• Proceedings of the Korean Vacuum Society Conference
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• 1997.07a
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• pp.114-114
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• 1997

• Journal of Multimedia Information System
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• v.5 no.2
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• pp.143-146
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• 2018

The eigen value problem of a coaxial cavity and a modified pill box cavity is investigated using the mode matching technique. The coaxial cavity has a cylindrical cavity with beam ports and center conductor. The pill box cavity is the same as a coaxial cavity without center conductor. The electric field and magnetic field are formulated in propagation region and resonance region. The boundary and orthogonal conditions are applied to the electric and magnetic fields. We derived the eigen value equation by the proposed procedure in a coaxial cavity and a modified pill box cavity. The electromagnetic field of the real structure is disturbed by the coaxial wire. The effect of the coaxial wire in pill box cavity with beam ports increase the dominant resonant frequency. The coaxial line method of the coupling impedance is not adequate for a cylindrical cavity. The results of the mode matching technique and simulation agree well. The results confirm the proposed formulation is valid.

• Proceedings of the Korean Vacuum Society Conference
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• 1998.02a
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• pp.68-69
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• 1998

Nano-crystalline silicon(nc-Si) thin films were directly depposited by ion beam assisted electron beam depposition (IBAED) method. The visibe luminescence in IBAED sampples were originated from not an oxygen bond but Si nano-crystallites. And we can conclude that the ion beam would be contribute to the suppression of the Si-O bond formation.

• Journal of Korean Society of Steel Construction
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• v.16 no.5 s.72
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• pp.505-517
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• 2004

This paper presented equations on the stress evaluation of steel frame pier connections that were composed of a box beam and a circular column. The existing equations, which transformed the circular column into an equivalent box column had some problems; they underestimated a shear lag stress as the joint angle decreased, and overestimated a shear stress as the joint angel increased. Therefore, FE analyses were performed with various parameters, such as joint angle(${\alpha}$), span length-width ratio(L/B), and circular column-to-box beam stiffness ratio(${\alpha}$), and new equations on stress evaluation were proposed based on FE analyses. Furthermore, material and geometric nonlinear analyses were performed to estimate ultimate strength and to confirm the validity of the proposed equations.

• Advances in materials Research
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• v.8 no.4
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• pp.259-274
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• 2019

Flexoelectric effect has a major role on mechanical responses of piezoelectric materials when their dimensions become submicron. Applying differential quadrature (DQ) method, the present article studies dynamic characteristics of a small scale beam made of piezoelectric material considering flexoelectric effect. In order to capture scale-dependency of such piezoelectric beams, nonlocal elasticity theory is utilized and also surface effects are included for better structural modeling. Governing equations have been derived by utilizing Hamilton's rule with the assumption that the scale-dependent beam is subjected to thermal environment leading to uniform temperature variation across the thickness. Obtained results based on DQ method are in good agreement with previous data on pizo-flexoelectric beams. Finally, it would be indicated that dynamic response characteristics and vibration frequencies of the nano-size beam depends on the existence of flexoelectric influence and the magnitude of scale factors.

• Proceedings of the Korean Vacuum Society Conference
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• 1997.02a
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• pp.115-115
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• 1997

• Steel and Composite Structures
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• v.1 no.3
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• pp.295-312
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• 2001

The purpose of this paper is to propose a new type of steel reinforced concrete (SRC) beam-column joints and to examine the structural performance of the proposed joints, which simplify the construction procedure of steel fabrication, welding works, concrete casting and joint strengthening. In the proposed beam-column joints, the steel element of columns forms continuously built-in crossing of H-sections (${\Box}$), with adjacent flanges of column being connected by horizontal stiffeners in a joint at the level of the beam flanges. In addition, simplified lateral reinforcement (${\Box}$) is adopted in a joint to confine the longitudinal reinforcing bars in columns. Experimental and analytical studies have been carried out to estimate the structural performance of the proposed joints. Twelve cruciform specimens and seven SRC beam-column subassemblage specimens were prepared and tested. The following can be concluded from this study: (1) SRC subassemblages with the proposed beam-column joints show adequate seismic performances which are superior to the demand of the current code; (2) The yield and ultimate strength capacities of the beam-to-column connections can be estimated by analysis based on the yield line theory; (3) The skeleton curves and the ultimate shear capacities of the beam-column joint panel are predicted with a fair degree of accuracy by considering a simple stress transfer mechanism.

• Journal of Korean Society of Steel Construction
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• v.18 no.2
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• pp.123-135
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• 2006

This paper investigates the design equations and the strength behavior of the diaphragm for steel box beams and circular-column connections. The strength of the connection is decided by the strength of the diaphragm and the strength of the beam and the column, because the connection diaphragm supports the concentration forces from the box beam's lower flange. In previous researches, however, the calculation procedure of the diaphragm stress from the indeterminate curved-beam model is to complicated to apply in process of the equation. Moreover, no reasonable design has yet ben made because the diaphragm's effect on the strength of the connection has not ben considered. Therefore, through nonlinear FEM analysis of the connection diaphragm, this study examines the strength behavior of a connection with diaphragm details. In addition, a great difference is confirmed between the theoretical and analytic behaviors. Fi naly, considering the strength of the connection and the rigidity capacity of the diaphragm, the diaphragm design method is proposed.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.1
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• pp.11-20
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• 2004

The main goal of this study is to develop MATLAB programming for an analysis of distortional deformations and stresses of the straight box girder. For this purpose, a distortional deformation theory is firstly summarized and then a BEF (Beam on Elastic Foundation) theory is presented using analogy of the corresponding variables. Finally, with governing equations of the beam-column element on elastic foundation, an exact element stiffness matrix of the beam element and nodal forces equivalent to concentrated and distributed loads are evaluated via a generalized linear eigenvalue problem. In order to verify the efficiency and accuracy of this method, distortional stresses of box girders with multiple diaphragms are presented and compared with results by FEA.

• Steel and Composite Structures
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• v.15 no.6
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• pp.585-603
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• 2013

Generally the required strength and stiffness of an I-shaped beam to the box-shaped column connection is achieved if continuity plates are welded to the column flanges from all sides. However, welding the forth edge of a continuity plate to the column flange may not be easily done and is normally accompanied by remarkable difficulties. This study was aimed to propose an alternative for box columns with continuity plates to diminish such problems. For this purpose a double-web I-shaped column was proposed. In this case the strength and rotational stiffness of the connection was provided by nearing the column webs to each other. Finite element studies on about 120 beam-column connections showed that the optimum proportion of the distance between two column webs and the width of the column flange (parameter ${\beta}$) was a function of the ratio of the beam flange width to the column flange width (parameter ${\alpha}$). Hence, based on the finite element results, an equation was proposed to estimate the optimum value of parameter ${\beta}$ in terms of parameter ${\alpha}$ to achieve the highest connection performance. Results also showed that the strength and ductility of post-Northridge connections of such columns are in average 12.5 % and 54% respectively higher than those of box-shaped columns with ordinary continuity plates. Therefore, a double-web I-shaped column of optimum arrangement might be a proper replacement for a box column with continuity plates when beams are rigidly attached to it.