• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.67-71
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• 2003

The propagation characteristics of the impulse wave discharged from the exit of a perforated pipe is investigated through a simple shock tube facility. The pressure histories and directivities of the impulse wave propagating outside from the exit of pipe with several different configurations are analyzed for the range of the incident weak shock wave Mach number between 1.02 and 1.2. In the shock tube experiments, the impulse wave are visualized by a Schlieren optical system for the purpose of understanding its propagation characteristics. The experimental results show that for the near sound field the impulse noise strongly propagates toward to the pipe axis, but for the far sound field the impulse noise uniformly propagates toward to the omnidirections, indicating that the directivity pattern is almost same regardless of the pipe type. Especially, it is shown that the perforated pipe has a little performance to reduce the impulse noise only for the near sound field

• Structural Engineering and Mechanics
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• v.48 no.2
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• pp.207-220
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• 2013

In this study, the vulnerability of two existing asymmetric steel building frames to Progressive Collapse (PC) is assessed. The buildings have different frame systems, steel sections and number of stories (nine and six). An alternate path method (APM) with a linear static analysis (LS) is carried out according to General Services Administration (GSA) 2003 guidelines. The Demand Capacity Ratio (DCR) of each primary element (beams and columns) is given with its specific details for all frames. The results show that the nine-story building with a dual frame system (moment frame with bracing system) has a lower susceptibility and greater resistance to PC than the six-story building with a simple building frame system (gravity system with bracing system). Implementing built-up box-shaped sections for columns is a better choice than using built-up I-shaped sections because there is no weak axis for the box section.

• Steel and Composite Structures
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• v.29 no.2
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• pp.161-173
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• 2018

Point bending is often used for cambering and curving structural steel girders. An analytical solution, applicable in the elasto-plastic range only, that relates applied loads to the desired curve was recently developed for inducing horizontal curves using four-point bending. This solution does not account for initial residual stresses and geometric imperfections built-in hot-rolled sections. This paper presents results from a full-scale test on a hot-rolled steel section curved using four-point bending. In parallel, a numerical analysis, accounting for both initial geometric imperfections and initial residual stresses, was carried out. The models were validated against the experimental results and a good agreement for lateral offset and for strain in the elasto-plastic and post-plastic ranges was achieved. The results show that the effect of initial residual stresses on deformation and strain is minimal. Finally, residual stresses due to cold bending calculated from the numerical analysis were assessed and a revised stress value for the service load design of the curved girder is proposed.

• Journal of the Korean Society for Railway
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• v.9 no.4 s.35
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• pp.467-472
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• 2006

This paper deals with the applicability of long-gauge deformation fiber optic sensors (FOS) to prestressed concrete structures. A main motivation is the desire to monitor the deflection of the railway bridges without intervenes of the signal intensity fluctuations. A 25 m long, 1.8 m deep PSC girder was fabricated compositely with 22 cm thick reinforced concrete deck. Two pairs of 3 m long-gauge sensors are attached to the prestressed concrete girder with parallel topology. Using the relationship between curvature and vortical deflection and the quadratic regression of curvatures at the discrete point, it is possible to extrapolate the deflection curve of the girder. The estimated deflection based on the developed method is compared with the results using conventional strain gauges and LVDTS. It has been demonstrated that the proposed instrumentation technique is capable of estimating the vertical deflection and neutral axis position of the prestressed concrete girder up to weak nonlinear region.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.1
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• pp.60.3-61
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• 2018

Abell 115 is a renowned cluster merger at z=0.197. It exhibits an asymmetric X-ray distribution with cometary tails and a megaparsec-sized radio relic stretching in the northeastern direction from the core of the northern cluster. Many observations have concluded that this cluster merger has a large impact parameter, but there has been no numerical analysis on the structure of Abell 115. In this study, we simulate Abell 115 with Gadget2 N-body/SPH code to reproduce the X-ray and weak lensing features of Abell 115. We find a new plausible merger scenario of Abell 115, wherein the northern cluster is currently in an outgoing phase. The predicted X-ray emission has a similar morphology to the observed tail of the northern cluster. However, in order to reproduce the observed line-of-sight velocity and projected distance while maintaining the two systems gravitationally bound, the system should possess a large projection angle, which makes the shock look considerably more diffused than the observed radio relic.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.943-948
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• 2003

