• Nuclear Engineering and Technology
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• v.20 no.3
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• pp.170-178
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• 1988

An automated ultrasonic flaw detection system was developed for thin-walled and short tubes such as Zircaloy-4 tubes used for cladding heavy-water reactor fuel. The system was based on the two channels immersion pulse-echo technique using 14 MHz shear wave and the specially developed helical scanning technique, in which the tube to be tested is only rotated and the small water tank with spherical focus ultrasonic transducers is translated along the tube length. The optimum angle of incidence of ultrasonic beam was 26 degrees, at which the inside and outside surface defects with the same size and direction could be detected with the same sensitivity. The maximum permissible defects in the Zircaloy-4 tubes, i.e., the longitudinal and circumferential v notches with the length of 0.76mm and 0.38mm, respectively and the depth of 0.04 mm on the inside and outside surface, could be easily detected by the system with the inspection speed of about 1 m/min and the very excellent reproducibility. The ratio of signal to noise was greater than 20 dB for the longitudinal defects and 12 dB for the circumferential defects.

• Journal of Mushroom
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• v.19 no.4
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• pp.316-321
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• 2021

Ligninolytic enzymes were produced by Pleurotus ostreatus No.42, cultivated in a new kind of bioreactor that has a rotating draft tube with a helical ribbon. Maximum laccase (Lac) production (about 8,200 U/bioreactor) was reached after 3 days of incubation, then production decreased. Production of manganese peroxidase (MnP) in this fermenter reached a maximum level of about 8,400 U/bioreactor after 6 days of incubation. Lignin peroxidase (LiP) was not detected under these growth conditions. These results indicate that the rotary draft tube bioreactor (RTB) is compatible with large scale production of ligninolytic enzymes. MnP produced under these fermentation conditions was purified via a multistep process that included chromatography on Sepharose CL-6B, prep grade Superdex 75, and Mono-Q. This major isoenzyme was confirmed to have an apparent molecular weight of 36,400 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and its isoelectric point (IEF) was determined to be 3.95. N-terminal sequencing of the major isoenzyme from this fermentation was identical to that reported for an MnP3 isoenzyme isolated under different cultivation conditions, including stationary and shaking culture.

• Imaging Science in Dentistry
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• v.37 no.4
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• pp.205-209
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• 2007

Purpose: To determine the physical properties of a newly developed cone beam computed tomography (CBCT). Materials and Methods: We measured and compared the imaging properties for the indirect-type flat panel detector (FPD) of a new CBCT and the single detector array (SDA) of conventional helical CT (CHCT). Results: First, the modulation transfer function (MTF) of the CBCT were superior to those of the CHCT. Second, the noise power spectrum (NPS) of the CBCT were worse than those of the CHCT. Third, detective quantum efficiency (DQE) of the indirect-type CBCT were worse than those of the CHCT at lower spatial frequencies, but were better at higher spatial frequencies. Although the comparison of contrast-to-noise ratio (CNR) was estimated in the limited range of tube current, CNR of CBCT were worse than those of CHCT. Conclusion: This study shows that the indirect-type FPD system may be useful as a CBCT detector because of high resolution.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.6
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• pp.763-772
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• 1998

The effects of an inserted coil on flow patterns and heat transport performance for a horizontal rotating heat pipe have been studied experimentally. Especially, the present study is to see an internally inserted helical coil inside a RHP would lead to the same kind of results as internal fins. Visualization test conducted for an acryl tube, charged water with at a volumetric rate of 20%. When the flow kept pool regime at a low RPM(less than 1,000 RPM), the movement of coil forced the water to flow in axial direction. But this pumping effect of coil disappeared, when the pool regime changed to annular one which could be created by increasing RPM. The pumping effects for RHP with an inserted coil resulted enhancement both in condensation heat transfer coefficient and heat transport limitation, as obtained in case of using internal fins. But all these effects became negligible in the range of higher RPM(above 1,000∼1,200) with the transition of flow regime to annular flow.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.464-467
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• 2002

