• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.507-510
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• 1999

Inspection of BGAs presents several challenges for modem measurement equipment. No only must these systems be fast and accurate, they must deal with the special challenges presented by very small shiny metal spheres. For accurate measurement, we propose an algorithm which fits for estimating the accurate ball height using 2-D curve-fitting algorithm. The real boundary between two adjacent pixels and the real ball diameter are measured with subpixel accuracy Experimental results show that the proposed method calculates the ball height and diameter with subpixel accuracy and is robust in local noise with low measurement error.

• East Asian mathematical journal
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• v.32 no.5
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• pp.717-728
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• 2016

In this paper, we give a necessary and sufficient condition for an essential simple loop on a 2-bridge sphere in an even Heckoid orbifold for the trivial knot to be null-homotopic, peripheral or torsion in the orbifold. We also give a necessary and sufficient condition for two essential simple loops on a 2-bridge sphere in an even Heckoid orbifold for the trivial knot to be homotopic in the orbifold.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.10a
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• pp.279-285
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• 1997

In this paper, the validity for the application of the diffuse sound field theory to the real sound filed, especially on the bounding surfaces of the rooms, was studied. Numerical simulations using ray tracing technique for two models, namely spheres and a reverberant room, were performed. Calculation results show that the distribution of the incident sound energy vs incident angles is approximated to Gaussian distribution, not to the uniform distribution.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.3
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• pp.910-932
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• 1996

A problem of determining the effective conductivity of a useful model of sphere-matrix type, disordered three-phase composite media is considered. Specifically, a three-phase media in which two-phase composite spheres, consisting of spheres of conductivity $k_2$((phase 2) and concentric shells of conductivity $k_3$(phase 3), are randomly distributed in a matrix of conductivity $k_1$( (phase 1) is considered. As for the structure models configuring three-phase composite media, three different structure models of PCS, PS-1 and PS-2 models are defined, which are analogous to well-established PCS, PS structure models of two-phase composite media. Futhermore, a generalized PS-PCS structure model is proposed to incorporate thesee three different models in one. Effective condectivity $k^{\ast}$of multiphaes composite media is greatly influenced by the phase connectivity of each disspersed phase material, as well as phase conductivities and phase volume fractions. Phase connectivity of three-phase PCS, PS-1, PS-2 composite media is quantified by the impentrability parameter $\lambda$. Mathematically rigorous first-order cluster bounds on $k^{\ast}$ are derived for these models of three-phase composite media, and as computation examples, first-order cluster bounds on $k^{\ast}$ for three-phase composites consisting of largely different phase conductivities are computed and compared as function of concnectivity parpmeter $\lambda$. Results and discussions are given.

• Korean Journal of Mathematics
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• v.25 no.4
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• pp.555-561
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• 2017

We show that a closed curve invariant under inversions with respect to two intersecting circles intersecting at angle of an irrational multiple of $2{\pi}$ is a circle. This generalizes the well known fact that a closed curve symmetric about two lines intersecting at angle of an irrational multiple of $2{\pi}$ is a circle. We use the result to give a different proof of that a compact embedded cmc surface in ${\mathbb{R}}^3$ is a sphere. Finally we show that a closed embedded cmc surface which is invariant under the spherical reflections about two spheres, which intersect at an angle that is an irrational multiple of $2{\pi}$, is a sphere.

• Journal of Institute of Control, Robotics and Systems
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• v.16 no.11
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• pp.1060-1067
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• 2010

In this paper, we present a new type of spherical robot having two arms. This robot, called KisBot, mechanically consists of three parts, a wheel-shaped body and two rotating semi-spheres. In side of each semi-sphere, there exists an arm which is designed based on slider-crank mechanism for space efficiency. KisBot has hybrid types of driving mode: rolling and wheeling. In the rolling mode, the robot folds its arms through inside of itself and uses them as pendulum, then the robot works like a pendulum-driven robot. In the wheeling mode, two arms are extended from inside of the robot and are contacted to the ground, then the robot works like a one-wheel car. The Robot arms can be used as a brake during rolling mode and add friction to the robot for climbing a slope during wheeling mode. We developed a remote controlled type robot for experiment. It contains two DC motors which are located in the center of each semi-sphere for main propulsion, two RC motors for each arm operation, speed controllers for each semi-sphere, batteries for main power source, and other mechanical components. Experiments for the rolling and wheeling mode verify the hybrid driving ability and efficiency of the our proposed spherical robot.

