• Structural Engineering and Mechanics
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• 제17권3_4호
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• pp.379-391
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• 2004

This paper deals with the development of h-version adaptive mesh refinement and recovery strategy using variable-node elements and its application to various engineering field problems with 2D quadrilateral and 3D hexahedral models. The variable-node elements which have variable mid-side nodes on edges or faces are effectively used in overcoming some problems in connecting the different layer patterns of the transition zone between the refined and coarse mesh. A modified recovery technique of gradients adequate for variable-node elements and proper selection of error norms for each engineering field problems are proposed. In the region in which the error is greater than the permissible refinement error, the mesh is locally refined by subdivision. Reversely, in some parts of the domain having the error smaller than the permissible recovery error, the mesh is locally recovered (coarsened) by combination. Hierarchical structures (e.g. quadtrees and octrees) and element-based storage structures are composed to perform this adaptive process of refinement and recovery. Some numerical examples of a 3D heat conduction analysis of the concrete with hydration heat and a 2D flow analysis of vortex shedding show effectiveness and validity of the proposed scheme.

• 한국지능시스템학회논문지
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• 제5권3호
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• pp.83-91
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• 1995

본 연구에서는 종래에 학습법으로 널리 이용되고 있는 역전파학습법의 문제점으로 지적되어 온 학습에 많은 시간이 걸리는 점과 국소적 최적해에 해가 수렴하여 오차가 충분히 작게 되지 않는 등의 문제점을 해결하기 위해, Hu에 의해 고안된 random tabu 탐색법을 이용하여 신경회로망의 연결강도를 최적화하는 학습알고리즘을 새로이 제안하였다. 그리고 이 방법을 배타적 논리합 문제에 적용하여 기존의 역전파학습법과 학습상수 $, $에 tabu탐색법을 이용한 결과와 비교 검토하여 본 방법이 국소적 최적해에 수렴하지 않고 수렴정도를 개선할 수 있음을 확인하였다.

• 제어로봇시스템학회논문지
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• 제15권9호
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• pp.916-921
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• 2009

The technology to inspect and measure an inner structure of micro parts has become an important tool in the semi-conductor industrial field with the development of automation and precision manufacturing. Especially, the inspection skill on the inside of highly integrated electronic device becomes a key role in detecting defects of a completely assembled product. X-ray inspection technology has been focused as a main method to inspect the inside structure. However, there has been insufficient research done on the customized inspection technology for the flip-chip assembly due to the interior connecting part of flip chip which connects the die and PCB electrically through balls positioned on the die. In this study, therefore, it is implemented to detect shape error of flip chip bonding without damaging chips using an x-ray inspection system. At this time, it is able to monitor the solder bump shape by introducing an edge-extracting algorithm (exponential approximation function) according to the attenuating characteristic and detect shape error compared with CAD data. Additionally, the bonding error of solder bumps is automatically detectable by acquiring numerical size information at the extracted solder bump edges.

• 한국주거학회:학술대회논문집
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• 한국주거학회 2000년도 학술발표대회논문집
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• pp.173-178
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• 2000

As a way of decreasing trial and error that can occur in design, we investigated many kinds of material information and image information. We apprehended structures of material database and image database to suggest one of design method that provides information by connecting both databases. This has potentiality to improve the quality of design. Ultimately, this potentiality makes a great contribution towards strengthening competitiveness in design.

• 한국컴퓨터정보학회논문지
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• 제20권6호
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• pp.151-159
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• 2015

In traditional programing education, computers were used as the main tool. Consequently, it was problematic to provide education in an environment without computers or for learners without computer skills. To address this problem, this study developed and validated an unplugged robot education system capable of computerless programming education. The key feature of the proposed system is that programing can be done only by connecting programming blocks in symbols of a flow chart with built-in commands. Validation of the system was performed by a specialist group. Validity was very high with values of content validity ratio (CVR) over 0.7 in all evaluation criteria except "Ease of error debugging" and "Linkages to educational curriculum," whose CVR values were each 0.6. Future directions include improvement in the two areas that scored lower than the others did by, respectively, system improvement to support debugging in error conditions that may occur during the programming process, and development of user guide to support linkages to educational curriculum.

