• Title/Summary/Keyword: Distribution Feeder

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Isotopic Evidence for Ontogenetic Shift in Food Resource Utilization during the Migration of the Slipmouth Leiognathus nuchalis in Gwangyang Bay, Korea (광양만 주둥치(Leiognathus nuchalis)의 서식처 이동에 의한 먹이원 변동 파악을 위한 안정동위원소 분석기법 적용)

  • Choi, Bohyung;Jo, Hyunbin;Park, Kiyun;Kwak, Ihn-Sil
    • Korean Journal of Ichthyology
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    • v.32 no.2
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    • pp.84-90
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    • 2020
  • We investigated carbon and nitrogen isotope ratios (δ13C and δ15N) of the slipmouth Leiognathus nuchalis to reveal the effects of body size, feeding strategy and spatial distribution on the food resource utilization during the migration in the Seomjin estuary and Gwangyang Bay. The δ13C values of L. nuchalis caught in the Seomjin estuary where the salinity is lower than 30 psu were much lower than those in the deep-bay area of Gwangyang Bay. Such a spatial heterogeneity in δ13C values of the L. nuchalis clearly indicates active feeding within the estuarine habitat. In contrast, the δ15N values of L. nuchalis showed a consistency among sites, indicating that this species occupies identical trophic level across the whole area. The slipmouth distributed throughout the bay area, reflecting its euryhaline characteristics. However, the distribution pattern appeared to be separated according to body size into smaller individuals in the low-saline estuary and larger ones in the deep bay. Overall results support the plastic feeding strategy of the slipmouth from zooplanktonic (estuarine habitat) to epibenthic (deep-bay habitat) feeder during the migration between estuarine to deep-bay habitats.

A Study on the Competitiveness Improvement of Coastal Shipping for Northeast Asia Logistics-Hub (동북아 물류거점화를 위한 연안해운 경쟁력 제고방안에 관한 연구)

  • Lee Yon-Jae;Ahn Ki-Myung;Kim Kwang-Hee;Kim Hyun-Duk
    • Journal of Navigation and Port Research
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    • v.29 no.6 s.102
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    • pp.501-508
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    • 2005
  • The purpose of this paper is to present the alternatives for improving coostal shipping logistics system to be a logistic hub-nation with a competitive edge. For this purpose, major environmental factors in Northeast Asia and accordingly its effects are analyzed And then the effects of coastal shipping system's development strategy is analysed using Structural Equation Model and Multiple Regression Model. Research results show that three types of coastal shipping development strategy( connected transportation system, structure of coastal shipping system, governmental support policy) will contribute much to being a logistics hub-nation. From the results, some implications are derived as follows. Firstly, environmental-friendly balanced ocean-coastal transport system is required Secondly, a excusive feeder port, Ro-Ro ship & high-speed ship are necessary to establish the one-stop logistics service system Finally, governmental support policy and subsidy(tax-exempted oil & various tax benefits) are required to reactivate lagged coastal shipping system to be a logistic hub-nation with a competitive edge.

A Study on a Planar Array Antenna Design with a Flat-Topped Radiation Pattern (구형 방사 패턴을 갖는 평면 배열 안테나 설계에 대한 연구)

  • Eom Soon-Young;Pyo Cheol-Sig;Jeon Soon-Ick;Kim Chang-Joo
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.15 no.9
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    • pp.896-905
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    • 2004
  • In this paper, the design, fabrication and experiment on a planar array antenna with a flat-topped radiation pattern for a mobile base station antenna were described. The current distribution of an antenna aperture, which is easily realizable in a feeding network compared with the conventional one of sin(x)/x was optimized for shaping a desired flat-topped radiation pattern. The planar array antenna designed in this paper has a rectangular lattice and is composed of array elements of 16${\times}$8. Each radiating element, which is a microstrip element fed coaxially, has a linear vertical polarization and the feed network which use a Wilkinson power divider and a 180$^{\circ}$ ring hybrid coupler as a base element is designed. The flat-topped radiation pattern with 90$^{\circ}$ is shaped by 16 array elements with the element spacing of 0.55 λ$_{ο}$ in the azimuth plane, and the normal radiation pattern with 10$^{\circ}$ is shaped by 8 array elements with the element spacing of 0.65 λ$_{ο}$ in the elevation plane. Also, the planar array antenna is symmetrically divided into four parts. It consists of one hundred-twenty-eight radiating elements, thirty-two 1-4 column dividers, low 1-8 row dividers and one 1-4 input power divider. In order to verify electrical performances of the planar way antenna proposed in this paper, the experimental breadboard operated in tile band of 1.92~2.17 GHz(IMT2000 band) was fabricated, and its experimental results were a good agreement with simulation ones.