Effect of boundary element details on the seismic deformation capacity of structural walls     

Young‐Hun Oh  Sang Whan Han  Li‐Hyung Lee 《地震工程与结构动力学》2002,31(8):1583-1602

The objective of this study is to investigate the effect of boundary element details of structural walls on their deformation capacities. Structural walls considered in this study have different sectional shapes and/or transverse reinforcement content at the boundaries of the walls (called boundary element details hereafter). Four full‐scale wall specimens (3000mm (h_w)×1500mm (l_w)×200mm (T)) were fabricated and tested. Three specimens are rectangular in section and the other specimen has a barbell‐shaped cross‐section (a wall with boundary columns). The rectangular wall specimens are reinforced according to the common practice used for reinforced concrete residence buildings in Korea and Chile. In this study, the primary variable for these rectangular specimens is the content of transverse reinforcement to confine the boundary elements of a wall. The barbell‐shaped specimen was designed in compliance with ACI 318‐95. The response of the barbell‐shaped specimen is compared with those of other rectangular specimens. The effective aspect ratio of the specimens is set to two in this study. Based on the experimental results, it is found that the deformation capacities of walls, which are represented by displacement ductility, drift ratio and energy dissipation capacities, are affected by the boundary element details. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Seasonal variations in pCO₂ and its controlling factors in surface seawater of the northern East China Sea   总被引：2，自引：0，他引：2  

JeongHee Shim  Dongseon Kim  Young Chul Kang  Jae Hak Lee  Sung-Tae Jang  Cheol-Ho Kim 《Continental Shelf Research》2007,27(20):2623-2636

Surface partial pressure of CO₂ (pCO₂), temperature, salinity, nutrients, and chlorophyll a were measured in the East China Sea (ECS; 31°30′–34°00′N to 124°00′–127°30′E) in August 2003 (summer), May 2004 (spring), October 2004 (early fall), and November 2005 (fall). The warm and saline Tsushima Warm Current was observed in the eastern part of the survey area during four cruises, and relatively low salinity waters due to outflow from the Changjiang (Yangtze River) were observed over the western part of the survey area. Surface pCO₂ ranged from 236 to 445 μatm in spring and summer, and from 326 to 517 μatm in fall. Large pCO₂ (values >400 μatm) occurred in the western part of the study area in spring and fall, and in the eastern part in summer. A positive linear correlation existed between surface pCO₂ and temperature in the eastern part of the study area, where the Tsushima Warm Current dominates; this correlation suggests that temperature is the major factor controlling surface pCO₂ distribution in that area. In the western part of the study area, however, the main controlling factor is different and seasonally complex. There is large transport in this region of Changjiang Diluted Water in summer, causing low salinity and low pCO₂ values. The relationship between surface pCO₂ and water stability suggests that the amount of mixing and/or upwelling of CO₂-rich water might be the important process controlling surface pCO₂ levels during spring and fall in this shallow region. Sea–air CO₂ flux, based on the application of a Wanninkhof [1992. Relationship between wind speed and gas exchange over the ocean. Journal of Geophysical Research 97, 7373–7382] formula for gas transfer velocity and a set of monthly averaged satellite wind data, were −5.04±1.59, −2.52±1.81, 1.71±2.87, and 0.39±0.18 mmol m⁻² d⁻¹ in spring, summer, early fall, and fall, respectively, in the northern ECS. The ocean in this study area is therefore a carbon sink in spring and summer, but a weak source or in equilibrium with the atmosphere in fall. If the winter flux value is assumed to have been the mean of autumnal and vernal values, then the northern ECS absorbs about 0.013 Pg C annually. That result suggests that the northern ECS is a net sink for atmospheric CO₂, a result consistent with previous studies.  相似文献   

The optical spectrum of the planetary nebula NGC 6543     

S. Hyung  L. H. Aller  W. A. Feibelman  W. B. Lee  A. de Koter 《Monthly notices of the Royal Astronomical Society》2000,318(1):77-91

With the Hamilton echelle spectrograph at the Lick Observatory, emission-rich spectral lines of the planetary nebula NGC 6543 were secured in the wavelength range from 3550 to 10 100 Å. We chose two bright regions, ∼8 arcsec east and ∼13 arcsec north of the central star, the physical conditions and chemical abundances of which may differ as a result of the different physical characteristics involving the mass ejection of different epochs. By combining Hamilton echelle observations with archive UV data secured with the International Ultraviolet Explorer ( IUE ), we obtain improved diagnostics and chemical compositions for the two observed regions. The diagnostic diagram gives the average value of T _e=8000∼8300 K, and the electron number density near N _e∼5000 cm⁻³ for most ions, while some low-excitation lines indicate much higher temperatures, i.e. T _e∼10 000 K. With the construction of a photoionization model, we try to fit the observed spectra in a self-consistent way: thus, for most elements, we employ the same chemical abundances in the nebular shell; and we adopt an improved Sobolev approximation model atmosphere for the hydrogen-deficient Wolf–Rayet type central star. Within the observational errors, the chemical abundances do not seem to show any positional variation except for helium. The chemical abundances of NGC 6543 appear to be the same as in average planetary nebulae. The progenitor star may have been an object of one solar mass, most of the heavier elements of which were less plentiful than in the Sun.  相似文献   

Unexpected nationwide nitrate declines in groundwater of Korea          下载免费PDF全文

Jin‐Yong Lee  Kideok D. Kwon  Yu‐Chul Park  Woo‐Hyun Jeon 《水文研究》2017,31(26):4693-4704

