Science.gov

Sample records for adaptive reflective surfaces

  1. Surfaces with adaptive radar reflection coefficients

    NASA Astrophysics Data System (ADS)

    Chambers, Barry

    1997-10-01

    Conventional (passive) radar-absorbing materials (RAM) have been in use now for over half a century, but it is only with recent advances in conducting polymer composite materials that large-area surfaces having controllable reflection coefficients at radar frequencies have become practicable. Techniques for utilizing these new materials in re-configurable electromagnetic, or `smart', surfaces are reviewed, with due emphasis given to the problem of system integration. The discussion is complemented by modelled and measured performance data on several smart surface configurations.

  2. Landsat surface reflectance data

    USGS Publications Warehouse

    ,

    2015-01-01

    Landsat satellite data have been produced, archived, and distributed by the U.S. Geological Survey since 1972. Users rely on these data for historical study of land surface change and require consistent radiometric data processed to the highest science standards. In support of the guidelines established through the Global Climate Observing System, the U.S. Geological Survey has embarked on production of higher-level Landsat data products to support land surface change studies. One such product is Landsat surface reflectance.

  3. Adaption of the MODIS aerosol retrieval algorithm using airborne spectral surface reflectance measurements over urban areas: a case study

    NASA Astrophysics Data System (ADS)

    Jäkel, E.; Mey, B.; Levy, R.; Gu, X.; Yu, T.; Li, Z.; Althausen, D.; Heese, B.; Wendisch, M.

    2015-12-01

    MODIS (MOderate-resolution Imaging Spectroradiometer) retrievals of aerosol optical depth (AOD) are biased over urban areas, primarily because the reflectance characteristics of urban surfaces are different than that assumed by the retrieval algorithm. Specifically, the operational "dark-target" retrieval is tuned towards vegetated (dark) surfaces and assumes a spectral relationship to estimate the surface reflectance in blue and red wavelengths. From airborne measurements of surface reflectance over the city of Zhongshan, China, were collected that could replace the assumptions within the MODIS retrieval algorithm. The subsequent impact was tested upon two versions of the operational algorithm, Collections 5 and 6 (C5 and C6). AOD retrieval results of the operational and modified algorithms were compared for a specific case study over Zhongshan to show minor differences between them all. However, the Zhongshan-based spectral surface relationship was applied to a much larger urban sample, specifically to the MODIS data taken over Beijing between 2010 and 2014. These results were compared directly to ground-based AERONET (AErosol RObotic NETwork) measurements of AOD. A significant reduction of the differences between the AOD retrieved by the modified algorithms and AERONET was found, whereby the mean difference decreased from 0.27±0.14 for the operational C5 and 0.19±0.12 for the operational C6 to 0.10±0.15 and -0.02±0.17 by using the modified C5 and C6 retrievals. Since the modified algorithms assume a higher contribution by the surface to the total measured reflectance from MODIS, consequently the overestimation of AOD by the operational methods is reduced. Furthermore, the sensitivity of the MODIS AOD retrieval with respect to different surface types was investigated. Radiative transfer simulations were performed to model reflectances at top of atmosphere for predefined aerosol properties. The reflectance data were used as input for the retrieval methods. It

  4. Baffle system employing reflective surfaces

    NASA Astrophysics Data System (ADS)

    Linlor, W. I.

    1983-12-01

    Reflective baffles are proposed to reject off-axis light entering a telescope. Toroidal surfaces and adjacent cones are positioned so that off-axis rays make multiple reflections between these two surfaces. Meridional rays are reflected approximately parallel to the entering direction. Skew rays are reflected obliquely, but leave the telescope aperture. The range of incident angles for which these reflections are obtained is approximately 45 deg. A system is described that is designed specifically for the Space Shuttle Infrared Telescope Facility (SIRTF). Because of its reflective properties, the proposed baffle system rejects about 90 deg of the heat load from the SIRTF sunshade that would be absorbed in systems of conventional black baffles.

  5. Bacterial surface adaptation

    NASA Astrophysics Data System (ADS)

    Utada, Andrew

    2014-03-01

    Biofilms are structured multi-cellular communities that are fundamental to the biology and ecology of bacteria. Parasitic bacterial biofilms can cause lethal infections and biofouling, but commensal bacterial biofilms, such as those found in the gut, can break down otherwise indigestible plant polysaccharides and allow us to enjoy vegetables. The first step in biofilm formation, adaptation to life on a surface, requires a working knowledge of low Reynolds number fluid physics, and the coordination of biochemical signaling, polysaccharide production, and molecular motility motors. These crucial early stages of biofilm formation are at present poorly understood. By adapting methods from soft matter physics, we dissect bacterial social behavior at the single cell level for several prototypical bacterial species, including Pseudomonas aeruginosa and Vibrio cholerae.

  6. Reflection of cylindrical surface waves.

    PubMed

    Gordon, Reuven

    2009-10-12

    The reflection of the radially polarized surface wave on a metal wire at an abrupt end is derived. This theory allows for straightforward calculation of the reflection coefficient, including the phase and the amplitude, which will prove useful to the many applications in nanoplasmonics and terahertz spectroscopy. The theory shows excellent quantitative agreement with past comprehensive numerical simulations for small wires and for predicting the minima in reflection for larger wires. Using this theory, the wavelength dependent reflection is calculated for gold rods of diameter 10 nm, 26 nm and 85 nm, from which the Fabry-Perot resonance wavelengths are found. The Fabry-Perot resonances show good agreement with experimentally measured surface plasmon resonances in nanorods. This demonstrates the predictive ability of the theory for applications involving widely-used nanorods, optical antennas and plasmonic resonators. PMID:20372593

  7. Venus: global surface radar reflectivity.

    PubMed

    Pettengill, G H; Ford, P G; Nozette, S

    1982-08-13

    Observations of the surface of Venus, carried out by the Pioneer Venus radar mapper at a wavelength of 17 centimeters, reveal a global mean reflectivity at normal incidence of 0.13 +/- 0.03. Over the surface, variations from a low of 0.03 +/- 0.01 to a high of 0.4 +/- 0.1 are found, with Theia Mons, previously identified as possibly volcanic, showing a value of 0.28 +/- 0.07. Regions of high reflectivity may consist of rocks with substantial inclusions of highly conductive sulfides. PMID:17817535

  8. Surface Reflectance and Ocean Temperature

    NASA Technical Reports Server (NTRS)

    2002-01-01

    MODIS's 36 spectral bands provide scientists the chance to study many of Earth's terrestrial and oceanic characteristics with a single instrument, for example, Sea Surface Temperature (SST) and Land Surface Reflectance (LSR). This image was made from data collected during the month of May 2001. The LSR portion of the image is made from data collected at three wavelengths: 645 nm (red), 555 nm (green), and 469 nm (blue). This combination is similar to what our eyes would see. Combined with the land surface data are MODIS's measurements of SST in May, using detectors that capture thermal radiation at 4.0 um, a design innovation that improves measurements in moist areas, such as the tropics, where persistent clouds often interfere with satellite measurements of SST. Large-scale temperature patterns are apparent, such as the Gulf Stream off the east coast of the United States, and the Kuroshio Circulation southeast of Japan

  9. Reflectance measurements from particulate surfaces

    NASA Astrophysics Data System (ADS)

    Peltoniemi, J.; Gritsevich, M.; Hakala, T.; Penttilä, A.; Eskelinen, J.; Dagsson-Waldhauserova, P.; Arnalds, O.; Guirado, D.; Muinonen, K.

    2014-07-01

    Asteroids consists of, e.g., metals and rocky materials, and comets consist of, e.g., icy and rocky materials and dust. Their surfaces can be covered by small particles. To certain extent, these surfaces can resemble some natural or artificial surfaces on the Earth, such as snow layers, sand, gravels, or silt. By measuring the reflectance from such surfaces, one can gain better understanding on how to interpret astronomical observations of asteroids and comets. Even if not completely analogous, these samples and measurements provide a strict test bed for the scattering models applied to interpret observations of small Solar System bodies. FIGIFIGO (Finnish Geodetic Institute's Field Gonio-spectro-polari- radiometer) can measure the bidirectional reflectance factor (BRF) of surface targets of a diameter of around 10 cm, in a selected angular range and resolution, in the spectral range of 400-2400 nm, at about 10-nm resolution, including linear polarisation (Stokes I, Q, and U, or reflection coefficient matrix elements R_{11}, R_{12}, and R_{13}). Using FIGIFIGO, over 500 samples have been measured over the past years, including over 100 snow samples and almost 100 samples resembling sand, silt, soil, dust, or gravel. For planetary studies, especially interesting are dark volcanic ash and silt samples from Eyjafjallajökull and Grímsvönt eruptions. These have been measured loose and compressed, smooth and rough, purely and deposited on snow. Further single-scattering measurements using the Granada setup and measurements using the Univ. Helsinki integrating sphere complement the picture. Generally, we have observed that the reflectance from volcanic materials behaves mostly as expected and modelled. BRF shows typical bowl shape with strong phase-angle dependence. Spectral features are smooth, with slight angular dependence. Polarisation depends strongly on the phase angle, weaker on other angles defining the scattering geometry, and smoothly on the wavelength. There

  10. Characteristic variations in reflectance of surface soils

    NASA Technical Reports Server (NTRS)

    Stoner, E. R.; Baumgardner, M. F. (Principal Investigator)

    1982-01-01

    Surface soil samples from a wide range of naturally occurring soils were obtained for the purpose of studying the characteristic variations in soil reflectance as these variations relate to other soil properties and soil classification. A total 485 soil samples from the U.S. and Brazil representing 30 suborders of the 10 orders of 'Soil Taxonomy' was examined. The spectral bidirectional reflectance factor was measured on uniformly moist soils over the 0.52 to 2.32 micron wavelength range with a spectroradiometer adapted for indoor use. Five distinct soil spectral reflectance curve forms were identified according to curve shape, the presence or absence of absorption bands, and the predominance of soil organic matter and iron oxide composition. These curve forms were further characterized according to generically homogeneous soil properties in a manner similar to the subdivisions at the suborder level of 'Soil Taxonomy'. Results indicate that spectroradiometric measurements of soil spectral bidirectional reflectance factor can be used to characterize soil reflectance in terms that are meaningful to soil classification, genesis, and survey.

  11. Environmental responses of solar reflective surfaces

    NASA Technical Reports Server (NTRS)

    Bouquet, F. L.

    1983-01-01

    An assessment is undertaken of the environmental responses of solar reflective surfaces, with emphasis on dish-type concentrator surfaces exposed to the conditions of Southern California. A generalized mathematical model for specific solar reflective surfaces can be formulated on the basis of either experimental or assumed site degradation/corrosion data. In addition, the fabrication parameters of a parabolic reflecting surface and its substrate can be used to model combined reflective characteristics for the postulated environmental conditions.

  12. Condenser optic with sacrificial reflective surface

    DOEpatents

    Tichenor, Daniel A.; Kubiak, Glenn D.; Lee, Sung Hun

    2007-07-03

    Employing collector optics that has a sacrificial reflective surface can significantly prolong the useful life of the collector optics and the overall performance of the condenser in which the collector optics are incorporated. The collector optics is normally subject to erosion by debris from laser plasma source of radiation. The presence of an upper sacrificial reflective surface over the underlying reflective surface effectively increases the life of the optics while relaxing the constraints on the radiation source. Spatial and temporally varying reflectivity that results from the use of the sacrificial reflective surface can be accommodated by proper condenser design.

  13. Condenser optic with sacrificial reflective surface

    DOEpatents

    Tichenor, Daniel A.; Kubiak, Glenn D.; Lee, Sang Hun

    2006-07-25

    Employing collector optics that have a sacrificial reflective surface can significantly prolong the useful life of the collector optics and the overall performance of the condenser in which the collector optics are incorporated. The collector optics are normally subject to erosion by debris from laser plasma source of radiation. The presence of an upper sacrificial reflective surface over the underlying reflective surface effectively increases the life of the optics while relaxing the constraints on the radiation source. Spatial and temporally varying reflectivity that results from the use of the sacrificial reflective surface can be accommodated by proper condenser design.

  14. In Their Own Words: Teachers' Reflections on Adaptability

    ERIC Educational Resources Information Center

    Vaughn, Margaret; Parsons, Seth A.; Burrowbridge, Sarah Cohen; Weesner, Janice; Taylor, Laurel

    2016-01-01

    Current research explores adaptability by gathering teachers' reflections on their adaptations. However, the field knows little of what the term "adaptability" means to teachers who currently teach in today's educational context. In this article, adaptability is discussed from the perspectives of 3 practicing classroom educators,…

  15. Low-Reflectance Surfaces For Solar Cells

    NASA Technical Reports Server (NTRS)

    Bailey, Sheila G.; Landis, Geoffrey A.; Fatemi, Navid; Jenkins, Phillip P.

    1994-01-01

    Improved method for increasing solar cell efficiency has potential application for space-based and terrestrial solar power systems and optoelectronic devices. Etched low-angle grooves help recover reflected light. Light reflected from v-grooved surface trapped in cover glass and adhesive by total internal reflection. Reflected light redirected onto surface, and greater fraction of incident light absorbed, producing more electrical energy in InP solar photovoltaic cell.

  16. Surface roughness effects on bidirectional reflectance

    NASA Technical Reports Server (NTRS)

    Smith, T. F.; Hering, R. G.

    1972-01-01

    An experimental study of surface roughness effects on bidirectional reflectance of metallic surfaces is presented. A facility capable of irradiating a sample from normal to grazing incidence and recording plane of incidence bidirectional reflectance measurements was developed. Samples consisting of glass, aluminum alloy, and stainless steel materials were selected for examination. Samples were roughened using standard grinding techniques and coated with a radiatively opaque layer of pure aluminum. Mechanical surface roughness parameters, rms heights and rms slopes, evaluated from digitized surface profile measurements are less than 1.0 micrometers and 0.28, respectively. Rough surface specular, bidirectional, and directional reflectance measurements for selected values of polar angle of incidence and wavelength of incident energy within the spectral range of 1 to 14 micrometers are reported. The Beckmann bidirectional reflectance model is compared with reflectance measurements to establish its usefulness in describing the magnitude and spatial distribution of energy reflected from rough surfaces.

  17. Active reflective components for adaptive optical zoom systems

    NASA Astrophysics Data System (ADS)

    Jungwirth, Matthew Edward Lewis

    This dissertation presents the theoretical and experimental exploration of active reflective components specifically for large-aperture adaptive optical zoom systems. An active reflective component can change its focal length by physically deforming its reflecting surface. Adaptive optical zoom (AOZ) utilizes active components in order to change magnification and achieve optical zoom, as opposed to traditional zooming systems that move elements along the optical axis. AOZ systems are theoretically examined using a novel optical design theory that enables a full-scale tradespace analysis, where optical design begins from a broad perspective and optimizes to a particular system. The theory applies existing strategies for telescope design and aberration simulation to AOZ, culminating in the design of a Cassegrain objective with a 3.3X zoom ratio and a 375mm entrance aperture. AOZ systems are experimentally examined with the development of a large-aperture active mirror constructed of a composite material called carbon fiber reinforced polymer (CFRP). The active CFRP mirror uses a novel actuation method to change radius of curvature, where actuators press against two annular rings placed on the mirror's back. This method enables the radius of curvature to increase from 2000mm to 2010mm. Closed-loop control maintains good optical performance of 1.05 waves peak-to-valley (with respect to a HeNe laser) when the active CFRP mirror is used in conjunction with a commercial deformable mirror.

  18. Weak shock wave reflection from concave surfaces

    NASA Astrophysics Data System (ADS)

    Gruber, Sebastien; Skews, Beric

    2013-07-01

    The reflection of very weak shock waves from concave curved surfaces has not been well documented in the past, and recent studies have shown the possible existence of a variation in the accepted reflection configuration evolution as a shock wave encounters an increasing gradient on the reflecting surface. The current study set out to investigate this anomaly using high-resolution photography. Shock tube tests were done on various concave circular and parabolic geometries, all with zero initial ramp angle. Although the results have limitations due to the achievable image resolution, the results indicate that for very weak Mach numbers, M S < 1.1, there may be a region in which the reflection configuration resembles that of a regular reflection, unlike for the stronger shock wave case. This region exists after the triple point of the Mach reflection meets the reflecting surface and prior to the formation of the additional shock structures that represent a transitioned regular reflection. The Mach and transitioned regular reflections at 1.03 < M s < 1.05 also exhibit no signs of a visible shear layer, or a clear discontinuity at the triple point, and are thus also apparently different in the weak shock regime than what has been described for stronger shocks, similar to what has been shown for weak shocks reflecting off a plane wedge.

  19. A climatology of visible surface reflectance spectra

    NASA Astrophysics Data System (ADS)

    Zoogman, Peter; Liu, Xiong; Chance, Kelly; Sun, Qingsong; Schaaf, Crystal; Mahr, Tobias; Wagner, Thomas

    2016-09-01

    We present a high spectral resolution climatology of visible surface reflectance as a function of wavelength for use in satellite measurements of ozone and other atmospheric species. The Tropospheric Emissions: Monitoring of Pollution (TEMPO) instrument is planned to measure backscattered solar radiation in the 290-740 nm range, including the ultraviolet and visible Chappuis ozone bands. Observation in the weak Chappuis band takes advantage of the relative transparency of the atmosphere in the visible to achieve sensitivity to near-surface ozone. However, due to the weakness of the ozone absorption features this measurement is more sensitive to errors in visible surface reflectance, which is highly variable. We utilize reflectance measurements of individual plant, man-made, and other surface types to calculate the primary modes of variability of visible surface reflectance at a high spectral resolution, comparable to that of TEMPO (0.6 nm). Using the Moderate-resolution Imaging Spectroradiometer (MODIS) Bidirection Reflectance Distribution Function (BRDF)/albedo product and our derived primary modes we construct a high spatial resolution climatology of wavelength-dependent surface reflectance over all viewing scenes and geometries. The Global Ozone Monitoring Experiment-2 (GOME-2) Lambertian Equivalent Reflectance (LER) product provides complementary information over water and snow scenes. Preliminary results using this approach in multispectral ultraviolet+visible ozone retrievals from the GOME-2 instrument show significant improvement to the fitting residuals over vegetated scenes.

  20. Specular Reflection from Rough Surfaces Revisited

    ERIC Educational Resources Information Center

    Yasuda, Kensei; Kim, Alvin; Cho, Hayley; Timofejev, Timofej; Walecki, Wojciech J.; Klep, James; Edelson, Amy S.; Walecki, Abigail S.; Walecki, Eve S.; Walecki, Peter S.

    2016-01-01

    In his beautiful paper, Hasan Fakhruddin reported observations of mirror-like reflections in the rough surface of a ground glass plate. Similar effects have been recently employed for metrology of the roughness of optical diffusers used in modern light emitting device illumination systems. We report the observations of specular reflection in…

  1. Tunable reflection minima of nanostructured antireflective surfaces

    NASA Astrophysics Data System (ADS)

    Boden, S. A.; Bagnall, D. M.

    2008-09-01

    Broadband antireflection schemes for silicon surfaces based on the moth-eye principle and comprising arrays of subwavelength-scale pillars are applicable to solar cells, photodetectors, and stealth technologies and can exhibit very low reflectances. We show that rigorous coupled wave analysis can be used to accurately model the intricate reflectance behavior of these surfaces and so can be used to explore the effects of variations in pillar height, period, and shape. Low reflectance regions are identified, the extent of which are determined by the shape of the pillars. The wavelengths over which these low reflectance regions operate can be shifted by altering the period of the array. Thus the subtle features of the reflectance spectrum of a moth-eye array can be tailored for optimum performance for the input spectrum of a specific application.

  2. Observation of surfaces by reflection electron holography.

    PubMed

    Osakabe, N

    1992-02-15

    Reflection electron holography is described as a method to observe sub-A surface morphology. Phase shift of a Bragg-reflected electron wave was measured by means of holographic interferometry using an electron microscope equipped with a field emission electron gun and an electron biprism. A short wavelength of high energy electrons is the essential key to the high vertical sensitivity of this method, since geometrical path differences produced by the surface topography are measured in units of wavelengths in interferometrical measuring. Phase shift at a monoatomic step and the displacement field around a dislocation emerging on the surface were observed.

  3. Simulation Tool for GNSS Ocean Surface Reflections

    NASA Astrophysics Data System (ADS)

    Høeg, Per; von Benzon, Hans-Henrik; Durgonics, Tibor

    2015-04-01

    GNSS coherent and incoherent reflected signals have the potential of deriving large scale parameters of ocean surfaces, as barotropic variability, eddy currents and fronts, Rossby waves, coastal upwelling, mean ocean surface heights, and patterns of the general ocean circulation. In the reflection zone the measurements may derive parameters as sea surface roughness, winds, waves, heights and tilts from the spectral measurements. Previous measurements from the top of mountains and airplanes have shown such results leading. The coming satellite missions, CYGNSS, COSMIC-2, and GEROS on the International Space Station, are focusing on GNSS ocean reflection measurements. Thus, simulation studies highlighting the assumptions for the data retrievals and the precision and the accuracy of such measurements are of interest for assessing the observational method. The theory of propagation of microwaves in the atmosphere is well established, and methods for propagation modeling range from ray tracing to numerical solutions to the wave equation. Besides ray tracing there are propagation methods that use mode theory and a finite difference solution to the parabolic equation. The presented propagator is based on the solution of the parabolic equation. The parabolic equation in our simulator is solved using the split-step sine transformation. The Earth's surface is modeled with the use of an impedance model. The value of the Earth impedance is given as a function of the range along the surface of the Earth. This impedance concept gives an accurate lower boundary condition in the determination of the electromagnetic field, and makes it possible to simulate reflections and the effects of transitions between different mediums. A semi-isotropic Philips spectrum is used to represent the air-sea interaction. Simulated GPS ocean surface reflections will be presented and discussed based on different ocean characteristics. The spectra of the simulated surface reflections will be analyzed

  4. Surface roughness effects on bidirectional reflectance.

    NASA Technical Reports Server (NTRS)

    Smith, T. F.; Hering, R. G.

    1973-01-01

    An experimental study of surface roughness effects on bidirectional reflectance of metallic surfaces is presented. Samples consisting of glass, aluminum alloy, and stainless steel materials were roughened using standard grinding techniques and coated with a radiatively opaque layer of pure aluminum. Surface roughness parameters, rms height and rms slope, were evaluated from digitized surface profile measurements and are less than 1.0 micron, and 0.28, respectively. Rough-surface specular, bidirectional, and directional reflectance measurements for selected values of polar angle and wavelength of incident energy within the range from 10 to 80 deg and from 1 to 14 microns, respectively, are reported. The influence of surface roughness is discussed in terms of rms height and rms slope.

  5. Method for producing highly reflective metal surfaces

    DOEpatents

    Arnold, J.B.; Steger, P.J.; Wright, R.R.

    1982-03-04

    The invention is a novel method for producing mirror surfaces which are extremely smooth and which have high optical reflectivity. The method includes depositing, by electrolysis, an amorphous layer of nickel on an article and then diamond-machining the resulting nickel surface to increase its smoothness and reflectivity. The machined nickel surface then is passivated with respect to the formation of bonds with electrodeposited nickel. Nickel then is electrodeposited on the passivated surface to form a layer of electroplated nickel whose inside surface is a replica of the passivated surface. The mandrel then may be-re-passivated and provided with a layer of electrodeposited nickel, which is then recovered from the mandrel providing a second replica. The mandrel can be so re-used to provide many such replicas. As compared with producing each mirror-finished article by plating and diamond-machining, the new method is faster and less expensive.

  6. Measuring Light Reflectance of BGO Crystal Surfaces

    SciTech Connect

    Janecek, Martin; Moses, William

    2008-07-28

    A scintillating crystal's surface reflectance has to be well understood in order to accurately predict and optimize the crystal?s light collection through Monte Carlo simulations. In this paper, we measure the inner surface reflectance properties for BGO. The measurements include BGO crystals with a mechanically polished surface, rough-cut surface, and chemically etched surface, and with various reflectors attached, both air- coupled and with coupling compound. The measurements are performed with a laser aimed at the center of a hemispherical shaped BGO crystal. The hemispherical shape eliminates any non-perpendicular angles for light entering and exiting the crystal. The reflected light is collected with an array of photodiodes. The laser can be set at an arbitrary angle, and the photodiode array is rotated to fully cover 2? of solid angle. The current produced in the photodiodes is readout with a digital multimeter connected through a multiplexer. The two rows of photodiodes achieve 5-degree by 4-degree resolution, and the current measurement has a dynamic range of 10^5:1. The acquired data was not described by the commonly assumed linear combination of specular and diffuse (Lambertian) distributions, except for a very few surfaces. Surface roughness proved to be the most important parameter when choosing crystal setup. The reflector choice was of less importance and of almost no consequence for rough-cut surfaces. Pure specular reflection distribution for all incidence angles was measured for polished surfaces with VM2000 film, while the most Lambertian distribution for any surface finish was measured for titanium dioxide paint. The distributions acquired in this paper will be used to create more accurate Monte Carlo models for light reflection distribution within BGO crystals.

  7. Anisotropic reflectance characteristics of natural Earth surfaces.

    PubMed

    Brennan, B; Bandeen, W R

    1970-02-01

    The patterns of reflection of solar radiation from cloud, water, and land surfaces were measured with an aircraft-borne medium resolution radiometer. Reflectances in the 0.2-4.0-micro and 0.55-0.85-micro portions of the electromagnetic spectrum were investigated. Results indicate that the reflectance characteristics of most of the surface types measured are anisotropic. The anisotropy is dependent on the type of surface and the angles of incidence and reflection. In general, the anisotropy increases with increasing solar zenith angle. Clouds and forests show similar reflectance patterns, with forward and backward scattering peaks. Ocean surfaces yield a pattern similar to those of the clouds and forests but with an additional peak which is associated with sun glitter. Reflectances measured in the 0.2-4.0-micro band are generally lower than those in the 0.55-0.85-micro band under cloudy conditions. Anisotropy and spectral bandwidth should be accounted for when computing the albedo of the earth from narrow field-of-view measurements from satellites; otherwise, large errors may be expected to occur.

  8. Surface reflectance degradation by microbial communities

    SciTech Connect

    Cheng, Meng -Dawn; Allman, Steve L.; Graham, David E.; Cheng, Karen R.; Pfiffner, Susan Marie; Vishnivetskaya, Tatiana A.; Desjarlais, Andre Omer

    2015-11-05

    Building envelope, such as a roof, is the interface between a building structure and the environment. Understanding of the physics of microbial interactions with the building envelope is limited. In addition to the natural weathering, microorganisms and airborne particulate matter that attach to a cool roof tend to reduce the roof reflectance over time, compromising the energy efficiency advantages of the reflective coating designs. We applied microbial ecology analysis to identify the natural communities present on the exposed coatings and investigated the reduction kinetics of the surface reflectance upon the introduction of a defined mixture of both photoautotrophic and heterotrophic microorganisms representing the natural communities. The result are (1) reflectance degradation by microbial communities follows a first-order kinetic relationship and (2) more than 50% of degradation from the initial reflectance value can be caused by microbial species alone in much less time than 3 years required by the current standard ENERGY STAR® test methods.

  9. Surface reflectance degradation by microbial communities

    DOE PAGES

    Cheng, Meng -Dawn; Allman, Steve L.; Graham, David E.; Cheng, Karen R.; Pfiffner, Susan Marie; Vishnivetskaya, Tatiana A.; Desjarlais, Andre Omer

    2015-11-05

    Building envelope, such as a roof, is the interface between a building structure and the environment. Understanding of the physics of microbial interactions with the building envelope is limited. In addition to the natural weathering, microorganisms and airborne particulate matter that attach to a cool roof tend to reduce the roof reflectance over time, compromising the energy efficiency advantages of the reflective coating designs. We applied microbial ecology analysis to identify the natural communities present on the exposed coatings and investigated the reduction kinetics of the surface reflectance upon the introduction of a defined mixture of both photoautotrophic and heterotrophicmore » microorganisms representing the natural communities. The result are (1) reflectance degradation by microbial communities follows a first-order kinetic relationship and (2) more than 50% of degradation from the initial reflectance value can be caused by microbial species alone in much less time than 3 years required by the current standard ENERGY STAR® test methods.« less

  10. Rotationally Adaptive Flight Test Surface

    NASA Technical Reports Server (NTRS)

    Barrett, Ron

    1999-01-01

    Research on a new design of flutter exciter vane using adaptive materials was conducted. This novel design is based on all-moving aerodynamic surface technology and consists of a structurally stiff main spar, a series of piezoelectric actuator elements and an aerodynamic shell which is pivoted around the main spar. The work was built upon the current missile-type all-moving surface designs and change them so they are better suited for flutter excitation through the transonic flight regime. The first portion of research will be centered on aerodynamic and structural modeling of the system. USAF DatCom and vortex lattice codes was used to capture the fundamental aerodynamics of the vane. Finite element codes and laminated plate theory and virtual work analyses will be used to structurally model the aerodynamic vane and wing tip. Following the basic modeling, a flutter test vane was designed. Each component within the structure was designed to meet the design loads. After the design loads are met, then the deflections will be maximized and the internal structure will be laid out. In addition to the structure, a basic electrical control network will be designed which will be capable of driving a scaled exciter vane. The third and final stage of main investigation involved the fabrication of a 1/4 scale vane. This scaled vane was used to verify kinematics and structural mechanics theories on all-moving actuation. Following assembly, a series of bench tests was conducted to determine frequency response, electrical characteristics, mechanical and kinematic properties. Test results indicate peak-to-peak deflections of 1.1 deg with a corner frequency of just over 130 Hz.

  11. Landsat Surface Reflectance Climate Data Records

    USGS Publications Warehouse

    ,

    2014-01-01

    Landsat Surface Reflectance Climate Data Records (CDRs) are high level Landsat data products that support land surface change studies. Climate Data Records, as defined by the National Research Council, are a time series of measurements with sufficient length, consistency, and continuity to identify climate variability and change. The U.S. Geological Survey (USGS) is using the valuable 40-year Landsat archive to create CDRs that can be used to document changes to Earth’s terrestrial environment.

  12. Surface composition of Mercury from reflectance spectrophotometry

    NASA Technical Reports Server (NTRS)

    Vilas, Faith

    1988-01-01

    The controversies surrounding the existing spectra of Mercury are discussed together with the various implications for interpretations of Mercury's surface composition. Special attention is given to the basic procedure used for reducing reflectance spectrophotometry data, the factors that must be accounted for in the reduction of these data, and the methodology for defining the portion of the surface contributing the greatest amount of light to an individual spectrum. The application of these methodologies to Mercury's spectra is presented.

  13. Specular Reflection from Rough Surfaces Revisited

    NASA Astrophysics Data System (ADS)

    Yasuda, Kensei; Kim, Alvin; Cho, Hayley; Timofejev, Timofej; Walecki, Wojciech J.; Klep, James; Edelson, Amy S.; Walecki, Abigail S.; Walecki, Eve S.; Walecki, Peter S.

    2016-10-01

    In his beautiful paper, Hasan Fakhruddin reported observations of mirror-like reflections in the rough surface of a ground glass plate. Similar effects have been recently employed for metrology of the roughness of optical diffusers used in modern light emitting device illumination systems. We report the observations of specular reflection in nontransparent rough surfaces at oblique angles, where roughness was treated as a variable. We present a simple trigonometry-based model explaining the observed phenomenon, which we experimentally validated using aluminum surfaces that have controlled roughness. The reported demonstration requires no special equipment, other than cellphone cameras, dielectric or metal plate, and sandpaper, and serves as an introduction to wave optics. This activity can be used to get further insight into everyday applications of wave optics for students already familiar with wave optics fundamentals.

  14. Method for producing highly reflective metal surfaces

    DOEpatents

    Arnold, Jones B.; Steger, Philip J.; Wright, Ralph R.

    1983-01-01

    The invention is a novel method for producing mirror surfaces which are extremely smooth and which have high optical reflectivity. The method includes electrolessly depositing an amorphous layer of nickel on an article and then diamond-machining the resulting nickel surface to increase its smoothness and reflectivity. The machined nickel surface then is passivated with respect to the formation of bonds with electrodeposited nickel. Nickel then is electrodeposited on the passivated surface to form a layer of electroplated nickel whose inside surface is a replica of the passivated surface. The electroplated nickel layer then is separated from the passivated surface. The mandrel then may be re-passivated and provided with a layer of electrodeposited nickel, which is then recovered from the mandrel providing a second replica. The mandrel can be so re-used to provide many such replicas. As compared with producing each mirror-finished article by plating and diamond-machining, the new method is faster and less expensive.

  15. Mercury: surface composition from the reflection spectrum.

    PubMed

    McCord, T B; Adams, J B

    1972-11-17

    The reflection spectrum for the integral disk of the planet Mercury was measured and was found to have a constant positive slope from 0.32 to 1.05 micrometers, except for absorption features in the infrared. The reflectivity curve matches closely the curve for the lunar upland and mare regions. Thus, the surface of Mercury is probably covered with a lunar-like soil rich in dark glasses of high iron and titanium content. Pyroxene is probably the dominant mafic mineral. PMID:17798540

  16. Reduction of Glass Surface Reflectance by Ion Beam Surface Modification

    SciTech Connect

    Mark Spitzer

    2011-03-11

    This is the final report for DOE contract DE-EE0000590. The purpose of this work was to determine the feasibility of the reduction of the reflection from the front of solar photovoltaic modules. Reflection accounts for a power loss of approximately 4%. A solar module having an area of one square meter with an energy conversion efficiency of 18% generates approximately 180 watts. If reflection loss can be eliminated, the power output can be increased to 187 watts. Since conventional thin-film anti-reflection coatings do not have sufficient environmental stability, we investigated the feasibility of ion beam modification of the glass surface to obtain reduction of reflectance. Our findings are generally applicable to all solar modules that use glass encapsulation, as well as commercial float glass used in windows and other applications. Ion implantation of argon, fluorine, and xenon into commercial low-iron soda lime float glass, standard float glass, and borosilicate glass was studied by implantation, annealing, and measurement of reflectance. The three ions all affected reflectance. The most significant change was obtained by argon implantation into both low-iron and standard soda-lime glass. In this way samples were formed with reflectance lower than can be obtained with a single-layer coatings of magnesium fluoride. Integrated reflectance was reduced from 4% to 1% in low-iron soda lime glass typical of the glass used in solar modules. The reduction of reflectance of borosilicate glass was not as large; however borosilicate glass is not typically used in flat plate solar modules. Unlike conventional semiconductor ion implantation doping, glass reflectance reduction was found to be tolerant to large variations in implant dose, meaning that the process does not require high dopant uniformity. Additionally, glass implantation does not require mass analysis. Simple, high current ion implantation equipment can be developed for this process; however, before the process

  17. Procedures to reduce reflection on polymer surfaces

    NASA Astrophysics Data System (ADS)

    Schulz, Ulrike; Munzert, Peter; Kaless, Antje; Lau, Kerstin; Kaiser, Norbert

    2005-09-01

    Antireflection (AR) properties are required for optical surfaces to avoid disturbing reflections as well as to improve the transmission of optical systems. The common method to reduce the reflection on optics is vacuum deposition of interference coatings. However, special efforts are required for each type of plastic to develop polymer-capable vacuum coating processes due to the manifold chemical and physical properties of optical polymers. An alternative procedure for the antireflection of polymers is the generation of surface structures that decrease the index of refraction in a surface region. In this paper, the suitability of the miscellaneous thermoplastic polymers for plasma-ion assisted deposition processes is evaluated. This comprises the study of damage effects caused by the contact with plasma and high-energy radiation as well as the development of special coating designs and of suitable process conditions. Coating properties achieved are discussed for PMMA and poly-cycloolefines. The same ion source arrangement as used for coating has been applied for etching an antireflective sub-wavelength surface structure into PMMA. In summary, the paper shows the practical application fields for both technologies.

  18. Quality assessment of Landsat surface reflectance products using MODIS data

    NASA Astrophysics Data System (ADS)

    Feng, Min; Huang, Chengquan; Channan, Saurabh; Vermote, Eric F.; Masek, Jeffrey G.; Townshend, John R.

    2012-01-01

    images for the 2000 epoch. As surface reflectance likely will be a standard product for future Landsat missions, the approach developed in this study can be adapted as an operational quality assessment system for those missions.

  19. Quality Assessment of Landsat Surface Reflectance Products Using MODIS Data

    NASA Technical Reports Server (NTRS)

    Feng, Min; Huang, Chengquan; Channan, Saurabh; Vermote, Eric; Masek, Jeffrey G.; Townshend, John R.

    2012-01-01

    images for the 2000 epoch. As surface reflectance likely will be a standard product for future Landsat missions, the approach developed in this study can be adapted as an operational quality assessment system for those missions.

  20. Effect of surface reflectivity on photonic Doppler velocimetry measurement

    NASA Astrophysics Data System (ADS)

    Wu, Xianqian; Xia, Weiguang; Wang, Xi; Song, Hongwei; Huang, Chenguang

    2014-05-01

    While photonic Doppler velocimetry (PDV) is becoming a common diagnostic for tracking velocity in shock physical experiments, its validity on measuring surfaces with different reflectivity is not studied. This paper investigates the effects of surface reflectivity on PDV measurement for tracking back free surface velocity in laser shock processing. Credible measurement results for coarse polished surfaces with low reflectivity are obtained, whereas fine polished surfaces with relatively high reflectivity lead to heterodyne fringes with high frequency and corresponding unreasonably fast velocities. This phenomenon reported in the paper is somewhat inconsistent with the general view that PDV has remarkable robustness to large changes in surface reflectivity. The reason might be ascribed to multiple reflections of light, which cause the generation of multiple Doppler shifts. The mixing of the reference light and those Doppler-shifted lights brings out high frequency heterodyne fringes resulting in high velocity. Low surface reflectivity is better suited for PDV measurements.

  1. Doppler shift estimation for GNSS reflectometry using a land topography adapted reflection model

    NASA Astrophysics Data System (ADS)

    Semmling, Maximilian; Peraza, Luis; Falck, Carsten; Gerland, Sebastian; Wickert, Jens

    2016-04-01

    A GNSS setup with a receiver capable for reflectometry is operated by GFZ at Kongsfjorden (Spitsbergen), 78°54'14''N, 11°52'37''E, 512 m above ellipsoid (WGS-84). This permanent station at the Zeppelin mountain outpost, operated by the Norwegian Polar Institute (NPI), accumulates data since Summer 2013 observing reflections over the fjord and the adjacent land surface. Especially the presence of sea ice over the fjord and snow cover over land are of interest for reflectometry to investigate altimetry and remote sensing applications. The setup contains a GORS (GNSS Occultation Reflectometry Scatterometry) two-frontend receiver, which is based on commercial JAVAD hardware. The receiver is connected to one up-looking and one horizon-looking patch antenna with right-handed and left-handed circular polarization, respectively. Both antennas are installed on the same mount approximately 475 m above the fjord mean sea level. Reflections are observed at low transmitter elevation angles (between 10 and 2°). For these geometries the relative Doppler shift (sea surface reflected relative to direct signal) is almost constant 0.5 to 0.6 Hz and can be calculated with an established reflection model. Rather easily, sea surface reflections are identified in the data and the corresponding reflection points are located. About 55 daily recurring reflection events over the fjord are observed. They form a fan-shaped swath with 3 to 13 km distance around the receiver, corresponding to elevations of 10° to 2°. Also signatures of potential land reflections are found in the data. About 13 daily recurring events extend mainly over land. The potential land signatures have a rather variable Doppler shift between 0.2 to 1Hz. The significant topography of the mountainous surrounding, which varies between sea level and 900 m altitude, prevents the use of established reflection models. A topography adapted reflection model, which considers sloped surface facets, is developed. It incorporates

  2. Anomalous reflections at photonic crystal surfaces.

    PubMed

    Yu, Xiaofang; Fan, Shanhui

    2004-11-01

    We explore the reflection phenomena when a light beam propagating in a photonic crystal is incident upon the interfaces between the crystal and a uniform dielectric. We prove that a generalized wave-vector conservation relation still applies even when the interface is not aligned with special crystal directions. Using this conservation relation, we show that neither the phase velocity nor the group velocity directions of the reflected beam satisfies Snell's law. Rather, the system exhibits remarkable and unusual reflection effects. In particular, total internal reflection is absent except at discrete angular values. The direction of the reflected beam can also be pinned along special crystal directions, independent of the orientation of the interface. And finally, at glancing incidences, strong backward reflections may occur. These effects may be important for creating integrated photonic circuits, and for on-chip image transfer.

  3. Reproduction-longevity trade-offs reflect diet, not adaptation.

    PubMed

    Attisano, A; Moore, A J; Moore, P J

    2012-05-01

    A tenet of life history evolution is that allocation of limited resources results in trade-offs, such as that between reproduction and lifespan. Reproduction and lifespan are also influenced proximately by differences in the availability of specific nutrients. What is unknown is how the evolution of the ability to use a nutritionally novel diet is reflected in this fundamental trade-off. Does the evolution of the ability to use a nutritionally novel food maintain the trade-off in reproduction and longevity, or do the proximate effects of nutrition alter the adapted trade-off? We tested this by measuring trade-offs in male milkweed bugs, Oncopeltus fasciatus, fed either an adapted diet of sunflower or the ancestral diet of milkweed. Sunflower-fed males lived longer but invested less in reproduction, both in mating and fertility. Milkweed-fed males invested in both mating and fertility at the expense of survival. The evolution of an expanded diet was not constrained by the existing trade-off, but instead was accompanied by a different trade-off between reproduction and longevity. We suggest that this occurs because diets differ in promoting germ line development or longevity. PMID:22356585

  4. Reflectivity Reconstruction Based on Adaptive Speed of Sound Estimation from Reflection Information

    NASA Astrophysics Data System (ADS)

    Yuan, Weiquan

    The reflectivity image reconstructed by the synthetic focus algorithm has been verified to be one of the highest in resolution of any ultrasound imaging systems. However present imaging systems with the synthetic focus algorithm suffer from signal registration problems due to diffraction and refraction effects. Recent research efforts on refraction correction for reflection imaging are based on speed of sound estimation. One approach is to determine the speed of the sound map from transmission information. In this technique, both reflection and transmission data are required. Unfortunately, it is difficult to acquire both transmission and reflection in many practical medical environments. In this dissertation, a new reflectivity reconstruction technique is investigated in which the speed of sound estimation is determined only from the reflection data. This method of speed of sound estimation is based on an optimization approach. The speed of sound of the imaging region is updated iterately based one optimization. The criterion employed is the minimization of an objective functional. In particular, the alignment error functional, correlation functional or brightness functional are defined and then investigated. These objective functionals are all dependent on the speed of sound. During the process of minimizing the objective functional with respect to the speed of sound, an approximation to the true speed of sound is determined adaptively. To minimize these specific objective functionals, the conjugate gradient method with line search and with quadratic approximation is investigated. For such a large optimization problem, an undesired local minimum is often found. The penalty function technique is suggested to overcome this local minimum problem. Due to the limitation of available computer capability, all the methods developed are first investigated by a 8 x 8 grid reconstruction of speed of sound. Finally, the simulation results for a lager 64 x 64 reflectivity

  5. Soft tissue adaptation to modified titanium surfaces.

    PubMed

    Lee, Shermin; Goh, Bee Tin; Wolke, Joop; Tideman, Henk; Stoelinga, Paul; Jansen, John

    2010-11-01

    Surface modification of titanium alloy implants to enhance soft tissue adherence is important to minimize soft tissue dehiscence. This study aimed to confirm if a dual acid etched "Osseotite®" titanium surface contributes to soft tissue adherence in muscle. It also aims to explore if a radio frequency magnetron sputtered hydroxyapatite (HA)/bioglass (BG) coating can serve this purpose and provides soft tissue adherence in mucosal tissue. The study was carried out in 18 Macaca fascicularis animals, 14 Osseotite® coated Ti6Al4V bullets inserted intramuscularly and 12 HA/BG coated Ti6Al4V plates inserted into the submucosa. These were compared with machined Ti6Al4V surfaces as controls. The histological and histomorphometrical results revealed that no significant difference existed in muscle tissue response between machined and Osseotite® surfaces. On the other hand, the HA/BG coated submucosal plates showed statistically significant differences with a thinner capsule quantity (p < 0.0001), an increased capsule quality (p < 0.0001) and interface quality score (p < 0.05). In conclusion, the deposited HA/BG coatings facilitated soft tissue (mucosa) adaptation at 1 month of implant installation, whereas the acid etched Osseotite® surface did not enhance muscular adaptation. PMID:20725967

  6. Derivation of scaled surface reflectances from AVIRIS data

    NASA Technical Reports Server (NTRS)

    Gao, Bo-Cai; Heidebrecht, Kathleen B.; Goetz, Alexander F. H.

    1993-01-01

    A method for retrieving 'scaled surface reflectances' assuming horizontal surfaces having Lambertian reflectances from spectral data collected by Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) is presented here. In this method, the integrated water vapor amount on a pixel by pixel basis is derived from the 0.94 micron and 1.14 micron water vapor absorption features. The transmission spectra of H2O, CO2, O3, N2O, CO, CH4, and O2 in the 0.4-2.5 micron region are simulated. The scattering effect due to atmospheric molecules and aerosols is modeled with the 5S computer code. The AVIRIS radiances are divided by solar irradiances above the atmosphere to obtain the apparent reflectances. The scaled surface reflectances are derived from the apparent reflectances using the simulated atmospheric gaseous transmittances and the simulated molecular and aerosol scattering data. The scaled surface reflectances differ from the real surface reflectances by a multiplicative factor. In order to convert the scaled surface reflectances into real surface reflectances, the slopes and aspects of the surfaces must be known.

  7. Adapting to life after burn injury--reflections on care.

    PubMed

    Dahl, Oili; Wickman, Marie; Wengström, Yvonne

    2012-01-01

    A burn injury is an unforeseen event that means physical and psychological trauma for the person afflicted. The trauma experienced by different individuals varies greatly, as do perceived problems during care, rehabilitation, and throughout the remainder of life. The purpose of this study was to explore burn patients' experiences of adapting to life after burn injury to acquire a deeper understanding of the most important issues for patients when providing care during and after a burn injury. A qualitative approach was applied, and interviews were conducted with 12 adult burn patients (8 men and 4 women) 6 to 12 months postburn. The interviews were analyzed using Kvales' method for structuring analysis and comprised a close reading and interpretation of the texts. Analysis focused on the personal experiences of burn patients living after burn injury and treatment. Struggling with the consequences of burn injury and how patients perceived life today after treatment are important issues for adapting to life after burn injury. New experiences of a fragile body, coping with daily life, and reflections of burn care were also prominent themes. Patients with burn injuries need adequate repeated information about the plan for their care, about the physiological changes, and more support to handle the trauma event. The patients would also like to be more involved in their care. A program of support and preparatory work to help the patient to cope with the new bodily sensations and new body image is necessary and should begin during hospital care. A multidisciplinary team approach for pain treatment needs to be prioritized. In addition, multidisciplinary follow-up after burns need to include patients with minor burns. PMID:22210069

  8. Genome fluctuations in cyanobacteria reflect evolutionary, developmental and adaptive traits

    PubMed Central

    2011-01-01

    Background Cyanobacteria belong to an ancient group of photosynthetic prokaryotes with pronounced variations in their cellular differentiation strategies, physiological capacities and choice of habitat. Sequencing efforts have shown that genomes within this phylum are equally diverse in terms of size and protein-coding capacity. To increase our understanding of genomic changes in the lineage, the genomes of 58 contemporary cyanobacteria were analysed for shared and unique orthologs. Results A total of 404 protein families, present in all cyanobacterial genomes, were identified. Two of these are unique to the phylum, corresponding to an AbrB family transcriptional regulator and a gene that escapes functional annotation although its genomic neighbourhood is conserved among the organisms examined. The evolution of cyanobacterial genome sizes involves a mix of gains and losses in the clade encompassing complex cyanobacteria, while a single event of reduction is evident in a clade dominated by unicellular cyanobacteria. Genome sizes and gene family copy numbers evolve at a higher rate in the former clade, and multi-copy genes were predominant in large genomes. Orthologs unique to cyanobacteria exhibiting specific characteristics, such as filament formation, heterocyst differentiation, diazotrophy and symbiotic competence, were also identified. An ancestral character reconstruction suggests that the most recent common ancestor of cyanobacteria had a genome size of approx. 4.5 Mbp and 1678 to 3291 protein-coding genes, 4%-6% of which are unique to cyanobacteria today. Conclusions The different rates of genome-size evolution and multi-copy gene abundance suggest two routes of genome development in the history of cyanobacteria. The expansion strategy is driven by gene-family enlargment and generates a broad adaptive potential; while the genome streamlining strategy imposes adaptations to highly specific niches, also reflected in their different functional capacities. A few

  9. Effects of reflection properties of natural surfaces in aerial reconnaissance.

    PubMed

    Coulson, K L

    1966-06-01

    Measurements of the reflecting and polarizing properties of various soils, sands, and vegetation in the visible-and near-ir spectral regions show that dark surfaces polarize the reflected radiation strongly while highly reflecting surfaces have relatively weak polarizing properties. In general, the reflectance of mineral surfaces increases, and the degree of polarization of the reflected radiation decreases, with increasing wavelength and increasing angle of incidence. There is little or no indication of specular reflection from the surfaces for which measurements were made. Introduction of the reflection data into the equation of radiative transfer for clear and slightly turbid models of the earth's atmosphere shows that the upward radiation that would be incident on a high-altitude aircraft or satellite would be dominated by surface-reflected radiation for the red and near-ir regions over highly reflecting surfaces such as deserts, whereas atmospheric scattering is most important for short wavelengths and dark surfaces. Because of polarization effects, atmospheric transmission of optical contrasts is better in one orthogonal intensity component than the other, the difference being sufficient to merit polarizing optics in reconnaissance instrumentation under certain conditions.

  10. Reflective overcoats for radiation control surfaces

    NASA Technical Reports Server (NTRS)

    White, Susan M.

    1991-01-01

    Theoretical models are developed to predict the surface properties of a coating layer composed of particles of a known size distribution, applied to an opaque substrate, such as a metal or reaction cured glass (RCG). The surface temperature attained at radiative equilibrium by an overcoated surface subject to a given heat flux is calculated. The incident radiation was assumed to exhibit the spectral distribution characteristic of a black body at different temperatures or equivalently, having different peak wavelengths, with the energy level scaled to give a range of desired surface radiative heat fluxes. This approach allows a straightforward comparison of the thernal response of a surface to incident radiation having the energy predominantly in a characteristic wavelength band and a well-defined spectral distribution. The ratio of the radiative heat flux to the total heat flux was varied, and the different geometric and material parameters of such overcoat layers were explored. The model was applied to representative surface heating rates to the Aeroasssisted Flight Experiment (AFE) and to Aeroassisted Space Transfer Vehicles (ASTVs). The predicted radiative energy flux to the surface of the AFE vehicle gives a single-point comparison of the surface temperatures attained with and without a selective-reflector overcoat on the vehicle surface. The specific objective of this work is to identify the most desirable radiative properties of an overcoat/substrate system for this environment.

  11. Reflections concerning triply-periodic minimal surfaces.

    PubMed

    Schoen, Alan H

    2012-10-01

    In recent decades, there has been an explosion in the number and variety of embedded triply-periodic minimal surfaces (TPMS) identified by mathematicians and materials scientists. Only the rare examples of low genus, however, are commonly invoked as shape templates in scientific applications. Exact analytic solutions are now known for many of the low genus examples. The more complex surfaces are readily defined with numerical tools such as Surface Evolver software or the Landau-Ginzburg model. Even though table-top versions of several TPMS have been placed within easy reach by rapid prototyping methods, the inherent complexity of many of these surfaces makes it challenging to grasp their structure. The problem of distinguishing TPMS, which is now acute because of the proliferation of examples, has been addressed by Lord & Mackay (Lord & Mackay 2003 Curr. Sci. 85, 346-362).

  12. Reflections concerning triply-periodic minimal surfaces

    PubMed Central

    Schoen, Alan H.

    2012-01-01

    In recent decades, there has been an explosion in the number and variety of embedded triply-periodic minimal surfaces (TPMS) identified by mathematicians and materials scientists. Only the rare examples of low genus, however, are commonly invoked as shape templates in scientific applications. Exact analytic solutions are now known for many of the low genus examples. The more complex surfaces are readily defined with numerical tools such as Surface Evolver software or the Landau–Ginzburg model. Even though table-top versions of several TPMS have been placed within easy reach by rapid prototyping methods, the inherent complexity of many of these surfaces makes it challenging to grasp their structure. The problem of distinguishing TPMS, which is now acute because of the proliferation of examples, has been addressed by Lord & Mackay (Lord & Mackay 2003 Curr. Sci. 85, 346–362). PMID:24098851

  13. A Reflective Gaussian Coronagraph for Extreme Adaptive Optics: Laboratory Performance

    NASA Astrophysics Data System (ADS)

    Park, Ryeojin; Close, Laird M.; Siegler, Nick; Nielsen, Eric L.; Stalcup, Thomas

    2006-11-01

    We report laboratory results of a coronagraphic test bench to assess the intensity reduction differences between a ``Gaussian'' tapered focal plane coronagraphic mask and a classical hard-edged ``top hat'' function mask at extreme adaptive optics (ExAO) Strehl ratios of ~94%. However, unlike a traditional coronagraph design, we insert a reflective focal plane mask at 45° to the optical axis. We also use an intermediate secondary mask (mask 2) before a final image in order to block additional mask-edge-diffracted light. The test bench simulates the optical train of ground-based telescopes (in particular, the 8.1 m Gemini North Telescope). It includes one spider vane, different mask radii (r = 1.9λ/D, 3.7λ/D, and 7.4λ/D), and two types of reflective focal plane masks (hard-edged top-hat and Gaussian tapered profiles). In order to investigate the relative performance of these competing coronagraphic designs with regard to extrasolar planet detection sensitivity, we utilize the simulation of realistic extrasolar planet populations (Nielsen et al.). With an appropriate translation of our laboratory results to expected telescope performance, a Gaussian tapered mask radius of 3.7λ/D with an additional mask (mask 2) performs best (highest planet detection sensitivity). For a full survey with this optimal design, the simulation predicts that ~30% more planets would be detected than with a top-hat function mask of similar size with mask 2. Using the best design, the point contrast ratio between the stellar point-spread function (PSF) peak and the coronagraphic PSF at 10λ/D (0.4" in the H band if D = 8.1 m) is ~10 times higher than a classical Lyot top-hat coronagraph. Hence, we find that a Gaussian apodized mask with an additional blocking mask is superior (~10 times higher contrast) to the use of a classical Lyot coronagraph for ExAO-like Strehl ratios.

  14. Functional connectivity patterns reflect individual differences in conflict adaptation.

    PubMed

    Wang, Xiangpeng; Wang, Ting; Chen, Zhencai; Hitchman, Glenn; Liu, Yijun; Chen, Antao

    2015-04-01

    Individuals differ in the ability to utilize previous conflict information to optimize current conflict resolution, which is termed the conflict adaptation effect. Previous studies have linked individual differences in conflict adaptation to distinct brain regions. However, the network-based neural mechanisms subserving the individual differences of the conflict adaptation effect have not been studied. The present study employed a psychophysiological interaction (PPI) analysis with a color-naming Stroop task to examine this issue. The main results were as follows: (1) the anterior cingulate cortex (ACC)-seeded PPI revealed the involvement of the salience network (SN) in conflict adaptation, while the posterior parietal cortex (PPC)-seeded PPI revealed the engagement of the central executive network (CEN). (2) Participants with high conflict adaptation effect showed higher intra-CEN connectivity and lower intra-SN connectivity; while those with low conflict adaptation effect showed higher intra-SN connectivity and lower intra-CEN connectivity. (3) The PPC-centered intra-CEN connectivity positively predicted the conflict adaptation effect; while the ACC-centered intra-SN connectivity had a negative correlation with this effect. In conclusion, our data demonstrated that conflict adaptation is likely supported by the CEN and the SN, providing a new perspective on studying individual differences in conflict adaptation on the basis of large-scale networks. PMID:25721566

  15. Surface reflection properties of oil paints under various conditions

    NASA Astrophysics Data System (ADS)

    Tominaga, Shoji; Nishi, Shogo

    2008-01-01

    This paper describes a method for measurement and analysis of surface reflection properties of oil paints under a variety of conditions. First, the radiance factor of a painting surface is measured at different incidence and viewing angles by using a gonio-spectro photometer. The samples are made from different oil paint materials on supporting boards with different paint thicknesses. Next, typical reflection models are examined for describing 3D reflection of the oil painting surfaces. The models are fitted to the observed radiance factors from the oil paint samples. The Cook- Torrance model describes well the reflection properties. The model parameters are estimated from the least-squared fitting to the genio-photometric measurements. Third, the reflection properties are analyzed on the basis of several material conditions such as pigment, supporting material, oil quantity, paint thickness, and support color.

  16. The polarization patterns of skylight reflected off wave water surface.

    PubMed

    Zhou, Guanhua; Xu, Wujian; Niu, Chunyue; Zhao, Huijie

    2013-12-30

    In this paper we propose a model to understand the polarization patterns of skylight when reflected off the surface of waves. The semi-empirical Rayleigh model is used to analyze the polarization of scattered skylight; the Harrison and Coombes model is used to analyze light radiance distribution; and the Cox-Munk model and Mueller matrix are used to analyze reflections from wave surface. First, we calculate the polarization patterns and intensity distribution of light reflected off wave surface. Then we investigate their relationship with incident radiation, solar zenith angle, wind speed and wind direction. Our results show that the polarization patterns of reflected skylight from waves and flat water are different, while skylight reflected on both kinds of water is generally highly polarized at the Brewster angle and the polarization direction is approximately parallel to the water's surface. The backward-reflecting Brewster zone has a relatively low reflectance and a high DOP in all observing directions. This can be used to optimally diminish the reflected skylight and avoid sunglint in ocean optics measurements.

  17. Reflection-polarization patterns at flat water surfaces and their relevance for insect polarization vision

    PubMed

    Horvath

    1995-07-01

    It has recently been shown that horizontally polarized ultraviolet light reflected from the surface of water is the main optical cue for habitat finding by insects living in, on, or near water. What are the polarization properties that make the skylight reflected by water attractive to flying water insects in nature? In this paper, as an approach to this problem, the patterns of the degree and direction of polarization of skylight visible over a flat water surface are computed for unpolarized light from an overcast sky and for partially polarized skylight as a function of the zenith distance of the sun. These patterns are compared with the corresponding celestial polarization patterns. The effect of depolarizing clouds on these reflection-polarization patterns is demonstrated. Reflectivity patterns of a flat water surface are also calculated for clear and overcast skies. The polarization of the blue sky is described by the semi-empirical Rayleigh model. It is assumed that the reflection polarization of skylight at the water surface is governed by the Fresnel formulae. The effect of some modifying factors on the reflection-polarization field is briefly discussed. The adaptations of the visual system of insects living in, on, or near water to reflection-polarization patterns at water surfaces are briefly reviewed and discussed by means of three representative species: the waterstrider (Gerris lacustris), the backswimmer (Notonecta glauca), and the dragonfly (Hemicordulia tau). Copyright 1995 Academic Press Limited

  18. Land Surface Albedo from MERIS Reflectances Using MODIS Directional Factors

    NASA Technical Reports Server (NTRS)

    Schaaf, Crystal L. B.; Gao, Feng; Strahler, Alan H.

    2004-01-01

    MERIS Level 2 surface reflectance products are now available to the scientific community. This paper demonstrates the production of MERIS-derived surface albedo and Nadir Bidirectional Reflectance Distribution Function (BRDF) adjusted reflectances by coupling the MERIS data with MODIS BRDF products. Initial efforts rely on the specification of surface anisotropy as provided by the global MODIS BRDF product for a first guess of the shape of the BRDF and then make use all of the coincidently available, partially atmospherically corrected, cloud cleared, MERIS observations to generate MERIS-derived BRDF and surface albedo quantities for each location. Comparisons between MODIS (aerosol-corrected) and MERIS (not-yet aerosol-corrected) surface values from April and May 2003 are also presented for case studies in Spain and California as well as preliminary comparisons with field data from the Devil's Rock Surfrad/BSRN site.

  19. Comparison of the bidirectional reflectance distribution function of various surfaces

    NASA Technical Reports Server (NTRS)

    Fernandez, Rene; Seasholtz, Richard G.; Oberle, Lawrence G.; Kadambi, Jaikrishnan R.

    1988-01-01

    Described is the development and use of a system to measure the Bidirectional Reflectance Distribution Function (BRDF) of various surfaces. The BRDF measurements are used in the analysis and design of optical measurement systems, such as laser anemometers. An argon ion laser (514 nm) is the light source. Preliminary results are presented for eight samples: two glossy black paints, two flat black paints, black glass, sand blasted aluminum, unworked aluminum, and a white paint. A BaSO4 white reflectance standard was used as the reference sample throughout the tests. The reflectance characteristics of these surfaces are compared.

  20. Light reflecting apparatus including a multi-aberration light reflecting surface

    DOEpatents

    Sawicki, Richard H.; Sweatt, William

    1987-01-01

    A light reflecting apparatus including a multi-aberration bendable light reflecting surface is disclosed herein. This apparatus includes a structural assembly comprised of a rectangular plate which is resiliently bendable, to a limited extent, and which has a front side defining the multi-aberration light reflecting surface and an opposite back side, and a plurality of straight leg members rigidly connected with the back side of the plate and extending rearwardly therefrom. The apparatus also includes a number of different adjustment mechanisms, each of which is connected with specific ones of the leg members. These mechanisms are adjustably movable in different ways for applying corresponding forces to the leg members in order to bend the rectangular plate and light reflecting surface into different predetermined curvatures and which specifically include quadratic and cubic curvatures corresponding to different optical aberrations.

  1. A light reflecting apparatus including a multi-aberration light reflecting surface

    DOEpatents

    Sawicki, R.H.; Sweatt, W.

    1985-11-21

    A light reflecting apparatus including a multi-aberration bendable light reflecting surface is disclosed herein. This apparatus includes a structural assembly comprised of a rectangular plate which is resiliently bendable, to a limited extent, and which has a front side defining the multi-aberration light reflecting surface and an opposite back side, and a plurality of straight leg members rigidly connected with the back side of the plate and extending rearwardly therefrom. The apparatus also includes a number of different adjustment mechanisms, each of which is connected with specific ones of the leg members. These mechanisms are adjustably movable in different ways for applying corresponding forces to the leg members in order to bend the rectangular plate and light reflecting surface into different predetermined curvatures and which specifically include quadratic and cubic curvatures corresponding to different optical aberrations.

  2. Global, long-term surface reflectance records from Landsat

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Global, long-term monitoring of changes in Earth’s land surface requires quantitative comparisons of satellite images acquired under widely varying atmospheric conditions. Although physically based estimates of surface reflectance (SR) ultimately provide the most accurate representation of Earth’s s...

  3. FOOD SURFACE TEXTURE MEASUREMENT USING REFLECTIVE CONFOCAL LASER SCANNING MICROSCOPY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Confocal laser scanning microscopy (CLSM) was used in the reflection mode to characterize the surface texture (roughness) of sliced food surfaces. Sandpapers of grit size between 150 and 600 were used as the height reference to standardize the CLSM hardware settings. Sandpaper particle sizes were v...

  4. Directional Reflective Surface Formed via Gradient-Impeding Acoustic Meta-Surfaces

    PubMed Central

    Song, Kyungjun; Kim, Jedo; Hur, Shin; Kwak, Jun-Hyuk; Lee, Seong-Hyun; Kim, Taesung

    2016-01-01

    Artificially designed acoustic meta-surfaces have the ability to manipulate sound energy to an extraordinary extent. Here, we report on a new type of directional reflective surface consisting of an array of sub-wavelength Helmholtz resonators with varying internal coiled path lengths, which induce a reflection phase gradient along a planar acoustic meta-surface. The acoustically reshaped reflective surface created by the gradient-impeding meta-surface yields a distinct focal line similar to a parabolic cylinder antenna, and is used for directive sound beamforming. Focused beam steering can be also obtained by repositioning the source (or receiver) off axis, i.e., displaced from the focal line. Besides flat reflective surfaces, complex surfaces such as convex or conformal shapes may be used for sound beamforming, thus facilitating easy application in sound reinforcement systems. Therefore, directional reflective surfaces have promising applications in fields such as acoustic imaging, sonic weaponry, and underwater communication. PMID:27562634

  5. Directional Reflective Surface Formed via Gradient-Impeding Acoustic Meta-Surfaces

    NASA Astrophysics Data System (ADS)

    Song, Kyungjun; Kim, Jedo; Hur, Shin; Kwak, Jun-Hyuk; Lee, Seong-Hyun; Kim, Taesung

    2016-08-01

    Artificially designed acoustic meta-surfaces have the ability to manipulate sound energy to an extraordinary extent. Here, we report on a new type of directional reflective surface consisting of an array of sub-wavelength Helmholtz resonators with varying internal coiled path lengths, which induce a reflection phase gradient along a planar acoustic meta-surface. The acoustically reshaped reflective surface created by the gradient-impeding meta-surface yields a distinct focal line similar to a parabolic cylinder antenna, and is used for directive sound beamforming. Focused beam steering can be also obtained by repositioning the source (or receiver) off axis, i.e., displaced from the focal line. Besides flat reflective surfaces, complex surfaces such as convex or conformal shapes may be used for sound beamforming, thus facilitating easy application in sound reinforcement systems. Therefore, directional reflective surfaces have promising applications in fields such as acoustic imaging, sonic weaponry, and underwater communication.

  6. Directional Reflective Surface Formed via Gradient-Impeding Acoustic Meta-Surfaces.

    PubMed

    Song, Kyungjun; Kim, Jedo; Hur, Shin; Kwak, Jun-Hyuk; Lee, Seong-Hyun; Kim, Taesung

    2016-01-01

    Artificially designed acoustic meta-surfaces have the ability to manipulate sound energy to an extraordinary extent. Here, we report on a new type of directional reflective surface consisting of an array of sub-wavelength Helmholtz resonators with varying internal coiled path lengths, which induce a reflection phase gradient along a planar acoustic meta-surface. The acoustically reshaped reflective surface created by the gradient-impeding meta-surface yields a distinct focal line similar to a parabolic cylinder antenna, and is used for directive sound beamforming. Focused beam steering can be also obtained by repositioning the source (or receiver) off axis, i.e., displaced from the focal line. Besides flat reflective surfaces, complex surfaces such as convex or conformal shapes may be used for sound beamforming, thus facilitating easy application in sound reinforcement systems. Therefore, directional reflective surfaces have promising applications in fields such as acoustic imaging, sonic weaponry, and underwater communication. PMID:27562634

  7. Terrain-Moisture Classification Using GPS Surface-Reflected Signals

    NASA Technical Reports Server (NTRS)

    Grant, Michael S.; Acton, Scott T.; Katzberg, Stephen J.

    2006-01-01

    In this study we present a novel method of land surface classification using surface-reflected GPS signals in combination with digital imagery. Two GPS-derived classification features are merged with visible image data to create terrain-moisture (TM) classes, defined here as visibly identifiable terrain or landcover classes containing a surface/soil moisture component. As compared to using surface imagery alone, classification accuracy is significantly improved for a number of visible classes when adding the GPS-based signal features. Since the strength of the reflected GPS signal is proportional to the amount of moisture in the surface, use of these GPS features provides information about the surface that is not obtainable using visible wavelengths alone. Application areas include hydrology, precision agriculture, and wetlands mapping.

  8. Preschoolers' use of reflective properties: identification of reflections on partially transparent surfaces.

    PubMed

    Costanzo, E S; Wittgenstein, K M; Benson, K

    2001-12-01

    This exploratory study extended past studies of children's ability to reference the mirror as a tool in locating the source of reflected images to preschoolers' ability to use the affordances of a transparency. Thirty-six children (3.5 to 5 years old) were shown nonreflected lights and lights reflected on a partially transparent, glassy surface. Children did not spontaneously locate the source of the reflected image. However, they were able to verbally discriminate reflected from nonreflected images following training. These findings indicate that, although preschoolers may not spontaneously use transparencies as a perceptual tool, the ability to distinguish visual differences of reflected from nonreflected images on transparencies is likely within preschool children's developmental capacity.

  9. Reflection properties of hydrogen ions at helium irradiated tungsten surfaces

    NASA Astrophysics Data System (ADS)

    Doi, K.; Tawada, Y.; Lee, H. T.; Kato, S.; Tanaka, N.; Sasao, M.; Kisaki, M.; Nishiura, M.; Matsumoto, Y.; Kenmotsu, T.; Wada, M.; Ueda, Y.; Yamaoka, H.

    2016-02-01

    Nanostructured W surfaces prepared by He bombardment exhibit characteristic angular distributions of hydrogen ion reflection upon injection of 1 keV H+ beam. A magnetic momentum analyzer that can move in the vacuum chamber has measured the angular dependence of the intensity and the energy of reflected ions. Broader angular distributions were observed for He-irradiated tungsten samples compared with that of the intrinsic polycrystalline W. Both intensity and energy of reflected ions decreased in the following order: the polycrystalline W, the He-bubble containing W, and the fuzz W. Classical trajectory Monte Carlo simulations based on Atomic Collision in Amorphous Target code suggests that lower atom density near the surface can make the reflection coefficients lower due to increasing number of collisions.

  10. Effect of wildfires on surface reflectance from a savanna ecosystem

    NASA Astrophysics Data System (ADS)

    Poudyal, R.; Gatebe, C. K.; Ichoku, C. M.; Varnai, T.

    2015-12-01

    During an airborne field campaign in South Africa in 2005, NASA's Cloud Absorption Radiometer (CAR) flew aboard South Africa Weather Service, Aerocommander 690A and measured surface bidirectional reflectance-distribution function (BRDF) over savanna comprised mostly of grasses and a few scattered trees. Savannas cover half the surface of Africa, large areas of Australia, South America, and India. . The region that was studied is located in Kruger National Park in northeastern South Africa, which was heavily affected by the wildfires. The CAR measured surface reflectance along its flight path covering both burned and unburned areas. . In this study, we compared surface reflectance between burnt and un-burnt areas at various wavelengths (340nm, 380nm, 472nm, 682nm, 870nm, 1036nm, 1219nm, 1273nm, and 2205nm) at satellite sub-pixel scales. We found a relative burnt surface reflectance decrease of between 8 and 65% due to fires. These results not only serve to highlight the importance of biomass burning and effects on the energy budgets, but also the need to determine the effects of albedo changes due to fires on soil moisture budget, evapotranspiration, infiltration, and runoff, all of which govern the land-surface component of the water cycle.

  11. Echo thresholds for reflections from acoustically diffusive architectural surfaces.

    PubMed

    Robinson, Philip W; Walther, Andreas; Faller, Christof; Braasch, Jonas

    2013-10-01

    When sound reflects from an irregular architectural surface, it spreads spatially and temporally. Extensive research has been devoted to prediction and measurement of diffusion, but less has focused on its perceptual effects. This paper examines the effect of temporal diffusion on echo threshold. There are several notable differences between the waveform of a reflection identical to the direct sound and one from an architectural surface. The onset and offset are damped and the energy is spread in time; hence, the reflection response has a lower peak amplitude, and is decorrelated from the direct sound. The perceptual consequences of these differences are previously undocumented. Echo threshold tests are conducted with speech and music signals, using direct sound and a simulated reflection that is either identical to the direct sound or has various degrees of diffusion. Results indicate that for a speech signal, diffuse reflections are less easily detectable as a separate auditory event than specular reflections of the same total energy. For a music signal, no differences are observed between the echo thresholds for reflections with and without temporal diffusion. Additionally, echo thresholds are found to be shorter for speech than for music, and shorter for spatialized than for diotic presentation of signals.

