• Korean Journal of Remote Sensing
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• v.13 no.2
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• pp.85-98
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• 1997

A geometric model of pushbroom-type linear CCD camera images is proposed in this paper. At present, this type of cameras are used for obtaining almost all kinds of high-resolution optical images from satellites. The proposed geometric model includes not only a forward transformation which is much more efficient. An inverse transformation function cannot be derived analytically in a closed form because the focal point of an image varies with time. In this paper, therefore, an iterative algorithm in which a focal point os converged to a given pixel position is proposed. Although the proposed model can be applied to any pushbroom-type linear CCD camera images, the geometric model of the high-resolution multi-spectral camera on-board KITSAT-3 is used in this paper as an example. The flight model of KITSAT-3 is in development currently and it is due to be launched late 1998.

• Journal of the Korea Convergence Society
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• v.10 no.11
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• pp.303-308
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• 2019

This study suggests a method for deriving earthquake response based on log-normal distribution in order to obtain realistic and reliable probability and statistical seismic response of structures. The development of three earthquake suites were presented, with a brief description of 2%, 10%, and 50% in 50 years probability of exceedance according the USGS Los Angeles probabilistic seismic hazard maps. In order to analyze the basic dynamic behavior, a Single-Degree-of-Freedom (SDOF) structure was selected and the seismic response spectrum representing the response of each natural period was plotted. Overall, the mean response values presented through the log-normal distribution is lower than the standard normal distribution. Thus, it is considered that the former method can be provided as the effective cost on performance-based seismic design more than the latter one.

• Journal of Digital Convergence
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• v.17 no.10
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• pp.251-258
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• 2019

In the future, various products are created in various fields using artificial intelligence. In this age, it is a very important problem to know the operation principle of artificial intelligence learning method and to use it correctly. This paper introduces artificial intelligence learning methods that have been known so far. Learning of artificial intelligence is based on the fixed point iteration method of mathematics. The GD(Gradient Descent) method, which adjusts the convergence speed based on the fixed point iteration method, the Momentum method to summate the amount of gradient, and finally, the Adam method that mixed these methods. This paper describes the advantages and disadvantages of each method. In particularly, the Adam method having adaptivity controls learning ability of machine learning. And we analyze how these methods affect digital signals. The changes in the learning process of digital signals are the basis of accurate application and accurate judgment in the future work and research using artificial intelligence.

• Journal of Digital Convergence
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• v.19 no.10
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• pp.63-73
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• 2021

Sudden implementation of online classes in higher education due to Covid19 pandemic implies a lot of worries about academic performance declining. Thus, this paper analyzed a class(CalculusI) taught 100% online which was the same as the offline class before. This class tried to maintain the same quality as the offline one by utilizing various teaching strategies. The result shows the academic achievement level was similar or higher than that of offline class, and so was the students' perception and satisfaction degree. However, this was not just the outcome of online class, but it came from the professor's well-designed teaching plan and smooth operation of the class. It implicates successful teaching methodology is more important factor than such medium difference as online or offline. This study suggests the potential of online classes after the Covid19 pandemic, and expects further studies verify the result in a lot more curricula.

• Journal of Digital Convergence
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• v.19 no.10
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• pp.253-263
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• 2021

Machine learning is the process of constructing a cost function using learning data used for learning and an artificial neural network to predict the data, and finding parameters that minimize the cost function. Parameters are changed by using the gradient-based method of the cost function. The more complex the digital signal and the more complex the problem to be learned, the more complex and deeper the structure of the artificial neural network. Such a complex and deep neural network structure can cause over-fitting problems. In order to avoid over-fitting, a weight decay regularization method of parameters is used. We additionally use the value of the cost function in this method. In this way, the accuracy of machine learning is improved, and the superiority is confirmed through numerical experiments. These results derive accurate values for a wide range of artificial intelligence data through machine learning.

