The prediction of the tooth size in the mixed dentition for Korean

Moon, Sung-Hwan,Kim, Seong-Oh,Yu, Hyung-Seong,Choi, Byung-Jai,Choi, Hyung-Jun,Lee, Jae-Ho 大韓小兒齒科學會 2006 大韓小兒齒科學會誌 Vol.33 No.2

이번 연구의 목적은 혼합치열기 아동에서 미맹출된 견치와 소구치의 크기를 예측하는데 있어서 한국인에 맞는 방정식을 만들기 위함이다. 미맹출 치아의 크기를 예측하는 것은 혼합치열기 교정 진단과 치료계획 수립에 있어서 매우 중요하다. 미맹출된 견치와 소구치 크기를 예측하는 방법은 몇가지가 있지만 그중에서도 가장 흔하게 쓰이는 것이 모이어의 예측표와 다나카와 존스턴의 방정식이 있다. 하지만 그것들은 백인을 위해서 제작된 것이고 치아 크기는 인종에 따라서 다르다고 알려져 있다. 이번 연구에서는 치아크기를 측정하여 하악 영구 절치의 크기 합과 견치 및 소구치의 크기 합 사이의 상관관계를 구하고 회귀방정식을 이용해서 한국인에 맞는 예측표를 만들었다. 연세대학교 치과대학에 재학중인 178명의 한국 학생(남 108명, 여 70명, 평균연령 21.63)을 대상으로 실험하였다. 영구치의 근원심 폭경을 석고모형상에서 calipers를 이용해서 측정하였다. 성별간의 치아 크기는 차이가 있었다(p<0.05). Correlation coefficient는 0.57에서 0.64의 범위였고, standard errors of the estimates 는 여성에서 0.6으로써 남성보다 우수하였다. r^(2)값은 0.27에서 0.41의 범위를 나타내었다. Estimating the size of unerupted teeth is an essential aspect of orthodontic diagnosis and treatment planning in the mixed dentition. Several methods were introduced and used for the prediction. The most common methods among these would be Moyers probability chart and Tanaka and Johnston equations. These are currently used widely, but they were developed for Caucasians. Because there are clear racial differences in teeth size, the objectives of this study were to produce correlation coefficients between the combined mesiodistal widths of the permanent mandibular incisors and those of the canines and premolars for each quadrant, and prediction tables with regression equations, specifically for Korean. 178 young adults (70 women, 108 men, mean age 21.63 years) were selected from the College of Dentistry, Yonsei University, Seoul, Korea. The mesiodistal crown diameters of the permanent teeth were measured with calipers. Significant sexual dimorphism was found in tooth sizes. The correlation coefficients between the total mesiodistal width of the mandibular permanent incisors and those of the maxillary and mandibular canines and premolars were found to be between 0.52 and 0.64. The standard error of the estimatation was better (0.60) for women and the r^(2) values ranged from 0.27 to 0.41 for both sexes, Prediction tables were prepared for Korean. This study showed larger canine and premolar diameters than Tanaka and Johnston's and Moyers' studies which might be due to the racial differences. Further investigations with a larger sample size will be needed for more representative data on the Korean population.

서울의 Penicillinase Producing Neisseria gonorrhoeae 발생빈도(1998)

김재홍,김준호,반재용,이정우,황성주,정준규,정성태,강진문,조흔정,홍창의,정혜신,이한승,김이선,이봉길,이종호,선영우,한기덕,윤성필,이성훈,안종성,박석범,문승현,조항래,김형섭,류지호,황재영,박준홍,손상욱 한양대학교 의과대학 2001 한양의대 학술지 Vol.21 No.1

In recent years, gonorrhea has been pandemic and remains one of the most common STDs in the world, especially in developing countries. For the detection of a more effective therapeutic regimen and assessing the prevalence of Penicillinase Producing Neisseria gonorrhoeae(PPNG), we have been trying to study the patients who have visited the Venereal Disease Clinic of Choong-Ku Public Health Center in Seoul since 1980 by menas of the chromogenic cephalosporin method. In 1998, 93 strians of N. genorrhoeae were isolated, among which 60(64.5%) were PPNG. The prevalence of PPNG in Seoul, which had been decreased to 39% in 1996 after a peak of 74.3% in 1993, is increased to 64.5% in 1998.