Elevated levels of nitrate in groundwater are an important concern for health and the environment. The overapplication of nitrogen fertilizer to croplands is one of the major sources of high nitrate content in groundwater. In this study, we analyse the nitrate concentrations in Korean groundwater based on data from groundwater quality monitoring wells (n = 1,022–2,072), which were sampled twice annually over a recent 13‐year analysis period (2001–2013). We report that groundwater nitrate levels are decreasing, despite steadily increasing groundwater use. The maximum nitrate concentration decreased from 168.91 to 48.11 mg/L, whereas the mean values also show a gradual decreasing trend. Non‐parametric Mann–Kendall tests on nitrate concentrations also confirm the decreasing trend. The nitrate decrease is more clearly evident in agricultural groundwater as compared to domestic and drinking groundwaters. This decrease of nitrate in groundwater coincides with a large decline in nitrogen fertilizer application due to reduced cropland areas, more sustainable agricultural practices, and progressive improvement of sewage disposal services. This study proposes that the long‐term adoption of best practices in agriculture has had a positive impact on groundwater nitrate control.  相似文献   

Biomarker-based Seawater Temperatures of Winter Sinking Particles and Core-top Sediment in the Ulleung Basin of the East Sea     

Park  Yu-Hyeon  Kim  Hyung Jeek  Son  Ju Won  Yoo  Chan Min  Khim  Boo-Keun 《Ocean Science Journal》2019,54(3):487-495

Ocean Science Journal - This study evaluates the application of biomarkerbased temperature proxy data (alkenone with its resultant $$U_{37}^{K'}$$ index and glycerol dialkyl glycerol tetraether...  相似文献   

Enhanced photobiological H2 production by the addition of carbon monoxide and hydrogen cyanide in two unicellular N2-fixing cyanobacterial strains isolated from Korean coasts     

Jong-Woo Park  Seung Won Nam  Hyung Seop Kim  Seok-Hyun Youn  Wonho Yih 《Ocean Science Journal》2014,49(1):11-18

Photobiological H₂ from marine cyanobacterial strains is widely accepted to be an ideal clean and renewable energy source. Using the two Korean N₂-fixing unicellular cyanobacterial strains (Cyanothece sp. KNU CB MAL-031 and Cyanothece sp. KNU CB MAL-058) and the Synechococcus sp. Miami strain BG043511 we performed flask-scale experiments to measure the effect of CO and HCN addition on photobiological H₂ production. For the test, 1, 5, 10 and 30% v/v of CO in the N₂ atmosphere was applied. Enhancement of H₂ production was remarkable at 1–5% concentration range of CO addition. At CO concentrations over 5% no further cost-effective enhancement of H₂ production was detectable, which suggests to us that 1–5% CO addition should be adopted for practical photobiological H₂ production by the cyanobacterial strains. Maximum enhancement of the photobiological H₂ production by CO additions was 2–6 times over the control flasks without CO. When 3 ppm of HCN was injected into the cell suspension of BG043511, the enhancement of hydrogen production was 50–60% of that under 5% CO. Present result implies the possible recycling of waste CO and HCN for the enhancement of the photobiological H₂ production using marine cyanobacterial strains.  相似文献   

Evaluation of ACCMIP simulated fine-mode AOD and its implication for aerosol direct forcing     

Hyein Park  Chul E. Chung  Annica M. L. Ekman  Jung-Ok Choi 《Asia-Pacific Journal of Atmospheric Sciences》2014,50(3):377-390

This study examines and evaluates simulated aerosol optical depth (AOD) and fine-mode AOD (fAOD) from the ACCMIP and CMIP5 global model archives. Satellite data nudged to AERONET data are used to construct reliable global observations of AOD and fAOD for validating the simulations. The difference in simulated global average AOD among models is of the order of a factor of 2, and the difference is even larger (～factor of 3) for fAOD. Compared to the observations, the models tend to underestimate AOD and fAOD significantly over eastern China. Another important discrepancy is that the models show larger fAOD over the Indus-Ganga Plain in summer than in winter, whereas the observations display an opposite feature. The models also overestimate the fAOD over the biomass burning regions of central Africa in DJF and underestimate the fAOD over the biomass burning regions of southern Africa in JJA. To evaluate the effect of the discrepancy between modeled and observed fAOD on aerosol direct radiative forcing, an offline radiation model is utilized. Comparing the model-fAODderived fine-mode forcing with the fine-mode forcing derived from the fAOD observation, the models tend to give too large (negative) value. This result implies that the calculated anthropogenic aerosol forcing in ACCMIP and CMIP5 models has a negative bias.  相似文献   

Studies of the White Sea System from onboard the R/V Ekolog in July 2010     

V. P. Shevchenko  R. A. Ananyev  A. I. Gusakova  N. N. Dmitrevskii  M. D. Kravchishina  A. V. Mishin  N. V. Politova  M. S. Potakhin  A. V. Tolstikov  A. S. Filippov  A. L. Chul’tsova 《Oceanology》2011,51(6):1074-1077

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Resumption of hydrogen sulfide contamination of the water column of deep basins in the Caspian Sea     

M. V. Ivanov  A. S. Savvichev  A. A. Klyuvitkin  A. L. Chul’tsova  E. E. Zakharova  I. I. Rusanov  A. Yu. Lein  A. P. Lisitsyn 《Doklady Earth Sciences》2013,453(1):1094-1099

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Complex studies of the White Sea during the expedition onboard the R/V Ekolog in July 2012     

A. A. Klyuvitkin  M. D. Kravchishina  A. S. Filippov  A. V. Tolstikov  L. E. Reykhard  A. D. Mutovkin  A. L. Chul’tsova 《Oceanology》2013,53(6):765-767

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