• Title/Summary/Keyword: Geometric Modeling

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Selective Histogram Matching of Multi-temporal High Resolution Satellite Images Considering Shadow Effects in Urban Area (도심지역의 그림자 영향을 고려한 다시기 고해상도 위성영상의 선택적 히스토그램 매칭)

  • Yeom, Jun-Ho;Kim, Yong-Il
    • Journal of Korean Society for Geospatial Information Science
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    • v.20 no.2
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    • pp.47-54
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    • 2012
  • Additional high resolution satellite images, other period or site, are essential for efficient city modeling and analysis. However, the same ground objects have a radiometric inconsistency in different satellite images and it debase the quality of image processing and analysis. Moreover, in an urban area, buildings, trees, bridges, and other artificial objects cause shadow effects, which lower the performance of relative radiometric normalization. Therefore, in this study, we exclude shadow areas and suggest the selective histogram matching methods for image based application without supplementary digital elevation model or geometric informations of sun and sensor. We extract the shadow objects first using adjacency informations with the building edge buffer and spatial and spectral attributes derived from the image segmentation. And, Outlier objects like a asphalt roads are removed. Finally, selective histogram matching is performed from the shadow masked multi-temporal Quickbird-2 images.

Auto-parametric resonance of framed structures under periodic excitations

  • Li, Yuchun;Gou, Hongliang;Zhang, Long;Chang, Chenyu
    • Structural Engineering and Mechanics
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    • v.61 no.4
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    • pp.497-510
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    • 2017
  • A framed structure may be composed of two sub-structures, which are linked by a hinged joint. One sub-structure is the primary system and the other is the secondary system. The primary system, which is subjected to the periodic external load, can give rise to an auto-parametric resonance of the second system. Considering the geometric-stiffness effect produced by the axially internal force, the element equation of motion is derived by the extended Hamilton's principle. The element equations are then assembled into the global non-homogeneous Mathieu-Hill equations. The Newmark's method is introduced to solve the time-history responses of the non-homogeneous Mathieu-Hill equations. The energy-growth exponent/coefficient (EGE/EGC) and a finite-time Lyapunov exponent (FLE) are proposed for determining the auto-parametric instability boundaries of the structural system. The auto-parametric instabilities are numerically analyzed for the two frames. The influence of relative stiffness between the primary and secondary systems on the auto-parametric instability boundaries is investigated. A phenomenon of the "auto-parametric internal resonance" (the auto-parametric resonance of the second system induced by a normal resonance of the primary system) is predicted through the two numerical examples. The risk of auto-parametric internal resonance is emphasized. An auto-parametric resonance experiment of a ${\Gamma}$-shaped frame is conducted for verifying the theoretical predictions and present calculation method.

Genetic Algorithm-based Generative Design for Creative Ring Design (독창적 반지 설계를 위한 유전자 알고리즘 기반의 변환생성 디자인)

  • Kim, Ko Uh;Kang, Sol Ji;Jee, Sang Hyeon;Lee, Seung Bok;Lee, Keon Myung
    • Journal of the Korean Institute of Intelligent Systems
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    • v.24 no.3
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    • pp.233-238
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    • 2014
  • Creativity is crucial in designing and producing attractive accessaries and daily supplies as well as art works. Generative design can be a paradigm to be used to obtain novel ideas or motifs for creative design works. This paper introduces a generative design method which comes up with unique ring models using genetic algorithm. It presents how the genetic algorithm works in terms of candidate solution coding, operators, and fitness evaluation function. The proposed method allows the customers to express their personal preference and later the preference to be reflected in fitness evaluation. In the final stage of the proposed method, several ring models are suggested for customers to choose on their own. The chosen ring models can be put into physical rings with the help of a 3D printer because the models are expressed in 3D geometric structures.

