• Smart Structures and Systems
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• v.9 no.5
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• pp.427-439
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• 2012

The present paper deals with the analytical solution of a functionally graded piezoelectric (FGP) cylinder in the magnetic field under mechanical, thermal and electrical loads. All mechanical, thermal and electrical properties except Poisson ratio can be varied continuously and gradually along the thickness direction of the cylinder based on a power function. The cylinder is assumed to be axisymmetric. Steady state heat transfer equation is solved by considering the appropriate boundary conditions. Using Maxwell electro dynamic equation and assumed magnetic field along the axis of the cylinder, Lorentz's force due to magnetic field is evaluated for non homogenous state. This force can be employed as a body force in the equilibrium equation. Equilibrium and Maxwell equations are two fundamental equations for analysis of the problem. Comprehensive solution of Maxwell equation is considered in the present paper for general states of non homogeneity. Solution of governing equations may be obtained using solution of the characteristic equation of the system. Achieved results indicate that with increasing the non homogenous index, different mechanical and electrical components present different behaviors along the thickness direction. FGP can control the distribution of the mechanical and electrical components in various structures with good precision. For intelligent properties of functionally graded piezoelectric materials, these materials can be used as an actuator, sensor or a component of piezo motor in electromechanical systems.

• Geomechanics and Engineering
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• v.20 no.4
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• pp.359-370
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• 2020

Prestressed ground anchors are important structural elements in geotechnical engineering. Despite their widespread usage, the design process is often significantly simplified. One of the major drawbacks of commonly used design methods is the assumption that skin friction is mobilized uniformly along an anchor's fixed length, one consequence of which is that a progressive failure phenomenon is neglected. The following paper introduces an alternative design approach - a computer algorithm employing the load-transfer method. The method is modified for the analysis of anchors and combined with a procedure for the derivation of load-transfer functions based on commonly available laboratory tests. The load-transfer function is divided into a pre-failure (hardening) and a post-failure (softening) segment. In this way, an aspect of non-linear stress-strain soil behavior is incorporated into the algorithm. The influence of post-grouting in terms of radial stress update, diameter enlargement, and grout consolidation is included. The axial stiffness of the anchor body is not held constant. Instead, it gradually decreases as a direct consequence of tensile cracks spreading in the grout material. An analysis of the program's operation is performed via a series of parametric studies in which the influence of governing parameters is investigated. Finally, two case studies concerning three investigation anchor load tests are presented.

• Proceeding of Spring/Autumn Annual Conference of KHA
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• 2004.11a
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• pp.349-354
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• 2004

In accordance with recent culture-advancement and national improvement in conscious level, the desire for cultural life is on increasing, so that it is also increasing tendency toward the planning and construction of large performance hall for the local residents, conducted by the provincial self-governing body. For the sake of a satisfiable acoustic efficiency at the said large performance hall, although it is designed and constructed with application of various methods of simulation from the planning stage, there could be appeared an error of the said simulation and defect occurred in the construction, and due to such reason, a situation unable to fulfill a satisfiable Acoustic efficiency to be generated thereat after opening of the hall. Accordingly, it is able to judge on the part which necessitates for betterment, also the region where acoustically weak, through measurement and evaluation on the acoustic efficiency in the completed performance all, and by its correction as well as supplement thereon based on the afore-mentioned, a performance hall equipped with the supreme acoustic condition could be established.

• Journal of Ocean Engineering and Technology
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• v.15 no.2
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• pp.11-21
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• 2001

The focus of this paper is on the numerical investigation of obliquely incident wav interactions with a system composed of fully submerged and floating dual buoy/vertical-flexible-membrane breakwaters placed in parallel with spacing between two systems. The fully submerged two systems allow surface and bottom gaps to enable wave transmission over and under the system. The problem is formulated based on the two-dimensional multi-domain hydro-elastic linear wave-body interaction theory. The hydrodynamic interaction of oblique incident waves with the combination of the rigid and flexible bodies was solved by the distribution of the simple sources (modified Bessel function of the second kind) that satisfy the Helmholz governing equation in fluid domains. A boundary element program for three fluid domains based on a discrete membrane dynamic model and simple source distribution method is developed. Using this developed computer program, the performance of various dual systems varying buoy radiuses and drafts, membrane lengths, gaps, spacing, mooring-lines stiffness, mooring types, water depth, and wave characteristics is thoroughly examined. It is found that the fully submerged and floating dual buoy/membrane breakwaters can, if it is properly tuned to the coming waves, have good performances in reflecting the obliquely incident waves over a wide range of wave frequency and headings.

• Structural Engineering and Mechanics
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• v.86 no.6
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• pp.751-764
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• 2023

In practical engineering such as aerial refueling pipes, the boundary of the fluid-conveying pipe is difficult to be completely immovable. Pipes under movable and immovable boundaries are controlled by different dominant nonlinear factors, where the boundary mobility will affect the nonlinear dynamic characteristics, which should be focused on for adopting different strategies for vibration suppression and control. The nonlinear dynamic instability characteristics of functionally graded fluid-conveying pipes lying on a viscoelastic foundation under movable and immovable boundary conditions are systematically studied for the first time. Nonlinear factors involving nonlinear inertia and nonlinear curvature for pipes with a movable boundary as well as tensile hardening and nonlinear curvature for pipes with an immovable boundary are comprehensively considered during the derivation of the governing equations of the principal parametric resonance. The stability boundary and amplitude-frequency bifurcation diagrams are obtained by employing the two-step perturbation- incremental harmonic balance method (TSP-IHBM). Results show that the movability of the boundary of the pipe has a great influence on the vibration amplitude, bifurcation topology, and the physical meanings of the stability boundary due to different dominant nonlinear factors. This research has guidance significance for nonlinear dynamic design of fluid-conveying pipe with avoiding in the instability regions.

