• Structural Monitoring and Maintenance
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• 제6권2호
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• pp.147-159
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• 2019

In present article, a size-dependent refined thick beam element has been established based upon nonlocal elasticity theory. Next, it is used to explore vibration response of porous metal foam nanobeams on elastic medium. The established beam element introduces ten degrees of freedom. Different porosity distributions called uniform, symmetric and asymmetric will be employed. Herein, introduced thick beam element contains shear deformations without using correction factors. Convergence and verification studies of obtained results from finite element method are also provided. The impacts of nonlocality factor, foundation factors, shear deformation, slenderness ratio, porosity kinds and porosity factor on vibration frequencies of metal foam nano-sized beams have been explored.

• 한국방재학회 논문집
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• 제7권5호
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• pp.37-46
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• 2007

본 연구는 강재 모멘트 골조의 비선형 지진 해석을 위한 부등단면 보 요소에 관한 두 개의 동반논문 중에서 두 번째 논문이다. 동반논문에서는 지진운동 하의 단면감소(RBS) 강재 보의 탄성 및 비탄성 거동을 정의하기 위한 부등단면 보(RBS 보) 요소를 제시하였고 본 연구에서는 RBS 보 요소에 대한 항복면, 강성 변수, 그리고 경화(혹은 연화) 법칙 변수의 결정과정을 기술하였고 RBS 보 요소의 해석결과를 실험 및 유한요소 해석(FEM) 결과와 비교하였다. RBS 보 요소의 해석결과는 실험 및 FEM 결과와 좋은 상관관계를 보였다.

• 한국자동차공학회논문집
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• 제14권2호
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• pp.107-113
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• 2006

The torsion beam axle type is widely used in the rear suspension for small passenger cars due to low cost, good performance, etc. To develop the torsion beam axle, it is necessary to estimate the characteristics of rear suspension from the design process. The characteristics estimation of the torsion beam axle is performed using FEM, dynamic simulation and is verified the real test. In this study, the natural frequency and roll stiffness of the torsion beam axle were measured by FEM, and the reliability of the FE model was evaluated according to the comparison of test data. This study presents a unique method for the finite element modeling and analysis of the torsion beam axle. The results of the FEA were verified using test data.

• 한국항행학회논문지
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• 제27권5호
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• pp.546-551
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• 2023

본 연구에서는 AESA 레이다의 근전계에서 송신/수신 모드에 대한 원전계 빔조향, 근전계 빔집속 등의 기능을 수행하기 위한 빔 조향 특성 측정 장치를 개발하였다. 빔조향 특성 측정장치는 구면형 근접전계 스캐너, 안테나 포지셔너, 근접전계 제어기, 네트워크 측정기, 레이다 제어시스템, 검증용 레이다 및 모의레이돔, AESA 레이다 등으로 구성된다. 개발한 시스템을 이용하여 AESA 레이다에 대한 레이돔장착전/후의 송/수신패턴특성을 측정하였고, 근접전계 측정 후 원전계로의 변환을 통해 빔패턴을 분석하였다. 그리고 레이다 안테나 장치의 보어사이트에러 를측정하였고, 모의 레이돔 장착 전후 메인로브가 동일하게 형성됨을 확인할 수 있었다.

• 대한방사선치료학회지
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• 제33권
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• pp.117-125
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• 2021

목 적: 본 연구는 뇌 정위 방사선수술에서 비 동일 면빔 사용 시 couch 회전에 따른 Set-up 오차에 대한 상관관계를 알아보고 선량 학적 차이 평가를 통해 치료 용적의 추가적인 margin 설정을 제안하고자 한다. 대상 및 방법: 4개의 Arc beam을 사용하였으며 전체 beam 중에 non coplanar beam의 빈도 수를 달리하는 각각의 시나리오 치료 계획을 만들었다. 이후 couch를 회전한 후 Exact system을 이용하여 couch Setup 오차 값을 측정하였다. 이를 적용하여 재 치료 계획을 만들어 선량적 정확성을 평가하였다. 결 과 : Couch가 30°, 45°, 60°, 90°로 회전하였을 시 X축 이동 값의 평균은 각 0.29 mm, 0.26 mm, 0.51 mm, 0.08 mm으로 측정되었다. Y축 이동 값의 평균은 각 0.75 mm, 0.5mm, 0.35 mm, 0.29 mm 으로 측정되었다. Z축 이동 값의 평균은 각 0.5 mm, 0.28 mm, 0.22 mm, 0.1 mm으로 측정되었다. 선량 학적 결과로는 1-NC VMAT, 2-NC VMAT, 3-NC VMAT 모두 각 initial plan 대비 D99에서 0.1%, 3.1%, 1.9% 선량 감소하였고 1-NC VMAT의 GTV의 CI(Conformity Index)는 0.8이며 2-NC VMAT는 0.79, 3-NC VMAT는 0.75이다. 결 론 : NC-VMAT의 뇌 정위 방사선수술 시 전체 beam의 개수 중 50% 이상의 non coplanar beam을 사용하여 치료하는 경우 couch 회전 시 image verification 이 각각 필요하다. 그러나 선형가속기 장비 특성상 couch가 회전된 상태에서 image verification이 가능하지 않다면 GTV에 couch 회전으로 인한 최대 오차 값을 포함하는 1.5 mm margin을 추가하여 치료 계획을 수립하는 것이 유용할 것으로 사료된다.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1997년도 추계학술대회
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• pp.164-167
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• 1997

The treatment setup of patients during irradiation is an important aspect in relation to the success of radiotherapy. Imaging with the treatment beam is a widely used method or verification of the radiation field position relative to the target area, prior to or during irradiation. In this paper, Real time digital radiography system was implemented or verification of local error between simulation plan and radiation therapy machine. Portal image can be acquired by CCD camera, image board and pentium PC after therapy Radiation was converted into light by a metal/fluorescent Screen. The resulting image quality is comparable to film, so the imaging system represents a promising alternative to film as a method of verifying patient positioning in radiotherapy. Edge detection and field size measurement were also implemented and detected automatically for verification of treatment position. Field edge was added to the original image or checking the anatomical treatment verification by therapy technicians. By means of therapy efficiency improvement and decrease of Radiation side effects with these techniques, Exact Radiation treatments are expected.

