• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.10
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• pp.270-276
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• 2019

According to the International Maritime Organization (IMO) 2020 Regulation, ships operating outside designated emission control areas (ECA) have to use low-sulfur oil with a sulfur content of 0.5% or less by January 2020. To minimize the consumption of high-priced low-sulfur oil, it is urgent to introduce efficient energy-saving devices (ESD), and contra-rotating propeller (CRP) systems are well known to be the most effective one. The shafting system that drives a CRP is composed of an inner shaft and an outer one and has a mutually influential system that is much more complex and heavier than a general shafting system. An initial design was carried out to install a CRP system for the first time in Korea. The purpose of this study is to verify whether the journal bearing meets the classification's design criteria through a bearing reaction force analysis for the classification's approval of the initial design. It is ideal for the thrust of the propeller to act on the center of the shaft, but thrust eccentricity occurs due to the uneven wake caused by the stern shape. Load conditions were applied while considering thrust eccentricity to perform the shaft analysis, and the results were compared with the classification's criteria.

• The Journal of the Acoustical Society of Korea
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• v.42 no.3
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• pp.243-249
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• 2023

The occurrence of cavitation on the propeller is directly linked to the naval ship's survivability, and it is necessary to design a propeller shape that delays the cavitation inception. However, the propeller cavitation can occur under various operating conditions, thus it is important to identify whether the propeller cavitation exists during operation as well as in the design phase. To this end, it is necessary to use noise or vibration signals on board to monitor the cavitation inception. In this study, a hydrophone and an accelerometer were installed on the ship hull right above the propeller to compare the performance of analyzing cavitation inception between acoustic and vibration signals. Also, a high speed camera was used to visually observe the occurrence of cavitation through an observation window. The measured results showed that the spectral shapes between acoustic and vibration signals were different, but the level increases at each frequency band and the overall level of the frequency band from 1 kHz to 10 kHz showed a similar tendency. The Detection of Envelope Modulation On Noise (DEMON) analysis also showed similar results for both acoustic and vibration signals, confirming that both hydrophones and accelerometers can be utilized in the analysis of cavitation inception.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.11 no.1
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• pp.49-63
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• 2016

In the 21st century when people're pursuing the qualitative improvement of life, the concern about the quality of housing is growing as living standards have been improved and the desire for life has been various. Life satisfaction can be found that basic needs of residential satisfaction have been met in life, and the quality of life will be higher with the fulfillment of these desires. Humans all live in social relations, which have a big impact on the quality of life of individuals in a variety of aspects. Thus, this researcher tried to investigate middle-aged people's residential environment and the actual situation of social capital and to examine the effect of social capital on the relationship between residential environment satisfaction and life satisfaction through an empirical study. The survey was conducted for middle-aged people to collect data, 500 copies of a questionnaire were distributed and 490 of them were collected, and then the actual analysis of 484 copies without missing values was done using SPSS Ver. 21.0. As a result, first, middle-aged people's residential environment had a significant effect on life satisfaction. Second, moderating effects of social capital between middle-aged people's residential environment satisfaction and life satisfaction showed a partly significant influence. Depending on these results, the researcher try to offer the direction for the improvement of the quality of life to middle-aged people and useful data to establish Korea housing policy.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.3
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• pp.1253-1259
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• 2011

This study is to inquire into the sexual consciousness and values of students majoring in public health-related subjects, as well as into whether there are differences between male students and female students. This study was conducted on randomly-selected students majoring in public health-related subjects at junior colleges in South Chungcheong Province. The questionnaire, used in this study, was remade on the basis of philological reviews and previous studies, and a total of 208 questionnaires were re-collected. In relation to the question about chance of sex education, 56.7% of respondents answered, '4 or more chances'. In relation to the question about the source of sex information, 37.5% of respondents referred to 'their friends.' In the case of premarital sex, 51.4% answered, 'it amounts to nothing in pairs of lovers.' In conclusion, the university authorities need to aggressively support students in order that desirable sex educations can be given to students and they can have right sexual consciousness and have the mature and responsible attitude to sex.

