Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Measurement”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 811 records · Page 45
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Direct Determination of Equilibrium Potentials for Hydrogen Oxidation/Production by Open Circuit Potential Measurements in Acetonitrile

Open circuit potentials were measured for acetonitrile solutions of a variety of acids and their conjugate bases under 1 atm H 2 . Acids examined were triethylammonium, dimethylformamidium, 2,6-dichloroanilinium, 4-cyanoanilinium, 4-bromoanilinium, and 4-anisidinium salts. These potentials, along with the pK a values of the acids, establish the value of the standard hydrogen electrode (SHE) potential in acetonitrile as -0.028(4) V vs the ferrocenium/ferrocene couple. Dimethylformamidium forms homoconjugates and other aggregates with dimethylformamide; open circuit potentials (OCPs) were used to quantify the extent of these reactions. Overpotentials for electrocatalytic hydrogen production and oxidation were determined from open circuit potentials and voltammograms of acidic or basic catalyst solutions under H 2 . For these solutions, agreement between OCP values and potentials calculated using the Nernst equation is within 12 mV. Finally, use of the measured equilibrium potential allows direct comparison of catalytic systems in different media; it requires neither pK a values, homoconjugation constants, nor the SHE potential.

electrocatalysis↗
DOE OSTI2024

Reassessment of Birch's Law on hcp‐Fe From Ultrasonic Sound Velocity Measurement and Implications on the Velocity Profiles of Earth's Inner Core

Here, we performed in situ X-ray diffraction and ultrasonic sound velocity measurements on hcp-Fe up to 15 GPa, 873 K in a multi-anvil apparatus. The elastic moduli and their pressure and temperature derivatives were determined by fitting the velocity and density data to the third-order finite strain equations, yielding K S0 = 169.0(57) GPa, K$^{′}_{S0}$ = 5.4(6), (∂K S /∂T) P = −0.031(3) GPa/K, G 0 = 104.5(27) GPa, G$^{′}_{0}$ = 1.7(2), (∂G/∂T) P = −0.060(2) GPa/K. Within the experimental P-T range, we find significant temperature effect on the density-velocity (ρ − V P or S ) relations and caution the use of the temperature-independent Birch's law for extrapolation to core conditions. Furthermore, temperature-induced velocity decrease is more significant in V S than in V P , offering a possible explanation for the high Poisson's ratio in the core. Extrapolations based on our results together with previous experimental data suggest that V P of hcp-Fe aligns with PREM at Earth's core conditions, while Vs and density are approximately 10% and 2.7% higher than PREM, respectively.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Measurement of the Generalized Spin Polarizabilities of the Neutron in the Low-Q{sup 2} Region

Understanding the nucleon spin structure in the regime where the strong interaction becomes truly strong poses a challenge to both experiment and theory. At energy scales below the nucleon mass of about 1 GeV, the intense interaction among the quarks and gluons inside the nucleon makes them highly correlated. Their coherent behaviour causes the emergence of effective degrees of freedom, requiring the application of non-perturbative techniques such as chiral effective field theory1. Here we present measurements of the neutron’s generalized spin polarizabilities that quantify the neutron’s spin precession under electromagnetic fields at very low energy-momentum transfer squared down to 0.035 GeV2. In this regime, chiral effective field theory calculations2–4 are expected to be applicable. Our data, however, show a strong discrepancy with these predictions, presenting a challenge to the current description of the neutron’s spin properties.

Sulkosky, Vincent↗
DOE OSTI2023

Mass measurements show slowdown of rapid proton capture process at waiting-point nucleus 64Ge

Abstract X-ray bursts are among the brightest stellar objects frequently observed in the sky by space-based telescopes. A type-I X-ray burst is understood as a violent thermonuclear explosion on the surface of a neutron star, accreting matter from a companion star in a binary system. The bursts are powered by a nuclear reaction sequence known as the rapid proton capture process (rp process), which involves hundreds of exotic neutron-deficient nuclides. At so-called waiting-point nuclides, the process stalls until a slower β + decay enables a bypass. One of the handful of rp process waiting-point nuclides is 64 Ge, which plays a decisive role in matter flow and therefore the produced X-ray flux. Here we report precision measurements of the masses of 63 Ge, 64,65 As and 66,67 Se—the relevant nuclear masses around the waiting-point 64 Ge—and use them as inputs for X-ray burst model calculations. We obtain the X-ray burst light curve to constrain the neutron-star compactness, and suggest that the distance to the X-ray burster GS 1826–24 needs to be increased by about 6.5% to match astronomical observations. The nucleosynthesis results affect the thermal structure of accreting neutron stars, which will subsequently modify the calculations of associated observables.

