Temporal occurrence patterns and habitat use of fish in the Mangyeong estuary on the western coast of Korea in 2003, before dike enclosure     

Sun Wan Hwang  Tae Won Lee  Hak Bin Hwang  Sun Do Hwang 《Ocean Science Journal》2011,46(4):307-314

We documented the temporal occurrence patterns and habitat use of fish in the Mangyeong River estuary on the western coast of Korea from February to December 2003 based on monthly samples collected with a stow net. A total of 46 fish species were collected during the study period. Chelon haematocheilus, Konosirus punctatus, Neosalanx jordani, Sardinella zunasi, Synechogobius hasta, and Thryssa kammalensis were the predominate species, accounting for 84.4% of the collected fish. We classified the fish as brackish water (BF), coastal migratory (CMF), diadromous (DF), or freshwater (FF) fish. BF such as C. haematocheilus, S. hasta, and Coilia nasus were the most abundant and were collected almost year-round. As water temperatures increased in spring, adult CMF, such as K. punctatus, S. zunasi, T. kammalensis, T. adelae, Johnius grypotus, Miichthys miiuy, and Larimichthys polyactis, entered the estuary. In summer, large numbers of their juvenile offspring were caught, indicating a peak in fish abundance. The juveniles grew in the estuary before moving out to deeper waters for overwintering. Diadromous juveniles, such as those of Anguilla japonica (commonly known as glass eel), were collected in the spring during their upstream migration. FF, such as Carassius cuvieri and Acheilognathus rhombeus, were collected during the rainy season. In terms of the number of species, the number of individuals, and the biomass, the ratio of BF to all other fish type classifications in the Mangyeong Estuary (without a dam) was higher than that in the Geum River estuary (with a dam). The fish assemblage in the Mangyeong Estuary still maintained estuarine characteristics before dike enclosure, providing habitats for BF, nursery grounds for CMF, and migratory pathways for DF.  相似文献   

Direct flows from the Ulleung Basin into the Yamato Basin in the East/Japan Sea     

Young-Gyu Park  Ara Choi  Young Ho Kim  Hong Sik Min  Jin Hwan Hwang  Sang-Hwa Choi 《Deep Sea Research Part I: Oceanographic Research Papers》2010,57(5):731-738

Using the trajectories of ARGO floats, we report direct flows from the Ulleung Basin into the Yamato Basin through a gap between the Oki Spur and the Yamato Rise over the southern part of the East/Japan Sea. The gap is subdivided into two narrow (northern and southern) passages by a seamount located in the middle. The flows, therefore, are narrow and this explains why this flow was not reported earlier. More than half of the 25 ARGO floats, which operated around the gap, drifted through the gap or area near it. The strength of the throughflow estimated using the trajectories of the floats at parking depth is comparable to the mean deep flow found over the southwestern part of the East/Japan Sea. A high resolution regional ocean model whose overall circulation pattern over the Ulleung Basin is consistent with those from previous studies shows that the flow through the gap is supplied mainly by eastward flows crossing the mouth of the basin, and secondarily by the cyclonic circulation following the outer perimeter of the basin. Thus the throughflow is an important component of the deep circulation over the southern East/Japan Sea, and the narrow gap, where the flow is well confined, would be a good place to study the deep circulation.  相似文献   

How did Cassiopeia a Explode? A Chandra VLP     

J. Martin Laming  Una Hwang 《Astrophysics and Space Science》2005,298(1-2):33-37

The Cassiopeia A supernova remnant will be observed by Chandra for 1 Ms this spring. We discuss our motivations and plans for acquiring and analyzing these data.  相似文献   

