• 대한치과보철학회지
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• 제26권1호
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• pp.153-169
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• 1988

There is a little scientific documentation reporting the stress, distribution to the edentulous mandible by different concepts of occlusal scheme. So, this study was to investigate the hypothesis that the magnitude and distribution of the occlusal stresses, transmitted through a mandibular complete denture base to the edentulous mandible, would be influenced by the lingualized occlusion. This investigation was performed to analyze the stresses induced in a three-dimensional photoelastic edentulous mandible, when a load is applied to the denture arranged into lingualized occlusion in centric relation, lateral and protrusive functional position. The mounted denture on a Dentatus Type ARO articulator was loaded in a pure vertical direction with 15kgs on the center of articulator in each case and the stresses were frozen into epoxy edentulous model at $127^{\circ}C$ in the stress freezing furnace. The stress-frozen epoxy models were sliced with diamond disc saw into 4mm thick. The slices were examined with a circular polariscope. The results were as follows: 1. In centric relation, the stresses were low at anteriors, and gradually increase to the premolar, molar area and highest at the first molar and gradually decrease from the second molar and lowest at the retromolar pad region. The lingual side showed higher stresses than labiobuccal side. 2. In lateral functional position, the working side showed higher stresses than the balancing side. In working side, the lingual side showed higher stresses than the buccal side and in balancing side, the buccal side showed higher stresses than the lingual side. 3. In protrusive position, stress distribution was symmetrical on the posteriors and the stresses were concentrated at the labial side of the anteriors.

• 대한치과보철학회지
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• 제45권4호
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• pp.506-521
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• 2007

Statement of problem: The cumulative success rate of wide implant is still controversial. Some previous reports have shown high success rate, and some other reports shown high failure rate. Purpose: The aim of this study was to analyze, and compare the biomechanics in wide implant system embeded in different width of crestal bone under different occlusal forces by finite element approach. Material and methods: Three-dimensional finite element models were created based on tracing of CT image of second premolar section of mandible with one implant embedded. One standard model (6mm-crestal bone width, 4.0mm implant diameter central position) was created. Varied crestal dimension(4, 6, 8 mm), different diameter of implants(3.3, 4.0, 5.5, 6.0mm), and buccal position implant models were generated. A 100-N vertical(L1) and 30 degree oblique load from lingual(L2) and buccal(L3) direction were applied to the occlusal surface of the crown. The analysis was performed for each load by means of the ANSYS V.9.0 program. Conclusion: 1. In all cases, maximum equivalent stress that applied $30^{\circ}$ oblique load around the alveolar bone crest was larger than that of the vertical load. Especially the equivalent stress that loaded obliquely in buccal side was larger. 2. In study of implant fixture diameter, stress around alveolar bone was decreased with the increase of implant diameter. In the vertical load, as the diameter of implant increased the equivalent stress decreased, but equivalent stress increased in case of the wide implant that have a little cortical bone in the buccal side. In the lateral oblique loading condition, the diameter of implant increased the equivalent stress decreased, but in the buccal oblique load, there was not significant difference between the 5.5mm and 6.0mm as the wide diameter implant. 3. In study of alveolar bone width, equivalent stress was decreased with the increase of alveolar bone width. In the vertical and oblique loading condition, the width of alveolar bone increased 6.0mm the equivalent stress decreased. But in the oblique loading condition, there was not a difference equivalent stress at more than 6.0mm of alveolar bone width. 4. In study of insertion position of implant fixture, even though the insertion position of implant fixture move there was not a difference equivalent stress, but in the case of little cortical bone in the buccal side, value of the equivalent stress was most unfavorable. 5. In all cases, it showed high stress around the top of fixture that contact cortical bone, but there was not a portion on the bottom of fixture that concentrate highly stress and play the role of stress dispersion. These results demonstrated that obtaining the more contact from the bucco-lingual cortical bone by installing wide diameter implant plays an important role in biomechanics.

• Tribology and Lubricants
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• 제35권6호
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• pp.382-388
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• 2019

It is currently well known that surface textures act as lubricant reservoirs, entrap wear debris, and hydrodynamic bearings, which can lead to certain increases in load-carrying capacities. Until recently, the vast majority of research has focused on parallel sliding machine components such as thrust bearings, mechanical face seals, piston rings, etc. However, most sliding bearings have a convergent film shape in the sliding direction and their hydrodynamic pressure is mainly generated by the wedge action. Following the first part of the present study that investigates the effect of groove position on the lubrication performances of inclined slider bearings, this paper focuses on the effects of groove depths and film thicknesses. Using a commercial computational fluid dynamics (CFD) code, FLUENT, the continuity and Navier-Stokes equations are numerically analyzed. The results show that the film thickness and groove depth have a significant influence on the pressure distribution. The maximum pressure occurs at the groove depth where the vortex is found and, as the depth increases, the pressure decreases. There is also a groove depth to maximize the supporting load with the film thickness. The friction force acting on the slider decreases with deeper grooves. Therefore, properly designed groove depths, depending on the operating conditions, can improve the load-carrying capacity of inclined slider bearings as compared to the bearings without a groove.

