• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.477-482
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• 2001

This paper is to study the effect of longitudinal reinforcement ratios and axial deformation on the frame analysis in reinforced concrete(RC) columns and to investigate the effect of confined concrete core, the length-width ratio and longitudinal steel ratios on frame analysis in Concrete-Filled steel Tubular(CFT) columns. An equation if derived to evaluate the modulus of elasticity for core concrete. The 34 reference data have been collected for the purpose and are processed by the mean of a multiple regression analysis technique. The equation and longitudinal reinforcement ratios was applied to RC columns for structural analysis. Then, the difference of beam moment was identified. In general, the results of analysis was indicated reasonable differences in beam moment, in case of longitudinal reinforcement ratios applied to RC columns when compared with the plain concrete columns. In CFT columns the equation was also applied in order to the effect of confined concrete core on structural analysis. Beam moment was increased as volumetric ratio of lateral steel was decreased. The effect of longitudinal steel ratios was investigated in CFT columns and was confirmed beam moment variety. The result was appeared reasonable difference in beam moment as longitudinal steel was increased.

• Smart Structures and Systems
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• v.22 no.1
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• pp.105-120
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• 2018

In this paper, the nonlinear free and forced vibration responses of sandwich nano-beams with three various functionally graded (FG) patterns of reinforced carbon nanotubes (CNTs) face-sheets are investigated. The sandwich nano-beam is resting on nonlinear Visco-elastic foundation and is subjected to thermal and electrical loads. The nonlinear governing equations of motion are derived for an Euler-Bernoulli beam based on Hamilton principle and von Karman nonlinear relation. To analyze nonlinear vibration, Galerkin's decomposition technique is employed to convert the governing partial differential equation (PDE) to a nonlinear ordinary differential equation (ODE). Furthermore, the Multiple Times Scale (MTS) method is employed to find approximate solution for the nonlinear time, frequency and forced responses of the sandwich nano-beam. Comparison between results of this paper and previous published paper shows that our numerical results are in good agreement with literature. In addition, the nonlinear frequency, force response and nonlinear damping time response is carefully studied. The influences of important parameters such as nonlocal parameter, volume fraction of the CNTs, different patterns of CNTs, length scale parameter, Visco-Pasternak foundation parameter, applied voltage, longitudinal magnetic field and temperature change are investigated on the various responses. One can conclude that frequency of FG-AV pattern is greater than other used patterns.

• Smart Structures and Systems
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• v.1 no.1
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• pp.29-46
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• 2005

In this study, a wavelet packet based method is proposed for identifying damage occurrence and damage location for beam-like structures. This method assumes that the displacement or the acceleration response time histories at various locations along a beam-like structure both before and after damage are available for damage assessment. These responses are processed through a proper level of wavelet packet decomposition. The wavelet packet signature (WPS) that consists of wavelet packet component signal energies is calculated. The change of the WPS curvature between the baseline state and the current state is then used to identify the locations of possible damage in the structure. Two numerical studies, one on a 15-storey shear-beam building frame and another on a simply-supported steel beam, and an experimental study on a simply-supported reinforced concrete beam are performed to validate the proposed method. Results show the WPS curvature change can be used to locate both single and sparsely-distributed multiple damages that exist in the structure. Also the accuracy of assessment does not seem to be affected by the presence of 20-15dB measurement noise. One advantage of the proposed method is that it does not require any mathematical model for the structure being monitored and hence can potentially be used for practical application.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.536-540
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• 2003

A new concept of adaptive focusing, using a Rotman lens, is presented in this paper. A Rotman lens is a microwave lens which is able to focus microwave power on its focal arc or generate multiple beams. By adding the array of phase shifters between a Rotman lens and antenna elements, the wavefront can be adaptively modulated to focus objects distributed in short range rather than far-field zone. From the optical point of view, the propagations of the lens have been simplified from the Fresnel diffraction integral to the Fourier transform. Using Fourier Transform, a beam propagation method has been developed to show improvement of the resolution by controlling wavefront of wave propagating from an aperture-type antenna array. The beam width(or spot size) and intensity have been calculated for a focused beam propagating from an array having $10{\lambda}$ of its size. For the beam with $20{\lambda},\;30{\lambda}$, and $50{\lambda}$ of geometrical focal length, the half-power beamwidth (spot size) is about $1.1{\lambda},\;1.3{\lambda}$, and $1.9{\lambda}$, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.12
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• pp.1359-1369
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• 2007

