• Nuclear Engineering and Technology
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• 제55권11호
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• pp.4167-4172
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• 2023

Miniaturized tissue equivalent proportional counters (mini-TEPCs) are proper for radiation dosimetry in medical application because the small size of the dosimeter could prevent pile-up effect under the high intensity of therapeutic beam. However, traditional methods of calibrating mini-TEPCs using internal alpha sources are not feasible due to their small size. In this study, we investigated the use of electron and proton edges on Monte Carlo-generated lineal energy spectra as markers for calibrating a 0.9 mm diameter and length mini-TEPC. Three possible markers for each spectrum were calculated and compared using different simulation tools. Our simulations showed that the electron edge markers were more consistent across different simulation tools than the proton edge markers, which showed greater variation due to differences in the microdosimetric spectra. In most cases, the second marker, y_δδ, had the smallest uncertainty. Our findings suggest that the lineal energy spectra from mini-TEPCs can be calibrated using Monte Carlo simulations that closely resemble real-world detector and source geometries.

• 센서학회지
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• 제24권2호
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• pp.93-95
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• 2015

We present an optical detection method for the fundamental vibrational mode of a tuning fork crystal oscillator in air. A focused He/Ne laser beam is directed onto the edge of one vibrating tine of the tuning fork; its vibrating motion chops the incoming laser beam and modulates the intensity. The beam with modulated intensity is then detected and converted to an electrical signal by a high-speed photo-detector. This electrical signal is a sinusoid at the resonant frequency of the tuning fork vibration, which is 32.76 kHz. Our scheme is robust enough that the sinusoidal signal is detectable at up to $40^{\circ}$ of rotation of the tuning fork.

• 한국의학물리학회지:의학물리
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• 제31권3호
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• pp.99-110
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• 2020

With hope and concern, the first Korean proton therapy facility was introduced to the National Cancer Center (NCC) in 2007. It added a new chapter to the history of Korean radiation therapy. There have been challenging clinical trials using proton beam therapy, which has seen many impressive results in cancer treatment. Compared to the rapidly increasing number of proton therapy facilities in the world, only one more proton therapy center has been added since 2007 in Korea. The Samsung Medical Center installed a proton therapy facility in 2015. Most radiation oncology practitioners would agree that the physical properties of the proton beam provide a clear advantage in radiation treatment. But the expensive cost of proton therapy facilities is still one of the main reasons that hospitals are reluctant to introduce them in Korea. I herein introduce the history of proton therapy and the cutting edge technology used in proton therapy. In addition, I will cover the role of a medical physicist in proton therapy and the future prospects of proton therapy, based on personal experience in participating in proton therapy programs from the beginning at the NCC.

• 한국의류학회지
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• 제15권1호
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• pp.70-75
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• 1991

본 연구에서는 레이저광선의 투영을 이용한 접촉각측정기구가 개발되었다. 이 새로운 방법은 편평한 표면분만 아니라 직격이 가는 섬유를 포함한 굴곡진 표면에서는 stationary, advancing그리고 receding contact angle-을 신속하고 정확하게 측정할 수 있게 하여 준다. 가는 레이저광선이 액체와 고체사이 계면의 끝을 통과하여 tangent screen의 각도를 재는 눈금상에 중심으로부터 방사상으로 두개의 선이 나타나게 된다. 이때 눈금상에 투영된 두개의 레이저광선 사이의 각도를 접촉각으로 결정한다. 이 새로운 기구를 사용한 결과, PMMA(Perspex-CQ)상에서의 접촉각은 문헌상의 접촉각과 일치함으로써 간편하고 정확한 접촉각 측정법임을 입증할 수 있었다.

• Current Optics and Photonics
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• 제4권3호
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• pp.229-237
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• 2020

In this study, a beam-coupling system is designed to improve the coupling efficiency of achip-integrated spectrometer when the waveguide is arranged in a linear and discrete manner. In the proposed system the beam is shaped to be anti-Gaussian, to deposit adequate energy in the edge waveguides. The beam is discretely coupled to the corresponding waveguide by a microlens array, to improve the coupling efficiency, and is compressed by a toroidal lens to match the linear discrete waveguides. Based on the findings of this study, the coupling efficiency of the spectrometer is shown to increase by a factor of 2.57. Accordingly, this study provides a reference basis for the improvement of the coupling efficiency of other similar spectrometers.

