• Radiation Oncology Journal
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• v.13 no.3
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• pp.277-283
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• 1995

Purpose : This study was performed to measure dose alteration at the air-tissue interface resulting from rebuild-up to the loss of charged particle equilibrium in the tissues around the air-tissue interfaces. Materials and Methods : The 6 and 10-MV photon beam in dual energy linear accelerator were used to measure the surface dose at the air-tissue interface The polystyrene phantom sized $25{\times}25{\times}5\;cm^3$ and a water phantom sized $29{\times}29{\times}48\;cm^3$ which incorporates a parallel-plate ionization chamber in the distal side of air gap were used in this study. The treatment field sizes were $5{\times}5\;cm^2,\;10{\times}10\;cm^2\;and\;20{\times}20\;cm^2$. Air cavity thickness was variable from 10 mm to 50 mm. The observed-expected ratio (OER) was defined as the ratio of dose measured at the distal junction that is air-tissue interface to the dose measured at the same point in a homogeneous phantom. Results : In this experiment, the result of OER was close or slightly over than 1.0 for the large field size but much less (about 0.565) than 1.0 for the small field size in both photon energy. The factors to affect the dose distribution at the air-tissue interface were the field size, the thickness of air cavity. and the photon energy. Conclusion : Thus, the radiation oncologist should take into account dose reduction at the air-tissue interface when planning the head and neck cancer especially pharynx and laryngeal lesions, because the dose can be less nearly $29{\%}$ than predicted value.

• The Journal of Engineering Geology
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• v.11 no.1
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• pp.101-113
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• 2001

Structural and geological engineering properties of the rock mass distributed in the Yokmang mountain area were investigated to detenninc the usable cut-out volume and quarrying efficiency. The study area is located in the southern tip of the Yangsan fault system which controls the geological structure of the Kvungsang basin. As a result, the study area is mainly composed of andesicic. rhyolitic. and granitic rocks of the Cretaceous Kyungsang Supergroup and a series of right-handed strike-slip faults is developed along NNE-SSW direction. These regional faults significantly affect the spatial and meclwnical characteristics of joints such as spacing, frequency, and compressive strength. The joint frequency is highest along the fault zones and decreases toward the remote region. Based on the geological information obtained from the field survey, the detailed structure of the Yokmang mountain was analyzed and the volume of the rock mass was assessed. Considering the minimum rock block size required for the construction of a coastal dumping site, potential cut-out volume is then estimated to be 4,018,000m$^3$ the volume % of which is 48% of Yokmang mountain including the soil and weathered rock and 61% of the unweathered rock mass.

• Weed & Turfgrass Science
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• v.2 no.3
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• pp.260-266
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• 2013

This study was conducted to investigate changes of vegetation and soil characteristics to tidal land of Saemangeum reclaimed land from 2010 to 2012. Soil salinity was 0.16-22.3 dS $m^{-1}$ in the first survey, while the three years later, it was decreased to 0.12-4.22 dS $m^{-1}$. Vegetations were classified as 6 families and 26 species but it was increased to 8 families and 31 species after three years. Numbers of average species in survey site were increased from 7.1 species to 10.6 species. Numbers of vegetation were increased at each survey sites except for survey site 7 : there was decreased halophyte according to decrease in the soil salinity. Biomass production was increased at low production site, and showed highest production in area of dominant vegetation as Phragmites communis. Simpson's dominance ratio(SDR) of main vegetation as Phragmites communis, Calamagrostis epigeios were increased but Suaeda maritima, Salicornia europaea, Puccinellia nipponica and Zoysia sinica were decreased.

