• Korean Journal of Remote Sensing
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• v.34 no.6_4
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• pp.1531-1544
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• 2018

We detected the coseismic ionospheric disturbance generated by the earthquakes of magnitude 5.0 and greater in Korean Peninsula. We considered the seismic events such as Gyeongju earthquake in September 2016 with magnitude 5.8, the Pohang earthquake in November 2017 with magnitude 5.4, and the underground nuclear explosion from North Korea in September 2017 with magnitude 5.7. Although all GPS stations were not detected, the ionospheric disturbance induced by these earthquakes occurred approximately 10-30 minutes and 40-60 minutes after the events. We inferred that the time difference within each variation is due to the different focal depth and the geometry of epicenter, satellite, and GPS station. In the case of the Gyeongju earthquake, the earthquake had relatively deeper depth than the other earthquakes. However, the seismic magnitude was bigger and it occurred at nighttime when the ionospheric activity was stable. So we could observe such anomalous variations. It is considered that the ionospheric disturbance caused by the difference in velocity of the upward propagating waves generated by earthquake appears more than once. Our results indicate that the detection of ionospheric disturbances varies depending on the geometry of the GPS station, satellite, and epicenter or the detection method and that the apparent growth of amplitude in the time series varies depending on the focal depth or the site-satellite-epicenter geometry.

• Korean Journal of Remote Sensing
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• v.34 no.6_3
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• pp.1445-1456
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• 2018

The purpose of this study is to compare the quality and characteristics of matching DEMs by using KOMPSAT-3 stereo pair capture in in-track and cross-track. For this purpose, two stereo pairs of KOMPSAT-3 were collected that were taken in the same area. The two stereo pairs have similar stereo geometry elements such as B/H, convergence angle. Sensor modeling for DEM production was performed with RFM affine calibration using multiple GCPs. The GCPs used in the study were extracted from the 0.25 m ortho-image and 5 meter DEM provided by NGII. In addition, matching DEMs were produced at the same resolution as the reference DEMs for a comparison analysis. As a result of the experiment, the horizontal and vertical errors at the CPs indicated an accuracy of 1 to 3 pixels. In addition, the shapes and accuracy of two DEMs produced in areas where the effects of natural or artificial surface land were low were almost similar.

• Journal of Industrial Convergence
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• v.20 no.10
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• pp.9-16
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• 2022

This study was attempted to confirm the correlation between anxiety, communication skills, and nursing professionalism due to the replacement on-campus practice of nursing students due to the COVID-19 outbreak. The subjects of this study were 131 nursing students in 3rd and 4th grade, and data were collected from October 30, 2021 to November 23, 2021. The collected data were analyzed with SPSS Statistics 28.0 using descriptive statistics, t-test, ANOVA, and Person's correlation. As a result of the study, it was found that there was a negative correlation between anxiety and nursing professionalism(r=-.332, p<.001), and there was a positive correlation between communication ability and nursing professionalism (r=.364, p=.000) Based on this study, it is necessary to develop and apply an effective clinical practice education intervention method that can reduce anxiety caused by on-campus practice to enhance nursing professionalism and enhance communication ability. Based on this study, it is necessary to understand the relationship between grade level and nursing professionalism, and to develop and apply an effective anxiety intervention method that can increase nursing professionalism by reducing anxiety caused by on-campus practice.

• Journal of Korea Water Resources Association
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• v.55 no.11
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• pp.903-911
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• 2022

Groundwater, one of the resources for supplying water, fluctuates in water level due to various natural factors. Recently, research has been conducted to predict fluctuations in groundwater levels using Artificial Neural Network (ANN). Previously, among operators in ANN, Gradient Descent (GD)-based Optimizers were used as Optimizer that affect learning. GD-based Optimizers have disadvantages of initial correlation dependence and absence of solution comparison and storage structure. This study developed Gradient Descent combined with Harmony Search (GDHS), a new Optimizer that combined GD and Harmony Search (HS) to improve the shortcomings of GD-based Optimizers. To evaluate the performance of GDHS, groundwater level at Icheon Yullhyeon observation station were learned and predicted using Multi Layer Perceptron (MLP). Mean Squared Error (MSE) and Mean Absolute Error (MAE) were used to compare the performance of MLP using GD and GDHS. Comparing the learning results, GDHS had lower maximum, minimum, average and Standard Deviation (SD) of MSE than GD. Comparing the prediction results, GDHS was evaluated to have a lower error in all of the evaluation index than GD.

• Journal of Industrial Convergence
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• v.21 no.4
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• pp.81-89
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• 2023

This study try to confirm the relationship between clinical reasoning competence, critical thinking propensity, and confidence in performing core basic nursing skills among nursing students. The subjects of the study were 157 third and fourth year nursing students at D University in Daejeon, and the survey was conducted through a self-questionnaire from Nov. 2 to Nov. 15, 2022. The collected materials were analyzed using the SPSS/WIN26.0 program. The results showed the correlation between clinical reasoning competence and critical thinking propensity (r=.417, p<.001), clinical reasoning competence and core basic nursing performance confidence (r=.659, p<.001), critical thinking propensity and core basic nursing performance confidence (r=.303, p<.001). Therefore, the results of this study can be used as a basis for developing various curriculums to increase the confidence of nursing college students in performing core basic nursing techniques.

