• Journal of Intelligence and Information Systems
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• v.20 no.4
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• pp.107-120
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• 2014

This study proposes a novel recommender system using the structural hole analysis to reflect qualitative and emotional information in recommendation process. Although collaborative filtering (CF) is known as the most popular recommendation algorithm, it has some limitations including scalability and sparsity problems. The scalability problem arises when the volume of users and items become quite large. It means that CF cannot scale up due to large computation time for finding neighbors from the user-item matrix as the number of users and items increases in real-world e-commerce sites. Sparsity is a common problem of most recommender systems due to the fact that users generally evaluate only a small portion of the whole items. In addition, the cold-start problem is the special case of the sparsity problem when users or items newly added to the system with no ratings at all. When the user's preference evaluation data is sparse, two users or items are unlikely to have common ratings, and finally, CF will predict ratings using a very limited number of similar users. Moreover, it may produces biased recommendations because similarity weights may be estimated using only a small portion of rating data. In this study, we suggest a novel limitation of the conventional CF. The limitation is that CF does not consider qualitative and emotional information about users in the recommendation process because it only utilizes user's preference scores of the user-item matrix. To address this novel limitation, this study proposes cluster-indexing CF model with the structural hole analysis for recommendations. In general, the structural hole means a location which connects two separate actors without any redundant connections in the network. The actor who occupies the structural hole can easily access to non-redundant, various and fresh information. Therefore, the actor who occupies the structural hole may be a important person in the focal network and he or she may be the representative person in the focal subgroup in the network. Thus, his or her characteristics may represent the general characteristics of the users in the focal subgroup. In this sense, we can distinguish friends and strangers of the focal user utilizing the structural hole analysis. This study uses the structural hole analysis to select structural holes in subgroups as an initial seeds for a cluster analysis. First, we gather data about users' preference ratings for items and their social network information. For gathering research data, we develop a data collection system. Then, we perform structural hole analysis and find structural holes of social network. Next, we use these structural holes as cluster centroids for the clustering algorithm. Finally, this study makes recommendations using CF within user's cluster, and compare the recommendation performances of comparative models. For implementing experiments of the proposed model, we composite the experimental results from two experiments. The first experiment is the structural hole analysis. For the first one, this study employs a software package for the analysis of social network data - UCINET version 6. The second one is for performing modified clustering, and CF using the result of the cluster analysis. We develop an experimental system using VBA (Visual Basic for Application) of Microsoft Excel 2007 for the second one. This study designs to analyzing clustering based on a novel similarity measure - Pearson correlation between user preference rating vectors for the modified clustering experiment. In addition, this study uses 'all-but-one' approach for the CF experiment. In order to validate the effectiveness of our proposed model, we apply three comparative types of CF models to the same dataset. The experimental results show that the proposed model outperforms the other comparative models. In especial, the proposed model significantly performs better than two comparative modes with the cluster analysis from the statistical significance test. However, the difference between the proposed model and the naive model does not have statistical significance.

• The Journal of Korean Society for Radiation Therapy
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• v.24 no.2
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• pp.107-114
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• 2012

Purpose: Unlike the existing linear accelerator with photon, proton therapy produces a number of second radiation due to the kinds of nuclide including neutron that is produced from the interaction with matter, and more attention must be paid on the exposure level of radiation workers for this reason. Therefore, thermoluminescence dosimeter (TLD) that is being widely used to measure radiation was utilized to analyze the exposure level of the radiation workers and propose a basic data about the radiation exposure level during the proton therapy. Materials and Methods: The subjects were radiation workers who worked at the proton therapy center of National Cancer Center and TLD Badge was used to compare the measured data of exposure level. In order to check the dispersion of exposure dose on body parts from the second radiation coming out surrounding the beam line of proton, TLD (width and length: 3 mm each) was attached to on the body spots (lateral canthi, neck, nipples, umbilicus, back, wrists) and retained them for 8 working hours, and the average data was obtained after measuring them for 80 hours. Moreover, in order to look into the dispersion of spatial exposure in the treatment room, TLD was attached on the snout, PPS (Patient Positioning System), Pendant, block closet, DIPS (Digital Image Positioning System), Console, doors and measured its exposure dose level during the working hours per day. Results: As a result of measuring exposure level of TLD Badge of radiation workers, quarterly average was 0.174 mSv, yearly average was 0.543 mSv, and after measuring the exposure level of body spots, it showed that the highest exposed body spot was neck and the lowest exposed body spot was back (the middle point of a line connecting both scapula superior angles). Investigation into the spatial exposure according to the workers' movement revealed that the exposure level was highest near the snout and as the distance becomes distant, it went lower. Conclusion: Even a small amount of exposure will eventually increase cumulative dose and exposure dose on a specific body part can bring health risks if one works in a same location for a long period. Therefore, radiation workers must thoroughly manage exposure dose and try their best to minimize it according to ALARA (As Low As Reasonably Achievable) as the International Commission on Radiological Protection (ICRP) recommends.

