Process development for porous Si-based ceramics by a decarburization method

박이현,Tatsuya Hinoki,Akira Kohyama 한양대학교 세라믹연구소 2009 Journal of Ceramic Processing Research Vol.10 No.3

Recently, there has been an increasing interest in the applications of porous SiC ceramics as functional materials. A number of manufacturing approaches have been applied to fabricate porous SiC including polymer pyrolysis, oxidation bonding, and reaction bonding. However, these processes are complicated and conventional porous SiC shows insufficient physical and chemical stability under a high temperature environment. Therefore, from the view point of safety and stability, it is necessary to develop an uncomplicated manufacturing method for high performance porous SiC ceramics. In this study, SiC nano-powder and carbon particles have been used as starting material and pore former, respectively. Mixed powders were hot-pressed under a pressure of 20 MPa at 1900℃ for 1 h. Carbon powder which was added to the sintered body was burned out by a decarburization process in air at 700℃. The porosity was measured by the Archimedes method with an immersion medium of water and an image analysis method. The microstructure was examined by scanning electron microscopy. Mechanical properties were investigated using three-point bend test. It was established that the critical additive amount of carbon particles for porous SiC ceramics was about 20 vol.%, through the microstructure and thermogravimetric analysis during the decarburization process. The porosity of the porous SiC ceramics could be controlled with a high degree of accuracy, from the relationship between the added amount of carbon particles and porosity. The flexural strength of the porous SiC ceramics with 50% pores, where spherical pores were introduced, was about 170MPa. These porous SiC ceramics exhibited a substantially high strength in comparison with other conventionally processed porous SiC ceramics, due to their robust microstructures consisting of spherical pores.

임신성 당뇨병이 동반된 산모의 임신경과 및 주산기예후

이현,신희철,윤보현,전종관,박교훈,장재원,이재학 대한산부인과학회 1996 Obstetrics & Gynecology Science Vol.39 No.11

Objectives: To evaluate the clinical course and outcome of pregnancies complicated with gestational diabetes. Methods: Gestational diabetes was diagnosed in 43 women by oral glucose tolerance test between August 1988 and April 1996. Retrospective review of these patients was performed, and available in 29 patients. Results: The median gestational age at birth was 39^(+5)(range 28^(+5)∼42^(+2)) weeks and the median birth weight was 3,300(range 2,470∼4,220)gm. The rate of preterm delivery($lt;37 weeks), cesarean delivery, and giant baby(birth weight ≥4,000gm) were 6.9%(2/29), 27.6%(8/29), and 3.5%(1/29), respectively. Insulin therapy was required in 55.1%(16/29) of cases. Nine cases(31.0%) developed maternal or neonatal complications: maternal complications included sepsis(n=1), preterm delivery(n=2), urinary tract infection(n=3), cesarean delivery for giant baby(birth weight≥4000gm)(n=1), and neonatal complications were hyperbilirubinemia(n=3), giant baby(n=1), hypoglycemia(n=1), intrauterine fetal death(n=1), respectively. Edward syndrome was diagnosed in the fetus of intrauterine death. Conclusion : Although about half of patients required insulin therapy during the course of pregnancy, most cases with gestational diabetes delivered at term vaginally without significant complications.

저방사화 철강재료 (JLF-1)/STS304 이종재 마찰용접의 인장강도특성

박이현(Y. H. Park),김재웅(J. W. Kim),공유식(Y. S. Kong),이진경(J. K. Lee),이상필(S. P. Lee),윤한기(H. K. Yoon) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.8

Development of reliable joints between JLF-1 steel and stainless steels are required. As known, different methods for joining various materials are assumed to be used for the construction of International Thermonuclear Experimental Reactor first wall, blanket, divertor and reactor vessel. Recently, joints technology development of JLF-1 steel (Fe-9Cr-2W-V-Ta) and Stainless steel(STS304) have been investigated for diffusion bonding, brazing, roll bonding, explosive bonding and hot isostatic pressing. On the other hand, a friction welding is one of the most popular welding method for joining between different materials such as a tube. Not only the development of optimizing of friction welding with more reliability and more applicability but also the development of in-process real-time weld quality evaluation technique by acoustic emission for dissimilar friction welding of nuclear reactor component(JLF-1 and STS304) were carried out.

