• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.2D
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• pp.311-318
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• 2009

Interactive terrain visualization is an important research area with applications in GIS, games, virtual reality, scientific visualization and flight simulators, besides having military use. This is a complex and challenging problem considering that some applications require precise visualizations of huge data sets at real-time rates. In general, the size of data sets makes rendering at real-time difficult since the terrain data cannot fit entirely in memory. In this paper, we suggest the effective Real-time LOD(level-of-detail) algorithm for displaying the huge terrain data and processing mass geometry. We used a hierarchy structure with $4{\times}4$ and $2{\times}2$ tiles for real-time rendering of mass volume DEM which acquired from Digital map, LiDAR, DTM and DSM. Moreover, texture mapping is performed to visualize realistically while displaying height data of normalized Giga Byte level with user oriented terrain information and creating hill shade map using height data to hierarchy tile structure of file type. Large volume of terrain data was transformed to LOD data for real time visualization. This paper show the new LOD algorithm for seamless visualization, high quality, minimize the data loss and maximize the frame speed.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.219-219
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• 2022

지구 온난화와 함께 발생하는 해수면 상승은 한반도의 해안지역을 비롯하여 울릉도 등 도서지역 전반에 걸쳐 진행 중이다. 또한 해수면의 온도 상승으로 인한 열대저기압의 생성 시 에너지 공급이 증가하며 연안으로 내습하는 파랑 내습 에너지가 커지게 된다. 경상북도 울릉군에 위치한 남양항은 최근 2019년 태풍 다나스 및 2020년 태풍 마이삭 등에 의해 고파랑 혹은 침수 피해가 발생하여 항 내에서는 물양장과 선박이 파괴되고 방파제가 전도되는 등의 피해가 속출하였다. 동해안의 태풍 내습, 지구 온난화와 저기압 발달에 의한 수위 상승 등과 같은 다양한 해양기후를 고려한 연안 구조물의 파랑 영향을 검토하는 것이 중요할 것으로 판단되었다. 기상청 태풍센터에서 제공하는 1979년부터 2020년까지 한반도 해역에 내습한 태풍 중 울릉도에 영향을 미친 태풍은 18개로 울릉도 인근에 영향을 준 내습 태풍을 10년 단위로 분석해 보면, 1980년대 3개, 1990년대 2개, 2000년대 8개, 2010년대 3개, 2020년 2개로 2000년대에 울릉도 영향권에 들어간 태풍이 가장 많았으며, 심해파 추산 기간 이후 2020년 1년 동안 울릉도 인근으로 마이삭, 하이선과 같은 2개의 태풍이 연속적으로 영향을 주었다. 울릉도에 영향을 미친 18개 태풍을 대상으로 일본 기상청(JMA)에서 제공하는 1시간 바람장을 이용하여 파랑 후측 수치 모의를 수행하였으며, 해양수산부와 기상청 관측 부이를 이용하여 파랑에 대한 정확도를 확보하였다. 고파랑 내습 시 연안에 조우하는 수위 조건은 파랑 에너지의 증가를 결정하게 되며, 항만 구조물의 설계에 적용되고 있는 약최고고조위 이상(4대분조의 최대 조위)의 최극조위 조건에서 해안 구조물에 월파 및 침수 피해를 주는 요인으로 작용할 수 있다. 이를 바탕으로 울릉도 남양항에서 폭풍 시 내습한 최극고조위(0.65m)와 IPCC 5차 보고서에 제시한 최악의 시나리오(RCP 8.5) 조건에서 울릉도에서 확인된 0.79 cm 상승고를 반영하여 범람위험평가를 광역에서의 계산 결과를 입력자료로 하여 준 3차원 비 정수압 파랑 변형 수치 모형인 MIKE 3 Wave를 사용하여 실험하였다. 해수면 상승에 의한 수위 상승고는 연안 파랑 증가에 영향을 주었으며 연안 구조물의 침수 피해에 영향을 줄 것으로 판단되었다. 월파 차단, 파랑 차폐의 목적으로 건설되는 구조물의 규모 및 천단고 등을 설정하는데 설계 수위의 선정은 중요하다. 수치 실험 결과를 바탕으로 방파제 및 호안의 범람 위험 평가를 수행하고 구조물 설계 시 이러한 해수면 상승고가 반영된 설계가 중요하다는 것을 위험 평가를 통해 확인할 수 있다.

