Academic literature on the topic 'Opacity maps'
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Journal articles on the topic "Opacity maps"
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Yuksel, Cem, and John Keyser. "Deep Opacity Maps." Computer Graphics Forum 27, no. 2 (2008): 675–80. http://dx.doi.org/10.1111/j.1467-8659.2008.01165.x.
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Faison, M. D., W. M. Goss та P. J. Diamond. "Mapping Small Scale Structure in Galactic H ɪ with the VLBA". International Astronomical Union Colloquium 164 (1998): 289–90. http://dx.doi.org/10.1017/s0252921100045607.
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AbstractWe present the first VLBA maps of Galactic H ɪ opacity towards the QSO 3C 138. The maps show significant opacity structure down to angular scales of 20 mas, which implies density structures in the cold neutral medium on physical scales of 10 AU or less
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C. Balachandran, Suchitra. "Beryllium in the Sun: Re-Measurement and Implications." Symposium - International Astronomical Union 198 (2000): 383–88. http://dx.doi.org/10.1017/s0074180900166951.
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The solar beryllium abundance is important because it provides a constraint on the depth to which mixing has occurred below the surface convective zone. Unlike helioseismology which only maps the present-day Sun, the solar beryllium abundance provides an integrated picture of mixing over the entire history of the Sun. In this review I outline the logic involving the ‘missing UV opacity’ that required that the solar beryllium abundance be re-determined. A brief summary of the empirical process of estimating the “missing UV opacity” is given along with a confirmation based on a recent re-calculation of the Fe I bound-free opacity. The addition of this opacity resulted in our finding that the solar beryllium abundance was meteoritic. The implications of this result in the context of mixing in solar-type stars is discussed.
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Bastien, Pierre, and Roger Hajjar. "Density Distribution in Disks around Protostellar Objects." Symposium - International Astronomical Union 202 (2004): 322–24. http://dx.doi.org/10.1017/s0074180900218135.
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A new method to find the density distribution in disks around protostellar objects, based on linear polarization maps, is presented. This method uses the displacement of the polarization null points as a function of wavelength. Variations in optical depth are converted into density variations with opacity tables for dust grains. The method has been applied with five linear polarization maps obtained at different wavelengths of the classical T Tauri star HL Tau. The slope of the density as a function of radius in the disk is compatible with the model of the standard protosolar nebula. The total mass of the disk is compatible with values determined by other methods. Other objects have been analyzed, with similar results, although with a smaller number of wavelength bands.
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Ott, Jürgen, Tony Wong, Jorge L. Pineda, et al. "The Molecular Ridge Close to 30 Doradus in the Large Magellanic Cloud." Publications of the Astronomical Society of Australia 25, no. 3 (2008): 129–37. http://dx.doi.org/10.1071/as07054.
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AbstractWith the ATNF Mopra telescope we are performing a survey in the 12CO(1–0) line to map the molecular gas in the Large Magellanic Cloud. For some regions we also obtained interferometric maps of the high density gas tracers HCO+ and HCN with the Australia Telescope Compact Array. Here we discuss the properties of the elongated molecular complex that stretches about 2 kpc southward from 30 Doradus. Our data suggest that the complex, which we refer to as the ‘molecular ridge’, is not a coherent feature but consists of many smaller clumps that share the same formation history. Likely triggers of molecular-cloud formation are shocks and shearing forces that are present in the surrounding south-eastern Hi overdensity region, a region influenced by strong ram pressure and tidal forces. The molecular ridge is at the western edge of the the overdensity region where a bifurcated velocity structure transitions into a single disk velocity component. We find that the 12CO(1–0) and Hi emission peaks in the molecular ridge are typically near each other but never coincide. A likely explanation is the conversion of warmer, low-opacity Hi to colder, high-opacity Hi from which H2 subsequently forms. On smaller scales we find that very dense molecular gas, as traced by interferometric HCO+ and HCN maps, is associated with star formation along shocked filaments and with rims of expanding shell-like structures, both created by feedback from massive stars.
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Ogaki, Shinji. "Generalized Light Portals." Proceedings of the ACM on Computer Graphics and Interactive Techniques 3, no. 2 (2020): 1–19. http://dx.doi.org/10.1145/3406176.
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Light portals are useful for accelerating the convergence of Monte Carlo path tracing when rendering interiors. However, they are generally limited to flat polygonal shapes. In this paper, we introduce a new concept that allows existing polygon meshes with arbitrary shaders in a scene to be used as generalized light portals. We also present an efficient sampling method that takes into account the pixel values of the environment map and ray guiding two-dimensional textures that are typically opacity or transparency maps. This novel sampling strategy can be combined with other sampling techniques by using multiple importance sampling.
