고속 화염 용사를 통하여 형성된 다중벽 탄소 나노튜브 알루미늄 복합소재 코팅의 특성 평가

강기철(Kicheol Kang),박형권(Hyungkwon Park),이창희(Changhee Lee) 한국표면공학회 2012 한국표면공학회지 Vol.45 No.1

Multi-walled carbon nanotube (MWCNT) aluminum composite powders were deposited to form coatings using a high velocity oxygen fuel (HVOF) spraying process. High thermal energy and contact with atmospheric oxygen were supplied as the MWCNT aluminum composite particles were exposed to a gas flow field at high temperature (~3.0 × 10<SUP>3</SUP> K) during HVOF spraying. As a result, the particles underwent full or partial melting and rapid solidification due to the high thermal energy, and the exposure to oxygen induced the interfacial reaction of MWCNTs within the particle. The electrical and mechanical properties of MWCNT aluminum composite coatings were evaluated based on microstructure analysis. Electrical resistivity, elastic modulus, and micro-hardness, of the MWCNT aluminum composite coatings were higher than those of pure aluminum coating. The contribution of MWCNTs to the aluminum matrix can be attributed to their high electrical conductivity, dispersion hardening and anchoring effects. The relationship among the properties and the interaction of the MWCNTs with the aluminum matrix is discussed.

저온 분사 공정에서 니켈이 코팅된 다이아몬드 적용을 통한 금속/다이아몬드 복합재료의 코팅성 향상

나현택(Hyuntaek Na),배규열(Gyuyeol Bae),강기철(Kicheol Kang),김형준(Hyungjun Kim),이창희(Changhee Lee) 한국표면공학회 2008 한국표면공학회지 Vol.41 No.6

Generally, deposition mechanism of diamond particle is mainly embedding effect in the kinetic spray process. Accordingly, in spite of high cost, helium gas was employed as process gas to get high diamond fraction in the composite coating. In this study, the deposition behavior of bronze/diamond by kinetic spray process was compared using different process gas (helium and nitrogen). Bare (mean size of 5 ㎛, 20 ㎛) and nickel coated diamond (mean size of 26 ㎛) were deposited on Al 6061-T6 substrate with fixed process temperature and pressure. For comparison with experimental results, plastic deformation behavior of nickel layer was simulated by finite element analysis (using ABAQUS/Explicit 6.7-2). The size, broken ratio, and fraction of diamond in the composite coating were analyzed through scanning electron microscopy and image analysis method. The uniform distribution and deposition efficiency of diamond particles in the coating layer could be achieved by tailoring the physical properties of the feedstock.

HELLP 증후군의 제왕절개술시 마취

강기철,정춘근,김혜경,임재빈 대한마취과학회 1999 Korean Journal of Anesthesiology Vol.36 No.5

Hemolysis, elevated liver enzymes and low platelets (HELLP) syndrome is a variant presentation of severe preeclampsia/eclampsia. A 24-year old woman presented herself at 34 wk of pregnancy. Based on the clinical and laboratory assessment, HELLP syndrome was diagnosed. Cesarean section was performed under general anesthesia without invasive monitoring due to stable blood pressure. The course of anesthesia and surgery was uneventful and she delivered female neonate weighing 1770 gram. After the operation, the patient was transferred to the intensive care unit immediately. During the intensive care bleeding started and signs of disseminated intravascular coagulopathy showed up. Any improvement was not made after transfusion and every other supportive therapy. By the request of guardian, she was transferred to tertiary hospital, where she died. (Korean J Anesthesiol 1999; 36: 906∼910)

Enflurane, 아산화질소, Thiopental과 소량의 Fentanyl을 이용한 마취유도시 기관삽관에 의한 빈맥과 수축기고혈압을 막기위한 Esmolol의 ED95

