• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.8C
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• pp.663-669
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• 2012

To solve the energy problem and finding new growth engines, interest for the smart grid is increasing and related technologies are making great efforts to secure in the world. AMI (Advanced Metering Infrastructure) Among them is the first to be constructed and getting attention as a key component of smart grid. A fusion of various technologies in technology development and demonstration is underway on Jeju Island Smart Grid Demonstration Complex in Korea, and focusing on broadband power line communication technology infrastructure is actively underway in Korea Electric Power Corporation. AMI system using power line communication technology without building a separate communication lines are available for power supply lines, but communication is impossible in occurs because admission to the power company or the ideal infrastructure for communication is not considered. In this paper, we analyze the requirements to build AMI system using Binary CDMA and powerline communications technology, and design the basic communication protocol based on Binary CDMA, implement network management and relay feature. By doing so, ways to apply Ad-hoc Binary CDMA indigenous technology to the AMI system were derived, and could build a system to make use of Wired (PLC) and wireless (Binary CDMA) simultaneously.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.55 no.7
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• pp.303-312
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• 2006

This paper proposes the architecture and protocol of a data communication network for the safety system in nuclear power plants. First, we establish four design criteria with respect to determinability, reliability, separation and isolation, and verification/validation. Next we construct the architecture of the safety network for the following systems: PPS (Plant Protection System), ESF-CCS (Engineered Safety Features-Component Control System) and CPCS (Core Protection Calculator System). The safety network consists of 12 sub-networks and takes the form of a hierarchical star. Among 163 communication nodes are about 1600 origin-destination (OD) pairs created on their traffic demands. The OD pairs are allowed to exchange data only during the pre-assigned time slots. Finally, the communication protocol is designed in consideration of design factors for the safety network. The design factors include a network topology of star, fiber-optic transmission media, synchronous data transfer mode, point-to-point link configuration, and a periodic transmission schedule etc. The resulting protocol is the modification of IEEE 802.15.4 (LR-WPAN) MAC combined with IEEE 802.3 (Fast Ethernet) PHY. The MAC layer of IEEE 802.15.4 is simplified by eliminating some unnecessary (unctions. Most importantly, the optional TDMA-like scheme called the guaranteed time slot (GTS) is changed to be mandatory to guarantee the periodic data transfer. The proposed protocol is formally specified using the SDL. By performing simulations and validations using Telelogic Tau SDL Suite, we find that the proposed safety protocol fits well with the characteristics and the requirements of the safety system in nuclear power plants.

• Journal of the Korea Convergence Society
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• v.9 no.7
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• pp.55-62
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• 2018

Recently, as the threat of cyber crime increases, the importance of security control to cope with cyber attacks on the information systems in the first place such as real-time detection is increasing. In the name of security control center, cyber terror response center and infringement response center, institutional control personnel are making efforts to prevent cyber attacks. Especially, we are detecting infringement accident by using network security equipment or utilizing control system, but it's not enough to prevent infringement accident by just controlling based on device-driven simple patterns. Therefore, the security control system is continuously being upgraded, and the development and research on the detection method are being actively carried out by the prevention activity against the threat of infringement. In this paper, we have defined the method of detecting infringement of major component module in order to improve the problem of existing infringement detection method. Through the performance tests for each module, we propose measures for effective security control and study effective infringement threat detection method by upgrading the control system using Security Information Event Management (SIEM).

• Journal of Electrochemical Science and Technology
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• v.11 no.2
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• pp.132-139
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• 2020

Solid oxide fuel cells (SOFCs) are among one of the promising technologies for efficient and clean energy. SOFCs offer several advantages over other types of fuel cells under relatively high temperatures (600℃ to 800℃). However, the thermal behavior of SOFC stacks at high operating temperatures is a serious issue in SOFC development because it can be associated with detrimental thermal stresses on the life span of the stacks. The thermal behavior of SOFC stacks can be influenced by operating or material properties. Therefore, this work aims to investigate the effects of the thermal conductivity of each component (anode, cathode, and electrolyte) on the thermal behavior of samarium-doped ceria-based SOFCs at intermediate temperatures. Computational fluid dynamics is used to simulate SOFC operation at 600℃. The temperature distributions and gradients of a single cell at 0.7 V under different thermal conductivity values are analyzed and discussed to determine their relationship. Simulations reveal that the influence of thermal conductivity is more remarkable for the anode and electrolyte than for the cathode. Increasing the thermal conductivity of the anode by 50% results in a 23% drop in the maximum thermal gradients. The results for the electrolyte are subtle, with a ~67% reduction in thermal conductivity that only results in an 8% reduction in the maximum temperature gradient. The effect of thermal conductivity on temperature gradient is important because it can be used to predict thermal stress generation.

• Composites Research
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• v.15 no.6
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• pp.16-23
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• 2002

In this work, the effect of anodic oxidation on surface characteristics of high strength PAN-based carbon fibers was investigated in mechanical interfacial properties of composites. The surface properties of the carbon fibers were determined by acid-base values, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and contact angles. And their mechanical interfacial properties of the composites were studied in interlaminar shear strength (ILSS) and critical stress intensity factor ($K_{IC}$). As a result, the acidity or the $O_{ls}/C_{ls}$ ratio of carbon fiber surfaces was increased, due to the development of the oxygen functional groups. Consequently, the anodic oxidation led to an increase in surface free energy of the carbon fibers, mainly due to the increase of its specific (or polar) component. The mechanical interfacial properties of the composites, including ILSS and $K_{IC}$, had been improved in the anodic oxidation on fibers. These results were explained that good wetting played an important role in improving the degree of adhesion at interfaces between fibers and epoxy resin matrix.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.8
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• pp.1045-1050
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• 2010

Fatigue analysis and lifetime evaluation are very important in design procedure for assuring the safety and reliability of rubber components for mechanical systems. Till recently, the technology for the design, analysis, and evaluation of rubber products was required to manufacture rubber products with high quality, fidelity, and reliability. However, in the rubber-manufacturing companies in Korea, the processes of compound mixing, manufacturing of rubber products, and improvement of rubber properties are based on the trial-and-error method and experience. The objectives of this study are to establish methods for testing rubber materials, to develop a database of the properties of rubber materials, to evaluate the performance of rubber components, and to develop a system for predicting fatigue life. A method to predict fatigue-life of rubber components was proposed; in this method, the finite-element analysis and fatigue damage parameter as determined from a fatigue test are incorporated.

