• 동력기계공학회지
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• 제20권4호
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• pp.44-51
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• 2016

An investigation on reliability of reanalysis wind data was conducted using the met mast wind data at four coastal regions, Jeju Island. Shinchang, Handong, Udo and Gangjeong sites were chosen for the met mast sites, and ERA-Interim and MERRA reanalysis data at two points on the sea around Jeju Island were analyzed for creating Wind Statistics of WindPRO software. Reliability of reanalysis wind data was assessed by comparing the statistics from the met mast wind data with those from Wind Statistics of WindPRO software. The relative error was calculated for annual average wind speed, wind power density and annual energy production. In addition, Weibull wind speed distribution and monthly energy production were analyzed in detail. As a result, ERA-Interim reanalysis data was more suitable for wind resource assessment than MERRA reanalysis data.

• Communications for Statistical Applications and Methods
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• 제15권6호
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• pp.909-923
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• 2008

본 논문에서는 수리가 가능한 시스템에 대하여 혼합보증이 종료된 이후의 교체모형과 예방보전모형을 고려하는데, 만약 보증기간이 종료된 이후에 시스템에 고장이 발생하면 최소수리를 수행한다. 최적의 교체정책과 최적의 예방보전정책을 결정하기 위한 기준으로는 기대비용과 기대비가동시간에 근거한 총밸류함수를 사용한다. 그리고 시스템의 고장시간이 와이블분포를 할 때 수치적 예를 통해서 제안된 최적의 교체정책 및 예방보전정책을 자세히 설명하고자 한다.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2006년도 학술발표회 논문집
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• pp.169-173
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• 2006

일반적으로 확률수문량을 산정하기 위해서는 수문자료에 대해 빈도해석을 실시한 후 확률수문량을 산정하게 된다. 재현기간이 커질수록 확률분포형에 따라 확률수문량의 값은 많은 차이를 나타내므로 적정 확률분포형의 선정은 매우 중요하다고 할 수 있다. 적정 확률분포형의 선정은 객관적인 기준에 의해 이루어져야 하나, 적정 확률분포형의 선정에 있어 명확한 기준이 마련되어 있지 않아 실무에서 확률수문량을 산정할 때 많은 어려움을 겪고 있는 실정이다. 따라서 본 연구에서는 적정 확률분포형의 선정기준으로 제시되어 있는 검정통계량을 이용한 방법의 적용성을 비교 검토하고자 한다. 이를 위해 우리나라에서 널리 사용되고 있는 Gumbel, GEV 분포형과 Weibull, Generalized logistic 분포형을 선택하고 각각의 분포형에 대해 자료의 크기별 모의를 통해 자료를 발생시킨 후 빈도해석을 수행하고, 적합도 검정 단계에서 산출되는 검정통계량을 비교하여 적정 확률분포형을 선정하여 적용성을 검토하고자 한다. 결과적으로 자료 발생에 이용된 분포형과는 관계없이 자료수가 작을수록 2변수 gamma, 자료수가 많을수록 5변수 Wakeby가 제일 많이 선정되는 것으로 나타났으며, Gumbel, GEV, generalized logistic 분포형의 경우는 대체로 자료의 수가 많아질수록 선정되는 빈도가 많은 것으로 나타났다.

• 한국신뢰성학회지:신뢰성응용연구
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• 제10권4호
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• pp.265-278
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• 2010

Module of the LED traffic signal is the core component for the care of driver and walker. Also it is important one to control the traffic. If it is against the criteria of brightness, it is the source of the people's death and traffic congestion. Therefore, it is a list of articles desired the security of stability. However, there is not the analysis of failure and not preserve the uniformity of quality. Therefore, it is necessary to establish the criteria of appreciation for the module of the LED traffic signal to analysis the data of failure. In this paper, we investigate the performance test, environment field test and test of reliability appreciation to improve the reliability. We also set up the criteria of success decision using the real measurement data.

• 한국세라믹학회지
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• 제38권3호
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• pp.212-217
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• 2001

The influence of granules characteristics and compaction pressure on the microstructure and mechanical properties of sintered as a function of slurry dispersion state. The characteristics and the compaction behavior of the spray dried alumina granules considerably affected the microstructure as well as the mechanical properties of the sintered body. In the green bodies formed with granules prepared with a dispersed slurry, the granules with dimple clearly existed and caused pore defects in sintered body. These dimples were clearly present even in the green body prepared at 180 MPa. The pores between the granules were not removed during pressing and sintering, and remained in the sintered body. In contrast, in the granules fabricated from a flocculated slurry, the destroy of granules at the contact points was observed with increasing pressure. Sintered bodies fabricated with fewer defects showed strength increase. For the sample fabricated with flocculated slurry, the pores at the boundaries of granules were small and more irregular shape compared with those of dispersed slurry.

