• Tribology and Lubricants
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• v.30 no.5
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• pp.271-277
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• 2014

Hydraulic reciprocating seals have been widely used to prevent fluid leakage and to provide lubricant film on counter surface in various hydraulic system. The degradation of the seal may cause the catastrophic failure of the hydraulic system. To assess the durability of the seals and the compatibility with counter surface, accelerated life testing (ALT) has been typically employed from industry. However, ALT often takes up to a few months to cause a failure of the seals, and therefore, there is a need to develop more efficient ALT methods. In this work, the degradation characteristics of polyurethane (PU) seals from field test are investigated and they are compared to those from the component and bench tests, with an aim to contribute to the development of ALT method. From the comparison of the cross-sectional profiles of the sealing surface of the PU specimens before and after the tests, both wear and compression set are found to be responsible for degradation of the PU seals. It is also shown that the major wear mechanisms of the PU seals from the field is abrasive wear and formation of pits. The component and bench tests performed in this work are shown to reproduce such wear mechanisms, and therefore, those test methods can be used as an ALT method for PU seals. In particular, the bench test proposed in this work may be effectively utilized to assess the durability and the compatibility of the seals with the counter surface. The results of this work are expected to aid in the design of ALT for PU seal.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.591-594
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• 2000

In the recent day, fatigue life prediction techniques play a major role in the design of components in the ground vehicle industry. Full scale durability testing in the laboratory is an essential of any fatigue life evaluation of components or structure of the automotive vehicle. Component testing is particulary important in today's highly competitive industries where the design to reduce weight and production costs must be balanced with the necessity to avoid expensive service failure. Generally, 3-axis durability testing device is used to carry out the fatigue test. In this paper, The operation software for simultaneously driving 3-axis vibration testing device is developed and the displacement of the 3-axis actuator is separately calibrated by LDT Moreover, the input and output data are displayed in windows of PC controller with real time.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.695-696
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• 2006

The inrush current of transformer cause saturation effects of recovery voltage for short-circuit power testing. the inrush current depends on the residual flux of the transformer core. when inrush current occurs, it is contains a d.c. component and the high harmonic content of the current are of importance to relay protection of testing circuit. this paper describes of decrease method of inrush current for high power short-circuit testing transformer.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.12
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• pp.1179-1185
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• 2007

This paper presents a new approach to automotive embedded systems development and validation. Recently automotive embedded systems become even more complex and the product life cycle is getting reduced. To overcome these problems AUTOSAR, a standardized software platform and component based approach, was introduced. Model-based approach has been widely applied in the development of embedded systems and has strong benefits such as early validation and automated testing. In this paper cooperative development and validation of AUTOSAR and model-based approach are introduced and automated testing techniques are proposed. With the proposed techniques we can improve complexity management through increased reuse and exchangeability of software module and automated testing is realized.

• Journal of the Korean Society for Nondestructive Testing
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• v.9 no.1
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• pp.69-76
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• 1989

Piezoelectric elements, backing and shoe material are the important components of the ultrasonic transducer. In this study, characteristic constants in the domestic and the foreign PZT ceramic elements are investigated, The acoustic properties of the domestic and the foreign backing and shoes are characterized. The effects of components characteristics, the kinds of the piezoelectric elements and the thickness of the wear plates are investigated for the manufactured normal beam ultrasonic transducers.

• Proceedings of the Acoustical Society of Korea Conference
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• 1987.11a
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• pp.48-51
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• 1987

In this paper, acoustic reflection microscope system has been built for the purpose of detecting subsurface defects in materials and demonstrated for nondestructive testing application. 100 won coin, aluminuim, ceramics, and IC component employed as experimental samples and acoustic reflection microscope was operated in the focused and defocused mode at a frequency of operation of 3 MHz. It has been found that acoustic reflection icroscope has the resolution of 500 ${\mu}{\textrm}{m}$ and it has been an excellent tool for nondestructive testing.

• Journal of the Korean Statistical Society
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• v.13 no.1
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• pp.32-41
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• 1984

An adaptive distribution-free test is proposed for testing the equality of k independent distributions against unrestricted alternatives. In this paper, several rank-sum test statistics are considered as teh components of the adaptive one. The emprical powers of the adaptive testing procedure are compared to those of the classical F test and the component tests through a Monte Carlo study. The results show that the adaptive test has good power properties over a wide class of underlying distributions.

• Journal of the Korean Data and Information Science Society
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• v.23 no.2
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• pp.403-409
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• 2012

We consider a life testing experiment in which several two-component shared parallel systems are put on test, and the test is terminated at a predesigned experiment time. In this thesis, the maximum likelihood estimators for parameters of Freund's bivariate exponential distribution under the system level life testing are obtained. Results of comparative studies based on Monte Carlo simulation are presented.

• Proceedings of the Korea Information Processing Society Conference
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• 2003.05c
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• pp.1821-1824
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• 2003

컴포넌트를 이용하여 작성된 소프트웨어의 테스팅은 컴포넌트의 다양한 특성 때문에 기존의 화잇박스 테스팅 기법을 적용하기 어렵다. 또한 컴포넌트의 통합으로 발생하는 인터액션 테스팅에 더 많은 비중을 둔다. 본 논문에서는 컴포넌트의 기본 및 행위 명세를 나타낸 컴포넌트 계약을 토대로 컴포넌트 테스팅을 수행하기 위한 방법을 제시한다. 컴포넌트 계약은 사전/사후 조건 및 불변 조건을 명시하는 OCL로 작성되며 테스트 케이스 생성과 인터액션 테스팅을 위해 이용된다.

• Journal of the Ergonomics Society of Korea
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• v.1 no.2
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• pp.11-15
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• 1982

There is the possibility that human error during testing and maintenance brings about the failure of the system, the reliability of which depends on mechanical failure and human error. This paper deals with the calculation of the reliability of the redundant system with the dependent hunman error through Karnaugh Map. Two cases are considered. One is the reli- ability of the system neglecting the test interval of each component and the other is that considering the test interval of each component.