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排序方式: 共有306条查询结果,搜索用时 140 毫秒
301.
We have investigated the characteristics of magnetic cloud (MC) and ejecta (EJ) associated coronal mass ejections (CMEs) based on the assumption that all CMEs have a flux rope structure. For this, we used 54 CMEs and their interplanetary counterparts (interplanetary CMEs: ICMEs) that constitute the list of events used by the NASA/LWS Coordinated Data Analysis Workshop (CDAW) on CME flux ropes. We considered the location, angular width, and speed as well as the direction parameter, D. The direction parameter quantifies the degree of asymmetry of the CME shape in coronagraph images, and shows how closely the CME propagation is directed to Earth. For the 54 CDAW events, we found the following properties of the CMEs: i) the average value of D for the 23 MCs (0.62) is larger than that for the 31 EJs (0.49), which indicates that the MC-associated CMEs propagate more directly toward the Earth than the EJ-associated CMEs; ii) comparison between the direction parameter and the source location shows that the majority of the MC-associated CMEs are ejected along the radial direction, while many of the EJ-associated CMEs are ejected non-radially; iii) the mean speed of MC-associated CMEs (946 km?s?1) is faster than that of EJ-associated CMEs (771 km?s?1). For seven very fast CMEs (≥?1500 km?s?1), all CMEs with large D (≥?0.4) are associated with MCs and the CMEs with small D are associated with EJs. From the statistical analysis of CME parameters, we found the superiority of the direction parameter. Based on these results, we suggest that the CME trajectory essentially determines the observed ICME structure. 相似文献
302.
Subramaniam Thatchaneshkanth Lee Hee-Jung Jeung Hee-Do Kang Hyun-Sil Kim Chul-Won Kim Hyung-Seop Cho Young-Ghan Choi Kwang-Sik 《Ocean Science Journal》2021,56(4):424-433
Ocean Science Journal - The Gray mussel Crenomytilus grayanus occurs in high density in the shallow rocky subtidal zone on the east coast of Korea, where the mussel dominates the shallow subtidal... 相似文献
303.
Kenji Horie Megumi Yamashita Yasutaka Hayasaka Yasuo Katoh Yukiyasu Tsutsumi Aya Katsube Hiroshi Hidaka Hyeoncheol Kim Moonsup Cho 《Precambrian Research》2010
U–Pb zircon geochronology of two Permo-Triassic granites (samples OT-52 and OT-272 with ages of 229 ± 8 Ma and 256 ± 2 Ma, respectively) in the Unazuki area, Hida Metamorphic Belt, southwest Japan, revealed the presence of Eoarchean to Paleoproterozoic inheritance. Inheritance is consistent with both samples showing low zircon saturation temperatures for their bulk compositions. In OT-52, dark in CL, low Th/U zircon domains have a mean 207Pb/206Pb age of 1940 ± 17 Ma, which is consistent with an age of 1937 ± 6 Ma for anatexis in the Precambrian Busan gneiss complex in Korea. Eoarchaean inherited zircons with 207Pb/206Pb ages from ca. 3750 to 3550 Ma are common in OT-272 but are few in OT-52, suggesting a source from rocks with affinities to those in the Anshan area in the northeast China part of the North China Craton. On the other hand, a Hida Metamorphic Belt metasedimentary gneiss into which the granites were intruded contains ca. 1840, 1130, 580, 360, 285 and 250 Ma zircons (Sano et al., 2000). These ages suggest that the Unazuki Mesozoic granites did not originate from proximal Hida Metamorphic Complex rocks, but instead from unrelated rocks obscured at depth. The predominance of Eoarchean to Paleoproterozoic age components, and the marked lack of 900–700 Ma components suggest that the source was the (extended?) fringe of the North China Craton, rather than from Yangtze Craton crust. The Mesozoic evolution of Japan and its linkages to northeast Asia are discussed in the context of these results. 相似文献
304.
