• 대한기계학회논문집A
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• 제33권9호
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• pp.982-989
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• 2009

Parallel Kinematic Mechanism (PKM) is a device to perform the various motion in three-dimensional space and it calls for six degree of freedom. For example, Parallel Kinematic Mechanism is applied to machine tools, medical equipments, MEMS, virtual reality devices and flight motion simulators. Recently, many companies have tried to develop new Parallel Kinematic Mechanism in order to improve the cycle time and the precisional tolerance. Parallel Kinematic Mechanism uses general universal joint and spherical joint, but such joints have accumulated tolerance problems. Therefore, it causes position control problem and dramatically life time reduction. This paper focused on the rolling element to improve sliding precision in new sliding ball joint development. Before the final design and production, it was confirmed that new sliding ball joint held a higher load and a good geometrical structure. FEM analysis showed a favorable agreement with tensile and compressive testing results by universal testing machine. In conclusions, a new sliding ball joint has been developed to solve a problem of accumulated tolerance and verified using tensile and compressive testing as well as FEM analysis.

• 대한기계학회논문집A
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• 제32권3호
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• pp.232-239
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• 2008

The position sensors used in a magnetic bearing system are desirable to provide some degree of fault-tolerance as the rotor position is necessary for the feedback control to overcome the open-loop instability. In this paper, we propose an inductive position sensor that can cope with a partial fault in the sensor. The sensor has multiple poles which can be combined to sense the in-plane motion of the rotor. When a high-frequency voltage signal drives each pole of the sensor, the resulting current in the sensor coil contains information regarding the rotor position. The signal processing circuit of the sensor extracts this position information. In this paper, we used the magnetic circuit model of the sensor that shows the analytical relationship between the sensor output and the rotor motion. The multi-polar structure of the sensor makes it possible to introduce redundancy which can be exploited for fault-tolerant operation. The proposed sensor is applied to a magnetically levitated turbo-molecular vacuum pump. Experimental results validate the fault-tolerance algorithm.

• International journal of advanced smart convergence
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• 제4권2호
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• pp.38-45
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• 2015

Peer-to-Peer(P2P) systems are generally classified into two categories; hybrid and pure P2P. Hybrid systems have a single central index server keeping the details of shared information, so that undesirable effects such as heavy load on that server and lack of fault-tolerance can be caused. Pure P2P causes the other problems such as message flooding and scalability although it shows high degree of fault-tolerance. Recently, mobile agent-based distributed computing has been receiving wide attention for its potential to support disconnected operations, high asynchrony, and thus saving network bandwidth. In this paper, a new scheme of peer coordination is proposed for a decentralized P2P network with self-organizing structure. We deployed mobile agents for incorporating the advantages of usage of mobile agents into our P2P network. Proposed P2P network has both advantages of hybrid and pure P2P. The problems of heavy load on the server and lack of fault-tolerance are improved by using multiple special peers called super-peers. And the problems of pure P2P can be reduced by using mobile agents.

• 한국조경학회지
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• 제40권6호
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• pp.70-78
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• 2012

경주 동궁과 월지의 생태적 수용력 연구를 위해 유적지내에서 관찰되어지는 7가지 이용행태에 따른 이용구간별 녹지 평균손상도를 산정하였다. 이를 위해 탐방객 이용행태의 이용인수 및 이용시간을 조사하고 손상도를 산정하였다. 각 이용행태별 손상도를 통하여 4가지 조사구의 적정수용력, 표준수용력과 한계수용력을 명확하게 파악할 수 있다. 각 조사구의 이용행태별 이용인수 및 이용시간에 따른 손상도를 산정한 결과, '걷다'의 경우 평균 2.15로 가장 높았고, '눕다'의 경우 0.05로 가장 낮은 것으로 나타났다. 그리고 각 조사구의 손상도는 조사구 4가 1.31로 가장 높았고, 조사구 3이 0.97, 조사구 1이 0.91, 조사구 2가 0.70의 순으로 나타났다. 각 조사구의 손상면적을 산정 후에 생태적 수용력을 추정한 결과, 조사구1, 2, 3, 4의 적정수용력은 각각 40인, 249인, 107인, 37인, 한계수용력은 각각 116인, 713인, 306인, 107인, 표준수용력은 각각 75인, 463인, 198인, 69인으로 추정된다. 경주 동궁과 월지의 바람직한 관리를 위한 최대의 생태적 수용력은 한계수용력 이하로 하는 것이 적합하다.

• 컴퓨터교육학회논문지
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• 제17권3호
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• pp.1-10
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• 2014

유비쿼터스의 기능이 결합된 뉴미디어의 보급으로 인터넷 중독뿐만 아니라 스마트폰 중독은 정보화의 역기능으로 심각한 사회문제가 되고 있다. 대학생의 인터넷 중독과 스마트폰 중독정도를 비교분석하고자 지역 인근 대학교의 일부 대학생들에게 한국형 성인 인터넷 중독 자가진단 척도인 K-척도와 스마트폰 중독 자가진단 척도인 S-척도를 시행하였다. 본 연구에서는 컴퓨터와 스마트폰을 이용하여 웹사이트에 접속하는 기본적인 인터넷 이용패턴을 취득하는 설문문항을 개발하여, K-척도와 S-척도로는 별견되지 않는 숨겨진 인터넷 중독자와 스마트폰 중독자를 찾아서 K-척도와 S-척도의 진단결과와 비교하였다. 또한 K-척도 및 S-척도와 달리 대학생들의 컴퓨터와 스마트폰을 통한 인터넷 주활동과 예상 및 실제 사용시간을 계산하여 구한 내성정도를 이용하여 중독을 진단하는 방법을 제안하고자 한다. SPSS 통계분석 프로그램을 사용하여 숨겨진 인터넷 및 스마트폰 중독자를 찾을 수 있었다.

