• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.5
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• pp.84-95
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• 2019

This paper reports the process of seismic fragility analysis for the rahman-type continuous bridge system. The target structure was the five span highway bridge with maximum pier hight of 72m. OpenSees software was used for the nonlinear time history analysis. In this study, 50 ground motions are considered for nonlinear time history analysis. For each ground motion, PGA was scaled from 0.1g to 2.0g with intervals of 0.1g in order to consider a wide range of the seismic intensity measure. In addition, yield displacement and ultimate displacement of each pier were calculated through section analysis. Based on the result of non linear time history analysis and section analysis, damage condition of target bridge was classified according to the definition of damage condition proposed by Barbat et al. As a result, it was predicted that Extensive Damage occurred at P1 when 0.731 g earthquake occurred in the longitudinal direction. Based on the seismic fragility analysis results, it is found that the probability of occurrence of Extensive Damage in the 4,800 - year period earthquake was about 4.2%. Therefore the target bridge has enough safety for earthquake.

• Journal of Navigation and Port Research
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• v.43 no.3
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• pp.209-218
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• 2019

Coastal cities suffer a great deal of storm and wind damage. The storm and wind characteristics vary between cities. Therefore, a storm and wind damage management system suited for specific characteristics is required for each coastal city. In this study, we analyze the current situation and establish the problem of storm and wind damage management system in regards to urban management, coastal management and disaster management. We also review the storm and wind damage management system for the USA and Japan. We consequently propose a plan to improve the storm and wind damage management system. As a result of the study, in terms of city management, we recommend the compulsory identification of disaster prevention districts, implementation of the integrated coastal city management plan, designation of natural disaster risk mitigation area as disaster prevention district, the division of disaster prevention district into wind damage prevention district, storm damage prevention district, erosion damage prevention district, the building of restrictions at the disaster prevention district by ordinance, etc. In regards to coastal management, we suggest the delegation of authority to delegate coastal erosion management area to the local government, the subdivision of coastal erosion management area into erosion serious area, erosion progress area, erosion concern area, the building restrictions at coastal erosion management area by ordinance, development of erosion prediction chart, etc. In relation to disaster management, we recommend the integration of "countermeasures against natural disasters act" and "disasters and safety management basic act", the local government-led disaster prevention system, the local disaster management network, and the customized local disaster prevention plan, etc.

• Journal of the Korean Geotechnical Society
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• v.35 no.9
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• pp.15-28
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• 2019

Long-term allowable compressive Loads of PHC piles were analyzed based on qualification tests results by 17 small and medium PHC pile producing companies and product specifications by 6 major and 17 small and medium PHC pile producing companies. At the present stage, an average long-term allowable compressive load of PHC pile was designed at 70% level from current design data, and safety factor of 4.0 was applied to long-term allowable compressive loads of PHC pile despite of its excellent quality. Most quality standards of PHC pile are specified at KS F 4306. But compressive strength test method of spun concrete is specified at KS F 2454. As a result of analyzing quality test data supplied by each manufacturer, all quality test results showed higher performances than standard values. Therefore, it was considered that the capacity of PHC pile can be used up to the maximum allowable compressive load of PHC pile when PHC pile is designed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.12
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• pp.910-917
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• 2018

This paper describes the developments to improve the feeling and safety of the remote control system of unmanned vehicles. Generally, in the case of the remote control systems, a joystick-type device or a simple steering-wheel are used. There are many cases, in which there are operations without considering the feedback to users and driving feel. Recently, as the application area of the unmanned vehicles has been extended, the problems caused by not considering the feedback are emphasized. Therefore, the need for a force feedback-haptic control arises to solve these problems. In this study, the force feedback-haptic control algorithm considering the vehicle parameters is proposed. The vehicle parameters include first the state variables of dynamics, such as the body side-slip angle (${\beta}$) and yawrate (${\gamma}$), and second, the parameters representing the driving situations. Force feedback-haptic control technology consists of the algorithms for general and specific situations, and considers the situation transition process. To verify the algorithms, a simulator was constructed using the vehicle dynamics simulation tool with CAN communication environment. Using the simulator, the feasibility of the algorithms was verified in various scenarios.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.55 no.1
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• pp.82-93
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• 2019

The International Labor Organization (ILO) selected fishing as the most dangerous group of jobs in the world, and it is well known in Korea as a 4D industry. Offshore large purse seine accounts for the largest portion of the fishing industry in the coastal region with high death rate and the accident rate. The repeated disaster rate survey by the Korea Maritime Institute (KMI) shows offshore large purse seiner is the highest at 22.3 percent and coastal gill nets and offshore stow net are following at 12.4 percent and 11.9 percent in order. Therefore, risk factors occurring in offshore large purse seiners were analyzed based on data from the National Federation of Fisheries Cooperatives (NFFC) for three years from 2015 to 2017 and 4M (Man, Machine, Media, Management) 3E (Engineering, Education, Enforcement) techniques were used to provide a safe fishing environment. The number of accidents on offshore large purse seiners each year was more than 150, and the number of accidents on every fishing boats was as high as 17 percent in 2015. If the accident rate and the risk level were divided by insurance, the accident resulting from contact with machinery was the highest, and the risk of a contact with gear was low but frequently occurring. This was caused by collisions and contact with gear in situations where death and disappearance risk are not high, and accident types in situations where death and loss risk are considered to be contact with machinery, falls or other accidents. Through these analysis techniques, the frequency and risk of each type of accident on a offshore large purse seiners can be demonstrated, and it is expected to raise awareness of a safer fishing environment and contribute to the reduction of accidents.

