• 한국측량학회지
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• 제14권2호
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• pp.119-126
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• 1996

TM투영은 일반적으로 측량 또는 지도제작에서 가장 널리 사용되고 있는 투영법이다. 그러나 복잡한 수학적 계산식으로 인하여 원리의 이해와 사용에 어려움이 있으며 또한 실제적인 적용에 있어서 계산공식을 어떻게 사용하며 어떻한 계수를 사용하는가에 따라 그 결과도 크게 달라진다. 이 연구에서는 무한급수로 전개되는 TM투영 계산공식을 급수 항의 수효에 따라 4가지 종류로 구분하고 이들이 최종 좌표에 미치는 영향에 대하여 고찰하였으며, 특히 좌표변환과정에서 필수적으로 사용되는 원주율$(\pi)$의 유효숫자가 미치는 영향에 대해서도 고찰하였다. 연구결과 경도차의 크기에 따라 오차도 달라져서, 경도차 $1^\circ$에서는 거의 변화가 없었으나 $2^\circ$와 $3^\circ$등 경도차가 클수록 더 큰 오차가 발생하였다. 또한 위도변화에 대해서는 위도가 낮을수록 더 큰 오차가 발생되었다. 특히, $\pi$값의 사용에서는 지상 1 mm의 정밀도를 유지하기 위해서는 소수 13자리까지 사용하여야 함을 알 수 있었다.

• Smart Structures and Systems
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• 제30권5호
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• pp.521-535
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• 2022

Efficient management of deteriorating civil infrastructure is one of the most important research topics in many developed countries. In particular, the remote displacement measurement of bridges using linear variable differential transformers, global positioning systems, laser Doppler vibrometers, and computer vision technologies has been attempted extensively. This paper proposes a remote displacement measurement system using closed-circuit televisions (CCTVs) and a computer-vision-based method for in-situ bridge bearings having relatively large displacement due to temperature change in long term. The hardware of the system is composed of a reference target for displacement measurement, a CCTV to capture target images, a gateway to transmit images via a mobile network, and a central server to store and process transmitted images. The usage of CCTV capable of night vision capture and wireless data communication enable long-term 24-hour monitoring on wide range of bridge area. The computer vision algorithm to estimate displacement from the images involves image preprocessing for enhancing the circular features of the target, circular Hough transformation for detecting circles on the target in the whole field-of-view (FOV), and homography transformation for converting the movement of the target in the images into an actual expansion displacement. The simple target design and robust circle detection algorithm help to measure displacement using target images where the targets are far apart from each other. The proposed system is installed at the Tancheon Overpass located in Seoul, and field experiments are performed to evaluate the accuracy of circle detection and displacement measurements. The circle detection accuracy is evaluated using 28,542 images captured from 71 CCTVs installed at the testbed, and only 48 images (0.168%) fail to detect the circles on the target because of subpar imaging conditions. The accuracy of displacement measurement is evaluated using images captured for 17 days from three CCTVs; the average and root-mean-square errors are 0.10 and 0.131 mm, respectively, compared with a similar displacement measurement. The long-term operation of the system, as evaluated using 8-month data, shows high accuracy and stability of the proposed system.

• Structural Engineering and Mechanics
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• 제76권4호
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• pp.551-559
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• 2020

On the basis of nonlocal strain gradient theory, considering the material properties of porous FGM changing with thickness and the influence of moment of inertia, the wave equation of FG nano circular plate is derived by using the first-order shear deformation plate theory, by introducing dimensionless parameters, we transform the equations into dimensionless wave equations, and the dispersion relations of bending wave, shear wave and longitudinal wave are obtained by Laplace and Hankel integral transformation method. The influence of nonlocal parameter, porosity volume fraction, strain gradient parameters and power law index on the propagation characteristics of bending wave, shear wave and longitudinal wave in FG nano circular plate.

• 대한전자공학회논문지SP
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• 제38권3호
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• pp.269-281
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• 2001

본 논문에서는 단일 글꼴에 의존하는 원형 패턴 벡터(circular pattern vectors)를 이용하여 위치 이동, 크기 변화 그리고 회전에 무관한 새로운 인쇄체 한글 인식 알고리즘을 제안한다. 제안한 알고리즘은 2진 형태론(binary morphology)을 이용하여 입력 문자에 존재하는 잡음(noise)을 제거한 후, 원형 패턴벡터를 추출한다. 추출된 원형 패턴 벡터는 주어진 문자의 무게 중심을 원의 중심으로 하여 그린 여러 원주 상에 위치한 공간적인 분포 값을 나타내는 것이다. 마지막으로, 실험 문자는 기준 원형 패턴 벡터와 실험 원형 패턴 벡터간의 거리가 최소가 되는 기준 문자로 인식하게 된다. 제안한 알고리즘의 성능을 평가하기 위해, 크기 변화와 회전 변형이 있는 완성형 바탕체 한글 2,350자를 대상으로 모의 실험을 수행하였다. 제안한 알고리즘은 기존의 고리 투영 알고리즘보다 크기 변화와 회전 변형이 있는 한글 인식에 있어서 우수함을 보였다.

