• Journal of the Korean Society of Radiology
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• v.18 no.3
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• pp.249-256
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• 2024

The study aimed to evaluate the efficacy of treatment plans using full Arc and Partial Arc Coplanar volumetric modulated arc therapy and Non-Coplanar volumetric modulated arc therapy to minimize radiation treatment side effects, such as pneumonia, and protect normal organs in esophageal cancer radiotherapy. 30 patients who underwent Concurrent Chemoradiotherapy for esophageal cancer were included. Compared planning target volume, lung, heart, spinal cord and total monitor units among three treatment plans: fVMAT(2 Full Arc), pVMAT(4 Partial Arc), and ncVMAT(2 Partial Arc + 2 Non-Coplanar Arc). All plans met the PTV criteria, showing uniform distribution. The average dose to the heart was 5.8 Gy for fVMAT, 6.97 Gy for pVMAT, and 7.6 Gy for ncVMAT, with the lowest value in fVMAT, which was statistically significant. However, the average lung dose was 9.01 Gy for fVMAT, 7.71 Gy for pVMAT, and 7.12 Gy for ncVMAT, with V_5Gy(%) values of 52.22%, 38.61%, 36.35% and V_10Gy(%) values of 37.8%, 27.33%, 24.15% respectively. ncVMAT showed the lowest values, while fVMAT had the highest, with statistical significance. In conclusion, ncVMAT effectively reduces lung radiation exposure in esophageal cancer radiotherapy, potentially reducing the incidence of side effects such as pneumonia. However, considering factors like setup accuracy and treatment time, applying an appropriate treatment plan may lead to better outcomes.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.637-637
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• 2012

본 연구에서는 내수침수 저감을 위하여 효율적(effective)인 우수저류조 설치에 따른 침수저감효과 극대화 방안을 제시하고자 한다. 여기서 효율성(effectiveness)은 침수저감량의 극대화 측면과 비용의 최소화 측면 두 가지로 구분된다. 최적 방재 시설물의 설치는 단순 설치비용 대비 저감량이 가장 큰 안을 제시하는 것은 의미가 없으며 일정 기준 이상의 방재성능을 발휘하면서 주어진 예산안에서 최적안을 찾아야 하므로 비용의 최소화 측면과 침수 저감량, 즉 맨홀에서의 월류 저감량을 최대화 하는 두 가지의 목적을 동시에 달성해야 한다. 따라서 본 연구에서는 다목적 최적화 알고리즘의 적용을 통하여 우수저류조 최적 설치지점을 선정하는 기법을 제안하였다. 본 연구에 적용한 다목적 최적화 방법으로는 목적함수의 최적해 탐색 효용성 측면에서 우수하다고 평가되고 있는 유전자 알고리즘을 적용하였다. 다목적 최적화의 경우 해의 우열을 판단하기 위한 적합도 함수는 실제 각 목적함수의 적합도 값(real fitness value)이 아닌 해의 상대적인 우열(dominance or non-dominance)에 따라 부여되는 등급(rank)에 의해서 해의 우열이 결정되며 여기서는 Fonseca and Fleming(1993)이 제안한 Ranking method를 적용하여 적합도를 결정하였다. 한편 도시 우수관망의 해석 및 우수저류조 설치에 따른 월류량 분석을 위하여 미 환경청(US Environmental Protection Agency; EPA)에서 제공하고 있는 EPA-SWMM 5.0 engine을 사용하였으며 최적화 알고리즘의 구성을 위하여 Visual C++와 SWMM DLL을 연동하여 사용하였다. 연구 대상유역은 인천 청라지구(3공구)를 대상으로 기법의 적용성을 검토하였으며 저류지 설치에 따른 비용함수는 EPA(2002)에서 제안한 저류지 체적대비 공사비용을 원화로 환산한 후 청라지구의 공시지가를 고려하여 결정하였다. 최적화 기법의 적용 결과 저류지 설치비용에 따라 최대로 월류량을 저감시킬 수 있는 우수저류조 최적 설치위치의 조합(Pareto-front)을 결정할 수 있었다.

