• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.1
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• pp.35-41
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• 2007

Recently, there are increasing social needs for stable supply of electric power and securing high quality of information and communication services. In this work, to propose the effective protection countermeasures of information-oriented equipments against lightning surges, the protection effects of surge protective devices(SPDs) were experimentally investigated using actual-sized test circuits in various installation conditions. As a result, it was found that the protection effect of SPDs is quite different depending on the factors, such as the grounding system of power source, numbers of branch circuits, wiring method of grounding leads, and etc. In case of installing SPDs for information-oriented equipments, including all electric power lines and communication lines, the common grounding should be the most effective. Wiring method containing grounding leads with power lines in metal conduit is suitable to improve the surge cutoff performance of SPDs.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.3
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• pp.558-564
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• 2016

The network interference gives positive and negative effects to security and QoS simultaneously by disturbing the decoding of receiver and eavesdropper. The transmission of artificial noise enables to indirectly control these contradicting effects. This paper proposed the secrecy enhancement technique via artificial noise with protected zones of transmitter and receiver and investigated its gain by using stochastic geometry. For given arbitrary artificial noise power ratio, we first analyzed connection outage probability and secrecy outage probability for four different scenarios (separated, overlapped, included secrecy protected zones- type A, B) according to distance and size of protected zones of the transmitter and receiver. We then derive the secrecy transmission rate and find the optimal artificial noise power ratio to maximize it. Finally, with numerical examples, we investigate the effects of the system parameters such as size of protected zones of transmitter and receiver on the optimal artificial noise power ratio.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.8C
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• pp.605-612
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• 2008

This paper researches the estimating location using repeater effect adjustment method in CDMA based system. Repeaters are commonly used by commercial and amateur radio operators to extend signals in the radio frequency range from one receiver to another. The repeater signals are increasing arrival time from base station to mobile station. So if we calculates the mobile station using repeater signals, the estimating position error is increased. However nobody researched about adjusting repeater effects. This paper proposes repeater effect adjustment algorithm. For adjusting repeater effects, we make the triangle using mobile station, reference base station and neighbor base station, and then detect the repeater effects using the triangle characteristic. The proposed method system showed the improved performance in estimating parameters and locating positions by computer simulations.

• Journal of Convergence Society for SMB
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• v.6 no.2
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• pp.37-43
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• 2016

Due to the remarkable improvement of ICT, with the popularization of mobile devices and every sector of society connected by networks, an era, in which peer to peer, peer to thing, thing to thing can be connected to one another everywhere, has begun. As all the electronic devices are connected to Internet, they have become more intellectualized and automated, making convergence and process of information through the connection of the devices possible to provide a lot better services. However, those devices communicate mutually to send information and they are exposed to various security threats. Therefore, this study analyzes ZigBee, CoAP, MQTT, XMPP, which are communication-related technology of IoT, draws security threats they have, and suggests requirements that components of IoT should have. Plus, it examines real cases about security threats in IoT, and suggests a countermeasure so as to contribute to establishment of a basis for IoT to be used much more safely in the future.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.40 no.1
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• pp.150-164
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• 2017

The development of an appropriate public service quality model has become increasingly recognised as an important subject of interest in the public sector as well as academia. In particular, the public systems enacted by governments are widely used and have a significant impact on national competitiveness. But few researches have been conducted to explore the quality dimensions of a public system service and empirically examine the relationship among related variables. Therefore, in this study, we strive to develop a quality measurement model of public system service that can be effectively used in practice. Using 601 samples gathered through a structured survey from project engineers, a conceptual quality model of public system is presented and discussed. Given the exploratory nature of this study, an exploratory factor analysis is used to investigate quality dimensions and partial least square (PLS) is employed in determining the structural relationships. From empirical results, we found that the quality dimensions of the public system had four distinct quality dimensions (design quality, environment quality, primary outcome quality, additive outcome quality). All four quality dimensions showed good representative factors in explaining user satisfaction. Perceived trust was proved to significantly mediate the relationship between quality dimensions and user satisfaction. Our research is expected to contribute to the literature by providing a good conceptual framework for assessing public system quality by linking four quality dimensions with user satisfaction. In particular, the developed model can elaborately measure process quality and multi-functional outcome quality of the system by the supplementation of design quality and additive outcome quality respectively. Practical implications are also suggested on the basis of our analysis.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.2
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• pp.24-31
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• 2000

The channel allocation strategy is very important in wireless multimedia networks since the mobility of users needs to be considered in addition to diversity of QoS requirements of multimedia traffic. A existing strategy to decrease the probability of handoff failure is guard channel method, which reserves channels at each base station for handoff calls. In this paper, we propose an efficient channel allocation strategy based on the prioritization of handoff calls used in the guard channel method. In the Proposed strategy guard channels are shared between non-real time and real time handoff calls. To decrease the probability of handoff failure, (when resources become scarce), the Call Admission Control takes some resources away from the active calls. The simulation results demonstrate that the Proposed strategy Provides higher channel utilization and lower probability of handoff failure than those of existing strategies.