Physics↗
DOE OSTI2017

Approach to fitting parameters and clustering for characterising measured voltage dips based on two-dimensional polarisation ellipses

An alternative approach to characterise real voltage dips is proposed and evaluated in this study. The proposed methodology is based on voltage-space vector solutions, identifying parameters for ellipses trajectories by using the least-squares algorithm applied on a sliding window along the disturbance. The most likely patterns are then estimated through a clustering process based on the k-means algorithm. The objective is to offer an efficient and easily implemented alternative to characterise faults and visualise the most likely instantaneous phase-voltage evolution during events through their corresponding voltage-space vector trajectories. This novel solution minimises the data to be stored but maintains extensive information about the dips including starting and ending transients. The proposed methodology has been applied satisfactorily to real voltage dips obtained from intensive field-measurement campaigns carried out in a Spanish wind power plant up to a time period of several years. A comparison to traditional minimum root mean square-voltage and time-duration classifications is also included in this study.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2017

Measurement of baryon acoustic oscillation correlations at z=2.3 with SDSS DR12 Lya-Forests [Measurements of BAO correlations at z = 2.3 with SDSS DR12 Lyα-Forests]

Here, we use flux-transmission correlations in Lyα forests to measure the imprint of baryon acoustic oscillations (BAO). The study uses spectra of 157,783 quasars in the redshift range 2.1 ≤ z ≤ 3.5 from the Sloan Digital Sky Survey (SDSS) Data Release 12 (DR12). Besides the statistical improvements on our previous studies using SDSS DR9 and DR11, we have implemented numerous improvements in the analysis procedure, allowing us to construct a physical model of the correlation function and to investigate potential systematic errors in the determination of the BAO peak position. The Hubble distance, D H = c/H(z), relative to the sound horizon is D H (z = 2.33)/r d = 9.07 ± 0.31. The best-determined combination of comoving angular-diameter distance, D M , and the Hubble distance is found to be D 0.7 H D 0.3 M /r d = 13.94 ± 0.35. This value is 1.028 ± 0.026 times the prediction of the flat- ΛCDM model consistent with the cosmic microwave background (CMB) anisotropy spectrum. The errors include marginalization over the effects of unidentified high-density absorption systems and fluctuations in ultraviolet ionizing radiation. Independently of the CMB measurements, the combination of our results and other BAO observations determine the open-ΛCDM density parameters to be Ω M = 0.296 ± 0.029, Ω Λ = 0.699 ± 0.100 and Ω k = –0.002 ± 0.119.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Cross section measurements at LANSCE for defense, science and applications

The Los Alamos Neutron Science Center (LANSCE) has three neutron sources that are used for nuclear science measurements. These sources are driven by an 800 MeV proton linear accelerator and cover an energy range from sub-thermal to hundreds of MeV. Research at the facilities is performed under the auspices of a US DOE user program under which research proposals are rated for merit by a program advisory committee and are scheduled based on merit and availability of beam time. A wide variety of instruments is operated at the neutron flight paths at LANSCE including neutron detector arrays, gamma-ray detector arrays, fission fragment detectors, and charged particle detectors. These instruments provide nuclear data for multiple uses that range from increasing knowledge in fundamental science to satisfying data needs for diverse applications such as nuclear energy, global security, and industrial applications. In addition, highlights of recent research related to cross sections measurements are presented, and future research initiatives are discussed.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

The direct measurement of ablation pressure driven by 351-nm laser radiation

The instantaneous scaling of ablation pressure to laser intensity is directly inferred for ramp compression of diamond targets irradiated by 351-nm light. Continuously increasing pressure profiles from 100 to 970 GPa are produced by direct-drive laser ablation at intensities up to 7 × 1013 W/cm2. The free-surface velocity on the rear of the target is used to directly infer the instantaneous ablation-pressure profile at the front of the target. The laser intensity on target is determined by laser power measurements and fully characterized laser spots. The ablation pressure is found to depend on the laser intensity as P(GPa)=42(±3)[I(TW/cm2)]0.71(±0.01).

