• Journal of Industrial Convergence
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• v.22 no.2
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• pp.23-32
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• 2024

This study utilized minimum number of demographic variables and first-semester GPA of students to predict the final academic status of students at a vocational college in Seoul. The results from XGBoost and LightGBM models revealed that these variables significantly impacted the prediction of students' dismissal. This suggests that early academic performance could be an important indicator of potential academic dropout. Additionally, the possibility that academic years required to award an associate degree at the vocational college could influence the final academic status was confirmed, indicating that the duration of study is a crucial factor in students' decisions to discontinue their studies. The study attempted to model without relying on psychological, social, or economic factors, focusing solely on academic achievement. This is expected to aid in the development of an early warning system for preventing academic dropout in the future.

• Journal of Preventive Medicine and Public Health
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• v.57 no.3
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• pp.269-278
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• 2024

Objectives: The Chepang people, an indigenous ethnic group in Nepal, experience substantial marginalization and socioeconomic disadvantages, making their communities among the most vulnerable in the region. This study aimed to determine the prevalence and factors associated with adolescent pregnancy in the Chepang communities of Raksirang Rural Municipality, Makwanpur District, Bagmati Province, Nepal. Methods: A cross-sectional study was conducted from October 2022 to April 2023 among 231 Chepang women selected using simple random sampling from Raksirang Rural Municipality. A semi-structured questionnaire was used for interviewing the mothers. Bivariate and multivariate logistic regression analyses were performed, using odds ratios with 95% confidence intervals (CIs). Variables with a variation inflation factor of more than 2 and a p-value of more than 0.25 were excluded from the final model. Results: The study revealed that the prevalence rate of adolescent pregnancy among Chepang women was 71.4% (95% CI, 65.14 to 77.16). A large percentage of participants (72.7%) were married before the age of 18 years. Poor knowledge of adolescent pregnancy (adjusted odds ratio [aOR], 10.3; 95% CI, 8.42 to 14.87), unplanned pregnancy (aOR, 13.3; 95% CI, 10.76 to 19.2), and lack of sex education (aOR, 6.57; 95% CI, 3.85 to 11.27) were significantly associated with adolescent pregnancy. Conclusions: The prevalence of adolescent pregnancy among the Chepang community was high. These findings highlighted the importance of raising awareness about the potential consequences of adolescent pregnancy and implementing comprehensive sexuality education programs for preventing adolescent pregnancies within this community.

• Animal Bioscience
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• v.37 no.8
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• pp.1367-1376
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• 2024

Objective: Parathyroid hormone like hormone (PTHLH), as an essential factor for bone growth, is involved in a variety of physiological processes. The aim of this study was to explore the role of PTHLH gene in the growth of antlers. Methods: The coding sequence (CDS) of PTHLH gene cDNA was obtained by cloning in sika deer (Cervus nippon), and the bioinformatics was analyzed. The quantitative real-time polymerase chain reaction (qRT-PCR) was used to analyze the differences expression of PTHLH mRNA in different tissues of the antler tip at different growth periods (early period, EP; middle period, MP; late period, LP). Results: The CDS of PTHLH gene was 534 bp in length and encoded 177 amino acids. Predictive analysis results revealed that the PTHLH protein was a hydrophilic protein without transmembrane structure, with its secondary structure consisting mainly of random coil. The PTHLH protein of sika deer had the identity of 98.31%, 96.82%, 96.05%, and 94.92% with Cervus canadensis, Bos mutus, Oryx dammah and Budorcas taxicolor, which were highly conserved among the artiodactyls. The qRT-PCR results showed that PTHLH mRNA had a unique spatio-temporal expression pattern in antlers. In the dermis, precartilage, and cartilage tissues, the expression of PTHLH mRNA was extremely significantly higher in MP than in EP, LP (p<0.01). In the mesenchyme tissue, the expression of PTHLH mRNA in MP was significantly higher than that of EP (p<0.05), but extremely significantly lower than that of LP (p<0.01). The expression of PTHLH mRNA in antler tip tissues at all growth periods had approximately the same trend, that is, from distal to basal, it was first downregulated from the dermis to the mesenchyme and then continuously up-regulated to the cartilage tissue. Conclusion: PTHLH gene may promote the rapid growth of antler mainly through its extensive regulatory effect on the antler tip tissue.