Analysis of Performance of Focused Beamformer Using Water Pulley Model Array (수차 모형 배열을 이용한 표적추정 (Focused) 빔형성기 성능분석)

  • 최주평;이원철
    • The Journal of the Acoustical Society of Korea
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    • v.20 no.5
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    • pp.83-91
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    • 2001
  • This paper proposes the Focused beamforming to estimate the location of target residing near to the observation platform in the underwater environment. The Focused beamforming technique provides the location of target by the coherent summation of a series of incident spherical waveforms considering distinct propagation delay times at the sensor array. But due to the movement of the observation platform and the variation of the underwater environment, the shape of the sensor array is no longer to be linear but it becomes distorted as the platform moves. Thus the Focused beamforming should be peformed regarding to the geometric shape variation at each time. To estimate the target location, the artificial image plane comprised of cells is constructed, and the delays are calculated from each cell where the target could be proximity to sensors for the coherent summation. After the coherent combining, the beam pattern can be obtained through the Focused beamforming on the image plane. Futhermore to compensate the variation of the shape of the sensor array, the paper utilizes the Nth-order polynomial approximation to estimate the shape of the sensor array obeying the water pulley modeling. Simulation results show the performance of the Focused beamforming for different frequency bands of the radiated signal.

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Modeling and Simulation of Aircraft Motion for Performance Assessment of Airborne AESA Radar Considering Wind and Vibration (바람과 진동을 고려한 항공기 탑재 AESA 레이다 성능 평가용 운동 모델링 및 시뮬레이션)

  • Lee, Donguk;Im, Jaehan;Lee, Haemin;Jung, Youngkwang;Jeong, Jaehyeon;Shin, Jong-Hwan;Lee, Sungwon;Park, June Hyune;Ahn, Jaemyung
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.48 no.11
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    • pp.903-910
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    • 2020
  • This paper introduces a simulator to assess the impacts of the wind and the airframe vibration on the performance of the Active Electronically Scanned Array (AESA) radar mounted in an aircraft. The AESA radar is mounted on the nose cone of an aircraft, and vibration occurs due to the drag force. This vibration affects the behavior of the AESA radar and can cause phase errors in signal. The simulator adopts the geometric model for nose cone, the mathematical models on the rigid-body dynamics of the aircraft, the average/turbulent winds, and the mode/ambient vibrations to compute the position and the attitude of the radar accurately. Numerical studies reflecting a set of test scenarios were conducted to demonstrate the effectiveness of the developed simulator.

An efficient multipath propagation prediction using improved vector representation (효율적 다중경로 전파 예측을 위한 Ray-Tracing의 개선된 벡터 표현법)

  • 이상호;강선미;고한석
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.24 no.12A
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    • pp.1974-1984
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    • 1999
  • In this paper, we introduce a highly efficient data structure that effectively captures the multipath phenomenon needed for accurate propagation modeling and fast propagation prediction. The proposed object representation procedure is called 'circular representation (CR)' of microwave masking objects such as buildings, to improve over the conventional vector representation (VR) form in fast ray tracing. The proposed CR encapsulates a building with a circle represented by a center point and radius. In this configuration, the CR essentially functions as the basic building block for higher geometric structures, enhancing the efficiency more than when VR is used alone. The simulation results indicate that the proposed CR scheme reduces the computational load proportionally to the number of potential scattering objects while its hierarchical structure achieves about 50% of computational load reduction in the hierarchical octree structure.

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A Development of NURBS-Based Pre and Post Processor for Structural Analysis of Free-Shaped Beam (자유형상 보요소 해석을 위한 NURBS기반의 전·후처리 모듈 개발)

  • Jung, Sung-Jin;Park, Se-Hee
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.16 no.10
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    • pp.6673-6678
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    • 2015
  • Recently, the free form buildings are constructed frequently. Exterior and interior components of these buildings have the free cross-section and a curved shape. So, There are many usages of classical finite element having tapered section and free-style shape. Some general commercial applications like ETABS, SAP2000, MIDAS are usually used for the safety evaluation of the free form structures. However, there are some limits in the accuracy of structural analysis and the length of analysis time because a very complicated finite element mesh have to be used. Therefore, In this study, a pre and post program module was developed to take advantage of general 3-D curved beam element which has a free-style curved shape and mathematical backgrounds. Pre-post processing module has been developed in this study was developed to control the curvature of the curved members by the NURBS control points. As a result, fast geometric modeling than was possible commercial applications. In addition, realistic depiction of the shape and behavior patterns were possible because of the free-form building allows visual check of the free form.

