• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.5
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• pp.876-883
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• 2007

The magnetic flux leakage(MFL) type nondestructive testing(NDT) method is widely used to detect corrosion, defects and mechanical deformation of the underground gas pipelines. The object pipeline is magnetically saturated by the magnetic system with permanent magnet and yokes. Hall sensors detect the leakage fields in the region of the defect. The defects are sometimes occurred in group. The accuracy of the detecting signals in this defect cluster become lowered because of the complexity of the defect cluster. In this paper, the effects of the multi -defects are analyzed. The detecting signals are computed by 3-dimensional finite element method and compared with real measurement. The results say that, rather than the size of the defects, the effects of the relative position of the multi-defects are very important on the detecting signals.

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.54-55
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• 2006

IEC 61850 기반의 변전소 자동화 시스템 구축을 위하여 현재 여러 제조업체에서 IED 개발이 이루어지고 있다. IEC 61850-10에서는 개발된 IED가 IEC 61850 국제표준을 만족하는지 검증하고자 하는 적합성 검사(Conformance Testing)에 대하여 기술한다. 본 논문은 IEC 61850-10에서 제시하는 적합성 검사에 대하여 기술하며 이를 보완하기 위한 UCA IUG(International Users Group)의 역할에 대하여 언급한다.

• Steel and Composite Structures
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• v.7 no.1
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• pp.35-52
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• 2007

The cold formed light-gauge profiled steel sheeting can offer considerable shear resistance acting in the steel building frame. This paper conducted the full-scale test on the shear behavior of stressed skin diaphragm using profiled sheeting connected by the self-tapping screws. A three-dimensional finite element model that simulates the stressed skin diaphragm was developed. The sheet was modeled using thin element model while the supporting members were simulated using beam elements. Fasteners were represented in the numerical model as equivalent springs. A joint test program was conducted to characterize the properties of these springs and results were reported in this study. Finite element model of the full-scale test was analyzed by use of the ANSYS package, considering nonlinearity caused by the large deflection and slip of fasteners. The experimental data was compared with the results acquired by the EUR formulas and finite element analysis.

• Proceedings of the KIEE Conference
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• 2002.11c
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• pp.257-263
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• 2002

Test scheduling of SoC becomes more important because it is one of the prime methods to minimize the testing time under limited power consumption of SoCs. In this paper, a heuristic algorithm, in which test resources are selected for groups and arranged based on the size of product of power dissipation and test time together with total power consumption in core-based SoCs is proposed. We select test resource groups which has maximum power consumption but does not exceed the constrained power consumption and make the testing time slot of resources in the test resource group to be aligned at the initial position to minimize the idle test time of test resources.

• The Korean Journal of Applied Statistics
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• v.7 no.2
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• pp.213-224
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• 1994

A diagnostic method useful for detecting outliers in testing the equality of two covariance metrics is developed using the influence curve approach. This method is easily generalized to more than two covariance matrices. A sample version for the influence measure of detecting outliers is considered based on the empirical distribution functions. The sample version includes as its component terms the well-known test statistic for detecting one outlier at a time introduced by Wilks and its generalization to the two-group case.

• International Journal of Reliability and Applications
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• v.3 no.4
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• pp.185-198
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• 2002

In the traditional life testing model, it is assumed that a certain number of identical items are tested under identical condition. This is due to statistical rather than practical considerations. The proportional hazards model can be used to develop a realistic approach to determine the performance of an item. That is also capable of modeling the failure rates of accelerated life testing when the covariates are applied stresses. The proportional hazards model is typically applied for a group of items to assess the importance of factors that may influence the reliability of an item. In this paper we considered the interarrival times of an item rather than the time to first failure for grouped items and provided the availability estimation for the determination of maintenance policy and overhaul time. In order to demonstrate the proposed approach, an example is presented.

• Proceedings of the KIEE Conference
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• 2003.11a
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• pp.403-405
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• 2003

본 논문에서는 대전류 표준측정에 대한 STL TC의 Ad-Hoc Working Group의 최종방안에 대해 자세히 소개하여 이를 계기로 국내에서도 필요한 사전준비에 만전을 기하고자 한다. 향후 연속적으로 해야 할 업무, Shunt의 소유, 경비 지불방법 등에 대한 사항과 함께 우리나라 대전류 표준측정시스템의 구축절차를 제안하였으며, 이를 통해 대전류 측정에 있어서 국제표준과의 소급성을 확보할 수 있기 때문에 국내에서 시행하는 각종 시험에서 대전류 측정이 국제적으로 유효하게 될 것이다.

• Proceedings of the KIEE Conference
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• 2003.11a
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• pp.409-411
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• 2003

본 논문에서는 대전류 표준측정에 대한 STL TC의 Ad-Hoc Working Group의 최종방안에 대한 기술적 배경을 소개하여 이를 계기로 국내에서도 대전류 표준확보에 필요한 사전준비에 만전을 기하고자 한다. STL의 대전류 reference shunt 요구사항, 측정 불확도 및 각 시험소에서 교정하여야 할 사항 등에 대하여 검토하고, 우리나라 대전류 표준측정시스템의 구축필요성, 구축절차 및 방안에 대하여 기술한다.

• Journal of the Korean Statistical Society
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• v.27 no.2
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• pp.165-187
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• 1998

Shin and Sarkar (1993, 1994) studied the problem of testing for a unit root in an AR(p) signal observed with MA(q) noise when the MA parameters are known. In this paper we consider the case when the MA parameters are unknown and to be estimated. Test statistics are defined using unit root parameter estimates based on three different estimation methods of Hannan and Rissanen (1982), Kohn (1979) and Shin and Sarkar (1995). An AR(p) process contaminated by MA(q) noise is a .estricted ARMA model, for which Shin and Sarkar (1995) derived an easy-to-compute Newton- Raphson estimator The two-stage estimation p.ocedu.e of Hannan and Rissanen (1982) is used to compute initial parameter estimates in implementing the iterative estimation methods of both Shin and Sarkar (1995) and Kohn (1979). In a simulation study we compare the relative performance of these unit root tests with respect to both size and power for p=q=1.

• International Journal of Computer Science & Network Security
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• v.21 no.2
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• pp.88-92
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• 2021

A method and a mathematical algorithm for finding a quasi-optimal assignment plan with rectangular efficiency matrices are proposed. The developed algorithm can significantly reduce the time and computer memory consumption for its implementation in comparison with optimal methods.