• 한국멀티미디어학회논문지
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• 제17권6호
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• pp.725-732
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• 2014

The Pancake graph is node symmetric and useful interconnection network in the field of data sorting algorithm. The Half Pancake graph is a new interconnection network that reduces the degree of the Pancake graph by approximately half and improves the network cost of the Pancake graph. In this paper, we analyze topological properties of the Half Pancake graph $HP_n$. Fist, we prove that $HP_n$ has maximally fault tolerance and recursive scalability. In addition, we show that in $HP_n$, there are isomorphic graphs of low-dimensional $HP_n$. Also, we propose that the Bubblesort $B_n$ can be embedded into Half Pancake $HP_n$ with dilation 5, expansion 1. These results mean that various algorithms designed for the Pancake graph and the Bubble sort graph can be executed on $HP_n$ efficiently.

• 한국수학교육학회지시리즈A:수학교육
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• 제31권2호
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• pp.121-132
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• 1992

FEM(Finite Element Method)의 pointwise convergence는 mesh size와 허용오차와의 관계를 분석해 보려는 것이다. 이들 상호 관계에 관한 연구는 FEM에 의한 근사식의 질을 높이는데 중요한 계기가 되어 결과 예측을 하는데 효과적이다. 본 논문은 1-irregular mesh를 이용한 세분화(refinement)로 미지점(unknon node)dlm 수를 최소화 하면서 원하는 점에서의 수렴성을 비교 분석하였다.

• 한국통신학회논문지
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• 제16권11호
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• pp.1194-1200
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• 1991

유한요소법(Finite Element Method)은 컴퓨터를 이용하여 미분방정식의 근사해를 얻기위한 수학적인 기법이다. 유한요소법의 pointwise convergence는 매쉬 크기와 허용 오차와의 관계를 분석해 보려는 것이다. 이들 상호 관계에 과난 연구는 유한요소법에 의한 근사식의 질을 높이는데 중요한 계기가 되어 결과를 예측 하는데 효과적이다. 본 논문을 1-Irregular 매쉬를 이용한 세분화(refinement) 및 형상 함수의 차수 변화에 따른 미지절점(unknown node) 수의 증가에 따른 수렴성을 분석하였다.

• 아시안잔디학회지
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• 제7권1호
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• pp.5-12
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• 1993

This experiment was conducted to study on the morphological change and growth retardation of Korean Lawograss (Zoysia japonica Steud.) under various shading degrees. Dada of plant height, No. of tiller, No. of stolon, No. of rhizome and fresh weight were measured on the l47days after transplanting in 1991. The results are summarized as follows. Plant height was increased at 30% shading degree or over, Maximum plant height was observed at 60% shadeing degree which was 24.2 cm. while full sunlight(control) was most shorted as 10.1 cm. Plant height rapidly was increased as to shading degree increase. The decreasing rate was lower in tiller number and stolon number(top parts of plant) compared with the rhizome number(under ground part) was severely decreased at 30% to 60% of shading. To increase the shading degree, rhizome number was most severely decreased under shading degrees. As degree of shading increase to 30%, 60% and 90%, fresh weight decrease to 66%, 44%, 22% to full sunlight, respectively. Relative growth retadation of Korean lawngrass was decreased by the order of number of rhizome, fresh weight, number of tiller, number of stolon. And these characters were highly significant accord-ing to the different shading degrees.

• 한국조경학회지
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• 제26권3호
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• pp.258-266
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• 1998

The purpose of this study is to investigate the actual conditions, to find problems, and to present an improvement plan of interior landscape in the subway stationis. Moreoiver, it will presume the possibilties to develop the subway and ways to utilie underground space effectively. The results are summarized as follows A light intensity was recorded 0-100 Lux as the lowest light and 500 Lux below as the highest in 61 subway stations. An average temperature of 12 $^{\circ}C$and an air humidity of 38% were recorded over a 4 month period from January to April, but includes a drastic variaton between -8.5$^{\circ}C$ and 21.5$^{\circ}C$. Soil acidity of pH 7 below and soil moisture of 1-2 wet degree were apeared in subway stations mostly. Plant forms consisted of artificial flower & flower. Plant species were recorded at a total of 54 species and appeared in the order of Araucaria heteropylla, Ophiophogon jaburan, Aspidistra elatior cv. 'Asahi' and Hedera helix. Plant height was, for the most part, below 0.5m. Plant species that was fined of conditions were Palm, Camellia japonica, Araucaria heterophylla as a high plant, dracaena fragrans, dracaena deremensis cv. Wakneckii as a middle plant, and Ophiopogon jaburan, Hedra helix, ytomium falcatum, Aspidistra elatior cv. Asahi as a low plant. It used to water materials such as small pool, small cascade, water cycles and natural materials such as natural rock, small rock, sand, bark and animal materials such as squirrels, birds, goldfish as an object for plants in the subway stations. From these actual conditions, First of all, It must make up physical environments such as light, temperature humidity, soil for plant growth, and is important to chooce suitable indoor plants and draw up systematic management in the subway environments. Also, it change plants frequently and uses variable objects for subway stationi individuatism, Moreover, indoor plants with strong environmental adaptation abities such as shade tolerance, drought tolerance and cold tolerance need to develope variable species possibly. If these improvements occur, utilization and amenity of subway stationis will increase, according to the use of interior landscape.