• Journal of Korean Society for Geospatial Information Science
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• v.21 no.3
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• pp.55-62
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• 2013

This paper aims to detect Speed Bump by using Omni-directional Camera and to suggest Real-time update scheme of Speed Bump through Vision Based Approach. In order to detect Speed Bump from sequence of camera images, noise should be removed as well as spot estimated as shape and pattern for speed bump should be detected first. Now that speed bump has a regular form of white and yellow area, we extracted speed bump on the road by applying erosion and dilation morphological operations and by using the HSV color model. By collecting huge panoramic images from the camera, we are able to detect the target object and to calculate the distance through GPS log data. Last but not least, we evaluated accuracy of obtained result and detection algorithm by implementing SLAMS (Simultaneous Localization and Mapping system).

• Geophysics and Geophysical Exploration
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• v.12 no.1
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• pp.99-104
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• 2009

We propose a waveform inversion method for SH-wave data obtained in a shallow seismic refraction survey, to determine a 2D inhomogeneous S-wave profile of shallow soils. In this method, a 2.5D equation is used to simulate SH-wave propagation in 2D media. The equation is solved with the staggered grid finite-difference approximation to the 4th-order in space and 2nd-order in time, to compute a synthetic wave. The misfit, defined using differences between calculated and observed waveforms, is minimised with a hybrid heuristic search method. We parameterise a 2D subsurface structural model with blocks with different depth boundaries, and S-wave velocities in each block. Numerical experiments were conducted using synthetic SH-wave data with white noise for a model having a blind layer and irregular interfaces. We could reconstruct a structure including a blind layer with reasonable computation time from surface seismic refraction data.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.4
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• pp.9-16
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• 2000

This paper shows the performance of a multiuser detection DS-CDMA receiver based on of the hybrid scheme of parallel interference cancellation (PIC) and successive interference cancellation (SIC). The proposed hybrid interference cancellation is presented and is compared with existing PIC, SIC and Hybrid It of other type schemes. The performance criteria used for comparison are complexity, delay and average bit error rate (BER) performance obtained by simulation in Rayleigh-fading channel (Jake's model) with additive white Gaussian noise (AWGN). In the proposed hybrid IC, the BER performance approximates the one of SIC and the delay is half of the SIC. And the number of cancellation of the hybrid It is reduced about a fourth.

• Ocean Systems Engineering
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• v.13 no.2
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• pp.173-193
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• 2023

Reliable prediction of the motion of FOWT (floating offshore wind turbine) and associated mooring line tension is important in both design and operation/monitoring processes. In the present study, a 5MW OC4 semisubmersible wind turbine is numerically modeled, simulated, and analyzed by the open-source numerical tool, OpenFAST and in-house numerical tool, Charm3D-FAST. Another commercial-level program FASTv8-OrcaFlex is also introduced for comparison for selected cases. The three simulation programs solve the same turbine-floater-mooring coupled dynamics in time domain while there exist minor differences in the details of the program. Both the motions and mooring-line tensions are calculated and compared with the DeepCWind 1/50 scale model-testing results. The system identification between the numerical and physical models is checked through the static-offset test and free-decay test. Then the system motions and mooring tensions are systematically compared among the simulated results and measured values. Reasonably good agreements between the simulation and measurement are demonstrated for (i) white-noise random waves, (ii) typical random waves, and (iii) typical random waves with steady wind. Based on the comparison between numerical results and experimental data, the relative importance and role of the differences in the numerical methodologies of those three programs can be observed and interpreted. These comparative-study results may provide a certain confidence level and some insight of potential variability in motion and tension predictions for future FOWT designs and applications.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.12 no.6
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• pp.612-618
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• 2019

In the unmanned vehicle industry, the market is exploding due to the rapid development of public and private demands along with the technological development of the 4th Industrial Revolution. In addition, unmanned mobiles are being used for communication services. In this paper, we analyzed the communication performance of unmanned aerial vehicle according to the characteristics of Doppler frequency. The Doppler frequency was calculated using the geometric model of the unmanned aerial vehicle, and the Doppler frequency of 10km, 30km, 300km, 1000km per hour and the BER performance by AWGN were measured by considering the unmanned high speed unmanned vehicle based on the position of the controller. The Doppler frequency model uses a Dent model and adds additive white Gaussian noise (AWGN) to check the bit errors of the transmitter and receiver. Low speed unmanned vehicles generally exhibited a BER performance of 0.2, while high speed unmanned vehicles generally exhibited a BER performance of 0.06. As the frequency band increases at the same speed, the BER performance increases, and when the speed increases in the same frequency band, the BER performance decreases. This is confirmed by the simulation results to predict theoretically predictable BER performance. In the frequency bands of 2.6 GHz, 5 GHz, and 28 GHz, the BER characteristics by Doppler frequency and the BER characteristics by controller function are verified. effect was confirmed.