주폐자충 폐렴으로 발현된 Felty 증후군 1예

김성호,남대근,문재현,김지홍,김보석,안진광,문태건,안병재,김성일 全南大醫大 2001 전남의대학술지 Vol.37 No.3

병원획득 Klebsiella pneumoniae 균혈증 분석을 통해 본 Ciprofloxacin 내성과 Extended-Spectrum β-Lactamase생성 간의 연관성

김미영,추은주,곽이경,송문희,나성수,송태준,김성혜,전재범,최상호,정진용,김남중,김양수,우준희,류지소 대한감염학회 2004 감염과 화학요법 Vol.36 No.5

목적 : K. pneumoniae는 ciprofloxacin내성 증가가 전세계적으로 문제가 되고있는 extended-spectrum beta-lactamase (ESBL)를 생성하는 대표적인 세균으로 최근 외국에서 ciprofloxacin 내성과 ESBL 생성사이에 관련이 있다는 2-3편의 보고들이 있었다. 본 연구에서는 병원획득 K. pneumoniae 패혈증이 있었던 환자들을 대상으로 ciprofloxacin 내성과 관련된 인자를 알아보고자 하였다. 재료 및 방법 : 2001년 1월 부터 2002년 12월 사이에 2200병상의 3차 의료기관인 한 대학병원에서 입원 후 72시간 이후에 나간 혈액배양에서 K. pneumoniae가 배양된 입원환자를 대상으로 의무기록과 전산기록을 분석하여 환자의 성별, 나이, 병동, 기저질환, 이전의 항생제 사용력, 패혈증 발생당시까지의 재원기간, 이전 입원력, 원인균의ESBL 생성유무 등을 파악하였고 이들 변수가 ciprofloxacin 내성과 관련이 있는지를 분석하였다. 재발성 패혈증의 경우는 첫 번째 경우만을 분석에 포함하였다. 결과 : 연구대상 환자는 총154명이었고 K. pneumoniae의 ciprofloxacin에 대한 내성률은 28.6% (44/154)였다. Ciprofloxacin 내성균주 중 ESBL 생성균주의 비율은 95.5% (42/44)였고 ciprofloxacin 감수성균주에서 ESBL 생성균주의 비율은 24.5% (27/110)였다(P<0.001). ESBL생성외에 단변량 분석에서 유의한 관련을 보인 변수로는 남자, 나이가 많은 경우, 패혈증 당시 중환자실 재원, 기저질환이 고형암, 혈액암, 담도계 질환인 경우, 패혈증 발생이전 1달 이내의 항생제 사용력, 3세대 cephalosporin, metronidazole, fluroquinolone, carbapenem 투여력이 있었다. 다변량 로지스틱 분석을 시행 하였을 때는 나이가 많은 경우(Adjusted odds ratio[A0R]; 1.04, 95%confidence interval[CI]; 1.01-1.06)와 ESBL 생성(AOR; 81.35, 95% CI; 17.76-372.53)이 유의하게 ciprofloxacin 내성과 관련이 있었다. 결론 : 패혈증을 일으킨 병원획득 K. pneumonias에서의 ciprofloxacin 내성은 ESBL 생성과 유의한 관련을 보였고 향후 이에 관련된 원인이나 기전을 분석하기위한 분자역학적·분자생물학적 연구가 필요하겠다. Background : Strains of ciprofloxacin-resistant Klebsiella pneumoniae have emerged worldwide. We investigated the epidemiology of ciprofloxacin resistance and its relationship to ESBL production in nosocomial K. pneumoniae bacteremia. Materials and Methods : Using the computerized database of clinical microbiology, we identified all patients whose blood culture had yielded K. pneumoniae between January 2001 and December 2002 at a 2200-bed university-affiliated tertiary-care hospital. During the study period, total of 392 episodes of K. pneumoniae bacteremia were documented of which 163 episodes were acquired nosocomially. 9 cases of recurrent episodes were excluded. Results : The resistance rates to ciprofloxacin was 28.6% (44/154). ESBL-production was significantly more common in ciprofloxacin-resistant isolates than in ciprofloxacin-susceptible isolates (95.9% [42/44] vs. 24.5% [27/110], P<0.001). In univariate analysis, following factors were significantly associated with resistance to ciprofloxacin: older age, male sex, ICU admission at the time of bacteremia, prior use of antibiotics within 1 month before bacteremia, solid tumor, hematological malignancy, or biliary disease as underlying disease, and ESBL-production. The prior use of 3^(rd)-generation cephalosprins, metronidazole, fluroquinolone, or carbapenem were also risk factors. Independent risk factors for ciprofloxacin resistance were older age (adjusted odds ratio [AOR]; 1.04, 95% confidence interval [CI]; 1.01-1.06) and ESBL production (AOR; 81.35, 95% CI; 17.76-372.53). Conclusion : The close relationship between ciprofloxacin resistance and ESBL production was documented in nosocomial K. pneumoniae bacteremia. Further epidemiological and molecular studies to determine factors and mechanisms involved in the relationship are needed.

