The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Robert Minařík - One of the best experts on this subject based on the ideXlab platform.
-
3-D reconstruction of an abandoned montane reservoir using UAV photogrammetry, aerial LiDAR and Field Survey
Applied Geography, 2018Co-Authors: Jakub Langhammer, Jan Kocum, Bohumír Janský, Robert MinaříkAbstract:The small reservoirs in the European montane landscape, which were built in past centuries for various purposes, represent specific cultural and technical heritage but also feature retention potential for mitigating the emerging impacts of climate change, namely, the course of flooding or droughts. However, the frequent lack of technical data on these historical structures, including their storage volume and flooded areas, prevents their consideration in water management planning. In this study, we used unmanned aerial vehicles (UAVs) to produce a detailed 3-D reconstruction of an abandoned montane reservoir that was built for timber flowing in the beginning of 19th century and that has not recently been used for any purpose. The UAV imaging and photogrammetric processing provided an ultra-high-resolution 3-D model of the reservoir basin (5 cm per pixel). Bathymetric analyses were performed based on this basin model to calculate the reservoir volume and flooded area for different water levels. The reliability of the UAV-based model was tested by comparing the results with those of elevation models derived from geodetic Field Survey using a total station and from conventional data sources based on available aerial LiDAR data. The data were compared to the historical estimates of the reservoir parameters found in the literature. Bathymetric reconstruction of the reservoir properties based on high-resolution UAV data revealed significant retention potential of the structure and historical underestimation of its capacity. The highly detailed UAV-based model helped to eliminate inaccuracies, resulting from the use of the generalized conventional elevation data, that affect the volumetric estimates in the flat topography of the reservoir basin. The study demonstrated the potential applicability of UAV technology for rapid and reliable reconstruction of landscape structures, which is significant for water management.
Kate Brand - One of the best experts on this subject based on the ideXlab platform.
-
mid infrared variability from the spitzer deep wide Field Survey
The Astrophysical Journal, 2010Co-Authors: Szymon Kozlowski, M L N Ashby, D Stern, M Brodwin, C S Kochanek, C Borys, Kate Brand, R J Assef, J Bock, M J I BrownAbstract:We use the multi-epoch, mid-infrared Spitzer Deep Wide-Field Survey to investigate the variability of objects in 8.1 deg^2 of the NOAO Deep Wide Field Survey Bootes Field. We perform a Difference Image Analysis of the four available epochs between 2004 and 2008, focusing on the deeper 3.6 and 4.5 μm bands. Out of 474, 179 analyzed sources, 1.1% meet our standard variability selection criteria that the two light curves are strongly correlated (r > 0.8) and that their joint variance (σ_(12)) exceeds that for all sources with the same magnitude by 2σ. We then examine the mid-IR colors of the variable sources and match them with X-ray sources from the XBootes Survey, radio catalogs, 24 μm selected active galactic nucleus (AGN) candidates, and spectroscopically identified AGNs from the AGN and Galaxy Evolution Survey (AGES). Based on their mid-IR colors, most of the variable sources are AGNs (76%), with smaller contributions from stars (11%), galaxies (6%), and unclassified objects, although most of the stellar, galaxy, and unclassified sources are false positives. For our standard selection criteria, 11%-12% of the mid-IR counterparts to X-ray sources, 24 μm AGN candidates, and spectroscopically identified AGNs show variability. The exact fractions depend on both the search depth and the selection criteria. For example, 12% of the 1131 known z>1 AGNs in the Field and 14%-17% of the known AGNs with well-measured fluxes in all four Infrared Array Camera bands meet our standard selection criteria. The mid-IR AGN variability can be well described by a single power-law structure function with an index of γ ≈ 0.5 at both 3.6 and 4.5 μm, and an amplitude of S _0 ≃ 0.1 mag on rest-frame timescales of 2 yr. The variability amplitude is higher for shorter rest-frame wavelengths and lower luminosities.
