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20% 황산 및 8% 황산 + 3% 옥살산에서 AA6061 합금 표면에 형성된 아노다이징 피막의 내전압 특성
박철기,장재확,현윤석,문성모 한국표면공학회 2024 한국표면공학회지 Vol.57 No.1
Anodizing of Al6061 alloy was conducted in two different electrolytes of 20% sulfuric acid and 8% sulfuric acid + 3 % oxalic acid solutions at a constant current or decreasing current density conditions, and its dielectric breakdown voltage was measured. The surface morphology of anodic oxide films was observed by TEM and thermal treatment was carried out at 400 ℃ for 2 h to evaluate the resistance of the anodic oxide films to crack initiation. The anodic oxide film formed in 8% sulfuric acid + 3 % oxalic acid solution showed higher dielectric breakdown voltage and better resistance to crack initiation at 400 ℃ than that formed in 20% sulfuric acid solution. The dielectric breakdown voltage increased 6 ~12% by applying decreasing current density comparing with a constant current density.
A Case of Esophageal Squamous Cell Carcinoma with Pancreatic Metastasis
박철기,장재영,김윤화,황은정,나기영,김경엽,박재현,장영운 대한소화기내시경학회 2013 Clinical Endoscopy Vol.46 No.2
Solitary pancreatic metastasis of esophageal cancer is extremely rare. We report the case of a 58-year-old male admitted with esophageal cancer. Additional asymptomatic solitary hepatic and pancreatic masses were observed in the staging work-up for esophageal cancer. The hepatic mass was confirmed as a primary hepatocellular carcinoma with an ultrasound-guided needle biopsy. An esophagectomy with a distal pancreatectomy and radiofrequency ablation for hepatocellular carcinoma were performed. Histologically, the pancreatic mass was confirmed to be a metastasis from the esophageal cancer. The patient has been followed up with chemotherapy.
박철기,한경수,정호인 원광대학교 치의학연구소 1992 圓光齒醫學 Vol.2 No.2
44 Temporomandibular Disorders(TMDs) patients with non-trauma and non-iatrogenic origin presented at Wonkwang University Dental Hospital. They were grouped into ewperimental subjects and 85 persons without TMDs were classified into control group. The objectives of this study was to investigate the effects of recent life changes on the symptom severity and treatment course of TMDs For that purpose, the author used several scales and indices, namely, Social Readjustment Rating Scale(SRRS) devised by Holmes and Rahe, SRRS-Korean revision by Hong and Jeong, Helkimo' s Anamnestic index, Clinical Dysfunction index, and Visual Analogue Scale treatment index(VAS Ti) transformend from VAS by the author. Data resulted from the investigation were collected by scale or index and processed with SPSS. The obtained results were as follows 1. Life change units(LCU) and values of indices of experimental group were higher than those of control group. 2. Life change units recorded with SRRS-Korean revision were higher than those with original SRRS in all cases and significant positive correlations existed, between The two. Therefore, clinical use of original SRRS in Korea is reliable and valid. 3. In experimental group, LCU were positively correlated with Helkimo' s Clinical Dysfunction index and VAS treatment index, but in control group LCU were not correlated with any items. From this, increase of life changes in patient with TMDs in likely to aggravate TMJ dysfunction and more likely to complicate treatment course.
박철기,황승균,곽호신,유헌,정영섭,백선하,김동규,정희원,김성연,홍승관,Park, Chul-Kee,Hwang, Sung Kyun,Gwak, Ho-Shin,Yoo, Heon,Chung, Young Seob,Paek, Sun Ha,Kim, Dong Gyu,Jung, Hee-Won,Kim, Seong Yeon,Hong, Seung Kuan 대한신경외과학회 2000 Journal of Korean neurosurgical society Vol.29 No.10
Objectives : The authors analyzed the surgical series of Cushing's disease to evaluate the proper treatment policy and to verify the possible prognostic factors. Material and Methods : Of 50 patients diagnosed as Cushing's disease and operated at Department of Neurosurgery of our institute between 1988 and 1999, 48 patients with available medical records were analyzed retrospectively. Mean follow-up period was 48 months(3 to 109 months). Preoperative diagnosis was made after evaluating the patients with multiple-stage endocrinological studies and 31 selective patients were evaluated with inferior petrosal sinus sampling(IPSS). Magnetic resonance imaging(MRI) and/or high resolution computerized tomography(CT) was done in all patients. A total of 51 transsphenoidal adenomectomy(TSA) were performed including 3 revision for initial surgical failure cases. Remission was decided on the basis of both endocrinological criteria and clinical status. Radiation and/or ketoconazole therapy were applied to failed cases. For the verification of prognostic factors, the authors evaluated the statistical significance of multiple variables over remission rate by chi-square test. Result : Sensitivity of IPSS for central localization was 93.5% which was better than that of MRI(87.5%). But for lateralization, it was 72.4% for IPSS versus MRI 90.5%. Success rate of TSA was 82%(42/51) and recurrence rate was 9%(4/48). When including adjuvant treatments for surgically failed cases, overall success rate was 89.6% and all of 3 reoperated cases(TSA) due to recurrence were successful. Significant complication occurred in 7.8%(4/51) after TSA including hypopituitarism, diabetes insipidus, and visual loss. Non-existence of tumor in MRI and prolonged symptom duration(>3 years) were significant prognostic factors. Conclusion : TSA can be considered as initial treatment for Cushing's disease. In surgically failed cases, multiple treatment modality may improve the overall outcome and repeated TSA for recurrent cases seem to provide similar success.
