• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권4호
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• pp.1006-1025
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• 2012

Improving the quality of service in IP networks is a major challenge for real-time voice communications. In particular, packet arrival-delay variation, so-called "jitter," is one of the main factors that degrade the quality of voice in mobile devices with the voice-over Internet protocol (VoIP). To resolve this issue, a receiver-based enhanced timing recovery algorithm combined with active jitter estimation is proposed. The proposed algorithm copes with the effect of transmission jitter by expanding or compressing each packet according to the predicted network delay and variations. Additionally, the active network jitter estimation incorporates rapid detection of delay spikes and reacts to changes in network conditions. Extensive simulations have shown that the proposed algorithm delivers high voice quality by pursuing an optimal trade-off between average buffering delay and packet loss rate.

• 한국디지털건축인테리어학회논문집
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• 제10권3호
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• pp.11-18
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• 2010

Cost estimation through fast and correct quantity take offs are crucial in the process of construction project. The existing methods for cost estimation are mainly based on 2D-based drawings and the estimation result tends to be different according to the estimator's experience, the quality and quantity of used information and estimation time. To solve these problems, the domestic construction industry have recently tried to use the data extracted from 3D data modeling based on BIM(Building Information Modeling) in order to achieve more accurate and objective cost estimation. However it tends to increase dramatically the quantity of information that can be used in cost estimation by estimators. Therefore in order to achieve quality information data from 3D data modeling, the characteristics of the project should be reflected on the 3D model and it is most important to extract information only for cost estimation from the whole 3D model fast and accurately. Thus this study aims to propose the 3D modeling method through Data Normalization which maximizes the usability of 3D Data modeling in cost estimation process.

• 한국환경과학회지
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• 제5권3호
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• pp.377-385
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• 1996

This study aims at the estimation of a river management flow in urban basin analyzing Sinchun basin to be the tributary of Kumho river basin. The river management flow has to satisfy a low flow as natural flow and an environmental preservation flow estimated by a dilution flow to satisfy a target water quality in drought flow. Therefore for the estimation of a river management flow in Sinchun in this study, first Tank model as a basin runoff model estimates a low flow, a drought flow from a flow duration curve in Sinchun, second QUAL2E model as water quality model simulates water quality in Sinchun and estimates environmental preservation flow to satisfy a target water qua%its, BOD 8 mg/l by a dilution flow derived from Kumho river, Nakdong river and around water. And the river management flow is estimated by addition of a use flow and a loss flow to more flow between a low-flow and an environmental preservation flow.

• International Journal of Internet, Broadcasting and Communication
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• 제12권2호
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• pp.21-29
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• 2020

This paper presents an effective single image haze removal using edge-preserving and adaptive transmission estimation to enhance the visibility of outdoor images vulnerable to weather and environmental conditions with computational complexity reduction. The conventional methods involve the time-consuming refinement process. The proposed transmission estimation however does not require the refinement, since it preserves the edges effectively, which selects one between the pixel-based dark channel and the patch-based dark channel in the vicinity of edges. Moreover, we propose an adaptive transmission estimation to improve the visual quality particularly in bright areas like sky. Experimental results with various hazy images represent that the proposed method is superior to the conventional methods in both subjective visual quality and computational complexity. The proposed method can be adopted to compose a haze removal module for realtime devices such as mobile devices, digital cameras, autonomous vehicles, and so on as well as PCs that have enough processing resources.

• 한국대기환경학회지
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• 제15권6호
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• pp.813-826
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• 1999

To understand the present status of air pollutant emission data for the greater Seoul area, existing air pollutant emission data were analyzed and compared. For the criteria pollutants, estimation methods of emissions from point, line, and area sources adopted in the previous studies were analyzed and their results were compared. Two sets of VOC emission estimation were also compared and analyzed. There exists a large discrepancy among previous emission data due to the differences in the scope of emission sources and the estimation method including emission factors employed in each estimation. Applications of previous air pollutant emission studies for air quality modeling and related problems were discussed.

