• 제어로봇시스템학회논문지
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• 제6권4호
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• pp.285-294
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• 2000

This paper shows that the proposed fuzzy-sliding mode control algorithm for a SCARA robot could reduce the chattering due to sliding mode control and is robust against a change of payload and parameter uncertainties. That is, the chattering can be reduced by changing control input for compensating disturbances into a control input by fuzzy rules within a pre-determined dead zone. The experimental results show that the chattering can be reduced more effectively by the fuzzy-sliding mode control algorithm than the sliding mode control with two dead zones. It is proved experimentally that the proposed control algorithm is robust to a change of payload. The proposed control algorithm is implemented to the SCARA robot using a DSP(board) for high speed calculations.

• Journal of Mechanical Science and Technology
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• 제15권3호
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• pp.339-350
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• 2001

To overcome problems in tracking error related to the unmodeled dynamics in the high speed operation of industrial robots, many researchers have used sliding mode control, which is robust against parameter variations and payload changes. However, these algorithms cannot reduce the inherent chattering which is caused by excessive switching inputs around the sliding surface. This study proposes a fuzzy-sliding mode control algorithm to reduce the chattering of the sliding mode control by fuzzy rules within a pre-determined dead zone. Trajectory tracking simulations and experiments show that chattering can be reduced prominently by the fuzzy-sliding mode control algorithm compared to a sliding mode control with two dead zones, and the proposed control algorithm is robust to changes in payload. The proposed control algorithm is implemented to the SCARA (selected compliance articulated robot assembly) robot using a DSP (digital signal processor) for high speed calculations.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1992년도 하계학술대회 논문집 A
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• pp.258-260
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• 1992

Existing methods for controlling systems containing unknown dead-zones show the limitations on the performances. To solve these problems, this paper proposes a novel two-layer structured Fuzzy controller by analyzing the output response of the existing Fuzzy PD controller and the precompensator.

• 한국환경생태학회지
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• 제34권1호
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• pp.42-54
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• 2020

지리산국립공원 내 자생하는 아고산대 침엽수(구상나무 등)의 주요 분포지를 대상으로 약 10년 전·후의 고해상도 항공영상을 활용해 고사목 증가량, 확산패턴 등을 분석하고자 하였다. 나아가 침엽수 고사목이 위치한 지점의 해발고도, 지형정보, 일사량, 수분환경 등을 분석하여 고사에 영향을 미칠 것으로 판단되는 입지요인을 파악하였다. 지리산국립공원 반야봉, 영신봉, 천왕봉 지역 모두 최근 10여 년간 아고산대 침엽수 고사목 개체수가 2~5배 증가한 것으로 나타났다. 반야봉은 약 2배, 영신봉은 약 3.9배, 천왕봉은 약 5.2배 증가한 것으로 나타나 천왕봉 지역의 증가세가 비교적 빠른 것으로 확인되었다. 높은 경사도로 토양수분함량이 낮고, 남향에 위치하여 높은 일사량으로 증발산량이 많은 건조 환경, 이에 더해 태양광에 의한 강한 일사량 및 강우의 체류시간이 짧아 토양이 건조할 것으로 추정되는 입지환경에 고사목이 주로 분포하는 것으로 판단된다. 즉, 건조한 입지환경에서 아고산대 침엽수 고사가 집중되고 있는 것으로 판단되며, 10여 년 전과 비교해도 동일한 경향이 이어지고 있는 것으로 판단된다.

• International Journal of Fluid Machinery and Systems
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• 제3권3호
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• pp.227-234
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• 2010

Numerical analyses have been performed to investigate the effects of geometric parameters of a straight groove micromixer on mixing performance and pressure drop. Three-dimensional Navier-Stokes equations with two working fluids, water and ethanol have been used to calculate mixing index and pressure drop. A parametric study has been carried out to find the effects of the number of grooves per cycle, arrangement of patterned walls, and additional grooves in triangular dead zones between half cycles of grooves. The three arrangements of patterned walls in a micromixer, i.e., single wall patterned, both walls patterned symmetrically, and both walls patterned asymmetrically, have been tested. The results indicate that as the number of grooves per cycle increases the mixing index increases and the pressure drop decreases. The microchannel with both walls patterned asymmetrically shows the best mixing performance among the three different arrangements of patterned walls. Additional grooves confirm the better mixing performance and lower pressure drop.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권5호
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• pp.1514-1531
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• 2014

Femtocell provides better coverage and higher spectrum efficiency in areas rarely covered by macrocells. However, serious two-tier interference emerging from randomly deploying femtocells may create dead zones where the service is unavailable for macro-users. In this paper, we present adopting cognitive radio spectrum overlay to avoid intra-tier interference and incorporating spectrum underlay and overlay to coordinate cross-tier interference. It is a novel centralized control strategy appropriate for both uplink and downlink transmission. We introduce the application of proper spectrum sharing strategy plus optimal power allocation to address the issue of OFDM-based femtocells interference-limited downlink transmission, along with, a low-complexity suboptimal solution proposed. Simulation results illustrate the proposed optimal scheme achieves the highest transmission rate on successfully avoiding two-tier interference, and outperforms the traditional spectrum underlay or spectrum overlay, via maximizing the opportunity to transmit. Moreover, the strength of our proposed schemes is further demonstrated by comparison with previous classic power allocation methods, in terms of transmission rate, computational complexity and signal peak-to-average power ratio.

