• Structural Engineering and Mechanics
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• 제32권1호
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• pp.37-53
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• 2009

In this paper the problem of calculating the probability that the responses of a wind-excited structure exceed specified thresholds within a given time interval is considered. The failure domain of the problem can be expressed as a union of elementary failure domains whose boundaries are of quadratic form. The Domain Decomposition Method (DDM) is employed, after being appropriately extended, to solve this problem. The probability estimate of the overall failure domain is given by the sum of the probabilities of the elementary failure domains multiplied by a reduction factor accounting for the overlapping degree of the different elementary failure domains. The DDM is extended with the help of Line Sampling (LS), from its original presentation where the boundary of the elementary failure domains are of linear form, to the current case involving quadratic elementary failure domains. An example involving an along-wind excited steel building shows the accuracy and efficiency of the proposed methodology as compared with that obtained using standard Monte Carlo simulations (MCS).

• 대한안전경영과학회지
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• 제16권3호
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• pp.209-218
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• 2014

An accident related with elevators can cause death or serious injury of operators or passengers. This kind of a fatal accident is due to a failure of elevator. The reduction of failures of elevators is important to reduce the occurrence of elevator accident. Thus, this paper presents the results of analysis for the failure of elevators using the failure data of elevator. The results of analysis can be used to make a maintenance process of elevators.

• Nuclear Engineering and Technology
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• 제53권3호
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• pp.932-941
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• 2021

This paper suggests a fracture simulation method for SFR metallic fuel pin under accident condition. Two major failure mechanisms - creep damage and eutectic penetration - are implemented in the suggested method. To simulate damaged element, stress-reduction concept to reduce stiffness of the damaged element is applied. Using the proposed method, the failure size of cladding can be predicted in addition to the failure time and failure site. To verify the suggested method, Whole-pin furnace (WPF) test and TREAT-M test conducted at Argonne National Laboratory (ANL) are simulated. In all cases, predicted results and experimental results are overall in good agreement. Based on the simulation result, the effect of eutectic-penetration depth representing failure behavior on failure size is studied.

• 콘크리트학회논문집
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• 제12권2호
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• pp.21-30
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• 2000

In the Ultimate Strength Design, the design strength of a member is determined by multiplying the strength reduction factor to the nominal strength. This concept may be a reasonable approach, however it can not consider failure modes appropriately. Moreover, column design strength diagram show an abrupt change at a low level of axial load, which does not seem to be reasonable. This research compares the design strength determined by the strength resistance factors. As the material resistance factors for flexure and compression, 0.65 and 0.90 are proposed for concrete and steel, respectively. The design strength calculation process by applying material resistance factors addresses failure modes more effectively than by applying member strength reduction factor, and provides more resnable design strength for reinforced concrete flexural and compression members.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.925-930
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• 2006

During the excavation of a tunnel portal, failure zones around the tunnel heading occur and also the ground supports itself. In a portal, its location and the ground characteristic have a great influence on the stability of the tunnel. Therefore, the failure mechanism of a tunnel heading and how to assess the stability of the tunnel are very important. In this paper, the numerical analyses were executed to evaluate the safety factor using strength reduction technique. The influence area of an excavation was also predicted through a case study in which no-support case and support case with the Pattern P-6 were compared in terms of the ground class and the shear strain.

• 한국소음진동공학회논문집
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• 제13권7호
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• pp.532-538
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• 2003

This paper studies on the noise reduction for a small automobile DC Motor (a window motor) using the 6 sigma process. The application of 6 sigma process suggested reliable and valuable statistical data for the quality of the DC motor at the production line. In the measurement step in 6 sigma process. the FMEA(failure mode effect analysis) were used for the detection of noise sources. The application of 6 sigma Process gave not only the improving method for the quality of the DC motor but also the confidence of improvement Itself since it was done on the basis of the test results for a number of DC motors at the production line. Consequently the 6 sigma process was proved very effective for the noise reduction at the production line.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• 제11권2호
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• pp.110-115
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• 2008

