• Proceedings of the KIPE Conference
• /
• 2006.06a
• /
• pp.213-215
• /
• 2006

Islanding phenomenon is undesirable because it lead to a safety hazard to utility service personnel and may cause damage to power generation and power supply facilities as a result of unsynchronized reclosure. In order to prevent the phenomenon, various anti-islanding methods have been studied. This paper proposes the variation method of inverter output current magnitude to prevent the islanding phenomenon as a novel method, which causes the large frequency variation of inverter output voltage after islanding. Unlike most active anti-islanding method deteriorating power quality, this novel method will have high performance of islanding detection and good power quality. For the verification of the proposed method, the simulated result and analyses are presented.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2007.05a
• /
• pp.1454-1458
• /
• 2007

The determination of feasible design flood is the most important to control flood damage in river management. Model parameters should be calibrated using observed discharge but due to deficiency of observed data the parameters have been adopted by engineer's empirical sense. Storage constant in the Clark unit hydrograph method mainly affects magnitude of peak flood. This study is to estimate the storage constant based on the observed rainfall-runoff data at the three stage stations in the Imjin river basin and the three stage stations in the Ansung river basin. In this study four methods have been proposed to estimate the storage constant from observed rainfall-runoff data. The HEC-HMS model has been adopted to execute the sensitivity of storage constant. A criteria has been proposed to determine storage constant based on the results of the observed hydrograph and the HEC-HMS model.

• Smart Structures and Systems
• /
• v.6 no.3
• /
• pp.211-223
• /
• 2010

Accurate sensing of mechanical strains in civil structures is critical for optimizing structure reliability and lifetime. For instance, combined with intelligent control systems, electromechanical sensor output feedback has the potential to be employed for nondestructive damage evaluation. Application of Ionic Polymer Transducers (IPTs) represents a relatively new sensing approach with more than an order of magnitude higher sensitivity than traditional piezoelectric sensors. The primary reason this sensor has not been widely used to date is an inadequate understanding of the physics responsible for IPT sensing. This paper presents models and experiments defending the hypothesis of a streaming potential sensing mechanism.

• Proceedings of the Korean Operations and Management Science Society Conference
• /
• 2002.05a
• /
• pp.456-463
• /
• 2002

Nowadays. risk management in the enterprise is considered as the important activity. Risk management ran be defined as the activity which is the analysis of risk factors related to damages, the estimation of the magnitude of risk, and the determination of investment to protect damage in a company. Initially, risk management was originated in financial areas. But the concept of risk has been expanded in the enterprise. Most companies have extended their activities in various areas. In this tendency, most activities must be considered in supply chain So, risk management must be ronsidered as the concept in the viewpoint of supply chain. The framework of risk management in supply chain and the related mathematical model are represented in this paper. Risk management in supply chain ran provide a positive opportunity not only to protect various damages, but also to improve the relationship between partners.

• Journal of the Korean Professional Engineers Association
• /
• v.28 no.2
• /
• pp.13-20
• /
• 1995

This paper Is to help the structural engineers for a better understanding of "Earthquake" with regard to the nature o( earthquake and the effect of earthquake on building structures. This reveals that the damage Inflicted upon by earthquake varies with many factors such as : magnitude of earthquake, distance from epicenter, site conditions, building structural characteristics and etc.. It is emphasized that in order to resist very strong earthquake, the ductility demand in the building structure Is important, and the proper duc-tility enables the structure to demonstrate inelastic rotation capacity of the joints and thus the structure may absorb and dissipate the seismic energy. This also presents a comparison between the current Americal UBC Code and the Korean Code, and the author expresses some points of concern on each code. Since earthquake almost invariably strikes at times and places, it is suggested that the current Korean Build-ing Code should be revised to enforce more stringent regulation against possible strong earthquake in the Korean peninsula.

