• East Asian mathematical journal
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• 제22권1호
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• pp.79-91
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• 2006

In this paper, we will show some relations between decomposition series {$\pi^{\alpha}q\;:\;{\alpha}$ is an ordinal} and topological series {$\tau_{\alpha}q\;:\;{\alpha}$ is an ordinal} for a convergence structure q and the formular ${\pi}^{\beta}(\tau_{\alpha}q)={\pi}^{{\omega^{\alpha}\beta}}q$, where $\omega$ is the first limit ordinal and $\alpha$ and $\beta({\geq}1)$ are ordinals.

• East Asian mathematical journal
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• 제23권1호
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• pp.111-122
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• 2007

In this paper, we will show some relations between decomposition series {${\nu}^{\alpha}\;:\;{\alpha}$ is an ordinal } and supratopological series {${\sigma}_{\alpha}{\nu}\;:\;{\alpha}$ is an ordinal} for a neighborhood structure $\nu$ and the formular ${\sigma}_{\alpha}{\nu}\;=\;{\nu}^{({\omega}^{\alpha})}$, where $\omega$ is the first limit ordinal.

• 전력전자학회논문지
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• 제13권2호
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• pp.110-118
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• 2008

기존의 저궤도 인공위성 전력계 시스템에 사용된 직렬 구조, 병렬 구조는 공전 주기 동안 두 번의 전력변환 과정을 거쳐 시스템의 효율을 감소시킨다. 직-병렬 구조는 한 번의 전력변환 과정을 거쳐 시스템의 효율을 향상시키지만 레귤레이터가 추가됨으로써 시스템의 비용과 무게, 크기를 증가시킨다. 본 논문에서는 레귤레이터의 추가 없이 시스템의 효율을 향상시키는 단순화된 직-병렬 구조를 제안한다. 인공위성이 지구를 공전하는 동안 상황에 따라 변화하는 제안한 구조의 동작을 네 가지 모드로 분류하고, 각 모드마다 제안한 시스템을 안정적인 동작을 확인하기 위하여 대신호 분석을 수행하였다. 실험을 통하여 기존의 직렬구조와 제안한 구조의 효율을 비교하였다. 제안한 구조의 안정적인 동작을 검증하기 위해 200W급 태양전지와 TMS320F2812 DSP로 제어되는 100W급 전력조절기 두 모듈을 병렬로 구성하여 실험하였다.

• 대한조선학회논문집
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• 제51권4호
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• pp.274-282
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• 2014

Time series of the dynamic response of a slender marine structure was predicted using quadratic Volterra series. The wave-structure interaction system was identified using the NARX(Nonlinear Autoregressive with Exogenous Input) technique, and the network parameters were determined through the supervised training with the prepared datasets. The dataset used for the network training was obtained by carrying out the nonlinear finite element analysis on the freely standing riser under random ocean waves of white noise. The nonlinearities involved in the analysis were both large deformation of the structure under consideration and the quadratic term of relative velocity between the water particle and structure in Morison formula. The linear and quadratic frequency response functions of the given system were extracted using the multi-tone harmonic probing method and the time series of response of the structure was predicted using the quadratic Volterra series. In order to check the applicability of the method, the response of structure under the realistic ocean wave environment with given significant wave height and modal period was predicted and compared with the nonlinear time domain simulation results. It turned out that the predicted time series of the response of structure with quadratic Volterra series successfully captures the slowly varying response with reasonably good accuracy. It is expected that the method can be used in predicting the response of the slender offshore structure exposed to the Morison type load without relying on the computationally expensive time domain analysis, especially for the screening purpose.

• 대한전기학회논문지:전력기술부문A
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• 제48권2호
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• pp.168-175
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• 1999

In this paper, a modified RBF(Radial Basis Function) network structure is suggested for the prediction of a time-series with non-linear, non-stationary characteristics. Coventional RBF network predicting time series by using past outputs sense the trajectory of the time series and react when there exists strong relation between input and hidden activation function's RBF center. But this response is highly sensitive to level and trend of time serieses. In order to overcome such dependencies, hidden activation functions are modified to react to the increments of input variable and multiplied by increment(or dectement) for prediction. When the suggested structure is applied to prediction of Macyey-Glass chaotic time series, Lorenz equation, and Rossler equation, improved performances are obtained.

