• Journal of the Korea Society of Computer and Information
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• v.29 no.4
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• pp.183-189
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• 2024

Against the backdrop of IMO's stricter environmental regulations due to global warming, Europe's Fit for 55 plan, and other initiatives, the establishment of infrastructure for the supply of environmentally friendly marine fuels and policy analysis are more critical than ever. This study comprehensively analyzes existing research and policies on the supply of environmentally friendly marine fuels, as well as trends in regulations, industry responses, and the current status of infrastructure for the supply of environmentally friendly fuels, to draw insightful conclusions. The results show that the establishment of infrastructure for the supply of environmentally friendly fuels is as important as the introduction of environmentally friendly ships, due to the strengthening of environmental regulations. LNG is a viable option in the short term, but a transition to carbon-free fuels is necessary in the long run. In this regard, a strategic approach is needed to focus support on fuels that are advantageous to produce, considering domestic industrial conditions from a long-term perspective. Therefore, the government should actively promote infrastructure development through measures such as supporting the development and supply of environmentally friendly fuels, improving regulations and providing incentives, attracting private investment, and strengthening international cooperation. This study is expected to serve as a valuable resource for setting policy directions for the transition to an environmentally friendly maritime industry. Future research will include a comparative analysis of the economic viability of environmentally friendly fuels and basic research on the selection of fuels that are advantageous to Korea.

• Journal of the Korean Society of Marine Environment & Safety
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• v.30 no.4
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• pp.358-364
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• 2024

Type A carrier structures that support blocks or equipment gradually deform over time with load changes, reducing the area in contact with the block and changing the load pattern from distributed to concentrated during construction work in the shipyard. This phenomenon has the potential to misrepresent actual service loads. In particular, A carriers are often used by small manufacturers, who often do not have specialized engineering capabilities, necessitating the development of a method for easy calculation of carrier safe working load. This study proposes a quick evaluation method for the long-term safe working load of Type A carriers, to predict the plastic deformation and safety issues resulting from changes in load distribution. Based on the results of finite element analysis (beam and shell modeling) of the centralized load, beam-theory was modified to propose a method for determining the distributed load conditions of the A-carrier. In beam modeling, the theoretical value was multiplied by a correction factor of 0.73 for concentrated loads and 0.69 for distributed loads to obtain a safe working load. For shell modeling, a correction factor of 0.75 can be used for concentrated loads and 0.69 for distributed loads. This study can serve as a basis for improving the safety of shipbuilding, enabling quick and effective decisions for determining safe working loads in actual working environments.

• The Journal of the Acoustical Society of Korea
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• v.43 no.4
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• pp.400-405
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• 2024

When cavitation noise occurs in ship propellers, the level of underwater radiated noise abruptly increases, which can be a critical threat factor as it increases the probability of detection, particularly in the case of naval vessels. Therefore, accurately and promptly assessing cavitation signals is crucial for improving the survivability of submarines. Traditionally, techniques for determining cavitation occurrence have mainly relied on assessing acoustic/vibration levels measured by sensors above a certain threshold, or using the Detection of Envelop Modulation On Noise (DEMON) method. However, technologies related to this rely on a physical understanding of cavitation phenomena and subjective criteria based on user experience, involving multiple procedures, thus necessitating the development of techniques for early automatic recognition of cavitation signals. In this paper, we propose an algorithm that automatically detects cavitation occurrence based on simple statistical features reflecting cavitation characteristics extracted from acoustic signals measured by sensors attached to the hull. The performance of the proposed technique is evaluated depending on the number of sensors and model test conditions. It was confirmed that by sufficiently training the characteristics of cavitation reflected in signals measured by a single sensor, the occurrence of cavitation signals can be determined.

• Journal of the Korean Society of Marine Environment & Safety
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• v.30 no.5
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• pp.450-459
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• 2024

Recently, the interest in eco-friendly energy sources, including liquefied natural gas (LNG), has considerably increased both domestically and internationally, and the development of LNG-handling facilities and berths is actively underway. Ulsan Port has been selected as a Northeast Asian oil and energy hub and is actively developing LNG and oil storage facilities and berths. The LNG terminal currently under construction in the North Port district of Ulsan New Port is a quay-type terminal rather than a dolphin-type terminal, which is the existing main-pier type. However, no domestic or international design standards for the mooring-system arrangement of quay-type LNG terminals exist. Therefore, in this study, to establish design standards for mooring systems for quay-type LNG terminals, we developed a pier that reflected the dolphin-type mooring system arrangement in the Harbour and Fishery Design Criteria and analyzed the sensitivity of mooring-evaluation parameter for actual target berthing vessels. The results showed that, compared to the mooring system arrangement of the existing quay-type pier, the tension of the mooring line, load of the QRH, reaction force of the fender, and ship motion of 6-DOF were generally reduced under the same environmental conditions, which are beneficial for improving ship and pier safety. The results of this study offer a foundation for developing design standards for quay-type LNG terminals.