This paper describes the technique of satellite direction finding and main beam steering of the adaptive array antenna system which is used for mobile TT&C(Tracking Telemetry&Command) system. To be able to control the satellite on mobile vehicle while moving, the relative directional information of the satellite to the mobile vehicle is necessary to make main beam to the direction of satellite. To do this MUSIC, which is one of the super-resolution algorithm of wave direction finding, is used and then the performance analysis and quantization problem of phase shifter are addressed. This paper is valuable in the respect of showing feasibility of designing the moble TT&C using adative array antenna system.

• Structural Engineering and Mechanics
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• v.13 no.2
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• pp.211-230
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• 2002

The objective of this study is to investigate the dynamic behavior of elastic beams subjected to moving loads. Although analytical methods are available, they have limitations with respect to complicated structures. The use of computer technology in recent years is an effective way to solve the problem; thus using the latest technology this study establishes a finite-element solution procedure to investigate dynamic behaviors of a typical elastic beam having a set of constant geometric properties and various span lengths. Both the dead load of the beam and traffic load are applied in which the traffic load is considered a concentrated moving force with various traveling passage speeds on the beam. Dynamic behaviors including deflection, shear, and bending moment due to moving loads are obtained by both analytical and finite element methods; for simple structures, they have an excellent agreement. The numerical results show that based on analytical methods the fundamental mode is good enough to estimate the dynamic deflection along the beam, but is not sufficient to simulate the total response of the shear force or the bending moment. The linear dynamic behavior of the elastic beams subjected to multiple exciting loads can easily be found by linear superposition, and the geometric nonlinear results caused by large deformation and axial force of the beam are always underestimated with only a few exceptions which are indicated. In order to make the results useful, they have been nondimensionalized and presented in graphical form.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04a
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• pp.585-590
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• 1995

This paper describes strain distribution analysis of a multiple parallel plate structure for a multi-componenet force and moment sensor. A parallel plate structure which has higher rigidity than a simple beam structure are widely used for multi-component force and moment sensor. The strain distribution in the beams of a parallel plate structure should be accurately calculated to design a high precision multi-component force and moment sensor. We derived equations to calculate the strains for multiple parallel plate structure. It reveals that results from finite element analysis and experiment are in good agreement with results from the derived equations.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.793-796
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• 2005

In this paper, we propose a method which can improve uniformity of a miniaturized electron beam array for inspection of very small pattern with high speed using vertical interconnection. This method enables the individual control of columns so that it can reduce the deviation of beam current, beam size, scan range and so on. The test device that used vertical interconnection method was fabricated by multiple wafer bonding and metal reflow. Two silicon and one glass wafers were bonded and metal interconnection by melting of electroplated AuSn was performed. The contact resistance was under $10{\Omega}$.

• Journal of the Korea Institute of Military Science and Technology
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• v.15 no.3
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• pp.343-349
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• 2012

To detect targets for autonomous navigation of unmanned ground vehicle, mounted sensors are required to work all-weather condition. In this point of view, the FMCW radar is quietly appropriate. In this paper, we present development results of target signal simulator for multi-beam type FMCW radar. A target signal simulator make pseudo target signals which simulates multiple moving targets. And we describe how to make hit information for each target in multi-beam type radar. The developed methods are utilized for target tracking device. Moreover it can be applied to similar target signal simulator.

• Journal of the Korean Society of Visualization
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• v.3 no.1
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• pp.63-70
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• 2005

Optical Line Patternator(OLP) has been applied to get a distribution of the spray at high ambient pressure. OLP is a combined technique of extinction measurement and image processing. The attenuated intensity of laser beam after traversing spray region was measured by using a photo-detector, and the line image of Mie-scattering was captured simultaneously in the path of each laser beam by using a CCD camera. The distribution of extinction coefficient in the spray is obtained by processing these data with the algebraic reconstruction technique. From the distribution of extinction coefficient, the surface distribution of spray can be reconstructed. OLP does not use laser sheet but use laser beam so that the noise effect of multiple scattering, caused by increasing number density of droplet in high pressure environment, is reduced drastically. OLP is expected as a suitable method which can investigate the characteristics of relatively large spray under the high pressure environment such as liquid rocket engine.