• Geomechanics and Engineering
• /
• v.21 no.2
• /
• pp.143-152
• /
• 2020

Korean society experienced successive earthquakes exceeding 5.0 magnitude in the past three years resulting in an increasing concern about earthquake stability of urban infrastructures. This study focuses on the significant aspects of earthquake risk assessment for the cut-and-cover underground railway station based on two-dimensional dynamic numerical analysis. Presented are features from a case study performed for the railway station in Seoul, South Korea. The PLAXIS2D was employed for numerical simulation and input of the earthquake ground motion was chosen from Pohang earthquake records (M5.4). The paper shows key aspects of earthquake risk for soil-structure system varying important parameters including embedded depth, supported ground information, and applied seismicity level, and then draws several meaningful conclusions from the analysis results such as seismic risk assessment.

• Nuclear Engineering and Technology
• /
• v.48 no.1
• /
• pp.211-217
• /
• 2016

Most nuclear power plants now utilize solid grounded low voltage systems. For safety and reliability reasons, the low voltage (LV) high resistance grounding (HRG) system is also increasingly used in the pulp and paper, petroleum and chemical, and semiconductor industries. Fault detection is easiest and fastest with a solidly grounded system. However, a solidly grounded system has many limitations such as severe fault damage, poor reliability on essential circuits, and electrical noise caused by the high magnitude of ground fault currents. This paper will briefly address the strengths and weaknesses of LV grounding systems. An example of a low voltage HRG system in the LV system of a nuclear power plant will be presented. The HRG system is highly recommended for LV systems of nuclear power plants if sufficient considerations are provided to prevent nuisance tripping of ground fault relays and to avoid the deterioration of system reliability.

• Vacuum Magazine
• /
• v.2 no.2
• /
• pp.17-23
• /
• 2015

Medium Energy Ion Scattering (MEIS) has been successfully used for ultrathin film analysis such as gate oxides and multilayers due to its single atomic depth resolution in compostional and structural depth profiling. Recently, we developed a time-of-flight (TOF) MEIS for the first time, which can analyze a $10{\mu}m$ small spot. Small spot analysis would be useful for test pattern analysis in semiconductor industry and various thin film technology. The ion beam damage problem is minimized due to its improved collection efficiency by orders of magnitude and the ion beam neutralization problem is removed completely for quantitative analysis. Newly developed TOF-MEIS has been applied for gate oxides, ultra shallow junctions, nanoparticles, FINFET structures to provide compositional and structural profiles. Further development for submicron spot analysis and applications for functional nano thin films and nanostructured materials are expected for various nanotechnology and biotehnology.

• Proceedings of the KSR Conference
• /
• 2002.10a
• /
• pp.208-213
• /
• 2002

Railway wheel and axle are the most critical components in railway system. A wheel and axle failure can cause a derailment with its attendant loss of life and property. The service conditions of railway vehicles have become severe in recent years due to a general increase in operating speeds. Therefore, more precise evaluation of wheelset strength and safety has been desired. Damages of railway wheel are a spatting by wheel/rail contact and thermal crack by braking heat etc. One of the main source of damage is a residual stress. therefore it is important to evaluate exactly. A Residual stress of wheel is formed at the process of heat treatment when manufacturing. it is changed by contact stress developed by wheel/rail contact and thermal stress from heat induced in braking. The objective of this paper is to estimate the variation and magnitude of the residual stress of railway wheel.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.24 no.10
• /
• pp.143-148
• /
• 2010

Recently, the KEPCO is constructing the PQMS(Power Quality Monitoring System) each of the distribution line and will establish the voltage sag standard based on the long time measurement data of PQMS. The voltage sag prospect is difficult for the power system manager, however, the voltage sag forecasted is very important because the damage effect of the voltage sag is very broad. This paper describes the prospect formula of the voltage sag magnitude in the PCC(Point Common Coupling) by the starting current when the high capacity equipment is connected with the distribution line. To achieve this, this paper has proposed the sag prospect formula revision of KEPCO for the reliability improvement and the proposed formula has been applied the voltage sag real case to inspect the calculation procedure and reliability.