• Journal of Astronomy and Space Sciences
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• v.37 no.3
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• pp.209-218
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• 2020

This paper describes the initial operations and preliminary results of the Instrument for the study of Stable/Storm-time Space (ISSS) onboard the microsatellite Next Generation Small Satellite-1 (NEXTSat-1), which was launched on December 4, 2018 into a sun-synchronous orbit at an altitude of 575 km with an orbital inclination angle of 97.7°. The spacecraft and the instruments have been working normally, and the results from the observations are in agreement with those from other satellites. Nevertheless, improvement in both the spacecraft/instrument operation and the analysis is suggested to produce more fruitful scientific results from the satellite operations. It is expected that the ISSS observations will become the main mission of the NEXTSat-1 at the end of 2020, when the technological experiments and astronomical observations terminate after two years of operation.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.1
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• pp.28-35
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• 2009

This paper derives the equation of coordinated attitude formulation taking into account the orbital dynamics of a target vehicle and the attitude of a tracking satellite in geostationary orbit. The coordinated attitude is always to communicate with the ground station during the target tracking. Because the tracking satellite could perform high angle maneuver, MRP parameters having no singular point are used. Also for the sequential tracking of several target vehicles, the equation automatically making a coordinated attitude is suggested. Coordinated attitude flying and sequential tracking are confirmed through simulations. In short, this paper shows that a satellite could track a target vehicle and communicate with ground station simultaneously using the derived equation of coordinated attitude even though without a accuracy sensor.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.17 no.4
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• pp.379-388
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• 1995

This study was based on a series of 369 patients with Oral and Maxillofacial injuries treated at Kumi Hospital, College of Medicine, Soon-Chun-Hyang University from Jan. 1992 to Dec. 1994. The results obtained were as follows : 1. The number of male patient was 310 and that of female was 59, leading to 5.3 : 1 of male-female ratio, and the 3rd decade was the highest age group in incidence. 2. Weekly incidence was the highest in Sun. & Sat. and monthly incidence was the highest in Nov.& Oct. 3. Causes as follows : traffic accident 41.9%, slip& fall down 25.4%, human trouble 16.5%, industrial accident 7.5%, sports 6.7%, etc. 4. Site distribution as follows : mandible fracture 32.3%, maxilla fracture 4.8%, zygoma fracture 21.4%, nasal bone fracture 34.1%, orbital& ethmoidal fracture 4.6%. 5. The most common site of mandible was symphysis & angle, and the ratio of OR & CR was 1.3 : 1. 6. The most common site of maxilla was Le Fort 1, 2, and the ratio of OR & CR was 3 : 1. 7. The most common site of zygoma was body, the ratio of OR & CR was 3.3 : 1. 8 . The mean period of intermaxillary fixation was 4.33weeks. 9. Combined injury in facial fracture was 35.8% : The facial fracture were most frequently combind with head & neck(47.0%), upper extremities and abdomen(9.8%). 10. The mean elapsed time from injury to hospital was 1.9days, and that to operation was 5.1days. 11. The mean number of combined teeth injury was 0.6, and percent of combined soft tissue injury of face was 51.3%. 12. Post-operative complication occurred in 4 out of 323 cases. all of that was infection.

• Proceedings of the Korean Biophysical Society Conference
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• 2003.06a
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• pp.75-75
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• 2003

We report here the results on N-acetyl-N'-dimethylamide of proline (Ac-Pro-NM $e_2$) calculated using the ab initio molecular orbital method with the self-consistent reaction field (SCRF) theory at the HF level with the 6-31+G(d) basis set to investigate the conformational preference of polyproline depending on the cis/trans peptide bonds and down/up puckerings along the backbone torsion angle $\square$ in the gas phase, chloroform, and water. In the gas phase, Ac-Pro-NM $e_2$ has seven local minima of tFd, tFu, cFd, cFu, cAu, tAu, and cAd conformations. In particular, polyproline conformations tFd, tFu, cFd, and cFu are found to be more stable than $\square$-helical conformations cAu, tAu, and cAd. In contrast, Ac-Pro-NHMe has seven local minima of tCd, tCu, cBd, cAu, tAu, cFd, and cFu conformations. Conformations tCd and tCu are found to be most stable, which is ascribed to the intramolecular hydrogen bond between C=O of acetyl group and $N^{~}$ H of N'-methyl amide group. The stability of the cFd conformation (i.e., the polyproline I structure) in chloroform is somewhat increased, relative to that in water, although tFd and tFu conformations (i.e., the polyproline II structure) are dominate both in chloroform and water. The population of backbone conformations feasible in chloroform and water is consistent with the experiments. This work is supported by a Korea Research Foundation Grant (KRF-2002-041-C00129).

