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배열회수보일러 케이싱 파손방지를 위한 열응력 저감 Heat Sink 설치 효과
최석민(Seok Min Choi),김선호(Seon Ho Kim),김풍일(Poongil Kim),고석재(Seok Jae Ko),정희봉(Hee Bong Chung),한봉기(Bong Gi Han),조형희(Hyung Hee Cho) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11
This study investigate thermal stress on the HRSG casing adopting heat sink by experimental data and numerical simulation. Heat sink is adopted on the HRSG casing to reduce the thermal stress. Thermocouples are installed on the operating HRSG casing to measure the temperature. Measured data shows that temperature gradient is rapid on the middle section of the HRSG casing. On the middle section, the temperature gradient is average 100℃ and it will cause extreme thermal stress. By numerical simulation we found out the local temperature data and measeared the thermal stress on the HRSG casing. Thermal stress on the middle section of HRSG casing is the highest and we can easily assume that the breakages are frequently happens on that position. So, we installed the heat sink on the vulnerable position on the HRSG casing to reduce the thermal stress. By installing the heat sink, we can reduce the peak thermal stress by 10% on the vulnerable position. As a result, heat sink can reduce the thermal stress on the HRSG casing.
Cascaded 멀티레벨 인버터의 고장 허용 제어를 위한 Level-Shifted PWM 기반의 새로운 변조 기법
김석민(Seok-Min Kim),이준석(June-Seok Lee),이교범(Kyo-Beum Lee) 대한전기학회 2015 전기학회논문지 Vol.64 No.5
This paper proposes a novel level-shifted PWM (LS-PWM) strategy for fault tolerant cascaded multilevel inverter. Most proposed fault-tolerant operation methods in many of studies are based on a phase-shifted PWM (PS-PWM) method. To apply these methods to multilevel inverter systems using LS-PWM, two additional steps will be implemented. During the occurrence of a single-inverter-cell fault, the carrier bands scheme is reconfigured and modulation levels of inverter cells are reassigned in this proposed fault-tolerant operation. The proposed strategy performs balanced three-phase line-to-line voltages and line currents when a switching device fault occurs in a cascaded multilevel inverter using LS-PWM. Simulation and experimental results are included in the paper to verify the proposed method.
Lung RPO 선량전달시, Carbon Couch Side Rail과 Vac-lok이 미치는 영향
김석민,곽근탁,이승훈,김정수,권형철,김양수,이선영,Kim, Seok Min,Gwak, Geun Tak,Lee, Seung Hun,Kim, Jung Soo,Kwon, Hyoung Cheol,Kim, Yang Su,Lee, Sun Young 대한방사선치료학회 2018 대한방사선치료학회지 Vol.30 No.1
목 적 : 폐의 우측후사방향 선량전달시, Carbon Side Rail과 환자 고정기구인 Vac-lok이 미치는 영향을 보고자 한다. 대상 및 방법 : Vac-lok의 오른쪽 부분을 10, 20, 30 mm 두께로 제작하였다. 측정은 유리선량계를 이용하여 측정하였고, 측정점은 팬텀 우측 폐의 center Point를 기준으로 좌, 우, 하, 상 방향 각각 A, B, C, D Point로 설정 하였다. 각 point에 유리선량계를 삽입한 후 couch의 Side Rail을 외측(Out)으로 뺀 후 vac-lok을 놓지 않은 no vac-lok, 그리고 10, 20, 30 mm의 vac-lok 위에 팬텀을 세팅하였다. 중심점에 6 MV 광자선을 조사야 $10{\times}10cm^2$, SAD 100 cm, 겐트리 각도 $225^{\circ}$로 하여 300 MU/min 선량률과 100 MU 조사선량을 전달하였다. 측정은 5회씩 실시하였고, 마찬가지로 Side Rail을 내측(In)으로 넣은 후 각 point에 대해서도 같은 조건으로 5 회씩 측정하여 평균값을 산출하였다. 결 과 : side rail에 따라서는 중심점, A, B, C, D Point 각각 -11.8 %, -12.3 %, -4.1 %, -12.3 %, -7.3 %의 선량 감소를 보였다. Side-Rail-Out에서 10 mm vac-lok의 경우 약 -0.9 %가 감소되었고, 20 mm vac-lok 사용 시 약 -2.0 %, 30 mm vac-lock 사용 시 약 -3.0 %가 감소되었다. Side-Rail-In에서 10 mm vac-lok의 경우 약 -1.0 %가 감소되었고, 20 mm vac-lok 사용 시 약 -2.1 %, 30 mm vac-lok 사용 시 약 -3.0 %가 감소되었다. Side-Rail-In 상태의 no vac-lok 선량 값을 기준으로 Side-Rail-Out 상태의 10, 20, 30 mm vac-lok을 사용할 때, side rail에 대한 선량 감소에 더하여 중심점에서는 약 -0.9 %, -1.8 % -2.4 %, A point에서는 -0.5 %, -1.6 %, -2.1 %, B point에서는 약 -0.9 %, -2.0 %, -3.2 %, C Point에서는 -1.0 %, -2.1 %, -3.1 %, D point에서는 약 -1.0 %, -1.6 %, -3.1 %의 추가적인 선량 감소를 나타냈다. 