만곡 근관에서 삼각 혹은 장방형 단면 구조의 니켈-티타늄 파일 응력 분포에 관한 3차원 유한요소 연구

김현주,이찬주,김병민,박정길,허복,김현철 대한치과보존학회 2009 Restorative Dentistry & Endodontics Vol.34 No.1

이 연구의 목적은 3차원 유한요소 모형 분석을 이용하여 삼각 대칭형과 S형태의 단면 및 변형된 사각 형태인 장방형 단면으로 분류되는 네 종류의 니켈티타늄 파일이 만곡 근관 적용 시의 응력 분포를 비교하는 것이다. 삼각 대칭형 단면 구조의 ProFile #30 / .06과 HeroShaper #30 / .06,장방형 단면구조의 Mtwo #30 / .05와 NRT #30 / .06 파일을 마이크로컴퓨터 단층촬영을 하고 reverse engineering을 통하여 파일의 구조를 얻고 삼차원 유한요소모형을 제작하였다. 모형 근관 내에서 파일이 근관장 끝까지 진입하여 회전할 때 발생하는 von Mises 응력 분포 및 파일의 제거후의 잔류 응력의 분포양상을 ABAQUS 프로그램을 이용하여 비교하였다. 근관 내 회전 시에 발생하는 응력을 관찰하였을 때 NRT 파일에서 가장 큰 응력을 나타냈으며 , 각 파일에서의 최고 응력과 최저 응력을 비교하였을 때 Mtwo파일에서 가장 큰 차이가 나타났다. 응력의 내부 분포 경향을 보았을때 장방형 구조의 단면을 가진 Mtwo 및 NRT 파일에서 불연속적인 응력의 집중 부위가 관찰되었으며 , 근관 외부로 파일을 제거하여 탄성 회복이 일어난 후의 잔류 응력도 NRT 파일에서 가장 높게 나타났다. 이상의 결과로 유추할 때, 삼각대칭 단면 구조를 가진 파일보다 S-형태의 단면과 변형된 사각 형태의 단면 등의 장방형 단면 구조의 파일이 파절의 위험성이 더 클 것으로 사료된다. The purpose of this study was to compare the stress distributions of NiTi rotary instruments bascd on their cross-sectional geometries of triangular shape-based cross-sectional design. S-shaped cross-sectional design and modified rectangular shape-based one using 3D FE models. NiTi rotary files of S-shaped and modified rectangular design of cross-section such as Mtwo or NRT showed larger stress change while file rotation during simulated shaping. The stress of files with rectangular cross-section design such as Mtwo, NRT was distributed as an intermittent pattern along the long axis of file. On the other hand, the stress of files with triangular cross-section design was distributed continuously. When the residual stresses which could increase the risk of file fatigue fracture were analyzed after their withdrawal, the NRT and Mtwo model also presented higher residual stresses. From this result, it can be inferred that S-shaped and modified rectangular shape-based files were more susceptible to file fracture than the files having triangular shape-based one.

세가지 니켈 티타늄 파일의 휨과 비틀림 조건에서의 응력 분포에 관한 3차원 유한요소 연구

김태오,이찬주,김병민,박정길,허복,김현철 大韓齒科保存學會 2008 Restorative Dentistry & Endodontics Vol.33 No.4

