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선형가속기 10 MV 광자선에서 산란판(Beam Spoiler) 사용 시 표면선량 변화
배성철,김준호,이철수,Bae, Seong-Cheol,Kim, Jun-Ho,Lee, Choul-Soo 대한방사선치료학회 2006 대한방사선치료학회지 Vol.18 No.1
Purpose: The purpose of this study is to find a optimal beam spoiler condition on the dose distribution near the surface, when treating a squamous cell carcinoma of the head and neck and a lymphatic region with 10 MV photon beam. The use of a optimal spoiler allows elivering high dose to a superficial tumor volume, while maintaining the skin-sparing effect in the area between the surface to the depth of 0.4 cm. Materials and Methods: The lucite beam spoiler, which were a tissue equivalent, were made and placed between the surface and the photon collimators of linear accelerator. The surface-dose, the dose at the depth of 0.4 cm, and the maximum dose at the dmax were measured with a parallel-plate ionization chamber for $5{\times}5cm\;to\;30{\times}30cm^2$ field sizes using lucite spoilers with different thicknesses at varying skin-to-spoiler separation (SSS). In the same condition, the dose was measured with bolus and compared with beam spoiler. Results: The spoiler increased the surface and build-up dose and shifted the depth of maximum dose toward the surface. With a 10 MV x-ray beam and a optimal beam spoiler when treating a patient, a similer build-up dose with a 6 MV photon beam could be achieved, while maintaining a certain amount of skin spring. But it was provided higher surface dose under SSS of less than 5 cm, the spoiler thickness of more than 1.8 cm or more, and larger field size than $20{\times}20cm^2$ provided higher surface dose like bolus and obliterated the spin-sparing effect. the effects of the beam spoiler on beam profile was reduced with increasing depths. Conclusion: The lucite spoiler allowed using of a 10 MV photon beam for the radiation treatment of head and neck caner by yielding secondary scattered electron on the surface. The dose at superficial depth was increased and the depth of maximum dose was moved to near the skin surface. Spoiling the 10 MV x-ray beam resulted in treatment plans that maintained dose homogeneity without the consequence of increased skin reaction or treat volume underdose for regions near the skin surface. In this, the optimal spoiler thickeness of 1.2 cm and 1.8 cm were found at SSS of 7 cm for $10{\times}10cm^2$ field. The surface doses were measured 60% and 64% respectively. In addition, It showed so optimal that 94% and 94% at the depth of 0.4 cm and dmax respectively.
터널링 자기저항 소자의 교류 전압 및 주파수 의존성 연구
배성철(Seong-Cheol Bae),윤석수(Seok Soo Yoon),김동영(Dong Young Kim) 한국자기학회 2016 韓國磁氣學會誌 Vol.26 No.6
In this report, we measured the impedance spectrum in TMR device, and the relaxation behavior of the real and imaginary impedance spectrum was analyzed by using the equilibrant circuit of tunneling capacitance (C<SUB>T</SUB>) and tunneling resistance (R<SUB>T</SUB>). The relaxation frequency was increased with AC voltage in both the parallel and antiparallel alignment of two magnetic layers. The R<SUB>T</SUB> with AC voltage showed the typical bias voltage dependence. However, the C<SUB>T</SUB> showed large value than the expected geometrical capacitance. The huge increase of C<SUB>T</SUB> was affecting as a limiting factor for the high speed operation of TMR devices. Thus, the supercapacitance of C<SUB>T</SUB> should be considered to design the high speed TMR devices.
원자짝 분포 함수를 이용한 칼슘 실리케이트 경화체의 나노 구조 변형 거동 해석
배성철 ( Bae Sung-chul ),장유현 ( Chang Yoo-hyun ),지현석 ( Jee Hyeon-seok ) 한국건축시공학회 2016 한국건축시공학회 학술발표대회 논문집 Vol.16 No.2
Calcium Silicate Hydrate (C-S-H), which takes up most of the hydration products of Portland Cement (PC), has the greatest impact on the mechanical behavior and strength development of concrete. The exact mechanism of its deformation, however, has not yet been elucidated. The present study aims to demonstrate the mechanism of nano-deformation behavior of C-S-H in tricalcium silicate paste under compressive loading, unloading and reloading by interpreting atomic pair distribution function (PDF) based on synchrotron X-ray scattering. The strain of the tricalcium silicate paste for a short-range of 0 ~ 20 A under compressive load exhibited two stages, I) nano-packing of interlayer of C-S-H and II) micro-packing of C-S-H globules, whereas the deformation for a long-range order of 20 ~ 40 A was similar to that of a calcium hydroxide phase measured by Bragg peak shift. Moreover, the residual strains due to the plastic deformation of C-S-H was clearly observed.