• Structural Engineering and Mechanics
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• v.78 no.2
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• pp.199-207
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• 2021

In the present paper, an analytical model is proposed to determine the flexural and shear strength of normal and high-strength reinforced concrete beams with longitudinal bars, in the presence of transverse stirrups. The model is based on evaluation of the resistance contribution due to beam and arch actions including interaction with stirrups. For the resistance contribution of the main bars in tension the residual bond adherence of steel bars, including the effect of stirrups and the crack spacing of R.C. beams, is considered. The compressive strength of the compressed arch is also verified by taking into account the biaxial state of stresses. The model was verified on the basis of experimental data available in the literature and it is able to include the following variables in the resistance provision: - geometrical percentage of steel bars; - depth-to-shear span ratio; - resistance of materials; - crack spacing; - tensile stress in main bars; - residual bond resistance including the presence of stirrups;- size effects. Finally, some of the more recent analytical expressions able to predict shear and flexural resistance of concrete beams are mentioned and a comparison is made with experimental data.

• Advances in concrete construction
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• v.13 no.3
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• pp.255-264
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• 2022

Vibration is expected to occur in microtubules as tubular heterodimers. They oscillate like electric dipoles. Several research studies have estimated a frequency of vibration using the orthotropic model, a beam or rod like models and shell models, considering the surface forces. The effects of body forces on the dynamics of the microtubules were not yet taken into account. This study seeks to capture the body force effects on the vibration modes generated and on the corresponding frequency for microtubules. An orthotropic elastic shell model for the structural details of microtubules is used for the analysis. The tests are conducted out for microtubules, exposed to electro-magnetic and gravitational forces, the transverse vibration, radial mode vibration, and axial mode of vibration have accomplished. We therefore, evaluate and compare microtubules' frequencies with prior results of vibration frequency without the effects of body force.

• The korean journal of orthodontics
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• v.43 no.2
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• pp.62-73
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• 2013

Objective: The purpose of this study was to assess new three-dimensional (3D) cephalometric variables, and to evaluate the relationships among skeletal and dentoalveolar variables through 3D cephalometric analysis. Methods: Cone-beam computed tomography (CBCT) scans were acquired from 38 young adults (18 men and 20 women; $22.6{\pm}3.2$ years) with normal occlusion. Thirty-five landmarks were digitized on the 3D-rendered views. Several measurements were obtained for selected landmarks. Correlations among different variables were calculated by means of Pearson's correlation coefficient values. Results: The body of the mandible had a longer curve length in men ($102.3{\pm}4.4$ mm) than in women ($94.5{\pm}4.7$ mm) (p < 0.001), but there was no significant difference in the maxillary basal curve length. Men had significantly larger facial dimensions, whereas women had a larger gonial angle ($117.0{\pm}4.0$ vs. $113.8{\pm}3.3$; p < 0.001). Strong-to-moderate correlation values were found among the vertical and transverse variables (r = 0.71 to 0.51). Conclusions: The normative values of new 3D cephalometric parameters, including the maxillary and mandibular curve length, were obtained. Strong-to-moderate correlation values were found among several vertical and transverse variables through 3D cephalometric analysis. This method of cephalometric analyses can be useful in diagnosis and treatment planning for patients with dentofacial deformities.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.76.1-76.1
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• 2015

