• Proceedings of the KIPE Conference
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• 2014.11a
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• pp.66-67
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• 2014

Stabilization of the DC bus voltage is an important task in DC-AC microgrid system with renewable energy source such as solar system. A battery energy storage system (BESS) has become a general solution to stabilize the DC-bus voltage in DC-AC microgrid. This paper develops the analog BESS controller which requires neither computation nor dc-bus voltage measurement, so that the system can be implemented simply and easily. Even though others methods can stabilize and control the DC-bus voltage, it has complicated structure in control and low adaptive capability. The proposed topology is simple but is able to compensate the solar source variation and stabilize the DC-bus voltage under any loads and distributed generation (DG) conditions. In addition, the design of analog controller is presented to obtain a robust system. In order to verify the effectiveness of the proposed control strategy, simulation is carried out by using PSIM software.

• International Journal of Control, Automation, and Systems
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• v.3 no.spc2
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• pp.262-269
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• 2005

In this paper, a nonlinear robust control approach is applied to design a controller for the Static Synchronous Compensator (STATCOM). A robust control dynamic model of STATCOM in a one-machine, infinite-bus system is established with consideration of the torque disturbance acting on the rotating shaft of the generator set and the disturbance to the output voltage of STATCOM. A novel recursive approach is utilized to construct the energy storage function of the system such that the solution to the disturbance attenuation control problem is acquired, which avoids the difficulty involved in solving the Hamilton-Jacobi-Issacs (HJI) inequality. Sequentially, the nonlinear disturbance attenuation control strategy of STATCOM is obtained. Simulation results demonstrate that STATCOM with the proposed controller can more effectively improve the voltage stability, damp the oscillation, and enhance the transient stability of power systems compared to the conventional PI+PSS controller.

• Proceedings of the Korean Society of Computer Information Conference
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• 2015.01a
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• pp.277-278
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• 2015

The volume sub-challenge requires novel approaches, often referred to as Big Data technologies and methodologies. Data is generated constantly in an ever growing number of places and by an ever growing number of actors while a large proportion of potentially re-usable data resides within silos within institutions or companies. These are needed when conventional database technologies cannot be applied to storage and computing issues. The issue of big data has been referred to as the next frontier in computing. In this paper, we research on factors to design an organizational value chain for Big Data.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 1998.11a
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• pp.221-224
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• 1998

Environmental pollution is continuously increasing with the economic growth and industrial development. With this trend, soil and groundwater pollution problem has been surfaced as important social issues. Recently, Korean government promulgated the Soil Environment Conservation Act. But there are many problems to control sound soil quality management. Anthropogenic source of pollution such as waste landfill, pesticides, fertilizer, underground storage oil tanks is important as well as natural source such as acid rain and forest fire. The regulation should be expanded to include groundwater preservation as well as soil quality, because soil pollution is closely related to groundwater pollution. Therefore, legal regulations must be expanded to these facilities and take into account technical feasibility and finance.

• Journal of Information Technology Applications and Management
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• v.12 no.1
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• pp.125-140
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• 2005

Nowadays, we have many embedded systems which store and process multimedia data. For multimedia systems using hard disks as storage media such as DVR, existing file systems are not the right choice to store multimedia data in terms of cost. performance and reliability. In this study we designed a reliable file system with very high performance for embedded multimedia applications. The proposed file system runs with quite simple disk layout to reduce time to initialize and to recover after power failures, uses a large data block to speed up the sequential accesses, incorporates a time-based indexing scheme to improve the time-based random accesses and boosts reliability by backing up the important meta data on a small NVRAM. We implemented the file system on a Linux-based DVR and verified the performance by comparing with existing file systems.

• Journal of Information Technology Applications and Management
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• v.22 no.1
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• pp.1-15
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• 2015

Software is not only control and operational technology of computer, various system, and machines, but also knowledge handling and service technology for production, storage, and utilization of digital information. Many nations invest enormous budget in SW R&D to acquire core and original technology, and commercialize. To select and concentrate on SW R&D investment by segmenting diverse functions and element technologies consisting of sw technology, introduction of evaluation and analysis methodology on technology level utilizing reliable patent and bibliometrics is demanded these days. The purpose of this paper is to suggest some analysis frameworks of national technology level in the field of sw technology. Another practical purpose is to verify sw technology policy using qualitative and quantative indicators of patent and bibliometrics.

• International Journal of Fluid Machinery and Systems
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• v.8 no.2
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• pp.63-72
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• 2015

Water hammer phenomena are important issues for the design and the operation of hydro power plants. Especially, if several reversible pump-turbines are coupled hydraulically there may be strong unit interactions. The precise prediction of all relevant transients is challenging. Regarding a recent pump-storage project, dynamic measurements motivate an improved turbine modeling approach making use of a Thoma number dependency. The proposed method is validated for several transient scenarios and turns out to improve correlation between measurement and simulation results significantly. Starting from simple scenarios, this allows better prediction of more complex transients. By applying a fully automated simulation procedure broad operating ranges of the highly nonlinear system can be covered providing a consistent insight into the plant dynamics. This finally allows the optimization of the closing strategy and hence the overall power plant performance.

• International Commerce and Information Review
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• v.11 no.2
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• pp.127-145
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• 2009

With increase in oil demand owing to economic growth in Northeast Asia, the establishment of an oil hub in Korea is recently considered by policy and academic circles. This paper aims to suggest strategic schemes on the establishment of Korea's oil hub in Northeast Asia by comparing Korea's conditions as an oil logistics hub with Singapore which has been an oil hub in East Asia until recent year. Quantitative and qualitative analysis methods were employed in order to examine the competitiveness of Korea's oil hub. This research concludes that Korea is very competitive as an oil logistics hub in Northeast Asia, but so much improvements for realizing the project are necessary such as expansion of storage facilities for oil, institutional instruments for facilitating oil logistics and trading and preparation for incentive schemes on foreign investments in oil and its related industries.

• Journal of Agricultural Extension & Community Development
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• v.4 no.2
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• pp.423-429
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• 1997

Under the WTO system in the world, our country's apple industry must be set in quite a new aspect. For new apple industry with competition power, we should establish apple industry development strategies as follows. First, to change the present apple trees to the lowered or dwarf tree with high density planting system using M9 rootstocks. Second, to expand the size of apple orchard management and to bring up as professional apple farmers. Third, to develop the integrated apple production system considering environment and human being. Fourth, to innovate improved harvest, storage and shipment system. Finally, Rural Extension Institution should activate the farmer's training and produce the apple nursery trees of better quality.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.189-190
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• 2015

본 논문은 배터리에너지저장장치(BESS)를 적용하여 전력계통의 2차 주파수조정 보조서비스를 제공하기 위한 제어 방안을 검토한다. BESS가 계통운영기관의 자동발전제어를 통한 2차 주파수조정 보조서비스에 참여하기 위해서는 제어 요구량에 대한 정확한 추종이 가능 해야하고 이를 위한 효율적인 SOC 관리가 요구된다. 이를 위해 본 논문에서는 2차 주파수조정 보조서비스 제어신호를 제어대상 배터리의 SOC에 따라 배분하고 SOC가 가용범위를 벗어 날 경우 SOC 회복제어를 수행하도록 제어 방안을 제안하였다.