• Journal of Surface Science and Engineering
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• v.50 no.6
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• pp.510-515
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• 2017

In this study, a transient liquid phase sintering (TLPS) process of Ag pastes mixed with a fusible metal alloy of Bi58Sn42 with the melting temperature of $138^{\circ}C$, was examined. After screen printing of the Ag pastes with and without Bi58Sn42 powders on polyimide (PI) substrates, the electrodes were heat-treated at different temperatures in the range between 150 and $300^{\circ}C$ for 60 min in air. Comparing the electrical conductivity of the Ag pastes with and without Bi58Sn42 alloy powder after the heat treatment, it was manifested that the low melting temperature alloy definitely played a major role in an increased conductivity when it is added into the Ag pastes by providing more electrical conduction paths between Ag particles. This can be explained by the fact that capillary force of the melts of Bi58Sn42 can contribute to the rearrangement of the Ag particles during the heat-treatment inducing better connectivity between the Ag particles.

• International Journal of Precision Engineering and Manufacturing
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• v.1 no.1
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• pp.111-117
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• 2000

One of the major limitations of productivity and quality in metal cutting is the machining accuracy of machine tools. The machining accuracy is affected by geometric errors, thermally-induced errors, and the deterioration of the machine tools. Geometric and thermal errors of machine tools should be measured and compensated to manufacture high quality products. In metal cutting, the machining accuracy is more affected by thermal errors than by geometric errors. This paper models the thermal errors for error analysis and develops an on-the-machine measurement system by which the volumetric errors are measured and compensated. The thermal error is modeled by means of angularity errors of a column and thermal drift error of the spindle unit which are measured by the touch probe unit with a star type styluses and a designed spherical ball artifact (SBA). Experiments show that the developed system provides a high measuring accuracy, with repeatability of $\pm$2$\mu\textrm{m}$ in X, Y and Z directions. It is believed that the developed measurement system can be also applied to the machine tools with CNC controller. In addition, machining accuracy and product quality can be also improved by using the developed measurement system when the spherical ball artifact is mounted on a modular fixture.

• Journal of Korean Society of Steel Construction
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• v.20 no.5
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• pp.633-644
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• 2008

The structural framework design uses high-strength bolts and welding in column splices. However, for the column under high compression, the number of the required high-strength bolts can be excessive and the increase of welding results in difficulty of quality inspection, the transformation of the structural steels, and the increase of erection time. According to the AISC criteria, when columns have bearing plates, or they are finished to bear at splices, there shall be sufficient connections to hold all parts securely in place. The Korean standard sets the maximum 25% of the load as criteria. Using direct contact makes it possible to transfer all compressive force through it. The objective of this study is to examine the generally applied stress path mechanism of welded or bolted columns and to verify the bending moment and compression transfer mechanism of the column splice according to metal touch precision. For this study,22 specimens of various geometric shapes were constructed according to the change in the variables for each column splice type, which includes the splice method, gap width, gap axis, presence or absence of splice material, and connector type. The results show that the application of each splice can be improved through the examination of the stress path mechanism upon metal contact. Moreover, the revision of the relative local code on direct contact needs to be reviewed properly for the economics and efficiency of the splices.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.4
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• pp.317-322
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• 2010

This paper reports the fabrication and characterization of surface micromachined poly 3C-SiC capacitive pressure sensors on silicon wafer operable in touch mode and normal mode for high temperature applications. FEM(finite elements method) simulation has been performed to verify the analytical mode. The sensing capacitor of the capacitive pressure sensor is composed of the upper metal and the poly 3C-SiC layer. Measurements have been performed in a temperature range from $25^{\circ}C$ to $500^{\circ}C$. Fabrication process of designed poly 3C-SiC touch mode capacitive pressure sensor was optimized and would be applicable to capacitive pressure sensors that are required high precision and sensitivity at high pressure and temperature.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2001.04a
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• pp.453-457
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• 2001

