• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1217_1218
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• 2009

현재 국내를 비롯하여 세계적으로 녹색성장, 친환경 등의 열풍이 고유가와 화석연료의 고갈위기와 맞물려 활발히 진행되고 있다. 이미 미국, 영국, 프랑스, 이태리, 일본 등의 선진국에서는 자연 친화적, 경제적 실리 추구 및 편리성을 추구하면서 청정 에너지를 사용하는 "미래형 이동수단"에 큰 관심을 갖고 우리보다 한발 앞서 나가고 있다. 2005년 2월 16일 발효된 기후변화의 주 요인인 온실가스 배출 감축을 위한 교토의 정서 또한 이러한 친환경이란 말과 무관하지 않다. 교토의정서의 발효 이후 세계 각국은 의무화된 규제조항을 만족하기 위해 막대한 자본을 투입하고 있다. 우리나라의 경우 온실가스 배출량이 세계 9위에 달하고 있으며, 전체 온실가스 배출량의 82.5% 정도가 화석에너지의 사용에 의해 발생되고 있다. 이중 이산화탄소의 경우 전체 배출량의 27%를 자동차에서 배출되며, 이로 인해 세계 각국에서는 자동차에서의 배출가스를 규제하는 조항을 법제화하고 있다. 이러한 규제는 앞서 미국의 경우 캘리포니아 주정부에서 1998년부터 전기자동차 사용을 의무화하는 ZEV 규제를 입법화하면서 본격화되었고, 무공해 및 저공해 자동차의 개발이 활발하게 진행되었다. 또한 고유가 시대로 접어들면서 대체에너지에 대한 필요성이 한층 고조되고 있는 실정이다. 이중 전기자전거는 배터리를 통해 무공해, 무소음이라는 장점을 가지고 있으며, 유지관리비가 거의 들지 않고 교통체증을 완화시켜주며, 주차에 신경쓰지 않아도 되어 교통수단에 혁신을 가져다 줄 것이라 생각된다. 또한 전기자전거의 경우 배터리를 동력원으로 사용하며 전동스쿠터 등에서의 문제점인 일충전 주행거리에 제약을 받지 않아 최근 중국 등에서 보급이 급격히 확산되고 있는 추세에 있다. 하지만 대부분 납축전지, 니켈-카드뮴 등의 배터리가 사용되고 있어 중량, 수명, 중금속에 의한 환경오염 등의 다양한 문제점을 내포하고 있다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.6
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• pp.996-1005
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• 2000

This paper proposed a novel broadband ceramic dielectric antenna by improving the conventional broadband technique that very high permittivity material is attaching to one side of low permittivity material. The broadband ceramic dielectric antenna can be designed by using our proposed method, and it overcomes the disadvantage of narrow bandwidth problem. For the proposed ceramic dielectric antenna, a 10 dB return-loss bandwidth of 33.9% has been achieved. The measurement and numerical results(Finite Element Method) are performed and confirmed to a good agreement with each other. The proposed ceramic dielectric antenna is designed and implemented to extend enough the coverage of dual band (PCS+IMT-2000).

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.5
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• pp.77-83
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• 1993

A modified Lanczos method combined with a substructure analysis technique was used for calculating natural frequencies and mode shapes of large structural systems. The method does not require generation and storage of stiffness and mass matrices of the entire structure. It only uses the stiffness and mass matrices of each substucture. No approximating assumptions are required other than the usual assumption of linear elastic system modelled by finite elements. Thus, natural frequencies and mode shapes for the finite element model employed are the same as those with or without the suhstructuring algorithm. To check the efficiency of the proposed method, first ten natural frequencies and the corresponding mode shapes of an open truss helicopter tail-boom structure are calculated by using it.

• Journal of IKEEE
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• v.6 no.1 s.10
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• pp.72-79
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• 2002

This paper presents an efficient face detection algorithm for color images with a complex background. The presented algorithm utilizes the color information and eigenface that is calculated by PCA-LDA (Principle Component Analysis - Linear Discriminant Analysis). The method of using the color information is faster than any other methods. Eigenface includes average information of the whole test faces. Therefore eigenface can decide that the candidate region is a face. The whole process is composed of two steps. First, it finds first face candidates region of skin tone using a color information in image. We can get a size and position of face candidate region. Second, we compare first face candidate region with eigenface, so decide that an image whether include a face or not. The advantages of the proposed approach include that increasing the detection speed by deciding a size and position of first face candidates region. Also, Betting 97% of the detection rate by comparing the eigenfaces calculated in PCA-LDA.

