• Kyungpook Mathematical Journal
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• 제61권1호
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• pp.181-190
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• 2021

Let M be a real hypersurface with almost contact metric structure (ϕ, ��, η, g) in a nonflat complex space form Mn(c). We denote S and R�� by the Ricci tensor of M and by the structure Jacobi operator with respect to the vector field �� respectively. In this paper, we prove that M is a Hopf hypersurface of type A in Mn(c) if it satisfies R��ϕ = ϕR�� and at the same time R��(Sϕ - ϕS) = 0.

• 한국수학교육학회지시리즈B:순수및응용수학
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• 제28권3호
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• pp.247-252
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• 2021

Let M be a real hypersurface in a complex space form M_n(c), c ≠ 0. In this paper, we prove that if (∇_Xϕ)Y + (∇_Yϕ)X = 0 holds on M, then M is a Hopf hypersurface, where ϕ is the tangential projection of the complex structure of M_n(c). We characterize such Hopf hypersurfaces of M_n(c).

• 한국항행학회논문지
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• 제7권2호
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• pp.180-190
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• 2003

실수축 상의 적분 방법에 의한 정확한 closed-form 그린함수를 이용하여 코플래너 도파로의 불연속에 대한 공간영역 full-wave 해석을 하였다. MPIE(Mixed Potential Integral Equation)를 풀기 위한 수치계산 방법으로는 삼각형 요소를 이용한 갤러킨 방법을 사용하였다. 경계면에서 삼각형 요소상의 기저함수로는 선형함수를 사용하였으며, 관측점과 전원점이 일치하는 특이점 근방의 적분 계산을 위해 면적분을 선적분 형태로 바꾸어 피적분 함수의 특이점이 사라지도록 하는 해석적인 방법을 사용하였다. 실수축 적분방법에 의한 그린함수를 이용함으로써 불연속에 대한 정확한 특성을 구하였다.

• 한국실내디자인학회논문집
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• 제16권5호
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• pp.126-133
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• 2007

This study is intended to set the concept of becoming meaning of digital space through digital technology and to study the influence of digital space on becoming of real space through derived keyword. The results of this study are summarized as follows. First, the digital concept is created in the process that the virtual space is changed into the real space with a priority given to form, space and time. Digital expression concept and image concept the structural becoming, and idea concept and creative concept creates the time becoming. Second, the concept of digital becoming exposes a physical visibility through the digital's virtual image, and non-space spatiality through the space simulation. It also continuously reveals a consecutive time and non-consecutive time through a statable progress, incremental progress, and dynamic progress. Third, as the influence of digital on becoming of real space, the digital visibly not only expresses the new and difficult becoming problem through conceptual virtuality, but also can review the real space's space concept with virtuality in the digital non-area. Digital's durability expresses the new space's existence by physically combining with the existing space through the virtual form creation.

• Journal of Mechanical Science and Technology
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• 제18권7호
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• pp.1150-1158
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• 2004

In this paper, we present an adaptive observer for nonlinear systems that include unknown constant parameters and are not necessarily observable. Sufficient conditions are given for a nonlinear system to be transformed by state-space change of coordinates into an adaptive observer canonical form. Once a nonlinear system is transformed into the proposed adaptive observer canonical form, an adaptive observer can be designed under the assumption that a certain system is strictly positive real. An illustrative example is included to show the effectiveness of the proposed method.

• 대한수학회지
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• 제55권3호
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• pp.735-747
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• 2018

Let M be a real hypersurface of a complex space form with constant curvature c. In this paper, we study the hypersurface M admitting Miao-Tam critical metric, i.e., the induced metric g on M satisfies the equation: $-({\Delta}_g{\lambda})g+{\nabla}^2_g{\lambda}-{\lambda}Ric=g$, where ${\lambda}$ is a smooth function on M. At first, for the case where M is Hopf, c = 0 and $c{\neq}0$ are considered respectively. For the non-Hopf case, we prove that the ruled real hypersurfaces of non-flat complex space forms do not admit Miao-Tam critical metrics. Finally, it is proved that a compact hypersurface of a complex Euclidean space admitting Miao-Tam critical metric with ${\lambda}$ > 0 or ${\lambda}$ < 0 is a sphere and a compact hypersurface of a non-flat complex space form does not exist such a critical metric.

• 대한수학회지
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• 제61권3호
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• pp.547-564
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• 2024

We study totally real and complex subsets of a right quarternionic vector space of dimension n + 1 with a Hermitian form of signature (n, 1) and extend these notions to right quaternionic projective space. Then we give a necessary and sufficient condition for a subset of a right quaternionic projective space to be totally real or complex in terms of the quaternionic Hermitian triple product. As an application, we show that the limit set of a non-elementary quaternionic Kleinian group 𝚪 is totally real (resp. commutative) with respect to the quaternionic Hermitian triple product if and only if 𝚪 leaves a real (resp. complex) hyperbolic subspace invariant.

• Architectural research
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• 제15권2호
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• pp.69-75
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• 2013

Within residential high-rise market there are many value determining factors. Site condition, view, program, units and structure are important parameters that are directly related to the financial aspect of the project. However, most of the studies of high-rise building design focus on the facade and the shape strategies from an esthetic point of view without considering these factors. The objective of this study is to investigate new design approach that incorporates site, program and structural information at an early stage as a generator of building form and explore a wide range of strategies to negotiate these factors in the process of design/decision making. Not being based on designer's subjective preference or style, architects still can create interesting building design through integration and negotiation of various building information. Since this form is based on real data, not just play of form, we can expect that this form has great potential to be developed into real one at the later design phase.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.115-118
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• 2005

A workpiece with a large surface area is likely to be uneven due to form error and waviness. These geometric disturbances can cause inaccurate micro shapes to be formed when micro features are micro-grooved into the surface and cause the resulting workpiece to fail to function as desired. Thus, real-time measurement and compensation is required to guarantee the form accuracy of micro features while machining a workpiece with a large surface area. In this study, a method is suggested for real-time measurement of geometric error for the micro grooving of a large flat surface using a laser displacement sensor. The measurements are demonstrated for the workpieces with large surface areas and the experimental results show that the waviness and form error are well detected.

• East Asian mathematical journal
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• 제16권1호
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• pp.135-145
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• 2000

The purpose of this paper is to study the Chern-type problem of the complete space-like submanifolds of an indefinite complex space form.