• Journal of Korean Society of Forest Science
• /
• v.110 no.3
• /
• pp.419-430
• /
• 2021

This study investigated spatiotemporal trends of sediment-related disasters in North Korea from 1960 to 2019 and post-disaster recovery cases based on a literature review and satellite images. Results showed that occurrence status of sediment-related disasters was initially externally reported in 1995 (during the Kim Jongil era); their main triggering factor was heavy summer rainfall. Furthermore, forest degradation rate was positively correlated with population density (R² = 0.4347, p = 0.02) and occurrence number of sediment-related disasters was relatively high on the west coast region, where both variables showed high values. This indicates that human activity was a major cause of forest degradation and thus, significantly affected sediment-related disasters in mountain regions. Finally, sediment- related disasters due to shallow landslides, debris flow, and slow-moving landslides were observed in undisturbed forest regions and human-impacted forest regions, including terraced fields, opencast mines, forest roads, and post-wildfire areas, via satellite image analysis. These disaster-hit areas remained mostly abandoned without any recovery works, whereas hillside erosion control work (e.g., treeplanting with terracing) or torrent erosion control work (e.g., check dam, debris flow guide bank) were implemented in certain areas. These findings can provide reference information to expand inter-Korean exchange and cooperation in forest rehabilitation and erosion control works of North Korea.

• Journal of fish pathology
• /
• v.26 no.1
• /
• pp.11-17
• /
• 2013

The cadmium (Cd) toxicological effects on the fertilized eggs, embryos and larvae were investigated in olive flounder, Paralichthys olivaceus water-borne exposed to Cd. The survival rate and hatching success of the embryos significantly diminished in treated groups in dependence of the Cd concentration. Significant differences were found at ${\geq}30{\mu}g\;L^{-1}$ exposed groups compared to the control group. A significant increase of malformation of the embryo was observed at ${\geq}20{\mu}g\;L^{-1}$ exposed groups. They usually include such symptoms as clouded yolk-sac abnormality, fin erosion and spinal curvature. A significant reduction in the survival rate of the larvae was observed in ${\geq}20{\mu}g\;L^{-1}$ exposed groups with accompanied by the disorder. Notably, in larvae, a concentration as low as $10{\mu}g\;L^{-1}$ exposed groups caused significant elevated abnormalities that is incidences of spinal cord deformation, abnormal eyes, deformation of the head region and severe developmental delay.

• Journal of the Korean Society for Precision Engineering
• /
• v.32 no.7
• /
• pp.627-631
• /
• 2015

Conventional etching technology is in the face of problems such as dishing, erosion resulting from non-uniform removal of film. Advanced printed circuit board (PCB) requires accurate wire formation with the aid of planarization by chemical mechanical polishing (CMP). Linear roll CMP is a line contact continuous process which removes the film by pressurization and rotation while slurry is supplied to polishing pad attached to the roll. This paper focuses on the design of floating nozzle on the linear roll CMP equipment which makes the slurry supply uniformly on the roll pad. Experimental results show that removal rate using the floating nozzle increases 3 times higher than that without it and non-uniformity is less than 15%.

• Proceedings of the Korean Society of Agricultural Engineers Conference
• /
• 2005.10a
• /
• pp.330-335
• /
• 2005

This study was performed for the analysis of the variation characteristics on riverbed according to the arrangement of stream. It was monitored of the variation progress of riverbed dependent on the elapsed time after the arrangement and It was studied that the hydraulic adjustment of the riverbed caused by the variation of the riverbed. The large amount of deposit just after the construction in which the riverbed was arranged to natural form was come from the reduction of flow rate by the installed artificialities such as weirs and stone weirs and by the stones or the concrete blocks attached to the stream sides of riverbanks. This phenomenon was well consistent with the usual characteristics that the accumulation is induced on upper stream of hydraulic artificialities and the erosion is induced on down stream of hydraulic artificialities. The large reduction of the deposit 1 year later after the construction showed that the riverbed eroded considerably because of the recovery of flow amount and the rise of flow rate.