• Information Systems Review
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• v.23 no.3
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• pp.177-200
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• 2021

Recently, the use of prepaid electronic payments such as electronic wallets, digital currency and prepaid points is gradually increasing. Prepaid electronic payments has the characteristic of being used after charging first. This study empirically investigated the factors affecting the intention to use online charging in order to help improve the service that require prepaid recharge by applying transformed TAM. Since there are not many previous studies for the intention to use online charging, we extract factors through preceding researches for electronic cash and mobile easy payment. Also we analyze the intention to use online charging for transportation card users, focusing on the moderating effects. As a result of the study, it was found that 'convenience', 'ubiquity', and 'self-efficacy' among the independent variables had a positive (+) effect on mediation variable 'perceived usefulness'. 'Perceived usefulness' was analyzed to have a significant influence on the dependent variable 'usage intention'. According to users' gender, internet usage time, internet shopping frequency, online charging frequency and transportation card usage type, the moderating effect was significant on 'perceived usefulness' and 'usage intention'. As an implication, it was suggested that service improvement and differentiated marketing are needed in direction of increasing the usefulness of services. Additional research directions were proposed for services such as e-wallets, prepaid points and digital currencies by adding other factors and moderate variables.

• Korean Journal of Environment and Ecology
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• v.37 no.5
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• pp.318-326
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• 2023

The floristic target species (FTS) has been widely used as a important tool for environmental assessment in Korea. Here the floristic district is a key criterion for the selection and evaluation of FTS. The aim of this study is to clarify the intellectual meaning of the floristic district i.e. a sort of phytogeographical subunit. We reviewed 7 main literatures related to the floristic district. Nakai's 1919 Ulleungdo flora survey report was first to mention a region and/or province in terms of general geographical divisions. In 1977, the floristic district map of the Korea vascular plants was first described by Oh. In 1978, Lee & Yim proposed a new floristic district map dividing the central and southern regions, and the district boundaries have been adjusted by many other researchers. In the end, the floristic district map modified slightly from Lee & Yim's map was nationally recognized in 2018. However, the boundaries of floristic districts were inconsistent, both in their setting and adjustment, as well as the indicator species of the district. No basis for this inconsistency could be confirmed. We concluded that all district maps depend on arbitrary lines drawn a priori, and finally proposed the following two ecological strategies to ensure the effectiveness and practicality of the FTS as a scientific means for environmental impact assessment and national flora evaluation: (i) designing to achieve the flora list and the floristic district based on nativeness of plant distribution, (ii) constructing a habitat-based floral monitoring system.

• Radiation Oncology Journal
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• v.27 no.2
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• pp.91-102
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• 2009

Purpose: To compare the accuracy and efficacy of EDR2 film, a 2D ionization chamber array (MatriXX) and an amorphous silicon electronic portal imaging device (EPID) in the pre-treatment QA of IMRT. Materials and Methods: Fluence patterns, shaped as a wedge with 10 steps (segments) by a multi-leaf collimator (MLC), of reference and test IMRT fields were measured using EDR2 film, the MatriXX, and EPID. Test fields were designed to simulate leaf positioning errors. The absolute dose at a point in each step of the reference fields was measured in a water phantom with an ionization chamber and was compared to the dose obtained with the use of EDR2 film, the MatriXX and EPID. For qualitative analysis, all measured fluence patterns of both reference and test fields were compared with calculated dose maps from a radiation treatment planning system (Pinnacle, Philips, USA) using profiles and $\gamma$ evaluation with 3%/3 mm and 2%/2 mm criteria. By measurement of the time to perform QA, we compared the workload of EDR2 film, the MatriXX and EPID. Results: The percent absolute dose difference between the measured and ionization chamber dose was within 1% for the EPID, 2% for the MatriXX and 3% for EDR2 film. The percentage of pixels with $\gamma$%>1 for the 3%/3 mm and 2%/2 mm criteria was within 2% for use of both EDR2 film and the EPID. However, differences for the use of the MatriXX were seen with a maximum difference as great as 5.94% with the 2%/2 mm criteria. For the test fields, EDR2 film and EPID could detect leaf-positioning errors on the order of -3 mm and -2 mm, respectively. However it was difficult to differentiate leaf-positioning errors with the MatriXX due to its poor resolution. The approximate time to perform QA was 110 minutes for the use of EDR2 film, 80 minutes for the use of the MatriXX and approximately 55 minutes for the use of the EPID. Conclusion: This study has evaluated the accuracy and efficacy of EDR2 film, the MatriXX and EPID in the pre-treatment verification of IMRT. EDR2 film and the EPID showed better performance for accuracy, while the use of the MatriXX significantly reduced measurement and analysis times. We propose practical and useful methods to establish an effective QA system in a clinical environment.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.517-528
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• 2007

