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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

In-medium similarity renormalization group with flowing 3-body operators, and approximations thereof

Here, we explore the impact of retaining three-body operators within the in-medium similarity renormalization group (IMSRG), as well as various approximations schemes. After studying two toy problems, identical fermions with a contact interaction and the Lipkin-Meshkov-Glick model, we employ the valence-space formulation of the IMSRG to investigate the even- A carbon isotopes with a chiral two-body potential. We find that retaining only those commutators expressions that scale as N 7 provides an excellent approximation of the full three-body treatment.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Anatomy of $tthh$ physics at the HL-LHC

The t t h h production at colliders contains rich information on the nature of the Higgs boson. In this article, we systematically studied its physics at the high-luminosity Large Hadron Collider (HL-LHC), using exclusive channels with multiple ( ≥ 5 ) b -jets and one lepton ( 5 b 1 ℓ ), multiple ( ≥ 5 ) b -jets and opposite-sign dilepton ( 5 b 2 ℓ ), same-sign dilepton ( SS 2 ℓ ), multiple leptons (multi- ℓ ), and ditau resonance ( τ τ ). The scenarios analyzed include: (1) the t t h h production in Standard Model; (2) the t t h h production mediated by anomalous cubic Higgs self-coupling and t t h h contact interaction; (3) heavy Higgs ( H ) production with t t H → t t h h ; and (4) pair production of fermionic top partners ( T ) with T T → t t h h . To address the complication of event topologies and the mess of combinatorial backgrounds, a tool of boosted-decision-tree was applied in the analyses. The 5 b 1 ℓ and SS 2 ℓ analyses define the two most promising channels. For the nonresonant t t h h production, a combination of these exclusive analyses allows for its measurement in the SM with a statistical significance ~ 0.9 σ (with S / B > 1 % ), and may partially break the sensitivity degeneracy with respect to a varying cubic Higgs self-coupling, a difficulty usually thought to exist in gluon fusion di-Higgs analysis at HL-LHC. These sensitivities were also projected to future hadron colliders at 27 TeV and 100 TeV. For the resonant t t h h productions, the heavy Higgs boson in type II two-Higgs-doublet-model could be efficiently searched for between the mass thresholds 2 m h < m H < 2 m t and even beyond that, for relatively small tan β (vacuum alignment), while the fermionic top partners in composite Higgs models could be probed up to ~ 1.5 TeV and ~ 1.7 TeV , for Br ( T → t h ) = 25 % and 50%, respectively.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Inflaton production of scalar dark matter through fluctuations and scattering

We study the effects on particle production of a Planck-suppressed coupling between the inflaton and a scalar dark matter candidate, X. In the absence of this coupling the dominant source for the relic density of X is the long wavelength modes produced from the scalar field fluctuations during inflation. In this case, there are strong constraints on the mass of the scalar and the reheating temperature after inflation from the present-day relic density of X (assuming X is stable). When a coupling σ⁢Φ 2 ⁢X 2 is introduced, with σ = ˜σm$^{2}_{Φ}$/$M$$^{2}_{P}$ ~10 –10 ⁢ ˜σ, where m Φ is the inflaton mass, the allowed parameter space begins to open up considerably even for ˜σ as small as ≳10 –7 . For ˜σ ≳ $\frac{9}{16}$, particle production is dominated by the scattering of the inflaton condensate, either through single graviton exchange or the contact interaction between Φ and X. In this regime, the range of allowed masses and reheating temperatures is maximal. For 0.004 < ˜σ < 50, constraints from isocurvature fluctuations are satisfied, and the production from parametric resonance can be neglected.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Toward extracting scattering phase shift from integrated correlation functions. III. Coupled channels

The formalism developed in the preceding papers that connects integrated correlation function of a trapped two-particle system to infinite volume scattering phase shift is further extended to coupled-channel systems in the present work. Using a trapped nonrelativistic two-channel system as an example, a new relation is derived that retains the same structure as in the single channel, and has explicit dependence on the phase shifts in both channels but not on the inelasticity. The relation is illustrated by a exactly solvable coupled-channel quantum mechanical model with contact interactions. It is further validated by path integral Monte Carlo simulation of a quasi-one-dimensional model that can admit general interaction potentials. In all cases, we found rapid convergence to the infinite volume limit as the trap size is increased, even at short times, making it potentially a good candidate to overcome signal-to-noise issues in Monte Carlo applications. Published by the American Physical Society 2025