• Tribology and Lubricants
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• v.40 no.5
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• pp.145-150
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• 2024

This study experimentally investigates the life of rolling bearings in electric vehicles under electrical erosion. The design and preparation of an electrical erosion simulation test rig, setting of accelerated life test conditions and test methods, and results of life analysis under electrical erosion are described. We selected a constant current as the acceleration factor for life under electrical erosion, and an electrical erosion life test was conducted using three current values. The bearing was determined to have failed when the root mean square value of the acceleration data from the bearing was 4 g or higher. Based on the test data, a formula to predict life under electrical erosion was developed and used to estimate life under electrical erosion when the bearing was exposed to a random current value. The Weibull distribution was used to estimate the life of the bearing under electrical erosion based on the results of the statistical analysis that used the accelerated life test data. The estimated values were presented considering the shape parameter, acceleration index for a constant current, and the uncertainty of the estimated life value. The acceleration indices for the shape parameter of the electrical erosion life data distribution and constant current were 3.391 and 0.776, respectively. The B10 life values were 51.7, 14.8, and 8.7 h when the supplied currents were 0.1, 0.5, and 1, respectively. This study provides empirical guidelines for predicting the life of ball bearings under electrical erosion.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.50 no.5
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• pp.243-252
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• 2024

Angiogenesis is a crucial molecular driver of fibrosis in various inflammatory lesions. Oral submucous fibrosis (OSMF) is a chronic inflammatory fibrotic disorder with malignant potential. The angiogenetic pathways in OSMF remain obscure due to limited research, necessitating an in-depth review. This review aimed to illuminate the cryptic pathogenetic mechanisms of angiogenesis in the disease progression/fibrosis of OSMF and its malignant transformation, providing insights for improved treatment. Extensive literature searches were conducted across an array of databases until October 2023. Original research articles on angiogenesis in OSMF were included, and the risk of bias was assessed using the modified Newcastle-Ottawa scale. RevMan ver. 5.4 (Cochrane Collaboration) was used for data analysis. Thirty-four articles were included for qualitative synthesis and seven for quantitative analysis. Findings revealed that angiogenesis was significantly increased in early-stage OSMF but decreased as the disease advanced. It was also associated with the severity of epithelial dysplasia and malignant transformation. A random-effects model confirmed the upregulation of angiogenesis as a significant risk factor in early-stage fibrosis and malignant transformation. The mounting evidence reinforces that angiogenesis plays a crucial role in the progression of early-stage fibrosis of OSMF and its malignant transformation, opening avenues for diagnostic and therapeutic interventions.

• Journal of The Korean Society of Integrative Medicine
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• v.12 no.3
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• pp.11-24
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• 2024

Purpose : This study aims to identify the factors influencing health-related quality of life through machine learning of the general characteristics of patients with hypertension and to provide a basis for related research on patients, such as intervention strategies and management guidelines in the field of physical therapy for health promotion. Methods : Annual data from the second Korean Health Panel (Version 2.0) from 2019 to 2020, conducted jointly by the Korea Health and Social Research Institute and the National Health Insurance Service, were analyzed (Korea Health Panel, 2024). The data used in this study was collected from January to July 2020, and the data was collected using computer-assisted face-to-face interviews. Of the 13,530 household members surveyed, 1,368 were selected as the final study participants after removing missing values from 3,448 individuals diagnosed with hypertension by a doctor. Results : The results showed that walking (P2) was the most significant factor affecting health-related quality of life in random forest, followed by perceived stress (HS1), body mass index (BMIc), total household income (TOTc), subjective health status (SRHc), marital status (Marr), and education level (Edu). Conclusion :To prevent and manage chronic diseases such as hypertension, as well as to provide customized interventions for patients in advanced stages of the disease, research should be conducted in the field of physical therapy to identify influencing factors using machine learning. Based on the findings of this study, we believe that there is a need for additional content that can be utilized in the field of physical therapy to improve the health-related quality of life of patients with hypertension, such as diagnostic assessment and intervention management guidelines for hypertension, and education on perceived stress and subjective health status.