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Brovelli, M. A., F. C. Fahl, M. Minghini, and M. E. Molinari. "LAND USER AND LAND COVER MAPS OF EUROPE: A WEBGIS PLATFORM." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-B7 (June 22, 2016): 913–17. http://dx.doi.org/10.5194/isprsarchives-xli-b7-913-2016.
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This paper presents the methods and implementation processes of a WebGIS platform designed to publish the available land use and land cover maps of Europe at continental scale. The system is built completely on open source infrastructure and open standards. The proposed architecture is based on a server-client model having GeoServer as the map server, Leaflet as the client-side mapping library and the Bootstrap framework at the core of the front-end user interface. The web user interface is designed to have typical features of a desktop GIS (e.g. activate/deactivate layers and order layers by drag and drop actions) and to show specific information on the activated layers (e.g. legend and simplified metadata). Users have the possibility to change the base map from a given list of map providers (e.g. OpenStreetMap and Microsoft Bing) and to control the opacity of each layer to facilitate the comparison with both other land cover layers and the underlying base map. In addition, users can add to the platform any custom layer available through a Web Map Service (WMS) and activate the visualization of photos from popular photo sharing services. This last functionality is provided in order to have a visual assessment of the available land coverages based on other user-generated contents available on the Internet. It is supposed to be a first step towards a calibration/validation service that will be made available in the future.
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Brovelli, M. A., F. C. Fahl, M. Minghini, and M. E. Molinari. "LAND USER AND LAND COVER MAPS OF EUROPE: A WEBGIS PLATFORM." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-B7 (June 22, 2016): 913–17. http://dx.doi.org/10.5194/isprs-archives-xli-b7-913-2016.
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This paper presents the methods and implementation processes of a WebGIS platform designed to publish the available land use and land cover maps of Europe at continental scale. The system is built completely on open source infrastructure and open standards. The proposed architecture is based on a server-client model having GeoServer as the map server, Leaflet as the client-side mapping library and the Bootstrap framework at the core of the front-end user interface. The web user interface is designed to have typical features of a desktop GIS (e.g. activate/deactivate layers and order layers by drag and drop actions) and to show specific information on the activated layers (e.g. legend and simplified metadata). Users have the possibility to change the base map from a given list of map providers (e.g. OpenStreetMap and Microsoft Bing) and to control the opacity of each layer to facilitate the comparison with both other land cover layers and the underlying base map. In addition, users can add to the platform any custom layer available through a Web Map Service (WMS) and activate the visualization of photos from popular photo sharing services. This last functionality is provided in order to have a visual assessment of the available land coverages based on other user-generated contents available on the Internet. It is supposed to be a first step towards a calibration/validation service that will be made available in the future.
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Ott, Jürgen, David S. Meier, Nico Krieger, and Matthew Rickert. "SWAG: Survey of Water and Ammonia in the Galactic Center." Proceedings of the International Astronomical Union 11, S322 (2016): 143–44. http://dx.doi.org/10.1017/s1743921316011789.
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AbstractSWAG (“Survey of Water and Ammonia in the Galactic Center”) is a multi-line interferometric survey toward the Center of the Milky Way conducted with the Australia Telescope Compact Array. The survey region spans the entire ~400 pc Central Molecular Zone and comprises ~42 spectral lines at pc spatial and sub-km/s spectral resolution. In addition, we deeply map continuum intensity, spectral index, and polarization at the frequencies where synchrotron, free-free, and thermal dust sources emit. The observed spectral lines include many transitions of ammonia, which we use to construct maps of molecular gas temperature, opacity and gas formation temperature (see poster by Nico Krieger et al., this volume). Water masers pinpoint the sites of active star formation and other lines are good tracers for density, radiation field, shocks, and ionization. This extremely rich survey forms a perfect basis to construct maps of the physical parameters of the gas in this extreme environment.
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Chiarelli, Antonio M., Kathy A. Low, Edward L. Maclin, et al. "The Optical Effective Attenuation Coefficient as an Informative Measure of Brain Health in Aging." Photonics 6, no. 3 (2019): 79. http://dx.doi.org/10.3390/photonics6030079.
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Aging is accompanied by widespread changes in brain tissue. Here, we hypothesized that head tissue opacity to near-infrared light provides information about the health status of the brain’s cortical mantle. In diffusive media such as the head, opacity is quantified through the Effective Attenuation Coefficient (EAC), which is proportional to the geometric mean of the absorption and reduced scattering coefficients. EAC is estimated by the slope of the relationship between source–detector distance and the logarithm of the amount of light reaching the detector (optical density). We obtained EAC maps across the head in 47 adults (age range 18–75 years), using a high-density dual-wavelength optical system. We correlated regional and global EAC measures with demographic, neuropsychological, structural and functional brain data. Results indicated that EAC values averaged across wavelengths were strongly associated with age-related changes in cortical thickness, as well as functional and neuropsychological measures. This is likely because the EAC largely depends on the thickness of the sub-arachnoid cerebrospinal fluid layer, which increases with cortical atrophy. In addition, differences in EAC values between wavelengths were correlated with tissue oxygenation and cardiorespiratory fitness, indicating that information about cortical health can be derived non-invasively by quantifying the EAC.