• Journal of the korean academy of Pediatric Dentistry
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• v.32 no.1
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• pp.158-163
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• 2005

It is rare that the complete avulsion, intrusive luxation, and extrusive luxation occurred by trauma at the same time. In July, 2003, 10-year and 2 month-old-girl was referred to Department of Pediatric dentistry, Chonnam National University Hospital due to complete avulsion of upper right lateral incisor, intrusive luxation of upper right cental incisor and extrusive luxation of upper left central incisor. Traumatized teeth were surgically repositioned and fixated with resin-wire splint at the same day. Endodontic treatment of avulsed tooth was performed 2 weeks after trauma. A radiograph was taken 3 months after trauma, which demonstrated root resorption of both upper central incisors. External root resorption was arrested by the root canal therapy with calcium hydroxide. It showed good results for 1 year and 4 month but further follow-up is needed to check root resorption and ankylosis.

• Korean Journal of Environmental Biology
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• v.25 no.3
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• pp.249-259
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• 2007

This study was carried out the analysis of forest vegetation structure using the phytosociological methods by Braun-Blanquet from April to November in 2006. The results were summarized as follows. The forest vegetation was classified into 23 communities and 3 forest ecosystem types such as slope forest type, valley forest type and artificial forest type. By the actual vegetation map, Quercus mongolica forest was widely distributed in the area and Pinus densiflora forest and Quercus variabilis forest in the southern parts of the slope and valley forest mainly in valley area, respectively. The importance value in the Q. mongolica forest and artificial forest was absolutely high for the species dominated in tree layer. The typical valley species of Lindera erythrocarpa and Styrax japonica were abundantly occupied in the all layers. Species diversity indices of Alnus hirsta forest was the lowest as 0.2191, and that of valley forest was about 0.9, the highest among the all forest types.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.58-58
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• 2009

선박의 선체부분인 선수, 선미 등을 이루고 있는 곡형 외판의 제작은 강판을 원하는 형상으로 성형하기 위하여 벤딩롤러 및 유압프레스를 이용한 냉간가공과 산소-프로판가스 화염을 적용한 선상가열, 삼각가열을 이용한 열간가공으로 크게 구분할 수 있다. 선상가열을 이용한 곡면가공의 원리는 가열토치를 이용하여 강판을 가열하면 가열부는 팽창하게 되고 냉각시에는 수축하게 된다. 이 때 두께방향으로의 소성변형으로 인한 수축량의 차이로 인해 굽혀지게 된다. 최근에는 선박이 고기능 및 대형화로 인해 3차원 곡형 외판 형상이 복잡해지고, 강도를 향상시키기 위하여 합금원소(C, Nb, V, Ti)를 첨가하거나 열처리(노말라이징)를 이용한 고장력강재인 중후판의 적용이 증가하고 있다. 이러한 고강도강재를 선상가열공정으로 제작한 곡형 외판재는 가열, 냉각의 열사이클로 인해 취화되어 인성이 저하 될 수 있다. 본 연구에서는 Normalizing 열처리재인 490MPa급 강재를 이용하여, 현장에서 작업자의 미숙련으로 인해 발생 할 수 있는 최대의 가혹한 조건과 재질에 큰 영향을 미치지 않는 범위를 선정하여 선상가열시의 가열, 냉각조건에 따른 강재의 재질특성을 조사하고자 한다. 이를 위해 가열시 가열부위의 정확한 온도 측정에 역점을 두었으며, 각각 다른 선상가열 조건에 따른 시편을 제작하기 위하여 선상가열 실험장치를 제작하였다. 선상가열 실험 결과 최고가열온도 $1300^{\circ}C,\;950^{\circ}C$에서 수냉 조건인 경우 급격한 인성저하 현상이 발생하며 비록 공냉이라 하더라도 결정립 조대화로 인성 저하가 발생하였다. $800^{\circ}C$가열 후 수냉개시온도를 $700^{\circ}C$이하로 수냉한 경우에는 인성 저하 현상이 개선되고 있음을 알 수 있다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.11a
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• pp.239-239
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• 2015