• Journal of Biomedical Engineering Research
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• v.14 no.3
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• pp.209-220
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• 1993

Microspheres are expected to be applied to biomedical areas such as solid-phase immunoassays, drug delivery systems, Immunomagnetic cell separation. To synthesize micro-spheres for biomedical application, "two stage shot growth method" was developed. The uniformity ratio or synthesized microspheres was always smatter than 1.05. And the surface charge density (or the number of ionizable functional groups) of the microspheres synthesized by "two stage shot growth method" was 6-13 times higher than thats of the ml crospheres synthesized by conventional seeded batch copolymerization. As a previous step for biomedical application, adsorption experiments of bovine albumin on microspheres were carried out under various conditions. The maximum adsorbed amount was obtained in the neighborhood of pH 4.5. Isoelectric point of bovine albumin Is pH 5.0, so experimental result shows that it shifted to acid area. The adsorption Isotherm was obtained, the plateau region was always reached at 2.Og/L (bulk concentration of bovine albumin ) . The effect of the kind and the amount of surface functional group was also examined.p was also examined.

• 한국전산유체공학회:학술대회논문집
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• 2003.10a
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• pp.21-22
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• 2003

We perform two kinds of computer simulations on polydisperse hard-sphere systems; a molecular-dynamics simulation on atomic systems and a Brownian-dynamics simulation on colloidal suspensions. Analyses of the mean square displacement, the radial distribution function, and the pressure suggest that there exist three phase regions, a liquid phase region, a metastable phase region, and a crystal phase region, where the freezing and melting points are shifted to the values higher than in monodisperse case. It is also shown that the long-time behavior of colloidal suspensions is exactly the same as that of atomic systems.

• Science of Emotion and Sensibility
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• v.12 no.4
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• pp.519-530
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• 2009

Today various interfaces are created with the advancement of technology. The flat 2D and static interfaces are general in the past but 3D and motion factors are imported in user interfaces today. It is important to use the motion factors adequately appropriate timing, situation and so on. This study focuses on the motion factor, especially the squash & stretch principle which affects the style of movement. This study investigates the effect of cartoon style(squash & stretch principle) for motion on attraction, emotion and attention. In experiment 1, participants evaluated attraction and emotion words relating to movement after they saw spheres applied to squash & stretch principle and spheres not applied to. The results indicate the squash & stretch principle can make motion not only more attractive but also brighter and more active than the general motion. In experiment 2, a sphere applied to squash & stretch principle and a sphere not applied to were presented at the same time and we measured the reaction time when participants detected change in one of the two spheres. As a result, the reaction time was faster when a sphere applied to squash & stretch principle changed. This suggests that the squash & stretch principle can make motion attract the attention of users.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.142.2-142.2
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• 2018

One-dimensional metal oxide nanostructures have attracted considerable research activities owing to their strong application potential as components for nanosize electronic or optoelectronic devices utilizing superior optical and electrical properties. In which, semiconducting $SnO_2$ material with wide-bandgap Eg = 3.6 eV at room temperature, is one of the attractive candidates for optoelectronic devices operating at room temperature [1, 2], gas sensor [3, 4], and transparent conducting electrodes [5]. The synthesis and gas sensing properties of semiconducting $SnO_2$ nanomaterials have become one of important research issues since the first synthesis of SnO2 nanowires. In this study, $SnO_2$ nanowire networks were synthesized on a basis of a two-step process. In step 1, Sn spheres (30-800 nm in diameter) embedded in $SiO_2$ on a Si substrate was synthesized by a chemical vapor deposition method at $700^{\circ}C$. In step 2, using the source of these Sn spheres, $SnO_2$ nanowire (20-40 nm in diameter; $1-10{\mu}m$ in length) networks on a spherical Sn surface were synthesized by a thermal oxidation method at $800^{\circ}C$. The Au layers were pre-deposited on the surface of Sn spherical and subsequently oxidized Sn surface of Sn spherical formed SnO2 nanowires networks. Field emission scanning electron microscopy and high-resolution transmission electron microscopy images indicated that $SnO_2$ nanowires are single crystalline. In addition, the $SnO_2$ nanowire is also a tetragonal rutile, with the preferred growth directions along [100] and a lattice spacing of 0.237 nm. Subsequently, the $NO_2$ sensing properties of the $SnO_2$ network nanowires sensor at an operating temperature of $50-250^{\circ}C$ were examined, and showed a reversible response to $NO_2$ at various $NO_2$ concentrations. Finally, details of the growth mechanism and formation of Sn spheres and $SnO_2$ nanowire networks are also discussed.