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소아에서 복부둔상 후 발견된 특발성 소장 궤양의 천공 1예
정연준,유희철,김재천,Jeong, Yeon-Jun,Yu, Hee-Chul,Kim, Jae-Chun 대한소아외과학회 1999 소아외과 Vol.5 No.2
Idiopathic small bowel ulceration distal to the duodenum is rare. Less than 5 % of the reported cases were in children. In the majority of the patients, a single ulcer of unknown cause is found in the jejunum or ileum. The diagnosis is difficult and usually made at the time of surgical exploration for complications, such as perforation, hemorrhage or obstruction. We treated a pediatric patient with perforation of an idiopathic ileal ulceration. The child was an 11-year-old boy who sustained blunt abdominal trauma. The involved ileal segment was resected. Pathologic findings were compatible with idiopathic small bowel ulceration. The clinical and pathological aspects of idiopathic ulcerations are discussed, and the literature reviewed.
정연준,김재천,Jeong, Yeon-Jun,Kim, Jae-Chun 대한소아외과학회 2003 소아외과 Vol.9 No.1
A 4 year old female with acute lower abdominal pain was admitted with the diagnosis of periappendiceal abscess made by ultrasonography. At laparotomy, the appendix was normal, but the left ovary was twisted and necrotic. Appendectomy and left salpingo-oophorectomy were performed. The pathology of the appendix was normal, and the left tube and ovary were ischemic and had hemorrhagic necrosis. Pediatric adnexal torsion may be difficult to diagnosis clinically. Sonography is the preferred imaging study. It usually confirms a pelvic mass but may not establish the diagnosis. The correct diagnosis of adnexal torsion is often made at exploration. The most common erroneous diagnosis is acute appendicitis or periappendiceal abscess. Therapy for adnexal torsion remains controversial. While extirpation has been the standard of treatment in the past, there are current proponents of conservative therapy with adnexal sparing. Early diagnosis may lead to more frequent salvage of affected adnexa.
정연준,유희철,조백환,김재천,Jeong, Yeon-Jun,Yu, Hee-Chul,Cho, Baik-Hwan,Kim, Jae-Chun 대한소아외과학회 2000 소아외과 Vol.6 No.1
Although intraperitoneal teratomas are rare, teratomas of the greater omentuma are seldom reported. A single case of omental teratoma with torsion in a 26-month-old girl is reported. The patient presented with abdominal pain and a palpable mass. Ultrasonography and CT of the abdomen showed a large cystic mass with a non homgenious solid component composed of fat and calcification. The lesion was surgically excised. Pathology revealed a mature omental teratoma. The hospital course was uneventful.
정연준 ( Yeon Jun Jeong ),홍승철 ( Seung Cheol Hong ) 한국산업보건학회 2014 한국산업보건학회지 Vol.24 No.4
Objectives: This study was conducted to investigate the patterns of exposure of welders to strong magnetic fields for extendedperiods of time on the basis of their daily activities as recorded in a logbook. Methods: Male workers whose main job is welding, specifically seven welders occupied with gas tungsten arc welding(GTAW), two performing shielded metal arc welding(SMAW), and ten engaged in gas metal arc welding(GMAW), were measured in terms of the degree to which they were exposed to extremely low frequency(ELF) magnetic fields over 24 hours by using an electromagnetic field meter(EMF meter), as well as based on a daily activity log. Results: The welders were exposed to 1.25±4.95 μT of magnetic field per day on average. For those who spent more than half a day-735.26 minutes, or 51.1% of the day-at work, the figure averages 3.88±8.85 μT with a maximum value of 221.28 μT. The subject welders spent 338.14±154.95 minutes per day at home. During their stays at home, they were exposed to an average of 0.17±0.06 μT with a maximum value of 3.50 μT. The maximum exposure of 221.28 μT occurred when welders performed GMAW. The average exposure reached its highest at 17.71±6.96 μT when conducting SMAW. Magnetic field exposure also depends upon posture: welders who sat while welding were exposed five times more than those who stood during work, and this difference is statistically significant. As for the relationship between distance from the welding power supply and maximum magnetic field exposure, maximum magnetic field exposure decreases as the distance increases. The average magnetic field exposure, in the meantime, showed no significant difference depending on distance. Conclusions: The following were observed through this study: 1) welders, while conducting jobs, are exposed to magnetic fields not only from the welding machine, but also from the surrounding base material due to the current flowing between the welding machine and base material, meaning that they are continuously exposed to a magnetic field; and 2) welders are more exposed to magnetic fields while they sit at a job compared to when they stand up.