-
mid infrared variability from the spitzer deep wide Field Survey
arXiv: Cosmology and Nongalactic Astrophysics, 2010Co-Authors: Szymon Kozlowski, M L N Ashby, D Stern, M Brodwin, C S Kochanek, C Borys, Kate Brand, R J Assef, J Bock, M J I BrownAbstract:We use the multi-epoch, mid-infrared Spitzer Deep, Wide-Field Survey to investigate the variability of 474,179 objects in 8.1 deg^2 of the NDWFS Bootes Field. We perform a Difference Image Analysis of the four available epochs between 2004 and 2008, focusing on the deeper 3.6 and 4.5 micron bands. We find that 1.1% of the studied sample meet our standard selection criteria for being classed as a variable source. We require that the 3.6 and 4.5 micron light-curves are strongly correlated (r>0.8) and that their joint variance exceeds that for all sources with the same magnitude by 2 sigma. We then examine the mid-IR colors of the variable sources and match them with X-ray sources from the XBootes Survey, radio catalogs, 24 micron-selected AGN candidates, and spectroscopically identified AGNs from the AGN and Galaxy Evolution Survey (AGES). Based on their mid-IR colors, most of the variable sources are AGNs (76%), with smaller contributions from stars (11%), galaxies (6%), and unclassified objects. Most of the stellar, galaxy and unclassified sources are false positives. For our standard selection criteria, 11-12% of the mid-IR counterparts to X-ray sources, 24 micron-selected AGN candidates and spectroscopically identified AGNs show variability. Mid-IR AGN variability can be well described by a single power-law structure function with a power-law index of 0.5 at both 3.6 and 4.5 microns, and an amplitude of 0.1 mag on rest-frame time scales of 2 years. The variability amplitude is higher for shorter rest-frame wavelengths and lower luminosities. (Abridged)
-
the spitzer deep wide Field Survey
The Astrophysical Journal, 2009Co-Authors: M L N Ashby, D Stern, M Brodwin, Roger L Griffith, Peter Eisenhardt, Szymon Kozlowski, C S Kochanek, J J Bock, C Borys, Kate BrandAbstract:The Spitzer Deep, Wide-Field Survey (SDWFS) is a four-epoch infrared Survey of 10 deg^(2) in the Bootes Field of the NOAO Deep Wide-Field Survey using the IRAC instrument on the Spitzer Space Telescope. SDWFS, a Spitzer Cycle 4 Legacy project, occupies a unique position in the area-depth Survey space defined by other Spitzer Surveys. The four epochs that make up SDWFS permit-for the first time-the selection of infrared-variable and high proper motion objects over a wide Field on timescales of years. Because of its large Survey volume, SDWFS is sensitive to galaxies out to z ~ 3 with relatively little impact from cosmic variance for all but the richest systems. The SDWFS data sets will thus be especially useful for characterizing galaxy evolution beyond z ~ 1.5. This paper explains the SDWFS observing strategy and data processing, presents the SDWFS mosaics and source catalogs, and discusses some early scientific findings. The publicly released, full-depth catalogs contain 6.78, 5.23, 1.20, and 0.96 x 10^(5) distinct sources detected to the average 5 sigma, 4"-diameter, aperture-corrected limits of 19.77, 18.83, 16.50, and 15.82 Vega mag at 3.6, 4.5, 5.8, and 8.0 mu m, respectively. The SDWFS number counts and color-color distribution are consistent with other, earlier Spitzer Surveys. At the 6 minute integration time of the SDWFS IRAC imaging, > 50% of isolated Faint Images of the Radio Sky at Twenty cm radio sources and > 80% of on-axis XBootes sources are detected out to 8.0 mu m. Finally, we present the four highest proper motion IRAC-selected sources identified from the multi-epoch imaging, two of which are likely Field brown dwarfs of mid-T spectral class.
M L N Ashby - One of the best experts on this subject based on the ideXlab platform.
