• Journal of the Society of Naval Architects of Korea
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• v.37 no.3
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• pp.11-20
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• 2000

The flow characteristics around the stern region of two VLCCs with the same forebody and slightly different afterbody are investigated along with propulsive performance of the ship. The local mean flow measurements and the resistance and self-propulsion tests are carried out in the towing tank for the two VLCC hull forms. The measured results clearly show the formation of bilge vortices and their effect on propulsive efficiency. The comparisons are made for the two VLCC hull forms and the relation between stern framelines and bilge vortex strength is explored. Experimental data can provide a good test case to validate the accuracy of numerical methods and turbulence model of CFD codes for ship flow calculation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.9
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• pp.480-485
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• 2017

The main reason for the heat induced accidents occurring at the after stern tube journal bearing is the excessive local pressure caused by the deflection of the propulsion shaft due to the propeller loads. It is expected that the contact area could beenlarged and the local pressure reduced accordingly by using a lining material having alow Young's modulus instead of the existing white metal. The purpose of this work is to investigate the characteristics of the pressure distribution and determine the allowable pressure value in the case where bearing products made of materials having a low Young's modulus are used. In this study, the propeller loads, heat effect, and hull deflection are considered in the evaluation of the local pressure of the ship propulsion shaft. Also, the Hertzian contact condition was applied. From the analysis results in the case where a lining material with a low Young's modulus was used, it was found that a robust design could be achieved and the local pressure could be reduced effectively independent of the load conditions. It will be possible to producenew products made of materials having a low Young's modulus if the manufacturer confirms the performance specifications drawn by this study.

• Journal of the Korean Society of Marine Environment & Safety
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• v.13 no.4
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• pp.119-125
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• 2007

In recent days, the consumption of stainless steel in the propulsion shafting systems for small-medium class vessel is increased due to its high corrosion protection with wear resistant properties. Unfortunately the small and medium class vessel that operated in the west-south sea area of Korean peninsula experienced heavy wear down due to the role of mud. In the event of wear or broken down, the propeller shaft must be replaced by new one, but the new shaft is very expensive and time-consuming for order made supply. In this case, the methods of built up for wear and broken shaft by welding is one of the most effective cases. In this study, the built up welding for austenitic stainless steel shaft has been accomplished by various pre-surface treatment, welding methods, post heattreatment and inspection. The results confirmed that the built-up welding was one of the effective methods for stainless steel shafting.

• Journal of Fisheries and Marine Sciences Education
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• v.28 no.3
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• pp.645-652
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• 2016

At the initial stage of propulsion shaft design, in line with shaft alignment, an intensified consideration of lateral vibration is needed to verify its operational safety. Recently the alignment problem affecting the lateral vibration has been becoming issues. However, the theoretical method of forced lateral vibration analysis is not cleary established so far and it is about to simply limited among the classification societies and international standards to avoid the blade natural frequency resonance cpm outside of ${\pm}20%$ of engine rpm at MCR. On the other hand, longer center distance between each support bearing shows an affirmative result normally in shaft alignment analysis whereas the blade order resonance speed may cause lowering near the limitation in the aspect of lateral vibration. Therefore, it is required careful attention to engineers as described above. As a method to solve the problem, it is mainly considered that remove forward stern tube bearing. In this paper, based on a medium size container ship case, theoretical study was carried out in the context of the forward stern tube bearing. The various effects and functions of forward stern tube bearing are reviewed and evaluated. Then an guidance note to lead the conclusion is proposed.

• Journal of the Society of Naval Architects of Korea
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• v.52 no.1
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• pp.61-69
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• 2015

In the beginning of the 1990's, numerous shaft bearing damages, especially in aft stern tube bearing, were reported. The main reasons of bearing damages were estimated that hull deflections have been increased by more flexible hulls and propeller dynamic loads have not been considered in shaft alignment. After that time, studies to take into account hull deflections in shaft alignment have been actively carried out, but for the latter leave much to be desired. In this study, the effects of the propeller forces on the propeller shaft bearing have been investigated by estimating thrust eccentricity as reasonable as possible although some assumptions to simulate turning of ship were introduced. Three dimensional nominal wake to estimate thrust eccentricity have been calculated by using CFD analysis and model test in the towing tank. This study presents the procedure to estimate the propeller eccentric forces and their influence on the stern tube bearing for a container carrier. As a result, it has been found that the lateral propeller forces in turning condition should be considered in shaft alignment to prevent shaft bearing damages.