• The Journal of Korean Society for Radiation Therapy
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• v.28 no.2
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• pp.87-99
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• 2016

Purpose : This study will evaluate the clinical utility by applying clinical schematic that uses monoenergy or dual energy as according to the location of tumors to the stereotactic radiotherapy to compare the change in actual dose given to the real tumor and the dose that locates adjacent to the tumor. Materials and Methods : CT images from a total of 10 patients were obtained and the clinical planning were planned based on the volumetric modulated arc therapy on monoenergy and dual energy. To analyze the change factor in the tumor, Comformity Index(CI) and Homogeneity Index(HI) and maximum dose quantity were each calculated and comparing the dose distribution on normal tissues, $V_{10}$ and $V_5$, first ~ fourth ribs closest to the tumor ($1^{st}{\sim}4^{th}$ Rib), Spinal Cord, Esophagus and Trachea were selected. Also, in order to confirm the accuracy on which the planned dose distribution is really measured, the 2-dimensional ion chamber array was used to measure the dose distribution. Results : As of the tumor factor, CI and HI showed a number close to 1 when the two energies were used. As of the maximum dose, the front chest wall showed 2% and the dorsal tumor showed equivalent value. As of normal tissue, the front chest wall tumors were reduced by 4%, 5% when both energies were used in the adjacent rib and as of trachea, reduced by 11%, 17%. As of the dose in the lung, as of $V_{10}$, it reduced by 1.5%, $V_5$ by 1%. As of the rear chest wall, when both energies were used, the ribs adjacent to the tumors showed 6%, 1%, 4%, 12% reduction, and in the lung dose distribution, $V_{10}$ reduced by 3%, and $V_5$ reduced by 3.1%. The dose measurement in all energies were in accordance to the results of Gamma Index 3mm/3%. Conclusion : It is considered that rather than using monoenergy, utilizing double energy in the clinical setting can be more effectively applied to the superficial tumors.

• The Journal of Korean Society for Radiation Therapy
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• v.23 no.1
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• pp.13-19
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• 2011

Purpose: It's essential to minimize the tumor motion and identify the exact location of the lesions to achieve the improvement in radiation therapy efficiency during SBRT. In this study, we made the established compression belt to reduce respiratory motion and evaluated the usefulness of clinical application in SBRT. Materials and Methods: We analyzed the merits and demerits of the established compression belt to reduce the respiratory motion and improved the reproducibility and precision in use. To evaluate the usefulness of improved compression belt for respiratory motion reduction in SBRT, firstly, we reviewed the spiral CT images acquired in inspiration and expiration states of 8 lung cancer cases, respectively, and analyzed the three dimensional tumor motion related to respiration. To evaluate isodose distribution, secondly, we also made the special phantom using EBT2 film (Gafchronic, ISP, USA) and we prepared the robot (Cartesian Robot-2 Axis, FARARCM4H, Samsung Mechatronics, Korea) to reproduce three dimensional tumor motion. And analysis was made for isodose curves and two dimensional isodose profiles with reproducibility of respiratory motion on the basis of CT images. Results: A respiratory motion reduction compression belt (Velcro type) that has convenient use and good reproducibility was developed. The moving differences of three dimensional tumor motion of lung cancer cases analyzed by CT images were mean 3.2 mm, 4.3 mm and 13 mm each in LR, AP and CC directions. The result of characteristic change in dose distribution using the phantom and rectangular coordinates robot showed that the distortion of isodose has great differences, mean length was 4.2 mm; the differences were 8.0% and 16.8% each for cranio-caudal and 8.1% and 10.9% each for left-right directions in underdose below the prescribed dose. Conclusion: In this study, we could develop the convenient and efficient compression belt that can make the organs' motion minimize. With this compression belt, we confirmed that underdose due to respiration can be coped with when CTV-PTV margins of mean 6 mm would be used. And we conclude that the respiratory motion reduction compression belt we developed can be used for clinical effective aids along with the gating system.

