• The Journal of Korean Academy of Prosthodontics
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• v.57 no.3
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• pp.296-303
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• 2019

In edentulous patient, not only mastication and pronunciation but also esthetics are compromised. By restoring an edentulous patient with complete dentures, masticatory function and esthetics can be rehabilitated. The advantages of the dentures using CAD/CAM are that they can be reconstructed ubiquitously with stored data, and the strength and density of CAD/CAM material are clinically acceptable. In this clinical report, interocclusal record was taken in a conventional manner and then two lab processing procedures were performed: conventional method and CAD/CAM method. Two types of processing procedures were compared and evaluated. Fair clinical results were obtained in both ways, satisfying the patient.

• Korean Journal of Materials Research
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• v.29 no.8
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• pp.469-476
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• 2019

A lead-free bulk ceramic having a chemical formula $Ba_{0.8}Ca_{0.2}(Ti_{0.8}Zr_{0.1}Ce_{0.1})O_3$ (further termed as BCTZCO) is synthesized using mixed oxide route. The structural, dielectric, impedance, and conductivity properties, as well as the modulus of the synthesized sample are discussed in the present work. Analysis of X-ray diffraction data obtained at room temperature reveals the existence of some impurity phases. The natural surface morphology shows close packing of grains with few voids. Attempts have been made to study the (a) effect of microstructures containing grains, grain boundaries, and electrodes on impedance and capacitive characteristics, (b) relationship between properties and crystal structure, and (c) nature of the relaxation mechanism of the prepared samples. The relationship between the structure and physical properties is established. The frequency and temperature dependence of the dielectric properties reveal that this complex system has a high dielectric constant and low tangent loss. An analysis of impedance and related parameters illuminates the contributions of grains. The activation energy is determined for only the high temperature region in the temperature dependent AC conductivity graph. Deviation from the Debye behavior is seen in the Nyquist plot at different temperatures. The relaxation mechanism and the electrical transport properties in the sample are investigated with the help of various spectroscopic (i.e., dielectric, modulus, and impedance) techniques. This lead free sample will serve as a base for device engineering.

• Fashion & Textile Research Journal
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• v.21 no.1
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• pp.88-95
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• 2019

The purpose of this study was to figure out the various characteristics of the thickness sensation among elements of tactile sensation using psychophysical method. Firstly, panel screening was processed to select sensitive thickness panel using the triangle test. As a result of discriminating the paper thickness difference from 1 to 4 pieces, the female students perceived the thickness difference more sensitively than the male students (p<.05). Secondly, JND (Just Noticeable Difference) was obtained at percentage of stimulus detection rate in order to detect the degree of thickness difference by psychophysical method. It was found that the difference threshold of the entire group was about 0.125mm, with male group being about 0.178mm and female group being about 0.095mm. Thirdly, Weber's law was used to find the minimum discrimination difference between the stimuli. The experiments were conducted by increasing the paper's base thickness from 1.950mm to 1.330mm, and it was found that the difference tendency increased when the size of the basic stimulus increased. At this time, the minimum discrimination difference increased, but the Weber' fraction was not proportional to the magnitude of the stimulus. The significance of this study was that sensory evaluation was applied to research in the fields of clothing science and it seems effective to further screen and train sensitive students as material discrimination experts.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.7
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• pp.265-271
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• 2019

The aim of this paper was to improve the shortcomings of Pitcher Concrete, a conventional ethylene-based polymer used in combination with the other components, and present basic data for use as improved road pavement material by applying an acrylic polymer. Existing ethylene polymer-based pitcher concrete materials were selected. Acrylic polymer was then added and the resulting mixture was evaluated. The compressive strength of the existing ethylene-based polymer pitcher concrete combination was low due to the large air gap, and a compressive strength of 24MPa was observed on the 28th day of road use, as defined by KS for an acrylic polymer-based pitcher concrete combination. Regarding the bending strength, the combined strength of the acrylic polymer-based pitcher concrete was excellent, and the factor of the pitcher was measured above the reference, 0.1(mm/s), in all variables. All parameters measured were less than 1%. The acrylic polymer mixing characteristics were able to maintain the dynamic modulus of elasticity for more than 120 cycles, but not more than 80 cycles for the other combinations. Therefore, the addition of more acrylic polymer than conventional ethylene polymer base is effective in improving the durability.

• Smart Structures and Systems
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• v.23 no.5
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• pp.449-466
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• 2019

Cable-stayed bridges are attractive due to their beauty, reducing material consumption, less harm to the environment and so on, in comparison with other kinds of bridges. As a massive structure with long period and low damping (0.3 to 2%) under many dynamic loads, these bridges are susceptible to fatigue, serviceability disorder, damage or even collapse. Tuned Mass Damper (TMD) is a suitable controlling system to reduce the vibrations and prevent the threats in such bridges. In this paper, Multi Tuned Mass Damper (MTMD) system is added to the Ahvaz cable stayed Bridge in Iran, to reduce its seismic vibrations. First, the bridge is modeled in SAP2000 followed with result verification. Dead and live loads and the moving loads have been assigned to the bridge. Then the finite element model is developed in OpenSees, with the goal of running a nonlinear time-history analysis. Three far-field and three near-field earthquake records are imposed to the model after scaling to the PGA of 0.25 g, 0.4 g, 0.55 g and 0.7 g. Two MTMD systems, passive and active, with the number of TMDs from 1 to 8, are placed in specific points of the main span of bridge, adding a total mass ratio of 1 to 10% to the bridge. The parameters of the TMDs are optimized using Genetic Algorithm (GA). Also, the optimum force for active control is achieved by Fuzzy Logic Control (FLC). The results showed that the maximum displacement of the center of the bridge main span reduced 33% and 48% respectively by adding passive and active MTMD systems. The RMS of displacement reduced 37% and 47%, the velocity 36% and 42% and also the base shear in pylons, 27% and 47%, respectively by adding passive and active systems, in the best cases.

