• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.963-966
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• 2000

Plasma display panel (PDP) is a type of flat panel display utilizing the light emission that is produced by gas discharge. Barrier Ribs of PDP separating each sub-pixel prevents optical and electrical crosstalk from adjacent sub-pixels. Mold for forming barrier ribs has been newly researched to overcome the disadvantages of conventional manufacturing process such as screen printing, sand-blasting and photosensitive glass methods. Mold for PDP barrier ribs have stripes of micro grooves transferring stripes of glass-material wall. In this paper. Stripes of grooves of which width 48 um, depth 124um, pitch 274um was acquired by machining the material of WC with dicing saw blade. Maximum roughness of the bottom and sidewall of the grooves was respectively 120 nm, 287 nm. Maximum tilt angle caused by difference between upper-most width and lower-most width was 2$^{\circ}$. Maximum Radius of curvature of bottom was 7.75 ${\mu}{\textrm}{m}$. This results meets the specification for barrier ribs of 50 inch XGA PDP. Forming the glass paste will be followed by using mold in the near future.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.290-290
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• 2009

Blu-ray Disk, the next generation optical information storing equipment used Blu-ray is the next generation leading storing equipment that has capacity is about from six times to thirty-five times bigger than the existing CDs, DVDs. Especially, we need elaborate optical pick-Up equipment to record and recognize detailed date. Moreover, Blu-ray disk has so narrow track-pitch so it is used high NA(Numerical Aperture) aspheric glass objective lens. In this research, we processed optical pick-up aspheric glass objective lens molding press core by parallel grinding method with ultra precision machining and mold core surface measured form accuracy(PV), surface roughness(Ra).

• Restorative Dentistry and Endodontics
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• v.7 no.1
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• pp.77-83
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• 1981

The purpose of this study was to observe the bonding strength between tooth surface (enamel and dentin) and restorative filling materials which are two composite resins (Clearfil and Concise) and Glass ionomer cement, after etching with 50% phoshoric acid and 37% citric acid. To measure the bonding strength in enamel, the labial surface of upper anterior tooth was cut flatly with using carborundum disk and polished with sand paper disk, and to measure in dentin, the dentin surface was prepared by grinding upper part of posterior tooth horizontally. After washing the tooth surface with water and drying with air blast, the prepared tooth surface was etched. In glass ionomer cement, 50% phosphoric acid and 37% citric acid were used, in Clearfil 40% phosphoric acid was used and in Concise, 50% phosphoric acid and 37% citric acid were used as etchant for 1 minute. After the copper band which is 5 mm in diameter and 5 mm in height was fixed on the prepared surface and each filling material was inserted into the copper band, the hooking loop was inserted into filled material in the copper band before setting to make it easily that the load is applied on the specimen. After all specimens were immersed in water at $37^{\circ}C$ for 1 week, this specimen was placed on the load cell of tensile test apparatus, and specimen was pulled at the cross-head speed of 0.8 mm per minute. The following results were obtained 1) In glass ionomer cement, the bond strength obtained by 37% citric acid was higher than one obtained by 50% phosphoric acid in enamel and dentin surfaces. The bond strength obtained in non-etched surface was much less than one by etchants in enamel and dentin surface. 2) In Clearfil, the bond strength obtained by 40% phosphoric acid was 4 times more than one obtained by non etch ant. 3) In Concise, the bond strength obtained by 50% phosphoric acid was almost same as one obtained by 37% citric acid, and the bond strength obtained by non etch ant was much less than one obtained by etchants.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.831-836
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• 2000

During machining, since more than 50% compliance of the cutting point in machine tool structures comes from headstocks, with the remainder coming from beds, slides and structural joints, the structural analysis of the headstock is very important to improve the static and dynamic performances. Especially, in case of machining hard and brittle materials such as glasses and ceramics with the grinding machine, the reinforced headstock with the high damping material is demanded. Since the fiber reinforced composite materials have excellent properties for structures, owing to its high specific modulus, high damping and low thermal expansion, it is expected that the dynamic and thermal characteristics of the headstock will be improved if they are employed as the materials fur headstock. In this paper, the design and the manufacturing methods as well as the static and dynamic characteristics of a steel-composite hybrid headstock were investigated analytically and experimentally to improve the performance of the grinding machine system.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.1
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• pp.110-115
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• 2003

Dens evaginatus is an anomalous tooth development arising during morphodifferentiation. It is most often reported in premolar, and familial occurrence has been reported. The primary dental complication of dens evaginatus is fracture or wear of the tubercle which leads to pulp exposure, pulpal necrosis and periapical infection. Pathosis of the pulp can occur before complete root formation with cessation of root development. A rational and conservative approach to the management of dens evaginatus in vital teeth includes early diagnosis and treatment to prevent fracture or attrition of the tubercle. This treatment would include careful sequential grinding, pulp capping, preventive resin restoration. When presented with a case of dens evaginatus in a nonvital tooth with incomplete root development, the treatment of choice has been extraction, apexification. We report two cases of dens evaginatus that appear in two sisters. In the elder, a periapical lesion on radiographs is shown, and it is treated by calcium hydroxide apexification. The other sister is early recognized of dens evaginatus, it is treated using glass ionomer cement reinforcing with sequential grinding.