시조문학의 가치와 위상, 그리고 세계화 방안 모색

김성문(Kim, Seong-Moon) 한국시조학회 2014 시조학논총 Vol.41 No.-

This paper is to try the globalization of Sijo, which is one of the representative Korean traditional literatures. For this goal, the values of Sijo as the ethnic literature have been searched and the necessity and method of reestablishing the position of Sijo have been studied. In 21th century, Korea has achieved a great economic development. But Korea has not achieved the international position equivalent to its economic growth. That may be closely related to that fact that the government’s support for and interest in our literature as well as Korean people’s sympathy and interest in it are not formed well enough. To overcome this situation, it is essential for us to check and reevaluate the position of the Sijo literature. In addition, it is required now to establish the detailed method for globalization of the Sijo in the long term perspective. Nowadays, as Sijo is wrongly deemed by Koreans that it is a form of difficult and old literatures, most of Korean people are not interested in Sijo. So, in this paper, the value of Sijo will be evaluated from new perspective by focusing on the fact that Sijo is one of Korean’s traditional literatures and has been together with Korean people for a long time. Sijo has described the idea and life of Korean people from Goryeo Period through Joseon Period to the present. During the Japanese imperialistic period, a sad period for Korean people, Sijo has been a means of expressing the sorrow and life of Korean people. At the same time, Sijo have played its role as one of independent movements in the name of Sijo recovery movement. In addition, in the moment of the independence from Japan, our ancestors expressed their joy through Sijo. So, it is evident that Sijo has a great value as the ethnic literature. Accordingly, we have to reestablish Sijo. As the ways to reestablish the Sijo, I suggest the “Expansion of education on Sijo”, “Competition of writing Sijo”, “Development and dissipation of Sijo card play”, “Continuation and expansion of the study on Sijo” and “Government’s support”. On the other hand, based on the love of all Korean people toward Sijo, it is necessary to let the Sijo known to people around the world. As a way of it, I have tried to register Sijo as “an intangible asset of UNECO World Heritage”. I found out that the prerequisite for registering with UNECSO is the registration of Sijo as the key intangible asset with Cultural Heritage Administration of Korea. So, I have suggested to the Government and scholars to make effort for it. Other than that, I suggested that we have to communicate with the overseas scholars and people who are interested in Sijo and focus more on the English Sijo and the translation of Sijo into English as well as the Government’s political and financial support such as Japanese Government’s support for Haiku. As these efforts specified above may not be achieved by the efforts of any individual or researcher only, they need the consistent efforts by both Government and scholars. These efforts would be consistent with those made to enhance the position of Korean in the world stage.

