Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Injection”

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 1,315 records · Page 73
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Upper Troposphere Smoke Injection From Large Areal Fires

Abstract Large areal fires, such as those ignited following a nuclear detonation, can inject smoke into the upper troposphere and lower stratosphere. Detailed fire simulations allow for assessment of how local weather interacts with these fires and affects smoke lofting. In this study, we employ the fire simulation package in the Weather Research and Forecasting (WRF‐Fire) model, Version 4.0.1, to explore how smoke lofting from a fire burning a homogeneous fuel bed changes with varying local winds, relative humidity, and atmospheric boundary‐layer stability for two different‐sized areal fires. The presence of moisture has the greatest influence on the results by raising the altitude of lofting, while faster wind speeds dampen lofting and lower the injection height. Stably stratified conditions inhibit plume propagation compared with neutrally stratified conditions, although the impact of stability is not as strong as that of moisture and winds. These findings highlight the importance of using an appropriate atmospheric profile when simulating large fires, as the local weather can have a meaningful influence on smoke lofting.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Seismic Diffusivity and the Influence of Heterogeneity on Injection‐Induced Seismicity

Abstract The spatiotemporal patterns of injection‐induced seismicity (IIS) are commonly interpreted with the concept of a triggering front, which propagates in a diffusion‐like manner with an associated diffusivity parameter. Here, we refer to this diffusivity as the “seismic diffusivity.” Several previous studies implicitly assume that seismic diffusivity is equivalent to the effective hydraulic diffusivity of the subsurface, which describes the behavior of the mean pressure field in heterogeneous porous media. Seismicity‐based approaches for hydraulic characterization or simulations of IIS using domains of homogeneous equivalent porous media are implicitly based on this assumed equivalence. However, seismicity is expected to propagate with the threshold triggering pressure, and thus not be controlled by the evolution of the mean pressure field. We present numerical simulations of fluid injection to compare the seismic and effective hydraulic diffusivities in heterogeneous formations (including fractured rock). The numerical model combines uncoupled, linear pressure diffusion with the Mohr‐Coulomb failure criterion to simulate IIS. We demonstrate that connected pathways of relatively high hydraulic diffusivity in heterogeneous media (particularly in fractured rock domains) allow the threshold triggering pressure to propagate more rapidly than predicted by the effective hydraulic diffusivity. As a result, the seismic diffusivity is greater than the effective hydraulic diffusivity in heterogeneous porous media, possibly by an order of magnitude or more. Additionally, we present a case study of IIS near Soultz‐sous‐Forêts where seismic diffusivity is found to be at least one order of magnitude larger than the effective hydraulic diffusivity.

Haagenson, Ryan↗
DOE OSTI2023

Active‐Source Seismic Imaging of Fault Re‐Activation and Leakage: An Injection Experiment at the Mt Terri Rock Laboratory, Switzerland

Abstract We conducted a time‐lapse seismic experiment utilizing automated active seismic source and sensor arrays to monitor a reactivated fault within the Opalinus clay formation at the Mont Terri Rock Laboratory (Switzerland), an analog caprock for geologic carbon storage. A series of six brine injections were conducted into the so‐called Main Fault to reactivate it. Seismic instrumentation in five monitoring boreholes on either side of the fault was used to continuously probe changes in P‐wave travel‐times associated with fault displacement and leakage. We performed time‐lapse travel‐time tomography on five hundred sequential data sets; this revealed a zone of decreased P‐wave velocity, up to 16 m/s, during each injection cycle, followed by a velocity increase during shut‐in. These results demonstrate varying elastic property perturbations, both spatially and temporally, along the fault plane during reactivation. We then interpreted these velocity changes in terms of fault dilation induced by pressurized fluids along the fault.

