• Wind and Structures
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• v.27 no.1
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• pp.11-27
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• 2018

The straight-cone steel cooling tower is a novel type of structure, which has a distinct aerodynamic distribution on the internal surface of the tower cylinder compared with conventional hyperbolic concrete cooling towers. Especially in the extreme weather conditions of strong wind and heavy rain, heavy rain also has a direct impact on aerodynamic force on the internal surface and changes the turbulence effect of pulsating wind, but existing studies mainly focus on the impact effect brought by wind-driven rain to structure surface. In addition, for the indirect air cooled cooling tower, different additional ventilation rate of shutters produces a considerable interference to air movement inside the tower and also to the action mechanism of loads. To solve the problem, a straight-cone steel cooling towerstanding 189 m high and currently being constructed is taken as the research object in this study. The algorithm for two-way coupling between wind and rain is adopted. Simulation of wind field and raindrops is performed with continuous phase and discrete phase models, respectively, under the general principles of computational fluid dynamics (CFD). Firstly, the rule of influence of 9 combinations of wind sped and rainfall intensity on flow field mechanism, the volume of wind-driven rain, additional action force of raindrops and equivalent internal pressure coefficient of the tower cylinder is analyzed. On this basis, the internal pressures of the cooling tower under the most unfavorable working condition are compared between four ventilation rates of shutters (0%, 15%, 30% and 100%). The results show that the 3D effect of equivalent internal pressure coefficient is the most significant when considering two-way coupling between wind and rain. Additional load imposed by raindrops on the internal surface of the tower accounts for an extremely small proportion of total wind load, the maximum being only 0.245%. This occurs under the combination of 20 m/s wind velocity and 200 mm/h rainfall intensity. Ventilation rate of shutters not only changes the air movement inside the tower, but also affects the accumulated amount and distribution of raindrops on the internal surface.

• Journal of Environmental Impact Assessment
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• v.29 no.4
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• pp.272-285
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• 2020

We investigated statistical evaluation parameters for 3D meteorological and air quality models and selected several quantitative indicator references, and summarized the reference values of the statistical parameters for domestic air quality modeling researcher. The finally selected 9 statistical parameters are MB (Mean Bias), ME (Mean Error), MNB (Mean Normalized Bias Error), MNE (Mean Absolute Gross Error), RMSE (Root Mean Square Error), IOA (Index of Agreement), R (Correlation Coefficient), FE (Fractional Error), FB (Fractional Bias), and the associated reference values are summarized. The results showed that MB and ME have been widely used in evaluating the meteorological model output, and NMB and NME are most frequently used for air quality model results. In addition, discussed are the presentation diagrams such as Soccer Plot, Taylor diagram, and Q-Q (Quantile-Quantile) diagram. The current results from our study is expected to be effectively used as the statistical evaluation parameters suitable for situation in Korea considering various characteristics such as including the mountainous surface areas.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.12
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• pp.213-221
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• 2017

This study was conducted to identify professional self-concept, academic self-efficacy and department satisfaction among 327 nursing students to determine whether professional self-concept or academic self-efficacy has an impact on department satisfaction. Data were collected from May 29 till June 12, 2017 and subjected to frequency and percentage, mean and standard deviation, t-test, ANOVA, Scheffe's test, Pearson's Correlation Coefficient, and multiple regression analyses using SPSS version 22.0. The results revealed that purpose of admission to school, relationship with peers, and academic achievement significantly influenced professional self-concept, academic self-efficacy and department satisfaction, whereas gender, age, and religion did not. Additionally, there was a positive correlation between professional self-concept, academic self-efficacy, and department satisfaction. The factor that had the greatest impact on department satisfaction was professional self-concept, although academic self-efficacy and consideration of aptitude for major were also significant influencing factors. Overall, the results indicate that there is a need to develop and apply a variety of programs that can be used to increase professional self-concept to increase department satisfaction among nursing students. Accordingly, further studies are needed to increase academic self-efficacy among students and consider aptitude when admitting students.

• Journal of Distribution Science
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• v.12 no.6
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• pp.49-57
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• 2014

