• Steel and Composite Structures
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• v.22 no.6
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• pp.1417-1443
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• 2016

Cellular and castellated steel beams are used to obtain higher stiffness and bending capacity using the same weight of steel. In addition, the beam openings may be used as a pass for different mechanical fixtures such as ducts and pipes. The aim of this study is to investigate the effect of different parameters on both elastic and inelastic critical buckling stresses of steel web plates with openings. These parameters are plate aspect ratio; opening shape (circular or rectangular); end distance to the first opening; opening spacing; opening size; plate slenderness ratio; steel grade; and initial web imperfection. The web/flange interaction has been simplified by web edge restraints representing simply supported boundary conditions. A numerical parametric study has been performed through linear and nonlinear finite element (FE) models, where the FE results have been verified against both experimental and numerical results in the literature. The web plates are subject to in-plane linearly varying compression with different loading patterns, ranging from uniform compression to pure bending. A buckling stress modification factor (${\beta}$-factor) has been introduced as a ratio of buckling stress of web plate with openings to buckling stress of the corresponding solid web plate. The variation of ${\beta}$-factor against the aforementioned parameters has been reported. Furthermore, the critical plate slenderness ratio separating elastic buckling and yielding has been identified and discussed for two steel grades of DIN-17100, namely: ST-37/2 and ST-52/3. The FE results revealed that the minimum ${\beta}$-factor is 0.9 for web plates under uniform compression and 0.7 for those under both compression and tension.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.8
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• pp.699-708
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• 2021

In this paper, the aerodynamic and aeroacoustic characteristics that vary depending on the rotation axial distance between the upper and lower rotor, which is one of the design parameters of the coaxial rotor, is analyzed in the hovering condition using the computational fluid dynamics. Aerodynamic analysis using the Reynolds Averaged Navier Stokes equation and the aeroacoustic analysis using the Ffowcs Williams ans Hawkings equation is performed and the results were compared. The upper and lower rotor of the coaxial rotor have different phase angle which changes periodically by rotation and have unsteady characteristics. As the distance between the upper and lower rotors increased, the aerodynamic efficiency of the thrust and the torque was increased as the flow interaction decreased. In the aeroacoustic viewpoint, the noise characteristics radiated in the direction of the rotational plane showed little effect by axis spacing. In the vertical downward direction of the axis increased, the SPL maintains its size as the frequency increases, which affects the increase in the OASPL. As the axial distance of the coaxial rotor increased, the noise characteristics of a coaxial rotor were similar with the single rotor and the SPL decreased significantly.

• Journal of the Korean Geotechnical Society
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• v.36 no.12
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• pp.125-132
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• 2020

Embedded joints in the rock mass are a major constituent influencing its mechanical behavior. Numerical analysis requires a rigorous modeling methodology for the rock mass with detailed information regarding joint properties, orientation, spacing, and persistence. This paper provides a mechanical model for a jointed rock mass based on the implicit joint-continuum approach. Stiffness tensors for rock mass are evaluated for an assemblage of intact rock separated by sets of joint planes. It is a linear summation of compliance of each joint sets and intact rock in the serial stiffness system. In the application example, kinematic analysis for a planar failure of rock slope is comparable with empirical daylight envelope and its lateral limits. Since the developed implicit joint-continuity model is formulated on a continuum basis, it will be a major tool for the numerical simulations adopting published plenteous thermal-hydro-chemical experimental results.

• Elastomers and Composites
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• v.56 no.2
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• pp.92-99
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• 2021

Microstructure-dependent changes in the crystalline properties of poly(ethylene-co-vinyl acetate) (EVA) was investigated using various EVAs at different VA contents via X-ray diffraction (XRD). The parameters analyzed herein were percentage crystallinity (X_c), interplanar crystal spacing (d_hkl), crystal stack size (D_hkl), and the number of crystal plane piles (N_hkl). The X_cs of [110] and [200] crystals were 21.0-4.1 and 6.7-1.4%, respectively, and they decreased by approximately 2.3 and 0.7% for every mol% of the VA content, respectively. The X_c ratios of the [110] and [200] crystals were approximately 3. The d₁₁₀s and d₂₀₀s values were 0.41-0.42 and 0.37-0.38 nm, respectively. The D₁₁₀s and D₂₀₀s values were 9.56 -21.92 and 7.00-16.42 nm, respectively. The d_hkls increased with an increase in the VA content, whereas the D_hkls decreased. The N₁₁₀s and N₂₀₀s were 22.7-51.3 and 18.3-43.2, respectively, and they decreased by increasing the VA content. EVA with the same VA content showed different crystalline properties as per the suppliers, and some EVAs deviated from the average trends. This could be explained by the difference in their microstructures such as the sizes and distribution uniformity of the ethylene sequences in EVA chains.

