• 한국환경보건학회지
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• 제35권6호
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• pp.491-499
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• 2009

The removal of turbidity from $TiO_2$ wastewater by an electrocoagulation/flotation process was studied in a batch reactor. The response surface methodology (RSM) was applied to evaluate the simple and combined effects of the three main independent parameters, current, NaCl dosage and initial pH of the $TiO_2$ solution on the turbidity removal efficiency, and to optimize the operating conditions of the treatment process. The reaction of electrocoagulation/flotation was modeled by use of the Box-Behnken method, which was used for the fitting of a 2nd order response surface model. The application of RSM yielded the following regression equation, which is an empirical relationship between the turbidity removal efficiency of $TiO_2$ wastewater and test variables in uncoded unit: Turbidity removal (%)=69.76+59.76Current+11.98NaCl+4.67pH+5.00Current${\times}$pH-160.11$Current^2-0.34pH^2$. The optimum current, NaCl dosage and pH of the $TiO_2$ solution to reach maximum removal rates were found to be 0.186 A, 0.161 g/l and 7.599, respectively. This study clearly showed that response surface methodology was one of the most suitable method to optimize the operating conditions for maximizing the turbidity removal. Graphical response surface and contour plots were used to locate the optimum point.

• Smart Structures and Systems
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• 제11권4호
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• pp.411-433
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• 2013

Due to its easy operation and wide applicability, the ambient vibration method is commonly adopted to determine the cable force by first identifying the cable frequencies from the vibration signals. With given vibration length and flexural rigidity, an analytical or empirical formula is then used with these cable frequencies to calculate the cable force. It is, however, usually difficult to decide the two required parameters, especially the vibration length due to uncertain boundary constraints. To tackle this problem, a new concept of combining the modal frequencies and mode shape ratios is fully explored in this study for developing an accurate method merely based on ambient vibration measurements. A simply supported beam model with an axial tension is adopted and the effective vibration length of cable is then independently determined based on the mode shape ratios identified from the synchronized measurements. With the effective vibration length obtained and the identified modal frequencies, the cable force and flexural rigidity can then be solved using simple linear regression techniques. The feasibility and accuracy of the proposed method is extensively verified with demonstrative numerical examples and actual applications to different cable-stayed bridges. Furthermore, several important issues in engineering practice such as the number of sensors and selection of modes are also thoroughly investigated.

• 사회복지연구
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• 제37호
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• pp.399-427
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• 2008

본 연구는 비행친구와의 교류가 청소년기 비행에 미치는 영향을 보호요인이 완충하고 있는지를 확인하고자 하였다. 비행친구와의 교류는 청소년기 비행을 유발하는 주요한 위험요인으로 제시되고 있다. 보호요인은 위험요인의 부정적 영향을 완화 완충시켜주는 역할을 하는데, 자아존중감과 부모애착, 부모의 지도감독은 비행의 발생을 막는 주요한 보호요인이다. 이에 높은 보호요인을 가지고 있는 경우 위험요인인 비행친구와의 교류가 비행에 미치는 영향이 감소하거나 사라지는지를 상호작용효과모형을 통해 알아 보았다. 분석자료로는 전국규모의 종단조사자료인 한국청소년패널자료를 이용하였다. 분석결과, 성별에 따라 비행친구와의 교류가 미치는 영향을 완충하는 보호요인의 효과는 상이한 것으로 나타났다. 여자청소년의 경우, 자아존중감, 부모애착, 지도감독은 모두 위험요인의 영향을 완충하는 조절효과를 갖는 것으로 나타났다. 반면 남자청소년에게서 보호요인의 조절효과는 확인되지 않았다. 성별에 따라 보호요인의 상이한 조절효과가 나타난 결과에 근거하여 실천적, 정책적 함의를 살펴보았고, 필요한 후속연구의 과제에 대해 제시하였다.

