• Clinical and Experimental Reproductive Medicine
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• 제50권3호
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• pp.185-191
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• 2023

Objective: Although intracytoplasmic sperm injection (ICSI) is a way to deal with in vitro fertilization failure, 3% of couples still experience repeated fertilization failure after attempted ICSI, despite having sperm within normal parameters. These patients are a challenging group whose sperm cannot fertilize the egg during ICSI. Unfortunately, no test can predict the risk of fertilization failure. Phospholipase C zeta (PLCζ) and transition nuclear proteins (TNPs) are essential factors for chromatin packaging during sperm maturation. This study aimed to assess PLCζ1 and TNP1 expression in the sperm of patients with fertilization failure and the correlations among the DNA fragmentation index, PLCζ1 and TNP1 gene and protein expression, and the risk of fertilization failure. Methods: In this study, 12 infertile couples with low fertilization rates (<25%) and complete failure of fertilization in their prior ICSI cycles despite normal sperm parameters were chosen as the case group. Fifteen individuals who underwent ICSI for the first time served as the control group. After sperm analysis and DNA fragmentation assays, quantitative reverse-transcription polymerase chain reaction (qRT-PCR) and Western blot analyses were performed to compare the gene and protein expression of PLCζ and TNP1 in both groups. Results: DNA fragmentation was significantly higher in the fertilization failure group. The qRT-PCR and Western blot results demonstrated significantly lower PLCζ and TNP1 gene and protein expression in these patients than in controls. Conclusion: The present study showed that fertilization failure in normozoospermic men was probably due to deficient DNA packaging and expression of TNP1.

• 한국항공운항학회지
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• 제27권4호
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• pp.21-26
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• 2019

The purpose of this study is to suggest a method for the efficient preventive maintenance of aircraft gas turbine engine turbine blades. For this study, the types and characteristics of gas turbine engines and its turbine blades were studied, the turbine blade defect types that caused an In-Flight Shut Down(IFSD) were analyzed, the blade failure rate according to the blade life cycle was analyzed through the Weibull distribution, one of the statistical techniques. Through these research results, it is possible to supplement the problems of the life cycle management and maintenance method of the turbine blade, and to suggest the measures to strengthen the preventive maintenance of the turbine blade. In this analysis, when total cycle of turbine blade exceeds 18,000 cycles, the failure rate is over 98%, and then the special management measures are required.

• 한국임상수의학회지
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• 제32권5호
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• pp.399-403
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• 2015

복막투석은 혈액에서부터 오는 체액과 노폐물을 교환하는 복강내의 막인 복막을 이용한 투석방법으로, 신부전과 중독증 환자에서의 치료법이다. 본 연구에서는 신부전증 개에서 자동투석기를 이용한 복막투석의 치료효율과 합병증에 대해 평가하였다. 10마리의 개를 대상으로 Swan neck 카테터(Neonatal, Coviden)와 자동 복막투석기를 사용하여 복막투석을 실시하였고, 그 효과는 요소감소율(urea reduction ratio)로 평가하였다. 평균 크레아틴닌 감소율과 평균 요소감소율은 $7.09{\pm}3.84$과 $145.8{\pm}48.5$였다. 평균 투석횟수는 $6{\pm}1$회 였다. 투석치료후 유의성 있는 요소의 감소가 7/10 개에서 관찰되었고, 유의성 있는 크레아틴의 감소가 9/10 개에서 관찰되었다. 요소의 감소율이 크레아틴 감소율보다 더 높게 관찰되었다. 1회 투석당 요소와 크레아틴닌의 감소율은 $0.064{\pm}0.023$과 $0.065{\pm}0.023$이 였다. 본 연구에서의 복막투석에 따른 합병증은 카테터 막힘, 투석액의 피하누출, 패혈성 복막염, 저알부민혈증, 과수화 등이었다. Swan neck 카테터와 자동 복막투석기를 이용한 복막투석은 임상에서 적용 가능하였으며 본 연구를 통하여 성공적인 복막투석의 가능성을 보여주었다. 하지만 합병증을 최소화하기 위해서는 주의 깊은 모니터링이 필요할 것으로 판단된다.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.623-624
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• 2006

The behavior of hardmetals under cyclic loads is investigated. Unnotched specimens were employed to obtain practical information regarding fatigue in hardmetals. All the tested hardmetals exhibit an increase in the number of cycles until failure with a decrease in the maximum stress, i.e., the hardmetals exhibit a high fatigue sensitivity. The fatigue strength increases with the cobalt content. Although distinct fatigue limits, as observed in metals, cannot be observed, the calculated fatigue limit stress at $10^7$ cycles is found to be approximately 70% of the flexural strength, and the stress value exhibits a linear relationship with the flexural stress.

• 대한금속재료학회지
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• 제46권2호
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• pp.80-87
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• 2008

Many researches related to the reliability of Pb-free solder joints with PCB (printed circuit board) surface finish under thermal or vibration stresses are in progress, because the electronics is operating in hash environment. Therefore, it is necessary to assess Pb-free solder joints life with PCB surface finish under thermal and mechanical stresses. We have investigated 4-points bending fatigue lifetime of Pb-free solder joints with OSP (organic solderability preservative) and ENIG (electroless nickel and immersion gold) surface finish. To predict the bending fatigue life of Sn-3.0Ag-0.5Cu solder joints, we use the test coupons mounted 192 BGA (ball grid array) package to be added the thermal stress by conducting thermal shock test, 500, 1,000, 1,500 and 2,000 cycles, respectively. An 4-point bending test is performed in force controlling mode. It is considered that as a failure when the resistance of daisy-chain circuit of test coupons reaches more than $1,000{\Omega}$. Finally, we obtained the solder joints fatigue life with OSP and ENIG surface finish using by Weibull probability distribution.