• The Journal of the Petrological Society of Korea
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• v.28 no.1
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• pp.1-13
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• 2019

The characteristics of the rock cleavage of Jurassic Geochang granite were analysed using the parameters from the length and spacing-cumulative frequency diagrams. The evaluation for three planes and three rock cleavages was performed using the 25 parameters such as (1~2) slope angle(${\alpha}^{\circ}$and ${\beta}^{\circ}$), (3) intersection angle(${\alpha}-{\beta}^{\circ}$), (4) exponent difference(${\lambda}_S-{\lambda}_L$), (5~12) length of line(oa, ob, ol, os, ss', ll' and sl') and (13~15) length ratio(ol/os, ss'/ll' and ll'/sl'), (16) mean length((ss'+ll')/2), (17~23) area (${\Delta}oaa^{\prime}$, ${\Delta}obb^{\prime}$, ${\Delta}obb^{\prime}$, ${\Delta}oaa_a^{\prime}$, ${\Delta}obb_a^{\prime}$, ${\Delta}ll^{\prime}s^{\prime}$, ${\Delta}ss^{\prime}l^{\prime}$ and ⏢$ll^{\prime}ss^{\prime}$) and (24~25) area difference(${\Delta}obb^{\prime}-{\Delta}oaa^{\prime}$ and ${\Delta}obb_a^{\prime}-{\Delta}oaa_a^{\prime}$). Firstly, the values of the 11 parameters(group I: No. 1, 3~4, 7, 9~10, 13, 15~16, 20 and 25), the 3 parameters(group II: No. 5, 8 and 17) and the 2 parameters(group III: No. 12 and 22) are in orders of H(hardway) < G(grain) < R(rift), R < G < H and G < H < R, respectively. On the contrary, the values of parameters belonging to the above three groups show reverse orders for three planes. Secondly, the generalized chart for three planes and three rock cleavages were made. From the related chart, the distribution types formed by the two diagrams related to lengths and spacings were derived. The diagrams related to spacings show upward curvature in the chart of rift plane(G1 & H1, R') and hardway(H1 & H2, H). On the contrary, the diagrams related to lengths show downward curvature. These two diagrams take the form of a convex lens in the upper section. Besides, the two diagrams cross each other in the lower section. The overall shape formed by the above two diagrams between three planes($H^{\prime}{\rightarrow}G^{\prime}{\rightarrow}R^{\prime}$) and three rock cleavages($R{\rightarrow}G{\rightarrow}H$) display in reverse order. Lastly, these types of correlation analysis is useful for discriminating three quarrying planes.

• Journal of the Korea Concrete Institute
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• v.17 no.5 s.89
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• pp.761-768
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• 2005

Lately outmoded and functionally obsolete buildings constructed in 1960s and 1970s are often remodelled and restored. Even though there are not serious structural defects in the existing buildings, many old buildings have been reconstructed to improve residence quality or to extend residence area of the buildings. The experimental or theoretical research on plane expansion of RC apartments is quite scare. In this research, 12 specimens and 19 RC slabs connected by hinged joints were tested. The new slab was connected to the existing slab by hinge joints injecting dowel bars between two slabs. Main parameters of the slabs are types of the dowel bars (D13 and D19), spacing of the dowel bars (150mm, 300mm, and 450mm), and the locations of the steel bars in the existing slabs. The test results indicated that the shear strength of the RC test slabs having various types of dowel bars was about twice that calculated by the ACI 318-02 code. All slabs failed in concrete spatting and the dowel steel bars did not reach their yield strengths.

• Geophysics and Geophysical Exploration
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• v.12 no.1
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• pp.69-76
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• 2009

