• Journal of Astronomy and Space Sciences
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• v.32 no.4
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• pp.379-386
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• 2015

This work presents fuel-optimal altitude maintenance of Low-Earth-Orbit (LEO) spacecrafts experiencing non-negligible air drag and J2 perturbation. A pseudospectral (direct) method is first applied to roughly estimate an optimal fuel consumption strategy, which is employed as an initial guess to precisely determine itself. Based on the physical specifications of KOrea Multi-Purpose SATellite-2 (KOMPSAT-2), a Korean artificial satellite, numerical simulations show that a satellite ascends with full thrust at the early stage of the maneuver period and then descends with null thrust. While the thrust profile is presumably bang-off, it is difficult to precisely determine the switching time by using a pseudospectral method only. This is expected, since the optimal switching epoch does not coincide with one of the collocation points prescribed by the pseudospectral method, in general. As an attempt to precisely determine the switching time and the associated optimal thrust history, a shooting (indirect) method is then employed with the initial guess being obtained through the pseudospectral method. This hybrid process allows the determination of the optimal fuel consumption for LEO spacecrafts and their thrust profiles efficiently and precisely.

• Korean Journal of Childcare and Education
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• v.15 no.6
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• pp.41-57
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• 2019

Objective: The purpose of this study was to investigate the moderate effect of the physical environmental-level between infant teachers' positive play beliefs and teacher-infant interaction. Methods: The subjects of this study were 483 teachers in charge of one-year-old and two-year-old infants in child care centers located in metropolitan areas. The data were collected by asking the teachers to respond to a questionnaire and the data collected were analyzed through correlation and hierarchical multi- regression analysis. Results: First, the positive play beliefs of the infant teacher, the physical environment level, and the teacher-infant interaction showed significant proportional correlations. Second, the physical environment level moderated the influence of the teacher's positive play beliefs on teacher-infant interaction. In particular, results showed that functional interior space configuration, outdoor playground composition and facilities among the sub-variables of the physical environment level had a moderating effect. Conclusion/Implications: The results of this study show that teachers with positive play beliefs have positive teacher-infant interaction when there is sufficient space available for infants and teachers. This indicates that the human and physical environments of child care centers can promote teacher-child interaction.

• Journal of the Korean Society of Costume
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• v.56 no.1 s.100
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• pp.121-130
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• 2006

Superimposition is a transforming technique that can facilitate the creation. Superimposition in previous studies, however, has only been fragmentary described as an expression technique, so the studies have not been conducted on the basis of its aesthetic value. The purpose of this study is to investigate how superimposition is applied and expressed in terms of forms of modern fashion based on multi-dimensional features of design processing. The codes of togetherness, ambivalence, sense of space and tension in dress were determined by using the expressional Superimposition. The forms of superimposition were limited to superimposition of clothing, superimposition of body and clothing and superimposition of body and Phenomenal body. This study found that superimposition has developed, in fashion forms/types, a new 'form' by overlapping various forms and thus provides a visual shock and a sense of mystery by using mismatched and arbitrary properties among the forms. Such a superimposition influences a methodology of fashion design through a designer's subjective tendencies, as well as influences a change in the view of the world. Also, a superimposition is expected to have a definite influence on new fashion trends.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.1
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• pp.29-36
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• 2016

Tensairity girder is a light weight inflatable fabric structural concept which can be used in road emergency transportation. It uses low pressure air to stabilize compression elements against buckling. With the purpose of obtaining the comprehensive target of minimum deflection and weight under ultimate load, the cross-section and the inner pressure of tensairity girder was optimized in this paper. The Variable Complexity Modeling (VCM) method was used in this paper combining the Kriging approximate method with the Finite Element Analysis (FEA) method, which was implemented by ABAQUS. In the Kriging method, the sample points of the surrogate model were outlined by Design of Experiment (DOE) technique based on Optimal Latin Hypercube. The optimization framework was constructed in iSIGHT with a global optimization method, Multi-Island Genetic Algorithm (MIGA), followed by a local optimization method, Sequential Quadratic Program (SQP). The result of the optimization gives a prominent conceptual design of the tensairity girder, which approves the solution architecture of VCM is feasible and efficient. Furthermore, a useful trend of sensitivity between optimization variables and responses was performed to guide future design. It was proved that the inner pressure is the key parameter to balance the maximum Von Mises stress and deflection on tensairity girder, and the parameters of cross section impact the mass of tensairity girder obviously.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.4
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• pp.467-475
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• 2016

