• The Journal of the Acoustical Society of Korea
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• v.19 no.4
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• pp.16-22
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• 2000

In order to predict the performance and the usefulness of the narrow-band underwater acoustic measurement system at design stage, whose error variance is not clearly described, in this study a boundary equation to estimate the measurement accuracy is proposed based on the confidency as SNR variation. The boundary is presented as a function of SNR and the number of samples. In this paper, the measurement performance for narrow-band signal is simulated by the proposed boundary equation and the results are reviewed in the biased noise condition and separately in the background noise rejected condition.

• The Journal of the Korea Contents Association
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• v.22 no.10
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• pp.691-702
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• 2022

This study verifies the diversification effect when non-financial asset such as fractional music royalties investment which is recently get interest from masses, is included in traditional global asset allocation portfolio. From Jan 2019 when Music Royalties index is announced to Jun 2022, compared traditional global asset allocation portfolio and the portfolio included with music royalties. To eliminate the enhancement effect from portfolio strategy itself rather than including non-financial asset, used the four basic portfolio strategy such as buy & hold, constant rebalanced, mean variance, risk parity. As a result, all the portfolios included with music royalties shows less risk with higher returns. This means the sharpe ratio has enhanced and that results the portfolio diversification effect is placed. The empirical analysis of the study found academic significance in that the portfolio included with music royalties investment has diversification effect, and show the possibilities the not only on the music royalties, other non-financial asset can be shown the portfolio diversification effect.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.88-88
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• 2020

수심평균 2차원 혼합모형은 하천환경에서 다양한 용존성 오염물질의 혼합현상을 모의하기 위해 널리 활용되어왔다. 2차원 혼합모형에서 분산계수는 하천의 전단 흐름에 의해 야기되는 오염물질의 퍼짐 현상을 표현하는 중요한 인자로서 작용하기 때문에 정교한 오염물질 혼합거동을 모의하기 위해서는 적합한 분산계수를 산정하는 것이 필수적이다. 분산계수를 실험적으로 산정하는 방법으로는 크게 모멘트법과 추적법으로 나뉘며, 비정상상태의 혼합거동에 대해 종방향 및 횡방향 분산계수를 동시에 산정할 수 있는 방법은 추적법 계열의 2차원 유관추적법(2D STRP)이 유일하다. 본 연구에서는 하천에 유입된 오염물질의 2차원 혼합해석을 위한 수치모형을 개발하였으며, 개발된 모형의 수치해를 바탕으로 다양한 Peclet 수의 범위에 대해 기존연구에서 제시된 2D STRP의 적용범위 및 성능을 정량적으로 분석하였다. 분석된 정보를 바탕으로 기존 2D STRP의 한계를 극복하기 위한 개선된 2차원 유관추적법(2D STRP-i)을 개발하고, 사행하천을 모형화한 실규모 하천실험시설에서 검증하였다. 기존 2D STRP의 성능평가 결과, Peclet 수가 낮은 조건일수록 농도분포의 예측 정확도가 감소하는 경향을 보였으며, 하안 경계에 도달하는 농도가 증가할수록 부정확한 결과를 초래하는 것으로 나타났다. 본 연구에서는 기존 2D STRP의 한계를 보완하여 더욱 정확한 분산계수를 산정하고자 하안 경계면 조건을 고려한 2차원 유관추적법(2D STRP-i)을 개발하였다. 2D STRP-i는 직교-곡선좌표계 기반의 2차원 이송-분산 방정식을 바탕으로 횡방향 유속분포 및 하안 경계조건을 고려할 수 있도록 개선되었다. 2D STRP-i는 공간적으로 상이한 이송효과 및 하안경계 조건을 적절히 반영함으로써 농도분포의 예측 정확도를 개선 시키는 것으로 평가되었으며, 하안경계면에서 농도가 증가하는 구간에서 기존 2D STRP의 결과와 비교하여 더욱 정확한 농도분포 및 분산계수를 제공하는 것으로 밝혀졌다.

