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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Molecular Insight into the Effects of Clustering on the Dynamics of Ionomers in Solutions

Ionizable groups tethered to polymers enable their many current and potential applications. However, these functionalities drive the formation of physical networks through clustering of the ionic groups, resulting in constrained dynamics of the macromolecules. Understanding the molecular origin of this hindrance remains a critical fundamental question, whose solution will directly impact the processing of ionizable polymers from molecules to viable materials. Here, in this work, using quasielastic neutron scattering accompanied by molecular dynamics simulations, segmental dynamics of slightly sulfonated polystyrene is studied in solutions as the cohesion of the ionic assemblies is tuned. We find that in cyclohexane the ionic assemblies act as centers of confinement, affecting dynamics both on macroscopic lengths and in the vicinity of the ionic assemblies. Addition of a small amount of ethanol affects the packing of the ionizable groups within the assemblies, which in turn enhances the chain dynamics.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Dynamic modification of pore opening of SAPO-34 by adsorbed surface methoxy species during induction of catalytic methanol-to-olefins reactions

Here, we report that the pore opening of SAPO-34 can be significantly modified by an adsorbed surface methoxy species during induction of the catalytic methanol-to-olefins process, which offers molecular sieving properties due to physical obstacle of the methoxy group and its adsorption modification to other hydrocarbons. X-ray powder diffraction and Rietveld refinement clearly reveal that the adsorbed single carbon atom as the methoxy group is dynamically created from methanol dehydration on a Brønsted acid site in close proximity to the pore windows. As a result, industrial desirable smaller olefins such as ethylene and propylene can be favourably made at the expenses of higher olefins. The structures and fundamental understanding in alteration in the olefins selectivity during induction may allow rational optimisation in catalytic performance under the complex fluidisation conditions.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2018

SolarPILOT: A power tower solar field layout and characterization tool

This paper develops and demonstrates a new SolarPower tower Integrated Layout and Optimization Tool (SolarPILOT). The tool uses the analytical flux image Hermite series approximation originally implemented in the DELSOL3 software developed by Sandia National Laboratory in the early 1980s. By applying the analytical model to individual heliostat images rather than large groups or zones of heliostats, SolarPILOT can characterize a wide variety of heliostat field layouts. The individual heliostat modeling approach increases computational expense in comparison with DELSOL3, so SolarPILOT implements a number of improvements to the analytical approximation method to improve model accuracy and computational efficiency. This paper discusses several of these methods, including dynamic heliostat grouping to reduce the expense of intercept factor evaluation, approximation of annual productivity with a subset of time steps throughout the year, polygon clipping to accurately calculate inter-heliostat shadowing and blocking, receiver and tower geometry optimization, and a trigonometric image transformation technique that ensures model accuracy for small heliostats. SolarPILOT also integrates a Monte-Carlo ray tracing engine (SolTrace), providing improved receiver optical modeling capability, a user-friendly front end for geometry definition, and side-by-side validation of the analytical algorithms.

14 SOLAR ENERGY↗
DOE OSTI2017

Quantum groups as generalized gauge symmetries in WZNW models. Part I. The classical model

Wess-Zumino-Novikov-Witten (WZNW) models over compact Lie groups G constitute the best studied class of (two dimensional, 2D) rational conformal field theories (RCFTs). A WZNW chiral state space is a finite direct sum of integrable representations of the corresponding affine (current) algebra, and the correlation functions of primary fields are monodromy invariant combinations of left times right sector conformal blocks solving the Knizhnik-Zamolodchikov equation. However, even in this very well understood case of 2D RCFT, the “internal” (gauge) symmetry that governs the ensuing fusion rules remains unclear. On the other hand, the canonical approach to the classical chiral WZNW theory developed by Faddeev, Alekseev, Shatashvili, Gawedzki and Falceto reveals its Poisson-Lie symmetry. After a covariant quantization, the latter gives rise to an associated quantum group symmetry which naturally requires an extension of the state space. This paper contains a review of earlier work on the subject with a special emphasis, in the case G = SU(n), on the emerging chiral “WZNW zero modes” which provide an adequate algebraic description of the internal symmetry structure of the model. Combining further left and right zero modes, one obtains a specific dynamical quantum group, the structure of its Fock representation resembling the axiomatic approach to gauge theories in which a “restricted” quantum group plays the role of a generalized gauge symmetry.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Control of multi-agent systems: Results, open problems, and applications

