• 한국해양공학회지
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• 제10권4호
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• pp.92-102
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• 1996

In this research, to develope the A1 7075/CFRP multilayered hybrid composites, CRALL(Carbon Reinforced aluminum lamiate) specimens were processed by autoclavecuring system that curing temperature, time, surface pretreatment condition of aluminum were constant. Andthe fatigye life and failure mechanism on CFRP volume fraction and fiber orientation of CRALLspecimens were investigated. A fatigue life was greatly influenced by effect of CFRP fiber volume fraction but it was less effected than those of fiber orientation. The fatigue failure arised from interface delamination of CFRP and aluminum sheet after shear fracture of aluminum layer. The failure mechanism is assumed that the aluminum laminates which divide the CFRP into many thim layers tend to arrest the failure propagation.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
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• pp.455-460
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• 2002

In this study, a numerical analysis that can effectively predict the effect of strengthening of cracked flexural members is developed using axial deformation link elements. Concrete and interface between concrete and repair material are considered as quasi-brittle material. Reinforcing bars and reinforcing steel plates are assumed to perform as elasto-plastic materials. Unloading behavior of axial deformation link element is implemented. In the developed numerical model, a flexural member is intentionally cracked by pre-loading, then, the cracked member is repaired using extra elements, and reloaded. The results from analysis of repaired flexural members agrees well with available experiment results. Also, it was shown that the effect of strengthening and the change of failure mode with respect to the time for strengthening and thickness of repair materials. Based on the results, it was determined that the developed numerical model has a good agreement for determining failure modes and effect of strengthening in cracked flexural members. By utilizing the developed numerical analysis, the time and dimension of external strengthening in an existing cracked flexural member with predition of failure mechanism can be determined.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2009년도 춘계 학술대회 제21권1호
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• pp.563-564
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• 2009

Ultra-High Performance Concrete (UHPC) compared to normal concrete is exhibiting extremely high strength characteristics with compressive strength and tensile strength reaching 200MPa and 15MPa, respectively. The mechanical characteristics of UHPC can be thus exploited advantageously in the construction of structure through the reduction of the cross-sectional area and fabrication of slim and light-weight of the structural members. In the case where the structural member is made of UHPC, the occurrence of crack can be prevented by releasing the restraint provided by the form in due time. This research performs parametric study of the failure characteristics of concrete such as failure energy and softening curve suggested by the viscous crack model approximating the failure of concrete. The scope of this research contains the results of tests performed to investigate the strength of UHPC during early elapsed time.

• 전기학회논문지P
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• 제63권4호
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• pp.345-350
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• 2014

DC electrolytic capacitor is widely used in the power converter including PWM inverter, switching power supply and PFC Boost converter system because of its large capacitance, small size and low cost. In this paper, basic characteristics of DC electrolytic capacitor vs. frequency is presented and the real-time estimation scheme of ESR and capacitance based on the bandpass filtering is adopted to the single phase boost converter of uninterruptible power supply to diagnose its split dc-link capacitors. The feasibility of this real-time failure prediction monitoring system is verified by the computer simulation of the 5[kW] singe phase PFC half-bridge boost converter.

• Journal of Chest Surgery
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• 제18권4호
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• pp.649-654
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• 1985

After first successful mitral valvotomy by Harken and Bailey in 1948, improvement of surgical technique and cardiac device may last rapidly for several years, but there after many patients deteriorate because of various causes, so incidence of reoperation for cardiac valvular disease has increased time by time. This paper is concerned with 21 patients in whom a second operation has been carried out from Jan. 1963 to Aug. 1984 at the department of Thoracic and Cardiovascular department, National Medical Center. Of 21 patients, 7 were male and 14 were female, and ages ranged from 14 to 37 years The second operation are classified into groups of secondary closed mitral commissurotomy [3 cases], open commissurotomy following closed mitral commissurotomy [1 case], Valve replacement following closed mitral commissurotomy [14 cases] or bioprosthetic valve replacement [3 cases]. Main cause of reoperation was restenosis or steno insufficiency, and that of bioprosthetic valve failure was bacterial endocarditis [1 case], fibrous tissue overgrowth on the Xenograft [1 case] and technical failure [1 case]. Early operative mortality was absent, but during follow-up, 4 patients died, so late mortality was 19.0%, and main cause of death was congestive heart failure.

• 융합정보논문지
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• 제12권5호
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• pp.15-20
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• 2022

본 연구는 소프트웨어 품질 특성인 기능적합성, 신뢰성, 사용성, 이식성, 유지보수성, 성능효율성, 보안성, 호환성 중에서 신뢰성에 대한 평가 방안을 연구하였다. 소프트웨어 품질 측정에 있어 신뢰성의 정량적 평가 방안을 제시한다. 본 연구는 소프트웨어 품질 특성 중 하나인 신뢰성 평가 중 성숙성에 포함되는 고장률을 측정하는 방법에 대해서 소개하고 고장 데이터의 형태에 따라 고장률이 어떻게 변화하는지에 대해 실험데이터를 가지고 연구한 내용이다. 소프트웨어 테스팅을 중심으로 매일의 고장 수를 중심으로 소프트웨어 신뢰성 성장 모델에 적용하여 고장률을 측정하여 고장 데이터의 형태에 따라 비교 분석하였다. 6일간의 테스트를 통해서 발견된 고장 시간을 중심으로 고장률을 측정하고 측정결과를 이용해서 국제표준 ISO/IEC 25023에서 제시하고 있는 고장률과 비교 하였으며 데이터 형태에 따라 적용방안을 검토하였다.

