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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Spin-orbit couplings within the equation-of-motion coupled-cluster framework: Theory, implementation, and benchmark calculations

We present a formalism and an implementation for calculating spin-orbit couplings (SOCs) within the EOM-CCSD (equation-of-motion coupled-cluster with single and double substitutions) approach. The following variants of EOM-CCSD are considered: EOM-CCSD for excitation energies (EOM-EE-CCSD), EOM-CCSD with spin-flip (EOM-SF-CCSD), EOM-CCSD for ionization potentials (EOM-IP-CCSD) and electron attachment (EOM-EA-CCSD). We employ a perturbative approach in which the SOCs are computed as matrix elements of the respective part of the Breit-Pauli Hamiltonian using zeroth-order non-relativistic wave functions. We follow the expectation-value approach rather than the response-theory formulation for property calculations. Both the full two-electron treatment and the mean-field approximation (a partial account of the two-electron contributions) have been implemented and benchmarked using several small molecules containing elements up to the fourth row of the periodic table. The benchmark results show the excellent performance of the perturbative treatment and the mean-field approximation. When used with an appropriate basis set, the errors with respect to experiment are below 5% for the considered examples. The findings regarding basis-set requirements are in agreement with previous studies. The impact of different correlation treatment in zeroth-order wave functions is analyzed. Overall, the EOM-IP-CCSD, EOM-EA-CCSD, EOM-EE-CCSD, and EOM-SF-CCSD wave functions yield SOCs that agree well with each other (and with the experimental values when available). Using an EOM-CCSD approach that provides a more balanced description of the target states yields more accurate results.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1994

A Unified Approach to Motion Control of Motion Robots

This paper presents a simple on-line approach for motion control of mobile robots made up of a manipulator arm mounted on a mobile base. The proposed approach is equally applicable to nonholonomic mobile robots, such as rover-mounted manipulators and to holonomic mobile robots such as tracked robots or compound manipulators. The computational efficiency of the proposed control scheme makes it particularly suitable for real-time implementation.

motion control↗
DOE OSTI2024

Supramolecular Motion Enables Chondrogenic Bioactivity of a Cyclic Peptide Mimetic of Transforming Growth Factor-β1

Transforming growth factor (TGF)-β1 is a multifunctional protein that is essential in many cellular processes that include fibrosis, inflammation, chondrogenesis, and cartilage repair. In particular, cartilage repair is important to avoid physical disability since this tissue does not have the inherent capacity to regenerate beyond full development. We report here on supramolecular coassemblies of two peptide amphiphile molecules, one containing a TGF-β1 mimetic peptide, and another which is one of two constitutional isomers lacking bioactivity. Using human articular chondrocytes, we investigated the bioactivity of the supramolecular copolymers of each isomer displaying either the previously reported linear form of the mimetic peptide or a novel cyclic analogue. Based on fluorescence depolarization and 1 H NMR spin–lattice relaxation times, we found that coassemblies containing the cyclic compound and the most dynamic isomer exhibited the highest intracellular TGF-β1 signaling and gene expression of cartilage extracellular matrix components. Here, we conclude that control of supramolecular motion is emerging as an important factor in the binding of synthetic molecules to receptors that can be tuned through chemical structure.

Antigens↗
DOE OSTI2017

Large Thermal Motion in Halide Perovskites

Solar cells based on hybrid perovskites have shown high efficiency while possessing simple processing methods. To gain a fundamental understanding of their properties on an atomic level, we investigate single crystals of CH 3 NH 3 PbI 3 with a narrow transition (~5 K) near 327 K. Temperature dependent structural measurements reveal a persistent tetragonal structure with smooth changes in the atomic displacement parameters (ADPs) on crossing T*. We show that the ADPs for I ions yield extended flat regions in the potential wells consistent with the measured large thermal expansion parameter. Molecular dynamics simulations reveal that this material exhibits significant asymmetries in the Pb-I pair distribution functions. We also show that the intrinsically enhanced freedom of motion of the iodine atoms enables large deformations. This flexibility (softness) of the atomic structure results in highly localized atomic relaxation about defects and hence accounts for both the high carrier mobility as well as the structural instability.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Origins of ion irradiation-induced Ga nanoparticle motion on GaAs surfaces