-
mid infrared variability from the spitzer deep wide Field Survey
The Astrophysical Journal, 2010Co-Authors: Szymon Kozlowski, M L N Ashby, D Stern, M Brodwin, C S Kochanek, C Borys, Kate Brand, R J Assef, J Bock, M J I BrownAbstract:We use the multi-epoch, mid-infrared Spitzer Deep Wide-Field Survey to investigate the variability of objects in 8.1 deg^2 of the NOAO Deep Wide Field Survey Bootes Field. We perform a Difference Image Analysis of the four available epochs between 2004 and 2008, focusing on the deeper 3.6 and 4.5 μm bands. Out of 474, 179 analyzed sources, 1.1% meet our standard variability selection criteria that the two light curves are strongly correlated (r > 0.8) and that their joint variance (σ_(12)) exceeds that for all sources with the same magnitude by 2σ. We then examine the mid-IR colors of the variable sources and match them with X-ray sources from the XBootes Survey, radio catalogs, 24 μm selected active galactic nucleus (AGN) candidates, and spectroscopically identified AGNs from the AGN and Galaxy Evolution Survey (AGES). Based on their mid-IR colors, most of the variable sources are AGNs (76%), with smaller contributions from stars (11%), galaxies (6%), and unclassified objects, although most of the stellar, galaxy, and unclassified sources are false positives. For our standard selection criteria, 11%-12% of the mid-IR counterparts to X-ray sources, 24 μm AGN candidates, and spectroscopically identified AGNs show variability. The exact fractions depend on both the search depth and the selection criteria. For example, 12% of the 1131 known z>1 AGNs in the Field and 14%-17% of the known AGNs with well-measured fluxes in all four Infrared Array Camera bands meet our standard selection criteria. The mid-IR AGN variability can be well described by a single power-law structure function with an index of γ ≈ 0.5 at both 3.6 and 4.5 μm, and an amplitude of S _0 ≃ 0.1 mag on rest-frame timescales of 2 yr. The variability amplitude is higher for shorter rest-frame wavelengths and lower luminosities.
-
mid infrared variability from the spitzer deep wide Field Survey
arXiv: Cosmology and Nongalactic Astrophysics, 2010Co-Authors: Szymon Kozlowski, M L N Ashby, D Stern, M Brodwin, C S Kochanek, C Borys, Kate Brand, R J Assef, J Bock, M J I BrownAbstract:We use the multi-epoch, mid-infrared Spitzer Deep, Wide-Field Survey to investigate the variability of 474,179 objects in 8.1 deg^2 of the NDWFS Bootes Field. We perform a Difference Image Analysis of the four available epochs between 2004 and 2008, focusing on the deeper 3.6 and 4.5 micron bands. We find that 1.1% of the studied sample meet our standard selection criteria for being classed as a variable source. We require that the 3.6 and 4.5 micron light-curves are strongly correlated (r>0.8) and that their joint variance exceeds that for all sources with the same magnitude by 2 sigma. We then examine the mid-IR colors of the variable sources and match them with X-ray sources from the XBootes Survey, radio catalogs, 24 micron-selected AGN candidates, and spectroscopically identified AGNs from the AGN and Galaxy Evolution Survey (AGES). Based on their mid-IR colors, most of the variable sources are AGNs (76%), with smaller contributions from stars (11%), galaxies (6%), and unclassified objects. Most of the stellar, galaxy and unclassified sources are false positives. For our standard selection criteria, 11-12% of the mid-IR counterparts to X-ray sources, 24 micron-selected AGN candidates and spectroscopically identified AGNs show variability. Mid-IR AGN variability can be well described by a single power-law structure function with a power-law index of 0.5 at both 3.6 and 4.5 microns, and an amplitude of 0.1 mag on rest-frame time scales of 2 years. The variability amplitude is higher for shorter rest-frame wavelengths and lower luminosities. (Abridged)
-
the spitzer deep wide Field Survey
The Astrophysical Journal, 2009Co-Authors: M L N Ashby, D Stern, M Brodwin, Roger L Griffith, Peter Eisenhardt, Szymon Kozlowski, C S Kochanek, J J Bock, C Borys, Kate BrandAbstract:The Spitzer Deep, Wide-Field Survey (SDWFS) is a four-epoch infrared Survey of 10 deg^(2) in the Bootes Field of the NOAO Deep Wide-Field Survey using the IRAC instrument on the Spitzer Space Telescope. SDWFS, a Spitzer Cycle 4 Legacy project, occupies a unique position in the area-depth Survey space defined by other Spitzer Surveys. The four epochs that make up SDWFS permit-for the first time-the selection of infrared-variable and high proper motion objects over a wide Field on timescales of years. Because of its large Survey volume, SDWFS is sensitive to galaxies out to z ~ 3 with relatively little impact from cosmic variance for all but the richest systems. The SDWFS data sets will thus be especially useful for characterizing galaxy evolution beyond z ~ 1.5. This paper explains the SDWFS observing strategy and data processing, presents the SDWFS mosaics and source catalogs, and discusses some early scientific findings. The publicly released, full-depth catalogs contain 6.78, 5.23, 1.20, and 0.96 x 10^(5) distinct sources detected to the average 5 sigma, 4"-diameter, aperture-corrected limits of 19.77, 18.83, 16.50, and 15.82 Vega mag at 3.6, 4.5, 5.8, and 8.0 mu m, respectively. The SDWFS number counts and color-color distribution are consistent with other, earlier Spitzer Surveys. At the 6 minute integration time of the SDWFS IRAC imaging, > 50% of isolated Faint Images of the Radio Sky at Twenty cm radio sources and > 80% of on-axis XBootes sources are detected out to 8.0 mu m. Finally, we present the four highest proper motion IRAC-selected sources identified from the multi-epoch imaging, two of which are likely Field brown dwarfs of mid-T spectral class.