Domestic or international existing researches regarding rail damage factors are focused on laying, vehicle conditions, driving speed and driving habits and overlook characteristics of track structure (elasticity, maintenance etc). Also in ballast track, as there is no special lateral spring stiffness of track also called as ballast lateral resistance in concrete track, generally, existing study shows concrete track has 2 time shorter life cycle for rail replacement than ballast track due to abrasion. As a result of domestic concrete track design and operation performance review, concrete track elasticity is lower than track elasticity of ballast track resulting higher damage on rail and tracks. Generally, concrete track has advantage in track elasticity adjustment than ballast track and in case of Europe, in concrete track design, it is recommended to have same or higher performance range of vertical elastic stiffness of ballast track but domestically or internationally review on lateral spring stiffness of track is very minimal. Therefore, through analysis of service line track on site measurement and analysis on performance of maintenance, in this research, dynamic characteristic behaviors of commonly used ballast and concrete track are studied to infer elasticity of service line track and experimentally prove effects of track lateral spring stiffness that influence curved rail damage as well as correlation between track elasticity by track system and rail damage to propose importance of appropriate elastic stiffness level for concrete and ballast track.

• Radiation Oncology Journal
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• v.11 no.1
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• pp.69-77
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• 1993

Treatment of cerebellar medulloblastoma has been much improved with modern surgical technique for gross total tumor removal and adequate radiation therapy for the whole craniospinal axis. Questions have been arosen about the optimal radiation dose for the preventive treatment of whole cranium and whole spinal axis. Recently, many authors have reported their treatment results as comparable to older data, using lower than conventional dose of 3,600 cGy-4,000 cGy. For 50 patients treated between 1981 and 1990 at the Department of Radiation Therapy of SNUH, retrospective analysis was done for the treatment result, especially the neuraxis control, by radiation dose for the presymptomatic area of the disease. Analysis only by total spinal dose did not give any significant difference. But further analysis by following patient group; 3,600 cGy/150 cGy (n=6), 3,000 cGy/150 cGy (n=10), 2,400 cGy/150 cGy (n=17) and 2,400 cGy/100-120 cGy (n=11) showed significant improvement of neuraxis control by decreasing order (p =0.003). There was no significant difference in overall survival between the groups. For the 19 patients who had been confirmed initially as having no neuraxis disease, TDF 30 was the cur-off value that could prevent neuraxis failure (p =0.004). We couldn't define any TDF value that give reasonable control for the patient group with positive CSF study at initial diagnosis.

• Radiation Oncology Journal
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• v.11 no.2
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• pp.267-275
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• 1993

