Stability of the time‐domain analysis method including a frequency‐dependent soil–foundation system          下载免费PDF全文

Alex Duarte Laudon  Oh‐Sung Kwon  Amir Reza Ghaemmaghami 《地震工程与结构动力学》2015,44(15):2737-2754

A number of methods have been proposed that utilize the time‐domain transformations of frequency‐dependent dynamic impedance functions to perform a time‐history analysis. Though these methods have been available in literature for a number of years, the methods exhibit stability issues depending on how the model parameters are calibrated. In this study, a novel method is proposed with which the stability of a numerical integration scheme combined with time‐domain representation of a frequency‐dependent dynamic impedance function can be evaluated. The method is verified with three independent recursive parameter models. The proposed method is expected to be a useful tool in evaluating the potential stability issue of a time‐domain analysis before running a full‐fledged nonlinear time‐domain analysis of a soil–structure system in which the dynamic impedance of a soil–foundation system is represented with a recursive parameter model. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

On drag coefficient parameterization with post processed direct fluxes measurements over the ocean     

Hyun-Mi Oh  Kyung-Ja Ha  Ki-Young Heo  Kyung-Eak Kim  Sang-Jong Park  Jae-Seol Shim  Larry Mahrt 《Asia-Pacific Journal of Atmospheric Sciences》2010,46(4):513-523

This study presents an evaluation of the atmospheric factors influencing the post-processing for fast-response data of horizontal momentum, vertical wind component, temperature, and water vapor to measure turbulent fluxes. They are observed at the Ieodo ocean research station over the Yellow Sea during the period of October 2004 to February 2008. The post process methods employed here are composed of quality control and tilt correction for turbulent flux measurement. The present result of quality control on the fast-response data shows that total removal ratio of the data generally depends on the factors such as a wind speed, relative humidity, significant wave height, visibility, and stability parameter (z/L). Especially, the removal ratio of water vapor data is significantly increased on light wind and strong stability conditions. The results show that the total removal ratio of water vapor data increases when wind speed is less than 3 m s^?1 and wave height is less than 1 m. The total removal ratio of water vapor data also increases with the value of the stability parameter. Three different algorithms of tilt correction methods (double rotation, triple rotation, and planar fit) are applied to correct the tilt of the sonic anemometer used in the observation. Friction velocities in near neutral state are greater than friction velocity in other states. Drag coefficients are categorized in terms of stabilities and seasons.  相似文献   

Diel vertical migration of the copepod Calanus sinicus before and during formation of the Yellow Sea Cold Bottom Water in the Yellow Sea     

KANG Jung-Hoon  SEO MinHo  KWON Oh Youn  KIM Woong-Seo 《海洋学报(英文版)》2013,32(9):99-106

To understand the effects of the Yellow Sea Cold Bottom Water(YSCBW)on the diel vertical migration(DVM)of the copepod Calanus sinicus,we surveyed vertical distribution of C.sinicus at a fixed station in the Yellow Sea before(spring)and during(summer)formation of the YSCBW.Cold water(<10 C)was observed in the bottom layer when the water column was thermally stratified in summer,but the water column was thermally well-mixed in spring 2010.Samples were collected from five different layers at 3-h intervals using an opening-closing net.Adult females(1–155 ind./m3)showed a clear normal DVM pattern throughout the entire water column in spring,whereas adult males did not migrate.DVM of copepodite V(CV)individuals was not clear,but the maximum abundance of CI–CIV occurred consistently in the upper 10–20 m layer,where there was a high concentration of chlorophyll-a(Chl-a)(0.49–1.19μg/L).In summer,weak DVM was limited to cold waters beneath the thermocline for adult females(<30 ind./m3),but not for adult males.The maximum abundance of CI–CIV also occurred consistently in the subsurface layer(20–40 m)together with high concentrations of Chl-a(0.81–2.36μg/L).CV individuals(1–272 ind./m3)moved slightly upward nocturnally to the near-surface layer(10–20 m),where the average temperature was 25.74 C,but they were not found in the surface layer(0–10 m;28.31 C).These results indicate that the existence of the YSBCW affected food availability at depth and the vertical temperature distribution,leading to variation in the amplitude and shape of stage-specific vertical distributions(CI to adults)in C.sinicus before and during the formation of cold waters in the Yellow Sea during the study period.  相似文献   

Effects of feed restriction to enhance the profitable farming of blackhead seabream Acanthopagrus schlegelii schlegelii in sea cages     

