Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “LENGTH”

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 919 records · Page 51
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

SU-E-J-141: Activity-Equivalent Path Length Approach for the 3D PET-Based Dose Reconstruction in Proton Therapy

Purpose: Ion beam therapy is sensitive to uncertainties from treatment planning and dose delivery. PET imaging of induced positron emitter distributions is a practical approach for in vivo, in situ verification of ion beam treatments. Treatment verification is usually done by comparing measured activity distributions with reference distributions, evaluated in nominal conditions. Although such comparisons give valuable information on treatment quality, a proper clinical evaluation of the treatment ultimately relies on the knowledge of the actual delivered dose. Analytical deconvolution methods relating activity and dose have been studied in this context, but were not clinically applied. In this work we present a feasibility study of an alternative approach for dose reconstruction from activity data, which is based on relating variations in accumulated activity to tissue density variations. Methods: First, reference distributions of dose and activity were calculated from the treatment plan and CT data. Then, the actual measured activity data were cumulatively matched with the reference activity distributions to obtain a set of activity-equivalent path lengths (AEPLs) along the rays of the pencil beams. Finally, these AEPLs were used to deform the original dose distribution, yielding the actual delivered dose. The method was tested by simulating a proton therapy treatment plan delivering 2 Gy on a homogeneous water phantom (the reference), which was compared with the same plan delivered on a phantom containing inhomogeneities. Activity and dose distributions were were calculated by means of the FLUKA Monte Carlo toolkit. Results: The main features of the observed dose distribution in the inhomogeneous situation were reproduced using the AEPL approach. Variations in particle range were reproduced and the positions, where these deviations originated, were properly identified. Conclusions: For a simple inhomogeneous phantom the 3D dose reconstruction from PET-activity induced by proton beams was shown to be feasible.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2023

Diverse Murine Vaccinations Reveal Distinct Antibody Classes to Target Fusion Peptide and Variation in Peptide Length to Improve HIV Neutralization

The HIV-1 fusion peptide has been identified as a site for elicitation of broadly neutralizing antibodies, with prior studies demonstrating that priming with fusion peptide-based immunogens and boosting with soluble envelope (Env) trimers can elicit cross-clade HIV-1-neutralizing responses. To improve the neutralizing breadth and potency of fusion peptide-directed responses, we evaluated vaccine regimens that incorporated diverse fusion peptide-conjugates and Env trimers with variation in fusion peptide length and sequence.

Virology↗
DOE OSTI2017

State switching kinetics for quasi-one-dimensional nanosystems: Effects of Finite length and irradiation

The state switching in an extended quasi-one-dimensional material is modeled by the stochastic formation of local new-state nuclei and their subsequent growth along the system axis. An analytical approach is developed to describe the influence of defects, dividing a sample into an ensemble of finite-length segments, on its state switching kinetics. As applied to magnetic systems, the method makes it possible to calculate magnetization curves for different defect concentrations and parameters of material.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Quark ensembles with the infinite correlation length

A number of exactly integrable (quark) models of quantum field theory with the infinite correlation length have been considered. It has been shown that the standard vacuum quark ensemble—Dirac sea (in the case of the space-time dimension higher than three)—is unstable because of the strong degeneracy of a state, which is due to the character of the energy distribution. When the momentum cutoff parameter tends to infinity, the distribution becomes infinitely narrow, leading to large (unlimited) fluctuations. Various vacuum ensembles—Dirac sea, neutral ensemble, color superconductor, and BCS state—have been compared. In the case of the color interaction between quarks, the BCS state has been certainly chosen as the ground state of the quark ensemble.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Spin–spin correlation length in a two-dimensional frustrated magnet and its relation to doping

