SEARCH · Engineering Papers

Results for “Air Sampling”

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 757 records · Page 42

All sources NASA NTRS DOE OSTI

DOE OSTI2014

On the validity of the Poisson assumption in sampling nanometer-sized aerosols

A Poisson process is traditionally believed to apply to the sampling of aerosols. For a constant aerosol concentration, it is assumed that a Poisson process describes the fluctuation in the measured concentration because aerosols are stochastically distributed in space. Recent studies, however, have shown that sampling of micrometer-sized aerosols has non-Poissonian behavior with positive correlations. The validity of the Poisson assumption for nanometer-sized aerosols has not been examined and thus was tested in this study. Its validity was tested for four particle sizes - 10 nm, 25 nm, 50 nm and 100 nm - by sampling from indoor air with a DMA- CPC setup to obtain a time series of particle counts. Five metrics were calculated from the data: pair-correlation function (PCF), time-averaged PCF, coefficient of variation, probability of measuring a concentration at least 25% greater than average, and posterior distributions from Bayesian inference. To identify departures from Poissonian behavior, these metrics were also calculated for 1,000 computer-generated Poisson time series with the same mean as the experimental data. For nearly all comparisons, the experimental data fell within the range of 80% of the Poisson-simulation values. Essentially, the metrics for the experimental data were indistinguishable from a simulated Poisson process. The greater influence of Brownian motion for nanometer-sized aerosols may explain the Poissonian behavior observed for smaller aerosols. Although the Poisson assumption was found to be valid in this study, it must be carefully applied as the results here do not definitively prove applicability in all sampling situations.

concentration measurement↗

DOE OSTI2013

Synthesis of Sr{sub 0.9}K{sub 0.1}FeO{sub 3-{delta}} electrocatalysts by mechanical activation

Potassium-substituted SrFeO{sub 3-{delta}} for possible application as oxygen evolution electrode in alkaline or molten salt media was prepared by mechanical activation and characterized by X-ray diffraction, dilatometric and thermogravimetric analysis, Moessbauer spectroscopy, and electrical conductivity measurements. Room temperature mechanical activation of a mixture of oxide precursors with subsequent thermal treatments at 700-900 Degree-Sign C results in the formation of Sr{sub 0.9}K{sub 0.1}FeO{sub 3-{delta}} with tetragonal perovskite-like structure. Such allows to decrease the synthesis temperature, if compared to the conventional solid-state route, and to prevent possible volatilization of potassium. The results of Moessbauer spectroscopy studies indicate that the oxygen nonstoichiometry in the samples annealed in air at 900-1100 Degree-Sign C with subsequent rapid cooling vary in the range {delta}=0.30-0.32. The electrical conductivity in air exhibits a metal-like behaviour at temperatures above 400 Degree-Sign C and semiconductor behaviour in the low-temperature range, reaching 13-30 S/cm under prospective operation conditions for alkaline electrolyzers ({<=}90 Degree-Sign C). - graphical abstract: XRD patterns of Sr{sub 0.9}K{sub 0.1}FeO{sub 3-{delta}} powders, as-prepared and after annealing at different temperatures. Log({sigma}{center_dot}T) vs. 1000/T plot of the electrical conductivity of Sr{sub 0.9}K{sub 0.1}FeO{sub 3-{delta}}. The inset shows the thermal variation of {sigma}. Ceramics used were prepared by mechanical activation followed by a two-step sintering process at 900 Degree-Sign C for 1 h and 1000 Degree-Sign C for 5 h (82% densification). Highlights: Black-Right-Pointing-Pointer Sr{sub 0.9}K{sub 0.1}FeO{sub 3-{delta}} was successfully obtained by mechanical activation of oxide precursors. Black-Right-Pointing-Pointer Synthesis temperature is significantly lower when compared to a conventional solid-state route. Black-Right-Pointing-Pointer Oxygen nonstoichiometry of annealed samples at 900-1100 Degree-Sign C vary in the range {delta}=0.30-0.32. Black-Right-Pointing-Pointer Sr{sub 0.9}K{sub 0.1}FeO{sub 3-{delta}} shows metal and semiconductor behaviour above and below 400 Degree-Sign C, respectively.

