• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.200-200
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• 2012

We investigated a flexible transparent film using the spinning multi-walled carbon nanotubes (MWCNTs). Spin-capable MWCNTs on iron catalyzed on a SiO2 wafer was grown by chemical vapor deposition, which was performed at $780^{\circ}C$ using C2H2 and H2 gas. The average diameter and length of MWCNTs grown on the substrate were ~15 nm and $250{\sim}300{\mu}m$, respectively. The MWCNT sheets were produced by continuously pulling out from well-aligned MWCNTs on a substrate. The MWCNT sheet films were produced simply by direct coating on the flexible film or grass. The thickness of sheet film was remarkably decreased by alcohol spraying on the surface of sheet. The alcohol splay increased transmittance and decreased electrical resistance of MWCNT sheet films. Single and double sheets were produced with sheet resistance of ~699 and ${\sim}349{\Omega}/sq$, respectively, transmittance of 81~85 % and 67~72%, respectively. The MWCNT sheet films were heated through the application of direct current power. The flexible transparent heaters showed a rapid thermal response and uniform distribution of temperature. In addition, MWCNT yarns were prepared by spinning a bundle of MWCNTs from vertically super-aligned MWCNTs on a substrate, and field emission from the tip and side of the yarns was induced in a scanning electron microscope. We found that the field emission behavior from the tip of the yarn was better than the field emission from the side. The field emission turn-on voltages from the tip and side of MWCNT yarns were 1.6 and $1.7V/{\mu}m$, respectively, after the yarn was subjected to an aging process. Both the configuration of the tip end and the body of the yarn were changed remarkably during the field emission. We also performed the field emission of the sheet films. The sheet films showed the turn on voltage of ${\sim}1.45V/{\mu}m$ during the field emission.

• Korean Journal of Environmental Agriculture
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• v.35 no.1
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• pp.1-5
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• 2016

BACKGROUND: Burcucumber(Sicyos angulatus L.) is an invasive plant species and disturbs ecosystems in Korea. The main method for prevention of burcucumber is cutting or pulling out. However, the studies accounting for the use of the by-product of burcucumber after cutting remain incomplete. Thus, the aim of this study was to investigate the applicability of burcucumber as a substitute for nitrogen fertilizer.METHODS AND RESULTS: Burcucmber plants only including stem, leaves, and petiole were collected from the Sky Park in Seoul and divided in to three categories based on the length of stem of burcucumber; 10-30 cm, 30-100 cm, and 100-200 cm. And they were input into soil with 20 kg-N/10 a. After 4 weeks aging, chemical properties of treated soils and the productivity of lettuce(Lactuca sativa L.) were examined. Both the inorganic nitrogen contents in soils and the growth of lettuce were increased with the decreases in length of burcucumber standing for young plant. And the inorganic nitrogen content and the productivity of lettuce were positively correlated(r= 0.9409).CONCLUSION: The C/N ratio of burcucumber was low, indicating fast decomposition and nitrogen supplying rate, resulting in the increase in lettuce growth. Burcucumber could be a good substitute for nitrogen organic fertilizer.

• Korean Journal of Agricultural Science
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• v.41 no.4
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• pp.473-480
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• 2014

Upon setting up a dedicated plastic greenhouse for tomato cultivation developed by the Rural Development Administration on the Gyehwa reclaimed land, this study was aimed at analyzing the problems can be occurred in the installation of plastic greenhouse on reclaimed lands as well as finding out solutions for improvement. A relatively cheaper wooden pile was used in the installation in order to supplement the soft ground conditions. Based on the results of ground investigation of the installation site, both the allowable bearing capacity and pulling resistance of the wooden pile with a diameter of 150 mm and a length of 10 m were computed and came out to be 30.645 kN. It was determined that the values were enough to withstand the maximum compressive force (17.206 kN) and the pullout force (20.435 kN) that are generally applied to the greenhouse footing. There are three problems aroused in the process of greenhouse installation, and the corresponding countermeasures are as follow. First, due to the slightly bent shape of the wooden pile, there were phenomenon such as deviation, torsion, and fracture when driving the pile. This could be prevented by the use of the backhoe (0.2) rotating tongs, which are holding the pile, to drive the pile while pushing to the direction of the driving and fixing it until 5 m below ground and applying a soft vibrating pressure until the first 2 m. Second, there exists a concrete independent footing between the column of the greenhouse and the wooden pile driven to the underground water level. Since it is difficult to accurately drive the pile on this independent footing, the problem of footing baseplate used to fix the column being off the independent footing was occurred. In order to handle with this matter, the diameter of the independent footing was changed from 200 mm to 300 mm. Last, after films were covered in the condition that the reinforcing frame and bracing are not installed, there was a phenomenon of columns being pushed away by the strong wind to the maximum of $11m{\cdot}s^{-1}$. It is encouraged to avoid constructions in winter, and the film covering jobs always to be done after the frame construction is completely over. The height of the independent footing was measured for 9 months after the completion of the greenhouse installation, and it was found to be within the margin of error meaning that there was no subsidence. The extent to the framework distortion and the value of inclinometers as well showed not much alteration. In other words, the wooden pile was designed to have a sufficient bearing capacity.

