• Journal of Electrical Engineering and Technology
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• v.3 no.4
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• pp.584-592
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• 2008

In this paper, we propose a new model of the magnetic control force exerted on the levitation object in magnetic levitation systems. The model assumes that the magnetic force is a function of the voltage applied to an electromagnet and the position of a levitation object. The function is not explicitly expressed but represented through a 2D lookup table constructed from the experimentally measured data. Unlike the conventional model that reveals only local characteristics of the magnetic force, the proposed model shows global characteristics satisfactorily. Specially devised measurement equipment is utilized in order to gather the data required for model construction. An experimental procedure to construct the model is presented. We apply the proposed model to designing a sliding mode controller for a lab-built magnetic system. The validity of the proposed model is illustrated by comparing the performances of the controller adopting the conventional model with that of the controller adopting the proposed model.

• Journal of the Society of Naval Architects of Korea
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• v.42 no.2 s.140
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• pp.98-104
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• 2005

The mathematical models of hydrodynamic force and moment acting on a ship at low speed range should be established differently from the ones at nominal cruising speed range since a ship moves with large drift angle or rotates in a stationary position. We modified widely used Yoshimura's cross flow model in order to apply the system identification method to estimate parameters in the model. The apparatus and the procedure of free running model test were suggested so that the parameters in the model be estimated. The validity of our proposing modified model and test procedure was confirmed by comparison with the results of simulated model test.

• YAKHAK HOEJI
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• v.41 no.1
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• pp.38-47
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• 1997

Using a concentric cylinder type, rheometer. the steady shear flow properties of vaseline were measured over the temperature range of 20~70${\circ}$C. In this paper, the shea rate and temperature dependencies of its flow behavior were investigated and the validity of some flow models was examined. In addition, the flow characteristics over a wide temperature range were quantitatively evaluated by calculating the various material parameters. Main findings obtained from this study can be summarized as follows: (1) At relatively lower temperature range, vaseline is a plastic fluid with a yield stress and its flow behavior shows shear-thinning characteristics. (2) As the temperature increases, the value of a yield stress and the degree of shear-thinning become smaller, consequently, the Newtonian flow behavior occurs at a lower shear rate range. (3) At temperature range lower than 45${\circ}$C, the flow behavior shows much stronger temperature dependence, and a larger activation energy is needed for flow. (4) The Herschel-Bulkley model is the most effective one g$^3$ to predict the flow behavior of vaseline having a yield stress. The validity of the Bingham and Casson models becomes more available with increasing temperature. The flow behavior of vaseline at temperature range higher than 45${\circ}$C can be perfectly described by the Newton model.

• Journal of Korean Academy of Nursing
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• v.49 no.4
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• pp.398-410
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• 2019

Purpose: This study used a system dynamics methodology to identify correlation and nonlinear feedback structures among factors affecting adolescent cyberbullying victims (CV) in Korea and to construct and verify a simulation model. Methods: Factors affecting CV were identified by reviewing a theoretical background in existing literature and referencing various statistical data. Related variables were identified through content validity verification by an expert group, after which a causal loop diagram (CLD) was constructed based on the variables. A stock-flow diagram (SFD) using Vensim Professional 7.3 was used to establish a CV model. Results: Based on the literature review and expert verification, 22 variables associated with CV were identified and the CLD was prepared. Next, a model was developed by converting the CLD to an SFD. The simulation results showed that the variables such as negative emotions, stress levels, high levels of conflict in schools, parental monitoring, and time spent using new media had the strongest effects on CV. The model's validity was verified using equation check, sensitivity analysis for timestep and simulation with 4 CV adolescent. Conclusion: The system dynamics model constructed in this study can be used to develop intervention strategies in schools that are focused on counseling that can prevent cyberbullying and assist in the victims' recovery by formulating a feedback structure and capturing the dynamic changes observed in CV. To prevent cyberbullying, it is necessary to develop more effective strategies such as prevention education, counseling and treatment that considers factors pertaining to the individual, family, school, and media.

• Journal of the Korean School Mathematics Society
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• v.9 no.3
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• pp.405-424
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• 2006

The purpose of this study was to develop the instruments which can measure behavior characteristics as a component of Mathematically Giftedness with in middle school period. This study prescribed the variable factors of measurement after classify the characteristics of Mathematically Giftedness through literature studies. And it produced instruments those are finally composed of 51 items through the preliminary test. The participants for the study were 424 Korean middle school students. Statistical analyses were carried out to verify the validities and reliability. Reliability(Cronbach $\alpha$) was in behavior characteristics, .95. Content validity was found to be satisfactory by internal validity evaluation on the test items. Internal validity were analyzed by BIGSTEPTS based on Rasch's 1-parameter item-response model. Construct validity was also found to be satisfactory through factor analysis which showed the four factors which the identification instruments were intended to measure such as, General mathematical mental ability, Mathematical Ability, Processing and Obtaining mathematical information Anility and Mathematical Disposition Ability. In conclusion, the instruments about behavior characteristics of Mathematically Giftedness during middle school period developed by this study are highly reliable on its reliability and validity.

• Korean Journal of Social Welfare
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• v.68 no.3
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• pp.149-180
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• 2016

The purpose of the present study was to examine the validity and reliability of the Korean version of PANSI(Positive and Negative Suicide Ideation: K-PANSI) scale which was developed to measure adolescents' suicide ideation. The study sample consisted of 552 middle school students using a questionnaire survey including the K-PANSI. A reliability analysis, a correlation analysis, and a confirmatory factor analysis were used to test internal consistency(Cronbach alpha), criterion validity (with respect to CES-D, BDI, RES, SWLS), and construct validity. Major study findings are as follows. First, Cronbach' ${\alpha}$ of the K-PANSI scale is supported to some degree by significant correlations with CES-D, BDI, RES, SWLS. Lastly, the confirmatory factor analysis of the K-PANSI scale showed that a two factor model was appropriate with 66.0 percent of explanatory power. These findings suggest that the K-PANSI scale could be used as a reliable and valid measure for adolescent' suicide ideation.

