• Communications for Statistical Applications and Methods
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• v.15 no.3
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• pp.353-365
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• 2008

The sample size in a clinical trial is determined by the hypothesis, the variance of observations, the effect size, the power and the significance level. Dropouts in clinical trials are inevitable, so we need to consider dropouts on the determination of sample size. It is common that some proportion corresponding to the expected dropout rate would be added to the sample size calculated from a mathematical equation. This paper proposes new equations for calculating sample size dealing with dropouts. Since we observe data longitudinally in most clinical trials, we can use a last observation to impute for missing one in the intention to treat (ITT) trials, and this technique is called last observation carried forward(LOCF). But LOCF might make deviations on the assumed variance and effect size, so that we could not guarantee the power of test with the sample size obtained from the existing equation. This study suggests the formulas for sample size involving information about dropouts and shows the properties of the proposed method in testing equality of means.

• Journal of dental hygiene science
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• v.21 no.2
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• pp.86-95
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• 2021

Background: This study aimed to investigate the effects of department satisfaction and career maturity on the perceived health status, relationship, and self-efficacy of dental hygiene college students based on Alderfer's existence-relationship-growth theory. Methods: We obtained convenience samples of dental hygiene students in Daejeon and Chungnam areas; 241 questionnaires were collected from 250 persons considering the dropout rate and used for the final analysis except for 9 careless responses. The differences in perceived health status, relationship, self-efficacy, department satisfaction, and career maturity according to general characteristics were analyzed using a t-test, one-way analysis of variance and Pearson's correlation coefficients. Moreover, structural equation modeling was performed to confirm the variables. GFI, AGFI,CFI, RMR, RMSEA, TLI, and NFI indices were calculated to verify the fitness of the path model. Results: There were significant differences in self-efficacy, department satisfaction, career maturity according to grade, and significant differences in academic performance for all variables except relationship. The school system also had a significant effect on department satisfaction. Perceived health status, relationship, self-efficacy, department satisfaction, and career maturity demonstrated statistically significant positive correlations (p<0.05). The factors affecting department satisfaction were relationship and self-efficacy. The indirect and total effects of perceived health status and relationship on career maturity were not statistically significant; however, the indirect and total effects of self-efficacy on career maturity were statistically significant. Conclusion: It is necessary to develop teaching methods according to student management plans for dental hygiene by comprehensively perceived health status, relationship, and self-efficacy affecting department satisfaction and career maturity.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.641-649
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• 2021

Fuel oil consumption (FOC) must be minimized to determine the economic route of a ship; hence, the ship power must be predicted prior to route planning. For this purpose, a numerical method using test results of a model has been widely used. However, predicting ship power using this method is challenging owing to the uncertainty of the model test. An onboard test should be conducted to solve this problem; however, it requires considerable resources and time. Therefore, in this study, a deep feed-forward neural network (DFN) is used to predict ship power using deep learning methods that involve data pattern recognition. To use data in the DFN, the input data and a label (output of prediction) should be configured. In this study, the input data are configured using ocean environmental data (wave height, wave period, wave direction, wind speed, wind direction, and sea surface temperature) and the ship's operational data (draft, speed, and heading). The ship power is selected as the label. In addition, various treatments have been used to improve the prediction accuracy. First, ocean environmental data related to wind and waves are preprocessed using values relative to the ship's velocity. Second, the structure of the DFN is changed based on the characteristics of the input data. Third, the prediction accuracy is analyzed using a combination comprising five hyperparameters (number of hidden layers, number of hidden nodes, learning rate, dropout, and gradient optimizer). Finally, k-means clustering is performed to analyze the effect of the sea state and ship operational status by categorizing it into several models. The performances of various prediction models are compared and analyzed using the DFN in this study.

• PNF and Movement
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• v.21 no.2
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• pp.255-263
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• 2023

Purpose: This study aims to investigate the immediate effects of electromyography (EMG) biofeedback training of the gluteus medius on dynamic balance during single leg squats in healthy individuals. Methods: The sample size in this study was estimated using the G-power program at an effect size of 0.4, a significance level (α) of 0.05, and a testing power of 0.90. In addition, as a result of considering the 10% dropout rate, this study recruited 21 healthy individuals (8 males and 13 females). All subjects measured the Y-balance test-lower quarter (YBT-LQ) and limits of stability (LOS) before and after a single leg squat (SLS) and SLS with EMG biofeedback training of the gluteus medius (SLSEB). They were trained for 10 minutes for each exercise, and two dynamic balance tests were performed three times. Results: There was a significant difference in the YBT-LQ score between the two exercises (p < 0.05). In the YBT-LQ score, there was a significant difference before and after SLS and SLSEB (p < 0.05). SLSEB showed a significantly higher YBT-LQ score than SLS (p < 0.05). There was a significant difference in LOM between the two exercises (p < 0.05). However, there was no significant difference between the two exercises. Conclusion: A single-leg squat with EMG biofeedback exercises is an effective method to improve dynamic balance, such as the YBT-LQ.

