• Communications of the Korean Institute of Information Scientists and Engineers
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• v.5 no.1
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• pp.04-10
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• 1987

We consider a time sharing computer system with a single processor where tasks ofK different types arrive at the system according to independent time homogeneous Poisson processes from outside. A task, after given a quantum for processing, leaves the system, or changes the type and rejoins the system according to specified probabilitycs. While many existing priority time sharing models determine the priorities of tasks strictly by their service time requirements, this paper develops a new scheduling rule wherein the importances or urgencies in addition to the service time requirements of tasks are counted, by inposing an appropriate reward structure on the system. Also presented is the algorithm through which to determine the rankings of K types according to this new scheduling rule.

• Journal of the Korea Society of Computer and Information
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• v.11 no.1 s.39
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• pp.63-69
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• 2006

There are many new studies on the contents for mobile devices that are all connected to networks in a seemingly ubiquitous environment. The purpose of this paper is to propose a framework for obtaining Internet content intended for computers on mobile devices. In other words, the primary concern of this paper is to select the best images for optimal performance and convert them into images that can be effectively reproduced on mobile devices. For this, the performance of the server is to be optimized through selecting high-priority images among the many available images and converting them while considering the display pixel rates (DPR) and the image distribution areas.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.1015-1016
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• 2015

VANET is a technology for building a robust ad-hoc network between mobile vehicles as well as, between vehicles and RSU. Vehicles are moving and they only stay in the RSU area for a short time. When the number of requests is increased, an important challenge is to implement a suitable scheduling algorithm which serves as more requests as possible. $D^*S$ algorithm uses a priority weight, DS_Value, for selection of a request to get service. Priority weight is influenced only by deadline and data size parameters. We propose a packet scheduling using multilevel queue and show that using this idea leads to higher service ratio compare to previous algorithms.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.2
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• pp.289-296
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• 2015

Wireless multimedia sensor network senses and transfers mass multimedia data. Also, it is sensitive to latency. This thesis proposes a routing technique based on traffic priority in order to improve the network efficiency by minimizing latency. In addition, it proposes a congestion control mechanism that uses packet service time, packet inter-arrival time, buffer usage, etc. In this thesis, we verified the reduction of packet latency in accordance with the quality level of packet as a result of the performance analysis through the simulation method. Also, we verified that the proposed mechanism maintained a reliable network state by preventing packet loss due to network overload.

• The KIPS Transactions:PartC
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• v.13C no.7 s.110
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• pp.933-938
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• 2006

Different multimedia services over networks not only require different amounts of bandwidth but also have different Qualify of Service (QoS) requirements. For example, QoS guarantees for higher priority calls is an important issue in multimedia communication networks. In this paper, we develop an adaptive bandwidth management algorithm, which is able to provide QoS guarantees for higher priority calls while accommodating as many heterogeneous multimedia call connections as possible. Our scheme, based on reservation and bandwidth adaptation, manages bandwidth based on real time estimates of current network conditions. Simulation results indicate the superior performance of our scheme providing excellent trade off between contradictory requirements.

• Journal of Korean Society of Transportation
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• v.28 no.3
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• pp.7-17
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• 2010

Bicycle is one of the most important eco-friendly transport mode which can cope with global warming. ICTs(information and communication technologies) on bicycles became a dominant factor for success to the spread of bicycles to public as we experienced Public Bike System. In this paper, conceptualization and classification of u-Bike services are fulfilled and its priority was examined using AHP method. Group capabilities technique of ECII, a computer fool of AHP was invited to minimize bias on appraisal. 12 u-Bike services were conceptualized. U-service with highest adoptability was 'bike and ride' service which can link bicycle to public transportation. 'Prevention system from abandonment and theft' and 'public bike system' similar to Velib system in Paris are also considered to be very important services in u-City.

