• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.6 no.1
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• pp.16-22
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• 2010

Cast austenitic stainless steel(CASS) is used in the primary cooling piping system of nuclear power plant for it's relative low cost, corrosion resistance and easy of welding. However, the coarse-grain structure of cast austenitic stainless steel can strongly affect the inspectability of ultrasonic testing. The major problems encountered during inspection are beam skewing, high attenuation and high background noise of CASS component. So far, the best inspection performance involving CASS components have been achieved using low frequency TRL(Transmitter/Receiver side-by-side L wave) angle beam probe. But TRL technique could not detect shallow defect and it contains an uncertainty for sizing capability. Currently, most of researchers are studying to overcome these challenge issue. In this study, low-frequency phased array TRL technique used to detect and sizing the flaws in CF8A cast austenitic stainless steel.As conclusion, we could detect and size not only axial flaw but also circumferential flaw using low frequency phased array technique.

• Journal of the Korean institute of surface engineering
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• v.33 no.2
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• pp.126-134
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• 2000

This study investigated the bath compositions and plating conditions and crystal structure used for achieving nickel-thallium-phosphorus deposits by means electroless plating. The electroless nickel-thallium-phosphorus deposits were achieved with a bath using sodium hypophosphite as the reducing agent and sodium citrate as the complexing agent. The depositing rate was 10.5mg.$cm^{2-1}$ .$hr^{-1 }$ from the optimistic bath composition, 0.1M nickel sulfate, 0.005M thallium sulfate, 0.2M sodium hypophosphite, and 0.05M sodium citrat and the recommended plating conditions, pH 5.5 and $90^{\circ}C$. The composition of alloy deposits determined by X-ray analysis (EDS) that the Thallium was increased with major increasing concentration of complexing agent and thallium ion in bath solution, it decreased according to the increasing concentrations of reduction agent in the bath solution, Bit Phosphorus showed a contrary to the thallium. It was observed from X-ray diffraction analysis, Scanning Electron Microscopy and Transmission Electron Microscopy. The crystalline structure of deposits was amorphous at the first deposited state but it was changed $Ni-T1-Ni_{5}$ $P_2$ polycrystalline when subjected to 1 hour heat treatment of more than $350^{\circ}C$. TEM observation demonstrated that the microstructure was identical to the result of the XRD at as deposited but it became $Ni-Tl-Ni_{5}$ $P_2$ polycrystalline when heated. And grain size was 10-50nm.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.36 no.2
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• pp.143-146
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• 1991

The present experiment was carried out to investigate the effects of direct sowing time culture of Perilla frutescens var. acuta KUPO on growth yield and it's components. The number of days from seeding to emergence was recognized linear negative correlation between seeding dates. Stem length was the longest in Apr. 1 seeding, and was short in the early, and the late seeding. Stem diameter was the thickest in Apr. 1 seeding, and was thin in the early, and the late seeding. Dry weight of leaf and stem was increased on Apr. 1 seeding. Grain yield was the highest in Apr. 1 seeding date. Therefore, optimum time for direct sowing was on Apr. 1.

• Journal of the Korean Vacuum Society
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• v.10 no.4
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• pp.403-410
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• 2001

Acceleration in integration density and speed performance of ULSI circuits require miniaturization of CMOS and interconnections as well as higher current density capabilities for transistors. A leading candidate to substitute Al-alloy is Cu, which has lower resistivity and higher melting point. So we can expect much higher electromigration resistance. In this paper, we are going to explain the major features of EM for MOCVD Cu according to variant conditions. We compared the life time and activation energy of MOCVD Cu with those of I-beam Cu and AA in the same conditions. The electromigration experiments were performed with Cu/Al/TiN multilayer. Experimental results shows that the deposition rate and electromigration characteristics of Cu thin film were improved by the Al interlayer.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.2
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• pp.190-195
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• 2009

Thin-gauged 3% silicon steel sheets having a highly grain-oriented texture have been developed as a core material for applications of middle-frequency (400 Hz ${\sim}$ 10 kHz) devices. The newly developed sheets with a tension coating showed an excellent reduction in iron loss at 400 Hz (iron loss at 1.0 T and 400 Hz = 4.677 W/kg, iron loss at 1.5 T and 400 Hz = 9.742 W/kg) due to high magnetic induction, $B_{10}$(measured induction at 1000 A/m), of over 1.9 T. In cases of frequencies below 400 Hz, magnetic induction, $B_{10}$, of the sample plays a major role to reduce its iron loss as excitation induction increases, whereas, in case of frequency of 1 kHz, thickness dependence becomes dominant due to a lower iron loss at relatively thinner sample. The sheets with a high magnetic induction, therefore, are favorable for high excitation induction (over 1.0 T) and low excitation frequency (below 400 Hz) applications, whereas the sheets that can reduce eddy current loss by reducing thickness or domain wall width are advantageous for low excitation induction (below 1.0 T) and high excitation frequency (around 1 kHz) applications.

