• Journal of the Korean Society of Industry Convergence
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• v.27 no.2_2
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• pp.467-473
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• 2024

Metaheuristics' impact is profound across many fields, yet domestic financial portfolio optimization research falls short, particularly in asset allocation. This study delves into metaheuristics for portfolio optimization, examining theoretical and practical benefits. Findings indicate portfolios optimized via metaheuristics outperform the Dow Jones Index in Sharpe ratios, underscoring their potential to enhance risk-adjusted returns significantly. Tabu search, in comparison to Simulated Annealing, demonstrates superior performance by efficiently navigating the search space. Despite these advancements, practical application remains challenging due to the complexities in metaheuristic implementation. The study advocates for broader algorithmic exploration, including population-based metaheuristics, to refine asset allocation strategies further. This research marks a step towards optimizing portfolios from an extensive array of financial assets, aiming for maximum efficacy in investment outcomes.

• The Journal of Korean Academic Society of Nursing Education
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• v.16 no.1
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• pp.92-100
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• 2010

Purpose: This study was conducted to investigate the cognition level and the performance level of universal precautions on blood-borne infections and to analyze related-factors on the performance level for universal precautions among the nurses. Method: A total of 166 nurses participated in the survey. We performed multiple linear regression to assess the related-factors on the performance level for universal precautions. Result: The mean scores of cognition and performance level for universal precautions were 65.61(${\pm}8.74$) and 53.98(${\pm}8.42$) respectively. The mean score of the cognition level was significantly lower than the performance level in all items. The cognition level was associated with the working field. The performance level was highest for nurses working over 36 years, nurses in university hospitals, and nurses in the operating room. The cognitive level for universal precautions, education level, exposure to blood-borne infection, family's income, and marital status significantly predicted the performance level for universal precautions in the multiple linear regression model (Adjusted $R^2=0.42$). Conclusion: The cognition level for universal precautions is the strongest predictor on the performance level for universal precautions. An integrated approach should incorporate training experiences to improve cognition and perception of risk on universal precautions for preventing blood-borne infections.

• Asia-Pacific Journal of Business
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• v.11 no.3
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• pp.199-215
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• 2020

Purpose - This article tries to test if the conditional consumption capital asset pricing model (CCAPM) with bank credit for household as a conditional variable can explain the cross-sectional variation of stock returns in Korea. The performance of conditional CCAPM is compared to that of multifactor asset pricing models based on Arbitrage Pricing Theory. Design/methodology/approach - This paper extends the simple CCAPM to the conditional version of CCAPM by using bank credit for household as conditioning information. By employing KOSPI and KOSDAQ stocks as test assets from the second quarter of 2003 to the first quarter of 2018, this paper estimates risk premiums of conditional CCAPM and a variety of multifactor linear models such as Fama-French three and five-factor models. The significance of risk factors and the adjusted coefficient of determination are the basis for the comparison in models' performances. Findings - First, the paper finds that conditional CCAPM with bank credit performs as well as the multifactor linear models from Arbitrage Pricing theory on 25 test assets sorted by size and book-to-market. When using long-term consumption growth, the conditional CCAPM explains the cross-sectional variation of stock returns far better than multifactor models. Not only that, although the performances of multifactor models decrease on 75 test assets, conditional CCAPM's performance is well maintained. Research implications or Originality - This paper proposes bank credit for household as a conditional variable for CCAPM. This enables CCAPM, one of the most famous economic asset pricing models, to conform with the empirical data. In light of this, we can now explain the cross-sectional variation of stock returns from an economic perspective: Asset's riskiness is determined by its correlation with consumption growth conditional on bank credit for household.

• Safety and Health at Work
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• v.15 no.2
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• pp.208-212
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• 2024

