• Journal of Institute of Control, Robotics and Systems
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• v.4 no.1
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• pp.10-18
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• 1998

불확실한 변수와 비선형성을 가지는 유연조인트 로봇의 견실제어 방안을 제시한다. 그리고 본 시스템에서 불확실구조는 일치성을 유지하지 않는 불일치성 불확실 시스템이다. 제어기는 리아노프의 방안에 근거를 두고있다. 견실제어는 연산토크법을 사용하고 삽입제어기법을 통하여 좌표변환을 통해 구성된다. 제어기 설계과정은 우선 연산토크방법에 의해 시스템 동역학에서 정격부분을 선형으로 2개의 부분시스템으로 구성한다. 이후 좌표변환을 이용하여 각 부분시스템에 제어기를 구축한다. 이 방안을 통하여 관성 행렬이 알려진 값인 경우 이 행렬의 상위한계 조건없이 제어기를 설계할 수 있다. 따라서 임의의 형태의 로봇에도 적용 가능한 제어알고리즘이 된다. 설계된 견실제어는 변환된 시스템이나 원시스템 모두 실용적 안정성을 보장한다. 이 변환은 단지 불확실변수의 최대 한계값의 정보만을 요구한다.

• 한국방재학회:학술대회논문집
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• 2007.02a
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• pp.587-590
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• 2007

한계자기회귀모형(TAR)을 응용하여 동시에 해조와 홍수의 영향을 받을 때 삽교천 감조구간의 삽교호수위관측소의 월 최고수위를 예측하는 모형을 구축하였으며, 모형구축과정에서 유전알고리즘으로 한계값과 자기회귀계수의 매개변수를 최적화한다. 계산결과 한계자기회귀모형은 감조하천의 비선형성특성을 모의 할 수 있으며, 예측의 정확도와 예측성능의 안정성을 확보할 수 있다. 연구결과 유전한계자귀회귀모형으로 감조하천구간의 월 최고수위를 예측하는 것이 가능하며, 또한 감조하천구간에서 기타 수문요소의 비선형성 서열예측 중에서도 광범한 실용가치가 있다고 본다.

• Journal of the Korean Geotechnical Society
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• v.29 no.11
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• pp.73-84
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• 2013

When a slope failure or a debris flow occurs, a shear strength on failure plane becomes nearly zero and soil begins to flow like a non-cohesive liquid. A consistency of cohesive soils changes as a water content increases. Even a cohesive soil existing at liquid limit state has a small amount of shear strength. In this study, a water content, at which a shear strength of cohesive soils is zero and then cohesive soils will start to flow, was proposed. Three types of clays (kaolinite, bentonite and kaolinite (50%)+bentonite (50%)) were mixed with three different solutions (distilled water, sea water and microbial solution) at liquid limit state and then their water contents were increased step by step. Then, their undrained shear strength was measured using a portable vane shear device called Torvane. The ranges of undrained shear strength at liquid and plastic limits are 3.6-9.2 kPa and 24-45 kPa, respectively. On the other hand, the water content that corresponds to the value of the undrained shear strength changing most rapidly is called flow water content. The flow limit refers to the water content when undrained shear strength of cohesive soils is zero. In order to investigate the relationship between liquid limit and flow limit, the cohesive index was defined as a value of the difference between flow limit and liquid limit. The new plasticity index was defined as the value of difference between flow limit and plastic limit. The new liquidity index was also defined using flow limit. The values of flow limit are 1.5-2 times higher than those of liquid limit. At the same time, the values of new plasticity index are 2-5.5 times higher than those of original plasticity index.

• Proceedings of the KIEE Conference
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• 2002.11b
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• pp.164-166
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• 2002

발전기 주변의 선로에서 사고가 발생하였을 때, 발전기의 출력이 선로를 통해서 흐르지 못해 그 결과 과도불안정현상이 생길 수 있다. 이러한 과도불 안정현상을 막기 위한 SPS가 설치, 운영되고 있는데 그 알고리즘의 하나로서 동면적법을 기반으로 한 알고리즘을 구현하였다. 대상 발전기군을 하나의 등가 발전기로 모델링 한 다음, 유효전력과 무효전력 출력의 측정값을 이용해서 계산을 통해 위상각-출력 곡선을 구하였다. 그런 다음 현재의 운동에너지와 안정도 한계값인 임계에너지의 값을 비교하여 안정도를 판별하고, 만일 불안정한 경우 필요한 발전기의 탈락량을 계산하였다. 이 알고리즘을 6기 5모선 계통에서 모의하여 결과를 검증하였다.

