Multiple Emission Angle Surface-Atmosphere Separations of MGS Thermal Emission Spectrometer Data

NASA Technical Reports Server (NTRS)

Bandfield, J. L.; Smith, M. D.

2001-01-01

Multiple emission angle observations taken by MGS-TES have been used to derive atmospheric opacities and surface temperatures and emissivities with increased accuracy and wavelength coverage. Martian high albedo region surface spectra have now been isolated. Additional information is contained in the original extended abstract.

Near band edge photoluminescence of ZnO nanowires: Optimization via surface engineering

NASA Astrophysics Data System (ADS)

Yan, Danhua; Zhang, Wenrui; Cen, Jiajie; Stavitski, Eli; Sadowski, Jerzy T.; Vescovo, Elio; Walter, Andrew; Attenkofer, Klaus; Stacchiola, Darío J.; Liu, Mingzhao

2017-12-01

Zinc oxide (ZnO) nanowire arrays have potential applications for various devices such as ultra-violet light emitting diodes and lasers, where photoluminescence of intense near band edge emission without defect emissions is usually desired. Here, we demonstrate, counter-intuitively, that the near band edge emission may become dominant by introducing certain surface defects to ZnO nanowires via surface engineering. Specifically, near band edge emission (NBE) is effectively enhanced after a low pressure O2 plasma treatment that sputters off surface oxygen species to produce a reduced and oxygen vacancy-rich surface. The effect is attributed to the lowered surface valence band maximum of the reduced ZnO surface that creates an accumulative band bending, which screens the photo-generated minority carriers (holes) from reaching or being trapped by the surface defects.

Near band edge photoluminescence of ZnO nanowires: Optimization via surface engineering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan, Danhua; Zhang, Wenrui; Cen, Jiajie

Zinc oxide (ZnO) nanowire arrays have potential applications for various devices including ultra-violet light emitting diodes and lasers, where photoluminescence of intense near band edge emission without defect emissions is usually desired. Here, we demonstrate, counter-intuitively, that the near band edge emission may become dominant by introducing certain surface defects to ZnO nanowires via surface engineering. Specifically, near band edge emission (NBE) is effectively enhanced after a low pressure O 2 plasma treatment that sputters off surface oxygen species to produce a reduced and oxygen vacancy-rich surface. The effect is attributed to the lowered surface valence band maximum of themore » reduced ZnO surface that creates an accumulative band bending, which screens the photo-generated minority carriers (holes) from reaching or being trapped by the surface defects.« less

Near band edge photoluminescence of ZnO nanowires: Optimization via surface engineering

DOE PAGES

Yan, Danhua; Zhang, Wenrui; Cen, Jiajie; ...

2017-12-04

Zinc oxide (ZnO) nanowire arrays have potential applications for various devices including ultra-violet light emitting diodes and lasers, where photoluminescence of intense near band edge emission without defect emissions is usually desired. Here, we demonstrate, counter-intuitively, that the near band edge emission may become dominant by introducing certain surface defects to ZnO nanowires via surface engineering. Specifically, near band edge emission (NBE) is effectively enhanced after a low pressure O 2 plasma treatment that sputters off surface oxygen species to produce a reduced and oxygen vacancy-rich surface. The effect is attributed to the lowered surface valence band maximum of themore » reduced ZnO surface that creates an accumulative band bending, which screens the photo-generated minority carriers (holes) from reaching or being trapped by the surface defects.« less

Separation of Atmospheric and Surface Spectral Features in Mars Global Surveyor Thermal Emission Spectrometer (TES) Spectra

NASA Technical Reports Server (NTRS)

Smith, Michael D.; Bandfield, Joshua L.; Christensen, Philip R.

2000-01-01

We present two algorithms for the separation of spectral features caused by atmospheric and surface components in Thermal Emission Spectrometer (TES) data. One algorithm uses radiative transfer and successive least squares fitting to find spectral shapes first for atmospheric dust, then for water-ice aerosols, and then, finally, for surface emissivity. A second independent algorithm uses a combination of factor analysis, target transformation, and deconvolution to simultaneously find dust, water ice, and surface emissivity spectral shapes. Both algorithms have been applied to TES spectra, and both find very similar atmospheric and surface spectral shapes. For TES spectra taken during aerobraking and science phasing periods in nadir-geometry these two algorithms give meaningful and usable surface emissivity spectra that can be used for mineralogical identification.

The surface emissions trap: a new approach in indoor air purification.

PubMed

Markowicz, Pawel; Larsson, Lennart

2012-11-01

A new device for stopping or reducing potentially irritating or harmful emissions from surfaces indoors is described. The device is a surface emissions trap prototype and consists of an adsorbent sheet with a semipermeable barrier surrounded by two thin nonwoven layers. The trap may be applied directly at the source of the emissions e.g. at moisture-affected floors and walls, surfaces contaminated by chemical spills etc. This results in an immediate stop or reduction of the emitting pollutants. The trap has a very low water vapor resistance thus allowing drying of wet surfaces. In laboratory experiments typically 98% reduction of air concentrations of volatile organic compounds and a virtually total reduction of mold particle-associated mycotoxins was observed. The surface emissions trap may represent a convenient and efficient way of restoring indoor environments polluted by microbial and other moisture-associated emissions. Copyright © 2012 Elsevier B.V. All rights reserved.

Dust emissions created by low-level rotary-winged aircraft flight over desert surfaces

NASA Astrophysics Data System (ADS)

Gillies, J. A.; Etyemezian, V.; Kuhns, H.; McAlpine, J. D.; King, J.; Uppapalli, S.; Nikolich, G.; Engelbrecht, J.

2010-03-01

There is a dearth of information on dust emissions from sources that are unique to U.S. Department of Defense testing and training activities. Dust emissions of PM 10 and PM 2.5 from low-level rotary-winged aircraft travelling (rotor-blade ≈7 m above ground level) over two types of desert surfaces (i.e., relatively undisturbed desert pavement and disturbed desert soil surface) were characterized at the Yuma Proving Ground (Yuma, AZ) in May 2007. Fugitive emissions are created by the shear stress of the outflow of high speed air created by the rotor-blade. The strength of the emissions was observed to scale primarily as a function of forward travel speed of the aircraft. Speed affects dust emissions in two ways: 1) as speed increases, peak shear stress at the soil surface was observed to decline proportionally, and 2) as the helicopter's forward speed increases its residence time over any location on the surface diminishes, so the time the downward rotor-generated flow is acting upon that surface must also decrease. The state of the surface over which the travel occurs also affects the scale of the emissions. The disturbed desert test surface produced approximately an order of magnitude greater emission than the undisturbed surface. Based on the measured emission rates for the test aircraft and the established scaling relationships, a rotary-winged aircraft similar to the test aircraft traveling 30 km h -1 over the disturbed surface would need to travel 4 km to produce emissions equivalent to one kilometer of travel by a light wheeled military vehicle also traveling at 30 km h -1 on an unpaved road. As rotary-winged aircraft activity is substantially less than that of off-road vehicle military testing and training activities it is likely that this source is small compared to emissions created by ground-based vehicle movements.

Study of the normal emissivity of molybdenum during thermal oxidation process

NASA Astrophysics Data System (ADS)

Xu, Yihan; Li, Longfei; Yu, Kun; Liu, Yufang

2018-04-01

The infrared normal spectral emissivity of the oxidized molybdenum was measured during thermal oxidation process, and the integral emissivity was calculated from the data of spectral emissivity. It is found that the surface oxidation has a remarkable effect on the spectral emissivity of molybdenum, and the spectral emissivity curves become more fluctuant with the increase in oxidation time. The integral emissivity grows exponentially with the oxidation time at 773 K, remains almost constant at 823 K, and fluctuates at 873 and 923 K. The X-ray fluorescence spectrometer, the X-ray diffraction, and the scanning electron microscopy were employed to analyze the changes in surface composition and surface morphology. The results show that the most probable reason for the variation of integral emissivity is the change in surface roughness caused by the variation in the size and shape of oxide particle on specimen surface.

Quantitative Surface Emissivity and Temperature Measurements of a Burning Solid Fuel Accompanied by Soot Formation

NASA Technical Reports Server (NTRS)

Piltch, Nancy D.; Pettegrew, Richard D.; Ferkul, Paul; Sacksteder, K. (Technical Monitor)

2001-01-01

Surface radiometry is an established technique for noncontact temperature measurement of solids. We adapt this technique to the study of solid surface combustion where the solid fuel undergoes physical and chemical changes as pyrolysis proceeds, and additionally may produce soot. The physical and chemical changes alter the fuel surface emissivity, and soot contributes to the infrared signature in the same spectral band as the signal of interest. We have developed a measurement that isolates the fuel's surface emissions in the presence of soot, and determine the surface emissivity as a function of temperature. A commercially available infrared camera images the two-dimensional surface of ashless filter paper burning in concurrent flow. The camera is sensitive in the 2 to 5 gm band, but spectrally filtered to reduce the interference from hot gas phase combustion products. Results show a strong functional dependence of emissivity on temperature, attributed to the combined effects of thermal and oxidative processes. Using the measured emissivity, radiance measurements from several burning samples were corrected for the presence of soot and for changes in emissivity, to yield quantitative surface temperature measurements. Ultimately the results will be used to develop a full-field, non-contact temperature measurement that will be used in spacebased combustion investigations.

Surface Emissivity Retrieved with Satellite Ultraspectral IR Measurements for Monitoring Global Change

NASA Technical Reports Server (NTRS)

Zhou, Daniel K.; Larar, Allen M.; Liu, Xu; Smith, William L.; Schluessel, Peter

2009-01-01

Surface and atmospheric thermodynamic parameters retrieved with advanced ultraspectral remote sensors aboard Earth observing satellites are critical to general atmospheric and Earth science research, climate monitoring, and weather prediction. Ultraspectral resolution infrared radiance obtained from nadir observations provide atmospheric, surface, and cloud information. Presented here is the global surface IR emissivity retrieved from Infrared Atmospheric Sounding Interferometer (IASI) measurements under "clear-sky" conditions. Fast radiative transfer models, applied to the cloud-free (or clouded) atmosphere, are used for atmospheric profile and surface parameter (or cloud parameter) retrieval. The inversion scheme, dealing with cloudy as well as cloud-free radiances observed with ultraspectral infrared sounders, has been developed to simultaneously retrieve atmospheric thermodynamic and surface (or cloud microphysical) parameters. Rapidly produced surface emissivity is initially evaluated through quality control checks on the retrievals of other impacted atmospheric and surface parameters. Surface emissivity and surface skin temperature from the current and future operational satellites can and will reveal critical information on the Earth s ecosystem and land surface type properties, which can be utilized as part of long-term monitoring for the Earth s environment and global climate change.

Two Surface Temperature Retrieval Methods Compared Over Agricultural Lands

NASA Technical Reports Server (NTRS)

French, Andrew N.; Schmugge, Thomas J.; Jacob, Frederic; Ogawa, Kenta; Houser, Paul R. (Technical Monitor)

2002-01-01

Accurate, spatially distributed surface temperatures are required for modeling evapotranspiration (ET) over agricultural fields under wide ranging conditions, including stressed and unstressed vegetation. Modeling approaches that use surface temperature observations, however, have the burden of estimating surface emissivities. Emissivity estimation, the subject of much recent research, is facilitated by observations in multiple thermal infrared bands. But it is nevertheless a difficult task. Using observations from a multiband thermal sensor, the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), estimated surface emissivities and temperatures are retrieved in two different ways: the temperature emissivity separation approach (TES) and the normalized emissivity approach (NEM). Both rely upon empirical relationships, but the assumed relationships are different. TES relies upon a relationship between the minimum spectral emissivity and the range of observed emissivities. NEM relies upon an assumption that at least one thermal band has a pre-determined emissivity (close to 1.0). The benefits and consequences of each approach will be demonstrated for two different landscapes: one in central Oklahoma, USA and another in southern New Mexico.

Derived Land Surface Emissivity From Suomi NPP CrIS

NASA Technical Reports Server (NTRS)

Zhou, Daniel K.; Larar, Allen M.; Liu, Xu

2012-01-01

Presented here is the land surface IR spectral emissivity retrieved from the Cross-track Infrared Sounder (CrIS) measurements. The CrIS is aboard the Suomi National Polar-orbiting Partnership (NPP) satellite launched on October 28, 2011. We describe the retrieval algorithm, demonstrate the surface emissivity retrieved with CrIS measurements, and inter-comparison with the Infrared Atmospheric Sounding Interferometer (IASI) emissivity. We also demonstrate that surface emissivity from satellite measurements can be used in assistance of monitoring global surface climate change, as a long-term measurement of IASI and CrIS will be provided by the series of EUMETSAT MetOp and US Joint Polar Satellite System (JPSS) satellites. Monthly mean surface properties are produced using last 5-year IASI measurements. A temporal variation indicates seasonal diversity and El Nino/La Nina effects not only shown on the water but also on the land. Surface spectral emissivity and skin temperature from current and future operational satellites can be utilized as a means of long-term monitoring of the Earth's environment. CrIS spectral emissivity are retrieved and compared with IASI. The difference is small and could be within expected retrieval error; however it is under investigation.

Control of formaldehyde and TVOC emission from wood-based flooring composites at various manufacturing processes by surface finishing.

PubMed

Kim, Sumin

2010-04-15

This paper assesses the reproducibility of testing formaldehyde and TVOC emission behavior from wood flooring composites bonded by urea-formaldehyde resin at various manufacturing steps for surface finishing materials. The surface adhesion step of laminate flooring for this research was divided into two steps; HDF only and HDF with LPMs. In the case of engineered flooring, the manufacturing steps were divided into three steps; plywood only, fancy veneer bonded on plywood and UV coated on fancy veneer with plywood. Formaldehyde and VOCs emission decreased at the process of final surface finishing materials; LPMs were applied on the surface of HDF for laminate flooring. Although emissions increased when fancy veneer was bonded onto plywood in the case of engineered flooring, emission was dramatically reduced up to similar level with plywood only when final surface finishing; UV-curable coating was applied on fancy veneer. This study suggests that formaldehyde and VOCs emission from floorings can be controlled at manufacturing steps for surface finishing. 2009 Elsevier B.V. All rights reserved.

Correlation of CVD Diamond Electron Emission with Film Properties

NASA Astrophysics Data System (ADS)

Bozeman, S. P.; Baumann, P. K.; Ward, B. L.; Nemanich, R. J.; Dreifus, D. L.

1996-03-01

Electron field emission from metals is affected by surface morphology and the properties of any dielectric coating. Recent results have demonstrated low field electron emission from p-type diamond, and photoemission measurements have identified surface treatments that result in a negative electron affinity (NEA). In this study, the field emission from diamond is correlated with surface treatment, surface roughness, and film properties (doping and defects). Electron emission measurements are reported on diamond films synthesized by plasma CVD. Ultraviolet photoemission spectroscopy indicates that the CVD films exhibit a NEA after exposure to hydrogen plasma. Field emission current-voltage measurements indicate "threshold voltages" ranging from approximately 20 to 100 V/micron.

Exoelectron emission from a clean, annealed magnesium single crystal during oxygen adsorption

NASA Technical Reports Server (NTRS)

Ferrante, J.

1976-01-01

Exoelectron emission was observed from a clean, annealed Mg (0001) surface during oxygen and chlorine adsorption at pressures of 6.5x10 0.00001- N/sq m and lower. the studies were performed in an ultrahigh vacuum system. The crystals were cleaned by argon ion bombardment and annealed at 300 C. Auger electron spectroscopy was used to verify surface cleanliness, and low energy electron diffraction was used to verify that the surface was annealed. The emission was found to be oxygen arrival rate dependent. Two peaks were observed in the electron emission with exposure. Evidence is presented that the formation of the second peak corresponds to oxidation of the Mg surface. No emission was observed from clean aluminum during adsorption. Results verify that electron emission occurs from a strain free surface simply upon adsorption of oxygen. A qualitative explanation for the mechanisms of emission in terms of chemical effects is presented.

Global Precipitation Measurement, Validation, and Applications Integrated Hydrologic Validation to Improve Physical Precipitation Retrievals for GPM

NASA Technical Reports Server (NTRS)

Peters-Lidar, Christa D.; Tian, Yudong; Kenneth, Tian; Harrison, Kenneth; Kumar, Sujay

2011-01-01

Land surface modeling and data assimilation can provide dynamic land surface state variables necessary to support physical precipitation retrieval algorithms over land. It is well-known that surface emission, particularly over the range of frequencies to be included in the Global Precipitation Measurement Mission (GPM), is sensitive to land surface states, including soil properties, vegetation type and greenness, soil moisture, surface temperature, and snow cover, density, and grain size. In order to investigate the robustness of both the land surface model states and the microwave emissivity and forward radiative transfer models, we have undertaken a multi-site investigation as part of the NASA Precipitation Measurement Missions (PMM) Land Surface Characterization Working Group. Specifically, we will demonstrate the performance of the Land Information System (LIS; http://lis.gsfc.nasa.gov; Peters-Lidard et aI., 2007; Kumar et al., 2006) coupled to the Joint Center for Satellite Data Assimilation (JCSDA's) Community Radiative Transfer Model (CRTM; Weng, 2007; van Deist, 2009). The land surface is characterized by complex physical/chemical constituents and creates temporally and spatially heterogeneous surface properties in response to microwave radiation scattering. The uncertainties in surface microwave emission (both surface radiative temperature and emissivity) and very low polarization ratio are linked to difficulties in rainfall detection using low-frequency passive microwave sensors (e.g.,Kummerow et al. 2001). Therefore, addressing these issues is of utmost importance for the GPM mission. There are many approaches to parameterizing land surface emission and radiative transfer, some of which have been customized for snow (e.g., the Helsinki University of Technology or HUT radiative transfer model;) and soil moisture (e.g., the Land Surface Microwave Emission Model or LSMEM).

40 CFR 270.27 - Specific Part B information requirements for air emission controls for tanks, surface...

Code of Federal Regulations, 2010 CFR

2010-07-01

... requirements for air emission controls for tanks, surface impoundments, and containers. 270.27 Section 270.27... information requirements for air emission controls for tanks, surface impoundments, and containers. (a) Except... containers that use air emission controls in accordance with the requirements of 40 CFR part 264, subpart CC...

40 CFR 270.27 - Specific Part B information requirements for air emission controls for tanks, surface...

Code of Federal Regulations, 2013 CFR

2013-07-01

... requirements for air emission controls for tanks, surface impoundments, and containers. 270.27 Section 270.27... information requirements for air emission controls for tanks, surface impoundments, and containers. (a) Except... containers that use air emission controls in accordance with the requirements of 40 CFR part 264, subpart CC...

40 CFR 270.27 - Specific Part B information requirements for air emission controls for tanks, surface...

Code of Federal Regulations, 2011 CFR

2011-07-01

... requirements for air emission controls for tanks, surface impoundments, and containers. 270.27 Section 270.27... information requirements for air emission controls for tanks, surface impoundments, and containers. (a) Except... containers that use air emission controls in accordance with the requirements of 40 CFR part 264, subpart CC...

40 CFR 270.27 - Specific Part B information requirements for air emission controls for tanks, surface...

Code of Federal Regulations, 2012 CFR

2012-07-01

... requirements for air emission controls for tanks, surface impoundments, and containers. 270.27 Section 270.27... information requirements for air emission controls for tanks, surface impoundments, and containers. (a) Except... containers that use air emission controls in accordance with the requirements of 40 CFR part 264, subpart CC...

40 CFR 270.27 - Specific Part B information requirements for air emission controls for tanks, surface...

Code of Federal Regulations, 2014 CFR

2014-07-01

... requirements for air emission controls for tanks, surface impoundments, and containers. 270.27 Section 270.27... information requirements for air emission controls for tanks, surface impoundments, and containers. (a) Except... containers that use air emission controls in accordance with the requirements of 40 CFR part 264, subpart CC...

Textured carbon on copper: A novel surface with extremely low secondary electron emission characteristics

NASA Technical Reports Server (NTRS)

Curren, A. N.; Jensen, K. A.

1985-01-01

Experimentally determined values of true secondary electron emission and relative values of reflected primary electron yield for a range of primary electron beam energies and beam impingement angles are presented for a series of novel textured carbon surfaces on copper substrates. (All copper surfaces used in this study were oxygen-free, high-conductivity grade). The purpose of this investigation is to provide information necessary to develop high-efficiency multistage depressed collectors (MDC's) for microwave amplifier traveling-wave tubes (TWT's) for communications and aircraft applications. To attain the highest TWT signal quality and overall efficiency, the MDC electrode surface must have low secondary electron emission characteristics. While copper is the material most commonly used for MDC electrodes, it exhibits relatively high levels of secondary electron emission unless its surface is treated for emission control. The textured carbon surface on copper substrate described in this report is a particularly promising candidate for the MDC electrode application. Samples of textured carbon surfaces on copper substrates typical of three different levels of treatment are prepared and tested for this study. The materials are tested at primary electron beam energies of 200 to 2000 eV and at direct (0 deg) to near-grazing (85 deg) beam impingement angles. True secondary electron emission and relative reflected primary electron yield characteristics of the textured surfaces are compared with each other and with those of untreated copper. All the textured carbon surfaces on copper substrate tested exhibited sharply lower secondary electron emission characteristics than those of an untreated copper surface.

Radiative decay engineering 3. Surface plasmon-coupled directional emission

PubMed Central

Lakowicz, Joseph R.

2009-01-01

A new method of fluorescence detection that promises to increase sensitivity by 20- to 1000-fold is described. This method will also decrease the contribution of sample autofluorescence to the detected signal. The method depends on the coupling of excited fluorophores with the surface plasmon resonance present in thin metal films, typically silver and gold. The phenomenon of surface plasmon-coupled emission (SPCE) occurs for fluorophores 20–250 nm from the metal surface, allowing detection of fluorophores over substantial distances beyond the metal–sample interface. SPCE depends on interactions of the excited fluorophore with the metal surface. This interaction is independent of the mode of excitation; that is, it does not require evanescent wave or surface-plasmon excitation. In a sense, SPCE is the inverse process of the surface plasmon resonance absorption of thin metal films. Importantly, SPCE occurs over a narrow angular distribution, converting normally isotropic emission into easily collected directional emission. Up to 50% of the emission from unoriented samples can be collected, much larger than typical fluorescence collection efficiencies near 1% or less. SPCE is due only to fluorophores near the metal surface and may be regarded as emission from the induced surface plasmons. Autofluorescence from more distal parts of the sample is decreased due to decreased coupling. SPCE is highly polarized and autofluorescence can be further decreased by collecting only the polarized component or only the light propagating with the appropriate angle. Examples showing how simple optical configurations can be used in diagnostics, sensing, or biotechnology applications are presented. Surface plasmon-coupled emission is likely to find widespread applications throughout the biosciences. PMID:14690679

A Theoretical and Experimental Study of Emission Spectroscopy of Planetary Surfaces

NASA Astrophysics Data System (ADS)

Henderson, Bradley Gray

1995-01-01

This thesis explores the spectral emissivity of particulate materials on planetary surfaces through theoretical modeling and supporting laboratory and field investigations. In the first part of the thesis, I develop a Monte Carlo ray tracing model to calculate the directional and spectral emissivity and the polarization state of the radiation emitted from a particulate, isothermal surface for emission angles 0^circ-90^ circ and wavelengths 7-16 mu m. The results show that roughness and scattering significantly affect the character of the emitted radiation field and should be taken into account when interpreting the physical properties of a planetary surface from IR spectrophotometry or spectropolarimetry. The remainder of the thesis focuses on understanding near-surface thermal gradients and their effects on emission spectra for different planetary environments. These gradients are formed by radiative cooling in the top few hundred microns of low conductivity particulate materials on planetary surfaces with little or no atmosphere. I model the heat transfer by conduction and radiation in the top few millimeters of a planetary regolith for scattering and non-scattering media. In conjunction with the modeling, I measure emission spectra of fine-grained quartz in an environment chamber designed to simulate the conditions on other planetary surfaces. The results show that significant thermal gradients will form in the near surface of materials on the surface of the Moon and Mercury. Their presence increases spectral contrast and creates emission maxima in the transparent regions of the spectrum. Thermal gradients are shown to be responsible for the observed wavelength shifts of the Christiansen emission peak with variations in thermal conductivity and grain size. The results are also used to analyze recent telescopic spectra of the Moon and Mercury and can explain certain features seen in those data. Thermal gradients are shown to be minor for the surface of Mars and negligible on Earth. I conclude that the spectral effects created by near-surface thermal gradients are predictable and might even provide an extra source of information about the physical nature of a planetary surface, and mid-IR emission spectroscopy should therefore prove to be useful for remote sensing of airless bodies.

Self-calibrated active pyrometer for furnace temperature measurements

DOEpatents

Woskov, Paul P.; Cohn, Daniel R.; Titus, Charles H.; Surma, Jeffrey E.

1998-01-01

Pyrometer with a probe beam superimposed on its field-of-view for furnace temperature measurements. The pyrometer includes a heterodyne millimeter/sub-millimeter-wave or microwave receiver including a millimeter/sub-millimeter-wave or microwave source for probing. The receiver is adapted to receive radiation from a surface whose temperature is to be measured. The radiation includes a surface emission portion and a surface reflection portion which includes the probe beam energy reflected from the surface. The surface emission portion is related to the surface temperature and the surface reflection portion is related to the emissivity of the surface. The simultaneous measurement of surface emissivity serves as a real time calibration of the temperature measurement. In an alternative embodiment, a translatable base plate and a visible laser beam allow slow mapping out of interference patterns and obtaining peak values therefor. The invention also includes a waveguide having a replaceable end portion, an insulating refractory sleeve and/or a source of inert gas flow. The pyrometer may be used in conjunction with a waveguide to form a system for temperature measurements in a furnace. The system may employ a chopper or alternatively, be constructed without a chopper. The system may also include an auxiliary reflector for surface emissivity measurements.

On the effect of surface emissivity on temperature retrievals. [for meteorology

NASA Technical Reports Server (NTRS)

Kornfield, J.; Susskind, J.

1977-01-01

The paper is concerned with errors in temperature retrieval caused by incorrectly assuming that surface emissivity is equal to unity. An error equation that applies to present-day atmospheric temperature sounders is derived, and the bias errors resulting from various emissivity discrepancies are calculated. A model of downward flux is presented and used to determine the effective downward flux. In the 3.7-micron region of the spectrum, emissivities of 0.6 to 0.9 have been observed over land. At a surface temperature of 290 K, if the true emissivity is 0.6 and unit emissivity is assumed, the error would be approximately 11 C. In the 11-micron region, the maximum deviation of the surface emissivity from unity was 0.05.

Directional Thermal Emission and Absorption from Surface Microstructures in Metalized Plastics

DTIC Science & Technology

2013-09-01

conductive surfaces for directional emission is presented. First, key accomplishments in exploiting surface plasmons for coherent thermal emission from...than as an absorbing coating . In the 2005 design proposed by Lee et al., thermally excited surface waves at a silicon carbide to photonic crystal stack...sufficiently to significantly effect the film durability and thermal conductivity , the profile of the cavity begins to change shape. Although a case

Frequency and Angular Variations of Land Surface Microwave Emissivities: Can we Estimate SSM/T and AMSU Emissivities from SSM/I Emissivities?

NASA Technical Reports Server (NTRS)

Prigent, Catherine; Wigneron, Jean-Pierre; Rossow, William B.; Pardo-Carrion, Juan R.

1999-01-01

To retrieve temperature and humidity profiles from SSM/T and AMSU, it is important to quantify the contribution of the Earth surface emission. So far, no global estimates of the land surface emissivities are available at SSM/T and AMSU frequencies and scanning conditions. The land surface emissivities have been previously calculated for the globe from the SSM/I conical scanner between 19 and 85 GHz. To analyze the feasibility of deriving SSM/T and AMSU land surface emissivities from SSM/I emissivities, the spectral and angular variations of the emissivities are studied, with the help of ground-based measurements, models and satellite estimates. Up to 100 GHz, for snow and ice free areas, the SSM/T and AMSU emissivities can be derived with useful accuracy from the SSM/I emissivities- The emissivities can be linearly interpolated in frequency. Based on ground-based emissivity measurements of various surface types, a simple model is proposed to estimate SSM/T and AMSU emissivities for all zenith angles knowing only the emissivities for the vertical and horizontal polarizations at 53 deg zenith angle. The method is tested on the SSM/T-2 91.655 GHz channels. The mean difference between the SSM/T-2 and SSM/I-derived emissivities is less than or equal to 0.01 for all zenith angles with an r.m.s. difference of approx. = 0.02. Above 100 GHz, preliminary results are presented at 150 GHz, based on SSM/T-2 observations and are compared with the very few estimations available in the literature.

Emission of dimers from a free surface of heated water

NASA Astrophysics Data System (ADS)

Bochkarev, A. A.; Polyakova, V. I.

2014-09-01

The emission rate of water dimers from a free surface and a wetted solid surface in various cases was calculated by a simplified Monte Carlo method with the use of the binding energy of water molecules. The binding energy of water molecules obtained numerically assuming equilibrium between the free surface of water and vapor in the temperature range of 298-438 K corresponds to the coordination number for liquid water equal to 4.956 and is close to the reference value. The calculation results show that as the water temperature increases, the free surface of water and the wetted solid surface become sources of free water dimers. At a temperature of 438 K, the proportion of dimers in the total flow of water molecules on its surface reaches 1%. It is found that in the film boiling mode, the emission rate of dimers decreases with decreasing saturation vapor. Two mechanisms of the emission are described.

40 CFR 63.3890 - What emission limits must I meet?

Code of Federal Regulations, 2011 CFR

2011-07-01

... Standards for Hazardous Air Pollutants for Surface Coating of Miscellaneous Metal Parts and Products... surface coating operations meet the applicability criteria of more than one of the subcategory emission.... (1) If the general use or magnet wire surface coating operations subject to only one of the emission...

Secondary electron emission from textured surfaces

NASA Astrophysics Data System (ADS)

Huerta, C. E.; Patino, M. I.; Wirz, R. E.

2018-04-01

In this work, a Monte Carlo model is used to investigate electron induced secondary electron emission for varying effects of complex surfaces by using simple geometric constructs. Geometries used in the model include: vertical fibers for velvet-like surfaces, tapered pillars for carpet-like surfaces, and a cage-like configuration of interlaced horizontal and vertical fibers for nano-structured fuzz. The model accurately captures the secondary electron emission yield dependence on incidence angle. The model shows that unlike other structured surfaces previously studied, tungsten fuzz exhibits secondary electron emission yield that is independent of primary electron incidence angle, due to the prevalence of horizontally-oriented fibers in the fuzz geometry. This is confirmed with new data presented herein of the secondary electron emission yield of tungsten fuzz at incidence angles from 0-60°.

Climate change impact of livestock CH4 emission in India: Global temperature change potential (GTP) and surface temperature response.

PubMed

Kumari, Shilpi; Hiloidhari, Moonmoon; Kumari, Nisha; Naik, S N; Dahiya, R P

2018-01-01

Two climate metrics, Global surface Temperature Change Potential (GTP) and the Absolute GTP (AGTP) are used for studying the global surface temperature impact of CH 4 emission from livestock in India. The impact on global surface temperature is estimated for 20 and 100 year time frames due to CH 4 emission. The results show that the CH 4 emission from livestock, worked out to 15.3 Tg in 2012. In terms of climate metrics GTP of livestock-related CH 4 emission in India in 2012 were 1030 Tg CO 2 e (GTP 20 ) and 62 Tg CO 2 e (GTP 100 ) at the 20 and 100 year time horizon, respectively. The study also illustrates that livestock-related CH 4 emissions in India can cause a surface temperature increase of up to 0.7mK and 0.036mK over the 20 and 100 year time periods, respectively. The surface temperature response to a year of Indian livestock emission peaks at 0.9mK in the year 2021 (9 years after the time of emission). The AGTP gives important information in terms of temperature change due to annual CH 4 emissions, which is useful when comparing policies that address multiple gases. Copyright © 2017 Elsevier Inc. All rights reserved.

A novel methodology to quantify nitrous oxide emissions from full-scale wastewater treatment systems with surface aerators.

PubMed

Ye, Liu; Ni, Bing-Jie; Law, Yingyu; Byers, Craig; Yuan, Zhiguo

2014-01-01

The quantification of nitrous oxide (N2O) emissions from open-surface wastewater treatment systems with surface aerators is difficult as emissions from the surface aerator zone cannot be easily captured by floating hoods. In this study, we propose and demonstrate a novel methodology to estimate N2O emissions from such systems through determination of the N2O transfer coefficient (kLa) induced by surface aerators based on oxygen balance for the entire system. The methodology is demonstrated through its application to a full-scale open oxidation ditch wastewater treatment plant with surface aerators. The estimated kLa profile based on a month-long measurement campaign for oxygen balance, intensive monitoring of dissolved N2O profiles along the oxidation ditch over a period of four days, together with mathematical modelling, enabled to determine the N2O emission factor from this treatment plant (0.52 ± 0.16%). Majority of the N2O emission was found to occur in the surface aerator zone, which would be missed if the gas hood method was applied alone. Copyright © 2013 Elsevier Ltd. All rights reserved.

Connecting Surface Emissions, Convective Uplifting, and Long-Range Transport of Carbon Monoxide in the Upper Troposphere: New Observations from the Aura Microwave Limb Sounder

NASA Technical Reports Server (NTRS)

Jiang, Jonathan H.; Livesey, Nathaniel J.; Su, Hui; Neary, Lori; McConnell, John C.; Richards, Nigel A. D.

2007-01-01

Two years of observations of upper tropospheric (UT) carbon monoxide (CO) from the Aura Microwave Limb Sounder are analyzed; in combination with the CO surface emission climatology and data from the NCEP analyses. It is shown that spatial distribution, temporal variation and long-range transport of UT CO are closely related to the surface emissions, deep-convection and horizontal winds. Over the Asian monsoon region, surface emission of CO peaks in boreal spring due to high biomass burning in addition to anthropogenic emission. However, the UT CO peaks in summer when convection is strongest and surface emission of CO is dominated by anthropogenic source. The long-range transport of CO from Southeast Asia across the Pacific to North America, which occurs most frequently during boreal summer, is thus a clear imprint of Asian anthropogenic pollution influencing global air quality.

Directional emissivity from two-dimensional infrared waveguide arrays

NASA Astrophysics Data System (ADS)

Burckel, D. Bruce; Davids, Paul S.; Finnegan, Patrick S.; Figueiredo, Pedro N.; Ginn, James C.

2015-09-01

Fabrication and optical characterization of surfaces covered with open-ended metallic waveguides are presented along with numerical modeling of these structures. Both modeling and measurement of the structures indicate that the 2-D array of 3D metallic waveguides modify both the direction and spectral content of the emissivity, resulting in directionality normal to the surface due to the optical axis of the waveguides and spectrally narrow emissivity due to the lateral dimensions of the waveguides. Furthermore, the optical behavior of these structures is placed in the broader context of other structured emission/absorption surfaces such as organ pipe modes, surface plasmon modes, and coherent thermal emission from gratings.

Electron reflection and secondary emission characteristics of sputter-textured pyrolytic graphite surfaces

NASA Technical Reports Server (NTRS)

Wintucky, E. G.; Curren, A. N.; Sovey, J. S.

1981-01-01

Low secondary and reflected primary electron emission from the collector electrode surfaces is important for optimum collector efficiency and hence for high overall efficiency of microwave amplifier tubes used in communication satellites and in military systems. Ion sputter texturing of the surface effectively suppresses electron emission from pyrolytic graphite, which is a promising collector electrode material. Secondary and reflected primary electron emission characteristics of sputter textured pyrolytic graphite surfaces with microstructures of various sizes and densities are presented. The microstructure with the lowest electron emission levels, less than those of soot, consists of a dense array of tall, thin spires.

Far-infrared surface emissivity and climate.

PubMed

Feldman, Daniel R; Collins, William D; Pincus, Robert; Huang, Xianglei; Chen, Xiuhong

2014-11-18

Presently, there are no global measurement constraints on the surface emissivity at wavelengths longer than 15 μm, even though this surface property in this far-IR region has a direct impact on the outgoing longwave radiation (OLR) and infrared cooling rates where the column precipitable water vapor (PWV) is less than 1 mm. Such dry conditions are common for high-altitude and high-latitude locations, with the potential for modeled climate to be impacted by uncertain surface characteristics. This paper explores the sensitivity of instantaneous OLR and cooling rates to changes in far-IR surface emissivity and how this unconstrained property impacts climate model projections. At high latitudes and altitudes, a 0.05 change in emissivity due to mineralogy and snow grain size can cause a 1.8-2.0 W m(-2) difference in the instantaneous clear-sky OLR. A variety of radiative transfer techniques have been used to model the far-IR spectral emissivities of surface types defined by the International Geosphere-Biosphere Program. Incorporating these far-IR surface emissivities into the Representative Concentration Pathway (RCP) 8.5 scenario of the Community Earth System Model leads to discernible changes in the spatial patterns of surface temperature, OLR, and frozen surface extent. The model results differ at high latitudes by as much as 2°K, 10 W m(-2), and 15%, respectively, after only 25 y of integration. Additionally, the calculated difference in far-IR emissivity between ocean and sea ice of between 0.1 and 0.2, suggests the potential for a far-IR positive feedback for polar climate change.

Far-infrared surface emissivity and climate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feldman, Daniel R.; Collins, William D.; Pincus, Robert

Presently, there are no global measurement constraints on the surface emissivity at wavelengths longer than 15 μm, even though this surface property in this far-IR region has a direct impact on the outgoing longwave radiation (OLR) and infrared cooling rates where the column precipitable water vapor (PWV) is less than 1 mm. Such dry conditions are common for high-altitude and high-latitude locations, with the potential for modeled climate to be impacted by uncertain surface characteristics. This paper explores the sensitivity of instantaneous OLR and cooling rates to changes in far-IR surface emissivity and how this unconstrained property impacts climate modelmore » projections. At high latitudes and altitudes, a 0.05 change in emissivity due to mineralogy and snow grain size can cause a 1.8–2.0 W m⁻² difference in the instantaneous clear-sky OLR. A variety of radiative transfer techniques have been used to model the far-IR spectral emissivities of surface types defined by the International Geosphere-Biosphere Program. Incorporating these far-IR surface emissivities into the Representative Concentration Pathway (RCP) 8.5 scenario of the Community Earth System Model leads to discernible changes in the spatial patterns of surface temperature, OLR, and frozen surface extent. The model results differ at high latitudes by as much as 2°K, 10 W m⁻², and 15%, respectively, after only 25 y of integration. The calculated difference in far-IR emissivity between ocean and sea ice of between 0.1 and 0.2, suggests the potential for a far-IR positive feedback for polar climate change.« less

Far-infrared surface emissivity and climate

PubMed Central

Feldman, Daniel R.; Collins, William D.; Pincus, Robert; Huang, Xianglei; Chen, Xiuhong

2014-01-01

Presently, there are no global measurement constraints on the surface emissivity at wavelengths longer than 15 μm, even though this surface property in this far-IR region has a direct impact on the outgoing longwave radiation (OLR) and infrared cooling rates where the column precipitable water vapor (PWV) is less than 1 mm. Such dry conditions are common for high-altitude and high-latitude locations, with the potential for modeled climate to be impacted by uncertain surface characteristics. This paper explores the sensitivity of instantaneous OLR and cooling rates to changes in far-IR surface emissivity and how this unconstrained property impacts climate model projections. At high latitudes and altitudes, a 0.05 change in emissivity due to mineralogy and snow grain size can cause a 1.8–2.0 W m−2 difference in the instantaneous clear-sky OLR. A variety of radiative transfer techniques have been used to model the far-IR spectral emissivities of surface types defined by the International Geosphere-Biosphere Program. Incorporating these far-IR surface emissivities into the Representative Concentration Pathway (RCP) 8.5 scenario of the Community Earth System Model leads to discernible changes in the spatial patterns of surface temperature, OLR, and frozen surface extent. The model results differ at high latitudes by as much as 2°K, 10 W m−2, and 15%, respectively, after only 25 y of integration. Additionally, the calculated difference in far-IR emissivity between ocean and sea ice of between 0.1 and 0.2, suggests the potential for a far-IR positive feedback for polar climate change. PMID:25368189

Far-infrared surface emissivity and climate

DOE PAGES

Feldman, Daniel R.; Collins, William D.; Pincus, Robert; ...

2014-11-03

Presently, there are no global measurement constraints on the surface emissivity at wavelengths longer than 15 μm, even though this surface property in this far-IR region has a direct impact on the outgoing longwave radiation (OLR) and infrared cooling rates where the column precipitable water vapor (PWV) is less than 1 mm. Such dry conditions are common for high-altitude and high-latitude locations, with the potential for modeled climate to be impacted by uncertain surface characteristics. This paper explores the sensitivity of instantaneous OLR and cooling rates to changes in far-IR surface emissivity and how this unconstrained property impacts climate modelmore » projections. At high latitudes and altitudes, a 0.05 change in emissivity due to mineralogy and snow grain size can cause a 1.8–2.0 W m⁻² difference in the instantaneous clear-sky OLR. A variety of radiative transfer techniques have been used to model the far-IR spectral emissivities of surface types defined by the International Geosphere-Biosphere Program. Incorporating these far-IR surface emissivities into the Representative Concentration Pathway (RCP) 8.5 scenario of the Community Earth System Model leads to discernible changes in the spatial patterns of surface temperature, OLR, and frozen surface extent. The model results differ at high latitudes by as much as 2°K, 10 W m⁻², and 15%, respectively, after only 25 y of integration. The calculated difference in far-IR emissivity between ocean and sea ice of between 0.1 and 0.2, suggests the potential for a far-IR positive feedback for polar climate change.« less

Interaction of surface plasmon polaritons in heavily doped GaN microstructures with terahertz radiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Melentev, G. A., E-mail: gamelen@spbstu.ru; Shalygin, V. A.; Vorobjev, L. E.

2016-03-07

We present the results of experimental and theoretical studies of the surface plasmon polariton excitations in heavily doped GaN epitaxial layers. Reflection and emission of radiation in the frequency range of 2–20 THz including the Reststrahlen band were investigated for samples with grating etched on the sample surface, as well as for samples with flat surface. The reflectivity spectrum for p-polarized radiation measured for the sample with the surface-relief grating demonstrates a set of resonances associated with excitations of different surface plasmon polariton modes. Spectral peculiarities due to the diffraction effect have been also revealed. The characteristic features of themore » reflectivity spectrum, namely, frequencies, amplitudes, and widths of the resonance dips, are well described theoretically by a modified technique of rigorous coupled-wave analysis of Maxwell equations. The emissivity spectra of the samples were measured under epilayer temperature modulation by pulsed electric field. The emissivity spectrum of the sample with surface-relief grating shows emission peaks in the frequency ranges corresponding to the decay of the surface plasmon polariton modes. Theoretical analysis based on the blackbody-like radiation theory well describes the main peculiarities of the observed THz emission.« less

Ecological controls on N2O emission in surface litter and near-surface soil of a managed grassland: modelling and measurements

NASA Astrophysics Data System (ADS)

Grant, Robert F.; Neftel, Albrecht; Calanca, Pierluigi

2016-06-01

Large variability in N2O emissions from managed grasslands may occur because most emissions originate in surface litter or near-surface soil where variability in soil water content (θ) and temperature (Ts) is greatest. To determine whether temporal variability in θ and Ts of surface litter and near-surface soil could explain this in N2O emissions, a simulation experiment was conducted with ecosys, a comprehensive mathematical model of terrestrial ecosystems in which processes governing N2O emissions were represented at high temporal and spatial resolution. Model performance was verified by comparing N2O emissions, CO2 and energy exchange, and θ and Ts modelled by ecosys with those measured by automated chambers, eddy covariance (EC) and soil sensors on an hourly timescale during several emission events from 2004 to 2009 in an intensively managed pasture at Oensingen, Switzerland. Both modelled and measured events were induced by precipitation following harvesting and subsequent fertilizing or manuring. These events were brief (2-5 days) with maximum N2O effluxes that varied from < 1 mgNm-2h-1 in early spring and autumn to > 3 mgNm-2h-1 in summer. Only very small emissions were modelled or measured outside these events. In the model, emissions were generated almost entirely in surface litter or near-surface (0-2 cm) soil, at rates driven by N availability with fertilization vs. N uptake with grassland regrowth and by O2 supply controlled by litter and soil wetting relative to O2 demand from microbial respiration. In the model, NOx availability relative to O2 limitation governed both the reduction of more oxidized electron acceptors to N2O and the reduction of N2O to N2, so that the magnitude of N2O emissions was not simply related to surface and near-surface θ and Ts. Modelled N2O emissions were found to be sensitive to defoliation intensity and timing which controlled plant N uptake and soil θ and Ts prior to and during emission events. Reducing leaf area index (LAI) remaining after defoliation to half that under current practice and delaying harvesting by 5 days raised modelled N2O emissions by as much as 80 % during subsequent events and by an average of 43 % annually. Modelled N2O emissions were also found to be sensitive to surface soil properties. Increasing near-surface bulk density by 10 % raised N2O emissions by as much as 100 % during emission events and by an average of 23 % annually. Relatively small spatial variation in management practices and soil surface properties could therefore cause the large spatial variation in N2O emissions commonly found in field studies. The global warming potential from annual N2O emissions in this intensively managed grassland largely offset those from net C uptake in both modelled and field experiments. However, model results indicated that this offset could be adversely affected by suboptimal land management and soil properties.

Emission-dominated gas exchange of elemental mercury vapor over natural surfaces in China

NASA Astrophysics Data System (ADS)

Wang, Xun; Lin, Che-Jen; Yuan, Wei; Sommar, Jonas; Zhu, Wei; Feng, Xinbin

2016-09-01

Mercury (Hg) emission from natural surfaces plays an important role in global Hg cycling. The present estimate of global natural emission has large uncertainty and remains unverified against field data, particularly for terrestrial surfaces. In this study, a mechanistic model is developed for estimating the emission of elemental mercury vapor (Hg0) from natural surfaces in China. The development implements recent advancements in the understanding of air-soil and air-foliage exchange of Hg0 and redox chemistry in soil and on surfaces, incorporates the effects of soil characteristics and land use changes by agricultural activities, and is examined through a systematic set of sensitivity simulations. Using the model, the net exchange of Hg0 between the atmosphere and natural surfaces of mainland China is estimated to be 465.1 Mg yr-1, including 565.5 Mg yr-1 from soil surfaces, 9.0 Mg yr-1 from water bodies, and -100.4 Mg yr-1 from vegetation. The air-surface exchange is strongly dependent on the land use and meteorology, with 9 % of net emission from forest ecosystems; 50 % from shrubland, savanna, and grassland; 33 % from cropland; and 8 % from other land uses. Given the large agricultural land area in China, farming activities play an important role on the air-surface exchange over farmland. Particularly, rice field shift from a net sink (3.3 Mg uptake) during April-October (rice planting) to a net source when the farmland is not flooded (November-March). Summing up the emission from each land use, more than half of the total emission occurs in summer (51 %), followed by spring (28 %), autumn (13 %), and winter (8 %). Model verification is accomplished using observational data of air-soil/air-water fluxes and Hg deposition through litterfall for forest ecosystems in China and Monte Carlo simulations. In contrast to the earlier estimate by Shetty et al. (2008) that reported large emission from vegetative surfaces using an evapotranspiration approach, the estimate in this study shows natural emissions are primarily from grassland and dry cropland. Such an emission pattern may alter the current understanding of Hg emission outflow from China as reported by Lin et al. (2010b) because a substantial natural Hg emission occurs in West China.

Plasma interaction with emmissive surface with Debye-scale grooves

NASA Astrophysics Data System (ADS)

Schweigert, Irina; Burton, Thomas S.; Thompson, Gregory B.; Langendorf, Samuel; Walker, Mitchell L. R.; Keidar, Michael

2018-04-01

The sheath development over emissive grooved surface in dc discharge plasma controlled by an electron beam is studied in the experiment and in 2D kinetic simulations. Grooved hexagonal boron nitride surfaces with different aspect ratios, designed to mimic the erosion channels, were exposed to an argon plasma. The characteristic size of the grooves (1 mm and 5 mm) is about of the Debye length. The secondary electrons emission from the grooved surfaces is provided by the bombardment with energetic electrons originated from the heated powered cathode. The transition between a developed and a collapsed sheaths near emissive surface takes place with an increase of the beam electron energy. For grooved emissive surfaces, the sheath transition happens at essentially higher voltage compared to the planar one. This phenomenon is analyzed in the terms of the electron energy distribution function.

Impacts of seasonal and regional variability in biogenic VOC emissions on surface ozone in the Pearl River Delta region, China

DOE Office of Scientific and Technical Information (OSTI.GOV)

Situ, S.; Guenther, Alex B.; Wang, X. J.

In this study, the BVOC emissions in November 2010 over the Pearl River Delta (PRD) region in southern China have been estimated by the latest version of a Biogenic Volatile Organic Compound (BVOC) emission model (MEGAN v2.1). The evaluation of MEGAN performance at a representative forest site within this region indicates MEGAN can estimate BVOC emissions reasonably well in this region except overestimating isoprene emission in autumn for reasons that are discussed in this manuscript. Along with the output from MEGAN, the Weather Research and Forecasting model with chemistry (WRF-Chem) is used to estimate the impacts of BVOC emissions onmore » surface ozone in the PRD region. The results show BVOC emissions increase the daytime ozone peak by *3 ppb on average, and the max hourly impacts of BVOC emissions on the daytime ozone peak is 24.8 ppb. Surface ozone mixing ratios in the central area of Guangzhou- Foshan and the western Jiangmen are most sensitive to BVOC emissions BVOCs from outside and central PRD influence the central area of Guangzhou-Foshan and the western Jiangmen significantly while BVOCs from rural PRD mainly influence the western Jiangmen. The impacts of BVOC emissions on surface ozone differ in different PRD cities, and the impact varies in different seasons. Foshan and Jiangmen being most affected in autumn, result in 6.0 ppb and 5.5 ppb increases in surface ozone concentrations, while Guangzhou and Huizhou become more affected in summer. Three additional experiments concerning the sensitivity of surface ozone to MEGAN input variables show that surface ozone is more sensitive to landcover change, followed by emission factors and meteorology.« less

Plasmon enhanced terahertz emission from single layer graphene.

PubMed

Bahk, Young-Mi; Ramakrishnan, Gopakumar; Choi, Jongho; Song, Hyelynn; Choi, Geunchang; Kim, Yong Hyup; Ahn, Kwang Jun; Kim, Dai-Sik; Planken, Paul C M

2014-09-23

We show that surface plasmons, excited with femtosecond laser pulses on continuous or discontinuous gold substrates, strongly enhance the generation and emission of ultrashort, broadband terahertz pulses from single layer graphene. Without surface plasmon excitation, for graphene on glass, 'nonresonant laser-pulse-induced photon drag currents' appear to be responsible for the relatively weak emission of both s- and p-polarized terahertz pulses. For graphene on a discontinuous layer of gold, only the emission of the p-polarized terahertz electric field is enhanced, whereas the s-polarized component remains largely unaffected, suggesting the presence of an additional terahertz generation mechanism. We argue that in the latter case, 'surface-plasmon-enhanced optical rectification', made possible by the lack of inversion symmetry at the graphene on gold surface, is responsible for the strongly enhanced emission. The enhancement occurs because the electric field of surface plasmons is localized and enhanced where the graphene is located: at the surface of the metal. We believe that our results point the way to small, thin, and more efficient terahertz photonic devices.

A Multi-Channel Method for Retrieving Surface Temperature for High-Emissivity Surfaces from Hyperspectral Thermal Infrared Images

PubMed Central

Zhong, Xinke; Labed, Jelila; Zhou, Guoqing; Shao, Kun; Li, Zhao-Liang

2015-01-01

The surface temperature (ST) of high-emissivity surfaces is an important parameter in climate systems. The empirical methods for retrieving ST for high-emissivity surfaces from hyperspectral thermal infrared (HypTIR) images require spectrally continuous channel data. This paper aims to develop a multi-channel method for retrieving ST for high-emissivity surfaces from space-borne HypTIR data. With an assumption of land surface emissivity (LSE) of 1, ST is proposed as a function of 10 brightness temperatures measured at the top of atmosphere by a radiometer having a spectral interval of 800–1200 cm−1 and a spectral sampling frequency of 0.25 cm−1. We have analyzed the sensitivity of the proposed method to spectral sampling frequency and instrumental noise, and evaluated the proposed method using satellite data. The results indicated that the parameters in the developed function are dependent on the spectral sampling frequency and that ST of high-emissivity surfaces can be accurately retrieved by the proposed method if appropriate values are used for each spectral sampling frequency. The results also showed that the accuracy of the retrieved ST is of the order of magnitude of the instrumental noise and that the root mean square error (RMSE) of the ST retrieved from satellite data is 0.43 K in comparison with the AVHRR SST product. PMID:26061199

Temperature and thermal emissivity of the surface of Neptune's satellite Triton

NASA Technical Reports Server (NTRS)

Nelson, Robert M.; Smythe, William D.; Wallis, Brad D.; Horn, Linda J.; Lane, Arthur L.; Mayo, Marvin J.

1990-01-01

Analysis of the preliminary results from the Voyager mission to the Neptune system has provided the scientific community with several methods by which the temperature of Neptune's satellite Triton may be determined. If the 37.5 K surface temperature reported by several Voyager investigations is correct, then the photometry reported by the imaging experiment on Voyager requires that Triton's surface have a remarkably low emissivity. Such a low emissivity is not required in order to explain the photometry from the photopolarimeter experiment on Voyager. A low emissivity would be inconsistent with Triton having a rough surface at the about 100-micron scale as might be expected given the active renewal processes which appear to dominate Triton's surface.

Ab initio investigation of the surface properties of dispenser B-type and scandate thermionic emission cathodes

NASA Astrophysics Data System (ADS)

Vlahos, Vasilios; Lee, Yueh-Lin; Booske, John H.; Morgan, Dane; Turek, Ladislav; Kirshner, Mark; Kowalczyk, Richard; Wilsen, Craig

2009-05-01

Scandate cathodes (BaxScyOz on W) are important thermionic electron emission materials whose emission mechanism remains unclear. Ab initio modeling is used to investigate the surface properties of both scandate and traditional B-type (Ba-O on W) cathodes. We demonstrate that the Ba-O dipole surface structure believed to be present in active B-type cathodes is not thermodynamically stable, suggesting that a nonequilibrium steady state dominates the active cathode's surface structure. We identify a stable, low work function BaxScyOz surface structure, which may be responsible for some scandate cathode properties and demonstrate that multicomponent surface coatings can lower cathode work functions.

Finding Blackbody Temperature and Emissivity on a Sub-Pixel Scale

NASA Astrophysics Data System (ADS)

Bernstein, D. J.; Bausell, J.; Grigsby, S.; Kudela, R. M.

2015-12-01

Surface temperature and emissivity provide important insight into the ecosystem being remotely sensed. Dozier (1981) proposed a an algorithm to solve for percent coverage and temperatures of two different surface types (e.g. sea surface, cloud cover, etc.) within a given pixel, with a constant value for emissivity assumed. Here we build on Dozier (1981) by proposing an algorithm that solves for both temperature and emissivity of a water body within a satellite pixel by assuming known percent coverage of surface types within the pixel. Our algorithm generates thermal infrared (TIR) and emissivity end-member spectra for the two surface types. Our algorithm then superposes these end-member spectra on emissivity and TIR spectra emitted from four pixels with varying percent coverage of different surface types. The algorithm was tested preliminarily (48 iterations) using simulated pixels containing more than one surface type, with temperature and emissivity percent errors of ranging from 0 to 1.071% and 2.516 to 15.311% respectively[1]. We then tested the algorithm using a MASTER image from MASTER collected as part of the NASA Student Airborne Research Program (NASA SARP). Here the temperature of water was calculated to be within 0.22 K of in situ data. The algorithm calculated emissivity of water with an accuracy of 0.13 to 1.53% error for Salton Sea pixels collected with MASTER, also collected as part of NASA SARP. This method could improve retrievals for the HyspIRI sensor. [1] Percent error for emissivity was generated by averaging percent error across all selected bands widths.

Systems and Methods for Integrated Emissivity and Temperature Measurement of a Surface

DOEpatents

Poulsen, Peter

2005-11-08

A multi-channel spectrometer and a light source are used to measure both the emitted and the reflected light from a surface which is at an elevated temperature relative to its environment. In a first method, the temperature of the surface and emissivity in each wavelength is calculated from a knowledge of the spectrum and the measurement of the incident and reflected light. In the second method, the reflected light is measured from a reference surface having a known reflectivity and the same geometry as the surface of interest and the emitted and the reflected light are measured for the surface of interest. These measurements permit the computation of the emissivity in each channel of the spectrometer and the temperature of the surface of interest.

Monitoring Surface Climate With its Emissivity Derived From Satellite Measurements

NASA Technical Reports Server (NTRS)

Zhou, Daniel K.; Larar, Allen M.; Liu, Xu

2012-01-01

Satellite thermal infrared (IR) spectral emissivity data have been shown to be significant for atmospheric research and monitoring the Earth fs environment. Long-term and large-scale observations needed for global monitoring and research can be supplied by satellite-based remote sensing. Presented here is the global surface IR emissivity data retrieved from the last 5 years of Infrared Atmospheric Sounding Interferometer (IASI) measurements observed from the MetOp-A satellite. Monthly mean surface properties (i.e., skin temperature T(sub s) and emissivity spectra epsilon(sub v) with a spatial resolution of 0.5x0.5-degrees latitude-longitude are produced to monitor seasonal and inter-annual variations. We demonstrate that surface epsilon(sub v) and T(sub s) retrieved with IASI measurements can be used to assist in monitoring surface weather and surface climate change. Surface epsilon(sub v) together with T(sub s) from current and future operational satellites can be utilized as a means of long-term and large-scale monitoring of Earth 's surface weather environment and associated changes.

Modeling and measurement of microwave emission and backscattering from bare soil surfaces

NASA Technical Reports Server (NTRS)

Saatchi, S.; Wegmuller, U.

1992-01-01

A multifrequency ground-based radiometer-scatterometer system working at frequencies between 3.0 GHz and 11.0 GHz has been used to study the effect of soil moisture and roughness on microwave emission and backscattering. The freezing and thawing effect of the soil surface and the changes of the surface roughness due to rain and erosion are reported. To analyze the combined active and passive data, a scattering model based on physical optics approximation for the low frequency and geometrical optics approximation for high frequency has been developed. The model is used to calculate the bistatic scattering coefficients from the surface. By considering the conservation of energy, the result has been integrated over a hemisphere above the surface to calculate the emissivity. The backscattering and emission model has been coupled with the observed data in order to extract soil moisture and surface roughness.

In-depth Analysis of Land Surface Emissivity using Microwave Polarization Difference Index to Improve Satellite QPE

NASA Astrophysics Data System (ADS)

Zheng, Y.; Kirstetter, P. E.; Hong, Y.; Wen, Y.; Turk, J.; Gourley, J. J.

2015-12-01

One of primary uncertainties in satellite overland quantitative precipitation estimates (QPE) from passive sensors such as radiometers is the impact on the brightness temperatures by the surface land emissivity. The complexity of surface land emissivity is linked to its temporal variations (diurnal and seasonal) and spatial variations (subsurface vertical profiles of soil moisture, vegetation structure and surface temperature) translating into sub-pixel heterogeneity within the satellite field of view (FOV). To better extract the useful signal from hydrometeors, surface land emissivity needs to be determined and filtered from the satellite-measured brightness temperatures. Based on the dielectric properties of surface land cover constitutes, Microwave Polarization Differential index (MPDI) is expected to carry the composite effect of surface land properties on land surface emissivity, with a higher MPDI indicating a lower emissivity. This study analyses the dependence of MPDI to soil moisture, vegetation and surface skin temperature over 9 different land surface types. Such analysis is performed using the normalized difference vegetation index (NDVI) from MODIS, the near surface air temperature from the RAP model and ante-precedent precipitation accumulation from the Multi-Radar Multi-Sensor as surrogates for the vegetation, surface skin temperature and shallow layer soil moisture, respectively. This paper provides 1) evaluations of brightness temperature-based MPDI from the TRMM and GPM Microwave Imagers in both raining and non-raining conditions to test the dependence of MPDI to precipitation; 2) comparisons of MPDI categorized into instantly before, during and immediately after selected precipitation events to examine the impact of modest-to-heavy precipitation on the spatial pattern of MPDI; 3) inspections of relationship between MPDI versus rain fraction and rain rate within the satellite sensors FOV to investigate the behaviors of MPDI in varying precipitation conditions; 4) analysis of discrepancies of MPDI over 10.65, 19.35, 37 and 85.8 GHz to identify the sensitivity of MPDS to microwave wavelengths.

Retrieval of Methane Source Strengths in Europe Using a Simple Modeling Approach to Assess the Potential of Spaceborne Lidar Observations

NASA Technical Reports Server (NTRS)

Weaver, C.; Kiemle, C.; Kawa, S. R.; Aalto, T.; Necki, J.; Steinbacher, M.; Arduini, J.; Apadula, F.; Berkhout, H.; Hatakka, J.

2014-01-01

We investigate the sensitivity of future spaceborne lidar measurements to changes in surface methane emissions. We use surface methane observations from nine European ground stations and a Lagrangian transport model to infer surface methane emissions for 2010. Our inversion shows the strongest emissions from the Netherlands, the coal mines in Upper Silesia, Poland, and wetlands in southern Finland. The simulated methane surface concentrations capture at least half of the daily variability in the observations, suggesting that the transport model is correctly simulating the regional transport pathways over Europe. With this tool we can test whether proposed methane lidar instruments will be sensitive to changes in surface emissions. We show that future lidar instruments should be able to detect a 50% reduction in methane emissions from the Netherlands and Germany, at least during summer.

Surface-induced brightness temperature variations and their effects on detecting thin cirrus clouds using IR emission channels in the 8-12 microns region

NASA Technical Reports Server (NTRS)

Gao, Bo-Cai; Wiscombe, W. J.

1994-01-01

A method for detecting cirrus clouds in terms of brightness temperature differences between narrowbands at 8, 11, and 12 microns has been proposed by Ackerman et al. In this method, the variation of emissivity with wavelength for different surface targets was not taken into consideration. Based on state-of-the-art laboratory measurements of reflectance spectra of terrestrial materials by Salisbury and D'Aria, it is found that the brightness temperature differences between the 8- and 11-microns bands for soils, rocks, and minerals, and dry vegetation can vary between approximately -8 and +8 K due solely to surface emissivity variations. The large brightness temperature differences are sufficient to cause false detection of cirrus clouds from remote sensing data acquired over certain surface targets using the 8-11-12-microns method directly. It is suggested that the 8-11-12-microns method should be improved to include the surface emissivity effects. In addition, it is recommended that in the future the variation of surface emissivity with wavelength should be taken into account in algorithms for retrieving surface temperatures and low-level atmospheric temperature and water vapor profiles.

Unpolarized infrared emissivity with shadow from anisotropic rough sea surfaces with non-Gaussian statistics.

PubMed

Bourlier, Christophe

2005-07-10

The emissivity of two-dimensional anisotropic rough sea surfaces with non-Gaussian statistics is investigated. The emissivity derivation is of importance for retrieval of the sea-surface temperature or equivalent temperature of a rough sea surface by infrared thermal imaging. The well-known Cox-Munk slope probability-density function, considered non-Gaussian, is used for the emissivity derivation, in which the skewness and the kurtosis (related to the third- and fourth-order statistics, respectively) are included. The shadowing effect, which is significant for grazing angles, is also taken into account. The geometric optics approximation is assumed to be valid, which means that the rough surface is modeled as a collection of facets reflecting locally the light in the specular direction. In addition, multiple reflections are ignored. Numerical results of the emissivity are presented for Gaussian and non-Gaussian statistics, for moderate wind speeds, for near-infrared wavelengths, for emission angles ranging from 0 degrees (nadir) to 90 degrees (horizon), and according to the wind direction. In addition, the emissivity is compared with both measurements and a Monte Carlo ray-tracing method.

An assessment of the land surface emissivity in the 8 - 12 micrometer window determined from ASTER and MODIS data

NASA Astrophysics Data System (ADS)

Schmugge, T.; Hulley, G.; Hook, S.

2009-04-01

The land surface emissivity is often overlooked when considering surface properties that effect the energy balance. However, knowledge of the emissivity in the window region is important for determining the longwave radiation balance and its subsequent effect on surface temperature. The net longwave radiation (NLR) is strongly affected by the difference between the temperature of the emitting surface and the sky brightness temperature, this difference will be the greatest in the window region. Outside the window region any changes in the emitted radiation by emissivity variability are mostly compensated for by changes in the reflected sky brightness. The emissivity variability is typically greatest in arid regions where the exposed soil and rock surfaces display the widest range of emissivity. For example, the dune regions of North Africa have emissivities of 0.7 or less in the 8 to 9 micrometer wavelength band due to the quartz sands of the region, which can produce changes in NLR of more than 10 w/m*m compared to assuming a constant emissivity. The errors in retrievals of atmospheric temperature and moisture profiles from hyperspectral infrared radiances, such as those from the Atmospheric Infrared Sounder (AIRS) on the NASA Aqua satellite result from using constant or inaccurate surface emissivities, particularly over arid and semi-arid regions here the variation in emissivity is large, both spatially and spectrally. The multispectral thermal infrared data obtained from the Advanced Spaceborne Thermal Emission and Reflection (ASTER) radiometer and MODerate resolution Imaging Spectrometer (MODIS) sensors on NASA's Terra satellite have been shown to be of good quality and provide a unique new tool for studying the emissivity of the land surface. ASTER has 5 channels in the 8 to 12 micrometer waveband with 90 m spatial resolution, when the data are combined with the Temperature Emissivity Separation (TES) algorithm the surface emissivity over this wavelength region can be determined. The TES algorithm has been validated with field measurements using a multi-spectral radiometer having similar bands to ASTER. The ASTER data have now been used to produce a seasonal gridded database of the emissivity for North America and the results compared to laboratory measured emissivities of in-situ rock/sand samples collected at ten validation sites in the Western USA during 2008. The directional hemispherical reflectance of the in-situ samples are measured in the laboratory using a Nicolet Fourier Transform Interferometer (FTIR), converted to emissivity using Kirchoff's law, and convolving to the appropriate sensor spectral response functions. This ASTER database, termed the North American ASTER Land Surface Emissivity Database (NAALSED), was validated using the laboratory results from these ten sites to within 0.015 (1.5%) in emissivity. MODIS has 3 channels in this waveband with 1km spatial resolution and almost daily global coverage. The MODIS data are composited to 5 km resolution and day night pairs of observations are used to derive the emissivities. These results have been validated using the ASTER emissivities over selected test areas.

Directional Emissivity Effects on Martian Surface Brightness Temperatures

NASA Astrophysics Data System (ADS)

Pitman, K. M.; Wolff, M. J.; Bandfield, J. L.; Clancy, R. T.; Clayton, G. C.

2001-11-01

The angular dependence of thermal emission from the surface of Mars has not been well characterized. Although nadir sequences constitute most of the MGS/TES Martian surface observations [1,2], a significant number scans of Martian surfaces at multiple emission angles (emission phase function (EPF) sequences) also exist. Such data can provide insight into surface structures, thermal inertias, and non-isotropic corrections to thermal emission measurements [3]. The availability of abundant EPF data as well as the added utility of such observations for atmospheric characterization provide the impetus for examining the phenomenon of directional emissivity. We present examples of directional emissivity effects on brightness temperature spectra for a variety of typical Martian surfaces. We examine the theoretical development by Hapke (1993, 1996) [4,5] and compare his algorithm to that of Mishchenko et al. (1999) [6]. These results are then compared to relevant TES EPF data. This work is supported through NASA grant NAGS-9820 (MJW) and JPL contract no. 961471 (RTC). [1] Smith et al. (1998), AAS-DPS meeting # 30, # 11.P07. [2] Kieffer, Mullins, & Titus (1998), EOS, 79, 533. [3] Jakosky, Finiol, & Henderson (1990), JGR, 17, 985--988. [4] Hapke, B. (1993), Theory of Reflectance & Emittance Spectroscopy, Cambridge Univ. Press, NY. [5] Hapke, B. (1996), JGR, 101, E7, 16817--16831. [6] Mishchenko et al. (1999), JQSRT, 63, 409--432.

Directional and dynamic modulation of the optical emission of an individual GaAs nanowire using surface acoustic waves.

PubMed

Kinzel, Jörg B; Rudolph, Daniel; Bichler, Max; Abstreiter, Gerhard; Finley, Jonathan J; Koblmüller, Gregor; Wixforth, Achim; Krenner, Hubert J

2011-04-13

We report on optical experiments performed on individual GaAs nanowires and the manipulation of their temporal emission characteristics using a surface acoustic wave. We find a pronounced, characteristic suppression of the emission intensity for the surface acoustic wave propagation aligned with the axis of the nanowire. Furthermore, we demonstrate that this quenching is dynamical as it shows a pronounced modulation as the local phase of the surface acoustic wave is tuned. These effects are strongly reduced for a surface acoustic wave applied in the direction perpendicular to the axis of the nanowire due to their inherent one-dimensional geometry. We resolve a fully dynamic modulation of the nanowire emission up to 678 MHz not limited by the physical properties of the nanowires.

Integrated Emissivity And Temperature Measurement

DOEpatents

Poulsen, Peter

2005-11-08

A multi-channel spectrometer and a light source are used to measure both the emitted and the reflected light from a surface which is at an elevated temperature relative to its environment. In a first method, the temperature of the surface and emissivity in each wavelength is calculated from a knowledge of the spectrum and the measurement of the incident and reflected light. In the second method, the reflected light is measured from a reference surface having a known reflectivity and the same geometry as the surface of interest and the emitted and the reflected light are measured for the surface of interest. These measurements permit the computation of the emissivity in each channel of the spectrometer and the temperature of the surface of interest.

Unpolarized emissivity with shadow and multiple reflections from random rough surfaces with the geometric optics approximation: application to Gaussian sea surfaces in the infrared band.

