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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Excited-state downfolding using ground-state formalisms

Downfolding coupled cluster (CC) techniques are powerful tools for reducing the dimensionality of many-body quantum problems. This work investigates how ground-state downfolding formalisms can target excited states using non-Aufbau reference determinants, paving the way for applications of quantum computing in excited-state chemistry. This study focuses on doubly excited states for which canonical equation-of-motion CC approaches struggle to describe unless one includes higher-than-double excitations. The downfolding technique results in state-specific effective Hamiltonians that, when diagonalized in their respective active spaces, provide ground- and excited-state total energies (and therefore excitation energies) comparable to high-level CC methods. The performance of this procedure is examined with doubly excited states of H 2 , Methylene, Formaldehyde, and Nitroxyl.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Magic state distillation from entangled states

We report that magic can be distributed non-locally in many-body entangled states, such as the low energy states of condensed matter systems. Using the Bravyi-Kitaev magic state distillation protocol, we find that non-local magic is distillable and can improve the distillation outcome. We analyze a few explicit examples and show that spin squeezing can be used to convert non-distillable states into distillable ones. Our analysis also suggests that the conventional product input states assumed by magic distillation protocols are extremely atypical among general states with distillable magic. It further justifies the need for studying a diverse range of entangled inputs that yield magic states with high probability.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

β -delayed neutron spectroscopy of Co 70 , 72 ground-state and isomeric-state decays

Here, the β-decaying states of 70,72 Co were studied at the National Superconducting Cyclotron Laboratory using the VANDLE neutron time-of-flight array. The (6 - ,7 - )⁢β-decaying state in 70 Co is near-spherical with a lifetime of 113 ± 7 ms, and the low-spin (1 + ,2 + )⁢β-decaying state is postulated to be the prolate deformed ground state with a lifetime of 508 ± 7 ms. Both decay predominantly to the bound states of 70 Ni. For the first time neutron-emissions from neutron unbound states from both the (6 - ,7 - ) and (1 + ,2 + )⁢β decays were measured. Even with the low statistics data, we were able to disentangle the neutron emission from both decays, which enabled a determination of β-decay strength above the neutron separation energy of 70 Ni. Neutron emission probabilities were measured to be 7.1 ± 1.5% and 9.4 ± 1.7%, respectively, for the (6 - ,7 - ) and (1 + ,2 + ) decays. The decay pattern of the 70 Co is driven by neutron f 5/2 to proton f 7/2 Gamow-Teller transformation. The observed population of neutron unbound states is attributed to the conversion of p 1/2 and p 3/2 neutrons to p 3/2 and p 1/2 protons excited across the Z = 28 closed shell.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS2021

Geospatial Cluster Analysis of the State, Duration and Severity of Drought Over Paraíba State, Northeastern Brazil

Droughts threaten water resources, agriculture, socio-economic activities and the population at the global and regional level, so identifying areas with homogeneous drought behaviors is an important consideration in improving the management of water resources. The objective of this study is to identify homogenous zones over Paraíba State in relation to the state, duration and severity of droughts that have occurred over the last 20 years (1998–2017) using hierarchical cluster analysis based on both gauge-measured and Tropical Rainfall Measuring Mission (TRMM) estimated rainfall data (TMPA 3B42). The drought series were calculated using the Standardized Precipitation Index (SPI) based on eight time scales and were grouped according to drought state, duration and severity time series. The integrated results of state, duration and severity of droughts indicate that there is a basis for dividing Paraíba State into two major regions (a) Zone I, formed by Mata Paraibana and Agreste Paraibano, and (b) Zone II, composed by Borborema and Sertão Paraibano. This division is evident when assessing short-term droughts, but in the case of long-term droughts, Paraíba State has a high similarity in terms of drought state, duration, and severity. Factors such as proximity to the ocean, active climatic systems, and the local relief configuration were identified as influencing the drought regime. Finally, it is concluded that TMPA rainfall estimates represent a valuable source of data to regionalize and identify drought patterns over this part of Brazil and that other studies of this type should be carried out to monitor these phenomena based on other satellite-based rainfall data, including the Global Precipitation Mission (GPM).