• 복식
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• 제55권3호
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• pp.1-18
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• 2005

In this study, the transition characteristics of purple series color names appearing in the clothing of the Joseon Dynasty were examined, and the associational meaning of each name were investigated through various methods. The results are as follows; First, Such characteristics as continuity, differentiation, substitution could be observed through the investigation of color names of purple-series appeared on the clothing in the Joseon Dynasty period. Secondly, the associational meaning could be subdivided into; social position symbolic meanings, usage meanings, economic meanings, and thought meanings. The social position symbolic meanings could be observed mainly in the single names which has been used since the ancient times, usage meanings could be observed in a wide variety according to the individual color names. The economic meanings could be observed by comparing the value of colored cloths and colored threads. The thought meanings were mainly related with the Confucianism. Thirdly, the associational semantic structure were established on the basis of associational meanings of purple-series color names. Individual color name on the social position symbolic semantic structure symbolizes [government official] and [servant]. Through usage semantic structure individual color names could be understood structurally according to the social position, sex distinction, wearing situation, items of clothing, and structure of clothing. Individual names on the economic semantic structure were segmented by the semantic components of the values in [high], [medium], [low] prices, kinds and quantity of dyes. The thought semantic structure could be subdivided [Confucianism] and [The Thought of Taeil] in its semantic structure.

• 한국수학사학회지
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• 제28권4호
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• pp.167-179
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• 2015

We study the solution of truncated series of Lee Sang-hyeog with the aspect of visualization. Lee Sang-hyeog solved a problem of truncated series by 4 ways: Shen Kuo' series method, splitting method, difference sequence method, and Ban Chu Cha method. As the structure and solution of truncated series in tertiary number is already clarified with algebraic symbols in some previous research, we express and explain it by visual representation. The explanation and proof of algebraic symbols about truncated series is clear in mathematical aspects; however, it has a lot of difficulties in the aspects of understanding. In other words, it is more effective in the educational situations to provide algebraic symbols after the intuitive understanding of structure and solution of truncated series with visual representation.

• 한국수학교육학회지시리즈E:수학교육논문집
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• 제31권1호
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• pp.71-84
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• 2017

테일러급수는 대학 전공 수학의 여러 개념을 포함하는 복잡한 구조를 가지고 있다. 이 주제는 미적분학, 해석학, 복소해석학 등의 수학뿐만 아니라 물리학, 공학 등 다른 학문에서도 유용성과 응용성을 가진 강력한 도구이다. 그러나 학생들은 이 주제의 수학적 구조를 제대로 이해하는데 어려움을 느낀다. 이에 본 연구에서는 어떻게 학생들이 테일러급수 수렴을 이해하는지를 알기 위해서 학생들의 수학적 특징을 세 유형으로 분류한다. 그 후에 테일러급수 수렴의 구조적 상(image)을 이용해서 테일러급수 수렴에 대한 이해도를 분석하고 이에 대한 결과를 제시하고자 한다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회논문집(I)
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• pp.801-809
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• 2000

Until recently as a method of repairing leaking problem, generally urethane series were used for many structures as subway, box culvert etc. However the lacking of sufficient penetration capacity have made it difficult to repair such structures completely. Now, we could achieve enhanced quality of repairing work by using new material which was compounded of urethane series and cement series properly. This material can penetrate concrete structure efficiently and move interactively with the structure in case of the thermal expansion. Besides of this, we could prevent expecting leakage through several improvements on the aspects of design, materials and site implementation.

• 산업기술연구
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• 제19권
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• pp.75-79
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• 1999

Rotary bending fatigue tests were performed to investigate the effects of 2-phase matrix structure on fatigue limit with prepared specimens in high strength ductile irons. Two types of the specimens with different microstructures have been used. Series A has sorbite and series B has bainite. Fatigue limits of both specimens are improved comparing with as cast specimen. The fatigue limit is higher in series B than in series A. The reason why the fatigue limit of series A shows inferiority to that of series B is due to the transition of micro fatigue cracks to mesocrack occurs very rapidly, so increased stress intensity factor drives the fatigue crack growth. The higher fatigue limit of series B which has bainite is caused by the ${\gamma}$ layer contained in microstructure impede the rapid growth of micro fatigue crack to mesocrack and ${\alpha}$ layer around graphite has the higher capacity for the absorption of plastic deformation energy than sorbite.