• Journal of the Korean Society of Systems Engineering
• /
• v.1 no.1
• /
• pp.61-66
• /
• 2005

In executing the large scale national project, such as development of space launch vehicle, it is most important to guarantee the technological reliability. However the reliability analysis of launch vehicle is different from other mass product goods because of the limitation of budget and number of tests. In this study, the reliability analysis technique of the propulsion system, which is one of the major sub-systems of launch vehicle is illustrated and applied to the liquid rocket engine of KSR-III.

• Magazine of korean Tunnelling and Underground Space Association
• /
• v.1 no.2
• /
• pp.50-58
• /
• 1999

The Discontinuous Deformation Analysis (DDA) method is a recently developed technique that can be classified as a DEM method. Shi (1988) first proposed the DDA method in his doctoral thesis; computer programs based on the method have been developed and some applications of the DDA method in rock mechanics have been presented in the doctoral thesis and various publications. During past 11 years (1988 - 1999), considerable progresses have been achieved in developments and applications of the DDA method in the rock mechanics. In this paper the basic theory and developments of the DDA method are presented and applications of DDA method in geotechnical engineering are reviewed.

• Structural Engineering and Mechanics
• /
• v.31 no.4
• /
• pp.393-405
• /
• 2009

The Purpose of this paper is to show the applicability of a methodology, developed by the authors, with which to perform the mechanical optimization of space truss structures strongly restricted. This methodology use a parameter call "Volumetric Displacement", as the Objective Function of the optimization process. This parameter considers altogether the structure weight and deformation whose effects are opposed. The Finite Element Method is employed to calculate the stress/strain state and the natural frequency of the structure through a structural linear static and natural frequency analysis. In order to show the potentially of this simple methodology, its application on a large diameter telescope structure (10 m) considering the strongly restriction that became of its use, is presented. This methodology, applied in previous works on continuous structures, such as shell roof and fluid storage vessels, is applied in this case to a space truss structure, with the purpose of generalize its applicability to different structural topology. This technique could be useful in the morphology design of deployable and retractable roof structures, whose use has extensively spread in the last years.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.13 no.4
• /
• pp.160-166
• /
• 2005

In recent, recreational vehicles, which efficiently provide wide inner space for various utilities, are highly preferred in automobile market. Though those vehicles enable to load much luggage in space behind the last seat, in case of frontal impact with high velocity the luggage strongly collides into the seat back and the passengers in. the last seat could be severely injured. Therefore, high strength against luggage intrusion is required for the last seat, and it is regulated by law of ECE R17. In this study, for a recreational vehicle under developing, an analysis technique for simulating seat crash in accordance with luggage intrusion test of ECE R17 was investigated. The results exhibited good correlation with the test ones.

• Journal of Astronomy and Space Sciences
• /
• v.29 no.2
• /
• pp.233-244
• /
• 2012

The Korea Astronomy and Space Science Institute and the Department of Astronomy at the University of Texas at Austin are developing a near infrared wide-band high resolution spectrograph, immersion grating infrared spectrometer (IGRINS). The compact white-pupil design of the instrument optics uses seven cryogenic mirrors, including three aspherical off-axis collimators and four flat fold mirrors. In this study, we introduce the optomechanical mount designs of three off-axis collimating mirrors and one flat slit-viewer fold mirror. Two of the off-axis collimators are serving as H and K-band pupil transfer mirrors, and are designed as system alignment compensators in combination with the H2RG focal plane array detectors in each channel. For this reason, the mount designs include tip-tilt and parallel translation adjustment mechanisms to properly perform the precision alignment function. This means that the off-axis mirrors' optomechanical mount designs are among the most sensitive tasks in all IGRINS system hardware. The other flat fold mirror is designed within its very limitedly allowed work space. This slit-viewer fold mirror is mounted with its own version of the six-point kinematic optics mount. The design work consists of a computer-aided 3D modeling and finite element analysis (FEA) technique to optimize the structural stability and the thermal behavior of the mount models. From the structural and thermal FEA studies, we conclude that the four IGRINS mirror mounts are well designed to meet all optical stability tolerances and system thermal requirements.

