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排序方式: 共有418条查询结果,搜索用时 15 毫秒
71.
D.L. Tucker S. Kent M.W. Richmond J. Annis J.A. Smith S.S. Allam C.T. Rodgers J.L. Stute J.K. Adelman‐McCarthy J. Brinkmann M. Doi D. Finkbeiner M. Fukugita J. Goldston B. Greenway J.E. Gunn J.S. Hendry D.W. Hogg S.‐I. Ichikawa
. Ivezi G.R. Knapp H. Lampeitl B.C. Lee H. Lin T.A. McKay A. Merrelli J.A. Munn E.H. Neilsen H.J. Newberg G.T. Richards D.J. Schlegel C. Stoughton A. Uomoto B. Yanny 《Astronomische Nachrichten》2006,327(9):821-843
The photometric calibration of the Sloan Digital Sky Survey (SDSS) is a multi‐step process which involves data from three different telescopes: the 1.0‐m telescope at the US Naval Observatory (USNO), Flagstaff Station, Arizona (which was used to establish the SDSS standard star network); the SDSS 0.5‐m Photometric Telescope (PT) at the Apache Point Observatory (APO), NewMexico (which calculates nightly extinctions and calibrates secondary patch transfer fields); and the SDSS 2.5‐m telescope at APO (which obtains the imaging data for the SDSS proper). In this paper, we describe the Monitor Telescope Pipeline, MTPIPE, the software pipeline used in processing the data from the single‐CCD telescopes used in the photometric calibration of the SDSS (i.e., the USNO 1.0‐m and the PT). We also describe transformation equations that convert photometry on the USNO‐1.0m u ′g ′r ′i ′z ′ system to photometry the SDSS 2.5m ugriz system and the results of various validation tests of the MTPIPE software. Further, we discuss the semi‐automated PT factory, which runs MTPIPE in the day‐to‐day standard SDSS operations at Fermilab. Finally, we discuss the use of MTPIPE in current SDSS‐related projects, including the Southern u ′g ′r ′i ′z ′ Standard Star project, the u ′g ′r ′i ′z ′ Open Star Clusters project, and the SDSS extension (SDSS‐II). (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
72.
Study of 1986 and 1987 heavy metal distribution in surface water of the Kuroshio area in the East China Sea showed regional and slight seasonal variations in distribution and concentration . Heavy metal levels in Taiwan Strait, the sea area north of Taiwan and the continental shelf are higher than those in the main axis of the Kuroshio . Dissolved Cu in summer and winter decreases with the increase of salinity , but dissolved Cd has no obvious change with salinity . 相似文献
73.
Masayuki UESUGI Takeshi AKAKI Minoru SEKIYA Tomoki NAKAMURA 《Meteoritics & planetary science》2005,40(7):1103-1114
Abstract— We calculated the trajectories of molten spheres of iron sulfide inclusions inside a melted chondrule during the nebular shock wave heating. Our calculations included the effects of high‐velocity internal flow in the melted chondrule and apparent gravitational force caused by the drag force of nebular gas flow. The calculated results show that large iron sulfide inclusions, which have radii 0.23 times larger than those of the parent chondrules, must reach the surface of the melted chondrule within a short period of time (<<1 s). This effect will provide us with very important information about chondrule formation by nebular shock wave heating. 相似文献
74.
Hidekazu Yoshida Koshi Yamamoto Yuki Murakami Nagayoshi Katsuta Toru Hayashi Takeshi Naganuma 《Environmental Geology》2008,55(6):1363-1374
Takashikozo is a phenomenon of Quaternary sediments in Japan. They are cylindrical Fe-oxyhydroxide nodules that form as plaques round
plant roots, where Fe is preferentially concentrated to develop a solid wall. Structural features suggest that after the roots
have decayed, the central space where the roots were situated acts as a flow path for oxidized water. Analysis of microbial
16S rDNA extracted from the nodules identified iron-oxidizing bacteria encrusted round the roots where they are the likely
initiators of nodule formation. Direct microscopic observation revealed an accumulation of Fe-oxyhydroxides that fill the
pore spaces and is also likely to be linked with the encrusting microbial colonies. Geological history and nanofossil evidence
suggest that these Fe-nodules may have been buried at a depth of up to several tens of meters for at least 105 years in reducing Quaternary sediments. Thus Fe-oxyhydroxide nodules that have formed in a geological environment at the
interfaces between water and rock by microbial mediation can persist under reducing conditions. If this is the case, the phenomenon
is significant as an analogue of post-closure conditions in radioactive waste repositories, since it could influence nuclide
migration. 相似文献
75.
