Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Process sensitivity”

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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Charged Pion Production Explorations Using the NOvA Near Detector

Measurements of neutrino-nucleus interactions in the few-GeV region provide crucial inputs to the neutrino oscillation program being carried out by currently running experiments (NOvA, SBN, T2K), and next-generation experiments (DUNE, 2HK). This poster presents the status of a measurement using the high-intensity NuMI beam and the NOvA Near Detector of the flux-integrated differential cross-section in pion kinetic energy for $\nu_\mu + N \rightarrow \mu^- + \pi^\pm + X$, where X does not include any charged pions. This signal is sensitive to inelastic processes with Delta resonance production, which dominate at neutrino energies relevant for NOvA and DUNE. To overcome the difficulty of reconstructing the energy of charged pions in a lower-spatial-resolution detector, a novel analysis technique is used that incorporates a multi-template fit to extract the number of events for two signal categories that differ from one another by their purity and resolution. The two signal categories are combined leveraging their complementary errors into a more informative cross section result.

Ewart, Erin [Indiana U.]↗
DOE OSTI2021

Soliton Generation in Negative Thermal Expansion Materials

Strain solitons have been observed statically in several 2D materials and dynamically in substrate materials using ultrafast laser pulses. The latter case relies on lattice relaxation in response to ultrafast heating in a light-absorbing transducer material, a process which is sensitive to the thermal expansion coefficient. Here we consider an unusual case where the sign of the thermal expansion coefficient is negative, a scenario which is experimentally feasible in light of rapid and recent advances in the discovery of negative thermal expansion materials. We present numerical solutions to a nonlinear differential equation which has been repeatedly demonstrated to quantitatively model experimental data and discuss the salient results using realistic parameters for material linear and nonlinear elasticity. The solitons that emerge from the initial value problem with negative and positive thermal expansion are qualitatively different in several ways. The new case of negative thermal expansion gives rise to a nearly-periodic soliton train with chirped profile and free of an isolated shock front. We suggest this unanticipated result may be realized experimentally and assess the potential for certain applications of this generic effect.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Nitrogen-Fixing Gamma Proteobacteria Azotobacter vinelandii—A Blueprint for Nitrogen-Fixing Plants?

The availability of fixed nitrogen limits overall agricultural crop production worldwide. The so-called modern “green revolution” catalyzed by the widespread application of nitrogenous fertilizer has propelled global population growth. It has led to imbalances in global biogeochemical nitrogen cycling, resulting in a “nitrogen problem” that is growing at a similar trajectory to the “carbon problem”. As a result of the increasing imbalances in nitrogen cycling and additional environmental problems such as soil acidification, there is renewed and increasing interest in increasing the contributions of biological nitrogen fixation to reduce the inputs of nitrogenous fertilizers in agriculture. Interestingly, biological nitrogen fixation, or life’s ability to convert atmospheric dinitrogen to ammonia, is restricted to microbial life and not associated with any known eukaryotes. It is not clear why plants never evolved the ability to fix nitrogen and rather form associations with nitrogen-fixing microorganisms. Perhaps it is because of the large energy demand of the process, the oxygen sensitivity of the enzymatic apparatus, or simply failure to encounter the appropriate selective pressure. Whatever the reason, it is clear that this ability of crop plants, especially cereals, would transform modern agriculture once again. Successfully engineering plants will require creating an oxygen-free niche that can supply ample energy in a tightly regulated manner to minimize energy waste and ensure the ammonia produced is assimilated. Nitrogen-fixing aerobic bacteria can perhaps provide a blueprint for engineering nitrogen-fixing plants. This short review discusses the key features of robust nitrogen fixation in the model nitrogen-fixing aerobe, gamma proteobacteria Azotobacter vinelandii, in the context of the basic requirements for engineering nitrogen-fixing plants.

