• The Journal of Korean Academy of Prosthodontics
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• v.52 no.2
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• pp.67-73
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• 2014

Purpose: The purpose of present study is to compare mechanical properties and microstructural characteristics of fractured surface for cast, 3-D printing laser sintered and CAD/CAM milled cobalt-chromium (Co-Cr) alloy specimens and to investigate whether laser sintered technique is adequate for dental applications. Materials and methods: Thirty six flat disc shape Co-Cr alloy specimens were fabricated for surface hardness test and divided into three groups according to the manufacturing methods; 12 specimens for casting (n=12), 12 specimens for laser sintered technology (n=12) and 12 specimens for milled technology (n=12). Twelve dumbbell shape specimens for each group were also fabricated for a tensile test. Statistical comparisons of the mechanical properties for the alloys were performed by Kruskal-Wallis test followed by Mann-Whitney and Bonferroni test. The microstructural characteristics of fractured surfaces were examined using SEM. Results: There were significant differences in the mean Vickers hardness values between all groups and the cast specimen showed the highest (455.88 Hv) while the CAD/CAM milled specimen showed the lowest (243.40 Hv). Significant differences were found among the three groups for ultimate tensile strength, 0.2% yield stress, elongation, and elastic modulus. The highest ultimate tensile strength value (1442.94 MPa) was shown in the milled group and the highest 0.2% yield strength (1136.15 MPa) was shown in the laser sintered group. Conclusion: Different manufacturing methods influence the mechanical properties and microstructure of the fractured surfaces in Co-Cr alloys. The cast Co-Cr alloy specimens showed the highest Vickers hardness, and the CAD/CAM milled specimens revealed the highest tensile strength value. All alloys represent adequate mechanical properties satisfying the ISO standards of dental alloy.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.1
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• pp.89-94
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• 2010

Patterning bacteria and cells on substrates has potential applications in molecular biology, antimicrobial drug screening, environmental monitoring and tissue engineering. We developed a technique to deposit two-dimensional array of bacterial cells onto an agar plate by modifying commercially available thermal inkjet printers. The concentration of the bacterial solution in the cartridge was carefully determined to ensure a single cell suspension in a droplet ejected from a nozzle. We measured quantitatively the effects of the bacterial concentration and the agar concentration on patterning performance. Bacterial patterning by inkjet printer is a low-cost and versatile technique which may replace the existing sophisticated methods.

• Journal of the Korean Society of Costume
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• v.60 no.10
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• pp.100-117
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• 2010

This thesis has three main purposes: first, will show kinds, patterns, types, expression techniques of modern korean women's trimmings by every ten years. Second, it is to trace the effect of each decade on women's Hanbok trimming designs. Third, it will point out factors. that caused the change of modern Korean women's Hanbok trimming design patterns. Henceforth, there comes the result of the research and analysis. Trimming design patterns of modern women's Hanbok can be divided into three categories temporally: The first period of from 1910s to the first half of 1950s saw that design patterns did not changed much from traditional ones. It is because there were many catastrophes such as the invasion of Japanese Empire and Korean War. The compound design had expressed people's wish to earn many sons and babies at the end of Joseon Dynasty. But it turned to wishing luck for individuals affected by individualism and liberalism imported from the west. Realistic designs are the most frequently used and the least lines made up patterns. The second period of from the latter half of 1950s to 1970s saw that women wore their Jeogories and Chimas as suits. Screen printing technique enabled for various design patterns to come out. And the development of textile industry introduced various expression techniques such as making lace, meshing, flocking, burn-out etc cetera. The third period of 1980s saw that Hanbok became a kind of luxurious clothe as people's living standard rose. Hanbok again came into the spotlight, Hanbok designers came forward and their individualities are respected. The characteristic expression technique of grey-dying and geometric design patterns are more frequently used for the simple and modern beauty.

• The Journal of Advanced Prosthodontics
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• v.13 no.5
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• pp.327-332
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• 2021

PURPOSE. The purpose of this in vitro study was to evaluate the accuracy of digitally designed removable partial denture (RPD) frameworks, constructed by additive and subtractive methods castable resin patterns, using comparative 3D analysis. MATERIALS AND METHODS. A Kennedy class III mod. 1 educational maxillary model was used in this study. The cast was scanned after modification, and a removable partial denture framework was digitally designed. Twelve frameworks were constructed. Two groups were defined: Group A: six frameworks were milled with castable resin, then casted by the lost wax technique into Co-Cr frameworks; Group B: six frameworks were printed with castable resin, then casted by the lost wax technique into Co-Cr frameworks. Comparative 3D analysis was used to measure the accuracy of the fabricated frameworks using Geomagic Control X software. Student's t-test was used for comparing data. P value ≤ .05 was considered statistically significant. RESULTS. Regarding the accuracy of the occlusal rests, group A (milled) (0.1417 ± 0.0224) showed significantly higher accuracy than group B (printed) (0.02347 ± 0.0221). The same results were found regarding the 3D comparison of the overall accuracy, in which group A (0.1501 ± 0.0205) was significantly more accurate than group B (0.179 ± 0.0137). CONCLUSION. In indirect fabrication techniques, subtractive manufacturing yields more accurate RPDs than additive manufacturing.

• The Journal of the Korea Contents Association
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• v.20 no.12
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• pp.460-470
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• 2020

In modern life, interior decoration has been transformed into a psychological synergistic effect of space, greatly affecting human sensibility. The main point of view in this paper is to study the discovery of new decorative effects and the possibility of products that can replace imported tiles, which account for more than 60% of the walls of indoor spaces closely related to daily life. The solution is to create point tiles using color glass plaster techniques developed in 2018 and to explore the possibility of decorating art walls to meet consumers' purchasing needs using simulations. The four patterns applied to the a paintbrush, resist printing, cutting technique, and inlaid patterns, and the traditional color development effect of the medium color suited to our sensibilities was studied. In addition, through simulation, art walls and acrylic using color glass styles were also used in the kitchen, living room and empty space of the bathroom. Based on this research, ceramic point tiles with a new perspective will be explored and the interior using walls will be activated.

