• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2021년도 학술발표회
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• pp.154-154
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• 2021

Since the development of Bubble Image Velocimetry (BIV) technique as the complementary technique of Particle Image Velocimetry (PIV), the application of digital imaging technique in the field of hydraulic and coastal engineering increased rapidly. BIV works very well in multi-phase flow (air-water) flows where the PIV technique doesn't. However, the velocity field obtained from BIV technique often resulted in a velocity vector on the outside of the flow (false velocity) since the Field of View (FOV) usually not only cover the air-water flow but also the area outside the flow. In this study, a simple technique of post processing velocity field was developed. This technique works based on the average of the pixel value in the interrogation area. An image of multi-phase flow of wave overtopping was obtained through physical experiment using BIV technique. The velocity calculation was performed based on the similar method in PIV. A velocity masking technique developed in this study then applied to remove the false velocity vector. Result from non-masking, manually removed and auto removed false velocity vector were presented. The masking technique show a similar result as manually removed velocity vector. This method could apply in a large number of velocity field which is could increase the velocity map post-processing time.

• 대한방사선치료학회지
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• 제21권1호
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• pp.17-23
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• 2009

목 적: 두경부암의 치료에 있어 상부 두경부의 양측면조사면과 하경부의 전방조사면의 접합부위에 균등한 선량을 조사하는 것은 매우 중요하다. 접합부위의 선량분포개선을 위하여 하경부 전방조사면의 치료시 Field-in-Field technique을 이용하여 부족선량(under dose)과 초과선량(over dose)으로 인한 선량불균등을 개선하고 일반치료와의 비교를 통하여 두경부암치료에 적용하고자 한다. 대상 및 방법: 상부 두경부의 양측면 조사시 빔의 확산으로 일어나는 입사점과 출사점의 선량차이를 알아보기 위하여 인체모형팬톰을 이용하였다. 인체모형팬톰을 전산화단층촬영하고 전산화치료계획에서 관심점의 선량비교를 시행하였고, 하경부 접합부위의 선량비율을 계산하여 이를 보정하였다. 조사면 접합부위의 선량분포를 알아보기 위하여 하경부의 접합부위에 저감도 필름을 놓고 일반적인 치료인 상부 두경부의 양측면조사와 하경부의 전방조사시 선량분포를 측정하였다. 또한, 상부 두경부 양측면 조사에 따른 빔의 확산을 고려한 Field-in-Field technique을 이용하여 하경부 전방조사를 할 때의 접합부위의 선량분포 차이를 측정하여 비교하였다. 접합부위의 관심점 선량을 알아보기 위하여 열형광선량계를 이용하여 인체모형팬톰내의 관심점에서의 선량변화를 비교, 분석하였다. 결 과: 전산화치료계획에서 하경부의 접합부위에 Field-in-Field technique을 적용하여 치료계획시 상부 두경부 양측면 조사와 선량합성을 한 경우 부족선량 영역의 선량이 4.7~8.65% 이상 증가하였다. 초과선량 영역의 선량도 2.75~10.45% 감소하였다. 또한, 저감도 필름을 이용한 측정에서는 부족선량영역에서 11.3% 증가, 초과선량영역에서 5.3% 감소한 것으로 나타났다. 열형광선량계를 이용한 관심점선량측정에서도 Field-in-Field technique 적용시 부족선량을 최소 7.5%에서 최대 17.6%까지 보정해주는 것으로 나타나 불균등한 선량분포를 개선할 수 있었다. 결 론: 전산화치료계획시 빔의 확산을 고려한 Field-in-Field technique을 적용하면 접합부위의 선량보정을 통해 냉점(cold spot)과 온점(hot spot)을 줄일 수 있었으며 특히, 빔의 확산에 따른 입사점의 부족선량을 보정할 수 있었다. 본 실험을 통해 Field-in-Field technique의 임상적용시 경부임파절의 저선량으로 인한 임파절전이에 대한 위험도를 감소시킬 수 있을 것으로 사료된다.

