Prediction of Retained Austenite Fraction in Quenching-and-Partitioning (Q&P) Steels Using the Gibbs Energy Balance Approach

Seong Hoon Kim,Ji Hoon Kim,Jae Hoon Lee,Dong‑Woo Suh,Jae Sang Lee 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.9

Prediction of retained austenite fraction is quite important in designing advanced high strength steels since retained austeniteis the source of transformation-induced plasticity. The present study investigates the phase constitution of a medium-carbonQ&P steel by comparing various approaches to the transformation stasis of bainitic ferrite and applying them to the partitioningprocess. Among them, the modified GEB approach gave the best agreement with the experimental observation, includingthe effects of heat-treatment condition and chemical composition on phase constitution. This indicates phase transformationduring partitioning can be effectively described by the physics of Gibbs energy balance approach.

Coating with boron nitride on SiC fiber using atomic substitution

Woo‑Seong Tak,Jin‑Uk Hwang,Young‑Keun Jeong,Woo‑Sik Kim 한국세라믹학회 2020 한국세라믹학회지 Vol.57 No.2

To increase the mechanical properties of ceramic matrix composite, it is important that formation of lubricant layer for crack deflection between matrix and fiber. Therefore, we fabricated uniform boron nitride (BN) lubricant layer using atomic substitution method. Silicon carbide (SiC) fiber surface was modified with amine groups using (3-amonipropyl)triethoxysilane to coat SiC fiber with BN as a solid lubricant. Then, surface was coated with graphene oxide (GO). Boric acid powder was supplied to the GO-coated fibers and the samples were heat-treated at 1200–1400 ℃ under N2 and NH3 atmospheres. An uniform BN layer could be coated on SiC fiber with 10 nm-1.11 μm. Crystallinity and thickness of BN layer could be controlled by reaction temperature. It was also confirmed that crystalline BN formed under process conditions of higher than 1400 ℃.

한국 천식아동의 기질특성

김승태,최성구,김상엽,정유숙,홍성도,김선우,이상일,이흥재 大韓神經精神醫學會 1997 신경정신의학 Vol.36 No.6

이 연구의 목적은 기관지 천식아동의 기질특성을 알아보기 위한 것이다. 저자중 일인의 예비연구에 의하면 천식아동집단은 습진이나 알러지성 비염 등의 만성질환을 가진 아동집단이나 정상아동과는 다른 기질특성을 갖는다. 세 살에서 일곱 살 사이의 정상아동과 기관지 천식을 앓는 아동 85명의 어머니들에게 한국판"부모기질설문(Parental Temperamental Questionnaire)"을 완성하도록 하여 기질을 측정하였다. 기질의 9가지 범주 및 요인 A점수를 비교하기 위하여 비모수적 통계법을 사용하였으며, 아동들의 기질진단을 비교하기 위하여 Chi-square통계법을 사용하였다. 그 결과 천식을 앓는 여아집단은 정상 여아집단에 비해 적응성과 반응의 역치 범주에서 통계적으로 유의하게 낮았다. 또 정상아동집단의 11%가 기질진단적으로 양육곤란형인 반면 천식아동집단은 22%를 차지했다. 두 집단은 기질진단면에서도 통계적으로 유의한 차이를 보였다. 이와 같은 결과는 천식아동에 특징적인 기질양상이 있음을 시사한다. 기질양상의 조기발견은 부모들에게 천식아동의 건강한 발달을 이해하고 행동장애 고위험집단인 만성질환을 앓는 소아들에게 적절한 양육을 제공하는데 도움을 줄 것이다. The objective of this study was to determine temperamental characteristics of children with bronchial asthma. An earlier preliminary study(Kim SP, Ferrara A, Chess 5, 1980) results show that the asthmatic children, as a group, are significantly different from two other control groups(1. children with eczema, allergic rhinitis, or both without asthma : Ⅱ. normal healthy children in their temperamental profile). The parents of 85 Korean children with bronchial asthma, ages 3 to 7 years, completed the Korean version of Parental Temperamental Questionnaire developed by Thomas and Chess. The data collected were of ordinal type, ranked from 1 to 7 and the non-parametric Mann-whitney U Test was utilized. Any child with a suspected history or diagnosis of premature birth, organic brain syndrome, mental retardation, childhood psychosis, congenital physical anomaly, hereditary disease or any other medical or surgical conditions, other than asthma, requiring continuous physicians care was excluded from the study population. The results showed that asthmatic female children were characterized by lower adaptability and lower threshold of responsiveness. And 22% of asthmatic children were of the difficult type, compared to 11% of normal children. Both groups were statistically different in terms of temperamental constellation. The findings strongly suggest the existence of a distinct temperamental profile of asthmatic children. Early detection of the profile may be of great value for parents and child health care providers in understanding the asthmatic children's correct developmental needs and in determining appropriate parenting approaches for the chronically ill children at the risk of behavioral disorder.

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.

