• Design Convergence Study
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• v.14 no.2
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• pp.151-168
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• 2015

As the market of music download stores moved into the mobile epoch the market was growing explosively. Recently, the digital music market tends to move from the mp3 download market to streaming service and the users can use the service on their mobile devices without reference to any inconvenient download and limited storage capacity. It was found that they mainly use the recommendation music playlist, instant player, main player and sharing of the functions of the streaming service from the user behavior research. This is noticeable features that set apart from the mp3 download service. However, the interface design of the streaming app followed the previous service and it needs the optimization of its UI design. In this study, the usability of high ranked three mobile streaming apps was evaluated. The result of the test was that Naver music and Bugs had high scores overall in four sections of the streaming service features. On the other hand, the Melon had primarily high score in color application on the service. The aim of this study is to suggest the direction of the UI design of music streaming service through the understanding of essence of streaming service and evaluation the usability test.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.61.3-61.3
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• 2019

The epochs of observation for the 28 determinative stars in the Shi Shi Xing Jing and Cheonsang Yeolcha Bunyajido are estimated by using two fitting methods. The coordinate values in these tables were thought to be measured with meridian instruments, and so they have the axis-misalignment errors and random errors. We adopt a Fourier method, and also we devise a least square fitting method. We do bootstrap resamplings to estimate the variance of the epochs. As results, we find that both data sets were made during the 1^st century BCE or the latter period of the Former Han dynasty. The sample mean of the epoch for the SSXJ data is earlier by about 15-20 years than that for the Cheonsang Yeolcha Bunyajido. However, their variances are so large that we cannot decide whether the Shi Shi Xing Jing data was formed around 77 BCE and the Cheonsang Yeolcha Bunyajido was measured in 52 BCE. We need either more data points or data points measured with better precision. We will discuss on the other 120 coordinates of stars listed in the Shi Shi Xing Jing.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.43-43
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• 2022

유해 조류 대발생은 전국 각지의 인공호소나 하천에서 다발적으로 발생하며, 경관을 해치고 수질을 오염시키는 등 수자원에 부정적인 영향을 미친다. 본 연구에서는 인공호소에서 발생하는 유해 조류 대발생을 예측하기 위해 심층학습 기법을 이용하여 예측 모델을 개발하고자 하였다. 대상 지점은 대청호의 추동 지점으로 선정하였다. 대청호는 금강유역 중류에 위치한 댐으로, 약 150만명에 달하는 급수 인구수를 유지 중이기에 유해 남조 대발생 관리가 매우 중요한 장소이다. 학습용 데이터 구축은 대청호의 2011년 1월부터 2019년 12월까지 측정된 수질, 기상, 수문 자료를 입력 자료를 이용하였다. 수질 예측 모델의 구조는 다중 레이어 퍼셉트론(Multiple Layer Perceptron; MLP)으로, 입력과 한 개 이상의 은닉층, 그리고 출력층으로 구성된 인공신경망이다. 본 연구에서는 인공신경망의 은닉층 개수(1~3개)와 각각의 레이어에 적용되는 은닉 노드 개수(11~30개), 활성함수 5종(Linear, sigmoid, hyperbolic tangent, Rectified Linear Unit, Exponential Linear Unit)을 각각 하이퍼파라미터로 정하고, 모델의 성능을 최대로 발휘할 수 있는 조건을 찾고자 하였다. 하이퍼파라미터 최적화 도구는 Tensorflow에서 배포하는 Keras Tuner를 사용하였다. 모델은 총 3000 학습 epoch 가 진행되는 동안 최적의 가중치를 계산하도록 설계하였고, 이 결과를 매 반복마다 저장장치에 기록하였다. 모델 성능의 타당성은 예측과 실측 데이터 간의 상관관계를 R2, NSE, RMSE를 통해 산출하여 검증하였다. 모델 최적화 결과, 적합한 하이퍼파라미터는 최적화 횟수 총 300회에서 256 번째 반복 결과인 은닉층 개수 3개, 은닉 노드 수 각각 25개, 22개, 14개가 가장 적합하였고, 이에 따른 활성함수는 ELU, ReLU, Hyperbolic tangent, Linear 순서대로 사용되었다. 최적화된 하이퍼파라미터를 이용하여 모델 학습 및 검증을 수행한 결과, R2는 학습 0.68, 검증 0.61이었고 NSE는 학습 0.85, 검증 0.81, RMSE는 학습 0.82, 검증 0.92로 나타났다.

