• Water for future
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• v.56 no.2
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• pp.62-68
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• 2023

• Journal of Electrical Engineering and Technology
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• v.12 no.1
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• pp.302-309
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• 2017

The ageing of XLPE cable insulation will lead to the accelerating accumulation of space charge, which will greatly affect the safe operation of the HVDC cable. In order to investigate the influence of different ageing modes on the space charge distribution of the HVDC cable, thermal stressed, electrical stressed and electro-thermal stressed endurance tests were carried out on the XLPE peelings. The tested XLPE peelings were obtained from 160kV HVDC cable insulation. The endurance tests were carried at thermal stress of 363K, electrical stress of 20kV/mm DC and a combination of both. The Pulsed Electro-Acoustic (PEA) method was used to measure the space charge distribution of the samples. The influences of ageing on the trap energy distribution were analyzed based on the isothermal relaxation theory and the decay characteristics of the space charge. The results showed that thermal ageing would help to improve the crystalline morphologies of the XLPE at the early stage. The total amount of space charge decreased compared to the ones before thermal ageing. The long term of electrical stress would result in the cleavage of polymer molecule chains which would intensify the accumulation of space charge and increase the density and depth of electron traps. With a combination of electrical and thermal stress, the injection and migration of space charge were more significant. Besides, the depth and density of electron traps increased rapidly with the increase of endurance time.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.46 no.6
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• pp.973-976
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• 2013

We observed the vertical distribution and feeding ecology of the Mirror dory, Zenopsis nebulosa, in the Southern Sea of Korea from 2009 to 2013 using an otter trawl. The total length of captured individuals ranged from 11 to 48 cm. Individuals captured at greater depths were significantly larger than those from shallower sites. Fish abundance was significantly related to depth and temperature. We found that 89% of the total catch was obtained at depths between 80 and 140 meters. Prey organisms, including fish, crustaceans, and cephalopods, were found in Z. nebulosa stomachs. Fishes were the main prey items for all size groups. Cephalopods were consumed by individuals > 25 cm in length. Our findings suggested that the vertical distribution of Z. nebulosa varied with depth and temperature, and that the fish are carnivores.

• Journal of the Korea Organic Resources Recycling Association
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• v.15 no.4
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• pp.93-99
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• 2007

Vertical distribution of tiger worm(Eisenia fetida) population in the earthworm rearing bed was investigated with feeding paper mill sludge. More than 50% of larva and adult population of Eisenia fetida lived within the depth of 5 cm from the surface of rearing bed. And more than 96% of the population of larva, adult and cocoon lived within the depth of 20 cm. Percental vertical distribution of Eisenia fetida population in the rearing bed was not much influenced by the changes in the height of rearing bed or density of earthworm population.

• Journal of Ecology and Environment
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• v.32 no.1
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• pp.27-31
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• 2009

Organic carbon (OC) distribution in 32-year-old pitch pine plantation at Mt. Hotae in Kongju, Korea, was studied from August 2007 to July 2008. In order to investigate the OC distribution, OC in plant biomass, litterfall, litter layer on forest floor, and soil within 50cm depth were estimated. The density of P. rigida plantation was 3,200 trees/ha, average DBH was $18.7{\pm}5.53cm$ and average tree height was $11.1{\pm}1.85m$. Organic carbon stored in plant biomass, litterlayer on forest floor and soil in 2008 was 89.46 ton C/ha (46.09%), 4.32 ton C/ha (2.23%) and 100.32 ton C $ha^{-1}$ 50cm-$depth^{-1}$ (51.68%), respectively. Amount of OC returned to forest floor via litterfall was 2.21 ton C $ha^{-1}\;yr^{-1}$. Total amount of OC stored in this P. rigida plantation was 194.1 ton C/ha. Net increase of OC in above- and below-ground biomass in this pitch pine plantation was 4.82 ton C $ha^{-1}\;yr^{-1}$.

• Geotechnical Engineering
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• v.12 no.1
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• pp.87-110
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• 1996

To simulate the three4imensional effect occurring near the tunnel face in a two -dimensional model, empirical load -dirtribution ratio concept is frequently used in tunnel design. In this paper, three -dimensional analysis is performed and its results are compared with those of two dimensional analysis'to investigate the applicability of the loadiistribution ratio concept. Especially, stress concentration near the tunnel face is investigated in depth. A parametric study is performed to investigate the effect of each factor on the load distribution ratio. The factors considered here include unsupported span length, initial stress, rock quality, tunnel size and the depth of tunnel location Moreover, the load -distribution ratios for the typical tunnel sections in Seoul Subway to be used in the tunnel design are suggested.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.3
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• pp.193-199
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• 2000

