• Journal of Digital Convergence
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• v.17 no.10
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• pp.373-379
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• 2019

Polymethyl methacrylate (PMMA), a self-polymerizing resin for removable orthodontic devices, has been used as a dental orthodontic device for many years because of its advantages such as color stability, volume stability, and tissue compatibility. However, such a removable orthodontic device has a disadvantage that the longer the use in the oral cavity due to the low strength of the PMMA fracture of the orthodontic device resin in use. In this study, zinc nanoparticles (ZNP) were mixed with orthodontic PMMA to introduce strength effect. Rectangular samples ($1.4{\times}3.0{\times}19.0mm$) of orthodontic PMMA (0, 0.5, 1.0, 2.0 and 4.0%) containing ZNP were prepared. The finished specimen was tested for three-point bending strength at a speed of 1 mm / min, and the Vickers hardness was measured three times using a hardness tester. The surface roughness was measured with a surface roughness. As a result, the 3-point bending strength did not change significantly (p>0.05). Surface energy increased significantly. As a result, we successfully synthesized ZNP in this study and prepared the dispersed resin specimen for calibration. It will be possible to develop high-density dental orthodontic resins.

• Polymer(Korea)
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• v.38 no.1
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• pp.74-79
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• 2014

Microfibrillated cellulose (MFC) was chemically modified with two different silane coupling agents (3-aminopropyltriethoxysilane and 3-mercaptopropyltriethoxysilane) and lauroyl chloride. The surface modification of MFC was confirmed by infrared spectroscopy (FTIR), energy dispersive X-ray spectroscopy (EDX), and contact angle measurements. Composite paper was successfully prepared with surface modified MFC and polyamide (PA) fiber. The surface modification of MFC not only prevented aggregation of MFC but also improved adhesive property between PA fiber and surface modified MFC. It was impossible to prepare papers of only PA fiber because there is no binder to connect PA fibers. That is, surface modified MFC as a binder in PA fiber played a crucial role in making composite paper. Composite paper with silane modified MFC showed higher tensile strength and modulus than composite paper with lauroyl moiety modified MFC. The structure, morphology, and mechanical properties of composite paper were analyzed by scanning electron microscope (SEM) and universal testing machine (UTM).

• Journal of Digital Convergence
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• v.19 no.12
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• pp.243-253
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• 2021

In this study, AHP analysis was conducted on potential residents who are willing or likely to live in a smart city. The purpose is to identify priorities for strategic objectives. In order to establish a hierarchical structure for the vision, core values, and strategic goals of the smart city business, we researched domestic and overseas smart city-related academic papers and research reports, business plans, and institutional websites. After reviewing professors, researchers, experts, and focus groups, 4 2nd tier and 12 3rd tier properties were finally selected and the hierarchical structure was confirmed. As a result of AHP analysis, it was found that residents place the highest importance on quality of life in smart city projects. As a result of the analysis of the lower-level factors, it was found that safety was the most important. The priorities were analyzed in the order of living convenience, eco-friendliness, and social inequality resolution. It is expected that the results of this analysis will be able to suggest strategies to be established when promoting smart city projects in the future.

• Korean Journal of Remote Sensing
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• v.34 no.6_3
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• pp.1427-1443
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• 2018

Object-based image analysis (OBIA) allows higher computation efficiency and usability of information inherent in the image, as it reduces the complexity of the image while maintaining the image properties. Superpixel methods oversegment the image with a smaller image unit than an ordinary object segment and well preserve the edges of the image. SLIC (Simple linear iterative clustering) is known for outperforming the previous superpixel methods with high image segmentation quality. Although the input parameter for SLIC, number of superpixels has considerable influence on image segmentation results, impact analysis for SLIC parameter has not been investigated enough. In this study, we performed optimal parameter analysis and evaluation of change detection for SLIC-based superpixel techniques using KOMPSAT data. Forsuperpixel generation, three superpixel methods (SLIC; SLIC0, zero parameter version of SLIC; SNIC, simple non-iterative clustering) were used with superpixel sizes in ranges of $5{\times}5$ (pixels) to $50{\times}50$ (pixels). Then, the image segmentation results were analyzed for how well they preserve the edges of the change detection reference data. Based on the optimal parameter analysis, image segmentation boundaries were obtained from difference image of the bi-temporal images. Then, DBSCAN (Density-based spatial clustering of applications with noise) was applied to cluster the superpixels to a certain size of objects for change detection. The changes of features were detected for each superpixel and compared with reference data for evaluation. From the change detection results, it proved that better change detection can be achieved even with bigger superpixel size if the superpixels were generated with high regularity of size and shape.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.31 no.6
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• pp.353-358
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• 2018

In this study, it is describe to an optimization analysis process for the weight reduction of the voltage converter in the electric vehicle charging systems. The optimization design is a technique that finds the optimal material distribution under a given material quantity constraint by combining the design sensitivity with the material properties and the mathematical optimization. Among the topology optimization, a lightweight design is performed by a solid isotropic material with penalization with simple formula and well-convergence. The lightweight design consists of three steps. As a first step, a finite element model for the basic design of the on-board voltage converter was constructed and static analysis was performed on the load. In the second step, the optimum shape is obtained for the lightweight by performing the topology optimization using the solid isotropic material with penalization applying the stiffness coefficient of the isotropic material to the static analysis result. As a final step, impact analysis was performed by applying a half-sinusoidal pulse shape impact load which satisfies the impact test standard of the vehicle-mounted part with respect to the optimum shape. In the topology optimization, the design domain was defined as the mounting bracket area, and the design technology was finally achieved by optimizing the mounting bracket to achieve a weight reduction of 20% over the basic design.