PubMed

Bourlier, Christophe

2006-08-20

The emissivity from a stationary random rough surface is derived by taking into account the multiple reflections and the shadowing effect. The model is applied to the ocean surface. The geometric optics approximation is assumed to be valid, which means that the rough surface is modeled as a collection of facets reflecting locally the light in the specular direction. In particular, the emissivity with zero, single, and double reflections are analytically calculated, and each contribution is studied numerically by considering a 1D sea surface observed in the near infrared band. The model is also compared with results computed from a Monte Carlo ray-tracing method.

Inference of Surface Chemical and Physical Properties Using Mid-Infrared (MIR) Spectral Observations

NASA Technical Reports Server (NTRS)

Roush, Ted L.

2016-01-01

Reflected or emitted energy from solid surfaces in the solar system can provide insight into thermo-physical and chemical properties of the surface materials. Measurements have been obtained from instruments located on Earth-based telescopes and carried on several space missions. The characteristic spectral features commonly observed in Mid-Infrared (MIR) spectra of minerals will be reviewed, along with methods used for compositional interpretations of MIR emission spectra. The influence of surface grain size, and space weathering processes on MIR emissivity spectra will also be discussed. Methods used for estimating surface temperature, emissivity, and thermal inertias from MIR spectral observations will be reviewed.

Modeling electron emission and surface effects from diamond cathodes

NASA Astrophysics Data System (ADS)

Dimitrov, D. A.; Smithe, D.; Cary, J. R.; Ben-Zvi, I.; Rao, T.; Smedley, J.; Wang, E.

2015-02-01

We developed modeling capabilities, within the Vorpal particle-in-cell code, for three-dimensional simulations of surface effects and electron emission from semiconductor photocathodes. They include calculation of emission probabilities using general, piece-wise continuous, space-time dependent surface potentials, effective mass, and band bending field effects. We applied these models, in combination with previously implemented capabilities for modeling charge generation and transport in diamond, to investigate the emission dependence on applied electric field in the range from approximately 2 MV/m to 17 MV/m along the [100] direction. The simulation results were compared to experimental data. For the considered parameter regime, conservation of transverse electron momentum (in the plane of the emission surface) allows direct emission from only two (parallel to [100]) of the six equivalent lowest conduction band valleys. When the electron affinity χ is the only parameter varied in the simulations, the value χ = 0.31 eV leads to overall qualitative agreement with the probability of emission deduced from experiments. Including band bending in the simulations improves the agreement with the experimental data, particularly at low applied fields, but not significantly. Using surface potentials with different profiles further allows us to investigate the emission as a function of potential barrier height, width, and vacuum level position. However, adding surface patches with different levels of hydrogenation, modeled with position-dependent electron affinity, leads to the closest agreement with the experimental data.

Enhanced flashover strength in polyethylene nanodielectrics by secondary electron emission modification

NASA Astrophysics Data System (ADS)

Wang, Weiwang; Li, Shengtao; Min, Daomin

2016-04-01

This work studies the correlation between secondary electron emission (SEE) characteristics and impulse surface flashover in polyethylene nanodielectrics both theoretically and experimentally, and illustrates the enhancement of flashover voltage in low-density polyethylene (LDPE) through incorporating Al2O3 nanoparticles. SEE characteristics play key roles in surface charging and gas desorption during surface flashover. This work demonstrates that the presence of Al2O3 nanoparticles decreases the SEE coefficient of LDPE and enhances the impact energy at the equilibrium state of surface charging. These changes can be explained by the increase of surface roughness and of surface ionization energy, and the strong interaction between nanoparticles and the polymer dielectric matrix. The surface charge and flashover voltage are calculated according to the secondary electron emission avalanche (SEEA) model, which reveals that the positive surface charges are reduced near the cathode triple point, while the presence of more nanoparticles in high loading samples enhances the gas desorption. Consequently, the surface flashover performance of LDPE/Al2O3 nanodielectrics is improved.

Ecological Controls on N2O Emission in Surface Litter and Near-surface Soil of a Managed Grassland: Modelling and Measurements

NASA Astrophysics Data System (ADS)

Grant, Robert; Neftel, Albrecht; Calanca, Pierluigi

2016-04-01

Large variability in N2O emissions from managed grasslands may occur because most emissions originate in surface litter or near-surface soil where variability in soil water content (q) and temperature (Ts) is greatest. To determine whether temporal variability in q and Ts of surface litter and near-surface soil could explain that in N2O emissions, a simulation experiment was conducted with ecosys, a comprehensive mathematical model of terrestrial ecosystems in which processes governing N2O emissions were represented at high temporal and spatial resolution. Model performance was verified by comparing N2O emissions, CO2 and energy exchange, and q and Ts modelled by ecosys with those measured by automated chambers, eddy covariance (EC) and soil sensors at an hourly time-scale during several emission events from 2004 to 2009 in an intensively managed pasture at Oensingen, Switzerland. Both modelled and measured events were induced by precipitation following harvesting and subsequent fertilizing or manuring. These events were brief (2 - 5 days) with maximum N2O effluxes that varied from < 1 mg N m-2 h-1 in early spring and autumn to > 3 mg N m-2 h-1 in summer. Only very small emissions were modelled or measured outside these events. In the model, emissions were generated almost entirely in surface litter or near-surface (0 - 2 cm) soil, at rates driven by N availability with fertilization vs. N uptake with grassland regrowth, and by O2 limitation from wetting relative to O2 demand from respiration. In the model, NOx availability relative to O2 limitation governed both the reduction of more oxidized electron acceptors to N2O and the reduction of N2O to N2, so that the magnitude of N2O emissions was not simply related to surface and near-surface q and Ts. Modelled N2O emissions were found to be sensitive to defoliation intensity and timing (relative to that of fertilization) which controlled plant N uptake and soil q and Ts prior to and during emission events. In a model sensitivity study, reducing LAI remaining after defoliation to one-half that under current practice and delaying harvesting by 5 days raised N2O emissions by as much as 80% during subsequent events and by an average of 43% annually. The global warming potential from annual N2O emissions in this intensively managed grassland largely offset those from net C uptake in both modelled and field experiments. However model results indicated that this offset could be adversely affected by suboptimal harvest intensity and timing.

Indirect estimation of emission factors for phosphate surface mining using air dispersion modeling.

PubMed

Tartakovsky, Dmitry; Stern, Eli; Broday, David M

2016-06-15

To date, phosphate surface mining suffers from lack of reliable emission factors. Due to complete absence of data to derive emissions factors, we developed a methodology for estimating them indirectly by studying a range of possible emission factors for surface phosphate mining operations and comparing AERMOD calculated concentrations to concentrations measured around the mine. We applied this approach for the Khneifiss phosphate mine, Syria, and the Al-Hassa and Al-Abyad phosphate mines, Jordan. The work accounts for numerous model unknowns and parameter uncertainties by applying prudent assumptions concerning the parameter values. Our results suggest that the net mining operations (bulldozing, grading and dragline) contribute rather little to ambient TSP concentrations in comparison to phosphate processing and transport. Based on our results, the common practice of deriving the emission rates for phosphate mining operations from the US EPA emission factors for surface coal mining or from the default emission factor of the EEA seems to be reasonable. Yet, since multiple factors affect dispersion from surface phosphate mines, a range of emission factors, rather than only a single value, was found to satisfy the model performance. Copyright © 2016 Elsevier B.V. All rights reserved.

Vehicle Emission Inspection and Maintenance (I/M) Provision in the Fixing America’s Surface Transportation (FAST) Act

EPA Pesticide Factsheets

This document is a memorandum regarding Vehicle Emission Inspection and Maintenance (I/M) Provision in Fixing America's Surface Transportation (FAST) Act, which provides long-term funding certainty for surface transportation infrastructure planning

Hyperspectral Thermal Infrared Remote Sensing of the Land Surface and Target Identification using Airborne Interferometry

DTIC Science & Technology

2009-10-01

variational data assimilation technique are profiles of temperature, water vapour and ozone , surface temperature and spectrally varying emissivity. HOW TO...that are insensitive to the land surface because of the complexity of the land surface emissivity. We have utilised the techniques described here for...state as well as surface properties. Furthermore with by utilising a variational assimilation technique and a state of the art Numerical Weather

Surface and Bulk Characteristics of Cesium Iodide (CsI) coated Carbon (C) Fibers for High Power Microwave (HPM) Field Emission Cathodes

NASA Astrophysics Data System (ADS)

Vlahos, Vasilios; Morgan, Dane; Booske, John H.; Shiffler, Don

2008-11-01

CsI coated C fibers [1] are promising field emission cathodes for HPM applications. Ab initio computational modeling has shown that atomically-thin CsI coatings reduce the work function of C substrates by a surface dipole mechanism [2]. Characterization measurements of the composition and morphology of the CsI-coated C fibers are underway for determining the properties and characteristics of the following important regions of the fiber: (i) the surface on the tip of the fiber where the majority of electron emission is believed to occur, (ii) the surface covering the body of the fiber and its role on the emission properties of the system, and (iii) the interior volume of the fiber and its effects on the CsI surface re-supply process and rate. The results will be interpreted in terms of surface electronic properties and theoretical electron emission models. [1]D. Shiffler, et al., Phys. Plasmas 11 (2004) 1680. [2]V.Vlahos et al., Appl. Phys. Lett. 91 (2007) 144102.

Surface spectral emissivity derived from MODIS data

NASA Astrophysics Data System (ADS)

Chen, Yan; Sun-Mack, Sunny; Minnis, Patrick; Smith, William L.; Young, David F.

2003-04-01

Surface emissivity is essential for many remote sensing applications including the retrieval of the surface skin temperature from satellite-based infrared measurements, determining thresholds for cloud detection and for estimating the emission of longwave radiation from the surface, an important component of the energy budget of the surface-atmosphere interface. In this paper, data from the Terra MODIS (MODerate-resolution Imaging Spectroradiometer) taken at 3.7, 8.5, 10.8, 12.0 micron are used to simultaneously derive the skin temperature and the surface emissivities at the same wavelengths. The methodology uses separate measurements of the clear-sky temperatures that are determined by the CERES (Clouds and Earth's Radiant Energy System) scene classification in each channel during the daytime and at night. The relationships between the various channels at night are used during the day when solar reflectance affects the 3.7 micron data. A set of simultaneous equations is then solved to derive the emissivities. Global results are derived from MODIS. Numerical weather analyses are used to provide soundings for correcting the observed radiances for atmospheric absorption. These results are verified and will be available for remote sensing applications.

Reducing the biases in simulated polar climate by incorporating realistic surface spectral emissivity into the global climate model

NASA Astrophysics Data System (ADS)

Huang, X.; Chen, X.; Flanner, M.; Yang, P.; Feldman, D.; Kuo, C.

2017-12-01

Surface longwave emissivity can be less than unity and vary significantly with frequency. The emissivities of water, ice, and bare land all exhibit different spectral dependence, for both the far-IR and mid-IR bands. However, most climate models still assume blackbody surface in the longwave (LW) radiation scheme of their atmospheric modules. This study incorporates realistic surface spectral emissivity into the RRTMG_LW, the LW radiation scheme in CAM, which is the atmospheric component of the NCAR Community Earth System Model (CESM) version 1.1.1. Then we evaluate its impact on simulated climatology, especially for the polar regions. By ensuring the consistency of the broadband longwave flux across different modules of the CESM, the TOA energy balance in the simulation can be attained without additional tuning of the model. While the impact on global mean surface temperature is small, the surface temperature differences in Polar Regions are statistically significant. The mean surface temperature in Arctic in the modified CESM is 1.5K warmer than that in the standard CESM, reducing the cold bias that the standard CESM has with respect to observations. Accordingly the sea ice fraction in the modified CESM simulation is less than that in the standard CESM simulation by as much as 0.1, which significantly reduces the positive biases in the simulated sea ice coverage by the CESM. The largest sea-ice coverage difference happens in August and September, when new sea ice starts to form. The similar changes can be seen for the simulated Antarctic surface climate as well. In a nutshell, incorporating realistic surface spectral emissivity helps improving the fidelity of simulated surface energy budget in the polar region, which leads to a better simulation of the surface temperature and sea ice coverage.

40 CFR 63.7905 - What emissions limitations or work practice standards must I meet for surface impoundments?

Code of Federal Regulations, 2014 CFR

2014-07-01

... ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) NATIONAL EMISSION STANDARDS FOR HAZARDOUS... Pollutants: Site Remediation Surface Impoundments § 63.7905 What emissions limitations or work practice...

40 CFR 63.7905 - What emissions limitations or work practice standards must I meet for surface impoundments?

Code of Federal Regulations, 2010 CFR

2010-07-01

... ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) NATIONAL EMISSION STANDARDS FOR HAZARDOUS... Pollutants: Site Remediation Surface Impoundments § 63.7905 What emissions limitations or work practice...

40 CFR 63.7905 - What emissions limitations or work practice standards must I meet for surface impoundments?

Code of Federal Regulations, 2012 CFR

2012-07-01

... ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) NATIONAL EMISSION STANDARDS FOR HAZARDOUS... Pollutants: Site Remediation Surface Impoundments § 63.7905 What emissions limitations or work practice...

40 CFR 63.7905 - What emissions limitations or work practice standards must I meet for surface impoundments?

Code of Federal Regulations, 2011 CFR

2011-07-01

... ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) NATIONAL EMISSION STANDARDS FOR HAZARDOUS... Pollutants: Site Remediation Surface Impoundments § 63.7905 What emissions limitations or work practice...

40 CFR 63.7905 - What emissions limitations or work practice standards must I meet for surface impoundments?

Code of Federal Regulations, 2013 CFR

2013-07-01

... ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) NATIONAL EMISSION STANDARDS FOR HAZARDOUS... Pollutants: Site Remediation Surface Impoundments § 63.7905 What emissions limitations or work practice...

Impacts of Climate Change on Surface Ozone and Intercontinental Ozone Pollution: A Multi-Model Study

NASA Technical Reports Server (NTRS)

Doherty, R. M.; Wild, O.; Shindell, D. T.; Zeng, G.; MacKenzie, I. A.; Collins, W. J.; Fiore, A. M.; Stevenson, D. S.; Dentener, F. J.; Schultz, M. G.;

VEM on VERITAS - Retrieval of global infrared surface emissivity maps of Venus and expectable retrieval uncertainties

NASA Astrophysics Data System (ADS)

Kappel, David; Arnold, Gabriele; Haus, Rainer; Helbert, Jörn; Smrekar, Suzanne; Hensley, Scott

2016-04-01

Even though Venus is in many respects the most Earth-like planet we know today, its surface composition and geology are not well understood yet. The major obstacle is the extremely dense, hot, and opaque atmosphere that complicates both in situ measurements and infrared remote sensing, the wavelength range of the latter often being the range of choice due to its coverage of many spectral properties diagnostic to the surface material's composition and texture. Thermal emissions of the hot surface depend on surface temperature and on spectral surface emissivity. As this emitted radiation wells upward, it is strongly attenuated through absorption and multiple scattering by the gaseous and particulate components of the dense atmosphere, and it is superimposed by thermal atmospheric emissions. While surface information this way carried to space is completely lost in the scattered sunlight on the dayside, a few narrow atmospheric transparency windows around 1 μm allow the sounding of the surface with nightside measurements. The successfully completed VEX ('Venus Express') mission, although not dedicated to surface science, enabled a first glimpse at much of the southern hemisphere's surface through the nightside spectral transparency windows covered by VIRTIS-M-IR ('Visible and InfraRed Thermal Imaging Spectrometer, Mapping channel in the IR', 1.0-5.1 μm). Two complementary approaches, a fast semi-empiric technique on the one hand, and a more fundamental but resource-intensive method based on a fully regularized Bayesian multi-spectrum retrieval algorithm in combination with a detailed radiative transfer simulation program on the other hand, were both successfully applied to derive surface emissivity data maps. Both methods suffered from lack of spatial coverage and a small SNR as well as from surface topography maps not sufficiently accurate for the definition of suitable boundary conditions for surface emissivity retrieval. The recently proposed VERITAS mission ('Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy') comprises two instruments, VEM ('Venus Emissivity Mapper') and VISAR ('Venus Interferometric Synthetic Aperture Radar'). This mission will yield a vastly improved data basis with respect to both high SNR Venus nightside radiance measurements at all transparency windows around 1 μm as well as topography maps. The new data will enable the derivation of much more complete and reliable global surface emissivity maps that are required to answer fundamental geologic questions. Here, we discuss the selection of the wavelength ranges covered by the spectral filters of VEM as well as improved estimates of expectable emissivity retrieval errors based on this selection. For this purpose, the locations of the relevant spectral transparency windows are studied with detailed line-by-line radiative transfer simulations in dependence on different spectral line databases. Recent work on VIRTIS-M-IR/VEX measurements indicated the presence of interferences due to ever-varying atmospheric parameters that cannot be derived from radiance measurements with limited spectral information content to be a dominant source of surface emissivity retrieval errors. This work is carried over to the configuration of VEM, and the retrieval pipeline is optimized to minimize such errors. A portion of this work was performed at the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA.

Transfer Printing Method to Obtain Polarized Light Emission in Organic Light-Emitting Device

NASA Astrophysics Data System (ADS)

Noh, Hee Yeon; Park, Chang-sub; Park, Ji-Sub; Kang, Shin-Won; Kim, Hak-Rin

2012-06-01

We demonstrate a transfer printing method to obtain polarized light emission in organic light-emitting devices (OLEDs). On a rubbed self-assembled monolayer (SAM), a spin-coated liquid crystalline light-emissive polymer is aligned along the rubbing direction because of the anisotropic interfacial intermolecular interaction. Owing to the low surface energy of the SAM surface, the light-emissive layer was easily transferred to a patterned poly(dimethylsiloxane) (PDMS) stamp surface without degrading the ordering. Finally, a polarized light-emissive OLED device was prepared by transferring the patterned light-emissive layer to the charge transport layer of the OLED structure.

Spectral identification/elimination of molecular species in spacecraft glow

NASA Technical Reports Server (NTRS)

Green, B. D.; Marinelli, W. J.; Rawlins, W. T.

1985-01-01

Computer models of molecular electronic and vibrational emission intensities were developed. Known radiative emission rates (Einstein coefficients) permit the determination of relative excited state densities from spectral intensities. These codes were applied to the published spectra of glow above shuttle surface and to the Spacelab 1 results of Torr and Torr. The theoretical high-resolution spectra were convolved with the appropriate instrumental slit functions to allow accurate comparison with data. The published spacelab spectrum is complex but N2+ Meinel emission can be clearly identified in the ram spectrum. M2 First Positive emission does not correlate well with observed features, nor does the CN Red System. Spectral overlay comparisons are presented. The spectrum of glow above shuttle surfaces, in contrast to the ISO data, is not highly structured. Diatomic molecular emission was matched to the observed spectral shape. Source excitation mechanisms such as (oxygen atom)-(surface species) reaction product chemiluminescence, surface recombination, or resonance fluorescent re-emission will be discussed for each tentative assignment. These assignments are the necessary first analytical step toward mechanism identification. Different glow mechanisms will occur above surfaces under different orbital conditions.

Atmospheric particulate emissions from dry abrasive blasting using coal slag.

PubMed

Kura, Bhaskar; Kambham, Kalpalatha; Sangameswaran, Sivaramakrishnan; Potana, Sandhya

2006-08-01

Coal slag is one of the widely used abrasives in dry abrasive blasting. Atmospheric emissions from this process include particulate matter (PM) and heavy metals, such as chromium, lead, manganese, nickel. Quantities and characteristics of PM emissions depend on abrasive characteristics and process parameters. Emission factors are key inputs to estimate emissions. Experiments were conducted to study the effect of blast pressure, abrasive feed rate, and initial surface contamination on total PM (TPM) emission factors for coal slag. Rusted and painted mild steel surfaces were used as base plates. Blasting was carried out in an enclosed chamber, and PM was collected from an exhaust duct using U.S. Environment Protection Agency source sampling methods for stationary sources. Results showed that there is significant effect of blast pressure, feed rate, and surface contamination on TPM emissions. Mathematical equations were developed to estimate emission factors in terms of mass of emissions per unit mass of abrasive used, as well as mass of emissions per unit of surface area cleaned. These equations will help industries in estimating PM emissions based on blast pressure and abrasive feed rate. In addition, emissions can be reduced by choosing optimum operating conditions.

Reporting central tendencies of chamber measured surface emission and oxidation.

PubMed

Abichou, Tarek; Clark, Jeremy; Chanton, Jeffery

2011-05-01

Methane emissions, concentrations, and oxidation were measured on eleven MSW landfills in eleven states spanning from California to Pennsylvania during the three year study. The flux measurements were performed using a static chamber technique. Initial concentration samples were collected immediately after placement of the flux chamber. Oxidation of the emitted methane was evaluated using stable isotope techniques. When reporting overall surface emissions and percent oxidation for a landfill cover, central tendencies are typically used to report "averages" of the collected data. The objective of this study was to determine the best way to determine and report central tendencies. Results showed that 89% of the data sets of collected surface flux have lognormal distributions, 83% of the surface concentration data sets are also lognormal. Sixty seven percent (67%) of the isotope measured percent oxidation data sets are normally distributed. The distribution of data for all eleven landfills provides insight of the central tendencies of emissions, concentrations, and percent oxidation. When reporting the "average" measurement for both flux and concentration data collected at the surface of a landfill, statistical analyses provided insight supporting the use of the geometric mean. But the arithmetic mean can accurately represent the percent oxidation, as measured with the stable isotope technique. We examined correlations between surface CH(4) emissions and surface air CH(4) concentrations. Correlation of the concentration and flux values using the geometric mean proved to be a good fit (R(2)=0.86), indicating that surface scans are a good way of identifying locations of high emissions. Copyright © 2010 Elsevier Ltd. All rights reserved.

Color-Tunable ZnO/GaN Heterojunction LEDs Achieved by Coupling with Ag Nanowire Surface Plasmons.

PubMed

Yang, Liu; Wang, Yue; Xu, Haiyang; Liu, Weizhen; Zhang, Cen; Wang, Chunliang; Wang, Zhongqiang; Ma, Jiangang; Liu, Yichun

2018-05-09

Color-tunable light-emitting devices (LEDs) have a great impact on our daily life. Herein, LEDs with tunable electroluminescence (EL) color were achieved via introducing Ag nanowires surface plasmons into p-GaN/n-ZnO film heterostructures. By optimizing the surface coverage density of coated Ag nanowires, the EL color was changed continuously from yellow-green to blue-violet. Transient-state and temperature-variable fluorescence emission characterizations uncovered that the spontaneous emission rate and the internal quantum efficiency of the near-UV emission were increased as a consequence of the resonance coupling interaction between Ag nanowires surface plasmons and ZnO excitons. This effect induces the selective enhancement of the blue-violet EL component but suppresses the defect-related yellow-green emission, leading to the observed tunable EL color. The proposed strategy of introducing surface plasmons can be further applied to many other kinds of LEDs for their selective enhancement of EL intensity and effective adjustment of the emission color.

Surface wind accuracy for modeling mineral dust emissions: Comparing two regional models in a Bodélé case study

NASA Astrophysics Data System (ADS)

Laurent, B.; Heinold, B.; Tegen, I.; Bouet, C.; Cautenet, G.

2008-05-01

After a decade of research on improving the description of surface and soil features in desert regions to accurately model mineral dust emissions, we now emphasize the need for deeper evaluating the accuracy of modeled 10-m surface wind speeds U 10 . Two mesoscale models, the Lokal-Modell (LM) and the Regional Atmospheric Modeling System (RAMS), coupled with an explicit dust emission model have previously been used to simulate mineral dust events in the Bodélé region. We compare LM and RAMS U 10 , together with measurements at the Chicha site (BoDEx campaign) and Faya-Largeau meteorological station. Surface features and soil schemes are investigated to correctly simulate U 10 intensity and diurnal variability. The uncertainties in dust emissions computed with LM and RAMS U 10 and different soil databases are estimated. This sensitivity study shows the importance of accurate computation of surface winds to improve the quantification of regional dust emissions from the Bodélé

Modeling electron emission and surface effects from diamond cathodes

DOE PAGES

Dimitrov, D. A.; Smithe, D.; Cary, J. R.; ...

2015-02-05

We developed modeling capabilities, within the Vorpal particle-in-cell code, for three-dimensional (3D) simulations of surface effects and electron emission from semiconductor photocathodes. They include calculation of emission probabilities using general, piece-wise continuous, space-time dependent surface potentials, effective mass and band bending field effects. We applied these models, in combination with previously implemented capabilities for modeling charge generation and transport in diamond, to investigate the emission dependence on applied electric field in the range from approximately 2 MV/m to 17 MV/m along the [100] direction. The simulation results were compared to experimental data. For the considered parameter regime, conservation of transversemore » electron momentum (in the plane of the emission surface) allows direct emission from only two (parallel to [100]) of the six equivalent lowest conduction band valleys. When the electron affinity χ is the only parameter varied in the simulations, the value χ = 0.31 eV leads to overall qualitative agreement with the probability of emission deduced from experiments. Including band bending in the simulations improves the agreement with the experimental data, particularly at low applied fields, but not significantly. In this study, using surface potentials with different profiles further allows us to investigate the emission as a function of potential barrier height, width, and vacuum level position. However, adding surface patches with different levels of hydrogenation, modeled with position-dependent electron affinity, leads to the closest agreement with the experimental data.« less

Surface Emissivity Maps for Satellite Retrieval of the Longwave Radiation Budget

NASA Technical Reports Server (NTRS)

Gupta, Shashi K.; Wilber, Anne C.; Kratz, David P.

1999-01-01

This paper presents a brief description of the procedure used to produce global surface emissivity maps for the broadband LW, the 8-12 micrometer window, and 12 narrow LW bands. For a detailed description of the methodology and the input data, the reader is referred to Wilber et al. (1999). These maps are based on a time-independent surface type map published by the IGBP, and laboratory measurements of spectral reflectances of surface materials. These maps represent a first attempt to characterize emissivity based on surface types, and many improvements to the methodology presented here are already underway. Effects of viewing zenith angle and sea state on the emissivity of ocean surface (Smith et al. 1996, Wu and Smith 1997, Masuda et al. 1988) will be taken into account. Measurements form ASTER and MODIS will be incorporated as they become available. Seasonal variation of emissivity based on changes in the characteristics of vegetation will be considered, and the variability of emissivity of barren land areas will be accounted for with the use of Zobler World Soil Maps (Zobler 1986). The current maps have been made available to the scientific community from the web site: http://tanalo.larc.nasa.gov:8080/surf_htmls/ SARB_surf.html

Mechanisms controlling the dependence of surface warming on cumulative carbon emissions over the next century in a suite of Earth system models

NASA Astrophysics Data System (ADS)

Williams, Richard; Roussenov, Vassil; Goodwin, Philip; Resplandy, Laure; Bopp, Laurent

2017-04-01

Insight into how to avoid dangerous climate may be obtained from Earth system model projections, which reveal a near-linear dependence of global-mean surface warming on cumulative carbon emissions. This dependence of surface warming on carbon emissions is interpreted in terms of a product of three terms: the dependence of surface warming on radiative forcing, the fractional radiative forcing contribution from atmospheric CO2 and the dependence of radiative forcing from atmospheric CO2 on cumulative carbon emissions. Mechanistically each of these dependences varies, respectively, with ocean heat uptake, the CO2 and non-CO2 radiative forcing, and the ocean and terrestrial uptake of carbon. An ensemble of 9 Earth System models forced by up to 4 Representative Concentration Pathways are diagnosed. In all cases, the dependence of surface warming on carbon emissions evolves primarily due to competing effects of heat and carbon uptake over the upper ocean: there is a reduced effect of radiative forcing from CO2 due to ocean carbon uptake, which is partly compensated by enhanced surface warming due to a reduced effect of ocean heat uptake. There is a wide spread in the dependence of surface warming on carbon emissions, undermining the ability to identify the maximum permitted carbon emission to avoid dangerous climate. Our framework reveals how uncertainty in the future warming trend is high over the next few decades due to relatively high uncertainties in ocean heat uptake, non-CO2 radiative forcing and the undersaturation of carbon in the ocean.

Time-Dependent Cryospheric Longwave Surface Emissivity Feedback in the Community Earth System Model

NASA Astrophysics Data System (ADS)

Kuo, Chaincy; Feldman, Daniel R.; Huang, Xianglei; Flanner, Mark; Yang, Ping; Chen, Xiuhong

2018-01-01

Frozen and unfrozen surfaces exhibit different longwave surface emissivities with different spectral characteristics, and outgoing longwave radiation and cooling rates are reduced for unfrozen scenes relative to frozen ones. Here physically realistic modeling of spectrally resolved surface emissivity throughout the coupled model components of the Community Earth System Model (CESM) is advanced, and implications for model high-latitude biases and feedbacks are evaluated. It is shown that despite a surface emissivity feedback amplitude that is, at most, a few percent of the surface albedo feedback amplitude, the inclusion of realistic, harmonized longwave, spectrally resolved emissivity information in CESM1.2.2 reduces wintertime Arctic surface temperature biases from -7.2 ± 0.9 K to -1.1 ± 1.2 K, relative to observations. The bias reduction is most pronounced in the Arctic Ocean, a region for which Coupled Model Intercomparison Project version 5 (CMIP5) models exhibit the largest mean wintertime cold bias, suggesting that persistent polar temperature biases can be lessened by including this physically based process across model components. The ice emissivity feedback of CESM1.2.2 is evaluated under a warming scenario with a kernel-based approach, and it is found that emissivity radiative kernels exhibit water vapor and cloud cover dependence, thereby varying spatially and decreasing in magnitude over the course of the scenario from secular changes in atmospheric thermodynamics and cloud patterns. Accounting for the temporally varying radiative responses can yield diagnosed feedbacks that differ in sign from those obtained from conventional climatological feedback analysis methods.

Quantification of surface emissions: An historical perspective from GEIA

NASA Astrophysics Data System (ADS)

Granier, C.; Denier Van Der Gon, H.; Doumbia, E. H. T.; Frost, G. J.; Guenther, A. B.; Hassler, B.; Janssens-Maenhout, G. G. A.; Lasslop, G.; Melamed, M. L.; Middleton, P.; Sindelarova, K.; Tarrason, L.; van Marle, M.; W Kaiser, J.; van der Werf, G.

2015-12-01

Assessments of the composition of the atmosphere and its evolution require accurate knowledge of the surface emissions of atmospheric compounds. The first community development of global surface emissions started in 1990, when GEIA was established as a component of the International Global Atmospheric Chemistry (IGAC) project. At that time, GEIA meant "Global Emissions Inventory Activity". Since its inception, GEIA has brought together people to understand emissions from anthropogenic, biomass burning and natural sources. The first goal of GEIA was to establish a "best" inventory for the base year 1985 at 1x1 degree resolution. Since then many inventories have been developed by various groups at the global and regional scale at different temporal and spatial resolutions. GEIA, which now means the "Global Emissions Initiative", has evolved into assessing, harmonizing and distributing emissions datasets. We will review the main achievements of GEIA, and show how the development and evaluation of surface emissions has evolved during the last 25 years. We will discuss the use of surface, in-situ and remote sensing observations to evaluate and improve the quantification of emissions. We will highlight the main uncertainties currently limiting emissions datasets, such as the spatial and temporal evolution of emissions at different resolutions, the quantification of emerging emission sources (such as oil/gas extraction and distribution, biofuels, etc.), the speciation of the emissions of volatile organic compounds and of particulate matter, the capacity building necessary for organizing the development of regional emissions across the world, emissions from shipping, etc. We will present the ECCAD (Emissions of Atmospheric Compounds and Compilation of Ancillary Data) database, developed as part of GEIA to facilitate the access and evaluation of emission inventories.

Can increasing CO2 cool Antarctica?

NASA Astrophysics Data System (ADS)

Schmithuesen, Holger; Notholt, Justus; König-Langlo, Gert; Lemke, Peter

2014-05-01

CO2 is the strongest anthropogenic forcing agent for climate change since pre-industrial times. Like other greenhouse gases, CO2 absorbs terrestrial surface radiation and causes emission from the atmosphere to space. As the surface is generally warmer than the atmosphere, the total long-wave emission to space is commonly less than the surface emission. However, this does not hold true for the high elevated areas of central Antarctica. Our investigations show, that for the high elevated areas of Antarctica the greenhouse effect (GHE) of CO2 is commonly around zero or even negative. This is based on the quantification of GHE as the difference between long-wave surface emission and top of atmosphere emission. We demonstrate this behaviour with the help of three models: a simple two-layer model, line-by-line calculations, and an ECMWF experiment. Additionally, in this region an increase in CO2 concentration leads to an instantaneous increased long-wave energy loss to space, which is a cooling effect on the earth-atmosphere system. However, short-wave warming by the weak absorption of solar radiation by CO2 are not taken into account here. The reason for this counter-intuitive behaviour is the fact that in the interior of Antarctica the surface is often colder than the stratosphere above. Radiation from the surface in the atmospheric window emitted to space is then relatively lower compared to radiation in the main CO2 band around 15 microns, which originates mostly from the stratosphere. Increasing CO2 concentration leads to increasing emission from the atmosphere to space, while blocking additional portions of surface emission. If the surface is colder than the stratosphere, this leads to additional long-wave energy loss to space for increasing CO2. Our findings for central Antarctica are in strong contrast to the generally known effect that increasing CO2 has on the long-wave emission to space, and hence on the Antarctic climate.

Sector-based VOCs emission factors and source profiles for the surface coating industry in the Pearl River Delta region of China.

PubMed

Zhong, Zhuangmin; Sha, Qing'e; Zheng, Junyu; Yuan, Zibing; Gao, Zongjiang; Ou, Jiamin; Zheng, Zhuoyun; Li, Cheng; Huang, Zhijiong

2017-04-01

Accurate depiction of VOCs emission characteristics is essential for the formulation of VOCs control strategies. As one of the continuous efforts in improving VOCs emission characterization in the Pearl River Delta (PRD) region, this study targeted on surface coating industry, the most important VOCs emission sources in the PRD. Sectors in analysis included shipbuilding coating, wood furniture coating, metal surface coating, plastic surface coating, automobile coating and fabric surface coating. Sector-based field measurement was conducted to characterize VOCs emission factors and source profiles in the PRD. It was found that the raw material-based VOCs emission factors for these six sectors ranged from 0.34 to 0.58kg VOCs per kg of raw materials (kg·kg -1 ) while the emission factors based on the production yield varied from 0.59kg to 13.72t VOCs for each production manufactured. VOCs emission factors of surface coating industry were therefore preferably calculated based on raw materials with low uncertainties. Source profiles differed greatly among different sectors. Aromatic was the largest group for shipbuilding coating, wood furniture coating, metal surface coating and automobile coating while the oxygenated VOCs (OVOCs) were the most abundant in the plastic and fabric surface coating sectors. The major species of aromatic VOCs in each of these six sectors were similar, mainly toluene and m/p-xylene, while the OVOCs varied among the different sectors. VOCs profiles in the three processes of auto industry, i.e., auto coating, auto drying and auto repairing, also showed large variations. The major species in these sectors in the PRD were similar with other places but the proportions of individual compounds were different. Some special components were also detected in the PRD region. This study highlighted the importance of updating local source profiles in a comprehensive and timely manner. Copyright © 2016 Elsevier B.V. All rights reserved.

Enhanced flashover strength in polyethylene nanodielectrics by secondary electron emission modification

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Weiwang; Li, Shengtao, E-mail: sli@xjtu.edu.cn; Min, Daomin

2016-04-15

This work studies the correlation between secondary electron emission (SEE) characteristics and impulse surface flashover in polyethylene nanodielectrics both theoretically and experimentally, and illustrates the enhancement of flashover voltage in low-density polyethylene (LDPE) through incorporating Al{sub 2}O{sub 3} nanoparticles. SEE characteristics play key roles in surface charging and gas desorption during surface flashover. This work demonstrates that the presence of Al{sub 2}O{sub 3} nanoparticles decreases the SEE coefficient of LDPE and enhances the impact energy at the equilibrium state of surface charging. These changes can be explained by the increase of surface roughness and of surface ionization energy, and themore » strong interaction between nanoparticles and the polymer dielectric matrix. The surface charge and flashover voltage are calculated according to the secondary electron emission avalanche (SEEA) model, which reveals that the positive surface charges are reduced near the cathode triple point, while the presence of more nanoparticles in high loading samples enhances the gas desorption. Consequently, the surface flashover performance of LDPE/Al{sub 2}O{sub 3} nanodielectrics is improved.« less

Mechanism of Prism-Coupled Scanning Tunneling Microscope Light Emission

NASA Astrophysics Data System (ADS)

Iida, Wataru; Ahamed, Jamal U.; Katano, Satoshi; Uehara, Yoichi

2011-09-01

We have investigated the mechanism of scanning tunneling microscope light emission (STM-LE) in a prism-coupled configuration using finite difference time domain analysis. In this configuration, the sample is a metallic thin film evaporated on the bottom surface of a hemispherical glass prism. STM light emitted into the prism (prism-side emission) through the metallic film is measured. Since both localized surface plasmons (LSP) and surface plasmon polaritons (SPP) contribute to prism-side emission, this emission is stronger than that in conventional STM-LE measured from the sample surface side, which is radiated by LSP alone. We show that the spatial resolution of prism-side emission is determined not by the propagation length of SPP, but by the lateral size of LSP, similarly to conventional (i.e., tip side) STM-LE. Thus, we conclude that, by using the prism-coupled configuration, the signal level of STM-LE improves without the loss of spatial resolution attained in tip side emission.

3D-CFD analysis of diffusion and emission of VOCs in a FLEC cavity.

PubMed

Zhu, Q; Kato, S; Murakami, S; Ito, K

2007-06-01

This study is performed as a part of research that examines the emission and diffusion characteristics of volatile organic compounds (VOCs) from indoor building materials. In this paper, the flow field and the emission field of VOCs from the surface of building materials in a Field and Laboratory Emission Cell (FLEC) cavity are examined by 3D Computational Fluid Dynamics (CFD) analysis. The flow field within the FLEC cavity is laminar. With a total flow of 250 ml/min, the air velocity near the test material surface ranges from 0.1 to 4.5 cm/s. Three types of emission from building materials are studied here: (i) emission phenomena controlled by internal diffusion, (ii) emission phenomena controlled by external diffusion, and (iii) emission phenomena controlled by mixed diffusion (internal + external diffusion). In the case of internal diffusion material, with respect to the concentration distribution in the cavity, the local VOC emission rate becomes uniform and the FLEC works well. However, in the case of evaporation type (external diffusion) material, or mixed type materials (internal + external diffusion) when the resistance to transporting VOCs in the material is small, the FLEC is not suitable for emission testing because of the thin FLEC cavity. In this case, the mean emission rate is restricted to a small value, since the VOC concentration in the cavity rises to the same value as the surface concentration through molecular diffusion within the thin cavity, and the concentration gradient normal to the surface becomes small. The diffusion field and emission rate depend on the cavity concentration and on the Loading Factor. That is, when the testing material surface in the cavity is partially sealed to decrease the Loading Factor, the emission rate become higher with the decrease in the exposed area of the testing material. The flow field and diffusion field within the FLEC cavity are investigated by CFD method. After presenting a summary of the velocity distributed over the surface of test material and the emission properties of different type materials in FLEC, the paper pointed out that there is a bias in the airflow inside the FLEC cavity but do not influence the result of test emission rate, and the FLEC method is unsuitable for evaporation type materials in which the mass transfer of the surface controls the emission rate.

Global modelling of Cryptosporidium in surface water

NASA Astrophysics Data System (ADS)

Vermeulen, Lucie; Hofstra, Nynke

2016-04-01

Introduction Waterborne pathogens that cause diarrhoea, such as Cryptosporidium, pose a health risk all over the world. In many regions quantitative information on pathogens in surface water is unavailable. Our main objective is to model Cryptosporidium concentrations in surface waters worldwide. We present the GloWPa-Crypto model and use the model in a scenario analysis. A first exploration of global Cryptosporidium emissions to surface waters has been published by Hofstra et al. (2013). Further work has focused on modelling emissions of Cryptosporidium and Rotavirus to surface waters from human sources (Vermeulen et al 2015, Kiulia et al 2015). A global waterborne pathogen model can provide valuable insights by (1) providing quantitative information on pathogen levels in data-sparse regions, (2) identifying pathogen hotspots, (3) enabling future projections under global change scenarios and (4) supporting decision making. Material and Methods GloWPa-Crypto runs on a monthly time step and represents conditions for approximately the year 2010. The spatial resolution is a 0.5 x 0.5 degree latitude x longitude grid for the world. We use livestock maps (http://livestock.geo-wiki.org/) combined with literature estimates to calculate spatially explicit livestock Cryptosporidium emissions. For human Cryptosporidium emissions, we use UN population estimates, the WHO/UNICEF JMP sanitation country data and literature estimates of wastewater treatment. We combine our emissions model with a river routing model and data from the VIC hydrological model (http://vic.readthedocs.org/en/master/) to calculate concentrations in surface water. Cryptosporidium survival during transport depends on UV radiation and water temperature. We explore pathogen emissions and concentrations in 2050 with the new Shared Socio-economic Pathways (SSPs) 1 and 3. These scenarios describe plausible future trends in demographics, economic development and the degree of global integration. Results and Conclusions GloWPa-Crypto is the first global model that can be used to analyse dynamics in surface water pathogen concentrations worldwide. Global human Cryptosporidium emissions are estimated at 1 x 10^17 oocysts/ year for the year 2010.We estimated future emissions for SSP1 and SSP3. Preliminary results show that for SSP1human emissions are approximately halved by 2050. The SSP3 human emissions are 1.5 times higher than the 2010 emissions due to increased population growth and urbanisation. Livestock Cryptosporidium emissions are expected to increase under both SSP1 and SSP3, as meat consumption continues to rise. We conclude that population growth, urbanization, changes in sanitation systems and treatment, and changes in livestock consumption and production systems are important processes that determine future Cryptosporidium emissions to surface water. References Hofstra N, Bouwman A F, Beusen A H W and Medema G J 2013 Exploring global Cryptosporidium emissions to surface water Sci. Total Environ. 442 10-9 Kiulia N M, Hofstra N, Vermeulen L C, Obara M A, Medema G J and Rose J B 2015 Global occurrence and emission of rotaviruses to surface waters Pathogens 4 229-55 Vermeulen L C, De Kraker J, Hofstra N, Kroeze C and Medema G J 2015 Modelling the impact of sanitation, population and urbanization estimates on human emissions of Cryptosporidium to surface waters - a case study for Bangladesh and India Environ. Res. Lett. 10

Self-referenced directional enhanced Raman scattering using plasmon waveguide resonance for surface and bulk sensing

NASA Astrophysics Data System (ADS)

Wan, Xiu-mei; Gao, Ran; Lu, Dan-feng; Qi, Zhi-mei

2018-01-01

Surface plasmon-coupled emission has been widely used in fluorescence imaging, biochemical sensing, and enhanced Raman spectroscopy. A self-referenced directional enhanced Raman scattering for simultaneous detection of surface and bulk effects by using plasmon waveguide resonance (PWR) based surface plasmon-coupled emission has been proposed and experimentally demonstrated. Raman scattering was captured on the prism side in Kretschmann-surface plasmon-coupled emission. The distinct penetration depths (δ) of the evanescent field for the transverse electric (TE) and transverse magnetic (TM) modes result in different detected distances of the Raman signal. The experimental results demonstrate that the self-referenced directional enhanced Raman scattering of the TE and TM modes based on the PWR can detect and distinguish the surface and bulk effects simultaneously, which appears to have potential applications in researches of chemistry, medicine, and biology.

NOX AND CO EMISSIONS FROM SOIL AND SURFACE LITTER IN A BRAZILIAN SAVANNA

EPA Science Inventory

Land clearing and burning in the tropics often results in increased solar irradiation of soil and surface organic matter. This increased light exposure and surface heating may impact the emissions of nitrogen oxides (NOx) and carbon monoxide (CO), trace gases that play an importa...

40 CFR 63.3890 - What emission limits must I meet?

Code of Federal Regulations, 2013 CFR

2013-07-01

...) National Emission Standards for Hazardous Air Pollutants for Surface Coating of Miscellaneous Metal Parts... each 12-month compliance period. (c) If your facility's surface coating operations meet the... alternatives in paragraph (c)(1) or (2) of this section. (1) If the general use or magnet wire surface coating...

40 CFR 63.3890 - What emission limits must I meet?

Code of Federal Regulations, 2014 CFR

2014-07-01

...) National Emission Standards for Hazardous Air Pollutants for Surface Coating of Miscellaneous Metal Parts... each 12-month compliance period. (c) If your facility's surface coating operations meet the... alternatives in paragraph (c)(1) or (2) of this section. (1) If the general use or magnet wire surface coating...

Using surface water application to reduce 1,3-dichloropropene emission from soil fumigation.

PubMed

Gao, Suduan; Trout, Thomas J

2006-01-01

High emissions from soil fumigants increase the risk of detrimental impact on workers, bystanders, and the environment, and jeopardize future availability of fumigants. Efficient and cost-effective approaches to minimize emissions are needed. This study evaluated the potential of surface water application (or water seal) to reduce 1,3-dichloropropene (1,3-D) emissions from soil (Hanford sandy loam) columns. Treatments included dry soil (control), initial water application (8 mm of water just before fumigant application), initial plus a second water application (2.6 mm) at 12 h, initial plus two water applications (2.6 mm each time) at 12 and 24 h, standard high density polyethylene (HDPE) tarp, initial water application plus HDPE tarp, and virtually impermeable film (VIF) tarp. Emissions from the soil surface and distribution of 1,3-D in the soil-gas phase were monitored for 2 wk. Each water application abruptly reduced 1,3-D emission flux, which rebounded over a few hours. Peak emission rates were substantially reduced, but total emission reduction was small. Total fumigant emission was 51% of applied for the control, 46% for initial water application only, and 41% for the three intermittent water applications with the remaining water treatment intermediate. The HDPE tarp alone resulted in 45% emission, while initial water application plus HDPE tarp resulted in 38% emission. The most effective soil surface treatment was VIF tarp (10% emission). Surface water application can be as effective, and less expensive than, standard HDPE tarp. Frequent water application is required to substantially reduce emissions.

In-use catalyst surface area and its relation to HC conversion efficiency and FTP emissions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Donahue, K.S.; Sabourin, M.A.; Larson, R.E.

1986-01-01

Surface area data, steady-state hydrocarbon conversion efficiency data, and hydrocarbon emissions results have been determined for catalysts collected by the U.S. Environmental Protection Agency from properly maintained 1981 and 1982 model year vehicles. Catalysts covered in this study were limited to those with three-way-plus-oxidation monolith technologies. Catalyst surface areas were measured using the BET method, conversion efficiencies were measured on an exhaust gas generator, and emissions results were determined using the Urban Driving Schedule of the Federal Test Procedure. Results indicate that correlation of catalyst surface area data with hydrocarbon conversion efficiency data and hydrocarbon emissions results is significant formore » the sample studied.« less

Surface slope characteristics from Thermal Emission Spectrometer emission phase function observations

NASA Astrophysics Data System (ADS)

Edwards, C. S.; Bandfield, J. L.; Christensen, P. R.

2006-12-01

It is possible to obtain surface roughness characteristics, by measuring a single surface from multiple emission angles and azimuths in the thermal infrared. Surfaces will have different temperatures depending on their orientation relative to the sun. A different proportion of sunlit versus shaded surfaces will be in the field of view based on the viewing orientation, resulting in apparent temperature differences. This difference in temperature can be utilized to calculate the slope characteristics for the observed area. This technique can be useful for determining surface slope characteristics not resolvable by orbital imagery. There are two main components to this model, a surface DEM, in this case a synthetic, two dimensional sine wave surface, and a thermal model (provided by H. Kieffer). Using albedo, solar longitude, slope, azimuth, along with several other parameters, the temperature for each cell of the DEM is calculated using the thermal model. A temperature is then predicted using the same observation geometries as the Thermal Emission Spectrometer (TES) observations. A temperature difference is calculated for the two complementary viewing azimuths and emission angles from the DEM. These values are then compared to the observed temperature difference to determine the surface slope. This method has been applied to TES Emission Phase Function (EPF) observations for both the spectrometer and bolometer data, with a footprint size of 10s of kilometers. These specialized types of TES observations measure nearly the same surface from several angles. Accurate surface kinetic temperatures are obtained after the application of an atmospheric correction for the TES bolometer and/or spectrometer. Initial results include an application to the northern circumpolar dunes. An average maximum slope of ~33 degrees has been obtained, which makes physical sense since this is near the angle of repose for sand sized particles. There is some scatter in the data from separate observations, which may be due to the large footprint size. This technique can be better understood and characterized by correlation with high resolution imagery. Several different surface maps will also be tested in addition to the two dimensional sine wave surface. Finally, by modeling the thermal effects on different particle sizes and land forms, we can further interpret the scale of these slopes.

Linking playa surface dust emission potential to feedbacks between surface moisture and salt crust expansion through high resolution terrestrial laser scanning measurements

NASA Astrophysics Data System (ADS)

Nield, J. M.; King, J.; Wiggs, G.

2012-12-01

The dust emissivity of salt pans (or playas) can be significant but is controlled by interactions between wind erosivity, surface moisture, salt chemistry and crust morphology. These surface properties influence the aeolian transport threshold and can be highly variable over both short temporal and spatial scales. In the past, field studies have been hampered by practical difficulties in accurately measuring properties controlling sediment availability at the surface in high resolution. Studies typically therefore, have investigated large scale monthly or seasonal change using remote sensing and assume a homogeneous surface when predicting dust emissivity. Here we present the first high resolution measurements (sub-cm) of salt crust expansion related to changes in diurnal moisture over daily and weekly time periods using terrestrial laser scanning (TLS, ground-based LiDAR) on Sua Pan, Botswana. The TLS measures both elevation and relative surface moisture change simultaneously, without disturbing the surface. Measurement sequences enable the variability in aeolian sediment availability to be quantified along with temporal feedbacks associated with crust degradation. On crusts with well-developed polygon ridges (high aerodynamic and surface roughness), daily surface expansion was greater than 30mm. The greatest surface change occurred overnight on the upper, exposed sections of the ridges, particularly when surface temperatures dropping below 10°C. These areas also experienced the greatest moisture variation and became increasingly moist overnight in response to an increase in relative humidity. In contrast, during daylight hours, the ridge areas were drier than the lower lying inter-ridge areas. Positive feedbacks between surface topography and moisture reinforced the maximum diurnal moisture variation at ridge peaks, encouraging crust thrusting due to overnight salt hydration, further enhancing the surface, and therefore, aerodynamic roughness. These feedbacks between surface roughness and moisture have implications for dust emissivity because crust expansion increases fluff production which is one of the main dust source materials. Further, increased roughness can locally increase wind erosivity and the potential evaporation of ridge areas. Crust thrusting also weakens the ridge peaks, developing cracked surfaces and exposing the sediment supply source below. These fast acting processes can have a major influence on wind erosion variability and dust emissivity from key dust source regions.; a-d) Elevation change overnight. e-f) Elevation change over 6 days.

Estimating source-attributable health impacts of ambient fine particulate matter exposure: global premature mortality from surface transportation emissions in 2005

NASA Astrophysics Data System (ADS)

Chambliss, S. E.; Silva, R.; West, J. J.; Zeinali, M.; Minjares, R.

2014-10-01

Exposure to ambient fine particular matter (PM2.5) was responsible for 3.2 million premature deaths in 2010 and is among the top ten leading risk factors for early death. Surface transportation is a significant global source of PM2.5 emissions and a target for new actions. The objective of this study is to estimate the global and national health burden of ambient PM2.5 exposure attributable to surface transportation emissions. This share of health burden is called the transportation attributable fraction (TAF), and is assumed equal to the proportional decrease in modeled ambient particulate matter concentrations when surface transportation emissions are removed. National population-weighted TAFs for 190 countries are modeled for 2005 using the MOZART-4 global chemical transport model. Changes in annual average concentration of PM2.5 at 0.5 × 0.67 degree horizontal resolution are based on a global emissions inventory and removal of all surface transportation emissions. Global population-weighted average TAF was 8.5 percent or 1.75 μg m-3 in 2005. Approximately 242 000 annual premature deaths were attributable to surface transportation emissions, dominated by China, the United States, the European Union and India. This application of TAF allows future Global Burden of Disease studies to estimate the sector-specific burden of ambient PM2.5 exposure. Additional research is needed to capture intraurban variations in emissions and exposure, and to broaden the range of health effects considered, including the effects of other pollutants.

Air-water CO2 and CH4 fluxes along a river-reservoir continuum: Case study in the Pengxi River, a tributary of the Yangtze River in the Three Gorges Reservoir, China.

PubMed

Huang, Yang; Yasarer, Lindsey M W; Li, Zhe; Sturm, Belinda S M; Zhang, Zengyu; Guo, Jinsong; Shen, Yu

2017-05-01

Water surface greenhouse gas (GHG) emissions in freshwater reservoirs are closely related to limnological processes in the water column. Affected by both reservoir operation and seasonal changes, variations in the hydro-morphological conditions in the river-reservoir continuum will create distinctive patterns in water surface GHG emissions. A one-year field survey was carried out in the Pengxi River-reservoir continuum, a part of the Three Gorges Reservoir (TGR) immediately after the TGR reached its maximum water level. The annual average water surface CO 2 and CH 4 emissions at the riverine background sampling sites were 6.23 ± 0.93 and 0.025 ± 0.006 mmol h -1  m -2 , respectively. The CO 2 emissions were higher than those in the downstream reservoirs. The development of phytoplankton controlled the downstream decrease in water surface CO 2 emissions. The presence of thermal stratification in the permanent backwater area supported extensive phytoplankton blooms, resulting in a carbon sink during several months of the year. The CH 4 emissions were mainly impacted by water temperature and dissolved organic carbon. The greatest water surface CH 4 emission was detected in the fluctuating backwater area, likely due to a shallower water column and abundant organic matter. The Pengxi River backwater area did not show significant increase in water surface GHG emissions reported in tropical reservoirs. In evaluating the net GHG emissions by the impoundment of TGR, the net change in the carbon budget and the contribution of nitrogen and phosphorus should be taken into consideration in this eutrophic river-reservoir continuum.

Surface exciton emission of MgO crystals

NASA Astrophysics Data System (ADS)

Kuang, Wen-Jian; Li, Qing; Chen, Yu-Xiang; Hu, Kai; Wang, Ning-Hui; Xing, Fang-Li; Yan, Qun; Sun, Shuai-Shuai; Huang, Yan; Tao, Ye; Tolner, Harm

2013-09-01

MgO crystals have been exposed to vacuum ultraviolet (VUV) radiation from a synchrotron, with energies up to 9 eV, and the emitted light, at wavelengths above 200 nm, was observed. It is concluded that bulk excitons, play an important role in the diffusion of energy inside MgO crystals, resulting in 5.85 eV (212 nm) emission from the MgO terraces of large (0.2-2 µm) MgO : F crystals. In the case of aliovalent impurity doping, then the bulk exciton energy is also transferred to the Vk centres and 5.3 eV (235 nm) light is emitted. Both fluorine and silicon doping appear to promote UV surface emission, acting similarly to an ns2 ion inside MgO, while strong scandium doping is killing the surface emission completely. The 212 nm surface UV emission and the 235 nm bulk UV emission can be excited only at the bandgap edge. Broadband visible light, centred around 400 nm, is also emitted. Contrary to the UV emission, this is not generated when excited at the bandgap edge; instead, we find that it is only excited at sub-bandgap energies, with a maximum at the 5C surface excitation energy of 5.71 eV (217 nm) for the MgO terraces.

IR spectral properties of dust and ice at the Mars south polar cap

NASA Astrophysics Data System (ADS)

Titus, T. N.; Kieffer, H. H.

2001-11-01

Removal of atmospheric dust effects is required to derive surface IR spectral emissivity. Commonly, the atmospheric-surface separation is based on radiative transfer (RT) spectral inversion methods using nadir-pointing observations. This methodology depends on a priori knowledge of the spectral shape of each atmospheric aerosol (e.g. dust or water ice) and a large thermal contrast between the surface and atmosphere. RT methods fail over the polar caps due to low thermal contrast between the atmosphere and the surface. We have used multi-angle Emission Phase Function (EPF) observations to estimate the opacity spectrum of dust over the springtime south polar cap and the underlying surface radiance, and thus, the surface emissivity. We include a few EPFs from Hellas Basin as a basis for comparisons between the spectral shape of polar and non-polar dust. Surface spectral emissivities over the seasonal cap are compared to CO2 models. Our results show that the spectral shape of the polar dust opacity is not constant, but is a two-parameter family that can be characterized by the 9 um and 20 um opacities. The 9 um opacity varies from 0.15 to 0.45 and characterizes the overall atmospheric conditions. The 9 um to 20 um opacity ratio varies from 2.0 to 5.1, suggesting changes in dust size distribution over the polar caps. Derived surface temperatures from the EPFs confirm that the slightly elevated temperatures (relative to CO2 frost temperature) observed in ``cryptic'' regions are a surface effect, not atmospheric. Comparison of broad-band reflectivity and surface emissivities to model spectra suggest the bright regions (e.g. perennial cap, Mountains of Mitchell) have higher albedos due to a thin surface layer of fine-grain CO2 (perhaps either frost or fractured ice) with an underlying layer of either coarse grain or slab CO2 ice.

Influence of water table fluctuations on subsurface methane dynamics and surface fluxes in seasonally flooded subtropical pastures.

NASA Astrophysics Data System (ADS)

Chamberlain, S.; Gomez-Casanovas, N.; Boughton, E.; Keel, E.; Walter, M. T.; Groffman, P. M.; Sparks, J. P.

2015-12-01

Seasonally flooded subtropical pastures are major sources of methane (CH4), and periodic flooding drives complex emission dynamics from these ecosystems. Understanding the mechanisms of belowground CH4 dynamics driving soil surface fluxes is needed to better understand emissions from these systems and their response to environmental change. We investigated subsurface CH4 dynamics in relation to net surface fluxes using laboratory water table manipulations and compared these results to eddy covariance-measured fluxes to link within-soil CH4 dynamics to observed ecosystem fluxes. Pronounced hysteresis was observed in ecosystem CH4 fluxes during precipitation driven flooding events. This dynamic was replicated in mesocosm experiments, with maximum CH4 fluxes observed during periods of water table recession. Hysteresis dynamics were best explained by oxygen dynamics during precipitation recharge events and the oxidation of CH4 produced in organic soil horizons during water table recession. We observed distinct CH4 dynamics between surface organic and deeper mineral soil horizons. In surface organic soil horizons, high levels of CH4 production were temporally linked to observed surface emissions. In contrast, high concentrations of CH4 observed in deeper mineral soils did not contribute to surface fluxes. Methane production potentials in surface organic soils were orders of magnitude higher than in mineral soils, suggesting that over longer flooding regimes CH4 produced in mineral horizons is unlikely to be a significant component of net surface emissions. Our results demonstrate that distinct CH4 dynamics may be stratified by depth, and flooding of the near-surface organic soils drives the high magnitude CH4 fluxes observed from subtropical pastures. These results suggest that relatively small changes in pasture water table dynamics can drive large changes in net CH4 emissions if surface organic soils remain saturated over longer time scales.

Multimodel Surface Temperature Responses to Removal of U.S. Sulfur Dioxide Emissions

NASA Astrophysics Data System (ADS)

Conley, A. J.; Westervelt, D. M.; Lamarque, J.-F.; Fiore, A. M.; Shindell, D.; Correa, G.; Faluvegi, G.; Horowitz, L. W.

2018-03-01

Three Earth System models are used to derive surface temperature responses to removal of U.S. anthropogenic SO2 emissions. Using multicentury perturbation runs with and without U.S. anthropogenic SO2 emissions, the local and remote surface temperature changes are estimated. In spite of a temperature drift in the control and large internal variability, 200 year simulations yield statistically significant regional surface temperature responses to the removal of U.S. SO2 emissions. Both local and remote surface temperature changes occur in all models, and the patterns of changes are similar between models for northern hemisphere land regions. We find a global average temperature sensitivity to U.S. SO2 emissions of 0.0055 K per Tg(SO2) per year with a range of (0.0036, 0.0078). We examine global and regional responses in SO4 burdens, aerosol optical depths (AODs), and effective radiative forcing (ERF). While changes in AOD and ERF are concentrated near the source region (United States), the temperature response is spread over the northern hemisphere with amplification of the temperature increase toward the Arctic. In all models, we find a significant response of dust concentrations, which affects the AOD but has no obvious effect on surface temperature. Temperature sensitivity to the ERF of U.S. SO2 emissions is found to differ from the models' sensitivity to radiative forcing of doubled CO2.

Characterizing the effects of regolith surface roughness on photoemission from surfaces in space

NASA Astrophysics Data System (ADS)

Dove, A.; Horanyi, M.; Wang, X.

2017-12-01

Surfaces of airless bodies and spacecraft in space are exposed to a variety of charging environments. A balance of currents due to plasma bombardment, photoemission, electron and ion emission and collection, and secondary electron emission determines the surface's charge. Photoelectron emission is the dominant charging process on sunlit surfaces in the inner solar system due to the intense solar UV radiation. This can result in a net positive surface potential, with a cloud of photoelectrons immediately above the surface, called the photoelectron sheath. Conversely, the unlit side of the body will charge negatively due the collection of the fast-moving solar wind electrons. The interaction of charged dust grains with these positively and negatively charged surfaces, and within the photoelectron and plasma sheaths may explain the occurrence of dust lofting, levitation and transport above the lunar surface. The surface potential of exposed objects is also dependent on the material properties of their surfaces. Composition and particle size primarily affect the quantum efficiency of photoelectron generation; however, surface roughness can also control the charging process. In order to characterize these effects, we have conducted laboratory experiments to examine the role of surface roughness in generating photoelectrons in dedicated laboratory experiments using solid and dusty surfaces of the same composition (CeO2), and initial comparisons with JSC-1 lunar simulant. Using Langmuir probe measurements, we explore the measured potentials above insulating surfaces exposed to UV and an electric field, and we show that the photoemission current from a dusty surface is largely reduced due to its higher surface roughness, which causes a significant fraction of the emitted photoelectrons to be re-absorbed within the surface. We will discuss these results in context of similar situations on planetary surfaces.

How increasing CO2 leads to an increased negative greenhouse effect in Antarctica

NASA Astrophysics Data System (ADS)

Schmithüsen, Holger; Notholt, Justus; König-Langlo, Gert; Lemke, Peter; Jung, Thomas

2015-12-01

CO2 is the strongest anthropogenic forcing agent for climate change since preindustrial times. Like other greenhouse gases, CO2 absorbs terrestrial surface radiation and causes emission from the atmosphere to space. As the surface is generally warmer than the atmosphere, the total long-wave emission to space is commonly less than the surface emission. However, this does not hold true for the high elevated areas of central Antarctica. For this region, the emission to space is higher than the surface emission; and the greenhouse effect of CO2 is around zero or even negative, which has not been discussed so far. We investigated this in detail and show that for central Antarctica an increase in CO2 concentration leads to an increased long-wave energy loss to space, which cools the Earth-atmosphere system. These findings for central Antarctica are in contrast to the general warming effect of increasing CO2.

A comparison between active and passive sensing of soil moisture from vegetated terrains

NASA Technical Reports Server (NTRS)

Fung, A. K.; Eom, H. J.

1985-01-01

A comparison between active and passive sensing of soil moisture over vegetated areas is studied via scattering models. In active sensing three contributing terms to radar backscattering can be identified: (1) the ground surface scatter term; (2) the volume scatter term representing scattering from the vegetation layer; and (3) the surface volume scatter term accounting for scattering from both surface and volume. In emission three sources of contribution can also be identified: (1) surface emission; (2) upward volume emission from the vegetation layer; and (3) downward volume emission scattered upward by the ground surface. As ground moisture increases, terms (1) and (3) increase due to increase in permittivity in the active case. However, in passive sensing, term (1) decreases but term (3) increases for the same reason. This self compensating effect produces a loss in sensitivity to change in ground moisture. Furthermore, emission from vegetation may be larger than that from the ground. Hence, the presence of vegetation layer causes a much greater loss of sensitivity to passive than active sensing of soil moisture.

A comparison between active and passive sensing of soil moisture from vegetated terrains

NASA Technical Reports Server (NTRS)

Fung, A. K.; Eom, H. J.

1984-01-01

A comparison between active and passive sensing of soil moisture over vegetated areas is studied via scattering models. In active sensing three contributing terms to radar backscattering can be identified: (1) the ground surface scatter term; (2) the volume scatter term representing scattering from the vegetation layer; and (3) the surface volume scatter term accounting for scattering from both surface and volume. In emission three sources of contribution can also be identified: (1) surface emission; (2) upward volume emission from the vegetation layer; and (3) downward volume emission scattered upward by the ground surface. As ground moisture increases, terms (1) and (3) increase due to increase in permittivity in the active case. However, in passive sensing, term (1) decreases but term (3) increases for the same reason. This self conpensating effect produces a loss in sensitivity to change in ground moisture. Furthermore, emission from vegetation may be larger than that from the ground. Hence, the presence of vegetation layer causes a much greater loss of sensitivity to passive than active sensing of soil moisture.

Why do Models Overestimate Surface Ozone in the Southeastern United States?

NASA Astrophysics Data System (ADS)

Travis, K.; Jacob, D.; Fisher, J. A.; Kim, S.; Marais, E. A.; Zhu, L.; Yu, K.; Miller, C. E.; Yantosca, R.; Payer Sulprizio, M.; Thompson, A. M.; Wennberg, P. O.; Crounse, J.; St Clair, J. M.; Cohen, R. C.; Laughner, J.; Dibb, J. E.; Hall, S. R.; Ullmann, K.; Wolfe, G.; Pollack, I. B.; Peischl, J.; Neuman, J. A.; Zhou, X.

2016-12-01

Ozone pollution in the Southeast US involves complex chemistry driven by emissions of anthropogenic nitrogen oxide radicals (NOx = NO + NO2) and biogenic isoprene. Model estimates of surface ozone concentrations tend to be biased high in the region and this is of concern for designing effective emission control strategies to meet air quality standards. We use detailed chemical observations from the SEAC4RS aircraft campaign in August and September 2013, interpreted with the GEOS-Chem chemical transport model at 0.25°×0.3125° horizontal resolution, to better understand the factors controlling surface ozone in the Southeast US. We find that the National Emission Inventory (NEI) for NO­x from the US Environmental Protection Agency (EPA) is too high in the Southeast and nationally by a factor of 2. This finding is based on SEAC4RS observations of NOx and its oxidation products, surface network observations of nitrate wet deposition fluxes, and OMI satellite observations of tropospheric NO2 columns. Upper tropospheric NO2 from lightning makes a large contribution to the satellite observations that must be accounted for when using these data to estimate surface NOx emissions. We find that only half of isoprene oxidation proceeds by the high-NOx pathway to produce ozone; this fraction is only moderately sensitive to changes in NOx emissions because isoprene and NOx emissions are spatially segregated. GEOS-Chem with reduced NOx emissions provides an unbiased simulation of ozone observations from the aircraft, and reproduces the observed ozone production efficiency in the boundary layer as derived from a regression of ozone and NOx oxidation products. However, the model is still biased high by 8±13 ppb relative to observed surface ozone in the Southeast US. Ozonesondes launched during midday hours show a 7 ppb ozone decrease from 1.5 km to the surface that GEOS-Chem does not capture. This may be caused by excessively dry conditions in the model, representing another factor important in the simulation of surface ozone.

Attribution of Trends and Variability in Surface Ozone over the United States

NASA Technical Reports Server (NTRS)

Strode, Sarah; Cooper, Owen; Damo, Megan; Logan, Jennifer; Rodriquez, Jose; Strahan, Susan; Witte, Jacquie

2013-01-01

Concentrations of tropospheric ozone, a greenhouse gas and air pollutant, are impacted by changes in precursor emissions as well meteorology and influx from the stratosphere. Observations show a decreasing trend in summertime surface ozone at rural stations in the eastern United States, while some western stations show increasing trends, particularly in springtime. We use the Global Modeling Initiative (GMI) global chemical transport model to investigate the roles of precursor emission changes, meteorological variability, and stratosphere-troposphere exchange (STE) in explaining observed trends in surface ozone from rural sites in the United States from 1991-2010. The model's interannual variability shows significant correlations with observations from many of the surface sites. We also compare the simulated ozone to ozonesonde data for several locations with sufficiently long records. We compare a simulation with time-dependent precursor emissions, including emission reductions over the United States and Europe and increases over Asia, to a simulation with fixed emissions to quantify the impact of changing emissions on the surface trends. The simulation with varying emissions reproduces much of the east-west difference in summertime ozone over the U.S., although it generally underestimates the negative trend in the East. In contrast, the fixed-emission simulation shows increasing ozone at both eastern and western sites. We will discuss possible causes of this behavior, including long-range transport and STE.

Apparatus and method for transient thermal infrared emission spectrometry

DOEpatents

McClelland, John F.; Jones, Roger W.

1991-12-24

A method and apparatus for enabling analysis of a solid material (16, 42) by applying energy from an energy source (20, 70) top a surface region of the solid material sufficient to cause transient heating in a thin surface layer portion of the solid material (16, 42) so as to enable transient thermal emission of infrared radiation from the thin surface layer portion, and by detecting with a spectrometer/detector (28, 58) substantially only the transient thermal emission of infrared radiation from the thin surface layer portion of the solid material. The detected transient thermal emission of infrared radiation is sufficiently free of self-absorption by the solid material of emitted infrared radiation, so as to be indicative of characteristics relating to molecular composition of the solid material.

