• 동력기계공학회지
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• 제15권1호
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• pp.24-31
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• 2011

Rectangular box type structures are used in many fields of civil, mechanical and marine engineering. Especially, Most ship structures are often in contact with inner or outer fluid, like ballast, fuel and stem tanks. Fatigue damages are sometimes observed in these tanks which seem to be caused by resonance with exciting force of engine and propeller. Vibration characteristics of these thin walled tanks in contact with fluid near engine and propeller are strongly affected by added mass of containing fluid. Therefore it is essentially important to estimate the added mass effect to predict vibration of the tanks. Many authors have studied vibration of rectangular tanks containing fluid. Few research on dynamic interaction among tank walls filled with fluid are reported in the vibration of rectangular tanks recently. In case of rectangular tanks, structural coupling between adjacent panels and effect of vibration modes of multiple panels on added mass of water have to be considered. In the previous report, a numerical analysis is performed for the coupling effect between panels of a tank on added mass of containing fluid, the effect of structural constraint between panels on each vibration mode for fluid region, and mode characteristics in accordance with changing breadth of the plates by using finite element method for plates and boundary element method for fluid region. In this paper, the coupling effect between panels of a tank on added mass of containing fluid, the effect of structural constraint between panels on each vibration mode for fluid region, and mode characteristics in accordance with changing length, thickness, and boundary condition of the plates are investigated numerically and discussed.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2005년도 후기학술대회논문집
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• pp.92-93
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• 2005

A contract for the shipbuilding is usually a complicated and involves statement of rights, obligations and responsibilities which each party agrees vis-a vis the other. The ultimate purpose of the contract is the sale and transfer of the finished ship by the builder to the buyer. Contracts for the construction and sale of ships are categorized as contracts for the sale of goods under English, United States, Germany and some countries law. On the other hand, The shipbuilding contract may be classified, not as a contract of sale but as a contract for work and materials under Korea, Japan and some countries law. Especially, most of countries are now well settled with regard to liability of a manufacturer in tort for physical injury and on the other for pure economic loss to remote owners of chattels. Where there is either a breach of contractual warranty or an implied warranty, there may be admiralty jurisdiction, depending once again on the situs of the event and its relationship to traditional maritime activity. Contract principles will be applied to the first type of warranty and tort principles will be applied to the second. First of all, this thesis is dealt with the contents of contract under English Law. Secondly, this thesis is analysed into the liability of shipbuilder in Products Liability under English, American and Korean Law comparisons. In conclusion, the author tries to give some suggestions as countermeasures of Products Liability to the shipbuilder in Korea.

• Computers and Concrete
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• 제22권1호
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• pp.123-132
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• 2018

Reinforced concrete (RC) columns which are the main vertical structural members are exposed to several static and dynamic effects such as earthquake and wind. However, impact loading that is sudden impulsive dynamic one is the most effective loading type acting on the RC columns. Impact load is a kind of impulsive dynamic load which is ignored in the design process of RC columns like other structural members. The behavior of reinforced concrete columns under impact loading is an area of research that is still not well understood; however, work in this area continues to be motivated by a broad range of applications. Examples include reinforced concrete structures designed to resist accidental loading scenarios such as falling rock impact; vehicle or ship collisions with buildings, bridges, or offshore facilities; and structures that are used in high-threat or high-hazard applications, such as military fortification structures or nuclear facilities. In this study, free weight falling test setup is developed to investigate the behavior effects on RC columns under impact loading. For this purpose, eight RC column test specimens with 1/3 scale are manufactured. While drop height and mass of the striker are constant, application point of impact loading, stirrup spacing and concrete compression strength are the experimental variables. The time-history of the impact force, the accelerations of two points and the displacement of columns were measured. The crack patterns of RC columns are also observed. In the light of experimental results, low-velocity impact behavior of RC columns were determined and interpreted. Besides, the finite element models of RC columns are generated using ABAQUS software. It is found out that proposed finite element model could be used for evaluation of dynamic responses of RC columns subjected to low-velocity impact load.

• 한국항해학회지
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• 제18권2호
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• pp.129-149
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• 1994

Sea casualties may happen in ship, cargo and the others concerned with sea transportation. : the shipo-wer, marine insurer and salvage company have been endeavored to compensate salvage award with some rule and regulation such as Marine Insurance Act, York Antwerp Rules and Average adjustment rules. Once sea casualties happened, the salvage contract is established between the owners, marine insurance and salvage company, the contract are divided into so many kinds of them. In this paper, we have an analysis on the character of the salvage contract whether the characteristic contents of them are in benefit to any party or not. In this connection with these positive or negative character of the contract, it is worthwhile to compare the actual salvage expenses contract with no cure no pay contract. LOF 1990 has been revised recently, which is based on no cure no pay, expecially, the special compensation, safety net clause of LOF 1990 could be understood in the view of the prevention of sea pollution and the preservation of sea circumstances in the world. Salvage has the complicated and quality, because the adjustment of almost salvage charges have been treated through the other sea casualties which is accompanied by and mixed with. Besides of the importance of salvage contracts, we are in need to understand that what the diversified character of salvage charges are. Furthermore the owners should carefully select the insured conditions on Hull Insurance according to the type of his company, operating ocean route, loading cargo and etc. In this paper, we would try to analyze the character of the salvage award such as General Average, Sue and Labour Charges and Particular charges. We would like to propose that the uniformed system of the salvage award. Compensation should be built up for the effective and efficient salvage operation and for reducing the claims and conflicts from the concerned parties. To this end, we could expect that the uniformed system for salvage award compensation will come to be the benefit of all owners, insurers, salvage company.