7개 대학 병원에서 조사한 지역사회 폐렴의 원인균

정문현,김성민,강문원,최희정,정희진,이경원,한성우,송재훈,신형식,김의종,최강원,김민자,박승철,배현주,정윤섭,김준명,백경란,신완식,이규만,김양리 대한감염학회 1997 감염 Vol.29 No.5

목 적 : 폐렴은 많이 발생하면서 사망률이 크게 줄지 않는 질환이며, 이를 적절히 치료하기 위해서는 원인균의 상대적 빈도, 기저 질환에 따른 변화, 항균제 내성률, 사망에 관련된 인자들을 알아야 한다. 원인균의 빈도는 지역마다 차이가 있고 국내에서는 항균제 내성률이 높아 지역사회에서 발생한 폐렴을 치료하기 위한 경험적 항균제 선택에 도움이 되기 위해 서울 소재 6개 대학 병원과 천안의 1개 대학 병원이 참여하여 위의 사항들에 대해 조사를 하였다. 방 법 : 1995년에 내과에 입원했던 16세 이상 환자를 대상으로 했다. 퇴원 진단명이 폐렴 또는 폐결핵인 병록지을 찾았고, 이중에서 병원 감염을 제외하였다. 특이도를 높이기 위해, 이들 중에서 호흡기 증상이 있고 발열이나 저체온이 있으면서 흉부 X-선에서 이상 음영이 있는 환자만을 대상으로 했다. 폐결핵은 위의 기준에 입원 초기에 항균제 치료를 하고 입원 7일 이후에야 항결핵제가 투여된 경우만을 폐렴의 원인균으로 하였다. 혈액 배양에서 양성, 객담에서 항상균이나 M. tuberculosis가 증명된 경우, 혈청학적으로 항체가가 4배 이상 증가된 경우, 조직에서 원인균이 진단된 경우는 확정(definitive) 원인균으로 하였고, 객담에서 배양된 균이 그람 도말과 일치할때, 항결액제에 대한 반응으로 진단한 폐결핵, 단일 항체가 양성이고 이에 대해 항균제를 사용했을 때는 가능(probable) 원인균으로 정의하였다. 다세균 감염균은 각각 다 른 원인균으로 처리하였다. 임상 조사와 함께 임상병리과에서 S. pneumoniae, H. influenzae, M. catarrhalis, mycoplasma, 항상균에 대해 검사 의뢰 건수, 배양 양성수, 항균제 감수성 결과를 조사하였다. 결 과 : 폐렴의 증례 정의에 부합하지 않은 135명과 폐결핵의 정의에 해당하지 않는 230명을 제외하고 남은 246명의 평균 나이는 58.2세이고 남성이 142명(58.2%) 이었고, 71%의 환자에서 기저 질환이 있었다. 진단 방법의 시행 횟수는 혈액 배양 77.6%, 혈청 검사 18.3%, 기관지경 검사는 4.1%였고, 세균의 항원 검사를 한 예는 없었다. 원인균이 밝혀진 예는 77명(31.3%)이었다. 다세균 감염이 4명에서 있었고, 원인균의 상대적 빈도는 결핵 20명(확정 17, 가능 3: 6개 병원 자료), 폐렴구균 18(확정8 가능 10)명과 폐렴구균이 아닌 Streptococcus 3명 (모두 확정), H. influenzae 11명(모두 가능), 그람음성간균 11명(확정 7, 가능 4) (K. pneumoniae 8건), Mycoplasma 5명(확정 1, 가능 4), S. aureus 4명(확정 2, 가능 2), mucormycosis 1명(확정)이었다. 평균 입원 기간은 19일이고, 중환자실 입원률과 인공 호흡기 사용율은 각각 18%와 9.3%였다. 사망률은 13.8%였고 사망까지 평균 기간은 14.6일 이었다. 다변량 분석에서 사망을 예측할 수 있는 인자는 저체온과 빈호흡이었다. 임상병리과에서 배양되었던 모든 폐렴구균의 Penicillin 내성률은 서울 3개 병원에서 82-88%, 천안에서 72%였다. 폐렴 환자의 혈액에서 배양된 7주는 모두 Penicillin에 감수성이 있었다. K. pneumoniae 8주 모두 cefotaxime과 gentamicin에 감수성을 보였다. 결 론 : 후향적 조사이고 병원마다 원인균 진단에 차이가 있지만, 원인이 밝혀진 경우에는 결핵과 폐렴균이 흔하였고, 무균 부위에서 배양된 폐렴구균의 항균제 내성률은 낮았다. 원인이 밝혀지지 않은 경우가 많고, 혈청검사로 진단되는 원인균이 드물며, 분리균주가 적어 항균제 내성 정도를 추정하기 어려워, 이를 밝히기 위한 전향적 조사가 필요하다. Background : Community-acquired pneumonia (CAP) is one of the leading causes of mortality and morbidity, but its management is still challenging. The limitation of diagnostic methods to identify etiologic agents rapidly make it necessary to use empiric antibiotics in almost all patients, and furthermore the discovery of new respiratory pathogens and the emergence of antibiotic-resistant organisms pose difficulties to the selection of an empiric regimen. To clarify the factors necessary for the optimal choice of empirical antibiotics, such as the frequency of etiologic agents, the attributable rates to death and antimicrobial resistance rates in the community, six university hospitals in Seoul and one university hospital in Cheonan were participating in this study. Methods : medical records of adults (>15 years of age) hospitalized for CAP or pulmonary tuberculosis between April 1995 and March 1996, were reviewed. Patients who satisfied all of the following criteria were included in the study: (1) fever or hypothermia; (2) respiratory symptoms; and (3) pulmonary infiltrates on chest roentgenogram. To exclude cases of pulmonary tuberculosis whose roentgenographic features were so typical that it could be easily differentiated from conventional pneumonia, two additional criteria were required for inclusion: antibiotic