• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.10
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• pp.855-862
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• 2017

Due to the weight reduction and miniaturization of satellites, there is a growing interest in low-cost launch vehicles, which are cheaper to launch than larger launch vehicles. One of the most cost-effective ways to reduce the cost of launch vehicles is the reuse of vehicles. Most companies that are developing low cost launch vehicles are also adopting a vehicles reuse approach. Along with this reuse purpose, the demand for environmentally friendly space launch vehicles has increased, so the choice of fuel used for low cost launch vehicles has also become very important. Methane and hydrogen-enriched compressed natural gas (HCNG), which makes more energy-efficient by adding hydrogen to methane, are considered to be the most suitable when considering other factors such as energy density among the fuels that are eco-friendly and capable of reusing the launch vehicles. This study investigated the trends of low-cost launch vehicle and rocket fuel in the world as a reference for setting up domestic space development after the development of Korea Space Launch Vehicle-II.

• Korean Institute of Interior Design Journal
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• v.18 no.5
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• pp.101-110
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• 2009

In case of general residential house, photovoltaic can be installed at roof, wall, and any other places. But, in case of apartment building, there has not enough roof space to install photovoltaic panels to supply enough electricity. Actually, apartment building roof and facade wall (exclude the balcony window space) is not enough space to produce and supply the electricity to residents by installing PV panel. Generally, the space of facade balcony with windows in facade wall at apartment building occupied about $70{\sim}80%$, in all facade space. So, if we could use the balcony and windows space in facade as PV to generating electricity, there could contribute the energy saying. But, PV cell is opacify. So if it installed at front window area in apartment building, residents may have displeasure for that opacity character. But the other hand, residents are not always in house especially in day time that is exactly good time for generating electricity by PV. If we can use PV at the facade balcony with window without collusion of resident's displeasure, there have good attraction to using sustainable energy. Hence, this study suggests the design of facade balcony window style PV by considering resident's living pattern in apartment building. The methods of this study are as follows. At first, this study surveyed to the residents about residential time in their home and asked user demand by Delphi survey. At second, this study designed balcony open style PV system which oriented to the user demand. At third, this study tests designed result performance by computer simulation that compared design result with old design. As a result, For the purpose of satisfying the resident demand, there designed sliding window style which slide the several door systems to the one side. That would be make balcony absolute open scenery to the residents. Hence, the designed system performance results were as follows. When we compare the small apartment and large apartment, smaller one has good performance than larger one. Because resident's residential time characteristic. And that has more good electronic performance than vertical style that is similar to roof style.

• Journal of the Korean Society for Marine Environment & Energy
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• v.12 no.1
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• pp.15-22
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• 2009

Auto-navigation algorithm have been studied to avoid collision and grounding of a ship due to human error. There have been many research on collision avoidance algorithms but they have been validated little on the real coastal traffic situation. In this study, a Collision Avoidance algorithm is developed by using Fuzzy algorithm and the concept of Changeable Action Space Searching (CAS). In the first step, on a basis of collision risk calculated from fuzzy algorithm in the current time(t=to), alternative Action Space for collision avoidance is planned. In the second step, next alternative Action Space for collision avoidance in the future($t=to+{\Delta}t$) is corrected and re-planned with re-evaluated collision risk. In the third step, the safest and most effective course among Action Space is selected by using optimization method in real time. In this paper, the main features of the developed collision avoidance algorithm (CAS) are introduced. CAS is implemented in the ship-handling simulator of MOERI. The performance of CAS is tested on the situation of open sea with 3 traffic ships, whose position is assumed to be informed from AIS. Own-ship is fully autonomously navigated by autopilot including the collision avoidance algorithm, CAS. Experimental results show that own-ship can successfully avoid the collision against traffic ships and the calculated courses from CAS are reasonable.