• 한국항해항만학회지
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• 제45권3호
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• pp.165-172
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• 2021

쇄파는 연안류, 표사이동, 충격파압, 에너지소산 등과 같은 연안에서 발생하는 다양한 물리현상과 직접적인 관계가 있으므로 항만 구조물의 설계시 반드시 고려되어야 하는 중요한 설계인자 중 하나이다. 쇄파에 대한 연구들은 쇄파가 가진 고유의 복잡성으로 인해 주로 수리모형실험을 통해 쇄파파고와 쇄파수심 등과 같은 쇄파지표를 예측하기 위한 많은 경험식이 제안되어 왔다. 하지만, 기존의 쇄파지표에 대한 경험식은 일정한 방정식의 가정하에 자료의 통계적 분석을 통해 가정한 방정식의 계수들을 결정하고 있다. 본 연구에서는 회귀 혹은 분류문제와 관련된 다양한 연구분야에 있어서 높은 예측성능을 보여주는 대표적인 선형기반의 머신러닝 기법을 적용하여 천수변형에 의해 발생하는 쇄파의 한계파고를 산정하기 위한 새로운 Munk형식의 경험식을 제안하였다. 새롭게 제안된 쇄파지표식은 단순한 형태의 다항식에도 불구하고 기존의 경험공식과 유사한 예측성능을 보였다.

• 농업과학연구
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• 제46권2호
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• pp.257-271
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• 2019

The use of food grade hexane (FGH) for edible oil extraction is responsible for the presence of benzene in the crude oil. Benzene is a Group 1 carcinogen and could pose a serious threat to the health of consumer. However, its detection still depends on classical methods using chromatography which requires a rapid non-destructive detection method. Hence, the aim of this study was to investigate the feasibility of using Fourier transform infrared (FTIR) spectroscopy combined with multivariate analysis to detect and quantify the benzene residue in edible oil (sesame and cottonseed oil). Oil samples were adulterated with varying quantities of benzene, and their FTIR spectra were acquired with an attenuated total reflectance (ATR) method. Optimal variables for a partial least-squares regression (PLSR) model were selected using the variable importance in projection (VIP) and the selectivity ratio (SR) methods. The developed PLS models with whole variables and the VIP- and SR-selected variables were validated against an independent data set which resulted in $R^2$ values of 0.95, 0.96, and 0.95 and standard error of prediction (SEP) values of 38.5, 33.7, and 41.7 mg/L, respectively. The proposed technique of FTIR combined with multivariate analysis and variable selection methods can detect benzene residuals in edible oils with the advantages of being fast and simple and thus, can replace the conventional methods used for the same purpose.

• 디지털융복합연구
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• 제19권1호
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• pp.99-105
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• 2021

본 논문은 일의 의미가 직무열의라는 동기적 요소를 거쳐서 직무수행에 정적인 영향을 미치고, 궁극적으로 개인차원의 긍정적인 결과인 번영에 정적인 영향을 미치는 이중매개 관계를 검증하고자 하였다. 이를 위해서 395명의 직장인을 대상으로 온라인 설문방식을 통해서 연구를 진행하였고, SPSS와 SPSS Process Macro를 활용하여 위계적회귀분석, 부트스트래핑 분석을 시행하였으며. 연구 결과는 다음과 같다. 일의 의미(WM), 직무열의(WE), 직무수행(JP), 그리고 번영(FL) 간의 상관관계는 모두 통계적으로 유의미한 것으로 나타났으며, 일의 의미(WM), 직무열의(WE), 번영(FL) 간의 단순 매개관계와 일의 의미(WM), 직무수행(JP), 번영(FL) 간의 단순 매개관계가 통계적으로 검증되었다. 그리고 일의 의미(WM), 직무열의(WE), 직무수행(JP), 그리고 번영(FL) 간의 이중매개관계가 통계적으로 유의미한 것으로 확인되었다. 본 연구는 자율성이 중요해지는 최근의 업무 환경에서 효과적인 직원 관리 방법에 대한 의미 있는 결과를 보여주었으며, 향후 종단적 연구를 통해서 이중 매개관계에 대한 실질적인 검증 연구의 시행이 필요할 것으로 보인다.