• Journal of Sleep Medicine
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• v.15 no.2
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• pp.37-42
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• 2018

Objectives: To assess the effect and safety of transcranial direct-current stimulation (tDCS) in primary chronic insomnia. Methods: A one-month, double-blind, randomized, sham-controlled trial was performed. A total of 7 patients with primary chronic insomnia received tDCS using anodal (n=3), cathodal (n=2), or sham stimulation (n=2). They were followed up at 1 week and 1 month after treatment. The primary outcome measures included improvement in total sleep time (TST), sleep latency (SL), and sleep efficiency (SE) at 1 month follow-up. Results: TST and SE were improved with tDCS at 1 month follow-up in all patients (100%) of the anodal group, one (50%) of the cathodal group, and one (50%) of the sham group. tDCS improved SL at 1 month follow-up in two patients (67%) of the anodal group, one (50%) of the cathodal group, and none (0%) of the sham group. With respect to adverse events, transient itching sensation occurred in one patient of the anodal group. None of the other groups reported adverse events. Conclusions: Our results suggest that tDCS may be effective and safe for treatment of primary chronic insomnia. A larger controlled study needs to be further investigated.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.6
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• pp.481-495
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• 2020

After the resonator on the basis of the wave-filter theory was designed to control the waves with a specific frequency range surging into the harbor, the several case with the use of resonator have been reported in some part of sea, including the port of Long Beach, USA, and yacht harbor at Rome, Italy in order to control the long-period wave motion from the vessels. Recently, the utility and applicability of the resonator has been sufficiently verified in respect of the control of tsunami approximated as the solitary wave and/or the super long-period waves. However, the case with the application of tsunami in the real sea have not been reported yet. In this research, the respective case with the use of existing resonator at the port of Mukho and Imwon located in the eastern coast of South Korea were studied by using the numerical analysis through the COMCOT model adapting the reduction rate of 1983 Central East Sea tsunami and 1993 Hokkaido Southwest off tsunami. Consequently, the effectiveness of resonator against tsunami in the real sea was confirmed through the reduction rate of maximum 40~50% at the port of Mukho, and maximum 21% at the port of Imwom, respectively. In addition, it was concluded that it is necessary to study about the various case with application of different shape, arrangement, and size of resonator in order to design the optimal resonator considering the site condition.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.6
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• pp.496-505
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• 2020

In the previous research, the effectiveness of resonator was confirmed through the numerical analysis on two cases with the use of existing resonator at the Mukho and Imwon ports located in the eastern coast of South Korea by discussing the reduction rates of 1983 Central East Sea tsunami, and 1993 Hokkaido Southwest off tsunami, respectively. In this study, the reduction rates of tsunami height with three different resonators, Type I, II-1, and II-2, at the Samcheok port were examined respectively through the numerical analysis using COMCOT model under the same condition as the previous study. It was discussed the spatial distribution of maximum height of tsunami, change of water level, and effectiveness of resonator with the presence of new types of resonator, and change of their sizes. As a result, the effectiveness of resonator was verified through the application of new types of resonator reducing about maximum 40% of tsunami height. In order to design the optimal resonator for the variety of site condition, it is necessary to research about the various cases applying different shape, arrangement, and size of resonator as further study.

• Korean Journal of Construction Engineering and Management
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• v.22 no.2
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• pp.21-30
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• 2021

The existing construction industry is classified into industries with low productivity compared to other industries. In order to solve the decline in productivity in the construction industry, the world is focusing on off-site construction (OSC), which is about 40% more productive than existing construction methods. This high productivity is possible because the three stages of production, transport to the site, and site assembly are consistently maintained in a continuous flow. This study conducted a functional survey through literature review, preliminary field survey, questionnaire, and expert interview. The surveyed function were classified into five categories: convenience, flexibility, manageability, communication, and safety, and the functional characteristics of flexibility, manageability, and communication were high. Because of the change according to the construction progress, the production schedule of the factory, and the variety of transportation time required. Finally, A functional block diagram was developed based on the 15 functions corresponding with an average score of 4 or more in the surveyed function score result. If the OSC transport system is established through this study, It can contribute to a successful construction OSC project and increase productivity.

• The Journal of Society for e-Business Studies
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• v.26 no.2
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• pp.1-17
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• 2021

This paper elucidates the effect of characteristics of service quality on continuance usage intention of digital healthcare service using mediating factors of user expectation and user utility. First, we classified independent factors into three types such as service system characteristics, user characteristics, and healthcare service characteristics from the previous studies, and investigated the effect of three independent factors on continuance usage intention of digital healthcare service. Second, we analyzed the impact of two mediating factors, user expectation and user utility, on the continuance usage intention. We developed a research model that includes three types of independent factors, mediated factors of user expectation and user utility, and a dependent factor of continuance usage intention. We surveyed a total of 357 samples from digital healthcare service users and analyzed the research model. The research results significantly show that Characteristics of Users is essential factor impacting a dependent factor of Continuance Usage Intention. The results indicate the followings: (1) Characteristics of Users including the variables of Innovation impacts User Expectation, and User Expectation affects Users Utility, and Users Utility also affects Continuance Usage Intention. (2) Characteristics of Service Systems including the variables of Functionality, Compatibility, and Convenience and Characteristics of users of Innovation variable impact the mediating factor of User Expectation, and User Expectation also affects the factor of Continuance Usage Intention. (3) Characteristics of Healthcare Services including the variables of Reliability, Ease of Operation, Safety, and Accuracy impact User Utility, and User Utility also affects Continuance Usage Intention.