• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.4
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• pp.31-36
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• 2012

In this paper, we proposed spectrum sensing using cooperative relay to solve problem of sensing performance degradation due to CPE (Customer-Premises equipments) which causes low SNR (signal-to-noise ratio) problem. In cooperative communication system, AF (amplify-and-forward) and DF (decoded-and-forward) is widely used for relay mechanism. Also, it is expected that cooperative relay scheme guarantees the high sensing performance by its diversity gain. Based on these backgrounds, in this paper, we apply to cooperative relay scheme to the CR (Cognitive Radio) system, and simulation results show comparison of the sensing performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.6
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• pp.1482-1489
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• 1998

This paper aims to extract characteristics of the spectrum of fingerprint image and to apply them to image enhancement techniques in spatial frequency domain. Based on 1$\times$64 window as a processing unit and the different record lengths(32, 16, 8), the estimate of power spectrum density for each length was made. Each acquired spectrum characteristics was applied to the re-synthesis process of the fingerprint image, an improved gray scale image was obtained. In order to select an optimal predictor and the Huffman table for the fingerprint iamge, the lossless JPEG algorithm was used. Experiments were performed for extracting distribution characteristics for the each of 7 predictors from the fingerprint image and modeling processes, and the result was applied to the data compression algorithm and the selection of the optimal predictor.

• Journal of Satellite, Information and Communications
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• v.7 no.1
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• pp.7-12
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• 2012

In this paper, we proposed spectrum sensing using cooperative relay to solve problem of sensing performance degradation due to CPE (Customer-Primise equipments) which causes low SNR (signal-to-noise ratio) problem. In cooperative communication system, AF (amplify-and-forward) and DF (decoded-and-forward) is widely used for relay mechanism. Also, it is expected that cooperative relay scheme guarantees the high sensing performance by its diversity gain. Based on these backgrounds, in this paper, we apply to cooperative relay scheme to the CR (cognitive radio) system, and simulation results show comparison of the sensing performance between AF and DF.

• ETRI Journal
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• v.37 no.4
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• pp.647-656
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• 2015

This paper proposes a single-RF MIMO receiver that adopts a beam-switching antenna (BSA) instead of a conventional array antenna. The beauty of the proposed single-RF MIMO receiver with BSA is that it can be deployed in a very small physical space while achieving a full spatial multiplexing gain. Our analysis has revealed that the use of a BSA inevitably results in the spectrum spreading effect at the RF output, which in turn causes an SNR decrease and adjacent channel interference (ACI). Two novel receiver techniques are proposed to mitigate the issues of redundant sub-band suppression and ACI avoidance. Numerical analysis results verify the performance improvement from the proposed receiver techniques.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.6 no.3
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• pp.31-42
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• 1986

The probabilistic model was developed to give a spatial simlation of precipitation series to solve the problem of future need of water resources. The simulation of daily precipitation series at the sub-base stations was induced from the spatial structure of rainfall occurrence probability between the base station and the sub-base stations in the watershed. In this study Hadong was chosen as the base station in Seomjin river basin and Imsil, Boseong, Soonchang, Dongbok, and Gurye were also selected as the sub-base stations. The results of this study are as follows; 1) The separation technique of spatial precipitation state showed effectiveness in the spatial simulation method because the occurrence probability by each precipitation state (Wet-Wet, Dry-Wet, Wet-Dry, and Dry- Dry system) represented the stable value. 2) The daily precipitation series of the sub-base stations which were simulated from those of the base station showed that the simulated annual mean precipitations were similar to the observed data, but the precipitations in summer were decreased slightly. 3) The correlogram and power spectrum of the simulated monthly precipitation for the sub-base stations showed those of the observed sample with good agreement.

• Nuclear Engineering and Technology
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• v.44 no.1
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• pp.53-60
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• 2012

The aim of this study was to explore the spatial and energy resolutions of a PET scanner that we have recently developed. The scanner, which consists of six detector modules with 1-layer LGSO crystals, has a hexagonal configuration with a faceto- face distance of 86.4 mm between two opposite PET modules; such properties facilitate the imaging of small animals. A $^{22}Na$ point source was employed to estimate horizontal and vertical spatial resolutions. To assess the energy resolution, a uniform $^{18}F$ cylindrical phantom was scanned. A software-based spectrum analysis of list-mode data was used to assign a local energy window centered on the photopeak position for every single crystal. For the image reconstruction, an ML-EM algorithm was used. The spatial resolutions at the center of the scanner were 0.99 mm in the horizontal direction and 1.13 mm in the vertical direction. The energy resolution averaged over each PMT ranged from 13.3%-14.3%, which gave an average value of 13.8%. These results show that this simple system is promising for small animal imaging with excellent spatial and energy resolutions.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.15 no.4
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• pp.277-282
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• 2015

Braincomputer interface (BCI) technology is making advances in the field of humancomputer interaction (HCI). To improve the BCI technology, we study the changes in the electroencephalogram (EEG) signals for six levels of grip strength: 10%, 20%, 40%, 50%, 70%, and 80% of the maximum voluntary contraction (MVC). The measured EEG data are categorized into three classes: Weak, Medium, and Strong. Features are then extracted using power spectrum analysis and multiclass-common spatial pattern (multiclass-CSP). Feature datasets are classified using a support vector machine (SVM). The accuracy rate is higher for the Strong class than the other classes.

• The Journal of the Acoustical Society of Korea
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• v.19 no.2E
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• pp.14-19
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• 2000

The forward propagated ultrasonic fields resulting from a circular plane or a concave transducer in layered fluid media as well as in homogeneous water are theoretically estimated by the angular spectrum method(ASMJ) combined with Rayleigh-Sommerfeld diffraction theory(RSDT), and measured by a precision 3-D scanning system with a needle-point hydrophone. To make the aliasing error negligible on the 2-D FFT in the theoretical estimation, the spatial discretization in the ASM are carefully considered for optimal selection of spatial sampling intervals and the size of discretization area. It is shown that the estimated fields agree reasonably with the measured ones.

• Journal of Korean Association for Spatial Structures
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• v.2 no.2 s.4
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• pp.45-49
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• 2002

Current seismic design codes for building structures are based on the methods which can provide enough capacity to satisfy objected performance level and exactly evaluate the seismic performance of buildings. This paper is to suggest the method of inference of inelastic earthquake response obtained from MDOF system by equivalent SDOF system, and to prove the validity. The analysis results form simple model shows a good application possibility.

• Current Optics and Photonics
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• v.2 no.4
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• pp.315-323
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• 2018

A new multiple-image encryption scheme that is based on a compressive ghost imaging concept along with a Fourier transform sampling principle has been proposed. This further improves the security of the scheme. The scheme adopts a Fourier transform to sample the original multiple-image information respectively, utilizing the centrosymmetric conjugation property of the spatial spectrum of the images to obtain each Fourier coefficient in the most abundant spatial frequency band. Based on this sampling principle, the multiple images to be encrypted are grouped into a combined image, and then the compressive ghost imaging algorithm is used to improve the security, which reduces the amount of information transmission and improves the information transmission rate. Due to the presence of the compressive sensing algorithm, the scheme improves the accuracy of image reconstruction.