이 연구의 목적은 세가지 니켈-티타늄 파일의 휨과 회전 조건 하에서의 응력 분포를 유한요소 모형을 이용하여 비교하는 것이다. ProFile .06/#30, ProTaper와 ProTaper Universal의 F3파일을 마이크로컴퓨터 단층촬영을 하고 reverse engineering을 통하여 세 니켈 티타늄 파일의 구조를 얻고 삼차원 유한요소모형을 제작하였다. 니켈 티타늄 합금의 비선형적인 물리적 성질을 반영하고 ABAQUS 프로그램을 이용하여 휨과 회전 조건 하에서의 기계적인 움직임을 수학적으로 예측 분석하였다. U-형태의 단면 구조를 가진 ProFile이 모형 가운데 가장 좋은 휨 성질을 나타냈다. 동일한 휨량 조건에서는 볼록한 삼각형 단면의 ProTaper가 다른모형보다 많은 힘을 필요로 하였으며, 반면에 가장 높은 von Mises 응력은 ProTaper Universal의 단면에서 움푹 파인 부위에 집중되었다. ProFile 모형은 동일한 크기의 회전력에 대해 가장 큰 응력 집중을 U-형 구 부위에 나타냈다. ProTaper 모형은 다른 모형에 비해 동일량을 비틀기 위해 더 많은 힘을 필요로 하였으며, 반면에 동량의 비틀림에서는 가장 높은 von Mises 응력이 ProTaper Universal의 단면에서 움푹 파인 부위에 집중되었다. Flexibility and fracture properties determine the performance of NiTi rotary instruments. The purpose of this study was to evaluate how geometrical differences between three NiTi instruments affect the deformation and stress distributions under bending and torsional conditions using finite element analysis. Three NiTi files (ProFile .06 / #30, F3 of ProTaper and ProTaper Universal) were scanned using a Micro-CT. The obtained structural geometries were meshed with linear, eight-noded hexahedral elements. The mechanical behavior (deformation and von Mises equivalent stress) of the three endodontic instruments were analyzed under four bending and rotational conditions using ABAQUS finite element analysis software. The nonlinear mechanical behavior of the NiTi was taken into account. The U-shaped cross sectional geometry of ProFile showed the highest flexibility of the three file models. The ProTaper, which has a convex triangular cross-section, was the most stiff file model. For the same deflection, the ProTaper required more force to reach the same deflection as the other models, and needed more torque than other models for the same amount of rotation. The highest von Mises stress value was found at the groove area in the cross-section of the ProTaper Universal. Under torsion, all files showed highest stresses at their groove area. The ProFile showed highest von Mises stress value under the same torsional moment while the ProTaper Universal showed the highest value under same rotational angle.

법량질 표면의 탈회 및 재광화 후 EPMA (electron probe micro-analysis)를 이용한 칼슘, 인, 불소 변화의 정량적 분석

홍경식,허복,이찬영,금기연 대한치과보존학회 2001 Restorative Dentistry & Endodontics Vol.26 No.5

The aim of this in vitro study was to analyze the composition of human tooth enamel in terms of there components, Ca, P, and F after demineralization and remineralization in acid buffer solution. A total of 8 human premolars without any defects and cracks were selected and buccal and lingual sides of the teeth were cleaned with an ultrasonic device and pumice without fluoride. 5×5mm windows were opened, and other areas were completely covered with 3-coats of nail varnish to prevent from being in contact with demineralized and remineralized solutions. After demineralization process, each tooth was sectioned into two slices, highly polished one of them withγ-alumina, and then analyzed the composition of the demineralized tooth with EPMA(electron probe micro-analyzer) . The ocher slices were put into the remineralized solution for 10 days, polished, and analyzed in the same manner. These data were statistically analyzed with one sample t-test(p<0.05) . The results were as follows. 1. Normal tooth enamel consists of 49.76% Ca, 39.80% P, and 0.28% F. 2. After demineralization, percentage of Ca and P ratio were decreased by about 5.57 and 5.07% respectively. Percentage of F ratio was also decreased by about 0.01%, which was not statistically significant. 3. After remineralization, percentage of Ca, P increased about by 4.47 and 4.35% respectively. Percentage of F decreased by about 0.01%, which was not statistically significant. In conclusion, remineralized solution used in our study has the potential to induce the uptake the Ca and P into the pore sites of the demineralized enamel. But, in the oral cavity, there were rapid temperature change, organic matrix that inhibits the movement of the ions, and limitation of continuous contact with this remineralized solution. Therefore, further in vivo study is necessary.