In a spherically symmetric self-consistent approach (SSSA), the spin-1/2 J{sub 1}–J{sub 2} Heisenberg model on a two-dimensional square lattice is considered for two-time retarded spin–spin Green’s functions. The spin excitation spectrum, ω(q), and spin gaps at symmetric points are obtained for the entire J{sub 1}–J{sub 2} diagram, i.e., for any ϕ, J{sub 1} = cosϕ, and J{sub 2} = sinϕ. The structure factor c{sub q} and the correlation length ξ at finite temperature are calculated in the entire range of parameters. A radical difference in the behavior of the system in the upper, frustrated (0 ⩽ ϕ ⩽ π), and the lower, nonfrustrated (π ⩽ ϕ ⩽ 2π), regions of the diagram is demonstrated. In the latter region, there is a first-order phase transition that is unique on the phase diagram. For a weakly frustrated antiferromagnet (J{sub 1} > J{sub 2} > 0), the results obtained are compared with the experimental dependence of ξ on temperature and doping level. A correspondence rule is proposed between frustration in a spin model and the doping of an antiferromagnet with holes.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

InGaN/GaN light-emitting diode microwires of submillimeter length

Microcrystalline wire-like InGaN/GaN light-emitting diodes designed as core–shell structures 400–600 μm in length are grown by metal–organic vapor-phase epitaxy on sapphire and silicon substrates. The technology of the titanium-nanolayer-induced ultrafast growth of nanowire and microwire crystals is used. As a current is passed through the microcrystals, an electroluminescence signal is observed in the blue–green spectral region.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Estimation of Evaporation Rate from Gold-Silicon Alloy Based on the Nucleation Time and Nanowire Length Distributions

Abstract—: Nanowires are one of the most promising building blocks for various nanoelectronic devices. Nanowires are usually grown via the so-called vapor-liquid-solid mechanism on the surfaces activated by the droplets of a catalyst (e.g., Au). Here we theoretically studied the impact of the evaporation from the droplet on the nucleation statistics. Within the semi-analyticalapproach, we obtain the relation between the nucleation time distributions and the evaporation rate of atoms from the droplet. We analyze the Si NW length-time dependences to estimate theeffective lifetime of a silicon atom in a gold-silicon alloy at 550°C is about 5 s.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Generation of Microwave Pulses with a Carrier Frequency of 3.8 GHz and a Length of 75 ns by a Relativistic Cherenkov Microwave Oscillator without a Guiding Magnetic Field

In the experiment with an electron energy of ≈500 keV, the long-pulse (~300T, where T is the oscillation period) the generation regime of a relativistic Cherenkov microwave oscillator without a guiding magnetic field at a carrier frequency of 3.8 GHz has been obtained. A high-power microwave radiation pulse length of ~75 ns, a peak generation power of 210 ± 30 MW, and a power conversion efficiency of 9 ± 2% were attained.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Influence of the surface ligand molecules length on the optical properties and photoconductivity of PbS quantum dot condensates

The influence of ligands—organic molecules on the quantum dot (QD) surface—on the optical properties of thin-layer condensates of lead sulfide QDs and the photoconductivity of diode structures based on them has been investigated. A decrease in the ligand length by a factor of 4 is shown to reduce significantly the luminescence-decay time and increase exponentially the conductivity.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

The Probe Length Effect on the Cantilever of an Atomic Force Microscope in Measuring the Mechanical Properties of Living Neurons

Living sensory neurons were studied by atomic force microscopy in the PeakForce QNM mode under near-physiological conditions. The dependence of the measured apparent Young modulus of cells on the ratio of the probe height to the beam length on a used cantilever was revealed. A qualitative explanation based on the analysis of beam strains in two limit cases, in which the probe slides over a studied object and the probe sticks to the latter, was given to the obtained result. It was proposed to classify native cells by the character of their interaction with the probe (sliding or sticking).

