• Proceedings of the KIEE Conference
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• 2006.04b
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• pp.130-132
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• 2006

For the reliability assessment of solenoid actuator, firstly, we analyzed the cause of major failures and the effect of each failure modes through FMEA and FTA, and decided the main test items through 2-stage QFD. And then, as a measure of life of solenoid actuator, TypeII censored five data were collected from and operation test which was performed as the life test of solenoid actuator. In this paper, we present the reliability parameters of solenoid actuator like shape parameter, scale parameter, etc., which they are produced by MINITAB analysis and marking of Weibull probability paper using the measure of life, and also present the 6 kinds of detailed failure mode analysis.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.672-675
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• 1995

Because of a sudden growth of the research of fatigue failure, recent machines or structures have been designed by damage tolerance design in many fields. Consequently, it is the most primary factor to clarity the specific character of fatique failure in the design of machines or structures considering reliability. A statistical analysis is required to analyze the outcome of an experiment or a life estimate by reason of that fatigue failure contains lots of random elements. Reliability analysis which has tukenn the place of the existing analyses in the consideration of the uncertainty of a material, is a very efficient way. Even reliability analysis, however, is not a perfect way to analyses the uncertainties of all the materials. This thesis would refer to a newly conceived data analysis that the coefficient of a system could cause the ambiguity of the relationship of an input and output.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1432-1435
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• 2005

We report failure mode observed in polymer EL blue devices, relating with life curve. The modes are analyzed by observing compositional and morphological variation using TEM-EDX, STM, and reverse engineering method as destructive ways, and also investigated mobility changes of hole and electron by measuring transient EL as a nondestructive way corresponding to life curve. We believe that the postulated failure modes in polymer EL devices can present right directions to obtain better performance, especially life time, of polymer devices in material and device structural designing points of view.

• Magazine of the Korean Society of Agricultural Engineers
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• v.45 no.2
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• pp.35-44
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• 2003

A system reliability method is proposed to decide reliable serviceability of agricultural irrigation system. Even though reliability method is applied to real engineering situations involving actual life environments and maintaining costs, a number of Issues arise as a modeling and analysis level. This article use concepts that can be described the probability of failure with time variant and series-parallel system reliability analysis model. A proposed method use survivor function that can simulate a time-variant performance function for a lifetime before it is required essential maintenance or replacement to define a target probability of failure in agricultural irrigation canal. In the further study, it is required a relationship between a state of probability of failure and current serviceability to make the optimum repair strategy to maintain appropriate serviceability of an irrigation system.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.722-727
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• 2004

The gear that is used in various mechanical components occurs easily damages due to the repeated torque and the high oil temperature. The main failure mode of the gear is the surface deterioration with the tooth surface fatigue. Therefore, the life evaluation and the failure analysis of the gear were very important since it may cause fatal damage of entire gear box system. In this paper, the failure mechanism and the life of the gear were evaluated using the durability analysis simulator such as MSC.FATIGUE. Moreover, the reliability analysis model of the spur gear with the accelerated life testing technique was proposed.

• Journal of the Korean Data and Information Science Society
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• v.23 no.4
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• pp.843-850
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• 2012

The inferences of data obtained from periodic inspection and type I censoring for the three step stress accelerated life test are studied in this paper. The failure rate function that a log-quadratic relation of stress and the tampered failure rate model are considered under the exponential distribution. The optimal stress change times which minimize the asymptotic variance of maximum likelihood estimators of parameters is determined and the maximum likelihood estimators of the model parameters are estimated. A numerical example will be given to illustrate the proposed inferential procedures.

• Journal of IKEEE
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• v.23 no.4
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• pp.1208-1217
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• 2019

The life-cycle prediction of the sub-module which is the unit system of MMC is very important from the viewpoint of maintenance and economic feasibility of HVDC system. However, the life-cycle prediction that considers only the type, number and combination of parts is a generalized result that does not take into account the operating condition of the sub-module, and may significantly differ from the life-cycle of the actual one. Therefore, we design a fault tree for the purpose of reflecting the operation characteristics of the full-bridge sub-module and apply the MIL-HDBK-217F to the failure rate of the basic event to predict the life-cycle of the full-bridge sub-module. It compares the life-cycle expectancy of the conventional failure rate analysis with the proposed fault-tree analysis and compares the lifetime according to whether the redundancy of the full-bridge sub-module is considered.

• Korean Medical Education Review
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• v.26 no.2
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• pp.155-166
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• 2024

This study utilized cohort data, student lifestyle surveys, and mental health examination results from a medical school to investigate the impact of factors such as hometown, alcohol use, smoking, university life adaptation, and aptitude on academic failure, with mental health serving as a mediator. We analyzed data from 409 of the 549 incoming students at Keimyung University School of Medicine, excluding 140 individuals with missing data, from the academic years 2015 to 2021. Significant differences were found according to hometown in feelings of depression, suicidal tendencies, and internet addiction. There were also significant differences based on university life adaptation in feelings of depression, suicidal tendencies, and internet addiction, as well as significant differences according to academic aptitude in feelings of depression and internet addiction. Academic failure showed significant differences based on hometown, university life adaptation, and academic aptitude. Furthermore, students' hometown had a complete mediating effect on academic failure together with feelings of depression, suicidal tendencies, and internet addiction. University life adaptation exhibited a complete mediating effect with suicidal tendencies and a partial mediating effect with feelings of depression and internet addiction. Academic aptitude demonstrated partial mediating effects on feelings of depression, suicidal tendencies, and internet addiction. Based on these results, we suggest establishing counseling programs tailored to the characteristics of medical students, and various programs for university life adaptation are necessary. There is also a need for diverse programs not only for clinical training, but also for different career paths.

• Reproductive and Developmental Biology
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• v.37 no.1
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• pp.23-27
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• 2013

This study was carried out to investigate the influence of artificial insemination (AI) failure in 1,619 Korean native cows at Gangwon East area, Korea. The average AI failure rate was 37.02% in the cows and the highest rate was 40.85% in Yangyang-city. Based on the parity in the cows, the AI failure rate was 49.14% and 29.91% in the first and fifth parity cows, respectively. Whereas cows until fifth parity were decreased in AI failure, cows with sixth or more parity showed an upturning AI failure trends with the increasing of parity number. AI failure rate incidence according to the rump fat thickness measured by ultrasound was 28.9% and 33.4% at 5 mm to 10 mm and over than 15 mm, respectively. There was a positive correlation (0.2186) between AI failure rate of mother and that of their offspring cows. That is, offspring of dams with high AI failure rate showed also higher AI failure than those of dams having lower AI failure rate. In conclusion, these results indicate that the AI failure rate was closely related to the rump fat thickness, parity number, and conception rate of mother cows. In addition, these results might strengthen the basis to improve the reproductive performance in Korean native cows.

• Journal of Applied Reliability
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• v.15 no.3
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• pp.139-144
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• 2015

Track drive unit adopted in the small sized excavator generally have been used in the construction equipment under the 10 tons as the driving device with forwarding and reversing of excavator. It is required to study the accelerated life test applied by over torque and speed to test the durability life test reflected the many driving modes of small sized excavator and also need to equip the comprehensive performance and life test equipments to do the various performance tests. This study had analyzed the failure modes of the components, and calculated the equivalent loads investigated the used loads in the real field conditions and elicits the acceleration factor adopted in the inverse power model. Also, this study have considered the changes of the acceleration factor and the durability test time in the case of the rotary group and the bearing through analyzing the main failure modes. It was calculated the no failure test time about 2 samples and confidence level 90% and elicited the accelerated life time 720 hours.