treatment during the first week of hospital admission and initiation of anti-tuberculosis medications thereafter. Organisms isolated from sterile body sites, acid-fast bacilli or Mycobacterium tuberculosis isolated from sputum, pathogens diagnosed by a 4-fold rising titer of antibodies to “atypical”pathogens, or pathogens revealed by histopathology were defined as definitive cause of pneumonia; isolates from sputum withcompatible Gram stain, pathogens diagnosed by a single diagnostic titer plus use of a specific antimicrobial agent, or tuberculosis diagnosed by clinucal response to anti- tuberculosis medications were considered probable cause of pneumonia. The records of the clinical microbiology were reviewed for isolates of S. pneumoniae, H. influenzae, M. catarrhalis, Mycobacterium or acid-fast bacilli, and Mycoplasma. Then the frequency of these agents, antimicrobial resistance rates of resiratory pathogens from all body sites, and their clinical significance were evaluated. Results: After excluding 365 patients (230 with pulmonary tuberculosis and 135 with CAP) who were screened for inclusion but did not meet the inclusion criteria,246 persons were enrolled in this study. Their mean age was 58.2 years old with slight male predominance (58.2%), and 171(71%) patients had underlying illnesses. Blood cultures were performed on 191 (77.6%) patients and serologic tests on 44(18.3%) patients. The etiologic agents were identified in 31.3%, and the list of individual agents, in decreasing order, was pulmonary tuberculosis (17 definite and 3 probable: data of six hospitals), S. pneumoniae (8 definite and 10 probable), non-pneumococci (3 definite), aerobic gram-negative bacilli (7 definite and 4 probable), Haemophilus spp. (11 probable), mycoplasma (1 definite and 4 probable), polymicrobial infections (2 definite and 2 probable: E. coli and S. agalactiae, M. tuberculosis and S. aureus, S. pneumoniae and H. influenzae and A. baumannii and K. pneumonias), S. aureus (2 definite and 2 probable) , and mucormycosis (1 definite). Among gram-negative bacilli, K. pneumoniae was the most common agent (8isolates). therates of admission to the intensive care unitand of using assisted ventilation were 18% and 9.3%, respectively. The mortality was 13.8% and logistic regression analysis showed that hypothermia and tachypnea were associated with death. Hospital stay averaged 19 days. Susceptible rates of S. pneumoniae isolated from all body sites to penicillin ranged from 8% to 28% but seven isolated from blood of patients with pneumonia were susceptible to penicillin. Also all 8 isolated of k> pneumoniae from patients with pneumonia were susceptible to cefotaxime and gentamicin. Conclusion: In Korea, in addition to S. pneumoniae, M. tuberculosis is an important agent causing community-acquired pneumonia. The low incidence of etiologic diagnosis is probably related to infrequent requesting of test "atypical" pathogens and does not represent the true incidence of infections by "atypical" pathogens, which well be answered by a prospective study. The antimicrobial resistance rates of major respiratory pathogens from sterile body sites are low, however, because of a small number of the isolates this result needs confirmation by a nationwide surveillance of antimicrobial resistance.

