• Nuclear Engineering and Technology
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• v.53 no.2
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• pp.423-429
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• 2021

The investigation of the utilization of enriched ²⁰⁸Pb as a coolant to enhance the performance of a long-life fast reactor with a Modified CANDLE (Constant Axial shape of Neutron flux, nuclide densities, and power shape During Life of Energy production) burnup scheme has performed. The analyzes were performed on a reactor with thermal power of 800 MegaWatt Thermal (MWTh) with a refueling process every 15 years. Uranium Nitride (enriched ¹⁵N), ²⁰⁸Pb, and High-Cr martensitic steel HT-9 were employed as fuel, coolant, and cladding materials, respectively. One of the Pb-nat isotopes, ²⁰⁸Pb, has the smallest neutron capture cross-section (0.23 mb) among other liquid metal coolants. Furthermore, the neutron-producing cross-section (n, 2n) of ²⁰⁸Pb is larger than sodium (Na). On the other hand, the inelastic scattering energy threshold of ²⁰⁸Pb is the highest among Na, ^natPb, and Bi. The small inelastic scattering cross-section of ²⁰⁸Pb can harden the neutron energy spectrum. Therefore, ²⁰⁸Pb is a better neutron multiplier than any other liquid metal coolant. The excess neutrons cause more production than consumption of ²³⁹Pu. Hence, it can reduce the initial fuel loading of the reactor. The selective photoreaction process was developing to obtain enriched ²⁰⁸Pb. The neutronic was calculated using SRAC and JENDL 4.0 as a nuclear data library. We obtained that the modified CANDLE reactor with enriched ²⁰⁸Pb as coolant and reflector has the highest k-eff among all reactors. Meanwhile, the ^natPb cooled reactor has the lowest k-eff. Thus, the utilization of the enriched ²⁰⁸Pb as the coolant can reduce reactor initial fuel loading. Moreover, the enriched ²⁰⁸Pb-cooled reactor has the smallest power peaking factor among all reactors. Therefore, the enriched ²⁰⁸Pb can enhance the performance of a long-life Modified CANDLE fast reactor.

• Structural Engineering and Mechanics
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• v.82 no.1
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• pp.107-120
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• 2022

The bracing members capable of active control against seismic loads to reduce earthquake damage have been widely utilized in construction projects. Effectively reducing the structural damage caused by earthquake events, bracing systems equipped with retrofitting damper devices, which take advantage of the energy dissipation and impact absorption, have been widely used in practical construction sites. Shape Memory Alloys (SMAs) are a new generation of smart materials with the capability of recovering their predefined shape after experiencing a large strain. This is mainly due to the shape memory effects and the superelasticity of SMA. These properties make SMA an excellent alternative to be used in passive, semi-active, and active control systems in civil engineering applications. In this research, a new system in diagonal braces with slit damper combined with SMA is investigated. The diagonal element under the effect of tensile and compressive force turns to shear force in the slit damper and creates tension in the SMA. Therefore, by creating shear forces in the damper, it leads to yield and increases the energy absorption capacity of the system. The purpose of using SMA, in addition to increasing the stiffness and strength of the system, is to create reversibility for the system. According to the results, the highest capacity is related to the case where the ratio of the width of the middle section to the width of the end section (b₁/b) is 1.0 and the ratio of the height of the middle part to the total height of the damper (h₁/h) is 0.1. This is mainly because in this case, the damper section has the highest cross-section. In contrast, the lowest capacity is related to the case where b₁/b=0.1 and the ratio h₁/h=0.8.

• Structural Engineering and Mechanics
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• v.52 no.4
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• pp.787-813
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• 2014

Starting with Hamilton's variational principle, the governing field equations for the steady state response of thin-walled beams under harmonic forces are derived. The formulation captures shear deformation effects due to bending and warping, translational and rotary inertia effects and as well as torsional flexural coupling effects due to the cross section mono-symmetry. The equations of motion consist of four coupled differential equations in the unknown displacement field variables. A general closed form solution is then developed for the coupled system of equations. The solution is subsequently used to develop a family of shape functions which exactly satisfy the homogeneous form of the governing field equations. A super-convergent finite element is then formulated based on the exact shape functions. Key features of the element developed include its ability to (a) isolate the steady state response component of the response to make the solution amenable to fatigue design, (b) capture coupling effects arising as a result of section mono-symmetry, (c) eliminate spatial discretization arising in commonly used finite elements, (d) avoiding shear locking phenomena, and (e) eliminate the need for time discretization. The results based on the present solution are found to be in excellent agreement with those based on finite element solutions at a small fraction of the computational and modelling cost involved.

