• Proceedings of the KSME Conference
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• 2001.06a
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• pp.920-925
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• 2001

A study on the topology optimization of a multi-spectral camera for space-use is presented. A multi-spectral camera for space-use experiences degradation of optical image in the space, which can not be detected on the optical test bench on the earth. An optical surface deformation of a primary mirror, which is a principal component of the camera system, under the self-weight loading is an important factor affecting the optical performance of the whole camera system. In this study, topology optimization of the primary mirror of the camera is presented. Total mass of the primary mirror is given as a constraint to the optimization problem. The sensitivities of the objective function and constraint are calculated by direct differentiation method. Optimization procedure is carried out by an optimality criterion method using the sensitivities of the objective function and the constraint. As a preliminary example, topology optimization considering a self-weight loading is treated. For practical use, the polishing pressure is included as a loading in the topology optimization of the primary mirror. Results of the optimized design topology for the primary mirror with varying mass ratios are presented.

• Proceedings of the Korean Association of Geographic Inforamtion Studies Conference
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• 2008.10a
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• pp.270-271
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• 2008

The positioning technology for a moving object is an important and essential component of ubiquitous communication computing environment and applications, for which Radio Frequency IDentification Identification(RFID) is has been considered as also a core technology for ubiquitous wireless communication. RFID-based positioning system calculates the position of moving object based on k-nearest neighbor(k-nn) algorithm using detected k-tags which have known coordinates and k can be determined according to the detection range of RFID system. In this paper, RFID-based positioning system determines the position of moving object not using weight factor which depends on received signal strength but assuming that tags within the detection range always operate and have same weight value. Because the latter system is much more economical than the former one. The geometries of tags were determined with considerations in huge buildings like office buildings, shopping malls and warehouses, so they were determined as the line in 1-Dimensional space, the square in 2-Dimensional space and the cubic in 3-Dimensional space. In 1-Dimensional space, the optimal detection range is determined as 125% of the tag spacing distance through the analytical and numerical approach. Here, the analytical approach means a mathematical proof and the numerical approach means a simulation using matlab. But the analytical approach is very difficult in 2- and 3-Dimensional space, so through the numerical approach, the optimal detection range is determined as 134% of the tag spacing distance in 2-Dimensional space and 143% of the tag spacing distance in 3-Dimensional space. This result can be used as a fundamental study for designing RFID-based positioning system.

• Korean Journal of Cognitive Science
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• v.13 no.3
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• pp.1-10
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• 2002

This study was performed to analyze the physical attributes of the faces and affective words on the fares. For analyzing physical attributes inside of a face, 36 facial features were selected and almost of them were the lengths or distance values. For analyzing facial contour 14 points were selected and the lengths from nose-end to them were measured. The values of these features except ratio values normalized by facial vortical length or facial horizontal length because the face size of each person is different. The principal component analysis (PCA) was performed and four major factors were extracted: 'facial contour' component, 'vortical length of eye' component, 'facial width' component, 'eyebrow region' component. We supposed the five-dimensional imaginary space of faces using factor scores of PCA, and selected representative faces evenly in this space. On the other hand, the affective words on faces were collected from magazines and through surveys. The factor analysis and multidimensional scaling method were performed and two orthogonal dimensions for the affections on faces were suggested: babyish-mature and sharp-soft.

• Journal of Astronomy and Space Sciences
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• v.33 no.3
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• pp.185-196
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• 2016

