• Korean Journal of Materials Research
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• v.10 no.4
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• pp.305-311
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• 2000

Applicability of crack arrest load measured from the Charpy V-notch impact test has been investigated to predict the fracture toughness of nuclear reactor pressure vessel (RPV) steels (ASME SA508 Cl.3). The temperature dependence of the crack arrest load was well described by the type of exponential function characterized by an index temperature at which the crack arrest load is 2kN. The specific index temperature, which also well correlated with $T_{NDT}\;and\;T_{41J}$ is expected to be representative index temperature characterizing the crack arrest fracture toughness of RPV steels. Also, the crack arrest load correlated well with the stable crack length measured from the fracture surface. From the measurements of the crack arrest load and the stable crack length, the lower bound fracture toughness, $K_{Ia}$ of RPV steels could be predicted with sufficient accuracy.

• Resources Recycling
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• v.29 no.3
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• pp.36-42
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• 2020

In the present study, gravity separation of speiss (6.74 g/㎤) and limestone (2.7 g/㎤) was investigated using a vibrating 1 mm-zirconia ball (5.6 g/㎤) bed as a medium. The floating ratio and separation efficiency with increasing the number of spiess and limestone granules were examined by changing the vibration frequency from 18 Hz to 26 Hz. During the vibration, the zirconia balls circulate inside the vessel, and the spiess granules sink with the zirconia balls, but limestone granules remain on the surface of the zirconia ball bed. As the number of particles of spiess and limestone granules increased, it was observed that the granules were congested in the path of the granule sinking, so the rate of particle sinking decreased, and that limestone granules overlapping with the spiess granule also sunk. Therefore, the separation efficiency decreases with increasing the number of granules, but when the vibrational frequency increases, there is no more congestion and the separation efficiency increases. When each of the three particles was added, a separation efficiency of 100% was acheived at 22 Hz, which indicates that a dry gravity separation process that does not require a drying process is possible.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.12
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• pp.1497-1502
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• 2013

When using hydrogen gas as an ecofriendly energy sources, it is necessary to conduct a safety assessment and ensure thereliability of the hydrogen pressure vessel against hydrogen embrittlement expected in the steel materials. In this study, by applying the in-situ SP test method, the gas hydrogen embrittlement behaviors in SA372 steel, which is commonly used as a pressurized hydrogen gas storage container, were evaluated. To investigate the hydrogen embrittlement behavior, SP tests at different punch velocities were conducted for specimens with differently fabricated surfaces at atmospheric pressure and under high-pressure hydrogen gas conditions. As a result, the SA372 steel showed significant hydrogen embrittlement under pressurized hydrogen gas conditions. The effect of punch velocity on the hydrogen embrittlement appeared clearly; the lower punch velocity case indicated significant hydrogen embrittlement resulting in lower SP energy. The fractographic morphologies observed after SP test also revealed the hydrogen embrittlement behavior corresponding to the punch velocity adopted. Under this pressurized gas hydrogen test condition, the influence of specimen surface condition on the extent of hydrogen embrittlement could not be determined clearly.

• Korean Journal of Metals and Materials
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• v.49 no.8
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• pp.628-634
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• 2011

SA508 Gr.4N Ni-Cr-Mo low alloy steel, in which Ni and Cr contents are higher than in commercial SA508 Gr.3 Mn-Mo-Ni low alloy steels, may be a candidate reactor pressure vessel (RPV) material with higher strength and toughness from its tempered martensitic microstructure. The inner surface of the RPV is weld-cladded with stainless steels to prevent corrosion. The goal of this study is to evaluate the microstructural properties of the clad interface between Ni-Cr-Mo low alloy steel and stainless weldment, and the effects of post weld heat treatment (PWHT) on the properties. The properties of the clad interface were compared with those of commercial Mn-Mo-Ni low alloy steel. Multi-layer welding of model alloys with ER308L and ER309L stainless steel by the SAW method was performed, and then PWHT was conducted at $610^{\circ}C$ for 30 h. The microstructural changes of the clad interface were analyzed using OM, SEM and TEM, and micro-Vickers hardness tests were performed. Before PWHT, the heat affected zone (HAZ) showed higher hardness than base and weld metals due to formation of martensite after welding in both steels. In addition, the hardness of the HAZ in Ni-Cr-Mo low alloy steel was higher than that in Mn-Mo-Ni low alloy steel due to a comparatively high martensite fraction. The hardness of the HAZ decreased after PWHT in both steels, but the dark region was formed near the fusion line in which the hardness was locally high. In the case of Mn-Mo-Ni low alloy steel, formation of fine Cr-carbides in the weld region near the fusion line by diffusion of C from the base metal resulted in locally high hardness in the dark region. However, the precipitates of the region in the Ni-Cr-Mo low alloy steel were similar to that in the base metal, and the hardness in the region was not greatly different from that in the base metal.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.6
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• pp.688-696
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• 2023