SPI↗
DOE OSTI2014

Ground states of nonlinear Schrödinger systems with saturable nonlinearity in R{sup 2} for two counterpropagating beams

Counterpropagating optical beams in nonlinear media give rise to a host of interesting nonlinear phenomena such as the formation of spatial solitons, spatiotemporal instabilities, self-focusing and self-trapping, etc. Here we study the existence of ground state (the energy minimizer under the L{sup 2}-normalization condition) in two-dimensional (2D) nonlinear Schrödinger (NLS) systems with saturable nonlinearity, which describes paraxial counterpropagating beams in isotropic local media. The nonlinear coefficient of saturable nonlinearity exhibits a threshold which is crucial in determining whether the ground state exists. The threshold can be estimated by the Gagliardo-Nirenberg inequality and the ground state existence can be proved by the energy method, but not the concentration-compactness method. Our results also show the essential difference between 2D NLS equations with cubic and saturable nonlinearities.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Ground-state modulation-enhancement by two-state lasing in quantum-dot laser devices

We predict a significant increase of the 3 dB-cutoff-frequency on the ground-state lasing wavelength for two-state-lasing quantum-dot lasers using a microscopically motivated multi-level rate-equation model. After the onset of the second lasing line, the excited state acts as a high-pass filter, improving the ground-state response to faster modulation frequencies. We present both numerically simulated small-signal and large-signal modulation results and compare the performance of single and two-state lasing devices. Furthermore, we give dynamical arguments for the advantages of two-state lasing on data-transmission capabilities.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2015

The high pressure structure and equation of state of 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105) up to 20 GPa: X-ray diffraction measurements and first principles molecular dynamics simulations

Recent theoretical studies of 2,6-diamino-3,5-dinitropyrazine-1-oxide (C{sub 4}H{sub 4}N{sub 6}O{sub 5} Lawrence Livermore Molecule No. 105, LLM-105) report unreacted high pressure equations of state that include several structural phase transitions, between 8 and 50 GPa, while one published experimental study reports equation of state (EOS) data up to a pressure of 6 GPa with no observed transition. Here we report the results of a synchrotron-based X-ray diffraction study and also ambient temperature isobaric-isothermal atomistic molecular dynamics simulations of LLM-105 up to 20 GPa. We find that the ambient pressure phase remains stable up to 20 GPa; there is no indication of a pressure induced phase transition. We do find a prominent decrease in b-axis compressibility starting at approximately 13 GPa and attribute the stiffening to a critical length where inter-sheet distance becomes similar to the intermolecular distance within individual sheets. The ambient temperature isothermal equation of state was determined through refinements of measured X-ray diffraction patterns. The pressure-volume data were fit using various EOS models to yield bulk moduli with corresponding pressure derivatives. We find very good agreement between the experimental and theoretically derived EOS.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Operation and Control of Soft Switching Solid State Transformer as a Virtual Synchronous Machine for Photovoltaic Application

Possibility for control and operation of a three-phase solid state soft switching transformer based as a virtual synchronous machine or synchronverter has been investigated in this paper. The soft switching solid state transformer is used as an interface between the ac grid and a photovoltaic power generation unit supported by a battery bank. The control architecture investigated in this paper is that of a synchronverter to achieve inertial support to the grid and local loads. The operation of the soft switching solid state transformer has also been investigated as a V S M during unbalanced/distorted grid voltage condition. Control objective to achieve oscillation free power transfer between the ports (photovoltaic, battery and grid) has been achieved. The presented architecture has been verified for several important case studies via numerical simulations based on MATLAB/Simulink domain.

grid current controller↗
DOE OSTI2017

Automatic Regionalization Algorithm for Distributed State Estimation in Power Systems

The deregulation of the power system and the incorporation of generation from renewable energy sources recessitates faster state estimation in the smart grid. Distributed state estimation (DSE) has become a promising and scalable solution to this urgent demand. In this paper, we investigate the regionalization algorithms for the power system, a necessary step before distributed state estimation can be performed. To the best of the authors' knowledge, this is the first investigation on automatic regionalization (AR). We propose three spectral clustering based AR algorithms. Simulations show that our proposed algorithms outperform the two investigated manual regionalization cases. With the help of AR algorithms, we also show how the number of regions impacts the accuracy and convergence speed of the DSE and conclude that the number of regions needs to be chosen carefully to improve the convergence speed of DSEs.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2018

Synchrophasor Data Correction under GPS Spoofing Attack: A State Estimation-Based Approach

GPS spoofing attack (GSA) has been shown to be one of the most imminent threats to almost all cyber-physical systems incorporated with the civilian GPS signal. Specifically, for our current agenda of the modernization of the power grid, this may greatly jeopardize the benefits provided by the pervasively installed phasor measurement units (PMU). In this paper, we consider the case where synchrophasor data from PMUs are compromised due to the presence of a single GSA, and show that it can be corrected by signal processing techniques. In particular, we introduce a statistical model for synchrophasorbased power system state estimation (SE), and then derive the spoofing-matched algorithms for synchrophasor data correction against GPS spoofing attack. Different testing scenarios in IEEE 14-, 30-, 57-, 118-bus systems are simulated to show the proposed algorithms’ performance on GSA detection and state estimation. Numerical results demonstrate that our proposed algorithms can consistently locate and correct the spoofed synchrophasor data with good accuracy as long as the system observability is satisfied. The accuracy of state estimation is significantly improved compared with the traditional weighted least square method and approaches the performance under the Genie-aided method.