Purpose - The world now recognizes environmental disruption as a serious issue when regarding growth-oriented strategies; therefore, environmental preservation issues become pertinent. Consequently, green distribution is continuously emphasized. However, studying the prediction and association of distribution and the environment is insufficient. Most existing studies about green distribution are about its necessity, detailed operation methods, and political suggestions; it is necessary to study the distribution service industry and environmental service industry together, for green distribution. Research design, data, and methodology - ARIMA (auto-regressive moving average model) was used to predict the environmental service and distribution service industries, and the Granger Causality Test based on VAR (vector auto regressive) was used to analyze the causal relationship. This study used 48 quarters of time-series data, from the 4th quarter in 2001 to the 3rd quarter in 2013, about each business type's production index, and used an unchangeable index. The production index about the business type is classified into the current index and the unchangeable index. The unchangeable index divides the current index into deflators to remove fluctuation. Therefore, it is easy to analyze the actual production index. This study used the unchangeable index. Results - The production index of the distribution service industry and the production index of the environmental service industry consider the autocorrelation coefficient and partial autocorrelation coefficient; therefore, ARIMA(0,0,2)(0,1,1)4 and ARIMA(3,1,0)(0,1,1)4 were established as final prediction models, resulting in the gradual improvement in every production index of both types of business. Regarding the distribution service industry's production index, it is predicted that the 4th quarter in 2014 is 114.35, and the 4th quarter in 2015 is 123.48. Moreover, regarding the environmental service industry's production index, it is predicted that the 4th quarter in 2014 is 110.95, and the 4th quarter in 2015 is 111.67. In a causal relationship analysis, the environmental service industry impacts the distribution service industry, but the distribution service industry does not impact the environmental service industry. Conclusions - This study predicted the distribution service industry and environmental service industry with the ARIMA model, and examined the causal relationship between them through the Granger causality test based on the VAR Model. Prediction reveals the seasonality and gradual increase in the two industries. Moreover, the environmental service industry impacts the distribution service industry, but the distribution service industry does not impact the environmental service industry. This study contributed academically by offering base line data needed in the establishment of a future style of management and policy directions for the two industries through the prediction of the distribution service industry and the environmental service industry, and tested a causal relationship between them, which is insufficient in existing studies. The limitations of this study are that deeper considerations of advanced studies are deficient, and the effect of causality between the two types of industries on the actual industry was not established.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.5
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• pp.332-338
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• 2016

This study examined the posttraumatic growth of North Korean defectors, the relation between their characteristics and posttraumatic growth and the factors influencing their posttraumatic growth, and explored methods of improving their mental health status. 145 North Korean defectors, who were trained in B city and G city, participated in the survey from February 1 to March 10, 2016. The posttraumatic growth, resilience, self-esteem, deliberate rumination, and impact of the (traumatic) event were measured using the PTGI (Posttraumatic Growth Inventory), RS (Rumination Scale, Resilience Scale), SES (Self-esteem Scale) and ISR (Impact of Event). The data were analyzed using the t-test, ANOVA, Pearson correlation coefficient and stepwise multiple regression. The mean scores were 29.64 for posttraumatic growth. There were significant positive correlations between posttraumatic growth and resilience and between posttraumatic growth and rumination. The influence of the independent variables on the total posttraumatic growth was examined using regression analysis. Models including the variables (resilience, positive self-esteem, and rumination) explained 54.2% of the variance for the posttraumatic growth. These findings demonstrate that it is essential for nurses to continuously intervene and help North Korean defectors so as to promote their posttraumatic growth and resilience. Furthermore, it is also necessary for nurses to find ways to develop ideal interventions in order to activate deliberate rumination.

• Journal of Wetlands Research
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• v.24 no.1
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• pp.59-67
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• 2022

The interest in LID facilities is increasing worldwide for recovery of natural water cycle system to destroy by urbanization. However, problems are raised when installation of LID because comprehensive analysis about design capacity adequacy of LID facilities was not conducted completely. In this research, removal efficiency and design volume adequacy of LID facilities were analyzed based on rainfall monitoring data in four LID facilities(Vegetated Swale, Vegetative Filter Strip, Bio-Retention and Permeable Pavement). As a result, group of LID facility designed on WQV was shown higher flow(37%) and pollutants(TSS, BOD, TN and TP) removal efficiencies(20 ~ 37%) than group of LID facility designed on WQF. SA/CA graph was drawn for evaluation of design volume adequacy based on rainfall monitoring data. In this SA/CA graph, coefficient of determination show over 0.5 in all parameter, especially, Flow and TP were show over 0.95. And, 'SA/CA & L/CA' graph considering difference of structure mechanism in LID facility suggested in this research was confirmed that improved coefficient of determination in flow, TSS and TP than SA/CA graph. According to this research results, feasibility of applying 'SA/CA & L/CA' graph for evaluation of design volume adequacy in LID facility, and it is necessary to follow up research for generalization and normalization.

• Wind and Structures
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• v.34 no.1
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• pp.115-125
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• 2022