Optical resonances of metallic or dielectric nanoantennas enable to effectively convert free-propagating electromagnetic waves to localized electromagnetic fields and vice versa. Plasmonic resonances of metal nanoantennas extremely modify the local density of optical states beyond the optical diffraction limit and thus facilitate highly-efficient light-emitting, nonlinear signal conversion, photovoltaics, and optical trapping. The leaky-mode resonances, or termed Mie resonances, allow dielectric nanoantennas to have a compact size even less than the wavelength scale. The dielectric nanoantennas exhibiting low optical losses and supporting both electric and magnetic resonances provide an alternative to their metallic counterparts. To extend the utility of metal and dielectric nanoantennas in further applications, e.g. metasurfaces and metamaterials, it is required to understand and engineer their scattering characteristics. At first, we characterize resonant plasmonic antenna radiations of a single-crystalline Ag nanowire over a wide spectral range from visible to near infrared regions. Dark-field optical microscope and direct far-field scanning measurements successfully identify the FP resonances and mode matching conditions of the antenna radiation, and reveal the mutual relation between the SPP dispersion and the far-field antenna radiation. Secondly, we perform a systematical study on resonant scattering properties of high-refractive-index dielectric nanoantennas. In this research, we examined Si nanoblock and electron-beam induced deposition (EBID) carbonaceous nanorod structures. Scattering spectra of the transverse-electric (TE) and transverse-magnetic (TM) leaky-mode resonances are measured by dark-field microscope spectroscopy. The leaky-mode resonances result a large scattering cross section approaching the theoretical single-channel scattering limit, and their wide tuning ranges enable vivid structural color generation over the full visible spectrum range from blue to green, yellow, and red. In particular, the lowest-order TM01 mode overcomes the diffraction limit. The finite-difference time-domain method and modal dispersion model successfully reproduce the experimental results.

• The korean journal of orthodontics
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• v.48 no.2
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• pp.98-106
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• 2018

Objective: This study aimed to explore the usefulness of adjunctive buccal and palatal corticotomy for adult maxillary expansion in an animal model using cone-beam computed tomography (CBCT). Methods: Twelve adult sheep were randomly divided into two groups (each n = 6): a control group, where no treatment was administered, and a treatment group, where buccal and palatal corticotomy-assisted maxillary expansion was performed. CBCT scans were taken before (T1) and after (T2) treatment. Differences in all transverse dental and alveolar dimensions, alveolar width at crest level, hard palate level, horizontal bone loss, interdental cusp width and inter-root apex were assessed using Wilcoxon signed-rank and Mann-Whitney U-tests. Kruskal-Wallis tests and pairwise comparisons were used to detect the significance of differences among the inter-premolar and inter-molar widths. Results: CBCT data revealed significant changes in all transverse dental and alveolar dimensions. The mean interpremolar alveolar width showed an increase of 2.29 to 3.62 mm at the hard palate level, 3.89 to 4.38 mm at the alveolar crest level, and 9.17 to 10.42 mm at the buccal cusp level. Dental changes in the vertical dimension were not significant. Conclusions: Our findings based on an adult animal model suggest that adjunctive buccal and palatal corticotomy can allow for both skeletal and dental expansion, with the amount of dental expansion exceeding that of skeletal expansion at alveolar crest and hard palate levels by two and three folds, respectively. Therefore, this treatment modality is potential to enhance the outcomes of maxillary expansion in adults.

• Journal of the Korea Concrete Institute
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• v.28 no.4
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• pp.407-417
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• 2016

In this study, concrete composite beams were tested under two-point loading to evaluate horizontal shear strength. The test variables were a type of composite members (PC+RC, PSC+RC, SFRC+RC), area ratio of high-strength (60MPa) to low-strength concrete (24 MPa), and transverse reinforcement ratio. The test results showed that the contribution of transverse reinforcements and interface conditions had influence on horizontal shear strength. Existing and previous test results were classified according to test methods and the interface conditions and were compared with the predictions of current design codes. On the basis of test results, an improved design method was proposed.

• Magazine of the Korea Concrete Institute
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• v.11 no.1
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• pp.173-181
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• 1999

To deepen the understanding of shear behaviour in beams without transverse reinforcement, the relative importance of five contributing factors to concrete shear resistance($v_c$), which are i)flexural compression zone, ii)friction at crack faces, iii)dowel action, iv)arch action and recently identified, v)residual tensile stresses across cracks, was explained physically using two analytical methods based on the truss concept. One is called "Modified Compression Field Theory(MCFT)" considering ii) and v) explicitly, and the other "Crack Friction Truss Model(CFTM)" more dominantly ii) in determining concrete resistance. To verify their effectiveness, the predictions using MCFT and CFTM were also made for twenty KAIST beam tests($f'_c$=53.7Mpa), designated more likely to the development of the size effect law based on the fracture mechanics concept. Experimental findings with varying of a/d, longitudinal reinforcement ratios, and obtained from MCFT enabled additional explanations for some phenomena which were difficult to measure in tests. However, MCFT seemed somewhat conservative for beams with higher longitudinal reinforcement, while somewhat unsafe for beams with larger depths. More tests are necessary leading to firm conclusions in these areas.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.201-204
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• 2008

