• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.8
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• pp.3585-3601
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• 2016

The error rate performance of circularly distributed antenna system is studied over Nakagami-m fading channels, where a dual-channel receiver is employed for the quadrature phase shift keying signals detection. To mitigate the Co-Channel Interference (CCI) caused by the adjacent cells and to save the transmit power, this work presents remote antenna unit selection transmission based on the best channel quality and the maximized path-loss, respectively. The commonly used Gaussian and Q-function approximation method in which the CCI and the noise are assumed to be Gaussian distributed fails to depict the precise system performance according to the central limit theory. To this end, this work treats the CCI as a random variable with random variance. Since the in-phase and the quadrature components of the CCI are correlated over Nakagami-m fading channels, the dependency between the in-phase and the quadrature components is also considered for the error rate analysis. For the special case of Rayleigh fading in which the dependency between the in-phase and the quadrature components can be ignored, the closed-form error rate expressions are derived. Numerical results validate the accuracy of the theoretical analysis, and a comparison among different transmission schemes is also performed.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.6
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• pp.591-602
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• 2009

The Compton backscatter technique has been applied to lap-joint in aircraft structure in order to determine mass loss due to exfoliative corrosion of the aluminum alloy sheet skin. The mass loss of each layer has been estimated from Compton backscatter A-scan including the aluminum sheet, the corrosion layer, and the sealant. A Compton backscattering imaging system has been also developed to obtain a cross-sectional profile of corroded lap-splices of aging aircraft using a specially designed slit-type camera. The camera is to focus on a small scattering volume inside the material from which the backscattered photons are collected by a collimated scintillator detector for interpretation of material characteristics. The cross section of the layered structure is scanned by moving the scattering volume through the thickness direction of the specimen. The theoretical model of the Compton scattering based on Boltzmann transport theory is presented for quantitative characterization of exfoliative corrosion through deconvolution procedure using a nonlinear least-square error minimization method. It produces practical information such as location and width of planar corrosion in layered structures of aircraft, which generally cannot be detected by conventional NDE techniques such as the ultrasonic method.

• Journal of KIISE:Computer Systems and Theory
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• v.34 no.10
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• pp.502-510
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• 2007

Private Matching is a problem of computing the intersection of private datasets of two parties. One could envision the usage of private matching for Insurance fraud detection system, Do-not-fly list, medical databases, and many other applications. In 2004, Freedman et at. [1] introduced a probabilistic solution for this problem, and they extended it to malicious adversary model and multi-party computation. In this paper, we propose a new deterministic protocol for private matching with perfect correctness. We apply this technique to adversary models, achieving more reliable and higher speed computation.

• Journal of Korea Game Society
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• v.15 no.1
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• pp.35-44
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• 2015

The purpose of this study is to analyze user-generated rules in online games and to define the way of players' identities are developed. This study focuses on the online game League of Legends, which originated from use map system. Based on rule theory, this study analyzes the characteristics of user-generated rules. As the result, this study proves that the main rule of online game is not the rules made by developers, but the emergent rules made by players. Through rule-detection and rule-selection process, user-generated rules change the game system. Therefore, the result of this study expects to show meaningful roles of players in game system.

• Phonetics and Speech Sciences
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• v.8 no.4
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• pp.103-113
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• 2016

This paper aims to propose articulatory features as novel predictors for automatic pronunciation assessment of English produced by Korean learners. Based on the distinctive feature theory, where phonemes are represented as a set of articulatory/phonetic properties, we propose articulatory Goodness-Of-Pronunciation(aGOP) features in terms of the corresponding articulatory attributes, such as nasal, sonorant, anterior, etc. An English speech corpus spoken by Korean learners is used in the assessment modeling. In our system, learners' speech is forced aligned and recognized by using the acoustic and pronunciation models derived from the WSJ corpus (native North American speech) and the CMU pronouncing dictionary, respectively. In order to compute aGOP features, articulatory models are trained for the corresponding articulatory attributes. In addition to the proposed features, various features which are divided into four categories such as RATE, SEGMENT, SILENCE, and GOP are applied as a baseline. In order to enhance the assessment modeling performance and investigate the weights of the salient features, relevant features are extracted by using Best Subset Selection(BSS). The results show that the proposed model using aGOP features outperform the baseline. In addition, analysis of relevant features extracted by BSS reveals that the selected aGOP features represent the salient variations of Korean learners of English. The results are expected to be effective for automatic pronunciation error detection, as well.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.65.1-65.1
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• 2013