New multiband BVRI light curves of NSVS 1461538 were obtained as a byproduct during the photometric observations of our program star PV Cas for three years from 2011 to 2013. The light curves indicate characteristics of a typical W-subtype W UMa eclipsing system, displaying a flat bottom at primary eclipse and the O'Connell effect, rather than those of an Algol/b Lyrae eclipsing variable classified by the northern sky variability survey (NSVS). A total of 35 times of minimum lights were determined from our observations (20 timings) and the SuperWASP measurements (15 ones). A period study with all the timings shows that the orbital period may vary in a sinusoidal manner with a period of about 5.6 yr and a small semi-amplitude of about 0.008 day. The cyclical period variation can be interpreted as a light-time effect due to a tertiary body with a minimum mass of 0.71 M_⊙. Simultaneous analysis of the multiband light curves using the 2003 version of the Wilson-Devinney binary model shows that NSVS 1461538 is a genuine W-subtype W UMa contact binary with the hotter primary component being less massive and the system shows a low mass ratio of q(m_c/m_h)=3.51, a high orbital inclination of 88.7°, a moderate fill-out factor of 30 %, and a temperature difference of ΔT=412 K. The O'Connell effect can be similarly explained by cool spots on either the hotter primary star or the cool secondary star. A small third-light corresponding to about 5 % and 2 % of the total systemic light in the B and V bandpasses, respectively, supports the third-body hypothesis proposed by the period study. Preliminary absolute dimensions of the system were derived and used to look into its evolutionary status with other W UMa binaries in the mass-radius and mass-luminosity diagrams. A possible evolution scenario of the system was also discussed in the context of the mass vs mass ratio diagram.

• Journal of the Korean Institute of Landscape Architecture
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• v.13 no.2
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• pp.37-70
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• 1985

The purpose of this study is to present objective basic data for environmental design by the quantitative analysis of visual quality emboded in physical environment. For this, as for the front garden of high schools, the spatial image was measured by the S.D. Scale Method, Factor Analysis was proceeded by the principal component analysis and the visual preference was investigated by the Paired Comparision Method. The scale values of plain and unpleasant road surface and external appearance of buildings, which are related to emotions of simpleness fell from straightness and stability, were found to be high. But, except for the road surface of Kyunggi High School, scale values of variables explaining the variation of the quality of materials, level of floor and rythm were generally low. For all green spaces, scale values of variables explaining the degree of pleasantness was found to be generally high. And, those explaining tidiness and characteristics of green spaces were not in the same tendency. But, the green spaces of Youngdong High school can be considered to the space with plenty of visual absorption uniqueness were high. As for the correlation between variables, variables for green spaces(12 and 26) and those for overall view of front garden( 1 and 4) revealed high positive correlation. Also, "order - disorder" and "convenient- incovenient" included in road surface variable can be regarded to have the same meaning since the correlation coefficient between them is very high, 0.7045. Image variables including road surface, external appearance of buildings, green spaces and overall view of front garden showed 91.21~61.08% of total variance. Thus, the remains can be considered to be the error valiance or specific variance. In Fctor I, II and III, main components explaining the road surface image of front gardens are order, hardness, texture, color, gradient and rythm. As for the external appearance of b wilding, variables of color, hardness, stability, peculiality and shape revealed high values of factor load. For all variables, communality was drastically high and ellen values and common variance were found to be very high in Factor I. As for the front gardens, variables explaining volume and peculiarity were found to be the main components of Factor I. In Factor II and III, variables of factor load were tidiness, pleasantness.

• Horticultural Science & Technology
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• v.29 no.3
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• pp.201-210
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• 2011

This experiment was conducted to investigate physical and chemical characteristics by volume fractions of root media using peatmoss, perlite, and vermiculite, along with effects on the growth of pot chrysanthemums (Dendranthema ${\times}$ grandiflorum 'Vemini') in a C-channel mat irrigation system. To evaluate the physico-chemical properties of 20 root media, the bulk density, particle density, total pore space, pore space, ash content, organic matter, pH, and electrical conductivity were measured and data were analyzed using principal component analysis (PCA). PCA scores revealed that physico-chemical properties changed by the blending of peatmoss, perlite, and vermiculite. The 20 root media were divided into three main groups by hierarchical cluster analysis. At the end of the experiment, the pH and EC of the root media were measured from media divided into four layers. The pH of root media without plants showed a strong linear relationship and the pH of root media with plants increased exponentially. The change of EC in the root medium was indicated as a hyperbolic curve. Plant growth characteristics according to growth in the 20 root media were analyzed by PCA. It was found that the mixing ratios of the root media affected plant growth characteristics. Therefore, mixing ratio is an important factor for pot-plant production in a subirrigation system.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.2
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• pp.85-93
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• 2021

In this paper, the aerodynamic characteristics of general tail controlled missile were predicted and corrected the result using semi-empirical analysis tool. The cause of the error was confirmed by comparing the aerodynamic characteristics prediction result of the semi-empirical analysis tool with the wind tunnel test result, and the main error factor of the semi-empirical analysis tool was the interference component between the main wing and the tail wing. The semi-empirical analysis results were corrected using the wind tunnel test results and the computational analysis results, and it was confirmed that the corrected data agrees well with the wind tunnel test results. Through this study, it was confirmed that the wing-tail interference component correction is needed when predicting the aerodynamic characteristics of a general tail controlled missile using a semi-empirical analysis tool.

