• 자원환경지질
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• 제33권1호
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• pp.41-50
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• 2000

Geo-radar survey which has the advantage of high-resolution and relatively fast survey has been widely used for engineering and environmental problems. Three-dimensional effects have to be considered in the interpretation of geo-radar for high-resolution. However, there exists a trouble on the analysis of the three dimensional effects. To solve this problem an efficient three dimension numerical modeling algorithm is needed. Numerical radar modeling in three dimensional case requires large memory and long calculating time. In this paper, a finite difference method time domain solution to Maxwell's equations for simulating electromagnetic wave propagation in three dimensional media was developed to make economic algorithm which requires smaller memory and shorter calculating time. And in using boundary condition Liao absorption boundary. The numerical result of cross-hole radar survey for tunnel is compared with real data. The two results are well matched. To prove application to three dimensional analysis, the results with variation of tunnel's incident angle to survey cross-section and the result when the tunnel is parallel to the cross-section were examined. This algorithm is useful in various geo-radar survey and can give basic data to develop dat processing and inversion program.

• ETRI Journal
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• 제42권6호
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• pp.815-826
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• 2020

We propose a two-dimensional (2D) scattering-center-extraction (SCE) method using sparse recovery based on the compressive-sensing theory, even with data missing from the received radar cross-section (RCS) dataset. First, using the proposed method, we generate a 2D grid via adaptive discretization that has a considerably smaller size than a fully sampled fine grid. Subsequently, the coarse estimation of 2D scattering centers is performed using both the method of iteratively reweighted least square and a general peak-finding algorithm. Finally, the fine estimation of 2D scattering centers is performed using the orthogonal matching pursuit (OMP) procedure from an adaptively sampled Fourier dictionary. The measured RCS data, as well as simulation data using the point-scatterer model, are used to evaluate the 2D SCE accuracy of the proposed method. The results indicate that the proposed method can achieve higher SCE accuracy for an incomplete RCS dataset with missing data than that achieved by the conventional OMP, basis pursuit, smoothed L0, and existing discrete spectral estimation techniques.

• 한국지리정보학회지
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• 제12권4호
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• pp.95-112
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• 2009

하천의 흐름해석 분야에서 모형이 요구하는 입력자료 중 하천단면은 매우 중요한 요소이다. 수치모형을 이용해서 자연하천의 2차원 흐름을 모의하고자 할 때 정확한 계산치를 얻기 위해서는 실제 하천단면의 하상을 정확하게 반영하여야 한다. 그러나 하천단면의 하상을 실제 상태의 모습 그대로 반영하는 것은 거의 불가능하다. 본 연구에서는 현재 실무에서 사용하는 하천측량 자료인 HEC단면과 ArcView를 연계하여 등간격 하도단면을 생성하고 유한요소망을 구축하는 방법을 제안하였다. 연구 대상지역은 한강 본류 구간과 낙동강 본류 구간을 선정하였고 등간격 하도단면 구축결과 실측 단면자료와 잘 일치함을 확인할 수 있었다. 또한 본 연구에서 제안한 등간격 하도단면을 이용하면 2차원 흐름해석 및 수질해석을 위한 양질의 유한요소망을 구축하여 유한요소해석 등에 유용하게 사용될 수 있을 것이다.

• Journal of Mechanical Science and Technology
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• 제19권11호
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• pp.2016-2024
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• 2005

In this work, a mixed beam approach that combines both the stiffness and the flexibility methods has been performed to analyze the coupled composite blades with closed, two-cell cross-sections. The Reissner's semi-complementary energy functional is used to derive the beam force-displacement relations. Only the membrane part of the shell wall is taken into account to make the analysis simple and also to deliver a clear picture of the mixed method. All the cross section stiffness coefficients as well as the distribution of shear across the section are evaluated in a closed-form through the beam formulation. The theory is validated against experimental test data, detailed finite element analysis results, and other analytical results for coupled composite blades with a two-cell airfoil section. Despite the simple kinematic model adopted in the theory, an accuracy comparable to that of two-dimensional finite element analysis has been obtained for cases considered in this study.

• Architectural research
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• 제13권4호
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• pp.53-60
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• 2011

Damage detection algorithms based on a one-dimensional beam model can detect damage within a beam span caused by flexure only but cannot detect damage at a joint with prescribed boundary conditions or at the middle part of a beam section where the neutral axis is located. Considering the damage at a welded joint of beam elements in steel structures and modeling the damage with twodimensional plane elements, this study presents a new approach to detecting damage in the depth direction of the joint and beam section. Three damage scenarios at the upper, middle, and lower parts of a welded joint of a rectangular symmetric section are investigated. The damage is detected by evaluating the difference in the receptance magnitude between the undamaged and damaged states. This study also investigates the effect of measurement locations and noise on the capability of the method in detecting damage. The numerical results show the validity of the proposed method in detecting damage at the beam's welded joint.