• The Journal of Korean Society for Radiation Therapy
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• v.27 no.1
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• pp.73-78
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• 2015

Purpose : Under the assumption of change to the amplitude based sorting, the study will use four dimensional computed tomography imaging (4DCT) arrayed using the phase based sorting to analyze the respiratory phase difference. Materials and Methods : The study analyzed the 4DCT (4-dimensional computed tomography) images of 10 liver cancer patients that were treated with respiratory gated radiotherapy from 2015 February to March. Using RPM respiratory gating (RPM 1.7.5, Varian, USA) equipment, imaging according to respiratory cycle of phase based sorting was acquired and using a treatment planning system (Pinnacle 9.2, Philips, USA) the acquired imaging according to respiratory cycle was used to measure the abdominal movement value by respiratory cycle. The measuring point was the point where the center point of the Marker Block and the body surface met in the 50% phase image and here the coordinate values Lateral, Vertical, Longitudinal (X, Y, Z) were set as reference points, and on the X, Z plane identical to the reference point, using the identical method the Y axis coordinate value of each 0%, 30%, 40%, 50%, 60%, 80% phase images were acquired to quantitatively measure the variation of distance to the Y axis. The abdominal movement value according to respiration was applied to the theoretical model that the value decreases linearly from maximum inhalation to maximum exhalation to divide the variation of my value to predict as amplitude value by respiratory cycle and conversely the variation in amplitude was recalculated with the phase variation deviation value to analyze. Results : The deviation value between expected value and actual location was the largest in the 30% phase with 0.24 cm, and standard deviation was also the largest in 30% phase with 0.13 cm. The effective value of the deviation value derived from the average of the deviation squared value of each patient appeared as minimum 0.7 cm, maximum 0.18 cm, average 0.12 cm, and standard deviation 0.4 cm. Also by dividing the actual movement distance value with the peak expiration value then converting it into %Phase, the deviation value with actual phase 16.5% in 30% phase, 10.0% and 40% phase, 10.0% and 60% phase, 15.4% and 80% phase, and overall average about 13%, and arraying based on amplitude, phase shift occurred and further it was from peak expiration the chance of deviation occurrence was increasingly measured. Conclusion : Based on the results of the study there were differences between value acquired based on theoretical model and actual value. Therefore in respiratory gated radiotherapy using external surrogates, there needs to be establishment of respiration gated radiation system that avoids the combination of two Sorting methods considering that there will be occurrence of treatment and corresponding clinical differences due to the phase difference that occur due to the Amplitude based Phase Sorting.

• Radiation Oncology Journal
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• v.21 no.1
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• pp.27-34
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• 2003

Purpose : To evaluate the efficacy of radiotherapy, and the factors affecting survival in patients of extrahepatic bile duct cancer, by analyzing the results of postoperative radiotherapy Materials and Methods : Between October 1991 and July 2001, 21 patients with extrahepatic bile duct cancer, who received radiotherapy after a radical resection, were retrospectively reviewed. The patients' ages ranged from 39 to 75 years, with a median of 61 years, and a male to female ratio of 16 to 5. The numbers of patients with proximal and distal bile duct cancer were 14 and 7, respectively. From the postoperative pathological examination, 19 of the patients were found to have microscopic residues, and 7 to be lymph node positive. Patients with AJCC stages I, II and III were 10, 10 and 1, respectively. The total radiation dose administered was 4,500$\~$6,300 cGy, with a median dose of 5,040 cGy. The follow up period was 20$\~$81 months, with a median of 57.5 months. Results : The overall and disease free survival rates at 3 and 5 years were 41.0 and 29.3$\%$, and 41.6 and 29.7$\%$, respectively. The influences of age, sex, tumor location, differentiation, microscopic residue, neural invasion, 7 and N stage, the stage itself, the dose of radiation and chemotherapy, on survival were evaluated. The T stage and the stage itself were found to be significant from a univariate analysis (p<0.05), but the degree of significance was limited by the small number of patients. A recurrence occurred in 12 patients (57.1$\%$), 5 in locoregional sites, 4 in distant sites and 3 in a combination of locoregional and distant sites, and the sites of distant metastasis were the liver, 6, and the bone, 1 Grade 2 or 3 acute leucopenias occurred in 2 patients and grade 2 chronic peptic ulcers occurred in 4, who were all recovered by conservative management. Conclusion : Postoperative radiotherapy is feasigbls in extrah데atic bile duct cancer, with tolerable toxicity, but prospective studies, with a large patient enrollment, are needed for the evaluation of the effects of postoperative radiotherapy and the related prognostic factors.

• Journal of the Korean Geographical Society
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• v.39 no.4
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• pp.643-664
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• 2004

This study aims to review what geographers have contributed to GIS industries and national needs. To-be-geographers and geographers are expected to meet the gap between what we have teamed in school and what we have to do after graduation. The characteristics of GIS industry in the 1990 are summarized with approximate evaluation of the contribution of geographers in each stage. Author introduced the requirement for the licenses of geomatics and geospatial engineering experts and the other licenses, which are important to get a job in GIS industry from 2003 to 2004. A set of questionnaire on the user's requirements was given to GIS people in private companies and public GIS research centers and analyzed. Author found that they put an emphasis on hands-on experiences and programming skills. no advantages or geography such as capability or integration and inter-disciplinary collaboration were not appreciated. The prospects for the GIS tend to be positive but the reflectance of the prospect was not accompanied by at the same degree of preference for geography. Most government strategies for the next ten years' GIS focus on new-growth leading industries. SWOT(strength, weakness, opportunity, threat) analysis of geography for GIS industry will give some directions such as telematics, regional marketing strategies with web-based GIS technology, location based service. That means intra-disciplinary study in geography will evoke the potentiality of GIS, compared with interdisciplinary studies.