We have examined the origins of ion irradiation-induced nanoparticle (NP) motion. Focused-ion-beam irradiation of GaAs surfaces induces random walks of Ga NPs, which are biased in the direction opposite to that of ion beam scanning. Although the instantaneous NP velocities are constant, the NP drift velocities are dependent on the off-normal irradiation angle, likely due to a difference in surface non-stoichiometry induced by the irradiation angle dependence of the sputtering yield. It is hypothesized that the random walks are initiated by ion irradiation-induced thermal fluctuations, with biasing driven by anisotropic mass transport.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Temporal resolution criterion for correctly simulating relativistic electron motion in a high-intensity laser field

Particle-in-cell codes are now standard tools for studying ultra-intense laser-plasma interactions. Motivated by direct laser acceleration of electrons in sub-critical plasmas, we examine temporal resolution requirements that must be satisfied to accurately calculate electron dynamics in strong laser fields. Using the motion of a single electron in a perfect plane electromagnetic wave as a test problem, we show surprising deterioration of the numerical accuracy with increasing wave amplitude a{sub 0} for a given time-step. We go on to show analytically that the time-step must be significantly less than λ/ca{sub 0} to achieve good accuracy. We thus propose adaptive electron sub-cycling as an efficient remedy.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

Asymmetries in the motional Stark effect emission on the DIII-D tokamak [Asymmetries in the motional Stark effect emission]

In this study, spectrometer measurements and filter upgrades to a motional Stark effect polarimeter measuring the outer half-radius of the DIII-D tokamak helped to identify asymmetries in the polarization angle of Stark-split emission. The measured polarization angle of the π components differs and is not orthogonal to the σ component. These differences persist over a range of densities and with low levels of background light. Lastly, it is suggested that the difference in the polarization angle between components is from a change in the ellipticity of the emitted light across the Stark components coupled with imperfect polarization preservation from an in-vessel mirror.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

Motional Stark effect imaging first results on the DIII-D tokamak

A motional Stark effect (MSE) imaging diagnostic was benchmarked against existing conventional MSE polarimeters on the DIII-D tokamak and delivered new capabilities for measuring the magnetic pitch angle from 2 neutral beams and on the high field side of DIII-D. Line integration across flux surfaces was considerable for the radial view utilised; yet, the imaging MSE measurements from both beams were self-consistent and in close agreement with conventional MSE measurements. The ferroelectric liquid crystal waveplate used in the imaging polarimeter was discovered to have spatially non-uniform retardance; thus, it is required for the calibration source to replicate the ray paths of the neutral beam emission through the optical system.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

Formation of a Keplerian disk in the infalling envelope around L1527 IRS: transformation from infalling motions to Kepler motions

We report Atacama Large Millimeter/submillimeter Array (ALMA) cycle 0 observations of the C{sup 18}O (J = 2-1), SO (J{sub N} = 6{sub 5}-5{sub 4}), and the 1.3 mm dust continuum toward L1527 IRS, a class 0 solar-type protostar surrounded by an infalling and rotating envelope. C{sup 18}O emission shows strong redshifted absorption against the bright continuum emission associated with L1527 IRS, strongly suggesting infall motions in the C{sup 18}O envelope. The C{sup 18}O envelope also rotates with a velocity mostly proportional to r {sup –1}, where r is the radius, whereas the rotation profile at the innermost radius (∼54 AU) may be shallower than r {sup –1}, suggestive of formation of a Keplerian disk around the central protostar of ∼0.3 M {sub ☉} in dynamical mass. SO emission arising from the inner part of the C{sup 18}O envelope also shows rotation in the same direction as the C{sup 18}O envelope. The rotation is, however, rigid-body-like, which is very different from the differential rotation shown by C{sup 18}O. In order to explain the line profiles and the position-velocity (PV) diagrams of C{sup 18}O and SO observed, simple models composed of an infalling envelope surrounding a Keplerian disk of 54 AU in radius orbiting a star of 0.3 M {sub ☉} are examined. It is found that in order to reproduce characteristic features of the observed line profiles and PV diagrams, the infall velocity in the model has to be smaller than the free-fall velocity yielded by a star of 0.3 M {sub ☉}. Possible reasons for the reduced infall velocities are discussed.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