Microbiology↗
DOE OSTI2024

A Quantum Mechanical MP2 Study of the Electronic Effect of Nonplanarity on the Carbon Pyramidalization of Fullerene C 60

Among C 60 ’s diverse functionalities, its potential application in CO 2 sequestration has gained increasing interest. However, the processes involved are sensitive to the molecule’s electronic structure, aspects of which remain debated and require greater precision. To address this, we performed structural optimization of fullerene C 60 using the QM MP2/6–31G* method. The nonplanarity of the optimized icosahedron is characterized by two types of dihedral angles: 138° and 143°. The 120 dihedrals of 138° occur between two hexagons intersecting at C–C bonds of 1.42 Å, while the 60 dihedrals of 143° are observed between hexagons and pentagons at C–C bonds of 1.47 Å. NBO analysis reveals less pyramidal sp 1.78 hybridization for carbons at the 1.42 Å bonds and more pyramidal sp 2.13 hybridization for the 1.47 Å bonds. Electrostatic potential charges range from -0.04 a.u. to 0.04 a.u. on the carbon atoms. Second-order perturbation analysis indicates that delocalization interactions in the C–C bonds of 1.42 Å (143.70 kcal/mol) and 1.47 Å (34.98 kcal/mol) are 22% and 38% higher, respectively, than those in benzene. MP2/Def2SVP calculations yield a correlation energy of 13.49 kcal/mol per electron for C 60 , slightly higher than the 11.68 kcal/mol for benzene. However, the results from HOMO-LUMO calculations should be interpreted with caution. This study may assist in the rational design of fullerene C 60 derivatives for CO 2 reduction systems.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Revealing the Nano-Scale Structure and Properties of Pinholes in SiOx Layers for POLO Contacts

In this contribution, we report on the charge collection characteristics of silicon photovoltaic devices with passivated contacts based on the c-Si/SiOx /poly-Si structure. Using electron-beam induced current (EBIC) imaging in plan-view and cross-section orientations, we find that charge collection in a device with a 1.5-nm-thick SiOx layer is fairly uniform in the p-n junction region and does not appear to be influenced by pyramidal surface texture. In contrast, a device with a 2.2-nm-thick oxide layer shows significant spatial variation in the charge-collection signal. The locations where we observe preferential collection of excess carriers is very sensitive to the processing conditions used to grow and breakup the SiOx passivation layer. In some cases the apexes of the pyramids exhibit reduced EBIC signal as the valleys between adjacent pyramids show the strongest collection. Other conditions yield enhanced charge collection at well defined spots on pyramid faces with no observable collection in the valleys.

EBIC↗
NASA NTRS1975

Oxygen systems engineering considerations

Special considerations for oxygen systems engineering with respect to system design, fabrication, and use are studied. The concerns for oxygen systems include the problems of leakage and erosion, difficulties that arise from dynamic processes, and the sensitivity of oxygen systems to contamination and cleaning requirements.

Source record↗
NASA NTRS1981

Receiver array for high-rate telemetry

RF carrier uses two receiver systems to increase signal-to-noise ratio and sensitivity. Signals separately processed are coherently combined at summing junction for improved reception of marginal high-rate signals frequently lost to system, atmosphere, and galactic noises. Two receivers improve ratio by 2.7 dB; improvement is made by arraying more receiver systems.

Brockman, M. H.↗
NASA NTRS1983

Improved Photosensor for Light Valves

Processing changes improve performance of liquid-crystal light valve for displaying projection TV images. New approach monitors performance of finished light valves for given changes in CdS process and experimentally to optimize process for good sensitivity and low negative memory.

Koda, N. J.↗
NASA NTRS1985

Studies of condensation effects on airfoil testing in a transonic cryogenic tunnel

In the context of an overall development of transonic, cryogenic wind tunnel technology, NASA has been investigating the onset of condensation effects in nitrogen gas. The temperature at which condensation occurs determines the minimum operating temperature (MOT) of cryogenic tunnels. The apparatus and airfoils are discussed, taking into account a description of the 0.3-m Transonic Cryogenic Tunnel (TCT), the drag rake, the airfoils, and the technique used for determining the onset of condensation effects. Attention is also given to the types of nucleation processes, the relative sensitivity of drag rake and surface pressure measurements, correlations between data and theory, the prediction of minimum operating temperatures for the 0.3-m TCT, and MOT's for different tunnels.

