• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.10 no.1
• /
• pp.142-149
• /
• 1999

In this paper, Aperture-coupled microstrip array antenna was designed and manufactured for satellite communication at Ka-Band. We analyzed a microstrip radiation element and designed power divider using $\lambda$g/4 transformer and T-junction power divider. A manufactured Aperture-coupled $2\times2$ microstrip array antenna has a resonant frequency of 20 GHz. The experimental results are as followings : resonant frequency of 19.62 GHz, VSWR 1.0692, return loss -29.61 dB, Bandwidth 1.76 GHz and -3 dB beamwidth $42^{\circ}$.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.22 no.4
• /
• pp.159-165
• /
• 2008

In this paper the signal analysis of eddy current test using transmit-receive(T/R) pancake coil of ECT array probe using electromagnetic finite element method(FEM) is performed. For characteristics analysis, the notch defect is used. The depth of defect is 40[%] of steam generator tube thickness, and inside defect and outside defect are used as simulation examples. The signal analysis is performed according to the variation of receive coil position. The receive coil is positioned $0[^{\circ}]$, $30[^{\circ}]$, $60[^{\circ}]$, $90[^{\circ}]$ of circumferential position of transmit coil. To obtain e electromagnetic characteristics of robes, the governing equation is derived from Maxwell's equations, and the problem is solved using the 3-dimensional finite element method. The signal magnitude of inside defect is bigger than that of outside defect, and the signal difference can be seen according to the variation of position of receive coil. The experimental signal and numerical signal of ASME standard tube show similar results. The results in this paper can be helpful when the ECT signals from ECT array probe are evaluated and analyzed.

• Geophysics and Geophysical Exploration
• /
• v.10 no.1
• /
• pp.50-59
• /
• 2007

The advent of towed geo-electrical array surveying on water and land has resulted in datasets of magnitude approaching that of airborne electromagnetic surveying and most suited to 1D inversion. Robustness and complete automation is essential if processing and reliable interpretation of such data is to be viable. Sharp boundaries such as river beds and the top of saline aquifers must be resolved so use of smoothness constraints must be minimised. Suitable inversion algorithms must intelligently handle low signal-to-noise ratio data if conductive basement, that attenuates signal, is not to be misrepresented. A noise-level aware inversion algorithm that operates with one elastic thickness layer per electrode configuration has been coded. The noise-level aware inversion identifies if conductive basement has attenuated signal levels so that they are below noise level, and models conductive basement where appropriate. Layers in the initial models are distributed to span the effective depths of each of the geo-electric array quadrupoles. The algorithm works optimally on data collected using geo-electric arrays with an approximately exponential distribution of quadrupole effective depths. Inversion of data from arrays with linear electrodes, used to reduce contact resistance, and capacitive-line antennae is plausible. This paper demonstrates the effectiveness of the algorithm using theoretical examples and an example from a salt interception scheme on the Murray River, Australia.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.25 no.1
• /
• pp.37-49
• /
• 2012

A structural model of the SNF(spent nuclear fuel) disposal canister for the PWR(pressurized water reactor) for about 10,000 years long term deposition at a 500m deep granitic bedrock repository has been developed through various structural safety evaluations. The SNF disposal baskets of this canister model have the array type whose four square cross section baskets stand parallel to each other and symmetrically with respect to the center of the canister section. However, whether this developed structural model of the SNF disposal canister is optimal is not determinable yet. Especially, there is still a problem in weight-reduction of the canister. The cross section shape of the SNF basket should be changed to solve this problem. There are two ways in changing the cross section shape of the SNF basket; the one is to rotate the cross section itself and the other is to change the cross section shape as other shape different from the square cross section. The previous study shows that the canister with $30{\sim}35^{\circ}$ rotated basket array is structurally more stable than the canister with un-rotated parallel basket array. However, whether this canister with rotated basket array is optimal is not either determinable as yet, because it is not revealed that the canister with other cross section different from the square cross section is structurally more stable than other canisters. Therefore, the structural analysis of the SNF disposal canister with other cross section shape which is also symmetric with respect to the canister center planes is very necessary. The structural analysis of the canister with various cross section shape basket array in which each basket is arrayed symmetrically with respect to the center planes is carried out in this paper. The structural analysis result shows that the SNF disposal canister with circular cross section shape baskets located symmetrically with respect to the center of the canister section is structurally more stable than the previously developed SNF disposal canister with the parallel basket array.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.15 no.4
• /
• pp.232-241
• /
• 2003

The interaction of incident monochromiatic waves with N bottom-mounted porous circular cylinders is investigated in the frame of three-dimensional linear potential theory. The fluid domain is divided into N+l regions i.e. a single exterior region and N interior regions, and the diffraction potential in each fluid region is expressed by an eigenfunction expansion method (Williams and Li,2000). The analytic results show that the porous structure reduces both the wave forces and the run-up wave around the cylinder. To verify the developed model, the systematic model test with a line array of porous cylinders is conducted at the wave tank (30m$\times$7m$\times$1.5m). The analytic results are in good agreement with the experimental results within measured frequency range. It is concluded that the breakwater constructed with an array of porous circular cylinders shows the performance of an effective wave barrier together with the seawater-exchange effect and is considered to have vast potentials for the use of seawater-exchanging breakwater in the future.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.41 no.2
• /
• pp.157-164
• /
• 2017