• Nuclear Engineering and Technology
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• 제53권4호
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• pp.1049-1078
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• 2021

The review summarizes the published data on the widely applied electron-beam, laser-beam, as well as resistance upset, projection, and spot welding of zirconium alloys for nuclear applications. It provides the results of their analysis to identify common patterns in this area. Great attention has been paid to the quality requirements, the edge preparation, up-to-date equipment, process parameters, as well as post-weld treatment and processing. Also, quality control and weld repair methods have been mentioned. Finally, conclusions have been drawn about a significant gap between the capabilities of advanced welding equipment to control the microstructure and, accordingly, the properties of welded joints of the zirconium alloys and existing algorithms that enable to realize them in the nuclear industry. Considering the ever-increasing demands on the high-burnup accident tolerant nuclear fuel assemblies, great efforts should be focused on the improving the welding procedures by implementing predefined heat input cycles. However, a lot of research is required, since the number of possible combinations of the zirconium alloys, designs and dimensions of the joints dramatically exceeds the quantity of published results on the effect of the welding parameters on the properties of the welds.

• 한국의학물리학회지:의학물리
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• 제19권3호
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• pp.186-190
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• 2008

본 연구에서는 금속 물체의 묘사를 위한 예비 연구로서 제한된 EPID 영상을 이용한 콘빔 재구성을 수행하였다. 콘빔 재구성에 제한된 영상이 이용되었기 때문에 일반적인 FDK 재구성 알고리즘에 에지 보존 평활화(edge preserving smoothing) 필터가 사용되었다. 사용된 영상의 수와의 상관관계를 비교해 보았을 때 금속 seed의 크기와 위치에 대한 결과는 거의 동일하다고 판명되었다. 콘빔 CT 재구성을 위하여 제한된 영상을 사용하였기 때문에 우리의 방법은 임상 적용에 있어 경제적이고, 효과적인 방법이 될 수 있을 것으로 사료된다.

• Composites Research
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• 제17권3호
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• pp.29-37
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• 2004

본 연구에서는 대변형 보이론을 이용하여 정지 비행 시 복합재 무베어링 로우터 시스템의 공력탄성학적 안정성 해석을 수행하였다. 무베어링 로우터 시스템은 유연보, 토오크 튜브, 피치 링크, 그리고 메인 블레이드로 구성된다. 유연보, 토오크 튜브, 그리고 메인 블레이드를 각각 플랩 굽힘, 리드-래그 굽힘, 비틀림 그리고 축 방향 변형의 탄성 운동을 하는 보로 가정하고, 1차원 보 요소로 모델링을 하였다. 또한, 유연보를 복합재료 적층판으로 구성된 비틀림에 유연한 직사각형 단면을 갖는 보로 모델링 하여, 1차원 보 해석에 필요한 유효 단면 상수를 얻었다. 외력으로는 2차원 준-정상 공기력 모델을 적용하였으며, 보의 유한 요소 지배방정식은 헤밀턴 원리(Hamilton's principle)를 이용하여 얻었다. 공력 탄성학적 안정성 해석을 수행하기 위하여 p-k 방법을 이용하였으며, 유연보의 적층각과 적층 순서에 따른 구조적 연성이 무베어링 로우터 시스템의 공란성 안정성에 미치는 영향을 알아보았다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제10권6호
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• pp.670-682
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• 2018

This paper presents the experimental and numerical investigation results of the response of low-temperature steel (LT-FH32 grade steel) beams under repeated impacts at room temperature and a single impact at a sub-zero temperature. After conducting tensile tests at room and sub-zero, repeated impact tests were conducted on two clamped single-beam models at room temperature, and single-impact tests of two other clamped single-beam models were conducted at $-50^{\circ}C$. The single and repeated impact tests were conducted by releasing a knife-edge striker using a drop testing machine. The permanent deflection of the model measured after each impact gradually increased with increasing number of impacts. Under the reduced temperature, the permanent deflection of the models slightly decreased. The numerical analyses were also performed to predict the damage response of the tested single-beam models. A comparison of the numerical prediction with those of experiments showed quite reasonable agreement.

• 한국전기전자재료학회논문지
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• 제24권7호
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• pp.578-583
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• 2011

We report on the design of a holographic homogenizer composed of a periodic hologram and a condensing lens. If the hologram is periodic, the homogenizer is free from the alignment error of the incident laser beam. Holographic homogenizer also has an advantage of the flexibility in the size of the target beam. We calculated theoretically the Fraunhofer diffracted wave function when a rectangular laser beam is incident on a periodic hologram. The diffracted wave is the sum of sinc functions at regular distance. The width of each sinc function depends on the size of the incident laser beam and the distance between the sinc functions depends on the period of the hologram. We calculated numerically the diffracted light intensity for various ratios of the size of the incident laser beam to the period of the hologram. The results show that it is possible to make the diffracted beam uniform at a certain value of the ratio. The uniformity is high at the central part of the target area and low near the edge. The more sinc functions are included in the target area, the larger portion of the area becomes uniform and the higher is the uniformity at the central part. Therefore, we can make efficient homogenizer if we design a hologram so that the maximum number of the diffracted beams may be included in the target area.