• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.6
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• pp.2225-2239
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• 2021

To assist in data collection, the use of a mobile sink has been widely suggested in the literature. Due to the limited sensor node's storage capacity, this manner to collect data induces huge latencies and drop packets. Their buffers will be overloaded and lead to network congestion. Recently, a new bio-inspired optimization algorithm appeared. Researchers were inspired by the swarming mechanism of salps and thus creating what is called the Salp Swarm Algorithm (SSA). This paper improves the sink mobility to enhance energy dissipation, throughput, and convergence speed by imitating the salp's movement. The new approach, named the Mobile Sink based on Modified Salp Swarm Algorithm (MSSA), is approved in a heterogeneous Wireless Sensor Network (WSN) data collection. The performance of the MSSA protocol is assessed using several iterations. Results demonstrate that our proposal surpass other literature algorithms in terms of lifespan and throughput.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.1
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• pp.34-45
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• 2013

Due to its self-configuring nature, the tactical mobile ad hoc network is used for communications between tactical units and the command and control center (CCC) in battlefields, where communication infrastructure is not available. However, when a tactical unit moves far away from the CCC or there are geographical constraints, the data link between two communicating nodes can be broken, which results in an invalid data route from the tactical units to CCC. In order to address this problem, in this paper we propose a hierarchical connectivity maintenance scheme, namely ADLCoM (Autonomous Data Link Connectivity Maintenance). In ADLCoM, each tactical unit has one or more GW (gateway), which checks the status of data links between tactical units. If there is a possibility of link breakage, GWs request ground or aerial unmanned vehicles to become a relay for the data link. The simulation results, based on tactical scenarios, show that the proposed scheme can significantly improve the network performance with respect to data delivery ratio.

• Journal of the Society of Disaster Information
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• v.17 no.3
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• pp.655-666
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• 2021

Purpose: This study is to develop a method for measuring dynamic speeding risks using vehicle trajectory big data and to demonstrate the feasibility of the devised speeding index. Method: The speed behaviors of vehicles were analysed in microscopic space and time using individual vehicle trajectories, and then the boundary condition of speeding (i.e., boundary speed) was determined from the standpoint of crash risk. A novel index for measuring the risk exposure of speeding was developed in microscopic space and time with the boundary speed. Result: A validation study was conducted with vehicle-GPS trajectory big data and ground-truth vehicle crash data. As a result of the analysis, it turned out that the index of speeding-risk exposure has a strong explanatory power (R²=0.7) for motorway traffic accidents. This directly indicates that speeding behaviors should be analysed at a microscopic spatiotemporal dimension. Conclusion: The spatial and temporal evolution of vehicle velocity is very variable. It is, hence, expected that the method presented in this study could be efficaciously employed to analyse the causal factors of traffic accidents and the crash risk exposure in microscopic space using mobility trajectory data.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37B no.9
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• pp.806-813
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• 2012

In a cloud computing environment, various solutions were introduced to provide the service to users such as Infrastructure as a Service (IaaS), Platform as a Service (PaaS), Software as a Service (SaaS) and Desktop as a Service (DaaS). Nowadays, Mobile as a Service (MaaS) to provide the mobility in a cloud environment. In other words, users must have access to data and applications even when they are moving. Thus, to support the mobility to a mobile Thin-Client is the key factor. Related works to support the mobility for mobile devices were Mobile IPv6 and Proxy Mobile IPv6 which showed performance drawbacks such as packet loss during hand-over which could be very critical when collaborating with cloud computing environment. The proposed model in this paper deploys middleware and replica servers to support the data transmission among cloud and PMIPv6 domain. It supports efficient mobility during high-speed movement as well as high-density of mobile nodes in local mobility anchor. In this paper, through performance evaluation, the proposed scheme shows the cost comparison between previous PMIPv6 and verifies its significant efficiency.