In the present study, free roll decay and resistance performances of fishing vessels were evaluated with the combinations and variations of in the parameters of appendages which are attached to improve motion performance of fishing vessels. Computational Ffluid Ddynamics was used to perform free roll decay and resistance analysis. The roll period and decay coefficient were derived by the variations in the combination and dimensions of the primary appendages of the bilge keel and the under keel. It was observed thatThe variations of in the length of the under keel did not significantly impact to the roll damping coefficient. Conversely, for the bilge keel, an increase in the length and angle resulted in an increase in the roll damping coefficient. Comparison of resistance performance was additionally assessed among the selected hulls with the appendages and bare hull. The resistance of the hull with the appendages was higher than that of the bare hull due owing to the changes of in the pressure on the surface of the hull and trim angle. Throughout the present study, the impact of appendage parameter and arrangement on the free roll decay and resistance performance of fishing vessels were was assessed,. which This will be beneficial for the application of appendages to fishing vessels.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.13 no.3
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• pp.229-236
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• 2008

The deep-sea miner is the tracked vehicle system which drives on the deep-seabed and gathers a manganese nodules. The miner is operated by remote control in real-time by the station of surface vessel. So operating S/W is a important part of miner remote operating. At present, the test miner has been designed and manufactured for near-shore sea-test. The test miner consists of mechanical parts, and electric-electronic parts. Because those parts should be controled and monitored remotely, operating S/W for control and monitoring is necessary by all means. In this paper, real-time operating S/W for a control and monitoring of the test miner was designed and developed using PXI, embedded controller and LabVIEW. This real-time operating S/W was developed for an efficient test of test miner in a near seabed area. Moreover, database management system(DBMS) was developed too for the data management of test miner monitoring using MS SQL and LabVIEW.

• Journal of Mushroom
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• v.12 no.3
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• pp.209-215
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• 2014

Changes in physical and chemical properties of oak sawdust were investigated by depth and time for 46 days during the fermentation process of 33 tons of the sawdust for oak mushroom cultivation. The degrees of change in the properties of the sawdust differed depending on the depth and fermentation period. Most of the physical-chemical properties except temperature and pH gradually changed during the fermentation. The temperature change was highly sensitive to the environment at the surface sawdust to 20 cm depth, while it gradually increased to the maximum $58.9^{\circ}C$ at 40~100 cm depths in 12 days and slowly to the maximum at 150 cm depth in 24 days. The moisture content of the sawdust decreased gradually from 31% to 26.5~28.0% in 24 days. Of the chemical properties during the fermentation, pH generally rose from 5.2 to 5.6, but it decreased to 4.4~4.7 at 150 cm depth in 16 days. While the carbon content of the sawdust was 68~70% without significant change, nitrogen content increased from 0.22% to 0.25% and thus C/N ratio gradually lowered from 320 to 280. P content in the sawdust gradually increased from 0.005% to 0.022% for 46 days. Osmotic concentration of the hot water extract of the sawdust varied 41.5~44.2 mmol/kg without significant change by the depth and time. The starch particles within initial ray parenchyma cells of sawdust decreased and fungal hyphae formed on the surface of the sawdust granules and within xylem vessel cells in 35 days. The effect of the sawdust fermentation on oak mushroom cultivation needs continued research.

• Journal of Chest Surgery
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• v.36 no.2
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• pp.63-72
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• 2003

