• Journal of the Korean Institute of Gas
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• v.18 no.4
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• pp.56-62
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• 2014

The present study investigated numerically heat and mass transfer characteristics of a fixed bed reactor by using a computational fluid dynamics (CFD) code of Fluent (ver. 13.0). The temperature and species fraction were estimated for different porosities. For modeling of the catalyst in a fixed bed tube, catalysts were regarded as the porous material, and the empirical correlation of pressure drop based on the modified Eugun equation was used for simulation. In addition, the averaged porosities were taken as 0.545, 0.409, and 0.443 and compared with non-porous state. The predicted results showed that the temperature at the tube wall became higher than that estimated along the center line of tube, leading to higher hydrogen generation by the endothermic reaction and heat transfer. As the mean porosity increases, the hydrogen yield and the outlet temperature decreased because of the pressure drop inside the reformer tube.

• Journal of KIBIM
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• v.8 no.3
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• pp.31-42
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• 2018

This study focuses on the BIM request for information(RFI) processing performance and quantitatively analyzes the performance of the BIM coordinator and the loss due to the waiting of the project participants. For these purposes, a method to quantitatively evaluate the performance of the BIM coordinator was proposed using a queueing model. For the verification, two projects in which BIM was applied in the construction phase were selected, and the BIM RFI data were collected through the analysis of the BIM monthly report and BIM coordinator work log of each project. In addition, the BIM input personnel, labor cost, and productivity data were collected through interviews with the experts of the case projects. The analysis of the BIM RFI processing performance of the BIM coordinator using the queueing model exhibited on a probabilistic basis that the waiting status of the project participants could vary depending on the preliminary BIM application to the design verification as well as the input number and level of the BIM coordinator personnel. In addition, the loss cost due to the waiting of the project participants was analyzed using the number of BIM RFIs waiting to be processed in the queueing system. Finally, the economic feasibility analysis for the optimal BIM coordinator input was performed considering the loss cost. The results of this study can be used to make decisions about the optimal BIM coordinator input and can provide grounds for the BIM return on investment (ROI) analysis considering the waiting cost of the project participants.

• Journal of Korea Port Economic Association
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• v.19 no.2
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• pp.1-32
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• 2003

The purpose of this study is to identify and evaluate the competitiveness of ports in ASEAN(Association of Southeast Asian Nations), which plays a leading role in basing the hub of global logistics strategies as a countermeasure in changes of logistics environments. This region represents most severe competition among Mega Hub ports in the world in terms of container cargo throughput at the onset of the 21st century. The research method in this study accounted for overlapping between attributes, and introduced the HFP method that can perform mathematical operations. The scope of this study was strictly confined to the ports of ASEAN, which cover the top 100 of 350 container ports that were presented in Containerization International Yearbook 2002 with reference to container throughput. The results of this study show Singapore in the number one position. Even when we compare with major ports in Korea (after getting comparative ratings and applying the same data and evaluation structure), the number one position still goes to Singapore and then Busan(2) and Manila(2), followed by Port Klang(4), Tanjung Priok(5), Tanjung Perak(6), Bangkok(7), Inchon(8), Laem Chabang(9) and Penang(9). In terms of the main contributions of this study, it is the first empirical study to apply the combined attributes of detailed and representative attributes into the advanced HFP model which was enhanced by the KJ method to evaluate the port competitiveness in ASEAN. Up-to-now, none has comprehensively conducted researches with sophisticated port methodology that has discussed a variety of changes in port development and terminal transfers of major shipping lines in the region. Moreover, through the comparative evaluation among major ports in Korea and ASEAN, the presentation of comparative competitiveness for Korean ports is a great achievement in this study. In order to reinforce this study, it needs further compensative research, including cost factors which could not be applied to modeling the subject ports by lack of consistently quantified data in ASEAN.

• Journal of Digital Convergence
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• v.16 no.7
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• pp.79-88
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• 2018

Previously, there have been many studies on the fraud of employees, internal customers of the company, but there have been a lot of studies on military affairs that are closely related to the improvement of army's combat power. Therefore, this study investigates how communication satisfaction is influenced by the characteristics of SNS. For empirical verification, 240 soldiers were surveyed in this study. The analysis method was to investigate the correlation between each variable using the Structural Equation Model (SEM). The results of this study show that the SNS characteristics have a positive effect on the overall model related to organizational communication satisfaction. Organizational communication satisfaction has a positive impact on military fraud and organizational communication satisfaction has been shown to mediate between army and SNS traits. Through this research, we intend to promote the morale of soldiers by activating communication among group members using appropriate level of social networking.

• Journal of Digital Contents Society
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• v.10 no.2
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• pp.357-365
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• 2009

To effectively exploit the underlying network bandwidth while maximizing user perceivable QoS, mandatory to make proper estimation on packet loss and queuing delay of the underling network. This issue is further emphasized in wireless network environment where network bandwidth is scarce resource. In this work, we focus our effort on developing performance model for wireless network. We collect packet trace from actually wireless network environment. We find that packet count process and bandwidth process in wireless environment exhibits long range property. We extract key performance parameters of the underlying network traffic. We develop an analytical model for buffer overflow probability and waiting time. We obtain the tail probability of the queueing system using Fractional Brown Motion (FBM). We represent average queuing delay from queue length model. Through our study based upon empirical data, it is found that our performance model well represent the physical characteristics of the IEEE 802.11b network traffic.

