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이형직,송두규,권혁병,정해경,윤상옥,이형복,이홍림 국립7개대학공동논문집간행위원회 2003 공업기술연구 Vol.3 No.-
소결첨가제나 바인더를 넣지않고 만든 무첨가 PZT 분말 성형체를 플라즈마 소결-로 열처리 후의 미세조직의 변화, PbO의 거동 그리고 이에 따른 유전특성을 로소결한 경우와 비교하여 다음과 같은 결과를 얻었다. 플라즈마 소결-로 열처리로 만든 PZT 시편이 로 소결 시편과 비교하여 입성장이 크게 일어나지 않은 미세조직을 나타내었으며, 또한 균일한 Pb, Zr, Ti 성분분포를 보였다. 유전특성에 있어서는 1kHz에서 20%정도의 유전율의 향상을 얻을 수 있었으며 유전소실 또한 40%정도 낮출 수 있었다. 상기의 결과는 DC 플라즈마 소결법의 특징인 소결초기의 급속가열 효과와 PbO의 증발 억제 효과에 의한 것으로 고려된다. PZT powder compacts without additives and binder were processed by plasma sintering-furnace annealing. Microstructures, PbO behaviour and dielectric properties were investigated, and compared to the specimen obtained by furnace sintering. The specimen prepared by plasma sintering-furnace annealing showed more not only fine microstructures but also homogeneous pb, Zr, Ti composition distribution, and revealed 20% higher dielectric constant as well as 40% lower dielectric loss (measured at 1kHz). Above results might be considered to be caused by rapid heating effects, high temperature sintering effects and preventing effects of PbO evaporation characterized by dc plasma sintering.
김정원,박영주,류진용,연준흠,홍기혁 대한마취과학회 1999 Korean Journal of Anesthesiology Vol.37 No.3
Background : Many methods are available for the monitoring of spinal cord injury during an operation. During anesthesia, somatosensily evoked potentials (SSEP) may undergo substantial changes in the latencies and amplitudes which may be interpreted as pathological. It is essential for the anesthesiologist to know the potential interactions between anesthetic drugs and neurophysiologic responses during operation. The depressant effect of inhalation agents on the central nervous system exceeds commonly used intravenous anesthetics. Therefore, intravenous anesthesia is preferred to inhalation agents. This study was designed to compare the effects of intravenous anesthetics (propofol and fentanyl) and inhalational anesthetics (enflurane and nitrous oxide) used in the operation room. Methods : According to the inclusion criteria of ASA I-II, 40 patients who were free of neurologic disease with electric abdominal operations were randomly selected. The baseline of the SSEPs were recorded with stimulation of the posterior tibial nerve at the ankle. After obtaining the baseline (preinduction) of the SSEPs, intravenous anesthetics (propofol 10 mg/kg/h, fentanyl 1 2 μg/kg) and inhalational anesthetics (end tidal enflurane concentration 1.0 vol %, 50% nitrous oxide in oxygen) were administered. 30 minutes after induction (steady state), additional SSEPs were recorded. Mean arterial pressure, heart rate, temperature and arterial blood carbon dioxide tension were monitored. Results : There were no significant differences in the baseline of SSEPs between the intravenous anesthetics group and the inhalational anesthetics group. There were no significant differences in latencies and amplitudes between the preanesthesia state and the postanesthetia state in the intravenous anesthetics group. But the inhalational anesthetics group revealed prolonged latencies in the postanestesia state as compared with their preanesthesia state. Conclusions : The above findings suggest that the use of intravenous anesthetics can be beneficial t intraoperative SSEP monitoring for possible damage to the central nervous system during operations. (Korean J Anesthesiol 1999; 37: 368∼374)