• Journal of Electrical Engineering and Technology
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• 제3권2호
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• pp.224-234
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• 2008

Multi-phase machines can be used in variable speed drives. Their applications include electric ship propulsion, 'more-electric aircraft' and traction applications, electric vehicles, and hybrid electric vehicles. Multi-phase machines enable independent control of a few numbers of machines that are connected in series in a particular manner with their supply being fed from a single voltage source inverter(VSI). The idea was first implemented for a five-phase series-connected two-motor drive system, but is now applicable to any number of phases more than or equal to five-phase. The number of series-connected machines is a function of the phase number of VSI. Theoretical and simulation studies have already been reported for number of multi-phase multi-motor drive configurations of series-connection type. Variable speed induction motor drives without mechanical speed sensors at the motor shaft have the attractions of low cost and high reliability. To replace the sensor, information concerning the rotor speed is extracted from measured stator currents and voltages at motor terminals. Open-loop estimators or closed-loop observers are used for this purpose. They differ with respect to accuracy, robustness, and sensitivity against model parameter variations. This paper analyses operation of an MRAS estimator based sensorless control of a vector controlled series-connected two-motor five-phase drive system with current control in the stationary reference frame. Results, obtained with fixed-voltage, fixed-frequency supply, and hysteresis current control are presented for various operating conditions on the basis of simulation results. The purpose of this paper is to report the first ever simulation results on a sensorless control of a five-phase two-motor series-connected drive system. The operating principle is given followed by a description of the sensorless technique.

• 수산해양기술연구
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• 제58권2호
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• pp.185-192
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• 2022

Fisheries is known as a high-risk industry in Korea, and various efforts have been made to reduce occupational accidents. Trap fisheries represent crustacean production, accounting for 4.7% of total fisheries production and 10.7% of its production value, which is classified as a relatively high-risk industry. With the disaster insurance payment data of the National Federation of Fisheries Cooperatives (NFFC) from 2016 to 2020, the accident rate of the entire fishery, the accident rate of trap fisheries, and the type of disasters in the past five years were analyzed. As a result, the average fishery accident rate for the past five years was 5.31%, but it was high at 6.15% for coastal trap fisheries and 5.59% for offshore trap fisheries. Slips and trips, struck by objects and contact with machinery were the most common types of the accident according to the characteristics of the work, and hand injuries were analyzed the most. Additional efforts, including education for accident prevention, development of personal protective equipment and improvement of the working environment, are needed to prevent accidents caused by repeated types of disasters.

• 수산해양교육연구
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• 제27권5호
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• pp.1265-1272
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• 2015

This study aims at comparison and analyzing of marine officer license system for fishing vessels between South Korea and New Zealand. It is urgently required to establish Republic of Korea-New Zealand mutual certification system for marine officers who are on board ships within applicable area given that New Zealand will force foreign fishing vessels within New Zealand area to reflag from 2016 in accordance with the amendment of Fisheries Act. Secondly, to compare and analyze systems between two countries will contribute to the preparatory work related to ratification STCW-F convention as New Zealand already have completed law amendment to adapt the convention. Maritime law of New Zealand, Seafarers Act and Ship Personnel Act of Republic of Korea were compared and analyzed as references. The result showed that an improvement to corresponding level to the international convention and development of safety training by vessel type, and job descriptions according to the license class are needed to Republic of Korea system. Furthermore, it is suggested to prepare specialized training for deckhands as required in STCW-F convention and standard fishing vessel officer training record for designated institute of education. Therefore institutional complementarity and framework is required as it is expected that the nations of fishing in piscary demand to reflag Korean deep-sea fishing vessels or to ratify the STCW-F convention.

