• KIEE International Transactions on Electrophysics and Applications
• /
• v.3C no.5
• /
• pp.194-198
• /
• 2003

A wide-band E-plane notch phased array antenna having bandwidths of 3:1 and a scan volume of $\pm$ 45 is designed considering the active element pattern (AEP) with analysis of the full structure of E-plane notch phased array antenna. Using the numerical E-plane waveguide simulator as an infinite linear array in the broadside angle, the active reflection coefficient (ARC) of the unit element is optimized in the design frequency range. To evaluate the convergence of the AEP, the simulation of full array as changing the number array is investigated, and the minimum numbers of array that have characteristics similar to the AEP of an infinite array are determined.

• Proceedings of the IEEK Conference
• /
• 1999.06a
• /
• pp.966-969
• /
• 1999

Using modal transmission-line theory (MTLT), we evaluate the power coupling of optical directional coupler composed by two parallel guiding slabs. The numerical results reveal that maximum power transfer occurs at a novel wavelength λ$_{opt}$, in which the excitation ratio of supermodes at input boundary is equal to each other, and it is generally different from minimum gap λ$_{min}$.in/.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.8 no.3
• /
• pp.221-230
• /
• 1996

The Suh and Park's analytical model. originally developed to calculate wave reflection from a conventional fully perforated caisson breakwater, is applied to a partially perforated caisson breakwater by approximating the vertical wall of the lower part of the front face of the caisson as a very steep sloping wall. Also, in the model, the inertial resistance term at the perforated wall is modified by using the blockage coefficient proposed by Kakuno and Liu. The model is compared against the hydraulic experimental data reported by Park et al. in 1993. Both the experimental data and the analytical model results show that the influence of inertial resistance is important so that wave reflection becomes minimum when B/L. is approximately 0.2 (in which R : wave chamber width, and 1, : wave length inside the wave chamber), which is somewhat smaller than the theoretical value B/L, : 0.25 obtained by assuming that the influence of inertial resistance is negligible. It is also shown that the analytical model based on a linear wave theory tends to overpredict the reflection coefficient as the wave nonlinearity increases, thus the model is preferably to be used for ordinary waves of small steepness.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2005.10a
• /
• pp.405-416
• /
• 2005

The rubblization technique is breaking the aged concrete pavement slab into rubblized concrete aggregate, and use it as an base material at its original position, then builds overlay above the rubblized base. This method has been successively used in USA due to the advantage of good contructibility, cost-effectiveness as well as the capability of preventing of reflection cracks. However, constructibility and economic performance of rubblization on typical Korean concrete pavements needed to be investigate since to typical Korean concrete pavements have thick slab, as well include lean concrete subbase course. This stud explored optimum breaking depth and suggested minimum 10cm based on reflection crack simulation test. Also proper head shape and impact energy were investigated based on small breaking field tests. It was found that $127kg/cm^2$ of stress with 52.3% of head contact area are breaking requirement. Also, Multi-head type breaker suitable for Korean condition was designed and developed. This multi-head type breaker was designed to rubblize old concrete to the suggested optimum rubblized-depth and rubblized-concrete-aggregate size to prevent reflection crack and maintain high bearing capacity. This machine was used for the test of rubblization of old concrete pavement on a non-use old concrete and a in-serviced road. In these two tests, engineering properties of rubblized base and constructability and cost were investigated. In both tests, the old concrete rubblized to targeted size and depth, and high-level bearing capacity was achieved. Also, superior constructability and lower cost compared with traditional reconstruction was examined.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.12 no.3
• /
• pp.440-449
• /
• 1988