Fratanduono, D. E.↗
DOE OSTI2012

Performance metrics for inertial confinement fusion implosions: Aspects of the technical framework for measuring progress in the National Ignition Campaign

The National Ignition Campaign (NIC) uses non-igniting 'tritium hydrogen deuterium (THD)' capsules to study and optimize the hydrodynamic assembly of the fuel without burn. These capsules are designed to simultaneously reduce DT neutron yield and to maintain hydrodynamic similarity with the DT ignition capsule. We will discuss nominal THD performance and the associated experimental observables. We will show the results of large ensembles of numerical simulations of THD and DT implosions and their simulated diagnostic outputs. These simulations cover a broad range of both nominal and off-nominal implosions. We will focus on the development of an experimental implosion performance metric called the experimental ignition threshold factor (ITFX). We will discuss the relationship between ITFX and other integrated performance metrics, including the ignition threshold factor (ITF), the generalized Lawson criterion (GLC), and the hot spot pressure (HSP). We will then consider the experimental results of the recent NIC THD campaign. We will show that we can observe the key quantities for producing a measured ITFX and for inferring the other performance metrics. We will discuss trends in the experimental data, improvement in ITFX, and briefly the upcoming tuning campaign aimed at taking the next steps in performance improvement on the path to ignition on NIF.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2012

Measurement of an inverse Compton scattering source local spectrum using k-edge filters

X-ray sources based on the inverse Compton scattering process are attracting a growing interest among scientists, due to their extremely fast pulse, quasi-monochromatic spectrum, and relatively high intensity. The energy spectrum of the x-ray beam produced by inverse Compton scattering sources in a fixed observation direction is a quasi-monochromatic approximately Gaussian distribution. The mean value of this distribution varies with the scattering polar angle between the electron beam direction and the x-ray beam observation direction. Previous works reported experimental measurements of the mean energy as a function of the polar angle. This work introduces a method for the measurement of the whole local energy spectrum (i.e., the spectrum in a fixed observation direction) of the x-ray beam yielded by inverse Compton scattering sources, based on a k-edge filtering technique.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2012

Measuring electron-positron annihilation radiation from laser plasma interactions

We investigated various diagnostic techniques to measure the 511 keV annihilation radiations. These include step-wedge filters, transmission crystal spectroscopy, single-hit CCD detectors, and streaked scintillating detection. While none of the diagnostics recorded conclusive results, the step-wedge filter that is sensitive to the energy range between 100 keV and 700 keV shows a signal around 500 keV that is clearly departing from a pure Bremsstrahlung spectrum and that we ascribe to annihilation radiation.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2013

Measurements of collective fuel velocities in deuterium-tritium exploding pusher and cryogenically layered deuterium-tritium implosions on the NIF

For the first time, quantitative measurements of collective fuel velocities in Inertial Confinement Fusion implosions at the National Ignition Facility are reported. Velocities along the line-of-sight (LOS) of the Magnetic Recoil neutron Spectrometer (MRS), positioned close to the equator (73 Degree-Sign -324 Degree-Sign ), were inferred from the measured mean energy of the deuterium-tritium (DT)-primary neutron peak. Substantial mean energy shifts up to 113 {+-} 16 keV were observed in DT gas-filled exploding-pusher implosions, driven in a polar-direct drive configuration, which corresponds to bulk fuel velocities up to 210 {+-} 30 km/s. In contrast, only marginal bulk fuel velocities along the MRS LOS were observed in cryogenically layered DT implosions. Integrated analysis of data from a large number of cryogenically layered implosions has recently identified a deficit in achieved hot-spot energy of {approx}3 kJ for these implosions [C. Cerjan et al., Phys. Plasmas (2013)]. One hypothesis that could explain this missing energy is a collective, directional fuel velocity of {approx}190 km/s. As only marginal bulk fuel velocities are observed in the MRS data, this might indicate that turbulent or radial flows would be a likely explanation for the missing energy. However, a directional velocity close to perpendicular to the MRS LOS cannot be ruled out.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