Ultrasonic propagation imaging (UPI) has shown great potential for detection of impairments in complex structures and can be used in wide range of non-destructive evaluation and structural health monitoring applications. The software implementation of such algorithms showed a tendency in time-consumption with increment in scan area because the processor shares its resources with a number of programs running at the same time. This issue was addressed by using field programmable gate arrays (FPGA) that is a dedicated processing solution and used for high speed signal processing algorithms. For this purpose, we need an independent and flexible block of logic which can be used with continuously evolvable hardware based on FPGA. In this paper, we developed an FPGA-based ultrasonic propagation imaging system, where FPGA functions for both data acquisition system and real-time ultrasonic signal processing. The developed UPI system using FPGA board provides better cost-effectiveness and resolution than digitizers, and much faster signal processing time than CPU which was tested using basic ultrasonic propagation algorithms such as ultrasonic wave propagation imaging and multi-directional adjacent wave subtraction. Finally, a comparison of results for processing time between a CPU-based UPI system and the novel FPGA-based system were presented to justify the objective of this research.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.7
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• pp.542-550
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• 2018

This paper presents design of a bearingless main rotor of SNUF (Seoul National University Flap) blade equipped with active trailing-edge flap to reduce the hub vibratory loads during helicopter forward flight. For that purpose, sectional design of the flexbeam is carried out using the thin-walled composite material rotating beam vibration analysis program (CORBA77_MEMB) in EDISON. Using the multi-body dynamics analysis program, DYMORE, blade dynamic characteristics and those of the loads control are examined using the active trailing-edge flap in terms of the flexbeam sectional design.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.10
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• pp.92-98
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• 2006

An 1 lbf of NASA standard monopropellant thruster, MRE-1, is used for KOMPSAT (Korea Multi-Purpose Satellite) which is launched in 2006 and provides reliable and cost-effective means for attitude and maneuvering control system. The monopropellant thruster obtains required thrust by thermal decomposition process of propellant through catalyst bed. During firing, the decomposition plays a role of a heat source that may occur an excessive radiation heat transfer to peripheral structures and electronics in relatively low temperature condition.Therefore, the radiation heat shield is needed to prevent the critical radiative heat exchange between thruster and satellite during firing. This paper summarizes an overall development process of radiation heat shield from the design engineering up to the manufacturing.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.05a
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• pp.628-629
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• 2018

Recently, residential spaces in urban areas have changed into multi - family residential spaces. There is a feature that smoke is charged when a fire occurs here. Also, the evacuation route and the direction of the outflow of smoke are the same, and the possibility of inhaling the smoke of the evacuees is very high. When fighting fire in a narrow residential space such as a dwelling in a downtown area, exploration is the most important. For this purpose, we implement EO / IR sensor which can be mounted on firefighter 's helmet and can be used for fire detection. By using the EO / IR operation test, we can derive the results that can be used for research and development of the fire search sensor.

• Journal of the Korean housing association
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• v.11 no.3
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• pp.99-107
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• 2000

The purpose of this study was to identify the universal design characteristics in residential environments. The subjects were 135 physically disabled persons who lived in the rental multi-family housing apartments in Pusan. Interview method was used for this study. They were an average age of 51 years and 63% were male. They were low income families and lived in 12 pyung ($39.75\textrm{m}^2$) apartments. They were asked about what housing characteristics were constraints in their daily living. They pointed out that the constraints in their apartments were as follows: 1) the small amount of space in the bathroom, kitchen, bedroom, and the entrance area of housing unit, 2) the unflat floor level between the bathroom and the hallway, or the balcony and the bedroom, 3) the slippery floor finish in the bathroom, 4) lack of grab bars or handrails in the bathroom and the ramp, 5) the kitchen work centers and the electric switches at improper height, and 6) the steep ramp. Therefore, the universal design characteristics in residential environments were the adequate amount of space, flat floor level, non-slippery floor finish, grab bars or handrails, accessible height, and ramp.

• Journal of the Korean housing association
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• v.24 no.6
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• pp.189-197
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• 2013

The purpose of the study was to analyze the improvement elements depended on housing quality measurement tool related to mental health. The data for the analysis was collected through questionnaire survey method from November 1, 2012 to January 17, 2013, and the sample consisted of 720 respondents living in single detached houses, multi-families detached houses, apartments, and town houses in 4 cities, Seoul, Busan, Daejeon, and Kwangju. The data were analyzed using descriptive statistics. The results of improvement elements are as follows: 1) Pedestrian-threaten street from cars in physical safety 2) A secluded or dark spot and fear of walking at night in social security, 3) Indoor noise, outdoor noise, and evidence of abandoned trash heap/bottle in neighborhood in health & sanitation, 4) Illegal parking and heating control system in facility convenience, 5) Extra kitchen, number of bathrooms, and community spaces in space convenience, 6) Openness and spaciousness of indoor room, and satisfaction of house and neighborhood in comfort, 7) Management common/sharing space in maintenance, 8) Energy saving facility and environment friendly materials use in sustainability, 9) Burden on housing cost, asset value on house, and school district in economic value, 10) Reflection of residents style, surrounding building's number of layers, and neighborhood appearance of preference in housing environment image.