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排序方式: 共有215条查询结果,搜索用时 23 毫秒
81.
Soon-Hwan Lee Soo-Jin Hwang Chan-Su Ryu 《Asia-Pacific Journal of Atmospheric Sciences》2010,46(3):355-367
In order to clarify the characteristics of Mesoscale Convective System (MCS) development and understand the impact of the trigger effect of isolated islands, observational and numerical analysis of the heavy rainfall were carried out over the southwestern part of the Korean Peninsula on July 14, 2004. Satellite based remote sensing data and numerical model MM5 with observational data adjustment were used in this study. The MCS development, in this case, was accompanied not by directional wind shear, but by speed shear which was strongly associated with development of the updraft cloud. An inversion layer at a 750 hPa level is one of the fundamental factors in increasing instability. Effective separation of the upper and lower level atmospheric structure due to an inversion layer at a 750 hPa level creates a suitable condition to develop a MCS. According to numerical analysis it has been found that isolated islands located off the southwestern part of the Korean Peninsula are not a principal factor in causing the heavy rainfall due to the evolution of MCS in this case. Transferable topographic forcing of the downwind side can often induce the variation of MCS intensity, while associated with the precipitation amount over the lee side of the isolated islands at a mature stage of MCS development. 相似文献
82.
83.
Isani Chan Jia-Jang Hung Shao-Hung Peng Li-Chun Tseng Tung-Yuan Ho Jiang-Shiou Hwang 《Marine pollution bulletin》2014
The response of metal accumulation in coral Tubastraea coccinea to various degrees of metal enrichment was investigated from the Yin-Yang Sea (YYS) receiving abandoned mining effluents, the Kueishan Islet (KI) hydrothermal vent field, and the nearshore area of remoted Green Island (GI). The concentrations of most dissolved metals were highest in seawater at YYS, followed by KI, and then GI, showing the effects of anthropogenic and venting inputs on metal levels. Five metals (Co, Fe, Mn, Ni, and Zn) yielded significant differences (p < 0.05) among the skeleton samples. We identified similar patterns in the metal–Ca ratios, indicating that the elevated metals in skeletons was a consequence of external inputs. The coral tissues were relatively sensitive in monitoring metal accumulation, showing significant differences among three locations for Cd, Co, Cu, Fe, Pb, Ni, and Zn. Specific bioconcentration factors provided strong support for the differential metal accumulation in skeletons and tissues. 相似文献
84.
85.
This paper reports the results of cyclic loading tests performed on four specimens consisting of reinforced concrete frames with brick infill walls. The brick infill is pre‐laid, followed by the cast in‐place RC columns and beams. Test parameters include the height‐to‐length ratio of the brick infill wall and the mortar compressive strength. Test results reveal that the in‐plane lateral strength of brick infill wall is related to the fracture path. The fracture path for brick infill walls with large height‐to‐length ratios includes bed joints, cross joints, and vertical splitting of bricks. As a result, the lateral strength of this type of brick infill wall is larger. In comparison, the fracture path for brick infill walls with small height‐to‐length ratios only passes through joints, which is the reason why they have lower lateral strength. Mortar with higher strength improves the lateral strength of brick infill wall. In addition to presenting experimental observations in detail, this paper compares the test results with those obtained from existing methods for assessment of seismic resistance. Comments and recommendations are offered with respect to the capabilities of the assessment methods in predicting stiffness, strength, and ultimate deformation capacity of brick infill walls. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
86.
Earthquake simulation tests were conducted on a 1 : 15‐scale 25‐story building model to verify the seismic performance of high‐rise reinforced‐concrete flat‐plate core‐wall building structures designed per the recent seismic code KBC 2009 or IBC 2006. The following conclusions can be drawn from the test results: (1) The vertical distribution of acceleration during the table excitations revealed the effect of the higher modes, whereas free vibration after the termination of the table excitations was governed by the first mode. The maximum values of base shear and roof drift during the free vibration are either similar to or larger than the values of the maximum responses during the table excitation. (2) With a maximum roof drift ratio of 0.7% under the maximum considered earthquake in Korea, the lateral stiffness degraded to approximately 50% of the initial stiffness. (3) The crack modes appear to be a combination of flexure and shear in the slab around the peripheral columns and in the coupling beam. Energy dissipation via inelastic deformation was predominant during free vibration after the termination of table excitation rather than during table excitation. Finally, (4) the walls with special boundary elements in the first story did not exhibit any significant inelastic behavior, with a maximum curvature of only 21% of the ultimate curvature, corresponding to an ultimate concrete compressive strain of 0.00638 m/m intended in the displacement‐based design approach. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
87.