• Journal of the Korean Society of Radiology
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• v.11 no.5
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• pp.303-312
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• 2017

The central goal of Gamma Knife radiosurgery(GKRS) is to maximize the conformity of the prescription isodose surface, and to minimize the radiation effect of the normal tissue surrounding the target volume. There are the various kinds of indices related with the quality of treatment plans such as conformity index, coverage, selectivity, beam-on time, gradient index(GI), and conformity/gradient index(CGI). As the best treatment plan evaluation tool, we must check by all means conformity index, GI, and CGI among them. Specially, GI and CGI related with complication of healthy normal tissue is more indispensible than conformity index. Then author calculated and statistically analysed CGI, the newly defined conformity/gradient index as well as GI being applied widely using the treatment planning system Leksell GammaPlan(LGP) and the verification method Variable Ellipsoid Modeling Technique(VEMT). In the study 10 patients with intracranial lesion treated by GKRS were included. Author computed the indices from LGP and VEMT requiring only four parameters: the prescribed isodose volume, the volume with dose > 30%, the target volume, and the volume of half the prescription isodose. All data were analyzed by paired t-test, which is statistical method used to compare two different measurement techniques. No statistical significance in GI at 10 cases was observed between LGP and VEMT. Differences in GI ranged from -0.14 to 0.01. The newly defined gradient index calculated by two methods LGP and VEMT was not statistically significant either. Author did not find out the statistical difference for the prescribed isodose volume between LGP and VEMT. CGI as the evaluation index for determining the best treatment plan is not significant statistically also. Differences in CGI ranged from -4 to 3. Similarly newly defined Conformity/Gradient index for GKRS was also estimated as the metric for the evaluation of the treatment plans through statistical analysis. Statistical analyses demonstrated that VEMT was in excellent agreement with LGP when considering GI, new gradient index, CGI, and new CGI for evaluating the best plans of GKRS. Due to the application of the fast and easy evaluation tool through LGP and VEMT author hopes CGI and newly defined CGI as well as gradient indices will be widely used.

• The Journal of Korean Society for Radiation Therapy
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• v.34
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• pp.43-50
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• 2022

Objective: The purpose of this study is to choose a treatment plan and equipment to maximize tangential irradiation to protect the normal brain tissues as much as possible during total scalp irradiation. Subjects and Methods: After zoning the total scalp of a phantom and selecting a target area for treatment, the study made a Helical TomoTherapy(HT) plan, a Helical TomoTherapy with a Complete Block(HTCB) plan, and a Volumetric Modulated Arc Therapy(VMAT) plan. All of these plans made sure that the volume of a treatment plan with 95% of a prescription dose(40 Gy) would not exceed 95% of the entire volume and that Dmax would not be more than 110% of the prescription dose. The therapy plans compared doses among organs at risk of damage including the brain. Doses in the brain tissues were assessed based on the volumetric criteria for normal tissues in Emami et al. Results: HT, HTCB, and VMAT had a dose of 21.68 Gy, 13.75 Gy, and 20.89 Gy, respectively, in brain tissues at D_33%, a dose of 7.06 Gy, 3.21 Gy, and 7.84 Gy, respectively, at D_67%, and a dose of 3.14 Gy, 1.75 Gy, and 3.84 Gy, respectively, at D_100%. They recorded a Dmean of 16.64 Gy, 11.78 Gy, and 16.64 Gy, respectively. These results show that the overall dose was low in the HTCB plan. When the volume of a low dose was calculated based on 5 Gy, they recorded 87%, 49%, and 96%, respectively, in V_5Gy. In addition, the maximum dose in the remaining organ(brain stem, hippocampus, and both lenses) except for the optic pathway was the lowest in HTCB Conclusion: The findings demonstrate that TomoTherapy with a complete block minimized a dose in organs at risk of damage including the brain and hippocampus on both sides and accordingly reduced the probability of side effects such as radiation-induced brain injuries and a resulting decrease in neurocognitive functions. In addition to total scalp irradiation, if additional studies on ring targets treated in various areas are conducted to establish the benefits of tangential irradiation, it is believed that TomoTherapy using Complete Block can be used to maximize tangential irradiation in treatment planning.

