• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.6
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• pp.523-530
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• 2017

Laser-Induced Breakdown Spectroscopy (LIBS) which a plasma is irradiated at a specific wavelength depending on the material when a high-energy laser is irradiated, and a Raman spectroscopy which measures rotation and vibration in molecules as light-scattering phenomenon occurs, are attracting attention as a space exploration technology because of the advantages of high accuracy and real-time analysis, and the ability to perform long-range detection. In this study, the tendency of the laser spectrum according to the change of the soil component was analyzed by laser spectroscopy and the two - dimensional chemical distribution was conducted based on the trend of laser spectrum. We have also established the environment of Mars (4-7 torr) and lunar atmosphere (<1 torr) in experimental setup, to prove that it is possible to measure by difference of soil chemical composition using LIBS and Raman spectroscopy even in artificial space environment.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.98-98
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• 2014

Due to the simple vertical structure of magnetic field, pores can be exploited to study the transport of mechanical energy by waves along the magnetic field to the chromosphere and corona. For a better understanding of physics of pores, we have investigated chromospheric traveling features running across two merged pores from their centers at the speed about 55 km s-1, in the active region AR 11828. The pores were observed on 2013 August 24 by using high time, spatial, and spectral resolution data from the Fast Imaging Solar Spectrograph (FISS) of the 1.6 meter New Solar Telescope (NST). We infer a LOS velocity by applying the bisector method to the Ca II $8542{\AA}$ band and $H{\alpha}$ band, and investigate intensity and the line-of-sight velocity changes at different wavelengths and different positions at the pores. We find that they have 3 minutes oscillations, and the intensity oscillation from the line center is preceded by that from the core ($-0.3{\AA}$) of the bands. There is no phase difference between the intensity and the LOS velocity oscillations at a given wavelength. The amplitude of LOS velocity from near the core spectra is greater than that from the far core spectra. These results support the interpretation of the observed wave as a slow magnetoacoustic wave propagating along the magnetic field lines in the pores. The apparent horizontal motion and a sudden decrease of its speed beyond the pores can be explained by the projection effect caused by inclination of the magnetic field with a canopy.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.5
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• pp.474-480
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• 2011

Space Imaging Sensor operated on LEO is affected from the Earth IR and Albedo as well as the Sun Radiation. The Imaging Sensor exposed to extreme environment needs thermal control subsystem to be maintained in operating/non-operating allowable temperature. Generally, units are periodically dissipated on spacecraft panel, which is designed as radiator. Because thermal design of the imaging sensor inside a spacecraft is isolated, heat pipes connected to radiators on the panel efficiently transfer dissipation of the units. First of all, preliminary thermal design of radiating area and heater power is performed through steady energy balance equation. Based on preliminary thermal design, on-orbit thermal analysis is calculated by SINDA, so calculation for thermal design could be easy and rapid. Radiators are designed to rib-type in order to maintain radiating performance and reduce mass. After on-orbit thermal analysis, thermal requirements for Space Imaging Sensor are verified.

• Bulletin of the Korean Space Science Society
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• 2009.10a
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• pp.28.4-29
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• 2009

The 'Amon-Ra' instrument of the proposed 'EARTHSHINE' satellite is a dual (i.e. imaging and energy) channel instrument for monitoring the total solar irradiance (TSI) and the Earth's irradiance at around the L1 halo orbit. Earlier studies for this instrument include, but not limited to, design and construction of breadboard Amon-Ra imaging channel, stray light suppression and system performance computation using Integrated Ray Tracing (IRT) technique. The Amon-Ra instrument is required to produce 0.3% in uncertainty for both Sunlight and Earthlight measurement. In this study, we report accurate estimation of the output electric signal derived from the orbital variation of radiant exitance from the Sun and the Earth arriving at the aperture and detector plane of the Amon-Ra. For this, orbital irradiance are computed analytically first and then confirmed by simulation using Integrated Ray Tracing (IRT) model. Specially, the results show the arriving power at the bolometer detector surface is $1.24{\mu}W$ for the Sunlight and $1.28{\mu}W$ for the Earthlight, producing the output signal pulses of 34.31 mV and 35.47 mV respectively. These results demonstrate successfully that the arriving radiative power is well within the bolometer detector dynamic range and, therefore, the proposed detector can be used for the in-orbit measurement sequence. We discuss the computational details and implications as well as the simulation results.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.4
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• pp.181-192
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• 2014

Light-shelf is one of the most efficient natural lighting systems due to the improved function of the inflow level of the outdoor natural light. However, the existing research on the light shelf limits to the rectangular parallelepiped space, so do not provide sufficient data for various shapes of spaces. Thus, this study aims at deriving proper plan and relationship of the light shelf through its performance assessment depending on the indoor space shapes and utilizing them as basic data of light shelf design. The conclusions are as follows : 1) for 6m space depth, standard intensity of illumination satisfaction depth has shown 8.3%~26.3% improvement through the adjustment of the angle and width when installing light shelf compared to no light shelf installation; 2) $-30^{\circ}$, $-20^{\circ}$ and $-10^{\circ}$ light shelves set by this study play only as a blind regardless of the shape of ceiling on the summer solstice, and it is unsuitable; and 3) this study has derived proper plan of light shelf upon space shapes based on energy reduction and indoor evenness. The study results provide expanded data of the performance assessment of the light shelves according to the different space shapes and light shelf factors, which serves as a basis of the light shelves designing.

