• Korean Journal of Mathematics
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• 제25권4호
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• pp.537-554
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• 2017

In this paper, we study the surfaces foliated by ellipses in three dimensional Euclidean space ${\mathbf{E}}^3$. We prove the following results: (1) The surface foliated by an ellipse have constant Gaussian curvature K if and only if the surface is flat, i.e. K = 0. (2) The surface foliated by an ellipse is a flat if and only if it is a part of generalized cylinder or part of generalized cone.

• 대한수학회지
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• 제61권1호
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• pp.161-181
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• 2024

We describe the moduli space of Higgs pairs on an irreducible nodal curve of arithmetic genus one and its geometric structures in terms of the Hitchin map and a flat degeneration of the moduli space of Higgs bundles on an elliptic curve.

• Kyungpook Mathematical Journal
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• 제46권3호
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• pp.417-423
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• 2006

The object of the present paper is to study a conformally flat quasi-Einstein space and its hypersurface.

• 대한수학회보
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• 제53권2호
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• pp.531-540
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• 2016

In this work, we introduce the complete Riemannian manifold $\mathbb{F}_3$ which is a three-dimensional real vector space endowed with a conformally flat metric that is a solution of the Einstein equation. We obtain a second order nonlinear ordinary differential equation that characterizes the helicoidal minimal surfaces in $\mathbb{F}_3$. We show that the helicoid is a complete minimal surface in $\mathbb{F}_3$. Moreover we obtain a local solution of this differential equation which is a two-parameter family of functions ${\lambda}_h,K_2$ explicitly given by an integral and defined on an open interval. Consequently, we show that the helicoidal motion applied on the curve defined from ${\lambda}_h,K_2$ gives a two-parameter family of helicoidal minimal surfaces in $\mathbb{F}_3$.

• 한국주거학회논문집
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• 제10권4호
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• pp.31-40
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• 1999

This study examines changes of internal structure and the ratios of room sizes of flat-type apartment housing and residents' demand of housing alteration. The main results are follows: First, the auxiliary space, such as multi-purpose room, storage ＆ receiving space, becomes an important component of flat-type apartment housing. Second, apartment housings should be supplied to residents focusing on functions of space rather than the number of rooms. Third, the ratios of living room and storage space sizes have been increased as living space increases. Since the current apartment housings do not meet residents' needs, we suggest that residents' age, number of family, and economic status must be considered when apartment space are planned.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.145-148
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• 2005

Recently the construction of high-rise reinforced concrete building is progressively increased as the social demands. It is significantly important factors such as economy, the safety of structure, and the flexibility of internal space. Therefore new structural system is also required to be attained the reduction of story height, the flexibility and efficient use of space. The most suitable structural system is with the economy and flexibility, flat plate slab system in high-rise reinforced concrete building. In this research, it was focused in the improvement of shear performance in the flat plate system using high ductile fiber reinforced mortar. It was evaluated the shear performance in the critical region of slab-column connection. The flat plate system, designed by the high performance and safety, was developed as a new technique in the application of high-rise R/C building.

• 천문학회보
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• 제36권2호
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• pp.155.2-155.2
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• 2011

We present development of the calibration system for IGRINS (the Immersion GRating Infrared Spectrograph). We mainly use Th-Ar and U hollow cathode lamp as the spectral calibration source and telluric features can be used additionally. For the flat source, we selected a 3000K tungsten halogen lamp with 2 inch integrating sphere. From Light Tools simulation, the result flat image through calibration optics satisfied <1% flatness error requirement. We also present mechanical design of calibration box that will be attached on the IGRINS dewar. Three moving stages are designed to perform switching mechanism between all of the observing modes - target observation, flat, precision RV measurement, and spectro-polarimetric observation.

• East Asian mathematical journal
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• 제28권1호
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• pp.25-36
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• 2012

We introduced a Finsler space $F^n$ with an approximate infinite series (${\alpha},{\beta}$-metric $L({\alpha},{\beta})={\beta}\sum\limits_{k=0}^r\(\frac{\alpha}{\beta}\)^k$, where ${\alpha}<{\beta}$ and investigated it with respect to Berwald space ([12]) and Douglas space ([13]). The present paper is devoted to finding the condition that is projectively at on a Finsler space $F^n$ with an approximate infinite series (${\alpha},{\beta}$)-metric above.

• 콘크리트학회논문집
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• 제12권4호
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• pp.113-119
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• 2000

The R/C flat plate system provides architectural flexibility, clear space, reduced building height, simple formwork, which consequently enhance constructibility. One of the serious problems in the flat plate system is brittle punching shear failure due to transfer of shear force and unbalanced moments in column-slab joint. Recently, the flat plate system accompanied with shear walls to resist the lateral loads is applied to high-rise buidings. Although the flat plate system is not considered in design as part of the lateral load-resisting system, it is required that this system keeps the ductile behavior for the lateral displacement of the building. However, it is unclear whether the column-slab joint possesses ductility enough to survive the lateral deformation. The objective of this paper is to investigate the major parameters that influence the ductility of R/C flat plate system by examining the existing experiments on column-slab joint. The effects of gravity load and shear reinforcement on the ductility of the flat plate system are presented.

• International Journal of Aeronautical and Space Sciences
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• 제17권3호
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• pp.324-331
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• 2016

The present study focuses on the characteristics of a supersonic jet flowing from a rectangular nozzle exit on a flat plate. Flow visualization techniques using schlieren and kerosene-lampblack tracing are utilized to investigate shock reflection structures and boundary-layer separations over a flat plate. Wall pressure measurements are also carried out to quantitatively analyze the flow structures. All observations are repeated for multiple jet flow boundary conditions by varying the flap length and nozzle pressure ratio. The experimental results show that the jet flow structures over the flat plate are highly three-dimensional with strong bleeding flows from the plate sides, and that they are sensitive to plate length and nozzle pressure ratio. A multi-component force measurement device is also utilized to observe the characteristics of the jet flow thrust vectoring over the plate. The maximum thrust deflection angle of the jet is about $8^{\circ}$, demonstrating the applicability of thrust vector control via a flat plate installed at the nozzle exit.