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졸-겔법으로 제조한 ZrO_2·SiO_2계 결정화 유리의 결정화 및 파괴인성에 관한 연구
신대용,한상목,강위수 강원대학교 산업기술연구소 2000 産業技術硏究 Vol.20 No.A
Precursor gels with the composition of xZrO_2·(100-x)SiO_2 systems (x=10,20 and 30mol%) were prepared by the sol-gel method. Kinetic parameter, such as activation energy, Avrami's exponent, n, and dimensionality crystal growth value, m, have been simultaneously calculated from the DTA data using Kissinger and Matusita equations. The crystallite size dependence on tetragonal to monoclinic transformation of ZrO_2 was investigated using XRD, in relation to the fracture toughness. The crystallization of tetragonal ZrO_2 occurred through 3-dimensional diffusion controlled growth(n=m=2) and the activation energy for crystallization was calculated using Kissinger and Matusita equations, as about 310∼325±10kJ/mol. The growth of t-ZrO_2, in proportion to the cube of radius, increased with increasing heating temperature and heat-treatment time. It was suggested that the diffusion of Zr4+ions by Ostwald ripening was rate-limiting process for the growth of t-ZrO_2 crystallite size. The fracture toughness of xZrO_2·(100-x)SiO_2 systems glass ceramics increased with increasing crystallite size of t-ZrO_2. The fracture toughness of 30ZrO_2·70SiO_2 system glass ceramics heated at 1,100℃ for 5h was 4.84 MPam^1/2 at a critical crystaliite size of 40 nm.
강성호,김진일,김재광,정인식,오수혁,위성헌,김병수 대한소화기내시경학회 1995 Clinical Endoscopy Vol.15 No.2
Tuberculous bronchoesophageal fistula is a rare disease. We experienced a case of the tuberculous bronchoesophageal fistula, which was found by endoscopy and surgically confirmed. A sixty seven years old female patient complained of foreign body sensation in the throat and frequent aspiration, especially after liquid meal. Esophagoscopic ex-aminatian showed the orifice of the fistula in the midesophagus at the level of 28 cm from the incisors. Esophagogram showed bronchoesophageal fistula between midesophagus and the right intermediate bronchus. A bronchoscopy visualized fistulous tract with granulation in the right intermediate bronchus. Biopsy specimens obtained from the bronchus revealed the esophageal tissue with granulation and multinucleated giant cells. Fistulectomy with wrapping procedure was performed successfully. Surgical pathologic findings confirmed a small focal granuloma and chronic inflammations, compatible with tuberculosis. There was no evidence of malignancy at the specimens. She was treated with anti-tuberculous agents and became well.
An Experimental Study on the Ultrasonic Machining Characteristics of Engineering Ceramics
Kang Ik Soo,Kim Jeong Suk,Seo Yong Wie,Kim Jeon Ha The Korean Society of Mechanical Engineers 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.2
Engineering ceramics have many unique characteristics both in mechanical and physical properties such as high temperature hardness, high thermal, chemical and electrical resistance. However, its machinability is very poor in conventional machining due to its high hardness and severe tool wear. In the current experimental study, alumina $(Al_2O_3)$ was ultrasonically machined using SiC abrasives under various machining conditions to investigate the material removal rate and surface quality of the machined samples. Under the applied amplitude of 0.02mm, 27kHz frequency, three slurry ratios of 1:1, 1:3 and 1:5 with different tool shapes and applied static pressure levels, the machining was conducted. Using the mesh number of 240 abrasive, slurry ratio of 1:1 and static pressure of $2.5kg/cm^2$, maximum material removal rate of $18.97mm^3/min$ was achieved. With mesh number of 600 SiC abrasives and static pressure of $3.0kg/cm^2$, best surface roughness of $0.76{\mu}m$ Ra was obtained.
강성호,이상헌,박성환,전희경,변병훈,김호연,이원영,조철수,위성헌,문윤기,정재열 대한내과학회 1996 대한내과학회지 Vol.50 No.1
Rheumatic manifestations in myelodysplastic syndroms(MDS) are divided into different categories' inflammatory arthritis, cutaneous vasculitis, neuropathy, and patients with both rheumatic disease and MDS. The followings are the characteristics of inflammatory arthritis in MDS: Serologic studies are repeatedly negative. Radiologic studies show no bony erosion. The arthritis responses to oral prednisolone with hematologic improvement. We report a case of 25-year-old female with seronegative inflammatory polyarthritis in MDS. She showed prompt response to oral prednisolone therapy with resolution of the arthritis and hematologic abnormalities.