Analysis of acoustic emission during abrasive waterjet machining of sheet metals

NASA Astrophysics Data System (ADS)

Mokhtar, Nazrin; Gebremariam, MA; Zohari, H.; Azhari, Azmir

2018-04-01

The present paper reports on the analysis of acoustic emission (AE) produced during abrasive waterjet (AWJ) machining process. This paper focuses on the relationship of AE and surface quality of sheet metals. The changes in acoustic emission signals recorded by the mean of power spectral density (PSD) via covariance method in relation to the surface quality of the cut are discussed. The test was made using two materials for comparison namely aluminium 6061 and stainless steel 304 with five different feed rates. The acoustic emission data were captured by Labview and later processed using MATLAB software. The results show that the AE spectrums correlated with different feed rates and surface qualities. It can be concluded that the AE is capable of monitoring the changes of feed rate and surface quality.

Method for surface plasmon amplification by stimulated emission of radiation (SPASER)

DOEpatents

Stockman, Mark I [Atlanta, GA; Bergman, David J [Ramat Hasharon, IL

2011-09-13

A nanostructure is used to generate a highly localized nanoscale optical field. The field is excited using surface plasmon amplification by stimulated emission of radiation (SPASER). The SPASER radiation consists of surface plasmons that undergo stimulated emission, but in contrast to photons can be localized within a nanoscale region. A SPASER can incorporate an active medium formed by two-level emitters, excited by an energy source, such as an optical, electrical, or chemical energy source. The active medium may be quantum dots, which transfer excitation energy by radiationless transitions to a resonant nanosystem that can play the same role as a laser cavity in a conventional laser. The transitions are stimulated by the surface plasmons in the nanostructure, causing the buildup of a macroscopic number of surface plasmons in a single mode.

Surface plasmon amplification by stimulated emission of radiation (SPASER)

DOEpatents

Stockman, Mark I [Atlanta, GA; Bergman, David J [Ramat Hasharon, IL

2009-08-04

A nanostructure is used to generate a highly localized nanoscale optical field. The field is excited using surface plasmon amplification by stimulated emission of radiation (SPASER). The SPASER radiation consists of surface plasmons that undergo stimulated emission, but in contrast to photons can be localized within a nanoscale region. A SPASER can incorporate an active medium formed by two-level emitters, excited by an energy source, such as an optical, electrical, or chemical energy source. The active medium may be quantum dots, which transfer excitation energy by radiationless transitions to a resonant nanosystem that can play the same role as a laser cavity in a conventional laser. The transitions are stimulated by the surface plasmons in the nanostructure, causing the buildup of a macroscopic number of surface plasmons in a single mode.

Study on temperature measurement of gas turbine blade based on analysis of error caused by the reflected radiation and emission angle

NASA Astrophysics Data System (ADS)

Li, Dong; Feng, Chi; Gao, Shan; Chen, Liwei; Daniel, Ketui

2018-06-01

Accurate measurement of gas turbine blade temperature is of great significance as far as blade health monitoring is concerned. An important method for measuring this temperature is the use of a radiation pyrometer. In this research, error of the pyrometer caused by reflected radiation from the surfaces surrounding the target and the emission angle of the target was analyzed. Important parameters for this analysis were the view factor between interacting surfaces, spectral directional emissivity, pyrometer operating wavelength and the surface temperature distribution on the blades and the vanes. The interacting surface of the rotor blade and the vane models used were discretized using triangular surface elements from which contour integral was used to calculate the view factor between the surface elements. Spectral directional emissivities were obtained from an experimental setup of Ni based alloy samples. A pyrometer operating wavelength of 1.6 μm was chosen. Computational fluid dynamics software was used to simulate the temperature distribution of the rotor blade and the guide vane based on the actual gas turbine input parameters. Results obtained in this analysis show that temperature error introduced by reflected radiation and emission angle ranges from  ‑23 K to 49 K.

Multi-wavelength emissivity measurement of stainless steel substrate

NASA Astrophysics Data System (ADS)

Zhang, Y. F. F.; Dai, J. M. M.; Zhang, L.; Pan, W. D. D.

2013-01-01

The emissivity is a key parameter to measure the surface temperature of materials in the radiation thermometry. In this paper, the surface emissivity of metallic substrates is measured by the multi-wavelength emissivity measurement apparatus developed by the Harbin Institute of Technology (HIT). The measuring principle of this apparatus is based on the energy comparison. Several radiation thermometers, whose emissivity coefficients corrected by the measured emissivity from this apparatus, are used to measure the surface temperature of stainless steel substrates. The temperature values measured by means of radiation thermometry are compared to those measured by means of contact thermometry. The relative error between the two means is less than 2% at temperatures from 700K to 1300K, it suggests that the emissivity of stainless steel substrate measured by the multi-wavelength emissivity measurement apparatus are accurate and reliable. Emissivity measurements performed with this apparatus present an uncertainty of 5.9% (cover factor=2).

Sideways Views of the Moon: Mapping Directional Thermal Emission with Diviner

NASA Astrophysics Data System (ADS)

Greenhagen, B. T.; Bandfield, J.; Bowles, N. E.; Hayne, P. O.; Sefton-Nash, E.; Warren, T.; Paige, D. A.

2017-12-01

Systematic off-nadir observations can be used to characterize the emission phase function and radiative balance of the lunar surface. These are critical inputs for thermophysical models used to derive surface properties and study a wide range of dynamic surface properties, such as the stability of volatiles and development and evolution of regolith, on the Moon and other airless bodies. After over eight years in operation and well into its 3rd extended science mission, NASA's Lunar Reconnaissance Orbiter (LRO) Diviner Lunar Radiometer (Diviner) continues to reveal the extreme nature of the Moon's thermal environments, thermophysical properties, and surface composition. Diviner data are also used to characterize thermal emission behavior that is fundamental to airless bodies with fine-particulate surfaces, including epiregolith thermal gradients and thermal-scale surface roughness. Diviner's extended operations have provided opportunities to observe the lunar surface with a wide range of viewing geometries. Together Diviner's self-articulation and LRO's non-sun-synchronous polar orbit offer a unique platform to observe the lunar surface and characterize the emission phase behavior and radiative balance. Recently, Diviner completed global off-nadir observations at 50° and 70° in the anti-sun (low phase) direction with 8 different local times each. This fall, we'll begin a third campaign to observe the Moon at 50° emission in the pro-sun (high phase) direction. Here we present this new global off-nadir dataset, highlight models and laboratory experiments used to interpret the data, and describe the role of these data in studying the Moon and other airless bodies.

VIRTIS on Venus Express: retrieval of real surface emissivity on global scales

NASA Astrophysics Data System (ADS)

Arnold, Gabriele E.; Kappel, David; Haus, Rainer; Telléz Pedroza, Laura; Piccioni, Giuseppe; Drossart, Pierre

2015-09-01

The extraction of surface emissivity data provides the data base for surface composition analyses and enables to evaluate Venus' geology. The Visible and InfraRed Thermal Imaging Spectrometer (VIRTIS) aboard ESA's Venus Express mission measured, inter alia, the nightside thermal emission of Venus in the near infrared atmospheric windows between 1.0 and 1.2 μm. These data can be used to determine information about surface properties on global scales. This requires a sophisticated approach to understand and consider the effects and interferences of different atmospheric and surface parameters influencing the retrieved values. In the present work, results of a new technique for retrieval of the 1.0 - 1.2 μm - surface emissivity are summarized. It includes a Multi-Window Retrieval Technique, a Multi-Spectrum Retrieval technique (MSR), and a detailed reliability analysis. The MWT bases on a detailed radiative transfer model making simultaneous use of information from different atmospheric windows of an individual spectrum. MSR regularizes the retrieval by incorporating available a priori mean values, standard deviations as well as spatial-temporal correlations of parameters to be retrieved. The capability of this method is shown for a selected surface target area. Implications for geologic investigations are discussed. Based on these results, the work draws conclusions for future Venus surface composition analyses on global scales using spectral remote sensing techniques. In that context, requirements for observational scenarios and instrumental performances are investigated, and recommendations are derived to optimize spectral measurements for Venus' surface studies.

Programmable thermal emissivity structures based on bioinspired self-shape materials

NASA Astrophysics Data System (ADS)

Athanasopoulos, N.; Siakavellas, N. J.

2015-12-01

Programmable thermal emissivity structures based on the bioinspired self-shape anisotropic materials were developed at macro-scale, and further studied theoretically at smaller scale. We study a novel concept, incorporating materials that are capable of transforming their shape via microstructural rearrangements under temperature stimuli, while avoiding the use of exotic shape memory materials or complex micro-mechanisms. Thus, programmed thermal emissivity behaviour of a surface is achievable. The self-shape structure reacts according to the temperature of the surrounding environment or the radiative heat flux. A surface which incorporates self-shape structures can be designed to quickly absorb radiative heat energy at low temperature levels, but is simultaneously capable of passively controlling its maximum temperature in order to prevent overheating. It resembles a “game” of colours, where two or more materials coexist with different values of thermal emissivity/ absorptivity/ reflectivity. The transformation of the structure conceals or reveals one of the materials, creating a surface with programmable - and therefore, variable- effective thermal emissivity. Variable thermal emissivity surfaces may be developed with a total hemispherical emissivity ratio (ɛEff_H/ɛEff_L) equal to 28.

Programmable thermal emissivity structures based on bioinspired self-shape materials

PubMed Central

Athanasopoulos, N.; Siakavellas, N. J.

2015-01-01

Programmable thermal emissivity structures based on the bioinspired self-shape anisotropic materials were developed at macro-scale, and further studied theoretically at smaller scale. We study a novel concept, incorporating materials that are capable of transforming their shape via microstructural rearrangements under temperature stimuli, while avoiding the use of exotic shape memory materials or complex micro-mechanisms. Thus, programmed thermal emissivity behaviour of a surface is achievable. The self-shape structure reacts according to the temperature of the surrounding environment or the radiative heat flux. A surface which incorporates self-shape structures can be designed to quickly absorb radiative heat energy at low temperature levels, but is simultaneously capable of passively controlling its maximum temperature in order to prevent overheating. It resembles a “game” of colours, where two or more materials coexist with different values of thermal emissivity/ absorptivity/ reflectivity. The transformation of the structure conceals or reveals one of the materials, creating a surface with programmable – and therefore, variable- effective thermal emissivity. Variable thermal emissivity surfaces may be developed with a total hemispherical emissivity ratio (εEff_H/εEff_L) equal to 28. PMID:26635316

Local surface plasmon enhanced polarization and internal quantum efficiency of deep ultraviolet emissions from AlGaN-based quantum wells.

PubMed

Zhang, Cai; Tang, Ning; Shang, Liangliang; Fu, Lei; Wang, Weiying; Xu, Fujun; Wang, Xinqiang; Ge, Weikun; Shen, Bo

2017-05-24

We report the enhancement of the polarization and internal quantum efficiency (IQE) of deep-UV LEDs by evaporating Al nanoparticles on the device surface to induce localized surface plasmons (LSPs). The deep-UV LEDs polarization is improved due to part of TM emission turns into TE emission through LSPs coupling. The significantly enhanced IQE is attributed to LSPs coupling, which suppress the participation of delocalized and dissociated excitons to non-radiative recombination process.

Impact of High Resolution Land-Use Data in Meteorology and Air Quality Modeling Systems

EPA Science Inventory

Accurate land use information is important in meteorology for land surface exchanges, in emission modeling for emission spatial allocation, and in air quality modeling for chemical surface fluxes. Currently, meteorology, emission, and air quality models often use outdated USGS Gl...

Volatile Organic Compound (VOC) emissions from feedlot pen surface materials as affected by within pen location, moisture, and temperature

USDA-ARS?s Scientific Manuscript database

A laboratory study was conducted to evaluate the effects of pen location, moisture, and temperature on emissions of volatile organic compounds (VOC) from surface materials obtained from feedlot pens where beef cattle were fed a diet containing 30% wet distillers grain plus solubles. Surface material...

40 CFR 63.5746 - How do I demonstrate compliance with the emission limits for aluminum wipedown solvents and...

Code of Federal Regulations, 2014 CFR

2014-07-01

...) to determine the density of each aluminum surface coating and wipedown solvent. (d) Compliance is... Surface Coating Operations § 63.5746 How do I demonstrate compliance with the emission limits for aluminum... (liters of solids per liter of coating, or volume fraction) of each aluminum surface coating, including...

40 CFR 63.5746 - How do I demonstrate compliance with the emission limits for aluminum wipedown solvents and...

Code of Federal Regulations, 2013 CFR

2013-07-01

...) to determine the density of each aluminum surface coating and wipedown solvent. (d) Compliance is... Surface Coating Operations § 63.5746 How do I demonstrate compliance with the emission limits for aluminum... (liters of solids per liter of coating, or volume fraction) of each aluminum surface coating, including...

Quantum theory of spontaneous and stimulated emission of surface plasmons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Archambault, Alexandre; Marquier, Francois; Greffet, Jean-Jacques

2010-07-15

We introduce a quantization scheme that can be applied to surface waves propagating along a plane interface. An important result is the derivation of the energy of the surface wave for dispersive nonlossy media without invoking any specific model for the dielectric constant. Working in Coulomb's gauge, we use a modal representation of the fields. Each mode can be associated with a quantum harmonic oscillator. We have applied the formalism to derive quantum mechanically the spontaneous emission rate of surface plasmon by a two-level system. The result is in very good agreement with Green's tensor approach in the nonlossy case.more » Green's approach allows also to account for losses, so that the limitations of a quantum approach of surface plasmons are clearly defined. Finally, the issue of stimulated versus spontaneous emission has been addressed. Because of the increasing density of states near the asymptote of the dispersion relation, it is quantitatively shown that the stimulated emission probability is too small to obtain gain in this frequency region.« less

Beam impingement angle effects on secondary electron emission characteristics of textured pyrolytic graphite

NASA Technical Reports Server (NTRS)

Curren, A. N.; Jensen, K. A.

1984-01-01

Experimentally determined values of true secondary electron emission and relative values of reflected primary electron yield for untreated and ion-textured pyrolytic graphite over a range of primary electron energy levels and electron beam impingement angles are presented. Information required to develop high efficiency multistage depressed collectors (MDC's) for microwave amplifier traveling-wave tubes for space communication and aircraft applications is provided. To attain the highest possible MDC efficiencies, the electrode surfaces must have low secondary electron emission characteristics. Pyrolytic graphite, a chemically vapor-deposited material, is a particularly promising candidate for this application. The pyrolytic graphite surfaces studied were tested over a range of primary electron beam energies and beam impingement angles from 200 to 2000 eV and direct (0 deg) to near-grazing angles (85 deg), respectively. Surfaces both parallel to and normal to the planes of material deposition were examined. The true secondary electron emission and reflected primary electron yield characteristics of the pyrolytic graphite surfaces are compared to those of sooted control surfaces.

Field emission study of carbon nanostructures

NASA Astrophysics Data System (ADS)

Zhao, Xin

Recently, carbon nanosheets (CNS), a novel nanostructure, were developed in our laboratory as a field emission source for high emission current. To characterize, understand and improve the field emission properties of CNS, a ultra-high vacuum surface analysis system was customized to conduct relevant experimental research in four distinct areas. The system includes Auger electron spectroscopy (AES), field emission energy spectroscopy (FEES), field emission I-V testing, and thermal desorption spectroscopy (TDS). Firstly, commercial Mo single tips were studied to calibrate the customized system. AES and FEES experiments indicate that a pyramidal nanotip of Ca and O elements formed on the Mo tip surface by field induced surface diffusion. Secondly, field emission I-V testing on CNS indicates that the field emission properties of pristine nanosheets are impacted by adsorbates. For instance, in pristine samples, field emission sources can be built up instantaneously and be characterized by prominent noise levels and significant current variations. However, when CNS are processed via conditioning (run at high current), their emission properties are greatly improved and stabilized. Furthermore, only H2 desorbed from the conditioned CNS, which indicates that only H adsorbates affect emission. Thirdly, the TDS study on nanosheets revealed that the predominant locations of H residing in CNS are sp2 hybridized C on surface and bulk. Fourthly, a fabricating process was developed to coat low work function ZrC on nanosheets for field emission enhancement. The carbide triple-peak in the AES spectra indicated that Zr carbide formed, but oxygen was not completely removed. The Zr(CxOy) coating was dispersed as nanobeads on the CNS surface. Although the work function was reduced, the coated CNS emission properties were not improved due to an increased beta factor. Further analysis suggest that for low emission current (<1 uA), the H adsorbates affect emission by altering the work function. In high emission current (>10 uA), thermal, ionic or electronic transition effects may occur, which differently affect the field emission process.

Responses of surface ozone air quality to anthropogenic nitrogen deposition in the Northern Hemisphere

NASA Astrophysics Data System (ADS)

Zhao, Yuanhong; Zhang, Lin; Tai, Amos P. K.; Chen, Youfan; Pan, Yuepeng

2017-08-01

Human activities have substantially increased atmospheric deposition of reactive nitrogen to the Earth's surface, inducing unintentional effects on ecosystems with complex environmental and climate consequences. One consequence remaining unexplored is how surface air quality might respond to the enhanced nitrogen deposition through surface-atmosphere exchange. Here we combine a chemical transport model (GEOS-Chem) and a global land model (Community Land Model, CLM) to address this issue with a focus on ozone pollution in the Northern Hemisphere. We consider three processes that are important for surface ozone and can be perturbed by the addition of atmospheric deposited nitrogen - namely, emissions of biogenic volatile organic compounds (VOCs), ozone dry deposition, and soil nitrogen oxide (NOx) emissions. We find that present-day anthropogenic nitrogen deposition (65 Tg N a-1 to the land), through enhancing plant growth (represented as increases in vegetation leaf area index, LAI, in the model), could increase surface ozone from increased biogenic VOC emissions (e.g., a 6.6 Tg increase in isoprene emission), but it could also decrease ozone due to higher ozone dry deposition velocities (up to 0.02-0.04 cm s-1 increases). Meanwhile, deposited anthropogenic nitrogen to soil enhances soil NOx emissions. The overall effect on summer mean surface ozone concentrations shows general increases over the globe (up to 1.5-2.3 ppbv over the western US and South Asia), except for some regions with high anthropogenic NOx emissions (0.5-1.0 ppbv decreases over the eastern US, western Europe, and North China). We compare the surface ozone changes with those driven by the past 20-year climate and historical land use changes. We find that the impacts from anthropogenic nitrogen deposition can be comparable to the climate- and land-use-driven surface ozone changes at regional scales and partly offset the surface ozone reductions due to land use changes reported in previous studies. Our study emphasizes the complexity of biosphere-atmosphere interactions, which can have important implications for future air quality prediction.

Incorporating realistic surface longwave spectral emissivity in the CESM and the impact on simulated current climate and climate changes

NASA Astrophysics Data System (ADS)

Chen, X.; Huang, X.; Flanner, M.; Yang, P.; Feldman, D.; Kuo, C.

2016-12-01

As of today, most state-of-the-art GCMs still assumes blackbody surface in their longwave radiation scheme. Recent works by Chen et al. (2014) and Feldman et al. (2014) have suggested that the surface spectral emissivity can impact the simulated radiation budget and climate change in a discernible way, especially in high latitudes. Using a recently developed global emissivity database that covers both far-IR and mid-IR, we incorporated the LW surface spectral emissivity into the radiation scheme of the CESM. Effort has been made to ensure a consistent treatment of surface upward LW broadband flux in both the land module and the atmospheric module of the CESM, an important aspect overlooked by the previous study. Then we assess impacts of the inclusion of surface spectral emissivity on simulated mean-state climate and climate changes by carrying out two sets of parallel runs. The first pair of experiments uses the standard slab-ocean CESM v1.1.1 to run two experiments: one control run using forcings at year 2000 level and one sensitivity run abruptly doubling the CO2. The second pair of experiment setup is identical to the first one but using the CESM that we have modified (Surface emissivity is a prognostic variable in our second pair of experiments). The current climate simulation results show that the Sahara desert region in the modified CESM has a warmer surface temperature than in the standard CESM by 2-3K. Over the high-latitude regions, the modified CESM tends to have a colder surface temperature than the standard CESM by 1-2.5K. As a result, the climatological sea ice coverage in the modified CESM is 8% more than it in the standard CESM in both Polar Regions. All these differences are statistically significant. As for simulated climate change in response to a doubling of CO2, the Arctic region in the modified CESM warms consistently faster than in the standard CESM by 1-2K while the Antarctic region shows a non-uniform pattern of differences between two models. Differences in the changes of sea ice coverage between two models show a zonally-uniform dipole pattern over both polar oceans. The reasons for such differences and its linkage with the change of surface spectral emissivity are further explained.

A Prototype Physical Database for Passive Microwave Retrievals of Precipitation over the US Southern Great Plains

NASA Technical Reports Server (NTRS)

Ringerud, S.; Kummerow, C. D.; Peters-Lidard, C. D.

2015-01-01

An accurate understanding of the instantaneous, dynamic land surface emissivity is necessary for a physically based, multi-channel passive microwave precipitation retrieval scheme over land. In an effort to assess the feasibility of the physical approach for land surfaces, a semi-empirical emissivity model is applied for calculation of the surface component in a test area of the US Southern Great Plains. A physical emissivity model, using land surface model data as input, is used to calculate emissivity at the 10GHz frequency, combining contributions from the underlying soil and vegetation layers, including the dielectric and roughness effects of each medium. An empirical technique is then applied, based upon a robust set of observed channel covariances, extending the emissivity calculations to all channels. For calculation of the hydrometeor contribution, reflectivity profiles from the Tropical Rainfall Measurement Mission Precipitation Radar (TRMM PR) are utilized along with coincident brightness temperatures (Tbs) from the TRMM Microwave Imager (TMI), and cloud-resolving model profiles. Ice profiles are modified to be consistent with the higher frequency microwave Tbs. Resulting modeled top of the atmosphere Tbs show correlations to observations of 0.9, biases of 1K or less, root-mean-square errors on the order of 5K, and improved agreement over the use of climatological emissivity values. The synthesis of these models and data sets leads to the creation of a simple prototype Tb database that includes both dynamic surface and atmospheric information physically consistent with the land surface model, emissivity model, and atmospheric information.

Responses of Surface Ozone Air Quality to Anthropogenic Nitrogen Deposition

NASA Astrophysics Data System (ADS)

Zhang, L.; Zhao, Y.; Tai, A. P. K.; Chen, Y.; Pan, Y.

2017-12-01

Human activities have substantially increased atmospheric deposition of reactive nitrogen to the Earth's surface, inducing unintentional effects on ecosystems with complex environmental and climate consequences. One consequence remaining unexplored is how surface air quality might respond to the enhanced nitrogen deposition through surface-atmosphere exchange. We combine a chemical transport model (GEOS-Chem) and a global land model (Community Land Model) to address this issue with a focus on ozone pollution in the Northern Hemisphere. We consider three processes that are important for surface ozone and can be perturbed by addition of atmospheric deposited nitrogen: emissions of biogenic volatile organic compounds (VOCs), ozone dry deposition, and soil nitrogen oxide (NOx) emissions. We find that present-day anthropogenic nitrogen deposition (65 Tg N a-1 to the land), through enhancing plant growth (represented as increases in vegetation leaf area index (LAI) in the model), could increase surface ozone from increased biogenic VOC emissions, but could also decrease ozone due to higher ozone dry deposition velocities. Meanwhile, deposited anthropogenic nitrogen to soil enhances soil NOx emissions. The overall effect on summer mean surface ozone concentrations show general increases over the globe (up to 1.5-2.3 ppbv over the western US and South Asia), except for some regions with high anthropogenic NOx emissions (0.5-1.0 ppbv decreases over the eastern US, Western Europe, and North China). We compare the surface ozone changes with those driven by the past 20-year climate and historical land use changes. We find that the impacts from anthropogenic nitrogen deposition can be comparable to the climate and land use driven surface ozone changes at regional scales, and partly offset the surface ozone reductions due to land use changes reported in previous studies. Our study emphasizes the complexity of biosphere-atmosphere interactions, which can have important implications for future air quality prediction.

Compact blackbody calibration sources for in-flight calibration of spaceborne infrared instruments

NASA Astrophysics Data System (ADS)

Scheiding, S.; Driescher, H.; Walter, I.; Hanbuch, K.; Paul, M.; Hartmann, M.; Scheiding, M.

2017-11-01

High-emissivity blackbodies are mandatory as calibration sources in infrared radiometers. Besides the requirements on the high spectral emissivity and low reflectance, constraints regarding energy consumption, installation space and mass must be considered during instrument design. Cavity radiators provide an outstanding spectral emissivity to the price of installation space and mass of the calibration source. Surface radiation sources are mainly limited by the spectral emissivity of the functional coating and the homogeneity of the temperature distribution. The effective emissivity of a "black" surface can be optimized, by structuring the substrate with the aim to enlarge the ratio of the surface to its projection. Based on the experiences of the Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS) calibration source MBB3, the results of the surface structuring on the effective emissivity are described analytically and compared to the experimental performance. Different geometries are analyzed and the production methods are discussed. The high-emissivity temperature calibration source features values of 0.99 for wavelength from 5 μm to 10 μm and emissivity larger than 0.95 for the spectral range from 10 μm to 40 μm.

Radio emission of sea surface at centimeter wavelengths and is fluctuations

NASA Technical Reports Server (NTRS)

Tseytlin, N. M.; Shutko, A. M.; Zhislin, G. M.

1981-01-01

The eigen thermal radio emission of the sea was examined as well as the agitated surface of the sea when the reflection (scattering) is similar in nature to diffused scattering. The contribution of this emission to the total emission of the sea is practically constant in time, and the time fluctuations of the radio emissions of the sea are basically determined only by a change in the eigen emission of the sea, connected with the agitation.

Fine Structure in the Secondary Electron Emission Peak for Diamond Crystal with (100) Negative Electron Affinity Surface

NASA Technical Reports Server (NTRS)

Asnin, V. M.; Krainsky, I. L.

1998-01-01

A fine structure was discovered in the low-energy peak of the secondary electron emission spectra of the diamond surface with negative electron affinity. We studied this structure for the (100) surface of the natural type-IIb diamond crystal. We have found that the low-energy peak consists of a total of four maxima. The relative energy positions of three of them could be related to the electron energy minima near the bottom of the conduction band. The fourth peak, having the lowest energy, was attributed to the breakup of the bulk exciton at the surface during the process of secondary electron emission.

Vertical Profiles as Observational Constraints on Nitrous Oxide (N2O) Emissions in an Agricultural Region

NASA Astrophysics Data System (ADS)

Pusede, S.; Diskin, G. S.

2015-12-01

We use diurnal variability in near-surface N2O vertical profiles to derive N2O emission rates. Our emissions estimates are ~3 times greater than are accounted for by inventories, a discrepancy in line with results from previous studies using different approaches. We quantify the surface N2O concentration's memory of local surface emissions on previous days to be 50-90%. We compare measured profiles both over and away from a dense N2O source region in the San Joaquin Valley, finding that profile shapes, diurnal variability, and changes in integrated near-surface column abundances are distinct according to proximity to source areas. To do this work, we use aircraft observations from the wintertime DISCOVER-AQ project in California's San Joaquin Valley, a region of intense agricultural activity.

Staircase and saw-tooth field emission steps from nanopatterned n-type GaSb surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kildemo, M.; Levinsen, Y. Inntjore; Le Roy, S.

2009-09-15

High resolution field emission experiments from nanopatterned GaSb surfaces consisting of densely packed nanocones prepared by low ion-beam-energy sputtering are presented. Both uncovered and metal-covered nanopatterned surfaces were studied. Surprisingly, the field emission takes place by regular steps in the field emitted current. Depending on the field, the steps are either regular, flat, plateaus, or saw-tooth shaped. To the author's knowledge, this is the first time that such results have been reported. Each discrete jump in the field emission may be understood in terms of resonant tunneling through an extended surface space charge region in an n-type, high aspect ratio,more » single GaSb nanocone. The staircase shape may be understood from the spatial distribution of the aspect ratio of the cones.« less

Pulsed ion beam investigation of the kinetics of surface reactions

NASA Technical Reports Server (NTRS)

Horton, C. C.; Eck, T. G.; Hoffman, R. W.

1989-01-01

Pulsed ion beam measurements of the kinetics of surface reactions are discussed for the case where the width of the ion pulse is comparable to the measured reaction time, but short compared to the time between successive pulses. Theoretical expressions are derived for the time dependence of the ion-induced signals for linear surface reactions. Results are presented for CO emission from surface carbon and CF emission from Teflon induced by oxygen ion bombardment. The strengths and limitations of this technique are described.

Space-Based Diagnosis of Surface Ozone Sensitivity to Anthropogenic Emissions

NASA Technical Reports Server (NTRS)

Martin, Randall V.; Fiore, Arlene M.; VanDonkelaar, Aaron

2004-01-01

We present a novel capability in satellite remote sensing with implications for air pollution control strategy. We show that the ratio of formaldehyde columns to tropospheric nitrogen dioxide columns is an indicator of the relative sensitivity of surface ozone to emissions of nitrogen oxides (NO(x) = NO + NO2) and volatile organic compounds (VOCs). The diagnosis from these space-based observations is highly consistent with current understanding of surface ozone chemistry based on in situ observations. The satellite-derived ratios indicate that surface ozone is more sensitive to emissions of NO(x) than of VOCs throughout most continental regions of the Northern Hemisphere during summer. Exceptions include Los Angeles and industrial areas of Germany. A seasonal transition occurs in the fall when surface ozone becomes less sensitive to NOx and more sensitive to VOCs.

Total hemispherical emissivity of very high temperature reactor (VHTR) candidate materials: Hastelloy X, Haynes 230, and Alloy 617

NASA Astrophysics Data System (ADS)

Maynard, Raymond K.

An experimental system was constructed in accordance with the standard ASTM C835-06 to measure the total hemispherical emissivity of structural materials of interest in Very High Temperature Reactor (VHTR) systems. The system was tested with304 stainless steel as well as for oxidized and un-oxidized nickel, and good reproducibility and agreement with the literature data was found. Emissivity of Hastelloy X was measured under different conditions that included: (i) "as received" (original sample) from the supplier; (ii) with increased surface roughness; (iii) oxidized, and; (iv) graphite coated. Measurements were made over a wide range of temperatures. Hastelloy X, as received from the supplier, was cleaned before additional roughening of the surface and coating with graphite. The emissivity of the original samples (cleaned after received) varied from around 0.18 to 0.28 in the temperature range of 473 K to 1498 K. The apparent emissivity increased only slightly as the roughness of the surface increased (without corrections for the increased surface area due to the increased surface roughness). When Hastelloy X was coated with graphite or oxidized however, its emissivity was observed to increase substantially. With a deposited graphite layer on the Hastelloy, emissivity increased from 0.2 to 0.53 at 473 K and from 0.25 to 0.6 at 1473 K; a finding that has strong favorable safety implications in terms of decay heat removal in post-accident VHTR environments. Although initial oxidation of Hastelloy X increased the emissivity prolonged oxidation did not significantly increase emissivity. However as there is some oxidation of Hastelloy X used in the construction of VHTRs, this represents an essentially neutral finding in terms of the safety implications in post-accident VHTR environments. The total hemispherical emissivity of Haynes 230 alloy, which is regarded as a leading candidate material for heat exchangers in VHTR systems, was measured under various surface conditions. The emissivity increased from 0.178 at 600 K to 0.235 at 1375 K for Haynes 230 as received sample. The emissivity increased significantly when its surface roughness was increased, or was oxidized in air, or coated with graphite dust, as compared to the as received material. The total hemispherical emissivity of Alloy 617 was measured as a function of temperature. The total emissivity increased from about 0.2 at 600 K to about 0.35 at 1275 K.

Effect of different emission inventories on modeled ozone and carbon monoxide in Southeast Asia

NASA Astrophysics Data System (ADS)

Amnuaylojaroen, T.; Barth, M. C.; Emmons, L. K.; Carmichael, G. R.; Kreasuwun, J.; Prasitwattanaseree, S.; Chantara, S.

2014-12-01

In order to improve our understanding of air quality in Southeast Asia, the anthropogenic emissions inventory must be well represented. In this work, we apply different anthropogenic emission inventories in the Weather Research and Forecasting Model with Chemistry (WRF-Chem) version 3.3 using Model for Ozone and Related Chemical Tracers (MOZART) gas-phase chemistry and Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) aerosols to examine the differences in predicted carbon monoxide (CO) and ozone (O3) surface mixing ratios for Southeast Asia in March and December 2008. The anthropogenic emission inventories include the Reanalysis of the TROpospheric chemical composition (RETRO), the Intercontinental Chemical Transport Experiment-Phase B (INTEX-B), the MACCity emissions (adapted from the Monitoring Atmospheric Composition and Climate and megacity Zoom for the Environment projects), the Southeast Asia Composition, Cloud, Climate Coupling Regional Study (SEAC4RS) emissions, and a combination of MACCity and SEAC4RS emissions. Biomass-burning emissions are from the Fire Inventory from the National Center for Atmospheric Research (NCAR) (FINNv1) model. WRF-Chem reasonably predicts the 2 m temperature, 10 m wind, and precipitation. In general, surface CO is underpredicted by WRF-Chem while surface O3 is overpredicted. The NO2 tropospheric column predicted by WRF-Chem has the same magnitude as observations, but tends to underpredict the NO2 column over the equatorial ocean and near Indonesia. Simulations using different anthropogenic emissions produce only a slight variability of O3 and CO mixing ratios, while biomass-burning emissions add more variability. The different anthropogenic emissions differ by up to 30% in CO emissions, but O3 and CO mixing ratios averaged over the land areas of the model domain differ by ~4.5% and ~8%, respectively, among the simulations. Biomass-burning emissions create a substantial increase for both O3 and CO by ~29% and ~16%, respectively, when comparing the March biomass-burning period to the December period with low biomass-burning emissions. The simulations show that none of the anthropogenic emission inventories are better than the others for predicting O3 surface mixing ratios. However, the simulations with different anthropogenic emission inventories do differ in their predictions of CO surface mixing ratios producing variations of ~30% for March and 10-20% for December at Thai surface monitoring sites.

Land Surface Temperature Measurements form EOS MODIS Data

NASA Technical Reports Server (NTRS)

Wan, Zhengming

1996-01-01

We have developed a physics-based land-surface temperature (LST) algorithm for simultaneously retrieving surface band-averaged emissivities and temperatures from day/night pairs of MODIS (Moderate Resolution Imaging Spectroradiometer) data in seven thermal infrared bands. The set of 14 nonlinear equations in the algorithm is solved with the statistical regression method and the least-squares fit method. This new LST algorithm was tested with simulated MODIS data for 80 sets of band-averaged emissivities calculated from published spectral data of terrestrial materials in wide ranges of atmospheric and surface temperature conditions. Comprehensive sensitivity and error analysis has been made to evaluate the performance of the new LST algorithm and its dependence on variations in surface emissivity and temperature, upon atmospheric conditions, as well as the noise-equivalent temperature difference (NE(Delta)T) and calibration accuracy specifications of the MODIS instrument. In cases with a systematic calibration error of 0.5%, the standard deviations of errors in retrieved surface daytime and nighttime temperatures fall between 0.4-0.5 K over a wide range of surface temperatures for mid-latitude summer conditions. The standard deviations of errors in retrieved emissivities in bands 31 and 32 (in the 10-12.5 micrometer IR spectral window region) are 0.009, and the maximum error in retrieved LST values falls between 2-3 K. Several issues related to the day/night LST algorithm (uncertainties in the day/night registration and in surface emissivity changes caused by dew occurrence, and the cloud cover) have been investigated. The LST algorithms have been validated with MODIS Airborne Simulator (MAS) dada and ground-based measurement data in two field campaigns conducted in Railroad Valley playa, NV in 1995 and 1996. The MODIS LST version 1 software has been delivered.

Life cycle Greenhouse gas emissions of current Oil Sands Technologies: surface mining and in situ applications.

PubMed

Bergerson, Joule A; Kofoworola, Oyeshola; Charpentier, Alex D; Sleep, Sylvia; Maclean, Heather L

2012-07-17

Life cycle greenhouse gas (GHG) emissions associated with two major recovery and extraction processes currently utilized in Alberta's oil sands, surface mining and in situ, are quantified. Process modules are developed and integrated into a life cycle model-GHOST (GreenHouse gas emissions of current Oil Sands Technologies) developed in prior work. Recovery and extraction of bitumen through surface mining and in situ processes result in 3-9 and 9-16 g CO(2)eq/MJ bitumen, respectively; upgrading emissions are an additional 6-17 g CO(2)eq/MJ synthetic crude oil (SCO) (all results are on a HHV basis). Although a high degree of variability exists in well-to-wheel emissions due to differences in technologies employed, operating conditions, and product characteristics, the surface mining dilbit and the in situ SCO pathways have the lowest and highest emissions, 88 and 120 g CO(2)eq/MJ reformulated gasoline. Through the use of improved data obtained from operating oil sands projects, we present ranges of emissions that overlap with emissions in literature for conventional crude oil. An increased focus is recommended in policy discussions on understanding interproject variability of emissions of both oil sands and conventional crudes, as this has not been adequately represented in previous studies.

Why do Models Overestimate Surface Ozone in the Southeastern United States?

NASA Technical Reports Server (NTRS)

Travis, Katherine R.; Jacob, Daniel J.; Fisher, Jenny A.; Kim, Patrick S.; Marais, Eloise A.; Zhu, Lei; Yu, Karen; Miller, Christopher C.; Yantosca, Robert M.; Sulprizio, Melissa P.;

Why do models overestimate surface ozone in the Southeast United States?

NASA Astrophysics Data System (ADS)

Travis, Katherine R.; Jacob, Daniel J.; Fisher, Jenny A.; Kim, Patrick S.; Marais, Eloise A.; Zhu, Lei; Yu, Karen; Miller, Christopher C.; Yantosca, Robert M.; Sulprizio, Melissa P.; Thompson, Anne M.; Wennberg, Paul O.; Crounse, John D.; St. Clair, Jason M.; Cohen, Ronald C.; Laughner, Joshua L.; Dibb, Jack E.; Hall, Samuel R.; Ullmann, Kirk; Wolfe, Glenn M.; Pollack, Illana B.; Peischl, Jeff; Neuman, Jonathan A.; Zhou, Xianliang

2016-11-01

Ozone pollution in the Southeast US involves complex chemistry driven by emissions of anthropogenic nitrogen oxide radicals (NOx ≡ NO + NO2) and biogenic isoprene. Model estimates of surface ozone concentrations tend to be biased high in the region and this is of concern for designing effective emission control strategies to meet air quality standards. We use detailed chemical observations from the SEAC4RS aircraft campaign in August and September 2013, interpreted with the GEOS-Chem chemical transport model at 0.25° × 0.3125° horizontal resolution, to better understand the factors controlling surface ozone in the Southeast US. We find that the National Emission Inventory (NEI) for NOx from the US Environmental Protection Agency (EPA) is too high. This finding is based on SEAC4RS observations of NOx and its oxidation products, surface network observations of nitrate wet deposition fluxes, and OMI satellite observations of tropospheric NO2 columns. Our results indicate that NEI NOx emissions from mobile and industrial sources must be reduced by 30-60 %, dependent on the assumption of the contribution by soil NOx emissions. Upper-tropospheric NO2 from lightning makes a large contribution to satellite observations of tropospheric NO2 that must be accounted for when using these data to estimate surface NOx emissions. We find that only half of isoprene oxidation proceeds by the high-NOx pathway to produce ozone; this fraction is only moderately sensitive to changes in NOx emissions because isoprene and NOx emissions are spatially segregated. GEOS-Chem with reduced NOx emissions provides an unbiased simulation of ozone observations from the aircraft and reproduces the observed ozone production efficiency in the boundary layer as derived from a regression of ozone and NOx oxidation products. However, the model is still biased high by 6 ± 14 ppb relative to observed surface ozone in the Southeast US. Ozonesondes launched during midday hours show a 7 ppb ozone decrease from 1.5 km to the surface that GEOS-Chem does not capture. This bias may reflect a combination of excessive vertical mixing and net ozone production in the model boundary layer.

Near Infrared Multispectral Mapping of Venus Supports the Hypothesis that Tessera Plateau Material was Formed in the Presence of Surface Water

NASA Astrophysics Data System (ADS)

Mueller, N. T.; Tsang, C.; Nunes, D. C.; Helbert, J.; Dyar, M. D.; Smrekar, S. E.

2017-12-01

The VIRTIS instrument on Venus Express observed surface thermal emission from the surface. Studies of 1020nm data showed that tessera plateaus, intensely tectonically deformed highlands that predate most other terrains, have significantly lower thermal emission than other highlands. Lower thermal emission could be due either to lower surface emissivity, supporting the hypothesis that tessera are analogous to continental crust on Earth, or to a bias of Magellan altimetry, which does not fully resolve the topographic relief of tessera terrain. To eliminate this ambiguity, we additionally investigate the spectral windows at 1100 and 1180nm. Data are reduced to surface emissivity using an atmospheric radiative transfer model to account for atmospheric scattering and absorption/emission. Magellan altimetry was used to model atmospheric column height and surface temperature. The model uses a binary (collision-induced) absorption coefficient for each window. It fits absolute radiance and gradient with surface elevation reasonably well, although there are indications that the assumed adiabatic temperature lapse rate is not appropriate globally. The 1100nm band has a relatively low signal-to-noise ratio at the latitudes of the tessera plateaus, but Alpha Regio is visible in both the 1020 and the 1180nm band. The difference in emissivity between Alpha and the adjacent corona Eve, which has a similar elevation as Alpha, is 3.6% at 1020nm, but only 2% at 1180nm. The altimetry bias equivalent to the 1020nm deviation is 230 m, while the equivalent is only 70m at 1180nm. An altimetry bias therefore cannot fully explain the observations, and there must be a real difference in emissivity. The observations are consistent with the hypothesis that Alpha Regio has a more felsic composition. The emissivity spectra of granites at Venus temperatures are lower than those of basalt at 1020nm, but the difference decreases or vanishes towards the 1180nm window. The most plausible explanation for continent-sized felsic plateaus would be a formation analogous to Earth's continents, i.e. differentiation of basaltic crust in the presence of water.

Why do Models Overestimate Surface Ozone in the Southeastern United States?

PubMed

Travis, Katherine R; Jacob, Daniel J; Fisher, Jenny A; Kim, Patrick S; Marais, Eloise A; Zhu, Lei; Yu, Karen; Miller, Christopher C; Yantosca, Robert M; Sulprizio, Melissa P; Thompson, Anne M; Wennberg, Paul O; Crounse, John D; St Clair, Jason M; Cohen, Ronald C; Laughner, Joshua L; Dibb, Jack E; Hall, Samuel R; Ullmann, Kirk; Wolfe, Glenn M; Pollack, Illana B; Peischl, Jeff; Neuman, Jonathan A; Zhou, Xianliang

2016-01-01

Ozone pollution in the Southeast US involves complex chemistry driven by emissions of anthropogenic nitrogen oxide radicals (NO x ≡ NO + NO 2 ) and biogenic isoprene. Model estimates of surface ozone concentrations tend to be biased high in the region and this is of concern for designing effective emission control strategies to meet air quality standards. We use detailed chemical observations from the SEAC 4 RS aircraft campaign in August and September 2013, interpreted with the GEOS-Chem chemical transport model at 0.25°×0.3125° horizontal resolution, to better understand the factors controlling surface ozone in the Southeast US. We find that the National Emission Inventory (NEI) for NO x from the US Environmental Protection Agency (EPA) is too high. This finding is based on SEAC 4 RS observations of NO x and its oxidation products, surface network observations of nitrate wet deposition fluxes, and OMI satellite observations of tropospheric NO 2 columns. Our results indicate that NEI NO x emissions from mobile and industrial sources must be reduced by 30-60%, dependent on the assumption of the contribution by soil NO x emissions. Upper tropospheric NO 2 from lightning makes a large contribution to satellite observations of tropospheric NO 2 that must be accounted for when using these data to estimate surface NO x emissions. We find that only half of isoprene oxidation proceeds by the high-NO x pathway to produce ozone; this fraction is only moderately sensitive to changes in NO x emissions because isoprene and NO x emissions are spatially segregated. GEOS-Chem with reduced NO x emissions provides an unbiased simulation of ozone observations from the aircraft, and reproduces the observed ozone production efficiency in the boundary layer as derived from a regression of ozone and NO x oxidation products. However, the model is still biased high by 8±13 ppb relative to observed surface ozone in the Southeast US. Ozonesondes launched during midday hours show a 7 ppb ozone decrease from 1.5 km to the surface that GEOS-Chem does not capture. This bias may reflect a combination of excessive vertical mixing and net ozone production in the model boundary layer.

Why do Models Overestimate Surface Ozone in the Southeastern United States?

PubMed Central

Travis, Katherine R.; Jacob, Daniel J.; Fisher, Jenny A.; Kim, Patrick S.; Marais, Eloise A.; Zhu, Lei; Yu, Karen; Miller, Christopher C.; Yantosca, Robert M.; Sulprizio, Melissa P.; Thompson, Anne M.; Wennberg, Paul O.; Crounse, John D.; St Clair, Jason M.; Cohen, Ronald C.; Laughner, Joshua L.; Dibb, Jack E.; Hall, Samuel R.; Ullmann, Kirk; Wolfe, Glenn M.; Pollack, Illana B.; Peischl, Jeff; Neuman, Jonathan A.; Zhou, Xianliang

2018-01-01

Ozone pollution in the Southeast US involves complex chemistry driven by emissions of anthropogenic nitrogen oxide radicals (NOx ≡ NO + NO2) and biogenic isoprene. Model estimates of surface ozone concentrations tend to be biased high in the region and this is of concern for designing effective emission control strategies to meet air quality standards. We use detailed chemical observations from the SEAC4RS aircraft campaign in August and September 2013, interpreted with the GEOS-Chem chemical transport model at 0.25°×0.3125° horizontal resolution, to better understand the factors controlling surface ozone in the Southeast US. We find that the National Emission Inventory (NEI) for NOx from the US Environmental Protection Agency (EPA) is too high. This finding is based on SEAC4RS observations of NOx and its oxidation products, surface network observations of nitrate wet deposition fluxes, and OMI satellite observations of tropospheric NO2 columns. Our results indicate that NEI NOx emissions from mobile and industrial sources must be reduced by 30–60%, dependent on the assumption of the contribution by soil NOx emissions. Upper tropospheric NO2 from lightning makes a large contribution to satellite observations of tropospheric NO2 that must be accounted for when using these data to estimate surface NOx emissions. We find that only half of isoprene oxidation proceeds by the high-NOx pathway to produce ozone; this fraction is only moderately sensitive to changes in NOx emissions because isoprene and NOx emissions are spatially segregated. GEOS-Chem with reduced NOx emissions provides an unbiased simulation of ozone observations from the aircraft, and reproduces the observed ozone production efficiency in the boundary layer as derived from a regression of ozone and NOx oxidation products. However, the model is still biased high by 8±13 ppb relative to observed surface ozone in the Southeast US. Ozonesondes launched during midday hours show a 7 ppb ozone decrease from 1.5 km to the surface that GEOS-Chem does not capture. This bias may reflect a combination of excessive vertical mixing and net ozone production in the model boundary layer. PMID:29619045

Dust emission from wet and dry playas in the Mojave Desert, USA

USGS Publications Warehouse

Reynolds, R.L.; Yount, J.C.; Reheis, M.; Goldstein, H.; Chavez, P.; Fulton, R.; Whitney, J.; Fuller, C.; Forester, R.M.

2007-01-01

The interactions between playa hydrology and playa-surface sediments are important factors that control the type and amount of dust emitted from playas as a result of wind erosion. The production of evaporite minerals during evaporative loss of near-surface ground water results in both the creation and maintenance of several centimeters or more of loose sediment on and near the surfaces of wet playas. Observations that characterize the texture, mineralogic composition and hardness of playa surfaces at Franklin Lake, Soda Lake and West Cronese Lake playas in the Mojave Desert (California), along with imaging of dust emission using automated digital photography, indicate that these kinds of surface sediment are highly susceptible to dust emission. The surfaces of wet playas are dynamic - surface texture and sediment availability to wind erosion change rapidly, primarily in response to fluctuations in water-table depth, rainfall and rates of evaporation. In contrast, dry playas are characterized by ground water at depth. Consequently, dry playas commonly have hard surfaces that produce little or no dust if undisturbed except for transient silt and clay deposited on surfaces by wind and water. Although not the dominant type of global dust, salt-rich dusts from wet playas may be important with respect to radiative properties of dust plumes, atmospheric chemistry, windborne nutrients and human health.

Surface chemical analysis and ab initio investigations of CsI coated C fiber cathodes for high power microwave sources

NASA Astrophysics Data System (ADS)

Vlahos, Vasilios; Morgan, Dane; LaCour, Matthew; Golby, Ken; Shiffler, Don; Booske, John H.

2010-02-01

CsI coated C fiber cathodes are promising electron emitters utilized in field emission applications. Ab initio calculations, in conjunction with experimental investigations on CsI-spray coated C fiber cathodes, were performed in order to better understand the origin of the low turn-on E-field obtained, as compared to uncoated C fibers. One possible mechanism for lowering the turn-on E-field is surface dipole layers reducing the work function. Ab initio modeling revealed that surface monolayers of Cs, CsI, Cs2O, and CsO are all capable of producing low work function C fiber cathodes (1 eV<Φ<1.5 eV), yielding a reduction in the turn-on E-field by as much as ten times, when compared to the bare fiber. Although a CsI-containing aqueous solution is spray deposited on the C fiber surface, energy dispersive x-ray spectroscopy and scanning auger microscopy measurements show coabsorption of Cs and I into the fiber interior and Cs and O on the fiber surface, with no surface I. It is therefore proposed that a cesium oxide (CsxOy) surface coating is responsible, at least in part, for the low turn E-field and superior emission characteristics of this type of fiber cathode. This CsxOy layer could be formed during preconditioning heating. CsxOy surface layers cannot only lower the fiber work function by the formation of surface dipoles (if they are thin enough) but may also enhance surface emission through their ability to emit secondary electrons due to a process of grazing electron impact. These multiple electron emission processes may explain the reported 10-100 fold reduction in the turn-on E-field of coated C fibers.

Optical emission generated by collisions of 5 eV O(3P) atoms with surface-absorbed hydrazine

NASA Technical Reports Server (NTRS)

Orient, O. J.; Martus, K. E.; Chutjian, A.; Murad, E.

1992-01-01

Optical emission has been observed corresponding to vibrational bands in the NH (A 3Pi - X 3Sigma(-)) electronic transition during collisions of 5 eV, ground-state oxygen O(3P) atoms with MgF2 and Ni surfaces continuously exposed to a beam of hydrazine (N2H4). The NH emission intensity is observed to be about five times greater for MgF2 than for Ni. No dependence on temperature was observed for either surface in the range 240 - 340 K, implying that the NH-producing intermediate species is tightly bound. The half-lifetime for desorption of hydrazine from each surface was measured. This was found to be 120 min for the MgF2 surface at 240 K, and less than 20 min for Ni. After exposure, the surface composition was measured using X-ray photoelectron spectroscopy on the exposed and unexposed areas of both targets.

Surface Optical Rectification from Layered MoS2 Crystal by THz Time-Domain Surface Emission Spectroscopy.

PubMed

Huang, Yuanyuan; Zhu, Lipeng; Zhao, Qiyi; Guo, Yaohui; Ren, Zhaoyu; Bai, Jintao; Xu, Xinlong

2017-02-08

Surface optical rectification was observed from the layered semiconductor molybdenum disulfide (MoS 2 ) crystal via terahertz (THz) time-domain surface emission spectroscopy under linearly polarized femtosecond laser excitation. The radiated THz amplitude of MoS 2 has a linear dependence on ever-increasing pump fluence and thus quadratic with the pump electric field, which discriminates from the surface Dember field induced THz radiation in InAs and the transient photocurrent-induced THz generation in graphite. Theoretical analysis based on space symmetry of MoS 2 crystal suggests that the underlying mechanism of THz radiation is surface optical rectification under the reflection configuration. This is consistent with the experimental results according to the radiated THz amplitude dependences on azimuthal and incident polarization angles. We also demonstrated the damage threshold of MoS 2 due to microscopic bond breaking under the femtosecond laser irradiation, which can be monitored via THz time-domain emission spectroscopy and Raman spectroscopy.

Surface and Atmospheric Contributions to Passive Microwave Brightness Temperatures

NASA Technical Reports Server (NTRS)

Jackson, Gail Skofronick; Johnson, Benjamin T.

2010-01-01

Physically-based passive microwave precipitation retrieval algorithms require a set of relationships between satellite observed brightness temperatures (TB) and the physical state of the underlying atmosphere and surface. These relationships are typically non-linear, such that inversions are ill-posed especially over variable land surfaces. In order to better understand these relationships, this work presents a theoretical analysis using brightness temperature weighting functions to quantify the percentage of the TB resulting from absorption/emission/reflection from the surface, absorption/emission/scattering by liquid and frozen hydrometeors in the cloud, the emission from atmospheric water vapor, and other contributors. The results are presented for frequencies from 10 to 874 GHz and for several individual precipitation profiles as well as for three cloud resolving model simulations of falling snow. As expected, low frequency channels (<89 GHz) respond to liquid hydrometeors and the surface, while the higher frequency channels become increasingly sensitive to ice hydrometeors and the water vapor sounding channels react to water vapor in the atmosphere. Low emissivity surfaces (water and snow-covered land) permit energy downwelling from clouds to be reflected at the surface thereby increasing the percentage of the TB resulting from the hydrometeors. The slant path at a 53deg viewing angle increases the hydrometeor contributions relative to nadir viewing channels and show sensitivity to surface polarization effects. The TB percentage information presented in this paper answers questions about the relative contributions to the brightness temperatures and provides a key piece of information required to develop and improve precipitation retrievals over land surfaces.

Road Asphalt Pavements Analyzed by Airborne Thermal Remote Sensing: Preliminary Results of the Venice Highway.

PubMed

Pascucci, Simone; Bassani, Cristiana; Palombo, Angelo; Poscolieri, Maurizio; Cavalli, Rosa

2008-02-22

This paper describes a fast procedure for evaluating asphalt pavement surface defects using airborne emissivity data. To develop this procedure, we used airborne multispectral emissivity data covering an urban test area close to Venice (Italy).For this study, we first identify and select the roads' asphalt pavements on Multispectral Infrared Visible Imaging Spectrometer (MIVIS) imagery using a segmentation procedure. Next, since in asphalt pavements the surface defects are strictly related to the decrease of oily components that cause an increase of the abundance of surfacing limestone, the diagnostic absorption emissivity peak at 11.2μm of the limestone was used for retrieving from MIVIS emissivity data the areas exhibiting defects on asphalt pavements surface.The results showed that MIVIS emissivity allows establishing a threshold that points out those asphalt road sites on which a check for a maintenance intervention is required. Therefore, this technique can supply local government authorities an efficient, rapid and repeatable road mapping procedure providing the location of the asphalt pavements to be checked.

Roughness effects on thermal-infrared emissivities estimated from remotely sensed images

NASA Astrophysics Data System (ADS)

Mushkin, Amit; Danilina, Iryna; Gillespie, Alan R.; Balick, Lee K.; McCabe, Matthew F.

2007-10-01

Multispectral thermal-infrared images from the Mauna Loa caldera in Hawaii, USA are examined to study the effects of surface roughness on remotely retrieved emissivities. We find up to a 3% decrease in spectral contrast in ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) 90-m/pixel emissivities due to sub-pixel surface roughness variations on the caldera floor. A similar decrease in spectral contrast of emissivities extracted from MASTER (MODIS/ASTER Airborne Simulator) ~12.5-m/pixel data can be described as a function of increasing surface roughness, which was measured remotely from ASTER 15-m/pixel stereo images. The ratio between ASTER stereo images provides a measure of sub-pixel surface-roughness variations across the scene. These independent roughness estimates complement a radiosity model designed to quantify the unresolved effects of multiple scattering and differential solar heating due to sub-pixel roughness elements and to compensate for both sub-pixel temperature dispersion and cavity radiation on TIR measurements.

Dust emissions from undisturbed and disturbed, crusted playa surfaces: cattle trampling effects

USDA-ARS?s Scientific Manuscript database

Dry playa lake beds can be significant sources of fine dust emission. This study used a portable field wind tunnel to quantify the PM10 emissions from a bare, fine-textured playa surface located in the far northern Chihuahua Desert. The natural, undisturbed crust and its subjection to two levels of ...

Two-step fabrication of ZnO-PVP composites with tunable visible emissions

NASA Astrophysics Data System (ADS)

Agulto, Verdad C.; Empizo, Melvin John F.; Kawano, Keisuke; Minami, Yuki; Yamanoi, Kohei; Sarukura, Nobuhiko; Yago, Allan Christopher C.; Sarmago, Roland V.

2018-02-01

We report a two-step fabrication of zinc oxide-polyvinylpyrrolidone (ZnO-PVP) composites for potential phosphor-based applications. The composites are fabricated by initially preparing ZnO microrods using hydrothermal growth method and then dip-coating the microrods into aqueous PVP solutions with varying molar concentrations. The as-prepared ZnO microrods exhibit smooth surfaces and broad visible emissions, while the ZnO-PVP composites have pitted surfaces with shifted and reduced visible emissions. These changes in the structural and optical properties, which are found to depend on the PVP concentration, are attributed to the adsorption of PVP on the microrod surface. Although the surface morphology and visible emission are modified by PVP, the composites still maintain a hexagonal wurtzite crystal structure and near-band-edge ultraviolet (UV) emission similar with the as-prepared microrods. Our results therefore suggest that the ZnO-PVP composites can be used as phosphors that offer not only properties found in both ZnO and PVP but also tunable visible emissions which can be controlled during material fabrication.

Coverage and velocity dependent sticking coefficient and particle emission kinetics in the Cl2gas + Ksolid reaction

NASA Astrophysics Data System (ADS)

Hellberg, Lars; Kasemo, Bengt

Some strongly exothermic and non-adiabatic surface adsorption events, especially those where electronegative molecules adsorb on very electropositive (low work function) surfaces, are accompanied by emission of (exo)electrons, photons, excited atoms and negative ions. The reaction of halogen molecules with halogen surfaces constitute an efficient model system for such studies. We have previously reported data for the emission of negative particles and photons in the zero coverage limit for a range of velocities of Cl2 molecules impinging on cold potassium surfaces as well as the mechanism behind these emission processes. In the present work, we focus on measurements of the kinetics, i.e. the exposure/coverage dependence, of these processes for the same system. Specifically, we present data for, (i) the separated contributions from electrons and Cl- ions of the emitted negative particles, (ii) the photon emission stemming both from excited Potassium atoms and from the equivalent process causing electron emission, (iii) the change of the work function during the initial exposure and, finally, (iv) the sticking coefficient for different Cl2 velocities and exposures.

Estimation of Multiple Parameters over Vegetated Surfaces by Integrating Optical-Thermal Remote Sensing Observations

NASA Astrophysics Data System (ADS)

Ma, H.

2016-12-01

Land surface parameters from remote sensing observations are critical in monitoring and modeling of global climate change and biogeochemical cycles. Current methods for estimating land surface parameters are generally parameter-specific algorithms and are based on instantaneous physical models, which result in spatial, temporal and physical inconsistencies in current global products. Besides, optical and Thermal Infrared (TIR) remote sensing observations are usually separated to use based on different models , and the Middle InfraRed (MIR) observations have received little attention due to the complexity of the radiometric signal that mixes both reflected and emitted fluxes. In this paper, we proposed a unified algorithm for simultaneously retrieving a total of seven land surface parameters, including Leaf Area Index (LAI), Fraction of Absorbed Photosynthetically Active Radiation (FAPAR), land surface albedo, Land Surface Temperature (LST), surface emissivity, downward and upward longwave radiation, by exploiting remote sensing observations from visible to TIR domain based on a common physical Radiative Transfer (RT) model and a data assimilation framework. The coupled PROSPECT-VISIR and 4SAIL RT model were used for canopy reflectance modeling. At first, LAI was estimated using a data assimilation method that combines MODIS daily reflectance observation and a phenology model. The estimated LAI values were then input into the RT model to simulate surface spectral emissivity and surface albedo. Besides, the background albedo and the transmittance of solar radiation, and the canopy albedo were also calculated to produce FAPAR. Once the spectral emissivity of seven MODIS MIR to TIR bands were retrieved, LST can be estimated from the atmospheric corrected surface radiance by exploiting an optimization method. At last, the upward longwave radiation were estimated using the retrieved LST, broadband emissivity (converted from spectral emissivity) and the downward longwave radiation (modeled by MODTRAN). These seven parameters were validated over several representative sites with different biome type, and compared with MODIS and GLASS product. Results showed that this unified inversion algorithm can retrieve temporally complete and physical consistent land surface parameters with high accuracy.

Titan's surface at 2.2-cm wavelength imaged by the Cassini RADAR radiometer: Calibration and first results

USGS Publications Warehouse

Janssen, M.A.; Lorenz, R.D.; West, R.; Paganelli, F.; Lopes, R.M.; Kirk, R.L.; Elachi, C.; Wall, S.D.; Johnson, W.T.K.; Anderson, Y.; Boehmer, R.A.; Callahan, P.; Gim, Y.; Hamilton, G.A.; Kelleher, K.D.; Roth, L.; Stiles, B.; Le, Gall A.

2009-01-01

The first comprehensive calibration and mapping of the thermal microwave emission from Titan's surface is reported based on radiometric data obtained at 2.2-cm wavelength by the passive radiometer included in the Cassini Radar instrument. The data reported were accumulated from 69 separate observational segments in Titan passes from Ta (October 2004) through T30 (May 2007) and include emission from 94% of Titan's surface. They are diverse in the key observing parameters of emission angle, polarization, and spatial resolution, and their reduction into calibrated global mosaic maps involved several steps. Analysis of the polarimetry obtained at low to moderate resolution (50+ km) enabled integration of the radiometry into a single mosaic of the equivalent brightness temperature at normal incidence with a relative precision of about 1 K. The Huygens probe measurement of Titan's surface temperature and radiometry obtained on Titan's dune fields allowed us to infer an absolute calibration estimated to be accurate to a level approaching 1 K. The results provide evidence for a surface that is complex and varied on large scales. The radiometry primarily constrains physical properties of the surface, where we see strong evidence for subsurface (volume) scattering as a dominant mechanism that determines the emissivity, with the possibility of a fluffy or graded-density surface layer in many regions. The results are consistent with, but not necessarily definitive of a surface composition resulting from the slow deposition and processing of organic compounds from the atmosphere. ?? 2008 Elsevier Inc.

Temporal dynamics of salt crust patterns on a sodic playa: implications for aerodynamic roughness and dust emission potential

NASA Astrophysics Data System (ADS)

Nield, Joanna; Bryant, Robert; Wiggs, Giles; King, James; Thomas, David; Eckardt, Frank; Washington, Richard

2015-04-01

Salt pans (or playas) are common in arid environments and can be major sources of windblown mineral dust, but there are uncertainties associated with their dust emission potential. These landforms typically form crusts which modify both their erosivity and erodibility by limiting sediment availability, modifying surface and aerodynamic roughness and limiting evaporation rates and sediment production. Here we show the relationship between seasonal surface moisture change and crust pattern development on part of the Makgadikgadi Pans of Botswana (a Southern Hemisphere playa that emits significant dust), based on both remote-sensing and field surface and atmospheric measurements. We use high resolution (sub-cm) terrestrial laser scanning (TLS) surveys over weekly, monthly and annual timescales to accurately characterise crustal ridge thrusting and collapse. Ridge development can change surface topography as much as 30 mm/week on fresh pan areas that have recently been reset by flooding. The corresponding change aerodynamic roughness can be as much as 3 mm/week. At the same time, crack densities across the surface increase and this raises the availability of erodible fluffy, low density dust source sediment stored below the crust layer. We present a conceptual model accounting for the driving forces (subsurface, surface and atmospheric moisture) and feedbacks between these and surface shape that lead to crust pattern trajectories between highly emissive degraded surfaces and less emissive ridged or continuous crusts. These findings improve our understanding of temporal changes in dust availability and supply from playa source regions.

Effects of surface preparation on quality of aluminum alloy weldments

NASA Technical Reports Server (NTRS)

Kizer, D.; Saperstein, Z.

1968-01-01

Study of surface preparations and surface contamination effects on the welding of 2014 aluminum involves several methods of surface analysis to identify surface properties conducive to weld defects. These methods are radioactive evaporation, spectral reflectance mass spectroscopy, gas chromatography and spark emission spectroscopy.

X-ray Probes of Magnetospheric Interactions with Jupiter's Auroral zones, the Galilean Satellites, and the Io Plasma Torus

NASA Technical Reports Server (NTRS)

Elsner, R. F.; Ramsey, B. D.; Waite, J. H., Jr.; Rehak, P.; Johnson, R. E.; Cooper, J. F.; Swartz, D. A.

2004-01-01

Remote observations with the Chandra X-ray Observatory and the XMM-Newton Observatory have shown that the Jovian system is a source of x-rays with a rich and complicated structure. The planet's polar auroral zones and its disk are powerful sources of x-ray emission. Chandra observations revealed x-ray emission from the Io Plasma Torus and from the Galilean moons Io, Europa, and possibly Ganymede. The emission from these moons is certainly due to bombardment of their surfaces of highly energetic protons, oxygen and sulfur ions from the region near the Torus exciting atoms in their surfaces and leading to fluorescent x-ray emission lines. Although the x-ray emission from the Galilean moons is faint when observed fiom Earth orbit, an imaging x-ray spectrometer in orbit around these moons, operating at 200 eV and above with 150 eV energy resolution, would provide a detailed mapping (down to 40 m spatial resolution) of the elemental composition in their surfaces. Here we describe the physical processes leading to x-ray emission fiom the surfaces of Jupiter's moons and the instrumental properties, as well as energetic ion flux models or measurements, required to map the elemental composition of their surfaces. We discuss the proposed scenarios leading to possible surface compositions. For Europa, the two most extreme are (1) a patina produced by exogenic processes such as meteoroid bombardment and ion implantation, and (2) upwelling of material fiom the subsurface ocean. We also describe the characteristics of X - m , an imaging x-ray spectrometer under going a feasibility study for the JIM0 mission, with the ultimate goal of providing unprecedented x-ray studies of the elemental composition of the surfaces of Jupiter's icy moons and Io, as well as of Jupiter's auroral x-ray emission.

Dust emission thresholds from sodic playas with varying geochemistry and environmental conditions

NASA Astrophysics Data System (ADS)

Nield, J. M.; McKenna Neuman, C.; O'Brien, P.

2014-12-01

Sodic playa surfaces can be major sources of dust emission but their erodibility depends on the surface salt crust characteristics. Here we determine dust emission thresholds in a wind tunnel for 22 different crusts with varying concentrations of sodium sulphate and sodium chloride. Crusts mimic those on Sua Pan, in the Makgadikgadi Basin, Botswana, which is one of the biggest dust hot spots in the Southern Hemisphere. Crusts were grown by encouraging capillary processes and subjected to several weeks of diurnal temperature variation to enable the development of hydrated and dehydrated salt crystals, along with low density, 'fluffy' sediment beneath the primary (and in some cases, secondary) crust. Spray on crusts and liquefied crusts were also developed for response comparison. Using laser scanning we tracked surface change and crystal growth, which we link to crust type and evaporation rates. We found that under pre-dawn and early morning Sua Pan conditions, crusts were typically non-emissive, but during mid-day temperature and humidity conditions typical of Sua Pan in August and September (dry and peak dust emission season), several crusts became friable and highly emissive above wind velocities of 7 m/s, which agrees with in-situ field observations. Thenardite capillary crusts were the most emissive, in contrast to supply limited, halite liquefied crusts which were relatively stable. Disturbances, or small crust fractures, common on polygonal surface patterns decreased the dust emission threshold values and enabled emission from more stable crusts. Our study confirms the potential of playa surfaces to emit dust without the presence of saltation, and highlights the sensitivity of emission thresholds to crust geochemistry, evaporation rates and temperature and humidity conditions.

Using Nadir and Directional Emissivity as a Probe of Particle Microphysical Properties

NASA Astrophysics Data System (ADS)

Pitman, Karly M.; Wolff, Michael J.; Bandfield, Joshua L.; Clayton, Geoffrey C.

Real surfaces are not expected to be diffuse emitters, thus observed emissivity values of surface dust deposits are a function of viewing geometry. Attempts to model infrared emission spectral profiles of surface dust deposits at nadir have not yet matured to match the sophistication of astrophysical dust radiative transfer codes. In the absence of strong thermal gradients, directional emissivity may be obtained theoretically via a combination of reciprocity and Kirchhoff's Law. Owing to a lack of laboratory data on directional emissivity for comparison, theorists have not explored the potential utility of directional emissivity as a direct probe of surface dust microphysical properties. Motivated by future analyses of MGS/TES emission phase function (EPF) sequences and the upcoming Mars Exploration Rover mini-TES dataset, we explore the effects of dust particle size and composition on observed radiances at nadir and off-nadir geometries in the TES spectral regime using a combination of multiple scattering radiative transfer and Mie scattering algorithms. Comparisons of these simulated spectra to laboratory spectra of standard mineral assemblages will also be made. This work is supported through NASA grant NAGS-9820 (MJW) and LSU Board of Regents (KMP).

