• Journal of Positioning, Navigation, and Timing
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• v.10 no.1
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• pp.55-66
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• 2021

In this paper, we propose a signal propagation modeling technique for generating a positioning fingerprint DB based on Long Term Evolution (LTE) signals. When a DB is created based on the location-based signal information collected in an urban area, gaps in the DB due to uncollected areas occur. The spatial interpolation method for filling the gaps has limitations. In addition, the existing gap filling technique through signal propagation modeling does not reflect the signal attenuation characteristics according to directions occurring in urban areas by considering only the signal attenuation characteristics according to distance. To solve this problem, this paper proposes a Deep Neural Network (DNN)-based signal propagation functionalization technique that considers distance and direction together. To verify the performance of this technique, an experiment was conducted in Seocho-gu, Seoul. Based on the acquired signals, signal propagation characteristics were modeled for each method, and Root Mean Squared Errors (RMSE) was calculated using the verification data to perform comparative analysis. As a result, it was shown that the proposed technique is improved by about 4.284 dBm compared to the existing signal propagation model. Through this, it can be confirmed that the DNN-based signal propagation model proposed in this paper is excellent in performance, and it is expected that the positioning performance will be improved based on the fingerprint DB generated through it.

• Journal of the Earthquake Engineering Society of Korea
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• v.25 no.1
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• pp.33-42
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• 2021

The design response spectrum presented in the seismic design standard reflects the characteristics of the tectonic environment at a site. However, since the design response spectrum does not represent the ground motion with a specific earthquake magnitude or distance, input ground motions for response history analysis need to be selected reasonably. It is appropriate to use observed ground motions recorded in Korea for the seismic design. However, recently recorded ground motions in the Gyeongju (2016) or Pohang (2017) earthquakes are not compatible with the design response spectrum. Therefore, it is necessary to convert the recorded ground motion in Korea to a model similar to the design response spectrum. In this study, several approaches to adjust the spectral acceleration level at each period range were tested. These are the intrinsic and scattering attenuation considering the earthquake environment, magnitude, distance change by the green function method, and a rupture propagation direction's directivity effect. Using these variables, the amplification ratio for the representative natural period was regressed. Finally, the optimum condition compatible with the design response spectrum was suggested, and the validation was performed by converting the recorded ground motion.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.4
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• pp.17-26
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• 2001

In order to estimate peak ground motions and frequency characteristics of strong ground motions in southern korea, we employed the stochastic simulation method with the moment magnitude(M$_{w}$) and the hypocentral distance(R). We estimated same input parameters that account for specific properties of source and propagation processes, and applied them to the stochastic simulation method. The stress drop($\Delta$$\sigma$) of 100-bar was estimated considering results of research in ENA, China, and southern korea. The attenuation parameter x was calculated by analyzing 57 seismograms recorded from September 1996 to October 1997 and the estimation result of the attenuation parameter x is 0.00112+0.000224 R where R is hypocenter distance. We estimated strong ground motion relations using the stochastic simulation method with suitable input parameters(e.g. $\Delta$$\sigma$, x, and so on). At last, we derived relations between hypocentral distances and ground motions(seismic attenuation equation) using results of the stochastic prediction.esults of the stochastic prediction.n.

• The Journal of the Korea institute of electronic communication sciences
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• v.6 no.4
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• pp.473-478
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• 2011

The extent of a rectangular conducting plane for measuring electromagnetic interference is discussed. Mutual coupling between the transmit and receive antennas is negligible, the effects of the ground plane on the normalized site attenuation(NSA) are considered by applying GTD(Geometric theory of diffraction). The calculation was done for the case that measuring distance(d) was 3 m for both horizontal and vertical polarizations. As the result, the size of the rectangular ground plane almost never affects upon NSA for horizontal polarization, but for vertical case, when both width and length of the rectangular plane are several times as long as distance, the effects of the edges are reduced under 1 dB.

• Journal of the Korean Institute of Gas
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• v.15 no.4
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• pp.15-20
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• 2011

This study presents the behavior characteristics of buried three-layered pipeline subjected to pile driving loads corresponding to its cover depth. The analysis considered the driving energy caused by 7 tonf of ram weight and 1.2m of stroke with 20m distance from buried pipeline for all the analysis cases. A cover depth of pipe is varied 0.6m to 3.8m for this research. Vibration Velocity and stress are investigated at the center section in longitudinal direction. With same distance from pile, attenuation ratio of vibration velocity for increment of cover depth has shown an increasing trend. Also, Stress attenuation ratio of inner pipe is increased with cover depth.

