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키토산을 첨가한 콤포짓트 레진의 기계적 성질과 항균성에 관한 연구
최낙찬,모웅남,이용준 조선대학교 구강생물학연구소 2003 口腔生物學硏究 Vol.27 No.1
The purpose of this study was to evaluate the mechanical and anti-microbial properties of newly prepared chitosan G for human gingival fibroblast. Compressive strength, diametral tensile strength and tensile strength of specimens of resin composite, with or without chitosan G incorporated, were measured. Using a SEM (S-4700, Hitach, Japan), pictures of microbes were taken and adherent capability of microbes to the surface of resin composite was investigated. The results were as follows; 1. The values of compressive strength, diametral tensile strength and tensile strength, composite resin containing 7㎎/㎖ chitosan G were higher than the control group(p>0.05) but composite resin containing 40 ㎎/㎖ chitosan G were either the same or lower than the control group(P<0.05) 2. The MIC of newly prepared chitosan G for S mutans KCTC 3065 and C albicans KCTC 7965 were more than 2 ㎎/㎖. 3. The adherent capability of microbes significantly decreased as the amount of chitosan G increased in the test specimens compared to the control group for C aibicans KCTC 7965 (P<0.05) but there was no statistical significance for S mutans KCTC 3065(p>0.05) . 4. The cytotoxicity of newly prepared chitosan G for human gingival fibroblast was not showed. In conclusion, resin composite with chitosan G incorporated did not show any statistically significant difference for mechanical properties (p>0.05) but it showed a significant antimicrobial effect against C albicans (P<0.05).
미백 처리된 치아의 표면처리법이 레진과의 결합에 미치는 영향 : A Confocal Laser Scanning Microscopy Study
최낙준,방몽숙 전남대학교 치의학연구소 2002 구강과학 Vol.14 No.3
The purpose of this study was to estimate the effect of a bleaching agent on tooth surfaces and to evaluate the resin bond strength according to different surface treatments on bleached teeth. To prepare for the experimental samples, first. extracted human third molars were used and the body portions of the crowns were cut into four equal-sized specimens. Next, each specimen was mounted in an plastic bottle with self-cured resin and highly polished to have them reveal the enamel or dentin surfaces. Then, the enamel(E) and dentin(D) specimens were divided into four;1)non-bleached, laser-treated(NBLA) group 2)bleached, laser-treated(BLLA) group 3)non-bleached, acid-treated(NBAC) group and 4)bleached, acid-treated(BLAC)ㅁroup. Here. opalescence®(10% carbamide peroxide) was used for bleaching agent. The treated specimens were observed by confocal laser scanning microscopy and bonded with composite resin for shear bond test. The following results were obtained from this experiment: 1. Compared with the ENB group, the EBL group was shown to be dyed about 20μm deeper with rhodamine B. The DBL group appeared to be caved in at the entry part of the dentinal tubules, was dyed about 20μm deeper and 5μm wider in diameter, compared with the DNB group. 2. In comparison with the EBLAC group. the ENBAC group looked evenly bonded with the resin, while the DNBAC group, compared to DBLAC group. was observed to have its resin tags penetrated about 50μm deeper. Other than those, however, no observable differences between ENBLA and EBLLA group or between DNBLA and DBLLA group were found. 3. At the shear bond test. the ENBAC group was shown to have statistically significant higher shear bond strength than the EBLAC group(p<(0.05). No statlstically significant differences between the ENBLA and the EBLLA groups were observed(f)0.05). 4. At the shear bond test, the DNBAC group was shown to have statistically significant higher shear bond strength than the DBLAC group(p<0.05) No statistically significant differences between the DNBLA and the DBLLA groups were observed(p>0.05). The in vitro observations above suggest that tooth-bleaching procedure brings a certain change on enamel and dentin surfaces and it weakens the shear bond strength with composite resin when the bleached tooth was acid-treated.
최낙준(Nak-Joon Choi),최경호(Kyoung-Ho Choi),서상호(Sang-Ho Suh) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
Pneumatic waste collection system (hereinafter “PWCS”) will be popularized by solving sanitary problems of conventional door-to-door waste collection system and meeting quality of living. Initial conceptual design and investigation of PWCS are very important because of difficulty in pipeline modification and security of design life over 20 years after installation of PWCS. Module design of PWCS is based on sub-assemblies and parts with parametric design and it can be re-used during modeling and design process. Module design can provide 3D modeling for computational fluid dynamics and structural analysis for PWCS performance evaluation effectively.
