• Journal of the Korean Institute of Telematics and Electronics
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• v.19 no.4
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• pp.15-20
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• 1982

Stabilization by decentralized control is an important problem in large scale systems and there has been an increasing interest in this area. The objective of this paper is to obtain the sufficient condition for an interconnected system to be stabilited by local feedback. Recently there has been many papers about this, and we further broaden the class of interconnections for which we can find a decentralized control to stabilize the overall system. The interconnection matrix may take any arbitrary time invariant values and this implies connective stability in some sense. The assumed model is mire general than most of previous ones, and as a special case, when each subsystem is given by companion form of a single inputs the result is compared with that of Ikeda and Siljak. The obtained result is illustrated by examples.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.133-133
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• 2023

풍화작용에 의해 생성된 유사는 자연 매체에 의해 이동하고 하천에 도달하기 이전이나 이후 퇴적되며, 해당 과정 중에서 하상변동, 홍수위 상승, 제방 안정성, 두부 침식, 생태환경 변화, 수질문제 등 다양한 침식과 퇴적 관련 문제들이 발생한다. 이러한 유사 문제의 해결과 지속적인 하천관리를 위해서는 유사의 생성, 이송, 그리고 퇴적 과정에 대한 충분한 이해와 정량적인 유사량을 파악하는 것이 필수적이다. 다양한 연구들을 통해서 유사량을 정량적으로 파악하기 위해 여러 종류의 모델과 공식들이 제안 되어져 왔다. 그 중 경험적 모델의 경우 실제로 관측된 값을 기반으로 하며, 복잡한 계산이나 요구하는 자료가 다른 종류의 모델들 보다 적어 쉽게 접근이 가능하다. 이러한 경험적 모델은 유사에 영향을 주는 인자를 규명하거나 특정 유역이나 지역에서 이송 및 퇴적 되는 유사의 출처와 특성을 규명하는 초기 단계에서 유용하게 이용된다. 국내 하천의 경우 여름에 강우가 집중되고 대부분의 국토가 산지로 이루어져있어 상류에서 침식이 주로 발생한다. 또한, 본류 및 하류 지역의 하천은 유사의 퇴적이 주로 일어나서 하천의 형태와 물길이 형성된 충적 하천 형태로 발전 되어있기 때문에 국내 하천에서는 전반적으로 국부적이며 다양한 형태의 유사 관련 문제가 발생한다. 국내 하천에서 발생하는 유사 관련 문제를 해결하기 위해 국내 하천의 유사량을 추정하는 다양한 경험적 모델들이 지속적으로 개발되어왔다. 하지만 과거에 개발된 모델들의 경우 계측 자료가 충분하지 않은 시기에 개발 되었으며, 현재에는 활용하기 불가능하다. 본 연구에서는 국내 하천의 비유사량을 예측하는 동시에 국내 하천의 유사 특성을 이해하기 위해 과거에 국내 하천을 대상으로 비유사량을 추정하기 위해 개발되었던 경험적 모델을 개선하였다. 본 연구를 통해 기존 경험 모델의 경우 주기적인 업데이트가 필요함을 확인하였으며, 개발된 모델의 경우 국내 하천 유사 관리를 위해 미래 유사량 예측하는 등 다양한 방면으로 활용 관리가 가능할 것으로 보인다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.2
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• pp.41-50
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• 2003

In this paper, nonlinear parallel structural analyses are introduced by using the parallel multifrontal solver and damage localization for 2D and 3D crack models is presented as the application of nonlinear parallel computation. The parallel algorithms related with nonliear reduce the amount of memory used is carried out because many variables should be utilized for this highly nonlinear damage analysis. Also, Riks' continuation method is parallelized to search the solution when strain softening occurs due to damage evolution. For damage localization problem, several computational models having up to around 1-million degree of freedoms are used. The parallel performance in this nonlinear parallel algorithm is shown through these examples and the local variation of damage at crack tip is compared among the models with different degree of freedoms.

• Journal of Advanced Navigation Technology
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• v.15 no.1
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• pp.140-146
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• 2011

In this paper, we propose a fast object classification method based on texture and color information for video surveillance. We take the advantage of local patches by extracting SURF and color histogram from images. SURF gives intensity content information and color information strengthens distinctiveness by providing links to patch content. We achieve the advantages of fast computation of SURF as well as color cues of objects. We use Bag of Word models to generate global descriptors of a region of interest (ROI) or an image using the local features, and Na$\ddot{i}$ve Bayes model for classifying the global descriptor. In this paper, we also investigate discriminative descriptor named Scale Invariant Feature Transform (SIFT). Our experiment result for 4 classes of the objects shows 95.75% of classification rate.