목 적: 장중첩증의 일차적인 치료로 사용되는 비수술적 관장 정복은 장천공, 쇼크 그리고 복막염 등과 같은 심각한 합병증과 불필요한 스트레스 및 과도한 방사선 노출의 위험이 있다. 본 연구에서는 무리한 비수술적 정복의 시도를 피하기 위하여 장중첩증 환자의 임상 양상 및 검사 소견 중 비수술적 정복 실패를 예측할 수 있는 인자를 파악하고자 하였다. 방 법: 고려대학교 의료원 안산병원에서 1998년 3월에서 2006년 7월까지 장중첩증으로 진단되어 치료받았던 환자 314명 중 비수술적 정복이 시도되었던 300명을 대상으로 하였다. 비수술적 정복의 성공 군과 실패군으로 나누어 성별, 연령, 임상증상 및 이학적 소견 그리고 증상의 시작에서 비수술적 정복술을 시도하기까지의 시간과 비수술적 정복 실패와의 연관성을 분석하였다. 결 과: 비수술적 정복 실패 군의 경우 성공 군에 비해 연령이 어렸고(12.3${\pm}$17.2개월 vs 18.0${\pm}$15.8개월, p=0.03), 정복 시도까지의 시간 경과가 길었으며(33.6${\pm}$29.0시간 vs 21.5${\pm}$20.3시간, p<0.01), 구토, 기면은 많았음(p<0.01)에 비해 복통이나 보챔은 적었다(p<0.01). 이러한 인자들의 다중회귀분석에서 비수술적 정복 실패와 연관된 인자는 6개월 미만 연령(odds ratio: 2.5, 95% confidence interval: 1.2~5.2, p=0.01), 24시간 경과(odds ratio: 2.1, 95% confidence interval: 1.2~4.2, p=0.03), 혈변(odds ratio: 4.8, 95% confidence interval: 1.9~12.2, p<0.01), 기면(odds ratio: 3.4, 95% confidence interval: 1.1~10.4, p=0.04), 복통 또는 보챔(odds ratio: 0.2, 95% confidence interval: 0.1~0.4, p<0.01)이었다. 결 론: 장중첩증에서 6개월 미만 어린 연령, 혈변이나 기면의 소견, 증상 시작 24시간이 경과된 경우 비수술적 정복 실패의 가능성이 많으므로 이러한 사항을 충분히 고려하여 시행 여부를 결정하는 것이 좋겠다.

• Steel and Composite Structures
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• 제24권5호
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• pp.615-633
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• 2017

Fatigue crack initiated in welded tubular joints due to cyclic loading may produce harmful effect on the integrity of the tubular structures. To study such effect, both fatigue and static tests on nine circular tubular T-joint specimens made of carbon steel materials were carried out. The specimens were subjected to tensile loading in both fatigue and static tests. The load-displacement relation, the crack propagation and the failure mode of the specimens are all analyzed. The deterioration of the static strength of the cracked T-joints is also investigated and evaluated through an area reduction factor. Experimental results indicate that the static strength of a tubular T-joint with a surface crack seems to decrease slightly while a through crack has relatively remarkable effect on the reduction of the static strength. Additionally, experimental results also show that the toughness of the materials and the geometry of the specimens play an important role on the failure process of cracked tubular T-joints.

• Structural Engineering and Mechanics
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• 제81권4호
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• pp.429-441
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• 2022

A probabilistic assessment of the seismic-excited buildings with a multiple-tuned-mass-damper (MTMD) system is carried out in the presence of uncertainties of the structural model, MTMD system, and the stochastic model of the seismic excitations. A free search optimization procedure of the individual mass, stiffness and, damping parameters of the MTMD system based on the snap-drift cuckoo search (SDCS) optimization algorithm is proposed for the optimal design of the MTMD system. Considering a 10-story structure in three cases equipped with single tuned mass damper (STMS), 5-TMD and 10-TMD, sensitivity analyses are carried out using Sobol' indices based on the Monte Carlo simulation (MCS) method. Considering different seismic performance levels, the reliability analyses are done using MCS and kriging-based MCS methods. The results show the maximum structural responses are more affected by changes in the PGA and the stiffness coefficients of the structural floors and TMDs. The results indicate the kriging-based MCS method can estimate the accurate amount of failure probability by spending less time than the MCS. The results also show the MTMD gives a significant reduction in the structural failure probability. The effect of the MTMD on the reduction of the failure probability is remarkable in the performance levels of life safety and collapse prevention. The maximum drift of floors may be reduced for the nominal structural system by increasing the TMDs, however, the complexity of the MTMD model and increasing its corresponding uncertainty sources can be caused a slight increase in the failure probability of the structure.

• 소성∙가공
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• 제3권2호
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• pp.147-155
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• 1994

The service life of tools in metal forming technology is to a large extent limited by wear and fatigue fracture of the active elements. This presents a basic request for tool cost minimization and reduction of extensive machine down time, caused by premature tool failure. Currents developments are dominated by steps to reduce the causes of tool failure. A main problem of forming technology remains the insufficient reliability of tools due to a large and incalculable life time fluctuation. Only a systematic investigation of the failure mechanisms and operational loading of tools can lead to future improvements in tool layout, that is optimization of tool usage.