• The korean journal of orthodontics
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• v.28 no.5 s.70
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• pp.877-891
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• 1998

This study was designed to observe the effects of various concentration of polyacrylic acid containing different concentration of sulfate ion on the crystal formation on the enamel surface. Experimental crystal growth solutions were made of $10\%,\;20\%,\;30\%\;and\;40\%$ polyacrylic acid(molecular weight,5,000) solutions which containing 0.1M, 0.2M, 0.3M, 0.5M, and 1.0M sulfate ion respectively. The extracted human first bicuspid enamel surface was contacted for n seconds with these solutions, washed for 15 seconds, dried, and then the crystal topography on the enamel surface was observed under the scanning electron microscope. The crystal topography were evaluated on the SEM photographs by degree of crystal coverage, crystal length, and consistency of crystal morphology, and conclusions were as the follows. 1. Polyacrylic acid solution etched slightly the enamel surface, and the difference of etching effect by its concentration was not observed. 2. The effect of concentration of polyacrylic acid on the crystal formation was less, especially that of $20\%\~40\%$ polyacrylic acid was almost not different. 3. Concentration of the sulfate ion was a determinant factor in precipitating crystals on the enamel. The experimental crystal growth solutions containing 0.1 M sulfate ion did not make crystal formation but those containing over 0.2 M sulfate ion did. 4. The degree of crystal coverage showed a tendency to increase and then decrease according to the concentration of sulfate ion in the $20\%-40\%$ polyacrylic acid. The experimental solutions containing 0.5 M sulfate ion showed the peak of degree of crystal coverage. 5. The crystal length showed a tendency to decrease by increment of sulfate ion in the polyacrylic acid solution. 6. There was a tendency to increase the frequency of random arragement of short crystals when increasing the concentration of sulfate ion in the polyacrylic acid solution. The lower concentration of sulfate ion in the polyacrylic acid solutions tended to make spherulitic arrangement of crystals, the higher concentration of sulfate ion, the more random arrangement of crystals. The experimental solutions containing 0.5M sulfate ion showed more spherulitic arrangement than random arrangement of crystals. 7. The best one of these experimental crystal growth solutions was $30\%$ polyacrylic acid solution containing 0.5M sulfate ion.

• The Korean Journal of Applied Statistics
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• v.28 no.6
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• pp.1047-1061
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• 2015

Stratified random sampling is a powerful sampling strategy to reduce variance of the estimators by incorporating useful auxiliary information to stratify the population. Sample allocation is the one of the important decisions in selecting a stratified random sample. There are two common methods, the proportional allocation and Neyman allocation if we could assume data collection cost for different observation units equal. Theoretically, Neyman allocation considering the size and standard deviation of each stratum, is known to be more effective than proportional allocation which incorporates only stratum size information. However, if the information on the standard deviation is inaccurate, the performance of Neyman allocation is in doubt. It has been pointed out that Neyman allocation is not suitable for multi-purpose sample survey that requires the estimation of several characteristics. In addition to sampling error, non-response error is another factor to evaluate sampling strategy that affects the statistical precision of the estimator. We propose new sample allocation methods using the available information about stratum response rates at the designing stage to improve stratified random sampling. The proposed methods are efficient when response rates differ considerably among strata. In particular, the method using population sizes and response rates improves the Neyman allocation in multi-purpose sample survey.

• Journal of Intelligence and Information Systems
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• v.28 no.2
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• pp.237-262
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• 2022