• Journal of Communications and Networks
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• v.10 no.3
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• pp.287-296
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• 2008

The IEEE 802.11 wireless standard uses the carrier sense multiple access with collision avoidance (CSMA/CA) as its MAC protocol (during the distributed coordination function period). This protocol is an adaptation of the CSMA/CD of the wired networks. CSMA/CA mechanism cannot guarantee quality of service (QoS) required by the application because orits random access method. In this study, we propose a new MAC protocol that considers different types of traffic (e.g., voice and data) and for each traffic type different priority levels are assigned. To improve the QoS of IEEE 802.11 MAC protocols over a multi-channel CSMA/CA, we have developed a new admission policy for both voice and data traffics. This protocol can be performed in direct sequence spread spectrum (DSSS) or frequency hopping spread spectrum (FHSS). For voice traffic we reserve a channel, while for data traffic the access is random using a CSMA/CA mechanism, and in this case a selective reject and push-out mechanism is added to meet the quality of service required by data traffic. To study the performance of the proposed protocol and to show the benefits of our design, a mathematical model is built based on Markov chains. The system could be represented by a Markov chain which is difficult to solve as the state-space is too large. This is due to the resource management and user mobility. Thus, we propose to build an aggregated Markov chain with a smaller state-space that allows performance measures to be computed easily. We have used stochastic comparisons of Markov chains to prove that the proposed access protocol (with selective reject and push-out mechanisms) gives less loss rates of high priority connections (data and voices) than the traditional one (without admission policy and selective reject and push-out mechanisms). We give numerical results to confirm mathematical proofs.

• The Journal of the Korea Contents Association
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• v.11 no.11
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• pp.521-535
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• 2011

The purpose of this study is to analyze the priority of curriculums on students preparing to become flight attendants using paired t-test, Borich method, and Herschknowiz's criticality function. As a result of this study, it was discovered that what flight attendants and students needed to study the most were foreign language subjects as English, Chinese, and Japanese. Therefore, a department of universities related to airline service should develop new curriculum to adapt to the trend of globalization. Also, flight attendants need curriculum including subjects related to tourism as an introduction to airline service. This means that the role of flight attendants needs to be expanded and specialized. In conclusion, a department related airline service should try to elevate its quality of education and design curriculum which will help flight attendants become specialists in their field.

• The Korean Journal of Health Service Management
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• v.7 no.4
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• pp.289-303
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• 2013

This study looks at priorities in managing public hospitals by figuring out categories needed to examine the quality of each hospital. In order to analyze priorities and relative importance of valuation indicator in Seoul municipal hospitals, surveys were sent via e-mail to medical professionals who have participated in evaluation of municipal hospitals. The analytic hierarchy process (AHP) was conducted using the Expert Choice 11.5 program. The results show that 'providing public service' is considered to be the most important category for all kinds of public hospitals, followed by 'improving the quality of medical care', 'hospital management and governance', and 'efficient hospital management'. The importance of 'hospital management and governance' and 'efficient hospital management' is different depending on the types of hospitals, but the importance of 'providing public service' and 'improving the quality of care' remains the same regardless of the types of hospitals. Based on these results, the study comes to a conclusion that public hospitals should place high value on certain categories and their management purposes should differ depending on their specific fields and characteristics. This study will help furthering discussions on the identity and roles of public hospitals.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.6A
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• pp.558-564
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• 2007

3G Long Term Evolution, which aims for various mobile multimedia service provision by enhanced wireless interface, proposes VoIP-based voice service through a Packet Switching (PS) domain. As delay and loss-sensitive VoIP traffic flows through the PS domain, more challenging technical difficulties are expected than in Circuit Switching (CS) domain based VoIP services. Moreover, since 3G LTE, which adopts the OFDM as its physical layer, introduces Physical Resource Block (PRB) as a unit for transmission resources, new types of resource management schemes are needed. This paper proposes a PRB scheduling algorithm of MAC layer for VoIP service in 3G LTE and shows the simulation results. The proposed algorithm has two key parts; dynamic activation of VoIP priority mode to satisfy VoIP QoS requirements and adaptive adjustment of the priority mode duration in order to minimize the degradation of resource utilization.