WinBlade 를 이용한 수평축 풍력터빈 유동-구조 해석 자동화
최낙준(NAK JOON CHOI),이동화(DONG HWA LEE),최경호(KYOUNG HO CHOI),김재성(JAE SUNG KIM) (사)한국CDE학회 2014 한국 CAD/CAM 학회 학술발표회 논문집 Vol.2014 No.8
Renewable energy has been actively studied as the new energy sources to replace fossil fuels recently. Among them, the wind energy is evenly distributed in the worldwide comparing to other renewable energy. The main parts of the horizontal axis wind turbine among the various wind turbine system are a turbine blade, main shaft, and tower. Design and simulation analysis can be very important role to evaluate the performance and structural stability of the wind turbine. However, the software of component design, system design and simulation is mostly dependent on the oversea products in Korea. Therefore, the design and simulation software developed on domestic is required at this time. For this reason, WinBlade was developed to be able to conduct the design and simulation of main components of wind turbine without expert knowledge. The objective in this paper is automation of design and simulation of main components of wind turbine using WinBlade.
레진전장관의 금속면 처리방법이 레진과 금속간 접착강도에 미치는 영향
최낙준,방몽숙 전남대학교 치과대학 1993 전남치대논문집 Vol.5 No.1
The purpose of this experiment was to determine the effects of various surface treatments on veneering resin to metal bond for Ni-Cr alloy. The metal surfaces were treated as follows. Group 1 : Ground with carborudum point and followed by silicoating Group 2 : Sandblasted with 50 ㎛ aluminum oxide and followed by silicoating Group 3 : Sandblasted with 250 ㎛ aluminum oxide and followed by silicoating Group 4 : Beaded with 200 ㎛ retention structures and followed by silicoating Group 5 : Silicoated in as cast condition Group 6 : Beaded with 200 ㎛ retention structures only All specimens were veneered with resin. Each group was consisted of 20 specimens. 10 specimens were storaged in 37℃ water for 3 days and the rest 10 specimens were thermocycled 1000 times at temperature of 5℃ to 55℃. The effects of various surface treatments on the bond strength between resin and metal interface were studied by means of four-point flexure test. The specimens which had been ground with carborundum point, sandblasted with 50 ㎛ and 250 ㎛ aluminum oxide, beaded with 200 ㎛ retention structures and not been treated were observed with SEM. The following results were obtained 1. The bond strength of groups 2, 3, 4 and 6 were higher than the that of groups 1 and 5 (p<0.05) in the case of being storaged in 37℃ water for 3 days, and there was no statistically significant difference in bond strength among groups 2, 3, 4 and 6, and between groups 1 and 5(p>0.05). 2. The bond strength of the case of being thermocycled decreased in the following orders : groups 2, group 4, group 3, group 6, group 1, group 5 and there was no statistically significant difference in bond strength among groups 2, 3 and 4, between groups 1 and 5(p>0.05). 3. A statistical difference in bond strength of each group between being storaged and being thermocycled was demonstrated for group 5(p<0.05). 4. The treated surfaces of groups 2, 3 and 4 had more fine undercut than the that of groups 1 and 5 with SEM.
Choi, Nak-Sun,Kim, Dong-Wook,Yang, Chang-Seob,Chung, Hyun-Ju,Kim, Hong-Joon,Kim, Dong-Hun The Korean Institute of Electrical Engineers 2011 Journal of Electrical Engineering & Technology Vol.6 No.6
This study presents three different magnetization models for identifying unknown magnetization of the ferromagnetic thin plate of a ship. First, the forward problem should be solved to accurately predict outboard magnetic fields due to the magnetization distribution estimated at a certain time. To achieve this, three different modeling methods for representing remanent magnetization (i.e., magnetic charge method, magnetic dipole array method, and magnetic moment method) were utilized. Material sensitivity formulas containing the first-order gradient information of an objective function were then adopted for an efficient search of an optimum magnetization distribution on the hull. The validity of the proposed methods was tested with a scale model ship, and field signals predicted from the three different models were thoroughly investigated with reference to the experimental data.
Design Optimization of Waveguide Filters Using Continuum Design Sensitivity Analysis
Nak-Sun Choi,Dong-Hun Kim,Giwoo Jeung,Joon-Goo Park,Jin-Kyu Byun IEEE 2010 IEEE transactions on magnetics Vol.46 No.8
<P>This paper presents a new methodology for design optimization of dielectric waveguide filters based on the continuum design sensitivity analysis in conjunction with standard electromagnetic analysis codes. To achieve this, first, an analytical sensitivity formula in the frequency domain is systematically derived by exploiting the augmented Lagrangian method, material derivative concept and adjoint variable method. Then unified program architecture integrating several engineering software packages into a design tool is proposed for optimum design of high-frequency devices. A 3-D dielectric resonator used in waveguide filters has been tested to prove the validity of the proposed method.</P>