• Journal of Astronomy and Space Sciences
• /
• v.14 no.2
• /
• pp.347-354
• /
• 1997

We developed a GPS phase data processing S/W system which calculates baseline vectors and distances between two points located in the surface of the Earth. For this development a Double-Difference mothod and L1 carrier phase data from GPS(Global positioning System) were used. This S/W system consists of four main parts: satellite position calculation, Single-Difference equation, Double-Difference equation, and correlation. To verify our S/W, we fixed KAO($N36^{circ}.37,E127^{circ}.37,H77.61m$), one of the International GPS Services for Geodynamics, which is located at Tae-Jon, and we measured baseline vectors and relative distances with data from observations at approximate baseline distances of 2.7, 42.1, 81.1, 146.6km. Then we compared the vectors and distances with the data which we obtained from the GPSurvey S/W system, with the L1/L2 ION-Free method and broadcast ephemeris. From the comparison of the vectors and distances with the data from the GPSurvey S/W system, we found baseline vectors X, Y, Z and baseline distances matched well within the extent of 50cm and 10cm, respectively.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.43 no.3
• /
• pp.265-271
• /
• 2015

In this study, optical design for small satellite camera equipped with online optical compensation movements has been conducted. Satellite camera equipped with compensation movements at M2 mirror and focal plane can guarantee the MTF performance through the focal plane image stabilization and the on-orbit optical alignment. The designed optical system is schmidt-cassegrain type that has M1 mirror of a diameter 200mm, GSD 3.8m at an altitude of 700km, and 50 % MTF performance. The performance of the designed optical system has been analyzed through the method of ray aberration curve, spot diagram, and MTF. It has been found by the optical performance analysis that the designed optical system satisfies the optical requirements of satellite camera equipped with online optical compensation movements.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.39 no.3
• /
• pp.225-231
• /
• 2011

The satellite clock anomalies, one of the abnormal signal factors of the GPS satellites, can have a significant impact on the GPS measurements. However, it can be difficult to detect the anomalies of the satellites clock before the range of the satellites clock error becomes bigger than the range of the other factors, due to the measurement including error of the orbit, ionosphere delay, troposphere delay, multipath and receiver clock. In order to perform quick and accurate detection by minimization of critical range in anomalies of the satellites clock, this paper suggested a solution to detect precise anomalies of the satellites clock after application of carrier smoothing filter from measurement by dual-frequency and adjustment of errors which can be occurred by other factor and the receiver clock errors. The performance of the proposed method was confirmed by comparing to the satellite clock biases which are provided by IGS.

• Journal of Astronomy and Space Sciences
• /
• v.24 no.4
• /
• pp.297-308
• /
• 2007

The AOPOD (Atmosphere Occultation and Precision Orbit Determination) system, the secondary payload of KOMPSAT (KOrea Multi-Purpose SATellite)-5 scheduled to be launched in 2010, shall provide GPS radio occultation data. In this paper, we simulated the GPS radio occultation characteristic of KOMPSAT-5 and retrieved electron density profiles using KROPS (KASI Radio Occultation Processing Software). The electron density retrieved from CHAMP (CHAllenging Minisatellite Payload) GPS radio occultation data on June 20, 2004 was compared with IRI (International Reference Ionosphere) - 2001, PLP (Planar Langmuir Probe), and ionosonde measurements. When the result was compared with ionosonde measurements, the discrepancies were 5 km on the $F_2$ peak height ($hmF_2$) and $3{\times}10^{10}el/m^3$ on the electron density of the $F_2$ peak height ($NmF_2$). By comparing with the Laugmuir Probe measurements of CHAMP satellite (PLP), both agrees with $1.6{\times}10^{11}el/m^3$ at the height of 365.6 km.

• Journal of Astronomy and Space Sciences
• /
• v.25 no.1
• /
• pp.43-52
• /
• 2008

As the next generation of global satellite navigation system, the Galileo project is about to witness an initial orbit validation stage as the successful test of navigation message transmission from Giove-A in 2007. The Space Geodesy division ana the Radio Astronomy division of the Korea Astronomy & Space Science Institute had collaborated on the field survey for the Galileo Sensor Station (GSS) RF environment of the proposed site near Jeju Tamla University from August 3rd to August 5th, 2006. The power spectrums were measured in full-band $(800{\sim}2000MHz)$ and in-band (E5, E6 and L1 band) in frequency domain for 24 hours respectively. Finally, we performed a time domain analysis to characterize strong in-band interference source based on the result of the previous step.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.40 no.3
• /
• pp.317-326
• /
• 2016

In this study, running stability and ride quality analyses, applying the 'ISO 3888 (double lane change)' and 'ISO 2631-1' (mechanical vibration and shock) tests, were performed for the suspension optimization of the Korean personal rapid transit (PRT) vehicle. The suspension optimization results for running stability and ride quality were derived by applying the multiresponse surface method. From the comparisons of the optimization results for different ratios of the objective functions of running stability and ride quality, we derived the best objective function ratio of 3.9-to-6.1 to improve both the running stability and the ride quality. With the optimized results, the suspension stiffness became 30.68 N/mm, between the value of the $S_2$ and $S_3$ models, and the damping coefficient equaled that of the $D_1$ model. When compared with the suspension of the current PRT vehicle, the roll angle, yaw rate, sideslip angle, and ride comfort were improved by 0.37, 0.37, 2.8, and 5, respectively.