• Journal of Navigation and Port Research
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• v.34 no.10
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• pp.781-786
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• 2010

In this study, a new concept of ocean transport system, called the mobile harbor serving for a short distance transport of containers with cargo handling cranes between mother containerships and coastal ports, is introduced. Instead of direct berthing a very large containership at the coastal port, Mobile Harbor is moving to the offshore mooring basin with enough water depth condition. Therefore, investigation of the coastal environment, technical condition and limitation of the domestic trade ports for the application of Mobile Harbor, is essential process. To figure out the accessibility of mobile harbor, the environmental conditions, the cargo handling capacity and marine traffic volume and flow pattern has been analyzed with the tools for marine traffic simulation and virtual navigation aids system. The most proper Mobile Harbor mooring areas among trade ports of the south and east coast are selected by analyzing the obtained information and evaluating its application: (1) Under natural environmental conditions such as air and sea weather, three candidate areas are selected such as Masan port, Ulsan port, and Busan(New port) port. (2) Under marine traffic and appropriateness of water facilities, three candidate areas are selected as Mokpo port, Busan(New port) port, and Donghae & Mookho port (3) For a region-based analysis considering handling capacity and the local managed trade ports in vicinity, three candidate areas are selected as Busan region, Yosu & KwangYang region, and Mokpo region. Through this study, the basic guideline for selection of optimum trade port and offshore mooring basin for mothership and Mobile Harbor is recommended. In order to apply the Mobile Harbor to the real water, navigaton aids as the virtual route identification with AIS must be introduced for maritime safety in the vicinity of Mobile Harbor area which berthing and cargo handling is being conducted.

• The Korean Journal of Malacology
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• v.18 no.2
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• pp.83-91
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• 2002

Reproductive cycle of natural population and artificial control experiments of gonadal development by the conditions of water temperatures-feeding and starvation of Ruditapes philippinarum were investigated by histological observations. The reproductive cycle of natural population in females and males can be categorized into five successive stages; early active (February to March), late active (April to May), ripe (April to August), partially spawned (May to October), and spent-inactive stage (August to March). In the artificial control experiments, gonadal development of this species was inhibited by the low water temperature (10$^{\circ}C$). In the experimental group which was exposed to artificial high water temperatures of 19$^{\circ}C$ and 22$^{\circ}C$, gonadal development was accelerated by the higher water temperatures and was faster (about one month) than that in natural populations. In the high water temperatures-feeding experimental group, the gonadal developmental phase was faster in the small-size group than that in the large-size group, and was faster in lower water temperature (10$^{\circ}C$)(p=0.01). The gonad developmental phases in the high water temperature (22-28$^{\circ}C$)-starvation experimental group showed faster (paired sample t-test, p=0.004) than those in the high water temperature-feeding group in females and males. In the high water temperature-feeding experimental group of female and male gonadal developments of small sized group were more sensitive than those in large sized group after 42 days cultivation, However, the gonadal development of male was more sensitive to the lower water temperature than female. On the whole, sexual maturation in the high water temperature experimental group was faster than those in the low water temperature group, and showed a significant difference (paired sample t-test, p=0.001) between female and male. In the starvation experimental group after 42 days, gonadal developments in the high water temperature-large male group showed faster than those in the high water temperature-large female group. However, in small size, gonad developmental phases showed the same pattern between feeding and starvation experimental groups. During the main spawning season, in the high water temperature-starvation experimental groups in females and males, their gonadal development showed faster than that in higher water temperature-feeding experimental group regardless of their sexes and individual sizes and showed a significant difference (paired sample t-test, p=0.004).