• 품질경영학회지
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• 제41권4호
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• pp.659-672
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• 2013

Purpose: The purpose of this study was to estimate life time of halogen lamps and acceleration factors using accelerated life test. Methods: Voltage was selected as an accelerating variable through the technical review about failure mechanism. The test was performed at 14.5V, 15.5V and 16.5 for 4,471 hours. It was assumed that the lifetime of Halogen lamps follow Weibull distribution and the inverse power life-stress relationship models. Results: Mean lifetimes of pin and screw types were 19,477 hours and 6,056 hours, respectively. In addition, acceleration factor of two items are calculated as 4.8 and 2.2 based on 15.5V, respectively. Conclusion: The life-stress relationship, acceleration factor, and MTTF at design condition are estimated by analyzing the accelerated life test data. These results suggest that voltage was very important factor to accelerate life time in the case of halogen lamps and the life time of pin type is three times longer than screw type lamps.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 추계학술대회 논문집 전기물성,응용부문
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• pp.19-21
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• 2003

In this paper, we studied on life-decision of underground cable of live-lines state. As all equipments have been wear, underground cables decided design-life on the whole 30 years because underground cable have been occurred aging as time goes. CV cable has been become about 30 years after installation in the South Korea, is come to a important point of time with estimation about life. Study target cable is 22 kV CV cables in this point of view and installation cable is about 10 years before and behind. Measurement method used dc leakage method of live-lines state that applied voltage of 50V in neutral point and data is analyzing result that is measured during 5 years. In this result, insulation resistance could confirm that change according to season and cause is effect of humidity, seasons and load current. Also, according as data is gone aging, insulation resistance by Weibull distribution could confirm functionally its decrease. As a result, the aging speed of cable that water tree is gone could confirm fastness very. Numerical analysis result, cable that water tree is not gone could confirm that life of cable that has passed 10 years remains about $10{\sim}20$ years.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 춘계학술대회 논문집 센서 박막재료연구회 및 광주 전남지부
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• pp.50-53
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• 2008

In this work, the $TiO_2$ pigment influence in HDPE dielectric strength was analyzed. Chemical and structural characterizations were made to identify changes during the processing and your influence in the electrical properties. Formulations containing 0, 0.5, 1, 2.5, 4 and 6 of titanium dioxide were processed by extrusion and injection molding with stabilization-antioxidants, ultraviolet stabilizers and plasticizers. The electrical strength tests were analyzed by the statistical distribution of Weibull, and the maximum likelihood method. The high concentrations present lower values to electrical strength. The $\beta$ parameter could be using to insulator particles dispersion. The $TiO_2$ concentration variation shows that these incorporations implicate strength values increase has a maximum (5,35MV/cm). High pigment concentration induces a little falls in property values. Observing the $\beta$ parameter, minimum experiment electric field (Ebmin) and electric strength value, found that the best electric perform formulation was the formulation with 2.5% $TiO_2$ weight.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
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• pp.58.2-58.2
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• 2011

본 연구에서는 5MW급 수평축 풍력터빈 블레이드에 대해 국내 서남해안의 풍속특성을 고려한 최적설계를 수행 하였다. 최적설계를 수행하기 위해 블레이드 해석은 Blade Element and Momentum Theory를 이용 하였으며, 설계 시 적용된 기저형상은 NREL에서 제안한 5MW급 풍력터빈 블레이드을 선정하였다. 최적설계를 수행하기 전 설계에 사용된 설계변수들이 풍속에 대해 어떠한 경향을 가지고 있는지 알아보기 위해 Parametric Study를 수행 하였으며, 최적설계는 다목적 최적화 유전 알고리즘인 NSGA-II를 이용하여 평균풍속이 낮은 서남해안의 연간에너지 생산량과 설비이용률을 최대화하였다. 최적화 결과들로부터 설계 조건에 맞는 최적해를 도출 할 수 있었으며, 이를 통해 기저형상의 연간에너지 생산량 및 설비이용률을 보다 향상 시킬 수 있었다.

• 한국신뢰성학회지:신뢰성응용연구
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• 제12권2호
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• pp.67-78
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• 2012

An electric double-layer capacitor(EDLC) is an electrochemical capacitor with relatively high energy density, typically hundreds of times greater than conventional electrolytic capacitors. EDLCs are widely used for energy storage rather than as general-purpose circuit components. They have a variety of commercial applications, notably in energy smoothing and momentary-load devices, and energy-storage and kinetic energy recovery system devices used in vehicles, etc. This paper presents an accelerated degradation test of an EDLC with rated voltage 2.7V, capacitance 100F, and usage temperature $-40^{\circ}C{\sim}65^{\circ}C$. The EDLCs are tested at $50^{\circ}C$, $60^{\circ}C$, and $70^{\circ}C$, respectively for 1,750hours, and their capacitances are measured at predetermined times by constant current discharge method. The failure times are predicted from their capacitance deterioration patterns, where the failure is defined as 30% capacitance decrease from the initial one. It is assumed that the lifetime distribution of EDLC follows Weibull and Arrhenius life-stress relationship holds. The life-stress relationship, acceleration factor, and $B_{10}$ life at design condition are estimated by analyzing the accelerated life test data.