결장직장암 환자의 임상적 고찰 : 조선대학교 부속병원의 10년 간의 결과

나은종,문성표,장정환,김권천,민영돈,김성환,조현진,김정용,김경종 朝鮮大學校 附設 醫學硏究所 2005 The Medical Journal of Chosun University Vol.30 No.2

Background and Objectives: The colorectal cancer rates 4th in the total cancer prevalence in Korea. The clinical patient demographics were considered with the incidence rate of the colon and rectal cancer. The clinicopathological factors were analyzed for the 5 year survival rate. Materials Methods: Of the 282 patients who were operated from Jan. 1, 1992 to Dec. 31, 2001 and diagnosed by pathological biopsy as colo-rectal cancer, 234 patients were followed up. The age, sex, location of the cancer, TNM stage, operation method, histopathological classification, metastatic region, complications after operation and the survival rate were investigated. Results: Of the 234 patients, male and female consisted of 120 cases (51.3%) and 114 cases (46.7%), with an average age of 61.6 years. The average follow up period was 52.3 months and the peri operative mortality was 5.6%. The site of the cancer was most frequent at the rectum with 127 cases (54.3%). The patients were classified according to the TNM stages with 38 cases of stage 1 (16.2%), 98 cases of II (41.9%), 72 cases of III (30.8%) and 26 cases of IV (11.1%). The 5 year survival rate in the age group older than 50 was 63.3 % and 73.5% in the group younger than 50. In regard to the operation type, the 5 year survival rate was 65.4% for elective operation and 65.8% for emergency operation. The 5 year survival rate for well differentiated, moderately differentiated, poorly differentiated cancer, and mucinous adenocarcinoma was 73.7%, 60.2%, 58.3%, and 92.6%, respectively. The 5 year survival rate of each of the TNM stage is 81.1%, 74.8%, 57.0%, and 11.5% for Classes I, II, III, and IV, respectively. Conclusion: The clinical factors were analyzed for the 5 year survival rate with no statistical significance for the age, sex, and location of the cancer. The TNM stage and histopathological differentiation were statistically significant. The colon cancer showed better prognosis compared to the rectal cancer.