58 GEOSCIENCES↗
DOE OSTI2025

Unsupervised Clustering of Microseismic Events and Focal Mechanism Analysis at the CO 2 Injection Site in Decatur, Illinois

Characterization of induced microseismicity at a carbon dioxide (CO 2 ) storage site is critical for preserving reservoir integrity and mitigating seismic hazards. We apply a multilevel machine learning (ML) approach that combines the nonnegative matrix factorization and hidden Markov model to extract spectral representations of microseismic events and cluster them to identify seismic patterns at the Illinois Basin-Decatur Project. Unlike traditional waveform correlation methods, this approach leverages spectral characteristics of first arrivals to improve event classification and detect previously undetected planes of weakness. By integrating ML-based clustering with focal mechanism analysis, we resolve small-scale fault structures that are below the detection limits of conventional seismic imaging. Our findings reveal temporal bursts of microseismicity associated with brittle failure, providing insights into the spatio-temporal evolution of fault reactivation during CO 2 injection. This approach enhances seismic monitoring capabilities at CO 2 injection sites by improving fault characterization beyond the resolution of standard geophysical surveys.

Willis, Rachel Marie [Sandia National Laboratories↗
DOE OSTI2016

Spin injection and inverse Edelstein effect in the surface states of topological Kondo insulator SmB 6

There has been considerable interest in exploiting the spin degrees of freedom of electrons for potential information storage and computing technologies. Topological insulators (TIs), a class of quantum materials, have special gapless edge/surface states, where the spin polarization of the Dirac fermions is locked to the momentum direction. This spin–momentum locking property gives rise to very interesting spin-dependent physical phenomena such as the Edelstein and inverse Edelstein effects. However, the spin injection in pure surface states of TI is very challenging because of the coexistence of the highly conducting bulk states. Here, we experimentally demonstrate the spin injection and observe the inverse Edelstein effect in the surface states of a topological Kondo insulator, SmB 6 . At low temperatures when only surface carriers are present, a clear spin signal is observed. Moreover, the magnetic field angle dependence of the spin signal is consistent with spin–momentum locking property of surface states of SmB6.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Gain dynamics in a soft X-ray laser ampli er perturbed by a strong injected X-ray eld

Seeding soft X-ray plasma ampli ers with high harmonics has been demonstrated to generate high-brightness soft X-ray laser pulses with full spatial and temporal coherence. The interaction between the injected coherent eld and the swept-gain medium has been modelled. However, no exper- iment has been conducted to probe the gain dynamics when perturbed by a strong external seed eld. Here, we report the rst X-ray pump X-ray probe measurement of the nonlinear response of a plasma ampli er perturbed by a strong soft X-ray ultra-short pulse. We injected a sequence of two time-delayed high-harmonic pulses (l518.9 nm) into a collisionally excited nickel-like molybdenum plasma to measure with femto-second resolution the gain depletion induced by the saturated ampli cation of the high-harmonic pump and its subsequent recovery. The measured fast gain recovery in 1.5 1.75 ps con rms the possibility to generate ultra-intense, fully phase-coherent soft X-ray lasers by chirped pulse ampli cation in plasma ampli ers.

Wang, Yong↗
DOE OSTI2020

Causal mechanism of injection-induced earthquakes through the M w 5.5 Pohang earthquake case study

Causal mechanisms for fluid injection-induced earthquakes remain a challenge to identify. Past studies largely established spatiotemporal correlations. Here, we propose a multi-process causal mechanism for injection-induced earthquakes through a case study of the 2017 M w 5.5 induced earthquake near Pohang Enhanced Geothermal System, Korea, where detailed hydraulic stimulation and on-site seismicity monitoring data provide an unprecedented opportunity. Pore pressure modeling reveals that pore pressure changes initiate seismicity on critically stressed faults and Coulomb static stress transfer modeling reveals that earthquake interactions promote continued seismicity, leading to larger events. On the basis of these results, we propose the following causal mechanism for induced seismicity: pore pressure increase and earthquake interactions lead to fault weakening and ultimately triggering larger earthquakes later in the process. We suggest that it is prudent that pore pressure change, initial seismicity locations, and Coulomb static stress transfer from seismicity earlier in the sequence are assessed in real-time.