• Korean Institute of Interior Design Journal
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• v.21 no.6
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• pp.224-232
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• 2012

Although evolution of construction materials brought about development of modern architecture, they caused destruction of the environment and pollution. This problem is not a new one in terms of ecological esthetics and materials of sustainable architecture in light of the Eastern view of nature and this idea became a background of this study. The basic concept is to try to find out their characteristics from a perspective of ecological esthetics in relation to traditional building materials that nature, architecture, and humans coexist and live with each other to balance. Based on ecological esthetics and precedent studies on materials of traditional architecture, we investigated connections, expressive methods and characteristics in traditional residential construction space. This attempt has meanings in that it can propose a new framework of forming various viewpoints and spatial perceptions in relation to esthetics and traditional construction materials. The current study examined the characteristics by dividing them into tangible and intangible elements based on expressive features of elements of nature. The characteristics found by this process are not simply notion of physical materials, but plays a key role aesthetically and ecologically. Nature and materials take circulation of the law of nature, regulate energy, increase efficiency and play a major role in an economic way. Nature in itself becomes natural alternative energy, and plays its role in an invisible fashion. It examined how expressive characteristics of construction materials are reflected through analyzing residential space and Korean traditional garden having relationships with Eastern viewpoint of nature in relation to Korean traditional construction materials from a perspective of ecological esthetics. Findings of the above study indicate that expressive characteristics of Korean traditional construction materials from a perspective of ecological esthetics are that nature, space, humans coexist and live together and they will provide a clue to an alternative to solve ecological and environmental problems modern society will have in the future. Through this process, it provided a possibility that traditional space and materials can be succeeded in creative and new ways, and it found out the way for nature, space, and humans to coexist and a possibility of ecological esthetics. It addition, it will provide a key base as an alternative of sustainable design of the future.

• Korean Journal of Heritage: History & Science
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• v.45 no.1
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• pp.174-189
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• 2012

This study aims to examine the traditional living space to reflect the environment-friendly design methods and principles of reestablishment. To do so, this study carried on a related literature study and field survey. The traditional living space in terms of the environmental friendliness is reflected on site selection and space composition, and utilization of natural energy and natural materials. Focused on the Kwangajeong in Yangdong Village, this study is to identify eco-friendly techniques on the traditional living space. As a result, it shows that Kwangajeong with the side of the southeast in site selection had been considered in aspect of environmental control such as sunshine and solar radiation. Also building construction techniques had been used to minimize the variation of terrain. In aspect of environmental conservation, Kwangajeong had structurally arranged the gate, an inner yard and an inner floor to allow good ventilation. In aspect of space composition, Kwangajeong with the emphasis of scenic view had utilized the methods that attract external landscape through the control of its fences. Environment-friendly techniques and control principles in traditional space had been developed by a long experience through the long periods and the traditional techniques suitable for local climate and local environment have been developed. The technical development of these techniques to resolve the global environmental and energy issues and create a more pleasant living environment of human beings might be critical.

• Journal of Astronomy and Space Sciences
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• v.18 no.1
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• pp.1-6
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• 2001

In this paper we investigate the properties of advection-dominated accretion flows (ADAFs) in case that outflows carry away infalling matter with its angular momentum and energy. Positive Bernoulli number in ADAFs allow a fraction of the gas to be expelled in a form of outflows. The ADAFs are also unstable to convection. We present self-similar solutions for advection-dominated accretion flows in the presence of outflows from the accretion flows(ADIOS). The axisymmetric flow is treated in variables integrated over polar sections and the effects of outflows on the accretion flow are parameterized for possible configurations compatible with the one dimensional self-similar ADAF solution. We explicitly derive self-similar solutions of ADAFs in the presence of outflows and show that the strong outflows in the accretion flows result in a flatter density profile, which is similar to that of the convection-dominated accretion flows(CDAFs) in which convection transports the angular momentum inward and the energy outward. There two different versions of the ADAF model should show similar behaviors in X-ray spectrum to some extent. Even though the two models may show similar behaviors, they should be distinguishable due to different physical properties. We suggest that for a central object of which mass is known these two different accretion flow should have different X-ray flux value due to deficient matter in the wind model.

