• Advances in aircraft and spacecraft science
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• v.3 no.3
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• pp.299-315
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• 2016

In this work, a strategy for passive vibration control of periodic structures is proposed which involves adding a periodic array of simple resonant devices for creating band gaps. It is shown that such band gaps can be generated at low frequencies as opposed to the well known Bragg scattering effects when the wavelengths have to meet the length of the elementary cell of a periodic structure. For computational purposes, the wave finite element (WFE) method is investigated, which provides a straightforward and fast numerical means for identifying band gaps through the analysis of dispersion curves. Also, the WFE method constitutes an efficient and fast numerical means for analyzing the impact of band gaps in the attenuation of the frequency response functions of periodic structures. In order to highlight the relevance of the proposed approach, numerical experiments are carried out on a 1D academic rod and a 3D aircraft fuselage-like structure.

• Fashion & Textile Research Journal
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• v.16 no.6
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• pp.921-926
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• 2014

The aim of this study is to develop upper bodice pattern for obese girls aged 10~12 by using 3D virtual garment simulation system. The criteria for subjects in this study were girls who had over 1.46 of the R$\ddot{o}$hrer Index. A total of 229 schoolgirls who met these criteria were enrolled. The results of this study are as follows: First, by using 3D virtual garment simulation, new upper bodice pattern considered obese-schoolgirls was development. The basic numerical formula were as follows ; bust girth B/2+4.5, armhole depth B/4-1, waist girth W/4+0.5+dart amount, front chest width B/6+2, back width B/6+2, neck width B/12-0.5 and neck depth B/12+0.5. Second, armhole darts were added to compensate the loose amount of front armhole and dart manipulation was used to ensure a better appearance on armhole in the design. The dart side line was modified concavely to help cover the protruding stomach. Curved lines on the armhole were significantly relieved using dart manipulation and the darts side line was modified concavely to reduce the tightness around the front waist darts. Third, according to the results of the new upper bodice pattern's appearance evaluation, it estimated more highly than existing pattern in silhouette and ease amount, confirming that new upper bodice pattern was appropriate for the obese-schoolgirls. This study is expected to serve as one of important basic data for ensuing studies that may utilize 3D virtual garment simulation system with 2D patterns.

• Tunnel and Underground Space
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• v.30 no.3
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• pp.242-255
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• 2020

The numerical simulations of Heater Experiment-D (HE-D) at the Mont Terri rock laboratory in Switzerland were performed to investigate an applicability of FLAC3D to reproduce the coupled thermo-hydro-mechanical (THM) behaviour in Opalinus Clay, as part of the DECOVLEX-2015 project Task B. To investigate the reliability of numerical simulations of the coupled behaviour using FLAC3D code, the simulation results were compared with the observations from the in-situ experiment, such as temperature at 16 sensors, pore pressure at 6 sensors, and strain at 22 measurement points. An anisotropic heat conduction model, fluid flow model, and transversely isotropic elastic model in FLAC3D successfully represented the coupled thermo-hydraulic behaviour in terms of evolution for temperature and pore pressure, however, performance of the models for mechanical behavior is not satisfactory compared with the measured strain.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.3 s.258
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• pp.217-224
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• 2007

A numerical analysis for a silencer with three baffles of 120mm tank gun has been performed. The Reynolds-Averaged Wavier-Stokes equations with Baldwin-Lomax turbulence model were employed to compute unsteady, compressible flow inside the tank gun and the silencer. An axisymmetric computational domain was constructed by using 12 multi block chimera grids. The resolution of flow field is observed by depicting calculated pressure and muzzle brake force. The peak blast pressure and noise through the silencer reduced approximately 99% and 41dB in comparison to the tank gun without the silencer at near filed.

• Ocean Systems Engineering
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• v.4 no.2
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• pp.83-97
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• 2014

Wave propagation in a three-dimensional (3D) fully nonlinear numerical wave tank (NWT) is studied based on velocity potential theory. The governing Laplace equation with fully nonlinear boundary conditions on the moving free surface is solved using the indirect desingularized boundary integral equation method (DBIEM). The fourth-order predictor-corrector Adams-Bashforth-Moulton scheme (ABM4) and mixed Eulerian-Lagrangian (MEL) method are used for the time-stepping integration of the free surface boundary conditions. A smoothing algorithm, B-spline, is applied to eliminate the possible saw-tooth instabilities. The artificial wave speed employed in MTF (multi-transmitting formula) approach is investigated for fully nonlinear wave problem. The numerical results from incorporating the damping zone (DZ), MTF and MTF coupled DZ (MTF+DZ) methods as radiation condition are compared with analytical solution. An effective MTF+DZ method is finally adopted to simulate the 3D linear wave, second-order wave and irregular wave propagation. It is shown that the MTF+DZ method can be used for simulating fully nonlinear wave propagation very efficiently.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.05a
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• pp.527-528
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• 2010

