• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.10
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• pp.924-931
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• 2015

When a target locates at low altitude over a curved earth surface and far away from a radar, we examine the accuracy of the conventional formulations to compute the radar echo signal. The 4-ray model is used to calculate the scattering by the target to consider the ground plane effect. In this paper, the diffracted wave is not included. Based on the required parameters able to be calculated by known equations for the estimation of the wave propagation phenomena, the radar echo signal is computed and verified by comparing with measured data sets.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.33-40
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• 2005

Impact-echo test, a kind of simple and economical method to evaluate the integrity of drilled piles has some limitations to use because the stress wave can be generated only on the head of a pile and the wave propagation in the pile with surrounding soils are very complicated. Numerical analyses and model tests in the laboratory have shown that both the ratio of length to diameter of a pile and the stiffness ratio of pile to soil have influence on the resolution of testing results. Full scale testing piles which have artificial defects were used to verify the capability of impact-echo technique as a tool for the pile integrity evaluation. Behaviour of the reflected signal of stress wave was investigated according to the type of defects. Elastic modulus of the pile was calculated using the wave velocity in the pile and the unconfined strength of concrete specimen. Influences of the stiffness difference between the pile and the ground on the characteristics of a wave signal were also examined.

• Journal of IKEEE
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• v.26 no.4
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• pp.524-530
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• 2022

When radar return contains strong jammers along with ground clutter echo, a STAP(space-time adaptive processing) algorithms tend to suppress jammer components more severely than it does the clutter. This hinders moving target detection in that the target echo is apt to be buried by clutter echo. This paper presents a two-step STAP algorithm in which the pre-suppression of jammer by the spatial filtering is applied, prior to applying the STAP algorithm. We propose how to find the coefficients of the spatial filter and show that the spatial filtering barely alter the spectra of the target and the clutter echo, having only to suppress the jammers. Finally, we simulate a STAP scenario with strong jammers and show the proposed algorithm can improve STAP performance.

• Proceedings of the KIEE Conference
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• 2001.11c
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• pp.30-33
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• 2001

This paper discusses the system design of a synthetic aperture radar system based on a pulse-echo radar. The design consists of an ultra-wide bandwidth antenna, an amplitude modulation, timing stabilities, and high speed a/d conversions with an equivalent-time sampling. Experiment results show that GPR(Ground Penetrating Radar) can be used to explore buried electric facilities.

• Korean Journal of Remote Sensing
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• v.19 no.6
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• pp.421-430
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• 2003

The extraction technique for Doppler information(Doppler centroid frequency(f$_{dc}$) and it's rate(f$_{r}$) is very important to make an image from the radar echo signal data. Clutterlock and auto-focusing techniques have been widely used to extract accurate Doppler information. But both techniques are not easy to implement in SAR processor and need quite lots of time to calculate accurate f$_{dc}$ and f$_{r}$ because they are generally based on echo signal data only. In this paper we suggest hybrid method for Doppler extraction using both of echo signal data and orbital and attitude information of satellite. In this method CDE(Correlation Doppler Estimation) technique is only used to estimate exact modular f$_{dc}$ using received echo signal data and rest of other algorithms are based on simple mathematical model of geometry between satellite and ground targets as well as the Doppler frequency ambiguity resolving problem. The experimental results using Radarsat-1 signal data shows that the proposed method can be effectively used for the extraction of Doppler information.

• 한국지구물리탐사학회:학술대회논문집
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• 2009.10a
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• pp.185-189
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• 2009

Integrated analysis of GPR, impact echo and impulse response for detection of the rear cavity of concrete was performed on the test-bed which was made in the same scale and component ratio to the real concrete structure. GPR survey may roughly delineate the location of the cavity, but applying the IE and IR technique to the test-bed, the location was clearly identified.

• Spatial Information Research
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• v.13 no.2 s.33
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• pp.157-166
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• 2005

LiDAR(Light Detection And Ranging) can make terrain model where above the ground and the mixed data between SBES(Single Beam Echo Sounder) and SSS(Side Scan Sonar) can make terrain model where bottom of water. So this research suggest that how to merge data which are got ken different devices and we developed the software which can display 2D/3D graphic and water volume calculation. And we compared accuracy between the commercial software'Surfer'and LiDAR and SBES data Merging Program.

• 한국정보통신설비학회:학술대회논문집
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• 2003.08a
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• pp.382-384
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• 2003

지하 30m 암반에 건설된 통신구 터널의 안전성을 검토하기 위하여 콘크리트 라이닝 두께를 지중레이다(Ground Penetrating Radar)와 충격반향기법(Impact-Echo Method)으로 추정하였다. 지중레이다에 의한 콘크리트 라이닝 단면의 연속적인 화상으로부터 라이닝 두께의 상대적인 변화를 파악하였으며, 라이닝 두께가 얇은 구간은 충격반향 기법에 의해 일정 간격으로 두께를 추정하였다. 터널 천장의 라이닝 두께는 31.85cm, 좌측 및 우측 측벽부의 라이닝 두께는 각각 32.45cm. 32.97cm로서 설계 값인 30cm와 비교적 잘 일치하는 것으로 파악되었다. 지중레이다와 충격반향기법을 조합한 본 방법은 터널 라이닝 콘크리트 두께를 추정하는데 있어서 매우 효율적이고 신뢰성 있는 방법으로 분석되었다.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.6
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• pp.1036-1044
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• 2021

A linear array acoustic transducer with 12 tonpilz elements mounted independently on a gradual wedge-shaped tail mass was fabricated, tested and analyzed. The compensated transducer, which is modified by including a series inductance of 137 µH in the developed linear array transducer, attained improved figure of merit (FOM) performance characteristics compared with the uncompensated transducer. The four resonant frequency bands were identified from the measured FOM curve. The FOM response patterns over the frequency ranges of 31 to 40 kHz and 50 to 60 kHz were relatively uniform, whereas sharp resonance peaks were observed at around 73 kHz and 84 kHz. These results indicate that the developed linear array transducer can be used as an enhanced broadband transducer of echo sounder, and the operating frequency can be selected for more effective echo surveys in the fishing ground.

• The Journal of the Acoustical Society of Korea
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• v.9 no.2
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• pp.42-52
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• 1990

A method of measuring impulse response of acoustic system, two kinds of cross-correlation methods (the direct correlation method and the M-sequence modulation correlation method) were applied. According to the direct correlation method, by using stationary random noise source and by calculating the cross-correlation function between the sourece and the output signal, equivalent impulse response can be obtained not being influenced by the back ground noises. By applying this method, the measurement of echo-time patterns in rooms and oblique incident sound absorption characteristics of sound absorbing materials was carried out. In the case of the M-sequence modulation correlation method which was contrived by Aoshima, an intermittent random nosie modulated by M-sequence signal is used as the source signal, and the cross-correlation function between the M-sequence signal and the squared output signal is calculated. According to this method, equivalent energy impulse response (squared impulse response) of te propagation system can be obtained without being influenced by the back ground noises and the air fluctuation caused by wind. As the applcaition of this measuring method to the architectural acoustics, the meaurements of echo-time patterns, reverberation decays and sound pressure lev디 distributions in rooms and sound insulation efficiencies in buildings were carried out. From these experimental studies, it has been found that this M-sequence modulation correlation method is markedly useful especially for the field masurement of sound insulation under high back ground noise condition.