• Journal of the Korean Solar Energy Society
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• v.32 no.spc3
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• pp.199-206
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• 2012

The purpose of this study is to understand the change of impression by comparing the uniformity lighting with the compound lighting. In previous study, we proposed a light controlling method to harmonize daylight from a window and artificial lights from a ceiling and obtained the results to support our method. We referred this method as the Adjusted Compound-Lighting Model (AC Model). The experiment is carried out with the scaled-models and mock-up spaces that were supposed to be an office space. One is lit by the uniform lighting and the other by the compound lighting in each experimental space. In order to present varying illuminance distributions, the two variables were used in this study. Subjects were asked to evaluate the point of difference by semantic differential rating on their overall impression after comparing with two rooms. The results showed that the impressions of compound lighting were more positive score than that of uniformity lighting on the items of 'dim-bright', 'dislike-like', 'artificial-natural' and 'closed-open', and that there was no significant difference in impressions between two spaces on other items.

• KIEAE Journal
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• v.12 no.5
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• pp.77-84
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• 2012

Daylighting is the controlled admission of natural light into a space, reducing electric lighting and saving energy. By providing a direct link to the dynamic and perpetually evolving patterns of outdoor illumination, daylighting helps create a visually stimulating and comfort environment for building occupants, while reducing energy costs. Especially, however, glare is the most important factor in daylighting, which is issued by incoming direct sunlight into windows. This study analyzed the discomfort glare on a daylighting window by using Image processing methodology and found a solution to problems with glare source of occupants. There are several ways to evaluate discomfort glare such as UGR (Unified Glare Rating) of CIE, DGI (Daylight Glare Index, Hopkinson, 1972) and VCP (Visual Comfort Probability) of IES. These are used to apply to the relatively little artificial light source and they cannot cover discomfort glare from a real daylighting window. In this regarding, this paper aimed to calculate DGI index of the real daylighting window in a experimental space by using image processing methodology. The variables and outcomes are luminance distribution of non-shading window, effect of venetian blind installed on the window and locations related to position index of DGI.

• International Journal of Aeronautical and Space Sciences
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• v.16 no.2
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• pp.223-246
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• 2015

Structural vibration control using a piezoelectric shunt is an established control technique. This technique involves connecting a piezoelectric patch, which is bonded onto or embedded into the vibrating structure, to an electric shunt circuit. Thus, vibration energy is converted into electrical energy and is dissipated through a network of electrical components. Different configurations of shunt have been researched, among which the negative capacitance-inductance shunt has gained prominence recently. It is basically an analog, active circuit consisting of operational amplifiers and passive elements to introduce real and imaginary impedance on the vibrating structure. The present study attempts to model the behavior of a negative capacitance-inductance shunt in terms of power output and efficiency using circuit modeling software. The shunt model is validated experimentally and is used to control the structural vibration of an aluminum beam, connected to a pair of piezoelectric patches, under broadband excitation. The model is also used to determine the optimal parameters of a negative capacitance-inductance shunt to increase the efficiency and predict the voltage output limit of op-amp against the supply voltage.

• Journal of The Korean Astronomical Society
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• v.37 no.5
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• pp.597-600
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• 2004

A substantial number of processes have been suggested as possible contributors to the extragalactic $\gamma$-ray background (EGRB). Yet another contribution to this background will be emission produced in hadronic interactions of cosmic-ray protons with the cluster thermal gas; this class of cosmic rays (CRs) has been shown to be responsible for the EUV emission in the Coma Cluster of galaxies. In this paper we assume the CRs in the Coma Cluster is prototypic of all clusters and derive the contribution to the EGRB from all clusters over time. We examine two different possibilities for the scaling of the CR flux with cluster size: the number density of the CRs scale with the number density of the thermal plasma, and alternatively, the energy density of the CRs scale with the energy density of the plasma. We find that in all scenarios the EGRB produced by this process is sufficiently low that it will not be observable in comparison with other mechanisms that are likely to produce an EGRB.