Confined groundwater system in Tokyo 总被引:1,自引:0,他引:1
Takeshi Endo 《Environmental Geology》1992,20(1):21-34
The Musashino Terrace and the Shitamachi Lowland, the main urban areas in the Tokyo metropolis, are in the eastern part of Tokyo and are underlain by thick Quaternary sediments. The geologic structrue of these sediments has a general strike of WNW—ESE, with a gentle dip to the east in the western part of the Musashino Terrace, and strikes generally to the E—W with a gentle dip to the north in the eastern part of the terrace and strikes WNW—ESE to N—S with a very gentle dip to the east in the Shitamachi Lowland. The basal sediments in this area consist chiefly of massive thick silty layers, whereas the sediments overlying them consist of alternating layers of silt, sand, and gravel, which act as confined aquifers throughout the Musashino Terrace and the Shitamachi Lowland. Confined groundwater systems are being developed in the Tama District, the western part of the terrace, and are mainly recharged with river water from the Tama River. The unconfined groundwater system is being developed in the surface layers such as terrace sand and gravel formations and the Kanto Loam Formation. These confined aquifers that are being developed throughout the terrace and the lowland have been exploited for household water supplies and industrial and air-conditioning use for nearly seven decades. The heavy utilization of the confined groundwater, however, has caused a major lowering of groundwater levels. As a result of the lowering of groundwater levels, land subsidence has occurred all over the Lowland and the terrace. At this time the national government and the Tokyo Metropolitan Government restricted groundwater withdrawals for industrial, air-conditioning use and the others except for household supply. Owing to these restrictions, not only have the water levels recovered, but land subsidence has rapidly declined since around 1973. 相似文献
76.
Chiyoe Koike Hiroichi Hasegawa Noriaki Asada Takeshi Hattori 《Astrophysics and Space Science》1981,79(1):77-85
Extinction measurements were made for some silicate and iron-oxide mineral grains in mid- and far-infrared region. For far-infrared region, high temperature magnesium silicates such as olivine and pyroxenes show the absorption spectra of steep dependence as –3 ( being the wavelength) with some peak structure, but the spectrum of magnetite shows –1 dependence. 相似文献
77.
Isao Kudo Takeshi Yoshimura Choon-Weng Lee Mitsuru Yanada Yoshiaki Maita 《Journal of Oceanography》2007,63(5):791-801
Nutrient regeneration and oxygen consumption after a spring bloom in Funka Bay were studied on monthly survey cruises from
February to November 1998 and from March to December 1999. A high concentration of ammonium (more than 4 μmol l−1) was observed near the bottom (80–90 m) after April. Phosphate and silicate gradually accumulated and dissolved oxygen decreased
in the same layer. Salinity near the bottom did not change until summer, leading to the presumption that the system in this
layer is semi-closed, so regenerated nutrients were preserved until September. Nitrification due to the oxidation of ammonium
to nitrate was observed after June. Nitrite, an intermediate product, was detected at 4–7 μmol L−1 in June and July 1999. Assuming that decomposition is a first order reaction, the rate constant for decomposition of organic
nitrogen was determined to be 0.014 and 0.008 d−1 in 1998 and 1999, respectively. The ammonium oxidation rate increased rapidly when the ambient ammonium concentration exceeded
5 μmol L−1. We also performed a budget calculation for the regeneration process. The total amount of N regenerated in the whole water
column was 287.4 mmol N m−2 in 4 months, which is equal to 22.8 gC m−2, assuming the Redfield C to N ratio. This is 34% of the primary production during the spring bloom and is comparable to the
export production of 25 gC m−2 measured by a sediment trap at 60 m (Miyake et al., 1998). 相似文献
78.
The two-dimensional problem of wave transformation by, and motions of, moored floating objects is solved numerically as a boundary value problem by direct use of Green's identity formula for a potential function. The cross-sectional shape of the floating object, the bottom configuration and the mooring arrangements may be all arbitrary. For a given incident wave, the three modes of body motion, the wave system and mooring forces are all solved at the same time. A laboratory experiment is conducted to verify the theory. Generally good agreements between the theory and experiments are obtained as long as the viscous damping due to flow separation is small. A numerical experiment indicates that a conventional sluck mooring is to worsen the wave attenuation by a floating breakwater and that a properly arranged elastic mooring can considerably improve the wave attenuation by a floating breakwater. 相似文献
79.
Takeshi Nakatsuka Nobuhiko Handa Naomi Harada Tatsuhiro Sugimoto Shigemi Imaizumi 《Deep Sea Research Part I: Oceanographic Research Papers》1997,44(12)
Sinking particles were analyzed for their nitrogen isotopic ratio δ15N) of total particulate nitrogen (PN), stable carbon isotopic ratio (δ13C) and radioactive isotopic ratio (δ14C) of total particulate organic carbon (POC), at three different latitudinal (temperate, subpolar and equatorial) and geomorphological (trench, proximal abyssal plain and distal abyssal plain) sites in the western North Pacific Ocean using year-long time series sediment trap systems, to clarify the common vertical trends of the isotopic signals in deep water columns. Although the δ15N and δ13C values of sinking particulate organic matter (POM) were partly affected by the resuspension of sedimentary POM from the sea floor, especially in the trench, the changes in δ15N and δ13C values owing to the resuspension could be corrected by calculation of the isotopic mass balance from δ14C of sinking POC. After this correction, common downward decreasing trends in δ15N and δ13C values were obtained in the deep water columns, irrespective of the latitudes and depths. These coincidental isotopic signals between δ15N and δ13C values provide new constraints for the decomposition process of sinking POM, such as the preferential degradation of 15N- and 13C-rich compounds and the successive re-formation of the sinking particles by higher trophic level organisms in the deep water column. 相似文献
80.
Baroclinic eddies south of Cheju Island in the East China Sea 总被引:3,自引:0,他引:3
The detailed structures of baroclinic eddies, that is, an anticlockwise circulation in the upper layer and a clockwise one in the lower layer south of Cheju Island in the East China Sea have been revealed by intensive field observation. Such baroclinic eddies are accompanied by the southward spreading of the Yellow Sea Bottom Cold Water. 相似文献