Dissertations / Theses on the topic "Opacity maps"
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Vinkelis, Mindaugas. "Pusiau skaidrių kūnų apšvietimo modeliavimo metodai trimatėje grafikoje." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2008. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2008~D_20080716_101352-97248.
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Šiame darbe pateikiamas apšvietimo algoritmas pusiau skaidriems, vientisiems kūnams, kai šviesos sklidimas gali būti išreikštas BTDF, algoritmas pritaikomas spalvotiems šešėliams. Jis yra realaus laiko, ir gali būti pilnai realizuojamas šiuolaikiniuose trimačio vaizdo spartintuvuose. Algoritmas suskaido vaizduojamą objektą į sluoksnius ir kiekviename sluoksnyje saugo informaciją apie tai, kiek šviesos sugeriama tame sluoksnyje, ir kokioje pozicijoje spindulys atsitrenkė į matomą objekto paviršių. Konkretaus taško piešimo metu imama informacija iš atitinkamo sluoksnio (peršviečiamumo žemėlapio) ir šviesos sugėrimo stiprumas tiesiškai interpoliuojamas tarp skirtinguose žemėlapiuose saugomų atstumų.<br>This thesis focuses on partially transparent objects lighting, where light distribution may be written in BTDF1, algorithm supports multi-colored shadows. It is real-time method and can be fully implemented in modern graphics hardware. Algorithm divides object into layers, in each of them is stored information about how much light is absorbed in that layer, and where light hit visible object surface. On rendering particular point we take appropriate layer (opacity map) and light absorption intensity is linearly interpolated between different distances stored in other opacity maps.
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Rådahl, Elmer. "Extinction in the solar neighborhood : A comparative study of two methods used to measure reddening towards individual stars." Thesis, Uppsala universitet, Observationell astrofysik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-296426.
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Interstellar extinction and reddening are inescapable sources of uncertainty in the study of astronomical objects. Many creative ways to measure its effects have been developed, two of them being evaluated in this study. I apply two recently improved methods to estimate extinction toward individual stars, one based on interstellar absorption of sodium and the other based on opacity maps of the interstellar medium. The methods are applied to 14 stars in the local neighborhood, all within a distance of 250 pc from the Sun, and their results are compared. I find that both methods have severe limitations and large uncertainties, but can still be useful under the right conditions. I also provide suggestions on how the methods can be improved.<br>Interstellär extinktion och rödfärgning är oundvikliga osäkerhetskällor i studiet av astronomiska objekt. Många kreativa sätt att mäta dess effekter har utvecklats, av vilka två utvärderas i denna studie. Jag tillämpar två nyligen förbättrade metoder för att uppskatta utsläckning mot enskilda stjärnor, en baserad på interstellär absorption av natrium och den andra baserad på opacitetskartor över det interstellära mediet. Metoderna tillämpas på 14 stjärnor i solens närområde, alla inom ett avstånd av 250 pc, och deras resultat jämförs. Jag finner att båda metoderna har allvarliga begränsningar och stora osäkerheter, men ändå kan vara användbara under rätt förutsättningar. Jag ger också förslag på hur metoderna kan förbättras.
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Jehl, Augustin. "Etude photométrique de la surface de Mars à partir de la caméra HRSC à bord de la sonde Mars ExpressPréparation aux observation orbitale multi-angulaire en exploration planétaire." Phd thesis, Université Paul Sabatier - Toulouse III, 2008. http://tel.archives-ouvertes.fr/tel-00276278.
