• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 C
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• pp.1593-1595
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• 2000

We present a new procedure to evaluate the degradation in a lCr-lMo-0.25V steel. The method is based on the existence of the peak of reversible permeability in the differential magnetization around the coercive field strength. The apparatus is based on the detection of the voltage induced in a surface type coil using a lock-in amplifier tuned to a frequency to the exciting one. Results obtained the reversible permeability and Vickers hardness on the annealed samples show the peak interval of reversible permeability and Vickers hardness decreased as ageing time increased. The correlation between Vickers hardness and the peak interval of reversible permeability could well be evaluated non destructively.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.624-627
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• 2000

The shielding effectiveness of materials is determined by measuring the ratio of the incident electromagnetic power which passes through the material under test. To measure the shielding effectiveness materials made by conductive polymer, the flanged coaxial transmission-line holder based in ASTM D4935-89, was fabricated. This apparatus has dynamic range between 95dB and 120dB in frequency range of 50Mhz-2Ghz. Furthermore, this system can be utilized to measure the shielding effectiveness of materials produced by conductive polymer and can be adapted for shielding materials design.

• 한국기계가공학회지
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• 제17권5호
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• pp.131-136
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• 2018

Research on space development and satellites is being actively pursued. An interesting field is the study of reliable low-cost space launch vehicles. Since chemical fuel-based launching systems are expensive and take a lot of time and cost to maintain, the EML system, which is an electromagnetic force launching apparatus, is attracting attention. The EML system converts electrical energy stored in a capacitor into magnetic energy, and converts magnetic energy into mechanical kinetic energy, thereby accelerating the projectile. Although studies are actively conducted in the field, it is difficult to solve the equation because the impedance and speedance change with time and the nonlinearity is strong. Many researchers have solved this equation in a variety of methods. In this paper, the velocity analysis of the projectile was carried out by FEM (finite element method) using the commercial electromagnetic analysis program MAXWELL.

• 한국전자파학회논문지
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• 제14권10호
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• pp.1017-1023
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• 2003

최근 전기전자기기 등의 사용에 의한 전자파 발생으로 인체 위해성에 대한 논쟁이 시작되었으며, 지난 20여년 동안 고압선로에서 발생되는 극저주파 전자기장에 만성적인 노출로 인한 인체 위해성에 관한 역학적 연구가 많은 나라에서 진행되어 왔다. 2 mG 이상의 자기장에 지속적으로 노출될 경우에 소아백혈병 등과 같은 암 질병이 발생한다는 연구논문이 발표되고 있다. 고압선로로부터 발생되는 전자파에 의한 장기적인 노출과 암 발생에 관한 상관관계가 과학적으로 명확하게 규명되지 않았고, 또한 잠재적인 건강 위험성에 대한 평가가 입증되지 않았음에도 불구하고, 2000년에 스위스는 민감한 정온시설 지역에 대하여 엄격한 예방적 원칙을 적용하고 있으며, 여러 국가들도 이러한 건강 위험성에 대한 저감정책의 일환으로 자기장 노출 가이드라인을 설정하려는 움직임을 보이고 있다. 다시 말하면, 과학적인 불확실성이 높은 상황에서도 과학적인 연구결과만을 기다리지 않고, 잠재적인 위험성을 예견하여 차후 심각한 위험성에 대한 조치를 미리 적용하는 관리정책이다. 우리나라에서는 아직 이러한 건강 위험성에 대한 관리정책이 아직 마련되어 있지 않은 상태이다. 따라서 고압선로에서 발생되는 전자기장에 만성적인 노출과 소아백혈병 발생과의 상관관계를 밝히기 위한 연구를 지속적으로 해야 하며, 유아원, 초등학교 등의 환경민감시설에 대한 단계별 전자파 방출 권고치를 설정하는 등의 예방적 관리정책을 부분적이나마 도입할 필요가 있다.

• 한국전기전자재료학회논문지
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• 제19권2호
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• pp.162-168
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• 2006

Recently, diagnosis techniques have been investigated to detect a Partial Discharge associated with a dielectric material defect in a high voltage electrical apparatus, However, the properties of detection technique of Partial Discharge aren't completely understood because the physical process of Partial Discharge. Therefore, this paper analyzes the process on surface discharge of polymer insulator using wavelet transform. Wavelet transform provides a direct quantitative measure of spectral content in the time~frequency domain. As it is important to develop a non-contact method for detecting the kaolin contamination degree, this research analyzes the electromagnetic waves emitted from Partial Discharge using wavelet transform. This result experimentally shows the process of Partial Discharge as a two-dimensional distribution in the time-frequency domain. Feature extraction parameter namely, maximum and average of wavelet coefficients values, wavelet coefficients value at the point of $95\%$ in a histogram and number of maximum wavelet coefficient have used electromagnetic wave signals as input signals in the preprocessing process of neural networks in order to identify kaolin contamination rates. As result, root sum square error was produced by the test with a learning of neural networks obtained 0.00828.

