• Journal of information and communication convergence engineering
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• v.13 no.2
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• pp.69-73
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• 2015

We focus on a sounding signal design for single-input single-output orthogonal frequency division multiplexing (SISO-OFDM) systems. We show that the frequency spectrum of an optimum sounding signal has a constant magnitude across the frequency band for the cases with or without Doppler effects. Simulation results show that the designed optimum sounding signal outperforms random sounding signals and that the performance of a maximal-length shift register sequence is indistinguishable from that of the optimum sounding signal.

• Geophysics and Geophysical Exploration
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• v.6 no.3
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• pp.119-125
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• 2003

The small-loop electromagnetic (EM) technique has been used successfully for many geophysical investigations, particularly for shallow engineering and environmental surveys. In conventional small loop EM operating at small induction numbers, geometric sounding has been widely used because the depth of penetration of EM energy depends only on the source-receiver separation. Recently developed small loop EM system, however, measures the secondary magnetic field, $H^S$, at multiple frequencies with a fixed source-receiver separation and frequency sounding is tried actively. In this study, we analyzed the behavior of in-phase and quadrature components of ${H^S}_z$, for horizonal coplanar (HCP) configuration over two-layer models. Through this theoretical analysis, it was found that the in-phase component of ${H^S}_z$ is more suitable for frequency sounding than the quadrature component. But, the in-phase component of ${H^S}_z$ is too small to measure, especially in resistive and noisy environment like Korea. Using the fact that the quadrature component is much greater than the in-phase component and the difference of quadrature component of ${H^S}_z$ measured at two frequencies shows the same behavoir as the in-phase component, we suggested an alternative frequency sounding technique. Also, we defined an apparent conductivity, which reflects well the conductivity of subsurface layers.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.23 no.2
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• pp.197-203
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• 2005

Dredging and reclaiming on coast, harbor construction etc. of when construct, the interest about efficiency and accuracy of sounding by measurement condition very rise. However, there are only a few studies on the accuracy improvement concerning water depth sounding condition. In this study, among the precision decline main causes of sounding, 1 suggested the characteristics of sounding data acquired by echo sounder with increasing of turbidity and the critical turbidity range under a given transducer frequency. For this, I acquired sounding data by inputting turbidity inducer artificially in artificial water tank. And then achieved regression analysis. Conclusion are as following Sounding Capabilities can be divided into three ranges according to the turbidity . normal range, critical range and the range where data can not be obtained by an echo sounder. When the turbidity exceeds $217\~259$ NTU which was considered as critical range, depth sounding was impossible.

• Geophysics and Geophysical Exploration
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• v.23 no.4
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• pp.223-229
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• 2020

Small-loop EM techniques have been used in many geophysical investigations, including shallow engineering and environmental surveys. Even though geometric and frequency soundings have been widely used, there is a debate regarding the effectiveness of frequency sounding, especially when the coil spacing is small. In this study, we analyzed the effectiveness of geometric as well as frequency soundings via the one-dimensional modeling of small-loop EM surveys. The numerical results reveal that geometric sounding can effectively provide underground information. Conversely, the frequency soundings are only effective when the loop spacing is relatively large, that is, when the induction number is large. On the contrary, the frequency soundings fail to provide any information concerning the subsurface layers if the loop spacing is not large.

• Journal of the Korean Wood Science and Technology
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• v.13 no.3
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• pp.34-40
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• 1985

The characteristics of Paulownia coreana wood used for sounding boards has been revealed through this study. The 80 specimens were selected from Paulownia coreana wood. The dynamic Young's modulus, the internal friction and resonant frequency of wood were measured by the method of making a rectangular bar resonate in the audio frequency range. The results obtained are summarized as follows: 1. The average values of the specific gravity, the dynamic Young's modulus and the internal friction concerning Paulownia coreana used for sounding boards are $0.252{\pm}0.022$, $(0.494{\pm}0.068){\times}10^{11}$ dyne/cm and $(7.89{\pm}1.692){\times}10^{-3}$ respectively. 2. The average values of resonant frequency, the velosity of sound, and K values are $504{\pm}24.298$ Hz, $5018{\pm}219.83$m/s, and $(9.907{\pm}2.05){\times}10^{-4}$ respectively. 3. The dynamic Young's modulus of Paulownia coreana increases with the increase of the specific gravity, and that on the contrary the internal friction decreases. 4. The dynamic Young's modulus was abruptly decreased as the moisture content of wood specimens was increased up to the fiber saturation point, and the internal friction was linearly increased as the moisture content of wood specimens were increased. 5. The vibration properties of Paulownia coreana are that the dynamic Young's modulus is fairly high, the internal friction is low, and the ratio of Young's modulus to specific gravity shows large value.

• Journal of the Korean Geophysical Society
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• v.5 no.3
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• pp.219-231
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• 2002

Single beam echo sounding was used to delineate bathymetry sea bottom in the area of hydrography and marine navigation. This research was aimed at measuring the thickness of floating silty clay sediment with dual frequencies echo sounding system. There occur discrepancies in penetrating depth through sea beds between high frequency(200 KHz) and low(33 KHz) frequency. RI density logging was employed to characterize the floating silty clay sediment of Guangyang bay, which was chosen to investigate the proposed site for reclamation field. The volume of floating silty clay sediment was used to design by estimating size of reclamation site. The estimation strategies developed in this study will be readily applicable to measure the Pattern of sedimentation via regular hydrographic survey in the future.