• Journal of the Korean Society of Combustion
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• v.10 no.2
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• pp.1-8
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• 2005

Incomplete combustion due to quenching in a narrow confinement has been a major problem for realization of a reliable micro combustion device. In most micro combustors, effects of flows are absent in the quenching because the flow is laminar and no severe stretch is present. In such circumstance, quenching is caused either by heat loss or by removal of active radicals to the wall surface of the confinement. An experimental investigation was carried out to investigate the relative significance of these two causes of quenching of a premixed flame. A premixed jet burner with a rectangular cross section at the exit was built. At the burner exit, the flame stands between two walls with adjustable distance. The gap between the two walls at which quenching occurs was measured at different wall surface conditions. The results were analyzed to estimate the relative significance of heat loss to the wall and the removal of radicals at the surface. The measurements indicated that the quenching distance was independent of the wall surface characteristics such as oxygen vacancy, grain boundary, or impurities at low temperature. At high temperature, however, the surface characteristics strongly affect the quenching distance, implying that radical removal at the wall plays a significant role in the quenching process.

• Korean Journal of Environmental Agriculture
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• v.19 no.5
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• pp.433-441
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• 2000

A feasibility study was performed to examine the agronomic application of treated sewage on paddy rice culture by field experiment for two consecutive years. The domestic sewage was treated by the constructed wetland system which was in subsurface flow type and consisted of sand and macrophyte. The effluent of the wetland system was used for irrigation water. The effluent was diluted to maintain the total nitrogen concentration below $26mg{\cdot}L^{-1}$ in the first year and used without dilution in the second year experiment. Growth components and yields were compared against the CONTROL plot where conventional method was applied. And also, soil characteristics of the plots before and after reclaimed sewage irrigation were analyzed. Generally, addition of the treated sewage to the irrigation water showed no adverse effects on paddy rice culture, and even enhancement was noticed in both growth and yield. Irrigation of treated sewage after concentration adjusted with conventional fertilization showed the better result, and the yield exceeded that of CONTROL case where clean water was irrigated. Soil characteristics changed after irrigation, and significant EC increasing was observed for the reclaimed sewage irrigation plots. From this study, it appears that reuse of treated sewage, as supplemental irrigation water could be a feasible and practical alternative. For full-scale application, further study is recommended on the specific guideline of major water quality components in treated sewage for irrigation and public health.

• Computers and Concrete
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• v.8 no.6
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• pp.677-692
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• 2011

Particle packing on meso-level has a significant influence on workability of fresh concrete and also on the mechanical and durability properties of the matured material. It was demonstrated earlier that shape exerts but a marginal influence on the elastic properties of concrete provided being packed to the same density, which is not necessarily the case with different types of aggregate. Hence, elastic properties of concrete can be treated as approximately structure-insensitive parameters. However, fracture behaviour can be expected structure-sensitive. This is supported by the present study based on discrete element method (DEM) simulated three-phase concrete, namely aggregate, matrix and interfacial transition zones (ITZs). Fracture properties are assessed with the aid of a finite element method (FEM) based on the damage materials model. Effects on tensile strength due to grain shape and packing density are investigated. Shape differences are shown to have only modest influence. Significant effects are exerted by packing density and physical-mechanical properties of the phases, whereby the ITZ takes up a major position.

• Journal of the Korean Home Economics Association
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• v.26 no.1
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• pp.97-108
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• 1988

The purpose of this study is to classify the type of the Korean document chest, mungab through the literature and market survey and to investigate the preference on characteristics of the mungab. It also attempts to find out the aesthetic perception of the type of mungab by using semantic differential scales. A pilot study was conducted to select the types and pictures of the mungab. Three types and six pictures of mungab were selected. Six hundred homemakers of middle and upper class residing in seoul area were selected for the survey and 449 among them were used for data analysis. Data were analyzed using the SPSS program. The major findings are as follows: 1) The esult of pilot test, the presentative characteristics of mungab were classified into naive type, unique type, and elaborate type. 2) it was found that the modernized style of traditional mungab was wood grain and the next one was Najonchiligi. In the characteristics of decoration which was symbolic pattern, Shi-Jang-Saeng was predominant. In wanting style when they buy, the modernized style of traditional Korean chest was predominant, too. 3) Young and low income group preferred modern style using transparent paint and Sa-Goon-Ja, letters in the symbolic patterns of decoration. Old and high income group preferred traditional style using splendid and expensive materials and Ship Jang Saeng in the symbolic decoration. 4) compared with types of mungab in aesthetic perception, modern style of the traditional mungab was evaluated more positively than traditional style. The young and low income group perceived the naive type and unique type positively, but the old and high income group perceived the elaborate type the most positively.

• ALGAE
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• v.33 no.2
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• pp.167-180
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• 2018

Benthic diatoms are ubiquitous in tidal flats and play major roles in maintaining coastal ecosystems. Spatio-temporal variations in diatom diversity have not been well-studied, mainly because of difficulties in morphological identification and the lack of appropriate genetic tools. To overcome these problems, we used the gene encoding the ribulose bisphosphate carboxylase large-subunit (rbcL) as a molecular marker, and sequenced these genes with the aid of the MiSeq platform. In this manner, we explored the genetic diversity of benthic diatoms in tidal flats of Guenso Bay on the west coast of Korea; differences in the spatial distributions of benthic diatoms were evident. The diatom communities were dominated by Nitzschia, Navicula, and Amphora; their relative distributions were affected by the sand proportion, grain size, and air exposure time. Our results suggest that meta-barcoding of the rbcL gene and next-generation sequencing can be used to explore the diversity of benthic diatoms.