• Proceedings of the Korean Information Science Society Conference
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• 2001.04a
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• pp.571-573
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• 2001

본 논문에서는 실시간 상태 기계(Real-time State Machine, RSM)로 명제된 실시간 시스템의 행위의 쉽고 간결한 이해, 분석을 위한 새로운 상태 최소화 방법을 기술한다. 시스템의 행위를 보여주는 RSM 실행에 대한 상태는 제어 변수, 자료 변수, 시간 변소의 집합에 의해 정의된다. 상태 최소화는 4단계 추상화인 계산(computation), 제너릭(generic) 패턴, 한계 간격(limit interval), 동일 범위(coordinate scope) 추상화를 통해 이루어진다. 계산 추상화 단계에서는 연속적인 계산으로 연결된 다수의 상태를 하나의 상태로, 일반 패턴 추상화 단계에서는 상수 또는 함수 관계에 있는 동일 제어의 연속된 일련의 상태들의 집합을 하나의 제너릭 패턴으로 통합한다. 한계 간격 추상화 단계에서는 특정 값으로부터 음의 무한대나 양의 무한대 값으로 단조 증가, 단조 감소하는 값 사이에 있는 상태들을 하나의 상태로 통합한다. 마지막으로, 동일 범위 추상화 단계에서는 같은 범위에 존재하는 일련의 상태들을 하나의 상태로 통합한다. 각 추상화의 적용은 제어, 데이터, 시간의 무한한 상태 공간을 유한한 상태공간으로 감소시킬 수 있으며 많은 상태 감소를 가능하게 한다. 따라서, 시스템 행위에 대한 이해와 분석이 복잡도가 적은 개념 단계에서 수행될 수 있다.

• Journal of IKEEE
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• v.26 no.2
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• pp.169-175
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• 2022

This paper introduces an interference elimination method using k-nearest neighbor (KNN) algorithm for precise distance estimation by reducing interference between ultrasonic sensors. Conventional methods compare current distance measurement result with previous distance measurement results. If the difference exceeds some thresholds, conventional methods recognize them as interference and exclude them, but they often suffer from imprecise distance prediction. KNN algorithm classifies input values measured by multiple ultrasonic sensors and predicts high accuracy outputs. Experiments of distance measurements are conducted where interference frequently occurs by multiple ultrasound sensors of same type, and the results show that KNN algorithm significantly reduce distance prediction errors. Also the results show that the prediction performance of KNN algorithm is superior to conventional voting methods.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.5
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• pp.1222-1228
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• 1998

Most of researchers have tried to find heuristic methods for near-optimal solutions of establishing light paths with minimum number of wavelengths in wavelengh-routed optical networks. In order to provide a performance measure for heuristic approaches, we propose a practical approach for a lower bound of the number of wavelengths which is required to provide full connections in WDM-based optical transport networks. This method is based on a path-flow formulation using K-shortest paths for each connection. Compared with a general link-flow formulation, the proposed method has much lower complexity and so needs much less calcuation tiem while it gives the same results as a general link-flow formulation in some sample networks.

• Economic and Environmental Geology
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• v.41 no.5
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• pp.563-575
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• 2008

The ore depositional and geochemical exploration on Bougouni area in Mali, central-western Africa covering $2,000\;Km^2$ was conducted for determining the detailed survey area. According to the results of this exploration, the highly potential area for the zinc-tin-gold-silver mineralization was found in Kolani and Riarako areas. The contents of zinc in heavy sand collected in the stream sediments range from 14 to 8,600 ppm, while the mean values of zinc in this area are 543 ppm with threshold($x+2{\sigma}$) of zinc anomalies being 1,000 ppm in Bougouni area. Generally zinc anomalies are associated with the tin and molybdenum anomalies and hence the anomalous area was selected for the detailed survey area for tracing the primary zinc and precious ore deposits related to these anomalies in following project.

• Fire Science and Engineering
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• v.23 no.5
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• pp.50-56
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• 2009

Explosion limit and autoignition temperature are the major properties used to determine the fire and explosion hazards of the flammable substances. Explosion limit and autoignition temperature for safe handling of ethylene were investigated. By using the literatures data, the lower and upper explosion limits of ethylene recommended 2.6vol% and 36vol%, respectively. Also autoignition temperatures of ethylene with ignition sources recommended $420^{\circ}C$ at the electrically heated crucible furnace (the whole surface heating) and recommended about $800^{\circ}C$ in the local hot surface. The new equations for predicting the temperature dependence and the pressure dependence of the lower explosion limits for ethylene are proposed. The values calculated by the proposed equations were a good agreement with the literature data.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.6
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• pp.11-20
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• 2013

In this paper, the quantitative damage index for reinforced concrete (RC) columns with non-seismic details were presented. They are necessary to carry out the postearthquake safety evaluation of RC buildings under 5 stories without seismic details. The static cyclic test of the RC frame sub-assemblage that was an one span and actual-sized was first conducted. The specimen collapsed by the shear failure after flexural yielding of a column, lots of cracks on the surfaces of columns and beam-column joints and the cover concrete splitting at the bottom of columns occurred. The damage levels of these kinds of columns with non-seismic details were classified to five based on the load-displacement relationship by the test result. The residual story drift ratios and crack widths were then adapted as the quantitative index to evaluate the damage limit states because those values were comparatively easy to measure right after earthquakes. The highest one among the residual story drift ratios under the similar maximum story drift ratio decided on the residual story drift ratio of each damage limit state. On the other hand, the lowest and average ones among the respective residual shear and flexural widths under the similar maximum story drift ratio decided on the residual shear and flexural widths of each damage limit state, respectively. These values for each damage limit state resulted in being smaller than those by the international damage evaluation guidelines that are for seismically designed members under the same deformations.