• Convergence Security Journal
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• v.7 no.3
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• pp.109-120
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• 2007

VoIP service provides various functions that PSTN phone service hasn't been able to provide. Since it also has superiority in service charge, the number of user is increasing these days. When we think of the other side in cost aspect, the spam caller can also send his/her commercial message over phone line using more economic way. This paper presents the characteristics that should be considered to detect the spam call using greylisting method. We have explored static and dynamic characteristics in VoIP calls, and analyzed the relation among them. Especially, we have surveyed the authentication and charging method of Korean VoIP service provider. We have analyzed each charging method using our spam call simulation result, and derived the charging method that can be favored by spam caller. The contribution of the work is in analysis result of static aspect for SPIT Level calculation in greylisting method.

• Journal of Convergence Society for SMB
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• v.5 no.2
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• pp.15-20
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• 2015

Recently, as smart phone technology is developing, wearable devices is also accelerating. But, the wearable device is necessary to operated for a long time with a small electric power because werable device is made compact. In this paper, we design and implement efficient lithium polymer battery model suitable to miniaturized wearable device in oder to maximize ease of use. The proposed model is characterized by a compact size of the battery by applying a thermal element and a light-weight battery. Also, proposed model gives greatly improve the life of wearable devices because it uses a method using the characteristics of the Peltier device using the temperature difference between the room temperature and body temperature of a person to generate power for charging. In particular, the proposed model can be used for the wearable device, as well as auxiliary charging of the smart phone.

• Journal of Satellite, Information and Communications
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• v.9 no.1
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• pp.74-78
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• 2014

In this paper, we proposed Interference suppression method of between AMI system and EV charging system. IEC12139-1 and HomePlug GreenPhy are using 2-30Mhz frequency band in power line communication. Both method while using the same frequency band, interference occurs in the system of each other. In this paper, we experiment a way to suppress the interference through the channel separation using a Walsh code.

• Journal of the Korean Institute of Intelligent Systems
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• v.26 no.5
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• pp.351-360
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• 2016

Rapid population growth with high living standards and high electronics use for personal comfort has raised the electricity demand exponentially. To fulfill this elevated demand, conventional energy sources are shifting towards low production cost and long term usable alternative energy sources. Hybrid renewable energy systems (HRES) are becoming popular as stand-alone power systems for providing electricity in remote areas due to advancement in renewable energy technologies and subsequent rise in prices of petroleum products. Wind and solar power are considered feasible replacement to fossil fuels as the prediction of the fuel shortage in the near future, forced all operators involved in energy production to explore this new and clean source of power. Presented paper proposes fuzzy logic based Energy Management System (EMS) for Wind Turbine (WT), Photo Voltaic (PV) and Diesel Generator (DG) hybrid micro-grid configuration. Battery backup system is introduced for worst environmental conditions or high load demands. Dump load along with dump load controller is implemented for over voltage and over speed protection. Fuzzy logic based supervisory control system performs the power flow control between different scenarios such as battery charging, battery backup, dump load activation and DG backup in most intellectual way.

• Journal of the Korean Institute of Gas
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• v.27 no.4
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• pp.70-77
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• 2023

In response to climate change, each country is proposing a goal to reduce greenhouse gases in its energy supply and demand plan, and the use of hydrogen gas is a topic that is always prioritized as an energy resource for implementation. A popular way to use this hydrogen gas is the use of hydrogen fuel cell vehicles, and expansion of hydrogen charging stations is essential for using these hydrogen fuel cell vehicles. However, there are several limitations to the expansion of hydrogen refueling stations, the most representative of which is resident acceptance. Most of the hydrogen charging stations currently built in Korea are located in the outskirts with low population density, so the inconvenience to hydrogen fuel cell vehicle users has not been resolved, and as a result, there has been no progress in the spread of hydrogen fuel cell vehicles. In this paper, we analyzed the consequences of accident damage to determine the risks of constructing a hydrogen charging station on a railroad site frequently used by citizens. The target hydrogen charging station site was a railroad depot in Busan, and there are trains, national highways, and commercial facilities around this site. Assuming the worst-case scenario, we would like to consider the safety of the hydrogen refueling station site by analyzing the area affected by the accident and its consequence.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.5
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• pp.786-791
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• 2017

In this paper, the run time of Li-polymer secondary cell with and without Active Balancing BMS is analyzed. The Active Balancing System using Flyback Converter with two-way power control facility, his designed for optimal characteristics of balancing. The run time of Li-polymer secondary cell is drastically increased employing the Flyback Convert Active Balancing BMS. The run time performance of Li-polymer secondary cell with or without Flyback Converter Active Balancing BMS is analyzed with the discharging and charging experiment of Li-polymer secondary cell.

• Journal of Information Technology Services
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• v.11 no.3
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• pp.287-304
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• 2012

Cloud computing, which means a new way of deploying information technology(IT) in organizations as a service and charging per use, has a deep impact on organizations' IT accessibility, agility and efficiency of its usage. More than that, the emergence of cloud computing surpasses a mere technological innovation, making business model innovation possible. We call this innovation realized by could computing a cloud business model. This study develops a comprehensive framework of business model, first, and then defines and analyzes the cloud business model through this framework. This study also examines the case of M-Pesa mobile payment as a cloud business model in which a new value creation and profit realization schemes have been realized and industry value network has changed. Finally, this study discusses the business implications from this new business model.

• Explosives and Blasting
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• v.14 no.4
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• pp.4-12
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• 1996

In '50, It was turnning point of tunneling technology that v-cut of single Face replaced by Burn cut.. Which was a standard Blasting formula. In '70, We faced Seoul Sub-Way construction by NATM. As it was damages to the Structure on the surface, finally we made empirical formula. For Granite $V=kw^{0.57}D^{1.75}$ For Grneiss $V=KW^{0.5}D^{1.75}$ For Concrete breaker $V=KW^{0.5}D^{1.75}$ (K=7) The magnitude of groun vibration can be reduced as using follow matters. First, by using explosive that have low dencity and low Velocity of detonation. Second adopting two stage deck charging, third, by using Milli Second electric Caps and Multi-Sequency blasting machine.

• The KSFM Journal of Fluid Machinery
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• v.15 no.1
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• pp.27-35
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• 2012

A numerical simulation for particle collection efficiency in a wire-plate electrostatic precipitator (ESP) has been performed. Method of characteristics and finite differencing method (MOC-FDM) were employed to obtain electric field and space charge density, and lattice boltzmann method (LBM) was used to predict the Electrohydrodynamic (EHD) flow according to the ion convection. Large eddy simulation (LES) was considered for turbulent flow and particle simulation was performed by discrete element method (DEM) which considered field charging, electric force, drag force and wall-collision. One way coupling from FDM to LBM was used with small and low density particle assumption. When the charged particle collided with the collecting plate, particle-wall collision was calculated for re-entertainment effect and the effect of gravity force was considered.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.6
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• pp.815-823
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• 1999

A dynamic simulation program may be used for the development of effective control algorithms for the ice storage cooling system. Simplified effective dynamic models for an ice-on-coil type storage tank, a screw chiller, a water-to-air heat exchanger, three way valves, pipes, pumps, temperature sensors, and controllers were developed. And a dynamic simulation program for the ice storage cooling system was developed by using these dynamic models. Control algorithms for the full storage system were also selected and analyzed in order to show the effectiveness of these models. From the simulation results, it may be concluded that the simulation program developed in this study can be effectively used for the development of improved control algorithms for the ice storage cooling system.