36 MATERIALS SCIENCE↗

NASA NTRS1994

On the effects of filtering on convective-core statistics

Analysis of convective events north of Australia during the equatorial Monsoon Experiment (EMEX) reinforces accumulating evidence that convective cores over the tropical ocean are weak, with small diameters and vertical velocities. Superposition of smaller-scale turbulence on the convective core signal could yield artificially small cores, and thus produce sampling bias by aircraft. To investigate this potential source of bias, a side-by-side analysis of filtered and unfiltered vertical velocity data was performed while investigating the EMEX convective cores. Data were collected by the NOAA P3 and NCAR Electra using filtered (Graham filter) and non-filtered cores. The effects of filtering vertical velocity data to identify updraft and downdraft cores were noticeable but smaller than expected. Updraft cores had a vertical velocity greater than 1 m/sec for at least 500 m, and downdraft cores were defined analogously so that the filter eliminated events with less than a 500 m apparent diameter. Median and 10 percent core diameters were increased by 20-25 percent at most, with larger increases at higher levels (fewer small events). The maximum vertical velocity was changed only by changing the individual events in the distribution, but changes were detectable. At the lower levels, where many small, weak cores are introduced by filtering, average vertical velocity for the updraft cores was lowered by up to around 10 percent. Mass flux was changed the least, since diameter and mean vertical velocity respond to filtering in opposite ways. The filtering procedure increased total mass flux slightly due to inclusion of more upward moving air into the sample.

Lemone, Margaret A.↗

NASA NTRS2010

Convective Distribution of Tropospheric Ozone and Tracers in the Central American ITCZ Region: Evidence from Observations During TC4

During the Tropical Composition, Clouds and Climate Coupling (TC4) experiment that occurred in July and August of 2007, extensive sampling of active convection in the ITCZ region near Central America was performed from multiple aircraft and satellite sensors. As part of a sampling strategy designed to study cloud processes, the NASA ER-2, WB-57 and DC-8 flew in stacked "racetrack patterns" in convective cells. On July 24, 2007, the ER-2 and DC-8 probed an actively developing storm and the DC-8 was hit by lightning. Case studies of this flight, and of convective outflow on August 5, 2007 reveal a significant anti-correlation between ozone and condensed cloud water content. With little variability in the boundary layer and a vertical gradient, low ozone in the upper troposphere indicates convective transport. Because of the large spatial and temporal variability in surface CO and other pollutants in this region, low ozone is a better convective indicator. Lower tropospheric tracers methyl hydrogen peroxide, total organic bromine and calcium substantiate the ozone results. OMI measurements of mean upper tropospheric ozone near convection show lower ozone in convective outflow. A mass balance estimation of the amount of convective turnover below the tropical tropopause transition layer (TTL) is 50%, with an altitude of maximum convective outflow located between 10 and 11 km, 4 km below the cirrus anvil tops. It appears that convective lofting in this region of the ITCZ is either a two-stage or a rapid mixing process, because undiluted boundary layer air is never sampled in the convective outflow.

Avery, Melody↗

DOE OSTI2011

Exfoliation and thermal transformations of Nb-substituted layered titanates

Single-layer Nb-substituted titanate nanosheets of ca. 1 nm thickness were obtained by exfoliating tetrabutylammonium (TBA)-intercalated Nb-substituted titanates in water. AFM images and turbidity measurements reveal that the exfoliated nanosheets crack and corrugate when sonicated. Upon heating, the thermal transformation into anatase and further to rutile is retarded. This suppression of the phase transition upon higher valent substitution may promote technological applications of anatase thin films, hereunder development of films with TCO properties. Depending on the oxygen partial pressure during the transformation, the Nb-substitution into TiO{sub 2} provokes different defect situations and also electronic properties. At reducing conditions, Nb is incorporated as Nb{sup V} and an equivalent amount of Ti{sup IV} is transformed to Ti{sup III} as evidenced by XPS. Magnetic susceptibility data show accordingly paramagnetic behavior. For samples heated in air Ti{sup IV} and Nb{sup V} cations prevail, the latter is compensated by cation vacancies. {sup 93}Nb MAS NMR data prove that Nb is finely dispersed into the transformed (Ti,Nb)O{sub 2} oxide matrices without sign of Nb{sub 2}O{sub 5} (nano)precipitates. The Nb-O-Ti bonds and defects at cation sites are considered key factors for increasing the transformation temperatures for conversion of the nanosheets to anatase and finally into rutile. It is further tempting to link the delay in crystallization to morphology limitations originating from the nanosheets. The present work shows that layered Nb-titanates are appropriate precursors for formation of highly oriented Nb-substituted anatase thin films via delamination, reconstruction and subsequent heat treatment. - Graphical abstract: Layered Nb-titanates are appropriate precursors for formation of highly oriented Nb-substituted anatase thin films via delamination, reconstruction and subsequent heat treatment. Highlights: Black-Right-Pointing-Pointer Single layer Nb-substituted nanosheets were obtained by exfoliation of layered titanates. Black-Right-Pointing-Pointer Nb(V) successfully introduced into anatase and rutile solid solutions. Black-Right-Pointing-Pointer Anatase obtained from reconstructed nanosheets exhibit enhanced thermal stability. Black-Right-Pointing-Pointer Oxygen partial pressure influences the valence of Nb in heat-treated samples. Black-Right-Pointing-Pointer Deposition of oriented thin Ti(Nb)O{sub 2} layers by spray coating was demonstrated.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS2014