This study presents predicts ocean tidal loading (OTL) effects using a Green’s function approach and validates a novel tidal
model for Taiwan. Numerical integration of OTL is performed using the Gauss quadrature method and a local tidal model for
the inner zone and a global model for the outer zone. Observed time series of GPS-derived vertical displacements and gravity
variations (3–7 days) at five co-located GPS-gravimeter stations along the South East China and Taiwan coasts were utilized
to assess the accuracy of the proposed models and two other models. The OTL-induced gravity variations are 3–16 μgal and the
vertical site displacements are 13–27 mm. Generally, an OTL model using a mixed global and local tidal model generates better
agreement with the observations than an OTL model using a global tidal model only. However, containing a local model inside
a global model does not always produce a good agreement with the observations. The relatively large discrepancies between
modeled and observed OTL values at some stations indicate that there is a need for an improved local tidal model in the study
area.
An erratum to this article can be found at 相似文献
88.
Groundwater Impacts from the M5.8 Earthquake in Korea as Determined by Integrated Monitoring Systems
Soo-Hyoung Lee Jae Min Lee Heesung Yoon Yongcheol Kim Seho Hwang Kyoochul Ha Yongje Kim 《Ground water》2020,58(6):951-961
This paper describes the impacts of the M5.8(5.1) Gyeongju earthquakes on groundwater levels using data obtained from a unique coastal monitoring well. The monitoring strategy integrates conventional water level monitoring with periodic, continuous measurements of temperature and electrical conductivity (EC) within the water column of the well. Another important component of the monitoring system is a new instrument, the InterfacEGG, which is capable of dynamically tracking the freshwater-saltwater interface. Although the system was set up to monitor seawater intrusion related to over-pumping, as well as rainfall and tidal effects, it recorded impacts associated with a large earthquake and aftershocks approximately 241 km away. Seismic energies associated with the M5.8(5.1) Gyeongju earthquakes induced groundwater flows to the monitoring well through fractures and joints in the crystalline basement rocks. Temperature and EC logging data showed that the EC vertical profile declined from an average of approximately 5300 to 4800 μS/cm following the earthquakes. The temperature profile showed a trend toward lower temperatures as the depth increased, a feature not commonly observed in previous studies. Data from the InterfacEGG suggested that the rise in EC was not due to the saltwater intrusion, but from the tendency for brackish water entering the borehole to induce convective mixing at deeper depths as the seismic waves travel through the well-aquifer system. The increase in groundwater levels was caused by pulse of colder, less brackish water flowing into the well because of the earthquake. This behavior reflects an enhancement in rock permeability by removing precipitates and colloidal particles from clogged fractures, which improve the hydraulic connection with a nearby unit with a higher hydraulic head. This study suggests there is value added with a more aggressive monitoring strategy. 相似文献
89.
Steven J. Berg Nancy R. Grosso Michael P. Sherrier Kevin Mudrick Matthias Ohr Hyoun-Tae Hwang Young-Jin Park Michael V. Callaghan Steven K. Frey Edward A. Sudicky 《Ground water》2019,57(1):21-35
The interaction between surface water and groundwater during flood events is a complex process that has traditionally been described using simplified analytical solutions, or abstracted numerical models. To make the problem tractable, it is common to idealize the flood event, simplify river channel geometry, and ignore bank soil heterogeneity, often resulting in a model that only loosely represents the site, thus limiting its applicability to any specific river cross-section. In this study, we calibrate a site-specific fully-integrated surface and subsurface HydroGeoSphere model using flood events for a cross-section along the South River near Waynesboro, VA. The calibration approach presented in this study demonstrates the incorporation of fining direction regularization with a highly parameterized inversion driven by natural stimuli, to develop several realistic realizations of hydraulic conductivity fields that reflect the depositional history of the system. Specifically, we calibrate a model with 365 unique material zones to multiple flood events recorded in a dense well network while incorporating possible fining sequences consistent with the depositional history of the riverbank. Over 25,000 individual simulations were completed using calibration software and a cloud platform specifically designed for highly parallelized computing environments. The results of this study demonstrate the use of fining direction regularization during model calibration to generate multiple calibrated model realizations that account for the depositional environment of the system. 相似文献
90.
Hwang?Lee Da-Eun?Byun Ju?Min?Kim Jung-Hwan?KwonEmail author 《Ocean Science Journal》2018,53(4):631-639
Microplastics provide an important medium for hydrophobic organic chemicals (HOCs), and the desorption of HOCs from microplastics is an important process for the dynamics of HOCs associated with microplastics. Although desorption kinetics has been studied for microplastics with ideal geometries, most of the microplastics isolated from the environment are irregular fragment-type microplastics. This study investigated the desorption of six model HOCs from polyethylene (PE) and polypropylene (PP) fragments to artificial seawater and compared the results with those predicted assuming ideal geometries (e.g., sphere and infinitely flat sheet) of microplastics. The experimental desorption was explained well by the model predictions with the characteristic radius for a sphere and the thickness for a plate estimated from visual imaging. The mass fraction remaining at the later stage of desorption was higher than the model simulation assuming a single characteristic length, likely due to the heterogeneity of the particle size distribution. Although there are inevitable uncertainties, it would be useful to assign a single length dimension in desorption modeling for even fragment-type microplastics, especially for the estimation of desorption half-life. 相似文献