• Journal of Korea Game Society
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• v.13 no.2
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• pp.59-70
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• 2013

Although the history of the game of Go is more than 2,500 years, the theoretical studies of Go are still insufficient. In recent years a lot of studies using Artificial Intelligent(AI) have been conducted, but they do not provide the prominent theoretical reality. We applied Principal Component Analysis(PCA) to the professional Go openings, which are the early stage in Go, to analyze them especially focused on the Go game records of the professional 9-dan player Lee Sedol who is the world's top professional Go player. The results showed that among the 361 eigenvectors the 48 most significant eigenvectors capture most of the variance (99.9%) and the 30 most significant eigenvectors enable to possess 90.5 percent of the total variance. This result would be expected to considerably contribute to pattern recognition research of the professional Go openings in the near future.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.5
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• pp.30-37
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• 2015

The estimation of system damping parameter of the response signal with lower natural frequency and higher damping parameter from free vibration is affected by the wavelet center frequency. This study discusses these considerations in the context of the wavelet's multi-resolution character and includes guidelines for selection of wavelet center frequency. The experiment with H-Beam and numerical examples with respect to three cases (i)single mode, (ii)separated modes and (iii)close modes demonstrate the validity of method to improve the accuracy of the estimated damping parameter. The localization of the corresponding scale for the total scales is determined by the natural frequency of the analysing mode and is affected by the wavelet center frequency. Thus, the reliability for the accuracy of the estimated damping parameter can be improved by the corresponding scale of the natural frequency for the analysing mode is localized at the half of the total scales.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.6
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• pp.147-154
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• 2014

The cable damages of the bridge structures induce very important impact on the structural safety, which implies the close monitoring of the cable damage is required to secure sustained safety of the bridges. Most usual available maintenance techniques are based on the monitoring the change of the natural frequency of the structures by damages. However, existing method are based on vibration method to calculate lateral vibration and system identification can calculate the axial stiffness using sensitivity equation by trial error method. But the frequency study by the longitudinal movement need because of the sag effect in system identification. This study proposes a new method to investigate the damage magnitudes and status. The method improves the accuracies in the magnitudes and status of damages by adopting the natural frequency of longitudinal movement. The study results have been validated by comparing them with the approximate solution of FEM. Thus, the relationship of cable damage and frequency appear with relation that the severe damage has the little frequency. If we know the real frequency we can estimate the cable damage severity using this relationship. This method can be possible the efficient management of the cable damage.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.1
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• pp.71.2-71.2
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• 2013

1 m 천체망원경에 대한 초기 광기계 구조해석이 진행되었다. 3개의 반사경으로 구성되는 광학계는 Richey-Cretien 방식으로써 두 개의 Nasmyth 초점을 제공하고, 초점비는 F/8이다. 결정된 반사경 마운트 방법에 의해 반사경면의 표면 RMS(Root Mean Square) 변형량은 모두 20 nm보다 작다. 전체 구조물에 대한 구조해석을 수행하기 위해 솔리드, 쉘, 빔 요소 등으로 구성된 정밀유한요소 모델이 NX 소프트웨어로 설계되었다. 전체 구조물은 첫 번째 고유모드는 68 Hz에서 병진모드가 발생했다. 중력에 대해서는 최대 응력이 18.2 MPa로써 미비하였고, 전체 최대 변위는 50.3 ${\mu}m$ 로써 계산되었다. 이 변위값은 광학설계 소프트웨어에 재입력되어 광학계의 성능이 재분석 될 것이다.

• Journal of Korean Society of Steel Construction
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• v.24 no.3
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• pp.337-348
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• 2012

This study investigated the characteristics of bifurcation and the instability due to the initial imperfection of the space truss, which is sensitive to the initial conditions, and the calculated buckling load by the analysis of Eigen-values and the determinant of tangential stiffness. A two-free nodes model, a star dome, and a three-ring dome model were selected as case studies in order to examine the unstable phenomenon due to the sensitivity to Eigen mode, and the influence of the rise-span ratio and the load parameter on the buckling load were analyzed. The sensitivity to the imperfection of the two-free nodes model changed the critical path after reaching the limit point through the bifurcation mode, and the buckling load level was reduced by the increase in the amount of imperfection. The two sensitive buckling patterns for the model can be explained by investigating the displaced position of the free node, and the asymmetric Eigen mode was a major influence on the unstable behavior due to the initial imperfection. The sensitive mode was similar to the in-extensional mechanism basis of the simplified model. Since the rise-span ratio was higher, the effect of local buckling is more prominent than the global buckling in the star dome, and bifurcation on the equilibrium path occurring as the value of the load parameter was higher. Additionally, the buckling load levels of the star dome and the three-ring model were about 50-70% and 80-90% of the limit point, respectively.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.1
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• pp.165-174
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• 2004

This research develops a technique which uses energy dissipation ratio in order to monitor the structural health on real time basis. For real-time monitoring, we employ the NExT and the ERA which enable us to obtain real-time data. Energy dissipation ratio is calculated from those data only with the damping and natural frequency of the structure, and from the calculated values we develop an algorithm (Energy dissipation method) which decides the damage degree of structure. The Energy dissipation method developed in this research is proved to be valid by comparison with other methods like the eigenparameter method and the MAC. Especially this method enables us to save measuring time and data which are the most important in real-time monitoring, and its use of the ambient vibration also makes it easy to monitor the whole structure and its damage points.