Climate Implications of the Heterogeneity of Anthropogenic Aerosol Forcing

NASA Astrophysics Data System (ADS)

Persad, Geeta Gayatri

Short-lived anthropogenic aerosols are concentrated in regions of high human activity, where they interact with radiation and clouds, causing horizontally heterogeneous radiative forcing between polluted and unpolluted regions. Aerosols can absorb shortwave energy in the atmosphere, but deplete it at the surface, producing opposite radiative perturbations between the surface and atmosphere. This thesis investigates climate and policy implications of this horizontal and vertical heterogeneity of anthropogenic aerosol forcing, employing the Geophysical Fluid Dynamics Laboratory's AM2.1 and AM3 models, both at a global scale and using East Asia as a regional case study. The degree of difference between spatial patterns of climate change due to heterogeneous aerosol forcing versus homogeneous greenhouse gas forcing deeply impacts the detection, attribution, and prediction of regional climate change. This dissertation addresses a gap in current understanding of these two forcings' response pattern development, using AM2.1 historical forcing simulations. The results indicate that fast atmospheric and land-surface processes alone substantially homogenize the global pattern of surface energy flux response to heterogeneous aerosol forcing. Aerosols' vertical redistribution of energy significantly impacts regional climate, but is incompletely understood. It is newly identified here, via observations and historical and idealized forcing simulations, that increased aerosol-driven atmospheric absorption may explain half of East Asia's recent surface insolation decline. Further, aerosols' surface and atmospheric effects counteract each other regionally---atmospheric heating enhances summer monsoon circulation, while surface dimming suppresses it---but absorbing aerosols' combined effects reduce summer monsoon rainfall. This thesis constitutes the first vertical decomposition of aerosols' impacts in this high-emissions region and elucidates the monsoonal response to aerosols' surface versus atmospheric forcing. Future aerosol emissions patterns will affect the distribution of regional climate impacts. This dissertation interrogates how international trade affects existing assumptions about East Asia's future black carbon aerosol emissions, using integrated assessment modeling, emissions and economic data, and AM3 simulations. Exports emerge as a uniquely large and potentially growing source of Chinese black carbon emissions that could impede projected regional emissions reductions, with substantial climate and health consequences. The findings encourage greater emissions projection sophistication and illustrate how societal decisions may influence future aerosol forcing heterogeneity.

Sensitivity of volatile organic compounds (VOCs) and ozone to land surface processes and vegetation distributions in California

NASA Astrophysics Data System (ADS)

Zhao, C.; Huang, M.; Fast, J. D.; Berg, L. K.; Qian, Y.; Guenther, A. B.; Gu, D.; Shrivastava, M. B.; Liu, Y.; Walters, S.; Jin, J.

2014-12-01

Current climate models still have large uncertainties in estimating biogenic trace gases, which can significantly affect secondary organic aerosol (SOA) formation and ultimately aerosol radiative forcing. These uncertainties result from many factors, including coupling strategy between biogenic emissions and land-surface schemes and specification of vegetation types, both of which can affect the simulated near-surface fluxes of biogenic volatile organic compounds (VOCs). In this study, sensitivity experiments are conducted using the Weather Research and Forecasting model with chemistry (WRF-Chem) to examine the sensitivity of simulated VOCs and ozone to land surface processes and vegetation distributions in California. The measurements collected during the California Nexus of Air Quality and Climate Experiment (CalNex) and the Carbonaceous Aerosol and Radiative Effects Study (CARES) conducted during May and June of 2010 provide a good opportunity to evaluate the simulations. First, the biogenic VOC emissions in the WRF-Chem simulations with the two land surface schemes, Noah and CLM4, are estimated by the Model of Emissions of Gases and Aerosols from Nature version one (MEGANv1), which has been publicly released and widely used with WRF-Chem. The impacts of land surface processes on estimating biogenic VOC emissions and simulating VOCs and ozone are investigated. Second, in this study, a newer version of MEGAN (MEGANv2.1) is coupled with CLM4 as part of WRF-Chem to examine the sensitivity of biogenic VOC emissions to the MEGAN schemes used and determine the importance of using a consistent vegetation map between a land surface scheme and the biogenic VOC emission scheme. Specifically, MEGANv2.1 is embedded into the CLM4 scheme and shares a consistent vegetation map for estimating biogenic VOC emissions. This is unlike MEGANv1 in WRF-Chem that uses a standalone vegetation map that differs from what is used in land surface schemes. Furthermore, we examine the impact of vegetation distribution on simulating VOCs and ozone by comparing coupled WRF-Chem-CLM-MEGANv2.1 simulations using multiple vegetation maps.

Strongly Enhanced THz Emission caused by Localized Surface Charges in Semiconducting Germanium Nanowires

PubMed Central

Lee, Woo-Jung; Ma, Jin Won; Bae, Jung Min; Jeong, Kwang-Sik; Cho, Mann-Ho; Kang, Chul; Wi, Jung-Sub

2013-01-01

A principal cause of THz emission in semiconductor nanostructures is deeply involved with geometry, which stimulates the utilization of indirect bandgap semiconductors for THz applications. To date, applications for optoelectronic devices, such as emitters and detectors, using THz radiation have focused only on direct bandgap materials. This paper reports the first observation of strongly enhanced THz emission from Germanium nanowires (Ge NWs). The origin of THz generation from Ge NWs can be interpreted using two terms: high photoexcited electron-hole carriers (Δn) and strong built-in electric field (Eb) at the wire surface based on the relation . The first is related to the extensive surface area needed to trigger an irradiated photon due to high aspect ratio. The second corresponds to the variation of Fermi-level determined by confined surface charges. Moreover, the carrier dynamics of optically excited electrons and holes give rise to phonon emission according to the THz region. PMID:23760467

Particle emission from artificial cometary materials

NASA Technical Reports Server (NTRS)

Koelzer, Gabriele; Kochan, Hermann; Thiel, Klaus

1992-01-01

During KOSI (comet simulation) experiments, mineral-ice mixtures are observed in simulated space conditions. Emission of ice-/dust particles from the sample surface is observed by means of different devices. The particle trajectories are recorded with a video system. In the following analysis we extracted the parameters: particle count rate, spatial distribution of starting points on the sample surface, and elevation angle and particle velocity at distances up to 5 cm from the sample surface. Different kinds of detectors are mounted on a frame in front of the sample to register the emitted particles and to collect their dust residues. By means of these instruments the particle count rates, the particle sizes and the composition of the particles can be correlated. The results are related to the gas flux density and the temperature on the sample surface during the insolation period. The particle emission is interpreted in terms of phenomena on the sample surface, e.g., formation of a dust mantle.

The airborne infrared scanner as a geophysical research tool

USGS Publications Warehouse

Friedman, Jules D.

1970-01-01

The infrared scanner is proving to be an effective anomaly-mapping tool, albeit one which depicts surface emission directly and heat mass transfer from depths only indirectly and at a threshold level 50 to 100 times the normal conductive heat flow of the earth. Moreover, successive terrain observations are affected by time-dependent variables such as the diurnal and seasonal warming and cooling cycle of a point on the earth's surface. In planning precise air borne surveys of radiant flux from the earth's surface, account must be taken of background noise created by variations in micrometeorological factors and emissivity of surface materials, as well as the diurnal temperature cycle. The effect of the diurnal cycle may be minimized by planning predawn aerial surveys. In fact, the diurnal change is very small for most water bodies and the emissivity factor for water (e) =~ 1 so a minimum background noise is characteristic of scanner records of calm water surfaces.

Modeling the non-grey-body thermal emission from the full moon

NASA Technical Reports Server (NTRS)

Vogler, Karl J.; Johnson, Paul E.; Shorthill, Richard W.

1991-01-01

The present series of thermophysical computer models for solid-surfaced planetary bodies whose surface roughness is modeled as paraboloidal craters of specified depth/diameter ratio attempts to characterize the nongrey-body brightness temperature spectra of the moon and of the Galilean satellites. This modeling, in which nondiffuse radiation properties and surface roughness are included for rigorous analysis of scattered and reemitted radiation within a crater, explains to first order the behavior of both limb-scans and disk-integrated IR brightness temperature spectra for the full moon. Only negative surface relief can explain lunar thermal emissions' deviation from smooth Lambert-surface expectations.

Microwave capillary torch as a means for modifying the electrophysical characteristics of metal surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Artem’ev, K. V.; Davydov, A. M.; Ivanov, V. A.

2016-07-15

An experiment layout based on a pulsed capillary microwave torch and making it possible to excite an explosive emission microplasma on a metal surface in open air is implemented for the first time. It is shown that a microrelief in the form of micron-size microcraters forms on the initially smooth surface under the action of microsparks. As a result, the maximum secondary electron emission yield σ{sub max} decreases from ∼2 for the untreated surface to ∼0.4 for the rough treated surface and remains low for a long time when exposed to atmospheric air.

Secondary Electron Emission Spectroscopy of Diamond Surfaces

NASA Technical Reports Server (NTRS)

Krainsky, Isay L.; Asnin, Vladimir M.; Petukhov, Andre G.

1999-01-01

This report presents the results of the secondary electron emission spectroscopy study of hydrogenated diamond surfaces for single crystals and chemical vapor-deposited polycrystalline films. One-electron calculations of Auger spectra of diamond surfaces having various hydrogen coverages are presented, the major features of the experimental spectra are explained, and a theoretical model for Auger spectra of hydrogenated diamond surfaces is proposed. An energy shift and a change in the line shape of the carbon core-valence-valence (KVV) Auger spectra were observed for diamond surfaces after exposure to an electron beam or by annealing at temperatures higher than 950 C. This change is related to the redistribution of the valence-band local density of states caused by hydrogen desorption from the surface. A strong negative electron affinity (NEA) effect, which appeared as a large, narrow peak in the low-energy portion of the spectrum of the secondary electron energy distribution, was also observed on the diamond surfaces. A fine structure in this peak, which was found for the first time, reflected the energy structure of the bottom of the conduction band. Further, the breakup of the bulk excitons at the surface during secondary electron emission was attributed to one of the features of this structure. The study demonstrated that the NEA type depends on the extent of hydrogen coverage of the diamond surface, changing from the true type for the completely hydrogenated surface to the effective type for the partially hydrogenated surface.

Simultaneous inversion of multiple land surface parameters from MODIS optical-thermal observations

NASA Astrophysics Data System (ADS)

Ma, Han; Liang, Shunlin; Xiao, Zhiqiang; Shi, Hanyu

2017-06-01

Land surface parameters from remote sensing observations are critical in monitoring and modeling of global climate change and biogeochemical cycles. Current methods for estimating land surface variables usually focus on individual parameters separately even from the same satellite observations, resulting in inconsistent products. Moreover, no efforts have been made to generate global products from integrated observations from the optical to Thermal InfraRed (TIR) spectrum. Particularly, Middle InfraRed (MIR) observations have received little attention due to the complexity of the radiometric signal, which contains both reflected and emitted radiation. In this paper, we propose a unified algorithm for simultaneously retrieving six land surface parameters - Leaf Area Index (LAI), Fraction of Absorbed Photosynthetically Active Radiation (FAPAR), land surface albedo, Land Surface Emissivity (LSE), Land Surface Temperature (LST), and Upwelling Longwave radiation (LWUP) by exploiting MODIS visible-to-TIR observations. We incorporate a unified physical radiative transfer model into a data assimilation framework. The MODIS visible-to-TIR time series datasets include the daily surface reflectance product and MIR-to-TIR surface radiance, which are atmospherically corrected from the MODIS data using the Moderate Resolution Transmittance program (MODTRAN, ver. 5.0). LAI was first estimated using a data assimilation method that combines MODIS daily reflectance data and a LAI phenology model, and then the LAI was input to the unified radiative transfer model to simulate spectral surface reflectance and surface emissivity for calculating surface broadband albedo and emissivity, and FAPAR. LST was estimated from the MIR-TIR surface radiance data and the simulated emissivity, using an iterative optimization procedure. Lastly, LWUP was estimated using the LST and surface emissivity. The retrieved six parameters were extensively validated across six representative sites with different biome types, and compared with MODIS, GLASS, and GlobAlbedo land surface products. The results demonstrate that the unified inversion algorithm can retrieve temporally complete and physically consistent land surface parameters, and provides more accurate estimates of surface albedo, LST, and LWUP than existing products, with R2 values of 0.93 and 0.62, RMSE of 0.029 and 0.037, and BIAS values of 0.016 and 0.012 for the retrieved and MODIS albedo products, respectively, compared with field albedo measurements; R2 values of 0.95 and 0.93, RMSE of 2.7 and 4.2 K, and BIAS values of -0.6 and -2.7 K for the retrieved and MODIS LST products, respectively, compared with field LST measurements; and R2 values of 0.93 and 0.94, RMSE of 18.2 and 22.8 W/m2, and BIAS values of -2.7 and -14.6 W/m2 for the retrieved and MODIS LWUP products, respectively, compared with field LWUP measurements.

Remote sensing of the surface emissivity at 9 microns over the globe. [over desert regions with IR Interferometer Spectrometer data

NASA Technical Reports Server (NTRS)

Prabhakara, C.; Dalu, G.

1976-01-01

The infrared spectral measurements made by the Nimbus 4 infrared interferometer spectrometer (Iris) for a period of about 10 months are used to study the surface emissivity properties over the globe. It is found that the surface emissivity at 9 microns, as measured by Iris with a circular field of view of about 100-km diameter, is significantly less than unity over arid and semiarid areas. The spectral features in the 8-12-micron window observed over these lands reveal emissivity characteristics essentially due to quartz (SiO2). It is found that these emissivity features are significantly weakened by the presence of clay, clay horizons, or pedogenic horizons in the soil. Low emissivity is observed over sandy or sandy loam areas (psamments) with no clay or pedogenic horizons.

Characterization of the NEXT Hollow Cathode Inserts After Long-Duration Testing

NASA Technical Reports Server (NTRS)

Mackey, J.; Shastry, R.; Soulas, G.

2017-01-01

Hollow dispenser cathode inserts are a critical element of electric propulsion systems, and should therefore be well understood during long term operation to ensure reliable system performance. This work destructively investigated cathode inserts from the NEXT long-duration test which demonstrated 51,184 hours of high-voltage operation, 918 kg of propellant throughput, and 35.5 MN-s of total impulse. The characterization methods used include scanning electron microscopy with energy dispersive spectroscopy and X-ray diffraction. Microscopy analysis has been performed on fractured surfaces, emission surfaces, and metallographically polished cross-sections of post-test inserts and unused inserts. Impregnate distribution, etch region thickness, impregnate chemical content, emission surface topography, and emission surface phase identification are the primary factors investigated.

Modeling of reduced effective secondary electron emission yield from a velvet surface

DOE PAGES

Swanson, Charles; Kaganovich, Igor D.

2016-12-05

Complex structures on a material surface can significantly reduce total secondary electron emission from that surface. A velvet is a surface that consists of an array of vertically standing whiskers. The reduction occurs due to the capture of low-energy, true secondary electrons emitted at the bottom of the structure and on the sides of the velvet whiskers. We performed numerical simulations and developed an approximate analytical model that calculates the net secondary electron emission yield from a velvet surface as a function of the velvet whisker length and packing density, and the angle of incidence of primary electrons. We foundmore » that to suppress secondary electrons, the following condition on dimensionless parameters must be met: (π/2) DΑ tan θ >> 1, where theta is the angle of incidence of the primary electron from the normal, D is the fraction of surface area taken up by the velvet whisker bases, and A is the aspect ratio, A = h/r, the ratio of height to radius of the velvet whiskers. We find that velvets available today can reduce the secondary electron yield by 90% from the value of a flat surface. As a result, the values of optimal velvet whisker packing density that maximally suppresses the secondary electron emission yield are determined as a function of velvet aspect ratio and the electron angle of incidence.« less

Venus Surface Composition Constrained by Observation and Experiment

NASA Astrophysics Data System (ADS)

Gilmore, Martha; Treiman, Allan; Helbert, Jörn; Smrekar, Suzanne

2017-11-01

New observations from the Venus Express spacecraft as well as theoretical and experimental investigation of Venus analogue materials have advanced our understanding of the petrology of Venus melts and the mineralogy of rocks on the surface. The VIRTIS instrument aboard Venus Express provided a map of the southern hemisphere of Venus at ˜1 μm allowing, for the first time, the definition of surface units in terms of their 1 μm emissivity and derived mineralogy. Tessera terrain has lower emissivity than the presumably basaltic plains, consistent with a more silica-rich or felsic mineralogy. Thermodynamic modeling and experimental production of melts with Venera and Vega starting compositions predict derivative melts that range from mafic to felsic. Large volumes of felsic melts require water and may link the formation of tesserae to the presence of a Venus ocean. Low emissivity rocks may also be produced by atmosphere-surface weathering reactions unlike those seen presently. High 1 μm emissivity values correlate to stratigraphically recent flows and have been used with theoretical and experimental predictions of basalt weathering to identify regions of recent volcanism. The timescale of this volcanism is currently constrained by the weathering of magnetite (higher emissivity) in fresh basalts to hematite (lower emissivity) in Venus' oxidizing environment. Recent volcanism is corroborated by transient thermal anomalies identified by the VMC instrument aboard Venus Express. The interpretation of all emissivity data depends critically on understanding the composition of surface materials, kinetics of rock weathering and their measurement under Venus conditions. Extended theoretical studies, continued analysis of earlier spacecraft results, new atmospheric data, and measurements of mineral stability under Venus conditions have improved our understanding atmosphere-surface interactions. The calcite-wollastonite CO2 buffer has been discounted due, among other things, to the rarity of wollastonite and instability of carbonate at the Venus surface. Sulfur in the Venus atmosphere has been shown experimentally to react with Ca in surface minerals to produce anhydrite. The extent of this SO2 buffer is constrained by the Ca content of surface rocks and sulfur content of the atmosphere, both of which are likely variable, perhaps due to active volcanism. Experimental work on a range of semiconductor and ferroelectric minerals is placing constraints on the cause(s) of Venus' anomalously radar bright highlands.

Experimental study of surface plasmon-phonon polaritons in GaAs-based microstructures

NASA Astrophysics Data System (ADS)

Galimov, A. I.; Shalygin, V. A.; Moldavskaya, M. D.; Panevin, V. Yu; Melentyev, G. A.; Artemyev, A. A.; Firsov, D. A.; Vorobjev, L. E.; Klimko, G. V.; Usikova, A. A.; Komissarova, T. A.; Sedova, I. V.; Ivanov, S. V.

2018-03-01

Optical properties of a heavily-doped GaAs epitaxial layer with a regular grating at its surface have been experimentally investigated in the terahertz spectral range. Reflectivity spectra for the layer with a profiled surface drastically differ from those for the as-grown epilayer with a planar surface. For s-polarized radiation, this difference is totally caused by the electromagnetic wave diffraction at the grating. For p-polarized radiation, additional resonant dips arise due to excitation of surface plasmon-phonon polaritons. Terahertz radiation emission under significant electron heating in an applied pulsed electric field has also been studied. Polarization measurements revealed pronounced peaks related to surface plasmon-phonon polariton resonances of the first and second order in the emission spectra.

Secondary-electron emission by 0.5-MeV/u H, He, and Li ions specularly reflected from a SnTe(001) surface: Possibility of the surface track potential reducing the secondary-electron yield at a semiconductor surface

NASA Astrophysics Data System (ADS)

Kimura, Kenji; Usui, Satoshi; Nakajima, Kaoru

2000-12-01

We have measured secondary-electron (SE) yield γ induced by 0.5 MeV/u H, He, and Li ions specularly reflected from a SnTe(001) surface. The position-dependent SE production rate is derived from the observed γ. The SE production rate normalized by the observed mean square charge of the reflected ions is almost independent of the atomic number of the projectile ion. This indicates that the surface track potential induced by the projectile ion is negligibly small to affect the SE emission at semiconductor surfaces probably due to rapid relaxation processes.

Distinguishing the road conditions of dry, aquaplane, and frozen by using a three-color infrared camera

NASA Astrophysics Data System (ADS)

Tabuchi, Toru; Yamagata, Shigeki; Tamura, Tetsuo

2003-04-01

There are increasing demands for information to avoid accident in automobile traffic increase. We will discuss that an infrared camera can identify three conditions (dry, aquaplane, frozen) of the road surface. Principles of this method are; 1.We have found 3-color infrared camera can distinguish those conditions using proper data processing 2.The emissivity of the materials on the road surface (conclete, water, ice) differs in three wavelength regions. 3.The sky's temperature is lower than the road's. The emissivity of the road depends on the road surface conditions. Therefore, 3-color infrared camera measure the energy reflected from the sky on the road surface and self radiation of road surface. The road condition can be distinguished by processing the energy pattern measured in three wavelength regions. We were able to collect the experimental results that the emissivity of conclete is differ from water. The infrared camera whose NETD (Noise Equivalent Temperature Difference) at each 3-wavelength is 1.0C or less can distinguish the road conditions by using emissivity difference.

Infrared camera assessment of skin surface temperature--effect of emissivity.

PubMed

Bernard, V; Staffa, E; Mornstein, V; Bourek, A

2013-11-01

Infrared thermoimaging is one of the options for object temperature analysis. Infrared thermoimaging is unique due to the non-contact principle of measurement. So it is often used in medicine and for scientific experimental measurements. The presented work aims to determine whether the measurement results could be influenced by topical treatment of the hand surface by various substances. The authors attempted to determine whether the emissivity can be neglected or not in situations of topical application of substances such as ultrasound gel, ointment, disinfection, etc. The results of experiments showed that the value of surface temperature is more or less distorted by the topically applied substance. Our findings demonstrate the effect of emissivity of applied substances on resulting temperature and showed the necessity to integrate the emissivity into calculation of the final surface temperature. Infrared thermoimaging can be an appropriate method for determining the temperature of organisms, if this is understood as the surface temperature, and the surrounding environment and its temperature is taken into account. Copyright © 2012 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Surface Passivation of CdSe Quantum Dots in All Inorganic Amorphous Solid by Forming Cd1-xZnxSe Shell.

PubMed

Xia, Mengling; Liu, Chao; Zhao, Zhiyong; Wang, Jing; Lin, Changgui; Xu, Yinsheng; Heo, Jong; Dai, Shixun; Han, Jianjun; Zhao, Xiujian

2017-02-07

CdSe quantum dots (QDs) doped glasses have been widely investigated for optical filters, LED color converter and other optical emitters. Unlike CdSe QDs in solution, it is difficult to passivate the surface defects of CdSe QDs in glass matrix, which strongly suppress its intrinsic emission. In this study, surface passivation of CdSe quantum dots (QDs) by Cd 1-x Zn x Se shell in silicate glass was reported. An increase in the Se/Cd ratio can lead to the partial passivation of the surface states and appearance of the intrinsic emission of CdSe QDs. Optimizing the heat-treatment condition promotes the incorporation of Zn into CdSe QDs and results in the quenching of the defect emission. Formation of CdSe/Cd 1-x Zn x Se core/graded shell QDs is evidenced by the experimental results of TEM and Raman spectroscopy. Realization of the surface passivation and intrinsic emission of II-VI QDs may facilitate the wide applications of QDs doped all inorganic amorphous materials.

Land Surface Microwave Emissivities Derived from AMSR-E and MODIS Measurements with Advanced Quality Control

NASA Technical Reports Server (NTRS)

Moncet, Jean-Luc; Liang, Pan; Galantowicz, John F.; Lipton, Alan E.; Uymin, Gennady; Prigent, Catherine; Grassotti, Christopher

2011-01-01

A microwave emissivity database has been developed with data from the Advanced Microwave Scanning Radiometer-EOS (AMSR-E) and with ancillary land surface temperature (LST) data from the Moderate Resolution Imaging Spectroradiometer (MODIS) on the same Aqua spacecraft. The primary intended application of the database is to provide surface emissivity constraints in atmospheric and surface property retrieval or assimilation. An additional application is to serve as a dynamic indicator of land surface properties relevant to climate change monitoring. The precision of the emissivity data is estimated to be significantly better than in prior databases from other sensors due to the precise collocation with high-quality MODIS LST data and due to the quality control features of our data analysis system. The accuracy of the emissivities in deserts and semi-arid regions is enhanced by applying, in those regions, a version of the emissivity retrieval algorithm that accounts for the penetration of microwave radiation through dry soil with diurnally varying vertical temperature gradients. These results suggest that this penetration effect is more widespread and more significant to interpretation of passive microwave measurements than had been previously established. Emissivity coverage in areas where persistent cloudiness interferes with the availability of MODIS LST data is achieved using a classification-based method to spread emissivity data from less-cloudy areas that have similar microwave surface properties. Evaluations and analyses of the emissivity products over homogeneous snow-free areas are presented, including application to retrieval of soil temperature profiles. Spatial inhomogeneities are the largest in the vicinity of large water bodies due to the large water/land emissivity contrast and give rise to large apparent temporal variability in the retrieved emissivities when satellite footprint locations vary over time. This issue will be dealt with in the future by including a water fraction correction. Also note that current reliance on the MODIS day-night algorithm as a source of LST limits the coverage of the database in the Polar Regions. We will consider relaxing the current restriction as part of future development.

The Australian methane budget: Interpreting surface and train-borne measurements using a chemistry transport model

NASA Astrophysics Data System (ADS)

Fraser, Annemarie; Chan Miller, Christopher; Palmer, Paul I.; Deutscher, Nicholas M.; Jones, Nicholas B.; Griffith, David W. T.

2011-10-01

We investigate the Australian methane budget from 2005-2008 using the GEOS-Chem 3D chemistry transport model, focusing on the relative contribution of emissions from different sectors and the influence of long-range transport. To evaluate the model, we use in situ surface measurements of methane, methane dry air column average (XCH4) from ground-based Fourier transform spectrometers (FTSs), and train-borne surface concentration measurements from an in situ FTS along the north-south continental transect. We use gravity anomaly data from Gravity Recovery and Climate Experiment to describe the spatial and temporal distribution of wetland emissions and scale it to a prior emission estimate, which better describes observed atmospheric methane variability at tropical latitudes. The clean air sites of Cape Ferguson and Cape Grim are the least affected by local emissions, while Wollongong, located in the populated southeast with regional coal mining, samples the most locally polluted air masses (2.5% of the total air mass versus <1% at other sites). Averaged annually, the largest single source above background of methane at Darwin is long-range transport, mainly from Southeast Asia, accounting for ˜25% of the change in surface concentration above background. At Cape Ferguson and Cape Grim, emissions from ruminant animals are the largest source of methane above background, at approximately 20% and 30%, respectively, of the surface concentration. At Wollongong, emissions from coal mining are the largest source above background representing 60% of the surface concentration. The train data provide an effective way of observing transitions between urban, desert, and tropical landscapes.

A Modeling Framework for Inference of Surface Emissions Using Mobile Observations

NASA Astrophysics Data System (ADS)

Fasoli, B.; Mitchell, L.; Crosman, E.; Mendoza, D. L.; Lin, J. C.

2016-12-01

Our ability to quantify surface emissions depends on the precision of observations and the spatial density of measurement networks. Mobile measurement techniques offer a cost effective strategy for quantifying atmospheric conditions over space without requiring a dense network of in-situ sites. However, interpretation of these data and inversion of dispersed measurements to estimate surface emissions can be difficult. We introduce a framework using the Stochastic Time-Inverted Lagrangian Transport (STILT) model that assimilates both spatially resolved observations and an emissions inventory to better estimate surface fluxes. Salt Lake City is a unique laboratory for the study of urban carbon emissions. It is the only U.S. city that utilizes light-rail trains to continuously measure high frequency carbon dioxide (CO2) and methane (CH4); it is home to one of the longest and most spatially resolved high precision CO2 measurement networks (air.utah.edu); and it is one of four cities in the world for which the Hestia anthropogenic emissions inventory has been produced which characterizes CO2 emissions at the scale of individual buildings and roadways. Using these data and modeling resources, we evaluate spatially resolved CO2 measurements and transported CO2 emissions on hourly timescales at a dense spatial resolution across Salt Lake City.

Surface emissivity and temperature retrieval for a hyperspectral sensor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Borel, C.C.

1998-12-01

With the growing use of hyper-spectral imagers, e.g., AVIRIS in the visible and short-wave infrared there is hope of using such instruments in the mid-wave and thermal IR (TIR) some day. The author believes that this will enable him to get around using the present temperature-emissivity separation algorithms using methods which take advantage of the many channels available in hyper-spectral imagers. A simple fact used in coming up with a novel algorithm is that a typical surface emissivity spectrum are rather smooth compared to spectral features introduced by the atmosphere. Thus, a iterative solution technique can be devised which retrievesmore » emissivity spectra based on spectral smoothness. To make the emissivities realistic, atmospheric parameters are varied using approximations, look-up tables derived from a radiative transfer code and spectral libraries. One such iterative algorithm solves the radiative transfer equation for the radiance at the sensor for the unknown emissivity and uses the blackbody temperature computed in an atmospheric window to get a guess for the unknown surface temperature. By varying the surface temperature over a small range a series of emissivity spectra are calculated. The one with the smoothest characteristic is chosen. The algorithm was tested on synthetic data using MODTRAN and the Salisbury emissivity database.« less

Analysis of particulate emissions from tropical biomass burning using a global aerosol model and long-term surface observations

NASA Astrophysics Data System (ADS)

Reddington, Carly L.; Spracklen, Dominick V.; Artaxo, Paulo; Ridley, David A.; Rizzo, Luciana V.; Arana, Andrea

2016-09-01

We use the GLOMAP global aerosol model evaluated against observations of surface particulate matter (PM2.5) and aerosol optical depth (AOD) to better understand the impacts of biomass burning on tropical aerosol over the period 2003 to 2011. Previous studies report a large underestimation of AOD over regions impacted by tropical biomass burning, scaling particulate emissions from fire by up to a factor of 6 to enable the models to simulate observed AOD. To explore the uncertainty in emissions we use three satellite-derived fire emission datasets (GFED3, GFAS1 and FINN1). In these datasets the tropics account for 66-84 % of global particulate emissions from fire. With all emission datasets GLOMAP underestimates dry season PM2.5 concentrations in regions of high fire activity in South America and underestimates AOD over South America, Africa and Southeast Asia. When we assume an upper estimate of aerosol hygroscopicity, underestimation of AOD over tropical regions impacted by biomass burning is reduced relative to previous studies. Where coincident observations of surface PM2.5 and AOD are available we find a greater model underestimation of AOD than PM2.5, even when we assume an upper estimate of aerosol hygroscopicity. Increasing particulate emissions to improve simulation of AOD can therefore lead to overestimation of surface PM2.5 concentrations. We find that scaling FINN1 emissions by a factor of 1.5 prevents underestimation of AOD and surface PM2.5 in most tropical locations except Africa. GFAS1 requires emission scaling factor of 3.4 in most locations with the exception of equatorial Asia where a scaling factor of 1.5 is adequate. Scaling GFED3 emissions by a factor of 1.5 is sufficient in active deforestation regions of South America and equatorial Asia, but a larger scaling factor is required elsewhere. The model with GFED3 emissions poorly simulates observed seasonal variability in surface PM2.5 and AOD in regions where small fires dominate, providing independent evidence that GFED3 underestimates particulate emissions from small fires. Seasonal variability in both PM2.5 and AOD is better simulated by the model using FINN1 emissions. Detailed observations of aerosol properties over biomass burning regions are required to better constrain particulate emissions from fires.

Ag-protein plasmonic architectures for surface plasmon-coupled emission enhancements and Fabry-Perot mode-coupled directional fluorescence emission

NASA Astrophysics Data System (ADS)

Badiya, Pradeep Kumar; Patnaik, Sai Gourang; Srinivasan, Venkatesh; Reddy, Narendra; Manohar, Chelli Sai; Vedarajan, Raman; Mastumi, Noriyoshi; Belliraj, Siva Kumar; Ramamurthy, Sai Sathish

2017-10-01

We report the use of silver decorated plant proteins as spacer material for augmented surface plasmon-coupled emission (120-fold enhancement) and plasmon-enhanced Raman scattering. We extracted several proteins from different plant sources [Triticum aestivum (TA), Aegle marmelos (AM), Ricinus communis (RC), Jatropha curcas (JC) and Simarouba glauca (SG)] followed by evaluation of their optical properties and simulations to rationalize observed surface plasmon resonance. Since the properties exhibited by protein thin films is currently gaining research interest, we have also carried out simulation studies with Ag-protein biocomposites as spacer materials in metal-dielectric-metal planar microcavity architecture for guided emission of Fabry-Perot mode-coupled fluorescence.

Exoelectronic emission of particles of lunar surface material

NASA Technical Reports Server (NTRS)

Mints, R. I.; Alimov, V. I.; Melekhin, V. P.; Milman, I. I.; Kryuk, V. I.; Kunin, L. L.; Tarasov, L. S.

1974-01-01

A secondary electron multiplier was used to study the thermostimulated exoelectronic emission of particles of lunar surface material returned by the Soviet Luna 16 automatic station. The natural exoemission from fragments of slag, glass, anorthosite, and a metallic particle was recorded in the isochronic and isothermal thermostimulation regimes. The temperature of emission onset depended on the type of regolith fragment. For the first three particles the isothermal drop in emission is described by first-order kinetic equations. For the anorthosite fragment, exoemission at constant temperature is characterized by a symmetric curve with a maximum. These data indicate the presence of active surface defects, whose nature can be due to the prehistory of the particles.

Surface Coating of Miscellaneous Metal Parts and Products: National Emission Standards for Hazardous Air Pollutants (NESHAP)

EPA Pesticide Factsheets

Read this regulation on emission standards for miscellaneous metal parts and surface coatings. Read the rule history and summary, and find related documents including fact sheets, related rules, and compliance timelines

Role of vanguard counter-potential in terahertz emission due to surface currents explicated by three-dimensional ensemble Monte Carlo simulation

NASA Astrophysics Data System (ADS)

Cortie, D. L.; Lewis, R. A.

2011-10-01

The discovery that short pulses of near-infrared radiation striking a semiconductor may lead to emission of radiation at terahertz frequencies paved the way for terahertz time-domain spectroscopy. Previous modeling has allowed the physical mechanisms to be understood in general terms but it has not fully explored the role of key physical parameters of the emitter material nor has it fully revealed the competing nature of the surface-field and photo-Dember effects. In this context, our purpose has been to more fully explicate the mechanisms of terahertz emission from transient currents at semiconductor surfaces and to determine the criteria for efficient emission. To achieve this purpose we employ an ensemble Monte Carlo simulation in three dimensions. To ground the calculations, we focus on a specific emitter, InAs. We separately vary distinct physical parameters to determine their specific contribution. We find that scattering as a whole has relatively little impact on the terahertz emission. The emission is found to be remarkably resistant to alterations of the dark surface potential. Decreasing the band gap leads to a strong increase in terahertz emission, as does decreasing the electron mass. Increasing the absorption dramatically influences the peak-peak intensity and peak shape. We conclude that increasing absorption is the most direct path to improve surface-current semiconductor terahertz emitters. We find for longer pump pulses that the emission is limited by a newly identified vanguard counter-potential mechanism: Electrons at the leading edge of longer laser pulses repel subsequent electrons. This discovery is the main result of our work.

Total vertical sediment flux and PM10 emissions from disturbed Chihuahuan Desert Surfaces

USDA-ARS?s Scientific Manuscript database

Desert surfaces are typically stable and represent some of the oldest landforms on Earth. For surfaces without vegetation, the evolution of a desert pavements of gravel protects the surface from erosive forces and vegetation further protects the surface in arid and semi-arid rangelands. The suscep...

Constraining the uncertainty in emissions over India with a regional air quality model evaluation

NASA Astrophysics Data System (ADS)

Karambelas, Alexandra; Holloway, Tracey; Kiesewetter, Gregor; Heyes, Chris

2018-02-01

To evaluate uncertainty in the spatial distribution of air emissions over India, we compare satellite and surface observations with simulations from the U.S. Environmental Protection Agency (EPA) Community Multi-Scale Air Quality (CMAQ) model. Seasonally representative simulations were completed for January, April, July, and October 2010 at 36 km × 36 km using anthropogenic emissions from the Greenhouse Gas-Air Pollution Interaction and Synergies (GAINS) model following version 5a of the Evaluating the Climate and Air Quality Impacts of Short-Lived Pollutants project (ECLIPSE v5a). We use both tropospheric columns from the Ozone Monitoring Instrument (OMI) and surface observations from the Central Pollution Control Board (CPCB) to closely examine modeled nitrogen dioxide (NO2) biases in urban and rural regions across India. Spatial average evaluation with satellite retrievals indicate a low bias in the modeled tropospheric column (-63.3%), which reflects broad low-biases in majority non-urban regions (-70.1% in rural areas) across the sub-continent to slightly lesser low biases reflected in semi-urban areas (-44.7%), with the threshold between semi-urban and rural defined as 400 people per km2. In contrast, modeled surface NO2 concentrations exhibit a slight high bias of +15.6% when compared to surface CPCB observations predominantly located in urban areas. Conversely, in examining extremely population dense urban regions with more than 5000 people per km2 (dense-urban), we find model overestimates in both the column (+57.8) and at the surface (+131.2%) compared to observations. Based on these results, we find that existing emission fields for India may overestimate urban emissions in densely populated regions and underestimate rural emissions. However, if we rely on model evaluation with predominantly urban surface observations from the CPCB, comparisons reflect model high biases, contradictory to the knowledge gained using satellite observations. Satellites thus serve as an important emissions and model evaluation metric where surface observations are lacking, such as rural India, and support improved emissions inventory development.

Surface charge accumulation of solid insulator under nanosecond pulse in vacuum: 3D distribution features and mechanism

NASA Astrophysics Data System (ADS)

Qi, Bo; Gao, Chunjia; Sun, Zelai; Li, Chengrong

2017-11-01

Surface charge accumulation can incur changes in electric field distribution, involved in the electron propagation process, and result in a significant decrease in the surface flashover voltage. The existing 2D surface charge measurement fails to meet the actual needs in real engineering applications that usually adopt the 45° conical frustum insulators. The present research developed a novel 3D measurement platform to capture surface charge distribution on solid insulation under nanosecond pulse in a vacuum. The results indicate that all surface charges are positive under a positive pulse and negative under a negative pulse. Surface charges tend to accumulate more near the upper electrode. Surface charge density increases significantly with the increase in pulse counts and amplitudes. Accumulation of surface charge results in a certain decrease of flashover voltage. Taking consideration of the secondary electron emission for the surface charge accumulation, four materials were obtained to demonstrate the effects on surface charge. Combining the effect incurred by secondary electron emission and the weighty action taken by surface charge accumulation on the flashover phenomena, the discharge mechanism along the insulator surface under nanosecond pulse voltage was proposed.

A generalised model for traffic induced road dust emissions. Model description and evaluation

NASA Astrophysics Data System (ADS)

Berger, Janne; Denby, Bruce

2011-07-01

This paper concerns the development and evaluation of a new and generalised road dust emission model. Most of today's road dust emission models are based on local measurements and/or contain empirical emission factors that are specific for a given road environment. In this study, a more generalised road dust emission model is presented and evaluated. We have based the emissions on road, tyre and brake wear rates and used the mass balance concept to describe the build-up of road dust on the road surface and road shoulder. The model separates the emissions into a direct part and a resuspension part, and treats the road surface and road shoulder as two different sources. We tested the model under idealized conditions as well as on two datasets in and just outside of Oslo in Norway during the studded tyre season. We found that the model reproduced the observed increase in road dust emissions directly after drying of the road surface. The time scale for the build-up of road dust on the road surface is less than an hour for medium to heavy traffic density. The model performs well for temperatures above 0 °C and less well during colder periods. Since the model does not yet include salting as an additional mass source, underestimations are evident under dry periods with temperatures around 0 °C, under which salting occurs. The model overestimates the measured PM 10 (particulate matter less than 10 μm in diameter) concentrations under heavy precipitation events since the model does not take the amount of precipitation into account. There is a strong sensitivity of the modelled emissions to the road surface conditions and the current parameterisations of the effect of precipitation, runoff and evaporation seem inadequate.

An Automatic Instrument to Study the Spatial Scaling Behavior of Emissivity

PubMed Central

Tian, Jing; Zhang, Renhua; Su, Hongbo; Sun, Xiaomin; Chen, Shaohui; Xia, Jun

2008-01-01

In this paper, the design of an automatic instrument for measuring the spatial distribution of land surface emissivity is presented, which makes the direct in situ measurement of the spatial distribution of emissivity possible. The significance of this new instrument lies in two aspects. One is that it helps to investigate the spatial scaling behavior of emissivity and temperature; the other is that, the design of the instrument provides theoretical and practical foundations for the implement of measuring distribution of surface emissivity on airborne or spaceborne. To improve the accuracy of the measurements, the emissivity measurement and its uncertainty are examined in a series of carefully designed experiments. The impact of the variation of target temperature and the environmental irradiance on the measurement of emissivity is analyzed as well. In addition, the ideal temperature difference between hot environment and cool environment is obtained based on numerical simulations. Finally, the scaling behavior of surface emissivity caused by the heterogeneity of target is discussed. PMID:27879735

The Chandra M10l Megasecond: Diffuse Emission

NASA Technical Reports Server (NTRS)

Kuntz, K. D.; Snowden, S. L.

2009-01-01

Because MIOl is nearly face-on, it provides an excellent laboratory in which to study the distribution of X-ray emitting gas in a typical late-type spiral galaxy. We obtained a Chandra observation with a cumulative exposure of roughly 1 Ms to study the diffuse X-ray emission in MlOl. The bulk of the X-ray emission is correlated with the star formation traced by the FUV emission. The global FUV/Xray correlation is non-linear (the X-ray surface brightness is roughly proportional to the square root of the FUV surface brightness) and the small-scale correlation is poor, probably due to the delay between the FUV emission and the X-ray production ill star-forming regions. The X-ray emission contains only minor contributions from unresolved stars (approximates less than 3%), unresolved X-ray point sources (approximates less than 4%), and individual supernova remnants (approximates 3%). The global spectrum of the diffuse emission can be reasonably well fitted with a three component thermal model, but the fitted temperatures are not unique; many distributions of emission measure can produce the same temperatures when observed with the current CCD energy resolution. The spectrum of the diffuse emission depends on the environment; regions with higher X-ray surface brightnesses have relatively stronger hard components, but there is no significant evidence that the temperatures of the emitting components increase with surface brightness.

A noncontacting scanning photoelectron emission technique for bonding surface cleanliness inspection

NASA Technical Reports Server (NTRS)

Gause, Raymond L.

1989-01-01

Molecular contamination of bonding surfaces can drastically affect the bond strength that can be achieved and therefore the structural integrity and reliability of the bonded part. The presence of thin contaminant films on bonding surfaces can result from inadequate or incomplete cleaning methods, from oxide growth during the time between cleaning (such as grit blasting) and bonding, or from failure to properly protect cleaned surfaces from oils, greases, fingerprints, release agents, or deposition of facility airborne molecules generated by adjacent manufacturing or processing operations. Required cleanliness levels for desired bond performance can be determined by testing to correlate bond strength with contaminant type and quantity, thereby establishing the degree of contamination that can be tolerated based on the strength that is needed. Once the maximum acceptable contaminant level is defined, a method is needed to quantitatively measure the contaminant level on the bonding surface prior to bonding to verify that the surface meets the established cleanliness requirement. A photoelectron emission technique for the nondestructive inspection of various bonding surfaces, both metallic and nonmetallic, to provide quantitative data on residual contaminant levels is described. The technique can be used to scan surfaces at speeds of at least 30 ft/min using a servo system to maintain required sensor to surface spacing. The fundamental operation of the photoelectron emission sensor system is explained and the automated scanning system and computer data acquisition hardware and software are described.

Analysis of Abrasive Blasting of DOP-26 Iridium Alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ohriner, Evan Keith; Zhang, Wei; Ulrich, George B

2012-01-01

The effects of abrasive blasting on the surface geometry and microstructure of DOP-26 iridium alloy (Ir-0.3% W-0.006% Th 0.005% Al) have been investigated. Abrasive blasting has been used to control emissivity of components operating at elevated temperature. The effects of abrasive blasting conditions on surface morphology were investigated both experimentally and by numerical modeling. The simplified model, based on finite element analysis of a single angular particle impacting on Ir alloy disk, calculates the surface deformation and residual strain distribution. The experimental results and modeling results both indicate that the surface geometry is not sensitive to the abrasive blast processmore » conditions of nozzle pressure and standoff distance considered in this study. On the other hand, the modeling results suggest that the angularity of the abrasive particle has an important role in determining surface geometry, which in turn, affects the emissivity. Abrasive blasting causes localized surface strains and localized recrystallization, but it does not affect grain size following extended exposure at elevated temperature. The dependence of emissivity of the DOP-26 alloy on mean surface slope follows a similar trend to that reported for pure iridium.« less

40 CFR 61.344 - Standards: Surface impoundments.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 9 2012-07-01 2012-07-01 false Standards: Surface impoundments. 61.344 Section 61.344 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) NATIONAL EMISSION STANDARDS FOR HAZARDOUS AIR POLLUTANTS National Emission Standard for Benzene...

40 CFR 61.344 - Standards: Surface impoundments.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 8 2010-07-01 2010-07-01 false Standards: Surface impoundments. 61.344 Section 61.344 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) NATIONAL EMISSION STANDARDS FOR HAZARDOUS AIR POLLUTANTS National Emission Standard for Benzene...

Double-pulse femtosecond laser peening of aluminum alloy AA5038: Effect of inter-pulse delay on transient optical plume emission and final surface micro-hardness

NASA Astrophysics Data System (ADS)

Ageev, E. I.; Bychenkov, V. Yu.; Ionin, A. A.; Kudryashov, S. I.; Petrov, A. A.; Samokhvalov, A. A.; Veiko, V. P.

2016-11-01

Double-pulse ablative femtosecond laser peening of the AA5038 aluminum alloy surface in the phase explosion regime results in its enhanced microhardness, which monotonously decreases till the initial value versus inter-pulse delay, increasing on a sub-nanosecond timescale. Optical emission spectroscopy of the double-pulse ablative plume reveals the same trend in the yield of the corresponding atomic and ion emission versus inter-pulse delay, enlightening the interaction of the second femtosecond laser pump pulse with the surface and the resulting plume.

Emission and evaporation properties of 75 at.% Re-25 at.% W mixed matrix impregnated cathode

NASA Astrophysics Data System (ADS)

Lai, Chen; Wang, Jinshu; Zhou, Fan; Liu, Wei; den Engelsen, Daniel; Miao, Naihua

2018-01-01

We present a comprehensive study on the phase, emission performance, surface composition, chemical states and evaporation properties of a 75 at.% Re-25 at.% W (75Re) mixed matrix impregnated cathode by several modern analyzers, including XRD, electron emission test device, in situ AES, XPS and Quartz Crystal Oscillation Instrument (QCOI). On the basis of experimental results, the adsorption energy and charge transfer of the Ba-O dipole adsorbed on cathode surface was investigated by the first-principles density functional theory calculations. The in situ AES analyses indicate that the atomic ratio of Ba:O of the active emission layer on the cathode surface converged to 3:2 for a conventional Ba-W cathode and to about 3:1 for the 75Re cathode. Due to the larger adsorption energy of Ba and Ba-O on 75Re cathode surface, the total evaporation rate of Ba and BaO in the 75Re cathode is much lower than that for the Ba-W cathode, which is agreed favorably with the experimental evaporation data. Our characterizations and calculations suggest that rhenium in the matrix of impregnated cathodes improves the stability of Ba-O dipole on the cathode surface and enhances the emission capability substantially.

Nitrous Oxide Emissions From Northern Forested and Harvested Ecosystems

NASA Astrophysics Data System (ADS)

Kavanaugh, K. M.; Kellman, L. M.

2005-12-01

Very little is known about how deforestation alters the soil subsurface production and surface emissions of N2O from northern forest soils. Soil N2O surface fluxes and subsurface concentrations from two 3 year old harvested and intact forest pairs of contrasting soil texture were monitored during the 2004 and 2005 growing seasons in the Acadian forest of Atlantic Canada in order to: 1) quantify N2O emissions associated with each land-use type, 2) examine spatial and temporal variations in subsurface concentrations and surface fluxes at each site, and 3) determine the suitability of a photoacoustic gas monitor (PGM) for in- situ field measurements vs. field sample collection and laboratory analysis on a gas chromatograph. Each site was instrumented with 11 permanent collars for surface flux measurements designed to capture the microsite variability at the sites. Subsurface soil gas samplers, designed to identify the important zones of N2O production in the vertical profile were installed at depths of 0, 10, 20 and 35 cm below the organic-mineral soil interface. Surface fluxes were measured with non-steady-state vented surface flux chambers with measurements of all surface flux and subsurface data made on a bi-weekly basis. Results suggest that spatial and temporal variability in surface emissions are very high and routinely close to zero. Subsurface profile concentration data shows vertical concentration profiles at intact forest sites with concentrations close to atmospheric, while harvested sites show a pattern of increasing N2O concentration with depth, reaching a maximum of approximately 27000ppb at 35cm.

Surface-emitting stimulated emission in high-quality ZnO thin films

NASA Astrophysics Data System (ADS)

Zhang, X. Q.; Suemune, Ikuo; Kumano, H.; Wang, J.; Huang, S. H.

2004-10-01

High-quality ZnO thin films were grown by plasma-enhanced molecular-beam epitaxy on sapphire substrates. Three excitonic transitions associated with the valence bands A, B, and C were clearly revealed in the reflectance spectrum measured at 33K. This result indicates that the ZnO thin films have the wurtzite crystalline structure. The emission spectra were measured with backscattering geometry at room temperature. When the excitation exceeded a certain value, linewidth narrowing, nonlinear rise of emission intensity, and the shortening of the carrier lifetime were clearly observed and these demonstrate the onset of stimulated emission. Together with the ZnO thickness dependence, we conclude that the observation of a stimulated emission in a direction perpendicular to the film surface is predominantly due to scattering of the in-plane stimulated emission by slightly remaining surface undulations in the ZnO films.

Ozone-surface interactions: Investigations of mechanisms, kinetics, mass transport, and implications for indoor air quality

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morrison, Glenn Charles

1999-12-01

In this dissertation, results are presented of laboratory investigations and mathematical modeling efforts designed to better understand the interactions of ozone with surfaces. In the laboratory, carpet and duct materials were exposed to ozone and measured ozone uptake kinetics and the ozone induced emissions of volatile organic compounds. To understand the results of the experiments, mathematical methods were developed to describe dynamic indoor aldehyde concentrations, mass transport of reactive species to smooth surfaces, the equivalent reaction probability of whole carpet due to the surface reactivity of fibers and carpet backing, and ozone aging of surfaces. Carpets, separated carpet fibers, andmore » separated carpet backing all tended to release aldehydes when exposed to ozone. Secondary emissions were mostly n-nonanal and several other smaller aldehydes. The pattern of emissions suggested that vegetable oils may be precursors for these oxidized emissions. Several possible precursors and experiments in which linseed and tung oils were tested for their secondary emission potential were discussed. Dynamic emission rates of 2-nonenal from a residential carpet may indicate that intermediate species in the oxidation of conjugated olefins can significantly delay aldehyde emissions and act as reservoir for these compounds. The ozone induced emission rate of 2-nonenal, a very odorous compound, can result in odorous indoor concentrations for several years. Surface ozone reactivity is a key parameter in determining the flux of ozone to a surface, is parameterized by the reaction probability, which is simply the probability that an ozone molecule will be irreversibly consumed when it strikes a surface. In laboratory studies of two residential and two commercial carpets, the ozone reaction probability for carpet fibers, carpet backing and the equivalent reaction probability for whole carpet were determined. Typically reaction probability values for these materials were 10 -7, 10 -5, and 10 -5 respectively. To understand how internal surface area influences the equivalent reaction probability of whole carpet, a model of ozone diffusion into and reaction with internal carpet components was developed. This was then used to predict apparent reaction probabilities for carpet. He combines this with a modified model of turbulent mass transfer developed by Liu, et al. to predict deposition rates and indoor ozone concentrations. The model predicts that carpet should have an equivalent reaction probability of about 10 -5, matching laboratory measurements of the reaction probability. For both carpet and duct materials, surfaces become progressively quenched (aging), losing the ability to react or otherwise take up ozone. He evaluated the functional form of aging and find that the reaction probability follows a power function with respect to the cumulative uptake of ozone. To understand ozone aging of surfaces, he developed several mathematical descriptions of aging based on two different mechanisms. The observed functional form of aging is mimicked by a model which describes ozone diffusion with internal reaction in a solid. He shows that the fleecy nature of carpet materials in combination with the model of ozone diffusion below a fiber surface and internal reaction may explain the functional form and the magnitude of power function parameters observed due to ozone interactions with carpet. The ozone induced aldehyde emissions, measured from duct materials, were combined with an indoor air quality model to show that concentrations of aldehydes indoors may approach odorous levels. He shows that ducts are unlikely to be a significant sink for ozone due to the low reaction probability in combination with the short residence time of air in ducts.« less

Areas of Weakly Anomalous to Anomalous Surface Temperature in Chaffee County, Colorado, as Identified from ASTER Thermal Data

DOE Data Explorer

Khalid Hussein

2012-02-01

Note: This "Weakly Anomalous to Anomalous Surface Temperature" dataset differs from the "Anomalous Surface Temperature" dataset for this county (another remotely sensed CIRES product) by showing areas of modeled temperatures between 1o and 2o above the mean, as opposed to the greater than 2o temperatures contained in the "Anomalous Surface Temperature" dataset. This layer contains areas of anomalous surface temperature in Chaffee County identified from ASTER thermal data and spatial based insolation model. The temperature is calculated using the Emissivity Normalization Algorithm that separate temperature from emissivity. The incoming solar radiation was calculated using spatial based insolation model developed by Fu and Rich (1999). Then the temperature due to solar radiation was calculated using emissivity derived from ASTER data. The residual temperature, i.e. temperature due to solar radiation subtracted from ASTER temperature was used to identify thermally anomalous areas. Areas that had temperature greater than 2o were considered ASTER modeled very warm surface exposures (thermal anomalies). Note: 'o' is used in this description to represent lowercase sigma.

Areas of Weakly Anomalous to Anomalous Surface Temperature in Garfield County, Colorado, as Identified from ASTER Thermal Data

DOE Data Explorer

Khalid Hussein

2012-02-01

Note: This "Weakly Anomalous to Anomalous Surface Temperature" dataset differs from the "Anomalous Surface Temperature" dataset for this county (another remotely sensed CIRES product) by showing areas of modeled temperatures between 1o and 2o above the mean, as opposed to the greater than 2o temperatures contained in the "Anomalous Surface Temperature" dataset. This layer contains areas of anomalous surface temperature in Garfield County identified from ASTER thermal data and spatial based insolation model. The temperature is calculated using the Emissivity Normalization Algorithm that separate temperature from emissivity. The incoming solar radiation was calculated using spatial based insolation model developed by Fu and Rich (1999). Then the temperature due to solar radiation was calculated using emissivity derived from ASTER data. The residual temperature, i.e. temperature due to solar radiation subtracted from ASTER temperature was used to identify thermally anomalous areas. Areas that had temperature between 1o and 2o were considered ASTER modeled warm surface exposures (thermal anomalies) Note: 'o' is used in this description to represent lowercase sigma.

Areas of Weakly Anomalous to Anomalous Surface Temperature in Routt County, Colorado, as Identified from ASTER Thermal Data

DOE Data Explorer

Khalid Hussein

2012-02-01

Note: This "Weakly Anomalous to Anomalous Surface Temperature" dataset differs from the "Anomalous Surface Temperature" dataset for this county (another remotely sensed CIRES product) by showing areas of modeled temperatures between 1o and 2o above the mean, as opposed to the greater than 2o temperatures contained in the "Anomalous Surface Temperature" dataset. This layer contains areas of anomalous surface temperature in Routt County identified from ASTER thermal data and spatial based insolation model. The temperature is calculated using the Emissivity Normalization Algorithm that separate temperature from emissivity. The incoming solar radiation was calculated using spatial based insolation model developed by Fu and Rich (1999). Then the temperature due to solar radiation was calculated using emissivity derived from ASTER data. The residual temperature, i.e. temperature due to solar radiation subtracted from ASTER temperature was used to identify thermally anomalous areas. Areas that had temperature between 1o and 2o were considered ASTER modeled warm surface exposures (thermal anomalies). Note: 'o' is used in this description to represent lowercase sigma.

Areas of Weakly Anomalous to Anomalous Surface Temperature in Dolores County, Colorado, as Identified from ASTER Thermal Data

DOE Data Explorer

Khalid Hussein

2012-02-01

Note: This "Weakly Anomalous to Anomalous Surface Temperature" dataset differs from the "Anomalous Surface Temperature" dataset for this county (another remotely sensed CIRES product) by showing areas of modeled temperatures between 1o and 2o above the mean, as opposed to the greater than 2o temperatures contained in the "Anomalous Surface Temperature" dataset. This layer contains areas of anomalous surface temperature in Dolores County identified from ASTER thermal data and spatial based insolation model. The temperature is calculated using the Emissivity Normalization Algorithm that separate temperature from emissivity. The incoming solar radiation was calculated using spatial based insolation model developed by Fu and Rich (1999). Then the temperature due to solar radiation was calculated using emissivity derived from ASTER data. The residual temperature, i.e. temperature due to solar radiation subtracted from ASTER temperature was used to identify thermally anomalous areas. Areas that had temperature greater than 2o were considered ASTER modeled very warm surface exposures (thermal anomalies) Note: 'o' is used in this description to represent lowercase sigma.

Areas of Weakly Anomalous to Anomalous Surface Temperature in Archuleta County, Colorado, as Identified from ASTER Thermal Data

DOE Data Explorer

Khalid Hussein

2012-02-01

Note: This "Weakly Anomalous to Anomalous Surface Temperature" dataset differs from the "Anomalous Surface Temperature" dataset for this county (another remotely sensed CIRES product) by showing areas of modeled temperatures between 1o and 2o above the mean, as opposed to the greater than 2o temperatures contained in the "Anomalous Surface Temperature" dataset. This layer contains areas of anomalous surface temperature in Archuleta County identified from ASTER thermal data and spatial based insolation model. The temperature is calculated using the Emissivity Normalization Algorithm that separate temperature from emissivity. The incoming solar radiation was calculated using spatial based insolation model developed by Fu and Rich (1999). Then the temperature due to solar radiation was calculated using emissivity derived from ASTER data. The residual temperature, i.e. temperature due to solar radiation subtracted from ASTER temperature was used to identify thermally anomalous areas. Areas that had temperature between 1o and 2o were considered ASTER modeled warm surface exposures (thermal anomalies). Note: 'o' is used in this description to represent lowercase sigma.

40 CFR 63.3092 - How must I control emissions from my electrodeposition primer system if I want to comply with the...

Code of Federal Regulations, 2011 CFR

2011-07-01

... electrodeposition primer system if I want to comply with the combined primer-surfacer, topcoat, final repair, glass bonding primer, and glass bonding adhesive emission limit? 63.3092 Section 63.3092 Protection of...-surfacer, topcoat, final repair, glass bonding primer, and glass bonding adhesive emission limit? If your...

40 CFR 63.3092 - How must I control emissions from my electrodeposition primer system if I want to comply with the...

Code of Federal Regulations, 2010 CFR

2010-07-01

... electrodeposition primer system if I want to comply with the combined primer-surfacer, topcoat, final repair, glass bonding primer, and glass bonding adhesive emission limit? 63.3092 Section 63.3092 Protection of...-surfacer, topcoat, final repair, glass bonding primer, and glass bonding adhesive emission limit? If your...

Emissivity measurement of coated copper and aluminum samples at 80 K

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, S. H.; Conway, Z. A.; Ostroumov, P. N.

Accelerator cryomodules reduce the radiative thermal load to the 1.8 – 4.5 K components by enclosing them within low-emissivity shields cooled to 70–100 K. These heat shields are not continuous and have many penetrations, or holes, to allow for the connection of support structures and the many subsystems running from room temperature. The penetrations have thermal baffles to reduce, or eliminate if possible, the direct line-of-sight between room temperature and the lower temperature components but leave many, low emissivity, paths with only a single reflection required for the room temperature photons to strike the 1.8 – 4.5 K surfaces. Tomore » reduce this we are coating our baffles such that the surfaces which face lower temperatures have a low-emissivity while the surfaces which the photons may reflect from but do not have line-of-sight to lower temperature surfaces have a high-absorption. We measure emissivities of different coatings from the heat balance between absorption, from background radiation and the heater attached on the sample, and emission powers. In this paper, design details of our experiment and measurement results will be presented.« less

Comparative study of radiometric and calorimetric methods for total hemispherical emissivity measurements

NASA Astrophysics Data System (ADS)

Monchau, Jean-Pierre; Hameury, Jacques; Ausset, Patrick; Hay, Bruno; Ibos, Laurent; Candau, Yves

2018-05-01

Accurate knowledge of infrared emissivity is important in applications such as surface temperature measurements by infrared thermography or thermal balance for building walls. A comparison of total hemispherical emissivity measurement was performed by two laboratories: the Laboratoire National de Métrologie et d'Essais (LNE) and the Centre d'Études et de Recherche en Thermique, Environnement et Systèmes (CERTES). Both laboratories performed emissivity measurements on four samples, chosen to cover a large range of emissivity values and angular reflectance behaviors. The samples were polished aluminum (highly specular, low emissivity), bulk PVC (slightly specular, high emissivity), sandblasted aluminum (diffuse surface, medium emissivity), and aluminum paint (slightly specular surface, medium emissivity). Results obtained using five measurement techniques were compared. LNE used a calorimetric method for direct total hemispherical emissivity measurement [1], an absolute reflectometric measurement method [2], and a relative reflectometric measurement method. CERTES used two total hemispherical directional reflectometric measurement methods [3, 4]. For indirect techniques by reflectance measurements, the total hemispherical emissivity values were calculated from directional hemispherical reflectance measurement results using spectral integration when required and directional to hemispherical extrapolation. Results were compared, taking into account measurement uncertainties; an added uncertainty was introduced to account for heterogeneity over the surfaces of the samples and between samples. All techniques gave large relative uncertainties for a low emissive and very specular material (polished aluminum), and results were quite scattered. All the indirect techniques by reflectance measurement gave results within ±0.01 for a high emissivity material. A commercial aluminum paint appears to be a good candidate for producing samples with medium level of emissivity (about 0.4) and with good uniformity of emissivity values (within ±0.015).

Comparison of in-situ measurements and satellite-derived surface emissivity over Italian volcanic areas

NASA Astrophysics Data System (ADS)

Silvestri, Malvina; Musacchio, Massimo; Cammarano, Diego; Fabrizia Buongiorno, Maria; Amici, Stefania; Piscini, Alessandro

2016-04-01

In this work we compare ground measurements of emissivity collected during dedicated fields campaign on Mt. Etna and Solfatara of Pozzuoli volcanoes and acquired by means of Micro-FTIR (Fourier Thermal Infrared spectrometer) instrument with the emissivity obtained by using single ASTER data (Advanced Spaceborne Thermal Emission and Reflection Radiometer, ASTER 05) and the ASTER emissivity map extract from ASTER Global Emissivity Database (GED), released by LP DAAC on April 2, 2014. The database was developed by the National Aeronautics and Space Administration's (NASA) Jet Propulsion Laboratory (JPL), California Institute of Technology. The database includes land surface emissivity derived from ASTER data acquired over the contiguous United States, Africa, Arabian Peninsula, Australia, Europe, and China. Through this analysis we want to investigate the differences existing between the ASTER-GED dataset (average from 2000 to 2008 seasoning independent) and fall in-situ emissivity measurement. Moreover the role of different spatial resolution characterizing ASTER and MODIS, 90mt and 1km respectively, by comparing them with in situ measurements, is analyzed. Possible differences can be due also to the different algorithms used for the emissivity estimation, Temperature and Emissivity Separation algorithm for ASTER TIR band( Gillespie et al, 1998) and the classification-based emissivity method (Snyder and al, 1998) for MODIS. Finally land surface temperature products generated using ASTER-GED and ASTER 05 emissivity are also analyzed. Gillespie, A. R., Matsunaga, T., Rokugawa, S., & Hook, S. J. (1998). Temperature and emissivity separation from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images. IEEE Transactions on Geoscience and Remote Sensing, 36, 1113-1125. Snyder, W.C., Wan, Z., Zhang, Y., & Feng, Y.-Z. (1998). Classification-based emissivity for land surface temperature measurement from space. International Journal of Remote Sensing, 19, 2753-2574.

Road Asphalt Pavements Analyzed by Airborne Thermal Remote Sensing: Preliminary Results of the Venice Highway

PubMed Central

Pascucci, Simone; Bassani, Cristiana; Palombo, Angelo; Poscolieri, Maurizio; Cavalli, Rosa

2008-01-01

This paper describes a fast procedure for evaluating asphalt pavement surface defects using airborne emissivity data. To develop this procedure, we used airborne multispectral emissivity data covering an urban test area close to Venice (Italy).For this study, we first identify and select the roads' asphalt pavements on Multispectral Infrared Visible Imaging Spectrometer (MIVIS) imagery using a segmentation procedure. Next, since in asphalt pavements the surface defects are strictly related to the decrease of oily components that cause an increase of the abundance of surfacing limestone, the diagnostic absorption emissivity peak at 11.2μm of the limestone was used for retrieving from MIVIS emissivity data the areas exhibiting defects on asphalt pavements surface.The results showed that MIVIS emissivity allows establishing a threshold that points out those asphalt road sites on which a check for a maintenance intervention is required. Therefore, this technique can supply local government authorities an efficient, rapid and repeatable road mapping procedure providing the location of the asphalt pavements to be checked. PMID:27879765

76 FR 36879 - Minnesota: Final Authorization of State Hazardous Waste Management Program Revision

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-23

... Phase II--Universal Treatment Standards, and Treatment Standards for Organic Toxicity Characteristic... Disposal Facilities and Hazardous Waste Generators; Organic Air Emissions Standards for Tanks, Surface... Generators; Organic Air Emissions Standards for Tanks, Surface Impoundments, and Containers; Clarification...

Influence of Agricultural Operations on Dust Emission During the 1930a Dust Bowl, Baca County, CO, USA.

NASA Astrophysics Data System (ADS)

Hodges, A. T.; Bolles, K.; Forman, S. L.

2017-12-01

The drought that struck the U.S. Great Plains during the 1930s was one of the most intensedroughts in the region in the last millennium, spurring a major environmental and public healthcrisis. A prominent explanation for the cause of the "dust bowl" centers on the expansion ofagriculture and poor land management practices leading to widespread soil erosion. Thisprevalent hypothesis largely excludes the impacts of naturally occurring land surface processesthat contribute to eolian erosion and dust emissivity, particularly during periods of drought. Priorwork generally focuses on economic and sociological factors in agricultural decision-making forindividual fields or farms.This study utilizes early aerial photography collected by the Soil Conservation Service in 1936 ofBaca County, Colorado, to identify and quantify spatial relationships between geomorphicprocesses and anthropogenic activities impacting dust emission. From the holdings at theNational Archives, 25 photos covering 125 km2 scanned at 1200dpi are combined into acontinuous mosaic, and geo-referenced at RMSE 78.6 m2 . Detailed land cover analyses areundertaken in ArcGIS to classify uncultivated and cultivated surfaces; cultivated surfaces arefurther divided by surface agricultural operations in relation to erosion and dust emission (e.g.listing, contour furrows, terraces, circuitous plowing, listing, eolian transport, and fallow fieldswith and without vegetation). The classified surface is overlaid with National ResourceConservation Service surveys and Soil Conservation Service reconnaissance surveys of land useand erosion carried out in 1936 to infer to potential emissivity of a given cultivated surface. Inthis way, it becomes possible to evaluate human influence on dust emission in one of theworst-struck counties of the Dust Bowl and potentially identify other causative factors to thissignificant period in American history.

Process Produces Low-Secondary-Electron-Emission Surfaces

NASA Technical Reports Server (NTRS)

Curren, A. N.; Jensen, K. A.; Roman, R. F.

1986-01-01

Textured carbon layer applied to copper by sputtering. Carbon surface characterized by dense, random array of needle-like spires or peaks that extend perpendicularly from local copper surface. Spires approximately 7 micrometers in height and spaced approximately 3 micrometers apart, on average. Copper substrate essentially completely covered by carbon layer, is tenacious and not damaged by vibration loadings representative of multistage depressed collector (MDC) applications. Process developed primarily to provide extremely low-secondary-electron-emission surface for copper for use as highefficiency electrodes in MDC's for microwave amplifier traveling-wave tubes (TWT's). Tubes widely used in space communications, aircraft, and terrestrial applications.

Frequency splitter based on the directional emission from surface modes in dielectric photonic crystal structures.

PubMed

Tasolamprou, Anna C; Zhang, Lei; Kafesaki, Maria; Koschny, Thomas; Soukoulis, Costas M

2015-06-01

We demonstrate the numerical design and the experimental validation of frequency dependent directional emission from a dielectric photonic crystal structure. The wave propagates through a photonic crystal line-defect waveguide, while a surface layer at the termination of the photonic crystal enables the excitation of surface modes and a subsequent grating layer transforms the surface energy into outgoing propagating waves of the form of a directional beam. The angle of the beam is controlled by the frequency and the structure operates as a frequency splitter in the intermediate and far field region.

Surface photonic crystal structures for LED emission modification

NASA Astrophysics Data System (ADS)

Uherek, Frantisek; Škriniarová, Jaroslava; Kuzma, Anton; Šušlik, Łuboš; Lettrichova, Ivana; Wang, Dong; Schaaf, Peter

2017-12-01

Application of photonic crystal structures (PhC) can be attractive for overall and local enhancement of light from patterned areas of the light emitting diode (LED) surface. We used interference and near-field scanning optical microscope lithography for patterning of the surface of GaAs/AlGaAs based LEDs emitted at 840 nm. Also new approach with patterned polydimethylsiloxane (PDMS) membrane applied directly on the surface of red emitting LED was investigated. The overall emission properties of prepared LED with patterned structure show enhanced light extraction efficiency, what was documented from near- and far-field measurements.

Frequency splitter based on the directional emission from surface modes in dielectric photonic crystal structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tasolamprou, Anna C.; Zhang, Lei; Kafesaki, Maria

2015-05-19

We demonstrate the numerical design and the experimental validation of frequency dependent directional emission from a dielectric photonic crystal structure. The wave propagates through a photonic crystal line-defect waveguide, while a surface layer at the termination of the photonic crystal enables the excitation of surface modes and a subsequent grating layer transforms the surface energy into outgoing propagating waves of the form of a directional beam. Furthermore, the angle of the beam is controlled by the frequency and the structure operates as a frequency splitter in the intermediate and far field region.

Temperature dependence of photon-enhanced thermionic emission from GaAs surface with nonequilibrium Cs overlayers

NASA Astrophysics Data System (ADS)

Zhuravlev, A. G.; Alperovich, V. L.