• Journal of the Korean Society of Radiology
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• v.13 no.3
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• pp.333-338
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• 2019

In the field of radiotherapy, the Quality Assurance(QA) procedure to verify the safety of treatment is considered to be very important. However, due to various problems of the conventional dosimeters used for the QA, researches on these dosimeters have been actively carried out to replace them. In this study, to maximize the sensitivity by visible light(VL) emitted from phosphors, blended hybrid sensors were fabricated by blending various weight percent(wt%) of $Gd_2O_2S:Tb$ which is a phosphor with excellent fluorescence efficiency into $PbI_2$. Then, the electrical properties to high energy radiation from the blended sensors and the pure $PbI_2$ sensor were compared and evaluated. As a result of the sensitivity evaluation, the sensor of 3wt% showed the highest value with more than 40% difference from the other sensors, and gradual decreasing in sensitivity was observed with increasing wt% except for the sensor of 3wt%. Also, in the reproducibility evaluation, the pure $PbI_2$ sensor exhibited a large variation in coefficient of variation(CV)>0.015, while all the blended sensors showed CV<0.015.

• Korean Journal of Heritage: History & Science
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• v.52 no.3
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• pp.222-239
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• 2019

This paper studied Joseon royal incense, Buyonghyang, focusing on the case of Sunjo Sunwonwanghoo Garyedogam Uigwe. Incense was introduced to Korea in the period of the Three States with Buddhist cultures. Buyonghyang is an incense that represented the royal family and was used in various rituals. Civilians also burned this incense in front of a bride's palanquin at a wedding ceremony. Buyonghyang had various uses-ceremonial uses, as a fragrance, to mothproof, and medical uses. Buyonghyang is a combined incense with ten different ingredients. This study tracked the supply and demand of the incense ingredients through Takjijunjeol, Sejong Shilok Jiriji, and The Annals of the Joseon Dynasty. This paper identified properties of the ingredients and studied recipes using ancient medical books-Jejungshinpyeon, Donguibogam, etc. Then the cooperation and treatment of incense by craftsman were examined using the records of The Annals of the Joseon Dynasty, and Seungjeongwon Ilgi. The significance of Buyonghyang during the Joseon dynasty was studied by examining its use at a royal wedding ceremony. This study considered Sunjo's wedding ceremony based on Sunjo Sunwonwanghoo Garyedogam Uigwe which is highly regarded as a well-organized system compared to other Uigwe. Buronghyang was burned during all of the ceremonies which took place in the palace. Conversely, it is considered that Buyonghyang was burned only during the Bisuchekui ceremony (investiture), which took place in the bride's place, according to the record of the mobilization of court ladies for various incense burners for the Bisuchekui ceremony. Since the incense was able to be used only after Bisuchekui, it is considered that only the royal family could use the incense, and it was a symbolic incense of the Joseon Royal Family.

• Journal of the Korean Society of Radiology
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• v.13 no.1
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• pp.39-44
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• 2019

Radiation safety management is being considered very important since radioactive isotopes such as Co-60 and Ir-192 are widely used in fields such as non-destructive test(NDT). In this study, the applicability of Mercury(II) Iodide($HgI_2$) source for tracing system was evaluated. To make sure the unit cell sensor's reliability, we evaluated the electrical properties of the sensor made with $HgI_2$, and then position dependence of the sensor was analyzed and compared with the dose distribution from the planning system. As a result of the evaluation, high reliability of the sensor was shown through the linearity of R-sq > 0.990 and reproducibility of CV < 0.015. In the position dependence evaluation, the maximum value was measured at the isocenter of the sensor and gradually decreased according to the distance. However, the dose distribution data from the planning system was turned out that has difference with that of the sensor up to 30%. This seems to come from the difference between single-point measuring based planning system and area measuring based sensor.

• The Journal of the Convergence on Culture Technology
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• v.5 no.1
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• pp.353-360
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• 2019

Trade credit is being used as a price discrimination strategy by the suppliers in order to increase the customer's demand. From the viewpoint of the customer, if delayed payment is allowed for a certain period of time from the supplier, the effect of reducing the inventory carrying cost will positively affect the customer's order quantity. Also, in deriving the economic order quantity(EOQ) formula, it is tacitly assumed that the customer's ordering cost is a fixed cost. However in many business transactions, the customer pays the freight cost for the transportation of his order and so, the customer's ordering cost contains not only a fixed cost but also a freight cost which is a function of the order size. Therefore, in this study, we analyzed the inventory model which considers that the customer's ordering cost contains not only a fixed cost but also a freight cost which is a function of the customer's order size when the supplier permits a delay in payments. For the analysis, it is also assumed that inventory is exhausted not only by customer's demand but also by deterioration. Investigation of the properties of an optimal solution allows us to develop an algorithm whose validity is illustrated using an example problem.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.7
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• pp.607-612
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• 2019

The softness of the crashpad part is one of the important factors which affect the interior perceived quality of the vehicle interior. And while improving the softness of the crashpad part, every effort to lower the production cost has been going on. The PU foaming process for the crashpad part depends on the understanding of a lot of processes, tools and material properties. Therefore, to achieve the requirement of the customer for the interior part's visual quality, the integrated design techniques are investigated to correlate the processes, tool design, material design and the computer aided analysis. In this paper, IMG (In Mold Grain) designed concept is firstly developed to integrate the skin preforming, plastic injection molding of the substrate and the foaming process in a tool within reduced processes. Through the application of this technology, softness of crashpad is improved by 40% compared to the conventional vacuum molding method, and the existing process is reduced by 50% by integrating the injection process and the manufacturing process. And by integrating the injection mold and the skin mold and removing the foaming mold, the number of molds are reduced from 3 to 1, resulting in 20% reduction in the cost of applying a medium-sized passenger car.