• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.55-56
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• 2002

Nanotribological characteristics of hydrophobic surfaces were studied experimentally using an atomic force microscope (AFM). Two kinds of thiolic self-assembled monolayers (SAM) having different spacer chains and their mixture were deposited onto gold-coated mica, where the deposited SAM resulted in the hydrophobic nature. Results showed that the mixed thiolic SAMs resulted in low adhesion and friction in nano-scale contact. It was argued that the water wetting characteristics played a central role on nano-scale adhesion and friction. Also the effect of mixing the thiolic SAMs were discussed on the basis of real area on contact and the stiffness of the SAM layers.

• Journal of the Korean Geographical Society
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• v.44 no.1
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• pp.56-76
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• 2009

The purpose of this study is to clarify the global commodity chains of the grafted cactus of Umseong region. The major findings of this study are as follows. Buying materials for cultivating the grafted cactus is based on the intra-Umseong local network. In addition, exporting grafted cactus using cheaper labor force means spatial division of labor from semi-periphery region to core region in terms of Wallerstein's world system theory. It is thought that buyer-driven commodity chains of farm products profit by division of labor caused by a sales network of the grafted cactus. And such situation means that high quality of the grafted cactus in Umseong maintains the spatial continuity by commodity chains.

• Journal of Pharmaceutical Investigation
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• v.36 no.2
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• pp.83-87
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• 2006

Poly(acrylic acid) (PAA) was identified to possess good mucoadhesive properties ensuring its application to extend the retention times of the formulations at the oral cavity, intended route of administration using the polymer. In the noncross-linked state, PAA will swell and become eroded owing to the presence of salivary flow from the site of application. The formation of cross-links between the polymer chains will allow swelling but prevents the erosion of the dosage form. In the current study, cross-linking was achieved by esterification of the PAA chains with sucrose. The density of crosslinking was modified by changing sucrose concentration and the duration of cure time. The cross-linking density of the polymer hydrogel was assessed by equilibrium swelling studies. The mucoadhesion testing method allowed a comparative study of the hydrogels prepared. An inverse relationship between equilibrium swelling and peak detachment force showed that increased PAA chain density per unit area enhanced the mucoadhesive interaction.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2006.05a
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• pp.1698-1701
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• 2006

In this research, fractal approach is applied to the realization of a virtual enterprise. Virtual enterprise is a temporarily built organization to cope with new business opportunity. It is composed of diverse business partners such as suppliers, manufacturers, customers, and service providers in value chains. Therefore, communication and interoperability problems between heterogeneous participants are one of the main concerns in developing collaboration models of a virtual enterprise. Fractal-based reference model can be a solution for this problem. The term 'fractal' is used to represent a participant of the value chains. There are many advantages when participants try to embody fractal-based collaboration model such as; (1) no restriction of inner configuration, (2) guarantee of autonomy, (3) easy implementation of interfaces, etc. Fractals are self-similar, however, this does not mean that they should have same configuration. In this paper, a fractal-based collaboration model for a virtual enterprise is proposed and described with (1) a formal formulation of fractal concept, (2) functional requirements and interfaces, and (3) a goal model as a driving force of the virtual enterprise.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.6
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• pp.871-883
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• 1997

Kinetodynamics of a cam driving slider mechanism consists of kinematic analysis and force analysis. The kinematic analysis is to determine the kinematic characteristics of a cam driving mechanism and a slider mechanism. The force analysis is to determine the joint forces of links, the contact forces of the cam and follower, and the driving torque of a main shaft. This paper proposes a close loop method and a tangent substitution method to formulate the relationships of kinematic chains and to calculate the displacement, velocity and acceleration of the cam driving slider mechanism. Also, and instant velocity center method is proposed to determine the cam shape from the geometric relationships of the cam and the roller follower. For dynamic analysis, the contact force and the driving torque of the cam driving slider mechanism are calculated from the required sliding forces, sliding motion and weight of the slider.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.223-224
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• 2002

