• 대한기계학회논문집B
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• 제35권3호
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• pp.321-330
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• 2011

본 연구는 전선화염의 전파특성에 직류전기장이 미치는 영향에 대한 실험적 연구이다. 화염전파는 은 0에서 ${\pm}7kV$ 범위의 음극과 양극의 전기장을 인가하여 실험되어졌다. 본 연구를 통해 앞선 전선화염 전파에 영향을 미치는 교류전기장 효과에 관한 연구결과와 비교하여 관찰된 다양한 화염 모양 변화의 원인을 알아보고, 화염 전파 속도의 가속특성에 대해서도 논의하고자 한다. 직류전기장의 인가가 전선화염에 미치는 영향은 크지 않지만 이온풍 효과에 따른 미미한 영향은 존재하며, 이것은 온도 균형 메커니즘과 연료 증발기체 분사 효과로 설명 될 수 있다.

• KIEE International Transactions on Electrophysics and Applications
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• 제11C권4호
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• pp.120-126
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• 2001

For the past five years, Inha University has been observing the electric fields produced by cloud-to-ground return strokes. This paper presents the summary of most recent results. Statistics on the zero-to-peak rise time, the zero-to-zero crossing time and the amplitude ratio of the second peak in the opposite polarity to the first peak were examined. The radiation electric fields produced by distant cloud-to-ground return strokes were substantially same pattern. The first return stroke field starts with a slowly increasing front and rises abruptly to peak. The rising portions of the electric fields produced by cloud-to-ground return strokes last 1 $mutextrm{s}$ to a few $mutextrm{s}$. The mean values of the zero-to-peak rise times of electric fields were 5.72 $mutextrm{s}$ and 4.12 $mutextrm{s}$ for the positive and the negative cloud-to-ground return strokes, respectively. The mean of the zero-to-zero crossing time for the positive return strokes was 29.48 $mutextrm{s}$ compared with 38.54 $mutextrm{s}$ for the negative return strokes. The depths of the dip after the peak of return stroke electric fields also have the dependence on the polarity of cloud-to-ground return stroke, and the mean values for the positive and negative cloud-to-ground return strokes were 33.55 and 28.19%, respectively.

• 한국공작기계학회논문집
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• 제12권1호
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• pp.78-83
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• 2003

Electro-rheological(ER) fluids are suspensions in which rheological properties show an abrupt change with variation of electric fields. We modeled the parallel-plates relating to ER-Valve system and yielded shear stress according to the strength of electric field. The purpose of the present study is to examine the flow characteristics of ER fluids according to the strength of electric field between parallel-plates. Then the steady relationship between pressure drop and flow rate of the ER fluids between parallel-plates under application of an electric fields was measured. The pressure drop and flow rates of ER fluids under the application of electric fields for steady flow were measured. For the experiment, we used the ER fluids, 35w% zeolite having hydrous particles and differential pressure gauge. This test reviewed experiment for the special changes of ER fluids in the steady flow condition.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 C
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• pp.2204-2206
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• 2000

In this paper, the magnetic fields measured experimentally from the electric home appliances were evaluated and the data were discussed on the bases of the international institutes recommendations. It is difficult to insulate magnetic flux completely from electric home appliances and impossible to simulate theoretically because of the different directions and magnitudes of magnetic fields according to the internal current of electric home appliances. The experimental measurements of magnetic flux density were carried out according to the increment of distance in the vicinity of electric home appliances. The magnetic flux density produced by the electric home appliances was drastically dropped with the increment of distance. The measured and analysed results of electric home appliances of 15 including computer monitor, TV, etc. were presented.

• 환경영향평가
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• 제13권5호
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• pp.243-250
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• 2004

Recently, concerns about health risks exposed to electromagnetic fields have been brought in the safety of electric power lines. A number of governmental and international organizations have advised to avoid the magnetic field exposure to the schools and residential areas. Some epidemiologic studies showed that electromagnetic fields should not exceed the exposure limits of 2-3mG to the people living near high-voltage transmission lines. In this study, the principles, ranges and survey methods of the assessment for powerfrequency electromagnetic fields were reviewed from the relevant research papers and documents. The ranges of electromagnetic fields were determined from 50m to 100m and have been defined according to the properties of each electric power lines and a new methodology was suggested in this study. It would be necessary to develop and improve specific assessment methods for various high-voltage transmission lines projects.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제53권6호
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• pp.330-336
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• 2004

