• Journal of Korean Society of Forest Science
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• v.84 no.2
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• pp.226-238
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• 1995

This research was conducted to investigate the influential factors of the runoff of water and hillslope erosion caused by the large-scale harvesting operation. It was carried out on harvested sites (13ha) and non-harvested sites(13ha) in Seoul National University Research Forest [(Mt.) Paekunsan], from 1993 to 1994. 1. The amount of runoff of water was increased as the unit of rainfall increases, and the amount of runoff on harvested sites was larger than that of non-harvested sites by 28% in the first year and 24.5% in the second year after harvesting. According to the multiple regression equation for surface runoff, unit and number of rainfall, amount of hillslope erosion and soil bulk density showed statistically significance($R^2$=0.91). 2. The amount of hillslope erosion on harvested sites was larger than that of non-harvested sites by 7 times during the first year of harvesting and 2 times during the second year. 3. The multiple regression equations for hillslope erosion showed that soil bulk density, surface runoff of water and unit of rainfall(these factors were not controllable) had statistically significance($R^2$=0.74). 4. Soil runoff in harvested and non harvested sites were maximum 6.7% and 1% of the amount of hillslope erosion, respectively during the first year of harvesting. And the second year of harvesting soil runoff in harvested and non harvested cites were maximum 5.7% and 1.9%of the amount of hillslope erosion. From the above results, when in planning for timber harvesting, the buffer strip-woods zone must be remained to diminish soil and water runoff and to preserve water quality.

• Nuclear Engineering and Technology
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• v.56 no.1
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• pp.70-77
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• 2024

A low energy ion irradiation system based on the deuterium arc ion source with a high perveance of 1 µP for a single extraction aperture has been successfully developed for the investigation of ion irradiation on plasma-facing components including the first mirror of plasma optical diagnostics system. Under the optimum operating condition for mirror testing, the ion source has a beam energy of 200 eV and a current density of 3.7 mA/cm². The ion source comprises a magnetic cusp-type plasma source, an extraction system, a target system with a Faraday cup, and a power supply control system to ensure stable long time operation. Operation parameters of plasma source such as pressure, filament current, and arc power with D₂ discharge gas were optimized for beam extraction by measuring plasma parameters with a Langmuir probe. The diode electrode extraction system was designed by IGUN simulation to optimize for 1 µP perveance. It was successfully demonstrated that the ion beam current of ~4 mA can be extracted through the 10 mm aperture from the developed ion source. The target system with the Faraday cup is also developed to measure the beam current. With the assistance of the power control system, ion beams are extracted while maintaining a consistent arc power for more than 10 min of continuous operation.

• Journal of Periodontal and Implant Science
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• v.26 no.4
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• pp.907-931
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• 1996

The purpose of this study was to study of the effects of the bioglass and the natural coral on healing process of the alveolar bone defects. Three adult dogs aged 1 to 2 years were used in this study. Experimental alveolar bone defects were created surgically with surgical bur and bone chisel at the furcation area of the buccal surface of the right and left mandibular 3rd, 4th premolars. Twelve experimental alveolar bone defects were devided into four groups according to the type of graft materials. The groups were as follows : 1. flap operation with root planing & curettage(Negative control group) 2. flap operation with autogenous bone(Positive control group) 3. flap operation with bioglass(BG group) 4. flap operation with natural coral(NC group) At 2, 4, and 8 weeks, the dogs were serially sacrificed and specimens were prepared with Hematoxylin-Eosin stain for light microscopic evaluation. The results of this study were as follows : 1. The defect areas were filled with granulation tissue at two weeks in negative control group. But in other groups, the appearance of connective tissues around graft materials were formed more densely and the response of inflammation by graft materials itself was not found. 2. In every control and experimental groups at two weeks, there was seen the accumulation of the formation of new bone trabeculae at the bottom of defects and gradually expanded toward the graft materials and in autogenous group there was slightly seen the formation of new cementum. 3. There was seen the erosion of central portion of bioglass particles at two weeks in BG group, and the erosion of the central portion was developed more progressively and was filled with bone-like tissues at eight weeks. 4. The natural coral particles were encapsulated by densely connective tissues and seen the formation of new bone tissues at four weeks and developed more new bone and cementum formation at eight weeks. From the results of this study, the bioglass and the natural coral may be biocompatible and have a weak adverse reaction to the periodontal tissues.

• Proceedings of KOSOMES biannual meeting
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• 2003.11a
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• pp.157-162
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• 2003

The sludge oils were produced necessarily in the ships operation, so that it will be the best way to manage the sludge oils inside ship itself from a viewpoint of the prevention of marine oil pollution from ship. The ultrasonic breaking systems which recycle the sludge oil from ship into usable oil to be brunt is recognized as a most possible recycling device. In this regards, the purpose of this study is to examine erosion damage on the SS400 specimen by cavitation and the effect of impact pressure generated from the demolition of the cavity of ultrasonic vibration in the marine sludge oil environment .. The erosion damage of specimen was investigated mainly on weight loss, weight loss rate and maximum erosion rate with variation of the oil temperature as well as the change of space between transducer horn and specimen. The experimental results showed that as the space between ultrasonic vibrator horn and specimen disk increased, the weight loss and weight loss rate decreased and the values were larger in SFO than in SLO. The experimental results can be useful to the development of sludge oil disposing systems and to consider a countermeasure for the prevention of erosion damages by cavitation.

