• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.11
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• pp.1-9
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• 1998

In this paper, an incoherent imaging of a high-contrast cylindrical cavity in a lossy medium illuminated by the time-harmonic cylindrical wave is obtained via the backprojections of the intensity patterns of the forward total electric field in the cross-borehole measurement configuration. The phenomenon that the interference fringes in the intensity pattern, which are caused by the superposition of the incident field and the scattered field with different optical paths, are removed in the backprojection process is interpreted numerically. This imaging method is validated by imaging an air circular cylinder in a lossy medium of $\varepsilon$$_{r}$=9 and $\sigma$ = 0.0005, 0.002 S/m, and the conditions for obtaining better images are investigated.d.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.3
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• pp.58-69
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• 1989

A theoretical analysis of strong double dips in the amplitude patterns of electromagnetic field scattered by an air cavity embedded in a dielectric medium is presented with the experimental and the numerical simulation. The strongest double dips occur at the locations corresponding to the top and the bottom of the cavity by adjusting the excitation wavelength nearly equal to its radius. In particular, it may be shown that these double dips always become two nulls at a particular sending frequency in the near-field region. The locus of the frequency providing the strongest dip as a function of the observation distance is plotted.

• Proceedings of the Korea Society for Industrial Systems Conference
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• 1997.11a
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• pp.211-220
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• 1997

체비셰프 삽입손실법을 이용하여 선택도가 높은 대역 여파기를 설계한다. 체비셰프 방식은 차단주파수 근방 곡선의 경사가 버터워쓰에 비해 급격하게 떨어지는 특징을 가진다. 인접 채널의 간섭을 최소화 하기위해 차단 대역의 감쇄를 70db이상으로 유지한다. 중심주파수는 885MHz에서 통과대역폭 10MHz의 여파기를 제작하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.12 no.2
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• pp.133-138
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• 1987

In this paper the tuning characteristics of resonant frequencies are experimentally studied through the variation of the length of the inner conducting rod in a re-enterant eavity resonator. The re-enterant eavity resonator consists of a coaxial cable and a cylindrical wave guide. The length of the inner conducting rod can be varied to the longitudinal direction. The resonant frequencies of TMonq modes are measured according to the arbitrary length. In order to verify the propriety of experimental results, experimental results are compared with other theoretical results. The results in this paper can be applied to wave meter and resonant circuit of amplifier. They will be use to vary resonant frequencies of a dielectric resonator in MIC and filter.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.7
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• pp.1015-1020
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• 2018

The cavity resonator is one of the widely used components in the microwave applications. The unloaded Q, the resonant frequency, and the coupling factor are basic parameters of a cavity. A simple unloaded Q factor measurement procedure of a cavity is proposed in a lossy coupling. The equivalent circuit of a cavity with coupling loss at near the resonant frequency is presented. The coupling loss resistance was found by the measurement of a cavity impedance. The cavity impedance compensated coupling loss was redrawn on the Smith Chart. The loaded Q and coupling factor were obtained based on the compensated impedance locus and then the unloaded Q factor was calculated. To verify the proposed procedure, the cavity with lossless coupling was measured. The two measurement results in the lossy and lossless coupling agree well. The results confirm the proposed procedure is valid.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.6
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• pp.57-61
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• 2015

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.3
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• pp.27-35
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• 2012

• The Journal of the Acoustical Society of Korea
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• v.27 no.4
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• pp.171-177
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• 2008

In this paper, we have measured the fundamental properties of chime stone for Pyeongyeong. The properties are measured by wave propagation in the stone without destroying the stones, the measured properties are the chime stone density, natural frequencies of extensional wave and bending wave, and Young's modulus which is calculated by the measured properties. To find a value for Young's modulus, the fundamental frequencies which are obtained through spectrum analysis of extensional wave and bending wave are used. We calculated Young's modulus of chime stone by theoretical study and measurement on extensional wave and bending wave of the beam. As a result, we obtained Young's modulus by the fundamental frequencies of extensional wave and bending wave which deviation is within 2%.

• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.1
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• pp.101-105
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• 2011

Determination of ultrasonic frequency and experimental design approach to optimization of ultrasonic soil-washing process for remediation of diesel contaminated soil were investigated. Ultrasonic frequencies of 35, 72, and 100 kHz were used for determination of optimal frequency. $MINITAB^{(R)}$ program was used for experimental design of optimal washing condition. The optimal ultrasonic frequency was 35 kHz. Even though the number of cavitation bubble is little, however cavitation bubbles involving larger energy compared with high frequency was generated. Therefore, the removal efficiency at low frequency was higher than at high frequency. However the input energy has to be considered when the process is applied. The statistical tests from a factorial experiment shows that the application of ultrasound and mechanical mixing are the most important factor for design of an ultrasonic soil washing process. The lab-scale experiments are required to get the optimal condition of ultrasound and mechanical mixing for application of ultrasonic soil washing process.

• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.2
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• pp.177-184
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• 2003

A series of experimental work has been conducted to evaluate the capability of Ground Penetrating Radar (GPR) system in detecting delamination inside concrete. Three antenna at 900 MHz, 1000 MHz, and 1500 MHz frequency are used in the experiments for laboratory size specimens, and 400 MHz antenna has been used for a large size specimen. The laboratory size specimens have the dimensions of 1,000 mm (length) ${\times}$ 600 mm (width) ${\times}$ 140 mm (thickness) with a delamination of 200 mm (length) ${\times}$ 600 mm (width) ${\times}$ 140 mm (thickness). The cover depth of the delamination is varied as follows: 20 mm, 30 mm, 60 mm, and 70 mm. In all cases, the delamination has been successfully identified. The property of three frequencies was seized about detecting delamination. Also, it was shown that the image results in GPR were improved by signal processing.