• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.35 no.2
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• pp.147-155
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• 1999

In this study, the stability analysis of a fishing vessel in a seaway was done. The stability analysis is an important item in the ship design, and so the ship registers of each nation constrain the ships to be followed the stability criterion. Stability variation, exciting forces due to wave and wind, and the broaching phenomena cause the capsizing of a ship. In this study, the stability analysis to study of the capsizing of a fishing vessel was performed. The relation between the speed of the ship and the wave length, that makes the encountering frequency vanish, was obtained. It was found that the encountering frequency tend to be zero when the wave whose length and direction are similar to those of ship. In this case, the possibility of dangerous situation becomes high. The calculated restoring arm becomes small when the ship is located near the wave crest. In general, the selected small fishing vessel is better than the large ship with respect to the stability, however the wave height becomes relatively high because of her small length Kim(l994) calculated the stability variation of the large cargo ship, the results of which showed the changes in stability great. But in the selected small fishing vessel in this study, the changes was small in comparison with the larger ship. This reason seems to be the shape of her midship section. In large cargo ships, the block coefficient is large, but that of the fishing vessel is relatively small and the small fishing vessel has chine, therefore the center of buoyancy moves much when the ship is inclined. It is desirable that the dynamic stability analysis for a fishing vessel, whose speed and direction are similar to those of waves, shall be done in the near future.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.4
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• pp.313-319
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• 2007

Long term wave climate of both extreme and operational wave height is essential for planning and designing coastal structures. Since the availability of the field wave data for the waters around Korean peninsula is limited to provide a reliable wave statistics, the wave climate information has been generated by means of long-term wave hindcasting using available meteorological data. In this paper, a set of deep water wave data obtained from KORDI(2003) were analyzed for extreme wave heights. These wave data at 67 stations off the Korean coast from 1979 to 1998 were arranged in the 16 directions. The probability distributions considered in this research were the FT-I and Weibull distribution. For each of these distributions, the method proposed by Goda(2004) was applied to estimate the parameters. For judgment of best fitting, MIR criterion proposed by Goda and Gobune(1990) was used. FT-I distribution which best fits to the 886 data, while Weibull(k=0.75) 81 data, Weibull(k=1.00) 105 data.

• Membrane Journal
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• v.30 no.1
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• pp.57-65
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• 2020

The purpose of this study was to compare the water channel morphology and the proton conductivity by changing the number of repeating units of the polymer backbone of PEMs, and to present a criterion for selecting an appropriate polymer model for MD simulation. In the model with the shortest polymer main chain, the movement of the main chain and the sulfonic acid group was observed to be large, but no change in the water channel morphology was found. In addition, due to the nature of the proton transport ability that is most affected by the water channel morphology, the proton conductivity did not show a significant correlation with the length of the polymer backbone. These results provide important information, particularly for the preparation of ionomers for binders. In general, a low molecular weight polymer electrolyte material is used for a binder ionomer. Since the movement of the main chain/sulfonic acid group is improved, it can play a role of enclosing the catalyst layer well. However, there is no change in its proton conducting performance. In conclusion, the preparation of ionomers for binders will require molecular weight and structure design with a focus on physical properties rather than proton transfer performance.

• Journal of Convergence for Information Technology
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• v.10 no.7
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• pp.153-159
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• 2020

In order to find out the condition of flow in sewer pipes, this study investigated the characteristics of tractive force of sewage flow estimated using actual measured values of water level, velocity, and flowrate in sewers located at uppermost portion in a treatment area during dry weather periods. When the scene of sewage flow was taken by CCTV after cohesive and non-cohesive solids (tofu and sand) were put on the sewer invert, it was found that the solids could be flushed without significant interruption. In sewer with slope of 0.00319, the frequency exceeding the minimum tractive force of sewage during a weekday was zero, while it was 10 per day with slope of 0.00603. During the week of the field observation, the event to exceed the minimum tractive force occurred once, suggesting that sewer odor would potentially increase. Maximum tractive force in sewer with steep slope was 2.9-3.1 N/㎡, but with gentle slope it decreased to 1.6-1.7N/㎡. It was also observed that the interval of time maintained below the criterion of minimum tractive force increased, during weekends compared to weekdays and for the sewage including non-cohesive particles which could enter combined sewers during a storm period. This study found that the sewer sediments formed by direct feces input into sewers, through sewer pipes which were designed meeting the standard sewer design criteria, could be flushed without staying as deposited solids state for a long time.