Background: Traffic accidents involving professional drivers have serious societal repercussions. Unique occupational stressors and health risks exacerbate the likelihood of traffic accidents among professional drivers. This study explores the association between presenteeism-impaired work performance due to working while unwell-and traffic accident risk among professional taxi drivers in Japan. Methods: A prospective cohort study was conducted from June 2022 to February 2023, involving taxi drivers from a single company in Fukuoka Prefecture, Japan. Presenteeism was assessed using the Work Functioning Impairment Scale (WFun). Primary outcome involved the number of self-reported minor traffic accidents. The incidence rate ratio (IRR) of minor traffic accident occurrences was estimated using a Poisson regression analysis, adjusted for confounders including sex, age, and driving experience. Results: Of 838 targeted drivers, 435 were included in the analysis. Higher baseline work functioning impairment was associated with a significant trend of increasing IRR of minor traffic accidents (p for trend = 0.045). A dose-response relationship was seen between the degree of presenteeism and incidence rate of minor traffic accidents. Conclusion: Higher levels of presenteeism were associated with an increased risk of traffic accidents among taxi drivers. The findings underscore the need for socio-economic support and prioritized health management to mitigate traffic accident risk among professional drivers. This study highlights the importance of managing non-critical health issues alongside serious health conditions for safer driving practices among professional drivers in Japan.

• The Korean Journal of Financial Management
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• v.22 no.2
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• pp.135-164
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• 2005

We analyze trade and balance records of 10,000 stock investment accounts of individual investors for the period of 1998 to 2003. Individual investors em an annual gross return of 12.3% while the KOSPI and the value weighted composite including KOSDAQ stocks yield 13.6% and 9.7% respectively during the same period. Net return performance is 8.3%, a drop of 5.3% mainly due to heavy trading. Individual investors' annual turnover amounts to over 270 percent. In an analysis of groups formed on the month's end position value, the performance of the top quintile is found comparable to the market while the rest yield significantly lower risk-adjusted returns than the market. We also find evidence rejecting the rational expectation model while supporting the overconfidence hypothesis which states overconfidence leads to a higher level of trading, resulting in poor performance. Individuals tilt their stock investment toward high-beta, small, and value stocks.

• The Journal of Korean Society for School & Community Health Education
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• v.20 no.3
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• pp.1-13
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• 2019

Objectives: The purpose of this study was to examine whether demographic and socio-economic characteristics, health behaviors and health status are related to academic achievement in Korean adolescents. Methods: Data from the 14th Korea Youth Risk Behaviors web-based Survey(KYRBWS) administered in 2018 were analyzed; 60,040 students in middle and high school participated in the survey. It was conducted frequency analysis, Rao-Scott chi-square test and multiple logistic regression analysis after adjusted for variables such as age, school grade. Results: The significant influencing factors on academic achievement were family economic status, living with parents, subjective health status, smoking experience, alcohol use experience, eating breakfast, sleeping, internet use during weekdays, depressive symptom(p<.001). The odds ratio for achieving higher academic achievement compared with those who never smoked was 1.50(p<.001). Conclusion: I found that students' undesirable health behaviors affect their academic performance. To improve academic achievement, I recommend intervention programmes such as school health promotion that reduce undesirable health related behaviors.

• Journal of the Ergonomics Society of Korea
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• v.32 no.6
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• pp.549-555
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• 2013

Objective: The purpose of this study was to compare the performance of drilling on the ceiling in three different postures (standing, standing on the ladder and supine on the height adjusted board) and the subjective responses of perceived discomfort after the drilling. Background: Overhead work has been identified as a major occupational risk factor and has been a main research subject. Method: Ten young participants drilled 20 holes at the pre-marked places on the ceiling in three different postures. The drilling duration, resting and drilling heart rate were measured. The levels of perceived discomfort at neck, shoulder, elbow, hand and overall body were asked at the end of each task. Results: The working posture affected the heart rate after the drilling. Perceived discomfort in the neck decreased significantly in supine compared to drilling on the ladder. Conclusion: The results of this study suggest that drilling in supine can be an alternative way to reduce the drilling heart rate and the level of perceived discomfort in the neck without sacrificing the productivity. Application: The results of this study would be considered when drilling on the ceiling is required in construction workers.

