• Journal of Mechanical Science and Technology
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• 제15권7호
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• pp.1013-1021
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• 2001

A series of rabbit common extensor tendon specimens of the humeral epicondyle were subjected to tensile tests under two displacement rates (100mm/min and 10mm/min) and different elbow flexion positions 45°, 90°and 135°. Biomechanical properties of ultimate tensile strength, failure strain, energy absorption and stiffness of the bone-tendon specimen were determined. Statistically significant differences were found in ultimate tensile strength, failure strain, energy absorption and stiffness of bone-tendon specimens as a consequence of different elbow flexion angles and displacement rates. The results indicated that the bone-tendon specimens at the 45°elbow flexion had the lowest ultimate tensile strength; this flexion angle also had the highest failure strain and the lowest stiffness compared to other elbow flexion positions. In comparing the data from two displacement rates, bone-tendon specimens had lower ultimate tensile strength at all flexion angles when tested at the 10mm/min displacement rate. These results indicate that creep damage occurred during the slow displacement rate. The major failure mode of bone-tendon specimens during tensile testing changed from 100% of midsubstance failure at the 90°and 135°elbow flexion to 40% of bone-tendon origin failure at 45°. We conclude that failure mechanics of the bone-tendon unit of the lateral epicondyle are substantially affected by loading direction and displacement rate.

• 한국가스학회지
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• 제7권2호
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• pp.14-21
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• 2003

도시가스 배관에서 위험을 유발할 수 있는 사건의 발생빈도를 구하기 위하여 주요 사고원인인 굴착공사, 외부부식, 지반침하 및 장치손상 등에 의한 사고발생빈도를 구하는 방법을 제시하였다. 굴착공사로 인한 손상은 FTA에 의해 기본사상(Basic event)을 도출하고, 부식에 의한 손상확률은 시간변화에 따른 부식결함의 잔존강도를 평가하는 평가식을 제시하였다. 지반침하로 인한 손상은 기준손상율을 구하고 여기에 손상모드인자 및 보정인자를 고려한 모델을 이용하여 구하였다. 장치원인에 의한 손상확률은 고유고장율과 특정고장율 자료를 모두 반영할 수 있는 방법을 제시하였으며 그 계산 예도 제시하였다.

• Journal of Chest Surgery
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• 제27권2호
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• pp.122-127
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• 1994

A retrospective study of 737 consecutive patients surviving the first 24 hours who underwent valve replacement surgery from July 1980 to June 1993 was undertaken to determine the prevalence, variables that could be used to predict outcome and results of therapy for postoperative acute renal failure[ARF]. Twenty-one patients[2.8 %] developed acute renal failure. Positive risk factors noted in the development of postoperative renal failure included age, New York Heart Association class III & IV, endocarditis and elevated preoperative concentration of serum creatinine. The duration of cardiopulmonary bypass, aortic cross-clamping and the total duration of the operation also closely correlated with the incidence of ARF. The mortality rate for established ARF was 38.1% and ARF was associated with a significant increase in the length of hospitalization, ventilator support and intensive care unit stay. The incidence and mortality rate of oliguric renal failure was 38.1% and 85.7%. The highest mortality rate was associated with two or more postoperative complications and serum creatinine value exceeded 5 mg/dl. We concluded that therapy should be aimed at prevention of oliguric renal failure, or at least its conversion to nonoliguric renal failure, and early institution of renal replacement therapy with intensive support probably gives the best chance for survival.

• 상하수도학회지
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• 제10권1호
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• pp.96-111
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• 1996

The failure of water pipelines is progressed by several compound factors and the collection and analysis of data about pipeline failure are inevitable for effective pipeline rehabilitation. Data analysis of pipeline failure was already performed in USA and Europe. Based on such phenomena, failure characteristics about metropolitan pipelines in Korea were analyzed: The conclusions of this study are as followings. 1. The failure cause of pipelines can be classified into natural cause and artificial cause. Artificial cause is 32% of total causes, so artificial failure as several constructions happens frequently in Korea. Although the failure by old pipe is greatest of any other causes m classtfied cause, failure cause is not classified in detail now. 2. The damaged part of pipelines is affected by cities, distribution system inventory, bedding conditions, and so on. In this study, the failure of pipeline body(67%) is greater than the failure of pipeline joint(33%) in natural failure. 3. In regard to pipe materials, failure rate of DCIP(0.8456), PEP(0.7288), and GSP(0.6643) is greater than that of CIP(0.3985) and CWSP(0.2348). 4. Usually, faIlure rate is increased in proportion to diameter of pipeline. In this study, CIP, DCIP, and CWSP have clear trends. But the trends of PEP is reverse, the case of GSP, HP is obscure due to data shortage. 5. There are no direct relationships between burial age and failure rate of pipelines. 6. Annual breaks and winter(Nov.~Feb.) breaks of pipelines are investigated. As a result, WInter breaks to annual breaks of CIP is 51.3%(Seoul), 51.1%(Taegu),38.7%(Pusan). This phenomena have direct correlation with average winter temp. of cities.