우리나라 지역 직업성질환 감시체계의 현황과 전망

임종한,장성실,김성아,문재동,채창호,홍윤철,김수영,김진석,김영욱,한상환,이혜숙,원종욱,송동빈,하은희,강성규 대한산업의학회 2001 대한직업환경의학회지 Vol.13 No.2

기존의 특수건강진단과 작업환경측정을 통한 직업병 관리가 진폐증, 소음성난청 등의 소수 특정질환에 국한되고 실제 직업병 발생 규모 파악이나 신종 직업병의 발견에 한계를 보인다는 사실은 산업의학전문가들 사이에서도 공감을 이루고 있다. 미국과 영국 등에서의 직업성질환 감시체계에 대한 경험은 우리 나라의 직업성질환 감시체계 구축에도 새로운 자극제가 되면서, 1998년이후 인천, 대전, 여천, 구미, 부울경 지역에서 지역 직업성질환감시체계를 산업보건관리의 중요한 시스템으로 구축하려는 노력이 확산되고 있다. 새로이 구축되어지는 이들 지역 직업성질환 감시체계는 감시하고자 하는 대상질환, 활용 가능한 인적자원 및 자료원, 지역 의료체계의 특수성 등에 따라서 목적과 방법을 달리하면서 독특한 형태로 발전을 하고 있다. 각 지역단위 감시체계들이 그 상황에 맞게 독특한 목적과 전략들을 발전 시키면서도, 향후 발전할 국가적인 차원의 직업성질환 감시체계 구축을 위하여 직업성질환 감시의 기본 전략 등을 공유하는 등의 노력이 필요하다. 환례 정의 및 기본적인 등록 서식의 공유, 직업성질환 감시 자료원의 발굴, 공동의 정보 네트워크 및 직업성질환 감시 데이터베이스 구축 등 직업성질환 감시활동을 지원하기 위한 여러 기초 인프라 구축에 힘을 모아야 할 것이다. 우리 나라에서 직업성질환 감시체계를 성공적으로 구축하기 위해서는 수집된 자료의 질 관리를 위한 직업성질환 감시의 원칙 제정과 감시 전략의 공유 등이 필요하며, 전국적인 직업성질환 감시체계의 하부구조라고 할 수 있는 지역감시체계의 기초 토대 마련과 강화작업이 절실하게 필요하다.

α상분율의 변화가 층상조직 TiAl 합금의 열적안정성에 미치는 영향

金聖雄,이호년,吳明勳,山口正治,韋當文 대한금속재료학회 2002 대한금속·재료학회지 Vol.40 No.6

The thermal stability of lamellar microstructure in TiAl-Mo PST crystals containing C or Si was investigated. In addition, the variation of α-phase volume fraction in Ti-Al-Mo-(C, Si) systems was also investigated at several temperatures. It was found that Ti-46Al-1.5Mo-O.2C and Ti-46Al-1.5Mo-1.0Si alloys were very stable during heat treatments at various heating rates and temperatures. Moreover, the, α-phase volume fraction of Ti-46A1-1.5Mo-0.2C and Ti-46A1-1.5Mo-1.OSi alloys (stable composition) was less changed than those of Ti-47Al and Ti-46Al-1.5Mo alloys (unstable composition). From these results, the instability of the latter alloys was thought to be resulted from relatively higher variation of α-phase volume fraction during heating. Therefore, it could be suggested that the variation of α-phase volume fraction is an important factor that control the thermal stability of lamellar microstructure.

WLL 기지국용 다운 컨버터 설계

김윤영,문성익,허광삼,양두영 濟州大學校 産業技術硏究所 2000 산업기술연구소논문집 Vol.11 No.1

In this paper, A down converter to convert RF signal into IF signal is designed at the WLL basestation. It consists of low noise amplifier module and down mixer module. The low noise amplifier module is composed of threestage and a feedback circuit is added in the first-stage low noise amplifier in order to obtain unconditional stability and good flatness. The configuration of the down mixer module is a single-ended type gate mixer. For the good isolation characteristic of each port, a bandpass filter and a lowpass filter are inserted in the input and output port. To design the down converter without the IF power amplifier. it is important to maximize conversion gain. So the down converter of this paper is designed for the purpose of obtaining a high conversion gain. From the results, the IF output power is -12.68dBm when the LO and the RF power level are 7dBm and -80dBm. respectively. Also when the LO power level is 7dBm. PldB is -0.19dBm. and the RF input power range shows 70dB on wide operating range.