• Korean Chemical Engineering Research
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• v.60 no.1
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• pp.132-138
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• 2022

In this study, a basic study was performed to systematically compare the changes in surface properties according to the post-processing method of the stereolithography (SLA) printing method, which is a photocuring 3D printing method, and to provide information on the post-processing method suitable for the application. Although it was possible to improve some of the transparency of the SLA-type output by regularly changing the irregular microstructure of the surface through polishing, it was difficult to secure sufficient transparency like glass. The change in contact angle characteristics due to grinding showed a tendency to slightly increase as the grinding time increased and the particle size of the sandpaper used was small, but the variation between samples was large and the average contact angle was 77~90°, showing no statistically significant difference. Surface treatment methods other than polishing were tried, and it was confirmed that it was possible to easily and simply improve the transparency by applying a commercially available vehicle scratch remover or silicone oil. In addition, a method for securing high transparency such as glass by using a scratch remover after sequential grinding while reducing the particle size of the sandpaper was proposed. Finally, even after surface treatment through polishing and various methods, it was difficult to secure a contact angle of 90° or more.

• Korean Journal of Materials Research
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• v.20 no.11
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• pp.559-569
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• 2010

The liquid-phase sintering method was used to prepare a glass lens forming core composed of SiC-$Al_2O_3-Y_2O_3$. Spark plasma sintering was used to obtain dense sintered bodies. The sintering characteristics of different SiC sources and compositions of additives were studied. Results revealed that, owing to its initial larger surface area, $\alpha$-SiC offers sinterability that is superior to that of $\beta$-SiC. A maximum density of $3.32\;g/cm^3$ (theoretical density [TD] of 99.7%) was obtained in $\alpha$-SiC-10 wt% ($6Al_2O_3-4Y_2O_3$) sintered at $1850^{\circ}C$ without high-energy ball milling. The maximum hardness and compression stress of the sintered body reached 2870 Hv and 1110 MPa, respectively. The optimum ultra-precision machining parameters were a grinding speed of 1243 m/min, work spindle rotation rate of 100 rpm, feed rate of 0.5 mm/min, and depth of cut of $0.2\;{\mu}m$. The surface roughnesses of the thus prepared final products were Ra = 4.3 nm and Rt = 55.3 nm for the aspheric lens forming core and Ra = 4.4 nm and Rt = 41.9 for the spherical lens forming core. These values were found to be sufficiently low, and the cores showed good compatibility between SiC and the diamond-like carbon (DLC) coating material. Thus, these glass lens forming cores have great potential for application in the lens industry.

• Journal of the Korean Society for Marine Environment & Energy
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• v.11 no.1
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• pp.50-54
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• 2008

There are several basic classes of recycling methods for FRP boats. The main one is 'Mechanical recycling' which involves shredding and grinding of the scrap FRP in a new product. That is one of the simpler and more technically proven methods. It recently has been reported that FRP can be recycled by separating into layers instead of crushing into powder. Many researchers should be more interested in these mechanical recycling for the eligibility. Nevertheless, because resins is very useful renewable energy, most of waste FRP regenerating methods depend on incineration (reclamation) or thermal recycling (pyrolysis). FRP is made up of laminated glass- fiber (roving cloth layer) which is also very unlikely to break into each layer. If there is an extracting method which is efficient and environment friendly removing glass fiber from waste FRP, it should also solve the another urgent problem. Laminated glass-fiber which is very limited renewable, is a serious barrier to wast FRP boat regenerating. This study is to propose a new extracting method which is efficient and environment friendly waste FRP regenerating system. And it should be applied to renewable energy applications with the waste resins of FRP. Also recycling glass fiber obtained by the separation of the roving layer from waste FRP will be consider to be useful for concrete products or structures.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.1053-1058
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• 2001

Contemporary architecture calls for a wide range of surface textures and treatments. A surface compatible with the architect's design may vary from a glass-smooth finish to one requiring special sculptured ornamentation. These surfaces require many different types of form sheathing and lining. Chemical retarders applied to the form surface make It possible to remove surface mortar and expose the aggregate after forms have been removed. Variation in finish may also be achieved by grinding, chiseling, hammering, and sandblasting after the concrete has set. Precast panels as forms or liners may provide the desired surface finish; sometimes a combination several of these techniques is used.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.34-34
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• 2004

정보의 급속한 발전, 컴퓨터, 가전기기, 자동차등 내구 소비재의 제품 개발기간 단축, 생산자의 지속적인 생산성 향상 활동, 소비자 선호의 다양성, 품질 요구 수준 상승 등 제반 환경변화는 절삭가공부분에 있어 핵심이 되고 있다. 여기에 전통적 제조업의 고부가가치화 및 새로운 시스템의 도입 등과 맞물려 최근의 초정밀 공작기계는 고속화, 고정밀화를 바탕으로 크게 발전하고 있다, 특히 21세기로 향하는 지금 공작기계 기술은 고속화, 정밀화, 개방화, 환경친화의 방향으로 혁신을 지속하고 있으며, 머지 않아 마이크로 프로세서의 급속한 발전에 힘입어 고속화 기술은 극 초고속화 단계로, 정밀화 기술은 극 초정밀화 단계로, CNC 기술은 오픈화 및 네트워크화를 통한 다양한 통신기술이 부가됨으로써 설계, 생산, 영업 및 서비스 정보와 연계시켜 통합제어를 통한 타 지역의 공작기계를 원격제어 할 수 있는 단계로 이르게 될 것이다.(중략)