• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.1
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• pp.23-33
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• 2020

In this study, the effect of surface roughness distribution and its influence on the inflight icing code was investigated. Previous numerical studies focused on the magnitude of surface roughness, and the effects were only addressed in terms of changes in thermal boundary layers with fully turbulent assumption. In addition, the empirical formula was used to take account the turbulent transition due to surface roughness, which was regarded as reducing the accuracy of ice shape prediction. Therefore, in this study, the turbulent transition model based on the two-equation turbulence model was applied to consider the effects of surface roughness. In order to consider the effect of surface roughness, the transport equation for roughness amplification parameter was applied, and the surface roughness distribution model was implemented to consider the physical properties. For validation, the surface roughness, convective heat transfer coefficient, and ice shape were compared with experimental results and other numerical methodology. As a result, it was confirmed that the excessive prediction of the heat transfer coefficient at the leading edge and the ice horn shape at the bottom of the airfoil were improved accordingly.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.86-92
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• 2017

In this study, a running performance evaluation and roller rig test was conducted to evaluate the applicability of a composite bogie frame, which has the role of the primary suspension. The composite bogie frame was made of a GEP224 glass/epoxy prepreg. Vehicle dynamic analysis was carried out on the composite bogie with three different kinds of side beam thicknesses (50 mm, 80 mm, and 150 mm). From the results, the composite bogie with a side beam thickness of 80 mm satisfied all the dynamic design requirements. Although the composite bogie with the side beam thickness of 50mm also met the design requirements, its critical speed was just a 2% margin to the requirement. In contrast, the model of the side beam thickness of 150mm did not meet the ride comfort. In addition, a composite bogie frame with the side beam thickness of 80 mm was fabricated and installed on a complete bogie. Moreover, the roller rig test using the fully equipped bogie was performed to evaluate the critical speed. During the test, the lateral excitation was imposed on the wheelsets to realize the rail irregularity. There was no divergence of the lateral displacement of the wheelsets while increasing the speed. The measured critical speed was similar to the predicted result.

• KIPS Transactions on Computer and Communication Systems
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• v.8 no.9
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• pp.209-216
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• 2019

Publish-subscribe communication model is popular for various type of distributed applications because of its loosely coupled style connections. Among the various architecture style for publish-subscribe system, peer-to-peer architecture has been used for the mission critical application domain since it provides high scalability and real-timeness. On the other hand, to utilize the bandwidth of given networks, message filtering is frequently used to reduce the number of messages on the system. Even if P2P provides superior scalability, it is hard to apply filtering to the its messaging system because the filtering process should be done on the peer-side in P2P architecture that are usually done on the broker server in conventional pub/sub architecture. In this paper, we propose a hierarchical subscription management structure as well as message forwarding scheme for efficient data dissemination. Our proposed scheme reduces the number of received messages by filter-out un-wanted messages and offloading the message dissemination work to other subscribers to enhance the messaging throughput.

• Journal of Convergence for Information Technology
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• v.12 no.4
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• pp.103-110
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• 2022

Online transactions are more familiar in various fields due to the development of the ICT and the increase in trading platforms. In particular, the amount of transactions is increasing due to the increase in used transaction platforms and users, and reliability is very important due to the nature of used transactions. Among them, the used car market is very active because automobiles are operated over a long period of time. However, used car transactions are a representative market to which information asymmetry is applied. In this paper presents a DID-based transaction model that guarantees reliability to solve problems with false advertisements and false sales in used car transactions. In the used car transaction model, sellers only register data issued by the issuing agency to prevent false sales at the time of initial sales registration. It is authenticated with DID Auth in the issuance process, it is safe from attacks such as sniping and middleman attacks. In the presented transaction model, integrity is verified with VP's Proof item to increase reliability and solve information asymmetry. Also, through direct transactions between buyers and sellers, there is no third-party intervention, which has the effect of reducing fees.

• Journal of Digital Convergence
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• v.20 no.2
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• pp.325-338
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• 2022

This study was conducted to explore the acceptance behavior of undergraduate students toward telemedicine, which is temporarily allowed in the COVID-19. We applied social cognitive theory and technology acceptance model in order to reflect the convergence characteristics between medical service and digital technology of telemedicine. Based on these theoretical backgrounds, we investigated perception toward telemedicine and determinants of intention to accept telemedicine. To examine the research model and hypothesis, an online survey was conducted for college students who have not used telemedicine from September 8 to 10, 2021. A total of 184 data were collected, and multiple regression analysis was conducted using the SPSS 28.0 program. The results showed that health technology self-efficacy, usefulness and convenience benefits, social norm, and trust in telemedicine providers had positive effects on intention to accept telemedicine. This study is meaningful in that it selected undergraduate students, who are digital natives, as new targets for telemedicine, and presented the basic direction of strategies to target them.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.4A
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• pp.353-359
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• 2010

Cementitious matrix based composites are vulnerable to the drying shrinkage crack during the curing process. In this study, the drying shrinkage induced fracture behavior of the fiber reinforced concrete is simulated and the effects of the fiber reinforcement conditions on the fracture characteristics are analysed. The numerical model is composed of conduit elements and rigid-body-spring elements on the identical irregular lattice topology, where the drying shrinkage is presented by the coupling of nonmechanical-mechanical behaviors handled by those respective element types. Semi-discrete fiber elements are applied within the rigid-body-spring network to model the fiber reinforcement. The shrinkage parameters are calibrated through the KS F 2424 free drying shrinkage test simulation and comparison of the time-shrinkage strain curves. Next, the KS F 2595 restrained drying shrinkage test is simulated for various fiber volume fractions and the numerical model is verified by comparison of the crack initiating time with the previous experimental results. In addition, the drying shrinkage cracking phenomenon is analysed with change in the length and the surface shape of the fibers, the measurement of the maximum crack width in the numerical experiment indicates the judgement of the crack controlling effect.

