• Journal of Communications and Networks
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• v.11 no.2
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• pp.175-186
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• 2009

A new medium access control (MAC) scheme embedding physical channels into multiband carrier sense multiple access/collision avoidance (CSMA/CA) networks is proposed to provide strict quality of service (QoS) guarantee to high priority users. In the proposed scheme, two priority classes of users, primary and secondary users, are supported. For primary users physical channels are provided to ensure strict QoS, whereas secondary users are provided with best-effort service using CSMA/CA modified for multiband operation. The performance of the proposed MAC scheme is investigated using a new multiband CSMA/CA Markov chain model capturing the primary user activity and the operation of secondary users in multiple bands. The throughput of secondary users is obtained as a function of the primary user activity and other CSMA/CA parameters. It is shown that the new MAC scheme yields larger throughput than the conventional single-band CSMA/CA when both schemes use the same bandwidth.

• ETRI Journal
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• v.39 no.4
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• pp.558-569
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• 2017

In this study, a non-preemptive M/G/1 queueing model of a spectrum handoff scheme for cognitive wireless networks is proposed. Because spectrum handoff gives secondary users an opportunity to carry on their transmissions, it is crucially important to determine the actions of primary users. In our queueing model, prioritized data traffic is utilized to meet the requirements of the secondary users. These users' packets are categorized into three different priority classes: urgent, real-time, and non-real time. Urgent data packets have the highest priority, while non-real time data packets have the lowest priority. Riverbed (OPNET) Modeler simulation software was used to simulate both reactive and proactive decision spectrum handoff schemes. The simulation results were consistent with the analytical results obtained under different load and traffic conditions. This study also revealed that the cumulative number of handoffs can be drastically decreased by exploiting priority classes and utilizing a decent spectrum handoff strategy, such as a reactive or proactive decision-based strategy.

• Journal of Navigation and Port Research
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• v.35 no.10
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• pp.837-846
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• 2011

Due to its vast range of areas and scopes of port logistics, professional training for port logistics experts has faced a limitation to raise manpower that the nation and companies ask for. This study looks at the current and expected demand and supply of workforce to identify necessary subjects and competitive factors in secondary education for training port logistics experts. Based on previous studies, this study proposes an assessment model by eliciting the priority of subjects in secondary education. and then, provides reasons for decision making.

• Journal of the Korea Institute of Military Science and Technology
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• v.15 no.4
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• pp.442-449
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• 2012

Cognitive Radio(CR) is the technology that allocates the frequency by using dynamic spectrum access. We proposed a model to calculate the optimal level of the cognitive radiotelegraph, where secondary users opportunistically share the spectrum with primary users through the spectrum sensing. When secondary user with cognitive radio detects the arrival of a primary user in its current channel, the secondary user moves to the idle channel or be placed in the virtual queue. We assume that the primary users have finite buffers and the population of secondary users is finite. Using a two-dimensional Makov model with preemptive priority queueing, we could derive the blocking and waiting probability as well as the optimal level of cognitive radiotelegraph under a various range of parameter circumstances.

• East Asian mathematical journal
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• v.29 no.1
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• pp.101-107
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• 2013

We consider a cognitive network with a primary and a secondary channel. Primary users have higher priority on the usage of the primary channel, and secondary users are allowed to opportunistically access the primary channel at times when the channel is not occupied by primary users. The secondary channel is dedicated only to secondary users. An analytical model is presented to obtain the performance of an opportunistic spectrum access using both the primary and secondary channels, and is validated by simulations.

• Journal of KIISE:Databases
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• v.29 no.1
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• pp.72-78
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• 2002

The distance join is a spatial join which finds data pairs in the order of distance between two spatial data sets using R-trees. The distance join stores node pairs in a priority queue, which are retrieved while traversing R-trees in a top-town manner, in the order of distance. This paper first shows that a priority strategy for the tied pairs in the priority queue during distance join processing has much effect on its performance, and then proposes an optimized secondary priority method. The experiments show that the proposed method is always better than the other methods in the performance perspectives.

• Journal of the Korean Data Analysis Society
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• v.20 no.6
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• pp.3155-3167
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• 2018

The purpose of this study was to investigate factor of principals' trust in teachers which principals of secondary school recognized and to explore their needs on building trust in teachers. For this purpose, this study used survey question of which investigated conception of principals' trust in teachers and performed with 296 secondary school principals. First, gap of two statuses was proven by t-test. Second, the order of priority was presented by Borich model. Third, the result of the locus for focus model was presented in the form of coordinate plane. Lastly, top priority and the second priority were determined. The result of this study was as following. 'Class management, instruction, and caring for students' category is highest in needs of secondary school principals on trust in teachers. Next, second priority category is 'partnership with parents'. It means secondary school principals recognize that students and parents are most important on education and their trust in teachers. Based on the review, finding and implications are discussed.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.35 no.4
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• pp.162-170
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• 2012

We propose a new priority discipline called the strict T-preemptive priority discipline, and derive the waiting time distributions of each class in the strict T-preemptive priority M/G/1 queue. Using this queueing analysis, we evaluate the performance of an opportunistic spectrum access in cognitive radio networks, where a communication channel is divided into time slots, a licensed primary user is assigned to one channel, and multiple unlicensed secondary users may opportunistically exploit time slots unused by the primary user. We also present a numerical example of the analysis of the opportunistic spectrum access where the arrival rates and service times distributions of each users are identical.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.7 no.11
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• pp.305-314
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• 2017

The purpose of this study is examining the status of Education Welfare Priority Support Project and providing constructive strategies for future direction. In order to collect data, we have used on-line survey, in-depth interview personnels in charge of 17 school districts and open forum with municipal board members of education along with related literature review. As results, since 2003, the effectiveness of the Education Welfare Priority Support Project has been proved and the areas have been expanded. Furthermore, institutional stability has been confirmed along with the supports of enforcement ordinance of the Elementary and Secondary Education Acts and Ministry of Education Ordinances. However, since the management authority of the project has transferred to 17 provincial offices of education, it shows the tendency of that the overall programs were not fully activated and gradually stagnated. According to these issues, we proposed various implemental policy suggestions though the revision of Article 28 of elementary and secondary education-related law.

• International Journal of Computer Science & Network Security
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• v.21 no.5
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• pp.168-174
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• 2021

The Cognitive radio (CR) is evolving technology for managing the spectrum bandwidth in wireless network. The security plays a vital role in wireless network where the secondary users are trying to access the primary user's bandwidth. During the allocation the any malicious user either he pretends to be primary user or secondary user to access the vital information's such as credentials, hacking the key, network jam, user overlapping etc. This research paper discusses on various types of attack and to prevent the attack in cognitive radio network. In this research, secondary users are identified by the primary user to access the primary network by the secondary users. The secondary users are given authorization to access the primary network. If any secondary user fails to provide the authorization, then that user will be treated as the malicious user. In this paper two approaches are suggested one by applying elliptic curve cryptography and the other method by using priority-based service access.