58 GEOSCIENCES↗
DOE OSTI2024

Room-temperature spin injection across a chiral perovskite/III–V interface

Spin accumulation in semiconductor structures at room temperature and without magnetic fields is key to enable a broader range of optoelectronic functionality. Current efforts are limited owing to inherent inefficiencies associated with spin injection across semiconductor interfaces. Here we demonstrate spin injection across chiral halide perovskite/III-V interfaces achieving spin accumulation in a standard semiconductor III-V (Al x Ga 1-x ) 0.5 In 0.5 P multiple quantum well light-emitting diode. The spin accumulation in the multiple quantum well is detected through emission of circularly polarized light with a degree of polarization of up to 15 ± 4%. The chiral perovskite/III-V interface was characterized with X-ray photoelectron spectroscopy, cross-sectional scanning Kelvin probe force microscopy and cross-sectional transmission electron microscopy imaging, showing a clean semiconductor/semiconductor interface at which the Fermi level can equilibrate. Finally, these findings demonstrate that chiral perovskite semiconductors can transform well-developed semiconductor platforms into ones that can also control spin.

14 SOLAR ENERGY↗
DOE OSTI2025

Stratospheric aerosol injection can weaken the carbon dioxide greenhouse effect

Abstract Stratospheric aerosol injection is a proposed method for offsetting greenhouse gas-induced warming by introducing scattering aerosols into the lower stratosphere to reflect sunlight. Here we explore a potentially more efficient alternative: weakening the Earth’s greenhouse effect by deploying absorptive aerosols in the upper stratosphere (~10 hPa). These aerosols warm the carbon dioxide emission level—where outgoing longwave radiation is most sensitive to temperature—thereby enhancing top-of-atmosphere infrared emission without altering atmospheric carbon dioxide concentrations. Idealized climate model simulations indicate that this approach can reduce global temperatures an order of magnitude more efficiently per unit aerosol mass than conventional scattering-based interventions. Although based on simplified model experiments lacking interactive aerosol processes and operational constraints, our results identify a distinct physical mechanism for climate intervention, arguing for further research into the impacts—especially potential unintended side effects—of injecting absorptive aerosols into the upper stratosphere as an alternative solar radiation management strategy.

Environmental Sciences & Ecology↗
DOE OSTI2024

Question-answering system extracts information on injection drug use from clinical notes

Background. Injection drug use (IDU) can increase mortality and morbidity. Therefore, identifying IDU early and initiating harm reduction interventions can benefit individuals at risk. However, extracting IDU behaviors from patients’ electronic health records (EHR) is difficult because there is no other structured data available, such as International Classification of Disease (ICD) codes, and IDU is most often documented in unstructured free-text clinical notes. Although natural language processing can efficiently extract this information from unstructured data, there are no validated tools. Methods. Here, to address this gap in clinical information, we design a question-answering (QA) framework to extract information on IDU from clinical notes for use in clinical operations. Our framework involves two main steps: (1) generating a gold-standard QA dataset and (2) developing and testing the QA model. We use 2323 clinical notes of 1145 patients curated from the US Department of Veterans Affairs (VA) Corporate Data Warehouse to construct the gold-standard dataset for developing and evaluating the QA model. We also demonstrate the QA model’s ability to extract IDU-related information from temporally out-of-distribution data. Results. Here, we show that for a strict match between gold-standard and predicted answers, the QA model achieves a 51.65% F1 score. For a relaxed match between the gold-standard and predicted answers, the QA model obtains a 78.03% F1 score, along with 85.38% Precision and 79.02% Recall scores. Moreover, the QA model demonstrates consistent performance when subjected to temporally out-of-distribution data. Conclusions. Our study introduces a QA framework designed to extract IDU information from clinical notes, aiming to enhance the accurate and efficient detection of people who inject drugs, extract relevant information, and ultimately facilitate informed patient care.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Spin-polarized current injection induced magnetic reconstruction at oxide interface

