• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.06a
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• pp.339-343
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• 2005

Laser material processing is a very fast growing technology for various industrial applications, because of many advantages. Its major advantage of less and controlled heat input has been exploited successfully for the very critical application of aluminium alloy welding. This study suggested the occurrence source of weld-defects and its solution methods in a welding of lithium ion battery by pulsed Nd:YAG laser. In experiment, battery case has changed over joint geometry from welding of side position to flat one. In case of a electrolyte injection hole in order to seal it, welding is carried out after pressing Al ball. At this time, an eccentric degree, contact length and gap are worked as a major parameters. As improving the method of Al ball pressing, it was able to reduce an eccentricity, increase the contact length and decrease gap. As a results of a experiment, a sound weld bead shape and crack-free weld bead can be obtained.

• Applied Science and Convergence Technology
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• v.23 no.4
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• pp.192-199
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• 2014

The electronic property of graphene was investigated by hydrazine treatment. Hydrazine ($N_2H_4$) highly increases electron concentrations and up-shifts Fermi level of graphene based on significant shift of Dirac point to the negative gate voltage. We have observed contact resistance and channel length dependent mobility of graphene in the back-gated device after hydrazine monohydrate treatment and continuously monitored electrical characteristics under Nitrogen or air exposure. The contact resistance increases with hydrazine-treated and subsequent Nitrogen-exposed devices and reduces down in successive Air-exposed device to the similar level of pristine one. The channel conductance curve as a function of gate voltage in hole conduction regime keeps analogous value and shape even after Nitrogen/Air exposure specially whereas, in electron conduction regime change rate of conductance along with the level of conductance with gate voltage are decreased. Hydrazine could be utilized as the highly effective donor without degradation of mobility but the stability issue to be solved for future application.

• Industry Promotion Research
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• v.3 no.1
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• pp.1-5
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• 2018

$SnO_2$ films were annealed in a vaccum atmosphere conditions to research the temperature dependency of current-voltage characteristics in according to the bonding structures. The $SnO_2$ film annealed in a vacuum became an amorphous structure but films annealed in an atmosphere condition had a crystal structure. The defects or depletion layer were formed by the electron-hole combination after annealing processes, and the electrical properties were changed depending on the crystal structure, binding energy and the variation of carriers. $SnO_2$ became more crystal-structural with increasing the annealing temperature, and the current increased at $SnO_2$ film annealed at $150^{\circ}C$ with Schottky current.

• Industry Promotion Research
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• v.1 no.2
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• pp.13-17
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• 2016

ZTO films were annealed in a vaccum atmosphere conditions to research the temperature dependency of current-voltage characteristics. The ZTO film annealed in a vacuum became an amorphous structure but films annealed in an atmosphere condition had a crystal structure. The defects or depletion layer were formed by the electron-hole combination after annealing processes, and the electrical properties were changed depending on the crystal structure, binding energy and the variation of carriers. ZTO became more crystal-structural with increasing the annealing temperature, and the current increased at ZTO film annealed at $150^{\circ}C$ with Schottky contact.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.1
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• pp.47-53
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• 2010

In this study, analyses on the stencil printing using solder paste were carried out. The key design parameters in the stencil printing process are printing conditions, stencil design, and solder paste properties. Among these parameters, the effects of physical properties of solder paste such as viscosity, surface tension, and contact angle on the stencil printing process were investigated. The analyses were performed for simple geometry and boundary conditions. In the analysis, solder paste was pushed into a stencil hole by pressure instead of printer pad. Considering the geometry and computational efficiency, axisymmetric analyses were adopted. A commercial software (COMSOL), which is well known in the area of micro-fluids analysis, was used. From the results, it was shown that viscosity of solder paste had an effect on the filling speed, while surface tension and contact angle had an effect on the filling shape.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.119-119
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• 2011

