SEARCH · Engineering Papers

Results for “N”

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.

SourceResearch connectionFrom yearThrough year

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

At least 307 records · Page 17

All sources NASA NTRS DOE OSTI

NASA NTRS2023

Ch. 12. A Theoretical Approach to Management of Limited Attentional Resources to Support the m:N Operation in Advanced Air Mobility Ecosystem

Advanced air mobility (AAM) technologies incorporate increasingly autonomous systems that allow fully remote, independent, and intelligent operation of air vehicles to support the transportation of goods and passengers within and across urban and rural areas. With a myriad of automated technologies enabling the AAM ecosystem, the human operator’s role will likely be a passive supervisory monitor of the air vehicles, involving increasingly fewer humans (m) that manage many more autonomous systems (N), or m:N operations. Unfortunately, the human performance literature suggests that human operators will exhibit poor supervision of numerous autonomous agents due to the limits of attentional resources in the operators. In the general human information-processing model, a human operator exercises a limited pool of attentional resources to engage various information-processing stages including detecting, perceiving, comprehending, and predicting objects around them. Yamani and Horrey (2018) expanded the human information-processing model to characterize a tradeoff between information-processing demand and resource relief that automation brings in the context of automated driving. In their model, a driver interacting with an automated driving system is assumed to reallocate resources “freed” by automation to support other information-processing stages required for successful task performance. A future AAM ecosystem enabled by an orchestration of advanced automated systems, however, requires a single operator to interact with more than one air vehicle with varying levels and degrees of automated systems, making the traditional framework of human-automation interaction insufficient. To address this gap, we provide a review of the literature on situation assessment and trust, two constructs identified as critical for a fuller understanding of intimate and intricate interactions between a human operator and multiple air vehicles equipped with increasingly autonomous systems. Then, we propose an expansion of Yamani and Horrey’s (2018) model to motivate systematic research on the human operator’s role, identify factors that influence resource allocation and guide human-centered design of an interface supporting the m:N operation in the AAM environment.

Advanced Air Mobility↗

NASA NTRS2024

m:N Working Group Meeting Summary November 2023

From November 28th to 30th, 2023 the m:N UAS working group and its subgroups [small Unmanned Aircraft Systems (sUAS), Large UAS, High Altitude Platform Systems (HAPS), and Urban Air Mobility (UAM)] met at the NASA Langley Research Center in Hampton, VA for an in person meeting. The subgroups meet multiple times throughout the year, virtually. Twice a year however, participants from all the subgroups come together in person to further identify and discuss challenges, and path forward ideas for incorporating UAS into the airspace. The m:N UAS working group is run by Jay Shively (Adaptive Aerospace) and Andy Thurling (Thurling Aero Consulting) and is comprised of members from government, industry, and academia in an effort to identify and reduce barriers to m:N operations. This effort also includes identifying requirements, use cases, and metrics to support organizations and groups including the FAA, RTCA, and ASTM. Each subgroup is run by a government/industry team (see below). sUAS Subgroup Garrett Sadler (NASA) Scott Scheff (HF Designworks) Large UAS Subgroup Conrad Rory (NASA) Brandon Suarez (Reliable Robotics) HAPS Subgroup Andy Thurling (Thurling Aero Consulting) Jeff Homola (NASA) UAM Subgroup Mike Politowicz (NASA) Scott Scheff (HF Designworks), member-at-large

m:N operations↗

NASA NTRS1974

Maximum power transfer in n ports with passive loads

The problem of drawing maximum power from an n port by suitably terminating it with another passive n port is studied. Methods are derived for determining sets of passive impedance matrices which are 'optimal' in the sense that they draw maximum power from a given n port. It is shown that, in all nontrivial cases, if there exists any (passive or otherwise) optimum-load impedance matrix, then there exist, in fact, infinitely many passive optimum-load impedance matrices.