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Parmi les études novatrices que l'on peut aborder depuis l'orbite martienne en utilisant les données multiangulaires de l'instrument HRSC (canaux nadir, stéréographique et photométrique) de Mars Express, figure la détermination des caractéristiques physiques de la surface, pour cartographier les variations des propriétés physiques des sols et des roches de Mars et les relier aux observations spectroscopiques et thermiques réalisées par les instruments OMEGA, TES et THEMIS. <br /> Les modèles de Minnaert et de fonction de phase à deux termes de Hapke s'accordent pour démontrer que les observations multiangulaires de HRSC acquises au cours de la mission sur le cratère Gusev et le flanc sud de Apollinaris peuvent, sous certaines limites, être assemblées pour produire une fonction de phase couvrant un grand intervalle d'angles de phase (5-95°) avec une résolution spatiale de l'ordre de 400 mètres à 1.6 kilomètres.<br /><br />Combiné à la rugosité de surface, l'effet d'opposition joue un rôle significatif, <br />suggérant que les propriétés optiques de l'état de surface au niveau de Gusev sont fortement influencées par la porosité, l'état de compaction et l'organisation de la couche superficielle du régolite. L'aspect cartographique de la présente étude photométrique est utile pour donner une meilleure signification aux variations observées. Selon les tendances générales de cette analyse, il est très probable que la variation photométrique observée, au moins pour les régions centre et Ouest du cratère Gusev, soit partiellement due aux régimes des vents dominants, ces derniers ayant une orientation Nord - Nord Ouest / Sud - Sud Est et induisant une perturbation de la couche supérieure de la surface. Les résultats de cette étude photométrique sont en accord avec des études indépendantes basées sur les données orbitales d'inertie thermique et de spectroscopie de réflectance, et également des données photométriques et d'imagerie microscopique réalisées in situ par les instrument du rover Spirit. Cela conforte l'idée de l'existence en surface d'une couche composée de poussière à grains fins qui aurait été enlevée au niveau des unités de faible albédo révélant ainsi un substrat basaltique sombre formé de matériaux à grains plus grossiers. <br /><br />Ces résultats ouvrent de nouvelles possibilités pour documenter les processus de surface sur les planètes.
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Jehl, Augustin. "Etude photométrique de la surface de Mars à partir de la caméra HRSC à bord de la sonde Mars express : préparation aux observations orbitales multi-angulaires en exploration planétaire." Toulouse 3, 2008. http://www.theses.fr/2008TOU30091.
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Parmi les études novatrices que l'on peut aborder depuis l'orbite martienne en utilisant les données multiangulaires de l'instrument HRSC (canaux nadir, stéréographique et photométrique) de Mars Express, figure la détermination des caractéristiques physiques de la surface, pour cartographier les variations des propriétés physiques des sols et des roches de Mars et les relier aux observations spectroscopiques et thermiques réalisées par les instruments OMEGA, TES et THEMIS. Les modèles de Minnaert et de fonction de phase à deux termes de Hapke s'accordent pour démontrer que les observations multiangulaires de HRSC acquises au cours de la mission sur le cratère Gusev et le flanc sud de Apollinaris peuvent, sous certaines limites, être assemblées pour produire une fonction de phase couvrant un grand intervalle d'angles de phase (5-95°) avec une résolution spatiale de l'ordre de 400 mètres à 1. 6 kilomètres. Combiné à la rugosité de surface, l'effet d'opposition joue un rôle significatif, suggérant que les propriétés optiques de l'état de surface au niveau de Gusev sont fortement influencées par la porosité, l'état de compaction et l'organisation de la couche superficielle du régolite. L'aspect cartographique de la présente étude photométrique est utile pour donner une meilleure signification aux variations observées. Selon les tendances générales de cette analyse, il est très probable que la variation photométrique observée, au moins pour les régions centre et Ouest du cratère Gusev, soit partiellement due aux régimes des vents dominants, ces derniers ayant une orientation Nord - Nord Ouest / Sud - Sud Est et induisant une perturbation de la couche supérieure de la surface. .<br>One of the new investigations from orbit that can be addressed with the multi-angular HRSC/ Mars-Express dataset generated with the nadir-looking, stereo and photometric channels, is to derive the surface photometric characteristics for mapping the variation of the soil/bedrock physical properties of Mars, and to relate them to the spectroscopic and thermal observations produced by OMEGA, TES and THEMIS instruments. Minnaert and two-term phase function Hapke models concur to demonstrate that HRSC multi-angular observations acquired over Gusev crater and Apollinaris southern flank along the ongoing Mars-Express mission can be, under some limitations, pieced together to derive integrated phase functions over a wide range of phase angles (5-95°) at moderate spatial resolution on the order of 400 m-1. 6 km. In combination with the surface roughness variation, the opposition effect appears to play a significant role suggesting that the surface state optical properties across Gusev are strongly influenced by the porosity and packing characteristics of the upper layer of the Martian regolith. The mapping aspect of the present photometric investigation is quite useful to get a better sense of the meaning of the observed variations. Given the overall patterns derived from this analysis, it is quite likely that the observed photometric variation at least for the western and central part of Gusev crater is partly driven by the prevailing wind regimes considered to be oriented north-northwest / south-southeast and disturbing the very upper surface layer. .
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Bean, Keri Marie. "Determining Nighttime Atmospheric Optical Depth Using Mars Exploration Rover Images." Thesis, 2013. http://hdl.handle.net/1969.1/151097.
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Martian clouds and dust play an important part of the radiative transfer and energy balance budget. To assist in fully understanding the impact of clouds and dust, the complete diurnal cycle needs to be characterized. One of the best methods to track diurnal variations on Mars is by measuring optical depth. The spatial and temporal trends of optical depth give insight into the dust and water cycles of the Martian atmosphere.