• 한국노년학
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• v.29 no.2
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• pp.489-511
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• 2009

While late-life suicide has been increasing and become an important issue for public health in Korea, little is known about the phenomenon and its contributing risk factors based on which effective preventive measures can be made. Since suicidal ideation is a major precursor to attempted and completed suicide, the objective of the present study was to reveal primary contributors to suicidal ideation. Data were collected from a cross-sectional survey of 247 community-dwelling Korean older adults (age≥60) in the mid-size city in Korea. The statistical methodology employed a robust hierarchical regression procedure that iteratively downweights outliers. Based on the stress-diathesis model, the study examined major diathesis and stressors directly explaining suicidal ideation. The study also explored the significant interaction among these factors. The findings revealed that living alone and depression were significant main antecedents of suicidal ideation. In addition, neuroticism X life events and neuroticism X depression were significant interaction terms with the strongest explanatory power, which provides an empirical evidence to support the stress-diathesis model in explaining suicidal phenomenon of the Korean elderly. The result demonstrates the theoretical implication as well as the practical implication for developing and implementing late-life suicide prevention strategies. Limitations and directions for future research are discussed.

• Journal of the Korean GEO-environmental Society
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• v.25 no.6
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• pp.19-24
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• 2024

Urban densification has necessitated the development of subterranean spaces such as subway networks and underground tunnels to facilitate the dispersal and movement of populations. Development of these underground spaces requires excavation from the ground surface, which can induce groundwater flow and potentially lead to ground subsidence and sinkholes, damaging structures. To mitigate these risks, it is essential to model groundwater flow prior to construction, analyze its characteristics, and predict potential groundwater discharge during excavation. In this study, we collected meteorological, topographical, and soil conditions data for the city of ○○, where tunnel construction was planned. Using the Visual MODFLOW program, we modeled the groundwater flow. Excavation sections were set as drainage points to monitor groundwater discharge during the excavation process, and the effectiveness of seepage control measures was assessed. The model was validated by comparing measured groundwater levels with those predicted by the model, yielding a coefficient of determination of 0.87. Our findings indicate that groundwater discharge is most significant at the beginning of the excavation. Additionally, the presence of seepage barriers was found to reduce groundwater discharge by approximately 59%.

• Journal of Food Hygiene and Safety
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• v.28 no.1
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• pp.7-12
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• 2013

This study presents the influence on growth properties determined using a novel predictive growth model of wild-type Salmonella spp. KSC 101 by variations in the temperature and time during cut packaging in cold, uncooked pork meat. The experiment performed for model development included an arrangement of different temperatures ($0^{\circ}C$, $5^{\circ}C$, $10^{\circ}C$, $15^{\circ}C$, and $20^{\circ}C$) and time durations (0, 1, 2, and 3 hours) that reflect actual pork-cut and packaging processes. No growth was observed at $0^{\circ}C$ and $5^{\circ}C$, whereas some growth was observed at $10^{\circ}C$, $15^{\circ}C$, and $20^{\circ}C$, with a mean increase of only 0.34 log CFU/g. The growth observed at $20^{\circ}C$ was more robust than that observed at $15^{\circ}C$, but the difference was not statistically significant (p > 0.05). However, compared with PMP (Pathogen Modeling Program), the wild-type Salmonella spp. KSC 101 showed a more rapid growth. We used the Gompertz 4 parameter equation as the primary model, and the exponential decay formula as the secondary model. The estimated $R^2$ values were 0.99 or higher. The developed model was evaluated by comparison of the experimental and predictive values, and the values were in agreement with the ${\pm}0.5$ log CFU/g, although the RMSE (Root mean square error) value was 0.103, which indicates a slight overestimation. Therefore, we suggest that the developed predictive growth model would be useful as a tool for evaluating sanitation criteria in pork cut-packaging processes.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.6
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• pp.209-218
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• 2017

This study examined the influence of social support (social support from family, social support from friends), psychological behavioral characteristics (self-esteem, interpersonal dependency, locus of control), and stress on the depression levels of college students. The study subjects were 546 college students in D city. The survey was conducted using a self-administered questionnaire in October 2015. As a result, the depression levels were significantly higher in the group showing lower family and friends' social support, self-esteem, and locus of control, while it was significantly higher in the group showing higher interpersonal dependency and stress. The depression levels of the subjects showed a negative correlation with family and friends' social support, self-esteem, and locus of control, but a positive correlation with interpersonal dependency and stress. Covariance structure analysis revealed an increase in the depression levels of college students when the awareness of the stress source was higher, and when the awareness of social support or psychological behavioral characteristics was lower. These results suggest that the depression levels of college students would be increased when the social support and psychological behavioral characteristics are low, and when stress is high. In particular, it was influenced much more by stress than other factors. Therefore, to decrease the depression levels of college students, it would be necessary to put efforts to understand their main stress sources and then reduce them.