제자리 화학중합을 통한 그래핀 옥사이드를포함하는 전도성 고분자 나노복합체의 제조와 특성 분석
정연준(Yeon Jun Jeong),문병철(Byung Chul Moon),장민채(Min Chae Jang),김양수(Yang Soo Kim) 한국고분자학회 2014 폴리머 Vol.38 No.2
그래핀옥사이드(GO)와 전도성 고분자(PPy, PANI, PEDOT)로 이루어진 나노복합체를 제자리 화학중합을 통하여 제조하였으며, 전도성 고분자의 함량 증가에 따른 특성변화를 분석하였다. GO에 존재하는 반응성 그룹 그리고GO-poly(4-styrene sulfonic acid)(PSSA) 복합체 및 세 종류 나노복합체에서 고분자의 존재를 확인하였으며, GO와PSSA 또는 전도성 고분자 사이의 상호작용이 제안되었다. GO-PSS/PEDOT 나노복합체의 경우 PEDOT 함량이 증가함에 따라 라만 스펙트럼의 ID/IG 값이 감소하였으며 특성 피크 위치도 크게 변화하였다. GO-PSS/PEDOT 나노복합체의 경우 PEDOT이 GO-PSSA 층을 박리시켜 그들 분자층 사이로 내부 삽입되어 있는 형태를 취하며 GO 또는GO-PSSA 분자층이 열차단층으로 작용하게 되어 나노복합체는 GO 또는 GO-PSSA보다 열안정성이 향상되었다. 또한 GO-PSSA와 PEDOT 사이에 형성된 균일한 hybridization 모폴로지를 확인하였으며, GO-PSS/PEDOT 나노복합체의 경우 가장 우수한 전기전도성을 보여 주었다. Nanocomposites including graphene oxide (GO) and conducting polymers (PPy, PANI and PEDOT) were pre-pared via an in-situ chemical polymerization process, and their characteristic properties depending upon the change of conducting polymer (CP) content were analyzed. A confirmation was made on not only the functional groups formed in GO but also the presence of CP existent in the nanocomposites. The molecular interaction between GO and poly(4-sty-rene sulfonic acid) (PSSA) or CP in the nanocomposites was proposed. With the increase of PEDOT content in the GO-PSS/PEDOT nanocomposite, the estimated value of ID/IG regarding the Raman analysis of them was decreased and a major change of their Raman spectra characteristic peaks was observed. In the GO-PSS/PEDOT nanocomposite, PEDOT molecules made an exfoliation of GO-PSSA layers and thus they were intercalated among layers. Such a unique molec-ular morphology induced the highest electrical conductivity for the GO-PSS/PEDOT nanocomposite among three kinds of nanocomposites prepared in this study. It is also noted that the uniform morphology confirmed in this study helped a thermal stability improvement in the nanocomposite due to the presence of GO or GO-PSSA acting as a thermal barrier.
정연준 ( Jeong¸ Yeon-jun ),팍멩하이 ( Phoeuk¸ Menghay ),최동영 ( Choi¸ Dong-yeong ),권민호 ( Kwon¸ Minho ) 한국구조물진단유지관리공학회 2023 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.27 No.2
This research presents an experimental investigation aimed at improving the reliability of engineering designs for CFRP-reinforced concrete structures. It focuses on the effects of alkaline and acidic solutions on CFRP grids, addressing the limitations of existing design codes such as ACI 440.1 and CAN/CSA S806, which often rely on general environmental reduction factors that can result in overly conservative or unsafe designs. The study involves a comprehensive evaluation of the mechanical properties, degradation mechanisms, microstructural alterations, and overall structural integrity of CFRP grids before and after exposure to these chemical environments. To achieve this, CFRP grid specimens were subjected to immersion in chemical solutions for various durations (30, 60, 90, and 180 days) at a temperature of 60°C. Two distinct chemical environments were simulated:an alkaline solution with a pH level of approximately 13.0 and an acidic solution with a pH value of approximately 1.0. Research findings provide engineers with valuable insight into designing CFRP-reinforced concrete structures in alkaline and acidic environments. This study provides more precise and customized environmental reduction factors, as well as a trade-off between structural integrity and construction costs that is optimal for each region and climate, as it addresses the diversity of environmental conditions construction projects may encounter.