• Journal of the Korean Chemical Society
• /
• v.34 no.3
• /
• pp.239-247
• /
• 1990

The gas-phase S_N2$ reactions can be classified into neutral bimolecular, solvated, and ionic reactions; the neutral bimolecular reaction proceeds via retention mechanism whereas the ionic reaction produces inversion products. In the reaction of solvated nucleophile with one solvent molecule, a six-center transition state (TS) is formed and the two processes i.e., retention and inversion, are found to compete with a favored path depending on the electronic effect of the nucleophile and substituents in the substrate and on the steric requirement. In the ionic reaction, the difference in the energy barrier between the two processes reduces to a small value when the substrate methyl group is made bulky, leaving ability of the leaving group is improved and at the same time the negative charge of the nucleophile is dispersed. When the reaction center atom in the $S_N2$ reaction is changed to a larger sized second row elements, the activation barrier decreases since the steric crowding in the penta-coordinated TS is relieved. However within the same row, the barrier was found to increase as the atomic size decreased. For the boron, B, the barrier height was the least since in addition to the relatively large atomic size compared to C and N, it forms tetra-coordinated TS so that the steric crowding becomes nearly negligible.

• Journal of Korean Society of Transportation
• /
• v.22 no.6
• /
• pp.35-47
• /
• 2004

Using data envelopment analysis, this paper annually estimates Malmquist total factor productivity indices and decomposes them into productive efficiency change, technical change, and scale change components for three publicly-owned rail transit properties: the Seoul Subway Corporation(SSC), the Seoul Metropolitan Electrified Railways Sector of Korea National Railroad (SMESRS) and the Busan Urban Transit Authority (BUTA). The paper then conceptualizes that the property produces a single output(car-kilometers) using four inputs(labor, electricity, car and maintenance, and track) and uses unbalanced panel data consisted of annual observations on SSC, SMESRS and BUTA. The results show that the average annual growth rate of productivity of the three properties is 6.6 percent, which is 0.5 percent less than the average annual increasing rate of their labor price. They also show that the greatest part of the growth in productivity is explained by technical change and to a lesser degree by scale change and changes in productive efficiency though each of the three components contributes more than 20 percent to the growth in productivity, These results suggest that the three properties should base the increasing rate of their wages on the growth rate of their productivity and utilize existing technologies more efficiently prior to introducing new ones to raise their productivity, and that all the three components should be considered to evaluate their productivity more correctly.

• Journal of Cadastre & Land InformatiX
• /
• v.50 no.1
• /
• pp.107-123
• /
• 2020

With stabilization of the recent multi-GNSS infrastructure, and as multi-GNSS has been proven to be effective in improving the accuracy of the positioning performance in various industrial sectors. In this study, in view that SF(Single frequency) GNSS receivers are widely used due to the low costs, evaluate effectiveness of SF Real Time Point Positioning(SF-RT-PP) based on four multi-GNSS surveying methods with RTCM-SSR correction streams in static and kinematic modes, and also derive response challenges. Results of applying SSR correction streams, CNES presented good results compared to other SSR streams in 2D coordinate. Looking at the results of the SF-RT-PP surveying using SF signals from multi-GNSS, were able to identify the common cause of large deviations in the altitude components, as well as confirm the importance of signal bias correction according to combinations of different types of satellite signals and ionospheric delay compensation algorithm using undifferenced and uncombined observations. In addition, confirmed that the improvement of the infrastructure of Multi-GNSS allows SF-RT-SPP surveying with only one of the four GNSS satellites. In particular, in the case of code-based SF-RT-SPP measurements using SF signals from GPS satellites only, the difference in the application effect between broadcast ephemeris and SSR correction for satellite orbits/clocks was small, but in the case of ionospheric delay compensation, the use of SBAS correction information provided more than twice the accuracy compared to result of the Klobuchar model. With GPS and GLONASS, both the BDS and GALILEO constellations will be fully deployed in the end of 2020, and the greater benefits from the multi-GNSS integration can be expected. Specially, If RT-ionospheric correction services reflecting regional characteristics and SSR correction information reflecting atmospheric characteristics are carried out in real-time, expected that the utilization of SF-RT-PPP survey technology by multi-GNSS and various demands will be created in various industrial sectors.