  12. UV 380 nm Reflectivity of the Earth's Surface

    NASA Technical Reports Server (NTRS)

    Herman, J. R.; Celarier, E.; Larko, D.

    2000-01-01

    The 380 nm radiance measurements of TOMS (Total Ozone Mapping Spectrometer) have been converted into a global data set of daily (1979 to 1992) Lambert equivalent reflectivities R of the Earth's surface and boundary layer (clouds, aerosols, surface haze, and snow/ice). Since UV surface reflectivity is between 2 and 8% for both land and water during all seasons of the year (except for ice and snow cover), reflectivities larger than the surface value indicates the presence of clouds, haze, or aerosols in the satellite field of view. Statistical analysis of 14 years of daily data show that most snow/ice-free regions of the Earth have their largest fraction of days each year when the reflectivity is low (R less than 10%). The 380 nm reflectivity data shows that the true surface reflectivity is 2 to 3% lower than the most frequently occurring reflectivity value for each TOMS scene. The most likely cause of this could be a combination of frequently occurring boundary-layer water or aerosol haze. For most regions, the observation of extremely clear conditions needed to estimate the surface reflectivity from space is a comparatively rare occurrence. Certain areas (e.g., Australia, southern Africa, portions of northern Africa) are cloud-free more than 80% of the year, which exposes these regions to larger amounts of UV radiation than at comparable latitudes in the Northern Hemisphere. Regions over rain-forests, jungle areas, Europe and Russia, the bands surrounding the Arctic and Antarctic regions, and many ocean areas have significant cloud cover (R greater than 15%) more than half of each year. In the low to middle latitudes, the areas with the heaviest cloud cover (highest reflectivity for most of the year) are the forest areas of northern South America, southern Central America, the jungle areas of equatorial Africa, and high mountain regions such as the Himalayas or the Andes. The TOMS reflectivity data show the presence of large nearly clear ocean areas and the effects

  13. Reflected fluxes for broken clouds over a Lambertian surface

    NASA Technical Reports Server (NTRS)

    Welch, Ronald M.; Wielicki, Bruce A.

    1989-01-01

    Reflected fluxes are calculated for broken cloudiness (i.e., nonplane parallel) as a function of cloud cover, cloud optical depth, solar zenith angle and surface albedo. These calculations extend previous results for broken cloud reflected fluxes over a black surface. The present study demonstrates that not only radiances but also radiative fluxes over high albedo surfaces may be decreased by the presence of broken cloudiness. Conventional wisdom states that cloud radiances (brightnesses) are always greater than the background. While most cloud retrieval schemes are built around this assumption, it is incorrect for clouds over high albedo surfaces such as found in polar regions. However, the most startling and counterintuitive conclusion of this study is that nonabsorbing finite clouds over a highly reflecting surface will decrease the system albedo. As a result, surface absorption is increased, the result of multiple scattering between surface and cloud layer, controlled by cloud morphology and cloud optical thickness. A simple parameterization of the effects of cloud contamination upon retrieved albedo is given in terms of solar zenith angle, cloud optical depth, surface albedo, cloud cover, and plane-parallel cloud albedo. In this way, the effects of broken cloudiness are modeled in terms of easily computed plane-parallel values.

  14. Reflections on the Adaptive Designs Accelerating Promising Trials Into Treatments (ADAPT-IT) Process—Findings from a Qualitative Study

    PubMed Central

    Guetterman, Timothy C.; Fetters, Michael D.; Legocki, Laurie J.; Mawocha, Samkeliso; Barsan, William G.; Lewis, Roger J.; Berry, Donald A.; Meurer, William J.

    2015-01-01

    Context The context for this study was the Adaptive Designs Advancing Promising Treatments Into Trials (ADAPT-IT) project, which aimed to incorporate flexible adaptive designs into pivotal clinical trials and to conduct an assessment of the trial development process. Little research provides guidance to academic institutions in planning adaptive trials. Objectives The purpose of this qualitative study was to explore the perspectives and experiences of stakeholders as they reflected back about the interactive ADAPT-IT adaptive design development process, and to understand their perspectives regarding lessons learned about the design of the trials and trial development. Materials and methods We conducted semi-structured interviews with ten key stakeholders and observations of the process. We employed qualitative thematic text data analysis to reduce the data into themes about the ADAPT-IT project and adaptive clinical trials. Results The qualitative analysis revealed four themes: education of the project participants, how the process evolved with participant feedback, procedures that could enhance the development of other trials, and education of the broader research community. Discussion and conclusions While participants became more likely to consider flexible adaptive designs, additional education is needed to both understand the adaptive methodology and articulate it when planning trials. PMID:26622163

  15. Influence of reflected UV irradiance on occupational exposure from combinations of reflective wall surfaces.

    PubMed

    Turner, Joanna; Parisi, Alfio V

    2013-09-01

    Outdoor workers who occupationally spend large periods of time exposed to ultraviolet irradiance are at increased risk of developing certain types of non-melanoma skin cancer in addition to being prone to erythema and eye damage. UV exposure to workers is affected by a number of factors including geographic location, season, individual biological factors and the local surroundings. Urban environments can provide surrounds that contain surfaces that reflect UV radiation which can enhance UV exposure to construction workers, in both the vertical as well as horizontal plane. However it was unknown how different constructed configurations of the surfaces may additionally influence UV exposure for a worker, such as corners opposed to walls. This study shows that for highly UV reflective surfaces the influence on erythemal UV exposure is approximately the same regardless of constructive type, but there is statistically significant difference observed for lower UV reflecting surfaces in conjunction with constructive type. This is comparable to influence of body site on relative UV exposure, and together may provide a method that may assist in reduction in UV exposures. Regression analysis provides a more effective means to determine a UV reflective factor for a surface type, than previously used averaging methods. Additionally, this knowledge may be used by workers, workplaces and advisory bodies to assist with developing further protective strategies that aim to provide more moderate UV exposures to outdoor workers.

  16. Spectrometers for particle measurements in space based on surface reflection

    NASA Astrophysics Data System (ADS)

    Barabash, S.; Wieser, M.; Wurz, P.

    2012-04-01

    This is a review talk on space particle spectrometers based on the surface reflection technique. We sum up the experience in development and operation of such instruments accumulated for the last 15 years at the Swedish Institute of space Physics, Kiruna, Sweden in close cooperation with University of Bern, Bern, Switzerland. The technique is relatively new and used in space for measurements of few eV - few keV particles. It was first introduced for neutral atom detection in the GAS instrument onboard the ESA/NASA Ulysses mission (Witte et al., 1992) and later for ion measurements (Barabash et al., 2007) onboard Indian Chandrayaan-1. When a particle hit a surface, secondary electrons release and the particle is either absorbed by the surface or get scattered or reflected. The charge state of the reflected particles normally does not depend on the initial charge state and is neutral but also includes a fraction of negative and positive ions. These charged particles can be analyzed by conventional ion optics. The secondary electrons can be used for triggering a time-of-flight system. The surface reflection technique is close to the usage of foils/ulta-thin foils for particle detections but has a number of advantages. First, it does not require high pre-acceleration potentials and thus allows making more compact and light weight instruments. Secondly, it permits detection of neutral atoms down to 10 eV. Despite the interaction with the surface modifies the original particle velocity, the proper design of the following analyzer section and ion optics can mitigate this effect. We shortly introduce main characteristics of the particle - surface interactions important for this application, describe designs of the instruments flown in space, and show performances of the surface reflection based ENA and ion spectrometers developed for Mars / Venus Express, Chandrayaan-1, BepiColombo, Phobos-Grunt, and Swedish PRISMA.

  17. Diet adaptation in dog reflects spread of prehistoric agriculture

    PubMed Central

    Arendt, M; Cairns, K M; Ballard, J W O; Savolainen, P; Axelsson, E

    2016-01-01

    Adaptations allowing dogs to thrive on a diet rich in starch, including a significant AMY2B copy number gain, constituted a crucial step in the evolution of the dog from the wolf. It is however not clear whether this change was associated with the initial domestication, or represents a secondary shift related to the subsequent development of agriculture. Previous efforts to study this process were based on geographically limited data sets and low-resolution methods, and it is therefore not known to what extent the diet adaptations are universal among dogs and whether there are regional differences associated with alternative human subsistence strategies. Here we use droplet PCR to investigate worldwide AMY2B copy number diversity among indigenous as well as breed dogs and wolves to elucidate how a change in dog diet was associated with the domestication process and subsequent shifts in human subsistence. We find that AMY2B copy numbers are bimodally distributed with high copy numbers (median 2nAMY2B=11) in a majority of dogs but no, or few, duplications (median 2nAMY2B=3) in a small group of dogs originating mostly in Australia and the Arctic. We show that this pattern correlates geographically to the spread of prehistoric agriculture and conclude that the diet change may not have been associated with initial domestication but rather the subsequent development and spread of agriculture to most, but not all regions of the globe. PMID:27406651

  18. The Effects of Reflective Activities on Skill Adaptation in a Work-Related Instrumental Learning Setting

    ERIC Educational Resources Information Center

    Roessger, Kevin M.

    2014-01-01

    In work-related instrumental learning contexts, the role of reflective activities is unclear. Kolb's experiential learning theory and Mezirow's transformative learning theory predict skill adaptation as an outcome. This prediction was tested by manipulating reflective activities and assessing participants' response and error rates…

  19. Advantages of wet work for near-surface seismic reflection

    USGS Publications Warehouse

    Miller, R.D.; Markiewicz, R.D.; Rademacker, T.R.; Hopkins, R.; Rawcliffe, R.J.; Paquin, J.

    2007-01-01

    Benefits of shallow water settings (0.1 to 0.5 m) are pronounced on shallow, high-resolution seismic reflection images and, for examples discussed here, range from an order of magnitude increased signal-to-noise ratio to resolution potential elevated by more than 8 times. Overall data quality of high-resolution seismic reflection data at three sites notorious for poor near-surface reflection returns was improved by coupling the source and/or receivers to a well sorted and fully saturated surface. Half-period trace-to-trace static offsets evident in reflections from receivers planted into a creek bank were eliminated by moving the geophones to the base of a shallow creek at the toe of the bank. Reflections from a dipping bedrock were recorded with a dominant frequency approaching 1 KHz from hydrophones in 0.5 m of water at the toe of a dam using a hammer impact source. A tamper impacted by a dead blow hammer in a shallow (10-20 cm) deep creek produced reflections with a dominant frequency over 400 Hz at depths as shallow as 6 ms. ?? 2007 Society of Exploration Geophysicists.

  20. Hybrid Surface Mesh Adaptation for Climate Modeling

    SciTech Connect

    Ahmed Khamayseh; Valmor de Almeida; Glen Hansen

    2008-10-01

    Solution-driven mesh adaptation is becoming quite popular for spatial error control in the numerical simulation of complex computational physics applications, such as climate modeling. Typically, spatial adaptation is achieved by element subdivision (h adaptation) with a primary goal of resolving the local length scales of interest. A second, less-popular method of spatial adaptivity is called “mesh motion” (r adaptation); the smooth repositioning of mesh node points aimed at resizing existing elements to capture the local length scales. This paper proposes an adaptation method based on a combination of both element subdivision and node point repositioning (rh adaptation). By combining these two methods using the notion of a mobility function, the proposed approach seeks to increase the flexibility and extensibility of mesh motion algorithms while providing a somewhat smoother transition between refined regions than is produced by element subdivision alone. Further, in an attempt to support the requirements of a very general class of climate simulation applications, the proposed method is designed to accommodate unstructured, polygonal mesh topologies in addition to the most popular mesh types.

  1. Hybrid Surface Mesh Adaptation for Climate Modeling

    SciTech Connect

    Khamayseh, Ahmed K; de Almeida, Valmor F; Hansen, Glen

    2008-01-01

    Solution-driven mesh adaptation is becoming quite popular for spatial error control in the numerical simulation of complex computational physics applications, such as climate modeling. Typically, spatial adaptation is achieved by element subdivision (h adaptation) with a primary goal of resolving the local length scales of interest. A second, less-popular method of spatial adaptivity is called "mesh motion" (r adaptation); the smooth repositioning of mesh node points aimed at resizing existing elements to capture the local length scales. This paper proposes an adaptation method based on a combination of both element subdivision and node point repositioning (rh adaptation). By combining these two methods using the notion of a mobility function, the proposed approach seeks to increase the flexibility and extensibility of mesh motion algorithms while providing a somewhat smoother transition between refined regions than is produced by element subdivision alone. Further, in an attempt to support the requirements of a very general class of climate simulation applications, the proposed method is designed to accommodate unstructured, polygonal mesh topologies in addition to the most popular mesh types.

  2. Criteria for evaluation of reflective surface for parabolic dish concentrators

    NASA Technical Reports Server (NTRS)

    Bouquet, F.

    1980-01-01

    Commercial, second surface glass mirror are emphasized, but aluminum and metallized polymeric films are also included. Criteria for sealing solar mirrors in order to prevent environmental degradation and criteria for bonding sagged or bent mirrors to substrate materials are described. An overview of the technical areas involved in evaluating small mirror samples, sections, and entire large gores is presented. A basis for mirror criteria was established that eventually may become part of inspection and evaluation techniques for three dimensional parabolic reflective surfaces.

  3. Polarized infrared emissivity of one-dimensional Gaussian sea surfaces with surface reflections.

    PubMed

    Li, Hongkun; Pinel, Nicolas; Bourlier, Christophe

    2011-08-10

    Surface reflection is an important phenomenon that must be taken into account when studying sea surface infrared emissivity, especially at large observation angles. This paper models analytically the polarized infrared emissivity of one-dimensional sea surfaces with shadowing effect and one surface reflection, by assuming a Gaussian surface slope distribution. A Monte Carlo ray-tracing method is employed as a reference. It is shown that the present model agrees well with the reference method. The emissivity calculated by the present model is then compared with measurements. The comparisons show that agreements are greatly improved by taking one surface reflection into account. The Monte Carlo ray-tracing results of sea surface infrared emissivity with two and three reflections are also determined. Their contributions are shown to be negligible.

  4. DETERMINING REFLECTANCE SPECTRA OF SURFACES AND CLOUDS ON EXOPLANETS

    SciTech Connect

    Cowan, Nicolas B.; Strait, Talia E.

    2013-03-01

    Planned missions will spatially resolve temperate terrestrial planets from their host star. Although reflected light from such a planet encodes information about its surface, it has not been shown how to establish surface characteristics of a planet without assuming known surfaces to begin with. We present a reanalysis of disk-integrated, time-resolved, multiband photometry of Earth obtained by the Deep Impact spacecraft as part of the EPOXI Mission of Opportunity. We extract reflectance spectra of clouds, ocean, and land without a priori knowledge of the numbers or colors of these surfaces. We show that the inverse problem of extracting surface spectra from such data is a novel and extreme instance of spectral unmixing, a well-studied problem in remote sensing. Principal component analysis is used to determine an appropriate number of model surfaces with which to interpret the data. Shrink-wrapping a simplex to the color excursions of the planet yields a conservative estimate of the planet's endmember spectra. The resulting surface maps are unphysical, however, requiring negative or larger-than-unity surface coverage at certain locations. Our ''rotational unmixing'' supersedes the endmember analysis by simultaneously solving for the surface spectra and their geographical distributions on the planet, under the assumption of diffuse reflection and known viewing geometry. We use a Markov Chain Monte Carlo to determine best-fit parameters and their uncertainties. The resulting albedo spectra are similar to clouds, ocean, and land seen through a Rayleigh-scattering atmosphere. This study suggests that future direct-imaging efforts could identify and map unknown surfaces and clouds on exoplanets.

  5. Polarized reflectance and transmittance distribution functions of the ocean surface.

    PubMed

    Hieronymi, Martin

    2016-07-11

    Two aspects of ocean modelling are treated: representation of ocean waves considering all size-classes of waves and tracing of light-interactions at the wavy sea surface. Nonlinear wave profiles are realized accounting for a wide range of climatologically relevant sea states and wind speeds. Polarized ray tracing is used to investigate air-incident and whitecap-free reflectance and transmittance distributions with high angular resolution subject to sea-characterizing parameters, such as significant wave height, peak wave period, wind speed, and surface roughness. Wave-shadowing effects of incident and multiple reflected rays are fully considered. Their influence mostly starts with incidence angles greater than 60°, i.e., when the sun is near the horizon, and is especially pronounced for steep sea states. The net effect of multiple reflections is a redistribution of reflectance and transmittance fractions in their respective hemispheres and a slight increase of the net transmission of light into the sea. Revised reflectance and transmittance distribution functions, RDF and TDF, are provided depending on surface roughness in terms of the mean-square slope; reference is made to other sea state parameters. In comparison with the slope statistics approach, uncertainties related to sun near the horizon are reduced and on average this study yields somewhat higher reflectance values with some variability related to the sea state. By means of provided data, irradiance and radiance reflectances can be computed using desired sky radiance distributions, e.g., clear sky, overcast or partly cloudy sky, as well as wind or sea state information including wave propagation direction. PMID:27410893

  6. Polarized reflectance and transmittance distribution functions of the ocean surface.

    PubMed

    Hieronymi, Martin

    2016-07-11

    Two aspects of ocean modelling are treated: representation of ocean waves considering all size-classes of waves and tracing of light-interactions at the wavy sea surface. Nonlinear wave profiles are realized accounting for a wide range of climatologically relevant sea states and wind speeds. Polarized ray tracing is used to investigate air-incident and whitecap-free reflectance and transmittance distributions with high angular resolution subject to sea-characterizing parameters, such as significant wave height, peak wave period, wind speed, and surface roughness. Wave-shadowing effects of incident and multiple reflected rays are fully considered. Their influence mostly starts with incidence angles greater than 60°, i.e., when the sun is near the horizon, and is especially pronounced for steep sea states. The net effect of multiple reflections is a redistribution of reflectance and transmittance fractions in their respective hemispheres and a slight increase of the net transmission of light into the sea. Revised reflectance and transmittance distribution functions, RDF and TDF, are provided depending on surface roughness in terms of the mean-square slope; reference is made to other sea state parameters. In comparison with the slope statistics approach, uncertainties related to sun near the horizon are reduced and on average this study yields somewhat higher reflectance values with some variability related to the sea state. By means of provided data, irradiance and radiance reflectances can be computed using desired sky radiance distributions, e.g., clear sky, overcast or partly cloudy sky, as well as wind or sea state information including wave propagation direction.

  7. Reflection of thermal Cs atoms grazing a polished glass surface

    SciTech Connect

    Anderson, A.; Haroche, S.; Hinds, E.A.; Jhe, W.; Meschede, D.; Moi, L.

    1986-10-01

    We present an experimental study which shows that a large fraction (> or =50%) of thermal Cs atoms are nearly specularly reflected by polished glass surfaces at grazing incidence. This effect is interesting in the context of projects aimed at storing cold alkali-metal atoms in boxes.

  8. Surface Reflectances and Human Color Constancy: Comment on Dannemiller (1989).

    ERIC Educational Resources Information Center

    Troost, Jimmy M.; And Others

    1991-01-01

    It is argued that a reflectance channel that requires priority information is shown to be less plausible for the human visual system than J. L. Dannemiller (1989) argued. In the response, Dannemiller replies that lightness is not an illuminant invariant surface descriptor when daylight illuminant substitutions are considered. (SLD)

  9. A User-Driven and Data-Driven Approach for Supporting Teachers in Reflection and Adaptation of Adaptive Tutorials

    ERIC Educational Resources Information Center

    Ben-Naim, Dror; Bain, Michael; Marcus, Nadine

    2009-01-01

    It has been recognized that in order to drive Intelligent Tutoring Systems (ITSs) into mainstream use by the teaching community, it is essential to support teachers through the entire ITS process: Design, Development, Deployment, Reflection and Adaptation. Although research has been done on supporting teachers through design to deployment of ITSs,…

  10. Surface Inspection Of Automotive Bodies By Reflective Computer Vision

    NASA Astrophysics Data System (ADS)

    Hung, Y. Y.; Jin, G. C.; Tang, S. H.

    1988-12-01

    A simple but practical optical technique for automated surface inspection of car bodies is presented. The method which is based on light reflection is applicable to inspecting specularly reflective surfaces such as painted car bodies. A structured light signal consists of linear grating is imaged by a video camera via the surface to be inspected. With this arrangement, the surface being inspected acts as a mirror. Presence of surface flaws causes the grating to be locally perturbed. The grating-image is digitized and analyzed by a computer. Several algorithms are developed which automatically identifies the surface flaws by analyzing the perturbation in the grating-image. The technique allows surface flaws to be quantified in terms of slope deviation or depth variation. The sensitivity of the technique is very high permitting minute flaws to be detected. In the paper the theory of the technique will be presented together with experimental validation. The technique possesses numerous practical features such as requiring no special surface preparation, allowing evaluation in place, requiring minimum environmental safeguards, allowing rapid testing and evaluation, providing reliable and quantitative results, and it can be automated. Therefore the technique has clearly exhibited a great potential for being developed into a production-line inspection tool.

  11. RTM-based Teleseismic Reflection Tomography with Free Surface Multiples

    NASA Astrophysics Data System (ADS)

    Burdick, S. A.; De Hoop, M. V.; van der Hilst, R. D.

    2013-12-01

    Receiver function analysis of teleseismic converted and free surface reflected phases has long been a cornerstone of lithospheric studies. Discontinuities in elastic properties are revealed by deconvolving the incident wavefield from scattered phases and projecting the time differences to depth to form an image. The accuracy of the image is determined to a large extent by the accuracy of the method and background velocity model used, but popular approaches for projecting receiver functions to depth commonly rely on simplifying assumptions of a 1D velocity and planar discontinuities. In tectonically complex regions like subduction zones and rift systems, strong heterogeneity can create an ambiguous tradeoff between the background velocity and the depth of the discontinuities. Furthermore, such structures are apt to create caustics at high frequencies, rendering ray-based methods inadequate. In order to better constrain the background velocity and correctly place the discontinuities at depth, we employ a novel reverse-time migration (RTM) based reflection tomography method. We adapt our reflection tomography from exploration seismology for use with teleseismic phases. Active source methods for exploration have focused on the annihilation of extended images - image gathers formed with different subsurface angle or offset information - as a means of judging the accuracy of the model. Applying these approaches to teleseismic data is untenable because 1) the sparse and uneven distribution of earthquake sources leads to the incomplete construction of extended image, 2) the imperfect separation and source deconvolution of the scattered wavefield render previous error measurements unreliable, and 3) the planar geometry of incoming arrivals makes measures of subsurface offset insensitive to perturbations in the model. To overcome these obstacles, we have developed a flexible approach based on pairwise single-source image correlations. We determine the success of the RTM and

  12. Copper-assisted, anti-reflection etching of silicon surfaces

    SciTech Connect

    Toor, Fatima; Branz, Howard

    2014-08-26

    A method (300) for etching a silicon surface (116) to reduce reflectivity. The method (300) includes electroless deposition of copper nanoparticles about 20 nanometers in size on the silicon surface (116), with a particle-to-particle spacing of 3 to 8 nanometers. The method (300) includes positioning (310) the substrate (112) with a silicon surface (116) into a vessel (122). The vessel (122) is filled (340) with a volume of an etching solution (124) so as to cover the silicon surface (116). The etching solution (124) includes an oxidant-etchant solution (146), e.g., an aqueous solution of hydrofluoric acid and hydrogen peroxide. The silicon surface (116) is etched (350) by agitating the etching solution (124) with, for example, ultrasonic agitation, and the etching may include heating (360) the etching solution (124) and directing light (365) onto the silicon surface (116). During the etching, copper nanoparticles enhance or drive the etching process.

  13. Mercury's Surface Magnetic Field Determined from Proton-Reflection Magnetometry

    NASA Technical Reports Server (NTRS)

    Winslow, Reka M.; Johnson, Catherine L.; Anderson, Brian J.; Gershman, Daniel J.; Raines, Jim M.; Lillis, Robert J.; Korth, Haje; Slavin, James A.; Solomon, Sean C.; Zurbuchen, Thomas H.; Zuber, Maria T.

    2014-01-01

    Solar wind protons observed by the MESSENGER spacecraft in orbit about Mercury exhibit signatures of precipitation loss to Mercury's surface. We apply proton-reflection magnetometry to sense Mercury's surface magnetic field intensity in the planet's northern and southern hemispheres. The results are consistent with a dipole field offset to the north and show that the technique may be used to resolve regional-scale fields at the surface. The proton loss cones indicate persistent ion precipitation to the surface in the northern magnetospheric cusp region and in the southern hemisphere at low nightside latitudes. The latter observation implies that most of the surface in Mercury's southern hemisphere is continuously bombarded by plasma, in contrast with the premise that the global magnetic field largely protects the planetary surface from the solar wind.

  14. Spontaneous Self-Distancing and Adaptive Self-Reflection Across Adolescence

    PubMed Central

    White, Rachel E.; Kross, Ethan; Duckworth, Angela L.

    2015-01-01

    Experiments performed primarily with adults show that self-distancing facilitates adaptive self-reflection. However, no research has investigated whether adolescents spontaneously engage in this process or whether doing so is linked to adaptive outcomes. In this study, 226 African American adolescents, aged 11 to 20, reflected on an anger-related interpersonal experience. As expected, spontaneous self-distancing during reflection predicted lower levels of emotional reactivity by leading adolescents to reconstrue (rather than recount) their experience and blame their partner less. Moreover, the inverse relation between self-distancing and emotional reactivity strengthened with age. These findings highlight the role that self-distancing plays in fostering adaptive self-reflection in adolescence, and begin to elucidate the role that development plays in enhancing the benefits of engaging in this process. PMID:25876213

  15. One Teacher's Instructional Adaptations and Her Students' Reflections on the Adaptations

    ERIC Educational Resources Information Center

    Parsons, Seth A.; Vaughn, Margaret

    2016-01-01

    Currently, much debate exists nationally regarding how to define and measure teacher effectiveness. Educators and researchers agree that adaptability is an important aspect of teacher effectiveness. Teachers must adapt their instruction to navigate the complexity of classroom instruction. However, little research has specifically examined teacher…

  16. Far-infrared emissivity measurements of reflective surfaces

    NASA Technical Reports Server (NTRS)

    Xu, J.; Lange, A. E.; Bock, J. J.

    1996-01-01

    An instrument developed to measure the emissivity of reflective surfaces by comparing the thermal emission of a test sample to that of a reference surface is reported. The instrument can accurately measure the emissivity of mirrors made from lightweight thermally insulating materials such as glass and metallized carbon fiber reinforced plastics. Far infrared measurements at a wavelength of 165 micrometers are reported. The instrument has an absolute accuracy of Delta epsilon = 9 x 10(exp -4) and can reproducibly measure an emissivity of as small as 2 x 10(exp -4) between flat reflective surfaces. The instrument was used to measure mirror samples for balloon-borne and spaceborne experiments. An emissivity of (6.05 +/- 1.24) x 10(exp -3) was measured for gold evaporated on glass, and (6.75 +/- 1.17) x 10(exp -3) for aluminum evaporated on glass.

  17. Moth's eye anti-reflection gratings on germanium freeform surfaces

    NASA Astrophysics Data System (ADS)

    Liu, Meng; Shultz, Jason A.; Owen, Joseph D.; Davies, Matthew A.; Suleski, Thomas J.

    2014-09-01

    Germanium is commonly used for optical components in the infrared, but the high refractive index of germanium causes significant losses due to Fresnel reflections. Anti-reflection (AR) surfaces based on subwavelength "moth's eye" gratings provide one means to significantly increase optical transmission. As found in nature, these gratings are conformal to the curved surfaces of lenslets in the eye of the moth. Engineered optical systems inspired by biological examples offer possibilities for increased performance and system miniaturization, but also introduce significant challenges to both design and fabrication. In this paper, we consider the design and fabrication of conformal moth's eye AR structures on germanium freeform optical surfaces, including lens arrays and Alvarez lenses. Fabrication approaches and limitations based on both lithography and multi-axis diamond machining are considered. Rigorous simulations of grating performance and approaches for simulation of conformal, multi-scale optical systems are discussed.

  18. Optical Design and Optimization of Translational Reflective Adaptive Optics Ophthalmoscopes

    NASA Astrophysics Data System (ADS)

    Sulai, Yusufu N. B.

    The retina serves as the primary detector for the biological camera that is the eye. It is composed of numerous classes of neurons and support cells that work together to capture and process an image formed by the eye's optics, which is then transmitted to the brain. Loss of sight due to retinal or neuro-ophthalmic disease can prove devastating to one's quality of life, and the ability to examine the retina in vivo is invaluable in the early detection and monitoring of such diseases. Adaptive optics (AO) ophthalmoscopy is a promising diagnostic tool in early stages of development, still facing significant challenges before it can become a clinical tool. The work in this thesis is a collection of projects with the overarching goal of broadening the scope and applicability of this technology. We begin by providing an optical design approach for AO ophthalmoscopes that reduces the aberrations that degrade the performance of the AO correction. Next, we demonstrate how to further improve image resolution through the use of amplitude pupil apodization and non-common path aberration correction. This is followed by the development of a viewfinder which provides a larger field of view for retinal navigation. Finally, we conclude with the development of an innovative non-confocal light detection scheme which improves the non-invasive visualization of retinal vasculature and reveals the cone photoreceptor inner segments in healthy and diseased eyes.

  19. Atmospheric and Science Complexity Effects on Surface Bidirectional Reflectance

    NASA Technical Reports Server (NTRS)

    Diner, D. J. (Principal Investigator); Martonchik, J. V.; Sythe, W. D.; Hessom, C.

    1985-01-01

    Among the tools used in passive remote sensing of Earth resources in the visible and near-infrared spectral regions are measurements of spectral signature and bidirectional reflectance functions (BDRFs). Determination of surface properties using these observables is complicated by a number of factors, including: (1) mixing of surface components, such as soil and vegetation, (2) multiple reflections of radiation due to complex geometry, such as in crop canopies, and (3) atmospheric effects. In order to bridge the diversity in these different approaches, there is a need for a fundamental physical understanding of the influence of the various effects and a quantiative measure of their relative importance. In particular, we consider scene complexity effects using the example of reflection by vegetative surfaces. The interaction of sunlight with a crop canopy and interpretation of the spectral and angular dependence of the emergent radiation is basically a multidimensional radiative transfer problem. The complex canopy geometry, underlying soil cover, and presence of diffuse as well as collimated illumination will modify the reflectance characteristics of the canopy relative to those of the individual elements.

  20. BOREAS RSS-1 PARABOLA SSA Surface Reflectance and Transmittance Data

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G. (Editor); Nickeson, Jaime (Editor); Deering, Donald D.; Eck, Thomas F.; Banerjee, Babu

    2000-01-01

    The BOREAS RSS-1 team collected surface reflectance and transmittance data from three forested sites in the SSA. This data set contains averaged reflectance factors and transmitted radiances measured by the PARABOLA instrument at selected sites in the BOREAS SSA at different view angles and at three wavelength bands throughout the day. PARABOLA measurements were made during each of the three BOREAS IFCs during the growing season of 1994 at three SSA tower flux sites as well as during the FFC-T. Additional measurements were made in early and mid-1996 during the FFC-W and during IFC-2. The data are stored in tabular ASCII files.

  1. Implementation of solar-reflective surfaces: Materials and utility programs

    SciTech Connect

    Bretz, S.; Akbari, H.; Rosenfeld, A.; Taha, H.

    1992-06-01

    This report focuses on implementation issues for using solar-reflective surfaces to cool urban heat islands, with specific examples for Sacramento, California. Advantages of solar-reflective surfaces for reducing energy use are: (1) they are cost-effective if albedo is increased during routine maintenance; (2) the energy savings coincide with peak demand for power; (3) there are positive effects on environmental quality; and (4) the white materials have a long service life. Important considerations when choosing materials for mitigating heat islands are identified as albedo, emissivity, durability, cost, pollution and appearance. There is a potential for increasing urban albedo in Sacramento by an additional 18%. Of residential roofs, we estimate that asphalt shingle and modified bitumen cover the largest area, and that built-up roofing and modified bitumen cover the largest area of commercial buildings. For all of these roof types, albedo may be increased at the time of re-roofing without any additional cost. When a roof is repaired, a solar-reflective roof coating may be applied to significantly increase albedo and extend the life of the root Although a coating may be cost-effective if applied to a new roof following installation or to an older roof following repair, it is not cost-effective if the coating is applied only to save energy. Solar-reflective pavement may be cost-effective if the albedo change is included in the routine resurfacing schedule. Cost-effective options for producing light-colored pavement may include: (1) asphalt concrete, if white aggregate is locally available; (2) concrete overlays; and (3) newly developed white binders and aggregate. Another option may be hot-rolled asphalt, with white chippings. Utilities could promote solar-reflective surfaces through advertisement, educational programs and cost-sharing of road resurfacing.

  2. The ultraviolet reflectance of Enceladus: Implications for surface composition

    NASA Astrophysics Data System (ADS)

    Hendrix, Amanda R.; Hansen, Candice J.; Holsclaw, Greg M.

    2010-04-01

    The reflectance of Saturn's moon Enceladus has been measured at far ultraviolet (FUV) wavelengths (115-190 nm) by Cassini's Ultraviolet Imaging Spectrograph (UVIS). At visible and near infrared (VNIR) wavelengths Enceladus' reflectance spectrum is very bright, consistent with a surface composed primarily of H 2O ice. At FUV wavelengths, however, Enceladus is surprisingly dark - darker than would be expected for pure water ice. Previous analyses have focused on the VNIR spectrum, comparing it to pure water ice (Cruikshank, D.P., Owen, T.C., Dalle Ore, C., Geballe, T.R., Roush, T.L., de Bergh, C., Sandford, S.A., Poulet, F., Benedix, G.K., Emery, J.P. [2005] Icarus, 175, 268-283) or pure water ice plus a small amount of NH 3 (Emery, J.P., Burr, D.M., Cruikshank, D.P., Brown, R.H., Dalton, J.B. [2005] Astron. Astrophys., 435, 353-362) or NH 3 hydrate (Verbiscer, A.J., Peterson, D.E., Skrutskie, M.F., Cushing, M., Helfenstein, P., Nelson, M.J., Smith, J.D., Wilson, J.C. [2006] Icarus, 182, 211-223). We compare Enceladus' FUV spectrum to existing laboratory measurements of the reflectance spectra of candidate species, and to spectral models. We find that the low FUV reflectance of Enceladus can be explained by the presence of a small amount of NH 3 and a small amount of a tholin in addition to H 2O ice on the surface. The presence of these three species (H 2O, NH 3, and a tholin) appears to satisfy not only the low FUV reflectance and spectral shape, but also the middle-ultraviolet to visible wavelength brightness and spectral shape. We expect that ammonia in the Enceladus plume is transported across the surface to provide a global coating.

  3. Comparison of multispectral airborne scanner reflectance images with ground surface reflectance measurements

    SciTech Connect

    Kollewe, M.; Bienlein, J.; Kollewe, T.; Spitzer, H.

    1996-11-01

    Simultaneously with an airborne data taking campaign near the city of Nurnberg (FRG), performed with an imaging 11-channel scanner of type Daedalus AADS 1268, ground reference measurements of reflectance spectra were conducted with a spectrally high resolving spectroradiometer of type IRIS at selected test sites. Based on a method developed reflectance images are calculated from the aerial raw data. Thus, physical quantities of the surfaces are generated, which are independent of illumination and registration conditions. The airborne scanner reflectance images are compared with ground reference reflectance measurements. The comparison yields deviations up to 35%. They can partially be explained by an inaccurate calibration of the airborne scanner. In addition, errors appear during calculation of the reflectances due to simplifying model assumptions and an inexact knowledge of the values of the model input parameters. It is shown that calibration of the airborne scanner data with the ground reference measurements improves the results, as compared to calibration based on laboratory testbench measurements. 8 refs., 4 figs., 1 tab.

  4. Surface inspection of transparent materials with a compact reflection sensor

    NASA Astrophysics Data System (ADS)

    Koscheck, Mathias; Kleuver, Wolfram; Weber, Juergen; Hartmann, Klaus

    1997-09-01

    Introduction of a compact sensor system to detect abnormalities on high graded, polished surfaces in production process. Usable for TQM in line of coating quality of lenses, glass plates, wafers or other high quality products. Optimized for non destructive, high speed scanning (2.5 m/s) of transparent materials with a low reflection rate and a resolution down to some micrometers 's. Reachable even in a noisy industrial environment. Available in a 19' rack with profibus data-link.

  5. Weissenberg reflection high-energy electron diffraction for surface crystallography.

    PubMed

    Abukawa, Tadashi; Yamazaki, Tomoyuki; Yajima, Kentaro; Yoshimura, Koji

    2006-12-15

    The principle of a Weissenberg camera is applied to surface crystallographic analysis by reflection high-energy electron diffraction. By removing inelastic electrons and measuring hundreds of patterns as a function of sample rotation angle phi, kinematical analysis can be performed over a large volume of reciprocal space. The data set is equivalent to a three-dimensional stack of Weissenberg photographs. The method is applied to analysis of an Si(111)-square root of 3 x square root of 3-Ag surface, and the structural data obtained are in excellent agreement with the known atomic structure.

  6. Color constancy - A method for recovering surface spectral reflectance

    NASA Technical Reports Server (NTRS)

    Maloney, L. T.; Wandell, B. A.

    1986-01-01

    An algorithm has been developed for estimating the surface reflectance functions of objects in a scene with incomplete knowledge of the spectral power distribution of the ambient light. An image processing system employing this algorithm can assign colors that are constant despite changes in the lighting of the scene; this capability is essential to correct color rendering in photography, TV, and in the construction of artificial visual systems for robotics. Attention is given to the way in which constraints on lights and surfaces in the environment make color-constancy possible for a visual system, and the algorithm's implications for human color vision are discussed.

  7. Ghost imaging for a reflected object with a rough surface

    SciTech Connect

    Wang Chunfang; Zhang Dawei; Chen Bin; Bai Yanfeng

    2010-12-15

    Ghost imaging for the reflected object with rough surface is investigated. The surface height variance {sigma}{sub h}{sup 2} and the correlation length l{sub c} have been introduced to characterize the rough surface. Based on a simple scattering model, we derive the analytical expressions which are used to describe the effects of {sigma}{sub h}{sup 2} and l{sub c} on ghost imaging. The results show that both {sigma}{sub h}{sup 2} and l{sub c} have no influence on the image resolution, while the convergence of the correlation decreases as {sigma}{sub h}{sup 2} increases. Additionally, the bucket detector used in the test arm can dramatically improve the visibility of ghost images. The results are backed up by numerical simulations, in which a Monte Carlo approach to generate a rough surface has been used.

  8. Emissivity measurements of reflective surfaces at near-millimeter wavelengths.

    PubMed

    Bock, J J; Parikh, M K; Fischer, M L; Lange, A E

    1995-08-01

    We have developed an instrument for directly measuring the emissivity of reflective surfaces at near-millimeter wavelengths. The thermal emission of a test sample is compared with that of a reference surface, allowing the emissivity of the sample to be determined without heating. The emissivity of the reference surface is determined by one's heating the reference surface and measuring the increase in emission. The instrument has an absolute accuracy of Δε = 5 × 10(-4) and can reproducibly measure a difference in emissivity as small as Δε = 10(-4) between flat reflective samples. We have used the instrument to measure the emissivity of metal films evaporated on glass and carbon fiber-reinforced plastic composite surfaces. We measure an emissivity of (2.15 ± 0.4) × 10(-3) for gold evaporated on glass and (2.65 ± 0.5) × 10(-3) for aluminum evaporated on carbon fiber-reinforced plastic composite.

  9. Microroughness, statistical surface models, and bidirectional reflection distribution function (BRDF): functions of smooth surfaces

    NASA Astrophysics Data System (ADS)

    Harnisch, Bernd; Weigel, Thomas

    1994-09-01

    The calculation of the BRDF (Bi-Directional-Reflection-Distribution-Function) from profile measurements was performed theoretically and verified by measurements on a BK7 sample. The assumptions on the surface topography and approximations done are highlighted.

  10. Laboratory laser reflectance measurement and applications to asteroid surface analysis

    NASA Astrophysics Data System (ADS)

    Shaw, A.; Daly, M. G.; Cloutis, E. A.; Tait, K. T.; Izawa, M. R. M.; Barnouin, O. S.; Hyde, B. C.; Nicklin, I.

    2014-07-01

    Introduction Laboratory reflectance measurement of asteroid analogs is an important tool for interpreting the reflectance of asteroids. One dominant factor affecting how measured reflectance changes as a function of phase angle (180° minus the scattering angle) is surface roughness [1], which is related to grain size. A major goal of this study is to be able to use the angular distributions (phase functions) of scattered light from various regions on an asteroid surface to determine the relative grain size between those regions. Grain size affects the spectral albedo and continuum slopes of surface materials, has implications in terms of understanding geologic processes on asteroids and is also valuable for the planning and operations of upcoming missions to asteroids, such as the New Frontiers OSIRIS-REx sample return mission to the asteroid (101955) Bennu [2]. Information on surface roughness is particularly powerful when combined with other datasets, such as thermal inertia maps (e.g., a smooth, low-backscatter surface of low thermal inertia likely contains fine grains). Approach To better constrain the composition and surface texture of Bennu, we are conducting experiments to investigate the laser return signature of terrestrial and meteorite analogs to Bennu. The objective is to understand the nature of laser returns given possible compositional, grain size and slope distributions on the surface of Bennu to allow surface characterization, particularly surface grain size, which would significantly aid efforts to identify suitable sites for sampling by the OSIRIS-REx mission. Setup A 1064-nm laser is used to determine the reflectance of Bennu analogs and their constituents (1064 nm is the wavelength of many laser altimeters including the one planned to fly on OSIRIS-REx). Samples of interest include serpentinites (greenalite, etc.), magnetite, and shungite. To perform the experiments, a goniometer has been built. This instrument allows reflectance measurements

  11. An adaptive interpolation scheme for molecular potential energy surfaces

    NASA Astrophysics Data System (ADS)

    Kowalewski, Markus; Larsson, Elisabeth; Heryudono, Alfa

    2016-08-01

    The calculation of potential energy surfaces for quantum dynamics can be a time consuming task—especially when a high level of theory for the electronic structure calculation is required. We propose an adaptive interpolation algorithm based on polyharmonic splines combined with a partition of unity approach. The adaptive node refinement allows to greatly reduce the number of sample points by employing a local error estimate. The algorithm and its scaling behavior are evaluated for a model function in 2, 3, and 4 dimensions. The developed algorithm allows for a more rapid and reliable interpolation of a potential energy surface within a given accuracy compared to the non-adaptive version.

  12. An adaptive interpolation scheme for molecular potential energy surfaces.

    PubMed

    Kowalewski, Markus; Larsson, Elisabeth; Heryudono, Alfa

    2016-08-28

    The calculation of potential energy surfaces for quantum dynamics can be a time consuming task-especially when a high level of theory for the electronic structure calculation is required. We propose an adaptive interpolation algorithm based on polyharmonic splines combined with a partition of unity approach. The adaptive node refinement allows to greatly reduce the number of sample points by employing a local error estimate. The algorithm and its scaling behavior are evaluated for a model function in 2, 3, and 4 dimensions. The developed algorithm allows for a more rapid and reliable interpolation of a potential energy surface within a given accuracy compared to the non-adaptive version. PMID:27586901

  13. An adaptive interpolation scheme for molecular potential energy surfaces.

    PubMed

    Kowalewski, Markus; Larsson, Elisabeth; Heryudono, Alfa

    2016-08-28

    The calculation of potential energy surfaces for quantum dynamics can be a time consuming task-especially when a high level of theory for the electronic structure calculation is required. We propose an adaptive interpolation algorithm based on polyharmonic splines combined with a partition of unity approach. The adaptive node refinement allows to greatly reduce the number of sample points by employing a local error estimate. The algorithm and its scaling behavior are evaluated for a model function in 2, 3, and 4 dimensions. The developed algorithm allows for a more rapid and reliable interpolation of a potential energy surface within a given accuracy compared to the non-adaptive version.

  14. Apparatus for and method of correcting for astigmatism in a light beam reflected off of a light reflecting surface

    DOEpatents

    Sawicki, R.H.; Sweatt, W.

    1985-11-21

    A technique for adjustably correcting for astigmatism in a light beam is disclosed herein. This technique defines a flat, rectangular light reflecting surface having opposite reinforced side edges and which is resiliently bendable, to a limited extent, into different concave and/or convex cylindrical curvatures about a particular axis and provides for adjustably bending the light reflecting surface into one of different curvatures depending upon the astigmatism to be corrected and for fixedly maintaining the curvature selected. In the embodiment disclosed, the light reflecting surface is adjustably bendable into the selected cylindrical curvature by application of a particular bending moment to the reinforced side edges of the light reflecting surface.

  15. Correlation between gloss reflectance and surface texture in photographic paper.

    PubMed

    Vessot, Kevin; Messier, Paul; Hyde, Joyce M; Brown, Christopher A

    2015-01-01

    Surface textures of a large collection of photographic papers dating from 1896 to the present were measured using a laser scanning confocal microscope (LSCM) with four different objective lenses. Roughness characterization parameters were calculated from the texture measurements and were compared with gloss measurements. Characterization by the area-scale fractal dimension (Das) and the area-scale fractal complexity (Asfc) provided the strongest correlations between gloss reflectance and surface texture. The measurements with the 5× and 10× objectives, which contained many large-scale, spiky measurement artifacts that distorted the measurement, resulted in the strongest correlations (R(2)  > 0.8) compared to the 20× and 50× (R(2)  < 0.5). The presence of spiky artifacts in the measurements, which increases when the magnification of the objective lens is decreased, appears to amplify surface features in such a way to improve the correlations.

  16. Asteroid surface materials: Mineralogical characterizations from reflectance spectra

    NASA Technical Reports Server (NTRS)

    Gaffey, M. J.; Mccord, T. B.

    1977-01-01

    Mineral assemblages analogous to most meteorite types, with the exception of ordinary chondritic assemblages, have been found as surface materials of Main Belt asteroids. C1- and C2-like assemblages (unleached, oxidized meteoritic clay minerals plus opaques such as carbon) dominate the population throughout the Belt, especially in the outer Belt. A smaller population of asteroids exhibit surface materials similar to C3 (CO, CV) meteoritic assemblages (olivine plus opaque, probably carbon) and are also distributed throughout the Belt. The majority of remaining studied asteroids (20) of 65 asteroids exhibit spectral reflectance curves dominated by the presence of metallic nickel-iron in their surface materials. The C2-like materials which dominate the main asteroid belt population appear to be relatively rare on earth-approaching asteroids.

  17. Simulation of radar reflectivity and surface measurements of rainfall

    NASA Technical Reports Server (NTRS)

    Chandrasekar, V.; Bringi, V. N.

    1987-01-01

    Raindrop size distributions (RSDs) are often estimated using surface raindrop sampling devices (e.g., disdrometers) or optical array (2D-PMS) probes. A number of authors have used these measured distributions to compute certain higher-order RSD moments that correspond to radar reflectivity, attenuation, optical extinction, etc. Scatter plots of these RSD moments versus disdrometer-measured rainrates are then used to deduce physical relationships between radar reflectivity, attenuation, etc., which are measured by independent instruments (e.g., radar), and rainrate. In this paper RSDs of the gamma form as well as radar reflectivity (via time series simulation) are simulated to study the correlation structure of radar estimates versus rainrate as opposed to RSD moment estimates versus rainrate. The parameters N0, D0 and m of a gamma distribution are varied over the range normally found in rainfall, as well as varying the device sampling volume. The simulations are used to explain some possible features related to discrepancies which can arise when radar rainfall measurements are compared with surface or aircraft-based sampling devices.

  18. Modulated surface nanostructures for enhanced light trapping and reduced surface reflection of crystalline silicon solar cells

    NASA Astrophysics Data System (ADS)

    Tayagaki, Takeshi; Hoshi, Yusuke; Hirai, Yuji; Matsuo, Yasutaka; Usami, Noritaka

    2016-05-01

    We demonstrated the fabrication of modulated surface nanostructures as a new surface texture design for thin wafer solar cells. Using a combination of conventional alkali etching and colloidal lithography, we fabricated surface textures with micrometer and nanometre scales on a Si substrate. These modulated surface nanostructures exhibit reduced surface reflection in a broad spectral range, compared with conventional micrometer textures. We investigated optical absorption using a rigorous coupled wave analysis simulation, which revealed a significant reduction in surface reflection over a broad spectral range and efficient light trapping (comparable to that of conventional micrometer-scale textures) for the modulated nanostructures. We found that the modulated surface nanostructures have a high potential of improving the performance of thin wafer crystalline Si solar cells.

  19. Total internal reflection microscopy: a surface inspection technique.

    PubMed

    Temple, P A

    1981-08-01

    Structure at and near the surface of a transparent sample or in a film on a transparent substrate can be observed by illuminating the sample from within using a well-collimated polarized laser beam incident at an angle equal to or greater than the critical angle of the sample material and examining the air side of the surface using an optical microscope. Although the technique is similar to dark-field microscopy, additional information can be obtained here concerning the size and depth of scattering sites on or near the surface. This technique, total internal reflection microscopy (TIRM), is complementary to phase contrast (Nomarski) microscopy. Two TIRM microscopes are shown, one of which is used as an attachment to a commercial Nomarski microscope and the second of which is used in laser damage measurements. This surface inspection technique had been used to study surface polishing and cleaning methods, laser damage nucleation sites, ion milling of optical surfaces, and thin film inclusions. A biological application for liquid medium studies is suggested. A description of the electric fields present at and near the air sample interface is given.

  20. Reflection spectra and magnetochemistry of iron oxides and natural surfaces

    NASA Technical Reports Server (NTRS)

    Wasilewski, P.

    1978-01-01

    The magnetic properties and spectral characteristics of iron oxides are distinctive. Diagnostic features in reflectance spectra (0.5 to 2.4 micron) for alpha Fe2O3, gamma Fe2O3, and FeOOH include location of Fe3(+) absorption features, intensity ratios at various wavelengths, and the curve shape between 1.2 micron and 2.4 micron. The reflection spectrum of natural rock surfaces are seldom those of the bulk rock because of weathering effects. Coatings are found to be dominated by iron oxides and clay. A simple macroscopic model of rock spectra (based on concepts of stains and coatings) is considered adequate for interpretation of LANDSAT data. The magnetic properties of materials associated with specific spectral types and systematic changes in both spectra and magnetic properties are considered.

  1. Shifting mirrors: adaptive changes in retinal reflections to winter darkness in Arctic reindeer.

    PubMed

    Stokkan, Karl-Arne; Folkow, Lars; Dukes, Juliet; Neveu, Magella; Hogg, Chris; Siefken, Sandra; Dakin, Steven C; Jeffery, Glen

    2013-12-22

    Arctic reindeer experience extreme changes in environmental light from continuous summer daylight to continuous winter darkness. Here, we show that they may have a unique mechanism to cope with winter darkness by changing the wavelength reflection from their tapetum lucidum (TL). In summer, it is golden with most light reflected back directly through the retina, whereas in winter it is deep blue with less light reflected out of the eye. The blue reflection in winter is associated with significantly increased retinal sensitivity compared with summer animals. The wavelength of reflection depends on TL collagen spacing, with reduced spacing resulting in shorter wavelengths, which we confirmed in summer and winter animals. Winter animals have significantly increased intra-ocular pressure, probably produced by permanent pupil dilation blocking ocular drainage. This may explain the collagen compression. The resulting shift to a blue reflection may scatter light through photoreceptors rather than directly reflecting it, resulting in elevated retinal sensitivity via increased photon capture. This is, to our knowledge, the first description of a retinal structural adaptation to seasonal changes in environmental light. Increased sensitivity occurs at the cost of reduced acuity, but may be an important adaptation in reindeer to detect moving predators in the dark Arctic winter.

  2. Dispersionless Manipulation of Reflected Acoustic Wavefront by Subwavelength Corrugated Surface

    PubMed Central

    Zhu, Yi-Fan; Zou, Xin-Ye; Li, Rui-Qi; Jiang, Xue; Tu, Juan; Liang, Bin; Cheng, Jian-Chun

    2015-01-01

    Free controls of optic/acoustic waves for bending, focusing or steering the energy of wavefronts are highly desirable in many practical scenarios. However, the dispersive nature of the existing metamaterials/metasurfaces for wavefront manipulation necessarily results in limited bandwidth. Here, we propose the concept of dispersionless wavefront manipulation and report a theoretical, numerical and experimental work on the design of a reflective surface capable of controlling the acoustic wavefront arbitrarily without bandwidth limitation. Analytical analysis predicts the possibility to completely eliminate the frequency dependence with a specific gradient surface which can be implemented by designing a subwavelength corrugated surface. Experimental and numerical results, well consistent with the theoretical predictions, have validated the proposed scheme by demonstrating a distinct phenomenon of extraordinary acoustic reflection within an ultra-broad band. For acquiring a deeper insight into the underlying physics, a simple physical model is developed which helps to interpret this extraordinary phenomenon and predict the upper cutoff frequency precisely. Generations of planar focusing and non-diffractive beam have also been exemplified. With the dispersionless wave-steering capability and deep discrete resolution, our designed structure may open new avenue to fully steer classical waves and offer design possibilities for broadband optical/acoustical devices. PMID:26077772

  3. Dispersionless Manipulation of Reflected Acoustic Wavefront by Subwavelength Corrugated Surface.

    PubMed

    Zhu, Yi-Fan; Zou, Xin-Ye; Li, Rui-Qi; Jiang, Xue; Tu, Juan; Liang, Bin; Cheng, Jian-Chun

    2015-01-01

    Free controls of optic/acoustic waves for bending, focusing or steering the energy of wavefronts are highly desirable in many practical scenarios. However, the dispersive nature of the existing metamaterials/metasurfaces for wavefront manipulation necessarily results in limited bandwidth. Here, we propose the concept of dispersionless wavefront manipulation and report a theoretical, numerical and experimental work on the design of a reflective surface capable of controlling the acoustic wavefront arbitrarily without bandwidth limitation. Analytical analysis predicts the possibility to completely eliminate the frequency dependence with a specific gradient surface which can be implemented by designing a subwavelength corrugated surface. Experimental and numerical results, well consistent with the theoretical predictions, have validated the proposed scheme by demonstrating a distinct phenomenon of extraordinary acoustic reflection within an ultra-broad band. For acquiring a deeper insight into the underlying physics, a simple physical model is developed which helps to interpret this extraordinary phenomenon and predict the upper cutoff frequency precisely. Generations of planar focusing and non-diffractive beam have also been exemplified. With the dispersionless wave-steering capability and deep discrete resolution, our designed structure may open new avenue to fully steer classical waves and offer design possibilities for broadband optical/acoustical devices. PMID:26077772

  4. Dispersionless Manipulation of Reflected Acoustic Wavefront by Subwavelength Corrugated Surface

    NASA Astrophysics Data System (ADS)

    Zhu, Yi-Fan; Zou, Xin-Ye; Li, Rui-Qi; Jiang, Xue; Tu, Juan; Liang, Bin; Cheng, Jian-Chun

    2015-06-01

    Free controls of optic/acoustic waves for bending, focusing or steering the energy of wavefronts are highly desirable in many practical scenarios. However, the dispersive nature of the existing metamaterials/metasurfaces for wavefront manipulation necessarily results in limited bandwidth. Here, we propose the concept of dispersionless wavefront manipulation and report a theoretical, numerical and experimental work on the design of a reflective surface capable of controlling the acoustic wavefront arbitrarily without bandwidth limitation. Analytical analysis predicts the possibility to completely eliminate the frequency dependence with a specific gradient surface which can be implemented by designing a subwavelength corrugated surface. Experimental and numerical results, well consistent with the theoretical predictions, have validated the proposed scheme by demonstrating a distinct phenomenon of extraordinary acoustic reflection within an ultra-broad band. For acquiring a deeper insight into the underlying physics, a simple physical model is developed which helps to interpret this extraordinary phenomenon and predict the upper cutoff frequency precisely. Generations of planar focusing and non-diffractive beam have also been exemplified. With the dispersionless wave-steering capability and deep discrete resolution, our designed structure may open new avenue to fully steer classical waves and offer design possibilities for broadband optical/acoustical devices.

  5. Multiple wall-reflection effect in adaptive-array differential-phase reflectometry on QUEST

    NASA Astrophysics Data System (ADS)

    Idei, H.; Mishra, K.; Yamamoto, M. K.; Fujisawa, A.; Nagashima, Y.; Hamasaki, M.; Hayashi, Y.; Onchi, T.; Hanada, K.; Zushi, H.; QUEST Team

    2016-01-01

    A phased array antenna and Software-Defined Radio (SDR) heterodyne-detection systems have been developed for adaptive array approaches in reflectometry on the QUEST. In the QUEST device considered as a large oversized cavity, standing wave (multiple wall-reflection) effect was significantly observed with distorted amplitude and phase evolution even if the adaptive array analyses were applied. The distorted fields were analyzed by Fast Fourier Transform (FFT) in wavenumber domain to treat separately the components with and without wall reflections. The differential phase evolution was properly obtained from the distorted field evolution by the FFT procedures. A frequency derivative method has been proposed to overcome the multiple-wall reflection effect, and SDR super-heterodyned components with small frequency difference for the derivative method were correctly obtained using the FFT analysis.

  6. Mars surface composition from reflectance spectroscopy - A summary

    NASA Technical Reports Server (NTRS)

    Singer, R. B.; Clark, R. N.; Mccord, T. B.; Adams, J. B.; Huguenin, R. L.

    1979-01-01

    Visible and near-infrared reflectance spectra and multispectral maps of the Martian surface are discussed, and implications of the data for the composition of the Martian surface are considered. Spacecraft and earth-based telescopic observations have confirmed the generally bimodal albedo distribution of the planet, dividing the surface into bright and dark regions. Mars spectra are characterized by the presence of strong Fe(+3) absorption, which is attributed to various ferric oxide minerals. Interpretations of the spectra from the dark regions indicate a basaltic or ultramafic source rock. Evidence for water ice or a highly desiccated metal hydrate has been obtained, along with evidence for CO2-ice only in the south polar cap. Mariner 9 observations of Martian dust suggest the presence of rather acidic rock or mineral particles, or a montmorillonite-type clay. Prospects for the future study of Martian surface composition include continuing earth-based spectrophotometric studies, and high-spectral-resolution mapping of a significant portion of the surface by the Galileo spacecraft and the next Mars mission.

  7. Human preocular mucins reflect changes in surface physiology

    PubMed Central

    Berry, M; Ellingham, R B; Corfield, A P

    2004-01-01

    Background/aims: Mucin function is associated with both peptide core and glycosylation characteristics. The authors assessed whether structural alterations occurring during mucin residence in the tear film reflect changes in ocular surface physiology. Methods: Ocular surface mucus was collected from normal volunteers as N-acetyl cysteine (NAcCys) washes or directly from the speculum after cataract surgery. To assess the influence of surface health on mucins, NAcCys washings were also obtained from patients with symptoms, but no clinical signs of dry eye (symptomatics). Mucins were extracted in guanidine hydrochloride (GuHCl) with protease inhibitors. Buoyant density of mucin species, a correlate of glycosylation density, was followed by reactivity with anti-peptide core antibodies. Mucin hydrodynamic volume was assessed by gel filtration on Sepharose CL2B. Results: Surface fluid and mucus contained soluble forms of MUC1, MUC2, MUC4, and MUC5AC and also the same species requiring DTT solubilisation. Reactivity with antibodies to MUC2 and MUC5AC peaked at 1.3–1.5 g/ml in normals, while dominated by underglycosylated forms in symptomatics. Surface mucins were predominantly smaller than intracellular species. MUC2 size distributions were different in symptomatics and normals, while those of MUC5AC were similar in these two groups. Conclusions: A reduction in surface mucin size indicates post-secretory cleavage. Dissimilarities in surface mucin glycosylation and individual MUC size distributions in symptomatics suggest changes in preocular mucin that might precede dry eye signs. PMID:14977773

  8. Airborne Interferometry using GNSS Reflections for Surface Level Estimation

    NASA Astrophysics Data System (ADS)

    Semmling, Maximilian; Beyerle, Georg; Schön, Steffen; Stosius, Ralf; Gerber, Thomas; Beckheinrich, Jamila; Markgraf, Markus; Ge, Maorong; Wickert, Jens

    2013-04-01

    The interferometric use of GNSS reflections for ocean altimetry can fill the gap in coverage of ocean observations. Today radar altimeters are used for large scale ocean observations to monitor e.g. global sea level change or circulation processes like El Niño. Spacial and temporal resolution of a single radar altimeter, however, is insufficient to observe mesoscale ocean phenomena like large oceanic eddies that are important indicators of climate change. The high coverage expected for a spaceborne altimeter based on GNSS reflections stimulated investigations on according interferometric methods. Several airborne experiments have been conducted using code observations. Carrier observations have a better precision but are severely affected by noise and have mostly been used in ground-based experiments. A new interferometric approach is presented using carrier observations for airborne application. Implementing a spectral retrieval noise reduction is achieved. A flight experiment was conducted with a Zeppelin airship on 2010/10/12 over Lake Constance at the border between Austria, Germany and Switzerland. The lake surface with an area of 536km2 is suitable for altimetric study as its decimeter range Geoid undulations are well-known. Three GNSS receiver were installed on the airship. A Javad Delta receiver recording direct signals for navigation. The DLR G-REX receiver recording reflected signals for scatterometry and the GORS (GNSS Occultation Reflectometry Scatterometry) receiver recording direct and reflected signals for interferometry. The airship's trajectory is determined from navigation data with a precision better than 10cm using regional augmentation. This presentation focuses on the interferometric analysis of GORS observations. Ray tracing calculations are used to model the difference of direct and reflected signals' path. Spectral retrieval is applied to determine Doppler residuals of modelled path difference and interferometric observations. Lake level

  9. Hydrodynamically Lubricated and Grooved Biomimetic Self-Adapting Surfaces

    PubMed Central

    Jackson, Robert L.; Lei, Jiang

    2014-01-01

    In many machines and mechanical components, there is a need for new bearing technologies to reduce friction and wear, and provide precision control of motion when the load is varied. This can be provided by electronically controlled actuators and sensors on the surfaces, but then the system reliability can be an issue. In contrast, biomimetic surfaces can be created that adapt mechanically to variations in load. This work uses numerical methods to research the use of self-adapting surfaces for bearings that are based on the deformable nature of biological materials such as articular cartilage. These surfaces are designed to change their profiles to achieve a desired behavior, without any external control. The surfaces change their profile to control the film height and tilt of the bearing to a near constant value for different loads. If the surfaces are tilted, the grooved self-adapting surfaces will also react with a larger restoring moment than a conventional grooved surface. These surfaces could be beneficial to applications where electrical systems and controls are not feasible. PMID:24956441

  10. An adaptive response surface method for crashworthiness optimization

    NASA Astrophysics Data System (ADS)

    Shi, Lei; Yang, Ren-Jye; Zhu, Ping

    2013-11-01

    Response surface-based design optimization has been commonly used for optimizing large-scale design problems in the automotive industry. However, most response surface models are built by a limited number of design points without considering data uncertainty. In addition, the selection of a response surface in the literature is often arbitrary. This article uses a Bayesian metric to systematically select the best available response surface among several candidates in a library while considering data uncertainty. An adaptive, efficient response surface strategy, which minimizes the number of computationally intensive simulations, was developed for design optimization of large-scale complex problems. This methodology was demonstrated by a crashworthiness optimization example.

  11. Optical sensor package for multiangle measurements of surface reflectance

    NASA Astrophysics Data System (ADS)

    Czapla-Myers, Jeffrey S.; Thome, Kurtis J.; Biggar, Stuart F.

    2002-01-01

    The Remote Sensing Group of the Optical Sciences Center at the University of Arizona has performed the vicarious calibration of satellite sensors since the 1980's. Ground- based measurements of atmospheric and surface properties, including the surface bidirectional reflectance distribution function (BRDF), are conducted during a satellite or airborne sensor overpass and the at-sensor radiance is calculated using these properties as input to a radiative transfer code. Recently, the Remote Sensing Group has investigated an imaging radiometer based on an astronomical- grade 1024 x 1024-pixel silicon CCD array that was developed and calibrated fro ground-based measurements of BRDF. The results of that study have been used to examine the feasibility of a lightweight instrument package for measurement of surface BRDF based on a combination of nonimaging radiometers and inexpensive digital cameras. The current work presents a preliminary design of such a system including specifications for ground-based operations of the system to characterize the BRDF of test sites used by the Remote Sensing Group. Also included is a preliminary evaluation of a Nikon 990 digital camera coupled with a 1.7- mm focal length fisheye lens to determine the level of accuracy that can be obtained in surface BRDF.

  12. Viscoelasticity evaluation of rubber by surface reflection of supersonic wave.

    PubMed

    Omata, Nobuaki; Suga, Takahiro; Furusawa, Hirokazu; Urabe, Shinichi; Kondo, Takeru; Ni, Qing-Qing

    2006-12-22

    The main characteristic of rubber is a viscoelasticity. So it is important to research the characteristic of the viscoelasticity of the high frequency band for the friction between a rubber material and the hard one with roughness, for instance, the tire and the road. As for the measurement of the viscoelasticity of rubber, DMA (dynamic mechanical analysis) is general. However, some problems are pointed out to the measurement of the high frequency band by DMA. Then, we evaluated the viscoelasticity characteristic by the supersonic wave measurement. However, attenuation of rubber is large, and when the viscoelasticity is measured by the supersonic wave therefore, it is inconvenient and limited in a past method by means of bottom reflection. In this report, we tried the viscoelasticity evaluation by the method of using complex surface reflection coefficient and we compared with the friction coefficient under wide-range friction velocity. As a result, some relationships had been found for two properties. We report the result that character of viscoelasticity of rubber was comparable to friction coefficient.

  13. Evaluation of thermal resistance of building insulations with reflective surfaces

    NASA Astrophysics Data System (ADS)

    Št'astník, S.

    2012-09-01

    The thermal resistance of advanced insulation materials, applied namely in civil engineering, containing reflective surfaces and air gaps, cannot be evaluated correctly using the valid European standards because of presence of the dominant nonlinear radiative heat transfer and other phenomena not included in the recommended computational formulae. The proper general physical analysis refers to rather complicated problems from classical thermodynamics, whose both existence theory and numerical analysis contain open questions and cannot be done in practice when the optimization of composition of insulation layers is required. This paper, coming from original experimental results, demonstrates an alternative simplified computational approach, taking into account the most important physical processes, useful in the design of modern insulation systems.

  14. Segmentation of branching vascular structures using adaptive subdivision surface fitting

    NASA Astrophysics Data System (ADS)

    Kitslaar, Pieter H.; van't Klooster, Ronald; Staring, Marius; Lelieveldt, Boudewijn P. F.; van der Geest, Rob J.

    2015-03-01

    This paper describes a novel method for segmentation and modeling of branching vessel structures in medical images using adaptive subdivision surfaces fitting. The method starts with a rough initial skeleton model of the vessel structure. A coarse triangular control mesh consisting of hexagonal rings and dedicated bifurcation elements is constructed from this skeleton. Special attention is paid to ensure a topological sound control mesh is created around the bifurcation areas. Then, a smooth tubular surface is obtained from this coarse mesh using a standard subdivision scheme. This subdivision surface is iteratively fitted to the image. During the fitting, the target update locations of the subdivision surface are obtained using a scanline search along the surface normals, finding the maximum gradient magnitude (of the imaging data). In addition to this surface fitting framework, we propose an adaptive mesh refinement scheme. In this step the coarse control mesh topology is updated based on the current segmentation result, enabling adaptation to varying vessel lumen diameters. This enhances the robustness and flexibility of the method and reduces the amount of prior knowledge needed to create the initial skeletal model. The method was applied to publicly available CTA data from the Carotid Bifurcation Algorithm Evaluation Framework resulting in an average dice index of 89.2% with the ground truth. Application of the method to the complex vascular structure of a coronary artery tree in CTA and to MRI images were performed to show the versatility and flexibility of the proposed framework.

  15. A Reflective Goal-Based System for Context-Aware Adaptation

    NASA Astrophysics Data System (ADS)

    Meng, Dejian; Poslad, Stefan

    Many context-aware applications exploit current world contexts to control information access and service adaptation. To support a user centric utility model for a context-aware system, user goals are supported by the system. However, traditional goal-based approaches such as planning are hard to achieve in a context-aware environment because environments and systems are dynamic. This can lead to inconsistencies and goal conflicts. In this research, a new goal-context based approach is introduced to guide service adaptation for context-aware applications. A reflection model is investigated and applied to the system to resolve ambiguities and inconsistencies between goal-based planning and actual service adaptation. The new system, with its improved flexibility and robustness, is demonstrated in the form of a mobile spatial routing application.

  16. Reflective Teaching via a Problem Exploration--Teaching Adaptations--Resolution Cycle: A Mixed Methods Study of Preservice Teachers' Reflective Notes

    ERIC Educational Resources Information Center

    Hayden, H. Emily; Chiu, Ming Ming

    2015-01-01

    We explore development of elementary preservice teachers' reflective practices as they solved problems encountered while teaching in a reading clinic. Written reflections (N = 175) were collected across 8 weeks from 23 preservice teachers and analyzed to investigate relationships among problem exploration, teaching adaptations, and problem…

  17. Anisotropy of Reflected Solar Short Wave Radiation on a Snow Surface: Ground Measurements and Modelling

    NASA Astrophysics Data System (ADS)

    Hendriks, E.; Greuell, W.; Oerlemans, J.; Knap, W.; Stammes, P.

    2004-05-01

    The retrieval of albedo of snow and ice masses by satellite is still troubled by the fact that these types of surfaces reflect anisotropically. This means that the reflectance of solar radiation on such an ice mass depends on viewing and insolation angle relative to its surface as well as its optical and (small and large scale) spatial characteristics. As in satellite observation the reflected radiation from a certain surface at a certain moment is usually recorded from one single viewing angle relative to the surface only, the interpretation of the measured reflectance value to total reflectance and albedo is not straightforward and corrections for anisotropy are necessary. To gain more knowledge of the anisotropy in the reflected radiation on snow and ice masses, we study the Bi-directional Reflectance Distribution Function (BRDF) as a function of insolation angle and for different ice mass types. This study includes ground measurements and modelling and covers both snow pack and glacier ice. Here we will only discuss BRDF of snow pack. In March 2003 BRDF of snow is measured in Davos (Switzerland) on snow pack of different type considering snow grain size and form, pollution with aerosol deposit (and sediment) and liquid water content in Landsat TM bands 2 and 4 and MODIS 5 and 6. From these measurements anisotropy shows to be mainly depending on the effective insolation angle, with strongest anisotropy for great insolation angles, especially in the forward scattering direction. Effects of snow metamorphosis were seen in BRDF exhibiting stronger anistropy variation with effective insolation angle after compared to before solar noon. Minimal effect of varying anisotropy with insolation angle or snow type is seen in near-nadir viewing angles. This spring our focus is on the modelling of snow BRDF with the aid of a radiative transfer model for an atmosphere with cirrus clouds, which is developed by Royal Netherlands Meteorological Institute (KMNI) and will be

  18. Reflectance characteristics and surface processes in stabilized dune environments

    NASA Technical Reports Server (NTRS)

    Jacobberger, P. A.

