• 한국HCI학회:학술대회논문집
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• 2006.02a
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• pp.878-883
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• 2006

반투명 물체(Translucent Object)는 불투명한 물체와는 달리 물체 내부에서 산란이 일어난다. 반투명 물체의 한 표면(Surface)을 렌더링하기 위해서는 그 표면의 정규 벡터뿐만 아니라 그 표면의 주변 기하 정보가 필요하다. 그러나 그래픽 하드웨어 구조는 반투명 물체의 실시간 렌더링의 구현에 많은 제약을 준다. 3D 기하 정보 대신에 라디언스 맵(Radiance map)과 깊이 맵(Depth map)과 같은 투영 영상(Projected Image)을 기반으로 하는 영상 공간 접근 방법(Image Space Approach)을 사용함으로써 GPU 상에서 반투명 재질을 실시간으로 표현할 수 있다. 본 논문에서는 영상 공간 접근 방법(Image Space Approach)의 연장선에서 시점을 달리한 여러 장의 투영 영상을 이용함으로써 기존의 한 장의 투영 영상만을 이용한 방법이 가지고 있는 가시성 한계점을 해결한다. 또한 복수 투영 영상의 이용에 따른 계산량 증가에 의해서 손실된 프레임 속도(Frame Rate)에 대해 분석한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2005.11a
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• pp.1407-1410
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• 2005

반투명 물체(Translucent Object)는 불투명한 물체와는 달리 물체 내부에서 산란이 일어난다. 따라서 반투명 물체의 한 표면(Surface)을 렌더링하기 위해서는 그 표면의 정규 벡터뿐만 아니라 그 표면의 주변 기하 정보가 필요하다. 그러나 그래픽 하드웨어 구조는 불투명한 표면의 렌더링에만 적합하게 설계 되었기 때문에, 반투명 물체의 실시간 렌더링의 구현에는 많은 제약이 따른다. 이 논문에서는 영상 공간 접근 방법(Image Space Approach)의 연장선에서 기존의 방법론이 가지고 있는 한계점을 해결함으로써, 반투명 재질의 실시간 렌더링을 위한 효과적인 방법을 제시한다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2014.11a
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• pp.180-181
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• 2014

Optically translucent Sialon ceramics was fabricated by hot pressed sintering method. The Sialon ceramics was laser textured and their tribological performance was observed. Starved lubrication method was applied on Sialon ceramics with different dimple spacing under a load of 10N and at room temperature. The material having high dimple spacing ($200{\mu}m$) shows low coefficient of friction. The material shows mild wear and therefore, wear rate of steel ball (meeting partner) was observed to measure wear rate. Different phases Sialon ceramics were analyzed by XRD patterns. Moreover, the mechanical properties of the Sialon ceramics were observed.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.205-206
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• 2006

A ball-shape alumina arc-tube for low-wattage lamp was developed by the PIM process. An ultra high purity translucentgrade alumina powder was used. In injection molding process, a hot-runner type mold was developed. The translucent-grade alumina powder was extremely sensitive to contamination so that the injection molding condition and atmosphere control in the furnace should be taken care of with extreme caution. Contamination sources were pinpointed with EPMA. The arc-tube was molded in half and two halves were bonded in the middle by a new bonding technique at room temperature developed in this study.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1998.06a
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• pp.993-996
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• 1998

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1998.06a
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• pp.997-1000
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• 1998

• Journal of the Korean Ceramic Society
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• v.50 no.1
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• pp.75-81
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• 2013

We fabricated translucent opal glass to replace the polycarbonate diffuser in LED lighting systems in order to solve the durability problem. Batch materials of opal glass with a composition of calcium phosphate were created and melted at $1550^{\circ}C$, and the effect of opaqueness was identified by an addition of 1~7% calcium phosphate as an opacifier raw material. As a result, translucent opal glass was obtained by the melting of the mixed batch materials with a composition of more than 5% calcium phosphate glass at $1550^{\circ}C$ for 2 hrs, which had excellent optical properties for the diffuser of a LED lighting system with no dazzling from direct light by a high haze value exceeding 90% and a low parallel transmittance value of about 5%. For the thermal properties, the thermal expansion coefficient was found to be $5.6{\sim}5.9{\times}10^{-6}/^{\circ}C$ and the softening point was $874{\sim}884^{\circ}C$. In addition, good thermal properties such as good thermal shock resistance and feasibility for use with a general manufacturing process during the forming of glass tubes and bulbs were noted. Therefore, it is concluded that this translucent opal glass can be used as a glass diffuser material for LED lighting due to its high heat resistance and high durability as a replacement for a polycarbonate diffuser.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.3
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• pp.120-126
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• 2014

