• Transactions on Electrical and Electronic Materials
• /
• v.6 no.1
• /
• pp.22-24
• /
• 2005

We studied the nematic liquid crystal (NLC) aligning capabilities using the new alignment material of the SiC (Silicon Carbide) thin film. The SiC thin film exhibits good chemical and thermal stability. The good thermal and chemical stability makes SiC an attractive candidate for electronic applications. A vertical alignment of nematic liquid crystal by ion beam exposure on the SiC thin film surface was achieved. The about $87{\circ}$ of stable pretilt angle was achieved at the range from $30{\circ}$ to $45{\circ}$ of incident angle. The good LC alignment is maintained by the ion beam alignment method on the SiC thin film surface at high annealing temperatures up to $300{\circ}C$.

• Proceedings of the KSME Conference
• /
• 2000.11b
• /
• pp.732-737
• /
• 2000

The purpose of this study is to compare the SMD(Sauter mean diameter) with different vibrant plates. Each vibrant plates have different surface roughness. Also liquid film thickness are measured for explanation how to concern atomization. Ultrasonic waves is used for vibration. Immersion liquid method is used for the measure of SMD and also liquid film thickness is measured using of point needle method. Distilled water and gasoline fuel are used to liquids. Supplied liquid flow rates are $18{\sim}296cc/min$. Centerline average roughness of vibrant plates are 0.5, 2.0, 4.7, $9.5\;{\mu}m$ and diameter of vibrant plate is 60mm. In result, good atomization of liquid is obtained in widen flow rates. The mean droplet size is increased in orders of 4.7, 2.0. 9.5, $0.5\;{\mu}m$ surface roughness. Distilled water has a big mean droplet size than gasoline fuel in low flow rate. Above the 78cc/min flow rates, distilled water has a small mean droplet size than gasoline fuel. Liquid films changes are measured with ultrasonic power. Also, cavitation effect on sprays is observed.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.24 no.7
• /
• pp.1010-1019
• /
• 2000

The main purpose of this article is to propose and assess a new spray impingement model considering film formation, which is capable of describing the droplet distribution and film flows in direct injection diesel engines. The spray-wall interaction model includes several mathematical formulae, newly made by the energy conservation law and some experimental results. The model consists of three representative regimes, rebound, deposition and splash. In addition, the film flow is described in the present model by solving the continuity and momentum equations for film flows using the integral method. To assess the new spray impingement model, the calculated results using the new model are compared with several experimental data for the normally impinging diesel sprays. The film model is also validated through comparing film radius and thickness against experimental data. The results show that the new model is generally in better agreement with experimental data and acceptable for prediction of the film radius and thickness.

• Journal of ILASS-Korea
• /
• v.26 no.1
• /
• pp.26-32
• /
• 2021

In this study, the thickness of the liquid sheet formed by two low speed impinging jets was measured by the direct contact method. The effects of jet velocity and liquid viscosity on the thickness were analyzed and the results were compared with theoretical modeling and optical thickness measurement results. The liquid film thickness decreased as the radius and circumferential angle increased. The jet velocity did not affect the liquid film thickness as predicted in theoretical modeling. In the theoretical modeling, there was no influence of the fluid properties on thickness, but in the case of low viscosity liquids, the thickness was predicted high, and it was well matched in high viscosity liquids. The direct measurement results showed no significant difference from the optical measurement results, thus confirming the reliability of the optical measurement method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.11a
• /
• pp.502-505
• /
• 2004

We studied the nematic liquid crystal (NLC) aligning capabilities using the new alignment material of a SiC (Silicon Carbide) thin film. SiC thin film exhibits good chemical and thermal stability. The good thermal and chemical stability make SiC an attractive candidate for electronic applications. A homeotropic alignment of nematic liquid crystal by ion beam (IB) exposure on the SiC thin film surface was achieved. The about $87^{\circ}$ of stable pretilt angle was achieved at the range from $30^{\circ}$ to $45^{\circ}$ of incident angle. The good LC alignment is maintained by the ion beam alignment method on the SiC thin film surface until annealing temperature of $300^{\circ}C$. Consequently, homeotropic alignment effect of liquid crystal and the good thermal stability by the ion beam alignment method on the SiC thin film layer can be achieved.