Vidyasagar, M.↗

NASA NTRS1975

N-body simulations of disks

The methods used in large-scale n-body simulations are discussed. However, the present review concentrates on results already obtained in n-body simulations using systems containing up to 200,000 simulation stars. Results are presented which show that the stability criterion developed for flattened systems applies only to truly axisymmetric instabilities. Purely stellar disks acquire rather large velocity dispersions, generally two or more times the velocity dispersion required by Toomre (1964) for axisymmetric stability. In computer simulations, the bar-forming instability can be prevented only by comparatively large velocity dispersions. However, simulations including the effects of the galactic halo and core as a fixed background field show that bar formation can be prevented for fixed halo components as large or larger than the self-consistent disk component. Experiments performed to determine the collisional relaxation time for large-scale gravitational n-body calculations show that these models are indeed 'collisionless'.

Hohl, F.↗

NASA NTRS1976

On the reaction of N/+/ ions with O2

The reaction of atomic nitrogen ions with molecular oxygen is a major loss mechanism for N(+) ions in the ionosphere and is a source of NO(+) ions and atomic nitrogen at certain altitudes. Ion cyclotron resonance methods are used to measure the product distribution of thermal energy N(+) ions reacting with O2. Three product channels are identified with the following fractional distributions: O2(+) + N, 0.65 plus or minus 0.04; NO(+) + O, 0.31 plus or minus 0.04; O(+) + NO, 0.04 plus or minus 0.02.

Huntress, W. T., Jr.↗

NASA NTRS1978

A maintenance model for k-out-of-n subsystems aboard a fleet of advanced commercial aircraft

Proposed highly reliable fault-tolerant reconfigurable digital control systems for a future generation of commercial aircraft consist of several k-out-of-n subsystems. Each of these flight-critical subsystems will consist of n identical components, k of which must be functioning properly in order for the aircraft to be dispatched. Failed components are recoverable; they are repaired in a shop. Spares are inventoried at a main base where they may be substituted for failed components on planes during layovers. Penalties are assessed when failure of a k-out-of-n subsystem causes a dispatch cancellation or delay. A maintenance model for a fleet of aircraft with such control systems is presented. The goals are to demonstrate economic feasibility and to optimize.

Miller, D. R.↗

NASA NTRS1977

Auroral recombination of N and O - A possible source for emission in the gamma and delta bands of NO

Radiative recombination of N and O provides a significant source for auroral emission in the gamma and delta bands of NO with selective population of vibrational levels in the A 2 Sigma(+) and C 2 Pi states. This mechanism may account for emissions detected near 2150 A. Models are derived for the auroral ionosphere and include estimates for the concentrations of N and NO. The concentration of NO is estimated to have a value of about 100 million per cu cm near 140 km in an IBC III aurora. The corresponding density for N is about 50 million per cu cm, and the concentration ratio NO(+)/O2(+) has a value of about 5.5.

Wofsy, S. C.↗

NASA NTRS1978

Gravitational N-body problem on the accretion process of terrestrial planets

Numerical integration of the gravitational N-body problem has been carried out for a variety of protoplanetary clusters in the range N = 100 to 200. Particles are assumed to coagulate at collisions irrespective of relative velocity and mass ratio of the particles. It is shown graphically how the dispersed N-bodies accumulate to a single planet through mutual collisions. The velocity distribution and size distribution of bodies are also investigated as functions of time in the accretion process. Accretion rates of planets are found to be dependent strongly on the initial number density distribution, the initial size distribution, and the initial velocity distribution of bodies. Formation of satellites of about 10% in the planet mass is common to most cases in the present study. A substantial mass of bodies also escapes from the cluster. Many satellites and escapers formed during the accretion process of planets may be source materials of heavy bombardment in the early history of planets.

