• Journal of the Society of Naval Architects of Korea
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• v.56 no.3
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• pp.231-241
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• 2019

In this study, a simplified analysis method was developed to evaluate the fatigue damage of an ice-going ship under broken ice condition. The global ice load, which is essentially calculated at the design stage of the Arctic vessel, and the hull form information were used to estimate the local ice load acting on the outer-shell of the ship. The local ice load was applied to the finite element analysis model, and the Weibull parameters for the target fatigue point were derived. Finally, fatigue damage was evaluated by applying the S-N curve and the Palmgren-Miner rule. For the verification of the proposed method, numerical analyses using direct approach were performed for the same conditions. A numerical model that implements the interaction between ice and structure was introduced to verify the local ice load and the stress calculated from the proposed method. Finally, the fatigue analyses of the Baltic Sea for actual ice conditions were performed, and the results of the proposed method, the method using numerical analysis, and the LR method were compared.

• Journal of the Society of Naval Architects of Korea
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• v.48 no.5
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• pp.390-395
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• 2011

The main purpose of ice model basin is to assess and evaluate the performance of the Arctic ships and offshore structures because the full-scale tests in ice covered sea are usually very expensive and difficult. There are various ice conditions, such as level ice, brash ice, pack ice and ice ridge, in the real sea. To estimate their capacities in ice tank accurately, an appropriate model ice sheet and prepared ice conditions copied from actual sea ice conditions are needed. Pack ice is a floating ice that has been driven together into a single mass and a mixture of ice fragments of varying size and age that are squeezed together and cover the sea surface with little or no open water. So Ice-class vessels and Icebreaker are usually operated in pack ice conditions for the long time of her voyage. The most ice model tests include the pack ice test with the change of pack ice concentration. In this paper, the effect of pack ice size and channel breadth in pack ice model test is conducted and analyzed. Also we presented some techniques for the calculation of pack ice concentration in the model test. Finally, we developed a new model test methodology of pack ice condition in square type ice tank.

• Journal of the Society of Naval Architects of Korea
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• v.58 no.3
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• pp.158-166
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• 2021

In this paper, a numerical analysis technique using a body force model is investigated to estimate the available net thrust of multi-pod-driven ice-breaking vessels under bollard pull and overload conditions. To employ the body force model in present flow simulations, drag and thrust components acting on the pod unit are calculated by using Propeller Open Water (POW) test data. The available net thrusts according to the direction of operation are evaluated in both bollard pull and overload conditions under deep water. The simulation results are compared with the model test data. The available net thrusts, calculated by the present analysis for ahead operating modes at 3~6 knots which are typical speeds of the target vessel in arctic field, are agreed well with the model test results. It is also found that the present result for astern operating mode appears approximately 6 % larger than the model test result. In addition, the available net thrusts are calculated under the both operating conditions accompanied by shallow water effects, and the main cause of the difference is studied. Based on the result of the present study, it is confirmed that the body force model can be applied to the performance evaluation of multi-pod propulsion system and the main engine selection in early design stage of the vessel.

• The Journal of Engineering Geology
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• v.32 no.1
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• pp.113-126
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• 2022

The tectonic history of the Chukchi Abyssal Plain in the Amerasia Basin, Arctic Ocean, has not been fully explored due to the harsh conditions of sea ice preventing detailed observation. Existing models of the tectonic history of the region provide contrasting interpretation of the timing of formation of the crust (Mesozoic to Cenozoic), crust type (from hyper-extended continental crust to oceanic crust), and formation process (from parallel/fan-shaped rifting to transformation faulting). To help determine the age of the oceanic crust, the geothermal gradient was measured at three stations in the south of abyssal plain at depth of 2,160-2,250 m below sea level. Heat flow measurement stations were located perpendicular to the spreading axis over a 40 km-long transect. In-situ thermal conductivity measurement, corrected by the laboratory test, gave observed marine heat flows of 55 to 61 mW/m². All measurements were taken during Arctic expeditions in 2018 (ARA09C expedition) and 2021 (ARA12C expedition) by the Korean ice-breaking research vessel (IBRV) Araon. Given the assumption of oceanic crust, the results correspond to formation in the Late Cretaceous (Mesozoic). The inferred age supports the hypothesis of formation activated by the opening of the Makarov Basin during the Late Mesozoic-Cenozoic. This would make it contemporaneous with rifting of the Chukchi Border Land immediately east of the abyssal plain. The heat flow data indicate the base of the gas hydrate stability zone is located 332-367 m below the seafloor, this will help to identify the gas hydrate-related bottom simulating reflector in the future seismic survey, as already identified on the Chukchi Plateau. Further geophysical surveys, including heat flow measurements, are required to increase our understanding of the formation process and thermal mantle structure of the abyssal plain.

