흙탕물 오염 시험법 개발 및 실차 시험 및 분석

김완철,임현택 한국신뢰성학회 2022 한국신뢰성학회 학술대회논문집 Vol.2022 No.11

급냉응고된 Mg-9Al-xCa 합금의 시효특성에 관한 연구

金完哲,朴祉河 홍익대학교 산업기술연구소 1999 産業技術 Vol.9 No.-

Mg-Al-Si-Ca alloys were fabricated into the ribbons by rapid solidification using a single-roll melt spinner. The time and temperature effect on age-hardening was investigated for the ribbons with varying Ca contents of 1, 3, 6 and 10 wt%. The behavior of precipitates, phase transitions, and mechanical properties were examined by measurements of micro-hardness, XRD analysis, and transmission electron microscopy. For the case of 1 hour's isochronal heat treatment, the temperature of 200℃ gave the most significant age hardening effect and the increase in Ca content caused enhanced hardening. In the aging treatment at 200℃, the hardness decreased with the increase in aging time from 1 up to 81 hour. The microstructural analysis for Ca-added sample showed uniformly distributed compounds of Al_4Ca and Al_2Ca, forming coherent precipitates with matrix. When the alloy contains more Ca than the solubility limit, the excess Ca precipitates as Mg_2Ca and an increased hardness is observed.

F-23 : 개정된 GOLD 진료지침에 따른 만성폐쇄성폐질환 환자의 임상양상

김완철,이승준,조유지,정이영,김호철,이종덕,황영실 대한결핵 및 호흡기학회 2013 대한결핵 및 호흡기학회 추계학술대회 초록집 Vol.116 No.-

목적: 만성폐쇄성폐질환(COPD)의 진료지침은 2011년 새로 개정되었으며 과거 진료지침과는 달리 기도폐쇄의 정도 이외에 환자의 증상 및 급성악화의 위험성에 따라 환자군을 분류하고 있다. 개정된 진료지침에 따른 환자군간 임상양상의 차이에 대해서는 연구된 바가 많지않아 저자들은 이를 알아보고자 하였다. 방법: 2011년 10월부터 2013년 9월까지 경상대학교병원 호흡기 내과에서 COPD를 진단받은 166명의 환자를 대상으로 연구를 하였다. COPD의 진단은 GOLD 기준에 따라 FEV1/FVC 비가 0.7 미만인 경우로 정의하였다. 의무기록 검토를 통하여 대상환자들의 기저 특성, 폐기능 및 폐기능 변화, 폐확산능, mMRC 점수, 1년간 급성악화 빈도, 동반질환, BODE index를 조사하였고 A, B, C, D군에 따라 각각의 항목들을 비교하였다. 추가적으로 이전 GOLD 분류에 따른 각 병기(stage)의 임상양상과 개정된 GOLD 분류에 따른 각 군(group)의 임상양 상을 비교하였다. 성적: 총 대상자는 166명 이었고 남자가 143명(86.1%), 여자가 23명(13.9%)이었고 평균연령은 70.9±8.0세였다. A, B, C, D군의 FEV1, mMRC, 1년간 급성악화 빈도는 각각 1.88L, 1,64L, 1.11L, 1.01L (p<0.001), 0.88, 1.54, 1.14, 2.25 (p<0.001), 0.04회, 0.38회, 0.43회, 1.16회(p<0.001)이었다 A, B, C, D군의 BODE 지수와, 폐확산능은 각각 1.4, 2.4, 3.2, 5.3(p<0.001), 85.9, 74.8, 83.0, 59.4 (p<0.001) 이었다 각군간의 동반질환 유무는 유의한 차이가 없었으며 1년간의 폐기능 변화도 유의한 차의가 없었다. 결론: 개정된 COPD 진료지침에 따른 환자군의 임상양상은 유의한 차이가 있으며 향후 대규모 환자들을 대상으로 한 전향적 연구가 필요할 것으로 생각된다.

기계적 합금화에 의한 급속냉각된 Al 분말의 조직과 기계적성질의 개선

金完哲 홍익대학교 산업기술연구소 1996 産業技術 Vol.6 No.-

Severe working of splats produced a very fine grain size and substructural strengthening. The dispersed particles were spherical and much finer then those obtained by conventional SAP. MA-AI splats extruded bars had the recrystallized grains when isothermally aged for 100 hours at 450℃. At higher temperature, hower, only the Al_2O_3 patricles pinned the grain boundaries. Accordingly grain size become smaller and grain boundary sliding was retarded, providing a superior high temperature hardness as the amount of Al_2O_3 increased.