Guo, Peng (ORCID:0000000265660881)↗
DOE OSTI2023

Rheology of dense fiber suspensions: Origin of yield stress, shear thinning, and normal stress differences

We explain the origins of yield stress, shear thinning, and normal stress differences in rigid fiber suspensions. We investigate the interplay between the hydrodynamic, noncontact attractive and repulsive, and interfiber contact interactions. The shear-thinning viscosity and finite yield stress obtained from the Immerse Boundary Method simulations are in quantitative agreement with experiential results from the literature. In this study, we show that attractive interactions result in yield stress and shear thinning rheology in the suspensions of rigid fibers. This is an important finding, given the ongoing discussion regarding the origin of the yield stress for suspensions of fibers. Finally, the ability of the proposed model to quantitatively predict the rheology is not limited to only shear thinning and yield stress but also extends to normal stresses.

42 ENGINEERING↗
DOE OSTI2020

Pairing Correlations across the Superfluid Phase Transition in the Unitary Fermi Gas

In the two-component Fermi gas with a contact interaction, a pseudogap regime can exist at temperatures between the superfluid critical temperature $T_c$ and a temperature $T^\ast > T_c$. This regime is characterized by pairing correlations without superfluidity. However, in the unitary limit of infinite scattering length, the existence of this regime is still debated. To help address this, we have applied finite-temperature auxiliary-field quantum Monte Carlo (AFMC) methods to study the thermodynamics of the superfluid phase transition and signatures of the pseudogap in the spin-balanced homogeneous unitary Fermi gas. We present results at finite filling factor $\textit{ν}$ ≃ 0.06 for the condensate fraction, an energy-staggering pairing gap, the spin susceptibility, and the heat capacity, and compare them to experimental data when available. In contrast to previous AFMC simulations, our model space consists of the complete first Brillouin zone of the lattice, and our calculations are performed in the canonical ensemble of fixed particle number. The canonical ensemble AFMC framework enables the calculation of a model-independent gap, providing direct information on pairing correlations without the need for numerical analytic continuation. We use finite-size scaling to estimate $T_c$ at the corresponding filling factor. In this work, we find that the energy-staggering pairing gap vanishes above $T_c$, showing no pseudogap effects, and that the spin susceptibility shows a substantially reduced signature of a spin gap compared to previously reported AFMC simulations.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

SU(1,1) Echoes for Breathers in Quantum Gases

Though the celebrated spin echoes have been widely used to reverse quantum dynamics, they are not applicable to systems whose constituents are beyond the control of the su(2) algebra. In this work, we design echoes to reverse quantum dynamics of breathers in three-dimensional unitary fermions and two-dimensional bosons and fermions with contact interactions, which are governed by an underlying su(1, 1) algebra. Geometrically, SU(1, 1) echoes produce closed trajectories on a single or multiple Poincaré disks and thus could recover any initial states without changing the sign of the Hamiltonian. In particular, the initial shape of a breather determines the superposition of trajectories on multiple Poincaré disks and whether the revival time has period multiplication. Our work provides physicists with a recipe to tailor collective excitations of interacting many-body systems.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2025

Solving reaction dynamics with quantum computing algorithms

The description of quantum many-body dynamics is extremely challenging on classical computers, as it can involve many degrees of freedom. However, the time evolution of quantum states is a natural application for quantum computers that are designed to efficiently perform unitary transformations. Here, in this paper, we study quantum algorithms for response functions, relevant for describing different reactions governed by linear response. We focus on nuclear-physics applications and consider a qubit-efficient mapping on the lattice, which can efficiently represent the large volumes required for realistic scattering simulations. For the case of a contact interaction, we develop an algorithm for time evolution based on the Trotter approximation that scales logarithmically with the lattice size and is combined with quantum phase estimation. We eventually focus on the nuclear two-body system and a typical response function relevant for electron scattering as an example. We also investigate ground-state preparation and examine the total circuit depth required for a realistic calculation and the hardware noise level required to interpret the signal.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Fourfold alkyl wrapping of a copper(II) porphyrin thwarts macrocycle π–π stacking in a compact supramolecular package

