• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.47 no.4
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• pp.281-289
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• 2011

The purpose of this study is to identify the flow resistance of the bottom trawl net. The bottom trawl net being used in the training ship of Chonnam National University was selected as a full-scale net, and model nets such as 1/10, 1/25 and 1/50 of the actual net were made. Total resistance of the net part, the height of the net mouth and the flow resistance of components of the net such as wing, bag and cod-end part was measured, converted into full-scale and compared. Additionally, the model rule of Tauti (1934), which has been most frequently used in fishing net modeling experiments, was applied to interpret flow resistance and scale effect of model experiment was investigated. Presumed that the flow resistance R is $R=kS{\upsilon}^2$ against the flow velocity of each net ${\upsilon}$, resistance coefficient k was calculated by substituting R, ${\upsilon}$ and S of the net. From the result, it was found that k decreases exponentially when u increases which makes $k=c{\upsilon}^{-m}$. Whereas m of each net is ranged between 0.13-0.16 and there was not significant difference between nets. c does not show big difference in 1/10 and 1/25 model and the value itself was relatively bigger than in 1/50 model. The height of the net mouth of 1/25 and 1/50 model net h decreases exponentially according as ${\upsilon}$ increases to make $h=d{\upsilon}^{-n}$. Whereas d and n values were almost same in two nets. Additionally, when resistance of cod-end, wing and bag part in 1/25 and 1/50 model nets, both nets showed big resistance in bag part when flow is 1m/s as more than 60%. Wing and cod-end part showed almost same value or wing part had little bit larger value. On the other hand, when reviewing the reasons why both models showed difference in 1/50 model while c value against the resistance coefficient k did not show big difference in 1/10 and 1/25 model, it is inferred that the difference occurred not from material difference but from the difference in net size according to scale. It was judged that they are the scale effects concomitant to the model experiments.

• Journal of the East Asian Society of Dietary Life
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• v.15 no.1
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• pp.49-56
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• 2005

The purpose of this study was to measure the changes of regional cerebral blood flow(rCBF) and blood pressure(BP) in rats, following the intravenous injection of Nelumbo nucifera water extract. The measurement was continually monitored by laser-doppler flowmeter and pressure transducer in anesthetized adult Sprague-Dawley rats for about 2 to 2 and half hours through the data acquisition system composed of MacLab and Macintosh computer. The results of this experiment were as follows. Nelumbo nucifera significantly increased the changes of rCBF in rats. The rCBF of Nelumbo nucifera was not changed by pretreated propranolol, atropine, L-NNA and indomethacin. But the rCBF of Nelumbo nucifera was decreased by pretreated methylene blue. Nelumbo nucifera decreased the BP significantly. The BP of Nelumbo nucifera was not changed by pretreated propranolol, atropine, L-NNA and indomethacin. But the BP of Nelumbo nucifera was decreased by pretreated methylene blue. These results indicated that Nelumbo nucifera might increase the rCBF and decrease the BP which related to guanylyl cyclase activity.

• Asian Journal of Innovation and Policy
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• v.5 no.2
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• pp.197-207
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• 2016

This paper seeks to measure the monetary value of technical development in the deep seabed manganese nodule mining by applying the compound option model (COM). The COM is appropriate for the project in terms of its decision-making structure and embedded uncertainty. The estimation results show that the deep seabed mining project has more economic potential than shown by the previously obtained results from the discounted cash flow (DCF) analysis. In addition, it is reasonable to invest in the project taking the various uncertainty factors into consideration, because the ratio of the value to the cost of the project is far higher than one. This information can be utilized in national ocean policy decision-making.

• Structural Engineering and Mechanics
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• v.54 no.5
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• pp.999-1016
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• 2015

In this paper, we introduce a new method for assembly of shipbuilding blocks at sea and present its feasibility focusing on structural safety. The core concept of this method is to assemble ship building blocks by use of bolting, gluing and welding techniques at sea without dock facilities. Due to its independence of dock facilities, shipyard construction capability could be increased considerably by the proposed method. To show the structural safety of this method, a bulk carrier and an oil tanker were employed, and we investigated the structural behavior of those ships to which the new block assembly method was applied. The ship hull models attached with connective parts are analyzed in detail through finite element analyses, and the cargo capacity of the bulk carrier is briefly discussed as well. The results of these studies show the potential for applying this new block assembly method to practical shipbuilding.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2001.05a
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• pp.220-221
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• 2001

Phytic acid (myo-inositol 1,2,3,4,5,6-hexakisdihydrogen phosphate) is one of the major storage form of phosphorous in the seeds of plants, which are the principal components of feed stuffs. Monogastric animals like Pigs and poultry as well as fish lack phytase activities in their digestive system and most undigested phytic acid was excreted in their manure. (omitted)

• Journal of the Korean GEO-environmental Society
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• v.15 no.3
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• pp.33-40
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• 2014

In this paper, mechanical and germination characteristics of stabilized dredged soils were investigated to recycle dredged soil in eco-friendly manner such as waterfront construction. Non sintering binder (NSB), which was developed by using interchemical reactions between slag, high-calcium fly ash, alkali activator on the dredged marine clay, was added to dredged soil. Ordinary portland cement was also used for the comparison of two binders. Experimental tests such as flow test and unconfined compressive test were carried out to evaluate characteristics of stabilized dredged soil. Leaching test, pH measure, vegetation germination test were also conducted to consider environmental applicability. The unconfined compressive tests shows that unconfined compressive strength (UCS) also increases with the increase of curing time and mixed ratio. UCS of NSB mixtures were higher than those of OPC mixtures. Germination tests showed that germination and sprouting date are better in NSB mixture than OPC mixture. It can be explained that germination decreased as pH and 7-day strength increased.