The purpose of this review article is to present some recent results on the modeling and control of large systems of agents. We focus on particular applications where the agents are capable of independent actions instead of simply reacting to external forces. In the literature, such agents were referred to as autonomous, intelligent, self-propelled, greedy, and others. The main applications we have in mind are social systems (as opinion dynamics), pedestrians’ movements (also called crowd dynamics), animal groups, and vehicular traffic. We note that the last three examples include physical constraints; however, the agents are able to inject energy into the system, thus preventing the typical conservation of momentum and energy. In addition, the control problems posed by such systems are new and require innovative methods. We illustrate some ideas developed recently, including the use of sparse controls, limiting the total variation of controls, and defining new control problems for measures. After reviewing various approaches, we discuss some future research directions of potential interest. The latter encompasses both new types of equations and new types of limiting procedures to connect several scales at which a system can be represented. We conclude by illustrating a recent real-life experiment using autonomous vehicles on an open highway to smooth traffic waves. This opens the door to a new era of interventions to control real-time multi-agent systems and to increase the societal impact of such interventions guided by control research.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2017

Galaxy And Mass Assembly (GAMA): A “No Smoking” Zone for Giant Elliptical Galaxies?

We study the radio emission of the most massive galaxies in a sample of dynamically relaxed and unrelaxed galaxy groups from the Galaxy and Mass Assembly survey. The dynamical state of the group is defined by the stellar dominance of the brightest group galaxy (BGG), e.g., the luminosity gap between the two most luminous members, and the offset between the position of the BGG and the luminosity centroid of the group. We find that the radio luminosity of the largest galaxy in the group strongly depends on its environment, such that the BGGs in dynamically young (evolving) groups are an order of magnitude more luminous in the radio than those with a similar stellar mass but residing in dynamically old (relaxed) groups. This observation has been successfully reproduced by a newly developed semi-analytic model that allows us to explore the various causes of these findings. We find that the fraction of radio-loud BGGs in the observed dynamically young groups is ∼2 times that of the dynamically old groups. We discuss the implications of this observational constraint on the central galaxy properties in the context of galaxy mergers and the super massive black hole accretion rate.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Quantum complexity in gravity, quantum field theory, and quantum information science

Quantum complexity quantifies the difficulty of preparing a state or implementing a unitary transformation with limited resources. Applications range from quantum computation to condensed matter physics and quantum gravity. Here, we seek to bridge the approaches of these fields, which define and study complexity using different frameworks and tools. We describe several definitions of complexity, along with their key properties. In quantum information theory, we focus on complexity growth in random quantum circuits. In quantum many-body systems and quantum field theory (QFT), we discuss a geometric definition of complexity in terms of geodesics on the unitary group. In dynamical systems, we explore a definition of complexity in terms of state or operator spreading, as well as concepts from tensor-networks. We also outline applications to simple quantum systems, quantum many-body models, and QFTs including conformal field theories (CFTs). Finally, we explain the proposed relationship between complexity and gravitational observables within the holographic anti-de Sitter (AdS)/CFT correspondence.

Baiguera, Stefano [Istituto Nazionale di Fisica Nu↗
DOE OSTI2016

Structural and Functional Influence of the Glycine-Rich Loop G 302 GGGY on the Catalytic Tyrosine of Histone Deacetylase 8

Histone deacetylase 8 (HDAC8) catalyzes the hydrolysis of acetyl-l-lysine to yield products l-lysine and acetate through a mechanism in which a nucleophilic water molecule is activated by a histidine general base and a catalytic metal ion (Zn 2+ or Fe 2+ ). Acetyl-l-lysine also requires activation by metal coordination and a hydrogen bond with catalytic tyrosine Y306, which also functions in transition state stabilization. Interestingly, Y306 is located in the conserved glycine-rich loop G 302 GGGY. The potential flexibility afforded by the tetraglycine segment may facilitate induced-fit conformational changes in Y306 between “in” and “out” positions, as observed in related deacetylases. To probe the catalytic importance of the glycine-rich loop in HDAC8, we rigidified this loop by preparing the G302A, G303A, G304A, and G305A mutants and measured their steady state kinetics and determined their X-ray crystal structures. Substantial losses of catalytic efficiency are observed (10–500-fold based on kcat/KM), particularly for G304A HDAC8 and G305A HDAC8. These mutants also exhibit the greatest structural changes for catalytic tyrosine Y306 (1.3–1.7 Å shifts of the phenolic hydroxyl group). Molecular dynamics simulations further indicate that G304 and G305 undergo pronounced structural changes as residue 306 undergoes a transition between “in” and “out” conformations. Thus, the G304A and G305A substitutions likely compromise the position and conformational changes of Y306 required for substrate activation and transition state stabilization. Here, the G302A and G303A substitutions have less severe catalytic consequences, and these substitutions may influence an internal channel through which product acetate is believed to exit.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Heterogeneous Electron-Transfer Dynamics through Dipole-Bridge Groups

