• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.6
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• pp.697-703
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• 2023

As a part of the global industrial efforts to reduce environmental pollution owing to air pollution, regulations have been established by the International Maritime Organization (IMO). The IMO has implemented various regulations such as EEXI, EEDI, and CII to reduce air pollution emissions from ships. They are also promoting measures to decrease the power consumption in ships, aiming to conserve energy. Most of the power used in ships is consumed by electric motors. Among the motors installed on ships, the engine room blower that takes up a significant load, operates at a constant irrespective of demand. Therefore, energy savings can be expected through frequency control. In this study, we demonstrated the efficacy of energy savings by controlling the frequency of the electric motor of the generator blower that supplies combustion air to the generator's turbocharger. The system was modeled based on the output data of the turboharger outlet temperature in response to the blower frequency inpu. A PI control system was established to control the frequency with the target being the turbocharger outlet temperature. By maintaining the turbocharger design standard outlet temperature and controlling the blower frequency, we achieved an annual energy saving of 15,552kW in power consumption. The effectiveness of energy savings through frequency control of blower fans was verified during the summer (April to September) and winter (March to October) periods. Based on this, we achieved annual fuel cost savings of 6,091 thousand won and reduction of 8.5 tons of carbon dioxide, 2.4 kg of SOx, and 7.8 kg of NOx air pollutants on the training ship.

• Korean Journal of Environmental Biology
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• v.36 no.1
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• pp.11-20
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• 2018

In planktonic ecosystems, the microplastics are considered as a potential food source for the zooplankton. To study a relationship between the zooplankton and the neustonic microplastics, a research experiment was carried out during May in the surface layers of the Yeosu coastal areas including Yeoja Bay, Gamak Bay, Yeosuhae Bay, and Botdol Sea. A neustonic zooplankton net (mesh size $300{\mu}m$; mouth area $30cm{\times}18cm$) was towed from the side of the ship in the event that it would not be affected by waves crashing by the ship at a speed of ca. 2.5 knots. All of the microplastic particles were separated from the zooplankton. The zooplankton and microplastics were appearing in a range of 61 to $763indiv.m^{-3}$ and 0.0047 to $0.3471particle\;m^{-2}$, respectively. It was noted that the Acartia omorii, Paracalanus parvus s. l., Labidocera euchaeta, A. hongi, decapod larvae, and cirriped larvae were predominantly seen in the experiment. For verifying relationships between zooplankton and environmental factors in addition to microplastics, a model redundancy analysis (RDA) was performed. The zooplankton were divided into two groups on the basis of feeding types (i.e. particle feeders, and carnivores), and the associated zooplankton larvae were also separately considered. A review of the additional environmental factors such as water temperature, salinity, turbidity, chlorophyll-${\alpha}$ concentration, diatom density, and dinoflagellate density were also contained in the analysis. The results showed that a noted zooplankton abundance had no close relation with the occurring number of microplastic particles, but rather was significantly related with other noted environmental factors such as temperature, salinity, turbidity, and chlorophyll-${\alpha}$ concentration. This fact implies that most zooplankton can feed themselves as a unit, by selecting the most likely available nutritious foods, rather than microplastics under the circumstance of food-richness areas, such what food resources are available as in the location of coastal waters.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.12 no.4
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• pp.209-215
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• 1979

The manoeuvrabilities of a ship are decided by the values of her manoeuvring indices. The manoeuvring indices consist of two kinds: indices K and T. The former decides a ship's turning ability and the latter, the length of time delay to a steady turning motion after her rudder has finished the turn of an ordered angle. In this paper, the author figured out the values of the manoeuvring indices of the m. s. 'SAEBADA' (GT: 2,275,7 ton), the training ship of tile National Fisheries University of Busan through her Z test and analyzed these values and the other data which were obtained from her Z test to study her manoeuvrabilities. The results of]tamed are summarized as follows: 1. The manoeuvring indices K' of the m. s. 'SAEBADA' were $1.052(at\;10{\circ}\;Z\;test)\;0.925(at\;20{\circ}\;Z\;test)\;and\;0.877(at\;30{\circ}\;Z\;test)$. Her manoeuvring indices $0.815(at\;10{\circ}\;Z\;test)\;0.502(at\;20{\circ}\;Z\;test)\;and\;0.441(at\;30{\circ}\;Z\;test)$. Her above calculated values K', T' showed that her obeying ability to the turn of her rudder was more increased when her rudder was used to large angle than to small angle, but on the other hand in this case her turning ability was slightly reduced. 2. As it appeared that the calculated K'-values of the m.s. 'SAEBADA' were slightly smaller than the standard K'-values of the fishing boats similar in length, and her overshoot angles at her Z test were greater than other general ships, her turning ability was found to t]e slightly lower. 3. When the m. s. 'SAEBADA' took a turn at her $10^{\circ}\;Z$ test, running distance was about 8.6 times her own length and didn't exceed the standard manoeuvrability distance, 5 to 11 times general ships' own length, therefore she was considered to have a good manoeuvrability synthetically.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.31 no.2
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• pp.142-152
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• 1995