2017-02-01

The temperature influence on the Cs/GaAs surface electronic properties, which determine the photon-enhanced thermionic emission (PETE), is studied. It was found that heating to moderate temperatures of about 100 °С leads to substantial changes in the magnitude and shape of Cs coverage dependences of photoemission current and surface band bending, along with the changes of relaxation kinetics after Cs deposition. A spectral proof of the PETE process is obtained under thermal cycling of the Cs/GaAs surface with 0.45 monolayer (ML) of Cs.

Effects of piston surface treatments on performance and emissions of a methanol-fueled, direct injection, stratified charge engine

NASA Astrophysics Data System (ADS)

West, B.; Green, J. B.

1994-07-01

The purpose of this study was to investigate the effects of thermal barrier coatings and/or surface treatments on the performance and emissions of a methanol-fueled, direct-injection, stratified-charge (DISC) engine. A Ricardo Hydra Mark III engine was used for this work and in previous experiments at Oak Ridge National Laboratory (ORNL). The primary focus of the study was to examine the effects of various piston insert surface treatments on hydrocarbon (HC) and oxides of nitrogen (NO(x)) emissions. Previous studies have shown that engines of this class have a tendency to perform poorly at low loads and have high unburned fuel emissions. A blank aluminum piston was modified to employ removable piston bowl inserts. Four different inserts were tested in the experiment: aluminum, stainless steel with a 1.27-mm (0.050-in.) air gap (to act as a thermal barrier), and two stainless steel/air-gap inserts with coatings. Two stainless steel inserts were dimensionally modified to account for the coating thickness (1.27-mm) and coated identically with partially stabilized zirconia (PSZ). One of the coated inserts then had an additional seal-coat applied. The coated inserts were otherwise identical to the stainless steel/air-gap insert (i.e., they employed the same 1.27-mm air gap). Thermal barrier coatings were employed in an attempt to increase combustion chamber surface temperatures, thereby reducing wall quenching and promoting more complete combustion of the fuel in the quench zone. The seal-coat was applied to the zirconia to reduce the surface porosity; previous research suggested that despite the possibly higher surface temperatures obtainable with a ceramic coating, the high surface area of a plasma-sprayed coating may actually allow fuel to adhere to the surface and increase the unburned fuel emissions and fuel consumption.

An ultrafast nanotip electron gun triggered by grating-coupled surface plasmons

NASA Astrophysics Data System (ADS)

Schröder, Benjamin; Sivis, Murat; Bormann, Reiner; Schäfer, Sascha; Ropers, Claus

2015-12-01

We demonstrate multiphoton photoelectron emission from gold nanotips induced by nanofocusing surface plasmons, resonantly excited on the tip shaft by a grating coupler. The tip is integrated into an electron gun assembly, which facilitates control over the spatial emission sites and allows us to disentangle direct grating emission from plasmon-triggered apex emission. The nanoscale source size of this electron gun concept enables highly coherent electron pulses with applications in ultrafast electron imaging and diffraction.

An ultrafast nanotip electron gun triggered by grating-coupled surface plasmons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schröder, Benjamin; Sivis, Murat; Bormann, Reiner

We demonstrate multiphoton photoelectron emission from gold nanotips induced by nanofocusing surface plasmons, resonantly excited on the tip shaft by a grating coupler. The tip is integrated into an electron gun assembly, which facilitates control over the spatial emission sites and allows us to disentangle direct grating emission from plasmon-triggered apex emission. The nanoscale source size of this electron gun concept enables highly coherent electron pulses with applications in ultrafast electron imaging and diffraction.

Enhanced biogenic emissions of nitric oxide and nitrous oxide following surface biomass burning

Treesearch

Iris C. Anderson; Joel S. Levine; Mark A. Poth; Philip J. Riggan

1988-01-01

Recent measurements indicate significantly enhanced biogenic soil emissions of both nitric oxide (NO) and nitrous oxide (N2O) following surface burning. These enhanced fluxes persisted for at least 6 months following the burn. Simultaneous measurements indicate enhanced levels of...

Surface-induced brightness temperature variations and their effects on detecting thin cirrus clouds using IR emission channels in the 8-12 micrometer region

NASA Technical Reports Server (NTRS)

Gao, Bo-Cai; Wiscombe, W. J.

1993-01-01

A method for detecting cirrus clouds in terms of brightness temperature differences between narrow bands at 8, 11, and 12 mu m has been proposed by Ackerman et al. (1990). In this method, the variation of emissivity with wavelength for different surface targets was not taken into consideration. Based on state-of-the-art laboratory measurements of reflectance spectra of terrestrial materials by Salisbury and D'Aria (1992), we have found that the brightness temperature differences between the 8 and 11 mu m bands for soils, rocks and minerals, and dry vegetation can vary between approximately -8 K and +8 K due solely to surface emissivity variations. We conclude that although the method of Ackerman et al. is useful for detecting cirrus clouds over areas covered by green vegetation, water, and ice, it is less effective for detecting cirrus clouds over areas covered by bare soils, rocks and minerals, and dry vegetation. In addition, we recommend that in future the variation of surface emissivity with wavelength should be taken into account in algorithms for retrieving surface temperatures and low-level atmospheric temperature and water vapor profiles.

Laser Infrared Desorption Spectroscopy to Detect Complex Organic Molecules on Icy Planetary Surfaces

NASA Technical Reports Server (NTRS)

Sollit, Luke S.; Beegle, Luther W.

2008-01-01

Laser Desorption-Infrared Spectroscopy (LD-IR) uses an IR laser pulse to desorb surface materials while a spectrometer measures the emission spectrum of the desorbed materials (Figure 1). In this example, laser desorption operates by having the incident laser energy absorbed by near surface material (10 microns in depth). This desorption produces a plume that exists in an excited state at elevated temperatures. A natural analog for this phenomenon can be observed when comets approach the sun and become active and individual molecular emission spectra can be observed in the IR [1,2,3,4,5]. When this occurs in comets, the same species that initially emit radiation down to the ground state are free to absorb it, reducing the amount of detectable emission features. The nature of our technique results in absorption not occurring, because the laser pulse could easily be moved away form the initial desorption plume, and still have better spatial resolution then reflectance spectroscopy. In reflectance spectroscopy, trace components have a relatively weak signal when compared to the entire active nature of the surface. With LDIR, the emission spectrum is used to identify and analyze surface materials.

Rear surface light emission measurements from laser-produced shock waves in clear and Al-coated polystyrene targets

NASA Astrophysics Data System (ADS)

McLean, E. A.; Deniz, A. V.; Schmitt, A. J.; Stamper, J. A.; Obenschain, S. P.; Lehecka, T.; Mostovych, A. N.; Seely, J.

1999-08-01

The Nike KrF laser, with its very uniform focal distributions, has been used at intensities near 10 14 W/cm 2 to launch shock waves in polystyrene targets. The rear surface visible light emission differed between clear polystyrene (CH) targets and targets with a thin (125 nm) Al coating on the rear side. The uncoated CH targets showed a relatively slowly rising emission followed by a sudden fall when the shock emerges, while the Al-coated targets showed a rapid rise in emission when the shock emerges followed by a slower fall, allowing an unambiguous determination of the time the shock arrived at the rear surface. A half-aluminized target allowed us to observe this difference in a single shot. The brightness temperature of both the aluminized targets and the non-aluminized targets was slightly below but close to rear surface temperature predictions of a hydrodynamic code. A discussion of preheat effects is given.

Investigation of argon ion sputtering on the secondary electron emission from gold samples

NASA Astrophysics Data System (ADS)

Yang, Jing; Cui, Wanzhao; Li, Yun; Xie, Guibai; Zhang, Na; Wang, Rui; Hu, Tiancun; Zhang, Hongtai

2016-09-01

Secondary electron (SE) yield, δ, is a very sensitive surface property. The values of δ often are not consistent for even identical materials. The influence of surface changes on the SE yield was investigated experimentally in this article. Argon ion sputtering was used to remove the contamination from the surface. Surface composition was monitored by X-ray photoelectron spectroscopy (XPS) and surface topography was scanned by scanning electron microscope (SEM) and atomic force microscope (AFM) before and after every sputtering. It was found that argon sputtering can remove contamination and roughen the surface. An ;equivalent work function; is presented in this thesis to establish the relationship between SE yield and surface properties. Argon ion sputtering of 1.5keV leads to a significant increase of so called ;work function; (from 3.7 eV to 6.0 eV), and a decrease of SE yield (from 2.01 to 1.54). These results provided a new insight into the influence of surface changes on the SE emission.

Modeling of reduced secondary electron emission yield from a foam or fuzz surface

DOE PAGES

Swanson, Charles; Kaganovich, Igor D.

2018-01-10

Complex structures on a material surface can significantly reduce the total secondary electron emission yield from that surface. A foam or fuzz is a solid surface above which is placed a layer of isotropically aligned whiskers. Primary electrons that penetrate into this layer produce secondary electrons that become trapped and do not escape into the bulk plasma. In this manner the secondary electron yield (SEY) may be reduced. We developed an analytic model and conducted numerical simulations of secondary electron emission from a foam to determine the extent of SEY reduction. We find that the relevant condition for SEY minimization ismore » $$\\bar{u}$$≡AD/2>>1 while D <<1, where D is the volume fill fraction and A is the aspect ratio of the whisker layer, the ratio of the thickness of the layer to the radius of the fibers. As a result, we find that foam cannot reduce the SEY from a surface to less than 0.3 of its flat value.« less

Modeling of reduced secondary electron emission yield from a foam or fuzz surface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Swanson, Charles; Kaganovich, Igor D.

Complex structures on a material surface can significantly reduce the total secondary electron emission yield from that surface. A foam or fuzz is a solid surface above which is placed a layer of isotropically aligned whiskers. Primary electrons that penetrate into this layer produce secondary electrons that become trapped and do not escape into the bulk plasma. In this manner the secondary electron yield (SEY) may be reduced. We developed an analytic model and conducted numerical simulations of secondary electron emission from a foam to determine the extent of SEY reduction. We find that the relevant condition for SEY minimization ismore » $$\\bar{u}$$≡AD/2>>1 while D <<1, where D is the volume fill fraction and A is the aspect ratio of the whisker layer, the ratio of the thickness of the layer to the radius of the fibers. As a result, we find that foam cannot reduce the SEY from a surface to less than 0.3 of its flat value.« less

Electronic structure of BaO/W cathode surfaces

NASA Technical Reports Server (NTRS)

Muller, Wolfgang

1989-01-01

The local electronic structure of the emissive layer of barium dispenser thermionic cathodes is investigated theoretically using the relativistic scattered-wave approach. The interaction of Ba and O with W, Os, and W-Os alloy surfaces is studied with atomic clusters modeling different absorption environments representative of B- and M-type cathodes. Ba is found to be strongly oxidized, while O and the metal substrate are in a reduced chemical state. The presence of O enhances the surface dipole and Ba binding energy relative to Ba on W. Model results for W-Os alloy substrates show only relatively small changes in Ba and O for identical geometries, but very large charge redistributions inside the substrate, which are attributed to the electronegativity difference between Os and W. If Os is present in the surface layer, the charge transfer from Ba to the substrate and the Ba binding energy increase relative to W. Explanations are offered for the improved electron emission from alloy surfaces and the different emission enhancement for different alloy substrates.

A Combined Model of Charging of the Surface and Bulk of a Dielectric Target by Electrons with the Energies 10-30 keV

NASA Astrophysics Data System (ADS)

Zykov, V. M.; Neiman, D. A.

2018-04-01

A physico-mathematical model of the processes of radiation-induced charging of dielectric materials with open surfaces, irradiated with monoenergetic electrons in the energy range 10-30 keV, is described. The model takes into account the relationship between the processes of surface and bulk charging for the given conditions of the experimental design, which accounts for the effect of anomalously long charging of dielectrics after the incident energy of primary electrons during charging is reduced to below the second critical energy for the secondary electronic emission coefficient. The initial fast phase of charging a high-resistivity dielectric material (Al2O3) is investigated. It is shown that as the incident electron energy is approaching the second critical energy during charging, the secondary electronic emission is partially suppressed due to negative charging of the open surface of the dielectric and formation of a near-surface inversion electrical field retarding the electronic emission yield.

X-MIME: An Imaging X-ray Spectrometer for Detailed Study of Jupiter's Icy Moons and the Planet's X-ray Aurora

NASA Technical Reports Server (NTRS)

Elsner, R. F.; Ramsey, B. D.; Waite, J. H.; Rehak, P.; Johnson, R. E.; Cooper, J. F.; Swartz, D. A.

2004-01-01

Remote observations with the Chandra X-ray Observatory and the XMM-Newton Observatory have shown that the Jovian system is a source of x-rays with a rich and complicated structure. The planet's polar auroral zones and its disk are powerful sources of x-ray emission. Chandra observations revealed x-ray emission from the Io Plasma Torus and from the Galilean moons Io, Europa, and possibly Ganymede. The emission from these moons is certainly due to bombardment of their surfaces of highly energetic protons, oxygen and sulfur ions from the region near the Torus exciting atoms in their surfaces and leading to fluorescent x-ray emission lines. Although the x-ray emission from the Galilean moons is faint when observed from Earth orbit, an imaging x-ray spectrometer in orbit around these moons, operating at 200 eV and above with 150 eV energy resolution, would provide a detailed mapping (down to 40 m spatial resolution) of the elemental composition in their surfaces. Such maps would provide important constraints on formation and evolution scenarios for the surfaces of these moons. Here we describe the characteristics of X-MIME, an imaging x-ray spectrometer under going a feasibility study for the JIMO mission, with the ultimate goal of providing unprecedented x-ray studies of the elemental composition of the surfaces of Jupiter's icy moons and Io, as well as of Jupiter's auroral x-ray emission.

White light emission from Mn2 + doped ZnS nanocrystals through the surface chelating of 8-hydroxyquinoline-5-sulfonic acid

NASA Astrophysics Data System (ADS)

Lü, Xiaodan; Yang, Jing; Fu, Yuqin; Liu, Qianqian; Qi, Bin; Lü, Changli; Su, Zhongmin

2010-03-01

White light emitting semiconductor nanocrystals (NCs) have been successfully synthesized from 8-hydroxyquinoline-5-sulfonic acid (HQS) decorated manganese doped ZnS NCs through fine tuning the surface-coordination emission and dopant emission of the NC host. The HQS functionalized manganese doped ZnS NCs (QS-ZnS:Mn), with a cubic crystal structure, have the same diameter of about 4.0 nm as ZnS:Mn NCs without HQS. The intensity of the surface-coordination emission peak increased with increasing HQS content or augmenting excited wavelength. The emission of white light was achieved by carefully controlling the dosage of HQS in NCs and appropriately tuning the excited wavelength. The color coordinates (0.35, 0.34) for the efficient white light emitting NCs were very close to the ideal Commission Internationale de l'Eclairage (CIE) chromaticity coordinates for pure white light (0.33, 0.33). The photoluminescence (PL) decay study revealed that the white light emitting NCs exhibited maximum lifetime values at different emission peaks for different NC samples. The study results also indicated that the HQS molecules were attached to the surface of ZnS:Mn NCs in a single coordination fashion due to the steric hindrance effect of the special spherical surface of NCs, which made the QS-ZnS:Mn NCs possess stable and high fluorescent properties in different organic solvents as compared with the conventional small molecule complexes.

Atmospheric emissions of methyl isothiocyanate and chloropicrin following soil fumigation and surface containment treatment in bare-root forest nurseries

Treesearch

D. Wang; J. Juzwik; Stephen W. Fraedrich; K. Spokas; Y. Zhang; W.C. Koskinen

2005-01-01

Methylisothiocyanate (MITC) and chloropicrin (CP) are alternatives to methyl bromide for soil fumigation. However, surface transport of MITC emission has been cited as the cause for seedling damage in adjacent fields at several bare-root forest-tree nurseries. Field experiments were conducted at nurseries in Wisconsin and Georgia to measure air emissions of MITC and CP...

Atmospheric emissions of methyl isothiocyanate and chloropicrin following soil fumigation and surface containment treatment in bare-root forest nurseries

Treesearch

D. Wang; J. Juzwik; S.W. Fraedrich; K. Spokas; Y. Zhang; W.C. Koskinen

2005-01-01

Methylisothiocyanate (MITC) and chloropicrin (CP) are alternatives to methyl bromide for soil fumigation. However, surface transport of MITC emission has been cited as the cause for seedling damage in adjacent fields at several bare-root forest-tree nurseries. Field experiments were conducted at nurseries to measure air emissions of MITC and CP after fumigation....

Surface-Enhanced Raman Optical Data Storage system

DOEpatents

Vo-Dinh, T.

1991-03-12

A method and apparatus for a Surface-Enhanced Raman Optical Data Storage (SERODS) System are disclosed. A medium which exhibits the Surface Enhanced Raman Scattering (SERS) phenomenon has data written onto its surface of microenvironment by means of a write-on procedure which disturbs the surface or microenvironment of the medium and results in the medium having a changed SERS emission when excited. The write-on procedure is controlled by a signal that corresponds to the data to be stored so that the disturbed regions on the storage device (e.g., disk) represent the data. After the data is written onto the storage device it is read by exciting the surface of the storage device with an appropriate radiation source and detecting changes in the SERS emission to produce a detection signal. The data is then reproduced from the detection signal. 5 figures.

Surface-enhanced raman optical data storage system

DOEpatents

Vo-Dinh, Tuan

1991-01-01

A method and apparatus for a Surface-Enhanced Raman Optical Data Storage (SERODS) System is disclosed. A medium which exhibits the Surface Enhanced Raman Scattering (SERS) phenomenon has data written onto its surface of microenvironment by means of a write-on procedure which disturbs the surface or microenvironment of the medium and results in the medium having a changed SERS emission when excited. The write-on procedure is controlled by a signal that corresponds to the data to be stored so that the disturbed regions on the storage device (e.g., disk) represent the data. After the data is written onto the storage device it is read by exciting the surface of the storage device with an appropriate radiation source and detecting changes in the SERS emission to produce a detection signal. The data is then reproduced from the detection signal.

Magnesium ion implantation on a micro/nanostructured titanium surface promotes its bioactivity and osteogenic differentiation function

PubMed Central

Wang, Guifang; Li, Jinhua; Zhang, Wenjie; Xu, Lianyi; Pan, Hongya; Wen, Jin; Wu, Qianju; She, Wenjun; Jiao, Ting; Liu, Xuanyong; Jiang, Xinquan

2014-01-01

As one of the important ions associated with bone osseointegration, magnesium was incorporated into a micro/nanostructured titanium surface using a magnesium plasma immersion ion-implantation method. Hierarchical hybrid micro/nanostructured titanium surfaces followed by magnesium ion implantation for 30 minutes (Mg30) and hierarchical hybrid micro/nanostructured titanium surfaces followed by magnesium ion implantation for 60 minutes (Mg60) were used as test groups. The surface morphology, chemical properties, and amount of magnesium ions released were evaluated by field-emission scanning electron microscopy, energy dispersive X-ray spectroscopy, field-emission transmission electron microscopy, and inductively coupled plasma-optical emission spectrometry. Rat bone marrow mesenchymal stem cells (rBMMSCs) were used to evaluate cell responses, including proliferation, spreading, and osteogenic differentiation on the surface of the material or in their medium extraction. Greater increases in the spreading and proliferation ability of rBMMSCs were observed on the surfaces of magnesium-implanted micro/nanostructures compared with the control plates. Furthermore, the osteocalcin (OCN), osteopontin (OPN), and alkaline phosphatase (ALP) genes were upregulated on both surfaces and in their medium extractions. The enhanced cell responses were correlated with increasing concentrations of magnesium ions, indicating that the osteoblastic differentiation of rBMMSCs was stimulated through the magnesium ion function. The magnesium ion-implanted micro/nanostructured titanium surfaces could enhance the proliferation, spreading, and osteogenic differentiation activity of rBMMSCs, suggesting they have potential application in improving bone-titanium integration. PMID:24940056

On the illumination of neutron star accretion discs

NASA Astrophysics Data System (ADS)

Wilkins, D. R.

2018-03-01

The illumination of the accretion disc in a neutron star X-ray binary by X-rays emitted from (or close to) the neutron star surface is explored through general relativistic ray tracing simulations. The applicability of the canonical suite of relativistically broadened emission line models (developed for black holes) to discs around neutron stars is evaluated. These models were found to describe well emission lines from neutron star accretion discs unless the neutron star radius is larger than the innermost stable orbit of the accretion disc at 6 rg or the disc is viewed at high inclination, above 60° where shadowing of the back side of the disc becomes important. Theoretical emissivity profiles were computed for accretion discs illuminated by hotspots on the neutron star surfaces, bands of emission and emission by the entirety of the hot, spherical star surface and in all cases, the emissivity profile of the accretion disc was found to be well represented by a single power law falling off slightly steeper than r-3. Steepening of the emissivity index was found where the emission is close to the disc plane and the disc can appear truncated when illuminated by a hotspot at high latitude. The emissivity profile of the accretion disc in Serpens X-1 was measured and found to be consistent with a single unbroken power law with index q=3.5_{-0.4}^{+0.3}, suggestive of illumination by the boundary layer between the disc and neutron star surface.

A Unified and Coherent Land Surface Emissivity Earth System Data Record

NASA Astrophysics Data System (ADS)

Knuteson, R. O.; Borbas, E. E.; Hulley, G. C.; Hook, S. J.; Anderson, M. C.; Pinker, R. T.; Hain, C.; Guillevic, P. C.

2014-12-01

Land Surface Temperature and Emissivity (LST&E) data are essential for a wide variety of studies from calculating the evapo-transpiration of plant canopies to retrieving atmospheric water vapor. LST&E products are generated from data acquired by sensors in low Earth orbit (LEO) and by sensors in geostationary Earth orbit (GEO). Although these products represent the same measure, they are produced at different spatial, spectral and temporal resolutions using different algorithms. The different approaches used to retrieve the temperatures and emissivities result in discrepancies and inconsistencies between the different products. NASA has identified a major need to develop long-term, consistent, and calibrated data and products that are valid across multiple missions and satellite sensors. This poster will introduce the land surface emissivity product of the NASA MEASUREs project called A Unified and Coherent Land Surface Temperature and Emissivity (LST&E) Earth System Data Record (ESDR). To develop a unified high spectral resolution emissivity database, the MODIS baseline-fit emissivity database (MODBF) produced at the University of Wisconsin-Madison and the ASTER Global Emissivity Database (ASTER GED) produced at JPL will be merged. The unified Emissivity ESDR will be produced globally at 5km in mean monthly time-steps and for 12 bands from 3.6-14.3 micron and extended to 417 bands using a PC regression approach. The poster will introduce this data product. LST&E is a critical ESDR for a wide variety of studies in particular ecosystem and climate modeling.

The Effect of Simulated Lunar Dust on the Absorptivity, Emissivity, and Operating Temperature on AZ-93 and Ag/FEP Thermal Control Surfaces

NASA Technical Reports Server (NTRS)

Gaier, James R.; Siamidis, John; Panko, Scott R.; Rogers, Kerry J.; Larkin, Elizabeth M. G.

2008-01-01

JSC-1AF lunar simulant has been applied to AZ-93 and AgFEP thermal control surfaces on aluminum or composite substrates in a simulated lunar environment. The temperature of these surfaces was monitored as they were heated with a solar simulator and cooled in a 30 K coldbox. Thermal modeling was used to determine the absorptivity ( ) and emissivity ( ) of the thermal control surfaces in both their clean and dusted states. Then, a known amount of power was applied to the samples while in the coldbox and the steady state temperatures measured. It was found that even a submonolayer of simulated lunar dust can significantly degrade the performance of both white paint and second-surface mirror type thermal control surfaces under these conditions. Contrary to earlier studies, dust was found to affect as well as . Dust lowered the emissivity by as much as 16 percent in the case of AZ-93, and raised it by as much as 11 percent in the case of AgFEP. The degradation of thermal control surface by dust as measured by / rose linearly regardless of the thermal control coating or substrate, and extrapolated to degradation by a factor 3 at full coverage by dust. Submonolayer coatings of dust were found to not significantly change the steady state temperature at which a shadowed thermal control surface will radiate.

Surface plasmon dispersion analysis in the metal-oxide-metal tunnel diode

NASA Technical Reports Server (NTRS)

Donohue, J. F.; Wang, E. Y.

1987-01-01

A detailed model of surface plasmon dispersion in the metal-oxide-metal tunnel diode is presented in order to clarify the spectral emission from this diode. The model predicts the location of the spectral peaks and the emission between the peaks by considering the effects of retardation on the surface plasmon. A nonradiative mode is found to play a major role in the transition from the visible to UV peaks in the diode spectra.

Derivation of martian surface slope characteristics from directional thermal infrared radiometry

NASA Astrophysics Data System (ADS)

Bandfield, Joshua L.; Edwards, Christopher S.

2008-01-01

Directional thermal infrared measurements of the martian surface is one of a variety of methods that may be used to characterize surface roughness and slopes at scales smaller than can be obtained by orbital imagery. Thermal Emission Spectrometer (TES) emission phase function (EPF) observations show distinct apparent temperature variations with azimuth and emission angle that are consistent with the presence of warm, sunlit and cool, shaded slopes at typically ˜0.1 m scales. A surface model of a Gaussian distribution of azimuth independent slopes (described by θ-bar) is combined with a thermal model to predict surface temperature from each viewing angle and azimuth of the TES EPF observation. The models can be used to predict surface slopes using the difference in measured apparent temperature from 2 separate 60-70° emission angle observations taken ˜180° in azimuth relative to each other. Most martian surfaces are consistent with low to moderate slope distributions. The slope distributions display distinct correlations with latitude, longitude, and albedo. Exceptionally smooth surfaces are located at lower latitudes in both the southern highlands as well as in high albedo dusty terrains. High slopes are associated with southern high-latitude patterned ground and north polar sand dunes. There is little apparent correlation between high resolution imagery and the derived θ-bar, with exceptions such as duneforms. This method can be used to characterize potential landing sites by assuming fractal scaling behavior to meter scales. More precisely targeted thermal infrared observations from other spacecraft instruments are capable of significantly reducing uncertainty as well as reducing measurement spot size from 10s of kilometers to sub-kilometer scales.

Unlocking the secrets of Venus surface mineralogy from orbit

NASA Astrophysics Data System (ADS)

Helbert, J.; Maturilli, A.; Ferrari, S.; Dyar, M. D.; Mueller, N. T.; Smrekar, S. E.; Koulen, J.

2016-12-01

The surface composition of a planet is a key to understand its interior and evolution. Proper interpretations of Venus surface observations in the near-infrared require a dedicated laboratory effort. The atmosphere of Venus dictates which spectral bands on the surface can be observed. This places severe constraints on the ability to identify rock-forming minerals. To complicate matters further, we cannot observe reflectance, as would be the standard at 1 mm. Observations are obtained on the night side where the thermal emission of the surface is measured directly. Finally, high surface temperatures are known to affect band positions of mineral spectra as expected from crystal field theory. Over the last year we have started at the Planetary Spectroscopy Laboratory (PSL) at DLR in Berlin, Germany to systematically build a spectral library for rocks and minerals under Venus thermal conditions. Using funding from the European Union as part of the EuroPlanet consortium we extended the spectral coverage for high temperature measurements down to 0.7 micron. The spectral library will be key in understanding and modeling differences in emissivity between ambient and Venus conditions, potentially enabling calibration transfer between datasets. We can show that the expected emissivity variation between felsic and mafic minerals would be observable even with the limited number of surface windows available. Furthermore the absolute emissivity derived from our laboratory measurements at Venus temperature match in situ reflectivity data from the Venera 9 and 10 landing sites in the same bands. Based on experience gained from using the VIRTIS instrument on Venus Express to observe the surface of Venus and the new high temperature laboratory experiments, we have developed the multi-spectral Venus Emissivity Mapper (VEM) to study the surface of Venus. VEM imposes minimal requirements on the spacecraft and mission design and can therefore be added to any future Venus mission. Ideally, the VEM instrument will be combined with a high-resolution radar mapper to provide accurate topographic information, as it will be the case for the proposed NASA Discovery VERITAS mission or the ESA EnVision M5 proposal.

Photoelectron emission from LiF surfaces by ultrashort electromagnetic pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Acuna, M. A.; Gravielle, M. S.; Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires

2011-03-15

Energy- and angle-resolved electron emission spectra produced by incidence of ultrashort electromagnetic pulses on a LiF(001) surface are studied by employing a distorted-wave method named the crystal surface-Volkov (CSV) approximation. The theory makes use of the Volkov phase to describe the action of the external electric field on the emitted electron, while the electron-surface interaction is represented within the tight-binding model. The CSV approach is applied to investigate the effects introduced by the crystal lattice when the electric field is oriented parallel to the surface plane. These effects are essentially governed by the vector potential of the external field, whilemore » the influence of the crystal orientation was found to be negligible.« less

Adsorbed Molecules and Surface Treatment Effect on Optical Properties of ZnO Nanowires Grown by MOCVD

NASA Astrophysics Data System (ADS)

Jabri, S.; Souissi, H.; Sallet, V.; Lusson, A.; Meftah, A.; Galtier, P.; Oueslati, M.

2017-07-01

We have investigated the optical properties of ZnO nanowires grown by metalorganic chemical vapor deposition (MOCVD) with nitrous oxide (N2O) as oxygen precursor. Photoluminescence (PL) and Raman measurements showed the influence of adsorbed molecules on the optical properties. Low-temperature (4 K) PL studies on the surface exciton (SX) at 3.3660 eV elucidated the nature and origin of this emission. In particular, surface treatment by annealing at high temperature under inert gas reduced the emission intensity of SX. Raman vibrational spectra proved that presence of a considerable amount of adsorbed molecules on the surface of ZnO nanowires plays a key role in the occurrence of surface excitons.

Slot-grating flat lens for telecom wavelengths.

PubMed

Pugh, Jonathan R; Stokes, Jamie L; Lopez-Garcia, Martin; Gan, Choon-How; Nash, Geoff R; Rarity, John G; Cryan, Martin J

2014-07-01

We present a stand-alone beam-focusing flat lens for use in the telecommunications wavelength range. Light incident on the back surface of the lens propagates through a subwavelength aperture and is heavily diffracted on exit and partially couples into a surface plasmon polariton and a surface wave propagating along the surface of the lens. Interference between the diffracted wave and re-emission from a grating patterned on the surface produces a highly collimated beam. We show for the first time a geometry at which a lens of this type can be used at telecommunication wavelengths (λ=1.55 μm) and identify the light coupling and re-emission mechanisms involved. Measured beam profile results at varying incident wavelengths show excellent agreement with Lumerical FDTD simulation results.

Surface Coating of Wood Building Products National Emission Standards for Hazardous Air Pollutants (NESHAP) Questions and Answers (Q&A's)

EPA Pesticide Factsheets

This September 2004 document contains questions and answers on the Surface Coating of Wood Building Products National Emission Standards for Hazardous Air Pollutants (NESHAP) regulation. The questions cover topics such as compliance, and applicability, etc

40 CFR 265.1090 - Recordkeeping requirements.

Code of Federal Regulations, 2013 CFR

2013-07-01

... DISPOSAL FACILITIES Air Emission Standards for Tanks, Surface Impoundments, and Containers § 265.1090... containers using Container Level 3 air emission controls in accordance with the requirements of § 265.1087 of... section when the tank, surface impoundment, or container is or would be operating at capacity or the...

40 CFR 265.1090 - Recordkeeping requirements.

Code of Federal Regulations, 2014 CFR

2014-07-01

... DISPOSAL FACILITIES Air Emission Standards for Tanks, Surface Impoundments, and Containers § 265.1090... containers using Container Level 3 air emission controls in accordance with the requirements of § 265.1087 of... section when the tank, surface impoundment, or container is or would be operating at capacity or the...

Vapor shielding effects on energy transfer from plasma-gun generated ELM-like transient loads to material surfaces

NASA Astrophysics Data System (ADS)

Kikuchi, Y.; Sakuma, I.; Asai, Y.; Onishi, K.; Isono, W.; Nakazono, T.; Nakane, M.; Fukumoto, N.; Nagata, M.

2016-02-01

Energy transfer processes from ELM-like pulsed helium (He) plasmas with a pulse duration of ˜0.1 ms to aluminum (Al) and tungsten (W) surfaces were experimentally investigated by the use of a magnetized coaxial plasma gun device. The surface absorbed energy density of the He pulsed plasma on the W surface measured with a calorimeter was ˜0.44 MJ m-2, whereas it was ˜0.15 MJ m-2 on the Al surface. A vapor layer in front of the Al surface exposed to the He pulsed plasma was clearly identified by Al neutral emission line (Al i) measured with a high time resolution spectrometer, and fast imaging with a high-speed visible camera filtered around the Al i emission line. On the other hand, no clear evaporation in front of the W surface exposed to the He pulsed plasma was observed in the present condition. Discussions on the reduction in the surface absorbed energy density on the Al surface are provided by considering the latent heat of vaporization and radiation cooling due to the Al vapor cloud.

Theoretical study for heterojunction surface of NEA GaN photocathode dispensed with Cs activation

NASA Astrophysics Data System (ADS)

Xia, Sihao; Liu, Lei; Wang, Honggang; Wang, Meishan; Kong, Yike

2016-09-01

For the disadvantages of conventional negative electron affinity (NEA) GaN photocathodes activated by Cs or Cs/O, new-type NEA GaN photocathodes with heterojunction surface dispensed with Cs activation are investigated based on first-principle study with density functional theory. Through the growth of an ultrathin n-type GaN cap layer on p-type GaN emission layer, a p-n heterojunction is formed on the surface. According to the calculation results, it is found that Si atoms tend to replace Ga atoms to result in an n-type doped cap layer which contributes to the decreasing of work function. After the growth of n-type GaN cap layer, the atom structure near the p-type emission layer is changed while that away from the surface has no obvious variations. By analyzing the E-Mulliken charge distribution of emission surface with and without cap layer, it is found that the positive charge of Ga and Mg atoms in the emission layer decrease caused by the cap layer, while the negative charge of N atom increases. The conduction band moves downwards after the growth of cap layer. Si atom produces donor levels around the valence band maximum. The absorption coefficient of GaN emission layer decreases and the reflectivity increases caused by n-type GaN cap layer.

The impact of historical land use change from 1850 to 2000 on secondary particulate matter and ozone

NASA Astrophysics Data System (ADS)

Heald, Colette L.; Geddes, Jeffrey A.

2016-12-01

Anthropogenic land use change (LUC) since preindustrial (1850) has altered the vegetation distribution and density around the world. We use a global model (GEOS-Chem) to assess the attendant changes in surface air quality and the direct radiative forcing (DRF). We focus our analysis on secondary particulate matter and tropospheric ozone formation. The general trend of expansion of managed ecosystems (croplands and pasturelands) at the expense of natural ecosystems has led to an 11 % decline in global mean biogenic volatile organic compound emissions. Concomitant growth in agricultural activity has more than doubled ammonia emissions and increased emissions of nitrogen oxides from soils by more than 50 %. Conversion to croplands has also led to a widespread increase in ozone dry deposition velocity. Together these changes in biosphere-atmosphere exchange have led to a 14 % global mean increase in biogenic secondary organic aerosol (BSOA) surface concentrations, a doubling of surface aerosol nitrate concentrations, and local changes in surface ozone of up to 8.5 ppb. We assess a global mean LUC-DRF of +0.017, -0.071, and -0.01 W m-2 for BSOA, nitrate, and tropospheric ozone, respectively. We conclude that the DRF and the perturbations in surface air quality associated with LUC (and the associated changes in agricultural emissions) are substantial and should be considered alongside changes in anthropogenic emissions and climate feedbacks in chemistry-climate studies.

Shear Behaviour and Acoustic Emission Characteristics of Bolted Rock Joints with Different Roughnesses

NASA Astrophysics Data System (ADS)

Wang, Gang; Zhang, Yongzheng; Jiang, Yujing; Liu, Peixun; Guo, Yanshuang; Liu, Jiankang; Ma, Ming; Wang, Ke; Wang, Shugang

2018-06-01

To study shear failure, acoustic emission counts and characteristics of bolted jointed rock-like specimens are evaluated under compressive shear loading. Model joint surfaces with different roughnesses are made of rock-like material (i.e. cement). The jointed rock masses are anchored with bolts with different elongation rates. The characteristics of the shear mechanical properties, the failure mechanism, and the acoustic emission parameters of the anchored joints are studied under different surface roughnesses and anchorage conditions. The shear strength and residual strength increase with the roughness of the anchored joint surface. With an increase in bolt elongation, the shear strength of the anchored joint surface gradually decreases. When the anchored structural plane is sheared, the ideal cumulative impact curve can be divided into four stages: initial emission, critical instability, cumulative energy, and failure. With an increase in the roughness of the anchored joint surface, the peak energy rate and the cumulative number of events will also increase during macro-scale shear failure. With an increase in the bolt elongation, the energy rate and the event number increase during the shearing process. Furthermore, the peak energy rate, peak number of events and cumulative energy will all increase with the bolt elongation. The results of this study can provide guidance for the use of the acoustic emission technique in monitoring and predicting the static shear failure of anchored rock masses.

Process system and method for fabricating submicron field emission cathodes

DOEpatents

Jankowski, A.F.; Hayes, J.P.

1998-05-05

A process method and system for making field emission cathodes exists. The deposition source divergence is controlled to produce field emission cathodes with height-to-base aspect ratios that are uniform over large substrate surface areas while using very short source-to-substrate distances. The rate of hole closure is controlled from the cone source. The substrate surface is coated in well defined increments. The deposition source is apertured to coat pixel areas on the substrate. The entire substrate is coated using a manipulator to incrementally move the whole substrate surface past the deposition source. Either collimated sputtering or evaporative deposition sources can be used. The position of the aperture and its size and shape are used to control the field emission cathode size and shape. 3 figs.

Process system and method for fabricating submicron field emission cathodes

DOEpatents

Jankowski, Alan F.; Hayes, Jeffrey P.

1998-01-01

A process method and system for making field emission cathodes exists. The deposition source divergence is controlled to produce field emission cathodes with height-to-base aspect ratios that are uniform over large substrate surface areas while using very short source-to-substrate distances. The rate of hole closure is controlled from the cone source. The substrate surface is coated in well defined increments. The deposition source is apertured to coat pixel areas on the substrate. The entire substrate is coated using a manipulator to incrementally move the whole substrate surface past the deposition source. Either collimated sputtering or evaporative deposition sources can be used. The position of the aperture and its size and shape are used to control the field emission cathode size and shape.

Organic light emitting diode with surface modification layer

DOEpatents

Basil, John D.; Bhandari, Abhinav; Buhay, Harry; Arbab, Mehran; Marietti, Gary J.

2017-09-12

An organic light emitting diode (10) includes a substrate (12) having a first surface (14) and a second surface (16), a first electrode (32), and a second electrode (38). An emissive layer (36) is located between the first electrode (32) and the second electrode (38). The organic light emitting diode (10) further includes a surface modification layer (18). The surface modification layer (18) includes a non-planar surface (30, 52).

49 CFR 325.75 - Ground surface correction factors. 1

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 5 2010-10-01 2010-10-01 false Ground surface correction factors. 1 325.75... MOTOR CARRIER NOISE EMISSION STANDARDS Correction Factors § 325.75 Ground surface correction factors. 1... account both the distance correction factors contained in § 325.73 and the ground surface correction...

49 CFR 325.75 - Ground surface correction factors. 1

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 5 2011-10-01 2011-10-01 false Ground surface correction factors. 1 325.75... MOTOR CARRIER NOISE EMISSION STANDARDS Correction Factors § 325.75 Ground surface correction factors. 1... account both the distance correction factors contained in § 325.73 and the ground surface correction...

Empirical Measurement and Model Validation of Infrared Spectra of Contaminated Surfaces

NASA Astrophysics Data System (ADS)

Archer, Sean

The goal of this thesis was to validate predicted infrared spectra of liquid contaminated surfaces from a micro-scale bi-directional reflectance distribution function (BRDF) model through the use of empirical measurement. Liquid contaminated surfaces generally require more sophisticated radiometric modeling to numerically describe surface properties. The Digital Image and Remote Sensing Image Generation (DIRSIG) model utilizes radiative transfer modeling to generate synthetic imagery for a variety of applications. Aside from DIRSIG, a micro-scale model known as microDIRSIG has been developed as a rigorous ray tracing physics-based model that could predict the BRDF of geometric surfaces that are defined as micron to millimeter resolution facets. The model offers an extension from the conventional BRDF models by allowing contaminants to be added as geometric objects to a micro-facet surface. This model was validated through the use of Fourier transform infrared spectrometer measurements. A total of 18 different substrate and contaminant combinations were measured and compared against modeled outputs. The substrates used in this experiment were wood and aluminum that contained three different paint finishes. The paint finishes included no paint, Krylon ultra-flat black, and Krylon glossy black. A silicon based oil (SF96) was measured out and applied to each surface to create three different contamination cases for each surface. Radiance in the longwave infrared region of the electromagnetic spectrum was measured by a Design and Prototypes (D&P) Fourier transform infrared spectrometer and a Physical Sciences Inc. Adaptive Infrared Imaging Spectroradiometer (AIRIS). The model outputs were compared against the measurements quantitatively in both the emissivity and radiance domains. A temperature emissivity separation (TES) algorithm had to be applied to the measured radiance spectra for comparison with the microDIRSIG predicted emissivity spectra. The model predicted emissivity spectra was also forward modeled through a DIRSIG simulation for comparisons to the radiance measurements. The results showed a promising agreement for homogeneous surfaces with liquid contamination that could be well characterized geometrically. Limitations arose in substrates that were modeled as homogeneous surfaces, but had spatially varying artifacts due to uncertainties with contaminant and surface interactions. There is high desire for accurate physics based modeling of liquid contaminated surfaces and this validation framework may be extended to include a wider array of samples for more realistic natural surfaces that are often found in real world scenarios.

Field-testing a portable wind tunnel for fine dust emissions

USDA-ARS?s Scientific Manuscript database

A protable wind tunnel has been developed to allow erodibility and dust emissions testing of soil surfaces with the premise that dust concentration and properties are highly correlated with surface soil properties, as modified by crop management system. In this study we report on the field-testing ...

Characterization of Emissions and Residues from Simulations of the Deepwater Horizon Surface Oil Burns

EPA Science Inventory

The surface oil burns conducted by the U.S. Coast Guard from April to July 2010 during the Deepwater Horizon disaster in the Gulf of Mexico were simulated by small scale burns to characterize the pollutants, determine emission factors, and gather particulate matter for subsequent...

Electron emission from tungsten surface induced by neon ions

NASA Astrophysics Data System (ADS)

Xu, Zhongfeng; Zeng, Lixia; Zhao, Yongtao; Cheng, Rui; Zhang, Xiaoan; Ren, Jieru; Zhou, Xianming; Wang, Xing; Lei, Yu; Li, Yongfeng; Yu, Yang; Liu, Xueliang; Xiao, Guoqing; Li, Fuli

2014-04-01

The electron emission from W surface induced by Neq+ has been measured. For the same charge state, the electron yield gradually increases with the projectile velocity. Meanwhile, the effect of the potential energy of projectile has been found obviously. Our results give the critical condition for "trampoline effect".

Understanding the role of Si doping on surface charge and optical properties: Photoluminescence study of intrinsic and Si-doped InN nanowires

NASA Astrophysics Data System (ADS)

Zhao, S.; Mi, Z.; Kibria, M. G.; Li, Q.; Wang, G. T.

2012-06-01

In the present work, the photoluminescence (PL) characteristics of intrinsic and Si-doped InN nanowires are studied in detail. For intrinsic InN nanowires, the emission is due to band-to-band carrier recombination with the peak energy at ˜0.64 eV (at 300 K) and may involve free-exciton emission at low temperatures. The PL spectra exhibit a strong dependence on optical excitation power and temperature, which can be well characterized by the presence of very low residual electron density and the absence or a negligible level of surface electron accumulation. In comparison, the emission of Si-doped InN nanowires is characterized by the presence of two distinct peaks located at ˜0.65 and ˜0.73-0.75 eV (at 300 K). Detailed studies further suggest that these low-energy and high-energy peaks can be ascribed to band-to-band carrier recombination in the relatively low-doped nanowire bulk region and Mahan exciton emission in the high-doped nanowire near-surface region, respectively; this is a natural consequence of dopant surface segregation. The resulting surface electron accumulation and Fermi-level pinning, due to the enhanced surface doping, are confirmed by angle-resolved x-ray photoelectron spectroscopy measurements on Si-doped InN nanowires, which is in direct contrast to the absence or a negligible level of surface electron accumulation in intrinsic InN nanowires. This work elucidates the role of charge-carrier concentration and distribution on the optical properties of InN nanowires.

Temporal Dynamics of Sodic Playa Salt Crust Patterns: Implications for Aeolian Dust Emission Potential

NASA Astrophysics Data System (ADS)

Nield, J. M.; King, J.; Bryant, R. G.; Wiggs, G.; Eckardt, F. D.; Thomas, D. S.; Washington, R.

2013-12-01

Salt pans (or playas) are common in arid environments and can be major sources of windblown mineral dust, but there are uncertainties associated with their dust emission potential. These landforms typically form crusts which modify both their erosivity and erodibility by limiting sediment availability, modifying surface and aerodynamic roughness and limiting evaporation rates and sediment production. Here we show the relationship between seasonal surface moisture change and crust pattern development based on both remote-sensing and field surface and atmospheric measurements. We use high resolution (sub-cm) terrestrial laser scanning (TLS; ground-based lidar) surveys over weekly, monthly and annual timescales to accurately characterise crustal ridge thrusting and collapse. This can be as much as 2 mm/day on fresh pan areas that have recently been reset by flooding. Over a two month period, this ridge growth can change aerodynamic roughness length values by 6.5 mm. At the same time, crack densities across the surface increase and this raises the availability of erodible fluffy, low density dust source sediment stored below the crust layer. Ridge spaces are defined in the early stages of crust development, as identified by Fourier Transform analysis, but wider wavelengths become more pronounced over time. We present a conceptual model accounting for the driving forces (subsurface, surface and atmospheric moisture) and feedbacks between these and surface shape that lead to crust pattern trajectories between highly emissive degraded surfaces and less emissive ridged or continuous crusts. These findings improve our understanding of temporal changes in dust availability and supply from playa source regions.

A new approach of the surface temperature measurement for a preventive conservation of the work of arts

NASA Astrophysics Data System (ADS)

Di Tuccio, Maria Concetta; De Grandi, Sandro; Vivarelli, Arianna; Becherini, Francesca; Pockelé, Luc; Bernardi, Adriana

2015-04-01

To conserve the work of arts (paintings, sculptures, etc..) in a preventive mode, a careful monitoring of the environment around these artifacts, as well as of their surface temperature, is necessary. The latter is the only physical variable which can be measured in a non-invasive way, following directly the thermal conditions and variations of the work of arts due to the dynamics of the microclimate. Considering that the works of art are often untouchable, an automated and accurate remote sensing could be very useful to prevent dangerous processes of deterioration. For these reasons a new sensor has been developed by a spin-off of the ISAC - CNR. This sensor allows to check in real-time the surface temperature changes of the artifacts both over time and at different predefined points. This automated sensor is a radiometer sensible to wavelengths ranging from 7,5 µm to 13,4 µm. A system rotating over three dimension "pan and tilt" allows to make multiple measures on a grid of points previously defined on the surface of the work of arts. The accuracy, obtained by means of a carefull calibration process, is  0,5 °C, more precise than the usual remote sensing (thermal camera and commercial radiometers), characterized by an accuracy value of  2°C. In order to obtain accurate measures of the surface temperature for a real body, the correct emissivity values need to be integrated in the calculation. Hence, an easy to use management software has been developed allowing to set the emissivity value in each point of the grid. For rejoinable points of the surface, the exact emissivity value could be determined comparing the measurements recorded by the new infrared sensor with the ones obtained by a very sensitive sensor (0,02 - 0,03)°C manually placed on the surface for a short time. In case of work of arts placed at great distance from the sersor, the emissivity values must be determined previously. The emissivity depends on a lot of variables and one of them is the surface roughness. Since the artifacts are often charaterized by a high surface roughness, such dependence has been studied in order to obtain accurate temperature measurements. The results obtained indicate an increase of the emissivity with increasing surface roughness. In conclusion, this study has allowed to develop a reliable, accurate and automatic control system, as well as a low cost sensor that, unlike the thermal camera, can also be used by less experienced operators. Besides, in order to support the museums managers in the preventive conservation of the artifacts, an alarm system is automatically activated when dangerously large thermal variations on the surface are detected.

Ground-based measurement of surface temperature and thermal emissivity

NASA Technical Reports Server (NTRS)

Owe, M.; Van De Griend, A. A.

1994-01-01

Motorized cable systems for transporting infrared thermometers have been used successfully during several international field campaigns. Systems may be configured with as many as four thermal sensors up to 9 m above the surface, and traverse a 30 m transect. Ground and canopy temperatures are important for solving the surface energy balance. The spatial variability of surface temperature is often great, so that averaged point measurements result in highly inaccurate areal estimates. The cable systems are ideal for quantifying both temporal and spatial variabilities. Thermal emissivity is also necessary for deriving the absolute physical temperature, and measurements may be made with a portable measuring box.

A noncoherent model for microwave emissions and backscattering from the sea surface

NASA Technical Reports Server (NTRS)

Wu, S. T.; Fung, A. K.

1973-01-01

The two-scale (small irregularities superimposed upon large undulations) scattering theory proposed by Semyonov was extended and used to compute microwave apparent temperature and the backscattering cross section from ocean surfaces. The effect of the small irregularities upon the scattering characteristics of the large undulations is included by modifying the Fresnel reflection coefficients; whereas the effect of the large undulations upon those of the small irregularities is taken into account by averaging over the surface normals of the large undulations. The same set of surface parameters is employed for a given wind speed to predict both the scattering and the emission characteristics at both polarizations.

Simultaneous detection of refractive index and surface charges in nanolaser biosensors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Watanabe, Keisuke; Kishi, Yoji; Hachuda, Shoji

2015-01-12

The emission intensity of a GaInAsP photonic crystal nanolaser is affected by the pH of the solution, in which the nanolaser is immersed. This phenomenon can be explained by the change in the redox potential, which modifies the filling of electrons at surface states of the semiconductor and hence the nonradiative surface recombination. This phenomenon allows the nanolaser to simultaneously and independently detect the refractive index and electric charges near the surface on the basis of the variation in emission wavelength and intensity, respectively. This paper demonstrates this function through alternate deposition of charged polyelectrolytes and hybridization of deoxyribonucleic acids.

Springtime microwave emissivity changes in the southern Kara Sea

NASA Technical Reports Server (NTRS)

Crane, Robert G.; Anderson, Mark R.

1994-01-01

Springtime microwave brightness temperatures over first-year ice are examined for the southern Kara Sea. Snow emissivity changes are revealed by episodic drops in the 37- to 18-GHz brightness temperature gradient ratio measured by the Nimbus 7 scanning multichannel microwave radiometer. We suggest that the negative gradient ratios in spring 1982 result from increased scatter at 37 GHz due to the formation of a near-surface hoar layer. This interpretation is supported by the results of a surface radiation balance model that shows the melt signature occurring at below freezing temperatures but under clear-sky conditions with increased solar input to the surface. Published observations from the Greenland ice cap show a surface hoar layer forming under similar atmospheric conditions owing to the increased penetration and absorption of solar radiation just below the surface layer. In spring/early summer 1984 similar gradient ratio signatures occur. They appear to be due to several days of freeze-thaw cycling following the movement of a low-pressure system through the region. These changes in surface emissivity represent the transition from winter to summer conditions (as defined by the microwave response) and are shown to be regional in extent and to vary with the synoptic circulations.

Voyager IRIS Measurements of Triton's Thermal Emission: Impllications for Pluto?

NASA Astrophysics Data System (ADS)

Stansberry, John A.; Spencer, John; Linscott, Ivan

2015-11-01

The New Horizons Pluto encounter data set includes unique observations obtained using the Radio Science experiment to measure the night-side thermal emission at centimeter wavelengths, well beyond the emission peak (in the 70 to 100 micron range). 26 years ago the Voyager 2 Infrared Interferometer Spectrometer (IRIS) obtained spectra in the 30 - 50 micron wavelength range to try and detect thermal emission from Pluto's sibling, Triton. Conrath etal. (1989) analyzed 16 of the IRIS spectra of Triton's dayside and derived a weak limit of 36 K - 41 K. We have analysed those, and an additional 75 spectra, to refine the limits on the temperature of Triton's surface, and to explore diurnal differences in the thermal emission. Triton results from other Voyager instruments provide important constraints on our interpretation of the IRIS data, as do Spitzer measurements of Pluto's thermal emission.For unit-emissivity, average temperature is 34 K, inconsistent with the pressure of Triton's atmosphere (13 - 19 microbar), the presence of beta-phase nitrogen ice on the surface, and the likely presence ofwarm regions on the surface. The atmospheric pressure requires nitrogen ice temperatures of 37.4 K - 38.1 K, which in turn requires emissivity of 0.31--0.53. Such a low emissivity in this spectral region might be expected if the surface is dominated by nitrogen or methane ice. Averages of data subsets show evidence for brightness temperature variations across Triton's surface. Surprisingly, the data seem to indicate that Triton's nightside equatorial region was warmer than on the dayside.These Voyager results for Triton provide a useful context for interpreting New Horizons and ALMA observations of emission from Pluto in the sub-millimeter and centimeter region. JWST will be capable of detecting Triton's and Pluto's 10 - 28 micron thermal emission, although scattered light from Neptune may be an issue for the Triton. Combined with new capabilities of ALMA to measure the sub-millimeter emission (and even resolve the disks of Pluto and Triton), it seems possible that we may gain significant new insights into the thermal properties of these bodies in the coming decade.

Electron emission and plasma generation in a modulator electron gun using ferroelectric cathode

NASA Astrophysics Data System (ADS)

Chen, Shutao; Zheng, Shuxin; Zhu, Ziqiu; Dong, Xianlin; Tang, Chuanxiang

2006-10-01

Strong electron emission and dense plasma generation have been observed in a modulator electron gun with a Ba 0.67Sr 0.33TiO 3 ferroelectric cathode. Parameter of the modulator electron gun and lifetime of the ferroelectric cathode were investigated. It was shown that electron emission from Ba 0.67Sr 0.33TiO 3 cathode with a positive triggering pulse is a sort of plasma emission. Electrons were emitted by the co-effect of surface plasma and non-compensated negative polarization charges at the surface of the ferroelectric. The element analyses of the graphite collector after emission process was performed to show the ingredient of the plasma consist of Ba, Ti and Cu heavy cations of the ceramic compound and electrode. It was demonstrated the validity of the Child-Langmuir law by introducing the decrease of vacuum gap and increase of emission area caused by the expansion of the surface plasma.

Role of regional wetland emissions in atmospheric methane variability

NASA Astrophysics Data System (ADS)

McNorton, J.; Gloor, E.; Wilson, C.; Hayman, G. D.; Gedney, N.; Comyn-Platt, E.; Marthews, T.; Parker, R. J.; Boesch, H.; Chipperfield, M. P.

2016-11-01

Atmospheric methane (CH4) accounts for 20% of the total direct anthropogenic radiative forcing by long-lived greenhouse gases. Surface observations show a pause (1999-2006) followed by a resumption in CH4 growth, which remain largely unexplained. Using a land surface model, we estimate wetland CH4 emissions from 1993 to 2014 and study the regional contributions to changes in atmospheric CH4. Atmospheric model simulations using these emissions, together with other sources, compare well with surface and satellite CH4 data. Modeled global wetland emissions vary by ±3%/yr (σ = 4.8 Tg), mainly due to precipitation-induced changes in wetland area, but the integrated effect makes only a small contribution to the pause in CH4 growth from 1999 to 2006. Increasing temperature, which increases wetland area, drives a long-term trend in wetland CH4 emissions of +0.2%/yr (1999 to 2014). The increased growth post-2006 was partly caused by increased wetland emissions (+3%), mainly from Tropical Asia, Southern Africa, and Australia.

Impact of Surface Emissions to the Zonal Variability of Tropical Tropospheric Ozone and Carbon Monoxide for November 2004

NASA Technical Reports Server (NTRS)

Bowman, K. W.; Jones, D.; Logan, J.; Worden, H.; Boersma, F.; Chang, R.; Kulawik, S.; Osterman, G.; Worden, J.

2008-01-01

The chemical and dynamical processes governing the zonal variability of tropical tropospheric ozone and carbon monoxide are investigated for November 2004 using satellite observations, in-situ measurements, and chemical transport models in conjunction with inverse-estimated surface emissions. Vertical ozone profile estimates from the Tropospheric Emission Spectrometer (TES) and ozone sonde measurements from the Southern Hemisphere Additional Ozonesondes (SHADOZ) network show the so called zonal 'wave-one' pattern, which is characterized by peak ozone concentrations (70-80 ppb) centered over the Atlantic, as well as elevated concentrations of ozone over Indonesia and Australia (60-70 ppb) in the lower troposphere. Observational evidence from TES CO vertical profiles and Ozone Monitoring Instrument (OMI) NO2 columns point to regional surface emissions as an important contributor to the elevated ozone over Indonesia. This contribution is investigated with the GEOS-Chem chemistry and transport model using surface emission estimates derived from an optimal inverse model, which was constrained by TES and Measurements Of Pollution In The Troposphere (MOPITT) CO profiles (Jones et al., 2007). These a posteriori estimates, which were over a factor of 2 greater than climatological emissions, reduced differences between GEOS-Chem and TES ozone observations by 30-40% and led to changes in GEOS-Chem upper tropospheric ozone of up to 40% over Indonesia. The remaining residual differences can be explained in part by upper tropospheric ozone produced from lightning NOx in the South Atlantic. Furthermore, model simulations from GEOS-Chem indicate that ozone over Indonesian/Australian is more sensitive to changes in surface emissions of NOx than ozone over the tropical Atlantic.

Correlations between Venus nightside near infrared emissions measured by VIRTIS/Venus Express and Magellan radar data

NASA Astrophysics Data System (ADS)

Mueller, N.; Helbert, J.; Hashimoto, G. L.; Tsang, C. C. C.; Erard, S.; Piccioni, G.; Drossart, P.

2008-09-01

Background The Venus Express Spacecraft images the nightside thermal emissions using the VIRTIS imaging spectrometer. At 1.02 micron thermal emission from the surface is penetrates the atmosphere but the signal is attenuated by scattering and absorption [1, 2]. Although the measured flux at top of the atmosphere is nonlinearly related to the original emission of the surface, it is still positively correlated with the product of surface temperature and surface emissivity [3]. The surface temperature of Venus is relatively well constrained as a monotonous function of altitude. Emissivity at 1 micron depends strongly on surface composition, in particular abundance of mafic minerals [3]. Mapping the thermal emission of the surface of Venus therefore supplements radar data as it allows to infer relative variation of surface composition. Data Processing This study examines the correlation of VIRTIS images showing a signal of the surface with all known parameters that govern radiance and applies semi empirical relations to remove the respective influences. 1. Stray sunlight is removed by subtraction of a spectrum template scaled to fit radiance at 1.4 ¹m [2] 2. Limb darkening is accounted for using a linear phase function consistent with results of radiative transfer modeling [4]. 3. Cloud opacity is determined from 1.31 ¹m and applied to 1.02 ¹m while accounting for multiple reflections between lower atmosphere and clouds [3]. Result is brightness temperature of thermal emission below the cloud deck but above the lowest 20 km of the atmosphere. 4. Influence of surface temperature and lower atmosphere absorption is determined by correlation of VIRTIS declouded brightness temperature and Magellan Topography data [5]. To further reduce the influence of cloud contrast and increase the signal of the surface, all suitable VIRTIS observations are map projected and stacked to create a map of the southern hemisphere of Venus. Observations and Interpretation As expected from the small diurnal, latitudinal and seasonal variations of temperature in the atmosphere of Venus, the map created from all retrieved brightness temperatures is highly correlated with Magellan altimetry (fig. 1). Local deviation from the globally averaged brightness to topography relation can be either ascribed to surface emissivity or unexpected temperature variations. Temperature variations e.g. due to active volcanism are unlikely to be persistent over the time of observations. The stacked data is here interpreted in terms of surface emissivity variation by removal of the influence of topography (fig. 2). The emissivity variation found is correlated with geomorphological features established from Magellan radar images. It is generally lower at tessera terrain. This might indicate felsic surface composition of tessera highlands, e.g. anorthosite or granite [6, 7]. Creation of felsic crust is unlikely under current conditions. Some, but not all volcanic edifices show increased emissivity. Large lava flows in the Lada terra - Lavinia planitia region also show an increased thermal emission. In particular Cavilaca and Juturna fluctus, emanating from Boala corona (70S 0E) inside Quetzalpetlatl corona, are characterized by an increased IR flux. This might be consistent with the large scale extrusive volcanism of ultramafic composition considered by [8] in the context of chemical differentiation in the upper mantle. Discussion These observations are however highly sensitive to errors in the altimetry applied. A known systematic error in the Magellan dataset stemming from spacecraft orbit determination uncertainty is qualitatively confirmed by comparison with VIRTIS data (see longitude -120 in fig. 1 and 2. Tessera terrain is known to strongly scatter radar waves which might influences accuracy of altimetry. An quantitative analysis and search for small scale systematic errors is in progress during the submission of this abstract. References [1] Lecacheux, J., P. Drossart, P. Laques, F. Deladerriere, and F. Colas (1993), Detection of the surface of Venus at 1.0 micrometer from ground-based observations, Planetary and Space Science, 41, 543-549. [2] Meadows, V. S., and D. Crisp (1996), Ground-based near-infrared observations of the Venus nightside: The thermal structure and water abundance near the surface, Journal of Geophysical Research, 101, 4595-4622. [3] Hashimoto, G. L., and S. Sugita (2003), On observing the compositional variability of the surface of Venus using nightside near-infrared thermal radiation, Journal of Geophysical Research (Planets), 108, 13-18. [4] Tsang, C. C. C., P. G. J. Irwin, F. W. Taylor, and C. F. Wilson (2008), A correlated-k model of radiative transfer in the near-infrared windows of venus, Journal of Quantitative Spectroscopy & Radiative Transfer, In press. [5] Ford, P. G., and G. H. Pettengill (1992), Venus topography and kilometer-scale slopes, Journal of Geophysical Research, 97, 13,103. [6] Nikolaeva, O. V., M. A. Ivanov, and V. K. Borozdin (1992), Evidence on the crustal dichotomy, pp. 129- 139, Venus Geology, Geochemistry, and Geophysics - Research results from the USSR. [7] Hashimoto, G. L., M. Roos-Serote, S. Sugita, M. S. Gilmore, L. W. Kamp, B. Carlson, and K. Baines (this issue), Galileo Near Infrared Mapping Spectrometer (NIMS) Data Suggests Felsic Highland Crust on Venus, Journal of Geophysical Research, submitted. [8] Head, J. W., E. M. Parmentier, and P. C. Hess (1994), Venus: Vertical accretion of crust and depleted mantle and implications for geological history and processes, Planetary and Space Science, 42, 803-811.

Sensitized luminescence from water-soluble LaF3:Eu nanocrystals via partially-capped 1,10-phenanthroline: time-gated emission and multiple lifetimes.

PubMed

Irfanullah, Mir; Bhardwaj, Navneet; Chowdhury, Arindam

2016-08-02

Water dispersible citrate-capped LaF3:Eu(5%) nanocrystals (NCs) have been partially surface-functionalized by 1,10-phenanthroline (phen) via a ligand exchange method to produce novel water dispersed citrate/phen-capped LaF3:Eu(5%) NCs in which citrate ligands preserve the water dispersibility of the NCs and phen ligands act as sensitizers of surface Eu(3+)-dopant sites. The partial ligand exchange and the formation of water dispersed NCs have been monitored by (1)H NMR spectroscopy, as well as luminescence measurements at different time intervals during the reaction. These NCs display a distinct phen-sensitized Eu(3+)-emission profile with enhanced intensity in water as compared to the emission profile and intensity obtained upon direct excitation. Time-resolved (or time-gated) emission spectroscopy (TRES) has been used to probe PL dynamics of Eu(3+)-sites of LaF3:Eu(5%) NCs by taking advantage of selectively sensitizing surface Eu(3+)-dopant sites by phen ligands as well as by exciting all the Eu(3+)-sites in the NCs upon direct excitation. TRES upon direct excitation of the citrate-capped LaF3:Eu(5%) NCs reveals that Eu(3+)-dopants occupy at least three different sites, each with a different emission profile and lifetime, and emission from purely interior Eu(3+)-sites has been resolved due to their long lifetime as compared to the lifetime of purely surface and near surface Eu(3+)-sites. In contrast, the phen-sensitized emission from citrate/phen-capped LaF3:Eu(5%) NCs displays similar emission profiles and lifetimes in TRES measurements, which reveal that phen truly sensitizes purely surface dopant sites of the NCs in water, all of which have nearly the same local environment. The phen-sensitized Eu(3+)-emission of the NCs in water remains stable even upon addition of various buffer solutions at physiological pH, as well as upon addition of water-miscible organic solvents. Furthermore, the two-photon excitation (λex. = 720 nm) of these water-soluble phen-capped NCs produces bright red Eu(3+) emission, which reveals that these NCs are promising for potential applications in biological imaging.

Ultraviolet emission enhancement in ZnO thin films modified by nanocrystalline TiO2

NASA Astrophysics Data System (ADS)

Zheng, Gaige; Lu, Xi; Qian, Liming; Xian, Fenglin

2017-05-01

In this study, nanocrystalline TiO2 modified ZnO thin films were prepared by electron beam evaporation. The structural, morphological and optical properties of the samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), UV-visible spectroscopy, fluorescence spectroscopy, respectively. The composition of the films was examined by energy dispersive X-ray spectroscopy (EDX). The photoluminescent spectrum shows that the pure ZnO thin film exhibits an ultraviolet (UV) emission peak and a strong green emission band. Surface analysis indicates that the ZnO thin film contains many oxygen vacancy defects on the surface. After the ZnO thin film is modified by the nanocrystalline TiO2 layer, the UV emission of ZnO is largely enhanced and the green emission is greatly suppressed, which suggests that the surface defects such as oxygen vacancies are passivated by the TiO2 capping layer. As for the UV emission enhancement of the ZnO thin film, the optimized thickness of the TiO2 capping layer is ∼16 nm. When the thickness is larger than 16 nm, the UV emission of the ZnO thin film will decrease because the TiO2 capping layer absorbs most of the excitation energy. The UV emission enhancement in the nanocrystalline TiO2 modified ZnO thin film can be attributed to surface passivation and flat band effect.

High Resolution CryoFESEM of Microbial Surfaces

NASA Astrophysics Data System (ADS)

Erlandsen, Stanley; Lei, Ming; Martin-Lacave, Ines; Dunny, Gary; Wells, Carol

2003-08-01

The outer surfaces of three microorganisms, Giardia lamblia, Enterococcus faecalis, and Proteus mirabilis, were investigated by cryo-immobilization followed by sublimation of extracellular ice and cryocoating with either Pt alone or Pt plus carbon. Cryocoated samples were examined at [minus sign]125°C in either an in-lens field emission SEM or a below-the-lens field emission SEM. Cryocoating with Pt alone was sufficient for low magnification observation, but attempts to do high-resolution imaging resulted in radiolysis and cracking of the specimen surface. Double coating with Pt and carbon, in combination with high resolution backscatter electron detectors, enabled high-resolution imaging of the glycocalyx of bacteria, revealing a sponge-like network over the surface. High resolution examination of bacterial flagella also revealed a periodic substructure. Common artifacts included radiolysis leading to “cracking” of the surface, and insufficient deposition of Pt resulting in the absence of detectable surface topography.

Inverse problem of flame surface properties of wood using a repulsive particle swarm optimization algorithm

NASA Astrophysics Data System (ADS)

Yoon, Kyung-Beom; Park, Won-Hee

2015-04-01

The convective heat transfer coefficient and surface emissivity before and after flame occurrence on a wood specimen surface and the flame heat flux were estimated using the repulsive particle swarm optimization algorithm and cone heater test results. The cone heater specified in the ISO 5660 standards was used, and six cone heater heat fluxes were tested. Preservative-treated Douglas fir 21 mm in thickness was used as the wood specimen in the tests. This study confirmed that the surface temperature of the specimen, which was calculated using the convective heat transfer coefficient, surface emissivity and flame heat flux on the wood specimen by a repulsive particle swarm optimization algorithm, was consistent with the measured temperature. Considering the measurement errors in the surface temperature of the specimen, the applicability of the optimization method considered in this study was evaluated.

Vacuum Surface Flashover Characteristics and Secondary Electron Emission Characteristics of Epoxy Resin and FRP Insulator

NASA Astrophysics Data System (ADS)

Yamano, Yasushi; Takahashi, Masahiro; Kobayashi, Shinichi; Hanada, Masaya; Ikeda, Yoshitaka

Neutral beam injectors (NBI) used for JT-60 are required to generate negative ions of 500 keV energies. To produce such high-energy ions, the electrostatic accelerators consisting of 3-stage of electrodes and three insulator rings are applied. The insulators are made of Fiberglass Reinforced Plastic (FRP) which is composed of epoxy resin and glass fibers. The surface discharges along the insulators are one of the most serious problems in the development of NBI. To increase the hold-off voltage against surface flashover events, it is necessary to investigate the FRP and epoxy resin insulator properties related to surface discharges in vacuum. This paper describes surface flashover characteristics for epoxy resin, FRP and Alumina samples under vacuum condition. In addition, the measurements of secondary electron emission (SEE) characteristics are also reported. These are important parameters to analyze surface discharge characteristics of insulators in vacuum.

Hydrothermal alteration of sediments associated with surface emissions from the Cerro Prieto geothermal field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Valette-Silver, J.N.; Esquer P., I.; Elders, W.A.

