• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.119.1-119.1
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• 2014

Toxic waste disposal: Many people think that when toxic waste is dumped into the ocean or into the air, it disappears. This belief is incorrect. Rather than disappearing, it accumulates over time and slowly destroys the environment. Ultimately, it leads to the destruction of human race. Plasma is environmentally friendly: Plasma is environmentally friendly because it is created and disappears. When plasma is formed on the earth, you need certain conditions such as accelerating electrons by an electrical discharge or a particle accelerator. When this is gone, plasma completely disappears, leaving no impact on the environment. Plasmas produce radicals: Even if plasma density is low at atmospheric pressure, many radicals (excited states of molecules) are created. These radicals are chemically very aggressive. So instead of using harmful chemicals, plasma can be utilized for less of an impact on the environment. Plasma can reach very high temperatures: Plasma is also useful because when you control the density, you can easily reach high temperatures up to $5000{\sim}6000^{\circ}C$ at atmosphere pressure. Because of this heat and the chemical aggressiveness of the plasma, there are many green applications for plasma technology. Pulsed power technology: Pulsed electric field for extraction, drying and killing bacteria. Treatment of biological tissue by pulsed electric fields: Extraction of substances from cells: Sterilisation, Medical applications, Growth stimulation, Food preparation. Each application has its specialities, especially with respect to pulse shape and electric field strength.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1322-1327
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• 2004

In the present work, a series of experiments have been performed on electro-hydrodynamic atomization of non-conducting liquid using a charge injection type nozzle. Effects of liquid flow rate, input voltage, and distance between the needle and the ground electrode (nozzle-embedded metal plate) have been examined. For fixed electrode distances, total and spray currents increase with increase of liquid flow rate and input voltage. When the distance between the needle and the ground electrode becomes closer, total, leakage and spray current increase, but the onset voltage for dielectric breakdown decreases. When the electric field strength of the liquid jet exceeds that for the air breakdown, a portion of the electric charges in the liquid jet is dissipated into the ambient air, and the charge density shows a limiting value. Atomization quality can be improved by increasing the flow rate because the higher charge density is achieved with the larger liquid velocity in addition to the enhanced aerodynamic effect.

• 대한기계학회논문집B
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• 제28권11호
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• pp.1376-1383
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• 2004

In the present work, a series of experiments have been performed on electro-hydrodynamic atomization of non-conducting liquid using a charge injection type nozzle. Effects of liquid flow rate, input voltage, and distance between the needle and the ground electrode (nozzle-embedded metal plate) have been examined. For fixed electrode distances, total and spray currents increase with the increase of liquid flow rate and input voltage. When the distance between the needle tip and the ground electrode becomes closer, the total, leakage and spray currents increase, while the onset voltage for the dielectric breakdown decreases. When the electric field strength of the liquid jet exceeds that for the air breakdown, a portion of the electric charges in the liquid jet is dissipated into the ambient air, and the charge density shows a limiting value. Atomization quality can be improved by increasing the liquid flow rate due to the higher charge density and the enhanced aerodynamic effect.

• Journal of Astronomy and Space Sciences
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• 제19권1호
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• pp.75-88
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• 2002

전리층의 전기 전도도와 전기장을 구함으로써 극지방 전리층의 기후학적 특성을 살펴보았다 이를 위해, 총 109일간의 Sondrestrom 비간섭 산란 레이더 자료를 이용하였다. 전기 전도도와 전기장을 이용하여 전리층 전류 분포를 추정하였고, 구해진 전리층 전류 밀도와 그로 인해 유발되는 지상 지자기 변화를 비교하였다. 또한 지상 지자기 변화(특히, D 성분)에 대한 연자기력선 전류의 효과도 검토되었다. Sondrestrom 상공 전리층에 대한 몇 가지 흥미로운 기후학적 특성을 본 연구로부터 알 수 있었다: (1) 주간의 전기 전도도 분포는 주로 태양 EUV복사에 의한 것이며, 야간에는 미약하다. (2) 극관 영역 전리층의 전기 전도도 분포는, 주간에는 태양 EUV복사에 의한 분포를 보이는 반면, 야간에는 Hall 및 Pedersen 전기 전도도의 시간 평균이 각각 1.6 및 1.2 siemen으로 아주 낮다. (3) 남북 성분 전기장의 최대치가 낮 영역에 나타나는 경향이 있다. 동서 성분 전기장은 Chatanika에 비해 강하다 (4) 동서 성분 전류는 낮 영역에서 강하게 흐른다. 정오 바로 전에 강한 남향 전류가 흐른다. (5) 오로라제트전류와 동시에 관측된 지상 지자기 변화 $({{\Delta}}H)$ 사이에 높은 상관관계를 나타낸다. 하지만 무한판상을 가정한 전류가 크게 과소평가 된다. 또한 ${{\Delta}}H$의 관계보다 더 높게 나타나며, 이것은 연자기력선 전류가 ${\Delta}7$에 영향을 미친다는 것을 의미한다.

