• Korean Journal of Fisheries and Aquatic Sciences
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• v.36 no.3
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• pp.239-246
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• 2003

We have examined the 16S-23S rRNA intergenic spacer region (ISR) of Vibrio vulnificus KCTC 2959. ISRs were amplified by primers complementary to conserved regions of 16S and 23S rRNA genes. ISR amplicons were cloned and sequenced. Analysis of the ISR sequences showed that V. vulnificus KCTC 2959 contains five types of polymorphic ISRs. Size of ISRs ranged from 424 to 741 bp in length and the number of tRNA genes ranged from one to four. The ISRs were designated as ISR-E $(tRNA^{Glu}),\;ISR-IA\;(tRNA^{Ile}-tRNA^{Ala})$, ISR-EKV $(tRNA^{Glu}-tRNA^{Lys}-tRNA^{Val})$, ISR-IAV $(tRNA^{Ile}-tRNA^{Ala}-tRNA^{val})$ and ISR-EKAV $(tRNA^{Glu}-tRNA^{Lys}-tRNA^{Ala}-tRNA^{Val})$ based on their tRNA genes. Multiple alignment of representative sequences from different Vibrio species revealed several domains of high sequence variability. We used the sequences of variable domains to design species-specific primer for detection PCR. Specificity of the primers was examined using genomic DNA prepared from 18 different Vibrio species. The results showed that the PCR using primers designed in this study can be used to detect V. vulnificus from other Vibrio species.

• Korean Journal of Microbiology
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• v.41 no.2
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• pp.117-124
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• 2005

Two bacterial isolates obtained from rotifer and diseased olive flounder larvae, Paralichthys olivaceus, were identified as Vibrio ichthyoenteri based on the results of phenotypic characterization. In an attempt to develop rapid PCR method for the detection of V. ichthyoenteri, we examined the 16S-23S rRNA intergenic spacer region(ISR) of V. ichthyoenteri and developed species-specific primer for V. ichthyoenteri. Analysis of the ISR sequences showed that V. ichthyoenteri contains one type of polymorphic ISRs. The size of ISRs was 348 bp length and did not contain tRNA genes. Mutiple alignment of representative sequences from different V. species revealed several domains of high sequence variability, and allowed to design species-specific primer for detection of V. ichthyoenteri. The specificity of the primer was examined using genomic DNA prepared from 19 different V. species, isolated 18group Vibrio species and most similar sequence of other known Vibrio species. The results showed that the PCR reaction using species-specific primer designed in this study can be used to detect V. ichthyoenteri.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.4
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• pp.86-92
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• 1999

A SiGe p-channel MESFET using $\delta$-doped layers is designed and the considerabel enhancement of the current driving capability of the device is observed from the result of simulation. The channel consists of double $\delta$-doped layers separated by a low-doped spacer which consists of Si and SiGe. A quantum well is formed in the valence band of the Si/SiGe heterojunction and much more holes are accumulated in the SiGe spacer than those in the Si spacer. The saturation current is enhanced by the contribution of the holes in the spacer. Among the design parameters that affect the performance of the device, the thickness of the SiGe layer and the Ge composition are studied. The thickness of 0~300$\AA$ and the Ge composition of 0~30% are investigated, and saturation current is observed to be increased by 45% compared with a double $\delta$-doped Si p-channel MESFET.

• Nuclear Engineering and Technology
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• v.24 no.3
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• pp.263-273
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• 1992

The study on the velocity distribution and the pressure drop characteristic of the nuclear fuel assembly is of importance for the thermal hydraulic design and safety analysis. The purpose of this experimental study is to investigate the hydraulic mixing behind the different kinds of spacer grids in the now or rod bundles. In this study, the detailed hydraulic characteristics in subchannels of 5$\times$5 PWR(Pressurized Water Reactor) rod bundles were measured using one-component He-Ne LDV(Laser Doppler Velocimeter). Measurements of the axial velocity, turbulent intensities and pressure drops were peformed Lateral velocity, turbulent intensities and Reynolds shear stress were also measured by adjust-ing LDV alignment. Friction factors in rod bundles and loss coefficients for spacer grids were evaluated from the measured pressure drops. Hydraulic mixing performance for different kinds of spacer grids could be investigated by estimating the turbulent cross-flow mixing rates between neighboring subchannels.

• Journal of Sensor Science and Technology
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• v.16 no.5
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• pp.325-330
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• 2007

For the application to optic devices, wafer level package including spacer with particular thickness according to optical design could be required. In these cases, the uniformity of spacer thickness is important for bonding strength and optical performance. Packaging process has to be performed at low temperature in order to prevent damage to devices fabricated before packaging. And if photosensitive material is used as spacer layer, size and shape of pattern and thickness of spacer can be easily controlled. This paper presents polymer bonding using thick, uniform and patterned spacing layer of SU-8 2100 photoresist for wafer level package. SU-8, negative photoresist, can be coated uniformly by spin coater and it is cured at $95^{\circ}C$ and bonded well near the temperature. It can be bonded to silicon well, patterned with high aspect ratio and easy to form thick layer due to its high viscosity. It is also mechanically strong, chemically resistive and thermally stable. But adhesion of SU-8 to glass is poor, and in the case of forming thick layer, SU-8 layer leans from the perpendicular due to imbalance to gravity. To solve leaning problem, the wafer rotating system was introduced. Imbalance to gravity of thick layer was cancelled out through rotating wafer during curing time. And depositing additional layer of gold onto glass could improve adhesion strength of SU-8 to glass. Conclusively, we established the coating condition for forming patterned SU-8 layer with $400{\mu}m$ of thickness and 3.25 % of uniformity through single coating. Also we improved tensile strength from hundreds kPa to maximum 9.43 MPa through depositing gold layer onto glass substrate.