• Proceedings of the Korean Society For Composite Materials Conference
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• 1999.11a
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• pp.227-233
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• 1999

This study is mainly concerned with phenomenon of cavitation-erosion on the several materials and corrosive liquids which were applied with vibrator (suggested by ASTM G-32, 20KHZ, 24{$mu}m$).The main results obtained are summarized as follows ; (1) The maximum erosion rate by cavitation erosion in both of fresh-water and sea-water appeared to be proportioned to their hardness and tensile strength. (2) Cavitation weight loss and rate of cast iron in sea-water condition were greater (approximately 3 times) than that in distilled-water condition, however in case of stainless and brass the cavitation weight loss and their rates were not so different in both of their conditions. (3) Cavitation weight loss of composite materials were shown as below on this test, DuraTough DL : Weight loss in sea-water condition were greater (approximately 2.3 times) than it's fresh-water condition. (4) As the result of observation with digital camea of specimens, the main tendency of cavitation erosion for metals, was that small damaged holes causing by cavitation e개sion was appeared with radial pattern, and composites materials was that small damaged holes were appeared randomly.

• Korean Journal of Optics and Photonics
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• v.10 no.2
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• pp.120-127
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• 1999

We discussed two main types-conformal and non-conformal (powered) - of holographic combiner. A theoretical model based on the Kogelnik's coupled wave theory was used to illustrate bandwidth and efficiency properties. Also we showed numerical values for the aberrations that are induced by a wavelength shift from construction to reconstruction and found optimum coordinates to reduce the chrolatic aberation of construction beams using aberration balancing techniques. The holographic combiner manufactured in conformal type with 60$^{\circ}$ incidence angle at 514.5 nm had narrow angular bandwidth (FWHM) of 4.1" and spectral bandwidth of 11.4 nm, while non-conformal one with 50$^{\circ}$, 30$^{\circ}$ incidence angle at 514.5 nm showed spectral and angular bandwidth of 10.7 nm and 5.5$^{\circ}$, respectively.vely.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.105-105
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• 2021

본 연구에서는 2차원 비선형 천수모형과 수심평균된 스칼라 이송모형을 해석하는 수치모형에 대해 기술하였다. 수치모형의 정확성을 보장함과 동시에 안정성을 높이기 위해 유한체적법, 플럭스 재구성 및 minmod 제한자를 사용하였다. 비선형 천수방정식의 이송항과 바닥 경사항은 계산된 수심의 양수 보존과 흐름의 정상 상태를 보장하기 위한 second order well-balanced positivity preserving central-upwind method를 이용하여 수치적으로 이산화되었다. 마찬가지로, 이송-확산 방정식 내 이송항은 동일한 2차 풍상차분법을 통해 수치적으로 풀이하였다. 격자점 경계면에서의 불연속으로 인한 수치진동을 방지하기 위해 이송항의 계산에 포함된 보존항의 차이로 인해 발생하는 스칼라의 수치확산을 최소화하기 위해 무차원의 비소산함수를 도입하였다. 또한, 확산항은 유한차분법을 이용하여 이산화하였다. 제안된 수치모형은 시간미분항의 계산을 위해 오일러 기법을 적용하여 계산된 수심 및 스칼라의 양수 보존여부와 함께 정지된 흐름의 정상 상태의 보존여부를 확인하였다. 제안된 수치모형의 해석 정확성을 평가하기 위해 1, 2차원 공간 내 다양한 흐름 조건에서의 해석해를 이용한 3개의 벤치마크 테스트를 수행하였다. 평균 제곱근 오차(Root Mean Squared Error, RMSE)를 산정하여 수치모형의 성능을 정량적으로 평가하였으며, 비소산함수를 적용함에 따라 스칼라의 수치확산이 감소하게 되었음을 확인하였다. 또한, 세 차례의 벤치마크 테스트 결과는 공통적으로 수치모형에 의해 계산된 결과값이 비소산함수를 고려함에 따라 해석해와 잘 일치함을 확인하였다.

• The Journal of Korean Society for Radiation Therapy
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• v.24 no.2
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• pp.85-93
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• 2012