• 한국세라믹학회지
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• 제55권3호
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• pp.290-298
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• 2018

In order to investigate the effect of thickness on the dielectric and piezoelectric properties of (001) PMN-29PT single crystals, three different types of PMN-29PT samples were prepared using the solid-state single crystal growth (SSCG) method: high density crystal [99%], low density crystal [95%], and high density crystal doped with Mn [98.5%]. When their thickness decreased from 0.5 mm to 0.05 mm, their dielectric constant ($K_3{^T}$), piezoelectric constants ($d_{33}$ and $g_{33}$), and electromechanical coupling factor ($k_t$) decreased continuously. However, their dielectric loss (tan ${\delta}$) increased. The addition of Mn to PMN-PT induced an internal bias electric field ($E_I$), increased the coercive electric field ($E_C$), and prevented local depoling. Therefore, Mn-doped PMN-PT crystals show high stability as well as high performance, even in the form of very thin plates (< 0.2 mm), and thus are suitable for application to high frequency composites, medical ultrasound probes, non-destructive testing devices (NDT), and flexible devices.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.777-783
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• 2006

The coarse grained materials are used in various construction field such as express way back fill, Dam etc. Especially, for dam construction, a huge mount of rock fill materials are needed, so around domestic stony mountains are generally developed to produce materials. Not an accurate theory, but design criteria is based on empirical factors that were constructed in advance for design of dam especially Concrete Face Rockfill Dam(CFRD). Considering the post facts, the modified design criteria are essential in the future with more theoretical and experimental ways. In this study, large scale direct shear tests are performed with various relative density conditions on coarse grained material of Yecheon area to compare test results and general CFRD design factors.

• Journal of Magnetics
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• 제20권4호
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• pp.450-459
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• 2015

In this paper, the safety distances and maximum permissible power (MPP) of resonant wireless power transfer systems are defined and derived with regard to human exposure to electromagnetic field (EMF). The definition is based on the calculated induced current density and electric field in the standard human model located between the transmitting and receiving coil. In order to avoid the adverse health effects such as stimulation of nerve tissues, the induced current and electric field must not exceed the basic restriction values specified in EMF safety guidelines. The different combinations of diameters of the coils and the distance between the two coils are investigated and their effects are analyzed. Two versions of EMF safety guidelines (ICNIRP 1998 and ICNIRP 2010) are used as bases for safety distance calculation and the difference between the two guidelines are discussed.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2002년도 학술대회 논문집
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• pp.221-224
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• 2002

Superconducting electrical devices are under development in a national project in Korea. And KEPCO and LGIS are in charge of development of a resistive type fault current limiters(FCLs) with YBCO thin films. In order to realize FCLs, the rated power of FCLs must be increased. For this purpose, it is of great interest to increase of allowed voltage of unit component without electrical and thermal damages. So, meander lines were widely used for the conducting path to increase maximum electric field. In this research, numerical simulations on the electromagnetic behaviors of the device were carried out, especially focusing on the effect of meander line structures on the YBCO thin films. To evaluate the structures of meander lines, three types of meander lines were considered for numerical analysis using finite element method (FEM). In this simulation, both normal state and fault conditions were considered for calculation of electric field, current density, magnetic field density. And the simulation resulted are compared to find the optimum design of meander lines for resistive FCLs.

• 한국세라믹학회지
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• 제32권3호
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• pp.371-377
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• 1995

Silicon oxide films were grown on single-crystal silicon substrates at low temperatures (25~205$^{\circ}C$) in a low pressure electron cyclotron resonance (ECR) oxygen plasma. The growth rate of the silicon oxide film increased as the temperature increased or the pressure decreased. Also, the thickness of the silicon oxide film increased at negative bias voltage, but not changed at positive bias voltage. The growth law of the silicon oxide film was approximated to the parabolic form. Capacitance-voltage (C-V) and current density-electric field (J-E) characteristics were studied using Al/SiO2/p-Si MOS structures. For a 10.2 nm thick silicon oxide film, the leakage current density at the electric field of 1 MVcm-1 was less than 1.0$\times$10-8Acm-2 and the breakdown field was higher than 10 MVcm-1. The flat band voltage of Al/SiO2/p-Si MOS capacitor was varied in the range of -2~-3 V and the effective dielectric constant was 3.85. These results indicate that high quality oxide films with properties that are similar to those of thermal oxide film can be fastly grown at low temperature using the ECR oxygen plasma.

• Transactions on Electrical and Electronic Materials
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• 제3권3호
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• pp.34-38
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• 2002

In this paper, efficiency estimation of toxicity fee fire resistance cable experiments was measured smoke density of toxicity free fire resistance polyolefin insulation material and electric field dependence of tree shape in low density polyethylene (LDPE). One of the most serious causes of failure in high-voltage cables, can be an electrical discharge across an internal gab or void in the insulating material. Treeing due to partial discharge is one of the main causes of breakdown in the insulating materials and reduction of the insulation life. Therefore the necessity for establishing a method to diagnose the aging of insulation materials and to predict the breakdown of insulation and research of the fire resistance character has become important. First, we have studied on electric field dependence of tree shape in LDPE about treeing phenomena occurring on the high electrical field. Second, the measurement method is the attenuation quantity of irradiation by smoke accumulating with in a closed chamber due to non-flaming heat decomposition and flaming combustion. A main cause of fire-growth and generating toxic gas when, it bums, should be dealt with great care in life. safety design. The fire gases were occurred carbon monoxide and decomposition than in polyolefin due to incomplete combustion of PVC, which has high content of carbon in chemical compound.