Porphyrins are valuable constituents in optoelectronic, catalytic, and other applications, yet control of intermolecular π–π stacking is invariably essential to attain the desired properties. Superstructures built onto the porphyrin, often via meso -aryl groups, can afford facial encumbrance that suppresses π–π stacking, although some molecular designs have provided insufficient facial coverage and many have entailed cumbersome syntheses. In this study, a copper(II) porphyrin bearing four meso substituents, namely, {10,20-bis[2,6-bis(octyloxy)phenyl]-5,15-dibromoporphinato}copper(II), [Cu(C 64 H 82 Br 2 N 4 O 4 )], was prepared by metalation of the corresponding free-base porphyrin and was characterized by single-crystal X-ray diffraction. The crystal structure reveals a dihedral angle of 111.1 (2)° for the plane of the meso -aryl group relative to the plane of the porphyrin, with both aryl groups tilted in the same direction. Each of the four octyloxy groups exhibits a gauche conformation for the –OCH 2 CH 2 – unit but is extended with four or five anti (–CH 2 CH 2 –/H) conformations thereafter, causing each octyl group to span the dimension of the macrocycle. In a global frame of reference where the two Br atoms define the north/south poles and the two aryl groups are at antipodes on the equator, two octyl groups of one aryl unit project over the northern hemisphere (covering pyrroles A and B ), whereas those of the other aryl unit project over the southern hemisphere (covering pyrroles C and D ). Together, the four octyl groups ensheath the two faces of the porphyrin in a self-wrapped assembly. The closest approach of the Cu atom to an octyl methylene C atom (position 6) is 3.5817 (18) Å, the mean separations of neighboring porphyrin planes are 8.059 (4) and 4.693 (8) Å along the a and c axes, respectively, and the center-to-center distances between the Cu atoms of neighboring porphyrins are 10.2725 (4), 12.2540 (6), and 12.7472 (6) Å along the a , b , and c axes, respectively. The Hirshfeld surface analysis and two-dimensional (2D) fingerprint plots provide information concerning contact interactions in the supramolecular assembly of the solid crystal.

Chemistry↗
DOE OSTI2022

Modeling and Analysis of a Novel Offshore Binary Species Free-Floating Longline Macroalgal Farming System

The investigation of innovative macroalgal cultivation is important and needed to optimize farming operations, increase biomass production, reduce the impact on the ecosystem, and lower system and operational costs. However, most macroalgal farming systems (MFSs) are stationary, which need to occupy a substantial coastal area, require extensive investment in farm infrastructure, and cost high fertilizer and anchoring expenses. This study aims to model, analyze, and support a novel binary species free-floating longline macroalgal cultivation concept. The expected outcomes could provide a basis for the design and application of the novel MFS to improve biomass production, decrease costs, and reduce the impact on the local ecosystem. In this paper, Saccharina latissima and Nereocystis luetkeana were modeled and validated, and coupled with longline to simulate the binary species MFS free float in various growth periods and associated locations along the US west coast. Further, the numerical predictions indicated the possibility of failure on the longline and breakage at the kelp holdfasts is low. However, the large forces due to an instantaneous change in dynamic loads caused by loss of hydrostatic buoyancy when the longline stretches out of the water would damage the kelps. Buoy-longline contact interactions could damage the buoy, resulting in the loss of the system by sinking. Furthermore, the kelp-longline and kelp-kelp entanglements could potentially cause kelp damage.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

