• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.11
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• pp.2085-2092
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• 2016

One of the most important properties of the IC substrate is that it should be uniform over large areas. Among the various physical approaches of wafer defect characterization, special attention is to be payed to the infrared techniques of inspection. In particular, a high spatial resolution, near infrared absorption method has been adopted to directly observe defects in semi-insulating GaAs. This technique, which relies on the mapping of infrared transmission, is both rapid and non-destructive. This method demonstrates in a direct way that the infrared images of GaAs crystals arise from defect absorption process. A new interpretation is presented for the observed reversal of contrast in the infrared absorption of nonuniformly distributed deep centers, related to EL2, in semi-insulating GaAs. The low temperature photoquenching experiment has demonstrated in a direct way that the contrast inverse images of GaAs wafers arise from both absorption and scattering mechanisms rather than charge re-distribution or local variation of bandgap.

• Journal of Aerospace System Engineering
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• v.14 no.1
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• pp.16-20
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• 2020

The fatigue happening during the road riding of the vehicle and for the moment the aircraft lands on the runway is closely related to the life cycle of the landing gear, the airframe, the vehicle's suspension, etc. The multiple loads acting on the wheel are longitudinal, lateral, vertical, and braking forces. To study the dynamic characteristics and fatigue stiffness of the vehicle, the dynamic fatigue simulator generally has been used to represent the real road vibration in the lab. It can save time and cost. In hardware, the critical factor in the hydraulic fatigue simulator structure is to decouple each axis and to endure several load vibration. In this paper, the inverse kinematic analysis method derives the magnitude of movement of the hydraulic servo actuator by the coupling after rendering the maximum movement displacement in the axial direction at the center of the dummy wheel. The result of the analysis is that the coupling between the axes is weak to reproduce the real road vibrations precisely.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.4
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• pp.39-49
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• 2003

This research is a part of a research program to develope a new design method for reinforced concrete bridge columns under axial load and cyclic lateral load. A nonlinear analytical method is proposed to obtain moment-curvature relationship and lateral load-displacement relationship. Various analytical models that contribute seismic behavior of reinforced concrete bridge columns are adopted and modified by comparing quasi-static test results of reinforced concrete columns with spirals of circular hoops. The analysis adopts confined concrete model, longitudinal reinforcement test result of reinforced concrete columns with spirals or circular hoops. The analysis adopts confined concrete model, etc. The results obtained using the propose analytical method agree well with test results and give conservative estimations particularly for deformation capacity and ductility.

• Journal of the Society of Naval Architects of Korea
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• v.31 no.3
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• pp.129-134
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• 1994

A Laser Cutter is designed for the precise fabrications in the shipyards recently. The cutter is a gantry type one with specified functions of movability and strength in order to satisfy the workability. The gantry frame should move with a certain velocity in a relatively short time for the proper cutting of the object materials. The gantry is fitted with ball screw and the acceleration field is formed by actuating this ball screw. The relative displacement should be within the allowable design criteria to make sure the precise cutting of the materials by the laser. In this paper, modal and structural analysis for a Laser Cutter which is commonly used in the shipyards, is carried out to check the design criteria of the system. The system is modeled by placing the proper shell and soils finite elements and fictitious mass properties to represent the real one. The way how to extract the loading conditions based on the given velocity criteria of the system is presented. Static structural analysis is performed and the results came out as expected. Modal analysis for finding eigen-values and mode shapes of the system is performed and it is shown that the time dependent dynamic analysis is unnecessary for this system for its operating circumstances.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.2
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• pp.23-28
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• 2004

In EIT, various image reconstruction algorithms have been used in order to compute the internal resistivity distribution of the unknown object with its electric potential data at the boundary. Mathematically the EIT image reconstruction algorithm is a nonlinear ill-posed inverse problem. In this paper, a SPSA approach is proposed for the solution of the EIT image reconstruction. Results of numerical experiments of EIT solved by the SPSA approach are presented and compared to that obtained by the modified Newton-Raphson(mNR) method.

