• Journal of KIISE:Information Networking
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• v.34 no.1
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• pp.62-72
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• 2007

Mobile Virtual Private Network (MVPN) provides VPN services without geographical restriction to mobile workers using mobile devices. Coexistence of Mobile IP (MIP) protocol for mobility and IPsec-based VPN technology are necessary in order to provide continuous VPN service to mobile users. However, Problems like registration failure or frequent IPsec tunnel re-negotiation occur when IPsec-based VPN Gateway (GW) and MIP are used together. In order to solve these problems, IETF proposes a mechanism which uses external home agent (x-HA) located external to the corporate VPN GW. In addition, based on the IETF proposal, a mechanism that assigns x-HA dynamically in the networks where MN is currently located was also proposed with the purpose to reduce handover latency as well as end-to-end delay. However, this mechanism has problems such as exposure of a session key for dynamic Mobility Security Association (MSA) or a long latency in case of the handover between different networks. In this paper, we propose a new MVPN protocol in order to minimize handover latency, enhance the security in key exchange, and to reduce data losses cause by handover. Through a course of simulation, the performance of proposed protocol is compared with the existing mechanism.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.15 no.4
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• pp.83-96
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• 2020

Traditionally social problems had been largely left to be handled by non-profit organizations, not because of lack of interests in social causes but mostly because of lack of innovative ideas to solve them in commercially viable ways. This market failure has recently been fixed by social enterprises, which manage to provide both solutions for social issues and commercially viable business models. As a result, we have been witnessing a sudden spike of public interests in these social enterprises as well as a call for empirical investigation on social enterprises by prior studies. However, empirically investigating a social enterprise has been a challenging endeavor mostly due to the insufficient number of successful social enterprises. Answering to the call in this study, we empirically investigate Goyohan Taxi, a successful social enterprise that partners with visually impaired cabdrivers and offers a taxi service, by both longitudinally interviewing the founder and adopting in vivo observation throughout the entrepreneurial journey of Goyohan Taxi. Based on the single case study method, we find that Goyohan Taxi adopts two distinctive decision-making mechanisms, the de-escalation of commitment and the orthogonality of commercial and social goals. Although generalizability of the our finding is minimal due to the limitation of single case study method, our finding contributes to the research of social entrepreneurship by offering new avenue of research in decision-making process of social entrepreneurs.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.4
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• pp.246-257
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• 2015

The progressive degradation paths of structures have quantitatively been tracked by using stochastic processes, such as Wiener process, gamma process and compound Poisson process, in order to consider both the sampling uncertainty due to the usual lack of damage data and the temporal uncertainty associated with the deterioration evolution. Several important features of stochastic processes which should carefully be considered in application of the stochastic processes to practical problems have been figured out through assessing cumulative damage and lifetime distribution as a function of time. Especially, the Wiener process and the gamma process have straightforwardly been applied to armors of rubble-mound breakwaters by the aid of a sample path method based on Melby's formula which can estimate cumulative damage levels of armors over time. The sample path method have been developed to calibrate the related-parameters required in the stochastic modelling of armors of rubble-mound breakwaters. From the analyses, it is found that cumulative damage levels of armors have surely been saturated with time. Also, the exponent of power law in time, that plays a significant role in predicting the cumulative damage levels over time, can easily be determined, which makes the stochastic models possible to track the cumulative damage levels of armors of rubble-mound breakwaters over time. Finally, failure probabilities with respect to various critical limits have been analyzed throughout its anticipated service life.