New physics in rare B decays after Moriond 2021

Abstract The anomalies in rare B decays endure. We present results of an updated global analysis that takes into account the latest experimental input – in particular the recent results on $$R_K$$ R K and BR $$(B_s \rightarrow \mu ^+\mu ^-)$$ ( B s → μ + μ - ) – and that qualitatively improves the treatment of theory uncertainties. Fit results are presented for the Wilson coefficients of four-fermion contact interactions. We find that muon specific Wilson coefficients $$C_9 \simeq -0.73$$ C 9 ≃ - 0.73 or $$C_9 = -C_{10} \simeq -0.39$$ C 9 = - C 10 ≃ - 0.39 continue to give an excellent description of the data. If only theoretically clean observables are considered, muon specific $$C_{10} \simeq 0.60$$ C 10 ≃ 0.60 or $$C_9=-C_{10} \simeq -0.35$$ C 9 = - C 10 ≃ - 0.35 improve over the Standard Model by $$\sqrt{\Delta \chi ^2} \simeq 4.7\sigma $$ Δ χ 2 ≃ 4.7 σ and $$\sqrt{\Delta \chi ^2} \simeq 4.6\sigma $$ Δ χ 2 ≃ 4.6 σ , respectively. In various new physics scenarios we provide predictions for lepton flavor universality observables and CP asymmetries that can be tested with more data. We update our previous combination of ATLAS, CMS, and LHCb data on BR $$(B_s \rightarrow \mu ^+\mu ^-)$$ ( B s → μ + μ - ) and BR $$(B^0\rightarrow \mu ^+\mu ^-)$$ ( B 0 → μ + μ - ) taking into account the full two-dimensional non-Gaussian experimental likelihoods.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2023

Versatility and Complexity: Common and Uncommon Facets of LysR-Type Transcriptional Regulators

LysR-type transcriptional regulators (LTTRs) form one of the largest families of bacterial regulators. They are widely distributed and contribute to all aspects of metabolism and physiology. Most are homotetramers, with each subunit composed of an N-terminal DNA-binding domain followed by a long helix connecting to an effector-binding domain. LTTRs typically bind DNA in the presence or absence of a small-molecule ligand (effector). In response to cellular signals, conformational changes alter DNA interactions, contact with RNA polymerase, and sometimes contact with other proteins. Many are dual-function repressor–activators, although different modes of regulation may occur at multiple promoters. This review presents an update on the molecular basis of regulation, the complexity of regulatory schemes, and applications in biotechnology and medicine. The abundance of LTTRs reflects their versatility and importance. While a single regulatory model cannot describe all family members, a comparison of similarities and differences provides a framework for future study.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Assessment of MOOSE-Based Tools for Calculating Radial Core Expansion

Radial core expansion in liquid-metal cooled fast reactor systems is a well-known phenomenon that produces strong reactivity feedback effects. An inherently safe reactor design takes advantage of negative reactivity feedback in accident scenarios by utilizing a core restraint system which produces a bowed shape that allows for radial expansion of the fuel regions. Detailed modeling and simulation of core radial expansion itself as well as subsequent reactivity feedback is a challenging task involving contact of many fuel assembly elements and physics feedback from neutronics, thermal hydraulics, and thermal mechanical response. A variety of physics codes have been developed to model aspects of radial core expansion but in general invoke geometrical or physics approximations. No code system currently exists which tightly and robustly couples these physics with enough detail to fully resolve the complex core radial expansion reactivity feedback effects. The future availability of such a code system is of vital importance to fully understanding the reactivity feedback effects that occur due to radial expansion, and consequently to optimizing the design of the core restraint system. A high-fidelity code will also be used to benchmark existing lower fidelity, faster running models to understand their benefits, limitations, and range of applications. A code development path using MOOSE-based tools is proposed in order to leverage the detailed geometry capabilities and natural tight coupling and robustness of MOOSE-based applications for modeling this complex phenomena. While simulation of the full phenomenon involves several physics, an assessment has been initiated on the capabilities and readiness of the currently available Tensor Mechanics module within MOOSE for calculation of the structural mechanical responses which occur within the reactor core. This report focuses on modeling the force-deformation response which mimics the physics of a duct contact deformation, as well as differential thermal expansion which produces a thermal bowed shaped for the fuel assemblies in a core. Simple examples were initially performed such as simple supported beam bending under load. The complexity of examples was progressively increased to better mimic the duct behavior by including a differential thermal example and inclusion of hexagonal cross-sections in the geometry. Further assessment of the structural mechanical response simulation capability is still required for modeling duct contact interactions and irradiation creep and swelling. Companion thermal hydraulic and neutronics assessments will also be required; these activities are planned for future years. Finally, integration of the multiple physics components through MOOSE is required to predict the core radial expansion and subsequent feedback effects.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2023