    1989-01-01

    Analysis of multitemporal TM data for three environmentally related field areas yields information on the response characteristics of stabilized dunes and desert-fringe environments. The three field sites studied include dune fields in Egypt, Mali, and Botswana, ranging in climate from hyperarid to semiarid, and may be classed as an environmental series relating surface processes under Saharan, Sahelian, and Savanna conditions. Sites were field mapped and monitored with TM data for lengths of time up to a year. The complexity of spectral response characteristics is greatest where vegetation is dense and diverse, but study of the three environments together places constraints on the importance of vegetation to spectral response as well as to mechanisms of sand transport. In both Mali and Botswana, the Sahelian and Savanna environments, contrast reversals occur on dune crests and reflectance patterns change through the dry season to resemble the response curves of the hyperarid study site in Egypt. In these analyses, overall surface brightness is controlled by sand composition, while spectral features are controlled by vegetation dynamics.

  19. Surface roughness effects on the solar reflectance of cool asphalt shingles

    SciTech Connect

    Akbari, Hashem; Berdahl, Paul; Akbari, Hashem; Jacobs, Jeffry; Klink, Frank

    2008-02-17

    We analyze the solar reflectance of asphalt roofing shingles that are covered with pigmented mineral roofing granules. The reflecting surface is rough, with a total area approximately twice the nominal area. We introduce a simple analytical model that relates the 'micro-reflectance' of a small surface region to the 'macro-reflectance' of the shingle. This model uses a mean field approximation to account for multiple scattering effects. The model is then used to compute the reflectance of shingles with a mixture of different colored granules, when the reflectances of the corresponding mono-color shingles are known. Simple linear averaging works well, with small corrections to linear averaging derived for highly reflective materials. Reflective base granules and reflective surface coatings aid achievement of high solar reflectance. Other factors that influence the solar reflectance are the size distribution of the granules, coverage of the asphalt substrate, and orientation of the granules as affected by rollers during fabrication.

  20. Apparatus for and method of correcting for astigmatism in a light beam reflected off of a light reflecting surface

    DOEpatents

    Sawicki, Richard H.; Sweatt, William

    1987-01-01

    A technique for adjustably correcting for astigmatism in a light beam is disclosed herein. This technique utilizes first means which defines a flat, rectangular light reflecting surface having opposite reinforced side edges and which is resiliently bendable, to a limited extent, into different concave and/or convex cylindrical curvatures about a particular axis and second means acting on the first means for adjustably bending the light reflecting surface into a particular selected one of the different curvatures depending upon the astigmatism to be corrected for and for fixedly maintaining the curvature selected. In the embodiment disclosed, the light reflecting surface is adjustably bendable into the selected cylindrical curvature by application of a particular bending moment to the reinforced side edges of the light reflecting surface.

  1. Consistent depth video segmentation using adaptive surface models.

    PubMed

    Husain, Farzad; Dellen, Babette; Torras, Carme

    2015-02-01

    We propose a new approach for the segmentation of 3-D point clouds into geometric surfaces using adaptive surface models. Starting from an initial configuration, the algorithm converges to a stable segmentation through a new iterative split-and-merge procedure, which includes an adaptive mechanism for the creation and removal of segments. This allows the segmentation to adjust to changing input data along the movie, leading to stable, temporally coherent, and traceable segments. We tested the method on a large variety of data acquired with different range imaging devices, including a structured-light sensor and a time-of-flight camera, and successfully segmented the videos into surface segments. We further demonstrated the feasibility of the approach using quantitative evaluations based on ground-truth data.

  2. Growth and adaptation of microorganisms on the cheese surface.

    PubMed

    Monnet, Christophe; Landaud, Sophie; Bonnarme, Pascal; Swennen, Dominique

    2015-01-01

    Microbial communities living on cheese surfaces are composed of various bacteria, yeasts and molds that interact together, thus generating the typical sensory properties of a cheese. Physiological and genomic investigations have revealed important functions involved in the ability of microorganisms to establish themselves at the cheese surface. These functions include the ability to use the cheese's main energy sources, to acquire iron, to tolerate low pH at the beginning of ripening and to adapt to high salt concentrations and moisture levels. Horizontal gene transfer events involved in the adaptation to the cheese habitat have been described, both for bacteria and fungi. In the future, in situ microbial gene expression profiling and identification of genes that contribute to strain fitness by massive sequencing of transposon libraries will help us to better understand how cheese surface communities function.

  3. Adaptive filtering for ECG rejection from surface EMG recordings.

    PubMed

    Marque, C; Bisch, C; Dantas, R; Elayoubi, S; Brosse, V; Pérot, C

    2005-06-01

    Surface electromyograms (EMG) of back muscles are often corrupted by electrocardiogram (ECG) signals. This noise in the EMG signals does not allow to appreciate correctly the spectral content of the EMG signals and to follow its evolution during, for example, a fatigue process. Several methods have been proposed to reject the ECG noise from EMG recordings, but seldom taking into account the eventual changes in ECG characteristics during the experiment. In this paper we propose an adaptive filtering algorithm specifically developed for the rejection of the electrocardiogram corrupting surface electromyograms (SEMG). The first step of the study was to choose the ECG electrode position in order to record the ECG with a shape similar to that found in the noised SEMGs. Then, the efficiency of different algorithms were tested on 28 erector spinae SEMG recordings. The best algorithm belongs to the fast recursive least square family (FRLS). More precisely, the best results were obtained with the simplified formulation of a FRLS algorithm. As an application of the adaptive filtering, the paper compares the evolutions of spectral parameters of noised or denoised (after adaptive filtering) surface EMGs recorded on erector spinae muscles during a trunk extension. The fatigue test was analyzed on 16 EMG recordings. After adaptive filtering, mean initial values of energy and of mean power frequency (MPF) were significantly lower and higher respectively. The differences corresponded to the removal of the ECG components. Furthermore, classical fatigue criteria (increase in energy and decrease in MPF values over time during the fatigue test) were better observed on the denoised EMGs. The mean values of the slopes of the energy-time and MPF-time linear relationships differed significantly when established before and after adaptive filtering. These results account for the efficacy of the adaptive filtering method proposed here to denoise electrophysiological signals.

  4. Bi-directional reflectance studies of prepared compact particulate surfaces

    NASA Astrophysics Data System (ADS)

    Zhang, Hao

    Controlled laboratory BRDF and transmission measurements on layers of polymer and glass spheres have been carried out to investigate the connection between single particle optics and the optics of a packed surface. The measurements show that despite being closely packed, significant features of single scattering, such as the rainbow peaks, are preserved even in aggregated sphere layers. The measurements have been compared to 5 radiative transfer model predictions: the Hapke's model and its improved version, the Lumme-Bowell model, Mishchenko et al.'s BRF algorithm and DISORT. It has been found that strict numerical RTE models predict the measurements well in some regions, but have errors in both forward and backward scattering directions. The discrepancies have been attributed to the non-ideal factors such as internal inhomogeneity and surface roughness and may be corrected using Lumme-Bowell's roughness correction factor for oblique incident light. The inadequacy of the semi-empirical models can be partly attributed to the exclusion of a diffraction contribution in the models. In-situ BRDF measurements on submerged sediments with grain sizes ranging from 300 mum to over 1000 mum have been carried out. For normally illuminated small grain size samples the BRDF was nearly Lambertian, but samples with larger grain sizes are less Lambertian, with the BRDF decreasing with increasing view angles. Under oblique incident angles the samples become increasingly non-Lambertian; the dominant feature in the BRDF is enhanced backscattering. An empirical model is presented for each sediment type which represents the data within the standard deviation of the sample variation. This model is well behaved at angles out to 90°, and thus can be incorporated into the radiative transfer models to improve the light field predictions in shallow water. The BRDF of both dry and wet ooid sand layers with different particle size distributions and layer thicknesses on a reflecting mirror have

  5. Analysis of ground reflection of jet noise obtained with various microphone arrays over an asphalt surface

    NASA Technical Reports Server (NTRS)

    Miles, J. H.

    1975-01-01

    Ground reflection effects on the propagation of jet noise over an asphalt surface are discussed for data obtained using a 33.02-cm diameter nozzle with microphones at several heights and distances from the nozzle axis. Ground reflection effects are analyzed using the concept of a reflected signal transfer function which represents the influence of both the reflecting surface and the atmosphere on the propagation of the reflected signal in a mathematical model. The mathematical model used as a basis for the computer program was successful in significantly reducing the ground reflection effects. The range of values of the single complex number used to define the reflected signal transfer function was larger than expected when determined only by the asphalt surface. This may indicate that the atmosphere is affecting the propagation of the reflected signal more than the asphalt surface. The selective placement of the reinforcements and cancellations in the design of an experiment to minimize ground reflection effects is also discussed.

  6. Landsat surface reflectance quality assurance extraction (version 1.7)

    USGS Publications Warehouse

    Jones, J.W.; Starbuck, M.J.; Jenkerson, C.B.

    2013-01-01

    The U.S. Geological Survey (USGS) Land Remote Sensing Program is developing an operational capability to produce Climate Data Records (CDRs) and Essential Climate Variables (ECVs) from the Landsat Archive to support a wide variety of science and resource management activities from regional to global scale. The USGS Earth Resources Observation and Science (EROS) Center is charged with prototyping systems and software to generate these high-level data products. Various USGS Geographic Science Centers are charged with particular ECV algorithm development and (or) selection as well as the evaluation and application demonstration of various USGS CDRs and ECVs. Because it is a foundation for many other ECVs, the first CDR in development is the Landsat Surface Reflectance Product (LSRP). The LSRP incorporates data quality information in a bit-packed structure that is not readily accessible without postprocessing services performed by the user. This document describes two general methods of LSRP quality-data extraction for use in image processing systems. Helpful hints for the installation and use of software originally developed for manipulation of Hierarchical Data Format (HDF) produced through the National Aeronautics and Space Administration (NASA) Earth Observing System are first provided for users who wish to extract quality data into separate HDF files. Next, steps follow to incorporate these extracted data into an image processing system. Finally, an alternative example is illustrated in which the data are extracted within a particular image processing system.

  7. Low energy electron elastic reflection from solid surfaces

    NASA Astrophysics Data System (ADS)

    Starý, Vladimír.; Zemek, Josef

    2004-09-01

    Using our Monte-Carlo (MC) code, we calculated the ratio of the coefficients of elastic reflection of electrons from Si, SiO 2 and Au to those of Cu and Al in the electron energy range 0.2-1.0 and 1.5 keV (Au-Cu), respectively. The electron scattering was simulated by a single scattering model. For the MC calculations, we compared the elastic differential cross-sections calculated using a static field approximation with relativistic partial wave analysis on either the Thomas-Fermi-Dirac potential of free atoms (TFD model) or the Hartree-Fock-Wigner-Seitz (muffin-tin) potential of atoms in the solid state (HFWS model). The MC data were compared with the experimental values. For both models, reasonably good agreement for Si-Cu and SiO 2-Cu systems was found. In the Au-Cu system, better agreement was achieved using the TFD model. The addition of C in a surface interaction layer of 2-5 nm improves the agreement between simulated and experimental values for the Si-Al and Si-SiO 2 systems.

  8. The Effect of Non-Lambertian Surface Reflectance on Aerosol Radiative Forcing

    SciTech Connect

    Ricchiazzi, P.; O'Hirok, W.; Gautier, C.

    2005-03-18

    Surface reflectance is an important factor in determining the strength of aerosol radiative forcing. Previous studies of radiative forcing assumed that the reflected surface radiance is isotropic and does not depend on incident illumination angle. This Lambertian reflection model is not a very good descriptor of reflectance from real land and ocean surfaces. In this study we present computational results for the seasonal average of short and long wave aerosol radiative forcing at the top of the atmosphere and at the surface. The effect of the Lambertian assumption is found through comparison with calculations using a more detailed bi-direction reflectance distribution function (BRDF).

  9. Interactions of light with rough dielectric surfaces - Spectral reflectance and polarimetric properties

    NASA Technical Reports Server (NTRS)

    Yon, S. A.; Pieters, C. M.

    1988-01-01

    The nature of the interactions of visible and NIR radiation with the surfaces of rock and mineral samples was investigated by measuring the reflectance and the polarization properties of scattered and reflected light for slab samples of obsidian and fine-grained basalt, prepared to controlled surface roughness. It is shown that the degree to which radiation can penetrate a surface and then scatter back out, an essential criterion for mineralogic determinations based on reflectance spectra, depends not only upon the composition of the material, but also on its physical condition such as sample grain size and surface roughness. Comparison of the experimentally measured reflectance and polarization from smooth and rough slab materials with the predicted models indicates that single Fresnel reflections are responsible for the largest part of the reflected intensity resulting from interactions with the surfaces of dielectric materials; multiple Fresnel reflections are much less important for such surfaces.

  10. Fiber optic displacement measurement model based on finite reflective surface

    NASA Astrophysics Data System (ADS)

    Li, Yuhe; Guan, Kaisen; Hu, Zhaohui

    2016-10-01

    We present a fiber optic displacement measurement model based on finite reflective plate. The theoretical model was derived, and simulation analysis of light intensity distribution, reflective plate width, and the distance between fiber probe and reflective plate were conducted in details. The three dimensional received light intensity distribution and the characteristic curve of light intensity were studied as functions of displacement of finite reflective plate. Experiments were carried out to verify the established model. The physical fundamentals and the effect of operating parameters on measuring system performance were revealed in the end.

  11. Fiber Bragg grating dynamic strain sensor using an adaptive reflective semiconductor optical amplifier source.

    PubMed

    Wei, Heming; Tao, Chuanyi; Zhu, Yinian; Krishnaswamy, Sridhar

    2016-04-01

    In this paper, a reflective semiconductor optical amplifier (RSOA) is configured to demodulate dynamic spectral shifts of a fiber Bragg grating (FBG) dynamic strain sensor. The FBG sensor and the RSOA source form an adaptive fiber cavity laser. As the reflective spectrum of the FBG sensor changes due to dynamic strains, the wavelength of the laser output shifts accordingly, which is subsequently converted into a corresponding phase shift and demodulated by an unbalanced Michelson interferometer. Due to the short transition time of the RSOA, the RSOA-FBG cavity can respond to dynamic strains at high frequencies extending to megahertz. A demodulator using a PID controller is used to compensate for low-frequency drifts induced by temperature and large quasi-static strains. As the sensitivity of the demodulator is a function of the optical path difference and the FBG spectral width, optimal parameters to obtain high sensitivity are presented. Multiplexing to demodulate multiple FBG sensors is also discussed. PMID:27139682

  12. Mercapto-based coupling agent for improved thermophotovoltaic device back surface reflector adhesion and reflectance

    DOEpatents

    Wernsman, Bernard; Fiedor, Joseph N.; Irr, Lawrence G.; Palmisiano, Marc N.

    2016-10-04

    A back surface reflector (BSR) is described. The BSR includes a reflecting layer, a substrate and an adhesion layer between the reflecting layer and the substrate. The adhesion layer includes 3-mercaptopropyl (trimethoxy) silane (a.k.a. Merc).

  13. Imaging objects behind a partially reflective surface with a modified time-of-flight sensor

    NASA Astrophysics Data System (ADS)

    Geerardyn, D.; Kuijk, M.

    2014-05-01

    Time-of-Flight (ToF) methods are used in different applications for depth measurements. There are mainly 2 types of ToF measurements, Pulsed Time-of-Flight and Continuous-Wave Time-of-Flight. Pulsed Time-of-Flight (PToF) techniques are mostly used in combination with a scanning mirror, which makes them not well suited for imaging purposes. Continuous-wave Time-of-Flight (CWToF) techniques are mostly used wide-field, hence they are much faster and more suited for imaging purposes but cannot be used behind partially-reflective surfaces. In commercial applications, both ToF methods require specific hardware, which cannot be exchanged. In this paper, we discuss the transformation of a CWToF sensor to a PToF camera, which is able to make images and measure the distances of objects behind a partially-reflective surface, like the air-water interface in swimming pools when looking from above. We first created our own depth camera which is suitable for both CWToF and PToF. We describe the necessary hardware components for a normal ToF camera and compare it with the adapted components which make it a range-gating depth imager. Afterwards, we modeled the distances and images of one or more objects positioned behind a partially-reflective surface and combine it with measurement data of the optical pulse. A scene was virtualized and the rays from a raytracing software tool were exported to Matlab™. Subsequently, pulse deformations were calculated for every pixel, which resulted in the calculation of the depth information.

  14. Surface identification from multiband LADAR reflectance with varied incidence angle via database mapping.

    PubMed

    Guiang, Chona; Jin, Xuemin; Levine, Robert Y

    2015-02-10

    Incident angle dependencies of LADAR reflection depend on bulk material reflectivity and surface texture properties that can be exploited for surface identification. In this paper, surface identification via multiband LADAR reflected radiance is assessed using the nonconventional exploitation factors data system database. A statistics-based dimension reduction algorithm, stochastic neighborhood embedding (t-SNE), is used to separate the data clouds resulting from the monostatic LADAR reflected radiance and corresponding band ratios. The application of t-SNE to multiband reflected radiance effectively separates the data clouds, making surface identification via multiband LADAR reflectance possible in the presence of unknown incident angle dependencies and uncertainties. It is demonstrated that, for both the multiband monostatic reflected radiance and band ratios, the application of t-SNE mapping yields a significant improvement in surface identification from measurements with unknown or varied incident angles.

  15. Earth-atmosphere system and surface reflectivities in arid regions from LANDSAT multispectral scanner measurements

    NASA Technical Reports Server (NTRS)

    Otterman, J.; Fraser, R. S.

    1976-01-01

    Programs for computing atmospheric transmission and scattering solar radiation were used to compute the ratios of the Earth-atmosphere system (space) directional reflectivities in the vertical direction to the surface reflectivity, for the four bands of the LANDSAT multispectral scanner (MSS). These ratios are presented as graphs for two water vapor levels, as a function of the surface reflectivity, for various sun elevation angles. Space directional reflectivities in the vertical direction are reported for selected arid regions in Asia, Africa and Central America from the spectral radiance levels measured by the LANDSAT MSS. From these space reflectivities, surface vertical reflectivities were computed applying the pertinent graphs. These surface reflectivities were used to estimate the surface albedo for the entire solar spectrum. The estimated albedos are in the range 0.34-0.52, higher than the values reported by most previous researchers from space measurements, but are consistent with laboratory measurements.

  16. Anti- reflective device having an anti-reflection surface formed of silicon spikes with nano-tips

    NASA Technical Reports Server (NTRS)

    Bae, Youngsman (Inventor); Mooasser, Sohrab (Inventor); Manohara, Harish (Inventor); Lee, Choonsup (Inventor); Bae, Kungsam (Inventor)

    2009-01-01

    Described is a device having an anti-reflection surface. The device comprises a silicon substrate with a plurality of silicon spikes formed on the substrate. A first metallic layer is formed on the silicon spikes to form the anti-reflection surface. The device further includes an aperture that extends through the substrate. A second metallic layer is formed on the substrate. The second metallic layer includes a hole that is aligned with the aperture. A spacer is attached with the silicon substrate to provide a gap between an attached sensor apparatus. Therefore, operating as a Micro-sun sensor, light entering the hole passes through the aperture to be sensed by the sensor apparatus. Additionally, light reflected by the sensor apparatus toward the first side of the silicon substrate is absorbed by the first metallic layer and silicon spikes and is thereby prevented from being reflected back toward the sensor apparatus.

  17. Anti-reflective device having an anti-reflective surface formed of silicon spikes with nano-tips

    NASA Technical Reports Server (NTRS)

    Bae, Youngsam (Inventor); Manohara, Harish (Inventor); Mobasser, Sohrab (Inventor); Lee, Choonsup (Inventor)

    2011-01-01

    Described is a device having an anti-reflection surface. The device comprises a silicon substrate with a plurality of silicon spikes formed on the substrate. A first metallic layer is formed on the silicon spikes to form the anti-reflection surface. The device further includes an aperture that extends through the substrate. A second metallic layer is formed on the substrate. The second metallic layer includes a hole that is aligned with the aperture. A spacer is attached with the silicon substrate to provide a gap between an attached sensor apparatus. Therefore, operating as a Micro-sun sensor, light entering the hole passes through the aperture to be sensed by the sensor apparatus. Additionally, light reflected by the sensor apparatus toward the first side of the silicon substrate is absorbed by the first metallic layer and silicon spikes and is thereby prevented from being reflected back toward the sensor apparatus.

  18. High resolution seismic imaging of Rainier Mesa using surface reflection and surface to tunnel tomography

    SciTech Connect

    Majer, E.L.; Johnson, L.R.; Karageorgi, E.K.; Peterson, J.E.

    1994-06-01

    In the interpretation of seismic data to infer properties of an explosion source, it is necessary to account for wave propagation effects. In order to understand and remove these propagation effects, it is necessary to have a model. An open question concerning this matter is the detail and accuracy which must be present in the velocity model in order to produce reliable estimates in the estimated source properties. While it would appear that the reliability of the results would be directly related to the accuracy of the velocity and density models used in the interpretation, it may be that certain deficiencies in these models can be compensated by the and amount of seismic data which is used in the inversion. The NPE provided an opportunity to test questions of this sort. In August 1993, two high resolution seismic experiments were performed in N-Tunnel and on the surface of Rainier Mesa above it. The first involved a surface-to-tunnel imaging experiment with sources on the surface and receivers in tunnel U12n.23 about 88 meters west of the NPE. It was possible to estimate the apparent average velocity between the tunnel and the surface. In a separate experiment, a high resolution reflection experiment was performed in order to image the lithology in Rainier Mesa. Good quality, broad band, reflections were obtained from depths extending into the Paleozoic basement. A high velocity layer near the surface is underlain by a thick section of low velocity material, providing a nonuniform but low average velocity between the depth of the NPE and the surface.

  19. Darkfield adapter for whole slide imaging: adapting a darkfield internal reflection illumination system to extend WSI applications.

    PubMed

    Kawano, Yoshihiro; Higgins, Christopher; Yamamoto, Yasuhito; Nyhus, Julie; Bernard, Amy; Dong, Hong-Wei; Karten, Harvey J; Schilling, Tobias

    2013-01-01

    We present a new method for whole slide darkfield imaging. Whole Slide Imaging (WSI), also sometimes called virtual slide or virtual microscopy technology, produces images that simultaneously provide high resolution and a wide field of observation that can encompass the entire section, extending far beyond any single field of view. For example, a brain slice can be imaged so that both overall morphology and individual neuronal detail can be seen. We extended the capabilities of traditional whole slide systems and developed a prototype system for darkfield internal reflection illumination (DIRI). Our darkfield system uses an ultra-thin light-emitting diode (LED) light source to illuminate slide specimens from the edge of the slide. We used a new type of side illumination, a variation on the internal reflection method, to illuminate the specimen and create a darkfield image. This system has four main advantages over traditional darkfield: (1) no oil condenser is required for high resolution imaging (2) there is less scatter from dust and dirt on the slide specimen (3) there is less halo, providing a more natural darkfield contrast image, and (4) the motorized system produces darkfield, brightfield and fluorescence images. The WSI method sometimes allows us to image using fewer stains. For instance, diaminobenzidine (DAB) and fluorescent staining are helpful tools for observing protein localization and volume in tissues. However, these methods usually require counter-staining in order to visualize tissue structure, limiting the accuracy of localization of labeled cells within the complex multiple regions of typical neurohistological preparations. Darkfield imaging works on the basis of light scattering from refractive index mismatches in the sample. It is a label-free method of producing contrast in a sample. We propose that adapting darkfield imaging to WSI is very useful, particularly when researchers require additional structural information without the use of

  20. Adaptive time steps in trajectory surface hopping simulations

    NASA Astrophysics Data System (ADS)

    Spörkel, Lasse; Thiel, Walter

    2016-05-01

    Trajectory surface hopping (TSH) simulations are often performed in combination with active-space multi-reference configuration interaction (MRCI) treatments. Technical problems may arise in such simulations if active and inactive orbitals strongly mix and switch in some particular regions. We propose to use adaptive time steps when such regions are encountered in TSH simulations. For this purpose, we present a computational protocol that is easy to implement and increases the computational effort only in the critical regions. We test this procedure through TSH simulations of a GFP chromophore model (OHBI) and a light-driven rotary molecular motor (F-NAIBP) on semiempirical MRCI potential energy surfaces, by comparing the results from simulations with adaptive time steps to analogous ones with constant time steps. For both test molecules, the number of successful trajectories without technical failures rises significantly, from 53% to 95% for OHBI and from 25% to 96% for F-NAIBP. The computed excited-state lifetime remains essentially the same for OHBI and increases somewhat for F-NAIBP, and there is almost no change in the computed quantum efficiency for internal rotation in F-NAIBP. We recommend the general use of adaptive time steps in TSH simulations with active-space CI methods because this will help to avoid technical problems, increase the overall efficiency and robustness of the simulations, and allow for a more complete sampling.

  1. Investigating the Impact of Formal Reflective Activities on Skill Adaptation in a Work-Related Instrumental Learning Setting

    ERIC Educational Resources Information Center

    Roessger, Kevin M.

    2013-01-01

    In work-related, instrumental learning contexts the role of reflective activities is unclear. Kolb's (1985) experiential learning theory and Mezirow's transformative learning theory (2000) predict skill-adaptation as a possible outcome. This prediction was experimentally explored by manipulating reflective activities and assessing participants'…

  2. Measurements of the reflection factor of flat ground surfaces

    NASA Technical Reports Server (NTRS)

    Ventres, C. S.; Myles, M. M.; Ver, I. L.

    1977-01-01

    Measurements are made of the reflection factors of asphalt, concrete, and sod at oblique angles of incidence. Initial measurements were carried out in an anechoic chamber to eliminate the effects of wind and temperature gradients. These were followed by measurements made outdoors over a wider frequency range. Data are presented for the magnitudes of the reflection factors of asphalt, concrete, and sod at angles of incidence of 38 deg and 45 deg.

  3. Special report, diffuse reflectivity of the lunar surface

    NASA Technical Reports Server (NTRS)

    Fastie, W. G.

    1972-01-01

    The far ultraviolet diffuse reflectivity of samples of lunar dust material is determined. Equipment for measuring the diffuse reflectivity of materials (e.g. paint samples) is already in existence and requires only minor modification for the proposed experiment which will include the measurement of the polarizing properties of the lunar samples. Measurements can be made as a function of both illumination angle and angle of observation.

  4. Speaker-Adaptive Speech Recognition Based on Surface Electromyography

    NASA Astrophysics Data System (ADS)

    Wand, Michael; Schultz, Tanja

    We present our recent advances in silent speech interfaces using electromyographic signals that capture the movements of the human articulatory muscles at the skin surface for recognizing continuously spoken speech. Previous systems were limited to speaker- and session-dependent recognition tasks on small amounts of training and test data. In this article we present speaker-independent and speaker-adaptive training methods which allow us to use a large corpus of data from many speakers to train acoustic models more reliably. We use the speaker-dependent system as baseline, carefully tuning the data preprocessing and acoustic modeling. Then on our corpus we compare the performance of speaker-dependent and speaker-independent acoustic models and carry out model adaptation experiments.

  5. Analysis for Mar Vel Black and acetylene soot low reflectivity surfaces for star tracker sunshade applications

    NASA Technical Reports Server (NTRS)

    Yung, E.

    1974-01-01

    Mar Vel Black is a revolutionary new extremely low reflectivity anodized coating developed by Martin Marietta of Denver. It is of great interest in optics in general, and in star trackers specifically because it can reduce extraneous light reflections. A sample of Mar Vel Black was evaluated. Mar Vel Black looks much like a super black surface with many small peaks and very steep sides so that any light incident upon the surface will tend to reflect many times before exiting that surface. Even a high reflectivity surface would thus appear to have a very low reflectivity under such conditions. Conversely, acetylene soot does not have the magnified surface appearance of a super black surface. Its performance is, however, predictable from the surface structure, considering the known configuration of virtually pure carbon.

  6. Understanding the changes of cone reflectance in adaptive optics flood illumination retinal images over three years.

    PubMed

    Mariotti, Letizia; Devaney, Nicholas; Lombardo, Giuseppe; Lombardo, Marco

    2016-07-01

    Although there is increasing interest in the investigation of cone reflectance variability, little is understood about its characteristics over long time scales. Cone detection and its automation is now becoming a fundamental step in the assessment and monitoring of the health of the retina and in the understanding of the photoreceptor physiology. In this work we provide an insight into the cone reflectance variability over time scales ranging from minutes to three years on the same eye, and for large areas of the retina (≥ 2.0 × 2.0 degrees) at two different retinal eccentricities using a commercial adaptive optics (AO) flood illumination retinal camera. We observed that the difference in reflectance observed in the cones increases with the time separation between the data acquisitions and this may have a negative impact on algorithms attempting to track cones over time. In addition, we determined that displacements of the light source within 0.35 mm of the pupil center, which is the farthest location from the pupil center used by operators of the AO camera to acquire high-quality images of the cone mosaic in clinical studies, does not significantly affect the cone detection and density estimation.

  7. Understanding the changes of cone reflectance in adaptive optics flood illumination retinal images over three years.

    PubMed

    Mariotti, Letizia; Devaney, Nicholas; Lombardo, Giuseppe; Lombardo, Marco

    2016-07-01

    Although there is increasing interest in the investigation of cone reflectance variability, little is understood about its characteristics over long time scales. Cone detection and its automation is now becoming a fundamental step in the assessment and monitoring of the health of the retina and in the understanding of the photoreceptor physiology. In this work we provide an insight into the cone reflectance variability over time scales ranging from minutes to three years on the same eye, and for large areas of the retina (≥ 2.0 × 2.0 degrees) at two different retinal eccentricities using a commercial adaptive optics (AO) flood illumination retinal camera. We observed that the difference in reflectance observed in the cones increases with the time separation between the data acquisitions and this may have a negative impact on algorithms attempting to track cones over time. In addition, we determined that displacements of the light source within 0.35 mm of the pupil center, which is the farthest location from the pupil center used by operators of the AO camera to acquire high-quality images of the cone mosaic in clinical studies, does not significantly affect the cone detection and density estimation. PMID:27446708

  8. Understanding the changes of cone reflectance in adaptive optics flood illumination retinal images over three years

    PubMed Central

    Mariotti, Letizia; Devaney, Nicholas; Lombardo, Giuseppe; Lombardo, Marco

    2016-01-01

    Although there is increasing interest in the investigation of cone reflectance variability, little is understood about its characteristics over long time scales. Cone detection and its automation is now becoming a fundamental step in the assessment and monitoring of the health of the retina and in the understanding of the photoreceptor physiology. In this work we provide an insight into the cone reflectance variability over time scales ranging from minutes to three years on the same eye, and for large areas of the retina (≥ 2.0 × 2.0 degrees) at two different retinal eccentricities using a commercial adaptive optics (AO) flood illumination retinal camera. We observed that the difference in reflectance observed in the cones increases with the time separation between the data acquisitions and this may have a negative impact on algorithms attempting to track cones over time. In addition, we determined that displacements of the light source within 0.35 mm of the pupil center, which is the farthest location from the pupil center used by operators of the AO camera to acquire high-quality images of the cone mosaic in clinical studies, does not significantly affect the cone detection and density estimation. PMID:27446708

  9. The theoretical reflectance of X-rays from optical surfaces

    NASA Technical Reports Server (NTRS)

    Neergaard, J. R.; Reynolds, J. M.; Fields, S. A.

    1976-01-01

    The theoretical reflectance of X-rays from various materials and evaporated films is presented. A computer program was written that computes the reflected intensity as a function of the angle of the incident radiation. The quantities necessary to generate the efficiency and their effect on the data are demonstrated. Five materials were chosen for evaluation: (1) fused silica, (2) chromium, (3) beryllium, (4) gold, and (5) a thin layer contaminant. Fused silica is a versatile and common material; chromium has high reflection efficiency at X-ray wavelengths and is in the middle of the atomic number range; beryllium contains a single atomic shell and has a low range atomic number; gold contains multiple atomic shells and has a high atomic number; the contaminant is treated as a thin film in the calculations and results are given as a function of thickness for selected wavelengths. The theoretical results are compared to experimental data at lambda = 8.34 A.

  10. Reflectance of Antarctic surfaces from multispectral radiometers: The correction of atmospheric effects

    SciTech Connect

    Zibordi, G. ); Maracci, G. )

    1993-01-01

    Monitoring reflectance of polar icecaps has relevance in climate studies. In fact, climate changes produce variations in the morphology of ice and snow covers, which are detectable as surface reflectance change. Surface reflectance can be retrieved from remotely sensed data. However, absolute values independent of atmospheric turbidity and surface altitude can only be obtained after removing masking effects of the atmosphere. An atmospheric correction model, accounting for surface and sensor altitudes above sea level, is described and validated through data detected over Antarctic surfaces with a Barnes Modular Multispectral Radiometer having bands overlapping those of the Landsat Thematic Mapper. The model is also applied in a sensitivity analysis to investigate error induced in reflectance obtained from satellite data by indeterminacy in optical parameters of atmospheric constituents. Results show that indeterminacy in the atmospheric water vapor optical thickness is the main source of nonaccuracy in the retrieval of surface reflectance from data remotely sensed over Antarctic regions.

  11. Photodetachment Spectrum of Hydrogen Negative Ion Near a Partially Reflecting Spherical Surface

    NASA Astrophysics Data System (ADS)

    Afaq, A.; Iqbal, Azmat; Rahman, Amin Ur; Khan, Naveed; Aleem, Fazal-e.-; Ansari, M. Mushraf

    2016-10-01

    Photodetachment of negative ions near surfaces is of great interest in view of its fundamental significance and technological applications. We reinvestigate the dynamics of photoelectrons in H - photodetachment near a partially reflecting spherical surface by the semiclassical closed-orbit theory. Reflection parameter R and curvature K is used to observe inelastic and spherical effects of the surface, respectively. The classical action is evaluated from the photodetached electron trajectories incident normally at the surface, arising simultaneously from the source and its image. The derived analytical formula of photodetachment cross section correctly recovers the results of reflective spherical surface published recently based on theoretical imaging method.

  12. 3DSEM++: Adaptive and intelligent 3D SEM surface reconstruction.

    PubMed

    Tafti, Ahmad P; Holz, Jessica D; Baghaie, Ahmadreza; Owen, Heather A; He, Max M; Yu, Zeyun

    2016-08-01

    Structural analysis of microscopic objects is a longstanding topic in several scientific disciplines, such as biological, mechanical, and materials sciences. The scanning electron microscope (SEM), as a promising imaging equipment has been around for decades to determine the surface properties (e.g., compositions or geometries) of specimens by achieving increased magnification, contrast, and resolution greater than one nanometer. Whereas SEM micrographs still remain two-dimensional (2D), many research and educational questions truly require knowledge and facts about their three-dimensional (3D) structures. 3D surface reconstruction from SEM images leads to remarkable understanding of microscopic surfaces, allowing informative and qualitative visualization of the samples being investigated. In this contribution, we integrate several computational technologies including machine learning, contrario methodology, and epipolar geometry to design and develop a novel and efficient method called 3DSEM++ for multi-view 3D SEM surface reconstruction in an adaptive and intelligent fashion. The experiments which have been performed on real and synthetic data assert the approach is able to reach a significant precision to both SEM extrinsic calibration and its 3D surface modeling. PMID:27200484

  13. 3DSEM++: Adaptive and intelligent 3D SEM surface reconstruction.

    PubMed

    Tafti, Ahmad P; Holz, Jessica D; Baghaie, Ahmadreza; Owen, Heather A; He, Max M; Yu, Zeyun

    2016-08-01

    Structural analysis of microscopic objects is a longstanding topic in several scientific disciplines, such as biological, mechanical, and materials sciences. The scanning electron microscope (SEM), as a promising imaging equipment has been around for decades to determine the surface properties (e.g., compositions or geometries) of specimens by achieving increased magnification, contrast, and resolution greater than one nanometer. Whereas SEM micrographs still remain two-dimensional (2D), many research and educational questions truly require knowledge and facts about their three-dimensional (3D) structures. 3D surface reconstruction from SEM images leads to remarkable understanding of microscopic surfaces, allowing informative and qualitative visualization of the samples being investigated. In this contribution, we integrate several computational technologies including machine learning, contrario methodology, and epipolar geometry to design and develop a novel and efficient method called 3DSEM++ for multi-view 3D SEM surface reconstruction in an adaptive and intelligent fashion. The experiments which have been performed on real and synthetic data assert the approach is able to reach a significant precision to both SEM extrinsic calibration and its 3D surface modeling.

  14. Adaptive surface meshing and multiresolution terrain depiction for SVS

    NASA Astrophysics Data System (ADS)

    Wiesemann, Thorsten; Schiefele, Jens; Kubbat, Wolfgang

    2001-08-01

    Many of today's and tomorrow's aviation applications demand accurate and reliable digital terrain elevation databases. Particularly future Vertical Cut Displays or 3D Synthetic Vision Systems (SVS) require accurate and hi-resolution data to offer a reliable terrain depiction. On the other hand, optimized or reduced terrain models are necessary to ensure real-time rendering and computing performance. In this paper a new method for adaptive terrain meshing and depiction for SVS is presented. The initial data set is decomposed by using a wavelet transform. By examining the wavelet coefficients, an adaptive surface approximation for various Level-of-Detail is determined. Additionally, the dyadic scaling of the wavelet transform is used to build a hierarchical quad-tree representation for the terrain data. This representation enhances fast interactive computations and real-time rendering methods. The proposed terrain representation is integrated into a standard navigation display. Due to the multi-resolution data organization, terrain depiction e.g. resolution is adaptive to a selected zooming level or flight phase. Moreover, the wavelet decomposition helps to define local regions of interest. A depicted terrain resolution has a finer grain nearby the current airplane position and gets coarser with increasing aircraft distance. In addition, flight critical regions can be depicted in a higher resolution.

  15. Scalable Lunar Surface Networks and Adaptive Orbit Access

    NASA Technical Reports Server (NTRS)

    Wang, Xudong

    2015-01-01

    Teranovi Technologies, Inc., has developed innovative network architecture, protocols, and algorithms for both lunar surface and orbit access networks. A key component of the overall architecture is a medium access control (MAC) protocol that includes a novel mechanism of overlaying time division multiple access (TDMA) and carrier sense multiple access with collision avoidance (CSMA/CA), ensuring scalable throughput and quality of service. The new MAC protocol is compatible with legacy Institute of Electrical and Electronics Engineers (IEEE) 802.11 networks. Advanced features include efficiency power management, adaptive channel width adjustment, and error control capability. A hybrid routing protocol combines the advantages of ad hoc on-demand distance vector (AODV) routing and disruption/delay-tolerant network (DTN) routing. Performance is significantly better than AODV or DTN and will be particularly effective for wireless networks with intermittent links, such as lunar and planetary surface networks and orbit access networks.

  16. Experimental study of influence of smooth surface reflectance and diffuse reflectance on estimation of root mean square roughness.

    PubMed

    Mendeleyev, V Ya; Skovorodko, S N

    2011-03-28

    To estimate the root mean square roughness (σ) of a surface from reflected power, it is necessary to know the diffuse reflectance (DR) and the reflectance (SSR) of a smooth surface made from the same material as the rough surface. In our study, σ is estimated from value of power reflected from one-dimensionally rough steel surfaces in the specular direction without considering SSR and DR. An expression describing dependence of an error of the estimation on SSR and DR is derived. Linear polarized light with λ=660 nm and the azimuth of polarization of 49° was used in the experiment. The angle of incidence was varied from 30° to 74°. It was found that absolute relative errors caused by influence of SSR and DR are smaller than 0.03 in the angular ranges of 46-54° and 30-58° for σ=10.2 nm and σ = 49.8 nm, respectively. Out of these ranges, SSR is the main reason for the errors lying in the wide range of ~0.05-2.5.

  17. Light Reflection from Water Surfaces Perturbed by Falling Rain Droplets

    ERIC Educational Resources Information Center

    Molesini, Giuseppe; Vannoni, Maurizio

    2009-01-01

    An account of peculiar light patterns produced by reflection in a pool under falling rain droplets was recently reported by Molesini and Vannoni (2008 Eur. J. Phys. 29 403-11). The mathematical approach, however, only covered the case of a symmetrical location of a light source and the observer's eyes with respect to the vertical of the falling…

  18. Acoustical imaging of spheres above a reflecting surface

    NASA Astrophysics Data System (ADS)

    Chambers, David; Berryman, James

    2003-04-01

    An analytical study using the MUSIC method of subspace imaging is presented for the case of spheres above a reflecting boundary. The field scattered from the spheres and the reflecting boundary is calculated analytically, neglecting interactions between spheres. The singular value decomposition of the response matrix is calculated and the singular vectors divided into signal and noise subspaces. Images showing the estimated sphere locations are obtained by backpropagating the noise vectors using either the free space Green's function or the Green's function that incorporates reflections from the boundary. We show that the latter Green's function improves imaging performance after applying a normalization that compensates for the interference between direct and reflected fields. We also show that the best images are attained in some cases when the number of singular vectors in the signal subspace exceeds the number of spheres. This is consistent with previous analysis showing multiple eigenvalues of the time reversal operator for spherical scatterers [Chambers and Gautesen, J. Acoust. Soc. Am. 109 (2001)]. [Work performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.

  19. Characterization of Surface Reflectance Variation Effects on Remote Sensing

    NASA Technical Reports Server (NTRS)

    Pearce, W. A.

    1984-01-01

    The use of Monte Carlo radiative transfer codes to simulate the effects on remote sensing in visible and infrared wavelengths of variables which affect classification is examined. These variables include detector viewing angle, atmospheric aerosol size distribution, aerosol vertical and horizontal distribution (e.g., finite clouds), the form of the bidirectional ground reflectance function, and horizontal variability of reflectance type and reflectivity (albedo). These simulations are used to characterize the sensitivity of observables (intensity and polarization) to variations in the underlying physical parameters both to improve algorithms for the removal of atmospheric effects and to identify techniques which can improve classification accuracy. It was necessary to revise and validate the simulation codes (CTRANS, ARTRAN, and the Mie scattering code) to improve efficiency and accommodate a new operational environment, and to build the basic software tools for acquisition and off-line manipulation of simulation results. Initial calculations compare cases in which increasing amounts of aerosol are shifted into the stratosphere, maintaining a constant optical depth. In the case of moderate aerosol optical depth, the effect on the spread function is to scale it linearly as would be expected from a single scattering model. Varying the viewing angle appears to provide the same qualitative effect as modifying the vertical optical depth (for Lambertian ground reflectance).

  20. Low-reflectance laser-induced surface nanostructures created with a picosecond laser

    NASA Astrophysics Data System (ADS)

    Sarbada, Shashank; Huang, Zhifeng; Shin, Yung C.; Ruan, Xiulin

    2016-04-01

    Using high-speed picosecond laser pulse irradiation, low-reflectance laser-induced periodic surface structures (LIPSS) have been created on polycrystalline silicon. The effects of laser fluence, scan speed, overlapping ratio and polarization angle on the formation of LIPSS are reported. The anti-reflective properties of periodic structures are discussed, and the ideal LIPSS for low surface reflectance is presented. A decrease of 35.7 % in average reflectance of the silicon wafer was achieved over the wavelength range of 400-860 nm when it was textured with LIPSS at high scan speeds of 4000 mm/s. Experimental results of broadband reflectance of silicon wafers textured with LIPSS have been compared with finite difference time domain simulations and are in good agreement, showing high predictability in reflectance values for different structures. The effects of changing the LIPSS profile, fill factor and valley depth on the surface reflectance were also analyzed through simulations.

  1. Socio-cultural reflections on heat in Australia with implications for health and climate change adaptation

    PubMed Central

    Banwell, Cathy; Dixon, Jane; Bambrick, Hilary; Edwards, Ferne; Kjellström, Tord

    2012-01-01

    Background Australia has a hot climate with maximum summer temperatures in its major cities frequently exceeding 35°C. Although ‘heat waves’ are an annual occurrence, the associated heat-related deaths among vulnerable groups, such as older people, suggest that Australians could be better prepared to deal with extreme heat. Objective To understand ways in which a vulnerable sub-population adapt their personal behaviour to cope with heat within the context of Australians’ relationship with heat. Design We draw upon scientific, historical and literary sources and on a set of repeat interviews in the suburbs of Western Sydney with eight older participants and two focus group discussions. We discuss ways in which this group of older people modifies their behaviour to adapt to heat, and reflect on manifestations of Australians’ ambivalence towards heat. Results Participants reported a number of methods for coping with extreme heat, including a number of methods of personal cooling, changing patterns of daily activity and altering dietary habits. The use of air-conditioning was near universal, but with recognition that increasing energy costs may become more prohibitive over time. Conclusions While a number of methods are employed by older people to stay cool, these may become limited in the future. Australians’ attitudes may contribute to the ill-health and mortality associated with excessive heat. PMID:23078748

  2. Testing the spectrum of infrared emission reflected by several surfaces with a FTIR

    NASA Astrophysics Data System (ADS)

    Wang, Xuanyu; Hu, Rui; Pang, Minhui; Bai, Haitao; Dong, Wenjie

    2014-09-01

    A set of sectional FTIR is applied to study the reflecting characteristics of several surfaces to infrared emission. The standard infrared source is separated from the host of the FTIR and set in a right-angled triangle with the reflecting plate and the entrance to make the reflecting infrared emission can easily pass into the detector through the route. The reflecting infrared emission from the FTIR source is measured by the FTIR detector. The reflecting plate includes metal plate, mirror, wood block and so on. A high intensity standard infrared source cooled by air is accepted and the testing background is atmosphere. The infrared emission reflected by the plate from the standard source is tested one by one. By the experiment, mirror has a good performance to reflect infrared emission, which is much better than unpainted iron plate or painted wood block. Certainly, unpainted iron plate has stronger capacity to reflect infrared emission than painted wood block, etc. As a result, the smoother the surface is, the stronger the reflecting performance is. The reflecting performance of painted surface to infrared emission is poorer than unpainted one. The various painted surfaces have not a visible difference upon their reflecting performance to infrared emission although they are made from different materials.

  3. Creating and maintaining dialogue on climate information - Reflections on the adaptation process in Sweden

    NASA Astrophysics Data System (ADS)

    Nilsson, C.

    2010-09-01

    Climate information can be communicated in many ways to various actors within society. Dialogue as a means to communicate is often emphasised as an important tool to deliver and receive information. However, a dialogue can be initiated and maintained in many different ways. In Sweden the Swedish Meteorological and Hydrological Institute, SMHI, can be seen as one of the actors in between the climate science experts and the society, and together with the Swedish Geotechnical Institute, SGI, they had recognised that the County Administrative Boards required climate information and knowledge in how to use and how not to use climate scenarios in order to start coordinating regional adaptation activities. At the same time the National Authorities called for a more detailed compilation on the needs in the counties, regarding climate information for decision making. Together the SMHI and SGI visited the 21 counties in Sweden with a start in the autumn of 2008, initiating a dialogue with the County Administrative Boards. The process continued with a first seminar in springtime 2009, on adaptation. In spring 2009 the County Administrative Boards were appointed as the formal foci of adaptation coordination in Sweden, and a new phase in the dialogue started, when the counties had specific goals with the interaction. Personal visits and seminars have continued to be the arena for the dialogue, and new climate information products have been initiated as a response to the interaction. Here, reflections are presented on the role of the dialogue in Sweden as a tool towards a sustainable way to communicate climate information.

  4. Towards GPS Surface Reflection Remote Sensing of Sea Ice Conditions

    NASA Technical Reports Server (NTRS)

    Komjathy, A.; Maslanik, J. A.; Zavorotny, V. U.; Axelrad, P.; Katzberg, S. J.

    2000-01-01

    This paper describes the research to extend the application of Global Positioning System (GPS) signal reflections, received by airborne instruments, to cryospheric remote sensing. The characteristics of the GPS signals and equipment afford the possibility of new measurements not possible with existing radar and passive microwave systems. In particular, the GPS receiving systems are small and light-weight, and as such are particularly well suited to be deployed on small aircraft or satellite platforms with minimal impact. Our preliminary models and experimental results indicate that reflected GPS signals have potential to provide information on the presence and condition of sea and fresh-water ice as well as the freeze/thaw state of frozen ground. In this paper we show results from aircraft experiments over the ice pack near Barrow, Alaska suggesting correlation between forward scattered GPS returns and RADARSAT backscattered signals.

  5. Spectral reflectance of surface soils - A statistical analysis

    NASA Technical Reports Server (NTRS)

    Crouse, K. R.; Henninger, D. L.; Thompson, D. R.

    1983-01-01

    The relationship of the physical and chemical properties of soils to their spectral reflectance as measured at six wavebands of Thematic Mapper (TM) aboard NASA's Landsat-4 satellite was examined. The results of performing regressions of over 20 soil properties on the six TM bands indicated that organic matter, water, clay, cation exchange capacity, and calcium were the properties most readily predicted from TM data. The middle infrared bands, bands 5 and 7, were the best bands for predicting soil properties, and the near infrared band, band 4, was nearly as good. Clustering 234 soil samples on the TM bands and characterizing the clusters on the basis of soil properties revealed several clear relationships between properties and reflectance. Discriminant analysis found organic matter, fine sand, base saturation, sand, extractable acidity, and water to be significant in discriminating among clusters.

  6. Plasma generation for controlled microwave-reflecting surfaces in plasma antennas

    SciTech Connect

    Bliokh, Yury P.; Felsteiner, Joshua; Slutsker, Yakov Z.

    2014-04-28

    The idea of replacing metal antenna elements with equivalent plasma objects has long been of interest because of the possibility of switching the antenna on and off. In general, two kinds of designs have so far been reported: (a) Separate plasma “wires” which are thin glass tubes filled with gas, where plasma appears due to discharge inside. (b) Reflecting surfaces, consisting of tightly held plasma wires or specially designed large discharge devices with magnetic confinement. The main disadvantages of these antennas are either large weight and size or too irregular surfaces for proper reflection. To design a microwave plasma antenna in the most common radar wavelength range of 1–3 cm with a typical gain of 30 dB, a smooth plasma mirror having a 10–30 cm diameter and a proper curvature is required. The plasma density must be 10{sup 12}–10{sup 14} cm{sup −3} in order to exceed the critical density for the frequency of the electromagnetic wave. To achieve this we have used a ferromagnetic inductively coupled plasma (FICP) source, where a thin magnetic core of a large diameter is fully immersed in the plasma. In the present paper, we show a way to adapt the FICP source for creating a flat switchable microwave plasma mirror with an effective diameter of 30 cm. This mirror was tested as a microwave reflector and there was found no significant difference when compared with a copper plate having the same diameter.

  7. Arrival-time fluctuations of coherent reflections from surface gravity water waves.

    PubMed

    Badiey, Mohsen; Eickmeier, Justin; Song, Aijun

    2014-05-01

    Arrival time fluctuations of coherent reflections from surface gravity waves are examined. A two-dimensional ray model with an evolving rough sea surface is used to explain the mechanism and formation of the deterministic striation patterns due to the surface reflection. Arrival time predictions from the ray model match qualitatively well with the measurements from bidirectional acoustic transmissions in a water depth of 100 m. PMID:24815293

  8. Arrival-time fluctuations of coherent reflections from surface gravity water waves.

    PubMed

    Badiey, Mohsen; Eickmeier, Justin; Song, Aijun

    2014-05-01

    Arrival time fluctuations of coherent reflections from surface gravity waves are examined. A two-dimensional ray model with an evolving rough sea surface is used to explain the mechanism and formation of the deterministic striation patterns due to the surface reflection. Arrival time predictions from the ray model match qualitatively well with the measurements from bidirectional acoustic transmissions in a water depth of 100 m.

  9. Spectral reflectance of surface soils: Relationships with some soil properties

    NASA Technical Reports Server (NTRS)

    Kiesewetter, C. H.

    1983-01-01

    Using a published atlas of reflectance curves and physicochemical properties of soils, a statistical analysis was carried out. Reflectance bands which correspond to five of the wavebands used by NASA's Thematic Mapper were examined for relationships to specific soil properties. The properties considered in this study include: Sand Content, Silt Content, Clay Content, Organic Matter Content, Cation Exchange Capacity, Iron Oxide Content and Moisture Content. Regression of these seven properties on the mean values of five TM bands produced results that indicate that the predictability of the properties can be increased by stratifying the data. The data was stratified by parent material, taxonomic order, temperature zone, moisture zone and climate (combined temperature and moisture). The best results were obtained when the sample was examined by climatic classes. The middle Infra-red bands, 5 and 7, as well as the visible bands, 2 and 3, are significant in the model. The near Infra-red band, band 4, is almost as useful and should be included in any studies. General linear modeling procedures examined relationships of the seven properties with certain wavebands in the stratified samples.

  10. A Harmonized Landsat-Sentinel-2 Surface Reflectance product: a resource for Agricultural Monitoring

    NASA Astrophysics Data System (ADS)

    Masek, J. G.; Claverie, M.; Ju, J.; Vermote, E.; Justice, C. O.

    2015-12-01

    The combination of Landsat and Sentinel-2 data offers a unique opportunity to observe globally the land every 2-3 days at medium (<30m) spatial resolution. The Harmonized Landsat-Sentinel-2 (HLS) project is a NASA initiative aiming to produce surface reflectance data from Landsat and Sentinel-2 missions and to deliver them to the community in a combined, seamless form. The HLS will be beneficial for global agricultural monitoring applications that require medium spatial resolution and weekly or more frequent observations. In particular, the provided opportunity to track crop phenology at the scale of individual fields will support detailed mapping of crop type and type-specific vegetation conditions. To create a compatible set of radiometric measurements, the HLS product relies on rigorous pre- and post-launch cross-calibration (Landsat-8 OLI and Sentinel-2 MSI) activities. The processing chain includes the following components: atmospheric correction, cloud/shadow masking, nadir BRDF-adjustment, spectral-adjustment, regridding, and temporal composite. The atmospheric correction and cloud masking is based on the OLI atmospheric correction developed at NASA-GSFC and has been adapted to the MSI data. The BRDF-adjustment is based on a disaggregation technique using MODIS-based BRDF coefficients. The technique has been evaluated using the multi-angular acquisition from the SPOT 4 and 5 (Take5) experiments. The spectral-adjustment relies on a linear regression that has been calibrated and evaluated using synthetic data and surface reflectance processed from a large number of hyperspectral EO-1 Hyperion scenes. Finally, significant effort is placed on product validation and evaluation. The delivered data set will include surface reflectance products at different levels: Using the native gridding, i.e. UTM, 30m for Landsat-8, and UTM, 10-20m for Sentinel-2 Using a common global gridding (Sinusoidal, 30m) Temporal composite (Sinusoidal, 30m, 5-day) During the first year of

  11. Adaptive integral dynamic surface control of a hypersonic flight vehicle

    NASA Astrophysics Data System (ADS)

    Aslam Butt, Waseem; Yan, Lin; Amezquita S., Kendrick

    2015-07-01

    In this article, non-linear adaptive dynamic surface air speed and flight path angle control designs are presented for the longitudinal dynamics of a flexible hypersonic flight vehicle. The tracking performance of the control design is enhanced by introducing a novel integral term that caters to avoiding a large initial control signal. To ensure feasibility, the design scheme incorporates magnitude and rate constraints on the actuator commands. The uncertain non-linear functions are approximated by an efficient use of the neural networks to reduce the computational load. A detailed stability analysis shows that all closed-loop signals are uniformly ultimately bounded and the ? tracking performance is guaranteed. The robustness of the design scheme is verified through numerical simulations of the flexible flight vehicle model.

  12. X-ray reflectivity measurements of surface roughness using energy dispersive detection

    SciTech Connect

    Chason, E.; Warwick, D.T.

    1990-01-01

    We describe a new technique for measuring x-ray reflectivity using energy dispersive x-ray detection. The benefits of this method are the use of a fixed scattering angle and parallel detection of all energies simultaneously. These advantages make the technique more readily useable with laboratory x-ray sources and more compatible with growth chambers. We find excellent agreement between the calculated Fresnel reflectivity and the reflectivity obtained from a smooth Ge (001) surface. Reflectivities obtained during 500 eV Xe ion bombardment of Ge surfaces demonstrate the sensitivity of the technique to be better than 1 {angstrom}. 9 refs., 4 figs.

  13. Polarization of the reflectivity of paints and other rough surfaces in the infrared

    NASA Astrophysics Data System (ADS)

    Oppenheim, Uri P.; Feiner, Yoram

    1995-04-01

    In this study the IR reflectivity of painted and rough surfaces was investigated, and an attempt was made to represent the surfaces by a complex refractive index. A CO2 laser was used as a collimated source in the thermal IR region, and the polarization properties of reflected radiation were measured. The samples chosen were flat surfaces of sandblasted aluminum, concrete, painted metal, and asphalt. Values of the bidirectional reflectance function were obtained in the two orthogonal states of polarization, based on sulfur as the Lambertian standard. Many samples, such as painted metals, showed specular behavior and could be characterized by Fresnel equations. For some of these surfaces optical constants were calculated from the reflectivity measurements. Good agreement was obtained between the calculated and measured values of the percent of polarization for these surfaces.

  14. Polarization of the reflectivity of paints and other rough surfaces in the infrared.

    PubMed

    Oppenheim, U P; Feiner, Y

    1995-04-01

    In this study the IR reflectivity of painted and rough surfaces was investigated, and an attempt was made to represent the surfaces by a complex refractive index. A CO(2) laser was used as a collimated source in the thermal IR region, and the polarization properties of reflected radiation were measured. The samples chosen were flat surfaces of sandblasted aluminum, concrete, painted metal, and asphalt. Values of the bidirectional reflectance function were obtained in the two orthogonal states of polarization, based on sulfur as the Lambertian standard. Many samples, such as painted metals, showed specular behavior and could be characterized by Fresnel equations. For some of these surfaces optical constants were calculated from the reflectivity measurements. Good agreement was obtained between the calculated and measured values of the percent of polarization for these surfaces.

  15. Polarization of the reflectivity of paints and other rough surfaces in the infrared.

    PubMed

    Oppenheim, U P; Feiner, Y

    1995-04-01

    In this study the IR reflectivity of painted and rough surfaces was investigated, and an attempt was made to represent the surfaces by a complex refractive index. A CO(2) laser was used as a collimated source in the thermal IR region, and the polarization properties of reflected radiation were measured. The samples chosen were flat surfaces of sandblasted aluminum, concrete, painted metal, and asphalt. Values of the bidirectional reflectance function were obtained in the two orthogonal states of polarization, based on sulfur as the Lambertian standard. Many samples, such as painted metals, showed specular behavior and could be characterized by Fresnel equations. For some of these surfaces optical constants were calculated from the reflectivity measurements. Good agreement was obtained between the calculated and measured values of the percent of polarization for these surfaces. PMID:21037709

  16. Analysis of ground reflection of jet noise obtained with various microphone arrays over an asphalt surface

    NASA Technical Reports Server (NTRS)

    Miles, J. H.

    1975-01-01

    Ground reflection effects on the propagation of jet noise over an asphalt surface are discussed for data obtained using a 33.02 cm (13-in.) diameter nozzle with microphones at several heights and distances from the nozzle axis. Analysis of ground reflection effects is accomplished using the concept of a reflected signal transfer function which represents the influence of both the reflecting surface and the atmosphere on the propagation of the reflected signal in a mathematical model. The mathematical model used as a basis for the computer program was successful in significantly reducing the ground reflection effects. The range of values of the single complex number used to define the reflected signal transfer function was larger than expected when determined only by the asphalt surface. This may indicate that the atmosphere is affecting the propagation of the reflected signal more than the asphalt surface. Also discussed is the selective placement of the reinforcements and cancellations in the design of an experiment to minimize ground reflection effects.

  17. Surface layering and melting in an ionic liquid studied by resonant soft X-ray reflectivity

    PubMed Central

    Mezger, Markus; Ocko, Benjamin M.; Reichert, Harald; Deutsch, Moshe

    2013-01-01

    The molecular-scale structure of the ionic liquid [C18mim]+[FAP]− near its free surface was studied by complementary methods. X-ray absorption spectroscopy and resonant soft X-ray reflectivity revealed a depth-decaying near-surface layering. Element-specific interfacial profiles were extracted with submolecular resolution from energy-dependent soft X-ray reflectivity data. Temperature-dependent hard X-ray reflectivity, small- and wide-angle X-ray scattering, and infrared spectroscopy uncovered an intriguing melting mechanism for the layered region, where alkyl chain melting drove a negative thermal expansion of the surface layer spacing. PMID:23431181

  18. (Synchrotron studies of x-ray reflectivity from surfaces)

    SciTech Connect

    Pershan, P.S.

    1992-03-03

    Following a long period of theoretical interest, but only limited measurements, there has recently been an increased number of attempts to expand the relative paucity of experimental information on the structure of liquid surfaces using techniques as diverse as ellipsometry, micro-force balances, non-linear optics, Auger and photoelectron spectroscopy, and x-ray scattering. Our group has played a leading role in the currently expanding application of scattering techniques to the general problem of characterizing the microscopic structure of liquid surfaces and we propose here that this work be extended specifically to liquid metals. In the following sections we will briefly describe the salient features of x-ray scattering that are relevant to the current project, the progress that we have made in the current grant period and the work that we propose to carry out in the forthcoming grant period.

  19. Surface Reflectance of Mars Observed by CRISM-MRO: 1. Multi-angle Approach for Retrieval of Surface Reflectance from CRISM Observations (mars-reco)

    NASA Technical Reports Server (NTRS)

    Ceamanos, Xavier; Doute, S.; Fernando, J.; Pinet, P.; Lyapustin, A.

    2013-01-01

    This article addresses the correction for aerosol effects in near-simultaneous multiangle observations acquired by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) aboard the Mars Reconnaissance Orbiter. In the targeted mode, CRISM senses the surface of Mars using 11 viewing angles, which allow it to provide unique information on the scattering properties of surface materials. In order to retrieve these data, however, appropriate strategies must be used to compensate the signal sensed by CRISM for aerosol contribution. This correction is particularly challenging as the photometric curve of these suspended particles is often correlated with the also anisotropic photometric curve of materials at the surface. This article puts forward an innovative radiative transfer based method named Multi-angle Approach for Retrieval of Surface Reflectance from CRISM Observations (MARS-ReCO). The proposed method retrieves photometric curves of surface materials in reflectance units after removing aerosol contribution. MARS-ReCO represents a substantial improvement regarding previous techniques as it takes into consideration the anisotropy of the surface, thus providing more realistic surface products. Furthermore, MARS-ReCO is fast and provides error bars on the retrieved surface reflectance. The validity and accuracy of MARS-ReCO is explored in a sensitivity analysis based on realistic synthetic data. According to experiments, MARS-ReCO provides accurate results (up to 10 reflectance error) under favorable acquisition conditions. In the companion article, photometric properties of Martian materials are retrieved using MARS-ReCO and validated using in situ measurements acquired during the Mars Exploration Rovers mission.

  20. Separation of surface and bulk reflectance by absorption of bulk scattered light.

    PubMed

    Johansson, Niklas; Neuman, Magnus; Andersson, Mattias; Edström, Per

    2013-07-01

    A method is proposed for separating light reflected from turbid media with a rough surface into a bulk and a surface component. Dye is added to the sample, thereby increasing absorption and canceling bulk scattering. The remaining reflected light is surface reflectance, which can be subtracted from the total reflectance of an undyed sample to obtain the bulk component. The method is applied to paper where the addition of dye is accomplished by inkjet printing. The results show that the bulk scattered light is efficiently canceled, and that both the spectrally neutral surface reflectance and the surface topography of the undyed paper is maintained. The proposed method is particularly suitable for characterization of dielectric, highly randomized materials with significant bulk reflectance and rough surfaces, which are difficult to analyze with existing methods. A reliable separation method opens up for new ways of analyzing, e.g., biological tissues and optical coatings, and is also a valuable tool in the development of more comprehensive reflectance models.

  1. SO2 frost - UV-visible reflectivity and Io surface coverage

    NASA Technical Reports Server (NTRS)

    Nash, D. B.; Fanale, F. P.; Nelson, R. M.

    1980-01-01

    The reflectance spectrum in the range 0.24-0.85 microns of SO2 frost is measured in light of the discovery of SO2 gas in the atmosphere of Io and the possible discovery of the frost on its surface. Frost deposits up to 1.5 mm thick were grown in vacuum at 130 K and bi-directional reflectance spectra were obtained. Typical SO2 frost is found to exhibit very low reflectivity (2-5%) at 0.30 microns, rising steeply at 0.32 microns to attain a maximum reflectivity (75-80%) at 4.0 microns and uniformly high reflectivity throughout the visible and near infrared. Comparison with the full disk spectrum of Io reveals that no more than 20% of the surface can be covered with optically thick SO2 frost. Combinations of surface materials including SO2 frost which can produce the observed spectrum are indicated.

  2. Oxidation-resistant reflective surfaces for solar dynamic power generation in near earth orbit

    NASA Technical Reports Server (NTRS)

    Gulino, Daniel A.; Egger, Robert A.; Banholzer, William F.

    1987-01-01

    Reflective surfaces for Space Station power generation systems are required to withstand the atomic oxygen-dominated environment of near earth orbit. Thin films of platinum and rhodium, which are corrosion resistant reflective metals, have been deposited by ion beam sputter deposition onto various substrate materials. Solar reflectances were then measured as a function of time of exposure to a RF-generated air plasma.

  3. A Universal Dynamic Threshold Cloud Detection Algorithm (UDTCDA) supported by a prior surface reflectance database

    NASA Astrophysics Data System (ADS)

    Sun, Lin; Wei, Jing; Wang, Jian; Mi, Xueting; Guo, Yamin; Lv, Yang; Yang, Yikun; Gan, Ping; Zhou, Xueying; Jia, Chen; Tian, Xinpeng

    2016-06-01

    Conventional cloud detection methods are easily affected by mixed pixels, complex surface structures, and atmospheric factors, resulting in poor cloud detection results. To minimize these problems, a new Universal Dynamic Threshold Cloud Detection Algorithm (UDTCDA) supported by a priori surface reflectance database is proposed in this paper. A monthly surface reflectance database is constructed using long-time-sequenced MODerate resolution Imaging Spectroradiometer surface reflectance product (MOD09A1) to provide the surface reflectance of the underlying surfaces. The relationships between the apparent reflectance changes and the surface reflectance are simulated under different observation and atmospheric conditions with the 6S (Second Simulation of the Satellite Signal in the Solar Spectrum) model, and the dynamic threshold cloud detection models are developed. Two typical remote sensing data with important application significance and different sensor parameters, MODIS and Landsat 8, are selected for cloud detection experiments. The results were validated against the visual interpretation of clouds and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation cloud measurements. The results showed that the UDTCDA can obtain a high precision in cloud detection, correctly identifying cloudy pixels and clear-sky pixels at rates greater than 80% with error rate and missing rate of less than 20%. The UDTCDA cloud product overall shows less estimation uncertainty than the current MODIS cloud mask products. Moreover, the UDTCDA can effectively reduce the effects of atmospheric factors and mixed pixels and can be applied to different satellite sensors to realize long-term, large-scale cloud detection operations.

  4. Cost/performance of solar reflective surfaces for parabolic dish concentrators

    NASA Technical Reports Server (NTRS)

    Bouquet, F.

    1980-01-01

    Materials for highly reflective surfaces for use in parabolic dish solar concentrators are discussed. Some important factors concerning performance of the mirrors are summarized, and typical costs are treated briefly. Capital investment cost/performance ratios for various materials are computed specifically for the double curvature parabolic concentrators using a mathematical model. The results are given in terms of initial investment cost for reflective surfaces per thermal kilowatt delivered to the receiver cavity for various operating temperatures from 400 to 1400 C. Although second surface glass mirrors are emphasized, first surface, chemically brightened and anodized aluminum surfaces as well as second surface, metallized polymeric films are treated. Conventional glass mirrors have the lowest cost/performance ratios, followed closely by aluminum reflectors. Ranges in the data due to uncertainties in cost and mirror reflectance factors are given.

  5. Modeling and verifying the polarizing reflectance of real-world metallic surfaces.

    PubMed

    Berger, Kai; Weidlich, Andrea; Wilkie, Alexander; Magnor, Marcus

    2012-01-01

    Using measurements of real-world samples of metals, the proposed approach verifies predictions of bidirectional reflectance distribution function (BRDF) models. It employs ellipsometry to verify both the actual polarizing effect and the overall reflectance behavior of the metallic surfaces. PMID:24804944

  6. Reflected Signal Analysis and Surface Albedo in the Mars Orbiter Laser Altimeter (MOLA) Investigation

    NASA Technical Reports Server (NTRS)

    Ivanov, Anton B.; Muhleman, Duane O.

    2001-01-01

    This work presents results from the analysis of the reflectivity data from the MOLA investigation. We will discuss calculation of the surface albedo using the MGS TES 9 micron opacity. We will also overview reflectivity data collected to date. Additional information is contained in the original extended abstract.

  7. Utilization of GPS Surface Reflected Signals to Provide Aircraft Altitude Verification for SVS

    NASA Technical Reports Server (NTRS)

    Gance, George G.; Young, Steven D.

    2005-01-01

    The Global Positioning System (GPS) consists of a constellation of Earth orbiting satellites that transmit continuous electromagnetic signals to users on or near the Earth surface. At any moment of time, at least four GPS satellites, and sometimes nine or more, are visible from any point. The electromagnetic signal transmitted from the satellites is reflected to at least some degree from virtually every place on the Earth. When this signal is received by a specially constructed receiver, its characteristics can be used to determine information about the reflected surface. One piece of information collected is the time delay encountered by the reflected signal versus the direct signal. This time delay can be used to determine the altitude (or height) above the local terrain when the terrain in the reflection area is level. However, given the potential of simultaneously using multiple reflections, it should be possible to also determine the elevation above even terrains where the reflecting area is not level. Currently an effort is underway to develop the technology to characterize the reflected signal that is received by the GPS Surface Reflection Experiment (GSRE) instrument. Recent aircraft sorties have been flown to collect data that can be used to refine the technology. This paper provides an update on the status of the instrument development to enable determination of terrain proximity using the GPS Reflected signal. Results found in the data collected to date are also discussed.

  8. Surface roughness and gloss study of prints: application of specular reflection at near infrared

    NASA Astrophysics Data System (ADS)

    Silfsten, P.; Dutta, R.; Pääkkönen, P.; Tåg, C.-M.; Gane, P. A. C.; Peiponen, K.-E.

    2012-12-01

    Absolute reflectance data were measured with a spectrophotometer in the visible and near infrared (NIR) spectral range. The specular reflectance data in the NIR were used for the assessment of the surface roughness of magenta, yellow, cyan and black prints on paper. In addition, surface roughness data obtained from the prints with a mechanical diamond stylus, an optical profiling system and the spectrophotometer are compared with each other. The surface roughness obtained with the aid of the spectrophotometer data suggests a smoother surface than when measured with the diamond stylus and the optical profiling system. The gloss of the prints can be obtained from the absolute specular reflectance spectra in the spectral region of visible light. It is shown that specular reflection data at a fixed wavelength in the NIR are useful also in the interpretation of gloss in the visible spectral range, but using an unconventional grazing angle of incidence.

