• Journal of Information Display
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• v.7 no.2
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• pp.12-15
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• 2006

We propose a patterning method of liquid crystal (LC) alignment layer for producing multi-domain LC structures. By controlling thermal conditions during micro-contact printing procedures and facilitating wetting properties of patterning materials, patterned LC orientation can be easily obtained on a bare ITO surface or other polymer films. The newly proposed patterning method is expected to be a very useful tool for fabricating multi-domain LC structures to enhance or design electro-optic properties of LC-based devices.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.569-572
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• 2003

In VLM-ST process, the fine detailed shape processing process is needed due to the use of thick sheets for layers. The developed process perform the fine detailed shape processing in VLM-ST parts using non-contact hot tool. To predict the heat-affected zone and temperature distribution of VLM-ST parts in detailed shaping, the heat flux from the tool to the surface was calculated for the finite element analysis by modeling the tool as a heat source of radiation. The dominant process parameters such as the radiated heat input, the tool speed, and the gap between the tool tip and the foam sheet (tool height) were considered in the analysis. The results showed a good agreement with the experiments.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.10
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• pp.805-812
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• 2003

This paper presents a method to investigate the characteristics of a ball bearing and the dynamics of a HDD spindle system due to temperature variation. Finite element model is developed for the rotating and stationary parts of a HDD spindle system separately to determine their thermal deformations by using ANSYS, a finite element program. Then, the relative position of the rotating part with respect to the stationary part is determined by solving the equilibrium equation of the contact force between upper and lower ball bearings. The validity of the proposed method is verified by comparing the theoretical natural frequencies of a HDD spindle system with the experimental ones before and after temperature variation. It shows that the elevated temperature results in the increase of contact angle and the decrease of bearing deformation, contact force and bearing stiffness, which result in the decrease of the natural frequencies of a HDD spindle system.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.381-386
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• 2000

The brake force of drum brakes for commercial vehicles is applied by a s-cam. First of all the influence of the s-cam load angles and elastic modulus of the pad on the contact pressure distribution between pad and drum was checked by using 3 dimensional finite element model. In the second part, temperature and thermal stress analyses were carried out by an axisymmetric model with constant heat flux and pressure-proportional heat flux. In the case of temperature analysis the heat conduction from the interface to the pad and the drum was modeled using a thin soft film element, so artificial division of the generated heat flux between pad and drum is not necessary. The analysis was performed by ABAQUS/Standard code.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.145-150
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• 2003

In this paper we have studied the characteristics of temperature fields in a Molded Case Circuit Breaker (MCCB). A switch and a trip device are arranged in narrow space of the MCCB. Thus, thermal factors have been risen to important problem. The temperature rise means an energy loss and it becomes the reason of fatal fault in devices. Also, the temperature rise on the connection and the contact parts is regulated up to $115^{\circ}C$ and $105^{\circ}C$, respectively. Therefore, a study for preventing the temperature rise should be investigated. A numerical analysis method that has confidence might be preceded for this purpose. In order to verify the confidence of temperature field analysis, the results of the numerical analysis are compared with those of experimental one for the same model. Comparison results show a qualitatively good agreement within ${\pm}5%$ errors.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.2
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• pp.304-311
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• 2001

The present work examines the influence of surface coating on the temperature and the thermo-mechanical stress field produced by friction due to sliding contact. A two-dimensional transient model of a layered medium submitted to a moving heat flux is prsented. A solution technique based on the boundary element method employing the multiregion technique is utilized. Results are presented showing the influence of coating thickness, thermal properties, Peclet number, and mechanical properties. It has been shown that the mechanical properties and thickness of coating have a significant influence on the stress field, even for low temperature increase. The effects of the ratios of shear modulus become more important for low temperature increase than the effects of the ratios of other mechanical properties.

• Electrical & Electronic Materials
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• v.10 no.10
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• pp.1034-1040
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• 1997

A solar cell conversion effiency was degraded by grain boundary effect in polycrystalline silicon. Grain boundaries acted as potential barriers as well as recombination centers for the photo-generated carriers. To reduce these effects of the grain boundaries we investigated various influencing factors such as emitter thickness thermal treatment preferential chemical etching of grain boundaries grid design contact metal and top metallization along boundaries. Pretreatment in $N_2$atmosphere and gettering by POCl$_3$and Al were performed to obtain multicrystalline silicon of the reduced defect density. Structural electrical and optical properties of slar cells were characterized before and after each fabrication process. Improved conversion efficiencies of solar cell were obtained by a combination of pretreatment above 90$0^{\circ}C$ emitter layer of 0.43${\mu}{\textrm}{m}$ Al diffusion in to grain boundaries on rear side fine grid finger top Yb metal and buried contact metallization along grain boundaries.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.4
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• pp.555-562
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• 1990

Alloyed ohmic contact properties of Au-Zn/Au, Au-Be/Au,Au-Zn/Cr/Au, and Au-Be/Cr/Au metal system to p-InP were investigated. Optimum alloying conditions were obtained at the annealing temperature of 425\ulcorner for all the metal systems using a rapid thermal annealing system. Surface AES analysis and auger depth profiling were done for each metal system annealed at the optimum conditions. Outdiffusions of In and P from the InP substrate were found in the metal systems without Cr intermediate layer. Also, small amount of In. P and Cr were detected at the surface in the case of Au-Zn/Cr/Au system, while there were occured no outdiffusion of In, P, and Cr for Au-Be/Cr/Au system. The best surface morpholoty and specific contact resistivity of 4.5x 10**-5 \ulcornercm\ulcornerhave been obtained in this Au-Be/Cr/Au material system alloyed at 425\ulcorner for 60 second.

• Journal of the Korean Ceramic Society
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• v.32 no.7
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• pp.817-824
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• 1995

TiB2 was simultaneously synthesized and densified with concurrent self-propagating high-temperature synthesis and direct contact-heating by electrcial power input and pressure. Density of TiB2 synthesized by self-propagating high-temperature synthesis and consolidated simultaneously by direct contact-heating and pressure was maximum 80% of the theoretical density (4.52g/㎤). Temperature profile was analyzed by solving heat balance equation with numerical method (FTCS method). The temperature of the sample was sufficiently raised to that temperature sufficient to be densified. It was ascertained that the density of the SHS synthesized TiB2 is exponentially proportinal to the input thermal energy per mass.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.738-739
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• 2006

This paper will describe a powder and processing method that facilitates single press-single sintered densities approaching $7.5g/cm^3$. At this sintered density, mechanical properties of the powder metal (P/M) component are significantly improved over current P/M technologies and begin to approach the performance of wrought steels. High performance gears have the added requirement of rolling contact fatigue durability that is dependent upon localized density and thermal processing. Combining high density processing of engineered P/M materials with selective surface densification enables powder metal components to achieve rolling contact fatigue durability and mechanical property performance that satisfy the performance requirements of many high strength automotive transmission gears. Data will be presented that document P/M part performance in comparison to conventional wrought steel grades.