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

$J/\psi $-p scattering length from the total and differential photoproduction cross sections

The J/ψ-p scattering length, αJ/ψp, can be extracted from the J/ψ photoproduction cross section near threshold using the Vector Meson Dominance (VMD) model to relate the reaction γp→J/ψp to J/ψp→J/ψp. Such estimates based on experimental data result in values for |αJ/ψp|, which are much lower than most of the theoretical predictions. In this work, we study the relations between the different results, depending on the use of the total or the differential cross sections, and the method of extrapolating the data to threshold in the case of a low-statistics data sample, such as the near threshold J/ψ photoproduction dataset. We estimate a range for |αJ/ψp| of 0.003–0.025 fm as extracted from experimental data within the VMD model and discuss possible reasons for such lower values compared to the theoretical results.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Determining the Length Scale of Transport Impedances in Li-Ion Electrodes: Li(Ni 0.33 Mn 0.33 Co 0.33 )O 2

Battery cathodes are complex multiscale, multifunctional materials. The length scale at which the dominant impedance arises may be difficult to determine even with the most advanced experimental characterization efforts, and thus modeling can play an important role in analysis. Discharge and voltage relaxation curves, interrogated with theory, are used to distinguish between transport impedance that arise on the scale of the active crystal and on the scale of agglomerates (secondary particles) comprised of nanoscale crystals. Model-selection algorithms are applied to determine that the agglomerate scale is dominant in the Li Ni 0.33 Mn 0.33 Co 0.33 O 2 electrode studied here. Furthermore, conditions where the agglomerate and crystal-scale models yield distinct simulation results are demonstrated, providing approaches that can be applied to other systems.

25 ENERGY STORAGE↗
DOE OSTI2021

Editors’ Choice—Ionomer Side Chain Length and Equivalent Weight Impact on High Current Density Transport Resistances in PEMFC Cathodes

Cell voltage at high current densities (HCD) of an operating proton-exchange membrane fuel cell (PEMFC) suffers from losses due to the local-O 2 and bulk-H + transport resistances in the cathode catalyst layer (CCL). Particularly, the interaction of perfluorosulfonic acid (PFSA) ionomer with the carbon supported platinum catalyst plays a critical role in controlling reactant transport to the active site. In this study, we perform a systematic analysis of the side chain length and equivalent weight (EW) of PFSA ionomers on the CCL transport resistances. Ex situ measurements were carried out to quantify the ionomer characteristics such as the molecular weight, proton conductivity and water uptake. Nanomorphology of ionomers cast as 60–120 nm thin-films is characterized using grazing-incidence X-ray scattering. In situ fuel cell electrochemical diagnostic measurements were carried out to quantify the reactant (H + /O 2 ) transport properties of the CCL. Ionomer EW was found to play a major role with decreasing EW yielding higher proton conductivity and water uptake that led to lower bulk-H + and local-O 2 transport resistances in the CCL. Finally, a 1D-semi-empirical performance model has been developed to quantify the impact of ionomer EW on cell voltage loss factors.

08 HYDROGEN↗
DOE OSTI2019

Human Lacrimal Production Rate and Wetted Length of Modified Schirmer's Tear Test Strips

Purpose: To assess and compare the wetting kinetics of sheathed and unsheathed Schirmer's tear test (STT) strips, and to determine the repeatability of 5-minute wetted length (WL) and basal tear production rate (BTPR). Methods:Seventeen subjects underwent two sheathed and unsheathed STTs each for both eyes on four visits on separate days. After administration of topical anesthetic, WLs were measured every 30 seconds for 5 minutes, and BTPRs were calculated for sheathed strips. Limits of agreement (LoA), difference-versus-mean plots (DVM), and the coefficient of repeatability (CR) assessed WL and BTPR repeatabilities. Variance estimates were used to calculate sample sizes for future study. Results: For the unsheathed STT, the mean (SD) difference in WLs between visits was 0.74 (5.05) mm, LoA were [-9.17, 10.64], and CR was 9.17 mm; for the sheathed STT, the mean (SD) intervisit difference was 0.16 (5.94) mm, LoA were [-11.49, 11.8], and CR was 10.53 mm. Eight of 48 sheathed STTs and 20 of 44 unsheathed STTs showed constant WL for the final 90 seconds of the test. The mean (SD) difference between repeated visits for BTPR was approximately 0.0 μL/min, LoA were [-1.82, 1.82], and CR was 1.91 μL/min. Conclusions: Repeatability of sheathed and unsheathed 5-minute WL and BTPR is inadequate for measuring within-subject changes, but is sufficient for group studies with moderate sample sizes. Constant WL for the fiant WL with the unsheathed STT can be explained by balancing evaporation and BTPR. Translational Relevance: Repeatability of the modified STT is evaluated clinically to establish quantitative BTPRs rather than inference from a strip WL.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Restrictive Intraoperative Fluid Therapy is Associated with Decreased Morbidity and Length of Stay Following Hyperthermic Intraperitoneal Chemoperfusion

