• Journal of Mechanical Science and Technology
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• 제14권9호
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• pp.1005-1012
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• 2000

Numerical optimization techniques combined with a three-dimensional thin-layer Navier-Stokes solver are presented to find an optimum shape of a stator blade in an axial compressor through calculations of single stage rotor-stator flow. Governing differential equations are discretized using an explicit finite difference method and solved by a multi-stage Runge-Kutta scheme. Baldwin-Lomax model is chosen to describe turbulence. A spatially-varying time-step and an implicit residual smoothing are used to accelerate convergence. A steady mixing approach is used to pass information between stator and rotor blades. For numerical optimization, searching direction is found by the steepest decent and conjugate direction methods, and the golden section method is used to determine optimum moving distance along the searching direction. The object of present optimization is to maximize efficiency. An optimum stacking line is found to design a custom-tailored 3-dimensional blade for maximum efficiency with the other parameters fixed.

• Advances in Computational Design
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• 제5권1호
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• pp.55-89
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• 2020

For the first time, an accurate analytical solution, based on coupled three-dimensional (3D) piezoelasticity equations, is presented for free vibration analysis of the angle-ply elastic and piezoelectric flat laminated panels under arbitrary boundary conditions. The present analytical solution is applicable to composite, sandwich and hybrid panels having arbitrary angle-ply lay-up, material properties, and boundary conditions. The modified Hamiltons principle approach has been applied to derive the weak form of governing equations where stresses, displacements, electric potential, and electric displacement field variables are considered as primary variables. Thereafter, multi-term multi-field extended Kantorovich approach (MMEKM) is employed to transform the governing equation into two sets of algebraic-ordinary differential equations (ODEs), one along in-plane (x) and other along the thickness (z) direction, respectively. These ODEs are solved in closed-form manner, which ensures the same order of accuracy for all the variables (stresses, displacements, and electric variables) by satisfying the boundary and continuity equations in exact manners. A robust algorithm is developed for extracting the natural frequencies and mode shapes. The numerical results are reported for various configurations such as elastic panels, sandwich panels and piezoelectric panels under different sets of boundary conditions. The effect of ply-angle and thickness to span ratio (s) on the dynamic behavior of the panels are also investigated. The presented 3D analytical solution will be helpful in the assessment of various 1D theories and numerical methods.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제5권12호
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• pp.2374-2391
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• 2011

A variety of reconstruction methods has been developed to convert a set of scattered points generated from real models into explicit forms, such as polygonal meshes, parametric or implicit surfaces. In this paper, we present a method to construct multi-scale implicit surfaces from scattered points using multiscale kernels based on kernel and multi-resolution analysis theories. Our approach differs from other methods in that multi-scale reconstruction can be done without additional manipulation on input data, calculated functions support level of detail representation, and it can be naturally expanded for n-dimensional data. The method also works well with point-sets that are noisy or not uniformly distributed. We show features and performances of the proposed method via experimental results for various data sets.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 E
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• pp.2287-2289
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• 1999

In this paper, a new method for calculating capacitance in multi-electrode system with arbitrarily shape is presented. This new approach based on divergence theorem and Gauss's law is achieved by Surface-Contacted Element(SCE) for Gaussian surface. To evaluate capacitance in multi-electrode system, two dimensional finite element method using only the elements which is contacted one nod (PE: Point-Element) or two nod (FE: Face-Element) with surface is employed. The proposed SCE method has short computing time to calculate capacitance which is because it uses only SCE elements and needs one calculation loop while exiting FEM method in servral loops. This method is verified by application in calculating capacitance using potential detection device model which is composed with anode, cathode, and floating electrode.

• Structural Engineering and Mechanics
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• 제83권3호
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• pp.283-292
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• 2022

A nonlinear vibrational analysis of sandwich curved panels having multi-scale face sheets has been performed in this article based on differential quadrature method (DQM). All mechanical properties of multi-scale skins have been established in the context of three-dimensional Mori-Tanaka scheme for which the influences of glass fibers and random carbon nanotubes (CNTs) have been taken into account. The governing equations for sandwich the panel have been developed based upon thin shell formulation in which geometry nonlinearities have been taken into account. Next, DQ approach has been applied to solve the governing equations for determining the relationships of frequencies with deflections for curved panels. It will be demonstrated that the relationships of frequencies with deflections are dependent on the changing of CNT weight fractions, fibers alignment, fibers volume, panel radius and skin thickness.

• Journal of information and communication convergence engineering
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• 제10권4호
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• pp.411-419
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• 2012

This paper proposes a semi-automatic image-based approach for 3-dimensional (3D) modeling of buildings along streets. Image-based urban 3D modeling techniques are typically based on the use of aerial and ground-level images. The aerial image of the relevant area is extracted from publically available sources in Google Maps by stitching together different patches of the map. Panoramic images are common for ground-level recording because they have advantages for 3D modeling. A panoramic video recorder is used in the proposed approach for recording sequences of ground-level spherical panoramic images. The proposed approach has two advantages. First, detected camera trajectories are more accurate and stable (compared to methods using multi-view planar images only) due to the use of spherical panoramic images. Second, we extract the texture of a facade of a building from a single panoramic image. Thus, there is no need to deal with color blending problems that typically occur when using overlapping textures.