• Journal of the korean Society of Automotive Engineers
• /
• v.2 no.1
• /
• pp.21-31
• /
• 1980

Two phase boundary layer equations of laminar filmwise condensation are solved by an approximate integral method under the following condition; saturated vapour flows vertically downward over a cooled surface of uniform temperature, the condensate film is so thin that the inertia and convection terms are neglected. The following conclusions are drawn under the above assumptions. 1. free convection In case of the linear temperature profile in a liquid film, numerical results for the average coefficients of heat transfer may be expressed as N $u_{m}$=4/3,(G $r_{l}$ /4.H)$^{1}$4/ and in case of the quadratic profile, numerical results may be expressed as N $u_{m}$=2/1.682,(G $r_{l}$ /H)$^{1}$4/. 2. Forced convection When the temperature profile is assumed to be linear in a liquid film, numerical results fir the average heat transfer coefficients may be expressed as N $u_{m}$=(A, R $e_{l}$ /H)$^{1}$2/. This expression is compared with the experimental results hitherto reported; For theoretical Nusselt number (N $u_{m}$)$_{th}$<2*10$^{4}$, the experimental Nusselt number (N $u_{m}$)$_{exp}$ is on the average larger than theoretical Nusselt number (N $u_{m}$)$_{th}$ by 30%. For (N $u_{m}$)$_{th}$>2*10$^{4}$, experimental Nusselt number (N $u_{m}$)$_{exp}$ is about 1.6 times as large as theoretical Nusselt number (N $u_{m}$)$_{th}$. These large deviation may be caused by the presence of turbulence in the liquid film. In case of the quadratic temperature profile in a liquid film, numerical results for the average coefficients of heat transfer may be expressed as N $u_{m}$'=(2,A,Re/H)$^{1}$2/. This formular shows that theoretical Nusselt number (N $u_{m}$)$_{th}$ is larger than experimental Nusselt number (N $u_{m}$)$_{exp}$ by 60%. It is speculated that when the temperature difference between cooled surface and saturated vapour is small, temperature profile in a liquid film is quadratic.quadratic.. quadratic.quadratic..atic..

• Journal of IKEEE
• /
• v.28 no.3
• /
• pp.261-270
• /
• 2024

In this study, a lanthanum gallium oxide (LaGaO) solution was prepared using a sol-gel method. By simply forming a LaGaO thin film through adjusting the curing temperature after applying the solution onto the substrate using a brush coating process, the potential for use as a liquid crystal (LC) alignment film in the LC display industry was validated. Through optical microscope observation, it was confirmed that the LC molecules were uniformly aligned as the curing temperature of the LaGaO thin film increased. It was confirmed that the LaGaO thin film cured at 230℃ had low pretilt angle, and that LaGaO particles were formed in a single direction as observed through an atomic force microscope. Through X-ray photoelectron spectroscopy, it was found that the LaGaO metal oxide thin film was well formed. Finally, it has been confirmed that LaGaO metal oxide has the potential as a novel LC alignment film material, as it exhibits excellent electrical and optical properties, along with high optical transmittance.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2006.11a
• /
• pp.311-312
• /
• 2006

We studied homeotropic alignment effect for a nematic liquid crystal (NLC) on the $SiO_x$, thin film irradiated by the new ion beam method $SiO_x$ thin films were deposited by plasma enhanced chemical vapor deposition (PECVD) and were treated by the DuoPIGatron ion source. A uniform liquid crystal alignment effect was achieved over 2100 eV ion beam energy. Tilt angle were about $90^{\circ}$ and were not affected by various ion beam energy.

• 한국연소학회:학술대회논문집
• /
• 2003.12a
• /
• pp.167-173
• /
• 2003

An experimental study on the behavior of droplets impinging on a solid flat surface was carried out in the present study. Breakup of a liquid droplet impinging on a solid surface has been investigated experimentally for various fuels with different properties. The fuel temperature and incident angle were chosen as major parameters. And fuel temperature and incident angle varied in the range from $-20^{\circ}C$ to $30^{\circ}C$ and from $30^{\circ}$ to $60^{\circ}$, respectively, were investigated. It was found that the variation of fuel temperature influences upon droplet mean diameter which were bounced out from the solid surface. As the increases of incident angle, the break-out mass flow rate increases. This causes the decrease of liquid film flow rate. The larger incident angle gives less liquid film flow rate.

• Bulletin of the Korean Chemical Society
• /
• v.23 no.4
• /
• pp.587-592
• /
• 2002

Photocrosslinkable chalcone-epoxy compound comprising 1,3-bis-(4-hydroxy-phenyl)-propenone was synthe-sized for fabricating the photo-alignment layer of liquid crystals. Chalcone group was introduced into the main chain unit of the epoxy oligomer. We observed a photodimerization behavior and an optical anisotropy of this material by irradiation of a linearly polarized UV(LP-UV) light. With a trace amount of cationic photoinitiator (TRS-HFA), polymerization of epoxy groups was also conducted at the similar wavelength range used for photodimerization. Linearly polarized UV irradiation on the chalcone-epoxy films with cationic photoinitiator induced optical anisotropy of the film and the resultant film can be used for alignment layers for low molecular weight nematic liquid crystals.