• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.7
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• pp.105-116
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• 2004

The design of pico-/nano-satellites is particularly challenging due to constraints in mass, volume, power, and surface area. An efficient low-cost picosatellite HAUSAT-1 Electrical Power Subsystem (EPS) is developed to supply the power for various loads during the full mission life. This paper addresses design and analysis results of solar arrays, batteries, power conditioning and distribution units. The component selection, manufacturing and test results are presented by considering appropriate development cost and performance. The simulation results of power system are also illustrated, according to operational modes, through energy balance analysis. Finally, the EFS design feasibility is verified by comparing analysis results with functional and environmental test results at the system and component levels, respectively.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.10
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• pp.1017-1026
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• 2009

The solar cell system operates by facing the sun-light. Minor cracks, static discharge, and thermal shock that can happen during production/testing phase can lead to degradation in performance during operation, since solar cells are exposed to extreme thermal/mechanical environment in space. In order to detect small cracks and internal damages in the solar cells due to thermal shocks, which are the core units of a solar cell system, expensive equipment, complicated test process, and much time are required. Therefore, a qualitative method for easily and quickly testing the 'health' of solar cell functionality is required. This dissertation describes a theoretical and technical grounds for quickly and easily evaluating the health of solar cells using electroluminescence effect of Gallium-Arsenide solar cells that are most widely used by spacecrafts in recent years. Also described in the dissertation is the technical issues and constraining factors for applying the proposed method to actual space-rated solar cell systems.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.240-240
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• 2016

인류문명의 발달과 함께 경제력도 크게 개선되었으나 인구가 집중되어 있는 도시지역에서의 침수가 반복되고 있다. 도시침수는 직간접적인 피해규모가 심각하므로 구조적인 대책과 비구조적인 대책을 통하여 홍수방재에 많은 투자가 이루어져 왔다. 또한 계획규모 또한 상향조정되어 있다. 그러나 실제로 향상된 계획규모에 적합하도록 전체 홍수방재시설을 개수하는 데는 많은 기간과 예산으로 인하여 진행이 이루어지고 있지 못하고 있으며 과거의 호우사상에서 살펴볼 수 있는 바와 같이 계획규모를 크게 초과되는 홍수는 자주 발생되어 왔으며 이로 인한 도시침수도 계속되어 왔다. 이러한 현상은 기후변화 및 돌발홍수 등으로 인하여 앞으로도 반복될 가능성이 매우 높아질 것으로 예측된다. 따라서 현재의 홍수방재시설에 대하여 향상된 계획규모의 호우사상 또는 이를 초과하는 극대호우사상에서의 홍수방재를 위한 방안수립이 시급한 상황이라고 판단된다. 본 연구에서는 계획규모를 초과하는 극대호우사상에 대비하여 최소한의 예산으로도 획기적으로 도시침수를 억제할 수 있는 방안을 제시하고자 하였다. 도시지역에서의 홍수방재는 침수억제가 가장 중요하므로 침수모의를 통하여 통수능이 부족한 경우라도 침수가 발생되지 않는 지역은 제외하고 침수에 취약한 지점만을 대상으로 침수원인을 파악하여 역경사 또는 경사부족구간의 개선, 소규모 분산형 저류지를 통한 침수억제 및 빗물저류조와 빗물펌프장에서의 운영강화 등을 통하여 경제적인 침수억제방안의 수립을 전제하여 침수모의를 수행하였다. 연구결과 최소한의 구조적 개선과 기존 방재시설의 운영강화로 기왕의 홍수사상에서 발생된 침수에 대비하여 침수발생을 크게 저감시킬수 있는 것으로 분석되었다. 따라서 전반적인 개수보다는 중요침수지역들을 대상으로 우선순위를 결정하여 침수원인을 해소 하는 방안으로 홍수방재계획을 추진한다면 빠른 기간에 작은 예산으로 도시침수를 크게 저감 시킬 수 있을 것으로 기대된다.

• Journal of Advanced Navigation Technology
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• v.27 no.6
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• pp.865-870
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• 2023

Recently, accidents caused by black ice, a road freezing phenomenon caused by natural power, are increasing. Black ice is difficult to identify directly with the human eye and is more likely to misunderstand it as standing water, so there is a high accident rate caused by car sliding. To solve this problem, this paper presents a method of detecting black ice centered on LiDAR sensors. With a small, inexpensive, and high-accuracy light detection and ranging (LiDAR) sensor, the temperature and inclination angle are set differently to detect black ice and asphalt by setting different reflection angles of asphalt and black ice differently in temperatures and inclinations. The LIDARO carried out in the study points out that additional research and improvement are needed to increase accuracy, and through this, more reliable black ice detection methods can be suggested. This method suggests a method of detecting black ice through early system design research by preventing accidents caused by black ice in advance.

