• Journal of Korean Society of Coastal and Ocean Engineers
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• v.6 no.4
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• pp.439-451
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• 1994

A numerical model for harbour oscillation is presented by use of Galerkin finite element method. The governing equation is used by the modified mild slope equation derived from Chen (1986) in which bottom friction is incorporated. Since the existing absorbing boundary condition. however. is shown to be incorrect correct boundary condition and forcing term due to an incident plane wave are rederived. Computation results for a rectangular harbour are shown in comparison with both laboratory data and existing numerical results. After the values of friction factor (f) and reflection coefficient (K$_{r}$) are discussed, the set (K$_{r}$=0, 94, f=0) is found to be best fitted to the laboratory data of the rectangular harbour.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.16 no.1
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• pp.1-9
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• 2004

In this study, several new types of floating breakwater are proposed according to the geometry of the vertical barrier and the existence of horizontal plate, and are compared to the steel floating breakwater adopted in Won-Jun fishing port and the performance of wave control is numerically investigated by using Green function method. From the numerical results, model attached the horizontal barrier under the vertical barrier is more efficient for reflection and transmission coefficient than the steel floating breakwater in Won-Jun fishing port. It is confirmed that the transmitted waves can be controlled efficiently by optimizing the length and distance of a vertical and horizontal barriers.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.30 no.4
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• pp.180-190
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• 2018

The preliminary study was carried out to utilize the rolling porous pendulum plate as a hybrid system combining blocking and extracting of wave energy. The Galerkin method suggested by Porter and Evans (1995) was used to solve the diffraction and radiation problems to obtain reflection and transmission coefficient, roll displacement, extracted power. The Galerkin method provides better convergence than the matched eigenfunction expansion method (MEEM), which improves the accuracy of the analytical solution even if the CPU time is shorter. The porous plate can not be said to be more effective than the impermeable plate in terms of wave energy extraction and wave blocking, but it has the advantage of reducing the wave load and exchanging seawater.

• Journal of Satellite, Information and Communications
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• v.6 no.2
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• pp.91-96
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• 2011

In this paper, we present measurement method of the unknown load impedance. Load impedance is continuously varied by external environment conditions. This arbitrarily varied load impedance can be calculated using 3-point voltage measurement on ${\lambda}/4$ sectioned transmission line. We derived several numerical formulas from 3-point voltage measurement results and drew load impedance selection algorithm from calculated load impedance results. These numerical formulas and load impedance selection algorithm are verified by ADS simulation. Simulation results showed that arbitrary load impedance can be correctly measured using above mentioned formulas and selection algorithm.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05b
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• pp.630-634
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• 2004

This paper describes the design of a two stage 1V power supply SiGe Low Noise Amplifier operating at 5.25 GHa for 802.lla wireless LAN application. The achieved performance includes a gain of 17 ㏈, noise figure of 2.7㏈, reflection coefficient of 15 ㏈, IIP3 of -5 ㏈m, and 1-㏈ compression point of -14㏈m. The total power consumption of the circuit was 7 mW including 0.5mW for the bias circuit.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.4
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• pp.825-834
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• 2000

In this paper, we have designed a bandpass filter with via-holes ground on K-band To pass only the 25 ~30% of the bandwidth at the center frequency of 19.6GHz, we have designed a six-order interdigital bandpass filter using microstrip lines. Simulation results of optimization according to via-holes size and numbers of interdigit bandpass filter shows a excellent agreement with theoretical values on passband frequency. Experimental results of BP filters show that mesaured center frequency is 19.150Hz, insertion loss, -4.1dB, reflection coefficient, -16.7dB. It proved that the vis-holes ground size and numbers must be considered to design the bandpass filter.

• Journal of information and communication convergence engineering
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• v.11 no.1
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• pp.56-61
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• 2013

Modern integrated circuits (ICs) are becoming an integrated parts of analog, digital, and radio frequency (RF) circuits. Testing these RF circuits on a chip is an important task, not only for fabrication quality control but also for tuning RF circuit elements to fit multi-standard wireless systems. In this paper, RF test circuits suitable for embedded testing are introduced: RF power detectors, power control circuits, directional couplers, and six-port reflectometers. Various types of embedded RF power detectors are reviewed. The conventional approach and our approach for the RF power control circuits are compared. Also, embedded tunable active directional couplers are presented. Then, six-port reflectometers for embedded RF testing are introduced including a 77-GHz six-port reflectometer circuit in a 130 nm process. This circuit demonstrates successful calibrated reflection coefficient simulation results for 37 well distributed samples in a Smith chart. The details including the theory, calibration, circuit design techniques, and simulations of the 77-GHz six-port reflectometer are presented in this paper.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.5
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• pp.1047-1056
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• 2007

Basically, an ultrasonic imaging system has two fundamental imaging modes available. One is the B-mode imaging modality which provides an image of reflection coefficient, and the other is the Doppler color flow mode that maps blood flow inside the human heart and blood vessels. This paper presents a new method of detecting and compensating for aliasing that occurs when the Doppler frequency exceeds one-half of the pulse-repetition frequency (PRF). Its validity is shown by computer simulation. The new method not only extends the measurable Doppler frequency, but also helps to reduce the effect of noise. The results show that the aliasing can be compensated for correctly fur signal-to-noise ratios down to 20 dB.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.358-360
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• 2007

For large scaled solar cells and photosensors CdS thin films of $2{\mu}m$ thickness have deposited on ITO glass substrate by chemical bath deposition methode in $300^{\circ}C$ electric furnace. The surface roughness and resistance of cadmium sulphide(CdS) thin films with different microstructures and morphologies was investigated by using a x-ray diffraction (XRD), a scanning electron microscope (SEM), an atomic force microscope (AFM), and a near-field scanning microwave microscope (NFMM). As the different substrate heat temperatures, the microwave reflection coefficient $S_{11}$ and intensity of the (002) diffraction peak was changed, and the surface morphology also has shown differently.

• Journal of the Korean Society for Nondestructive Testing
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• v.34 no.2
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• pp.119-127
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• 2014

An epoxy coating applied to the concrete surface of a containment building deteriorates in hazardous environments such as those containing radiation, heat, and moisture. Unlike metals, the epoxy coating on a concrete liner absorbs and discharges moisture during the degradations process, so it has a different density and volume during service. In this study, acoustic impedance was adopted for characterizing the degradation of a glass-reinforced epoxy coating using the acoustic reflection coefficient (reflectance) on a rough epoxy coating. For estimating the acoustic reflectance on a wavy epoxy coating surface, a probabilistic model was developed to represent the multiple irregular reflections of the acoustic wave from the wavy surface on the basis of the simulated annealing technique. A number of epoxy-coated concrete specimens were prepared and exposed to accelerated aging conditions to induce an artificial aging degradation in them. The acoustic impedance of the degraded epoxy coating was estimated successfully by minimizing the error between a waveform calculated from the mathematical model and a waveform measured from the surface of the rough coating.