• Journal of applied mathematics & informatics
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• 제23권1_2호
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• pp.397-410
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• 2007

Visualization of 2D and 3D data, which arises from some scientific phenomena, physical model or mathematical formula, in the form of curve or surface view is one of the important topics in Computer Graphics. The problem gets critically important when data possesses some inherent shape feature. For example, it may have positive feature in one instance and monotone in the other. This paper is concerned with the solution of similar problems when data has convex shape and its visualization is required to have similar inherent features to that of data. A rational cubic function [5] has been used for the review of visualization of 2D data. After that it has been generalized for the visualization of 3D data. Moreover, simple sufficient constraints are made on the free parameters in the description of rational bicubic functions to visualize the 3D convex data in the view of convex surfaces.

• 한국지리정보학회지
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• 제12권1호
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• pp.106-118
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• 2009

1m급 전후의 고해상도 위성영상들이 지구관측 및 모니터링으로부터 국토의 디지털 지도제작에 이르기까지 폭넓게 활용되고 있다. IKONOS 영상의 경우 Pro와 Precision 제품은 상당히 고가이므로 정확한 지도를 제작하는데 저가의 Geo제품과 영상공급자에 의해 제공된 RPC계수를 이용하는 것은 바람직하다. IKONOS 고해상도 영상은 엄밀한 센서모델 대신 RF에 의해 설명되어진다. 본 연구에서는 RF 모델을 기반으로 추출되는 지상좌표의 정확도를 개선하기 위하여 대상물공간과 상공간에서 각각 정의된 4개의 모델, 즉 선형이동 모델, 축척 및 선형이동 모델, Affine 모델, 2차 다항식 모델을 제시하였다. RF 모델을 기반으로 한 지상좌표 산출 알고리즘과 산출된 지상좌표의 정확도 개선 알고리즘을 개발하고 실험을 통하여 다항식 보정모델별 개선효과를 분석하였다. 또한 지상기준점의 수와 배치유형, 측량의 정확도와 같은 여러 가지 지도제작 매개변수들이 지상좌표의 정확도에 미치는 효과를 평가하였다. 적용실험 결과, RF 모델에 의해 1차적으로 산출된 3차원 지상좌표의 RMSE는 X 방향에서 8.035m, Y 방향에서 10.020m, Z 방향에서 13.318m이었으나 다항식 보정 알고리즘을 통하여 X 방향 2.791m, Y 방향 2.520m, Z 방향 1.441m까지 RMSE를 낮춤으로써 수평위치에서 약 65%, 수직방향에서 약 89%까지 정확도를 크게 개선할 수 있었다.

• ETRI Journal
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• 제33권4호
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• pp.537-546
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• 2011

This paper introduces an automated method for building height recovery through the integration of high-resolution satellite images and digital vector maps. A cross-correlation matching method along the vertical line locus on the Ikonos images was deployed to recover building heights. The rational function models composed of rational polynomial coefficients were utilized to create a stereopair of the epipolar resampled Ikonos images. Building footprints from the digital maps were used for locating the vertical guideline along the building edges. The digital terrain model (DTM) was generated from the contour layer in the digital maps. The terrain height derived from the DTM at each foot of the buildings was used as the starting location for image matching. At a preset incremental value of height along the vertical guidelines derived from vertical line loci, an evaluation process that is based on the cross-correlation matching of the images was carried out to test if the top of the building has reached where maximum correlation occurs. The accuracy of the reconstructed buildings was evaluated by the comparison with manually digitized 3D building data derived from aerial photographs.

• Structural Engineering and Mechanics
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• 제46권4호
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• pp.549-569
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• 2013

A passive control using flaps will be an alternative solution for flutter stability and buffeting response of a long suspension bridge. This method not only enables a lightweight economic stiffening girder without an additional stiffness for aerodynamic stability but also avoid the problems from the malfunctions of control systems and energy supply system of an active control by winglets and flaps. A time domain approach for predicting the coupled flutter and buffeting response of bridge deck with flaps is investigated. First, the flutter derivatives of bridge deck and flaps are found by experiment. Next, the derivation of time domain model of self-excited forces and control forces of sectional model is reported by using the rational function approximation. Finally, the effectiveness of passive flap control is investigated by the numerical simulation. The results show that the passive control by using flaps can increase the flutter speed and decrease the buffeting response. The experiment results are matched with numerical ones.