• Journal of the Society of Naval Architects of Korea
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• v.44 no.6
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• pp.666-674
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• 2007

It is very important to estimate static squeezing pressure distributions for lining material of sterntube after bearing at dry dock stage since the maximum squeezing pressure value can be one of the significant characteristics representing coming navigation performances of the propulsion system. Moderate oil film pressure between lining material and propulsion shaft is also essential for safe ship service. In this paper, Hertz contact theory is explained to derive static squeezing pressure. Reynolds equation simplified from Navier-Stokes equation is centrally differentiated to numerically obtain dynamic oil film pressures. New shaft alignment technology of nonlinear elastic multi-support bearing elements is also used in order to obtain external forces acting on lining material of bearing. For 300K DWT class VLCC with synthetic bush of sterntube after bearing, static squeezing pressures are calculated using derived external forces and Hertz contact theory. Optimum partial slope of the after bush is presented by parametric shaft alignment analyses. Dynamic oil film pressures are comparatively evaluated for partially bored and unbored after bush. Finally it is proved that the partial slope can drastically reduce oil film pressure during engine running.

• Journal of Korean Society of Archives and Records Management
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• v.4 no.1
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• pp.177-201
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• 2004

Since it was founded in Korea in 1784, Korean Catholic Church has grown rapidly even under persecution. And now, its various activities have considerable influence on Korean society. However, the Korean Catholic Church record management not much is being done in excess of general record management for administrative purposes. Therefore, this study attempted to construct records management system that could systematically manage records of the Korean Catholic Church with Diocese Archives as the central figure. In order to do this, first the special characteristics of the Catholic Church records were analyzed, and the actual status of records management of Catholic Church was investigated. Next, applied the theory of records management to the Catholic Church system.

• Journal of the Society of Naval Architects of Korea
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• v.34 no.2
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• pp.11-19
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• 1997

The new definition of calibration coefficients is proposed for a five-hole Pitot tube. Two-angle chart calibration other than one-angle variation is considered to improve the accuracy in the measurement of the three-dimensional velocity fields. Several sets of correlation coefficients are introduced for different shapes of the probe tip. The calibration method with one-angle variation is compared with the new two-angle chart calibration method and the improvement of the present method is clearly shown.

• Journal of dental hygiene science
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• v.15 no.6
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• pp.721-727
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• 2015

The purpose of this study was to examine the impact of stress on the habits of temporomandibular disorder in college students. The subjects in this study were 396 male and female students who were in their first to fourth years at five different colleges located in Jeollabuk-do. The findings of the study were as follows: As for the degree of bad oral habits, "sleeping on one side" was the most common bad oral habit, followed by "enjoying caffeinated beverages," "resting the chin on the hand or a thing" and "chewing food in one side of the mouth only." As a result of analyzing their stress by general characteristics including gender, there were significant differences according to gender in stress about school life problems, one's own problems and economic difficulties, and only stress about one's own problems statistically significantly varied with academic year. When the correlation of the factors was analyzed, perceived stress about school life problems and one's own problems had a significant positive correlation with bad oral habit scores. When a multiple linear regression analysis was made to determine the influence of general characteristics and perceived stress on bad oral habit scores, gender, academic year, self-rated oral health status, stress about school life problems and stress about one's own problems were identified as significant variables. The findings of the study illustrated that there was an organic relationship between the bad oral habits and stress of the college students.

• Journal of dental hygiene science
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• v.5 no.4
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• pp.239-244
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• 2005

The purpose of this study was to delve into the work values of dental hygiene students. The subjects in this study were 465 students who attended three different colleges in Gyeonggi province. After a survey was conducted, the collected data were analyzed with SPSSWIN 12.0 program. The findings of the study were as follows: (1) As for the type of work values, the largest group of the students investigated attached importance to pay and reputation, as they gave a mean of 4.18 to those things. In detail, they put the most emphasis on economic compensation since they gave it a mean of 4.42. (2) Regarding their detailed outlook, there was significantly strong positive correlation between their view of achievement and of competency, between their view of economic compensation and of position, and between their view of recognition and of position. (3) As to the impacts of their general characteristics, their work values in pursuit of self-realization was statistically significantly different according to their motivation of choosing dental hygiene(P = .042). Their school(P = .011), academic school year(P = .023), actual work experience as a dental hygienist(P = .045) and motivation of choosing dental hygiene (P = .023) made a statistically significant difference to their contribution- oriented view of occupation. And their work values that accentuated pay and reputation varied statistically significantly with their school(P = .000) and academic school year(P = .000).