A parallel slide gate valve (PSGV) is located between the heat recovery steam generator (HRSG) and the steam turbine in a combined cycle power plant (CCPP). It is used to control the flow of steam and runs with repetitive operations such as startups, load changes, and shutdowns during its operation period. Therefore, it is necessary to evaluate the fatigue damage and the structural integrity under a large compressive thermal stress due to the temperature difference through the valve wall thickness during the startup operations. In this paper, the thermal-structural analysis and the fatigue life evaluation of a 16-inch PSGV, which is installed on the HP steam line, is performed according to the fatigue life assessment method described in the ASME B&PVC VIII-2; the method uses the equivalent stress from the elastic stress analysis.

• Journal of Korean Society of Steel Construction
• /
• v.23 no.5
• /
• pp.607-614
• /
• 2011

This study deals with thegeometrical nonlinear dynamic behavior of laminated plates made of advanced composite materials (ACMs), which contain central cutouts. Based on the first-order shear deformation plate theory (FSDT), the Newmark method and Newton-Raphson iteration wereused for the nonlinear dynamic solution. The effects of the cutout sizes and lay-up sequences on the nonlinear dynamic response for various parameters werestudied using a nonlinear dynamic finite element program that was developed for this study. The several numerical results agreed well with those reported by other investigators for square composite plates with or without central cutouts, and the new results reported in this paper showed significant interactions between the cutout and the layup sequence in the laminate. Key observation points are discussed and a brief design guide for laminates with central cutouts is given.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.35 no.9
• /
• pp.923-932
• /
• 2011

Because of the instability of a flow pattern in the inlet transition square duct (hereinafter referred to as "transition duct") of a heat recovery steam generator (hereinafter referred to as "HRSG") in a combined cycle power plant, the Reynolds number in the first row of a tube bank is differs sharply from that in the sectional area of the transition duct. This causes differences in the heat flux in each tube in the tube bank. The computational fluid dynamics (CFD) predictions provide three-dimensional results for velocity, temperature, and other flow parameters over the entire domain of the duct and HRSG. A renormalization group theory (RNG) based k-${\epsilon}$�� turbulent model is used for obtaining the results cited in this study. A porous media option is used for modeling the tube banks and the number of transfer units method is used for determining the heat transfer characteristics. This study describes a comparison between the numerical simulation results and actual design output.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.25 no.2
• /
• pp.163-173
• /
• 2012

This study covers the nonlinear analysis of anchor head for high strength prestressing strand and presents necessary process in improving the performance of anchor head. The surface of wedge for strand is contacted to the surface of the wedge hole on anchor head when it is fitted into the wedge hole, and the contact condition changes according to the level of load applied through the wedge. In order to analyze detailed behavior, nonlinear material model and contact element were used in analysis. It was found from the analysis that the behavior of anchor head is affected by the interaction with the wedge contacted so that the wedge in FE model should have the same figure as the actual object. Circular array of wedge hole presents better stress distribution than layer array even though the small difference in maximum deformation. Increment of thickness of anchor head and distance of wedge hole also improve the performance of anchor head.

• Geophysics and Geophysical Exploration
• /
• v.9 no.1
• /
• pp.73-85
• /
• 2006

Array observations of the vertical component of microtremors are frequently conducted to estimate a subsurface layered-earth structure on the assumption that microtremors consist predominantly of the fundamental mode Rayleigh waves. As a useful tool in the data collection, processing and analysis, the spatial autocorrelation (SPAC) method is widely used, which in practice requires a circle array consisting of M circumferential stations and one centre station (called "M-station circle array", where M is the number of stations). The present paper considers the minimum number of stations required for a circle array for efficient data collection in terms of analytical efficacy and field effort. This study first rearranges the theoretical background of the SPAC algorithm, in which the SPAC coefficient for a circle array with M infinite is solely expressed as the Bessel function, $J_0(rk)$ (r is the radius and k the wavenumber). Secondly, the SPAC coefficient including error terms independent of the microtremor energy field for an M-station circle array is analytically derived within a constraint for the wave direction across the array, and is numerically evaluated in respect of these error terms. The main results of the evaluation are: 1) that the 3-station circle array when compared with other 4-, 5-, and 9-station arrays is the most efficient and favourable for observation of microtremors if the SPAC coefficients are used up to a frequency at which the coefficient takes the first minimum value, and 2) that the Nyquist wavenumber is the most influential factor that determines the upper limit of the frequency range up to which the valid SPAC coefficient can be estimated.