Sung-Yong Oh  Min-Suk Kim  Joon Yeong Kwon  B. A. Venmathi Maran 《Ocean Science Journal》2013,48(3):263-268

The feed intake, growth and body composition of juvenile blackhead seabream Acanthopagrus schlegelii schlegelii (Sparidae) (5.6 g fish^?1) were investigated for 16 weeks in sea cages under seven repetitive feeding cycles: every day feeding (control), 6-day feeding and 1-day fasting (F_6.1), 5-day feeding and 1-day fasting (F_5.1), 4-day feeding and 1-day fasting (F_4.1), 3-day feeding and 1-day fasting (F_3.1), 2-day feeding and 1-day fasting (F_2.1), and 1-day feeding and 1-day fasting (F_1.1). The survival of the fish during the experimental period was not different among the feeding cycles. The greatest weight gain of fish was observed in the control, but not significantly different from that of the F_6.1 and F_5.1 groups (p > 0.05). Total feed intake and daily feed intake decreased with the increase of fasting frequency, however, actual feed intake, feed efficiency and protein efficiency ratio increased with the increase of the fasting frequency. Proximate composition of the whole body of fish was not affected by different feeding cycles. These results suggest that juvenile blackhead seabreams subjected to repetitive feeding cycles of 6- or 5-days feeding and 1 day fasting for 16 weeks could achieve compensatory growth, and that such mild feeding deprivation could save significant amounts of feed without causing any profit reduction that might result from a decrease in fish size or quality.  相似文献   

Prediction of East Asian summer precipitation via independent component analysis     

Yaeji Lim  Seongil Jo  Jaeyong Lee  Hee-Seok Oh  Hyun-Suk Kang 《Asia-Pacific Journal of Atmospheric Sciences》2012,48(2):125-134

A new statistical postprocessing method is proposed for seasonal climate prediction. The proposed method is based on a combination of independent component analysis (ICA) and canonical correlation analysis (CCA). Since the classical CCA cannot handle high-dimensional data wherein the number of variables is larger than the number of observations, ICA is pre-performed to reduce the dimension of the data. It is well known that empirical orthogonal function (EOF) analysis is a popular method for dimension reduction in the climatology community; however, loss of information occurs when the data is not Gaussian distributed. To extend the scope of distribution assumption and improve the prediction ability simultaneously, we propose the ICA-based method. This study focuses on the prediction of future precipitation for the boreal summer (June?CJuly?CAugust; JJA) through 29 years (1979?C2007) on East Asia region. Results of the proposed ICA-based method show an improvement in seasonal climate prediction in terms of correlation and root mean square error as compared with those of the GCM simulation and the EOF/CCA method.  相似文献   

Prediction of ground subsidence in Samcheok City,Korea using artificial neural networks and GIS   总被引：4，自引：0，他引：4  

Ki-Dong Kim  Saro Lee  Hyun-Joo Oh 《Environmental Geology》2009,58(1):61-70

This study shows the construction of a hazard map for presumptive ground subsidence around abandoned underground coal mines (AUCMs) at Samcheok City in Korea using an artificial neural network, with a geographic information system (GIS). To evaluate the factors governing ground subsidence, an image database was constructed from a topographical map, geological map, mining tunnel map, global positioning system (GPS) data, land use map, digital elevation model (DEM) data, and borehole data. An attribute database was also constructed by employing field investigations and reinforcement working reports for the existing ground subsidence areas at the study site. Seven major factors controlling ground subsidence were determined from the probability analysis of the existing ground subsidence area. Depth of drift from the mining tunnel map, DEM and slope gradient obtained from the topographical map, groundwater level and permeability from borehole data, geology and land use. These factors were employed by with artificial neural networks to analyze ground subsidence hazard. Each factor’s weight was determined by the back-propagation training method. Then the ground subsidence hazard indices were calculated using the trained back-propagation weights, and the ground subsidence hazard map was created by GIS. Ground subsidence locations were used to verify results of the ground subsidence hazard map and the verification results showed 96.06% accuracy. The verification results exhibited sufficient agreement between the presumptive hazard map and the existing data on ground subsidence area. An erratum to this article can be found at  相似文献   

Neoproterozoic tectonic evolution of the Hongseong area, southwestern Gyeonggi Massif, South Korea; implication for the tectonic evolution of Northeast Asia     

C.W. Oh  S.-G. Choi  J. Seo  V.J. Rajesh  J.H. Lee  M. Zhai  P. Peng 《Gondwana Research》2009,16(2):272