The mechanisms of formation of transfer film under the condition of wear of Steel AISI1020 by natural rubber were investigated. The transfer film was observed and the formation mechanisms were clarified. The formation process of transfer film on the worn surface of the steel could be divided into two stages. Firstly, the adhesive layer emerged on the worn surface of the steel by adhesion of natural rubber. in which the macromolecular chains of natural rubber joined to the surface of the steel by Van der Waals' force. And then, the iron atom and metal oxide reacted with the macromolecular of natural rubber in the adhesive layer and produced Fe-polymer compound. As a result, the transfer film was formed on the worn surface of the steel. The transfer film was joined to the worn surface of the steel by the chemical bonds and electrostatic force.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.350-350
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• 2006

We investigated, via atomic force microscopy and transmission electron microscopy, the effect of shear force on the interfacial morphology of a reactive bilayer polymer system composed of PS-mCOOH and PMMAGMA. It has been observed that in the absence of oscillatory shearing the roughness of the interface increased with reaction period, while at large values of ${\gamma}_{0}\;and\;{\omega}$ it became less than that observed in the absence of oscillatory shearing. This observation may be attributable to the possibility that oscillatory shearing might have hindered the diffusion of polymer chains, which are located away from the interface, to the interface of the layers. However, the effect of ${\gamma}_{0}\;and\;{\omega}$ on the roughness of the interface of (PS-mCOOH)/(PMMA-GMA) bilayer is found to be quite different.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.6
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• pp.756-760
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• 2011

This paper proposed an alignment stage driven by piezo actuators for alignment process of a contact-type lithography. Among contact-type lithography processes, an UV-curable nanoimprint process is an unique process to be able to align patterns on upper and lower layers. An alignment stage of the UV-curable nanoimprint process requires nano-level resolution as well as high stiffness to overcome friction force due to contact moving. In this paper, the alignment stage consists of a compliant mechanism using flexure hinges, piezo actuators for high force generation, and capacitive sensors for high-resolution measurement. The compliant mechanism is implemented by four prismatic-prismatic compliant chains for two degree-of-freedom translations. The compliant mechanism is composed of flexure hinges with high stiffness, and it is directly actuated by the piezo actuators which increases the stiffness of the mechanism, also. The performance of the ultra-precision stage is demonstrated by experiments.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.2
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• pp.171-177
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• 2010

This paper presents the development of a new 6-DOF parallel-kinematic motion simulator. The moving platform is connected to the fixed base by six P-S-U (Prismatic-Spherical-Universal) serial chains. Comparing with the well-known Gough-Stewart platform-type motion simulator, it uses commercialized linear actuators mounted at the fixed base whereas a 6-UPS manipulator uses telescopic linear ones. Therefore, the proposed motion simulator has the advantages of easier fabrication and lower inertia over a 6-UPS counterpart. Furthermore, since most forces acting along the legs are transmitted to the structure of linear actuators, smaller actuation forces are required. The inverse position and Jacobian matrix are analyzed. In order to further increase workspace, inclined arrangement of universal joints is introduced. The optimal design considering workspace and force transmission capability has been performed. The prototype motion simulator and PC-based real-time controller have been developed. Finally, position control experiment on the prototype has been performed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.439-440
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• 2006

This research proposes a novel method of shape display to present 3-dimensional objects. Shape displays allow us to feel the actual volume of the object, unlike conventional 2D visual displays of 3D objects. The proposed method employs a wire frame structure to present 3D objects. The wire frame is composed of small units driven by shape memory alloy(SMA) actuators. The drive unit is analogous to the agonist-antagonist system of animal musculoskeletal systems, where the SMA actuators serve as agonist and antagonist muscles. The force in the SMA actuator is controlled by electrical current. The drive unit is equipped with the locking mechanism so that it can sustain the external force exerted by the user as well as the own weight of the wire frame structure. By controlling the current into the SMA actuator and locking mechanism, we call control the angle of the drive unit. A chain of drive units enables presentation of 2 dimensional objects. 3 dimensional presentations are possible by collecting the chains of drive units.