• 한국공간정보시스템학회 논문지
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• 제10권3호
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• pp.1-18
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• 2008

공간 네트워크 상을 움직이는 많은 이동객체들의 궤적 분석을 통해서 많은 정보를 얻을 수 있다. 이를 위해서, 궤적을 효과적으로 검색 할 수 있는 궤적 기반 색인 구조가 필요하다. 하지만 도로와 같은 공간 네트워크상의 궤적 기반 색인 구조에 대한 연구는 FNR-트리나 MON-트리를 제외하고는 연구가 많이 부족한 실정이다. 또한, FNR-트리나 MON-트리는 에지를 지난 이동객체의 이동정보인 세그먼트만을 저장할 뿐 전체 궤적을 유지하지 못하며, 궤적 질의에 대해 비효율적이다. 따라서 본 논문에서는 공간 네트워크상의 이동객체를 위한 시그니처 기반의 궤적 색인 구조인 SigMO-트리를 제안한다. 이를 위해, 이동객체를 공간과 시간 특성으로 분류하고, 전체 궤적을 유지함으로써 영역질의와 궤적질의를 동시에 처리할 수 있는 색인 구조를 설계한다. 아울러, 사용자 질의를 시공간영역 내 궤적 질의, 시간영역 내 유사궤적 질의로 분류하고, 이들을 처리 하기 위한 질의 처리 알고리즘을 제안한다. 각 질의처리 알고리즘은 효율적인 검색을 위하여 시그니처 파일 기법을 이용하여 궤적을 검색한다. 마지막으로 성능평가를 통해 본 논문에서 제안한 궤적 기반 색인 구조가 기존의 색인구조인 FNR-트리, MON-트리보다 성능이 우수함을 보인다.

• 한국해양공학회지
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• 제17권5호
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• pp.57-65
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• 2003

This paper proposes an optimum design method of structural and control systems, using a 2-D truss structure as an example. The structure is subjected to initial static loads and disturbances. For the structure, a FEM model is formed. Using modal transformation, the equation of motion is transformed into modal coordinates, in order to decrease D.O.F. of the FEM model. To suppress the effect of the disturbances, the structure is controlled by an output feedback $H_{\infty}$ controller. The design variables of the combined optimal design of the control-structure systems are the cross sectional areas of truss members. The structural objective function is the structural weight. The control objective function is the $H_{\infty}$ norm, the performance index of control. The second structural objective function is the energy of the response related to the initial state, which is derived from the time integration of the quadratic form of the state in the closed-loop system. In a numerical example, simulations have been perform. Through the consideration of structural weight and $H_{\infty}$ norm, an advantage of the combined optimum design of structural and control systems is shown. Moreover, since the performance index of control is almost nearly optimiz, we can acquire better design of structural strength.

• International Journal of Ocean Engineering and Technology Speciallssue:Selected Papers
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• 제6권1호
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• pp.60-68
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• 2003

This paper proposes an optimum design method of structural and control systems, using a 2-D truss structure as an example. The structure is subjected to initial static loads and disturbances. For the structure, a FEM model is formed. Using modal transformation, the equation of motion is transformed into modal coordinates, in order to decrease D.O.F. of the FEM model. To suppress the effect of the disturbances, the structure is controlled by an output feedback $H_{\infty}$ controller. The design variables of the combined optimal design of the control-structure systems are the cross sectional areas of truss members. The structural objective function is the structural weight. The control objective function is the $H_{\infty}$ norm, the performance index of control. The second structural objective function is the energy of the response related to the initial state, which is derived from the time integration of the quadratic form of the state in the closed-loop system. In a numerical example, simulations have been perform. Through the consideration of structural weight and $H_{\infty}$ norm, an advantage of the combined optimum design of structural and control systems is shown. Moreover, since the performance index of control is almost nearly optimiz, we can acquire better design of structural strength.

• Earthquakes and Structures
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• 제18권4호
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• pp.519-526
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• 2020

Non-stationary random seismic response and reliability of multi-degree of freedom hysteretic structure system are studied based on the cumulative damage failure mechanism. First, dynamic Eqs. of multi-degree of freedom hysteretic structure system under earthquake action are established. Secondly, the random seismic response of a multi-degree freedom hysteretic structure system is investigated by the combination of virtual excitation and precise integration. Finally, according to the damage state level of structural, the different damage state probability of high-rise frame structure is calculated based on the boundary value of the cumulative damage index in the seismic intensity earthquake area. The results show that under the same earthquake intensity and the same floor quality and stiffness, the lower the floor is, the greater the damage probability of the building structure is; if the structural floor stiffness changes abruptly, the weak layer will be formed, and the cumulative damage probability will be the largest, and the reliability index will be relatively small. Meanwhile, with the increase of fortification intensity, the reliability of three-level structure fortification is also significantly reduced. This method can solve the problem of non-stationary random seismic response and reliability of high-rise buildings, and it has high efficiency and practicability. It is instructive for structural performance design and estimating the age of the structure.