  9. Specular reflection of very slow metastable neon atoms from a solid surface.

    PubMed

    Shimizu, F

    2001-02-01

    An ultracold narrow atomic beam of metastable neon in the 1s3[(2s)(5)3p:1P0] state is used to study specular reflection of atoms from a solid surface at extremely slow incident velocity. The reflectivity on a silicon (1,0,0) surface and a BK7 glass surface is measured at the normal incident velocity between 1 mm/s and 3 cm/s. The reflectivity above 30% is observed at about 1 mm/s. The observed velocity dependence is explained semiquantitatively by the quantum reflection that is caused by the attractive Casimir-van der Waals potential of the atom-surface interaction.

  10. Nonlinear fitness space structure adaptation and principal component analysis in genetic algorithms: an application to x-ray reflectivity analysis

    NASA Astrophysics Data System (ADS)

    Tiilikainen, J.; Tilli, J.-M.; Bosund, V.; Mattila, M.; Hakkarainen, T.; Airaksinen, V.-M.; Lipsanen, H.

    2007-01-01

    Two novel genetic algorithms implementing principal component analysis and an adaptive nonlinear fitness-space-structure technique are presented and compared with conventional algorithms in x-ray reflectivity analysis. Principal component analysis based on Hessian or interparameter covariance matrices is used to rotate a coordinate frame. The nonlinear adaptation applies nonlinear estimates to reshape the probability distribution of the trial parameters. The simulated x-ray reflectivity of a realistic model of a periodic nanolaminate structure was used as a test case for the fitting algorithms. The novel methods had significantly faster convergence and less stagnation than conventional non-adaptive genetic algorithms. The covariance approach needs no additional curve calculations compared with conventional methods, and it had better convergence properties than the computationally expensive Hessian approach. These new algorithms can also be applied to other fitting problems where tight interparameter dependence is present.

  11. The phenomenon of simplified scattering from rough surfaces to reflection in fractional space

    NASA Astrophysics Data System (ADS)

    Safdari, Hadiseh; Vahabi, Mahsa; Jafari, Gholamreza

    2015-11-01

    In this paper, the scattering of incident plane waves from rough surfaces has been modeled in a fractional space. It is shown how wave scattering from a rough surface could correspond to a simple reflection problem in a fractional space. In an integer dimensional space, fluctuations of the surface result in wave scattering, while in the fractional space, these fluctuations are compensated by the geometry of space. In the fractional space, reflection is equivalent to scattering from the integer dimensional space. Comparing scattered wave functions from different self-affine rough surfaces in the framework of the Kirchhoff theory with the results from the fractional space, we see good agreement between them.

  12. Constraints on the origins of lunar magnetism from electron reflection measurements of surface magnetic fields

    NASA Technical Reports Server (NTRS)

    Lin, R. P.

    1979-01-01

    The paper describes a new method of detecting lunar surface magnetic fields, summarizes electron reflection measurements and correlations of surface field anomalies to moon geologic features, and discusses the constraints on the origin of lunar magnetism. Apollo 15 and 16 measurements of lunar surface magnetic fields by the electron reflection method show patches of strong surface fields distributed over the lunar surface, and a positive statistical correlation is found in lunar mare regions between the surface field strength and the geologic age of the surface. However, there is a lack of correlation of surface field with impact craters indicating that the mare does not have a strong large-scale uniform magnetization as may be expected from an ancient lunar dynamo. Fields were found in lunar highlands which imply that the rille has a strong magnetization associated with it as intrusive, magnetized rock or as a gap in a uniformly magnetic layer of rock.

  13. Coherent Reflection of He Atom Beams from Rough Surfaces at Grazing Incidence

    SciTech Connect

    Zhao, Bum Suk; Schewe, H. Christian; Meijer, Gerard; Schoellkopf, Wieland

    2010-09-24

    We report coherent reflection of thermal He atom beams from various microscopically rough surfaces at grazing incidence. For a sufficiently small normal component k{sub z} of the incident wave vector of the atom the reflection probability is found to be a function of k{sub z} only. This behavior is explained by quantum reflection at the attractive branch of the Casimir-van der Waals interaction potential. For larger values of k{sub z} the overall reflection probability decreases rapidly and is found to also depend on the parallel component k{sub x} of the wave vector. The material specific k{sub x} dependence for this classic reflection at the repulsive branch of the potential is discussed in terms of an averaging out of the surface roughness under grazing incidence conditions.

  14. Airborne Visible/Infrared Imaging Spectrometer (AVIRIS): Inflight radiometric calibration and the determination of surface reflectance

    NASA Technical Reports Server (NTRS)

    Conel, J. E.; Vane, G.; Green, R. O.; Alley, R. E.; Carere, V.; Gabell, A.; Bruegge, C. J.

    1988-01-01

    The inflight radiometric performance of AVIRIS is presented together with a comparison of methods of recovering surface spectral reflectance from the data. Performance is evaluated by comparing radiance predicted from AVIRIS with radiance generated from the LOWIRAN 6 atmospheric model and measured surface reflectance. Comparisons show apparent agreement to within a few percent between 1800 and 2450 nm. Between 600 and 1800 nm the response of AVIRIS is systematically low by as much as 70 percent, and between 400 and 600 nm it is higher than expected. These problems are traced to thermal distortions of the instrument, and to detachment during flight of optical fibers connecting foreoptics to two of four spectrometers in the instrument. Of three methods studied, an empirical one involving calibration curves constructed from field reflectance measurements returns accurate predictions of the surface reflectance independent of the actual radiometric significance of the flight data.

  15. Tunable natural nano-arrays: controlling surface properties and light reflectance

    NASA Astrophysics Data System (ADS)

    Watson, Jolanta A.; Myhra, Sverre; Watson, Gregory S.

    2006-01-01

    The general principles of optical design based on the theories of reflection, refraction and diffraction have been rigorously developed and optimized over the last three centuries. Of increasing importance has been the ability to predict and devise new optical technologies designed for specific functions. A key design feature of many of today's optical materials is the control of reflection and light transmittance through the medium. A sudden transition or impedance mismatch from one optical medium to another can result in unwanted reflections from the surface plane. Modification of a surface by creation of a gradual change in refractive index over a significant portion of a wavelength range will result in a reduction in reflection. An alternative surface modification to the multi layered stack coating (gradient index coating) is to produce a surface with structures having a period and height shorter than the light wavelength. These structures act like a pseudo-gradient index coating and can be described by the effective medium theory. Bernhard and Miller some forty years ago were the first to observe such structures found on the surface of insects. These were found in the form of hexagonally close packed nanometre sized protrusions on the corneal surface of certain moths. In this study we report on similar structures which we have found on certain species of cicada wings demonstrating that the reflective/transmission properties of these natural nano-structures can be tuned by controlled removal of the structure height using Atomic Force Microscopy (AFM).

  16. The application of specular neutron reflection to the study of surfaces and interfaces

    NASA Astrophysics Data System (ADS)

    Penfold, J.

    1992-06-01

    In recent years the specular reflection of neutrons has proved to be a valuable new technique for determining the structure of surfaces and interfaces, and a widespread application to a range of problems in surface chemistry, solid films and surface magnetism has emerged. The white beam time of flight (TOF) method for reflection measurements, exploited on a pulsed neutron source, has proved to be particularly important. Recent developments on the instrumentation and analysis methods at ISIS are presented and recent experimental results, covering a range of scientific applications are discussed.

  17. Simulation of a polarized laser beam reflected at the sea surface: modeling and validation

    NASA Astrophysics Data System (ADS)

    Schwenger, Frédéric

    2015-05-01

    A 3-D simulation of the polarization-dependent reflection of a Gaussian shaped laser beam on the dynamic sea surface is presented. The simulation considers polarized or unpolarized laser sources and calculates the polarization states upon reflection at the sea surface. It is suitable for the radiance calculation of the scene in different spectral wavebands (e.g. near-infrared, SWIR, etc.) not including the camera degradations. The simulation also considers a bistatic configuration of laser source and receiver as well as different atmospheric conditions. In the SWIR, the detected total power of reflected laser light is compared with data collected in a field trial. Our computer simulation combines the 3-D simulation of a maritime scene (open sea/clear sky) with the simulation of polarized or unpolarized laser light reflected at the sea surface. The basic sea surface geometry is modeled by a composition of smooth wind driven gravity waves. To predict the input of a camera equipped with a linear polarizer, the polarized sea surface radiance must be calculated for the specific waveband. The s- and p-polarization states are calculated for the emitted sea surface radiance and the specularly reflected sky radiance to determine the total polarized sea surface radiance of each component. The states of polarization and the radiance of laser light specularly reflected at the wind-roughened sea surface are calculated by considering the s- and p- components of the electric field of laser light with respect to the specular plane of incidence. This is done by using the formalism of their coherence matrices according to E. Wolf [1]. Additionally, an analytical statistical sea surface BRDF (bidirectional reflectance distribution function) is considered for the reflection of laser light radiances. Validation of the simulation results is required to ensure model credibility and applicability to maritime laser applications. For validation purposes, field measurement data (images and

  18. Light scattering by a rough surface of human skin. 2. Diffuse reflectance

    SciTech Connect

    Barun, V V; Ivanov, A P

    2013-10-31

    Based on the previously calculated luminance factors, we have investigated the integral characteristics of light reflection from a rough surface of the skin with large-scale inhomogeneities under various conditions of the skin illumination. Shadowing of incident and scattered beams by relief elements is taken into account. Diffuse reflectances by the Gaussian and the quasi-periodic surfaces are compared and, in general, both these roughness models are shown to give similar results. We have studied the effect of the angular structure of radiation multiply scattered deep in the tissue and the refraction of rays as they propagate from the dermis to the surface of the stratum corneum on the reflection characteristics of the skin surface. The importance of these factors is demonstrated. The algorithms constructed can be included in the schemes of calculation of the light fields inside and outside the medium in solving various direct and inverse problems of optics of biological tissues. (biophotonics)

  19. Effects of aerosols and surface shadowing on bidirectional reflectance measurements of deserts

    NASA Technical Reports Server (NTRS)

    Bowker, David E.; Davis, Richard E.

    1987-01-01

    Desert surfaces are probably one of the most stable of the Earth's natural targets for remote sensing. The bidirectional reflectance properties of the Saudi Arabian desert was investigated during the Summer Monsoon Experiment (Summer Monex). A comparison of high-altitude with near-surface measurements of the White Sands desert showed significant differences. These discrepancies have been attributed to forward scattering of the dust-laden atmosphere prevalent during Summer Monex. This paper is concerned in general with modeling the effects of atmospheric aerosols and surface shadowing on the remote sensing of bidirectional reflectance factors of desert targets, and in particular with comparing the results of these models with flight results. Although it is possible to approximate the latter, it is felt that a surface reflectance model with a smaller specular component would have permitted using a more realistic set of atmospheric conditions in the simulations.

  20. Measurement of the configuration of a concave surface by the interference of reflected light

    NASA Technical Reports Server (NTRS)

    Kumazawa, T.; Sakamoto, T.; Shida, S.

    1985-01-01

    A method whereby a concave surface is irradiated with coherent light and the resulting interference fringes yield information on the concave surface is described. This method can be applied to a surface which satisfies the following conditions: (1) the concave face has a mirror surface; (2) the profile of the face is expressed by a mathematical function with a point of inflection. In this interferometry, multilight waves reflected from the concave surface interfere and make fringes wherever the reflected light propagates. Interference fringe orders. Photographs of the fringe patterns for a uniformly loaded thin silicon plate clamped at the edge are shown experimentally. The experimental and the theoretical values of the maximum optical path difference show good agreement. This simple method can be applied to obtain accurate information on concave surfaces.

  1. Measuring and modeling the effect of surface moisture on the spectral reflectance of coastal beach sand.

    PubMed

    Nolet, Corjan; Poortinga, Ate; Roosjen, Peter; Bartholomeus, Harm; Ruessink, Gerben

    2014-01-01

    Surface moisture is an important supply limiting factor for aeolian sand transport, which is the primary driver of coastal dune development. As such, it is critical to account for the control of surface moisture on available sand for dune building. Optical remote sensing has the potential to measure surface moisture at a high spatio-temporal resolution. It is based on the principle that wet sand appears darker than dry sand: it is less reflective. The goals of this study are (1) to measure and model reflectance under controlled laboratory conditions as function of wavelength (λ) and surface moisture (θ) over the optical domain of 350-2500 nm, and (2) to explore the implications of our laboratory findings for accurately mapping the distribution of surface moisture under natural conditions. A laboratory spectroscopy experiment was conducted to measure spectral reflectance (1 nm interval) under different surface moisture conditions using beach sand. A non-linear increase of reflectance upon drying was observed over the full range of wavelengths. Two models were developed and tested. The first model is grounded in optics and describes the proportional contribution of scattering and absorption of light by pore water in an unsaturated sand matrix. The second model is grounded in soil physics and links the hydraulic behaviour of pore water in an unsaturated sand matrix to its optical properties. The optical model performed well for volumetric moisture content θ < 24% (R2 > 0.97), but underestimated reflectance for θ between 24-30% (R2 > 0.92), most notable around the 1940 nm water absorption peak. The soil-physical model performed very well (R2 > 0.99) but is limited to 4% > θ < 24%. Results from a field experiment show that a short-wave infrared terrestrial laser scanner (λ = 1550 nm) can accurately relate surface moisture to reflectance (standard error 2.6%), demonstrating its potential to derive spatially extensive surface moisture maps of a natural coastal beach.

  2. Measuring and modeling the effect of surface moisture on the spectral reflectance of coastal beach sand.

    PubMed

    Nolet, Corjan; Poortinga, Ate; Roosjen, Peter; Bartholomeus, Harm; Ruessink, Gerben

    2014-01-01

    Surface moisture is an important supply limiting factor for aeolian sand transport, which is the primary driver of coastal dune development. As such, it is critical to account for the control of surface moisture on available sand for dune building. Optical remote sensing has the potential to measure surface moisture at a high spatio-temporal resolution. It is based on the principle that wet sand appears darker than dry sand: it is less reflective. The goals of this study are (1) to measure and model reflectance under controlled laboratory conditions as function of wavelength (λ) and surface moisture (θ) over the optical domain of 350-2500 nm, and (2) to explore the implications of our laboratory findings for accurately mapping the distribution of surface moisture under natural conditions. A laboratory spectroscopy experiment was conducted to measure spectral reflectance (1 nm interval) under different surface moisture conditions using beach sand. A non-linear increase of reflectance upon drying was observed over the full range of wavelengths. Two models were developed and tested. The first model is grounded in optics and describes the proportional contribution of scattering and absorption of light by pore water in an unsaturated sand matrix. The second model is grounded in soil physics and links the hydraulic behaviour of pore water in an unsaturated sand matrix to its optical properties. The optical model performed well for volumetric moisture content θ < 24% (R2 > 0.97), but underestimated reflectance for θ between 24-30% (R2 > 0.92), most notable around the 1940 nm water absorption peak. The soil-physical model performed very well (R2 > 0.99) but is limited to 4% > θ < 24%. Results from a field experiment show that a short-wave infrared terrestrial laser scanner (λ = 1550 nm) can accurately relate surface moisture to reflectance (standard error 2.6%), demonstrating its potential to derive spatially extensive surface moisture maps of a natural coastal beach

  3. High-resolution seismic reflection survey near SPR surface collapse feature at Weeks Island, Louisiana

    SciTech Connect

    Miller, R.D.; Xia, J.; Harding, R.S. Jr.; Steeples, D.W.

    1994-12-31

    Shallow high resolution 2-D and 3-D seismic reflection techniques are assisting in the subsurface delineation of a surface collapse feature (sinkhole) at Weeks Island, Louisiana. Seismic reflection surveys were conducted in March 1994. Data from walkaway noise tests were used to assist selection of field recording parameters. The top of the salt dome is about 180 ft below ground surface at the sinkhole. The water table is an estimated 90 ft below the ground surface. A single coherent reflection was consistently recorded across the entire area of the survey, although stacking velocity and spectral content of the event varied. On the basis of observed travel times and stacking velocities, the coherent reflection event appears to originate above the top of the salt, possibly at or near the water table. Identification of this reflector will be made form borehole investigations currently planned for the sinkhole site. A depression or time sag in this reflection event is clearly evident in both the 2-D and 3-D seismic data in the immediate vicinity of the sinkhole. The time sag appears to be related to the subsurface structure of the reflector and not to near surface topography or velocity effects. Elsewhere in the survey area, observed changes in reflection travel times and wavelet character appear to be related to subsurface geologic structure. These seismic observations may assist in predicting where future sinkholes will develop after they have been tied to borehole data collected at the site.

  4. Voltage-induced broad-spectrum reflectivity change with surface-plasmon waves

    NASA Technical Reports Server (NTRS)

    Wang, Yu; Russell, Stephen D.; Shimabukuro, Randy L.

    2005-01-01

    Voltage-induced broad-spectrum reflectivity change with surface-plasmon waves is reported. When white light is incident at a metal/electro-optical material interface, surface-plasmon waves can be excited under phase match conditions. This surface-plasmon resonance depends on the dielectric constants of both the metal and the electro-optical material. Photons in the surface-plasmon resonance wavelength range are absorbed by the interface. Since metals have large imaginary parts of their dielectric constants, the surface-plasmon resonances are broad and may cover all visible wavelengths. Applying voltage to the electro-optical material to change its dielectric constant can result in a change in the reflectivity at the interface. Experimental results showed a reflectivity change from almost 0% to about 40% under an applied voltage using a liquid-crystal and nickel film structure, and the results had good agreement with theoretical calculations. The theoretical calculations also predicted a 90% reflectivity recovery by exciting surface-plasmon waves at a Rh-Al/electro-optical material interface. These results demonstrate that a high efficiency white light modulator can be built using surface-plasmon excitations.

  5. Suppressing light reflection from polycrystalline silicon thin films through surface texturing and silver nanostructures

    SciTech Connect

    Akhter, Perveen; Huang, Mengbing Kadakia, Nirag; Spratt, William; Malladi, Girish; Bakhru, Hassarum

    2014-09-21

    This work demonstrates a novel method combining ion implantation and silver nanostructures for suppressing light reflection from polycrystalline silicon thin films. Samples were implanted with 20-keV hydrogen ions to a dose of 10¹⁷/cm², and some of them received an additional argon ion implant to a dose of 5×10¹⁵ /cm² at an energy between 30 and 300 keV. Compared to the case with a single H implant, the processing involved both H and Ar implants and post-implantation annealing has created a much higher degree of surface texturing, leading to a more dramatic reduction of light reflection from polycrystalline Si films over a broadband range between 300 and 1200 nm, e.g., optical reflection from the air/Si interface in the AM1.5 sunlight condition decreasing from ~30% with an untextured surface to below 5% for a highly textured surface after post-implantation annealing at 1000°C. Formation of Ag nanostructures on these ion beam processed surfaces further reduces light reflection, and surface texturing is expected to have the benefit of diminishing light absorption losses within large-size (>100 nm) Ag nanoparticles, yielding an increased light trapping efficiency within Si as opposed to the case with Ag nanostructures on a smooth surface. A discussion of the effects of surface textures and Ag nanoparticles on light trapping within Si thin films is also presented with the aid of computer simulations.

  6. Comparison of Deep Blue and Land Surface Reflectance in the San Joaquin Valley

    NASA Astrophysics Data System (ADS)

    Lehmuth, S.; Agrawal, P.; Fisher, D.; Nguyen, A.; Roberts, K.; Strawa, A. W.; Johnson, L. F.; Skiles, J. W.

    2009-12-01

    lation standards for the past several years. While previous studies show strong correlations between the Moderate Resolution Imaging Spectroradiometer (MODIS) derived Aerosol Optical Thickness (AOT) and surface PM measurements on the East Coast of the United States, weak correlations have been found on the West Coast. Specific causes for this discrepancy have not been identified. The Deep Blue algorithm was created in order to correct AOT calculations over arid, non-vegetated regions. Although slight improvements were seen, numbers over California remained problematic. This study aims to understand the poor correlation on the West Coast, specifically in the SJV, by targeting surface reflectance as a factor for the inaccuracy. This was done by comparing land surface reflectances derived from MODIS Aqua to ground reflectance measurements for the region, in order to examine their correlation. Presumably, an undesirable effect on AOT calculations would occur if these surface reflectance values are imprecise. Results show that there is little correlation between the data sets. MODIS Land Surface Reflectance matched closest to the mixed ground measurements. In all products, the red band (0.620 - 0.670 μm) values vary more than the blue band (0.459 - 0.479 μm) values. Most data fall in a horizontal linear trend line, not the expected 1:1 line.

  7. Adaptive Impedance Analysis of Grooved Surface using the Finite Element Method

    SciTech Connect

    Wang, L; /SLAC

    2007-07-06

    Grooved surface is proposed to reduce the secondary emission yield in a dipole and wiggler magnet of International Linear Collider. An analysis of the impedance of the grooved surface based on adaptive finite element is presented in this paper. The performance of the adaptive algorithms, based on an element-element h refinement technique, is assessed. The features of the refinement indicators, adaptation criteria and error estimation parameters are discussed.

  8. Forming high efficiency silicon solar cells using density-graded anti-reflection surfaces

    DOEpatents

    Yuan, Hao-Chih; Branz, Howard M.; Page, Matthew R.

    2014-09-09

    A method (50) is provided for processing a graded-density AR silicon surface (14) to provide effective surface passivation. The method (50) includes positioning a substrate or wafer (12) with a silicon surface (14) in a reaction or processing chamber (42). The silicon surface (14) has been processed (52) to be an AR surface with a density gradient or region of black silicon. The method (50) continues with heating (54) the chamber (42) to a high temperature for both doping and surface passivation. The method (50) includes forming (58), with a dopant-containing precursor in contact with the silicon surface (14) of the substrate (12), an emitter junction (16) proximate to the silicon surface (14) by doping the substrate (12). The method (50) further includes, while the chamber is maintained at the high or raised temperature, forming (62) a passivation layer (19) on the graded-density silicon anti-reflection surface (14).

  9. Forming high-efficiency silicon solar cells using density-graded anti-reflection surfaces

    SciTech Connect

    Yuan, Hao-Chih; Branz, Howard M.; Page, Matthew R.

    2015-07-07

    A method (50) is provided for processing a graded-density AR silicon surface (14) to provide effective surface passivation. The method (50) includes positioning a substrate or wafer (12) with a silicon surface (14) in a reaction or processing chamber (42). The silicon surface (14) has been processed (52) to be an AR surface with a density gradient or region of black silicon. The method (50) continues with heating (54) the chamber (42) to a high temperature for both doping and surface passivation. The method (50) includes forming (58), with a dopant-containing precursor in contact with the silicon surface (14) of the substrate (12), an emitter junction (16) proximate to the silicon surface (14) by doping the substrate (12). The method (50) further includes, while the chamber is maintained at the high or raised temperature, forming (62) a passivation layer (19) on the graded-density silicon anti-reflection surface (14).

  10. Highly reflective and adhesive surface of aluminized polyvinyl chloride film by vacuum evaporation

    NASA Astrophysics Data System (ADS)

    Li, Denian; Tai, Qile; Feng, Qiang; Li, Qi; Xu, Xizhe; Li, Hairong; Huang, Jing; Dong, Lijie; Xie, Haian; Xiong, Chuanxi

    2014-08-01

    Aluminized poly(vinyl chloride) (PVC) film with high reflectivity and strong adhesion was facilely fabricated by vacuum evaporation. The technical study revealed that both alkali-pretreatment of the PVC matrix and thermal annealing after aluminization could greatly promote the peeling adhesion force of this metal/polymer composite by producing interfacial active chemical groups and removing the inner stress, respectively. Reflectivity test and AFM study indicated that the reflecting capacitance of the aluminum coating was closely related to the surface roughness, which can be easily controlled by modulating deposition of aluminum. Moreover, the formation of aluminum layer follows an island model process, and a continuous and smooth coating with highest reflectivity and lowest surface resistance was achieved at deposition time of 60 s. We anticipate that the cost-effective metallized PVC film by this strategy may find extensive applications in light harvesting, solar energy, and flexible mirrors, among others.

  11. On the reflectivity of complex mesh surfaces. [of space-deployable reflector antennas

    NASA Technical Reports Server (NTRS)

    Imbriale, William A.; Galindo-Israel, Victor; Rahmat-Samii, Yahya

    1991-01-01

    Poorer than expected surface reflectivity was observed in an early Tracking and Data Relay Satellite System antenna utilizing a tricot mesh weave. This poor reflectivity was determined to be caused by inadequate electrical contact at wire crossover points. A proper mathematical and numerical approach to assess the impact of wire junctions on reflectivity performance is developed. A mathematical method is presented for computing the surface reflectivity of complex mesh configurations like those on unfurlable-type spacecraft antennas. The method is based on the Floquet mode expansion to establish an integral equation for mesh wire currents. The equation is solved using the method of moments with triangular basis functions. It is observed that it is necessary to give special attention to the junction treatment among different branches of the mesh configurations. A vector junction current approach that resulted in satisfactory solutions for the current is described. The results of numerical simulations are compared against measured data and excellent agreement is observed.

  12. Comparison Between Sea Surface Wind Speed Estimates From Reflected GPS Signals and Buoy Measurements

    NASA Technical Reports Server (NTRS)

    Garrison, James L.; Katzberg, Steven J.; Zavorotny, Valery U.

    2000-01-01

    Reflected signals from the Global Positioning System (GPS) have been collected from an aircraft at approximately 3.7 km altitude on 5 different days. Estimation of surface wind speed by matching the shape of the reflected signal correlation function against analytical models was demonstrated. Wind speed obtained from this method agreed with that recorded from buoys to with a bias of less than 0.1 m/s, and with a standard derivation of 1.3 meters per second.

  13. Simple equation to approximate the bidirectional reflectance from vegetative canopies and bare soil surfaces

    NASA Technical Reports Server (NTRS)

    Walthall, C. L.; Norman, J. M.; Blad, B. L.; Welles, J. M.; Campbell, G.

    1985-01-01

    A simple equation has been developed for describing the bidirectional reflectance of some vegetative canopies and bare soil surfaces. The equation describes directional reflectance as a function of zenith and azimuth view angles and solar azimuth angle. The equation works for simulated and field measured red and IR reflectance under clear sky conditions. Hemispherical reflectance can be calculated as a function of the simple equation coefficients by integrating the equation over the hemisphere of view angles. A single equation for estimating soil bidirectional reflectance was obtained using the relationships between solar zenith angles and the simple equation coefficients for medium and rough soil distributions. The equation has many useful applications such as providing a lower level boundary condition in complex plant canopy models and providing an additional tool for studying bidirectional effects on pointable sensors.

  14. Hexagonal arrays of round-head silicon nanopillars for surface anti-reflection applications

    NASA Astrophysics Data System (ADS)

    Yan, Wensheng; Dottermusch, Stephan; Reitz, Christian; Richards, Bryce S.

    2016-10-01

    We designed and fabricated an anti-reflection surface of hexagonal arrays of round-head silicon nanopillars. The measurements show a significant reduction in reflectivity across a broad spectral range. However, we then grew a conformal titanium dioxide coating via atomic layer deposition to achieve an extremely low weighted average reflection of 2.1% over the 460-1040 nm wavelength range. To understand the underlying reasons for the reduced reflectance, the simulations were conducted and showed that it is due to strong forward scattering of incident light into the silicon substrate. The calculated normalized scattering cross section demonstrates a broadband distribution feature, and the peak has a red-shift to longer wavelengths. Finally, we report two-dimensional weighted average reflectance as a function of both wavelength and angle of incidence and present the resulting analysis contour map.

  15. Reflectance spectra for sodium and potassium doped ammonia frosts - Implications for Io's surface

    NASA Technical Reports Server (NTRS)

    Rosen, M. D. A.; Pipkin, F. M.

    1978-01-01

    This paper reports measurements of the reflection spectra of sodium- and potassium-doped ammonia frosts as a function of alkali metal concentration for the wavelength range 0.35-2.5 microns. The purpose of the measurements was to determine whether or not the reflection spectra for such a solid was compatible with the spectra albedo of Io. The data show that, with a sufficiently large alkali metal concentration, the reflection spectra of the doped ammonia frosts do not display the characteristic ammonia features at 2.0 and 2.25 micron. The high reflectance of the more concentrated samples and the character of the observed reflection spectrum make it difficult to rule out sodium-doped ammonia frost as a surface constituent on Io on the basis of existing data.

  16. Reduction of reflection losses in ZnGeP2 using motheye antireflection surface relief structures

    NASA Astrophysics Data System (ADS)

    Aydin, C.; Zaslavsky, A.; Sonek, G. J.; Goldstein, J.

    2002-04-01

    We report the reduction of surface reflection losses in zinc germanium phosphide (ZnGeP2, or ZGP) crystals by fabricating an antireflection (AR) structure in the substrate itself using subwavelength motheye surface patterns. The motheye AR patterning works by creating a region of gradually varying effective refractive index between air and the ternary nonlinear crystal. Motheye structures were created using interference lithography and reactive-ion etching in a SiCl4 plasma. The ZGP crystal with motheye patterning on the output surface reached a transmittance of ˜67% at a cutoff wavelength of 3.8 μm (close to the theoretical maximum of 73%), with negligible surface contamination from the motheye etching process. The motheye patterning technique could be applied to other nonlinear crystals where surface reflection losses are a concern.

  17. Empirical Models for the Shielding and Reflection of Jet Mixing Noise by a Surface

    NASA Technical Reports Server (NTRS)

    Brown, Clifford A.

    2016-01-01

    Empirical models for the shielding and reflection of jet mixing noise by a nearby surface are described and the resulting models evaluated. The flow variables are used to non-dimensionalize the surface position variables, reducing the variable space and producing models that are linear function of non-dimensional surface position and logarithmic in Strouhal frequency. A separate set of coefficients are determined at each observer angle in the dataset and linear interpolation is used to for the intermediate observer angles. The shielding and reflection models are then combined with existing empirical models for the jet mixing and jet-surface interaction noise sources to produce predicted spectra for a jet operating near a surface. These predictions are then evaluated against experimental data.

  18. Second-surface silvered glass solar mirrors of very high reflectance

    NASA Astrophysics Data System (ADS)

    Butel, Guillaume P.; Coughenour, Blake M.; Macleod, H. Angus; Kennedy, Cheryl E.; Olbert, Blain H.; Angel, J. Roger P.

    2011-10-01

    This paper reports methods developed to maximize the overall reflectance second-surface silvered glass. The reflectance at shorter wavelengths is increased with the aid of a dielectric enhancing layer between the silver and the glass, while at longer wavelengths it is enhanced by use of glass with negligible iron content. The calculated enhancement of reflectance, compared to unenhanced silver on standard low-iron float glass, corresponds to a 4.4% increase in reflectance averaged across the full solar spectrum, appropriate for CSP, and 2.7% for CPV systems using triple junction cells. An experimental reflector incorporating these improvements, of drawn crown glass and a silvered second-surface with dielectric boost, was measured at NREL to have 95.4% solar weighted reflectance. For comparison, non-enhanced, wetsilvered reflectors of the same 4 mm thickness show reflectance ranging from 91.6 - 94.6%, depending on iron content. A potential drawback of using iron-free drawn glass is reduced concentration in high concentration systems because of the inherent surface errors. This effect is largely mitigated for glass shaped by slumping into a concave mold, rather than by bending.

  19. Assessment of biases in MODIS surface reflectance due to Lambertian approximation

    SciTech Connect

    Cook, Robert B; SanthanaVannan, Suresh K

    2010-08-01

    Using MODIS data and the AERONET-based Surface Reflectance Validation Network (ASRVN), this work studies errors of MODIS atmospheric correction caused by the Lambertian approximation. On one hand, this approximation greatly simplifies the radiative transfer model, reduces the size of the look-up tables, and makes operational algorithm faster. On the other hand, uncompensated atmospheric scattering caused by Lambertian model systematically biases the results. For example, for a typical bowl-shaped bidirectional reflectance distribution function (BRDF), the derived reflectance is underestimated at high solar or view zenith angles, where BRDF is high, and is overestimated at low zenith angles where BRDF is low. The magnitude of biases grows with the amount of scattering in the atmosphere, i.e., at shorter wavelengths and at higher aerosol concentration. The slope of regression of Lambertian surface reflectance vs. ASRVN bidirectional reflectance factor (BRF) is about 0.85 in the red and 0.6 in the green bands. This error propagates into the MODIS BRDF/albedo algorithm, slightly reducing the magnitude of overall reflectance and anisotropy of BRDF. This results in a small negative bias of spectral surface albedo. An assessment for the GSFC (Greenbelt, USA) validation site shows the albedo reduction by 0.004 in the near infrared, 0.005 in the red, and 0.008 in the green MODIS bands.

  20. Developmental prosopagnosia and super-recognition: no special role for surface reflectance processing

    PubMed Central

    Russell, Richard; Chatterjee, Garga; Nakayama, Ken

    2011-01-01

    Face recognition by normal subjects depends in roughly equal proportions on shape and surface reflectance cues, while object recognition depends predominantly on shape cues. It is possible that developmental prosopagnosics are deficient not in their ability to recognize faces per se, but rather in their ability to use reflectance cues. Similarly, super-recognizers’ exceptional ability with face recognition may be a result of superior surface reflectance perception and memory. We tested this possibility by administering tests of face perception and face recognition in which only shape or reflectance cues are available to developmental prosopagnosics, super-recognizers, and control subjects. Face recognition ability and the relative use of shape and pigmentation were unrelated in all the tests. Subjects who were better at using shape or reflectance cues were also better at using the other type of cue. These results do not support the proposal that variation in surface reflectance perception ability is the underlying cause of variation in face recognition ability. Instead, these findings support the idea that face recognition ability is related to neural circuits using representations that integrate shape and pigmentation information. PMID:22192636

  1. Correlated imaging for a reflective target with a smooth or rough surface

    NASA Astrophysics Data System (ADS)

    Gong, Wenlin

    2016-08-01

    Correlated imaging for a reflective target with a smooth or rough surface is investigated. Our analytical results, which are backed up by numerical simulations, demonstrate that for a reflective target with a smooth surface, the quality of ghost imaging is related with the transverse sizes of both the source and the detector in the object path, and the target’s information can also be obtained by the technique of Fourier-transform ghost diffraction. However, for a reflective target with a rough surface, the target’s whole image can be reconstructed by ghost imaging even using a single point-like detector but Fourier-transform ghost diffraction is invalid. The application of correlated imaging in remote sensing is also discussed based on the above results.

  2. The derivation and verification of surface reflectances using airborne MSS data and a radiative transfer model

    SciTech Connect

    Ramsey, E.W. III; Jensen, J.R.

    1988-01-01

    Surface reflectance images were derived from airborne MSS data using a radiative transfer model to eliminate atmospheric effects and to derive downwelling irradiances. Input radiative transfer model parameters and Brightness Value (BV) to radiance conversion gain and bias factors were generated for each band using an optimization procedure to minimize the difference between modelled and image BV. Subsequently, reflectance images were derived at five wavelengths from the blue to red bands using the optimized parameters as inputs into the radiative transfer model. Modelled surface reflectance images were evaluated for accuracy by statistical comparison to measured reflectances, and for improved contrast by subjective comparison to the original images. Daedalus DS-1260 MSS bands 3, 4 and 5 modelled reflectances explained 25%, 75% and 72% of the measured reflectance variances, respectively; while bands 2 and 7 correlation were not significant (p < .05). Finally, the generated reflectance images showed dramatic improvement in contrast, revealing textures that were not apparent in the original images. 20 refs., 4 figs., 3 tabs.

  3. Surface scattering properties estimated from modeling airborne multiple emission angle reflectance data

    NASA Technical Reports Server (NTRS)

    Guinness, Edward A.; Arvidson, Raymond E.; Irons, J. R.; Harding, D. J.

    1991-01-01

    Here, researchers apply the Hapke function to airborne bidirectional reflectance data collected over three terrestrial surfaces. The objectives of the study were to test the range of natural surfaces that the Hapke model fits and to evaluate model parameters in terms of known surface properties. The data used are multispectral and multiple emission angle data collected during the Geologic Remote Sensing Field Experiment (GRSFE) over a mud-cracked playa, an artificially roughened playa, and a basalt cobble strewn playa at Lunar Lake Playa in Nevada. Airborne remote sensing data and associated field measurements were acquired at the same time. The airborne data were acquired by the Advanced Solid State Array Spectroradiometer (ASAS) instrument, a 29-spectral band imaging system. ASAS reflectance data for a cobble-strewn surface and an artificially rough playa surface on Lunar Lake Playa can be explained with the Hanke model. The cobble and rough playa sites are distinguishable by a single scattering albedo, which is controlled by material composition; by the roughness parameter, which appears to be controlled by the surface texture and particle size; and the symmetry factor of the single particle phase function, which is controlled by particle size and shape. A smooth playa surface consisting of compacted, fine-grained particles has reflectance variations that are also distinct from either the cobble site or rough playa site. The smooth playa appears to behave more like a Lambertian surface that cannot be modeled with the Hapke function.

  4. A New Fast Algorithm to Completely Account for Non-Lambertian Surface Reflection of The Earth

    NASA Technical Reports Server (NTRS)

    Qin, Wen-Han; Herman, Jay R.; Ahmad, Ziauddin; Einaudi, Franco (Technical Monitor)

    2000-01-01

    Surface bidirectional reflectance distribution function (BRDF) influences not only radiance just about the surface, but that emerging from the top of the atmosphere (TOA). In this study we propose a new, fast and accurate, algorithm CASBIR (correction for anisotropic surface bidirectional reflection) to account for such influences on radiance measured above TOA. This new algorithm is based on a 4-stream theory that separates the radiation field into direct and diffuse components in both upwelling and downwelling directions. This is important because the direct component accounts for a substantial portion of incident radiation under a clear sky, and the BRDF effect is strongest in the reflection of the direct radiation reaching the surface. The model is validated by comparison with a full-scale, vector radiation transfer model for the atmosphere-surface system. The result demonstrates that CASBIR performs very well (with overall relative difference of less than one percent) for all solar and viewing zenith and azimuth angles considered in wavelengths from ultraviolet to near-infrared over three typical, but very different surface types. Application of this algorithm includes both accounting for non-Lambertian surface scattering on the emergent radiation above TOA and a potential approach for surface BRDF retrieval from satellite measured radiance.

  5. Surface characteristics of Venus derived from Pioneer Venus altimetry, roughness, and reflectivity measurements

    NASA Astrophysics Data System (ADS)

    Head, J. W.; Peterfreund, A. R.; Garvin, J. B.

    1985-07-01

    The three primary data sets for the Pioneer Venus orbiter radar experiment (topography, roughness, and reflectivity) contain important information about the geological and textural characteristics of the surface of Venus. The authors have subdivided the range of roughness and reflectivity values into three categories as follows: roughness, in degrees rms slope: relatively smooth (1° - 2.5°), transitional from smooth to rough (2.5° - 5°), and relatively rough (>5°); and Fresnel reflectivity: surface dominated by soil or porous material (<0.1), surfaces dominated by rock material (0.1 - 0.2), and surfaces with a significant percentage of anomalously high dielectric material (>0.2). The authors have analyzed each of these data sets and their relationships to each other in order to define areas of the surface that are characterized by distinctive properties (e.g., rough rocky surfaces, smooth soil surfaces). They then describe the abundance and areal distribution of such areas and locally calibrate the geological significance of some of the surface types by examining high-resolution images from spacecraft and earth-based observatories.

  6. Solid sulfur in vacuum: Sublimation effects on surface microtexture, color and spectral reflectance, and applications to planetary surfaces

    NASA Technical Reports Server (NTRS)

    Nash, D. B.

    1987-01-01

    A form of sulfur that is white at room temperature and very fluffy in texture has been found in laboratory experiments on the effects of vacuum sublimation (evaporation) on solid sulfur. This work is an outgrowth of proton sputtering experiments on sulfur directed toward understanding Jovian magnetospheric effects on the surface of Io. Fluffy white sulfur is formed on the surface of solid yellow, tan, or brown sulfur melt freezes in vacuum by differential (fractional) evaporation of two or more sulfur molecular species present in the original sulfur; S(8) ring sulfur is thought to be the dominant sublimination phase lost to the vacuum sink, and polymeric chain sulfur S(u) the dominant residual phase that remains in place, forming the residual fluffy surface layer. The reflectance spectrum of the original sulfur surface is greaty modified by formation of the fluffy layer: the blue absorption band-edge and shoulder move 0.05 to 0.06 microns toward shorter wavelengths resulting in a permanent increase in reflectivity near 0.42 to 0.46 microns; the UV reflectivity below 0.40 microns is reduced. This form of sulfur should exist in large quantity on the surface of Io, especially in hotspot regions if there is solid free sulfur there that has solidified from a melt. Its color and spectra will indicate relative crystallization age on a scale of days to months and/or surface temperature distribution history.

  7. A surface reflectance scheme for retrieving aerosol optical depth over urban surfaces in MODIS Dark Target retrieval algorithm

    NASA Astrophysics Data System (ADS)

    Gupta, Pawan; Levy, Robert C.; Mattoo, Shana; Remer, Lorraine A.; Munchak, Leigh A.

    2016-07-01

    The MODerate resolution Imaging Spectroradiometer (MODIS) instruments, aboard the two Earth Observing System (EOS) satellites Terra and Aqua, provide aerosol information with nearly daily global coverage at moderate spatial resolution (10 and 3 km). Almost 15 years of aerosol data records are now available from MODIS that can be used for various climate and air-quality applications. However, the application of MODIS aerosol products for air-quality concerns is limited by a reduction in retrieval accuracy over urban surfaces. This is largely because the urban surface reflectance behaves differently than that assumed for natural surfaces. In this study, we address the inaccuracies produced by the MODIS Dark Target (MDT) algorithm aerosol optical depth (AOD) retrievals over urban areas and suggest improvements by modifying the surface reflectance scheme in the algorithm. By integrating MODIS Land Surface Reflectance and Land Cover Type information into the aerosol surface parameterization scheme for urban areas, much of the issues associated with the standard algorithm have been mitigated for our test region, the continental United States (CONUS). The new surface scheme takes into account the change in underlying surface type and is only applied for MODIS pixels with urban percentage (UP) larger than 20 %. Over the urban areas where the new scheme has been applied (UP > 20 %), the number of AOD retrievals falling within expected error (EE %) has increased by 20 %, and the strong positive bias against ground-based sun photometry has been eliminated. However, we note that the new retrieval introduces a small negative bias for AOD values less than 0.1 due to the ultra-sensitivity of the AOD retrieval to the surface parameterization under low atmospheric aerosol loadings. Global application of the new urban surface parameterization appears promising, but further research and analysis are required before global implementation.

  8. Polarization Ray Tracing Calculation of Polarized Bidirectional Reflectance Distribution Function (pBRDF) of Microfaceted Surfaces to Investigate Multiple Reflection Effects

    NASA Astrophysics Data System (ADS)

    Bradley, C. L.; Kupinski, M.; Xu, F.; Diner, D. J.; Chipman, R. A.

    2015-12-01

    Remote sensing algorithms for aerosol retrieval rely on surface reflectance models for the extraction of path radiance of aerosol scattering in top of atmosphere measurements. A well-defined surface boundary condition is necessary due to the variability in the surface albedo and bidirectional reflectance distribution function. Polarization measurements can help constrain the surface model. Prior work features polarization measurements taken by Jet Propulsion Laboratory's Ground-based Multiangle SpectroPolarimetric Imager (GroundMSPI). This work has shown that an analytical model that assumes singly reflected light from a rough surface comprised of microfacets sufficiently represents the polarized reflectance of natural surfaces (such as grass), but is less successful for manmade objects. For the linear Stokes parameters (I, Q, U), a single reflection of unpolarized light will result in a null U Stokes parameter relative to the scattering plane. However, some GroundMSPI measurements exhibit a non-zero U Stokes parameter. We show that multiple reflections may be a cause for this discrepancy by using a polarization ray trace (PRT) routine to calculate the polarized Bidirectional Reflectance Distribution Function (pBRDF) for a microfaceted surface. While the effect of multiple reflections, particularly for double reflections, is an order of magnitude smaller compared to single reflections, we show non-zero U Stokes parameters generated from multiple reflections. Furthermore, we have found that for illumination-view geometries with scattering angles less than ~45 degrees, Q and U parameters can have similar magnitude. We report on the magnitude of this effect and compare the PRT simulations to non-zero U measurements from GroundMSPI.

  9. High Contrast Reflectance Imaging of Simulated Lesions on Tooth Occlusal Surfaces at Near-IR Wavelengths

    PubMed Central

    Fried, William A.; Fried, Daniel; Chan, Kenneth H.; Darling, Cynthia L.

    2015-01-01

    Introduction In vivo and in vitro studies have shown that high contrast images of tooth demineralization can be acquired in the near-infrared (near-IR) without the interference of stain. The purpose of this study is to compare the lesion contrast in reflectance at near-IR wavelengths coincident with high water absorption with those in the visible, the near-IR at 1,300 nm and with fluorescence measurements for early lesions in occlusal surfaces. Methods Twenty-four human molars were used in this in vitro study. Teeth were painted with an acid-resistant varnish, leaving a 4 × 4 mm window in the occlusal surface of each tooth exposed for demineralization. Artificial lesions were produced in the exposed windows after 1- and 2-day exposure to a demineralizing solution at pH 4.5. Lesions were imaged using near-IR reflectance at three wavelengths, 1,300, 1,460, and 1,600 nm using a high definition InGaAs camera. Visible light reflectance, and fluorescence with 405 nm excitation and detection at wavelengths greater than 500 nm were also used to acquire images for comparison. Crossed polarizers were used for reflectance measurements to reduce interference from specular reflectance. Results The contrast of both the 1- and 2-day lesions were significantly higher (P < 0.05) for near-IR reflectance imaging at 1,460 and 1,600 nm than it was for near-IR reflectance imaging at 1,300 nm, visible reflectance imaging, and fluorescence. Conclusion The markedly higher contrast at 1,460 and 1,600 nm wavelengths, coincident with higher water absorption, suggest that these wavelengths are better suited than 1,300 nm for imaging early/shallow demineralization on tooth surfaces. PMID:23857066

  10. Improved x-ray reflectivity calculations for rough surfaces and interfaces

    NASA Astrophysics Data System (ADS)

    Fujii, Yoshikazu

    2011-09-01

    We have investigated the fact that the calculated x-ray reflectivity based on the Parratt formalism, coupled with the use of the Nevot-Croce representation of roughness, show a strange phenomenon where the amplitude of the oscillation due to interference effects increases for a rougher surface. Here, we propose that the strange result has its origin in a currently used equation due to a serious mistake in which the Fresnel transmission coefficient in the reflectivity equation is increased at a rough interface, and the increase in the transmission coefficient completely overpowers any decrease in the value of the reflection coefficient because of a lack of consideration of diffuse scattering. The mistake in Nevot and Croce's treatment originates in the fact that the modified Fresnel coefficients were calculated based on the theory which contains the x-ray energy conservation rule at surface and interface. In their discussion, the transmission coefficients were replaced approximately by the reflection coefficients by the ignoring diffuse scattering term at the rough interface, and according to the principle of conservation energy at the rough interface also. The errors of transmittance without the modification cannot be ignored. It is meaningless to try to precisely match the numerical result based on a wrong calculating formula even to details of the reflectivity profile of the experimental result. Thus, because Nevot and Croce's treatment of the Parratt formalism contains a fundamental mistake regardless of the size of roughness, this approach needs to be corrected. In the present study, we present a new accurate formalism that corrects this mistake, and thereby derive an accurate analysis of the x-ray reflectivity from a multilayer surface, taking into account the effect of roughness-induced diffuse scattering. The calculated reflectivity obtained by the use of this accurate reflectivity equation gives a physically reasonable result, and should enable the

  11. Evaluation of Experimental Data from the GAINS Balloon GPS Surface Reflection Instrument

    NASA Technical Reports Server (NTRS)

    Gance, George G.; Johnson, Thomas A.

    2004-01-01

    The GPS Surface Reflection Instrument was integrated as an experiment on the GAINS (Global Airocean IN-situ System) 48-hour balloon mission flown in September 2001. The data collected by similar instruments in the past has been used to measure sea state from which ocean surface winds can be accurately estimated. The GPS signal has also been shown to be reflected from wetland areas and even from subsurface moisture. The current version of the instrument has been redesigned to be more compact, use less power, and withstand a greater variation in environmental conditions than previous versions. This instrument has also incorporated a new data collection mode to track 5 direct satellites (providing a continuous navigation solution) and multiplex the remaining 7 channels to track the reflected signal of the satellite tracked in channel 0. The new software mode has been shown to increase the signal to noise ratio of the collected data and enhance the science return of the instrument. During the 48-hour flight over the Northwest US, the instrument will measure surface reflections that can be detected over the balloon's ground track. Since ground surface elevations in this area vary widely from the WGS-84 ellipsoid altitude, the instrument software has been modified to incorporate a surface altitude correction based on USGS 30-minute Digital Elevation Models. Information presented will include facts about instrument design goals, data collection methodologies and algorithms, and results of the science data analyses for the 48-hour mission.

  12. Early Evaluation of the VIIRS Calibration, Cloud Mask and Surface Reflectance Earth Data Records

    NASA Technical Reports Server (NTRS)

    Vermote, Eric; Justice, Chris; Csiszar, Ivan

    2014-01-01

    Surface reflectance is one of the key products fromVIIRS and as withMODIS, is used in developing several higherorder land products. The VIIRS Surface Reflectance (SR) Intermediate Product (IP) is based on the heritageMODIS Collection 5 product (Vermote, El Saleous, & Justice, 2002). The quality and character of surface reflectance depend on the accuracy of the VIIRS Cloud Mask (VCM), the aerosol algorithms and the adequate calibration of the sensor. The focus of this paper is the early evaluation of the VIIRS SR product in the context of the maturity of the operational processing system, the Interface Data Processing System (IDPS). After a brief introduction, the paper presents the calibration performance and the role of the surface reflectance in calibration monitoring. The analysis of the performance of the cloud mask with a focus on vegetation monitoring (no snow conditions) shows typical problems over bright surfaces and high elevation sites. Also discussed is the performance of the aerosol input used in the atmospheric correction and in particular the artifacts generated by the use of the Navy Aerosol Analysis and Prediction System. Early quantitative results of the performance of the SR product over the AERONET sites showthatwith the fewadjustments recommended, the accuracy iswithin the threshold specifications. The analysis of the adequacy of the SR product (Land PEATE adjusted version) in applications of societal benefits is then presented. We conclude with a set of recommendations to ensure consistency and continuity of the JPSS mission with the MODIS Land Climate Data Record.

  13. Evaluation of Experimental Data from the Gains Balloon GPS Surface Reflection Instrument

    NASA Technical Reports Server (NTRS)

    Ganoe, George G.; Johnson, Thomas A.; Somero, John Ryan

    2002-01-01

    The GPS Surface Reflection Instrument was integrated as an experiment on the GAINS (Global Airocean IN-situ System) 48-hour balloon mission flown in June 2002. The data collected by similar instruments in the past has been used to measure sea state from which ocean surface winds can be accurately estimated. The GPS signal has also been shown to be reflected from wetland areas and even from subsurface moisture. The current version of the instrument has been redesigned to be more compact, use less power, and withstand a greater variation in environmental conditions than previous versions. This instrument has also incorporated a new data collection mode to track 5 direct satellites (providing a continuous navigation solution) and multiplex the remaining 7 channels to track the reflected signal of the satellite tracked in channel 0. The new software mode has been shown to increase the signal to noise ratio of the collected data and enhance the science return of the instrument. During the GAINS balloon flight over the Northwest US, the instrument measured surface reflections as they were detected over the balloon's ground track. Since ground surface elevations in this area vary widely from the WGS-84 ellipsoid altitude, the instrument software has been modified to incorporate a surface altitude correction based on USGS 30-minute Digital Elevation Models. Information presented will include facts about instrument design goals, data collection methodologies and algorithms, and will focus on results of the science data analyses for the mission.

  14. Characterising soil surface condition and carbon vulnerability using spatial statistics and directional reflectance

    NASA Astrophysics Data System (ADS)

    Croft, H.; Anderson, K.

    2008-12-01

    Soils can experience rapid structural degradation in response to land cover changes, resulting in reduced soil productivity, increased erodibility and a loss of Soil Organic Matter (SOM). The breakdown of soil aggregates through slaking and raindrop impact is linked to soil organic matter turnover, with subsequently eroded material often displaying proportionally more SOM. A reduction in aggregate stability is reflected in a decline in soil surface roughness, indicating that a physical soil structural change can be used to highlight soil vulnerability to SOM loss through mineralisation or erosion. Remotely sensed data can provide a cost- effective means of monitoring changes in soil surface condition over broad spatial extents. Growing recognition of the importance of the directional reflectance domain has highlighted their potential application for monitoring changes in soil surface roughness, associated with the breakdown of macro-aggregates and therefore SOM release. This is particularly relevant for soil condition monitoring because during soil structural degradation, changes in the self-shadowing effects of soil aggregates has a measurable effect on directional reflectance factors measured by proximal remote sensing devices. Field and laboratory data are therefore required for an empirical understanding of soil directional reflectance, underpinning subsequent model development. This experiment details the use of hyperspectral multiple view angle, proximal reflectance data (400-2500 nm) for describing changes in soil surface structure. Five different soil crusting states were produced, simulating a progressive decline in soil surface structure using artificial rainfall. Each stage was characterised using a close-range laser scanning device with a 2 mm spatial sampling methodology. Data were analysed within a geostatistical framework, where variogram analysis quantitatively confirmed the change in soil surface structure during crusting (sill variance = 0

  15. Atomic Scale Flatness of Chemically Cleaned Silicon Surfaces Studied by Infrared Attenuated-Total-Reflection Spectroscopy

    NASA Astrophysics Data System (ADS)

    Sawara, Kenichi; Yasaka, Tatsuhiro; Miyazaki, Seiichi; Hirose, Masataka

    1992-07-01

    Hydrogen-terminated Si(111) and Si(100) surfaces obtained by aqueous HF or pH-modified (pH{=}5.3) buffered-HF (BHF) treatments have been characterized by a Fourier transform infrared (FT-IR) attenuated-total-reflection (ATR) technique. The BHF treatment provides better surface flatness than the HF treatment. Pure water rinse is effective for improving the Si(111) surface flatness, while this is not the case for Si(100) because the pure water acts as an alkaline etchant and promotes the formation of (111) microfacets or microdefects on the (100) surface.

  16. Surface reflectance retrieval from satellite and aircraft sensors - Results of sensors and algorithm comparisons during FIFE

    NASA Technical Reports Server (NTRS)

    Markham, B. L.; Halthore, R. N.; Goetz, S. J.

    1992-01-01

    Visible to shortwave infrared radiometric data collected by a number of remote sensing instruments on aircraft and satellite platforms were compared over common areas in the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE) site on August 4, 1989, to assess their radiometric consistency and the adequacy of atmospheric correction algorithms. The instruments in the study included the Landsat 5 Thematic Mapper (TM), the SPOT 1 high-resolution visible (HRV) 1 sensor, the NS001 Thematic Mapper simulator, and the modular multispectral radiometers (MMRs). Atmospheric correction routines analyzed were an algorithm developed for FIFE, LOWTRAN 7, and 5S. A comparison between corresponding bands of the SPOT 1 HRV 1 and the Landsat 5 TM sensors indicated that the two instruments were radiometrically consistent to within about 5 percent. Retrieved surface reflectance factors using the FIFE algorithm over one site under clear atmospheric conditions indicated a capability to determine near-nadir surface reflectance factors to within about 0.01 at a reflectance of 0.06 in the visible (0.4-0.7 microns) and about 0.30 in the near infrared (0.7-1.2 microns) for all but the NS001 sensor. All three atmospheric correction procedures produced absolute reflectances to within 0.005 in the visible and near infrared. In the shortwave infrared (1.2-2.5 microns) region the three algorithms differed in the retrieved surface reflectances primarily owing to differences in predicted gaseous absorption. Although uncertainties in the measured surface reflectance in the shortwave infrared precluded definitive results, the 5S code appeared to predict gaseous transmission marginally more accurately than LOWTRAN 7.

  17. Surface reflectance retrieval from satellite and aircraft sensors: Results of sensor and algorithm comparisons during FIFE

    NASA Astrophysics Data System (ADS)

    Markham, B. L.; Halthore, R. N.; Goetz, S. J.

    1992-11-01

    Visible to shortwave infrared radiometric data collected by a number of remote sensing instruments on aircraft and satellite platforms were compared over common areas in the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE) site on August 4, 1989, to assess their radiometric consistency and the adequacy of atmospheric correction algorithms. The instruments in the study included the Landsat 5 thematic mapper (TM), the SPOT 1 high-resolution visible (HRV) 1 sensor, the NS001 thematic mapper simulator, and the modular multispectral radiometers (MMRs). Atmospheric correction routines analyzed were an algorithm developed for FIFE, LOWTRAN 7, and 5S. A comparison between corresponding bands of the SPOT 1 HRV 1 and the Landsat 5 TM sensors indicated that the two instruments were radiometrically consistent to within about 5%. Retrieved surface reflectance factors using the FIFE algorithm over one site under clear atmospheric conditions indicated a capability to determine near-nadir surface reflectance factors to within about 0.01 at a reflectance of 0.06 in the visible (0.4-0.7 μm) and about 0.30 in the near infrared (0.7-1.2 μm) for all but the NS001 sensor. All three atmospheric correction procedures produced absolute reflectances to within 0.005 in the visible and near infrared. In the shortwave infrared (1.2-2.5 μm) region the three algorithms differed in the retrieved surface reflectances primarily owing to differences in predicted gaseous absorption. Although uncertainties in the measured surface reflectance in the shortwave infrared precluded definitive results, the 5S code appeared to predict gaseous transmission marginally more accurately than LOWTRAN 7.

  18. Smectic order induced at homeotropically aligned nematic surfaces: a neutron reflection study.

    PubMed

    Lau, Y G J; Richardson, Robert M; Cubitt, R

    2006-06-21

    Neutron reflection was used to measure the buildup of layers at a solid surface as the smectic phase is approached from higher temperatures in a nematic liquid crystal. The liquid crystal was 4-octyl-4'-cyanobiphenyl (8CB), and the solid was silicon with one of five different surface treatments that induce homeotropic alignment: (i) silicon oxide; (ii) a cetyltrimethylammonium bromide coating; (iii) an octadecyltrichlorosilane monolayer; (iv) an n-n-dimethyl-n-octadecyl-3- aminopropyltrimethyloxysilyl chloride monolayer; and (v) a lecithin coating. The development of surface smectic layers in the nematic phase of 8CB was followed by measuring specular reflectivity and monitoring the pseudo-Bragg peak from the layers. The scattering data were processed to remove the scattering from short-ranged smecticlike fluctuations in the bulk nematic phase from the specular reflection. The pseudo-Bragg peak at scattering vector Q approximately 0.2 A(-1) therefore corresponded to the formation of long-range smectic layers at the surface. The amplitude of the smectic density wave decayed with increasing distance from the surface, and the characteristic thickness of this smectic region diverged as the transition temperature was approached. It was found that the characteristic thickness for some of the surface treatments was greater than the correlation length in the bulk nematic. The different surfaces gave different values of the smectic order parameter at the surface. This suggests that the interaction with the surface is significantly different from a "hard wall" which would give the same values of the smectic order parameter and penetration depths similar to the bulk correlation length. Comparison of the different surfaces also suggested that the strength and range of the surface smectic ordering may be varied independently. PMID:16821956

  19. Smectic order induced at homeotropically aligned nematic surfaces: A neutron reflection study

    NASA Astrophysics Data System (ADS)

    Lau, Y. G. J.; Richardson, Robert M.; Cubitt, R.

    2006-06-01

    Neutron reflection was used to measure the buildup of layers at a solid surface as the smectic phase is approached from higher temperatures in a nematic liquid crystal. The liquid crystal was 4-octyl-4'-cyanobiphenyl (8CB), and the solid was silicon with one of five different surface treatments that induce homeotropic alignment: (i) silicon oxide; (ii) a cetyltrimethylammonium bromide coating; (iii) an octadecyltrichlorosilane monolayer; (iv) an n-n-dimethyl-n-octadecyl-3- aminopropyltrimethyloxysilyl chloride monolayer; and (v) a lecithin coating. The development of surface smectic layers in the nematic phase of 8CB was followed by measuring specular reflectivity and monitoring the pseudo-Bragg peak from the layers. The scattering data were processed to remove the scattering from short-ranged smecticlike fluctuations in the bulk nematic phase from the specular reflection. The pseudo-Bragg peak at scattering vector Q ˜0.2Å-1 therefore corresponded to the formation of long-range smectic layers at the surface. The amplitude of the smectic density wave decayed with increasing distance from the surface, and the characteristic thickness of this smectic region diverged as the transition temperature was approached. It was found that the characteristic thickness for some of the surface treatments was greater than the correlation length in the bulk nematic. The different surfaces gave different values of the smectic order parameter at the surface. This suggests that the interaction with the surface is significantly different from a "hard wall" which would give the same values of the smectic order parameter and penetration depths similar to the bulk correlation length. Comparison of the different surfaces also suggested that the strength and range of the surface smectic ordering may be varied independently.

  20. Reconstruction of Two-Dimensional Randomly Rough Surfaces Based on Bidirectional Reflectance Distribution Function

    NASA Astrophysics Data System (ADS)

    Xuan, Yimin; Han, Yuge; Zhou, Yue

    2013-03-01

    This article presents an inverse method for reconstructing two-dimensional randomly rough surfaces based on the available (experimental or given) data of the bidirectional reflectance distribution function (BRDF). The Maxwell's equations of electromagnetic waves are applied to describe the light scattering process of rough surfaces by accounting for the near-field effect. Such a forward problem is numerically solved with the finite-difference time-domain algorithm. The inverse scattering problem of reconstructing the surface profile is handled by means of an optimization technique—the particle swarm optimizer algorithm. As an example, reconstruction of a Gaussian rough surface is conducted based on the experimental data of BRDFs. The retrieved results of the surface profile are compared with those measured by atomic force microscopy from the samples, which shows that the reconstruction algorithm can provide the credible prediction of surface profiles. The reconstruction approach studied in this study can make reliable predictions of the actual or required surface profiles.

  1. Angular distributions of surface produced H{sup −} ions for reflection and desorption processes

    SciTech Connect

    Wada, M. Kasuya, T.; Kenmotsu, T.; Sasao, M.

    2014-02-15

    A numerical simulation code, Atomic Collision in Amorphous Target, has been run to clarify the effects due to the incident angle of hydrogen flux onto surface collision cascade in the subsurface region of a Cs covered Mo plasma grid. The code has taken into account the threshold energy for negative hydrogen (H{sup −}) ions to leave the surface. This modification has caused the shift of energy distribution functions of H{sup −} from that of hydrogen atoms leaving the surface. The results have shown that large incident angle of hydrogen particle tilt the angular distribution of reflection component, while it caused a small effect onto the angular distribution of desorption component. The reflection coefficient has increased, while the desorption yield has decreased for increased angle of incidence measured from the surface normal.

  2. Angular distributions of surface produced H(-) ions for reflection and desorption processes.

    PubMed

    Wada, M; Kasuya, T; Kenmotsu, T; Sasao, M

    2014-02-01

    A numerical simulation code, Atomic Collision in Amorphous Target, has been run to clarify the effects due to the incident angle of hydrogen flux onto surface collision cascade in the subsurface region of a Cs covered Mo plasma grid. The code has taken into account the threshold energy for negative hydrogen (H(-)) ions to leave the surface. This modification has caused the shift of energy distribution functions of H(-) from that of hydrogen atoms leaving the surface. The results have shown that large incident angle of hydrogen particle tilt the angular distribution of reflection component, while it caused a small effect onto the angular distribution of desorption component. The reflection coefficient has increased, while the desorption yield has decreased for increased angle of incidence measured from the surface normal.

  3. The geometrical-optics law of reflection for electromagnetic waves in magnetically confined plasmas: Specular reflection of rays at the last closed flux surface

    SciTech Connect

    Bizarro, Joao P. S.

    2010-10-15

    Within the geometrical-optics approximation, it is shown that the reflection of rays describing the propagation of electromagnetic waves in fusion-grade, magnetically confined plasmas and impinging on the last closed flux surface, or plasma surface, is necessarily specular or mirror-like. More precisely, the component of the wave vector tangential to that surface does not change, whereas the component normal to it reverses its sign while keeping its magnitude. The well-known law of reflection, stating that the angle of incidence equals that of reflection, is thus generalized to anisotropic media.

  4. Reconstructing surface wave profiles from reflected acoustic pulses using multiple receivers.

    PubMed

    Walstead, Sean P; Deane, Grant B

    2014-08-01

    Surface wave shapes are determined by analyzing underwater reflected acoustic signals collected at multiple receivers. The transmitted signals are of nominal frequency 300 kHz and are reflected off surface gravity waves that are paddle-generated in a wave tank. An inverse processing algorithm reconstructs 50 surface wave shapes over a length span of 2.10 m. The inverse scheme uses a broadband forward scattering model based on Kirchhoff's diffraction formula to determine wave shapes. The surface reconstruction algorithm is self-starting in that source and receiver geometry and initial estimates of wave shape are determined from the same acoustic signals used in the inverse processing. A high speed camera provides ground-truth measurements of the surface wave field for comparison with the acoustically derived surface waves. Within Fresnel zone regions the statistical confidence of the inversely optimized surface profile exceeds that of the camera profile. Reconstructed surfaces are accurate to a resolution of about a quarter-wavelength of the acoustic pulse only within Fresnel zones associated with each source and receiver pair. Multiple isolated Fresnel zones from multiple receivers extend the spatial extent of accurate surface reconstruction while overlapping Fresnel zones increase confidence in the optimized profiles there. PMID:25096095

  5. Oxidation-resistant reflective surfaces for solar dynamic power generation in near Earth orbit

    NASA Technical Reports Server (NTRS)

    Gulino, D. A.; Mgf2, Sio2, Al2o3, and si3n4, we

    1986-01-01

    Reflective surfaces for space station power generation systems are required to withstand the atomic oxygen-dominated environment of near Earth orbit. Thin films of platinum and rhodium, which are corrosion resistant reflective metals, have been deposited by ion beam sputter deposition onto various substrate materials. Solar reflectances were then measured as a function of time of exposure to a RF-generated air plasma. Similarly, various protective coating materials, including MgF2, SiO2, Al2O3, and Si3N4, were deposited onto silver-coated substrates and then exposed to the plasma. Analysis of the films both before and after exposure by both ESCA and Auger spectroscopy was also performed. The results indicate that Pt and Rh do not suffer any loss in reflectance over the duration of the tests. Also, each of the coating materials survived the plasma environment. The ESCA and Auger analyses are discussed as well.

  6. Reflectance spectroscopy - Quantitative analysis techniques for remote sensing applications. [in planetary surface geology

    NASA Technical Reports Server (NTRS)

    Clark, R. N.; Roush, T. L.

    1984-01-01

    The empirical methods and scattering theories that are important for solving remote sensing problems are among the methods for remotely sensed reflectance data analysis presently compared. In the case of the photon mean optical path length concept's implications for reflectance spectra modeling, it is shown that the mean optical path length in a particulate surface is in roughly inverse proportion to the square root of the absorption coefficient. Absorption bands, which are Gaussian in shape when plotted as true absorptance vs photon energy, are also Gaussians in apparent absorptance, although they have a smaller intensity. An apparent continuum in a reflectance spectrum is modeled as a mathematical function that is used to isolate a particular absorption feature for analysis, and it is noted that this continuum should be removed by dividing it into the reflectance spectrum.

  7. Long-wave infrared surface reflectance spectra retrieved from Telops Hyper-Cam imagery

    NASA Astrophysics Data System (ADS)

    Adler-Golden, S. M.; Conforti, P.; Gagnon, M.; Tremblay, P.; Chamberland, Martin

    2014-06-01

    Processing long-wave infrared (LWIR) hyperspectral imagery to surface emissivity or reflectance units via atmospheric compensation and temperature-emissivity separation (TES) affords the opportunity to remotely classify and identify solid materials with minimal interference from atmospheric effects. This paper describes an automated atmospheric compensation and TES method, called FLAASH®-IR (Fast Line-of-sight Atmospheric Analysis of Spectral Hypecubes-- Infrared), and its application to ground-to-ground imagery taken with the Telops Inc. Hyper-Cam interferometric hyperspectral imager. The results demonstrate that clean, quantitative surface spectra can be obtained, even with highly reflective (low emissivity) objects such as bare metal and in the presence of some illumination from the surroundings. In particular, the atmospheric compensation process suppresses the spectral features due to atmospheric water vapor and ozone, which are especially prominent in reflected sky radiance.

  8. Methods of Creating Solar-Reflective Nonwhite Surfaces and theirApplication to Residential Roofing Materials

    SciTech Connect

    Levinson, Ronnen; Berdahl, Paul; Akbari, Hashem; Miller, William; Joedicke, Ingo; Reilly, Joseph; Suzuki, Yoshi; Vondran, Michelle

    2005-05-24

    We describe methods for creating solar-reflective nonwhitesurfaces and their application to a wide variety of residential roofingmaterials, including metal, clay tile, concrete tile, wood, and asphaltshingle. Reflectance in the near-infrared (NIR) spectrum (0.7 2.5mu m) ismaximized by coloring a topcoatwith pigments that weakly absorb and(optionally) strongly backscatter NIR radiation, and adding anNIR-reflective basecoat (e.g., titanium dioxide white) if both thetopcoat and substrate weakly reflect NIR radiation. Coated steel andglazed clay tile roofing products achieved NIRreflectances of up to 0.50and 0.75, respectively, using only cool topcoats. Gray concrete tilesachieve NIR reflectances as high as 0.60 when thickly coated withNIR-scattering pigments, and could attain an NIR reflectances as high as0.85 by overlaying a titanium-dioxide basecoat with a topcoat colored byNIR-transparent organic pigments. Granule-surfaced asphalt shinglesachieved NIR reflectances as high as 0.45 when a cool color topcoat wasapplied over a thick white basecoat.

  9. Reflections Over Coupled Surfaces by Means of a High Resolution Setup

    NASA Astrophysics Data System (ADS)

    Geva, Meital; Ram, Omri; Sadot, Oren; Ben-Gurion University of the Negev, Isreal Team

    2015-11-01

    The reflection patterns over two coupled cylindrical surfaces are studied using a high spatial and high temporal resolution experimental setup. This fully automated setup enabled the repetition of experiments many times while retaining extremely high repeatability. For the investigated moderate shock strengths, the repeatability was less than 0.01 in the Mach number. Each experiment produced a single image with a pixel size of 0.03 mm. All images were later sequentially merged generating a detailed description of a single reflection process. Unlike previous studies in which analysis was subject to human inconsistency, an automatic image processing procedure was used to locate the triple point in each image. The high resolution enabled the experimental detection of the early stages of Mach-reflection as were never demonstrated before. The experimental results were compared with numerical computation and a suitable uncertainty analysis was performed. The reflection over the first model enabled the transitions between MR -->RR -->MR. These successive transitions have proven the existence of a non-stationary hysteresis shock-wave reflection phenomenon. The reflection over the second model enabled the monitoring of the RR -->MR transition and the evolution of a newly three-shock configuration established on the Mach stem of the original reflection (MRMR). It was found that the MRMR -->MRRR transition angles could be adjusted to match those obtained over a single cylinder.