• 품질경영학회지
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• 제38권4호
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• pp.480-490
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• 2010

In this paper, two estimation methods(least square estimation and maximum likelihood estimation) were compared for Weibull distribution and Type I censoring. Data obtained by Monte Carlo simulation were analyzed using two estimation methods and analysis results were compared by MSE(Mean Squared Error). Comparison results show that maximum likelihood estimator is better for censored data and complete data with more than 30 samples and least square estimator is better for small size complete data(less than and equal to 20 samples).

• Journal of Welding and Joining
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• 제18권3호
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• pp.114-121
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• 2000

Since resistance spot welding has become one of the most popular sheet metal fabrication processes, a strong emphasis is being put on the quality of the welds. Throughout the years many quality estimation systems have been developed by many researchers to ensure weld quality. In this study, the process variables, which were monitored in the primary circuit of the welding machine, are used to estimate the weld quality with Hopfield neural network. The primary dynamic resistance is vectorized and stored as five patterns in the network. As the welding is done, the dynamic resistance patterns are recognized and the quality is estimated with the proposed method. Due to the primary process variables, it is possible to utilize this algorithms as an in-process real time quality monitoring system.

• 한국생산제조학회지
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• 제7권6호
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• pp.102-109
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• 1998

As the fundamental study of an active suspension system, computer simulation is performed using a quarter model. Design data for the development of active suspension system are presented through performance estimation of active control laws in the time and frequency domain. The verification of compromise between ride quality and handling characteristics is carried out.

• 한국음향학회지
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• 제32권2호
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• pp.157-166
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• 2013

본 논문은 패킷 손실의 영향을 이용한 비 침입적 음질 평가 방법을 제안한다. 패킷 손실은 패킷 기반의 통신 시스템에서 음질을 저하시키는 주된 요소이며 그 영향은 코덱에 내장된 패킷 손실 은닉 알고리듬에 의해 결정된다. 패킷 손실 영향을 반영한 음질평가 시스템을 위해 VoIP 에서 협대역 코덱으로 사용되는 코덱 중 하나인 G.729를 선택하였으며, 음성 특징에 따른 패킷 손실 영향을 구분하기 위해서 G.729 코덱의 음성 파라미터를 이용한 한 음성 특성 분류기를 설계하였다. 이후, 각각의 패킷 특성에 따른 음질 저하의 정도를 수치화하기 위해 원 PESQ-LQ점수와 상관계수를 최대화하는 음질 저하 가중치를 반복적으로 구하였으며, 최종 음질 저하는 가중합으로 구하였다. 그 결과 제안한 모델과 PESQ-LQ의 상관계수는 칩입 모델 에서는 0.8950를, 비 침입 모델 에서는 0.8911의 결과를 나타내었다.

• 한국항행학회논문지
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• 제16권6호
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• pp.975-981
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• 2012

서로 다른 품질을 요구하는 데이터들의 동시 전송 또는 효율적인 영상전송시스템에 응용될 수 있는 계층 16QAM (Quadrature Amplitude Modulation) 시스템에 대한 SNR 추정성능에 대해 분석한다. 계층 16QAM은 계층 변조파라미터를 제어하여 성좌점들의 형태를 변형시켜 사용자에게 고품질과 저품질 데이터서비스를 동시에 제공할 수 있는 변조 시스템이다. AWGN (Additive White Gaussian Noise) 채널환경에서 계층 16QAM 시스템에서 계층변조파라미터와 성좌점별 특성을 고려한 SNR (Signal to Noise power Ratio) 추정성능 특성을 분석하였다. 시뮬레이션 결과, 계층 16QAM의 여러성좌점들 중에 SNR 추정이 상대적으로 정확하게 이루어지는 성좌점이 존재함을 확인하였고, 계층변조파라미터 값에 따라 SNR 추정이 유리한 영역이 달라진다는 것을 알아내었다.