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Effects of Tropospheric Mapping Functions on GPS Data Processing
원지혜,박관동,하지현,조정호 한국우주과학회 2010 Journal of Astronomy and Space Sciences Vol.27 No.1
In processing space geodetic data, mapping functions are used to convert the tropospheric signal delay along the zenith direction to the line of sight direction. In this study, we compared three mapping functions by evaluating their effects on the tropospheric signal delay and position estimates in GPS data processing. The three mapping functions tested are Niell Mapping Function (NMF), Vienna Mapping Function 1 (VMF1), and Global Mapping Function (GMF). The tropospheric delay and height estimates from VMF1 and GMF are compared with the ones obtained with NMF. The differences among mapping functions show annual signals with the maximum occurring in February or August. To quantitatively estimate the discrepancies among mapping functions, we calculated the maximum difference and the amplitude using a curve fitting technique. Both the maximum difference and amplitude have high correlations with the latitude of the site. Also, the smallest difference was found around 30°N and the amplitudes increase toward higher latitudes. In the height estimates, the choice of mapping function did not significantly affect the vertical velocity estimate, and the precision of height estimates was improved at most of the sites when VMF1 or GMF was used instead of NMF.
원지혜,김두식 사단법인 항법시스템학회 2015 Journal of Positioning, Navigation, and Timing Vol.4 No.2
In this study, the temporal and spatial variation in precipitable water vapor (PWV) was analyzed for typhoon Ewiniar which had made landfall in the Korean peninsula in 2006. To make a contour map of PWV, zenith total delay (ZTD) was calculated using about 60 GPS permanent stations in Korea, and the pressure and temperature data of nearby AWS stations were interpolated and applied to the equation for calculating the PWV. While Typhoon Ewiniar was migrating north from the southern coast to the eastern coast of Korea, the PWV migrated showing a spatial distribution similar to that of rainfall. Also, the fluctuating pattern of the normalized PWV was analyzed, and the moving speed of the PWV was estimated using the delay time of the increase/decrease pattern in the eight-test stations. The result indicated that the moving speed of the PWV was about 35 km/h, which was similar to the average moving speed of the typhoon (38.9 km/h).
원지혜,박관동,김두식,하지현 한국우주과학회 2011 Journal of Astronomy and Space Sciences Vol.28 No.4
The atmospheric infrared sounder (AIRS) sensor loaded on the Aqua satellite observes the global vertical structure of atmosphere and enables verification of the water vapor distribution over the entire area of South Korea. In this study, we performed a comparative analysis of the accuracy of the total precipitable water (TPW) provided as the AIRS level 2 standard retrieval product by Jet Propulsion Laboratory (JPL) over the South Korean area using the global positioning system (GPS) TPW data. The analysis TPW for the period of one year in 2008 showed that the accuracy of the data produced by the combination of the Advanced Microwave Sounding Unit sensor with the AIRS sensor to correct the effect of clouds (AIRS-X) was higher than that of the AIRS IR-only data (AIRS-I). The annual means of the root mean square error with reference to the GPS data were 5.2 kg/m^2 and 4.3 kg/m^2 for AIRS-I and AIRS-X, respectively. The accuracy of AIRS-X was higher in summer than in winter while measurement values of AIRS-I and AIRS-X were lower than those of GPS TPW to some extent.
우울증에 영향을 받는 파킨슨병의 진행 과정을 예측하는 영상 유전학적 접근법
원지혜(J.H.Won),박현진(H.Park) 대한전자공학회 2017 대한전자공학회 학술대회 Vol.2017 No.6
Depression occurs in around 40-45% of patients diagnosed with Parkinson’s disease (PD) and it often becomes worse as PD progress. Although underlying mechanisms of depression in PD are not clear, alteration in brain structure and genetic variants are known to contribute to its development. In this study, we aimed to explain clinical score of PD progression for PD patients with depression and non-PD patients with depression by features obtained from imaging genetics approach. Imaging genetics is a novel approach to identify genetic variants related to imaging features. All imaging and genetic data were obtained from openly accessible research database (PPMI). Imaging features were obtained through connectivity analysis derived from tractography of diffusion magnetic resonance imaging (MRI). We then identified genetic variants using the imaging features as intermediate phenotype according to the imaging genetics approach. The linear regression model was constructed to combine neuroimaging features and genetic factors to explain clinical scores of PD progression. We confirmed this linear model explains the clinical score well (coefficient of R<SUP>2</SUP> of 0.728 and adjusted R<SUP>2</SUP>of0.57)