• Korean Journal of Mineralogy and Petrology
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• v.36 no.2
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• pp.125-134
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• 2023

The Naedeokri and Nonggeori granites are early Proterozoic granites of the Taebaek-Sangdong area in the northeastern part of the Yeongnam Massif. In this paper, rare earth elements (REEs) concentrations of the minerals in Naedeokri and Nonggeori granites and Rb-Sr mineral isochron age are reported. Except zircon, the constituent minerals such as mica, feldspar, quartz, and tourmaline show LREE-enriched and HREE-depleted REE patterns with relatively large Eu negative anomaly. However, zircon has geochemical characteristic of LREE- and HREE-enriched REE pattern with large Eu positive anomaly. This pattern suggests that zircon should be hydrothermal zircon due to deuteric hydrothermal alteration. In addition, the Rb-Sr mineral age of Naedeokri granite indicates an age value of 1.814±142(2σ) Ma. The Rb-Sr whole rock age including pervious data of Naedeokri and Nogggeori granite indicates an age value of 1,707±74(2σ) Ma. This value is younger than the Sm-Nd isochron of 1.87 Ga, indicating that the Rb-Sr isotope system may be re-homogenized by hydrothermal alteration during the transition from a magmatic to a hydrothermal system.

• Journal of the Korean earth science society
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• v.39 no.6
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• pp.519-532
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• 2018

We investigated the effect of galactic plane toward molecular motion and kinematics in the northern filament (NF) of Orion Molecular Clouds Complex (OMC) using $^{12}CO$ (J=1-0) line. Observed data were from three areas including NF1, NF2, and NF3 in far-out order from galactic plane, for a total 270 hours by Seoul National University Radio Astronomy Observatory (SRAO) 6m telescope, with 2arcmin spatial resolution. galactic plane and OMC NF were connected to each other along the magnetic field at a density of 3% for $^{12}CO$ (J=2-1) and 9% for the case of dust. $^{12}CO$ (J=1-0), $^{12}CO$ (J=2-1), and interstellar dusts were distributed uniformly in NF3, but only in certain regions with relatively high density in NF1 and NF2. NF showed a single structure, partial shrinking motion in NF1, and rotational motion at the bottom of NF2, and spiral rotation associated with magnetic field only in NF3. The position-velocity analysis showed that the materials including $^{12}CO$ (J=1-0) could flow toward galactic plane along NF2 and NF3. However, there was no clear cause for the material to flow toward galactic plane in this result. Further detailed observation for rotational motion at the top of NF1 and NF2 might help to confirm it.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.8
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• pp.757-764
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• 2015

Mathematical modeling of focal plane compensation device in the small earth-observation satellite camera has been conducted experimently for compensation of micro-vibration disturbance. The PZT actuators are used as control actuators for compensation device. It is quite difficult to build up mathematical model because of hysteresis characteristic of PZT actuators. Therefore, the compensation device system is assumed as a $2^{nd}$ order linear system and modeled by using MATLAB System Identification Toolbox. It has been found that four linear models of compensation device are needed to meet 10% error in the input frequency range of 0~50Hz. These models describe accurately the dynamics of compensation device in the 4 divided domains of the input frequency range of 0~50Hz, respectively. Micro-vibration disturbance can be compensated by feedback control strategy of switching four models appropriately according to the input frequency.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.3
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• pp.109-118
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• 2018

Korea Aerospace Research Institute has developed a staged combustion cycle rocket (SCCR) engine with high specific impulse to send a 3-ton class satellite into geostationary orbit while conducting a Korean Space Launch Vehicle (KSLV) II project. The SCCR engine is different from the KSLV-II engine, which is an open cycle engine using a gas-generator. The SCCR engine with a closed cycle engine is composed of a pre-burner, a turbo pump, and a main combustor. The technology demonstration model (TDM0) was assembled and tested in the 7ton-class engine combustion test facility of Naro Space Center, and the combustion test was successfully conducted.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.1
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• pp.80-87
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• 2016

In this work, we conduct a thermal pointing error analysis of the observation satellites considering seasonal and daily temperature variation with interpolated temperature based on prescribed average temperature (PAT) method. Maximum 200 degree temperature excursion is applied to the observation satellites during on-orbit operation, which cause the line of sight (LOS) to deviate from the designated pointing direction due to thermo-elastic deformation. To predict and adjust such deviation, the thermo-elastic deformation analysis with a fine structural finite element model is accomplished with interpolated thermal maps calculated from the results of on-station thermal analysis with a coarse thermal model. After verifying the interpolated temperatures by PAT with two benchmark problems, we evaluate the thermal pointing error.

• Korean Journal of Remote Sensing
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• v.26 no.2
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• pp.277-285
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• 2010

Geostationary Ocean Color Imager(GOCI-I), the world's first space-borne ocean color observation geostationary satellite, will be launched on June 2010. Development of GOCI-I took about 6 years, and its expected lifetime is about 7 years. The mission and user requirements of GOCI-II are required to be defined at this moment. Because baseline of the main mission of GOCI-II must be defined during the development time and early operational period of GOCI-I. The main difference between these missions is the global-monitoring capability of GOCI-II, which will meet the necessity of the monitoring and research on climate change in the long-term. The user requirements of GOCI-II will have higher spatial resolution, $250m{\times}250m$, and 12 spectral bands to fulfill GOCI-I's user request, which could not be implemented on GOCI-I for technical reasons. A dedicated panchromatic band will be added for the nighttime observation to obtain fishery information. GOCI-II will have a new capability, supporting user-definable observation requests such as clear sky area without clouds and special-event areas, etc. This will enable higher applicability of GOCI-II products. GOCI-II will perform observations 8 times daily, the same as GOCI-I's. Additionally, daily global observation once or twice daily is planned for GOCI-II. In this paper, we present an improved development and organization structure to solve the problems that have emerged so far. The hardware design of the GOCI-II will proceed in conjunction with domestic or foreign space agencies.