태아의 선천성 횡격막탈장이 동반된 임신의 임상양상과 주산기예후

이현,신희철,윤보현,전종관,박교훈,장재원,이용찬 대한산부인과학회 1996 Obstetrics & Gynecology Science Vol.39 No.11

Objectives: To evaluate the incidence, the rate and patterns of associated anomalies and perinatal outcome of fetuses with congenital diaphragmatic hernia. Methods: This retrospective study was done by the review of medical records of 15 cases which were diagnosed as(congenital) diaphragmatic hernia during pregnancy between January 1986 and May 1996 at Seoul National University Hospital. Results: Congenital diaphragmatic hernia was found in 15 cases(0.07%), among 19,510 women who delivered at our unit during the study period. Sixty-three percent of affected fetuses was diagnosed prenatally. Overall mortality was 80%(12/15) and perinatal mortality was 78%(11/14). Among 12 live births, 10 were actively managed including six cases of operation, therefore 3 cases(30%) survived. Sixty percent(9/15) of affected fetuses had associated anomalies, and congenital heart diease constituted the majority of associated anomalies. Eighty-eight percent(7/8) of cases with associated anomaly was succumbed and all cases with congenital heart disease were succumbed. The incidence of an abnormal karyotype was 13%(1/8). And that case has multiple organ anomalies, died immediately after birth. One case with polyhydramnios was succumbed, but 30%(3/10) of cases without polyhydramnios survived. Three cases with presentation before 25 weeks gestation were all succumbed, but 30%(3/10) of cases with presentation after 25 weeks gestation were survived. One of seven cases with herniation of stomach survived, and two of six cases without herniation of stomach survived. Two of eleven cases with left-sided defect survived, and one of three cases with right-sided defect survived. Conclusion: Our data indicate that 1) 20%(3/15) of cases with congenital diaphragmatic hernia survived, 2) 605(9/15) of cases with congenital diaphragmatic hernia had associated anomalies and 88%(8/9) of them died.

LPS-SiC 세라믹스 제조특성에 미치는 소결온도의 영향

박이현(Yi-Hyun Park),정헌채(Hun-Chae Jung),김동현(Dong-Hyun Kim),윤한기(Han-Ki Yoon),A. Kohyama 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4

SiC materials have been extensively studied for high temperature components in advanced energy system and advanced gas turbine. However, the brittle characteristics of SiC such as low fracture toughness and low strain-to fracture still impose a severe limitation on practical applications of SiC materials. For these reasons, SiC<SUB>f</SUB>/SiC composites can be considered as a promising for various structural materials, because of their good fracture toughness compared with monolithic SiC ceramics. But, high temperature and pressure lead to the degradation of the reinforcing fiber during the hot pressing. Therefore, reduction of sintering temperature and pressure is key requirements for the fabrication of SiC<SUB>f</SUB>/SiC composites by hot pressing method. In the present work, Monolithic LPS-SiC was fabricated by hot pressing method in Ar atmosphere at 1760 ℃, 1780 ℃, 1800 ℃ and 1820 ℃ under 20 MPa using Al₂O₃ - Y₂O₃ system as sintering additives in order to low sintering temperature. The starting powder was high purity β-SiC nano-powder with an average particle size of 30 ㎚. Monolithic LPS-SiC was evaluated in terms of sintering density, micro-structure, flexural strength, elastic modulus and so on. Sintered density, flexural strength and elastic modulus of fabricated LPS-SiC increased with increasing the sintering temperature. In the micro-structure of this specimen, it was found that grain of sintered body was grown from 30 ㎚ to 200 ㎚.