Phasor measurement units, Global Positioning Syste↗
DOE OSTI2025

Local order, disorder, and everything in between: using 91 Zr solid-state NMR spectroscopy to probe zirconium-based metal–organic frameworks

Characterization of metal centers in metal–organic frameworks (MOFs) is critical for rational design and further understanding of structure–property relationships. The short-range structure about Zr atoms is challenging to properly elucidate in many Zr MOFs, particularly when local disorder is present. Static 91 Zr solid-state NMR spectra of the seven zirconium MOFs UiO-66, UiO-66-NH 2 , UiO-67, MOF-801, MOF-808, DUT-68 and DUT-69 have been acquired at high magnetic fields of 35.2 T and 19.6 T, yielding valuable information on the local structure, site symmetry and order about Zr. 91 Zr NMR is very sensitive to differences in MOF short-range structure caused by guest molecules, linker substitution and post-synthetic treatment. Complementary density functional theory (DFT) calculations assist in the interpretation and assignment of 91 Zr solid-state NMR spectra, lend insight into structural origins of 91 Zr NMR parameters and enable determination of local Zr coordination environments. This approach can be extended to many other materials containing zirconium.

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

Noise-canceling quantum feedback: Non-Hermitian dynamics with applications to state preparation and magic state distillation

Time-continuous quantum measurement allows for the tracking of a quantum system in real time via sequences of short, and individually weak, measurement intervals. Such measurements are necessarily invasive, imparting backaction to the system, and allowing the observer to update their state estimate based on stochastic measurement outcomes. Feedback control then involves real-time interventions by an observer, conditioned on the time-continuous measurement signal that they receive. Here, we consider here diffusive quantum trajectories and focus on the “noise-canceling” subset of feedback protocols that aim to minimize the degree of stochasticity in the dynamics. We derive such a class of feedback operations, showing that under the idealized assumptions of pure states, unit measurement efficiency, and zero time delay in implementing feedback operations, perfectly noise-canceling feedback always exists. We consider the resulting noise-canceled dynamics generated by an effective non-Hermitian Hamiltonian; while non-Hermitian Hamiltonians from continuous monitoring generally describe rare dynamics (accessible by costly postselection), the use of noise-canceling feedback here leads to non-Hermitian dynamics that occur deterministically. We demonstrate this via examples of entangled state preparation and stabilization. We then illustrate the potential for the application of noise cancellation to boost success rates in magic state distillation protocols. We show that adding feedback based on noise cancellation into a time-continuous five-to-one distillation protocol leads to higher probabilities of successful distillation across a range of input errors and increases the threshold on input errors for which the protocol is effective. Our results highlight the efficacy of noise-canceling feedback-aided protocols for quantum state preparation and stabilization tasks.

Karmakar, Tathagata [University of California, Ber↗
DOE OSTI2022

A weighted state redistribution algorithm for embedded boundary grids

State redistribution is an algorithm that stabilizes cut cells for embedded boundary grid methods. This work extends the earlier algorithm in several important ways. First, state redistribution is extended to three spatial dimensions. Second, we discuss several algorithmic changes and improvements motivated by the more complicated cut cell geometries that can occur in higher dimensions. In particular, we introduce a weighted version with less dissipation in an easily generalizable framework. Third, we demonstrate that state redistribution can also stabilize a solution update that includes both advective and diffusive contributions. Notably, the stabilization algorithm is shown to be effective for incompressible as well as compressible reacting flows. Finally, we discuss the implementation of the algorithm for several exascale-ready simulation codes based on AMReX, demonstrating ease of use in combination with domain decomposition, hybrid parallelism and complex physics.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2016

Synthetic routes to a nanoscale inorganic cluster [Ga{sub 13}(μ{sub 3}-OH){sub 6}(μ{sub 2}-OH){sub 18}(H{sub 2}O)](NO{sub 3}){sub 15} evaluated by solid-state {sup 71}Ga NMR

