• Journal of the Society of Naval Architects of Korea
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• v.53 no.5
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• pp.420-427
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• 2016

The marine equipment companies expanding facility investment in accordance with the booming economy are suffering from the reduced demand and the growth of chinese businesses. In this regard, the risk of overinvestment and the importance of prudent equipment investment must be reconsidered. Thus, in this study we performed a productivity and economical efficiency analysis in order to evaluate the investment value on production facilities in a company under the present conditions. The freezer of a fishing vessel manufactured by N company is selected as the subject of our study, while the assembly and welding cooling plates are configured as the scope of automation. Analysis on productivity and economical efficiency was conducted through CYCLONE (Cyclic Operation Network) simulation and economic analysis methods after analyzing the production process of freezer. The proposed analytical technique can be used to support the investment decision in production automation equipment of fishing vessels freezer.

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.1
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• pp.9-17
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• 2015

In order to elucidate the current state of marine pollution of heavy metals around major shipyards in Korea, seawater samples were collected at eleven sampling stations and four control stations around 4 major shipyards located in the southeastern coast of Korea in summer 2010, and 6 kinds of metals such as copper(Cu), zinc(Zn), iron(Fe), cadmium(Cd), lead(Pb) and mercury(Hg) in seawater samples were analyzed. The analyses of heavy metals in seawater showed that the mean Cu concentrations in seawater around 4 major shipyards were in the range of $0.817{\sim}1.638{\mu}g/L$ which were lower than Korean environmental standards of $20{\mu}g/L$ for the protection of human health(PHH) and of $3{\mu}g/L$ for short-term protection of marine ecosystem(SPME) but higher than Cu concentration at control station by a factor of up to 2.75. The mean Zn concentrations were in the range of $0.228{\sim}0.567{\mu}g/L$ which were lower than Korean environmental standards of $100{\mu}g/L$ for PHH and $34{\mu}g/L$ for SPME but higher than Zn concentration at control station by a factor of up to 5.91. The mean Fe concentrations were in the range of $3.332{\sim}7.410{\mu}g/L$ which were higher than Fe concentration at control station by a factor of up to 6.75. The mean Cd concentrations were in the range of $0.013{\sim}0.028{\mu}g/L$ which were lower than Korean environmental standards of $10{\mu}g/L$ for PHH and $19{\mu}g/L$ for SPME but higher than Cd concentration at control station by a factor of up to 2.33. The mean Pb concentrations were in the range of $0.007{\sim}0.126{\mu}g/L$ which were lower than Korean environmental standards of $50{\mu}g/L$ for PHH and $7.6{\mu}g/L$ for SPME. The mean Hg concentrations were in the range of $0.002{\sim}0.004{\mu}g/L$ which were lower than Korean environmental standards of $0.5{\mu}g/L$ for PHH and $1.8{\mu}g/L$ for SPME. Although the concentrations of metals such as Cu, Zn and Fe which were used in shipbuilding works were lower than Korean environmental standards for PHH and SPME, the fact that the concentrations of Cu, Zn and Fe at sampling stations around major shipyards were higher than those at control stations implies that the works in shipyards had some effects on marine water quality around shipyards. Therefore, marine environment management such as the prevention and control of the discharge of various pollutants from shipyards is required on national level.

• Korean Journal of Heritage: History & Science
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• v.48 no.1
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• pp.4-23
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• 2015

In the Buddhist paintings of the four devas, there is a change in the paper material of V aisravana(多聞天) in the early Joseon Dynasty. Until Goryeo Dynasty, Damuncheonwang, who holds a tower(塔) on the right side of Buddha was changed to the form which holds a mandolin(琵琶) in the early Joseon Dynasty. This change was first checked in Byeonsangdo in the Yuan period "The Avatamska Sutra(大方廣佛華嚴經, 1330~1336)", however the actual paper material change in the Buddhist painting is found first as a mural at the Tibetan temples, Cheolbangsa(哲蚌寺), Odunsa(吳屯寺), Baekgeosa(白居寺), which showed the change of tower which Vaisravaṇa held into mongoose. In Joseon Dynasty, also, new distribution of the four devas appeared first, which showed the change of paper material in the first floor roof-stones of Wongaksaji sipcheung seoktap, . However, the position of the four devas which held a tower and a mandolin consistently appear in the Buddhist paintings in the early Joseon Dynasty by mixing on the left and the right. This means the possibility that the paper material and the position of the four devas might be flexible in the early Joseon Dynasty. Just like reflecting this, painting image of the four devas in illustration of "saddharma-pundari-ka-$s{\bar{u}}tra$(Ming 1432, National Museum of Korea)" and illustration of "Jebulsejonyeorae-bosaljonjamyeongching-gagok(제불세존여래 보살존자명칭가곡, 1417)" has opposite position from each other. Therefore, the phenomenon in the Buddhist paintings of the early Joseon had a transitional characteristic which did not secure the fixed form of painting image by illustration of two copies where paper materials of the four devas were different, which characteristic can be said to be the characteristic of art in the transitional period.

