• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.19 no.1
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• pp.27-37
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• 2001

Soil erosion by outflow of water or rainfall has caused many environmental problems as declining agricultural productivity, damaging pasture and preventing flow of water. As the interest in environment is increasing lately, soil erosion is considered as a serious problem, whereas the systematic regulation and analysis for that have not established yet. This research shows the method of extracting factor entered model which expects soil erosion by GSIS. There are several erosion model such as ANSWER, WEPP, RUSLE. The research used RUSLE erosion model which could expect general soil erosion connected easily with GSIS data. RUSLE's input factors are composed of rainfall runoff factor(R). soil erodibility factor(K), slope length factor(L), slope steepness factor(S), cover management factor(C) and support practice factor(P). The general equation used to extract L, S factor on the RUSLE to be oriented for agricultural area has some limitation to apply whole watershed. So, on this study we used a revised empirical equation applicable to the watershed by grid on the GSIS. Also, we analyzed RUSLE factors by watershed being analyzed with watershed extraction algorithm. Then we could calculate the minimum, maximum. mean and standard deviation of RUSLE factors by watershed.

• Bulletin of the Korean Chemical Society
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• v.23 no.12
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• pp.1744-1748
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• 2002

Trifluoroacetate anion as a connector has been studied on $AgCF_3CO_2$ with 3,3'-$Py_2X$(X=O vs S) produces 1 : 1 adducts of [Ag($CF_3CO_2$)(3,3'-$Py_2X<$)]. Crystallographic characterization of [Ag($CF_3CO_2$)(3,3'-$Py_2X$)](monoclinic $P2_1$a=7.383(1)$\AA$b=19.801(3)$\AA$c=9.297(3)$\AA$,$\beta$=$100.26(2)^{\circ}$,V=1337.4(5) $\AA^3$, Z=2, R=0.0386) reveals that the 3,3'-$Py_2O$ spacer connects two silver ions to give a single strand and that the single strands are linked via the trifluoroacetate anions in an "up and down even-bridge" to give an elegant molecular grid. The framework of [$Ag(CF_3CO_2)(3,3'-Py_2X)$](monoclinic $P2_1/c$a=8.331(2)$\AA$b=14.010(2)$\AA$,c=11.926(3 $\AA$$\beta$=$93.70(2)^{\circ}$=1385.1(6)$\AA^3$, Z=4, R=0.0589) is a single-strand. The single strands are connected via the trifluoroacetate anions in a double-bridge, resulting in a typical molecular chicken-wire. The trifluoroacetate anion as a connector appears to be primarily associated with its moderately coordinating ability. Their structural features have been discussed based on the anion exchangeability. Thermal analyses indicate that the compounds are stable up to approximately $200^{\circ}C$.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.14 no.4
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• pp.31-38
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• 2000

Wide operating range and speed control is needed for wind power generating and a Doubly Fed Induction Generator(DFIG) has good adaptivity for that purpose. This paper deals with the speed, power, and power factor control using the Grid connected DFIG in the super-synchronous speed regions, by controlling frequency and voltage fed to the rotor. Power flow of the DFIG and steady-state algebraic equations of the equivalent circuit are analyzed. The wind turbine speed and constant stator power were controlled by the rotor exciting frequency. For a normal operating region, in which the generator ratings were not exceeded, rotor exciting frequency. For a normal operating region, in which the generator ratings were not exceeded, the rotor current was either less than or equal to the rated value. Accordingly, the optimal power factor can be selected relative to the permissible rated current at the rotor coil which controls the magnitude of the injected rotor voltage to the rotor according to a given rotor frequency. Consequently, it is possible to determine the optimal drive of a DFIG for wind power generation application.

• Journal of the Korea Institute of Military Science and Technology
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• v.19 no.5
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• pp.645-653
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• 2016

The terrestrial wireless backbone network and satellite communications system have been independently developed depending on their own purposes and operational concepts, which results in different characteristics in terms of network architecture and routing protocol operation. In this paper, we propose a method for structurally integrating them in consideration of routing mechanism in an autonomous system. Our approach is that the routers of satellite network operate the OSPF in PTP mode on their interfaces connected to the routers of terrestrial wireless backbone network with grid connectivity, whereas the OSPF in satellite network whose topology is of hub-spoke type runs in NBMA mode. We perform some simulations to verify that the satellite communications system can be integrated and interwork with the terrestrial wireless backbone network by our proposed approach. From simulation results, it is also found that the increases of network convergence time and routing overhead are acceptable.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.7
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• pp.1-8
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• 1999

In this paper, we have proposed and evaluated the performance of the routiong protocols servicing the mobile and fixed subscribers in a large e scale circuit switched telecommunication network, connected by gateways. The large scale network consists of several subnetworks, and a subnetwork is composed of $M{\times}N$ nodes in grid topology. When a call for mobile subscriber occurs, the current routing protocols search the whole large scale network to find a mobile subscriber. Therefore, it causes many redundant packets and long call setup delay. So, we have proposed a new routing protocol, in which the destination subscriber is first searched at the subnetwork where the call is proposed protocol is better than that of the current protocol.