• 대한간호학회지
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• 제51권4호
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• pp.489-504
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• 2021

Purpose: This study was investigated the mediating effect of coping behaviors in the relationship between the second victim experiences after patient safety incidents and the nursing practice changes. Methods: A cross-sectional survey was performed using structured questionnaires. Participants were 218 clinical nurses in general tertiary hospitals in South Korea. Data were collected through an online survey and snowball sampling from August 11 to September 6 2020. Data were analyzed using SPSS 23.0 program. A mediation analysis was performed using multiple regression and a simple mediation model applying the PROCESS macro with 95% bias-corrected bootstrap confidence interval. Results: The mean scores of second victim experiences was 3.41/5. Approach coping (β = .55, p < .001) and the avoidant coping (β = - .23, p = .001) showed mediation effects in the relationship between second victim experiences and constructive change in nursing practice. Avoidant coping (β = .29, p < .001) showed a mediation effect in the relationship between second victim experiences and defensive change in nursing practice. Conclusion: Coping behaviors has a mediating effect on the relationship between second victim experiences and nursing practice changes. To ensure that nurses do not experience second victim, medical institutions should have a culture of patient safety that employs a systematic approach rather than blame individuals. They also need to develop strategies that enhance approach coping and reducing avoidant coping to induce nurses' constructive practice changes in clinical nurses in experiencing second victims due to patient safety incidents.

• 산업경영시스템학회지
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• 제45권3호
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• pp.49-56
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• 2022

ROK Navy intends to secure the Korean-type aircraft carrier in order to effectively prepare for various future security threats. In general, the Korean national competency is considered to be at the level of having an aircraft carrier, but it is unclear what scale aircraft carrier would be appropriate. In this study, the efficiency was evaluated through the relative comparison between national competency(national power, economic power) and the scale of aircraft carriers, and the optimal scale of the Korean-type aircraft carrier that could be acquired was presented. A DEA(Data Envelopment Analysis) model was applied to aircraft carriers(19 aircraft carriers in 11 countries) currently in operation and scheduled to be possessed in the world. As input variables, CINC(Composite Index of National Capability) and GDP(Gross Domestic Product), which are the most widely used as indicators of national and economic power, and as output variables, the full-load displacement, length, and width of aircraft carriers were selected. ARIMA(short-term within 5 years) and simple regression(long-term over 5 years) were used to estimate the future national competency of each country at the time of aircraft carriers acquisition. The relative efficiency score of the Korean-type aircraft carrier currently being evaluated is 1.062, and it was evaluated as small-scale aircraft carrier compared to the national competency. Based on Korean national competency, the optimal scale of the Korean-type aircraft carrier calculated by aggregating benchmark groups, is 58,308.1 tons of full-load displacement, 279.4m in length, and 68.3m in width.

• Journal of Preventive Medicine and Public Health
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• 제57권3호
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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.

• 한국응용과학기술학회지
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• 제40권6호
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• pp.1238-1248
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• 2023

본 연구는 헤어디자이너의 직무스트레스가 번영에 미치는 영향을 알아보고, 이러한 과정에 있어서 직무열의와 경력몰입 두 변인의 이중매개 효과를 검증하는데 목적이 있다. 이를 위하여 국내 B 브랜드에 종사하는 다양한 직급의 177명의 헤어디자이너를 대상으로 실시한 설문조사를 통계패키지 SPSS 21.0과 매크로 프로그램인 SPSS PROCESS Macro의 부트스트래핑 방법을 활용하여 직무스트레스와 번영의 관계와 직무열의와 경력몰입의 이중매개 효과를 검증하였다. 분석의 결과는 다음과 같다. 첫째, 헤어디자이너의 직무스트레스가 번영에 유의미하게 부적(-)인 영향을 미치는 것으로 확인되었고 둘째, 이 과정에서 직무열의와 경력몰입 두 변인이 이중매개로 투입되면서 직무스트레스가 번영에 있어서 부적(-)으로 유의미한 간접효과를 미치는 반면, 직접적으로는 헤어디자이너의 직무스트레스가 번영에 미치는 영향이 유의미하지 않게 바뀌면서 완전 이중매개 효과가 있는 것으로 확인되었다. 결과적으로, 헤어디자이너의 직무스트레스 요인들의 점수가 높으면 직무열의 수준이 떨어지고, 결국 자신의 경력에 몰입하지 못하게 되며 행복감과 사회적 성공을 의미하는 번영의 수준이 떨어지는 과정을 확인한 데 본 연구의 의의가 있다.