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.

A Numerical Study on Heat Transfer Enhancement by Pulsatile Flow in a Plate Heat Exchanger using Parallel Computation.

Nahmkeon Hur,long-Tack Park,Chan-Shik Won,Byung Ha Kang 한국전산유체공학회 2006 한국전산유체공학회 학술대회논문집 Vol.2006 No.5

대장암 및 충수돌기 주위 농양으로 오인된 복부 방선균증

김병상,손수호,허규찬,박승국 대한소화기내시경학회 2000 Clinical Endoscopy Vol.21 No.3

Background/Aims: Colonic actinomycosis is a rare disease with clinical and radiographic findings that overlap those of other inflammatory and neoplastic conditions. We performed this study to analyze clinical manifestation, characteristic radiologic findings of 5 cases of abdominal actinomycosis, which was initially diagnosed as a colorectal cancer or periappendiceal abscess. Methods: We analyzed chief complaint, predisposing factor, presence of leukocytosis and sulfur granule, involved site, presence of LN involvement and abdominal CT findings, retrospectively. Results: The most common clinical manifestation was abdominal pain. In 3 cases, predisposing factors were identifiable, which were intrauterine contraceptive device (IUD), previous appendectomy, and diabetes mellitus (DM) respectively. Leukocytosis was noted in 4 cases (80%) and sulfur granule in all 5 cases. Sigmoid colon was the most common involved site (4 cases) followed by appendix and rectum. On computed tomography, inhomogeneous mass or severe inflammation along the bowel wall or serosa was noted. Explorations were performed in 4 cases. Preoperative diagnosis was a colorectal cancer in 3 cases and periappendiceal abscess in 1 case. Conclusions: Actinomycosis should be born in mind in the differential diagnosis of patients with IUD, previous appendectomy and DM, presenting leukocytosis and CT finding of inhomogeneous mass and relatively uncommon LN involvement to eliminate unnecessary exnlorations.

Feasibility of Selective Lateral Node Dissection Based on Magnetic Resonance Imaging in Rectal Cancer After Preoperative Chemoradiotherapy

Park, Byung Kwan,Lee, Sang Jae,Hur, Bo Yun,Kim, Min Ju,Chan Park, Sung,Chang, Hee Jin,Kim, Dae Yong,Oh, Jae Hwan Elsevier 2018 The Journal of surgical research Vol.232 No.-

<P><B>Abstract</B></P> <P><B>Background</B></P> <P>Lateral pelvic node metastasis is one of the major causes of local recurrence in advanced rectal cancer after preoperative chemoradiotherapy (CRT). However, lateral pelvic node dissection (LPND) is still a challenging surgical procedure in terms of surgical morbidity. This study aimed to investigate the feasibility and safety of LPND in patients with advanced rectal cancer after preoperative CRT.</P> <P><B>Materials and methods</B></P> <P>Records of 80 consecutive patients who underwent total mesorectal excision (TME) with LPND for initially enlarged lateral pelvic nodes (LPNs) (short-axis diameter ≥5 mm on magnetic resonance imaging before preoperative CRT) between 2011 and 2016 were retrospectively reviewed. Surgical outcomes of these patients were compared with those of 281 patients who underwent TME alone.</P> <P><B>Results</B></P> <P>Ninety-nine LPND procedures were performed, including 19 bilateral LPNDs. Pathologically proven LPN metastasis was identified in 32 (32.3%) LPND cases after preoperative CRT. Multiple (odds ratio = 12.908, 95% confidence interval: 3.355-49.660, <I>P</I> < 0.001) and persistently enlarged LPNs (odds ratio = 27.093, 95% confidence interval: 6.072-120.896, <I>P</I> < 0.001) were independently associated with LPN metastasis. The rates of overall postoperative 30-d morbidity (42.5% <I>versus</I> 32.4%, <I>P</I> = 0.093) and urinary retention (11.3% <I>versus</I> 7.1%, <I>P</I> = 0.230) were similar between the TME with LPND and TME-only groups.</P> <P><B>Conclusions</B></P> <P>The postoperative morbidity of TME with LPND was comparable with TME-only group. The rate of LPN metastasis remained high after preoperative CRT, especially in patients with multiple or persistently enlarged LPNs.</P>