• Nuclear Engineering and Technology
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• v.47 no.5
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• pp.523-533
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• 2015

Three-dimensional flow phenomena in a wire-wrapped 37-pin fuel assembly mock-up of a Japanese loop-type sodium-cooled fast reactor, Monju, were investigated with a numerical analysis using a general-purpose commercial computational fluid dynamics code, CFX. Complicated and vortical flow phenomena in the wire-wrapped 37-pin fuel assembly were captured by a Reynolds-averaged Navier-Stokes flow simulation using a shear stress transport turbulence model. The main purpose of the current study is to understand the three-dimensional complex flow phenomena in a wire-wrapped fuel assembly to support the license issue for the core design. Computational fluid dynamics results show good agreement with friction factor correlation models. The secondary flow in the corner and edge subchannels is much stronger than that in an interior subchannel. The axial velocity averaged in the corner and edge subchannels is higher than that averaged in the interior subchannels. Three-dimensional multiscale vortex structures start to be formed by an interaction between secondary flows around each wire-wrapped pin. Behavior of the large-scale vortex structures in the corner and edge subchannels is closely related to the relative position between the hexagonal duct wall and the helically wrapped wire spacer. The small-scale vortex is axially developed in the interior subchannels. Furthermore, a driving force on each wire spacer surface is closely related to the relative position between the hexagonal duct wall and the wire spacer.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.4
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• pp.353-358
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• 2022

Bulky iron-core potential transformers (PT) are installed in a tank of gas insulated switchgears (GIS) for a system voltage measurement in power substations. In this paper, we studied an electronic voltage transformer (EVT) embedded in a spacer for miniaturization, eco-friendliness, and performance improvement of GIS. The prototype EVT consists of a capacitive probe (CP) that can be embedded in a spacer and a voltage Follower with a high input and a low output impedance. The CP was fabricated in the form of a Flexible-PCB to acquire the insulation performance and to withstand vibration and shock during operation. Voltage ratio of the prototype EVT is about 42,270, and the frequency bandwidth of -3 dB ranges from 0.33 Hz to 3.9 MHz. The voltage ratio error evaluated at about 6%, 12% and 18% of the rated voltage of 170 kV was 0.32%, and the phase error was 12.9 minutes. These results were within the accuracy for the class 0.5 specified in IEC 60044-7 and satisfy even in ranges from 80% to 120% of the rated voltage. If the prototype EVT replaces the conventional iron-core potential transformer, it is expected that the height of the GIS could be reduced by 11% and the amount of SF₆ will be reduced by at least 10%.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.4
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• pp.582-587
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• 2012

Recently, the low-emissivity glass has been used to reduce the energy loss through building windows. However, it simply reduces the inflow of solar rays and has a relatively high heat transmission coefficient. To solve the problems, a high-efficiency vacuum glazing has been under development but it has not been actively used due to its high price and insufficient performance. In this paper, the effects of internal pressure, pillar (spacer) height, pillar diameter, pillar interval, emissivity etc. on the performance of vacuum glazing have been analyzed with three-dimensional computational fluid dynamics and structural analysis. As a result, the performance of vacuum glazing was predicted more accurately and major factors that determine the performance of vacuum glazing were optimized.

• Journal of the Korean Society of Safety
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• v.17 no.2
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• pp.85-91
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• 2002

A research on the performance of retrofit anchors was conducted using adhesives for rehabilitation. From the pull-out tests of the chemical anchors, the effect of the hole diameter, spacer, temperature, moisture, embedment depth, and aging time were investigated. The spacer did not directly increased the pull-out load hilt increased post-yielding resistance therefore the ductility of the retrofit anchors. When the hole was cleaned and dried after the immersion, the pull-out load was greatly increased compared to the wet hole. A design equation was unposed depending on the embedment depth of the anchor bolt.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.4
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• pp.333-338
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• 2007

The object of this study is to find the optimal insulation design conditions of a HTS power cable cryostat. The optimum condition of a cable cryostat is obtained by varying types of MLIs, cable core weights, spacer diameters, winding pitches and MLI layer numbers. As the weight of cable core is increased, conduction heat transfer from surroundings to cable cryostat is increased. But as the spacer pitch is increased from 120 mm to 200 mm, the heat leak of cable cryostat remains almost constant. The optimal number of MLI layers is suggested. Double ply MLI is more effective than triple ply MLI and the insulation effect is best when the number of MLI layers is 36.