• Korean Journal of Metals and Materials
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• v.50 no.4
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• pp.338-343
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• 2012

The early osseointegration of titanium (Ti) dental implants is related to the initial cell morphology. The morphology of the cells (mesenchymal stem cells, MSC) was observed on three different Ti disc surfaces, which were mechanically treated by polishing, blasting, and scratching. A non-directional surface (isotropic texture) was obtained by the blasting of HA grits on cp-Ti discs, and a unidirectional surface (anisotropic texture) was obtained by the scratching of SiC papers. The cell attachment and arrangement in the initial periods were quite similar, but those in the later periods were significantly affected by the texture of the cp-Ti discs. After 1 week, the blasted Ti discs showed non-directional arrangement or spreading of the cells, whereas the scratched cp-Ti discs showed unidirectional properties parallel to the direction of the scratched grooves on the surface. The surface roughness of the cp-Ti discs significantly affects cell proliferation. Cell proliferation on the blasted and scratched surfaces was about 60% and 40% higher compared to the control result (polishing group) after 1 week (P<0.05). Cell proliferation on the blasted and scratched surfaces after 1 week was slightly enhanced with increasing surface roughness. It is believed that the direction of cell attachment and arrangement is closely related to the surface texture of the substrate surfaces, but cell proliferation after a relatively long period of time is directly enhanced by the surface roughness, not by the surface texture.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.12
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• pp.67-76
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• 2020

The purpose of this study was to derive the directionality of technology development of high-power electromagnetic pulse (EMP) shielding concrete and standardization of a shielding performance evaluation method. Because the EMP shielding mechanism of concrete has not been identified clearly, and the verification method for EMP shielding performance has not been standardized, it is difficult to compare the research results between researchers. The development direction of EMP shielding concrete was derived from a consideration of the electromagnetic wave loss mechanism of metal. The standardization direction for verifying the EMP shielding performance of concrete was derived from a consideration of the electrical properties of concrete and the shielding performance evaluation methods of previous studies. As a result, the development of electrically conductive concrete is required, and test methods classified by the electromagnetic wave loss mechanism should be applied. For quality verification, the development of EMP shielding concrete will be feasible and its performance can be evaluated if a test method referencing the generalized shielding evaluation method (MIL-STD, etc.) is applied.

• Journal of Digital Convergence
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• v.19 no.2
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• pp.409-414
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• 2021

In this paper, we investigated the touch gestures of the scroll direction of a small and long UI due to the characteristics of a device in a smartphone environment that has become popular and used. Touch gestures are touched and directed by triggers such as metaphors and affordances based on past experiences. Different types of touch gestures are used depending on the type of navigation, motion, and transformation gesture, but scrolling is the most frequently used among them. In general, the scroll is vertically scrolled, but recently, a design pattern that can be scrolled left and right inside is arranged to cause cognitive dissonance of users. In the use of an inner scroll that can scroll left and right by covering a part of the right content, the mixing of a non-scrollable design pattern becomes a factor that requires attention to the user. Therefore, it was found that the use of triggers and the use of consistent design patterns can enhance the user experience even in the inner scroll environment.

• Journal of Convergence for Information Technology
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• v.11 no.2
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• pp.41-46
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• 2021

The method of the edge detection algorithm based on grayscale mathematical morphology has the advantage that image noise can be removed and processed in parallel, and the operation speed is fast. However, the method of detecting the edge of an image using a single structural scale element may be affected by image information. The characteristics of grayscale morphology may be limited to the edge information result of the operation result by repeatedly performing expansion, erosion, opening, and containment operations by repeating structural elements. In this paper, we propose an edge detection algorithm that applies a structural element with strong directionality to noise and then applies weighted entropy to each pixel information in the element. The result of applying the multi-scale structural element applied to the image and the result of applying the directional weighted entropy were compared and analyzed, and the simulation result showed that the proposed algorithm is superior in edge detection.

• Journal of Powder Materials
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• v.28 no.3
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• pp.216-220
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• 2021

The effect of tert-butyl alcohol (TBA) as a freezing solvent on the pore structure of a porous tungsten body prepared by freeze-drying is analyzed. TBA slurries with a WO3 content of 10 vol% are prepared by mixing with a small amount of dispersant and binder at 30℃. The slurries are frozen at -25℃, and pores are formed in the frozen specimens by the sublimation of TBA during drying in air. After hydrogen reduction at 800℃ and sintering at 1000℃, the green body of WO₃ is completely converted to porous W with various pore structures. Directional pores from the center of the specimen to the outside are observed in the sintered bodies because of the columnar growth of TBA. A decrease in pore directionality and porosity is observed in the specimens prepared by long-duration drying and sintering. The change in pore structure is explained by the growth of the freezing solvent and densification.