• The Journal of the Korea Contents Association
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• v.21 no.9
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• pp.42-50
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• 2021

As the Internet environment develops, data-analysis-based applications have been widely and extensively used in the past decade. However, these applications potentially have a privacy problem in that users' personal information may be leaked to unauthorized parties. To tackle such a problem, researchers have suggested several techniques including data perturbation and cryptography. The homomorphic encryption algorithm is a relatively new cryptography technology that allows arithmetic operations for encrypted values as it is without decryption. Since original values are not required, we believe that this method provides better privacy protection than other existing solutions. In this work, we propose to apply a homomorphic encryption algorithm that protects personal information while enabling data analysis.

• Food Engineering Progress
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• v.15 no.2
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• pp.116-121
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• 2011

This study was aimed to analyze the changes in rheological properties of sausages added tenderizer made with over-matured used-up fruits such as kiwifruit, grape, and pear. The tenderizers were manufactured by various concentration of fruit extract and added to the sausage at different heating temperatures. Failure stress and stress relaxation of beef sausage mixed with different tenderizers were measured with Rheometer, and analyzed with 3-element Maxwell model. As a result of the rheological measurements, over-matured kiwifruit extract showed the best tenderness effect among other fruit extracts, and the more kiwi contents were added, the beef texture turned to softer. The instantaneous stress and elastic component of beef mixed with various tenderizers were decreased at higher concentrations and lower heating temperatures. This study was well expressed the numerical magnitude of viscoelastic components of beef sausages to determine the tenderizer effect.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.3
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• pp.1-7
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• 2019

In this paper, we propose an approach to design a practical filter and a mathematical modeling for images. In the areas of signal processing, including high-dimensional image processing, the filtering process has been fundamental and crucial in diverse practical applications such as image processing, computer vision, and pattern recognition. In general, the ideal filter is modeled as circular-shaped in the 2D frequency domain as the rectangular shape is ideal for the 1D frequency domain. This paper proposes an approach to modeling practical and efficient image filter in the 2D frequency domain. Instead of employing a circular-shaped filter, this study proposes a polygon-shaped filter inspired by the concept of a hexagon cellular system for frequency reuse in wireless communication systems. By employing the concept of frequency reuse, bandwidth efficiency is also achieved in the frequency domain. To substantiate the proposed approach, quantitative evaluation is performed using PSNR.

• Journal of the Korea Society for Simulation
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• v.27 no.4
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• pp.9-18
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• 2018

This paper proposes new algorithms of accessibility indices to analyze the connectivity of the Korean highway network. First of all, we find a transportation network that presents Korea's highway network in graphs in 2011 and 2017. And we analyze and compare the nation's highway network in 2011 and 2017 using concepts such as associated number, the relative distance, the accessibility, the degree of connectivity, the index of dispersion, the diameter of graph theory. To do this, an algorithm is presented which can easily obtain various accessibility indices from a given transportation network. Using the simulation results of this study, we can find city that is the center of traffic in the highway transportation network. In addition, cities that are included in the network but are relatively underdeveloped can be found and used as basic data for enhancing the connectivity of the nationwide traffic in the future. Moreover, the proposed algorithms of accessibility indices, which are modeled on highway transport networks, can help identify the accessibility space structure of each city and provide criteria for efficient and reasonable selection of alternatives in various regional planning processes, including transportation.

• The Journal of Engineering Geology
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• v.28 no.4
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• pp.741-753
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• 2018

Local drought in South Korea has recently increased interest in the efficient use of groundwater and then induces a growing need to introduce artificial recharge of groundwater that stores water in sedimentary layer. In order to evaluate the potential artificial recharge sites in the alluvial basins in Chungcheongnamdo province, an AHP (Analytical hierarchy process) model consisting of three primary and seven secondary factors was developed in this study. In the AHP model, adding candidate sites changes final evaluation score through a mathematical calculation process. By contrast ANN (Artificial neural network) model always provides an unchanged score for each candidate area. Therefore, the score can be used as a selection criterion for artificial recharge sites. It is concluded that the possibility of artificial recharge is relatively low if the score of the ANN model is less than about 1.5. Further studies and field surveys on the other regions in Korea will lead to draw out a more applicable ANN model.