• 한국조명전기설비학회:학술대회논문집
• /
• 한국조명전기설비학회 2000년도 학술대회논문집
• /
• pp.241-245
• /
• 2000

In this paper, VHF(30~230[MHz]) electromagnetic waves radiated from partial discharge(PD) at two-type electrodes in air are measured and the peculiar patterns of their spectra are reported. Also, the polarization and distance characteristics of electromagnetic wave rediated by PD, were investigated. In case of epoxy insulator in inserted, the noise level of radiated electromagnetic waves is 0.6~6.2[dB] higher than the case in air at below 90[MHz]. The frequency spectrum distribution of radiated electromagnetic waves appears different in the whole frequency range according to the arrangement of antenna.

• Journal of electromagnetic engineering and science
• /
• 제4권1호
• /
• pp.43-49
• /
• 2004

A low-frequency coaxial reflectometer(LCR) with a thin-wire inner conductor is designed and constructed to measure nondestructively the absorbing performance of electromagnetic absorbers in the frequency range of 10 MHz to 200 MHz. The LCR consists of a square coaxial transmission line and a network analyzer with a time-domain measurement capability. Inherent characteristics of a square coaxial line with a thin-wire inner conductor which deteriorate the impedance matching of the input port of the LCR are addressed. And the characteristics are improved by employing a multiwire inner conductor. Measured and calculated reflection losses of a flat ferrite tile absorber are presented.

• Smart Structures and Systems
• /
• 제1권2호
• /
• pp.217-233
• /
• 2005

Elastic and electromagnetic waves can be used to gather important information about particulate materials. To facilitate smart geophysical characterization of particulate materials, their fundamental properties are discussed and experimental procedures are presented for both elastic and electromagnetic waves. The first application is related to the characterization of particulate materials using shear waves, concentrating on changes in effective stress during consolidation, multi-phase phenomena with relation to capillarity, and microscale characteristics of particles. The second application involves electromagnetic waves, focusing on stratigraphy detection in layered soils, estimation of void ratio and its spatial distribution, and conduction in unsaturated soils. Experimental results suggest that shear waves allow studying particle contact phenomena and the evolution of interparticle forces, while electromagnetic waves give insight into the characteristics of the fluid phase and its spatial distribution.

• 디지털산업정보학회논문지
• /
• 제17권4호
• /
• pp.31-42
• /
• 2021

In the modern era, radio wave analysis is necessary for various fields of engineering, and interpretation of this is also indispensable. Self-driving cars need multiple different electronic components, and thus accurate and fast electromagnetic simulator for this kind of complex radio environment is required for self-driving simulations. Accordingly, the demand for self-driving simulators as well as existing electromagnetic analysis software has increased. This paper briefly describes the characteristics of numerical analysis techniques for electromagnetic analysis, self-driving simulation software, and conventional electromagnetic simulation software and also summarizes the characteristics of each software. Finally, the verification of the result from in-house code compared to HFSS is demonstrated.

• 조명전기설비학회논문지
• /
• 제18권5호
• /
• pp.112-117
• /
• 2004

본 연구에서는 뇌전자장 펄스에 관한 상세한 정보를 얻기 위한 목적으로 운방전에 의해서 방사되는 전자파 펄스를 측정하고, 이의 특성과 파라미터를 통계적으로 분석하였다. 운방전에 의해서 방사된 전자파 펄스는 낙뢰에 의한 것과는 확연하게 달랐으며, 후속 스토로크로 갈수록 주 방전에 의한 양방성 전자파 펄스의 영점교차시간과 펄스폭은 짧게 나타났다. 또한 주 방전에 의한 양방성 전자파 펄스의 파두부분에는 좁고 빠른 리더펄스가 중첩되어 나타났으며, 이 중첩된 리더펄스의 평균 개수는 정극성에서 61$\pm$0.74, 부극성에서 1.75$\pm$0.73이었다.

• 한국항해학회지
• /
• 제22권4호
• /
• pp.51-57
• /
• 1998

According to the rapid development of the electric industry, the demand of the frequency allocation and the usage of electromagnetic wave are increased due to automation of modem society. Electromagnetic wave absorbers for anechoic chamber are needed to broaden the effective frequency bandwidth, reduce the thickness, and decrease the weight. There are various absorbers proposed for the above conditions, but they could not decisively solve the above requirements. The Electromagnetic wave absorber made by a conventional ferrite tile has, for example, broadened the effective frequency bandwidth by the way of forming air layer(practically in urethane foam, etc.) on the ferrite tile. Therefore, an air layer is formed between a reflection plate and a sintered Ni-Zn ferrite tile of 7 mm in thickness, which has reflectivity less than -20 dB from 30 MHz to 400 MHz in bandwidth. In this paper, a broadband electromagnetic wave absorber are designed, which has the reflection characteristics less than -20 dB from 30 MHz to 8,000 MHz in the bandwidth. A super broadband electromagnetic wave absorber is achieved by inserting square Ferrite Cylinders Type with the thickness less than 23.5 mm and with the frequency band from 30 MHz to 8,000 MHz under the above tolerance limits. The purpose of this research is on the development of a universal anechoic chamber for measuring radiated electromagnetic wave or immunity of electronic equipments, GTEM-cell and also a wall material for preventing TV ghost, etc.

• 소음진동
• /
• 제7권4호
• /
• pp.663-668
• /
• 1997

In general, the noise of alternator is generated by structure of attachment and structural characteristics of alternator itself. In this paper, general phenomena and causes of alternator noise have been considered. Especially, electromagnetic noise source of alternator has been discussed by consideration about the vibration of stator teeth. Also experimental method and simulation method have been used for the proof.

• 한국항해학회지
• /
• 제19권4호
• /
• pp.93-102
• /
• 1995

A design method of an electromagnetic wave absorber with ferrite fins in the second layer, which has very wide band frequency characteristics, is proposed and discussed. A theoretical model using the equivalent material constants method is adopted, assessed for its accuracy by comparision with the Hashin-Shtrikman formulas and compared with the conventional absorbers. Based on the model, a wide band electromagnetic wave absorber with excellent reflectivity frequency characteristics in frequency range of 30MHZ to 3530MHZ has been designed.

• 한국항해학회지
• /
• 제19권2호
• /
• pp.99-106
• /
• 1995

A wide band design method of an electromagnetic wave absorber with square ferrite cylinders in the second layer, which has very wide band frequency characteristics, is proposed and discussed. A theoretical model using the equivalent material constants method is also evaluated and proposed for its accuracy by comparison with Hashin-Shtrikman formulas. Based on the developed model, wide band electromagnetic wave absorbers with excellent reflective frequency characteristics in the frequency range of 30MHz to 3, 690MHz were designed.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
• /
• pp.1318-1320
• /
• 2005

This paper presents the characteristics analysis of an electromagnetic pump using the linear induction motor(LIM). The characteristics of the pump are analyzed solving two equations : the electromagnetic equation and hydrodynamic one.