• 한국수자원학회논문집
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• 제51권7호
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• pp.543-554
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• 2018

혼성제 직립 케이슨의 활동에 대한 부분안전계수 산정과 Level I 신뢰성 기반 설계법에 의한 단면 결정 과정을 자세히 제시하였다. 특히 본 연구에서는 형식의 일치성과 실무에서의 적용 편이성을 위하여 부력 및 자중과 직접적으로 관련된 수위 및 케이슨을 구성하는 재료의 불확실성을 고려할 수 있는 수학적 모형을 제시하였다. 또한 양압력에 대한 영향을 정확히 고려하여 활동에 대해 안정한 혼성제 직립 케이슨 단면을 산정할 수 있는 설계기준식을 유도하였다. 본 연구에서 제시한 부분안전계수를 가지고 Level I 신뢰성 기반 설계법에 의해 산정된 단면이 동일한 목표파괴확률에 대한 Level II AFDA의 결과 및 Level III MCS의 결과와 매우 잘 일치하였다. 그러나 미국 및 일본의 항만 설계기준에서 제시한 부분안전계수를 이용한 결과는 그 보다 훨씬 크거나 작은 단면을 산정하고 있다. 마지막으로 부분안전계수의 목표수준과 Level I 신뢰성 기반 설계법으로 결정된 단면의 안정성 수준에 대한 일치성 여부를 확인하기 위한 다각적인 신뢰성 재해석이 수행되었다.

• 산업경영시스템학회지
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• 제37권3호
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• pp.82-88
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• 2014

The government expands its investment on R&D programs for economic growth, thus there is growing attention on the result of R&D Programs. This study proposes more improved measuring method for efficiency when the number of R&D programs is not enough to be for measuring efficiency analysis. It provides more various application method of factors on efficiency analysis. This study analyzes the influence of each input factor on efficiency by using partial efficiency concept. And it also determines input factors in similar influence throughout Spearman correlation coefficient. Finally, it suggests new method to improve discriminatory power of efficiency analysis by determining representative factors. Also, the proposed method can be practiced not only for national R&D programs, but also for other fields of research.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.2021_2022
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• 2009

Partial discharges(PD) is a important factor to evaluate the insulation state in high voltage electric machinery. However, measuring PD under the circumstances of power plant is occasionally impossible due to the relatively high magnitude of noise which is emanated from the operating machinery. In some case, the instrument measuring PD can not even perform a calibration that initializes tools and enhance the accuracy. This paper presents that we devised a noise reduction method and demonstrated the usefulness in acquiring reliable PD signals. We attached a series of filter and transformer at the input of power source of the instruments which refrains high noise signals from incoming to the instruments. We experimented the efficiency of noise reduction applying the device into the Dangjin Power Plant and Factory. As a result of testing with the filter and transformer, we can easily calibrate the PD signal compared to the case without the device. Additionally, we can detect the small PD signal which was unperceived with a normal device.

• 대한기계학회논문집A
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• 제24권6호
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• pp.1565-1574
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• 2000

Surface edge crack subjected to contact stresses is analysed. A punch with corner radii is considered to press the semi-infinite plane. Partial slip problem is solved when a shear force is applied to the punch. Dislocation density function method is used to solve the present mixed mode crack problem. The crack length of positive K1 is examined, which is affected by the ratio of the flat portion to the total width of the punch. Surface traction during one cycle of the shear force is evaluated to simulate the fretting condition. The compliance change of the contact surface is also investigated during the shear cycle. It is found that the crack grows during only a part of the cycle, which may be termed as effective period of crack growing. A design method for restraining the fretting failure is discussed, from which recommendable geometry of the punch is suggested.

• International Journal of Advanced Culture Technology
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• 제10권3호
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• pp.263-271
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• 2022

The purpose of this study is to identify the degree of participation and the impact of social media sports contact motivation on sports activities. In order to clarify the purpose of this study, a total of 300 students from 150 male and 150 female university students in Gwangju and Jeonnam provinces in 2020 were selected by the convenience sampling method. The survey tool used to achieve the purpose of this study is the questionnaire method. Therefore, the questionnaire, which has already been verified for reliability and validity in domestic and foreign previous studies, was re-quoted, modified, or supplemented for the purpose of this study. For data processing, SPSS Windows 20.0 Version was used. For specific statistical analysis, frequency analysis, exploratory factor analysis, reliability analysis, and multiple regression analysis were performed according to the purpose of analysis. The results obtained through these results are as follows. First, it was found that the contact motivation for social media sports partially affected the degree of participation in social media sports. Second, it was found that social media sports contact motivation has a partial influence on sports participation. Third, the degree of social media sports participation was found to have a partial influence on sports participation.

