• Journal of the Korea Convergence Society
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• v.2 no.4
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• pp.21-27
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• 2011

Recently, new distributed power sources such as photovoltaic, wind power, fuel cell systems etc. are energetically interconnected and operated in the distribution feeders, as one of the national projects for alternative energy. When new power sources are considered to be interconnected to distribution systems, bi-directional power flow and interconnection conditions of new power sources may cause several power quality problems like voltage sag, voltage swell, harmonics, since new power sources can change typical characteristics of distribution systems. Under these situations, this paper deals with the analysis the power quality problems at primary and secondary feeders in distribution systems, when new power sources like photovoltaic (PV) systems are interconnected, by using the test devices for PV systems based on the LabVIEW S/W. This paper presents the test device which is consisted with model distribution system and model PV systems. By performing the simulation for power quality operation characteristic based on the test facilities, this paper presents the optimal countermeasures for power quality.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.2
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• pp.186-193
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• 2018

Generally, it is difficult to operate moveable-weir due to the expensive cost of the facility management and manpower consumption. Also, when it is installed in a remote area, there is a problem that the cost of connection for power system increases as well as the operating cost. Therefore, this paper proposes an optimal design algorithm to replace an existing power system with an Eco-friendly power supply system for movable-weir using PCS, PV module and lithium-ion battery. Also, this paper proposes a modeling method of environment-friendly power supply system for a movable-weir based on the PSCAD/EMTDC S/W and implements 5[kW] prototype environment-friendly power supply system. As a result of the performance test using the S/W modeling and the prototype system, it is confirmed that the proposed system has stable characteristics in the independent operation mode and the interconnection mode.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.7
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• pp.824-832
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• 2018

According to the government's policy to demonstrate and expand the renewable energy sources, distributed generators such as PV and WP are installed and operated in distribution systems. However, there are many issues related to power quality problems including over voltage and under voltage of customers. In order to overcome these problems, the electric power company have installed a step voltage regulator (SVR) in primary feeders interconnected with distributed generators, and also have established the technical guidelines for the distributed generators to stabilize the customer voltages in distribution systems. However, it is difficult to maintain the customer voltages within allowable limit. Therefore, this paper reviews the problems of voltage control by SVR in a distribution systems interconnected with a large amount of PV systems, and proposes characteristics of operating range and voltage control limit of the small hydropower generators. Also, with the estimation of the influence to the power system voltages from the voltage control mode of generators, this paper proposes the optimal voltage control algorithm of the small hydropower generators. By programming the proposed algorithm into control simulator of exciter, it is confirmed that the proposed algorithm can contribute the voltage stabilization in distribution systems interconnected with large scaled PV systems.

• Journal of KIISE:Software and Applications
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• v.34 no.2
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• pp.160-168
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• 2007

For developing a text classifier using supervised learning, a manually labeled corpus of large size is required. However, it takes a lot of time and human effort. Recently a research paradigm was proposed to use a raw corpus and a small amount of seed information instead of manually labeled corpus. In this paper we introduce an unsupervised learning method that makes it possible to achieve better performance than other related works. The characteristics of our approach is that average mutual information is used to learn representative words and their weights and then update of the weights is done using a technique inspired by the works in information retrieval. By iterating this teaming process it was shown that a high performance system can be developed.

• Journal of the Korean association of regional geographers
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• v.12 no.6
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• pp.671-692
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• 2006

In recent years, it seems that a considerable stratum of working poor as a new urban poverty among labor population within large cities has been generated, deepening socio-spatial conflicts. This paper is to bring focus on the working poor which can be seen as a newly emerged special problem intermingling labor and poverty. It first begins with a consideration of definitions on the working poor, then discusses on the internal relationship between labor and poverty problems by analyzing causes of the generation of the working poor and looking into actual conditions of working poor from both static and dynamic perspectives, and finally considers existing policies for supporting the working poor, suggesting some alternative policy tasks for resolving the problem of the working poor.

