텔레스코픽 크라운 임플란트 지지 피개의치와 치아 지지 피개의치의 하악골내 응력분포에 관한 유한요소분석

이창규,백장현,김태훈,김민정,김형섭,권긍록,우이형 대한치과보철학회 2012 대한치과보철학회지 Vol.50 No.1

PURPOSE. The purpose of this study was to investigate the stress distribution in mandibular implant-supported overdentures and tooth-supported overdentures with telescopic crowns. MATERIALS AND METHODS. The assumption of this study was that there were 2, 3, 4 natural teeth and implants which are located in the second premolar and canine regions in various distributed conditions. The mandible, teeth (or implants and abutments), and connectors are modeled, and analyzed with the commercial software, ANSYS Version 10.1. Stress distribution was evaluated under 150 N vertical load bilaterally on 3 experimental conditions - between canine areas, canine and 2nd premolars, 10 mm posterior to 2nd premolars. RESULTS. Overall, the case of the implant group showed more stress than the case of the teeth group in stress distribution to bone. In stress distribution to superstructures of tooth and implants, there was no significant difference between TH group and IM group and the highest stress appeared in TH-IV and IM-IV. The stress caused from bar was much higher than those of implant and tooth. TH group showed less stress than IM group in stress distribution to abutment teeth and implant. CONCLUSION. The results shows that it is crucial to make sure that distance between impact loading point and abutment tooth does not get too far apart, and if it does, it is at best to set abutment tooth on premolar tooth region. It will be necessary to conduct more experiments on effects on implants, natural teeth and bone, in order to apply these results to a clinical treatment. 연구 목적: 이 연구의 목적은 텔레스코픽 크라운 하악 임플란트 지지 피개의치와 치아 지지 피개의치에서 지대치의 수와 위치에 따른 응력 분산을 비교하기 위함이다. 연구 재료 및 방법: 본 연구에서는 임플란트를 4개 식립하고 임플란트 지지 피개의치로 설계하였고, 식립 위치를 견치와 소구치 부위에 위치 별로 3개 또는 2개 존재시를 실험군으로 설정하였다. 자연치아를 갖는 경우도 견치와 제2소구치 4개를 가진 경우를 대조군으로 설정하고 부위별로 3개 또는 2개를 가지는 경우를 실험군으로 설정하였다. ANSYS Version 10.1 (Swanson, Inc., USA)로 분석하였다. 결과: 악골내 응력의 경우, 전반적으로 임플란트(IM)로만 구성된 경우가 치아(TH)로만 구성된 경우에 비해 응력이 크게 발생하였다. 상부구조의 경우, 치아군(TH)과 임플란트군(IM) 사이의 차이는 크게 없었으며 편측 견치와 제2소구치에 지대치 또는 임플란트가 위치하는 경우 가장 큰 응력이 나타났고 바(bar)에서 발생된 응력이 임플란트와 치아에서 발생되는 응력에 비해 상대적으로 훨씬 크게 발생하였다. 지대치와 임플란트의 경우, 치아군(TH)이 임플란트군(IM)보다 응력이 작게 발생하였다. 결론: 본 연구의 결과로부터 지대치(임플란트 또는 치아)를 설정할 때는 하중작용점과 지대치 사이의 거리가 너무 길어지지 않도록 지대치의 수와 위치를 확보해야 하며 소구치 자리에 지대치를 확보하는 것이 유리하다. 앞으로, 실제 임상에 적용하였을 경우, 임플란트 및 자연치아와 악골에 미치는 결과에 대한 연구가 더 필요할 것으로 생각된다.

CFD CODE DEVELOPMENT WITH ADAPTIVE MESH REFINEMENT FOR A CHEMICALLY REACTING FLOW

Tae-Hyeong Yi 한국전산유체공학회 2011 한국전산유체공학회 학술대회논문집 Vol.2011 No.11

A computational fluid dynamics code with adaptive mesh refinement for three-dimensional, multi-species, Euler equations is developed to investigate the phenomena of a detonation wave. A gas is assumed to be thermally perfect and in chemically non-equilibrium. The stiffness due to chemical reactions is properly taken care of by using a time-operator splitting method. By this method, the governing equations can be divided into two steps: homogeneous partial differential equations for the fluid dynamics and ordinary differential equations for chemical reactions. In the first step, a finite volume approach with a cell-centered scheme is employed for spatial integration. For temporal terms, the equations are discretized by a second-order, three-step Runge-Kutta method. The second step is a system of ordinary differential equations. This system of ordinary differential equations can be solved using a variable-coefficient ordinary differential equation. Detailed chemistry of a hydrogen and air mixture extracted from GRI-Mech is involved in this study. Due to a large range of spatial scales in detonation simulations, adaptive mesh refinement is employed to prevent poor numerical efficiency that causes an increase in computational time and resources. Code verification is performed with a non-reacting wedge flow and a detonation wave propagating in one- and two-dimensional rectangular tubes.