1981-01-01

A study of the mineralogical changes associated with these hydrothermal vents was initiated with the aim of developing possible exploration tools for geothermal resources. The Cerro Prieto reservoir has already been explored by extensive deep drilling so that relationships between surface manifestations and deeper hydrothermal processes could be established directly. Approximately 120 samples of surface sediments were collected both inside and outside of the vents. The mineralogy of the altered sediments studied appears to be controlled by the type of emission. A comparison between the changes in mineralogy due to low temperature hydrothermal activity in the reservoir, seen in samplesmore » from boreholes, and mineralogical changes in the surface emission samples shows similar general trends below 180 C: increase of quartz, feldspar and illite, with subsequent disappearance of kaolinite, montmorillonite, calcite and dolomite. These mineral assemblages seem to be characteristic products of the discharge from high intensity geothermal fields.« less

Field-Induced and Thermal Electron Currents from Earthed Spherical Emitters

NASA Astrophysics Data System (ADS)

Holgate, J. T.; Coppins, M.

2017-04-01

The theories of electron emission from planar surfaces are well understood, but they are not suitable for describing emission from spherical surfaces; their incorrect application to highly curved, nanometer-scale surfaces can overestimate the emitted current by several orders of magnitude. This inaccuracy is of particular concern for describing modern nanoscale electron sources, which continue to be modeled using the planar equations. In this paper, the field-induced and thermal currents are treated in a unified way to produce Fowler-Nordheim-type and Richardson-Schottky-type equations for the emitted current density from earthed nanoscale spherical surfaces. The limits of applicability of these derived expressions are considered along with the energy spectra of the emitted electrons. Within the relevant limits of validity, these equations are shown to reproduce the results of precise numerical calculations of the emitted current densities. The methods used here are adaptable to other one-dimensional emission problems.

Spectral and temperature-dependent infrared emissivity measurements of painted metals for improved temperature estimation during laser damage testing

NASA Astrophysics Data System (ADS)

Baumann, Sean M.; Keenan, Cameron; Marciniak, Michael A.; Perram, Glen P.

2014-10-01

A database of spectral and temperature-dependent emissivities was created for painted Al-alloy laser-damage-testing targets for the purpose of improving the uncertainty to which temperature on the front and back target surfaces may be estimated during laser-damage testing. Previous temperature estimates had been made by fitting an assumed gray-body radiance curve to the calibrated spectral radiance data collected from the back surface using a Telops Imaging Fourier Transform Spectrometer (IFTS). In this work, temperature-dependent spectral emissivity measurements of the samples were made from room temperature to 500 °C using a Surface Optics Corp. SOC-100 Hemispherical Directional Reflectometer (HDR) with Nicolet FTS. Of particular interest was a high-temperature matte-black enamel paint used to coat the rear surfaces of the Al-alloy samples. The paint had been assumed to have a spectrally flat and temperatureinvariant emissivity. However, the data collected using the HDR showed both spectral variation and temperature dependence. The uncertainty in back-surface temperature estimation during laser-damage testing made using the measured emissivities was improved from greater than +10 °C to less than +5 °C for IFTS pixels away from the laser burn-through hole, where temperatures never exceeded those used in the SOC-100 HDR measurements. At beam center, where temperatures exceeded those used in the SOC-100 HDR, uncertainty in temperature estimates grew beyond those made assuming gray-body emissivity. Accurate temperature estimations during laser-damage testing are useful in informing a predictive model for future high-energy-laser weapon applications.

Structural and emission characteristics of ion-irradiated Reticulated Vitreous Carbon

NASA Astrophysics Data System (ADS)

Chacon, Judith Rebecca

Cathodes formed from Reticulated Vitreous Carbon (RVC) were treated under varying conditions of Argon-ion beam current, beam voltage and irradiation duration. Surface structures, such as balls, cones, nanowires, and nanowhiskers were formed in the RVC network through a series of ion-impact sputtering and self-diffusion reactions. Raman shifts to the D and E2g' peak suggest C=C bonding within the original RVC structure was converted to the lesser-bound C-C bonding structure. Cathodes demonstrating the most stable electronic configuration exhibited significant vertical growth to graphitic domains as determined by calculations based on XRD measurements. Carbon nanotubes at the surface were observed at the surface through micro-Raman techniques. The surface structures formed by argon-bombardment, are responsible for cathodes exhibiting lower field-emission extraction fields. The electric field required for the onset of electron emission was measured to change from 6.03 V/micron in non-irradiated RVC to 1.62V/micron for RVC irradiated for 15 minutes at a beam voltage of 1200V and beam current of 200mA (ion-beam current density 2.24mA/cm2). Treated surfaces were also responsible for increased stability in emission over time. For untreated RVC, the field required for emission dropped 25% over a 48 hour training period, whilst modestly treated RVC (15min, 1200V, 100mA, or 1.52mA/cm2) rose as little as 3%. Field-emissive RVC, is an inexpensively produced, mechanically robust cathode with potential applications in lighting, displays and microwave sources.

SeO2 adsorption on CaO surface: DFT and experimental study on the adsorption of multiple SeO2 molecules

NASA Astrophysics Data System (ADS)

Fan, Yaming; Zhuo, Yuqun; Li, Liangliang

2017-10-01

SeO2 adsorption mechanisms on CaO surface were firstly investigated by both density functional theory (DFT) calculations and adsorption experiments. Adsorption of multiple SeO2 on the CaO (001) surface was investigated using slab model. Based on the results of adsorption energy and surface property, a double-layer adsorption mechanisms were proposed. In experiments, the SeO2 adsorption products were prepared in a U-shaped quartz reactor at 200 °C. The surface morphology was investigated by field emission scanning electron microscopy (FE-SEM). The superficial and total SeO2 mass fractions were measured by X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma atomic emission spectroscopy (ICP-AES), respectively. The surface valence state and bulk structure are determined by XPS and X-Ray Diffraction (XRD). The experimental results are in good agreement with the DFT results. In conclusion, the fundamental SeO2 chemisorption mechanisms on CaO surface were suggested.

Processing of materials for uniform field emission

DOEpatents

Pam, L.S.; Felter, T.E.; Talin, A.; Ohlberg, D.; Fox, C.; Han, S.

1999-01-12

This method produces a field emitter material having a uniform electron emitting surface and a low turn-on voltage. Field emitter materials having uniform electron emitting surfaces as large as 1 square meter and turn-on voltages as low as 16V/{micro}m can be produced from films of electron emitting materials such as polycrystalline diamond, diamond-like carbon, graphite and amorphous carbon by the method of the present invention. The process involves conditioning the surface of a field emitter material by applying an electric field to the surface, preferably by scanning the surface of the field emitter material with an electrode maintained at a fixed distance of at least 3 {micro}m above the surface of the field emitter material and at a voltage of at least 500V. In order to enhance the uniformity of electron emission the step of conditioning can be preceded by ion implanting carbon, nitrogen, argon, oxygen or hydrogen into the surface layers of the field emitter material. 2 figs.

Processing of materials for uniform field emission

DOEpatents

Pam, Lawrence S.; Felter, Thomas E.; Talin, Alec; Ohlberg, Douglas; Fox, Ciaran; Han, Sung

1999-01-01

This method produces a field emitter material having a uniform electron emitting surface and a low turn-on voltage. Field emitter materials having uniform electron emitting surfaces as large as 1 square meter and turn-on voltages as low as 16V/.mu.m can be produced from films of electron emitting materials such as polycrystalline diamond, diamond-like carbon, graphite and amorphous carbon by the method of the present invention. The process involves conditioning the surface of a field emitter material by applying an electric field to the surface, preferably by scanning the surface of the field emitter material with an electrode maintained at a fixed distance of at least 3 .mu.m above the surface of the field emitter material and at a voltage of at least 500V. In order to enhance the uniformity of electron emission the step of conditioning can be preceeded by ion implanting carbon, nitrogen, argon, oxygen or hydrogen into the surface layers of the field emitter material.

Effect of CO on the field emission properties of tetrapod zinc oxide cathode.

PubMed

Wang, Jinchan; Zhang, Xiaobing; Lei, Wei; Mao, Fuming; Cui, Yunkang; Xiao, Mei

2012-08-01

Tetrapod zinc oxide (T-ZnO), being a kind of nano-material, has large specific surface area and surface binding energy, which will make it sensitive to the ambient gas condition. So the field emission properties will be influenced by the gas adsorption when being applied as the cathode materials of field emission devices. Carbon monoxide is the main residual gas in T-ZnO field emission devices. In this paper, carbon monoxide was introduced into a field emission device with T-ZnO emitters. The field emission currents of tetrapod ZnO were compared before and after exposure to CO.

Method and apparatus for real time weld monitoring

DOEpatents

Leong, Keng H.; Hunter, Boyd V.

1997-01-01

An improved method and apparatus are provided for real time weld monitoring. An infrared signature emitted by a hot weld surface during welding is detected and this signature is compared with an infrared signature emitted by the weld surface during steady state conditions. The result is correlated with weld penetration. The signal processing is simpler than for either UV or acoustic techniques. Changes in the weld process, such as changes in the transmitted laser beam power, quality or positioning of the laser beam, change the resulting weld surface features and temperature of the weld surface, thereby resulting in a change in the direction and amount of infrared emissions. This change in emissions is monitored by an IR sensitive detecting apparatus that is sensitive to the appropriate wavelength region for the hot weld surface.

A novel emissive projection display (EPD) on transparent phosphor screen

NASA Astrophysics Data System (ADS)

Cheng, Botao; Sun, Leonard; Yu, Ge; Sun, Ted X.

2017-03-01

A new paradigm of digital projection is on the horizon, based on innovative emissive screen that are made fully transparent. It can be readily applied and convert any surface to a high image quality emissive digital display, without affecting the surface appearance. For example, it can convert any glass window or windshield to completely see-through display, with unlimited field of view and viewing angles. It also enables a scalable and economic projection display on a pitch-black emissive screen with black level and image contrast that rivals other emissive displays such as plasma display or OLED.

Surface Winds and Dust Biases in Climate Models

NASA Astrophysics Data System (ADS)

Evan, A. T.

2018-01-01

An analysis of North African dust from models participating in the Fifth Climate Models Intercomparison Project (CMIP5) suggested that, when forced by observed sea surface temperatures, these models were unable to reproduce any aspects of the observed year-to-year variability in dust from North Africa. Consequently, there would be little reason to have confidence in the models' projections of changes in dust over the 21st century. However, no subsequent study has elucidated the root causes of the disagreement between CMIP5 and observed dust. Here I develop an idealized model of dust emission and then use this model to show that, over North Africa, such biases in CMIP5 models are due to errors in the surface wind fields and not due to the representation of dust emission processes. These results also suggest that because the surface wind field over North Africa is highly spatially autocorrelated, intermodel differences in the spatial structure of dust emission have little effect on the relative change in year-to-year dust emission over the continent. I use these results to show that similar biases in North African dust from the NASA Modern Era Retrospective analysis for Research and Applications (MERRA) version 2 surface wind field biases but that these wind biases were not present in the first version of MERRA.

Broadband enhancement of photoluminance from colloidal metal halide perovskite nanocrystals on plasmonic nanostructured surfaces.

PubMed

Zhang, Si; Liang, Yuzhang; Jing, Qiang; Lu, Zhenda; Lu, Yanqing; Xu, Ting

2017-11-07

Metal halide perovskite nanocrystals (NCs) as a new kind of promising optoelectronic material have attracted wide attention due to their high photoluminescence (PL) quantum yield, narrow emission linewidth and wideband color tunability. Since the PL intensity always has a direct influence on the performance of optoelectronic devices, it is of vital importance to improve the perovskite NCs' fluorescence emission efficiency. Here, we synthesize three inorganic perovskite NCs and experimentally demonstrate a broadband fluorescence enhancement of perovskite NCs by exploiting plasmonic nanostructured surface consisting of nanogrooves array. The strong near-field optical localization associated with surface plasmon polariton-coupled emission effect generated by the nanogrooves array can significantly boost the absorption of perovskite NCs and tailor the fluorescence emissions. As a result, the PL intensities of perovskite NCs are broadband enhanced with a maximum factor higher than 8-fold achieved in experimental demonstration. Moreover, the high efficiency PL of perovskite NCs embedded in the polymer matrix layer on the top of plasmonic nanostructured surface can be maintained for more than three weeks. These results imply that plasmonic nanostructured surface is a good candidate to stably broadband enhance the PL intensity of perovskite NCs and further promote their potentials in the application of visible-light-emitting devices.

Surface Nitrification: A Major Uncertainty in Marine N2O Emissions

NASA Technical Reports Server (NTRS)

Zamora, Lauren M.; Oschlies, Andreas

2014-01-01

The ocean is responsible for up to a third of total global nitrous oxide (N2O) emissions, but uncertainties in emission rates of this potent greenhouse gas are high (approaching 100%). Here we use a marine biogeochemical model to assess six major uncertainties in estimates of N2O production, thereby providing guidance in how future studies may most effectively reduce uncertainties in current and future marine N2O emissions. Potential surface N2O production from nitrification causes the largest uncertainty in N2O emissions (estimated up to approximately 1.6 Tg N/yr (sup -1) or 48% of modeled values), followed by the unknown oxygen concentration at which N2O production switches to N2O consumption (0.8 Tg N/yr (sup -1)or 24% of modeled values). Other uncertainties are minor, cumulatively changing regional emissions by less than 15%. If production of N2O by surface nitrification could be ruled out in future studies, uncertainties in marine N2O emissions would be halved.

The Influence of Anthropogenic Greenhouse Gases and Aerosols on the Surface Heat and Moisture Budgets.

NASA Astrophysics Data System (ADS)

Ramaswamy, V.; Freidenreich, S.; Ginoux, P. A.; Ming, Y.; Paynter, D.; Persad, G.; Schwarzkopf, M. D.

2017-12-01

Emissions of greenhouse gases and aerosols alter atmospheric composition and `force' major perturbations in the radiative fluxes at the top-of-the-atmosphere and surface. In this paper, we discuss the radiative changes caused by anthropogenic greenhouse gases and aerosols at the surface, and its importance in the context of effects on the global hydrologic cycle. An important characteristic of imbalances forced by radiative species is the tendency for responses to occur in the non-radiative components, in order for the surface energy and moisture budgets to re-establish equilibrium. Using the NOAA/ GFDL global climate models used in CMIP3 and CMIP5, and to be used in CMIP6, we investigate how the surface energy balance has evolved with time under the action of the emissions, and the manner of changes in the surface radiative, sensible and latent heat components. We diagnose the relative importance of the forcings on the global and continental scales, the differing mechanisms due to greenhouse gases and aerosols on surface heat and moisture budgets, and the relative roles of the atmospheric constituents on precipitation and evaporation. Scattering and absorbing properties of aerosols can have contrasting effects on precipitation, with the aerosol indirect effect presenting another complication owing to the uncertainty in its magnitude. We compare the modeled surface flux changes against observations made from multiple platforms over the 20th and the early period of the 21st centuries, and asses the models' strengths and weaknesses. We also explore the consequences for the surface balance and precipitation in the 21st century under various emission scenarios.

Surface contamination analysis technology team overview

NASA Astrophysics Data System (ADS)

Burns, H. Dewitt, Jr.

1996-11-01

The surface contamination analysis technology (SCAT) team was originated as a working roup of NASA civil service, Space Shuttle contractor, and university groups. Participating members of the SCAT Team have included personnel from NASA Marshall Space Flight Center's Materials and Processes Laboratory and Langley Research Center's Instrument Development Group; contractors-Thiokol Corporation's Inspection Technology Group, AC Engineering support contractor, Aerojet, SAIC, and Lockheed MArtin/Oak Ridge Y-12 support contractor and Shuttle External Tank prime contractor; and the University of Alabama in Huntsville's Center for Robotics and Automation. The goal of the SCAT team as originally defined was to develop and integrate a multi-purpose inspection head for robotic application to in-process inspection of contamination sensitive surfaces. One area of interest was replacement of ozone depleting solvents currently used for surface cleanliness verification. The team approach brought together the appropriate personnel to determine what surface inspection techniques were applicable to multi-program surface cleanliness inspection. Major substrates of interest were chosen to simulate space shuttle critical bonding surface or surfaces sensitive to contamination such as fuel system component surfaces. Inspection techniques evaluated include optically stimulated electron emission or photoelectron emission; Fourier transform infrared spectroscopy; near infrared fiber optic spectroscopy; and, ultraviolet fluorescence. Current plans are to demonstrate an integrated system in MSFC's Productivity Enhancement Complex within five years from initiation of this effort in 1992. Instrumentation specifications and designs developed under this effort include a portable diffuse reflectance FTIR system built by Surface Optics Corporation and a third generation optically stimulated electron emission system built by LaRC. This paper will discuss the evaluation of the various techniques on a number of substrate materials contaminated with hydrocarbons, silicones, and fluorocarbons. Discussion will also include standards development for instrument calibration and testing.

Fabrication, Light Emission, and Magnetism of Silica Nanoparticles Hybridized with AIE Luminogens and Inorganic Nanostructures

NASA Astrophysics Data System (ADS)

Faisal, Mahtab

Much research efforts have been devoted in developing new synthetic approaches for fluorescent silica nanoparticles (FSNPs) due to their potential high-technological applications. However, light emissions from most of the FSNPs prepared so far have been rather weak. This is due to the emission quenching caused by the aggregation of fluorophores in the solid state. We have observed a novel phenomenon of aggregation-induced emission (AIE): a series of propeller-shaped molecules such as tetraphenylethene (TPE) and silole are induced to emit efficiently by aggregate formation. Thus, they are ideal fluorophors for the construction of FSNPs and my thesis work focuses on the synthesis of silica nanoparticles containing these luminogens and magnetic nanostructures. Highly emissive FSNPs with core-shell structures are fabricated by surfactant-free sol-gel reactions of tetraphenylethene- (TPE) and silole-functionalized siloxanes followed by the reactions with tetraethoxysilane. The FSNPs are uniformly sized, surface-charged and colloidally stable. The diameters of the FSNPs are tunable in the range of 45--295 nm by changing the reaction conditions. Whereas their TPE and silole precursors are non-emissive, the FSNPs emit strong visible lights, thanks to the novel aggregation-induced emission characteristics of the TPE and silole aggregates in the hybrid nanoparticles. The FSNPs pose no toxicity to living cells and can be utilized to selectively image cytoplasm of HeLa cells. Applying the same tool in the presence of citrate-coated magnetite nanoparticles, uniform magnetic fluorescent silica nanoparticles (MFSNPs) with smooth surfaces are fabricated. These particles exhibit appreciable surface charges and hence good colloidal stability. They are superparamagnetic, exhibiting no hysteresis at room temperature. UV irradiation of a suspension of MFSNPs in ethanol gives strong blue and green emissions. The MFSNPs can selectively stain the cytoplasmic regions of the living cells. Sol-gel reaction in the presence of (3-aminopropyl)triethoxysilane has generated MFSNP-NH2 with numerous amino functionalities decorated on the surfaces, enabling them to immobilize bovine serum albumin efficiently. FSNPs with strong light emissions are facilely fabricated by thio-click chemistry, Cu(I)-catalyzed 1,3-dipolar cycloaddition, and sol-gel reaction. The FSNPs are characterized by SEM, TEM, IR, PL, and zeta potential analyses. They are uniformly sized with smooth surfaces. Upon photoexcitation, the FSNPs emit strong visible lights with fluorescence quantum yields up to 25.5%. Sugar-functionalized fluorescent silica nanoparticles are facilely fabricated by click reaction of azide-modified FSNPs with sugar- containing phenylacetylene catalyzed by Cu(PPh3)3Br in THF. The nanoparticles are uniformly sized and emit efficient light upon photoexcitation. They can function as fluorescent visualizers for intracellular imaging and can target specific cancer cells. Folic acid-functionalized fluorescent silica nanoparticles are facilely fabricated by surface functionalization of FSNPs with folic acid. The nanoparticles are spherical in shape. They possess high zeta potentials and hence exhibit excellent colloidal stability. UV irradiation of suspensions of the nanoparticles in ethanol gives strong blue and green emissions at 465 and 490 nm with absolute fluorescence quantum yields up to 47%. Carboxylic acid and thiol-functionalized fluorescent silica nanoparticles (FSNP-COOH and FSNP-SH) with uniform particle sizes, narrow size distributions, and smooth surface morphologies are fabricated. The nanoparticles possess high surface charges and exhibit strong light emissions upon photoexcitation. They can adsorb lysozyme strongly on their surfaces and for 5 mg of FSNP-COOH and FSNP-SH, they can take 209 and 86 mug of lysozyme. Thus, they are potential carriers for protein and fluorescent probes or biosensors for an array of biological applications.

Aerosol reductions could dominate regional climate responses in low GHG emission scenarios

NASA Astrophysics Data System (ADS)

Samset, B. H.; Sand, M.; Smith, C. J.; Bauer, S.; Forster, P.; Fuglestvedt, J. S.; Osprey, S. M.; Schleussner, C. F.

2017-12-01

Limiting global warming to current political goals requires strong, rapid mitigation of anthropogenic greenhouse gas (GHG) emissions. Concurrently, emissions of anthropogenic aerosols will decline sharply, due to co-emission with greenhouse gases, and future measures to improve air quality. As the net climate effect of GHG and aerosol emissions over the industrial era is poorly constrained, predicting the impact of strong aerosol emission reductions remains challenging. Here we investigate the isolated and compound climate impacts from removing present day anthropogenic emissions of black carbon (BC), organic carbon (OC) and SO2, and moderate, near term GHG dominated global warming, using four coupled climate models. As the dominating effect of aerosol emission reduction is a removal of cooling from sulphur, the resulting climate impacts amplify those of GHG induced warming. BC emissions contribute little to reducing surface warming, but have stronger regional impacts. For the major aerosol emission regions, extreme weather indices are more sensitive to aerosol removal than to GHG increases, per degree of surface warming. East Asia in particular stands out, mainly due to the high present regional aerosol emissions. We show how present climate models indicate that future regional climate change will depend strongly on changes in loading and distribution of aerosols in the atmosphere, in addition to surface temperature change.

Prism-coupled light emission from tunnel junctions

NASA Technical Reports Server (NTRS)

Ushioda, S.; Rutledge, J. E.; Pierce, R. M.

1985-01-01

Completely p-polarized light emission has been observed from smooth Al-AlO(x)-Au tunnel junctions placed on a prism coupler. The angle and polarization dependence demonstrate unambiguously that the emitted light is radiated by the fast-mode surface plasmon polariton. The emission spectra suggest that the dominant process for the excitation of the fast mode is through conversion of the slow mode to the fast mode mediated by residual roughness on the junction surface.

Feedbacks between Climate and Fire Emissions

DTIC Science & Technology

2011-11-29

CH4 2. Direct emission of short-lived climate forcers - Black Carbon - Particulate organic matter 3. Production of tropospheric ozone and secondary... tropospheric ozone and secondary organic particulate matter 4. Changes in land surface properties - Black carbon on snow - Albedo Radiative Forcing of Black...lived  climate forcers:  particles 3.  Ozone   production 4. Change in  surface properties Fires Impacts on the Climate System 1. Emission of long lived

Reanalysis of and attribution to near-surface ozone concentrations in Sweden during 1990-2013

NASA Astrophysics Data System (ADS)

Andersson, Camilla; Alpfjord, Heléne; Robertson, Lennart; Karlsson, Per Erik; Engardt, Magnuz

2017-11-01

We have constructed two data sets of hourly resolution reanalyzed near-surface ozone (O3) concentrations for the period 1990-2013 for Sweden. Long-term simulations from a chemistry-transport model (CTM) covering Europe were combined with hourly ozone concentration observations at Swedish and Norwegian background measurement sites using retrospective variational data analysis. The reanalysis data sets show improved performance over the original CTM when compared to independent observations. In one of the reanalyses, we included all available hourly near-surface O3 observations, whilst in the other we carefully selected time-consistent observations. Based on the second reanalysis we investigated statistical aspects of the distribution of the near-surface O3 concentrations, focusing on the linear trend over the 24-year period. We show that high near-surface O3 concentrations are decreasing and low O3 concentrations are increasing, which is reflected in observed improvement of many health and vegetation indices (apart from those with a low threshold). Using the CTM we also conducted sensitivity simulations to quantify the causes of the observed change, focusing on three factors: change in hemispheric background concentrations, meteorology and anthropogenic emissions. The rising low concentrations of near-surface O3 in Sweden are caused by a combination of all three factors, whilst the decrease in the highest O3 concentrations is caused by European O3 precursor emissions reductions. While studying the impact of anthropogenic emissions changes, we identified systematic differences in the modeled trend compared to observations that must be caused by incorrect trends in the utilized emissions inventory or by too high sensitivity of our model to emissions changes.

Thermal infrared data of active lava surfaces using a newly-developed camera system

NASA Astrophysics Data System (ADS)

Thompson, J. O.; Ramsey, M. S.

2017-12-01

Our ability to acquire accurate data during lava flow emplacement greatly improves models designed to predict their dynamics and down-flow hazard potential. For example, better constraint on the physical property of emissivity as a lava cools improves the accuracy of the derived temperature, a critical parameter for flow models that estimate at-vent eruption rate, flow length, and distribution. Thermal infrared (TIR) data are increasingly used as a tool to determine eruption styles and cooling regimes by measuring temperatures at high temporal resolutions. Factors that control the accurate measurement of surface temperatures include both material properties (e.g., emissivity and surface texture) as well as external factors (e.g., camera geometry and the intervening atmosphere). We present a newly-developed, field-portable miniature multispectral thermal infrared camera (MMT-Cam) to measure both temperature and emissivity of basaltic lava surfaces at up to 7 Hz. The MMT-Cam acquires emitted radiance in six wavelength channels in addition to the broadband temperature. The instrument was laboratory calibrated for systematic errors and fully field tested at the Overlook Crater lava lake (Kilauea, HI) in January 2017. The data show that the major emissivity absorption feature (around 8.5 to 9.0 µm) transitions to higher wavelengths and the depth of the feature decreases as a lava surface cools, forming a progressively thicker crust. This transition occurs over a temperature range of 758 to 518 K. Constraining the relationship between this spectral change and temperature derived from this data will provide more accurate temperatures and therefore, more accurate modeling results. This is the first time that emissivity and its link to temperature has been measured in situ on active lava surfaces, which will improve input parameters of flow propagation models and possibly improve flow forecasting.

Derivation of Mars Surface Scattering Properties from OMEGA Spot Pointing Observations

NASA Astrophysics Data System (ADS)

Pinet, P. C.; Daydou, Y.; Cord, A.; Chevrel, S. C.; Poulet, F.; Erard, S.; Bibring, J.-P.; Langevin, Y.; Melchiorri, R.; Bellucci, G.; Altieri, F.; Arvidson, R. E.; OMEGA Co-Investigator Team

2005-03-01

OMEGA emission phase function (EPF) observation shows that one may access from orbit to geology-driven surface scattering properties such as surface roughness. It has implications for spectroscopic interpretation and for CRISM observations to come.

Atmospheric characterization through fused mobile airborne and surface in situ surveys: methane emissions quantification from a producing oil field

NASA Astrophysics Data System (ADS)

Leifer, Ira; Melton, Christopher; Fischer, Marc L.; Fladeland, Matthew; Frash, Jason; Gore, Warren; Iraci, Laura T.; Marrero, Josette E.; Ryoo, Ju-Mee; Tanaka, Tomoaki; Yates, Emma L.

2018-03-01

Methane (CH4) inventory uncertainties are large, requiring robust emission derivation approaches. We report on a fused airborne-surface data collection approach to derive emissions from an active oil field near Bakersfield, central California. The approach characterizes the atmosphere from the surface to above the planetary boundary layer (PBL) and combines downwind trace gas concentration anomaly (plume) above background with normal winds to derive flux. This approach does not require a well-mixed PBL; allows explicit, data-based, uncertainty evaluation; and was applied to complex topography and wind flows. In situ airborne (collected by AJAX - the Alpha Jet Atmospheric eXperiment) and mobile surface (collected by AMOG - the AutoMObile trace Gas - Surveyor) data were collected on 19 August 2015 to assess source strength. Data included an AMOG and AJAX intercomparison transect profiling from the San Joaquin Valley (SJV) floor into the Sierra Nevada (0.1-2.2 km altitude), validating a novel surface approach for atmospheric profiling by leveraging topography. The profile intercomparison found good agreement in multiple parameters for the overlapping altitude range from 500 to 1500 m for the upper 5 % of surface winds, which accounts for wind-impeding structures, i.e., terrain, trees, buildings, etc. Annualized emissions from the active oil fields were 31.3 ± 16 Gg methane and 2.4 ± 1.2 Tg carbon dioxide. Data showed the PBL was not well mixed at distances of 10-20 km downwind, highlighting the importance of the experimental design.

In situ diagnosis of pulsed UV laser surface ablation of tungsten carbide hardmetal by using laser-induced optical emission spectroscopy

NASA Astrophysics Data System (ADS)

Li, Tiejun; Lou, Qihong; Wei, Yunrong; Huang, Feng; Dong, Jingxing; Liu, Jingru

2001-12-01

Surface ablation of cobalt cemented tungsten carbide hardmetal with pulsed UV laser has been in situ diagnosed by using the technique of laser-induced optical emission spectroscopy. The dependence of emission intensity of cobalt lines on number of laser shots was investigated at laser fluence of 2.5 J/cm 2. As a comparison, the reliance of emission intensity of cobalt lines as a function of laser pulse number by using pure cobalt as ablation sample was also studied at the same laser condition. It was found that for surface ablation of tungsten carbide hardmetal at laser fluence of 2.5 J/cm 2, the intensities of cobalt lines fell off dramatically in the first 300 consecutive laser shots and then slowed down to a low stable level with even more shots. For surface ablation of pure cobalt at the same laser condition, the intensities of cobalt lines remained constant more or less even after 500 laser shots and then reduced very slowly with even more shots. It was concluded that selective evaporation of cobalt at this laser fluence should be responsible for the dramatic fall-off of cobalt lines with laser shots accumulation for surface ablation of tungsten carbide hardmetal. In contrast, for surface ablation of pure cobalt, the slow reduction of cobalt lines with pulse number accumulation should be due to the formation of laser-induced crater effect.

A field wind tunnel study of fine dust emissions in sandy soils

USDA-ARS?s Scientific Manuscript database

A portable field wind tunnel has been developed to allow measurements of dust emissions from soil surfaces to test the premise that dust concentration and properties are highly correlated with surface soil properties, as modified by crop management system. In this study, we report on the effect of ...

Stimulated emission of surface plasmons by electron tunneling in metal-barrier-metal structures

NASA Technical Reports Server (NTRS)

Siu, D. P.; Gustafson, T. K.

1978-01-01

It is shown that correlation currents arising from the superposition of pairs of states on distinct sides of a potential barrier in metal-barrier-metal structures can result in inelastic tunneling through the emission of surface plasmons. Net gain of an externally excited plasmon field is possible.

Laboratory evaluation of surface amendments for controlling greenhouse gas emissions from beef cattle feedlots.

USDA-ARS?s Scientific Manuscript database

Pen surface amendments for mitigating emissions of greenhouse gases (GHGs), such as nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2), from beef cattle feedlots, were evaluated under controlled laboratory conditions. Amendments were organic residues (i.e., sorghum straw, prairie grass, wo...

Characterizing Exoplanet Habitability with Emission Spectroscopy

NASA Astrophysics Data System (ADS)

Robinson, Tyler

2018-01-01

Results from NASA’s Kepler mission and other recent exoplanet surveys have demonstrated that potentially habitable exoplanets are relatively common, especially in the case of low-mass stellar hosts. The next key question that must be addressed for such planets is whether or not these worlds are actually habitable, implying they could sustain surface liquid water. Only through investigations of the potential habitability of exoplanets and through searches for biosignatures from these planets will we be able to understand if the emergence of life is a common phenomenon in our galaxy. Emission spectroscopy for transiting exoplanets (sometimes called secondary eclipse spectroscopy) is a powerful technique that future missions will use to study the atmospheres and surfaces of worlds orbiting in the habitable zones of nearby, low-mass stars. Emission observations that span the mid-infrared wavelength range for potentially habitable exoplanets provide opportunities to detect key habitability and life signatures, and also allow observers to probe atmospheric and surface temperatures. This presentation will outline the case for using emission spectroscopy to understand if an exoplanet can sustain surface liquid water, which is believed to be a critical precursor to the origin of life.

Mechanisms of high-gradient microwave breakdown on metal surfaces in high power microwave source

NASA Astrophysics Data System (ADS)

Xie, Jialing; Chen, Changhua; Chang, Chao; Wu, Cheng; Huo, Yankun

2017-12-01

A breakdown cavity was designed to study the high-gradient microwave breakdown on a metal surface. The breakdown cavity can be distinguished into an electron emission boundary and a bombardment boundary as there is an evident difference in amplitude of the electric field between the two planes in the cavity. Breakdown tracks on the cavity were studied with an electron scanning microscope. The tracks on the electron emission boundary with the higher electric field were eroded; a component analysis indicates that these tracks contain an emission boundary material. On the bombardment boundary with a lower electric field, two kinds of tracks exist: an erosion track containing a bombardment boundary material and a sputtered track containing an emission boundary material. From these tracks, the mechanisms of high-gradient microwave breakdown on a metal surface have been analyzed.

Evidence for a positron bound state on the surface of a topological insulator

NASA Astrophysics Data System (ADS)

Shastry, K.; Weiss, A. H.; Barbiellini, B.; Assaf, B. A.; Lim, Z. H.; Joglekar, P. V.; Heiman, D.

2015-06-01

We describe experiments aimed at probing the sticking of positrons to the surfaces of topological insulators using the Positron Annihilation induced Auger Electron Spectrometer (PAES). A magnetically guided beam was used to deposit positrons at the surface of Bi2Te2Se sample at energy of ∼2eV. Peaks observed in the energy spectra and intensities of electrons emitted as a result of positron annihilation showed peaks at energies corresponding to Auger peaks in Bi, Teand Se providing clear evidence of Auger emission associated with the annihilation of positrons in a surface bound state. Theoretical estimates of the binding energy of this state are compared with estimates obtained by measuring the incident beam energy threshold for secondary electron emission and the temperature dependence positronium(Ps) emission. The experiments provide strong evidence for the existence of a positron bound state at the surface of Bi2Te2Se and indicate the practicality of using positron annihilation to selectively probe the critically important top most layer of topological insulator system.

An assessment of surface emissivity variation effects on plasma uniformity analysis using IR cameras

NASA Astrophysics Data System (ADS)

Greenhalgh, Abigail; Showers, Melissa; Biewer, Theodore

2017-10-01

The Prototype-Material Plasma Exposure eXperiment (Proto-MPEX) is a linear plasma device operating at Oak Ridge National Laboratory (ORNL). Its purpose is to test plasma source and heating concepts for the planned Material Plasma Exposure eXperiment (MPEX), which has the mission to test the plasma-material interactions under fusion reactor conditions. In this device material targets will be exposed to high heat fluxes (>10 MW/m2). To characterize the heat fluxes to the target a IR thermography system is used taking up to 432 frames per second videos. The data is analyzed to determine the surface temperature on the target in specific regions of interest. The IR analysis has indicated a low level of plasma uniformity; the plasma often deposits more heat to the edge of the plate than the center. An essential parameter for IR temperature calculation is the surface emissivity of the plate (stainless steel). A study has been performed to characterize the variation in the surface emissivity of the plate as its temperature changes and its surface finish is modified by plasma exposure.

On the methane paradox: Transport from shallow water zones rather than in situ methanogenesis is the major source of CH4 in the open surface water of lakes

NASA Astrophysics Data System (ADS)

Encinas Fernández, Jorge; Peeters, Frank; Hofmann, Hilmar

2016-10-01

Estimates of global methane (CH4) emissions from lakes and the contributions of different pathways are currently under debate. In situ methanogenesis linked to algae growth was recently suggested to be the major source of CH4 fluxes from aquatic systems. However, based on our very large data set on CH4 distributions within lakes, we demonstrate here that methane-enriched water from shallow water zones is the most likely source of the basin-wide mean CH4 concentrations in the surface water of lakes. Consistently, the mean surface CH4 concentrations are significantly correlated with the ratio between the surface area of the shallow water zone and the entire lake, fA,s/t, but not with the total surface area. The categorization of CH4 fluxes according to fA,s/t may therefore improve global estimates of CH4 emissions from lakes. Furthermore, CH4 concentrations increase substantially with water temperature, indicating that seasonally resolved data are required to accurately estimate annual CH4 emissions.

The difference between laboratory and in-situ pixel-averaged emissivity: The effects on temperature-emissivity separation

NASA Technical Reports Server (NTRS)

Matsunaga, Tsuneo

1993-01-01

Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is a Japanese future imaging sensor which has five channels in thermal infrared (TIR) region. To extract spectral emissivity information from ASTER and/or TIMS data, various temperature-emissivity (T-E) separation methods have been developed to date. Most of them require assumptions on surface emissivity, in which emissivity measured in a laboratory is often used instead of in-situ pixel-averaged emissivity. But if these two emissivities are different, accuracies of separated emissivity and surface temperature are reduced. In this study, the difference between laboratory and in-situ pixel-averaged emissivity and its effect on T-E separation are discussed. TIMS data of an area containing both rocks and vegetation were also processed to retrieve emissivity spectra using two T-E separation methods.

Dynamics of a Sonoluminescing Bubble in Sulfuric Acid

NASA Astrophysics Data System (ADS)

Hopkins, Stephen D.; Putterman, Seth J.; Kappus, Brian A.; Suslick, Kenneth S.; Camara, Carlos G.

2005-12-01

The spectral shape and observed sonoluminescence emission from Xe bubbles in concentrated sulfuric acid is consistent only with blackbody emission from a spherical surface that fills the bubble. The interior of the observed 7000 K blackbody must be at least 4 times hotter than the emitting surface in order that the equilibrium light-matter interaction length be smaller than the radius. Bright emission is correlated with long emission times (˜10ns), sharp thresholds, unstable translational motion, and implosions that are sufficiently weak that contributions from the van der Waals hard core are small.

Dynamics of a sonoluminescing bubble in sulfuric acid.

PubMed

Hopkins, Stephen D; Putterman, Seth J; Kappus, Brian A; Suslick, Kenneth S; Camara, Carlos G

2005-12-16

The spectral shape and observed sonoluminescence emission from Xe bubbles in concentrated sulfuric acid is consistent only with blackbody emission from a spherical surface that fills the bubble. The interior of the observed 7000 K blackbody must be at least 4 times hotter than the emitting surface in order that the equilibrium light-matter interaction length be smaller than the radius. Bright emission is correlated with long emission times (approximately 10 ns), sharp thresholds, unstable translational motion, and implosions that are sufficiently weak that contributions from the van der Waals hard core are small.

Future heat waves and surface ozone

NASA Astrophysics Data System (ADS)

Meehl, Gerald A.; Tebaldi, Claudia; Tilmes, Simone; Lamarque, Jean-Francois; Bates, Susan; Pendergrass, Angeline; Lombardozzi, Danica

2018-06-01

A global Earth system model is used to study the relationship between heat waves and surface ozone levels over land areas around the world that could experience either large decreases or little change in future ozone precursor emissions. The model is driven by emissions of greenhouse gases and ozone precursors from a medium-high emission scenario (Representative Concentration Pathway 6.0–RCP6.0) and is compared to an experiment with anthropogenic ozone precursor emissions fixed at 2005 levels. With ongoing increases in greenhouse gases and corresponding increases in average temperature in both experiments, heat waves are projected to become more intense over most global land areas (greater maximum temperatures during heat waves). However, surface ozone concentrations on future heat wave days decrease proportionately more than on non-heat wave days in areas where ozone precursors are prescribed to decrease in RCP6.0 (e.g. most of North America and Europe), while surface ozone concentrations in heat waves increase in areas where ozone precursors either increase or have little change (e.g. central Asia, the Mideast, northern Africa). In the stabilized ozone precursor experiment, surface ozone concentrations increase on future heat wave days compared to non-heat wave days in most regions except in areas where there is ozone suppression that contributes to decreases in ozone in future heat waves. This is likely associated with effects of changes in isoprene emissions at high temperatures (e.g. west coast and southeastern North America, eastern Europe).

Topographic Effects on the Surface Emissivity of a Mountainous Area Observed by a Spaceborne Microwave Radiometer

PubMed Central

Pulvirenti, Luca; Pierdicca, Nazzareno; Marzano, Frank S.

2008-01-01

A simulation study to understand the influence of topography on the surface emissivity observed by a satellite microwave radiometer is carried out. We analyze the effects due to changes in observation angle, including the rotation of the polarization plane. A mountainous area in the Alps (Northern Italy) is considered and the information on the relief extracted from a digital elevation model is exploited. The numerical simulation refers to a radiometric image, acquired by a conically-scanning radiometer similar to AMSR-E, i.e., flying at 705 km of altitude with an observation angle of 55°. To single out the impact on surface emissivity, scattering of the radiation due to the atmosphere or neighboring elevated surfaces is not considered. C and X bands, for which atmospheric effects are negligible, and Ka band are analyzed. The results indicate that the changes in the local observation angle tend to lower the apparent emissivity of a radiometric pixel with respect to the corresponding flat surface characteristics. The effect of the rotation of the polarization plane enlarges (vertical polarization), or attenuates (horizontal polarization) this decrease. By doing some simplifying assumptions for the radiometer antenna, the conclusion is that the microwave emissivity at vertical polarization is underestimated, whilst the opposite occurs for horizontal polarization, except for Ka band, for which both under- and overprediction may occur. A quantification of the differences with respect to a flat soil and an approximate evaluation of their impact on soil moisture retrieval are yielded. PMID:27879773

Impact of surface ozone interactions on indoor air chemistry: A modeling study.

PubMed

Kruza, M; Lewis, A C; Morrison, G C; Carslaw, N

2017-09-01

An INdoor air Detailed Chemical Model was developed to investigate the impact of ozone reactions with indoor surfaces (including occupants), on indoor air chemistry in simulated apartments subject to ambient air pollution. The results are consistent with experimental studies showing that approximately 80% of ozone indoors is lost through deposition to surfaces. The human body removes ozone most effectively from indoor air per square meter of surface, but the most significant surfaces for C 6 -C 10 aldehyde formation are soft furniture and painted walls owing to their large internal surfaces. Mixing ratios of between 8 and 11 ppb of C 6 -C 10 aldehydes are predicted to form in apartments in various locations in summer, the highest values are when ozone concentrations are enhanced outdoors. The most important aldehyde formed indoors is predicted to be nonanal (5-7 ppb), driven by oxidation-derived emissions from painted walls. In addition, ozone-derived emissions from human skin were estimated for a small bedroom at nighttime with concentrations of nonanal, decanal, and 4-oxopentanal predicted to be 0.5, 0.7, and 0.7 ppb, respectively. A detailed chemical analysis shows that ozone-derived surface aldehyde emissions from materials and people change chemical processing indoors, through enhanced formation of nitrated organic compounds and decreased levels of oxidants. © 2017 The Authors. Indoor Air Published by John Wiley & Sons Ltd.

Space shuttle ram glow: Implication of NO2 recombination continuum

NASA Technical Reports Server (NTRS)

Swenson, G. R.; Mende, S. B.; Clifton, S.

1985-01-01

The ram glow data gathered to data from imaging experiments on space shuttle suggest the glow is a continuum (within 34 angstrom resolution); the continuum shape is such that the peak is near 7000 angstroms decreasing to the blue and red, and the average molecular travel leading to emission after leaving the surface is 20 cm (assuming isotropic scattering from the surface). Emission continuum is rare in molecular systems but the measured spectrum does resemble the laboratory spectrum of NO2 (B) recombination continuum. The thickness of the observed emission is consistent with the NO2 hypothesis given an exit velocity of approx. 2.5 km/sec (1.3 eV) which leaves approx. 3.7 eV of ramming OI energy available for unbonding the recombined NO2 from the surface. The NO2 is formed in a 3-body recombination of OI + NO + m = NO2 + m where OI originates from the atmosphere and NO is chemically formed on the surface from atmospheric NI and OI. The spacecraft surface then acts as the n for the reaction: Evidence exists from orbital mass spectrometer data that the NO and NO2 chemistry described in this process does occur on surfaces of spectrometer orifices in orbit. Surface temperature effects are likely a factor in the NO sticking efficiency and, therefore, glow intensities.

Space shuttle Ram glow: Implication of NO2 recombination continuum

NASA Astrophysics Data System (ADS)

Swenson, G. R.; Mende, S. B.; Clifton, S.

1985-09-01

The ram glow data gathered to data from imaging experiments on space shuttle suggest the glow is a continuum (within 34 angstrom resolution); the continuum shape is such that the peak is near 7000 angstroms decreasing to the blue and red, and the average molecular travel leading to emission after leaving the surface is 20 cm (assuming isotropic scattering from the surface). Emission continuum is rare in molecular systems but the measured spectrum does resemble the laboratory spectrum of NO2 (B) recombination continuum. The thickness of the observed emission is consistent with the NO2 hypothesis given an exit velocity of approx. 2.5 km/sec (1.3 eV) which leaves approx. 3.7 eV of ramming OI energy available for unbonding the recombined NO2 from the surface. The NO2 is formed in a 3-body recombination of OI + NO + m = NO2 + m where OI originates from the atmosphere and NO is chemically formed on the surface from atmospheric NI and OI. The spacecraft surface then acts as the n for the reaction: Evidence exists from orbital mass spectrometer data that the NO and NO2 chemistry described in this process does occur on surfaces of spectrometer orifices in orbit. Surface temperature effects are likely a factor in the NO sticking efficiency and, therefore, glow intensities.

Modeling quantum yield, emittance, and surface roughness effects from metallic photocathodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dimitrov, D. A.; Bell, G. I.; Smedley, J.

Here, detailed measurements of momentum distributions of emitted electrons have allowed the investigation of the thermal limit of the transverse emittance from metal photocathodes. Furthermore, recent developments in material design and growth have resulted in photocathodes that can deliver high quantum efficiency and are sufficiently robust to use in high electric field gradient photoinjectors and free electron lasers. The growth process usually produces photoemissive material layers with rough surface profiles that lead to transverse accelerating fields and possible work function variations, resulting in emittance growth. To better understand the effects of temperature, density of states, and surface roughness on themore » properties of emitted electrons, we have developed realistic three-dimensional models for photocathode materials with grated surface structures. They include general modeling of electron excitation due to photon absorption, charge transport, and emission from flat and rough metallic surfaces. The models also include image charge and field enhancement effects. We report results from simulations with flat and rough surfaces to investigate how electron scattering, controlled roughness, work function variation, and field enhancement affect emission properties. Comparison of simulation results with measurements of the quantum yield and transverse emittance from flat Sb emission surfaces shows the importance of including efficient modeling of photon absorption, temperature effects, and the material density of states to achieve agreement with the experimental data.« less

Modeling quantum yield, emittance, and surface roughness effects from metallic photocathodes

DOE PAGES

Dimitrov, D. A.; Bell, G. I.; Smedley, J.; ...

2017-10-26

Here, detailed measurements of momentum distributions of emitted electrons have allowed the investigation of the thermal limit of the transverse emittance from metal photocathodes. Furthermore, recent developments in material design and growth have resulted in photocathodes that can deliver high quantum efficiency and are sufficiently robust to use in high electric field gradient photoinjectors and free electron lasers. The growth process usually produces photoemissive material layers with rough surface profiles that lead to transverse accelerating fields and possible work function variations, resulting in emittance growth. To better understand the effects of temperature, density of states, and surface roughness on themore » properties of emitted electrons, we have developed realistic three-dimensional models for photocathode materials with grated surface structures. They include general modeling of electron excitation due to photon absorption, charge transport, and emission from flat and rough metallic surfaces. The models also include image charge and field enhancement effects. We report results from simulations with flat and rough surfaces to investigate how electron scattering, controlled roughness, work function variation, and field enhancement affect emission properties. Comparison of simulation results with measurements of the quantum yield and transverse emittance from flat Sb emission surfaces shows the importance of including efficient modeling of photon absorption, temperature effects, and the material density of states to achieve agreement with the experimental data.« less

A study of areas of low radio-thermal emissivity on Venus

NASA Astrophysics Data System (ADS)

Wilt, Robert Joseph

1992-01-01

Observations performed by the Magellan radiometer experiment have confirmed previous findings that a few regions on Venus, primarily at higher elevations, possess unexpectedly low values of radiothermal emissivity, occasionally reaching as low as 0.3. Values of emissivity below 0.7 occur over about 1.5 percent of the surface, and are associated with several types of features, including highlands, volcanoes, tectonically uplifted terrain, and impact craters. There is a strong correlation of low emissivity and high elevation, but rather than decreasing gradually with elevation, the emissivity drops rapidly in a small altitude range above a certain 'critical radius'. The altitude at which the change in emissive properties occurs varies from feature to feature; on average, it lies at a planetary radius of about 6054 km. Notable exceptions to the association of low emissivity and high elevation exist; for example, Lakshmi Planum, Maat Mons, and the summits of many volcanoes display high emissivities at high elevations, while in some impact craters and plains areas we find low emissivities at low elevations. Two possible explanations for low emissivities have been advanced: (1) emission from a highly reflective single interface between the atmosphere and a surface material having a bulk dielectric constant of order 80 ('high-dielectric' model); and (2) emission from the surface of a low-loss soil having a more usual permittivity (of order 2) which contains subsurface scatterers composed of ordinary rock materials ('volume scattering' model). Theoretical results and Monte Carlo simulations are used to show that the previously proposed volume scattering model cannot account for the observed emissivities; however, scattering from a material with very low loss (loss factor of order 10-3 or less) containing subsurface voids could produce the observed results. Consideration of the two models in light of the Magellan observations leads us to believe that the low emissivities on Venus result from the creation of a high-dielectic material by surface-atmosphere interaction, probably a loaded dielectric containing a conductive mineral.

On the Surface Mapping using Individual Cluster Impacts

PubMed Central

Fernandez-Lima, F.A.; Eller, M.J.; DeBord, J.D.; Verkhoturov, S.V.; Della-Negra, S.; Schweikert, E.A.

2011-01-01

This paper describes the advantages of using single impacts of large cluster projectiles (e.g. C60 and Au400) for surface mapping and characterization. The analysis of co-emitted time-resolved photon spectra, electron distributions and characteristic secondary ions shows that they can be used as surface fingerprints for target composition, morphology and structure. Photon, electron and secondary ion emission increases with the projectile cluster size and energy. The observed, high abundant secondary ion emission makes cluster projectiles good candidates for surface mapping of atomic and fragment ions (e.g., yield >1 per nominal mass) and molecular ions (e.g., few tens of percent in the 500 < m/z < 1500 range). PMID:22393269

Retrieving Land Surface Temperature and Emissivity from Multispectral and Hyperspectral Thermal Infrared Instruments

NASA Astrophysics Data System (ADS)

Hook, Simon; Hulley, Glynn; Nicholson, Kerry

2017-04-01

Land Surface Temperature and Emissivity (LST&E) data are critical variables for studying a variety of Earth surface processes and surface-atmosphere interactions such as evapotranspiration, surface energy balance and water vapor retrievals. LST&E have been identified as an important Earth System Data Record (ESDR) by NASA and many other international organizations Accurate knowledge of the LST&E is a key requirement for many energy balance models to estimate important surface biophysical variables such as evapotranspiration and plant-available soil moisture. LST&E products are currently generated from sensors in low earth orbit (LEO) such as the NASA Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on the Terra and Aqua satellites as well as from sensors in geostationary Earth orbit (GEO) such as the Geostationary Operational Environmental Satellites (GOES) and airborne sensors such as the Hyperspectral Thermal Emission Spectrometer (HyTES). LST&E products are generated with varying accuracies depending on the input data, including ancillary data such as atmospheric water vapor, as well as algorithmic approaches. NASA has identified the need to develop long-term, consistent, and calibrated data and products that are valid across multiple missions and satellite sensors. We will discuss the different approaches that can be used to retrieve surface temperature and emissivity from multispectral and hyperspectral thermal infrared sensors using examples from a variety of different sensors such as those mentioned, and planned new sensors like the ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) and the Hyperspectral Infrared Imager (HyspIRI). We will also discuss a project underway at NASA to develop a single unified product from some the individual sensor products and assess the errors associated with the product.

SURFACE-COATING-FREE MATERIALS WORKSHOP SUMMARY REPORT

EPA Science Inventory

The report documents a pollution prevention workshop that explored the concenpt of surface-coating-free materials (SCFMs) and the potential impact of this type of amterial on volatile organic compound (VOC) and air toxic emissions from surface coating operations. he report summar...

Research on effect of emission uniformity on X-band relativistic backward oscillator using conformal PIC code

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Zaigao

2016-07-15

Explosive emission cathodes (EECs) are adopted in relativistic backward wave oscillators (RBWOs) to generate intense relativistic electron beam. The emission uniformity of the EEC can render saturation of the power generation unstable and the output mode impure. However, the direct measurement of the plasma parameters on the cathode surface is quite difficult and there are very few related numerical study reports about this issue. In this paper, a self-developed three-dimensional conformal fully electromagnetic particle in cell code is used to study the effect of emission uniformity on the X-band RBWO; the electron explosive emission model and the field emission modelmore » are both implemented in the same cathode surface, and the local field enhancement factor is also considered in the field emission model. The RBWO with a random nonuniform EEC is thoroughly studied using this code; the simulation results reveal that when the area ratio of cathode surface for electron explosive emission is 80%, the output power is unstable and the output mode is impure. When the annular EEC does not emit electron in the angle range of 30°, the RBWO can also operate normally.« less

Simultaneous and multi-point measurement of ammonia emanating from human skin surface for the estimation of whole body dermal emission rate.

PubMed

Furukawa, Shota; Sekine, Yoshika; Kimura, Keita; Umezawa, Kazuo; Asai, Satomi; Miyachi, Hayato

2017-05-15

Ammonia is one of the members of odor gases and a possible source of odor in indoor environment. However, little has been known on the actual emission rate of ammonia from the human skin surface. Then, this study aimed to estimate the whole-body dermal emission rate of ammonia by simultaneous and multi-point measurement of emission fluxes of ammonia employing a passive flux sampler - ion chromatography system. Firstly, the emission fluxes of ammonia were non-invasively measured for ten volunteers at 13 sampling positions set in 13 anatomical regions classified by Kurazumi et al. The measured emission fluxes were then converted to partial emission rates using the surface body areas estimated by weights and heights of volunteers and partial rates of 13 body regions. Subsequent summation of the partial emission rates provided the whole body dermal emission rate of ammonia. The results ranged from 2.9 to 12mgh -1 with an average of 5.9±3.2mgh -1 per person for the ten healthy young volunteers. The values were much greater than those from human breath, and thus the dermal emission of ammonia was found more significant odor source than the breath exhalation in indoor environment. Copyright © 2017 Elsevier B.V. All rights reserved.

Review on peculiar issues of field emission in vacuum nanoelectronic devices

NASA Astrophysics Data System (ADS)

Filip, Valeriu; Filip, Lucian Dragoş; Wong, Hei

2017-12-01

Some of the modern aspects of field emission based electron sources have been collated in a short and comprehensive review. The usually overlooked peculiar aspects in this research field have been particularly emphasized in order to increase the interest in further fundamental studies and technological applications. The vast material was roughly split in two main branches which occasionally overlap: the electron emission devices based on chemically homogeneous nanostructured surfaces and the more complex nanocomposite emitting surfaces.

Improvement in thin cirrus retrievals using an emissivity-adjusted CO2 slicing algorithm

NASA Astrophysics Data System (ADS)

Zhang, Hong; Menzel, W. Paul

2002-09-01

CO2 slicing has been generally accepted as a useful algorithm for determining cloud top pressure (CTP) and effective cloud amount (ECA) for tropospheric clouds above 600 hPa. To date, the technique has assumed that the surface emissivity is that of a blackbody in the long-wavelength infrared radiances and that the cloud emissivities in spectrally close bands are approximately equal. The modified CO2 slicing algorithm considers adjustments of both surface emissivity and cloud emissivity ratio. Surface emissivity is adjusted according to the surface types. The ratio of cloud emissivities in spectrally close bands is adjusted away from unity according to radiative transfer calculations. The new CO2 slicing algorithm is examined with Moderate Resolution Imaging Spectroradiometer (MODIS) Airborne Simulator (MAS) CO2 band radiance measurements over thin clouds and validated against Cloud Lidar System (CLS) measurements of the same clouds; it is also applied to Geostationary Operational Environmental Satellite (GOES) Sounder data to study the overall impact on cloud property determinations. For high thin clouds an improved product emerges, while for thick and opaque clouds there is little change. For very thin clouds, the CTP increases by about 10-20 hPa and RMS (root mean square bias) difference is approximately 50 hPa; for thin clouds, the CTP increase is about 10 hPa bias and RMS difference is approximately 30 hPa. The new CO2 slicing algorithm places the clouds lower in the troposphere.

Tailoring of quantum dot emission efficiency by localized surface plasmon polaritons in self-organized mesoscopic rings.

PubMed

Margapoti, Emanuela; Gentili, Denis; Amelia, Matteo; Credi, Alberto; Morandi, Vittorio; Cavallini, Massimiliano

2014-01-21

We report on the tailoring of quantum dot (QD) emission efficiency by localized surface plasmon polaritons in self-organized mesoscopic rings. Ag nanoparticles (NPs) with CdSe QDs embedded in a polymeric matrix are spatially organised in mesoscopic rings and coupled in a tuneable fashion by breath figure formation. The mean distance between NPs and QDs and consequently the intensity of QD photoluminescence, which is enhanced by the coupling of surface plasmons and excitons, are tuned by acting on the NP concentration.

The effects of soil moisture, surface roughness, and vegetation on L-band emission and backscatter

NASA Technical Reports Server (NTRS)

Wang, James R.; Shiue, J. C.; Engman, Edwin T.; Schmugge, Thomas J.; Mo, Tsan

1987-01-01

Measurements performed with SIR-B at 1.28 GHz and an airborne multiple-beam push-broom radiometer at 1.4 GHz over agricultural fields near Fresno, California are examined. A theoretical model (Kirchhoff approximation) was used to assess the effects of surface roughness and vegetation (alfalfa and lettuce) with respect to the responses of microwave emission and backscatter to soil-moisture variations. It is found that the surface roughness plays a dominant role compared to the vegetation cover in the microwave backscatter.

Properties of dust and clouds in the Mars atmosphere: Analysis of Viking IRTM emission phase function sequences

NASA Technical Reports Server (NTRS)

Clancy, R. T.; Lee, S. W.

1991-01-01

An analysis of emission-phase-function (EPF) observations from the Viking Orbiter Infrared Thermal Mapper (IRTM) yields a wide variety of results regarding dust and cloud scattering in the Mars atmosphere and atmospheric-corrected albedos for the surface of Mars. A multiple scattering radiative transfer model incorporating a bidirectional phase function for the surface and atmospheric scattering by dust and clouds is used to derive surface albedos and dust and ice optical properties and optical depths for these various conditions on Mars.

The dynamics of a surface plasma generated by an independent source in the field of laser emission

NASA Astrophysics Data System (ADS)

Kovalev, A. S.; Popov, A. M.; Seleznev, B. V.; Feoktistov, V. A.

1986-09-01

A study is made of the evolution of a plasma formation generated by a high-power short pulse of an Nd laser on a metal surface, with the relatively weak emission of a CO2 laser focused on the surface. The thresholds of a sustained breakdown plasma are measured as a function of the plasma-generating pulse energy. The dynamics of plasma front propagation along the target surface and in the direction opposite to the laser beam direction is investigated. It is shown that the use of an additional laser with an energy less than that of the CO2 laser by 2-3 orders of magnitude makes it possible to generate a surface plasma capable of absorbing and transferring to the target a significantly greater fraction of the CO2 laser energy.

A Global Model Simulation of Aerosol Effects of Surface Radiation Budget- Toward Understanding of the "Dimming to Brightening" Transition

NASA Technical Reports Server (NTRS)

Chin, Mian; Diehl, Thomas; Bian, Huisheng; Yu, Hongbin

2008-01-01

We present a global model study on the role aerosols play in the change of solar radiation at Earth's surface that transitioned from a decreasing (dimming) trend to an increasing (brightening) trend. Our primary objective is to understand the relationship between the long-term trends of aerosol emission, atmospheric burden, and surface solar radiation. More specifically, we use the recently compiled comprehensive global emission datasets of aerosols and precursors from fuel combustion, biomass burning, volcanic eruptions and other sources from 1980 to 2006 to simulate long-term variations of aerosol distributions and optical properties, and then calculate the multi-decadal changes of short-wave radiative fluxes at the surface and at the top of the atmosphere by coupling the GOCART model simulated aerosols with the Goddard radiative transfer model. The model results are compared with long-term observational records from ground-based networks and satellite data. We will address the following critical questions: To what extent can the observed surface solar radiation trends, known as the transition from dimming to brightening, be explained by the changes of anthropogenic and natural aerosol loading on global and regional scales? What are the relative contributions of local emission and long-range transport to the surface radiation budget and how do these contributions change with time?

In situ investigation of helium fuzz growth on tungsten in relation to ion flux, fluence, surface temperature and ion energy using infrared imaging in PSI-2

NASA Astrophysics Data System (ADS)

Möller, S.; Kachko, O.; Rasinski, M.; Kreter, A.; Linsmeier, Ch

2017-12-01

Tungsten is a candidate material for plasma-facing components in nuclear fusion reactors. In operation it will face temperatures >800 K together with an influx of helium ions. Previously, the evolution of special surface nanostructures called fuzz was found under these conditions in a limited window of surface temperature, ion flux and ion energy. Fuzz potentially leads to lower heat load tolerances, enhanced erosion and dust formation, hence should be avoided in a fusion reactor. Here the fuzz growth is reinvestigated in situ during its growth by considering its impact on the surfaces infrared emissivity at 4 μm wavelength with an infrared camera in the linear plasma device PSI-2. A hole in the surface serves as an emissivity reference to calibrate fuzz thickness versus infrared emissivity. Among new data on the above mentioned relations, a lower fuzz growth threshold of 815 ± 24 K is found. Fuzz is seen to grow on rough and polished surfaces and even on the hole’s side walls alike. Literature scalings for thickness, flux and time relations of the fuzz growth rate could not be reproduced, but for the temperature scaling a good agreement to the Arrhenius equation was found.

Environmental factors controlling fluxes of dimethyl sulfide in a New Hampshire fen

NASA Technical Reports Server (NTRS)

Demello, William Zamboni; Hines, Mark E.

1992-01-01

The major environmental factors controlling fluxes of dimethyl sulfide (DMS) in a Sphagnum-dominated peatland were investigated in a poor fen in New Hampshire. DMS emissions from the surface of the peatland varied greatly over 24 hours and seasonally. Maximum DMS emissions occurred in summer with minima in the late fall. Temperature was the major environmental factor controlling these variabilities. There was also some evidence that the changes in water table height might have contributed to the seasonable variability in DMS emission. The influence of the water table was greater during periods of elevated temperature. DMS and MSH were the most abundant dissolved volatile sulfur compound (VSC) in the surface of the water table. Concentrations of dissolved VSC's varied with time and space throughout the fen. Dissolved MDS, MSH, and OCS in the surface of the water table were supersaturated with respect to their concentrations in the atmosphere suggesting that the peat surface was a source of VSC's in the peatland. VCS in peatlands seemed to be produced primarily by microbial processes in the anoxic surface layers of the peat rich in organic matter and inorganic sulfide. Sphagnum mosses were not a direct source of VSC's. However, they increased transport of DMS from the peat surface to the atmosphere.

Ion induced electron emission statistics under Agm- cluster bombardment of Ag

NASA Astrophysics Data System (ADS)

Breuers, A.; Penning, R.; Wucher, A.

2018-05-01

The electron emission from a polycrystalline silver surface under bombardment with Agm- cluster ions (m = 1, 2, 3) is investigated in terms of ion induced kinetic excitation. The electron yield γ is determined directly by a current measurement method on the one hand and implicitly by the analysis of the electron emission statistics on the other hand. Successful measurements of the electron emission spectra ensure a deeper understanding of the ion induced kinetic electron emission process, with particular emphasis on the effect of the projectile cluster size to the yield as well as to emission statistics. The results allow a quantitative comparison to computer simulations performed for silver atoms and clusters impinging onto a silver surface.

Quantitative measurements of acoustic emissions from cavitation at the surface of a stone in response to a lithotripter shock wave.

PubMed

Chitnis, Parag V; Cleveland, Robin O

2006-04-01

Measurements are presented of acoustic emissions from cavitation collapses on the surface of a synthetic kidney stone in response to shock waves (SWs) from an electrohydraulic lithotripter. A fiber optic probe hydrophone was used for pressure measurements, and passive cavitation detection was used to identify acoustic emissions from bubble collapse. At a lithotripter charging voltage of 20 kV, the focused SW incident on the stone surface resulted in a peak pressure of 43 +/- 6 MPa compared to 23 +/- 4 MPa in the free field. The focused SW incident upon the stone appeared to be enhanced due to the acoustic emissions from the forced cavitation collapse of the preexisting bubbles. The peak pressure of the acoustic emission from a bubble collapse was 34 +/- 15 MPa, that is, the same magnitude as the SWs incident on the stone. These data indicate that stresses induced by focused SWs and cavitation collapses are similar in magnitude thus likely play a similar role in stone fragmentation.

Using Directional Emissivity as a Probe of Particle Microphysical Properties

NASA Astrophysics Data System (ADS)

Pitman, K. M.; Wolff, M. J.; Bandfield, J. L.; Clayton, G. C.

2002-09-01

Real surfaces are not expected to be diffuse emitters, thus observed emissivity values are a function of viewing geometry. This fact has strong implications for analyses of the MGS/TES emission phase function (EPF) sequences and the upcoming Mars Exploration Rover mini-TES dataset. As reviewed previously [1], in the absence of strong thermal gradients, directional emissivity may be obtained via a combination of reciprocity and Kirchhoff's Law. Here we focus on the potential utility of directional emissivity as a direct probe of surface particle microphysical properties. We explore the effects of particle size and composition on observed radiances in the TES spectral regime using a combination of multiple scattering radiative transfer and Mie scattering algorithms. Comparisons of these simulated spectra to TES EPF observations of typical surface units (e.g., high and low albedo regions) will also be made. This work is supported through NASA grant NAGS-9820 (MJW) and LSU Board of Regents (KMP). [1] Pitman, K.M., et al. (2001), AAS-DPS meeting # 33, # 36.01.

Nanoparticle-density-dependent field emission of surface-decorated SiC nanowires

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dong, Qizheng; School of Materials and Chemical Engineering, Ningbo University of Technology, Ningbo City 315016; State Key Lab of New Fine Ceramics and Fine Processing, Tsinghua University, Beijing City 100084

2016-08-22

Increasing the electron emission site density of nanostructured emitters with limited field screening effects is one of the key issues for improving the field emission (FE) properties. In this work, we reported the Au-nanoparticles-density-dependent field emission behaviors of surface-decorated SiC nanowires. The Au nanoparticles (AuNPs) decorated around the surface of the SiC nanowires were achieved via an ion sputtering technique, by which the densities of the isolated AuNPs could be adjusted by controlling the fixed sputtering times. The measured FE characteristics demonstrated that the turn-on fields of the SiC nanowires were tuned to be of 2.06, 1.14, and 3.35 V/μm withmore » the increase of the decorated AuNPs densities, suggesting that a suitable decorated AuNPs density could render the SiC nanowires with totally excellent FE performances by increasing the emission sites and limiting the field screening effects.« less

Dust Emissions from Undisturbed and Disturbed, Crusted Playa Surfaces: Cattle Trampling Effect

USDA-ARS?s Scientific Manuscript database

Dry playa lake beds can be a significant source of fine dust emissions during high wind events in arid and semiarid landscapes. The physical and chemical properties of the playa surface control the amount and properties of the dust emitted. In this study, we use a field wind tunnel to quantify the...

Greenhouse gas emissions from beef feedlot surface materials as affected by diet, moisture, temperature, and time

USDA-ARS?s Scientific Manuscript database

A laboratory study was conducted to measure the effects of diet, moisture, temperature, and time on greenhouse gas (GHG) emissions from feedlot surface materials (FSM). The FSM were collected from open-lot pens where beef cattle were fed either a dry-rolled corn (DRC) diet containing no wet distille...

Volatile organic compound (VOC) emissions from beef feedlot pen surface as affected by within pen location, moisture, and temperature

USDA-ARS?s Scientific Manuscript database

A laboratory study was conducted to determine effects of pen location, moisture, and temperature on emissions of volatile organic compounds (VOC). Feedlot surface material (FSM) was obtained from pens where cattle were fed a diet containing 30% wet distillers grain plus soluble (WDGS). The FSM were ...

Electromagnetic radiation detector

DOEpatents

Benson, Jay L.; Hansen, Gordon J.

1976-01-01

An electromagnetic radiation detector including a collimating window, a cathode member having a photoelectric emissive material surface angularly disposed to said window whereby radiation is impinged thereon at acute angles, an anode, separated from the cathode member by an evacuated space, for collecting photoelectrons emitted from the emissive cathode surface, and a negatively biased, high transmissive grid disposed between the cathode member and anode.

The effect of surface oxide layer on the rate of hydrogen emission from aluminum and its alloys in a high vacuum

NASA Technical Reports Server (NTRS)

Makarova, V. I.; Zyabrev, A. A.

1979-01-01

The influence of surface oxide layers on the kinetics of hydrogen emission at the high vacuum of 10 to the minus 8th power torr was investigated at temperatures from 20 to 450 C using samples of pure AB00 aluminum and the cast alloy AMg. Cast and deformed samples of AMts alloy were used to study the effect of oxide film thickness on the rate of hydrogen emission. Thermodynamic calculations of the reactions of the generation and dissociation of aluminum oxide show that degasification at elevated temperatures (up to 600 C) and high vacuum will not reduce the thickness of artificially-generated surface oxide layers on aluminum and its alloys.

Recent NASA/GSFC cryogenic measurements of the total hemispheric emissivity of black surface preparations

NASA Astrophysics Data System (ADS)

Tuttle, J.; Canavan, E.