We propose the use of visible scintillation light for monitoring the X-ray CT in the gantry of a diagnostic CT for its performance test and maintenance works. We placed a disk of bare plastic scintillator disk in the gantry opening area of a helical X-ray CT. When we operated the CT, we could observe the emission of blue scintillation light from the scintillator in a dark room. Visible light was identified under all scanning conditions of diagnostic uses. As a result, we observed the direction and the spread of the incident X-ray in the scintillator. We also observed the change of the part of the scintillator where visible light was generated, and the move that took place associating with the rotation of the X-ray tube during one CT scan. On the basis of the observation, we examined the usefulness of the visible scintillation light as a convenient performance-evaluating tool as well as a maintenance tool of the CT.

• International Journal of Air-Conditioning and Refrigeration
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• v.8 no.1
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• pp.50-61
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• 2000

The effects of an inserted coil on flow . patterns and heat transfer performance for a horizontal rotating heat pipe have been studied experimentally. Especially, the present study is to see an internally inserted helical coil inside a RHP would lead to the same kind of results as internal fins. Visualization test conducted for an acryl tube, charged water with at a volumetric rate of 20%. When the flow kept pool regime at a low rpm(less than 1,000rpm), the movement of coil forced the water to flow in axial direction. But this pumping effect of coil disappeared, when the pool regime changed to annular one which could be created by increasing rpm. The pumping effects for RHP with an inserted coil resulted in the enhancement in both condensation heat transfer coefficient and heat transport limitation, as obtained in case of using internal fins. But all these effects became negligible in the range of higher rpm(above 1,000-1,200) with the transition of flow regime to annular flow.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.113.2-113.2
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• 2012

An innovative solar observing satellite, Hinode, has successfully observed the detailed evolution of a rapidly developing emerging flux region from the beginning of its appearance at the solar surface. The high spatial and temporal resolution provided by the satellite enables to capture the prominent dynamic processes such as the rotational motion of a polarity region with intense magnetic flux which is reminiscent of a cyclone on the Earth, and a running wave that spreads ahead of this rotating polarity region. This 'solar cyclone' is, on the other hand, generated differently from terrestrial cyclones, and a possible generating mechanism for it is demonstrated with a three-dimensional magnetohydrodynamic simulation of a twisted magnetic flux tube emerging from the solar interior into the solar atmosphere. The simulation shows that the rotational motion is caused by a strong downflow of plasma along the twisted field lines that form a helical pillar standing upright on the Sun.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.550-551
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• 2013

Large-area RF-driven ion source is being developed at Germany for the heating and current drive of ITER plasmas. Negative hydrogen (deuterium) ion sources are major components of neutral beam injection systems in future large-scale fusion experiments such as ITER and DEMO. RF ion sources for the production of positive hydrogen ions have been successfully developed at IPP (Max-Planck- Institute for Plasma Physics, Garching) for ASDEX-U and W7-AS neutral beam injection (NBI) systems. In recent, the first NBI system (NBI-1) has been developed successfully for the KSTAR. The first and second long-pulse ion sources (LPIS-1 and LPIS-2) of NBI-1 system consist of a magnetic bucket plasma generator with multi-pole cusp fields, filament heating structure, and a set of tetrode accelerators with circular apertures. There is a development plan of large-area RF ion source at KAERI to extract the positive ions, which can be used for the second NBI (NBI-2) system of KSTAR, and to extract the negative ions for future fusion devices such as ITER and K-DEMO. The large-area RF ion source consists of a driver region, including a helical antenna (6-turn copper tube with an outer diameter of 6 mm) and a discharge chamber (ceramic and/or quartz tubes with an inner diameter of 200 mm, a height of 150 mm, and a thickness of 8 mm), and an expansion region (magnetic bucket of prototype LPIS in the KAERI). RF power can be transferred up to 10 kW with a fixed frequency of 2 MHz through a matching circuit (auto- and manual-matching apparatus). Argon gas is commonly injected to the initial ignition of RF plasma discharge, and then hydrogen gas instead of argon gas is finally injected for the RF plasma sustainment. The uniformities of plasma density and electron temperature at the lowest area of expansion region (a distance of 300 mm from the driver region) are measured by using two electrostatic probes in the directions of short- and long-dimension of expansion region.

