• Journal of Korea Foundry Society
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• v.26 no.6
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• pp.258-266
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• 2006

The purpose of this study was to investigate the effects of silicon and nickel additions that influenced the impact and tensile properties of heavy section as-cast ductile irons for wind mill. Based on the results of the metallographic analysis and the mechanical testing on the 2.0 wt.%Si (LS group) and 2.4 wt.%Si (HS group) ductile irons, which contains 0.0, 0.3, 0.6 and 0.9 wt.%Ni, respectively, the following conclusions could be obtained. The nickel additions increased the tensile properties, the microhardness of pearlite, and the pearlite fraction of matrix for the specimen with the same silicon content. The mechanical properties of LS group specimen were in the range of the specification for the ductile iron wind mill castings. The LS group specimens showed higher absorbed impact energy at room temperature and $-20^{\circ}C$ than that of the HS group specimens. However, the absorbed impact energy at $-20^{\circ}C$ for the HS group specimens was observed to be sharply decreased under 10 J by addition of the nickel.

• Corrosion Science and Technology
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• v.6 no.3
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• pp.90-95
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• 2007

Cathodic protection technology has been widely used on ship's outer hull and inner side of ballast water tanks as a supplementary corrosion protection measure in combination with protective organic coatings. Impressed current cathodic protection system is typically opted for the ship's hull and, sacrificial anode system, for ballast water tanks. The anticipation and interest in cathodic protection system for ships has been surprisingly low-eyed to date in comparison with protective coatings. Computational analysis for the verification of cathodic protection design has been tried sometimes for offshore marine structures, however, in commercial shipbuilding section, decades old design practice is still applied, and no systematic or analytical verification work has been done for that. In this respect, over-rotection from un-erified initial design protocol has been also concerned by several experts. Especially, it was frequently reported in sacrificial anode system that even after full design life time, anode was remaining nearly intact. Another issue for impressed current system, for example, is that the anode shield area design for ship's outer hull should be compromised with actual application situation, because the state-of-the-art design equation is quite impractical from the applicator's stand. Besides that, in this study, some other critical design issues for sacrificial anode and impressed current cathodic protection system were discussed.

• Journal of Ocean Engineering and Technology
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• v.29 no.4
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• pp.300-308
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• 2015

With the increases in oil and gas prices, and energy consumption, drillship construction has increased during the last decade. A drillship using a dynamic positioning (DP) system to maintain its position and heading angle during drilling operations. In addition, a drillship is equipped with a moonpool structure to allow its drilling systems to be operated in the midship section. A drillship for the North Sea is specially designed to endure harsh environmental loads. For safe operation in the North Sea, the drillship should have good motion response and robust hull strength. A break water should be considered on the bow and side deck to prevent the green water on deck phenomenon from incoming waves. In addition, the moonpool should be designed to reduce the speed loss and resonance motion. In this study, the hydrodynamic characteristics of a drillship for the North Sea were examined in relation to the motion, wave loads, green water, and moonpool resonance in the initial design stage.

• Journal of Electrical Engineering and Technology
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• v.5 no.4
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• pp.631-636
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• 2010

Gas-insulated transmission lines (GITL) are valued as technological solutions in hydro-power stations due to their enormous power handling capabilities. The performance of GITL is a function of the size of metallic particles inside the gas-insulated chamber. Electrostatic field (E-field) enhancement is a common phenomenon in gas-insulated lines due to these metallic particles. In this study, the E-field enhancement factor is calculated by considering metallic particles at various locations in the gas-insulated line/bus section, such as high-tension (HT) conductor, high-voltage shields, support insulator, and inner surface of grounded enclosure. For this purpose, a two-dimensional model based on finite element (FE) method is developed. The length of the metallic particle is in the range of 1 to 10 mm while the diameter is between 1 to 3 mm. E-field enhancement is also computed for various particle configurations of the gas-insulated system, with focus on dielectric coating made of epoxy on HT conductor and inner surface of grounded enclosure.

• Membrane and Water Treatment
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• v.11 no.1
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• pp.11-23
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• 2020

The effectiveness of in situ sediment capping as a technique for heavy metal risk mitigation in Hyeongsan River estuary, South Korea was studied. Sites in the estuary were found previously to show moderate to high levels of contamination of mercury, methylmercury and other heavy metals. A 400 m × 50 m section of the river was selected for a thin layer capping demonstration, where the total area was divided into 4 sections capped with different combinations of capping materials (zeolite, AC/zeolite, AC/sand, zeolite/sand). Pore water concentrations in the different sites were studied using diffusive gradient in thin film (DGT) probes. All capping amendments showed reduction in the pore water concentration of the different heavy metals with top 5 cm showing %reduction greater than 90% for some heavy metals. The relative maxima for the different metals were found to be translated to lower depths with addition of the caps. For two-layered cap with AC, order of placement should be considered since AC can easily be displaced due to its relatively low density. Investigation of methylmercury (MeHg) in the site showed that MeHg and %MeHg in pore water corresponds well with maxima for sulfide, Fe and Mn suggesting mercury methylation as probably coupled with sulfate, Fe and Mn reduction in sediments. Our results showed that thin-layer capping of active sorbents AC and zeolite, in combination with passive sand caps, are potential remediation strategy for sediments contaminated with heavy metals.

