• Journal of the Society of Naval Architects of Korea
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• v.38 no.4
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• pp.48-55
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• 2001

In this paper, sensitivity analysis for the coupled axial and torsional undamped free vibration of ship propulsion shafting is proposed. The purpose of this study is to effectively and optimally design the resonance frequencies of propulsion shafting affecting barred speed range of main engine by modifying the diameters of intermediate and propeller shafts. The presented method is validated by the sensitivity analysis for the natural frequencies of propulsion shafting of two real large merchant ships. In addition, the changes of natural frequency and resonance main engine speed are discussed in case that the diameter is varied within the range regulated by the rule of shipping register.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.3
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• pp.90-101
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• 1992

Some practical methods have already been proposed for predicting the characteristics of ship manoeuvring motions at relatively high advance speed. However, these methods can hardly be applied to motions of ships in starting, stoppint, backing and slow steaming conditions, even though such extensive motions are of vital importance from a safety point of view particularly in harbour areas. The method presented here aims at predicting the characteristics of ship manoeuvring at low advance speed, which covers starting, stopping, backing and slow steaming conditions. The force mathematical models at large angles of incidence to the hull as well as under the tilde range of propeller operations are formulated. Simulations of various manoeuvres at low advance speed are carried out for two types of merchant ship, i.e. a LNGC and a VLCC. Comparisons between simulations and corresponding full-scale measurements or free-running model tests provide a first verification of the proposed mathematical models.

• Journal of the Korean Institute of Navigation
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• v.4 no.1
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• pp.31-50
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• 1980

It does not seem necessarily practicable to keep the system always in optimal condition, athough the control system of the follow-up mechanism on the most marine gyro compasses is to be adjusted by the operator through the gain adjustment. Sometimes a sustained oscillation or an incorrect gyro reading occurs to the system. For such a system any systematical research or theoretical basis of the guide for the optimal gain adjustment has not been reported yet. As a basic investigation of the theoretical system analysis to solve the problems concerned, the author attempts in this paper to express the system in a mathematical model deduced from the results of the theoretical approach and the experimental observation of each element contained in the follow-up mechanism of Hokshin D-1 gyro compass, and to constitute an over-all closed loop transfer function. This funciton being reverted to a fourth orderlinear differential equation, the first order simultaneous differential equations are obtained by means of the state-variables. The latter equations are solved by the Runge-Kutta method with digital computer. By comparing the characteristic of the simulated over-all output with that of the experimental result, it is shown that both outputs are nearly consistent with each other. It is also expected that the system representation proposed by this paper is valid and will be a prospective means in a further study on the design and optimal adjustment of the system.

• Journal of Navigation and Port Research
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• v.41 no.5
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• pp.287-296
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• 2017

The Formal Safety Assessment (FSA) is a structured and systematic methodology developed by the IMO, aimed at assessing the risk of vessels and recommending the method to control intolerable risks, thereby enhancing maritime safety, including protection of life, health, the marine environment and property, by using risk analysis and cost-benefit assessment. While the FSA has mostly been applied to merchant vessels, it has rarely been applied to a DP vessel, which is one of the special purpose vessels in the offshore industry. Furthermore, most of the FSA has been conducted so far by using the Fault Tree Analysis tool, even though there are many other risk analysis tools. This study carried out the FSA for safe operation of DP vessels by using the Bayesian network, under which conditional probability was examined. This study determined the frequency and severity of DP LOP incidents reported to the IMCA from 2001 to 2010, and obtained the Risk Index by applying the Bayesian network. Then, the Risk Control Options (RCOs) were identified through an expert brainstorming and DP vessel simulations. This study recommends duplication of PRS, regardless of the DP class and PRS type and DP system specific training. Finally, this study verified that the Bayesian network and DP simulator can also serve as an effective tool for FSA implementation.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.3
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• pp.320-327
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• 2019

The purpose of this paper is to compare seafarers' behavior according to traffic conditions of a road and an onshore locations. Behaviors are classified into three categories: Skill-, Rule- and knowledge-based mode. Experimental data were collected using the questionnaires for navigators, working in a merchant ship. To compare the behaviors, we used the four analysis method; the degree of frequency, reliability test, correlation and linear regression. As a result of the study, it was found that Skill-based behavior shows more higher in the road traffic than the maritime traffic, and rule-based behavior shows more higher in the maritime traffic than the road traffic. Also, the behavior in the navigation situation showed statistical significance. Especially, in the case of Rule-based behavior, a high correlation between road and maritime was found. This study can be expected to apply to complementary system utilization between error management system of onshore and maritime traffic.

• Structural Engineering and Mechanics
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• v.83 no.4
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• pp.563-576
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• 2022

This study aimed to evaluate the progressive collapse potential of buildings designed using conventional design codes for the merchant occupancy classification and subjected to a sudden column failure. For this purpose, three reinforced concrete buildings having different story numbers were designed according to the seismic design recommendations of TSCB-2019. Later on, the buildings were analyzed using the GSA-2016 and UFC 4-023-03 to observe their progressive collapse responses. Three columns were removed independently in the structures from different locations. Nonlinear dynamic analysis method for the alternate path direct design approach was implemented for the design evaluation. The plasticity of the structural members was simulated by using nonlinear fiber hinges. The moment, axial, and shear force interaction on the hinges was considered by the Modified Compression Field Theory. Moreover, an existing experimental study investigating the progressive collapse behavior of reinforced concrete structures was used to observe the validation of nonlinear fiber hinges and the applied analysis methodology. The study results deduce that a limited local collapse disproportionately more extensive than the initial failure was experienced on the buildings designed according to TSCB-2019. The mercantile structures designed according to current seismic codes require additional direct design considerations to improve their progressive collapse resistance against the risk of a sudden column loss.

