• Transactions on Electrical and Electronic Materials
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• 제14권4호
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• pp.221-224
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• 2013

Effects of ambient temperature on the ac electrical treeing and breakdown behaviors in an epoxy/layered silicate (1 wt%) were carried out in needle-plate electrode geometry. A layered silicate was exfoliated in an epoxy base resin,, using our ac electric field apparatus. To measure the treeing initiation and propagation, and the breakdown rate, constant alternating current (ac) of 10 kV (60 Hz) was applied to the specimen in a needle-plate electrode arrangement, at $30^{\circ}C$, $90^{\circ}C$ or $130^{\circ}C$ of insulating oil bath. At $30^{\circ}C$, the treeing initiation time and the breakdown time in the epoxy/layered silicate (1 wt%) system were 1.4 times higher than those of the neat epoxy resin. At $90^{\circ}C$ (lower than Tg), electrical treeing was initiated in 55 min, and propagated until 1,390 min at the speed of $0.35{\times}10^{-3}mm/min$, which was 4.4 times higher than that at $30^{\circ}C$; however, there was almost no further treeing propagation after 1,390 min. At $130^{\circ}C$ (higher than Tg), electrical treeing was initiated in 44 min, and propagated until 2,000 min at the speed of $0.96{\times}10^{-3}mm/min$. Typical branch type electrical treeing was obtained from the neat epoxy and epoxy/layered silicate at $30^{\circ}C$, while bush type treeing was observed out from the needle tip at $90^{\circ}C$ and $130^{\circ}C$.

• The Korean Journal of Pain
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• 제22권1호
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• pp.52-57
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• 2009

Background: Transforaminal epidural injection (TEI) may be useful to treat unilateral pain that has a dermatomal distribution. In this approach, the needle tip can be placed closer to the dorsal root ganglion and ventral aspect of the nerve root. However many studies have reported that serious complications following TEI occurred more frequently when it was conducted at the cervical level. One of the presumptive mechanisms of the complication is intravascular injection. Therefore this study was conducted to identify the incidence of complications in response to intravascular injections at cervical segments. Methods: This study included all patients, who visited our pain clinic and had radicular symptoms or herpes zoster associated pain. All procedures were conducted under fluoroscopic guidance with contrast enhancement by one of the authors. After the ideal needle position was confirmed by biplanar fluoroscopy, the blood aspiration through the needle hub was evaluated, and a 3 ml mixture of nonionic contrast (2 ml) with normal saline (1 ml) was injected at a rate of 0.3-0.5 ml/sec continuously under real time fluoroscopic visualization. We then classified the contrast spreading pattern as neural, simultaneous neural and vascular, or vascular. Results: A total 71 cervical TEIs were performed. In 26 cases (36.6%), the contrast only spread to the nerve sheath. However, 45 cases (63.4%) showed an intravascular spreading pattern, 37 (52.1%) of which showed a neural and vascular pattern and 8 (11.3%) of which showed only a vascular pattern. Conclusions: Approximately two thirds of the cases of cervical TEI were found to lead to intravascular spreading, which is much higher than the incidence reported in previous studies.

• 조명전기설비학회논문지
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• 제22권8호
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• pp.67-74
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• 2008

이 논문은 수중의 침 대 평판 전극에서 임펄스전안의 크기와 극성, 물의 저항률 등과 같은 다양한 조건에 따른 방전특성을 나타낸다. 스트리머코로나가 침전극 끝단에서 발생하며 평판전극을 향하여 진전하여 최종적으로 전극 사이가 섬락에 이르게 된다. 동일한 전압에서 물의 저항률이 작을 때 스트리머코로나의 분기로는 물의 저항률이 클때 보다 더욱 굵고 밝게 나타났다. 정극성에 비해서 부각성 스트리머코로나가 더욱 많은 분기로를 형성하며 더욱 넓게 퍼지는 것으로 나타났다. 스트리머코로나의 개시 후 방전의 진전과 더불어 수 백 [mA]에서 수 [A]에 이르는 많은 수의 전류펄스가 발생하였다. 정극성의 절연파괴까지의 지연시간은 부극성에 비하여 매우 짧았으며, 전극에 공급되는 전구방전에너지는 물의 저항률에 반비례하였다.

• 조명전기설비학회논문지
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• 제17권4호
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• pp.74-80
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• 2003

직류 고전압이 침 대 평판전극에 인가된 불평등전장에서 코로나방전이 발생하게 되면 하전입자들의 이동에 의한 이온풍이 발생한다. 코로나 방전현상은 오존발생장치, 전기집진장치, 정전 냉각과 도색 등의 응용분야에서 다각도로 연구되어 왔으며, 최근 이온풍은 열전달장치, 공기순환장치 등에 이용되기도 한다. 본 연구에서는 침 대 중공평판전극에 직류 고전압을 인가하였을 때 발생하는 이온풍의 속도와 풍량의 제어 특성을 분석할 목적으로 인가전압, 중공의 크기, 전극간 거리의 변동에 따른 풍속의 변화를 측정하였다. 결과로서 이온풍에 의한 기류가 침전극으로부터 평판전극을 향하는 방향으로 발생하였으며, 중공평판전극의 후면의 100~200 [mm]지점에서 측정한 이온풍의 풍속은 인가전압에 따라 1~3[㎧]의 범위에서 증가하였다.

