• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.36-40
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• 2003

The considered satellite is supposed to operate in the earth-point mode and sun-point mode in accordance with the mission requirements. The magnetic field correction is based on the orbit geometry using a set of measured magnetic field data from the three-axis-magnetometer and its algorithm excludes the earth’s magnetic field model. Moreover, the usefulness of the proposed method is investigated throughout the simulation of KOMPSAT-1.

• Journal of Korean Ophthalmic Optics Society
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• v.18 no.1
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• pp.75-84
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• 2013

Purpose: Changes of refractive correction value in different age group were investigated. Regarding the inhibitive effects against myopia progression after wearing reverse geometry contact lenses and myopia control lenses (MC lenses), the effects after wearing single vision lenses were compared. Methods: We organized children between the ages of six and fifteen into three groups by age, and distributed fifty-seven reverse geometry contact lenses, fifty-six MC lenses and seventy-eight single vision lenses among them to be worn. Group 1 consisted of children aged ten and under, Group 2 consisted of children between the ages of eleven and fifteen, and Group 3 represents all of the study participants. The aim of this study was to learn the inhibitive effects against myopia progression attained by changes of refractive correction value and to verify their statistical significance at twelve months and under, thirteen to twenty-four months and twenty-five to thirty-six months. Results: Changes of refractive correction value by each length of use in Group 3 were as follows. For the age group of under twelve months, participants using the reverse geometric contact lens showed no change, while those using the MC or single vision lens had significant changes (P<0.05) of $-0.36{\pm}0.10$ D and $-0.67{\pm}0.52$ D, respectively. Users of all three lens types displayed significant change (P<0.05), in the age group of between thirteen and twenty-four months, of $0.18{\pm}0.49$ D, $0.60{\pm}0.42$ D and $1.37{\pm}0.72$ D for users of the reverse geometry contact lens, the MC lens and the single vision lens, respectively. There were significant changes (P<0.05) of $0.29{\pm}0.61$ D, $0.93{\pm}0.57$ D and $1.72{\pm}0.78$ in the same respective order as the above in the age group of twenty-five to thirty-six months. Refractive correction value showed changes with different age group. Group 1 displayed significant changes (P<0.05) of $0.29{\pm}0.73$ D, $1.07{\pm}0.59$ D and $1.75{\pm}0.74$ D for users of the reverse geometry contact lens, MC lens and single vision lens, respectively, up to thirty-six months of lens wearing; Group 2, also up to thirty-six months, displayed significant changes (P<0.05) of $0.28{\pm}0.42$ D, $0.75{\pm}0.49$ D and $1.70{\pm}0.84$ D in the same respective order, and changes in refractive correction for the age group under ten years was significantly greater (P<0.05) for the age group of eleven and older. Conclusions: The results found in this study demonstrate that there were no changes of refractive correction value for the case of wearing reversing geometry contact lens up to twelve month or less. MC lens showed less changes in variations of visual acuity for all users which might be resulted in inhibiting progression of myoptia. When both reverse geometry contact lens and the MC lens are wearing for the period from 13 to 36 month, both lens showed less changes in variation of visual acuity for all users. The results suggested that the less changes in variation of visual acuity of both lens had an effect on inhibiting progression of myopia.

• Journal of Welding and Joining
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• v.24 no.5
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• pp.37-42
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• 2006

The robotic arc welding is widely employed in the fabrication industry fer increasing productivity and enhancing product quality by its high processing speed, accuracy and repeatability. Basically, the bead geometry plays an important role in determining the mechanical properties of the weld. So that it is very important to select the process variables for obtaining optimal bead geometry. In this paper, the possibilities of the Infrared camera in sensing and control of the bead geometry in the automated welding process are presented. Both bead width and thermal images from infrared thermography are effected by process parameters. Bead width and isotherm radii can be expressed in terms of process parameters(welding current and welding speed) using mathematical equations obtained by empirical analysis using infrared camera. A linear relationship exists between the isothermal radii producted during the welding process and bead width.

• International Journal of Korean Welding Society
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• v.1 no.1
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• pp.23-30
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• 2001

Among the various welding conditions, the welding current that is inversely proportional to the tip-to-work-piece distance is an essential parameter as to monitor the GMAW process and to implement the welding automation. Considering the weld pool surface geometry including weld defects, it should modify the signal processing method for automatic seam tracking in horizontal fillet welding. To meet the above necessities, a mathematical model related with the weld pool geometry was proposed as in a conjunction with the two-dimensional heat flow analysis of the horizontal fillet welding. The signal processing method based on the artificial neural network (Adaptive Resonance Theory) was proposed for discriminating the sound weld pool surface from that with the weld defects. The reliability of the numerical model and the signal processing method proposed were evaluated through the experiments of which showed that they are effective for predicting the weld bead shape with or without the weld defects in a horizontal fillet welding.