구간 Algebra와 시점 Algebra간의 체계적 전환
박철기(Park Chul-ki) 한국정보과학회 1988 한국정보과학회 학술발표논문집 Vol.15 No.1
시간적 지식에 대한 표현방법(temporal representation)과 추론과정(temporal reasoning)은 점차적으로 중요한 연구분야가 되고 있다. 현재까지 연구된 바로는 구간대수(interval algebra)와 시점대수(point algebra)가 그 대표적인 표현방법이다. 추론 과정상에서 볼 때 계산측면은 구간대수가 시점대수보다 다루기에 힘들지만 표현능력에 있어서는 시점대수에 대해 상대적으로 우수하다. 결국 두 표현방법의 장점을 살리기 위하여 구간대수를 시점대수로 전환시키는 방법이 필요하게 되었다. 본 고에서는 이점에 촛점을 맞추어 구간대수와 시점대수간의 체계적인 전환방법을 마련하였다. 또한 전환된 시점대수를 통해 일관성 있는 추론이 가능해지도록 시점대수를 이용하는 경우의 제약중식 방법(constraint propagation algorithm)을 제시하였다.
Al6061합금의 PEO 피막 형성에 미치는 AC 전류밀도의 영향
박철기(Cheolgi Park),문성모(Sungmo Moon),정인모(Inmo Cheong),윤대수(Daesoo Yun) 한국표면공학회 2019 한국표면공학회지 Vol.52 No.3
In this work, PEO (Plasma Electrolytic Oxidation) film formation behavior of Al6061 alloy was investigated as a function of applied current density of AC at 310 Hz in the range from 120 mA/cm² to 300 mA/cm² in 0.5 M Na₂SiO₃ solution. When applied current density is lower than a critical voltage of about 132 mA/cm², voltage reaches a steady-state values less than 120 V without generation of arcs and metallic color of the alloy surface remains. On the other hand, when applied current density exceeds about 132 mA/cm², voltage increases continuously with time and arcs are generated at more than 175 V, resulting in the formation of PEO films with grey colors. Two different types of arcs, large size and small number of arcs with orange color, and small size and large number of arcs with white color, were generated at the same time when the PEO film thickness exceeds about 50 μm, irrespective of applied current density. Formation efficiency of the PEO films was found to increase with increasing applied current density and the growth rate was obtained to be about 5 μm/min at 300 mA/cm². It was also found that surface roughness of the PEO films with 70 μm thickness is not dependent on the applied current density.
TEXTROLL : 텍스트 데이타 지원 데이타베이스 관리 시스템
박철기(Park Cheol-ki),김광훈(Kim kwang-hoon),김병휘(Kim Byoung-whi),김한경(Kim Han-Kyoung) 한국정보과학회 1988 한국정보과학회 학술발표논문집 Vol.15 No.1
본 고는 Troll 관계형 데이타베이스 관리 시스템이 텍스트 데이타(Text-oriented Data) 형태를 지원할 수 있도록 그 기능을 확장시킨 “Textroll”의 설계에 관하여 기술한 것이다. Textroll의 주요 목적은 기존의 Troll 데이타베이스 관리 시스템이 한글 데이타를 기본으로 하는 Long Field(Text) 데이타를 지원할 수 있도록 그 기능을 확장시킴으로서 데이타베이스 사용자들에게 유용한 정보 관리 시스템을 제공하는데 있다. 그리고 텍스트 데이타를 위한 질의어 처리 프로세스와 화일 시스템을 통한 데이타 처리 프로세스를 설계하였으며, 텍스트 데이타를 수용하기 위한 새로운 구조의 공간과 이의 접근 방법을 제시하였다.
박철기 ( Choul Ki Park ),주광로 ( Kwang Ro Joo ),김경엽 ( Kyung Yup Kim ),오원택 ( Won Taek Oh ),맹치훈 ( Chi Hoon Maeng ),임성직 ( Sung Jig Lim ),이정일 ( Joung Il Lee ) 대한내과학회 2008 대한내과학회지 Vol.75 No.5
간내 원발성 종괴가 없는 간외담관 간세포암은 간세포암의 매우 드문 형태로 진단함에 있어 간외담관암과 감별이 매우 힘든 질환이다. 저자들은 황달을 주소로 내원한 69세 여자 환자에서 수 차례의 ERCP를 통한 조직 검사로 상기 질환을 진단하였기에 문헌고찰과 함께 보고한다. Obstructive jaundice associated with hepatocellular carcinoma (HCC) is an uncommon symptom caused by intraductal tumor growth, the migration of tumor necrosis, blood clots within the biliary tract, or compression of the biliary tract by the tumor. Most cases of icteric-type HCC involve a main tumor in the liver parenchyma. Bile duct HCC without a primary hepatic tumor is extremely rare, but because it shows similar clinical manifestations and imaging results to extrahepatic bile duct cancer, it is possible to misdiagnose this condition as a primary bile duct tumor or choldocholithiasis. Recently, we experienced a case of obstructive jaundice associated with an extrahepatic bile duct tumor in a 69-year-old woman. Upon radiologic studies and endoscopic cholangiography, the cause of obstructive jaundice was initially attributed to the bile duct tumor itself. However, subsequent analysis indicated that the condition was, in fact, due to bile duct thrombi associated with extrahepatic bile duct HCC. (Korean J Med 75:559-563, 2008)