• Journal of Periodontal and Implant Science
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• 제45권1호
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• pp.8-13
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• 2015

Purpose: The aim of this study was to evaluate the transfer of different occlusal forces in various skeletal malocclusions using finite element analysis (FEA). Methods: Three representative human cone-beam computed tomography (CBCT) images of three skeletal malocclusions were obtained from the Department of Orthodontics, Yonsei University Dental Hospital, Seoul, South Korea. The CBCT scans were read into the visualization software after separating bones and muscles by uploading the CBCT images into Mimics (Materialise). Two separate three-dimensional (3D) files were exported to visualize the solid morphology of skeletal outlines without considering the inner structures. Individual dental impressions were taken and stone models were scanned with a 3D scanner. These images were integrated and occlusal motions were simulated. Displacement and Von Mises stress were measured at the nodes of the FEA models. The displacement and stress distribution were analyzed. FEA was performed to obtain the 3D deformation of the mandibles under loads of 100, 150, 200, and 225 kg. Results: The distortion in all three skeletal malocclusions was comparable. Greater forces resulted in observing more distortion in FEA. Conclusions: Further studies are warranted to fully evaluate the impact of skeletal malocclusion on masticatory performance using information on muscle attachment and 3D temporomandibular joint movements.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 2000년도 THE THIRD INTERNATIONAL CONFERENCE ON AGRICULTURAL MACHINERY ENGINEERING. V.III
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• pp.513-520
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• 2000

An integrated grader which measures soluble solid content, color and weight of fresh apples was developed by NAMRI. The prototype grader consists of the near infrared spectroscopy and machine vision system. Image processing system and an algorithm to evaluate color were developed to speed up the color evaluation of apples. To avoid the light glare and specular reflection, an half-spherical illumination chamber was designed and fabricated to detect the color images of spherical-shaped apples more precisely. A color revision model based on neural network was developed. Near-infrared(NIR) spectroscopy system using NIR reflectance method developed by Lee et al(1998) of NAMRI was used to evaluate soluble solid content. In order to observe the performance of the grader, tests were conducted on conditions that there are 3 classes in weight sorting, 4 classes in combination of color and soluble solid content, and thus 12 classes in combined sorting. The average accuracy in weight, color and soluble solid content is more than about 90 % with the capacity of 3 fruits per second.

• 대한조선학회논문집
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• 제45권2호
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• pp.168-174
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• 2008

To calculate the fluid-structure interaction(FSI) problem rationally, it should be the basic technology to analyse each domain of fluid and structure accurately. In this paper, a new FSI analysis algorithm was introduced using the 3D solid finite element for structural analysis and CFD code based on the HCIB method for viscous flow analysis. The fluid and structural domain were analysed successively and alternatively in time domain. The structural domain was analysed by the Newmark-b direct time integration scheme using the pressure field calculated by the CFD code. The results for example calculation were compared with other research and it was shown that those coincided each other. So we can conclude that the developed algorithm can be applied to the general FSI problems.

• 한국통신학회:학술대회논문집
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• 한국통신학회 1991년도 추계종합학술발표회논문집
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• pp.69-72
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• 1991

This paper proposes an efficient algorithm that constructs 3 dimensional solid object from orthographic views. The 3D object construction algorithm inputs vertices and edges information of 3 orthogonal views, generates 2 dimensional surfaces of input views, 3 dimensional possible vertices, possible edges and possible surfaces, compares 2 dimensional projections of 3 dimensional possible surface with two dimensional surfaces from orthogonal views and then determines the solution. This algorithm has been proved to be efficient in reducing the time taken and is useful for CAD system, 3 dimensional scene analysis system and object modellings for 3D graphics. The algorithm has been implemented in C language on the IBM PC/AT.

• 한국산학기술학회논문지
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• 제13권8호
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• pp.3295-3300
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• 2012

3차원 유한요소법은 구조물에 존재하는 표면균열과 내재균열들의 응력확대계수를 구하는데 이용되어 진다. 기하모델, 즉 솔리드모델은 3차원 균열들을 포함하고 있다. 국부적인 절점밀도가 선택되어 지면 자동적으로 기하모델 영역에 중첩되어 지며 절점은 버블패깅 방법에 의해 생성되어지고 10절점 사변형 솔리드요소는 데라우니 삼각화 기술에 의해 생성하였다. 시스템의 정확도와 효용성을 체크하기 위해 인장하중을 받는 평판에 하나의 균열이 존재하는 경우의 응력확대계수를 구해 Raju-Newnam식과 비교하여 5%이내의 차이를 보였다. 또한, 인장하중을 받는 평판에 두개 균열이 존재하는 경우의 해석을 통해 상호 간섭 효과를 분석하였다.

• Steel and Composite Structures
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• 제34권5호
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• pp.657-670
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• 2020

In this paper, vibration analysis of functionally graded nanoshell is studied based on the sinusoidal higher-order shear and normal deformation theory to account thickness stretching effect. To account size-dependency, Eringen nonlocal elasticity theory is used. For more accurate modeling the problem and corresponding numerical results, sinusoidal higher-order shear and normal deformation theory including out of plane normal strain is employed in this paper. The radial displacement is decomposed into three terms to show variation along the thickness direction. Governing differential equations of motion are derived using Hamilton's principle. It is assumed that the cylindrical shell is made of an arbitrary composition of metal and ceramic in which the local material properties are measured based on power law distribution. To justify trueness and necessity of this work, a comprehensive comparison with some lower order and lower dimension works and also some 3D works is presented. After presentation of comparative study, full numerical results are presented in terms of significant parameters of the problem such as small scale parameter, length to radius ratio, thickness to radius ratio, and number of modes.