Hall, R. M.↗
NASA NTRS1986

Studies of condensation effects on airfoil testing in the Langley 0.3-meter transonic cryogenic tunnel

In the context of an overall development of transonic, cryogenic wnd tunnel technology, NASA has been investigating the onset of condensation effects in nitrogen gas. The temperature at which condensation occurs determines the minimum operating temperature (MOT) of cryogenic tunnels. The apparatus and airfoils are discussed, taking into account a description of the 0.3-m Transonic Cryogenic Tunnel (TCT), the drag rake, the airfoils, and the technique used for determining the onset of condensation effects. Attention is also given to the types of nucleation processes, the relative sensitivity of drag rake and surface pressure measurements, correlations between data and theory, the prediction of minimum operating temperatures for the 0.3-m TCT, and MOT's for different tunnels.

Hall, R. M.↗
NASA NTRS1988

Flexible Docking Tunnel

Brief report proposes use of flexible tunnel to provide "soft docking" between Space Shuttle Orbiter and space station during resupply visits. Soft docking reduces risks of structural damage to either spacecraft during docking maneuvers, provides adaptable docking interface, and avoids jarring sensitive material-processing experiments in space station. After docking, tunnel pressurized to enable exchange of people and cargo between two spacecraft.

Michaud, Roger↗
NASA NTRS1988

Pupil measures of alertness and mental load

A study of eight adults given active and passive search tasks showed that evoked pupillary response was sensitive to information processing demands. In particular, large pupillary diameter was observed in the active search condition where subjects were actively processing information relevant to task performance, as opposed to the passive search (control) condition where subjects passively viewed the displays. However, subjects may have simply been more aroused in the active search task. Of greater importance was that larger pupillary diameter, corresponding to longer search time, was observed for noncoded than for color-coded displays in active search. In the control condition, pupil diameter was larger with the color displays. The data indicate potential usefulness of pupillary responses in evaluating the information processing requirements of visual displays.

Backs, Richard W.↗
NASA NTRS1987

Combustion rate limits of hydrogen plus hydrocarbon fuel: Air diffusion flames from an opposed jet burner technique

Combustion of H2/hydrocarbon (HC) fuel mixtures may be considered in certain volume-limited supersonic airbreathing propulsion applications. Effects of HC addition to H2 were evaluated, using a recent argon-bathed, coaxial, tubular opposed jet burner (OJB) technique to measure the extinction limits of counterflow diffusion flames. The OJB flames were formed by a laminar jet of (N2 and/or HC)-diluted H2 mixture opposed by a similar jet of air at ambient conditions. The OJB data, derived from respective binary mixtures of H2 and methane, ethylene, or propane HCs, were used to characterize BLOWOFF and RESTORE. BLOWOFF is a sudden breaking of the dish-shaped OJB flame to a stable torus or ring shape, and RESTORE marks sudden restoration of the central flame by radial inward flame propagation. BLOWOFF is a measure of kinetically-limited flame reactivity/speed under highly stretched, but relatively ideal impingement flow conditions. RESTORE measures inward radial flame propagation rate, which is sensitive to ignition processes in the cool central core. It is concluded that relatively small molar amounts of added HC greatly reduce the reactivity characteristics of counterflow hydrogen-air diffusion flames, for ambient initial conditions.

