• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.5
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• pp.493-501
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• 2001

A study on the community structure of macrobenthos was accomplished around Kadugdo, a south coast of Korea. Sampling was performed bimonthly using a Smith-McIntyre grab ($0.05 m^2$) at ten stations from January to November, 1998. A total of 260 species was sampled with mean density of $1,729 ind./m^2$and biomass of $154.7 gwwt./m^2$during the study periods. Of these species, there were 96 species of arthropods ($37.0\%$), 89 species of annelids ($34.2\%$), 45 species of molluscs ($17.3\%$) and 30 species of others ($11.5\%$). Annelids were density-dominant faunal group with a mean density of $1,263 ind./m^2$which occupied $73.0\%$ of the total individual of benthic animals. Molluscs were represented as biomass-dominant faunal group with a mean biomass of $99.5 gwwt./m^2$ ($64.3\%$ of total biomass). The density-dominant species were a bivalvia Theora fragilis ($194 ind./m^2$) and five species of polychaetes, Lumbrineris longifolia ($177 ind./m^2$), Chaetozone setosa ($150 ind./m^2$), Sternaspis scutata ($116 ind./m^2$), Sigambra tentaculata ($106 ind./m^2$) and Hemipodus yenourensis ($94 ind./m^2$). And major biomass-dominant species was a bivalvia Ruditapes philippinarum ($45.6 gwwt./m^2$). Clustering analysis showed that the study area could be divided into two station groups and three stations: southwestern part of Kadugdo effected on Chinhae Bay, fisheries farming area and eastern part of Kadugdo effected on Nakdong River estuary.

• Journal of Korean Society for Atmospheric Environment
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• v.34 no.3
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• pp.393-405
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• 2018

Volatile organic compounds (VOCs) are representative air pollutants due to their detrimental effects on human health and their role in formation of secondary organic aerosols. Assessments and monitoring programs of VOCs using periodic grab sampling like Tedlar bags, canisters, and sorbent traps provide limited information, often with delay times of days or weeks. Selected ion flow tube mass spectrometry (SIFT-MS) is an emerging analytical technique for the real-time quantification of VOCs in air. It relies on chemical ionization of the VOCs molecules in air introduced into helium carrier gas using $H_3O^+$, $NO^+$, and $O_2{^+}$ precursor ions. Real-time monitoring method of 60 VOCs in the ambient air was developed using TO-15 standard gas mixture. Calibration curves, method detection limit, and quantitation reproducibility of the target compounds were tested. Dynamic dilution system was used to dilute standard gas from 0.174 ppbv to 100 ppbv, where calibration curves showed good linearity with $r^2$> 0.95 in all target analytes. Limit of detection (LOD) all compounds were sub ppbv, and some halogenated compounds showed pptv levels. Seven consecutive analyses of target compounds showed good repeatability with relative standard deviation of less than 10%. One day monitoring of VOCs in ambient air was conducted in Geoje. Average concentration of target VOCs in Geoje were relatively lower than other regions, among which formaldehyde showed the highest concentration ($15.4{\pm}5.78ppbv$). SIFT-MS provided good temporal resolution data (1 data per 3.2 minute), which can be used for identifying ephemeral short-term event. It is expected that SIFT-MS will be a versatile monitoring platform for VOCs in ambient air.

• Economic and Environmental Geology
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• v.39 no.6 s.181
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• pp.719-738
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• 2006

Simrad EM950 multibeam data and surficial sediment grab samples were acquired to correlate backscatter strength with surficial sediment properties in the eastern Yellow Sea which tidal sand ridges are dominantly developed. The study area is divided into the western sand ridge zone characterized by well sorted, fine sandy sediment, and the eastern non-sand ridge zone characterized by poorly sorted, medium sand with some gravels and shell fragments. In spite of minor difference in grain size between two zones, the variations of backscatter strength between two zones are distinct. Multibeam backscatter strength of study area shows good correlation with the grain size of surface sediment as well as the carbonate contents. High occurrence of carbonate shell fragments can increase grain size and bottom roughness. The dominance of higher backscatter strength in the eastern non-sand ridge zone may reflect the effects of coarse grain size and high shell fragments contents.

