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가교한 PI/PVDF 블렌드로부터 유도된 탄소 나노섬유 전극의 에너지 저장 특성
이도근(Do Geun Lee),류경범(Gyeong Beom Ryoo),정경혜(Kyung-Hye Jung) 한국고분자학회 2021 폴리머 Vol.45 No.6
슈퍼커패시터는 전극과 전해질 계면의 이온 접촉으로 에너지를 저장하기 때문에 전극의 표면적과 다공성이 에너지 저장 특성을 결정하는 주요 요인이다. 전극 물질로 탄소 나노섬유(CNF)가 많이 연구되고 있는데, 주로 전구체 고분자를 전기방사하고 열 처리하여 합성한다. 본 연구에서는 전구체 고분자의 화학 구조 조절을 통하여 탄소나노섬유의 에너지 저장 특성을 개선하였다. 방향족 폴리이미드(PI)와 폴리비닐리덴 플루오라이드(PVDF) 블렌드를 전구체로 사용하였고, 열처리 전 가교 처리를 하여 표면 특성을 개선하였다. 코인 셀을 조립하여 전기화학적 특성을 평가한 결과, 가교한 PI/PVDF로 합성한 CNF전극의 비정전용량이 322 F/g(10 mV/s), 에너지 밀도가 11.6 Wh/kg(0.5 A/g)로 가교를 하지 않은 전극 대비 높은 에너지 저장 특성을 보였다. Supercapacitor stores energy through the interfacial contact of ions between electrodes and electrolytes; thus, the surface area and porosity of electrode materials are critical to determining the energy performance of the supercapacitor. Carbon nanofibers (CNFs) have been widely investigated as supercapacitor electrodes, which are generally synthesized by thermal treatment of electrospun precursor polymer nanofibers. In this study, the energy storage performance of CNFs was improved by modifying the chemical structures of precursor polymers. A blend of aromatic polyimide (PI) and polyvinylidene fluoride (PVDF) was chosen as a precursor and it was crosslinked before thermal treatment to improve the surface properties. Electrochemical properties were measured by assembling coin cells, and CNF electrodes derived from crosslinked PI/PVDF exhibited a specific capacitance of 322 F/g (10 mV/s) and energy density of 11.6 Wh/kg (0.5 A/g), which showed significantly higher energy storage properties than those of non-crosslinked one.
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타워크레인 텔레스코핑 작업의 풍속 및 하중에 대한 구조 안전성 연구
정성룡,이도근,백신원,신상연,Jung, Sung-Lyoung,Lee, Do-Geun,Paik, Shinwon,Shin, Sang-Yeon 한국안전학회 2021 한국안전학회지 Vol.36 No.1
This study analyses the load imbalance of the tower crane used in telescoping work for structural safety, owing to the difference in wind speed and balance weight position. This is because wind speed and position of the balance weight have a significant impact on the structural stresses of a tower crane during telescoping work. Therefore, structural analysis was performed on the 290HC model, which is often used at construction sites and has only one cylinder installed. Moreover, two models were classified to determine the load acting on the connecting part of the telescopic cage to slewing platform and the cylinder. Five types of balance weight positions were applied at regular intervals from jibs; moreover, four types of wind load criteria were differently applied. Hence, the telescopic cage columns were destroyed at all balance weight positions at a wind speed of 30 m/s and only at certain locations at a wind speed of 20 m/s. Furthermore, failures occurred for cylinders, torsional, and bending at wind speeds of 30 m/s and 20 m/s, load imbalances above the allowable thresholds considering the safety factor. In addition, the load imbalance in the telescoping work also varied depending on the position of the balance weights. The results of these studies have validated that the current standards of adjusting the appropriate position of the balance weights on the jib are completely valid, with the telescoping work to be executed only at wind speeds of less than equal to 10 m/s.
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kV Cone Beam Computed Tomography (CBCT)를 이용한 전립선암 영상유도방사선치료 시 흡수선량 및 유효선량에 관한 고찰
나종억,이도근,김진수,백금문,권경태,Na, Jong-Eok,Lee, Do-Geun,Kim, Jin-Soo,Baek, Geum-Mun,Kwon, Kyung-Tae 대한방사선치료학회 2009 대한방사선치료학회지 Vol.21 No.2
Purpose: To evaluate the results of absorbed and effective doses using two different modes, standard mode (A-mode) and low-dose mode (B-mode) settings for prostate cancer IGRT from CBCT. Materials and Methods: This experimental study was obtained using Clinac iX integrated with On Board Imager (OBI) System and CBCT. CT images were obtained using a GE Light Speed scanner. Absorbed dose to organs from ICRP recommendations and effective doses to body was performed using A-mode and B-mode CBCT. Measurements were performed using a Anderson rando phantom with TLD-100 (Thermoluminescent dosimeters). TLD-100 were widely used to estimate absorbed dose and effective dose from CBCT with TLD System 4000 HAWSHAW. TLD-100 were calibrated to know sensitivity values using photon beam. The measurements were repeated three times for prostate center. Then, Evaluations of effective dose and absorbed dose were performed among the A-mode and B-mode CBCT. Results: The prostate absorbed dose from A-mode and B mode CBCT were 5.5 cGy 1.1 cGy per scan. Respectively Effective doses to body from A mode and B-mode CBCT were 19.1 mSv, 4.4 mSv per scan. Effective dose from A-mode CBCT were approximately 4 times lower than B-mode CBCT. Conclusion: We have shown that it is possible to reduce the effective dose considerably by low dose mode(B-mode) or lower mAs CBCT settings for prostate cancer IGRT. Therefore, we should try to select B-mode or low condition setting to decrease extra patient dose during the IGRT for prostate cancer as possible.
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김정대 ( Jeong Dae Kim ),전지혜 ( Ji Hye Jeon ),이명선 ( Myong Seon Lee ),이도근 ( Do Geun Lee ),지홍련 ( Hong Lyun Jee ),박시홍 ( Si Hong Park ),최현경 ( Hyeun Gyong Choi ) 대한산부인과학회 1997 Obstetrics & Gynecology Science Vol.40 No.12
Objective: Our purpose was to review of clinical aspect of incompetent internal os of cervix. Study Design: A retrospective review of incidence and etiology of IIOC patients at one institution from 1991 to 1996, and analysis of fetal salvage after McDonald operation was performed. Results: The incidence of operation for IIOC was 0.27% of total delivery. The most frequentage group was from 25 to 29 age group and the average number of pregnancy before operation was 4 times. The significant contributory factor of previous history wasthe induced abortion. In all cases, cerclage method was McDonald operation. The average fetal salvage rate after operation was 84.8%. The causes of fetal loss were preterm labor in 4 cases(57%), abortion in 2 cases(29%) and premature rupture of membrane in 1 case(14%) in order. The delivery methods after operation were vaginal delivery(39 cases: 84.4%) and abdominal delivery(7 cases :15.2%). Conclusion: We conclude that all the patients had a history compatible with incompetent cervix requiring a cerclage.We further conclude that with strict indications McDonald operation offers a high rate of fetal salvage with a minimum of complications in patients with extremely poor obstetric histories because of cervical incompetence.
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