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1.
We have investigated numerically how a temperature difference between electrons and protons is produced in a flaring loop by adopting a one-fluid, two-temperature model instead of a single-temperature model. We have treated a case in which flare energy is released in the form of heating of electrons located in the top part of the loop.In this case, a large temperature difference (T
e/T
p 10) appears in the corona in the energy-input phase of the flare. When the material evaporated from the chromosphere fills the corona, the temperature difference in the loop begins to shrink rapidly from below. Eventually, in the loop apex, the proton temperature exceeds the electron temperature mainly due to cooling of the electrons by conduction down the loop and heating of the protons by compression of the ascending material. In the late phase of the flare (t 15 min from the flare onset), the temperature difference becomes less than 2% of the mean temperature of electrons and protons at every point in the loop. 相似文献
2.
A detailed investigation of the fluvial geochemistry of the Han River system allows to estimate the rates of chemical weathering and the consumption of CO2. The Han River drains approximately 26,000 km2 and is the largest river system in South Korea in terms of both water discharge and total river length. It consists of two major tributaries: the North Han River (NHR) and the South Han River (SHR). Distinct differences in basin lithology (silicate vs. carbonate) between the NHR and SHR provide a good natural laboratory in which to examine weathering processes and the influence of basin geology on water quality. The concentrations of major elements and the Sr isotopic compositions were obtained from 58 samples collected in both summer and winter along the Han River system in both 2000 and 2006. The concentrations of dissolved loads differed considerably between the NHR and SHR; compared with the SHR, the NHR had much lower total dissolved solids (TDS), Sr, and major ion concentrations but a higher Si concentration and 87Sr/86Sr ratio. A forward model showed that the dissolved loads in the NHR came primarily from silicate weathering (55 ± 11%), with a relatively small portion from carbonates (30 ± 14%), whereas the main contribution to the dissolved loads in the SHR was carbonate weathering (82 ± 3%), with only 11 ± 4% from silicates. These results are consistent with the different lithologies of the two drainage basins: silicate rocks in the NHR versus carbonate rocks in the SHR. Sulfuric acid derived from sulfide dissolution in coal-containing sedimentary strata has played an important role in carbonate weathering in the SHR basin, unlike in the NHR basin. The silicate weathering rate (SWR) was similar between the NHR and SHR basins, but the rate of CO2 consumption in the SHR basin was lower than in the NHR basin due to an important role of sulfuric acid derived from pyrite oxidation. 相似文献
3.
Spatial variability in the primary productivity in the East China Sea and its adjacent waters 总被引:7,自引:0,他引:7
Primary productivity in the East China Sea and its adjacent area was measured by the13C tracer method during winter, summer and fall in 1993 and 1994. The depth-integrated primary productivity in the Kuroshio
Current ranged from 220 to 350 mgC m−2d−1, and showed little seasonal variability. High primary productivity (above 570 mgC m−2d−1) was measured at the center of the continental shelf throughout the observation period. The productivity at the station nearest
to the Changjiang estuary exhibited a distinctive seasonal change from 68 to 1,500 mgC m−2d−1. Depth-integrated primary productivity was 2.7 times higher in the shelf area than the rates at the Kuroshio Current. High
chlorophyll-a specific productivity (mgC mgChl.-a−2d−1) throughout the euphotic zone was mainly found in the shelf area rather than off-shelf area, probably due to higher nutrient
availability and higher activity of phytoplankton at the subsurface layer in the shelf area. 相似文献
4.
将现代人工神经网络方法应用于地质学的判别分析,通过实例计算表明,无论是对于两组判别分析还是多组判别分析,人工神经网络方法都是切实可行的。 相似文献
5.
Generally, the underwater flight vehicle (UFV) depth control system operates with the following problems: it is a multi-input multi-output (MIMO) system, it requires robustness, a continuous control input, and further, it has the speed dependency of controller parameters. To solve these problems, an expanded adaptive fuzzy sliding mode controller (EAFSMC), which is based on the decomposition method designed by using an expert knowledge and the decoupled sub-controllers and composition method designed by using the fuzzy basis function expansions (FBFEs), is proposed. To verify the performance of the EAFSMC, the depth control of UFV in various operating conditions is performed. Simulation results show that the EAFSMC solves all problems experienced in the UFV depth control system online. 相似文献
6.
