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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 OSTI2019

Triple autoionization of atomic ions

A time-dependent close-coupling method for four-electron atomic systems is formulated to calculate the triple autoionization of atomic ions. Initial excited states are obtained by relaxation of the Schrodinger equation in imaginary time using a Schmidt orthogonalization method involving interior subshells. Autoionization rates are obtained by propagation in real time using projections onto products of bound and continuum single particle states. For the ($2{s}^{2}2{p}^{2}$) excited configuration of the ${{\rm{C}}}^{2+}$ atomic ion, we obtain total, double, and triple autoionization rates. The total autoionization rates are in reasonable agreement with single autoionization rates obtained using configuration-average distorted-wave theory.

Pindzola, M. S.↗
DOE OSTI2017

How to Make Distinct Dynamical Systems Appear Spectrally Identical

We show that a laser pulse can always be found that induces a desired optical response from an arbitrary dynamical system. As illustrations, driving fields are computed to induce the same optical response from a variety of distinct systems (open and closed, quantum and classical). As a result, the observed induced dipolar spectra without detailed information on the driving field are not sufficient to characterize atomic and molecular systems. The formulation may also be applied to design materials with specified optical characteristics. These findings reveal unexplored flexibilities of nonlinear optics.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2020

Validation of finite-element models using full-field experimental data: Levelling finite-element analysis data through a digital image correlation engine

Full-field data from digital image correlation (DIC) provide rich information for finite-element analysis (FEA) validation. However, there are several inherent inconsistencies between FEA and DIC data that must be rectified before meaningful, quantitative comparisons can be made, including strain formulations, coordinate systems, data locations, strain calculation algorithms, spatial resolutions and data filtering. As such, in this paper, we investigate two full-field validation approaches: (1) the direct interpolation approach, which addresses the first three inconsistencies by interpolating the quantity of interest from one mesh to the other, and (2) the proposed DIC-levelling approach, which addresses all six inconsistencies simultaneously by processing the FEA data through a stereo-DIC simulator to ‘level’ the FEA data to the DIC data in a regularisation sense. Synthetic ‘experimental’ DIC data were generated based on a reference FEA of an exemplar test specimen. The direct interpolation approach was applied, and significant strain errorswere computed, even though therewas no model form error, because the filtering effect of theDIC enginewas neglected. In contrast, the levelling approach provided accurate validation results, with no strain error when no model form error was present. Next, model form error was purposefully introduced via a mismatch of boundary conditions. With the direct interpolation approach, the mismatch in boundary conditions was completely obfuscated, while with the levelling approach, it was clearly observed. Finally, the ‘experimental’ DIC datawere purposefully misaligned slightly fromthe FEA data. Both validation techniques suffered from the misalignment, thus motivating continued efforts to develop a robust alignment process. In conclusion, direct interpolation is insufficient, and the proposed levelling approach is required to ensure that the FEA and the DIC data have the same spatial resolution and data filtering. Only after the FEA data have been ‘levelled’ to the DIC data can meaningful, quantitative error maps be computed.

42 ENGINEERING↗
DOE OSTI2013

Hadro-quarkonia dynamics and Z{sub b} states

Dynamics of hadro-quarkonium system is formulated, based on the channel coupling of a light hadron (h) and heavy quarkonium <##> } ( } Q } Q }&#x00AF;<!-- ?? --> ) $ /left( {Q/bar Q} /right) $ (Q Q-bar ) </##> to heavy-light mesons (<##> } Q } } q }&#x00AF;<!-- ?? --> $ Q{sub {/bar q}} $ Q{sub q-bar } </##>, <##> } } Q }&#x00AF;<!-- ?? --> q $ /bar Q{sub q} $ Q-bar {sub q} </##>). Equations for hadro-quarkonium amplitudes and resonance positions are written explicitly, and numerically calculated for the special case of πϒ(nS) (n = 1, 2, 3). It is also shown that the recently observed by Belle two peaks Z{sub b}(10610) and Z{sub b}(10650) are in agreement with the proposed theory. It is demonstrated that theory predicts peaks at the BB*, B*B* thresholds in all available πϒ(nS) channels.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Defense strategies for cloud computing multi-site server infrastructures