• 구강회복응용과학지
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• 제29권3호
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• pp.259-271
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• 2013

임플란트 고정체-지대주 결합구조체의 형태에 따른 교합부하의 반응이 다양하여 본 연구에서는 하중위치 및 결합구조체 접촉 비율에 따라 3단 계단형 결합구조체와 경사형에서 어떠한 차이가 있는 지를 3차원 유한요소분석을 시행하였다. 2종의 임플란트-지대주 결합 구조체에 연결된 상부 치관을 제작하여 각 치관에 설정된 하중위치에 200 N의 하중을 부여하였다. 임플란트 중심 부위에서 하중조건이 멀어질수록 피질골정에 가해지는 응력이 증가되기에 하중조건은 응력발생에 영향을 미치는 주요 요소이며 다음으로 결합구조형태에도 영향을 받았다. 또한 수직 하중에 비해 빗금 경사 하중이 부여된 경우 계단형은 경사형에 비해 유리한 응력 분포를 보였다. 그리고 지대주 결합구조체가 고정체의 내벽에 대해 접촉이 많아 질수록 골질에 대한 응력분산이 유리한 것으로 나타났다. 결론적으로 고정체 폭경에서 벗어난 빗김 수직 및 경사 하중은 결합구조체의 종류와 관계없이 피질골정에 응력을 집중시키므로 저작기능시 교합접촉면을 고정체의 폭경 내에 위치하도록 하는 것이 생체역학적으로 바람직 할 것으로 사료되었다.

• Ocean Systems Engineering
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• 제8권3호
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• pp.345-360
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• 2018

Increasing demand for large-sized Floating, Storage and Regasification Units (FSRUs) for oil and gas industries led to the development of novel geometric form of Buoyant Leg Storage and Regasification Platform (BLSRP). Six buoyant legs support the deck and are placed symmetric with respect to wave direction. Circular deck is connected to buoyant legs using hinged joints, which restrain transfer of rotation from the legs to deck and vice-versa. Buoyant legs are connected to seabed using taut-moored system with high initial pretension, enabling rigid body motion in vertical plane. Encountered environmental loads induce dynamic tether tension variations, which in turn affect stability of the platform. Postulated failure cases, created by placing eccentric loads at different locations resulted in dynamic tether tension variation; chaotic nature of tension variation is also observed in few cases. A detailed numerical analysis is carried out for BLSRP using Mathieu equation of stability. Increase in the magnitude of eccentric load and its position influences fatigue life of tethers significantly. Fatigue life decreases with the increase in the amplitude of tension variation in tethers. Very low fatigue life of tethers under Mathieu instability proves the severity of instability.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.2365-2372
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• 2011

BLDC 모터와 같은 동기전동기에서 소음과 진동의 원인이 되는 코깅토크는 전동기내의 비 균일 토크로서 전동기 시스템의 자기 에너지가 최소인 위치로 이동하려는 접선방향의 힘으로 부하전류와 상관없이 회전자 영구자석과 고정자 슬롯의 상호작용에 의해 발생한다. 이러한 코깅토크는 전동기의 소음과 진동의 주요 원인이 되므로 전동기 설계 시 반드시 고려해야 한다. 코깅토크는 영구자석이 부착된 회전자에 의하여 공극 중에 비교적 저차의 고조파 자속밀도와 고정자 철심 슬롯의 상호작용으로 발생한다는 점을 중시하여 본 논문에서는 실험계획법의 일종인 반응표면 법을 사용하여 코깅토크를 저감하는 방법에 대해 제시하였다.

• Structural Engineering and Mechanics
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• 제81권1호
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• pp.11-28
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• 2022

This paper considers the combination of cyclic and axial loads to investigate the hysteretic performance of H-section 6061-T6 aluminum alloy members. The hysteretic performance of aluminum alloy members is the basis for the seismic performance of aluminum alloy structures. Despite the prevalence of aluminum alloy reticulated shells structures worldwide, research into the seismic performance of aluminum alloy structures remains inadequate. To address this deficiency, we design and conduct cyclic axial load testing of three H-section members based on a reliable testing system. The influence of slenderness ratios and bending direction on the failure form, bearing capacity, and stiffness degradation of each member are analyzed. The experiment results show that overall buckling dominates the failure mechanism of all test members before local buckling occurs. As the load increases after overall buckling, the plasticity of the member develops, finally leading to local buckling and fracture failure. The results illustrate that the plasticity development of the local buckling position is the main reason for the stiffness degradation and failure of the member. Additionally, with the increase of the slenderness ratio, the energy-dissipation capacity and stiffness of the member decrease significantly. Simultaneously, a finite element model based on the Chaboche hybrid strengthening model is established according to the experiment, and the rationality of the constitutive model and validity of the finite element simulation method are verified. The parameter analysis of twenty-four members with different sections, slenderness ratios, bending directions, and boundary conditions are also carried out. Results show that the section size and boundary condition of the member have a significant influence on stiffness degradation and energy dissipation capacity. Based on the above, the appropriate material constitutive relationship and analysis method of H-section aluminum alloy members under cyclic loading are determined, providing a reference for the seismic design of aluminum alloy structures.

