• Journal of the Korean Society for Precision Engineering
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• v.22 no.6 s.171
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• pp.127-134
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• 2005

The machine vision has been applied to a number of industrial applications for quality control and automations to improve the manufacturing processes. In this paper, the automation system using the machine vision is developed, which is applicable to the marking process in a steel production process line. The working environment is very harsh to workers so that the automatic system in the steel industry is required increasingly. The developed automatic marking system consists of several mechanical and electrical elements such as the laser position detecting sensor system fur a structured laser beam which is projected to the billet in order to detect the geometry of the billet. An image processing algorithm has been developed to percept the two center positions of a camera and a billet, respectively, and to align two centers. A series of experiments has been conducted to investigate the performance of the proposed algorithm. The results show that two centers of the camera and the billet could be detected very well and differences between two center positions could be also decreased via the proposed location error decreasing algorithm.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.9
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• pp.9-17
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• 1999

This investigation is the result of the structural analysis by finite element method for optimal design of the cross beam with circular holes of the electric car-body. in order to install the air pipe and electric wire pipe that correspond signal between electric machines for the control system and to reduce the weight of the electric car-body, several circular areas from a cross beam should be taken off. What we want to perform is the optimal design of a cross beam with circular holes to posses equal stress in comparison with no hole cross beam. first, no hole cross beam as basic modal be chosen, executing the analysis, reviewing the distribution of stress and displacement at each location. several parameter should be adopted from the cross beam geometry like the location and shape of the hole to affect the maximum stress and displacement. So the analysis was executed by finite element analysis for finding optimal design parameter to the change of the location and shape of the circular hole. finally, the optimal design of the cross beam with circular holes was obtained and the maximum equivalent stress was compared with no hole cross beam at each location.

• The Mathematical Education
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• v.40 no.2
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• pp.317-333
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• 2001

The equations of figures given by rectangular coordinates are used to look into the properties of them, which are very restricted in examining them in the school mathematics. Therefore, it is quite natural to consider the figures in terms of parameters without restriction to coordinates and also, it is possible for the students to analyze them. Thus, the visualization of figures is important for students in mathematics education. In particular, the teaching-learning methods using computers make loose the difficulties of geometry education, and from the viewpoint that various abstract figures can be visualized and that can be obtained by means of this visualization the learning of figures can be accomplished through the direct experience or control. This study is intended to present concretely the aim and its utility to visualize figures represented as parameters with Mathematics. In this paper, we introduce a new teaching-learning method of figures represented by parameters using Mathematica so that the learners establish themselves their knowledge obtained through their search, investigation, supposition and they accomplish the positive transition to advanced learning. So the leasers extend their ability of sensuous intuition to their ability of logical reasoning through their logical intuition. Consequently they can develop the ability of thinking mathematically, so many natural phenomena and physical ones.

• Macromolecular Research
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• v.17 no.3
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• pp.181-186
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• 2009

We fabricated ordered micro/nano patterns induced by controlled dewetting on the topographically patterned PS/P4VP bilayer thin film. The method is based on utilizing microimprinting lithography to induce a topographically heterogeneous bilayer film that allows the controlled dewetting upon subsequent thermal annealing. The dewetting that was initiated strictly at the boundary of the thicker and thinner regions was guided by the presence of the topographic structure. The dewetting front velocity of the microdomains in the confined regions was linearly proportional to the measurement time, which enabled us to control the size of the dewet domain with annealing time. In particular, the submicron sized dot arrays between lines were generated with ease when the dewetting was confined into geometry with a few microns in size. The kinetically driven, non-lithographical pattern structures accompanied the pattern reduction to 400%. The pattern arrays on a transparent glass substrate were especially useful for non-circular microlens arrays where the focal length of the lens was easily tunable by controlling the thermal annealing.

• Korean Journal of Optics and Photonics
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• v.32 no.3
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• pp.114-119
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• 2021

A large-area graphene sheet has been successfully grown on a copper-foil substrate by chemical vapor deposition (CVD) for industrial use. To screen out unsatisfactory graphene films as quickly as possible, noninvasive optical characterization in reflection geometry is necessary. Based on the optical conductivity of graphene, developed by the single-electron tight-binding method, we have investigated the optical-reflectance contrast. Depending on the four independent control parameters of layer number, chemical potential, hopping energy, and temperature, the optical-reflectance contrast can change dramatically enough to reveal the quality of the grown graphene sheet.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.6
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• pp.8-16
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• 2003

Aerodynamic characteristics over Micro Aerial Vehicle(MAV) in low Reynolds number regime are numerically studied using 3-D unsteady, incompressible Navier-Stokes flow solver with single partitioning method for multi-block grid. For more efficient computation of unsteady flows, this flow solver is parallel-implemented with MPl(Message Passing Interface) programming method. Firstly, MAV wing with not complex geometry is considered and then, we analyze aerodynamic characteristics over full MAV configuration varying the angle of attack. Present computational results show a better agreement with the experimental data by MACDL(Micro Aerodynamic Control and Design Lab.), Seoul National University. We can also find the conceptually designed MAV by MACDL has the static stability.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.383-388
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• 2005