• Journal of Korean Biological Nursing Science
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• v.20 no.1
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• pp.11-19
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• 2018

Purpose: The purposes of this study were to perform items analysis using the classical test theory (CTT) and the item response theory (IRT), and to establish the validity and reliability of the Korean version of pressure ulcer prevention knowledge. Methods: The 26-item pressure ulcer prevention knowledge instrument was translated into Korean, and the item analysis of the 22 items having an adequate content validity index (CVI), was conducted. A total of 240 registered nurses in 2 university hospitals completed the questionnaire. Each item was analyzed applying CTT and IRT according to 2-parameter logistic model. Response alternatives quality, item difficulty and item discrimination were evaluated. For testing validity and reliability, Pearson correlation coefficient and Kuder Richardson-20 (KR-20) were used. Results: Scale CVI was .90 (Item-CVI range= .75-1.00). The total correct answer rate for this study population was relatively low as 52.5%. The quality of response alternatives was found to be relatively good (range= .02-.83). The item difficulty of the questions ranged form .10 to .86 according to CTT and -12.19 to 29.92 according to the IRT. This instrument had 12-low, 2-medium and 8-high item difficulty applying IRT. The values for the item discrimination ranged .04-.57 applying CTT and .00-1.47 applying IRT. And overall internal consistency (KR-20) was .62 and stability (test-retest) was .82. Conclusion: The instrument had relatively weak construct validity, item discrimination according to the IRT. Therefore, the cautious usage of a Korean version of this instrument would be recommended for discrimination because there are so many attractive response alternatives and low internal consistency.

• The Journal of the Korea Contents Association
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• v.18 no.12
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• pp.218-228
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• 2018

The purpose of this study was to present a educational content developed for training of dental extraction skill in a virtual environment. The development of the content consists of five steps: learning content analysis, draw a design model, development, test of validity, rectification and complete of the content. We developed the virtual reality (VR) simulator with producing an animation of surgical stages on the 3D models of human face for simulating dental extraction procedure. The results of validity tests for the content were mean 4.81 (SD, 0.72) for interface validity and mean 4.66 (SD, 0.71) for content validity, which represents strong evidence for the validity of the content. The data of the study indicates that the educational content developed for training of dental extraction skill using VR technology can be suitable to improve surgical skill of dental extraction in clinical field. We expect that further development of the education contents based on the VR technology to improve various surgical skills in clinical field will be addressed in the future.

• Research in Community and Public Health Nursing
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• v.31 no.4
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• pp.416-426
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• 2020

Purpose: The aim of this study was to evaluate the validity and reliability of the Korean version of Short-form Health Literacy Scale (HLS-SF-K12) for Adults. Methods: The English HLS-SF12 was translated into Korean with forward and backward translation. Survey data were collected from 204 adults who visited two hospitals in Korea. Content validity, construct validity, and known-groups validity were evaluated. Cronbach's α for internal consistency and test-retest were used to assess reliability. SPSS 21.0 and AMOS 21.0 software were used for data analysis. Results: The HLS-SF-K12 was composed of 12 items, and three subscales (health care, disease prevention, and health promotion). The instrument explained reliable internal consistency with Cronbach's α for the total scale of .89, and .74~.81 for subscales. The model of three subscales for the HLS-SF-K12 was validated by confirmatory factor analysis (Normed χ2=2.14 (p<.001), GFI=.92, RMR=.04, RMSEA=.08, CFI=.94, TLI=.92, IFI=.94). The hypothesis testing which analyzed the differences in health literacy by age and education level was satisfied. Conclusion: The HLS-SF-K12 is a valid and reliable instrument for measuring health information comprehension for adults in Korea.

• Journal of Korean Academy of Nursing
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• v.52 no.2
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• pp.173-186
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• 2022

Purpose: Climate change has various negative effects on human health, which has resulted in increased burden on the health care system. Nurses contribute significantly to assessing climate-related health risks and creating a healthy environment. This study aimed to evaluate the reliability and validity of the Korean version of the Climate, Health, and Nursing Tool (K-CHANT) to measure nurses' awareness, motivation, concern, and behaviors at work and at home regarding climate change and health. Methods: The 22 items of English CHANT were translated into Korean with forward-backward translation techniques. Internal consistency reliability, test-retest reliability, and construct validity using confirmatory factor analysis were performed using SPSS WIN (25.0) and AMOS (26.0). Survey data were collected from 220 master's, doctoral, and post-doctoral nursing students. Results: The K-CHANT consists of 20 items across 5 domains. Two items of the original CHANT were excluded because of low content validity index and standardized regression weights. The internal consistency reliability of the K-CHANT, assessed by Cronbach's α was .81, with an intraclass correlation coefficient of .66~.90. The five subscales model was validated by confirmatory factor analysis (SRMR < .08, RMSEA < .08, AGFI > .70, CFI > .70). Conclusion: The K-CHANT has satisfactory construct validity and reliability to measure nurses' awareness, motivation, concern, and behaviors at work and at home regarding climate change and health. Future research should examine nurses' perceptions and behaviors related to the health effects of climate change and develop an action plan to improve it.