• Korean Journal of Remote Sensing
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• v.17 no.3
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• pp.211-218
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• 2001

We have performed the calculation of total radiances for the KOMPSAT-2 Multispectral Camera (MSC) using a radiative transfer model of MODTRAN and examined its results. To simulate four seasonal conditions in the model calculation, we used model atmospheres of mid-latitude winter and summer for calculations of January 15 and July 15, and US standard for April 15 and October 15, respectively. Orbital parameters of KOMPSAT-2 and the seasonal solar zenith angles were taken into account. We assumed that the meteorological range is the tropospheric aerosol extinction of 50 km and surface albedo is the global average of clear-sky albedo of 0.135. MSC contract values are found to be considerably greater in the MSC spectral range than the total radiances calculated with the above general conditions. It is also shown that the spectral behavior of model results with the constant surface albedo differs from the pattern of MSC contract values. From these results, it can be inferred that the forthcoming MSC images would be somewhat dark.

• Journal of Positioning, Navigation, and Timing
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• v.4 no.2
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• pp.43-55
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• 2015

In the case of satellite navigation positioning, the shielding of satellite signals is determined by the environment of the region at which a user is located, and the navigation performance is determined accordingly. The accuracy of user position determination varies depending on the dilution of precision (DOP) which is a measuring index for the geometric characteristics of visible satellites; and if the minimum visible satellites are not secured, position determination is impossible. Currently, the GLObal NAvigation Satellite system (GLONASS) of Russia is used to supplement the navigation performance of the Global Positioning System (GPS) in regions where GPS cannot be used. In addition, the European Satellite Navigation System (Galileo) of the European Union, the Chinese Satellite Navigation System (BeiDou) of China, the Quasi-Zenith Satellite System (QZSS) of Japan, and the Indian Regional Navigation Satellite System (IRNSS) of India are aimed to achieve the full operational capability (FOC) operation of the navigation system. Thus, the number of satellites available for navigation would rapidly increase, particularly in the Asian region; and when integrated navigation is performed, the improvement of navigation performance is expected to be much larger than that in other regions. To secure a stable and prompt position solution, GPS-GLONASS integrated navigation is generally performed at present. However, as available satellite navigation systems have been diversified, finding the minimum satellite constellation combination to obtain the best navigation performance has recently become an issue. For this purpose, it is necessary to examine and predict the navigation performance that could be obtained by the addition of the third satellite navigation system in addition to GPS-GLONASS. In this study, the current status of the integrated navigation performance for various satellite constellation combinations was analyzed based on 2014, and the navigation performance in 2020 was predicted based on the FOC plan of the satellite navigation system for each country. For this prediction, the orbital elements and nominal almanac data of satellite navigation systems that can be observed in the Korean Peninsula were organized, and the minimum elevation angle expecting signal shielding was established based on Matlab and the performance was predicted in terms of DOP. In the case of integrated navigation, a time offset determination algorithm needs to be considered in order to estimate the clock error between navigation systems, and it was analyzed using two kinds of methods: a satellite navigation message based estimation method and a receiver based method where a user directly performs estimation. This simulation is expected to be used as an index for the establishment of the minimum satellite constellation for obtaining the best navigation performance.

• Journal of Astronomy and Space Sciences
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• v.25 no.2
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• pp.181-198
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• 2008

Designing satellite constellations providing partial coverage of certain regions becomes more important as small low-altitude satellites receives an increasing attention due to its cost-effectiveness analysis. Generally, Walker's method is a standard constellation method for global coverage but not effective for partial coverage. The purpose of this study is to design optimal constellation of satellites for effective observation in Korean peninsula regions. In this study, a new constellation design method is presented for partial coverage, using direct control of satellites' orbital elements. And also, a ground repeating circular orbit is considered for each satellite's orbit with the Earth oblateness effect. As the results, at least four satellites are required to observe the Korean peninsula regions effectively when minimum elevation angle is assumed as 12 degrees. The results from new method are better than those from the best Walker method. The proposed algorithm will be useful to design satellite constellation missions of Korea in future.

