• 한국연소학회:학술대회논문집
• /
• 한국연소학회 2006년도 제32회 KOSCO SYMPOSIUM 논문집
• /
• pp.137-143
• /
• 2006

The effect of electric fields on flame speed has been investigated experimentally by observing propagating premixed flames in a tube for methane/air mixtures. The flame speeds were measured in both the normal and micro gravity conditions to substantiate the measurements. The results show that the flame speeds were enhanced by both the AC and DC electric fields, as the flame approached to the high voltage electrode located on the one end of the tube. The enhancement of flame speed was proportional to the square root of the electric field intensity, defined as the voltage applied divided by the distance of flame from the high voltage electrode, when the electric field intensity is sufficiently large. When the electric field intensity was low, there existed critical intensities, below which the electric fields did not influence the flame speed. This critical electric field intensity correlated well with the flame speed.

• 한국연소학회:학술대회논문집
• /
• 한국연소학회 2006년도 제33회 KOSCO SYMPOSIUM 논문집
• /
• pp.253-259
• /
• 2006

The effect of DC electric fields on the flame extinction was investigated experimentally in counterflow configurations for the methane/oxygen/nitrogen diffusion flame. The electric fields was applied by connecting the high voltage and ground terminals to the upper and lower burners, respectively. In case of having electric fields, several modes of flame extinction was observed according to the electric field intensity and strain rate defined by the exit velocity. To visualize and characterize the flame structure and intensity, planar LIF technique was adopted for OH radicals. Consequently, several length scales, including the flame width, thickness, and height from the burner tip, were introduced to explain the various flame behaviors and to characterize the flame extinctions. It was found that the variation of flame width and the chemical reaction are strongly related to a critical electric field intensity, thus the various modes of diffusion flame extinction could be observed due to the electric fields.

• 한국연소학회:학술대회논문집
• /
• 한국연소학회 2006년도 제33회 KOSCO SYMPOSIUM 논문집
• /
• pp.220-226
• /
• 2006

The effect of electric fields on the propagation speed of tribrachial flames has been investigated in a coflow jet by observing the transient flame propagation behavior after ignition. Without having electric fields, the propagation speed of tribrachial flame edges showed a typical behavior by having an inverse proportionality to the mixture fraction gradient at the flame edge. The behavior of flame propagation with the electric fields was investigated by applying high voltage to the central fuel nozzle and the enhancement of propagation speed has been observed by varying the applied voltage and frequency for AC electric fields. The propagation speed of tribrachial flame was also investigated by applying negative and positive DC voltages to the nozzle and similar improvements of the propagation speed were also observed. The propagation speeds of tribrachial flames in both the AC and DC electric fields were correlated well with the electric field intensity, defined by the electric voltage divided by the distance between the nozzle electrode and the edge of tribrachial flames.

• 조명전기설비학회논문지
• /
• 제12권3호
• /
• pp.51-58
• /
• 1998

이 논문은 옥내 변전소의 변압기와 가스절연개폐장치(GIS) 주변에서 상용주파수의 전장과 자장의 분포에 관한 것으로 전장과 자장의 측정은 지표상 Hill]의 높이에서 1차원과 3차원 측정기로 수행되었다. 변압기 주변에서 전 장과 자장의 분포는 2차원적 평면도로써 나타내었으며, 전장의 세기는 2.3~9[v/m]으로 비교적 작은 값이었고, 자장의 세기는 $0.3~20.3[{\mu}T]$이었다. 또한 GIS의 주변에서 전장의 세기는 2.2~2.5[V/m]이고, 자장의 세기는 주 로 GIS의 중간부위에서 국부적으로 크게 나타났으며 $1.2~39.5[{\mu}T]$의 값이었다. 변압기와 GIS의 금속 외함은 전장을 감소시키는 역할을 하고, 자장은 변압기와 GIS의 외함으로부터 거리에 따라 급속하게 감소하는 특정을 보이고 있다.

• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2000년도 춘계학술발표대회 논문집
• /
• pp.105-108
• /
• 2000

• 폴리머
• /
• 제25권2호
• /
• pp.293-301
• /
• 2001

새로운 복합재료 제조 기술인 electron-ion technology (EIT)를 이용하여 전도성 탄소섬유/고밀도 폴리에틸렌 (CF/HDPE) 복합필름을 제조하고 탄소섬유 에폭시 sizing이 제조된 필름의 체적비저항과 인장강도 그리고 계면 특성에 미치는 영향에 대하여 연구하였다. 에폭시 sizing은 tunneling 효과를 좋게 해서 복합재료 필름의 전도성을 향상시키는 반면, 극성인 에폭시 sizing은 무극성인 폴리에틸렌과의 친화성이 없어서 탄소섬유와 폴리에틸렌간의 계면결합력을 감소시키므로 에폭시 sized 탄소섬유(CF(S))는 unsized 탄소섬유(CF(U))에 비하여 필름의 체적비저항과 인장강도를 감소시켰다. 에폭시 sizing은 탄소섬유의 nucleating efficiency를 떨어뜨려서 CF(S)/HDPE 필름이 CF(U)/HDPE 필름보다 불규칙적이고 덜 발달된 transcrystalline layer를 형성함을 관찰할 수 있었다.