• The Journal of Information Systems
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• v.14 no.2
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• pp.293-317
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• 2005

Female customers form a major customer group for Internet shopping and their trust on Internet stores seems to be significantly related with their transactions. This paper focuses on female customers' trust on Internet stores, hypothesizing that online service quality has a positive impact on trust and that trust, in turn, together with service quality has a positive effect on loyalty. We investigate trust from three dimensions(benevolence, integrity, and ability) and at the same time, unlike existing research, treat service quality to have five dimensions (intangibles, reliability, responsiveness, assurance, and empathy) as known in SERVQUAL(Parasuraman et al., 1988). Survey data is obtained from the female college student sample. Our research model is justified in terms of construct validity, internal consistency, and goodness of fit. Research hypotheses are tested using SEM(Structural Equation Modeling). The results are as follows: First, assurance and empathy dimensions of service quality have significant impacts on benevolence/integrity dimension of trust. Second, out of the five service quality dimensions, only assurance has a positive effect on ability dimension of trust. Third, assurance dimension of service quality and ability dimension of trust are positively related with customer loyalty. The most important factors for female customers' loyalty are found to be assurance(service quality) and ability(trust). The significance of assurance is in line with findings from existing research. But its relationship with the trust dimensions is uncovered in this research, and the only dimension that impacts on ability is assurance. We find that female customers build trust about internet stores based on their ability rather than on their benevolence/integrity and that the female customers' perception on the internet stores' ability can be improved by higher service quality from the aspect of assurance. Importantly enough, these findings offer practical guidelines to Internet stores to boost female customers' loyalty.

• The Journal of Society for e-Business Studies
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• v.22 no.1
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• pp.37-49
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• 2017

In order to maximize the efficiency and the quality of care in a hospital, hospitals in general operate by appointments. Patient no-shows or missed appointments waste the time of staffs who prepare for appointments, deprive patients of needed care, and increase burden on clinic capacity. The purpose of this study is to examine the importance and significance of factors that affect patient no-shows. The actual data of 50,000 outpatient appointments is compiled and analyzed from a VAMC in the United States with aims to identify the factors that contribute to outpatient no-shows and to draw meaningful implications. Random forest along with logistic regression analysis identify the factors affecting no-shows; appointment leadtime, show-up rate, travel distance, no-show rate in previous period, patient age, severity, complexity of disease, chronic pain, depression, drug dependence. The appointment leadtime, show-up rate, travel distance and previous no-show rate can be improved by enhancing SMS pre-notification and by improving afterwards telephone counseling. For other factors, it needs to study on the service differentiation with the characteristics of each patient group.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.3
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• pp.73-81
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• 2020

Today's massively multiplayer online games(MMOGs) can contain millions of synchronous players scattered across the world and participating with each other within a single shared game. The increase in the number of players in MMOGs has led to some issues with the demand of server which generates a significant increase in costs for the game industry and impacts to the quality of service offered to players. In dealing with a considerable scale of MMOGs, we propose a cloud computing and peer-to-peer(P2P) hybrid architecture in this paper. Given the two nearly independent functionalities of P2P and cloud architectures, we consider the possibility of fusing these two concepts and researching the application of the resultant amalgamation in MMOGs. With an efficient and effective provisioning of resources and mapping of load, the proposed hybrid architecture relieves a lot of computational power and network traffic, the load on the servers in the cloud while exploiting the capacity of the peers. The simulation results show that MMOGs based on the proposed hybrid architecture have better performance and lower traffic received compared with MMOGs based on traditional client-server system.

• The Journal of Korean Association of Computer Education
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• v.3 no.2
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• pp.87-94
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• 2000

Software productivity doesn't satisfy the need of service of software users and software quality isn't improved. Moreover, we still have difficulty in software maintenance. As a plan to counteract solving this crisis, the technology that is called CBSE or Componentware is introduced. Componet Based Software Architecture, one of the technologies associated with CBSE, as a structural description of system, describes both the components composed system of and interaction among these components. Software Architecture provides the technology and the methodology of composition among components in the field of CBSE. is accepted one of core technologies. In this thesis, we analyse information necessary for component specification and then proposed that component specificaton activities using formal specification language Z which is verified with the ability of analysis and logicality. The proposed activities are composed of 9 tasks. By presenting specific 11 products, it is also proposed that component specification activities which is the base of CBSD(ComponentBased Software Development) for reusing.