Analysis of Corrosion Behavior of KOFA Zircaloy-4 Cladding

Lee, Chan-Bock,Kim, Ki-Hang Korean Nuclear Society 1998 Nuclear Engineering and Technology Vol.30 No.2

The corrosion behavior of KOFA cladding which is a standard Zircaloy-4 manufactured by Westinghouse Specialty Metal Plant according to the Siemens/KWU's HCW (Highly Cold Worked) standard Zircaloy-4 specification was analyzed using the oxide measurement data of KOFA fuel irradiated in Kori-2 nuclear power plant. Analysis of the measured KOFA cladding oxidation showed that oxidation of KOFA cladding was lower than the design prediction based upon Siemens/KWU's HCW standard Zircaloy-4 cladding. Although the measured fuel rods have relatively low burnup and oxidation and the amount of the measured data are small, analysis of manufacturing and in-reactor operation conditions of KOFA cladding indicates that the differences in the manufacturing processes and chemical composition of the Siemens/KWU's HCW (Highly Cold Worked) standard Zircaloy-4 and KOFA cladding may have somewhat contributed to lower corrosion of KOFA cladding than the expected.

Evaluation of the Corrosion Behavior of the Aluminum Cladding in the KMRR Fuel

Lee, Chan-Bock,Sohn, Dong-Seong Korean Nuclear Society 1994 Nuclear Engineering and Technology Vol.26 No.4

For the evaluation of the corrosion behavior of the aluminum cladding in the KMRR(Korea Multipurpose Research Reactor) fuel, a modified Griess correlation was derived by introducing a heat flux factor derived from the comparison of the measured in-reactor corrosion data with the prediction of the Griess correlation. As a design criterion on the corrosion to maintain the KMRR fuel integrity, prevention of the oxide spallation was conservatively selected, which is conservatively assumed to occur when the temperature difference across the oxide layer exceeds 114$^{\circ}C$. A bounding power history of the KMRR fuel was determined by examining all the power histories of the KMRR fuel from cycle 1 to equilibrium cycle, and used to predict the maximum possible corrosion. Results of the corrosion prediction of the KMRR fuel with the bounding power history showed that the maximum local thickness of the oxide layer would be below 50$\mu$m and the design criterion on the oxide spallation would be satisfied with a factor of two margin. Therefore, it can be said that corrosion of the cladding will not impair the integrity of the KMRR fuel. Nevertheless, the applicability of the modified Griess correlation to the KMRR needs to be further verified through the KMRR fuel corrosion surveillance.

Development of One Dimensional Kinetics Program

Chan Bock Lee,Chang Hyun Chung,Bub Dong Chung Korean Nuclear Society 1986 Nuclear Engineering and Technology Vol.18 No.2

원자로 노심을 축방향으로 일차원 해석을 하고, 가입경수로형원자로의 안전성 해석에 적용할 수 있는 중성자 동특성프로그램 BIK를 개발하였다. BIK프로그램내에서 공간변수에 대해서는 유한차분법이, 시간변수에 대해서는 $\theta$-시간적분법이 채택되었다. 또한 도플러 및 감속재 궤환과 제어봉구동 등을 자세히 묘사하는 모델들이 포함되었다 핵모델의 검증은 ANL검증문제를 통해 이루어졌고, 고리 1호기의 제어봉 인출사고시의 노심출력 변화를 계산하였다. 이상의 계산결과 BIK동특성프로그램이 노심의 중성자 속 변화를 일차원해석의 한계내에서 비교적 정착하게 묘사할 수 있으며, 가압경수로형 원자로의 안전성 해석에 유용하게 사용될 수 있다는 것이 증명되었다. A one dimensional neutron kinetics program, BIK which is applicable to the safety analyses of PWR's is developed to analyze the reactor core in axial dimension. The BIK employs the finite difference technique in space and $\theta$-time integration method in time. Detailed models for the Doppler and moderator feedbacks and control rod motion are included. The benchmark of the nuclear model is carried out through the ANL benchmark problem and the time dependent nuclear power change in the rod ejection accident of KNU1 is calculated by BIK code. The results indicate that the BIK can predict the neutron dynamics with fair accuracy within the limits of one dimensional analysis and it is useful for the safety analyses of PWR's.