Matsui, T.↗

NASA NTRS1977

Stabilization of n-type semiconductors to photoanodic dissolution by competitive electron transfer processes

The behavior of n-type CdX (X = S, Se, Te) and GaP, GaAs, and InP in alkaline electrolytes containing X(--) and X sub n(--) ions is reviewed. Of the 18 combinations of electrode and electrolyte, 12 alliances are completely stable to photoanodic dissolution of the n-type photoanode. In each case the oxidation of the chalcogenide species at the photoanode is reversed at the cathode to complete an electrochemical cycle involving no net chemical change. The best system in terms of light-to-electric energy conversion seems to be the CdTe-based cell employing the Te(--)/Te2(--) electrolyte, with roughly 10% efficiency at an output voltage of 0.35 V for monochromatic 633 nm input optical energy at about 25 mW/sq cm.

Wrighton, M. S.↗

NASA NTRS1979

Solar cell with improved N-region contact and method of forming the same

An improved solar cell, and method of forming the same are disclosed. It is characterized by a semiconductor silicon wafer of P-type material having diffused therein a shallow N-type region. A sintered silver contact is affixed to the surface of the N-type region at the outer surface. The improved solar cell is formulated from silver powder blended with silver metaphosphate for establishing a zone of increased carrier concentration. An aluminum or silver-aluminum alloy contact is affixed to the P-type wafer at the outer surface opposite the N-type region.

Bube, K. R.↗

NASA NTRS1979

The TIROS-N high resolution infrared radiation sounder

The high-resolution infrared radiation sounder (HIRS/2) was developed and flown on the Television and Infrared Observation Satellite, N Series (TIROS-N) as one means of obtaining atmospheric vertical profile information. The HIRS/2 receives visible and infrared spectrum radiation through a single telescope and selects 20 narrow spectral channels by means of a rotating filter wheel. A passive radiant cooler provides an operating temperature of 106.7K for the HgCdTe and InSb detectors while the visible detector operates at instrument frame temperature. Low noise amplifiers and digital processing provide 13 bit data for spacecraft data multiplexing and transmission. The qualities of system performance that determine sounding capability are the dynamic range of data collection, the noise equivalent radiance of the system, the registration of the air columns sampled in each channel, and the ability to upgrade the calibration of the instrument to maintain the performance standard throughout life. The basic performance of the instrument in test is described. Early orbital information from the TIROS-N launched on October 13, 1978 are given and some observations on system quality are made.

Koenig, E. W.↗

NASA NTRS1979

Studies of silicon p-n junction solar cells

To provide theoretical support for investigating different ways to obtain high open-circuit voltages in p-n junction silicon solar cells, an analytical treatment of heavily doped transparent-emitter devices is presented that includes the effects of bandgap narrowing, Fermi-Dirac statistics, a doping concentration gradient, and a finite surface recombination velocity at the emitter surface. Topics covered include: (1) experimental determination of bandgap narrowing in the emitter of silicon p-n junction devices; (2) heavily doped transparent regions in junction solar cells, diodes, and transistors; (3) high-low-emitter solar cell; (4) determination of lifetimes and recombination currents in p-n junction solar cells; (5) MOS and oxide-charged-induced BSF solar cells; and (6) design of high efficiency solar cells for space and terrestrial applications.

Neugroschel, A.↗

NASA NTRS1979

Rapid data comparison technique development for N-ray/X-ray analysis

An operational N-ray/X-ray computer analysis system for nondestructive testing problems was realized by developing: (1) more efficient data transfer routines for use in existing image processing systems; (2) the capability to store and analyze multiple N-ray/X-ray images; (3) an efficient 2-D Fast Fourier Transform; and (4) transfer functions compensation capability to correct for distortions and nonlinearities of N-rays/X-rays. Applications of the technique are summarized for the following: thermal protection system tile with hydraulic fluid; thermal protection system tile with corrosion; thermal protection system tile debonding; stainless steel tubing corrosion; defective electrical devices; fast film restoration and deblur; corrosion tracking over time; reduction of source vignetting, and identification of materials (0 rings, Teflon parts, soft goods) via table look up.