• The Journal of Advanced Prosthodontics
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• v.14 no.1
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• pp.22-31
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• 2022

PURPOSE. The purpose of this study was to investigate the misfit and screw preload at the implant abutment connection of implant supported fixed dental prosthesis with cantilever (ICFDP) manufactured using different digital manufacturing techniques and to compare the screw preload before and after cyclic loading. MATERIALS AND METHODS. Mandibular jaw model with four intra-foraminal implants was scanned using digital scanner. Stereolithography file was used to design a framework with nonengaging (NE) abutments and 10 mm cantilever distal to one terminal implant. Five frameworks were constructed using combined digital-conventional techniques (CAD-cast), and five frameworks were constructed using three-dimensional printing (3DP). Additional CAD-cast framework was constructed in a way that ensures passive fit (PF) to use as control. Scanning electron microscope (SEM) measured the implant abutment connection misfit. Sixty screws were used on the corresponding frameworks. Screws were torqued and pre-cyclic loading reverse torque value (RTV) was recorded. Frameworks were subjected to 200,000 loading cycles with a loading point 9 mm from the center of terminal implants adjacent to the cantilever and post-cyclic loading RTVs were recorded. RESULTS. Microscopic readings showed significant differences between frameworks. PF demonstrated the lowest measurements of 16.04 (2.6) ㎛ while CAD-cast demonstrated the highest measurements of 29.2 (3.1) ㎛. In all groups, RTVs were significantly lower than the applied torque. Post-cyclic loading RTV was significantly lower than pre-cyclic loading RTV in PF and 3DP frameworks. Differences in RTVs between the three manufacturing techniques were insignificant. CONCLUSION. Although CAD-cast and three-dimensionally printed (3DP) both produce frameworks with clinically acceptable misfit, 3DP might not be the technique of choice for maintaining screw's preload stability under an aggressive loading situation.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1824-1826
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• 1999

In order to develop key technologies for a kW class for polymer electrolyte fuel cell (PEFC), various membranes (Nafion(112, 115, 117), Dow, Flemion, Gore, and Hanwha), and electrocatalysts (Pt/C, PtNi/C PtNiCo/C and PtRu/C) were used in the fabrication of the MEAs by using transfer printing technique. The effects of the thickness of Nafion membranes, electrocatalysts and the operating conditions (e.g. temperature, reactant gas pressure, and composition) on the performance of the MEA were investigated in the PEFC single cell($O_2/H_2$, and Air/$H_2$ cell). The performances of the MEAs for $O_2/H_2$ and Air/$H_2$ cells has been evaluated.

• Transactions of the Society of Information Storage Systems
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• v.3 no.3
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• pp.129-134
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• 2007

Boron nitride (BN) is a highly attractive material for wear resistant applications of mechanical components. BN is super hard and it is the second hardest of all known materials. It also has a high thermal stability, high abrasive wear resistance, and in contrast to diamond, BN does not react with ferrous materials. The motivation of this work is to investigate the tribological properties of BN for potential applications in ultra-precision components for data storage, printing, and other precision devices. In this work, the wear characteristics of BN thin films deposited on DLC or Ti buffer layer with silicon substrate using RF-magnetron sputtering technique were analyzed. Wear tests were conducted by using a pin-on-disk type tester and the wear tracks were measured with a surface profiler. Experimental results showed that wear characteristics were dependent on the sputtering conditions and buffer layer. Particularly, BN coated on DLC layer showed better wear resistant behavior. The range of the wear rates for the BN films tested in this work was about 20 to $100{\mu}m^3$/cycle.

• Korean Journal of Materials Research
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• v.14 no.3
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• pp.224-228
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• 2004

Respectively the powder made of ZnO added $SnO_2$ was prepared by coprecipitation method and the thick film gas sensor was fabricated by screen-printing technique, The morphology and phase of the powder and film was investigated by SEM and XRD. The specific area of the particle was linearly increased with ZnO contents. Target gas was di(propylene glycol) methylether ($CH_3$($OC_3$$H_{6}$ )$_2$OH, DPGME), which is simulant gas of blister gas. The gas sensing characteristics for DPGME were examined with flow type measurement system and the concentrations of target gas were controlled from 500 ppb to 1500 ppb. ZnO (2 wt%) added $SnO_2$ showed maximum sensitivity to DPGME at $300^{\circ}C$.

• Korean Journal of Acupuncture
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• v.29 no.4
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• pp.537-553
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• 2012

Objectives : Ever Since it was made in the middle of 17th century by Saamdoin, Saam acupuncture method has been handed down to acupuncturists as a written form, playing a huge role in using for treating diseases of people in Korea. Saam acupuncture method development of any process, and have been propagated in a foreign country to study. Methods : Analysis of ancient medical books, we studied the evolution of Saam acupuncture method. And we looked abroad Saam acupuncture method have been propagated abroad by examining how. Results : At the end of Joseon Dynasty, lots of clinical cases were added to Saam acupuncture method and as a result, it helped acupuncturists understand how it really worked. During the Japanese colonial era, it was introduced to more people thanks to the development of a printing technique. After Korea's liberation from Japan, many scholars have studied Saam's acupuncture method, and they also have applied it to clinical cases in various ways. Conclusions : With its superiority and creativeness, Saam acupuncture method spread to Japanese acupuncturists in the name of Meridian Therapy during the Japanese colonial era. It had a great impact on medicine in China and many other countries, as well.