• 한국기계가공학회지
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• 제19권12호
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• pp.34-41
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• 2020

Ready-mixed concrete is unconsolidated concrete typically transported to construction sites by using mixer trucks. A proper rotation of concrete is necessary to prevent its solidification in mixer trucks during transport: in accordance with the manufacturing method and quality inspection prescribed in KSF4009, this movement is maintained after the manufacturing of concrete in professional production plants and the addition of water, solid materials, and admixtures. Unfortunately, mixer truck parts wear out over long periods of time. In order to improve the wear resistance of the main part of mixer trucks, we used a steel plate with good wear resistance or partially added a reinforcement plate. In this study, we first tested the properties of concrete (as required for the DEM), and then carried out mixing and discharge simulations to define the actual operating conditions of mixer trucks. For each condition, we calculated the amount and location of wear. The reliability of our results was finally verified by comparing them with the measurement values. Overall, this study provided basic data for an optimal design of mixer trucks: one that would reduce the vehicles' weight and production costs.

• Journal of Sport and Applied Science
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• 제6권3호
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• pp.1-7
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• 2022

Purpose: The purpose of this study is to provide basic data for developing an educational program that can be practically applied in the field of survival swimming education. Research design, data, and methodology: This study reviewed prior literature including governmental reports, journal articles related to survival swimming programs at home and abroad. Based on the basic data collected through literature, domestic and foreign educational institutions and national educational programs were cataloged and analyzed. Results: The study found that among the goals of swimming education, the prevention of water accidents and the cultivation of water safety skills along with improving swimming ability are very important educational goals. Currently, domestic survival swimming education programs are divided into classes and training sessions, so it is necessary to develop an educational program according to each individual's swimming ability and a unified and systematic program through education for each level of survival swimming learners. Conclusions: It is thought that the reinforcement of the leader's capacity for quality improvement will have a positive effect for the development of survival swimming. Further implications were discussed.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권12호
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• pp.4385-4399
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• 2021

The Internet of Things (IoT) eHealth systems composed by Wireless Body Area Network (WBAN) has emerged recently. Sensor nodes are placed around or in the human body to collect physiological data. WBAN has many different applications, for instance health monitoring. Since the limitation of the size of the battery, besides speed, reliability, and accuracy; design of WBAN protocols should consider the energy efficiency and time delay. To solve these problems, this paper adopt the end-edge-cloud orchestrated network architecture and propose a transmission based on reinforcement algorithm. The priority of sensing data is classified according to certain application. System utility function is modeled according to the channel factors, the energy utility, and successful transmission conditions. The optimization problem is mapped to Q-learning model. Following this online power control protocol, the energy level of both the senor to coordinator, and coordinator to edge server can be modified according to the current channel condition. The network performance is evaluated by simulation. The results show that the proposed power control protocol has higher system energy efficiency, delivery ratio, and throughput.

• 감성과학
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• 제25권4호
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• pp.139-156
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• 2022

This study aimed to examine the cause and consequence of emotional labor strategies based on the emotional labor framework. To investigate the boundary condition of the current research model, the study proposed that job autonomy would moderate the effects of emotional labor on employees' well-being. To achieve the purpose of the study, it was first tested whether neuroticism and extroversion of employees predicted the focal outcomes (i.e., burnout and work engagement) via distinct emotional labor strategies. Second, the moderation effects of job autonomy were tested for each emotional labor strategy in predicting the focal outcomes. Third, the conditional indirect effects of job autonomy on the mediation process were examined. The results revealed that surface acting partially mediated the relationship between neuroticism and burnout, whereas deep acting fully mediated the relationship between extraversion and work engagement. Regarding the moderating effects of job autonomy, it significantly moderated the relationship between surface acting and burnout and between deep acting and work engagement. In addition, from the moderated mediation effects, the conditional indirect effects of job autonomy were significant. Finally, theoretical and practical implications are discussed and limitations and future research directions were suggested.