• Geomechanics and Engineering
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• 제8권2호
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• pp.283-303
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• 2015

To research and analyze the differential settlements of foundations specifically, site investigations of existing railways and metro were firstly carried out. Then, the centrifugal test was used to observe differential settlements in different position between foundations on the basis of investigation. The theoretical model was established according to the stress diffusion method and Fourier method to establish an analytical solution of embankment differential settlement between different foundations. Finally, theoretical values and experimental values were analyzed comparatively. The research results show that both in horizontal and vertical directions, evident differential settlement exists in a limited area on both sides of the vertical interface between different foundations. The foundation with larger elastic modulus can transfer more additional stress and cause relatively less settlement. Differential settlement value decreases as the distance to vertical interface decreases. In the vertical direction of foundation, mass differential settlement also exists on both sides of the vertical interface and foundation with larger elastic modulus can transfer more additional stress. With the increase of relative modulus of different foundations, foundation with lower elastic modulus has larger settlement. Meanwhile, differential settlement is more obvious. The main error sources in theoretical and experimental values include: (a) different load form; (b) foundation characteristics differences; (c) modulus conversion; (d) effect of soil internal friction.

• Structural Engineering and Mechanics
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• 제58권3호
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• pp.515-532
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• 2016

The elastoplastic response of functionally graded material (FGM) beams resting on a nonlinear elastic foundation to an eccentric axial load is investigated by using the finite element method. The FGM is assumed to be formed from ceramic and metal phases with their volume fraction vary in the thickness direction by a power-law function. A bilinear elastoplastic behavior is assumed for the metallic phase, and the effective elastoplastic properties of the FGM are evaluated by Tamura-Tomota-Ozawa (TTO) model. Based on the classical beam theory, a nonlinear finite beam element taking the shift in the neutral axis position into account is formulated and employed in the investigation. An incremental-iterative procedure in combination with the arc-length control method is employed in computing the equilibrium paths of the beams. The validation of the formulated element is confirmed by comparing the equilibrium paths obtained by using the present element and the one available in the literature. The numerical results show that the elastoplastic post-buckling of the FGM beams is unstable, and the post-buckling strength is higher for the beams associated with a higher ceramic content. Different from homogeneous beams, yielding in the FGM beam occurs in the layer near the ceramic layer before in the layer near metal surface. A parametric study is carried out to highlight the effect of the material distribution, foundation support and eccentric ratio on the elastoplastic response of the beams.

• 구강회복응용과학지
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• 제36권3호
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• pp.176-182
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• 2020

목적: 수복물에 교합력을 가할때 식립된 임플란트의 개수, 배열 및 위치에 따른 임플란트, 보철물 및 지지 골에 발생하는 응력의 차이를 분석하고자 한다. 연구 재료 및 방법: 하악에 임플란트가 식립되어 고정성 보철물을 지지하는 4 종류의 3D 유한요소 모형을 제작하였다. 모델 M1은 2개의 임플란트 가운데에 가공치를 배열하였고, 모델 M2는 2개의 임플란트 외측에 캔티레버 가공치를 배열하였다. 모델 M3과 M4는 3개의 임플란트를 각각 일렬로 배열되거나, 엇갈리게 배열하였다. 총 120 N 크기의 수직력과 45도 측방력을 가하였고, 유한요소 응력 분석을 시행하였다 결과: 측방력 하중에 의해 발생한 최대 응력은 수직력 하중에 의한 것 보다 임플란트 부위에서 3.4 - 5.1배 더 컸고, 지지골 내에서는 3.5 - 8.3배 더 컸다. 모델 M2 의 고정성 보철물의 캔티레버 연결부에서 가장 큰 응력이 집중되었다. 임플란트 개수가 3개인 모델들이 2개인 경우보다 더 낮은 응력이 발생하였으나 M3과 M4에서 일렬 배열과 엇갈린 배열간의 응력 발생 차이는 작았다. 결론: 임플란트 배열의 엇갈림 정도는 응력 크기에 별 차이를 발생하지 않았으나, 캔티래버의 존재나 임플란트의 개수의 차이는 큰 영향을 주었다.