• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.6
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• pp.824-834
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• 1993

In cellular mobile communication systems, if the size of a cell is decreasing for economic utilization of frequency resources, frequent handovers may be requested because the time a mobile stays in a cell is decreasing. In general the measured parameters to decide handover including RSSI, BER, and the distance between mobile station and base station, are usually incorrect and handover decision using single parameter insufficient. Therefore, the better handover algorithm should take over the problems of this uncertain measurements, and make the decision more robust and flexible by the consideration of all those decision parameters at the same time. We propose a novel handover algorithm based the multicriteria decision making, in which those parameters are participated in the decision process using aggregation function in fuzzy set theory. As a simulation results, the overall decision making is more reliable and flexible than the conventional method using only one parameter, RSSI in terms of call force ratio, and handover request ratio.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.165-171
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• 2011

A Consider the dead man's switch installed in each and every locomotive cab, which support operational safety on railways around the world. The concept is very simple - every 150 to 180 seconds an illuminated push-button demands to be acknowledged so as to know that the Train Driver is alive and active. In the absence of a response over a period of minutes, the vigilance control will automatically apply the train brakes and bring the train to a stand. If we multiply the resetting of the vigilance control 60 times per hour by a 10-hour shift it equals 600 presses of the button during the shift that a Train Driver must pay attention to and acknowledge. This adds a fair bit of pressure on the train driver's job, particularly when he/she is driving through stations, with passengers moving about on platforms in an environment of complex signaling arrangements - all the while looking out for restricting signals. From this perspective, the Vigilance System's demand to be acknowledged every 150/180 seconds is disturbing and can unnecessarily take a driver's attention away from what is happening outside the confines of the cab. A much more dramatic situation can happen when a train driver is driving hour after hour at night when, by Mother's Nature request - people need to sleep. Experience and research shows that the the dead man's switch can be pressed by train driver in a state of deep relaxation and 'micro-sleep'. The vigilance control system which is applied to reduce the drive load considering bio-response multiple unit train is proposed.

• Korean Journal of Construction Engineering and Management
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• v.7 no.6
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• pp.121-131
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• 2006

Since "Act on Private Participation in Infrastructure" were changed in January 2005, BTL(Build-Transfer-Lease) projects of Private Participation In Infrastructure was introduced in the domestic construction market for the purpose of providing public facilities with the public. Selecting the most qualified Promoter should be considered discreetly in BTL projects because BTL projects is for projects with approximately thirty year project life cycle, plan, construction, operating, maintenance and obviously the success of the project totally depends on the capability and role of concessionaire. However, score for cost is likely to influence designating concessionaire to take the project. Accordingly, low bid contract with too much competition could decrease the quality of the construction plan and operating plan. Thus, this study did preliminary research and documents on problems of evaluation criteria for designating concessionaire in BTL projects, and proposed improvement program by doing questionnaire over specialists of each field.

• Journal of Intelligence and Information Systems
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• v.11 no.3
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• pp.129-139
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• 2005

The rapid growth of IT technologies enables the quality of human's daily life to be improved dramatically, Contrasting to the services in previous computing environment directed by user's request, the services in ubiquitous computing era of new IT technology are provided through recognizing users intention and utilizing context-aware information suited to the user. According to the contextual information, agents need to set a dynamic goal to achieve and work collaboratively with other agents. Agents that take control over their behaviors with capability of communicating with other agents become a thrust in this up-coming computing environment. This work focuses on building ontologies, shared knowledge bases among agents, to improve semantical interoperability among agents. More attention is given to the construction and effective management of ontology repository along with its requirement and organization. Ontology agent suggested takes an initiative role to manage the repository in a distributed manner and to facilitate the use of ontology in a multi-agent environment.

• Journal of Computing Science and Engineering
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• v.1 no.1
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• pp.56-73
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• 2007

Demands have been growing in safety-critical application fields for producing networked real-time embedded computing (NREC) systems together with acceptable assurances of tight service time bounds (STBs). Here a service time can be defined as the amount of time that the NREC system could take in accepting a request, executing an appropriate service method, and returning a valid result. Enabling systematic composition of large-scale NREC systems with STB certifications has been recognized as a highly desirable goal by the research community for many years. An appealing approach for pursuing such a goal is to establish a hard-real-time (HRT) component model that contains its own STB as an integral part. The TMO (Time-Triggered Message-Triggered Object) programming scheme is one HRT distributed computing (DC) component model established by the first co-author and his collaborators over the past 15 years. The TMO programming scheme has been intended to be an advanced high-level RT DC programming scheme that enables development of NREC systems and validation of tight STBs of such systems with efforts far smaller than those required when any existing lower-level RT DC programming scheme is used. An additional goal is to enable maximum exploitation of concurrency without damaging any major structuring and execution approaches adopted for meeting the first two goals. A number of previously untried program structuring approaches and execution rules were adopted from the early development stage of the TMO scheme. This paper presents new concrete justifications for those approaches and rules, and also discusses new extensions of the TMO scheme intended to enable further exploitation of concurrency in NREC system design and programming.