강기철,양병이 대한마취과학회 1999 Korean Journal of Anesthesiology Vol.36 No.2

Background: Esmolol has been used combined with small dose of fentanyl to prevent tachycardia and hypertension induced by tracheal intubation, but there has been few studies about the appropriate doses of esmolol when used combined with fentanyl. Methods: According to esmolol dose, 140 patients were randomly allocated to 7 groups of 20 patients. After 2 μg/kg of fentanyl, 4 mg/kg of thiopental and 0.12 mg/kg of vecuronium were intravenously administered, mask ventilation for 3 minutes with enflurane, nitrous oxide and oxygen was followed. Then one of the doses of esmolol, 0, 0.2, 0.3, 0.45, 0.6, 0.8 or 1.0 mg/kg was administered. Ninty seconds later, tracheal intubation by direct laryngoscopy was performed. After then heart rate was monitored continuously and blood pressure was measured 5 times with 1 minute interval. The highest heart rate and systolic blood pressure were recorded. We calculated the doses of esmolol which reduce the incidence of tachycardia (increased above 100 bpm or by more than 40% ofpreinduction level) and systolic hypertension (increased above 170 mmHg or by more than 40% of preinduction level) below 5% respectively. Results: The ED95 of esmolol for prevention of tachycardia induced by tracheal intubation was 0.56 mg/kg (95% CI: 0.44∼0.81 mg/kg). But the incidence of systolic hypertension was so low even without esmolol injection that the esmolol dose was not significant factor. Conclusions: In anesthetic induction and tracheal intubation with enflurane, nitrous oxide, thiopental, vecuronium, and fentanyl 2 μg/kg, esmolol 0.56 mg/kg was ED95 of preventing tachycardia. But the incidence of systolic hypertension was acceptably low even without esmolol injection. (Korean J Anesthesiol 1999; 36: 225∼231)

척추마취에 사용되는 고비중 Tetracaine 10 mg의 최소유효마취농도에 대한 연구

주진수,강기철,정춘근,박재건 대한마취과학회 1999 Korean Journal of Anesthesiology Vol.36 No.6

Background : Minimum effective anesthetic concentration (MEAC) of local anesthetics for spinal anesthesia, defined as the concentration at which a spinal anesthetic agent produces surgical anesthesia within 20 minutes of administration in 50% of patients. This concept is similar to the concept of minimum alveolar concentration (MAC) for inhalation anesthetic. Furthermore, as MEAC may vary with the administered dose, it will be determined using 10 mg of hyperbaric tetracaine. Methods : 10 mg hyperbaric tetracaine containing dextrose 10 % was administered intrathecally to 12 patients (ASA I-II, age 20∼40 yr), who were undergoing lower limb or urological procedures within 90 minutes, at concentrations ranging from 0.07∼0.1%. The choice of tetracaine concentration was determined by Dixon's up-and-down method. Complete anesthesia was defined as: (1) pinprick anesthesia at or higher than T10 and (2) complete leg paralysis; all occurring in both lower extremities within 20 min. General anesthesia was initiated ispinal anesthesia was incomplete. Results : MEAC of 10 mg hyperbaric tetracaine was 0.083 %. Mean anesthetic duration was 75.2 minutes (range: 40∼100 min). The maximum sensory block level ranged from T3∼T8. Conclusions : The aim of this study was to establish new concept of minimum effective anesthetic concentration of hyperbaric tetracaine for spinal anesthesia. We recognized that spinal anesthesia can be accomplished with very dilute solution. As fixed dose, no correlation was found between concentration of the spinal tetracaine solution with the highest sensory level, anesthetic duration and the degree of mean arterial pressure decreased. (Korean J Anesthesiol 1999; 36: 967∼972)