MEASUREMENT OF WELD ZONE PROPERTIES OF LASER-WELDED TAILOR-WELDED BLANKS AND ITS APPLICATION TO DEEP DRAWING

Yong Chan Hur,Daeyong Kim,Byung-Min Kim,Chung-Yun Kang,Myoung-Gyu Lee,Ji Hoon Kim 한국자동차공학회 2020 International journal of automotive technology Vol.21 No.3

Weld zones in tailor welded blanks have different mechanical properties than the base metals and thus have significant effects on formability. In this work, flow stresses of weld zones in laser-welded dissimilar dual-phase steels were measured. Strains at the weld zones of notched specimens were measured using the digital image correlation method and the flow stress data were corrected considering the anisotropy. For validation, finite element simulations were performed for the cup drawing process by considering the measured weld zone properties, and the weld line movements were compared with the measurements.

수압(水壓)이 구조물(構造物)에 미치는 영향 -토교지(土橋池)를 중심(中心)으로-

윤선병 ( Sun Byung Yun ),허찬 ( Chan Hur ) 한국농공학회 1976 韓國農工學會誌 : 전원과 자원 Vol.18 No.2

Target achievement with maximal statin-based lipid-lowering therapy in Korean patients with familial hypercholesterolemia: A study supported by the Korean Society of Lipid and Atherosclerosis

Oh, Jaewon,Lee, Chan Joo,Kim, Doo Il,Rhee, Moo-Yong,Lee, Byoung-Kwon,Ahn, Youngkeun,Cho, Byung Ryul,Woo, Jeong-Taek,Hur, Seung-Ho,Jeong, Jin-Ok,Jang, Yangsoo,Lee, Sang-Hak Wiley (John WileySons) 2017 Clinical cardiology Vol.40 No.12

<P>Conclusions: The target achievement of LDL-C < 100 mg/dL was low, and 50% LDL-C reduction was moderately achieved in Korean patients with FH receiving maximal statin-based LLT. Pretreatment LDL-C levels and diabetes mellitus were associated with target achievement. Our results provide rare and informative data on FH treatment in Asian patients.</P>

CONSTITUTIVE MODELING OF ASYMMETRIC HARDENING BEHAVIOR OF TRANSFORMATION-INDUCED PLASTICITY STEELS

Jaebong Jung,Yong Chan Hur,Sungwook Jun,Hyun-Seok Lee,Byung-Min Kim,김지훈 한국자동차공학회 2019 International journal of automotive technology Vol.20 No.Supp

Transformation-induced plasticity (TRIP) steels are part of advanced high strength steels capable of phase transformation, having good strength and ductility. The transformation rate is known to be dependent on the stress state, which may lead to asymmetric hardening behaviour for TRIP steels with compressive flow stresses larger than tensile ones. Sheet stamping products of TRIP steels show complex springback because of the asymmetry in addition to the large strength, which will complicate the analysis of sheet metal forming processes. In this work, the asymmetric hardening behaviour of a TRIP steel with a tensile strength of 1180 MPa was measured using the sheet tension–compression tester. An asymmetric hardening model was developed by introducing an off-centred bounding surface for the kinematic back-stress evolution, to depict the asymmetric hardening behaviour. The model parameters of the proposed constitutive equations were obtained from the stress– strain curves under tension followed by compression. The stress–strain curves were well captured by the developed constitutive model, whereas the conventional symmetric model fails to describe the asymmetric hardening behaviour of the TRIP steel. For validation, load-displacement curve and springback angles of three-point bending test were compared with the predictions by the proposed model.

수압이 구조물에 미치는 영향 -토교지를 중심으로-

윤선병,허찬,Yun, Sun-Byung,Hur, Chan 한국농공학회 1976 한국농공학회논문집 Vol.18 No.2