Although a variety of synthetic vascular grafts are available in modern vascular surgery, no ideal prosthesis ha,4 yet been developed. Small-caliber vascular grafts with low flow, as used in the lower extremity, continue to become thrombosed at unacceptable rates. We have developed and evaluated the new antithrombogenic blood contacting surfaces in canine model. Material and Method: Two now antithrombogenic blood contacting surfaces(Polyvinylalcohol -Polyurethane(PVA-PU) blend and natural Graphite-polyurethane(G-PU) blend) have been developed and evaluated in canine model, using vascular grafts and patches. The luminal surfaces of the test vascular grafts(5 mm ID) were fabricated by dipping a glass rod in PVA-PU blend solution(50 % PVA) using phase separation method. Mongrel dogs of either sex weighing 18-22 kg were anesthetized by endotracheal intubation using halothane and their lungs were ventilated with a volume-cycled ventilator, Maintenance anesthesia with 0.5-1.0% halothane and supplemental oxygen was used. Two pairs were used for comparison in the bilateral femoral arteries for both vascular grafts(PVA-PU vs. PU) and vascular patches(G-PU vs. PU). Bilateral groin incisions were made and the arteries were exposed and clamped. After an excision of 1 cm of the artery between clamps, a grail of 2.5 cm in length was implanted end-to-end using 6-0 polypropylene suture. The vascular patch was implanted as a form of on-lay patch. Animals were sacrificed at 1, 2, 4, 6, 8 and 16 weeks for vascular grafts and 1, 2. 4 and 6 weeks for vascular patches. Result The vascular grafts of PVA-PU blends showed patent lumina in the 2 and 16 weeks animals, while those of PU showed a patent lumen in 2 weeks animal. PVA-PU graft of 16 weeks showed a fairly clean luminal surface. A light microscopic finding of this graft demonstrated good tissue infiltration through porosity, The animals with vascular patches showed patent arteries in both groups except 2 weeks animal. Scanning electron microscopy of the luminal surfaces of G-PU patches in 4 and 6 weeks animals showed endothelial cell covering with microvilli. PU patches showed qualitatively less endothelial cell covering. Conclusion: In conclusion, PVA-PU and G-PU blends can be a promising blood contacting surfaces for application in a synthetic vascualr graft. However, further animal study is needed to determine the real long-term effects of these methods of surface modifications.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.39 no.1
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• pp.8-18
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• 2003

In order to investigate the oceanic condition of fishing ground in the adjacent sea of Naro Island, the oceanographic observation were carried out by the training vessel of Yosu National University on winter, spring, summer, and autumn in 2000. Main features in the observation are as follows; 1) the ranges of temperature, salinity, and chlorophyll-a were from 4.$3\circ_C$ to 10.$1\circ_C$, from 33.1 psu to 34.9 psu, and from 0.1 $ug$/$\Omega$ to 26.2 $ug$/$\Omega$ in winter, from 8.$1\circ_C$ to 13.$7\circ_C$, from 33.1 psu to 34.3 psu, and from 0.1 $ug$/$\Omega$ to 24.4 $ug$/$\Omega$ in spring, from 14.$5\circ_C$ to 24.$2\circ_C$, from 30.5 psu to 34.1 psu, and from 0.1 $ug$/$\Omega$ to 30.0 $ug$/$\Omega$ in summer, and from 14.$8\circ_C$ to 18.$6\circ_C$, from 30.1 psu to 34.0 psu, and from 0.1 $ug$/$\Omega$ to 19.1 $ug$/$\Omega$ in autumn, respectively, 2) the temperature in the coastal region was higher than that in the open ocean while salinity was lower, and the convection was identified between the surface and the bottom during in winter and autumn, and the thermocline were made between surface and 20m layer with vertical gradients of 4.$0\circ_C$/7m in summer, 3) the chlorophyll-a in the this region was varied in each season, being highly distributed in spring, on bottom and coastal region, and 4) an evidence of sea water intrusion toward Sori Island was observed, and of inner water intrusion from Yeoja Bay was observed.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.39 no.1
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• pp.19-26
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• 2003

In order to investigate the seasonal variation of watermass in the adjacent sea of Naro Island, oceanographic observation on the fishing grounds were carried out by the training vessel of Yosu National University on winter, spring, summer, and autumn in 2000. The results obtained are summarized as follows ; 1) the watermass in the fishing ground were divided into the coastal water (30.0∼31.4psu), mixing water (31.5∼32.9psu) and the offshore water (33.0∼35.0psu) according to the distribution of salinity from T-S diagram plotted all salinity data observed on winter, spring, summer, and autumn in 2000. 2) the ranges of temperature and salinity were from 4.$3\circ_C$ to 10.1$^{\circ}C$ and from 33.1psu to 34.9psu in winter, from 8.$1\circ_C$ to 13.$7\circ_C$ and from 33.1psu to 34.3psu in spring, from 14.5$^{\circ}C$ to 24.$2\circ_C$ and from 30.5psu to 34.1psu in summer, and from 14.$5\circ_C$ to 18.$6\circ_C$ and from 30.1psu to 34.0psu in autumn, respectively. 3) the distribution of watermass in the fishing ground varied largely each seasons, but a general tendency on the distribution was obtained. That is, in winter and spring the offshore water was distributed most widely and in summer the coastal and mixing water occupied the fishing ground but in autumn the mixing water prevailed. 4) variation of temperature and salinity were appeared between the surface and 20m layer in the sea aduacent to Naro Island. Therefore, in the summer the thermocline were made between surface and 20m layer with vertical gradients of 4.$0\circ_C$/7m.