• Applied Microscopy
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• v.48 no.4
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• pp.128-129
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• 2018

Soft ferromagnetic materials are utilized for various electromagnetic devices such as magnetic recording heads and magnetic shielding. In situ observation of magnetic microstructures and domain wall motions are prerequisite for understanding and improving their magnetic properties. In this work, by the Fresnel (out-of-focus) method of Lorentz microscopy, we observe the domain wall motions of polycrystalline Ni/Ti thin film layers triggered by single-shot laser pulse. Random motions of domain walls were visualized at every single pulse.

• International Journal of Automotive Technology
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• v.7 no.4
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• pp.493-500
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• 2006

Investigation on the fuel adhering on a wall was carried out experimentally to clarify the characteristics of impinging diesel sprays. Diesel sprays were injected into a high-pressure chamber of cold state and impinged to a wall having various impingement distances and ambient pressures. Photographs of both the fuel film and the post-impingement spray were taken through a transparent wall. Adhered fuel mass on a wall was measured by means of dividing into two types of fuel state: the fuel film itself; and sparsely adhered fuel droplets. Adhering fuel ratio was predicted and further the distribution of fuel mass for impinging diesel spray was analyzed as a function of time. As result, with an increase of the ambient pressure, both the maximum fuel film diameter and the adhered fuel ratio decreased. Based on some assumptions, the adhering fuel mass increased rapidly until the fuel film diameter approached the maximum value, and then increased comparatively gradually.

• Journal of computational fluids engineering
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• v.13 no.2
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• pp.68-72
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• 2008

NUFLEX is a general purpose thermo/fluid flow analysis program which has various physical models including spray. In NUFLEX, spray models are composed of breakup and collision models of droplet. However, in case of diesel engine, interaction between wall-film and impingement model considering heat transfer is not coded in NUFLEX. In this study, Lee & Ryou impingement & wall-film model considering heat transfer is applied to NUFLEX. For the verification of this NUFLEX program, numerical results are compared with experimental data. Differences of film thickness and radius between numerical results and experimental data are within 10% error range. The results show that NUFLEX can be used for comprehensive analysis of spray phenomena.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.71-72
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• 2006

The stochiometric mixture of evaporating materials for the $ZnIn_2S_4$ single crystal thin film was prepared from horizontal furnace. To obtain the $ZnIn_2S_4$ single crystal thin film. $ZnIn_2S_4$ mixed crystal was deposited on throughly etched semi-insulating GaAs(100). In the Hot Wall Epitaxy(HWE) system. From the photocurrent spectrum by illumination of perpendicular light on the c-axis of the $ZnIn_2S_4$ single crystal thin film, we have found that the values of spin orbit splitting ${\Delta}So$ and the crystal field splitting ${\Delta}Cr$ were 0.0148 eV and 0.1678 eV at $10_{\circ}K$, respectively.

• 한국연소학회:학술대회논문집
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• 2003.12a
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• pp.237-242
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• 2003

The measurement study of instantaneous temperature at combustion chamber wall and the temperature of combustion gas has been under lots of research and development to conclude the temperature process in internal combustion engine for combustion characteristics analysis. The measurement with fast responsibility should be used for temperature measurement inside combustion chamber wall since temperature of wall changes, due to the various gas temperature, irregularly during the combustion. Therefore, thin film instantaneous surface temperature probe, which characterizes the fastest and the most accurate responsibility among contact typed temperature measurement, was used for the experiments. This new thin film instantaneous surface temperature probe improved the problems of noise and durability. The optimal coating thickness of thin film instantaneous surface temperature probe was proven to be $10{\mu}m$ for the best responsibility and durability. It also allowed the stable temperature measurement be taken up to $1,200^{\circ}C$ and proven to be read possibly from the combustion chamber wall.