Clinical Characteristics of the Development of Pneumothorax in Mechanically Ventilated Patients in Intensive Care Units

김완철,임수진,김경영,이승준,조유지,정이영,박미정,전경녀,이종덕,황영실,김호철 대한중환자의학회 2014 Acute and Critical Care Vol.29 No.1

Background: Pneumothorax (PTX) can occur as a complication of positive pressure ventilation in mechanically ventilated patients. Methods: We retrospectively reviewed the clinical characteristics of patients who developed PTX during mechanical ventilation (MV) in the intensive care unit (ICU). Results: Of the 326 patients admitted (208 men and 118 women; mean age, 65.3 ± 8.74 years), 15 (4.7%) developed PTX, which was MV-associated in 11 (3.3%) cases (6 men and 5 women; mean age, 68.3 ± 9.12 years) and procedure-associated in 4. Among the patients with MV-associated PTX, the underlying lung diseases were acute respiratory distress syndrome in 7 patients, interstitial lung disease in 2 patients, and chronic obstructive pulmonary disease in 2 patients. PTX diagnosis was achieved by chest radiography alone in 9 patients and chest computed tomography alone in 2 patients. Nine patients were using assist-control mode MV with the mean applied positive end-expiratory pressure, 9 ± 4.6 cmH2O and the mean tidal volume, 361 ± 63.7 ml at the diagnosis of PTX. Two patients died as a result of MV-associated PTX and their systolic pressure was below 80 mmHg and heart rates were less than 80/min. Ten patients were treated by chest tube insertion, and 1 patient was treated by percutaneous pigtail catheter insertion. Conclusions: PTX can develop in patients undergoing MV, and may cause death. Early recognition and treatment are necessary to prevent hemodynamic compromise in patients who develop PTX.

Al-Cr 합금 분말 압출재의 마멸 특성

金完哲 홍익대학교 산업기술연구소 1997 産業技術 Vol.7 No.-

The structure and mechanial properties of the extruded specimens were investigated in rapid solidified Al-(3,5)Cr splats after mechanical alloying. Finer lamellar microstructure could no longer be resolved in the bars obatained by extrusion of the spherical particles after 200 min of processing time. The structure of extruded bars are highly depended on the processing time on splats. The isothermal annealing of the extruded bars showed that all the alloys had good thermal stability up to 400℃ and did not show recrystallization phenomena. Severe working of Al-5 Cr splats produced a very fine grain size and substructural

프린지 필드에 의해 구동되는 하이브리드형 네마틱 액정 셀에서 러빙방향에 따른 전기광학 특성

김완철,안명환,이승희 한국전기전자재료학회 2004 전기전자재료학회논문지 Vol.17 No.1

We have studied the influence of rubbing directions on electro-optic characteristics of the fringe field driven hybrid aligned nematic liquid crystal (LC) cell by computer simulation. When a LC with positive dielectric anisotropy is used, the results show that the driving voltage and transmittance decreases as the rubbing direction with respect to horizontal electric field direction increases. The reason for decrease in light transmission is the increase of tilt angle on the center of common electrode. In this paper, we have studied how the rubbing angle effects on the transmittance of the cell by investigating a distribution of electric field and LC director.

집중조명 : 충남 연기군 ; 연기군의 지역 정체성과 새 천년의 비전

김완철 한국지방행정연구원 2000 지방포럼 Vol.5 No.-

압연한 Mg합금의 미세구조와 인장 특성

金完哲,金圭石 홍익대학교 산업기술연구소 2006 産業技術 Vol.16 No.-

In this study the effects of Ca addition on the rollability, microstructures and tensile properties of hot rolled Mg alloys were evaluated. In Ca containing alloys, reduction ratio and preheating temperature are the most important variables to make good sheet without any crack. The number and length of side crack increased with increasing Ca content. With increasing the reduction ratio per pass and decreasing the preheating temperature, crack initiates easily at the side. The dendritic grains were changed to fine equiaxed grains through hot rolling by dynamic recrystallization. The Al_(2)Ca Precipitates which were segregated to grain boundaries during solidification were rearranged parallel to the rolling direction. The tensile properties of hot-rolled Mg Alloys were decreased slightly by addition of Ca.

Ca 첨가한 AZ31합금의 열간압연 특성

金完哲 弘益大學校 産業技術硏究所 2004 産業技術 Vol.14 No.-

The effects of homogenization on hot rolling properties of gravity cast AZ31-xCa (x=0~2.0wt.%) alloys were evaluated by examination of surface and microstructures of sheets. The side cracking during hot rolling was decreased by homogenization by the elimination of local inhomogeneity and dissolution of brittle precipitate into matrix. The coarse grains in raw materials were changed to fine grains with the average particle size of 5~10μm by the dynamic recrystallization during repeated hot rolling . A deformation twinning was more favorably formed in the hot-rolled sheets after homogenization. It is considered that the grains grow and the precipitates are solved into the matrix during homogenization heat treatment, which results in increasing the possibility of formation of deformation twinning during hot rolling.