• The Journal of the Korea Contents Association
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• v.22 no.10
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• pp.404-413
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• 2022

As non-face-to-face classes have been adopted as an essential class method in universities after COVID-19, interest in ways to encourage student engagement is increasing. Class engagement is a prerequisite for improving the quality of education, so it is inevitably an even more important requirement in non-face-to-face classes. Therefore, this study examined the efforts and concerns based on the teaching experiences of three professors of D University, which have been operated by mixing non-face-to-face or non-face-to-face classes since 2020. As a result, both professors and students went through trial and error in the early stages of non-face-to-face classes, but over time, it was confirmed that students not only actively expressed their opinions but also voluntarily expanded the class activity. This study is meaningful in that it found the possibility that professors-led classes can develop into learner-participating classes through appropriate harmony between face-to-face and non-face-to-face and the use of various media. Data were collected through an autobiographical method.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.4
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• pp.241-250
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• 2022

This paper addresses the Feasible Angular Momentum(FAM) chart that can be used as an indicator for maneuverability analysis of spacecraft installed with control moment gyros(CMGs). Recently, as the demands for high agility of spacecraft has been increasing in order to perform the space mission given to spacecraft more effectively, interest in CMGs, which is a high torque generator is increasing. However, since the CMG has a singularity problem that does not generate the control torque in the specific directions, in this paper, we consider the two pairs of parallel control moment gyros(TPCMGs) that follows the roof-type configuration. The Gimbal space was newly defined except for the space where singularity can be generated and the space where torque error is generated due to the hardware limits. The feasible angular momentum space is defined as a FAM chart, and it is very meaningful that it is possible to analyze the spacecraft's rotational maneuverability effectively by deriving the spacecraft's 3-axis parameters in the corresponding gimbal space mathematically.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.1
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• pp.41.2-41.2
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• 2021

In this study, we generate He I 1083 nm images from Solar Dynamic Observatory (SDO)/Atmospheric Imaging Assembly (AIA) images using a novel deep learning method (pix2pixHD) based on conditional Generative Adversarial Networks (cGAN). He I 1083 nm images from National Solar Observatory (NSO)/Synoptic Optical Long-term Investigations of the Sun (SOLIS) are used as target data. We make three models: single input SDO/AIA 19.3 nm image for Model I, single input 30.4 nm image for Model II, and double input (19.3 and 30.4 nm) images for Model III. We use data from 2010 October to 2015 July except for June and December for training and the remaining one for test. Major results of our study are as follows. First, the models successfully generate He I 1083 nm images with high correlations. Second, the model with two input images shows better results than those with one input image in terms of metrics such as correlation coefficient (CC) and root mean squared error (RMSE). CC and RMSE between real and AI-generated ones for the model III with 4 by 4 binnings are 0.84 and 11.80, respectively. Third, AI-generated images show well observational features such as active regions, filaments, and coronal holes. This work is meaningful in that our model can produce He I 1083 nm images with higher cadence without data gaps, which would be useful for studying the time evolution of chromosphere and coronal holes.

• The Journal of Korean Institute of Next Generation Computing
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• v.13 no.2
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• pp.35-48
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• 2017

There are many and various devices like sensors, displays, smart phone, etc. in smart environment. And contents can be provided by using these devices. Vast amounts of contents are provided to users, but in most environments, there are no regard for user or some simple elements like location and time are regarded. So there's a limit to provide meaningful contents to users. In this paper, I suggest the contents recommendation system that can recommend contents to users by reasoning context of users, devices and contents. The contents recommendation system suggested in this paper recommend the contents by calculating the user preferences using the situation reasoned with the contextual data acquired from various devices and the user profile received from the user directly. To organize this process, the method on how to model ontology with domain knowledge and how to design and develop the contents recommendation system are discussed in this paper. And an application of the contents recommendation system in Centum City, Busan is introduced. Then, the evaluation methods how the contents recommendation system is evaluated are explained. The evaluation result shows that the mean absolute error is 0.8730, which shows the excellent performance of the proposed contents recommendation system.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.85-85
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• 2020

