• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.3
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• pp.293-299
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• 2012

The thermodynamic efficiency characteristics of R245fa and water as working fluids have been analyzed for the electricity generation system applying the Rankine cycle to recover the waste heat of the exhaust gas from a diesel engine for the propulsion of a large ship. The theoretical calculation results showed that the cycle, system, and total efficiencies were improved as the turbine inlet pressure was increased for R245fa at a fixed mass flow rate. In addition, the net work rate generated by the Rankine cycle was elevated with increasing turbine inlet pressure. In the case of water, however, the maximum system efficiencies were demonstrated at relatively small ratios of mass flow rate and turbine inlet pressure, respectively, compared to those of R245fa. The optimized values of the net power of the cycle, system efficiency, and total efficiency for water had relatively large values compared to those of R245fa.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2012.06a
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• pp.225-226
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• 2012

Recently, In the domestic is used mainly fiberglass reinforced plastic(GRP) and is built for maritime leisure vessel & structures. but it less attention is insufficient for ship of structural strength assessment of maritime leisure vessel. Therefore, The structural strength evaluation suitable for the domestic situation formulate and is applied to domestic regulations of "Guidance for Recreational Crafts" of Korea register of shipping(KR) & "Reinforced plastic line structure standards" of Ministry of Land, Transport and Maritime Affairs. the structural design and finite element analysis(FEA) to ensure the reliability.

• Journal of the Society of Naval Architects of Korea
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• v.48 no.3
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• pp.246-253
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• 2011

This paper presents estimation of deterministic damage extents and locations due to collision and grounding which are defined by ABS guideline and DNV ship rules. It is noted that the overall extents of damages from DNV are larger than those from ABS. Nonlinear FEAs are carried out to predict residual longitudinal strength of hull girder with asymmetric severe damages. The accuracy of the applied FEA procedure is proved by comparing FEA result with test result of a 1/3-scaled frigate. The investigated vessels are a VLCC and a large-sized bulker for which evenly distributed heeling angles from $0^{\circ}$(sagging) to $180^{\circ}$(hogging) by $30^{\circ}$ due to damage-induced flooding are taken into account. The reduction ratios of the ultimate residual strength for the damaged cases to those for the intact sagging case are shown. It is proved that the grounding damage case under DNV assumption reveals most critical the residual strength. The design formulas are presented to assure minimum residual ultimate moment after damage.

• Journal of Ocean Engineering and Technology
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• v.33 no.6
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• pp.641-647
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• 2019

Yearly world vehicle production has continued to increase, and the global seaborne trade volumes also are recovering. Based on these positive trends, as demand for cargo ships increases in the freight transportation market, Pure car and truck carriers (PCTCs) with large gaps between decks continue to be ordered. The structural analysis of the cargo hold was performed in order to confirm its structural safety in accordance with the guidance for the direct strength assessment of the Korean Register (KR) of Shipping. And, according to the type of cargo, the maximum deflection and structurally weak area that occurred in deck 5 was confirmed. Also, it was found that the weight of the cargo had a significant effect on the deck, the primary members of the deck's structure, and pillars. The results of the structural analysis conducted in this study were added to the existing cargo load planning software. This was done so that the prediction of the maximum stress and the deflection of the deck based on the information about the cargo could be confirmed quickly. In addition, the data will be used as the basic data for rapid information management response to changes in cargo items.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.6
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• pp.582-588
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• 2013

Solid Oxide Fuel Cell (SOFC) has been focused as a promising power source, which can replace a diesel engine regarding as major source of air pollution by the ship, due to high efficiency and eco-friendly. High operating temperature of SOFC is enable to secure of high efficiency, use various fuels and no need of high priced catalyst, but it may damage to components of SOFC. Therefore temperature control system has to be designed and validated before employing the fuel cell system for securing high efficiency and reliability. In this paper, instead of using typical method to validate performance of the controller, which consumes high cost and time, performance validation system using Hardware-in-the-loop simulation was developed and validated performence of the designed temperature controller for SOFC system.