• Applied Science and Convergence Technology
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• 제24권6호
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• pp.250-253
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• 2015

High contrast grating (HCG) is the structure made up of the sub-wavelength grating of high-index and the surrounding layer of low-index, which reveals high contrast between two materials. Its advantages include high reflectivity over a broad bandwidth, polarization and wavelength selectivity, optical high-Q resonator, and phase modulation. In this work, the HCG structure comprising of indium tin oxide (ITO) and Silicon (Si), for the surrounding layer and the grating layer respectively, was studied. Its theoretical model was established, and transmittance, phase and optical behavior were calculated by rigorous coupled-wave analysis and finite element method. Furthermore, the established structure was fabricated to validate its feasibility. The fabricated structure shows the focusing capability whose length is about $10{\mu}m$, and the feasibility of the structure was demonstrated. It is also meaningful that ITO layer can contribute to the fabrication of the HCG structure, leading to enable the structure to be electrical-driven.

• Structural Engineering and Mechanics
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• 제67권4호
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• pp.327-336
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• 2018

In this study, an efficient damage index is proposed to identify multiple damage cases in structural systems using the concepts of frequency response function (FRF) matrix and strain energy of a structure. The index is defined based on the change of strain energy of an element due to damage. For obtaining the strain energy stored in elements, the columnar coefficients of the FRF matrix is used. The new indicator is named here as frequency response function strain energy based index (FRFSEBI). In order to assess the performance of the proposed index for structural damage detection, some benchmark structures having a number of damage scenarios are considered. Numerical results demonstrate that the proposed index even with considering noise can accurately identify the actual location and approximate severity of the damage. In order to demonstrate the high efficiency of the proposed damage index, its performance is also compared with that of the flexibility strain energy based index (FSEBI) provided in the literature.

• 대한수학회보
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• 제41권4호
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• pp.779-783
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• 2004

A group G is said to satisfy the minimal condition on normal subgroups of infinite index if there does not exist an infinite properly descending chain $G_1$ > $G_2$ > ... of normal subgroups of infinite index in G. We characterize the structure of locally nilpotent groups satisfying this chain condition.

• 한국정보처리학회논문지
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• 제6권10호
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• pp.2574-2586
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• 1999

SGML문서는 정보 표현의 기본 단위인 엘리먼트로 구성되어져 있기 때문에 SGML 정보 검색은 기존의 정보 검색에서의 문서 단위 검색뿐만 아니라 엘리먼트 단위 검색이 이루어져야 한다. 또한, SGML 인덱스 구조는 동적 환경을 위해 문서의 부분 삭제와 부분 삽입을 지원해야 한다. 이를 위해 본 연구에서는 동적 환경하에서 구조 질의에 적합한 SGML 인덱스 구조를 제안한다. 그리고, 제안된 인덱스 구조에 근거하여 내용 및 구조-기반 검색을 효율적으로 지원하는 인덱스 관리자를 설계하고, O2시스템을 기반으로 SGML 정보 검색 인덱스 관리자를 구현하며, 기존 인덱스 관리자와 성능 비교를 수행한다. 검색성능 비교 결과, 본 연구에서 제안한 방법이 기존의 K-ray 완전 트리를 사용한 방법보다 더 우수함을 나타낸다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 가을 학술발표회 논문집(I)
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• pp.161-166
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• 1998

The concrete structures designed and constructed by conventional design concept based on structural performance consideration show sometimes serious durability problem when the structures are exposed to aggressive environment. Because present design system focuses on the structure safety and considers durability indirectly by the concrete mix design and cover depth, the durability of concrete structure cannot be ensured. As the first step to develope the durability design for concrete structure, durability index which represents internal concrete resistance and environment index which represents external environmental exposure are derived quantitatively. In the next step, the durability design system is developed by checking durability limit state with computed two indexes under service life condition by considering of the reliability of structure. Finally, the proposed system is verified with a model problem.

• 한국통신학회논문지
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• 제22권1호
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• pp.81-88
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• 1997

Wavelength tunable, narrowbandwidth wvelength filters in compound semiconductor have been modeled, fabricated, and characterized. In order to obtain a narrow bandpass characteristics at 1.55.$\mu$m, a highly asymmertrical directional coupler structure composed of a strongly guided ridge waveguide and a weakly guided strip-loaded waveguide was used. The optimized filter structure modeling has been obtained by using the spectral index method, effective index method, and the coupled mode theory. Operation at a center wavelength a 1.537.mu.m with a bandwidth of 1.8nm and transfer efficiency of 50-70% is experimentally achieved. For the purpose of center wavelength tuning, the carrier injection in p-n diode structure has been theoretically investigated. It has been found that the tuning range of nanometer can be easily obtained by moderate amount carrier injection. We also found that the bandwidth becomes broad as the center wavelength tuning increases.