• Polymer(Korea)
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• v.29 no.3
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• pp.266-270
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• 2005

Iron oxide nanoparticles were prepared by the thermal decomposition of iron pentacarbonyl (Fe(CO)$_5$) Poly(vinylpyrrolidone) (PVP) was used as surface-modifying agent to control the size of the iron oxide nanoparticles. The crystalline structure of PVP coated iron oxide nanoparticles was determined by XRD. The size of PVP coated iron oxide nanoparticles was determined by TEM and ELS. The particle sizes of PVP coated iron oxide nanoparticles were controlled by adjusting the molar ratio of PVP/Fe (CO)$_5$, solvent and molecular weight of PVP Particle sizes increased with increasing PVP content. Spherical $50\~100$ nm sized iron oxide nanoclusters were produced when dimethylformamide was used as a solvent. And well-defined 10 nm iron oxide nanoparticles were produced in Carbitol. The prepared PVP coated iron oxide nanoparticles exhibited a well-dispersed property in water. The results obtained in this study confirmed the feasibility of the PVP-coated iron oxide nanoparticles as a biomaterial for MRI contrast agent.

• Journal of the Society of Naval Architects of Korea
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• v.49 no.2
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• pp.116-123
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• 2012

This study aims to analyze the strength of pressure hull of a small submarine. The pressure hull of a submarine has to withstand very large differential pressure between hydrostatic pressure in submarine operating depth and atmospheric pressure in inner space of a submarine. To do that, the pressure hull is generally ring-stiffened cylindrical shell under external pressure. In this situation, there are some foreseeable failure modes of the pressure hull such as shell yielding, axisymmetric shell buckling, asymmetric shell buckling, overall buckling and buckling of end closure. We calculated collapse pressures of these failure modes with approximation and empirical formulas. And, to analyze critical buckling pressure, we performed eigenvalue analysis with finite element method tools.

• Journal of the Society of Naval Architects of Korea
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• v.49 no.2
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• pp.109-115
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• 2012

Slamming phenomenon may occur when a ship navigates a high sea region, where the response of ship can be expected as elastic behaviour and the resultant wave loads may increase. In this paper, numerical analysis of ship motions and wave loads including momentum slamming was performed using the strip theory with regular waves. In order to analyze the effect of slamming force on the global ship motions, time histories of each mode of displacement and forces were simulated by using Newmark-beta time integration scheme. The added mass and damping coefficients calculated by Lewis form method were compared with the results of given references. For verification of numerical results, the motion RAOs of a S175 containership were calculated as an example of application and time histories of respective displacement and vertical bending moment were compared with the results of ITTC workshop benchmark test.

• Journal of the Society of Naval Architects of Korea
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• v.51 no.6
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• pp.503-509
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• 2014

This paper describes the time-domain numerical method for prediction of slamming loads on a ship in waves using the strip theory. The slamming loads was calculated considering the relative vertical velocity between the instantaneous ship motion and wave elevation. For applying the slamming force on a ship section, the momentum slamming theory and the empirical formula-based bottom slamming force were used corresponding to the vertical location of wetted body surface. Using the developed method, the vertical bending moments, relative vertical velocities, and impact forces of S175 containership were compared in the time series for various section locations and wave conditions.

• Journal of the Society of Naval Architects of Korea
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• v.46 no.5
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• pp.545-551
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• 2009

In naval architecture and offshore engineering, the development and a broad use has been achieved in the field of flow control valves for pipe system. Butterfly valves are also widely used for flow control, but there are not many studies for triple-eccentric butterfly valves. Moreover, if the fluid of pipeline flows in the bi-direction then it makes more complicate to adapt triple-eccentric butterfly valves to flow control. In this study, we are trying to develop a bi-directional triple-eccentric butterfly valve through sealing mechanism and stem design study. Digital mockup using 3D CAD was constructed for shape interference check and structural analysis was conducted for structural safety. Also we performed leakage test to check out the durability of the bi-directional pressure for the developed valve.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.3
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• pp.388-397
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• 2010

A two-dimensional time-domain, potential-theory-based fully nonlinear numerical wave tank (NWT) was developed by using boundary element method and the mixed Eulerian-Lagrangian (MEL) approach for free-surface node treatment. The NWT was applied to prediction of primary wave energy conversion efficiency of a bottom-mounted oscillating water column (OWC) wave power device. The nonlinear free-surface condition inside the chamber was specially devised to represent the pneumatic pressure due to airflow velocity and viscous energy loss at the chamber entrance due to wave column motion. The newly developed NWT technique was verified through comparison with given experimental results. The maximum energy extraction was estimated with various chamber-air duct volume ratios.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.3
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• pp.350-358
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• 2010

The present paper deals with the comparative study of resistance performance with refrigerated ice and synthetic ice according to the variation of hull form characteristics. The resistance test has been conducted in pack ice condition in each concentration condition. Stem angle has been chosen as main parameters for the variation of hull form characteristics. The correlation of performance between with the refrigerated ice and with the synthetic ice has been shown according to the variation for stem angles. The present study show the possibility of ice test in general towing tank with synthetic ice for the time-consuming research such as hull form optimization although that is confined in pack ice condition. The more parametric study for the properties of synthetic ice is expected to be conducted to have more close correspondence for the test results of refrigerated ice in near future.