  10. Hyperspectral surface reflectance data detect low moisture status of pecan orchards during flood irrigation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    For large fields, remote sensing might permit plant low moisture status to be detected early, and this may improve drought detection and monitoring. The objective of this study was to determine whether canopy and soil surface reflectance data derived from a handheld spectroradiometer can detect mois...

  11. A Cylindrical Microlens With An Internally Reflective Surface And A Method Of Fabrication

    DOEpatents

    Beach, Raymond J.; Freitas, Barry L.

    2005-09-27

    A fast (high numerical aperture) cylindrical microlens, which includes an internally reflective surface, that functions to deviate the direction of the light that enters the lens from its original propagation direction is employed in optically conditioning laser diodes, laser diode arrays and laser diode bars.

  12. Cylindrical microlens with an internally reflecting surface and a method of fabrication

    DOEpatents

    Beach, Raymond J.; Freitas, Barry L.

    2004-03-23

    A fast (high numerical aperture) cylindrical microlens, which includes an internally reflective surface, that functions to deviate the direction of the light that enters the lens from its original propagation direction is employed in optically conditioning laser diodes, laser diode arrays and laser diode bars.

  13. Correlation between x-ray reflectivity measurements and surface roughness of AXAF coated witness samples

    NASA Astrophysics Data System (ADS)

    Clark, Anna M.; Bruni, Ricardo J.; Romaine, Suzanne E.; Schwartz, Daniel A.; van Speybroeck, Leon P.; Yip, P. W.; Drehman, A. J.; Shapiro, Alan P.

    1996-07-01

    One of the specifications used to polish the AXAF witness samples was that the rms surface roughness be reflectivity of the surfaces. In particular, the reflectivity data from the AXAF flight optic witness samples indicate sample to sample differences of a few percent which do not correlate with the optical profilometry results for these samples. Further investigations were carried out to measure rms surface roughness using atomic force microscopy (AFM). The differences shown by AFM surface roughness measurements correlates to differences found in reflectivity for these same samples. One-dimensional power spectral density data is presented from both AFM and WYKO measurements along with the reflectivity results at 8 keV for the AXAF witness samples. The results indicate that to obtain accurate prediction of x-ray performance it is necessary to look at the scanning probe metrology data provided by the AFM, in addition to the optical profilometry data.

  14. An Undergraduate Experiment to Measure the Reflectances of a Dielectric Surface

    ERIC Educational Resources Information Center

    Driver, H. S. T.

    1978-01-01

    Describes an experiment for the measurement of the reflectances of dielectric surface. The experiment is analyzed in terms of the Stokes parameters and the Mueller calculus, and Malus law is derived. The experiment also provides an introduction to the properties of real linear polarizers. (Author/GA)

  15. Observations of Reflectivity of the Martian Surface in the Mars Orbiter Laser Altimeter (MOLA) Investigation

    NASA Technical Reports Server (NTRS)

    Ivanov, Anton B.; Muhleman, Duane O.

    2000-01-01

    We are presenting results of calculation of the surface albedo of Mars at 1 micron wavelength from the Mars Orbiter Laser Altimeter (MOLA) reflectivity measurements. The Mars Global Surveyor Thermal Emission Spectrometer (MGS TES) 9 micron opacity is employed to remove opacity from the MOLA measurements.

  16. Adsorption of polystyrene sulfonate to the air surface of water by neutron reflectivity

    SciTech Connect

    YIM,HYUN; KENT,MICHAEL S.; MATHESON,AARON J.; IVKOV,R.; SATIJA,S.; MAJEWSKI,J.; SMITH,G.S.

    2000-05-16

    The adsorption of the strong polyelectrolyte polystyrene sulfonate (PSS) to the air surface of dilute aqueous solutions was investigated as a function of molecular weight and salt concentration. Detailed segment profiles of the deuterated polymer were determined by neutron reflection. Surface activity was also examined through surface tension measurements. In general, the segment profiles are composed of a thin layer (10--20 {angstrom} thick) of high concentration at the air surface, followed by a distinct second layer of much lower segment concentration that extends to larger depths into the liquid. The high segment density at the air surface is due to a strong surface attraction, arising from the low surface tension of the PSS backbone relative to the surface tension of water. At low salt concentration, the profiles tend toward a single dense layer, suggesting that the chains lie nearly flat at the interface in that limit. The adsorbed amount increases with salt concentration, with a stronger dependence for higher molecular weight chains. The adsorbed amounts at the air/water interface are higher than reported previously for PSS adsorbed onto neutral solid surfaces, consistent with the fact that the air-liquid interface provides a stronger surface attraction. While the trends of adsorbed amount and layer thickness with salt concentration and molecular weight are in good agreement with numerical self-consistent field lattice calculations, the measured bilayer profiles are rather different from the smoothly decaying theoretical profiles. The surface tensions of the PSS solutions are significantly lowered relative to those of pure salt solutions. Combining the reflectivity and surface tension measurements, an approximately linear relationship is established between the surface pressure and the PSS adsorbed amount.

  17. Tracking daily land surface albedo and reflectance anisotropy with moderate-resolution imaging spectroradiometer (MODIS)

    NASA Astrophysics Data System (ADS)

    Shuai, Yanmin

    A new algorithm provides daily values of land surface albedo and angular reflectance at a 500-m spatial resolution using data from the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments currently in orbit on NASA's Terra and Aqua satellite platforms. To overcome the day-to-day variance in observed surface reflectance induced by differences in view and solar illumination angles, the algorithm uses the RossThickLiSparse-Reciprocal bidirectional reflectance model, which is fitted to all MODIS observations of a 500-m resolution cell acquired during a 16-day moving window. Individual observations are weighted by their quality, observation coverage, and proximity to the production date of interest. Product quality is measured by (1) the root mean square error (RMSE) of observations against the best model fit; and (2) the ability of the angular sampling pattern of the observations at hand to determine reflectance model parameters accurately. A regional analysis of model fits to data from selected MODIS data tiles establishes the bounds of these quality measures for application in the daily algorithm. The algorithm, which is now available to users of direct broadcast satellite data from MODIS, allows daily monitoring of rapid surface radiation and land surface change phenomena such as crop development and forest foliage cycles. In two demonstrations, the daily algorithm captured rapid change in plant phenology. The growth phases of a winter wheat crop, as monitored at the Yucheng agricultural research station in Yucheng, China, matched MODIS daily multispectral reflectance data very well, especially during the flowering and heading stages. The daily algorithm also captured the daily change in autumn leaf color in New England, documenting the ability of the algorithm to work well over large regions with varying degrees of cloud cover and atmospheric conditions. Daily surface albedos measured using ground-based instruments on towers at the agricultural and

  18. Evaluation of MODIS surface reflectance products for wheat leaf area index (LAI) retrieval

    NASA Astrophysics Data System (ADS)

    Yi, Yonghong; Yang, Dawen; Huang, Jingfeng; Chen, Daoyi

    The accuracy of leaf area index (LAI) retrieval depends critically on the quality of the input reflectance. MODIS Collection 4 (C4) and Collection 5 (C5) land surface reflectance data are used for wheat LAI retrieval. Results are compared with in situ measurements. The uncertainty in the reflectance data of the two collections (C4 and C5) from both Terra and Aqua sensors is analyzed and its influence on LAI retrieval is discussed. The discrepancies of blue and near infrared reflectances between Terra and Aqua in the C5 data are less than the discrepancies between the sensors in the C4 data. For both Terra and Aqua, the C5 data have much lower blue reflectance than do the C4 data. This can be attributed to improvements in the atmospheric correction algorithm for the C5 data including cloud mask definition and aerosol retrieval. Using both empirical vegetation indices and inversion methods, the LAI is derived from the C4 and C5 surface reflectances. For daily C4 data, only Aqua Normalized difference water indices (NDWI) have significant correlations with the LAI (at a 99% confidence level); in contrast, for the daily C5 data, all the vegetation indices have significant correlations with the LAI. A three-layer neural network is used to invert a one-dimensional (1-D) radiative transfer model for LAI estimation. For the daily C4 data, the correlation between the modeled and measured LAIs is poor and the root mean square error (RMSE) is larger than 1.1; in comparison, the RMSE for the daily C5 data is 0.7. For both C4 and C5 collections, the LAI tends to be overestimated when the sensor is operated with a large view zenith angle in the backscattering direction. The error is either due to the mismatch between the measured reflectance and the modeled reflectance from the simple 1-D radiative transfer model in this direction or due to the assumption of a Lambertian surface in the MODIS atmospheric correction. Additionally, for both methods the results from the 8-day

  19. Investigating the structural changes of β-amyloid peptide aggregation using attenuated-total-reflection surface-enhanced Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Chiu, K.-C.; Yu, L.-Y.; Yih, J.-N.; Chen, S.-J.

    2007-02-01

    This study utilizes a surface-enhanced Raman spectroscopy (SERS) based on the attenuated-total-reflection (ATR) method to investigate that the structural information of the biomolecular monolayer on sensing surface can be dynamically observed with a higher signal-to-noise ratio signal. The secondary structures of long oligonucleotides and their influence on the DNA hybridization on the sensing surface are investigated. The SERS spectrum provides the structural information of the oligonucleotides with the help of a silver colloidal nanoparticle monolayer by control of the size and distribution of the nanoparticles adapted as a Raman active substrate. It is found that the ring-breathing modes of adenine, thymine, guanine, and cytosine in Raman fingerprint associated with three 60mer oligonucleotides with prominent secondary structures are lower than those observed for the two oligonucleotides with no obvious secondary structures. It is also determined that increasing the DNA hybridization temperature from 35°C to 45°C reduces secondary structure effects. The ATR-SERS biosensing technique will be used to provide valuable structural information regarding the short-term reversible interactions and long-term polymerization events in the Aβ aggregates on the sensing surface.

  20. Surface-enhanced infrared absorption of nucleic acids on gold substrate in FTIR reflectance mode

    NASA Astrophysics Data System (ADS)

    Dovbeshko, G. I.; Chegel, Vladimir I.; Gridina, Nina Y.; Repnytska, O. P.; Sekirin, I. V.; Shirshov, Yuri M.

    2001-06-01

    Data on surface enhanced infrared absorption (SEIRA) of nucleic acids deposited on the metal surface have been obtained in the experiment in FTIR reflectance mode. As metal surface, we used Au of 200 - 500 Angstrom thickness on quartz substrate. Roughness of Au was not greater than 50 Angstrom. In our experimental conditions, the enhancement factor of SEIRA was about 3 - 7. We obtained different enhancement factors for different vibrations of nuclei acids. Application of this method to the tumour brain nucleic acid gave a possibility to reveal some structural peculiarities of their sugar-phosphate backbone.

  1. Surface reflectance correction and stereo enhancement of Landsat thematic mapper imagery for structural geologic exploration

    SciTech Connect

    Thiessen, R.L.; Johnson, L.K.; Foote, H.P.; Eliason, J.R.

    1986-11-01

    Structural remote sensing analysis techniques for exploration have focussed on mapping of crustal fracture zones which can provide pathways for mineralization as well as permeability for movement and/or accumulation of oil, gas, and geothermal fluids. These analyses have relied heavily on manual lineament analysis of enhanced imagery. These image products contain shadow effects that preferentially enhance or suppress lineaments. This study was conducted to evaluate a digital technique for surface reflectance correction for shadows and subsequent stereo enhancement to provide shadow corrected stereo models for structural geologic exploration. Image products were produced from digital Landsat Thematic Mapper (TM) data and a digital elevation model (DEM). The Paiute Ridge quadrangle, Nevada, was selected as a test area for the analysis. Landsat TM data were registered to the DEM and processed to reduce topographic shadowing effects. A Minnaert reflectance model was used to approximate the topographic lighting effects. This reflectance model provided quantitative evaluation of each pixel in the image and was directly used to create a shadow image. These reflectance values were utilized to remove shadow effects from the TM data to produce the corrected surface reflectance. The DEM was used to stereo enhance the shadow corrected TM image. Fracture orientations determined from the original TM and shadow images show similar bias resulting from solar illumination. This bias was not present in the results from the shadow corrected and the corrected stereopair images, with the best correlation to the trends observed in the field data given by the latter.

  2. Infrared reflection-absorption spectroscopy of hyperfine layers on surfaces of semiconductors and dielectrics

    NASA Astrophysics Data System (ADS)

    Gruzinov, S. N.; Tolstoy, V. P.

    1988-02-01

    Infrared reflection-absorption spectroscopy of film son surfaces of transparent or weakly absorbing semiconductor and dielectric substrates is analyzed theoretically, the purpose being to establish the conditions for maximum sensitivity of this method. The absorption factor, namely the relative change of the reflection coefficient upon formation of a film on the substrate surface, is selected as the sensitivity criterion. The analysis is based on exact relations, one for a homogeneous isotopic absorbing film between substrate and ambient medium with plane-parallel boundaries and one for a reflecting layer with the possibility of multiple reflections taken into account. Calculations have been programmed on a computer for up to 60 nm thick SiO2 films on various substrates and infrared radiation within the 8 to 11 gmm waveband. The results indicate that the dependence of the absorption factor on the radiation wavelength and on the film thickness is different with the radiation s-polarized than with the radiation p-polarized. Calculations have also yielded the dispersion of optical constants characterizing a SiO2 film. According to these results, infrared spectroscopy is most sensitive to films on substrates with a small refractive index and when done with p-polarized radiation incident at exactly or approximately the Brewster angle for a determination of their presence and their composition respectively, also when no multiple reflections occur.

  3. Lipid remodelling in the reef-building honeycomb worm, Sabellaria alveolata, reflects acclimation and local adaptation to temperature

    PubMed Central

    Muir, Anna P.; Nunes, Flavia L. D.; Dubois, Stanislas F.; Pernet, Fabrice

    2016-01-01

    Acclimation and adaptation, which are key to species survival in a changing climate, can be observed in terms of membrane lipid composition. Remodelling membrane lipids, via homeoviscous adaptation (HVA), counteracts membrane dysfunction due to temperature in poikilotherms. In order to assess the potential for acclimation and adaptation in the honeycomb worm, Sabellaria alveolata, a reef-building polychaete that supports high biodiversity, we carried out common-garden experiments using individuals from along its latitudinal range. Individuals were exposed to a stepwise temperature increase from 15 °C to 25 °C and membrane lipid composition assessed. Our results suggest that S. alveolata was able to acclimate to higher temperatures, as observed by a decrease in unsaturation index and 20:5n-3. However, over the long-term at 25 °C, lipid composition patterns are not consistent with HVA expectations and suggest a stress response. Furthermore, unsaturation index of individuals from the two coldest sites were higher than those from the two warmest sites, with individuals from the thermally intermediate site being in-between, likely reflecting local adaptation to temperature. Therefore, lipid remodelling appears limited at the highest temperatures in S. alveolata, suggesting that individuals inhabiting warm environments may be close to their upper thermal tolerance limits and at risk in a changing climate. PMID:27762300

  4. Aerosol optical retrieval and surface reflectance from airborne remote sensing data over land.

    PubMed

    Bassani, Cristiana; Cavalli, Rosa Maria; Pignatti, Stefano

    2010-01-01

    Quantitative analysis of atmospheric optical properties and surface reflectance can be performed by applying radiative transfer theory in the Atmosphere-Earth coupled system, for the atmospheric correction of hyperspectral remote sensing data. This paper describes a new physically-based algorithm to retrieve the aerosol optical thickness at 550 nm (τ(550)) and the surface reflectance (ρ) from airborne acquired data in the atmospheric window of the Visible and Near-Infrared (VNIR) range. The algorithm is realized in two modules. Module A retrieves τ(550) with a minimization algorithm, then Module B retrieves the surface reflectance ρ for each pixel of the image. The method was tested on five remote sensing images acquired by an airborne sensor under different geometric conditions to evaluate the reliability of the method. The results, τ(550) and ρ, retrieved from each image were validated with field data contemporaneously acquired by a sun-sky radiometer and a spectroradiometer, respectively. Good correlation index, r, and low root mean square deviations, RMSD, were obtained for the τ(550) retrieved by Module A (r(2) = 0.75, RMSD = 0.08) and the ρ retrieved by Module B (r(2) ≤ 0.9, RMSD ≤ 0.003). Overall, the results are encouraging, indicating that the method is reliable for optical atmospheric studies and the atmospheric correction of airborne hyperspectral images. The method does not require additional at-ground measurements about at-ground reflectance of the reference pixel and aerosol optical thickness. PMID:22163558

  5. Aerosol Optical Retrieval and Surface Reflectance from Airborne Remote Sensing Data over Land

    PubMed Central

    Bassani, Cristiana; Cavalli, Rosa Maria; Pignatti, Stefano

    2010-01-01

    Quantitative analysis of atmospheric optical properties and surface reflectance can be performed by applying radiative transfer theory in the Atmosphere-Earth coupled system, for the atmospheric correction of hyperspectral remote sensing data. This paper describes a new physically-based algorithm to retrieve the aerosol optical thickness at 550nm (τ550) and the surface reflectance (ρ) from airborne acquired data in the atmospheric window of the Visible and Near-Infrared (VNIR) range. The algorithm is realized in two modules. Module A retrieves τ550 with a minimization algorithm, then Module B retrieves the surface reflectance ρ for each pixel of the image. The method was tested on five remote sensing images acquired by an airborne sensor under different geometric conditions to evaluate the reliability of the method. The results, τ550 and ρ, retrieved from each image were validated with field data contemporaneously acquired by a sun-sky radiometer and a spectroradiometer, respectively. Good correlation index, r, and low root mean square deviations, RMSD, were obtained for the τ550 retrieved by Module A (r2 = 0.75, RMSD = 0.08) and the ρ retrieved by Module B (r2 ≤ 0.9, RMSD ≤ 0.003). Overall, the results are encouraging, indicating that the method is reliable for optical atmospheric studies and the atmospheric correction of airborne hyperspectral images. The method does not require additional at-ground measurements about at-ground reflectance of the reference pixel and aerosol optical thickness. PMID:22163558

  6. Reflection electron energy-loss spectroscopy and imaging for surface studies in transmission electron microscopes.

    PubMed

    Wang, Z L; Bentley, J

    1992-02-15

    A review is given on the techniques and applications of high-energy reflection electron energy-loss spectroscopy (REELS) and reflection electron microscopy (REM) for surface studies in scanning transmission electron microscopes (STEM) and conventional transmission electron microscopes (TEM). A diffraction method is introduced to identify a surface orientation in the geometry of REM. The surface dielectric response theory is presented and applied for studying alpha-alumina surfaces. Domains of the alpha-alumina (012) surface initially terminated with oxygen can be reduced by an intense electron beam to produce Al metal; the resistance to beam damage of surface domains initially terminated with Al+3 ions is attributed to the screening effect of adsorbed oxygen. Surface energy-loss near-edge structure (ELNES), extended energy-loss fine structure (EXELFS), and microanalysis using REELS are illustrated based on the studies of TiO2 and MgO. Effects of surface resonances (or channeling) on the REELS signal-to-background ratio are described. The REELS detection of a monolayer of oxygen adsorption on diamond (111) surfaces is reported. It is shown that phase contrast REM image content can be significantly increased with the use of a field emission gun (FEG). Phase contrast effects close to the core of a screw dislocation are discussed and the associated Fresnel fringes around a surface step are observed. Finally, an in situ REM experiment is described for studying atomic desorption and diffusion processes on alpha-alumina surfaces at temperatures of 1,300-1,400 degrees C.

  7. Reflectivity dependence of threshold current in GaInAsP/InP surface emitting laser

    SciTech Connect

    Oshikiri, M.; Kawasaki, H.; Koyama, F.; Iga, K.

    1989-01-01

    The authors have made a systematic study on changing the reflectivity of Si/SiO/sub 2/ mirror for 1.3 ..mu..m GaInAsP/InP surface emitting lasers. The effective threshold current of 4.5 mA at 77K continuous operation has been obtained. This indicates a possibility of a sub-mA threshold at 77K and greater than or equal to20m at 300K by optimizing the mirror reflectivity.

  8. Direct observation of surface plasmons in YBCO by attenuated total reflection of light in the infrared

    NASA Astrophysics Data System (ADS)

    Walmsley, D. G.; Smyth, C. C.; Sellai, A.; McCafferty, P. G.; Dawson, P.; Morrow, T.; Graham, W. G.

    1994-02-01

    Surface plasmons have been observed directly in YBCO films in an Otto-geometry attenuated total reflection measurement at a wavelength of 3.392 μm. The laser deposited films are c-axis oriented on an MgO substrate. This observation confirms theoretical deductions from complex dielectric function data. Measured data have been fitted to a theoretical model and are compared with the optical constants determined by Bozovic [1]. The investigations have been extended to films with other orientations to investigate whether material anisotropy is reflected in the results and non-metallic behaviour is found.

  9. [A Method to Reconstruct Surface Reflectance Spectrum from Multispectral Image Based on Canopy Radiation Transfer Model].

    PubMed

    Zhao, Yong-guang; Ma, Ling-ling; Li, Chuan-rong; Zhu, Xiao-hua; Tang, Ling-li

    2015-07-01

    Due to the lack of enough spectral bands for multi-spectral sensor, it is difficult to reconstruct surface retlectance spectrum from finite spectral information acquired by multi-spectral instrument. Here, taking into full account of the heterogeneity of pixel from remote sensing image, a method is proposed to simulate hyperspectral data from multispectral data based on canopy radiation transfer model. This method first assumes the mixed pixels contain two types of land cover, i.e., vegetation and soil. The sensitive parameters of Soil-Leaf-Canopy (SLC) model and a soil ratio factor were retrieved from multi-spectral data based on Look-Up Table (LUT) technology. Then, by combined with a soil ratio factor, all the parameters were input into the SLC model to simulate the surface reflectance spectrum from 400 to 2 400 nm. Taking Landsat Enhanced Thematic Mapper Plus (ETM+) image as reference image, the surface reflectance spectrum was simulated. The simulated reflectance spectrum revealed different feature information of different surface types. To test the performance of this method, the simulated reflectance spectrum was convolved with the Landsat ETM + spectral response curves and Moderate Resolution Imaging Spectrometer (MODIS) spectral response curves to obtain the simulated Landsat ETM+ and MODIS image. Finally, the simulated Landsat ETM+ and MODIS images were compared with the observed Landsat ETM+ and MODIS images. The results generally showed high correction coefficients (Landsat: 0.90-0.99, MODIS: 0.74-0.85) between most simulated bands and observed bands and indicated that the simulated reflectance spectrum was well simulated and reliable. PMID:26717721

  10. Slow Cone Reflectance Changes during Bleaching Determined by Adaptive Optics Scanning Laser Ophthalmoscope in Living Human Eyes

    PubMed Central

    Hirota, Masakazu; Miyagawa, Suguru; Kanda, Hiroyuki; Endo, Takao; Lohmann, Tibor Karl; Miyoshi, Tomomitsu; Morimoto, Takeshi; Fujikado, Takashi

    2015-01-01

    To investigate the changes in the reflectance of human cone photoreceptors by an adaptive optics scanning laser ophthalmoscope (AO-SLO) during photobleaching. A custom-built AO-SLO with an observation light of 840-nm was used to measure the cone densities and the reflectance changes during bleaching by 630 nm red light emitting diodes. Measurements were made at 1° and 3° temporal to the fovea within an area of 1° × 1° in 8 eyes of 8 normal subjects. After dark-adaptation, images of the cone mosaics were recorded continuously for 5-min before, 5-min during, and after 5-min of light stimulation with a sampling rate of 5-Hz. The first positive peak (P1) was observed at 72.2 ± 15.0-s and a second positive peak (P2) at 257.5 ± 34.5-s at 1°. The increase of the reflectance of P1 was significantly larger at 1° (34.4 ± 13.9%) than at 3° (26.0 ± 10.5%; P = 0.03, Wilcoxon’s signed rank test). The average cone density at 1° (51123.13 ± 1401.23 cells/mm2) was significantly larger than that at 3° (30876.13 ± 1459.28 cells/mm2; P <0.001, Wilcoxon’s signed rank test). The changes in the reflectance of the cones during bleaching by red light had two peaks. The two peaks may be caused by regeneration of cone photopigment during bleaching. PMID:26121666

  11. Slow Cone Reflectance Changes during Bleaching Determined by Adaptive Optics Scanning Laser Ophthalmoscope in Living Human Eyes.

    PubMed

    Hirota, Masakazu; Miyagawa, Suguru; Kanda, Hiroyuki; Endo, Takao; Lohmann, Tibor Karl; Miyoshi, Tomomitsu; Morimoto, Takeshi; Fujikado, Takashi

    2015-01-01

    To investigate the changes in the reflectance of human cone photoreceptors by an adaptive optics scanning laser ophthalmoscope (AO-SLO) during photobleaching. A custom-built AO-SLO with an observation light of 840-nm was used to measure the cone densities and the reflectance changes during bleaching by 630 nm red light emitting diodes. Measurements were made at 1° and 3° temporal to the fovea within an area of 1° × 1° in 8 eyes of 8 normal subjects. After dark-adaptation, images of the cone mosaics were recorded continuously for 5-min before, 5-min during, and after 5-min of light stimulation with a sampling rate of 5-Hz. The first positive peak (P1) was observed at 72.2 ± 15.0-s and a second positive peak (P2) at 257.5 ± 34.5-s at 1°. The increase of the reflectance of P1 was significantly larger at 1° (34.4 ± 13.9%) than at 3° (26.0 ± 10.5%; P = 0.03, Wilcoxon's signed rank test). The average cone density at 1° (51123.13 ± 1401.23 cells/mm2) was significantly larger than that at 3° (30876.13 ± 1459.28 cells/mm2; P <0.001, Wilcoxon's signed rank test). The changes in the reflectance of the cones during bleaching by red light had two peaks. The two peaks may be caused by regeneration of cone photopigment during bleaching.

  12. X-ray Reflectivity Study of AlPdMn Quasicrystal Fivefold Surface Oxidation

    NASA Astrophysics Data System (ADS)

    Gu, Tianqu; Goldman, Alan I.; Pinhero, P. J.

    1997-03-01

    By means of X-ray reflectivity measurement, a fivefold surface of AlPdMn single quasicrystal is studied after being treated in different environments: normal air, humid air and water. An electron density profile of the surface is acquired after each treatment. The difference of the density profile obtained with different treatment indicates that water molecule plays an important role in the oxidation of quasicrystal surface. The surface exposed to normal air has a sharper electron density profile and less surface oxidation thickness than that exposed to humid air and immersed in water. The thickness of the oxidation layer is about 30Åand 58Åfor normal air treatment and humid air and water treatment, respectively.

  13. Experimental Study of a Membrane Antenna Surface Adaptive Control System

    NASA Technical Reports Server (NTRS)

    Fang, H.; Quijano, U.; Bach, V.; Hill, J.; Wang, K. W.

    2011-01-01

    Due to their ultra lightweight and high packaging efficiency, membrane reflectors are getting more and more attentions for mission architectures that need extremely large inspace deployable antennas. However how to maintain the surface shape of a membrane reflector to the instrument precision requirements is a very challenging problem. This experimental study investigated using PVDF membrane piezoelectric material as actuators to control the surface figures of membrane reflectors. The feasibility of this approach is demonstrated by several sets of test results.

  14. Redistribution of neural phase coherence reflects establishment of feedforward map in speech motor adaptation.

    PubMed

    Sengupta, Ranit; Nasir, Sazzad M

    2015-04-01

    Despite recent progress in our understanding of sensorimotor integration in speech learning, a comprehensive framework to investigate its neural basis is lacking at behaviorally relevant timescales. Structural and functional imaging studies in humans have helped us identify brain networks that support speech but fail to capture the precise spatiotemporal coordination within the networks that takes place during speech learning. Here we use neuronal oscillations to investigate interactions within speech motor networks in a paradigm of speech motor adaptation under altered feedback with continuous recording of EEG in which subjects adapted to the real-time auditory perturbation of a target vowel sound. As subjects adapted to the task, concurrent changes were observed in the theta-gamma phase coherence during speech planning at several distinct scalp regions that is consistent with the establishment of a feedforward map. In particular, there was an increase in coherence over the central region and a decrease over the fronto-temporal regions, revealing a redistribution of coherence over an interacting network of brain regions that could be a general feature of error-based motor learning in general. Our findings have implications for understanding the neural basis of speech motor learning and could elucidate how transient breakdown of neuronal communication within speech networks relates to speech disorders.

  15. An effective medium study of surface plasmon polaritons in nanostructured gratings using attenuated total reflection

    SciTech Connect

    Tyboroski, M. H.; Anderson, N. R.; Camley, R. E.

    2014-01-07

    Recent work studied surface plasmon resonances in structured materials by the method of attenuated total reflection using a prism on top of a metallic grating. That calculation considered Transverse Magnetic polarized radiation, involved an expansion in 121 Fourier modes, and found a number of interesting features. Many of these features were attributed to localized plasmons or other factors, which arise from a discrete structure. We use a simple effective medium theory to address the same problem, and find many of the same reflection features observed in the more complex calculation, indicating that localization is not an important factor. We also evaluate the possibility of using some of the new features in the reflection spectrum for bio-sensing and find that the sensitivity of the system to small changes in relative permittivity is increased compared to some standard methods.

  16. Surface quality monitoring for process control by on-line vibration analysis using an adaptive spline wavelet algorithm

    NASA Astrophysics Data System (ADS)

    Luo, G. Y.; Osypiw, D.; Irle, M.

    2003-05-01

    The dynamic behaviour of wood machining processes affects the surface finish quality of machined workpieces. In order to meet the requirements of increased production efficiency and improved product quality, surface quality information is needed for enhanced process control. However, current methods using high price devices or sophisticated designs, may not be suitable for industrial real-time application. This paper presents a novel approach of surface quality evaluation by on-line vibration analysis using an adaptive spline wavelet algorithm, which is based on the excellent time-frequency localization of B-spline wavelets. A series of experiments have been performed to extract the feature, which is the correlation between the relevant frequency band(s) of vibration with the change of the amplitude and the surface quality. The graphs of the experimental results demonstrate that the change of the amplitude in the selective frequency bands with variable resolution (linear and non-linear) reflects the quality of surface finish, and the root sum square of wavelet power spectrum is a good indication of surface quality. Thus, surface quality can be estimated and quantified at an average level in real time. The results can be used to regulate and optimize the machine's feed speed, maintaining a constant spindle motor speed during cutting. This will lead to higher level control and machining rates while keeping dimensional integrity and surface finish within specification.

  17. Reflective SOA fiber cavity adaptive laser source for measuring dynamic strains

    NASA Astrophysics Data System (ADS)

    Wei, Heming; Tao, Chuanyi; Krishnaswamy, Sridhar

    2016-04-01

    Smart sensors based on Optical fiber Bragg gratings (FBGs) are suitable for structural health monitoring of dynamic strains in civil, aerospace, and mechanical structures. In these structures, dynamic strains with high frequencies reveal acoustic emissions cracking or impact loading. It is necessary to find a practical tool for monitoring such structural damages. In this work, we explore an intelligent system based on a reflective semiconductor optical amplifier (RSOA)- FBG composed as a fiber cavity for measuring dynamic strain in intelligent structures. The ASE light emitted from a RSOA laser and reflected by a FBG is amplified in the fiber cavity and coupled out by a 90:10 coupler, which is demodulated by a low frequency compensated Michelson interferometer using a proportional-integral-derivative (PID) controller and is monitored via a photodetector. As the wavelength of the FBG shifts due to dynamic strain, the wavelength of the optical output from the laser cavity shifts accordingly, which is demodulated by the Michelson Interferometer. Because the RSOA has a quick transition time, the RSOA- FBG fiber cavity shows an ability of high frequency response to the FBG reflective spectrum shift, with frequency response extending to megahertz.

  18. Measuring and modeling near-surface reflected and emitted radiation fluxes at the FIFE site

    NASA Technical Reports Server (NTRS)

    Blad, Blaine L.; Walter-Shea, Elizabeth A.; Starks, Patrick J.; Vining, Roel C.; Hays, Cynthia J.; Mesarch, Mark A.

    1990-01-01

    Information is presented pertaining to the measurement and estimation of reflected and emitted components of the radiation balance. Information is included about reflectance and transmittance of solar radiation from and through the leaves of some grass and forb prairie species, bidirectional reflectance from a prairie canopy is discussed and measured and estimated fluxes are described of incoming and outgoing longwave and shortwave radiation. Results of the study showed only very small differences in reflectances and transmittances for the adaxial and abaxial surfaces of grass species in the visible and infrared wavebands, but some differences in the infrared wavebands were noted for the forbs. Reflectance from the prairie canopy changed as a function of solar and view zenith angles in the solar principal plane with definite asymmetry about nadir. The surface temperature of prairie canopies was found to vary by as much as 5 C depending on view zenith and azimuth position and on the solar azimuth. Aerodynamic temperature calculated from measured sensible heat fluxes ranged from 0 to 3 C higher than nadir-viewed temperatures. Models were developed to estimate incoming and reflected shortwave radiation from data collected with a Barnes Modular Multiband Radiometer. Several algorithms for estimating incoming longwave radiation were evaluated and compared to actual measures of that parameter. Net radiation was calculated using the estimated components of the shortwave radiation streams, determined from the algorithms developed, and from the longwave radiation streams provided by the Brunt, modified Deacon, and the Stefan-Boltzmann models. Estimates of net radiation were compared to measured values and found to be within the measurement error of the net radiometers used in the study.

  19. Three-dimensional reconstruction of specular reflecting technical surfaces using structured light microscopy

    NASA Astrophysics Data System (ADS)

    Kettel, Johannes; Müller, Claas; Reinecke, Holger

    2014-11-01

    In computer assisted quality control the three-dimensional reconstruction of technical surfaces is playing an ever more important role. Due to the demand on high measurement accuracy and data acquisition rates, structured light optical microscopy has become a valuable solution for the three-dimensional measurement of technical surfaces with high vertical and lateral resolution. However, the three-dimensional reconstruction of specular reflecting technical surfaces with very low surface-roughness and local slopes still remains a challenge to optical measurement principles. Furthermore the high data acquisition rates of current optical measurement systems depend on highly complex and expensive scanning-techniques making them impractical for inline quality control. In this paper we present a novel measurement principle based on a multi-pinhole structured light solution without moving parts which enables the threedimensional reconstruction of specular and diffuse reflecting technical surfaces. This measurement principle is based on multiple and parallel processed point-measurements. These point measurements are realized by spatially locating and analyzing the resulting Point Spread Function (PSF) in parallel for each point measurement. Analysis of the PSF is realized by pattern recognition and model-fitting algorithms accelerated by current Graphics-Processing-Unit (GPU) hardware to reach suitable measurement rates. Using the example of optical surfaces with very low surface-roughness we demonstrate the three-dimensional reconstruction of these surfaces by applying our measurement principle. Thereby we show that the resulting high measurement accuracy enables cost-efficient three-dimensional surface reconstruction suitable for inline quality control.

  20. Variability in constancy of the perceived surface reflectance across different illumination statistics.

    PubMed

    Motoyoshi, Isamu; Matoba, Hiroaki

    2012-01-15

    In contrast to the classical findings of lightness constancy, recent psychophysical studies show the strong dependency of the perceived reflectance of a surface on the structure of the natural illumination. The present study examined this inconstancy for systematic variations in the light field and an image-based explanation for it. Observers matched the specular and diffuse reflectance of a three-dimensional object in a complex scene under a fixed light field to that in the scene under different light fields with variable mean, contrast, and gamma. For the both specular and diffuse components, the matched reflectance was relatively constant against changes in the mean illuminance but varied extensively with changes in the contrast and gamma of the light field. We found that the matching data were well predicted by the similarity of the subband histograms of the images. The results support the notion that early spatial filtering can provide a unified account of both the constancy in the perceived surface reflectance against mean illuminance and the inconstancy for higher-order illumination statistics.

  1. Energy loss of MeV protons specularly reflected from metal surfaces

    SciTech Connect

    Juaristi, J.I.

    1996-05-01

    A parameter-free model is presented to study the energy loss of fast protons specularly reflected from metal surfaces. The contributions to the energy loss from excitation of valence-band electrons and ionization of localized target-atom electronic states are calculated separately. The former is calculated from the induced surface wake potential using linear response theory and the specular-reflection model, while the latter is calculated in the first Born approximation. The results obtained are in good agreement with available experimental data. However, the experimental qualitative trend of the energy loss as a function of the angle of incidence is obtained when the valence-band electron model is replaced by localized target atom electron states, though with a worse quantitative agreement. {copyright} {ital 1996 The American Physical Society.}

  2. Recent Surface Reflectance Measurement Campaigns with Emphasis on Best Practices, SI Traceability and Uncertainty Estimation

    NASA Technical Reports Server (NTRS)

    Helder, Dennis; Thome, Kurtis John; Aaron, Dave; Leigh, Larry; Czapla-Myers, Jeff; Leisso, Nathan; Biggar, Stuart; Anderson, Nik

    2012-01-01

    A significant problem facing the optical satellite calibration community is limited knowledge of the uncertainties associated with fundamental measurements, such as surface reflectance, used to derive satellite radiometric calibration estimates. In addition, it is difficult to compare the capabilities of calibration teams around the globe, which leads to differences in the estimated calibration of optical satellite sensors. This paper reports on two recent field campaigns that were designed to isolate common uncertainties within and across calibration groups, particularly with respect to ground-based surface reflectance measurements. Initial results from these efforts suggest the uncertainties can be as low as 1.5% to 2.5%. In addition, methods for improving the cross-comparison of calibration teams are suggested that can potentially reduce the differences in the calibration estimates of optical satellite sensors.

  3. Surface-reflection-initiated pulse-contrast degradation in an optical parametric chirped-pulse amplifier.

    PubMed

    Wang, Jing; Yuan, Peng; Ma, Jingui; Wang, Yongzhi; Xie, Guoqiang; Qian, Liejia

    2013-07-01

    We study a novel mechanism of pre-pulse generation in an optical parametric chirped-pulse amplification (OPCPA) system through an analytical approach together with numerical simulations. The acquired pre-pulses are initiated from the surface-reflection-induced modulation of the seed spectrum and occur as a consequence of high-order distortion of such modulated spectrum due to the instantaneous gain saturation effect. We demonstrate that the intensities of pre-pulses increase quadratically with the initial temporal modulation-depth of the stretched signal pulse as well as the conversion efficiency prior to substantial pump-depletion. Explicit formulas for estimating the contrast limit due to surface reflections are present. We also discuss the impact of group-velocity mismatch on the pre-pulse generation. The results of this work may deepen our cognition on the complexity of the pulse-contrast problem in OPCPA systems. PMID:23842344

  4. Genome complexity in the coelacanth is reflected in its adaptive immune system

    USGS Publications Warehouse

    Saha, Nil Ratan; Ota, Tatsuya; Litman, Gary W.; Hansen, John; Parra, Zuly; Hsu, Ellen; Buonocore, Francesco; Canapa, Adriana; Cheng, Jan-Fang; Amemiya, Chris T.

    2014-01-01

    We have analyzed the available genome and transcriptome resources from the coelacanth in order to characterize genes involved in adaptive immunity. Two highly distinctive IgW-encoding loci have been identified that exhibit a unique genomic organization, including a multiplicity of tandemly repeated constant region exons. The overall organization of the IgW loci precludes typical heavy chain class switching. A locus encoding IgM could not be identified either computationally or by using several different experimental strategies. Four distinct sets of genes encoding Ig light chains were identified. This includes a variant sigma-type Ig light chain previously identified only in cartilaginous fishes and which is now provisionally denoted sigma-2. Genes encoding α/β and γ/δ T-cell receptors, and CD3, CD4, and CD8 co-receptors also were characterized. Ig heavy chain variable region genes and TCR components are interspersed within the TCR α/δ locus; this organization previously was reported only in tetrapods and raises questions regarding evolution and functional cooption of genes encoding variable regions. The composition, organization and syntenic conservation of the major histocompatibility complex locus have been characterized. We also identified large numbers of genes encoding cytokines and their receptors, and other genes associated with adaptive immunity. In terms of sequence identity and organization, the adaptive immune genes of the coelacanth more closely resemble orthologous genes in tetrapods than those in teleost fishes, consistent with current phylogenomic interpretations. Overall, the work reported described herein highlights the complexity inherent in the coelacanth genome and provides a rich catalog of immune genes for future investigations.

  5. Genome complexity in the coelacanth is reflected in its adaptive immune system.

    PubMed

    Saha, Nil Ratan; Ota, Tatsuya; Litman, Gary W; Hansen, John; Parra, Zuly; Hsu, Ellen; Buonocore, Francesco; Canapa, Adriana; Cheng, Jan-Fang; Amemiya, Chris T

    2014-09-01

    We have analyzed the available genome and transcriptome resources from the coelacanth in order to characterize genes involved in adaptive immunity. Two highly distinctive IgW-encoding loci have been identified that exhibit a unique genomic organization, including a multiplicity of tandemly repeated constant region exons. The overall organization of the IgW loci precludes typical heavy chain class switching. A locus encoding IgM could not be identified either computationally or by using several different experimental strategies. Four distinct sets of genes encoding Ig light chains were identified. This includes a variant sigma-type Ig light chain previously identified only in cartilaginous fishes and which is now provisionally denoted sigma-2. Genes encoding α/β and γ/δ T-cell receptors, and CD3, CD4, and CD8 co-receptors also were characterized. Ig heavy chain variable region genes and TCR components are interspersed within the TCR α/δ locus; this organization previously was reported only in tetrapods and raises questions regarding evolution and functional cooption of genes encoding variable regions. The composition, organization and syntenic conservation of the major histocompatibility complex locus have been characterized. We also identified large numbers of genes encoding cytokines and their receptors, and other genes associated with adaptive immunity. In terms of sequence identity and organization, the adaptive immune genes of the coelacanth more closely resemble orthologous genes in tetrapods than those in teleost fishes, consistent with current phylogenomic interpretations. Overall, the work reported described herein highlights the complexity inherent in the coelacanth genome and provides a rich catalog of immune genes for future investigations.

  6. Genome complexity in the coelacanth is reflected in its adaptive immune system

    PubMed Central

    Ota, Tatsuya; Litman, Gary W.; Hansen, John; Parra, Zuly; Hsu, Ellen; Buonocore, Francesco; Canapa, Adriana; Cheng, Jan-Fang; Amemiya, Chris T.

    2014-01-01

    We have analyzed the available genome and transcriptome resources from the coelacanth in order to characterize genes involved in adaptive immunity. Two highly distinctive IgW-encoding loci have been identified that exhibit a unique genomic organization, including a multiplicity of tandemly repeated constant region exons. The overall organization of the IgW loci precludes typical heavy chain class switching. A locus encoding IgM could not be identified either computationally or by using several different experimental strategies. Four distinct sets of genes encoding Ig light chains were identified. This includes a variant sigma-type Ig light chain previously identified only in cartilaginous fishes and which is now provisionally denoted sigma-2. Genes encoding α/β and γ/δ T-cell receptors, and CD3, CD4 and CD8 co-receptors also were characterized. Ig heavy chain variable region genes and TCR components are interspersed within the TCR α/δ locus; this organization previously was reported only in tetrapods and raises questions regarding evolution and functional cooption of genes encoding variable regions. The composition, organization and syntenic conservation of the major histocompatibility complex locus have been characterized. We also identified large numbers of genes encoding cytokines and their receptors, and other genes associated with adaptive immunity. In terms of sequence identity and organization, the adaptive immune genes of the coelacanth more closely resemble orthologous genes in tetrapods than those in teleost fishes, consistent with current phylogenomic interpretations. Overall, the work reported described herein highlights the complexity inherent in the coelacanth genome and provides a rich catalog of immune genes for future investigations. PMID:24464682

  7. Immobility in the forced swim test is adaptive and does not reflect depression.

    PubMed

    Molendijk, Marc L; de Kloet, E Ronald

    2015-12-01

    The forced swim test is based on the progressive immobility a rodent displays when immersed in a beaker filled with water from where no escape is possible. While the test was originally designed to identify the antidepressant potential of drugs, over the past decade a rapidly growing number of publications (more than 2000) portray this immobility response anthropomorphically as a measure for depression and despair. This is incorrect. The response to the forced swim stressor should be considered for what it shows: a switch from active to passive behavior in the face of an acute stressor, aligned to cognitive functions underlying behavioral adaptation and survival.

  8. Improved system calibration for specular surface measurement by using reflections from a plane mirror.

    PubMed

    Zhou, Tian; Chen, Kun; Wei, Haoyun; Li, Yan

    2016-09-01

    In this paper, we introduce a flexible and simple system calibration method for specular surface metrology based on the combination of reflection rays determined by the varied points on a screen and reflection images of a plane mirror without fiducials placed at three different locations. This calibration procedure involves three steps. The camera is first calibrated based on plane patterns. Then the reflection ray directions are measured via correspondence matching. The last calibration step is the pose estimation by the orthogonal iteration algorithm and reflections in a plane mirror. Basically, the concept of replacing the coordinates of the camera center with the reflection ray can alleviate the trouble of imaging aberration. Then global optimization can be operated with the orthogonal projection defined by the reflection ray, providing precise initial values for the process of bundle adjustment, compared to the classical calibration approach directly using the local optimization algorithm. Simulations and experiments both demonstrate the validity, efficiency, and robustness of the proposed improved method. In the simulations, the proposed method achieves the absolute errors of the camera parameters within 3 pixels and the relative errors of the screen pose are below 0.5% when the noise level is 0.6 pixel. Furthermore, the calibration method shows strong anti-noise ability, relying on the application of the reflection rays and the global optimization before the final bundle adjustment. In addition, the reconstruction accuracy in our experiment improves by 60.11% by the proposed method compared with the calibration procedure, which only utilizes the bundle adjustment optimization. In general, this novel calibration method can make the measurement achieve high accuracy and robustness at a low cost and with a simple setup, providing an efficient, economical, and flexible approach for a phase measuring deflectometry system in practical situations. PMID:27607278

  9. Transitioning MODIS to VIIRS observations for Land: Surface Reflectance results, Status and Long-term Prospective

    NASA Astrophysics Data System (ADS)

    Vermote, E.

    2015-12-01

    Surface reflectance is one of the key products from VIIRS and as with MODIS, is used in developing several higher-order land products. The VIIRS Surface Reflectance (SR) IP is based on the heritage MODIS Collection 5 product (Vermote et al. 2002). The quality and character of surface reflectance depends on the accuracy of the VIIRS Cloud Mask (VCM) and aerosol algorithms and of course on the adequate calibration of the sensor. Early evaluation of the VIIRS SR product in the context of the maturity of the operational processing system known as the Interface Data Processing System (IDPS), has been a major focus of work to-date, but is now evolving into the development of a VIIRS suite of Climate Data Records produced by the NASA Land Science Investigator Processing System (SIPS). We will present the calibration performance and the role of the surface reflectance in calibration monitoring, the performance of the cloud mask with a focus on vegetation monitoring (no snow conditions), the performance of the aerosol input used in the atmospheric correction with quantitative results of the performance of the SR product over AERONET sites. Based on those elements and further assessment, we will address the readiness of the SR product for the production of higher-order land products such as Vegetation Indices, Albedo and LAI/FPAR, the its application to agricultural monitoring and in particular the integration of VIIRS data into the global agricultural monitoring (GLAM) system developed at UMd. Finally from the lessons learned, we will articulate a set of critical recommendations to ensure consistency and continuity of the JPSS mission with the MODIS data record.

  10. Combined analysis of surface reflection imaging and vertical seismic profiling at Yucca Mountain, Nevada

    SciTech Connect

    Daley, T.M.; Majer, E.L.; Karageorgi, E.

    1994-08-01

    This report presents results from surface and borehole seismic profiling performed by the Lawrence Berkeley Laboratory (LBL) on Yucca Mountain. This work was performed as part of the site characterization effort for the potential high-level nuclear waste repository. Their objective was to provide seismic imaging from the near surface (200 to 300 ft. depth) to the repository horizon and below, if possible. Among the issues addressed by this seismic imaging work are location and depth of fracturing and faulting, geologic identification of reflecting horizons, and spatial continuity of reflecting horizons. The authors believe their results are generally positive, with tome specific successes. This was the first attempt at this scale using modem seismic imaging techniques to determine geologic features on Yucca Mountain. The principle purpose of this report is to present the interpretation of the seismic reflection section in a geologic context. Three surface reflection profiles were acquired and processed as part of this study. Because of environmental concerns, all three lines were on preexisting roads. Line 1 crossed the mapped surface trace of the Ghost Dance fault and it was intended to study the dip and depth extent of the fault system. Line 2 was acquired along Drill Hole wash and was intended to help the ESF north ramp design activities. Line 3 was acquired along Yucca Crest and was designed to image geologic horizons which were thought to be less faulted along the ridge. Unfortunately, line 3 proved to have poor data quality, in part because of winds, poor field conditions and limited time. Their processing and interpretation efforts were focused on lines 1 and 2 and their associated VSP studies.

  11. Reflection of polarized light by rough surfaces: Monte Carlo modeling compared to measurements

    NASA Astrophysics Data System (ADS)

    Guirado, Daniel; Marcos Sanz, Juan; María Saiz, José; Muñoz, Olga; Stam, Daphne M.

    2013-04-01

    A Monte Carlo model of light scattering in a dense medium was developed in order to simulate the reflection of polarized light by rough surfaces [1]. This model calculates all four Stokes parameters of light scattered in all directions by a surface made of any material. Although multiple scattering is allowed, there is a limitation in the packing density of the medium, as independent scattering is assumed. The model can be applied to the study of light scattering by fluffy icy/dusty surfaces, e.g., various types of planetary or lunar regolith-type surfaces, icy moons or comets. The main goal of this work is to test the model by comparing scattering matrix elements calculated with the Monte Carlo model to experimentally measured scattering matrix elements as functions of the phase angle. We use a Sahara sand surface for this. The experimental scattering matrix is measured at the new apparatus developed at the University of Cantabria (Spain) [2]. Sample surfaces are prepared by putting together dust grains with a water-diluted glue coating. A surface's top layer was made with pure sand, to preserve the air-sand refractive index ratio. Calibration measurements have already been carried out successfully by using Spectralon as a Lambertian surface. After calibration, measurements of a surface made of Sahara sand were performed. In such measurements, deviations from Lambertian behavior were found, as well as a very prominent forward peak in the (1,1)-element of the matrix for grazing illumination angles. The values of I and -Q/I calculated by the model for the vertical scattering plane and non-polarized incident light were compared to the measured F11 and -F21/F11 elements for several incident directions. A good agreement between measurements and calculations was achieved. The forward-scattering peak of the (1,1)-element can be interpreted as a result of single scattering of horizontally incident light by the small features of the non-flat surface. In this case, light

  12. Computer-aided high-accuracy testing of reflective surface with reverse Hartmann test.

    PubMed

    Wang, Daodang; Zhang, Sen; Wu, Rengmao; Huang, Chih Yu; Cheng, Hsiang-Nan; Liang, Rongguang

    2016-08-22

    The deflectometry provides a feasible way for surface testing with a high dynamic range, and the calibration is a key issue in the testing. A computer-aided testing method based on reverse Hartmann test, a fringe-illumination deflectometry, is proposed for high-accuracy testing of reflective surfaces. The virtual "null" testing of surface error is achieved based on ray tracing of the modeled test system. Due to the off-axis configuration in the test system, it places ultra-high requirement on the calibration of system geometry. The system modeling error can introduce significant residual systematic error in the testing results, especially in the cases of convex surface and small working distance. A calibration method based on the computer-aided reverse optimization with iterative ray tracing is proposed for the high-accuracy testing of reflective surface. Both the computer simulation and experiments have been carried out to demonstrate the feasibility of the proposed measurement method, and good measurement accuracy has been achieved. The proposed method can achieve the measurement accuracy comparable to the interferometric method, even with the large system geometry calibration error, providing a feasible way to address the uncertainty on the calibration of system geometry. PMID:27557245

  13. Computer-aided high-accuracy testing of reflective surface with reverse Hartmann test.

    PubMed

    Wang, Daodang; Zhang, Sen; Wu, Rengmao; Huang, Chih Yu; Cheng, Hsiang-Nan; Liang, Rongguang

    2016-08-22

    The deflectometry provides a feasible way for surface testing with a high dynamic range, and the calibration is a key issue in the testing. A computer-aided testing method based on reverse Hartmann test, a fringe-illumination deflectometry, is proposed for high-accuracy testing of reflective surfaces. The virtual "null" testing of surface error is achieved based on ray tracing of the modeled test system. Due to the off-axis configuration in the test system, it places ultra-high requirement on the calibration of system geometry. The system modeling error can introduce significant residual systematic error in the testing results, especially in the cases of convex surface and small working distance. A calibration method based on the computer-aided reverse optimization with iterative ray tracing is proposed for the high-accuracy testing of reflective surface. Both the computer simulation and experiments have been carried out to demonstrate the feasibility of the proposed measurement method, and good measurement accuracy has been achieved. The proposed method can achieve the measurement accuracy comparable to the interferometric method, even with the large system geometry calibration error, providing a feasible way to address the uncertainty on the calibration of system geometry.

  14. Does Variation in Genome Sizes Reflect Adaptive or Neutral Processes? New Clues from Passiflora

    PubMed Central

    Fonseca, Tamara C.; Salzano, Francisco M.; Bonatto, Sandro L.; Freitas, Loreta B.

    2011-01-01

    One of the long-standing paradoxes in genomic evolution is the observation that much of the genome is composed of repetitive DNA which has been typically regarded as superfluous to the function of the genome in generating phenotypes. In this work, we used comparative phylogenetic approaches to investigate if the variations in genome sizes (GS) should be considered as adaptive or neutral processes by the comparison between GS and flower diameters (FD) of 50 Passiflora species, more specifically, within its two most species-rich subgenera, Passiflora and Decaloba. For this, we have constructed a phylogenetic tree of these species, estimated GS and FD of them, inferred the tempo and mode of evolution of these traits and their correlations, using both current and phylogenetically independent contrasted values. We found significant correlations among the traits, when considering the complete set of data or only the subgenus Passiflora, whereas no correlations were observed within Decaloba. Herein, we present convincing evidence of adaptive evolution of GS, as well as clues that this pattern is limited by a minimum genome size, which could reduce both the possibilities of changes in GS and the possibility of phenotypic responses to environment changes. PMID:21464897

  15. A fast smoothing algorithm for post-processing of surface reflectance spectra retrieved from airborne imaging spectrometer data.

    PubMed

    Gao, Bo-Cai; Liu, Ming

    2013-10-14

    Surface reflectance spectra retrieved from remotely sensed hyperspectral imaging data using radiative transfer models often contain residual atmospheric absorption and scattering effects. The reflectance spectra may also contain minor artifacts due to errors in radiometric and spectral calibrations. We have developed a fast smoothing technique for post-processing of retrieved surface reflectance spectra. In the present spectral smoothing technique, model-derived reflectance spectra are first fit using moving filters derived with a cubic spline smoothing algorithm. A common gain curve, which contains minor artifacts in the model-derived reflectance spectra, is then derived. This gain curve is finally applied to all of the reflectance spectra in a scene to obtain the spectrally smoothed surface reflectance spectra. Results from analysis of hyperspectral imaging data collected with the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data are given. Comparisons between the smoothed spectra and those derived with the empirical line method are also presented.

  16. A fiber-coupled displacement measuring interferometer for determination of the posture of a reflective surface.

    PubMed

    Mao, Shuai; Hu, Peng-Cheng; Ding, Xue-Mei; Tan, Jiu-Bin

    2016-08-01

    A fiber-coupled displacement measuring interferometer capable of determining of the posture of a reflective surface of a measuring mirror is proposed. The newly constructed instrument combines fiber-coupled displacement and angular measurement technologies. The proposed interferometer has advantages of both the fiber-coupled and the spatially beam-separated interferometer. A portable dual-position sensitive detector (PSD)-based unit within this proposed interferometer measures the parallelism of the two source beams to guide the fiber-coupling adjustment. The portable dual PSD-based unit measures not only the pitch and yaw of the retro-reflector but also measures the posture of the reflective surface. The experimental results of displacement calibration show that the deviations between the proposed interferometer and a reference one, Agilent 5530, at two different common beam directions are both less than ±35 nm, thus verifying the effectiveness of the beam parallelism measurement. The experimental results of angular calibration show that deviations of pitch and yaw with the auto-collimator (as a reference) are less than ±2 arc sec, thus proving the proposed interferometer's effectiveness for determination of the posture of a reflective surface. PMID:27587101

  17. A fiber-coupled displacement measuring interferometer for determination of the posture of a reflective surface

    NASA Astrophysics Data System (ADS)

    Mao, Shuai; Hu, Peng-Cheng; Ding, Xue-Mei; Tan, Jiu-Bin

    2016-08-01

    A fiber-coupled displacement measuring interferometer capable of determining of the posture of a reflective surface of a measuring mirror is proposed. The newly constructed instrument combines fiber-coupled displacement and angular measurement technologies. The proposed interferometer has advantages of both the fiber-coupled and the spatially beam-separated interferometer. A portable dual-position sensitive detector (PSD)-based unit within this proposed interferometer measures the parallelism of the two source beams to guide the fiber-coupling adjustment. The portable dual PSD-based unit measures not only the pitch and yaw of the retro-reflector but also measures the posture of the reflective surface. The experimental results of displacement calibration show that the deviations between the proposed interferometer and a reference one, Agilent 5530, at two different common beam directions are both less than ±35 nm, thus verifying the effectiveness of the beam parallelism measurement. The experimental results of angular calibration show that deviations of pitch and yaw with the auto-collimator (as a reference) are less than ±2 arc sec, thus proving the proposed interferometer's effectiveness for determination of the posture of a reflective surface.

  18. Lagrangian flows within reflecting internal waves at a horizontal free-slip surface

    NASA Astrophysics Data System (ADS)

    Zhou, Qi; Diamessis, Peter J.

    2015-12-01

    In this paper sequel to Zhou and Diamessis ["Reflection of an internal gravity wave beam off a horizontal free-slip surface," Phys. Fluids 25, 036601 (2013)], we consider Lagrangian flows within nonlinear internal waves (IWs) reflecting off a horizontal free-slip rigid lid, the latter being a model of the ocean surface. The problem is approached both analytically using small-amplitude approximations and numerically by tracking Lagrangian fluid particles in direct numerical simulation (DNS) datasets of the Eulerian flow. Inviscid small-amplitude analyses for both plane IWs and IW beams (IWBs) show that Eulerian mean flow due to wave-wave interaction and wave-induced Stokes drift cancels each other out completely at the second order in wave steepness A, i.e., O(A2), implying zero Lagrangian mean flow up to that order. However, high-accuracy particle tracking in finite-Reynolds-number fully nonlinear DNS datasets from the work of Zhou and Diamessis suggests that the Euler-Stokes cancelation on O(A2) is not complete. This partial cancelation significantly weakens the mean Lagrangian flows but does not entirely eliminate them. As a result, reflecting nonlinear IWBs produce mean Lagrangian drifts on O(A2) and thus particle dispersion on O(A4). The above findings can be relevant to predicting IW-driven mass transport in the oceanic surface and subsurface region which bears important observational and environmental implications, under circumstances where the effect of Earth rotation can be ignored.

  19. Estimation of the remote-sensing reflectance from above-surface measurements.

    PubMed

    Mobley, C D

    1999-12-20

    The remote-sensing reflectance R(rs) is not directly measurable, and various methodologies have been employed in its estimation. I review the radiative transfer foundations of several commonly used methods for estimating R(rs), and errors associated with estimating R(rs) by removal of surface-reflected sky radiance are evaluated using the Hydrolight radiative transfer numerical model. The dependence of the sea surface reflectance factor rho, which is not an inherent optical property of the surface, on sky conditions, wind speed, solar zenith angle, and viewing geometry is examined. If rho is not estimated accurately, significant errors can occur in the estimated R(rs) for near-zenith Sun positions and for high wind speeds, both of which can give considerable Sun glitter effects. The numerical simulations suggest that a viewing direction of 40 deg from the nadir and 135 deg from the Sun is a reasonable compromise among conflicting requirements. For this viewing direction, a value of rho approximately 0.028 is acceptable only for wind speeds less than 5 m s(-1). For higher wind speeds, curves are presented for the determination of rho as a function of solar zenith angle and wind speed. If the sky is overcast, a value of rho approximately 0.028 is used at all wind speeds.

  20. Reliability of internal prediction/estimation and its application. I. Adaptive action selection reflecting reliability of value function.

    PubMed

    Sakaguchi, Yutaka; Takano, Mitsuo

    2004-09-01

    This article proposes an adaptive action-selection method for a model-free reinforcement learning system, based on the concept of the 'reliability of internal prediction/estimation'. This concept is realized using an internal variable, called the Reliability Index (RI), which estimates the accuracy of the internal estimator. We define this index for a value function of a temporal difference learning system and substitute it for the temperature parameter of the Boltzmann action-selection rule. Accordingly, the weight of exploratory actions adaptively changes depending on the uncertainty of the prediction. We use this idea for tabular and weighted-sum type value functions. Moreover, we use the RI to adjust the learning coefficient in addition to the temperature parameter, meaning that the reliability becomes a general basis for meta-learning. Numerical experiments were performed to examine the behavior of the proposed method. The RI-based Q-learning system demonstrated its features when the adaptive learning coefficient and large RI-discount rate (which indicate how the RI values of future states are reflected in the RI value of the current state) were introduced. Statistical tests confirmed that the algorithm spent more time exploring in the initial phase of learning, but accelerated learning from the midpoint of learning. It is also shown that the proposed method does not work well with the actor-critic models. The limitations of the proposed method and its relationship to relevant research are discussed. PMID:15312837

  1. The reflection and transmission properties of a triple band dichroic surface

    NASA Technical Reports Server (NTRS)

    Schneider, S. W.; Munk, B. A.

    1990-01-01

    The development of a triple-band dichroic surface design is detailed that is reflective in the Ka-band from 22.5 to 27.3 GHz and the Ku-band from 13.7 to 15.1 GHz, yet transparent in the S-band from 2.0 to 2.3 GHz, for all planes of incidence, and for all angles of incidence out to eta = 45 deg. The design is comprised of two gangbuster whole-surfaces separated by a distance, d, that is comparable to a fraction of a wavelength in S-band, and enhanced by the addition of a dielectric matching plate. The gangbuster array is comprised of tightly packed straight skewed dipole elements referred to as half-surfaces. Two of these half-surfaces are oriented orthogonal to each other and placed an array separation distance, s, apart to form the gangbuster whole-surface which allows any arbitrary plane of incidence. Results are given for the triple-band design with and without dielectric and conduction losses. The cross polarization properties of the dichroic surface was further investigated. It is shown that the reflection cross polarized component is dominated by the geometry of the front whole surface of the design (particularly the array separation s) and is never more than -22.5 dB in the frequency band 0 to 30 GHz. The transmission cross polarization component is dependent on both whole-surfaces and is never more than -30 dB in the same frequency band.

  2. Task Adaptive Walking Robots for Mars Surface Exploration

    NASA Technical Reports Server (NTRS)

    Huntsberger, Terry; Hickey, Gregory; Kennedy, Brett; Aghazarian, Hrand

    2000-01-01

    There are exciting opportunities for robot science that lie beyond the reach of current manipulators, rovers, balloons, penetrators, etc. Examples include mobile explorations of the densely cratered Mars highlands, of asteroids, and of moons. These sites are believed to be rich in geologic history and mineralogical detail, but are difficult to robotically access and sample. The surface terrains are rough and changeable, with variable porosity and dust layering; and the small bodies present further challenges of low-temperature, micro-gravity environments. Even the more benign areas of Mars are highly variegated in character (>VL2 rock densities), presenting significant risk to conventional rovers. The development of compact walking robots would have applications to the current mission set for Mars surface exploration, as well as enabling future Mars Outpost missions, asteroid rendezvous missions for the Solar System Exploration Program (SSE) and the mechanical assembly/inspection of large space platforms for the Human Exploration and Development of Spaces (HEDS).

  3. ChemCam passive reflectance spectroscopy of surface materials at the Curiosity landing site, Mars

    NASA Astrophysics Data System (ADS)

    Johnson, Jeffrey R.; Bell, J. F.; Bender, S.; Blaney, D.; Cloutis, E.; DeFlores, L.; Ehlmann, B.; Gasnault, O.; Gondet, B.; Kinch, K.; Lemmon, M.; Le Mouélic, S.; Maurice, S.; Rice, M.; Wiens, R. C.

    2015-03-01

    The spectrometers on the Mars Science Laboratory (MSL) ChemCam instrument were used in passive mode to record visible/near-infrared (400-840 nm) radiance from the martian surface. Using the onboard ChemCam calibration targets' housing as a reflectance standard, we developed methods to collect, calibrate, and reduce radiance observations to relative reflectance. Such measurements accurately reproduce the known reflectance spectra of other calibration targets on the rover, and represent the highest spatial resolution (0.65 mrad) and spectral sampling (<1 nm) visible/near-infrared reflectance spectra from a landed platform on Mars. Relative reflectance spectra of surface rocks and soils match those from orbital observations and multispectral data from the MSL Mastcam camera. Preliminary analyses of the band depths, spectral slopes, and reflectance ratios of the more than 2000 spectra taken during the first year of MSL operations demonstrate at least six spectral classes of materials distinguished by variations in ferrous and ferric components. Initial comparisons of ChemCam spectra to laboratory spectra of minerals and Mars analog materials demonstrate similarities with palagonitic soils and indications of orthopyroxene in some dark rocks. Magnesium-rich "raised ridges" tend to exhibit distinct near-infrared slopes. The ferric absorption downturn typically found for martian materials at <600 nm is greatly subdued in brushed rocks and drill tailings, consistent with their more ferrous nature. Calcium-sulfate veins exhibit the highest relative reflectances observed, but are still relatively red owing to the effects of residual dust. Such dust is overall less prominent on rocks sampled within the "blast zone" immediately surrounding the landing site. These samples were likely affected by the landing thrusters, which partially removed the ubiquitous dust coatings. Increased dust coatings on the calibration targets during the first year of the mission were documented by

  4. Reflectance spectroscopy of palagonite and iron-rich montmorillonite clay mixtures: Implications for the surface composition of Mars

    NASA Technical Reports Server (NTRS)

    Orenberg, J. B.; Handy, J.

    1991-01-01

    Because of the power of remote sensing reflectance spectroscopy in determining mineralogy, it was used as the major method of identifying possible mineral analogs of the Martian surface. A summary of proposed Martian surface compositions from reflectance spectroscopy before 1979 was presented. Since that time, iron-rich montmorillonite clay, nanocrystalline or nanophase hematite, and palagonite were suggested as Mars soil analog materials.

  5. Applying Parallel Adaptive Methods with GeoFEST/PYRAMID to Simulate Earth Surface Crustal Dynamics

    NASA Technical Reports Server (NTRS)

    Norton, Charles D.; Lyzenga, Greg; Parker, Jay; Glasscoe, Margaret; Donnellan, Andrea; Li, Peggy

    2006-01-01

    This viewgraph presentation reviews the use Adaptive Mesh Refinement (AMR) in simulating the Crustal Dynamics of Earth's Surface. AMR simultaneously improves solution quality, time to solution, and computer memory requirements when compared to generating/running on a globally fine mesh. The use of AMR in simulating the dynamics of the Earth's Surface is spurred by future proposed NASA missions, such as InSAR for Earth surface deformation and other measurements. These missions will require support for large-scale adaptive numerical methods using AMR to model observations. AMR was chosen because it has been successful in computation fluid dynamics for predictive simulation of complex flows around complex structures.

  6. Negotiated meanings of disability simulations in an adapted physical activity course: learning from student reflections.

    PubMed

    Leo, Jennifer; Goodwin, Donna

    2014-04-01

    Disability simulations have been used as a pedagogical tool to simulate the functional and cultural experiences of disability. Despite their widespread application, disagreement about their ethical use, value, and efficacy persists. The purpose of this study was to understand how postsecondary kinesiology students experienced participation in disability simulations. An interpretative phenomenological approach guided the study's collection of journal entries and clarifying one-on-one interviews with four female undergraduate students enrolled in a required adapted physical activity course. The data were analyzed thematically and interpreted using the conceptual framework of situated learning. Three themes transpired: unnerving visibility, negotiating environments differently, and tomorrow I'll be fine. The students described emotional responses to the use of wheelchairs as disability artifacts, developed awareness of environmental barriers to culturally and socially normative activities, and moderated their discomfort with the knowledge they could end the simulation at any time.

  7. Immature visual neural system in children reflected by contrast sensitivity with adaptive optics correction

    PubMed Central

    Liu, Rong; Zhou, Jiawei; Zhao, Haoxin; Dai, Yun; Zhang, Yudong; Tang, Yong; Zhou, Yifeng

    2014-01-01

    This study aimed to explore the neural development status of the visual system of children (around 8 years old) using contrast sensitivity. We achieved this by eliminating the influence of higher order aberrations (HOAs) with adaptive optics correction. We measured HOAs, modulation transfer functions (MTFs) and contrast sensitivity functions (CSFs) of six children and five adults with both corrected and uncorrected HOAs. We found that when HOAs were corrected, children and adults both showed improvements in MTF and CSF. However, the CSF of children was still lower than the adult level, indicating the difference in contrast sensitivity between groups cannot be explained by differences in optical factors. Further study showed that the difference between the groups also could not be explained by differences in non-visual factors. With these results we concluded that the neural systems underlying vision in children of around 8 years old are still immature in contrast sensitivity. PMID:24732728

  8. The Escherichia coli O157:H7 bovine rumen fluid proteome reflects adaptive bacterial responses

    PubMed Central

    2014-01-01

    Background To obtain insights into Escherichia coli O157:H7 (O157) survival mechanisms in the bovine rumen, we defined the growth characteristics and proteome of O157 cultured in rumen fluid (RF; pH 6.0-7.2 and low volatile fatty acid content) obtained from rumen-fistulated cattle fed low protein content “maintenance diet” under diverse in vitro conditions. Results Bottom-up proteomics (LC-MS/MS) of whole cell-lysates of O157 cultured under anaerobic conditions in filter-sterilized RF (fRF; devoid of normal ruminal microbiota) and nutrient-depleted and filtered RF (dRF) resulted in an anaerobic O157 fRF-and dRF-proteome comprising 35 proteins functionally associated with cell structure, motility, transport, metabolism and regulation, but interestingly, not with O157 virulence. Shotgun proteomics-based analysis using isobaric tags for relative and absolute quantitation used to further study differential protein expression in unfiltered RF (uRF; RF containing normal rumen microbial flora) complemented these results. Conclusions Our results indicate that in the rumen, the first anatomical compartment encountered by this human pathogen within the cattle gastrointestinal tract (GIT), O157 initiates a program of specific gene expression that enables it to adapt to the in vivo environment, and successfully transit to its colonization sites in the bovine GIT. Further experiments in vitro using uRF from animals fed different diets and with additional O157 strains, and in vivo using rumen-fistulated cattle will provide a comprehensive understanding of the adaptive mechanisms involved, and help direct evolution of novel modalities for blocking O157 infection of cattle. PMID:24559513

  9. An equivalent configuration approach for the moiré patterns appearing due to the reflecting surface in display system.

