• Journal of KIISE:Computer Systems and Theory
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• v.27 no.1
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• pp.89-100
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• 2000

Recently, studies on the mobile computing environments that enable mobile hosts to move while retaining its network connection are in progress. In these mobile computing environments, one of the necessary components is the distributed file system supporting mobile hosts, and there are several issues for the design and implementation of the shared file system. Among these issues, there are problems caused by network traffic on limited bandwidth of wireless media. Also, there are consistency maintenance issues that are caused by update-conflicts on the shared files in the distributed file system. In this paper, we propose TWB(Trickle Write-Back) scheme that utilizes weak connectivity for cache management of mobile clients. This scheme focuses on saving bandwidth, reducing waste of disk space, and reducing risks caused by disconnection. For such goals, this scheme lets mobile clients write back intermediate states periodically or on demand while delaying unnecessary write-backs. Meanwhile, this scheme is based on the existing distributed file system architecture and provides transparency.

• The Journal of the Korea Contents Association
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• v.11 no.6
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• pp.90-97
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• 2011

The availability of computers and the wide network of the internet of the 'Information Society' has created a new space: Cyberspace. In this situations, the matters of individual identities and morality are more important problems. Korean classical novel, Gu Wun Mong, embodied the exploration process of identities in virtual spaces, has gravity of a situation. Seong Jin, the hero experienced the life of Yang so you went throughing virtual life, be born again. And he met eight taoist fairy in that virtual world. In this process, Seong Jin overcame a dualistic world of view and established identity of genuine truth-seeker. The 'Dream-fantasy' experience differentiation real world and virture world and give to Seong Jin a new identity, So You. Seong Jin used avatar, So You was free from limits of self and became obtain multiple personalities. Finally, Seong Jin realized the fact that real world and virtual one is the same, for development self-perception. Seong Jin's enlightment provided solutions for modern netizens, who is ambivalent about contradiction the real and virtual, infinity and clash of desire.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.9
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• pp.740-746
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• 2013

Design with crashworthiness concept has been emphasized for almost aircraft and motor vehicles. However, crashes accompanied serious injury and death have been continuously occurred, and will be occurred subsequently. What was worse, it is a well-known fact that there were a good many crashes classified as survivable accidents in which fatal injuries were reported. But we cannot say that fatal injuries were inevitable consequences of those crashes. If crashworthy design for seat, restraint systems, and cabin strength were adequate or right, survivability in a crash event could be maximized greatly. To substantiate the right crashworthiness, we must thoroughly understand the characteristics of human tolerance under abrupt acceleration change, and the cabin design should be combined with proper use of energy absorbing technologies that reduce accelerations experienced by the occupants. In this paper, the emphasis on the human tolerance under abrupt accelerations as well as the necessity of change in design requirements for crash environment will be stressed to widen the belt of consensus for the right crashworthy design.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.6
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• pp.625-630
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• 2016

This paper contributes to the development of an early detection system to detect the alteration of a target ship during early stages using the steering wheel signal via AIS communication. The feasibility of this system is also verified with a real ship trial. It was confirmed that the rudder angle on ECDIS was ordinarily marked green or red by the used rudder angle after the steering wheel operation. We were able to detect intentions for a change in course by a target ship quickly and efficiently avoid collisions. This system will contribute to more active VTS services and the analysis of marine accidents using the General Information Center On Maritime Safety & Security (GICOMS).

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.6
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• pp.660-670
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• 2016

This study expresses the necessity of recognizing Pyeongtaek Port as a specific traffic safety area to ensure the safety of the vessels that navigate there using quantitative data. The number of foggy days, pilotage distance, the number of large vessels and the number of fishing vessels that traveled between Pyeongtaek Port and 6 ports chosen as comparative study objects were compared and analyzed. The results showed that Pyeongtaek Port was more frequently affected by restricted visibility. With these perverse conditions, Pyeongtaek Port has a longer pilotage distance than Busan, Busan Newport, Ulsan or Pohang Ports by as much as 3.5-6 times. Especially from May to July, when fisheries were most functional, large vessels were required to navigate in an opposite direction to avoid 35 fishing vessels that were observed, creating an increased possibility for collisions among vessels. Therefore, the navigational safety of Pyeongtaek Port should be further secured by defining the approaching waters as specific traffic safety areas, giving large vessels legal priority over fishing vessels.