We report an implementation of the Ground Penetrating Radar (GPR) survey at a site that corresponds to a ruined castle. The objective of the survey was to characterise buried archaeological structures such as walls and tiles in Van Khan Tooril's Ruin, Mongolia, by 2D and 3D GPR techniques. GPR datasets were acquired in an area 10mby 9 m, with 10 cm line spacing. Two datasets were collected, using GPR with 500MHz and 800MHz frequency antennas. In this paper, we report the use of instantaneous parameters to detect archaeological targets such as tile, brick, and masonry by polarimetric GPR. Radar polarimetry is an advanced technology for extraction of target scattering characteristics. It gives us much more information about the size, shape, orientation, and surface condition of radar targets. We focused our interpretation on the strongest reflections. The image is enhanced by the use of instantaneous parameters. Judging by the shape and the width of the reflections, it is clear that moderate to high intensity response in instantaneous amplitude corresponds to brick and tiles. The instantaneous phase map gave information about the location of the targets, which appeared as discontinuities in the signal. In order to increase our ability to interpret these archaeological targets, we compared the GPR datasets acquired in two orthogonal survey directions. A good correlation is observed for the alignments of reflections when we compare the two datasets. However, more reflections appear in the north-south survey direction than in the west-east direction. This is due to the electric field orientation, which is in the horizontal plane for north-south survey directions and the horizontally polarised component of the backscattered high energy is recorded.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.6
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• pp.418-424
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• 2000

Pure $TiO_2$and 10 mol % Pb-doped $TiO_2(Pb_xTi_{1-x}O_2$(x = 0.1)) powder and thin films have been prepared by the sol-gel method. Titanium isopropoxide and ethanol are used for pure $TiO_2$, lead acetate trihydrate and titanium triisopropoxide monoacethylacetonate are used for Pb-doped $TiO_2$, respectively. Films are coated on p-type Si(100) wafer and ITO glass substrates by the sol-gel spin-coating method. The powder and multi-coated films are annealed at different temperature (400~$800^{\circ}C$) for phase formation and crystallization. TGA/DTA, XRD analysis, SEM and UV-visible transmission spectroscopy have been used to study the characteristics of the powder and films. XRD results show that the films are polycrystalline, anatase type and oriented predominantly to the A(101) plane. A slight shift in the d-spacing for the Pb-doped film indicates the incorporation of the Pb into $TiO_2$lattice. A shift of the absorption wavelength in the transmission spectrum towards longer wavelength has been observed about $Pb_xT_{1-x}O_2$(x = 0.1) thin film, which indicates a decrease in the bandgap of $TiO_2$upon Pb-doping.

• Journal of IKEEE
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• v.23 no.1
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• pp.14-21
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• 2019

In this paper, we implemented an on-board miniaturization antenna operating 2.4 GHz using MZR(Mu Zero Resonator). It is must be operating under the constraint that the size of the small terminal PCB should be $78{\times}38{\times}0.8mm^3$ and the size of the system should be $63{\times}38{\times}0.8mm^3$ and the size of the radiating part should be $15{\times}38{\times}0.8mm^3$. The feeding structure uses a CPW structure for stable feeding and a feeding point at the upper left of the system board. A magnetic field coupling structure is used for coupling the feeding part and the antenna. The resonance frequency of the MZR is determined by the series inductance and capacitance of the cell, so the gap between the cells, the length of the cell, the length of the interdigital capacitor, and the spacing between the radiation part and the ground plane are analyzed. The antenna was designed and fabricated using the results. The total size of the antenna including the feed structure is $20.8{\times}9.0{\times}0.8mm^3$, and the electrical length is $0.1664{\lambda}_0{\times}0.072{\lambda}_0{\times}0.0064{\lambda}_0$. The measurement result for 10 dB bandwidth, gain and directivity are 440 MHz(18.3%), 0.4405 dB, and 2.722 dB respectively. It is confirmed that the radiation pattern has omnidirectional characteristics and it can be applied to ultra small terminal antenna.

• The Journal of Korean Academy of Prosthodontics
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• v.61 no.1
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• pp.33-43
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• 2023

Pathological wear across the entire dentition causes problems such as collapsed occlusal plane, reduced vertical dimension, anterior premature contact, inadequate anterior guidance, and tooth migration, thereby induce symptoms such as temporomandibular joint disorder, reduced masticatory efficiency, and tooth hypersensitivity. For the treatment of patients with excessive wear, evaluation of vertical dimension should be preceded along with analysis of the cause. The patient in this case was a 45-year-old female with a history of orthognathic surgery. Through clinical examination, radiographic examination, and model analysis, overall tooth wear, interdental spacing in the anterior maxillary region, retruded condylar position, and insufficient interocclusal space for prosthetic restoration were confirmed. Full mouth rehabilitation with increased vertical dimension was planned, the patient's adaptation to the new vertical dimension was evaluated with a removable occlusal splint and temporary prosthesis, and cross-mounting was performed based on the temporary restoration to fabricate the definitive zirconia prosthesis, maintaining the adjusted vertical dimension. It showed satisfactory functional and esthetic results through stable restoration of the occlusal relationship.