Butterfield, R. L.↗

NASA NTRS1980

Some n-p (Hg,Cd)Te photodiodes for 8-14 micrometer heterodyne applications

The results describing the dc and CO2 laser heterodyne characteristics of a three element photodiode array and single element and four element photodiode arrays are presented. The measured data shows that the n(+)-p configuration is capable of achieving bandwidths of 475 to 725 MHz and noise equivalent powers of 3.2 x 10 to the minus 20th power W/Hz at 77 K and 1.0 x 10 to the minus 19th power W/Hz at 145 K. The n(+)-n(-)-p photodiodes exhibited wide bandwidths (approximately 2.0 GHz) and fairly good effective heterodyne quantum efficiencies (approximately 13-30 percent at 2.0 GHz). Noise equivalent powers ranging from 1.44 x 10 to the minus 19th power W/Hz to 6.23 x 10 to the minus 20th power W/Hz were measured at 2.0 GHz.

Shanley, J. F.↗

NASA NTRS1979

Deep-level transient spectroscopy studies of Ni- and Zn-diffused vapor-phase-epitaxy n-GaAs

The paper presents deep-level transient spectroscopy studies of Ni- and Zn-diffused vapor-phase epitaxy n-GaAs. Nickel diffused into VPE n-GaAs reduces the hole diffusion length L sub p from 4.3 to 1.1 microns. Deep-level transient spectroscopy was used to identify energy levels in Ni-diffused GaAs; the as-grown VPE GaAs contains traces of these levels and an electron trap. Ni diffusion reduces the concentration of this level by an amount that matches the increase in concentration of each of the two Ni-related levels. A technique for measuring minority-carrier capture cross sections was developed, which indicates that L sub p in Ni-diffused VPE n-GaAs is controlled by the E sub c - 0.39 eV defect level.

Partin, D. L.↗

NASA NTRS1980

Thermal reaction of ethynylphthalimides and hydration of N-/4-ethynylphenyl/phthalimide

Three ethynyl substituted phenylphthalimides were prepared and characterized by high pressure liquid chromatography, differential scanning calorimetry, and mass spectroscopy. When the preparation of N-(4-ethynylphenyl)phthalimide was attempted by the thermal cyclodehydration of N-(4-ethynylphenyl)-2-carboxybenzamide, N-(4-acetylphenyl)phthalimide was obtained as the major component. This unusual hydration of an ethynyl group was investigated and a mechanism was proposed to explain it.

Hergenrother, P. M.↗

NASA NTRS1980

Forward- and reverse-bias tunneling effects in n/+/p silicon solar cells

Excess currents due to field-assisted tunneling in both forward and reverse bias directions have been observed in n(+)-p silicon solar cells. These currents arise from the effect of conducting paths produced in the depletion layer by n(+) diffusion and cell processing. Forward-bias data indicate a small potential barrier with height of 0.04 eV at the n(+) end of conducting paths. Under reverse bias, excess tunneling currents involve a potential barrier at the p end of the conducting paths, the longer paths being associated with smaller barrier heights and dominating at the lower temperatures. Low-reverse-bias data give energy levels of 0.11 eV for lower temperatures (253-293 K) and 0.35 eV for higher temperatures (293-380 K). A model is suggested to explain the results.

Garlick, G. F. J.↗

NASA NTRS1980

A multiple p-n junction structure obtained from as-grown Czochralski silicon crystals by heat treatment - Application to solar cells

Multiple p-n junctions have been prepared in as-grown Czochralski p-type silicon through overcompensation near the oxygen periodic concentration maxima by oxygen thermal donors generated during heat treatment at 450 C. Application of the multiple p-n-junction configuration to photovoltaic energy conversion has been investigated. A new solar-cell structure based on multiple p-n-junctions was developed. Theoretical analysis showed that a significant increase in collection efficiency over the conventional solar cells can be achieved.

Chi, J. Y.↗