• Proceedings of the KAIS Fall Conference
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• 2012.05b
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• pp.512-516
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• 2012

Recently the Korean government's green energy growth policy has been taken at the national level due to the sufficient supply of renewable energy. Some specific technique should be taken in consideration for the operation of the grid voltage and power quality management. In this case, there may have some chance of operational problems. Typical problems arise when grid-connected solar power produced by Pacific sunshine. The power flow in the reverse direction can create overvoltage on the distribution line and gives value of malfunction on the system. Line voltage and overvoltage adjustment practice can stop these symptoms occurred. Under these circumstances, this paper presents an interconnection test devices for photovoltaic(PV) systems composed of distribution system simulator, PV system simulator and control and monitoring systems using the LabVIEW S/W, and simulates the customer voltage characteristics considering the 3 parameters on the introduction capacity for PV systems, system configuration and Power factor. This paper also proposes a new calculation algorithm for voltage profile to make comparison between calculation values and test device values. The results show that the simulation results for the normal operation characteristics of PV systems which are very practical and effective.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.6
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• pp.2698-2706
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• 2011

This paper deals with the optimal operation algorithm of SVR(Step Voltage Regulator) which is located with primary feeders and proposes the optimal operation system to evaluate customer voltage. The existing algorithm of SVR adapts the constant sending voltage method, which may cause the power quality problems such as overvoltage and under voltage variations in case where the distributed generations are interconnected with the primary feeders. Therefore, this paper proposes the optimal algorithm of LDC method for SVR using least square method to obtain the optimal setting values. Also, this paper presents the optimal evaluation system based on the former algorithm. The simulation results according to the types and capacities of distributed generations shows the effectiveness.

• Journal of the Korea Society for Simulation
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• v.27 no.2
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• pp.11-24
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• 2018

The purpose of the present study is to develop an analysis model to analyze the design parameter sensitivity of a high-power drifter suitable for implementation in Korean hydraulic drills. This study aims to establish a basis for the optimization of the impact performance and stability of a high-power drifter by investigating the effects of each design parameter on the impact performance via design parameter sensitivity analysis. To begin, an analysis model of drifter dynamics is developed, and the reliability of the analysis model is verified by comparing the analysis results to the experimental results. The drifter is then redesigned for compatibility with Korean hydraulic drills. Finally, design parameter sensitivity analysis of the redesigned drifter is conducted to determine the effects of the design parameters on the impact performance, and to extract the high-sensitivity parameters. SimulationX, which is multi-physics analysis software, is used to develop the analysis model, and EasyDesign is employed for design parameter sensitivity analysis.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.40 no.4
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• pp.237-247
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• 2003

The Motion Estimation (ME) process is an important part of a video encoding systems since they can significantly reduce bitrate with keeping the output quality of an encoded sequence. Unfortunately this process may dominate the encoding time using straightforward full search algorithm (FS). Up to now, many fast algorithms can reduce the computation complexity by limiting the number of searching locations. This is accomplished at the expense of less accuracy of motion estimation. In this paper, we introduce a new fast motion estimation method based on the spatio-temporal correlation of adjacent blocks. A reliable predicted motion vector (RPMV) is defined. The reliability of RPMV is shown on the basis of motion vectors achieved by FS. The scalar and the direction of RPMV are used in our proposed scheme. The experimental results show that the proposed method Is about l1~14% faster than the nearest neighbor method which is a wellknown conventional fast scheme.

• Tuberculosis and Respiratory Diseases
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• v.52 no.3
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• pp.283-287
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• 2002

Scrub typhus is an acute, febrile disease of humans that is caused by Orientia Tsutsugamushi. It is transmitted through the bite of chiggers. The spectrum of the clinical severity for scrub typhus ranges from mild to severe with fatal complication such as meningoencephalitis, pneumonitis, myocarditis. Severe pulmonary involvement e.g. acute respiratory distress syndrome(ARDS) and meningoencephalitis have rarely been observed since the introduction of specific antibiotic therapy. We experienced a case of scrub typhus manifested with ARDS and meningoencephalitis. The patient was treated with doxycycline, anticonvulsant and mechanical ventilator therapy.