Heterogeneous electron transfer (HET) between photoexcited molecules and colloidal TiO 2 has been investigated for a set of zinc porphyrin chromophores attached to the semiconductor by linkers that allow the level alignment to be changed by 200 meV through reorientation of the dipole moment. These unique dye molecules were studied by femtosecond transient absorption spectroscopy in solution and adsorbed on a TiO 2 colloidal film in a vacuum. In solution, energy transfer from the excited chromophore to the dipole group was identified as a slow relaxation pathway competing with S 2 –S 1 internal conversion. On the film, heterogeneous electron transfer was found to occur in 80 fs, much faster than all intramolecular pathways. Despite a difference of 200 meV in level alignment of the excited state with respect to the semiconductor conduction band, identical electron-transfer times were measured for different linkers. The measurements were then compared to a quantum-mechanical model that accounts for electronic–vibronic coupling and a finite bandwidth for the acceptor states. We conclude that HET occurs into a distribution of transition states that differ from regular surface states or bridge-mediated states.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Spatiotemporal quenches for efficient critical ground state preparation in the two-dimensional transverse field Ising model

Quantum simulators have the potential to shed light on the study of quantum many-body systems and materials, offering unique insights into various quantum phenomena. Although adiabatic evolution has been conventionally employed for state preparation, it faces challenges when the system evolves too quickly or the coherence time is limited. In such cases, shortcuts to adiabaticity, such as spatiotemporal quenches, provide a promising alternative. This paper numerically investigates the application of spatiotemporal quenches in the two-dimensional transverse field Ising model with ferromagnetic interactions, focusing on the emergence of the ground state and its correlation properties at criticality when the gap vanishes. We demonstrate the effectiveness of these quenches in rapidly preparing ground states in critical systems. Our simulations reveal the existence of an optimal quench front velocity at the emergent speed of light, leading to minimal excitation energy density and correlation lengths of the order of finite system sizes we can simulate. These findings emphasize the potential of spatiotemporal quenches for efficient ground state preparation in quantum systems, with implications for the exploration of strongly correlated phases and programmable quantum computing.

2-dimensional systems↗
DOE OSTI2025

A Novel Approach for Computing Rigid Body Motion Using Linear Accelerations

Here, a novel approach is presented for computing general rigid body motion based on a few known linear accelerations. This method utilizes linear acceleration data obtained from three distinct points on the body, all within a body-fixed reference frame. The only requirement is that the three chosen points must not be collinear. A system of differential-algebraic equations is derived, combining principles of rigid body kinematics with theory of the rotation group SO(3). These equations provide a framework for numerically computing various motion parameters, including angular velocity, angular acceleration, body orientation, velocity field, acceleration field, and displacement field. By numerically solving this system of equations, we can fully characterize rigid body motion in three-dimensional space. A numerical example is provided to demonstrate the practical implementation and efficacy of the proposed technique, illustrating its potential for accurate motion computation in various applications.

42 ENGINEERING↗
DOE OSTI2022

Integrated Optimization and Control of a Hybrid Gas Turbine/sCO 2 Power System

During phase-I, the project team led by Echogen Power Systems (EPS) had two primary objectives based on investigating the application of gas turbines with supercritical carbon dioxide (sCO 2 ) power cycles. The first objective was to improve the overall efficiency and performance of a hybrid gas turbine/sCO 2 power system through a joint optimization of the two subsystems (gas turbine and sCO 2 power cycle) using non-linear optimization techniques that simultaneously evaluate thermal performance of the combined cycle. The hybrid power system included several points of interaction, including (but not limited to) gas turbine exhaust, fuel heating, inlet chilling and turbine cooling. The second objective was to establish a baseline transient response model of the hybrid power system and a notional microgrid and begin steps to integrate the control systems of the three major elements (gas turbine, sCO 2 cycle and grid controller). The project team established a baseline performance for a combined cycle power plant using a production gas turbine and scaled sCO 2 power cycle only utilizing exhaust heat recovery. Echogen’s non-linear techno-economic optimization code was extended by adding gas turbine component models derived from a in-house developed gas turbine design code. With the two cycles coupled by the gas turbine exhaust, design parameters of both cycles were allowed to vary simultaneously to determine performance opportunity versus isolated designs. Returning to the baseline gas turbine/sCO 2 power cycle transient models: Echogen had in-house developed sCO 2 cycle transient model in GT-Suite system simulation software, and had partnered with Siemens Finspång for gas turbine transient model, and Siemens PTI group to provide micro-grid load profile as well as hybrid power cycle generated load (power and frequency) analysis. The transient model for the SGT-750 Siemens gas turbine was a “black-box” functional mock-up interface (FMI) model developed by Siemens Industrial Turbomachinery in Finspång, Sweden. The SGT-750 is a twin-shaft gas turbine that produces 40 MW electricity with an efficiency of about 40% at ISO conditions. At 100% gas turbine throttle (load), the SGT-750 has average exhaust conditions of 114.6 kg/s and 469.8°C. The transient model for sCO 2 power cycle was developed by Echogen in GT-SUITE 1D system simulation software platform. The basic CO 2 flow circuit has single-shaft turbomachinery with net 11.5 MW electrical power output at design conditions. The power turbine has a double-ended shaft with one end connected to synchronous generator through a fixed-ratio gearbox. The other end of power turbine is connected to the compressor through a continuously variable transmission. The major components of the sCO 2 power cycle modeled include air cooled condenser/cooler, CO 2 compressor, recuperator, two waste heat exchanger coils, power turbine, continuous variable transmission, gearbox and generator. Integration of SGT-750 transient model and sCO 2 power cycle transient model was done in Matlab Simulink. In the integrated model, the gas turbine and sCO 2 power cycle interacted at two points, first one being the gas turbine exhaust gas flow rate and temperature, which were inputs to sCO 2 power cycle model. The second point was the distribution of micro-grid load demand signal between the SGT-750 generator and sCO 2 cycle generator. For a given combined-cycle load demand, the gas turbine load demand was equal to the total demand minus the sCO 2 cycle power generated. In the present study the integrated model was simulated for two cases of grid load demand: (i) for a step change, both positive-step and negative-step, in grid load demand (ii) for a micro-grid load demand curve provided by Siemens PTI group. Finally, the time series plots representing load demand versus integrated system response were presented including the sCO 2 power cycle control system performance plots. The actual generated power and frequency of both the generators, gas turbine and sCO 2 power cycle, was supplied to Siemens PTI group for dynamic grid assessment, results of which are provided in appendices.