Recent Advances in Water Analysis with Gas Chromatograph Mass Spectrometers

We report on progress made in developing a water sampling system for detection and analysis of volatile organic compounds in water with a gas chromatograph mass spectrometer (GCMS). Two approaches are described herein. The first approach uses a custom water pre-concentrator for performing trap and purge of VOCs from water. The second approach uses a custom micro-volume, split-splitless injector that is compatible with air and water. These water sampling systems will enable a single GC-based instrument to analyze air and water samples for VOC content. As reduced mass, volume, and power is crucial for long-duration, manned space-exploration, these water sampling systems will demonstrate the ability of a GCMS to monitor both air and water quality of the astronaut environment, thereby reducing the amount of required instrumentation for long duration habitation. Laboratory prototypes of these water sampling systems have been constructed and tested with a quadrupole ion trap mass spectrometer as well as a thermal conductivity detector. Presented herein are details of these water sampling system with preliminary test results.

quadrupole ion trap↗

DOE OSTI2013

ARM Airborne Continuous carbon dioxide measurements

The heart of the AOS CO2 Airborne Rack Mounted Analyzer System is the AOS Manifold. The AOS Manifold is a nickel coated aluminum analyzer and gas processor designed around two identical nickel-plated gas cells, one for reference gas and one for sample gas. The sample and reference cells are uniquely designed to provide optimal flushing efficiency. These cells are situated between a black-body radiation source and a photo-diode detection system. The AOS manifold also houses flow meters, pressure sensors and control valves. The exhaust from the analyzer flows into a buffer volume which allows for precise pressure control of the analyzer. The final piece of the analyzer is the demodulator board which is used to convert the DC signal generated by the analyzer into an AC response. The resulting output from the demodulator board is an averaged count of CO2 over a specified hertz cycle reported in volts and a corresponding temperature reading. The system computer is responsible for the input of commands and therefore works to control the unit functions such as flow rate, pressure, and valve control.The remainder of the system consists of compressors, reference gases, air drier, electrical cables, and the necessary connecting plumbing to provide a dry sample air stream and reference air streams to the AOS manifold.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2013

ARM Airborne Continuous carbon dioxide measurements

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2018

Effect of Gamma Irradiation on Fully Aliphatic Poly(Propylene/Neopentyl Cyclohexanedicarboxylate) Random Copolymers

The widespread use of conventional petrochemical-based plastics and their low biodegradability led to a growing pollution issue. Among the class of the aliphatic polyesters, poly(propylene/neopentyl cyclohexanedicarboxylate) [P(PCExNCEy)] random copolymers combine promising physical–chemical properties and biodegradability features but they are characterized by slow degradability. The effect of gamma radiation on both chemical-physical properties and compostability was evaluated by several techniques on different samples irradiated in air at absorbed doses up to 500 kGy and in water or under oxidative atmosphere up to 100 kGy. According to the results obtained, exposure to radiation significantly affects polymer molecular weight and hydrophilicity, while crystallinity remains unaltered and biodegradability is only slightly influenced. In particular, among the different irradiation environments used, irradiation in water seems to favor the polymer degradation in compost.