• Child Health Nursing Research
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• v.21 no.1
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• pp.11-19
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• 2015

Purpose: The purposes of this study were to develop an infant sleep health education program using a video for SIDS prevention education and to measure the effects of the program. Methods: The infant sleep health education program consisted of presentations and motor images. The formation of educational material was directed by the systematic design of instruction. Participants in this study were 59 primiparous women from postpartum care centers. The instruments used in this study were criterion referenced test items for knowledge about infant sleep health and confidence inventory. Experimental group I was given the treatment of infant sleep health education program. Experimental group II was given the program using a video reinforcement after 2 weeks. On the other hand, control group was given no treatment. Results: There was a significant increase in knowledge and confidence in the performance of mother's roles of both experimental group I and experimental group II over the control group. No significant difference was founds for knowledge and confidence in the performance of mother's roles between experimental group I and II. Conclusion: The results indicate that this program is a very effective intervention for better sleep health in infants by helping the mothers increase confidence in their role performance.

• Journal of Korea Water Resources Association
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• v.45 no.1
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• pp.1-13
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• 2012

Various input data required for water quality modeling have considerable impacts on modeling results and relevant analysis due to the absence of data standardization and lack of data accuracy. With this in mind, this study mainly focused on the designing Korean Reach File for more effective water quality modeling through the supply of database composed with accurate hydraulic and hydrologic data. The Korean Reach File is the hydraulic database with the locational information of individual reaches, and each reach represents the stream reach of homogeneous hydraulic characteristics. In detail, it has reach code designating each stream reach, and topological information including catalog unit, segment, marker and index. It was also designed considering linkage of existing codes such as stream name and stream code. The devised reach code was implemented to Kyungan River at the City of Gwangju of Kyunggi Province and the results showed that the reach code could effectively support the input database integrating basic numerous data required for water quality modeling based on a criterion as well as easier linkage and utilization with existing database. In addition, more systematic water quality management was enabled through the linkage of existing data such as treatment facilities, pollutant data, and management institutes using the reach codes defined for each stream section. In the future, more efforts need to be made to adopt the reach code as the national standard data thereby enabling utilization of numerous relevant database through the assigning of reach code to individual stream reaches nationwide.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.7
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• pp.645-653
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• 2013

Seoul National University flap(SNUF) blade is a small-scale rotor blade incorporating a small trailing-edge flap control surface driven by piezoelectric actuators at higher harmonics for vibration attenuation. Initially, the blade was designed using two-dimensional cross-section analysis and geometrically exact one-dimensional beam analysis, and its material configuration was finalized. A flap-deflection angle of ${\pm}4^{\circ}$ was established as the criterion for enhanced vibration reduction based on an earlier simulation. The flap-linkage mechanism was designed and static bench tests were conducted for verifying the performance of the flap-actuation mechanism. Different versions of test beds were developed and tested with the designed flap and the selected APA 200M piezoelectric actuators. Through significant improvements, a maximum deflection of ${\pm}3.7^{\circ}$ was achieved. High-frequency experiments were conducted for evaluating the performance, and the transfer function of the test bed was determined experimentally. With the static tests almost complete, the rotor power required for testing the blade in a whirl tower (centrifugal environment) was calculated, and further preparations are underway.

