• Journal of Radiation Protection and Research
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• v.41 no.2
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• pp.111-115
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• 2016

Background: The scattered photons cause reduction of the contrast of radiographic image and it results in the degradation of the quality of the image. In order to acquire better quality image, an anti-scattering x-ray gird should be equipped in radiography system. Materials and Methods: The X-ray anti-scattering grid of the inclined type based on the hybrid concept for that of parallel and focused type was tested by MCNP code. The MCNPX 2.7.0 was used for the simulation based test. The geometry for the test was based on the IEC 60627 which was an international standard for diagnostic X-ray imaging equipment-Characteristics of general purpose and mammographic anti-scatter grids. Results and Discussion: The performance of grids with four inclined shielding material types was compared with that of the parallel type. The grid with completely tapered type the best performance where there were little performance difference according to the degree of inclination. Conclusion: It was shown that the grid of inclined type had better performance than that of parallel one.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.39 no.4
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• pp.7-13
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• 2007

Effects of pulp type, refining and filler type on the pore characteristics and physical properties of paper were investigated. HwBKP, SwBKP and BCTMP are used to study the effect of pulp type in this study. The effects of each filler (PCC, GCC and talc) and the combination of PCC/GCC were also studied. Highest bulk, pore volume and light scattering are obtained from BCTMP and PCC. It was found that the pore size and pore volume are important in light scattering in paper structure. It was found that PCC was the most effective filler for the improvement of the bulk and light scattering because of the increase in pore volume which can scatter light, but the increase of PCC content was not so effective in the improvement of bulk.

• Transactions of Materials Processing
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• v.9 no.6
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• pp.653-662
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• 2000

Wrinkling is one of the major defects in sheet metal products together with tearing, springback and other geometric and surface defects. The initiation and growth of wrinkles are influenced by many factors such as stress ratios, mechanical properties of the sheet material, geometry of the workpiece, contact condition, etc. It is difficult to analyze the wrinkling initiation and growth considering all the factors because the effects of the factors are very complex and the wrinkling behavior may show a wide scatter of data even for small deviations of factors. The finite element analyses of the wrinkling initiation and growth in the sheet metal forming process provide the detailed information about the wrinkling behavior of sheet metal. The direct analyses of the wrinkling initiation and growth, however, bring about a little difficulty in complex industrial problems because it needs large memory size and long computation time. In the present study, therefore, a global-local analysis technique is introduced for the computational efficiency. Through the analysis of wrinkling in the door inner stamping process, the efficiency of the global-local analysis technique is investigated.

• Journal of Welding and Joining
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• v.7 no.4
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• pp.56-67
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• 1989

In this study, the possibility of evaluating the peculiar fracture strength of weldment in high strength steels was investigated by means of a small punch(SP) test. In order to obtain the ductile-brittle transition temperature(DBTT) of SP energy by which the fracture strength of weldment in structural steels such as SS41 and SM53B steels had been evaluated in our preceding publication, the effects of notches and loading rates on SP energy were discussed. It was found that the correspondence of SP energy to critical COD at test temperature -196.deg. C showed a linear relation with some deviation. The empirical correlation with scatter band, Esp/(Esp)p = 1.67[.delta./(.delta./sub c//(.delta./sub c/)/sub p/]-0.55, was developed between the SP energy ratio and critical COD ratio of each weld structure compared with parent material at test temperature -196.deg. C. In addition, there did not appear to be a significant effect of test materials and specimen size etc. on the correlation.