36 MATERIALS SCIENCE↗

DOE OSTI2012

The effect of native oxide on ion-sputtering-induced nanostructure formation on GaSb surfaces

We have investigated the influence of native oxides on ion-sputtering-induced nanostructure formation on GaSb using in situ low energy ion scattering spectroscopy (LEISS) and X-ray photoelectron spectroscopy (XPS). Comparing an oxygen-free sample with a native oxide sample, LEISS and XPS reveal the effect of oxygen in generating higher surface Ga fractions during early stages (fluences of 1 Multiplication-Sign 10{sup 15}-1 Multiplication-Sign 10{sup 16} cm{sup -2}) of low energy (<100 eV) Ar+ irradiation. Enhanced surface Ga and Ga{sub 2}O{sub 3} fractions were also observed on 'oxide free' samples exposed to air following irradiation. The results suggest preferential Ga oxidation and segregation on the top of the amorphous layer if oxygen is present on the surface. In addition, the native oxide also increases the fluence threshold for nanopatterning of GaSb surfaces by almost a factor of four during low energy irradiation.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2014

Formation of laser-induced periodic surface structures on niobium by femtosecond laser irradiation

The surface morphology of a Niobium sample, irradiated in air by a femtosecond laser with a wavelength of 800 nm and pulse duration of 100 fs, was examined. The period of the micro/nanostructures, parallel and perpendicularly oriented to the linearly polarized fs-laser beam, was studied by means of 2D Fast Fourier Transform analysis. The observed Laser-Induced Periodic Surface Structures (LIPSS) were classified as Low Spatial Frequency LIPSS (periods about 600 nm) and High Spatial Frequency LIPSS, showing a periodicity around 300 nm, both of them perpendicularly oriented to the polarization of the incident laser wave. Moreover, parallel high spatial frequency LIPSS were observed with periods around 100 nm located at the peripheral areas of the laser fingerprint and overwritten on the perpendicular periodic gratings. The results indicate that this method of micro/nanostructuring allows controlling the Niobium grating period by the number of pulses applied, so the scan speed and not the fluence is the key parameter of control. A discussion on the mechanism of the surface topology evolution was also introduced.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2015

On the role of Fe ions on magnetic properties of doped TiO{sub 2} nanoparticles

The role of iron doping on magnetic properties of hydrothermal anatase TiO{sub 2}:{sup 57}Fe (0–1 at. %) nanoparticles is investigated by combining superconducting quantum interference device magnetometry with Mössbauer and electron paramagnetic resonance techniques. The results on both as-prepared and thermally treated samples in reduced air atmosphere reveal complexity of magnetic interactions, in connection to certain iron ion electron configurations and defects (oxygen vacancies, F-center, and Ti{sup 3+} ions). The distribution of iron ions is predominantly at nanoparticle surface layers. Formation of weak ferromagnetic domains up to 380 K is mainly related to defects, supporting the bound magnetic polaron model.

77 NANOSCIENCE AND NANOTECHNOLOGY↗

DOE OSTI2015

Evaporation-condensation synthesis and optical property of In{sub 2}O{sub 3} octahedrons

Synthesis of In{sub 2}O{sub 3} octahedrons is carried out successfully by heating Indium metal pieces in air ambient. The sample is characterized by scanning electron microscopy (SEM), Energy dispersive X-ray spectroscope (EDS), X-ray diffraction (XRD) and Raman spectroscopy. The as-prepared In{sub 2}O{sub 3} octahedrons are highly crystalline and exhibit body centered cubic structure. Room temperature and temperature (293-453K) dependence photoluminescence reveals a deep levelbroad emission of yellowish-orange spectra centered around 605 nm. The emission is due to the presence of defect levels in the band gap of materials.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2017

Assessment of personal airborne exposures and surface contamination from x-ray vaporization of beryllium targets at the National Ignition Facility

Here, this article presents air and surface sampling data collected over the first two years since beryllium was introduced as a target material at the National Ignition Facility. Over this time, 101 experiments with beryllium-containing targets were executed. The data provides an assessment of current conditions in the facility and a baseline for future impacts as new, reduced regulatory limits for beryllium are being proposed by both the Occupational Safety and Health Administration and Department of Energy. This study also investigates how beryllium deposits onto exposed surfaces as a result of x-ray vaporization and the effectiveness of simple decontamination measures in reducing the amount of removable beryllium from a surface. Based on 1,961 surface wipe samples collected from entrant components (equipment directly exposed to target debris) and their surrounding work areas during routine reconfiguration activities, only one result was above the beryllium release limit of 0.2 µg/100 cm 2 and 27 results were above the analytical reporting limit of 0.01 µg/100 cm 2 , for a beryllium detection rate of 1.4%. Surface wipe samples collected from the internal walls of the NIF target chamber, however, showed higher levels of beryllium, with beryllium detected on 73% and 87% of the samples during the first and second target chamber entries (performed annually), respectively, with 23% of the samples above the beryllium release limit during the second target chamber entry. The analysis of a target chamber wall panel exposed during the first 30 beryllium-containing experiments (cumulatively) indicated that 87% of the beryllium contamination remains fixed onto the surface after wet wiping the surface and 92% of the non-fixed contamination was removed by decontaminating the surface using a dry wipe followed by a wet wipe. Personal airborne exposures assessed during access to entrant components and during target chamber entry indicated that airborne beryllium was not present in workers' breathing zones. Finally, all the data thus far have shown that beryllium has been effectively managed to prevent exposures to workers during routine and non-routine work.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2021