Electrical manipulation of magnetism presents a promising way towards using the spin degree of freedom in very fast, low-power electronic devices. Though there has been tremendous progress in electrical control of magnetic properties using ferromagnetic (FM) nanostructures, an opportunity of manipulating antiferromagnetic (AFM) states should offer another route for creating a broad range of new enabling technologies. Here we selectively probe the interface magnetization of SrTiO 3 /La 0.5 Ca 0.5 MnO 3 /La 0.7 Sr 0.3 MnO 3 heterojunctions and discover a new spin-polarized current injection induced interface magnetoelectric (ME) effect. The accumulation of majority spins at the interface causes a sudden, reversible transition of the spin alignment of interfacial Mn ions from AFM to FM exchange-coupled, while the injection of minority electron spins alters the interface magnetization from C-type to A-type AFM state. In contrast, the bulk magnetization remains unchanged. We attribute the current-induced interface ME effect to modulations of the strong double-exchange interaction between conducting electron spins and local magnetic moments. As a result, the effect is robust and may serve as a viable route for electronic and spintronic applications.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Analysis of neoclassical tearing mode stabilization experiment by electron cyclotron injection in KSTAR

We report the neoclassical tearing mode (NTM) stabilization experimental results by injection of the electron cyclotron (EC) beam in KSTAR, and its analysis with integrated modelling. In the KSTAR experiment, NTM was intentionally induced and the EC beam was injected by the plasma control system (PCS) to stabilize it. Here, the EC angle was controlled based on the minimum seeking algorithm for the island growth rate. Although the EC angle was not changed significantly, the island width significantly decreased towards the end of the experiment followed by the recovery of plasma performance. To assess the NTM stabilization experiment from a stability perspective, we performed integrated modelling with TRIASSIC utilizing the reconstructed equilibrium with magnetic diagnostics and motional stark effect diagnostics. As a result, we observed that the NTM is stabilized by EC.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

Validation of single-fluid and two-fluid magnetohydrodynamic models of the helicity injected torus spheromak experiment with the NIMROD code

We present a comparison study of 3-D pressureless resistive MHD (rMHD) and 3-D presureless two-fluid MHD models of the Helicity Injected Torus with Steady Inductive helicity injection (HIT-SI). HIT-SI is a current drive experiment that uses two geometrically asymmetric helicity injectors to generate and sustain toroidal plasmas. The comparable size of the collisionless ion skin depth d{sub i} to the resistive skin depth predicates the importance of the Hall term for HIT-SI. The simulations are run with NIMROD, an initial-value, 3-D extended MHD code. The modeled plasma density and temperature are assumed uniform and constant. The helicity injectors are modeled as oscillating normal magnetic and parallel electric field boundary conditions. The simulations use parameters that closely match those of the experiment. The simulation output is compared to the formation time, plasma current, and internal and surface magnetic fields. Results of the study indicate 2fl-MHD shows quantitative agreement with the experiment while rMHD only captures the qualitative features. The validity of each model is assessed based on how accurately it reproduces the global quantities as well as the temporal and spatial dependence of the measured magnetic fields. 2fl-MHD produces the current amplification (I{sub tor}/I{sub inj}) and formation time τ{sub f} demonstrated by HIT-SI with similar internal magnetic fields. rMHD underestimates (I{sub tor}/I{sub inj}) and exhibits much a longer τ{sub f}. Biorthogonal decomposition (BD), a powerful mathematical tool for reducing large data sets, is employed to quantify how well the simulations reproduce the measured surface magnetic fields without resorting to a probe-by-probe comparison. BD shows that 2fl-MHD captures the dominant surface magnetic structures and the temporal behavior of these features better than rMHD.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

Reduction of plasma density in the Helicity Injected Torus with Steady Inductance experiment by using a helicon pre-ionization source

A helicon based pre-ionization source has been developed and installed on the Helicity Injected Torus with Steady Inductance (HIT-SI) spheromak. The source initiates plasma breakdown by injecting impurity-free, unmagnetized plasma into the HIT-SI confinement volume. Typical helium spheromaks have electron density reduced from (2–3) × 10{sup 19} m{sup −3} to 1 × 10{sup 19} m{sup −3}. Deuterium spheromak formation is possible with density as low as 2 × 10{sup 18} m{sup −3}. The source also enables HIT-SI to be operated with only one helicity injector at injector frequencies above 14.5 kHz. A theory explaining the physical mechanism driving the reduction of breakdown density is presented.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