One of the major limitations of productivity and quality in metal cutting is the machining accuracy of machine tools. The machining accuracy is affected by geometric and thermal errors of the machine tools. In this study, the compensation device is manufactured in order to compensate thermal error of machine tools under the real-time. This paper models of the thermal errors for error analysis and develops on-the-machine measurement system by which the volumetric error are measured and compensated. The thermal error is modeled by means of angularity errors of a column and thermal drift error of the spindle unit which are measured by the touch probe unit with a star type styluses, a designed spherical ball artifact, and five gap sensors. In order to compensate thermal characteristics under several operating conditions, experiments performed with five gap sensors and manufactured compensation device on the horizontal machining center.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.10a
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• pp.449-453
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• 2000

In metal cutting, the machining accuracy is more affected by thermal errors than by geometric errors. This paper models of the thermal errors for error analysis and develops on-the-machine measurement system by which the volumetric error are measured and compensated. The thermal error is modeled by means of angularity errors of a column and thermal drift error of the spindle unit which are measured by the touch probe unit with a star type styluses, a designed spherical ball artifact, and five gap sensors. In order to analyze the thermal characteristics under several operating conditions, experiments performed with the touch probe unit and five gap sensors on the vertical and horizontal machining centers.

• Journal of the Korean Ceramic Society
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• v.50 no.5
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• pp.309-318
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• 2013

Graphene has attracted considerable attention since its first production from graphite in 2004, due to its outstanding physical and chemical properties. The development of production methodsfor large scale, high quality graphene films is an essentialstep toward realizing graphene applications such as transparent, conductive film. Chemical deposition methods, using metal catalystsand gaseous carbon sources, have been extensively developed for large area synthesis. In this paper, wereview recent progress ingraphene production, and survey the role of graphene electrodes in various electronic devices such as touch panels, solar cells, solid statelighting and microelectronic devices.

• Proceedings of the KWS Conference
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• v.43
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• pp.171-173
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• 2004

Electromagnetic force is one of the most important factor that effect on metal transfer mode, short-circuit rate, spatter generation rate and mechanical properties of weld metal etc. Also, shielding gas and welding current have influence on metal transfer mode in GMAW. In this paper, different ways for external electromagnetic forces are applied by attaching cylindrically rounded conducting wire solenoid on touch tip holding. With the applied electromagnetic field, the arc transfer mode changes from normal mode to rotating mode and spatter generation decreased in electromagnetic fields(N-pole). In MIG welding, the influences of electromagnetic force on the spatter generation showed different tendency as in the $CO_2$ welding. It is possible reasons were discussed.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1155-1156
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• 2015

This study demonstrates hybrid-type transparent electrodes for touch screen panels. The hybrid-type electrodes were fabricated by coating carbon nanotubes (CNTs) on metal meshes. For the formation of metal meshes, thin films of silver (Ag) were deposited on glass substrates using a sputtering method and then pattenrned via photolithography to obtain mesh structures of which line width was $10{\mu}m$ and line-to-line spacing was $300{\mu}m$. CNTs were coated on Ag meshes by using electrophoretic deposition (EPD). For the samples of Ag meshes with/without CNTs, their surface morphologies, visible-range transmittances, and reflectances were characterized and compared. The experimental results indicated that the reflectance of Ag mesh electrodes was substantially reduced by coating of CNTs. Especially, the hybrid electrodes of Ag meshes with EPD-coated CNTs showed excellent properties such as transmittance higher than 90%, reflectance lower than 8%.

• Journal of the Semiconductor & Display Technology
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• v.14 no.1
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• pp.55-59
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• 2015

This study demonstrates hybrid-type transparent electrodes for touch screen panels. The hybrid-type electrodes were fabricated by coating carbon nanotubes (CNTs) on metal meshes. To form the metal-meshes, thin films of silver (Ag) were deposited on glass substrates using the sputtering method and then patterned via photolithography to obtain mesh structures whose line width was $10{\mu}m$ and line-to-line spacing was $300{\mu}m$. CNTs were coated on Ag-meshes by using two different methods, such as spray coating and electrophoretic deposition (EPD). For the samples of a Ag-meshes and CNTs-coated Ag-meshes, their surface morphologies, electrical sheet resistances, and visible-range transmittances and reflectances were characterized and compared. The experimental results indicated that the reflectance of Ag-mesh electrodes was substantially reduced by coating of CNTs. Especially, the hybrid electrodes of Ag-meshes with EPD-coated CNTs showed excellent properties such as sheet resistance lower than $20{\Omega}/{\Box}$, transmittance higher than 90 %, and reflectance lower than 8%.