차세대 DSRC 패킷 통신 기술 개발

이현,박인성,신창섭,오현석,임춘식,조경록 한국ITS학회 2003 한국ITS학회논문지 Vol.2 No.1

본 논문에서는 한국전자 통신 연구원에서 연구 개발한 차세대 DSRC 패킷 통신 기술을 소개하였다. 차세대 DSRC 패킷 통신 시스템의 요구 사항, 목표 시스템 규격, 차세대 DSRC 패킷 통신시스템의 구조에 대하여 설명하였다. 차세대 DSRC 시스템은 최대 24 Mbps 데이터를 5.8GHz 대역으로 전송하는 고속 패킷 통신 시스템으로 기존의 ITS 서비스뿐 아니라 모바일 오피스 서비스를 지원한다. 현재 차세대 DSRC 시스템은 각 모듈 별 기능 시험을 실시하였으며 차세대 DSRC RE 모듈의 front end부분에 대한 MMIC(microwave monolithic integrated circuit) 개발하였다. 본 차세대 DSRC 패켓 통신 시스템은 Mobile PC 제조산업, 차량 탑재 무선 인터넷 산업, 차세대 이동통신으로 차량에 탑재되는 고속 무선 인터넷 단말기로서 모바일 인터넷, 게임 등 모바일 오피스 응용 및 텔레매틱스 서비스 차세대 이동통신 산업 발전에 기여할 것으로 기대된다 In this farer, An ADSRC(Advanced Dedicated Short Range Communication) packet communication system developed by ETRI is introduced. The ADSRC system has been developed to provide high-speed, short-range wireless racket communication in roadside environment for mobile office services. The requirements of the ADSRC system for mobile office services and the system design specification to meet them with regard to mobile of nce environment are discussed. The ADSRC packet communication systems consist of the MAC(Medium Access Control) Processor block the OFDM() modem block and the RF block. The MAC processor block handles medium access control. The OFDM modem transmits data packets at up to 24Mbps adaptively and recovers the data from RF block. The ADSRC packet communication system architecture is described.

F-33 Once-Daily Dosing of Amikacin for Treatment of Mycobacterium abscessus Lung Disease

이현,손유민,고진영,이수연,전병우,박혜윤,전경만,김대훈,김수영,최지은,문일준,신성재,박효정,고원중 대한결핵 및 호흡기학회 2016 대한결핵 및 호흡기학회 추계학술대회 초록집 Vol.121 No.-

Although once-daily dosing of intravenous amikacin is recommended for the treatment of Mycobacterium abscessus lung disease, the pharmacokinetic parameters and incidence of toxicities are largely unknown. The aim of this study was to evaluate pharmacokinetic parameters and toxicities of once-daily dosing of amikacin for M. abscessus lung disease. We retrospectively evaluated medical records of 48 patients with M. abscessus lung disease who received once-daily dosing of amikacin for 4 weeks between January 2012 and June 2015. With a starting dose of 15 mg/kg/day and adjustment of amikacin dose according to peak serum level (Cmax), the Cmax target of 55-65 g/mL was achieved in 31.3% (15/48) of patients in the first week, 68.8% (33/48) in week 2, 91.7% (44/48) in week three, and 95.8% (46/48) in week four. Transient nephrotoxicity developed in 6.3% (3/48) of patients and ototoxicity in 25.0% (6/24), which was determined by audiogram as hearing loss and which was asymptomatic in five patients, with tinnitus in one patient. Multivariate analysis revealed that the highest drug concentration at 12 hr following administration was the only pharmacokinetic parameter associated with development of toxicities (adjusted odds ratio = 1.862, 95% confidence interval = 1.009-3.437, P = 0.047). Our results suggest that once-daily dosing of amikacin for 4 weeks with a target Cmax of 55-65 g/mL can be used in patients with M. abscessus lung disease with careful monitoring of toxicity.

