• Structural Engineering and Mechanics
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• v.32 no.5
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• pp.685-699
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• 2009

Current research and development of high performance concrete, together with study of phenomena that are pertinent to impact resistance, have lead to a new generation of barriers with improved properties to resist impact loads. The paper reviews major properties and mechanisms that affect impact resistance of concrete barriers as per criteria that characterize the resistance. These criteria are the perforation limit, penetration depth and the amount of front and rear face damage. From the long-known, single strength parameter that used to represent the barriers' impact resistance, more of the concrete mix ingredients are now considered to be effective in determining it. It is shown that the size and hardness of the aggregates, use of steel fibers and micro-silica have different effects on performance under impact and on the resistance. Additional pertinent phenomena, such as the rate and size effects, confinement and local versus global response, are pointed out with their reference to possible future developments in the design of impact resisting concrete barriers.

• Journal of the Optical Society of Korea
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• v.7 no.3
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• pp.193-196
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• 2003

We have developed a laser welding monitoring system to monitor laser welding process conditions such as sample feed rate, laser focal position, and laser power. A 2 ㎾ Nd:YAG CW laser beam has been applied to the welding of a stainless steel plate (SUS306) to investigate the welding monitoring. Theradiation signal from the weld pool was guided back through the focusing optics and the laser delivery fiber, and measured by a photo detector. By changing the focus of the laser beam along the z-direction, the penetration depth of the welding material has been measured. That shows the penetration depth depends on the frequency fluctuations of the plume signals which can be used in welding quality control.

• Transactions of Materials Processing
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• v.7 no.5
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• pp.481-488
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• 1998

The active metal brazing was applied to bond Alumina and Ni-Cr steel by Ag-Cu-Zr-Sn alloy and the interfacial microstructure and reaction mechanism were investigated. Polycrystalline monoclinic $ZrO_2$ with a very fine grain of 100-150 nm formed at the alumina grain boundary contacted with Zr segregation layer at the interface. The $ZrO_2$ layer containing the inclusions and cracks were developed at the boundary of inclusion/$ZrO_2$ due to the difference in specific volume. The development of $ZrO_2$ at the interface was successfully explained by the preferential penetration of $ZrO_2$ at the interface was successfully explained by the preferential penetration of Zr atoms a higher concentration of oxygen and a high diffusion rate of Al ions into molten brazing alloy.

• Journal of Embryo Transfer
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• v.14 no.1
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• pp.9-15
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• 1999

This study was conducted to investigate the effect of $\alpha$-tocopherol and cysteamine with Whitten's medium in supporting the development on in vitro maturation(IVM), in vitro fertilization (IVF) and in culture(IVC) on porcine oocytes. When the immature oocytes were cultured of $\alpha$-tocopherol for 40h, the nuclear maturation rates were 39, 4, 52.5 and 54.1%, respectivley. The nuclear maturation rates of treat groups were signficantly (P<0.05) higher than those of non-treat groups. After matureation, the oocytes were inseminated in vitro in medium 199 with ejaculated spermatoza for examination of sperm penetration, polyspermy, male pronuclear(MPN) formation, and cleavage rate. Sperm penetration rates of treat higher than the control groups(P<0.05), and MPN formation rates were significantly(P<0.05) higher on treated groups (24.3~53.1%) than control groups(14.2~21.4%). After insemination, the cleavage rates at 120hr were groups higher than control groups(P<0.05).