03 NATURAL GAS↗
DOE OSTI2022

NNSA Advanced Photon Source Sector Opportunities Workshop (Workshop Summary)

An NNSA-Argonne National Laboratory workshop to define NNSA and external partner mission needs and opportunities at the Advanced Photon Source was held February 15-17, 2022. This workshop summary provides a fresh look at NNSA’s evolving mission needs, partner agency and university interests, x-ray photon characteristics, and technical requirements to meet those needs. The workshop was organized according to four breakout groups: Coupling dynamic drivers to a synchrotron, High explosives and chemical sciences, Process-structure-performance: X-ray experiments to understand materials behaviors, and Process-structure-performance: manufacturing and aging. This summary report describes the workshop outcomes, and the preliminary conceptual design for a dedicated Defense Materials Science Sector (DMSS) at the Advanced Photon Source.

36 MATERIALS SCIENCE↗
DOE OSTI2021

OSSOS. XXI. Collision Probabilities in the Edgeworth–Kuiper Belt

Here, we present results on the intrinsic collision probabilities, P {sub I}, and range of collision speeds, V {sub I}, as a function of the heliocentric distance, r, in the trans-Neptunian region. The collision speed is one of the parameters that serves as a proxy for a collisional outcome (e.g., disruption and scattering of fragments, or formation of a crater, as both processes are related to the impact energy). We utilize an improved and debiased model of the trans-Neptunian object (TNO) region from the “Outer Solar System Origins Survey” (OSSOS). It provides a well-defined model of TNO orbital distribution, based on multiple opposition observations of more than 1000 bodies. We compute collisional probabilities for the OSSOS models of the main classical, resonant, detached+outer, and scattering TNO populations. The intrinsic collision probabilities and collision speeds are computed using Öpik’s approach, as revised and modified by Wetherill for noncircular and inclined orbits. The calculations are carried out for each of the dynamical TNO groups, allowing for inter-population collisions as well as collisions within each TNO population, resulting in 28 combinations in total. Our results indicate that collisions in the trans-Neptunian region are possible over a wide range in (r, V {sub I}) phase space. Although collisions are calculated to happen within r ∼ 20–200 au and V {sub I} ∼ 0.1 km s{sup −1} to as high as V {sub I} ∼ 9 km s{sup −1}, most of the collisions are likely to happen at low relative velocities V {sub I} < 1 km s{sup −1} and are dominated by the main classical belt.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Aggregation of cyclic polypeptoids bearing zwitterionic end-groups with attractive dipole–dipole and solvophobic interactions: a study by small-angle neutron scattering and molecular dynamics simulation

Aggregation behavior of cyclic polypeptoids bearing zwitterionic end-groups in methanol has been studied using a combination of experimental and simulation techniques. Here, the data from SANS and cryo-TEM indicate that the solution contains small clusters of these cyclic polypeptoids, ranging from a single polypeptoid chain to small oligomers, while the linear counterpart shows no cluster formation. Atomistic molecular dynamics simulations reveal that the driving force for this clustering behavior is due to the interplay between the effective repulsion due to the solvation of the dipoles formed by the charged end-groups in each polypeptoid chain and the attractive forces due to dipole–dipole interactions and the solvophobic effect.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