• 한국정밀공학회지
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• 제14권9호
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• pp.101-107
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• 1997

A sectional analysis of auto-body panel stamping is carried out by using the rigid-plastic FEM based on the membrane theory. The auto-body panel material is assumed to possess normal anisotropy and to obey Hill's new yield criterion and its associated flow rule. A method of contact treatment is proposed in which the skew boundary condition for arbitarily shaped tools is successively used during iteration. Deformation of each section of trunk-lid panel is simulated and composed to get the three-dimensional shape by using CAD technique. It was shown that the composition of the two-dimensional section analysis gives almost the same results as the full three-dimensional analysis.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.221-224
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• 2006

For structural engineers, design of pile cap causes difficulties since design of this member is not specifically addressed by codes. In general, pile cap is considered as deep beam and designed for shear and moment at specified critical section. This is called as traditional section method. However, many international design codes suggest the application of strut tie method for better design of this member. In this paper, a brief application of strut tie method to the design check of pile cap structure designed by section method is presented. Unlike well known pile cap with single column, the example pile cap has two columns. In order to find out proper load path under various load condition, three dimensional finite element method was carried out. The result indicates that provided reinforcement by traditional section method has sufficient capacity to meet the design requirements.

• Wind and Structures
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• 제10권5호
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• pp.421-435
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• 2007

A two-dimensional flutter analysis method (2d-3DOF method) was developed to simultaneously investigate the relationship between oscillation parameters and aerodynamic derivatives of three degrees of freedom, and to clarify the coupling effects of different degrees of freedom in flutter instability. With this method, the flutter mechanism of two typical bridge deck sections, box girder section and two-isolated-girder section, were numerically investigated, and both differences and common ground in these two typical flutter phenomena are summarized. Then the flutter stabilization effect and its mechanism for long-span bridges with box girders by using central-slotting were studied by experimental investigation of aerodynamic stability and theoretical analysis of stabilizing mechanism. Possible explanation of new findings in the evaluation trend of critical wind speed through central vent width is finally presented.

• 한국정밀공학회지
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• 제12권12호
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• pp.38-44
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• 1995

This paper presents a method to measure the position and orientation of a Cylindrical Object(unknown the eiameter and length) lying on a floor, using a camera. The two extreme cross section of the cylinder will be viewed as distorted ellipese or circular are, while its limb edge will be shown as two straight lines. The diameter of the cylinder is determined from the geometric properties of the two straight lines, which in turn provides information regarding the length of the cylinder. From the 3-dimensional measurement, the 3D coordinates of the center points of the two extreme cross sections are determined to give the position and orientation of the cylinder. This method is used for automated pick-and-place operations of cylinder, such as sheet coils, or drums in warehouses.

• 한국의류학회지
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• 제29권11호
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• pp.1399-1409
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• 2005

The purpose of this study was to analyze the shape of gathered skirts using a three-dimensional measurement system. And in this experiment, I try to accumulate three-dimensional data of wearing model and to figure out analyzing method made by shape of clothes. The experimental design consists of two factorial designs. I set up three different kinds of fabrics, ratio of gathers. Therefore nine samples were made. The instrument and tools for three-dimensional measurement was whole body 3D scanner. Analysis program used in experiment is RapidForm 2004 PP1 and Pattern Design 2000. Data analysis utilizes SPSS WIN 10.0 Package. T-test to effect an inspection of evidence, there was difference about measurement times. One-way ANOVA to analysis effect of gather made by gathering conditions. The following results were obtained; 1. As a result of inspecting an error several times using a three-dimension measurement system, convinced data was obtained. 2. At front, distribution of gap amount was larger than back. And as ratio of gathers increased, distribution of gap amount showed regularly. 3. After analyzing horizontal sectional figure of skirts, as a height of skirt changed from waist to the bottom of skirts, the results showed as follows. While section width, section thickness, node width, node depth increased, node count decreased. 4. With the horizontal section levels of gather skirt, the silhouette on middle hip section was similar with the silhouette of body line. And as ratio of gathers around hip section increased, nodes showed regularly. At the bottom of skirts showed different nodes by different gathering condition.