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排序方式: 共有598条查询结果,搜索用时 250 毫秒
1.
Jiunn-Shyang Chiou Zhi-Wei Xu Cheng-Chang Tsai Jin-Hung Hwang 《Marine Georesources & Geotechnology》2018,36(5):554-563
Lateral cyclic load tests were performed on an aluminum model pile in dry sand. Two levels of loading were adopted to represent different service load conditions. The maximum number of loading cycles was 1,000. From the test results, it was found that the even though in the service load condition, the pile response was still affected by cyclic effects and a larger load level would produce more significant influence. In a global point of view, the lateral displacement and maximum moment increased with loading cycles, while the secant stiffness within a cycle decreased with cycles. The cyclic effect was more significant on the lateral displacement than on the moment. In a local point of view, cyclic loading would degrade the equivalent subgrade stiffness for the soil shallower than about seven times diameter. In addition, the secant subgrade stiffness within a cycle increased with loading cycles. Some experimental relationships of lateral pile response and loading cycles were built and compared with those in the literature. 相似文献
2.
Natural Hazards - Future storm-induced inundation risks were assessed by performing storm surge modeling based on Typhoon Maemi (2003) under the generic climate change scenarios proposed by IPCC... 相似文献
3.
The aim of this study is to determine the acoustic characteristics of sailfin sandfish over a wide frequency range. The acoustic survey was conducted in Fe 相似文献
4.
Ki‐mook Kang Duk‐jin Kim Yunjee Kim Eunhee Lee Bong‐Gwan Kim Seung Hee Kim Kyoochul Ha Dong‐Chan Koh Yang‐Ki Cho Guebuem Kim 《水文研究》2019,33(7):1089-1100
Submarine groundwater discharge (SGD) plays an important role in coastal biogeochemical processes and hydrological cycles, particularly off volcanic islands in oligotrophic oceans. However, the spatial and temporal variations of SGD are still poorly understood owing to difficulty in taking rapid SGD measurements over a large scale. In this study, we used four airborne thermal infrared surveys (twice each during high and low tides) to quantify the spatiotemporal variations of SGD over the entire coast of Jeju Island, Korea. On the basis of an analytical model, we found a linear positive correlation between the thermal anomaly and squares of the groundwater discharge velocity and a negative exponential correlation between the anomaly and water depth (including tide height and bathymetry). We then derived a new equation for quantitatively estimating the SGD flow rates from thermal anomalies acquired at two different tide heights. The proposed method was validated with the measured SGD flow rates using a current meter at Gongcheonpo Beach. We believe that the method can be effectively applied for rapid estimation of SGD over coastal areas, where fresh groundwater discharge is significant, using airborne thermal infrared surveys. 相似文献
5.
Shyh‐Lung Hwang Pouyan Shen Hao‐Tsu Chu Tzen‐Fu Yui Yoshiyuki Iizuka Hans‐Peter Schertl 《Journal of Metamorphic Geology》2019,37(8):1079-1098
Metamorphic garnet commonly contains needle‐like rutile inclusions as well as equant rutile inclusions that surround quartz inclusions and range in size from submicrometer to nanometer. Although the origin of these equant rutile inclusions, that is, exsolution or non‐exsolution, has important implications for petrological and tectonic processes, the crystallographic characteristics of these inclusions have rarely been studied because of the small sizes and analytical difficulties involved. Here, we report the crystallographic characteristics pertinent to the genetic origin of minute equant rutile inclusions in cloudy, nearly spherically shaped garnet domains with Ti‐depleted compositions surrounding quartz inclusions in ultrahigh‐pressure garnet from several diamondiferous Erzgebirge quartzofeldspathic gneissic rock samples. TEM analyses show that the equant rutile crystals in cloudy garnet domains are partially bounded by the low‐energy {100}rt ± {110}rt ± {101}rt facets and have rather random crystallographic orientation relationships (CORs) with the garnet host, with preferential alignment of low‐energy lattice planes, for example, {100}rt//{112}grt, for some rutile crystals. Although the rather random CORs are unlikely to be attributed to solid‐state exsolution subjected to the stringent topotactic garnet lattice constraints, the characteristic subhedral {100}rt ± {110}rt ± {101}rt crystal forms of rutile can be rationalized by a metasomatic dissolution‐reprecipitation mechanism via a fluid phase. In this scenario, the quartz+fluid inclusions in garnet were first subjected to decompression microcracking during rock exhumation, followed by dissolution of Ti‐bearing garnet matrix at the crack tips or along the crack surfaces and subsequent reprecipitation of rutile, apatite, gahnite, akdalaite, and Ti‐depleted garnet. The rapid coalescence between rutile and garnet crystals in fluid or direct attachment of rutile crystals onto the dissolving crack surfaces would then yield the rather random CORs as reported here. These results, along with previous work on rutile needles, indicate rather diverse genesis of rutile inclusions in various crystal forms, thus shedding light on the controversial exsolution origin for other inclusion suite/microstructure in minerals. 相似文献
6.