• Journal of the Institute of Convergence Signal Processing
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• v.24 no.1
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• pp.51-56
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• 2023

This study investigates the effect of sEMG sampling frequency on CNN learning performance at Korean finger number recognition application. Since the bigger sampling frequency of sEMG signals generates bigger size of input data and takes longer CNN's learning time. It makes making real-time system implementation more difficult and more costly. Thus, there might be appropriate sampling frequency when collecting sEMG signals. To this end, this work choose five different sampling frequencies which are 1,024Hz, 512Hz, 256Hz, 128Hz and 64Hz and investigates CNN learning performance with sEMG data taken at each sampling frequency. The comparative study shows that all CNN recognized Korean finger number one to five at the accuracy of 100% and CNN with sEMG signals collected at 256Hz sampling frequency takes the shortest learning time to reach the epoch at which korean finger number gestures are recognized at the accuracy of 100%.

• Journal of The Korean Astronomical Society
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• v.56 no.2
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• pp.201-212
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• 2023

The inscription of Cheonsang Yeolcha Bunyajido (天象列次分野之圖) has the sun's locations at the equinoxes, which must have been copied from the astronomical treatises in Chinese historical annals, Songshu (宋書) and Jinshu (晉書). According to the treatises, an astronomer Wang Fan (王蕃, 228-266 CE) referred those values from a calendrical system called Qianxiangli (乾象曆, 223 CE), from which it is confirmed that it adopted the sun's location at the winter solstice of the $(21{\frac{1}{4}})^{th}$ du of the 8th lunar lodge Dou (斗) as the reference direction for equatorial lodge angles. This indicates that the sun's locations at equinoxes and solstices in the calendrical system are the same as those in Jingchuli (景初曆, 237 CE). Hence, we propose that the sun's location at the autumnal equinox in Cheonsang Yeolcha Bunyajido should be corrected from 'wu du shao ruo' (五度少弱), meaning the $(5{\frac{1}{6}})^{th}$ du, to 'wu du ruo' (五度弱), meaning the $(4{\frac{11}{12}})^{th}$ du, of the first lunar lodge Jiao (角), as seen in Jingchuli. We reconstruct the polar coordinate system used in circular star charts, assuming that the mean motion rule was applied and its reference direction was the sun's location at the winter solstice. Considering the precession, we determined the observational epoch of the sun's location at the winter solstice to be t_o = -18.3 ± 43.0 adopting the observational error of the so-called archaic determinatives (古度). It is noteworthy that the sun's locations at equinoxes inscribed in Cheonsang Yeolcha Bunyajido originated from Houhan Sifenli (後漢 四分曆) of the Latter Han dynasty (85 CE), while the coordinate origin in the star chart is related to Taichuli (太初曆) of the Former Han dynasty (104 BCE).

• Journal of Industrial Convergence
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• v.22 no.2
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• pp.13-22
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• 2024

In the current epoch of educational technology (EdTech), the realization of a personalized learning system has become increasingly important. This is due to the growing diversity of today's learners in terms of backgrounds, learning styles, and abilities. Traditional educational methods that deliver the same content to all learners often fail to take this diversity into account. This paper identifies models that comprehensively analyze learners' characteristics, interests, and learning histories to meet the growing demand for learner-centered education. Based on these models, we have designed a personalized learning system. This system is structured to support autonomous learning tailored to the learner's current level and goals by identifying strengths and weaknesses based on the learner's learning history. In addition, the system is designed to extend necessary learning elements without changing its architecture. Through this research, we can identify the essential foundations for constructing a user-tailored learning system and effectively develop a system architecture to support personalized learning.

• Information Systems Review
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• v.22 no.1
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• pp.113-124
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• 2020

In the operation of farms, it is very important to evaluate the quality of harvested crops and to classify defective products. However, farmers have difficulty coping with the cost and time required for quality assessment due to insufficient capital and manpower. This study thus aims to detect defects by analyzing the epidermis of fruit using deep learning algorithm. We developed a model that can analyze the epidermis by applying YOLOv3 algorithm based on Region Convolutional Neural Network to video images of peach. A total of four classes were selected and trained. Through 97,600 epochs, a high performance detection model was obtained. The crop failure detection model proposed in this study can be used to automate the process of data collection, quality evaluation through analyzed data, and defect detection. In particular, we have developed an analytical model for peach, which is the most vulnerable to external wounds among crops, so it is expected to be applicable to other crops in farming.