• Journal of Advanced Marine Engineering and Technology
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• 제40권5호
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• pp.403-411
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• 2016

Usually shell and tube heat exchangers are employed to recover energy between fluids. Recently, numerous papers on these heat exchangers have been published; however, the velocity and temperature profiles or comparison of the features of the flow with or without inside tubes have rarely been described. In this research, experimental and numerical studies were carried out to investigate the characteristics of the flow around the spiral baffle plates without inside tubes in a horizontal circular tube using a particle image velocimetry method and ANSYS 14.0~15.0 version (Fluent). The results showed that swirling flow was produced between the spiral baffle plates. The tangential components were strong between the two spiral baffles; however, the axial or radial velocities components were indicating nearly zero. From the spiral motion in the space of the two baffles, it is considered that there were no dead zones between the spiral baffle.

• 한국농촌건축학회논문집
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• 제12권2호
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• pp.135-142
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• 2010

This research aims to examine the characteristics of tomb sites including tomb mound and attached buildings and also to find out the principles reflected in the traditional oriental Feng-Shui location and spatial composition of Junkyung and Youngkyung tomb at Samcheok. The results of this study are as follows. These tombs harmonize with each other in the cosmic dual forces because Junkyung tomb is men's sex symbol and tiger to lie on his belly and Youngkyung tomb is women's sex symbol in geographical feature. Spatial structure in these tomb sites were placed in a reflected line following the hierarchy of metaphysics by standing high Geumchunkyo(Bridge)-Hongsalmun(Gate)-Jegak(Pavilion)-Bongbun(Tomb mound). Axis structure of these tombs is irregular bent-axis type from Geumchunkyo to Bongbun, specially in case of Youngkyung tomb it is getting more refractive. These tombs are divided into and characterized by three zones. Firstly the space for living people constitutes from Geumchunkyo to Hongsalmun, secondly the semi-sacred space constitutes from Hongsalmun to Jegak, and lastly the space for the dead constitutes from the back of Jegak to Bongbun. - type Jegak instead of T type Jegak generally used at Chosun Dynasty was installed because of claypan stretched out in front of Junkyung tomb and Bongbun of Youngkyung tomb located at a ravine between two mountain ranges.

• Advances in concrete construction
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• 제5권5호
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• pp.451-468
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• 2017

The problem of reducing the self-weight of reinforced concrete structures is very important issue. There are two approaches which may be used to reduced member weight. The first is tackled through reducing the cross sectional area by using voids and the second through using light weight materials. Reducing the weight of slabs is very important as it constitutes the effective portion of dead loads in the structural building. Eleven slab specimens was casted in this research. The slabs are made one way though using two simple supports. The tested specimens comprised three reference solid slabs and eight styropor block slabs having (23% and 29%) reduction in weight. The voids in slabs were made using styropor at the ineffective concrete zones in resisting the tensile stresses. All slab specimens have the dimensions ($1100{\times}600{\times}120mm$) except one solid specimens has depth 85 mm (to give reduction in weight of 29% which is equal to the styropor block slab reduction). Two loading positions or cases (A and B) (as two-line monotonic loads) with shear span to effective depth ratio of (a/d=3, 2) respectively, were used to trace the structural behavior of styropor block slab. The best results are obtained for styropor block slab strengthened by minimum shear reinforcement with weight reduction of (29%). The increase in the strength capacity was (8.6% and 5.7%) compared to the solid slabs under loading cases A and B respectively. Despite the appearance of cracks in styropor block slab with loads lesser than those in the solid slab, the development and width of cracks in styropor block slab is significantly restricted as a result of presence a mesh of reinforcement in upper concrete portion.

• 지구물리와물리탐사
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• 제8권2호
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• pp.145-155
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• 2005

경상북도 포항시 흥해읍 일대에서 지열자원 개발을 위한 심부 파쇄대 탐지를 목적으로 수행된 자기지전류 (MT) 탐사에서 경북 안동과 충북 청원시의 대청호 및 일본의 Kyushu에 원거리 기준점을 설치하고 이를 이용한 자료처리 결과의 상호 비교를 통하여 원거리 기준점에 따른 겉보기 비저항과 위상 자료의 질을 검토하였다. 대상지역에서 약 165 km떨어진 대청호 자료를 이용한 경우는 전력주파수인 60 Hz대역과 자연 전자기장 신호가 미약한 $10^{-1}Hz\~1\;Hz$ 대역을 제외한 주파수 대역에서 매우 좋은 자료를 얻을 수 있었으며, 약 480 km 떨어진 Kyushu 원거리 기준점 자료를 이용해서 거의 모든 주파수 대역에서 연속성이 매우 좋은 전기비저항과 위상 곡선을 얻을 수 있었다. 이를 이용하여 2차원 역산을 수행한 결과, 지표의 10ohm-m 이내의 전기비저항을 보이는 반고결 이암층은 대상지역의 남쪽에서는 약 500 m 이상, 북쪽에서는 200 m 이내의 두께로 분포하며 북에서 남으로 경사진 형태로 나타났다. 심도 $500\~1,500m$에서 저비저항(L-2)과 고비저항(H-2)의 경계면은 단층면으로 해석되며 측점 206, 112와 414를 지나는 대략 $N15^{\circ}E$의 주향을 보인다. 1 km 이내의 천부의 저비저항 이상(L-4)은 파쇄대로 해석되며 측점 105를 지나면서 데략 $N60^{\circ}W$의 주향을 보인다. 또한, 북쪽의 큰 하천을 따라 저비저항 이상대가 공통적으로 나타나 구조선일 가능성을 시사한다. 그리고, 대상지역의 서쪽과 서남쪽의 $2\~3km$ 하부에서 10 ohm-m이내의 저비저항 이상대(L-3)가 나타나는데 이 층에 대해서는 향후 추가적인 연구가 요구된다.