• 한국해양공학회지
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• 제29권1호
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• pp.45-55
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• 2015

Because of the high stress concentration near the toe of a welded joint, the calculation of local stress using the finite element method which is relevant to the fatigue strength of the weld toe crack, is a challenging task. This is mainly caused by the sensitivity of finite element analysis, which usually occurs near the area of a dramatically changing stress field. This paper presents a novel numerical method through which a less mesh-sensitive local stress calculation can be achieved based on the 3D solid finite element, strictly sticking to the original definition of hot spot stress. In order to achieve the goal, a traction stress, defined at 0.5t and 1.5t away from the weld toe, was calculated using either a force-equivalent or work-equivalent approach, both of which are based on the internal nodal forces on the imaginary cut planes. In the force-equivalent approach, the traction stress on the imaginary cut plane was calculated using the simple force and moment equilibrium, whereas the equivalence of the work done by both the nodal forces and linearized traction stress was employed in the work-equivalent approach. In order to confirm the validity of the proposed method, five typical welded joints widely used in ships and offshore structures were analyzed using five different solid element types and four different mesh sizes. Finally, the performance of the proposed method was compared with that of the traditionally used surface stress extrapolation method. It turned out that the sensitivity of the hot spot stress for the analyzed typical welded joints obtained from the proposed method outperformed the traditional extrapolation method by far.

• The Journal of Advanced Prosthodontics
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• 제12권4호
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• pp.218-224
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• 2020

PURPOSE. The objectives of this study were to evaluate the fracture strength and fracture patterns of provisional crowns fabricated from different materials and techniques after receiving stress from a simulated oral condition. MATERIALS AND METHODS. A monomethacrylate-based resin (Unifast Trad) and a bis-acryl-based (Protemp 4) resin were used to fabricate provisional crowns using conventional direct technique. A milled monomethacrylate resin (Brylic Solid) and a 3D-printed bis-acrylate resin (Freeprint Temp) were chosen to fabricate provisional crowns using the CAD/CAM process. All cemented provisional crowns (n=10/group) were subjected to thermal cycling (5,000 cycles at 5°-55℃) and cyclic occlusal load (100 N at 4 Hz for 100,000 cycles). Maximum force at fracture was tested using a universal testing machine. RESULTS. Maximum force at fracture (mean ± SD, N) of each group was 657.87 ± 82.84 for Unifast Trad, 1125.94 ± 168.07 for Protemp4, 953.60 ± 58.88 for Brylic Solid, and 1004.19 ± 122.18 for Freeprint Temp. One-way ANOVA with Tamhane post hoc test showed that the fracture strength of Unifast Trad was statistically significantly lower than others (P<.01). No statistically significant difference was noted among other groups. For failure pattern analysis, Unifast Trad and Brylic Solid showed less damage than Protemp 4 and Freeprint Temp groups. CONCLUSION. Provisional crowns fabricated using the CAD/CAM process and the conventionally fabricated bis-acryl resins exhibited significant higher fracture strength compared to conventionally fabricated monomethacrylate resins after the aging regimen. Therefore, CAD/CAM milling and 3D printing of provisional restorations may be good alternatives for long term provisionalization.

• Macromolecular Research
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• 제16권2호
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• pp.113-119
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• 2008

A series of amphiphilic dendrons n-18 (n: generation number, 18: octadecyl chain) based on an aliphatic polyether denderitic core and octadecyl peripheries were synthesized using a convergent dendron synthesis consisting of a Williamson etherification and hydroboration/oxidation reactions. This study investigated their thermal and self-assembling behavior in the solid state using differential scanning calorimetry (DSC), Fourier transform infrared (FT-IR) absorption spectroscopy, and small angle X-ray scattering (SAXS). DSC indicated that the melting transition and the corresponding heat of the fusion of the octadecyl chain decreased with each generation. FT-IR showed that the hydroxyl focal groups were hydrogen-bonded with one another in the solid state. DSC and FT-IR indicated microphase-separation between the hydrophilic dendritic cores and hydrophobic octadecyl peripheries. SAXS data analysis in the solid state suggested that the lower-generation dendrons 1-18 and 2-18 self-assemble into lamellar structures based upon a bilayered packing of octadecyl peripheries. In contrast, the analyzed data of higher-generation dendron 3-18 is consistent with 2-D oblique columnar structures, which presumably consist of elliptical cross sections. The data obtained could be rationalized by microphase-separation between the hydrophilic dendritic core and hydrophobic octadecyl peripheries, and the degree of interfacial curvature associated with dendron generation.

• 전자통신동향분석
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• 제36권3호
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• pp.76-86
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• 2021

Technologies for lithium secondary batteries are now increasingly expanding to simultaneously improve the safety and higher energy and power densities of large-scale battery systems, such as electric vehicles and smart-grid energy storage systems. Next-generation lithium batteries, such as lithium-sulfur (Li-S) and lithium-air (Li-O₂) batteries by adopting solid electrolytes and lithium metal anode, can be a solution for the requirements. In this analysis of battery technology trends, solid electrolytes, including polymer (organic), inorganic (oxides and sulfides), and their hybrid (composite) are focused to describe the electrochemical performance achievable by adopting optimal components and discussing the interfacial behaviors that occurred by the contact of different ingredients for safe and high-energy lithium secondary battery systems. As next-generation rechargeable lithium batteries, Li-S and Li-O₂ battery systems are briefly discussed coupling with the possible use of solid electrolytes. In addition, Electronics and Telecommunications Research Institutes achievements in the field of solid electrolytes for lithium rechargeable batteries are finally introduced.