• 한국신뢰성학회지:신뢰성응용연구
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• 제11권4호
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• pp.433-445
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• 2011

Duty cycle is determined as the ratio of operating time to total time. Duty cycle in reliability prediction is one of the significant factors to be considered. In duty cycle application, non-operating time failure rate has been easily ignored even though the failure rate in non-operating period has not been proved to be small enough. Ignorance of non-operating time failure rate can result in over-estimated system reliability calculation. Furthermore, utilization of duty cycle in reliability prediction has not been evaluated in its effectiveness. In order to address these problems, two reliability models, such as MIL-HDBK-217F and RIAC-HDBK-217Plus, were used to analyze non-operating time failure rate. This research has proved that applying duty cycle in 217F model is not reasonable by the quantitative comparison and analysis.

• Structural Engineering and Mechanics
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• 제30권2호
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• pp.177-190
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• 2008

Material failure behavior is generally dependent on loading rate. Especially in brittle and quasi-brittle materials, rate dependent material behavior can be significant. Empirical formulations are often used to predict the rate dependency, but such methods depend on extensive experimental works and are limited by practical constraints of physical testing. Numerical simulation can be an effective means for extracting knowledge about rate dependent behavior and for complementing the results obtained by testing. In this paper, the failure behavior of a brittle material under different loading rates is simulated by molecular dynamics analysis. A notched specimen is modeled by sub-million particles with a normalization scheme. Lennard-Jones potential is used to describe the interparticle force. Numerical simulations are performed with six different loading rates in a direct tensile test, where the loading velocity is normalized to the ratio of the pseudo-sonic speed. As a consequence, dynamic features are achieved from the numerical experiments. Remarkable failure characteristics, such as crack surface interaction/crack arrest, branching, and void nucleation, vary in case of the six loading cases. These characteristics are interpreted by the energy concept approach. This study provides insight into the change in dynamic failure mechanism under different loading rates.

• 한국품질경영학회:학술대회논문집
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• 한국품질경영학회 1998년도 The 12th Asia Quality Management Symposium* Total Quality Management for Restoring Competitiveness
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• pp.571-579
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• 1998

In this paper we propose smooth nonparametric estimator of Mean Residual Life(MRL) based on a complete sample. This estimator is constructed using estimator of cumulative failure rate which is derived as the maximum likelihood estimate of cumulative failure rate in the class of distributions which have piecewise linear failure rate functions between each pair of observations. We derive the asymptotic properties of the our estimator. The proposed estimator is compared with previously known estimator by Monte Carlo study.

• Communications for Statistical Applications and Methods
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• 제14권1호
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• pp.93-109
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• 2007

In this paper we study a number of new exponentiated distributions. The survival function, failure rate and moments of the distributions have been derived using certain special functions. The behavior of the failure rate has also been studied.

• 품질경영학회지
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• 제25권3호
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• pp.51-61
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• 1997

We introduce a method of estimating an unknown failure rate function based on sample data. We estimate failure rate function by a function s from a space of cubic splines constrained to be linear (or constant) in tails using maximum likelihood estimation. The number of knots are determined by Bayesian Information Criterion(BIC). Examples using simulated data are used to illustrate the performance of this method.

• 한국신뢰성학회:학술대회논문집
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• 한국신뢰성학회 2000년도 추계학술대회
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• pp.365-371
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• 2000

The problem of trend change in the failure rate is great interest in the reliability and survival analysis. In this paper we develop a test statistic for testing whether or not the failure rate changes its trend using random censored data. The asymptotic normality of the test statistic is established. We discuss the efficiency values of loss due to censoring.