• Title/Summary/Keyword: geometric transformation

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The Effects of Cooperative Learning on Children's Understanding of Geometry (협동학습활동이 유아 기하 학습에 미치는 영향)

  • Kwon, Young-Re;Lee, Kyung-Jin;Shin, Ok-Ja
    • Korean Journal of Child Studies
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    • v.32 no.2
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    • pp.71-85
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    • 2011
  • This study was carried out in order to better understand how cooperative learning effects the geometric understanding of young children. The geometry tasks used in the study included the geometric relationship between two dimensional shapes and three dimensional shapes, coordination, symmetry and transformation visualization and spacial reasoning. The subjects were composed of children aged five years and were taken from two kindergartens in a relatively new city close to Seoul. The experimental group of children the comparative learning in geometry. The comparative group of children were enrolled in a kindergarten that uses an the intergrated curriculum. The results indicated that cooperative learning impacted positively on the children's understanding of geometry. The specific results are as follows : The scores that the experimental acquired were higher in terms of p < .001 level. than the scores of the comparative group studying the geometric relationships between two dimensional shapes and three dimensional shapes, coordination, symmetry and transformation visualization & spacial reasoning.

Planar Error Sensitivity Analysis in a CNC Turning Cen (2차원 CNC 선반에서 평면오차 민감도 분석)

  • 여규환;이진현;양승한
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1995.10a
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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.

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Generation of 2-D Parametric Surfaces with Highly Irregular Boundaries

  • Sarkar, Subhajit;Dey, Partha Pratim
    • International Journal of CAD/CAM
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    • v.8 no.1
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    • pp.11-20
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    • 2009
  • The conventional methods of boundary-conformed 2D surfaces generation usually yield some problems. This paper deals with two boundary-conformed 2D surface generation methods, one conventional approach, the linear Coons method, and a new method, boundary-conformed interpolation. In this new method, unidirectional 2D surface has been generated using some of the geometric properties of the given boundary curves. A method of simultaneous displacement of the interpolated curves from the opposite boundaries has been adopted. The geometric properties considered for displacements include weighted combination of angle bisector and linear displacement vectors at all the data-points of the two opposite generating curves. The algorithm has one adjustable parameter that controls the characteristics of transformation of one set of curves from its parents. This unidirectional process has been extended to bi-directional parameterization by superimposing two sets of unidirectional curves generated from both boundary pairs. Case studies show that this algorithm gives reasonably smooth transformation of the boundaries. This algorithm is more robust than the linear Coons method and capable of resolving the 2D boundary-conformed parameterization problems.

Digital Watermarking Scheme based on SVD and Triplet (SVD 및 트리플릿 기반의 디지털 워터마킹 기법)

  • Park, Byung-Su;Chu, Hyung-Suk;An, Chong-Koo
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.58 no.5
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    • pp.1041-1046
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    • 2009
  • In this paper, we proposed a robust watermark scheme for image based on SVD(Singular Value Transform) and Triplet. First, the original image is decomposed by using 3-level DWT, and then used the singular values changed for embedding and extracting of the watermark sequence in LL3 band. Since the matrix of singular values is not easily altered with various signal processing noises, the embedded watermark sequence has the ability to withstand various signal processing noise attacks. Nevertheless, this method does not guarantee geometric transformation(such as rotation, cropping, etc.) because the geometric transformation changes the matrix size. In this case, the watermark sequence cannot be extracted. To compensate for the above weaknesses, a method which uses the triplet for embedding a barcode image watermark in the middle of frequency band is proposed. In order to generate the barcode image watermark, the pattern of the watermark sequence embedded in a LL3 band is used. According to this method, the watermark information can be extracted from attacked images.

Sensitivity Analysis and Confidence Evaluation for Planar Errors of a Vertical Turning Center (수직형 선반의 평면 오차 민감도 분석 및 신뢰도 평가)

  • 여규환;양승환
    • Journal of the Korean Society for Precision Engineering
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    • v.15 no.11
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    • pp.67-75
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    • 1998
  • Geometric and thermal errors are key contributors to the errors of a computer numerically controlled turning center. A planar error synthesis model is obtained by synthesizing 11 geometric and thermal error components of a turning center with homogeneous coordinate transformation method. This paper shows the sensitivity analysis on the temperature change, the confidence evaluation on the uncertainty Of measurement systems, and the error contribution analysis from the planar error synthesis model. Planar error in the z direction was very sensitive to the temperature change. and planar errors in the x and z directions were not affected by the uncertainty of measurement systems. The error contribution analysis ,which is applicable to designing a new turning center, was helpful to find the large error components which affect planar errors of the turning center.