• Asian Pacific Journal of Cancer Prevention
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• v.14 no.2
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• pp.753-757
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• 2013

Objective: To evaluate the relationships between lymph node ratio (LNR, the ratio of positive lymph nodes in excised axillary lymph nodes) and disease-free survival (DFS) by comparing with traditional absolute positive lymph node number (pN classification) for prediction of breast cancer (BC) progrnosis. Methods and Patients: We retrospectively reviewed patients who received comprehensive therapy in Department of Breast Surgery, Hubei Cancer Hospital, China from Jan 2002 to Dec 2006 (Group A), and Department of Breast and Thyroid Surgery, Renmin Hospital of Wuhan University, China from Jun 2008 to May 2012 (Group B). Patients were allocated to low-risk (${\leq}0.20$), intermediate-risk (> 0.20 but ${\leq}0.65$), high-risk (>0.65) groups by LNR. The primary endpoint was 5-DFS. Results: A total of 294 patients were included in our study. LNR was verified as a negative prognostic factor for DFS (P=0.002 in Group A, P<0.0001 in Group B). Then we found the effects of pN and LNR delamination on disease-free survival (DFS) had statistical significance (P=0.012 for pN and P=0.031 for LNR stratification in Group A, both of them P<0.001 in Group B). Compared to pN staging, LNR staging displayed superior performance in prognosis, the adjusted hazard ratio of recurrence being 2.07 (95%CI, 1.07 to 4.0) for intermediate risk group (P=0.030) and 2.44 (95%CI, 1.21 to 4.92) for high risk group (P=0.013) in Group A. Conclusions: LNR stratification proved an adverse prognostic factor of DFS in lymph nodes positive invasive BC using cut-off values 0.20 and 0.65, and was more predictive than traditional pN classification for 5-DFS.

• Journal of the Korean Society of School Health
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• v.33 no.1
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• pp.28-38
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• 2020

Purpose: This study aimed to identify the prevalence of alcohol and cigarette use and assess its relationship with socio-environmental, psychological, violent and behavioral factors among a sample of high school students from Lima and Callao, Peru. Methods: We utilized the data from a cross-sectional study conducted by the Yonsei Global Health Center in collaboration with the Korea International Cooperation Agency (KOICA) Peru office in November 2016. The total sample size of this study was 1,477 students. For analysis, we used bivariate and multivariate logistic regression to calculate the unadjusted and adjusted odds ratios and their respective 95% confidence intervals. Results: The current prevalence of alcohol and cigarette use among adolescents was found to be 24.2% and 12.1%, respectively. Alcohol use was affected by age, friends' alcohol use, experience of physical fighting, and involvement in other risk behaviors (smoking, drug use, and sexual intercourse). Cigarette use was affected by perceived academic performance, friends' cigarette use, and involvement in other risk behaviors (drinking, drug use, and sexual intercourse). Furthermore, students who received affection from their parents and whose parents monitored their activities were less likely to report using both alcohol and cigarettes. Conclusion: Alcohol and cigarette use among Lima and Callao adolescents is affected by socio-environmental, violent and behavioral factors. Alcohol and cigarette use prevention initiatives should promote positive parenting practices, family togetherness, and a supportive school climate. In addition, it is needed to establish peer-led programs that promote behavioral changes in students and strengthen social relations without the presence of alcohol, cigarettes, and other harmful substances.

• Korean Journal of Radiology
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• v.20 no.5
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• pp.844-853
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• 2019

Objective: To evaluate the learning curve for C-arm cone-beam computed tomography (CBCT) virtual navigation-guided percutaneous transthoracic needle biopsy (PTNB) and to determine the amount of experience needed to develop appropriate skills for this procedure using cumulative summation (CUSUM). Materials and Methods: We retrospectively reviewed 2042 CBCT virtual navigation-guided PTNBs performed by 7 novice operators between March 2011 and December 2014. Learning curves for CBCT virtual navigation-guided PTNB with respect to its diagnostic performance and the occurrence of biopsy-related pneumothorax were analyzed using standard and risk-adjusted CUSUM (RA-CUSUM). Acceptable failure rates were determined as 0.06 for diagnostic failure and 0.25 for PTNB-related pneumothorax. Results: Standard CUSUM indicated that 6 of the 7 operators achieved an acceptable diagnostic failure rate after a median of 105 PTNB procedures (95% confidence interval [CI], 14-240), and 6 of the operators achieved acceptable pneumothorax occurrence rate after a median of 79 PTNB procedures (95% CI, 27-155). RA-CUSUM showed that 93 (95% CI, 39-142) and 80 (95% CI, 38-127) PTNB procedures were required to achieve acceptable diagnostic performance and pneumothorax occurrence, respectively. Conclusion: The novice operators' skills in performing CBCT virtual navigation-guided PTNBs improved with increasing experience over a wide range of learning periods.