• Journal of IKEEE
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• v.3 no.2 s.5
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• pp.250-258
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• 1999

This paper presents a decentralized adaptive controller design for a Magnetically Levitated Fine Manipulator to follow the given trajectory as close as possible in spite of coupling effects between motion axes(degree of freedoms or subsystems). The present controller consists of two parts: the model reference controls based on known subsystems and the local adaptive controls. The former stabilizes the motion of the manipulator so as to follow that of the reference model. The latter reduces tracking errors due to coupling disturbances by adjusting the local gains to such levels that override interactions and assure the stability of the overall system. Through several experimental results, it has been shown that the decentralized adaptive control scheme has better tracking performances comparing to the PID controller case as well as good disturbance(coupling) rejection property.

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.2 s.42
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• pp.47-58
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• 2005

Dynamic response analysis in time dimain is conducted for floating bridges with discrete pontoons subject to spatial variation of ground motions. The Spatial variation of ground motions is considered with the coherency function model which represents wave passage, incoherence and local site effects. The superstructure of the bridge is represented by space frame and elastic catenary cable elements, the abutment us modelde with the spring element of FHWA guideline for considering soil structure interaction and the concept of retardation function is utilized to consider the frequency dependency of the hydrodynamic coefficients which are obtainde by boundary element method. multiple support excitations considering the spatial variation. The noticeable amplification of the response can be shown when the spatial variation of ground motions is incorporated in the anallysis of floating bridges.

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.227-232
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• 2008

The present study was investigated the local heat transfer characteristics and temperature distribution on the louver fin by using the expansion model. Heat transfer rate, frost mass and temperature distribution of the louver fin under frosting condition were experimentally investigated. Local heat transfer rate and heat flux on the louver were analyzed by the conduction heat transfer between top and lower part of the louver. The experimental key parameter was brine inlet temperature(-5, -10, $-15^{\circ}C$). The heat transfer performance and frost mass at brine temperature of $-15^{\circ}C$ were increased by maximum 3 time than the brine temperature of $-5^{\circ}C$. At all experimental case, local heat transfer rate and heat flux of the louver were almost symmetry at the louver number of 6. Especially, local heat transfer rate and heat flux were maximum increased on the louver number of 4 and 8.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.1
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• pp.190-200
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• 1991

Certain structural components are exposed to high temperatures. At high temperature, under thermal and mechanical loading, metal components exhibit both creep and plastic behavior. The unified constitutive theory is to model both the time-dependent behavior(creep) and the time-independent behavior(plasticity) in one set of equations. Microscopically both creep and plasticity are controlled by the motion of dislocations. A finite element method is presented encorporating a unified constitutive model for the transient analysis of viscoplastic behavior of structures exposed to high temperature.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.11
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• pp.32-41
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• 2000

A new anatomical head model was implemented based on the MR and CT images of the head of a volunteer whose head shape is close to the domestic standard. In order to compare SARs (specific absorption rates) of heads with different shapes, we calculated SARs in the two anatomical head models. The one is the new model and the other is that of the black race and was made at National Library Medicine in USA. The head model and a phone model were arranged in the computational space to be the touch or cheek position of CENELEC (European Committee for Electrotechnical Standardisation) and FCC guidelines. From the obtained results, we can see that the smaller head produces the higher whole head-averaged SAR. However, it seems that the localized SAR averaged over 1 g or 10 g is more dependent on the shape of the auricle rather than that of the head size.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.1
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• pp.65-72
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• 2008

The use of hybrid FRP-concrete structures with a dual purpose of both permanent formwork and reinforcement, has been considered in some studies recently. For the FRP plank and the concrete to act as a composite structural member a satisfactory bond at the interface between the smooth surface of the pultruded plank and the cast-in-place concrete must be developed. Sand was bonded to the pultruded FRP plank using a commercially available epoxy system. In applying general analysis techniques to evaluate the performance of composite structures with FRP stay-in-place forming, it is essential that characteristics of the bond stress-slip relation be identified. In this study I would like to propose a simplified bilinear bond stress-slip model for FRP composite structures.