• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.187-190
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• 2002

Confocal microscopy is very popular technology in bio-medical inspection due to its ability to reject background signals and to measure very thin slide of thick specimens, which is called optical sectioning. But intensity of detected signal in fluorescence type confocal microscopy is so small that only 0.2% of emitted fluorescence light can be detected in the best case. In this paper, we proposed the reflecting optical system to improve the detection intensity and designed the optical system by optimal design method. At the end of the paper, we analyzed the characteristics of the proposed reflecting optical system.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.5 no.3
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• pp.31-39
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• 1996

The objective of this study is to investigate the influence of welding residual stresses on the fatigue crack growth behavior of cracks located transverse to the weld bead. For this purpose, G. T. A (Gas Tungsten Arc) welding was performed on hte Al alloy 1100-O plate and the same initial crack is made on HAZ(Heat Affected Zone), weld metal and base meta respectively. Specimens were used CT(Compact Tension) specimens. Initial welding residual stresses were measured by using strai gage sectioning method. All specimens were tested under constant amplitude load with stress ratio R=0.1, It is possible to predict fatigue crack growth behaviors and the fatigue life, using numerical analysis together with distribution of initial residual stress and the values of C and m obtained from $da/dN-{\Delta}K$

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.1878-1884
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• 2010

Currently in Korea, neutral sections in front of substations and sectioning posts are greatly divided into AC/DC sections and AC/AC sections. Considering catenary damage and safety issues trains pass crossover by coasting driving at notch-off. However in cases of Japan, China, or Taiwan, the usage of automatic crossover system makes it possible to pass at notch-on, enhancing high-speed railway operation for efficiency, and stability. These are the purposes of developing automatic power crossover system in neutral sections. This paper introduces two methods to detect the position of a train required to activate automatic crossover systems in neutral sections. The optimal method is expected in terms of the distance of neutral section.

• Applied Microscopy
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• v.24 no.2
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• pp.37-47
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• 1994

Using mouse tissue, we studied electron opacity effect of tannic acid for transmission electron microscopic staining. Tannic acid-glutaraldehyde in 0.1M phosphate buffer was used as a fixative. To compare with this we have tested another method consisting of heavy metal staining after treatment of tannic acid in sodium tetraborate (borax) on glutaraldehyde-fixed sections. We have achieved equally consistent electron opacity in both methods. The elastin, collagen, basal lamina of skin and gap junctions of the epithelial cells gave excellent results, while it was good for glycogen, cilia, and plasma. Also fat cells and lipid droplets gave good preservation when tannic acid was added in the fixative. However, prolonged fixation in tannic acid-added fixative was hazardous for further processing, i.e., sectioning problem and deep electron opacity background.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1996.03a
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• pp.177-182
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• 1996

The objective of this thesis is to investigate the influence of welding residual stresses on the fatigue growth behavior of welding residual stresses on the fatigue growth behavior of cracks located transverse to the weld bead. For this purpose, G.T.A. (Gas Tungsten Arc) welding was performed on the Al. Alloy 1100-0 plate and the same initial crack is made on HAZ(Heat Affected Zone), weld metal and base metal respectively. C.T.(Compact Tension) specimens were used as experimental material. Initial welding residual stresses were measured by using strain gage sectioning method. All specimens were tested under constant amplitude load with stress ratio R=0.1

• Korean Journal of Optics and Photonics
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• v.20 no.6
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• pp.361-365
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• 2009

We describe a simple method to obtain an optical sectioning in a conventional wide-field microscope by projecting a single spatial frequency grid pattern onto the object. Using a patterned beam, we have measured the height of BGA with a rough surface that provide the coherence noise. The configuration of the height measurement system using pattern beam is simple. The image acquired by this system is not depend on the coherence noises. This system is also applicable to the sample reference plan that has no pattern on ground. The reappearance and accuracy are outstanding and applicable to many industrial optical metrology.

• Proceedings of the KSR Conference
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• 2006.11b
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• pp.1320-1325
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• 2006

Railway track supports and guides train and it directly affects ride quality and safety. To maintain track quality, regular maintenance activity is essential but it degrades track usage since maintenance activity occupies the track during the work. To achieve maximum track efficiency, track inspection should be performed at commercial running speed. In this paper, we designed and developed high speed rail profile measurement system using laser light sectioning method with line laser generator, digital camera and DSP based image processing system. The measurement system can supports rail profile measurement at the speed of 300 Km/h that can be applied to KTX.

• Journal of the Korean Society for Nondestructive Testing
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• v.12 no.3
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• pp.7-11
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• 1992

Accurate measurement of green density of compacted part in the powder metallurgy industry is rather fundamental but extremely important process that decide the quality of the sintered part. In case of green sheet P/M product, the green density as well as the distribution of the density must be examined for the same reasons. Currently in most cases, density measuring process is being performed applying conventional Archimedes principles. However this method is not only time-consuming but also often inaccurate because of the inherent nature of the process, such as part sectioning, closing of surface porosity with wax and weighing in air and in water. Therefore, it is necessary to develop a faster and more accurate method to measure the density of green sheet P/M product. In this work, a nondestructive density measurement device using gamma-ray absorption principles was constructed and the optimum condition for measuring green density of P/M sheet and its distribution was sought. The results showed that this method was very effective in terms of measuring time and accuracy.

• Applied Microscopy
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• v.39 no.1
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• pp.65-72
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• 2009

Cryo-SEM which enables specimens to be observed in frozen form has been used to study liquid specimens in their native states. Cryo-methods, sample preparation for cryo-SEM, are quite complex and involve several discrete but vitally interconnected steps which are rapid cooling, fracturing, sectioning, etching and coating. It is important to select practical techniques and to optimize conditions of each steps considering analytic purpose and specimen characters, viz., sample dimension, water contents. In this study, etching methods and sample preparation before freezing had been studied for observation of cyanobacteria, Synechocystis sp. PCC 6803 using cryo-SEM and their cryo-SEM images were compared to Conventional SEM (CSEM) images treated by chemical fixation. We could observe the improved morphological images of the pili of the surface and membranes of Synechocystis sp. PCC 6803 and the three-dimensional architectures of their biofilm, which were difficult to observe using chemical fixation and CSEM. These results suggest that cryo-methods/cryo-SEM are useful techniques for morphological study of biological specimen.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.372-377
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• 2002

Residual stress by welding should be reduced because that decreases the reliability on strength of welded structure. The reason is that the total stiffness of structure decreases by non-linear behavior of weldment under external load. The release of residual stress by mechanical loading and unloading is often performed in the fabrication of box structure for steel bridge. The proper degree of loading and unloading is significant at release method of residual stress by mechanical loading because that degree is changed by material and geometric shape of welded structure. Therefore, the simulation model that could exactly analyze the release of residual stress by mechanical loading is to be necessary. This simulation model should be established on the based of variable and accurate measurement data. In this study, the non-linear behavior of weldments under external loading and unloading, such as the decrease and increase of structure stiffness, was investigated by monitoring of nominal stress and strain. Tensile loading and unloading test under variable load was performed and the proper degree of stress relaxation was measured by sectioning technique using strain gauge.