• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.1
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• pp.66-76
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• 2003

The arbitrary V-notched crack problem is considered. The general expressions for the stress components on this problem are obtained as explicit series forms composed of independent unknown coefficients which are denoted by coefficients of eigenvector. For this results eigenvalue equation is performed first through introducing complex stress functions and applying the traction free boundary conditions. Next solving this equation, eigenvalues and corresponding eigenvectors are obtained respectively, and finally inserting these results into stress components, the general equations are obtained. These results are also shown to be applicable to the symmetric V-notched crack or straight crack. It can be shown that this solutions are composed of the linear combination of Mode I and Mode II solutions which are obtained from different characteristic equations, respectively. Through performing asymptotic analysis for stresses, the stress intensity factor is given as a closed form equipped with the unknown coefficients of eigenvector. In order to calculate the unknown coefficients. based on these general explicit equations, numerical programming using the overdetermined boundary collocation method which is algorithmed originally by Carpenter is also worked out. As this programming requires the input data, the commercial FE analysis for stresses is performed. From this study, for some V-notched problems, unknown coefficients can be calculated numerically and also fracture parameters are determined.

• Journal of Information Technology Applications and Management
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• v.11 no.4
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• pp.133-145
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• 2004

The two main purposes of this paper are to 1) investigate critical components of university information systems for information resources management, 2) develop a comprehensive framework model of university information systems for e-Business Era. Through a literature review and by employing group decision making techniques with managers of K University, critical components for developing university information systems were identified. The critical components of university information systems are 1) academic affaires. 2) general administration. (3) research administration. (4) information services. (5) management support, (6) cyber education. (7) knowledge management, (8) e-library. (9) mobile service. and (10) IT infrastructures. In the second stage. by employing IT experts in K University and other institutes. a comprehensive framework of university information systems for e-Business era was developed. The comprehensive framework shows that major components for university information resources management are (1) information infrastructure. (2) common operating environments. (3) applications/information services. The results of this study expect to help managers. who are in charge of university information systems. plan to develop information systems based on the framework proposed in this paper.

• Journal of Applied Reliability
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• v.12 no.3
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• pp.187-199
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• 2012

In general, accelerated life testing is performed to reduce testing time. But it is difficult to apply accelerated life testing to a system besides components. This paper developed a software which estimates reliability measures of the system from results of accelerated life testing of components building the system. This software can handle the system with a large number of components and complex topology. Multiple failure modes of a component were also considered in this software. Based on the software, reliability measures of a gearbox example at several conditions were estimated from the accelerated life testing results of three components of the gearbox.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.1
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• pp.88-93
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• 2004

In general, a fundamental structural design consideration for an automobile is the overall dynamic behavior in bending and torsion. Dynamic behavior of the automobile are mainly influenced by the structural stiffness of B.I.W.(body-in-white) and the physical property of trim components. In this paper, the modeling techniques for various trim components of middle-sized bus are presented, and the dynamic effects of the trim components on the vibration characteristics of the bus are investigated. The $1^{st}$ torsional frequency is decreased by attaching windshield and backlite to the B.I.W., but the $1^{st}$ vertical bending frequency and the $1^{st}$ lateral bending frequency are increased. The natural frequencies of the bus are decreased by attaching doors and windows. And also, the natural frequencies of the bus are large decreased by attaching seats, instrument panel etc. The study shows that the dynamic characteristics of the bus can be effectively predicted in the initial design stage.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.6
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• pp.90-101
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• 1996

Determination of assembly sequence of components is a key issue in assembly operation. Although a number of articles dealing with assembly sequence determination have appeared, an efficient and general methodology for complex products has yet to appear. The objective of this paper is to present the problems and models used to generate assembly sequence from design data. An essential idea of this research is to acquire a finite number of voxels from any complex geometric entity, such as 3D planar polygons, hollow spheres, cylinders. cones, tori, etc. In order to find a feasible assembly sequence, the following four steps are needed: (1) The components composing of an assembly product are identified and then the geometric entities of each component are extracted. (2) The geometric entities extracted in the first step are translated into a number of voxels. (3) All the mating or coupling relations between components are found by considering relations between voxels. (4) The components to be disassembled are determined using CCGs (Component Coupling Graph).

• Journal of Power System Engineering
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• v.14 no.6
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• pp.61-66
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• 2010

Engineering asset management (EAM) requires the accurate assessment of current and the prediction of future asset health condition. Suitable mathematical models that are capable of predicting time-to-failure and the probability of failure in future time are essential. In general reliability models, lifetime of component and system is estimated using failure time data. This paper deals with the reliability assessment of elevators using life of main components. Especially this work is concerned with the stochastic nature of life of elevator components. First, we investigate the Weibull statistical analysis of lifetime data for the components. The final goal is to establish the mathematical model for reliability assessment. This work provides more perspectives to future research in the fields of reliability and maintainability.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2005.11a
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• pp.389-390
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• 2005

• Communications for Statistical Applications and Methods
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• v.8 no.1
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• pp.173-184
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• 2001

We present an algorithm for the complexity reduction of a general Gaussian mixture model by using a penalized likelihood method. One of our important assumptions is that we begin with an overfitted model in terms of the number of components. So our main goal is to eliminate redundant components in the overfitted model. As shown in the section of simulation results, the algorithm works well with the selected densities.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.11 no.18
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• pp.35-39
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• 1988

In general, the characteristics of components which consist of multi component system can not be the same. This paper proposes a maintenance model of multi-component system according to the characteristics of each component. In this paper multi-component system is divided into three components-critical component, major component and minor component, respectively. Then we determine the optimal age replacement time of the system which minimizes total maintenance cost. Numerical examples are shown to illustrate the result.

• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.1292-1294
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• 1996

The general output circuit for PWM output is pushpull using a complimentary MOSFET. The gate driver coupled directly at gate can switch easy upto a high frequency. However, a high reverse recovery current and parastic components make a oscillation output. This paper analyses this phenomenon and proposes a novel output circuit preventing the oscillation.