• The Mathematical Education
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• v.44 no.2 s.109
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• pp.307-323
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• 2005

The purpose of this study was to develop a program to cultivate mathematical creativity based on open-ended problem and to investigate its effect. The major features of this innovative program are (a) breaking up fixations, (b) multiple answers, (c) various strategies, (d) problem posing, (e) exploring strategies, (f) selecting and estimating, (g) active exploration through open-ended problems. 20 units for 7th grade mathematics were developed. This study hypothesizes that experimental students may develop more divergent thinking abilities than their traditional counterparts. The participants were 7th grade students attending middle schools in Seoul. Instruments were pre and post tests to measure mainly divergent thinking skills through open-ended problems. The results indicated that the experimental students achieved better than the comparison students on overall and each component of fluency, flexibility, and originality of divergent thinking skills, when deleting the effect of covariance of the pretest. The developed program can be a useful resource for teachers to use in enhancing their students' creative thinking skills. Further this open-ended approach can be served as a model to implement in classes. This study suggests that further investigations are needed in order to examine effects on affective domains such as motivation and task perseverance which are also considered as important factors of creativity.

• Journal of IKEEE
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• v.19 no.3
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• pp.440-446
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• 2015

This study has examined susceptibility of LNA(Low Noise Amplifier) due to Front-Door Coupling under Narrow-Band high power electromagnetic wave. M/DFR(Malfunction/Destruction Failure Rate) was measured to investigate the diagnostic of IC test. In addition, decapsulation analysis was used to understand the inside of the chip state in LNA devices. The experiments is employed as an open-ended waveguide to study the destruction effects of LNA using a 2.45 GHz Magnetron as a high power electromagnetic wave. The susceptibility level of LNA was assessed by electric field strength, and its failure modes were observed. The malfunction of LNA device has showed as the type of self-reset and power-reset. The electric field strength of malfunction threshold is 524 V/m and 1150 V/m respectively. Also, he electric field of destruction threshold is 1530 V/m. Three types of damaged LNA were observed by decapsulation analysis: component, onchipwire, and bondwire destruction. Based on these results, the susceptibility of the LNA can be applied to a database to help elucidate the effects of microwaves on electronic equipment.

• Journal of Korea Port Economic Association
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• v.17 no.2
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• pp.183-204
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• 2001

This study is intended for the development of urgent facing strategies for the designation of a CFZ(Customs Free Zone) in Incheon city. First, it analyzes the current status of the Incheon CFZ. Next, it suggests several strategies for successfully growing the CFZ of Incheon City. Finally, it develops and proposes a method for establishing an integrated management system for the effective management of the CFZ. The key findings of this study are as follows: First, the CFZ should provide state-of-the-art movement of port logistics, create new added value caused by the movement of logistics, and provide other public support. The Incheon CFZ should be developed in three stages: an inducement stage in 2002-2005, a growth stage in 2005-2008, and an implementation stage in 2008-2011. Second, The parties responsible for the management of the CFZ would be as follows: for the port area, the Ministry of Maritime and Fisheries; for the back space of CFZ, Incheon City; and for port management, port management companies. However, a committee for CFZ management is strongly suggested for the improved efficiency and effectiveness of CFZ management. Furthermore, additional regulations ensuring the role of local government will likely be necessary for the sucessful designation and sustainable management of the CFZ. Third, For the creation of additional revenue, reformation of the current laws of the CFZ are recommended in the area of business administration. Fourth, A strategic marketing plan that supports the successful management of the companies of the CFZ will be a key component in the success of the CFZ. Thus, the new marketing plan should be developed in the near future based on case studies of other CFZs. Fifth A method for an integrated CFZ management system was developed and suggested for the comprehensive and transparent management of port logistics.

• Health Policy and Management
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• v.20 no.2
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• pp.40-52
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• 2010

Health insurance fees are set by relative value scales and conversion factors. Since 2008 the conversion factor has been classified into 7 according to the provider type, and a separate contract has been made respectively. As such classification of the conversion factor reflects only the different characteristics of providers, however, further classification to reflect the different cost structures of providers is proposed. Cost varies according to the type of not only providers but also services each provider supply. In fact different cost structures of providers are the result of their different services. This study analyzed the cost structure of medical services to propose a new approach to the classification of the conversion factor. This study analyzed the cost structure of medical services using cost data constructed in the revision study of relative value scales. The cost data consist of doctor's fee, support staff's fee, cost of medical equipments, cost of medical supplies and indirect cost. The proportion of each cost component to the total cost was analyzed in terms of service department and service type. 72 service groups are defined in terms of the combination of service department and service type. Through cluster analysis, 72 service groups were reduced into 7 clusters each of which has a similar cost structure. Conversion factor is contracted annually to reflect the change in the cost of providing medical services. So the classification of conversion factor has to be based on the cost structures of medical services, not the characteristics of providers. Service clusters derived in this study can be used as a new classification for health insurance fee contract.