This study examined the synthesis of large area graphene and the change of its characteristics depending on the ratio of CH4/H2 by using the thermal CVD methods and performed the experiments to control the electron-hole conduction and Dirac-point of graphene by using chemical doping methods. Firstly, with regard to the characteristics of the large area graphene depending on the ratio of CH4/H2, hydrophobic characteristics of the graphene changed to hydrophilic characteristics as the ratio of CH4/H2 reduces. The angle of contact also increased to 78$^{\circ}$ from 58$^{\circ}$. According to the results of Raman spectroscopy showing the degree of defect, the ratio of I(D)/I(G) increases to 0.42% from 0.25% and the surface resistance also increased to 950 ${\Omega}$ from 750 ${\Omega}$/sq. As for the graphene synthesis at the high temperature of 1,000$^{\circ}$ by using CH4/H2 in a Cu-Foil, the possibility of graphene formation was determined as a function of the ratio of H2 included in the fixed quantity of CH4 as per specifications of every equipment. It was observed that the excessive amount of H2 prevented graphene from forming, as extra H-atoms and molecules activated the reaction to C-bond of graphene. Secondly, in the experiment for the electron-hole conduction and the Dirac-point of graphene using the chemical doping method, the shift of Dirac-point and the change in the electron-hole conduction were observed for both the N-type (PEI) and the P-type (Diazonium) dopings. The ID-VG results show that, for the N-type (PEI) doped graphene, Dirac-point shifted to the left (-voltage direction) by 90V at an hour and by 130 V at 2 hours respectively, compared to the pristine graphene. Carrier mobility was also reduced by 1,600 cm2/Vs (1 hour) and 1,100 cm2/Vs (2 hours), compared to the maximum hole mobility of the pristine graphene.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.393-394
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• 2004

To get rid of cell assembly margin and have more process room of upper substrate, we developed truly COT (Color Filter On TFF Array) LCDs in that B/M (Black Matrix) as well as C/F (Color Filter) layer is located on TFT substrate. Novel B/M material is also developed for this COT structure. Difficulty in making contact hole through C/F layer was solved by making each C/F pattern isolated from others. We think this configuration will be core technology for prominent COT LCDs.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.05a
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• pp.159-162
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• 2001

A combined finite element and experimental study based on the characteristic length method is performed to investigate the strength and behavior of the pin joint in composite control rod. The failure is estimated by the Yamada-Sun and Tsai-Wu criteria on the characteristic curve. The gap elements are used to simulate the contact between the pin and the composite fitting with hole. The accuracy and applicability of the method are validated by the joint tests. All the specimens were failed in the bearing mode in the test and finite element analysis, and good agreement was found between the predicted and test results on the joint strength of composite control rod.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.690-695
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• 2004

A new dimension measuring method for the measurement of diameter of an object has been developed using laser triangulation. The 3-D data of an object was calculated from the 2dimensional image information obtained by the laser stripe using the laser triangulation. The system can measure the diameter of hole not only in a normal plane but also in an incline plane. We can experiment with magnification that is optimized according to size of object using zoom lens. In this paper, the theoretical formula and calibration of the system were described. The measuring precision of the system was investigated by experiment.

• Journal of the Korean Society of Safety
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• v.18 no.1
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• pp.19-27
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• 2003

This paper presented an experimental modal analysis of clamped perforated rectangular plates submerged in water. The penetration of holes in the plates had a triangular pattern with P/D (pitch to diameter) 1.750, 2.125, 2.500, 3.000 and 3.750. The natural frequencies of the perforated plates in air were obtained by the Rayleigh-Ritz method and compared with the experimental results. Good agreement was obtained between the analytical solution and experimental result. The experimental results in water showed that the mode shapes are not sensitive to the depth of submergence. The natural frequencies were shown to decrease drastically once the perforated plates come in contact with water. However, the natural frequencies decrease with the depth of submergence until a certain depth is reached, and become the asymptotic values beyond this depth of submergence. The depth of submergence did not affect the damping ratio greatly.