• Journal of Digital Convergence
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• v.14 no.8
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• pp.555-564
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• 2016

Space perception is generally treated as a problem relevant to the ability to recognize objects. Alternatively, the data from shape perception studies contributes to discussions about the geometry of visual space. This geometry is generally acknowledged not to be Euclidian, but instead, elliptical, hyperbolic or affine, which is to say, something that admits the distortions found in so many shape perception studies. The purpose of this review article is to understand perceived shape and the geometry of visual space in the context of visually guided action. Thus, two prominent approaches that explain the relation between perception and action were compared. It is important to understand the fundamental information of how human perceive visual space and perform visually guided action for the convergence on embodied cognition, and further on artificial intelligence researches.

• Tunnel and Underground Space
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• v.20 no.1
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• pp.65-72
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• 2010

Crack-controlled blasting method which utilizes notched charge hole has been proposed in order to achieve smooth fracture plane and minimize the excavation damage zone. In this study, the blast models, which have a notched charge hole, were analyzed using dynamic fracture process analysis software to investigate the effect of the geometry of a notched charge hole and decoupling indexes of the charge hole on crack growth control in blasting. As a result, crack extension increased and damage crack decreased with the notch length. Ultimately, stress increment factors and resultant fracture patterns with different notch length and width were analyzed in order to examine the effect factors on the crack growth controlling in rock blasts using a notched charge hole.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.5
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• pp.438-445
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• 2007

A Helmholtz resonator as a stabilization device to control high-frequency combustion instabilities in liquid rocket engine is adopted and its damping capacity is verified by linear acoustic analysis and atmospheric acoustic tests. To compare the results of acoustic attenuation effect in accordance with uni-resonator's geometry, quantitative analyses were made in the cases of various orifice diameters and lengths. Next, in the experiments to compare the results of acoustic attenuation effect by a difference in the number of resonators, damping capacity of harmful resonant frequency was improved by the increase of the number of resonators. On the other hand, attenuation efficiency of the frequency tended rather to lower due to over damping from the point of view of absorption coefficient. As the result, tuning the suitable geometry for the resonator to the resonant frequency is required for the control using the resonator. Also, the design of resonator's geometry and the choice of its number are important to put up the optimal efficiency in consideration of restriction of its volume.

• Korean Journal of Remote Sensing
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• v.18 no.4
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• pp.233-242
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• 2002

In this paper, an epipolar model without the ephemeris data is proposed. Also, various epipolar models such as the epipolar geometry of perspective sensor, the one proposed by Gupta and Hartley and the one based on the Orun and Natarajan's sensor model are reviewed and their accuracy are quantitatively analyzed using devised measure. Modeling data from ground control points, ground control points, ephemeris data and independent checking points are selected on SPOT over Taejon and Boryung area and KOMPSAT over Taejon and Nonsan area. Based on the results, the epipolar model of perspective sensor and the one by Gupta and Hartley have the average accuracy within 1 pixel but show high errors in several checking points. The proposed epipolarity model provides better results than that of perspective sensor and by Gupta and Hartley. Also, it shows the accuracy similar to the one based on Orun and Natarajan's sensor model.

• Steel and Composite Structures
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• v.37 no.6
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• pp.663-678
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• 2020

This paper proposes a novel topology optimization method generating multiple materials for external linear plane crack structures based on the combination of IsoGeometric Analysis (IGA) and eXtended Finite Element Method (X-FEM). A so-called eXtended IsoGeometric Analysis (X-IGA) is derived for a mechanical description of a strong discontinuity state's continuous boundaries through the inherited special properties of X-FEM. In X-IGA, control points and patches play the same role with nodes and sub-domains in the finite element method. While being similar to X-FEM, enrichment functions are added to finite element approximation without any mesh generation. The geometry of structures based on basic functions of Non-Uniform Rational B-Splines (NURBS) provides accurate and reliable results. Moreover, the basis function to define the geometry becomes a systematic p-refinement to control the field approximation order without altering the geometry or its parameterization. The accuracy of analytical solutions of X-IGA for the crack problem, which is superior to a conventional X-FEM, guarantees the reliability of the optimal multi-material retrofitting against external cracks through using topology optimization. Topology optimization is applied to the minimal compliance design of two-dimensional plane linear cracked structures retrofitted by multiple distinct materials to prevent the propagation of the present crack pattern. The alternating active-phase algorithm with optimality criteria-based algorithms is employed to update design variables of element densities. Numerical results under different lengths, positions, and angles of given cracks verify the proposed method's efficiency and feasibility in using X-IGA compared to a conventional X-FEM.

• Magazine of the Korea Concrete Institute
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• v.23 no.3
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• pp.56-58
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• 2011