• 전자공학회논문지 IE
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• v.47 no.1
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• pp.56-60
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• 2010

The widespread development of IT, growth of Web 2.0 application, the proliferation of personal hand held devices with access to the internet, and the availability of wireless networks, each have played an important role in creating the cloud computing model. Cloud computing is a business model and new trend of web application technology. The term is often used in the same context as grid computing or utility computing. In the cloud computing environment, we are able to use the same all of hardware resources in the server and share information easily. In this paper, we aimed a study to apply e-learning part to cloud computing environment. For this purpose, we proposed an application of LMS and LCMS based e-learning in the cloud computing environment. So LMS including LCMS connected to data center of cloud computing.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.7
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• pp.1039-1046
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• 2017

Campus microgrid is designed and built by considering not only power generation but also power consumption management as connected microgrid type because the main goal of the campus microgrid is to save power consumption costs. There are many functions to achieve the goal and they are mainly to use generation-based functions such as islanding operation for peak management and for emergency events. In power distribution operation, Conservation Voltage Reduction (CVR) is applied in order to reduce power consumption. The CVR is defined as a function for load consumption reduction by voltage reduction in order to reduce peak demands and energy consumption. However, application of CVR to microgrid is difficult because the microgrid cannot control a tap of transformer in a substation and the microgrid normally is not designed with phase modifying equipment like a step-voltage-regulator which can control voltage in power distribution system operation. In addition, an impact of the CVR is depended on load characteristics such as a normal load, a rated power, and synchronous motors. Therefore, this paper proposes an application of CVR using linear voltage control based AVR in campus microgrid with power consumption reduction considering characteristics of load and component in the microgrid. The proposed system can be applied to each buildings by a configuration of power distribution cables; and the application results and CVR factor are presented in this paper.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.12
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• pp.1682-1688
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• 2017

In modern society, the number of industrial customers using equipment sensitive particularly to voltage sags is rapidly increasing. As voltage sags can cause loss of information as well as false operation of the control device, it results in the vast economic damage in industrial processes. One way to mitigate voltage sags in the sensitive loads is the installation of distributed generation (DGs) on the periphery of these loads. In addition, renewable energy sources are currently in the spot light as the potential solution for the energy crisis and environmental issues. In particular, wind power generation which is connected to a grid is rising rapidly because it is energy efficient and also economically feasible compared to other renewable energy sources. On the basis of the above information, in this paper, with Wind Turbine Generators (WTGs) installed nearby the sensitive load, the analysis of the mitigating effect comparison by types of WTGs is performed using voltage sag assessment on the IEEE-30 bus test system. That is, the areas of vulnerability according to types of WTGs are expected to be different by how much reactive power is produced or consumed as WTG reactive power capability is related to the types of WTGs. Using the concept of 'Vulnerable area' with the failure rate for buses and lines, the annual number of voltage sags at the sensitive load with the installation of WTGs per type is studied. This research will be anticipated to be useful data when determining the interconnection of wind power generation in the power system with the consideration of voltage sags.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.12
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• pp.1675-1681
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• 2017

As recently the demand on electric power has been increasing, the requirement of power supply reliability has been increased. Accordingly, the number of HVDC transmission systems in the world has been steadily increased, which have been installed in the power system to transmit a large capacity power to the long distant and interconnect the power grid between different countries. etc. #1 HVDC Transmission System was installed between Haenam and Jeju island in 1998, which is the first HVDC system furnished in korea. and has been operated until now. Before #1 HVDC Transmission System being installed, the power system of the Jeju Island is a isolated power system from that of Korea mainland. After the construction of #1 HVDC the system has made the Jeju power system more reliable and also been able to supply the mainland power, which was cheaper than that of Jeju island, to Jeju island. The construction of additional HVDC transmission system between mainland and the Jeju Island has been currently underway to cope with recent changes of the power market of the Jeju island, for examples the increase of power demand and the capacity of wind power generation. etc. #2 HVDC Transmission System construction was completed in 2012. #3 HVDC Transmission System will be also installed according to the plan. If all goes as planned, the Jeju power system will be operated with Multi-Infeed HVDC system connected to mainland power system. So the additional studies are needed in order to maintain the stability of the Jeju power system and get the efficiency of the Multi-Infeed HVDC system. Therefore, in this paper, the optimal operation strategies of the Multi-Infeed HVDC system between the mainland of Korea and the Jeju are suggested to ensure the stability of the power system in Jeju Island when the Multi-Infeed HVDC system is operated between two power system.

• Journal of Power Electronics
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• v.15 no.2
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• pp.455-468
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• 2015

A microgrid (MG) with integrated renewable energy resources can benefit both utility companies and customers. As a result, they are attracting a great deal of attention. The control of a MG is very important for the stable operation of a MG. The droop-control method is popular since it avoids circulating currents among the converters without using any critical communication between them. Traditional droop control methods have the drawback of an inherent trade-off between power sharing and voltage and frequency regulation. An adaptive droop control method is proposed, which can operate in both the island mode and the grid-connected mode. It can also ensure smooth switching between these two modes. Furthermore, the voltage and frequency of a MG can be restored by using the proposed droop controller. Meanwhile, the active power can be dispatched appropriately in both operating modes based on the capacity or running cost of the Distributed Generators (DGs). The global information (such as the average voltage and output active power of the MG and so on) required by the proposed droop control method to restore the voltage and frequency deviations can be acquired distributedly based on the Multi Agent System (MAS). Simulation studies in PSCAD demonstrate the effectiveness of the proposed control method.