• Structural Engineering and Mechanics
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• 제18권4호
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• pp.441-459
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• 2004

This paper explores the potential use of neural networks (NNs) in the field of contact mechanics. A neural network model is developed for predicting, with sufficient approximation, the contact lengths between the elastic layer and two elastic circular punches. A backpropagation neural network of three layers is employed. First contact problem is solved according to the theory of elasticity with integral transformation technique, and then the results are used to train the neural network. The effectiveness of different neural network configurations is investigated. Effect of parameters such as load factor, elastic punch radii and flexibilities that influence the contact lengths is also explored. The results of the theoretical solution and the outputs generated from the neural network are compared. Results indicate that NN predicted the contact length with high accuracy. It is also demonstrated that NN is an excellent method that can reduce time consumed.

• 천문학회보
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• 제37권2호
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• pp.160.1-160.1
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• 2012

We present an alternative approach for satellite formation reconfiguration by an optimal impulsive-thrust strategy to minimize the total characteristic velocity in a near-circular-orbit. Linear transformation decouples the Hill-Clohessy-Wiltshire(HCW) dynamics into a new block-diagonal system matrix consisting of 1-dimensional harmonic oscillator and 2-dimensional subsystem. In contrast to a solution based on the conventional primer vector theory, the optimal solution and the necessary conditions are represented as times and directions of impulses. New analytical expression of the total characteristic velocity is found for each sub systems under general boundary conditions including transfer time constraint. To minimize the total characteristic velocity, necessary conditions for times and directions of impulses are analytically solved. While the solution to the 1-dimensional harmonic oscillator has been found, the solution to the 2-dimensional subsystem is currently under construction. Our approach is expected to be applicable to more challenging problems.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제28권2호
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• pp.59-70
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• 2024

In this paper we present the approximation method of the circular helix by G² cubic polynomial curves. The approximants are G¹ Hermite interpolation of the circular helix and their approximation order is four. We obtain numerical examples to illustrate the geometric continuity and the approximation order of the approximants. The method presented in this paper can be extended to approximating the elliptical helix. Using the property of affine transformation invariance we show that the approximant has G² continuity and the approximation order four. The numerical examples are also presented to illustrate our assertions.

• 대한기계학회논문집
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• 제11권1호
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• pp.170-176
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• 1987

본 논문에서는 원환 또는 많은 축 대칭 구조물은 가공의 불균일성, 재질의 불 균일성, 불순물 또는 결함의 존재, 부분적인 질량 및 강성의 증감에 의하여 원래 하나 의 모우드로 있었던 모우드의 분리 현상이 일어나고 원주방향, 반경방향의 진동모우드 의 절선(nodal line)과 반절선의 위치가 급격하게 변한다. 그러므로 전체 진동응답 의 양상이 이상화된 원환 또는 축대칭 셸의 경우와 매우 큰 차이를 나타나게 된다. 이러한 현상은 과거종의 진동의 수치해석 및 실험에서 이미 관찰되었으나 현재까지 미 소 비대칭요소를 가지는 축대칭 구조(원환 또는 축대칭 셸)의 이론해 및 근사해에 대 한 연구보고는 매우 적다. 미소 비채칭을 갖는 축 대칭구조의 진동연구의 기본이 되 는 연구로서 축 대칭 셸의 기본요소 중 하나인 원환의 진동에 대한 집중질량의 영향을 이론적으로 규명하고 실험을 통하여 검증하였다.

• Applied Microscopy
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• 제44권4호
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• pp.138-143
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• 2014

Transmission electron microscope (TEM) is an excellent tool for studying the structure and properties of nanostructured materials. As the development of $C_s$-corrected TEM, the direct analysis of atomic structures of nanostructured materials can be performed in the high-resolution transmission electron microscopy (HRTEM). Especially, fast Fourier transform (FFT) technique in image processing is very useful way to determine the crystal structure of HRTEM images in reciprocal space. To apply FFT technique in HRTEM analysis in more reasonable and friendly manner, we made a new circular region of interest (C-ROI) FFT script and tested it for several HRTEM analysis. Consequentially, it was proved that the new FFT application shows more quantitative and clearer results than conventional FFT script by removing the streaky artifacts in FFT pattern images. Finally, it is expected that the new FFT script gives great advantages for quantitative interpretation of HRTEM images of many nanostructured materials.

• Journal of Information Technology Applications and Management
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• 제28권3호
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• pp.109-125
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• 2021

For the government of president Moon's AI SW HRD policy, he proclaimed AI democracy that anyone can utilize artificial intelligence technology to spread AI education for the people of the country. Through cognitive map analysis, this study presents expected policy outcomes due to the input of policy factors to overcome crisis factors and utilize opportunity factors. According to the cognitive guidance analysis, first, the opportunity factor is recognized as accelerating the digital transformation to Covid 19 if AI SW HRD is well nurtured. Second, the crisis factor refers to the rapid paradigm shift caused by the intelligence information society, resulting in job losses in the manufacturing sector and deepening imbalance in manpower supply and demand, especially in the artificial intelligence sector. Third, the comprehensive cognitive map shows a circular process for creating an AI SW ecosystem in response to threats caused by untact caused by Corona and a circular process for securing AI talent in response to threats caused by deepening imbalance in manpower supply and demand in the AI sector. Fourth, in order to accelerate the digital circulation that has been accelerated by Corona, we found a circular process to succeed in the Korean version of digital new deal by strengthening national and corporate competitiveness through AI-utilized capacity and industrial and regional AI education. Finally, the AI utilization empowerment strengthening rotation process is the most dominant of the four mechanisms, and we also found a relatively controllable feedback loop to obtain policy outputs.