• Korean Journal of Remote Sensing
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• v.34 no.6_3
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• pp.1415-1425
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• 2018

Kompsat-5 is the first Earth Observation Satellite which is equipped with an SAR in Korea. SAR images are generated by receiving signals reflected from an object by microwaves emitted from a SAR antenna. Because the wavelengths of microwaves are longer than the size of particles in the atmosphere, it can penetrate clouds and fog, and high-resolution images can be obtained without distinction between day and night. However, there is no color information in SAR images. To overcome these limitations of SAR images, colorization of SAR images using Cycle GAN, a deep learning model developed for domain translation, was conducted. Training of Cycle GAN is unstable due to the unsupervised learning based on unpaired dataset. Therefore, we proposed MS Cycle GAN applying multi-scale discriminator to solve the training instability of Cycle GAN and to improve the performance of colorization in this paper. To compare colorization performance of MS Cycle GAN and Cycle GAN, generated images by both models were compared qualitatively and quantitatively. Training Cycle GAN with multi-scale discriminator shows the losses of generators and discriminators are significantly reduced compared to the conventional Cycle GAN, and we identified that generated images by MS Cycle GAN are well-matched with the characteristics of regions such as leaves, rivers, and land.

• Atmosphere
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• v.31 no.2
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• pp.241-249
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• 2021

A smart city utilizes data collected from various sensors through the internet of things (IoT) and improves city operations across the urban area. Recently substantial research is underway to examine all aspects of data that requires for the smart city operation. Atmospheric data are an essential component for successful smart city implementation, including Urban Air Mobility (UAM), infrastructure planning, safety and convenience, and traffic management. Unfortunately, the current level of conventional atmospheric data does not meet the needs of the new city concept. New and innovative approaches to developing high spatiotemporal resolution of observational and modeling data, resolving the complex urban structure, are expected to support the future needs. The geographic information system (GIS) integrates the atmospheric data with the urban structure and offers information system enhancement. In this study we proposed the necessity and applicability of the high resolution urban meteorological dataset based on heavy fog cases in the smart city region (e.g., Sejong and Pusan) in Korea.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.5
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• pp.15-21
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• 2021

Electrically powered airplanes can reduce CO₂ emissions from fossil fuel use and reduce airplane costs in the long run through efficient energy use. For this reason, advanced aviation countries such as the United States and the European Union are leading the development of innovative technologies to implement the full-electric airplane in the future. Currently, the research and development to convert existing two-seater engine airplanes to electric-powered airplanes are underway domestically. The airplane converted to electric propulsion is the KLA-100, which aims to carry out a 30-minute flight test with a battery pack installed using the engine mounting space and copilot space. The lithium-ion battery installed on the airplane converted to electric propulsion was designed with a specific power of 150Wh/kg, weight of 200kg, and a C-rate 3~4. This study confirmed the possibility of a 30-minute flight with a designed battery pack before conducting a flight test of a modified electrically propelled airplane. The battery performance was verified by dividing the 30-minute flight profile into start/run stage, take-off stage, climbing stage, cruise stage, descending stage, and landing/run stage. The final target of the 30-minute flight was evaluated by calculating the battery capacity required for each stage. Furthermore, the flight performance of the electrically propelled airplane was determined by calculating the flight availability time and navigation distance according to the flight speed.

• Korean Journal of Mineralogy and Petrology
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• v.36 no.3
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• pp.199-212
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• 2023

Diffusion is a powerful tool to understand geological processes recorded in terrestrial rocks as well as extraterrestrial materials. Since the diffusive exchange of elements or isotopes may have occurred differently in the solar nebula (high temperature and rapid cooling) and on the parent bodies (fluid-assisted thermal metamorphism at relatively low temperature), it is particularly important to model elemental or isotopic diffusion profiles within the mineral grains to better understand the evolution of the early solar system. A numerical model with the finite difference method for the fast grain boundary diffusion was established for the exchange of elements or isotopes between constituent minerals in a closed system. The fast grain boundary diffusion numerical model was applied to 1) ²⁶Mg variation in plagioclase of an amoeboid olivine aggregate (AOA) from a CH chondrite and 2) Fe-Mg interdiffusion between chondrules, AOA, and matrix minerals in a CO chondrite. Equilibrium isotopic fractionation and equilibrium partitioning were also included in the numerical model, based on the assumption that equilibrium can be reached at the interfaces of mineral crystals. The numerical model showed that diffusion profiles observed in chondrite samples likely resulted from the diffusive exchange of elements or isotopes between the constituent minerals. This study also showed that the closure temperature is determined not only by the mineral with the slowest diffusivity in the system, but also strongly depends on the constituent mineral abundances.