7.
Evidence for significant clockwise rotations of the Korean Peninsula during Cretaceous 总被引:1,自引:0,他引:1
Youn Soo Lee Hyun-Chul Han Jae Ha Hwang Weon-Seo Kee Bok Chul Kim 《Gondwana Research》2011,20(4):904-918
In an effort to evaluate the Cretaceous magnetostratigraphy for the Korean Peninsula and to establish the tectonic coherence of its various elements, we collected paleomagnetic data from 121 samples from 20 sites within the Chilgok Formation (108.3–109.9 Ma) in the Gyeongsang Basin. Together with previously published data, we evaluate the results from a total of 163 sites in the basin.We combine our age model with results from recent stratigraphic, paleomagnetic and radiometric geochemical studies. In this study, we found that two distinct declination shifts decrease with younging direction, indicating two clockwise rotational events of the Korean Peninsula with respect to the Eurasia continent. The earlier event took place during 130–100 Ma (Phase I, newly termed “Goguryeo Disturbance”) and a later one during 80–50 Ma (Phase III, belonging to “Bulguksa Orogeny”). The mean rotation rate in the interval from 115.2 to 103.8 Ma (Phase I) is about 0.74°/Ma, while the rate from 90.9 to 79.8 Ma (Phase II) is 0.19°/Ma. Based on paleolatitude change during Phase I, we infer that the Korean Peninsula (eastern part of the Sino-Korea Block) migrated southward about 300 km after the complete amalgamation of the Sino-Korea Block into the Eurasian continent resulting in N–S compression within the Korean peninsula and Manchuria. Large-scale strike-slip faults (e.g., Tan-Lu Fault, Okcheon Boundary Fault) were probably rejuvenated in the Sino-Korea Block during Phase I. 相似文献
8.
Gil Young Kim Bo Yeon Yi Dong Geun Yoo Byong Jae Ryu Michael Riedel 《Marine and Petroleum Geology》2011,28(10):1979-1985
The Gas Hydrate Research and Development Organization (GHDO) of Korea successfully accomplished both coring (hydraulic piston and pressure coring) and logging (logging-while-drilling, LWD, and wireline logging) to investigate the presence of gas hydrate during the first deep drilling expedition in the Ulleung Basin, East Sea of Korea (referred to as UBGH1) in 2007. The LWD data from two sites (UBGH1-9, UBGH1-10) showed elevated electrical resistivity (>80 Ω-m) and P-wave velocity (>2000 m/s) values indicating the presence of gas hydrate. During the coring period, the richest gas hydrate accumulation was discovered at these intervals. Based on log data, the occurrence of gas hydrate is primarily controlled by the presence of fractures. The gas hydrate saturation calculated using Archie’s relation shows greater than 60% (as high as ∼90%) of the pore space, although Archie’s equation typically overestimates gas hydrate saturation in near-vertical fractures. The saturation of gas hydrate is also estimated using the modified Biot-Gassmann theory (BGTL) by Lee and Collett (2006). The saturation values estimated rom BGTL are much lower than those calculated from Archie’s equation. Based on log data, the hydrate-bearing sediment section is approximately 70 m (UBGH1-9) to 130 m (UBGH1-10) in thickness at these two sites. This was further directly confirmed by the recovery of gas hydrate samples and pore water freshening collected from deep drilling core during the expedition. LWD data also strongly support the interpretation of the seismic gas hydrate indicators (e.g., vent or chimney structures and bottom-simulating reflectors), which imply the probability of widespread gas hydrate presence in the Ulleung Basin. 相似文献
9.