쇄골하정맥도관 삽입시 적절한 깊이를 정하기 위한 흉부 방사선 사진의 이용법

김혜경,조대현,강기철,정춘근 대한마취과학회 1999 Korean Journal of Anesthesiology Vol.37 No.4

Background: Cardiac tamponade is a rare but fatal complication of subclavian catheter insertion and maintenance. This happens due to erosion of the cardiac wall or the superior vena cava distal to the CLPR (cephalic limit of pericardial reflection). This study is designed to present a method of locating the catheter tip proximal to the CLPR, and to evaluate its results. Methods: Forty adult patients with intracranial hemorrhages who needed craniotomies and central venous catheter insertions were recruited. The right subclavian vein was selected as the insertion route. On Chest AP film, clavicle, supraclavicular notch and trachobronchial tree were used as landmarks. The CLPR was assumed to be at the level of the angle between the right main bronchus and the trachea. Needle depth was measured from the skin puncture site to the point where blood was regurgitated by the Chest AP landmarks. Intravascular depth was measured from the point where blood was regurgitated to the CLPR. The sum of these two points was regarded as being the appropriate depth of the subclavian catheter insertion. In the control group (n = 40), the right subclavian catheter was inserted to the depth of height (cm)/10 minus 2 cm. Results: In study group, the catheter tips were located proximal to the CLPR in about 2/3 (27/40) of the patients, and there was no case in which catheter tip was distal to the superior vena cava-right atrium junction. In the control group, catheter tips were proximal to the CLPR in only 10% of the patients and distal to the SVC/RA junction in 42.5%. Conclusions: This method decreased the incidence of locating the tip of the catheter distal to the CLPR, and prevented any intracardial location of the catheter tip. (Korean J Anesthesiol 1999; 37: 563∼568)

전신 마취후 발생한 전율현상에 대한 Tramadol의 치료 효과

김용주,정준석,강기철 대한마취과학회 1999 Korean Journal of Anesthesiology Vol.36 No.6

Background : Tramadol is a centrally acting analgesic with weak opioid agonist properties and has effect on the spinal inhibition of pain. This study was designed to evaluate the efficacy of tramadol in the treatment of postanesthetic shivering. Methods : Sixty patients (ASA class I/II) who showed postanesthetic shivering were randomly assigned into three groups (n=20): Normal saline group; normal saline 10 ml, tramadol (TRD) 0.5 mg/kg group; tramadol 0.5 mg/kg, TRD 1.0 mg/kg group; tramadol 1.0 mg/kg. And all patients received standard postoperative management in the recovery room. Evaluation of the grade of shivering was done at 30 seconds, 2, 5 and 10 minutes from the beginning of the treatment by the same investigator who had injected the drug. The age, sex, weight, duration of anesthesia and axillary temperature were recorded. Results : By 30 seconds, 2 minutes, 5 minutes, and 10 minutes, 0, 4, 9, 9 patients of the 0.5 mg/kg tramadol group (n=20) and 7, 18, 19, 19 patients of the 1.0 mg/kg tramadol group (n=20) stopped the shivering respectively. But in 3 patients of 0.5 mg/kg tramadol group who stopped shivering by 5 minutes, shivering was recurred within 10 minutes and in 3 patients who had not stopped shivering by 5 minutes, shivering stopped by 10 minutes. In the placebo group, only 1 patient stopped shivering by 5 minutes. Conclusions : 1.0 mg/kg of tramadol was effective for the treatment of postanesthetic shivering but 0.5 mg/kg of tramadol was ineffective. (Korean J Anesthesiol 1999; 36: 1003∼1007)

후두마스크를 이용한 백내장수술 마취시 근 이완제는 꼭 필요한가?

김명희,조대현,강기철,양병이,임재빈 대한마취과학회 1999 Korean Journal of Anesthesiology Vol.36 No.6

Background : The recovery of spontaneous ventilation is delayed in elderly patients in whom muscle relaxants has been administered for general anesthesia. We evaluated the appropriateness of microscopic cataract surgery without using muscle relaxants in elderly patients. Methods : Forty two ASA physical status I and II patients for cataract surgery were randomly assigned to two groups. Glycopyrrolate 0.2 mg, fentanyl 2 mcg/kg and propofol 2 mg/kg were administered intravenously followed by vecuronium 1 mg/kg iv in group I and 10% lidocaine 1.5 mg/kg spray into oropharynx in group II. Laryngeal mask (LMA) was inserted for airway management and anesthesia was maintained by only propofol infusion in both groups. Whether the patient moved during the surgery, whether ephedrine was administered and the propofol infusion rate were recorded. Results : Six patients of group I and 1 patient of group II were moved during surgery. Only in group II, 7 patients received intravenously ephedrine administration. Mean infusion rate of propofol was 0.114 mg/kg/min in group I and 0.159 mg/kg/min in group II. Conclusion : In general anesthesia for microscopic cataract surgery, the combination of fentanyl 2 mcg/kg, propofol 2 mg/kg and infusion, 10% lidocaine spray and laryngeal mask without muscle relaxants is a good alternate method of keeping airway. (Korean J Anesthesiol 1999; 36: 944∼948)