• The Journal of Advanced Prosthodontics
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• 제14권3호
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• pp.182-202
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• 2022

PURPOSE. The aim of this study is to summarize various biomechanical aspects in evaluating the long-term stability of dental implants based on finite element method (FEM). MATERIALS AND METHODS. A comprehensive search was performed among published studies over the last 20 years in three databases; PubMed, Scopus, and Google Scholar. The studies are arranged in a comparative table based on their publication date. Also, the variety of modeling is shown in the form of graphs and tables. Various aspects of the studies conducted were discussed here. RESULTS. By reviewing the titles and abstracts, 9 main categories were extracted and discussed as follows: implant materials, the focus of the study on bone or implant as well as the interface area, type of loading, element shape, parts of the model, boundary conditions, failure criteria, statistical analysis, and experimental tests performed to validate the results. It was found that most of the studied articles contain a model of the jaw bone (cortical and cancellous bone). The material properties were generally derived from the literature. Approximately 43% of the studies attempted to examine the implant and surrounding bone simultaneously. Almost 42% of the studies performed experimental tests to validate the modeling. CONCLUSION. Based on the results of the studies reviewed, there is no "optimal" design guideline, but more reliable design of implant is possible. This review study can be a starting point for more detailed investigations of dental implant longevity.

• 대한통합의학회지
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• 제6권3호
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• pp.43-57
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• 2018

Purpose : The act of reporting child abuse by people obliged to report child abuse is a way to detect long-term incidents of child abuse in early stages and to prevent a vicious cycle of social crimes. Thus, this study intends to enhance the reporting of child abuse through a study on the perception of people obliged to report child abuse through the public service announcement on child abuse. Methods : First, in order to identify the demographic characteristics of the subjects, the frequency and percentage were calculated. Second, in order to verify the reliability of the variables, Cronbach ${\alpha}$ was calculated. Third, in order to examine the perception of people obliged to report child abuse and the perception of reporting, a t-test (verification) and One-way ANOVA were conducted. Fourth, in order to identify the relationship between variables, a Correlation analysis was conducted. Result : The results show that people obliged to report child abuse did not perceive the public service announcement on child abuse positively and it varied depending on their jobs. The correlation between the public service announcement on child abuse and sub-factor of perceptions of reporting showed that a positive correlation was found in reliability, interest, understanding, perceiving the public service announcement on child abuse, perceiving severity and effectiveness, whereas a negative correlation was found in perceiving hazards. Conclusion : The education for preventing child abuse is required by the job type of people obliged to report. It is necessary to convey the message of effective public service announcement. The public service announcements on child abuse must be nationwide and long-term projects.

• 에너지공학
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• 제19권2호
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• pp.62-72
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• 2010

고체산화물연료전지(SOFCs)는 연료가스를 전기화학반응을 통하여 전기에너지로 직접 전환한다. SOFCs의 이점은 수소인프라가 구축되기 이전이라도 연료의 다양성으로 연료전지를 효과적으로 구동할 수 있다. 한편 낮춰진 운전온도의 IT-SOFCs는 일부 재료의 개발은 다소 여유가 있으나 SOFCs의 완성을 위한 긴 수명과 내구성의 달성을 위한 도전은 계속되고 있다. SOFCs에 유용하게 사용하는 연료는 탄화수소인 천연가스이다. 애노드 재료로 가장 보편적으로 사용하는 재료는 Ni/YSZ서멧이다. 그러나 이는 몇 가지 단점을 가져 연료조건하에서 혼합전도도를 나타내는 새로운 애노드 재료의 개발이 필요하다. 이 논문은 SOFCs 애노드 재료개발에 대한 최근 동향을 기술한다.

• 한국추진공학회지
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• 제26권6호
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• pp.43-52
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• 2022

유도무기용 일회성 터보엔진은 장기간 저장 후에도 운용 신뢰성이 보장되어야 한다. 터보엔진의 운용 신뢰성에 큰 영향을 미치는 구름 베어링은 장시간 저장에 의해 궤도면 및 전동체에 산화층이 형성될 수 있으며, 이로 인해 미세 치수의 변화를 유발하여 고장이 발생할 수 있다. 본 연구에서는 실제 장기 저장된 일회성 터보엔진 베어링을 획득하고, 전동체 조도의 열화 데이터를 이용하여 저장 수명을 예측하였다. 저장 수명은 와이베이즈(Weibayes) 분석 방법과 선형 열화식의 계수를 난수로 생성하는 난수 생성 기반 분석 기법을 통해서 예측하였다. 본 연구에서는 두 가지 수명평가 방법의 결과를 상호 비교하고 이에 따른 장단점을 분석하였다. 향후, 추가적인 장기저장 시편을 확보하고, 명확한 고장 조도 기준을 수립하면 베어링의 저장 수명 예측정확도를 높일 수 있을 것이며, 터보엔진의 효율적인 정비 주기 설정에 기여할 수 있을 것이다.