• Journal of Astronomy and Space Sciences
• /
• v.30 no.4
• /
• pp.315-320
• /
• 2013

Space geodetic techniques can be used to obtain precise shape and rotation information of the Earth. To achieve this, the representative combination solution of each space geodetic technique has to be produced, and then those solutions need to be combined. In this study, the representative combination solution of very long baseline interferometry (VLBI), which is one of the space geodetic techniques, was produced, and the variations in the position coordinate of each station during 7 years were analyzed. Products from five analysis centers of the International VLBI Service for Geodesy and Astrometry (IVS) were used as the input data, and Bernese 5.0, which is the global navigation satellite system (GNSS) data processing software, was used. The analysis of the coordinate time series for the 43 VLBI stations indicated that the latitude component error was about 15.6 mm, the longitude component error was about 37.7 mm, and the height component error was about 30.9 mm, with respect to the reference frame, International Terrestrial Reference Frame 2008 (ITRF2008). The velocity vector of the 42 stations excluding the YEBES station showed a magnitude difference of 7.3 mm/yr (30.2%) and a direction difference of $13.8^{\circ}$ (3.8%), with respect to ITRF2008. Among these, the 10 stations in Europe showed a magnitude difference of 7.8 mm/yr (30.3%) and a direction difference of $3.7^{\circ}$ (1.0%), while the 14 stations in North America showed a magnitude difference of 2.7 mm/yr (15.8%) and a direction difference of $10.3^{\circ}$ (2.9%).

• Journal of Korean Society of Rural Planning
• /
• v.10 no.4 s.25
• /
• pp.19-28
• /
• 2004

In order to revitalize rural areas fundamentally through multifunctional utilization of their resources, it should be necessary to prepare the rational development plan to the areal characteristics and conditions, and the first priority of its planning works should be given to spatial planning. The space syntax method, a powerful objective and quantitative analysis tool on the relationship between social and spatial characteristics, was introduced in this study. Five Comprehensive Rural Clustered Villages Development Areas in the Jeonnam-province were selected as case study areas, of which total area's and included villages' spatial variables were measured and analyzed. Rural villages analyzed in this study have the spatial structure badly systematized and much complicated, which results from low integration and deep spatial depth of them. And, by virtue of relatively many axial lines, there should be few differences between villages in terms of local integration, connectivity and control, while being significant difference in terms of global integration showing the whole areal characteristics. Intelligibility, the correlation coefficient between connectivity(local variable) and integration(global one) is low, which means that the spatial structure of the study areas is difficult for visitors to understand the area or village well. Spatial configuration analysis results in the case study areas showed that each development area has a unique spatial structure and is differentiated in terms of not only local spatial variables but also global spatial variables. Therefore, global and local characteristics should be considered in spatial analysis of development areas.

• Journal of Environmental Impact Assessment
• /
• v.31 no.6
• /
• pp.438-448
• /
• 2022

This study is to improve the quantitative estimation index of biotop area ratio, which is an environmental planning index and environmental ecological planning technique, as a planning means that can induce the improvement of ecological soundness in the spatial planning stage. It is intended to identify the relative importance of space types and calculation indicators currently in operation, and to find alternatives through opinion analysis on improvement of space types and weights. As the method of this study, AHP analysis was performed to evaluate the relative importance of spatial types for in-depth analysis of spatial types and calculation indicators. In order to secure the reliability and objectivity of the study, 50 experts participated. Through this study, it can be linked with the improvement of technologies and construction methods, maintenance efficiency, economic feasibility, and construction technology, which are developed through analysis on the limitations and improvements by type of biotop area ratio. And it is expected to contribute to the improvement of the urban environment and vitalization of the biotop area ratio through the application of the biotop area ratio.

• Proceedings of the KSRS Conference
• /
• 2005.10a
• /
• pp.209-212
• /
• 2005

Hyperspectral data consists of more than 200 spectral bands that are highly correlated. In order to utilize hyperspectral data for classification, dimensional reduction or feature extraction is desired. By applying feature extraction, computational complexity of classification can be reduced and classification accuracy may be improved. In this paper, a genetic algorithm based feature extraction technique is proposed. Measure from discriminant analysis is utilized as optimization criterion. A subset of spectral bands is selected by genetic algorithm. Dimension of feature space is further reduced by linear transformation. Feasibility of the proposed technique is evaluated with AVIRIS data.

• Journal of Mechanical Science and Technology
• /
• v.20 no.2
• /
• pp.185-190
• /
• 2006

An ultrasonic self-calibrating technique for the characterization of a ceramic which was fabricated by change pressing time during the HIP process has been applied by using the ratio of the reflection and transmission coefficients of normal incidence longitudinal waves. The ratio is self-compensated, in that it is independent of the characteristics for transmission and reception of ultrasound by the transducer and the condition of the couplant. The insensitive direction in parameter space is defined as the direction in which the variation of the ratio to changes of two parameters vanishes. For inverse problem the distribution of minima in an error surface is investigated.