• Journal of Electrochemical Science and Technology
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• v.8 no.1
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• pp.43-52
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• 2017

In this paper, for the first time, the electroanalytical study of Triethylenediamine, TEDA was done on a typically graphene modified carbon paste electrode (Gr/CPE) in pH=10.5 of phosphate buffer solutions (PBS). The surface morphology of the bare and modified electrodes was characterized by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The electro-oxidation of TEDA was investigated at the surface of modified electrode. The results revealed that the oxidation peak current of TEDA at the surface of Gr/CPE is 2.70 times than that shown at bare-CPE. A linear calibration plot was observed in the range of 1.0 to 202.0 ppm. In this way, the detection limit was found to be 0.18 ppm. The method was then successfully applied to determination of TEDA in aqueous samples obtained from two kinds of activated carbon from the masks of war. On the other hand, density functional theory (DFT) method at B3LYP/6-311++G** level of theory and a conductor-like Polarizable Continuum Model (CPCM) was used to calculate the $pK_a$ values of TEDA. The energies of lowest unoccupied molecular orbital ($E_{LUMO}$) and highest occupied molecular orbital ($E_{HOMO}$), gap energy (${\Delta}E$) and some thermodynamic parameters such as Gibbs free energy of TEDA and its conjugate acid ($HT^+$) were calculated. The results of calculated $pK_a$ were found to be in good agreement with the experimental values.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.11
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• pp.1448-1454
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• 2018

In an optical observing system, three pairs of observations at equal time intervals are required for the orbit determination method to obtain orbital information of an unknown space objects. In this paper, we propose a method of estimating a streak for acquiring three pairs of observations using one streak image information. Satellite trajectory simulation data were generated for nine cases using the STK program in order to verify the characteristics of the orbit of space object and estimation performance. Simulation was performed by applying three approaches that can estimate the next streak position after a few seconds from one streak image information, and the estimation performance was evaluated. Linear vector method and Kalman Filter method based on the linear assumption tend to increase the estimation error in the region where the nonlinearity is large. However estimation method using the polynomial curve fitting based on the least square method showed smaller and uniform error result than the previous methods.

• Bulletin of the Korean Chemical Society
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• v.31 no.7
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• pp.1875-1880
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• 2010

A dicycle pyrazoline derivative, 1-phenyl-5-(p-fluorophenyl)-3,4-($\alpha$-p-fluoro-tolylenecyclohexano) pyrazoline, was synthesized and characterized by elemental analysis, IR, UV-vis, fluorescence spectra and X-ray single crystal diffraction. Density function theory (DFT) calculations were performed by using B3LYP method with 6-$311G^{**}$ basis set. The optimized geometry can well simulate the molecular structure. Vibrational frequencies were predicted, assigned and compared with the experimental values, which suggest that B3LYP/6-$311G^{**}$ method can well predict the IR spectra. Both the experimental electronic absorption spectra and the predicted ones by B3LYP/6-$311G^{**}$ method reveal three electron-transition bands, with the theoretical ones having some red shifts compared with the experimental data. Natural bond orbital analyses indicate that the absorption bands are mainly derived from the contribution of n $\rightarrow\pi^*$ and $\pi\rightarrow\pi^*$ transitions. Fluorescence spectra determination shows that the title compound can emit blue-light at about 478 nm. On the basis of vibrational analysis, the thermodynamic properties of title compound at different temperature have been calculated, revealing the correlations between $C^0_{p,m}$, $S^0_m$, $H^0_m$ and temperature.

• International Journal of Aeronautical and Space Sciences
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• v.13 no.4
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• pp.484-490
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• 2012

This paper is devoted to investigate the feasibility of using a medium power ground-based laser to produce a torque on LEO satellites of various shapes. The laser intensity delivered to a satellite is calculated using a simple model of laser propagation in which a standard atmospheric condition and linear atmospheric interaction mechanism is assumed. The laser force is formulated using a geocentric equatorial system in which the Earth is an oblate spheroid. The torque is formulated for a cylindrical satellite, spherical satellites and for satellites of complex shape. The torque algorithm is implemented for some sun synchronous low Earth orbit cubesats. Based on satellites perigee height, the results demonstrate that laser torque affecting on a cubesat has a maximum value in the order of $10^{-9}$ which is comparable with that of solar radiation. However, it has a minimum value in the order of $10^{-10}$ which is comparable with that of gravity gradient. Moreover, the results clarify the dependency of the laser torque on the orbital eccentricity. As the orbit becomes more circular it will experience less torque. So, we can conclude that the ground based laser torque has a significant contribution on the low Earth orbit cubesats. It can be adjusted to obtain the required control torque and it can be used as an active attitude control system for cubesats.