• Geomechanics and Engineering
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• v.37 no.1
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• pp.49-64
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• 2024

Rocks undergoing repeated loading and unloading over an extended period, such as due to earthquakes, human excavation, and blasting, may result in the gradual accumulation of stress and deformation within the rock mass, eventually reaching an unstable state. In this study, a CNN-CCM is proposed to address the mechanical behavior. The structure and hyperparameters of CNN-CCM include Conv2D layers × 5; Max pooling2D layers × 4; Dense layers × 4; learning rate=0.001; Epoch=50; Batch size=64; Dropout=0.5. Training and validation data for deep learning include 71 rock samples and 122,152 data points. The AI Rock Constitutive Model learned by CNN-CCM can predict strain values(ε₁) using Mass (M), Axial stress (σ₁), Density (ρ), Cyclic number (N), Confining pressure (σ₃), and Young's modulus (E). Five evaluation indicators R², MAPE, RMSE, MSE, and MAE yield respective values of 0.929, 16.44%, 0.954, 0.913, and 0.542, illustrating good predictive performance and generalization ability of model. Finally, interpreting the AI Rock Constitutive Model using the SHAP explaining method reveals that feature importance follows the order N > M > σ₁ > E > ρ > σ₃.Positive SHAP values indicate positive effects on predicting strain ε₁ for N, M, σ₁, and σ₃, while negative SHAP values have negative effects. For E, a positive value has a negative effect on predicting strain ε₁, consistent with the influence patterns of conventional physical rock constitutive equations. The present study offers a novel approach to the investigation of the mechanical constitutive model of rocks under cyclic loading and unloading conditions.

• Animal Systematics, Evolution and Diversity
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• v.10 no.1
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• pp.97-123
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• 1994

The author devided th period of 1876-1945 into three epochs ; the Opening of Ports in 1876 -before the Political Reform in 1894 , the Political Reform- the Japanese annexation of Korea in 1910 , and the Epoch of Japanese Colony during 1910-1945. As civilization through including educational reform rised. The modern school system began to be introduced nongovernmentally and governmentally to Korea in the 1880's without any school laws. Were chronologycally established school regulation by Korea Government in 1895-1893, school laws by Korean Government under the supervision of the Japanese Residency-General of Korea in 1906-1910, and the educational laws of Korea by the Japanese Government-General of Korea in 1911-1943. In these epochs, the numbers of elementary , secondary and higher educational institutions and the numbers of pupils and students had increased slowly. Japanese had developed sonwhat primary education and secondary technical education, but it had checked extremely the Korean peoples to receive secondary liberal education and higher education, On the epoch of Japanese colony, Japanese occupied nearly half of elementary school teachers, almost of public secondary school teachers educated in Japan, and nearly all of professor educated in Japan in public and national colleges which were technical, and in one imperial university . Forty or more Korean teachers taught natural history chief at private secondary schools for Koreans , more than half of them being graduates of colleges of agriculture and forestry in Korea and Japan. The author mentioned curricula , and subjects and textbooks connected with biology of elementary, secondary and higher educational institutions. The pup8ls and students received biological knowledge through learning sciences at primary schools ; natural history (plants, animals and minerals ) at secondary schools including normal schools ; botany, zoology, genetics and major subjects related with biology such as anatomy, physiology, bacteriology, pland breeding at medical colleges and colleges of agriculture and forestry. There were no departments of biology , botany or zoology in Korea. Only seven Koreas graduated from departments of biology, botany or zoology at imperial universities in Japan. Some of them played the leading parts to develop education and researches of biology in the universities after 1945 Liberation.

• Journal of Christian Education in Korea
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• v.63
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• pp.91-120
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• 2020

This study suggests a spiritual education for the Christian family as a strategy to cope with the risky situation of the Korean Church during the Covid-19 pandemic. Today, we live in a chaotic epoch since the rapid development of the science caused the Fourth Industrial Revolution and the Covid-19 pandemic gave rise to a wide array of changes throughout the society. Korean Church in these circumstances is required to have relevant responses to the kaleidoscopic changes. Especially, not to mention the face-to-face public worship service, in the situation where the congregation members even find it difficult to meet one another in a small group, it becomes a crucial issue how Christians maintain their faith and community in the healthy spirituality. As such, viewing that Christian education within the family will become much more important, this study conducts research for familial-spiritual education. For the research, this paper, first of all, attempts to understand the era of Covid-19. It is to see what the Novel Corona Virus is and what the feature of the epoch of Covid-19 might be. Based upon the understanding, this research discusses what Christian spirituality is asked for and the orientation towards which Christian education should go on. It is particularly to say that a spiritual education for the family becomes integral. The education for the family might be possible through Bibliodrama so that this study establishes a specific model of Christian education employing Bibliodrama. The discussion above shows three academic significances. First, this paper, within the domain of Christian education, suggests an alternative research which is to solve Korean Church's diverse problems caused by Covid-19. Second, this research attempts an analytical understanding of the Covid-19 period within the Christian education area. Finally, when specific and practical research for the field of Christian education during the Covid-19 pandemic is required, this study considers that Christian education within the family is overarching, thus proposing a specific model for familial-spiritual education hiring Bibliodrama.