• Journal of Electrical Engineering and Technology
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• 제10권6호
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• pp.2277-2287
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• 2015

In recent times, multilevel inverters are given high priority in many large industrial drive applications. However, the reliability of multilevel inverters are mainly affected by the failure of power electronic switches. In this paper, open-switch and short-switch failure of multilevel inverters and its identification using a high performance diagnostic system is discussed. Experimental and simulation studies were carried out on five level cascaded H-Bridge multilevel inverter and its output voltage waveforms were analyzed at different switch fault cases and at different modulation index values. Salient frequency domain features of the output voltage signal were extracted using the discrete wavelet transform multi resolution signal decomposition technique. Real time application of the proposed fault diagnostic system was implemented through the LabVIEW software. Artificial neural network was trained offline using the Matlab software and the resultant network parameters were transferred to LabVIEW real time system. In the proposed system, it is possible to precisely identify the individual faulty switch (may be due to open-switch (or) short-switch failure) of multilevel inverters.

• Structural Engineering and Mechanics
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• 제20권1호
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• pp.1-20
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• 2005

The present paper deals with the seismic response analysis and the evaluation of most likely failure modes for a water storage structure. For the stress analysis, a 3-D mathematical model has been adopted to represent the structure appropriately. The structure has been analyzed for both static and seismic loads. Seismic analysis has been carried out considering the hydrodynamic effects of the contained water. Based on the stress analyses results, the most likely failure modes viz. tensile cracking and compressive crushing of concrete for the various structural elements; caused by the seismic event have been investigated. Further an attempt has also been made to quantify the initial leakage rate and average emptying time for the structure during seismic event after evaluating the various crack parameters viz. crack-width and crack-spacing at the locations of interest. The results are presented with reference to peak ground acceleration (PGA) of the seismic event. It has been observed that, an increase in PGA would result in significant increase in stresses and crack width in the various structural members. Significant increase in initial leakage rate and decrease in average emptying time for the structure has also been observed with the increase in PGA.

• 한국항만경제학회지
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• 제39권1호
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• pp.47-63
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• 2023

스마트 항만 및 항만 자동화에 수직 배치형 컨테이너 터미널을 적용하여 운영하는 사례가 늘고 있다. 본 연구는 수평 배치형과 수직 배치형 컨테이너 터미널에서의 본선작업 시간을 분석함으로써 각 터미널간 생산성을 비교하고, 향후 수직 배치형 컨테이너 터미널의 운영 효율성 증대 방안을 제시하고자 한다. 이를 위해 각각을 대표하는 터미널을 선정하여, 2018년부터 2022년까지 최근 5년 선석배정현황 데이터를 수집하였으며, 모수적 생존분석 기법인 가속실패시간모형(Accelerated Failure Time, AFT)을 활용하여 분석을 실시하였다. C/C 작업 조건이 '동일하다'는 가정 하에서, 수직 배치형 컨테이너 터미널에서의 본선 작업 생산성이 보다 좋은 것으로 나타났으며, 코로나19 기간에는 생산성이 감소한 결과를 나타냈다. 작업량이 많은 선박의 경우와 유럽 선사의 선박의 경우, 본선작업 시간이 감소하는 걸 알 수 있다. 적정 C/C의 투입 및 효율적 운영, 장비들 간 원활한 운영, shifting 작업은 증가, C/C를 포함한 하역 장비들의 준비시간 감소 및 고장/사고 최소화 등 수직 형태 컨테이너 터미널의 생산성을 높이기 위한 방안을 제시하였다.

• Archives of Pharmacal Research
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• 제26권11호
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• pp.979-983
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• 2003

The pharmacokinetic of tolbutamide was studied after the oral administration to normal rabbits or rabbits with mild to medium folate-induced renal failure. The plasma concentrations of tolbutamide were significantly elevated (p<0.05) during 9 to 24 h in rabbits with mild or medium folate-induced renal failure. Consequently, the area under the plasma concentration-time curves (AUC) was significantly higher in mild (p<0.05) and medium (p<0.01) folate-induced renal failure rabbits (i.e., 2906 $\mu$g/mL$.$h for mild renal failure and 4074 $\mu$g/mL$.$h for moderate renal failure) than that in normal rabbits (i.e., 2295 $\mu$g/mL$.$h). The cumulative urinary excretion of tolbutamide was significantly depressed (p<0.05) in medium folate-induced renal failure rabbits (i.e., 3.3 mg) compared with that in normal rabbits (i.e., 5.9 mg). The elimination rate constant (Kel) of tolbutamide was significantly decreased in medium renal failure rabbits (i.e., 0.027 $h^{-1}$) than that in normal rabbits (i.e., 0.044 $h^{-1}$ ); As a result, the terminal half-life of tolbutamide in medium folate-induced renal failure rabbits (i.e., 25.5 h) was significantly longer (p<0.01) than that in normal rabbits (i.e., 15.7 h). The change in pharmacokinetic parameters is consistent with the hypothesis that the alteration is mediated by the depressed metabolic elimination of the drug by the induction of renal failure. Therefore, these observations indicated that the dosage adjustment may be necessary for tolbutamide in patients with renal insufficiency.