두께의 불확실성을 갖는 풍동시험 익형모델의 공력특성에 관한 수치해석 연구

이태형(Tae-Hyeong Yi),권기정(Ki-Jung Kwon),김근택(Keun-Taek Kim),안석민(Seokmin Ahn) 한국항공우주학회 2012 韓國航空宇宙學會誌 Vol.40 No.6

익형 풍동시험 시 모델의 제작오차에 의해 시험 익형과 지지대 익형의 두께에서 차이가 있을 경우 시험 익형의 공력특성에 주는 영향을 양력, 항력 및 모멘트 값의 변화를 수치해석하여 비교 및 분석하였다. 이를 위해 익형모델을 세 부분으로 나누어 제작하는 경우 가운데 위치하는 시험 익형을 기준 형상으로 하여 시험 익형 양쪽에 부착하여 지지대 역할을 하는 익형의 최대두께를 가운데 익형에 비해 작게 설정하였다. 익형모델은 NACA64- 418을 사용하였으며, 난류모델은 천이현상을 잘 예측할 수 있는 Transition SST를 사용하였다. 다양한 받음각과 레이놀즈 수에서 지지대 역할을 하는 익형모델과 두께차이가 매우 큰 경우에도 가운데 위치한 시험 익형의 공력특성에 미치는 영향이 매우 작음을 확인하였다. Numerical investigation is performed to understand the effects of thickness uncertainty of a supporting airfoil due to manufacturing processes on the aerodynamic characteristics of an airfoil used for measuring data in a wind tunnel testing. This is done by comparing the coefficients of lift, drag and moment of the airfoils. In this work, the airfoil model consists of three parts, one located in the center for measuring and two outer parts used for supporting. The study is carried out with a NACA64-418 airfoil and the turbulence model of Transition SST. It is found that the effect of thickness uncertainty of the airfoils used for supporting is not significant to the performance of the test airfoil at various angles of attack and Reynolds numbers.

미래형 개인용 항공기 기술개발 동향 및 분석

이태형(Yi Tae-Hyeong),김근택(Kim Keun-Taek),안석민(Ahn Seokmin),이대성(Lee Dae Sung) 한국항공우주연구원 2011 항공우주산업기술동향 Vol.9 No.1

자동차와 항공기가 결합된 신개념 운송수단인 미래형 개인용 항공기의 개발 현황을 살펴보고, 이러한 개인용 항공기의 개념을 분석하여 향후 기술 개발 시 필요한 요구사항을 정리하였다. 최근 들어 미래형 개인용 항공기의 차세대 운송수단으로서의 그 가능성을 인지하여 미국을 중심으로 정부, 민간회사, 학계에서 미래형 개인용 항공기와 관련된 다양한 연구를 수행하고 있다. 본 논문에서는 미래형 개인용 항공기의 개발 프로그램인 AGATE, PAVE, SATS 및 NGATS 등을 먼저 알아보고, 현재 상용화가 진행 중인 Terrafugia사의 Transition과 Moller International사의 M400 Skycar의 개발 현황, 기체의 특징 및 응용 기술을 분석하였다. 이를 바탕으로 추후 미래형 개인용 항공기를 개발 시 필요한 핵심기술을 제시한다. The current development trend and status of a personal air vehicle, known as the novel concept of a transportation that combines a personal car with a light general aviation aircraft, is summarized to investigate its feasibility as a future transportation. In the paper, the development programs of a personal air vehicle such as AGATE, PAVE, SATS and NGATS are first summarized, and then the design, technical development and testing activities of Terrafugia’s Transition and Moller International’s M400 Skycar, which will be commercialized in a short time, are reviewed. Based on the assessment of technical issues with those vehicles, the key technologies for the future development of the personal air vehicle are suggested with two basic requirements of safety and mobility.

Time integration of unsteady nonhydrostatic equations with dual time stepping and multigrid methods

Elsevier 2018 Journal of computational physics Vol.374 No.-

<P><B>Abstract</B></P> <P>A time integration method based on dual time stepping coupled with a multigrid and implicit iterative solver is discussed for overcoming the temporal stiffness associated with modeling unsteady atmospheric flows. Adopting the dual time stepping allows solving an unsteady flow problem as a steady-state one by introducing a pseudo-time derivative into the governing equations. Consequently, the model uses a large time step and leads to a reduction in computational time. In the framework of the dual time stepping, a full approximation storage multigrid and lower–upper symmetric Gauss–Seidel implicit solver are employed to accelerate convergence in a structured, quadrilateral grid. The discretization of a physical-time derivative is based on a second-order backward differentiation formula or a family of singly diagonally implicit Runge–Kutta methods. The spatial terms of nonhydrostatic equations are discretized with a second-order Roe scheme in the finite volume method. To assess the performance of the model in terms of accuracy and efficiency, which are indicated by the normalized error norms and wall-clock time, respectively, three idealized tests are performed with the unsteady flow problems of isentropic vortex, rising thermal bubble and inertia-gravity waves. The results of numerical experiments consistently demonstrate that the dual time stepping coupled with explicit-first, singly diagonally implicit Runge–Kutta and multigrid methods is more efficient than the three-stage, third-order explicit Runge–Kutta method with comparable accuracy. The numerical experiment also indicates that the dual time stepping is more efficient when a stretched grid is employed. The efficiency in the framework of the dual time stepping is dependent on various numerical factors, including a multigrid level and cycle, Butcher coefficients, an implicit solver and a physical-time step.</P>