• Journal of the Korean Magnetics Society
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• v.22 no.3
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• pp.103-108
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• 2012

Having a de Broglie wavelength of a few ${\AA}$ with its corresponding energies in the range of a few to a few hundreds meV, neutrons are ideally suited for the studies of structure and dynamics in condensed matter research. Neutron scattering has been developed over the past 60 years or so and become a very mature and established experimental technique in the very broad range of material sciences. In this short introductory article, we have explained its working principles and provided few selected examples of application.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.8
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• pp.8-14
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• 2019

Bird-strike is one of the most important design factors for safety in the aviation industry. Bird-strikes have been the cause of significant damage to aircraft and rotorcraft structures and the loss of life. This study used DYTRAN software to simulate the transient response of an Euler-Lagrangian composite helicopter blade that has been impacted by a bird. The Arbitrary Lagrangian Eulerian (ALE) method and a suitable equation of state were applied to model the bird. ALE was applied to the bird-strike analysis due to the large difference between the properties of the blade and bird. The debris of the bird was assumed to be a fluid and applied as Euler elements after the collision. Through the analysis of bird impacts, the leading-edge of the rotor blade (50.8 mm) was used to identify a positive margin of 1.18 based on the TSAI-FILL criteria. The results are assessed to be sufficiently reliable and may be evaluated to replace tests with various analysis conditions. The structural stability of the rotor blade could be assessed by applying various load conditions and different modeling methods in the future.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.4
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• pp.153-157
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• 2023

In order to manufacture a semiconductor circuit, etching, cleaning, and deposition processes are repeated. During these processes, the inside of the processing chamber is exposed to corrosive plasma. Therefore, the coating of the inner wall of the semiconductor equipment with a plasma-resistant material has been attempted to minimize the etching of the coating and particle contaminant generation. In this study, we mixed AlF₃ powder with the solid-state reacted yttrium oxyfluoride (YOF) in order to increase plasma-etching resistance of the plasma spray coated YOF layer. Effects of the mixing ratio of AlF₃ with YOF powder on crystal structure, microstructure and chemical composition were investigated using XRD and FE-SEM. The plasma-etching ratios of the plasma-spray coated layers were calculated and correlation with AlF₃ mixing ratio was analyzed.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.5
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• pp.196-201
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• 2023

In order to improve the efficiency of the water splitting system for hydrogen energy production, the high overvoltage in the electrochemical reaction caused by the catalyst in the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) must be reduced. Among them, transition metal-based compounds (hydroxide, sulfide, etc.) are attracting attention as catalyst materials to replace currently used precious metals such as platinum. In this study, Ni foam, an inexpensive metal porous material, was used as a support and β-Ni(OH)₂ microcrystals were synthesized through a hydrothermal synthesis process. In addition, changes in the crystal morphology, crystal structure, and water splitting characteristics of β-Ni(OH)₂ microcrystals synthesized by doping Fe to improve electrochemical properties were observed, and applicability as a catalyst in a commercial water electrolysis system was examined.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.34 no.1
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• pp.30-35
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• 2024

In order to improve the efficiency of the water splitting system for hydrogen production, the high overvoltage in the electrochemical reaction caused by the catalyst in the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) must be reduced. Among them, transition metal-based compounds are attracting attention as catalyst materials that can replace precious metals such as platinum that are currently used. In this study, nickel foam, an inexpensive metal porous material, was used as a support, and Fe-doped β-Ni(OH)₂ microcrystals were synthesized through a hydrothermal synthesis process. In addition, in order to improve OER properties, changes in the shape, crystal structure, and water splitting characteristics of Fe-Mo co-doped β-Ni(OH)₂ microcrystals synthesized by co-doping with Mo were observed. The changes in the shape, crystal structure, and applicability as a catalyst for water splitting were examined.

• Journal of Environmental Science International
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• v.22 no.4
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• pp.471-479
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• 2013

The present study was conducted to judge the applicability of field quality control by children's goods manufacturers by assessing the contents of heavy metals such as Pb and Cd in outdoor play goods for children through measurement using Portable XRF and comparing the results through detailed analyses using ICP. Heavy metal contents of 711 part samples of 505 products were measured using XRF. According to the results, the ratio of products that exceeded the Pb and Cd content standards specified under the Quality Management and Safety Control of Industrial Products Act were 2.4% and 2.6%. Many products certified for self-regulated safety exceeded the standards and thus it was considered that harmful chemical material centered safety management systems would be necessary. Detailed ICP analyses of some products were compared and the results showed deviations of 0.9~80.8% from XRF results. The reasons for this are deviations in the characteristics of measured cross sections and the homogeneity of samples resulting from sample preparation methods, etc. Therefore, it is considered that field quality control will be applicable if measuring methods are efficiently established based on product characteristics and calibration curve preparation methods are established through quality control.