    PubMed

    Byun, Seok-Joo; Byun, Seok Yong; Lee, Jangkyo; Kim, Won Mok; Lee, Taek-Sung

    2014-10-01

    A new moiré pattern appearing in the off-state of a display system with a reflecting surface under illumination of an external ambient light source was analyzed. The origin of the new moiré pattern was attributed to the moiré pattern which is formed on the reflecting surface by external light and plays as a new light source with intensity profile. Configuring an optically equivalent system with no reflecting surface layer was proposed in order to overcome the limitation of new simulation program, which was previously proved to be very efficient in computation time but unable to handle a non-sequential system containing a reflecting surface. It was verified that the new simulation algorithm combined with an equivalent configuration could provide an accurate and computation time-efficient analyses even for a system containing non-sequential stacked layer such as a reflecting surface.

  10. Formation of Random, RIE-Textured Silicon Surfaces with Reduced Reflection and Enhanced Near IR Absorption

    SciTech Connect

    ZAIDI, SALEEM H

    2001-04-01

    The authors have developed novel metal-assisted texturing processes that have led to optically favorable surfaces for solar cells. Large area ({approximately} 200 cm{sup 2}) uniform texturing has been achieved. The physical dimensions of the chamber limited texturing of even larger wafers. Surface contamination and residual RIE-induced damage were removed by incorporation of a complete RCA clean process followed by wet-chemical etching treatments. RIE-textured solar cells with optimized profiles providing performance comparable to the random, wet-chemically etched cells have been demonstrated. A majority of the texture profiles exhibit an enhanced IQE response in the near IR region.using scanning electron microscope measurements, they carried out a detailed analysis of the microstructure of random RIE-textured surfaces. The random microstructure represents a superposition of sub-{micro}m grating structures with a wide distribution of periods, depths, and profiles as determined by the SEM measurements. These structures were modeled using GSOLVER{trademark} software for periodic patterns. The enhanced IR response from random, RIE-textured surfaces is attributed to enhanced coupling of light into the transmitted diffraction orders. These obliquely propagating diffraction orders generate electron-hole pairs closer to the surface, thus, reducing bulk recombination losses relative to a non-scattering, planar surface with identical hemispherical reflection. The optimized texture and damage removal processes have been applied to large area (100--132 cm{sup 2}) multi-crystalline wafers. initial results have demonstrated improved performance relative to planar, control wafers. However, the texture and solar cell fabrication processes require further optimization in the RCA clean, DRE treatments, and emitter formation in order to fully realize the benefits of the low-reflection ({approximately}1-2%) textured surfaces.

  11. Immunoglobulin surface-binding kinetics studied by total internal reflection with fluorescence correlation spectroscopy.

    PubMed Central

    Thompson, N L; Axelrod, D

    1983-01-01

    An experimental application of total internal reflection with fluorescence correlation spectroscopy (TIR/FCS) is presented. TIR/FCS is a new technique for measuring the binding and unbinding rates and surface diffusion coefficient of fluorescent-labeled solute molecules in equilibrium at a surface. A laser beam totally internally reflects at the solid-liquid interface, selectively exciting surface-adsorbed molecules. Fluorescence collected by a microscope from a small, well-defined surface area approximately 5 micron2 spontaneously fluctuates as solute molecules randomly bind to, unbind from, and/or diffuse along the surface in chemical equilibrium. The fluorescence is detected by a photomultiplier and autocorrelated on-line by a minicomputer. The shape of the autocorrelation function depends on the bulk and surface diffusion coefficients, the binding rate constants, and the shape of the illuminated and observed region. The normalized amplitude of the autocorrelation function depends on the average number of molecules bound within the observed area. TIR/FCS requires no spectroscopic or thermodynamic change between dissociated and complexed states and no extrinsic perturbation from equilibrium. Using TIR/FCS, we determine that rhodamine-labeled immunoglobulin and insulin each nonspecifically adsorb to serum albumin-coated fused silica with both reversible and irreversible components. The characteristic time of the most rapidly reversible component measured is approximately 5 ms and is limited by the rate of bulk diffusion. Rhodamine-labeled bivalent antibodies to dinitrophenyl (DNP) bind to DNP-coated fused silica virtually irreversibly. Univalent Fab fragments of these same antibodies appear to specifically bind to DNP-coated fused silica, accompanied by a large amount of nonspecific binding. TIR/FCS is shown to be a feasible technique for measuring absorption/desorption kinetic rates at equilibrium. In suitable systems where nonspecific binding is low, TIR

  12. New methods for engineering site characterization using reflection and surface wave seismic survey

    NASA Astrophysics Data System (ADS)

    Chaiprakaikeow, Susit

    This study presents two new seismic testing methods for engineering application, a new shallow seismic reflection method and Time Filtered Analysis of Surface Waves (TFASW). Both methods are described in this dissertation. The new shallow seismic reflection was developed to measure reflection at a single point using two to four receivers, assuming homogeneous, horizontal layering. It uses one or more shakers driven by a swept sine function as a source, and the cross-correlation technique to identify wave arrivals. The phase difference between the source forcing function and the ground motion due to the dynamic response of the shaker-ground interface was corrected by using a reference geophone. Attenuated high frequency energy was also recovered using the whitening in frequency domain. The new shallow seismic reflection testing was performed at the crest of Porcupine Dam in Paradise, Utah. The testing used two horizontal Vibroseis sources and four receivers for spacings between 6 and 300 ft. Unfortunately, the results showed no clear evidence of the reflectors despite correction of the magnitude and phase of the signals. However, an improvement in the shape of the cross-correlations was noticed after the corrections. The results showed distinct primary lobes in the corrected cross-correlated signals up to 150 ft offset. More consistent maximum peaks were observed in the corrected waveforms. TFASW is a new surface (Rayleigh) wave method to determine the shear wave velocity profile at a site. It is a time domain method as opposed to the Spectral Analysis of Surface Waves (SASW) method, which is a frequency domain method. This method uses digital filtering to optimize bandwidth used to determine the dispersion curve. Results from testings at three different sites in Utah indicated good agreement with the dispersion curves measured using both TFASW and SASW methods. The advantage of TFASW method is that the dispersion curves had less scatter at long wavelengths as a

  13. Neuromechanical adaptation induced by jumping on an elastic surface.

    PubMed

    Márquez, Gonzalo; Aguado, Xavier; Alegre, Luis M; Férnandez-Del-Olmo, Miguel

    2013-02-01

    Jumping on an elastic surface produces a number of sensory and motor adjustments. This effect caused by jumping on the trampoline has been called "trampoline aftereffect". The objective of the present study was to investigate the neuromuscular response related with this effect. A group of 15 subjects took part in an experimental session, where simultaneous biomechanical and electromyographic (EMG) recordings were performed during the execution of maximal countermovement jumps (CMJs) before and after jumping on an elastic surface. We assessed motor performance (leg stiffness, jump height, peak force, vertical motion of center of mass and stored and returned energy) and EMG activation patterns of the leg muscles. The results showed a significant increase (p ≤ 0.05) of the RMS EMG of knee extensors during the eccentric phase of the jump performed immediately after the exposure phase to the elastic surface (CMJ(1)), and a significant increase (p ≤ 0.05) in the levels of co-activation of the muscles crossing the ankle joint during the concentric phase of the same jump. Results related with motor performance of CMJ(1) showed a significant increase in the leg stiffness (p ≤ 0.01) due to a lower vertical motion of center of mass (CoM) (p ≤ 0.005), a significant decrease in jump height (p ≤ 0.01), and a significantly smaller stored and returned energy (p ≤ 0.01). The changes found during the execution of CMJ(1) may result from a mismatch between sensory feedback and the efferent copy.

  14. [The research of the relationship between snow properties and the bidirectional polarized reflectance from snow surface].

    PubMed

    Sun, Zhong-Qiu; Wu, Zheng-Fang; Zhao, Yun-Sheng

    2014-10-01

    In the context of remote sensing, the reflectance of snow is a key factor for accurate inversion for snow properties, such as snow grain size, albedo, because of it is influenced by the change of snow properties. The polarized reflectance is a general phenomenon during the reflected progress in natural incident light In this paper, based on the correct measurements for the multiple-angle reflected property of snow field in visible and near infrared wavelength (from 350 to 2,500 nm), the influence of snow grain size and wet snow on the bidirectional polarized property of snow was measured and analyzed. Combining the results measured in the field and previous conclusions confirms that the relation between polarization and snow grain size is obvious in infrared wavelength (at about 1,500 nm), which means the degree of polarization increasing with an increase of snow grain size in the forward scattering direction, it is because the strong absorption of ice near 1,500 nm leads to the single scattering light contributes to the reflection information obtained by the sensor; in other word, the larger grain size, the more absorption accompanying the larger polarization in forward scattering direction; we can illustrate that the change from dry snow to wet snow also influences the polarization property of snow, because of the water on the surface of snow particle adheres the adjacent particles, that means the wet snow grain size is larger than the dry snow grain size. Therefore, combining the multiple-angle polarization with reflectance will provide solid method and theoretical basis for inversion of snow properties. PMID:25739241

  15. Application of binocular vision probe on measurement of highly reflective metallic surface

    NASA Astrophysics Data System (ADS)

    Zhang, Hongwei; Zhang, Guoxiong; Shi, Ying; Zhao, Xiaosong

    2005-01-01

    Reverse engineering of free-form surfaces is one of the most challenging technologies in advanced manufacturing. With the development of industry more and more sculptured surfaces, such as molds and turbine blades, are required to measure quickly and accurately. Optical non-contact probes possess many advantages, such as high speed, no measuring force, in comparison with contact ones. The ability of stereo vision probe with CCD cameras in gathering a large amount of information simultaneously makes it the most popularly used one in sculptured surface measurements. So a non-contact measurement system is built which consists of CMM and a vision probe with many techniques. It distinguishes itself by high efficiency, high accuracy and reliability, as well as applicability for on-line measurement of complicated sculptured surfaces. With a virtual 3D target in form of a grid plate, all the intrinsic and extrinsic parameters of CCD camera including the uncertainty of image scale factor and optical center of camera can be readily calibrated. Through measuring cylindrical section and surface of gauge block, this system is viable to measure free-form surface and high-reflective metallic surface.

  16. Effects of surface reflectance on local second order shape estimation in dynamic scenes.

    PubMed

    Dövencioğlu, Dicle N; Wijntjes, Maarten W A; Ben-Shahar, Ohad; Doerschner, Katja

    2015-10-01

    In dynamic scenes, relative motion between the object, the observer, and/or the environment projects as dynamic visual information onto the retina (optic flow) that facilitates 3D shape perception. When the object is diffusely reflective, e.g. a matte painted surface, this optic flow is directly linked to object shape, a property found at the foundations of most traditional shape-from-motion (SfM) schemes. When the object is specular, the corresponding specular flow is related to shape curvature, a regime change that challenges the visual system to determine concurrently both the shape and the distortions of the (sometimes unknown) environment reflected from its surface. While human observers are able to judge the global 3D shape of most specular objects, shape-from-specular-flow (SFSF) is not veridical. In fact, recent studies have also shown systematic biases in the perceived motion of such objects. Here we focus on the perception of local shape from specular flow and compare it to that of matte-textured rotating objects. Observers judged local surface shape by adjusting a rotation and scale invariant shape index probe. Compared to shape judgments of static objects we find that object motion decreases intra-observer variability in local shape estimation. Moreover, object motion introduces systematic changes in perceived shape between matte-textured and specular conditions. Taken together, this study provides a new insight toward the contribution of motion and surface material to local shape perception.

  17. A perturbative analysis of surface acoustic wave propagation and reflection in interdigital transducers

    NASA Astrophysics Data System (ADS)

    Thoma, Carsten Hilmar

    1997-12-01

    The coupling of stress and strain fields to electric fields present in anisotropic piezoelectric crystals makes them ideal for use as electromechanical transducers in a wide variety of applications. In recent years such crystals have been utilized to produce surface acoustic wave devices for signal processing applications, in which an applied metallic grating both transmits and receives, through the piezoelectric effect, electromechanical surface waves. The design of such interdigital transducers requires an accurate knowledge of wave propagation and reflection. The presence of the metal grating in addition to its ideal transduction function, by means of electrical and mechanical loading, also introduces a velocity shift as well as reflection into substrate surface waves. We seek to obtain a consistent formulation of the wave behavior due to the electrical and mechanical loading of the substrate crystal by the metallic grating. A perturbative solution up to second order in h//lambda is developed, where h is the maximum grating height and λ the acoustic wavelength. For the operating frequencies and physical parameters of modern surface acoustic wave devices such an analysis will provide an adequate description of device behavior in many cases, thereby circumventing the need for more computationally laborious methods. Numerical calculations are presented and compared with available experimental data.

  18. Automatic and improved radiometric correction of Landsat imagery using reference values from MODIS surface reflectance images

    NASA Astrophysics Data System (ADS)

    Pons, X.; Pesquer, L.; Cristóbal, J.; González-Guerrero, O.

    2014-12-01

    Radiometric correction is a prerequisite for generating high-quality scientific data, making it possible to discriminate between product artefacts and real changes in Earth processes as well as accurately produce land cover maps and detect changes. This work contributes to the automatic generation of surface reflectance products for Landsat satellite series. Surface reflectances are generated by a new approach developed from a previous simplified radiometric (atmospheric + topographic) correction model. The proposed model keeps the core of the old model (incidence angles and cast-shadows through a digital elevation model [DEM], Earth-Sun distance, etc.) and adds new characteristics to enhance and automatize ground reflectance retrieval. The new model includes the following new features: (1) A fitting model based on reference values from pseudoinvariant areas that have been automatically extracted from existing reflectance products (Terra MODIS MOD09GA) that were selected also automatically by applying quality criteria that include a geostatistical pattern model. This guarantees the consistency of the internal and external series, making it unnecessary to provide extra atmospheric data for the acquisition date and time, dark objects or dense vegetation. (2) A spatial model for atmospheric optical depth that uses detailed DEM and MODTRAN simulations. (3) It is designed so that large time-series of images can be processed automatically to produce consistent Landsat surface reflectance time-series. (4) The approach can handle most images, acquired now or in the past, regardless of the processing system, with the exception of those with extremely high cloud coverage. The new methodology has been successfully applied to a series of near 300 images of the same area including MSS, TM and ETM+ imagery as well as to different formats and processing systems (LPGS and NLAPS from the USGS; CEOS from ESA) for different degrees of cloud coverage (up to 60%) and SLC

  19. Mars - Near-infrared spectral reflectance of surface regions and compositional implications

    NASA Astrophysics Data System (ADS)

    McCord, T. B.; Clark, R. N.; Singer, R. B.

    1982-04-01

    Both morphological and compositional information are needed to define and characterize surface geologic units on Mars. A description is presented of new, near-infrared spectra (0.65 to 2.50 micrometers) for 11 regions on the Martian surface observed in 1978. The high photometric quality of these data combined with increased near-infrared spectral coverage provide new information about the spectral behavior and, therefore, the composition and physical nature of Martian surface materials. The spectral reflectances were obtained with the aid of a 2.2-m telescope located on Mauna Kea, Hawaii. A cooled (to 77 K) circular variable filter spectrometer with an InSb detector was used to measure alternatively Mars and the standard star Beta Geminorum. Attention is given to general spectral characteristics, the dark region composition, spectral evidence for water, and the 2.3 micrometer absorption.

  20. Computing diffuse reflection from particulate planetary surface with a new function.

    PubMed

    Wolff, M

    1981-07-15

    An equation is derived to compute the amount of diffuse light reflected by a particulate surface such as on Mars or an asteroid. The method traces the paths of rays within an ensemble of randomly shaped grains and finds the eventual probability of emission. The amount of diffuse, unpolarized emitted light is obtained in terms of the real index of refraction, the imaginary index, and the average diameter of particles making up the surface. The equation is used to compute the empirical rule for obtaining the planetary albedo from the slope of its polarization curve. Accuracy of the equation, estimated at +/-4%, seems justified because of quantitative agreement with experimental measures of the empirical rule. It is also shown that the equation can be applied to bubble-enclosing surfaces such as volcanic foams. Results for the indices of the moon, Mars, Io, and Europa are obtained and compared with other data.

  1. Surface reflectance retrieval from satellite and aircraft sensors: Results of sensor and algorithm comparisons during FIFE

    SciTech Connect

    Markham, B.L. ); Halthore, R.N.; Goetz, S.J. )

    1992-11-30

    This work is part of the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE), an international land-surface-atmosphere experiment aimed at improving the way climate models represent energy, water, heat, and carbon exchanges, and improving the utilization of satellite based remote sensing to monitor such parameters. This paper reports on comparison of measurement systems which were deployed to measure surface reflectance factors, from aircraft or satellites. These instruments look over the general range of 0.4 to 2.5[mu]m. Instruments studied include Landsat 5 thematic mapper (TM), the SPOT 1 high-resolution visible sensor (HRV) 1, the NS001 thematic mapper simulator, and the modular multispectral radiometers (MMRs). The study looked at the radiometric consistency of the different instruments, and the adequacy of the atmospheric correction routines applied to data analysis.

  2. The influence of surface reflectance anisotropy on estimation of soil properties

    NASA Astrophysics Data System (ADS)

    Bartholomeus, Harm; Roosjen, Peter; Clevers, Jan

    2014-05-01

    The spatial variation in soil properties is an important factor for agricultural management. Unmanned airborne vehicles (UAV's) equipped with a hyperspectral mapping system may provide these data, but anisotropic reflectance effects may have an influence on the derived soil properties. Besides influencing the reflectance, angular observations may deliver added information about soil properties. We investigated the anisotropic behavior of 59 soil samples with a large variation in soil composition, by measuring their reflectance (350-2500 nm) over 92 different angles using a robot-based laboratory goniometer system. The results show that the anisotropic behavior of the soils influences the measured reflectance significantly, which limits the accurate prediction of soil properties (OM and clay especially). However, prediction accuracies of OM increase when spectra are measured under specific angles. Prediction accuracies further increase when a combination of observation angles is being used. Apart from that, using UAV's the wavelength range is limited to about 1000 nm. In general, this will decrease the model performance, but our results show that this effect can largely be compensated by combining multiple observation angles. Altogether, we demonstrate that surface anisotropy influences the prediction of soil properties negatively. This effect can be reduced by combining spectra acquired under different angles. Moreover, predictions can be improved if combinations of different observation angles are used.

  3. The Normalization of Surface Anisotropy Effects Present in SEVIRI Reflectances by Using the MODIS BRDF Method

    NASA Technical Reports Server (NTRS)

    Proud, Simon Richard; Zhang, Qingling; Schaaf, Crystal; Fensholt, Rasmus; Rasmussen, Mads Olander; Shisanya, Chris; Mutero, Wycliffe; Mbow, Cheikh; Anyamba, Assaf; Pak, Ed; Sandholt, Inge

    2014-01-01

    A modified version of the MODerate resolution Imaging Spectroradiometer (MODIS) bidirectional reflectance distribution function (BRDF) algorithm is presented for use in the angular normalization of surface reflectance data gathered by the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) aboard the geostationary Meteosat Second Generation (MSG) satellites. We present early and provisional daily nadir BRDFadjusted reflectance (NBAR) data in the visible and near-infrared MSG channels. These utilize the high temporal resolution of MSG to produce BRDF retrievals with a greatly reduced acquisition period than the comparable MODIS products while, at the same time, removing many of the angular perturbations present within the original MSG data. The NBAR data are validated against reflectance data from the MODIS instrument and in situ data gathered at a field location in Africa throughout 2008. It is found that the MSG retrievals are stable and are of high-quality across much of the SEVIRI disk while maintaining a higher temporal resolution than the MODIS BRDF products. However, a number of circumstances are discovered whereby the BRDF model is unable to function correctly with the SEVIRI observations-primarily because of an insufficient spread of angular data due to the fixed sensor location or localized cloud contamination.

  4. Effects of Spectralon absorption on reflectance spectra of typical planetary surface analog materials.

    PubMed

    Zhang, Hao; Yang, Yazhou; Jin, Weidong; Liu, Chujian; Hsu, Weibiao

    2014-09-01

    Acquiring accurate visible and near-infrared (VisNIR) reflectance values of atmosphereless celestial bodies is very important in inferring the physical and geological properties of their surficial materials. When a calibration target with inherent non-trivial absorption features is used, the calibrated reflectance would essentially always contain spurious spectral features and the spectroscopic data may easily be misinterpreted if the artifact is not properly taken care of. We demonstrate with laboratory reflectance measurements that the VisNIR spectra of three typical planetary surface analog materials, lunar simulant JSC-1A, olivine and pyroxene grains, have an artificial peak at 2.1 µm when Spectralon-type plaque made of polytetrafluoroethylene is used as the calibration target in the NIR region. The degree of severity of this artifact is dependent on the strength of the 2.0 µm absorption feature of the mineral. Empirical methods are proposed to remove this artifact to bring the spectra close to that calibrated by a gold mirror which does not have any conspicuous absorption features in the NIR region. The correction methods may be applied to reflectance data acquired by the VisNIR imaging spectrometer onboard the Yutu Rover of the Chinese Chang'E 3 lunar mission which employed an onboard Spectralon-type calibration target. PMID:25321507

  5. Effects of Spectralon absorption on reflectance spectra of typical planetary surface analog materials.

    PubMed

    Zhang, Hao; Yang, Yazhou; Jin, Weidong; Liu, Chujian; Hsu, Weibiao

    2014-09-01

    Acquiring accurate visible and near-infrared (VisNIR) reflectance values of atmosphereless celestial bodies is very important in inferring the physical and geological properties of their surficial materials. When a calibration target with inherent non-trivial absorption features is used, the calibrated reflectance would essentially always contain spurious spectral features and the spectroscopic data may easily be misinterpreted if the artifact is not properly taken care of. We demonstrate with laboratory reflectance measurements that the VisNIR spectra of three typical planetary surface analog materials, lunar simulant JSC-1A, olivine and pyroxene grains, have an artificial peak at 2.1 µm when Spectralon-type plaque made of polytetrafluoroethylene is used as the calibration target in the NIR region. The degree of severity of this artifact is dependent on the strength of the 2.0 µm absorption feature of the mineral. Empirical methods are proposed to remove this artifact to bring the spectra close to that calibrated by a gold mirror which does not have any conspicuous absorption features in the NIR region. The correction methods may be applied to reflectance data acquired by the VisNIR imaging spectrometer onboard the Yutu Rover of the Chinese Chang'E 3 lunar mission which employed an onboard Spectralon-type calibration target.

  6. A surface vitrinite reflectance anomaly related to Bell Creek oil field, Montana, U.S.A.

    USGS Publications Warehouse

    Barker, C.E.; Dalziel, M.C.; Pawlewicz, M.J.

    1983-01-01

    Vitrinite reflectance measurements from surface samples of mudrock and coal show anomalously high values over the Bell Creek oil field. The average vitrinite reflectance (Rm) increases to a maximum of 0.9 percent over the field against background values of about 0.3 percent. The Rm anomaly coincides with a geochemical anomaly indicated by diagenetic magnetite in surface rocks and a geobiologic anomaly indicated by ethane-consuming bacteria. These samples were taken from the Upper Cretaceous Hell Creek and Paleocene Fort Union Formations which form an essentially conformable sequence. The depositional environment is similar in both formations, and we expect little variation in the source and composition of the organic matter. The surface R m should be approximately constant because of a uniform thermal history across the field. Temperature studies over local oil fields with similar geology suggest the expected thermal anomaly would be less than 10?C (50?F), which is too small to account for the significantly higher rank over the field. Coal clinkers are rare in the vicinity of Bell Creek and an Rm anomaly caused by burning of the thin, discontinuous coal seams is unlikely. The limited topographic relief, less than 305 m (1,000 ft), over the shallow-dipping homoclinal structure and the poor correlation between Rm and sample locality elevation (r = -0.2) indicate that the Rm anomaly is not due to burial, deformation and subsequent erosion. We conjecture that activity by petroleum-metabolizing bacteria is a possible explanation of the Rm anomaly. Microseepage from oil reservoirs supports large colonies of these organisms, some of which can produce enzymes that can cleave hydrocarbon side-chains on the kerogen molecule. The loss of these side chains causes condensation of the ring structures (Stach and others, 1982) and consequently increases its reflectance. These data indicate that vitrinite reflectance may be a useful tool to explore for stratigraphic traps in the

  7. Effects of scanning orientation on outlier formation in 3D laser scanning of reflective surfaces

    NASA Astrophysics Data System (ADS)

    Wang, Yutao; Feng, Hsi-Yung

    2016-06-01

    Inspecting objects with reflective surfaces using 3D laser scanning is a demanded but challenging part inspection task due to undesirable specular reflections, which produce extensive outliers in the scanned point cloud. These outliers need to be removed in order to alleviate subsequent data processing issues. Many existing automatic outlier removal methods do not detect outliers according to the outlier formation properties. As a result, these methods only offer limited capabilities in removing extensive and complex outliers from scanning objects with reflective surfaces. This paper reports an empirical study which experimentally investigates the outlier formation characteristics in relation to the scanning orientation of the laser probe. The objective is to characterize the scanning orientation effects on outlier formation in order to facilitate the development of an effective outlier detection and removal method. Such an experimental investigation was hardly done before. It has been found in this work that scanning orientation can directly affect outlier extensity and occurrence in 3D laser scanning. A general guidance on proper scan path planning can then be provided with an aim to reduce the occurrence of outliers. Further, the observed dependency of outlier formation on scanning orientation can be exploited to facilitate effective and automatic outlier detection and removal.

  8. The surface epithelium of teleostean fish gills. Cellular and junctional adaptations of the chloride cell in relation to salt adaptation

    PubMed Central

    1979-01-01

    Various species of teleostean fishes were adapted to fresh or salt water and their gill surface epithelium was examined using several techniques of electron microscopy. In both fresh and salt water the branchial epithelium is mostly covered by flat respiratory cells. They are characterized by unusual outer membrane fracture faces containing intramembranous particles and pits in various stages of ordered aggregation. Freeze fracture studies showed that the tight junctions between respiratory cells are made of several interconnecting strands, probably representing high resistance junctions. The organization of intramembranous elements and the morphological characteristics of the junctions do not vary in relation to the external salinity. Towards the base of the secondary gill lamellae, the layer of respiratory cells is interrupted by mitochondria-rich cells ("chloride cells"), also linked to respiratory cells by multistranded junctions. There is a fundamental reorganization of the chloride cells associated with salt water adaptation. In salt water young adjacent chloride cells send interdigitations into preexisting chloride cells. The apex of the seawater chloride cell is therefore part of a mosaic of sister cells linked to surrounding respiratory cells by multistranded junctions. The chloride cells are linked to each other by shallow junctions made of only one strand and permeable to lanthanum. It is therefore suggested that salt water adaptation triggers a cellular reorganization of the epithelium in such a way that leaky junctions (a low resistance pathway) appear at the apex of the chloride cells. Chloride cells are characterized by an extensive tubular reticulum which is an extension of the basolateral plasma membrane. It is made of repeating units and is the site of numerous ion pumps. The presence of shallow junctions in sea water-adapted fish makes it possible for the reticulum to contact the external milieu. In contrast in the freshwater-adapted fish the

  9. Density of muscle spindles in prosimian shoulder muscles reflects locomotor adaptation.

    PubMed

    Higurashi, Yasuo; Taniguchi, Yuki; Kumakura, Hiroo

    2006-01-01

    We examined the correlation between the density of muscle spindles in shoulder muscles and the locomotor mode in three species of prosimian primates: the slow loris (Nycticebus coucang), Garnett's galago (Otolemur garnettii), and the ring-tailed lemur (Lemur catta). The shoulder muscles (supraspinatus, infraspinatus, teres major, teres minor, and subscapularis) were embedded in celloidin and cut into transverse serial thin sections (40 microm); then, every tenth section was stained using the Azan staining technique. The relative muscle weights and the density of the muscle spindles were determined. The slow loris muscles were heavier and had sparser muscle spindles, as compared to Garnett's galago. These features suggest that the shoulder muscles of the slow loris are more adapted to generating propulsive force and stabilizing the shoulder joint during locomotion and play a less controlling role in forelimb movements. In contrast, Garnett's galago possessed smaller shoulder muscles with denser spindles that are suitable for the control of more rapid locomotor movements. The mean relative weight and the mean spindle density in the shoulder muscles of the ring-tailed lemur were between those of the other primates, suggesting that the spindle density is not simply a consequence of taxonomic status. PMID:17361082

  10. Density of muscle spindles in prosimian shoulder muscles reflects locomotor adaptation.

    PubMed

    Higurashi, Yasuo; Taniguchi, Yuki; Kumakura, Hiroo

    2006-01-01

    We examined the correlation between the density of muscle spindles in shoulder muscles and the locomotor mode in three species of prosimian primates: the slow loris (Nycticebus coucang), Garnett's galago (Otolemur garnettii), and the ring-tailed lemur (Lemur catta). The shoulder muscles (supraspinatus, infraspinatus, teres major, teres minor, and subscapularis) were embedded in celloidin and cut into transverse serial thin sections (40 microm); then, every tenth section was stained using the Azan staining technique. The relative muscle weights and the density of the muscle spindles were determined. The slow loris muscles were heavier and had sparser muscle spindles, as compared to Garnett's galago. These features suggest that the shoulder muscles of the slow loris are more adapted to generating propulsive force and stabilizing the shoulder joint during locomotion and play a less controlling role in forelimb movements. In contrast, Garnett's galago possessed smaller shoulder muscles with denser spindles that are suitable for the control of more rapid locomotor movements. The mean relative weight and the mean spindle density in the shoulder muscles of the ring-tailed lemur were between those of the other primates, suggesting that the spindle density is not simply a consequence of taxonomic status.

  11. Variability in thermal and phototactic preferences in Drosophila may reflect an adaptive bet‐hedging strategy

    PubMed Central

    Kain, Jamey S.; Zhang, Sarah; Akhund‐Zade, Jamilla; Samuel, Aravinthan D. T.; Klein, Mason; de Bivort, Benjamin L.

    2015-01-01

    Organisms use various strategies to cope with fluctuating environmental conditions. In diversified bet‐hedging, a single genotype exhibits phenotypic heterogeneity with the expectation that some individuals will survive transient selective pressures. To date, empirical evidence for bet‐hedging is scarce. Here, we observe that individual Drosophila melanogaster flies exhibit striking variation in light‐ and temperature‐preference behaviors. With a modeling approach that combines real world weather and climate data to simulate temperature preference‐dependent survival and reproduction, we find that a bet‐hedging strategy may underlie the observed interindividual behavioral diversity. Specifically, bet‐hedging outcompetes strategies in which individual thermal preferences are heritable. Animals employing bet‐hedging refrain from adapting to the coolness of spring with increased warm‐seeking that inevitably becomes counterproductive in the hot summer. This strategy is particularly valuable when mean seasonal temperatures are typical, or when there is considerable fluctuation in temperature within the season. The model predicts, and we experimentally verify, that the behaviors of individual flies are not heritable. Finally, we model the effects of historical weather data, climate change, and geographic seasonal variation on the optimal strategies underlying behavioral variation between individuals, characterizing the regimes in which bet‐hedging is advantageous. PMID:26531165

  12. Adaptive gene loss reflects differences in the visual ecology of basal vertebrates.

    PubMed

    Davies, Wayne L; Collin, Shaun P; Hunt, David M

    2009-08-01

    The agnathans (lampreys and hagfishes) are representatives of the jawless fishes and constitute the first lineage of extant vertebrates to evolve within chordate phylogenetic history. Previously, we showed that the southern hemisphere pouched lamprey Geotria australis has the potential for pentachromacy with the expression of five visual pigment (opsin) genes (LWS, SWS1, SWS2, RhA, and RhB) in five different cone-like photoreceptors for life in a brightly lit environment exposed to a broad spectrum of light. In contrast, the northern hemisphere sea lamprey Petromyzon marinus dwells in a wide range of depths that are relatively deeper than the epipelagic waters inhabited by G. australis. Thus, the light levels of the habitat in which the sea lamprey resides are greatly diminished and different regions of the light spectrum are differentially absorbed. Therefore, the visual systems of these two species of lamprey constitute a natural experiment in which to study the selection pressures underlying opsin gene expression and the evolution of color discrimination. By analyzing the opsin genes of P. marinus, we show the expression of two intact retinal opsins, RhA and LWS, which, when regenerated with 11-cis retinal, give peak spectral sensitivities (lambda(max) values) of 501 and 536 nm, respectively. In contrast to G. australis, the genome of P. marinus possesses remnants of SWS1 and SWS2 pseudogenes, which with the loss of RhB, suggests that P. marinus is a dichromat. Using site-directed mutagenesis, we show that a single amino acid substitution (Ser to Pro) at site 164 is responsible for a blue shift of 19 nm of the LWS visual pigment of P. marinus compared with G. australis, which may reflect habitat differences between the two species. Based on these studies, we propose that gene loss (or duplication) and subsequent mutation plays an important role in the evolution of color vision and that the complement and tuning of these visual pigments reflect the ecology and

  13. Investigating the secondary structures of long oligonucleotides using attenuated-total-reflection surface-enhanced Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Chiu, K.-C.; Yih, J.-N.; Yu, L.-Y.; Chen, S.-J.

    2006-08-01

    This study utilizes a surface-enhanced Raman spectroscopy (SERS) based on the attenuated-total-reflection method to investigate the secondary structures of long oligonucleotides and their influence on the DNA hybridization. It is found that the ring-breathing modes of adenine, thymine, guanine, and cytosine in Raman fingerprint associated with three 60mer oligonucleotides with prominent secondary structures are lower than those observed for the two oligonucleotides with no obvious secondary structures. It is also determined that increasing the DNA hybridization temperature from 35°C to 45°C reduces secondary structure effects. The kinetics of biomolecular interaction analysis can be performed by using surface plasmons resonance biosensor, but the structural information of the oligonucleotides can not observed directly. The SERS spectrum provides the structural information of the oligonucleotides with the help of a silver colloidal nanoparticle monolayer by control of the size and distribution of the nanoparticles adapted as a Raman active substrate. Also, the detection limit of the DNA Raman signal has been successfully improved to reach sub-micro molarity of DNA concentration.

  14. 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. PMID:16892130

  15. Measuring surface dynamics of biomolecules by total internal reflection fluorescence with photobleaching recovery or correlation spectroscopy.

    PubMed

    Thompson, N L; Burghardt, T P; Axelrod, D

    1981-03-01

    The theoretical basis of a new technique for measuring equilibrium adsorption/desorption kinetics and surface diffusion of fluorescent-labeled solute molecules at solid surfaces has been developed. The technique combines total internal reflection fluorescence (TIR) with either fluorescence photobleaching recovery (FPR) or fluorescence correlation spectroscopy (FCS). A laser beam totally internally reflects at a solid/liquid interface; the shallow evanescent field in the liquid excites the fluorescence of surface adsorbed molecules. In TIR/FPR, adsorbed molecules are bleaching by a flash of the focused laser beam; subsequent fluorescence recovery is monitored as bleached molecules exchange with unbleached ones from the solution or surrounding nonilluminated regions of the surface. In TIR/FCS, spontaneous fluorescence fluctuations due to individual molecules entering and leaving a well-defined portion of the evanescent field are autocorrelated. Under appropriate experimental conditions, the rate constants and surface diffusion coefficient can be readily obtained from the TIR/FPR and TIR/FCS curves. In general, the shape of the theoretical TIR/FPR and TIR/FCS curves depends in a complex manner upon the bulk and surface diffusion coefficients, the size of the iluminated or observed region, and the adsorption/desorption/kinetic rate constants. The theory can be applied both to specific binding between immobilized receptors and soluble ligands, and to nonspecific adsorption processes. A discussion of experimental considerations and the application of this technique to the adsorption of serum proteins on quartz may be found in the accompanying paper (Burghardt and Axelrod. 1981. Biophys. J. 33:455). PMID:7225515

  16. Radiative Transfer Simulations of the Two-Dimensional Ocean Glint Reflectance and Determination of the Sea Surface Roughness

    NASA Technical Reports Server (NTRS)

    Lin, Zhenyi; Li, Wei; Gatebe, Charles; Poudyal, Rajesh; Stamnes, Knut

    2016-01-01

    An optimized discrete-ordinate radiative transfer model (DISORT3) with a pseudo-two-dimensional bidirectional reflectance distribution function (BRDF) is used to simulate and validate ocean glint reflectances at an infrared wavelength (1036 nm) by matching model results with a complete set of BRDF measurements obtained from the NASA cloud absorption radiometer (CAR) deployed on an aircraft. The surface roughness is then obtained through a retrieval algorithm and is used to extend the simulation into the visible spectral range where diffuse reflectance becomes important. In general, the simulated reflectances and surface roughness information are in good agreement with the measurements, and the diffuse reflectance in the visible, ignored in current glint algorithms, is shown to be important. The successful implementation of this new treatment of ocean glint reflectance and surface roughness in DISORT3 will help improve glint correction algorithms in current and future ocean color remote sensing applications.

  17. Angular and Seasonal Variation of Spectral Surface Reflectance Ratios: Implications for the Remote Sensing of Aerosol over Land

    NASA Technical Reports Server (NTRS)

    Remer, L. A.; Wald, A. E.; Kaufman, Y. J.

    1999-01-01

    We obtain valuable information on the angular and seasonal variability of surface reflectance using a hand-held spectrometer from a light aircraft. The data is used to test a procedure that allows us to estimate visible surface reflectance from the longer wavelength 2.1 micrometer channel (mid-IR). Estimating or avoiding surface reflectance in the visible is a vital first step in most algorithms that retrieve aerosol optical thickness over land targets. The data indicate that specular reflection found when viewing targets from the forward direction can severely corrupt the relationships between the visible and 2.1 micrometer reflectance that were derived from nadir data. There is a month by month variation in the ratios between the visible and the mid-IR, weakly correlated to the Normalized Difference Vegetation Index (NDVI). If specular reflection is not avoided, the errors resulting from estimating surface reflectance from the mid-IR exceed the acceptable limit of DELTA-rho approximately 0.01 in roughly 40% of the cases, using the current algorithm. This is reduced to 25% of the cases if specular reflection is avoided. An alternative method that uses path radiance rather than explicitly estimating visible surface reflectance results in similar errors. The two methods have different strengths and weaknesses that require further study.

  18. Reflections on a sticky situation: how surface contact pulls the trigger for bacterial adhesion.

    PubMed

    Kirkpatrick, Clare L; Viollier, Patrick H

    2012-01-01

    Adhesion of bacterial cells to surfaces can be mediated by a wide variety of extracellular structures, which can either recognize specific molecular motifs or adhere in non-specific ways to multiple types of surfaces. The attachment is thought to be highly regulated, but the underlying sensory mechanism(s) are poorly understood. In the α-proteobacterium Caulobacter crescentus, the formation of adhesive organelles is 'hardwired' into the cell cycle regulatory circuitry. In this issue of Molecular Microbiology, Li et al. (2011) employed this model organism to examine the adhesion process and the transition from temporary to permanent attachment using total internal reflection fluorescence (TIRF) microscopy. Surprisingly, they observed that adhesin production was not only under developmental control, but was also stimulated by surface contact. Initial reversible contact of the pili with the surface was followed by flagellum rotation arrest and subsequent induction of the holdfast to allow irreversible surface adhesion. These findings demonstrate that Caulobacter produces its holdfast only at the appropriate time for surface attachment, preventing premature export of the adhesin, which could then be inactivated by 'curing' or be masked by occluding particles. Importantly, their results support the notion that the flagellum serves as a mechanosensor for adhesion.

  19. Reflection of X-rays from a rough surface at extremely small grazing angles.

    PubMed

    Wen, Mingwu; Kozhevnikov, Igor V; Wang, Zhanshan

    2015-09-21

    Peculiarities of X-ray diffraction from a rough surface at an extremely small grazing angle of an incident beam are theoretically studied. The interrelation of four diffraction channels (coherent reflectance, coherent transmittance, diffuse scattering in vacuum, and scattering into the matter depth) is analyzed for different limiting cases (large and small correlation length of roughness and large and extremely small grazing angle of incident radiation). Both the Debye-Waller and the Nevot-Croce factors are demonstrated to describe improperly the features of X-ray diffraction at extremely small grazing angles. More appropriate simple analytic expressions for the specular reflectivity and total integrated scattering in vacuum are obtained instead. Transformation of one limiting diffraction regime into another one with variation in the correlation length of roughness is discussed.

  20. Transient Heat Transfer in a Semitransparent Radiating Layer with Boundary Convection and Surface Reflections

    NASA Technical Reports Server (NTRS)

    Siegel, Robert

    1996-01-01

    Surface convection and refractive index are examined during transient radiative heating or cooling of a grey semitransparent layer with internal absorption, emission and conduction. Each side of the layer is exposed to hot or cold radiative surroundings, while each boundary is heated or cooled by convection. Emission within the layer and internal reflections depend on the layer refractive index. The reflected energy and heat conduction distribute energy across the layer and partially equalize the transient temperature distributions. Solutions are given to demonstrate the effect of radiative heating for layers with various optical thicknesses, the behavior of the layer heated by radiation on one side and convectively cooled on the other, and a layer heated by convection while being cooled by radiation. The numerical method is an implicit finite difference procedure with non-uniform space and time increments. The basic method developed in earlier work is expanded to include external convection and incident radiation.

  1. Dynamics of surface thermal expansion and diffusivity using two-color reflection transient gratings

    SciTech Connect

    Pennington, D.M.; Harris, C.B.

    1993-02-01

    We report ultrafast measurements of the dynamic thermal expansion of a surface and the temperature dependent surface thermal diffusivity using a two-color reflection transient grating technique. Studies were performed on p-type, n-type, and undoped GaAs(100) samples at several temperatures. Using a 75 fs ultraviolet probe with visible excitation beams, the electronic effects that dominate single color experiments become negligible; thus surface expansion due to heating and the subsequent contraction caused by cooling provide the dominant influence on the diffracted probe. The diffracted signal was composed of two components, thermal expansion of the surface and heat flow away from the surface, allowing the determination of the rate of expansion as well as the surface thermal diffusivity. At room temperature a signal rise due to thermal expansion was observed, corresponding to a maximum average displacement of {approx} 1 {angstrom} at 32 ps. Large fringe spacings were used, thus the dominant contributions to the signal were expansion and diffusion perpendicular to the surface. Values for the surface thermal diffusivity of GaAs were measured and found to be in reasonable agreement with bulk values above 50{degrees}K. Below 50{degrees}K, the diffusivity at the surface was more than an order of magnitude slower than in the bulk due to increased phonon boundary scattering. Comparison of the results with a straightforward thermal model yields good agreement over a range of temperatures (12--300{degrees}K). The applicability and advantages of the transient grating technique for studying photothermal and photoacoustic phenomena are discussed.

  2. Genomic and functional adaptation in surface ocean planktonic prokaryotes.

    PubMed

    Yooseph, Shibu; Nealson, Kenneth H; Rusch, Douglas B; McCrow, John P; Dupont, Christopher L; Kim, Maria; Johnson, Justin; Montgomery, Robert; Ferriera, Steve; Beeson, Karen; Williamson, Shannon J; Tovchigrechko, Andrey; Allen, Andrew E; Zeigler, Lisa A; Sutton, Granger; Eisenstadt, Eric; Rogers, Yu-Hui; Friedman, Robert; Frazier, Marvin; Venter, J Craig

    2010-11-01

    The understanding of marine microbial ecology and metabolism has been hampered by the paucity of sequenced reference genomes. To this end, we report the sequencing of 137 diverse marine isolates collected from around the world. We analysed these sequences, along with previously published marine prokaryotic genomes, in the context of marine metagenomic data, to gain insights into the ecology of the surface ocean prokaryotic picoplankton (0.1-3.0 μm size range). The results suggest that the sequenced genomes define two microbial groups: one composed of only a few taxa that are nearly always abundant in picoplanktonic communities, and the other consisting of many microbial taxa that are rarely abundant. The genomic content of the second group suggests that these microbes are capable of slow growth and survival in energy-limited environments, and rapid growth in energy-rich environments. By contrast, the abundant and cosmopolitan picoplanktonic prokaryotes for which there is genomic representation have smaller genomes, are probably capable of only slow growth and seem to be relatively unable to sense or rapidly acclimate to energy-rich conditions. Their genomic features also lead us to propose that one method used to avoid predation by viruses and/or bacterivores is by means of slow growth and the maintenance of low biomass.

  3. Infrared reflectance spectroscopy as a characterization probe for polymer surfaces and interfaces

    NASA Astrophysics Data System (ADS)

    Riou, Sophie Annick

    1998-12-01

    Only recently has external reflectance infrared spectroscopy been used to acquire structural information at the molecular level at air-liquid interfaces, and particularly to characterize in situ molecular chains adsorbed at the air-water interface. This technique has been applied for the determination of chain orientation, chain conformation and packing density of small molecules such as phospholipids, fatty acids and fatty alcohols on the surface of water, and more recently of macromolecular systems. Vibrational spectroscopy, a nondestructive technique, is especially successful in the determination of the conformational order or disorder of alkyl chains (e.g. trans/gauche ratio) as well as in the evaluation of coil, helical or extended conformations in poly(amino acids). In this thesis work, the construction of a microcomputer controlled Langmuir trough optically coupled to a FT-IR instrument has allowed the direct investigation of molecular films spread at air-liquid interfaces. Order-disorder transitions and relaxation behaviors in vinyl comb-like polymeric Langmuir films have been examined using simultaneously external reflection infrared spectroscopy and surface tensiometry. The structures of several poly(amino acid) films have also been studied as a function of surface packing density at the air-water interface.

  4. Monte Carlo simulation of light reflection from cosmetic powder particles near the human skin surface

    NASA Astrophysics Data System (ADS)

    Okamoto, Takashi; Kumagawa, Tatsuya; Motoda, Masafumi; Igarashi, Takanori; Nakao, Keisuke

    2013-06-01

    The reflection and scattering properties of light incident on human skin covered with powder particles have been investigated. A three-layer skin structure with a pigmented area is modeled, and the propagation of light in the skin's layers and in a layer of particles near the skin's surface is simulated using the Monte Carlo method. Assuming that only single scattering of light occurs in the powder layer, the simulation results show that the reflection spectra of light from the skin change with the size of powder particles. The color difference between normal and discolored skin is found to decrease considerably when powder particles with a diameter of approximately 0.25 μm are present near the skin's surface. The effects of the medium surrounding the particles, and the influence of the distribution of particle size (polydispersity), are also examined. It is shown that a surrounding medium with a refractive index close to that of the skin substantially suppresses the extreme spectral changes caused by the powder particles covering the skin surface.

  5. Analyzed polarized reflectance model of typical surface types over China based on the PARASOL measurements

    NASA Astrophysics Data System (ADS)

    Xiang, Kun-Sheng; Cheng, Tian-Hai; Gu, Xing-Fa; Guo, Hong; Chen, Hao; Wang, Ying; Wei, Xi; Bao, Fang-Wen; Kong, Fan-Ping

    2016-09-01

    In this paper, the parameters of four types of polarization reflectance models (the Breon physical model, the Nadal-Breon semi-empirical model, the Maignan et al. single parameter model, and the Litvinov et al. model) were analyzed based on the PARASOL observation of three typical features in China three sites (forest, grassland, and desert). Subsequently, combined with the model analysis, the polarization reflectance characteristics of each typical feature were studied. The results reveal that 1) the imitative effect of the Litvinov et al. model about forest was the best, as the linear slope was greater than 0.9 and R2 was better than 0.8; 2) the linear slope and R2 of the Nadal-Breon model about all surfaces were higher than 0.8; 3) although fitting slope of the Maignan et al. model was bad under the forest (0.15surface type and provide a priori knowledge for the quantitative inversion of surface atmospheric parameters.

  6. Quantifying Libya-4 Surface Reflectance Heterogeneity With WorldView-1, 2 and EO-1 Hyperion

    NASA Technical Reports Server (NTRS)

    Neigh, Christopher S. R.; McCorkel, Joel; Middleton, Elizabeth M.

    2015-01-01

    The land surface imaging (LSI) virtual constellation approach promotes the concept of increasing Earth observations from multiple but disparate satellites. We evaluated this through spectral and spatial domains, by comparing surface reflectance from 30-m Hyperion and 2-m resolution WorldView-2 (WV-2) data in the Libya-4 pseudoinvariant calibration site. We convolved and resampled Hyperion to WV-2 bands using both cubic convolution and nearest neighbor (NN) interpolation. Additionally, WV-2 and WV-1 same-date imagery were processed as a cross-track stereo pair to generate a digital terrain model to evaluate the effects from large (>70 m) linear dunes. Agreement was moderate to low on dune peaks between WV-2 and Hyperion (R2 <; 0.4) but higher in areas of lower elevation and slope (R2 > 0.6). Our results provide a satellite sensor intercomparison protocol for an LSI virtual constellation at high spatial resolution, which should start with geolocation of pixels, followed by NN interpolation to avoid tall dunes that enhance surface reflectance differences across this internationally utilized site.

  7. Monte Carlo simulation of light reflection from cosmetic powder particles near the human skin surface.

    PubMed

    Okamoto, Takashi; Kumagawa, Tatsuya; Motoda, Masafumi; Igarashi, Takanori; Nakao, Keisuke

    2013-06-01

    The reflection and scattering properties of light incident on human skin covered with powder particles have been investigated. A three-layer skin structure with a pigmented area is modeled, and the propagation of light in the skin's layers and in a layer of particles near the skin's surface is simulated using the Monte Carlo method. Assuming that only single scattering of light occurs in the powder layer, the simulation results show that the reflection spectra of light from the skin change with the size of powder particles. The color difference between normal and discolored skin is found to decrease considerably when powder particles with a diameter of approximately 0.25 μm are present near the skin's surface. The effects of the medium surrounding the particles, and the influence of the distribution of particle size (polydispersity), are also examined. It is shown that a surrounding medium with a refractive index close to that of the skin substantially suppresses the extreme spectral changes caused by the powder particles covering the skin surface.

  8. Reflected solar radiation from horizontal, vertical and inclined surfaces: ultraviolet and visible spectral and broadband behaviour due to solar zenith angle, orientation and surface type.

    PubMed

    Turner, J; Parisi, A V; Turnbull, D J

    2008-07-24

    Ultraviolet (UV) radiation affects human life and UV exposure is a significant everyday factor that individuals must be aware of to ensure minimal damaging biological effects to themselves. UV exposure is affected by many complex factors. Albedo is one factor, involving reflection from flat surfaces. Albedo is defined as the ratio of reflected (upwelling) irradiance to incident (downwelling) irradiance and is generally accepted only for horizontal surfaces. Incident irradiance on a non horizontal surface from a variety of incident angles may cause the reflectivity to change. Assumptions about the reflectivity of a vertical surface are frequently made for a variety of purposes but are rarely quantified. As urban structures are dominated by vertical surfaces, using albedo to estimate influence on UV exposure is limiting when incident (downwelling) irradiance is not normal to the surface. Changes to the incident angle are affected by the solar zenith angle, surface position and orientation and surface type. A new characteristic describing reflection from a surface has been used in this research. The ratio of reflected irradiance (from any surface position of vertical, horizontal or inclined) to global (or downwelling) irradiance (RRG) has been calculated for a variety of metal building surfaces in winter time in the southern hemisphere for both the UV and visible radiation spectrum, with special attention to RRG in the UV spectrum. The results show that the RRG due to a vertical surface can exceed the RRG due to a horizontal surface, at smaller solar zenith angles as well as large solar zenith angles. The RRG shows variability in reflective capacities of surface according to the above mentioned factors and present a more realistic influence on UV exposure than albedo for future investigations. Errors in measuring the RRG at large solar zenith angles are explored, which equally highlights the errors in albedo measurement at large solar zenith angles. PMID:18490174

  9. Method and apparatus for detecting the presence and thickness of carbon and oxide layers on EUV reflective surfaces

    DOEpatents

    Malinowski, Michael E.

    2005-01-25

    The characteristics of radiation that is reflected from carbon deposits and oxidation formations on highly reflective surfaces such as Mo/Si mirrors can be quantified and employed to detect and measure the presence of such impurities on optics. Specifically, it has been shown that carbon deposits on a Mo/Si multilayer mirror decreases the intensity of reflected HeNe laser (632.8 nm) light. In contrast, oxide layers formed on the mirror should cause an increase in HeNe power reflection. Both static measurements and real-time monitoring of carbon and oxide surface impurities on optical elements in lithography tools should be achievable.

  10. Smart, passive sun facing surfaces

    DOEpatents

    Hively, Lee M.

    1996-01-01

    An article adapted for selectively utilizing solar radiation comprises an absorptive surface and a reflective surface, the absorptive surface and the reflective surface oriented to absorb solar radiation when the sun is in a relatively low position, and to reflect solar radiation when the sun is in a relatively high position.

  11. Smart, passive sun facing surfaces

    DOEpatents

    Hively, L.M.

    1996-04-30

    An article adapted for selectively utilizing solar radiation comprises an absorptive surface and a reflective surface, the absorptive surface and the reflective surface oriented to absorb solar radiation when the sun is in a relatively low position, and to reflect solar radiation when the sun is in a relatively high position. 17 figs.

  12. Lagrangian flows within reflecting internal waves at a horizontal free-slip surface

    SciTech Connect

    Zhou, Qi; Diamessis, Peter J.

    2015-12-15

    In this paper sequel to Zhou and Diamessis [“Reflection of an internal gravity wave beam off a horizontal free-slip surface,” Phys. Fluids 25, 036601 (2013)], we consider Lagrangian flows within nonlinear internal waves (IWs) reflecting off a horizontal free-slip rigid lid, the latter being a model of the ocean surface. The problem is approached both analytically using small-amplitude approximations and numerically by tracking Lagrangian fluid particles in direct numerical simulation (DNS) datasets of the Eulerian flow. Inviscid small-amplitude analyses for both plane IWs and IW beams (IWBs) show that Eulerian mean flow due to wave-wave interaction and wave-induced Stokes drift cancels each other out completely at the second order in wave steepness A, i.e., O(A{sup 2}), implying zero Lagrangian mean flow up to that order. However, high-accuracy particle tracking in finite-Reynolds-number fully nonlinear DNS datasets from the work of Zhou and Diamessis suggests that the Euler-Stokes cancelation on O(A{sup 2}) is not complete. This partial cancelation significantly weakens the mean Lagrangian flows but does not entirely eliminate them. As a result, reflecting nonlinear IWBs produce mean Lagrangian drifts on O(A{sup 2}) and thus particle dispersion on O(A{sup 4}). The above findings can be relevant to predicting IW-driven mass transport in the oceanic surface and subsurface region which bears important observational and environmental implications, under circumstances where the effect of Earth rotation can be ignored.

  13. Highly directive Fabry-Perot leaky-wave nanoantennas based on optical partially reflective surfaces

    SciTech Connect

    Lorente-Crespo, M.; Mateo-Segura, C.

    2015-05-04

    Nanoantennas enhance the conversion between highly localized electromagnetic fields and far-field radiation. Here, we investigate the response of a nano-patch partially reflective surface backed with a silver mirror to an optical source embedded at the centre of the structure. Using full wave simulations, we demonstrate a two orders of magnitude increased directivity compared to the isotropic radiator, 50% power confinement to a 13.8° width beam and a ±16 nm bandwidth. Our antenna does not rely on plasmonic phenomena thus reducing non-radiative losses and conserving source coherence.

  14. [Study on the surface diffuse reflectance ultraviolet-visible spectra of the multicomponent metal catalysts].

    PubMed

    Tang, B; Jiang, Q; He, X; Shen, H

    1999-02-01

    In this paper, the surface diffuse reflectance ultraviolet-visible spectra (DRUVS) of two and three components supported metal catalysts for methanation of CO2 by hydrogenation were studied, and the relationship between the activity of catalytic-hydrogenation and the interaction among the components of the catalysts was revealed. Based on the analysis of the DRUVS of the catalysts with defferent amount of promoters in two component catalysts system, the dependence relationship between the characteristic strength of the DRUVS and the catalytic activity was worked out. PMID:15818931

  15. Polarization and Color Filtering Applied to Enhance Photogrammetric Measurements of Reflective Surfaces

    NASA Technical Reports Server (NTRS)

    Wells, Jeffrey M.; Jones, Thomas W.; Danehy, Paul M.

    2005-01-01

    Techniques for enhancing photogrammetric measurement of reflective surfaces by reducing noise were developed utilizing principles of light polarization. Signal selectivity with polarized light was also compared to signal selectivity using chromatic filters. Combining principles of linear cross polarization and color selectivity enhanced signal-to-noise ratios by as much as 800 fold. More typical improvements with combining polarization and color selectivity were about 100 fold. We review polarization-based techniques and present experimental results comparing the performance of traditional retroreflective targeting materials, cornercube targets returning depolarized light, and color selectivity.

  16. New figuring model based on surface slope profile for grazing-incidence reflective optics.

    PubMed

    Zhou, Lin; Huang, Lei; Bouet, Nathalie; Kaznatcheev, Konstantine; Vescovi, Matthew; Dai, Yifan; Li, Shengyi; Idir, Mourad

    2016-09-01

    Surface slope profile is widely used in the metrology of grazing-incidence reflective optics instead of surface height profile. Nevertheless, the theoretical and experimental model currently used in deterministic optical figuring processes is based on surface height, not on surface slope. This means that the raw slope profile data from metrology need to be converted to height profile to perform the current height-based figuring processes. The inevitable measurement noise in the raw slope data will introduce significant cumulative error in the resultant height profiles. As a consequence, this conversion will degrade the determinism of the figuring processes, and will have an impact on the ultimate surface figuring results. To overcome this problem, an innovative figuring model is proposed, which directly uses the raw slope profile data instead of the usual height data as input for the deterministic process. In this paper, first the influence of the measurement noise on the resultant height profile is analyzed, and then a new model is presented; finally a demonstration experiment is carried out using a one-dimensional ion beam figuring process to demonstrate the validity of our approach. PMID:27577760

  17. Multipitched Diffraction Gratings for Surface Plasmon Resonance-Enhanced Infrared Reflection Absorption Spectroscopy.

    PubMed

    Petefish, Joseph W; Hillier, Andrew C

    2015-11-01

    We demonstrate the application of metal-coated diffraction gratings possessing multiple simultaneous pitch values for surface enhanced infrared absorption (SEIRA) spectroscopy. SEIRA increases the magnitude of vibrational signals in infrared measurements by one of several mechanisms, most frequently involving the enhanced electric field associated with surface plasmon resonance (SPR). While the majority of SEIRA applications to date have employed nanoparticle-based plasmonic systems, recent advances have shown how various metals and structures lead to similar signal enhancement. Recently, diffraction grating couplers have been demonstrated as a highly tunable platform for SEIRA. Indeed, gratings are an experimentally advantageous platform due to the inherently tunable nature of surface plasmon excitation at these surfaces since both the grating pitch and incident angle can be used to modify the spectral location of the plasmon resonance. In this work, we use laser interference lithography (LIL) to fabricate gratings possessing multiple pitch values by subjecting photoresist-coated glass slides to repetitive exposures at varying orientations. After metal coating, these gratings produced multiple, simultaneous plasmon peaks associated with the multipitched surface, as identified by infrared reflectance measurements. These plasmon peaks could then be coupled to vibrational modes in thin films to provide localized enhancement of infrared signals. We demonstrate the flexibility and tunability of this platform for signal enhancement. It is anticipated that, with further refinement, this approach might be used as a general platform for broadband enhancement of infrared spectroscopy. PMID:26458177

  18. Mesoscale climatic simulation of surface air temperature cooling by highly reflective greenhouses in SE Spain.

    PubMed

    Campra, Pablo; Millstein, Dev

    2013-01-01

    A long-term local cooling trend in surface air temperature has been monitored at the largest concentration of reflective greenhouses in the world, at the Province of Almeria, SE Spain, associated with a dramatic increase in surface albedo in the area. The availability of reliable long-term climatic field data at this site offers a unique opportunity to test the skill of mesoscale meteorological models describing and predicting the impacts of land use change on local climate. Using the Weather Research and Forecast (WRF) mesoscale model, we have run a sensitivity experiment to simulate the impact of the observed surface albedo change on monthly and annual surface air temperatures. The model output showed a mean annual cooling of 0.25 °C associated with a 0.09 albedo increase, and a reduction of 22.8 W m(-2) of net incoming solar radiation at surface. Mean reduction of summer daily maximum temperatures was 0.49 °C, with the largest single-day decrease equal to 1.3 °C. WRF output was evaluated and compared with observations. A mean annual warm bias (MBE) of 0.42 °C was estimated. High correlation coefficients (R(2) > 0.9) were found between modeled and observed values. This study has particular interest in the assessment of the potential for urban temperature cooling by cool roofs deployment projects, as well as in the evaluation of mesoscale climatic models performance. PMID:24074145

  19. New figuring model based on surface slope profile for grazing-incidence reflective optics.

    PubMed

    Zhou, Lin; Huang, Lei; Bouet, Nathalie; Kaznatcheev, Konstantine; Vescovi, Matthew; Dai, Yifan; Li, Shengyi; Idir, Mourad

    2016-09-01

    Surface slope profile is widely used in the metrology of grazing-incidence reflective optics instead of surface height profile. Nevertheless, the theoretical and experimental model currently used in deterministic optical figuring processes is based on surface height, not on surface slope. This means that the raw slope profile data from metrology need to be converted to height profile to perform the current height-based figuring processes. The inevitable measurement noise in the raw slope data will introduce significant cumulative error in the resultant height profiles. As a consequence, this conversion will degrade the determinism of the figuring processes, and will have an impact on the ultimate surface figuring results. To overcome this problem, an innovative figuring model is proposed, which directly uses the raw slope profile data instead of the usual height data as input for the deterministic process. In this paper, first the influence of the measurement noise on the resultant height profile is analyzed, and then a new model is presented; finally a demonstration experiment is carried out using a one-dimensional ion beam figuring process to demonstrate the validity of our approach.

  20. Multipitched Diffraction Gratings for Surface Plasmon Resonance-Enhanced Infrared Reflection Absorption Spectroscopy.

    PubMed

    Petefish, Joseph W; Hillier, Andrew C

    2015-11-01

    We demonstrate the application of metal-coated diffraction gratings possessing multiple simultaneous pitch values for surface enhanced infrared absorption (SEIRA) spectroscopy. SEIRA increases the magnitude of vibrational signals in infrared measurements by one of several mechanisms, most frequently involving the enhanced electric field associated with surface plasmon resonance (SPR). While the majority of SEIRA applications to date have employed nanoparticle-based plasmonic systems, recent advances have shown how various metals and structures lead to similar signal enhancement. Recently, diffraction grating couplers have been demonstrated as a highly tunable platform for SEIRA. Indeed, gratings are an experimentally advantageous platform due to the inherently tunable nature of surface plasmon excitation at these surfaces since both the grating pitch and incident angle can be used to modify the spectral location of the plasmon resonance. In this work, we use laser interference lithography (LIL) to fabricate gratings possessing multiple pitch values by subjecting photoresist-coated glass slides to repetitive exposures at varying orientations. After metal coating, these gratings produced multiple, simultaneous plasmon peaks associated with the multipitched surface, as identified by infrared reflectance measurements. These plasmon peaks could then be coupled to vibrational modes in thin films to provide localized enhancement of infrared signals. We demonstrate the flexibility and tunability of this platform for signal enhancement. It is anticipated that, with further refinement, this approach might be used as a general platform for broadband enhancement of infrared spectroscopy.

  1. A study of protein reactions with surface-bound molecular targets using oblique-incidence reflectivity difference microscope

    PubMed Central

    Landry, J. P.; Sun, Y. S.; Zhu, X. D.

    2009-01-01

    We applied oblique-incidence reflectivity difference (OI-RD) microscopes (a form of polarization-modulated nulling ellipsometry) to detection of biomolecular microarrays without external labeling in a study of protein reactions with surface-immobilized targets. We show that the optical reflectivity difference signals can be quantitatively related to changes in surface mass density of molecular layers as a result of the reactions. Our experimental results demonstrate the feasibility of using oblique-incidence reflectivity difference microscopes for high-throughput proteomics research such as screening unlabeled protein probes against libraries of surface-immobilized small-molecules. PMID:18566623

  2. Context dependence in complex adaptive landscapes: frequency and trait-dependent selection surfaces within an adaptive radiation of Caribbean pupfishes.

    PubMed

    Martin, Christopher H

    2016-06-01

    The adaptive landscape provides the foundational bridge between micro- and macroevolution. One well-known caveat to this perspective is that fitness surfaces depend on ecological context, including competitor frequency, traits measured, and resource abundance. However, this view is based largely on intraspecific studies. It is still unknown how context-dependence affects the larger features of peaks and valleys on the landscape which ultimately drive speciation and adaptive radiation. Here, I explore this question using one of the most complex fitness landscapes measured in the wild in a sympatric pupfish radiation endemic to San Salvador Island, Bahamas by tracking survival and growth of laboratory-reared F2 hybrids. I present new analyses of the effects of competitor frequency, dietary isotopes, and trait subsets on this fitness landscape. Contrary to expectations, decreasing competitor frequency increased survival only among very common phenotypes, whereas less common phenotypes rarely survived despite few competitors, suggesting that performance, not competitor frequency, shapes large-scale features of the fitness landscape. Dietary isotopes were weakly correlated with phenotype and growth, but did not explain additional survival variation. Nonlinear fitness surfaces varied substantially among trait subsets, revealing one-, two-, and three-peak landscapes, demonstrating the complexity of selection in the wild, even among similar functional traits. PMID:27130447

  3. Modified coherent gradient sensing method for slope measurement of reflective surfaces

    NASA Astrophysics Data System (ADS)

    Ma, Kang; Xie, Huimin

    2015-05-01

    A phase shifting method was developed for Coherent Gradient Sensing (CGS) using a three-step phase shifting method. Three different inteferograms were obtained by changing the distance between two gratings. The phase filed can be calculated accurately from the three inteferograms. The interference fringes (phase field) in reflection mode represent the gradient contours of the out-of-plane displacement of a surface. The curvatures and shape of the surface both can be calculated by numerical methods using the fringe patterns. The measurement principle and experimental setup were introduced in detail. As an application, a standard specimen with a curvature radius of 5 m was measured. From the analysis of the experimental results, we find that the relative error of the curvature using this method was about 0.78%. The method has good potentials for measuring the slopes, curvatures and shapes of thin film/substrate systems.

  4. Evaluation of lateral resolution of scanning surface microscopy by total internal reflection with thermal lens effect.

    PubMed

    Shimosaka, Takuya; Izako, Masakazu; Uchiyama, Katsumi; Hobo, Toshiyuki

    2003-06-01

    We have developed a novel method for in situ and non-destructive surface analyses, or a total internal reflection with thermal lens spectroscopy (TIR-TLS), which has sufficient sensitivity to monitor phenomena in thin films, such as lipid bilayers. In this study, we applied TIR-TLS to microscopy for surface analyses, and we experimentally obtained its lateral resolution using the edge of a chromium film made by a photolithography technique. The obtained resolution was 20 microm, which was 60% of the diameter of an excitation beam at the interface. The estimated resolution with a simple model agreed with the experimental one, and from this model, TIR-TLS microscopy has the same resolution as that of ordinary optical microscopy. The microscopy by TIR-TLS was applied to a sample whose contrast was too weak to be visually seen, and an image of the sample was obtained without any loss of resolution.

  5. Light scattering by a rough surface of human skin. 1. The luminance factor of reflected light

    SciTech Connect

    Barun, V V; Ivanov, A P

    2013-08-31

    Based on the analytical solution of Maxwell's equations, we have studied the angular structure of the luminance factor of light reflected by the rough skin surface with large-scale relief elements, illuminated by a directed radiation beam incident at an arbitrary angle inside or outside the medium. The parameters of the surface inhomogeneities are typical of human skin. The calculated angular dependences are interpreted from the point of view of the angular distribution function of micro areas. The results obtained can be used for solving direct and inverse problems in biomedical optics, in particular for determining the depth of light penetration into a biological tissue, for studying the light action spectra on tissue chromophores under the in vivo conditions, for developing diagnostic methods of structural and biophysical parameters of a medium, and for optimising the mechanisms of interaction of light with biological tissues under their noninvasive irradiation through skin. (biomedical optics)

  6. Interaction of mineral surfaces with simple organic molecules by diffuse reflectance IR spectroscopy (DRIFT)

    SciTech Connect

    Thomas, Joan E.; Kelley, Michael J.

    2008-06-01

    Diffuse reflectance Fourier-transform infrared spectroscopy (DRIFTS) was used to characterize multi-layers of lysine, glutamic acid and salicylic acid on -alumina and kaolinite surfaces. The results agreed well with those previously obtained by ATR-IR in aqueous media where available, indicating that DRIFT may be regarded as effectively an in-situ spectroscopy for these materials. In the case of salicylic acid adsorption onto γ-alumina, DRIFTS was used to identify monolayer coverage and to detect molecules down to coverage of 3% of a monolayer. The spectroscopic results as to coverage were confirmed by analysis of the solutions used for treatment. The spectra obtained allowed identification of changes in the bonding environment with increasing surface coverage. DRIFTS, offers several advantages in terms of materials, experimental technique and data treatment, motivating further investigations.

  7. Soil magnetic susceptibility reflects soil moisture regimes and the adaptability of tree species to these regimes

    USGS Publications Warehouse

    Wang, J.-S.; Grimley, D.A.; Xu, C.; Dawson, J.O.

    2008-01-01

    Flooded, saturated or poorly drained soils are frequently anaerobic, leading to dissolution of the strongly magnetic minerals, magnetite and maghemite, and a corresponding decrease in soil magnetic susceptibility (MS). In this study of five temperate deciduous forests in east-central Illinois, USA, mean surface soil MS was significantly higher adjacent to upland tree species (31 ?? 10-5 SI) than adjacent to floodplain or lowland tree species (17 ?? 10-5 SI), when comparing regional soils with similar parent material of loessal silt. Although the sites differ in average soil MS for each tree species, the relative order of soil MS means for associated tree species at different locations is similar. Lowland tree species, Celtis occidentalis L., Ulmus americana L., Acer saccharinum L., Carya laciniosa (Michx. f.) Loud., and Fraxinus pennsylvanica Marsh. were associated with the lowest measured soil MS mean values overall and at each site. Tree species' flood tolerance rankings increased significantly, as soil MS values declined, the published rankings having significant correlations with soil MS values for the same species groups. The three published classifications of tree species' flood tolerance were significantly correlated with associated soil MS values at all sites, but most strongly at Allerton Park, the site with the widest range of soil drainage classes and MS values. Using soil MS measurements in forests with soil parent material containing similar initial levels of strongly magnetic minerals can provide a simple, rapid and quantitative method to classify soils according to hydric regimes, including dry conditions, and associated plant composition. Soil MS values thus have the capacity to quantify the continuum of hydric tolerances of tree species and guide tree species selection for reforestation. ?? 2007 Elsevier B.V. All rights reserved.

  8. Three-layer model for the surface second-harmonic generation yield including multiple reflections

    NASA Astrophysics Data System (ADS)

    Anderson, Sean M.; Mendoza, Bernardo S.