• 전력전자학회논문지
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• 제11권2호
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• pp.142-148
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• 2006

본 논문에서는 역률개선과 고효율로 동작되는 새로운 승압형 AC-DC 컨버터를 제안한다. 제안된 컨버터는 입력전류 불연속제어로 구동되고, 스위치의 시비율 일정제어에 의해 입력전류는 교류 입력전압의 크기에 비례된 불연속적인 정현파 형태로 주어진다. 그 결과 입력역률은 거의 단위역률로 주어지고, 시비율 일정제어에 의해 제안된 컨버터는 제어기법이 간단하게 된다. 일반적으로 전류불연속 제어에 의한 컨버터의 경우, 사용된 스위치의 턴-온 동작은 영전류 스위칭으로 되는 장점이 있지만, 스위치의 턴-오프 동작은 최대 전류에서 스위칭되어 스위칭 손실을 증대시키고 스위치의 과중한 스트레스를 가져오게 된다. 이것은 컨버터의 효율을 저하시키는 요인이다. 본 논문에서는 부분적인 공진회로 동작에 의한 새로운 소프트 스위칭 회로가 설계되어 사용된 제어스위치들의 턴-온, 턴-오프 동작을 소프트 스위칭으로 만들어 컨버터의 효율을 증대시킨다.

• 조명전기설비학회논문지
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• 제19권7호
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• pp.45-52
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• 2005

본 논문은 전류불연속 제어에 의한 고역률, 고효율로 동작되는 승압형 AC-DC 컨버터에 대해 연구된다. 전류불 연속 제어 컨버터는 제어회로 구성이 간단하고 구성소자의 수를 줄일 수 있는 장점을 가진다. 제안된 컨버터의 입력전류는 듀티율 일정제어에 의한 교류 입력전압의 크기에 비례된 불연속적인 정현파 형태로 된다. 그 결과 입력역률은 거의 단위역률로 주어지며 듀티율 일정제어에 의해 제어기법이 간단하다. 또한 제안된 컨버터의 스위칭 소자들은 부분공진 기법에 의해 소프트 스위칭 동작으로 되어 스위칭 손실이 매우 낮으며 컨버터의 효율을 증대시킨다. 부분공진 회로부는 승압용으로 사용된 인덕터와 무손실 스너버 커패시터에 의해 설계되어 컨버터의 회로 토폴로지가 간단하다. 제안된 컨버터는 컴퓨터 시뮬레이션과 실험결과에 의해 그 타당성이 입증된다.

• Journal of applied mathematics & informatics
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• 제40권3_4호
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• pp.491-505
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• 2022

This paper is concerned with singularly perturbed convection-diffusion parabolic partial differential equations which have time-delayed. We used the Crank-Nicolson(CN) scheme to build a fitted operator to solve the problem. The underling method's stability is investigated, and it is found to be unconditionally stable. We have shown graphically the unstableness of CN-scheme without fitting factor. The order of convergence of the present method is shown to be second order both in space and time in relation to the perturbation parameter. The efficiency of the scheme is demonstrated using model examples and the proposed technique is more accurate than the standard CN-method and some methods available in the literature, according to the findings.

• Journal of Welding and Joining
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• 제23권1호
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• pp.48-54
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• 2005

Laser keyhole welding is investigated using a three-dimensional Gaussian heat source, and the heat source parameters such as the keyhole depth, welding efficiency and power density distribution factor are determined in a systematic way. For partial penetration, the keyhole depth is same as the penetration and is predicted using the experimental data. The welding efficiency is calculated using the ray-tracing method and the power density distribution factor is determined from the bead shape. Full penetration is classified into the transition, normal and excessive modes depending on the degree of keyhole opening. Thermal analysis of the bead-on-plate welds is conducted using the Gaussian heat source, and the calculated weld geometries show reasonably good agreements with the experimental results.

• Wind and Structures
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• 제12권5호
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• pp.425-439
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• 2009

The expediency of revising universal rules for the combination of gravity and lateral actions of wind force-resisting steel structures recommended by the Standards EN 1990 and ASCE/SEI 7-05 is discussed. Extreme wind forces, gravity actions and their combinations for the limit state design of structures are considered. The effect of statistical uncertainties of extreme wind pressure and steel yield strength on the structural safety of beam-column joints of wind force-resisting multistory steel frames designed by the partial factor design (PFD) and the load and resistance factor design (LRFD) methods is demonstrated. The limit state criterion and the performance process of steel frame joints are presented and considered. Their long-term survival probability analysis is based on the unsophisticated method of transformed conditional probabilities. A numerical example illustrates some discrepancies in international design standards and the necessity to revise the rule of universal combinations of loads in wind and structural engineering.