Young-Ok Kim Eun Jin Yang Jung-Hoon Kang Kyoungsoon Shin Man Chang Cheol Soo Myung 《Ocean Science Journal》2007,42(1):9-17
The summer distributions of planktonic microbial communities (heterotrophic and phtosynthetic bacteria, phtosynthetic and
heterotrophic nanoflagellates, ciliate plankton, and microphytoplankton) were compared between inner and outer areas of Lake
Sihwa, divided by an artificial breakwater, located on the western coast of Korea, in September 2003. The semienclosed, inner
area was characterized by hyposaline surface water (<17 psu), and by low concentrations of dissolved oxygen (avg. 0.4 mg L1) and high concentrations of inorganic nutrients (nitrogenous nutrients >36 μM, phosphate <4 μM) in the bottom layer. Higher
densities of heterotrophic bacteria and nanoflagellates also occurred in the inner area than did in the outer area, while
microphytoplankton (mainly diatoms) occurred abundantly in the outer area. A tiny tintinnid ciliate, Tintinnopsis nana, bloomed
into more than 106 cells L1 at the surface layer of the inner area, while its abundance was much lower (103-104 cells L1) in the outer area of the breakwater. Ciliate abundance was highly correlated with heterotrophic bacteria (r = 0.886, p <
0.001) and heterotrophic flagellates (r = 0.962, p < 0.001), indicating that rich food availability may have led to theT. nana bloom. These results suggest that the breakwater causes the eutrophic environment in artificial lakes with limited flushing
of enriched water and develops into abundant bacteria, nanoflagellates, and ciliates. 相似文献
7.
8.
By using existing data obtained in the offshore area from the Boso Peninsula to the Joban Coast, it was shown that the double
structure of the Kuroshio Front — which is usually found along the northern edge of the Kuroshio Extension to the east 143°E
(Nagataet al., 1986 ; Shinet al., 1988) — is hardly found at the edge of the Kuroshio when it is flowing along the Japanese coast or in the area to the west
of 142°E. It was suggested that the cold and fresh water core beneath the density front of the double structure originates
from the fresh and cold Oyashio Water which is captured beneath the Kuroshio Front just off the Kashima Coast. The double
structure of the Kuroshio Front would be generated and developed very rapidly in the region between 142°E and 143°E just after
the Kuroshio leaves the Japanese coast. 相似文献
9.
The origin and biogeochemistry of organic matter in surface sediments of Lake Shihwa and Lake Hwaong
To understand the origin and biogeochemistry of the organic matter in surface sediments of Lake Shihwa and Lake Hwaong, organic
nitrogen, inorganic nitrogen, labile organic carbon, and residual organic carbon contents as well as stable isotope ratios
for carbon and nitrogen were determined by KOBr-KOH treatment. Ratios of organic carbon to organic nitrogen (Corg/Norg) (mean = 24) were much higher than ratios of organic carbon to total nitrogen (Corg/Ntot) (mean=12), indicating the presence of significant amounts of inorganic nitrogen in the surface sediments of both lakes.
Stable isotope ratios for organic nitrogen were, on average, 5.2‰ heavier than ratios of inorganic nitrogen in Lake Shihwa,
but those same ratios were comparable in Lake Hwaong. This might be due to differences in the origin or the degree of degradation
of sedimentary organic matter between the two lakes. In addition, stable isotope ratios for labile organic carbon were, on
average, 1.4‰ heavier than those for residual organic carbon, reflecting the preferential oxidation of13C-enriched organic matter. The present study demonstrates that KOBr-KOH treatment of sedimentary organic matter can provide
valuable information for understanding the origin and degradation state of organic matter in marine and brackish sediments.
This also suggests that the ratio of Corg/Norg and stable isotope ratios for organic nitrogen can be used as indexes of the degree of degradation of organic matter. 相似文献
10.
N. Takafuji K. Fujino T. Nagai Y. Seto D. Hamane 《Physics and Chemistry of Minerals》2006,33(10):651-654
High-pressure and temperature experiments (28–62 GPa, and 1,490–2,000 K, corresponding to approximately 770–1,500 km depth in the mantle) have been conducted on a MgCO3 + SiO2 mixture using a laser-heated diamond anvil cell combined with analytical transmission electron microscope observation of the product phases to constrain the fate of carbonates carried on the subducting basalt into the lower mantle. At these conditions, the decarbonation reaction MgCO3 (magnesite) + SiO2 (stishovite) → MgSiO3 (perovskite) + CO2 (solid) has been recognized. This indicates that above reaction takes place as a candidate for decarbonation of the carbonated subducting mid ocean ridge basalts in the Earth’s lower mantle. 相似文献