• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.83-85
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• 1996

Major cause of defects in steam generator tubes at nuclear power plant is the accumulation of magnetite and other byproducts of corrosion in the crevice gap between support plates and tubes. Since damaged tubes result in contamination of the secondary coolant by the radioactive primary coolant, they represent a safety hazard. Early detection of magnetite buildup is, therefore, imperative in order to take remedial measures such as chemical flushing. Although the eddy current testing is being used for the inspection of steam generator tubes, the interpretation of resulting signals is generally a difficult task. This paper uses the phase of sensor coil emf as the test signal to find a way of easier signal interpretation. Numerical study using FEM shows that the shape of resulting signal is good for identifying the relative position of the probe to the support plate, and for discreminating the different shapes and degrees of magnetite buildup in the crevice gap region.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.11a
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• pp.35-38
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• 2012

Spacers which we have studied is the secondary product of the concrete to apply on concrete structure. It is needed to secure equal or greater performance than structural concrete that it is applied. There is a tendency that concrete structures are strengthened more and more. Therefore, designed set up position of reinforcement is used more and more, so it is needed increasingly high strength spacer. We have been doing a series of research to develop the different typed high strength spacer having crack resistance during constructing. The bearing load of different type spacer shows approximately 35% lower load than those in the general spacers.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.3
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• pp.404-412
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• 2008

As a suitable volute configuration in the range of low specific speed, circular casing is suggested in this study. The internal flows in a centrifugal pump with the circular and spiral casings are measured by PIV and analyzed by CFD. The results show that the head and efficiency of the pump by a circular casing of very small radius are almost same as those by the spiral casing. Even at the best efficiency point, the internal flow of the pump by circular casing is asymmetric, and vortex and strong secondary flow occurs in the impeller passage. The radial velocity becomes higher remarkably only near the region of the discharge throat. The flow in the impeller outlet is strongly controlled by the circular casing because the velocity distribution almost does not affected by the position of the impeller blades.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1282-1287
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• 2007

The nature of the signal collected by an SEM(Scanning Electron Microscope) in order to form images are all dependent on the detector used to collect them, and the quality of an acquired images is strongly influenced by detector performance. Therefore, the development of detector with high performance is very important for improving on the resolution of SEM. This paper presents the manufacture of secondary electron detector and the optimal position of electron detector through numerical analysis in SEM.

• Journal of Astronomy and Space Sciences
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• v.37 no.3
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• pp.165-170
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• 2020

Muons and neutrons are representative secondary particles that are generated by interactions between primary cosmic ray particles (mostly protons) and the nuclei of atmospheric gas compounds. Previous studies reported that muons experience seasonal variations because of the meteorological effects of temperature. The intensity of neutrons has a typical modulation with various periods and reasons, such as diurnal and solar variation or transient events. This paper reports that cosmic ray particles, which were observed by neutron monitors, have seasonal variations using the daily data at the Oulu neutron monitor. To eliminate the effects of solar activity across time, the daily data were normalized by two different transformations: transformations with respect to the grand mean and yearly mean. The data after transformation with respect to the yearly mean showed more statistical stability and clear seasonal variations. On the other hand, it is difficult to determine if the seasonal variation results from terrestrial effects, such as meteorological factors, or extraterrestrial effects, such as the position of the Earth in its orbit of revolution.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.5
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• pp.85-90
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• 2011

In this paper a design procedure via computer-aided molding simulation is presented to optimize the air-trap locations in a speaker encloser of mobile phone. The molding flow simulation reveals that the race-tracking phenomenon is the dominant feature in the current mold design. In obtaining an optimal filling pattern, the local modifications of the wall thickness such as in a flow leader attachment are considered as the primary control factor, and both the gate position and the filling time become the secondary control factor. In the one-at-a-time approach, the last location to be filled in the mold cavity could be successfully moved to the extremities of the part, allowing a natural ventilation of entrapped air through the mold parting plane.

• Journal of Photoscience
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• v.8 no.2
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• pp.55-60
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• 2001

Ginseng (Panax genus) is one of the most medicinally important genera and consists of highly regarded medicines. Among the species of Panax, the ginseng species is widely known to have most medicinal quality. P. ginseng has 3 varieties, Jakyung, Chunggyung and Hwangsook, discovered in nature with different colors of stem and fruit, Jakyung has two cultivars, Yunpoong and Chunpoong. Rigorous phylogenetic analysis of these varieties and cultivars has been conducted with sequencing of rDNA region. The sequences of ITS1, ITS2 of every varieties and cultivars within P. ginseng were identical. The sequence of 5.8S rDNAs of Hwangsook variety were different from the sequences of 5.8S rDNAs of others by only one base pair at nucleotide position 14. In phylogenetic analysis and predicted RNA secondary structure study, it is assumed that evolution has proceeded from Hwangsook to other varieties. recently.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.2
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• pp.185-191
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• 2004

This study describes the scheme of vector drive system without speed sensor for AC servo motor using theory of a flux observer and based on the field oriented vector control. The new method of speed estimation is presented from operate with the position and magnitude of the secondary flux which obtain from the voltage reference and detected current. As the estimated speed is settled by the flux and the machine-specific parameters. this method don't need to adjust the gain of the parameter. Based on the derived theory for vector control. the scheme for sensorless vector drive of AC servo motor is designed and realized. And the experiment verifies it passable to realize the sensorless vector drive based on a field-oriented type.

• Journal of Microbiology
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• v.45 no.1
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• pp.75-78
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• 2007

Nucleotide and amino acid substitution pattern in vif gene of the Korean clade of HIV-1 isolated from Koreans were analyzed using consensus sequences. At nucleotide level, transition/transversion substitution ratio was 1.88, and nonsynonymous/synonymous substitution ratio was 2.67, suggesting a divergent evolution in the Korean clade. At amino acid level, there were 17 substitutions and $G{\rightarrow}E$ substitution at position 37 may be responsible for change in predicted secondary structure.

• Advances in pediatric surgery
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• v.3 no.1
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• pp.68-70
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• 1997

One case of primary omental torsion in a 10 year-old, 43 kg boy is presented. He presented with a history of acute, continuous pain in the upper abdomen, aggravated by changes of position. Physical examination of his abdomen showed board-like rigidity. tenderness and rebound tenderness over the entire abdomen. The preoperative diagnosis was perforated peptic ulcer. Exploratory laparatomy revealed torsion of the greater omentum. The torsed omentum was excised and the outcome was good. Omental torsion is a rare surgical condition and is difficult to diagnose prior to operation. Therefore, in case of negative exploration for acute abdomen, the omentum should be included among the organs examined. In addition, careful search for an inflammatory focus should be made, because secondary omental torsion with intraabdominal sepsis is much more common than primary torsion.