• Journal of the Computational Structural Engineering Institute of Korea
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• v.13 no.3
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• pp.285-294
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• 2000

In this paper, a practical procedure for the design optimization of tubular-steel-pile-type substructure in a mooring dolphin is investigated and numerically evaluated. In the finite-dimensional optimum design formulation, geometry and cross-sectional shapes of classified group of piles are identified as design variables. The design objective is the total weight of piles, and the design constraints on stresses, penetration depth, and size limits are imposed. Several classes of practical design alternatives are sought through the linking and fixing of design variables. Among the available numerical optimization codes, both PLBA program and DNCONF subroutine in IMSL library are used. They are based on SQP algorithm and relatively easy to get. A dolphin of numerical example has 20 tubular steel piles, 4 vertical and 16 inclined. Optimum designs for different cases are successfully obtained for the practical purpose.

• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.2
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• pp.131-137
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• 1998

The solar cells should be operated at the maximum power point because its output characteristics are greatly fluctuated on the variation of insolation, temperature and load. Photovoltaic system needs an inverter which can interface the dc output power of solar cell with the residential ac load. The inverter has to supply a sinusoidal current and voltage to the load and the utility line with a high power factor. This paper proposes an utility interactive photovoltaic system designed with a step-up chopper and a PWM voltage source inverter. The step-up chopper operates in continuous mode by adjusting the duty ratio so that the photovoltaic system tracks the maximum power points of solar cell without any influence on the variation of insolation and temperature. The voltage source inverter operates in a manner that its output voltage is in phase with the utility voltage. The inverter supplies an ac power with high factor and low level of harmonics to the load and the utility power system.

• Journal of Advanced Navigation Technology
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• v.20 no.4
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• pp.265-274
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• 2016

In this study, the system was composed of the booster chopper and the power converter, which is a pulse width modulation (PWM) voltage inverter using a hybrid power generation system solar cell energy and wind force, Furthermore, in order to compensate the PWM voltage type inverter was linked with the general commercial power source, and through a normal operation of energy storage system (ESS), the system operated the LED Taxi Light by Wavelength according to Meteorological Changes at the airport in an efficient manner. The performance of the system was compared with the solar cell characteristics specification. In addition, for phase synchronization with the PWM voltage type inverter, the grid voltage was detected so as to operate the grid voltage and inverter output in the same phase and to connect the surplus electric power with the system. Finally, by developing a control circuit at the same time from which an excellent dynamic characteristics can be obtained through applying to the airport runway taxi light, it was concluded that a variety of taxi light can be pursued.

• Journal of the Korean Association of Geographic Information Studies
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• v.10 no.1
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• pp.73-83
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• 2007

Network modeling of irrigation system that links irrigation facilities with stream is necessary to establish complicated rural water management system and to manage agricultural water effectively. This study attempted a network modeling for an agricultural water district called "ANGO" located in Anseongcheon watershed by connecting ArcHydro Model developed to control geographical information data in the field of water resources and AWDS(Agricultural Water Demand & Supply Estimation System) developed by KRC (Korea Rural Community & Agriculture Corporation). Network modeling was embodied by build topology between spatial objects of total 70 agricultural irrigation facilities (24 reservoirs, 18 pumping stations, 28 weirs) and stream network using ArcHydro Model. In addition, new menus were added in ArcGIS system for query and visualization of text-based AWDS outputs such as irrigation facilities information, water demand and supply analysis.

• Journal of Digital Convergence
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• v.18 no.11
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• pp.59-71
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• 2020

The paper reports on a systematic literature review results concerning the smart factory research in Korea. 144 papers were identified from the articles published in Korean journals listed in the Korean citation index by keyword search related to smart factory. Bibliometric analyses were conducted by way of co-occurrence and network analysis using the VOSViewer. Automation, intelligence, and bigdata were identifed as three critical clusters of research while, operating systems, international policy and cases, concept analysis as other three clusters of research. Internet of Things turned out to be a key technology of smart factory linking all of these areas. Servitization studies were small in numbers but seemed to have a lot of potential. Security researches seemed to be lacking connections with other areas of studies. Results of this study can be used as a milestone for identifying future research issues in smart factories.

• Journal of the Korean Society of Radiology
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• v.4 no.3
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• pp.31-37
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• 2010

In this paper, a photovoltaic system is designed with PWM(Pulse Width Modulation) voltage source inverter. Proposed synchronous signal and control signal was processed by 56F8323 microprocessor for stable modulation. The PWM voltage source inverter using inverter consists of complex type of electric power converter to compensate for the defect, that is solar cell cannot be developed continuously by connecting with the source of electric power for ordinary use. It can cause the effect of saving electric power, from 10 to 20[%]. The PWM voltage source inverter operates in situation that its output voltage is in same phase with the utility voltage. In addition, I connected extra power to the system through operation the system voltage and inverter power in a synchronized way by extracting the system voltage so that the phase of the system and PWM voltage inverter can be synchronized. In the system of this research showed good results after being controlled in order to provide stable power to the load and the system through maintaining and low output power of harmonics.

