• The korean journal of orthodontics
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• v.25 no.5 s.52
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• pp.525-541
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• 1995

This study was designed to investigate force systems and tooth movements produced by retraction archwire during retraction of four maxillary incisors after the maxillary canine retraction into the maxillary first premolar extraction space using the computer-aided three-dimensional finite element method. A three-dimensional finite element model, consisting of 2248 elements and 3194 nodes, was constructed. The model consisted of maxillary teeth and surrounding periodontal membranes, .022'$\times$.028'-slot brackets, and 5 types of retraction archwires(.019'$\times$.025' stainless steel archwire) modeled using the beam elements. The contact between the wire and the bracket slot was modeled using the gap elements because of the non-linear elastic behaviors of the contact between them. The forces and moments, End displacements produced by retraction archwire were measured at various conditions to investigate the difference according to types of loops, magnitudes of activation force, gable angle, and anterior lingual root torque. The results were expressed quantitative and visual ways in the three-dimensional method. The following conclusions can be drawn from this study.1. When the tear-drop loop archwire was activated, the mesio-distal and lingual translational movements of the teeth helped to close the extraction space, but unwanted movements of the teeth including intrusions and extrusions, and rotational movements in each direction occurred. 2. Activation of T-loop archwire compared with those of other types of retraction archwires produced the least translational movements of the teeth helped to space closure and also the least unwanted movements of the teeth. 3. Increasing amount of activation in the tear-drop archwire led not only to increase of translational movements of the teeth helped to space closure, but also to increase of unwanted movements of the teeth. 4. Addition of gable bend in the tear-drop archwire helped anterior teeth to translational movements in the mesio-distal direction, but increased unwanted movements of the teeth 5. Addition of anterior lingual root torque in the tear-drop archwire helped central and lateral incisor to improve their facio-lingual inclination, but increased unwanted movements of the teeth.

• Geophysics and Geophysical Exploration
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• v.18 no.4
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• pp.223-231
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• 2015

Self-potential (SP) is sensitive to groundwater flow and there are many causes to generate SP. Among many mechanisms of SP, pore-fluid flow in porous media can generate potential without any external current source, which is referred to as electrokinetic potential or streaming potential. When calculating SP responses on the surface due to geothermal fluid within an engineered geothermal system (EGS) reservoir, SP anomaly is usually considered to be generated by fluid injection or production within the reservoir. However, SP anomaly can also result from geothermal water fluid within EGS reservoirs experiencing temperature changes between injection and production wells. For more precise simulation of SP responses, we developed an algorithm being able to take account of SP anomalies produced by not only water injection and production but also the fluid of geothermal water, based on three-dimensional finite-element-method employing tetrahedron elements; the developed algorithm can simulate electrical potential responses by both point source and volume source. After verifying the developed algorithm, we assumed a simple geothermal reservoir model and analyzed SP responses caused by geothermal water injection and production. We are going to further analyze SP responses for geothermal water in the presence of water production and injection, considering temperature distribution and geothermal water flow in the following research.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.4
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• pp.245-253
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• 2020

In this study, natural frequencies are compared using several pile-soil interaction (PSI) models to evaluate the effects of each model on resonance safety checks for a monopile type of wind turbine structure. Base spring, distributed spring, and three-dimensional brick-shell models represented the PSIs in the finite element model. To analyze the effects of the PSI models on a natural frequency, after a stiffness matrix calculation and Winkler-based beam model for base spring and distributed spring models were presented, respectively; natural frequencies from these models were investigated for monopiles with different geometries and soil properties. These results were compared with those from the brick-shell model. The results show that differences in the first natural frequency of the monopiles from each model are small when the small diameter of monopile penetrates hard soil and rock, while the distributed spring model can over-estimate the natural frequency for large monopiles installed in weak soil. Thus, an appropriate PSI model for natural frequency analyses should be adopted by considering soil conditions and structure scale.

• Journal of the Korean Geotechnical Society
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• v.22 no.2
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• pp.41-53
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• 2006

The brittle materials like rocks show complicated strain-softening behavior after the peak which is hard to model using the classical constitutive models based on the relation between strain and stress tensors. A kinematically constrained three-dimensional microplane constitutive model is developed for granite. The model is verified by fitting the experimented data of Westerly granite and Bonnet granite. The triaxial behavior of granite is well reproduced by the model as well as the uniaxial behavior. We studied the development of the fracture zone in granite during blasting impact using the model with the standard finite element method. All the results obtained from the microplane model developed are compared to those from the linear elasticity model which is commonly used in many researches and practices. It is found that the nonlinearity of rocks sigificantly affects the results of analysis.