• Korean Journal of Geomatics
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• v.4 no.1
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• pp.1-8
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• 2004

In the middle-resolution remote sensing, the Ground Sampled Distance (GSD) that the detector senses and samples is generally larger than the actual size of the objects (or materials) of interest, and so several objects are embedded in a single pixel. In this case, as it is impossible to detect these objects by the conventional spatial-based image processing techniques, it has to be carried out at sub-pixel level through spectral properties. In this paper, we explain the sub-pixel analysis algorithm, also known as the Linear Spectral Mixing (LSM) model, which has been experimented using the Hyperion data. To find Endmembers used as the prior knowledge for LSM model, we applied the concept of the convex geometry on the two-dimensional scatter plot. The Atmospheric Correction and Minimum Noise Fraction techniques are presented for the pre-processing of Hyperion data. As LSM model is the simplest approach in sub-pixel analysis, the results of our experiment is not good. But we intend to say that the sub-pixel analysis shows much more information in comparison with the image classification.

• Journal of the Society of Naval Architects of Korea
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• v.61 no.5
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• pp.352-358
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• 2024

The susceptibility of warships denotes the hit probability by anti-ship missiles in a hostile environment. The distribution characteristics of the hit location directly influence the vulnerability. This paper proposes a simulation method to determine the hit location of radar-homing anti-ship missiles by their approach direction. The method uses high-frequency analysis theory to calculate electromagnetic scatterers and determines the equivalent scattering center position corresponding to the hit location. The proposed method was implemented to an in-house software called SCTracer/RCS, which follows the process: importing numerical analysis model, defining calculation condition, calculating electromagnetic wave scattering centers, storing to database, calling scattering center data, estimating equivalent scattering center, and analyzing hit-point distribution. To validate the feasibility and practical applicability of this software, the hit-point distribution is examined for a 90-meter-class virtual warship.

• Journal of Radiation Protection and Research
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• v.48 no.4
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• pp.167-174
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• 2023

Background: A nondestructive test is commonly used to inspect the surface defects and internal structure of an object without any physical damage. X-rays generated from an electron accelerator or a tube are one of the methods used for nondestructive testing. The high penetration of X-rays through materials with low atomic numbers makes it difficult to discriminate between these materials using X-ray imaging. The interaction characteristics of neutrons with materials can supplement the limitations of X-ray imaging in material discrimination. Materials and Methods: The radiation image acquisition process for air-cargo security inspection equipment using X-rays and neutrons was simulated using a GEometry ANd Tracking (Geant4) simulation toolkit. Radiation images of phantoms composed of 13 materials were obtained, and the R-value, representing the attenuation ratio of neutrons and gamma rays in a material, was calculated from these images. Results and Discussion: The R-values were calculated from the simulated X-ray and neutron images for each phantom and compared with those obtained in the experiments. The R-values obtained from the experiments were higher than those obtained from the simulations. The difference can be due to the following two causes. The first reason is that there are various facilities or equipment in the experimental environment that scatter neutrons, unlike the simulation. The other is the difference in the neutron signal processing. In the simulation, the neutron signal is the sum of the number of neutrons entering the detector. However, in the experiment, the neutron signal was obtained by superimposing the intensities of the neutron signals. Neutron detectors also detect gamma rays, and the neutron signal cannot be clearly distinguished in the process of separating the two types of radiation. Despite these differences, the two results showed similar trends and the viability of using simulation-based radiation images, particularly in the field of security screening. With further research, the simulation-based radiation images can replace ones from experiments and be used in the related fields. Conclusion: The Korea Atomic Energy Research Institute has developed air-cargo security inspection equipment using neutrons and X-rays. Using this equipment, radiation images and R-values for various materials were obtained. The equipment was reconstructed, and the R-values were obtained for 13 materials using the Geant4 simulation toolkit. The R-values calculated by experiment and simulation show similar trends. Therefore, we confirmed the feasibility of using the simulation-based radiation image.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.11
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• pp.1011-1020
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• 2017

