• Spatial Information Research
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• 제22권1호
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• pp.35-43
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• 2014

본 연구에서는 세계측지계 변환에 있어서 삼각형 와핑을 이용한 변환방법을 제시하였다. 삼각형 와핑에 의한 좌표변환방법과 기존의 국가좌표변환계수에 의한 좌표변환방법을 비교하기 위하여 의왕시의 공통점을 활용하여 정확도를 분석하였고, 그 결과 적은 수의 공통점을 이용하고 왜곡량 보정 없이 1/1,000이상 축척의 평면 위치 정확도 기준에 만족하는 결과를 확보하였다. 또한 세계측지계로 변환 작업을 마무리한 구리시, 평택시에 대해서도 본 방법을 적용한 결과 5cm 이내의 평면위치 정확도가 계산되었다. 본 연구에서 제안된 방법은 1/1,000이상의 대축척 지리정보를 세계측지계로 변환하는 과정에서 정확도를 확보하기 위하여 지역별로 많은 공통점을 확보해야하는 문제점을 개선하고, 변환계수를 적용하는 과정에서 서로 인접하는 경계지역에서 불일치되는 오류의 발생 가능성이 최소화됨을 확인하였다. 따라서 대축척의 지형도, 지적도, GIS DB와 연속지적도에 대한 세계측지계 좌표변환을 수행하는데 있어 삼각형 와핑에 의한 좌표변환 방법을 사용함으로서 공통점 사용을 최소화할 수 있었으며, 이를 통해 경제성과 정확성을 확보할 수 있을 것으로 판단된다.

• 대한기계학회논문집
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• 제15권1호
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• pp.218-228
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• 1991

Since heat exchangers are composed of bank of tubes, the knowledge on the flow and heat transfer characteristics of the tube bank are required for the optimum design and selection of heat exchangers. In this paper, the turbulent flow fields and heat transfers normal to a staggered tube bank are solved numerically employing K-.epsilon. 2 equation turbulence model and non-orthogonal coordinate transformation for the treatment of curved surface of tubes. Predicted mean Nusselt numbers of tube bank agree reasonably well with Grimision's correlation

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 춘계학술발표대회 논문집
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• pp.57-60
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• 2002

The stiffness model has been proposed to predict elastic constants of twisted yarn composites. The model is based upon the unit cell structure, the coordinate transformation, and the volume averaging of compliance constants for constituent materials. For the correlation of analytic results with experiments, composite samples of various yarn twist angle were tested. The samples were fabricated by the RTM process using glass yarns and epoxy resin. The correlations of elastic constants showed relatively good agreements. The model provides the predictions of the three-dimensional engineering constants, which are valuable input data for the analytic characterization of textile composites made of twisted yarn.

• 대한기계학회논문집
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• 제19권1호
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• pp.271-276
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• 1995

This paper presents a systematic method for the dynamic analysis of flexible mechanical systems containing closed kinematic loops. Kinematics between pairs of contiguous flexible bodies is described with the joint coordinates and the deformation modal coordinates. The cut-joint constraint equations associated with the closed kinematic loops are derived, simply using the geometric conditions. The equations of motions are initially written in terms of the joint and modal coordinates using the velocity transformation technique. Lagrange multipliers associated with the cut-joint constraints for closed-loop systems are then eliminated systematically using the generalized coordinate partitioning method, resulting to a minimal set of equations of motion.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.1017-1021
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• 1995

Geometric and thermal errors are responsible for major components of the errors of a computer numerically controlled turning center. The planar error of a CNC turning center are comprised of 11 geometric and thermal error components. The error synthesis model is formulated by homogeneous coordinate transformation method and expresses the effect of such error components on the planar error of a CNC turning center. In this paper, the sensitivity analysis of the model on the noises through sensing and the change of temperature is addressed. The sensitivity analysis show that the error systhesis model is robust on the noses and z planar error is much affected by the change of temperatures.

• 대한기계학회논문집A
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• 제21권11호
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• pp.1757-1764
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• 1997

The geometric and elastic models based on the unit cell have been proposed to predict the geometric characteristics and the engineering constants of plain and satin woven composites. In the geometric model, length and inclined angle of the yarn crimp and the fiber volume fraction of woven composites have been predicted. In the elastic model, the coordinate transformation has been utilized to transform the elastic constants of the yarn crimp to those of woven composites, and the effective elastic constants have been determined from the volume averaging of the constituent materials. Good correlations between the model predictions and the experimental results of carbon/epoxy and glass/epoxy woven composites have been observed. Based on the model, the effect of various geometric parameters and materials on the three-dimensional elastic properties of woven composites can be identified.

• International Journal of Aeronautical and Space Sciences
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• 제4권2호
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• pp.26-36
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• 2003

The objective of this study is to enhance neural-network guidance to consider the impact condition. The optimal impact condition in this study is defined as an head-on attack. Missile impact-angle error, which is a measure of the degree to which the missile is not steering for a head-on attack, can also have an influence on the final miss distance. Therefore midcourse guidance is used to navigate the missile, reducing the deviation angle from head on, given some constraints on the missile g performance. A coordinate transformation is introduced to simplify the three-dimensional guidance law and, consequently, to reduce training data. Computer simulation results show that the neural-network guidance law with the coordinate transformation reduces impact-angle errors effectively.

• 대한전기학회논문지:시스템및제어부문D
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• 제49권7호
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• pp.370-377
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• 2000

This paper presents a decentralized compensator design procedure for large scale systems. By using a coordinate transformation method, interconnection terms in t도 subsystem are decoupled and a decentralized observer is designed independently as a form of Luenberger-type for each subsystem. And the decentralized compensator which can select the observer and controller gain independently is designed as a form of observer based controller for each subsystem. The proposed method has a simplicity and conciseness in the aspects of the determination of coordinate transformation matrices and the derivation of the separation principle which is adopted independently for each subsystem.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.740-745
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• 2003

The so-called boundary node method (or NDIF method) that was developed by the authors has been extended for free vibration analysis of arbitrarily shaped plates with free edges. Since the proposed method is based on the collocation method, no integration procedure is needed on boundary edges of the plates and only a small amount of numerical calculation is required. A special coordinate transformation has been devised to consider the complicated free boundary conditions at boundary nodes. By the use of the special coordinate transformation, the radius of curvature involved in the free boundary conditions can be successfully dealt with. Finally, verification examples show that natural frequencies obtained by the present method agree well with those given by exact method and other analytical methods.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.523-526
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• 2000

This paper performs the motion analysis for a disk cam and a follower mechanism using a circular arc method, a coordinate transformation method and an instant velocity method in order to find a contact point between the cam and the follower. Based on the proposed method, the displacement and the velocity are calculated by using the geometric relationships of the cam mechanism. Also, the acceleration is determined on using the central difference method. As the results, this paper presents the original curve and the analyzed curve for the motion analysis of the disk cam for an example.