• Journal of Convergence for Information Technology
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• v.9 no.4
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• pp.8-13
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• 2019

In this paper, based on the production technology and infrastructure of local cultural contents, it is determined that reconstruction and commercialization of local culture resources are necessary due to absence of character brand products centered on storytelling. It is expected to contribute to the expansion of the supply of advanced ceramic products along with the foundation of various contents production as it becomes the foundation to establish the developed business base through the differentiation strategy of the character product development based on the storytelling. In addition, due to the manual production, only a small amount of production can be produced and the production period is lengthened. On the other hand, the production period of gypsum mold is shortened by making mock-up through 3D program and 3D printing, It was effective in developing a wide variety of pottery products.

• Journal of Powder Materials
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• v.28 no.5
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• pp.396-402
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• 2021

Stainless steel, a type of steel used for high-temperature parts, may cause damage when exposed to high temperatures, requiring additional coatings. In particular, the Cr₂O₃ product layer is unstable at 1000℃ and higher temperatures; therefore, it is necessary to improve the oxidation resistance. In this study, an aluminide (Fe₂Al₅ and FeAl₃) coating layer was formed on the surface of STS 630 specimens through Al diffusion coatings from 500℃ to 700℃ for up to 25 h. Because the coating layers of Fe₂Al₅ and FeAl₃ could not withstand temperatures above 1200℃, an Al₂O₃ coating layer is deposited on the surface through static oxidation treatment at 500℃ for 10 h. To confirm the ablation resistance of the resulting coating layer, dynamic flame exposure tests were conducted at 1350℃ for 5-15 min. Excellent oxidation resistance is observed in the coated base material beneath the aluminide layer. The conditions of the flame tests and coating are discussed in terms of microstructural variations.

• Korean Journal of Materials Research
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• v.29 no.10
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• pp.631-638
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• 2019

As automation systems become more common, there is growing interest in functional labeling systems using organic and inorganic hybrid materials. Especially, the demand for thermally and chemically stable labeling paper that can be used in a high temperature environment above $300^{\circ}C$ and a strong acid and base atmosphere is increasing. In this study, a composite coating solution for the development of labeling paper with excellent thermal and chemical stability is prepared by mixing a silica inorganic binder and titanium dioxide. The silica inorganic binder is synthesized using a sol-gel process and mixed with titanium dioxide to improve whiteness at high-temperature. Adhesion between the polyimide substrate and the coating layer is secured and the surface properties of the coating layer, including the thermal and chemical stability, are investigated in detail. The effects of the coating solution dispersion on the surface properties of the coating layer are also analyzed. Finally, it is confirmed that the developed functional labeling paper showed excellent printability.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.10
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• pp.105-110
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• 2020

Radioactive Oxides are formed on the surface of the primary equipment in a nuclear power plant. In order to remove the oxide film that is formed on the surfaces of the equipment, chemical and physical decontamination technologies are used. The disadvantage of traditional technologies is that they produce secondary radioactive wastes. Therefore, in this study, the short-pulsed laser eco-friendly technology was used in order to reduce production of the secondary radioactive wastes. They were also used to minimize the damages that were caused on the base material and to remove the contaminated oxide film. The study was carried out using a Stainless steel 304 specimen that was coated with nickel-ferrite particles. Further, the laser source was selected with two different wavelengths. Furthermore, the depth of the coating layer was analyzed using a 3D laser microscope by changing the laser ablation conditions. Based on the analysis, the optimal conditions of ablation were determined using a 1064nm short-pulsed laser ablation technique in order to remove the radioactively contaminated oxide film from the irradiated stainless steel surface.

• Korean Journal of Metals and Materials
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• v.50 no.9
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• pp.659-667
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• 2012

Alloy 617 is a Ni-base superalloy and a candidate material for the intermediate heat exchanger (IHX) of a very high temperature gas reactor (VHTR) which is one of the next generation nuclear reactors under development. The high operating temperature of VHTR enables various applications such as mass production of hydrogen with high energy efficiency. Alloy 617 has good creep resistance and phase stability at high temperatures in an air environment. However, it was reported that the mechanical properties decreased at a high temperature in an impure helium environment. In this study, high-temperature corrosion tests were carried out at $850^{\circ}C-950^{\circ}C$ in a helium environment containing the impurity gases $H_2$, CO, and $CH_4$, in order to examine the corrosion behavior of Alloy 617. Until 250 h, Alloy 617 specimens showed a parabolic oxidation behavior at all temperatures. The activation energy for oxidation in helium environment was 154 kJ/mol. The SEM and EDS results elucidated a Cr-rich surface oxide layer, Al-rich internal oxides and depletion of grain boundary carbides. The thickness and depths of degraded layers also showed a parabolic relationship with time. A normal grain growth was observed in the Cr-rich surface oxide layer. When corrosion tests were conducted in a pure helium environment, the oxidation was suppressed drastically. It was elucidated that minor impurity gases in the helium would have detrimental effects on the high-temperature corrosion behavior of Alloy 617 for the VHTR application.