Climatic regime shifts and their impacts on marine ecosystem and fisheries resources in Korean waters   总被引：1，自引：0，他引：1  

Chang Ik Zhang  Jae Bong Lee  Suam Kim  Jai-Ho Oh 《Progress in Oceanography》2000,47(2-4)

There were climatic regime shifts over the North Pacific in 1976 and 1988 which affected the dynamics of the marine ecosystem and fisheries resources in Korean waters. Precipitation in Korean waters showed a decadal scale climatic jump, especially of Ullungdo Island, reflecting the regime shift that occurred in the North Pacific. The variation was also detected in East Asian atmospheric systems. The Aleutian Low and North Pacific High Pressure Systems showed substantial changes in 1976 and around 1987–89. 1976 was an unusually warm year for Korea; mean sea surface temperature (SST) was higher than ‘normal’ and was accompanied by a northward shift in the thermal front. Post 1976, the volume transport of the Kuroshio Current increased and higher seawater and air temperatures persisted until 1988. Other shifts occurred after 1976 such as an increase in mixed layer depth (MLD) and biological changes in the ecosystem of Korean waters including decreases in spring primary production and an increase in autumn primary production. Primary production increased again after 1988, and was followed by a significant increase in zooplankton biomass after 1991. The 1976 regime shift was manifested by a decreased biomass and production of saury, but an increase in biomass and production of sardine and filefish in Korean waters. After 1988, recruitment, biomass, and production of sardine collapsed while those of mackerel substantially increased. Based on these observations, hypotheses on the relationship between the climate-driven oceanic changes and changes in fisheries resources were developed and are discussed.  相似文献   

Biomass and trophic structure of the plankton community in subtropical and temperate waters of the northwestern Pacific Ocean     

Chang-Rae Lee  Keun-Hyung Choi  Hyung-Ku Kang  Eun Jin Yang  Jae Hoon Noh  Dong Han Choi 《Journal of Oceanography》2012,68(3):473-482

This study examined the biomass structure of autotrophic and heterotrophic plankton along a trophic gradient in the northwestern Pacific Ocean in an attempt to understand planktonic food web structure. Autotrophic biomass exceeded that of heterotrophic organisms in all sampling regions, but with lesser contribution to total planktonic biomass at stations of higher phytoplankton biomass, including the northern East China Sea, compared to the regions of lower phytoplankton biomass. The proportion of the biomass of heterotrophic bacteria, nanoflagellates (HNF), and dinoflagellates (HDF) relative to that of phytoplankton was all inversely related to phytoplankton biomass, but positive relationships were observed for both ciliates and mesozooplankton. Mesozooplankton biomass inclined greater than phytoplankton along the gradient of phytoplankton biomass, with biomass rise being most closely associated with ciliate and HDF biomass and, to a lesser degree, with large phytoplankton (>3?μm). Both bacteria and picophytoplankton were significantly and positively related to the biomass ratio of mesozooplankton to the sum of HDF and ciliates (i.e., proxy of mesozooplankton predation on protozoans), but no positive relationship was apparent either for HNF or for large phytoplankton. Such relationships may result from predation relief on lower food webs associated with mesozooplankton feeding on protistan plankton.  相似文献   

Timeline analysis and wavelet multiscale analysis of the AKARI All-Sky Survey at 90 μm     

Lingyu Wang  Michael Rowan-Robinson  Issei Yamamura  Hiroshi Shibai  Rich Savage  Seb Oliver  Matthew Thomson  Nurur Rahman  Dave Clements  Elysandra Figueredo  Tomotsugu Goto  Sunao Hasegawa  Woong-Seob Jeong  Shuji Matsuura  Thomas G. Müller  Takao Nakagawa  Chris P. Pearson  Stephen Serjeant  Mai Shirahata  Glenn J. White 《Monthly notices of the Royal Astronomical Society》2008,387(2):601-615

We present a careful analysis of the point-source detection limit of the AKARI All-Sky Survey in the WIDE-S 90-μm band near the North Ecliptic Pole (NEP). Timeline analysis is used to detect IRAS ( Infrared Astronomy Satellite ) sources and then a conversion factor is derived to transform the peak timeline signal to the interpolated 90-μm flux of a source. Combined with a robust noise measurement, the point-source flux detection limit at signal-to-noise ratio  (S/N) > 5  for a single detector row is  1.1 ± 0.1 Jy  which corresponds to a point-source detection limit of the survey of ∼0.4 Jy.
Wavelet transform offers a multiscale representation of the Time Series Data ( tsd ). We calculate the continuous wavelet transform of the tsd and then search for significant wavelet coefficients considered as potential source detections. To discriminate real sources from spurious or moving objects, only sources with confirmation are selected. In our multiscale analysis, IRAS sources selected above 4σ can be identified as the only real sources at the Point Source Scales. We also investigate the correlation between the non- IRAS sources detected in timeline analysis and cirrus emission using wavelet transform and contour plots of wavelet power spectrum. It is shown that the non- IRAS sources are most likely to be caused by excessive noise over a large range of spatial scales rather than real extended structures such as cirrus clouds.  相似文献   

Effective periods and seismic performance of steel moment resisting frames designed for risk categories I and IV according to IBC2009          下载免费PDF全文

