• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.6
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• pp.553-581
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• 2022

Shortly after tunnel boring machine (TBM) was introduced in the tunneling industry, the use of TBM has surprisingly increased worldwide due to its performance together with the benefit of being safely and environmentally friendly. One of the main cost items in the TBM tunneling in rock and soil is changing damaged or worn cutters. It is because that the cutter change is a time-consuming and costly activity that can significantly reduce the TBM utilization and advance rate and has a major effect on the total time and cost of TBM tunneling projects. Therefore, the importance of accurately evaluating the cutter life can never be overemphasized. However, the prediction of cutter wear in soil, rock including mixed face is very complex and not yet fully clarified, subsequently keeping engineers busy around the world. Various prediction models for cutter wear have been developed and introduced, but these models almost usually produce highly variable results due to inherent uncertainties in the models. In this study, a case study of design and construction of disc cutter change is introduced and analyzed, rather than proposing a prediction model of cutter wear. As the disc cutter is strongly affected by the geological condition, TBM machine characteristic and operation, authors believe it is very hard to suggest a generalized prediction model given the uncertainties and limitations therefore it would be more practical to analyze a real case and provide a detailed discussion of the difference between prediction and result for the cutter change. By doing so, up-to-date idea about planning and execution of cutter change in practice can be promoted.

• Journal of Korea Water Resources Association
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• v.54 no.12
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• pp.1295-1304
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• 2021

For the efficient use and management of water resources, a reliable rainfall-runoff analysis is necessary. Still, continuous hydrological data and rainfall-runoff data are insufficient to secure through measurements and models. In particular, as part of the reasonable improvement of a rainfall-runoff model in the case of an ungauged watershed, regionalization is being used to transfer the parameters necessary for the model application to the ungauged watershed. In this study, the GR4J model was selected, and the SCEM-UA method was used to optimize parameters. The rainfall-runoff model for the analysis of the correlation between watershed characteristics and parameters obtained through the model was regionalized by the Copula function, and rainfall-runoff analysis with the regionalized parameters was performed on the ungauged watershed. In the process, the intermediate state variables of the rainfall-runoff model were extracted, and the correlation analysis between water level and the ground water level was investigated. Furthermore, in the process of rainfall-runoff analysis, the Standardized State variable Drought Index (SSDI) was calculated by calculating and indexing the state variables of the GR4J model. and the calculated SSDI was compared with the standardized Precipitation index (SPI), and the hydrological suitability evaluation of the drought index was performed to confirm the possibility of drought monitoring and application in the ungauged watershed.

• Journal of the Korean Society of Radiology
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• v.15 no.2
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• pp.239-246
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• 2021

Portal Dosimetry was verified using EPID to secure the clinical application and reliability of the existing research dose evaluation. The dose distribution of Geant4 was compared with the measured value by 360° rotational irradiation with a 2.5 cm cone for stereotactic brain surgery. To confirm the dose distribution of patients with brain metastasis, the dose distribution investigated by inserting a Gafchromic EBT film into the parietal phantom and the dose distribution obtained from the parietal phantom using VMAT are compared and applied to actual patients. As a result of the analysis, it was confirmed that the accuracy of the beam center and the center of the couch coincide accurately with an error within 1mm as a result of QA through a pin ball. In addition, it was confirmed that the EBT3 film has excellent linearity in the range of 0 to 10 Gy according to various dose irradiation. In the same setting as the two cervical phantoms, we confirm that the implementation and simulation results calculations of dose calculations based on Geant4 using photon beams match the experimental data within the treatment planning volume (PTV). Therefore, volume modulated arc treatment (VMAT) 360° rotational irradiation was performed, and the result of iso-dose distribution analysis by rotational irradiation confirmed that it is appropriate to include a virtual tumor.

• Journal of the korean academy of Pediatric Dentistry
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• v.48 no.1
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• pp.31-41
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• 2021

The aim of this retrospective study was to evaluate the correlation between the midpalatal suture maturation and skeletal maturation in growing children aged 7 - 15 years and predict the maturational stages of the midpalatal suture corresponding to skeletal maturity assessed by the skeletal maturation indicators (SMI) and middle phalanx of the third finger (MP3) stages. The group of this retrospective study was consisted of randomly selected 132 male and 135 female in age from 7 - 15 years. The maturation of the midpalatal suture was evaluated by using images from cone-beam computed tomography (CBCT) while the skeletal age was assessed by hand-wrist radiography. CBCT images and hand-wrist radiographs used in this study were obtained from all subjects for orthodontic diagnosis before orthodontic treatment. The maturational stages of the midpalatal suture showed strong correlations with both SMI and MP3 stages. The correlation between the midpalatal suture maturation and SMI (Spearman's correlation coefficient, ϒ_S = 0.905, p < 0.05) was slightly greater than that of MP3 stages (ϒ_S = 0.830, p < 0.05). There was a positive significant correlation between the midpalatal suture maturation and chronological age (ϒ_S = 0.868,p < 0.05). CBCT for evaluation of the midpalatal suture maturational stages may be unnecessary in every pediatric patients because SMI and MP3 stages were both replaceable useful methods for assessing maturation of the midpalatal suture before orthopedic treatment. In this retrospective study, the diagnostic reliability of the SMI method for estimating midpalatal suture maturation showed better reliability than the MP3 method.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.6
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• pp.379-389
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• 2019