• 대한전기학회논문지:전력기술부문A
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• 제49권6호
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• pp.259-265
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• 2000

The purpose of this paper is to detect and identify topological errors in order to maintain a reliable database for the state estimator. In this paper, a two stage estimation procedure is used to identify the topology errors. At the first stage, the WSAV state estimator which has characteristics to remove bad data during the estimation procedure is run for finding out the suspected branches at which topology errors take place. The resulting residuals are normalized and the measurements with significant normalized residuals are selected. A set of suspected branches is formed based on these selected measurements; if the selected measurement is a line flow, the corresponding branch is suspected; if it is an injection, then all the branches connecting the injection bus to its immediate neighbors are suspected. A new WLAV state estimator adding the branch flow errors in the state vector is developed to identify the branch topology errors. Sample cases of single topology error and topology error with a measurement error are applied to IEEE 14 bus test system.

• 한국과학교육학회지
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• 제28권6호
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• pp.675-684
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• 2008

이 연구에서는 다중 표상을 활용한 화학 개념 학습에서 연계 오류 감소를 위한 처방적인 교수 전략의 효과를 학생들의 장독립성-장의존성에 따라 조사했다. 남녀공학 중학교 1학년 126명을 통제 집단과 처치 집단으로 배치한 후, '보일의 법칙'과 '샤를의 법칙'에 대해 2차시 동안 수업을 진행했다. 연구 결과, 개념 이해도 검사에서 처치 집단의 점수가 통제 집단의 점수보다 통계적으로 유의미한 차이로 높았다. 학습 동기 검사에서는 학습 동기 전체와 하위 영역 중 '주의집중' 영역에서, 처치 집단 학생들의 점수가 통제 집단 학생들의 점수보다 통계적으로 유의미한 차이로 높았다. 그러나 두 검사에서 모두 수업 처치와 장독립성-장의존성 사이의 상호작용 효과는 없었다. 처치 집단 학생들의 대부분이 새로운 교수 전략에 대해 인지적, 동기적 측면에서 긍정적으로 인식하는 것으로 나타났다.

• 전기학회논문지
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• 제63권4호
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• pp.589-595
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• 2014

The error of instrument transformers is measured by connecting the external burden with the secondary terminal of the instrument transformers. Because the error of transformer is affected by the apparent power and power factor of the external burden, an accurate measurement of burden is important for transformer evaluation. We have developed the burden evaluation equipment for both potential transformer and current transformer by employing the series resistor in the range of $20m{\Omega}{\sim}5{\Omega}$ and the parallel resistor in the range of $1M{\Omega}{\sim}500{\Omega}$, respectively, together with visual basic program. We could reduce testing time more than 5 times by employing method developed in this study, compared with that developed in past. This method shows more better reliability by analyzing the evaluation results and fitting graphs of burden measurements. The test results of the developed system is compared with those obtained in the power meter analyzer to verify the validity.

• 한국정보전자통신기술학회논문지
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• 제10권5호
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• pp.396-401
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• 2017

본 논문은 블루투스와 다른 장치를 연결하였을 때 블루투스와의 간섭 현상에 대한 해결 방안을 제시한다. 랜덤 주파수 도약 기법은 무선랜 간섭을 고려하지 않고 블루투스 전체 채널을 이용하여 도약 패턴을 생성하는 기법이다. 제안된 적응적 주파수 도약 기법은 블루투스의 주기적인 캐리어 센싱을 통해 무선랜 간섭을 고려하여 블루투스 채널의 도약 패턴을 생성하는 기법이다. 모의실험을 통해 무선랜 간섭이 혼잡한 상황에서도 블루투스 캐리어 센싱 간격이 줄어들수록 적응적 주파수 도약 기법을 사용하면 패킷 오류율이 감소되는 것을 확인하였다. 특히 주파수 도약 기법은 적응적 주파수 도약 기법 대비 평균 패킷 오류율은 약 13%의 성능 향상이 있었다.

• 한국철도학회논문집
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• 제11권1호
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• pp.69-74
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• 2008

철도차량 간 통신에 적용 가능한 SNMP기반 전력선 통신 시스템의 운영 정보베이스(MIB)의 설계 및 구현에 관한 연구로, "Basic Information", "Configuration", "Stats", 그리고 "Alarm"의 네 가지 노드를 갖는 MIB를 정의하고 구현한다. 특히 통신 성능의 향상을 위한 "Alarm"운용 함수들로서 사용자 간섭 없이 장비와의 자동 연결을 가능하게 하는 ACF, 데이터 손실과 에러의 유무를 검사하는 DEC, 그리고 에러를 포함한 데이터의 손실을 방지하는 DLPF를 정의하고 구현한다. 제안된 MIB의 평가를 위해 전력선 통신 실험 장치를 만들어 실험을 수행한다. 제안된 MIB를 갖는 전력선 통신 시스템은 종래의 것을 개선하는데 기여한 바가 있다.