• Structural Engineering and Mechanics
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• 제68권2호
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• pp.193-201
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• 2018

This paper describes an experimental study on the seismic performance of steel reinforced concrete (SRC) T-shaped columns. The lateral loads were applied along the web of the column with different loading histories, such as monotonic loading, mixed loading of variable amplitude cyclic loading and monotonic loading, constant amplitude cyclic loading and variable amplitude cyclic loading. The failure modes, load-displacement curves, characteristic loads and displacements, ductility, strength and stiffness degradations and energy dissipation capacity of the column were analyzed. The effects of loading history on the seismic performance were focused on. The test results show that the specimens behaved differently in the aspects of the failure mode subject to different loading history, although all the failure modes can be summarized as flexural failure. The hysteretic loops of specimens are plump, and minimum values of the failure drift angles and ductility coefficients are 1/24 and 4.64, respectively, which reflect good seismic performance of SRC T-shaped column. With the increasing numbers of loading cycles, the column reveals lower bearing capacity and ductility. The strength and stiffness of the column with variable amplitude cyclic loading degrades more rapidly than that with constant amplitude cyclic loading, and the total cumulative dissipated energy of the former is less.

• 대한기계학회논문집A
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• 제35권7호
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• pp.799-804
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• 2011

본 논문에서는 칩저항을 실장하는 솔더에 대한 온도사이클 시험을 수행하고, 그 결과로부터 고장 예지 실현을 위한 열하중에서의 솔더실장의 고장메커니즘을 연구하였다. 시험 중 솔더의 고장을 모니터링하기 위하여 실장된 칩저항 양단간의 저항 변화를 데이터 측정기로 실시간 관찰하였다. 관찰 데이터로부터 솔더의 크랙 진전 중과 크랙 진전 완료 시점의 고장 메커니즘을 제시하였다. 제시된 고장 메커니즘을 유한요소법으로 검증하여 솔더의 크랙이 진전 중에는 저온조건에서 크랙이 열리고 저항이 증가하며, 크랙의 진전이 완료된 후에는 고온조건에서 크랙이 열리고 저항이 증가하는 조건으로 바뀜을 보였다. 이런 결과에 기반하여 온도 사이클에서 저항측정을 통해 칩저항 실장 솔더의 고장예지가 가능함을 제시하였다.

• 대한기계학회논문집A
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• 제24권2호
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• pp.438-448
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• 2000

Mechanical press joining technique has been used in sheet metal joining processes because of its simple process and possibility of joining dissimiliar metals, such as steel and aluminum. The static and cyclic behavior of single overlap AI-alloy and steel(SPCC) joints has been investigate. Relationships were developed to estimate the strength of the joint taking into consideration base metal strength properties and the geometry of the joint. Fatigue test results have shown that fatigue resistance of the SPCC mechanical press joints is almost equal to that of the spot weld at the life of $10^6$ cycles. Also, the dissimilar material jointed specimen with upper SPCC plate and button diameter corresponding to the nugget diameter of the spot welded specimen has almost same strength as the same material jointed specimen and as the spot welded specimen.

• 한국신뢰성학회지:신뢰성응용연구
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• 제16권2호
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• pp.162-170
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• 2016

Purpose: The purpose of this study was to analyze the failure modes of an auto transfer switch (ATS), determine the most common failure mechanisms, and iterate the design to improve reliability. Methods: We carried out failure mode and effect analysis (FMEA) to determine the failure modes and mechanisms. We identified the parts or modules that required improvement via two-stage quality function deployment based on FMEA, and improvements to reliability were monitored using the Gomperz growth model. Results: The main failure modes of the ATS were damage to, and deformation of, the stator / movable element due to repetitive movements. Five iterations of design modification were carried out, and the mean time to failure (MTTF) increased to 14,539 cycles, corresponding to 85% of the target MTTF. The Gompertz growth model indicates that the 10th iteration of design modification is expected to achieve the target MTTF. Conclusion: We improved the reliability of mechanical parts via failure mode analysis, and characterized the iterative improvements in the MTTF using the Gompertz growth model.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.161-164
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• 2008

구조물은 사용연한 경과에 따른 노후화 및 용도 변경 등에 의한 보수.보강시 널리 행해지는 부착공법 중 탄소섬유, 아라미드섬유, 유리섬유 등을 이용한 섬유보강 폴리머(Fiber-reinforced polymer,FRP) 보강공법은 섬유 자체의 내화학성, 내구성과 우수한 시공성 등의 장점을 지니고 있다. 현재 FRP 부착공법을 이용한 보강설계 및 보강구조물의 내력 계산시, 콘크리트 부재와의 부착력을 완전부착으로 가정하고 있으나 콘크리트 구조물이 내부적 요인 및 외부 환경요인에 의해 열화될 경우 내력저하 및 1차적인 표면부 열화로 인한 FRP 부착면적의 손실발생이 우려된다. 하게 된다. 따라서 노후화에 따라 내력저하를 보이는 철근콘크리트 구조물에 FRP 보강시 열화에 따른 FRP 보강부재와 콘크리트 모재 간의 부착력 손실에 관한 연구가 필요하며, 본 연구에서는 환경적 요인에 의해 열화되는 철근콘크리트 부재의 파괴양상 및 구조성능과 FRP 보강부재와 콘크리트 모재와의 부착성능 저하현상을 분석하기 위하여 동결융해에 따른 CFRP 쉬트의 보강성능을 실험적으로 규명하고자 한다.