• Proceedings of the Membrane Society of Korea Conference
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• 2004.05a
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• pp.191-194
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• 2004

A novel type of intelligent microcapsule reactor system was prepared. The reactor can recognize pH change in the medea and control reaction rate by itself. For the reactor system, acrylic acid (AA), N-isopropylacrylamide (NIPAM), and glucose oxidase (GOD) were selected as a pH-responsive device, a gating device according and a reaction device, respectively. Poly(NIPAM-co-AA) (P-NIPAM-co-AA) are known to change its hydrophilicity-hydrophobicity due to pH change. They were integrated in a core-shell microcapsule space. GOD was loaded inside the core space and the pores in the outside shell layer were filled with P-NIPAM-co-AA linear grafted chains as pH-responsive gates by plasma graft filling polymerization method. When P-NIPAM-co-AA gates are hydrophilic at high pH value, this microcapsule permits glucose penetration into the core space and GOD reaction proceeds. However, when P-NIPAM-co-AA gates are hydrophobic at low pH value, this microcapsule forbids glucose penetration and GOD reaction will not occur. The accuracy of this concept was examined.

• Applied Microscopy
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• v.46 no.4
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• pp.188-192
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• 2016

Proper sample preparation prior to microscopy is necessary for maintaining the components of tissues in a state as close to a living state as possible. For optimal preservation of biological samples, the sampling conditions are as important as the fixation itself. Various factors influence the selection and fixation efficiencies of a fixative, including sample size, osmolarity, pH, penetration rate and depth, fixative temperature, fixation time, fixative concentration, fixative amount, and retention time. Therefore, several factors for selecting and administering fixation procedures are evaluated pertaining to optimal sample preparation for transmission electron microscopy.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.3
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• pp.131-137
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• 2005

Ultra high pressure injection equipment was developed to estimate and analyze the spray characteristics in ultra high pressure injection. Spray patterns were visualized by schlieren method and analyzed in ultra high pressure. Spray tip penetration, spray thickness, spray volume, and entrained air mass increased with the increase of the injection pressure. But over 2,800 bars of the injection pressure region, it was shown that the rate of improvement was not increased remarkably ,and the spray characteristics such as spray penetration, volume, and entrained air mass were reversed and got worse at 4,140 bars.

• Journal of Surface Science and Engineering
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• v.50 no.6
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• pp.447-454
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• 2017

Al1050 and Al7075 alloy specimens were exposed to atmospheric conditions for maximum 12 months and analyzed by Transmission Electron Microscopy (TEM) to characterize the early-stage corrosion behavior and thin surface oxide layers. By comparing of oxide films between Al1050 and Al7075 alloys, it is concluded that Al7075 has a relatively thicker surface oxide film than Al1050 but Al1050 has relatively more significant oxygen penetration through grain boundaries. The oxygen penetration through grain boundaries appeared to be influenced by intermetallic particles at the grain boundary. In the case of aluminum alloys, localized corrosion like pitting or intergranular corrosion should be considered as well as uniform corrosion when estimating the atmospheric corrosion rate.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.10a
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• pp.53-56
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• 2004

The mixing characteristics of a multiple transverse injection system in a scramjet combustor were studied with numerical methods. The distance among injectors on mixing characteristics were investigated. The three-dimensional Wavier-Stokes equations including k-w SST turbulence model were solved. It was shown that the mixing characteristics of a multiple transverse injection system were very different from those of a single and a dual injection system; the rear injection flow was strongly influenced by blocking effect due to the momentum flux of the front injection flow and thus had higher expansion and penetration than the front injection flow. The multiple injection system had higher mixing rate, higher penetration but had more losses of stagnation pressure than the single injection system.

• Journal of the Korean Institute of Gas
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• v.16 no.3
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• pp.29-34
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• 2012

Investigating safer ways to design and use to prevent a loss of life and property by failure of the structures are necessary and assessing total fatigue life with initiation and propagation of fatigue crack accurately through fatigue analysis is very important. The object of this study is to examine the initial life and propagation life when the fatigue crack is introduced from the root which is likely to appear in LOP(Lack of Penetration) cruciform fillet welded structure including bridges, ships and gas storage facilities which are impossible to be fully penetrated and to measure the rate of fatigue life until the final cleavage failure. As the result, each rate of fatigue life for fatigue failure is somewhat different in the range of 5% according to the thickness of material, however, the overall rate of initial life is in the range of 34~39% and propagation life showed the range of 61~66%.