GC/NPD를 이용한 다성분 잔류농약의 동시분석

김우성,이선화,김상엽,정동윤,김재이,이영자,이홍재,정성욱,박흥재 한국환경과학회 2003 한국환경과학회지 Vol.12 No.10

Pesticides were extracted from samples with 70% acetone and methylene chloride in order, and then cleaned up via open-column chromatography apparatus packed with fiorisil, and finally analyzed simultaneously the organophosphorus pesticides using GC/NPD, Ultra-2 and Ultra-1 fused silica capillary columns were used to separate and identify the products. Recovery of most analytes from soybean sample, taken from pesticide residues well, was greater than(80%) for all except(6) analytes. This method can simultaneously determine multiple pesticides with a high degree of accuracy and precision.

생물전극 반응조를 이용한 영양물질 제거

김성완,윤철종,최성우,김성우,우성훈,신남철,박승조 동아대학교 환경문제연구소 1999 硏究報告 Vol.22 No.2

We have investigated a performance of bio-electrode reactor for removal of nutrient like a nitrogen, phosphorus and organic substrate. Lab scale of bio-electrode reactor was operated with synthetic and tannery wastewater. Iron bar and stainless steel used for anode and cathode respectively. In experiment with synthetic wastewater, we were able to obtain the optimal current density range of 2.4-40 mA/dm² after 48 hrs operating time. And in that experiment, about 70~73% of ammonia nitrogen and 54~64% of phosphorus were removed. In experiment with tannery wastewater at 2.4-4.0 mA/dm², the removal rate of ammonia nitrogen, phosphorus and organic substract were about 62-69%, 45~59% and beyond 79% respectively.

관상동맥 스텐트 시술 후의 재협착에 관한 연구

김윤철,이정우,김보영,강정아,임대승,이민수,김정희,성보영,최성준,성인환,전은석 충남대학교 의과대학 지역사회의학연구소 2000 충남의대잡지 Vol.27 No.1

Coronary stent implacement is known as an effective treatment in the intimal dissection after percutaneous transluminal coronary angioplasty and the prevention of restenosis. However, In-stent restenosis still remains a major concern in clinical stenting. The stents were placed in 103 patients from July 1996 to March 1999 and performed follow-up coronary angiograms in 59(57.3%) patients. To identify the clinical, angiographic and procedurerelated variables 'which predict late restenosis within the stented artery, 59 patients(58.3±9.9, M:F= 41:18) were studied. The clinical characteristics of the patients were stable angina in 23(39.0%), unstable angina in 14(23.7%), acute myocardial infarction in 21(35.6%) and old myocardial infarction in 1(1.7%). Coronary stenting was performed in 1 patient(1.7%) for primary lesion, 50 patients(84.7%) for suboptimal results after PTCA, 6 patients(10.2%) for bail-out procedure, and 2 patients(3.4%) for restenotic lesions. All patients were treated with aspirin and ticlopidinc. The follow-up angiograms were obtained at 7±4 months. The overall in-stent restenosis rate was 27.1%. The coronary angiographic findings were 32 single vessel(54.2%), 19 two vessel(32.2%) and 8 three vessel disease(13.6%). The angiographic morphological characteristics were type A in 33(55.9%), type B in 14(23.7%), type C in 12(20. 3%) cases. Variables of 16 patients with restenosis were compared with those of 43 patients without restenosis. Previously known predictors for in-stent restenosis were multiple stenting, stenting for restenotic lesions, residual stenosis after stenting, stenting for total occlusion lesions, reference diameter, balloon to vessel ratio, acute gain and minimal luminal diameter after procedure, design and characteristics of stents, ostial lesion of aorta, high pressure method for stenting, lesion length, diabetes mellitus, size of artheroma, saphenous vein grafts, ulcerlating lesions and calcified lesions. In this study, Reference diameter before stenting(2.43±0.54mm vs. 2.88±0.65mm, p=0.016) and balloon-to-artery ratio(1.28±0.26 vs. 1.11±0.18, p=0.006) were predictors for in-stent restenosis. 1) The overall in-stent restenosis rate was 27.1%. 2) In the analysis of predictors for in-stent restenosis, there was no significant differences in clinical, angiographic factors between group with restenosis and without restenosis. But, Only reference diameter before stenting and balloon-toartery ratio were predictors of late in-stent restenosis. In conclusion, stenting is effective revascularisation method for selected patients with ischemic heart disease, and to minimize in-stent restenosis rate, stent implanting is achieved in a large vessel on the basis of an artery-to-stnet ration of 1:1, if possible.

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.