• Journal of fish pathology
• /
• v.20 no.3
• /
• pp.257-267
• /
• 2007

The hypo-salinity effects on fertilized eggs, embryos and larvae were investigated in olive flounder (Paralichthys olivaceus) obtained from hatcheries in Cheju-Island, Yeosu and Chungnam. Those were treated to eight concentration; 0, 3.4, 6.7, 10.1, 13.4, 20.2, 27.4 and 33.6 ‰. It was not discrepancy in the survival rate and hatching success rate of fertilized embryos obtained from different regions. Also, in the larvae, the regional difference was not appeared. The survival rate and hatching ability of embryos significantly diminished in the lower groups than 13.4 ‰ compared to 33.6 ‰. After fertilization, namely embryos are tolerant of a wide range of salinity (13.4 - 33.6 ‰). Reduced salinity induced an increase of the malformed embryo and larvae including various deformities; irregular embryos membrane (or yolk sac depression), fin erosion and swim bladder inflation in the flounder embryo. The hatching success of embryos was significantly reduced in lower salinity than 13.4 ‰. Notably, the reduction of larval survival rate significantly was observed in ≤10.1 ‰ treated groups with the same manner of survival rates of the embryos. Additionally, olive flounder was found to be adequate model for measuring external impulses because there are no the regional differences.

• Journal of the Korean Society of Environmental Restoration Technology
• /
• v.9 no.6
• /
• pp.123-132
• /
• 2006

This research was studied to inverstigate the effect of plant mixtures and tackifibers on the vegetation of slope sites. 5 type plant mixtures(tree type, forest type, native herbaceous plant type, foreign herbaceous plant type, and cool-season turfgrass type) and 3 different tackifibers (Guar tackifibers, Polyarchrylamide tackifibers and Cellulose methyl starch) were treated with 3 replications on the experimented slope. The germination and coverage rate were high on native and foreign herbaceous plants and low on cool-season turfgrass, forest and tree types. We could notice that herbaceous plant types were effective on the vegetation of slope in the short term. Because tree or forest type vegetations similar to natural plant habitat, however, were preferable on slope vegetation in the long term, tree species of high germination rate should be selected in this experiment for tree or forest type slope vegetations. Tackifiber treatments increased the germination rate during the early treatment stage. However, the effect of tackifiber treatment on germination rate was decreased on the elapse of time. Guar tackifiber treatment was most effective on the vegetation of slope. As far as soil erosion control was concerned, all tackifiber treatments were effective compared to control.

• Journal of Ecology and Environment
• /
• v.35 no.3
• /
• pp.167-175
• /
• 2012

Coastal sand dune systems are particularly fragile and threaten the environment. However, these systems provide fundamental ecosystem services to the nearby urban areas, acting, for example, as protective buffers against erosion. In this paper, we attempt to classify the biotope types of coastal sand dune ecosystems and select an index for the assessment of the conservation value. The types of biotopes are categorized based on the vegetation map; floras are examined in order to research the effects of hinterlands on coastal sand dunes. In addition, a naturalization rate and an urbanization index for each biotope type in hinterlands are analyzed. In the ecosystem of coastal sand dunes, the urbanization index and naturalization rate shows a higher value in sand dunes with areas of road, residential, and idle land in farm villages, rice fields, and fields. On the contrary, a lower value in the urbanization index and naturalization rate is present when typical biotope types, such as sand dune vegetation and natural Pinus thunbergii forests, are widely distributed. Based on these results, urbanization index and naturalization rate should be used as critical indices for the assessment of the ecosystem of costal sand dunes.