Small vibration displacements may be measured by optical interferometers, based on the Michelson method. The standard Michelson interferometer works well when the mirror displacements are relatively large compared to the optical wavelength. But it does not work for displacements less than approximately a quater of optical wavelength. Several multiple reflection laser interferometers, simply modified standard Michelson interferometer, have been developed to decrease the minimum detectable limits. Among these a relatively simple and easy multiple reflection system is used to measure the small vibration displacements. This multiple reflection system is constructed with a right angle prism and a convex lens. Therefore this system makes it possible to measure a vibration displacement of the small area on the vibrating structure. The fringe interpolation method and curve fitting method are used to determine accurately the small vibration displacements from the measured interference fringe patterns. Also computer simulation technique is used to check the accuracies of these method. According to the results of the computer simulation technique, the curve fitting method is more accurate than the fringe interpolation method. The optically measured results are in good agreement with those of the standard accelerometer with high accuracy and it is possible to measure the peak vibration displacement as small as 9.01nm using multiple reflection system and curve fitting method.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.32 no.5B
• /
• pp.295-300
• /
• 2012

Reflection coefficients of wave due to the types of a submerged breakwater on the inclined incident wave are numerically computed by using boundary element method. The analysis method is based on the wave pressure function with the continuity in the analytical region including fluid and structures. When compared with the existing results on the inclined incident wave, the results of this study show good agreement. It is found that both maximum and minimum values of the reflection coefficient are appeared frequently, as the width of a submerged breakwater becomes wider, and the reflection coefficient increase, as the wave period is longer. In addition, the effect on the reflection coefficient due to the change of submerged breakwater hight is lager than that due to the change of submerged breakwater width. The results indicate that dissipating characteristics of wave due to the types of a submerged breakwater own high dependability regarding the change of inclined incident waves. Therefore, the results of this study is estimated to be applied as an accurate numerical analysis referring to inclined incident waves in real sea.

• Proceedings of the KIEE Conference
• /
• 1987.07b
• /
• pp.1243-1246
• /
• 1987

To characterize the biological tissues, the new methods to measure the frequency dependent attenuation are presented in this paper. In general, ultrasonic phase information was assumed by linear function of the frequency. But, the minimum phase function which characterizes the frequency dispersion of tissue was derived in [l]. It is very significant to measure the attenuation by using the minimum phase function to characterize the frequency dispersion of tissue. Therefore, a more efficient method measuring the frequency dependent attenuation are proposed by using the estimated sound velocity and polarity of reflected signal. To verify the algorithms, pulse reflection experiments are performed.

• Proceedings of the KSR Conference
• /
• 2004.10a
• /
• pp.842-847
• /
• 2004

This study presents the minimum spring stiffness of resilient track pad considering the safety of running train. A nonlinear static 3-D finite element is used for the modeling of railway superstructure, especially for the reflection of nonlinear resistance of rail fastening system. Moreover, ballast is considered as an elastic foundation. As the input load, eccentric wheel and lateral force are used and they are derived from ' Lateral-force/Wheel-load Estimation Equations '. Analysis results are compared with following two values : allowable lateral displacement of rail head (derived from the geometrical derailment evaluation of wheel/rail) and operation standard value (derived from the field test results of track).

• Electrical & Electronic Materials
• /
• v.7 no.3
• /
• pp.220-224
• /
• 1994

In this study, we discussed the optical property to find the optimal condition of Te-based antireflection trilayer(ART) structure for a high density optical recording. It was found that the optical property was improved by suggesting the environmental parameters satisfied the optimum condition. As the results, the optimized(.lambda.=8.000${\AA}$.) thickness of the recording layer is 27${\AA}$, and the 1st and 2nd minimum ART conditions of dielectric layers are 1080${\AA}$, 3820${\AA}$, respectively. And the high SNR, the contrast ratio and the sensitivity are achieved by using the ART conditions.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.11 no.6
• /
• pp.38-43
• /
• 1974

A design problem is studied for a nonuniform transmission line (NUTL) section to be inserted between an arbitrary source impedance and an arbitary load impedance for the purpose of impedance matching or providing a minimum input reflection coefficient over a frequency ranee as wide as possible. A special class of NUTL's, yet comprehensive enough to include almost all smoothly varying lines, are considered. Power series expansions of the ABCD parameters of such lines are used in the calculation of the input reflection coefficient. The design problem is formulated as a nonlinear programming problem withnonlinear constraints and is solved by a combined use of the sequential unconstrained minimization technique and tile Fletcher-Powell method. As a result, a line section was obtained which shows a marked improvement over any one hitherto published as a wide-band impedance matching device.