• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.4
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• pp.223-230
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• 2014

In this paper, the wind-induced response characteristics of freeform shaped tall building is studied by using FSI analysis. The analytical models are twist shaped ones at representing type of atypical tall building, and this study focused on the relationship between twist angle and wind acceleration. Firstly, 1-way FSI analysis is performed, so maximum lateral displacement of the analytical model for 100 years return period wind speed is calculated, then the elastic modulus of a structure that satisfies the constraints condition is evaluated. And 2-way FSI analysis is carried out. so acceleration of the analytical model for the evaluated modulus of elasticity and arbitrary density is predicted through time history analysis. The basic model is a set of a square shape, height is 400m, slenderness ratio is 8, and twist model is rotated at square model from 0 to 90 degrees at intervals of 15 degrees and from 90 to 360 degrees at intervals of 90 degrees. According to the result of predicting wind acceleration by the shape of each model, the wind vibration effect of square shape model is confirmed to be sensitive more than a twist shape ones.

• Structural Engineering and Mechanics
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• v.57 no.5
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• pp.951-968
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• 2016

Long-span cross-strait bridges extending into deep-sea waters are exposed to complex marine environments. During the construction stage, the flexible freestanding bridge towers are more vulnerable to environmental loads imposed by wind and wave loads. This paper presents an experimental investigation on the dynamic responses of a 389-m-high freestanding bridge tower model in a test facility with a wind tunnel and a wave flume. An elastic bridge model with a geometric scale of 1:150 was designed based on Froude similarity and was tested under wind-only, wave-only and wind-wave combined conditions. The dynamic responses obtained from the tests indicate that large deformation under resonant sea states could be a structural challenge. The dominant role of the wind loads and the wave loads change according to the sea states. The joint wind and wave loads have complex effects on the dynamic responses of the structure, depending on the approaching direction angle and the fluid-induced vibration mechanisms of the waves and wind.

• Coupled systems mechanics
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• v.2 no.3
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• pp.231-253
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• 2013

The impact of spar-nacelle-blade coupling on edgewise dynamic responses of spar-type floating wind turbines (S-FOWT) is investigated in this paper. Currently, this coupling is not considered explicitly by researchers. First of all, a coupled model of edgewise vibration of the S-FOWT considering the aerodynamic properties of the blade, variable mass and stiffness per unit length, gravity, the interactions among the blades, nacelle, spar and mooring system, the hydrodynamic effects, the restoring moment and the buoyancy force is proposed. The aerodynamic loads are combined of a steady wind (including the wind shear) and turbulence. Each blade is modeled as a cantilever beam vibrating in its fundamental mode. The mooring cables are modeled using an extended quasi-static method. The hydrodynamic effects calculated by using Morison's equation and strip theory consist of added mass, fluid inertia and viscous drag forces. The random sea state is simulated by superimposing a number of linear regular waves. The model shows that the vibration of the blades, nacelle, tower, and spar are coupled in all degrees of freedom and in all inertial, dissipative and elastic components. An uncoupled model of the S-FOWT is then formulated in which the blades and the nacelle are not coupled with the spar vibration. A 5MW S-FOWT is analyzed by using the two proposed models. In the no-wave sea, the coupling is found to contribute to spar responses only. When the wave loading is considered, the coupling is significant for the responses of both the nacelle and the spar.

• Korean Journal of Food Science and Technology
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• v.25 no.1
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• pp.15-21
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• 1993