Background: Recent data have demonstrated multiple benefits of intra- and postoperative fluid restriction in major abdominal surgery; however, data regarding the outcomes of fluid restriction in cytoreductive surgery and hyperthermic intraperitoneal chemoperfusion (CRS/HIPEC) are limited. This study evaluates the safety and short-term clinical outcomes of restricted intraoperative fluid therapy in CRS/HIPEC. Methods: This was a single-institution, retrospective review of all CRS/HIPEC procedures performed at the University of Massachusetts Medical School between January 2009 and July 2017. Recorded variables included demographics, intraoperative factors, 60-day postoperative complications, and length of stay (LOS). Outcomes based on the use of intraoperative permissive fluid therapy (PFT) versus restrictive fluid therapy (RFT) were compared. Results: Overall, 169 CRS/HIPEC cases were performed during the study period; 84 were managed with PFT and 85 were managed with RFT. No significant differences were identified in patient demographics. There was a decrease in intraoperative administration of crystalloid (8.0 vs. 4.4 L, p < 0.01), colloid (900 vs. 300 mL, p < 0.01), and blood transfusion (0.26 vs. 0.04 units, p < 0.01) in the RFT cohort. LOS was reduced from 11.5 to 9.7 days (p < 0.01) and the incidence of any 60-day complication decreased from 45 to 28% (p = 0.02) in the RFT group. The overall 90-day mortality rate was 0.6% (n = 1). Adjusted logistic regression demonstrated the odds of having a Clavien–Dindo grade III or higher complication was 0.31 (95% confidence interval 0.10–0.95) with RFT. Conclusion: Intraoperative RFT with standard anesthesia monitoring devices can be safely used in CRS/HIPEC and is associated with a decreased LOS and decreased rate of postoperative complications.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2025

Full Rod Length Gamma Spectroscopy Measurements of LWR Used Fuel Rods

Twenty-five high-burnup pressurized water reactor used fuel rods were scanned in the Irradiated Fuels Examination Laboratory at Oak Ridge National Laboratory with a high-resolution gamma spectrometer. A planar high-purity germanium detector was used across an energy range from 60 keV to 3 MeV. Gamma spectra of individual fuel rods were collected in 4.5 mm steps along the entire length of each rod. Additional spectra were collected on select rods in rotational increments of 30 degrees to provide data on the distribution of fission products along the rod perimeter.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2013

Scrape-off layer flows with pressure gradient scale length ~ ρ p

A heuristic model for the plasma scrape-off width balances magnetic drifts against parallel loss at c s /2, resulting in a SOL width ~ ρ p . T sep is calculated from Spitzer–Härm parallel thermal conduction. This results in a prediction for the power scrape-off width in quantitative agreement both in magnitude and scaling with recent experimental data. To achieve the ~ c s /2 flow assumed in this model and measured experimentally sets requirements on the ratio of upstream to total SOL particle sources, relative to the square-root of the ratio of target to upstream temperature. The Pfisch-Schlüter model for equilibrium flows has been modified to allow near-sonic flows, appropriate for gradient scale lengths of order ρ p , resulting in a new quadrupole radial flow pattern. The strong parallel flows and plasma charging implied by this model suggest a mechanism for H-mode transition, consistent with many observations

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