Progress and plans for the dynamical core module development at KIAPS

Tae-Jin Oh,Tae-Hyeong Yi,Suk-Jin Choi,Shin-Hoo Kang,Ja-Rin Park,Young-Joon Kim 한국기상학회 2013 한국기상학회 학술대회 논문집 Vol.2013 No.4

The Records of Origin and Transport of Sediments From the Past to the Present in the Yellow Sea

Yi, Hi-Il,Chun, Jong-Hwa,Shin, Im-C.,Shin, Dong-Hyeok,Jou, Hyeong-Tae The Korean Society of Oceanography 2004 Journal of the Korean Society of Oceanography Vol.39 No.1

A total of 116 surface sediment samples were obtained on the Yellow Sea and analyzed for grain size and geochemical elements in order to interpret the present sediment transportation. Thirty-nine cores and 3,070 line-km shallow seismic profiles are analyzed for sedimentary records of Yellow Sea in the past. Results show that the boundary of sediment transport between Korean side and Chinese side is about between $123^{\circ}E$ and $124^{\circ}E$. The similar result is produced from Shi et al. (in this publication). Two cyclonic patterns of surface sediments are recognized in the northeastern and southwestern Yellow Sea, while the strong front zone of the mud patch and sandy sediments are found in the southeastern Yellow Sea (the southwestern part of Korean coasts). The formation of fine-particle sediment packages, called for Northwest Mudbelt Deposit (NWMD), Hucksan Mudbelt Deposit (HSMD) and Jeju Mudbelt Deposit (JJMD), are resulted from eddies (gyres) of water circulations in the Yellow Sea. NWMD has been formed by cyclonic (anticlockwise) eddy. NWMD is composed of thick, homogeneous, relatively semi-consolidated gray clay-dominated deposit. On the other hand, HSMD and JJMD are formed by anticyclonic (clockwise) eddies. They are thick, homogeneous, organic-rich gray, silt-dominated deposit. Both core and surface sediments show that the middle zone across Chinese and Korean side contains bimodal frequency of grain-size distribution, indicating that two different transport mechanisms exist. These mud packages are surrounded by sand deposits from both Korea and China seas, indicating that Yellow Sea, which is the shallow sea and epicontinental shelf, is formed mostly by sand deposits including relict sands. The seismic profiles show such as small erosional/non-depositional channels, sand-ridges and sand-waves, Pleistocene-channelfilled deposits, a series of channels in the N-S major channel system, and thick Holocene sediment package, indicating that more complex sedimentary history exists in the Yellow Sea.

태반 유착을 동반한 만삭 자궁각임신

김태희 ( Tae Hee Kim ),이해혁 ( Hae Hyeong Lee ),정수호 ( Soo Ho Chung ),이범하 ( Boem Ha Yi ) 대한산부인과학회 2010 Obstetrics & Gynecology Science Vol.53 No.6

Angular pregnancy is rare, in which the embryo in the lateral angle of uterine cavity and located medial to the utero-tubal junction. Angular pregnancy is differentiated from interstitial pregnancy. There is no report about term angular pregnancy in Republic of Korea, a few reports in other countries. Angular pregnancy has different clinical characteristics according to the trimester. We diagnosed angular pregnancy by ultrasonography and computed tomography (CT). The CT is a useful diagnostic method. We report a case of term angular pregnancy with placenta accreta and review the diagnostic process and complications.

원자력 발전소 RCB 내 중요배관의 KEPIC 코드에 의한 내진 안전성 설계

이형복(Hyeong Bok Yi),이진규(Jin Kyu Lee),강태인(Tae In Kang) Korean Society for Precision Engineering 2011 한국정밀공학회지 Vol.28 No.2

In piping design of nuclear power plant facilities, the load stress according to self-weight is important for design values in test run(shutdown and starting). But sometimes it needs more studies, such as seismic analysis of an earthquake of power plant area and fatigue life and stress of thermal expansion and anchor displacement in operating run. In this paper, seismic evaluations were performed to nuclear piping system of Shin-Kori NO. 3&4 being built in Pusan lately. Results of seismic analysis are evaluated on basis of KEPIC MN code. The structural integrity on RCB piping system was proved.

기관지의 과립세포종

박태병 ( Tae Byung Park ),송영구 ( Young Goo Song ),구성현 ( Sung Hyun Ku ),고영윤 ( Young Yoon Ko ),황성철 ( Sung Chul Hwang ),이이형 ( Yi Hyeong Lee ),주희재 ( Hee Jae Joo ) 대한결핵 및 호흡기학회 1996 Tuberculosis and Respiratory Diseases Vol.43 No.2