• Tuberculosis and Respiratory Diseases
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• v.55 no.1
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• pp.31-40
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• 2003

Background : A CT scan is a useful modality for the diagnosis and evaluation of disease activity in patients with pulmonary tuberculosis. However, the CT diagnosis of pulmonary tuberculosis is sometimes difficult in patients with an atypical CT pattern, especially with lobar consolidation mimicking pneumonia. The aim of this study was to evaluate the clinical and CT features of pulmonary tuberculosis, simulating pneumonia, from a CT scan. Materials and Methods : The clinical and CT features in 21 patients, where the CT diagnosis was pneumonia, or the CT differential diagnosis included pneumonia, were retrospectively analyzed. Results : Of the 21 patients, 6 were immunocompromised, 15 presented with fever or leukocytosis and 15 showed positive sputum smear test for acid fast bacilli. Also, 17 of the 21 patients showed a positive sputum culture test. On the CT scan, consolidation was noted in all patients (100%), volume loss of the involved lobe or segment in 12 (57%), bronchogenic spread in 15 (71%), a cavity in 7 (33%) and bronchial wall thickening also in 7 (33%). The location of the consolidation revealed a relatively even distribution, with no specific predilection site. The other associated pulmonary diseases included ARDS, bronchiectasis, severe pulmonary emphysema, idiopathic pulmonary fibrosis and pulmonary alveolar proteinosis. Conclusion : In the immunocompromised patients, or patients with an underlying pulmonary disease, whose CT scans showed pulmonary consolidation, especially in association with findings of bronchogenic spread, a cavity or bronchial wall thickening, meticulous examination for pulmonary tuberculosis is recommended.

• The Journal of the Korean bone and joint tumor society
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• v.16 no.1
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• pp.1-7
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• 2010

Purpose: With advances in various treatment modalities, limb salvage surgery has been commonly used in osteosarcoma of extremities. An alternative method for skeletal reconstruction is reimplantation of the tumor bearing bone following extracorporeal irradiation (ECI). We report the long-term results of ECI autograft in aspect of the oncological and functional outcomes, and complications. Materials and Methods: We retrospectively reviewed 31 osteosarcoma patients who underwent reconstruction with ECI between July 1995 and January 2006. There were 24 males and 7 females with a mean age of 24 (7-74 years) and a mean follow-up of 117 months (17-177 months). Twenty-five cases were reconstructed with ECI autograft, 6 cases with ECI autograft-prosthesis composite. The pathologic subtypes were conventional in 29 cases, periosteal in 1 case, and parosteal in 1 case. The most common location of tumor was distal femur (15 cases) followed by humerus (3), proximal fibula (3) and proximal tibia (3). Musculoskeletal Tumor Society (MSTS) score was used for functional evaluation. The overall survival rate, local recurrence, complications were analyzed. Results: The overall survival rate was 80.6% and the disease-free survival rate was 64.5%. Five patients died of distant metastasis. One patient required above-knee amputation due to local recurrence. All of them, twenty-three complications occurred, which included nonunion in 7 cases, deep infection in 5 cases, joint instability in 4 cases, metal failure in 2 cases, Limb-length discrepancy (LLD) in 2 cases, periprosthetic fracture in 1 case, epiphyseal collapse in 1, local recurrence in 1 case. The mean MSTS functional score was 62.5%. Conclusion: Extracorporeal irradiated autograft can be achieved relatively good result in aspect of oncological and functional aspect, but is needed to be additional research about occurring many complications. The reconstruction with ECI after intercalary or fragmentary resection is effective reconstruction in aspect of oncological and functional result, complications.

• Progress in Medical Physics
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• v.20 no.3
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• pp.139-144
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• 2009

Recently, the mathematical analysis of stent simulation has been improved, with the help of development of various tool which measure mechanical property and location of stent in artery. The most crucial part of the stent modeling is how to design ideal stent and to evaluate the interaction between stent and artery. While there has been great deal of researches on the evaluation of the expansion, stress distribution, deformation of the stent in terms of the various parameters, few verification through computer simulation has been performed about deformation and stress distribution of the stent. In this study, we have produced the corresponding results between experimental test using Universal Testing Machine and computer simulation for the ideal model of stent. Also, we have analyzed and compared stress distribution of stent in the cases of that with membrane and that without membrane. The results of this study would provide minimum change of plan and good quality for ideal stent replacing damaged artery through the analysis using computer simulation in the early stage of stent design.