스웨징(swagging) 작업자에서 수지진동증후군 및 신경전도장애

김성아,김상우,정상재,이채용,김규상,정보우,박상규 大韓産業醫學會 2002 대한직업환경의학회지 Vol.14 No.2

목 적 : 스웨징작업자들에서 발생한 수지진동증후군 사례를 실제 진동수준 평가와 함께 보고하고, 진단시 신경전도검사의 소견에 대한 해석을 검토하고자 하였다. 방 법 : 2001년 4월과 5월에 구미소재 스웨징작업 종사자 8인을 대상으로 병력문진, 자각증상평가, 이학적 검사를 실시하고 수지진동증후군의심자 4인에대해 냉각부하검사와 신경전도검사를 실시하였다. 작업장조사는 진동측정장비들을 이용하여 실제 작업환경에서 측정후 국제표준화기구에 따라 평가하였으며, 수근관증후군의 동시 가능성을 알아보고자 인간 공학적 요인에 대해 조사평가 하였다. 6개월후인 12월에는 이들 4인에 대해 진동각검사와 싱경전도검사를 추적검사하였다. 결 과 : 진동수준은 주파수가중가속도값이 단일작업은 0.99∼10.79 m/sec^2, 2개의 복합작업은 3.03 ∼12.98 m/sec^2로서 ISO의 권고치를 초과하고 있었다. 1차 대상근로자 8인의 근무기간은 평균 8.7년(범위 0.8∼15)이었고, 1인은 당뇨병자이었다. 스톡홀름 분류에 의한 증상평가, 손톱압박검사, 진동각검사에서 비교적 진동노출수준과 비려하여 임상소견을 나타내었고, 2차 평가대상자 4인의 경우 신경전도검사에서 1인은 정상, 2인은 수근관증후군, 1인은 말초신경병증으로 해석되었다. 그러나, 문헌 고찰을 통해 수근관증후군으로 나온 신경전도검사결과는 오히려 진동으로 인한 다병소 신경장해로 판단하였다. 6개월후 추적 신경전도검사에서 4인 모두 진동으로 인한 다병소 신경자해를 확인하였다. 그러나, 1인에서는 수근관증후군의 동시존재 가능성을 고려하였다. 결 론 : 고정된 진동공구인 스웨징사용자들에서 수지진동증후군발생을 확인하고, 진동노출수준을 실제로 측정하여 그 양-반응관계를 동시에 평가하였다. 신경전도검사의 해석과 관련하여 수지진동증후군에서 종종 동시 존재하는 수근관증후군과의 연관성 및 감별점을 실례로써 제시함으로써 향후 진동장해를 평가하는데 도움을 주고자 하였다. Objectives : To investigate the hand-arm vibration syndrome (HAVS) among symptomatic swagging workers exposed to hand-arm vibration, using medical evaluation and measurement of workplace vibration. Furthermore, to evaluate the neurophysiological findings. Methods : Four workers showing symptoms relevant to HAVS were evaluated. Medical evaluation consisted of medical interview, questionnaire, nail-bed compression test, and sensory perception tests for vibration and pain. Some other diseases were excluded by a medical interview, hematological assessment, and urinalysis. Cold provocation test was used to assess the peripheral vascular changes, and a nerve conduction velocity (NCV) test was implemented to ascertain the peripheral neural changes. Pegboard, hole plate, and tapping board tests were performed to assess motor nerve function. The hand-arm vibration acceleration levels of the swagging machines were measured. Six months later, follow-up NCV tests were performed. Results : The actual exposure time to vibration was not longer than 15 minutes per day. The hand-arm vibration acceleration levels of the swagging machines, according to actual exposure time, were from 3.63 to 12.98 m/sec^2, by ISO 5349. The vibratory perception thresholds and the recovery time of a nail color following finger cooling were significantly increased in all four workers. The perception of pain was mildly increased. The nerve conduction studies at first diagnosis and follow-up showed multifocal neural impairment caused by vibration. However, we could not rule out the concomitant presence of the carpal tunnel syndrome in one worker. Conclusions : These results show that HAVS can be caused by hand-arm vibration in swagging workers. Interestingly, the NCV results suggested that vibration-induced neural conduction impairments could vary, and need to be interpreted cautiously.

메탈라스와 와이어메쉬로 횡구속된 철근 콘크리트 기둥의 내력 및 연성에 관한 연구

김병철,이우진,정덕우,윤승조,김성수,한천구 대한건축학회 2003 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.23 No.1(구조계)

Generally, transverse steel in reinforced concrete column serves the three-fold function of confining the compressed concrete, preventing lateral buckling of the longitudinal reinforcing steel, and acting as shear reinforcement. However, the amount of confining steel required in the form of rectangular hoops is still argument. This paper summarizes the results of an experimental program where 10 short columns with compressive strength 21MPa are designed with variable lateral confinements such as Metal Lath and Wire Mesh were tested under monotonic axial compression to failure. The columns were 300mm square and 750mm high. The purpose of this study is to investigate the ductility and strength of columns with variable lateral confinement. Test results indicate that specimen confined by metal lath and hoop, and wire mesh and hoop show 1.89 times ductility than NO.I specimen using hoop only. However, effect of lateral confinement by metal lath and wire mesh is how or same than NO.I specimen in maximum strength.