• Journal of Dental Rehabilitation and Applied Science
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• v.28 no.2
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• pp.147-161
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• 2012

This study is to assess the effect of horizontal misfit of an implant supported 3-unit fixed prosthodontics on the stress development at the marginal cortical bone surrounding implant neck. Two finite element models consisting of a three unit fixed prosthodontics and an implant/bone complex were constructed on a three dimensional basis. The three unit fixed prosthodontics were designed either shorter (d=17.8mm model) or longer (d=18.0mm model) by 0.1mm than the span of two implants placed at the mandibular second premolar and second molar areas 17.9mm apart. Fitting of the fixed prosthodontics onto the implant abutments was simulated by a total of 6 steps, that is to say, 0.1mm displacement per each step, using DEFORM 3D (ver 6.1, SFTC, Columbus, OH, USA) program. Stresses in the fixed prosthodontics and implants were evaluated using von-Mises stress, maximum compressive stress, and radial stress as necessary. The d=17.8mm model assembled successfully on to the implant abutments while d=18.0mm model did not. Regardless if the fixed prosthodontics fitted onto the abutments or not, excessively higher stresses developed during the course of assembly trial and thereafter. On the marginal cortical bone around implants during the assembly, the peak tensile and compressive stresses were as high as 186.9MPa and 114.1MPa, respectively, even after the final sitting of the fixed prosthodontics (for d=17.8mm model). For this case, the area of marginal bone subject to compressive stresses above 55MPa, equivalent of the $4,000{\mu}{\varepsilon}$, i.e. the reported threshold strain to inhibit physiological remodeling of human cortical bone, extended up to 2mm away from implant during the assembly. Horizontal misfit of 0.1mm can produce excessively high stresses on the marginal cortical bone not only during the fixed prosthodontics assembly but also thereafter.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.3 no.1
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• pp.29-37
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• 1991

A two-dimensional numerical model. using finite element method. was applied to calculation of the tides and tidal currents of four major tidal constituents($M_2, ;S_2, ;K_1, ;O_1$) in the southern part of the East Sea. The model results were compared with the observed data and with the existing tidal charts. and the computed results showed good agreement with the observation. As a result, the detailed tidal charts for four major tidal constituents and the tidal current ellipses of the M$_2$and $K_1$tides were produced respectively. The results indicate that the amphidromic point of diurnal tide locates near Korean coastal lines closer than that of the chart drawn by Nishida(1980).

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.597-598
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• 2006

자기누설탐상법은 비파괴검사 방법의 하나로 대상물체를 외부에서 착자시켜 결함이 발생할 경우에 결함부위에서 자기누설이 발생하도록 하여, 누설된 자기장을 측정하여 결함의 유무와 크기 등을 판정하는 시스템이다. 본 논문에서는 MFL 방식의 범용 NDT 검사기의 개발을 위해 영구자석을 이용하여 소형 비파괴 검사기를 설계하고, 3차원 유한요소법을 이용하여 해석하고 실제 데이터를 측정하여 그 결과를 비교 분석하였다.

• Proceedings of the KIEE Conference
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• 2006.07d
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• pp.2229-2230
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• 2006

자기누설탐상법은 비파괴검사 방법의 하나로 대상물체를 외부에서 착자시켜 결함이 발생할 경우에 결함부위에서 자기누설이 발생하도록 하여, 누설된 자기장을 측정하여 결함의 유무와 크기 등을 판정하는 시스템이다. 본 논문에서는 MFL 방식의 범용 NDT 검사기의 개발을 위해 영구자석을 이용하여 소형 비파괴 검사기를 설계하고, 3차원 유한요소법을 이용하여 해석하고 실제 데이터를 측정하여 그 결과를 비교 분석하였다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.11
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• pp.1306-1313
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• 2009

Dynamic and static behaviors of a three-dimensional catenary system for a high-speed railway are analyzed by using the finite element method. Considering tensions in the contact wire and the messenger wire, we drive the equations of motion for the catenary system. These equations are for the longitudinal, transverse, vertical and torsional motions. After establishing the weak form, the weak forms are spatially discretized with newly defined two-node beam elements. With the discretized equations, a finite element computer program is developed for the static and dynamic analyses. The static deflections of the catenary system, which are important for good contact between the pantograph and the contact line, are computed when the gravity is applied. On the other hand, we analyze the natural frequencies and the corresponding natural modes of the catenary system. The dynamic responses of the system are also investigated when applying a load to the contact line. For verification of the developed finite element program, vibrations of the catenary system are measured and they are compared to computed time responses.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.1263-1264
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• 2006

자기누설탐상법은 비파괴검사 방법의 하나로 대상물체를 외부에서 착자시켜 결함이 발생할 경우에 결함부위에서 자기누설이 발생하도록 하여, 누설된 자기장을 측정하여 결함의 유무와 크기 등을 판정하는 시스템이다. 본 논문에서는 MFL 방식의 범용 NDT 검사기의 개발을 위해 영구자석을 이용하여 소형 비파괴 검사기를 설계하고, 3차원 유한요소법을 이용하여 해석하고 실제 데이터를 측정하여 그 결과를 비교 분석하였다.