• Economic and Environmental Geology
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• v.28 no.3
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• pp.199-211
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• 1995

The deep sea camera system could render it possible to obtain the detailed information of the nodule distribution, but difficult to estimate nodule abundance quantitatively. In order to estimate nodule abundance quantitatively from deep seabed photographs, the nodule abundance equation was derived from the box core data obtained in KODOS area(long.: $154^{\circ}{\sim}151^{\circ}W$, lat.: $9^{\circ}{\sim}12^{\circ}N$) during two survey cruises carried out in 1989 and 1990. The regression equation derived by considering extent of burial of nodule to Handa's equation compensates for the abundance error attributable to partial burial of some nodules by sediments. An average long axis and average extent of burial of nodules in photographed area are determined according to the surface textures of nodules, and nodule coverage is calculated by the image analysis method. Average nodule abundance estimated from seabed photographs by using the equation is approximately 92% of the actual average abundance in KODOS area. The measured sampling points by box core or free fall grab are in general very sparse and hence nodule abundance distribution should be interpolated and extrapolated from measured data to uncharacterized areas. The another goal of this study is to depict continuous distribution of nodule abundance in KODOS area by using PC-version of geostatistical model in which several stages are systematically proceeded. Geostatistics was used to analyse spatial structure and distribution of regionalized variable(nodule abundance) within sets of real data. In order to investigate the spatial structure of nodule abundance in KODOS area, experimental variograms were calculated and fitted to a spherical models in isotropy and anisotropy, respectively. The spherical structure models were used to map out distribution of the nodule abundance for isotropic and anisotropic models by using the kriging method. The result from anisotropic model is much more reliable than one of isotropic model. Distribution map of nodule abundance produced by PC-version of geostatistical model indicates that approximately 40% of KODOS area is considered to be promising area(nodule abundance > $5kg/m^2$) for mining in case of anisotropy.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.25 no.2
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• pp.115-132
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• 1992

This study was conducted to clarify the distribution pattern of macrobenthic soft-bottom dwelling animals near the shellfish farming ground in Chinhae Bay, Korea Sampling was seasonally performed with van Veen grab$(0.1m^2)$ from October 1990 to July 1991. Benthic animals collected during the study comprised 107 species which amounted to 6,978 individuals: 52 species from polychaetes$(48.6\%)$, 34 species from crustaceans$(31.8\%),$ 14 species from molluscs$(13.1\%)$ and 7 species from other faunal groups$(6.5\%)$. The dominant species were four polychaetes and one amphipod: Lumbrineis longifolia, Capitella capitate, Mediomastus sp., Sigambra tentaculata and Erictonius pugnax. The study area could be divided into 3 regions based on the faunal similarity which was closely related to the content of organic matter in the surface sediment. The benthic community located near the shellfish farming ground showed large spatial and seasonal variations in species diversity and evenness in contrast to the stable values off the farming area. The oxygen deficient water mass below 2 ml/l In thi bottom layer during the summer stressed and depauperated the benthic community in the autumn of 1990. However, the benthic community did recover during the winter. It is postulated that the cyclic phenomenon of summer mortality followed by winter recovery may be a common characteristic in benthic communities subjected to a high level of organic pollution.

• Journal of Intelligence and Information Systems
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• v.17 no.4
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• pp.75-94
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• 2011

In this paper, we explore the information diffusion mechanism under social network environments by investigating the effect of message characteristics on the volume and speed of retweeting in Twitter, a popular online social media service. To this end, we select eight main keywords (i.e., '무상급식', '반값등록금', '나가수', '평창', '김연아', '박태환', '아이폰', '갤럭시') that have been popular on online social media in recent days. Each keyword represents various social aspects of Korea that recently grab people's attention such as political issues, entertainment, sports celebrities, and the latest digital products, and eventually holds distinctive message characteristics. Analyzing the frequency and velocity of retweeting for each keyword, we find that more than half of the sample messages posted on Twitter contain personal opinions for the certain keyword, but we also find that the tweets which include objective messages with hyperlink are the fastest ones when being retweeted by other followers. In overall, when being retweeted, the group of messages related to the certain keyword present distinctive diffusion patterns and speed according to message characteristics. From academic perspective, the findings in the study broaden our theoretical knowledge of information diffusion mechanism over online social media. For practitioners, the results also provide managerial implications regarding how to strategically utilize online social media for marketing communications with customers.