• Journal of IKEEE
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• v.24 no.1
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• pp.154-160
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• 2020

This paper presents a grid current control algorithm for a grid connected inverter (GCI) system in a stationary reference frame. When a Proportional Integral (PI) controller at a stationary reference frame is used in a GCI system, steady state error and phase lags are presented because AC signals are controlled at a stationary reference frame. In this paper, a feedforward controller is applied to the PI controller to compensate the steady state error and phase lags by improving command tracking performance. In addition, disturbance rejection control is applied to the PI controller to protect the GCI system by eliminating disturbance, grid voltage in a GCI system, when a grid fault such as line-to-line fault, happens. The proposed GCI current control algorithm is analyzed in a frequency domain and a simulation model of the proposed GCI current control system is developed for verification of the performance.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.805-808
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• 2013

As the development type of domestic technology on information & communications have changed from following development to leading devalopment, developing new technology and creating new market through securing basic technology and IPR has been more essential than ever before. At the same time, it is required to increase the possibility of commercialization on developed technology. Therefore, it is necessary to formulate the consensus on the value and function of project at project planning phase for creative & innovative idea to be adopted into project and to be performed successfully. Accordingly, this paper proposes use case developing methodology adopted to creative & innovative project by analysing use case developing method in software engineering. Also, new methodology is appled to LASA display developing project to prove the reliability. Since the demands on new technology is henceforth expected to increase gradually, it is necessary to continue to study on the methodology of being more formal and logically related between phases as well as on that of analysing relationship among use cases and proving logical reliability of use case.

• Journal of the Korean Geographical Society
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• v.31 no.2
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• pp.317-328
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• 1996

The purpose of this paper is to review the trend of research in geographical education since the launching of the Korean Geographical Society in 1945 and to suggest the areas and directions for future oriented research in geographical education. 422 articles (including 12 books) were reviewed and analized for this paper. The outputs of research in geographical education contributed in developing and improving the geographical education in primary and secondary school geography. But to achieve stable and desirable status as a subject in the school curriculum, research in geographical education has to be changed in its target areas and methods. The results and the suggestions of this study are summarized as follows: First, research in geographical education in diverse areas, especially in the areas of significance, aims and objectives, and psychology of geographical education should be preceded the revision of the school curriclum so that the results could be used as the basis information and evidences in decision making about the curriculum. Second, research in geographical education for affective domain and skill development should be implemented more actively in accordance to the trend of integration centering around the dicipline-inquiry skill and citizenship skill. More close relationship between the circles of geographical education and geography would be one of the ways to satisfy the social needs. Third, the linkage between primary and secondary school geography is crucial to the research in geographical education. Considering the sequence in human development research in geographical education for two levels of school should be conducted in more wide school-year span. Fourth, critical and prescriptive research in geographical education focusing on the individual, diciplinary, and social relevancy of the content of geographical education may be recommended. Finally, the outputs of the research in geographical education should be publicized more widely so that the rationale for justification of subject geography and geographical education may be shared with among the researchers, educational administrators, and practioners.

• Journal of Korea Port Economic Association
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• v.32 no.2
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• pp.1-24
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• 2016

Northeast Asia is changing rapidly, including becoming an increasingly important part of the world economy. Various logistical systems and networks are being established in this area, including South and North Korea, China, Japan, Russia, and Mongolia. Thus, a new systematic logistical network and development strategy is required. The division of the Korean peninsula has for a long time made the region ineffective in terms of land logistics. South Korea's connection to Eurasia is blocked by North Korea, which means it is essentially treated as an island. Furthermore, South Korea does not have an efficient logistics system or effective vision and strategy. Northeast Asia has the potential to be one of the largest economic communities in the world, similar to the EU and North America. Thus, a united Korea can play an important role as the land bridge of Northeast Asia and the logistical hub of the region. This study reviews the logistical position, tasks, and problems of the Korean peninsula and suggests a desirable development strategy and vision. Specifically, after examining the conditions for a land logistical system, focusing on railways, this study proposes several future-oriented development strategies and tactics that will position the peninsula as a logistical hub in Northeast Asia. We anticipate that this study will serve as the basis for future research that will investigate the topics presented here in more detail.