• Culinary science and hospitality research
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• v.19 no.5
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• pp.11-22
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• 2013

This study aimed to identify the relationships between the quality and image of school meal service and satisfaction perceived from high school students and to access the moderating effect of its distribution types. For the empirical analysis, this study used SPSS 18.0 and AMOS 18.0 and conducted frequency analysis, reliability analysis, exploratory and confirmatory factor analysis, path analysis and chi-square difference test. As a result of the analyses, the validity and reliability were identified showing over 0.4 factor loading value, ${\chi}^2$=258.831, d.f.=98, RMR=0.059, GFI=.822, AGFI=.776, NFI=0.908, IFI=0.941, CFI=0.940. The results of the structural equation modeling analysis are as follows: first, the quality of school meal service had a significant influence on its image; next, the image of school meal service had a significant influence on satisfaction with the service; last, there is a significant moderating effect of distribution types in the relationship between the image of school meal service and satisfaction with the service.

• The Journal of Society for e-Business Studies
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• v.15 no.1
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• pp.173-189
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• 2010

This study empirically explores the relationship among knowledge management success factors (leadership, organizational culture, information technology, measurement, incentive, knowledge quality), knowledge management activities(knowledge creation and knowledge use), and task performance in disaster management area. Findings suggest that (1) organization culture, information technology, incentive and quality of knowledge are significantly related to knowledge creation activities while leadership, information technology, incentive and quality of knowledge are significantly related to knowledge use activities, (2) higher level of knowledge creation is related to high level of knowledge use, and (3) the level of knowledge use activities seems to be significantly related to task performance in disaster management, while knowledge creation activities are not.

• Membrane and Water Treatment
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• v.7 no.3
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• pp.223-240
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• 2016

In this study, poly(vinyl-alcohol) and water insoluble ${\beta}$-cyclodextrin polymer (${\beta}$-CDP) cross-linked with citric acid, have been used as macrocyclic carrier in the preparation of polymer inclusion membranes (PIMs) for aniline (as molecule model) extraction from aqueous media. The obtained membranes were firstly characterized by X-ray diffraction, Fourier transform infrared and water swelling test. The transport of aniline was studied in a two-compartment transport cell under various experimental conditions, such as carrier content in the membranes, stirring rate and initial aniline concentration. The kinetic study was performed and the kinetic parameters were calculated as rate constant (k), permeability coefficient (P) and flux (J). These first results demonstrated the utility of such polymeric membranes for environmental decontamination of toxic organic molecules like aniline. Predictive modeling of transport flux through these materials was then studied using design of experiments; the design chosen was a two level full factorial design $2^k$. An empirical correlation between aniline transport flux and independent variables (Poly ${\beta}$-CD membrane content, agitation speed and initial aniline concentration) was successfully obtained. Statistical analysis showed that initial aniline concentration of the solution was the most important parameter in the study domain. The model revealed the existence of a strong interaction between the Poly ${\beta}$-CD membrane content and the stirring speed of the source solution. The good agreement between the model and the experimental transport data confirms the model's validity.

• Journal of Korea Society of Industrial Information Systems
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• v.12 no.5
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• pp.23-38
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• 2007

Since the players in online games seek fun, emotional aspects may be important factors in the pleasure-oriented information systems. This study attempted to verify the effects of characteristic factors of games (fun, challenge, compensation, and diversity) on emotion and customer satisfaction in game portal sites. The study established the research model on the foundation of precedent researches related to online games, emotion, and customer satisfaction. The study conducted online and offline survey on individuals with experiences in using online game portal sites. 206 samples were used to test the research hypotheses. By using Structural Equation Modeling, The study found the following results. First, it was revealed that characteristics of games had positive effects on emotion in game portal sites and indirect effects on user satisfaction. Second, the study analyzed the difference between low user group and high user group. It was revealed that the characteristics of games had positive effects on emotion in the low user group, but only challenge factor influenced on emotion in the high user group.

• Research in Community and Public Health Nursing
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• v.11 no.2
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• pp.321-332
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• 2000

The purpose of this study was to test the hypothetical model designed to explain nursing students' perceived stress, coping levels, and stress outcomes. This hypothetical model was based on the Kim. Jung Hee(l987)' s stress model and stress-related literature. Exogenous variables were self-efficacy. hardiness. social support. and exercise. Endogenous variables were stress perception. coping levels. and stress outcomes. Empirical data for testing the hypothetical model consisted of 205 nursing students. SAS PC Program and LISREL 8.12a program were used for descriptive statistics and linear structural relationship(LISREL) modeling. The results were as follows. 1) The overall fit of the hypothetical model to the data was good( $x^2$=78.41(p=0.010), $x^2$/ df=1.50. RMSEA=0.05, standardized RMR= 0.05, GFI=0.95, AGFI=0.91, NNFI=0.90, NFI=0.94). 2) The results of statistical testing of the hypotheses were as follows. (1) As expected. self-efficacy had a significant effect on stress perception. But. hardiness. social support, and exercise did not have a significant effect on stress perception. Self-efficacy, hardiness. social support, and exercise explained 12% of the total variance of stress perception. (2) As expected, self-efficacy, hardiness, social support, exercise, and stress perception had a significant effect on coping behavior, Self-efficacy, hardiness, social support, exercise, and stress perception explained 53% of the total variance of coping behavior. (3) As expected, stress perception and coping behavior had a significant effect on stress outcomes. Stress perception and coping behavior explained 84% of the total variance of stress outcomes. In conclusion, the hypothetical model of this study was confirmed in explaining and predicting stress perception, coping levels, and stress outcomes in nursing students. And these findings suggest the need to develop nursing intervention to enhance self-efficacy, hardiness, social support, and exercise to decrease the harmful outcomes of stress.