Hyo Jin Lee Sang Hee Hong Moonkoo Kim Sung Yong Ha Soon Mo An Won Joon Shim 《Ocean Science Journal》2011,46(2):95-103
Masan and Haengam Bays in Korea are highly polluted and semi-enclosed. Domestic and industrial effluents are directly or indirectly
discharged into the bays through sewage treatment plants (STP) and creeks. In this study, 15 dissolved sterol compounds were
determined in order to understand their sources and relative contribution. Freshwater samples were taken from 13 creeks and
at two STP sites on a monthly basis. Total dissolved sterol concentrations ranged from 993 to 4158 ng/L. The concentrations
of sterols in winter were higher than in summer. Among the sterols analyzed, cholesterol, β-sitosterol, coprostanol and cholestanone
were major compounds in creek water. Seawater samples were concurrently collected at 21 stations in Masan Bay. Total sterol
concentrations ranged 118–6,956 ng/L. Inner bay showed high concentrations of sterols in summer, while outer bay showed high
sterol concentrations in winter. Among the sterols, cholesterol, β-sitosterol and brassicasterol were major compounds in seawater.
In order to examine the contribution of urban sewage, the concentration of coprostanol and fecal sterol ratios were calculated.
Most of the creek water, inner bay and near STP outlet samples were affected by sewage. Terrestrial organic matters accounted
for a high proportion of dissolved organic matter origin. Fecal origins were relatively high in the inner bay areas and in
the STP outlet, while sterols of marine origin were high in the outer bay areas. 相似文献
10.
Min Kyung Lee Yong Il Lee Hyoun Soo Lim Jae Il Lee Jeong Heon Choi Ho Il Yoon 《Journal of Paleolimnology》2011,45(2):127-135
Both radiocarbon and optically stimulated luminescence (OSL) dating methods were applied to test their suitability for establishing
a chronology of arid-zone lacustrine sediments using a 5.88-m-long core drilled from Lake Ulaan, southern Mongolia. Although
the radiocarbon and OSL ages agree in some samples, the radiocarbon ages are older than the corresponding OSL ages at the
550-cm depth horizon (late Pleistocene) and in the 100–300-cm interval (early to late Holocene). In the early to late Holocene,
radiocarbon ages are consistently older than OSL ages by 4,100–5,800 years, and in the late Pleistocene by 2,700–3,000 years.
Grain-size analysis of early to late Holocene sediments and one late Pleistocene sediment sample (550-cm depth) indicates
that eolian processes were the dominant sediment-transport mechanism. Also, two late Pleistocene sediments samples (from 400-
to 500-cm depths) are interpreted to have been deposited by both eolian and glaciofluvial processes. Accordingly, the radiocarbon
ages that were older than the corresponding OSL ages during the Holocene seem to have been a consequence of the influx of
14C-deficient carbon delivered from adjacent soils and Paleozoic carbonate rocks by the westerly winds, a process that is also
active today. In addition to the input of old reworked carbon by eolian processes, the late Pleistocene sediments were also
influenced by old carbon delivered by deglacial meltwater. The results of this study suggest that when eolian sediment transport
is suspected, especially in lakes of arid environments, the OSL dating method is superior to the radiocarbon dating method,
as it eliminates a common ‘old-carbon’ error problem. 相似文献