Morphology of Seyfert Galaxies     

Y.-C. Chen  C.-Y. Hwang 《Astronomy Reports》2018,62(12):853-858

We probed the relation between properties of Seyfert nuclei and morphology of their host galaxies. We selected Seyfert galaxies from the Sloan Digital Sky Survey with redshifts less than 0.2 identified by the Vé ron Catalog (13th). We used the FracDev parameter from SDSS galaxy fitting models to represent the bulge fractions of the Seyfert host galaxies. We found that the host galaxies of Seyfert 1 and Seyfert 2 are dominated by large bulge fractions, and Seyfert 2 galaxies are more likely to be located in disk galaxies whereas most of the Seyfert 1 galaxies are located in bulge-dominant galaxies. These results indicate that the types of AGNs are related to their host galaxies and cannot be explained by the traditional unification model of Seyfert galaxies.  相似文献   

A new measure for assessing the efficiency of hydrological data-driven forecasting models     

Seok Hwan Hwang  Dae Heon Ham 《水文科学杂志》2013,58(7):1257-1274

Abstract

There is a lack of consistency and generality in assessing the performance of hydrological data-driven forecasting models, and this paper presents a new measure for evaluating that performance. Despite the fact that the objectives of hydrological data-driven forecasting models differ from those of the conventional hydrological simulation models, criteria designed to evaluate the latter models have been used until now to assess the performance of the former. Thus, the objectives of this paper are, firstly, to examine the limitations in applying conventional methods for evaluating the data-driven forecasting model performance, and, secondly, to present new performance evaluation methods that can be used to evaluate hydrological data-driven forecasting models with consistency and objectivity. The relative correlation coefficient (RCC) is used to estimate the forecasting efficiency relative to the naïve model (unchanged situation) in data-driven forecasting. A case study with 12 artificial data sets was performed to assess the evaluation measures of Persistence Index (PI), Nash-Sutcliffe coefficient of efficiency (NSC) and RCC. In particular, for six of the data sets with strong persistence and autocorrelation coefficients of 0.966–0.713 at correlation coefficients of 0.977–0.989, the PIs varied markedly from 0.368 to 0.930 and the NSCs were almost constant in the range 0.943–0.972, irrespective of the autocorrelation coefficients and correlation coefficients. However, the RCCs represented an increase of forecasting efficiency from 2.1% to 37.8% according to the persistence. The study results show that RCC is more useful than conventional evaluation methods as the latter do not provide a metric rating of model improvement relative to naïve models in data-driven forecasting.

Editor D. Koutsoyiannis, Associate editor D. Yang

Citation Hwang, S.H., Ham, D.H., and Kim, J.H., 2012. A new measure for assessing the efficiency of hydrological data-driven forecasting models. Hydrological Sciences Journal, 57 (7), 1257–1274.  相似文献   

Erratum to: Relationship of ground level enhancements with?solar, interplanetary and geophysical parameters     

K. A. Firoz  J. Hwang  I. Dorotovi?  T. Pintér  Subhash C. Kaushik 《Astrophysics and Space Science》2011,332(1):219

  相似文献   

Characterization of bacterial communities associated with seasonal water masses from Tongyoung in South Sea of Korea     

Sung-Suk Suh  Mirye Park  Jinik Hwang  Sukchan Lee  Sang Hyun Moh  Ki Hwan Park  Taek-Kyun Lee 《Ocean Science Journal》2014,49(3):193-200

Understanding the patterns of microbial diversity and their composition in seawater is necessary to assess the impacts of microbes on marine ecosystem. Although the potential roles of microbes in the ocean have been studied, their diversity and relationship with environmental factors remain unclear. In this study, we adopted a 16S rRNA gene tag-pyrosequencing technique to investigate the bacterial communities associated with two different water masses from Tongyoung in the South Sea of Korea. Our results revealed highly diverse bacterial communities up to 900 Operational Taxonomic Units (OTUs) estimated from each seawater which was collected in the month of March and May, when the environmental conditions including temperature differed significantly: 7.2°C and 17.6°C in March and May, respectively. Altogether, 13 bacterial phyla were recovered from the seawater, of which Proteobacteria was the most dominant group. In addition, the value of the Shannon index, which measures the evenness of the distribution of individuals among OTUs, in May is higher than that in March, indicating that it displays a wider diversity of bacteria. Interestingly, the proportion of pathogenic bacteria was significantly increased in the month of May compared to March, suggesting that pathogenic bacteria were increasingly emerging in May. In particular, Pseudoalteromonas and Vibrio spp. were determined as major pathogenic bacteria from both water masses, of which Vibrio spp. were dominant.  相似文献   