Seong‐Hoon Jeong  Oh‐Sung Kwon  Kwang‐Ho Lee 《地震工程与结构动力学》2015,44(9):1427-1447

In current seismic design, structures that are essential for post‐disaster recovery, and hazardous facilities are classified as risk category IV and are designed with higher importance factors and stringent drift limits. These structures are expected to perform better in an earthquake event because a larger base shear and more stringent drift limit are used. Although this provision has been in the seismic design code over the last three decades, few studies have investigated the performance of essential structures. The aim of this study is to quantify the impact of higher importance factors and stringent drift limits on the seismic performance of steel moment resisting frames. A total of 16 steel structures are designed for Los Angeles and Seattle. Different risk categories are used for the design. The effects of the risk categories on the structural periods, and thus on the seismic force demand, are investigated. A suite of inelastic time history analyses are carried out to understand the probability of exceeding a specified limit state when the structures are subjected to different levels of earthquake events. The results show that the periods of the structures in risk category IV decrease by a factor of 0.5 to 0.8, and the strengths increase by a factor of 1.5 to 3.2. Seismic fragility analysis shows that the structures in risk category IV generally satisfy the probabilistic performance objectives. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Full Waveform Inversion Using Student’s t Distribution: a Numerical Study for Elastic Waveform Inversion and Simultaneous-Source Method   总被引：1，自引：0，他引：1  

Woodon Jeong  Minji Kang  Shinwoong Kim  Dong-Joo Min  Won-Ki Kim 《Pure and Applied Geophysics》2015,172(6):1491-1509

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Experimental evaluation of dynamic characteristics of seesaw energy dissipation system for vibration control of structures          下载免费PDF全文

Jae‐Do Kang  Hiroshi Tagawa 《地震工程与结构动力学》2014,43(12):1889-1895

Seesaw energy dissipation system (SEDS), a vibration control system used to provide enhanced seismic protection, has been proposed and investigated numerically. Because of its complicated arrangement, verification experiments are necessary to demonstrate the SEDS damping capacity. This paper presents the results of experimental investigation of the SEDS using fluid viscous dampers. Free vibration tests are conducted to demonstrate the SEDS damping capacity. Results of the free vibration test show that the SEDS has sufficient damping capacity for reduction of the seismic response of the frames. Parametric experimental investigations of the SEDS were conducted, the results of which demonstrate the effects of the system parameter on the damping capacity. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Three‐dimensional modelling of controlled‐source electromagnetic surveys using an edge finite‐element method with a direct solver     

Jeong‐Sul Son  Tae Jong Lee  Hee Joon Kim  Changsoo Shin 《Geophysical Prospecting》2014,62(6):1468-1483

A fully three‐dimensional finite‐element algorithm has been developed for simulating controlled‐source electromagnetic surveys. To exploit the advantages of geometric flexibility, frequency‐domain Maxwell's equations of the secondary electric field were discretised using edge‐based finite elements while the primary field was calculated analytically for a horizontally layered‐earth model. The resulting system of equations for the secondary field was solved using a parallel version of direct solvers. The accuracy of the algorithm was successfully verified by comparisons with integral‐equations and iterative solutions, and the applicability to models containing large conductivity contrasts was verified against published data. The advantages of geometry‐conforming meshes have been demonstrated by comparing different mesh systems to simulate an inclined sheet model. A comparison of the performance between direct and iterative solvers demonstrated the superior efficiency of direct solvers, particularly for multisource problems.  相似文献   

MgO‐Based Binder for Treating Contaminated Sediments: Characteristics of Metal Stabilization and Mineral Carbonation          下载免费PDF全文

Kyung‐Yup Hwang  Jeong‐Yun Seo  Hoang Q. H. Phan  Jun‐Young Ahn  Inseong Hwang 《洁净——土壤、空气、水》2014,42(3):355-363

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Effects of <Emphasis Type="Italic">Urechis unicinctus</Emphasis> juveniles on chemical characteristics of organically contaminated coastal sediment     

Kyoung Ho Kang  Zhifeng Zhang  Jae Min Kim  Seung Chun Seon  Mingyu Shao 《中国海洋大学学报(英文版)》2010,9(1):48-52

Biological activities of marine benthos such as burrowing and feeding may change sediment characteristics. We conducted three experiments to examine the potential of using juveniles of a spoon worm Urechis unicinctus to improve the quality of organically contaminated coastal sediment. Sediment samples were collected from a site that was heavily contaminated with organic matter (Seonso) and two sites that were clean (Myo-do, Dolsan-do). Urechis juveniles, obtained by artificial fertilization and cultured in the laboratory, were introduced to the sediment (weight 3 kg, depth 10 cm) at a density of 500 individuals per aquarium (length 50 cm, width 35 cm, height 30 cm) (Experiment 1), or at densities ranging from 100 to 900 individuals per beaker (Experiment 2). To examine how sediment contamination can be modified by the effects of Urechis, 500 individuals (per aquarium) were exposed to the Seonso contaminated sediment that had been mixed with 0–100% clean sand (Experiment 3). Each experiment lasted two months and sediment samples were collected every 15 d to determine the several indexes of sediment quality, which included acid volatile sulfide (AVS), chemical oxygen demand (COD) and total ignition loss (TIL). In Experiment 1, the existence of Urechis did not result in significant changes in quality indexes in the sediments collected from Myo-do, Dolsan-do. However, AVS, COD and TIL of the Seonso sediment all decreased significantly after co-incubation with Urechis juveniles for 30 to 45 d. Experiment 2 showed that a density of at least 300 juveniles per beaker was necessary to significantly reduce all three quality indexes, and the magnitude of reduction was positively correlated with juvenile density. Experiment 3 revealed that Urechis juveniles were effective in reducing the AVS, COD and TIL of the Seonso sediment that had been mixed with 60%, 80%, and 80% of clean sand, respectively. The results of the present study therefore indicated that juveniles of this spoon worm have the potential to be used to improve the quality of organically contaminated sediment in coastal waters.  相似文献   

Incorporation of Heavy Metals Bioavailability into Risk Characterization     

Hyerim Ryu  Jae Shik Chung  Taekwoo Nam  Hee Sun Moon  Kyoungphile Nam 《洁净——土壤、空气、水》2010,38(10)

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