• Bulletin of the Korean Space Science Society
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• 2011.04a
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• pp.26.2-26.2
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• 2011

Flyby anomaly (unexpected energy increase during Earth Gravity Assists) indicates existence of an unknown non-conservative perturbation which affects hyperbolic trajectories. This presentation focuses on first order position and velocity perturbation formulas derived in terms of classical orbital element variations for hyperbolic orbit. By using both the perturbation formulas and numerical approach, we analyze effects of hypothetical acceleration models proposed by Hasse (2009), Lewis (2009), Gerrad and Sumner (2008), and Busack (2007). Based on analysis of perturbation effect on low earth orbit, we find that typical position perturbation is about 10m which is much larger than current orbit determination accuracy. From this, we deduce that anomalous acceleration only affects hyperbolic orbit or behaves differently in bound orbit. On the other hand, based on analysis of perturbation effects on hyperbolic trajectories, we find that position and velocity perturbations are highly different from acceleration models, and all of proposed models fail to explain observed range and Doppler data. Thus, it can be concluded that not only energy variations but also kinematics gives us crucial clues on the flyby anomaly, and kinematical characteristic should be considered in modeling flyby anomaly.

• Journal of Astronomy and Space Sciences
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• v.18 no.2
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• pp.137-144
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• 2001

This paper presents the REA thrusters performance estimation results for the KOREASAT F1&F2 launched in 1995 The satellite tracking data obtained from the ground system from end of 1999 to beginning of the 2000 are used to estimate the thruster performance. The estimation algorithm is derived from the least square estimation theory and designed to estimate the velocity change induced by the on-boarded thruster firing as well as the orbit parameter. The estimation results show that the Koreasat F1 thruster are in bad thruster condition of 64% performance for REA when it fires in on-pulse mode. Here, the performance is defined by the ratio of the resulted velocity change to that of planned. But, in the case o( the Koreasat F2, it is found that the performance approximately reaches up to 100%, even after the 5 years of the mission.

• Proceedings of the KSRS Conference
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• v.2
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• pp.748-751
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• 2006

Positioning accuracy by the Global Positioning System (GPS) is of great concern in a variety of research tasks. It is limited due to error sources such as ionospheric effect, orbital uncertainty, antenna phase center variation, signal multipath, and tropospheric influence. In this study, the tropospheric influence, primarily due to water vapour inhomogeneity, on GPS positioning height is investigated. The data collected by the GPS receivers along with co-located surface meteorological instruments in 2003 are utilized. The GPS receivers are established as continuously operating reference stations by the Ministry of the Interior (MOI), Central Weather Bureau (CWB), and Industrial Technology Research Institute (ITRI) of Taiwan, and International GNSS Service (IGS). The total number of GPS receivers is 21. The surface meteorological measurements include temperature, pressure, and humidity. They are introduced to GPS data processing with 24 troposphere parameters for the station heights, which are compared with those obtained without a priori knowledge of surface meteorological measurements. The results suggest that surface meteorological measurements have an expected impact on the GPS height. The daily correction maximum with the meteorological effect may be as large as 9.3 mm for the cases of concern.

• Journal of the Korean Chemical Society
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• v.19 no.4
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• pp.218-224
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• 1975

The ground state SCF IMO theory was applied to the Diels-Alder reactions of cyclopentadiene with 2-substituted acrylonitriles. The CNDO/2 MO of the separate systems, including both $\sigma$ and $\pi$ electrons, was used as starting point. The qualitative prediction of the relative reactivity was made with the calculated primary interaction energies. Here the calculated activation energies appeared to be realistic. The stereoselectivity determined by the calculated secondary interaction energies represented the endo-selectivity for all the substituents. The reason for the slightly unsymmetrical ring closure at the transition state was discussed in terms of valence inactive electron densities of the reacting atoms.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.2
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• pp.240-252
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• 2016

In this paper, an on-board orbit propagator and compressing trajectory method based on B-spline for a lunar explorer are proposed. An explorer should recognize its own orbit for a successful mission operation. Generally, orbit determination is periodically performed at the ground station, and the computed orbit information is subsequently uploaded to the explorer, which would generate a heavy workload for the ground station and the explorer. A high-performance computer at the ground station is employed to determine the orbit required for the explorer in the parking orbit of Earth. The method not only reduces the workload of the ground station and the explorer, but also increases the orbital prediction accuracy. Then, the data was compressed into coefficients within a given tolerance using B-spline. The compressed data is then transmitted to the explorer efficiently. The data compression is maximized using the proposed methods. The methods are compared with a fifth order polynomial regression method. The results show that the proposed method has the potential for expansion to various deep space probes.

• Korean Journal of Crystallography
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• v.14 no.1
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• pp.16-23
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• 2003

The electronic structure and chemical bonding of β-MnO₂ were theoretically investigated by DV-X/sub α/ (the discrete variation X/sub α/) method. which is a sort of the first principle molecular orbital method using Hatre-Fock-Slater approximation. The calculations on several cluster models having different sizes were carried out for the determination of a model suited for analyzing bulk state. The Mn/sub 15/O/sub 56/ model was selected as a sufficiently suitable model for the calculation of electronic state and chemical bonding by the comparison of the calculated XPS (X-ray photo-electron spectrum) and experimentally measured XPS. By using this model, the electron energy level, the density of state, the bond overlap population, the charge density distribution, and the net ionic transfer between cations and anions were calculated and discussed.