Eun-Hee Lee Jaisoo Kim Ji-Young Kim So-Yeon Koo Sang-Dong Lee Kyung-Seok Ko Dong-Chan Ko Byoung-Woo Yum Kyung-Suk Cho 《Environmental Earth Sciences》2010,60(2):371-382
This research has been performed to determine the differences in microbial communities according to physicochemical properties
such as concentrations of volatile aromatic hydrocarbons such as benzene, toluene, ethylbenzene, and xylene (BTEX), dissolved
oxygen (DO), electron acceptors, etc., in oil-contaminated groundwaters at Kyonggi-Do, South Korea. The properties of bacterial
and microbial communities were analyzed by 16S polymerase chain reaction (PCR) denaturing gradient gel electrophoresis (DGGE)
fingerprinting method and community-level physiological profiling (CLPP) using Eco-plate, respectively. Based on the DGGE
fingerprints, the similarities of bacterial community structures were high with similar DO levels, and low with different
DO levels. Whereas the dominant bacterial groups in GW13 (highest BTEX and lowest DO) were acidobacteria, α-proteobacteria,
β-proteobacteria, γ-proteobacteria, δ-proteobacteria, and spirochetes, those in GW7 (highest BTEX and highest DO) were actinobacteria,
α-proteobacteria, β-proteobacteria, γ-proteobacteria, δ-proteobacteria, and sphingobacteria. Based on the CLPP results, the
groundwater samples were roughly divided into three groups: above 4 mg/L in DO (group 1: GW3 and GW7), below 4 mg/L in DO
(group 2: GW8, W1, W2, W3, and BH10), and highly contaminated with BTEX (group 3: GW13). Shannon index showed that the microbial
diversities and equitabilities were higher in shallower aquifer samples. Overall, this study verified that the greatest influencing
factors on microbial/bacterial communities in groundwaters were DO and carbon sources, although BTEX concentration was one
of the major factors. 相似文献
305.
We report the first finding of Ediacaran mafic magmatism in northern Victoria Land of the Ross orogen, Antarctica, based on ca. 600–590 Ma magmatic zircon cores in Cambrian eclogites. The mafic magmatism could be either linked to ca. 615–590 Ma incipient convergent margin magmatism in central segment of the Ross orogen, or ca. 600–580 Ma continental rift-related volcanism widespread in eastern Australia. The latter is preferred based on the trace-element compositions distinctive from those of arc-related basalts and the depleted mantle-like Hf isotopic compositions of zircon. Our results suggest dual rifting episodes during both the Ediacaran and Cryogenian (ca. 670–650 Ma) in the East Antarctic margin, correlative with those in eastern Australia. A spatial distribution of coeval rifting and subduction along the Ediacaran margin of East Antarctica is readily accounted for by rift inheritance; the upper- and lower-plate geometry resulting from detachment and transform faulting. 相似文献
306.
Sangheon Yi Chang-Gyun Han Keun-Chang Oh In Sun Seo Dongwook Kim Jaeyoung Lee Min Han Hanwoo Choi Jaesoo Lim Sujeong Park Chang-Pyo Jun Taesop Cho 《第四纪科学杂志》2022,37(1):100-113
We comprehensively analyzed sediments obtained from an archeological excavation. A trench sediment profile of Maedun Cave (MC), South Korea, was analyzed geoarchaeologically. Multi-proxy analyses (palynomorphs, grain size, magnetic susceptibility, animal bones and artifacts) reflected the vegetation, hydroclimate and lives of prehistoric people at Marine Isotope Stage (MIS) 3 (ca. 40–30k cal a bp ) in the early Late Paleolithic. The palynoflora consisted of pollen and non-pollen palynomorphs. Under the air-circulation system in the cave, anemophilous pollen flowed in during the day, whereas waterborne pollen and spores, and freshwater algae, were transported by flooding during the summer monsoon rainy season. Mixed conifer and deciduous broad-leaved forest with an understory of pteridophytes flourished around the north-east central Korean Peninsula during MIS 3. Freshwater algae and grass pollen records may reflect precipitation intensity. It is assumed that they had flowed in during flooding caused by high precipitation during the enhanced East Asian summer monsoon, corresponding to Dansgaard–Oeschger (D/O) events 5 and 8 of δ18O GISP2 and Hulu Cave. The prehistoric people hunted herbivorous animals in the area around MC and sheltered inside it seasonally. They also used the grains of oats growing near the dwelling as a source of food. 相似文献