Dongmei Zhou - One of the best experts on this subject based on the ideXlab platform.
-
Field Survey study on the difference in cd accumulation capacity of rice and wheat in rice wheat rotation area
Journal of Soils and Sediments, 2020Co-Authors: Jiangli Yang, Long Cang, Xia Wang, Hongting Xu, Dongmei ZhouAbstract:In the rice-wheat rotation area, Cd contamination affects food safety of rice and wheat. However, there have been conflicting results and different conclusions on the difference in Cd accumulation capacity of rice and wheat, and the factors that led to the difference were not clear. A Field Survey study was conducted by collecting 60 soil and grain samples in pairs during rice and wheat harvest in 30 long-term rice-wheat rotation areas with clean and mild Cd contamination in Jiangsu Province, China. The soil physicochemical properties, total Cd, soil available Cd, and grain Cd were determined, and the factors affecting Cd accumulation in rice and wheat were analyzed. The soil pH during wheat season (22 sampling points) was slightly higher than that during rice season; thus, soil available Cd in wheat was generally lower (with an average three times lower) than that in rice soil. The mean Cd content in rice grain was only half of that in wheat grain, and the Cd concentration in rice and bioconcentration factor of rice at 26 sampling points (86.7% of total samples) were lower than those of wheat, indicating that Cd accumulation capacity of wheat was stronger than that of rice. Pearson correlation coefficient and multivariate linear regression models revealed that the main factors affecting the difference of Cd accumulation in rice and wheat were soil pH and available Cd content in soil. The Cd accumulation capacity of wheat was higher than that of rice, especially in neutral and alkaline soil, and the Cd contents in rice and wheat grain depended on the soil pH and available Cd content. The food security risk of wheat was more noteworthy than rice in rice-wheat rotation area.
Szymon Kozlowski - One of the best experts on this subject based on the ideXlab platform.
-
mid infrared variability from the spitzer deep wide Field Survey
The Astrophysical Journal, 2010Co-Authors: Szymon Kozlowski, M L N Ashby, D Stern, M Brodwin, C S Kochanek, C Borys, Kate Brand, R J Assef, J Bock, M J I BrownAbstract:We use the multi-epoch, mid-infrared Spitzer Deep Wide-Field Survey to investigate the variability of objects in 8.1 deg^2 of the NOAO Deep Wide Field Survey Bootes Field. We perform a Difference Image Analysis of the four available epochs between 2004 and 2008, focusing on the deeper 3.6 and 4.5 μm bands. Out of 474, 179 analyzed sources, 1.1% meet our standard variability selection criteria that the two light curves are strongly correlated (r > 0.8) and that their joint variance (σ_(12)) exceeds that for all sources with the same magnitude by 2σ. We then examine the mid-IR colors of the variable sources and match them with X-ray sources from the XBootes Survey, radio catalogs, 24 μm selected active galactic nucleus (AGN) candidates, and spectroscopically identified AGNs from the AGN and Galaxy Evolution Survey (AGES). Based on their mid-IR colors, most of the variable sources are AGNs (76%), with smaller contributions from stars (11%), galaxies (6%), and unclassified objects, although most of the stellar, galaxy, and unclassified sources are false positives. For our standard selection criteria, 11%-12% of the mid-IR counterparts to X-ray sources, 24 μm AGN candidates, and spectroscopically identified AGNs show variability. The exact fractions depend on both the search depth and the selection criteria. For example, 12% of the 1131 known z>1 AGNs in the Field and 14%-17% of the known AGNs with well-measured fluxes in all four Infrared Array Camera bands meet our standard selection criteria. The mid-IR AGN variability can be well described by a single power-law structure function with an index of γ ≈ 0.5 at both 3.6 and 4.5 μm, and an amplitude of S _0 ≃ 0.1 mag on rest-frame timescales of 2 yr. The variability amplitude is higher for shorter rest-frame wavelengths and lower luminosities.