Purpose: It is essential to minimize the respiratory-induced motion of involved organs in the Tomotherapy for tumor located in the chest and abdominal region. However, the application of breathing control system to Tomotherapy is limited. This study was aimed to investigate the possible application of the ABCHES system and its efficacy as a means of breathing control in the tomotherapy treatment. Materials and Methods: Five subjects who were treated with a Hi-Art Tomotherapy system for lung, liver, gallbladder and pancreatic tumors. All patients undertook trained on two breathing methodes using an ABCHES, free breathing methode and shallow breathing methode. When the patients could carry out the breathing control, 4D-CT scan was a total of 10 4D tomographic images were acquired. A radiologist resident manually drew the tumor region, including surrounding nomal organs, on each of CT images at the inhalation phase, the exhalation phase and the 40% phase (mid-inhalation) and average CT image. Those CT images were then exported to the Tomotherapy planning station. Data exported from the Tomotherapy planning station was analyzed to quantify characteristics of dose-volume histograms and motion of tumors. Organ motions under free breathing and shallow breathing were examined six directions, respectively. Radiation exposure to the surrounding organs were also measured and compared. Results: Organ motion is in the six directions with more than a 5 mm displacement. A total of 12 Organ motions occurred during free breathing while organ motions decreased to 2 times during shallow breathing under the use of Abches. Based on the quantitative analysis of the dose-volume histograms shallow breathing showed lower resulting values, compared to free breathing, in every measure. That is, treatment volume, the dose of radiation to the tumor and two surrounding normal organs (mean doses), the volume of healthy tissue exposed to radiation were lower at the shallow breathing state. Conclusion: This study proposes that the use of ABCHES is effective for the Tomotherapy treatment as it makes shortness of breathing easy for patients. Respiratory-induced tumor motion is minimized, and radiation exposure to surrounding normal tissues is also reduced as a result.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.8
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• pp.759-769
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• 2013

Electronic equipment has been applied to virtually every area associated with commercial, industrial, and military applications. Specifically, electronics have been incorporated into avionics components installed in aircraft. This equipment is exposed to dynamic loads such as vibration, shock, and acceleration. Especially, avionics components installed in a helicopter are subjected to simultaneous sine and random base excitations. These are denoted as sine on random vibrations according to MIL-STD-810F, Method 514.5. In the past, isolators have been applied to avionics components to reduce vibration and shock. However, an isolator applied to an avionics component installed in a helicopter can amplify the vibration magnitude, and damage the chassis, circuit card assembly, and the isolator itself via resonance at low-frequency sinusoidal vibrations. The objective of this study is to investigate the dynamic characteristics of an avionics component installed in a helicopter and the structural dynamic modification of its tray plate without an isolator using both a finite element analysis and experiments. The structure is optimized by dynamic loads that are selected by comparing the vibration, shock, and acceleration loads using vibration and shock response spectra. A finite element model(FEM) was constructed using a simplified geometry and valid element types that reflect the dynamic characteristics. The FEM was verified by an experimental modal analysis. Design parameters were extracted and selected to modify the structural dynamics using topology optimization, and design of experiments(DOE). A prototype of a modified model was constructed and its feasibility was evaluated using an FEM and a performance test.

• Progress in Medical Physics
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• v.27 no.1
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• pp.14-24
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• 2016

Since the head and neck region is densely located with organs at risk (OAR), OAR-sparing is an important issue in the treatment of head and neck cancers. This study-in which different treatment plans were performed varying the head tilt angle on brain tumor patients-investigates the optimal head elevation angle for sparing normal organs (e.g. the hippocampus) and further compares the dosimetric characteristics of different types of radiation equipment. we performed 3D conformal radiation therapy (3D-CRT), intensity-modulated radiation therapy (IMRT), and tomotherapy on 10 patients with brain tumors in the frontal lobe while varying the head tilt angle of patients to analyze the dosimetric characteristics of different therapy methods. In each treatment plan, 95% of the tumor volume was irradiated with a dose of 40 Gy in 10 fractions. The step and shoot technique with nine beams was used for IMRT, and the same prescription dose was delivered to the tumor volume for the 3D-CRT and tomotherapy plans. The homogeneity index, conformity index, and normal tissue complication probability (NTCP) were calculated. At a head elevation angle of $30^{\circ}$, conformity of the isodose curve to the target increased on average by 53%, 8%, and 5.4%. In 3D-CRT, the maximum dose received by the brain stem decreased at $15^{\circ}$, $30^{\circ}$, and $40^{\circ}$, compared to that observed at $0^{\circ}$. The NTCP value of the hippocampus observed in each modality was the highest at a head and neck angle of $0^{\circ}$ and the lowest at $30^{\circ}$. This study demonstrates that the elevation of the patients' head tilt angle in radiation therapy improves the target region's homogeneity of dose distribution by increasing the tumor control rate and conformity of the isodose curve to the target. Moreover, the study shows that the elevation of the head tilt angle lowers the NTCP by separating the tumor volume from the normal tissues, which helps spare OARs and reduce the delivered dose to the hippocampus.