In this work, in order to obtain the detailed information about lightning electromagnetic pulses, the electric fields radiated from multiple lightning return strokes were measured and analyzed statistically. The electric field measuring system consists of a hemisphere antenna of 30cm in diameter, integrator and data acquisition device, and its frequency bandwidth ranges from 200Hz to 1.56MHz, and the sensitivity is 0.96㎷/V/m. The electric field signals are digitized every 200ns with the transient signal analyzer having the resolution of 12-bit and the recording length of 5 kilowords and are registered at personal computer. As a result, the electric fields produced by the first return stroke begin with a slow initial part or front, which starts just after or during the last stepped leader. On the average the rise times of the electric fields for the positive first, second and third strokes are 4.21${\mu}\textrm{s}$, 3.94${\mu}\textrm{s}$ and 2.75${\mu}\textrm{s}$, respectively, and those for the negative first, second and third strokes are 3.46${\mu}\textrm{s}$, 3.15${\mu}\textrm{s}$ and 2.79${\mu}\textrm{s}$, respectively. The zero-crossing times of the electric fields for first return strokes range from about 10 to 80${\mu}\textrm{s}$. The mean zero-crossing times for subsequent return strokes are shorter than those for first lightning return strokes.

• 조명전기설비학회논문지
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• 제13권2호
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• pp.46-54
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• 1999

최근 전자환경은 가전 제춤의 보급과 전력소비의 증가와 더불어 변화되고 잇다. 대부분 관심이 집중되고 있는 자료들은 전력 주파수의 전장과 자장의 노출된 인체에 미치는 영향에 대해 많은 관심이 집중되고 있으며, 이에 대한 정확한 측정과 분석이 요구되고 있다 본 논문에서는 22.9[kV] 배전선로에 발생하는 극저주파 영역의 전장과 자장의 측정과 분석이 수행되었고, 배전선로를 가로지르는 방법으로 측정하였으며, 측정값과 비교를 위해 FIELDS 프로그램을 사용하여 이론적으로 계산하였다. 전장과 자장의 세기는 배전선로 아래에서 강하였고, 횡방향 거리에 반비례하여 감소하였다. 전장의 분포곡선은 M자형태이고 자장은 $\bigcap$자 형태이었으며, 측정값은 이론값고 거의 흡사한 양상을 보였다. 그리고, 전장과 자장의 세기는 모두 측정높이가 증가함에 따라 강하게 나타남을 알 수 있었다. 전장의 분포는 3상 도체의 배치에 의해 영향을 받으며 자장의 분포 특성은 상전류의 불평형에 의해 최대값이 중앙점으로부터 이동되는 것을 알았다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2015년도 제51회 KOSCO SYMPOSIUM 초록집
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• pp.79-81
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• 2015

The experimental study on gasesous laminar free-jet flow was investigated by applying high voltage alternating current (AC) to the nozzle. The jet flows were affedcted significatly by AC electric fields particularly at high voltages for applied frequencies less than 80 Hz, while those were not responded to further increased frequencies. Under certain AC conditions of applied voltgae and frequency, the laminar gaseous fuel stem was broken down at an axial distance and subsequently separtaed into some parts. The velocity fields in jet flows interactiong with applied electric fields were compared with those without having electric field. Interaction of applying electric fields with laminar free jet flow was discussed in detail, and the possible mechanism was also explained.

• 조명전기설비학회논문지
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• 제30권2호
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• pp.78-84
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• 2016

This paper is focused on the measurement and analysis of an atmospheric electric field which is caused by thunderclouds. The electric field due to thunderclouds changes very slowly. For this reason, the extremely low frequency E-field sensor needs to be used for measuring the atmospheric electric field strength. The balloon-carried E-field sensor system with the time constant of 1sec was designed and fabricated. The electric field sensor consists of $100mm{\times}100mm$ copper plate, active integrator, high pass and low pass filters and batteries. The measurements of atmospheric electric fields were made by the balloon-carried E-field sensor and radiosonde, which sends the data back to ground in real time. From the calibration experiments, the response sensitivity of the E-field sensor was 0.154mV/kV/m in the frequency range of less than 1kHz. As a result from the actual experiment of the atmospheric electric field, the electric field signals were observed from the altitude of about 2.5km. Also, as the altitude was increased, the detected electric field wave oscillated with the fluctuation of sensing plate. The proposed method seems suitable for measurements of atmospheric electric fields, because it is inexpensive, simple to use and launch.

• 대한기계학회논문집A
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• 제33권3호
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• pp.265-268
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• 2009

We present the experimental study to realize a DNA separation chip using asymmetrically-switched nonuniform electric fields. The DNA separation chip redistributes DNA molecules within a specific area based on the size- and field-dependent nonlinearity of DNA drift velocity. The present chip is composed of a width variable channel to distribute nonuniform electric field, a DNA loading slit and a pair of electrodes to apply electric field. We focus on the design of DNA separation chips with identifying the nonlinearity of DNA drift velocity using three different DNA molecules (11.1kbp, 15.6kbp, and 48.5kbp) in the chips. It is demonstrated that different size of DNA shows different net migration in different direction under the asymmetrically-switched nonuniform electric field.