• Computational Structural Engineering
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• v.10 no.4
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• pp.205-216
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• 1997

In order to trace the lateral post-buckling behaviors of thin-wafled space frames, a geometrically nonlinear finite element formulation is presented by applying incremental equilibrium equations based on the updated Lagrangian formulation and introducing Vlasov's assumption. The improved displacement field for symmetric thin-walled cross sections is introduced based on inclusion of second order terms of finite rotations, and the potential energy corresponding to the semitangential rotations and moments is consistently derived. For finite element analysis, tangent stiffness matrices of the thinwalled space frame element with 7 degrees of freedom including the restrained warping for each node are derived by using the Hermition polynomials as shape functions. A co-rotational formulation in order to evaluate the unbalanced loads is presented by separating the rigid body rotations and pure deformations from incremental displacements and evaluating the updated direction cosines of the frame element due to rigid body rotations and incremental member forces from pure deformations. Finite element solutions for the spatial buckling and post-buckling analysis of thin-walled space frames are presented and compared with available solutions and other researcher's results.

• Computational Structural Engineering
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• v.10 no.1
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• pp.201-211
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• 1997

A clearly consistent finite element formulation for geometrically non-linear analysis of space frames is presented by applying incremental equilibrium equations based on the updated Lagrangian formulation and introducing Vlasov's assumption. The improved displacement field for symmetric cross sections is introduced based on inclusion of second order terms of finite rotations, and the potential energy corresponding to the semitangential rotations and moments is consistently derived. For finite element analysis, elastic and geometric stiffness matrices of the space frame element are derived by using the Hermitian polynomials as shape functions. A co-rotational formulation in order to evaluate the unbalanced loads is presented by separating the rigid body rotations and pure deformations from incremental displacements and evaluating the updated direction cosines of the frame element due to rigid body rotations and incremental member forces from pure deformaions. Finite element solutions for the spatial buckling and post-buckling analysis of space frames are compared with available solutions and other researcher's results.

• Corrosion Science and Technology
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• v.19 no.3
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• pp.131-137
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• 2020

A number of piping components in the secondary system of nuclear power plants (NPPs) are exposed to aging mechanisms, such as flow-accelerated corrosion (FAC), cavitation, flashing, solid particle erosion, and liquid droplet impingement erosion. Those mechanisms may lead to thinning, leaking, or rupture of the components. Due to the pipe ruptures caused by wall thinning in Surry unit 2 in the USA in 1986 and Mihama unit 3 in Japan in 1994, pipe wall thinning management has emerged as one of the most important issues in the nuclear industry. To manage pipe wall thinning, a foreign program has been utilized for NPPs in Korea since 1996. As our experience and knowledge of pipe wall thinning management have accumulated, our program needs to reflect our experience, requests from users, and the result of recent experiments using Flow Accelerated Corrosion Testing System (FACTS). FACTS is the empirical experimental facility developed by Korea Atomic Energy Research Institute (KAERI) for tests. Accordingly, KEPCO-E&C developed a 3D-based pipe wall thinning management program called ToSPACE in 2016. This paper describes a comparison between the FAC analysis results using ToSPACE and the experimental results using FACTS to verify their applicability to pipe wall thinning management in NPPs.

• Journal of the Architectural Institute of Korea Planning & Design
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• v.35 no.6
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• pp.27-37
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• 2019

This study focused on the possibility of reducing the cooling load through the change of micro climate in the outdoor space during summer season. This study proposes an efficient planning model by comparing the effects of urban heat island mitigation through wind path planning, outdoor space vegetation, and exterior material change by using the basic model of the street-oriented block housing proposed in the previous research by the same author. As a result, the most effective wind path planning strategy in the street-oriented block housing was the change of the air flow through the mass height adjustment. When the tall building masses were staggered and arranged in a balanced manner, the overall wind environment could be improved. The greater the height difference between low and high masses, the better the air flow was shown. It was also important to arrange the building masses so that the inlet of the main wind was open and to allow the external space to connect to the adjacent block to create a continuous flow. The change of outdoor space vegetation and flooring, and the formation of wind paths through the opening of lower part also showed the effect of heat island reduction. In addition, the change of PMV in summer was the biggest influence of shadow by tall building mass. Attention should be paid to the fact that high-albedo exterior materials are adversely affected by multiple reflections in dense street-oriented block housing. The use of albedo of the exterior material showed that it is necessary to pay attention to apply in the high density block housing. This is attributed to the rise of the temperature due to the absorption of energy into the low-albedo flooring, where the high-albedo exterior causes multiple reflections.

• Journal of Environmental Impact Assessment
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• v.32 no.3
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• pp.176-186
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• 2023

Urban Heat Island (UHI) is caused by an energy imbalance in urban areas, where building design and land cover contribute to its amplification. To mitigate UHI, increasing green space is one of the well known and the most effective approach. This study aims aimed to identify specific components of green spaces that lower temperatures and demonstrate the cooling effects based on their size and composition. Forests within green spaces have had a greater impact on temperature reduction due to shading and blocking solar radiation. Although lakes also contributed to temperature reduction, the effect to cooling intensity was not significant. The cooling distance does not depended on green space size or composition. The study emphasizes that initial temperature has a strongerinfluence on cooling intensity than green space size, highlighting the importance of vegetation type within green spaces to achieve a cooling effect. These findings provide valuable insights for urban planning and the design of green spaces to mitigate the effects of the urban heat island.