• 제어로봇시스템학회논문지
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• 제18권11호
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• pp.989-996
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• 2012

The purpose of this paper is to analyze GPS (Global Positioning System) satellite orbital mechanics, and then to propose a novel long-term GPS satellite orbit prediction scheme including virtual planet perturbation. The GPS orbital information is a necessary prerequisite to pinpointing the location of a GPS receiver. When a GPS receiver has been shut down for a long time, however, the time needed to fix it before its reuse is too long due to the long-standing GPS orbital information. To overcome this problem, the GPS orbital mechanics was studied, such as Newton's equation of motion for the GPS satellite, including the non-spherical Earth effect, the luni-solar attraction, and residual perturbations. The residual perturbations are modeled as a virtual planet using the least-square algorithm for a moment. Through the modeling of the virtual planet with the aforementioned orbital mechanics, a novel GPS orbit prediction scheme is proposed. The numerical results showed that the prediction error was dramatically reduced after the inclusion of virtual planet perturbation.

• 대한화학회지
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• 제56권2호
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• pp.195-200
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• 2012

In this study we present a new approach for computing the partial atomic charge derived from the wavefunctions of molecules. This charge, which we call the "y_charge", was calculated by taking into account the energy level and orbital populations in each molecular orbital (MO). The charge calculations were performed in the software, which was developed by us, developed using the C# programming language. Partial atomic charges cannot be calculated directly from quantum mechanics. According to a partitioning function, the electron density of constituent molecular atoms depends on the electrostatic attraction field of the nucleus. Taking into account the Boltzmann population of each MO as a function of its energy and temperature we obtain a formula of partial charges.

• Bulletin of the Korean Chemical Society
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• 제17권12호
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• pp.1112-1117
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• 1996

The electronic structures of twenty-seven isomers of a macrocyclic fulleropyrrolidine are investigated with semi-empirical extended Huckel (EH) molecular orbital method. The geometry of each isomer is determined by the molecular mechanics and dynamics methods based on UFF (universal force field) empirical force field. The calculated geometries, such as the carbon-carbon distances of the fullerene moiety, are in good agreement with those of related fullerene derivatives. The EH calculation shows that the formation of macrocyclic pyrrolidine ring on fullerene moiety results in the reduction of the HOMO-LUMO energy gap. From the graphical analysis of the DOS (density of states), PDOS (projected DOS), and MOOP (molecular orbital overlap population) curves, we can find that this reduction is due to splitting of the HOMO of fullerene moiety, which results from the symmetry-breaking and the distortion of the buckminsterfullerene framework from its ideal icosahedral structure.

• 항공우주시스템공학회지
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• 제14권1호
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• pp.36-43
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• 2020

위성 열 설계의 시작은 운용궤도의 열 환경 분석을 통한 최악의 운용 환경을 예측하는 것이다. 위성은 주어진 임무에 맞는 다양한 형태의 운용궤도를 가지기 때문에 노출되는 열 환경 또한 다르다. 따라서, 위성의 궤도조건을 고려한 외부 열 환경 분석이 필수이며, 이를 통해 선정된 위성의 최악의 조건에 대해 열적 안정성을 보장하는 설계를 수행하게 된다. 궤도 열 환경 분석을 위해서는 궤도역학은 물론 우주 열 환경과 위성체 사이의 열 교환 관계에 대한 이해가 필요하다. 이에 본 논문에서는 지구궤도 내 우주 열 환경에 관한 기초자료를 제공하고, 위성체에 유입되는 우주 열 유입량을 계산하는 열 관계식을 서술함으로써 궤도 열 환경 분석의 이해를 돕고자 하였다. 또한, 가상의 위성 예제를 통해 임무기간 중 궤도 열 환경을 분석하는 전반적인 과정을 보였다.

• Journal of Photoscience
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• 제2권2호
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• pp.95-98
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• 1995

The photodimers with cyclobutane rings and C$_2$ symmetry, derived from coumarin (syn, head to tail and anti, head to head) have been calculated by PM3-UHF-CI and Molecular Mechanics force field. The photocycloaddition to coumarin and 5,7-dimethoxycoumarin(DMC) dimers were deduced to be formed by their preferable frontier orbital interactions and via more stable cycloaddition by the C$_3$, C$_4$ bond. These results are consistent with the coumarin dimer model that the theoretical C$_4$-photocyclodimer of coumarin is predicted much more than the experimental C$_4$-photocyclodimer.