• 산업경영시스템학회지
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• 제22권53호
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• pp.69-78
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• 1999

We developed an apparatus for odorous stimuli control to record olfactory evoked potentials from human scalp. The characteristics of the apparatus were as follows. 1. Translating the subjects respiration into electric signals with a sensor attached to the nose. The period and timing of odorous stimuli could be adjusted, so that stimuli could be synchronous with respiration. 2. The respirations translated into electric signals were made constant in amplitude by using an auto gain control circuit. 3. The interstimulus interval of odorous could be arbitrarily selected once every 1 to 9 respirations so that adaptation could be prevented. We obtained olfactory - evoked potentials (OEPs) to odorous stimuli using this apparatus from the site of Cz, whose positive peak latencies were approximately $180{\pm}23ms$. Such response were not recorded if oxygen stimuli were used instead of odorous or with click sounds produced by the switching electromagnetic valve.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부 C
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• pp.904-906
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• 1998

PD pulses have about one nanosecond rise time in the $SF_6$ gas insulation. These pulses propagate in the apparatus to PD sensors in the form of the voltage oscillation, high frequency current and the electromagnetic radiation. In this paper, we investigated the characteristics of two types of PD sensors, by putting high frequency signals in the form of sine waves and pulse into the test apparatus in air. Also, we measured PD quantity from the needle electrode and the sensitivity of the sensors. We found that PD of 70pC could be detected with this method and the study in $SF_6$ gas should be carried out for application to $SF_6$ GIS.

• Journal of electromagnetic engineering and science
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• 제7권3호
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• pp.134-137
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• 2007

This paper presents the design of the compact UHF Bandpass filter of CT-type with a novel mixed coupling topology. In further detail, this new coupling structure mathematically equals the transmission zero that enables particularly the better rejection performance in the stopband without increasing the filter's order. To envision this design concept, we fabricated a microstrip filter whose measurement proves to agree with the predicted performance and the suggested coupling structure reduces the overall size, and will be possibly used in the miniaturized UHF apparatus such as the RFID system.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2000년도 종합학술발표회 논문집 Vol.10 No.1
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• pp.277-281
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• 2000

본 논문에서 생체실험용 대형 2축 자기장 발생장치를 설계하였다. 생체실험 대상이 유동적이지 않고 홀더(holder)내에 고정될 경우 이는 방향성(orientation)의 논란이 불가피하며 이 영향을 줄이기 위해 각 축에 4개씩 총 8개의 코일을 사용하여 2축 4중코일 구조로 장치를 설계하였다. 원하는 특정 자기장에 대한 권선수 및 전류치를 결정하기 위해 정육면체 구조의 자기장 발생장치를 원통형으로 근사화시켜 간소하게 수식을 유도하였으며 각 코일의 최적위치 및 최적 권선비는 별도의 최적화 시뮬레이션을 통하여 수치를 추출하였다. 이렇게 얻어진 수치들을 MATLAB으로 제작한 시뮬레이터에 적용하여 설계 조건과 동일하게 모델링한 발생장치 주변에서의 자기장 분포를 시뮬레이션 해보았으며, 각 축에서의 균일도를 평가하여 균인 자기장 분포영역 또는 사용가능영역을 도출하였다. 장치해석 결과, 임의의 기준 자기장에 대해 약 5%의 오차범위를 인정할 경우, 최소 60% 이상의 사용가능영역을 확보할 수 있었으며, 이 영역 내에서는 고도의 균일 자기장이 분포함을 확인할 수 있었다.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2003년도 종합학술발표회 논문집 Vol.13 No.1
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• pp.13-17
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• 2003

In this paper, the design parameters for the magnetic field source at extremely low frequency are proposed. This facility can be used for in vivo experiments with small animals to investigate biological response to the driving magnetic fields. In case that the exposed animals are motionless, the animals may be affected by the directivity of driving field. To avoid this effect, a 2-axis ELF magnetic field driving apparatus was designed, The optimum location and number of turns of each coil were obtained by numerical analysis. Applying these data to the MATLAB code (for computation), the magnetic field distribution was obtained. The calculation result for a well-designed facility showed that the space in which the amplitude of the magnetic field lies within the 95% of the magnetic field distribution was more than 60% of each axis length.