• The Korean Journal of Pain
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• 제36권1호
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• pp.98-105
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• 2023

Background: Ultrasound-guided first sacral transforaminal epidural steroid injection (S1 TFESI) is a useful and easily applicable alternative to fluoroscopy or computed tomography (CT) in lumbosacral radiculopathy. When a needle approach is used, poor visualization of the needle tip reduces the accuracy of the procedure, increasing its difficulty. This study aimed to improve ultrasound-guided S1 TFESI by evaluating radiological S1 posterior foramen data obtained using three-dimensional CT (3D-CT). Methods: Axial 3D-CT images of the pelvis were retrospectively analyzed. The radiological measurements obtained from the images included 1st posterior sacral foramen depth (S1D, mm), 1st posterior sacral foramen width (S1W, mm), the angle of the 1st posterior sacral foramen (S1A, °), and 1st posterior sacral foramen distance (S1ds, mm). The relationship between the demographic factors and measured values were then analyzed. Results: A total of 632 patients (287 male and 345 female) were examined. The mean S1D values for males and females were 11.9 ± 1.9 mm and 10.6 ± 1.8 mm, respectively (P < 0.001); the mean S1A 28.2 ± 4.8° and 30.1 ± 4.9°, respectively (P < 0.001); and the mean S1ds, 24.1 ± 2.9 mm and 22.9 ± 2.6 mm, respectively (P < 0.001); however, the mean S1W values were not significantly different. Height was the only significant predictor of S1D (β = 0.318, P = 0.004). Conclusions: Ultrasound-guided S1 TFESI performance and safety may be improved with adjustment of needle insertion depth congruent with the patient's height.

• Journal of Biosystems Engineering
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• 제25권6호
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• pp.463-470
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• 2000

For maximum seeding efficiency of a nozzle type seeder, the performance of the nozzle should be considered sufficiently. This study was carried out to investigate the optimum operating conditions of a seeder attached the vacuum nozzle which was modified syringe needle acting on the plug seedling tray and the seed plate. Such operating factors as the hole diameter of the nozzle (d), the distance from the nozzle tip to the bottom plate of seed hopper(D) the absorbing air pressure of the nozzle tip(P) the bounding height of seed from the vibrated bottom plate of seed hopper and the seeding speed were selected based on the weight of a grain of seed(W). The treated materials were pepper seed as the flat type, cucumber seed as the oval type and radish seed as the spherical type. The optimum operating conditions of the experimental seeder were revealed as follows: 1. The height of the seed bounding from the bottom plate of seed hopper and the distance from nozzle tip to bounded seed were 5 mm and 0.5 mm at all seeds. The hole diameter of the nozzle and the absorbing pressure for pepper seed, cucumber seed and radish seed was 0.45 mm, 0.65 mm. 0.65mm and 39.2 kPa, 88.3 kPa, 58.8 kPa, respectively. 2. The absorbing pressure P was represented as P=η.4W/$\pi$d$^2$ where η was 100. The seeding speed using a 128 cell tray was 2.4 cm/s which was same transfer as 2.5 trays per minute. 3. The maximum seeding rate in case of the pepper seed was 97% the cucumber seed was 95% and the radish seed was 100% under the optimum operating conditions of the seeder.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2007년도 추계학술대회 논문집
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• pp.239-241
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• 2007

In this paper we describe streamer propagations characterizing underwater pre-breakdown and breakdown behaviour under impulse voltages. Streamer corona branches in lower resistivities are much thicker and brighter than those in higher resistivities. The negative streamer channels not only have more branches but also widely spread out than the positive streamer channels. The succession of streamer coronas during re-breakdown produces a stepwise propagation. The pre-breakdown currents consist of the conduction current and streamer corona current pulses.

• 대한기계학회논문집B
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• 제26권10호
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• pp.1451-1457
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• 2002

When an aqueous liquid such as water having high electric conductivity and high surface tension is discharged from a nozzle under a strong DC electric field, fine drops ranging from 30 to 450 microns can be obtained only through the spindle mode. In the present study, effects of the electric conductivity and the surface wettability of nozzle materials on formation of drops with this mode were investigated. For that, three nozzles with the same size but with different materials were prepared and tested; a stainless steel needle, and a plain and a metal (gold)-coated (except for the tip portion) silica needles. Uniform drops were obtained with the gold-coated silica nozzle over the wider range of the DC voltage input. That is, formation of the liquid cone and detachment of the liquid spindle (ligament) can be more stabilized and frequent with the needles having high electric conductivity but with low surface wettability at their tips.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 1993년도 Proceedings of International Conference for Agricultural Machinery and Process Engineering
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• pp.284-290
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• 1993

In order to improve the adaptability of rice transplanter to seeding with different length when transplanting multicropping rice in south China. The seedling separating planting mechanism is resynthesized in the paper. According to the agronomy requirements of seedling's transplanting, optimum motional path of the tip point of planting needle is obtained. by applying the established kinematic model of the separating planting mechanism, the relevant software is compiled. On the basis of the features of the problem, the constrained optimization method is utilized to solve the problem with 24 restrictions. Thus, the optimum structure parameters are obtained to satisfy the path points accurately.

• 한국분무공학회지
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• 제3권2호
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• pp.24-33
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• 1998

The characteristics of liquefied butane spray are expected to be different from conventional diesel fuel spray, because a kind of flash boiling spray is expected when the back pressure is below the saturation vapor pressure of the butane(0.23MPa at $25^{\circ}C$). An accumulator type pintle injector and its fuel delivery system has been simulated in ruder to give injection pressure, needle lift and rate of fuel injected. The governing equation were solved by finite difference metho. The injection duration was controlled by solenoid valve. Spray behaviors such as a transient spray tip penetration, spray angle and SMD were calculated based on the empirical correlations in case that the back pressure is both above the vapor pressure of the butane and below that of butane. When the back preassure is below the vapor pressure of the fuel, conventional correlation is modified to represent the effect of flash boiling.