Transport and chemistry of isoprene and its oxidation products in deep convective clouds

Deep convective clouds can transport trace gases from the planetary boundary layer into the upper troposphere where subsequent chemistry may impact aerosol particle formation and growth. In this modelling study, we investigate processes that affect isoprene and its oxidation products injected into the upper troposphere by an isolated deep convective cloud in the Amazon. We run a photochemical box model with coupled cloud microphysics along hundreds of individual air parcel trajectories sampled from a cloud-resolving model simulation of a convective event. The box model simulates gas-phase chemical reactions, gas scavenging by liquid and ice hydrometeors, and turbulent dilution inside a deep convective cloud. The results illustrate the potential importance of gas uptake to anvil ice in regulating the intensity of the isoprene oxidation and associated low volatility organic vapour concentrations in the outflow. Isoprene transport and fate also depends on the abundance of lightning-generated nitrogen oxide radicals (NO x = NO + NO 2 ). If gas uptake on ice is efficient and lightning activity is low, around 30% of the boundary layer isoprene will survive to the cloud outflow after approximately one hour of transport, while all the low volatile oxidation products will be scavenged by the cloud hydrometeors. If lightning NO x is abundant and gas uptake by ice is inefficient, then all isoprene will be oxidised during transport or in the immediate outflow region, while several low volatility isoprene oxidation products will have elevated concentrations in the cloud outflow. Reducing uncertainties associated with the uptake of vapours on ice hydrometeors, especially HO 2 and oxygenated organics, is essential to improve predictions of isoprene and its oxidation products in deep convective outflows and their potential contribution to new particle formation and growth.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2014

Controllable nitrogen doping in as deposited TiO{sub 2} film and its effect on post deposition annealing

In order to narrow the band gap of TiO{sub 2}, nitrogen doping by combining thermal atomic layer deposition (TALD) of TiO{sub 2} and plasma enhanced atomic layer deposition (PEALD) of TiN has been implemented. By altering the ratio between TALD TiO{sub 2} and PEALD TiN, the as synthesized TiO{sub x}N{sub y} films showed different band gaps (from 1.91 eV to 3.14 eV). In situ x-ray diffraction characterization showed that the crystallization behavior of these films changed after nitrogen doping. After annealing in helium, nitrogen doped TiO{sub 2} films crystallized into rutile phase while for the samples annealed in air a preferential growth of the anatase TiO{sub 2} along (001) orientation was observed. Photocatalytic tests of the degradation of stearic acid were done to evaluate the effect of N doping on the photocatalytic activity.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2011

Prism-pair interferometry by homodyne interferometers with a common light source for high-accuracy measurement of the absolute refractive index of glasses

A prism-pair interferometer comprising two homodyne interferometers with a common light source was developed for high-precision measurements of the refractive index of optical glasses with an uncertainty of the order of 10{sup -6}. The two interferometers measure changes in the optical path length in the glass sample and in air, respectively. Uncertainties in the absolute wavelength of the common light source are cancelled out by calculating a ratio between the results from the interferometers. Uncertainties in phase measurement are suppressed by a quadrature detection system. The combined standard uncertainty of the developed system is evaluated as 1.1x10{sup -6}.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2021

RASA Field Performance at US International Monitoring Stations

This report attempts to collate, analyze, and summarize RASA performance over time at each of 11 US operated IMS stations. The performance over time was compared to routine maintenance operations. The data, in general, were summarized into a set analyzed almost exclusively in Excel. The data set allows for further probing into RASA performance over time. The data set would permit data to be routinely added for continued analysis. In general, all RASA systems ran within the CTBTO mandated the MDA requirements over their current lifetime of operations. The largest impacts to performance appeared to arise from variabilities of Germanium gamma detectors as they were replaced. It is noted that the air volumes of samples were not provided and had to be assumed to be constant over the period analyzed.

61 RADIATION PROTECTION AND DOSIMETRY↗