• The Journal of the Acoustical Society of Korea
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• v.41 no.4
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• pp.468-479
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• 2022

To detect targets with active sonar system in the underwater environments, the targets are localized by receiving the echoes of the transmitted sounds reflected from the targets. In this case, reverberation from the scatterers is also generated, which prevents detection of the target echo. To detect the target effectively, reverberation suppression techniques such as pre-whitening based on autoregressive model and principal component inversion have been studied, and recently a Non-negative Matrix Factorization (NMF)-based technique has been also devised. The NMF-based reverberation suppression technique shows improved performance compared to the conventional methods, but the geometry of the transducer and receiver and attenuation by distance have not been considered. In this paper, the performance is improved through preprocessing such as the directionality of the receiver, Doppler related thereto, and attenuation for distance, in the case of using a continuous wave with a bistatic sonar. In order to evaluate the performance of the proposed system, simulation with a reverberation model was performed. The results show that the detection probability performance improved by 10 % to 40 % at a low false alarm probability of 1 % relative to the conventional non-negative matrix factorization.

• The Journal of the Acoustical Society of Korea
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• v.40 no.3
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• pp.247-253
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• 2021

Directional ultrasonic speakers that are used to hear sound only in a specific area have been continuously researched on various improvements in terms of sound quality and cost compared to general speakers. In this paper, we propose a DSP based hybrid-type ultrasonic speaker that can be heard at the same time as a general speaker in order to compensate for the sound in the low-band range, considering that it is difficult to hear the low-band sound below 500 Hz due to the sensor characteristics of the ultrasonic speaker. In the case of the system that is implemented by simply connecting a general speaker and an ultrasonic speaker, there are issues of high cost and difficulties of control as two amplifiers are used to playback ultrasonic and general sound sources. In addition, sound quality deteriorates due to the difference in playback time between ultrasonic and general sound sources. In order to improve issues of cost, control and sound quality, we developed hybrid-type ultrasonic speaker with a DSP based amplifier that can simultaneously playback by synchronizing the general sound source with the regenerated ultrasonic sound source, in addition to implement the existing CODEC functions such as Dynamic Range Control (DRC) and Equalizer (EQ).

• Journal of radiological science and technology
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• v.46 no.3
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• pp.219-229
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• 2023

In this study, basic characteristics such as reproducibility, linearity, and directionality of RPL glass dosimeters were evaluated to improve the reliability of dose evaluation through RPL glass dosimeters, and uncertainty elements such as sensitivity by glass element and magazine slot sensitivity were evaluated. Using a mathematical model to calibrate the measured values of the RPL glass dosimeter, the measurement uncertainty was calculated assuming an example. As a result of the characteristic evaluation, the RPL glass dosimeter showed excellent performance with a standard deviation of ±1% (1 SD) for the reproducibility of the reading process, a coefficient of determination for linearity of 0.99997. And the read-out of the RPL glass dosimeter are affected by the circular rotation direction of the glass dosimeter during irradiation, fading according to the period after irradiation, the number of laser pulses of the reader, and response degradation due to repeated reading, it is judged that measurement uncertainty can be reduced by irradiation and reading in consideration of these factors. In addition, it was confirmed that the dose should be determined by calculating the correction factors for the sensitivity of each element and, the sensitivity of each reading magazine slot. It is believed that the reliability of dosimetry using glass dosimeters can be improved by using a mathematical model for correction of glass dosimeter readings and calculating measurement uncertainty.

• Journal of the Korea Institute of Building Construction
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• v.23 no.6
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• pp.761-772
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• 2023

The fire resistance design of timber structures involves calculating the residual section based on charring depth, which is then utilized in structural design. Charring depth is determined from fire-resistance test results in Korea, which currently do not account for the charring properties of the adhesive used in Glued Laminated Timber(GLT) production. This study fabricated GLT using various adhesives employed in domestic GLT production, comparing the charring properties by adhesive type and the fire resistance performance relative to the directionality of the laminated surface. Melamine demonstrated the most advantageous fire resistance performance, followed by resorcinol and polyurethane. Furthermore, it was established that the laminated section exhibited a higher charring rate, influenced by the adhesive, compared to the laminated surface, which significantly impacts the fire resistance performance.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.44 no.2
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• pp.141-147
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• 2024

In this study, micro CT images were used to confirm the tensile fracture strength according to the pore distribution characteristics of 3D printed concrete. Unlike general specimens, concrete structures printed by 3D printing techniques have the direction of pores (voids) depending on the stacking direction and the presence of filaments contact surfaces. Accordingly, the pore distribution of 3D printed concrete specimens was analyzed through quantitative and qualitative methods, and the tensile strength by direction was analyzed through a finite element technique. It was confirmed that the pores inside the 3D printed specimen had directionality, resulting in their anisotropic behavior. This study aims to analyze the characteristics of 3D concrete printing specimen and correlate them with simulation-based mechanical properties to improve performance of 3D printed material and structure.