuations. The mapping closure models for the probability density function (PDF) and conditional dissipation rates of sensible enthalpy are proposed. The proposed models are found to capture the characteristics of reactive scalar mixing.

42 ENGINEERING↗

DOE OSTI2025

Compressed Liquid (${{p}}$-${{\rho}}$-${{T}}$) Measurements of trans-1,2-Dichloroethene [R-1130(E)]

Pressure-density-temperature (${{p}}$-${{\rho}}$-${{T}}$) data for the refrigerant R-1130(E) (trans-1,2-dichloroethene) were measured in the compressed liquid phase using an automated vibrating-tube densimeter. Overall, the measurements covered temperatures from 270 K to 410 K and pressures from 0.5 MPa to 30 MPa. Relative combined, expanded (95% confidence level) uncertainties ranged from approximately 0.05% to 0.06%. Here, we present measurement results, along with comparisons to available literature data and to a generalized extended corresponding states model.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2013

Determination of interfacial mechanical properties of ceramic composites by the compression of micro-pillar test specimens

A novel method to determine the fiber-matrix interfacial properties of ceramic matrix composites is proposed and evaluated; where micro- pillar samples containing inclined fiber/matrix interfaces were prepared from a SiC fiber reinforced SiC matrix composites then compression-tested using the nano-indentation technique. This new test method employs a simple geometry and mitigates the uncertainties associated with complex stress state in the conventional single filament push-out method for the determination of interfacial properties. Based on the test results using samples with different interface orientations , the interfacial debond shear strength and the internal friction coefficient are explicitly determined and compared with values obtained by other test methods.

Shih, Chunghao↗

DOE OSTI2018

Compressed H{sub 3}S, Superfluid Density and the Quest for Room-Temperature Superconductivity

The discovery of superconductivity at 203 K in highly compressed sulphur hydride validates the ideas put forward by Ashcroft 50 years ago and galvanises the quest for room-temperature superconductivity. But at such temperatures, thermal fluctuations might be expected to break up Cooper pairs. For example, in the cuprates, fluctuations reduce T{sub c} by 30% or more below the mean-field value. Similar effects are found in iron pnictides. Here, we ask: how does superconductivity survive in sulphur hydride at such high temperatures? To answer this, we examine the superfluid density which is the key parameter for quantifying fluctuations in both amplitude and phase. We show that dimensionality plays a key role in suppressing or enhancing thermal fluctuations to the benefit of hydrogen sulphide and the detriment of its more layered 2D competitors. We find that the temperature scale for phase fluctuations, T{sub φ}, in superconducting H{sub 3}S exceeds 1200 K, and therefore, these are irrelevant at 200 K. But the amplitude fluctuation temperature scale, T{sub amp}, at around 300 K is much lower and this has important implications for the ongoing quest for room temperature superconductivity. Appealing to the way in which superfluid density, T{sub φ}, T{sub amp} and T{sub c} scale with each other it seems that room temperature superconductivity is nearly ruled out, but perhaps not quite. It will require 3D systems with a large Fermi velocity to achieve this goal.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2017

Slip Boundary Conditions for the Compressible Navier–Stokes Equations

The slip boundary conditions for the compressible Navier–Stokes equations are derived systematically from the Boltzmann equation on the basis of the Chapman–Enskog solution of the Boltzmann equation and the analysis of the Knudsen layer adjacent to the boundary. The resulting formulas of the slip boundary conditions are summarized with explicit values of the slip coefficients for hard-sphere molecules as well as the Bhatnagar–Gross–Krook model. These formulas, which can be applied to specific problems immediately, help to prevent the use of often used slip boundary conditions that are either incorrect or without theoretical basis.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2026

Memory-efficient nonsmooth dynamic optimization using adaptive randomized compression

Dynamic optimization problems arise in many applications including flow control, full waveform inversion, and medical imaging. These problems are plagued by significant computational challenges. One such challenge — and the focus of this work — is the memory limitation induced by the size of the underlying dynamical system. In particular, the entire dynamic trajectory is required for derivative computation and therefore must be stored or recomputed using, e.g., checkpointing. Although recent work demonstrated the use of adaptive randomized sketching to overcome the memory challenge, that work only applies to smooth unconstrained problems, prohibiting its use for nonsmooth regularized and constrained problems. The inclusion of nonsmooth regularizers and constraints is critical as they often arise in an attempt to preserve certain physical properties or to promote sparsity. To solve these problems, we introduce a trust-region algorithm for minimizing the sum of a smooth nonconvex function and a nonsmooth convex function that leverages randomized sketching to compress the dynamical system trajectories and adaptively adjust the sketch rank to satisfy a gradient inexactness condition. We prove convergence of this algorithm and demonstrate that it achieves substantial memory reduction on three discretized PDE-constrained optimization applications.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2025

Characterization of Recrystallized Grains During Static Recrystallization of Hot-Compressed Mg–Zn–Ca Alloys Using In Situ Far-Field High-Energy Diffraction Microscopy

In this study, we explored the effect of Zn content on the static recrystallization of three 80 pct hot-compressed alloys, Mg–0.5Zn–0.1Ca wt pct (ZX050), Mg–1Zn–0.1Ca wt pct (ZX10), and Mg–3.2Zn–0.1Ca wt pct (ZX30), using far-field high-energy microscopy (ff-HEDM). Individual recrystallized grains were tracked and their 3D centroid, relative volume, and grain-averaged crystallographic orientation were measured during annealing. These measurements were used to compare the recrystallization kinetics and texture evolution of recrystallized grains in ZX alloys as a function of the Zn content. Fully recrystallized microstructures were observed for the ZX30 and the ZX10 alloys after annealing at 230 °C and 330 °C, respectively. In contrast, only a partially recrystallized microstructure for the ZX050 alloy was observed after > 1 hour of annealing at 430 °C. The resistance to recrystallization with decreasing Zn content was also confirmed by detecting faster growth rates of recrystallized grains in the ZX10 and ZX30 alloys, and slower growth rates in the ZX050 alloy. The significant recrystallization texture weakening of the ZX10 and ZX30 alloys and the development of a basal texture in the ZX05 alloy were described based on the orientation dependency of nucleation and growth of recrystallized grains. The analysis demonstrated that texture weakening was associated with increasing Zn content in Mg–Zn–Ca alloys.

Roumina, Reza [Univ. of Michigan, Ann Arbor, MI (U↗