• Korean Institute of Interior Design Journal
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• no.28
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• pp.100-108
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• 2001

The purpose of this study is to develop recommendation of sign system and color codes in making the public interior environment more accessible for the visually impaired persons. The appropriate guidelines in designing the sign system and the color codes in the public interior environment can increase the accessibility, the mobility and the safety for the visually impaired persons including the increasing elderly. By selecting the effective sign system much more desirable results can be brought: Improvement of accessibility, mobility, increase of safety, work efficiency and the psychological stability. Sign system and the color is more important for the weak-sighted people than the normal-sighted in way finding and the orientation strategies. 53 visually impaired persons participated for this study, the answers of the questionaires by the weak-sighted persons are focused on in this research. The data, the needs of users is analysed on the basis of users-oriented. The result of this study can be considered as a basic direction of sign system design and color codes in our codes in our public environment for all people especially visually impaired persons.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.8A
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• pp.909-917
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• 2004

Mobility support is one of the most important functions to provide seamless data transfer for real-time multimedia services in wireless networks. In this paper, we analyze and compare the handoff delay performances for several architectures such as MIP-RO, SIP, MIP-RO/CIP and SIP/CIP, which are expected to be a promising solution to support IP mobility management. For the analysis, we make the detailed message flows of those architectures in handoffs, and then make an analytical model to compute the handoff delay for each scheme. Numerical results showed that the SIP/CIP approach outperformed other schemes in the viewpoints of the handoff delay.

• Journal of Distribution Science
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• v.18 no.4
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• pp.5-12
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• 2020

The Purpose: This study aims to identify the characteristics of customer satisfaction of the restaurants delivery applications that is increasing globally, especially in Korea. Due to demographic changes, social trends and the development of food science, customers no longer want to visit restaurants. This represents an important change in the restaurant business, and related research is also very urgent. Research design, data, and methodology: With 296 surveyed questionnaire, the study analyzed to verify the validity and reliability of measured variables in Korea. And structural equation model was used for hypotheses test of the research. Results: The result showed that consumers' usefulness, mobility, and reliability influenced on satisfaction. Specifically, mobility and reliability influencing the satisfaction and loyalty as well. And significant impact of satisfaction and loyalty are also corroborated. However, the path from informative to both satisfaction and loyalty was not statistically significant. This means food application developers should no longer focus on providing too many information, instead, concentrate on improving mobility and trust of mobile applications. Conclusions: This study analyzed the influence of attributes of food delivery applications on satisfaction and loyalty, and suggested crucial strategic implications of delivery marketing companies involved in the implementation of mobile application developers.

• Journal of Korean Public Health Nursing
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• v.26 no.3
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• pp.504-517
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• 2012

Purpose: The aim of this study was to investigate gender differences in risk factors and sleep, depression, and mobility of Korean elderly with and without low back pain and sciatica. Methods: Data were derived from the 2011 Korean National Survey on Older Adults. Participants included 10,674 community-dwelling elderly. The group of elderly subjects with low back pain and sciatica and the group of elderly subjects without low back pain and sciatica were compared according to gender. Result: Age, monthly income, exercise, arthritis, osteoporosis, and providing caring support were significant risk factors for low back pain and sciatica in elderly male subjects. On the other hand, monthly income, living arrangement, arthritis, osteoporosis, providing caring support, and television watching time were significant risk factors in elderly female subjects. Significant differences in depression and mobility according to low back pain and sciatica were observed in both genders. Conclusion: Risk factors for low back pain and sciatica in elderly differed according to gender. Low back pain and sciatica showed an association with depression and mobility. These findings should be considered in planning for nursing intervention for low back pain and sciatica.

• IE interfaces
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• v.17 no.1
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• pp.22-32
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• 2004

The most complicated and difficult area in the simulation of evacuation process is the area of human behavior. However, it is generally very difficult to understand and quantify human behaviors since the factors involved vary significantly according to the types of accidents and the environment. The walking speed of passenger is especially affected by dynamic effect and list due to damage and ship motion in wave. There are various methods to get the useful data for evacuation simulation. The onboard experimental approach is one of the strongest method. This paper discusses the onboard experimental results of human mobility of passengers in evacuation from ship. To realize ship trim and heel due to maritime casuality, the passage model for experiment is made. The experiment was carried out at dynamic and static condition respectively using the ship with passage model. The result was evaluated and it will be reflected in evacuation simulation tool.

• Journal of Advanced Navigation Technology
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• v.24 no.5
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• pp.358-367
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• 2020

With the increases of average commuting time of office workers in the Seoul metropolitan area and the cost of traffic congestion on roads, the need for new transportation is increasing and urban air mobility (UAM) is emerging as an alternative. Therefore, in this paper, the vertiport locations were selected and routes were established using population, traffic and commuting data of Seoul and Gyeonggi Province. Vector thrust type and multicopter type of eVTOL compatible for UAM were selected by analyzing the types of eVTOLand time required for selected routes was calculated. In addition, the time required when we utilize other transportations was compared with UAM. Finally, it was verified that the commuting time can be sharply reduced when we use UAM.