2015-12-01

High-emissivity (black) surfaces are commonly used on deep-space radiators and thermal radiation absorbers in test chambers. Since 2011 NASA Goddard Space Flight Center has measured the total hemispheric emissivity of such surfaces from 20 to 300 K using a test apparatus inside a small laboratory cryostat. We report the latest data from these measurements, including Aeroglaze Z307 paint, Black Kapton, and a configuration of painted aluminum honeycomb that was not previously tested. We also present the results of batch-to- batch reproducibility studies in Ball Infrared BlackTM and painted aluminum honeycomb. Finally, we describe a recently-adopted temperature control method which significantly speeds the data acquisition, and we discuss efforts to reduce the noise in future data.

Areas of Anomalous Surface Temperature in Archuleta County, Colorado, as Identified from ASTER Thermal Data

DOE Data Explorer

Khalid Hussein

2012-02-01

This layer contains areas of anomalous surface temperature in Archuleta County identified from ASTER thermal data and spatial based insolation model. The temperature is calculated using the Emissivity Normalization Algorithm that separate temperature from emissivity. The incoming solar radiation was calculated using spatial based insolation model developed by Fu and Rich (1999). Then the temperature due to solar radiation was calculated using emissivity derived from ASTER data. The residual temperature, i.e. temperature due to solar radiation subtracted from ASTER temperature was used to identify thermally anomalous areas. Areas that had temperature greater than 2o were considered ASTER modeled very warm surface exposures (thermal anomalies). Note: 'o' is used in this description to represent lowercase sigma

Areas of Anomalous Surface Temperature in Dolores County, Colorado, as Identified from ASTER Thermal Data

DOE Data Explorer

Khalid Hussein

2012-02-01

This layer contains areas of anomalous surface temperature in Dolores County identified from ASTER thermal data and spatial based insolation model. The temperature is calculated using the Emissivity Normalization Algorithm that separate temperature from emissivity. The incoming solar radiation was calculated using spatial based insolation model developed by Fu and Rich (1999). Then the temperature due to solar radiation was calculated using emissivity derived from ASTER data. The residual temperature, i.e. temperature due to solar radiation subtracted from ASTER temperature was used to identify thermally anomalous areas. Areas that had temperature greater than 2o were considered ASTER modeled very warm surface exposures (thermal anomalies). Note: 'o' is used in this description to represent lowercase sigma

Areas of Anomalous Surface Temperature in Chaffee County, Colorado, as Identified from ASTER Thermal Data

DOE Data Explorer

Khalid Hussein

2012-02-01

This layer contains areas of anomalous surface temperature in Chaffee County identified from ASTER thermal data and spatial based insolation model. The temperature is calculated using the Emissivity Normalization Algorithm that separate temperature from emissivity. The incoming solar radiation was calculated using spatial based insolation model developed by Fu and Rich (1999). Then the temperature due to solar radiation was calculated using emissivity derived from ASTER data. The residual temperature, i.e. temperature due to solar radiation subtracted from ASTER temperature was used to identify thermally anomalous areas. Areas that had temperature greater than 2o were considered ASTER modeled very warm surface exposures (thermal anomalies). Note: 'o' is used in this description to represent lowercase sigma

Areas of Anomalous Surface Temperature in Garfield County, Colorado, as Identified from ASTER Thermal Data

DOE Data Explorer

Khalid Hussein

2012-02-01

This layer contains areas of anomalous surface temperature in Garfield County identified from ASTER thermal data and spatial based insolation model. The temperature is calculated using the Emissivity Normalization Algorithm that separate temperature from emissivity. The incoming solar radiation was calculated using spatial based insolation model developed by Fu and Rich (1999). Then the temperature due to solar radiation was calculated using emissivity derived from ASTER data. The residual temperature, i.e. temperature due to solar radiation subtracted from ASTER temperature was used to identify thermally anomalous areas. Areas that had temperature greater than 2o were considered ASTER modeled very warm surface exposures (thermal anomalies). Note: 'o' is used in this description to represent lowercase sigma.

Areas of Anomalous Surface Temperature in Routt County, Colorado, as Identified from ASTER Thermal Data

DOE Data Explorer

Khalid Hussein

2012-02-01

This layer contains areas of anomalous surface temperature in Routt County identified from ASTER thermal data and spatial based insolation model. The temperature is calculated using the Emissivity Normalization Algorithm that separate temperature from emissivity. The incoming solar radiation was calculated using spatial based insolation model developed by Fu and Rich (1999). Then the temperature due to solar radiation was calculated using emissivity derived from ASTER data. The residual temperature, i.e. temperature due to solar radiation subtracted from ASTER temperature was used to identify thermally anomalous areas. Areas that had temperature greater than 2o were considered ASTER modeled very warm surface exposures (thermal anomalies). Note: 'o' is used in this description to represent lowercase sigma.

Full-spectrum multiwavelength pyrometry for nongray surfaces

NASA Technical Reports Server (NTRS)

Ng, Daniel; Williams, W. D.

1992-01-01

A full-spectrum (encompassing radiation on both sides of the Wien displacement peak) multiwavelength pyrometer was developed. It measures the surface temperature of arbitrary nongray ceramics by curve fitting a spectrum in this spectral region to a Planck function of temperature T. This function of T is modified by the surface spectral emissivity. The emissivity function was derived experimentally from additional spectra that were obtained by using an auxiliary radiation source and from application of Kirchhoff's law. This emissivity was verified by results that were obtained independently by using electromagnetic and solid-state theories. In the presence of interfering reflected radiation this general pyrometry improves the accuracy of the measured temperature by measuring an additional spectrum that characterizes the interfering radiation source.

Surface ozone seasonality under global change: Influence from dry deposition and isoprene emissions at northern mid-latitudes

NASA Astrophysics Data System (ADS)

Clifton, O.; Paulot, F.; Fiore, A. M.; Horowitz, L. W.; Malyshev, S.; Shevliakova, E.; Correa, G. J. P.; Lin, M.

2017-12-01

Identifying the contributions of nonlinear chemistry and transport to observed surface ozone seasonal cycles over land using global models relies on an accurate representation of ozone uptake by vegetation (dry deposition). It is well established that in the absence of ozone precursor emission changes, a warming climate will increase surface ozone in polluted regions, and that a rise in temperature-dependent isoprene emissions would exacerbate this "climate penalty". However, the influence of changes in ozone dry deposition, expected to evolve with climate and land use, is often overlooked in air quality projections. With a new scheme that represents dry deposition within the NOAA GFDL dynamic vegetation land model (LM3) coupled to the NOAA GFDL atmospheric chemistry-climate model (AM3), we simulate the impact of 21st century climate and land use on ozone dry deposition and isoprene emissions. This dry deposition parameterization is a version of the Wesely scheme, but uses parameters explicitly calculated by LM3 that respond to climate and land use (e.g., stomatal conductance, canopy interception of water, leaf area index). The parameterization includes a nonstomatal deposition dependence on humidity. We evaluate climatological present-day seasonal cycles of ozone deposition velocities and abundances with those observed at northern mid-latitude sites. With a set of 2010s and 2090s decadal simulations under a high climate warming scenario (RCP8.5) and a sensitivity simulation with well-mixed greenhouse gases following RCP8.5 but air pollutants held at 2010 levels (RCP8.5_WMGG), we examine changes in surface ozone seasonal cycles. We build on our previous findings, which indicate that strong reductions in anthropogenic NOx emissions under RCP8.5 cause the surface ozone seasonal cycle over the NE USA to reverse, shifting from a summer peak at present to a winter peak by 2100. Under RCP8.5_WMGG, we parse the separate effects of climate and land use on ozone dry deposition vs. isoprene emissions to quantify the impact of each process on surface ozone seasonal cycles and compare to the changes induced by declining anthropogenic NOx emissions (RCP8.5).

Performance evaluation of four directional emissivity analytical models with thermal SAIL model and airborne images.

PubMed

Ren, Huazhong; Liu, Rongyuan; Yan, Guangjian; Li, Zhao-Liang; Qin, Qiming; Liu, Qiang; Nerry, Françoise

2015-04-06

Land surface emissivity is a crucial parameter in the surface status monitoring. This study aims at the evaluation of four directional emissivity models, including two bi-directional reflectance distribution function (BRDF) models and two gap-frequency-based models. Results showed that the kernel-driven BRDF model could well represent directional emissivity with an error less than 0.002, and was consequently used to retrieve emissivity with an accuracy of about 0.012 from an airborne multi-angular thermal infrared data set. Furthermore, we updated the cavity effect factor relating to multiple scattering inside canopy, which improved the performance of the gap-frequency-based models.

Multispectral thermal infrared mapping of the 1 October 1988 Kupaianaha flow field, Kilauea volcano, Hawaii

USGS Publications Warehouse

Realmuto, V.J.; Hon, K.; Kahle, A.B.; Abbott, E.A.; Pieri, D.C.

1992-01-01

Multispectral thermal infrared radiance measurements of the Kupaianaha flow field were acquired with the NASA airborne Thermal Infrared Multispectral Scanner (TIMS) on the morning of 1 October 1988. The TIMS data were used to map both the temperature and emissivity of the surface of the flow field. The temperature map depicted the underground storage and transport of lava. The presence of molten lava in a tube or tumulus resulted in surface temperatures that were at least 10?? C above ambient. The temperature map also clearly defined the boundaries of hydrothermal plumes which resulted from the entry of lava into the ocean. The emissivity map revealed the boundaries between individual flow units within the Kupaianaha field. In general, the emissivity of the flows varied systematically with age but the relationship between age and emissivity was not unique. Distinct spectral anomalies, indicative of silica-rich surface materials, were mapped near fumaroles and ocean entry sites. This apparent enrichment in silica may have resulted from an acid-induced leaching of cations from the surfaces of glassy flows. Such incipient alteration may have been the cause for virtually all of the emissivity variations observed on the flow field, the spectral anomalies representing areas where the acid attack was most intense. ?? 1992 Springer-Verlag.

Land surface temperature measurements from EOS MODIS data

NASA Technical Reports Server (NTRS)

Wan, Zhengming

1995-01-01

A significant progress has been made in TIR instrumentation which is required to establish the spectral BRDF/emissivity knowledge base of land-surface materials and to validate the land-surface temperature (LST) algorithms. The SIBRE (spectral Infrared Bidirectional Reflectance and Emissivity) system and a TIR system for measuring spectral directional-hemispherical emissivity have been completed and tested successfully. Optical properties and performance features of key components (including spectrometer, and TIR source) of these systems have been characterized by integrated use of local standards (blackbody and reference plates). The stabilization of the spectrometer performance was improved by a custom designed and built liquid cooling system. Methods and procedures for measuring spectral TIR BRDF and directional-hemispheric emissivity with these two systems have been verified in sample measurements. These TIR instruments have been used in the laboratory and the field, giving very promising results. The measured spectral emissivities of water surface are very close to the calculated values based on well established water refractive index values in published papers. Preliminary results show that the TIR instruments can be used for validation of the MODIS LST algorithm in homogeneous test sites. The beta-3 version of the MODIS LST software is being prepared for its delivery scheduled in the early second half of this year.

Enhanced stability of Janus nanoparticles by covalent cross-linking of surface ligands.

PubMed

Song, Yang; Klivansky, Liana M; Liu, Yi; Chen, Shaowei

2011-12-06

A mercapto derivative of diacetylene was used as the hydrophilic ligand to prepare Janus nanoparticles by using hydrophobic hexanethiolate-protected gold (AuC6, diameter 5 nm) nanoparticles as the starting materials. The amphiphilic surface characters of the Janus nanoparticles were verified by contact angle measurements, as compared to those of the bulk-exchange counterparts where the two types of ligands were distributed rather homogeneously on the nanoparticle surface. Dynamic light scattering studies showed that the Janus nanoparticles formed stable superstructures in various solvent media that were significantly larger than those by the bulk-exchange counterparts. This was ascribed to the amphiphilic characters of the Janus nanoparticles that rendered the particles to behave analogously to conventional surfactant molecules. Notably, because of the close proximity of the diacetylene moieties on the Janus nanoparticle surface, exposure to UV irradiation led to effective covalent cross-linking between the diacetylene moieties of neighboring ligands, as manifested in UV-vis and fluorescence measurements where the emission characteristics of dimers and trimers of diacetylene were rather well-defined, in addition to the monomeric emission. In contrast, for bulk-exchange nanoparticles, no trimer emission could be identified, and the intensity of dimer emission was markedly lower (though the intensity increased with increasing diacetylene coverage on the particle surface) under the otherwise identical experimental conditions. This is largely because the diacetylene ligands were distributed on the entire particle surface, and it was difficult to find a large number of ligands situated closely so that the stringent topochemical principles for the polymerization of diacetylene derivatives could be met. Importantly, the cross-linked Janus nanoparticles were found to exhibit marked enhancement of the structural integrity, which was attributable to the impeded surface diffusion of the thiol ligands on the nanoparticle surface, as manifested in fluorescence measurements of aged nanoparticles. © 2011 American Chemical Society

Secondary emission from dust grains: Comparison of experimental and model results

NASA Astrophysics Data System (ADS)

Richterova, I.; Pavlu, J.; Nemecek, Z.; Safrankova, J.; Zilavy, P.

The motion, coalescence, and other processes in dust clouds are determined by the dust charge. Since dust grains in the space are bombarded by energetic electrons, the secondary emission is an important process contributing to their charge. It is generally expected that the secondary emission yield is related to surface properties of the bombarded body. However, it is well known that secondary emission from small bodies is determined not only by their composition but an effect of dimension can be very important when the penetration depth of primary electrons is comparable with the grain size. It implies that the secondary emission yield can be influenced by the substrate material if the surface layer is thin enough. We have developed a simple Monte Carlo model of secondary emission that was successfully applied on the dust simulants from glass and melanine formaldehyd (MF) resin and matched very well experimental results. In order to check the influence of surface layers, we have modified the model for spheres covered by a layer with different material properties. The results of model simulations are compared with measurements on MF spheres covered by different metals.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shao, Jiahang; Antipov, Sergey P.; Baryshev, Sergey V.

Field emission from a solid metal surface has been continuously studied for a century over macroscopic to atomic scales. It is general knowledge that, other than the surface properties, the emitted current is governed solely by the applied electric field. A pin cathode has been used to study the dependence of field emission on stored energy in an L-band rf gun. The stored energy was changed by adjusting the axial position (distance between the cathode base and the gun back surface) of the cathode while the applied electric field on the cathode tip is kept constant. Avery strong correlation ofmore » the field-emission current with the stored energy has been observed. While eliminating all possible interfering sources, an enhancement of the current by a factor of 5 was obtained as the stored energy was increased by a factor of 3. It implies that under certain circumstances a localized field emission may be significantly altered by the global parameters in a system.« less

Graphene surface plasmons mediated thermal radiation

NASA Astrophysics Data System (ADS)

Li, Jiayu; Liu, Baoan; Shen, Sheng

2018-02-01

A graphene nanostructure can simultaneously serve as a plasmonic optical resonator and a thermal emitter when thermally heated up. The unique electronic and optical properties of graphene have rendered tremendous potential in the active manipulation of light and the microscopic energy transport in nanostructures. Here we show that the thermally pumped surface plasmonic modes along graphene nanoribbons could dramatically modulate their thermal emission spectra in both near- and far-fields. Based on the fluctuating surface current method implemented by the resistive boundary method, we directly calculate the thermal emission spectrum from single graphene ribbons and vertically paired graphene ribbons. Furthermore, we demonstrate that both the near- and far-field thermal emission from graphene nanostructures can be optimized by tuning the chemical potential of doped graphene. The general guideline to maximize the thermal emission is illustrated by the our recently developed theory on resonant thermal emitters modulated by quasi-normal modes.

The Sensitivity of U.S. Surface Ozone Formation to NOx, and VOCs as Viewed from Space

NASA Technical Reports Server (NTRS)

Duncan, Bryan N.; Yoshida, Yasuko; Sillman, Sanford; Retscher, Christian; Pickering, Kenneth E.; Martin, Randall V.; Celarier, Edward A.

2009-01-01

We investigated variations in the sensitivity of surface ozone formation in summer to precursor species concentrations of volatile organic compounds (VOCs) and nitrogen oxides (NO(x)) as inferred from the ratio of tropospheric columns of formaldehyde and nitrogen dioxide from the Aura Ozone Monitoring Instrument (OMI). The data indicate that ozone formation became: 1. more sensitive to NO(x) over most of the U.S, from 2005 to 2007 because of substantial decreases in NO(x) emissions primarily from stationary sources, and 2. more sensitive to NO(x) with increasing temperature, in part because emissions of highly reactive, biogenic isoprene increase with temperature, thus increasing the total VOC reactivity. Based on our interpretation of the data, current strategies implemented to reduce unhealthy levels of surface ozone should focus more on reducing NO(x) emissions, except in some downtown areas which have historically benefited from reductions in VOC emissions.

Surface characterization of carbon fiber reinforced polymers by picosecond laser induced breakdown spectroscopy

NASA Astrophysics Data System (ADS)

Ledesma, Rodolfo; Palmieri, Frank; Connell, John; Yost, William; Fitz-Gerald, James

2018-02-01

Adhesive bonding of composite materials requires reliable monitoring and detection of surface contaminants as part of a vigorous quality control process to assure robust and durable bonded structures. Surface treatment and effective monitoring prior to bonding are essential in order to obtain a surface which is free from contaminants that may lead to inferior bond quality. In this study, the focus is to advance the laser induced breakdown spectroscopy (LIBS) technique by using pulse energies below 100 μJ (μLIBS) for the detection of low levels of silicone contaminants in carbon fiber reinforced polymer (CFRP) composites. Various CFRP surface conditions were investigated by LIBS using ∼10 ps, 355 nm laser pulses with pulse energies below 30 μJ. Time-resolved analysis was conducted to optimize the gate delay and gate width for the detection of the C I emission line at 247.9 nm to monitor the epoxy resin matrix of CFRP composites and the Si I emission line at 288.2 nm for detection of silicone contaminants in CFRP. To study the surface sensitivity to silicone contamination, CFRP surfaces were coated with polydimethylsiloxane (PDMS), the active ingredient in many mold release agents. The presence of PDMS was studied by inspecting the Si I emission lines at 251.6 nm and 288.2 nm. The measured PDMS areal densities ranged from 0.15 to 2 μg/cm2. LIBS measurements were performed before and after laser surface ablation. The results demonstrate the successful detection of PDMS thin layers on CFRP using picosecond μLIBS.

Localization of burn mark under an abnormal topography on MOSFET chip surface using liquid crystal and emission microscopy tools.

PubMed

Lau, C K; Sim, K S; Tso, C P

2011-01-01

This article focuses on the localization of burn mark in MOSFET and the scanning electron microscope (SEM) inspection on the defect location. When a suspect abnormal topography is shown on the die surface, further methods to pin-point the defect location is necessary. Fault localization analysis becomes important because an abnormal spot on the chip surface may and may not have a defect underneath it. The chip surface topography can change due to the catastrophic damage occurred at layers under the chip surface, but it could also be due to inconsistency during metal deposition in the wafer fabrication process. Two localization techniques, liquid crystal thermography and emission microscopy, were performed to confirm that the abnormal topography spot is the actual defect location. The tiny burn mark was surfaced by performing a surface decoration at the defect location using hot hydrochloric acid. SEM imaging, which has the high magnification and three-dimensional capabilities, was used to capture the images of the burn mark. Copyright © 2011 Wiley Periodicals, Inc.

How Well Can Infrared Sounders Observe the Atmosphere and Surface Through Clouds?

NASA Technical Reports Server (NTRS)

Zhou, Daniel K.; Larar, Allen M.; Liu, Xu; Smith, William L.; Strow, L. Larrabee; Yang, Ping

2010-01-01

Infrared sounders, such as the Atmospheric Infrared Sounder (AIRS), the Infrared Atmospheric Sounding Interferometer (IASI), and the Cross-track Infrared sounder (CrIS), have a cloud-impenetrable disadvantage in observing the atmosphere and surface under opaque cloudy conditions. However, recent studies indicate that hyperspectral, infrared sounders have the ability to detect cloud effective-optical and microphysical properties and to penetrate optically thin clouds in observing the atmosphere and surface to a certain degree. We have developed a retrieval scheme dealing with atmospheric conditions with cloud presence. This scheme can be used to analyze the retrieval accuracy of atmospheric and surface parameters under clear and cloudy conditions. In this paper, we present the surface emissivity results derived from IASI global measurements under both clear and cloudy conditions. The accuracy of surface emissivity derived under cloudy conditions is statistically estimated in comparison with those derived under clear sky conditions. The retrieval error caused by the clouds is shown as a function of cloud optical depth, which helps us to understand how well infrared sounders can observe the atmosphere and surface through clouds.

The effect of magnetic topography on high-latitude radio emission at Neptune

NASA Technical Reports Server (NTRS)

Sawyer, C. B.; Warwick, James W.; Romig, J. H.

1992-01-01

Occultation by a local elevation on the surface of constant magnetic field is proposed as a new interpretation for the unusual properties of Neptune high-latitude emission. Abrupt changes in intensity and polarization of this broadband smooth radio emission were observed as the Voyager 2 spacecraft passed near the north magnetic pole before closest approach. The observed sequence of cutoffs with polarization reversal would not occur during descent of the spacecraft through regular surfaces of increasing magnetic field. The sequence can be understood in terms of constant-frequency (constant-field) surfaces that are not only offset from the planet center but are locally highly distorted by an elevation that occults the outgoing extraordinary-mode beam. The required occulter is similar to the field enhancement observed directly by the magnetometer team when Voyager reached lower altitude farther to the west. Evidence is presented that the sources of the high-altitude emission are located near the longitude of the minimum-B anomaly associated with the dipole offset and that the local elevation of constant-B surfaces extends eastward from the longitude where it is directly measured by the magnetometer to the longitude where occultation of the remote radio source is observed. Together, the radio and magnetometer experiments indicate that the constant-frequency surfaces are distorted by an elevation that extends 0.3 rad in the longitudinal direction.

Experiment of Rain Retrieval over Land Using Surface Emissivity Map Derived from TRMM TMI and JRA25

NASA Astrophysics Data System (ADS)

Furuzawa, Fumie; Masunaga, Hirohiko; Nakamura, Kenji

2010-05-01

We are developing a data-set of global land surface emissivity calculated from TRMM TMI brightness temperature (TB) and atmospheric profile data of Japanese 25-year Reanalysis Project (JRA-25) for the region identified as no-rain by TRMM PR, assuming zero cloud liquid water beyond 0-C level. For the evaluation, some characteristics of global monthly emissivity maps, for example, dependency of emissivity on each TMI frequency or each local time or seasonal/annual variation are checked. Moreover, these data are classified based on JRA25 land type or soilwetness and compared. Histogram of polarization difference of emissivity is similar to that of TB and mostly reflects the variability of land type or soil wetness, while histogram of vertical emissivity show a small difference. Next, by interpolating this instantaneous dataset with Gaussian function weighting, we derive an emissivity over neighboring rainy region and assess the interpolated emissivity by running radiative transfer model using PR rain profile and comparing with observed TB. Preliminary rain retrieval from the emissivities for some frequencies and TBs is evaluated based on PR rain profile and TMI rain rate. Moreover, another method is tested to estimate surface temperature from two emissivities, based on their statistical relation for each land type. We will show the results for vertical and horizontal emissivities of each frequency.

DISAGGREGATION OF GOES LAND SURFACE TEMPERATURES USING SURFACE EMISSIVITY

USDA-ARS?s Scientific Manuscript database

Accurate temporal and spatial estimation of land surface temperatures (LST) is important for modeling the hydrological cycle at field to global scales because LSTs can improve estimates of soil moisture and evapotranspiration. Using remote sensing satellites, accurate LSTs could be routine, but unfo...

The response of the SSM/I to the marine environment. Part 2: A parameterization of the effect of the sea surface slope distribution on emission and reflection

NASA Technical Reports Server (NTRS)

Petty, Grant W.; Katsaros, Kristina B.

1994-01-01

Based on a geometric optics model and the assumption of an isotropic Gaussian surface slope distribution, the component of ocean surface microwave emissivity variation due to large-scale surface roughness is parameterized for the frequencies and approximate viewing angle of the Special Sensor Microwave/Imager. Independent geophysical variables in the parameterization are the effective (microwave frequency dependent) slope variance and the sea surface temperature. Using the same physical model, the change in the effective zenith angle of reflected sky radiation arising from large-scale roughness is also parameterized. Independent geophysical variables in this parameterization are the effective slope variance and the atmospheric optical depth at the frequency in question. Both of the above model-based parameterizations are intended for use in conjunction with empirical parameterizations relating effective slope variance and foam coverage to near-surface wind speed. These empirical parameterizations are the subject of a separate paper.

Biogenic Emission Inventories: Scaling Local Biogenic Measurements to Regions

NASA Astrophysics Data System (ADS)

Lamb, B.; Pressley, S.; Westberg, H.; Guenther, A.

2002-12-01

Biogenic Hydrocarbons, such as isoprene, are important trace gas species that are naturally emitted by vegetation and that affect the oxidative capacity of the atmosphere. Biogenic emissions are regulated by many environmental variables; the most important variables are thought to be temperature and light. Long-term isoprene flux measurements are useful for verifying existing canopy models and exploring other correlations between isoprene fluxes and environmental parameters. Biogenic Emission Models, such as BEIS (Biogenic Emission Inventory System) rely on above canopy environmental parameters and below canopy scaling factors to estimate canopy scale biogenic hydrocarbon fluxes. Other models, which are more complex, are coupled micrometeorological and physiological modules that provide feedback mechanisms present in a canopy environment. These types of models can predict biogenic emissions well, however, the required input is extensive, and for regional applications, they can be cumbersome. This paper presents analyses based on long-term isoprene flux measurements that have been collected since 1999 at the AmeriFlux site located at the University of Michigan Biological Station (UMBS) as part of the Program for Research on Oxidants: PHotochemistry, Emissions, and Transport (PROPHET). The goals of this research were to explore a potential relationship between the surface energy budget (primarily sensible heat flux) and isoprene emissions. Our hypothesis is that the surface energy flux is a better model parameter for isoprene emissions at the canopy scale than temperature and light levels, and the link to the surface energy budget will provide a significant improvement in isoprene emission models. Preliminary results indicate a significant correlation between daily isoprene emissions and sensible heat fluxes for a predominantly aspen/oak stand located in northern Michigan. Since surface energy budgets are an integral part of mesoscale meteorological models, this could potentially be a useful tool for including biogenic emissions into regional atmospheric models. Comparison of measured isoprene fluxes with current BEIS estimates will also be shown as an example of where emission inventories currently stand.

Changes in the emission properties of metallic targets upon exposure to repetitively pulsed laser radiation

NASA Astrophysics Data System (ADS)

Konov, V. I.; Pimenov, S. M.; Prokhorov, A. M.; Chapliev, N. I.

1988-02-01

A scanning electron microscope and a repetitively pulsed CO2 laser are used to reveal the relationships which govern the correlation of the transforming metal surface microrelief with the emission of charged particles and the surface luminescence upon exposure to multipulse laser focusing. It is shown that the effect of sorption and laser-stimulated desorption on the emission signals can manifest itself in different ways depending on the current oscillation mode in the target-vacuum chamber circuit.

Rough-surface model for surface temperature calculations on Vesta

NASA Astrophysics Data System (ADS)

Palmer, E.; Sykes, M.

2014-07-01

We model observations by the Dawn Visual and Infrared spectrometer (VIR) [1] to reproduce the observed surface temperature of Vesta. The VIR instrument has collected over 3,700 spectral cubes of Vesta out to 5.1 microns. The observed surface temperature is derived by matching the irradiance near 5 microns with a grey body, the Planck function after removing a reflected-light component per previous procedures [2--5] with similar results. We noted that the observed surface temperatures are significantly hotter than what simple theoretical models would predict [2]. To better understand this, we used a high-resolution topographic model of Vesta [6] that provided exact phase, incidence, and emission angles for every VIR pixel. We assume an emissivity of 0.9, Bond albedo of between 0.16 and 0.22 [5], and a variety of thermal inertia values for a low-contrast, highly degraded, homogenous crater. We have created a ''rough-surface'' thermal model that takes into account how irregular grains create sub-pixel variations in the thermal spectrum and describe the effect it has on the observed surface temperatures of Vesta. We have applied this method to the VIR observations of Vesta, which produced a high level of agreement with the observed surface temperatures.

Surface Power Radiative Cooling Tests

NASA Astrophysics Data System (ADS)

Vaughn, Jason; Schneider, Todd

2006-01-01

Terrestrial nuclear power plants typically maintain their temperature through convective cooling, such as water and forced air. However, the space environment is a vacuum environment, typically 10-8 Torr pressure, therefore in proposed missions to the lunar surface, power plants would have to rely on radiative cooling to remove waste heat. Also, the Martian surface has a very tenuous atmosphere (e.g. ~5 Torr CO2), therefore, the main heat transfer method on the Martian surface is also radiative. Because of the lack of atmosphere on the Moon and the tenuous atmosphere on Mars, surface power systems on both the Lunar and Martian surface must rely heavily on radiative heat transfer. Because of the large temperature swings on both the lunar and the Martian surfaces, trying to radiate heat is inefficient. In order to increase power system efficiency, an effort is underway to test various combinations of materials with high emissivities to demonstrate their ability to survive these degrading atmospheres to maintain a constant radiator temperature improving surface power plant efficiency. An important part of this effort is the development of a unique capability that would allow the determination of a materials emissivity at high temperatures. A description of the test capability as well as initial data is presented.

Global Occurrence and Emission of Rotaviruses to Surface Waters

PubMed Central

Kiulia, Nicholas M.; Hofstra, Nynke; Vermeulen, Lucie C.; Obara, Maureen A.; Medema, Gertjan; Rose, Joan B.

2015-01-01

Group A rotaviruses (RV) are the major cause of acute gastroenteritis in infants and young children globally. Waterborne transmission of RV and the presence of RV in water sources are of major public health importance. In this paper, we present the Global Waterborne Pathogen model for RV (GloWPa-Rota model) to estimate the global distribution of RV emissions to surface water. To our knowledge, this is the first model to do so. We review the literature to estimate three RV specific variables for the model: incidence, excretion rate and removal during wastewater treatment. We estimate total global RV emissions to be 2 × 1018 viral particles/grid/year, of which 87% is produced by the urban population. Hotspot regions with high RV emissions are urban areas in densely populated parts of the world, such as Bangladesh and Nigeria, while low emissions are found in rural areas in North Russia and the Australian desert. Even for industrialized regions with high population density and without tertiary treatment, such as the UK, substantial emissions are estimated. Modeling exercises like the one presented in this paper provide unique opportunities to further study these emissions to surface water, their sources and scenarios for improved management. PMID:25984911

Diminished mercury emission from waters with duckweed cover

NASA Astrophysics Data System (ADS)

Wollenberg, Jennifer L.; Peters, Stephen C.

2009-06-01

Duckweeds (Lemnaceae) are a widely distributed type of floating vegetation in freshwater systems. Under suitable conditions, duckweeds form a dense vegetative mat on the water surface, which reduces light penetration into the water column and limits gas exchange at the water-air interface by decreasing the area of open water surface. Experiments were conducted to determine whether duckweed decreases mercury emission by limiting gas diffusion across the water-air interface and attenuating light, or, conversely, enhances emission via transpiration of mercury vapor. Microcosm flux chamber experiments indicate that duckweed decreases mercury emission from the water surface compared to open water controls. Fluxes under duckweed were 17-67% lower than in controls, with lower fluxes occurring at higher percent cover. The decrease in mercury emission suggests that duckweed may limit emission through one of several mechanisms, including limited gas transport across the air-water interface, decreased photoreactions due to light attenuation, and plant-mercury interactions. The results of this experiment were applied to a model lake system to illustrate the magnitude of potential effects on mercury cycling. The mercury retained in the lake as a result of hindered emission may increase bioaccumulation potential in lakes with duckweed cover.

A Sensitivity Analysis of the Nocturnal Boundary-Layer Properties to Atmospheric Emissivity Formulations

NASA Astrophysics Data System (ADS)

Siqueira, Mario B.; Katul, Gabriel G.

2010-02-01

A one-dimensional model for the mean potential temperature within the nocturnal boundary layer (NBL) was used to assess the sensitivity of three NBL properties (height, thermal stratification strength, and near-surface cooling) to three widely used atmospheric emissivity formulations. The calculations revealed that the NBL height is robust to the choice of the emissivity function, though this is not the case for NBL Richardson number and near-surface cooling rate. Rather than endorse one formulation, our analysis highlights the importance of atmospheric emissivity in modelling the radiative properties of the NBL especially for clear-sky conditions.

Temperature and emissivity determination of liquid steel S235

NASA Astrophysics Data System (ADS)

Schöpp, H.; Sperl, A.; Kozakov, R.; Gött, G.; Uhrlandt, D.; Wilhelm, G.

2012-06-01

Temperature determination of liquid metals is difficult but a necessary tool for improving materials and processes such as arc welding in the metal-working industry. A method to determine the surface temperature of the weld pool is described. A TIG welding process and absolute calibrated optical emission spectroscopy are used. This method is combined with high-speed photography. 2D temperature profiles are obtained. The emissivity of the radiating surface has an important influence on the temperature determination. A temperature dependent emissivity for liquid steel is given for the spectral region between 650 and 850 nm.

Fluorescence excitation and imaging of single molecules near dielectric-coated and bare surfaces: a theoretical study.

PubMed

Axelrod, Daniel

2012-08-01

Microscopic fluorescent samples of interest to cell and molecular biology are commonly embedded in an aqueous medium near a solid surface that is coated with a thin film such as a lipid multilayer, collagen, acrylamide, or a cell wall. Both excitation and emission of fluorescent single molecules near film-coated surfaces are strongly affected by the proximity of the coated surface, the film thickness, its refractive index and the fluorophore's orientation. For total internal reflection excitation, multiple reflections in the film can lead to resonance peaks in the evanescent intensity versus incidence angle curve. For emission, multiple reflections arising from the fluorophore's near field emission can create a distinct intensity pattern in both the back focal plane and the image plane of a high aperture objective. This theoretical analysis discusses how these features can be used to report film thickness and refractive index, and fluorophore axial position and orientation. © 2012 The Author Journal of Microscopy © 2012 Royal Microscopical Society.

Effects of future land use and ecosystem changes on boundary-layer meteorology and air quality

NASA Astrophysics Data System (ADS)

Tai, A. P. K.; Wang, L.; Sadeke, M.

2017-12-01

Land vegetation plays key roles shaping boundary-layer meteorology and air quality via various pathways. Vegetation can directly affect surface ozone via dry deposition and biogenic emissions of volatile organic compounds (VOCs). Transpiration from land plants can also influence surface temperature, soil moisture and boundary-layer mixing depth, thereby indirectly affecting surface ozone. Future changes in the distribution, density and physiology of vegetation are therefore expected to have major ramifications for surface ozone air quality. In our study, we examine two aspects of potential vegetation changes using the Community Earth System Model (CESM) in the fully coupled land-atmosphere configuration, and evaluate their implications on meteorology and air quality: 1) land use change, which alters the distribution of plant functional types and total leaf density; and 2) ozone damage on vegetation, which alters leaf density and physiology (e.g., stomatal resistance). We find that, following the RCP8.5 scenario for 2050, global cropland expansion induces only minor changes in surface ozone in tropical and subtropical regions, but statistically significant changes by up to +4 ppbv in midlatitude North America and East Asia, mostly due to higher surface temperature that enhances biogenic VOC emissions, and reduced dry deposition to a lesser degree. These changes are in turn to driven mostly by meteorological changes that include a shift from latent to sensible heat in the surface energy balance and reduced soil moisture, reflecting not only local responses but also a northward expansion of the Hadley Cell. On the other hand, ozone damage on vegetation driven by rising anthropogenic emissions is shown to induce a further enhancement of ozone by up to +6 ppbv in midlatitude regions by 2050. This reflects a strong localized positive feedback, with severe ozone damage in polluted regions generally inducing stomatal closure, which in turn reduces transpiration, increases surface temperature, and thus enhances biogenic VOC emissions and surface ozone. Our findings demonstrate the importance of considering meteorological responses to vegetation changes in future air quality assessment, and call for greater coordination among land use, ecosystem and air quality management efforts.

A New Neural Network Approach Including First-Guess for Retrieval of Atmospheric Water Vapor, Cloud Liquid Water Path, Surface Temperature and Emissivities Over Land From Satellite Microwave Observations

NASA Technical Reports Server (NTRS)

Aires, F.; Prigent, C.; Rossow, W. B.; Rothstein, M.; Hansen, James E. (Technical Monitor)

2000-01-01

The analysis of microwave observations over land to determine atmospheric and surface parameters is still limited due to the complexity of the inverse problem. Neural network techniques have already proved successful as the basis of efficient retrieval methods for non-linear cases, however, first-guess estimates, which are used in variational methods to avoid problems of solution non-uniqueness or other forms of solution irregularity, have up to now not been used with neural network methods. In this study, a neural network approach is developed that uses a first-guess. Conceptual bridges are established between the neural network and variational methods. The new neural method retrieves the surface skin temperature, the integrated water vapor content, the cloud liquid water path and the microwave surface emissivities between 19 and 85 GHz over land from SSM/I observations. The retrieval, in parallel, of all these quantities improves the results for consistency reasons. A data base to train the neural network is calculated with a radiative transfer model and a a global collection of coincident surface and atmospheric parameters extracted from the National Center for Environmental Prediction reanalysis, from the International Satellite Cloud Climatology Project data and from microwave emissivity atlases previously calculated. The results of the neural network inversion are very encouraging. The r.m.s. error of the surface temperature retrieval over the globe is 1.3 K in clear sky conditions and 1.6 K in cloudy scenes. Water vapor is retrieved with a r.m.s. error of 3.8 kg/sq m in clear conditions and 4.9 kg/sq m in cloudy situations. The r.m.s. error in cloud liquid water path is 0.08 kg/sq m . The surface emissivities are retrieved with an accuracy of better than 0.008 in clear conditions and 0.010 in cloudy conditions. Microwave land surface temperature retrieval presents a very attractive complement to the infrared estimates in cloudy areas: time record of land surface temperature will be produced.

Underestimated role of the secondary electron emission in the space

NASA Astrophysics Data System (ADS)

Nemecek, Zdenek; Richterova, Ivana; Safrankova, Jana; Pavlu, Jiri; Vaverka, Jakub; Nouzak, Libor

2016-07-01

Secondary electron emission (SEE) is one of many processes that charges surfaces of bodies immersed into a plasma. Until present, a majority of considerations in theories and experiments is based on the sixty year old description of an interaction of planar metallic surfaces with electrons, thus the effects of a surface curvature, roughness, presence of clusters as well as an influence of the material conductance on different aspects of this interaction are neglected. Dust grains or their clusters can be frequently found in many space environments - interstellar clouds, atmospheres of planets, tails of comets or planetary rings are only typical examples. The grains are exposed to electrons of different energies and they can acquire positive or negative charge during this interaction. We review the progress in experimental investigations and computer simulations of the SEE from samples relevant to space that was achieved in course of the last decade. We present a systematic study of well-defined systems that starts from spherical grains of various diameters and materials, and it continues with clusters consisting of different numbers of small spherical grains that can be considered as examples of real irregularly shaped space grains. The charges acquired by investigated objects as well as their secondary emission yields are calculated using the SEE model. We show that (1) the charge and surface potential of clusters exposed to the electron beam are influenced by the number of grains and by their geometry within a particular cluster, (2) the model results are in an excellent agreement with the experiment, and (3) there is a large difference between charging of a cluster levitating in the free space and that attached to a planar surface. The calculation provides a reduction of the secondary electron emission yield of the surface covered by dust clusters by a factor up to 1.5 with respect to the yield of a smooth surface. (4) These results are applied on charging of the lunar surface and the dust grains levitating above it, and it is shown that the SEE is more important for isolated dust grains than for the lunar surface covered by them.

Sources of springtime surface black carbon in the Arctic: an adjoint analysis for April 2008

NASA Astrophysics Data System (ADS)

Qi, Ling; Li, Qinbin; Henze, Daven K.; Tseng, Hsien-Liang; He, Cenlin

2017-08-01

We quantify source contributions to springtime (April 2008) surface black carbon (BC) in the Arctic by interpreting surface observations of BC at five receptor sites (Denali, Barrow, Alert, Zeppelin, and Summit) using a global chemical transport model (GEOS-Chem) and its adjoint. Contributions to BC at Barrow, Alert, and Zeppelin are dominated by Asian anthropogenic sources (40-43 %) before 18 April and by Siberian open biomass burning emissions (29-41 %) afterward. In contrast, Summit, a mostly free tropospheric site, has predominantly an Asian anthropogenic source contribution (24-68 %, with an average of 45 %). We compute the adjoint sensitivity of BC concentrations at the five sites during a pollution episode (20-25 April) to global emissions from 1 March to 25 April. The associated contributions are the combined results of these sensitivities and BC emissions. Local and regional anthropogenic sources in Alaska are the largest anthropogenic sources of BC at Denali (63 % of total anthropogenic contributions), and natural gas flaring emissions in the western extreme north of Russia (WENR) are the largest anthropogenic sources of BC at Zeppelin (26 %) and Alert (13 %). We find that long-range transport of emissions from Beijing-Tianjin-Hebei (also known as Jing-Jin-Ji), the biggest urbanized region in northern China, contribute significantly (˜ 10 %) to surface BC across the Arctic. On average, it takes ˜ 12 days for Asian anthropogenic emissions and Siberian biomass burning emissions to reach the Arctic lower troposphere, supporting earlier studies. Natural gas flaring emissions from the WENR reach Zeppelin in about a week. We find that episodic transport events dominate BC at Denali (87 %), a site outside the Arctic front, which is a strong transport barrier. The relative contribution of these events to surface BC within the polar dome is much smaller (˜ 50 % at Barrow and Zeppelin and ˜ 10 % at Alert). The large contributions from Asian anthropogenic sources are predominately in the form of chronic pollution (˜ 40 % at Barrow, 65 % at Alert, and 57 % at Zeppelin) on about a 1-month timescale. As such, it is likely that previous studies using 5- or 10-day trajectory analyses strongly underestimated the contribution from Asia to surface BC in the Arctic.

Chemical changes in secondary electron emission during oxidation of nickel /100/ and /111/ crystal surfaces

NASA Technical Reports Server (NTRS)

Holloway, P. H.; Hudson, J. B.

1975-01-01

Changes in the secondary electron spectra (which include chemical shifts of Auger transitions) between 0-70 eV during the oxidation of both (100) and (111) nickel surfaces are reported. The reaction sequence between oxygen and nickel is also briefly described. Emission rate changes are correlated with changes in the work function of the solid.

Improving the indoor air quality by using a surface emissions trap

NASA Astrophysics Data System (ADS)

Markowicz, Pawel; Larsson, Lennart

2015-04-01

The surface emissions trap, an adsorption cloth developed for reducing emissions of volatile organic compounds and particulate matter from surfaces while allowing evaporation of moisture, was used to improve the indoor air quality of a school building with elevated air concentrations of 2-ethyl-1-hexanol. An improvement of the perceived air quality was noticed a few days after the device had been attached on the PVC flooring. In parallel, decreased air concentrations of 2-ethyl-1-hexanol were found as well as a linear increase of the amounts of the same compound adsorbed on the installed cloth as observed up to 13 months after installation. Laboratory studies revealed that the performance of the device is not affected by differences in RH (35-85%), temperature (30-40 °C) or by accelerated aging simulating up to 10 years product lifetime, and, from a blinded exposure test, that the device efficiently blocks chemical odors. This study suggests that the device may represent a fast and efficient means of restoring the indoor air quality in a building e.g. after water damage leading to irritating and potentially harmful emissions from building material surfaces indoors.

Determination of current and rotational transform profiles in a current-carrying stellarator using soft x-ray emissivity measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, X.; Cianciosa, M. R.; Ennis, D. A.

In this research, collimated soft X-ray (SXR) emissivity measurements from multi-channel cameras on the Compact Toroidal Hybrid (CTH) tokamak/torsatron device are incorporated in the 3D equilibrium reconstruction code V3FIT to reconstruct the shape of flux surfaces and infer the current distribution within the plasma. Equilibrium reconstructions of sawtoothing plasmas that use data from both SXR and external magnetic diagnostics show the central safety factor to be near unity under the assumption that SXR iso-emissivity contours lie on magnetic flux surfaces. The reconstruction results are consistent with those using the external magnetic data and a constraint on the location of qmore » = 1 surfaces determined from the sawtooth inversion surface extracted from SXR brightness profiles. The agreement justifies the use of approximating SXR emission as a flux function in CTH, at least within the core of the plasma, subject to the spatial resolution of the SXR diagnostics. Lastly, this improved reconstruction of the central current density indicates that the current profile peakedness decreases with increasing external transform and that the internal inductance is not a relevant measure of how peaked the current profile is in hybrid discharges.« less

Spectroscopic characterization of ligands on the surface of water dispersible NaGdF4:Ln3+ nanocrystals

NASA Astrophysics Data System (ADS)

Cichos, J.; Karbowiak, M.

2012-05-01

For electronic or biomedical applications it is desirable to have ligand-free water-dispersible nanocrystals (NCs). The commonly used FTIR spectroscopy often provides a direct evidence for molecules on the surface. In some cases, however, the strong bands of solvent molecules may obscure the peaks of surface bounded ligands. We show that in this regard the emission spectroscopy may be used as a more reliable probing tool. The relevant information can be obtained from emission and excitation spectra, emission decay times as well as from analysis of relative efficiency of excitation energy transfer from Gd3+ to Eu3+ ions. Using these methods we tested samples obtained by various synthetic routes and indicated that only nitrosonium tetrafluoroborate (NOBF4) removes successfully the organic ligands from the nanocrystals surface, yielding organic ligand-free NCs dispersible in aqueous solutions. The conclusions drawn from emission spectroscopy are useful for interpretation of results of FTIR, Raman and NMR studies. The detailed assignment of FTIR peaks for oleate-capped and oleate-free NCs is also provided. Finally, we point to the risk of drawing erroneous conclusions about colloidal stability of nanocrystals if refractive indexes of NCs and medium are similar.

Determination of current and rotational transform profiles in a current-carrying stellarator using soft x-ray emissivity measurements

NASA Astrophysics Data System (ADS)

Ma, X.; Cianciosa, M. R.; Ennis, D. A.; Hanson, J. D.; Hartwell, G. J.; Herfindal, J. L.; Howell, E. C.; Knowlton, S. F.; Maurer, D. A.; Traverso, P. J.

2018-01-01

Collimated soft X-ray (SXR) emissivity measurements from multi-channel cameras on the Compact Toroidal Hybrid (CTH) tokamak/torsatron device are incorporated in the 3D equilibrium reconstruction code V3FIT to reconstruct the shape of flux surfaces and infer the current distribution within the plasma. Equilibrium reconstructions of sawtoothing plasmas that use data from both SXR and external magnetic diagnostics show the central safety factor to be near unity under the assumption that SXR iso-emissivity contours lie on magnetic flux surfaces. The reconstruction results are consistent with those using the external magnetic data and a constraint on the location of q = 1 surfaces determined from the sawtooth inversion surface extracted from SXR brightness profiles. The agreement justifies the use of approximating SXR emission as a flux function in CTH, at least within the core of the plasma, subject to the spatial resolution of the SXR diagnostics. This improved reconstruction of the central current density indicates that the current profile peakedness decreases with increasing external transform and that the internal inductance is not a relevant measure of how peaked the current profile is in hybrid discharges.

Determination of current and rotational transform profiles in a current-carrying stellarator using soft x-ray emissivity measurements

DOE PAGES

Ma, X.; Cianciosa, M. R.; Ennis, D. A.; ...

2018-01-31

In this research, collimated soft X-ray (SXR) emissivity measurements from multi-channel cameras on the Compact Toroidal Hybrid (CTH) tokamak/torsatron device are incorporated in the 3D equilibrium reconstruction code V3FIT to reconstruct the shape of flux surfaces and infer the current distribution within the plasma. Equilibrium reconstructions of sawtoothing plasmas that use data from both SXR and external magnetic diagnostics show the central safety factor to be near unity under the assumption that SXR iso-emissivity contours lie on magnetic flux surfaces. The reconstruction results are consistent with those using the external magnetic data and a constraint on the location of qmore » = 1 surfaces determined from the sawtooth inversion surface extracted from SXR brightness profiles. The agreement justifies the use of approximating SXR emission as a flux function in CTH, at least within the core of the plasma, subject to the spatial resolution of the SXR diagnostics. Lastly, this improved reconstruction of the central current density indicates that the current profile peakedness decreases with increasing external transform and that the internal inductance is not a relevant measure of how peaked the current profile is in hybrid discharges.« less

Quantifying Uncertainties in Land Surface Microwave Emissivity Retrievals

NASA Technical Reports Server (NTRS)

Tian, Yudong; Peters-Lidard, Christa D.; Harrison, Kenneth W.; Prigent, Catherine; Norouzi, Hamidreza; Aires, Filipe; Boukabara, Sid-Ahmed; Furuzawa, Fumie A.; Masunaga, Hirohiko

2012-01-01

Uncertainties in the retrievals of microwave land surface emissivities were quantified over two types of land surfaces: desert and tropical rainforest. Retrievals from satellite-based microwave imagers, including SSM/I, TMI and AMSR-E, were studied. Our results show that there are considerable differences between the retrievals from different sensors and from different groups over these two land surface types. In addition, the mean emissivity values show different spectral behavior across the frequencies. With the true emissivity assumed largely constant over both of the two sites throughout the study period, the differences are largely attributed to the systematic and random errors in the retrievals. Generally these retrievals tend to agree better at lower frequencies than at higher ones, with systematic differences ranging 14% (312 K) over desert and 17% (320 K) over rainforest. The random errors within each retrieval dataset are in the range of 0.52% (26 K). In particular, at 85.0/89.0 GHz, there are very large differences between the different retrieval datasets, and within each retrieval dataset itself. Further investigation reveals that these differences are mostly likely caused by rain/cloud contamination, which can lead to random errors up to 1017 K under the most severe conditions.

Particle sensing with confined optical field enhanced fluorescence emission (Cofefe).

PubMed

Kenison, John P; Fast, Alexander; Matthews, Brandon M; Corn, Robert M; Potma, Eric Olaf

2018-05-14

We describe the development and performance of a new type of optical sensor suitable for registering the binding/dissociation of nanoscopic particles near a gold sensing surface. The method shares similarities with surface plasmon resonance microscopy but uses a completely different optical signature for reading out binding events. This new optical read-out mechanism, which we call confined optical field enhanced fluorescence emission (Cofefe), uses pulsed surface plasmon polariton fields at the gold/liquid interface that give rise to confined optical fields upon binding of the target particle to the gold surface. The confined near-fields are sufficient to induce two-photon absorption in the gold sensor surface near the binding site. Subsequent radiative recombination of the electron-hole pairs in the gold produces fluorescence emission, which can be captured by a camera in the far-field. Bound nanoparticles show up as bright confined spots against a dark background on the camera. We show that the Cofefe sensor is capable of detecting gold and silicon nanoparticles, as well as polymer nanospheres and sub-μm lipid droplets in a label-free manner with average illumination powers of less than 10 μW/μm 2 .

What Is the Emissivity of Active Basaltic Lava Flows?

NASA Astrophysics Data System (ADS)

Lee, R.; Ramsey, M. S.

2016-12-01

The emissivity of molten lava surfaces has been a topic of study for some time because it directly affects the cooling efficiency of the flow, thermo-rheological models of flow evolution, as well as the accurate interpretation of the bulk composition. Despite past studies, it remains unclear whether the emissivity of molten lava truly is different than that of the cooled surface. Measuring emissivity on flows is complicated with errors arising due to changes in the surface glass content and vesicularity, as well as mixing of multiple temperatures, as the lava cools. We therefore see determination of correct surface emissivity and its change with time to be of great importance to anyone working with thermal infrared (TIR) data or modeling of lava flows. A series of high-resolution melting experiments on basalts has been conducted using a novel micro-furnace and TIR spectrometer, producing high-resolution accurate emissivity measurements at known temperatures transitioning from molten to solid state. These results are compared to data from active analog and natural lava surfaces acquired from a newly-developed field-based multispectral camera system, which is capable of generating lower-resolution emissivity spectra. We present the results of these comparative studies conducted at the Syracuse University Lava Project facility in order to test and calibrate the camera system under controlled conditions. The facility conducts large-scale pours of degassed Palisades Sill basalt, an acceptable analog for natural basalt. In addition, several samples of the analog lava were re-melted in the micro-furnace/spectrometer setup to provide a direct comparison of higher and lower resolution IR spectral data. These results, together with data from the Kilauea lava lake, have allowed us to calibrate and fully test the efficacy of this camera system in a field environment for future deployments as well as provide a means of constraining TIR data from satellite observations.

Laboratory estimates of trace gas emissions following surface application and injection of cattle slurry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Flessa, H.; Beese, F.

2000-02-01

Applying cattle slurry to soil may induce emissions of the greenhouse gases N{sub 2}O and CH{sub 4}. Their objective was to determine the effects of different application techniques (surface application and slit injection) of cattle (Bostaurus) slurry on the decomposition of slurry organic matter and the emissions of N{sub 2}O and CH{sub 4}. The effects of slurry application (43.6 m{sup 3} ha{sup {minus}1}) were studied for 9 wk under controlled laboratory conditions using a soil microcosm system with automated monitoring of the CO{sub 2}, N{sub 2}O, and CH{sub 4} fluxes. The soil used was a silty loam (Ap horizon ofmore » a cambisol) with a constant water-filled pore space of 67% during the experiment. About 38% of the organic matter applied with the slurry was decomposed within 9 wk. Production of CO{sub 2} was not affected by the application technique. Emissions of N{sub 2}O and CH{sub 4} from the injected slurry were significantly higher than from the surface-applied slurry, probably because of restricted aeration at the injected-slurry treatment. Total N{sub 2}O-N emissions were 0.2% (surface application) and 3.3% (slit injection) of the slurry N added. Methane emission occurred only during the first few days following application. The total net flux of CH{sub 4}-C for 2 wk was {minus}12 g ha{sup {minus}1} for the control (CH{sub 4} uptake), 2 g ha{sup {minus}1} for the surface-applied slurry, and 39 g ha{sup {minus}1} for the injected slurry. Slurry injection, which is recommended to reduce NH{sub 3} volatilization, appears to increase emissions of the greenhouse gases N{sub 2}O and CH{sub 4} from the fertilized fields.« less

Color-tunable mixed photoluminescence emission from Alq3 organic layer in metal-Alq3-metal surface plasmon structure.

PubMed

Chen, Nai-Chuan; Liao, Chung-Chi; Chen, Cheng-Chang; Fan, Wan-Ting; Wu, Jin-Han; Li, Jung-Yu; Chen, Shih-Pu; Huang, Bohr-Ran; Lee, Li-Ling

2014-01-01

This work reports the color-tunable mixed photoluminescence (PL) emission from an Alq3 organic layer in an Au-Alq3-Au plasmonic structure through the combination of organic fluorescence emission and another form of emission that is enabled by the surface plasmons in the plasmonic structure. The emission wavelength of the latter depends on the Alq3 thickness and can be tuned within the Alq3 fluorescent spectra. Therefore, a two-color broadband, color-tunable mixed PL structure was obtained. Obvious changes in the Commission Internationale d'Eclairage (CIE) coordinates and the corresponding emission colors of Au-Alq3-Au samples clearly varied with the Alq3 thickness (90, 130, and 156 nm).

Color-tunable mixed photoluminescence emission from Alq3 organic layer in metal-Alq3-metal surface plasmon structure

PubMed Central

2014-01-01

This work reports the color-tunable mixed photoluminescence (PL) emission from an Alq3 organic layer in an Au-Alq3-Au plasmonic structure through the combination of organic fluorescence emission and another form of emission that is enabled by the surface plasmons in the plasmonic structure. The emission wavelength of the latter depends on the Alq3 thickness and can be tuned within the Alq3 fluorescent spectra. Therefore, a two-color broadband, color-tunable mixed PL structure was obtained. Obvious changes in the Commission Internationale d’Eclairage (CIE) coordinates and the corresponding emission colors of Au-Alq3-Au samples clearly varied with the Alq3 thickness (90, 130, and 156 nm). PMID:25328506

[Study of the microwave emissivity characteristics over different land cover types].

PubMed

Zhang, Yong-Pan; Jiang, Ling-Mei; Qiu, Yu-Bao; Wu, Sheng-Li; Shi, Jian-Cheng; Zhang, Li-Xin

2010-06-01

The microwave emissivity over land is very important for describing the characteristics of the lands, and it is also a key factor for retrieving the parameters of land and atmosphere. Different land covers have their emission behavior as a function of structure, water content, and surface roughness. In the present study the global land surface emissivities were calculated using six month (June, 2003-August, 2003, Dec, 2003-Feb, 2004) AMSR-E L2A brightness temperature, MODIS land surface temperature and the layered atmosphere temperature, and humidity and pressure profiles data retrieved from MODIS/Aqua under clear sky conditions. With the information of IGBP land cover types, "pure" pixels were used, which are defined when the fraction cover of each land type is larger than 85%. Then, the emissivity of sixteen land covers at different frequencies, polarization and their seasonal variation were analyzed respectively. The results show that the emissivity of vegetation including forests, grasslands and croplands is higher than that over bare soil, and the polarization difference of vegetation is smaller than that of bare soil. In summer, the emissivity of vegetation is relatively stable because it is in bloom, therefore the authors can use it as its emissivity in our microwave emissivity database over different land cover types. Furthermore, snow cover can heavily impact the change in land cover emissivity, especially in winter.

Evolution of anthropogenic emissions at the global and regional scale during the past three decades

NASA Astrophysics Data System (ADS)

Granier, C.; Bessagnet, B. B.; Bond, T. C.; D'Angiola, A.; Denier van der Gon, H.; Frost, G. J.; Heil, A.; Kaiser, J.; Kinne, S. A.; Klimont, Z.; Kloster, S.; Lamarque, J.; Liousse, C.; Masui, T.; Meleux, F.; Mieville, A.; Ohara, T.; Raut, J.; Riahi, K.; Schultz, M. G.; Smith, S.; Thomson, A. M.; van Aardenne, J.; van der Werf, G.; van Vuuren, D.

2010-12-01

The knowledge of the distributions of surface emissions of gases and aerosols is essential for an accurate modeling and analysis of the distribution and evolution of the concentration of gaseous and particulate chemical species. The quantification of surface fluxes by source of origin is furthermore central to the assessment of effects and the development of control measures. Over the past few years, different ranges of emission fluxes have been proposed by several studies, which have provided emissions at different spatial and temporal scales. We have compared the emissions of several chemical compounds, i.e. carbon monoxide, nitrogen oxides, sulfur dioxide and black carbon, as provided by global and regional emissions inventories in different regions of the world for the past thirty years. The presentation will focus on the United States, Europe and China. Significant differences between the datasets providing emissions in these regions have been identified, reaching for example 60% and 35% for anthropogenic emissions of carbon monoxide and nitrogen oxides in both regions, respectively. We will assess the current uncertainties on surface emissions and their recent trends. This analysis is often hindered because of differences in base years and in species considered in the different datasets. Current work aiming at compiling comparable metrics for such species for the analysis of regional and global emission datasets will be discussed.

Infrared non-destructive evaluation method and apparatus

DOEpatents

Baleine, Erwan; Erwan, James F; Lee, Ching-Pang; Stinelli, Stephanie

2014-10-21

A method of nondestructive evaluation and related system. The method includes arranging a test piece (14) having an internal passage (18) and an external surface (15) and a thermal calibrator (12) within a field of view (42) of an infrared sensor (44); generating a flow (16) of fluid characterized by a fluid temperature; exposing the test piece internal passage (18) and the thermal calibrator (12) to fluid from the flow (16); capturing infrared emission information of the test piece external surface (15) and of the thermal calibrator (12) simultaneously using the infrared sensor (44), wherein the test piece infrared emission information includes emission intensity information, and wherein the thermal calibrator infrared emission information includes a reference emission intensity associated with the fluid temperature; and normalizing the test piece emission intensity information against the reference emission intensity.

Surface emissivity of a reinforced carbon composite material with an oxidation-inhibiting coating

NASA Technical Reports Server (NTRS)

Wakefield, R. M.

1973-01-01

Total effective emissivity and spectral emissivity over the wavelength range of 0.65 to 6.3 microns were determined for temperatures from 1300 t0 2250 deg K. A multi channel radiometer was used in the arcjet and laboratory tests. The black-body-hole method was used to independently check radiometer results. The results show the silicon-carbide coated reinforced carbon composite material is a nongray radiator. The total effective emissivity and the spectral emissivity at 0.65 micron both decreased with increasing temperature, respectively, from approximately 0.8 to 0.6, and from 0.4 to 0.25, over the temperature range. The emissivity values were the same when the sample was viewed normal to the surface or at a 45 deg angle. Recommended emissivity values are presented.

Assessment of a landfill methane emission screening method using an unmanned aerial vehicle mounted thermal infrared camera - A field study.

PubMed

Fjelsted, L; Christensen, A G; Larsen, J E; Kjeldsen, P; Scheutz, C

2018-05-28

An unmanned aerial vehicle (UAV)-mounted thermal infrared (TIR) camera's ability to delineate landfill gas (LFG) emission hotspots was evaluated in a field test at two Danish landfills (Hedeland landfill and Audebo landfill). At both sites, a test area of 100 m 2 was established and divided into about 100 measuring points. The relationship between LFG emissions and soil surface temperatures were investigated through four to five measuring campaigns, in order to cover different atmospheric conditions along with increasing, decreasing and stable barometric pressure. For each measuring campaign, a TIR image of the test area was obtained followed by the measurement of methane (CH 4 ) and carbon dioxide (CO 2 ) emissions at each measuring point, using a static flux chamber. At the same time, soil temperatures measured on the surface, at 5 cm and 10 cm depths, were registered. At the Hedeland landfill, no relationship was found between LFG emissions and surface temperatures. In addition, CH 4 emissions were very limited, on average 0.92-4.52 g CH 4  m -2  d -1 , and only measureable on the two days with decreasing barometric pressure. TIR images from Hedeland did not show any significant temperature differences in the test area. At the Audebo landfill, an area with slightly higher surface temperatures was found in the TIR images, and the same pattern with slightly higher temperatures was found at a depth of 10 cm. The main LFG emissions were found in the area with the higher surface temperatures. LFG emissions at Audebo were influenced significantly by changes in barometric pressure, and the average CH 4 emissions varied between 111 g m -2  d -1 and 314 g m -2  d -1 , depending on whether the barometric pressure gradient had increased or decreased, respectively. The temperature differences observed in the TIR images from both landfills were limited to between 0.7 °C and 1.2 °C. The minimum observable CH 4 emission for the TIR camera to identify an emission hotspot was 150 g CH 4  m -2  d -1 from an area of more than 1 m 2 . Copyright © 2018 Elsevier Ltd. All rights reserved.

FIBER AND INTEGRATED OPTICS: Influence of diffraction-induced emission of light on resonant conversion of surface waves in diffraction-coupled optical waveguides

NASA Astrophysics Data System (ADS)

Kiselev, V. A.; Shaposhnikov, S. N.

1989-09-01

An investigation is reported of diffraction-induced emission of surface waves under conditions of resonant transfer of light between different regular and corrugated waveguides. It is shown that the part of the emitted light flux carried by surface waves along diffraction-coupled waveguides depends strongly on the ratio of the effective refractive indices of the guides. The dependences of the optical coupling length and of the corresponding emitted light flux on the distance between the waveguides and on the difference between their refractive indices are given.

Real-time first-principles simulations of thermionic emission from N-doped diamond surfaces

NASA Astrophysics Data System (ADS)

Shinozaki, Tomoki; Hagiwara, Satoshi; Morioka, Naoya; Kimura, Yuji; Watanabe, Kazuyuki

2018-06-01

We investigate thermionic emission from N-doped C(100) surfaces terminated with H or Li atoms using finite-temperature real-time density functional theory simulations. The current–temperature characteristics are found to follow the Richardson–Dushman (RD) equation, which was derived from a semiclassical theory. However, the Richardson constants are two orders of magnitude smaller than the ideal values from the RD theory. This considerable reduction is attributed primarily to the extremely low transmission probability of electrons from the surfaces toward the vacuum. The present method enables straightforward evaluation of the ideal efficiency of a thermionic energy converter.

Optical Johnson noise thermometry

NASA Technical Reports Server (NTRS)

Shepard, R. L.; Blalock, T. V.; Maxey, L. C.; Roberts, M. J.; Simpson, M. L.

1989-01-01

A concept is being explored that an optical analog of the electrical Johnson noise may be used to measure temperature independently of emissivity. The concept is that a laser beam may be modulated on reflection from a hot surface by interaction of the laser photons with the thermally agitated conduction electrons or the lattice phonons, thereby adding noise to the reflected laser beam. If the reflectance noise can be detected and quantified in a background of other noise in the optical and signal processing systems, the reflectance noise may provide a noncontact measurement of the absolute surface temperature and may be independent of the surface's emissivity.

Effects of surface diffusion on high temperature selective emitters

DOE PAGES

Peykov, Daniel; Yeng, Yi Xiang; Celanovic, Ivan; ...

2015-01-01

Using morphological and optical simulations of 1D tantalum photonic crystals at 1200K, surface diffusion was determined to gradually reduce the efficiency of selective emitters. This was attributed to shifting resonance peaks and declining emissivity caused by changes to the cavity dimensions and the aperture width. Decreasing the structure’s curvature through larger periods and smaller cavity widths, as well as generating smoother transitions in curvature through the introduction of rounded cavities, was found to alleviate this degradation. An optimized structure, that shows both high efficiency selective emissivity and resistance to surface diffusion, was presented.

The Influence of the Surface Neutralization of Active Impurities on the Field-Electron Emission Properties of p-Type Silicon Crystals

NASA Astrophysics Data System (ADS)

Yafarov, R. K.

2017-12-01

Correlation dependences between variations of the structural-phase composition, morphology characteristics, and field-electron-emission (FEE) properties of surface-structured p-type silicon singlecrystalline (100)-oriented wafers have been studied during their stepwise high-dose carbon-ion-beam irradiation. It is established that the stepwise implantation of carbon decreases the FEE threshold and favors an increase in the maximum FEE-current density by more than two orders of magnitude. Physicochemical mechanisms involved in this modification of the properties of near-surface layers of silicon under carbon-ion implantation are considered.

Infrared Radiation Filament And Metnod Of Manufacture

DOEpatents

Johnson, Edward A.

1998-11-17

An improved IR radiation source is provided by the invention. A radiation filament has a textured surface produced by seeded ion bombardment of a metal foil which is cut to a serpentine shape and mounted in a windowed housing. Specific ion bombardment texturing techniques tune the surface to maximize emissions in the desired wavelength range and to limit emissions outside that narrow range, particularly at longer wavelengths. A combination of filament surface texture, thickness, material, shape and power circuit feedback control produce wavelength controlled and efficient radiation at much lower power requirements than devices of the prior art.

Correlation Analysis of Experimental Remote-Sensing Data and Models of Microwave Rough Sea-Surface Emission

NASA Astrophysics Data System (ADS)

Sazonov, D. S.

2017-12-01

A correlation analysis of the model calculations and experimental measurements of wind-speed sensitivity of a rough sea-surface microwave emission at a frequency of 37.5 GHz are presented. The field data used in the research were collected over 3 years in the summer and autumn periods at the oceanographic platform of the Marine Hydrophysical Institute, Russian Academy of Sciences (RAS). A hypothesis about a significant correlation between the model calculations and experimentally measured sea-surface emission ability caused by wind forcing was formulated and tested to reveal this correlation. An evaluation of the discrepancy between the model and experimental data has been performed by an analysis of residuals. Our studies have shown that among the selected models not a single one adequately describes the experimental data.

Hexagonal Ag nanoarrays induced enhancement of blue light emission from amorphous oxidized silicon nitride via localized surface plasmon coupling.

PubMed

Ma, Zhongyuan; Ni, Xiaodong; Zhang, Wenping; Jiang, Xiaofan; Yang, Huafeng; Yu, Jie; Wang, Wen; Xu, Ling; Xu, Jun; Chen, Kunji; Feng, Duan

2014-11-17

A significant enhancement of blue light emission from amorphous oxidized silicon nitride (a-SiNx:O) films is achieved by introduction of ordered and size-controllable arrays of Ag nanoparticles between the silicon substrate and a-SiNx:O films. Using hexagonal arrays of Ag nanoparticles fabricated by nanosphere lithography, the localized surface plasmons (LSPs) resonance can effectively increase the internal quantum efficiency from 3.9% to 13.3%. Theoretical calculation confirms that the electromagnetic field-intensity enhancement is through the dipole surface plasma coupling with the excitons of a-SiNx:O films, which demonstrates a-SiNx:O films with enhanced blue emission are promising for silicon-based light-emitting applications by patterned Ag arrays.

Areas of Anomalous Surface Temperature in Alamosa and Saguache Counties, Colorado, as Identified from ASTER Thermal Data

DOE Data Explorer

Khalid Hussein

2012-02-01

This layer contains areas of anomalous surface temperature in Alamosa and Saguache Counties identified from ASTER thermal data and spatial based insolation model. The temperature is calculated using the Emissivity Normalization Algorithm that separate temperature from emissivity. The incoming solar radiation was calculated using spatial based insolation model developed by Fu and Rich (1999). Then the temperature due to solar radiation was calculated using emissivity derived from ASTER data. The residual temperature, i.e. temperature due to solar radiation subtracted from ASTER temperature was used to identify thermally anomalous areas. Areas that had temperature greater than 2o were considered ASTER modeled very warm surface exposures (thermal anomalies) Note: 'o' is used in this description to represent lowercase sigma.

Top-down Estimates of Biomass Burning Emissions of Black Carbon in the Western United States

NASA Astrophysics Data System (ADS)

Mao, Y.; Li, Q.; Randerson, J. T.; Liou, K.