F-84 : Free Paper Presentation ; Scoring System for CT in Allergic Bronchopulmonary Aspergillosis

이현,이용철,김소리,임정호,이양근,이흥범,박성주,최영훈,박승용 대한결핵 및 호흡기학회 2013 대한결핵 및 호흡기학회 추계학술대회 초록집 Vol.116 No.-

Background: There have been few reliable biomarkers for assessment of severity, progression, and therapeutic response of ABPA. HRCT is one of useful tools in the evaluation of ABPA. However, there is little information on the application of HRCT to assess progress of ABPA, especially using the analysis of HRCT images by scoring system. Methods: Patients diagnosed as ABPA by the Patterson criteria from Jan 2001 to Dec 2011 were enrolled in a single teaching hospital. Medical, radiological, and laboratory records of 14 patients (male:six, female:eight) were reviewed. For the analysis of HRCT images, one chest radiologist reviewed the CT images and scored the radiologic characteristics of patients` CT scans based on the scoring system developed in this center. Results: The mean age of patients was 49.6±14.3 years. The most common symptoms were cough(92.9%) and sputum(85.7%). All patients underwent HRCT for the initial diagnosis and for the follow up after treatment; follow up CT were performed at 92±4.7 days after the first day of treatment. CT scores for the radiologic features were markedly reduced from 8.5±3.2 to 3.2±3.1, meaning the improvement of radiologic abnormalities, mainly consolidation and high attenuation by mucus. The scores were correlated positively with clinical scores (p=0.042) and FEV1 (p=0.023). Conclusion: This study suggests that CT scores are correlated closely with clinical status and pulmonary function in patients with ABPA indicating that CT scoring system can be a useful toool in the evaluation of clinical status and treatment response of ABPA.Background: There have been few reliable biomarkers for assessment of severity, progression, and therapeutic response of ABPA. HRCT is one of useful tools in the evaluation of ABPA. However, there is little information on the application of HRCT to assess progress of ABPA, especially using the analysis of HRCT images by scoring system. Methods: Patients diagnosed as ABPA by the Patterson criteria from Jan 2001 to Dec 2011 were enrolled in a single teaching hospital. Medical, radiological, and laboratory records of 14 patients (male:six, female:eight) were reviewed. For the analysis of HRCT images, one chest radiologist reviewed the CT images and scored the radiologic characteristics of patients` CT scans based on the scoring system developed in this center. Results: The mean age of patients was 49.6±14.3 years. The most common symptoms were cough(92.9%) and sputum(85.7%). All patients underwent HRCT for the initial diagnosis and for the follow up after treatment; follow up CT were performed at 92±4.7 days after the first day of treatment. CT scores for the radiologic features were markedly reduced from 8.5±3.2 to 3.2±3.1, meaning the improvement of radiologic abnormalities, mainly consolidation and high attenuation by mucus. The scores were correlated positively with clinical scores (p=0.042) and FEV1 (p=0.023). Conclusion: This study suggests that CT scores are correlated closely with clinical status and pulmonary function in patients with ABPA indicating that CT scoring system can be a useful toool in the evaluation of clinical status and treatment response of ABPA.

P-94 : Poster ; Pulmonary Paragonimiasis Mimicking Pulmonary Tuberculosis

이현,이용철,김소리,이양근,이흥범,박성주,최영훈,박승용 대한결핵 및 호흡기학회 2013 대한결핵 및 호흡기학회 추계학술대회 초록집 Vol.116 No.-