Local correlated motions in aqueous solution of sodium chloride

Real-space motions of molecules and ions in an aqueous solution of sodium chloride are studied with high-resolution inelastic x-ray scattering. In this study, we focus on the correlated dynamics of water molecules and salt ions, instead of the instantaneous structure and the rotational and reorientation dynamics that have been studied using scattering techniques and optical spectroscopy, respectively. The real-space analysis in terms of the Van Hove function illustrates the effect of salt ions to slow down the local correlated dynamics of surrounding water in the hydration shells.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Convective and Turbulent Motions in Nonprecipitating Cu. Part III: Characteristics of Turbulence Motions

Velocity field in a nonprecipitating Cu under BOMEX conditions, simulated by SAM with 10-m resolution and spectral bin microphysics is separated into the convective part and the turbulent part, using a wavelet filtering. In Part II of the study properties of convective motions of this Cu were investigated. Here in Part III of the study, the parameters of cloud turbulence are calculated in the cloud updraft zone at different stages of cloud development. The main points of this study are (i) application of a fine-scale LES model of a single convective cloud allowed a direct estimation of turbulence parameters using the resolved flow in the cloud and (ii) the separation of the resolved flow into the turbulence flow and the nonturbulence flow allowed us to estimate different turbulent parameters with sufficient statistical accuracy. We calculated height and time dependences of the main turbulent parameters such as turbulence kinetic energy (TKE), spectra of TKE, dissipation rate, and the turbulent coefficient. It was found that the main source of turbulence in the cloud is buoyancy whose contribution is described by the buoyancy production term (BPT). The shear production term (SPT) increases with height and reaches its maximum near cloud top, and so does BPT. In agreement with the behavior of BPT and SPT, turbulence in the lower cloud part (below the inversion level) is weak and hardly affects the processes of mixing and entrainment. The fact that BPT is larger than SPT determines many properties of cloud turbulence. For instance, the turbulence is nonisotropic, so the vertical component of TKE is substantially larger than the horizontal components. Another consequence of the fact that BPT is larger than STP manifests itself in the finding that the turbulence spectrum largely obeys the -11/5 Bolgiano–Obukhov scaling. The classical Kolmogorov -5/3 scaling dominates for the low part of a cloud largely at the dissolving stage of cloud evolution. Using the spectra obtained we evaluated an “effective” dissipation rate which increases with height from nearly zero at cloud base up to 20 cm 2 s -3 near cloud top. The coefficient of turbulent diffusion was found to increase with height and ranged from 5 m 2 s -1 near cloud base to 25 m 2 s -1 near cloud top. In conclusion, the possible role of turbulence in the process of lateral entrainment and mixing is discussed.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

R.U.N. Motion VR Boots: Realistic Unimpeded Natural (RUN) Motion Boots for VR gaming in the comfort of your home

Virtual reality (VR) gaming has experienced increasingly widespread adoption in recent years largely due to the development of affordable, consumer-grade headsets equipped with high quality, miniature displays and compact sensors for motion tracking. These devices are now able to provide users with immersive experiences that far surpass what traditional video games can achieve. However, despite these technological strides, a fundamental limitation remains: VR users are unable to move freely in their physical environment without the risk of colliding with real-world obstacles and hazards. This safety concern significantly restricts the level of immersion and natural movement possible in VR gaming.

42 ENGINEERING↗
NASA NTRS1967

Rigid-body motion extracted from total motion of a flexible body

Control system eliminates or reduces flexibility effects on the manual and automatic control of large flexible vehicles. It extracts rigid-body and flexible-body motion and adapts well when a flexible-body frequency coincides or nearly coincides with the control mode frequency.

Howard, J. C.↗
NASA NTRS1973

Motion compensator for holographic motion picture camera

When reference beam strikes target it undergoes Doppler shift dependent upon target velocity. To compensate, object beam is first reflected from rotating cylinder that revolves in direction opposite to target but at same speed. When beam strikes target it is returned to original frequency and is in phase with reference beam. Alternatively this motion compensator may act on reference beam.

Kurtz, R. L.↗