Until now, spacecraft could only obtain optical depth during the day. In this thesis, nighttime images from the Mars Exploration Rover Spirit are used to calculate nighttime optical depth using photometric methods to capture star flux. Bright stars in well-known constellations are used in this analysis. The observed flux was compared to the expected flux to give nighttime optical depth values. The observed nighttime optical depth was consistently similar to the daytime optical depth values on both an individual image and sol-averaged basis.
Recommendations are made going forward to use the Mars Science Laboratory Curiosity for conducting an optimal nighttime optical depth campaign to fully characterize the diurnal dust and water cycles of Mars. The Curiosity rover is well suited for nighttime imaging and can potentially provide valuable insight into the nighttime dust and cloud trends.
Books on the topic "Opacity maps"
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Saha, Prasenjit, and Paul A. Taylor. The Main Sequence of Stars. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198816461.003.0007.
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This chapter introduces the basics of radiative transfer, which is a primary energy-transport mechanism inside stars, and also contributes to keeping stars ‘inflated’ and balanced against gravity. The roles of opacity and cross-sections in scattering photons are described. With the help of some drastic but still insightful approximations, the luminosity of a star can be related to its mass, and its surface temperature to its interior temperature. Not all types of stars are covered with analytical approximations, and only the simplest cases are studied here: the high-mass main sequence stars where radiation-pressure dominates, and the intermediate mass range that includes the Sun, where gas pressure dominates but convection is not yet important.
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Jones, Benjamin. The electric vehicle revolution: Economic and policy implications for natural resource exporters in developing countries. UNU-WIDER, 2020. http://dx.doi.org/10.35188/unu-wider/2020/915-0.
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The emergence of a mass market for electric vehicles (EVs) offers considerable development opportunities for resource exporters, given their intensive raw material requirements, including for cobalt, nickel, lithium, copper, aluminium, and manganese. To exploit the benefits of new demand, empirical evidence on the ‘resource curse’ increasingly points to the benefits of strengthening institutions for effective policy management and to mitigate the risk of poorly directed, often excessively procyclical, investment. With many developing countries staking major claims for expanding domestic electric vehicle raw material industries, these issues appear highly pertinent, not least given their complexity, opacity, and volatility. This paper analyses both the outlook for electric vehicle demand and associated raw material usage, as well as the key drivers and sensitivities required to track future market transformation. It subsequently assesses key fiscal, regulatory, and institutional reform priorities and market barriers bearing on successful domestic resource mobilization in these resource chains.
Book chapters on the topic "Opacity maps"
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Kim, Tae-Yong, and Ulrich Neumann. "Opacity Shadow Maps." In Eurographics. Springer Vienna, 2001. http://dx.doi.org/10.1007/978-3-7091-6242-2_16.
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Whitworth, Anthony, and Douglas Boyd. "Minimum Mass for Opacity-Limited Fragmentation in Dynamically Triggered Star Formation." In The Initial Mass Function 50 Years Later. Springer Netherlands, 2005. http://dx.doi.org/10.1007/978-1-4020-3407-7_65.
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Dziembowski, W. A. "The New Opacites and B-Star Pulsations." In Pulsation, Rotation and Mass Loss in Early-Type Stars. Springer Netherlands, 1994. http://dx.doi.org/10.1007/978-94-011-1030-3_20.
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Walsh, Michael. "Transparency Versus Opacity in Aboriginal Placenames." In The Land is a Map: Placenames of Indigenous Origin in Australia. ANU Press, 2009. http://dx.doi.org/10.22459/lm.03.2009.03.
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Walker, Christopher M. "Upper and Middle Lobe Atelectasis." In Chest Imaging. Oxford University Press, 2019. http://dx.doi.org/10.1093/med/9780199858064.003.0017.
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Upper and middle lobe atelectasis discusses the radiographic and computed tomography (CT) manifestations of upper and middle lobe atelectasis. The most common radiographic signs of right upper lobe atelectasis include upward and medial displacement of the minor fissure, superior displacement of adjacent structures such as the hilum and main bronchus, and ipsilateral shift of the mediastinal structures. The S sign of Golden results from a centrally obstructing lung cancer as the cause of the atelectasis and manifests as a reverse S configuration of the minor fissure outlined by atelectatic lung and central mass. Left upper lobe atelectasis manifests with a veil-like opacity on frontal radiography with leftward shift of upper mediastinal structures such as the trachea and upward shift of the left main bronchus and left hemidiaphragm. The Luftsichel sign or air crescent sign may be seen and represents the hyperexpanded superior segment of the left lower lobe outlining the transverse aortic arch. Lobar atelectasis in the inpatient setting is most commonly secondary to an obstructing mucus plug. Lobar atelectasis in the outpatient setting is often a heralding sign of a centrally obstructing lung cancer and should be further evaluated with contrast-enhanced CT and/or bronchoscopy.