• Korean Journal of Soil Science and Fertilizer
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• v.35 no.3
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• pp.153-161
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• 2002

The installation of subsurface drainage equipment is required for generalized use of paddy field and to improve soil productivity. The internal drainage of paddy field has improved root condition from the increasing of oxygen supply and removing noxious elements. This experiment was carried out to determine the effects of fertilization and drainage system on soil characteristic, growth and lodging trait of rice in paddy soil. A subsurface drainage system was installed a depth of 0.8m. Three fertilizer treatments were applied : 1) Conventional fertilized plot, 2) Controlled-release fertilized plot, 3) No-fertilized plot. In conventional plot, 110 kg N (as urea 46%), 45 kg P (as fused phosphate 20%) and 57 kg K (as potassium chloride 60%) per hectare fertilizers were applied. Controlled-release fertilizer was applied by 70% of N compared to the conventional plot. During the rice cropping, the water depth decrease was two times higher in subsurface drainage(SD) plot than non-drained(ND) plot. After harvesting of rice, the bulk density of sub-soil(10-20cm depth) was lower in SD plot than ND plot. After the experiment, the surface soil pH was high at SD plot but sub-soil was high at ND plot. Organic matter content was higher in all soil layer for SD plot than fro ND plot. Available $P_2O_5$ was not different between SD and ND plot for surface soil, but was high for SD plot for sub soil. The $NH_4{^+}-N$ content of soil, shoot dry matter, total nitrogen and $K_2O$ of rice plant were greater after panicle formation stage in SD plot. Total nitrogen content, $P_2O_5$ and $K_2O$ of rice root were high in SD plot after heading. Though the gravity center and 3rd internode length were greater, pulling force of rice root was higher in SD plot than ND plot. Rice yield in SD plot were low at conventional and controlled-release fertilized plot because of the greater field lodging, but yield in SD plot was high at no-fertilized plot. This study indicates that the fertilization level should be decrease on subsurface drainage system for rice cropping.

• Restorative Dentistry and Endodontics
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• v.32 no.6
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• pp.522-529
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• 2007

The purpose of this study was to compare the apical leakage of the root canal filled with the System B and the EndoTwinn(the combined application of heat and ultrasonic vibration). Sixty extracted premolars with straight root were cleaned and shaped to size 35. Group SB was obturated using System B and Group ET was filled with EndoTwinn. A size 35 of 0.06 tapered gutta-percha and Adseal were used and the plugger which could be introduced to 4 mm short of working length was selected in the obturation procedure. As the positive control, Group PC was not filled. In Group SB, ET and PC, all external surfaces of each tooth were coated with nail varnish leaving only 1 mm area around the apical foramen. In the negative control of Group NSB and Group NET, all of external tooth surface including apical foramen was coated with the nail varnish. The specimens were immersed in methylene blue dye solution for 2 days. Then the specimens were sectioned at each 1 mm from apex to 5 mm level. The final score of one specimen was given by summing up of the points at all levels. The dye leakage of Group ET was significantly less than that observed in Group SB (p < 0.05). And the frequency of gutta-percha pulling out from root canal when the plugger was removed was more often with the System B than with EndoTwinn but there was no significant difference.

• Journal of Wetlands Research
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• v.26 no.4
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• pp.380-388
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• 2024

Solidago altissima, an invasive alien species, is distributed nationwide in Korea. However, the areas surrounding the Dongjin River and Mankyung River are characterized by a large area with high-density distribution, making management urgent. Therefore, the regional environmental office conducted two physical removal operations in 2022. The first operation involved local residents who removed S. altissima by hand, pulling the plants out by the roots from an area of approximately 900m². The second operation used heavy machinery, including excavators and agricultural equipment, to remove the above-ground parts and till the soil over an area of about 17,60m². A vegetation survey was conducted, and growth characteristics (stem diameter, shoot length, and number of shoots) and physiological responses (chlorophyll fluorescence (Fv/Fm) and chlorophyll content) were measured at both the control plots, where S. altissima was not removed, and the treatment plots, where it was removed, to evaluate the effectiveness of the removal. As a result, the importance value of S. altissima was lower in the treatment plots than in the control plots, while species diversity within the treatment plots increased. The number of shoots per unit area was lower in the treatment plots compared to the control plots. These findings indicate that removing the above-ground parts of S. altissima and tilling the soil using heavy machinery in high-density community effectively inhibited the growth of the S. altissima population. Meanwhile, chlorophyll fluorescence (Fv/Fm) values were higher in the treatment plots, reflecting the density-dependent characteristics of the plant. This suggests that continuous removal efforts are necessary for effective management.Continuous removal efforts must be accompanied by rigorous and ongoing monitoring, and annual development of tailored management plans is essential.