Depth recovery in robot vision is an essential problem to infer the three dimensional geometry of scenes from a sequence of the two dimensional images. In the past, many studies have been proposed for the depth estimation such as stereopsis, motion parallax and blurring phenomena. Among cues for depth estimation, depth from lens translation is based on shape from motion by using feature points. This approach is derived from the correspondence of feature points detected in images and performs the depth estimation that uses information on the motion of feature points. The approaches using motion vectors suffer from the occlusion or missing part problem, and the image blur is ignored in the feature point detection. This paper presents a novel approach to the defocus technique based depth from lens translation using sequential SVD factorization. Solving such the problems requires modeling of mutual relationship between the light and optics until reaching the image plane. For this mutuality, we first discuss the optical properties of a camera system, because the image blur varies according to camera parameter settings. The camera system accounts for the camera model integrating a thin lens based camera model to explain the light and optical properties and a perspective projection camera model to explain the depth from lens translation. Then, depth from lens translation is proposed to use the feature points detected in edges of the image blur. The feature points contain the depth information derived from an amount of blur of width. The shape and motion can be estimated from the motion of feature points. This method uses the sequential SVD factorization to represent the orthogonal matrices that are singular value decomposition. Some experiments have been performed with a sequence of real and synthetic images comparing the presented method with the depth from lens translation. Experimental results have demonstrated the validity and shown the applicability of the proposed method to the depth estimation.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.252.2-252.2
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• 2013

ZnO nanostructures have a lot of interest for decades due to its varied applications such as light-emitting devices, power generators, solar cells, and sensing devices etc. To get the high performance of these devices, the factors of nanostructure geometry, spacing, and alignment are important. So, Patterning of vertically- aligned ZnO nanowires are currently attractive. However, many of ZnO nanowire or nanorod fabrication methods are needs high temperature, such vapor phase transport process, metal-organic chemical vapor deposition (MOCVD), metal-organic vapor phase epitaxy, thermal evaporation, pulse laser deposition and thermal chemical vapor deposition. While hydrothermal process has great advantages-low temperature (less than $100^{\circ}C$), simple steps, short time consuming, without catalyst, and relatively ease to control than as mentioned various methods. In this work, we investigate the dependence of ZnO nanowire alignment and morphology on si substrate using of nanosphere template with various precursor concentration and components via hydrothermal process. The brief experimental scheme is as follow. First synthesized ZnO seed solution was spun coated on to cleaned Si substrate, and then annealed $350^{\circ}C$ for 1h in the furnace. Second, 200nm sized close-packed nanospheres were formed on the seed layer-coated substrate by using of gas-liquid-solid interfacial self-assembly method and drying in vaccum desicator for about a day to enhance the adhesion between seed layer and nanospheres. After that, zinc oxide nanowires were synthesized using a low temperature hydrothermal method based on alkali solution. The specimens were immersed upside down in the autoclave bath to prevent some precipitates which formed and covered on the surface. The hydrothermal conditions such as growth temperature, growth time, solution concentration, and additives are variously performed to optimize the morphologies of nanowire. To characterize the crystal structure of seed layer and nanowires, morphology, and optical properties, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Raman spectroscopy, and photoluminescence (PL) studies were investigated.

• Journal of the Korea Concrete Institute
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• v.22 no.3
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• pp.409-417
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• 2010

This paper discusses a series of experiments including material improvement in order to ensure quality of grouting for the post-tensioned structure. In prestressed concrete, grouting refers to the construction procedure of filling empty space of duct enclosing with strands using cementitious material, To date, adequate quality control of the grouting has not been established in Korea because the relationship between the grouting and durability of post-tensioned structure is not well-recognized. The Korean standard does not consider the important material characteristic, wick effect, which is caused by strands in the ducts and current standard testing method unlikely quantify reasonable material segregation. As a result, the grout material, which meets the current material standards, may exhibit excessive bleeding water or shrinkage during construction. In this study, international codes and standards related to grouting were surveyed. The ratio of constituents and novel admixtures were suggested to meet equivalently with these standards. Performance of this enhanced grout was compared to common domestic grout using the international standard testing method. A series of mock-up specimens considering geometry of PC beam was constructed and grout flow pattern was observed as the grout was injected. It was observed that the grouting performance was highly influenced by material properties and filling characteristic can be varied depending on geometry of ducts.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.2
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• pp.91-99
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• 2014

The common-rail injectors are the most critical component of the CRDI diesel engines that dominantly affect engine performances through high pressure injection with exact control. Thus, from now on the advanced combustion technologies for common-rail diesel injection engine require high performance fuel injectors. Accordingly, the previous studies on the numerical and experimental analysis of the diesel injector have focused on a optimum geometry to induce proper injection rate. In this study, computational predictions of performance of the diesel injector have been performed to evaluate internal flow characteristics for various needle lift and the spray pattern at the nozzle exit. To our knowledge, three-dimensional computational fluid dynamics (CFD) model of the internal flow passage of an entire injector duct including injection and return routes has never been studied. In this study, major design parameters concerning internal routes in the injector are optimized by using a CFD analysis and Response Surface Method (RSM). The computational prediction of the internal flow characteristics of the common-rail diesel injector was carried out by using STAR-CCM+7.06 code. In this work, computations were carried out under the assumption that the internal flow passage is a steady-state condition at the maximum needle lift. The design parameters are optimized by using the L16 orthogonal array and polynomial regression, local-approximation characteristics of RSM. Meanwhile, the optimum values are confirmed to be valid in 95% confidence and 5% significance level through analysis of variance (ANOVA). In addition, optimal design and prototype design were confirmed by calculating the injection quantities, resulting in the improvement of the injection performance by more than 54%.