• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.5 s.98
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• pp.595-603
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• 2005

In this work, the multiple dynamic absorber( MDA ) is introduced to reduce several vibration modes of shadow mask simultaneously and its design method is developed from the theory of the simple dynamic absorber. When designing the dynamic absorber, there are three significant design parameters such as mass, damping ratio and tuning frequency. Therefore the sensitivity analysis for those parameters has been executed in order to find out the design criteria of multiple dynamic absorber using the finite element model of shadow mask. The multiple dynamic absorber(MDA) designed by the proposed method is tested theoretically and experimentally to estimate the efficiency of vibration reduction. From the results, it is verified that the method is feasible to apply the system having the multiple nitration modes and more efficient than the thin wire-type damper used commercially to reduce the vibration of shadow mask.

• ETRI Journal
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• v.33 no.3
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• pp.310-319
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• 2011

In this paper, a new soft-fusion approach for multiple-receiver wireless communication systems is proposed. In the proposed approach, each individual receiver provides the central receiver with a confidence level rather than a binary decision. The confidence levels associated with the local receiver are modeled by means of soft-membership functions. The proposed approach can be applied to wireless digital communication systems, such as amplitude shift keying, frequency shift keying, phase shift keying, multi-carrier code division multiple access, and multiple inputs multiple outputs sensor networks. The performance of the proposed approach is evaluated and compared to the performance of the optimal diversity, majority voting, optimal partial decision, and selection diversity in case of binary noncoherent frequency shift keying on a Rayleigh faded additive white Gaussian noise channel. It is shown that the proposed approach achieves considerable performance improvement over optimal partial decision, majority voting, and selection diversity. It is also shown that the proposed approach achieves a performance comparable to the optimal diversity scheme.

• Korean Journal of Community Nutrition
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• v.3 no.2
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• pp.273-280
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• 1998

This study was designed to estimate the improvement of Validity for food frequency questionnaire(FFQ) by offering multiple choice portion size in developing a questionnaire. Validity of the two methods(food frequency questionnaire I=FFQ I & Food frequency questionnaire II=FFQ II) was tested in comparison with reference method of the 7-day weighed record(7DWR). Dietary consumption data of the three methods(FFQ I, FFQ II & 7DWR) were collected from 101 female university students for the analysis. Validity was measured in two categories : One was the nutrient intake value from the three methods, the other was the identification of between individual variation within the group. Spearman's rank order correlation test and distribution graphs were used for the analysis. The result showed that individual intake value of the FFQII was closer to that of the 7DWR than that of the FFQ I.Spearman's rank order correlation between the FFQII and the 7DWR did not show any improved correlation. The distribution graphs of nutrient intake derived from both the FFQ I and the FFQII were different from that of the 7DWR. Therefore, it could be suggested that single one portion size food frequency questionnaire is an equally efficient method as a multiple choice food frequency questionnaire to be adopted in epidemiologic studies.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1991.10a
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• pp.63-68
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• 1991

The frequency window method has been extended to include strong coupling and multiple connections between the primary structure and the secondary structures. The rational polynomial expansion of the eigenvalue problem and the analytical methods for its solution are novel and distinguish this work from other eigenvalue analysis methods. The key results are the identification of parameters which quantify the resonance and coupling characteristics; the derivation of analytical dosed-form expressions describing the fundamental modal properties of the frequency windows; and the development of an iterative procedure which yields accurate convergent results for strongly-coupled primary-secondary structures.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.13 no.6
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• pp.453-460
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• 1988

The error probability for coherent frequency-hopped spread-spectrum multiple-access communications is computed by using characteristic function method. We employ PSK as a modulation scheme. The channel capacity is performance measure and the minimum bit signal-to-noise ratio for reliable communications is obtained.

• ETRI Journal
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• v.26 no.5
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• pp.384-390
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• 2004

We propose a new bandwidth-efficient technique that achieves high data rates over a wideband wireless channel. This new scheme is targeted for a multiple-input multiple- output orthogonal frequency-division multiplexing (MIMO-OFDM) system that achieves transmit diversity through a space frequency block code and capacity enhancement through the iterative joint processing of zero-forcing detection and maximum a posteriori (MAP) decoding. Furthermore, the proposed scheme is compared to the coded Bell Labs Layered Space-Time OFDM (BLAST-OFDM) scheme.

• Journal of the Optical Society of Korea
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• v.3 no.1
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• pp.10-14
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• 1999

Via THz Time domain spectroscopy, the characterization of high conductive n-type, 1.31Ω cm silicon can be measured by directly analyzing the multiple reflections using Fabry-Perot theory. The magnitude and phase difference of total transmission show good agreement between theoretical and experimental values over a 2.5 THz frequency range with complex index of refraction and power absorption. The measured absorption and dispersion are strongly frequency-dependent, and all of the results are well fit by a Cole-Davidson type distribution.

• ETRI Journal
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• v.26 no.6
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• pp.622-634
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• 2004

In this paper, we discuss the design problem and the robustness of space-frequency trellis codes (SFTCs) for multiple input multiple output, orthogonal frequency division multiplexing (MIMO-OFDM) systems. We find that the channel constructed by the consecutive subcarriers of an OFDM block is a correlated fading channel with the regular correlation function of the number and time delay of the multipaths. By introducing the first-order auto-regressive model, we decompose the correlated fading channel into two independent components: a slow fading channel and a fast fading channel. Therefore, the design problem of SFTCs is converted into the joint design in both slow fading and fast fading channels. We present an improved design criterion for SFTCs. We also show that the SFTCs designed according to our criterion are robust against the multipath time delays. Simulation results are provided to confirm our theoretic analysis.

• Journal of Communications and Networks
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• v.17 no.1
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• pp.27-33
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• 2015

In this paper, we consider a joint frequency-domain scheduling and user-pairing problem for virtual MIMO in the single carrier frequency division multiple access (SC-FDMA) system, e.g., the uplink transmission for third generation partnership project-long term evolution (3GPP-LTE) standard. Due to the subcarrier adjacency constraint inherent to SC-FDMA, its complexity becomes unmanageable. We propose a greedy heuristic algorithm for PF scheduling so as to deal with the complexity issue in this joint problem. It has been shown that its performance can reach up to 90% of its upper bound.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.2
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• pp.389-396
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• 1999

In this paper, we propose a multiple underwater object classification and tracking algorithm using the narrowband tonal and frequency line features extracted from the frequency spectrum of the acoustic signal. The general algorithm using the wideband and narrowband energy has a high tracking error when objects are close and cross each other. But the proposed algorithm shows a good tracking performance for the simulation scenarios generated by the real acoustic data.