The experimental study for oblong section was carried out by the column test in weak axis. The column specimens had 3 types of transverse steel configurations, such as interlocking spirals, interlocking circular hoop ties and rectangular ties. The oblong columns with interlocking spirals and with interlocking circular hoop ties showed better seismic performance than the rectangular columns with rectangular hoops and cross-ties. The objectives of this study were to provide experimental data on the behavior of interlocking spiral columns under cyclic loading, to compare the performance of columns with interlocking spirals to columns with various transverse steel configurations, to study the flexural detailing of interlocking spirals, interlocking circular hoops, and other transverse steel configurations as the transverse reinforcement, and to make recommendations for the design of bridge columns incorporating interlocking spirals, circular hoops as the transverse reinforcement.

• Korean Journal of Mathematics
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• v.20 no.4
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• pp.507-515
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• 2012

We investigate the number of the solutions for the elliptic boundary value problem. We obtain a theorem which shows the existence of six weak solutions for the elliptic problem with jumping nonlinearity crossing three eigenvalues. We get this result by using the geometric mapping defined on the finite dimensional subspace. We use the contraction mapping principle to reduce the problem on the infinite dimensional space to that on the finite dimensional subspace. We construct a three dimensional subspace with three axis spanned by three eigenvalues and a mapping from the finite dimensional subspace to the one dimensional subspace.

• Journal of the Korean Society of Clothing and Textiles
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• v.30 no.1 s.149
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• pp.137-145
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• 2006

This study offers the basis of the image making in categorizing one's personal style and investigation its features and image differences, according to the image making on the subject of Korean female entertainers. The image factors are Activeness, Attractiveness, Extroversions and Intimacy that has occupied by $56.34\%$ out of total. The type of the personal style of Korean female entertainers are classified into five groups and nine small groups that refer to Elegant style(Noble, Sophisticated), Natural style, Tough style, Romantic style(Cute, Delicate), Sexy style(Vivid, Cool, Healthy). The image according to the type of personal style has presented meaningful differences in all composed factors, in particular, the most significant differences are shown in the factors of Attractiveness and Activeness. The axis of the personal positioning far Korean female entertainers are divided into Elegant-Active, Cool-Warm, Weak-Tough. Artificial -Natural.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2001.04a
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• pp.189-196
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• 2001

Recent days composite bridge deck is gaining attraction due to many advantages such as light weight, high strength, corrosion resistance, and high durability. In this study, composite sandwich deck models of hat, box, and triangular section type were fabricated by VARTM process. For those models, three point flexural test was carried out both in strong and weak axis. The experimental results are compared with each other to determine efficient section type. Also finite element analysis was performed and compared with experiments to verify analysis model. It has been demonstrated that composite sandwich deck can be used as bridge deck in the new construction and rehabilitation work.

• Korean Journal of Materials Research
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• v.16 no.7
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• pp.401-407
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• 2006

ZnO is well-known as a promising material for optical communication systems and electronic displays. ZnO:Er thin films were deposited on c-plane sapphire substrates by rf magnetron sputtering, and the effects of sputtering parameters and the annealing conditions on the luminescence in the visible range were investigated. Luminescent properties depended on the crystallinity of films and annealing atmosphere. Highly c-axis oriented ZnO:Er films showed a strong emission band at 465 nm and a weak emission at 525 nm due to the energy transition of $^{4}I_{15/2}-^{4}F_{5/2}\;and\;^{4}I_{15/2}-^{2}H_{11/2}$, respectively. ZnO:Er thin films annealed at air atmosphere were superior to those annealed in $H_2$ in photoluminescence intensity.