• Journal of the Korean Society of Food Science and Nutrition
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• v.13 no.1
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• pp.97-106
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• 1984

The Antarctic krill, Euphausia superba, is drawing attention over the world as the largest source of unutilized proteins in the ocean. For the use of krill as a human food, processing conditions of krill sauce by autolysis and/or commercial proteolytic enzyme digestion were examined. The krill was chopped and mixed with equal weight of water, and hydrolyzed by autolysis and/or commercial proteolytic enzyme digestion. The optimal conditions for hydrolysis of krill were $52.5^{\circ}C$, pH 7.0-7.5, 3 hours by autolysis, $52.5^{\circ}C$, pH 6.3, 3hours by bromelain (0.5 %) digestion, and $52.5^{\circ}C$, pH 7.0-7.5, 3 hours by commercial complex enzyme (5 %) digestion, respectively The maximum hydrolyzing rate of protein were 83.2 % by autolysis, 89.7 % by bromelain digestion, 92.7 % by commercial complex enzyme digestion. After krill meat hydrolyzed by autolysis at optimum condition, inactivated at $100^{\circ}C$ for 20 minutes and filtered with Buchner funnel. Two kinds of products were prepared with krill hydrolysate and preservatives: one contained 10 % of sodium chloride and 0.06 % of benzoic acid and the other 10 % of sodium chloride and 3 % of ethyl alcohol. These products were filled in the sterilized glass bottle and sealed. The pH, volatile basic nitrogen, amino nitrogen, color value (L, a and b values) and viable counts of bacteria were determined during storage at $37^{\circ}C$. The results showed that the products could be preserved in good condition during one month at $37^{\circ}C$. As a method to reduce the sodium level in krill sauce, it is convinced that sodium chloride could be replaced half in partially by potassium chloride. In the products prepared from krill by autolysis, bromelain or commercial complex enzyme digestion, hypoxanthine and 5'-IMP were abundant among the nucleotides and their related compounds as 15.3-20.4 ${\mu}mole/g$, dry solid, 2.2-2.5 ${\mu}mole/g$, dry solid, respectively. The abundant free amino acids were lysine, leucine, proline, alanine and valine. The contents of these amino acids were 67.4 %, 69.4 %, 69.8 % of the total free amino acids of each products. And TMAO, betaine and total creatinine were low in contents. The flavor of krill sauce prepared from krill by autolysis or enzyme digestion was not inferior to that of traditional Kerean soy sauce by sensory evaluation.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.29 no.1
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• pp.28-41
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• 2024

The carbon balance serves as a valuable indicator of a plant's physiological status under diverse environmental conditions. We investigated the photosynthetic and respiratory responses of the Asian surfgrass Phyllospadix iwatensis along the northeast coast of the Korean peninsula in response to changing water temperature (ranging from 5℃ to 30℃) to estimate the seasonal whole-plant carbon balance through a series of incubation experiments. The maximum gross photosynthetic rate (P_max) showed a significant difference among the temperature treatments, while there was no significant difference in photosynthetic efficiency (α). The maximum gross photosynthetic rate of P. iwatensis reached its peaks at 20℃ treatment (101.65 μmol O₂ g^-1 DW h^-1) but decreased rapidly at 30℃. The saturation irradiance (I_k), compensation irradiance (I_c), and respiration rate (R) of P. iwatensis exhibited significant differences among the temperature treatments. The saturation irradiance increased up to 20-25℃ (121.59-124.50 μmol photons m^-2 s^-1) and sharply decreased at 30℃. The compensation irradiance and respiration rate increased steadily with rising water temperature. The ratio of P_max to R (P_max:R ratio) was the highest at 5℃ but dramatically decreased at 30℃. The whole-plant carbon balance, calculated based on photosynthetic parameters, respiration rates, and biomass, exhibited distinct seasonal variation, increasing during winter and spring and decreasing during summer and fall, which is consistent with the highest in situ growth in spring and severely limited growth at the highest water temperature conditions. Phyllospadix iwatensis displayed a negative carbon balance during late summer, fall, and winter, but demonstrated a positive carbon balance during spring and early summer. Our findings suggest that the rising seawater temperatures associated with climate change may lead to significant alterations in the seagrass ecosystem functioning along the rocky shores of the Korean east coast.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.18 no.1
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• pp.40-46
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• 2013