The combined bottom trawl and hydroacoustic survey was conducted by using the training ship Oshoro Maru belong to Hokkaido University in November 1989-1992 and the training ship Nagasaki Maru belong to Nagasaki University in April 1994 in the East China Sea, respectively. The aim of the investigations was to collect the target strength data of fish school in relation to the biomass estimation of fish in the survey area. The hydroacoustic survey was performed by using the scientific echo sounder system operating at three frequencies of 25, 50 and 100kHz with a microcomputer-based echo integrator. Fish samples were collected by bottom trawling and during the trawl surveys, the openings of otter board and net mouth were measured. The target strength of fish school was estimated from the relationship between the volume back scattering strength for the depth strata of bottom trawling and the weight per unit volume of trawl catches. A portion of the trawl catches preserved in frozon condition on board, the target strength measurements for the defrosted samples of ten species were conducted in the laboratory tank, and the relationship between target strength and fish weight was examined. In order to investigate the effect of swimbladder on target strength, the volume of the swimbladder of white croaker, Argyrosomus argentatus, sampled by bottom trawling was measured by directly removing the gas in the swimbladder with a syringe on board. The results obtained can be summarized as follows: 1.The relationship between the mean volume back scattering strength (, dB) for the depth strata of trawl hauls and the weight(C, $kg/\textrm{m}^3$) per unit volume of trawl catches were expressed by the following equations : 25kHz : = - 29.8+10Log(C) 50kHz : = - 32.4+10Log(C) 100kHz : = - 31.7+10Log(C) The mean target strength estimates for three frequencies of 25, 50 and 100 kHz derived from these equations were -29.8dB/kg, -32.4dB/kg and -31.7dB/kg, respectively. 2. The relationship between target strength and body weight for the fish samples of ten species collected by trawl surveys were expressed by the following equations : 25kHz : TS = - 34.0+10Log($W^{\frac{2}{3}}$) 100kHz : TS = - 37.8+10Log($W^{\frac{2}{3}}$) The mean target strength estimates for two frequencies of 25 and 100 kHz derived from these equations were -34.0dB/kg, -37.8dB/kg, respectively. 3. The representative target strength values for demersal fish populations of the East China Sea at two frequencies of 25 and 100 kHz were estimated to be -31.4dB/kg, -33.8dB/kg, respectively. 4. The ratio of the equivalent radius of swimbladder to body length of white croaker was 0.089 and the volume of swimbladder was estimated to be approximately 10% of total body volume.

• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.4
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• pp.375-381
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• 2013

To assess the risk of marine traffic environments, with high confidential level, the risk factors comprising it should be identified and the risk acceptance criteria should be also provided. Furthermore, the relative importance of each risk factor(the weight of each risk factor on total risk) should be analyzed because the risk is expressed as the sum of risk factors comprising it. The twenty kinds of risk factors and its assessment criteria were suggested for the domestic marine traffic environments by an examination of the existing risk assessment models on the previous studies. The relative importance of each risk factor was also analyzed through the questionnaire using analytic hierarchy process by the marine traffic experts on the same studies. Based on these previous studies, the risk was evaluated at the port of Mokpo and its approaches on this study. The port of Mokpo and its approaches were divided into four sectors for the comparative evaluation, the result of the comparative evaluation on four sectors showed that the risk of the Jeongdeung-hae passage is the highest due to higher risk level of some risk factors(water movements, complexities, tug boats, pilotage, VTS) than the other sectors. The result of this evaluation is in accord with the analysis results of the other studies using various qualitative or quantitative risk analysis methods at the same sea areas.

• Journal of the Korean Society of Marine Environment & Safety
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• v.18 no.6
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• pp.610-616
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• 2012

All the countries in the world is currently facing the full scale of energy-climate era currently, and making strong energy policy that will lead to green growth of the future energy resources by utilizing renewable energy as the basis of entering the advanced country becomes the goal of development that satisfies the demand for energy in 21st century. Recently, ocean energy attracted the attention along with the necessity of developing renewable energy. Ocean energy is the one of most prominent recyclable and clean resources that has not been developed yet. So, it is highly required to develop good tidal current energy conversion system in coastal area. The inflow angle that acts against tidal current turbine, seabed effect and the change of efficiency along the occurrence of cavitation were investigated through the wake flow characteristics in this study. Power coefficient degradation by seabed effect did not appear in the condition of this calculation. Efficiency degradation appeared from above $10^{\circ}$ regarding inflow angle and power coefficient was calculated as lower by 7 % at $45^{\circ}$. Torque and power coefficient increased as inflow velocity rose, but power coefficient degradation appeared from above 3m/s when the cavitation happened. So, it was recognized that the larger inflow angle and occurrence of cavitation become the reason for power degradation through the flow characteristics.