South Korea experiences few large scale erosion and sedimentation problems, however, there are numerous local sedimentation problems. A reliable and consistent approach to modelling and management for sediment processes are desirable in the country. In this study, field measurements of sediment concentration from 34 alluvial river basins in South Korea were used with the Modified Einstein Procedure (MEP) to determine the total sediment load at the sampling locations. And then the Flow Duration-Sediment Rating Curve (FD-SRC) method was used to estimate the specific degradation for all gauging stations. The specific degradation of most rivers were found to be typically 50-300 tons/㎢·yr. A model tree data mining technique was applied to develop a model for the specific degradation based on various watershed characteristics of each watershed from GIS analysis. The meaningful parameters are: 1) elevation at the middle relative area of the hypsometric curve [m], 2) percentage of wetland and water [%], 3) percentage of urbanized area [%], and 4) Main stream length [km]. The Root Mean Square Error (RMSE) of existing models is in excess of 1,250 tons/㎢·yr and the RMSE of the proposed model with 6 additional validations decreased to 65 tons/㎢·yr. Erosion loss maps from the Revised Universal Soil Loss Equation (RUSLE), satellite images, and aerial photographs were used to delineate the geospatial features affecting erosion and sedimentation. The results of the geospatial analysis clearly shows that the high risk erosion area (hill slopes and construction sites at urbanized area) and sedimentation features (wetlands and agricultural reservoirs). The result of physiographical analysis also indicates that the watershed morphometric characteristic well explain the sediment transport. Sustainable management with the data mining methodologies and geospatial analysis could be helpful to solve various erosion and sedimentation problems under different conditions.

• Korean Journal of Culture and Social Issue
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• v.25 no.4
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• pp.305-323
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• 2019

The Satisfaction With Life Scale (SWLS) is the most widely used instrument to measure life satisfaction. This study examined the factor structure and measurement equivalence of SWLS across age and gender in Korea. A total of 936 data were analyzed, comprising 433 college students (195 males and 238 females) and 503 middle-aged adults (237 males and 266 females). The results are as follows. Firstly, the data supported a modified single-factor model with correlations between error variances of items 4 and 5. Therefore, items 4 and 5 reflecting the past were found to share a distinct meaning with other items. Secondly, SWLS showed full strict invariance by gender, but only showed partial strict invariance between college students and middle-aged adults. These results indicate that meaningful comparisons of SWLS scores across gender may be valid, but careful attention should be paid when comparing age groups.

• The Korean Journal of Archival Studies
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• no.80
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• pp.129-165
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• 2024

This study aims to emphasize the importance and activation of citizen oral history. As is well known, research on oral history gradually began in earnest in Korea from the 1980s. Until now, citizen interviews by researchers and elite interviews by researchers have steadily increased in quantity. However, citizen interviews by citizens are insignificant. The "Digital Life-history Archiving" project, which has been under the supervision of the Ministry of Culture, Sports and Tourism since 2021, is a new and meaningful attempt. Citizens are educated on archiving and oral history to conduct interviews and produce archives. It is producing high-quality oral archives, securing citizens' archiving capabilities, and building local cultural resources. Based on the experience of participating in this project in 2021, I evaluated the performance and limitations and looked at the implications. I expect it to help reduce trial and error in the future. I also proposed a plan to actively produce and utilize citizen oral archives. To this end, specific cooperation between oral-history institutions and oral archives platforms were also proposed.

• The Journal of the Acoustical Society of Korea
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• v.26 no.3
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• pp.102-108
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• 2007

A high-Performance scalable speech codec generally requires a very low-rate first layer and a fine granule second layer, and this codec can be implemented with the harmonic codec and the MDCT-based transform codec for each layer. In this structure, however. each codec requires independent frequency transform and the time delay of each codec is accumulated. resulting in long time delay for the overall codec. In this paper, new MDCT structure in the second layer is Proposed. where MDCT is forced to share the look-ahead region of the first layer in order to prevent the time delay accumulation and the resulting functional error of MDCT is analyzed and removed after IMDCT The Proposed delayless MDCT requires no additional bits and Provides the equivalent coding performance with the reduced time delay, yielding a meaningful enhancement of the overall codec.

