Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “attributes”

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 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Source attribution of Arctic black carbon and sulfate aerosols and associated Arctic surface warming during 1980–2018

Observations show that the concentrations of Arctic sulfate and black carbon (BC) aerosols have declined since the early 1980s. Previous studies have reported that reducing sulfate aerosols potentially contributed to the recent rapid Arctic warming. In this study, a global aerosol–climate model (Community Atmosphere Model, version 5) equipped with Explicit Aerosol Source Tagging (CAM5-EAST) is applied to quantify the source apportionment of aerosols in the Arctic from 16 source regions and the role of aerosol variations in affecting changes in the Arctic surface temperature from 1980 to 2018. The CAM5-EAST simulated surface concentrations of sulfate and BC in the Arctic had a decrease of 43% and 23%, respectively, in 2014–2018 relative to 1980–1984 mainly due to the reduction of emissions from Europe, Russia and local Arctic sources. Increases in emissions from South and East Asia led to positive trends in Arctic sulfate and BC in the upper troposphere. All aerosol radiative impacts are considered including aerosol–radiation and aerosol–cloud interactions, as well as black carbon deposition on snow- and ice-covered surfaces. Within the Arctic, sulfate reductions caused a top-of-atmosphere (TOA) warming of 0.11 and 0.25 W m -2 through aerosol–radiation and aerosol–cloud interactions, respectively. While the changes in Arctic atmospheric BC has little impact on local radiative forcing, the decrease in BC in snow and ice led to a net cooling of 0.05 W m -2 . By applying climate sensitivity factors for different latitudinal bands, global changes in sulfate and BC during 2014–2018 (with respect to 1980–1984) exerted a +0.088 and 0.057 K Arctic surface warming, respectively, through aerosol–radiation interactions. Through aerosol–cloud interactions, the sulfate reduction caused an Arctic warming of +0.193 K between the two time periods. The weakened BC effect on snow–ice albedo led to an Arctic surface cooling of -0.041 K. The changes in atmospheric sulfate and BC outside the Arctic produced a total Arctic warming of +0.25 K, the majority of which is due to the midlatitude changes in radiative forcing. Our results suggest that changes in aerosols over the midlatitudes of the Northern Hemisphere have a larger impact on Arctic temperature than other regions through enhanced poleward heat transport. The combined total effects of sulfate and BC produced an Arctic surface warming of +0.297 K, explaining approximately 20% of the observed Arctic warming since the early 1980s.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Source attribution of near-surface ozone trends in the United States during 1995–2019

Emissions of ozone (O 3 ) precursors in the United States have decreased in recent decades, and near-surface O 3 concentrations showed a significant decrease in summer but an increase in winter. In this study, an O 3 source tagging technique is utilized in a chemistry–climate model to investigate the source contributions to O 3 mixing ratios in the US from various emitting sectors and regions of nitrogen oxides (NO x ) and reactive carbon species during 1995–2019. We show that domestic emission reductions from energy and surface transportation are primarily responsible for the decrease in summertime O 3 during 1995–2019. However, in winter, the emission control also weakens the NO x titration process, resulting in considerable increases in O 3 levels from natural sources. Additionally, increases in aviation and shipping emissions and transpacific transport of O 3 from Asia largely contribute to the winter O 3 increase. We also found that changes in large-scale circulation favoring O 3 transport from the upper atmosphere and foreign transport from Asia also explain 15 % of the increase in the US near-surface O 3 levels in winter.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

A new aerial approach for quantifying and attributing methane emissions: implementation and validation

Methane (CH 4 ) is a powerful greenhouse gas that is produced by a diverse set of natural and anthropogenic emission sources. Biogenic methane sources generally involve anaerobic decay processes such as those occurring in wetlands, melting permafrost, or the digestion of organic matter in the guts of ruminant animals. Thermogenic CH 4 sources originate from the breakdown of organic material at high temperatures and pressure within the Earth's crust, a process which also produces more complex trace hydrocarbons such as ethane (C 2 H 6 ). Here, we present the development and deployment of an uncrewed aerial system (UAS) that employs a fast (1 Hz) and sensitive (1–0.5 ppb s -1 ) CH 4 and C 2 H 6 sensor and ultrasonic anemometer. The UAS platform is a vertical-takeoff, hexarotor drone (DJI Matrice 600 Pro, M600P) capable of vertical profiling to 120 m altitude and plume sampling across scales up to 1 km. Simultaneous measurements of CH 4 and C 2 H 6 concentrations, vector winds, and positional data allow for source classification (biogenic versus thermogenic), differentiation, and emission rates without the need for modeling or a priori assumptions about winds, vertical mixing, or other environmental conditions. The system has been used for direct quantification of methane point sources, such as orphan wells, and distributed emitters, such as landfills and wastewater treatment facilities. With detectable source rates as low as 0.04 and up to ~1500 kg h -1 , this UAS offers a direct and repeatable method of horizontal and vertical profiling of emission plumes at scales that are complementary to regional aerial surveys and localized ground-based monitoring.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1977

Study of limitations and attributes of microprocessor testing techniques

All microprocessor units have a similar architecture from which a basic test philosophy can be adopted and used to develop an approach to test each module separately in order to verify the functionality of each module within the device using the input/output pins of the device and its instruction set; test for destructive interaction between functional modules; and verify all timing, status information, and interrupt operations of the device. Block and test flow diagrams are given for the 8080, 8008, 2901, 6800, and 1802 microprocessors. Manufacturers are listed and problems encountered in testing the modules are discussed. Test equipment and methods are described.