• Journal of Korea Trade
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• v.25 no.8
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• pp.1-24
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• 2021

Purpose - This study categorizes factors that influence the utilization of preferential tariffs based on the characteristics of rules of origin (RoO) and identifies and analyzes the influence of these characteristics on the utilization of preferential tariffs and the trade performance of companies. Design/methodology - In this study, we categorized factors that have an influence on the utilization of preferential tariffs based on the characteristics of RoO and investigated and tested the influence of these characteristics on the utilization of preferential tariffs and the trade performance of companies. For empirical analysis, we categorized the characteristics of RoO into restrictiveness, complexity, and uncertainty. We then developed a research model and formulated hypotheses based on previous studies, and tested the hypotheses using statistical software-(SPSS 25.0 and AMOS 18.0.) Findings - Previous studies suggested that each characteristic of RoO is determined by unique features of a Regional Trade Agreement (RTA). This study conducted an empirical analysis on the influence of the characteristics of RoO on the utilization of preferential tariffs and trade performance. The results confirmed that, overall, the characteristics of preferential rules of origin (PRoO) are related to and influence Korean companies' utilization of preferential tariffs and trade performance. As for the degree of the influence, the characteristics were in the order of uncertainty> restrictiveness> complexity. Nevertheless, complexity turned out not to have an influence large enough to change a company's decision on the utilization of preferential tariffs. Based on these results, this study identified unique features of PRoO and related problems for Korean companies that want to utilize preferential tariffs and suggested countermeasures for their effective utilization of preferential tariffs in the future. Originality/value - Companies that want to use preferential tariffs in international trade have to satisfy PRoO. The issue of origin can be regarded as an essential part of an RTA and RoO, are a crucial criterion in using preferential tariffs. The rules are requirements to claim benefits of preferential trade agreements and are the primary reasons companies have trouble in utilizing preferential tariffs. In this sense, this study categorized the characteristics of RoO, which are a key part of an RTA, and surveyed working-level professionals in charge of international trade at Korean companies to investigate the relationship between these characteristics and the utilizations of preferential tariffs and trade performance of the companies.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.4
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• pp.580-586
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• 2021

The CAT methodology is a numerical analysis technique using CAE. Recently, a methodology of applying artificial intelligence techniques to a simulation has been studied. A previous study compared the deformation results according to the injection molding process using a machine learning technique. Although MLP has excellent prediction performance, it lacks an explanation of the decision process and is like a black box. In this study, data was generated using Autodesk Moldflow 2018, an injection molding analysis software. Several Machine Learning Algorithms models were developed using RapidMiner version 9.5, a machine learning platform software, and the root mean square error was compared. The decision-tree showed better prediction performance than other machine learning techniques with the RMSE values. The classification criterion can be increased according to the Maximal Depth that determines the size of the Decision-tree, but the complexity also increases. The simulation showed that by selecting an intermediate value that satisfies the constraint based on the changed position, there was 7.7% improvement compared to the previous simulation.

• Journal of Navigation and Port Research
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• v.42 no.6
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• pp.415-420
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• 2018

The Energy Efficiency Design Index (EEDI) introduced by the Marine Environment P rotection Committee(MEPC) in International Maritime Organization(IMO) has significantly assisted in regulating CO2 emissions. However, in adverse weather conditions, it can lead to accidents due to slow steaming of vessels and low engine propulsion power. In response to this issue, the MEPC presented guidelines for the minimum propulsion power of the main engine for maintaining the course of vessels in adverse weather conditions. However, the guidelines are only applicable for vessels with a deadweight of 20,000 tons, leaving out small and medium ships. This study evaluated vessels subject to the guidelines of minimum propulsion power and proposed revised guidelines. In addition, relevant cases of marine accidents were investigated with the aim of investigating the minimum propulsion power of main engine for medium and small ships not covered by the guidelines. In order to achieve this, engine propulsion power was analyzed according to the size of the affected vessels. The results obtained from this study could be used as a minimum power criterion that can be considered for ship building to reduce marine accidents in adverse weather for small and medium ships.