• The Korean Journal of Quaternary Research
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• v.17 no.2
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• pp.33-38
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• 2003

This study is conducted to examine the data of climate or environmental change in the northeastern Asia during the last glacial maximum. A remarkable feature of the 18,000 BP biome reconstructions for China is the mid-latitude extention of steppe and desert biomes to the modem eastern coast. Terrestrial deposits of glacial maximum age from the northern part of Yellow Sea suggest that this region of the continental shelf was occupied by desert and steppe vegetation. And the shift from temperate forest to steppe and desert implies conditions very much drier than present in eastern Asia. Dry conditions might be explained by a strong winter monsoon and/or a weak summer monsoon. A very strong depression of winter temperatures at LGM. has in the center of continent has influenced in northeast Asia similarly. The vegetation of Hokkaido at LGM was subarctic thin forest distributed on the northern area of middle Honshu and cool and temperate mixed forest at southern area of middle Honshu in Japan. The vegetation landscape of mountain- and East coast region of Korea was composed of herbaceous plants with sparse arctic or subarctic trees. The climate of yellow sea surface and west region of Korea was much drier and temperate steppe landscape was extended broadly. It is supposed that a temperate desert appeared on the west coast area of Pyeongan-Do and Cheolla-Do of Korea. The reconstruction of year-round conditions much colder than today right across China, Korea and Japan is consistent with biome reconstruction at the LGM.

• Journal of Ocean Engineering and Technology
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• v.33 no.6
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• pp.627-631
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• 2019

Recently, researchers in Korea and abroad actively have conducted research activities using the ARAON, a Korean icebreaking research vessel. The ARAON regularly conduct research activities in the Arctic and Antarctic waters every year. The icebreaking mode, which can be either continuous breaking or ramming, is determined by the conditions of the ice and the ice-covered waters. When the icebreaker encounters thick sea ice or an ice ridge, ramming is used. At that time, the speed of the ship generally is slower than that of continuous icebreaking. In this study, the ice load signal at the time of repetitive ramming during ARAON's 2012 Antarctic research voyage was analyzed. The time history of the ice load signal and the change in the speed of the ship used in ramming were compared with these values during continuous icebreaking.

• Korean Journal of Environmental Biology
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• v.35 no.1
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• pp.1-5
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• 2017

A native species to the European ocean, the tunicate Ciona intestinalis now appears worldwide, from sub-Arctic to tropical regions. C. intestinalis generally occurs as an opportunistic fouling organism on artificial substrates in harbors or aquaculture. This study focused on estimating the early growth pattern of C. intestinalis under various temperature conditions. Adults were collected from the Guryungpo harbour in November 2016, and their artificially inseminated eggs were used for the study. The growth of the C. intestinalis was investigated at 8 constant temperatures, ranging from $12^{\circ}C$ to $26^{\circ}C$, at 30 psu. Results indicate that the growth of C. intestinalis increased with increasing temperature. The growth was sluggish at $12^{\circ}C$, and decreased at $26^{\circ}C$. The optimal temperature for growth of C. intestinalis was therefore estimated to be between $20^{\circ}C$ and $24^{\circ}C$.