• Archives of Plastic Surgery
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• 제34권6호
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• pp.724-728
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• 2007

Purpose: The objective of this study is to prevent postoperative lower eyelid retraction and scleral show. There are several approaches for orbital rim reconstruction. But these techniques are sometimes difficult to perform, and have some merits and faults. Maybe most common unwanted and unpleasant result that we have experienced by subciliary incision preseptal approach is the lower eyelid retraction and the scleral show. Therefore, I want to find out the causes and the solutions for such complication. We must know the mechanics for those unpleasant result first of all. Methods: We conducted a comparison of postoperative photographs between retroseptal approach group and preseptal approach group, both with subciliary incision. In experimental retroseptal group, incision was applied at subciliary region. After elevating skin flap to preserve pretarsal muscle, not with muscle flap elevation, but direct oblique incision through the muscle, retroseptal dissection was applied to the ROOF and the septum. Fixating fracture line, periosteal and septal repair was followed by skin repair. The light compressive dressings and protection were kept in place for 7 days. The effectiveness of this operative method was made comparison with control group which the preseptal approach was applied to, by postoperative 2nd week and 2nd month. Results: Author's technique had been used in 20 patients and control group was composed of 50 patients over 19months period. There were better results in experimental group than in control group and all of experimental group had no complaint about the lower eyelid retraction and the scleral show. Conclusion: It must be known about the reason of the lower eyelid retraction and the scleral show induced by subciliary and preseptal approach. Mechanically it can be easily proved. And the solution maybe will be easier if we get more information about the mechanics. I recommend the retroseptal subciliary approach

• Journal of Astronomy and Space Sciences
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• 제31권3호
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• pp.187-197
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• 2014

We have investigated the dynamical stability of the proposed companions orbiting the Algol type short-period eclipsing binary SW Lyncis (Kim et al. 2010). The two candidate companions are of stellar to substellar nature, and were inferred from timing measurements of the system's primary and secondary eclipses. We applied well-tested numerical techniques to accurately integrate the orbits of the two companions and to test for chaotic dynamical behavior. We carried out the stability analysis within a systematic parameter survey varying both the geometries and orientation of the orbits of the companions, as well as their masses. In all our numerical integrations we found that the proposed SW Lyn multi-body system is highly unstable on time-scales on the order of 1000 years. Our results cast doubt on the interpretation that the timing variations are caused by two companions. This work demonstrates that a straightforward dynamical analysis can help to test whether a best-fit companion-based model is a physically viable explanation for measured eclipse timing variations. We conclude that dynamical considerations reveal that the proposed SW Lyncis multi-body system most likely does not exist or the companions have significantly different orbital properties from those conjectured in Kim et al. (2010).

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 하계종합학술대회 논문집(1)
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• pp.143-146
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• 2004

Signals of the short wave part of centimetre, millimetre and optic wave length ranges are being broadly used in the communication, location and remote sensing systems with space channels. In this case the presence of discrete non-uniform mediums like orbital debris, space dust and other discrete formations in the propagation channel may have substantial influence upon the characteristics of wave processes. and thus upon the data system quality. Mathematical models for studying the discrete non-uniform mediums effect on the characteristics of electromagnetic wave propagation are analyzed in this paper.

• 천문학회지
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• 제35권2호
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• pp.75-85
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• 2002

We present N-body simulations of globular clusters including gravitational field of the Galaxy, in order to study effects of tidal field systematically on the shape of outer parts of globular clusters using NBODY6. The Galaxy is assumed to be composed of central bulge and outer halo. We mvestigate the cluster of multi-mass models with a power-law initial mass function (IMF) starting with different initial masses, initial number of particles, different slopes of the IMF and different orbits of the cluster. We have examined the general evolution of the clusters, the shape of outer parts of the clusters, density profiles and the direction of tidal tails. The density profiles appear to become somewhat shallower just outside the tidal boundary consistent with some observed data. The position angle of the tidal tall depends on the location in the Galaxy as well as the direction of the motion of. clusters. We found that the clusters become more elongated at the apogalacticon than at the pengalacticon. The tidal tails may be used to trace the orbital paths of globular clusters.

• Journal of Astronomy and Space Sciences
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• 제37권2호
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• pp.117-129
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• 2020

In a Satellite communication system, a link budget analysis is the detailed investigation of signal gains and losses moving through a channel from a sender to receiver. It inspects the fading of passed on data signal waves due to the process of spreading or propagation, including transmitter and receiver antenna gains, feeder cables, and related losses. The extent of the proposed tool is to make an effective, efficient, and user-friendly approach to calculate link budget analysis. It is also related to the satellite communication correlation framework by building up a graphical interface link analysis tool utilizing STK^® software with the interface of C# programming. It provides better kinds of graphical display techniques, exporting and importing data files, printing link information, access data, azimuth-elevation-range (AER), and simulation is also possible at once. The components of the link budget analysis tool include transmitter gain, effective isotropic radiated power (EIRP), free space loss, propagation loss, frequency Doppler shift, flux density, link margin, elevation plot, etc. This tool can be useful for amateur users (e.g., CubeSat developers in the universities) or nanosat developers who may not know about the RF communication system of the satellite and the orbital mechanics (e.g., orbit propagators) principle used in the satellite link analysis.