Crude ${\beta}-glucan$ extracted from Barley was purified by stepwise enzyme treatment (Thermostable ${\alpha}-amylase$, amyloglucosidase, protease). The Intrinsic Viscosity $[{\eta}]$ of the purified ${\beta}-glucan$ was determined by Cannon Fenske Capillary Viscometer (size 50, Cannon Instruments, State, College pa.) at different pH (2, 4, 7, 9, 11) and various salt concentration (0.01 M, 0.03 M, 0.05 M, 0.07 M, 0.1 M and 0.2 M). The $[{\eta}]$ of purified ${\beta}-glucan$ was ranged from $0.997{\sim}2.290\;dl/g$. The $[{\eta}]$ of purified ${\beta}-glucan$ at both alkali, acid condition were lower than those at pH 7. However, the alkali condition of puified ${\beta}-glucan$ solution showed less $[{\eta}]$ than the acid condition of this solution. From 0 M to 0.2 M salt concentration, the $[{\eta}]$ of purified ${\beta}-glucan$ solution was decreased to 0.03 M then increased to 0.05 M NaCl and remained constant to 0.2 M NaCl. The chain stiffness parameter of purified ${\beta}-glucan$ was not affected by temperature from $15^{\circ}C$ to $65^{\circ}C$. The shear rates of various ${\beta}-glucan$ conditions were determined by Bohlin Rheometer (Lund, Sweden). The ${\beta}-glucan$ concentration of 1.0 g/dl and 2.0 g/dl behaved as Newtonian fluid. However, above the concentration of 3.0 g/dl ${\beta}-glucan$ solution, it showed thixotropic and psedoplastic characteristics. Barley ${\beta}-glucan$ appears a damping at 0.5 frequency for the 4.0 g/dl solution. Below 0.5 frequency, it appears a viscous behavior property and above 0.5 frequency, it appears a elastic behavior property.

• 한국지구물리탐사학회:학술대회논문집
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• 2006.06a
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• pp.201-206
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• 2006

Earth sciences is undergoing a gradual but massive shift from description of the earth and earth systems, toward process modeling, simulation, and process visualization. This shift is very challenging because the underlying physical and chemical processes are often nonlinear and coupled. In addition, we are especially challenged when the processes take place in strongly heterogeneous systems. An example is two-phase fluid flow in rocks, which is a nonlinear, coupled and time-dependent problem and occurs in complex porous media. To understand and simulate these complex processes, the knowledge of underlying pore-scale processes is essential. This paper presents a new attempt to use pore-scale simulations for understanding physical properties of rocks. A rigorous pore-scale simulator requires three important traits: reliability, efficiency, and ability to handle complex microstructures. We use the Lattice-Boltzmann (LB) method for singleand two-phase flow properties, finite-element methods (FEM) for elastic and electrical properties of rocks. These rigorous pore-scale simulators can significantly complement the physical laboratory, with several distinct advantages: (1) rigorous prediction of the physical properties, (2) interrelations among the different rock properties in a given pore geometry, and (3) simulation of dynamic problems, which describe coupled, nonlinear, transient and complex behavior of Earth systems.

• Journal of the Korean Geotechnical Society
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• v.31 no.6
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• pp.27-44
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• 2015

An analytical solution of dynamic responses for seabed in finite and infinite thicknesses including shallow has been developed under flow and partial standing wave with arbitrary reflection ration coexisting field at a constant water depth condition. In the analytical solution, a field was simply transited to a coexisting field of progressive wave and flow when reflection ratio was 0 and to a coexisting field of fully standing wave and flow when reflection ratio was 1. Based on the Biot's consolidation theory, the seabed was assumed as a porous elastic media with the assumptions that pore fluid is compressible and Darcy law governs the flow. The developed analytical solution was compared with the existing results and was verified. Using the analytical solution the deformation, pore pressure, effective and shear stresses were examined under various given values of reflection ratio, flow velocity, incident wave's period and seabed thickness. From this study, it was confirmed that the dynamic response of seabed was quite different depending on consideration of flow, which causes changing period and length of incident and reflection waves. It was also confirmed that dynamic response significantly depends on the magnitude of reflection ratio.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.2
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• pp.118-134
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• 2015

An analytical solution of dynamic responses for seabed in shallow, finite and infinite thicknesses has been developed under flow and standing wave coexisting field at a constant water depth condition. To do this, based on the Biot's consolidation theory, the seabed is assumed as a porous elastic media with the assumptions that pore fluid is compressible and Darcy law governs the flow. The developed analytical solution is compared with the previous results and is verified. Using the analytical solution the deformation, pore pressure, effective and shear stresses of seabed are examined under various given values of flow velocity, incident wave period and seabed thickness. From this study, it is confirmed that the seabed response is quite different depending on consideration of flow, which causes changing period and length of incident and reflection waves.