• Journal of Environmental Impact Assessment
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• v.25 no.5
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• pp.333-344
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• 2016

In this study, the efficiency of natural attenuation was evaluated through the hydrogeological characteristics such as monitoring and analyses, tracer tests, chemical composition analysis of the groundwater at a military site contaminated by petroleum hydrocarbon in korea. Also, based on the results, the natural attenuation rate by distance and the expressed biodegradation capacity(EBC) was evaluated. The regression slope of -0.0248($K/V_x$) and bulk attenuation rate of $1.7{\times}10^{-3}/day$ were calculated respectively. The range of total expressed biodegradation capacity(EBC) of BTEX was shown from 9.1 mg/L to 10.0 mg/L(average 9.7 mg/L). It was confirmed that the denitrification which was expressed about 63.6% in the total EBC is the largest influence redox process. Consequently, the biodegradation capacity is considered to be sufficient for remediation in the BTEX average concentration of 1.326 mg/L.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.1
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• pp.217-223
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• 2019

In this study, the acceleration changes of the surrounding ground when crushed stones were installed in a strip-type were analyzed using the 1-G shaking table test. The ground was constructed from clay, and the foundation was installed using crushed stone of strip-type form. The response acceleration and response spectrum for various input seismic motions were analyzed. The change in acceleration was examined according to the adjacent distance to the strip-type crushed stone foundation. In the Hachinohe seismic motion results, there was no significant decrease in acceleration, but the maximum response acceleration for the two seismic motions was inversely proportional to the distance from the crushed stone foundation. As a result of the response spectrum analysis, the attenuation period in the long period and the short period input wave were different from each other, and the change in response spectrum affected the maximum acceleration value. As the distance from the crushed stone foundation was increased, the attenuation was larger in the period between 0.08 and 0.5 sec in the Hachinohe seismic motion, the attenuation was larger in the period of less than 0.2 seconds in the Northridge seismic motion.

• Transactions on Control, Automation and Systems Engineering
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• v.2 no.1
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• pp.69-75
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• 2000

The aim of the work described in this paper is to develop a complex underground acoustic system which detects and localizes the origin of an underground hammering sound using an array of hydrophones located about 100m underground. Three different methods for the sound localization will be presented, a time-delay method, a power-attenuation method and a hybrid method. In the time-delay method, the cross correlation of the signals received from the array of sensors is used to calculate the time delays between those signals. In the power-attenuation method, the powers of the received signals provide a measure of the distances of the source from the sensors. In the hybrid method, both informations of time-delays and power-ratios are coupled together to produce better performance of position estimation. A new acoustic imaging technique has been developed for improving the hybrid method. This new acoustic imaging method shows the multi-dimensional distribution of the normalized cost function, so as to indicate the trend of the minimizing direction toward the source location. For each method the sound localization is carried out in three dimensions underground. The distance between the true and estimated origins of the source is 28m for a search area of radius 250m.

• Proceedings of the KIPE Conference
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• 2006.06a
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• pp.456-458
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• 2006

Power line communication: PLC which easy to install at anywhere near outlet for electric machine. PLC uses transmission line for voltage of which is 60 Hz. Signals don't affect to electric machine in PLC because they are very small voltage. One of the important thing is the processes of adding signal to power line and extracting the signal from power line, the other is to choose the strong modulation method which sends signals long distance without loosing in PLC channel. but PLC channel have very high and variable noise and attenuation and then it is very hard to transmit optimally between the transmitter and the receiver. After all, impedance and noise problems of PLC channel must be overcame. Noises of 2 kinds which are AWGN abd impulse noise and attenuation are orated. To overcome the noise. Recently, Multi-carrier Modulation: MCM methods like as OFDM and DMT which are divide the channel into many sub-channel have been studied. those are powerful communication methods in PLC. In this paper, PLC channels made up of 3 numbers of noise and attenuation are simulated for getting BER by Matlab simulink.

• The Journal of Korea Robotics Society
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• v.11 no.3
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• pp.156-162
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• 2016

For the underwater localization, acoustic sensor systems are widely used due to greater penetration properties of acoustic signals in underwater environments. On the other hand, the good penetration property causes multipath and interference effects in structured environment too. To overcome this demerit, a localization method using the attenuation of electro-magnetic(EM) waves was proposed in several literatures, in which distance estimation and 2D-localization experiments show remarkable results. However, in 3D-localization application, the estimation difficulties increase due to the nonuniform (doughnut like) radiation pattern of an omni-directional antenna related to the depth direction. For solving this problem, we added a depth sensor for improving underwater 3D-localization with the EM wave method. A micro scale pressure sensor is located in the mobile node antenna, and the depth data from the pressure sensor is calibrated by the curve fitting algorithm. We adapted the depth(z) data to 3D EM wave pattern model for the error reduction of the localization. Finally, some experiments were executed for 3D localization with the fast calculation and less errors.