We consider cloud computing server infrastructures for big data applications, which consist of multiple server sites connected over a wide-area network. The sites house a number of servers, network elements and local-area connections, and the wide-area network plays a critical, asymmetric role of providing vital connectivity between them. We model this infrastructure as a system of systems, wherein the sites and wide-area network are represented by their cyber and physical components. These components can be disabled by cyber and physical attacks, and also can be protected against them using component reinforcements. The effects of attacks propagate within the systems, and also beyond them via the wide-area network.We characterize these effects using correlations at two levels using: (a) aggregate failure correlation function that specifies the infrastructure failure probability given the failure of an individual site or network, and (b) first-order differential conditions on system survival probabilities that characterize the component-level correlations within individual systems. We formulate a game between an attacker and a provider using utility functions composed of survival probability and cost terms. At Nash Equilibrium, we derive expressions for the expected capacity of the infrastructure given by the number of operational servers connected to the network for sum-form, product-form and composite utility functions.

Rao, Nageswara S.↗
DOE OSTI2015

Development and Validation of Multidimensional Models of Supercritical CO 2 Energy Conversion Systems for Nuclear Power Reactors

A general objective of this project was to develop, verify and validate mechanistic multidimensional models of local flow and heat transfer in supercritical carbon dioxide (S-CO 2 ) devices and systems, and to demonstrate the application of the new models to selected components of S-CO 2 nuclear energy transport systems. Both steady-state and time-dependent operating conditions have been investigated. The overall workscope consisted of the following three major parts: Development, testing and validation of a mechanistic model of forced-convection heat transfer in heated channels cooled using S-CO 2 at slightly supercritical pressures; Development, testing and verification/validation of a new model of the dynamics of closed- loop S-CO 2 heat transport systems; and, Formulation, testing and verification of a mechanistic model for the analysis of flow and pressure distribution in S-CO 2 compressors. The results of the work performed for the project have been documented in several publications.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2018

Conversion of Plastic Work to Heat: A full-field study of thermomechanical coupling

This project targeted a full-field understanding of the conversion of plastic work into heat using advanced diagnostics (digital image correlation, DIC, combined with infrared, IR, imaging). This understanding will act as a catalyst for reformulating the prevalent simplistic model, which will ultimately transform Sandia's ability to design for and predict thermomechanical behavior, impacting national security applications including nuclear weapon assessments of accident scenarios. Tensile 304L stainless steel dogbones are pulled in tension at quasi-static rates until failure and full-field deformation and temperature data are captured, while accounting for thermal losses. The IR temperature fields are mapped onto the DIC coordinate system (Lagrangian formulation). The resultant fields are used to calculate the Taylor-Quinney coefficient, β, at two strain rates rates (0.002 s -1 and 0.08 s -1 ) and two temperatures (room temperature, RT, and 250°C).

36 MATERIALS SCIENCE↗
DOE OSTI2024

Identifying Hydropower Operational Flexibilities in Presence of Streamflow and Net-load Uncertainty (Final Technical report)

In the existing operations, hydropower contributions to future system flexibility are generally modeled while maintaining traditional operating rules and constraints in supporting grid operation, such as the balancing of variable renewable energy production. Moreover, operation of large scale hydropower systems on major rivers has been investigated for decades, utilizing various systems engineering approaches, with the evolving electric grid, as the result of renewable resources integration, compounded by the changing climate (variability of river flows, intensification of hydrologic cycle resulting in more frequent extreme events) affecting water availability, the need for more advanced stochastic modeling and effective uncertainty analysis approaches have become necessary. The research results supported by this funding and presented in this report provide a new look at hydropower operational flexibility enforced by the changes identified above. Understanding how hydropower operates in response to the underlying uncertainties with respect to the system constraints is crucial in identifying its operational flexibility potentials. In this project, the flexibility of the operating hydropower facility is described by capturing uncertainties in both water and power system and formulating the operations as a multistage stochastic optimization problem. The proposed approach supports short- to seasonal-term operations and planning decision horizons.

