• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.23 no.2
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• pp.15-15
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• 1987

In this study, the characteristics of TRC (tensile restraint crack) critical stress in the gravity type underwater wet welding process and in the in-air welding have been investigated for Y, y and 45°r grooves using the KR Grade A-3 steel plates and the E4303 covered electrodes. The following results were obtained: (1) In the TRC tests, the initial critical stress of Y groove is higher than those of the 45°r single bebel grooves in both in-air and underwater weldings, and the cold fracture sensitivity is higher in the underwater welding than in the in-air welding. (2) The hardness of underwater weld metal is the highest in heat affected zone is about Hk 365 in the in-air weld but Hk 670 in the underwater weld which is higher for cooling speed is more rapid, resulting in the lower critical stress by increase of fracture sensitivity. (3) The diffusible hydrogen quantity for 48 hours is about 18cc/100g-weld-metal in the in-air welding but 48cc/100g-weld-metal in the underwater welding. So that, in the case of underwater welding the diffusible hydrogen penetrates about 3 times more than that in the in-air welding.

• Journal of Energy Engineering
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• v.20 no.3
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• pp.185-190
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• 2011

This paper describes design, fabrication, and evaluation of the conduction cooled high temperature superconducting (HTS) magnet for superconducting magnetic energy storage (SMES). The HTS magnet is composed of twenty-two of double pancake coils made of 4-ply conductors that stacked two Bi-2223 multi-filamentary tapes with the reinforced brass tape. Each double pancake coil consists of two solenoid coils with an inner diameter of 500 mm, an outer diameter of 691 mm, and a height of 10 mm. The aluminum plates of 3 mm thickness were arranged between double pancake coils for the cooling of the heat due to the power dissipation in the coil. The magnet was cooled down to 5.6 K with two stage Gifford McMahon (GM) cryocoolers. The maximum temperature at the HTS magnet in discharging mode rose as the charging current increased. 1 MJ of magnetic energy was successfully stored in the HTS magnet when the charging current reached 360A without quench. In this paper, thermal and electromagnetic behaviors on the conduction cooled HTS magnet for SMES are presented and these results will be utilized in the optimal design and the stability evaluation for conduction cooled HTS magnets.

• Journal of the Korean earth science society
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• v.18 no.6
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• pp.559-564
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• 1997

The New Hebrides Basin is an inactive non back-arc basin located at the convergent boundary of the Pacific and Info-Australian plates. This basin was formed from 46 Ma to 60 Ma. The basin has two spreading episodes with rates of 34 mm/a for 42 to 47 Ma and 17 mm/a for 47 to 60 Ma. The sediments covered in the basin has uniform thickness of 0.65 sec. The age-depth correlation curve of the New Hebrides Basin can be represented by the following equation: $Depth(m)=2689+312\sqrt{Age}(Ma)$ The coefficient of 312 in this equation is close to that for major oceans, 350. This suggests that the cooling processes of the lithospheres in the New Hebrides Basin and major oceans are similar to each other. Free-air gravity anomalies of the basin varying from -22.3 mgal to +59.0 mgal. The mean value is +30.2 mgal higher than those of the normal oceans. Moderately large free-air gravity anomalies in the New Hebrides Basin are presumably owing to its location on a marginal swell along the New Hebrides Trench. It is generally observed that the ocean floor is very gently uplifted in a zone about 200 km oceanward of the trench axis. Positive free-air gravity anomalies amounting to $50{\sim}60$ mgal are usually observed on the crest of the swell. This topography is presumably by bending of the oceanic lithosphere so as to dynamically maintain nonisostatic states for some duration.