• 대한방사선치료학회지
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• 제17권1호
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• pp.9-17
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• 2005

목적 : 방사선치료에 있어 치료부위내의 균등한 선량분포는 환자의 치료성적 및 장해를 좌우하는 매우 중요한 인자이다. 이러한 치료부위내의 균등한 선량분포를 얻기 위해 사용하는 여러 가지 방법 중 간단한 Field-in-Field Technique의 유용성을 평가하고 다양한 크기의 전뇌(whole brain)치료 환자에게 적용가능성을 알아보고자 한다. 대상 및 방법 : 전뇌(whole brain)의 일반적인 치료기법인 대향2문조사와 Field-in-Field Technique을 적용했을 때의 선량분포도를 비교하기 위하여 phantom(acryl 16 cm spheral phantom)을 대상으로 치료계획을 수립하였으며, 선량분포평가를 위하여 저감도필름(X-Omat V-film)과 열형광선량계(TLD)를 사용하여 측정하였다. 또한 다양한 두께의 환자20명(대, 중, 소 및 소아-각각 5명)을 대상으로 Field-in-Field Technique의 적용가능성을 평가 하였다 결과 : 전뇌(whole brain)치료에 대향2문조사와 Field-in-Field Technique을 적용한 경우 각각의 치료부위내의 선량분포 및 DVH를 비교한 결과, Field-in-Field Technique을 사용한 경우 고선량(high dose)영역을 $3{\sim}4\%$이하로 줄일 수 있었고, 저감도필름(X-Omat V-film)과 열형광선량계(TLD)에 의한 측정결과 또한 유사한 수치를 얻을 수 있었다. 이러한 Field-in-Field Technique을 다양한 두께의 환자에게 동일하게 적용해도 선량분포의 변화는 $1{\sim}2\%$로 나타났다. 결론 : 전뇌(whole brain)치료에 Field-in-Field Technique를 이용하여 치료계획을 수립하여 적용하면 치료부위내의 균등한 선량분포를 얻을 수 있으므로 추가적인 치료가 필요한 경우 선량합성이 용이하여 쉽게 치료계획을 수립할 수 있었다. 그리고 균등한 선량분포를 얻기 위해 사용하는 wedge filter 및 3D compensator 의 역할을 대체 할 수 있으며, 방사선 치료 시 고선량 영역으로 인해 발생되는 장해를 최소화할 수 있을 것으로 사료된다.

• 한국의학물리학회지:의학물리
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• 제24권4호
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• pp.230-236
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• 2013

Our purpose is to present a novel technique for delivering craniospinal irradiation in the supine position using a perfect match, field-in-field (FIF) intrafractional feathering, and simple forward-optimization technique. To achieve this purpose, computed tomography simulation was performed with patients in the supine position. Half-beam, blocked, opposed, lateral, cranial fields with a collimator rotation were matched to the divergence of the superior border of an upper-spinal field. Fixed field parameters were used, and the isocenter of the upper-spinal field was placed at the same source-to-axis distance (SAD), 20 cm inferior to the cranial isocenter. For a lower-spinal field, the isocenter was placed 40 cm inferior to the cranial isocenter at a constant SAD. Both gantry and couch rotations for the lower-spinal field were used to achieve perfect divergence match with the inferior border of the upper-spinal field. A FIF technique was used to feather the craniospinal and spinal-spinal junction daily by varying the match line over 2 cm. The dose throughout the target volume was modulated using the FIF simple forward optimization technique to obtain homogenous coverage. Daily, image-guided therapy was used to assure and verify the setup. This supine-position, perfect match craniospinal irradiation technique with FIF intrafractional feathering and dose modulation provides a simple and safe way to deliver treatment while minimizing dose inhomogeneity.

• 대한방사선기술학회지:방사선기술과학
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• 제41권6호
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• pp.561-566
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• 2018

Field-in-Field Technique is applied to the radiation therapy of breast cancer patients, and it is possible to compensate the difference in breast thickness and deliver uniform dose in the breast. However, there are several fields in the treatment field that result in a more complex dose delivery than a single field dose delivery. If the patient's respiration is irregular during the delivery of the dose by several fields and the change of respiration occurs, the dose distribution in the breast changes. Therefore, based on the computed tomography images of breast cancer patients, a human model was created by using a 3D printer (Builder Extreme 1000) to describe the volume in the same manner. A computerized tomography (CT) of the human body model was performed and a treatment plan of 260 cGy / fx was established using a 6-MV field-in-field technique using a computerized treatment planning system (Eclipse 13.6, Varian, USA). The distribution of the dose in the breast according to the change of the respiration was measured using a moving phantom at 0.1 cm, 0.3 cm, 0.5 cm amplitude, using a MOSOXIDE Silicon Field Effect Transistor (MOSFET, Best Medical, Canada) Were measured and compared. The distribution of dose in the breast according to the change of respiration showed similar value within ${\pm}2%$ in the movement up to 0.3 cm compared to the treatment plan. In this experiment, we found that the dose distribution in the breast due to the change of respiration when the change of respiration was increased was not much different from the treatment plan.