13 HYDRO ENERGY↗
DOE OSTI2024

LLNL FESP Theory Highlights: October 2024

I. Novikau, I. Y. Dodin, E. A. Startsev, I. Joseph, Quantum algorithms for simulating dissipative linear and nonlinear dynamics of plasmas. Invited talk at the 66th Annual Meeting of the APS Division of Plasma Physics, Atlanta, Georgia. Novikau I., Dodin I.Y., Startsev E.A., Encoding of linear kinetic plasma problems in quantum circuits via data compression, Journal of Plasma Physics. 2024;90(4):805900401, doi:10.1017/S0022377824000795. We propose an algorithm for encoding linear kinetic plasma problems in quantum circuits. The focus is on modelling electrostatic linear waves in a one-dimensional Maxwellian electron plasma. The waves are described by the linearized Vlasov–Ampère system with a spatially localized external current that drives plasma oscillations. This system is formulated as a boundary-value problem and cast in the form of a linear vector equation to be solved by using the quantum signal processing algorithm. The latter requires encoding of a matrix in a quantum circuit as a sub-block of a unitary matrix. We propose how to encode in a circuit in a compressed form and discuss how the resulting circuit scales with the problem size and the desired precision.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1968

Maintainability methodology and maintenance analyses

Initial approach in performing maintainability studies involves detailed description of methodology used. Maintenance analyses are formulated for system, subsystem, and component levels. These are performed to ensure that complete, integrated, logistics system support elements are identified.

Beach, R. E.↗
NASA NTRS1968

Application of a truncated normal failure distribution in reliability testing

Statistical truncated normal distribution function is applied as a time-to-failure distribution function in equipment reliability estimations. Age-dependent characteristics of the truncated function provide a basis for formulating a system of high-reliability testing that effectively merges statistical, engineering, and cost considerations.

Groves, C., Jr.↗
NASA NTRS1972

Study of aerodynamic surface control of space shuttle boost and reentry, volume 1

The optimization technique is described which was used in the study for applying modern optimal control technology to the design of shuttle booster engine reaction control systems and aerodynamic control systems. Complete formulations are presented for both the ascent and reentry portions of the study. These formulations include derivations of the 6D perturbation equations of motion and the process followed in the control and blending law selections. A total hybrid software concept applied to the study is described in detail. Conclusions and recommendations based on the results of the study are included.

Chang, C. J.↗
NASA NTRS1974

Kinetics of homogeneous nucleation in many component systems

Reiss's classical treatment of the kinetics of homogeneous nucleation in a system containing two chemical components is extended to many-component systems. The formulation is analogous to the pseudo-stationary state theory of chemical reaction rates with the free energy as a function of the composition of the embryo taking the place of the potential energy as a function of interatomic distances.

Hirschfelder, J. O.↗
NASA NTRS1974

Nonlinear aerodynamics of aircraft in high-angle-of-attack maneuvers

A nonlinear aerodynamic moment system is formulated for arbitary motions of aircraft at high angles of attack. The total moment is shown to be compounded of the contributions from three simple motions. The basic motion is coning, where the nose of the aircraft describes a circle around the velocity vector, while the remaining motions are oscillatory perturbations carried out in the presence of coning. A re-examination of the assumptions underlying the formulation enables a characterization of aerodynamic phenomena whose effects can and cannot be treated within the scope of the formulation. Recommendations are made as to the most appropriate types of wind-tunnel tests that could be undertaken in fulfillment of the formulation's requirements.

Tobak, M.↗
NASA NTRS1975

Theoretical investigations of plasma processes in the ion bombardment thruster

A physical model for a thruster discharge was developed, consisting of a spatially diverging plasma sustained electrically between a small ring cathode and a larger ring anode in a cylindrical chamber with an axial magnetic field. The associated boundary-value problem for the coupled partial differential equations with mixed boundary conditions, which describe the electric potential and the plasma velocity fields, was solved in closed form. By means of quantum-mechanical perturbation theory, a formula for the number S(E) of atoms sputtered on the average by an ion of energy E was derived from first principles. The boundary-value problem describing the diffusion of the sputtered atoms through the surrounding rarefied electron-ion plasma to the system surfaces of ion propulsion systems was formulated and treated analytically. It is shown that outer boundary-value problems of this type lead to a complex integral equation, which requires numerical resolution.

Wilhelm, H. E.↗