• Korean Journal of Remote Sensing
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• v.16 no.1
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• pp.55-64
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• 2000

The Tropical Rainfall Measuring Mission(TRMM) Satellite was launched in November 1997, carving into orbit the first space-borne Precipitation Radar(PR). The main objective of the TRMM is to obtain and study multi-year science data sets of tropical and subtropical rainfall measurements. In the present investigation, the characteristics of heavy rainfall cases over Korea in 1998 and 1999 are analyzed using the TRMM/PR dat3. We compare the rainrate measured from TRMM/PR with the accumulated rainfall data for 10 minutes tv Automatic Weather System(AWS). Especially, horizontal cross-section of rainrate with height and longitude in the precipitating clouds are investigated. As a result of the comparison with GMS-5 IR1, the TRMM/PR data delineate well the rain type( i.e. convective, stratiform cloud and others), height of storm top and instantaneous rainrate in the precipitating clouds. The vertical structure with height and horizontal cross-section of rainrate along the longitude show the orographic effect on the rainfall. TRMM/PR instrument measures the rainrate below 6 ㎜/hr more than AWS rainguages and inclined to underestimate the rainrate than rainguages for the whole area.

• The Journal of Internal Korean Medicine
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• v.39 no.6
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• pp.1168-1180
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• 2018

Objective: As the number of sarcopenic patients worldwide is increasing, the need for the treatment of sarcopenia is increasing. Ginseng has been reported to be a major herbal supplement. We tested whether red ginseng would be effective for sarcopenia using red ginseng preparation which can be easily obtained locally in Korea. Methods: 30 rats were randomly divided into three groups: the control group (n=10) (Group C), the group with Dexamethasone -induced sarcopenia (n=10) (Group D), and the group to which red ginseng was administered group after induced sarcopenia with Dexamethasone (n=10) (Group DH). Dexamethasone was intraperitoneally administered to group D and group DH for 7 days to make sarcopenic model. After that, the red ginseng tablets prepared by Korea Ginseng Corporation were diluted in distilled water and administered orally to the DH group for 2 weeks. Body weight and grip strength were measured 8 times during the experiment. At the end of the experiment, blood was collected by cardiac puncture. In addition, the tibialis muscle was extracted, a myofibril cross section was measured by immunohistochemical staining and MyHC (myosin heavy chain) was quantified by Western blotting. Results: The ratio of the area on myofibril cross-section showed significant differences after administration of the red ginseng tablet. Conclusions: Red ginseng has a significant effect on the recovery of myofibril cross-section on sarcopenia. This experiment will be helpful for future clinical studies on drug effects in sarcopennia.

• Journal of the Society of Naval Architects of Korea
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• v.46 no.5
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• pp.536-544
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• 2009

The performance of radars operated near an offshore wind farm region may be degraded due to the distorted signals by wind turbines. This degradation of radar systems includes ghost effects and doppler effects by a tower, nacelle, and turbine blades consisting of the wind turbine. In this paper, electromagnetic wave backscatterings from a offshore wind turbine are numerically simulated in terms of temporal radar cross section and radar cross section spectra, using a quasi-static approach based on physical optics and physical theory of diffraction. The simulations are carried out at 3.05 GHz for the seven yaw angles and four blade pitch angles. From the results, radar cross section values and doppler effect as turbine blades rotate are investigated.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.800-807
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• 2006

Sea dyke construction is simply defined that the cutting procedure of sea water flow. Sea dyke construction is more difficult than in-land construction because it’s placed on deep seabed and exposed sea wave attack. Especially, the final closure of sea dyke is most dangerous due to the fast velocity of tidal flow. The final closure section is consisted with vast rubble and heavy stone gabion, therefore the discharge velocity at land side of final close section is irregularly and sometime occur the fast discharge velocity. In this study, the seepage model test performed to evaluate seepage behavior with tidal variation of final closure and continuous sea dyke section such as discharge velocity, hydraulic gradient, and phreatic line. Based on the seepage model test results, the maximum discharge velocity of final closure section is 1.7m/sec. Also the local discharge velocity increment and vortex is occurred.

• Journal of Korean Society of Transportation
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• v.30 no.1
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• pp.75-83
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• 2012

This study is to find a shortcoming embedded in the current Korean Highway Capacity Manual (KHCM) on reflecting a heavy vehicle effect to the highway capacity. The KHCM suggests to handle the percent heavy vehicle to deal with its effect to a capacity regardless of density levels. Authors hypothesized in this study that the effect of heavy vehicles would vary at different levels of traffic density - the effect would be comparably insignificant when a density is low and it becomes comparably significant when it becomes high. Field data from a freeways located in Seoul were collected for 360 hours (15 days) and categorized them into a set of operation conditions grouped by 15 minutes and by the LOS density levels. Comparison between the field measured and the estimated by the KHCM method showed that the KHCM method overestimated the effect of heavy vehicles in LOS B and C but underestimated in LOS E. The results suggested that there be a difference pattern from the one the KHCM expected and brought discussion on further studies.