• Journal of the Korea Institute of Military Science and Technology
• /
• v.11 no.6
• /
• pp.74-80
• /
• 2008

Analysis of the electromagnetic environment on topside of a ship is needed for optimal arrangement of all kinds of antennas to be installed on the shipboard in order to minimize the probability of EMI of equipment and subsystems in real ship after construction phase. In this paper we analyze the characteristics of electric-fields such as radiation patterns and near E-fields of V/UHF antennas installed on a shipboard. We compare simulated results with measurements on the real ship for near E-fields to verify the reliability of the computed electromagnetic environment. Although there are various factors causing errors such as cable loss and impedance mismatching etc. when measuring near E-field, both data show similar trends in the range of the acceptable tolerance.

• KIEE International Transactions on Power Engineering
• /
• v.5A no.4
• /
• pp.366-370
• /
• 2005

To meet increasing power demand, 500 kV power systems are under consideration in the regions of some Middle Asian countries. As the power system voltage becomes higher, the cost for the power system insulation increases significantly. 500 kV transmission systems will become the basis of a region's power system and they require much higher system reliability. Consequently, by the methods of limiting overvoltages effectively, a reasonable insulation design and coordination must be accomplished. In particular, the Substations must be constructed to be of outdoor type. In order to determine the various factors for the insulation design, the EMTP (Electro-magnetic transient program) is used for the magnification of transient phenomena of the 500 kV systems in the planned network. In this paper, we will explain the calculation results of lightning overvoltages by the EMTP for lightning protection design for the 500 kV substations. To obtain reliable results, the multi-story tower model and EMTP/TACS model are introduced for the simulation of dynamic arc characteristics.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2001.09a
• /
• pp.38-42
• /
• 2001

우리나라는 1968년 이후에 154kV급 송전 계통망을 비접지 방식에서 직접 접지방식으로 변경함에 따라, 전력선의 1선 지락고장시 송전선으로부터 지락전류 즉, 고장전류가 크게 되어 이 결과 송전선 주변에 있는 통신선에 유도문제가 발생하게 되었다. 본 논문에서는 전력선에 의한 통신선측의 유도전압 예측계산식을 제시하고, 유도예측 계산치가 일정 기준을 초과할 경우, 통신선측과 전력선측에서 강구할 수 있는 대책방안에 대해 소개하고자 한다.

• Proceedings of the KIEE Conference
• /
• 1999.07c
• /
• pp.1357-1359
• /
• 1999

This paper presents fault detection in cables. We developed the device for detecting pinpoint location of faults in power cables using acoustic method. The proposed device consists of hardware and software for the fault detection. Using the device, we explain how to detect the pinpoint of faults and introduce that the other method use the time delay between electro-magnetic and acoustic signals for the pinpoint of the faults.

• Journal of Institute of Control, Robotics and Systems
• /
• v.11 no.7
• /
• pp.595-601
• /
• 2005

A mobile robot system utilizing NDT (Non-Destructive Testing) method is designed and fabricated f3r automatic integrity evaluation of large sized industrial reservoirs and pipelines. The developed mobile robot can crawl over the outer surface of the industrial facilities even though the shape of the structures is various and unsymmetric. The robot detects defects such as pinholes, cracks and thickness reduction at the wall of the facilities using EMAT (Electro-Magnetic Acoustic Transducer). Image processing technology for weld line detection at the surface of the target and host programs including defect detecting algorithms are also developed. Automation of defect detection for these kinds of large facilities using mobile robots is helpful to prevent significant troubles of the structures without danger of human beings under harmful environment.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
• /
• v.7 no.2
• /
• pp.17-29
• /
• 1996

현대 산업사회에서의 자동차는 사회 및 경제활동에 있어서 없어서는 안되는 필수 불가결한 생활의 일부분으로 자리잡은지 이미 오래이며, 국내에서도 1987년 이후로 급격한 증가추세에 있다. 또 한 갈수록 발전되는 첨단 전자제품의 개발로 자동차도 초기의 기계적인 제어에서 현재는 많은 부분이 전자 제어화 되고 있는 실정이다. EMI(ElectroMagnetic Interference)의 측면에서 자동차는 점화장치가 가장 많은 불요전자파를 발생 하고 잇으나, 지난 수십 년간의 법규제(유럽 및 북미)등을 적용하여 이미 자동차 제작사들은 이를 고 려하여 개발, 평가를 하여 불요전자파의 발생을 줄이고 있다. 그러나, 계속되는 전자화 및 첨단 전자 제품의 개발에 따라 자동차에도 고성능의 전자소자 등을 적용하게 되었으며 이는 새로운 EMI 측면의 문제를 발생시켰으며 EMS(ElectroMagnetic Suseptibility) 측면에서는 자동차의 기능이 오작동하여 시스템의 기능 불이행, 수송수단의 손실, 심지어는 인명의 손실 등 위해가 심각한 문제로 대두되었다.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1997.10a
• /
• pp.180-183
• /
• 1997

The forming process of metal matrix composites by the die casting and squeeze casting process are limited in size and dimension in term of final parts without machining. The thixoforming process for metal matrix composites has numerous advantages compared to die casting, squeeze casting and compocasting. The characteristics of thixoforming process can decrease the liquid segregation because of he improvement in fluidity in a globular microstructure state and utilizes flow without air entrapment. Therefore, in order to obtain the sound parts of metal matrix composites by using thixoforming process which as co-existing solidus-liquidus pahse, it si very important to obtain reheating condition. However, for he thixoforming process, the billet with the desired volume fraction must be heated to obtain a uniform temperature distribution over the entire cross-sectional areas. To obtain the reheating conditions of composites, the particulate reinforced metal matrix composites for thixoforming were fabricated by combined stirring process which is simultaneously performed with electro-magnetic stirring process which is simultaneously performed with electro-magnetic stirring and mechanical stirring process.

• Journal of Institute of Control, Robotics and Systems
• /
• v.11 no.3
• /
• pp.187-192
• /
• 2005

This paper presents the design of the Automatic Gain Control (AGC) system for the drive axis of a electro-magnetic driven cylinder gyroscope. The simulation and experimental results show that the designed AGC excites the cylinder at its natural frequency and maintains a specified amplitude of oscillations, and also track the natural frequency shifts due to temperature variations. The sensing performance of the AGC driven gyroscope is shown to be greatly improved compared to that of the open-loop driven one.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.25 no.4
• /
• pp.209-213
• /
• 1989

The author suggested control method of partial cavitation with electro-magnetic accelerator and showed that the cavity shape decreased with this suggestion which compared with the theoretical ones. Using the cavity flow method proposed by the author in this paper, it is predicted that cavitation volume of the shape is less than the previous type one. Comparisons were performed in order to verify these facts, using both shape which calculated by the method. It was found that the difference of cavitation performance between the two shape of volume were decreased, because of the new method accelerated of flow more than previous theoretical ones.

• Aerospace Engineering and Technology
• /
• v.12 no.2
• /
• pp.74-82
• /
• 2013

This paper deals with a single stage coilgun which is a variety of EML(ElectroMagnetic Launcher) and can be applied to launching a small satellite. We propose a mathematical and physical model in order to design a single stage coilgun and study physical characteristics related to design parameters. A proposed mathematical and physical model is verified by electromagnetic FEM software FEMM 4.2.