삼성, LG전자 등 다양한 사업부의 White Anodizing구현기술의 Need는 항상 존재하고 있으며, 특히 White와 Black Color의 콤비네이션으로 친환경 이미지 강조 및 핸드폰의 고급화에 필연적인 메탈화로 작년부터 White Anodizing의 수요요청이 쇄도하고 있다. 그러나 현행 공업용 Anodizing 기술(황산법)은 봉공처리 전 착색공정에서 Red, Blue, Black 등 염료분자와 달리 염료 분자가 비교적 큰 White 염료는 Anodizing으로 성장된 다공성피막 내부로 들어가지 못해 국내 Anodizing전문기업 뿐만아니라 일본 기업 및 연구소 등에서도 무수한 시도를 하고 있지만 현재까지는 완벽한 White Anodizing구현기술이 전무한 상태이다. 이에 당사는 알루미늄합금을 White의 안료나 염료가 아닌 알칼리전해액의 Pulse전류인가 PEO(Plasma electrolytic oxidation)처리 공정에 의거 White Anodizing기술을 개발하고자 하였다. 알칼리 전해질에 의한 Anodizing 처리기술로 White와 유사한 색상을 구현하고 있으나, 수요자가 요구하는 White Anodizing으로 제품을 양산하는데 어려움이 있어 기존 Anodizing 처리 대신 Pulse전류인가 PEO처리기술로 White Color를 구현하여 수요요청이 쇄도한 국내외 기업체에 공급하고자 한다. 본 기술은 알카리 전해액을 사용하므로 친환경적이며, 다공성 피막으로 인한 우수한 도장 밀착성, 실링처리에 의한 내식성 향상, PEO 피막의 우수한 경도 및 내마모성 등을 나타내며, 알루미늄뿐만 아니라 마그네슘합금, 티타늄 등에도 공히 적용이 가능하며, White Anodizing의 특화된 기술로 표면처리기술 우위 선점 및 원가절감 등이 가능하다. 당사는 알루미늄 아노다이징 전문 기업으로서 내식성 목적의 연질 아노다이징 처리 및 고내마모성을 목적으로 하는 자동차 부품 및 기계 부품용 경질 아노다이징 처리를 주로 수행하고 있다. 본 발표에서는 당사의 표면처리 기술 및 알루미늄의 아노다이징에 대한 소개를 하고자 한다.

• Journal of the korean academy of Pediatric Dentistry
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• v.39 no.1
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• pp.97-102
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• 2012

Odontoma is a mixed tumor formed by the overgrowth of ectodermal epithelial cells and mesodermal cells. It arises during normal tooth development and only grows to a certain level. It is not a true neoplasm and therefore it is considered as hamartomas. Odontomas are classified into compound and complex types based on morphology. Compound odontoma is commonly found in the anterior region of the maxilla, and has a radiopaque lesion that resembles small teeth. Usually, odontoma is treated by conservative surgical removal and there is little probability of recurrence. This paper describes three cases of compound odontoma diagnosed in children with 1 year of follow-up. These case reports present patients having eruption disturbance of primary and permanent teeth due to the presence of compound odontoma. In order to induce spontaneous eruption, conservative surgical removal was performed showing favorable results.

• Bulletin of the Society of Naval Architects of Korea
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• v.26 no.3
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• pp.29-40
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• 1989

A new blade section of propeller is developed to obtain higher propeller efficiency and better cavitation performance. Eleven foil sections are carefully designed and manufactured to compare the lift-drag characteristics and cavitation performances. It is expected that the developed section behaves better in the vicinity of the ship's wake, where the angle of attack variation is large, because of its wider width in lift-drag and cavitation-free bucket diagrams. A propeller design method using the selected foil section is presented. Three chordwise loading shapes are selected to investigate the influence of the lift-drag ratios on the propeller efficiencies and cavitation performances. Three propellers are designed, which correspond to the selected chordwise loading shapes. Two more propellers which use existing foil sections are designed to compare the section performance.