• Journal of Electrical Engineering and Technology
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• v.1 no.3
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• pp.271-278
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• 2006

This paper scrutinized the damping effects of installing the prototype PSSs by a transient analysis for eight buses of faults in the South Korean power system. The PSSs used have the co-PSS blocks for IEEEST model with a single input and the co+power PSS blocks for PSS2A model with dual inputs. The simulation tool was a TSAT(Transient Security Assessment Tool) developed by Powertech Labs Inc. The voltages of the transmission line for simulations were 765kV and 345kV, and the faults for eight cases were sequenced by considering the open state and the close state of the lines. In the simulations, the three-phase line to ground (L-G) fault generated different points for each region. The simulations were compared to the cases of no PSS, partial IEEEST and PSS2A, absolute IEEEST, and absolute PSS2A to show that the power system oscillation can be effectively damped by PSS modules. Simulations were conducted to confirm the effectiveness for the KEPCO (Korea Electric Power Corporation) power system.

• The Journal of Engineering Geology
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• v.19 no.3
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• pp.323-330
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• 2009

Electrical resistivity survey is applied for estimation of inferred fault and fractured zone in civil engineering and environment field. While 15 m diameter and 3 lines tunnels are excavated. It is recognized that core stone and fractured zone is existed in the weathered slope of the entrance to a tunnel. To make confirmation geological characteristics, dipole-dipole electric resistivity survey was carried out in weathered slope of the entrance to a tunnel. Core stone distribution and fracture zone characteristics are estimated by reverse analysis and 2D-resistivity structure using FDM.

• Journal of the Korean Geographical Society
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• v.39 no.1
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• pp.56-69
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• 2004

We investigated the distribution and geomorphic development of alluvial fan in Gyeongju City including Cheonbuk area. According to a relative height to a river bed, alluvial fans of this area are divided into Higher surface, Middle surface, and Lower surface. As alluvial fans of Bulguk temple∼Ulsan bay area, the confluent fans in Cheonbuk and Gyeongju areas were formed by the Quaternary climatic change alternating glacial and interglacial stages, and the development of N-S and NW-SE fault lines. The Gyeongju alluvial fan, the largest in Korea, has been provided as the significant space for human activity since the prehistoric age. Bukcheon river formed the Gyeongju alluvial fan had not flowed over during the prehistoric and the ancient times. In contrast with general geomorphic characteristics, many springs in the Gyeongju alluvial fan are located in the middle part of the fan because ground water reaches to the surface. It is supposed that sedimental materials were not sufficiently piled up at lower reach of Bukcheon river due to the large deposits at upper and middle reach of the basin.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10b
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• pp.1659-1663
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• 1991

A new control design methodology is presented here which is based on a nonlinear time-series reference model. It is indicated by highly nonlinear simulations that such designs successfully stabilize troublesome aircraft maneuvers undergoing large changes in angle of attack as well as large electric power transients due to line faults. In both applications, the nonlinear controller was significantly better than the corresponding linear adaptive controller. For the electric power network, a flexible a.c. transmission system (FACTS) with series capacitor power feedback control is studied. A bilinear auto-regressive moving average (BARMA) reference model is identified from system data and the feedback control manipulated according to a desired reference state. The control is optimized according to a predictive one-step quadratic performance index (J). A similar algorithm is derived for control of rapid changes in aircraft angle of attack over a normally unstable flight regime. In the latter case, however, a generalization of a bilinear time-series model reference includes quadratic and cubic terms in angle of attack. These applications are typical of the numerous plants for which nonlinear adaptive control has the potential to provide significant performance improvements. For aircraft control, significant maneuverability gains can provide safer transportation under large windshear disturbances as well as tactical advantages. For FACTS, there is the potential for significant increase in admissible electric power transmission over available transmission lines along with energy conservation. Electric power systems are inherently nonlinear for significant transient variations from synchronism such as may result for large fault disturbances. In such cases, traditional linear controllers may not stabilize the swing (in rotor angle) without inefficient energy wasting strategies to shed loads, etc. Fortunately, the advent of power electronics (e.g., high-speed thyristors) admits the possibility of adaptive control by means of FACTS. Line admittance manipulation seems to be an effective means to achieve stabilization and high efficiency for such FACTS. This results in parametric (or multiplicative) control of a highly nonlinear plant.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.35 no.4
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• pp.343-352
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• 1999

Because stow net being used in now is doing throwing net and hauling net through a ship's side, the work is very complicated and the fishing boat needs many seamen and it could cause a loss of lives and ship in stormy weather. We are now using small mesh size 36~500mm and it even catches young fish, so we call it the fishing gear of resource reduction type.Therefore we must make manpower reduction in automatic operation, safe operation of throwing net and hauling net in the stern and the stern-typed stow net of resource management using large mesh. And we performed three-typed model tests to examine the fishing gear. The obtained results are as follows;1. The fishing gear being used in the ship's side type stow net has inappropriate standard and arrangement of the net, resistance increase of the fishing gear and frequent breakdown of the net.2. To supplement the fault of A-typed stow net, we schemed fishing gear developed as both B-type(12-seamed net) and C-types(8-seamed net) of the stern-typed stow net. 3. In model tests, C-typed model net(mesh size 40~1,600mm) was proved good fishing gear because the resistance in accordance with the flowing speed was comparatively small and it's mouth area was broad. 4. A-typed stow net had the spreading device attached to side panel of the net, but the stern-typed stow net had the spreading device consisted of 4 lines far behind about 6m from side panel of the net mouth. In the flowing speed 2knot, the spreading condition of fishing gear was proved batter than the former.