As an energetic focused-ion beam(FIB) is irradiated on an inorganic amorphous thin film a majority of ions without a reflection at surface, is randomly collided with constituent atoms in thin film. but their distribution exhibits generally a systematic form of distribution. In our previous paper we reported the concentration distribution and the transmission per unit depth of Ga$^{+}$ ions penetrated int a-Se$_{75}$ /Ge$_{25}$ thin film using the LSS-based calculation. In this paper these simulated results are compared with those obtained by a conventional profile code(ISC) and a practical SIMS profile. Then the results of LSS-based calculation have only a small difference with those of code and SIMS Especially. in the case of Ga$^{+}$-FIB with an accelerating energy of 15keV. the depth of the maximum ion concentration is coincident with each other in an error range of $\pm$5$\AA$.EX>.

• Journal of Ecology and Environment
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• v.30 no.1
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• pp.17-21
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• 2007

The organic carbon (OC) distribution of Pinus densiflora forest in Songgye valley at Mt. Worak National Park were studied as a part of the National Long-Term Ecological Research in Korea. In order to investigate the OC distribution, OC in plant biomass, litterfall, litter layer on forest floor, and soil were estimated. The density of P. densiflora forest was 1,300 trees/ha, average DBH was $15.2{\pm}6.17\;cm$ and average tree height was $10.7{\pm}2.56\;m$. The shrub layer was dominated by shrubby Quercus variabilis, Fraxinus sieboldiana and lndigofera kirilowii with low frequency, and herb layer was dominated by Pteridium aquilinum and Miscanthus sinensis. Total amount of OC stored in this pine forest was 142.78 ton C/ha. Organic carbon stored in soil and plant biomass accounted for 59.2% and 37.8%, respectively. Amount of OC distributed in trees, shrubs, herbs and litter layer in this pine forest was 51.79, 2.03, 0.12 and 4.29 ton C/ha, respectively. Amount of OC returned to forest floor via litterfall was $1.50\;ton\;C\;ha^{-1}\;yr^{-1}$. Soil organic carbon (SOC) decreased along the soil depth. Total amount of SOC within 50cm soil depth was $84.55\;ton\;C\;ha^{-1}\;50\;cm-depth^{-1}$.

• Journal of the Korea Concrete Institute
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• v.28 no.3
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• pp.267-278
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• 2016

In this study, the ultimate strength of 335 simply supported reinforced concrete beams with shear span-to-effective depth ratio of less than 3 was evaluated by the ACI 318-14's strut-tie model approach implemented with the indeterminate strut-tie models and load distribution ratios of the companion paper. The ultimate strength of the beams was also estimated by using the experimental shear strength models, the theoretical shear strength models, and the current strut-tie model design codes. The validity of the proposed strut-tie models and load distribution ratios was examined by comparing the strength analysis results classified according to the prime design variables of the shear span-to-effective depth ratio, flexural reinforcement ratio, and compressive strength of concrete.

• Ocean and Polar Research
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• v.29 no.2
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• pp.123-134
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• 2007

Distribution patterns of sandy bottom macrobenthic communities were studied around the Hupo coastal area. The seasonal surveys were conducted at 15 chosen sites within a depth range of 10 to 50 m along 10 km of the coastline using a Smith-McIntyre grab $(0.05\;m^2)$ in 2005. Overall depth distribution following the direction of the offshore become deeper parallel to the coastline. A total of 319 macrobenthic species were sampled with a mean density of $1,972\;ind./m^2$, and mean biomass was 82.5 wet-weight $g/m^2$. The major individual-dominant species were three polychaetes Spiophanes bombyx ($436\;ind./m^2$), Scoletoma longifolia ($250\;ind./m^2$) and Magelona japonica ($170\;ind./m^2$), and bivalve Adontorhina subquadrata ($73\;ind./m^2$). Cluster analysis and non-metric multidimensional scaling (nMDS) analysis based on Bray-Curtis similarity identified 2 major station groups which corresponded to macrobenthic faunal assemblages and their characteristic species. In addition, environmental conditions were significantly different between station groups. Group I contained mostly 20 and 50 m deep sites and was associated with sandy mud. Group I was characterized by high abundance of S. bombyx, S. longifolia, A. subquadrata. It was divided into two sub-groups (I-I and I-II) in relation to depth. Sub-group I-I was associated with deeper sites than sub-group I-II. Group II included mostly inshore area shallower than 15 m and was associated with coarse and medium sand. Group II was characterized by Lumbrinerides hayashii and Urothoe grimaldii japonica.