The high-Reynolds number flow around a rectangular cylinder, having streamwise to crossflow length ratio equal to 5 is analyzed in the present paper. The flow is characterized by shear-layer separation from the upstream edges. Vortical structures of different size form from the roll-up of these shear layers, move downstream and interact with the classical vortex shedding further downstream in the wake. The corresponding mean flow is characterized by a recirculation region along the lateral surface of the cylinder, ending by mean flow reattachment close to the trailing edge. The mean flow features on the cylinder side have been shown to be highly sensitive to set-up parameters both in numerical simulations and in experiments. The results of 21 Large Eddy Simulations (LES) are analyzed herein to highlight the impact of the lateral mean recirculation characteristics on the near-wake flow features and on some bulk quantities. The considered simulations have been carried out at Reynolds number Re=DU_∞/ν=40 000, being D the crossflow dimension, U_∞ the freestream velocity and ν the kinematic viscosity of air; the flow is set to have zero angle of attack. Some simulations are carried out with sharp edges (Mariotti et al. 2017), others with different values of the rounding of the upstream edges (Rocchio et al. 2020) and an additional LES is carried out to match the value of the roundness of the upstream edges in the experiments in Pasqualetto et al. (2022). The dimensions of the mean recirculation zone vary considerably in these simulations, allowing us to single out meaningful trends. The streamwise length of the lateral mean recirculation and the streamwise distance from the upstream edge of its center are the parameters controlling the considered quantities. The wake width increases linearly with these parameters, while the vortex-shedding non-dimensional frequency shows a linear decrease. The drag coefficient also linearly decreases with increasing the recirculation length and this is due to a reduction of the suctions on the base. However, the overall variation of C_D is small. Finally, a significant, and once again linear, increase of the fluctuations of the lift coefficient is found for increasing the mean recirculation streamwise length.

• Journal of Korean Tunnelling and Underground Space Association
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• v.11 no.1
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• pp.71-83
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• 2009

Shotcrete is an important primary support for tunnelling in rock. The quality control of shotcrete is a core issue in the safe construction and maintenance of tunnels. Although shotcrete may be applied well initially onto excavated rock surfaces, it is affected by blasting, rock deformation and shrinkage and can debond from the excavated surface, causing problems such as corrosion, buckling, fracturing and the creation of internal voids. This study suggests an effective non-destructive evaluation method of the tunnel shotcrete bonding state applied onto hard rocks using the impact-echo (IE) method and ground penetration radar (GPR). To verify previous numerical simulation results, experimental study carried out. Generally, the bonding state of shotcrete can be classified into void, debonded, and fully bonded. In the laboratory, three different bonding conditions were modeled. The signals obtained from the experimental IE tests were analyzed at the time domain, frequency domain, and time-frequency domain (i.e., the Short- Time Fourier transform). For all cases in the analyses, the experimental test results were in good agreement with the previous numerical simulation results, verifying this approach. Both the numerical and experimental results suggest that the bonding state of shotcrete can be evaluated through changes in the resonance frequency and geometric damping ratio in a frequency domain analysis, and through changes in the contour shape and correlation coefficient in a time-frequency analysis: as the bonding state worsens in hard rock condition, the autospectral density increases, the geometric damping ratio decreases, and the contour shape in the time-frequency domain has a long tail parallel to the time axis. The correlation coefficient can be effectively applied for a quantitative evaluation of bonding state of tunnel shotcrete. Finally, the bonding state of shotcrete can be successfully evaluated based on the process suggested in this study.

• Journal of Industrial Convergence
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• v.22 no.5
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• pp.107-116
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• 2024

This study is a descriptive research study to determine the extent to which end-of-life care stress, death awareness, and prior decision-making attitudes of nurses at a hospice and palliative nursing institution have an impact on end-of-life care performance. The subjects of this study were 200 nurses working at a hospice and palliative nursing institution. Data collection for this study was conducted from August 9 to September 30, 2021, using two methods: written questionnaire and internet survey. The data analysis method used Pearson's correlation coefficient to analyze the relationship between the subjects' end-of-life care stress, death awareness, prior decision-making attitude, and end-of-life care performance. Hierarchical Regression was used to identify factors affecting the subject's end-of-life care performance. The results of this study showed a significant correlation between end-of-life care performance and death awareness (r=.22, p=.002), and end-of-life care performance and prior decision-making attitude (r=.20, p=.004). And prior decision-making attitude and death awareness had a significant impact on end-of-life care performance. As death awareness and prior decision-making attitudes increased, end-of-life care performance increased, and end-of-life care stress did not appear to be a statistically significant factor influencing end-of-life care performance. In order to improve hospice nurses' ability to provide end-of-life care, intervention that takes into account the influencing factors is required.

• Journal of the Korea Institute of Building Construction
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• v.24 no.3
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• pp.381-391
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• 2024

This study examined the factors influencing safety scores in air conditioning installation projects, with a specific focus on the characteristics of safety managers and project-specific details. Given the increase in industrial accidents within this sector and the lack of research on smaller-scale operations, this analysis of 7,046 safety data records from Company A aimed to address this gap. The results indicate that the month of project commencement has the most significant impact on safety scores(correlation coefficient of 0.21), followed by the age of the safety manager(correlation coefficient of 0.06). Interestingly, the educational background of the managers did not appear to influence safety outcomes. Furthermore, project cost was found to have a negative correlation with safety scores(-0.1), suggesting that lower-cost projects may be associated with higher risk levels. These findings underscore the importance of developing tailored safety checklists that take into account the specific timing and scale of air conditioning installation projects. Additionally, the results suggest that incorporating both experienced(older) and less experienced(younger) safety managers into safety strategies may be beneficial for achieving optimal safety outcomes. This balanced approach could leverage the strengths of both groups, potentially enhancing overall risk assessment and mitigation efforts.