Conference papers on the topic "Opacity maps"
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Zemba, Stephen G., Edmund A. C. Crouch, Michael E. Miller, and Laura C. Green. "Pink Sky in the Morning, Should There Be a Warning?" In 2013 21st Annual North American Waste-to-Energy Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/nawtec21-2721.
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Unexpected and unusual emissions from a large, mass-burn, waste-to-energy facility caused persistent and elevated opacity readings of the facility’s continuous opacity monitor (COM), and generated a visible pink-purple-tinted plume emanating from the exhaust stack. Non-radioactive iodine associated with medical wastes was determined to be responsible. As iodine is a known respiratory irritant, questions arose regarding potential short-term health risks to nearby residents. The rate of emission of the apparent release was estimated by two different methods, and then compared with facility-specific knowledge of waste composition. First, based on inverse, worst-case air dispersion modeling, the level of iodine emission that would be necessary to cause potential discomfort/mild irritation to people living near the facility was determined. Second, the level of iodine emission that would be necessary to account for elevations of in-stack opacity observed throughout the event was calculated. The level of iodine emissions necessary to cause mild health effects was found to be substantially greater than the actual release level as inferred from the opacity data. Moreover, based on descriptions of visual inspections of the waste stream and potential opacity interferences created by complex in-stack chemistry, it is likely that the opacity-based calculations overestimate the amount of iodine released. Accordingly, actual impacts are likely to have been smaller than those estimated herein. This paper discusses the process and procedures used to assess the health risk from this incident.
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Yue, Lindsey, Nathan Schroeder, and Clifford K. Ho. "Particle Flow Testing of a Multistage Falling Particle Receiver Concept: Staggered Angle Iron Receiver (STAIR)." In ASME 2020 14th International Conference on Energy Sustainability. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/es2020-1666.
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Abstract Falling particle receivers are an emerging technology for use in concentrating solar power systems. In this work, a staggered angle iron receiver concept is investigated, with the goals of increasing particle curtain stability and opacity in a receiver. The concept consists of angle iron-shaped troughs placed in line with a falling particle curtain in order to collect particles and rerelease them, decreasing the downward velocity of the particles and the curtain spread. A particle flow test apparatus has been fabricated. The effect of staggered angle iron trough geometry, orientation, and position on the opacity and uniformity of a falling particle curtain for different particle linear mass flow rates is investigated using the particle flow test apparatus. For the baseline free falling curtain and for different trough configurations, particle curtain transmissivity is measured, and profile images of the particle curtain are taken. Particle mass flow rate and trough position affect curtain transmissivity more than trough orientation and geometry. Optimal trough position for a given particle mass flow rate can result in improved curtain stability and decreased transmissivity. The case with a slot depth of 1/4″, hybrid trough geometry at 36″ below the slot resulted in the largest improvement over the baseline curtain: 0.40 transmissivity for the baseline and 0.14 transmissivity with the trough. However, some trough configurations have a detrimental effect on curtain stability and result in increased curtain transmissivity and/or substantial particle bouncing.
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Ho, Clifford K., Joshua M. Christian, David Romano, Julius Yellowhair, and Nathan Siegel. "Characterization of Particle Flow in a Free-Falling Solar Particle Receiver." In ASME 2015 9th International Conference on Energy Sustainability collocated with the ASME 2015 Power Conference, the ASME 2015 13th International Conference on Fuel Cell Science, Engineering and Technology, and the ASME 2015 Nuclear Forum. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/es2015-49421.
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Falling particle receivers are being evaluated as an alternative to conventional fluid-based solar receivers to enable higher temperatures and higher efficiency power cycles with direct storage for concentrating solar power applications. This paper presents studies of the particle mass flow rate, velocity, particle-curtain opacity and density, and other characteristics of free-falling ceramic particles as a function of different discharge slot apertures. The methods to characterize the particle flow are described, and results are compared to theoretical and numerical models for unheated conditions.
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Christian, Joshua, Clifford Ho, William Kolb, John Kelton, and Daniel Ray. "Design and Evaluation of an On-Sun Prototype Falling-Particle Cavity Receiver." In ASME 2014 8th International Conference on Energy Sustainability collocated with the ASME 2014 12th International Conference on Fuel Cell Science, Engineering and Technology. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/es2014-6446.
