• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2004년도 추계학술대회 논문집
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• pp.369-374
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• 2004

Web-based analysis programs for reliability assessment of machine tools were developed in this study. First, the reliability data analysis program was developed to search for failure rate using failure data and reliability test data of mechanical part. Second, failure mode analysis was developed through performance tests like circular movement test vibration test for machine tools. This analysis program shows correlation between failure mode and performance test result. Third, tool life was predicted by correlation between flank wear and cutting time, using the extended Taylor tool life equation in turning data and the equivalently converted equation in order to apply ball endmill data to Taylor tool life equation in milling data. All the information related to input and result data can be stored in theses programs.

• Archives of Pharmacal Research
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• 제24권4호
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• pp.333-337
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• 2001

The pharmacokinetic changes of diltiazem (DTZ) and its main metabolite, deacetyldiltiazem (DAD) were studied after oral administration of DTZ to normal rabbits and mild and medium folate-induced renal failure rabbits. DTZ 10 mg/kg was given to the rabbits either orally (n=6). Plasma concentrations of DTZ and DAD were determined by a high performance liquid chromatography assay. The area under the plasma concentration-time curves (AUC) and maximum plasma concentration ($C_{max}$) of DTZ were significantly increased in mild and medium folate-induced renal failure rabbits. The metabolite ratio of the DTZ to DAD were significantly decreased in mild and medium folate-induced renal failure rabbits. The volume of distribution ($V_{d}$) and total body clearance ($CL_{t}$) of DTZ were significantly decreased in mild and medium folate-induced renal failure rabbits. The elimination rate constant ($\beta$) of DTZ was significantly decreased in folate-induced renal failure rabbits, but that of DAD was significantly increased. These findings suggest that the hepatic metabolism of DTZ was inhibited and the $V_{d}$, $CL_{t}$ and $\beta$ of DTZ were significantly decreased in mild and medium folate-induced renal failure rabbits.

• Journal of Computing Science and Engineering
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• 제8권1호
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• pp.17-24
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• 2014

In this paper, we propose a new implementation of a failure detector. The implementation uses a dual model of heartbeat and interaction. First, the heartbeat model is adopted to shorten the detection time, if the detection process does not receive the heartbeat message in the expected time. The interaction model is then used to check the process further. The expected time is calculated using the exponential smoothing method. Exponential smoothing can be used to estimate the next arrival time not only in the random data, but also in the data of linear trends. It is proven that the new detector in the paper can eventually be a perfect detector.

• Transactions on Control, Automation and Systems Engineering
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• 제2권1호
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• pp.31-39
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• 2000

We present a robust and reliable H$\infty$ state-feedback controller design for linear uncertain systems, which have norm-bounded time-varying uncertainty in the state matrix, and their prespecified sets of actuators are susceptible to failure. These controllers should guarantee robust stability of the systems and H$\infty$ norm bound against parameter uncertainty and/or actuator failures. Based on the linear matrix inequality (LMI) approach, two state-feedback controller design methods are constructed by formulating to a set of LMIs corresponding to all failure cases or a single LMI that covers all failure cases, with an additional costraint. Effectiveness and geometrical property of these controllers are validated via several numerical examples. Furthermore, the proposed LMI frameworks can be applied to multiobjective problems with additional constraints.

• 한국안전학회지
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• 제14권2호
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• pp.155-162
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• 1999

reliability from components reliability. In this case, it assumes that components failure is mutually independent, but it may not true in real systems. In this study, the mean cost per unit time is computed as the ratio of mean life to the mean cost. The mean life is obtained by the reliability function under power rule model. The mean cost is obtained by the mathematical model based on the inspection interval. A heuristic method is proposed to determine the optimal number of redundant units and the optimal inspection interval to minimize the mean cost per unit time. The assumptions of this study are as following : First, in the load-sharing k-out-of-n:G system, total loads are applied to the system and shared by the operating components. Secondly, the number of failed components affects the failure rate of surviving components as a function of the total load applied. Finally, the relation between the load and the failure rate of surviving components is set by the power rule model. For the practical application of the above methods, numerical examples are presented.