There has been a growing interest in IPOs (Initial Public Offerings) due to the profitable returns that IPO stocks can offer to investors. However, IPOs can be speculative investments that may involve substantial risk as well because shares tend to be volatile, and the supply of IPO shares is often highly limited. Therefore, it is crucially important that IPO investors are well informed of the issuing firms and the market before deciding whether to invest or not. Unlike institutional investors, individual investors are at a disadvantage since there are few opportunities for individuals to obtain information on the IPOs. In this regard, the purpose of this study is to provide individual investors with the information they may consider when making an IPO investment decision. This study presents a model that uses machine learning and text analysis to predict whether an IPO stock price would move up or down after the first 5 trading days. Our sample includes 691 Korean IPOs from June 2009 to December 2020. The input variables for the prediction are three tone variables created from IPO prospectuses and quantitative variables that are either firm-specific, issue-specific, or market-specific. The three prospectus tone variables indicate the percentage of positive, neutral, and negative sentences in a prospectus, respectively. We considered only the sentences in the Risk Factors section of a prospectus for the tone analysis in this study. All sentences were classified into 'positive', 'neutral', and 'negative' via text analysis using TF-IDF (Term Frequency - Inverse Document Frequency). Measuring the tone of each sentence was conducted by machine learning instead of a lexicon-based approach due to the lack of sentiment dictionaries suitable for Korean text analysis in the context of finance. For this reason, the training set was created by randomly selecting 10% of the sentences from each prospectus, and the sentence classification task on the training set was performed after reading each sentence in person. Then, based on the training set, a Support Vector Machine model was utilized to predict the tone of sentences in the test set. Finally, the machine learning model calculated the percentages of positive, neutral, and negative sentences in each prospectus. To predict the price movement of an IPO stock, four different machine learning techniques were applied: Logistic Regression, Random Forest, Support Vector Machine, and Artificial Neural Network. According to the results, models that use quantitative variables using technical analysis and prospectus tone variables together show higher accuracy than models that use only quantitative variables. More specifically, the prediction accuracy was improved by 1.45% points in the Random Forest model, 4.34% points in the Artificial Neural Network model, and 5.07% points in the Support Vector Machine model. After testing the performance of these machine learning techniques, the Artificial Neural Network model using both quantitative variables and prospectus tone variables was the model with the highest prediction accuracy rate, which was 61.59%. The results indicate that the tone of a prospectus is a significant factor in predicting the price movement of an IPO stock. In addition, the McNemar test was used to verify the statistically significant difference between the models. The model using only quantitative variables and the model using both the quantitative variables and the prospectus tone variables were compared, and it was confirmed that the predictive performance improved significantly at a 1% significance level.

• Korean Journal of Environment and Ecology
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• v.29 no.3
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• pp.333-343
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• 2015

This research aims at identifying the goshawk's possible and replaceable breeding ground by using the MaxEnt prediction model which has so far been insufficiently used in Korea, and providing evidence to expand possible protection areas for the goshawk's breeding for the future. The field research identified 10 goshawk's nests, and 23 appearance points confirmed during the 3rd round of environmental research were used for analysis. 4 geomorphic, 3 environmental, 7 distance, and 9 weather factors were used as model variables. The final environmental variables were selected through non-parametric verification between appearance and non-appearance coordinates identified by random sampling. The final predictive model (MaxEnt) was structured using 10 factors related to breeding ground and 7 factors related to appearance area selected by statistics verification. According to the results of the study, the factor that affected breeding point structure model the most was temperature seasonality, followed by distance from mixforest, density-class on the forest map and relief energy. The factor that affected appearance point structure model the most was temperature seasonality, followed by distance from rivers and ponds, distance from agricultural land and gradient. The nature of the goshawk's breeding environment and habit to breed inside forests were reflected in this modeling that targets breeding points. The northern central area which is about $189.5 km^2$(2.55 %) is expected to be suitable breeding ground. Large cities such as Cheongju and Chungju are located in the southern part of Chungcheongbuk-do whereas the northern part of Chungcheongbuk-do has evenly distributed forests and farmlands, which helps goshawks have a scope of influence and food source to breed. Appearance point modeling predicted an area of $3,071 km^2$(41.38 %) showing a wider ranging habitat than that of the breeding point modeling due to some limitations such as limited moving observation and non-consideration of seasonal changes. When targeting the breeding points, a specific predictive area can be deduced but it is difficult to check the points of nests and it is impossible to reflect the goshawk's behavioral area. On the other hand, when targeting appearance points, a wider ranging area can be covered but it is less accurate compared to predictive breeding point since simple movements and constant use status are not reflected. However, with these results, the goshawk's habitat can be predicted with reasonable accuracy. In particular, it is necessary to apply precise predictive breeding area data based on habitat modeling results when enforcing an environmental evaluation or establishing a development plan.