• 천문학회보
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• 제34권1호
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• pp.119.1-119.1
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• 2009

• 한국실내디자인학회논문집
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• 제21권4호
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• pp.87-95
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• 2012

This study is for the analysis to which element of space the users observing the lobby at a public space pay more attention for their visual perception. It is focused on the typology process of observation characters. The subjects, in the observation process, came to be interested in the circumstantial clues for space perception and the detailed characters drawing their interest. I could analyze the observation characters of the subjects observing the space by the comprehension and typology of their observation characters. First, from the viewpoint of successive 9 times of observations, each subject observed for 0.32 second to get the visual perception in the applied space, but spent another 0.39 second for the exploration of another observation object or the space roaming. The observation character of the subjects at the lobby of the public space selected for this experiment was that they spent more time on space exploration than on concentration on a point in the space. Second, I analyzed the typology process through the time range. Since the subjects' frequency varied depending on the way to set up the time range, the necessity was proposed that the time range for the analysis of observation characters should be set up more objectively. Third, in case of analyzing the observation characters by 10-second-unit time range, the concentration in the beginning and the middle was 25%, and that in the beginning and the final 41.7%, which showed that 75% of the subjects concentrated in the beginning of the observation time when the concentration in the beginning is added to it. Fourth, the type 3 categorized as "concentration in the beginning and the middle" is the group 47.1 percent of the subjects belong to, and each subject concentrated 1.1 times in the beginning and 2.1 times in the final, which showed that the concentration in the final was 1.75 times as high as that in the beginning.

• ETRI Journal
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• 제38권6호
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• pp.1240-1249
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• 2016

With the number of IP cores in a multicore system-on-chip increasing to up to tens or hundreds, the role of on-chip interconnection networks is vital. We propose a networks-on-chip-style bus network as a compromise and redefine the exploration problem to find the best IP tiling patterns and communication path combinations. Before solving the problem, we estimate the time complexity and validate the infeasibility of the solution. To reduce the time complexity, we propose two fast exploration algorithms and develop a program to implement these algorithms. The program is executed for several experiments, and the exploration time is reduced to approximately 1/22 and 7/1,200 at the first and second steps of the exploration process, respectively. However, as a trade-off for the time saving, the time cost (TC) of the searched architecture is increased to up to 4.7% and 11.2%, respectively, at each step compared with that of the architecture obtained through full-case exploration. The reduction ratio can be decreased to 1/4,000 by simultaneously applying both the algorithms even though the resulting TC is increased to up to 13.1% when compared with that obtained through full-case exploration.

• Journal of Astronomy and Space Sciences
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• 제26권4호
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• pp.677-692
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• 2009

최근 미국, 유럽, 일본 등 우주선진국을 중심으로 달, 화성 등 행성 탐사를 위한 로버(Rover) 시스템에 대해 많은 연구 개발이 진행되고 있다. 행성탐사용 로버 시스템 기술 중 특히 주행장치, 자율 주행 알고리즘, 탑재체 등을 중심으로 많은 연구가 수행되고 있다. 이 논문에서는 실제 행성탐사에 앞서 지상에서 로버 주행장치의 주행성 및 안정성을 평가하기 위해 지상시험모델용 로버의 주행장치에 대한 개념 설계 내용을 소개하였다. 또한, 로버 주행장치의 기술적인 관점에서 해외 연구개발 사례를 분석, 기술하였다. 이를 통해 로버 주행장치 개발을 위한 요구사항들을 주행성과 안정성 관점을 고려하여 도출하였다. 설계된 로버 주행장치는 높은 주행성과 안정성을 만족하기 위해 6족을 가지고 있으며, 각 다리의 관절을 제어하는 능동 서스펜션(Active Suspension)을 적용하였다. 이러한 종류의 주행장치 개념은 근미래 (Constellation 프로그램)에 수행될 유인달 탐사에서 이동 및 거주 장치로써 NASA의 ATHELE을 통해 처음 적용하여 개발하고 있다. 이 연구에서 제안된 장치 개념은 이와 달리 우리나라에서 앞으로 수행할 무인소형 달탐사에 적용하고자 설계되었다. 이 논문에서 소개된 내용은 향후 국내에서 행성탐사용 로버시스템을 본격적으로 개발하고자 할 때 유용한 참고자료 및 경험을 제공할 것 이다.

• 천문학회보
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• 제42권1호
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• pp.57.2-57.2
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• 2017

Remote and robotic telescopes are the most effective instrument for astronomical survey projects. The system is based on the dynamic operation of all astronomical instruments such as dome and telescope control system (TCS), focuser, filter wheel and data taking camera. We adopt the ASCOM driver platform to control the instruments through the integrated software. It can convert different interface libraries from various manufacturers into a uniform standard library. This allows us to effectively control astronomical instruments without modifying codes. We suggest a conceptual design of software for automation of a small telescope such as the new wide-field 0.25m telescope at McDonald Observatory. It can also be applied to operation of multi-telescopes in future projects.

• International Journal of Aeronautical and Space Sciences
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• 제7권1호
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• pp.1-12
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• 2006

In this study, a surrogate model is applied to multi-objective aerodynamic optimization design. For the balanced exploration and exploitation, each objective function is converted into the Expected Improvement (EI) and this value is used as fitness value in the multi-objective optimization instead of the objective function itself. Among the non-dominated solutions about EIs, additional sample points for the update of the Kriging model are selected. The present method was applied to a transonic airfoil design. Design results showed the validity of the present method. In order to obtain the information about design space, two data mining techniques are applied to design results: Analysis of Variance (ANOVA) and the Self-Organizing Map (SOM).