The Sectional Design Model(AASHTO LRFD) is appropriate for the design of typical bridge girders, slabs, and other regions of components where the assumptions of traditional engineering beam theory are valid. The shear resistance of a concrete member may be separated into a component, $V_c$, that relies on tensile stresses in the concrete, $V_s$, that relies on tensile stresses in the transverse reinforcement. The expressions for $V_c$ and $V_s$ apply to both prestressed and nonprestressed section, with the terms ${\beta}$ and ${\theta}$ depending on the applied loading(M, V, N, and T) and the properties of the section. With ${\beta}$ taken as 2.0 and ${\theta}$ as 45$^{\circ}$, the expressions for shear strength become essentially identical to those traditionally used for evaluating shear resistance. Recent large-scale experiments, however, have demonstrated that these traditional expression can be seriously unconservative for large members not containing transverse reinforcement. And This paper can present only a brief introduction to shear design of AASHTO LRFD and is to review of the technical difficulty.

• ETRI Journal
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• v.38 no.5
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• pp.981-987
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• 2016

We present a cost-effective dual polarization quadrature phase-shift coherent receiver module using a silica planar lightwave circuit (PLC) hybrid assembly. Two polarization beam splitters and two $90^{\circ}$ optical hybrids are monolithically integrated in one silica PLC chip with an index contrast of $2%-{\Delta}$. Two four-channel spot-size converter integrated waveguide-photodetector (PD) arrays are bonded on PD carriers for transverse-electric/transverse-magnetic polarization, and butt-coupled to a polished facet of the PLC using a simple chip-to-chip bonding method. Instead of a ceramic sub-mount, a low-cost printed circuit board is applied in the module. A stepped CuW block is used to dissipate the heat generated from trans-impedance amplifiers and to vertically align RF transmission lines. The fabricated coherent receiver shows a 3-dB bandwidth of 26 GHz and a common mode rejection ratio of 16 dB at 22 GHz for a local oscillator optical input. A bit error rate of $8.3{\times}10^{-11}$ is achieved at a 112-Gbps back-to-back transmission with off-line digital signal processing.

• Steel and Composite Structures
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• v.27 no.6
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• pp.691-702
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• 2018

This paper presents experimental and analytical results of fiber reinforced polymer (FRP) confined steel tubular columns under transverse impact loads. Influences of applied impact energy, thickness of FRP jacket and impact position were discussed in detail, and then the impact responses of FRP confined steel tubes were compared with bare steel tubes. The test results revealed that the FRP jacket contributes to prevent outward buckling deformation of steel at the clamped end and inward buckling of steel at the impact position. For the given applied impact energy, specimens wrapped with one layer and three layers of FRP have the lower peak impact loads than those of the bare steel tubes, whereas specimens wrapped with five layers of FRP exhibit the higher peak impact loads. All the FRP confined steel tubular specimens displayed a longer duration time than the bare steel tubes under the same magnitude of impact energy, and the specimen wrapped with one layer of FRP had the longest duration time. In addition, increasing the applied impact energy leads to the increase of peak impact load and duration time, whereas increasing the distance of impact position from the clamped end results in the decrease of peak impact load and the increase of duration time. The dynamic analysis software Abaqus Explicit was used to simulate the mechanical behavior of FRP confined steel tubular columns, and the numerical results agreed well with the test data. Analytical solution for lateral displacement of an equivalent cantilever beam model subjected to impact load was derived out. Comparison of analytical and experimental results shows that the maximum displacement can be precisely predicted by the present theoretical model.