• The Journal of Economics, Marketing and Management
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• v.10 no.1
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• pp.15-26
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• 2022

Purpose: The purpose of this study is to analyze the method of calculating the usage fee, rent, and lease rights of public goods necessary for the operation and management of the underground shopping mall, and to suggest systematic improvement points for the operation of the underground shopping mall. Data and Methodology: First, ordinances and regulations related to common property were investigated. Second, previous studies were analyzed. A survey was conducted with five questions that conflict with the interests of underground shopping mall merchants among the ordinances and operating systems related to the current underground shopping malls' common property. Results: Underpass merchants wanted monthly payment for the use of common property, and merchant organizations wanted to limit the increase rate with the right to use. They asked for the property value due to donation to be excluded from the loan fee, they wanted to revise the Common Property Act on the transfer of lease rights, and they wanted to revise the loan contract renewal period. Conclusion: There is a need to improve the laws and systems for underground shopping malls, and it will have to be negotiated according to the opinions of the merchants gathered among them, and it will have to be implemented in stages in the long term.

• Corrosion Science and Technology
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• v.14 no.2
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• pp.54-58
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• 2015

A heavy oil of low quality has been mainly used in the diesel engine of the merchant ship as the oil price has been significantly jumped for several years. Thus, a combustion chamber of the engine has been often exposed to severely corrosive environment more and more because temperature of the exhaust gas of the combustion chamber has been getting higher and higher with increasing of using the heavy oil of low quality. As a result, wear and corrosion of the engine parts such as exhaust valve, piston crown and cylinder head surrounded with combustion chamber are more serious compared to the other parts of the engine. Therefore, an optimum repair welding for these engine parts is very important to prolong their lifetime in a economical point of view. In this study, 1.25Cr-0.5Mo filler metal was welded with SMAW method in the forged steel which would be generally used with piston crown material. And the corrosion properties of weld metal, heat affected and base metal zones were investigated using electrochemical methods such as measurement of corrosion potential, anodic polarization curves, cyclic voltammogram and impedance etc. in 35% $H_2SO_4$ solution. The weld metal and base metal zones exhibited the highest and lowest values of hardness respectively. And, the corrosion resistance of the heat affected and weld metal zones was also increased than that of the base metal zone. Furthermore, it appeared that the corrosive products with red color and local corrosion like as a pitting corrosion were more frequently observed on the surface of the base metal zone compared to the heat affected and weld metal zones. Consequently, it is suggested that the mechanical and corrosion characteristics of the piston crown can be predominantly improved by repair welding method using the 1.25Cr-0.5Mo electrode.

• Journal of architectural history
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• v.16 no.3
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• pp.95-114
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• 2007

Since the 17th century, the society of Joseon dynasty belongs to a period of rapid transition in many fields. As the building is a result to be produced on the basis of a society and economy, the general transition in a society is to be reflected into a process of building construction. Especially, a study on the material supply system of economic base in a process of building construction is one of vely important factors in an understanding or estimate of a building. On the premise, this paper is to examine the supply system of iron materials and the tools in the construction of the government managed buildings in the late of Joseon dynasty on a viewpoint of productivity. Construction reports and other documents in those days are examined for the study. Following conclusions have been reached through the study. 1) The general supply method of iron materials for a large-scale government construction was based on 'byulgong', that is, a kind of tribute. 2) Various methods were selected in the supply method of iron materials for government use in the late of Joseon dynasty. The priority order of choice in its government policy was put on an easiness of amount security, on a minimum of expenditure, and on an efficiency of construction execution. 3) The manufacturing technique of weaponry was used in the production method of iron materials and the tools for government use. The cooperation of the official, the army, and the merchant had improved the manufacturing technique of building construction.

• Journal of the Korean Society of Marine Environment & Safety
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• v.3 no.1
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• pp.33-49
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• 1997

One of the most important missons that are imposed on merchant ship at sea is to accomplish the safe transportation of cargo loaded. Recently, a study on the seakeeping performance has been carried out on the development of evaluation system related to the synthetic safety of a ship at sea. The seakeeping performance is the ship's ability sailing at, and executing its misson against adverse environmental factors successfully and safely. Until now, however, there has not been any method of quantitative evaluation on the dynamic safety of the ship's cargo loaded. In this regards, this paper has introduced the evaluation method of dynamic safety of the ship's cargo. In order to evaluate the dynamic safety of cargo, the vertical and lateral acceleration which causes the collapse, racking and local structure failure of cargo was adopted as the evaluation factors in the ship's motions. The response amplitude of ship's motions in regular waves is manipulated by NSM (New Strip Method) on a given 2,700 TEU full container vessel under the wind forces of 7, 8 and 9 Beaufort scale. Each response of ship's motions induced by NSM was applied to short-crested irregular waves for stochastic process on evaluation factors and then vertical and lateral acceleration of each cargo was compared with significant amplitude of each acceleration. A representative dangerous factor was determined by comparing permissible values of stacking and racking forces occurred typically to the vertical and transverse directions with the container strength required on ISO 1496 at the positions of forecastle, poop and ship's midship respectively. Through the occurrence probability of the determined factor by Rayleigh's probability density function, the dangerousness which limits loads on container's side wall as an evaluation was applied in judging of the danger of the ship's cargo loaded.