• Journal of KIISE:Computer Systems and Theory
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• v.37 no.1
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• pp.35-42
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• 2010

Guest operating systems running over the virtual machines share a variety of resources. Since CPU is allocated in a time division manner it consequently leads them to having the unknown physical time. It is not regarded as a serious problem in the server virtualization fields. However, it becomes critical in embedded systems because it prevents guest OS from executing real time tasks when it does not occupy CPU. In this paper we propose a hypercall to register a timer service to notify the timer request related real time. It enables hypervisor to schedule a virtual machine which has real time tasks to execute, and allows guest OS to take CPU on time to support real time. The following experiment shows its implementation on Xen-Arm and para-virtualized Linux. We also analyze the real time performance with response time of test application and frames per second of Mplayer.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1846-1850
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• 2005

This paper presents a constrained-based routing (CBR) algorithm called, Dynamic Possible Path per Link (D-PPL) routing algorithm, for MultiProtocol Label Switching (MPLS) networks. In MPLS on-line routing, future traffics are unknown and network resource is limited. Therefore many routing algorithms such as Minimum Hop Algorithm (MHA), Widest Shortest Path (WSP), Dynamic Link Weight (DLW), Minimum Interference Routing Algorithm (MIRA), Profiled-Based Routing (PBR), Possible Path per Link (PPL) and Residual bandwidth integrated - Possible Path per Link (R-PPL) are proposed in order to improve network throughput and reduce rejection probability. MIRA is the first algorithm that introduces interference level avoidance between source-destination node pairs by integrating topology information or address of source-destination node pairs into the routing calculation. From its results, MIRA improves lower rejection probability performance. Nevertheless, MIRA suffer from its high routing complexity which could be considered as NP-Complete problem. In PBR, complexity of on-line routing is reduced comparing to those of MIRA, because link weights are off-line calculated by statistical profile of history traffics. However, because of dynamic of traffic nature, PBR maybe unsuitable for MPLS on-line routing. Also, both PPL and R-PPL routing algorithm we formerly proposed, are algorithms that achieve reduction of interference level among source-destination node pairs, rejection probability and routing complexity. Again, those previously proposed algorithms do not take into account the dynamic nature of traffic load. In fact, future traffics are unknown, but, amount of previous traffic over link can be measured. Therefore, this is the motivation of our proposed algorithm, the D-PPL. The D-PPL algorithm is improved based on the R-PPL routing algorithm by integrating traffic-per-link parameters. The parameters are periodically updated and are dynamically changed depended on current incoming traffic. The D-PPL tries to reserve residual bandwidth to service future request by avoid routing through those high traffic-per-link parameters. We have developed extensive MATLAB simulator to evaluate performance of the D-PPL. From simulation results, the D-PPL improves performance of MPLS on-line routing in terms of rejection probability and total throughput.

• The KIPS Transactions:PartA
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• v.11A no.6
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• pp.419-424
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• 2004

Mobile Internet using mobile devices provides Portability to users and is Spreading throughout out lives. But Practical use of the mobile Internet is insufficient due to it's fundamental limitations. Especially, mobile resources are not sufficient because they are not closely connected under current mobile Internet services which are provided with pre-designed structure. For these reasons it will take a lot more time and effort for mobile Internet to grow as a popular service. In this paper, we are focusing to overcome the local limitation and to enhance the 'Sharing of Mobile Resources' by expanding mutual connectivity between resource objects scattered over the mobile Internet environment. To archive this, we propose the MRSS(Mobile Resources Sharing System). MRSS automatically converts single request from user to multiple instructions based on 'Context-Awareness' to search for proper information. Using MRSS, we can expect 'Mobile Ubiquitous Computing' environment which users can reach to information anywhere, anytime.

• Journal of Digital Convergence
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• v.11 no.3
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• pp.273-277
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• 2013

Phishing attacks have been implemented in smarter, more advanced ways with the passage of time. Hackers use intelligent phishing attacks to take over computers and to penetrate internal networks in major organizations. So, in this paper, a model for a prevention of phishing attack spread is conceptual designed in order to protect internal users and sensitive or important information from sophisticated phishing attacks. Internal users simultaneously utilize both external web and organizational mail services. And hackers can take the both side equally as a vector. Thus, packets in each service must be monitored and stored to recognize threatening elements from both sides. The model designed in this paper extends the mail server based security structure used in conventional studies for the protection of Internet mail services accessed by intranet users. This model can build a list of phishing sites as the system checks e-mails compared to that of the method that directly intercepts accesses to phishing sites using a proxy server, so it represents no standby time for request and response processes.

• Journal of the Korea Society of Computer and Information
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• v.26 no.6
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• pp.145-154
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• 2021

While welcoming the distributing of the powers of the Ministry of Education, which is currently being promoted, to the city and provincial offices of education, I am very concerned that this will expand and amplify the powers concentrated in one central institution to 17 local institutions closer to the field. Until now, the Ministry of Education and the Office of Education have served as co-cause providers as important reasons for hindering school education. The transfer of the authority of the Ministry of Education is highly likely to be deformed as soon as it results in the quantitative reduction of the functions and roles of the existing Ministry of Education and the quantitative expansion of the roles and functions of the city and provincial offices of education. In the reality that no legal device for school autonomy has been established, it is highly likely that emphasizing the principle of school autonomy in our educational climate, which is deeply rooted in the vertical bureaucratic administrative culture, will end with a simple measure or stop at the level of imitation. Therefore, a more stable device is needed to check the authority of the city and provincial office of education and the superintendent of education to take over the authority of the Ministry of Education. This is also a system that is still required even when school autonomy becomes legal. Therefore, it is necessary to revitalize the independent education committee, establish a local education committee in the city and province education office, and activate the resident participation system (resident proposal system, resident voting system, resident litigation system, resident audit request system).