• Journal of the Korean Geographical Society
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• v.37 no.4
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• pp.357-370
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• 2002

Present work aims to investigate the species composition, physiognomy and distribution of arctic-alpine and alpine plants(AAP) of the Korean Peninsula. The dominance of AAP in the northern Korea may be due to the frequent exchanges of floras with circumpolar regions for the seek of the glacial refugia during the alternate Pleistocene glacial epochs. The post-glacial climatic amelioration pushed AAP back northwards and upwards, so they now shows disjunctive distribution on separate mountain tops. The diverse morphological adaptations of AAP to severe environmental conditions, viz. the dominance of perennial species, stunted tree growth, multiple protection of leaves, krummholz, and dwarf shrubs, are the result of long-term graduall development which have safeguarded the survival of AAP in a such a harsh cryo-climatic area. The appearance of the Korean endemic AAP reflects the long-term isolation of species in Korea, and the local environmental diversities which have both accentuated this isolation and aided the development of genetic diversity. Evergreen broad-leaved AAP at c. 1,500m to 1,800m and above are now endangered because of the competition from down-slope plants, and from the global warming.

• Economic and Environmental Geology
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• v.56 no.1
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• pp.1-11
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• 2023

In this study, we explore the morphological and geochemical characteristics for 440 manganese nodules collected from two different water depths [ARA12B-St52 (150 m, n = 239) and ARA12B-St58i (73 m, n = 201)] on the continental shelf of the East Siberian Sea from the ARA12B expedition in 2021. We also discussed the variations in the characteristics of manganese nodules with varying water depths in the Arctic Sea. The sizes of the nodules are generally greater than 3 cm at both sites. However, there is an obvious difference in the morphology with water depths. For the nodules collected at 150 m, brown-black colored tabular, tube, and ellipsoidal shapes with a rough surface texture are dominant. On the other hand, yellow-brown tabular shapes with a smooth surface texture are common for the nodules collected at 73 m. Furthermore, the slope of trend line between size and weight is significantly different at both sites: particularly, the slopes of nodules at 150 and 73 m are 1.60 and 0.84, respectively. This indicates the difference in the internal structure, porosity, and constituting elements between both nodules. Micro X-ray Flourescence (µ-XRF) results clearly demonstrate that the internal textures and chemical compositions are different with water depths. The nodules at 150 m are composed of a thick Mn-layer and a thin Fe-layer centered on the nucleus, while the nodules at 73 m are alternately grown with thin Mn- and Fe- layers around the nucleus. The average chemical compositions obtained by µ-XRF are 40.6 wt% Mn, 5.2 wt% Fe, and 7.9 Mn/Fe ratio at 150 m, and 10.3 wt% Mn, 19.0 wt% Fe, and 0.6 Mn/Fe ratio at 73 m. The chemical compositions of the nodules at 150 m are similar to those of nodules from the Peru Basin in the Pacific Ocean, while the compositions of the nodules at 73 m are similar to those of nodules from the Cook Islands or the Baltic Sea. The observed morphological and geochemical characteristics of the nodules show a clear difference at the two sites, which indicates that the aqueous conditions and formation processes of the nodules in the Arctic Sea vary with the water depths.

• Korean Journal of Plant Resources
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• v.19 no.4
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• pp.530-536
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• 2006

Hardwood cutting propagation and early growth characteristics were investigated in order to develop the method of cutting propagation and to find out growth characteristics in the low altitude for in situ and ex situ conservation of Empetrum nigrum var. japonicum K. Koch, which is typical arctic alpine plants on Mt. Halla. The growth of roots and shoots was different depending on hormone concentrations or soil conditions. The survival rate, rooting rate, root growth, number of root and shoot growth increased with treatment of 100 mg/l or 500 mg/l NAA. Consequently, optimum condition of hardwood cutting was at treatment with 100 mg/l or 500 mg/l NAA. When plantlets from hardwood cuttings were exposed to the field condition, after 7 months survival rate was 73.3% without shading while $91.1{\sim}94.4%$ at shading conditions. In the green house, however, survival rate of plantlets were $95.6{\sim}97.8%$ without shading. The growth of plantlets was different depending on sites and shading conditions. Particularly, the best growth was obtained when the plantlets were grown in shading conditions. It indicates that relative humidity and light intensity are correlated with the growth in the low altitude area.