• Journal of Ocean Engineering and Technology
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• v.28 no.1
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• pp.77-84
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• 2014

Recently, CFRP composites have often been used as the materials for lightweight pleasure yacht hulls. Because CFRP composites not only make the hull light but also have good physical characteristics, in the leading countries of the marine industries, CFRP yachts are being sold at a higher price. The design and construction of FRP composite yachts, including those made of CFRP, have to follow rules based on ISO 12215, such as the hull structure rules of the international classification societies. On the other hand, there are no rules related to CFRP composites in the Guidance for Recreational Crafts, which was newly revised by the Korean Register of Shipping. In this paper, ISO 12215-5 and Part B, RINA Pleasure Yacht (REGISTRO ITALIANO NAVALE) on the design pressure and scantling of CFRP hull structures are compared and analyzed. Through a comparative study and the application to a cruise yacht design, we try to understand how to design CFRP hull structures using the international standards, ISO 12215, and the rules of the international classification society, RINA.

• Journal of Welding and Joining
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• v.27 no.3
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• pp.38-43
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• 2009

The optimization of the welding parameters was studied to maximize the weldability and minimize the amount of spatter in the MAG welding of automotive steel sheets under different shielding gas composition ratio. JS-EFSC, JS-SPHC steel plates and Ar mixture gases were used as a substrate and shielding gas for welding respectively. The five welding parameters were selected through preliminary experiments and their effects on the weldability were analyzed. Experiments were performed using the Taguchi experimental method. As results, appropriate range for welding could be achieved. Amount of spatter in 80%Ar+20%$CO_2$ shielding gas was 20% of that of $CO_2$welding. Therefore, in terms of high productivity and welding cost, Ar mixture gas(80%Ar+20%$CO_2$) was recommended as a shielding gas for application of MAG process, indicating the low spatter and good weld quality.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.9
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• pp.937-944
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• 2012

The thermodynamic characteristics of a trilateral cycle with water as a working fluid have been theoretically investigated for an electric generation system to recover the waste heat of the exhaust gas from a diesel engine used for the propulsion of a large ship. As a result, when a heat source was given, the efficiencies of energy and exergy were maximized by the specific conditions of the pressure and mass flow rate for the working fluid at the turbine(expander) inlet. In this case, as the condensation temperature increased, the volume expansion ratio of the turbine could be reduced properly; however, the exergy loss of the heat source and exergy destruction of the condenser increased. Therefore, in order to recover the waste exergy from the topping cycle, the combined cycle with a bottoming cycle such as an organic Rankine cycle, which is utilized at relatively low temperatures, was found to be useful.

• Korean journal of applied entomology
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• v.56 no.3
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• pp.229-239
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• 2017

The South Korean hermit beetle has previously been identified as Osmoderma opicum, which is distributed in Japan. Because of its rarity, this species is classified as an endangered species. To date, however, the identity of this species in South Korea has not been conclusively confirmed. To assess the taxonomic status of the hermit beetle occurring in South Korea, we performed a comparative study with the beetle's Eurasian congeners, based on morphological examination and molecular analysis using COI gene sequences. The results clearly showed that the South Korean hermit beetle is identical to Osmoderma caeleste, which has been described from the Russian Far East. Therefore, we suggest that the taxonomic identity of the South Korean hermit beetle is O. caeleste.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.1
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• pp.82-93
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• 2008

The flowfield behind two cylinders and flow-induced noise generated from the cylinders in various arrangement are numerically investigated based on the finite difference lattice Boltzmann model with 21 velocity bits. which is introduced a flexible specific heat ${\gamma}$ to simulate diatomic gases like air. In an isolated cylinder with two type of mesh. some flow parameters such as Strouhal number $S_t$ and acoustic pressure ${\Delta}p$ simulated from the solution are given and quantitatively compared with those provided the previous works. The effects of the center-to-center pitch ratio $L_{cc}/d=2.0$ in staggered circular cylinders as shown in Fig. 1 and angles of incidence ${\alpha}=30^{\circ}(T_{cc}/d=0.5)$, $45^{\circ}(T_{cc}/d =0.707)$ and $60^{\circ}\;(T_{cc}/d=0.866)$, respectively, are studied. Our analysis focuses on the small-scale instabilities of vortex shedding, which occurs in staggered arrangement. With the results of drag $C_d$ and lift $C_l$ coefficients and vorticity contours. the mechanisms of the interference phenomenon and its interaction with the two-dimensional vortical structures are present in the flowfields under $Re\;{\le}\;200$. The results show that we successively capture very small pressure fluctuations, with the same frequency of vortex shedding, much smaller than the whole pressure fluctuation around pairs of circular cylinders. The upstream cylinder behaves like an isolated single cylinder, while the downstream one experiences wake-induced flutter. It is expected that, therefore, the relative position of the downstream cylinder has significant effects on the flow-induce noise, hydrodynamic force and vortex shedding characteristics of the cylinders.