• International Journal of Aeronautical and Space Sciences
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• v.17 no.4
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• pp.526-534
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• 2016

A MEMS solid propellant thruster array shall be operated within an allowable range of operating temperatures to avoid ignition failure by incomplete combustion due to a time delay in ignition. The structural safety of the MEMS thruster array under severe on-orbit thermal conditions can also be guaranteed by a suitable thermal control. In this study, we propose a thermal control strategy to perform on-orbit verification of a MEMS thruster module, which is expected to be the primary payload of the STEP Cube Lab mission. The strategy involves, the use of micro-igniters as heaters and temperature sensors for active thermal control because an additional heater cannot be implemented in the current design. In addition, we made efforts to reduce the launch loads transmitted to the MEMS thruster module at the system level structural design. The effectiveness of the proposed thermo-mechanical design strategy has been demonstrated by numerical analysis.

• Journal of Astronomy and Space Sciences
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• v.37 no.1
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• pp.1-9
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• 2020

Frozen orbit is an attractive option for orbital design owing to its characteristics (its argument of pericenter and eccentricity are kept constant on an average). Solar sails are attractive solutions for massive and expensive missions. However, the solar radiation pressure effect represents an additional force on the solar sail that may greatly affect its orbital behavior in the long run. Thus, this force must be included as a perturbation force in the dynamical model for more accuracy. This study shows the calculations of initial conditions for a lunar solar sail frozen orbit. The disturbing function of the problem was developed to include the lunar gravitational field that is characterized by uneven mass distribution, third body perturbation, and the effect of solar radiation. An averaging technique was used to reduce the dynamical problem to a long period system. Lagrange planetary equations were utilized to formulate the rate of change of the argument of pericenter and eccentricity. Using the reduced system, frozen orbits for the Moon sail orbiter were constructed. The resulting frozen orbits are shown by two 3Dsurface (semi-major, eccentricity, inclination) figures. To simplify the analysis, we showed inclination-eccentricity contours for different values of semi-major axis, argument of pericenter, and values of sail lightness number.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.203-207
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• 2014

According to the advanced study, Increase of ceiling air space could cause increase of floor impact sound by air-spring effect. So in this research, we studied the increase of floor impact sound caused by ceiling air space in apartment buildings. At first, we evaluated the change of floor impact noise in the condition of with or without ceiling air-space. And then we installed perforated ceiling systems and glass wool at ceiling area. we expected that perforated ceiling systems could prevent air-spring effect in ceiling space. As a result, ceiling air space caused increasement of floor heavy impact noise about 2~4dB. But perforated ceiling & sound-absorbing materials system could give us reduction of heavy floor impact noise about 3dB. So this systems could be a good alternative to obey national regulations, because it can reduce heavy impact noise additional to floating floor systems.

• Journal of Korean Medicine Rehabilitation
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• v.30 no.1
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• pp.125-135
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• 2020

To report the effect of an Korean medical treatment, including Space spinal conduction exercise and manipulation treatment for a patient suffering with spondylolisthesis. Three patients were treated by oriental medical treatment including acupuncture, oriental medicine, Space spinal conduction exercise and manipulation treatment and the results were assessed with a numerical rating scale (NRS), walking condition, and back pain, sciatica. After treatment, the NRS changed from 8~9 to 1~2 and walking condition get better. The patient's back pain and sciatica have improved. In this study, oriental medical treatment, including Space spinal conduction exercise and manipulation treatment was an effective treatment for patients with spondylolisthesis. However, additional studies are needed, as are more and observations of these patients.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.42.1-42.1
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• 2016

We examined thousands of light curves of stars brighter than 18.0 mag in I band and less than mean magnitude error of 0.1 mag in V band from the OGLE-III eclipsing binary catalogue, and found 90 new binary systems exhibiting apsidal motion. In this study, the samples of apsidal motion stars in the SMC were increased by 250 percent than previously known. In order to determine the period of the apsidal motion for the binaries, we analysed in detail both light curves and eclipse timings using the MACHO and OGLE photometric database obtained for about 20 yrs. For the eclipse timing diagrams of the systems, new times of minimum light were derived from the full light curve combined at intervals of one yr from the survey data. The binaries presented in this paper have apsidal motion periods in the range of 12-918 yrs. An additional short-term oscillation was detected in five systems (OGLE-SMC-ECL-1634, 1947, 3035, 4946, and 5382), which most likely arise from the existence of a third body orbiting each eclipsing binary. All of the selected systems can be used for the statistical study of the interior structure of the stars in the SMC through their apsidal motions due to the homogeneous data and consistent analysis methods.