2001년부터 2006년까지 지역사회 획득 급성 신우신장염 여성환자의 임상상 및 원인균의 내성 양상
위성헌,장우임,김형욱,김영식,김수영,허지안,김상일,김양리,강문원 대한감염학회 2007 감염과 화학요법 Vol.39 No.1
목적 : 급성 신우신장염은 지역사회에서 발생하는 가장 흔한 감염질환 중의 하나이며 균혈증이나 신장농양과 동반될 수 있다. 원인균은 대부분 E. coli이고 여러 항균제에 대한 내성이 효율적인 항균제의 선택에서 중요하며 최근 항균제 내성 양상의 변화는 효율적인 항균제의 선택을 위해 확인해야할 매우 중요한 요소이다. 재료 및 방법 : 2001년 1월부터 2006년 12월까지 가톨릭대학교 수원 성빈센트병원에 급성 신우신장염으로 입원한 16세 이상의 여성 중에서 요 배양에서 요로 감염균이 10^(5)CFU/mL 이상의 집락을 형성한 577명을 대상으로 임상적 특성 및 치료 결과를 조사하였고 검출된 원인균의 각 항균제에 대한 감수성 양상을 확인하고 연도별 변화를 분석하였다. 결과 : 환자들의 평균 연령은 51세였고 신우신장염 환자군 382명, 균혈 증 환자군 161명, 신장농양 환자군 34명으로 구분되었다. 균혈 증 환자군이 신우신장염 환자군에 비해 연령, 초기 체온 및 혈액 C-반응 단백 수치가 더 높았다. 항균제 투여 후 체온이 정상화되는데 걸린 시간은 균혈증 환자군과 신장농양 환자군이 각각 76.4시간과 91.2시간으로 신우신장염 환자군의 44.6시간 보다 길었다. 분리된 554개의 E. coli 균주는 ampicillin, gentamicin, ciprofloxacin, cefuroxime, amikacin에 대해 각각 38.3%, 81.3%, 86.3%, 97.3%, 98.7%의 감수성을 보였으며 2001년부터 2006년까지의 연도별 ciprofloxacin에 대한 감수성이 감소하는 추세를 보였다. 결론 : 급성 신우신장염으로 입원한 환자군에서 광범위 β-lactam 항균제나 fluoroquinolone의 사용을 최소화하면서 aminoglycoside 단독요법이나 정주용 2세대 cephalosporin을 초기 경험적 항균제로 사용하고 감수성 결과에 따라 적절한 경구용 전환 항균제를 사용할 수 있었다. 신우신장염, 균혈증 및 신장농양 환자군의 임상적 차이점을 분석하고 원인균의 감수성 결과를 기초로 적절한 항균제를 선택해야하며 분리된 E. coli에서 ciprofloxacin 내성율이 증가하고 있어 지역사회 전체에서 fluoroquinolone계열의 항균제를 더욱 아껴서 사용하는 노력이 요구되고 있다. Background : Acute pyelonephritis in women is one of the most common infections within the community; some patients also suffer from related bacteremia and renal abscess. The predominant pathogen in acute pyelonephritis is Escherichia coli and the changes in antimicrobial resistance over time is a very important factor in the choice of effective and economic antibiotics. Materials and Methods:We investigated clinical features and antibiotic sensitivities of 577 organisms isolated from the urine cultures of 577 patients, admitted to Catholic University St Vincent's Hospital for community-acquired acute pyelonephritis from January 2001 to December 2006. We analyzed the patterns of antimicrobial resistance of urinary isolates and the clinical courses of the patients. Results : Patients demographics revealed a mean age of 51, (age:16 to 91), with bacteremic patients representing 30.8% of patients and renal abscess patients representing 5.9% of the group. Sixteen (4.2%) of 382 in the pyelonephritis group and five (3.1%) of 161 in the bacteremia group revealed clinical manifestations of therapeutic failure such as persistent fever and pyuria. The mean time to defervescence was 44.6 h for the pyelonephritis group, 76.4 h for the bacteremia group and 91.2 h for the renal abscess group. Among the 577 isolates, 554 isolates were E. coli, 10 were K. pneumoniae, three were S. saprophyticus, three were Proteus mirabilis. two were K. oxytoca, and two were Enterobacter aerogenes. Among 554 E. coli, the rates of susceptibility to ampicillin was 38.3%; to sulfamethoxazole 62.1%; to gentamicin 81.3%; to ciprofloxacin 86.3%; to cefuroxime 97.3%; to amikacin 98.7%; to cefotaxime 99.5%. Conclusion : In hospitalized patients, initial intravenous treatment with an aminoglycoside or a second -generation cephalosporin, and then switch to oral first, second-cephalosporin, amoxicillin and sulfamethoxazole is recommended. In vitro resistance to fluoroquinolones appears to be increasing, and therefore close monitoring of antibiotic susceptibility patterns in isolates of urinary tract infections and the use of fluoroquinolone-sparing agents are required.
An Experimental Study on the Ultrasonic Machining Characteristics of Engineering Ceramics
Ik Soo Kang,Jeong Suk Kim,Yong Wie Seo,Jeon Ha Kim 대한기계학회 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.2
Engineering ceramics have many unique characteristics both in mechanical and physical properties such as high temperature hardness, high thermal, chemical and electrical resistance. However, its machinability is very poor in conventional machining due to its high hardness and severe tool wear. In the current experimental study, alumina (Al₂O₃) was ultrasonically machined using SiC abrasives under various machining conditions to investigate the material removal rate and surface quality of the machined samples. Under the applied amplitude of 0.02㎜ 27㎑ frequency, three slurry ratios of 1:1. 1:3 and 1:5 with different tool shapes and applied static pressure levels, the machining was conducted. Using the mesh number of 240 abrasive, slurry ratio of 1:1 and static pressure of 2.5㎏/㎠, maximum material removal rate of 18.97㎣ /min was achieved. With mesh number of 600 SiC abrasives and static pressure of 3.0㎏/㎠, best surface toughness of 0.76㎛ Ra was obtained.