• Journal of the Korean Geographical Society
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• v.52 no.1
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• pp.105-122
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• 2017

The purpose of this study is to understand the urbanization process and identify the Origin-Destination(O-D) of migration in the period of the Japanese occupation, based on the census data about Bu and Jijung-myeon. For this, the study analysed the types and the location of the immigrants' origin(birthplace) whose headed for an urban area. In 1930, as the destinations in the inter-regional migration, the urban areas could be divided into three categories according to the distance: long-, medium- and short-distance. The new urban areas which developed for effective colonial rule by Japanese pulled the long distance immigrant across the Korean Peninsula, and the Chosun Dynasty's traditional cities had the inflow of population from the near and hinterland. All in all, it is proposed that the dual settlement systems of colonial and traditional structures, is the key to understand the Korean urbanization processes basedd on the inter-regional migration during Japanese colonial period.

• Proceedings of the Korea Contents Association Conference
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• 2011.05a
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• pp.191-192
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• 2011

X선 촬영을 통한 집단 건강검진은 경제성, 신속성, 대량처리 능력을 충족시키고 있으며 찾아가는 이동 의료서비스에서 중요한 부분을 차지하고 있다. 이와 함께 X선 촬영을 통한 집단 건강검진 시스템도 발전하여 간접촬영방식에서 Digital Radiography를 이용한 직접촬영방식으로 기술력이 향상되었고 이로써 검진차량에서 검진을 받는 환자나 종사자들에 대한 피폭선량의 증가하고 있으나 차량 외부의 누설방사선량에 대한 조사는 아직도 미미하다 할 수 있다[1]. 이에 본 연구에서 실험을 통한 결과는 다음과 같이 나타났다. 누설방사설량이 가장 많이 발생하는 곳은 출입문과 후면(검출기)에서는 우측, 양측면에서는 중앙이 가장 많은 누설방사선량이 나타났고, 측정위치별로는 검출기가 인접한 후면에서 누설방사선량이 가장 높았다. 기준치에 크게 벗어나지는 않았지만 누설방사선량은 다양하게 나타났다. 특히 후면에서의 누설방사선량은 기준치를 크게 웃돌아 방사선 차폐시설이 잘 갖추어지지 않은 것을 알 수 있으며 향후 이동검진차량의 방사선 차폐시설을 갖추는데 있어 각별한 관심이 필요하리라 사료된다.

• Journal of Korean Society of Disaster and Security
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• v.14 no.4
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• pp.29-36
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• 2021

Recently, due to climate change, the slope is increasing, and the risk of steep slope disasters such as the occurrence of slope collapse in the east coast and Busan region in 2019 and the Gokseong landslide in 2020 is increasing. Particularly, most national parks are made up of mountainous areas, and the risk of disasters on steep slopes is increasing. As the ground of the national park is aging and the weathering and jointing of the bedrock are accelerating due to climate change, the slope collapse and rockfall are increasing, and the annual number of visitors is increasing, it is necessary to manage steep slopes adjacent to multi-use facilities with many users. In this study, dangerous steep slopes that affect multi-use facilities in national parks were analyzed using GIS and verified through field surveys. As a process for extracting steep slopes adjacent to multi-use facilities in national parks, the slope was made in DEM and slopes of 34 degrees or higher were extracted. The difference between the maximum and minimum heights of the extracted slopes was used to confirm that the slopes met the standard for steep slopes, and the analysis of the slope direction was used to confirm whether it had an effect on the multi-use facilities. After that, precision aerial images and field photos were analyzed to finally identify risks at 4 sites, and field surveys were conducted. As a result of the field survey, all 4 sites were found to be steep slopes, 3 were graded D and 1 was graded C, so it was confirmed that management was required as a risk of collapse. All steep slopes extracted through GIS were found to be dangerous, so it is judged that the extraction of steep slopes through GIS would be appropriate.

• Journal of the Korean earth science society
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• v.24 no.5
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• pp.467-476
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• 2003

For the seafloor acoustic image mapping of side scan sonar, the beginning step of the procedure is to fix the absolute sonar (tow-fish) position since the sonar is not hull mounted but towed astern. The technical algorithm used to calculate the actual sonar position without any other additional sub-system, i.e., the underwater acoustic position tracking system or the sonar attitude measuring device, was proposed. In the seafloor image mosaic mapping results using the sonar track (not ship track) developed in this study, any ambiguity or inconsistency of seafloor features was not found. The incidental effect from the sonar position determination procedure orients the towing direction of sonar to be smooth, consequently the swath pattern on the across-track direction becomes stable and the blanking phenomenon of the insonification area is reduced conspicuously. This technical method is considered to be an useful tool when applied toother underwater towing vehicle surveys.