• Journal of the Korean BIBLIA Society for library and Information Science
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• v.19 no.2
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• pp.85-105
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• 2008

The purpose of this study is to provide guidelines and recommendations on the process of planning and designing library space and it also reflects on developments which should be considered when planning new library space. The methodology of estimating library space needs of IFLA, a guide for public library building in New South Wales of Australia, and the recommendations for academic libraries in French were analysed. The results given throughout theses guidelines and recommendations are able to develop the guide for public library space in Korea. The guide suggested defines six broad types of library space; collection area, readers and library users, library staff, conference, meeting and cultural space, mechanical and support services, additional services areas. It is import to remember however that each library building and the service it provides is unique and should reflect the needs and aspiration of its community.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.6
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• pp.675-683
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• 2015

The room-and-pillar construction method for underground space is adopted from the room-and-pillar mining method which is one of the most popular underground mining method in the world. Drainage system in the room-and-pillar underground construction method can be similar with the concept of single shell in tunnel because additional reinforcement except the TSL (thin spray-on liner) is not applied in the room-and-pillar construction method. That is, to decrease groundwater level and maintain safety in tunnel, the drainage pin hole inside lining (shotcrete) can be used. However, if total amount of outflow in the underground structure is relatively small or groundwater is not detected, such drainage system will not be useful and cause additional construction cost. In this study, outflow of conventional tunnels in South Korea was investigated and the criteria to determine whether the drainage pin hole is effective was suggested. And the guided drainage system was suggested when drainage pin hole was not applied in the room-and-pillar construction method.

• Korean Institute of Interior Design Journal
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• v.23 no.4
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• pp.169-180
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• 2014

Since Seoul city supplied 'Sangsang Children's Park', domestic children's parks are changing from formal facilities to creative play space recently. From eco-friendly safe playground model development project, the awareness of eco-friendly playground, namely children's park is increasing and its necessity is magnified. However, we could not know how well most children's parks aimed at the eco-friendly playground reflect eco-friendly features and whether they are eco-friendly or not because there are not the specific planning guidelines and evaluation standards for making the eco-friendly playground or children's park. Therefore, in this study we established the environment-friendliness evaluation standards of children's parks and estimated the environment-friendly features of the 9 parks built on the subject of green among Sangsang Children's Parks. In the observational survey of the 9 parks, we evaluated the environment-friendliness of these parks in the 8 fields(location and placement, ecological environment, play space, play equipment and facilities, additional facilities, materials and resources, energy saving, environmental load reduction) according to the levels(suitable, partial reflection, unsuitable, non-reflection) of reflection of eco-friendly planning factors. The assessment results showed that 4 items (location and placement, additional facilities, play space, play equipment and facilities) were suitable and others (energy saving, environmental load reduction, ecological environment, materials and resources) were partial reflection or unsuitable. Therefore, on the basis of these results, this study proposed the planning indicators to be considered first and the planning factors that should be complemented and improved in the construction of eco-friendly children's park in future.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.676-678
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• 2010

Conventional Augmented Reality has used data gloves or markers for smooth interaction between objects and background. This causes inconvenience of use and lower immersion. To build up immersion in Augmented Reality, additional input devices must be removed. This paper proposes a method to create virtual space coordinates for interaction without wearing additional input devices so as to improve immersion in Augmented Reality. The acquired image was projected to a two-dimensional space and vanishing lines were extracted to calculate the virtual space coordinates. Then the sizes of the inserted objects were varied in accordance with the size of the virtual coordinates area based on the image projected onto the two-dimensional coordinates. This resulted in improved immersion. This method can increase the efficiency of object creation by excluding the use of a 3D modeler for creation of three-dimensional objects.

• The Journal of the Korea Contents Association
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• v.21 no.12
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• pp.375-383
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• 2021

Due to COVID-19, people are building new lifestyles such as online shopping, online travel, and video conferencing by limiting going out and gatherings. Such rapid social change is causing new problems and deepening existing problems at the same time. In particular, as online consumption increases significantly, traffic congestion, air pollution, and the heavy workload of delivery drivers are deepening in the daily logistics industry, and face-to-face delivery is emerging as a new problem. With the advent of the 4th industrial revolution, unmanned delivery using drones, artificial intelligence, and autonomous driving is emerging as an alternative to the existing logistics industry. However, space for logistics facilities and securing additional logistics sites due to drone flight are emerging as new problems to be solved. Therefore, it is intended to link additional services such as logistics movement, storage, and delivery by utilizing the existing transportation business, the subway, as a space for a logistics facility for drones that can solve existing problems and new problems.