• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.1
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• pp.64-72
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• 2021

The feeding habits of the Japanese jack mackerel Trachurus japonicus were studied in the Southern Sea of the Republic of Korea. To assess the effects of season, sampling was conducted in February (winter), May (spring), and August (summer), 2020. The total length of each fish was measured in 1 cm intervals. Diet composition showed the highest species diversity during winter. Diet composition changed from copepods to euphausiids as the total length of jack mackerel increased, except during winter. The most important seasonal prey were copepods in winter and summer and euphausiids in spring. Species diversity of the zooplankton community structure was highest in winter. Among the zooplankton communities, copepods were dominant in all seasons. Species with a high electivity index in all seasons were relatively large zooplankton of ≥2 mm. Jack mackerel had ontogenetic diet change, exhibited diet selectivity depending on size, and its feeding habits were affected by the zooplankton community structure.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.47 no.4
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• pp.356-368
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• 2011

Species composition of fishes and the recruitment properties of jack mackerel, Trachurus japonicus, in the waters around the Geumo Islands in the mid-South Sea were investigated by using both sides fyke nets every month from February to December 2010. During study period, a total of 30,503 fishes (1,380.4 kg) were collected and classified into 2 classes, 16 orders, 61 families and 121 species. The dominant species was jack mackerel occupying 80.5% of total individuals and 44.4% of total biomass. The fork length range of jack mackerel was 5.5-26.8 cm and individuals about 6 cm was appeared only in the middle and southern area of the Geumo Islands in May. The new recruitment of jack mackerel appeared from May in the waters around the Geumo Islands is probably caused by the warm water intrusion associated with the development of stratification due to the extinction of seasonal coastal cold waters by the increase of solar radiation heat. Furthermore, the jack mackerels less than 6 cm recruiting in the mid-South Sea in spring were considered as mixed ones by individuals spawned in the East China Sea and in the waters around the Jeju Island considering the collected time, migration period and spawning time of them.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.1
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• pp.44-50
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• 2017

Vehicle Holding Device(VHD) has a role that holding the launch vehicle on its launch pad until the engine therust reaches a steady condition. The analytical study of shape parameters and dynamic characteristics of hydraulic cylinders is carried out. The contraction of cylinder is considered as the major factor of releasing mechanism. Through the analysis, the decreasing of cylinder slit size and increasing initial charging pressure increase the contraction force. Through the transient analysis, cylinder load, displacement and inner pressure distribution are confirmed. The cylinder contraction force is converged to the cylinder external force when the cylinder starts to move. Also, the pressure distribution in the hydraulic cylinder is constant.

• Korean Journal of Ichthyology
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• v.2 no.1
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• pp.36-46
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• 1990

Samples were obtained with a set net during 7 months between March and October in 1987 off the coast of Hwasun, southern part of Cheju Island. Most of organisms, representing 36 species, were less than 20cm(96%) in length, and 30g(74%) in weight. The four most abundant species were jack mackerel, Trachurus japonicus ; squid, Todarodes pacificus ; mackerel, Scomber japonicus ; and Apogon semilineatus, which comprised about 89% of the total individuals and about 70% of the total weight. Diversity index, the number of species and information index for individual were high in early spring, even though biomass was not abundant. On the other hand, diversity index and information index for individual were relatively high in August in spite of low occurrence of the species number. A cluster analysis of 24 species which appeared more than twice during the 7 samplings were illustrated from the similarity matrix. All of the 24species were grouped at the 0.14 similarity level. They were divided into four groups at 0.50 level.

• Journal of English Language & Literature
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• v.54 no.1
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• pp.77-105
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• 2008

Even though Paule Marshall and Ishmael Reed have differences of gender, generation, and literary techniques, they share common points in dealing with cultural conflicts and racial discrimination in the United States as Afro-American Writers. As black minority writers, Marshall and Reed write out of a perspective of forced immigrant/fragmentary native consciousness. The purpose of this paper is to investigate the protagonist's reaction to racial prejudice, different cultures and their attempts to reconcile and to coexist with other races and their culture in these writers' representative works. Marshall's uniqueness as a contemporary black female artist stems from her ability to write from the three levels, that is, African American and Caribbean black. So, Marshall's Brown Girl, Brownstones represents an attempt to identify, analyze, and resolve the conflict between cultural loss/displacement and cultural domination/hegemony. Reed's Japanes by Spring offers a blistering attack upon the various cultural and racial factions of the academy and the bankrupt value systems in America. Reed's depiction of Jack London College's existing racial problems-later compounded by the cultural dilemmas that accompany the Japanese occupation of the institution-reveals his interest in highlighting the ways in which any monoculturalist ideology ultimately results in racist and culturally exclusive policies. Marshall's and Reed's novels provide opportunities for reader to explore various manifestations of intercultual and interethnic dynamics. They present the possibility of reconciliation and coexistence between different race and ethnic cultures through asserting a cultural hybridity and multiculturalism.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.2 no.1
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• pp.21-30
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• 1997

The present study reports the density, growth and production of a razor clam, Sinollovacula constricta, which is known to be one of the important fishreies catches from the Korean tidal flat. The annual yield reached to about 6,000 metric tons per year till 1994. The study was conducted on the Hwaseong tidal flat located on the central west coast, 40 kilometers south-west from Seoul. The annual yield of the razor clam in this area reached to about 50% of the total catch from the whole Korean coast. Samples were colleted monthly at 14 occasions from May 1992 to August 1993. Density of S. constricta ranged from 92~165 individuals per square meter during the study period. General trend of decreasing density was observed when the animal became older, but an exception was the year class of 1991 whose density was lower than that of 1990. The size of the shell was clearly separated into two classes during fall and winter (from September to February), however, the maximum frequency of the length of small size classes moved to right after February. It indicates a fast growth of young clams from spring to summer. Fast growth of the shell could also be examined by the growth curve. The shell growth of the whole life span was described by the von Bertalanffy equation of $L_t=89.3{\times}[1{\exp}\{-0.58{\times}(t+0.73\}]$. The growth in flesh dry weight was well fitted to the Gompertz growth model with the equation, $W_t=5.00{\times}{\exp}\{-4.31{\times}{\exp}(-0.043{\times}t)\}$. The clam lost about 30% of the body weight during spawning in August. The annual production calculated based on the data from September 1992 to August 1993 amounted to 150 g $DW{\cdot}m^{-2}{\cdot}yr^{-1}$ which was 2~50 fold higher than those of other bivalves occurred in Korea. This estimate was patitioned by each year classes; 87.5 by 1992, 53.4 by 1991, 59.0 by 1990 and -30.0 g $DW{\cdot}m^{-2}{\cdot}yr^{-1}$ by 1989 year class.