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Measurement Error Modeling for On-Machine Measurement of Sculptured Surfaces

  • Cho, Myeong-Woo;Lee, Se-Hee;Seo, Tae-Il
    • International Journal of Precision Engineering and Manufacturing
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    • v.2 no.2
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    • pp.73-80
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    • 2001
  • The objective of this research is to develop a measurement error model for sculptured surface in On-Machine Measurement(OMM) process based on a closed-loop configuration. The geometric error model of each axis of a vertical CNC machining center is derived using a 4$\times$4 homogeneous transformation matrix. The ideal locations of a touch-type probe for the sculptured surface measurement are calculated from the parametric surface representation and X-, Y- directional geometric errors of the machine. Also the actual coordinates of the probe are calculated by considering the pre-travel variation of a probe and Z-directional geometric errors. Then, the step-by-sep measurement error analysis method is suggested based on a closed-loop configuration of the machining center including workpiece and probe errors. The simulation study shows the simplicity and effectiveness of the proposed error modeling strategy.

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Three Dimensional Geometric Feature Detection Using Computer Vision System and Laser Structured Light (컴퓨터 시각과 레이저 구조광을 이용한 물체의 3차원 정보 추출)

  • Hwang, H.;Chang, Y.C.;Im, D.H.
    • Journal of Biosystems Engineering
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    • v.23 no.4
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    • pp.381-390
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    • 1998
  • An algorithm to extract the 3-D geometric information of a static object was developed using a set of 2-D computer vision system and a laser structured lighting device. As a structured light pattern, multi-parallel lines were used in the study. The proposed algorithm was composed of three stages. The camera calibration, which determined a coordinate transformation between the image plane and the real 3-D world, was performed using known 6 pairs of points at the first stage. Then, utilizing the shifting phenomena of the projected laser beam on an object, the height of the object was computed at the second stage. Finally, using the height information of the 2-D image point, the corresponding 3-D information was computed using results of the camera calibration. For arbitrary geometric objects, the maximum error of the extracted 3-D feature using the proposed algorithm was less than 1~2mm. The results showed that the proposed algorithm was accurate for 3-D geometric feature detection of an object.

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Geometric Correction of Mouth Based Key Points of Lips (입술 특징점에 기반한 입의 기하학적 왜곡 보정)

  • 황동국;박희정;전병민
    • Proceedings of the Korea Contents Association Conference
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    • 2003.11a
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    • pp.271-275
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    • 2003
  • In this paper, we propose a method that corrects the geometric distortion of mouth in an image. the method is composed of two steps - detecting key points and correcting geometric distortion. First, key points of lips in source and destination images are found by using lips detection algorithm. Then, the two images are mapped by using affine transformation and information found in first step. In experiment result for various mouths with different geometric distortion, we found that the proposed method have satisfactory efficiency.

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On-Machine Measurement of Sculptured Surfaces Based on CAD/CAM/CAI Integration : I. Measurement Error Modeling (CAD/CAM/CAI 통합에 기초한 자유곡면의 On-Machine Measurement : I. 측정오차 모델링)

  • Cho, Myeong-Woo;Lee, Se-Hee;Seo, Tae-Il
    • Journal of the Korean Society for Precision Engineering
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    • v.16 no.10
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    • pp.172-181
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    • 1999
  • The objective of this research is to develop a measurement error model for sculptured surfaces in On-Machine Measurement (OMM) process based on a closed-loop configuration. The geometric error model of each axis of a vertical CNC Machining center is derived using a 4${\times}$4 homogeneous transformation matrix. The ideal locations of a touch-type probe for the scupltured surface measurement are calculated from the parametric surface representation and X-, Y- directional geometric errors of the machine. Also, the actual coordinates of the probe are calculated by considering the pre-travel variation of a probe and Z-directional geometric errors. Then, the step-by-step measurement error analysis method is suggested based on a closed-loop configuration of the machining center including workpiece and probe errors. The simulation study shows the simplicity and effectiveness of the proposed error modeling strategy.

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