• Atmosphere
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• v.30 no.4
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• pp.361-376
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• 2020

This study evaluates multiple Regional Climate Models (RCMs) in simulating temperature and precipitation over the Far East Asia (FEA) and estimates the portions of the total uncertainty originating in the RCMs and the driving Global Climate Models (GCMs) using nine present-day (1981~2000) climate data obtained from combinations of three GCMs and three RCMs in the CORDEX-EA phase2. Downscaling using the RCMs generally improves the present temperature and precipitation simulated in the GCMs. The mean temperature climate in the RCM simulations is similar to that in the GCMs; however, RCMs yield notably better spatial variability than the GCMs. In particular, the RCMs generally yield positive added values to the variability of the summer temperature and the winter precipitation. Evaluating the uncertainties by the GCMs (VARGCM) and the RCMs (VARRCM) on the basis of two-way ANOVA shows that VARRCM is greater than VARGCM in contrast to previous studies which showed VARGCM is larger. In particular, in the winter temperature, the ocean has a very large VARRCM of up to 30%. Precipitation shows that VARRCM is greater than VARGCM in all seasons, but the difference is insignificant. In the following study, we will analyze how the uncertainty of the climate model in the present-day period affects future climate change prospects.

• Steel and Composite Structures
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• v.38 no.2
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• pp.223-239
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• 2021

This paper presents the analytical modeling and finite element (FE) analysis, using ABAQUS software, of the new types of steel reinforced lightweight aggregate concrete (SRLAC) columns with cross-shaped (+shaped and X-shaped) steel section, using proposed three analytical and two FE models in total. The stress-strain material models for different components in the columns, including the confined zones of the lightweight aggregate concrete (LWAC) using three and four concrete zones divisions approaches and with and without taking into account the stirrups reaction effect, are established first. The analytical models for determining the axial load-deformation behavior of the SRLAC columns are drawn based on the materials models. The analytical and FE models' results are compared with previously reported test results of the axially loaded SRLAC columns. The proposed analytical and FE models accurately predict the axial behavior and capacities of the new types of SRLAC columns with acceptable agreements for the load-displacement curves. The LWAC strength, steel section ratio, and steel section configuration affect the contact stress between the concrete and steel sections. The average ratios of the ultimate test load to the three analytical models and FEA model loads, Put /Pa1, Put /Pa2, Put /Pa3, and Put /PFE1, for the tested specimens are 0.96, 1.004, 1.016, and 1.019, respectively. Finally, the analytical parametric studies are also studied, in terms of the effects of confinement, LWAC strength, steel section ratio, and the reinforcement ratio on the axial capacity of the SRLAC column. When concrete strength, confinements, area of steel sections, or reinforcement bars ratio increased, the axial capacities increased.

• Composites Research
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• v.35 no.2
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• pp.61-68
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• 2022

Composite materials have been used in aerospace industry and many applications because of many advantages such as specific strength and stiffness and corrosion resistance etc. However, it is vulnerable to impacts, these impact lead to formation of cracks in composite laminate and failure of structures. In this paper, we analyzed Mode I fracture toughness of Carbon/Epoxy laminates using acoustic emission signal. DCB test was carried out to analyze Mode I failure characterization of Carbon/Epoxy laminates, and AE sensor was attached to measure AE signal induced by failure of specimen. Fracture toughness was calculated using cumulative AE energy and measured crack length using camera. The calculated fracture toughness was applied in FE model and the result of FE analysis compared with DCB test results. The results show good agreement with between FEM and DCB test results.

• The Journal of the Convergence on Culture Technology
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• v.9 no.4
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• pp.593-599
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• 2023

There is risk of derailment due to various factors such as vehicle-track load imbalance in curved parts, so urban railways install and operate derailing prevent guard rails. The angle-type derailing prevent guard rail is composed of various parts including the guard angle. Even if derailment does not occur, various damages occur in the components, so continuous maintenance is required. Through the damage status analysis, the components of the angle-type derailing prevent guard rail with high damage frequency were classified, and conditions for the occurrence of various damages were investigated. In addition, a numerical analysis using a precise 3D numerical model was performed to analyze the cause of the damage analytically. In order to analytically simulate the derailment situation, the static ultimate load condition was applied, and the actual drawing of the angle-type derailing prevent guard rails, rails, and wheels was used for modeling. By analyzing the results of the damage status investigation and finite element analysis, we tried to investigate the damage of the components.