• Transactions of Materials Processing
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• v.9 no.5
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• pp.504-511
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• 2000

Hydroforming is a forming process enabling circular metal tubes to be produced in complex cross sections along curved axial paths. This forming process is widely used to manufacture parts in automotive industry. This paper presents bending and forming results to following angle of weld line positions. These compare to good bending, bad bending and without weld line model case. And then this result of after forming compare to each forming cases. The purpose of this paper is found that adaptive weld line position for bended final shape.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.542-543
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• 2012

• Wind and Structures
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• v.37 no.3
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• pp.229-243
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• 2023

This study analyzes the response of a tall building with an H-shaped cross-section when subjected to wind loading generated by the same H-shape. As normative standards usually adopt regular geometries for determining the wind loading, this paper shows unpublished results which compares results of the dynamic response of H-shaped buildings with the response of simplified section buildings. Computational Fluid Dynamics (CFD) is employed to determine the steady wind load on the H-shaped building. The CFD models are validated by comparison with wind tunnel test data for the k-ε and k-ω models of turbulence. Transient wind loading is determined using the Synthetic Wind Method. A new methodology is presented that combines Stochastic and CFD methods. In addition, time-history dynamic structural analysis is performed using the HHT method for a period of 60 seconds on finite element models. First, the along-wind response is studied for wind speed variations. The wind speeds of 28, 36, 42, and 50 m/s at 0° case are considered. Subsequently, the dynamic response of the building is studied for wind loads at 0°, 45°, and 90° with a wind speed of 42 m/s, which approximates the point of resonance between gusts of wind and the structure. The response values associated with the first two directions for the H-shaped building are smaller than those for the R-shaped (Equivalent Rectangular Shape) one. However, the displacements of the H-shaped building associated with the latter wind load are larger.

• Journal of Korea Multimedia Society
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• v.5 no.3
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• pp.255-262
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• 2002

A boundary sequence can be a good representation of arbitrary shapes, because it can represent them simply and precisely. However, boundary sequences have not been used as a representation of arbitrary shapes, because the pixel-based shape-features such as area, centroid, orientation, projection and so forth, could not be computed directly from them. In this paper, we show that the shape-features can be easily computed from the boundary sequences by introducing the cross-sections that are defined as vertical (or horizontal) line segments in a shape. A cross-section generation method is proposed, which generates cross-sections of the shape efficiently by tracing the boundary sequence of the shape once. Furthermore, a boundary sequence extraction method is also proposed, which generates a boundary sequence for each shape in a binary image automatically The proposed methods work well even if a shape has holes. Eventually, we show that a boundary sequence can be used effectively for representing arbitrary shapes.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.9
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• pp.1106-1111
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• 2014

This paper has a purpose to find out the characteristics of pressure distribution according to the POD shape installed in the Hydrofoil vessel, using the CFD. The results showed that as we cut the POD cross-section's basic shape along the x-axis from 0 to 8cm, the viscous resistance had decreased, but then the pressure resistance had increased modestly. However, the cutoff length of POD cross-section shape has close to 9cm, the viscous drag had increased and the pressure drag had decreased. As a result, we found out that the pressure resistance made more effects in POD shape than the viscous resistance, and the total resistance decreased near the 9cm of cutoff length.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.93-100
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• 2000

In this study, we used photoelastic coating method which is a kind of model test for examining the stress condition of rock masses around underground structures. Using this method, we could know adaptability and usefulness of photoelastic coating method for various shape of tunnel models. And, in spite of higher cross section efficiency, square shape model showed unstable status because of high stress concentration. So, we cut the slits at the each corner of tunnel, and we could make more stable stress condition by means of moving high stress concentration to rock mass.

• Journal of Mechanical Science and Technology
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• v.18 no.2
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• pp.246-252
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• 2004

The modal characteristics of rotating structures vary with the rotating speed. The material and the geometric properties of the structures as well as the rotating speed influence the variations of their modal characteristics. Very often, the modal characteristics of rotating structures need to be specified at some rotating speeds to meet their design requirements. In this paper, rotating cantilever beam is chosen as a design target structure. Optimization problems are formulated and solved to find the optimal shapes of rotating beams with rectangular cross section.