Translucent green colored opal glass was fabricated to substitute polycarbonate diffuser of LED lighting in order to solve the durability problem. Batch materials of green colored opal glass with the composition of calcium phosphate for opacifier and iron oxide for colorant were made and melted at $1550^{\circ}C$. As the results, translucent green colored opal glass was obtaind, which had excellent optical properties compare with nomal color glass for the diffuser of LED lighting, with no dazzling from direct light by high haze value over 90 % and low parallel transmittance value about 1 %. Therefore, it is concluded that this translucent green colored opal glass can be used for the glass diffuser materials of LED lighting with high heat resistance and high durability to substitute polycarbonate diffuser.

• The Journal of Advanced Prosthodontics
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• v.11 no.6
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• pp.324-330
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• 2019

PURPOSE. The aim of the study was to evaluate and compare the fracture resistance and modes of fracture of monolithic zirconia crowns with two preparation designs. MATERIALS AND METHODS. Forty human maxillary first premolar teeth were extracted for orthodontic purposes and divided into two main groups (n=20): Group A: monolithic traditional zirconia; Group B: monolithic translucent zirconia. The groups were further subdivided into two subgroups (n=10): (A1, B1) shoulder margin design; (A2, B2) feather-edge margin design. Teeth were prepared with either a 1 mm shoulder margin design or a feather-edge margin design. The prepared teeth were scanned using a digital intraoral scanner. The crowns were cemented using self-adhesive resin cement. All cemented teeth were stored in water for 7 days and thermocycling was done before testing. All samples were subjected to compressive axial loading until fracture. The fractographic analysis was done to assess the modes of fracture of the tested samples. RESULTS. The highest mean values of fracture resistance were recorded in kilo-newton and were in the order of subgroup A1 (2.903); subgroup A2 (2.3); subgroup B1 (1.854) and subgroup B2 (1.523). One-way ANOVA showed a statistically significant difference among the 4 subgroups. Concerning modes of fracture, the majority of samples in subgroups A1 and B1 were fracture of restoration and/or tooth, while in subgroups A2 and B2, the majority of samples fractured through the central fossa. CONCLUSION. Even though all the tested crowns fractured at a higher level than the maximum occlusal forces, the shoulder margin design was better than the feather-edge margin design and the monolithic traditional zirconia was better than the monolithic translucent zirconia in terms of fracture strength.

• The Journal of Advanced Prosthodontics
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• v.14 no.2
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• pp.96-107
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• 2022

PURPOSE. Microstructural and physico-mechanical characterization of highly translucent zirconia, prepared by milling technology (CAD-CAM) and repeated firing cycles, was the main aim of this in vitro study. MATERIALS AND METHODS. Two groups of samples of two commercial highly-translucent yttria-stabilized dental zirconia, VITA YZ-HT^White (Group A) and Zolid HT + White (Group B), with dimensions according to the ISO 6872 "Dentistry - Ceramic materials", were prepared. The specimens of each group were divided into two subgroups. The specimens of the first subgroups (Group A₁ and Group B₁) were merely the sintered specimens. The specimens of the second subgroups (Group A₂ and Group B₂) were subjected to 4 heat treatment cycles. The microstructural features (microstructure, density, grain size, crystalline phases, and crystallite size) and four mechanical properties (flexural strength, modulus of elasticity, Vickers hardness, and fracture toughness) of the subgroups (i.e. before and after heat treatment) were compared. The statistical significance between the subgroups (A₁/A₂, and B₁/B₂) was evaluated by the t-test. In all tests, P values smaller than 5% were considered statistically significant. RESULTS. A homogenous microstructure, with no residual porosity and grains sized between 500 and 450 nm for group A and B, respectively, was observed. Crystalline yttria-stabilized tetragonal zirconia was exclusively registered in the X-ray diffractograms. The mechanical properties decreased after the heat treatment procedure, but the differences were not statistically significant. CONCLUSION. The produced zirconia ceramic materials can be safely (i.e., according to the ISO 6872) used in extensive fixed prosthetic restorations, such as substructure ceramics for three-unit prostheses involving the molar restoration and substructure ceramics for prostheses involving four or more units. Consequently, milling technology is an effective manufacturing technology for producing zirconia substructures for dental fixed all-ceramic prosthetic restorations.