Pulmonary paragonimiasis is a parasitic disease of lung caused by intake of undercooked freshwater crabs or crayfish. The common radiologic features of pulmonary paragonimiasis on CT scan include pleural effusion, subpleural or subfissural nodules or consolidation, and cysts. Although these CT findings are helpful for the diagnosis, pulmonary paragonimiasis is often difficult to distinguish from other pulmonary disorders. Therefore, some cases of pulmonary paragonimiasis are mis- or delayed diagnosed without clinician`s medical suspicion. In this report, we describe a 54-year old woman diagnosed as pulmonary paragonimiasis by the pathologic examination for the lung tissues obtained through percutaneous transthoracic needle biopsy (PTNB). CT scans showed multiple consolidative lesions combined with bronchiectasis and ground glass opacities on right upper lobe, which were comparable to the radiologic findings of pulmonary tuberculosis. This current case suggests that clinicians should include pulmonary paragonimiasis in the differential diagnoses for unresolved and delayed resolved multiple pulmonary consolidative lesions and that the pathologic confirmation is very useful in this situation. Pulmonary paragonimiasis is a parasitic disease of lung caused by intake of undercooked freshwater crabs or crayfish. The common radiologic features of pulmonary paragonimiasis on CT scan include pleural effusion, subpleural or subfissural nodules or consolidation, and cysts. Although these CT findings are helpful for the diagnosis, pulmonary paragonimiasis is often difficult to distinguish from other pulmonary disorders. Therefore, some cases of pulmonary paragonimiasis are mis- or delayed diagnosed without clinician`s medical suspicion. In this report, we describe a 54-year old woman diagnosed as pulmonary paragonimiasis by the pathologic examination for the lung tissues obtained through percutaneous transthoracic needle biopsy (PTNB). CT scans showed multiple consolidative lesions combined with bronchiectasis and ground glass opacities on right upper lobe, which were comparable to the radiologic findings of pulmonary tuberculosis. This current case suggests that clinicians should include pulmonary paragonimiasis in the differential diagnoses for unresolved and delayed resolved multiple pulmonary consolidative lesions and that the pathologic confirmation is very useful in this situation.

P-101 : Poster ; Endobronchial Hamartoma Combined with Recurrent Pneumonia

이현,이용철,김소리,이양근,이흥범,박성주,최영훈,박승용 대한결핵 및 호흡기학회 2013 대한결핵 및 호흡기학회 추계학술대회 초록집 Vol.116 No.-

High resolution computerized tomography (HRCT) is a valuable diagnostic tool for the lung parenchymal disorders such as pneumonia. In fact, HRCT has the considerable diagnostic accuracy on endobronchial lesions. However, in case of obstructive pneumonic consolidation combined with an endobronchial mass lesion, the power of resolution and the diagnostic accuracy become weaker. An enbobronchial lesion should be considered when recurrent pneumonia is developed in the same site. We experienced a case of benign endobronchial hamartoma in a-64-old female patient who had taken the antibiotic treatment for the recurrent pneumonia. Repeated HRCT scans missed the endobronchial mass lesion obstructing the lumens of right lower basal segments. At the third episode of pneumonia on the same site, she underwent bronchoscopy, which showed the causative endobronchial mass on right lower basal segments (RB9-10). Our current case indicates that there is the limitation of HRCT scan on endobronchial lesion of obstructive pneumonia and that the bronchoscopy is a classic and useful diagnostic tool for the evaluation of recurrent pneumonia despite the advancement of radiologic techniques. High resolution computerized tomography (HRCT) is a valuable diagnostic tool for the lung parenchymal disorders such as pneumonia. In fact, HRCT has the considerable diagnostic accuracy on endobronchial lesions. However, in case of obstructive pneumonic consolidation combined with an endobronchial mass lesion, the power of resolution and the diagnostic accuracy become weaker. An enbobronchial lesion should be considered when recurrent pneumonia is developed in the same site. We experienced a case of benign endobronchial hamartoma in a-64-old female patient who had taken the antibiotic treatment for the recurrent pneumonia. Repeated HRCT scans missed the endobronchial mass lesion obstructing the lumens of right lower basal segments. At the third episode of pneumonia on the same site, she underwent bronchoscopy, which showed the causative endobronchial mass on right lower basal segments (RB9-10). Our current case indicates that there is the limitation of HRCT scan on endobronchial lesion of obstructive pneumonia and that the bronchoscopy is a classic and useful diagnostic tool for the evaluation of recurrent pneumonia despite the advancement of radiologic techniques.