• Journal of the Korean Home Economics Association
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• v.29 no.2
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• pp.1-15
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• 1991

The purpose of this study was to understand the diversity and speciality of Aztec dress which has not been well known, and to overcome ethnocentrism in clothing perceptions. From 15 century to early 16 century, the Aztec empire based on the unique view of the world, most flourished in Mesoamerica. Ritualistic and official side of Aztec life was reflected well on dress. Most Aztec garments consisted of unsewn pieces of cloth, draped on the body as loincloth, mantle and wraparound skirt. Slightly more complicated garments such as women's blouses(huipils) and men's simple jackets were created by sewing together two or more pieces of material. In the sharply stratified world of Aztec, strict sumptuary laws controlled dress. The garments of lower classes were made of maguey or yucca fiber, and only the upper classes were allowed to wear cotton clothing. In addition to material, color, elaborateness and even manner of tieing the mantle were carefully controlled by government edict. As the Aztec empire expanded and became wealthier, the sumptuary laws could not actually dictate what people wore everyday but rather provided a set of rules governing clothing for ceremonial occasions. Aztec's warrior costumes, consisted of headdress, towering back devices, feather garments, were sufficient to suggest the theatrical grandeur of what must have been one of the most magnificiently attired armies ever assembled.

• Journal of the Korean Institute of Landscape Architecture
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• v.26 no.2
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• pp.133-142
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• 1998

This paper reviews the difference between the selected village groves and seaside groves in Chonbuk-Do province. In Chonbuk-Do province, village groves were principally found in the east mountainous region and seaside groves were found only in the south seaside. The village groves were located in the roadside and village entrance, but seaside groves were located in the front of crop land for the purpose of windbreak. The planting motive of village groves was historical and cultural background, but that of seaside groves was protection of cropland and village from strong wind. The form of village groves was various, but that of seaside groves was linear and rectangular. Both were small scale in comparison with other province. Both were formed on the slopeless land. In ownership, the rate of seaside groes owned by the slf governing body is higher than village groves. Billage groves were almostly owned by village. In vegetatioin structure, both were one class forest composed of only tall tree of upper class. Principal dominent species of seaside groves in upper tree was Pinus thunbergii, but those of village groves were Pinus densiflora, Carpinus tschonoskii, Zelkova serrata etc. Seaside groves were not growing normally in aspect of height and breast diameter of tree in comparison with village groves. The planting density of seaside groves was 3.7 times higher than village groves in Chonbuk-Do province.

• Water for future
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• v.23 no.4
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• pp.445-457
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• 1990

In order to predict the dispersion of a thermal discharge with strong turbulent and buoyant effects, the development of a numerical model using turbulence model and its application are significantly increased. In this study, a 3-dimensional steady-state model for the surface discharge of heated water into quiescent water body is developed. For the model closure of turbulent terms the 4-equation turbulence model is used. For economic numerical simulation, the elliptic governing equations are transformed to the partially parabolic equations. In general, the simulated results by the present model agree well to the experimental results by Pande and Rajaratnam. The model characteristics are presented in comparison with the predicted results of the 2-equation turbulence model by McGuirk and Rodi. Applying the 4-equation turbulence model to the Korea nuclear unit 1 at Kori site, feasibility and efficiency of the present model are validated.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.2
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• pp.188-195
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• 2010

Green water load is an important parameter to be considered in designing a modern ship or offshore structures like FPSO and FSRU. In this research, a numerical simulation method for green water phenomenon is introduced. The Navier-Stokes equations and the continuity equation are used as governing equations. The equations are calculated using Finite Difference Method(FDM) in rectangular staggered grid system. To increase the numerical accuracy near the body, the Cartesian cut cell method is employed. The nonlinear free-surface during green water incident is defined by Marker-density method. The green waters on a box in regular waves are simulated. The simulation results are compared with other experimental and computational results for verification. To check the applicability to moving ship, the green water of the ship which is towed by uniform force in regular wave, is simulated. The ship is set free to heave and to surge.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.2
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• pp.169-177
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• 2018

Twisted rudder, twisted rudder with bulb, and twisted rudder with bulb and fin have been developed computationally for 3,000 TEU container ship through parametric study. The objective function is to minimize delivered power in model scale. Design variables are twisted angle, rudder bulb diameter and fin angle. The governing equation is Reynolds averaged Navier-Stokes equations in an unsteady turbulent flow and the Reynolds stress model applied for the turbulent closure. A double body model is used for the treatment of free-surface. The calculation was carried out in towing and self-propulsion conditions at design speed. The sliding mesh technique was employed to simulate the flow around the propeller. Form factor is obtained from the towing computation. Self-propulsion point is obtained from the self-propelled computations at two propeller rotating speeds. The delivered power due to the designed twisted rudder, twisted rudder with bulb, and twisted rudder with bulb and fin are reduced by 1.1%, 1.6%, and 2.0%, respectively.