• The Journal of the Korea Contents Association
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• v.17 no.10
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• pp.19-29
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• 2017

Purpose : To describe and understand the experience of QI (quality improvement) nurses related to the hospital QI activities in public general hospitals. Methods : Purposive sampling was conducted 10 QI nurses and who have QI work experience for more than 1 year. Data were collected through focus group interviews. Interviews were recorded, transcribed and analyzed with qualitative content analysis using Strauss and Corbin's methodology. Results : The core categories of experience with QI activities were 'the success and failure of the medical care and overall health service sector', 'the degree of activation of current QI activities', 'characteristics of public hospital QI activities', 'what is needed to activate future QI activities'. The key themes were derived as follows. 'Success of quality enhancement activities according to the characteristic of public hospitals', 'activation of public hospital QI activities through leadership and QI education', 'reorganizing the role of regional hospitals in public hospitals'. Conclusion : Physician participation is important in the success of QI activities in public hospital practice. To lead these physician participation, Sharing doctor's QI experience and providing the necessary knowledge in QI activities and helping their leadership in QI activities are needed. QI nurses at public hospitals should lead QI activities to improve national hospitals' care quality through cooperating with local hospitals.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.11
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• pp.711-717
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• 2017

The railway is a public transportation system that provides large-scale passenger transportation and service, whose reliability and safety is the top priority. The wiring of railway vehicles is classified into train control lines (train lines) and communication lines. The train lines are used for input / output signals related to vehicle driving and safety functions, and the communication lines are used for the input / output signals for passenger services such as broadcasting. In order to measure the reliability of railway vehicles, a train line is applied to the input / output interface of the control signals between the electric control devices in the vehicle, and there are many electromechanical devices such as relays and contactors for the control logic. In fact, since the vehicle control circuit is composed of several thousand contacts, it is difficult to check for errors such as contact failure, and it is impossible to check the real-time status, so a lot of manpower and time is required for regular maintenance. Therefore, we analyze the current state of the train line design of the electric equipment used for driving and services in domestic railway cars and propose three wiring reduction methods to improve it. Based on the analysis of domestic electric vehicles, it was confirmed that the wiring reduction effect is 35% or more.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.12
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• pp.5893-5900
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• 2012

It is very critical to promptly maintain airway of cardiac arrest cases or serious traumatic cases. The purpose of this study is to compare intubation rate, successful rate and pre-/post-education self-confidence between laryngeal tube (LTS) and proseal laryngeal mask (PLMA), so that it may contribute to improving the ability of 119 emergency team - a pivotal role in pre-hospitalization process - to carry out advanced airway management. In order to achieve the purpose, total 60 paramedics (Class I) who worked for incumbent 119 emergency team were asked to join a practical experiment and were also divided into two groups (LTS group: 30 people, PLMA group: 30 people). In details, they were all asked to take 3 sessions of practice (5 minutes per session) using dummy model to quantitatively measure the time and success/failure of intubation and the change of their self-confidence. As a result, it was found that there were statistically significant differences in the time of intubation between LTS and PLMA group (p=.000), but there was no significant difference in the rate of successful intubation between these two groups, and self-confidence of two groups tended to significantly increase after experiment (p=.000). Conclusively, if it is necessary to promptly apply intubation to traumatic cases with immobilized cervical vertebral and lingual edema, LTS can be useful as an effective means of intubation. And it is expected that continuing intubation training using LTS will improve the ability of emergency team to perform advanced airway management for traumatic cases.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.2
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• pp.469-475
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• 2010

The railway signalling system plays an essential role in the safe and efficient train operation as serving control functions of train operation intervals and train routes. The reliability and safety of the system are very important because the failure of the railway signalling system can lead to train collision or derailment as well as train operation stop. Until now, in railway signalling system the conventional wayside signal mode has been used generally. There are, however, the risk of accidents such as human mistakes caused by that the driver identifies the signal lamp status and controls train speed with the naked eye. It is also necessary to refurbish the obsolete system. Thereby, It is being effective that the onboard signal mode has been recently introduced and applied in order to transmit the speed control information to train by using the computer and communication equipment. It is necessary to switch over the system in a way while providing passengers with an operation service to replace the obsolete signal system. In this paper, we verify the cases through trial assessment which are solved by the way of adding specific functionalities in the problems of interference among the procedure of switch-over processes and a serial of processes for system verification while a train is operated in the new system in parallel to the existing system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.1
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• pp.579-584
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• 2017