Analysis of High Burnup Fuel Behavior Under Rod Ejection Accident in the Westinghouse-Designed 950 MWe PWR

Chan Bock Lee 한국원자력학회 1998 Nuclear Engineering and Technology Vol.30 No.3

Magnetically-separable and highly-stable enzyme system based on crosslinked enzyme aggregates shipped in magnetite-coated mesoporous silica

Lee, Jinwoo,Na, Hyon Bin,Kim, Byoung Chan,Lee, Jin Hyung,Lee, Byoungsoo,Kwak, Ja Hun,Hwang, Yosun,Park, Je-Geun,Gu, Man Bock,Kim, Jaeyun,Joo, Jin,Shin, Chae-Ho,Grate, Jay W.,Hyeon, Taeghwan,Kim, Jungb Royal Society of Chemistry 2009 Journal of materials chemistry Vol.19 No.42

<P>A magnetically-separable and highly-stable enzyme system was developed by adsorption of enzymes in superparamagnetic hierarchically ordered mesocellular mesoporous silica (M-HMMS) and subsequent enzyme crosslinking. Superparamagnetic nanoparticles were homogeneously incorporated into hierarchically-ordered mesocellular mesoporous silica (HMMS) by the decomposition of a preformed iron propionate complex. The size of the incorporated superparamagnetic nanoparticles was around 5 nm, generating a magnetically separable host with high pore volumes and large pores (M-HMMS). α-chymotrypsin (CT) was adsorbed into M-HMMS with high loading (∼30 wt%) in less than 30 minutes. Glutaraldehyde (GA) treatment of adsorbed CT resulted in nanometer scale crosslinked enzyme aggregates in M-HMMS (CLEA-M). The activity of these CT aggregates in M-HMMS (CLEA-M-CT) was 34 times than that of simply adsorbed CT in M-HMMS, due to an effective prevention of enzyme leaching during washing <I>via</I> a ship-in-a-bottle approach. CLEA-M-CT maintained the initial activity not only under shaking (250 rpm) for 30 days, but also under recycled uses of 35 times. The same approach was employed for the synthesis of CLEA-M of lipase (CLEA-M-LP), and proven to be effective in improving the loading, activity, and stability of enzyme when compared to those of adsorbed LP in M-HMMS.</P> <P>Graphic Abstract</P><P>Crosslinked enzyme aggregates in magnetitie-coated mesoporous silica, fabricated <I>via</I> a two-step procedure of enzyme adsorption and crosslinking, were highly active, highly stable, and easily recyclable using a magnet. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b909109b'> </P>

A Study on Mesoscale Atmospheric Dispersion of Radioactive Particles Released from Nuclear Power Plants

Lee, Gab-Bock,Lee, Myung-Chan,Song, Young-Il 대한방사선방어학회 1997 방사선방어학회지 Vol.22 No.4

우리나라 원전이 위치하고 있는 해안지역에서 빈번히 발생하는 해륙풍 등과 같은 국지순환에 따른 방사성 물질의 대기확산 특성을 알아보기 위해 월성원전 주변지역을 대상으로 삼차원 해륙풍 모델과 라그랑지안 입자확산모델을 이용하여 봄철 약한 북풍이 부는 맑은 날과 강한 북풍이 부는 맑은 날에 대해 방사성 물질 확산에 관한 삼차원 시뮬레이션을 수행하였다. 시뮬레이션 결과, 해륙풍과 같은 국지순환의 발달여부에 따라 방사성 입자의 대기확산이 서로 다르게 나타남을 알 수 있었다. 또한 해륙풍과 육풍의 풍향교체에 따른 입자의 재순환 현상이 대기 중 농도분포에 중요한 역할을 하는 것을 확인할 수 있었다. A three dimensional sea-land breeze model and Lagrangian particle dispersion model have been employed for the study on the mesoscale atmospheric dispersion of radioactive materials released from Wolsung NPPs. In this study, atmospheric dispersion simulations are carried out under two synoptic weather conditions : the geostrophic flow is a weak northerly wind(CASE 1) and a strong northerly wind(CASE 2) on a clear day in spring. The results show that atmospheric dispersion is affected by sea-land breeze and the recirculation of particles by the change of wind direction between sea breeze and land breeze plays an important role in atmospheric concentration distribution of radoactive materials.

Analysis of Corrosion Behavior of KOFA Zircaloy-4 Cladding

Chan Bock Lee 한국원자력학회 1998 Nuclear Engineering and Technology Vol.30 No.2