• 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.

• Journal of The Korean Society of Clinical Toxicology
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• v.19 no.2
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• pp.110-126
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• 2021

Purpose: The purpose of this study is to find out the current status of toxicology laboratory operated by six locations nationwide and to investigate the satisfaction of emergency medical professionals who working at local and regional emergency medical centers. Methods: This survey was conducted prospective. It was conducted on 665 emergency medical professionals working at regional and regional emergency medical centers across the South Korea. Among them, the analysis was conducted with data that 510 emergency medical professionals who respond to this survey. The questionnaire was conducted on an online basis for a month. To ensure statistical significance, consider a dropout rate of 10% based on a minimum response recovery rate of 70%. 506 people were selected for the survey. Results: According to a survey on the status of addiction analysis room usage, the average monthly usage of addiction test rooms among respondents were 406 cases.71.0 cases (17.4%) of toxicology laboratory in Seoul and 71 cases (17.4%) in Gwangju. 32 cases (7.8%), 118 cases (29.0%) requested by toxicology laboratory in Busan, and the toxicology laboratory in Daegu. Eighty two cases (20.1%), Daejeon area 25 cases (6.1%), Wonju area toxicology laboratory was 78 (19.6%). According to a survey on the satisfaction of the addiction analysis room,Seoul (4.9±2.71) and Gwangju (4.8±2.52) showed high satisfaction. Conclusion: Due to the limited operation time of the four addiction analysis rooms currently in operation, the satisfaction level of addiction analysis by emergency medical professionals in the area is low due to the delay until the result is notified.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.6
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• pp.389-402
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• 2020

This study aimed to develop an educational program for improving the learning competencies of major courses for Chinese graduate students who account for more than 70% of international students in Korea. In this study, the program was developed using Caffarella and Daffron's interactive model. Due to the internationalization of education, the number of foreigners who study in Korea for degree courses has already exceeded 100,000, but the dropout rate has increased due to the maladjustment to university life. More specifically, they face difficulties in academic achievement because of a lack of understanding lecture contents, conducting research, and presenting in class. Therefore, this study surveyed the Chinese students in the graduate course to identify the difficulties and needs in their study of major courses and to reflect those needs (major knowledge, communication, assignment writing, and presentation) in program development. This study focused on developing an educational program for improving their learning competencies of major courses rather than simply improving Korean language skills or adapting to university life. The results of the study are expected to help Chinese Graduate students perform well in their major course studies and make their study abroad successful.

• Journal of the Korean Society of School Health
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• v.12 no.1
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• pp.27-44
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• 1999

Obesity in children is a major concern of public health. This study was performed to illuminate its effect on weight control program and the associated factors of obesity-related habits and obesity index in primary school obese children. Weight control program consisted of behavioral modification, nutrition education and exercise during 17 weeks. The sample consisted of treatment group(n=42) and control group(n=41). There was no statistical difference between the two groups in obesity index, socioeconomic status and grade. To assess the effects of weight control program, the subjects were given pre-test and post-test such as the measurement of anthropometric values and self-reporting questionnaire. This result of this study were as follows; 1. After weight control program was applied, there was a significant decrease in obesity index among the treatment group. Obesity-related habits score of the treatment group increased significantly, While there was not much difference between the pre-test and the post-test among the control group. But exercise habit didn't increase significantly in the both groups. 2. Correlation between obesity-related habits and obesity index were not evident. 3. After application of weight control program, the factors associated with change of eating habit were children's past experience of weight control, motivational change toward weight control program and friends' support for treatment group. The factors associated with change of exercise habit were post-test motivation score and friends' support. Motivational change toward weight control and pre-test self-efficacy of exercise behavior were counter-related to exercise habit. For change of other obesity-related habits, initial obesity index, motivational change, post-test self-efficacy score of exercise behavior and paternal educational status were closely associated. But post-test self-efficacy score of eating behavior was unrelated. 4. Only the factor of experience of weight control was associated with change of obesity index. 5. For the both groups, the factors associated with change of eating habits were post-test self-efficacy of eating behavior and family's support. The factors associated with change of exercise behavior were self-efficacy changes of exercise behavior and friends' support. The factors associated with change of other obesity-related habits were self-efficacy change of eating behavior. Initial obesity index was associated with change of obesity index. 6. The rate of dropouts from weight control program was 28.6% (12/42) in treatment group. Initial obesity index, other obesity-related habits except eating exercise habits, friend's support were associated with dropout. In conclusion, these results indicated that weight control program in primary school settings was effective. Direct exercise regimen and practice was demanded. In addition to the program itself, much of the success is dependent on the degree of motivation of the children involved and support provided by their parents and friends. Further study need to be performed under the condition that the weight control progrom is applied for a longer period.