• Journal of Korean Society for Geospatial Information Science
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• v.10 no.2 s.20
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• pp.57-66
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• 2002

This paper establised GPS network consist of 75km average baseline lengths over Jeollanamdo and Jeollabukdo nine point station and fixed Gwangju point station. We quantitavely analyzed how much precision of the baseline determination is improved for GPS survey when using the precise eqhemeris instead of tile broadcast ephemeris of GPS satellites. The observed data for each baseline were processed two times with the same conditions alternately changing the broadcast and the precise ephemeris. The standard deviations from the repeated measurments for each baseline ara compared between the results of using the broadcast ephemeris and the precise ephemeris. As the results, the precision, stability and reliability of the baseline determination using the precise ephemeris is better than those of using the broadcast ephemeris for all baselines.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.10
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• pp.1508-1517
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• 1993

In this paper, we propose the modeling of a wireless communication system using CSMA protocol, present analytical evalution and simulation as a function of arrival rate and mean END-to-END delay in the distributed packet radio network. Asynchronous 1-persistent CSMA protocol is used in wireless communication system with half duplex. We assume that all terminals are to be in the close range of each other, suitably located in the local area. The traffic presented to a common channel is assumed to be poisson distribution. Analytical model is based on a M/D/1 with breakdown. In conclusion for wireless network model proposed in this paper is suitable for packet arrival rate of 2 packet/sec with mean packet delay time less than 2 times the packet transmission time.

• The KIPS Transactions:PartB
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• v.15B no.6
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• pp.595-602
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• 2008

The focused word of each sentence is a help in recognizing and understanding spoken Korean. To find the method of focused word spotting at spoken speech signal, we made an analysis of the average and variance of Fundamental Frequency and the average energy extracted from a focused word and the other words in a sentence by experiments with the speech data from 100 spoken sentences. The result showed that focused words have either higher relative average F0 or higher relative variances of F0 than other words. Our findings are to make a contribution to getting prosodic characteristics of spoken Korean and keyword extraction based on natural language processing.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.2
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• pp.219-226
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• 2013

Distributed multi-hop relay scheme to reduce delay-constrained outage probability for broadcast network is proposed. We consider multi-hop relay scheme, which is similar to distributed beamforming, where multiple nodes simultaneously relay packets, and we propose channel access control and power control for relaying nodes to satisfy energy constraint. Compared with flooding which is multi-hop relay scheme used for ZigBee, the proposed scheme is better in terms of outage probability and average reception throughput.

• Journal of Korea Water Resources Association
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• v.36 no.2
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• pp.143-152
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• 2003

This paper suggests the improvement of the Sumjinkang for the estimation of areal averages of heavy rainfall events based on the optimal network and three existing networks. The problem consists of minimizing an objective function which includes both the accuracy of the areal mean estimation as expressed by the Kriging variance and the economic cost of the data collection. The wellknown geostatistical variance-reduction method is used in combination with SATS which is an algorithm of minimization. At the first stage, two kinds of optimal solutions are obtained by two trade-off coefficients. One of them is a optimal solution, the other is an alternative. At the second stage, a quasi optimal network and a quasi alternative are suggested so that the existing raingages near to the selected optimal raingages are included in the two solutions instead of gages of new gages.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.6
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• pp.1238-1249
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• 1989

본 연구에서는 분무체적에 영향을 미치는 분사차압, 주위공기밀도, 노즐공의 직경과 분무각을 변수로 하여 상관관계식을 이론적으로 유도하고 이를 근거로 하여 분 무의 평균공연비 증대를 향상시키는 방안을 제시하였다.

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.90-93
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• 1999

본 논문에서는 캐리어의 동기가 맞았다는 가정 하에서 초기동기 직렬탐색 방식중의 하나인 Multiple Dwell 방식을 사용하여 각각의 초기동기 평균 획득시간과 분산 값을 비교하였다. 문턱값의 설정은 Maximum Likelihood 방식을 도입하여 MATLAB으로 이론값을 계산하고, 이를 SPW라는 시뮬레이션 툴로 모델링을 하여 시뮬레이션 값과 이론값을 비교 분석하였다. 신호 대 잡음비에 대한 Multiple Dwell 방식의 성능을 비교 분석한 결과. Dwell의 수가 증가할수록 성능은 개선되지만 Dwell의 수가 2일 때가 성능 개선 폭이 가장 컸고 Dwell의 수가 4이상에서는 개선 폭이 아주 작아짐 을 보였다.