Eighty five patients of oral cavity cancer, treated with radiation at the Department of Therapeutic Radiology, Korea Cancer Center Hospital, during the period from March 1985 to September 1990 were analyzed retrospectively. Among 85 patients, 37 patients were treated with radiation only and 48 patients were treated with radiation following surgery. And 70 patients received external irradiation only by $^{60}Co$ with or without electron, the others were 7 patients for external irradiation plus interstitial implantation and 8 patients for external irradiation plus oral cone electron therapy. Primary sites were mobile tongue for 40 patients, mouth floor for 17 patients, palate for 12 patients, gingiva including retromolar trigone for 10 patients, buccal mucosa for 5 patients, and lip for 1 patient. According to pathologic classification, squamous cell carcinoma was the most common (77 patients). According to AJC TNM stage, stage I + II were 28 patients and stage III+IV were 57 patients. Acturial overall survival rate at 3 years was $43.9\%,$ 3 year survival rates were $60.9\%$ for stage I + II, and $23.1\%$ for stage III+IV, respectively. As a prognostic factor, primary T stage was a significant factor (p<0.01). The others, age, location, lymph node metastasis, surgery, radiation dose, and cell differentiation were not statistically significant. Among those factors, radiation plus surgery was more effective than radiation only in T3+T4 or in any N stage although it was not statistically sufficient (p<0.1). From those results, it was conclusive that definitive radiotherapy was more effective than surgery especially In the view of pertainig of anatomical integrity and function in early stage, and radiation plus surgery was considered to be better therapeutic tool in advanced stage.

• Nuclear Medicine and Molecular Imaging
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• v.43 no.4
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• pp.287-293
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• 2009

Purpose: This study is to evaluate rib fractures on bone scan in breast cancer patients treated with breast cancer surgery and radiation therapy and to evaluate its relation with radiation therapy and operation modality. Materials and Methods: Two hundred seventy cases that underwent serial bone scan after breast cancer surgery and radiation therapy were enrolled. Bone scan and chest a findings of rib fracture were analyzed. Results: The rib uptake was seen in 74 of 270 cases (27.4%) on bone scan and 50 cases (18.5%) were confirmed to have rib fracture by chest CT. The rate of modified radical mastectomy in patients with rib fracture was significantly higher than that in patients without rib fracture (66.0% vs. 27.0%, p = 0.000). The rate of additional radiation therapy to axillar or supraclavicular regions in patients with rib fracture was significantly higher than that in patients without rib fracture (62.0% vs. 28.6%, p =0.000). Rib fracture was seen most frequently at 1-2 years after radiation therapy (51.9%) and single rib fracture was seen most frequently (55.2%). Of total 106 rib fractures, focal rib uptake was seen in 94 ribs (88.7%) and diffuse rib uptake was seen in 12 ribs (11.3%). On one year follow-up bone scan, complete resolution of rib uptake was seen in 15 ribs (14.2%). On chest a, the rate of fracture line in ribs with intense uptake was significantly higher than that in ribs with mild or moderate uptake (p = 0.000). The rate of presence of fracture line in ribs with focal uptake was significantly higher than that in ribs with diffuse uptake (p = 0.001). Conclusion: Rib fracture in breast cancer patients after radiation therapy was related to radiation portal and operation modality. It should be interpreted carefully as a differential diagnosis of bone metastasis.

• The Journal of Korean Academy of Prosthodontics
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• v.53 no.4
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• pp.310-317
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• 2015

Purpose: The purpose of this study was to evaluate the validity of reference points for edentulous patient by examining the correlation of teeth and face, and intraoral anatomic landmarks. Materials and methods: We examined a facial outline, length, bizygomatic width, nasion - gnathion length, glabella - nasion distance in 270 men and 280 women satisfied with inclusion criteria from Seoul National School of Dentistry. The shape of maxillary central incisor, mesiodistal crown width and length of maxillary 6 incisors, distance from incisive papilla to labial surface of maxillary central incisor, and perpendicular distance from incisive papilla to intercanine line were measured in the stone model. We analyzed the ratio and relevant relation statistically. Results: The probability on having the same shape of face and the relative same shape maxillary incisor was 55.56% and 46.43% for men and women. The facial length proved to be a more valuable measurement in women in the tooth selection. The ratio of bizygomatic width to mesiodistal width of maxillary central incisor, and the ratio of bizygomatic width to width of maxillary 6 incisors were 16.8 : 1 and 3.0 : 1 and were positively correlated with each other. The distance of the canines from the maxillary incisal papilla was $1.33{\pm}1.28mm$. The distance between the center of the incisal papilla and the labial surface of their maxillary central incisor was $9.23{\pm}1.20mm$. Conclusion: It was showed that anatomical reference points in tooth selection and arrangement for edentulous patient are useful and have validity in our limited study.