• 한국품질경영학회:학술대회논문집
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• 한국품질경영학회 1998년도 The 12th Asia Quality Management Symposium* Total Quality Management for Restoring Competitiveness
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• pp.287-292
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• 1998

As business looks towards the $21^{\st}$ century, a long-term strategy that focuses on global sourcing will be the vital factor in whether companies win or lose. At the same time, with electronic components, it is important to ensure stable quality and reliability, together with other important parameters. In order to achieve this, creating an effective mechanism of failure analysis and database management for electronic components is essential. The authors introduce the actual mechanism employed by NEC and explain the ideas and insight they have obtained from their experience.

• 한국신뢰성학회지:신뢰성응용연구
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• 제7권4호
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• pp.173-181
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• 2007

Out door exposure to daylight and weather climate conditions can cause adverse effect on the properties of automotive plastic materials. The effects of sunlight exposure, especially ultra violet (UV) radiation, can break down the chemical bonds in a polymeric material. This degradation process is called photo-degradation and ultimately leads to color changes, cracking, chalking, the loss of physical properties and deterioration of other properties. To explore the effect of sunlight exposure on the automotive materials, this study investigated photo-oxidation degree and surface property change of molding parts by analytical methods. For the further study, accelerated weathering test methods are proposed, which can correlate with out door weathering, to predict long term performance of automotive plastic materials.

• 한국신뢰성학회지:신뢰성응용연구
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• 제9권1호
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• pp.37-45
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• 2009

Recently mechanical watt-hour meters are being replaced by electronic watt-hour meters. The replacement period of mechanical watt-hour meters is 7 years. This period is based on long term historical data. The replacement period of electronic watt-meters is also 7 years. This period is determined using the replacement period of mechanical watt-hour meters. However lifetime of mechanical watt-hour meters is different from the lifetime of electronic meters. In order to determine desirable replacement period of electronic watt-hour meters, accelerated life tests of major components in electronic watt-hour meters were performed. The test results showed that LCD was the component which had the shortest lifetime. In this paper, lifetime of electronic watt-hour meters manufactured by 3 company was estimated and life test standard for LCD was developed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 A
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• pp.552-554
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• 2000

This paper presents algorithm to plan construction and expanding of substation considering contingency accidents by proposing utilization factor according to configuration of bank system. In this paper, at first, proper sphere of supply area in each district which could be standardized with respect to its supply capacity is established under assumption which was made long term load forecasting in district respectively. Secondly, goal of utilization ratio according to configuration of substation bank was set to keep reliability by remaining sound bank when it happen to one bank accidents Finally, optimal construction and expanding of substation considering economy and reliability simultaneously about substation to exceed these ratio could be anticipated.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 A
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• pp.748-750
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• 2005

This paper approaches a methodology for deciding the optimal reliability criteria for an optimal composite power system expansion planning considering generation and transmission systems simultaneously. A probabilisticreliability criterion, $LOLE_R$(Loss of Load Expectation), is used in this study. The optimalreliability criterion $LOLE_R*$ is decided at minimum cost point of total cost curve which is the sum of the utility cost associated with construction cost and the customer outage cost associated with supply interruptions for load considering forced outage rates of elements(generators and lines) in long term forecasting. The characteristicsand effectiveness of this methodology are illustrated by the case study using MRBTS size system.

• 마이크로전자및패키징학회지
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• 제27권3호
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• pp.21-27
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• 2020

The importance of floating photovoltaic systems has recently been emerging to address some issues arising from the installation of conventional ground-mounted photovoltaics. Floating photovoltaics have a few advantages such as cutting down land usage, reducing water evaporation or creating algae. Though there is still necessity to supplement with technical issues: mechanical stability, reliability and long-term durability of floaters and modules. In this paper, we focus the current level of packaging development and introduce research trends that could be applied to next-generation floating photovoltaics.