• Journal of Korean Society of Steel Construction
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• v.17 no.5 s.78
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• pp.581-591
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• 2005

This paper proposes a design formulae that evaluates the design strength of T-joints made of cold-formed square hollow steel sections with longitudinal branch plate. The T-joints had a configuration that a branch member used to longitudinal plate to the main chord in the plane. This study focused on the branch plate T-joints governed by the main chord flange failure mode among the experimental results. Based on the test results of the longitudinal branch plate T-joint in the square hollow sections, the ultimate strength on the T-joints was defined as 1.5 times the load at 1% B the strength of joints that governed the serviceability in control for $16.7{\leq}2\gamma(B/T){\leq}31.3$ and $0.20{\leq}{\beta}(b1/B){\leq}0.75$. Existing yield line models for normal T-joints were investigated to be the main chord flange failure for the branch plate T-joint, and this proposal design formula was based on the theory of the yield line model. Finally, the value of the finite element method compared with the value of the test and theory for the T-joints verified the validity of the design formulae.

• Journal of Navigation and Port Research
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• v.31 no.3 s.119
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• pp.271-279
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• 2007

Ship structures are basically an assembly of plate elements and estimation load-carrying capacity or the ultimate strength is one of the most important criterion for estimated safety assessment and rational design on the ship structure. Also, Structural elements making up ship plated structures do not work separately against external load. One of the critical collapse events of a ship structure is the occurrence of overall buckling and plastic collapse of deck or bottom structure subjected to longitudinal bending. So, the deck and the bottom plates are reinforced by a number af longitudinal stiffeners to increase their strength and load-carrying capacity. For a rational design avoiding such a sudden collapse, it is very important to know the buckling and plastic behaviour or collapse pattern of the stiffened plate under axial compression. In this present study, to investigate effect af modeling range, the finite element method are used and their results are compared varying the analysis ranges. When making the FEA model, six types of structural modeling are adopted varying the cross section of stiffener. In the present paper, a series of FEM elastoplastic large deflection analyses is performed on a stiffened plate with fiat-bar, angle-bar and tee-bar stiffeners. When the applied axial loading, the influences of cross-sectional geometries on collapse behaviour are discussed. The purpose of the present study is examined to numerically calculate the characteristics of buckling and ultimate strength behavior according to the analysis method of ship's stiffened plate subject to axial loading.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.5
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• pp.286-291
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• 2014

In this study, novel ultrasonic rotary motor of hexadecagon shape stator was proposed. Stator of the hexadecagon ultrasonic motor was composed of an elastic ring and ceramics. The elastic ring had sixteen sides and sixteen angular points. Eight ceramics were attached on the outer surface of the eight sides of the ring. When rotor of cylindrical shaft was inserted inside of the ring stator, central lines of the sixteen sides of the stator hold the shaft by the slight pressures(frictions). This slight pressure was a preload of the motor and it could be controlled by radius and thickness of the ring. When two sinusoidal voltages which have 90 degree phase difference were applied to each four ceramics, elliptical displacements of inner surface of the ring were obtained. These elliptical displacements of the inner surface rotated the shaft rotor through the frictions. The proposed hexadecagon ultrasonic motor was designed and analyzed by using the finite element method (FEM), depending on materials of the elastic ring. Based on the FEM results, one model of motor which showed maximum displacement at contact points was chosen and fabricated. And characteristics of the motor were compared with simulated results. When the motor was fabricated with these results, EL20ET0.5CT0.5CW2 model showed 115[rpm] speed about input voltage of 60[Vrms] at 65.6[kHz]. And the maximum torque of 6[gfcm] was obtained. From these results, the hexadecagon shaped ultrasonic motor can be used to actuator for optical device which needs detailed position control. Also it can be used to medical and portable device by reducing size and weight.