Mccaskill, R.↗
NASA NTRS1976

Further characterization of spectral features attributable to titanium on the moon

The following transitions are observed in the electronic absorption spectra of lunar titanaugites: Fe(2+) spin-allowed and spin-forbidden crystal field; Ti(3+) spin allowed and Jahn-Teller split crystal field; Ti(3+)-Ti(4+) CT; Fe(2+)-Ti(4+) CT; and O(2-)-Fe(2+), Ti(3+), Ti(4+) CT. Of these, the transitions involving Ti(3+) are unique to lunar or nonferric-bearing titanaugites. All titanaugites have the Fe(2+) crystal field and Fe(2+)-Ti(4+) CT transitions in common. These features in the diffuse reflectance spectra of lunar materials give rise to the '1.0 band' and to the observed absorption around 0.5-0.6 micron, respectively. Since regolith contains a variety of phases with coexisting Fe(2+), Ti(3+), and Ti(4+) ions, several metal-metal charge transfer processes are possible.

Burns, R. G.↗
NASA NTRS1977

Multi-attribute subjective evaluations of manual tracking tasks vs. objective performance of the human operator

A computational method to deal with the multidimensional nature of tracking and/or monitoring tasks is developed. Operator centered variables, including the operator's perception of the task, are considered. Matrix ratings are defined based on multidimensional scaling techniques and multivariate analysis. The method consists of two distinct steps: (1) to determine the mathematical space of subjective judgements of a certain individual (or group of evaluators) for a given set of tasks and experimental conditionings; and (2) to relate this space with respect to both the task variables and the objective performance criteria used. Results for a variety of second-order trackings with smoothed noise-driven inputs indicate that: (1) many of the internally perceived task variables form a nonorthogonal set; and (2) the structure of the subjective space varies among groups of individuals according to the degree of familiarity they have with such tasks.

Siapkaras, A.↗
NASA NTRS1979

Investigation of reliability attributes and accelerated stress factors on terrestrial solar cells

The results of accelerated stress testing of four different types of silicon terrestrial solar cells are discussed. The accelerated stress tests used included bias-temperature tests, bias-temperature-humidity tests, thermal cycle and thermal shock tests, and power cycle tests. Characterization of the cells was performed before stress testing and at periodic down-times, using electrical measurement, visual inspection, and metal adherence pull tests. Electrical parameters measured included short-circuit current, open circuit voltage, and output power, voltage, and current at the maximum power point. Incorporated in the report are the distributions of the prestress electrical data for all cell types. Data were also obtained on cell series and shunt resistance.

Prince, J. L.↗
NASA NTRS1979

Engineering Area Investigation of Reliability Attributes and Accelerated Stress Factors on Terrestrial Solar Cells

Results obtained include the definition of a simplified stress test schedule for terrestrial solar cells based on the work performed during the first program year, and the design and fabrication of improved jigs and fixtures for electrical measurement and stress testing. Implementation of these advanced techniques for accelerated stress testing is underway on three solar cell types. In addition, review of the literature on second quadrant phenomena was begun and some preliminary second-quadrant electrical measurements were performed. Results obtained at the first down time for 75 C B-T testing and biased and unbiased T-H pressure cooker testing of type F cells showed little or no degradation in electrical parameters. Significant physical effects (large solder bubbles) were noted for type F cells subjected to the pressure cooker stress test.

Lathrop, J. W.↗
NASA NTRS1981

Investigation of reliability attributes and accelerated stress factors on terrestrial solar cells

Major effort during this reporting period was devoted to two tasks: improvement of the electrical measurement instrumentation through the design and construction of a microcomputer controlled short interval tester, and better understanding of second quadrant behavior by developing a mathematical model relating cell temperature to electrical characteristics. In addition, some preliminary work is reported on an investigation into color changes observed after stressing.

Lathrop, J. W.↗
NASA NTRS1982

Investigation of reliability attributes and accelerated stress factors on terrestrial solar cells

The accelerated stress test results obtained on all terrestrial solar cells since the inception of the program are summarized. Tested cells were grouped according to the method used to form the conductive metallization layer: solder dipped, vacuum deposited, screen printed, and copper plated. Although metallization systems within each group were quite similar, they differed in numerous details according to the procedures employed by each manufacturer. Test results were summarized for all cells according to both electrical degradation and catastrophic mechanical changes. These results indicated a variability within each metallization category which was dependent on the manufacturer. Only one manufacturer was represented in the copper plated category and, although these showed no signs of detrimental copper diffusion during high temperature testing, their metallization was removed easily during high humidity pressure cooker testing. Preliminary testing of encapsulated cells showed no major differences between encapsulated and unencapsulated cells when subjected to accelerated testing.

Lathrop, J. W.↗
NASA NTRS1983

Space station needs, attributes, and architectural options study

The top level, time-phased total space program support system architecture is described including progress from the use of ground-based space shuttle, teleoperator system, extended duration orbiter, and multimission spacecraft, to an initial 4-man crew station at 29 deg inclination in 1991, to a growth station with an 8-man crew with capabilities for OTV high energy orbit payload placement and servicing, assembly, and construction of mission payloads in 1994. System Z, proposed for Earth observation missions in high inclination orbit, can be accommodated in 1993 using a space station derivative platform. Mission definition, system architecture, and benefits are discussed.

Source record↗