• Journal of information and communication convergence engineering
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• 제8권3호
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• pp.267-272
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• 2010

For the last decade, recurrent neural networks (RNNs) have been commonly applied to communications channel equalization. The major problems of gradient-based learning techniques, employed to train recurrent neural networks are slow convergence rates and long training sequences. In high-speed communications system, short training symbols and fast convergence speed are essentially required. In this paper, the derivative-free Kalman filter, so called the unscented Kalman filter (UKF), for training a fully connected RNN is presented in a state-space formulation of the system. The main features of the proposed recurrent neural equalizer are fast convergence speed and good performance using relatively short training symbols without the derivative computation. Through experiments of nonlinear channel equalization, the performance of the RNN with a derivative-free Kalman filter is evaluated.

• ETRI Journal
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• 제34권4호
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• pp.613-616
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• 2012

A multi-spot-beam satellite is an attractive technique for future satellite communications since it can support high data rates by projecting high power density to each spot beam and can reuse a frequency in different cells to increase the total system capacity. In this letter, we propose a resource management technique adjusting the bandwidth of each beam to minimize the difference between the traffic demand and allocated capacity. This represents a reasonable solution for dynamic bandwidth allocation, considering a trade-off between the maximum total capacity and fairness among the spot beams with different traffic demands.

• ETRI Journal
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• 제31권1호
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• pp.65-67
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• 2009

We introduce an advanced terrestrial digital multimedia broadcasting (AT-DMB) system that overcomes the limitation of data transmission rates of T-DMB by doubling it with the same frequency bandwidth. In this letter, we propose an efficient algorithm which generates a scalable transport stream in AT-DMB by multiplexing certain types of elementary streams encoded using scalable video coding and an MPEG-surround audio coder for high-quality multimedia services.

• 대한전기학회논문지
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• 제38권2호
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• pp.127-136
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• 1989

This paper describes the parameter convergence properties of an adaptive system to identify a single-input single-output plant model. It is demonstrated that, by using power spectrum analysis, the persistency of excitation (PE) condition in order to guarantee the exponential stability of the adaptive control system can be transformed into the positive definite behavior for the auto-correlation function matrix of adaptive signal. The existence of parameter nominal values can be analyzed by this condition and the convergence rates of parameter are determined by examining the auto-correlation function. We may use the sufficient richness (SR) of input spectrum instead of the PE condition to analyze the parameter boundedness. It can be shown that the eigen values of the auto-correlation function are always related with adaptive gain, input amplitude and positions or numbers of input spectra. In each case, the variation of parameter convergence rate can be also verified.

• 한국멀티미디어학회논문지
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• 제22권2호
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• pp.311-321
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• 2019

Virtual reality applications in Head-Mounted Displays require high frame rates and low latency rendering techniques. Ray tracing offers many benefits, such as high-quality image generation, but has not been utilized due to lower performance than rasterization. But that can obtain good result combined with gaze-tracking technology and human visual system's operation principle. In this paper, we propose a method to optimize the foveated sampling map and to maintain the visual quality through the fast voronoi nearest interpolation. The proposed method further reduces the computational cost that has been improved by the previous foveated sampling. It also smoothes the voronoi boundary using adaptive sibson interpolation, which was not possible in real-time. As a result, the proposed method can render real-time high-quality images with low visual difference.

• 한국융합학회논문지
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• 제8권10호
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• pp.231-238
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• 2017

본 연구에서는 융합 시대를 맞이하여 국내 수출에 영향을 미치는 지표들을 찾고자 금리와 원/달러, 원/엔, 원/위안화를 선정하였다. 지난 2000년 1월 이후 210개월 동안 상관관계와 회귀분석, 지표분석, 모형분석 등을 시도하였다. 분석결과 상관분석에서는 수출이 원/달러, 원/위안화, 원/엔 환율과 음(-)의 관계를 보여 서로 방향성이 다르게 나타났다. 회귀분석에서는 수출에 대해 금리와 원/달러만 통계적으로 유의하게 나타났다. Coefficient가 금리는 양(+)의 값으로, 원/달러는 음(-)의 값으로 산출되었다. 원/달러 하락이 수출 증가에 긍정적으로 작용하는 것으로 추정되었다. 본 연구에서 원/달러 환율이 하락하면 수출이 증가하는 것으로 나타나 기존 선행연구와 다르게 나타났다. 그래서 시간차에 의한 선후행 관계를 다시 살펴볼 필요성이 제기되었다. 우리나라는 수출에 대한 의존도가 높은 편이다. 따라서 수출 증가를 위해 수출에 영향을 미치는 지표들에 관한 연구가 지속되어야 할 것이다.

• 한국농공학회지
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• 제39권2호
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• pp.32-43
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• 1997

Abstract A series of permeability tests was performed on the mixtures with specific mixing rates of sand and bentonite using modified rigid-wall permeameter. Sand-bentonite mixtures were permeated by organics, ethanol and TCE. Permeability of bentonite with several mixing rates had a tendency to decrease up to initial one pore volume and permeability was thereafter converged to a constant value. When sand-bentonite mixtures was permeated by water, permeability was decreased at the beginning but it was thereafter converged to a constant. Among several mixing rates, permeability was greatly decreased at 15% of mixing rate. When sand-bentonite mixtures with 15% mixing rate was permeated by ethanol, permeability was about 10 times larger value than permeability of water. Peameability was shown greater values when permeated by TCE (TrichloroEthylene) followed by ethanol. Suitable mixing rate of sand-bentonite for a liner of waste landfills was detected.

• Applied Science and Convergence Technology
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• 제26권5호
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• pp.95-109
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• 2017

There are several contributions to the gas load of a system of which often the most important is outgassing. Adsorption occurs via two main processes, physisorption and chemisorption, and can be described using five (or six) classifying isotherms. Outgassing is the result of desorption of previously adsorbed molecules, bulk diffusion, permeation and vapourisation. Looking at the desorption rate, pumping speed and readsorption on surfaces, the net outgassing of the system can be calculated. There is significant variation in measured outgassing rates between different materials but also between published rates for the same materials, in part due to the number of different methods used to measure outgassing. This article aims to review the outgassing process, outgassing rates, measurement methods and techniques that can be used to reduce the outgassing of a system.

• 한국콘텐츠학회논문지
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• 제4권3호
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• pp.99-105
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• 2004

이 논문은 다층퍼셉트론의 학습을 빠르게 하기 위한 최적 학습률을 제안한다. 이 학습률은 한 뉴런에 연결된 가중치들에 대한 학습률과, 중간층에 가상의 목표값을 설정하기 위한 학습률로 나타난다. 그 결과, 중간층 가중치의 최적 학습률은 가상의 중간층 목표값 할당 성분과 중간층 오차함수를 최소화 시키고자하는 성분의 곱으로 나타난다. 제안한 방법은 고립단어인식과 필기체 숫자 인식 문제의 시뮬레이션으로 효용성을 확인하였다.

• 디지털융복합연구
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• 제3권1호
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• pp.115-148
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• 2005

This study is intended to suggest a more reasonable and practical method of estimating discount & capitalization rate for valuation of closely-held culture content business, that is, to modify the Buildup Summation Model(which is recommended for the closely-held business by the NACVA) by adopting the weighted ratings in the CT Project Investment Evaluation of the Korea Culture Contents Association to risk factors of the Buildup Summation Model. This method is ease to apply for closely-held culture content business and has advantages in applying the weighted rates based on the characteristics of respective culture contents. And it can make up for the Weighted Average Cost of Capital (WACC) which shows generally low discount rates.