• Proceedings of KOSOMES biannual meeting
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• 2005.11a
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• pp.41-46
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• 2005

It have been known that the probability of accidental happening in towing-barge is higher than that of other merchant vessels. Because the towing-barge is restricted in thier manoeuvring ability due to its towingline. A report from ministry maritime affairs and fisheries said that the rate of collision accident for towing-barge is $40\%$ high tlnn other transport system in sea. A number of researches have been carried out to improve the safety policy in the towing-barge sea transportation system by the gorvernment. This study examined the safety status in domestic towing-barge sea transportation system The registration status, safety operational policy and post accidental data were also examined A survey research of experts relating to towing-barge operation also was carried out to find the detailed of safety status. This study would be applicable to set up safety policy for towing-barge marine transportation system.

• The Journal of the Korea Contents Association
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• v.18 no.7
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• pp.401-411
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• 2018

This study includes three students' whose country origin is of a political and economic success, therefore the pursuit to learn English is important. The participants evaluated in this study are two students of Korean descent and one Chinese student. The purpose was to evaluate their overall language learning experiences outside of their home country. While the participants in this study share similar cultures and learning styles their process towards second language readiness is different. The internal factors (readiness) that motivated them to study abroad were synonymous. However, the classroom situations (assessment), social settings (environment), and strategies used were disparate. The methodology of this paper used a holistic approach with a snowball sampling technique. The responses were collected by a prepared questionnaire and unstructured interviews, then later analyzed by the inductive reasoning process. The 3 specific categories identified were despondency, culture and communication conflict. The present study revealed that the participants' earlier preparation from their home country plays a significant contribution to their success abroad.

• Journal of Korea Multimedia Society
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• v.12 no.2
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• pp.323-328
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• 2009

Natural Phenomena are simulated to make computer users feel verisimilitude and be immersed in games or virtual reality. The important factor in simulating fluid such as water or sea using 3D rendering technology in games or virtual reality is real-time interaction and reality. There are many difficulties in simulating fluid models because it is controlled by many equations of each specific situation and many parameter values. In addition, it needs a lot of time in processing physically-based simulation. In this paper, I suggest simplified fluid-surface model in order to represent interaction between rigid body and fluid, and it can make faster simulation by improved processing. Also, I show movement of fluid surface which is come from collision of rigid body caused by reaction of fluid in representing interaction between rigid body and fluid surface. This natural fluid-surface model suggested in this paper is represented realistically in real-time using fluid dynamics veri similarly. And the fluid-surface model will be applicable in games or animation by realizing it for PC environment to interact with this.

• The Journal of the Korea Contents Association
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• v.18 no.3
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• pp.11-18
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• 2018

To interact with a virtual object in immersive virtual environment, the target object should be selected quickly and accurately. Conventional 3D ray casting method using a direction of user's hand or head allows the user to select an object quickly. However, accuracy problem occurs when selecting an object using conventional methods among occlusion of objects. In this paper, we propose a region of interest based selection method that enables to select an object among occlusion of objects using a combination of gaze tracking and hand gesture recognition. When a user looks at a group of occlusion of objects, the proposed method recognizes user's gaze input, and then region of interest is set by gaze input. If the user wants to select an object among them, the user gives an activation hand gesture. Then, the proposed system relocates and visualizes all objects on a virtual active window. The user can select an object by a selecting hand gesture. Our experiment verified that the user can select an object correctly and accurately.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.8
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• pp.33-41
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• 2007

The IEEE 802.11 DCF channel access function allows single transmission inside two-hop network in order to avoid collisions and eliminate the hidden and exposed terminal problems. Singular transmission capability causes data frames waiting for the entire roundtrip time in the transmitter neighborhood, and results in increased frame latency and lower network throughput. Real-time and pervasive applications are severely affected for the lower medium utilization; especially with high network traffic. This work proposes a new scheme with the help of Frame Aggregation technique in IEEE802.11n and overcomes the single transmission barrier maintaining the basic DCF functionality. Proposed scheme allows parallel transmissions in non-interfering synchronized slots. Parallel transmissions bypass the conventional physical carrier sense and random Backoff time for several cases and reduce the frame latency and increase the medium utilization and network capacity.