• Child Health Nursing Research
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• v.7 no.3
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• pp.308-321
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• 2001

Behavior modification is an approach to decrease degree of obesity through changing maladaptive eating habit and life style. It produces small amount of weight loss but it has few side effects and low dropout rate. It also has great effectiveness on maintenance of decreased weight. This study was performed to investigate effects of behavior modification on physical variables, fat and thin habit, and self-esteem in obese elementary school children. Sixty two students of 4th, 5th, and 6th grade were selected from two elementary schools located in the suburbs of Seoul. Thirty four children in one school were assigned to experimental group and twenty eight children in another school were assigned to control group. All subjects were healthy and were not on any type of obesity control. Behavior modification, in this study, was consisted of introduction, self-monitoring and stimuli control, education about diet and physical activities, individual counseling and reinforcement, requesting personal assistance, cognitive restructuring, and closing and long-term planning. Experimental group was received 60～70 minutes of behavior modification once a week for 8 weeks from October 16 to December 22, 2000. Control group was not received any intervention. Data were collected before and after intervention by measuring physical variables, fat and thin habit, and self-esteem. Physical variables consisted of obesity index, skinfold thickness, body fat(percentage of body fat, fat mass, fat free mass), serum lipids(total cholesterol, HDL-C, LDL-C, triglyceride) and serum leptin. The results were as follows ; 1. physical variables 1) Obesity index of the experimental group was significantly decreased after behavior modification. But there was no significant difference between two groups. 2) The increase of skinfold thickness was significantly low in the experimental group compared to the control group. 3) Percentage of body fat and fat mass were significantly decreased in the experimental group. Fat free mass was significantly increased in the experimental group. 4) Total cholesterol, HDL-C, triglyceride and serum leptin between the experimental group and control group showed no significant difference. LDL-C was significantly decreased in the control group. 2. Thin habit score was significantly increased in the experimental group. In subcategories of habit, thin scores of life style, attitude, social relationship, nutrition were signifi- cantly increased in the experimental group. 3. Self-esteem score was significantly increased in the experimental group. These results indicate that behavior modification is effective in decreasing percentage of body fat and fat mass, in less increasing skinfold thickness and in increasing fat free mass, thin habit, and self-esteem. In conclusion, behavior modification can be used as safe and effective strategy for managing obesity in elementary school children.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.9 no.9
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• pp.1-16
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• 2019

This study was carried out to develop a physics education program for foreign students of university in Korea to improve their ability to major in the field and to prevent them from becoming dropout. The subjects of the study are five Chinese students attending a natural science and engineering college. Prior to the development of the physics education program, the researchers developed basic physics textbooks for the foreign students and questionaries for diagnosis and summative evaluation, and utilized them to apply a total of seven classes. After the application of the classes, the results of the student's diagnosis and summative evaluation, the teacher's diaries, the observer's diaries, and the transcripts were analyzed by triangulation method. In addition, Nvivo12 was used for the analysis of the teacher's and observer's diaries to help with qualitative analysis. The results of the study are as follows: First, the oder and contents of physics education program for students of the natural science and engineering college were presented in detail, and basic physics textbooks and tools for diagnosis and summative assessment were developed. Second, as a result of the analysis of the diagnosis and summative assessment results of the program, the students' basic physics achievement improved by an average of 40 points due to the application of the developed program. Third, as a result of the application of the program using Nvivo12, meaningful node and actual cases were extracted. There were 10 types of nodes created such as understanding of the students, teaching method, rate of the participation, level differences, language problems, relevance to majors, curriculum and methods of education in the country of origin, cooperative learning, and interest inducement. The researcher provided suggestions on physics education methods for students of science and engineering colleges in Korea based on the related cases.