3D Analysis of Crack Growth in Metal Using Tension Tests and XFEM (인장 실험과 XFEM을 이용한 금속 균열 성장의 3 차원적 분석)

  • Lee, Sunghyun;Jeon, Insu
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.38 no.4
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    • pp.409-417
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    • 2014
  • To prevent the occurrence of fractures in metal structures, it is very important to evaluate the 3D crack growth process in those structures and any related parts. In this study, tension tests and two simulations, namely, Simulation-I and Simulation-II, were performed using XFEM to evaluate crack growth in three dimensions. In the tension test, Mode I crack growth was observed for a notched metal specimen. In Simulation-I, a 3D reconstructed model of the specimen was created using CT images of the specimen. Using this model, an FE model was constructed, and crack growth was simulated using XFEM. In Simulation-II, an ideal notch FE model of the same geometric size as the actual specimen was created and then used for simulation. Obtained crack growth simulation results were then compared. Crack growth in the metal specimen was evaluated in three dimensions. It was shown that modeling the real shape of a structure with a crack may be essential for accurately evaluating 3D crack growth.

A four variable trigonometric integral plate theory for hygro-thermo-mechanical bending analysis of AFG ceramic-metal plates resting on a two-parameter elastic foundation

  • Tounsi, Abdelouahed;Al-Dulaijan, S.U.;Al-Osta, Mohammed A.;Chikh, Abdelbaki;Al-Zahrani, M.M.;Sharif, Alfarabi;Tounsi, Abdeldjebbar
    • Steel and Composite Structures
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    • v.34 no.4
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    • pp.511-524
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    • 2020
  • In this research, a simple four-variable trigonometric integral shear deformation model is proposed for the static behavior of advanced functionally graded (AFG) ceramic-metal plates supported by a two-parameter elastic foundation and subjected to a nonlinear hygro-thermo-mechanical load. The elastic properties, including both the thermal expansion and moisture coefficients of the plate, are also supposed to be varied within thickness direction by following a power law distribution in terms of volume fractions of the components of the material. The interest of the current theory is seen in its kinematics that use only four independent unknowns, while first-order plate theory and other higher-order plate theories require at least five unknowns. The "in-plane displacement field" of the proposed theory utilizes cosine functions in terms of thickness coordinates to calculate out-of-plane shear deformations. The vertical displacement includes flexural and shear components. The elastic foundation is introduced in mathematical modeling as a two-parameter Winkler-Pasternak foundation. The virtual displacement principle is applied to obtain the basic equations and a Navier solution technique is used to determine an analytical solution. The numerical results predicted by the proposed formulation are compared with results already published in the literature to demonstrate the accuracy and efficiency of the proposed theory. The influences of "moisture concentration", temperature, stiffness of foundation, shear deformation, geometric ratios and volume fraction variation on the mechanical behavior of AFG plates are examined and discussed in detail.

Gravity and Magnetic Model Study of Block Ⅵ-2, Offshore Korea (한국근해 제 6광구에 대한 중력 및 자력 모델 연구)

  • Baag Czango;Baag Chang-Eob
    • The Korean Journal of Petroleum Geology
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    • v.1 no.1 s.1
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    • pp.37-46
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    • 1993
  • Two-dimensional gravity and magnetic models were constructed for seismic profiles in Block Ⅵ-2, offshore Korea. For each seismic profile, a longer length model showing geometric configurations of all employed polygonal bodies and an expanded version of the area of interests were made. The results of this modeling study indicate 1) that the depth to the deeper basement surface appear to be shallower than indicated in the seismic sections, 2) that the Middle Miocene section (the bottom formations in the models) appears to contain significant amounts of volcanic materials, 3) that identification and/or determination of depth to the top of basement is difficult in the study area due to thick volcanic materials in the lowermost formation (Middle Miocene), and 4) that the study area is unfavorable for hydrocarbon generation and accumulation due to wide spread volcanic activities during the Middle Miocene Epoch. The maximum calculated depth to the magnetic basement in the study area is approximately $4{\cal}km$ sub-sea.

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