• 환경영향평가
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• 제20권6호
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• pp.879-890
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• 2011

The GOSAT (Greenhouse gases Observing SATellite) data provide new opportunities the most regionally complete and up-to-date assessment of $CO_2$. However, in practice, GOSAT records often suffer from missing data values mainly due to unfavorable meteorological condition in specific time periods of data acquisition. The aim of this research was to identify optimal spatial interpolation techniques to ensure the continuity of $CO_2$ from samples taken in the North East Asia. The accuracy among ordinary kriging (OK), universal kriging (UK) and simple kriging (SK) was compared based on the combined consideration of $R^2$ values, Root Mean Square Error (RMSE), Mean Error (ME) for variogram models. Cross validation for 1312 random sampling points indicate that the (UK) kriging is the best geostatistical method for spatial predictions of $CO_2$ in the East Asia region. The results from this study can be useful for selecting optimal kriging algorithm to produce $CO_2$ map of various landscapes. Also, data users may benefit from a statistical approach that would allow them to better understand the uncertainty and limitations of the GOSAT sample data.

• 컴퓨터교육학회논문지
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• 제9권1호
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• pp.89-95
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• 2006

컴퓨터그래픽스에서 다루어지는 3차원 물체들에 대한 곡률과 같은 기하학적 특성들은 메쉬의 모양을 해석함에 있어 매우 중요한 역할을 한다. 부드러운 곡면에서 정의되는 곡률은 메쉬와 같은 이산적 형태에서는 수학적으로 정의할 수 없다. 그러므로 이러한 이산곡률을 어떻게 정의하느냐에 따라 기하학적 연산들의 결과는 많은 영향을 받는다. 본 논문에서는 기존의 곡률 계산법에서 사용하고 있는 단면곡률 계산법의 오류를 지적하고 이에 대한 해결책으로 베이지어 곡선을 이용한 포물선-기반 이산 곡률 계산법을 제시한다. 제안된 방법을 통하면 보다 뾰족한 형태의 정점과 완만한 형태의 정점을 구분할 수 있어서 메쉬 간략화와 같은 기하학적 연산에 쉽게 적용가능하다.

• 한국정보통신학회논문지
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• 제4권2호
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• pp.407-416
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• 2000

본 논문은 트리구조의 필터뱅크를 이용하여 필터링을 할 때 데시메이션으로 인해서 생기는 왜곡을 보상하기 위해서 보조 필터(엘리어싱 제거기)를 사용하는 방법을 제안하고 이를 이용하여 잡음을 제거하여 음질을 향상시키는 실험을 행했다. 입력신호는 두 채널의 분석필터에 의해 서브밴드로 분해된 후 데시메이션되고 다시 각 서브밴드로 분해된 신호를 적응필터를 이용하여 필터링을 한다. 이러한 기법으로 각 주파수 대역을 균일한 대역으로 분해할 수 있으며 각 서브밴드별로 각기 다른 수렴상수를 사용할 수 있어서 수렴속도를 향상시킬 수 있는 장점이 있다. 특히 잡음 제거나 음질 향상에 서브밴드 적응 필터뱅크를 응용할 경우 수렴속도가 빨라야 하며, 임펄스 응답의 길이가 긴 시스템을 모델링하는 데 응용할 수 있는 장점이 있다. 적응필터 계수의 갱신 방법으로는 VSS(Variable Step Size) LMS 알고리듬을 사용하였으며, 실험 결과, 기존의 서브밴드 구조보다 제안한 구조가 최소 평균 오차나 수렴성능 면에서 우수한 성능을 보였다.

• 전기전자학회논문지
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• 제15권3호
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• pp.235-240
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• 2011

지상파 DTV 표준인 DVB-T에 채택된 분산 파일럿은 블록 형태와 빗 형태의 파일럿 배치의 장점을 모두 가지며 전송 효율을 증가시킨다. 데이터 부반송파에 대한 채널 추정을 위해 파일럿 부반송파를 이용한 시간 및 주파수 영역 추정이 필요하다. MSE (mean square error) 관점에서 최적인 2D Wiener 추정기는 너무 복잡하여 실현성이 떨어진다. 본 논문에서는 가산 백색 가우스 잡음의 전력을 추정하여 이를 채널 추정치에서 제거하는 새로운 채널 추정 방식을 제안한다. 또한 모의 실험을 통해 제안된 방식이 페이딩 채널에서 2차원 선형 보간 방식보다 채널 추정 성능이 우수함을 보인다.

• 한국광학회지
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• 제15권6호
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• pp.539-546
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• 2004

고밀도 AWG (Arrayed-Waveguide Grating)의 광 경로차 에러를 정확히 측정하기 위하여 개선된 형태의 저간섭 광원 간섭계를 구성하였고, 새로운 해석방법을 제시하였다. 소프트웨어적인 방법을 이용하여 하드웨어면에서 실험장치를 간략화할 수 있었다. 또한 인접 간섭신호들 사이의 실제 피크 위치 차이를 보간법을 이용하여 정확히 측정할 수 있다. 특정 AWG의 위상 에러를 측정하였고, 이 에러를 가정하여 계산한 파장 투과 특성이 실제 AWG의 파장투과 특성과 유사함을 보임으로써, 제시한 측정 장치의 정확성을 입증하였다.