The damper oil seal of a high-speed railway vehicle is made from nitrile butadiene rubber (NBR) in order to prevent lubricant from leaking into the damper and to stop harmful contaminants from entering the external environment while in service. Oil leakage through the seal primarily occurs from fatigue failure of the damper. Cumulative damage of the seal occurs due to the contact force between the rod and the rubber during movement due to track irregularities and cants, among other factors. Thus, the design of the oil seal should minimize the maximum principal strain at weak points. In this study, the optimal cross section of the damper oil seal was found using the multi-island genetic algorithm method to improve the durability of the damper. The optimal shape of the oil seal was derived using process automation and design optimization software. Nonlinear material properties for finite element analysis (FEA) of the rubber were determined by Marlow's model. The nonlinear FEA confirmed that the maximum principal strain at the oil leakage point was decreased 24% between the initial design and the optimum design.

• Journal of Korea Water Resources Association
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• v.51 no.8
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• pp.703-711
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• 2018

Water distribution system (WDS) pipe bursts are caused from excessive pressure, pipe aging, and ground shift from temperature change and earthquake. Prompt detection of and response to the failure event help prevent large-scale service interruption and catastrophic sinkhole generation. To that end, this study proposes a improved Western Electric Company (WECO) method to improve the detection effectiveness and efficiency of the original WECO method. The original WECO method is an univariate Statistical Process Control (SPC) technique used for identifying any non-random patterns in system output data. The improved WECO method multiples a threshold modifier (w) to each threshold of WECO sub-rules in order to control the sensitivity of anomaly detection in a water distribution network of interest. The Austin network was used to demonstrated the proposed method in which normal random and abnormal pipe flow data were generated. The best w value was identified from a sensitivity analysis, and the impact of measurement frequency (dt = 5, 10, 15 min etc.) was also investigated. The proposed method was compared to the original WECO method with respect to detection probability, false alarm rate, and averaged detection time. Finally, this study provides a set of guidelines on the use of the WECO method for real-life WDS pipe burst detection.

• Culinary science and hospitality research
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• v.22 no.7
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• pp.58-71
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• 2016

This study aimed to gauge the public awareness of the cultural value and superiority of Korean traditional sweets. Furthermore, it evaluated the obstacles that the Korean traditional sweet industry faces in the modern society, and a method to popularize it. It also analyzed the awareness of Korean traditional sweets. Both male and female study subjects showed the highest awareness of yakgwa and the lowest of chasugwa. Female respondents showed significantly (p<0.05~p<0.001) higher awareness of Osaekdasik, Hukimjadasik, Bellflower-junggwa, and Genseng-junggwa than male respondents. Maejakgwa, Osaekdasik, Rice-dasik, and Hukimjada- sik showed significant difference in awareness by the area survey respondents originated. Contrarily, Walnut-gangjung had significantly (p<0.001) higher awareness in rural areas than in more urban areas (e.g., large cities and small and medium-sized cities). Both male and female respondents answered (OR indicated) that the obstacles facing the Korean traditional sweet industry are uncommon products and expensive price. Both male and female respondents said that they had Korean traditional sweets less because it was harder to purchase than western sweets (due to limited access to these sweets), less delicious, and too expensive. Both male and female respondenst suggested that the urgent tasks to popularize the Korean traditional sweets were diversification in shape and ingredient, developing various new flavors, and cheaper products. Both male and female respondents responded that product diversification and strengthened marketing were urgent tasks to industrialize Korean traditional sweets. Therefore, it was believed that failure in generalization was the urgent problem of the Korean traditional sweet industry, and that Korean traditional sweets were harder to purchase because of lower accessibility than western sweets. To popularize Korean traditional sweets, it may be necessary to develop sweets in various shapes and ingredients, flavors suiTable to modern people, become cheaper in price, and have fancier (OR better) packaging.