Highly polarized emission from electrical spin injection into an InGaAs quantum well with free carriers

We report on a highly polarized emission from InGaAs/GaAs-quantum well light-emitting diodes in which we inject spin-polarized electrons from an Fe/Schottky contact. The emission spectra consist of the e{sub 1}h{sub 1} free exciton (FX) and a feature 12 meV below FX attributed to band-to-band (BB) recombination. The FX exhibits a maximum circular polarization of 22%, with a magnetic-field dependence characteristic of spin injection from Fe. The BB emission on the other hand exhibits a polarization that is strongly bias and temperature dependent, with intriguing magnetic-field dependence: The polarization exhibits a maximum of 78% at 2.5 T and 2 K, then decreases linearly with field and reaches −78% at 7 T, attributed to magnetic-field dependent spin relaxation in the presence of excess electrons.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2013

Terahertz graphene lasers: Injection versus optical pumping

We analyze the formation of nonequilibrium states in optically pumped graphene layers and in forward-biased graphene structures with lateral p-i-n junctions and consider the conditions of population inversion and lasing. The model used accounts for intraband and interband relaxation processes as well as deviation of the optical phonon system from equilibrium. As shown, optical pumping suffers from a significant heating of both the electron-hole plasma and the optical phonon system, which can suppress the formation of population inversion. In the graphene structures with p-i-n junction, the injected electrons and holes have relatively low energies, so that the effect of cooling can be rather pronounced, providing a significant advantage of the injection pumping in realization of graphene terahertz lasers.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Tailoring of polarization in electron blocking layer for electron confinement and hole injection in ultraviolet light-emitting diodes

The influence of the AlGaN electron blocking layer (EBL) with graded aluminum composition on electron confinement and hole injection in AlGaN-based ultraviolet light-emitting diodes (LEDs) are investigated. The light output power of LED with graded AlGaN EBL was markedly improved, comparing to LED with conventional EBL. In experimental results, a high increment of 86.7% can be obtained in light output power. Simulation analysis shows that via proper modification of the barrier profile from the last barrier of the active region to EBL, not only the elimination of electron overflow to p-type layer can be achieved but also the hole injection into the active region can be enhanced, compared to a conventional LED structure. The dominant factor to the performance improvement is shown to be the modulation of polarization field by the graded Al composition in EBL.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Organic integrated circuits for information storage based on ambipolar polymers and charge injection engineering

Ambipolar semiconducting polymers, characterized by both high electron (μ{sub e}) and hole (μ{sub h}) mobility, offer the advantage of realizing complex complementary electronic circuits with a single semiconducting layer, deposited by simple coating techniques. However, to achieve complementarity, one of the two conduction paths in transistors has to be suppressed, resulting in unipolar devices. Here, we adopt charge injection engineering through a specific interlayer in order to tune injection into frontier energy orbitals of a high mobility donor-acceptor co-polymer. Starting from field-effect transistors with Au contacts, showing a p-type unbalanced behaviour with μ{sub h} = 0.29 cm{sup 2}/V s and μ{sub e} = 0.001 cm{sup 2}/V s, through the insertion of a caesium salt interlayer with optimized thickness, we obtain an n-type unbalanced transistor with μ{sub e} = 0.12 cm{sup 2}/V s and μ{sub h} = 8 × 10{sup −4} cm{sup 2}/V s. We applied this result to the development of the basic pass-transistor logic building blocks such as inverters, with high gain and good noise margin, and transmission-gates. In addition, we developed and characterized information storage circuits like D-Latches and D-Flip-Flops consisting of 16 transistors, demonstrating both their static and dynamic performances and thus the suitability of this technology for more complex circuits such as display addressing logic.

36 MATERIALS SCIENCE↗