• Proceedings of the KWS Conference
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• 2002.10a
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• pp.469-474
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• 2002

Laser and hot air reflow soldering of PBGA solder ball was investigated. Experimental results showed that surface quality and shear strength of solder bumps reflowed by laser was superior than the solder bumps reflowed by hot air, and the microstructure inside the solder bumps reflowed by laser was much finer. Analysis on interfacial reaction showed that eutectic solder reacted with Au/Ni/Cu pad shortly after the solder was melted. Interface of solder bump reflowed by laser consists of a continuous AuSn$_4$ layer and remnant Au element. Needle-like AuSn$_4$ grew sidewise from interface, and then spread out to the entire interface region. A thin layer of Ni$_3$Sn$_4$ intermetallic compound was found at the interface of solder bump reflowed by hot air, AuSn$_4$ particles distributed inside the whole solder bump randomly. It is the combination effect of the continuous AuSn$_4$ layer and finer eutectic microstructure inside the solder bump reflowed by laser that resulted in higher shear strength.

• Journal of ILASS-Korea
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• v.13 no.4
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• pp.200-205
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• 2008

Spray formation mechanism was controlled by a cavitation inside an injection nozzle. Nozzle geometry affects spray characteristics and formation behavior, which could determine engine performance and pollutant formation. A study was carried out on the influence of aspect ratio on cavitation inside a nozzle. The cavitation model available in Star-CD code was used to obtain cavitation behavior inside nozzle, which was compared with previous experimental results. In this paper, a CFD approach combining multiphase Volume-of-Fluid(VOF) and k-model was applied. The numerical results are similar with the experimental results.

• 한국전산유체공학회:학술대회논문집
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• 1998.11a
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• pp.133-140
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• 1998

A Navier-Stokes code based on a unstructured finite volume method is used to simulate the MIT flapping foil experiment. A low Reynolds number $k-{\varepsilon}$ turbulence model is used to close the Reynolds averaged Navier-Stokes equations. Computations are carried out for a domain involving two flapping foils and a downstream hydrofoil. The computational domain is meshed with unstructured quadrilateral elements, partly structured. Numerical solutions show good agreement with experiment. Unsteadiness inside boundary layer is entrained when a unsteady vortex impinge on the blade surface. It shoves that local peak value inside the boundary layer and also local minimum near the edge of boundary layer as it developes along the blade surface. The unsteadiness inside the boundary layer is almost isolated from the free stream unsteadiness and being convected at local boundary layer speed, less than the free stream value.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.733-736
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• 2002

The inside configuration of intake nozzle of vacuum cleaner greatly affects the dust-collection efficiency and acoustic-noise effect generated from flow separation Interaction between high-speed flow and internal structure. In order to improve the performance of the vacuum cleaner, flow fields inside the intake nozzles were investigated using flow visualization and FIV (Particle Image Vetocimetry) technique. The measurement to aerodynamic power, suction efficiency and noise level were also carried out. Valuable information was obtained from the experiments, revealing how to modify the intake nozzle. In this paper, the results of visualization, velocity distribution of flow fields, aerodynamic power, suction efficiency and noise level are discussed.

• Tribology and Lubricants
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• v.24 no.2
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• pp.82-89
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• 2008

The purpose of this study is to develop the proto type sensor installed inside an oil filter in order to detect oil deterioration level. The sensor is made up with two concentric cylinders with constant gap in between and a filter element inside the central area. The size will be designed as similar as real oil filters. The sensor will be tested on a test rig, which is circulating engine oil, with the same size of an oil filter adapting housing as real engines'. It will be measured the capacitance of a sample engine oil, then be able to be gotten the dielectric constant. The changes in the dielectric constant could be correlated with the engine oil deterioration level if the sensor development would be completed. In this paper, it will be shown the test results carrying out under variable temperature conditions at atmosphere pressure.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.04a
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• pp.161-165
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• 2013

In this paper, possibility of controlling motion of a floating structure using a tuned liquid damper (TLD) is numerically investigated. A TLD is a tank partially filled with liquid. Sloshing phenomena of liquid inside a tank can suppress movement of the tank subject to external excitations at specific frequency. The effects of sloshing phenomena inside a rectangular floating body on its sway motion are investigated by varying excitation frequency. First, a grid-refinement study is carried out to ensure validity of grid independent numerical solutions using present numerical techniques. Then, sway motion of the floating body subjected to wave with five different frequencies are simulated. The normalized amplitudes of sway motion of the target floating body are compared over the frequency, for cases with and without water inside the floating body. It is shown that the motion of the floating body can be minimized by matching the sloshing natural frequency to excitation frequency.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.301-304
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• 2005

The waterproofing in slab and wall of underground structure, have a couple of construction methods which are inside waterproofing methods for inner surface, and outside waterproofing methods for out wall and slab surface waterproofing. In resent years, however, it has been adapted the inside waterproofing construction method, as increasing of construction expenses cost and low workability and technology, nevertheless, outside waterproofing has set a most high value construction method. In inside waterproofing construction method, it is difficult to repair and assure durability and safety for concrete which has direct water-press. So, It is necessary for adopt the outside waterproofing method.

• Journal of the Korean housing association
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• v.15 no.1
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• pp.195-204
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• 2004

This study was carried out to understand the architectural characteristics of farmhouse among the commons house. The subject of study are selected the seventeen farmhouse built 50-60 years ago at Hyunri in Munkyung. It was analyzed and classified the architectural characteristics of plan and arrangement at a farmhouse. In conclusing, their farmhouses are appeared the different characteristics in comparison with other area. With the arrangement of building and composition of plan, it was discovered that it connotes an idea of the confucian ideas from separation of the inside and outside space; men and women. Also, it was found that it has become to the rational separation of spaces from location of entrance, division of the outside space(Madang) and arranged space of inside at farmhouse.

• Journal of The Korean Astronomical Society
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• v.33 no.2
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• pp.75-80
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• 2000

In order to identify the candidates of emission-line galaxies inside the southern Hydra Void, photo-graphic objective-prism observations with the UK Schmidt Telescope were carried out using the Tech-Pan films for five fields. All observed prism plates were scanned with the APM Facility and the scanned data was processed to determine the APM plate parameters and to draw spectra. For all galaxy spectra, the emission features, the distance between emission features of H$\beta$4861, [OIII]${\lambda}{\lambda}$ 4959, 5007 and the overlapping by nearby objects were investigated by eyeballing. A total of 7 candidates of emission-line galaxies inside the Hydra Void were identified.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.10
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• pp.1294-1302
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• 1997

For the purpose of investigating the impulsive noise at the exit of high-speed railway tunnel and the pressure transients inside the tunnel, experiments were carried out using a shock tube with an open end. A great deal of experimental data were obtained and explored to analyze the peak pressures and maximum pressure gradients in the pressure waves. The effects of the distance and cross-sectional area ratio between two-continuous tunnels on the characteristics of the pressure waves were investigated. The peak pressure inside the second tunnel decreases for the distance and cross-sectional area ratio between two tunnels to increase. Also the peak pressure and maximum pressure gradient of the pressure wave inside the second tunnel increase as the maximum pressure gradient of initial compression wave increases.