• 대한토목학회논문집
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• 제32권1D호
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• pp.89-94
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• 2012

범용센서모델의 한 종류인 비례다항식 모델(RFM: Rational Function Model)은 광학영상의 센서모델링분야에서 활발히 활용되고 있으나 SAR영상에 대한 적용은 미진한 실정이다. 본 연구에서는 스테레오 TerraSAR-X영상을 대상으로 RF 모델링을 적용하여 적용방법의 타당성과 효율성에 대해 분석하였다. 또한 본 연구성과의 DSM(Digital Surface Model)과 기존 상용 소프트웨어에서 생성된 DSM을 다양한 측면에서 비교 분석하였다. 그 결과 RF 모델링 기법이 SAR영상의 적용 시에도 매우 효과적이며 실용적으로 적용 가능함을 알 수 있었다.

• 국제학술발표논문집
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• The 6th International Conference on Construction Engineering and Project Management
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• pp.620-621
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• 2015

In this study, the multi-criteria decision-making model based on Quality Function Deployment Method is proposed. Multicriteria decision-making is an attempt to link QFD method with the TOPSIS. By this effort, a model that makes client's decision-making more rational and objective in design phase is suggested. The multi-criteria decisionmaking model confirming to the Owner's requirements will improve the productivity of the construction industry and the satisfaction of the customer. Further study extending the range of the requirements, not only the Owner's requirement will be necessary to cover the various factors as much as possible. And then, finally as a flexible platform to achieve a sustainable quality management, web-based multi-criteria decision-making model can be utilized by the relevant stakeholders simultaneously with the feed-back and sharing the necessary informations.

• Wind and Structures
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• 제9권2호
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• pp.159-178
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• 2006

For the slender and flexible cable supported bridges, identification of all the flutter derivatives for the vertical, lateral and torsional motions is essential for its stability investigation. In all, eighteen flutter derivatives may have to be considered, the identification of which using a three degree-of-freedom elastic suspension system has been a challenging task. In this paper, a system identification technique, known as covariance-driven stochastic subspace identification (COV-SSI) technique, has been utilized to extract the flutter derivatives for a typical bridge deck. This method identifies the stochastic state-space model from the covariances of the output-only (stochastic) data. All the eighteen flutter derivatives have been simultaneously extracted from the output response data obtained from wind tunnel test on a 3-DOF elastically suspended bridge deck section-model. Simplicity in model suspension and measurements of only output responses are additional motivating factors for adopting COV-SSI technique. The identified discrete values of flutter derivatives have been approximated by rational functions.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.287-292
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• 2005

This paper presents a rational polynomial approximation method to estimate modal parameters of wind excited structures using incomplete noisy measurements of structural responses and partial measurements of wind velocities only. A stochastic model of the excitation wind force acting on the structure is estimated from partial measurements of wind velocities. Then the transfer functions of the structure are approximated as rational polynomial functions. From the poles and zeros of the estimated rational polynomial functions, the modal parameters, such as natural frequencies, damping ratios, and mode shapes are extracted. Since the frequency characteristics of wind forces acting on structures can be assumed as a smooth Gaussian process especially around the natural frequencies of the structures according to the central limit theorem (Brillinger, 1969; Yaglom, 1987), the estimated modal parameters are robust and reliable with respect to the assumed stochastic input models. To verify the proposed method, the modal parameters of a TV transmission tower excited by gust wind are estimated. Comparison study with the results of other researchers shows the efficacy of the suggested method.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.1143-1145
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• 2003

Some of satellites such as IKONOS don't provide the orbital elements so that we can’ utilize the physical sensor model. Therefore, Rational Function Model(RFM) which is one of mathematical models could be a feasible solution. In order to improve 3D geopositioning accuracy of IKONOS stereo imagery, Rational Polynomial Coefficients(RPCs) of the RFM need to be updated with Ground Control Points(GCPs). In this paper, a method to improve RPCs of RFM using GCPs and 3D cube is proposed. Firstly, the image coordinates of GCPs are observed. And then, using offset values and scale values of RPC provided, the image coordinates and ground coordinates of 3D cube are initially determined and updated RPCs are computed by the iterative least square method. The proposed method was implemented and analyzed in several cases: different numbers of 3D cube layers and GCPs. The experimental results showed that the proposed method improved the accuracy of RPCs in great amount.

• Wind and Structures
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• 제12권5호
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• pp.457-474
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• 2009

Techniques for stabilising slender bridges under wind loads are presented in this article. A mathematically consistent description of the acting aerodynamic forces is essential when investigating these ideas. Against this background, motion-induced aerodynamic forces are characterised using a linear time-invariant transfer element in terms of rational functions. With the help of these functions, the aeroelastic system can be described in the form of a linear, time-invariant state-space model. It is shown that the divergence wind speed constitutes an upper bound for the application of the selected mechanical actuators. Even active control with full state feedback cannot overcome this limitation. The results are derived and explained with methods of control theory.