• International Journal of Contents
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• v.11 no.1
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• pp.62-68
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• 2015

Many severe earthquakes have occurred along the main fault lines in the world. In recent years, there has been a high incidence of small- and large-scale earthquakes in our country. These occurrences of earthquakes have become increasingly serious, owing to a degrading earth environment. An earthquake, in general, causes far more serious damages like disruptions in electricity or gas facilities, and fire disasters from its annexed effects than by its vibrations or the shock itself. In this paper, we present a countermeasure and its necessity in safeguarding against fire disasters in regional heritage villages such as "Asan Oeam," "Jeonju Hanok," and "Andong Hahoe." A more systematic and effective strategy for prevention systems against severe fire disasters is proposed after performing various related investigations and analyses of existing domestic and international systems. We investigated the existing fire security systems and their historical records with the tendency of earthquake occurrences in these three folk villages. In this proposal, we present a strategic approach for safeguarding against fire damages in our regional heritage villages derived from ICT (information communication technology)-based DPD (disaster prevention design), after examining the laws and regulations of fire-prevention strategies in Japan, America, and Europe.

• Journal of the Korean Society of Groundwater Environment
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• v.4 no.4
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• pp.185-190
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• 1997

Electrical surveys were conducted at the Seokdae waste landfill in July,1996. Within the landfill, 4 lines of dipole-dipole surveys and 7 Schlumberger soundings were carried out and 2 soundings in front of the landfill. In the landfill, interpretations of the survey data show low resistivity zones below 10 Ωm to a depth of 50 m from the surface and such low resistivity zones of the D block are thicker than those of the other blocks by about 2~10 m. Considering the depth of the bedrock and the height of waste reclamation, no evidence of bedrock contamination by leachate is indicated. But it is inferred that the weathered zones are contaminated in the landfill. In the block A and B, minor fault having the strike of N$70^{\circ}$W have been confirmed by dipole-dipole surveys, so future contamination of the bedrock by leachate is possible The degree of ground contamination is the highest in the D block due to the leachate plume mainly heading for this block. On the other hand, electrical soundings do not indicate ground contamination by leachate in the front area of the landfill.

• Fire Science and Engineering
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• v.17 no.3
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• pp.61-73
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• 2003

Most of the accidents occurred from the chemical plants are related to the catastrophic gas release events when the large amount of toxic materials is leaked from its storage tank or transmitting pipe lines. In this case, the greatest concerns are how the spreading behaviors of leakages are depended on the ambient conditions such as air stability and other environmental factors. Hence, we have focused on the risk assessments and consequential analysis for chlorine as an illustrative example. As appeared in the result, Fire & Explosion Index depicted it a bit dangerous with presenting the comprehensive degrees of hazard 90.7. And as a result of Phast6.0/ALOHA, the trends of each scenario appeared considerably identical although there are some differences in the resulting effects according to the input data for the Gas Model. The consequence analysis is performed numerically based on the dense gas mode. In the future, using more correct input data, material properties, and topographical configuration, the method of this research will be useful for the guideline of the risk assessment when the release of toxicants breaks out.

• Journal of the Korean association of regional geographers
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• v.22 no.1
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• pp.225-239
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• 2016

The Jeogchung Chogye Basin shows perfect basin formation surrounded with divides, excluding outlet where Sannae River combining various small rivers escapes the basin. High mountains distribute at southwestern, southern and southeastern divides of the basin consisting of hornfels, while hilly mountains are found at northern divide consisting of sedimentary rock. Alluvial fans and flood plains occupy bottom of the basin. While extensive alluvial fans are found at the front of southern divide where rivers with large drainage areas rise, alluvial fans toward eastern and western divides become small due to low elevation of divides. Flood deposits by Hwang River are attributed to development for most of flood plains at northern part of the basin. The basin seems to be developed not by differential erosion or meteorite impact, but by bedrock weathering along lineament or fault lines by ground motion.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.12
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• pp.2109-2112
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• 2016

The rate of rise of the fault current in DC grids is very high compared to AC grids because of the low line impedance of DC lines. In AC grids the arc of the circuit breaker under current interruption is extinguished by the zero current crossing which is provided naturally by the system. In DC grids the zero current crossing must be provided by the circuit breaker itself. Unlike AC girds, the magnetic energy of DC grids is stored in the system inductance. The DC circuit breaker must dissipate the stored energy. In addition the DC breaker must withstand the residual overvoltage after the current interruption. The main contents of this paper are to ${\cdot}$ Explain the theoretical background for the design of DC circuit breaker. ${\cdot}$ Develop the simulation model in PSIM of the real scaled DC circuit breaker for 1,800V DC railway. ${\cdot}$ Suggest design guidelines for the DC circuit breaker based on the experimental work, simulations and design process.