결 론 : 폐를 비롯한 우측후사방향 방사선 치료 시 side rail에 대해 주의를 기울이고, vac-lok 제작 시 vaclok 두께에 대해 관심을 갖는다면 더 나은 치료 효과를 기대해 볼 수 있으리라 사료된다. Purpose : To evaluate the effect of carbon couch side rail and vacuum immobilization device in case of lung RPO irradiation. Materials and Methods : The 10, 20, 30 mm thickness of vac-lok's right side were obtained. To measure of doses, glass dosimeters were used and measured reference point is left lung center at the phantom. A, B, C, and D points are left, right, down, and up directions based on the center point. In the state of Side-Rail-Out, place the without vac-lok, with the thickness of 10, 20, and 30 mm vac-lok. After the glass dosimeters was inserted in center, A, B, C, and D points, 100 MU of 6 MV X-ray were irradiated to the referenced center point in the condition of $10{\times}10cm^2$ field size, SAD 100 cm, gantry angle 225, 300 MU/min dose rate. Five measurements were made for each point. In the state of Side-Rail-In, five measurement were made for each point under the same conditions. The average is measured on each of the five Side-Rail-Out and Side-Rail-In measurements. Results : In the presence of side rail, the dose reduction ratio was -11.8 %, -12.3 %, -4.1 %, -12.3 %, -7.3 % for each A, B, C, and D points. In the state of Side-Rail-Out, the dose reduction ratio for the using 10 mm thickness of vac-lok was -0.9 % than without vac-lok. The dose reduction ratio for the using 20 mm thickness of vac-lok was -2.0 %, for the using 30 mm thickness of the vac-lok was -3.0 % than without vac-lok. In the state of Side-Rail-In, the dose reduction ratio for the using 10 mm thickness of vac-lok was -1.0 % than without vac-lok. The dose reduction ratio for the using 20 mm vac-lok was -2.1 %, for the using 30 mm vac-lok was -3.0 % than without vac-lok. Based on the value of no vac-lok dose in the Side-Rail-In state, The dose reduction ratios for the using 10 mm, 20 mm and 30 mm thickness of vac-loks In the Side-Rail-Out that the center point were -12.7 %, -13.7 %, -14.2 % and -12.8 %, -13.8 %, -14.5 % respectively at point A. The dose reduction ratios for the same conditions to the B point were -4.9 %, -6.1 %, -7.1 % and -13.4 %, -14.4 %, -15.5 % respectively at point C. The dose reduction ratios for the same conditions to the D point were -8.4 %, -9.0 %, -10.4 % respectively. Conclusion : The attenuation was caused by presence of side rails and thickness of vac-lok. Pay attention to these attenuation factors, making it a more effective radiation therapy.
김석민(Seok Min Kim),박동성(Dong Sung Park) 대한치과의사협회 2007 대한치과의사협회지 Vol.45 No.6
The aim of this study was to investigate the effect of the hybrid instrumentation method with ProTaper and ProFile on the change of root canal area and distance from the canal to the root surface after canal shaping. The mesial canals of twenty extracted mandibular first molars having 10-20°? curvature were scanned using X-ray micro-computed tomography (XMCT)-scanner before root canals were instrumented. They were divided into four groups (n=10 canals per group). In Group 1, root canals were instrumented by the step-back technique with stainless steel K-Flexofile after coronal flaring. The remainders were instrumented by the crown-down technique with, ProTaper system (Group 2), ProFile (Group 3) or ProTaper and ProFile (Group 4). All canals were prepared up to size 25 at the end-point of preparation and scanned again. Pre-and post-operative cross-sectional images of 1, 3, 5, and 7㎜ from the apical foramen were compared. For each level, change of cross-sectional canal area and distance to the nearest external root surface was calculated using Adobe Photoshop 6.0 and image software program. In the change of cross-sectional area, Group 4 was less than Group 2 at 3 ㎜ and 5 ㎜ level (p<0.05). In the difference of the distance from the canal to the root surface after canal shaping, Group 4 was least among the other groups at 7 ㎜ level (p<0.05). According to the results, the methods using ProFile or K file only and the hybrid instrumentation technique using ProTaper and ProFile are more appropriate methods of canal preparation than ProTaper system for narrow or curved canals.