• Journal of the Korean Society of Safety
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• v.11 no.4
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• pp.143-150
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• 1996

This is an explicit-Implicit, finite element analysis for linear as well as nonlinear hygrothermal stress problems. Additional features, such as moisture diffusion equation, crack element and virtual crack extension(VCE ) method for evaluating J-integral are implemented in this program. The Linear Elastic Fracture Mechanics(LEFM) Theory is employed to estimate the crack driving force under the transient condition for and existing crack. Pores in materials are assumed to be saturated with moisture in the liquid form at the room temperature, which may vaporize as the temperature increases. The vaporization effects on the crack driving force are also studied. The Ideal gas equation is employed to estimate the thermodynamic pressure due to vaporization at each time step after solving basic nodal values. A set of field equations governing the time dependent response of porous media are derived from balance laws based on the mixture theory Darcy's law Is assumed for the fluid flow through the porous media. Perzyna's viscoplastic model incorporating the Von-Mises yield criterion are implemented. The Green-Naghdi stress rate is used for the invariant of stress tensor under superposed rigid body motion. Isotropic elements are used for the spatial discretization and an iterative scheme based on the full newton-Raphson method is used for solving the nonlinear governing equations.

• Tunnel and Underground Space
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• v.29 no.3
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• pp.197-213
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• 2019

We simulated the fault reactivation experiment conducted at 'Main Fault' intersecting the low permeability clay formations of Mont Terri Underground Research Laboratory in Switzerland using TOUGH-FLAC simulator. The fluid flow along a fault was modelled with solid elements and governed by Darcy's law with the cubic law in TOUGH2, whereas the mechanical behavior of a single fault was represented by creating interface elements between two separating rock blocks in FLAC3D. We formulate the hydro-mechanical coupling relation of hydraulic aperture to consider the elastic fracture opening and failure-induced dilation for reproducing the abrupt changes in injection flow rate and monitoring pressure at fracture opening pressure. A parametric study was conducted to examine the effects of in-situ stress condition and fault deformation and strength parameters and to find the optimal parameter set to reproduce the field observations. In the best matching simulation, the fracture opening pressure and variations of injection flow rate and monitoring pressure showed good agreement with field experiment results, which suggests the capability of the numerical model to reasonably capture the fracture opening and propagation process. The model overestimated the fault displacement in shear direction and the range of reactivated zone, which was attributed to the progressive shear failures along the fault at high injection pressure. In the field experiment results, however, fracture tensile opening seems the dominant mechanism affecting the hydraulic aperture increase.

• Journal of Korean Foot and Ankle Society
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• v.23 no.1
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• pp.12-17
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• 2019

Purpose: This study examined the clinical outcomes and usefulness of triamcinolone acetonide (TA) injections as an option in the conservative treatment of patients with lateral malleolar bursitis of the ankle. Materials and Methods: A total of 27 patients (27 ankles), in whom TA injection had been performed between March 2016 and June 2017, were reviewed retrospectively. After the aspiration of fluid in the lateral malleolar bursal sac, 1 mL (40 mg) of TA was injected into the malleolar bursal sac. After the injection, the ankle was compressed with an elastic cohesive bandage for 2 to 4 weeks. The clinical outcomes and side effects were evaluated at the following time points: 2 weeks, 4 weeks, 3 months, 6 months, and 1 year after TA injection therapy. The responses to treatment were assessed according to the degree of fluctuation, shrinkage of the bursal sac, and soft tissue swelling. Results: The mean age was 62.1 years (range, 41~81 years); there were 19 males and 8 females. Complete resolution was observed in 26 patients (96.3%) after the first or second application of a TA injection, and a partial response was observed in 1 patient (3.7%) after the first TA injection. The physical component scores of Medical Outcomes Study 36-item Short-Form Health Survey improved from 71.1 to 76.0 at the last follow-up (p=0.001). Associated complications were 1 patient (3.7%) with skin atrophy and 3 patients (11.1%) with transient hyperglycemia in diabetes mellitus. Conclusion: TA injection is a useful and safe procedure for patients not responding to the usual conservative treatment of lateral malleolar bursitis of the ankle.