• Journal of Korean Society of Transportation
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• v.26 no.4
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• pp.195-204
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• 2008

Multi-Criteria Analysis is one method for optimizing decisions that include numerous characteristics and objective functions. The Analytic Hierarchy Process (AHP) is used as a general Multi-Criteria Analysis considering many critical issues. However, since validation procedures for the decision reliability of AHP valuers had been left off existing methodologies, a new methodology including such validation procedures is required to make more reliable decisions. In this research, idea decision results are derived using Monte Carlo Simulation in cases where AHP valuers do not have expertise in the specific project, and these results are compared with the results derived from experts to develop a new analysis model to make more reliable decisions. Finally, this new analysis is applied to various field case studies of road and rail carried out by the Korea Development Institute (KDI) between 2003 and 2006 to validate the new analysis model. The study found that approximately 20% of decisions resulting from the existing methodology are considered prudent. In future studies, the authors suggest analyzing the correlation between initial weights and final results since final results are enormously influenced by the initial weight.

• Journal of Korean Society of Steel Construction
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• v.16 no.4 s.71
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• pp.463-470
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• 2004

In this study, the bearing pressure distribution and design method of rectangular steel tubular column base plates under concentric loading were investigated. In general, the size and thickness of the baseplate are determined with the assumption that the bearing pressure of the column baseplate is uniformly distributed. When the column is loaded lightly, however, the size of the baseplate becomes smaller, the thickness becomes thinner and the bearing pressure of the baseplate is not distributed evenly. In this study, the distribution of the bearing pressure was investigated using the experimental and analytical methods. Four test specimens of the rectangular steel column baseplate were fabricated and tested. The analysis of the specimens was done using the finite element analysis program ANSYS. The result was that it was appropriate to use the effective width method to design the lightly loaded column baseplate, because the bearing pressure was not distributed evenly and was only concentrated under the column section.

• The Journal of the Acoustical Society of Korea
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• v.19 no.1
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• pp.54-60
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• 2000

There are many works to analyze a simple expansion chamber involving higher order modes. These works are classified to mode matching method, velocity potential method and finite element method. Among these methods, mode matching method has good performance at analyzing a concentric expansion chamber. Generally inlet/outlet pipe cross section area is smaller than middle chamber cross section area. So the number of higher order modes of inlet/outlet pipe can be fewer than that of middle chamber. But mode matching method must use the same number of higher order modes at inlet pipe, middle chamber and outlet pipe. Therefore the redundant modes of inlet/outlet pipe makes the computation time of mode matching method longer. In this paper, the new method, which can select number of each higher order modes of inlet pipe, middle chamber and outlet pipe, was suggested. And this method was compared to conventional mode matching method and finite element method in order to demonstrate the accuracy of the new method and to show that the new method can reduce a calculating time.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.24_25
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• 2009

PMU 정보를 이용하여 실시간으로 전압안정도를 감시하는 기술은 계속적으로 연구가 진행되고 있다. 전압안정도를 해석하는 수많은 방법 중에서 국내계통에 가장 잘 맞는 알고리즘을 찾는 것이 무엇보다도 중요하다. 또한 PMU의 설치는 현재에는 한정적일 수 밖에 없으므로 최소의 PMU를 가장 적절한 위치에 설치하여 계통의 전압 안정도를 감시하는 것이 중요 하다. 본 논문에서는 소수의 PMU를 이용하여 실시간으로 전압안정도를 감시하는 기술을 제안하고자 한다. 계통데이터 중선로임피던스를 이용하여 최소한의 PMU로부터 전압안정도를 감시하도록 한다. 본 방법을 검증하기 위하여 한전 실계통을 사용하도록 한다.

• Annual Conference on Human and Language Technology
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• 1994.11a
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• pp.355-362
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• 1994

언어처리에 통계 확률적인 방법이 도입되면서 현실적으로 상당한 진전이 있었지만 한국어의 경우에는 대부분 형태소 해석과 품사 태깅에 그치고 있다. 본 논문에서는 구문분석 수준에서의 통계적인 한국어 분석에 쓰일 자료 구축으로서의 구문 태깅의 방법론과 그 자동화에 대해 보고한다.