• Journal of Communications and Networks
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• v.13 no.1
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• pp.50-55
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• 2011

Spectrum leasing for cognitive radio (CR) networks is an effective way to improve the spectrum utilization. This paper presents an opportunistic relaying based spectrum leasing for CR networks where the primary users lease their frequency band to the cognitive users. The cognitive users act as relays for the primary users to improve the channel capacity, and this improved capacity is used for the transmission of secondary users' data. We show that the cognitive users can use a significant portion of the communication resource of primary networks while maintaining a fixed target data rate for the primary users. Moreover, the primary network is also benefited by the cooperating cognitive users in terms of outage probability. Information theoretic analysis and simulation results are presented to evaluate the performances of both primary and cognitive networks.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.6
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• pp.3-8
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• 2014

Recently, a spectrum sensing technique employing the maximum value of a received power spectrum as a test statistic has been presented in the literature for the purpose of detecting a wireless microphone signal in TV bands This detects the presence of a primary user by comparing the test statistic with some threshold, which depends on the background noise power level as well as a target false alarm rate. Therefore its performance may deteriorate when the noise power uncertainty occurs. As a means to mitigate this difficulty, we present a spectrum sensing strategy adopting the ratio of the maximum and the minimum value of the power spectrum as a test statistic and analyze its performance of spectrum sensing.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.8
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• pp.42-46
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• 2010

Energy detection based spectrum sensing compares the energy of a received signal from a primary user with a detection threshold and decides whether it is active or not in the frequency band of interest. Here the detection threshold depends on not only a target false alarm probability but also the level of the noise energy in the band. So, if the noise energy changes, the detection threshold must be adjusted accordingly to maintain the given false alarm probability. Most previous works on energy detection for spectrum sensing are based on the assumption that noise energy is known a priori. In this paper, we present a new energy detection scheme updating its detection threshold under the assumption that the noise is white, and analyze its detection performance. Analytic results show that the proposed scheme can maintain a target false alarm rate without regard to the noise energy level and its spectrum sensing performance gets better as the time bandwidth product of the signal used to estimate the noise energy increases.

• Phonetics and Speech Sciences
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• v.4 no.3
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• pp.103-110
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• 2012

In this paper, a target signal detection method using multiple signal classification (MUSIC) algorithm is proposed. The MUSIC algorithm is a subspace-based direction of arrival (DOA) estimation method. Using the inverse of the eigenvalue-weighted eigen spectra, the algorithm detects the DOAs of multiple sources. To apply the algorithm in target signal detection for GSC-based beamforming, we utilize its spectral response for the DOA of the target source in noisy conditions. The performance of the proposed target signal detection method is compared with those of the normalized cross-correlation (NCC), the fixed beamforming, and the power ratio method. Experimental results show that the proposed algorithm significantly outperforms the conventional ones in receiver operating characteristics (ROC) curves.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.236-239
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• 1999

Target signal feature parameters are very important to classify target by active sonar. Two highly correlated broadband pulses separated by time T have a time separation pitch (TSP) of 1/THz, equal to the spacing between ripples of its spectrum. In this study, TSP is applied to scaled-target echoes to be used as a feature parameter. The TSP from the target sign리 when source signals are CW short, CW long, and LFM long was investigated. It is also found the TSP can be applied to the target signal with doppler shift. It is shown that the position and magnitude of highlight can be found for LSEM based on TSP.

• Journal of the Earthquake Engineering Society of Korea
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• v.24 no.6
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• pp.243-251
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• 2020

In seismic design standards such as KDS 41 17 00 and ASCE 7, three procedures are provided to estimate seismic demands: equivalent lateral force (ELF), response spectrum analysis (RSA), and response history analysis (RHA). In this study, two steel special moment frames (SMFs) were designed with ELF and RSA, which have been commonly used in engineering practice. The collapse probabilities of the SMFs were evaluated according to FEMA P695 methodology. It was observed that collapse probabilities varied significantly in accordance with analysis procedures. SMFs designed with RSA (RSA-SMFs) had a higher probability of collapse than SMFs designed with ELF (ELF-SMFs). Furthermore, RSA-SMFs did not satisfy the target collapse probability specified in ASCE 7-16 whereas ELF-SMFs met the target probability.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.10
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• pp.994-1001
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• 2009

CSS (Chirp Spread Spectrum) specified in IEEE 802.15.4a can be used for ranging applications. In this paper, we apply the CSS to estimate the coordinates of a mobile robot. Four anchor nodes are installed at known positions and a tag node is attached to the target mobile robot. By CSS ranging, we measure the distances between each anchor and the tag node. Based on the measured distances, the coordinates of the mobile robot can be calculated by the method of trilateration. However the calculated coordinates are not accurate because of the errors of the measured distances. Therefore we propose an algorithm for reducing the effect of the errors. The proposed algorithm is executed with the extended Kalman filter. Through localization experiments, we show the performance of the proposed algorithm and the accuracy of the estimated position.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2006.03a
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• pp.479-486
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• 2006

This paper presents tile results of experimental studies of the isolated Model EDG Systems. For the experimental work, the scaled model of EDG system and the isolation systems were developed. The target EDG model is 16PC2-5V400 which was manufactured by the SEMT Pielstick corporation. The Coil Spring and Viscous Damper Systems were selected for the isolation system. The Coil Spring and Viscous Damper systems can reduce not only seismic forces but also the operating vibration. For the input seismic motions, the scenario earthquake and the artificial earthquakes which were developed as NRC design spectrum and Uniform hazard Spectrum(UHS) were selected. As a result, at least 20% of seismic forces were decreased as the isolation system.

• Nuclear Engineering and Technology
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• v.53 no.12
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• pp.4067-4071
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• 2021

The ¹³C (α,n)¹⁶O reaction cross-section is important data for nuclear physics, astrophysical, and neutrino physics experiments, however, they exhibit uncertainties due to the discrepancies in the experimental data. In this study, using the Nedis-2m program code, the energy spectrum of α-induced neutrons in a thin carbon target was calculated and the corresponding reaction cross-section was refined in the alpha particle energy range of 5-8 MeV. The results were used to calculate the intensity and energy spectrum of background neutrons produced in the liquid scintillator of KamLAND. The results will be useful in a variety of astrophysical and neutrino experiments especially those based on LS or Gd-LS detectors.

• Journal of the Earthquake Engineering Society of Korea
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• v.23 no.2
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• pp.109-117
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• 2019

In this study, a design procedure for the practical application of the dampers to building structures under earthquake loads was presented by using earthquake response spectrum. Nonlinear time history results using a 10 story building structure installed with damper verified the effectiveness of the proposed procedure by showing that the structural response could be reduced to the target performance level for seismic loads. Since the proposed design procedures are based on response spectrum seismic analysis result of the original structure, the capacity, location and the number of damper and the consequent response reduction effects can be preliminarily determined without performing the nonlinear time history analysis.