• Journal of Korea Water Resources Association
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• v.56 no.1
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• pp.63-74
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• 2023

High-reliability prediction of dam inflow is necessary for efficient dam operation. Recently, studies were conducted to predict the inflow of dams using Multi Layer Perceptron (MLP). Existing studies used the Gradient Descent (GD)-based optimizer as the optimizer among MLP operators to find the optimal correlation between data. However, the GD-based optimizers have disadvantages in that the prediction performance is deteriorated due to the possibility of convergence to the local optimal value and the absence of storage space. This study improved the shortcomings of the GD-based optimizer by developing Adaptive moments combined with Improved Harmony Search (AdamIHS), which combines Adaptive moments among GD-based optimizers and Improved Harmony Search (IHS). In order to evaluate the learning and prediction performance of MLP using AdamIHS, Daecheong Dam inflow was learned and predicted and compared with the learning and prediction performance of MLP using GD-based optimizer. Comparing the learning results, the Mean Squared Error (MSE) of MLP, which is 5 hidden layers using AdamIHS, was the lowest at 11,577. Comparing the prediction results, the average MSE of MLP, which is one hidden layer using AdamIHS, was the lowest at 413,262. Using AdamIHS developed in this study, it will be possible to show improved prediction performance in various fields.

• Journal of Korea Water Resources Association
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• v.56 no.11
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• pp.801-813
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• 2023

Recently, as studies about Artificial Neural Network (ANN) are actively progressing, studies for predicting water quality of rivers using ANN are being conducted. However, it is difficult to analyze the operation process inside ANN, because ANN is form of Black-box. Although eXplainable Artificial Intelligence (XAI) is used to analyze the computational process of ANN, research using XAI technology in the field of water resources is insufficient. This study analyzed Multi Layer Perceptron (MLP) to predict Water Temperature (WT), Dissolved Oxygen (DO), hydrogen ion concentration (pH) and Chlorophyll-a (Chl-a) at the Dasan water quality observatory in the Nakdong river using Layer-wise Relevance Propagation (LRP) among XAI technologies. The MLP that learned water quality was analyzed using LRP to select the optimal input data to predict water quality, and the prediction results of the MLP learned using the optimal input data were analyzed. As a result of selecting the optimal input data using LRP, the prediction accuracy of MLP, which learned the input data except daily precipitation in the surrounding area, was the highest. Looking at the analysis of MLP's DO prediction results, it was analyzed that the pH and DO a had large influence at the highest point, and the effect of WT was large at the lowest point.

• The Journal of the Korea Contents Association
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• v.20 no.11
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• pp.268-280
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• 2020

This research conducted an empirical analysis of factors that influence the process of job choices and start-ups among the youth. By conducting a comparative analysis on 6 countries with adequate career systems and booming startup industries (China, Indonesia, the UK, Germany, Israel, the US.). The statistical sample is based on the Global Entrepreneurship Trend Ratio and covers a total of 7,082 youth across 7 countries. Multivariate variance analysis and correlational analysis were conductedto compare the average figures among different countries and analyze the regulation effect of parental influence. Job satisfaction, parental influence, and willingness to change future job were selected as the factors that influence job choices. Korea's job satisfaction was the lowest among 7 countries and a willingness to change future job was the highest. Meanwhile, Korea's parental influence was at a medium level among 7 countries. It was proven that job satisfaction had a quasi-control effect on the process of influencing willingness to change future job. Entrepreneurial education, willingness to start-up, job satisfaction, and parental influence were chosen as the factors that influence start-up. Two-way ANOVA were conducted to comparatively analyze each country's average, mutual influence among different factors, and analyze the regulation effect of parental influence. In all countries, start-up education has the effect of raising the willingness to start-up. Also, it was verified that parental influence had a quasi-control effect in the process of career satisfaction influencing the willingness to start-up. The research results will provide meaningful implications for the government and educational institutes including universities when designing policy directions to guide overall career for the youth in the future.

• Journal of the Korean Electrochemical Society
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• v.16 no.2
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• pp.85-90
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• 2013

Graphite is a commercial anode material to have the specific capacity of 372 mAh/g and the true density of 2.2 g/ml. Many effort had been pouring to find out the better material than graphite. Good candidates are silicon, tin, etc. Zinc is also a plausible candidate to have the specific capacity of 412 mAh/g and the true density of 7.14 g/ml. In this study, the Zn based anode material including indium and nickel as minor additives was synthesised. In order to get the homogeneouly mixed Zn-In-Ni composite material, the sol-gel method was used. The anode prepared by Zn-In-Ni composite material has the $1^{st}$ specific capacity of 910 mAh/g. Through prolonged charge-discharge cycling, the specific capacities were reduced to 365 (at $31^{st}$ cycle) and 378 mAh/g (at $62^{th}$ cycle). The $1^{st}$ Ah efficiency was 45% and Ah efficiencies were exhibited at the prolonged cycle.

• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.3
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• pp.49-56
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• 2012

Rupture disks are a kind of safety device in high pressure equipment and they are used to control rupture pressure in the solid rocket motor. In this paper, a series of rupture experiments was performed using rupture disks made of AISI 316L and rupture pressure of rupture disks was calculated through various assumptions in relation between elasto-plastic material properties and true stress-strain curve. Experiment and FEA indicated rupture pressure is determined by size of rupture disks. As a result of elasto-plastic analysis, only multi-linear stress-strain curve was able to calculate meaningful estimations. Experimental results also showed rupture location are decided by the size of rupture disks. Experimental and FEA results will be applied to control rupture pressure of disks.