• Proceedings of the Korean Association of Geographic Inforamtion Studies Conference
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• 2008.10a
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• pp.297-302
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• 2008

The positioning technology for a moving object is an important and essential component of ubiquitous computing environment and applications, for which Radio Frequency Identification(RFID) has been considered as a core technology. RFID-based positioning system calculates the position of moving object based on k-nearest neighbor(k-nn) algorithm using detected k-tags which have known coordinates and kcan be determined according to the detection range of RFID system. In this paper, RFID-based positioning system determines the position of moving object not using weight factor which depends on received signal strength but assuming that tags within the detection range always operate and have same weight value. Because the latter system is much more economical than the former one. The geometries of tags were determined with considerations in huge buildings like office buildings, shopping malls and warehouses, so they were determined as the line in I-Dimensional space, the square in 2-Dimensional space. In 1-Dimensional space, the optimal detection range is determined as 125% of the tag spacing distance through the analytical and numerical approach. Here, the analytical approach means a mathematical proof and the numerical approach means a simulation using matlab. But the analytical approach is very difficult in 2-Dimensional space, so through the numerical approach, the optimal detection range is determined as 134% of the tag spacing distance in 2-Dimensional space. This result can be used as a fundamental study for designing RFID-based positioning system.

• Geomechanics and Engineering
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• v.16 no.3
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• pp.321-329
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• 2018

Classic braced walls use struts and wales to minimize ground movements induced by deep excavation. However, the installation of struts and wales is a time-consuming process and confines the work space. To secure a work space around the retaining structure, an anchoring system works in conjunction with a braced wall. However, anchoring cannot perform well when the shear strength of soil is low. In such a case, innovative retaining systems are required in excavation. This study proposes an innovative earth-retaining wall that uses in situ soil confined in dual sheet piles as a structural component. A numerical study was conducted to evaluate the stability of the proposed structure in cohesionless dry soil and establish a design chart. The displacement and factor of safety of the structural member were monitored and evaluated. According to the results, an increase in the clearance distance increases the depth of safe excavation. For a conservative design to secure the stability of the earth-retaining structure in cohesionless dry soil, the clearance distance should exceed 2 m, and the embedded depth should exceed 40% of the wall height. The results suggest that the proposed method can be used for 14 m of excavation without any internal support structure. The design chart can be used for the preliminary design of an earth-retaining structure using in situ soil with dual steel sheet piles in cohesionless dry soil.

• Journal of Electrical Engineering and Technology
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• v.12 no.4
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• pp.1471-1483
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• 2017

The low-frequency characteristics of four-switch three-phase (FSTP) inverter are investigated in this paper. Firstly, a general space vector pulse width modulation (SVPWM) directly involved the neutral point voltage of DC-link is proposed, where no sector identifications and trigonometric function calculations are needed. Subsequently, to suppress the DC offset in the neutral point voltage, the relationship between the neutral point voltage and the ${\beta}-axis$ component of the load current is derived, and then a new neutral point voltage control scheme is proposed where no low pass filter is adopted. Finally, the relationship between the load power factor and the maximum linear modulation index of the FSTP inverter is revealed. Since the operational region for the FSTP inverter in low frequency is reduced by the enlarged amplitude of the neutral point voltage, a linear modulation range enlargement scheme is proposed. A permanent magnet synchronous motor with preset rotary speed serves as the low-frequency load of the FSTP inverter. Experimental results verify that the new neutral point voltage control scheme is effective in the deviation suppression of the neutral point voltage, and the proposed scheme is able to provide a larger linear operational region in low frequency.