• Journal of Electrical Engineering and Technology
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• 제6권6호
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• pp.760-768
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• 2011

The performance of transmission lines and its shielding design during a lightning phenomenon are quite essential in the maintenance of a reliable power supply to consumers. The leader progression model, as an advanced approach, has been recently developed to calculate the shielding failure rate (SFR) of transmission lines using geometrical data and physical behavior of upward and downward lightning leaders. However, such method is quite time consuming. In the present paper, an effective method that utilizes artificial neural networks (ANNs) to create a metamodel for calculating the SFR of a transmission line based on shielding angle and height is introduced. The results of investigations on a real case study reveal that, through proper selection of an ANN structure and good training, the ANN prediction is very close to the result of the detailed simulation, whereas the Processing time is by far lower than that of the detailed model.

• 한국국방경영분석학회지
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• 제22권1호
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• pp.114-128
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• 1996

In this paper, a life distribution fitting method based on generalized phase-type distributions(GPH) is presented. By fitting the life distribution to a GPH, we can utilize various useful properties of the GPH. Two different approaches are used according to the properties of the given failure time data. One is an approximation to a GPH through the piecewise Weibull failure rate(PWF) model and the other is a direct approximation to a GPH using the empirical distribution function. Two numerical examples are also presented. In the first example, both of the two approaches are utilized and compared for an incomplete data set. And in the second example, the direct approximation method from an empirical distribution is utilized for the analysis of a complete data set. In both cases, we could confirm the validity of the proposed method.

• 한국국방경영분석학회지
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• 제16권2호
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• pp.135-150
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• 1990

This paper classifies faults into three types : simple, degenerated, and regenerated faults. This paper also deals with the characteristics of each type of fault to determine the software reliability based on the assumption; i. e., a system consisting of several subsystems (modules) which may be debugged simultaneously. For each type of fault, several formulas are developed to obtain the failure rate and the expected number of failures found during debugging. A model is developed based on the formulas of the failure rate and the expected number of failures to decide the optimal release time of a new software: minimizing the total cost with constraints restricting to the failure rate of each module in the software. By using this model, optimal release times are found for some cases; the eliminated faults are assumed simple faults only, regenerated faults only, simple and degenerated faults, and so on.

• 한국신뢰성학회:학술대회논문집
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• 한국신뢰성학회 2005년도 학술발표대회 논문집
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• pp.327-337
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• 2005

Accelerated life test models and procedure are developed to assess the reliability of Door switch. The main function of door switch is to operate bulb lamp and fan motor. The accelerated life test method and test equipments are developed using the relationship between stresses and life characteristics of the products. Using the developed accelerated life test method, the parameters of the ALT model and life time distribution are estimated and the reliability of the Door S/W at use condition if assessed. The proposed accelerated life test method and procedure may be extended and applied to testing similar kinds of products to reduce test time and costs of the tests remarkably.

• 대한기계학회논문집A
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• 제34권10호
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• pp.1521-1527
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• 2010

잉크젯 프린팅이 전자 및 디스플레이 산업의 생산라인에 적용됨에 따라, 생산효율을 극대화하기 위해 잉크액적 토출불량 검사 소요시간의 단축이 요구되고 있다. 기존의 잉크액적 토출불량 검사방법은 주로 고배율 렌즈와 CCD 카메라를 직선운동을 하는 스테이지 상에 설치하여 잉크젯 프린트 헤드의 노즐배열과 평행한 방향으로 순차적으로 이동시키면서 토출되는 잉크액적을 비젼검사하는 것이었다. 그러나, 기존 방식은 60 초 혹은 그 이상의 검사시간을 요구하며, 특히 잉크액적 토출불량을 장시간 지속적으로 검사하는 것은 불필요한 기계적 진동을 야기시키는 문제점이 있었다. 본 연구에서는 회전미러 방식의 고속 잉크젯 모니터링 모듈을 설계하여 검사시간을 18 초 내외로 단축하였으며, 검사 소요시간 단축을 위한 모듈의 설계 고려사항들에 대해 논의하도록 한다.