The isotope ratios of $^{13}C/^{12}C$ and $^{18}O/^{16}O$ for a sample in a mass spectrometer are measured relative to those of a pure $CO_2$ reference gas (i.e., laboratory working standard). Thus, the calibration of a laboratory working standard gas to the international isotope scales (Pee Dee Belemnite (PDB) for ${\delta}^{13}C$ and Vienna Standard Mean Ocean Water (V-SMOW) for ${\delta}^{18}O$) is essential for comparisons between data sets obtained by other groups on other mass spectrometers. However, one often finds difficulties in getting well-calibrated standard gases, because of their production time and high price. Additional difficulty is that fractionation processes can occur inside the gas cylinder most likely due to pressure drop in long-term use. Therefore, studies on laboratory production of pure $CO_2$ isotope standard gas from stable solid calcium carbonate standard materials, have been performed. For this study, we propose a method to extract pure $CO_2$ gas without isotope fractionation from a solid calcium carbonate material. The method is similar to that suggested by Coplen et al., (1983), but is better optimized particularly to make a large amount of pure $CO_2$ gas from calcium carbonate material. The $CaCO_3$ releases $CO_2$ in reaction with 100% pure phosphoric acid at $25^{\circ}C$ in a custom designed, evacuated reaction vessel. Here we introduce optimal procedure, reaction conditions, and samples/reactants size for calcium carbonate-phosphoric acid reaction and also provide the details for extracting, purifying and collecting $CO_2$ gas out of the reaction vessel. The measurements for ${\delta}^{18}O$ and ${\delta}^{13}C$ of $CO_2$ were performed at Seoul National University using a stable isotope ratio mass spectrometer (VG Isotech, SIRA Series II) operated in dual-inlet mode. The entire analysis precisions for ${\delta}^{18}O$ and ${\delta}^{13}C$ were evaluated based on the standard deviations of multiple measurements on 15 separate samples of purified $CO_2$. The pure $CO_2$ samples were taken from 100-mg aliquots of a solid calcium carbonate (Solenhofen-ori $CaCO_3$) during 8-day experimental period. The multiple measurements yielded the $1{\sigma}$ precisions of ${\pm}0.01$‰ for ${\delta}^{13}C$ and ${\pm}0.05$‰ for ${\delta}^{18}O$, comparable to the internal instrumental precisions of SIRA. Therefore, we conclude the method proposed in this study can serve as a way to produce an accurate secondary and/or laboratory $CO_2$ standard gas. We hope this study helps resolve difficulties in placing a laboratory working standard onto the international isotope scales and does make accurate comparisons with other data sets from other groups.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.4
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• pp.339-347
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• 2000

An algicidal bacterium, Micrococcus sp. LG-5 against the harmful dinoflagellate, Cochlodinium polykrikoides was isolated. The optimal conditions for the highest algicidal activity of bacterial culture filtrate showed in the range of $20{\~}30^{\circ}C$, at pH 7.0 and $3.0{\%}$ of NaCl concentration. In addition, $IC_(50)(mean of 50{\%} inhibitory concentration)$ of the culture filtrate against C. polykrikoides after incubation of 5 days was $0.482{\%}$. To investigate heat and pH stability of the culture filtrate of Micrococcus sp. LG-5, the culture filtrate ($pore size, 0.1 {\mu}m$) was heated to $121^{\circ}C for 15 min$ and adjusted pH from 2.0 to 10.0. There were no significant changes in algicidal activity by heat treatment and the pH change between pH from 5.0 to 10.0. The algicidal substances produced from Micrococcus sp. LG-5 were mainly detected in the fraction of $10,000{\~}1,000$ MWCO (molecular weight cut-off). The culture filtrate of Micrococous sp. LG-5 showed antimicrobial activity against Enterococcus faecalis, Escheiichia coli, Uebsiella pneunioniae and Vibrio altinolyticus, but did not show against Pseudomonas aeminosa, P. Buorescens, Salmonella typhi, Staphylococcus aureus, V. cholerae and V parahaemolyicus. The culture filtrate of Micrococcus sp. LG-5 was examined against 16 phytoplankton species and showed the algicidal activity against Ajexandzium tuarense, Eutreptiella Drnnastin, Gymnodinium catenatum, G. mikimotoi, G. sanguineum, eyodinium impuaicum, Heterocapsa triquetra, Heterosipa akashiwo, Prorocentrum micans and Pyraminonas sp.. However no algicidal effects of Micrococcus sp. LG-5 were observed against Chlamydomonas sp., Cylindrotheoa closterium, P. mininum, P. triestimum, Pseudonieschia sp. and Sczipuiella trochoidea. On the other hand, algicidal activity on the tested marinelivefood was not detected except for Isochrysis galbana. In addition, physiological responses of cultured olive flounder (Paralichthys oliraceus) exposed to $1 and 10{\%}$ of the culture filtrate of Micrococcus sp. LG-5 were measured. There were no clear changes in AST, GGT, creatinine, urea, total cholesterol, total protein, albumine, $Mg^(+2), Ca^(+2), Na^+, K^+, and Cl^-$. These results indicate that olive flounders were not affected when they were exposed to the culture filtrate of Micrococcus sp. LG-5.