• 국제학술발표논문집
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• The 6th International Conference on Construction Engineering and Project Management
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• pp.683-684
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• 2015

Project Financing (PF) is the long-term financing of infrastructure and industrial projects based upon the projected cash flows of the project rather than the balance sheets of its sponsors. However, the financial institution, the subject of financing in the case of PF in Korea, the lack of validation system of business, rather than to assess the feasibility of the project, requested a credit reinforcement to the construction company, the fact is Construction Company on loans of the employer is the guarantor or debt argument commitments accordingly. As a result, PF contingent liabilities, which are indirect debt, are triggered in the construction company, not included in the financial statements, along with the disclosure standards established according to 2009 PF contingent liabilities, and major can be a management item. In this study, PF contingent liabilities is of Pearson of the index and the PF debt ratio showing the main financial ratios and risk by classifying the credit rating and contractors Ranking of construction companies in order to analyze the impact on the financial condition of the company was performed correlation analyzes, through the Pearson correlation coefficient analysis indicated quantitative or negative relationship to derive the explicit indication.

• Restorative Dentistry and Endodontics
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• 제45권4호
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• pp.43.1-43.9
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• 2020

A variety of therapeutic modalities can be used for the endodontic treatment of a traumatized tooth with internal root resorption (IRR). The authors present a case report of the successful restoration of a traumatized upper central incisor that was weakened due to severe IRR and subsequent periapical lesion formation. A 20-year-old female patient was referred to our clinic with severe internal resorption and subsequent periapical pathosis destroying the buccal bone wall. Root canal treatment had been initiated previously at another dental practice, but at that time, the patient's condition could not be managed even with several treatments. After cone-beam computed tomography imaging and proper chemomechanical cleaning, the tooth was managed with a mineral trioxide aggregate plug followed by root canal filling using short fiber-reinforced composite, known as the Bioblock technique. This report is the first documentation of the use of the Bioblock technique in the restoration of a traumatized tooth. The Bioblock technique appears to be ideal for restoring wide irregular root canals, as in cases of severe internal resorption, because it can uniquely fill out the hollow irregularities of the canal. However, further long-term clinical investigations are required to provide additional information about this new technique.

• 한국터널지하공간학회 논문집
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• 제19권6호
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• pp.1045-1058
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• 2017

본 연구는 도로하부를 통과하는 저토피 터널의 거동특성에 관한 논문이다. 저토피 터널 굴착중에 발생하는 지반변형 특성을 파악하기 위해 시공 중인 도로하부의 저토피 터널 통과구간에 수평 지중 침하계를 설치하였으며, 계측 및 분석을 실시하였다. 또한 현장 계측 값의 비교를 위해 MIDAS NX를 이용하여 지반 조건 및 시공단계가 적용된 3차원 수치해석을 실시하였다. 현장 계측 결과, 터널굴착 시점부에서 선행 침하가 발생되었으며, 지반조건이 불량한 저토피 굴착 시점부에서 큰 침하량이 발생되었다. 수치해석 결과, 지반조건이 불량한 저토피 시점부에서 가장 큰 선행 침하량이 발생 되었다. 수치해석결과 및 현장 계측 값 비교 결과 지반조건이 불량한 저토피 시점부에서 침하량이 크게 발생 되었다. 따라서, 지반조건이 불량하고 충분한 토피고가 확보되지 못하여 터널 주변지반의 아칭 효과를 기대할 수 없는 저토피 구간에서는 강성보강대책의 적용 및 지반이완이 최소화되도록 철저한 주의를 기울여야 한다.

• 비교문화연구
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• 제35권
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• pp.315-338
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• 2014

The purpose of this study is to propose actual operation condition of Japanese lecture based on social welfare organizations located in Seoul to investigate the current status and problems of Japanese language education in terms of lifelong education. According to the result of this study, the remarkable point was that a majority of Japanese lecture courses are highly focused on the elderly and 86% of the welfare organizations are providing free education. Regarding the effect of specialized business for the aged run by social welfare community center, it says, as Korea changing to aging society at the beginning of 21st century, it has put focus on strengthening personal competences of seniors through opportunities for participation in lifelong education, recreational activity programs and culture classes. It means foreign language classes are operating as one of the lifelong education programs for reinforcement of individual capability. Considering this tendency, it is expected that the lifelong education participation rate of the elder in Seoul will be raised. So, systematic improvements will be needed for this. First, it is required to recognize the existence of Educational and Cultural Industry and work hard to make it public so it could be invigorated and utilized by people usefully at the same time. Second, Japanese language training that mostly 55-year-old or more than 60-year-old people receive at the welfare center needs to be systematized for preparations on proper studying environment which provides the older with appropriate education method and content as well. Third, stable and systematic operation should be available through the link with experts in the field of Japanese language education and elderly education. Fourth, education program development is needed, which is able to satisfy one's desires for learning. Hence, targeting Japanese learners at each welfare center, we need to know the estimation of satisfaction degree and consciousness on learning Japanese. Finally, it has not been studied sufficiently regarding the instructors on teaching Japanese language in this paper, but it has been reported that most of social welfare centers, where Japanese language lectures are provided, are run by volunteers who can teach Japanese. Thus, the study on actual condition for Japanese language instructors will be conducted as well later on.