• 한국광학회:학술대회논문집
• /
• 한국광학회 2001년도 제12회 정기총회 및 01년도 동계학술발표회
• /
• pp.4-5
• /
• 2001

Advent of lasers offering high intensity beam has opened the glass to the nonlinear optic (NLO). The high electric field associated with such laser beams can be so large that high order components of the glass polarization can be measured. Such development is of scientific and technological interests in particular in systems involving an intensity-dependent refractive index and/or ultra-fast response (＜10$\^$-12/s). From a scientific viewpoint the NLO response intensity must be understood as a function of the glass composition. On the other hand, large family of applications are presently under investigation in various fields of optical materials or systems e.g. laser glasses for fusion energy, soliton propagation for ultra-long distances, ultra-fast-switching, optical storage etc....(omitted)

• 폴리머
• /
• 제24권2호
• /
• pp.268-275
• /
• 2000

고전기장을 이용하여 제조한 도전성 탄소섬유/폴리에틸렌 복합필름에 있어서 고분자 점착하층의 두께가 제조된 필름의 체적비저항과 인장강도에 미치는 효과에 대하여 연구하였다. 탄소섬유(CF) 함량과 CF 층밀도에 따라 제조된 필름의 체적비저항과 인장강도의 점착하층에 대한 의존성의 양상은 복잡하게 나타났다. 이는 점착하층의 증가에 따라서 필름 하층면에 중심부나 위쪽에 비하여 CF 농도가 낮은 절연성 고분자층의 두에가 증가하고 필름 상층면 근처에서는 CF의 함침에 필요한 고분자 매트릭스의 양이 적어져 매트릭스 함침이 불충분하여 기공이 포함된 구조를 형성시키는 효과와 증가된 매트릭스의 유동성을 바탕으로 CF 분산성이 향상되고 동시에 보다 치밀한 구조가 형성되는 두 가지 상반되는 효과의 상대적 기여 정도의 차이를 통하여 설명할 수 있었다. 이들 결과는 전자파 차폐용 고도전성 고분자 차폐필름의 제조에 있어서 전기적 성질과 기계적 성질의 최적화하는데 중요하다.

• Food Science and Biotechnology
• /
• 제16권6호
• /
• pp.1082-1084
• /
• 2007

Ultra-high temperature (UHT) processed full fat milk inoculated with Escherichia coli, Pseudomonas fluorescens, and Bacillus stearothermophilus was exposed to 30-60 kV/cm square wave pulsed electric field (PEF) with $1\;{\mu}sec$ pulse width, and $26-210\;{\mu}sec$ treatment time in a continuous PEF treatment system. Eight log reduction was obtained for E. coli and P. fluorescens and 3 logs reduced for B. stearothermophilus under PEF treatment conditions of $210\;{\mu}sec$ treatment time, 60 kV/cm pulse intensity at $50^{\circ}$. There was no significant change in pH and titration acidity of milk after PEF treatment. The electrical energy required to achieve 8 log reduction for E. coli and P. fluorescens was estimated to be about 0.74 kJ/L.

• The Korean Journal of Ceramics
• /
• 제7권1호
• /
• pp.30-35
• /
• 2001

The contribution of the non-$180^{\circ}C$ domains to the electric-field-induced strains (EFI-strains) of PZT ceramics was evaluated by an XRD method and by an interferometric method. The XRD intensity ratio of 200 and 002 diffraction peaks of tetragonal PZT was measured under strong electric fields. The amount of the $90^{\circ}$ domain reorientation was evaluated and the strain due to the domain reorientation was calculated. It was confirmed that the EFI-strain of PZT ceramics was equal to the sum of the strain calculated from the d$_33$ constant determined by the resonance-antiresonance method and the strain due to the $90^{\circ}$ domain reorientation. The amount of the $90^{\circ}$domain reorientation has a linear relation with the c/a ratio in the "soft" PZT ceramics. A Mech-Zehnder interferometer was constructed to measure the EFI-strains vs. electric-field curves of PZT ceramics as a function of frequency. The EFI-strain vs. electric-field curve showed a hysteresis due to the effect of the non-$180^{\circ}$ domain reorientation when the applied voltage was high and its frequency was low. The apparent piezoelectric constant increased from the d$_33$ value determined by the resonance-antiresonance method with decreasing frequency. This deviation was attributed to the non-$180^{\circ}$ domain contribution.tribution.