This study was conducted to investigate the material properties of stainless steel 316L specimens of untreated and UNSM treated material, hydrogen attacked material(100 bar, $300^{\circ}C$ at 120 h) and UNSM treated hydrogen attacked material at room temperature. Results demonstrated that the hydrogen attacked materials showed a tendency toward a slightly decreased fatigue strength, while the hydrogen embrittlement effect was smaller than the S-N curve of conventional untreated material. As compared to untreated material, the fatigue limit of the UNSM treated material increased by 43.8%, while it was 57.1％ higher in the UNSM treated hydrogen attacked material than in untreated hydrogen attacked material. The plastic deformation layer was ${\sim}152{\mu}m$ thick, as confirmed by maps showing the level of local plastic deformation affected by the UNSM treatment in three ways: an image quality map, inverse pole figure map, and kernel average misorientation map captured via electron back scatter diffraction. Owing to hydrogen embrittlement, about 90％ of surface cracks were smaller than the average grain size of $35{\mu}m$.

• Korean Journal of Radiology
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• v.22 no.7
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• pp.1077-1086
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• 2021

Objective: To investigate the diagnostic performance of quantitative ultrasound (US) parameters for the assessment of hepatic steatosis in patients with nonalcoholic fatty liver disease (NAFLD) using magnetic resonance imaging proton density fat fraction (MRI-PDFF) as the reference standard. Materials and Methods: In this single-center prospective study, 120 patients with clinically suspected NAFLD were enrolled between March 2019 and January 2020. The participants underwent US examination for radiofrequency (RF) data acquisition and chemical shift-encoded liver MRI for PDFF measurement. Using the RF data analysis, the attenuation coefficient (AC) based on tissue attenuation imaging (TAI) (AC-TAI) and scatter-distribution coefficient (SC) based on tissue scatter-distribution imaging (TSI) (SC-TSI) were measured. The correlations between the quantitative US parameters (AC and SC) and MRI-PDFF were evaluated using Pearson correlation coefficients. The diagnostic performance of AC-TAI and SC-TSI for detecting hepatic fat contents of ≥ 5% (MRI-PDFF ≥ 5%) and ≥ 10% (MRI-PDFF ≥ 10%) were assessed using receiver operating characteristic (ROC) analysis. The significant clinical or imaging factors associated with AC and SC were analyzed using linear regression analysis. Results: The participants were classified based on MRI-PDFF: < 5% (n = 38), 5-10% (n = 23), and ≥ 10% (n = 59). AC-TAI and SC-TSI were significantly correlated with MRI-PDFF (r = 0.659 and 0.727, p < 0.001 for both). For detecting hepatic fat contents of ≥ 5% and ≥ 10%, the areas under the ROC curves of AC-TAI were 0.861 (95% confidence interval [CI]: 0.786-0.918) and 0.835 (95% CI: 0.757-0.897), and those of SC-TSI were 0.964 (95% CI: 0.913-0.989) and 0.935 (95% CI: 0.875-0.972), respectively. Multivariable linear regression analysis showed that MRI-PDFF was an independent determinant of AC-TAI and SC-TSI. Conclusion: AC-TAI and SC-TSI derived from quantitative US RF data analysis yielded a good correlation with MRI-PDFF and provided good performance for detecting hepatic steatosis and assessing its severity in NAFLD.

• Journal of the Korean Society for information Management
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• v.15 no.1
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• pp.83-108
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• 1998

Recently, information on international trade goes on increasing in quantity because of the globalism and many related areas of the field. Most of libraries and informatin centers in Korea are using Dewey Decimal Classification(DDC), Library of congress Classification(LCC), and Korean Decimal Classification(KDC) to classify library materials on the subject. The application of three classification shcemes, DDC, LCC, and KDC were queried to determine the classification of materials on international trade. And analyses of the parts of international trade in three classification shemes were done in order to identify what major changes have made with the development of the field. There was subject scatter in DDC and LCC; there was an overlap among the classes of the three systems; and there was little change between present editions and the previous editions. The revision for international trade field of the KDC, the 4t edtition was suggested to help cover some deficiencies of the classification scheme. Inorder to develop a better KDC, the 5th edition, continuous revisions based upon the opinions of subject specialists and catalogers in the field are highly recommended.