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Cavity receivers have been an integral part of Concentrated Solar Power (CSP) plants for many years. However, falling solid particle receivers (SPR) which employ a cavity design are only in the beginning stages of on-sun testing and evaluation. A prototype SPR has been developed which will be fully integrated into a complete system to demonstrate the effectiveness of this technology in the CSP sector. The receiver is a rectangular cavity with an aperture on the north side, open bottom (for particle collection), and a slot in the top (particle curtain injection). The solid particles fall from the top of the cavity through the solar flux and are collected after leaving the receiver. There are inherent design challenges with this type of receiver including particle curtain opacity, high wall fluxes, high wall temperatures, and high heat losses. CFD calculations using ANSYS FLUENT were performed to evaluate the effectiveness of the current receiver design. The particle curtain mass flow rate needed to be carefully regulated such that the curtain opacity is high (to intercept as much solar radiation as possible), but also low enough to increase the average particle temperature by 200°C. Wall temperatures were shown to be less than 1200°C when the particle curtain mass flow rate is 2.7 kg/s/m which is critical for the receiver insulation. The size of the cavity was shown to decrease the incident flux on the cavity walls and also reduced the wall temperatures. A thermal efficiency of 92% was achieved, but was obtained with a higher particle mass flow rate resulting in a lower average particle temperature rise. A final prototype receiver design has been completed utilizing the computational evaluation and past CSP project experiences.
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Kumar, Apurv, Jin-Soo Kim, and Wojciech Lipiński. "Radiation Characteristics of a Particle Curtain in a Free-Falling Particle Solar Receiver." In ASME 2017 Heat Transfer Summer Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/ht2017-5117.
Full textAbstract:
Radiation absorption by a particle curtain formed in a solar free falling particle receiver is investigated using a Eulerian-Eulerian granular two-phase model to solve the two-dimensional mass and momentum equations (CFD). The radiative transfer equation is subsequently solved by the Monte-Carlo (MC) ray-tracing technique using the CFD results to quantify the radiation intensity through the particle curtain. The CFD and MC results provide reliable opacity predictions and are validated with the experimental results available in literature. The particle curtain was found to absorb the solar radiation efficiently for smaller particles at high flowrates due to higher particle volume fraction and increased radiation extinction. However, at low mass-flowrates the absorption efficiency decreases for small and large particles.
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Niemi, Seppo, Jukka Pippola, Pekka Nousiainen, and Mika Laure´n. "Reduction of Particle Number and Mass Emissions of a Modern Off-Road Diesel Engine." In ASME 2009 Internal Combustion Engine Division Fall Technical Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/icef2009-14011.
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The oxides of nitrogen (NOx) and particulate matter (PM) form the main challenge for diesel engine exhaust cleaning. Despite the emissions reduction, the fuel economy should be kept at a sufficient level to also prevent CO2 increase. In the present project, a turbocharged, inter-cooled, common-rail, direct-injection, off-road diesel engine, largely used in tractors, forest machines etc., is optimized to make the engine comply with the US EPA Tier 4i/4 emissions legislation. The present study focused on pulse turbocharging and open-flow or partial diesel particulate filter system (pDPF). PM mass and PM number concentrations were determined both up- and downstream the pDPF. The engine was operated according to the steady and transient non-road emissions cycles (NRSC, Non-Road Steady Cycle; NRTC, Non-Road Transient Cycle, respectively). The main aim of the current study was to reduce PM emissions since a catalyst based on SCR technology was selected for NOx removal. Clear benefits in PM emissions were achieved with pulse turbocharging, especially during the transient engine operation. A very slight increase in the brake specific NOx (BSNOx) was detected with both studied pulse manifolds while PM decreased by 20% or more. CO also decreased clearly with Pulse 1 but HC remained almost constant. The opacity peaks recorded during the NRTC measurement also decreased considerably compared with the baseline constant-pressure turbocharging. The pDPF also proved efficient both for particle number levels and PM mass. In steady-state engine operation, the DOC containing filter system removed exhaust CO and HC effectively. BSNOx also decreased slightly. The exhaust particle number generally decreased usually the more, the larger the particles. Over the transient cycle with the pDPF, the weighed PM decreased by 77% and was clearly below the US EPA Tier 4i limit. The filter also reduced smoke opacity peaks effectively. The BSNOx decreased more than in the steady cycle, as did CO and HC.
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Osara, Jude A., Timothy T. Diller, Matthew J. Hall, Ronald D. Matthews, and Jakob Heinrich. "Particulate Matter Emissions From a High-Emitting Diesel Vehicle Measured With an On-Board Electronic PM Sensor." In ASME 2010 Internal Combustion Engine Division Fall Technical Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/icef2010-35055.
Full textAbstract:
Measurements of time-resolved particulate matter emissions from a high-emitting light-duty diesel vehicle were made using an electronic particulate matter sensor developed at the University of Texas. The sensor, which is threaded directly through the exhaust pipe wall, detects the time-resolved mass concentration of carbonaceous PM in undiluted vehicle exhaust. The sensor works by detecting an electrical current that is created between two electrodes that have a large potential difference across them; a current is created when particles are present. The sensor was used to characterize the PM emissions from a Chevrolet Equinox SUV which had its original gasoline engine replaced with a 1.9 liter Fiat/Opel turbo-diesel. The vehicle was without a diesel particulate filter (DPF) and had transient PM emission concentrations during accelerations as high as 1000 g/m3. The sensor’s output closely followed exhaust opacity. PM emissions were found to be highest for rapid accelerations and were strongly correlated with pedal position, which can be taken as a surrogate for the fuel delivery per cycle. The sensor was calibrated against gravimetric filter measurements of dry PM mass captured from the vehicle’s exhaust in sample bags.