    2016-09-01

    We present the three-layer model to calculate the surface second-harmonic generation (SSHG) yield. This model considers that the surface is represented by three regions or layers. The first layer is the vacuum region with a dielectric function ɛv(ω ) =1 from where the fundamental electric field impinges on the material. The second layer is a thin layer (ℓ ) of thickness d characterized by a dielectric function ɛℓ(ω ) , and it is in this layer where the SSHG takes place. The third layer is the bulk region denoted by b and characterized by ɛb(ω ) . Both the vacuum and bulk layers are semi-infinite. The model includes the multiple reflections of both the fundamental and the second-harmonic (SH) fields that take place at the thin layer ℓ . We obtain explicit expressions for the SSHG yield for the commonly used s and p polarizations of the incoming 1 ω and outgoing 2 ω electric fields, where no assumptions for the symmetry of the surface are made. These symmetry assumptions ultimately determine which components of the surface nonlinear second-order susceptibility tensor χ (-2 ω ;ω ,ω ) are different from zero, and thus contribute to the SSHG yield. Then, we particularize the results for the most commonly investigated surfaces, the (001), (110), and (111) crystallographic faces, taking their symmetries into account. We use the three-layer model and compare it against the experimental results of a Si(111)(1 ×1 ):H surface, as a test case, and use it to predict the SSHG yield of a Si(001)(2 ×1 ) surface.

  9. Effects of light polarization and waves slope statistics on the reflectance factor of the sea surface.

    PubMed

    D'Alimonte, Davide; Kajiyama, Tamito

    2016-04-18

    Above-water radiometry depends on estimates of the reflectance factor ρ of the sea surface to compute the in situ water-leaving radiance. The Monte Carlo code for ocean color simulations MOX is used in this study to analyze the effect of different environmental components on ρ values. A first aspect is examining the reflectance factor without and by accounting for the sky-radiance polarization. The influence of the sea-surface statistics at discrete grid points is then considered by presenting a new scheme to define the variance of the waves slope. Results at different sun elevations and sensor orientations indicate that the light polarization effect on ρ simulations reduces from ∼17 to ∼10% when the wind speed increases from 0 to 14m s-1. An opposite tendency characterizes the modeling of the sea-surface slope variance, with ρ differences up to ∼12% at a wind speed of 10m s-1. The joint effect of polarization and the the sea-surface statistics displays a less systematic dependence on the wind speed, with differences in the range ∼13 to ∼18%. The ρ changes due to the light polarization and the variance of the waves slope become more relevant at sky-viewing geometries respectively lower and higher than 40° with respect to the zenith. An overall compensation of positive and negative offsets due to light polarization is finally documented when considering different sun elevations. These results address additional investigations which, by combining the modeling and experimental components of marine optics, better evaluate specific measurement protocols for collecting above-water radiometric data in the field.

  10. Effects of light polarization and waves slope statistics on the reflectance factor of the sea surface.

    PubMed

    D'Alimonte, Davide; Kajiyama, Tamito

    2016-04-18

    Above-water radiometry depends on estimates of the reflectance factor ρ of the sea surface to compute the in situ water-leaving radiance. The Monte Carlo code for ocean color simulations MOX is used in this study to analyze the effect of different environmental components on ρ values. A first aspect is examining the reflectance factor without and by accounting for the sky-radiance polarization. The influence of the sea-surface statistics at discrete grid points is then considered by presenting a new scheme to define the variance of the waves slope. Results at different sun elevations and sensor orientations indicate that the light polarization effect on ρ simulations reduces from ∼17 to ∼10% when the wind speed increases from 0 to 14m s-1. An opposite tendency characterizes the modeling of the sea-surface slope variance, with ρ differences up to ∼12% at a wind speed of 10m s-1. The joint effect of polarization and the the sea-surface statistics displays a less systematic dependence on the wind speed, with differences in the range ∼13 to ∼18%. The ρ changes due to the light polarization and the variance of the waves slope become more relevant at sky-viewing geometries respectively lower and higher than 40° with respect to the zenith. An overall compensation of positive and negative offsets due to light polarization is finally documented when considering different sun elevations. These results address additional investigations which, by combining the modeling and experimental components of marine optics, better evaluate specific measurement protocols for collecting above-water radiometric data in the field. PMID:27137234

  11. Photosynthetic adaptation strategy of Ulva prolifera floating on the sea surface to environmental changes.

    PubMed

    Zhao, Xinyu; Tang, Xuexi; Zhang, Huanxin; Qu, Tongfei; Wang, Ying

    2016-10-01

    For 8 consecutive years, a green tide has originated in the southern Yellow Sea and spread to the Qingdao offshore area. The causative species, Ulva prolifera, always forms a very thick thallus mat that is capable of drifting long distances over long periods. During this process, although the thalli face disturbance by complex environmental factors, they maintain high biomass and proliferation. We hypothesized that some form of photosynthetic adaptation strategy must exist to protect the thalli. Therefore, we studied the different photosynthetic response characteristics of the surface and lower layers of the floating thallus mats, and investigated the physiological and molecular-level adaptation mechanisms. The results showed that: (1) U. prolifera has strong photosynthetic capability that ensures it can gain sufficient energy to increase its biomass and adapt to long-distance migration. (2) Surface layer thalli adapt to the complex environment by dissipating excess energy via photosynthetic quantum control (energy quenching and energy redistribution between PSII/PSI) to avoid irreversible damage to the photosynthetic system. (3) Lower layer thalli increase their contents of Chlorophyll a (Chl a) and Chlorophyll b (Chl b) and decrease their Chl a/Chl b ratio to improve their ability to use light energy. (4) U. prolifera has strong photosynthetic plasticity and can adapt to frequent exchange between the surface and lower layer environments because of wave disturbance. Pigment component changes, energy quenching, and energy redistribution between PSII/PSI contribute to this photosynthetic plasticity.

  12. Photosynthetic adaptation strategy of Ulva prolifera floating on the sea surface to environmental changes.

    PubMed

    Zhao, Xinyu; Tang, Xuexi; Zhang, Huanxin; Qu, Tongfei; Wang, Ying

    2016-10-01

    For 8 consecutive years, a green tide has originated in the southern Yellow Sea and spread to the Qingdao offshore area. The causative species, Ulva prolifera, always forms a very thick thallus mat that is capable of drifting long distances over long periods. During this process, although the thalli face disturbance by complex environmental factors, they maintain high biomass and proliferation. We hypothesized that some form of photosynthetic adaptation strategy must exist to protect the thalli. Therefore, we studied the different photosynthetic response characteristics of the surface and lower layers of the floating thallus mats, and investigated the physiological and molecular-level adaptation mechanisms. The results showed that: (1) U. prolifera has strong photosynthetic capability that ensures it can gain sufficient energy to increase its biomass and adapt to long-distance migration. (2) Surface layer thalli adapt to the complex environment by dissipating excess energy via photosynthetic quantum control (energy quenching and energy redistribution between PSII/PSI) to avoid irreversible damage to the photosynthetic system. (3) Lower layer thalli increase their contents of Chlorophyll a (Chl a) and Chlorophyll b (Chl b) and decrease their Chl a/Chl b ratio to improve their ability to use light energy. (4) U. prolifera has strong photosynthetic plasticity and can adapt to frequent exchange between the surface and lower layer environments because of wave disturbance. Pigment component changes, energy quenching, and energy redistribution between PSII/PSI contribute to this photosynthetic plasticity. PMID:27262405

  13. From Intensity Profile to Surface Normal: Photometric Stereo for Unknown Light Sources and Isotropic Reflectances.

    PubMed

    Lu, Feng; Matsushita, Yasuyuki; Sato, Imari; Okabe, Takahiro; Sato, Yoichi

    2015-10-01

    We propose an uncalibrated photometric stereo method that works with general and unknown isotropic reflectances. Our method uses a pixel intensity profile, which is a sequence of radiance intensities recorded at a pixel under unknown varying directional illumination. We show that for general isotropic materials and uniformly distributed light directions, the geodesic distance between intensity profiles is linearly related to the angular difference of their corresponding surface normals, and that the intensity distribution of the intensity profile reveals reflectance properties. Based on these observations, we develop two methods for surface normal estimation; one for a general setting that uses only the recorded intensity profiles, the other for the case where a BRDF database is available while the exact BRDF of the target scene is still unknown. Quantitative and qualitative evaluations are conducted using both synthetic and real-world scenes, which show the state-of-the-art accuracy of smaller than 10 degree without using reference data and 5 degree with reference data for all 100 materials in MERL database.

  14. Surface profile measurement of highly reflective silicon wafer using wavelength tuning interferometer

    NASA Astrophysics Data System (ADS)

    Kim, Yangjin; Sugita, Naohiko; Mitsuishi, Mamoru

    2016-03-01

    In phase-shifting Fizeau interferometers, phase-shift errors and multiple-beam interference are the most common sources of systematic error affecting high-precision phase measurements. Nonsinusoidal waveforms can be minimized by applying synchronous detection with more than four samples. However, when phase-shift calibration is inaccurate, these algorithms cannot eliminate the effects of nonsinusoidal characteristics. Moreover, when measuring the surface profile of highly reflective samples, the calculated phase is critically determined not only by the decrease in the fringe contrast, but also by the coupling error between the harmonics and phase-shift errors. In this study, we calculate phase errors using phase-shifting algorithms that take into account the coupling error. We show that the 4N - 3 algorithm, which consists of a polynomial window function and a discrete Fourier transform term, results in the smallest phase error. As a demonstration, the surface profile of a highly reflective silicon wafer is measured using a wavelength-tuning Fizeau interferometer and the 4N - 3 algorithm.

  15. Kinetics of vacancy diffusion on Si(111) surfaces studied by scanning reflection electron microscopy

    NASA Astrophysics Data System (ADS)

    Watanabe, Heiji; Ichikawa, Masakazu

    1996-08-01

    The kinetics of vacancy diffusion on Si(111) surfaces is studied by using scanning reflection electron microscopy (SREM). Two types of layer-by-layer etching are observed during low-energy Ar ion irradiation (500 eV) at elevated substrate temperatures. One is step retreat, which is a reversal of step-flow growth, and the other is two-dimensional vacancy island nucleation. These results show that vacancies created by low-energy ion impact diffuse on the surfaces, and are annihilated at the step edges. The vacancy diffusion kinetics on the surfaces are examined by using a SREM technique. An activation energy of 3.0+/-0.2 eV is obtained from the vacancy diffusion length estimated from the width of the denuded zone, which is created on both sides of the atomic step by thermal heating after vacancy introduction by ion irradiation at room substrate temperature. These results indicate that vacancy diffusion kinetics is dominated by monovacancy formation and diffusion. These processes require thermal excitation to overcome the potential barrier for surface diffusion of adatoms, and to overcome the barrier for lateral binding energy to release adatoms from the step edges.

  16. Surface plasmons in doped graphene excited by the Attenuated Total Reflection technique in the THz regime

    NASA Astrophysics Data System (ADS)

    Ramos-Mendieta, F.; Hernandez-Lopez, J. A.; Palomino-Ovando, M.

    2015-03-01

    Surface plasmons of transverse electric (TE) and transverse magnetic (TM) polarization in doped free-standing graphene are numerically investigated at THz frequencies. For detecting these modes sufficient sensitivity of the prism-based Otto configuration is demonstrated. Complete agreement with the TM dispersion relation is found in doped graphene of Fermi level μ = 0.8 eV; perfect absorption due to wave interference is also observed. On the other hand, TE surface plasmons are special surface vibrations without induced surface charge; they are self-sustained current oscillations (unique of graphene) that arise in frequency ranges where the imaginary part of the graphene dynamical conductivity is negative. We found that TE plasmons are excited for angles of incidence very close to the critical angle between prism and air, as predicted from their dispersion relation. Reflection profiles and field intensities of these waves are presented for μ = 0.2, 0.3 eV. This work was supported by SESIC Mexico, Promep Grant FOFM-2008 and by CONACyT, Mexico.

  17. Characterization of the annealed (0001) surface of sapphire (alpha-Al2O3) and interaction with silver by reflection electron microscopy and scanning reflection electron microscopy.

    PubMed

    Ndubuisi, G C; Liu, J; Cowley, J M

    1992-02-15

    Annealed (0001) surfaces of single-crystal sapphire (alpha-Al2O3) rod have been studied in the electron microscope using reflection electron microscopy (REM), scanning reflection electron microscopy (SREM), and reflection high energy electron diffraction (RHEED). Annealed surfaces of (0001) sapphire are vicinal and characterized by close-packed (0001)-oriented terraces separated by faceted multiple-height steps, with edges parallel to energetically preferred low-index directions (less than 1010 greater than and less than 1120 greater than). These structural features are not seen on cleaved surfaces or polished surfaces treated at temperatures less than 1,250 degrees C. Oxygen-annealing produces clean surfaces which prove useful for investigating the interaction of deposited metals with the (0001) sapphire. Both REM and SREM (with microdiffraction spots) techniques have been used to observe fine structure of flat Ag islands on the scale of 1-100 nm on the (0001)-oriented terraces as well as aggregations at the steps. A preliminary result on interaction with Cu is also included.

  18. Time-of-flight analyzer system to detect reflected particles from a solid surface following low-energy particle injection

    SciTech Connect

    Yamaoka, H.; Tanaka, N.; Tsumori, K.; Nishiura, M.; Kenmotsu, T.; Hirouchi, T.; Kisaki, M.; Shinto, K.; Sasao, M.; Matsumoto, Y.; Wada, M.

    2008-02-15

    We have developed a time-of-flight analyzer to measure energy distributions of reflected particles from solid surfaces bombarded by low-energy (1-2 keV) ions. The analyzer yields energy distributions of neutrals which can be compared with the energy distributions of charged particles measured by a magnetic deflection-type momentum analyzer. We have tested the system to measure the angular dependence of energy and intensity for neutrals reflected from a polycrystalline W target. The energies of the reflected neutrals are much smaller than the incident ion energies, suggesting multiple scattering in the target. No angular dependence is observed under the condition that the sum of the incident and reflected angles is constant. The intensity of the reflected neutrals takes the maximum around the mirror angle. We compare these characteristics of neutral particle reflections with those of reflected ions.

  19. Inferring hemispherical reflectance of the earth's surface for global energy budgets from remotely sensed nadir or directional radiance values

    NASA Technical Reports Server (NTRS)

    Kimes, D. S.; Sellers, P. J.

    1985-01-01

    The relationship between directional reflectances spanning the entire reflecting hemisphere and hemispherical reflectance (albedo) and the effect of solar zenith angle and cover type on these relationships were investigated, using the results obtained from NOAA's 7/8 AVHRR ground-level reflectance measurements. Bands 1 (0.58-0.6B microns) and 2 (0.73-1. 1 microns) were used for reflectance measurements of 11 natural vegetation surfaces ranging from bare soils to dense vegetation canopies. The results show that errors in inferring hemispherical reflectance from nadir reflectance can be between 11 and 45 percent for all cover types and solar angles, depending on the viewing angles. A technique is described in which a choice of two specific view angles reduces this error to less than 6 percent for both bands and for all sun angles and cover types.

  20. "Intelligent Ensemble" Projections of Precipitation and Surface Radiation in Support of Agricultural Climate Change Adaptation

    NASA Technical Reports Server (NTRS)

    Taylor, Patrick C.; Baker, Noel C.

    2015-01-01

    Earth's climate is changing and will continue to change into the foreseeable future. Expected changes in the climatological distribution of precipitation, surface temperature, and surface solar radiation will significantly impact agriculture. Adaptation strategies are, therefore, required to reduce the agricultural impacts of climate change. Climate change projections of precipitation, surface temperature, and surface solar radiation distributions are necessary input for adaption planning studies. These projections are conventionally constructed from an ensemble of climate model simulations (e.g., the Coupled Model Intercomparison Project 5 (CMIP5)) as an equal weighted average, one model one vote. Each climate model, however, represents the array of climate-relevant physical processes with varying degrees of fidelity influencing the projection of individual climate variables differently. Presented here is a new approach, termed the "Intelligent Ensemble, that constructs climate variable projections by weighting each model according to its ability to represent key physical processes, e.g., precipitation probability distribution. This approach provides added value over the equal weighted average method. Physical process metrics applied in the "Intelligent Ensemble" method are created using a combination of NASA and NOAA satellite and surface-based cloud, radiation, temperature, and precipitation data sets. The "Intelligent Ensemble" method is applied to the RCP4.5 and RCP8.5 anthropogenic climate forcing simulations within the CMIP5 archive to develop a set of climate change scenarios for precipitation, temperature, and surface solar radiation in each USDA Farm Resource Region for use in climate change adaptation studies.

  1. Adaptive tool servo diamond turning for enhancing machining efficiency and surface quality of freeform optics.

    PubMed

    Zhu, Zhiwei; To, Suet

    2015-08-10

    Fast tool servo/ slow tool servo (FTS/STS) diamond turning is a very promising technique for the generation of freeform optics. However, the currently adopted constant scheme for azimuth sampling and side-feeding motion possesses no adaptation to surface shape variation, leading to the non-uniform surface quality and low machining efficiency. To overcome this defect, this paper reports on a novel adaptive tool servo (ATS) diamond turning technique which is essentially based on the novel two-degree-of-freedom (2-DOF) FTS/STS. In the ATS, the sampling interval and the side-feeding motion are actively controlled at any cutting point to adapt the machining process to shape variation of the desired surface, making both the sampling induced interpolation error and the side-feeding induced residual tool mark be within the desired tolerances. Characteristic of the required cutting motion suggests that besides the conventional z-axis servo motion, another servo motion along the x-axis synthesizing by the c-axis is mandatory for implementing the ATS. Comparative studies of surface generation of typical micro-structured surfaces in FTS/STS and ATS are thoroughly conducted both theoretically and experimentally. The result demonstrates that the ATS outperforms the FTS/STS with improved surface quality while simultaneously enhanced machining efficiency.

  2. Reflection of resonant light from a plane surface of an ensemble of motionless point scatters: Quantum microscopic approach

    NASA Astrophysics Data System (ADS)

    Kuraptsev, A. S.; Sokolov, I. M.

    2015-05-01

    On the basis of general theoretical results developed previously in [JETP 112, 246 (2011), 10.1134/S106377611101016X], we analyze the reflection of quasiresonant light from a plane surface of dense and disordered ensemble of motionless point scatters. Angle distribution of the scattered light is calculated both for s and p polarizations of the probe radiation. The ratio between coherent and incoherent (diffuse) components of scattered light is calculated. We analyze the contributions of scatters located at different distances from the surface and determine on this background the thickness of surface layer responsible for reflected beam generation. The inhomogeneity of dipole-dipole interaction near the surface is discussed. We study also dependence of total reflected light power on the incidence angle and compare the results of the microscopic approach with predictions of the Fresnel reflection theory. The calculations are performed for different densities of scatters and different frequencies of a probe radiation.

  3. Adaptation de maillage pour les problemes a surfaces libres en mecanique des fluides

    NASA Astrophysics Data System (ADS)

    Mokwinski, Yvan

    This Ph.D. thesis deals with mesh adaptivity for the numerical simulation of free surface problems in fluids mechanics. We study various aspects of the modeling and the numerical simulation of free surface flows. We use an Eulerian approach for the modeling of the dynamics of the interface. We opt for the pseudo-concentration method so that topologic changes do not add to the algorithmic complexity of the overall numerical strategy. The challenges related to the use of this interface capturing method are detailed and we propose a set of cures to improve the accuracy of the numerical computations when the methodology is not well chosen. Mesh adaptivity is a central component of the proposed methodology. A good mesh helps making the pseudo-concentration method competitive. We pursue three specific objectives in this thesis. To be able to model problems with surface tension, we developed a numerical methodology for the computation of capillary force. The developed methodology includes the reinitialization of the Eulerian marker to allow the accurate modeling of the physics of the problems under study. Finally, in order to perform mesh adaptivity to transient simulations, we propose a methodology which includes the definition of appropriate metrics, the interpolation of finite element functions between meshes and the introduction of a predictor in the mesh adaptivity process. The numerical simulation of verification problems involving the modeling of the dynamics of free surfaces illustrates the contributions.

  4. Algebraic grid adaptation method using non-uniform rational B-spline surface modeling

    NASA Technical Reports Server (NTRS)

    Yang, Jiann-Cherng; Soni, B. K.

    1992-01-01

    An algebraic adaptive grid system based on equidistribution law and utilized by the Non-Uniform Rational B-Spline (NURBS) surface for redistribution is presented. A weight function, utilizing a properly weighted boolean sum of various flow field characteristics is developed. Computational examples are presented to demonstrate the success of this technique.

  5. Nonlinear reflection from the surface of neutron stars and features of radio emission from the pulsar in the Crab nebula

    NASA Astrophysics Data System (ADS)

    Kontorovich, V. M.

    2016-08-01

    There are no explanations for the high-frequency component of the emission from the pulsar in the Crab nebula, but it may be a manifestation of instability in nonlinear reflection from the star's surface. Radiation from relativistic positrons flying from the magnetosphere to the star and accelerated by the electric field of the polar gap is reflected. The instability involves stimulated scattering on surface waves.

  6. A prototype for automation of land-cover products from Landsat Surface Reflectance Data Records

    NASA Astrophysics Data System (ADS)

    Rover, J.; Goldhaber, M. B.; Steinwand, D.; Nelson, K.; Coan, M.; Wylie, B. K.; Dahal, D.; Wika, S.; Quenzer, R.

    2014-12-01

    Landsat data records of surface reflectance provide a three-decade history of land surface processes. Due to the vast number of these archived records, development of innovative approaches for automated data mining and information retrieval were necessary. Recently, we created a prototype utilizing open source software libraries for automatically generating annual Anderson Level 1 land cover maps and information products from data acquired by the Landsat Mission for the years 1984 to 2013. The automated prototype was applied to two target areas in northwestern and east-central North Dakota, USA. The approach required the National Land Cover Database (NLCD) and two user-input target acquisition year-days. The Landsat archive was mined for scenes acquired within a 100-day window surrounding these target dates, and then cloud-free pixels where chosen closest to the specified target acquisition dates. The selected pixels were then composited before completing an unsupervised classification using the NLCD. Pixels unchanged in pairs of the NLCD were used for training decision tree models in an iterative process refined with model confidence measures. The decision tree models were applied to the Landsat composites to generate a yearly land cover map and related information products. Results for the target areas captured changes associated with the recent expansion of oil shale production and agriculture driven by economics and policy, such as the increase in biofuel production and reduction in Conservation Reserve Program. Changes in agriculture, grasslands, and surface water reflect the local hydrological conditions that occurred during the 29-year span. Future enhancements considered for this prototype include a web-based client, ancillary spatial datasets, trends and clustering algorithms, and the forecasting of future land cover.

  7. Multilayers at the surface of solutions of exogenous lung surfactant: direct observation by neutron reflection.

    PubMed

    Follows, D; Tiberg, F; Thomas, R K; Larsson, M

    2007-02-01

    Pharmacy-grade exogenous lung surfactant preparations of bovine and porcine origin, dispersed in physiological electrolyte solution have been studied. The organization and dynamics at the air/water interface at physiological temperature was analysed by neutron reflection. The results show that a well-defined surface phase is formed, consisting of a multilayer structure of lipid/protein bilayers alternating with aqueous layers, with a repetition period of about 70 A and correlation depths of 3 to >25 bilayers, depending on electrolyte composition and time. The experimental surfactant concentration of 0.15% (w/w) is far below that used in therapeutic application of exogenous surfactants and it is therefore likely that similar multilayer structures are also formed at the alveolar surface in the clinical situation during surfactant substitution therapy. Lung surfactant preparations in dry form swell in aqueous solution towards a limit of about 60% (w/w) of water, forming a lamellar liquid-crystalline phase above about 34 degrees C, which disperses into lamellar bodies at higher water concentrations. The lamellar spacings in the surface multilayers at the air/water interface are smaller than those in the saturated limit even though they are in contact with much greater water concentrations. The surface multilayers are laterally disordered in a way that is consistent with fragments of Lalpha-phase lamellae. The near surface layers of the multilayer structure have a significant protein content (only SP-B and SP-C are present in the preparations). The results demonstrate that a multilayer structure can be formed in exogenous surfactant even at very low concentrations and indicate that multilayers need to be incorporated into present interpretations of in vitro studies of similar lung surfactant preparations, which are largely based on monolayer models.

  8. Towards a more comprehensive usage of reflection seismic in near-surface characterization

    NASA Astrophysics Data System (ADS)

    Blouin, M.; Gloaguen, E.; Bellefleur, G.; Pugin, A.

    2014-12-01

    For more than a decade, research groups such as the Geological Survey of Canada built the interest for near-surface reflection seismic by proposing small vibrating sources and three components (3C) landstreamers. Developments in the instrumentation combined with extensive use of shear-wave profiling to image stratigraphy of unconsolidated environments at high resolution got this geophysical method more versatile, more accurate, increased cost effectiveness and allowed to cover greater distance per day. With those major upgrades as a starting point and in a context of regional aquifer characterization in St-Lawrence Lowlands in the province of Quebec, Canada, the present study propose a workflow to further enhance reflection seismic usage for near-surface characterization. First, as high resolution near surface surveys require small shot intervals and multiple channels on three axis, a lot of the acquisition information is received under a raw form yielding to unproductive quality control (QC). Hence, a tool was developed to process data "on the fly" and allow adequate real-time QC and on-site decision making. The algorithm was constructed in a Python environment and is accessible through a graphical user interface where the user is prompted for geometry parameters inputs and desired processing flow steps. Second, at the scale of seismic wavelengths, fine grain and poorly consolidated sediments such as marine clay of the St-Lawrence Lowlands can be viewed as a homogeneous medium presenting anisotropy. This section of the study showed that such geological settings yield to significant seismic velocity variations with angle of propagation that should not be ignore for normal move-out correction, migration or time to depth conversion. Finally, accurate delineation of stratigraphic horizons is an important task of any environmental or hydrogeological characterization study. A methodology was put forward to help integrate geophysical measurements with geological

  9. Adapt

    NASA Astrophysics Data System (ADS)

    Bargatze, L. F.

    2015-12-01

    Active Data Archive Product Tracking (ADAPT) is a collection of software routines that permits one to generate XML metadata files to describe and register data products in support of the NASA Heliophysics Virtual Observatory VxO effort. ADAPT is also a philosophy. The ADAPT concept is to use any and all available metadata associated with scientific data to produce XML metadata descriptions in a consistent, uniform, and organized fashion to provide blanket access to the full complement of data stored on a targeted data server. In this poster, we present an application of ADAPT to describe all of the data products that are stored by using the Common Data File (CDF) format served out by the CDAWEB and SPDF data servers hosted at the NASA Goddard Space Flight Center. These data servers are the primary repositories for NASA Heliophysics data. For this purpose, the ADAPT routines have been used to generate data resource descriptions by using an XML schema named Space Physics Archive, Search, and Extract (SPASE). SPASE is the designated standard for documenting Heliophysics data products, as adopted by the Heliophysics Data and Model Consortium. The set of SPASE XML resource descriptions produced by ADAPT includes high-level descriptions of numerical data products, display data products, or catalogs and also includes low-level "Granule" descriptions. A SPASE Granule is effectively a universal access metadata resource; a Granule associates an individual data file (e.g. a CDF file) with a "parent" high-level data resource description, assigns a resource identifier to the file, and lists the corresponding assess URL(s). The CDAWEB and SPDF file systems were queried to provide the input required by the ADAPT software to create an initial set of SPASE metadata resource descriptions. Then, the CDAWEB and SPDF data repositories were queried subsequently on a nightly basis and the CDF file lists were checked for any changes such as the occurrence of new, modified, or deleted

  10. Are boundary conditions in surface productivity at the Southern Polar Front reflected in benthic activity?

    NASA Astrophysics Data System (ADS)

    Brandt, Angelika; Vanreusel, Ann; Bracher, Astrid; Jule Marie Hoppe, Clara; Lins, Lidia; Meyer-Löbbecke, Anna; Altenburg Soppa, Mariana; Würzberg, Laura

    2014-10-01

    In austral summer 2012, during the expedition ANT-XXVIII/3 on board RV Polarstern, two sites were sampled 1600 km apart in the South Polar Front area (52°S) at the boundary of different productivity regimes for meio- and macrobenthos using a multiple-corer and an epibenthic sledge, respectively. Patterns in density and abundance data were compared between different size classes of the benthos and interpreted in relation to surface primary productivity data and sediment oxygen consumption. We tested the hypothesis that long-term satellite-derived surface phytoplankton biomass, in situ real time biomass, and productivity measurements at the surface and throughout the euphotic zone are reflected in abyssal benthos densities, abundances and activity. Specifically, we investigated the effect of boundary conditions for lower and higher surface productivity. Surface and integrated to 100 m depth biomass and primary productivity measurements vary stations, with the lowest values at station 85 (0.083 mg Chl-a m-3 at surface, 9 mg Chl-a m-2 and 161 mg C m-2 d-1- integrated over the first 100 m depth), and the highest values at station 86 (2.231 mg Chl-a m-3 at surface, 180 mg Chl-a m-2 and 2587 mg C m-2 d-1 integrated over first 100 m depth). Total meiofaunal densities varied between 102 and 335 individuals/10 cm². Densities were the highest at station 86-30 (335 individuals) and lowest at station 81-13 (102 individuals). Total macrofaunal densities (individuals/1000 m²) varied between 26 individuals at station 81-17 and 194 individuals at station 86-24. However, three EBS hauls were taken at station 86 with a minimum of 80 and a maximum of 194 individuals. Sediment oxygen consumption did not vary significantly between stations from east to west. Bentho-pelagic coupling of meio- and macrobenthic communities could not be observed in the South Polar Front at the boundary conditions from low to high surface productivity between stations 81 and 86.

  11. Neutron reflectivity study of substrate surface chemistry effects on supported phospholipid bilayer formation on (1120) sapphire.

    SciTech Connect

    Oleson, Timothy A.; Sahai, Nita; Wesolowski, David J; Dura, Joseph A; Majkrzak, Charles F; Giuffre, Anthony J.

    2012-01-01

    Oxide-supported phospholipid bilayers (SPBs) used as biomimetric membranes are significant for a broad range of applications including improvement of biomedical devices and biosensors, and in understanding biomineralization processes and the possible role of mineral surfaces in the evolution of pre-biotic membranes. Continuous-coverage and/or stacjed SPBs retain properties (e.,g. fluidity) more similar to native biological membranes, which is desirable for most applications. Using neutron reflectivity, we examined face coverage and potential stacking of dipalmitoylphosphatidylcholine (DPPC) bilayers on the (1120) face of sapphire (a-Al2O3). Nearly full bilayers were formed at low to neutral pH, when the sapphire surface is positively charged, and at low ionic strength (l=15 mM NaCl). Coverage decreased at higher pH, close to the isoelectric point of sapphire, and also at high I>210mM, or with addition of 2mM Ca2+. The latter two effects are additive, suggesting that Ca2+ mitigates the effect of higher I. These trends agree with previous results for phospholipid adsorption on a-Al2O3 particles determined by adsorption isotherms and on single-crystal (1010) sapphire by atomic force microscopy, suggesting consistency of oxide surface chemistry-dependent effects across experimental techniques.

  12. Attenuated total reflectance Fourier-transform infrared spectroscopy of carboxylic acids adsorbed onto mineral surfaces

    NASA Astrophysics Data System (ADS)

    Kubicki, J. D.; Schroeter, L. M.; Itoh, M. J.; Nguyen, B. N.; Apitz, S. E.

    1999-09-01

    A suite of naturally-occurring carboxylic acids (acetic, oxalic, citric, benzoic, salicylic and phthalic) and their corresponding sodium salts were adsorbed onto a set of common mineral substrates (quartz, albite, illite, kaolinite and montmorillonite) in batch slurry experiments. Solution pH's of approximately 3 and 6 were used to examine the effects of pH on sorption mechanisms. Attenuated total reflectance Fourier-transform infrared (ATR FTIR) spectroscopy was employed to obtain vibrational frequencies of the organic ligands on the mineral surfaces and in solution. UV/visible spectroscopy on supernatant solutions was also employed to confirm that adsorption from solution had taken place for benzoic, salicylic and phthalic acids. Molecular orbital calculations were used to model possible surface complexes and interpret the experimental spectra. In general, the tectosilicates, quartz and albite feldspar, did not chemisorb (i.e., strong, inner-sphere adsorption) the carboxylate anions in sufficient amounts to produce infrared spectra of the organics after rinsing in distilled water. The clays (illite, kaolinite and montmorillonite) each exhibited similar ATR FTIR spectra. However, the illite sample used in this study reacted to form strong surface and aqueous complexes with salicylic acid before being treated to remove free Fe-hydroxides. Chemisorption of carboxylic acids onto clays is shown to be limited without the presence of Fe-hydroxides within the clay matrix.

  13. Reflectance spectra of 'featureless' materials and the surface mineralogies of M- and E-class asteroids

    NASA Technical Reports Server (NTRS)

    Cloutis, Edward A.; Smith, Dorian G.; Lambert, Richard St. J.; Gaffey, Michael J.

    1990-01-01

    In a search for diagnostic spectral parameters which can be used to distinguish different materials on the surface of asteroids and to provide information on the detection limits for mafic silicates, the 0.3- to 2.6-micron reflectance spectra of meteoritic enstatite (nearly pure MgSiO3), iron meteorite metal, magnetite, and amorphous carbon as well as various mixtures of these materials with mafic silicates were examined. Results are presented on the dependence of the spectral detectability of mafic silicates associated with metal, carbon, and magnetite on the particle sizes of the phases, their chemistries, crystal structures, and abundances. It is shown that the observational data for a representative M-class asteroid, (16) Psyche, are largely consistent with a fine-grained metal-rich surface assemblage, whereas data for the E-class asteroid (44) Nysa indicate that its surface is composed of fine-grained material similar to enstatite achondrites, with a small amount of material comparable to the chondritic inclusions found in the Cumberland Falls aubrite.

  14. An accurate adaptive solver for surface-tension-driven interfacial flows

    NASA Astrophysics Data System (ADS)

    Popinet, Stéphane

    2009-09-01

    A method combining an adaptive quad/octree spatial discretisation, geometrical Volume-Of-Fluid interface representation, balanced-force continuum-surface-force surface-tension formulation and height-function curvature estimation is presented. The extension of these methods to the quad/octree discretisation allows adaptive variable resolution along the interface and is described in detail. The method is shown to recover exact equilibrium (to machine accuracy) between surface-tension and pressure gradient in the case of a stationary droplet, irrespective of viscosity and spatial resolution. Accurate solutions are obtained for the classical test case of capillary wave oscillations. An application to the capillary breakup of a jet of water in air further illustrates the accuracy and efficiency of the method. The source code of the implementation is freely available as part of the Gerris flow solver.

  15. Interactions of satellite-speed helium atoms with satellite surfaces. 2: Energy distributions of reflected helium atoms

    NASA Technical Reports Server (NTRS)

    Liu, S. M.; Knuth, E. L.

    1976-01-01

    Energy transfer in collisions of satellite-speed (7,000 m/sec) helium atoms with a cleaned 6061-T6 satellite-type aluminum surface was investigated using the molecular-beam technique. The amount of energy transferred was determined from the measured energy of the molecular-beam and the measured spatial and energy distributions of the reflected atoms. Spatial distributions of helium atoms scattered from a 6061-T6 aluminum surface were measured. The scattering pattern exhibits a prominent backscattering, probably due to the gross surface roughness and/or the relative lattice softness of the aluminum surface. Energy distributions of reflected helium atoms from the same surface were measured for six different incidence angles. For each incidence angle, distributions were measured at approximately sixty scattering positions. At a given scattering position, the energy spectra of the reflected helium atoms and the background gas were obtained using the retarding-field energy analyzer.

  16. Bio-inspired, subwavelength surface structures to control reflectivity, transmission, and scattering in the infrared

    NASA Astrophysics Data System (ADS)

    Lora Gonzalez, Federico

    Controlling the reflection of visible and infrared (IR) light at interfaces is extremely important to increase the power efficiency and performance of optics, electro-optical and (thermo)photovoltaic systems. The eye of the moth has evolved subwavelength protuberances that increase light transmission into the eye tissue and prevent reflection. The subwavelength protuberances effectively grade the refractive index from that of air (n=1) to that of the tissue (n=1.4), making the interface gradual, suppressing reflection. In theory, the moth-eye (ME) structures can be implemented with any material platform to achieve an antireflectance effect by scaling the pitch and size of protuberances for the wavelength range of interest. In this work, a bio-inspired, scalable and substrate-independent surface modification protocol was developed to realize broadband antireflective structures based on the moth-eye principle. Quasi-ordered ME arrays were fabricated in IR relevant materials using a colloidal lithography method to achieve highly efficient, omni-directional transmission of mid and far infrared (IR) radiation. The effect of structure height and aspect ratio on transmittance and scattering is explored, with discussion on experimental techniques and effective medium theory (EMT). The highest aspect ratio structures (AR = 9.4) achieved peak single-side transmittance of 98%, with >85% transmission for lambda = 7--30 microns. A detailed photon balance constructed by transmission, forward scattering, specular reflection and diffuse reflection measurements to quantify optical losses due to near-field effects will be discussed. In addition, angle-dependent transmission measurements showed that moth-eye structures provide superior antireflective properties compared to unstructured interfaces over a wide angular range (0--60° incidence). Finally, subwavelength ME structures are incorporated on a Si substrate to enhance the absorption of near infrared (NIR) light in PtSi films to

  17. Detecting moisture status of pecan orchards and the potential of remotely-sensed surface reflectance data

    NASA Astrophysics Data System (ADS)

    Othman, Yahia Abdelrahman

    Demand for New Mexico's limited water resources coupled with periodic drought has increased the need to schedule irrigation of pecan orchards based on tree water status. The overall goal of this research was to develop advanced tree water status sensing techniques to optimize irrigation scheduling of pecan orchards. To achieve this goal, I conducted three studies in the La Mancha and Leyendecker orchards, both mature pecan orchards located in the Mesilla Valley, New Mexico. In the first study, I screened leaf-level physiological changes that occurred during cyclic irrigation to determine parameters that best represented changes in plant moisture status. Then, I linked plant physiological changes to remotely-sensed surface reflectance data derived from Landsat Thematic Mapper (TM) and Enhanced Thematic Mapper (ETM+). In the second study, I assessed the impact of water deficits that developed during the flood irrigation dry-down cycles on photosynthesis (A) and gas exchange and established preliminary water deficit thresholds of midday stem water potential (Psi smd) critical to A and gas exchange of pecans. In a third study, I investigated whether hyperspectral data obtained from a handheld spectroradiometer and multispectral remotely-sensed data derived from Landsat 7 ETM+ and Landsat 8 Operational Land Imager (OLI) could detect moisture status in pecans during cyclic flood irrigations. I conducted the first study simultaneously in both orchards. Leaf-level physiological responses and remotely-sensed surface reflectance data were collected from trees that were either well watered or in water deficit. Midday stem water potential was the best leaf-level physiological response to detect moisture status in pecans. Multiple linear regression between Psismd and vegetation indices revealed a significant relationship (R 2 = 0.54) in both orchards. Accordingly, I concluded that remotely-sensed multispectral data form Landsat TMETM+ holds promise for detecting the moisture

  18. Global Landsat Surface Reflectance Products Derived Using GLS 2000 and 2005 Images

    NASA Astrophysics Data System (ADS)

    Narasimhan, R.; Feng, M.; Sexton, J. O.; Huang, C.; Channan, S.; Vermote, E. F.; Masek, J. G.; Townshend, J. R.

    2010-12-01

    Calculated by accounting for radiometric calibration errors and atmospheric effects, Surface Reflectance (SR) is considered a more accurate representation of the spectral property of the land surface than raw satellite radiometry. While atmospheric correction algorithms have been applied to MODIS data to produce SR as a standard MODIS product, such algorithms have not been applied to Landsat images on a routine basis. As part of the Global Forest Cover Change (GFCC) project, we applied a MODIS-based atmospheric algorithm to the GLS 2000 and 2005 images, and for the first time, produced global surface reflectance products at Landsat resolution. Since MODIS SR products have been validated comprehensively through previous studies, we used them to evaluate the Landsat SR products. All GLS 2000 images are Landsat7 ETM+ (L7) images, while the GLS2005 data set consist of 7381 gap-filled L7 images and 2175 Landsat5 TM (L5) images. L7 derived SR images are validated against the MODIS Daily SR product and the L5 derived SR images are validated against the MODIS NBAR composited products covering the same period as the L5 images. On a global scale, average R2 for the GLS2000 L7 and MODIS Daily SR range from 0.77 to 0.89 with greater correlation observed in the longer wavelengths. A similar R2 range (0.76-0.88) was observed in the GLS2005 L7 and MODIS Daily SR comparison. In both cases, standard deviations of R2 for each band are less than 0.26. The averaged slope values for the L7 bands range from 0.907 to 1.007 and intercept values range from -0.087 to 0.17 percent of reflectance. When divided by the mean to reduce statistical artifacts at high reflectance, Co-efficient of deviation (CD) shows that the GLS2000 and GLS2005 L7 vs. MODIS Daily SR estimates agree best for the near-infrared band (0.07 and 0.08) and are the worst for the blue band (0.34 & 0.35) in both cases. These global trends in CD are a reflection of regional differences where for most bands, the L7 - MODIS

  19. Grain size of the surface regolith of asteroid 4 Vesta estimated from its reflectance spectrum in comparison with HED meteorites

    NASA Technical Reports Server (NTRS)

    Hiroi, Takahiro; Pieters, Carle M.; Takeda, Hiroshi

    1994-01-01

    The grain-size distribution of the regolith of asteroid 4 Vesta has been estimated by comparing its reflectance spectra (0.3-2.6 microns) with those of HED meteorites. The finest grain-size separate (less than 25 micrometers) of a particular howardite has a reflectance spectrum most similar to Vesta's. In order to better simulate Vesta's surface mineralogy, reflectance spectra of those finest HED meteorite powders were linearly combined, and Vesta's spectrum was scaled for the best fit between them. Both the albedo and the shape of reflectance spectrum of Vesta were well reproduced by regional mixtures of the finest (less than 25 micrometers) powders of HED meteorites. The result suggests the heterogeneity of Vesta's surface and provides an estimate of the visible reflectance of Vesta that is close to its Infrared Astronomical Satellite (IRAS) albedo. Thus, this suggests that fine grains can be generated and retained by relatively small bodies (Vesta is approximately 500 km in diameter).

  20. Sliding mode control of wind-induced vibrations using fuzzy sliding surface and gain adaptation

    NASA Astrophysics Data System (ADS)

    Thenozhi, Suresh; Yu, Wen

    2016-04-01

    Although fuzzy/adaptive sliding mode control can reduce the chattering problem in structural vibration control applications, they require the equivalent control and the upper bounds of the system uncertainties. In this paper, we used fuzzy logic to approximate the standard sliding surface and designed a dead-zone adaptive law for tuning the switching gain of the sliding mode control. The stability of the proposed controller is established using Lyapunov stability theory. A six-storey building prototype equipped with an active mass damper has been used to demonstrate the effectiveness of the proposed controller towards the wind-induced vibrations.

  1. Surface plasmon resonance spectroscopy of single bowtie nano-antennas using a differential reflectivity method

    NASA Astrophysics Data System (ADS)

    Kaniber, M.; Schraml, K.; Regler, A.; Bartl, J.; Glashagen, G.; Flassig, F.; Wierzbowski, J.; Finley, J. J.

    2016-03-01

    We report on the structural and optical properties of individual bowtie nanoantennas both on glass and semiconducting GaAs substrates. The antennas on glass (GaAs) are shown to be of excellent quality and high uniformity reflected by narrow size distributions with standard deviations for the triangle and gap size of = 4.5 nm = 2.6 nm and = 5.4 nm = 3.8 nm, respectively. The corresponding optical properties of individual nanoantennas studied by differential reflection spectroscopy show a strong reduction of the localised surface plasmon polariton resonance linewidth from 0.21 eV to 0.07 eV upon reducing the antenna size from 150 nm to 100 nm. This is attributed to the absence of inhomogeneous broadening as compared to optical measurements on nanoantenna ensembles. The inter-particle coupling of an individual bowtie nanoantenna, which gives rise to strongly localised and enhanced electromagnetic hotspots, is demonstrated using polarization-resolved spectroscopy, yielding a large degree of linear polarization of ρmax ~ 80%. The combination of highly reproducible nanofabrication and fast, non-destructive and non-contaminating optical spectroscopy paves the route towards future semiconductor-based nano-plasmonic circuits, consisting of multiple photonic and plasmonic entities.

  2. Surface plasmon resonance spectroscopy of single bowtie nano-antennas using a differential reflectivity method.

    PubMed

    Kaniber, M; Schraml, K; Regler, A; Bartl, J; Glashagen, G; Flassig, F; Wierzbowski, J; Finley, J J

    2016-03-23

    We report on the structural and optical properties of individual bowtie nanoantennas both on glass and semiconducting GaAs substrates. The antennas on glass (GaAs) are shown to be of excellent quality and high uniformity reflected by narrow size distributions with standard deviations for the triangle and gap size of = 4.5 nm = 2.6 nm and = 5.4 nm = 3.8 nm, respectively. The corresponding optical properties of individual nanoantennas studied by differential reflection spectroscopy show a strong reduction of the localised surface plasmon polariton resonance linewidth from 0.21 eV to 0.07 eV upon reducing the antenna size from 150 nm to 100 nm. This is attributed to the absence of inhomogeneous broadening as compared to optical measurements on nanoantenna ensembles. The inter-particle coupling of an individual bowtie nanoantenna, which gives rise to strongly localised and enhanced electromagnetic hotspots, is demonstrated using polarization-resolved spectroscopy, yielding a large degree of linear polarization of ρmax ~ 80%. The combination of highly reproducible nanofabrication and fast, non-destructive and non-contaminating optical spectroscopy paves the route towards future semiconductor-based nano-plasmonic circuits, consisting of multiple photonic and plasmonic entities.

  3. Surface plasmon resonance spectroscopy of single bowtie nano-antennas using a differential reflectivity method

    PubMed Central

    Kaniber, M.; Schraml, K.; Regler, A.; Bartl, J.; Glashagen, G.; Flassig, F.; Wierzbowski, J.; Finley, J. J.

    2016-01-01

    We report on the structural and optical properties of individual bowtie nanoantennas both on glass and semiconducting GaAs substrates. The antennas on glass (GaAs) are shown to be of excellent quality and high uniformity reflected by narrow size distributions with standard deviations for the triangle and gap size of = 4.5 nm = 2.6 nm and = 5.4 nm = 3.8 nm, respectively. The corresponding optical properties of individual nanoantennas studied by differential reflection spectroscopy show a strong reduction of the localised surface plasmon polariton resonance linewidth from 0.21 eV to 0.07 eV upon reducing the antenna size from 150 nm to 100 nm. This is attributed to the absence of inhomogeneous broadening as compared to optical measurements on nanoantenna ensembles. The inter-particle coupling of an individual bowtie nanoantenna, which gives rise to strongly localised and enhanced electromagnetic hotspots, is demonstrated using polarization-resolved spectroscopy, yielding a large degree of linear polarization of ρmax ~ 80%. The combination of highly reproducible nanofabrication and fast, non-destructive and non-contaminating optical spectroscopy paves the route towards future semiconductor-based nano-plasmonic circuits, consisting of multiple photonic and plasmonic entities. PMID:27005986

  4. Effects of surface reflectance on skylight polarization measurements at the Mauna Loa Observatory

    NASA Astrophysics Data System (ADS)

    Dahlberg, Andrew R.; Pust, Nathan J.; Shaw, Joseph A.

    2011-08-01

    An all-sky imaging polarimeter was deployed in summer 2008 to the Mauna Loa Observatory in Hawaii to study clear-sky atmospheric skylight polarization. The imager operates in five wavebands in the visible and near infrared spectrum and has a fisheye lens for all-sky viewing. This paper describes the deployment and presents comparisons of the degree of skylight polarization observed to similar data observed by Coulson with a principal-plane scanning polarimeter in the late 1970s. In general, the results compared favorably to those of Coulson. In addition, we present quantitative results correlating a variation of the maximum degree of polarization over a range of 70-85% to fluctuation in underlying surface reflectance and upwelling radiance data from the GOES satellite.

  5. Effects of surface reflectance on skylight polarization measurements at the Mauna Loa Observatory.

    PubMed

    Dahlberg, Andrew R; Pust, Nathan J; Shaw, Joseph A

    2011-08-15

    An all-sky imaging polarimeter was deployed in summer 2008 to the Mauna Loa Observatory in Hawaii to study clear-sky atmospheric skylight polarization. The imager operates in five wavebands in the visible and near infrared spectrum and has a fisheye lens for all-sky viewing. This paper describes the deployment and presents comparisons of the degree of skylight polarization observed to similar data observed by Coulson with a principal-plane scanning polarimeter in the late 1970s. In general, the results compared favorably to those of Coulson. In addition, we present quantitative results correlating a variation of the maximum degree of polarization over a range of 70-85% to fluctuation in underlying surface reflectance and upwelling radiance data from the GOES satellite. PMID:21934965

  6. Polarization radiation in the planetary atmosphere delimited by a heterogeneous diffusely reflecting surface

    NASA Technical Reports Server (NTRS)

    Strelkov, S. A.; Sushkevich, T. A.

    1983-01-01

    Spatial frequency characteristics (SFC) and the scattering functions were studied in the two cases of a uniform horizontal layer with absolutely black bottom, and an isolated layer. The mathematical model for these examples describes the horizontal heterogeneities in a light field with regard to radiation polarization in a three dimensional planar atmosphere, delimited by a heterogeneous surface with diffuse reflection. The perturbation method was used to obtain vector transfer equations which correspond to the linear and nonlinear systems of polarization radiation transfer. The boundary value tasks for the vector transfer equation that is a parametric set and one dimensional are satisfied by the SFC of the nonlinear system, and are expressed through the SFC of linear approximation. As a consequence of the developed theory, formulas were obtained for analytical calculation of albedo in solving the task of dissemination of polarization radiation in the planetary atmosphere with uniform Lambert bottom.

  7. Analytical model for the excitation of leaky surface plasmon polaritons in the attenuated total reflection configuration

    NASA Astrophysics Data System (ADS)

    Jia, Hongwei; Xie, Yunya; Liu, Haitao; Zhong, Ying

    2016-05-01

    We propose a fully-analytical model for the excitation of leaky surface plasmon polariton (SPP) in the attenuated total reflection (ATR) configuration under illumination by a finite-width beam of electromagnetic wave. The model is built up on the basis of the general unconjugated-form reciprocity theorem and is able to predict the excitation amplitude and phase of the leaky SPP at a quantitative level. The validity of the model is carefully supported through a comparison with the numerical results obtained with the mode orthogonality. With the model a physical understanding of the resonant excitation of the leaky SPP is achieved and the optimal parameters such as the incidence angle and the beam width to ensure an efficient SPP excitation are demonstrated for design tasks.

  8. Modification of nanostructured fused silica for use as superhydrophobic, IR-transmissive, anti-reflective surfaces

    NASA Astrophysics Data System (ADS)

    Boyd, Darryl A.; Frantz, Jesse A.; Bayya, Shyam S.; Busse, Lynda E.; Kim, Woohong; Aggarwal, Ishwar; Poutous, Menelaos; Sanghera, Jasbinder S.

    2016-04-01

    In order to mimic and enhance the properties of moth eye-like materials, nanopatterned fused silica was chemically modified to produce self-cleaning substrates that have anti-reflective and infrared transmissive properties. The characteristics of these substrates were evaluated before and after chemical modification. Furthermore, their properties were compared to fused silica that was devoid of surface features. The chemical modification imparted superhydrophobic character to the substrates, as demonstrated by the average water contact angles which exceeded 170°. Finally, optical analysis of the substrates revealed that the infrared transmission capabilities of the fused silica substrates (nanopatterned to have moth eye on one side) were superior to those of the regular fused silica substrates within the visible and near-infrared region of the light spectrum, with transmission values of 95% versus 92%, respectively. The superior transmission properties of the fused silica moth eye were virtually unchanged following chemical modification.

  9. Development of sheet molding compound solar collectors with molded-in silvered glass reflective surfaces

    SciTech Connect

    Champion, R. L.; Allred, R. E.

    1980-01-01

    An approach to the fabrication of a line-focusng parabolic trough reflector structure which offers the potential of high performance while utilizing mass production type technology with potential for low cost is discussed. The concept is one of a molded structure of fiber reinforced plastic with an integrally molded silvered glass reflective surface. Sheet molding compound (SMC), a mixture of glass fibers and inorganic fillers in polyester resin, has been selected for evaluation as representative of reinforced plastic molding materials. The purpose of the work was to establish the feasibility of molding glass mirrors into SMC structural trough panels. If the effort proved successful, the next stage of development would be demonstration of the structure in a trough collector which incorporates individual SMC reflector panels. The trough has a 2 x 6 m aperture with six individual SMC panels mounted on a torque tube as the main support structure. Results are described. (WHK)

  10. Effect of silver nanoisland-embedded grating for surface plasmon based total internal reflection fluorescence imaging

    NASA Astrophysics Data System (ADS)

    Kim, Kyujung; Kim, Dong Jun; Kim, Donghyun

    2009-02-01

    We present the enhancement of total internal reflection fluorescence microscopy by the excitation of localized surface plasmons using nanoisland embedded subwavelength grating. The presence of nanoislands may provide additional field enhancement even at moderate grating period. For fabrication of nanoisland embedded grating patterns, a silver film was first evaporated on a glass substrate. Next, silver grating was patterned by e-beam lithography. Subsequently, nanoisland shapes were chemically formed. Field enhancement was measured by fluorescent excitation of microbeads on periodic silver nanoislands. The performance is compared to the microbead excitation on a silver nanograting without nanoislands and nanoislands formed on a thin film without grating patterns as controls. The result confirms additional field enhancement by nanoisland embedded periodic patterns.

  11. BOREAS Level-2 MAS Surface Reflectance and Temperature Images in BSQ Format

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G. (Editor); Newcomer, Jeffrey (Editor); Lobitz, Brad; Spanner, Michael; Strub, Richard; Lobitz, Brad

    2000-01-01

    The BOReal Ecosystem-Atmosphere Study (BOREAS) Staff Science Aircraft Data Acquisition Program focused on providing the research teams with the remotely sensed aircraft data products they needed to compare and spatially extend point results. The MODIS Airborne Simulator (MAS) images, along with other remotely sensed data, were collected to provide spatially extensive information over the primary study areas. This information includes biophysical parameter maps such as surface reflectance and temperature. Collection of the MAS images occurred over the study areas during the 1994 field campaigns. The level-2 MAS data cover the dates of 21-Jul-1994, 24-Jul-1994, 04-Aug-1994, and 08-Aug-1994. The data are not geographically/geometrically corrected; however, files of relative X and Y coordinates for each image pixel were derived by using the C130 navigation data in a MAS scan model. The data are provided in binary image format files.

  12. Fan-shaped gold nanoantennas above reflective substrates for surface-enhanced infrared absorption (SEIRA).

    PubMed

    Brown, Lisa V; Yang, Xiao; Zhao, Ke; Zheng, Bob Y; Nordlander, Peter; Halas, Naomi J

    2015-02-11

    Here, we report a new nanoantenna for surface-enhanced infrared absorption (SEIRA) detection, consisting of a fan-shaped Au structure positioned at a well-specified distance above a reflective plane with an intervening silica spacer layer. We examine how to optimize both the antenna dimensions and the spacer layer for optimal SEIRA enhancement of the C-H stretching mode. This tunable 3D geometry yields a theoretical SEIRA enhancement factor of 10(5), corresponding to the experimental detection of 20-200 zeptomoles of octadecanethiol, using a standard commercial FTIR spectrometer. Experimental studies illustrate the sensitivity of the observed SEIRA signal to the gap dimensions. The optimized antenna structure exhibits an order of magnitude greater SEIRA sensitivity than previous record-setting designs.

  13. Fine Surface Images That Reflect Cytoskeletal Structures in Cultured Glial Cells by Atomic Force Microscopy

    NASA Astrophysics Data System (ADS)

    Yamane, Yukako; Hatakeyama, Dai; Tojima, Takuro; Kawabata, Kazushige; Ushiki, Tatsuo; Ogura, Shigeaki; Abe, Kazuhiro; Ito, Etsuro

    1998-06-01

    The morphology of cultured glial cells was examined using a combination of atomic force microscopy (AFM) and immunofluorescence staining for cytoskeletons. The meshwork of type-1 astrocytes consisted of thick longitudinal and thin lateral lines on the cell surfaces observed by AFM; the former lines were confirmed to be reflections of actin filaments. The astrocytic processes of type-2 astrocytes were observed to be rugged on AFM. These structures were mainly affected by microtubules. Immunofluorescence imaging of microglia revealed that actin filaments and microtubules were arranged radially and wavily along the cell edge, respectively. AFM could detect these radial and wavy structures clearly. These results show that AFM can provide information on the cytoskeletons of glial cells, indicating that AFM is a useful tool for the morphological characterization of cells.

  14. Control of dynamic stability during adaptation to gait termination on a slippery surface.

    PubMed

    Oates, Alison R; Frank, James S; Patla, Aftab E

    2010-02-01

    An unexpected slip during gait termination results in a generalised slip response designed to regain stability and prevent a fall. With knowledge of and experience with a slippery surface, locomotor behaviour adapts to proactively diminish the effect of the slip and improve the reactive control during the slip. Our purpose was to examine the organisation of the adaptation to a slippery surface during gait termination. After receiving an unexpected slip during gait termination, participants (N = 8) experienced cued gait termination trials in which they were given knowledge of the surface characteristics (i.e., slippery or non-slippery). The observed strategy used to repeatedly stop on a slippery surface involves proactively diminishing the size of the slip perturbation through a flattened foot at heel contact, anterior shift of the COM, shorter step, stance leg extension and swing limb slowing, as well as improving the reaction to the slippery surface through decreased muscle activity and an appropriate decrease in the braking force generation. The implications of this research are that a combination of knowledge of and experience with a slippery surface enables proactive and reactive adjustments in behaviour to effectively and more safely stop walking on a slippery surface. PMID:19834697

  15. Impact of differences in the solar irradiance spectrum on surface reflectance retrieval with different radiative transfer codes

    NASA Technical Reports Server (NTRS)

    Staenz, K.; Williams, D. J.; Fedosejevs, G.; Teillet, P. M.

    1995-01-01

    Surface reflectance retrieval from imaging spectrometer data as acquired with the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) has become important for quantitative analysis. In order to calculate surface reflectance from remotely measured radiance, radiative transfer codes such as 5S and MODTRAN2 play an increasing role for removal of scattering and absorption effects of the atmosphere. Accurate knowledge of the exo-atmospheric solar irradiance (E(sub 0)) spectrum at the spectral resolution of the sensor is important for this purpose. The present study investigates the impact of differences in the solar irradiance function, as implemented in a modified version of 5S (M5S), 6S, and MODTRAN2, and as proposed by Green and Gao, on the surface reflectance retrieved from AVIRIS data. Reflectance measured in situ is used as a basis of comparison.

  16. Fracture Detection in Alluvial Fan Deposits Using Near-Surface Seismic Reflection Techniques

    NASA Astrophysics Data System (ADS)

    Black, R. A.; Miller, B.

    2012-12-01

    In this study we document the observation of probable extensive shallow vertical fracture systems in unprocessed 2-D source gathers from near-surface seismic reflection surveys conducted over unconsolidated materials in alluvial fans environments. Mapping of fracture and fault systems within the sedimentary sections at hydrocarbon exploration scales has become common practice. This is due to the advent of post-stack attribute analysis of 3-D seismic images worldwide. However, examples of fracture detection and imaging in the near-surface are currently lacking in the literature. In addition, examples of fracture detection and mapping in the pre-stack domain are also lacking. In this study, unprocessed seismic source gathers from very high-resolution reflection surveys over alluvial fan deposits in tectonically active areas appear to display distinct patterns of amplitude drop off, geometrically similar to patterns expected for vertical fracture systems. The patterns can also be extracted by attribute analysis using techniques such as envelope and coherency analyses. Simple standard processing steps such as trace editing, muting, and bandpass filtering enhance interpretability. The patterns appear to be consistent and spatially fixed in the subsurface from source location to source location. These are observed in areas of obvious recent local large-scale fault movement. Examples are given from two areas, eastern Queen Valley in California and eastern Fish Lake Valley in Nevada. The stratigraphic and sedimentation patterns are quite complicated in both areas, and sediment characteristics vary considerably between sites. The surface sediments in the Queen Valley case are, in general, much coarser with many more boulder-sized clasts in the shallow subsurface. The seismic source consisted of a 30-06 rifle fired downhole at a depth of 0.5m. While the boulders interfered with seismic source operations, the record quality was excellent. The alluvial materials, especially

  17. Effects of surface reflectance and 3D shape on perceived rotation axis.

    PubMed

    Doerschner, Katja; Yilmaz, Ozgur; Kucukoglu, Gizem; Fleming, Roland W

    2013-09-10

    Surface specularity distorts the optic flow generated by a moving object in a way that provides important cues for identifying surface material properties (Doerschner, Fleming et al., 2011). Here we show that specular flow can also affect the perceived rotation axis of objects. In three experiments, we investigate how three-dimensional shape and surface material interact to affect the perceived rotation axis of unfamiliar irregularly shaped and isotropic objects. We analyze observers' patterns of errors in a rotation axis estimation task under four surface material conditions: shiny, matte textured, matte untextured, and silhouette. In addition to the expected large perceptual errors in the silhouette condition, we find that the patterns of errors for the other three material conditions differ from each other and across shape category, yielding the largest differences in error magnitude between shiny and matte, textured isotropic objects. Rotation axis estimation is a crucial implicit computational step to perceive structure from motion; therefore, we test whether a structure from a motion-based model can predict the perceived rotation axis for shiny and matte, textured objects. Our model's predictions closely follow observers' data, even yielding the same reflectance-specific perceptual errors. Unlike previous work (Caudek & Domini, 1998), our model does not rely on the assumption of affine image transformations; however, a limitation of our approach is its reliance on projected correspondence, thus having difficulty in accounting for the perceived rotation axis of smooth shaded objects and silhouettes. In general, our findings are in line with earlier research that demonstrated that shape from motion can be extracted based on several different types of optical deformation (Koenderink & Van Doorn, 1976; Norman & Todd, 1994; Norman, Todd, & Orban, 2004; Pollick, Nishida, Koike, & Kawato, 1994; Todd, 1985).

  18. Tuning the optical reflection property of metal surfaces via micro-nano particle structures fabricated by ultrafast laser

    NASA Astrophysics Data System (ADS)

    Fan, Peixun; Zhong, Minlin; Bai, Benfeng; Jin, Guofan; Zhang, Hongjun

    2015-12-01

    Optical functional surfaces are key components of nearly every optical device and they have become a special focus in both academia and industry. The no contact, one step, direct, and maskless laser surface texturing technique is one of the most encouraging approaches for realizing the surface functions. We use a high power and high repetition rate ultrafast laser system to produce micro-nano structures on metal surfaces. We demonstrate that metal surface micro-nano structures and correspondingly their optical responses can be facilely tailored by simple controlling the ultrafast laser processing parameters. Nano particles of tens to hundreds nm, sub-micro particles of 0.5-1 μm, fine-micro particles of 1-10 μm, micro particles of 10-50 μm, and coarse-micro particles larger than 50 μm have been fabricated on Cu surfaces. And surface reflection of copper surfaces has been tuned from 10% to 90% in spectra level and from UV to MIR in spectrum range, with unique optical properties like visible selective reflection, linear changing reflection, band reflection, and broadband absorption being achieved. The formation processes of those particle structures as well as the underlying mechanisms for their optical responses are discussed.

  19. Seasonal lake surface water temperature trends reflected by heterocyst glycolipid-based molecular thermometers

    NASA Astrophysics Data System (ADS)

    Bauersachs, T.; Rochelmeier, J.; Schwark, L.

    2015-06-01

    preserved in the sediment record of Lake Schreventeich reflect summer surface water temperatures. As N2-fixing heterocystous cyanobacteria are widespread in present-day freshwater and brackish environments, we conclude that the distribution of HGs in sediments may allow for the reconstruction of surface water temperatures of modern and potentially ancient lacustrine settings.

  20. An analytical and numerical study of the nonlinear reflection at a stress-free surface

    NASA Astrophysics Data System (ADS)

    Romer, Anne; Kim, Jin-Yeon; Jacobs, Laurence J.

    2015-03-01

    Implementation of the ultrasonic second harmonic generation has typically been restricted to simple setups such as through-transmission or Rayleigh surface waves. Recent research has evaluated the second harmonic waves generation in P- and SV- waves reflected from a stress-free surface to enable the single-sided interrogation of a specimen. This research considers the second harmonic generation in an aluminum specimen, which is analytically evaluated using an approach based on a perturbation method. Here, the model is chosen to mimic an experimental setup where the longitudinal wave is generated at oblique angle using a wedge transducer. Due to the mode conversion at the interface of the wedge and the specimen, it is necessary to evaluate longitudinal and shear waves, determining all second harmonic waves generated in the bulk and at the stress-free boundary. The theoretically developed model is then implemented in a commercial finite element code, COMSOL, using increasing fundamental wave amplitudes for different values of third order elastic constants. The results of this computational model verify the analytical approach and the proposed measurement setup, taking into account assumptions and approximations of the solution procedure. Furthermore, the computational model is used to draw important conclusions relevant to the experimental setup, including the need to avoid interaction with diffracted waves.

  1. An analytical and numerical study of the nonlinear reflection at a stress-free surface

    SciTech Connect

    Romer, Anne Kim, Jin-Yeon; Jacobs, Laurence J.

    2015-03-31

    Implementation of the ultrasonic second harmonic generation has typically been restricted to simple setups such as through-transmission or Rayleigh surface waves. Recent research has evaluated the second harmonic waves generation in P- and SV- waves reflected from a stress-free surface to enable the single-sided interrogation of a specimen. This research considers the second harmonic generation in an aluminum specimen, which is analytically evaluated using an approach based on a perturbation method. Here, the model is chosen to mimic an experimental setup where the longitudinal wave is generated at oblique angle using a wedge transducer. Due to the mode conversion at the interface of the wedge and the specimen, it is necessary to evaluate longitudinal and shear waves, determining all second harmonic waves generated in the bulk and at the stress-free boundary. The theoretically developed model is then implemented in a commercial finite element code, COMSOL, using increasing fundamental wave amplitudes for different values of third order elastic constants. The results of this computational model verify the analytical approach and the proposed measurement setup, taking into account assumptions and approximations of the solution procedure. Furthermore, the computational model is used to draw important conclusions relevant to the experimental setup, including the need to avoid interaction with diffracted waves.

  2. An optical metamaterial with simultaneously suppressed optical diffraction and surface reflection

    NASA Astrophysics Data System (ADS)

    Kivijärvi, V.; Nyman, M.; Shevchenko, A.; Kaivola, M.

    2016-03-01

    Diffraction-free propagation of light has been demonstrated in free space for Bessel-like beams and for arbitrary beams in specially designed photonic crystals and metamaterials. The phenomenon is called self-collimation in photonic crystals and canalization in metamaterials, as the approaches to obtaining the effect are different. In both cases, however, diffraction-free propagation of light is achieved by making the dispersion surface of the material at a given frequency flat. In photonic crystals this is done by tuning the unit-cell dimensions close to the band-gap regime, and in metamaterials by tuning a hyperbolic-type metamaterial towards its transition to an ordinary elliptical metamaterial. In this work, we propose an alternative way to suppress optical diffraction in a metamaterial by adjusting the anisotropy of the finite-sized three-dimensional metamolecules and the material’s spatial dispersion. The approach allows matching the wave impedance of the material to that of the surrounding medium in a wide range of incidence angles and thereby also suppressing optical reflection from the material’s surface.

  3. The effect of psychoemotional load on ventricular repolarization reflected in integral body surface potential maps.

    PubMed

    Kellerová, E; Regecová, V; Katina, S; Titomir, L I; Aidu, E A I; Trunov, V G; Szathmáry, V

    2006-01-01

    The aim of the present study was to investigate the reflection of psychoemotional stress in the body surface potential distribution as documented by isointegral maps of cardiac activation and recovery. In 72 young men (18.3+/- 7.3 y.) with no cardiovascular history body surface potential maps (BSPMs) at rest and during the test of mental arithmetic were recorded. The digitalized data for each point of the QRS, STT and QRST integral maps, for each subject in both situations, were processed and evaluated by methods of univariate as well as spatial mathematical and statistical modeling. The results showed during MA a significant decrease of repolarization integral values over the sternum and right precordium, which contributed to analogically localized decrements also in the QRST BSM. The decrease occurred in more than 2/3 of lead points. The most pronounced changes were observed in the right precordial area, where potentials decreased in more than in 70 % of subjects. In conclusion, the discriminative power of the difference STT and QRST integral maps was strong enough to distinguish the mental arithmetic induced changes in the superficial cardiac electric field. These adrenergic transient alterations in ventricular recovery may be of importance in subjects at risk for ventricular arrhythmias.

  4. A Monte Carlo study of reflection electron energy loss spectroscopy spectrum of a carbon contaminated surface

    SciTech Connect

    Da, B.; Li, Z. Y.; Chang, H. C.; Ding, Z. J.; Mao, S. F.

    2014-09-28

    It has been experimentally found that the carbon surface contamination influences strongly the spectrum signals in reflection electron energy loss spectroscopy (REELS) especially at low primary electron energy. However, there is still little theoretical work dealing with the carbon contamination effect in REELS. Such a work is required to predict REELS spectrum for layered structural sample, providing an understanding of the experimental phenomena observed. In this study, we present a numerical calculation result on the spatially varying differential inelastic mean free path for a sample made of a carbon contamination layer of varied thickness on a SrTiO{sub 3} substrate. A Monte Carlo simulation model for electron interaction with a layered structural sample is built by combining this inelastic scattering cross-section with the Mott's cross-section for electron elastic scattering. The simulation results have clearly shown that the contribution of the electron energy loss from carbon surface contamination increases with decreasing primary energy due to increased individual scattering processes along trajectory parts carbon contamination layer. Comparison of the simulated spectra for different thicknesses of the carbon contamination layer and for different primary electron energies with experimental spectra clearly identifies that the carbon contamination in the measured sample was in the form of discontinuous islands other than the uniform film.

  5. ePortfolios: Promoting Special Educator Adaptive Expertise through Reflection in a Web-Based Learning Community

    ERIC Educational Resources Information Center

    De Arment, Serra T.; Wetzel, Angela P.; Reed, Evelyn

    2013-01-01

    In an era of accountability, teachers must be prepared to adapt to the variability they encounter in today's classrooms. Instead of knowing only routine responses to the challenges of practice, teachers need a repertoire that is characterized by adaptive expertise. Preservice preparation can foster teacher candidates' adaptive expertise through…

  6. The laboratory investigation of surface envelope solitons: reflection from a vertical wall and collisions of solitons

    NASA Astrophysics Data System (ADS)

    Slunyaev, Alexey; Klein, Marco; Clauss, Günther F.

