• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.204.1-204.1
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• 2012

We present SCOTS test simulation for on axis segment of the GMT secondary mirror that is ellipsoidal shape surface of 1.064m in diameter, 4.166747m in radius of curvature, -0.7154 in conic constant and $18.023{\mu}m$ P-V in asphericity. SCOTS test comprises a screen(diffusing sinusoidal fringe source), test surface(GMT secondary mirror), and a camera(CCD detector). We report ray tracing simulation result that is distorted sinusoidal fringe pattern detected at the camera. This simulation is to be used for analysis of experimental design, sensitivity from uncertainty, errors on fabrication and design.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1994.03a
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• pp.37-46
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• 1994

In metal forming, there ar problems with recurrent geometric characteristics and without explicitly prescribed boundary conditions. In such problems, so-called recurrent boundary conditions must be introduced. The present study deals with nonsteady-state three-dimensional finite element analysis for extrusion of a trocoidal helical gear through a curved die. The boundary-directed remeshing scheme based on the modular remeshing technique is developed to reduce the errors arising in fitting old and new mesh systems. The computed extrusion pressure in reaching the near steady-state loading stage is compared with the results of the experiment and the steady-state analysis. The three-dimensional deformed pattern involving warping at the extruded end due to torsional deformation mode is demonstrated.

• The Mathematical Education
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• v.46 no.4
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• pp.423-443
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• 2007

Based on the framework of Huffered-Ackles, Fuson and Sherin(2004), data were analyzed in terms of 3 components: explaining(E), questioning(Q) and justifying(J) of students' mathematical concepts and problem solving in a math classroom. The students used varied presentations to explain and justify their mathematical concepts and ideas. They corrected their mathematical errors or misconceptions through discourses. In addition, they constructed and clarified their concepts and thinking while they were interacted. We were able to recognize there was a special feature in discourses that encouraged the students to construct and develop their mathematical concepts. As they participated in math class and received feedback on their learning, the whole class worked cooperatively in a positive way. Their discourse was improved from the level of the actual development to the level of the potential development and the pattern of interaction moved from ERE(Elicitaion-Response-Elaboration to PD(Proposition Discussion).

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.1035-1037
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• 2001

This paper presents an improved hys- teresis current control method for three-phase PWM power inverters using 3-level comparator. Hysteresis current controller using 3-level comparator has an advantage of constant switching frequency compared with conventional hysteresis current controller. However, this method has disadvantage that the longer sampling period, the larger current error because the switching is performed without considering current error magnitude of each phase. The proposed method improves the control performance by selecting the optimum switching pattern in which the magnitudes of current errors are considered introducing space vector concept. Simulation results using Matlab/Simulink show that the proposed control method reduces current error keeping the merit of previous hysteresis current control method.

• Proceedings of the IEEK Conference
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• 1998.06a
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• pp.815-818
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• 1998

Hardware formal verification involves the use of analytical techniques to prove that the implementation of a system confroms to the specification. The specification could be a set of properties that the system must have or it could be an alternative representation of the system behavior. We can represent our behavioral specification to be written in VHDL coding. In this paper, we proposed a new hardware design verification method. For theis method, we assumed that a verification pattern already exists and try to make an algorithm to find a place where a design error occurred. This method uses an hierarchical approach by making control flow graph(CFG) hierarchically. From the simulation, this method was turned out to be very effective that all the assumed design errors could be detected.

• Proceedings of the KSPS conference
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• 2007.05a
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• pp.274-277
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• 2007

The purpose of this study is 1) to describe the phoneme inventories of cochlear implant(CI) children and 2) to describe their utterances using narrow phonetic transcription method. All the subjects had more than 2 year-experience with CI and showed more than 87% open-set sentence perception abilities. Average consonant accuracy was 81.36% and it was improved up to 87.41% when distortion errors were not counted. They showed different error patterns from hearing aid users. The prominent error pattern was weakening of consonants.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.8 no.4
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• pp.201-206
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• 2009

The third generation mobile communications system requiring the reliable multimedia data transmission has provided with the reliable voice, data and video services over the variable propagation environment. However the broadband wireless multiple access technologies cause Inter Symbol Interference (ISI) or Multiple Access Interference (MAI) to degrade the performance of W-CDMA (Code Division Multiple Access) system. Constant Modulus Algorithm (CMA) which is frequently used as the adaptive blind equalizers to remove the interfering signal has ill-convergence phenomenon without proper initialization. In this paper, new blind equalization method based on conventional CMA is proposed to improve the channel efficiency, and through computer simulation this is tested over the time varying fading environment of mobile communication system. Consequently, new blind equalization method into concatenated Kalman filter with CMA is verified better than conventional CMA through adopting minimum mean square errors and eye-pattern obtained from algorithm are compared.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.6
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• pp.82-87
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• 2006

Availability of defect test algorithm that recognizes exact and standardized defect information in order to fundamentally resolve generated defects in industrial sites by giving artificial intelligence to SAT(Scanning Acoustic Tomograph), which previously depended on operator's decision, to find various defect information in a semiconductor package, to decide defect pattern, to reduce personal errors and then to standardize the test process was verified. In order to apply the algorithm to the lately emerging Neural Network theory, various weights were used to derive results for performance advancement plans of the defect test algorithm that promises excellent field applicability.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.1
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• pp.37-45
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• 1990

In this paper, a knowledge base editor is presented as a supporting environment for an expert system building tool, OPS5. The knowledge base editor is especially useful for the fast and easy development of a knowledge base when the OPS5 production language is used. This knowledge base editor has some special facilities such as syntax and type checking, rule browsing and automatic bokkeeping. The syntax and type checking provides the facilities to find syntax and type errors in an edited knowledge base, respectively. The rule browsing facility offers various pattern matching schemes to see the causes and effects of a concerned rule. Automatic bookkeeping keeps the updated date and user name of a rule for the later reference whenever a user adds or changes a rule.

• Proceedings of the Korean Information Science Society Conference
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• 2010.06b
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• pp.47-52
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• 2010

실세계와 연동되는 컴퓨팅환경이 가속화 될수록 물리적 오류에 대한 중요성은 점차 커지고 있다. 물리적 오류는 자연현상과 밀접하게 관련되어 있기 때문에, 다양한 변수가 존재하며 오류 예측이 어렵다. 따라서 본 연구에서는 이러한 자연현상에서 발생하는 인자를 수집하고, 이를 분석하여 예측할 수 있도록 데이터마이닝을 적용한 시스템을 제안한다. 본 연구의 현실성 입증을 위해 제안한 시스템을 라인트레이서를 모델로 하여 구현해 보았다.