-
mid infrared variability from the spitzer deep wide Field Survey
arXiv: Cosmology and Nongalactic Astrophysics, 2010Co-Authors: Szymon Kozlowski, M L N Ashby, D Stern, M Brodwin, C S Kochanek, C Borys, Kate Brand, R J Assef, J Bock, M J I BrownAbstract:We use the multi-epoch, mid-infrared Spitzer Deep, Wide-Field Survey to investigate the variability of 474,179 objects in 8.1 deg^2 of the NDWFS Bootes Field. We perform a Difference Image Analysis of the four available epochs between 2004 and 2008, focusing on the deeper 3.6 and 4.5 micron bands. We find that 1.1% of the studied sample meet our standard selection criteria for being classed as a variable source. We require that the 3.6 and 4.5 micron light-curves are strongly correlated (r>0.8) and that their joint variance exceeds that for all sources with the same magnitude by 2 sigma. We then examine the mid-IR colors of the variable sources and match them with X-ray sources from the XBootes Survey, radio catalogs, 24 micron-selected AGN candidates, and spectroscopically identified AGNs from the AGN and Galaxy Evolution Survey (AGES). Based on their mid-IR colors, most of the variable sources are AGNs (76%), with smaller contributions from stars (11%), galaxies (6%), and unclassified objects. Most of the stellar, galaxy and unclassified sources are false positives. For our standard selection criteria, 11-12% of the mid-IR counterparts to X-ray sources, 24 micron-selected AGN candidates and spectroscopically identified AGNs show variability. Mid-IR AGN variability can be well described by a single power-law structure function with a power-law index of 0.5 at both 3.6 and 4.5 microns, and an amplitude of 0.1 mag on rest-frame time scales of 2 years. The variability amplitude is higher for shorter rest-frame wavelengths and lower luminosities. (Abridged)
-
the spitzer deep wide Field Survey
The Astrophysical Journal, 2009Co-Authors: M L N Ashby, D Stern, M Brodwin, Roger L Griffith, Peter Eisenhardt, Szymon Kozlowski, C S Kochanek, J J Bock, C Borys, Kate BrandAbstract:The Spitzer Deep, Wide-Field Survey (SDWFS) is a four-epoch infrared Survey of 10 deg^(2) in the Bootes Field of the NOAO Deep Wide-Field Survey using the IRAC instrument on the Spitzer Space Telescope. SDWFS, a Spitzer Cycle 4 Legacy project, occupies a unique position in the area-depth Survey space defined by other Spitzer Surveys. The four epochs that make up SDWFS permit-for the first time-the selection of infrared-variable and high proper motion objects over a wide Field on timescales of years. Because of its large Survey volume, SDWFS is sensitive to galaxies out to z ~ 3 with relatively little impact from cosmic variance for all but the richest systems. The SDWFS data sets will thus be especially useful for characterizing galaxy evolution beyond z ~ 1.5. This paper explains the SDWFS observing strategy and data processing, presents the SDWFS mosaics and source catalogs, and discusses some early scientific findings. The publicly released, full-depth catalogs contain 6.78, 5.23, 1.20, and 0.96 x 10^(5) distinct sources detected to the average 5 sigma, 4"-diameter, aperture-corrected limits of 19.77, 18.83, 16.50, and 15.82 Vega mag at 3.6, 4.5, 5.8, and 8.0 mu m, respectively. The SDWFS number counts and color-color distribution are consistent with other, earlier Spitzer Surveys. At the 6 minute integration time of the SDWFS IRAC imaging, > 50% of isolated Faint Images of the Radio Sky at Twenty cm radio sources and > 80% of on-axis XBootes sources are detected out to 8.0 mu m. Finally, we present the four highest proper motion IRAC-selected sources identified from the multi-epoch imaging, two of which are likely Field brown dwarfs of mid-T spectral class.