• Corrosion Science and Technology
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• v.17 no.3
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• pp.109-115
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• 2018

Electrical Resistance Welding (ERW) on a longitudinal seam-welded pipe has been extensively used in oil and gas pipelines. It is well known that the weld zone commonly suffers from grooving corrosion in ERW pipes. In this paper, the grooving corrosion performances of API X65 grade non-sour service (steel-A) and API X70 grade sour gas resistant (steel-B) steel electrical resistance welding pipelines were evaluated. The microstructure of the bondline is composed of coarse polygonal ferrite grains and several elongated pearlites. The elongated pattern is mainly concentrated in the center of the welded area. The grooving corrosion test and electrochemical polarization test were conducted to study the corrosion behavior of the given materials. A V-shaped corrosion groove was found at the center of the fusion zone in both the steel-A and steel-B ERW pipes, as the corrosion rate of the bondlines is higher than that of the base metal. Furthermore, the higher volume fraction of pearlite at the bondline was responsible for the higher corrosion rate at the bondline of both types of steel.

• Korean Journal of Ecology and Environment
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• v.54 no.1
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• pp.12-23
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• 2021

As fish communities are sensitive to natural environmental changes as well as anthropogenic pressures, their composition and characteristics help us to assess the aquatic ecosystem health. The fish fauna and the length-weight relationship of Zacco platypus in the Seomjin River system were investigated from July 2018 to May 2019. The collected species during the survey period were 49 species belong to 14 families including 19 Korean endemic and two endangered species. According to Bray-Curtis similarities, 14 sites were divided into four groups based on the fish community composition; two groups(group A, B) and two uncategorized sites(group C, D). There were significant differences between groups A and B(analysis of similarities, R=0.722, p=0.002). A similarity percentage analysis revealed that Z. koreanus(8.55%), Micropterus salmoides(6.90%), and Lepomis macrochirus (4.90%) contributed to these differences of fish assemblages between group A and B. Group A showed higher relative abundances of exotic species such as M. salmoides and L. macrochirus, while Z. platypus and Z. koreanus which are the common species in Korea, were the most dominant species in group B. Based on the length-weight relationship of Z. platypus, b values were varied from 2.82 to 3.80, indicating that growth patterns of the species were spatially different. This study could be served as baseline data for understanding fish fauna, assessing habitat characteristics based on the fauna, and identifying health conditions of Z. platypus in the Seomjin River system.

• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.1
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• pp.530-541
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• 2019

To improve our current understanding of tsunami-like solitary waves interacting with a row of vertical slotted piles on a sloping beach, a 3D numerical wave tank based on the CFD tool $OpenFOAM^{(R)}$ was developed in this study. The Navier-Stokes equations were employed to solve the two-phase incompressible flow, combining with an improved VOF method to track the free surface and a LES model to resolve the turbulence. The numerical model was firstly validated by our laboratory measurements of wave, flow and dynamic pressure around both a row of piles and a single pile on a slope subjected to solitary waves. Subsequently, a series of numerical experiments were conducted to analyze the breaking wave force in view of varying incident wave heights, offshore water depths, spaces between adjacent piles and beach slopes. Finally, a slamming coefficient was discussed to account for the breaking wave force impacting on the piles.

• Journal of fish pathology
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• v.30 no.1
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• pp.41-49
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• 2017

Probiotic principles can be applied in aquaculture for the purpose of growth and immunity stimulation, disease prevention and eventually better production performance. This study was to assess effects of combinations of microbes containing two Bacillus sp., plus one Lactobacillus sp. as the basal preparation (BSL-LAB), and additional Nitrosomonas sp. (nitrifying bacteria consortium, NBS) in olive flounder (Paralichthys olivaceus). The effects examined were growth parameters, hematologic parameters, innate immunity and pathogen challenge test. Fish were assigned to 4 treatments as Control (no probiotics), Group A (Bacillius and Lactobacillus to culture water), Group B (Bacillius and Lactobacillus both in water and feed), Group C (same as Group B with additional Nitrosomonas in feed). Fish were allocated to the above 4 groups, each group being composed of triplicate 30 fish, for a 7-week feeding in the laboratory. Positive effects were observed both in growth and pathogen sensitivity with all three probiotic combinations. Such effects were attributed to improved innate immune functions. This result indicates that the tested probiotic microbes are beneficial to olive flounder aquaculture.