• 한국전산유체공학회:학술대회논문집
• /
• 2008.03b
• /
• pp.224-227
• /
• 2008

The present study performs a test of a change in a condenser pressure on two kinds of power plants having different condenser pressure-heat rate correction curve and evaluates the results. According to a result of the test, it is confirmed that a sub-critical drum type steam power plant is optimally operated at the condenser pressure of 38㎜Hga that is designed, even during winters. On the other hand, it can be found that a supercritical once through type steam power plant operated at the condenser pressure that is reduced below a design value, that is, up to 28㎜Hga during winters is advantageous in view of turbine efficiency and is operated without a problem in facility operation such as moisture erosion, turbine vibration, etc. Also, the present study compares and reviews a condenser pressure-heat rate correction curve proposed by a manufacturer and a test value. The present study proposes optimum condenser operation pressure capable of concurrently satisfying the stable operation and efficiency improvement of the power plant facility that is operating, making it possible to support an efficient operation of a power plant.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.4 no.2
• /
• pp.127-135
• /
• 1999

Grain-size distribution and accumulation rate of surface sediments on the tidal flats in Hampyong Bay, southwestern coast of Korea, were investigated in a sequential interval of 2 months for the period of 27 months (1994. 10~1996. 12). Seasonal variation of grain-size distribution is prevalent on the Shimock tidal flat in the southern side of the innerbay, rather than the Anarc tidal flat in the northern side around the baymouth. This variation, in particular, more distinctive in the areas around the both high and low tide water levels. The Shimock tidal flat shows typical seasonal variation of sedimentary processes, expected under monsoonal climate. Deposition of tine-grained sediments in summer dominates over erosion in winter, resulting in an annual accumulation rate of 3.7 mm/yr. In contrast, sedimentary processes on the Anarc tidal flat is abnormal that have experienced slight deposition of fine-grained sediments in the winter and severe erosion in the summer time, showing a negative annual accumulation rate of -49.6 mm/yr. Erosional processes in this area is interpreted due mainly to change of strength and direction of tidal currents, caused by the artificial construction of dyke for reclamation in the mid-tidal flat. As a result, It is immoderate to conclude whether sedimentary processes of Hampyong Bay is erosional or depositional at current situation. Further studies on sedimentary budget at the entrance to the bay are needed.

• Journal of the Korean Society of Environmental Restoration Technology
• /
• v.13 no.2
• /
• pp.105-113
• /
• 2010

To investigate the restoration procedure on soil physical properties at the surface of visiting road affected by rest-year system. This study was carried out at visiting roads of stream of Chilsun in Jirisan. Mean soil strength in 20cm of soil depth was lower in the Rest-Year System areas (1.5-1.9 times in Site 2, 1.1-7.5 times in Site 3) than in the control (Site 1). Soil strength was recovered by the Rest-Year System in the national park. Mesopore rate (pF 2.7) in 0-15 cm of soil depth was higher in the Rest-Year System areas (1.2 times) than in the control. This indicates that mesopore rate is rapidly restoring in the Rest-Year System areas. Pore space rate in 0-7.5 cm of soil depth was higher in the Rest-Year System areas (23.2% in Site 2, 23.6% in Site 3) than in the control (22.4% in Site 1). Pore space rate in 7.5-15 cm of soil depth was also higher in the Rest-Year System areas (22.9% in Site 2 and Site 3) than in the control (18.9% in Site 1). Soil pore space was remediable by the Rest-Year System. Bulk density in 0-7.5 cm of soil depth was lower in the Rest-Year System areas (1.674g/$cm^3$ in Site 2, 1.668g/$cm^3$ in Site 3) than in the control (1.723g/$cm^3$ in Site 1). Bulk density in 7.5-15 cm of soil depth was lower in the Rest-Year System areas (1.785g/$cm^3$ in Site 2 and 1.721g/$cm^3$ in Site 3) than in the control (1.721g/$cm^3$ in Site 1). Soil bulk density was decreased in the Rest-Year System areas of the national park. Amount of soil erosion was lower in the Rest-Year System areas ($0.017m^3$/km/yr in site 2, $0.023m^3$/km/yr in site 3) than in the control ($0.054m^3$/km/yr in site 1).