• The korean journal of orthodontics
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• v.41 no.3
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• pp.184-190
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• 2011

Objective: The purpose of this study was to investigate the relationship between the enamel thickness of proximal surfaces and the morphologic features of mandibular incisors. Methods: Mesiodistal/faciolingual (MD/FL) index, MD width, and height of contour width/cervical width ratio were measured in 40 incisors extracted from Koreans. For determining the height of contour width/cervical width ratio, the cervical width was measured as the distance between proximal cementoenamel junctions. Then, the labial surface was ground to the height of the contour level to measure enamel thickness. Pearson correlation analysis was used to investigate the correlation between enamel thickness and morphologic features. Results: Enamel thickness was $0.75{\pm}0.07mm$ per side, and MD width was $5.56{\pm}0.40mm$. Enamel thickness and MD width were significantly correlated. However, a significant relationship was not observed between enamel thickness and MD/FL index or the height of contour width/cervical width ratio. Conclusions: The results suggest that enamel thickness is affected only by MD width. Therefore, if the MD width is the same for mandibular incisors with a large MD/FL index or triangular shape and mandibular incisors with normal shape, then the limit of enamel reduction for reproximation will be the same.

• Journal of the korean academy of Pediatric Dentistry
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• v.49 no.1
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• pp.65-75
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• 2022

The aim of this study was to evaluate QLF (quantitative light-induced fluorescence) technology for the caries detection in primary teeth and validate the relationships between the cavity volume of carious lesions and QLF analysis results. Total 125 tooth surfaces include 53 occlusal surfaces, and 72 proximal surfaces were investigated with the portable QLF device for detection of dental caries in primary molars. Micro-CT radiograph was also performed to classify carious lesions and calculate the cavity volume. QLF showed good accuracy and reliability (sensitivity 0.75 - 0.94, specificity 0.82 - 0.95, and AUROC 0.88 - 0.98) for the caries detection in primary teeth except 𝚫R average results of proximal caries which showed relatively low values. Statistically significant relationships were found between 𝚫F average, QS-Index and the cavity volume according to Spearman rank-order correlation coefficients (r = 0.805 - 0.832, p < 0.001). QLF detection method would be a harmless and reliable way for children to diagnose dental caries without the concern about radiation exposure.

• Journal of Gastric Cancer
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• v.6 no.4
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• pp.263-269
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• 2006

Purpose: The aim of this study was to investigate the causes of under-staging in patients with advanced gastric cancer that was proven to be unresectable after a laparotomy. Materials and Methods: We retrospectively analyzed 25 gastric cancer patients who had undergone a diagnostic laparotomy between 2001 and 2005. For the preoperative evaluation, spiral CT and multidetector-row CT were performed. We analyzed the clinicopathologic features of patients and compared the image findings and the results of surgery. The causes of under-staging were divided into 3 groups; patient factor, CT factor, and interpretation factor. Results: Grossly, there were 12 cases of Borrmann type-III tumors and 13 cases of Borrmann type-IV tumors. The most frequent histologic type was poorly differentiated adenocarcinomas (8 cases) and signet ring cell carcinomas (7 cases). There were 13 cases of adjacent organ invasion, and the pancreas was the most frequently invaded organ (9 cases). There were 17 cases of peritoneal metastasis, and 3 cases of distant lymph node metastasis. For the cause of under-staging, there were four cases of patient factor, 19 cases of interpretation factor, and 9 cases of CT factor. In three cases, the cause of under-staging could not be identified. Conclusion: CT interpretation factor was the most frequent cause of under-staging in the preoperative diagnosis with gastric cancer patients. Therefore, more cautious CT interpretation is necessary to avoid unnecessary laparotomies in gastric cancer patients.