Biomagnification of persistent chlorinated and brominated contaminants in food web components of the Yellow Sea     

Gyo-Hyuk Byun  Hyo-Bang Moon  Jung-Hwa Choi  Jeomshik Hwang  Chang-Keun Kang 《Marine pollution bulletin》2013

Concentrations of polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), and polybrominated diphenyl ethers (PBDEs) were measured in 32 species inhabiting the Yellow Sea to assess their bioaccumulation potentials. The concentrations in these samples were lower than those reported for other countries or locations. Relatively high levels of BDE 209 in biota suggest an ongoing source of deca-BDE technical mixing within the Yellow Sea. The accumulation profiles of PCBs were uniform between species, but the concentrations of OCPs and PBDEs varied widely. Pelagic and benthic food-chain components were separated by their δ¹³C values. Significant positive correlations between δ¹⁵N and PCB 153, PCB 138, p,p′-DDE, oxy-chlordane, and trans-nonachlordane were found only for pelagic consumers, indicating that the pelagic food chain is an important bioaccumulation pathway for selected PCB and OCP compounds. The other compounds did not show any biomagnification through benthic and pelagic food chains, suggesting the lower bioaccumulation potentials of these contaminants.  相似文献   

Seismic health monitoring of RC frame structures using smart aggregates     

Wen-I Liao  C.H.Lin  J.S.Hwang  G.Song 《地震工程与工程振动(英文版)》2013,12(1):25-32

Structural health monitoring of RC structures under seismic loads has recently attracted much attention in the earthquake engineering research community. In this study, a piezoceramic-based device called "smart aggregate" was used for the health monitoring of RC frame structures under earthquake excitations. Three RC moment frames instrumented with smart aggregates were tested using a shaketable with different ground excitation intensities. Distributed piezoceramic- based smart aggregates were embedded in the RC structures and used to monitor their health condition during the tests. The sensitivity and effectiveness of the proposed piezoceramic-based approach were investigated and evaluated by analyzing the measured responses. The displacement ductility demand of the structural members was calculated and compared with the damage index determined from the health monitoring system. The comparison shows that the damage index is compatible with the calculated ductility demand.  相似文献   

Analysis of seasonal water pollution based on rainfall feature at Anyang river basin in Korea     

J. G. Han  Y. K. Lee  T. H. Kim  E. J. Hwang 《Environmental Geology》2005,48(4-5):599-608

To determine selected water pollution parameters of the Anyang River (one of the biggest contributory branches of the Han River in Korea) and its main tributaries, the geological and topographical and rainfall features in its basin were investigated, and the resulting data were tabulated. Samples were collected at the upper, mid and down parts of the Anyang River and its branches and were analyzed based on biochemical and chemical methods, Korean biotic index (KBI) and Saprobien systems. Selected parameters of concern include BOD, heavy metals, nonpoint pollution and sewage discharge. The Anyang River basin has a torrential heavy rainfall; however, the rate of rainfall significantly varies from season to season. Water pollution levels in the dry season increase dramatically. The mainstream of the Anyang River is classified as fifth grade polysaprobic water according to Saprobien system. In addition, the biotic index is over 2.5 in overall. General pollution at the junction of the Anyang River and each branch stream varies. Possible countermeasures to improve the water quality of the river include intercept the non-treated waste water and sewage at the Anyang River junction and each branch stream, enforcement of water management during the rainy season, and continuous investment on environmental restoration.  相似文献