• Journal of Korean Society of Steel Construction
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• v.14 no.6
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• pp.765-772
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• 2002

Many researchers have studied several vibration control devices such as TMD, TLD, and VED to reduce the acceleration level for tall buildings. Advantages of TLD (tuned liquid damper) include easy installation, low cost, and less maintenance. However, the dynamic characteristics of TLD must be verified by experiment and analysis due to the difficulties in evaluating the characteristics of water sloshing. In this study, free vibration and dynamic excitation experiments of structure with TLD were conducted to verify vibration control force of the proposed TLD for high-rise building. The parameters were mass ratio of water to structure, number of damping nets, and aspect ratio. From the test results, the responses of structure with water tank were observed to be smaller than those of structure alone. Furthermore, better damping effect could be achieved with larger mass ratio, more damping nets, and larger aspect ratio. However, in the case of water tank with no damping net, little damping effect was obtained.

• Journal of Satellite, Information and Communications
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• v.6 no.1
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• pp.75-79
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• 2011

Wireless devices can communicate between each other without existing infrastructure in mobile Ad-hod network. Ad hoc networks can be used under difficult conditions, where it is difficult to construct infrastructures, such as shadowing areas, disaster areas, war area, and so on. In order to support to considerable and various wireless services, more spectrum resources are needed. However, efficient utilization of the frequency resource is difficult because of spectrum scarcity and the conventional frequency regulation. Ad-hoc networks employing cognitive radio (CR) system that guarantee high spectrum utilization provide effective way to increase the network capacity. In this paper, we simulate and compare the performance of conventional single and cooperative spectrum sensing with CR system using ad-hoc networks in additive white Gaussian noise (AWGN) and Rayleigh channel model. And we demonstrate performance improvement by analyzing the system performance.

• Earthquakes and Structures
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• v.14 no.4
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• pp.337-347
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• 2018

This paper presents some shaking table tests conducted on a 1/4-scaled model with 5-story steel reinforced concrete (SRC) spatial frame with irregular section columns under a series of base excitations with gradually increasing acceleration peaks. The test frame was subjected to a sequence of seismic simulation tests including 10 white noise vibrations and 51 seismic simulations. Each seismic simulation was associated with a different level of seismic disaster. Dynamic characteristic, strain response, acceleration response, displacement response, base shear and hysteretic behavior were analyzed. The test results demonstrate that at the end of the loading process, the failure mechanism of SRC frame with irregular section columns is the beam-hinged failure mechanism, which satisfies the seismic code of "strong column-weak beam". With the increase of acceleration peaks, accumulated damage of the frame increases gradually, which induces that the intrinsic frequency decreases whereas the damping ratio increases, and the peaks of acceleration and displacement occur later. During the loading process, torsion deformation appears and the base shear grows fast firstly and then slowly. The hysteretic curves are symmetric and plump, which shows a good capacity of energy dissipation. In summary, SRC frame with irregular section columns can satisfy the seismic requirements of "no collapse under seldom earthquake", which indicates that this structural system is suitable for the construction in the high seismic intensity zone.

• Journal of the Society of Naval Architects of Korea
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• v.51 no.4
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• pp.274-282
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• 2014

Time series of the dynamic response of a slender marine structure was predicted using quadratic Volterra series. The wave-structure interaction system was identified using the NARX(Nonlinear Autoregressive with Exogenous Input) technique, and the network parameters were determined through the supervised training with the prepared datasets. The dataset used for the network training was obtained by carrying out the nonlinear finite element analysis on the freely standing riser under random ocean waves of white noise. The nonlinearities involved in the analysis were both large deformation of the structure under consideration and the quadratic term of relative velocity between the water particle and structure in Morison formula. The linear and quadratic frequency response functions of the given system were extracted using the multi-tone harmonic probing method and the time series of response of the structure was predicted using the quadratic Volterra series. In order to check the applicability of the method, the response of structure under the realistic ocean wave environment with given significant wave height and modal period was predicted and compared with the nonlinear time domain simulation results. It turned out that the predicted time series of the response of structure with quadratic Volterra series successfully captures the slowly varying response with reasonably good accuracy. It is expected that the method can be used in predicting the response of the slender offshore structure exposed to the Morison type load without relying on the computationally expensive time domain analysis, especially for the screening purpose.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.47 no.5
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• pp.1-8
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• 2010

In this paper, a sound externalization method is proposed for out-of-the-head localization in a headphone listening environment. In order to reduce timbre distortion by the conventional methods using a measured a head-related transfer function (HRTF) or early reflections, the proposed method integrates a model-based HRTF with reverberation. In addition, for improving frontal externalization performance, techniques such as decorrelation and spectral notch filtering are included. To evaluate the performance of the proposed externalization method, subjective listening tests are conducted by using different types of sound sources such as white noise, sound effects, speech, and music. It is shown from the test results that the proposed externalization method can localize sound sources farther away from out of the head than the conventional method.