• The Journal of the Acoustical Society of Korea
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• v.34 no.6
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• pp.411-422
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• 2015

This paper presents an overview of the geological environment investigation and underwater acoustic measurements for the purpose of "Study on the Relationship between the Geological Environment and Acoustic Propagation in Shallow Water", which are jointly carried out by KIOST (Korea Institute of Ocean Science & Technology) and Hanyang University in the western shallow water off the Taean peninsula in the Yellow Sea in April-May 2013. The experimental site was made up of various sediment types and bedforms due to the strong tidal currents and coastal geomorphological characteristics. The geological characteristics of the study area were intensively investigated using multi-beam echo sounder, sub-bottom profiler, sparker system and grab sampler. Acoustic measurements with a wide range of research topics in a frequency range of 20~16,000 Hz: 1) low frequency sound propagation, 2) mid-frequency bottom loss, 3) spatial coherence analysis of ambient noise, and 4) mid- frequency bottom backscattering were performed using low- and mid-frequency sound sources and vertical line array. This paper summarizes the topics that motivated the experiment, methodologies of the acoustic measurements, and acoustic data analysis based on the measured geological characteristics, and describes summary results of the geological, meteorological, and oceanographic conditions found during the experiments.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.2 no.2
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• pp.101-109
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• 1997

The present study was carried out to investigate the temporal and spatial changes in species composition and abundance of polychaetes in Lake Shihwa. Macrobenthic fauna were collected from eight sampling surveys performed in March, June, September and December of 1994, March and October of 1995, February and August of 1996, using a modified van Veen grab with 0.1 $m^2$ coverage area. Polychaete worms, the most abundant macrofaunal group, comprised of 1~22 species at each investigation; number of species continuously decreased during the survey period. The mean density of polychaete was $794{\pm}1,275\;indiv.{\cdot}m^{-2}$ and showed a large fluctuation over time. The variation in abundance was mainly coupled with the domination of Polydora ligni occupying 83% in total density. The next dominant species were Pseudopolydora kempi (mean density of 31 $indiv.{\cdot}m^{-2}$) and Capitella capitata (mean density of 23 $indiv.{\cdot}m^{-2}$). Abundant polychaetes in Lake Shihwa are known to be tolerant to sediment pollution. Ecological indices such as diversity (H') and dominance (D) also indicated that the number of species significantly decreased and a few species predominated in Lake Shihwa after the dike construction. The azoic zone were extended from the upper reach of Lake Shihwa to the vicinity of the dike over time. The reduced number of species, predominance of pollution indicator species and development of an azoic zone reflect severe deterioration of benthic environments in Lake Shihwa.

• 한국해양학회지
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• v.28 no.3
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• pp.241-258
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• 1993

To investigate the sedimentary environments on the coastal areas of Imja to Nakweol islands which show very complex shorelines and several zonal sand ridges in NE-SW direction, southwestern coast of Korea, a total of forty samples were taken by a grab sampler and sedimentological and micropaleontological studies on those samples were carried out. The present study area are classified into muddy sandy gravel, sand, city sand, sandy silt and silt facies. With statistical moment parameters such as mean, sorting, skewness and ketosis for the sediments in the study area, the sediments are generally categorized as shallow sedimentary facies. The characters that are observed in quartz grains among the sandy sediments of the study area imply the existence of high energy environments, temporal exposures in atmosphere and the mixing of clastic sediments of the several different origins. In the sediments of the study area, one genera belonging to six silicoflagellata species and five genera belonging to five nannoplankton species were detected. On the basis of the micro-organism assemblage, the study area seems to be influenced by active reworking dominantly under warm water masses. In addition, organic matter ad carbonate contents in the sediments did not show a definite relation with the occurrences of the micro-organisms in the study area.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.3
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• pp.230-237
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• 2000

An ecological study of the benthic macrofauna was carried out using a modified van Veen grab in September 1997, in Namdaechon estuary, Yangyang, Korea. A total of 17 macro-invertebrates was collected and examined from eleven stations in the study area, including 3,795 individuals and 738.63 g wet weight. Arthropods, annelids and molluscs were most abundant and occupied more than $95{\%}$ of the total number of species, individuals and biomass. Namdaechon estuary in Yangyang was very poor in macrobenthic biodiversity, and numerically dominated and characterized by the polychaetes Heteromastus filiformis, Hediste japonica, Eteone longa, an unidentified oligochaete Oligochaeta sp., a corbulid bivalve Corbicula japonica, and an estuarine isopod Cyathura higoensis. Species composition, species dominance, density, and species evenness were compared among stations. The macrofaunal azoic zone appeared in the bottom of 7 m in depth nearby the artificial bank to catch the salmons to return to the livers for spawning. It probably resulted from the oxygen depletion following strong stratification in summer, which can cause major effect on the ecological conditions and then finally kill bottom macro-invertebrates in this area. Moreover, some opportunistic species thrived in nearby another station and this is of vital importance in terms of the ecological succession in a benthic polluted area.