• 한국주거학회논문집
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• 제18권1호
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• pp.53-60
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• 2007

Storytelling approach is the way to formulate and solve problems using stories. Story is a means to understand and react everyday life that can be regarded as multi-dimensional problems. The approach becomes popular in various fields in conjunction with digital technology. In particular, it is used to solve problems in relation to whole context. In design, storytelling approach is used to clarify design constraints. It can be used to clarify and communicate thoughts for design artifacts, and to understand how the artifacts might be used in particular circumstances. In particular, the approach is useful to use under uncertain circumstances. In architecture, storytelling approach can be used in the area of design generation, design critique and capturing design knowledge. In design generation, it can be used to describe and formulate design experiences rather than simple designing artifacts. The approach formalizes design based on stories of user experiences. Digital technology such as virtual reality can be used to experience designed spaces for design modifications. In design critique area, it can be used to fill uncertain facts for historical buildings as welt as different from present status. Such stories can be used to build digital modeling and used to open criticism. Stories can be used to formalize knowledge in architectural domain as a form of implicit knowledge for certain projects. In architecture, it often is required to design types of environment never experienced before as well as to accomodate fast changing technologies. Storytelling methodology can be used as a method to cope with uncertainty and complexity in design requirements along with accumulating design knowledge.

• 한국콘텐츠학회논문지
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• 제10권11호
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• pp.403-413
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• 2010

이 연구는 1996년 한국에 소개된 이후 최근 활발히 연구되기 시작한 레크리에이션 전문화의 연구동향 및 성과를 체계적으로 정리하고 연구수행의 문제와 향후 발전과제를 제시하는데 그 목적이 있다. 이를 위해 KISS와 RISS의 데이터베이스를 통해 레크리에이션 전문화 관련 연구를 수집하였으며, 총34편을 분석에 활용하였다. 연구결과 I형(레크리에이션 전문화 소개 및 제언 연구), T형(해외 레크리에이션 전문화 연구동향 연구), U형(단일차원 분석을 이용한 양적연구), M형(다차원 분석을 이용한 양적연구), Q형(질적연구), S형(구조모형을 이용한 변인간의 관계연구)의 6개 연구유형으로 분류되었다. 선행연구 고찰을 통해 도출된 문제점은 다음과 같다. 첫째, 최근까지도 레크리에이션 전문화의 단일차원 분석이 이루어지고 있다. 둘째, 해외에서 개발된 레크리에이션 전문화 척도를 그대로 번안해서 사용하고 있어 그 타당성의 검증이 필요하다. 셋째, 해외의 연구흐름을 답습하는 경향을 보인다. 넷째, 연구방법과 연구자들의 다양성이 부족하다. 이에 따른 추후 발전 방향은 다음과 같다. 첫째, 한국문화에 적합한 레크리에이션 전문화 척도의 개발이 시급하다. 둘째, 레크리에이션 전문화의 연구대상의 다양화가 필요하다. 마지막으로, 연구방법의 다양화가 필요하다.

• 대한기계학회논문집B
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• 제21권3호
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• pp.414-426
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• 1997

Numerical computations were conducted to characterize the three-dimensional laminar flow through an injector orifice having an inclined angle of 30 .deg.. For this study, the incompressible Navier-Stokes equations in generalized curvilinear coordinates, using a pseudocompressibility approach for continuity equation, were solved. The computations were performed using the finite difference implicit, approximately factored scheme of Beam and Warming and multi-block grids of complete continuity at block interfaces. The multi-block computations were validated for the steady state using direct comparison of multi-block solutions with equivalent single-block ones, including 2-D 180.deg. TAD and 3-D 90.deg. pipe bend. The comparisons between the numerical solutions and the flow field measurements for a tube with sudden contraction were presented in this work for solution validation. Computational results showed the nature of complex flow fields within the inclined injector orifice, including strong pressure-driven secondary flows in the cross stream induced by the effect of streamline curvature. In addition, asymmetric secondary flows were induced in the Reynolds number range above assumed laminar flow regime considered. However, turbulence calculations and grid dependency studies are needed for more accurate computations.

• 소성∙가공
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• 제26권1호
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• pp.28-34
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• 2017

Multi-pass shape rolling is performed to produce long products of arbitrary cross-sectional shapes. In the past, the multi-pass shape rolling process has been designed by the trial and error method or the experience of experts based on the empirical approach. Particularly, the design of roll caliber in shape rolling is important to improve product quality and dimensional accuracy. In this paper, the caliber design and pass schedule of multi-pass shape rolling were proposed for manufacturing piston ring wire. In order to design roll caliber, major shape parameter and dimension was determined by analysis of various caliber design. FE-simulation was conducted to verify effectiveness of proposed process design. At first, forming simulation was performed to predict shape of the product. Then, fracture of the wire was evaluated by critical damage value using normalized Cockcroft-Latham criteria. The experiment was carried out and the results are within the allowable tolerance.