• 한국정밀공학회지
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• 제12권10호
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• pp.40-49
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• 1995

This paper presents the performance and problems in analysis method and testing system of Electronic Speckle Pattern Interferometry (ESPI) method, in measuring two - dimensional in-plane displacement. The anyalysis result of measurement by ESPE is quite comparable to that tof measurement by strain gauge method. This implies that the method of ESPE is a very effective tool in non-contact two-dimensional in-plane strain analysis. But there is a controversal point, measurment error. This error is discussed to be affected not by ESPE method itself, but by its analysis scheme of the interference fringe, where the first-order interpolation has been applied to the points of strain measured. In this case, it is turned out that the more errors would be occurred in the large interval of fringe. And so this paper describes a computer method for drawing when the height is available only for some arbitrary collection of points. The method is based on a distance-weighted, last- squares approximation technique with the weight varying with the distance of the data points.

• 한국도로학회논문집
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• 제15권4호
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• pp.21-29
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• 2013

PURPOSES : The objective of this study is to provide for the overall SPL (Sound Pressure Level) prediction model by using the NCPX (Noble Close Proximity) measurement method in terms of regression equations. METHODS: Many methods can be used to measure the traffic noise. However, NCPX measurement can powerfully measure the friction noise originated somewhere between tire and pavement by attaching the microphone at the proximity location of tire. The overall SPL(Sound Pressure Level) calculated by NCPX method depends on the vehicle speed, and the basic equation form of the prediction model for overall SPL was used, according to the previous studies (Bloemhof, 1986; Cho and Mun, 2008a; Cho and Mun, 2008b; Cho and Mun, 2008c). RESULTS : After developing the prediction model, the prediction model was verified by the correlation analysis and RMSE (Root Mean Squared Error). Furthermore, the correlation was resulted in good agreement. CONCLUSIONS: If the polynomial overall SPL prediction model can be used, the special cautions are required in terms of considering the interpolation points between vehicle speeds as well as overall SPLs.

• Journal of Positioning, Navigation, and Timing
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• 제3권4호
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• pp.155-161
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• 2014

The purpose of this study is to develop precise point positioning (PPP) algorithms based on GLONASS code-pseudorange, verify their performance and present their utility. As the basic correction models of PPP, we applied Inter Frequency Bias (IFB), relativistic effect, satellite antenna phase center offset, and satellite orbit and satellite clock errors, ionospheric errors, and tropospheric errors that must be provided on a real-time basis. The satellite orbit and satellite clock errors provided by Information-Analytical Centre (IAC) are interpolated at each observation epoch by applying the Lagrange polynomial method and linear interpolation method. We applied Global Ionosphere Maps (GIM) provided by International GNSS Service (IGS) for ionospheric errors, and increased the positioning accuracy by applying the true value calculated with GIPSY for tropospheric errors. As a result of testing the developed GLONASS PPP algorithms for four days, the horizontal error was approximately 1.4 ~ 1.5 m and the vertical error was approximately 2.5 ~ 2.8 m, showing that the accuracy is similar to that of GPS PPP.

• 동력기계공학회지
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• 제10권4호
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• pp.56-64
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• 2006

This paper shows the development process of a straight-type five-hole pressure probe for measuring three-dimensional flow velocity components. The data reduction method using a bi-cubic curve-fitting program in a new calibration map was introduced in this study. This new calibration map can be applied up to the application angle, ${\pm}55^{\circ}$ of a probe. As a result, for the application angle of ${\pm}45^{\circ}$, an error for yaw and pitch angles appeared from $-1.76^{\circ}\;to\;1.83^{\circ}$ and from $-1.91^{\circ}\;to\;1.75^{\circ}$, respectively. Moreover, an error for a vector magnitude and a static pressure compared with a dynamic one showed from -7.83% to 4.87% and from -0.73 to 0.77, respectively. Even though this data reduction method showed unsatisfactory errors in a vector magnitude, it resulted in an easy and simple application method. Especially, when it was applied to an actual flow field including a swirling flow, a good result came out on the whole. However, in order to obtain a better result, it is thought that a more sophisticated interpolation method needs to be introduced.

• Journal of information and communication convergence engineering
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• 제5권2호
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• pp.83-87
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• 2007

This research studies real time interaction and dynamic data shared through 3D scenes in virtual network environments. In a distributed virtual environment of client-server structure, consistency is maintained by the static information exchange; as jerks occur by packet delay when updating messages of dynamic data exchanges are broadcasted disorderly, the network bottleneck is reduced by predicting the movement path by using the Dead-reckoning algorithm. In Dead-reckoning path prediction, the error between the estimated and the actual static values which is over the threshold based on the shared object location requires interpolation and multicasting of the previous location by the ESPDU of DIS. The shared dynamic data of the 3D virtual environment is implementation using the VRML.