• Journal of Advanced Marine Engineering and Technology
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• 제15권4호
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• pp.29-45
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• 1991

Lip type stern tube sealing systems have used in almost all the middle or large ships which are being constructed in these days. It seems that the pressure fluctuation of the seal ring interspace, the cross-section profile and the materials quality of the seal rings have great effects on the sealing fuction of this sealing system. In this paper, the mechanical movement of lip seal ring which plays the most important role in stern tube sealing system and the possibility of leakage caused by pressure fluctuation are studied by theory and experiment. Using the finite element method for the axi-symetric object which receives the torsional load, the displacement and stress analysis of the seal rings, and also the possibility of crack occurance is checked by theoretical analysis. If the force which seal ring lip periphery receives is too small, there will be the possibility of leakage caused by the pressure fluctuation of the seal ring interspace, and if this force is too large, the frictional force between the seal ring and the liner will become problematical. The possibility of leakage caused by hardening of seal ring materials and creep phenomena of tested seal rings are also examined. The trial seal rings were designed and manufactured using the program of displacement and stress analysis developed in this study and the experimental apparatus to test the trial seal rings was also designed and manufactured. This trial seal rings were fitted in the experimental apparatus which was made in the same form as an actual stern tube. The one side of this apparatus was filled with sea water and the other side of it was filled with the lubricating oil. The leakage of oil and sea water was checked and the temperature was measured, rotating the propeller shaft at the constant velocity by D.C. motor. It was proved that the trial seal rings made in Viton rubber functioned excellenty but the trial seal rings made in N.B.R. rubber had problem in its durability.

• 한국수산과학회지
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• 제36권6호
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• pp.743-748
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• 2003

An oil boom was set up in order to contain diffused oil from spills and for the retrenchment of damage caused by oil Pollution. Therefore, the oil boom anchor needed proper holding power to endure high resistance from flowing streams and to secure the oil boom around the spill, and must dredge directly into the seabed when it is dropped and block oil outflow immediately. This study investigated the holding power of the danforth anchor and the coastal fishing vessel anchor used for oil booms in the KMPRC (Korea Marine Pollution Response Corporation). For each type, a 30 kg and 20 kg anchor were used. The holding power of the danforth anchors were measured by dropping both weights 10 times. However the coastal fishing vessel anchors were dropped only 5 times each, because no substantial differences were found between drops. In the results of the danforth anchors, an anchor awoke occurred in 2 drops of the 30 kg anchor and in 4 drops of the 20 kg anchor, wherein there was no holding power to be measured. With exception to the anchor awoke cases, the maximum holding power of the danforth 30 kg and 20 kg anchors was 250-520 kg and 123-233 kg, respectively. In the case of the coastal fishing vessel anchors of 30 kg and 20 kg, throughout the experiment, there was no occurrence of an anchor awoke. For the 30 kg and 20 kg anchors, the maximum holding power was measured to be 209-230 kg and 155-170 kg, respectively. Therefore, the holding power of the coastal fishing vessel anchor was shown to be much poorer than that of the danforth anchor. However, the holding power of the danforth anchor was very unstable. Due to the occurrences of anchor awoke, there was no holding power and the measurement value of maximum holding power showed too much variation among the drop tests. Also, after the maximum holding power was achieved, anchor awoke occurred easily. In the case of the coastal fishing vessel anchor was much more stabile, because there was no anchor awoke and no instance where holding power failed. Also the maximum holding power was reached quickly and almost no variation occurred among the drop tests.

• 대한간호학회지
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• 제25권3호
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• pp.549-561
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• 1995

This study was designed to identify the relation-ship of perceived social support on self-esteem and hopelessness in patients with chronic renal failure who are hemodialysis. The subjects of this study were the 50 patients who were registered in the hemodialysis department of the two hospitals. The data were collected using a questionnaire and The period of the data collection was from August 9 to 16, 1993. The instruments for this study were the perceived social support scale designed by Park Ji-Won, the self -esteem scale designed by Rosenberg and the hopelessness scale designed by Beck et al. The data were analyzed using frequencies, percentages, t-test, ANOVA, and .Pearson correlation coefficient. The results are summarized as follows ; 1. The degree of support according to the type of perceived social support ranged down in the fol-lowing order from high to low the mean emotion-al support 21.12, the mean informational support 19.58, the mean appraisal support 17.00, the mean material support 15.22, the man self-esteem was 32.00 and the mean hopelessness was 60.48. 2. Test for hypothesis ; Hypothesis 1, "The higher the level of perceived social support in patients on hemodialysis, the higher their level of self-esteem will be. " was not supported(r=.05, p=0.74). Hypothesis 2, "The higher the level of perceived social support in patients on hemodialysis, the lower their level of hopelessness will be. " was supported(r=-0.53, p=0.00). 3. The relations between general characteristics and the level of perceived social support, self-esteem, and hopelessness ; (1) The 'Gender'(P=0.04), 'Occupation'(P=0.04), 'Education'(P=0.00), 'Married state'(P=0.00) 'Duration of Hemodialysis'(P=0.00) and 'In-come'(P=0.00) of the subjects were related to perceived social support and showed a statistically significant difference. (2) No general characteristics of the subjects were related self-esteem in a statistically significant way. (3) The 'Education'(P=0.00) , 'Income'(P=0.00) of the subjects were related to hopelessness and showed a statistically significant difference. Thus, it is concluded that social support must be included in nursing interventions for patients with chronic renal failure on hemodialysis.