Previous experimental results performed by many researchers for a couple of decades in South Korea have shown that an absorbing sheet inserted in a conventional floating slab system for thermal insulation or vibration absorption may amplify the vibration of the slab system at specific frequency ranges depending on the material properties of the sheet. The amplified vibration, consequently, results in the heavy weight floor impact noise exceeding the sound level limit for an apartment house, 50dB. In this study, the amplification mechanism is examined through numerical analysis and a new slab system is proposed to reduce the amplification and control the noise. The new slab system consists of studs connecting the base slab and upper concrete finishing yielding the dramatically increased stiffness of the slab. The numerical simulation is performed to investigate the effect of the slab system with studs on the vibration and noise control. The results show that the performance of the slab is sensitive to the number and location of studs, and the heavy weight floor impact noise can be reduced up to 6-7dB compared to the conventional slab system at the optimal stud location.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.4
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• pp.285-291
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• 2017

In this study, a case analysis for thermal design of electronic equipment using a phase change material(PCM) was performed numerically using ANSYS Fluent. Experiments were conducted to find the temperature increase(${\Delta}T_m$), melting temperature($T_m$), and volume expansion of the PCM under the melting process. To verify the accuracy of the Fluent solver model, $T_m$, ${\Delta}T_m$, and the melting time were compared with experimental results. To simulate the temperature stagnation phenomenon under the melting process, the equivalent specific heat method was applied to calculate the thermal properties of the PCM in the solver model. To determine the thermal stability of electronic equipment, we paid special attention to finding a thermal design for the PCM using fins. Further, an additional numerical analysis is currently underway to find an optimum design.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.4B
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• pp.429-439
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• 2008

The purpose of this study is to examine the characteristics of run-up height over sandy beach due to the shape of submerged breakwater. For the discussion on it in detail, 3-Dimensional numerical model with Large Eddy Simulation, which is able to simulate directly interaction of Wave Structure Sandy beach (hereafter, LES-WASS-3D; Hur and Lee, 2007) has been used to simulate run-up height over sandy beach as well as wave field around submerged breakwaters. Using the results obtained from numerical simulation, the effects of the shape of submerged breakwaters (crown height, crown width, crown length and submerged breakwater's slope gradient) on run-up height over sandy beach have been discussed related to the wave height distribution and characteristics of up-layer flow around ones.

• Fashion & Textile Research Journal
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• v.12 no.1
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• pp.86-93
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• 2010

The purpose of this study was to develop torso pattern of Middle-aged obese women by using the virtual twin and 3D virtual garment simulation system. The results were as follows; 1. By using 3D Virtual Garment Simulation, new torso pattern considered obese women was development. The basic numerical formula were as follows ; bust girth B/2+5, armhole depth B/6+5, front waist girth W/4+2+0.5, back waist girth W/4+1-0.5, front hip girth H/4+1+0.5, back hip girth H/4+2-0.5, chest width B/6+2.5, back width B/6+2.5 and back neck width B/20+2.5. 2. According to the results of the new torso pattern's appearance evaluation, it estimated more highly than existing pattern in silhouette and ease amount, confirming that new torso pattern is appropriate for the obese women. Also, new torso pattern was evaluated to allow proper space length of bust, waist, abdomen and hip. Virtual models production through 3D body scan data, pattern draft and virtual garment digital program were applied to prototypic design method so as to enhance the fitness of ready-made garments. This study is expected to serve as one of important basic data for ensuing studies that may utilize 3D Virtual Garment Simulation System with 2D patterns, and also for future 3D Pattern Production Program development.

• Geomechanics and Engineering
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• v.29 no.4
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• pp.471-486
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• 2022

The effect of segmental joints is one of main importance for the segmental lining design when tunnels are excavated by a mechanized process. In this paper, segmental tunnel linings are analyzed by two numerical methods, namely the Beam-Spring Method (BSM) and the Solid-Interface Method (SIM). For this purpose, the Tehran Subway Line 6 Tunnel is considered to be the reference case. Comprehensive 2D numerical simulations are performed considering the soil's calibrated plastic hardening model (PH). Also, an advanced 3D numerical model was used to obtain the stress relaxation value. The SIM numerical model is conducted to calculate the average rotational stiffness of the longitudinal joints considering the joints bending moment distribution and joints openings. Then, based on the BSM, a sensitivity analysis was performed to investigate the influence of the ground rigidity, depth to diameter ratios, slippage between the segment and ground, segment thickness, number of segments and pattern of joints. The findings indicate that when the longitudinal joints are flexible, the soil-segment interaction effect is significant. The joint rotational stiffness effect becomes remarkable with increasing the segment thickness, segment number, and tunnel depth. The pattern of longitudinal joints, in addition to the joint stiffness ratio and number of segments, also depends on the placement of longitudinal joints of the key segment in the tunnel crown (similar to patterns B and B').