• Journal of Industrial Technology
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• v.32 no.A
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• pp.29-33
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• 2012

We demonstrated the viability of fully microfabricating SWCNT(single-wall carbon nanotube) film strain sensors for force and weight sensing. Our spray-deposited SWCNT film strain sensors showed good linearity over a range from 0 to 400 microstrain, and much higher sensitivity compared to commercial metal foil-type gauges. The number of grids and the thickness of the SWCNT film were found to have a significant effect on the strain sensing properties of the SWCNT film gauges. A strain sensing methode for the CNT-based strain gauges was also investigated using a binocular type beam load cells. Preliminary results indicate that the microfabrication method shown here is promising for developing a commercial strain gauge using a spray-coated SWCNT thin film. In the near future, various studies will be performed to further enhance the properties of the spray-coated SWCNT film strain sensors.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.8
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• pp.116-122
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• 1999

According to the stringent exhaust emission regulation, precise control of air fuel ratio is one of the most important issues on gasoline engine. Although many researches have been carried out to identify the fuel transport phenomena in a port fueled gasoline engine, complexity of fuel film behavior in the intake port makes it difficult. The fuel film behavior was investigated recently by using visualization method and these gave us qualitative understanding. The purpose of this study is to estimate of wall wetting fuel in the intake port and the inducted fuel mass was predicted by using wall wetting fuel model . The model coefficient($\alpha$,$\beta$) and fuel film mass on the port wall were determined from measured in-cylinder HC concentration using FRFID after injection off. The fuel film mass was increased, but $\alpha$(ratio of directly inducted fuel mass into cylinder from injected fuel mass) was decreased with increasing load at the same engine speed. $\beta$is nearly constant value(0.8~0.9). when injected fuel mass is varied at 1500rpm , the calculated air fuel ratio using well wetting fuel model was nearly the same as measured by UEGO.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.8
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• pp.621-628
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• 2008

A numerical study for the flow, heat and mass transfer characteristics of the evaporating tube with the films flowing down on both the inside and outside tube walls has been carried out. The condensation occurs along the outside wall while the evaporation occurs at the free surface of the inside film. The transport equations for momentum and energy are parabolized by the boundary-layer approximation and solved by using the marching technique. The calculation domain of 2 film flow regions (evaporating and condensation films at the inside and outside tube wall respectively) and tube wall is solved simultaneously. The coupling technique for the problem with the 3 different regions and the 2 interfaces of them has been developed to calculate the temperature field. The velocity and temperature fields and the amount of the condensed and evaporated mass as well as the position where the evaporating film is completely dried out are successfully predicted for various inside pressures and inside film inlet flow rates.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.6
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• pp.1572-1581
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• 1994

Heat transfer characteristics in a rotating heat pipe with evaporator of the rotating disc and the condenser of the screwed groove is investigated by numerical method for various dimensionless film thicknesses, Re, C_{p}{\Delta}T/h_{fg}$, rotational speed and working fluids. The temperature difference between evaporator wall and vapor increases a little, but the temperature difference between condenser wall and vapor decreases rapidly as Re increases. As the dimensionless film thickness decreases, the temperature difference of evaporator and condenser decreases. As the rotational speed increases, the temperature difference between evaporator wall and vapor increases but the temperature difference between condenser wall and vapor decreases. The Nusselt number can be shown as a function of dimensionless film thickness and Re, that is $Nu=0.963\cdot(\delta^{-1}(\omega/\vpsilon)^{-1/2}{\cdot}Re^{0.5025})$.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.10
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• pp.1849-1860
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• 1994

Domain wall dynamics in thin film of amorphous Rare Earth-Transistion Metal alloys were investigated using numerical integration of the Landau-Lifshitz-Gilbert equation. The thin film was divided into a two-dimensional square lattice ($30\times30$) of dipoles. Nearest-neighbor exchange interaction magnetic anisotropy, applied magnetic field, and demagnetiing field of interacting anisotropy, applied magnetic field, and demagnetizing field of interacting dipoles were considered. It was assumed that the film had perfect uniaxial anisotropy in the perpendicular direction and the magnetization reversal existed in the film. The time of domain wall creation and the thickness of the wall were investigated. Also the motion of domain walls under an applied field was considered. Simulation results showed that the time of domain wall creation was decreased significantly and the average velocity of domain wall was increased somewhat when the demagnetizing field was considered.