• Journal of the Korean Society for Nondestructive Testing
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• v.31 no.5
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• pp.459-465
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• 2011

It has been reported that the femoral morphology has a major correlation to femoral neck fractures(FNF). Previous studies to analyze these correlations have relied on mechanical testing and finite element methods. However, these methods have not been widely applied to various femur samples and models. It is because of the availability of the samples from both patients and cadavers, and also of the geometric limitations in changing the shape of the models. In this study we analyzed femoral neck fractures using a parameterized femoral model that could provide flexibility in changing the geometry of the model for the wide applications of FNF analysis. With the parameterization a variety of models could be generated by changing four major dimensions: femoral head diameter(FHD), femoral neck diameter(FND), femoral neck length(FNL), and neck-shaft angle(NSA). We have performed FEA on the models to compute the stress distributions and reaction forces, and compare them with the data previously generated from mechanical testing. The analysis results indicate that the FND is significantly related with the FNF and the FHD is not significantly related with the FNF.

• Journal of the Korea Convergence Society
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• v.9 no.6
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• pp.175-182
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• 2018

In this study, the theoretical method and the finite element analysis were designed in parallel to fabricate basic research data on the production of tool horn for cutting machine with ultrasonic vibration energy. In order to perform high-performance ultrasonic cutting, it is necessary to vibrate only with longitudinal vibration instead of transverse vibration. In order to efficiently transmit the mechanical vibration energy, the maximum amplitude should be generated at the output portion. Therefore, the tool horn must be designed so that the excitation frequency of the oscillator and the natural frequency of the tool horn are the same. In order to design the resonance of the tool horn, there are a theoretical approach using the one-dimensional wave equation and a method of reflecting the finite element analysis result to the design model. In this study, the approximate dimensions of the tool horn are first determined through the one- Based on the results of the finite element analysis, the optimal model was selected and reflected in the final shape of the tool horn. We will use this information as the basic data of actual tool horn for cutting, and will compare the production and experimental data with the contents of this research.

• Journal of Dental Rehabilitation and Applied Science
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• v.19 no.4
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• pp.257-268
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• 2003

The purpose of this study was to assess the loading distributing characteristics of implant prosthesis according to position and direction of load, under vertical and inclined loading using FEA analysis. The finite element model was designed according to standard fixture (4.1mm restorative component x 11.5mm length). The crown for mandibular first molar was made using UCLA abutment. Each three-dimensional finite element model was created with the physical properties of the implant and surrounding bone. This study simulated loads of 200N at the central fossa in a vertical direction (loading condition A), 200N at the outside point of the central fossa with resin filling into screw hole in a vertical direction (loading condition B), 200N at the centric usp in a $15^{\circ}$ inward oblique direction (loading condition C), 200N at the in a $30^{\circ}$ inward oblique direction (loading condition D) or 200N at the centric cusp in a $30^{\circ}$ outward oblique direction (loading condition E) individually. Von Mises stresses were recorded and compared in the supporting bone, fixture, and abutment screw. The following results have been made based on this study: 1. Stresses were concentrated mainly at the ridge crest around implant in both vertical and oblique loading but stresses in the cancellous bone were low in both vertical and oblique loading. 2. Bending moments resulting from non-axial loading of dental implants caused stress concentrations on cortical bone. The magnitude of the stress was greater with the oblique loading than with the vertical loading. 3. An offset of the vertical occlusal force in the buccolingual direction relative to the implant axis gave rise to increased bending of the implant. 4. The relative positions of the resultant line of force from occlusal contact and the center of rotation seems to be more important. 5. The magnitude of the stress in the supporting bone, fixture and abutment screw was greater with the outward oblique loading than with the inward oblique loading and was the greatest under loading at the centric cusp in a $30^{\circ}$ outward oblique direction. Conclusively, this study provides evidence that bending moments resulting from non-axial loading of dental implants caused stress concentrations on cortical bone. But it seems to be more important that how long is the distance from center of rotation of the implant itself to the resultant line of force from occlusal contact(leverage). The goal of improving implants should be to avoid bending of the implant.