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Mills, Brantley, Reid Shaeffer, Clifford K. Ho, and Lindsey Yue. "Modeling the Thermal Performance of Falling Particle Receivers Subject to External Wind." In ASME 2019 13th International Conference on Energy Sustainability collocated with the ASME 2019 Heat Transfer Summer Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/es2019-3913.
Full textAbstract:
Abstract Falling particle receivers (FPRs) are an important component of future falling particle concentrating solar power plants to enable next-generation energy generation. High thermal efficiencies in a FPR are required to high thermodynamic efficiencies of the system. External winds can significantly impact the thermal performance of cavity-type FPRs primarily through changing the air flow in and out of the aperture. A numerical parametric study is performed in this paper to quantify the effect of wind on the thermal performance of a FPR. Wind direction was found to be a significant parameter that can affect the receiver thermal efficiency. The particle mass flow rate did not significantly change the overall effect of wind on the receiver. The receiver efficiency was strong function of the particle diameter, but this was primarily a result of varying curtain opacity with different diameters and not from varying effects with wind. Finally, the model was used to demonstrate that receiver efficiencies of 90% were achievable under the assumption that the effect of wind/advective losses were mitigated.
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Wong, Kau-Fui V., Bradley L. Bon, Santina Vu, and Sing Samedi. "Study of Nanofluid Natural Convection Phenomena in Rectangular Enclosures." In ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-41156.
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Buoyancy induced flows in rectangular enclosures using nanofluids were investigated. The effects of mass fraction concentration of nanoparticles, enclosure aspect ratio and inclination were observed. The nanofluid under investigation was a water-based alumina nanofluid. Since water exhibits an anomalous density extremum near 4°C the additional effect of buoyancy force reversal will also be observed. The opacity of nanofluid does not permit the use of particle image velocimetry, laser induced fluorescence or any other means of flow visualization or visual temperature measurement of the local fluid temperature. Therefore to investigate the temperature field a non-invasive method, namely ultrasound thermometry, will be used to observe the temperature field. The experimental enclosure was validated using water as the initial fluid; measured values of the local fluid temperature were compared with numerical simulations utilizing COMSOL Multiphysics. Nanofluid mass fractions of 10% and 25% were used for comparative purposes of the effects of concentration on the temperature field. Buoyancy force reversal effects were witnessed in both 10% and 25% concentrations. The nanofluid also prolonged the multicellular effects that occur in buoyancy inversion flows. A Rayleigh number inversion was observed for the 25% mass fraction nanofluid. The multicellular regime transitions to boundary layer regime at about Ra=1E+07 when the aspect ratio is 2.625 and at about Ra=2E+08 when the aspect ratio is 1.000, for different concentrations of nanofluid. For these concentrations of nanofluid and aspect ratio equal to 2.625, instability in the core region occurred at about Ra=1.2E+07.
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Wendel, Mark, Ashraf Abdou, and Bernard Riemer. "Choked-Flow Inlet Orifice Bubbler for Creating Small Bubbles in Mercury." In ASME 2013 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/fedsm2013-16017.
Full textAbstract:
Pressure waves created in liquid mercury pulsed spallation targets like the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory, induce cavitation damage on the target container. The cavitation damage is thought to limit the lifetime of the target for power levels at and above 1 MW. One way to mitigate the damage would be to absorb the pressure pulse energy into a dispersed population of small bubbles, however, creating a bubble size distribution that is sufficiently large and disperse in mercury is challenging due to the high surface tension. Also, measuring the population is complicated by the opacity and the high level of turbulent mixing. Recent advances in bubble diagnostics by batch sampling the mercury made it possible to compare bubble populations for different techniques in a SNS-1/20th scale test loop. More than 10 bubblers were tested and the most productive bubblers were taken for in-beam testing at the Los Alamos Neutron Science Center (LANSCE) WNR user facility. One bubbler design, referred to as the inlet-orifice bubbler, that showed moderate success in creating populations also has an added advantage that it could easily be included in the existing SNS full-scale mercury target configuration. Improvements to the bubbler were planned including a reduction of the nozzle size to choke the gas injection, thus steadying the injected mass flow and allowing multiple nozzles to work off of a common plenum. For the first time, reliable bubble population data are available in the prototypical target geometry and can be compared with populations that mitigated cavitation damage. This paper presents those experimental results.