• Ecology and Resilient Infrastructure
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• v.6 no.4
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• pp.217-226
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• 2019

Optimum engineering methods for bank protection were classified based on steepness of bank slope and an existence of waterfront facility in the floodplain, and a new concept of eco-hybrid rolling mat method which could be applicable for the unfitted cases with previously developed countermeasures was suggested in this study. The eco-hybrid rolling mat method can be constructed while maintaining the river environment and ecosystem that does not interfere with the ground and slopes, when bank erosion occurs, it is an economical and efficient construction method that can protect the revetment and the bank slope immediately. The developed eco-hybrid rolling mat method was verified for the designed structure, system, function and effect based on large-scale river experiments including field exposure and decomposition test. As a result, the normal operation and effect of the rolling mat ted under low and high velocity conditions were confirmed with respect to bank protection. The effect of bank erosion prevention was quantitatively validated by sediment concentration monitoring and analysis, and the product specification of the eco-hybrid rolling mat was presented based on the standardized mat applied in real-scale tests.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.5
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• pp.496-501
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• 2009

The thruster head unit of a 300 W cylindrical Hall thruster was developed for the propulsion system of small satellites. The magnetic topology in the thruster channel is a key parameter to achieve high performances. Two types of magnetic circuit structures were designed and manufactured to compare the thrust levels and efficiencies. Also the endurance test was conducted to measure the stable operation duration of the thruster head and to find degree of erosion after extended operation.

• Journal of Wetlands Research
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• v.19 no.2
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• pp.181-192
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• 2017

Analysis using a numerical model is important to understand the sediment transport mechanism associated with erosion and sedimentation near weirs and other hydraulic structures within riverine systems. The local riverbed change near a hydraulic structure (Gangjeong-Goryong multi-function weir in the Nakdong river) was analyzed in order to examine the effect of hydraulic structures on local bed change. A 2D numerical model (CCHE-2D) was employed to simulate the sedimentation and erosion over a reach (25 km) including the weir. For the calibration and verification of the model, rainfall data from a real event (Typoon 'Ewiniar' in 2006) were used for flow and stage simulation. And the simulated results show a good agreement with the observed data for the whole domain. From the result, it was found that the installation and operation of the weir could aggravate bed changes by typhoon between movable weirs, and which resulted in redistribution of sediment.

• Journal of Chest Surgery
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• v.39 no.2 s.259
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• pp.150-153
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• 2006

Percutaneous transcatheter closure of atrial septal defects as a therapeutic alternative in appropriate patients provides superior cosmetic results, is less invasive, and allows for shorter hospital stays. Unfortunately, however, such percutaneous procedures can be associated with catastrophic procedure complications that may require immediate surgical intervention. We report a case of aorta-to-right atrial fistula two months after transcatheter occlusion of an atrial septal defect by an Amplatzer septal occluder. Revealed by dyspnea, palpitation and hemolysis, this complication needed an emergency surgical operation. The fistula between the noncoronary Valsalva sinus of the aorta and the right atrium was repaired. The atrial septal defect was closed by patch. The cause of this serious complication appears to be erosion into the aorta by the right atrial disk.

• Journal of Korean Society on Water Environment
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• v.25 no.6
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• pp.821-831
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• 2009

The study was aimed to assess the expected impact of climate change on the water cycle and soil losses in Daecheong Reservoir watershed, Korea using the Soil and Water Assessment Tool (SWAT) that was validated for the watershed in a previous study. Future climate data including precipitation, temperature and humidity generated by introducing a regional climate model (Mesoscale Model Version 5, MM5) to dynamically downscale global circulation model (European Centre Hamburg Model Version 4, ECHAM4) were used to simulate the hydrological responses and soil erosion processes in the future 100 years (2001~2100) under the Special Report on Emissions Scenario (SRES) A1B. The results indicated that the climate change may increase in the amount of surface runoff and thereby sediment load to the reservoir. Spatially, the impact was relatively more significant in the subbasin Bocheongcheon because of its lower occupation rate of forest land compared to other subbasins. Seasonally, the increase of surface runoff and soil losses was more significant during late summer and fall season when both flood control and turbidity flow control are necessary for the reservoir and downstream. The occurrence of extreme turbidity flow events during these period is more vulnerable to reservoir operation because the suspended solids that remained water column can be resuspended by vertical mixing during winter turnover period. The study results provide useful information for the development of adaptive management strategy for the reservoir to cope with the expected impact of future climate change.

• Journal of Environmental Science International
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• v.15 no.1
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• pp.33-43
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• 2006

Revetment Mattress/Filter is the porous structure filled fillers in meshed structure so that it cail use the fillers of various sizes and form various pores. The porous structure of the Mattress/Filter increases drainage so that it decreases the energy and erosion of flow therefore the tractive force is decreased and the erosion of revetment is mitigated. The filler of Mattress/Filter uses gravels, waste concretes and slags so that the surface is rough and the roughness coefficient increases and the increase of the roughness coefficient decreases flow velocity and tractive force. On the other hand Mattress/Filter and vegetation are combined so that the increase of roughness coefficient and flow velocity still more progress therefore the effect of decrease of tractive force is increased after a few months have passed since the Mattress/Filter is constructed so that the vegetation is developed and be stabilized. The vegetation channel of Mattress/Filter is set tip and the inspection comes into operation by varing flowrate and vegetation spacing to examine these characters of the Mattress/Filter The coefficient of flow velocity U/U*' is decreased exponentially as vegetation esity aH' or $\lambda$ is increased and the coefficient of friction f is increased as vegetation desity aH' is increased but decreased as the coefficient of flow velocity U/U*' is increased. The effective tractive force $F_0$ is decreased exponentially as the vegetation desity aH' is increased. From the inspection the results are obtained that the porous and vegetation structure of the revetment Mattress/Filter system increases the coefficient of friction of revetment so that flow velocity and effective are decreased therefore greatly contributes the stability of the revetment.