Two types of Neoproterozoic metabasites occur together with regionally intruded arc-related Neoproterozoic granitoids (ca. 850–830 Ma) in the Hongseong area, southwestern Gyeonggi Massif, South Korea, which is the extension of the Dabie–Sulu collision belt in China. The first type of metabasite (the Bibong and Baekdong metabasites) is a MORB-like back-arc basin basalt or gabbro formed at ca. 890–860 Ma. The Bibong and Baekdong metabasites may have formed during back-arc opening by diapiric upwelling of deep asthenospheric mantle which was metasomatized by large ion lithophile element (LILE) enriched melt or fluid derived from the subducted slab and/or subducted sediment beneath the arc axis. The second type of metabasite (the Gwangcheon metabasite) formed in a plume-related intra-continental rift setting at 763.5 ± 18.3 Ma and is geochemically similar to oceanic island basalt (OIB). These data indicate a transition in tectonic setting in the Hongseong area from arc to intra-continental rift between ca. 830 and 760 Ma. This transition is well correlated to the Neoproterozoic transition from arc to intra-continental rift tectonic setting at the margin of the Yangtze Craton and corresponds to the amalgamation and breakup of Rodinia Supercontinent.  相似文献   

Potential for heavy metal (copper and zinc) removal from contaminated marine sediments using microalgae and light emitting diodes     

Hyeong Kyu Kwon  Jin Young Jeon  Seok Jin Oh 《Ocean Science Journal》2017,52(1):57-66

The effects of monochromatic (blue, yellow and red LED) and mixed wavelengths (fluorescent lamp) on the adsorption and absorption of Cu and Zn by Phaeodactylum tricornutum, Nitzschia sp., Skeletonema sp., and Chlorella vulgaris were investigated. In addition, we confirmed the potential of microalgae for phytoremediation of these heavy metals from contaminated marine sediment by using microcosm experiments that incorporated LEDs and semipermeable membrane (SPM) tube containing microalgae. Among the four microalgae, C. vulgaris grown under red LED exhibited the highest Cu and Zn removal with values of 17.5 × 10^-15 g Cu/cell and 38.3 × 10^-15 g Zn/cell, respectively. Thus, C. vulgaris could be a useful species for phytoremediation. In the microcosm experiments with SPM containing C. vulgaris, the highest Cu and Zn removal from sediment and interstitial water showed under red LED. Therefore, phytoremediation using LED and SPM tube containing microalgae could be utilized as an eco-friendly technique for remediating contaminated marine sediment.  相似文献   

Effects of nutrients on crude oil biodegradation in the upper intertidal zone   总被引：10，自引：0，他引：10  

Oh YS  Sim DS  Kim SJ 《Marine pollution bulletin》2001,42(12):1367-1372

To enhance biodegradation, nutrients in the form of slow-release fertilizer (SRF) were applied to oil-contaminated microcosms (3%, v/v) which simulated intertidal environmental systems. Although nutrient concentrations in the interstitial water were not proportional to those in amended SRF, microbial activity, growth of oil-degrading microorganisms, and oil-degradation rate were closely related to the concentration of nutrients in the interstitial water. Adding nutrients at higher dose (microcosm I, 144.4 mg C/kg sand/day, versus microcosm II, 8.5 mg C/kg sand/day) had a positive effect on oil degradation rate, which was especially obvious during the early phase of treatment. Use of pristane, phytane, and nor-hopane as biomarkers enabled the detection of significant treatment differences in hydrocarbon biodegradation, which were not reliable enough when the data were normalized to sand mass.  相似文献   

伴随韩国雨季开始和结束早晚的关联场分析   总被引：4，自引：0，他引：4  

Lu Riyu  Huang Ronghui  Hee-Jeong Baek  Jai-Ho Oh  Baek-Jo Kim 《大气科学进展》2001,18(6):1066-1080

分析了与韩国雨季开始和结束的年际变化相关联的一些要素场发生的变化。分别对雨季开始和结束早晚的个例进行了合成分析。６月月平均资料用来分析与雨季开始早晚相关联的要素场变化，而在分析与雨季结束早晚相关联的要素场变化时则利用７月月平均资料。结果表明，对应雨季开始（或结束）早晚，大气环流和表面温度等要素不仅在东亚地区、而且在远离东亚的地方具有显著的差异。在东亚地区的显著差异主要是高空急流和西太平佯副热带高压。远离东亚的显著差异主要是印度季风和ＥＮＳＯ现象。印度季风与韩国雨季开始和结束均有关联，但ＥＮＳＯ现象只与雨季开始显著相关、而与结束并没有显著的关联。  相似文献