• Geophysics and Geophysical Exploration
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• v.15 no.2
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• pp.51-56
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• 2012

One of the most critical and essential procedures in the interpretation of gravity and magnetic data is to separate the anomaly due to the specific geologic structure from the summation of effects from a broad variety of geologic sources, especially those of different depths. Separation of the residual anomaly from the regional field is the most simple case of the vertical separation. If the anomaly due to a layer of specific depth can be separated or the depth of the separated layer can be quantitatively determined, it may deserve the separation-sounding. We suggest a wavelength filter whose cutoff frequency is determined by log-power spectrum analysis, as a separation-sounding filter. We applied this filter both to synthetic and real gravity data acquired at Heunghae area, and compared the results with those of Jacobsen's upward continuation filter. These showed that the proposed separation-sounding filter could be a useful tool for interpretation of the vertical geologic structure by stripping the gravity effects of geologic sources down to the desired depth.

• International Union of Geodesy and Geophysics Korean Journal of Geophysical Research
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• v.22 no.1
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• pp.1.2-5
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• 1994

Ionospheric sounding experiments have been conducted at RRL (Radio Research Laboratory), Ministry of Communications, using Digisonde 256 since its installation in 1990. Routine observations of the vertical sounding are carried out 48 times (or 39 times) a day, at every 24 hour. In addition, we also made oblique sounding experiments to obtain the real time data of Maximum Usable Frequency (MUF) and detect the anomalous HF propagation, as a part of the joint study between RRL and CRL (Communications Research Laboratory) of Japan. The two stations involved in the study were Anyang (RRL, Korea) and Kokubunji (CRL, Japan). The ionosondes used in both stations were Digisonde 256, developed by ULCAR (University of Lowell, Center for Atmospheric Research), U. S. A. , and the synchronization of time was accomplished with the help of GPS receiver. During most part of the experiments RRL transmitted non-modulated pulses, and CRL received them. The experiment was scheduled from October 25 through October 29, 1993. However, the ionosphere was not developed well enough to conduct the experiment with pre-set operation parameters. The experiment became successful (from 0500 UT to 0800 UT, October 29) only after the operation parameters had been changed, and the continuous ionograms were obtained by CRL at 0718 UT and 0733 UT in October 29, 1993. We believe this type of experiment will ensure the qualitative enhancement of solar-terrestrial physics research and a routine observation of the oblique ionospheric sounding. In this report, we present the results of the fore-mentioned oblique sounding as well as the vertical sounding results obtained by Digisonde 256 at Anyang station of RRL.

• Journal of Biosystems Engineering
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• v.14 no.4
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• pp.251-261
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• 1989

The amount of grain loss incurred during harvesting operation through the chaff-outlet of combine may not be negligible. To minimize this grain loss and optimize condition of combining, it may be necessary that the amount of chaff-outlet loss dependent on varying crop condition is to be estimated as exactly as possible. This study was thus intended to develop the monitor that could indicate the amount of grain loss occurred through the chaff-outlet of combine during harvesting operation. The function of this monitor is to measure at the sounding board the impact sound of paddy kernels which could be distinguished from those of other threshing products through chaff-outlet, and from vibration or noise created by the combine engine and other moving parts. To develop such monitor, the frequency distributions of each sound generated by the impact of grain and chaff, the sound generated by the impact of the mixture of grain and chaff, and vibration or noise created by the combine engine and other moving parts were investigated experimentally. From the results of frequency analyses, the trainsducer adequate for the monitering system was selected and sounding board was constructed. The grain loss monitor thus obtained was tested by attaching the sounding board to the chaff-outlet of combine.

• Journal of the Korean Wood Science and Technology
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• v.18 no.4
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• pp.65-78
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• 1990

For the purpose of Improving the sounding boards for the conventional GAYAKUM, I was making approximately 202 specimens of radial board, 371 specimens of tangential board by cutting along the grain and the part of stem and 31 specimens of the disjointed traditional GAYAKUM made in Paulownia coreana. And it was conducted to measure specific gravity, dynamic Young's modulus, internal friction, resonant frequency, velosity of sound and width of annual ring by the method of the frexural vibration in a free-free bar in the audio frequency range. And it confirmed the juvenile wood by measuring wood fiber length of specimens. It was also conducted to investigate dynamic properties and moisture absorption by various heat-treatment and to test dynamic Young's modulus and internal friction for the disjointed conventional GAYAKUM. The results obtained were summarized as follow: 1. The Juvenile wood is located within about 7 annual rings from the pith in Paulownia coreana. 2. As increased with the specific gravity, the dynamic Young's modulus had more and more increased, but the internal friction had slightly decreased. 3. I think that radial board would be good for sounding board wood. because radial board is higher than tangential board in dynamic Young's mudulus and internal friction is lower than tangential board. 4. The value of mean dynamic Young's modulus on the conventional GAYAKUM, radial board and tangential board of 604 samples is $0.4283\pm0.037(\times10^{11}dyne/cm^2)$, $0.4316\pm(\times10^{11}dyne/cm^2)$ and $0.4234\pm0.112(\times10^{11}dyne/cm^2)$ respectively. The value of the radial board showed little higher than that of conventional GAYAKUM, but It had a similar tendency between conventional GAYAKUM and tangential board. 5. The annual ring width by four aspect is more narrow in north and west than that of others. 6. The values of specific gravity and dynamic Young's modulus in the mature wood showed higher than those of juvenile wood. 7. As the grain angle in the butt wood more increased to bark from pith, the dynamic Young's modulus were low. Then it was not good for sounding board. 8. It appeared that the heat-treatment for sounding board wood had a more effect to do the treatment of hotiron on surface after heat-treatment during 24 hours in $60^{\circ}C$ temperature. 9. As increased with the temperature, the rate of moisture absorption of heat-treatment wood had decreased. In conclusion, I thought that the sounding board wood for GAYAKUM would had the most effect to do the treatment of hotiron on surface after heat-treatment during 24 hours in $60^{\circ}C$ temperature using the radial board of mature wood.