    2016-04-01

    Envelope soliton solutions are key elements governing the nonlinear wave dynamics within a simplified theory for unidirectional weakly modulated weakly nonlinear wave groups on the water surface. Within integrable models the solitons preserve their structure in collisions with other waves; they do not disperse and can carry energy infinitively long. Steep and short soliton-like wave groups have been shown to exist in laboratory tests [1] and, even earlier, in numerical simulations [2, 3]. Thus, long-living wave groups may play important role in the dynamics of intense sea waves and wave-structure interactions. The solitary wave groups may change the wave statistics and can be taken into account when developing approaches for the deterministic forecasting of dangerous waves, including so-called rogue waves. An experimental campaign has been conducted in the wave basin of the Technical University of Berlin on simulations of intense solitary wave groups. The first successful experimental observation of intense envelope solitons took place in this facility [1]. The new experiments aimed at following main goals: 1) to reproduce intense envelope solitons with different carrier wave lengths; 2) to estimate the rate of envelope soliton dissipation; 3) to consider the reflection of envelope solitons on a vertical wall; 4) to consider head-on collisions of envelope solitons, and 5) to consider overtaking interactions of envelope solitons. Up to 9 wave gauges were used in each experimental run, which enabled registration of the surface movement at different distances from the wavemaker, at different locations across the wave flume and near the wall. Besides surface displacements, the group envelope shapes were directly recorded, with use of phase shifts applied to the modulated waves generated by the wavemaker. [1] A. Slunyaev, G.F. Clauss, M. Klein, M. Onorato, Simulations and experiments of short intense envelope solitons of surface water waves. Phys. Fluids 25, 067105

  7. Independent introduction of two lactase-persistence alleles into human populations reflects different history of adaptation to milk culture.

    PubMed

    Enattah, Nabil Sabri; Jensen, Tine G K; Nielsen, Mette; Lewinski, Rikke; Kuokkanen, Mikko; Rasinpera, Heli; El-Shanti, Hatem; Seo, Jeong Kee; Alifrangis, Michael; Khalil, Insaf F; Natah, Abdrazak; Ali, Ahmed; Natah, Sirajedin; Comas, David; Mehdi, S Qasim; Groop, Leif; Vestergaard, Else Marie; Imtiaz, Faiqa; Rashed, Mohamed S; Meyer, Brian; Troelsen, Jesper; Peltonen, Leena

    2008-01-01

    The T(-13910) variant located in the enhancer element of the lactase (LCT) gene correlates perfectly with lactase persistence (LP) in Eurasian populations whereas the variant is almost nonexistent among Sub-Saharan African populations, showing high prevalence of LP. Here, we report identification of two new mutations among Saudis, also known for the high prevalence of LP. We confirmed the absence of the European T(-13910) and established two new mutations found as a compound allele: T/G(-13915) within the -13910 enhancer region and a synonymous SNP in the exon 17 of the MCM6 gene T/C(-3712), -3712 bp from the LCT gene. The compound allele is driven to a high prevalence among Middle East population(s). Our functional analyses in vitro showed that both SNPs of the compound allele, located 10 kb apart, are required for the enhancer effect, most probably mediated through the binding of the hepatic nuclear factor 1 alpha (HNF1 alpha). High selection coefficient (s) approximately 0.04 for LP phenotype was found for both T(-13910) and the compound allele. The European T(-13910) and the earlier identified East African G(-13907) LP allele share the same ancestral background and most likely the same history, probably related to the same cattle domestication event. In contrast, the compound Arab allele shows a different, highly divergent ancestral haplotype, suggesting that these two major global LP alleles have arisen independently, the latter perhaps in response to camel milk consumption. These results support the convergent evolution of the LP in diverse populations, most probably reflecting different histories of adaptation to milk culture. PMID:18179885

  8. Chromatic X-ray magnifying method and apparatus by Bragg reflective planes on the surface of Abbe sphere

    DOEpatents

    Thoe, Robert S.

    1991-01-01

    Method and apparatus for producing sharp, chromatic, magnified images of X-ray emitting objects, are provided. The apparatus, which constitutes an X-ray microscope or telescope, comprises a connected collection of Bragg reflecting planes, comprised of either a bent crystal or a synthetic multilayer structure, disposed on and adjacent to a locus determined by a spherical surface. The individual Bragg planes are spatially oriented to Bragg reflect radiation from the object location toward the image location. This is accomplished by making the Bragg planes spatially coincident with the surfaces of either a nested series of prolate ellipsoids of revolution, or a nested series of spheres. The spacing between the Bragg reflecting planes can be tailored to control the wavelengths and the amount of the X-radiation that is Bragg reflected to form the X-ray image.

  9. Optical reflectivity changes induced by adsorption on metal surfaces: The origin and applications to monitoring adsorption kinetics

    NASA Astrophysics Data System (ADS)

    Dvorak, Joseph; Dai, Hai-Lung

    2000-01-01

    It is observed that when a monolayer of CO and acetylene is chemisorbed on the Cu(100) surface, the reflectivity of the metal surface at the He-Ne laser wavelength of 632 nm is reduced on the order of 1%, while the physisorption of water, methanol, and acetone induces a reflectivity change on the order of 0.01%. The small reflectivity change induced by physisorption can be described by a three-layer model taking into account the molecular layer refractive index. The much bigger reflectivity change induced by the chemisorbed adsorbates, on the other hand, is a result of bonding perturbations to the electronic structure of the metal surface layer. The latter is supported by an electron scattering model description of the reflectivity change up to 1.96 eV on Cu. For both CO and acetylene, the optical reflectivity change is found to be linearly proportional to the submonolayer coverage. The phenomenon thus offers an excellent method to measure surface kinetics. It is found from the reflectivity change measurements that the initial sticking coefficient for both adsorbates is nearly unity at 110 K; 0.85 for CO and 1.0 for acetylene. The temperature and coverage dependence of the sticking coefficient shows that the adsorption behavior of both molecules is well described as direct adsorption mediated with an extrinsic precursor. For acetylene adsorption, the sticking coefficient shows little dependence on the substrate temperature suggesting that the "extrinsic precursor" is not a thermally equilibrated species. For CO, the transition into a compression phase beyond 0.5 ML results in a corresponding change in the sticking coefficient deduced from the reflectivity data.

  10. Objective and Subjective Evaluation of Reflecting and Diffusing Surfaces in Auditoria

    NASA Astrophysics Data System (ADS)

    Cox, Trevor John

    Available from UMI in association with The British Library. Requires signed TDF. The performance of reflectors and diffusers used in auditoria have been evaluated both objectively and subjectively. Two accurate systems have been developed to measure the scattering from surfaces via the cross correlation function. These have been used to measure the scattering from plane panels, curved panels and quadratic residue diffusers (QRDs). The scattering measurements have been used to test theoretical prediction methods based on the Helmholtz-Kirchhoff integral equation. Accurate prediction methods were found for all surfaces tested. The limitations of the more approximate methods have been defined. The assumptions behind Schroeder's design of the QRD have been tested and the local reacting admittance assumption found to be valid over a wide frequency range. It was found that the QRD only produces uniform scattering at low frequencies. For an on-axis source the scattering from a curved panel was as good as from a QRD. For an oblique source the QRD produced much more uniform scattering than the curved panel. The subjective measurements evaluated the smallest perceivable change in the early sound field, the part most influenced by reflectors and diffusers. A natural sounding simulation of a concert hall field within an anechoic chamber was used. Standard objective parameters were reasonable values when compared to values found in real halls and subjective preference measurements. A difference limen was measured for early lateral energy fraction (.048 +/-.005); inter aural cross correlation (.075 +/-.008); clarity index (.67 +/-.13 dB); and centre time (8.6 +/- 1.6 ms). It was found that: (i) when changes are made to diffusers and reflectors, changes in spatial impression will usually be larger than those in clarity; and (ii) acousticians can gain most by paying attention to lateral sound in auditoria. It was also found that: (i) diffuse reflections in the early sound field

  11. Fresnel-like formulas for the reflection and transmission of surface phonon-polaritons at a dielectric interface

    NASA Astrophysics Data System (ADS)

    Ordonez-Miranda, Jose; Tranchant, Laurent; Gluchko, Sergei; Antoni, Thomas; Volz, Sebastian

    2014-10-01

    The reflection and transmission coefficients of a surface phonon-polariton propagating along the surface of a thin film of SiO2 and crossing the interface of two dielectric media are analytically determined. Based on the expansion of the electrical and magnetic fields in terms of normal modes, explicit expressions for the reflectivity and transmissivity of the radiation fields generated at the dielectric interface are also obtained. Symmetrical and simple Fresnel-like formulas are derived for nanofilms. For the dielectric interfaces of air/BaF2 and air/Al2O3, it is shown that: (i) The polariton reflectivity (transmissivity) decreases (increases) as the film thickness increases, while its radiation equivalent follows the opposite behavior. (ii) In the polariton and radiation fields, the transmissivity is significantly more sensitive than the reflectivity to the changes on the permittivity mismatch of the dielectric interface. For a 143-nm-thick film, the polariton transmissivity (reflectivity) changes 13.2% (1.9%), when this mismatch varies by 50%. (iii) The reflectivity and transmissivity of the radiation fields are smaller than their polariton counterparts, which together account for around 82% of the total energy. The proposed formalism accurately fulfills the principle of conservation of energy for describing the reflection and transmission of both the polariton and radiation fields generated at a dielectric interface.

  12. Adaptation response surfaces from an ensemble of wheat projections under climate change in Europe

    NASA Astrophysics Data System (ADS)

    Ruiz-Ramos, Margarita; Ferrise, Roberto

    2016-04-01

    The uncertainty about climate change (CC) complicates impact adaptation and risk management evaluation at the regional level. Approaches for managing this uncertainty and for simulating and communicating climate change impacts and adaptation opportunities are required. Here we apply an ensemble of crop models for adapting rainfed winter wheat at Lleida (NE Spain), constructing adaptation response surfaces (ARS). Our methodology has been adapted from Pirttioja et al. (2015). Impact response surfaces (IRS) are plotted surfaces showing the response of an impact variable (here crop yield Y) to changes in two explanatory variables (here precipitation P and temperature T). By analyzing adaptation variables such as changes in crop yield (ΔY) when an adaptation option is simulated, these can be interpreted as the adaptation response to potential changes of P and T, i.e. ARS. To build these ARS, we explore the sensitivity of an ensemble of wheat models to changes in T and P. Baseline (1981-2010) T and P were modified using a delta change approach with changes in the seasonal patterns. Three levels of CO2 (representing future conditions until 2050) and two actual soil profiles are considered. Crop models were calibrated with field data from Abeledo et al. (2008) and Cartelle et al. (2006). Most promising adaptation options to be analyzed by the ARS approach are identified in a pilot stage with the models DSSAT4.5 and SiriusQuality v.2, subsequently simulating the selected adaptation combinations by the whole ensemble of 11 crop models. The adaptation options identified from pilot stage were: a cultivar with no vernalisation requirements, shortening or extending a 10 % the crop cycle of the standard cultivar, sowing 15 days earlier and 30 days later than the standard date, supplementary irrigation with 40 mm at flowering and full irrigation. These options and those of the standard cultivar and management resulted in 54 combinations and 450.000 runs per crop model. Our

  13. Optical performance of random anti-reflection structures on curved surfaces

    NASA Astrophysics Data System (ADS)

    Taylor, C.; Major, K. J.; Joshi, R.; Busse, L. E.; Frantz, J.; Sanghera, J. S.; Aggarwal, I. D.; Poutous, M. K.

    2015-03-01

    Random anti-reflection structured surfaces (rARSS) have been reported to improve transmittance of optical-grade fused silica planar substrates to values greater than 99%. These textures are achieved using reactive-ion etching techniques and often result in transmitted spectra with no measurable interference effects (fringes) for a wide range of wavelengths. The inductively-coupled reactive ion plasma (ICP-RIE) used in the fabrication process to etch the rARSS is anisotropic, and thus well-suited for planar components. The improvement in spectral transmission has been found to be independent of optical incidence angles, for values from 0° to ±30°. Qualifying and quantifying the rARSS performance on curved substrates, such as concave and convex lenses, is required to optimize the fabrication of a desirable AR effect on opticalpower elements. In this work, rARSS was fabricated on fused silica plano-convex and plano-concave lenses, using an optimized ICP-RIE process, to maximize optical transmission in the range from 500 nm to 1100 nm. Results are presented from optical transmission tests of matched sets of varying curvature lenses with rARSS at a wavelength of 633nm. The transmission was measured as a function of radial distance from the apex of each lens, and shows the anisotropic dependence of the etch process. The transmittance profiles between the different sphericity of the tested lenses as well as the matched sets of concave and convex surfaces are compared. The measured angle-of-incidence dependence of planar silica versus silica lenses with rARSS is also presented.

  14. Adaptation response surfaces from an ensemble of wheat projections under climate change in Europe

    NASA Astrophysics Data System (ADS)

    Ruiz-Ramos, Margarita; Ferrise, Roberto

    2016-04-01

    The uncertainty about climate change (CC) complicates impact adaptation and risk management evaluation at the regional level. Approaches for managing this uncertainty and for simulating and communicating climate change impacts and adaptation opportunities are required. Here we apply an ensemble of crop models for adapting rainfed winter wheat at Lleida (NE Spain), constructing adaptation response surfaces (ARS). Our methodology has been adapted from Pirttioja et al. (2015). Impact response surfaces (IRS) are plotted surfaces showing the response of an impact variable (here crop yield Y) to changes in two explanatory variables (here precipitation P and temperature T). By analyzing adaptation variables such as changes in crop yield (ΔY) when an adaptation option is simulated, these can be interpreted as the adaptation response to potential changes of P and T, i.e. ARS. To build these ARS, we explore the sensitivity of an ensemble of wheat models to changes in T and P. Baseline (1981-2010) T and P were modified using a delta change approach with changes in the seasonal patterns. Three levels of CO2 (representing future conditions until 2050) and two actual soil profiles are considered. Crop models were calibrated with field data from Abeledo et al. (2008) and Cartelle et al. (2006). Most promising adaptation options to be analyzed by the ARS approach are identified in a pilot stage with the models DSSAT4.5 and SiriusQuality v.2, subsequently simulating the selected adaptation combinations by the whole ensemble of 11 crop models. The adaptation options identified from pilot stage were: a cultivar with no vernalisation requirements, shortening or extending a 10 % the crop cycle of the standard cultivar, sowing 15 days earlier and 30 days later than the standard date, supplementary irrigation with 40 mm at flowering and full irrigation. These options and those of the standard cultivar and management resulted in 54 combinations and 450.000 runs per crop model. Our

  15. Non-invasive identification of metal-oxalate complexes on polychrome artwork surfaces by reflection mid-infrared spectroscopy.

    PubMed

    Monico, Letizia; Rosi, Francesca; Miliani, Costanza; Daveri, Alessia; Brunetti, Brunetto G

    2013-12-01

    In this work a reflection mid-infrared spectroscopy study of twelve metal-oxalate complexes, of interest in art conservation science as alteration compounds, was performed. Spectra of the reference materials highlighted the presence of derivative-like and/or inverted features for the fundamental vibrational modes as result of the main contribution from the surface component of the reflected light. In order to provide insights in the interpretation of theses spectral distortions, reflection spectra were compared with conventional transmission ones. The Kramers-Kronig (KK) algorithm, employed to correct for the surface reflection distortions, worked properly only for the derivative-like bands. Therefore, to pay attention to the use of this algorithm when interpreting the reflection spectra is recommended. The outcome of this investigation was exploited to discriminate among different oxalates on thirteen polychrome artworks analyzed in situ by reflection mid-infrared spectroscopy. The visualization of the νs(CO) modes (1400-1200 cm(-1)) and low wavenumber bands (below 900 cm(-1)) in the raw reflection profiles allowed Ca, Cu and Zn oxalates to be identified. Further information about the speciation of different hydration forms of calcium oxalates were obtained by using the KK transform. The work proves reflection mid-infrared spectroscopy to be a reliable and sensitive spectro-analytical method for identifying and mapping different metal-oxalate alteration compounds on the surface of artworks, thus providing conservation scientists with a non-invasive tool to obtain information on the state of conservation and causes of alteration of artworks.

  16. Analysis of reflection, transmission and absorption of frequency selective surfaces in the infrared

    NASA Astrophysics Data System (ADS)

    Puscasu, Irina

    Frequency-selective surfaces (FSSs) are commonly used as dichroic filters in the microwave portion of the spectrum. These filters are typically configured as periodic arrays of metallic patches supported by a dielectric substrate, or as an array of apertures on a metallic sheet. To first order, the current-wave resonance of the individual patches or apertures determines the spectral behavior of the structure. The resonant dimension of the structures is on the order of a wavelength of the incident radiation. Using the high- resolution capabilities of direct-write electron-beam lithography (DEBL), the functionality of an FSS can be extended toward shorter wavelengths-into the infrared (IR), and even to visible wavelengths. Design of FSSs at these short wavelengths presents new problems-the usual assumption of perfect metal conductivity is not valid in the IR. In our method-of- moments model, we use a frequency-dependent complex conductivity to characterize the metallic structure, which allows prediction of the location, magnitude, and spectral width of the resonance. We compare the measured behavior of our IR FSSs to the theoretical predictions and find good agreement over a wide range of structure sizes and materials. Treating the loss mechanism in this way allows us to predict resonant effects not only for reflection and transmission, but for absorption as well. Kirchoff's Law, which states that absorption and emissivity are equal on a spectral basis, provides a means to develop IR FSSs for which the spectral emissivity can be enhanced over a desired range of wavelengths. This characteristic has potential application in development of new sources for IR spectroscopy, and in IR-signature management. Fabrication of IR FSSs by DEBL allows fine control over the dimensions of the metallic elements, but the direct write process is slow and hence too expensive for practical development of large-area IR FSSs. We investigated precision imprint embossing as a candidate

  17. An adaptive learning approach for 3-D surface reconstruction from point clouds.

    PubMed

    Junior, Agostinho de Medeiros Brito; Neto, Adrião Duarte Dória; de Melo, Jorge Dantas; Goncalves, Luiz Marcos Garcia

    2008-06-01

    In this paper, we propose a multiresolution approach for surface reconstruction from clouds of unorganized points representing an object surface in 3-D space. The proposed method uses a set of mesh operators and simple rules for selective mesh refinement, with a strategy based on Kohonen's self-organizing map (SOM). Basically, a self-adaptive scheme is used for iteratively moving vertices of an initial simple mesh in the direction of the set of points, ideally the object boundary. Successive refinement and motion of vertices are applied leading to a more detailed surface, in a multiresolution, iterative scheme. Reconstruction was experimented on with several point sets, including different shapes and sizes. Results show generated meshes very close to object final shapes. We include measures of performance and discuss robustness.

  18. The Swedish monitoring of surface waters: 50 years of adaptive monitoring.

    PubMed

    Fölster, Jens; Johnson, Richard K; Futter, Martyn N; Wilander, Anders

    2014-01-01

    For more than 50 years, scientific insights from surface water monitoring have supported Swedish evidence-based environmental management. Efforts to understand and control eutrophication in the 1960s led to construction of wastewater treatment plants with phosphorus retention, while acid rain research in the 1970s contributed to international legislation curbing emissions. By the 1990s, long-time series were being used to infer climate effects on surface water chemistry and biology. Monitoring data play a key role in implementing the EU Water Framework Directive and other legislation and have been used to show beneficial effects of agricultural management on Baltic Sea eutrophication. The Swedish experience demonstrates that well-designed and financially supported surface water monitoring can be used to understand and manage a range of stressors and societal concerns. Using scientifically sound adaptive monitoring principles to balance continuity and change has ensured long-time series and the capability to address new questions over time.

  19. The Swedish monitoring of surface waters: 50 years of adaptive monitoring.

    PubMed

    Fölster, Jens; Johnson, Richard K; Futter, Martyn N; Wilander, Anders

    2014-01-01

    For more than 50 years, scientific insights from surface water monitoring have supported Swedish evidence-based environmental management. Efforts to understand and control eutrophication in the 1960s led to construction of wastewater treatment plants with phosphorus retention, while acid rain research in the 1970s contributed to international legislation curbing emissions. By the 1990s, long-time series were being used to infer climate effects on surface water chemistry and biology. Monitoring data play a key role in implementing the EU Water Framework Directive and other legislation and have been used to show beneficial effects of agricultural management on Baltic Sea eutrophication. The Swedish experience demonstrates that well-designed and financially supported surface water monitoring can be used to understand and manage a range of stressors and societal concerns. Using scientifically sound adaptive monitoring principles to balance continuity and change has ensured long-time series and the capability to address new questions over time. PMID:25403966

  20. Observation of surface reduction of NiO to Ni by surface-sensitive total reflection X-ray spectroscopy using Kramers-Kronig relations

    NASA Astrophysics Data System (ADS)

    Abe, Hitoshi; Nakayama, Takeshi; Niwa, Yasuhiro; Nitani, Hiroaki; Kondoh, Hiroshi; Nomura, Masaharu

    2016-06-01

    We have developed a promising surface-sensitive X-ray absorption fine structure (XAFS) measurement method. This method is based on total reflection detection and Kramers-Kronig relations, and has been named the KK-XAFS method. Total reflection spectra are transformed via Kramers-Kronig relations to obtain XAFS spectra. KK-XAFS experiments give us surface-sensitive structural parameters, while usual EXAFS analyses yield bulk structural parameters. The total reflection spectra themselves are useful for observing and discussing time evolutions of chemical reactions at surfaces by quick scanning measurements. Chemical species are analyzed to estimate their fractions during reactions. The whole method would be named total reflection X-ray spectroscopy (TREXS). A reduction of the NiO layer at the surface of Ni (30 nm)/Si was observed in a laboratory-built TREXS in situ cell. The method would be applicable to observe chemical reactions starting at surfaces and to study their kinetics and mechanisms.

  1. An attenuated total reflectance IR study of silicic acid adsorbed onto a ferric oxyhydroxide surface

    NASA Astrophysics Data System (ADS)

    Swedlund, Peter J.; Miskelly, Gordon M.; McQuillan, A. James

    2009-07-01

    Silicic acid (H 4SiO 4) can have significant effects on the properties of iron oxide surfaces in both natural and engineered aquatic systems. Understanding the reactions of H 4SiO 4 on these surfaces is therefore necessary to describe the aquatic chemistry of iron oxides and the elements that associate with them. This investigation uses attenuated total reflectance infrared spectroscopy (ATR-IR) to study silicic acid in aqueous solution and the products formed when silicic acid adsorbs onto the surface of a ferrihydrite film in 0.01 M NaCl at pH 4. A spectrum of 1.66 mM H 4SiO 4 at pH 4 (0.01 M NaCl) has an asymmetric Si-O stretch at 939 cm -1 and a weak Si-O-H deformation at 1090 cm -1. ATR-IR spectra were measured over time (for up to 7 days) for a ferrihydrite film (≈1 mg) approaching equilibrium with H 4SiO 4 at concentrations between 0.044 and 0.91 mM. Adsorbed H 4SiO 4 had a broad spectral feature between 750 and 1200 cm -1 but the shape of the spectra changed as the amount of H 4SiO 4 adsorbed on the ferrihydrite increased. When the solid phase Si/Fe mole ratio was less than ≈0.01 the ATR-IR spectra had a maximum intensity at 943 cm -1 and the spectral shape suggests that a monomeric silicate species was formed via a bidentate linkage. As the solid phase Si/Fe mole ratio increased to higher values a discrete oligomeric silicate species was formed which had maximum intensity in the ATR-IR spectra at 1001 cm -1. The spectrum of this species suggests that it is larger than a dimer and it was tentatively identified as a cyclic tetramer. A small amount of a polymeric silica phase with a broad spectral feature centered at ≈1110 cm -1 was also observed at high surface coverage. The surface composition was estimated from the relative contribution of each species to the area of the ATR-IR spectra using multivariate curve resolution with alternating least squares. For a ferrihydrite film approaching equilibrium with 0.044, 0.14, 0.40 and 0.91 mM H 4SiO 4 the

  2. Surface Material Analysis of the S-type Asteroids: Removing the Space Weathering Effect from Reflectance Spectrum

    NASA Technical Reports Server (NTRS)

    Ueda, Y.; Miyamoto, M.; Mikouchi, T.; Hiroi, T.

    2003-01-01

    Recent years, many researchers have been observing a lot of asteroid reflectance spectra in the UV, visible to NIR at wavelength region. Reflectance spectroscopy of asteroid at this range should bring us a lot of information about its surface materials. Pyroxene and olivine have characteristic absorption bands in this wavelength range. Low-Ca pyroxene has two absorption bands around 0.9 microns and 1.9 microns. The more Ca and Fe content, the longer both absorption band centers. On the other hand, reflectance spectrum of olivine has three complicated absorption bands around 1 m, and no absorption feature around 2 microns. In general, reflectance spectra of many asteroids that are considered to be silicate rich (i.e., S- and A type asteroids) show redder slope and more subdued absorption bands than those of terrestrial minerals and meteorites. These features are now believed to be caused by the space weathering effect, which is probably caused by micrometeorite bombardment and/or solar wind. This process causes nanophase reduced iron (npFe(sup 0)) particles near the surface of mineral grains, which leads the optical change. Therefore, the space weathering effect should be removed from asteroid reflectance spectra to compare with those of meteorite and terrestrial minerals. In this report, we will apply the expanded modified Gaussian model (MGM) to the reflectance spectra of S-type asteroids 7 Iris and 532 Herculina and compare them with those of meteorites.

  3. Land surface reflectance retrieval from hyperspectral data collected by an unmanned aerial vehicle over the Baotou test site.

    PubMed

    Duan, Si-Bo; Li, Zhao-Liang; Tang, Bo-Hui; Wu, Hua; Ma, Lingling; Zhao, Enyu; Li, Chuanrong

    2013-01-01

    To evaluate the in-flight performance of a new hyperspectral sensor onboard an unmanned aerial vehicle (UAV-HYPER), a comprehensive field campaign was conducted over the Baotou test site in China on 3 September 2011. Several portable reference reflectance targets were deployed across the test site. The radiometric performance of the UAV-HYPER sensor was assessed in terms of signal-to-noise ratio (SNR) and the calibration accuracy. The SNR of the different bands of the UAV-HYPER sensor was estimated to be between approximately 5 and 120 over the homogeneous targets, and the linear response of the apparent reflectance ranged from approximately 0.05 to 0.45. The uniform and non-uniform Lambertian land surface reflectance was retrieved and validated using in situ measurements, with root mean square error (RMSE) of approximately 0.01-0.07 and relative RMSE of approximately 5%-12%. There were small discrepancies between the retrieved uniform and non-uniform Lambertian land surface reflectance over the homogeneous targets and under low aerosol optical depth (AOD) conditions (AOD = 0.18). However, these discrepancies must be taken into account when adjacent pixels had large land surface reflectance contrast and under high AOD conditions (e.g. AOD = 1.0).

  4. Land Surface Reflectance Retrieval from Hyperspectral Data Collected by an Unmanned Aerial Vehicle over the Baotou Test Site

    PubMed Central

    Duan, Si-Bo; Li, Zhao-Liang; Tang, Bo-Hui; Wu, Hua; Ma, Lingling; Zhao, Enyu; Li, Chuanrong

    2013-01-01

    To evaluate the in-flight performance of a new hyperspectral sensor onboard an unmanned aerial vehicle (UAV-HYPER), a comprehensive field campaign was conducted over the Baotou test site in China on 3 September 2011. Several portable reference reflectance targets were deployed across the test site. The radiometric performance of the UAV-HYPER sensor was assessed in terms of signal-to-noise ratio (SNR) and the calibration accuracy. The SNR of the different bands of the UAV-HYPER sensor was estimated to be between approximately 5 and 120 over the homogeneous targets, and the linear response of the apparent reflectance ranged from approximately 0.05 to 0.45. The uniform and non-uniform Lambertian land surface reflectance was retrieved and validated using in situ measurements, with root mean square error (RMSE) of approximately 0.01–0.07 and relative RMSE of approximately 5%–12%. There were small discrepancies between the retrieved uniform and non-uniform Lambertian land surface reflectance over the homogeneous targets and under low aerosol optical depth (AOD) conditions (AOD = 0.18). However, these discrepancies must be taken into account when adjacent pixels had large land surface reflectance contrast and under high AOD conditions (e.g. AOD = 1.0). PMID:23785513

  5. Attenuated total reflection infrared study of the protonation of a trans-retinylidene schiff base on crystal surfaces

    NASA Astrophysics Data System (ADS)

    Badilescu, S.; Lussier, L. S.; Sandorfy, C.; Le Thanh, H.; Vocelle, D.

    1987-01-01

    On the surfaces of thallium bromide iodide, zinc selenide, germanium and silicon crystals used in the attenuated total reflection technique retinylidene Schiff bases become protonated to a large extent and this, in the absence of any added acid. It is suggested that the protonating agent is the hydronium ion formed at the crystal surfaces and that there is an analogy between this event and the protonation of the chromophore in rhodopsins.

  6. Diffuse Reflectance Mid-Infrared Spectroscopy as a Tool for the Identification of Surface Contamination on Sandblasted Metals

    NASA Technical Reports Server (NTRS)

    Powell, Louis G.; Barber, Tye E.; Neu, John T.; Nerren, Billy H.

    1997-01-01

    The SOC 400 Surface Inspection Machine/Infrared (SIMIR) is a small, ruggedized Fourier transform infrared spectrometer having dedicated diffuse reflectance optics. The SOC 400 was designed for the purpose of detecting (qualitatively and quantitatively) oil stains on the inside surface of solid rocket motor casings in the as-sandblasted and cleaned condition at levels approaching 1 mg. sq ft. The performance of this instrument is described using spectral mapping techniques.

  7. Diffuse reflectance mid-infrared spectroscopy as a tool for the identification of surface contamination on sandblasted metals

    SciTech Connect

    Powell, G.L.; Barber, T.E.; Neu, J.T.; Nerren, B.H.

    1996-07-30

    The SOC 400 Surface Inspection Machine/Infrared (SIMIR) is a small, ruggedized Fourier transform infrared spectrometer having dedicated diffuse reflectance optics. The SOC 400 was designed for the purpose of detecting (qualitatively and quantitatively) oil stains on the inside surface of solid rocket motor casings in the as-sandblasted and cleaned condition at levels approaching 1 mg ft{sup {minus}2}. The performance of this instrument is described using spectral mapping techniques.

  8. Adaptive filtering of ECG interference on surface EEnGs based on signal averaging.

    PubMed

    Garcia-Casado, Javier; Martinez-de-Juan, Jose L; Ponce, Jose L

    2006-06-01

    An external electroenterogram (EEnG) is the recording of the small bowel myoelectrical signal using contact electrodes placed on the abdominal surface. It is a weak signal affected by possible movements and by the interferences of respiration and, principally, of the cardiac signal. In this paper an adaptive filtering technique was proposed to identify and subsequently cancel ECG interference on canine surface EEnGs by means of a signal averaging process time-locked with the R-wave. Twelve recording sessions were carried out on six conscious dogs in the fasting state. The adaptive filtering technique used increases the signal-to-interference ratio of the raw surface EEnG from 16.7 +/- 6.5 dB up to 31.9 +/- 4.0 dB. In addition to removing ECG interference, this technique has been proven to respect intestinal SB activity, i.e. the EEnG component associated with bowel contractions, despite the fact that they overlap in the frequency domain. In this way, more robust non-invasive intestinal motility indicators can be obtained with correlation coefficients of 0.68 +/- 0.09 with internal intestinal activity. The method proposed here may also be applied to other biological recordings affected by cardiac interference and could be a very helpful tool for future applications of non-invasive recordings of gastrointestinal signals.

  9. Spectral data of specular reflectance, narrow-angle transmittance and angle-resolved surface scattering of materials for solar concentrators

    PubMed Central

    Good, Philipp; Cooper, Thomas; Querci, Marco; Wiik, Nicolay; Ambrosetti, Gianluca; Steinfeld, Aldo

    2015-01-01

    The spectral specular reflectance of conventional and novel reflective materials for solar concentrators is measured with an acceptance angle of 17.5 mrad over the wavelength range 300−2500 nm at incidence angles 15–60° using a spectroscopic goniometry system. The same experimental setup is used to determine the spectral narrow-angle transmittance of semi-transparent materials for solar collector covers at incidence angles 0–60°. In addition, the angle-resolved surface scattering of reflective materials is recorded by an area-scan CCD detector over the spectral range 350–1050 nm. A comprehensive summary, discussion, and interpretation of the results are included in the associated research article “Spectral reflectance, transmittance, and angular scattering of materials for solar concentrators” in Solar Energy Materials and Solar Cells. PMID:26862556

  10. Fluorine-containing composition for forming anti-reflection film on resist surface and pattern formation method

    DOEpatents

    Nishi, Mineo; Makishima, Hideo

    1996-01-01

    A composition for forming anti-reflection film on resist surface which comprises an aqueous solution of a water soluble fluorine compound, and a pattern formation method which comprises the steps of coating a photoresist composition on a substrate; coating the above-mentioned composition for forming anti-reflection film; exposing the coated film to form a specific pattern; and developing the photoresist, are provided. Since the composition for forming anti-reflection film can be coated on the photoresist in the form of an aqueous solution, not only the anti-reflection film can be formed easily, but also, the film can be removed easily by rinsing with water or alkali development. Therefore, by the pattern formation method according to the present invention, it is possible to form a pattern easily with a high dimensional accuracy.

  11. Spectral data of specular reflectance, narrow-angle transmittance and angle-resolved surface scattering of materials for solar concentrators.

    PubMed

    Good, Philipp; Cooper, Thomas; Querci, Marco; Wiik, Nicolay; Ambrosetti, Gianluca; Steinfeld, Aldo

    2016-03-01

    The spectral specular reflectance of conventional and novel reflective materials for solar concentrators is measured with an acceptance angle of 17.5 mrad over the wavelength range 300-2500 nm at incidence angles 15-60° using a spectroscopic goniometry system. The same experimental setup is used to determine the spectral narrow-angle transmittance of semi-transparent materials for solar collector covers at incidence angles 0-60°. In addition, the angle-resolved surface scattering of reflective materials is recorded by an area-scan CCD detector over the spectral range 350-1050 nm. A comprehensive summary, discussion, and interpretation of the results are included in the associated research article "Spectral reflectance, transmittance, and angular scattering of materials for solar concentrators" in Solar Energy Materials and Solar Cells.

  12. In vivo macroscopic HPD fluorescence reflectance imaging on small animals bearing surface ARO/NPA tumor

    NASA Astrophysics Data System (ADS)

    Autiero, Maddalena; Celentano, Luigi; Laccetti, Paolo; Marotta, Marcello; Mettivier, Giovanni; Montesi, Maria C.; Riccio, Patrizia; Russo, Paolo; Roberti, Giuseppe

    2005-08-01

    Recently multimodal imaging systems have been devised because the combination of different imaging modalities results in the complementarity and integration of the techniques and in a consequent improvement of the diagnostic capabilities of the multimodal system with respect to each separate imaging modality. We developed a simple and reliable HematoPorphyrin (HP) mediated Fluorescence Reflectance Imaging (FRI) system that allows for in vivo real time imaging of surface tumors with a large field of view. The tumor cells are anaplastic human thyroid carcinoma-derived ARO cells, or human papillary thyroid carcinoma-derived NPA cells. Our measurements show that the optical contrast of the tumor region image is increased by a simple digital subtraction of the background fluorescence and that HP fluorescence emissivity of ARO tumors is about 2 times greater than that of NPA tumors, and about 4 times greater than that of healthy tissues. This is also confirmed by spectroscopic measurements on histological sections of tumor and healthy tissues. It was shown also the capability of this system to distinguish the tumor type on the basis of the different intensity of the fluorescence emission, probably related to the malignancy degree. The features of this system are complementary with those ones of a pixel radionuclide detection system, which allows for relatively time expensive, narrow field of view measurements, and applicability to tumors also deeply imbedded in tissues. The fluorescence detection could be used as a large scale and quick analysis tool and could be followed by narrow field, higher resolution radionuclide measurements on previously determined highly fluorescent regions.

  13. A tutorial solution to scattering of radiation in a thin atmosphere bounded below by a diffusely reflecting, absorbing surface

    NASA Technical Reports Server (NTRS)

    Buglia, J. J.

    1982-01-01

    A simple tutorial method, based on a photon tracking procedure, is described to determine the spherical albedo for a thin atmosphere overlying a reflecting surface. This procedure is used to provide a physical structure with which to interpret the more detailed but highly mathematical analyses presented. The final equations are shown to be in good numerical agreement with more exact solutions for thin atmospheres.

  14. Evaluation of the Aerosol Type Effect on the Surface Reflectance Retrieval Using Chris/proba Images Over Land

    NASA Astrophysics Data System (ADS)

    Tirelli, C.; Manzo, C.; Curci, G.; Bassani, C.

    2015-04-01

    Surface reflectance has a central role in the analysis of land surface for a broad variety of agricultural, geological and urban studies. An accurate atmospheric correction, obtained by an appropriate selection of aerosol type and loading, is the first requirement for a reliable surface reflectance estimation. The aerosol type is defined by its micro-physical properties, while the aerosol loading is described by optical thickness at 550 nm. The aim of this work is to evaluate the radiative impact of the aerosol model on the surface reflectance obtained from CHRIS (Compact High Resolution Imaging Spectrometer) hyperspectral data over land by using the specifically developed algorithm CHRIS@CRI (CHRIS Atmospherically Corrected Reflectance Imagery) based on the 6SV radiative transfer model. Five different aerosol models have been used: one provided by the AERONET inversion products (used as reference), three standard aerosol models in 6SV, and one obtained from the output of the GEOS-Chem global chemistry-transport model (CTM). As test case the urban site of Bruxelles and the suburban area of Rome Tor Vergata have been considered. The results obtained encourages the use of CTM in operational retrieval and provides an evaluation of the role of the aerosol model in the atmospheric correction process, considering the different microphysical properties impact.

  15. Use of attenuated total reflectance Fourier transform infrared spectroscopy to identify microbial metabolic products on carbonate mineral surfaces.

    PubMed

    Bullen, Heather A; Oehrle, Stuart A; Bennett, Ariel F; Taylor, Nicholas M; Barton, Hazel A

    2008-07-01

    This paper demonstrates the use of attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy to detect microbial metabolic products on carbonate mineral surfaces. By creating an ATR-FTIR spectral database for specific organic acids using ATR-FTIR spectroscopy we were able to distinguish metabolic acids on calcite surfaces following Escherichia coli growth. The production of these acids by E. coli was verified using high-performance liquid chromatography with refractive index detection. The development of this technique has allowed us to identify microbial metabolic products on carbonate surfaces in nutrient-limited cave environments.

  16. Learning to See Beneath the Surface: A Qualitative Analysis of Family Medicine Residents' Reflections About Communication.

    PubMed

    Duggan, Ashley P; Vicini, Andrea; Allen, Lucas; Shaughnessy, Allen F

    2015-01-01

    Patients share straightforward statements with physicians such as describing their fears about their diagnosis. Physicians need to also understanding implicit, indirect, subtle communication cues that give broader context to patients' illness experiences. This project examines physicians' written reflections that offer insight into their interpretation of both the stated and the tacit aspects of their observations about communication, their resulting responses, and their intended actions. Tufts University Family Medicine residents (N = 33) of the Tufts Family Medicine Cambridge Health Alliance completed three reflective exercises each week over the course of 1 year (756 reflective entries). An interdisciplinary research team identified communication-related concepts within the reflections. Identified themes include (a) physicians recognizing and discovering mutual interplay of their communication with and patient disclosure, (b) physicians paying attention to subtleties of patient behavior as indicative of a fuller picture of patients' lives and their coping with illness, and (c) physician images of growth and awareness about communication indicative of their potential for growth and improvement. The project extends the literature in communication and medical education by examining explicit and tacit points of reflection about communication. The project (a) allows for unpacking the multifaceted aspects of reflection and (b) bridges reflective theory and medical education with communication foundations.

  17. Learning to See Beneath the Surface: A Qualitative Analysis of Family Medicine Residents' Reflections About Communication.

    PubMed

    Duggan, Ashley P; Vicini, Andrea; Allen, Lucas; Shaughnessy, Allen F

    2015-01-01

    Patients share straightforward statements with physicians such as describing their fears about their diagnosis. Physicians need to also understanding implicit, indirect, subtle communication cues that give broader context to patients' illness experiences. This project examines physicians' written reflections that offer insight into their interpretation of both the stated and the tacit aspects of their observations about communication, their resulting responses, and their intended actions. Tufts University Family Medicine residents (N = 33) of the Tufts Family Medicine Cambridge Health Alliance completed three reflective exercises each week over the course of 1 year (756 reflective entries). An interdisciplinary research team identified communication-related concepts within the reflections. Identified themes include (a) physicians recognizing and discovering mutual interplay of their communication with and patient disclosure, (b) physicians paying attention to subtleties of patient behavior as indicative of a fuller picture of patients' lives and their coping with illness, and (c) physician images of growth and awareness about communication indicative of their potential for growth and improvement. The project extends the literature in communication and medical education by examining explicit and tacit points of reflection about communication. The project (a) allows for unpacking the multifaceted aspects of reflection and (b) bridges reflective theory and medical education with communication foundations. PMID:26147857

  18. 2-D finite difference time domain model of ultrasound reflection from normal and osteoarthritic human articular cartilage surface.

    PubMed

    Kaleva, Erna; Liukkonen, Jukka; Toyras, Juha; Saarakkala, Simo; Kiviranta, Panu; Jurvelin, Jukka

    2010-04-01

    Quantitative high-frequency ultrasonic evaluation of articular cartilage has shown a potential for the diagnosis of osteoarthritis, where the roughness of the surface, collagen and proteoglycan contents, and the density and mechanical properties of cartilage change concurrently. Experimentally, these factors are difficult to investigate individually and thus a numerical model is needed. The present study is the first one to use finite difference time domain modeling of pulse-echo measurements of articular cartilage. Ultrasound reflection from the surface was investigated with varying surface roughness, material parameters (Young's modulus, density, longitudinal, and transversal velocities) and inclination of the samples. The 2-D simulation results were compared with the results from experimental measurements of the same samples in an identical geometry. Both the roughness and the material parameters contributed significantly to the ultrasound reflection. The angular dependence of the ultrasound reflection was strong for a smooth cartilage surface but disappeared for the samples with a rougher surface. These results support the findings of previous experimental studies and indicate that ultrasound detects changes in the cartilage that are characteristic of osteoarthritis. In the present study there are differences between the results of the simulations and the experimental measurements. However, the systematic patterns in the experimental behavior are correctly reproduced by the model. In the future, our goal is to develop more realistic acoustic models incorporating inhomogeneity and anisotropy of the cartilage. PMID:20378451

  19. Production of nanostructures on bulk metal samples by laser ablation for fabrication of low-reflective surfaces

    NASA Astrophysics Data System (ADS)

    Hopp, Béla; Smausz, Tomi; Csizmadia, Tamás; Vass, Csaba; Tápai, Csaba; Kiss, Bálint; Ehrhardt, Martin; Lorenz, Pierre; Zimmer, Klaus

    2013-11-01

    Nanostructure formation on bulk noble metals (copper, gold and silver) by a femtosecond laser was studied aiming at the production of low-reflectivity surfaces. The target surface was irradiated with the beam of a 775 nm wavelength and 150 fs pulse duration Ti:sapphire laser. The fluence was in the 16-2000 mJ/cm2 range, while the average pulse number was varied between 10 and 1000 depending on the scanning speed of the sample stage. The reflectivity of the treated surfaces was measured with a visible-near-infrared microspectrometer in the 450-800 nm range, while the morphology was studied with a scanning electron microscope. A strong correlation was found between the decreasing reflectivity and the nanostructure formation on the irradiated surface; however, the morphology of silver significantly differed from those of copper and gold. For the two latter metals a dense coral-like structure was found probably as a result of cluster condensation in the ablation plume followed by diffusion-limited aggregation. In the case of silver the surface was covered by nanodroplets, which formation was probably influenced by the ‘spitting’ caused by ambient oxygen absorption in the molten silver followed by its fast release during the resolidification.

  20. Estimation of surface energy balance from radiant surface temperature and NOAA AVHRR sensor reflectances over agricultural and native vegetation. [AVHRR (advanced very high resolution radiometer)

    SciTech Connect

    Huang Xinmei; Lyons, T.J. ); Smith, R.C.G. ); Hacker, J.M.; Schwerdtfeger, P. )

    1993-08-01

    A model is developed to evaluate surface heat flux densities using the radiant surface temperature and red and near-infrared reflectances from the NOAA Advanced Very High Resolution Radiometer sensor. Net radiation is calculated from an empirical formulation and albedo estimated from satellite observations. Infrared surface temperature is corrected to aerodynamic surface temperature in estimating the sensible heat flux and the latent flux is evaluated as the residual of the surface energy balance. When applied to relatively homogeneous agricultural and native vegetation, the model yields realistic estimates of sensible and latent heat flux density in the surface layer for cases where either the sensible or latent flux dominates. 29 refs., 10 figs., 3 tabs.

  1. BIOLOGICAL ADHESIVES. Adaptive synergy between catechol and lysine promotes wet adhesion by surface salt displacement.

    PubMed

    Maier, Greg P; Rapp, Michael V; Waite, J Herbert; Israelachvili, Jacob N; Butler, Alison

    2015-08-01

    In physiological fluids and seawater, adhesion of synthetic polymers to solid surfaces is severely limited by high salt, pH, and hydration, yet these conditions have not deterred the evolution of effective adhesion by mussels. Mussel foot proteins provide insights about adhesive adaptations: Notably, the abundance and proximity of catecholic Dopa (3,4-dihydroxyphenylalanine) and lysine residues hint at a synergistic interplay in adhesion. Certain siderophores—bacterial iron chelators—consist of paired catechol and lysine functionalities, thereby providing a convenient experimental platform to explore molecular synergies in bioadhesion. These siderophores and synthetic analogs exhibit robust adhesion energies (E(ad) ≥-15 millijoules per square meter) to mica in saline pH 3.5 to 7.5 and resist oxidation. The adjacent catechol-lysine placement provides a "one-two punch," whereby lysine evicts hydrated cations from the mineral surface, allowing catechol binding to underlying oxides. PMID:26250681

  2. BIOLOGICAL ADHESIVES. Adaptive synergy between catechol and lysine promotes wet adhesion by surface salt displacement.

    PubMed

    Maier, Greg P; Rapp, Michael V; Waite, J Herbert; Israelachvili, Jacob N; Butler, Alison

    2015-08-01

    In physiological fluids and seawater, adhesion of synthetic polymers to solid surfaces is severely limited by high salt, pH, and hydration, yet these conditions have not deterred the evolution of effective adhesion by mussels. Mussel foot proteins provide insights about adhesive adaptations: Notably, the abundance and proximity of catecholic Dopa (3,4-dihydroxyphenylalanine) and lysine residues hint at a synergistic interplay in adhesion. Certain siderophores—bacterial iron chelators—consist of paired catechol and lysine functionalities, thereby providing a convenient experimental platform to explore molecular synergies in bioadhesion. These siderophores and synthetic analogs exhibit robust adhesion energies (E(ad) ≥-15 millijoules per square meter) to mica in saline pH 3.5 to 7.5 and resist oxidation. The adjacent catechol-lysine placement provides a "one-two punch," whereby lysine evicts hydrated cations from the mineral surface, allowing catechol binding to underlying oxides.

  3. Reflection and transmission at the boundary surface of modified couple stress thermoelastic media

    NASA Astrophysics Data System (ADS)

    Kumar, R.; Kumar, K.

    2016-02-01

    In this paper the reflection and transmission at a plane interface in modified couple stress generalized thermoelastic solid half spaces in the context of Loard-Shulman (LS) and Green-Lindsay (GL) theories in welded contact are investigated. Amplitude ratios of various reflected and transmitted waves are obtained due to incidence of a set of coupled longitudinal waves and coupled transverse waves. It is found that the amplitude ratios of various reflected and transmitted waves are functions of the angle of incidence, frequency and are affected by the couple stress properties of the media. Some special cases are deduced from the present formulation.

  4. Bidirectional Reflectance of Flat, Optically Thick Particulate Layers: An Efficient Radiative Transfer Solution and Applications to Snow and Soil Surfaces

    NASA Technical Reports Server (NTRS)

    Mishchenko, Michael I.; Dlugach, Janna M.; Yanovitsku, Edgard G.; Zakharova, Nadia T.

    1999-01-01

    We describe a simple and highly efficient and accurate radiative transfer technique for computing bidirectional reflectance of a macroscopically flat scattering layer composed of nonabsorbing or weakly absorbing, arbitrarily shaped, randomly oriented and randomly distributed particles. The layer is assumed to be homogeneous and optically semi-infinite, and the bidirectional reflection function (BRF) is found by a simple iterative solution of the Ambartsumian's nonlinear integral equation. As an exact Solution of the radiative transfer equation, the reflection function thus obtained fully obeys the fundamental physical laws of energy conservation and reciprocity. Since this technique bypasses the computation of the internal radiation field, it is by far the fastest numerical approach available and can be used as an ideal input for Monte Carlo procedures calculating BRFs of scattering layers with macroscopically rough surfaces. Although the effects of packing density and coherent backscattering are currently neglected, they can also be incorporated. The FORTRAN implementation of the technique is available on the World Wide Web at http://ww,,v.giss.nasa.gov/-crmim/brf.html and can be applied to a wide range of remote sensing, engineering, and biophysical problems. We also examine the potential effect of ice crystal shape on the bidirectional reflectance of flat snow surfaces and the applicability of the Henyey-Greenstein phase function and the 6-Eddington approximation in calculations for soil surfaces.

  5. Morphology and phase structures of CW laser-induced oxide layers on iron surface with evolving reflectivity and colors

    NASA Astrophysics Data System (ADS)

    Wu, Taotao; Wang, Lijun; Wei, Chenghua; Zhou, Menglian; He, Minbo; Wu, Lixiong

    2016-11-01

    Laser-induced oxidation will change the laser reflectivity and color features of metal surface. Both changes can be theoretically calculated based on the oxidation kinetics and the optical constants of oxides. For the purpose of calculation, the laser-induced oxidation process of pure polycrystalline iron was studied. Samples with various color features were obtained by continuous wave Nd:YAG fiber laser (1.06 μm) irradiation depending on progressive durations in the intensity of 1.90 W/cm2. The real-time reflectivity and temperature were measured with integral sphere and thermocouples. The irradiated surface morphology and phase structures were characterized by microscope, X-ray diffraction and Raman spectrum. It was found that the first formed magnetite made the surface reflectivity decline rapidly and caused the "positive feedback" effect because of molecular absorption. The later formed hematite oscillated the reflectivity by interference effect. The oxide films were thin, orientated and badly crystallized. The oxidation process was influenced by the grain orientation of the metal substrate. These results made the mechanism of laser-induced oxidation of iron clear and provided available experimental data for accurate modeling of the oxidation kinetics.

  6. Reflectance spectroscopy of palagonite and iron-rich montmorillonite clay mixtures - Implications for the surface composition of Mars

    NASA Technical Reports Server (NTRS)

    Orenberg, James; Handy, Jonathan

    1992-01-01

    The diffuse reflectance spectra of Hawaiian palagonite mixtures with an Fe-rich montmorillonite have prompted their present use as spectral analogs of the Martian surface. Like the Mars spectrum and unlike clays, the 2.2-micron reflectance spectrum absorption band is not present in the palagonite sample; neither is the 2.2-micron Al-OH clay lattice band seen in palagonite-montmorillonite mixtures, where the latter component remains below 15 wt pct. Fe-rich montmorillonite clay may therefore be present in Mars, in combination with palagonite, while remaining undetected in remotely sensed spectra.

  7. 3-component HR seismic reflection, a new paradigm for near surface exploration of aquifers and aquitards

    NASA Astrophysics Data System (ADS)

    Pugin, A.; Pullan, S. E.; Oldenborger, G. A.; Crow, H.; Hunter, J. A.; Near Surface Geophysics

    2011-12-01

    The recent development of landstreamers towed by vibroseis sources at the Geological Survey of Canada and the resulting typical acquisition of up to 6 km of seismic line per day, has greatly enhanced our capacity to provide regional data for groundwater modeling. In a single pass of acquisition, the recording of 3-component (3-C) data allows us to observe and process P-waves, S-waves and converted PS-waves. The testing of this technique over various types of unconsolidated sediment has yielded very meaningful observations. We have observed in general that the P-wave is mostly vertically polarised, while the PS wave can be seen in the vertical and the in-line component, and the S-wave can be seen on all receiver-components with a polarisation that may evolve between vertical and horizontal depending on the geological materials encountered. The polarisation of S-wave data is observed whether the seismic source position is in a vertical or in a horizontal mode. The use of common-midpoint, normal-moveout velocity analyses, calibrated with geophysical logs and resistivity profiling data, has shown us that seismic velocities can be used to characterise the lithologies present in the seismic sections. In the St Lawrence Lowlands in eastern Canada, aquifers in the form of tunnel-shaped eskers and coarse sediment layers buried by up to 100 m of glacio-marine silts have been imaged very successfully using this innovative seismic technique. Shear wave seismic sections acquired in this environment provide subsurface resolution on a scale previously only observed using waterborne seismic methods. The sections show erosional surfaces and vertical structures interpreted to be gas and/or water escape features present in the silt deposits. These high-resolution data are providing critical new insights into the structural geometry of this type of aquitard. In central and western Canada our seismic system has been used for regional mapping of buried valley aquifers protected and

  8. Effect of the aerosol type uncertainty on the surface reflectance retrieval using CHRIS/PROBA hyperspectral images over land.

    NASA Astrophysics Data System (ADS)

    Tirelli, C.; Manzo, C.; Curci, G.; Bassani, C.

    2014-12-01

    The surface reflectance is crucial for the quantitative analysis of land surface properties in geological, agricultural and urban studies. The first requirement for a reliable surface reflectance estimation is an accurate atmospheric correction obtained by an appropriate selection of aerosol loading and type. The aerosol optical thickness at 550nm is widely used to describe the aerosol loading. Recent works have highlighted the relevant role of the aerosol types on the atmospheric correction process defined by their micro-physical properties. The aim of this work is to evaluate the radiative impact of the aerosol type on the surface reflectance obtained from CHRIS (Compact High Resolution Imaging Spectrometer) hyperspectral data over land. CHRIS on PROBA satellite is an high resolution multi-angular imaging spectrometer, operating in the visible near-infrared spectral domain (400 to 1000 nm). As test case the urban site of Brussels has been selected. The physically-based algorithm CHRIS@CRI (CHRIS Atmospherically Corrected Reflectance Imagery) has been developed specifically for CHRIS data by using the vector version of 6S (6SV) radiative transfer model. The atmospheric data needed for the atmospheric correction were obtained from CIMEL CE-318 of the Brussels AERONET station. CHRIS images were selected if simultaneous AERONET data were available. Other specific requirements for imagery acquisition were high aerosol loading and high solar irradiation. The aerosol radiative impact has been investigated comparing the reflectance obtained by applying the CHRIS@CRI algorithm with different aerosol types: the three aerosol standard of 6SV and two characterized by specific microphysical properties provided by the AERONET station and calculated with FlexAOD code (a post-processing tool of the chemical transport model GEOS-Chem), respectively. The results show a clear dependence of the atmospheric correction results on the aerosol absorption properties.

  9. A relation between landsat digital numbers, surface reflectance, and the cosine of the solar zenith angle

    USGS Publications Warehouse

    Kowalik, William S.; Marsh, Stuart E.; Lyon, Ronald J. P.

    1982-01-01

    A method for estimating the reflectance of ground sites from satellite radiance data is proposed and tested. The method uses the known ground reflectance from several sites and satellite data gathered over a wide range of solar zenith angles. The method was tested on each of 10 different Landsat images using 10 small sites in the Walker Lake, Nevada area. Plots of raw Landsat digital numbers (DNs) versus the cosine of the solar zenith angle (cos Z) for the the test areas are linear, and the average correlation coefficients of the data for Landsat bands 4, 5, 6, and 7 are 0.94, 0.93, 0.94, and 0.94, respectively. Ground reflectance values for the 10 sites are proportional to the slope of the DN versus cos Z relation at each site. The slope of the DN versus cos Z relation for seven additional sites in Nevada and California were used to estimate the ground reflectances of those sites. The estimates for nearby sites are in error by an average of 1.2% and more distant sites are in error by 5.1%. The method can successfully estimate the reflectance of sites outside the original scene, but extrapolation of the reflectance estimation equations to other areas may violate assumptions of atmospheric homogeneity.

  10. Native SrTiO3 (001) surface layer from resonant Ti L2,3 reflectance spectroscopy

    SciTech Connect

    Valvidares, Manuel; Huijben, Mark; Yu, Pu; Ramesh, Ramamoorthy; Kortright, Jeffrey

    2010-11-03

    We quantitatively model resonant Ti L2,3 reflectivity Rs,p(q, hn) from several SrTiO3 (001) single crystals having different initial surface preparations and stored in ambient conditions before and between measurements. All samples exhibit unexpected 300 K Rs(hn) - Rp(hn) anisotropy corresponding to weak linear dichroism and tetragonal distortion of the TiO6 octahedra indicating a surface layer with properties different from cubic SrTiO3. Oscillations in Rs(q) confirm a ubiquitous surface layer 2-3 nm thick that evolves over a range of time scales. Resonant optical constant spectra derived from Rs,p(hn) assuming a uniform sample are refined using a single surface layer to fit measured Rs(q). Differences in surface layer and bulk optical properties indicate that the surface is significantly depleted in Sr and enriched in Ti and O. While consistent with the tendency of SrTiO3 surfaces toward non-stoichiometry, this layer does not conform simply to existing models for the near surface region and apparently forms via room temperature surface reactions with the ambient. This new quantitative spectral modeling approach is generally applicable and has potential to study near-surface properties of a variety of systems with unique chemical and electronic sensitivities.

  11. Adaptive wettability-enhanced surfaces ordered on molded etched substrates using shrink film

    NASA Astrophysics Data System (ADS)

    Jayadev, Shreshta; Pegan, Jonathan; Dyer, David; McLane, Jolie; Lim, Jessica; Khine, Michelle

    2013-01-01

    Superhydrophobic surfaces in nature exhibit desirable properties including self-cleaning, bacterial resistance, and flight efficiency. However, creating such intricate multi-scale features with conventional fabrication approaches is difficult, expensive, and not scalable. By patterning photoresist on pre-stressed shrink-wrap film, which contracts by 95% in surface area when heated, such features over large areas can be obtained easily. Photoresist serves as a dry etch mask to create complex and high-aspect ratio microstructures in the film. Using a double-shrink process, we introduce adaptive wettability-enhanced surfaces ordered on molded etched (AWESOME) substrates. We first create a mask out of the children’s toy ‘Shrinky-Dinks’ by printing dots using a laserjet printer. Heating this thermoplastic sheet causes the printed dots to shrink to a fraction of their original size. We then lithographically transfer the inverse pattern onto photoresist-coated shrink-wrap polyolefin film. The film is then plasma etched. After shrinking, the film serves as a high-aspect ratio mold for polydimethylsiloxane, creating a superhydrophobic surface with water contact angles >150° and sliding angles <10°. We pattern a microarray of ‘sticky’ spots with a dramatically different sliding angle compared to that of the superhydrophobic region, enabling microtiter-plate type assays without the need for a well plate.

  12. Robotic automation for space: planetary surface exploration, terrain-adaptive mobility, and multirobot cooperative tasks

    NASA Astrophysics Data System (ADS)

    Schenker, Paul S.; Huntsberger, Terrance L.; Pirjanian, Paolo; Baumgartner, Eric T.; Aghazarian, Hrand; Trebi-Ollennu, Ashitey; Leger, Patrick C.; Cheng, Yang; Backes, Paul G.; Tunstel, Edward; Dubowsky, Steven; Iagnemma, Karl D.; McKee, Gerard T.

    2001-10-01

    During the last decade, there has been significant progress toward a supervised autonomous robotic capability for remotely controlled scientific exploration of planetary surfaces. While planetary exploration potentially encompasses many elements ranging from orbital remote sensing to subsurface drilling, the surface robotics element is particularly important to advancing in situ science objectives. Surface activities include a direct characterization of geology, mineralogy, atmosphere and other descriptors of current and historical planetary processes-and ultimately-the return of pristine samples to Earth for detailed analysis. Toward these ends, we have conducted a broad program of research on robotic systems for scientific exploration of the Mars surface, with minimal remote intervention. The goal is to enable high productivity semi-autonomous science operations where available mission time is concentrated on robotic operations, rather than up-and-down-link delays. Results of our work include prototypes for landed manipulators, long-ranging science rovers, sampling/sample return mobility systems, and more recently, terrain-adaptive reconfigurable/modular robots and closely cooperating multiple rover systems. The last of these are intended to facilitate deployment of planetary robotic outposts for an eventual human-robot sustained scientific presence. We overview our progress in these related areas of planetary robotics R&D, spanning 1995-to-present.

  13. Simultaneous Retrieval of Aerosol Optical Depth and Surface Reflectance over Land within Short Temporal Interval Using MSG Data

    NASA Astrophysics Data System (ADS)

    Li, C.; Xue, Y.; Li, Y. J.; Yang, L. K.; Hou, T. T.

    2012-04-01

    Aerosols cause a major uncertainty in the research of climatology and global change, whereas satellite aerosol remote sensing over land still remains a big challenge. Due to their short time repeat cycle, geostationary satellites are capable of monitoring the temporal features of aerosols, while its limited number of visible bands is an obstacle. On the other hand, a main uncertainty in aerosol retrieval is the difficulty to separate the relatively weaker contribution of the atmosphere to the signal received by the satellite from the contribution of the Earth's surface. In this paper, an analytical retrieval strategy is presented to solve the both problems above. For the lack of surface reflectance, we use the Ross-Li BRDF (Bidirectional Reflectance Distribution Function) model and assume that the surface reflective property changes mainly due to the change of illumination geometry in a short time interval while the kernals of Ross-Li model remain the same. For the limited visible band, we take advantage of the Aerosol Optical Depth (AOD) consistence within short distances, thus to reduce the number of unknown parameters. A parameterization of the atmospheric radiative transfer model is used which is proved to be proper to retrieve aerosol and surface parameters by sensitivity analysis. Taking the three kernels of kernel-driven BRDF model and AOD as unknown parameters and based on prior knowledge of aerosol types, a series of nonlinear equations can be established then. Both AOD and surface reflectance can be obtained by using a numerical method to solve these equations. By applying this method, called LABITS-MSG (Land Aerosol and Bidirectional reflectance Inversion by Time Series technique for MSG), to data from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) observations on board Meteosat Second Generation (MSG), we obtain regional maps of AOD and surface reflectance in July 11, 2010 within a temporal interval of as short as 1 hour, and a spatial

  14. Modification of the surface state of rough substrates by two different varnishes and influence on the reflected light

    NASA Astrophysics Data System (ADS)

    Elias, Mady; René de la Rie, E.; Delaney, John K.; Charron, Eric; Morales, Kathryn M.

    2006-10-01

    Modification of the visual appearance when a rough surface is covered by a varnish is mostly attributed to the levelling of the substrate surface, which depends on the molecular weight of the varnish. The topography of varnished surfaces, however, has never been measured directly. Surfaces of varnishes applied over glass substrates of varying roughness were studied, therefore, using mechanical profilometry. Two different varnishes made with a low and a high molecular weight resin were studied. Both varnishes lower the r.m.s. roughness of the substrates and filter the high spatial frequencies. These results are amplified for the varnish containing the low molecular weight resin. The light reflected by the varnished samples is modelled from these topographical data. Its angular distribution, calculated from the probability density of slopes is presented, taking into account separately the air/varnish and the varnish/substrate interfaces. These analyses are presented in a back-scattering configuration. They show that varnishing significantly reduces the angular width of the reflected light and that this effect is magnified for the low molecular weight resin. Modelling furthermore shows that the influence of the roughness of the varnish/substrate interface is negligible in the total reflected light.

  15. Effects of surface contamination on the infrared emissivity and visible-light scattering of highly reflective surfaces at cryogenic temperatures

    NASA Technical Reports Server (NTRS)

    Viehmann, W.; Eubanks, A. G.

    1972-01-01

    A technique is described for the simultaneous in situ measurement of film thickness, refractive index, total normal emissivity, visible-light scattering, and reflectance of contaminant films on a highly reflective liquid-nitrogen cooled, stainless steel substrate. Emissivities and scattering data are obtained for films of water, carbon dioxide, silicone oil, and a number of aromatic and aliphatic hydrocarbons as a function of film thickness between zero and 20 microns. Of the contaminants investigated, water has by far the greatest effect on emissivity, followed by silicone oil, aliphatic hydrocarbons, aromatic hydrocarbons, and carbon dioxide. The emissivity increases more rapidly with film thickness between zero and 2.5 microns than at thicknesses greater than 2.5 microns. Scattering of visible light changes very little below 2 microns thickness but increases rapidly with thickness beyond 2 to 3 microns. The effect of contaminant films on passive radiation coolers is discussed.

  16. Photometric Modeling of Asteroids 2867-Steins and 21-Lutetia Surfaces and Grain Size Estimate using Hapke's Bidirectional Reflectance

    NASA Astrophysics Data System (ADS)

    La Forgia, F.; Magrin, S.; Bertini, I.; Lazzarin, M.; Pajola, M.; Barbieri, C.

    2013-09-01

    We present a photometric method for the interpretation of the reflectance properties of atmosphereless bodies such as asteroids and comets nuclei. The method is self-consistent, easily reusable for any space mission target and independent of the shape model of the object. We investigated the reflectance dependence on the phase angle, interpreted in terms of the Hapke theory of bidirectional reflectance. We then present a method for the estimate of the grain size of the regolith on the surfaces of the asteroids. We applied the method to the two Main Belt asteroids 2867-Steins and 21- Lutetia observed from the OSIRIS camera onboard Rosetta spacecraft on 5 September 2008 and on 10 July 2010 respectively.

  17. Analysis of the reflectance spectra of oil emulsion spilled on the sea surface

    NASA Astrophysics Data System (ADS)

    Sicot, Guillaume; Lennon, Marc; Miegebielle, Veronique; Dubucq, Dominique

    2014-10-01

    Airborne remote sensing appears useful for monitoring oil spill accident or detecting illegal oil discharges. In that context, hyperspectral imagery in the SWIR range shows a high potential to describe oil spills. Indeed reflectance spectra of an oil emulsion layer show a wide variety of shapes according to its thickness or emulsion rate. Although based on laboratory measurements, it seems that these two parameters are insufficient to completely describe them. It appears that the way emulsion is performed leads to different reflectance spectra. Hence this paper will present a model which tends to simulate reflectance spectra of an oil emulsion layer over the sea water. To derive an analytical expression, some approximations and assumptions will be done. The result of this model shows high similarities with laboratory measurements and seems able to simulate most of the shapes of reflectance spectra. It also shows that a key parameter to define the shape of the reflectance spectra is the statistical distribution of water bubbles size in the emulsion. The description of this distribution function, if measurable, should be integrated into the methodology of elaboration of spectral libraries in the future.

  18. Characteristics of hypervelocity impact craters on LDEF experiment S1003 and implications of small particle impacts on reflective surfaces

    NASA Technical Reports Server (NTRS)

    Mirtich, Michael J.; Merrow, James E.

    1992-01-01

    The Ion Beam Textured and Coated Surfaces Experiment (IBEX) was designated S1003 on the Long Duration Exposure Facility (LDEF) at a location of 98 degrees relative to the ram direction. Thirty-six diverse materials were exposed to the micrometeoroid (and some debris) environment for 5.8 years. Optical property measurements indicated no changes for almost all of the materials except S-13G, Kapton, and Kapton-coated surfaces, and these changes can be explained by other environmental effects. From the predicted micrometeoroid flux of NASA SP-8013, no changes in optical properties of the surfaces due to micrometeoroids were expected. However, there were hypervelocity impacts on the various diverse materials flown on IBEX. The characteristics of these craters were documented using scanning electron microscopy (SEM) and are presented. Interest in placing large solar concentrator/solar dynamic systems in space for power generation has again brought up a concern for maintaining the integrity of the optical properties of highly specular reflecting surfaces in the near-Earth space environment. It has been shown that highly reflective polished metals and thin film coatings degrade when exposed to simulated micrometeoroids in the laboratory. At LeRC, a shock tube was used to simulate the phenomenon of micrometeoroid optical properties of surfaces exposed to this impact were then evaluated. A calibrated sensor, 2000 A Al/stainless steel, was developed to not only detect the small size micrometeoroid environment, but also to evaluate the degradation of the optical properties of thin aluminum films in space. This sensor was flown on LDEF experiment S1003 and also on the OSO 3 and SERT 2 satellites that were launched in 1967 and 1970, respectively. No changes in the optical properties of the highly reflective surface sensor on SERT 2 were measured during 20 years in space. The results, as determined by the accuracy of the sensor, indicate that a highly reflective surface should

  19. Applications of high power lasers. [using reflection holograms for machining and surface treatment

    NASA Technical Reports Server (NTRS)

    Angus, J. C.

    1979-01-01

    The use of computer generated, reflection holograms in conjunction with high power lasers for precision machining of metals and ceramics was investigated. The Reflection holograms which were developed and made to work at both optical wavelength (He-Ne, 6328 A) and infrared (CO2, 10.6) meet the primary practical requirement of ruggedness and are relatively economical and simple to fabricate. The technology is sufficiently advanced now so that reflection holography could indeed be used as a practical manufacturing device in certain applications requiring low power densities. However, the present holograms are energy inefficient and much of the laser power is lost in the zero order spot and higher diffraction orders. Improvements of laser machining over conventional methods are discussed and addition applications are listed. Possible uses in the electronics industry include drilling holes in printed circuit boards making soldered connections, and resistor trimming.

  20. Comparison of P- and S-wave velocity profiles obtained from surface seismic refraction/reflection and downhole data

    USGS Publications Warehouse

    Williams, R.A.; Stephenson, W.J.; Odum, J.K.

    2003-01-01

    High-resolution seismic-reflection/refraction data were acquired on the ground surface at six locations to compare with near-surface seismic-velocity downhole measurements. Measurement sites were in Seattle, WA, the San Francisco Bay Area, CA, and the San Fernando Valley, CA. We quantitatively compared the data in terms of the average shear-wave velocity to 30-m depth (Vs30), and by the ratio of the relative site amplification produced by the velocity profiles of each data type over a specified set of quarter-wavelength frequencies. In terms of Vs30, similar values were determined from the two methods. There is <15% difference at four of the six sites. The Vs30 values at the other two sites differ by 21% and 48%. The relative site amplification factors differ generally by less than 10% for both P- and S-wave velocities. We also found that S-wave reflections and first-arrival phase delays are essential for identifying velocity inversions. The results suggest that seismic reflection/refraction data are a fast, non-invasive, and less expensive alternative to downhole data for determining Vs30. In addition, we emphasize that some P- and S-wave reflection travel times can directly indicate the frequencies of potentially damaging earthquake site resonances. A strong correlation between the simple S-wave first-arrival travel time/apparent velocity on the ground surface at 100 m offset from the seismic source and the Vs30 value for that site is an additional unique feature of the reflection/refraction data that could greatly simplify Vs30 determinations. ?? 2003 Elsevier Science B.V. All rights reserved.