Solid-state {sup 71}Ga NMR was used to characterize a series of [Ga{sub 13}(μ{sub 3}-OH){sub 6}(μ{sub 2}-OH){sub 18}(H{sub 2}O)](NO{sub 3}){sub 15} “Ga{sub 13}” molecular clusters synthesized by multiple methods. These molecular clusters are precursors to thin film electronics and may be employed in energy applications. The synthetic routes provide varying levels of impurities in the solid phase, and these impurities often elude traditional characterization techniques such as powder X-ray diffraction and Raman spectroscopy. Solid-state NMR can provide a window into the gallium species even in amorphous phases. This information is vital in order to prevent the impurities from causing defect sites in the corresponding thin films upon gelation and condensation (polymerization) of the Ga{sub 13} clusters. This work demonstrates the resolving power of solid-state NMR to evaluate structure and synthetic quality in the solid state, and the application of high-field NMR to study quadrupolar species, such as {sup 71}Ga. - Graphical abstract: The various synthetic routes and {sup 71}Ga solid-state NMR spectra of the nanoscale inorganic cluster [Ga{sub 13}(μ{sub 3}-OH){sub 6}(μ{sub 2}-OH){sub 18}(H{sub 2}O)](NO{sub 3}){sub 15}. - Highlights: • Solid-state {sup 71}Ga NMR of hydroxo-aquo metal clusters and the impurities present. • High-field NMR capability allows for quadrupolar species, such as {sup 71}Ga, to be routinely studied. • Efficient and environmentally friendly synthetic routes have been developed to prepare hydroxo-aquo metal clusters.

36 MATERIALS SCIENCE↗
DOE OSTI2018

In Situ Strain Tuning of the Dirac Surface States in Bi 2 Se 3 Films

Elastic strain has the potential for a controlled manipulation of the band gap and spin-polarized Dirac states of topological materials, which can lead to pseudomagnetic field effects, helical flat bands, and topological phase transitions. However, practical realization of these exotic phenomena is challenging and yet to be achieved. Here we show that the Dirac surface states of the topological insulator Bi 2 Se 3 can be reversibly tuned by an externally applied elastic strain. Performing in situ X-ray diffraction and in situ angle-resolved photoemission spectroscopy measurements during tensile testing of epitaxial Bi 2 Se 3 films bonded onto a flexible substrate, we demonstrate elastic strains of up to 2.1% and quantify the resulting changes in the topological surface state. Our study establishes the functional relationship between the lattice and electronic structures of Bi 2 Se 3 and, more generally, demonstrates a new route toward momentum-resolved mapping of strain-induced band structure changes.

Flötotto, David↗
DOE OSTI2014

Calculation of state-to-state cross sections for triatomic reaction by the multi-configuration time-dependent Hartree method

A framework for quantum state-to-state integral and differential cross sections of triatomic reactive scattering using the Multi-Configuration Time-Dependent Hartree (MCTDH) method is introduced, where a modified version of the Heidelberg MCTDH package is applied. Parity of the system is adopted using only non-negative helicity quantum numbers, which reduces the basis set size of the single particle functions in angular degree of freedom almost by half. The initial wave packet is constructed in the space-fixed frame, which can accurately account for the centrifugal potential. By using the reactant-coordinate-based method, the product state-resolved information can be accurately extracted. Test calculations are presented for the H + H{sub 2} reactive scattering. This work demonstrates the capability of the MCTDH method for extracting accurate state-to-state integral and differential cross sections. As an efficient scheme for high-dimensional problems, the MCTDH method may be promising for the study of product state-resolved cross sections for polyatomic reactive systems.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2014

A complex guided spectral transform Lanczos method for studying quantum resonance states

A complex guided spectral transform Lanczos (cGSTL) algorithm is proposed to compute both bound and resonance states including energies, widths, and wavefunctions. The algorithm comprises of two layers of complex-symmetric Lanczos iterations. A short inner layer iteration produces a set of complex formally orthogonal Lanczos polynomials. They are used to span the guided spectral transform function determined by a retarded Green operator. An outer layer iteration is then carried out with the transform function to compute the eigen-pairs of the system. The guided spectral transform function is designed to have the same wavefunctions as the eigenstates of the original Hamiltonian in the spectral range of interest. Therefore, the energies and/or widths of bound or resonance states can be easily computed with their wavefunctions or by using a root-searching method from the guided spectral transform surface. The new cGSTL algorithm is applied to bound and resonance states of HO{sub 2}, and compared to previous calculations.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