• Journal of Fisheries and Marine Sciences Education
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• v.16 no.2
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• pp.257-270
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• 2004

The two-phase closed thermosyphon is a heat transfer device capable of transfer large quantities of heat from a source to a sink by taking advantage of the high heat transfer rates associated with the evaporation and condensation of a working fluid within the device. A study was carried out with the performance of the heat transfer of the thermosyphon having 50, 60, 70, 80, 90 internal micro grooves in which boiling and condensation occur. A plain thermosyphon having the same inner and outer diameter as the grooved thermosyphon is also tested for comparison. Water, methanol and ethanol have been used as the working fluids. The liquid filling as the ratio of working fluid volume to total volume of thermosyphon, the inclination angle, micro grooves and operating temperature have been used as the experimental parameters. The heat flux and the boiling and the condensation heat transfer coefficient and overall heat transfer coefficient at the condenser and evaporator zone are estimated from the experimental results. The experimental results have been assessed and compared with existing correlations. Imura's and Kusuda's correlation for boiling showed in good agreement with experimental results within ${\pm}20$％ in plain thermosyphon. The maximum heat transfer rate was obtained when the liquid fill ratio was about 25%. The high heat transfer coefficient was found between 25o and 30o of inclination angle for water and between 20o and 25o for methanol and ethanol. The relatively high rates of heat transfer have been achieved in the thermosyphon with internal micro grooves. The micro grooved thermosyphon having 60 grooves shows the best heat transfer coefficient in both condensation and boiling. The maximum enhancement (i.e. the ratio of the heat transfer coefficients of the micro grooved thermosyphon to plain thermosyphon) is 2.5 for condensation and 2.3 for boiling.

• Journal of radiological science and technology
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• v.29 no.3
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• pp.167-175
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• 2006

With the recent prevalence of helical CT and multi-slice CT, which deliver higher radiation dose than conventional CT due to overbeaming effect in X-ray exposure and interpolation technique in image reconstruction. Although multi-detector and helical CT scanner provide a variety of opportunities for patient dose reduction, the potential risk for high radiation levels in CT examination can't be overemphasized in spite of acquiring more diagnostic information. So much more concerns is necessary about dose characteristics of CT scanner, especially dose efficient design as well as dose modulation software, because dose efficiency built into the scanner's design is probably the most important aspect of successful low dose clinical performance. This study was conducted to evaluate z-axis geometric dose efficiency in single detector CT and each level multi-detector CT, as well as to compare z-axis dose efficiency with change of technical scan parameters such as focal spot size of tube, beam collimation, detector combination, scan mode, pitch size, slice width and interval. The results obtained were as follows ; 1. SDCT was most highest and 4 MDCT was most lowest in z-axis geometric dose efficiency among SDCT, 4, 8, 16, 64 slice MDCT made by GE manufacture. 2. Small focal spot was 0.67-13.62% higher than large focal spot in z-axis geometric dose efficiency at MDCT. 3. Large beam collimation was 3.13-51.52% higher than small beam collimation in z-axis geometric dose efficiency at MDCT. 4. Z-axis geometric dose efficiency was same at 4 slice MDCT in all condition and 8 slice MDCT of large beam collimation with change of detector combination, but was changed irregularly at 8 slice MDCT of small beam collimation and 16 slice MDCT in all condition with change of detector combination. 5. There was no significant difference for z-axis geometric dose efficiency between conventional scan and helical scan, and with change of pitch factor, as well as change of slice width or interval for image reconstruction. As a conclusion, for reduction of patient radiation dose delivered from CT examination we are particularly concerned with dose efficiency of equipment and have to select proper scanning parameters which increase z-axis geometric dose efficiency within the range of preserving optimum clinical information in MDCT examination.