• Journal of Astronomy and Space Sciences
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• v.22 no.3
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• pp.249-262
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• 2005

Optimization problems are formulated to calculate optimal impulses for deflecting Earth-Crossing Objects using a Nonlinear Programming. This formulation allows us to analyze the velocity changes in normal direction to the celestial body's orbital plane, which is neglected in many previous studies. The constrained optimization in the three-dimensional space is based on a patched conic method including the Earth's gravitational effects, and yields impulsive ${\Delta}V$ to deflect the target's orbit. The optimal solution is dependent on relative positions and velocities between the Earth and the Earth-crossing objects, and can be represented by optimal magnitude and angle of ${\Delta}V $ as a functions of a impulse time. The perpendicular component of ${\Delta}V $ to the orbit plane can sometimes play un-negligible role as the impulse time approaches the impact time. The optimal ${\Delta}V $ is increased when the original orbit of Earth-crossing object is more similar to the Earth's orbit, and is also exponentially increased as the impulse time reaches to the impact time. The analyses performed in present paper can be used to the deflection missions in the future.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.37 no.6
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• pp.439-447
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• 2011

Introduction: In today's society, the rapid and appropriate care of the dental emergency patients is much more important. So, a retrospective study on the characteristics of emergency dental injuries and diseases will be very meaningful. Materials and Methods: This retrospective clinical study was carried by reviewing the radiographic films and emergency chart of 11,493 patients who had visited the emergency room of Hallym Sacred heart Hospital and were treated in the Department of Oral and Maxillofacial Surgery from January 2006 to December 2010. Results: The male to female ratio was 1.9:1. The highest monthly incidence was observed in May (10.4%) and June (8.9%) and the peak age distribution was the first decade (56.0%), followed by the second decade (16.0%). Trauma was the most common cause in dental emergency patients, followed in order by toothache, odontogenic infection, temporomandibular joint (TMJ) disorder and oral hemorrhage. Soft tissue injury was most prevalent in the trauma group, followed by tooth injury and facial bone fractures. In the tooth injury group, tooth fracture (56.7%) showed the highest incidence followed in order by tooth subluxation (18.2%), tooth concussion (16.9%), tooth avulsion (11.5%) and alveolar bone fractures (3.7%). In the facial bone fracture group, mandibular fractures (81.8%) showed the highest incidence followed in order by maxilla fractures (15.7%), nasal bone fractures (9.0%), zygomaticomaxillary complex fractures (5.4%), orbital bone fractures (2.5%). In mandibular bone fractures, the most common location was the symphysis (70.1%), followed in order by the mandibular angle (33.0%), mandibular condyle (22.8%) and mandibular body (13.6%). In the infection group, a submandibular space abscess (46.2%) was most common followed in order by a buccal space abscess (17.4%), canine space abscess (16.9%) and submental space abscess (12.3%). TMJ dislocation (89.3%) showed the highest incidence in the TMJ disorder group, followed by TMJ derangement (10.7%). In the other group, a range of specific symptoms due to post operation complications, trigeminal neuralgia, chemical burns and foreign body aspiration were reported. Conclusion: For the rapid and appropriate care of the dental emergency patients, well-organized system should be presented in oral and maxillofacial surgery. And it is possible under analysis of pattern and the variation of the dental emergency patients.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.28 no.2
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• pp.247-254
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• 2010

In this paper, a new approach has been studied correcting the geometric distortion of SPOT 4 imagery. Two new equations were induced by the relationship between satellite and the Earth in the space. line-of-sight (LOS) vector adjustment model for SPOT 4 imagery was implemented in this study. This model is to adjust LOS vector under the assumption that the orbital information of satellite provided by receiving station is uncertain and this uncertainty makes a constant error over the image. This model is verified using SPOT 4 satellite image with high look angle and thirty five ground points, which include 10 GCPs(Ground Control Points) and 25 check points, measured by the GPS. In total thirty five points, the geometry of satellite image calculated by given satellite information(such as satellite position, velocity, attitude and look angles, etc) from SPOT 4 satellite image was distorted with a constant error. Through out the study, it was confirmed that the LOS vector adjustment model was able to be applied to SPOT4 satellite image. Using this model, RMSEs (Root Mean Square Errors) of twenty five check points taken by increasing the number of GCPs from two to ten were less than one pixel. As a result, LOS vector adjustment model could efficiently correct the geometry of SPOT4 images with only two GCPs. This method also is expected to get good results for the different satellite images that are similar to the geometry of SPOT images.