• Asia-Pacific Journal of Business
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• v.14 no.4
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• pp.233-254
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• 2023

Purpose - This study aims to verify whether the effect of tax avoidance on corporate value is non-linear in the Korean financial markets. Design/methodology/approach - This study believes that the cause of the inconsistent empirical analysis results of previous studies that verified the relationship between tax avoidance and firm value may be an error in assuming linearity, and verifies whether a nonlinear relationship exists. The sample company in this study is a December settlement corporation listed on the Korean stock market, and the analysis period is from 2000 to 2021. In the empirical analysis model, Tobin's Q is used as a proxy for corporate value, tax avoidance is used as the main independent variable, and a regression model is designed with corporate size, growth rate, and debt ratio set as control variables. Findings - As a result of the empirical analysis, it can be confirmed that there is an inverted U-shaped nonlinear relationship between tax avoidance and corporate value. In the additional analysis using Ohlson (1995) firm valuation model for the robustness of the results of the empirical analysis, the same nonlinear value relationship between tax avoidance can be confirmed. Research implications or Originality - This study is considered to be meaningful in that it verifies the non-linear relationship of tax avoidance, which has not been attempted in previous studies. The meaning of the inverted U-shaped nonlinear relationship presented in this study is that corporate tax avoidance acts as a factor that increases corporate value up to a certain level, but rather becomes a factor that decreases corporate value when it exceeds a critical point. These results are expected to provide new perspectives and perspectives on tax avoidance to companies belonging to the Korean capital market.

• Korean Journal of Remote Sensing
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• v.39 no.5_1
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• pp.669-681
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• 2023

Studies have tried to apply remote sensing technology, a non-destructive survey method, instead of the existing destructive survey, which requires relatively large labor input and a long time to estimate chlorophyll content, which is an important indicator for evaluating the growth of fruit trees. This study was conducted to non-destructively evaluate the chlorophyll content of pear tree leaves using unmanned aerial vehicle-based hyperspectral imagery for two years(2021, 2022). The reflectance of the single bands of the pear tree canopy extracted through image processing was band rationed to minimize unstable radiation effects depending on time changes. The estimation (calibration and validation) models were developed using machine learning algorithms of elastic-net, k-nearest neighbors(KNN), and support vector machine with band ratios as input variables. By comparing the performance of estimation models based on full band ratios, key band ratios that are advantageous for reducing computational costs and improving reproducibility were selected. As a result, for all machine learning models, when calibration of coefficient of determination (R²)≥0.67, root mean squared error (RMSE)≤1.22 ㎍/cm², relative error (RE)≤17.9% and validation of R²≥0.56, RMSE≤1.41 ㎍/cm², RE≤20.7% using full band ratios were compared, four key band ratios were selected. There was relatively no significant difference in validation performance between machine learning models. Therefore, the KNN model with the highest calibration performance was used as the standard, and its key band ratios were 710/714, 718/722, 754/758, and 758/762 nm. The performance of calibration showed R²=0.80, RMSE=0.94 ㎍/cm², RE=13.9%, and validation showed R²=0.57, RMSE=1.40 ㎍/cm², RE=20.5%. Although the performance results based on validation were not sufficient to estimate the chlorophyll content of pear tree leaves, it is meaningful that key band ratios were selected as a standard for future research. To improve estimation performance, it is necessary to continuously secure additional datasets and improve the estimation model by reproducing it in actual orchards. In future research, it is necessary to continuously secure additional datasets to improve estimation performance, verify the reliability of the selected key band ratios, and upgrade the estimation model to be reproducible in actual orchards.