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As a step towards a physically realistic model of a fast dynamo, we study numerically a kinematic dynamo driven by convection in a rapidly rotating cylindrical annulus. Convection maintains the quasi-geostrophic balance whilst developing more complicated time-dependence as the Rayleigh number is increased. We incorporate the effects of Ekman suction and investigate dynamo action resulting from a chaotic flow obtained in this manner. We examine the growth rate as a function of magnetic Prandtl number Pm, which is proportional to the magnetic Reynolds number. Even for the largest value of Pm considered, a clearly identifiable asymptotic behaviour is not established. Nevertheless the available evidence strongly suggests a fast dynamo process. 相似文献
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Tintinnid species as biological indicators for monitoring intrusion of the warm oceanic waters into Korean coastal waters 总被引：2，自引：0，他引：2
Young-Ok Kim Kyoungsoon Shin Pung-Guk Jang Hyun-Woo Choi Jae-Hoon Noh Eun-Jin Yang Eung Kim Dongchull Jeon 《Ocean Science Journal》2012,47(3):161-172
This study examined seasonal and annual occurrences of warm oceanic tintinnid species in southern Korea coastal waters. The indicative species of tintinnids was monitored using three approaches: monitoring from cruises traveling from the warm pool in the western North Pacific to the Korea Strait; biweekly or monthly monitoring in the Korea Strait; and daily monitoring in the nearshore water. Annual pulses of warm oceanic indicator species were regularly observed in the Korea Strait. In September 2008 recorded a maximum species number of warm water indicators, a representative species for warm oceanic waters, Climacocylis scalaroides was simultaneously detected in the nearshore water as well as the Korea Strait. The result indicates that the greater warm water extension into Korean coastal areas was in September 2008. Sharp declines in species diversity were observed in the transitional area between neritic and Kuroshio zone in East China Sea (ECS). Epiplocyloides reticulata, reported previously as a Kuroshio indicator, was considered an ECS indicator species, as it was undetected in the western North Pacific central zone but was found abundantly in the ECS. Tintinnid species can be used as biological indicators to detect the inflow of warm oceanic waters into Korean coastal waters. 相似文献
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Jae-Hwan Cho Kyung-Rae Dong Yong-Jin Ju Woon-Kwan Chung Seon-Chil Kim Jong-Woong Lee Yong-Soon Park Eun-Jin Choi Ho-Sung Kim Yeong-Cheol Heo Hyon-Chol Jang 《Environmental Earth Sciences》2013,70(4):1515-1523
The purpose of this study was to measure, compare, and analyze the air concentration of radon that was emitted to the atmosphere from construction materials such as cement brick, tile, red clay tile, and gypsum tile. The study method was to use continuous radon monitoring equipment (RTM 1688-2) to measure concentrations of radon and thoron contained in brick, tile, red clay tile, and gypsum tile. According to the measurement results, the cement brick among the four samples showed the highest measurement value for radon, while the red clay tile showed the highest measurement value for thoron. When the radon emission concentration was estimated based on materials required for construction per unit area (3.3 m2) in an actual construction, the cement brick had the highest measurement values for radon and thoron. This study confirmed the degree of radon emission from construction materials. The purpose of this study was also to suggest a method to examine the effects of radon and reduce the dose of personal radiation exposure. It is believed that the government should be active in publicizing and managing use of construction materials that have lower levels of radon emission. 相似文献
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We investigate the kinematic and dynamic dynamos that result when the magnetic field is assumed to be spatially periodic on a scale twice that of the periodicity of the underlying driving velocity, the CP flow of Galloway and Proctor (1992). In the kinematic regime four distinct modes are possible; all appear to exhibit fast dynamo action. In the nonlinear regime mode coupling may occur and different saturated states are possible for the same parameter values. 相似文献
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Dongseon Kim Eun-Jin Yang Seung Ho Baek Kyung-Hee Kim Jin-Hyun Jeong Young-Ok Kim 《Ocean Science Journal》2014,49(3):223-230
Dissolved inorganic carbon (DIC) and alkalinity were precisely measured for surface and bottom waters in Gwangyang Bay, Korea, during the four seasons to assess seasonal variations of aragonite saturation state (Ωarag). Both the surface and bottom waters were undersaturated with respect to aragonite during summer but were supersaturated during the other seasons. The summertime undersaturation of the surface waters with respect to aragonite may have been a result of the dilution effect caused by higher seasonal river runoff. In the bottom waters, the average DIC concentration increased by 40.6 μmol kg?1 from spring to summer, while the average alkalinity decreased by 74.7 μeq kg?1. As a result, the alkalinity/DIC ratio decreased from 1.07 in spring to 1.01 in summer and pH also decreased from 7.91 to 7.48, which resulted in the summertime undersaturation of the bottom waters. 相似文献
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