2011-12-01

We apply a Bayesian linear inversion to derive top-down estimates of biomass burning emissions of black carbon (BC) in the western United States (WUS) for May-November 2006 by inverting surface BC concentrations from the IMPROVE network using the GEOS-Chem chemical transport model. Model simulations are conducted at both 2°×2.5° (globally) and 0.55°×0.66° (nested over North America) horizontal resolutions. We first improve the spatial distributions and seasonal and interannual variations of the BC emissions from the Global Fire Emissions Database (GFEDv2) using MODIS 8-day active fire counts from 2005-2007. The GFEDv2 emissions in N. America are adjusted for three zones: boreal N. America, temperate N. America, and Mexico plus Central America. The resulting emissions are then used as a priori for the inversion. The a posteriori emissions are 2-5 times higher than the a priori in California and the Rockies. Model surface BC concentrations using the a posteriori estimate provide better agreement with IMPROVE observations (~20% increase in the Taylor skill score), including improved ability to capture the observed variability especially during June-July. However, model surface BC concentrations are still biased low by ~30%. Comparisons with the Fire Locating and Modeling of Burning Emissions (FLAMBE) are included.

Top-down Estimates of Biomass Burning Emissions of Black Carbon in the Western United States

NASA Astrophysics Data System (ADS)

Mao, Y.; Li, Q.; Randerson, J. T.; CHEN, D.; Zhang, L.; Liou, K.

2012-12-01

We apply a Bayesian linear inversion to derive top-down estimates of biomass burning emissions of black carbon (BC) in the western United States (WUS) for May-November 2006 by inverting surface BC concentrations from the IMPROVE network using the GEOS-Chem chemical transport model. Model simulations are conducted at both 2°×2.5° (globally) and 0.5°×0.667° (nested over North America) horizontal resolutions. We first improve the spatial distributions and seasonal and interannual variations of the BC emissions from the Global Fire Emissions Database (GFEDv2) using MODIS 8-day active fire counts from 2005-2007. The GFEDv2 emissions in N. America are adjusted for three zones: boreal N. America, temperate N. America, and Mexico plus Central America. The resulting emissions are then used as a priori for the inversion. The a posteriori emissions are 2-5 times higher than the a priori in California and the Rockies. Model surface BC concentrations using the a posteriori estimate provide better agreement with IMPROVE observations (~50% increase in the Taylor skill score), including improved ability to capture the observed variability especially during June-September. However, model surface BC concentrations are still biased low by ~30%. Comparisons with the Fire Locating and Modeling of Burning Emissions (FLAMBE) are included.

Biochar Amendment to the Soil Surface Reduces Fumigant Emissions and Enhances Soil Microorganism Recovery.

PubMed

Shen, Guoqing; Ashworth, Daniel J; Gan, Jay; Yates, Scott R

2016-02-02

During soil fumigation, it is ideal to mitigate soil fumigant emissions, ensure pest control efficacy, and speed up the recovery of the soil microorganism population established postapplication. However, no current fumigant emission reduction strategy can meet all these requirements. In the present study, replicated soil columns were used to study the effect of biochar derived from rice husk (BR) and green waste (BG) applied to the soil surface on 1,3-dichloropropene (1,3-D) and chloropicrin (CP) emissions and soil gas distribution, and on microorganism population re-establishment. Relative to fumigated bare soil (no emission reduction strategy), high-density polyethylene (HDPE), and ammonium thiosulfate (ATS) treatments, BR gave dramatic emission reductions for both fumigants with no obvious emission peak, whereas BG was very effective only for 1,3-D. With BR application, the concentration of fumigant in the soil gas was higher than in the bare soil and ATS treatment. After the soil column experiment, mixing the BR with the fumigated soil resulted in higher soil respiration rates than were observed for HDPE and ATS treatments. Therefore, biochar amendment to the soil surface may be an effective strategy for fumigant emission reduction and the recovery of soil microorganism populations established postapplication.

Uncertainties of fluxes and 13C / 12C ratios of atmospheric reactive-gas emissions

NASA Astrophysics Data System (ADS)

Gromov, Sergey; Brenninkmeijer, Carl A. M.; Jöckel, Patrick

2017-07-01

We provide a comprehensive review of the proxy data on the 13C / 12C ratios and uncertainties of emissions of reactive carbonaceous compounds into the atmosphere, with a focus on CO sources. Based on an evaluated set-up of the EMAC model, we derive the isotope-resolved data set of its emission inventory for the 1997-2005 period. Additionally, we revisit the calculus required for the correct derivation of uncertainties associated with isotope ratios of emission fluxes. The resulting δ13C of overall surface CO emission in 2000 of -(25. 2 ± 0. 7) ‰ is in line with previous bottom-up estimates and is less uncertain by a factor of 2. In contrast to this, we find that uncertainties of the respective inverse modelling estimates may be substantially larger due to the correlated nature of their derivation. We reckon the δ13C values of surface emissions of higher hydrocarbons to be within -24 to -27 ‰ (uncertainty typically below ±1 ‰), with an exception of isoprene and methanol emissions being close to -30 and -60 ‰, respectively. The isotope signature of ethane surface emission coincides with earlier estimates, but integrates very different source inputs. δ13C values are reported relative to V-PDB.

Synthesis of Carbon Dots with Multiple Color Emission by Controlled Graphitization and Surface Functionalization.

PubMed

Miao, Xiang; Qu, Dan; Yang, Dongxue; Nie, Bing; Zhao, Yikang; Fan, Hongyou; Sun, Zaicheng

2018-01-01

Multiple-color-emissive carbon dots (CDots) have potential applications in various fields such as bioimaging, light-emitting devices, and photocatalysis. The majority of the current CDots to date exhibit excitation-wavelength-dependent emissions with their maximum emission limited at the blue-light region. Here, a synthesis of multiple-color-emission CDots by controlled graphitization and surface function is reported. The CDots are synthesized through controlled thermal pyrolysis of citric acid and urea. By regulating the thermal-pyrolysis temperature and ratio of reactants, the maximum emission of the resulting CDots gradually shifts from blue to red light, covering the entire light spectrum. Specifically, the emission position of the CDots can be tuned from 430 to 630 nm through controlling the extent of graphitization and the amount of surface functional groups, COOH. The relative photoluminescence quantum yields of the CDots with blue, green, and red emission reach up to 52.6%, 35.1%, and 12.9%, respectively. Furthermore, it is demonstrated that the CDots can be uniformly dispersed into epoxy resins and be fabricated as transparent CDots/epoxy composites for multiple-color- and white-light-emitting devices. This research opens a door for developing low-cost CDots as alternative phosphors for light-emitting devices. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ion beam microtexturing and enhanced surface diffusion

NASA Technical Reports Server (NTRS)

Robinson, R. S.

1982-01-01

Ion beam interactions with solid surfaces are discussed with particular emphasis on microtexturing induced by the deliberate deposition of controllable amounts of an impurity material onto a solid surface while simultaneously sputtering the surface with an ion beam. Experimental study of the optical properties of microtextured surfaces is described. Measurements of both absorptance as a function of wavelength and emissivity are presented. A computer code is described that models the sputtering and ion reflection processes involved in microtexture formation.

The influence of surface properties on the plasma dynamics in radio-frequency driven oxygen plasmas: Measurements and simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Greb, Arthur; Niemi, Kari; O'Connell, Deborah

2013-12-09

Plasma parameters and dynamics in capacitively coupled oxygen plasmas are investigated for different surface conditions. Metastable species concentration, electronegativity, spatial distribution of particle densities as well as the ionization dynamics are significantly influenced by the surface loss probability of metastable singlet delta oxygen (SDO). Simulated surface conditions are compared to experiments in the plasma-surface interface region using phase resolved optical emission spectroscopy. It is demonstrated how in-situ measurements of excitation features can be used to determine SDO surface loss probabilities for different surface materials.

Vented Cavity Radiant Barrier Assembly And Method

DOEpatents

Dinwoodie, Thomas L.; Jackaway, Adam D.

2000-05-16

A vented cavity radiant barrier assembly (2) includes a barrier (12), typically a PV module, having inner and outer surfaces (18, 22). A support assembly (14) is secured to the barrier and extends inwardly from the inner surface of the barrier to a building surface (14) creating a vented cavity (24) between the building surface and the barrier inner surface. A low emissivity element (20) is mounted at or between the building surface and the barrier inner surface. At least part of the cavity exit (30) is higher than the cavity entrance (28) to promote cooling air flow through the cavity.

Cherenkov emission of terahertz surface plasmon polaritons from a superluminal optical spot on a structured metal surface.

PubMed

Bakunov, M I; Tsarev, M V; Hangyo, M

2009-05-25

We propose to launch terahertz surface plasmon polaritons on a structured metal surface by using a femtosecond laser pulse obliquely incident on a strip of an electro-optic material deposited on the surface. The laser pulse creates a nonlinear polarization that moves along the strip with a superluminal velocity and emits surface terahertz waves via the Cherenkov radiation mechanism. We calculate the radiated fields and frequency distribution of the radiated energy for a grooved perfect-conductor surface with a GaAs strip illuminated by Ti:sapphire laser. This technique can be used to perform surface terahertz spectroscopy.

What is the sensitivity of the mineral dust cycle at the regional scale to surface wind speed? First insights from the DRUMS project.

NASA Astrophysics Data System (ADS)

Bouet, Christel; Siour, Guillaume; Poulet, David; Bergametti, Gilles; Laurent, Benoit; Brocheton, Fabien; Forêt, Gilles; Xu, Yiwen; Marticorena, Béatrice

2017-04-01

Modelling of the mineral dust cycle is still a challenging issue both at the global and regional scales: during the last decade, several exercises of model intercomparison highlighted the wide variability of the existing dust models to estimate dust emission fluxes and atmospheric load at both scales. For instance, within the framework of the international AEROCOM Project (http://aerocom.met.no/), 15 different global dust models provide a range of possible dust emission fluxes from 400 to 2200 Tg yr-1 for North Africa and from 26 to 526 Tg yr-1 for the Middle East, i.e. still a factor of 5 and 20 respectively (Huneeus et al., 2011). Whatever the scale, a critical aspect for any dust model is the sensitivity to the meteorological fields used to compute dust emission fluxes (external forcing or simulated by the coupled meteorological or climatic model). Indeed, the intensity of dust emission varies as a power 3 of the surface wind speed, and the number of dust emission events is the number of times the surface wind speed exceeds the wind erosion threshold. As a result, the simulations of dust emissions are extremely sensitive to the way the surface wind speeds are accounted for both in global and regional models. In this context, the aim of the DRUMS (DeseRt dUst Modeling: performance and Sensitivity evaluation) project was to investigate the sensitivity of a regional dust model (CHIMERE) to this parameter. This sensitivity study was conducted for 3 years from 2006 to 2008 over the North of Africa (45°N-0°N; 45°W-55°E), where dust emissions are the most intense. Emission fluxes can be simulated there with the most relevant data set of surface properties controlling dust emissions and accounting for the heterogeneity of land surfaces (surface roughness, soil size distribution and texture) of desert regions (Laurent et al., 2008). Meteorological products (forecasts and re-analysis) provided by the most recognized international meteorological centres (US NCEP and ECMWF), and thus the most widely used for the simulations of the mineral dust cycle, were tested. In addition, the benefit provided by the use of the WRF model to downscale the meteorological forcing was evaluated. The estimation of the performance of the CHIMERE model forced by the different meteorological fields was conducted using a unique validation data set compiled during the project by analysing and evaluating (i) the large number of experimental data resulting from the AMMA (African Monsoon Multidisciplinary Analysis) field campaigns, (ii) long-term aerosol monitoring over West Africa (Sahelian Dust Transect) and downwind the Sahara/Sahel region (AERONET), and (iii) recent satellite aerosol products (SeaWIFS AOD). This dataset allowed to validate the main characteristics of the dust cycle (emission, transport, and deposit).

The effects of aircraft on climate and pollution. Part II: 20-year impacts of exhaust from all commercial aircraft worldwide treated individually at the subgrid scale.

PubMed

Jacobson, M Z; Wilkerson, J T; Naiman, A D; Lele, S K

2013-01-01

This study examines the 20-year impacts of emissions from all commercial aircraft flights worldwide on climate, cloudiness, and atmospheric composition. Aircraft emissions from each individual flight worldwide were modeled to evolve from the subgrid to grid scale with the global model described and evaluated in Part I of this study. Simulations with and without aircraft emissions were run for 20 years. Aircraft emissions were found to be responsible for -6% of Arctic surface global warming to date, -1.3% of total surface global warming, and -4% of global upper tropospheric warming. Arctic warming due to aircraft slightly decreased Arctic sea ice area. Longer simulations should result in more warming due to the further increase in CO2. Aircraft increased atmospheric stability below cruise altitude and decreased it above cruise altitude. The increase in stability decreased cumulus convection in favor of increased stratiform cloudiness. Aircraft increased total cloud fraction on average. Aircraft increased surface and upper tropospheric ozone by -0.4% and -2.5%, respectively and surface and upper-tropospheric peroxyacetyl nitrate (PAN) by -0.1% and -5%, respectively. Aircraft emissions increased tropospheric OH, decreasing column CO and CH4 by -1.7% and -0.9%, respectively. Aircraft emissions increased human mortality worldwide by -620 (-240 to 4770) deaths per year, with half due to ozone and the rest to particulate matter less than 2.5 micrometers in diameter (PM2.5).

Direct green waste land application: How to reduce its impacts on greenhouse gas and volatile organic compound emissions?

PubMed

Zhu-Barker, Xia; Burger, Martin; Horwath, William R; Green, Peter G

2016-06-01

Direct land application as an alternative to green waste (GW) disposal in landfills or composting requires an understanding of its impacts on greenhouse gas (GHG) and volatile organic compound (VOC) emissions. We investigated the effects of two approaches of GW direct land application, surface application and soil incorporation, on carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4), and VOC emissions for a 12month period. Five treatments were applied in fall 2013 on fallow land under a Mediterranean climate in California: 30cm height GW on surface; 15cm height GW on surface; 15cm height GW tilled into soil; control+till; control+no till. In addition, a laboratory experiment was conducted to develop a mechanistic understanding of the influence of GW application on soil O2 consumption and GHG emission. The annual cumulative N2O, CO2 and VOC emissions ranged from 1.6 to 5.5kgN2O-Nha(-1), 5.3 to 40.6MgCO2-Cha(-1) and 0.6 to 9.9kgVOCha(-1), respectively, and were greatly reduced by GW soil incorporation compared to surface application. Application of GW quickly consumed soil O2 within one day in the lab incubation. These results indicate that to reduce GHG and VOC emissions of GW direct land application, GW incorporation into soil is recommended. Copyright © 2016 Elsevier Ltd. All rights reserved.

The total hemispheric emissivity of painted aluminum honeycomb at cryogenic temperatures

NASA Astrophysics Data System (ADS)

Tuttle, J.; Canavan, E.; DiPirro, M.; Li, X.; Knollenberg, P.

2014-01-01

NASA uses high-emissivity surfaces on deep-space radiators and thermal radiation absorbers in test chambers. Aluminum honeycomb core material, when coated with a high-emissivity paint, provides a lightweight, mechanically robust, and relatively inexpensive black surface that retains its high emissivity down to low temperatures. At temperatures below about 100 Kelvin, this material performs much better than the paint itself. We measured the total hemispheric emissivity of various painted honeycomb configurations using an adaptation of an innovative technique developed for characterizing thin black coatings. These measurements were performed from room temperature down to 30 Kelvin. We describe the measurement technique and compare the results with predictions from a detailed thermal model of each honeycomb configuration.

Industrial surface coatings: Wood furniture and fixtures emission inventory development. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anex, R.P.; Lund, J.R.; Chang, D.P.Y.

1998-06-01

The purpose of this study is to update the methods for estimating emissions from the industrial coatings subcategory of wood furniture and fixtures. The wood furniture and fixture industry encompasses the manufacture of diverse products including cabinets, office furniture, store fixtures, and residential furniture. Specific objectives of this work are to: (1) estimate the amount of coating used in the industrial surface coating of wood furniture and fixtures; (2) develop emissions factors for each coating application category; (3) estimate variability of both coating use and emission factors; and (4) specify a source of information and method to revise and updatemore » the industrial coating of wood furniture and fixtures emission inventory.« less

Pulsar Emission: Is It All Relative?

NASA Technical Reports Server (NTRS)

Harding, Alice K.

2004-01-01

Thirty-five years after the discovery of pulsars, we still do not understand the fundamentals of their pulsed emission at any wavelength. The fact that even detailed pulse profiles cannot identlfy the origin of the emission in a magnetosphere that extends fiom the neutron star surface to plasma moving at relativistic speeds near the light cylinder compounds the problem. I will discuss the role of special and general relativistic effects on pulsar emission, fiom inertial frame-dragging near the stellar surface to aberration, time-of-flight and retardation of the magnetic field near the light cylinder. Understanding how these effects determine what we observe at different wavelengths is critical to unraveling the emission physics.

The Total Hemispheric Emissivity of Painted Aluminum Honeycomb at Cryogenic Temperatures

NASA Technical Reports Server (NTRS)

Tuttle, J.; Canavan, E.; DiPirro, M.; Li, X.; Knollenberg, K.

2013-01-01

NASA uses high-emissivity surfaces on deep-space radiators or thermal radiation absorbers in test chambers. Aluminum honeycomb core material, when coated with a high-emissivity paint, provides a lightweight, mechanically robust, and relatively inexpensive black surface that retains its high emissivity down to low temperatures. At temperatures below about 100 Kelvin, this material performs much better than the paint itself. We measured the total hemispheric emissivity of various painted honeycomb configurations using an adaptation of an innovative technique developed for characterizing thin black coatings. These measurements were performed from room temperature down to 30 Kelvin. We describe the measurement technique and compare the results with predictions from a detailed thermal model of each honeycomb configuration.

Emissivity model of steel 430 during the growth of oxide layer at 800-1100 K and 1.5 μm

NASA Astrophysics Data System (ADS)

Xing, Wei; Shi, Deheng; Sun, Jinfeng; Zhu, Zunlue

2018-01-01

This work studied the variation in spectral emissivity with growth of oxide layer at the different temperatures. For this reason, we measured the normal spectral emissivity during the growth of oxide layer on the sample surface at a wavelength of 1.5 μm over a temperature range 800-1100 K. In the experiment, the temperature was measured by the two thermocouples, which were symmetrically welded onto the front surface of specimens. The average of their readings was regarded as the true temperature. The detector should be perpendicular to the specimen surface as accurately as possible. The variation in spectral emissivity with growth of oxide layer was evaluated at a certain temperature. Altogether 11 emissivity models were evaluated. The conclusion was gained that the more the number of parameters used in the models was, the better the fitting accuracy became. On the whole, all the PEE models, the four-parameter LEE model and the five-parameter PFE, PLE and LEE models could be employed to well fit this kind of variation. The variation in spectral emissivity with temperature was determined at a certain thickness of oxide film. Almost all the models studied in this paper could be used to accurately evaluate this variation. The approximate models of spectral emissivity as a function of temperature and oxide-layer thickness were proposed. The strong oscillations of spectral emissivity were observed, which were affirmed to arise from the interference effect between the two radiations stemming from the oxide layer and from the substrate. The uncertainties in the temperature of steel 430 generated only by the surface oxidization were approximately 4.1-10.7 K in this experiment.

WE-AB-303-04: A Tissue Model of Cherenkov Emission From the Skin Surface During Megavoltage X-Ray Radiotherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wiles, A. N.; Loyalka, S. K.; Izaguirre, E. W.

Purpose: To develop a tissue model of Cherenkov radiation emitted from the skin surface during external beam radiotherapy. Imaging Cherenkov radiation emitted from human skin allows visualization of the beam position and potentially surface dose estimates, and our goal is to characterize the optical properties of these emissions. Methods: We developed a Monte Carlo model of Cherenkov radiation generated in a semi-infinite tissue slab by megavoltage x-ray beams with optical transmission properties determined by a two-layered skin model. We separate the skin into a dermal and an epidermal layer in our model, where distinct molecular absorbers modify the Cherenkov intensitymore » spectrum in each layer while we approximate the scattering properties with Mie and Rayleigh scattering from the highly structured molecular organization found in human skin. Results: We report on the estimated distributions of the Cherenkov wavelength spectrum, emission angles, and surface distribution for the modeled irradiated skin surface. The expected intensity distribution of Cherenkov radiation emitted from skin shows a distinct intensity peak around 475 nm, the blue region of the visible spectrum, between a pair of optical absorption bands in hemoglobin and a broad plateau beginning near 600 nm and extending to at least 700 nm where melanin and hemoglobin absorption are both low. We also find that the Cherenkov intensity decreases with increasing angle from the surface normal, the majority being emitted within 20 degrees of the surface normal. Conclusion: Our estimate of the spectral distribution of Cherenkov radiation emitted from skin indicates an advantage to using imaging devices with long wavelength spectral responsivity. We also expect the most efficient imaging to be near the surface normal where the intensity is greatest; although for contoured surfaces, the relative intensity across the surface may appear to vary due to decreasing Cherenkov intensity with increased angle from the skin normal. This research was supported in part by a GAANN Fellowship from the Department of Education.« less

Evaluation of reanalysis near-surface winds over northern Africa in Boreal summer

NASA Astrophysics Data System (ADS)

Engelstaedter, Sebastian; Washington, Richard

2014-05-01

The emission of dust from desert surfaces depends on the combined effects of surface properties such as surface roughness, soil moisture, soil texture and particle size (erodibility) and wind speed (erosivity). In order for dust cycle models to realistically simulate dust emissions for the right reasons, it is essential that erosivity and erodibility controlling factors are represented correctly. There has been a focus on improving dust emission schemes or input fields of soil distribution and texture even though it has been shown that the use of wind fields from different reanalysis datasets to drive the same model can result in significant differences in the dust emissions. Here we evaluate the representation of near-surface wind speed from three different reanalysis datasets (ERA-Interim, CFSR and MERRA) over the North African domain. Reanalysis 10m wind speeds are compared with observations from SYNOP and METAR reports available from the UK Meteorological Office Integrated Data Archive System (MIDAS) Land and Marine Surface Stations Dataset. We compare 6-hourly observations of 10m wind speed between 1 January 1989 and 31 December 2009 from more the 500 surface stations with the corresponding reanalysis values. A station data based mean wind speed climatology for North Africa is presented. Overall, the representation of 10m winds is relatively poor in all three reanalysis datasets with stations in the northern parts of the Sahara still being better simulated (correlation coefficients ~ 0.5) than stations in the Sahel (correlation coefficients < 0.3) which points at the reanalyses not being able to realistically capture the Sahel dynamics systems. All three reanalyses have a systematic bias towards overestimating wind speed below 3-4 m/s and underestimating wind speed above 4 m/s. This bias becomes larger with increasing wind speed but is independent of the time of day. For instance, 14 m/s observed wind speeds are underestimated on average by 6 m/s in the ERA-Interim reanalysis. Given the cubic relationship between wind speed and dust emission this large underestimation is expected to significantly impact the simulation of dust emissions. A negative relationship between observed and ERA-Interim wind speed is found for winds above 14 m/s indicating that high wind speed generating processes are not well (if at all) represented in the model.

Conductorlike behavior of a photoemitting dielectric surface

NASA Technical Reports Server (NTRS)

De, B. R.

1979-01-01

It has been suggested in the past that a uniformly illuminated photoemitting dielectric surface of finite extent acquires in the steady state a surface charge distribution as if the surface were conducting (i.e., the surface becomes equipotential). In this paper an analytical proof of this conductorlike behavior is given. The only restrictions are that the photoelectron emission from the surface has azimuthal symmetry and that the photosheath may be assumed to be collisionless. It is tacitly assumed that a steady state is attainable, which means that the photoelectron spectrum has a high-energy cutoff.

Unoccupied Surface State on Ag(110) as Revealed by Inverse Photoemission

NASA Astrophysics Data System (ADS)

Reihl, B.; Schlittler, R. R.; Neff, H.

1984-05-01

By use of the new technique of k-resolved inverse photoemission spectroscopy, an unoccupied s-like surface state on Ag(110) has been detected, which lies within the projected L2'-->L1 gap of the bulk. At the X¯ point of the surface Brillouin zone, the energy of the surface state is 1.65 eV above the Fermi level EF, and exhibits a band dispersion E(k∥) towards higher energies. The surface-state emission is immediately quenched when the surface is exposed to very small amounts of oxygen or hydrogen.

40 CFR 61.271 - Emission standard.

Code of Federal Regulations, 2010 CFR

2010-07-01

... provide a projection below the liquid surface. Except for automatic bleeder vents, rim space vents, roof... floating roof means a cover that rests on the liquid surface (but not necessarily in complete contact with... floating on the liquid surface at all times, except during initial fill and during those intervals when the...

40 CFR 61.271 - Emission standard.

Code of Federal Regulations, 2014 CFR

2014-07-01

... provide a projection below the liquid surface. Except for automatic bleeder vents, rim space vents, roof... floating roof means a cover that rests on the liquid surface (but not necessarily in complete contact with... floating on the liquid surface at all times, except during initial fill and during those intervals when the...

Impacts of interactive dust and its direct radiative forcing on interannual variations of temperature and precipitation in winter over East Asia: Impacts of Dust on IAVs of Temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lou, Sijia; Russell, Lynn M.; Yang, Yang

We used 150-year pre-industrial simulations of the Community Earth System Model (CESM) to quantify the impacts of interactively-modeled dust emissions on the interannual variations of temperature and precipitation over East Asia during the East Asian Winter Monsoon (EAWM) season. The simulated December-January-February dust column burden and dust optical depth are lower over northern China in the strongest EAWM years than those of the weakest years, with regional mean values lower by 38.3% and 37.2%, respectively. The decrease in dust over the dust source regions (the Taklamakan and Gobi Deserts) and the downwind region (such as the North China Plain) leadsmore » to an increase in direct radiative forcing (RF) both at the surface and top of atmosphere by up to 1.5 and 0.75 W m-2, respectively. The effects of EAWM-related variations in surface winds, precipitation and their effects on dust emissions and wet removal contribute about 67% to the total dust-induced variations of direct RF at the surface and partly offset the cooling that occurs with the EAWM strengthening by heating the surface. The variations of surface air temperature induced by the changes in wind and dust emissions increase by 0.4-0.6 K over eastern coastal China, northeastern China, and Japan, which weakens the impact of EAWM on surface air temperature by 3–18% in these regions. The warming results from the combined effects of changes in direct RF and easterly wind anomalies that bring warm air from the ocean to these regions. Moreover, the feedback of the changes in wind on dust emissions weakens the variations of the sea level pressure gradient on the Siberian High while enhancing the Maritime Continent Low. Therefore, cold air is prevented from being transported from Siberia, Kazakhstan, western and central China to the western Pacific Ocean and decreases surface air temperature by 0.6 K and 2 K over central China and the Tibetan Plateau, respectively. Over eastern coastal China, the variations of large-scale precipitation induced by the feedback of EAWM-related changes in wind on dust emissions increase by 10-30% in winter because of the increase in surface air temperature and the anomalous circulation.« less

Dust emission at Franklin Lake Playa, Mojave Desert (USA): Response to meteorological and hydrologic changes 2005-2008

USGS Publications Warehouse

Reynolds, Richard L.; Bogle, Rian; Vogel, John; Goldstein, Harland L.; Yount, James

2009-01-01

Playa type, size, and setting; playa hydrology; and surface-sediment characteristics are important controls on the type and amount of atmospheric dust emitted from playas. Soft, evaporite-rich sediment develops on the surfaces of some Mojave Desert (USA) playas (wet playas), where the water table is shallow (< 4 m). These areas are sources of atmospheric dust because of continuous or episodic replenishment of wind-erodible salts and disruption of the ground surface during salt formation by evaporation of ground water. Dust emission at Franklin Lake playa was monitored between March 2005 and April 2008. The dust record, based on day-time remote digital camera images captured during high wind, and compared with a nearby precipitation record, shows that aridity suppresses dust emission. High frequency of dust generation appears to be associated with relatively wet periods, identified as either heavy precipitation events or sustained regional precipitation over a few months. Several factors may act separately or in combination to account for this relation. Dust emission may respond rapidly to heavy precipitation when the dissolution of hard, wind-resistant evaporite mineral crusts is followed by the development of soft surfaces with thin, newly formed crusts that are vulnerable to wind erosion and (or) the production of loose aggregates of evaporite minerals that are quickly removed by even moderate winds. Dust loading may also increase when relatively high regional precipitation leads to decreasing depth to the water table, thereby increasing rates of vapor discharge, development of evaporite minerals, and temporary softening of playa surfaces. The seasonality of wind strength was not a major factor in dust-storm frequency at the playa. The lack of major dust emissions related to flood-derived sediment at Franklin Lake playa contrasts with some dry-lake systems elsewhere that may produce large amounts of dust from flood sediments. Flood sediments do not commonly accumulate on the surface of Franklin Lake playa because through-going drainage prevents frequent inundation and deposition of widespread flood sediment.

Influence of electrical properties of treated surface on RF-excited plasma needle at atmospheric pressure

NASA Astrophysics Data System (ADS)

Sakiyama, Y.; Graves, D. B.; Stoffels, E.

2008-05-01

We present a comparison of a finite element analysis of the atmospheric pressure RF-excited plasma needle interacting with different surfaces with corresponding experimental observations of light emission spatial profiles. The gas used is helium with 1 ppm nitrogen as an impurity. The needle has a point-to-plane geometry with a radius of 30 µm at the tip and an inter-electrode gap of 1 mm. We employ a fluid model in two-dimensional axisymmetric coordinates. Our simulation results indicate that the plasma structure strongly depends on the electrical properties of the treated surface as well as the discharge mode. In the lower power corona mode with a dielectric surface, the plasma is confined near the needle tip. As a result, particle fluxes to the dielectric surface are relatively low and follow a Gaussian-like radial profile. In the higher power glow mode with a dielectric surface, the particle fluxes to the surface are orders of magnitude higher and the spatial distribution of the particle fluxes becomes radially more uniform due to a uniform ionization layer just above the treated surface. When a conductive plate replaces the dielectric surface in the glow mode, a quite intense ionization spot appears near the surface closest to the needle tip. Consequently, the particle fluxes to the surface peak near the symmetry axis under these conditions. These simulation results are validated by experimental observation of light emission spatial profiles.

X-Ray Probes of Jupiter's Auroral Zones, Galilean Moons, and the Io Plasma Torus

NASA Technical Reports Server (NTRS)

Elsner, R. F.; Ramsey, B. D.; Swartz, D. A.; Rehak, P.; Waite, J. H., Jr.; Cooper, J. F.; Johnson, R. E.

2005-01-01

Remote observations from the Earth orbiting Chandra X-ray Observatory and the XMM-Newton Observatory have shown the the Jovian system is a rich and complex source of x-ray emission. The planet's auroral zones and its disk are powerful sources of x-ray emission, though with different origins. Chandra observations discovered x-ray emission from the Io plasma torus and from the Galilean moons Io, Europa, and possibly Ganymede. The emission from the moons is due to bombardment of their surfaces by highly energetic magnetospheric protons, and oxygen and sulfur ions, producing fluorescent x-ray emission lines from the elements in their surfaces against an intense background continuum. Although very faint when observed from Earth orbit, an imaging x-ray spectrometer in orbit around the icy Galilean moons would provide a detail mapping of the elemental composition in their surfaces. Here we review the results of Chandra and XMM-Newton observations of the Jovian system and describe the characteristics of X-MIME, an imaging x-ray spectrometer undergoing study for possible application to future missions to Jupiter such as JIMO. X-MIME has the ultimate goal of providing detailed high-resolution maps of the elemental abundances of the surfaces of Jupiter's icy moons and Io, as well as detailed study of the x-ray mission from the Io plasma torus, Jupiter's auroral zones, and the planetary disk.

Towards the Consideration of Surface and Environment variables for a Microwave Precipitation Algorithm Over Land

NASA Astrophysics Data System (ADS)

Wang, N. Y.; You, Y.; Ferraro, R. R.; Guch, I.

2014-12-01

Microwave satellite remote sensing of precipitation over land is a challenging problem due to the highly variable land surface emissivity, which, if not properly accounted for, can be much greater than the precipitation signal itself, especially in light rain/snow conditions. Additionally, surfaces such as arid land, deserts and snow cover have brightness temperatures characteristics similar to precipitation Ongoing work by NASA's GPM microwave radiometer team is constructing databases for the GPROF algorithm through a variety of means, however, there is much uncertainty as to what is the optimal information needed for the wide array of sensors in the GPM constellation, including examination of regional conditions. The at-launch database focuses on stratification by emissivity class, surface temperature and total precipitable water (TPW). We'll perform sensitivity studies to determine the potential role of environmental factors such as land surface temperature, surface elevation, and relative humidity and storm morphology such as storm vertical structure, height, and ice thickness to improve precipitation estimation over land, including rain and snow. In other words, what information outside of the satellite radiances can help describe the background and subsequent departures from it that are active precipitating regions? It is likely that this information will be a function of the various precipitation regimes. Statistical methods such as Principal Component Analysis (PCA) will be utilized in this task. Databases from a variety of sources are being constructed. They include existing satellite microwave measurements of precipitating and non-precipitating conditions, ground radar precipitation rate estimates, surface emissivity climatology from satellites, surface temperature and TPW from NWP reanalysis. Results from the analysis of these databases with respect to the microwave precipitation sensitivity to the variety of environmental conditions in different climate regimes will be discussed.

Correlation between the plasma characteristics and the surface chemistry of plasma-treated polymers through partial least-squares analysis.

PubMed

Mavadat, Maryam; Ghasemzadeh-Barvarz, Massoud; Turgeon, Stéphane; Duchesne, Carl; Laroche, Gaétan

2013-12-23

We investigated the effect of various plasma parameters (relative density of atomic N and H, plasma temperature, and vibrational temperature) and process conditions (pressure and H2/(N2 + H2) ratio) on the chemical composition of modified poly(tetrafluoroethylene) (PTFE). The plasma parameters were measured by means of near-infrared (NIR) and UV-visible emission spectroscopy with and without actinometry. The process conditions of the N2-H2 microwave discharges were set at various pressures ranging from 100 to 2000 mTorr and H2/(N2+H2) gas mixture ratios between 0 and 0.4. The surface chemical composition of the modified polymers was determined by X-ray photoelectron spectroscopy (XPS). A mathematical model was constructed using the partial least-squares regression algorithm to correlate the plasma information (process condition and plasma parameters as determined by emission spectroscopy) with the modified surface characteristics. To construct the model, a set of data input variables containing process conditions and plasma parameters were generated, as well as a response matrix containing the surface composition of the polymer. This model was used to predict the composition of PTFE surfaces subjected to N2-H2 plasma treatment. Contrary to what is generally accepted in the literature, the present data demonstrate that hydrogen is not directly involved in the defluorination of the surface but rather produces atomic nitrogen and/or NH radicals that are shown to be at the origin of fluorine atom removal from the polymer surface. The results show that process conditions alone do not suffice in predicting the surface chemical composition and that the plasma characteristics, which cannot be easily correlated with these conditions, should be considered. Process optimization and control would benefit from plasma diagnostics, particularly infrared emission spectroscopy.

Effects of Atmospheric Water and Surface Wind on Passive Microwave Retrievals of Sea Ice Concentration: a Simulation Study

NASA Astrophysics Data System (ADS)

Shin, D.; Chiu, L. S.; Clemente-Colon, P.

2006-05-01

The atmospheric effects on the retrieval of sea ice concentration from passive microwave sensors are examined using simulated data typical for the Arctic summer. The simulation includes atmospheric contributions of cloud liquid water, water vapor and surface wind on the microwave signatures. A plane parallel radiative transfer model is used to compute brightness temperatures at SSM/I frequencies over surfaces that contain open water, first-year (FY) ice and multi-year (MY) ice and their combinations. Synthetic retrievals in this study use the NASA Team (NT) algorithm for the estimation of sea ice concentrations. This study shows that if the satellite sensor's field of view is filled with only FY ice the retrieval is not much affected by the atmospheric conditions due to the high contrast between emission signals from FY ice surface and the signals from the atmosphere. Pure MY ice concentration is generally underestimated due to the low MY ice surface emissivity that results in the enhancement of emission signals from the atmospheric parameters. Simulation results in marginal ice areas also show that the atmospheric effects from cloud liquid water, water vapor and surface wind tend to degrade the accuracy at low sea ice concentration. FY ice concentration is overestimated and MY ice concentration is underestimated in the presence of atmospheric water and surface wind at low ice concentration. This compensating effect reduces the retrieval uncertainties of total (FY and MY) ice concentration. Over marginal ice zones, our results suggest that strong surface wind is more important than atmospheric water in contributing to the retrieval errors of total ice concentrations in the normal ranges of these variables.

Large enhancement of UV luminescence emission of ZnO nanoparticles by coupling excitons with Ag surface plasmons

NASA Astrophysics Data System (ADS)

Kuiri, Probodh K.; Pramanik, Subhamay

2018-04-01

For an emitter based on bandgap emission, defect mediated emission has always been considered as the most important loss. Here, a novel approach which can overcome such emission loss is proposed using films of ZnO nanoparticles (NPs) on Ag NPs embedded in silica. The effects of the size of Ag NPs on the enhancement of ultra-violet (UV) photoluminescence (PL) of ZnO NPs for such a system have been studied. For the ZnO NPs without Ag NPs, two emission bands have been seen: one in the UV region and the other one in the visible region. This UV PL emission intensity has been seen to increase significantly with a drastic reduction of the visible PL emission intensity in the case of the sample containing ZnO NPs on silica embedded Ag NPs. A linear increase in UV emission with increase in the size of Ag NPs has been found. For the largest size of Ag NPs (˜10 nm, considered in the present study), the PL emission enhancement becomes about 4 times higher than that of sample without Ag NPs. The observed enhancement of the UV PL emission was caused by coupling between spontaneous emission in ZnO and surface plasmons of Ag. The larger Ag NPs provided a larger scattering cross section in coupling surface plasmons to light leading to an increase in UV emission. Thus, it is possible to convert the useless defect emission to the useful excitonic emission with a large enhancement factor.

Surface emission from neutron stars and implications for the physics of their interiors.

PubMed

Ozel, Feryal

2013-01-01

Neutron stars are associated with diverse physical phenomena that take place in conditions characterized by ultrahigh densities as well as intense gravitational, magnetic and radiation fields. Understanding the properties and interactions of matter in these regimes remains one of the challenges in compact object astrophysics. Photons emitted from the surfaces of neutron stars provide direct probes of their structure, composition and magnetic fields. In this review, I discuss in detail the physics that governs the properties of emission from the surfaces of neutron stars and their various observational manifestations. I present the constraints on neutron star radii, core and crust composition, and magnetic field strength and topology obtained from studies of their broadband spectra, evolution of thermal luminosity, and the profiles of pulsations that originate on their surfaces.

Hybridization-based biosensor containing hairpin probes and use thereof

DOEpatents

Miller, Benjamin L.; Strohsahl, Christopher M.

2010-10-12

A sensor chip that includes: a fluorescence quenching surface; a nucleic acid probe that contains first and second ends with the first end bound to the fluorescence quenching surface, and is characterized by being able to self-anneal into a hairpin conformation; and a first fluorophore bound to the second end of the first nucleic acid molecule. When the first nucleic acid molecule is in the hairpin conformation, the fluorescence quenching surface substantially quenches fluorescent emissions by the first fluorophore; and when the first nucleic acid molecule is in a non-hairpin conformation, fluorescent emissions by the fluorophore are substantially free of quenching by the fluorescence quenching surface. Various nucleic acid probes, methods of making the sensor chip, biological sensor devices that contain the sensor chip, and their methods of use are also disclosed.

Electron-emission-induced cooling of boundary region in fusion devices

NASA Astrophysics Data System (ADS)

Mishra, Sanjay K.; Avinash, K.; Kaw, Predhiman; Kaw

2014-12-01

In this brief communication we have explored whether the electron emission from the boundary region surfaces (or from additional fine structured dust particles/droplets of some benign material put purposely in the area surrounding the surfaces) can act as an efficient cooling mechanism for boundary region surfaces/dust electrons and hence the lattice. In order to estimate the contribution of this cooling process a simple kinetic model based on charge flux balance and associated energetics has been established. Along with some additional sophistication like suitable choice of material and modification in the work function via surface coating, the estimates show that it is possible to keep the temperature of the plate/particles well within the critical limit, i.e. melting/sublimation point for the desired regime of incident heat flux.

Annual land cover change mapping using MODIS time series to improve emissions inventories.

NASA Astrophysics Data System (ADS)

López Saldaña, G.; Quaife, T. L.; Clifford, D.

2014-12-01

Understanding and quantifying land surface changes is necessary for estimating greenhouse gas and ammonia emissions, and for meeting air quality limits and targets. More sophisticated inventories methodologies for at least key emission source are needed due to policy-driven air quality directives. Quantifying land cover changes on an annual basis requires greater spatial and temporal disaggregation of input data. The main aim of this study is to develop a methodology for using Earth Observations (EO) to identify annual land surface changes that will improve emissions inventories from agriculture and land use/land use change and forestry (LULUCF) in the UK. First goal is to find the best sets of input features that describe accurately the surface dynamics. In order to identify annual and inter-annual land surface changes, a times series of surface reflectance was used to capture seasonal variability. Daily surface reflectance images from the Moderate Resolution Imaging Spectroradiometer (MODIS) at 500m resolution were used to invert a Bidirectional Reflectance Distribution Function (BRDF) model to create the seamless time series. Given the limited number of cloud-free observations, a BRDF climatology was used to constrain the model inversion and where no high-scientific quality observations were available at all, as a gap filler. The Land Cover Map 2007 (LC2007) produced by the Centre for Ecology & Hydrology (CEH) was used for training and testing purposes. A prototype land cover product was created for 2006 to 2008. Several machine learning classifiers were tested as well as different sets of input features going from the BRDF parameters to spectral Albedo. We will present the results of the time series development and the first exercises when creating the prototype land cover product.

Proceeding of the 18th Intl. Workshop on Inelastic Ion-Surface Collisions (IISC-18)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reinhold, Carlos O; Krstic, Predrag S; Meyer, Fred W

2011-01-01

The main topics of this proceedings were: (1) Energy loss of particles at surfaces; (2) Scattering of atoms, ions, molecules and clusters; (3) Charge exchange between particles and surfaces; (4) Ion induced desorption, electronic and kinetic sputtering; (5) Defect formation, surface modification and nanostructuring; (6) Electron, photon and secondary ion emission due to particle impact on surfaces; (7) Sputtering, fragmentation, cluster and ion formation in SIMS and SNMS; (8) Cluster/molecular and highly charged ion beams; and (9) Laser induced desorption.

Gas cluster ion beam surface treatments for reducing field emission and breakdown of electrodes and SRF cavities

NASA Astrophysics Data System (ADS)

Swenson, D. R.; Wu, A. T.; Degenkolb, E.; Insepov, Z.

2007-08-01

Sub-micron-scale surface roughness and contamination cause field emission that can lead to high-voltage breakdown of electrodes, and these are limiting factors in the development of high gradient RF technology. We are studying various Gas Cluster Ion Beam (GCIB) treatments to smooth, clean, etch and/or chemically alter electrode surfaces to allow higher fields and accelerating gradients, and to reduce the time and cost of conditioning high-voltage electrodes. For this paper, we have processed Nb, stainless steel and Ti electrode materials using beams of Ar, O2, or NF3 + O2 clusters with accelerating potentials up to 35 kV. Using a scanning field emission microscope (SFEM), we have repeatedly seen a dramatic reduction in the number of field emission sites on Nb coupons treated with GCIB. Smoothing effects on stainless steel and Ti substrates, evaluated using SEM and AFM imaging, show that 200-nm-wide polishing scratch marks are greatly attenuated. A 150-mm diameter GCIB-treated stainless steel electrode has shown virtually no DC field emission current at gradients over 20 MV/m.

Directional Canopy Emissivity Estimation Based on Spectral Invariants

NASA Astrophysics Data System (ADS)

Guo, M.; Cao, B.; Ren, H.; Yongming, D.; Peng, J.; Fan, W.

2017-12-01

Land surface emissivity is a crucial parameter for estimating land surface temperature from remote sensing data and also plays an important role in the physical process of surface energy and water balance from local to global scales. To our knowledge, the emissivity varies with surface type and cover. As for the vegetation, its canopy emissivity is dependent on vegetation types, viewing zenith angle and structure that changes in different growing stages. Lots of previous studies have focused on the emissivity model, but few of them are analytic and suited to different canopy structures. In this paper, a new physical analytic model is proposed to estimate the directional emissivity of homogenous vegetation canopy based on spectral invariants. The initial model counts the directional absorption in six parts: the direct absorption of the canopy and the soil, the absorption of the canopy and soil after a single scattering and after multiple scattering within the canopy-soil system. In order to analytically estimate the emissivity, the pathways of photons absorbed in the canopy-soil system are traced using the re-collision probability in Fig.1. After sensitive analysis on the above six absorptions, the initial complicated model was further simplified as a fixed mathematic expression to estimate the directional emissivity for vegetation canopy. The model was compared with the 4SAIL model, FRA97 model, FRA02 model and DART model in Fig.2, and the results showed that the FRA02 model is significantly underestimated while the FRA97 model is a little underestimated, on basis of the new model. On the contrary, the emissivity difference between the new model with the 4SAIL model and DART model was found to be less than 0.002. In general, since the new model has the advantages of mathematic expression with accurate results and clear physical meaning, the model is promising to be extended to simulate the directional emissivity for the discrete canopy in further study.

Emission quenching of magnetic dipole transitions near an absorbing nanoparticle (Conference Presentation)

NASA Astrophysics Data System (ADS)

Chigrin, Dmitry N.; Kumar, Deepu; von Plessen, Gero

2016-09-01

Emission quenching is analysed at nanometer distances from the surface of an absorbing nanoparticle. It is demonstrated that emission quenching at small distances to the surface is much weaker for magnetic-dipole (MD) than for electric-dipole (ED) transitions. This difference is explained by the fact that the electric field induced by a magnetic dipole has a weaker distance dependence than the electric field of an electric dipole. It is also demonstrated that in the extreme near-field regime the non-locality of the optical response of the metal results in additional emission quenching for both ED and MD transitions.

Selective emission multilayer coatings for a molybdenum thermophotovoltaic radiator

DOEpatents

Cockeram, Brian Vern

2004-01-27

Multilayer coating designs have been developed to provide selective emission for a molybdenum thermophotovoltaic (TPV) radiator surface. These coatings increase the surface emissivity of a molybdenum TPV radiator substrate in the wavelength range that matches the bandgap of the TPV cells to increase the power density of the TPV system. Radiator emission at wavelengths greater than the bandgap energy of the TPV cells is greatly reduced through the use of these coatings, which significantly increases the efficiency of the TPV system. The use of this coating greatly improves the performance of a TPV system, and the coating can be tailored to match the bandgap of any practical TPV system.

Electron reflection and secondary emission characteristics of sputter-textured pyrolytic graphite surfaces

NASA Technical Reports Server (NTRS)

Wintucky, E. G.; Curren, A. N.; Sovey, J. S.

1981-01-01

Measurements are presented of secondary electron emission and reflected primary electron characteristics of sputter-textured pyrolitic graphite surfaces with microstructures of various sizes and densities, made with an Auger cylindrical mirror analyzer in a high-vacuum chamber at pressures below 1.33 x 10 to the -7th N/sq m (10 to the -9th torr). A dense, tall, thin, spire-like microstructure, obtained at ion energies of 1000 eV and ion current densities of 5 mA/sq cm, is the most effective. The secondary electron emission from such a surface is lower than that of soot, whose secondary emission is among the lowest of any material. At a primary electron energy of 1000 eV, the secondary electron emission yield of smooth CU is about 350% greater than the lowest value obtained for sputter-textured pyrolitic graphite. The reflected primary electron index of smooth Cu is a factor of 80 greater. If the secondary electron emission yield is reduced to 0.3, which is possible with sputter-textured pyrolitic graphite, the traveling wave tube collector efficiency could be improved by as much as 4% over that for smooth copper.

2D surface temperature measurement of plasma facing components with modulated active pyrometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amiel, S.; Loarer, T.; Pocheau, C.

2014-10-01

In nuclear fusion devices, such as Tore Supra, the plasma facing components (PFC) are in carbon. Such components are exposed to very high heat flux and the surface temperature measurement is mandatory for the safety of the device and also for efficient plasma scenario development. Besides this measurement is essential to evaluate these heat fluxes for a better knowledge of the physics of plasma-wall interaction, it is also required to monitor the fatigue of PFCs. Infrared system (IR) is used to manage to measure surface temperature in real time. For carbon PFCs, the emissivity is high and known (ε ~more » 0.8), therefore the contribution of the reflected flux from environment and collected by the IR cameras can be neglected. However, the future tokamaks such as WEST and ITER will be equipped with PFCs in metal (W and Be/W, respectively) with low and variable emissivities (ε ~ 0.1–0.4). Consequently, the reflected flux will contribute significantly in the collected flux by IR camera. The modulated active pyrometry, using a bicolor camera, proposed in this paper allows a 2D surface temperature measurement independently of the reflected fluxes and the emissivity. Experimental results with Tungsten sample are reported and compared with simultaneous measurement performed with classical pyrometry (monochromatic and bichromatic) with and without reflective flux demonstrating the efficiency of this method for surface temperature measurement independently of the reflected flux and the emissivity.« less

Effect of the three-dimensional structure of laser emission on the dynamics of low-threshold optical breakdown plasmas

NASA Astrophysics Data System (ADS)

Anisimov, V. N.; Arutiunian, R. V.; Bol'Shov, L. A.; Derkach, O. N.; Kanevskii, M. F.

1989-03-01

The effect of the transverse structure of pulsed CO2 laser emission on the dynamics of laser-induced detonation waves propagating from a metal surface and on plasma transparency recovery is investigated theoretically and experimentally. Particular attention is given to breakdown initiation near the surface. It is suggested that the inclusion of refraction in the plasma into a self-consistent numerical mode is essential for the adequate quantitative description of experimental data on the interaction of laser emission with low-threshold optical breakdown plasmas.

FLASH_TISA_Terra+Aqua_Version3C

Atmospheric Science Data Center

2018-04-04

... Cloud Particle Phase Cloud Infrared Emissivity Cloud Base Pressure Surface (Radiative) Flux TOA Flux Surface Types Albedo LW Flux Order Data:  Earthdata Search:  Order Data Guide Documents:  ...

Atmospheric correction for retrieving ground brightness temperature at commonly-used passive microwave frequencies.

PubMed

Han, Xiao-Jing; Duan, Si-Bo; Li, Zhao-Liang

2017-02-20

An analysis of the atmospheric impact on ground brightness temperature (Tg) is performed for numerous land surface types at commonly-used frequencies (i.e., 1.4 GHz, 6.93 GHz, 10.65 GHz, 18.7 GHz, 23.8 GHz, 36.5 GHz and 89.0 GHz). The results indicate that the atmosphere has a negligible impact on Tg at 1.4 GHz for land surfaces with emissivities greater than 0.7, at 6.93 GHz for land surfaces with emissivities greater than 0.8, and at 10.65 GHz for land surfaces with emissivities greater than 0.9 if a root mean square error (RMSE) less than 1 K is desired. To remove the atmospheric effect on Tg, a generalized atmospheric correction method is proposed by parameterizing the atmospheric transmittance τ and upwelling atmospheric brightness temperature Tba↑. Better accuracies with Tg RMSEs less than 1 K are achieved at 1.4 GHz, 6.93 GHz, 10.65 GHz, 18.7 GHz and 36.5 GHz, and worse accuracies with RMSEs of 1.34 K and 4.35 K are obtained at 23.8 GHz and 89.0 GHz, respectively. Additionally, a simplified atmospheric correction method is developed when lacking sufficient input data to perform the generalized atmospheric correction method, and an emissivity-based atmospheric correction method is presented when the emissivity is known. Consequently, an appropriate atmospheric correction method can be selected based on the available data, frequency and required accuracy. Furthermore, this study provides a method to estimate τ and Tba↑ of different frequencies using the atmospheric parameters (total water vapor content in observation direction Lwv, total cloud liquid water content Lclw and mean temperature of cloud Tclw), which is important for simultaneously determining the land surface parameters using multi-frequency passive microwave satellite data.

Impact of Conifer Forest Litter on Microwave Emission at L-Band

NASA Technical Reports Server (NTRS)

Kurum, Mehmet; O'Neill, Peggy E.; Lang, Roger H.; Cosh, Michael H.; Joseph, Alicia T.; Jackson, Thomas J.

2011-01-01

This study reports on the utilization of microwave modeling, together with ground truth, and L-band (1.4-GHz) brightness temperatures to investigate the passive microwave characteristics of a conifer forest floor. The microwave data were acquired over a natural Virginia Pine forest in Maryland by a ground-based microwave active/passive instrument system in 2008/2009. Ground measurements of the tree biophysical parameters and forest floor characteristics were obtained during the field campaign. The test site consisted of medium-sized evergreen conifers with an average height of 12 m and average diameters at breast height of 12.6 cm. The site is a typical pine forest site in that there is a surface layer of loose debris/needles and an organic transition layer above the mineral soil. In an effort to characterize and model the impact of the surface litter layer, an experiment was conducted on a day with wet soil conditions, which involved removal of the surface litter layer from one half of the test site while keeping the other half undisturbed. The observations showed detectable decrease in emissivity for both polarizations after the surface litter layer was removed. A first-order radiative transfer model of the forest stands including the multilayer nature of the forest floor in conjunction with the ground truth data are used to compute forest emission. The model calculations reproduced the major features of the experimental data over the entire duration, which included the effects of surface litter and ground moisture content on overall emission. Both theory and experimental results confirm that the litter layer increases the observed canopy brightness temperature and obscure the soil emission.

A study of variation characteristics of Gobi broadband emissivity based on field observational experiments in northwestern China

NASA Astrophysics Data System (ADS)

Zheng, Zhi-yuan; Wei, Zhi-gang; Wen, Zhi-ping; Dong, Wen-jie; Li, Zhen-chao; Wen, Xiao-hang; Zhu, Xian; Chen, Chen; Hu, Shan-shan

2018-02-01

Land surface emissivity is a significant variable in energy budgets, land cover assessments, and environment and climate studies. However, the assumption of an emissivity constant is being used in Gobi broadband emissivity (GbBE) parameterization scheme in numerical models because of limited knowledge surrounding the spatiotemporal variation characteristics of GbBE. To address this issue, we analyzed the variation characteristics of GbBE and possible impact factor-surface soil moisture based on long-term continuous and high temporal resolution field observational experiments over a typical Gobi underlying surface in arid and semiarid areas in northwestern China. The results indicate that GbBE has obvious daily and diurnal variation features, especially diurnal cycle characteristics. The multi-year average of the daily average of GbBE is in the range of 0.932 to 0.970 with an average of 0.951 ± 0.008, and the average diurnal GbBE is in the range of 0.880 to 0.940 with an average of 0.906 ± 0.018. GbBE varies with surface soil moisture content. We observed a slight decrease in GbBE with an increase in soil moisture, although this change was not very obvious because of the low soil moisture in this area. Nevertheless, we think that soil moisture must be one of the most significant impact factors on GbBE in arid and semiarid areas. Soil moisture must be taken into account into the parameterization schemes of bare soil broadband emissivity in land surface models. Additional field experiments and studies should be carried out in order to clarify this issue.

Earth system responses to cumulative carbon emissions

NASA Astrophysics Data System (ADS)

Steinacher, M.; Joos, F.

2015-07-01

Information on the relationship between cumulative fossil carbon emissions and multiple climate targets are essential to design emission mitigation and climate adaptation strategies. In this study, the transient responses in different climate variables are quantified for a large set of multi-forcing scenarios extended to year 2300 towards stabilization and in idealized experiments using the Bern3D-LPJ carbon-climate model. The model outcomes are constrained by 26 physical and biogeochemical observational data sets in a Bayesian, Monte-Carlo type framework. Cumulative fossil emissions of 1000 Gt C result in a global mean surface air temperature change of 1.88 °C (68 % confidence interval (c.i.): 1.28 to 2.69 °C), a decrease in surface ocean pH of 0.19 (0.18 to 0.22), and in steric sea level rise of 20 cm (13 to 27 cm until 2300). Linearity between cumulative emissions and transient response is high for pH and reasonably high for surface air and sea surface temperatures, but less pronounced for changes in Atlantic Meridional Overturning, Southern Ocean and tropical surface water saturation with respect to biogenic structures of calcium carbonate, and carbon stocks in soils. The slopes of the relationships change when CO2 is stabilized. The Transient Climate Response is constrained, primarily by long-term ocean heat observations, to 1.7 °C (68 % c.i.: 1.3 to 2.2 °C) and the Equilibrium Climate Sensitivity to 2.9 °C (2.0 to 4.2 °C). This is consistent with results by CMIP5 models, but inconsistent with recent studies that relied on short-term air temperature data affected by natural climate variability.

Structure and method for controlling the thermal emissivity of a radiating object

DOEpatents

DeSteese, John G.; Antoniak, Zenen I.; White, Michael; Peters, Timothy J.

2004-03-30

A structure and method for changing or controlling the thermal emissivity of the surface of an object in situ, and thus, changing or controlling the radiative heat transfer between the object and its environment in situ, is disclosed. Changing or controlling the degree of blackbody behavior of the object is accomplished by changing or controlling certain physical characteristics of a cavity structure on the surface of the object. The cavity structure, defining a plurality of cavities, may be formed by selectively removing material(s) from the surface, selectively adding a material(s) to the surface, or adding an engineered article(s) to the surface to form a new radiative surface. The physical characteristics of the cavity structure that are changed or controlled include cavity area aspect ratio, cavity longitudinal axis orientation, and combinations thereof. Controlling the cavity area aspect ratio may be by controlling the size of the cavity surface area, the size of the cavity aperture area, or a combination thereof. The cavity structure may contain a gas, liquid, or solid that further enhances radiative heat transfer control and/or improves other properties of the object while in service.

Surface Spectroscopy Center Of Excellence Project

NASA Technical Reports Server (NTRS)

Wooden, Diane

2014-01-01

We propose to develop a national center of excellence in Regolith Radiative Transfer (RRT), i.e., in modeling spectral reflectivity and emissivity of grainy or structured surfaces. The focus is the regime where the structural elements of grainy surfaces have grain sizes and separations of tens of microns, comparable to the wavelengths carrying diagnostic compositional information. This regime is of fundamental interest to remote sensing of planetary and terrestrial surfaces.

Dust Grain Charge above the Lunar terminator

NASA Astrophysics Data System (ADS)

Vaverka, Jakub; Richterova, Ivana; Nemecek, Zdenek; Safrankova, Jana; Pavlu, Jiri; Vysinka, Marek

Interaction of a lunar surface with the solar wind and magnetosphere leads to its charging by several processes as photoemission, a collection of primary particles, and secondary electron emission. Nevertheless, charging of the lunar surface is complicated by a shielding of solar light and solar wind ions by hills, craters, and boulders that can locally influence the surface potential. Moreover, a presence of a plasma wake can strongly affect this potential at the night side of the Moon. A typical surface potential varies from slightly positive (dayside) to negative values of the order of several hundred volts (night side). An electric field above the charged surface can lead to a levitation of dust grains as it has been observed by several spacecraft and by astronauts during Apollo missions. Although charging and transport of dust grains above the lunar surface are in the center of interest for many years, these phenomena are not still completely understood. We present calculation of an equilibrium potential of dust grains above the lunar surface. We focus on a terminator area during the Earth’s plasma sheet crossing. We use the secondary electron emission model for dust grains which takes into account an influence of the grain size, material, and surface roughness and findings from laboratory experiments with charging of lunar dust simulants by an electron beam.

Auger mediated positron sticking on graphene and highly oriented pyrolytic graphite

NASA Astrophysics Data System (ADS)

Chirayath, V. A.; Chrysler, M.; McDonald, A.; Lim, Z.; Shastry, K.; Gladen, R.; Fairchild, A.; Koymen, A.; Weiss, A.

Positron annihilation induced Auger electron spectroscopy (PAES) measurements on 6-8 layers graphene grown on polycrystalline copper and the measurements on a highly oriented pyrolytic graphite (HOPG) sample have indicated the presence of a bound surface state for positrons. Measurements carried out with positrons of kinetic energies lower than the electron work function for graphene or HOPG have shown emission of low energy electrons possible only through the Auger mediated positron sticking (AMPS) process. In this process the positron makes a transition from a positive energy scattering state to a bound surface state. The transition energy is coupled to a valence electron which may then have enough energy to get ejected from the sample surface. The positrons which are bound to surface state are highly localized in a direction perpendicular to surface and delocalized parallel to it which makes this process highly surface sensitive and can thus be used for characterizing graphene or graphite surfaces for open volume defects and surface impurities. The measurements have also shown an extremely large low energy tail for the C KVV Auger transition at 263eV indicative of another physical process for low energy emission. This work was supported by NSF Grant No. DMR 1508719 and DMR 1338130.

An integrated approach for estimation of methane emissions from wetlands and lakes in high latitude regions

NASA Astrophysics Data System (ADS)

Chiu, C.; Bowling, L. C.; Podest, E.; Bohn, T. J.; Lettenmaier, D. P.; Schroeder, R.; McDonald, K. C.

2009-04-01

In recent years, there has been increasing evidence of significant alteration in the extent of lakes and wetlands in high latitude regions due in part to thawing permafrost, as well as other changes governing surface and subsurface hydrology. Methane is a 23 times more efficient greenhouse gas than carbon dioxide; changes in surface water extent, and the associated subsurface anaerobic conditions, are important controls on methane emissions in high latitude regions. Methane emissions from wetlands vary substantially in both time and space, and are influenced by plant growth, soil organic matter decomposition, methanogenesis, and methane oxidation controlled by soil temperature, water table level and net primary productivity (NPP). The understanding of spatial and temporal heterogeneity of surface saturation, thermal regime and carbon substrate in northern Eurasian wetlands from point measurements are limited. In order to better estimate the magnitude and variability of methane emissions from northern lakes and wetlands, we present an integrated assessment approach based on remote sensing image classification, land surface modeling and process-based ecosystem modeling. Wetlands classifications based on L-band JERS-1 SAR (100m) and ALOS PALSAR (~30m) are used together with topographic information to parameterize a lake and wetland algorithm in the Variable Infiltration Capacity (VIC) land surface model at 25 km resolution. The enhanced VIC algorithm allows subsurface moisture exchange between surface water and wetlands and includes a sub-grid parameterization of water table position within the wetland area using a generalized topographic index. Average methane emissions are simulated by using the Walter and Heimann methane emission model based on temporally and spatially varying soil temperature, net primary productivity and water table generated from the modified VIC model. Our five preliminary study areas include the Z. Dvina, Upper Volga, Yeloguy, Syum, and Chaya river basins. The temporally-variable inundation extent simulated by the VIC model is compared to 25 km resolution inundation products developed from combined QuikSCAT, AMSR-E and MODIS data sets covering the time period from 2002 onward. The seasonal variation in methane emissions associated with sub-grid variability in water table extent is explored between 1948 and 2006. This work was carried out at Purdue University, at the University of Washington, and at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the NASA.

Anomalous photoelectric emission from Ag on zinc-phthalocyanine film

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tanaka, Senku, E-mail: senku@ele.kindai.ac.jp; Otani, Tomohiro; Fukuzawa, Ken

2014-05-12

Photoelectric emission from organic and metal thin films is generally observed with irradiation of photon energy larger than 4 eV. In this paper, however, we report photoelectric emission from Ag on a zinc-phthalocyanine (ZnPc) layer at a photon energy of 3.4 eV. The threshold energy for this photoelectric emission is much smaller than the work function of Ag estimated by conventional photoelectron spectroscopy. The photoelectric emission by low-energy photons is significant for Ag thicknesses of less than 1 nm. Photoelectron spectroscopy and morphological study of the Ag/ZnPc suggest that the anomalous photoelectric emission from the Ag surface is caused by a vacuum levelmore » shift at the Ag/ZnPc interface and by surface plasmons of the Ag nanoparticles.« less

The effect of impurities and incident angle on the secondary electron emission of Ni(110)

NASA Astrophysics Data System (ADS)

Lazar, Hadar; Patino, Marlene; Raitses, Yevgeny; Koel, Bruce E.; Gentile, Charles; Feibush, Eliot

2015-11-01

The investigation of secondary electron emission (SEE) of conducting materials used for magnetic fusion devices and plasma thrusters is important for determining device lifetime and performance. Methods to quantify the secondary electron emission from conducting materials and to characterize the effects that impurities and incident angles have on secondary electron emission were developed using 4-grid low energy electron diffraction (LEED) optics. The total secondary electron yield from a Ni(110) surface was continuously measured from the sample current as surface contamination increased from reactions with background gases in the ultrahigh vacuum chamber. Auger electron spectroscopy (AES) and temperature programmed desorption (TPD) were used to examine the composition and impurity levels on the Ni(110) surface. The total secondary electron yield was also measured at different incident angles. Thank you to the Princeton Plasma Physics Laboratory and the Department of Energy for the opportunity to work on this project through the Science Undergraduate Laboratory Internships.

Discovery and observation of BY Draconis variables

NASA Astrophysics Data System (ADS)

Bopp, B. W.; Noah, P. V.; Klimke, A.; Africano, J.

1981-10-01

The discovery of BY Draconis variables was efficiently accomplished by a spectroscopic survey of dK-M stars for weak H-alpha emissions, using 1-2 A resolution. The four BY Dra variables discovered are all spectroscopic binaries with P values lower than about 10 d, in light of which, it is noted that the onset of high surface activity and appearance of H-alpha emission occur sharply at v(equator) of approximately 5 km/sec. At v(equator) of about 3 km/sec, dK-M stars have low levels of surface activity. It is found that while there is a range of Ca II emission strength, and only the strongest emitters of this line are BY Dra and/or flare stars, the H-alpha feature changes abruptly to an emission feature signaling the onset of flaring and/or the BY Dra syndrome. An increase of the rotation rate above v(equator) 5 km/sec does not appear to increase the level of surface activity.

Reversed oxygen sensing using colloidal quantum wells towards highly emissive photoresponsive varnishes

PubMed Central

Lorenzon, Monica; Christodoulou, Sotirios; Vaccaro, Gianfranco; Pedrini, Jacopo; Meinardi, Francesco; Moreels, Iwan; Brovelli, Sergio

2015-01-01

Colloidal quantum wells combine the advantages of size-tunable electronic properties with vast reactive surfaces that could allow one to realize highly emissive luminescent-sensing varnishes capable of detecting chemical agents through their reversible emission response, with great potential impact on life sciences, environmental monitoring, defence and aerospace engineering. Here we combine spectroelectrochemical measurements and spectroscopic studies in a controlled atmosphere to demonstrate the ‘reversed oxygen-sensing’ capability of CdSe colloidal quantum wells, that is, the exposure to oxygen reversibly increases their luminescence efficiency. Spectroelectrochemical experiments allow us to directly relate the sensing response to the occupancy of surface states. Magneto-optical measurements demonstrate that, under vacuum, heterostructured CdSe/CdS colloidal quantum wells stabilize in their negative trion state. The high starting emission efficiency provides a possible means to enhance the oxygen sensitivity by partially de-passivating the particle surfaces, thereby enhancing the density of unsaturated sites with a minimal cost in term of luminescence losses. PMID:25910499

The effects of impurities and incidence angle on the secondary electron emission of Ni(110)

NASA Astrophysics Data System (ADS)

Lazar, Hadar; Patino, Marlene; Raitses, Yevgeny; Koel, Bruce; Gentile, Charles; Feibush, Eliot

The investigation of secondary electron emission (SEE) of conducting materials used for magnetic fusion devices and plasma thrusters is important for determining device lifetime and performance. Methods to quantify the secondary electron emission from conducting materials and to characterize the effects that impurities and incidence angles have on secondary electron emission were developed using 4-grid low energy electron diffraction (LEED) optics. The total secondary electron yield from a Ni(110) surface was continuously measured from the sample current as surface contamination increased from reactions with background gases in the ultrahigh vacuum chamber. Auger electron spectroscopy (AES) and temperature programmed desorption (TPD) were used to examine the composition and impurity levels on the Ni(110) surface. The total secondary electron yield was also measured at different incidence angles. Thank you to the Princeton Plasma Physics Laboratory (PPPL) and the Department of Energy (DOE) for the opportunity to work on this project through the Science Undergraduate Laboratory Internships (SULI).

Structural, Optical and Electrical Properties of ZnS/Porous Silicon Heterostructures

NASA Astrophysics Data System (ADS)

Wang, Cai-Feng; Li, Qing-Shan; Lv, Lei; Zhang, Li-Chun; Qi, Hong-Xia; Chen, Hou

2007-03-01

ZnS films are deposited by pulsed laser deposition on porous silicon (PS) substrates formed by electrochemical anodization of p-type (100) silicon wafer. Scanning electron microscope images reveal that the surface of ZnS films is unsmoothed, and there are some cracks in the ZnS films due to the roughness of the PS surface. The x-ray diffraction patterns show that the ZnS films on PS surface are grown in preferring orientation along cubic phase β-ZnS (111) direction. White light emission is obtained by combining the blue-green emission from ZnS films with the orange-red emission from PS layers. Based on the I-V characteristic, the ZnS/PS heterojunction exhibits the rectifying junction behaviour, and an ideality factor n is calculated to be 77 from the I-V plot.

40 CFR 63.5752 - How do I calculate the organic HAP content of aluminum recreational boat surface coatings?

Code of Federal Regulations, 2011 CFR

2011-07-01

... content of aluminum recreational boat surface coatings? 63.5752 Section 63.5752 Protection of Environment... AIR POLLUTANTS FOR SOURCE CATEGORIES National Emission Standards for Hazardous Air Pollutants for Boat Manufacturing Standards for Aluminum Recreational Boat Surface Coating Operations § 63.5752 How do I calculate...