• Nuclear Engineering and Technology
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• 제55권10호
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• pp.3700-3708
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• 2023

The stochastic origin ensembles method with resolution recovery (SOE-RR) has been proposed to reconstruct proton-induced prompt gammas (PGs), and the reconstructed PG image was used for range verification. However, due to low detection efficiency, the number of valid events is low. Such a low-count condition can degrade the accuracy of the SOE-RR method for proton range verification. In this study, we proposed two strategies to improve the reconstruction of the SOE-RR algorithm for low-count PG imaging. We also studied the number of iterations and repetitions required to achieve reliable range verification. We simulated a proton beam (10⁸ protons) irradiated on a water phantom and used a two-layer Compton camera to detect 4.44-MeV PGs. Our simulated results show that combining the SOE-RR algorithm with restricted volume (SOE-RR-RV) can reduce the error of the estimation of the Bragg peak position from 5.0 mm to 2.5 mm. We also found that the SOE-RR-RV algorithm initialized using a back-projection image could improve the convergence rate while maintaining accurate range verification. Finally, we observed that the improved SOE-RR algorithm set for 60,000 iterations and 25 repetitions could provide reliable PG images. Based on the proposed reconstruction strategies, the SOE-RR algorithm has the potential to achieve a positioning error of 2.5 mm for low-count PG imaging.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.189-191
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• 2002

In the proton therapy using a gantry system, periodical verification of iso-center position is very important to assure precision of patient positioning system at any gantry angles in proton treatment. In the gantry system, there are three different types of iso-center; 1) in a geometrical view, 2) in an X-ray beam's eye view, 3) in a proton beam's eye view. Idealistically, they would be an identical point. They could, however, be different points. It may be a source of errors in patient positioning. At PMRC, we have established a system of verification for iso-center positions using a stainless ball of 2-cm in diameter and an imaging plate. This system provides the relation among a center of a patient target position, a center of proton irradiation field, and/or a center of X-ray field in accuracy of 50$\square$m in the 2) and 3) views, as images of a center of the stainless ball and a center of a 100 mm${\times}$100 mm-aperture brass collimator recorded on the imaging plate, which is setup at 1-cm behind the ball. In addition, it provides simultaneously the images of the ball and the collimator on an imaging intensifier (II), which is setup downstream of the proton or X-ray beam. We present a method of quality assurance (QA) for calibration of iso-center position in a rotation gantry system at PMRC and the performance of this system. A proton beam position on the 1$\^$st/ scatterer in the nozzle of the gantry affects less sensitive (reduced by a factor of 1/5) to the results of the iso-center position. The effect is systematically correctable. The effect of the nozzle (or the collimator) position is less than 0.5 mm at the maximum extraction (390 mm).

• Journal of Radiation Protection and Research
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• 제44권2호
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• pp.72-78
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• 2019

Background: In the calibration and testing laboratory of Korea Atomic Energy Research Institute, the old X-ray generator used for the production of reference X-ray fields was replaced with a new one. For this newly installed X-ray irradiation system, beam alignment as well as the verification of beam qualities was conducted. Materials and Methods: The existing X-ray generator, Phillips MG325, was replaced with YXLON Y.TU 320-D03 in order to generate reference X-ray fields. Theoretical calculations and Monte Carlo simulations were used to determine initial filter thickness. Beam alignment was performed in three steps to deliver a homogeneous radiation dosage to the target at different distances. Finally, the half-value layers were measured for different X-ray fields to verify beam qualities by using an ion chamber. Results and Discussion: Beam alignment was performed in three steps, and collimators and other components were arranged to maintain the uniformity of the mean air kerma rate within ${\pm}2.5%$ at the effective beam diameter of 28 cm. The beam quality was verified by using half-value layer measurement methods specified by American National Standard Institute (ANSI) N13.11-2009 and International Organization for Standardization (ISO)-4037. For each of the nine beams than can be generated by the new X-ray irradiation system, air kerma rates for X-ray fields of different beam qualifies were measured. The results showed that each air kerma rate and homogeneity coefficient of the first and second half-value layers were within ${\pm}5%$ of the recommended values in the standard documents. Conclusion: The results showed that the new X-ray irradiation system provides beam qualities that are as high as moderate beam qualities offered by National Institute of Standards and Technology in ANSI N13.11-2009 and those for narrow-spectrum series of ISO-4037.

• 한국방재학회 논문집
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• 제7권5호
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• pp.27-35
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• 2007

본 연구는 지진운동의 영향 하에서 강제 모멘트 골조로 이루어진 post-Northridge 연결부를 갖는 보의 탄성 및 비탄성 거동을 모델하기 위한 부등단면 보 요소를 제시한다. 단면감소 연결부를 갖는 부등단면 보의 탄성강성 행렬은 수치적분이 필요치 많은 수식으로 표현된다. 소성모델은 분포형이며 강체링크로 연결된 일련의 비선형 힌지로 구성 되어있고 경화법칙은 단조 및 임의 주기 하중에 대한 비탄성 거동과 국부좌굴의 효과를 고려할 수 있다. 모델의 대조와 검증은 동반논문에 제시되어있다.