The study empirically investigates financial factors that may influence on corporate R&D intensity during the post-era of the global financial turmoil (from 2010 to 2015) to mitigate possible spillover effect associated with the crisis. Concerning the empirical research settings of the study, chaebol firms listed in the KOSPI stock market are used as sample data with adopting various econometric estimation methods to enhance validity of the results. In the first hypothesis test, it is found that there exist inter-industry financial differences in terms of the ratio of R&D expenditure across all the sample years, but the statistical differences may arise from only a few domestic industries beloning to the high-growth sector. Moreover, it is also interesting to identify that, for the high-tech sector, 3 explanatory variables such as R&D intensity in a prior year, firm size and change in cash holdings are proved to be financial factors to discriminate between chaebol firms and their counterparts of non-chaebol firms, whereas a proportion of tangible assets over total assets as well as the former two variables are shown to be significant factors on the R&D intensity for the low-tech sector.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.6
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• pp.557-564
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• 2019

The characteristics of the torque and torque ripple of Interior Permanent Magnet Synchronous Motor(IPMSM) are influenced by the size and position of the rotor magnet and the size of the stator slot. This paper deals with the optimal design method for improving torque and torque ripplerate for IPMSM using Response Surface Methodology(RSM). Two objective functions of torque output and torque ripple were derived from the sensitivity analysis by Plackett-Burmann(PB) for the characteristic variables affecting torque and torque ripple. Secondary characteristic variables were selected from the derived objective function and RSM secondary regression model function was estimated by the experiment schedule and analysis results according to the Central Composite Design (CCD). The reliability of the secondary regression model was verified using ANOVA table. The analysis according to the experimental schedule was verified by JMAG(Ver. 18.0) which is Finite Element Method(FEM) software. The torque output of IPMSM applied with final characteristic variables was increased torque output by 11.5 % and the torque ripplerate was reduced by 9.1 %.

• Journal of Advanced Navigation Technology
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• v.22 no.6
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• pp.530-536
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• 2018

Recently, many studies for interoperability of UAV in the NAS has been performed since the application range and demand of UAV are continuously increased. For the interoperation of UAV in the NAS, technical standards and certification system for UAV which is equivalent to the commercial aircraft are required and test and evaluation methodology must be presented by standards. In this paper, qualification test and evaluation methodology aboutfor the UAV navigation system is proposed. For the research, the mission profile and operation environment of UAV were analyzed. Thereafter the test criteria were derived and the test methodology were established. Finally, the simulation and demonstration using test-bed UAV were performed. As a result of the test, it was confirmed that the navigation system of test UAV has a position accuracy about 1.4 meters at 95% confidence level in the entire flight stage.

• Korean Journal of Heritage: History & Science
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• v.41 no.1
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• pp.99-108
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• 2008

The paleogenetic analysis has become an increasingly important subject of archaeological, anthropological, biological as well as public interest. Recently, scientific research for human skeletal remains was more activated because of increasing awareness of the valuable archaeological information by the ancient DNA analysis. State of preservation of organic remains vary in different soil and burying environmental condition. Almost all available tissue disappear to analysis ancient DNA of bone in acidic soil caused by climate and geological features in Korea. Many preserved human remains excavated in the 'Heogwakmyo'(limelayered tomb of Chosun Dynasty Period) is able to explain through the relationship between burial conditions and bone survival form the burial method and ceremony. Ancient DNA analysis of excavated human bone form ancient tomb requires to remove contaminants such as microorganism's DNA and soil components that affect authentic results. Particularly, contamination control of contemporary human DNA is major serious problem and should verified by criteria of authenticity. In order to understand migration and culture of ancient population, when possible, ancient DNA studies needs to go abreast both radiocarbon and stable isotope studies because the dietary inferences will suggest ancient subsistence and settlement patterns. Also when the paleogenetic research supported with the arts and humanities research such as physical anthropology and archaeology, more valuable ancient genetic information is providing a unique results about evolutionary and population genetics studies to reconstruct the past.

• The Journal of the Korea Contents Association
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• v.19 no.6
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• pp.565-574
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• 2019

In this study, we evaluated the usefulness of an automatic blood typing analyzer using QWALYS-2 up (Diagast, Loos Cedex, France). During a month( 01OCT2013 - 31OCT2013) we performed 1,636 tests for ABO & RhD blood typing, 1,374 tests for antibody screen & identification tests and compared the results by automatic blood type analyzer with previous manual methods and column agglutination tests. And we analyzed the economic performance by comparison the test unit price between automatic blood type analyzer and manual methods. In ABO & RhD blood typing tests, there were complete concordances between manual and automated blood typing analyzer for 200 clinical samples. In Antibody screen tests, the concordance rate between manual and automated blood typing analyzer was 98.5% and more strong reaction in automated blood typing analyzer than manual methods. Therefore, the introduction of an automated blood typing analyzer, reagents costs were increased but labor costs were decreased. Considering the importance of transfusion safety and economic advantages, the introduction of an automated blood typing analyzer was very useful.

• The Journal of Engineering Geology
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• v.29 no.2
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• pp.99-112
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• 2019

Rainfall infiltration through the unsaturated zone is influenced by a range of factors including topography, geology, soil, rainfall intensity, temperature and vegetation; the actual infiltration varies largely in time and space. The infiltration capacity of soil is a critical factor in identifying groundwater recharge and leakage of surface water. It may differ depending on soil types and geological features of a particular basin or territory as well as on the usage of the land. This study was conducted in forest and farmland region of the mid-mountain area (EL. 50~300 m) of Jeju Island to test soil infiltration capacity of the area where rainfall contributes to groundwater. Results were analyzed using the four soil group classification methods presented by Jeong et al. (1995) and NAS (2007) to discover that the method offered by NAS (2007) is more reliable in the mid-mountain area of Jeju Island. The study compares and reviews the existing classification methods using the results of infiltration capacity tests executed on different soil groups throughout the whole region of the Jeju mid-mountain area. It is expected that this work will serve as a guideline for evaluating surface water recharge and hydraulic characteristics of Jeju Island.