• Journal of Magnetics
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• 제20권1호
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• pp.62-68
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• 2015

This paper presents an experimental technique to accurately separate a permanent magnetic field and an induced one from the total magnetic fields generated by a steel ship, through compensating for the Earth's magnetic field. To achieve this, an Earth's magnetic field simulator was constructed at a non-magnetic laboratory, and the field separation technique was developed, which consisted of five stages. The proposed method was tested with a scaled model ship, and its permanent and induced magnetic fields were successfully extracted from the magnetic field created by the ship. Finally, based on the separated permanent magnetic field data, the permanent magnetization distribution on the hull was predicted by solving an inverse problem. Accordingly, the permanent magnetic fields generated by the ship can easily be calculated at any depth of water.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.1069-1072
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• 2009

Field sequential display has some advantages but color breakup (CBU) is the significant problem. Many researches had introduced several methods to reduce CBU phenomenon, however there are no reliable methods to measure the degree of CBU. In this report, a novel CBU measurement technique which was based on the image processing method and subjective analysis results had proposed to evaluate the degree of CBU. Color Breakup Index (CBI) was presented to be a useful index to recognize the CBU phenomenon in the different field sequential technique displays.

• 건축역사연구
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• 제31권5호
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• pp.7-20
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• 2022

Traditional building technique has been used as the main technology in the field of architectural heritage conservation in South Korea. It has remained this way with very little resistance until now. But the time has come to question the appropriateness of traditional technique as conservation technique. In this paper a study was done on the properties of the traditional technique and the architectural heritage conservation technique in order to define the appropriateness between the two techniques. As a result the traditional technique was found to be unfit for conservation technique. The reasons are as follows. First, there is a time gap between the traditional technique and the time when the heritage was first built. Second, conservation work is about retaining the values of being a heritage while the traditional technique is about safeness and practicality. Third, the use of traditional technique comes with using the tools of its time which cannot ensure the safety of the heritage. The traditional technique must be looked upon as one of an option in the field of conservation. We must develop a better conservation technology by finding balance between the traditional technique and modern science. And further more an aggressive investment must be made in order to realize this objective.

• Journal of Magnetics
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• 제20권1호
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• pp.8-10
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• 2015

The magnetic anisotropy field plays an important role in spin-orbit-torque-induced magnetization dynamics with electric current injection. Here, we propose a magnetometric technique to measure the magnetic anisotropy field in nanostructured ferromagnetic thin films. This technique utilizes a magneto-optical Kerr effect microscope equipped with two-axis electromagnets. By measuring the out-of-plane hysteresis loops and then analyzing their saturated magnetization with respect to the in-plane magnetic field, the magnetic anisotropy field is uniquely quantified within the context of the Stoner-Wohlfarth theory. The present technique can be applied to small nanostructures, enabling in-situ determination of the magnetic anisotropy field of nanodevices.

• 대한기계학회논문집B
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• 제29권11호
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• pp.1182-1188
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• 2005

An x-ray PIV (Particle Image Velocimetry) technique was developed to measure quantitative information on flows inside opaque conduits and on opaque-fluid flows. At first, the developed x-ray PIV technique was applied to flow in an opaque Teflon tube. To acquire x-ray images suitable for PIV velocity field measurements, refraction-based edge enhancement mechanism was employed using detectable tracer particles. The optimal distance between with the sample and detector was experimentally determined. The resulting amassed velocity field data were in reasonable agreement with the theoretical prediction. The x-ray PIV technique was also applied to blood flow in a microchannel. The flow pattern of blood was visualifed by enhancing the diffraction/interference -bas ed characteristic s of blood cells on synchrotron x-rays without any contrast agent or tracer particles. That is, the flow-pattern image of blood was achieved by optimizing the sample (blood) to detector distance and the sample thickness. Quantitative velocity field information was obtained by applying PIV algorithm to the enhanced x-ray flow images. The measured velocity field data show a typical flow structure of flow in a macro-scale channel.