Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “diffuse_transmittance”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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

6 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Thermochromic VO{sub 2} nanorods made by sputter deposition: Growth conditions and optical modeling

Reactive dc magnetron sputtering onto glass-based substrates yielded deposits of thermochromic VO{sub 2} with well-developed nanorods and nanowires. Their formation was promoted by high substrate temperature (above {approx}500 Degree-Sign C), sufficient film thickness, proper inlet of the reactive gas, dispersed gold 'seeds,' and pronounced substrate roughness. Rutherford back scattering ascertained mass thicknesses, scanning electron microscopy depicted the nanostructures, and glancing incidence X-ray diffraction proved that single-phase VO{sub 2} was normally formed. Spectrophotometric measurements of total and diffuse transmittance and reflectance on VO{sub 2} thin films, at room temperature and {approx}100 Degree-Sign C, allowed us to determine complex dielectric functions below and above the 'critical' temperature for thermochromic switching ({approx}68 Degree-Sign C). These data were then used in computations based on the Bruggeman effective medium theory applied to randomly oriented prolate spheroidal structural units to derive the optical properties of the deposits. Experimental and computed data on spectral absorptance were found to be in good qualitative agreement.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2011

Method for more accurate transmittance measurements of low-angle scattering samples using an integrating sphere with an entry port beam diffuser

For most integrating sphere measurements, the difference in light distribution between a specular reference beam and a diffused sample beam can result in significant errors. The problem becomes especially pronounced in integrating spheres that include a port for reflectance or diffuse transmittance measurements. The port is included in many standard spectrophotometers to facilitate a multipurpose instrument, however, absorption around the port edge can result in a detected signal that is too low. The absorption effect is especially apparent for low-angle scattering samples, because a significant portion of the light is scattered directly onto that edge. In this paper, a method for more accurate transmittance measurements of low-angle light-scattering samples is presented. The method uses a standard integrating sphere spectrophotometer, and the problem with increased absorption around the port edge is addressed by introducing a diffuser between the sample and the integrating sphere during both reference and sample scan. This reduces the discrepancy between the two scans and spreads the scattered light over a greater portion of the sphere wall. The problem with multiple reflections between the sample and diffuser is successfully addressed using a correction factor. The method is tested for two patterned glass samples with low-angle scattering and in both cases the transmittance accuracy is significantly improved.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Shortwave Array Spectroradiometer–Hemispheric (SASHe) Instrument Handbook

The Shortwave Array Spectroradiometer–Hemispheric (SASHe) provides measurements of direct solar, hemispheric diffuse, and total hemispheric shortwave irradiance over a continuous spectral range from approximately 300 nm to 1700 nm at a rate of about 30 seconds. The SASHe design connects an optical collector located outdoors to a pair of spectrometers and data collections systems located indoors within a climate-controlled building via an umbilical cable of fiber optic and electrical cables. The light collector uses a small Spectralon button as a hemispheric diffuser with a shadowband to distinguish signal from diffuse sky and direct sun.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2016

Shortwave Array Spectroradiometer–Zenith (SASZe) Instrument Handbook

The Shortwave Array Spectroradiometer – Zenith (SASZe) provides measurements of zenith spectral shortwave radiance at 1Hz over a continuous spectral range from approximately 300 nm to 1700 nm. The SASZe design connects an optical collector located outdoors to a pair of spectrometers and data collections system located indoors within a climate-controlled building via an umbilical cable of fiber optic and electrical cables. The light collector incorporates a collimator yielding a 1-degree Full Width at Half Maximum (FWHM) field of view. The data-acquisition electronics and spectrometers include an in-line fiber optic shutter and two Avantes fiber-coupled grating spectroradiometers within a temperature-controlled container. The Avantes Avaspec ULS 2048 charge-coupled device (CCD) spectrometer covers the wavelength range from about 300-1100 nm with a pixel spacing of less than 0.6 nm and a spectral resolution of about 2.4 nm FWHM. The Avantes Avaspec NIR256-1.7 spectrometer covers the wavelength range from about 950 nm to 1700 nm with a pixel spacing of less than 4 nm and a spectral resolution of about 6 nm FWHM.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2016

Measurements of Aerosols, Radiation, and Clouds over the Southern Oceans (MARCUS) Science Plan

The Southern Ocean (SO) is the stormiest place on earth, buffeted by winds and waves that circle the ice of Antarctica, and sheathed in clouds that mantle a dynamic ocean with rich ecosystems. The remote and usually pristine environment, typically removed from anthropogenic and natural continental aerosol sources, makes the SO unique for examining cloud-aerosol interactions for liquid and ice clouds, and the role of primary and secondary marine biogenic aerosols and sea salt. There is strong seasonality in aerosol sources and sinks over the SO that are poorly understood. Weather and climate models are challenged by uncertainties and biases in the simulation of SO clouds, aerosols, and air-sea exchanges that trace to poor physical understanding of these processes, and by cloud feedbacks (e.g., phase changes) in response to warming. Models almost universally underestimate sunlight reflected by near surface cloud, particularly in the cold sector of cyclonic storm systems, and this may be due to difficulties in representing pervasive supercooled and mixed-phase boundary-layer (BL) clouds. Motivated by these issues, a large international multi-agency effort called the Southern Ocean Clouds Radiation Transport Aerosol Transport Experimental Study (SOCRATES) has been proposed to improve our understanding of clouds, aerosols, air-sea exchanges and their interactions over the SO. Coincident with SOCRATES, the Measurements of Aerosols, Radiation and CloUds over the Southern Oceans (MARCUS) experiment will be conducted where the second U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility’s Mobile Facility (AMF2) will be installed on the Australian Antarctic supply vessel Aurora Australis (AA) as it makes routine transits between Hobart, Australia and the Antarctic, visiting the Australian Antarctic stations Mawson, Davis, and Casey, as well as Macquarie Island. During MARCUS, the AMF-2 will acquire comprehensive observations of aerosols (including cloud condensation nuclei [CCN] and ice nucleating particles [INP]) in the BL, vertical distributions of macrophysical and microphysical properties of liquid and mixed-phase clouds, and downwelling radiative fluxes over the SO during a 7-month period (September 2017 to April 2018) centered upon the Austral summer. The MARCUS observations will be self-standing and unique in that they will capture the variability in aerosol and cloud properties across the SO from spring to autumn, especially in cold waters at latitudes poleward 55° S, where supercooled and mixed-phase BL clouds in the cold sector of cyclones are frequent and where past and planned SO observations are most sparse.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2011

sasheniraod

ARM Instrument: Aerosol Optical Depth, derived from atmospheric extinction of solar irradiance

54 ENVIRONMENTAL SCIENCES↗