Pellett, Gerald L.↗
NASA NTRS1989

Tidal disruption of open clusters in their parent molecular clouds

A simple model of tidal encounters has been applied to the problem of an open cluster in a clumpy molecular cloud. The parameters of the clumps are taken from the Blitz, Stark, and Long (1988) catalog of clumps in the Rosette molecular cloud. Encounters are modeled as impulsive, rectilinear collisions between Plummer spheres, but the tidal approximation is not invoked. Mass and binding energy changes during an encounter are computed by considering the velocity impulses given to individual stars in a random realization of a Plummer sphere. Mean rates of mass and binding energy loss are then computed by integrating over many encounters. Self-similar evolutionary calculations using these rates indicate that the disruption process is most sensitive to the cluster radius and relatively insensitive to cluster mass. The calculations indicate that clusters which are born in a cloud similar to the Rosette with a cluster radius greater than about 2.5 pc will not survive long enough to leave the cloud. The majority of clusters, however, have smaller radii and will survive the passage through their parent cloud.

Long, Kevin↗
NASA NTRS1988

Response of convective-diffusive transport to spatial and temporal variations in effective gravity

The response of heat, mass, and momentum transport to conditions characteristic of the microgravity environment is studied. It is found that the orientation of the experiment with respect to the steady component of the residual gravity is a crucial factor in determining the suitability of the spacecraft as a means of suppressing or eliminating unwanted effects caused by buoyant fluid motion. The process is highly sensitive to transient disturbances.

Alexander, J. Iwan D.↗
NASA NTRS1993

Transition effects on compressible dynamic stall of transiently pitching airfoils

Experimental results and analysis of the effects of boundary layer tripping on dynamic stall of a transiently pitching airfoil are presented. At low Mach numbers, the tripped airfoil exhibits qualitative similarity with the behavior of the untripped airfoil. However, the local supersonic flow at Mach numbers greater than 0.3 is significantly modified by the trip leading to vastly different shock/boundary layer interactions, dynamic stall onset and vortex formation angles. The formation of the laminar separation bubble is found to have a favorable influence in delaying dynamic stall on the untripped airfoil flow. In both Mach number regimes, the tripped flow actually stalls at slightly lower angles of attack. Further experimentation with three trips on an oscillating airfoil showed that the dynamic stall process is very sensitive to the state of the turbulence in the boundary layer. This sensitivity points to a need for finer turbulence modeling techniques for use in dynamic stall computations.

Wilder, M. C.↗
NASA NTRS1992

Land surface interaction

The topics covered include the following: land and climate modeling; sensitivity studies; the process of a land model; model-specific parameterizations; water stress; within-canopy resistances; partial vegetation; canopy temperature; and present experience with a land model coupled to a general circulation model.

Dickinson, Robert E.↗
NASA NTRS1992

Carbon cycling in high-latitude ecosystems

The carbon-rich soils and peatlands of high-latitude ecosystems could substantially influence atmospheric concentrations of CO2 and CH4 in a changing climate. Currently, cold, often waterlogged conditions retard decomposition, and release of carbon back to the atmosphere may be further slowed by physical protection of organic matter in permafrost. As a result, many northern ecosystems accumulate carbon over time (Billings et al., 1982; Poole and Miller, 1982), and although such rates of accumulation are low, thousands of years of development have left Arctic ecosystems with an extremely high soil carbon content; Schlesinger's (1984) average value of 20.4 kg C/m(sup 2) leads to a global estimate of 163 x 10(exp 15) g C. All GCM simulations of a doubled CO2 climate predict the greatest warming to occur in the polar regions (Dickinson, 1986; Mitchell, 1989). Given the extensive northern carbon pools and the strong sensitivity of decomposition processes to temperature, even a slight warming of the soil could dramatically alter the carbon balance of Arctic ecosystems. If warming accelerates rates of decomposition more than rates of primary production, a sizeable additional accumulation of CO2 in the atmosphere could occur. Furthermore, CH4 produced in anaerobic soils and peatlands of the Arctic already composes a good percentage of the global efflux (Cicerone and Oremlund, 1988); if northern soils become warmer and wetter as a whole, CH4 emissions could dramatically rise. A robust understanding of the primary controls of carbon fluxes in Arctic ecosystems is critical. As a framework for a systematic examination of these controls, we discussed a conceptual model of regional-scale Arctic carbon turnover, including CH4 production, and based upon the Century soil organic matter model.

Townsend, Alan↗