Our understanding of how brown dwarfs form is limited by observational evidence. We report identification of a L328-IRS as a proto-brown dwarf embedded in an isolated dense molecular core. This source exhibits typical properties of a protostar, however, its luminosity (~0.05 $L{\odot}$) is far below than expected from the least massive protostar by the standard star formation theory. The most likely mass accretion rate (~2.4 10-7 $M{\odot}$ yr-1) inferred from its small bipolar outflow is an order of magnitude less than the canonical value for a protostar. The mass available in its envelope is less than 0.1 $M{\odot}$. These points suggest that L328-IRS will accrete the mass of a brown dwarf, but not that of a star. L328 is found to be fairly well isolated from other nearby clouds and seems to be forming three sub-cores simultaneously through a gravitational fragmentation process. Altogether with these, our direct detection of inward motions in L328 which harbors this proto-brown dwarf clearly supports the idea that a brown dwarf forms like a normal star.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.4 no.2
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• pp.24-33
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• 1993

In indoor radio systems, vehicular communication systems, and land mobile systems, a very important problem is that of maintaing stable communications at all locations. Therefore solutions for the indoor propagation problem are an important aspects of the mobile communication system. Leaky coaxial cables finding increasing use in communications systems involving mines, tunnels, railroads, and highways, and in new obstacle detection, or guided radar, schemes for ground transpor- tation and perimeter surveilance. In this paper a leaky coaxial cable having periodic slots in the outer conductor is described to obtain the propagation modes in the various environments. We use an essentric cylindrical model to develop the theory for surface-wave propagation on the cable. Numerical Results are also included for the propagation constants, field distribution and impedance as functions of various parameters. First, we derive the electromagnetic equation for leaky coaxial cable having periodic slots using mode-matching method and Floguet's theorem, and then find various modes, propagation constants, field distribution, etc.

• Journal of Sensor Science and Technology
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• v.29 no.2
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• pp.118-122
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• 2020

This paper proposes a specific sensor-design strategy and the possibility of improving the sensing performance, which can be obtained by replacing part of the existing plasmonic sensor based on the Kretschmann configuration method with an effective refractive-index layer. By replacing the metal layer with an effective refractive-index layer composed of gold and the material to be sensed, an improvement in the detection performance, accompanied by an increase in the sensed incident angle, is observed, and the gold-composition ratio that demonstrates the best result is presented. Subsequently, an increase in the sensed incident angle generated in the previous step can be suppressed by randomly etching a portion of the prism adjacent to the metal layer in a sub-wavelength scale. Finally, this study analyzes the optimization of the metal-layer thickness in a given sensor structure. An effective refractive thin-film surface plasmon resonance sensor design that can achieve optimal sensing performance is then proposed.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.1
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• pp.95-102
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• 2014

This paper presents zero crossing point(ZCP) estimation methods considering discretization error for a high speed brushless DC(BLDC) motor drive. The ZCP is estimated by detecting the change of back-EMF polarity for the BLDC sensorless drive, and the discretization error exist on the estimated ZCP. The discretization error of the ZCP is a cause of the delay of a commutation timing of current and increment of a current ripple factor. Besides a delay of a ZCP estimation brings on the limitation of a speed range for the BLDC sensorless drive. The compensation method based on the error analysis with probability theory for reducing the effects of the discretization error of the ZCP is proposed. Also a ZCP estimation method according to the Back-EMF patterns is proposed to widen the speed range for the BLDC sensorless drive. The proposed methods are verified by the experiment.

• Computers and Concrete
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• v.14 no.2
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• pp.145-161
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• 2014

The article presents the statistical method of grouping the results of the compressive strength of concrete in continuous production. It describes the method of dividing the series of compressive strength results into batches of statistically stable strength parameters at specific time intervals, based on the standardized concept of "concrete family". The article presents the examples of calculations made for two series of concrete strength results, from which sets of decreased strength parameters were separated. When assessing the quality of concrete elements and concrete road surfaces, the principal issue is the control of the compressive strength parameters of concrete. Large quantities of concrete mix manufactured in a continuous way should be subject to continuous control. Standardized approach to assessing the concrete strength proves to be insufficient because it does not allow for the detection of subsets of the decreased strength results, which in turn makes it impossible to make adjustments to the concrete manufacturing process and to identify particular product or area on site with decreased concrete strength. In this article two independent methods of grouping the test results of concrete with statistically stable strength parameters were proposed, involving verification of statistical hypothesis based on statistical tests: Student's t-test and Mann - Whitney - U test.