• Composites Research
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• 제35권4호
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• pp.248-254
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• 2022

본 연구에서는 가스압 함침공정을 이용하여 고체적률 TiB₂-steel 복합재료를 제조하였으며, 미세조직 분석과 압축강도 및 경도를 측정하였다. 복합재료의 미세조직과 기계적 물성과의 연관성을 고찰하고자, 압축시험 후 시편의 파면을 분석하고 압축시험 중 시편의 파괴 거동을 예측하였다. 파면 분석 결과, 기지금속과 강화상 입자간의 계면파괴 흔적이 관찰되었으며, 이에 기지금속과 강화상의 계면을 TEM을 사용하여 분석하였다. 제조된 복합재료의 미세조직 분석 결과, TiB₂ 강화상 및 steel 기지상 이외에 TiC 상과 조대한 (Fe,M)₂B (M=Cr,Mn)상이 생성된 것을 확인할 수 있었으며, 열역학 계산을 통하여 공정조건에서 TiC와 (Fe,M)₂B가 안정상으로 생성될 수 있음을 확인하였다. 제조된 TiB₂-steel 복합재료는 기지 금속 대비 경도가 크게 상승하였으며, 상온 압축강도 및 탄성계수는 각각 3.07배, 1.95배 향상되었다. 복합재료 내부 전반에 생성된 조대한 (Fe,M)₂B (M=Cr,Mn)상이 기계적 물성 저하를 일으키는 것으로 보이며, (Fe,M)₂B (M=Cr,Mn)상의 생성을 제어함으로써 TiB₂-steel 복합재료의 기계적 물성을 추가적으로 향상시킬 수 있을 것이라 생각한다.

• 한국지반환경공학회 논문집
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• 제13권12호
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• pp.81-89
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• 2012

도심지 내에서 교통량 증가로 인하여 차선확대가 요구되는 경우, 기존 터널은 증가된 차선만큼 단면을 확대할 필요가 있다. 터널 단면확대 공사로 발생되는 터널주변의 교통정체를 해소하기 위하여 터널 내에 직사각형 단면의 프로텍터를 설치하여 프로텍터 내부로 교통흐름을 유지하기도 한다. 프로텍터를 사용하면 터널 측벽 하부에서 프로텍터와 굴착 면 사이의 공간이 협소하여 록볼트 시공이 불가능할 수도 있다. 본 연구에서는 터널 측벽 하부의 협소한 공간에서 록볼트를 시공하지 않고 숏크리트 두께를 증가시켜 터널의 안정성을 확보하는 방법을 제안하였다. 기존 2차선 재래식 터널을 3차선 및 4차선 NATM터널로 확대 시공할 경우에 대하여 수치해석을 수행하였다. 터널 측벽 하부에 록볼트를 시공한 경우, 록볼트를 시공하지 않은 경우 및 록볼트를 시공하지 않고 숏크리트 두께만 증가시킨 경우에 대하여 터널의 천단변위, 내공변위 및 숏크리트에 발생한 응력을 비교분석하였다. 천단변위 및 상반 내공변위는 차이가 거의 없었으며, 하반 내공변위는 터널 측벽 하부에 록볼트를 시공하지 않은 경우가 록볼트를 시공한 경우보다 최대 1.3mm 크게 발생하였다. 또한 숏크리트에 발생한 휨압축응력은 터널 측벽 하부에 록볼트를 시공하지 않은 경우가 록볼트를 시공한 경우보다 최대 1.3MPa 크게 발생하였다. 록볼트 미시공에 의해 추가 발생된 숏트리트 응력을 감소시키기 위하여 기존 숏트리크 두께의 20%(250mm ${\rightarrow}$ 300mm, 4차선 터널)및 25%(200mm ${\rightarrow}$ 250mm, 3차선 터널)를 추가 시공하면 록볼트를 시공할 경우와 비슷한 응력수준을 나타내는 것으로 분석되었다.