Rheology of dense fiber suspensions: Origin of yield stress, shear thinning, and normal stress differences

We use high-fidelity computational model of fiber suspension to investigate suspension rheology. We investigate the interplay between the hydrodynamic, noncontact attractive and repulsive, and interfiber contact interactions. The shear-thinning viscosity and finite yield stress obtained from the Immerse Boundary Method simulations align quantitatively with experimental findings from the literature. The study demonstrates that attractive interactions lead to both yield stress and shear thinning behavior in rigid fiber suspensions. This discovery holds significance as it contributes to the ongoing debate on the source of yield stress in fiber suspensions. The proposed model is used to quantify normal stresses in addition to shear thinning and yield stress.

Ardekani, Arezoo↗
NASA NTRS1979

Global operators for delta functions - Extension to scattering states and the inclusion of spin

The paper presents an extension of the identities of Hiller, Sucher, and Feinberg for the evaluation of bound-state matrix elements of delta function operators, to scattering states. Attention is given to the technical difficulties encountered in the application of the scattering-state identities and how they can be overcome, including infrared singularities which arise if Coulomb forces are present and the velocity of the incident particle is small. In addition, both the scattering and bound-state identities are generalized to include spin-dependent contact interactions and spin-dependent Hamiltonians. Finally, it is stressed that the identities can be used to improve the accuracy of calculations of interest for diverse physical phenomena, ranging from positron annihilation to hyperfine structure.

Sucher, J.↗
NASA NTRS1987

Laser magnetic resonance in supersonic plasmas - The rotational spectrum of SH(+)

The rotational spectrum of v = 0 and v = 1X3Sigma(-)SH(+) was measured by laser magnetic resonance. Rotationally cold (Tr = 30 K), vibrationally excited (Tv = 3000 K) ions were generated in a corona excited supersonic expansion. The use of this source to identify ion signals is described. Improved molecular parameters were obtained; term values are presented from which astrophysically important transitions may be calculated. Accurate hyperfine parameters for both vibrational levels were determined and the vibrational dependence of the Fermi contact interaction was resolved. The hyperfine parameters agree well with recent many-body perturbation theory calculations.

Hovde, David C.↗
NASA NTRS1990

Statistical mechanics models for motion and force planning

The models of statistical mechanics provide an alternative to the methods of classical mechanics more traditionally used in robotics. They have a potential to: improve analysis of object collisions; handle kinematic and dynamic contact interactions within the same frmework; and reduce the need for perfect deterministic world model information. The statistical mechanics models characterize the state of the system as a probability density function (p.d.f.) whose time evolution is governed by a partial differential equation subject to boundary and initial conditions. The boundary conditions when rigid objects collide reflect the conservation of momentum. The models are being developed to embedd in remote semi-autonomous systems with a need to reason and interact with a multiobject environment.

Rodriguez, G.↗
NASA NTRS1991

Industrial Code Development

The industrial codes will consist of modules of 2-D and simplified 2-D or 1-D codes, intended for expeditious parametric studies, analysis, and design of a wide variety of seals. Integration into a unified system is accomplished by the industrial Knowledge Based System (KBS), which will also provide user friendly interaction, contact sensitive and hypertext help, design guidance, and an expandable database. The types of analysis to be included with the industrial codes are interfacial performance (leakage, load, stiffness, friction losses, etc.), thermoelastic distortions, and dynamic response to rotor excursions. The first three codes to be completed and which are presently being incorporated into the KBS are the incompressible cylindrical code, ICYL, and the compressible cylindrical code, GCYL.

Shapiro, Wilbur↗