• Journal of Aerospace System Engineering
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• v.14 no.5
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• pp.130-138
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• 2020

In this paper, a plan to expand the scale of the domestic MRO industry was proposed by finding the technical common points between the aviation MRO and naval vessel MRO industries. The aviation MRO industry is led by Europe, North America, and Singapore. Europe and North America have very large aviation industries. The reason for the development of the MRO industry in Singapore is that the aviation MRO and ship MRO industries gathered to expand the industrial scale. The MRO field is an industry that spans all fields from research & development, production, manufacturing, operation, disposal, and crew training. The MRO industry is divided into military and civilian use. However, most of them are only differences in the needs of users, and there are no significant technical differences. The weapon system used by the military is steadily developing. It is impossible for the military to maintain all equipment at a time when troops are reduced. For that reason, it is necessary to share roles in each field. There is a need for an MRO industry in which civil and military operations cooperate to maintain all weapon systems at optimal performance. And the MRO industry development should be based on the civil market. The scale of the MRO industry should be expanded by gathering equipment commonly used in aircraft and naval vessels. This can increase military availability and reduce maintenance budgets.

• Journal of Fisheries and Marine Sciences Education
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• v.13 no.1
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• pp.99-116
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• 2001

Testing is a procedure used to measure a sample of behaviour in order to discover how well a seafarer performs, usually in comparison with others, or compared with identified performance criteria. In this context It is important that the test, in whatever form it is being used, yields consistent results by being valid, reliable and practical. Whilst we can only take a sample of a person's knowledge or comprehension about topic in this way, testing methods do provide a more reliable estimate of performance than most other observational techniques; unsystematic or irregular observation being too unreliable. The method of examination has been specified in the provisions of Regulation 12 of the Decree of the ship officers act as followings. Other necessary matters for conducting oral and written examinations have been set out by the Minister. But written examination is too shortage of period and small number of question to cover the qualification of each level and oral test is just simple and namely Traditionally, written examinations have been provided as the only means for determining the acquisition of knowledge by the mariner. Typically, the examination formats have taken the format of either an essay or multiple choice examinations. Essay items, used in the vast majority of subject examination(not in Korea), consisted of three basic types: situational, descriptive and computational. The level of certificate being examined determined the number and mix of the type of essay questions selected. Oral question has again been used by assessors of seafarer in a wide variety of contexts. Also, oral questioning is often used when observation of performance is undertaken to ask why a certain action has been taken, or to be broaden the scope of what has been observed. At end, Each techniques have their own advantage and disadvantage, so we have to choose some or all of the following techniques, depending upon the certificate, qualification or job for which the trainee is aiming. But in high lank, we have to use both of essay type and multiple choice and with enough time of oral test at least 30 minutes. Who would be the assessor? According to the STCW Code Section A-I/6, instructors, supervisor and assessors are appropriately qualified for particular types and levels of training or assessment of competence of seafarers either on board or ashore, as required under the Convention, in accordance with the provisions of this section.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.6
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• pp.626-632
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• 2015

The International Maritime Organization (IMO) has adopted several regulations for the prevention of air pollution from ships. In addition, there is a requirement for shipping liners to reduce greenhouse gas emissions. Accordingly, we need to take measurements to ensure that the steps taken are both efficient and environmentally friendly. It has been determined that the application of the Miller cycle in diesel engines has the effect of both reducing the amount of NOx and improving thermal efficiency. However, this method requires a considerably larger charge air pressure. Therefore, we consider a two-stage turbo-charging system, which not only results in a high charging pressure, but also improves the part load performance with an exhaust-gas bypass system or the application of the Miller cycle. Because of complications associated with the two-stage turbo-charging system, it is complex and difficult to realize a design that optimizes matching between diesel engine and turbo-chargers. Accordingly, it is necessary to perform a quantitative analysis to determine the effects and optimal conditions of these different systems in the early stage of system design. In this paper, we develop a simulation program to model these systems, and we verify that the results of this program are reliable. Further, we discuss methods that can be employed to improve its efficiency.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.26 no.2
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• pp.143-150
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• 1990

A cooperative Korea-Japan investigation for the demersal fisheries resources of the East China Sea was carried out by using the training ship Oshoro Maru belong to Hokkaido University Japan, during 5-12 November, 1989. The research vessel sampled 24 stations with demersal trawls on the East China Sea continental shelf, and 96 nautical miles of track line were surveyed hydroacoustically. The echo sounder used during the survey was of a scientific type having echo integration capabilities and the computer system was programmed to obtain echo integration data for each depth stratum between the transducer and the bottom. The target strength of fish school(TS per 1kg) was estimated from the relationship between mean volume backscattering strength and catches caught by the demersal trawls. The results obtained can be summarized as follows: 1. Approximately 96 species were identified from survey catches. 2. The mean volume backscattering strength for the layer occupied by bottom trawls at 25 and 100 KHz were-63.9 dB and -67.3 dB, respectively. Then the average catch per unit time of each trawl haul was 58.8 kg/hour. 3. The mean volume backscattering strength for the entire layer between the transducer and the bottom at 25 and 100KHz were -61.9 dB and -67.0 dB, respectively. 4. The mean fish school target strength per unit weight(TS/kg) at 25 and 100 KHz were -23.6 dB/kg and -26.6 dB/kg, respectively.