• Nuclear Engineering and Technology
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• 제47권6호
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• pp.678-699
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• 2015

Although the harsh space environment imposes many severe challenges to space pioneers, space exploration is a realistic and profitable goal for long-term humanity survival. One of the viable and promising options to overcome the harsh environment of space is nuclear propulsion. Particularly, the Nuclear Thermal Rocket (NTR) is a leading candidate for nearterm human missions to Mars and beyond due to its relatively high thrust and efficiency. Traditional NTR designs use typically high power reactors with fast or epithermal neutron spectrums to simplify core design and to maximize thrust. In parallel there are a series of new NTR designs with lower thrust and higher efficiency, designed to enhance mission versatility and safety through the use of redundant engines (when used in a clustered engine arrangement) for future commercialization. This paper proposes a new NTR design of the second design philosophy, Korea Advanced NUclear Thermal Engine Rocket (KANUTER), for future space applications. The KANUTER consists of an Extremely High Temperature Gas cooled Reactor (EHTGR) utilizing hydrogen propellant, a propulsion system, and an optional electricity generation system to provide propulsion as well as electricity generation. The innovatively small engine has the characteristics of high efficiency, being compact and lightweight, and bimodal capability. The notable characteristics result from the moderated EHTGR design, uniquely utilizing the integrated fuel element with an ultra heat-resistant carbide fuel, an efficient metal hydride moderator, protectively cooling channels and an individual pressure tube in an all-in-one package. The EHTGR can be bimodally operated in a propulsion mode of $100MW_{th}$ and an electricity generation mode of $100MW_{th}$, equipped with a dynamic energy conversion system. To investigate the design features of the new reactor and to estimate referential engine performance, a preliminary design study in terms of neutronics and thermohydraulics was carried out. The result indicates that the innovative design has great potential for high propellant efficiency and thrust-to-weight of engine ratio, compared with the existing NTR designs. However, the build-up of fission products in fuel has a significant impact on the bimodal operation of the moderated reactor such as xenon-induced dead time. This issue can be overcome by building in excess reactivity and control margin for the reactor design.

• 대한임베디드공학회논문지
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• 제11권4호
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• pp.201-208
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• 2016

Non-volatile counter is a counter that maintains the value without external power supply. It has been used for the applications related to warranty issues to count and record certain events such as power cycles, operating time, hard resets, and timeouts. It has been conventionally implemented with volatile memory-based counter and battery backup or non-volatile memory such as EEPROM. Both of them have a lifetime issue due to the limited lifetime of the battery and the endurance of the non-volatile memory cells, which incurs significant redundancy in design. In this paper, we introduce a hybrid architecture of volatile (SRAM) and non-volatile memory (EEPROM) cells to achieve required lifetime of the non-volatile counter with smaller cost. We conduct a design space exploration of the proposed hybrid architecture with the parameters of various kinds of non-volatile memories. The analysis result shows that the proposed hybrid non-volatile counter can extend the lifetime up to 6 times compared to the battery-backup volatile memory-based implementation.

• International Journal of Aeronautical and Space Sciences
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• 제18권4호
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• pp.651-661
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• 2017

A truss-braced wing (TBW) aircraft has recently received increasing attention due to higher aerodynamic efficiency compared to conventional cantilever wing aircraft. For conceptual TBW aircraft design, we developed a propulsion-and-airframe integrated design environment by replacing a semi-empirical turbofan engine model with a thermodynamic cycle-based one built upon the numerical propulsion system simulation (NPSS). The constructed NPSS model benefitted TBW aircraft design study, as it could handle engine installation effects influencing engine fuel efficiency. The NPSS model also contributed to broadening TBW aircraft design space, for it provided turbofan engine design variables involving a technology factor reflecting progress in propulsion technology. To effectively consolidate the NPSS propulsion model with the TBW airframe model, we devised a rapid, approximate substitute of the NPSS model by reduced-order modeling (ROM) to resolve difficulties in model integration. In addition, we formed an artificial neural network (ANN) that associates engine component attributes evaluated by object-oriented weight analysis of turbine engine (WATE++) with engine design variables to determine engine weight and size, both of which bring together the propulsion and airframe system models. Through propulsion-andairframe design space exploration, we optimized TBW aircraft design for fuel saving and revealed that a simple engine model neglecting engine installation effects may overestimate TBW aircraft performance.

• Journal of Preventive Medicine and Public Health
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• 제54권3호
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• pp.208-217
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• 2021

Objectives: In spite of the importance of green space for reducing obesity-related problems, there has been little exploration of whether access to green space (e.g., parks and recreational facilities) influences the obesity rate of adults in the United States. The purpose of the study was to investigate the relationships among accessibility of green space, obesity rates, and socioeconomic and demographic variables among adults living in the State of Indiana, United States. Methods: We conducted a secondary data analysis to investigate the relationships among accessibility to green space, obesity rates, and socio-demographic variables with employing Geographic Information System in order to measure the accessibility of green space. Results: This study found that accessibility of green space served as a strong predictor of reduced obesity rates among adults (β=-2.478; p<0.10). In addition, adults with higher education levels, as well as better access to green space, were found to have even lower obesity rates (β=-0.188; p<0.05). Other control variables such as unemployment rates, food security, and physical inactivity are additional factors that influence obesity rates among adults. Conclusions: Accessibility of green space may play an important role in facilitating physical activity participation and reducing obesity rates.